LCOV - code coverage report
Current view: top level - kernel/trace - ring_buffer.c (source / functions) Hit Total Coverage
Test: Real Lines: 115 1229 9.4 %
Date: 2020-10-17 15:46:43 Functions: 0 109 0.0 %
Legend: Neither, QEMU, Real, Both Branches: 0 0 -

           Branch data     Line data    Source code
       1                 :            : // SPDX-License-Identifier: GPL-2.0
       2                 :            : /*
       3                 :            :  * Generic ring buffer
       4                 :            :  *
       5                 :            :  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
       6                 :            :  */
       7                 :            : #include <linux/trace_events.h>
       8                 :            : #include <linux/ring_buffer.h>
       9                 :            : #include <linux/trace_clock.h>
      10                 :            : #include <linux/sched/clock.h>
      11                 :            : #include <linux/trace_seq.h>
      12                 :            : #include <linux/spinlock.h>
      13                 :            : #include <linux/irq_work.h>
      14                 :            : #include <linux/security.h>
      15                 :            : #include <linux/uaccess.h>
      16                 :            : #include <linux/hardirq.h>
      17                 :            : #include <linux/kthread.h>        /* for self test */
      18                 :            : #include <linux/module.h>
      19                 :            : #include <linux/percpu.h>
      20                 :            : #include <linux/mutex.h>
      21                 :            : #include <linux/delay.h>
      22                 :            : #include <linux/slab.h>
      23                 :            : #include <linux/init.h>
      24                 :            : #include <linux/hash.h>
      25                 :            : #include <linux/list.h>
      26                 :            : #include <linux/cpu.h>
      27                 :            : #include <linux/oom.h>
      28                 :            : 
      29                 :            : #include <asm/local.h>
      30                 :            : 
      31                 :            : static void update_pages_handler(struct work_struct *work);
      32                 :            : 
      33                 :            : /*
      34                 :            :  * The ring buffer header is special. We must manually up keep it.
      35                 :            :  */
      36                 :          0 : int ring_buffer_print_entry_header(struct trace_seq *s)
      37                 :            : {
      38                 :          0 :         trace_seq_puts(s, "# compressed entry header\n");
      39                 :          0 :         trace_seq_puts(s, "\ttype_len    :    5 bits\n");
      40                 :          0 :         trace_seq_puts(s, "\ttime_delta  :   27 bits\n");
      41                 :          0 :         trace_seq_puts(s, "\tarray       :   32 bits\n");
      42                 :          0 :         trace_seq_putc(s, '\n');
      43                 :          0 :         trace_seq_printf(s, "\tpadding     : type == %d\n",
      44                 :            :                          RINGBUF_TYPE_PADDING);
      45                 :          0 :         trace_seq_printf(s, "\ttime_extend : type == %d\n",
      46                 :            :                          RINGBUF_TYPE_TIME_EXTEND);
      47                 :          0 :         trace_seq_printf(s, "\ttime_stamp : type == %d\n",
      48                 :            :                          RINGBUF_TYPE_TIME_STAMP);
      49                 :          0 :         trace_seq_printf(s, "\tdata max type_len  == %d\n",
      50                 :            :                          RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
      51                 :            : 
      52                 :          0 :         return !trace_seq_has_overflowed(s);
      53                 :            : }
      54                 :            : 
      55                 :            : /*
      56                 :            :  * The ring buffer is made up of a list of pages. A separate list of pages is
      57                 :            :  * allocated for each CPU. A writer may only write to a buffer that is
      58                 :            :  * associated with the CPU it is currently executing on.  A reader may read
      59                 :            :  * from any per cpu buffer.
      60                 :            :  *
      61                 :            :  * The reader is special. For each per cpu buffer, the reader has its own
      62                 :            :  * reader page. When a reader has read the entire reader page, this reader
      63                 :            :  * page is swapped with another page in the ring buffer.
      64                 :            :  *
      65                 :            :  * Now, as long as the writer is off the reader page, the reader can do what
      66                 :            :  * ever it wants with that page. The writer will never write to that page
      67                 :            :  * again (as long as it is out of the ring buffer).
      68                 :            :  *
      69                 :            :  * Here's some silly ASCII art.
      70                 :            :  *
      71                 :            :  *   +------+
      72                 :            :  *   |reader|          RING BUFFER
      73                 :            :  *   |page  |
      74                 :            :  *   +------+        +---+   +---+   +---+
      75                 :            :  *                   |   |-->|   |-->|   |
      76                 :            :  *                   +---+   +---+   +---+
      77                 :            :  *                     ^               |
      78                 :            :  *                     |               |
      79                 :            :  *                     +---------------+
      80                 :            :  *
      81                 :            :  *
      82                 :            :  *   +------+
      83                 :            :  *   |reader|          RING BUFFER
      84                 :            :  *   |page  |------------------v
      85                 :            :  *   +------+        +---+   +---+   +---+
      86                 :            :  *                   |   |-->|   |-->|   |
      87                 :            :  *                   +---+   +---+   +---+
      88                 :            :  *                     ^               |
      89                 :            :  *                     |               |
      90                 :            :  *                     +---------------+
      91                 :            :  *
      92                 :            :  *
      93                 :            :  *   +------+
      94                 :            :  *   |reader|          RING BUFFER
      95                 :            :  *   |page  |------------------v
      96                 :            :  *   +------+        +---+   +---+   +---+
      97                 :            :  *      ^            |   |-->|   |-->|   |
      98                 :            :  *      |            +---+   +---+   +---+
      99                 :            :  *      |                              |
     100                 :            :  *      |                              |
     101                 :            :  *      +------------------------------+
     102                 :            :  *
     103                 :            :  *
     104                 :            :  *   +------+
     105                 :            :  *   |buffer|          RING BUFFER
     106                 :            :  *   |page  |------------------v
     107                 :            :  *   +------+        +---+   +---+   +---+
     108                 :            :  *      ^            |   |   |   |-->|   |
     109                 :            :  *      |   New      +---+   +---+   +---+
     110                 :            :  *      |  Reader------^               |
     111                 :            :  *      |   page                       |
     112                 :            :  *      +------------------------------+
     113                 :            :  *
     114                 :            :  *
     115                 :            :  * After we make this swap, the reader can hand this page off to the splice
     116                 :            :  * code and be done with it. It can even allocate a new page if it needs to
     117                 :            :  * and swap that into the ring buffer.
     118                 :            :  *
     119                 :            :  * We will be using cmpxchg soon to make all this lockless.
     120                 :            :  *
     121                 :            :  */
     122                 :            : 
     123                 :            : /* Used for individual buffers (after the counter) */
     124                 :            : #define RB_BUFFER_OFF           (1 << 20)
     125                 :            : 
     126                 :            : #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
     127                 :            : 
     128                 :            : #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
     129                 :            : #define RB_ALIGNMENT            4U
     130                 :            : #define RB_MAX_SMALL_DATA       (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
     131                 :            : #define RB_EVNT_MIN_SIZE        8U      /* two 32bit words */
     132                 :            : #define RB_ALIGN_DATA           __aligned(RB_ALIGNMENT)
     133                 :            : 
     134                 :            : /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
     135                 :            : #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
     136                 :            : 
     137                 :            : enum {
     138                 :            :         RB_LEN_TIME_EXTEND = 8,
     139                 :            :         RB_LEN_TIME_STAMP =  8,
     140                 :            : };
     141                 :            : 
     142                 :            : #define skip_time_extend(event) \
     143                 :            :         ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
     144                 :            : 
     145                 :            : #define extended_time(event) \
     146                 :            :         (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
     147                 :            : 
     148                 :            : static inline int rb_null_event(struct ring_buffer_event *event)
     149                 :            : {
     150                 :          0 :         return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
     151                 :            : }
     152                 :            : 
     153                 :            : static void rb_event_set_padding(struct ring_buffer_event *event)
     154                 :            : {
     155                 :            :         /* padding has a NULL time_delta */
     156                 :          0 :         event->type_len = RINGBUF_TYPE_PADDING;
     157                 :          0 :         event->time_delta = 0;
     158                 :            : }
     159                 :            : 
     160                 :            : static unsigned
     161                 :            : rb_event_data_length(struct ring_buffer_event *event)
     162                 :            : {
     163                 :            :         unsigned length;
     164                 :            : 
     165                 :          0 :         if (event->type_len)
     166                 :          0 :                 length = event->type_len * RB_ALIGNMENT;
     167                 :            :         else
     168                 :          0 :                 length = event->array[0];
     169                 :          0 :         return length + RB_EVNT_HDR_SIZE;
     170                 :            : }
     171                 :            : 
     172                 :            : /*
     173                 :            :  * Return the length of the given event. Will return
     174                 :            :  * the length of the time extend if the event is a
     175                 :            :  * time extend.
     176                 :            :  */
     177                 :            : static inline unsigned
     178                 :          0 : rb_event_length(struct ring_buffer_event *event)
     179                 :            : {
     180                 :          0 :         switch (event->type_len) {
     181                 :            :         case RINGBUF_TYPE_PADDING:
     182                 :          0 :                 if (rb_null_event(event))
     183                 :            :                         /* undefined */
     184                 :            :                         return -1;
     185                 :          0 :                 return  event->array[0] + RB_EVNT_HDR_SIZE;
     186                 :            : 
     187                 :            :         case RINGBUF_TYPE_TIME_EXTEND:
     188                 :            :                 return RB_LEN_TIME_EXTEND;
     189                 :            : 
     190                 :            :         case RINGBUF_TYPE_TIME_STAMP:
     191                 :            :                 return RB_LEN_TIME_STAMP;
     192                 :            : 
     193                 :            :         case RINGBUF_TYPE_DATA:
     194                 :          0 :                 return rb_event_data_length(event);
     195                 :            :         default:
     196                 :          0 :                 BUG();
     197                 :            :         }
     198                 :            :         /* not hit */
     199                 :            :         return 0;
     200                 :            : }
     201                 :            : 
     202                 :            : /*
     203                 :            :  * Return total length of time extend and data,
     204                 :            :  *   or just the event length for all other events.
     205                 :            :  */
     206                 :            : static inline unsigned
     207                 :            : rb_event_ts_length(struct ring_buffer_event *event)
     208                 :            : {
     209                 :            :         unsigned len = 0;
     210                 :            : 
     211                 :          0 :         if (extended_time(event)) {
     212                 :            :                 /* time extends include the data event after it */
     213                 :            :                 len = RB_LEN_TIME_EXTEND;
     214                 :          0 :                 event = skip_time_extend(event);
     215                 :            :         }
     216                 :          0 :         return len + rb_event_length(event);
     217                 :            : }
     218                 :            : 
     219                 :            : /**
     220                 :            :  * ring_buffer_event_length - return the length of the event
     221                 :            :  * @event: the event to get the length of
     222                 :            :  *
     223                 :            :  * Returns the size of the data load of a data event.
     224                 :            :  * If the event is something other than a data event, it
     225                 :            :  * returns the size of the event itself. With the exception
     226                 :            :  * of a TIME EXTEND, where it still returns the size of the
     227                 :            :  * data load of the data event after it.
     228                 :            :  */
     229                 :          0 : unsigned ring_buffer_event_length(struct ring_buffer_event *event)
     230                 :            : {
     231                 :            :         unsigned length;
     232                 :            : 
     233                 :          0 :         if (extended_time(event))
     234                 :          0 :                 event = skip_time_extend(event);
     235                 :            : 
     236                 :          0 :         length = rb_event_length(event);
     237                 :          0 :         if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
     238                 :            :                 return length;
     239                 :          0 :         length -= RB_EVNT_HDR_SIZE;
     240                 :          0 :         if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
     241                 :          0 :                 length -= sizeof(event->array[0]);
     242                 :          0 :         return length;
     243                 :            : }
     244                 :            : EXPORT_SYMBOL_GPL(ring_buffer_event_length);
     245                 :            : 
     246                 :            : /* inline for ring buffer fast paths */
     247                 :            : static __always_inline void *
     248                 :            : rb_event_data(struct ring_buffer_event *event)
     249                 :            : {
     250                 :          0 :         if (extended_time(event))
     251                 :          0 :                 event = skip_time_extend(event);
     252                 :          0 :         BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
     253                 :            :         /* If length is in len field, then array[0] has the data */
     254                 :          0 :         if (event->type_len)
     255                 :          0 :                 return (void *)&event->array[0];
     256                 :            :         /* Otherwise length is in array[0] and array[1] has the data */
     257                 :          0 :         return (void *)&event->array[1];
     258                 :            : }
     259                 :            : 
     260                 :            : /**
     261                 :            :  * ring_buffer_event_data - return the data of the event
     262                 :            :  * @event: the event to get the data from
     263                 :            :  */
     264                 :          0 : void *ring_buffer_event_data(struct ring_buffer_event *event)
     265                 :            : {
     266                 :          0 :         return rb_event_data(event);
     267                 :            : }
     268                 :            : EXPORT_SYMBOL_GPL(ring_buffer_event_data);
     269                 :            : 
     270                 :            : #define for_each_buffer_cpu(buffer, cpu)                \
     271                 :            :         for_each_cpu(cpu, buffer->cpumask)
     272                 :            : 
     273                 :            : #define TS_SHIFT        27
     274                 :            : #define TS_MASK         ((1ULL << TS_SHIFT) - 1)
     275                 :            : #define TS_DELTA_TEST   (~TS_MASK)
     276                 :            : 
     277                 :            : /**
     278                 :            :  * ring_buffer_event_time_stamp - return the event's extended timestamp
     279                 :            :  * @event: the event to get the timestamp of
     280                 :            :  *
     281                 :            :  * Returns the extended timestamp associated with a data event.
     282                 :            :  * An extended time_stamp is a 64-bit timestamp represented
     283                 :            :  * internally in a special way that makes the best use of space
     284                 :            :  * contained within a ring buffer event.  This function decodes
     285                 :            :  * it and maps it to a straight u64 value.
     286                 :            :  */
     287                 :          0 : u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
     288                 :            : {
     289                 :            :         u64 ts;
     290                 :            : 
     291                 :          0 :         ts = event->array[0];
     292                 :          0 :         ts <<= TS_SHIFT;
     293                 :          0 :         ts += event->time_delta;
     294                 :            : 
     295                 :          0 :         return ts;
     296                 :            : }
     297                 :            : 
     298                 :            : /* Flag when events were overwritten */
     299                 :            : #define RB_MISSED_EVENTS        (1 << 31)
     300                 :            : /* Missed count stored at end */
     301                 :            : #define RB_MISSED_STORED        (1 << 30)
     302                 :            : 
     303                 :            : #define RB_MISSED_FLAGS         (RB_MISSED_EVENTS|RB_MISSED_STORED)
     304                 :            : 
     305                 :            : struct buffer_data_page {
     306                 :            :         u64              time_stamp;    /* page time stamp */
     307                 :            :         local_t          commit;        /* write committed index */
     308                 :            :         unsigned char    data[] RB_ALIGN_DATA;  /* data of buffer page */
     309                 :            : };
     310                 :            : 
     311                 :            : /*
     312                 :            :  * Note, the buffer_page list must be first. The buffer pages
     313                 :            :  * are allocated in cache lines, which means that each buffer
     314                 :            :  * page will be at the beginning of a cache line, and thus
     315                 :            :  * the least significant bits will be zero. We use this to
     316                 :            :  * add flags in the list struct pointers, to make the ring buffer
     317                 :            :  * lockless.
     318                 :            :  */
     319                 :            : struct buffer_page {
     320                 :            :         struct list_head list;          /* list of buffer pages */
     321                 :            :         local_t          write;         /* index for next write */
     322                 :            :         unsigned         read;          /* index for next read */
     323                 :            :         local_t          entries;       /* entries on this page */
     324                 :            :         unsigned long    real_end;      /* real end of data */
     325                 :            :         struct buffer_data_page *page;  /* Actual data page */
     326                 :            : };
     327                 :            : 
     328                 :            : /*
     329                 :            :  * The buffer page counters, write and entries, must be reset
     330                 :            :  * atomically when crossing page boundaries. To synchronize this
     331                 :            :  * update, two counters are inserted into the number. One is
     332                 :            :  * the actual counter for the write position or count on the page.
     333                 :            :  *
     334                 :            :  * The other is a counter of updaters. Before an update happens
     335                 :            :  * the update partition of the counter is incremented. This will
     336                 :            :  * allow the updater to update the counter atomically.
     337                 :            :  *
     338                 :            :  * The counter is 20 bits, and the state data is 12.
     339                 :            :  */
     340                 :            : #define RB_WRITE_MASK           0xfffff
     341                 :            : #define RB_WRITE_INTCNT         (1 << 20)
     342                 :            : 
     343                 :            : static void rb_init_page(struct buffer_data_page *bpage)
     344                 :            : {
     345                 :            :         local_set(&bpage->commit, 0);
     346                 :            : }
     347                 :            : 
     348                 :            : /*
     349                 :            :  * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
     350                 :            :  * this issue out.
     351                 :            :  */
     352                 :          0 : static void free_buffer_page(struct buffer_page *bpage)
     353                 :            : {
     354                 :          0 :         free_page((unsigned long)bpage->page);
     355                 :          0 :         kfree(bpage);
     356                 :          0 : }
     357                 :            : 
     358                 :            : /*
     359                 :            :  * We need to fit the time_stamp delta into 27 bits.
     360                 :            :  */
     361                 :          0 : static inline int test_time_stamp(u64 delta)
     362                 :            : {
     363                 :          0 :         if (delta & TS_DELTA_TEST)
     364                 :            :                 return 1;
     365                 :          0 :         return 0;
     366                 :            : }
     367                 :            : 
     368                 :            : #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
     369                 :            : 
     370                 :            : /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
     371                 :            : #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
     372                 :            : 
     373                 :          0 : int ring_buffer_print_page_header(struct trace_seq *s)
     374                 :            : {
     375                 :            :         struct buffer_data_page field;
     376                 :            : 
     377                 :          0 :         trace_seq_printf(s, "\tfield: u64 timestamp;\t"
     378                 :            :                          "offset:0;\tsize:%u;\tsigned:%u;\n",
     379                 :            :                          (unsigned int)sizeof(field.time_stamp),
     380                 :            :                          (unsigned int)is_signed_type(u64));
     381                 :            : 
     382                 :          0 :         trace_seq_printf(s, "\tfield: local_t commit;\t"
     383                 :            :                          "offset:%u;\tsize:%u;\tsigned:%u;\n",
     384                 :            :                          (unsigned int)offsetof(typeof(field), commit),
     385                 :            :                          (unsigned int)sizeof(field.commit),
     386                 :            :                          (unsigned int)is_signed_type(long));
     387                 :            : 
     388                 :          0 :         trace_seq_printf(s, "\tfield: int overwrite;\t"
     389                 :            :                          "offset:%u;\tsize:%u;\tsigned:%u;\n",
     390                 :            :                          (unsigned int)offsetof(typeof(field), commit),
     391                 :            :                          1,
     392                 :            :                          (unsigned int)is_signed_type(long));
     393                 :            : 
     394                 :          0 :         trace_seq_printf(s, "\tfield: char data;\t"
     395                 :            :                          "offset:%u;\tsize:%u;\tsigned:%u;\n",
     396                 :            :                          (unsigned int)offsetof(typeof(field), data),
     397                 :            :                          (unsigned int)BUF_PAGE_SIZE,
     398                 :            :                          (unsigned int)is_signed_type(char));
     399                 :            : 
     400                 :          0 :         return !trace_seq_has_overflowed(s);
     401                 :            : }
     402                 :            : 
     403                 :            : struct rb_irq_work {
     404                 :            :         struct irq_work                 work;
     405                 :            :         wait_queue_head_t               waiters;
     406                 :            :         wait_queue_head_t               full_waiters;
     407                 :            :         bool                            waiters_pending;
     408                 :            :         bool                            full_waiters_pending;
     409                 :            :         bool                            wakeup_full;
     410                 :            : };
     411                 :            : 
     412                 :            : /*
     413                 :            :  * Structure to hold event state and handle nested events.
     414                 :            :  */
     415                 :            : struct rb_event_info {
     416                 :            :         u64                     ts;
     417                 :            :         u64                     delta;
     418                 :            :         unsigned long           length;
     419                 :            :         struct buffer_page      *tail_page;
     420                 :            :         int                     add_timestamp;
     421                 :            : };
     422                 :            : 
     423                 :            : /*
     424                 :            :  * Used for which event context the event is in.
     425                 :            :  *  NMI     = 0
     426                 :            :  *  IRQ     = 1
     427                 :            :  *  SOFTIRQ = 2
     428                 :            :  *  NORMAL  = 3
     429                 :            :  *
     430                 :            :  * See trace_recursive_lock() comment below for more details.
     431                 :            :  */
     432                 :            : enum {
     433                 :            :         RB_CTX_NMI,
     434                 :            :         RB_CTX_IRQ,
     435                 :            :         RB_CTX_SOFTIRQ,
     436                 :            :         RB_CTX_NORMAL,
     437                 :            :         RB_CTX_MAX
     438                 :            : };
     439                 :            : 
     440                 :            : /*
     441                 :            :  * head_page == tail_page && head == tail then buffer is empty.
     442                 :            :  */
     443                 :            : struct ring_buffer_per_cpu {
     444                 :            :         int                             cpu;
     445                 :            :         atomic_t                        record_disabled;
     446                 :            :         struct ring_buffer              *buffer;
     447                 :            :         raw_spinlock_t                  reader_lock;    /* serialize readers */
     448                 :            :         arch_spinlock_t                 lock;
     449                 :            :         struct lock_class_key           lock_key;
     450                 :            :         struct buffer_data_page         *free_page;
     451                 :            :         unsigned long                   nr_pages;
     452                 :            :         unsigned int                    current_context;
     453                 :            :         struct list_head                *pages;
     454                 :            :         struct buffer_page              *head_page;     /* read from head */
     455                 :            :         struct buffer_page              *tail_page;     /* write to tail */
     456                 :            :         struct buffer_page              *commit_page;   /* committed pages */
     457                 :            :         struct buffer_page              *reader_page;
     458                 :            :         unsigned long                   lost_events;
     459                 :            :         unsigned long                   last_overrun;
     460                 :            :         unsigned long                   nest;
     461                 :            :         local_t                         entries_bytes;
     462                 :            :         local_t                         entries;
     463                 :            :         local_t                         overrun;
     464                 :            :         local_t                         commit_overrun;
     465                 :            :         local_t                         dropped_events;
     466                 :            :         local_t                         committing;
     467                 :            :         local_t                         commits;
     468                 :            :         local_t                         pages_touched;
     469                 :            :         local_t                         pages_read;
     470                 :            :         long                            last_pages_touch;
     471                 :            :         size_t                          shortest_full;
     472                 :            :         unsigned long                   read;
     473                 :            :         unsigned long                   read_bytes;
     474                 :            :         u64                             write_stamp;
     475                 :            :         u64                             read_stamp;
     476                 :            :         /* ring buffer pages to update, > 0 to add, < 0 to remove */
     477                 :            :         long                            nr_pages_to_update;
     478                 :            :         struct list_head                new_pages; /* new pages to add */
     479                 :            :         struct work_struct              update_pages_work;
     480                 :            :         struct completion               update_done;
     481                 :            : 
     482                 :            :         struct rb_irq_work              irq_work;
     483                 :            : };
     484                 :            : 
     485                 :            : struct ring_buffer {
     486                 :            :         unsigned                        flags;
     487                 :            :         int                             cpus;
     488                 :            :         atomic_t                        record_disabled;
     489                 :            :         atomic_t                        resize_disabled;
     490                 :            :         cpumask_var_t                   cpumask;
     491                 :            : 
     492                 :            :         struct lock_class_key           *reader_lock_key;
     493                 :            : 
     494                 :            :         struct mutex                    mutex;
     495                 :            : 
     496                 :            :         struct ring_buffer_per_cpu      **buffers;
     497                 :            : 
     498                 :            :         struct hlist_node               node;
     499                 :            :         u64                             (*clock)(void);
     500                 :            : 
     501                 :            :         struct rb_irq_work              irq_work;
     502                 :            :         bool                            time_stamp_abs;
     503                 :            : };
     504                 :            : 
     505                 :            : struct ring_buffer_iter {
     506                 :            :         struct ring_buffer_per_cpu      *cpu_buffer;
     507                 :            :         unsigned long                   head;
     508                 :            :         struct buffer_page              *head_page;
     509                 :            :         struct buffer_page              *cache_reader_page;
     510                 :            :         unsigned long                   cache_read;
     511                 :            :         u64                             read_stamp;
     512                 :            : };
     513                 :            : 
     514                 :            : /**
     515                 :            :  * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
     516                 :            :  * @buffer: The ring_buffer to get the number of pages from
     517                 :            :  * @cpu: The cpu of the ring_buffer to get the number of pages from
     518                 :            :  *
     519                 :            :  * Returns the number of pages used by a per_cpu buffer of the ring buffer.
     520                 :            :  */
     521                 :          0 : size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu)
     522                 :            : {
     523                 :          0 :         return buffer->buffers[cpu]->nr_pages;
     524                 :            : }
     525                 :            : 
     526                 :            : /**
     527                 :            :  * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
     528                 :            :  * @buffer: The ring_buffer to get the number of pages from
     529                 :            :  * @cpu: The cpu of the ring_buffer to get the number of pages from
     530                 :            :  *
     531                 :            :  * Returns the number of pages that have content in the ring buffer.
     532                 :            :  */
     533                 :          0 : size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu)
     534                 :            : {
     535                 :            :         size_t read;
     536                 :            :         size_t cnt;
     537                 :            : 
     538                 :          0 :         read = local_read(&buffer->buffers[cpu]->pages_read);
     539                 :          0 :         cnt = local_read(&buffer->buffers[cpu]->pages_touched);
     540                 :            :         /* The reader can read an empty page, but not more than that */
     541                 :          0 :         if (cnt < read) {
     542                 :          0 :                 WARN_ON_ONCE(read > cnt + 1);
     543                 :            :                 return 0;
     544                 :            :         }
     545                 :            : 
     546                 :          0 :         return cnt - read;
     547                 :            : }
     548                 :            : 
     549                 :            : /*
     550                 :            :  * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
     551                 :            :  *
     552                 :            :  * Schedules a delayed work to wake up any task that is blocked on the
     553                 :            :  * ring buffer waiters queue.
     554                 :            :  */
     555                 :          0 : static void rb_wake_up_waiters(struct irq_work *work)
     556                 :            : {
     557                 :            :         struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
     558                 :            : 
     559                 :          0 :         wake_up_all(&rbwork->waiters);
     560                 :          0 :         if (rbwork->wakeup_full) {
     561                 :          0 :                 rbwork->wakeup_full = false;
     562                 :          0 :                 wake_up_all(&rbwork->full_waiters);
     563                 :            :         }
     564                 :          0 : }
     565                 :            : 
     566                 :            : /**
     567                 :            :  * ring_buffer_wait - wait for input to the ring buffer
     568                 :            :  * @buffer: buffer to wait on
     569                 :            :  * @cpu: the cpu buffer to wait on
     570                 :            :  * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
     571                 :            :  *
     572                 :            :  * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
     573                 :            :  * as data is added to any of the @buffer's cpu buffers. Otherwise
     574                 :            :  * it will wait for data to be added to a specific cpu buffer.
     575                 :            :  */
     576                 :          0 : int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full)
     577                 :            : {
     578                 :            :         struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
     579                 :          0 :         DEFINE_WAIT(wait);
     580                 :            :         struct rb_irq_work *work;
     581                 :            :         int ret = 0;
     582                 :            : 
     583                 :            :         /*
     584                 :            :          * Depending on what the caller is waiting for, either any
     585                 :            :          * data in any cpu buffer, or a specific buffer, put the
     586                 :            :          * caller on the appropriate wait queue.
     587                 :            :          */
     588                 :          0 :         if (cpu == RING_BUFFER_ALL_CPUS) {
     589                 :          0 :                 work = &buffer->irq_work;
     590                 :            :                 /* Full only makes sense on per cpu reads */
     591                 :            :                 full = 0;
     592                 :            :         } else {
     593                 :          0 :                 if (!cpumask_test_cpu(cpu, buffer->cpumask))
     594                 :            :                         return -ENODEV;
     595                 :          0 :                 cpu_buffer = buffer->buffers[cpu];
     596                 :          0 :                 work = &cpu_buffer->irq_work;
     597                 :            :         }
     598                 :            : 
     599                 :            : 
     600                 :            :         while (true) {
     601                 :          0 :                 if (full)
     602                 :          0 :                         prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
     603                 :            :                 else
     604                 :          0 :                         prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
     605                 :            : 
     606                 :            :                 /*
     607                 :            :                  * The events can happen in critical sections where
     608                 :            :                  * checking a work queue can cause deadlocks.
     609                 :            :                  * After adding a task to the queue, this flag is set
     610                 :            :                  * only to notify events to try to wake up the queue
     611                 :            :                  * using irq_work.
     612                 :            :                  *
     613                 :            :                  * We don't clear it even if the buffer is no longer
     614                 :            :                  * empty. The flag only causes the next event to run
     615                 :            :                  * irq_work to do the work queue wake up. The worse
     616                 :            :                  * that can happen if we race with !trace_empty() is that
     617                 :            :                  * an event will cause an irq_work to try to wake up
     618                 :            :                  * an empty queue.
     619                 :            :                  *
     620                 :            :                  * There's no reason to protect this flag either, as
     621                 :            :                  * the work queue and irq_work logic will do the necessary
     622                 :            :                  * synchronization for the wake ups. The only thing
     623                 :            :                  * that is necessary is that the wake up happens after
     624                 :            :                  * a task has been queued. It's OK for spurious wake ups.
     625                 :            :                  */
     626                 :          0 :                 if (full)
     627                 :          0 :                         work->full_waiters_pending = true;
     628                 :            :                 else
     629                 :          0 :                         work->waiters_pending = true;
     630                 :            : 
     631                 :          0 :                 if (signal_pending(current)) {
     632                 :            :                         ret = -EINTR;
     633                 :            :                         break;
     634                 :            :                 }
     635                 :            : 
     636                 :          0 :                 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
     637                 :            :                         break;
     638                 :            : 
     639                 :          0 :                 if (cpu != RING_BUFFER_ALL_CPUS &&
     640                 :          0 :                     !ring_buffer_empty_cpu(buffer, cpu)) {
     641                 :            :                         unsigned long flags;
     642                 :            :                         bool pagebusy;
     643                 :            :                         size_t nr_pages;
     644                 :            :                         size_t dirty;
     645                 :            : 
     646                 :          0 :                         if (!full)
     647                 :            :                                 break;
     648                 :            : 
     649                 :          0 :                         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
     650                 :          0 :                         pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
     651                 :          0 :                         nr_pages = cpu_buffer->nr_pages;
     652                 :          0 :                         dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
     653                 :          0 :                         if (!cpu_buffer->shortest_full ||
     654                 :          0 :                             cpu_buffer->shortest_full < full)
     655                 :          0 :                                 cpu_buffer->shortest_full = full;
     656                 :          0 :                         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
     657                 :          0 :                         if (!pagebusy &&
     658                 :          0 :                             (!nr_pages || (dirty * 100) > full * nr_pages))
     659                 :            :                                 break;
     660                 :            :                 }
     661                 :            : 
     662                 :          0 :                 schedule();
     663                 :          0 :         }
     664                 :            : 
     665                 :          0 :         if (full)
     666                 :          0 :                 finish_wait(&work->full_waiters, &wait);
     667                 :            :         else
     668                 :          0 :                 finish_wait(&work->waiters, &wait);
     669                 :            : 
     670                 :          0 :         return ret;
     671                 :            : }
     672                 :            : 
     673                 :            : /**
     674                 :            :  * ring_buffer_poll_wait - poll on buffer input
     675                 :            :  * @buffer: buffer to wait on
     676                 :            :  * @cpu: the cpu buffer to wait on
     677                 :            :  * @filp: the file descriptor
     678                 :            :  * @poll_table: The poll descriptor
     679                 :            :  *
     680                 :            :  * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
     681                 :            :  * as data is added to any of the @buffer's cpu buffers. Otherwise
     682                 :            :  * it will wait for data to be added to a specific cpu buffer.
     683                 :            :  *
     684                 :            :  * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
     685                 :            :  * zero otherwise.
     686                 :            :  */
     687                 :          0 : __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
     688                 :            :                           struct file *filp, poll_table *poll_table)
     689                 :            : {
     690                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
     691                 :            :         struct rb_irq_work *work;
     692                 :            : 
     693                 :          0 :         if (cpu == RING_BUFFER_ALL_CPUS)
     694                 :          0 :                 work = &buffer->irq_work;
     695                 :            :         else {
     696                 :          0 :                 if (!cpumask_test_cpu(cpu, buffer->cpumask))
     697                 :            :                         return -EINVAL;
     698                 :            : 
     699                 :          0 :                 cpu_buffer = buffer->buffers[cpu];
     700                 :          0 :                 work = &cpu_buffer->irq_work;
     701                 :            :         }
     702                 :            : 
     703                 :          0 :         poll_wait(filp, &work->waiters, poll_table);
     704                 :          0 :         work->waiters_pending = true;
     705                 :            :         /*
     706                 :            :          * There's a tight race between setting the waiters_pending and
     707                 :            :          * checking if the ring buffer is empty.  Once the waiters_pending bit
     708                 :            :          * is set, the next event will wake the task up, but we can get stuck
     709                 :            :          * if there's only a single event in.
     710                 :            :          *
     711                 :            :          * FIXME: Ideally, we need a memory barrier on the writer side as well,
     712                 :            :          * but adding a memory barrier to all events will cause too much of a
     713                 :            :          * performance hit in the fast path.  We only need a memory barrier when
     714                 :            :          * the buffer goes from empty to having content.  But as this race is
     715                 :            :          * extremely small, and it's not a problem if another event comes in, we
     716                 :            :          * will fix it later.
     717                 :            :          */
     718                 :          0 :         smp_mb();
     719                 :            : 
     720                 :          0 :         if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
     721                 :          0 :             (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
     722                 :            :                 return EPOLLIN | EPOLLRDNORM;
     723                 :            :         return 0;
     724                 :            : }
     725                 :            : 
     726                 :            : /* buffer may be either ring_buffer or ring_buffer_per_cpu */
     727                 :            : #define RB_WARN_ON(b, cond)                                             \
     728                 :            :         ({                                                              \
     729                 :            :                 int _____ret = unlikely(cond);                          \
     730                 :            :                 if (_____ret) {                                         \
     731                 :            :                         if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
     732                 :            :                                 struct ring_buffer_per_cpu *__b =       \
     733                 :            :                                         (void *)b;                      \
     734                 :            :                                 atomic_inc(&__b->buffer->record_disabled); \
     735                 :            :                         } else                                          \
     736                 :            :                                 atomic_inc(&b->record_disabled); \
     737                 :            :                         WARN_ON(1);                                     \
     738                 :            :                 }                                                       \
     739                 :            :                 _____ret;                                               \
     740                 :            :         })
     741                 :            : 
     742                 :            : /* Up this if you want to test the TIME_EXTENTS and normalization */
     743                 :            : #define DEBUG_SHIFT 0
     744                 :            : 
     745                 :          0 : static inline u64 rb_time_stamp(struct ring_buffer *buffer)
     746                 :            : {
     747                 :            :         /* shift to debug/test normalization and TIME_EXTENTS */
     748                 :          3 :         return buffer->clock() << DEBUG_SHIFT;
     749                 :            : }
     750                 :            : 
     751                 :          3 : u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
     752                 :            : {
     753                 :            :         u64 time;
     754                 :            : 
     755                 :          3 :         preempt_disable_notrace();
     756                 :            :         time = rb_time_stamp(buffer);
     757                 :          3 :         preempt_enable_notrace();
     758                 :            : 
     759                 :          3 :         return time;
     760                 :            : }
     761                 :            : EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
     762                 :            : 
     763                 :          3 : void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
     764                 :            :                                       int cpu, u64 *ts)
     765                 :            : {
     766                 :            :         /* Just stupid testing the normalize function and deltas */
     767                 :            :         *ts >>= DEBUG_SHIFT;
     768                 :          3 : }
     769                 :            : EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
     770                 :            : 
     771                 :            : /*
     772                 :            :  * Making the ring buffer lockless makes things tricky.
     773                 :            :  * Although writes only happen on the CPU that they are on,
     774                 :            :  * and they only need to worry about interrupts. Reads can
     775                 :            :  * happen on any CPU.
     776                 :            :  *
     777                 :            :  * The reader page is always off the ring buffer, but when the
     778                 :            :  * reader finishes with a page, it needs to swap its page with
     779                 :            :  * a new one from the buffer. The reader needs to take from
     780                 :            :  * the head (writes go to the tail). But if a writer is in overwrite
     781                 :            :  * mode and wraps, it must push the head page forward.
     782                 :            :  *
     783                 :            :  * Here lies the problem.
     784                 :            :  *
     785                 :            :  * The reader must be careful to replace only the head page, and
     786                 :            :  * not another one. As described at the top of the file in the
     787                 :            :  * ASCII art, the reader sets its old page to point to the next
     788                 :            :  * page after head. It then sets the page after head to point to
     789                 :            :  * the old reader page. But if the writer moves the head page
     790                 :            :  * during this operation, the reader could end up with the tail.
     791                 :            :  *
     792                 :            :  * We use cmpxchg to help prevent this race. We also do something
     793                 :            :  * special with the page before head. We set the LSB to 1.
     794                 :            :  *
     795                 :            :  * When the writer must push the page forward, it will clear the
     796                 :            :  * bit that points to the head page, move the head, and then set
     797                 :            :  * the bit that points to the new head page.
     798                 :            :  *
     799                 :            :  * We also don't want an interrupt coming in and moving the head
     800                 :            :  * page on another writer. Thus we use the second LSB to catch
     801                 :            :  * that too. Thus:
     802                 :            :  *
     803                 :            :  * head->list->prev->next        bit 1          bit 0
     804                 :            :  *                              -------        -------
     805                 :            :  * Normal page                     0              0
     806                 :            :  * Points to head page             0              1
     807                 :            :  * New head page                   1              0
     808                 :            :  *
     809                 :            :  * Note we can not trust the prev pointer of the head page, because:
     810                 :            :  *
     811                 :            :  * +----+       +-----+        +-----+
     812                 :            :  * |    |------>|  T  |---X--->|  N  |
     813                 :            :  * |    |<------|     |        |     |
     814                 :            :  * +----+       +-----+        +-----+
     815                 :            :  *   ^                           ^ |
     816                 :            :  *   |          +-----+          | |
     817                 :            :  *   +----------|  R  |----------+ |
     818                 :            :  *              |     |<-----------+
     819                 :            :  *              +-----+
     820                 :            :  *
     821                 :            :  * Key:  ---X-->  HEAD flag set in pointer
     822                 :            :  *         T      Tail page
     823                 :            :  *         R      Reader page
     824                 :            :  *         N      Next page
     825                 :            :  *
     826                 :            :  * (see __rb_reserve_next() to see where this happens)
     827                 :            :  *
     828                 :            :  *  What the above shows is that the reader just swapped out
     829                 :            :  *  the reader page with a page in the buffer, but before it
     830                 :            :  *  could make the new header point back to the new page added
     831                 :            :  *  it was preempted by a writer. The writer moved forward onto
     832                 :            :  *  the new page added by the reader and is about to move forward
     833                 :            :  *  again.
     834                 :            :  *
     835                 :            :  *  You can see, it is legitimate for the previous pointer of
     836                 :            :  *  the head (or any page) not to point back to itself. But only
     837                 :            :  *  temporarily.
     838                 :            :  */
     839                 :            : 
     840                 :            : #define RB_PAGE_NORMAL          0UL
     841                 :            : #define RB_PAGE_HEAD            1UL
     842                 :            : #define RB_PAGE_UPDATE          2UL
     843                 :            : 
     844                 :            : 
     845                 :            : #define RB_FLAG_MASK            3UL
     846                 :            : 
     847                 :            : /* PAGE_MOVED is not part of the mask */
     848                 :            : #define RB_PAGE_MOVED           4UL
     849                 :            : 
     850                 :            : /*
     851                 :            :  * rb_list_head - remove any bit
     852                 :            :  */
     853                 :            : static struct list_head *rb_list_head(struct list_head *list)
     854                 :            : {
     855                 :          3 :         unsigned long val = (unsigned long)list;
     856                 :            : 
     857                 :          3 :         return (struct list_head *)(val & ~RB_FLAG_MASK);
     858                 :            : }
     859                 :            : 
     860                 :            : /*
     861                 :            :  * rb_is_head_page - test if the given page is the head page
     862                 :            :  *
     863                 :            :  * Because the reader may move the head_page pointer, we can
     864                 :            :  * not trust what the head page is (it may be pointing to
     865                 :            :  * the reader page). But if the next page is a header page,
     866                 :            :  * its flags will be non zero.
     867                 :            :  */
     868                 :            : static inline int
     869                 :            : rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
     870                 :            :                 struct buffer_page *page, struct list_head *list)
     871                 :            : {
     872                 :            :         unsigned long val;
     873                 :            : 
     874                 :          0 :         val = (unsigned long)list->next;
     875                 :            : 
     876                 :          0 :         if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
     877                 :            :                 return RB_PAGE_MOVED;
     878                 :            : 
     879                 :          0 :         return val & RB_FLAG_MASK;
     880                 :            : }
     881                 :            : 
     882                 :            : /*
     883                 :            :  * rb_is_reader_page
     884                 :            :  *
     885                 :            :  * The unique thing about the reader page, is that, if the
     886                 :            :  * writer is ever on it, the previous pointer never points
     887                 :            :  * back to the reader page.
     888                 :            :  */
     889                 :          0 : static bool rb_is_reader_page(struct buffer_page *page)
     890                 :            : {
     891                 :          0 :         struct list_head *list = page->list.prev;
     892                 :            : 
     893                 :          0 :         return rb_list_head(list->next) != &page->list;
     894                 :            : }
     895                 :            : 
     896                 :            : /*
     897                 :            :  * rb_set_list_to_head - set a list_head to be pointing to head.
     898                 :            :  */
     899                 :            : static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
     900                 :            :                                 struct list_head *list)
     901                 :            : {
     902                 :            :         unsigned long *ptr;
     903                 :            : 
     904                 :            :         ptr = (unsigned long *)&list->next;
     905                 :          3 :         *ptr |= RB_PAGE_HEAD;
     906                 :          3 :         *ptr &= ~RB_PAGE_UPDATE;
     907                 :            : }
     908                 :            : 
     909                 :            : /*
     910                 :            :  * rb_head_page_activate - sets up head page
     911                 :            :  */
     912                 :            : static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
     913                 :            : {
     914                 :            :         struct buffer_page *head;
     915                 :            : 
     916                 :          3 :         head = cpu_buffer->head_page;
     917                 :          3 :         if (!head)
     918                 :            :                 return;
     919                 :            : 
     920                 :            :         /*
     921                 :            :          * Set the previous list pointer to have the HEAD flag.
     922                 :            :          */
     923                 :          3 :         rb_set_list_to_head(cpu_buffer, head->list.prev);
     924                 :            : }
     925                 :            : 
     926                 :            : static void rb_list_head_clear(struct list_head *list)
     927                 :            : {
     928                 :            :         unsigned long *ptr = (unsigned long *)&list->next;
     929                 :            : 
     930                 :          3 :         *ptr &= ~RB_FLAG_MASK;
     931                 :            : }
     932                 :            : 
     933                 :            : /*
     934                 :            :  * rb_head_page_deactivate - clears head page ptr (for free list)
     935                 :            :  */
     936                 :            : static void
     937                 :            : rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
     938                 :            : {
     939                 :            :         struct list_head *hd;
     940                 :            : 
     941                 :            :         /* Go through the whole list and clear any pointers found. */
     942                 :          3 :         rb_list_head_clear(cpu_buffer->pages);
     943                 :            : 
     944                 :          3 :         list_for_each(hd, cpu_buffer->pages)
     945                 :            :                 rb_list_head_clear(hd);
     946                 :            : }
     947                 :            : 
     948                 :          0 : static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
     949                 :            :                             struct buffer_page *head,
     950                 :            :                             struct buffer_page *prev,
     951                 :            :                             int old_flag, int new_flag)
     952                 :            : {
     953                 :            :         struct list_head *list;
     954                 :          0 :         unsigned long val = (unsigned long)&head->list;
     955                 :            :         unsigned long ret;
     956                 :            : 
     957                 :            :         list = &prev->list;
     958                 :            : 
     959                 :          0 :         val &= ~RB_FLAG_MASK;
     960                 :            : 
     961                 :          0 :         ret = cmpxchg((unsigned long *)&list->next,
     962                 :            :                       val | old_flag, val | new_flag);
     963                 :            : 
     964                 :            :         /* check if the reader took the page */
     965                 :          0 :         if ((ret & ~RB_FLAG_MASK) != val)
     966                 :            :                 return RB_PAGE_MOVED;
     967                 :            : 
     968                 :          0 :         return ret & RB_FLAG_MASK;
     969                 :            : }
     970                 :            : 
     971                 :            : static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
     972                 :            :                                    struct buffer_page *head,
     973                 :            :                                    struct buffer_page *prev,
     974                 :            :                                    int old_flag)
     975                 :            : {
     976                 :          0 :         return rb_head_page_set(cpu_buffer, head, prev,
     977                 :            :                                 old_flag, RB_PAGE_UPDATE);
     978                 :            : }
     979                 :            : 
     980                 :            : static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
     981                 :            :                                  struct buffer_page *head,
     982                 :            :                                  struct buffer_page *prev,
     983                 :            :                                  int old_flag)
     984                 :            : {
     985                 :          0 :         return rb_head_page_set(cpu_buffer, head, prev,
     986                 :            :                                 old_flag, RB_PAGE_HEAD);
     987                 :            : }
     988                 :            : 
     989                 :            : static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
     990                 :            :                                    struct buffer_page *head,
     991                 :            :                                    struct buffer_page *prev,
     992                 :            :                                    int old_flag)
     993                 :            : {
     994                 :          0 :         return rb_head_page_set(cpu_buffer, head, prev,
     995                 :            :                                 old_flag, RB_PAGE_NORMAL);
     996                 :            : }
     997                 :            : 
     998                 :          0 : static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
     999                 :            :                                struct buffer_page **bpage)
    1000                 :            : {
    1001                 :          0 :         struct list_head *p = rb_list_head((*bpage)->list.next);
    1002                 :            : 
    1003                 :          0 :         *bpage = list_entry(p, struct buffer_page, list);
    1004                 :          0 : }
    1005                 :            : 
    1006                 :            : static struct buffer_page *
    1007                 :          0 : rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
    1008                 :            : {
    1009                 :            :         struct buffer_page *head;
    1010                 :            :         struct buffer_page *page;
    1011                 :            :         struct list_head *list;
    1012                 :            :         int i;
    1013                 :            : 
    1014                 :          0 :         if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
    1015                 :            :                 return NULL;
    1016                 :            : 
    1017                 :            :         /* sanity check */
    1018                 :          0 :         list = cpu_buffer->pages;
    1019                 :          0 :         if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
    1020                 :            :                 return NULL;
    1021                 :            : 
    1022                 :          0 :         page = head = cpu_buffer->head_page;
    1023                 :            :         /*
    1024                 :            :          * It is possible that the writer moves the header behind
    1025                 :            :          * where we started, and we miss in one loop.
    1026                 :            :          * A second loop should grab the header, but we'll do
    1027                 :            :          * three loops just because I'm paranoid.
    1028                 :            :          */
    1029                 :          0 :         for (i = 0; i < 3; i++) {
    1030                 :            :                 do {
    1031                 :          0 :                         if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
    1032                 :          0 :                                 cpu_buffer->head_page = page;
    1033                 :          0 :                                 return page;
    1034                 :            :                         }
    1035                 :            :                         rb_inc_page(cpu_buffer, &page);
    1036                 :          0 :                 } while (page != head);
    1037                 :            :         }
    1038                 :            : 
    1039                 :          0 :         RB_WARN_ON(cpu_buffer, 1);
    1040                 :            : 
    1041                 :          0 :         return NULL;
    1042                 :            : }
    1043                 :            : 
    1044                 :          0 : static int rb_head_page_replace(struct buffer_page *old,
    1045                 :            :                                 struct buffer_page *new)
    1046                 :            : {
    1047                 :          0 :         unsigned long *ptr = (unsigned long *)&old->list.prev->next;
    1048                 :            :         unsigned long val;
    1049                 :            :         unsigned long ret;
    1050                 :            : 
    1051                 :          0 :         val = *ptr & ~RB_FLAG_MASK;
    1052                 :          0 :         val |= RB_PAGE_HEAD;
    1053                 :            : 
    1054                 :          0 :         ret = cmpxchg(ptr, val, (unsigned long)&new->list);
    1055                 :            : 
    1056                 :          0 :         return ret == val;
    1057                 :            : }
    1058                 :            : 
    1059                 :            : /*
    1060                 :            :  * rb_tail_page_update - move the tail page forward
    1061                 :            :  */
    1062                 :          0 : static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
    1063                 :            :                                struct buffer_page *tail_page,
    1064                 :            :                                struct buffer_page *next_page)
    1065                 :            : {
    1066                 :            :         unsigned long old_entries;
    1067                 :            :         unsigned long old_write;
    1068                 :            : 
    1069                 :            :         /*
    1070                 :            :          * The tail page now needs to be moved forward.
    1071                 :            :          *
    1072                 :            :          * We need to reset the tail page, but without messing
    1073                 :            :          * with possible erasing of data brought in by interrupts
    1074                 :            :          * that have moved the tail page and are currently on it.
    1075                 :            :          *
    1076                 :            :          * We add a counter to the write field to denote this.
    1077                 :            :          */
    1078                 :          0 :         old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
    1079                 :          0 :         old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
    1080                 :            : 
    1081                 :          0 :         local_inc(&cpu_buffer->pages_touched);
    1082                 :            :         /*
    1083                 :            :          * Just make sure we have seen our old_write and synchronize
    1084                 :            :          * with any interrupts that come in.
    1085                 :            :          */
    1086                 :          0 :         barrier();
    1087                 :            : 
    1088                 :            :         /*
    1089                 :            :          * If the tail page is still the same as what we think
    1090                 :            :          * it is, then it is up to us to update the tail
    1091                 :            :          * pointer.
    1092                 :            :          */
    1093                 :          0 :         if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
    1094                 :            :                 /* Zero the write counter */
    1095                 :          0 :                 unsigned long val = old_write & ~RB_WRITE_MASK;
    1096                 :          0 :                 unsigned long eval = old_entries & ~RB_WRITE_MASK;
    1097                 :            : 
    1098                 :            :                 /*
    1099                 :            :                  * This will only succeed if an interrupt did
    1100                 :            :                  * not come in and change it. In which case, we
    1101                 :            :                  * do not want to modify it.
    1102                 :            :                  *
    1103                 :            :                  * We add (void) to let the compiler know that we do not care
    1104                 :            :                  * about the return value of these functions. We use the
    1105                 :            :                  * cmpxchg to only update if an interrupt did not already
    1106                 :            :                  * do it for us. If the cmpxchg fails, we don't care.
    1107                 :            :                  */
    1108                 :          0 :                 (void)local_cmpxchg(&next_page->write, old_write, val);
    1109                 :          0 :                 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
    1110                 :            : 
    1111                 :            :                 /*
    1112                 :            :                  * No need to worry about races with clearing out the commit.
    1113                 :            :                  * it only can increment when a commit takes place. But that
    1114                 :            :                  * only happens in the outer most nested commit.
    1115                 :            :                  */
    1116                 :          0 :                 local_set(&next_page->page->commit, 0);
    1117                 :            : 
    1118                 :            :                 /* Again, either we update tail_page or an interrupt does */
    1119                 :          0 :                 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
    1120                 :            :         }
    1121                 :          0 : }
    1122                 :            : 
    1123                 :          3 : static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
    1124                 :            :                           struct buffer_page *bpage)
    1125                 :            : {
    1126                 :          3 :         unsigned long val = (unsigned long)bpage;
    1127                 :            : 
    1128                 :          3 :         if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
    1129                 :            :                 return 1;
    1130                 :            : 
    1131                 :          3 :         return 0;
    1132                 :            : }
    1133                 :            : 
    1134                 :            : /**
    1135                 :            :  * rb_check_list - make sure a pointer to a list has the last bits zero
    1136                 :            :  */
    1137                 :          3 : static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
    1138                 :            :                          struct list_head *list)
    1139                 :            : {
    1140                 :          3 :         if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
    1141                 :            :                 return 1;
    1142                 :          3 :         if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
    1143                 :            :                 return 1;
    1144                 :          3 :         return 0;
    1145                 :            : }
    1146                 :            : 
    1147                 :            : /**
    1148                 :            :  * rb_check_pages - integrity check of buffer pages
    1149                 :            :  * @cpu_buffer: CPU buffer with pages to test
    1150                 :            :  *
    1151                 :            :  * As a safety measure we check to make sure the data pages have not
    1152                 :            :  * been corrupted.
    1153                 :            :  */
    1154                 :          3 : static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
    1155                 :            : {
    1156                 :          3 :         struct list_head *head = cpu_buffer->pages;
    1157                 :            :         struct buffer_page *bpage, *tmp;
    1158                 :            : 
    1159                 :            :         /* Reset the head page if it exists */
    1160                 :          3 :         if (cpu_buffer->head_page)
    1161                 :          0 :                 rb_set_head_page(cpu_buffer);
    1162                 :            : 
    1163                 :            :         rb_head_page_deactivate(cpu_buffer);
    1164                 :            : 
    1165                 :          3 :         if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
    1166                 :            :                 return -1;
    1167                 :          3 :         if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
    1168                 :            :                 return -1;
    1169                 :            : 
    1170                 :          3 :         if (rb_check_list(cpu_buffer, head))
    1171                 :            :                 return -1;
    1172                 :            : 
    1173                 :          3 :         list_for_each_entry_safe(bpage, tmp, head, list) {
    1174                 :          3 :                 if (RB_WARN_ON(cpu_buffer,
    1175                 :            :                                bpage->list.next->prev != &bpage->list))
    1176                 :            :                         return -1;
    1177                 :          3 :                 if (RB_WARN_ON(cpu_buffer,
    1178                 :            :                                bpage->list.prev->next != &bpage->list))
    1179                 :            :                         return -1;
    1180                 :          3 :                 if (rb_check_list(cpu_buffer, &bpage->list))
    1181                 :            :                         return -1;
    1182                 :            :         }
    1183                 :            : 
    1184                 :            :         rb_head_page_activate(cpu_buffer);
    1185                 :            : 
    1186                 :            :         return 0;
    1187                 :            : }
    1188                 :            : 
    1189                 :          3 : static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
    1190                 :            : {
    1191                 :            :         struct buffer_page *bpage, *tmp;
    1192                 :          3 :         bool user_thread = current->mm != NULL;
    1193                 :            :         gfp_t mflags;
    1194                 :            :         long i;
    1195                 :            : 
    1196                 :            :         /*
    1197                 :            :          * Check if the available memory is there first.
    1198                 :            :          * Note, si_mem_available() only gives us a rough estimate of available
    1199                 :            :          * memory. It may not be accurate. But we don't care, we just want
    1200                 :            :          * to prevent doing any allocation when it is obvious that it is
    1201                 :            :          * not going to succeed.
    1202                 :            :          */
    1203                 :          3 :         i = si_mem_available();
    1204                 :          3 :         if (i < nr_pages)
    1205                 :            :                 return -ENOMEM;
    1206                 :            : 
    1207                 :            :         /*
    1208                 :            :          * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
    1209                 :            :          * gracefully without invoking oom-killer and the system is not
    1210                 :            :          * destabilized.
    1211                 :            :          */
    1212                 :            :         mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
    1213                 :            : 
    1214                 :            :         /*
    1215                 :            :          * If a user thread allocates too much, and si_mem_available()
    1216                 :            :          * reports there's enough memory, even though there is not.
    1217                 :            :          * Make sure the OOM killer kills this thread. This can happen
    1218                 :            :          * even with RETRY_MAYFAIL because another task may be doing
    1219                 :            :          * an allocation after this task has taken all memory.
    1220                 :            :          * This is the task the OOM killer needs to take out during this
    1221                 :            :          * loop, even if it was triggered by an allocation somewhere else.
    1222                 :            :          */
    1223                 :          3 :         if (user_thread)
    1224                 :            :                 set_current_oom_origin();
    1225                 :          3 :         for (i = 0; i < nr_pages; i++) {
    1226                 :            :                 struct page *page;
    1227                 :            : 
    1228                 :          3 :                 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
    1229                 :            :                                     mflags, cpu_to_node(cpu));
    1230                 :          3 :                 if (!bpage)
    1231                 :            :                         goto free_pages;
    1232                 :            : 
    1233                 :          3 :                 list_add(&bpage->list, pages);
    1234                 :            : 
    1235                 :            :                 page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
    1236                 :          3 :                 if (!page)
    1237                 :            :                         goto free_pages;
    1238                 :          3 :                 bpage->page = page_address(page);
    1239                 :            :                 rb_init_page(bpage->page);
    1240                 :            : 
    1241                 :          3 :                 if (user_thread && fatal_signal_pending(current))
    1242                 :            :                         goto free_pages;
    1243                 :            :         }
    1244                 :          3 :         if (user_thread)
    1245                 :            :                 clear_current_oom_origin();
    1246                 :            : 
    1247                 :            :         return 0;
    1248                 :            : 
    1249                 :            : free_pages:
    1250                 :          0 :         list_for_each_entry_safe(bpage, tmp, pages, list) {
    1251                 :            :                 list_del_init(&bpage->list);
    1252                 :          0 :                 free_buffer_page(bpage);
    1253                 :            :         }
    1254                 :          0 :         if (user_thread)
    1255                 :            :                 clear_current_oom_origin();
    1256                 :            : 
    1257                 :            :         return -ENOMEM;
    1258                 :            : }
    1259                 :            : 
    1260                 :          3 : static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
    1261                 :            :                              unsigned long nr_pages)
    1262                 :            : {
    1263                 :          3 :         LIST_HEAD(pages);
    1264                 :            : 
    1265                 :          3 :         WARN_ON(!nr_pages);
    1266                 :            : 
    1267                 :          3 :         if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
    1268                 :            :                 return -ENOMEM;
    1269                 :            : 
    1270                 :            :         /*
    1271                 :            :          * The ring buffer page list is a circular list that does not
    1272                 :            :          * start and end with a list head. All page list items point to
    1273                 :            :          * other pages.
    1274                 :            :          */
    1275                 :          3 :         cpu_buffer->pages = pages.next;
    1276                 :            :         list_del(&pages);
    1277                 :            : 
    1278                 :          3 :         cpu_buffer->nr_pages = nr_pages;
    1279                 :            : 
    1280                 :          3 :         rb_check_pages(cpu_buffer);
    1281                 :            : 
    1282                 :          3 :         return 0;
    1283                 :            : }
    1284                 :            : 
    1285                 :            : static struct ring_buffer_per_cpu *
    1286                 :          3 : rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
    1287                 :            : {
    1288                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    1289                 :            :         struct buffer_page *bpage;
    1290                 :            :         struct page *page;
    1291                 :            :         int ret;
    1292                 :            : 
    1293                 :          3 :         cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
    1294                 :            :                                   GFP_KERNEL, cpu_to_node(cpu));
    1295                 :          3 :         if (!cpu_buffer)
    1296                 :            :                 return NULL;
    1297                 :            : 
    1298                 :          3 :         cpu_buffer->cpu = cpu;
    1299                 :          3 :         cpu_buffer->buffer = buffer;
    1300                 :          3 :         raw_spin_lock_init(&cpu_buffer->reader_lock);
    1301                 :            :         lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
    1302                 :          3 :         cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
    1303                 :          3 :         INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
    1304                 :            :         init_completion(&cpu_buffer->update_done);
    1305                 :            :         init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
    1306                 :          3 :         init_waitqueue_head(&cpu_buffer->irq_work.waiters);
    1307                 :          3 :         init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
    1308                 :            : 
    1309                 :          3 :         bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
    1310                 :            :                             GFP_KERNEL, cpu_to_node(cpu));
    1311                 :          3 :         if (!bpage)
    1312                 :            :                 goto fail_free_buffer;
    1313                 :            : 
    1314                 :          3 :         rb_check_bpage(cpu_buffer, bpage);
    1315                 :            : 
    1316                 :          3 :         cpu_buffer->reader_page = bpage;
    1317                 :            :         page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
    1318                 :          3 :         if (!page)
    1319                 :            :                 goto fail_free_reader;
    1320                 :          3 :         bpage->page = page_address(page);
    1321                 :            :         rb_init_page(bpage->page);
    1322                 :            : 
    1323                 :          3 :         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
    1324                 :          3 :         INIT_LIST_HEAD(&cpu_buffer->new_pages);
    1325                 :            : 
    1326                 :          3 :         ret = rb_allocate_pages(cpu_buffer, nr_pages);
    1327                 :          3 :         if (ret < 0)
    1328                 :            :                 goto fail_free_reader;
    1329                 :            : 
    1330                 :            :         cpu_buffer->head_page
    1331                 :          3 :                 = list_entry(cpu_buffer->pages, struct buffer_page, list);
    1332                 :          3 :         cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
    1333                 :            : 
    1334                 :            :         rb_head_page_activate(cpu_buffer);
    1335                 :            : 
    1336                 :          3 :         return cpu_buffer;
    1337                 :            : 
    1338                 :            :  fail_free_reader:
    1339                 :          0 :         free_buffer_page(cpu_buffer->reader_page);
    1340                 :            : 
    1341                 :            :  fail_free_buffer:
    1342                 :          0 :         kfree(cpu_buffer);
    1343                 :          0 :         return NULL;
    1344                 :            : }
    1345                 :            : 
    1346                 :          0 : static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
    1347                 :            : {
    1348                 :          0 :         struct list_head *head = cpu_buffer->pages;
    1349                 :            :         struct buffer_page *bpage, *tmp;
    1350                 :            : 
    1351                 :          0 :         free_buffer_page(cpu_buffer->reader_page);
    1352                 :            : 
    1353                 :            :         rb_head_page_deactivate(cpu_buffer);
    1354                 :            : 
    1355                 :          0 :         if (head) {
    1356                 :          0 :                 list_for_each_entry_safe(bpage, tmp, head, list) {
    1357                 :            :                         list_del_init(&bpage->list);
    1358                 :          0 :                         free_buffer_page(bpage);
    1359                 :            :                 }
    1360                 :            :                 bpage = list_entry(head, struct buffer_page, list);
    1361                 :          0 :                 free_buffer_page(bpage);
    1362                 :            :         }
    1363                 :            : 
    1364                 :          0 :         kfree(cpu_buffer);
    1365                 :          0 : }
    1366                 :            : 
    1367                 :            : /**
    1368                 :            :  * __ring_buffer_alloc - allocate a new ring_buffer
    1369                 :            :  * @size: the size in bytes per cpu that is needed.
    1370                 :            :  * @flags: attributes to set for the ring buffer.
    1371                 :            :  *
    1372                 :            :  * Currently the only flag that is available is the RB_FL_OVERWRITE
    1373                 :            :  * flag. This flag means that the buffer will overwrite old data
    1374                 :            :  * when the buffer wraps. If this flag is not set, the buffer will
    1375                 :            :  * drop data when the tail hits the head.
    1376                 :            :  */
    1377                 :          3 : struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
    1378                 :            :                                         struct lock_class_key *key)
    1379                 :            : {
    1380                 :            :         struct ring_buffer *buffer;
    1381                 :            :         long nr_pages;
    1382                 :            :         int bsize;
    1383                 :            :         int cpu;
    1384                 :            :         int ret;
    1385                 :            : 
    1386                 :            :         /* keep it in its own cache line */
    1387                 :          3 :         buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
    1388                 :            :                          GFP_KERNEL);
    1389                 :          3 :         if (!buffer)
    1390                 :            :                 return NULL;
    1391                 :            : 
    1392                 :            :         if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
    1393                 :            :                 goto fail_free_buffer;
    1394                 :            : 
    1395                 :          3 :         nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
    1396                 :          3 :         buffer->flags = flags;
    1397                 :          3 :         buffer->clock = trace_clock_local;
    1398                 :          3 :         buffer->reader_lock_key = key;
    1399                 :            : 
    1400                 :            :         init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
    1401                 :          3 :         init_waitqueue_head(&buffer->irq_work.waiters);
    1402                 :            : 
    1403                 :            :         /* need at least two pages */
    1404                 :          3 :         if (nr_pages < 2)
    1405                 :            :                 nr_pages = 2;
    1406                 :            : 
    1407                 :          3 :         buffer->cpus = nr_cpu_ids;
    1408                 :            : 
    1409                 :          3 :         bsize = sizeof(void *) * nr_cpu_ids;
    1410                 :          3 :         buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
    1411                 :            :                                   GFP_KERNEL);
    1412                 :          3 :         if (!buffer->buffers)
    1413                 :            :                 goto fail_free_cpumask;
    1414                 :            : 
    1415                 :          3 :         cpu = raw_smp_processor_id();
    1416                 :            :         cpumask_set_cpu(cpu, buffer->cpumask);
    1417                 :          3 :         buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
    1418                 :          3 :         if (!buffer->buffers[cpu])
    1419                 :            :                 goto fail_free_buffers;
    1420                 :            : 
    1421                 :          3 :         ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
    1422                 :          3 :         if (ret < 0)
    1423                 :            :                 goto fail_free_buffers;
    1424                 :            : 
    1425                 :          3 :         mutex_init(&buffer->mutex);
    1426                 :            : 
    1427                 :          3 :         return buffer;
    1428                 :            : 
    1429                 :            :  fail_free_buffers:
    1430                 :          0 :         for_each_buffer_cpu(buffer, cpu) {
    1431                 :          0 :                 if (buffer->buffers[cpu])
    1432                 :          0 :                         rb_free_cpu_buffer(buffer->buffers[cpu]);
    1433                 :            :         }
    1434                 :          0 :         kfree(buffer->buffers);
    1435                 :            : 
    1436                 :            :  fail_free_cpumask:
    1437                 :            :         free_cpumask_var(buffer->cpumask);
    1438                 :            : 
    1439                 :            :  fail_free_buffer:
    1440                 :          0 :         kfree(buffer);
    1441                 :          0 :         return NULL;
    1442                 :            : }
    1443                 :            : EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
    1444                 :            : 
    1445                 :            : /**
    1446                 :            :  * ring_buffer_free - free a ring buffer.
    1447                 :            :  * @buffer: the buffer to free.
    1448                 :            :  */
    1449                 :            : void
    1450                 :          0 : ring_buffer_free(struct ring_buffer *buffer)
    1451                 :            : {
    1452                 :            :         int cpu;
    1453                 :            : 
    1454                 :          0 :         cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
    1455                 :            : 
    1456                 :          0 :         for_each_buffer_cpu(buffer, cpu)
    1457                 :          0 :                 rb_free_cpu_buffer(buffer->buffers[cpu]);
    1458                 :            : 
    1459                 :          0 :         kfree(buffer->buffers);
    1460                 :            :         free_cpumask_var(buffer->cpumask);
    1461                 :            : 
    1462                 :          0 :         kfree(buffer);
    1463                 :          0 : }
    1464                 :            : EXPORT_SYMBOL_GPL(ring_buffer_free);
    1465                 :            : 
    1466                 :          0 : void ring_buffer_set_clock(struct ring_buffer *buffer,
    1467                 :            :                            u64 (*clock)(void))
    1468                 :            : {
    1469                 :          0 :         buffer->clock = clock;
    1470                 :          0 : }
    1471                 :            : 
    1472                 :          0 : void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
    1473                 :            : {
    1474                 :          0 :         buffer->time_stamp_abs = abs;
    1475                 :          0 : }
    1476                 :            : 
    1477                 :          0 : bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
    1478                 :            : {
    1479                 :          0 :         return buffer->time_stamp_abs;
    1480                 :            : }
    1481                 :            : 
    1482                 :            : static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
    1483                 :            : 
    1484                 :            : static inline unsigned long rb_page_entries(struct buffer_page *bpage)
    1485                 :            : {
    1486                 :          0 :         return local_read(&bpage->entries) & RB_WRITE_MASK;
    1487                 :            : }
    1488                 :            : 
    1489                 :          0 : static inline unsigned long rb_page_write(struct buffer_page *bpage)
    1490                 :            : {
    1491                 :          0 :         return local_read(&bpage->write) & RB_WRITE_MASK;
    1492                 :            : }
    1493                 :            : 
    1494                 :            : static int
    1495                 :          0 : rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
    1496                 :            : {
    1497                 :            :         struct list_head *tail_page, *to_remove, *next_page;
    1498                 :            :         struct buffer_page *to_remove_page, *tmp_iter_page;
    1499                 :            :         struct buffer_page *last_page, *first_page;
    1500                 :            :         unsigned long nr_removed;
    1501                 :            :         unsigned long head_bit;
    1502                 :            :         int page_entries;
    1503                 :            : 
    1504                 :            :         head_bit = 0;
    1505                 :            : 
    1506                 :          0 :         raw_spin_lock_irq(&cpu_buffer->reader_lock);
    1507                 :          0 :         atomic_inc(&cpu_buffer->record_disabled);
    1508                 :            :         /*
    1509                 :            :          * We don't race with the readers since we have acquired the reader
    1510                 :            :          * lock. We also don't race with writers after disabling recording.
    1511                 :            :          * This makes it easy to figure out the first and the last page to be
    1512                 :            :          * removed from the list. We unlink all the pages in between including
    1513                 :            :          * the first and last pages. This is done in a busy loop so that we
    1514                 :            :          * lose the least number of traces.
    1515                 :            :          * The pages are freed after we restart recording and unlock readers.
    1516                 :            :          */
    1517                 :          0 :         tail_page = &cpu_buffer->tail_page->list;
    1518                 :            : 
    1519                 :            :         /*
    1520                 :            :          * tail page might be on reader page, we remove the next page
    1521                 :            :          * from the ring buffer
    1522                 :            :          */
    1523                 :          0 :         if (cpu_buffer->tail_page == cpu_buffer->reader_page)
    1524                 :          0 :                 tail_page = rb_list_head(tail_page->next);
    1525                 :            :         to_remove = tail_page;
    1526                 :            : 
    1527                 :            :         /* start of pages to remove */
    1528                 :          0 :         first_page = list_entry(rb_list_head(to_remove->next),
    1529                 :            :                                 struct buffer_page, list);
    1530                 :            : 
    1531                 :          0 :         for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
    1532                 :          0 :                 to_remove = rb_list_head(to_remove)->next;
    1533                 :          0 :                 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
    1534                 :            :         }
    1535                 :            : 
    1536                 :          0 :         next_page = rb_list_head(to_remove)->next;
    1537                 :            : 
    1538                 :            :         /*
    1539                 :            :          * Now we remove all pages between tail_page and next_page.
    1540                 :            :          * Make sure that we have head_bit value preserved for the
    1541                 :            :          * next page
    1542                 :            :          */
    1543                 :          0 :         tail_page->next = (struct list_head *)((unsigned long)next_page |
    1544                 :            :                                                 head_bit);
    1545                 :            :         next_page = rb_list_head(next_page);
    1546                 :          0 :         next_page->prev = tail_page;
    1547                 :            : 
    1548                 :            :         /* make sure pages points to a valid page in the ring buffer */
    1549                 :          0 :         cpu_buffer->pages = next_page;
    1550                 :            : 
    1551                 :            :         /* update head page */
    1552                 :          0 :         if (head_bit)
    1553                 :          0 :                 cpu_buffer->head_page = list_entry(next_page,
    1554                 :            :                                                 struct buffer_page, list);
    1555                 :            : 
    1556                 :            :         /*
    1557                 :            :          * change read pointer to make sure any read iterators reset
    1558                 :            :          * themselves
    1559                 :            :          */
    1560                 :          0 :         cpu_buffer->read = 0;
    1561                 :            : 
    1562                 :            :         /* pages are removed, resume tracing and then free the pages */
    1563                 :            :         atomic_dec(&cpu_buffer->record_disabled);
    1564                 :          0 :         raw_spin_unlock_irq(&cpu_buffer->reader_lock);
    1565                 :            : 
    1566                 :          0 :         RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
    1567                 :            : 
    1568                 :            :         /* last buffer page to remove */
    1569                 :            :         last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
    1570                 :            :                                 list);
    1571                 :            :         tmp_iter_page = first_page;
    1572                 :            : 
    1573                 :            :         do {
    1574                 :          0 :                 cond_resched();
    1575                 :            : 
    1576                 :            :                 to_remove_page = tmp_iter_page;
    1577                 :            :                 rb_inc_page(cpu_buffer, &tmp_iter_page);
    1578                 :            : 
    1579                 :            :                 /* update the counters */
    1580                 :          0 :                 page_entries = rb_page_entries(to_remove_page);
    1581                 :          0 :                 if (page_entries) {
    1582                 :            :                         /*
    1583                 :            :                          * If something was added to this page, it was full
    1584                 :            :                          * since it is not the tail page. So we deduct the
    1585                 :            :                          * bytes consumed in ring buffer from here.
    1586                 :            :                          * Increment overrun to account for the lost events.
    1587                 :            :                          */
    1588                 :          0 :                         local_add(page_entries, &cpu_buffer->overrun);
    1589                 :          0 :                         local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
    1590                 :            :                 }
    1591                 :            : 
    1592                 :            :                 /*
    1593                 :            :                  * We have already removed references to this list item, just
    1594                 :            :                  * free up the buffer_page and its page
    1595                 :            :                  */
    1596                 :          0 :                 free_buffer_page(to_remove_page);
    1597                 :          0 :                 nr_removed--;
    1598                 :            : 
    1599                 :          0 :         } while (to_remove_page != last_page);
    1600                 :            : 
    1601                 :          0 :         RB_WARN_ON(cpu_buffer, nr_removed);
    1602                 :            : 
    1603                 :          0 :         return nr_removed == 0;
    1604                 :            : }
    1605                 :            : 
    1606                 :            : static int
    1607                 :          0 : rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
    1608                 :            : {
    1609                 :          0 :         struct list_head *pages = &cpu_buffer->new_pages;
    1610                 :            :         int retries, success;
    1611                 :            : 
    1612                 :          0 :         raw_spin_lock_irq(&cpu_buffer->reader_lock);
    1613                 :            :         /*
    1614                 :            :          * We are holding the reader lock, so the reader page won't be swapped
    1615                 :            :          * in the ring buffer. Now we are racing with the writer trying to
    1616                 :            :          * move head page and the tail page.
    1617                 :            :          * We are going to adapt the reader page update process where:
    1618                 :            :          * 1. We first splice the start and end of list of new pages between
    1619                 :            :          *    the head page and its previous page.
    1620                 :            :          * 2. We cmpxchg the prev_page->next to point from head page to the
    1621                 :            :          *    start of new pages list.
    1622                 :            :          * 3. Finally, we update the head->prev to the end of new list.
    1623                 :            :          *
    1624                 :            :          * We will try this process 10 times, to make sure that we don't keep
    1625                 :            :          * spinning.
    1626                 :            :          */
    1627                 :            :         retries = 10;
    1628                 :            :         success = 0;
    1629                 :          0 :         while (retries--) {
    1630                 :            :                 struct list_head *head_page, *prev_page, *r;
    1631                 :            :                 struct list_head *last_page, *first_page;
    1632                 :            :                 struct list_head *head_page_with_bit;
    1633                 :            : 
    1634                 :          0 :                 head_page = &rb_set_head_page(cpu_buffer)->list;
    1635                 :          0 :                 if (!head_page)
    1636                 :            :                         break;
    1637                 :          0 :                 prev_page = head_page->prev;
    1638                 :            : 
    1639                 :          0 :                 first_page = pages->next;
    1640                 :          0 :                 last_page  = pages->prev;
    1641                 :            : 
    1642                 :          0 :                 head_page_with_bit = (struct list_head *)
    1643                 :          0 :                                      ((unsigned long)head_page | RB_PAGE_HEAD);
    1644                 :            : 
    1645                 :          0 :                 last_page->next = head_page_with_bit;
    1646                 :          0 :                 first_page->prev = prev_page;
    1647                 :            : 
    1648                 :          0 :                 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
    1649                 :            : 
    1650                 :          0 :                 if (r == head_page_with_bit) {
    1651                 :            :                         /*
    1652                 :            :                          * yay, we replaced the page pointer to our new list,
    1653                 :            :                          * now, we just have to update to head page's prev
    1654                 :            :                          * pointer to point to end of list
    1655                 :            :                          */
    1656                 :          0 :                         head_page->prev = last_page;
    1657                 :            :                         success = 1;
    1658                 :          0 :                         break;
    1659                 :            :                 }
    1660                 :            :         }
    1661                 :            : 
    1662                 :          0 :         if (success)
    1663                 :            :                 INIT_LIST_HEAD(pages);
    1664                 :            :         /*
    1665                 :            :          * If we weren't successful in adding in new pages, warn and stop
    1666                 :            :          * tracing
    1667                 :            :          */
    1668                 :          0 :         RB_WARN_ON(cpu_buffer, !success);
    1669                 :          0 :         raw_spin_unlock_irq(&cpu_buffer->reader_lock);
    1670                 :            : 
    1671                 :            :         /* free pages if they weren't inserted */
    1672                 :          0 :         if (!success) {
    1673                 :            :                 struct buffer_page *bpage, *tmp;
    1674                 :          0 :                 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
    1675                 :            :                                          list) {
    1676                 :            :                         list_del_init(&bpage->list);
    1677                 :          0 :                         free_buffer_page(bpage);
    1678                 :            :                 }
    1679                 :            :         }
    1680                 :          0 :         return success;
    1681                 :            : }
    1682                 :            : 
    1683                 :          0 : static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
    1684                 :            : {
    1685                 :            :         int success;
    1686                 :            : 
    1687                 :          0 :         if (cpu_buffer->nr_pages_to_update > 0)
    1688                 :          0 :                 success = rb_insert_pages(cpu_buffer);
    1689                 :            :         else
    1690                 :          0 :                 success = rb_remove_pages(cpu_buffer,
    1691                 :          0 :                                         -cpu_buffer->nr_pages_to_update);
    1692                 :            : 
    1693                 :          0 :         if (success)
    1694                 :          0 :                 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
    1695                 :          0 : }
    1696                 :            : 
    1697                 :          0 : static void update_pages_handler(struct work_struct *work)
    1698                 :            : {
    1699                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
    1700                 :            :                         struct ring_buffer_per_cpu, update_pages_work);
    1701                 :          0 :         rb_update_pages(cpu_buffer);
    1702                 :          0 :         complete(&cpu_buffer->update_done);
    1703                 :          0 : }
    1704                 :            : 
    1705                 :            : /**
    1706                 :            :  * ring_buffer_resize - resize the ring buffer
    1707                 :            :  * @buffer: the buffer to resize.
    1708                 :            :  * @size: the new size.
    1709                 :            :  * @cpu_id: the cpu buffer to resize
    1710                 :            :  *
    1711                 :            :  * Minimum size is 2 * BUF_PAGE_SIZE.
    1712                 :            :  *
    1713                 :            :  * Returns 0 on success and < 0 on failure.
    1714                 :            :  */
    1715                 :          0 : int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
    1716                 :            :                         int cpu_id)
    1717                 :            : {
    1718                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    1719                 :            :         unsigned long nr_pages;
    1720                 :            :         int cpu, err = 0;
    1721                 :            : 
    1722                 :            :         /*
    1723                 :            :          * Always succeed at resizing a non-existent buffer:
    1724                 :            :          */
    1725                 :          0 :         if (!buffer)
    1726                 :          0 :                 return size;
    1727                 :            : 
    1728                 :            :         /* Make sure the requested buffer exists */
    1729                 :          0 :         if (cpu_id != RING_BUFFER_ALL_CPUS &&
    1730                 :            :             !cpumask_test_cpu(cpu_id, buffer->cpumask))
    1731                 :          0 :                 return size;
    1732                 :            : 
    1733                 :          0 :         nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
    1734                 :            : 
    1735                 :            :         /* we need a minimum of two pages */
    1736                 :          0 :         if (nr_pages < 2)
    1737                 :            :                 nr_pages = 2;
    1738                 :            : 
    1739                 :          0 :         size = nr_pages * BUF_PAGE_SIZE;
    1740                 :            : 
    1741                 :            :         /*
    1742                 :            :          * Don't succeed if resizing is disabled, as a reader might be
    1743                 :            :          * manipulating the ring buffer and is expecting a sane state while
    1744                 :            :          * this is true.
    1745                 :            :          */
    1746                 :          0 :         if (atomic_read(&buffer->resize_disabled))
    1747                 :            :                 return -EBUSY;
    1748                 :            : 
    1749                 :            :         /* prevent another thread from changing buffer sizes */
    1750                 :          0 :         mutex_lock(&buffer->mutex);
    1751                 :            : 
    1752                 :          0 :         if (cpu_id == RING_BUFFER_ALL_CPUS) {
    1753                 :            :                 /* calculate the pages to update */
    1754                 :          0 :                 for_each_buffer_cpu(buffer, cpu) {
    1755                 :          0 :                         cpu_buffer = buffer->buffers[cpu];
    1756                 :            : 
    1757                 :          0 :                         cpu_buffer->nr_pages_to_update = nr_pages -
    1758                 :          0 :                                                         cpu_buffer->nr_pages;
    1759                 :            :                         /*
    1760                 :            :                          * nothing more to do for removing pages or no update
    1761                 :            :                          */
    1762                 :          0 :                         if (cpu_buffer->nr_pages_to_update <= 0)
    1763                 :          0 :                                 continue;
    1764                 :            :                         /*
    1765                 :            :                          * to add pages, make sure all new pages can be
    1766                 :            :                          * allocated without receiving ENOMEM
    1767                 :            :                          */
    1768                 :          0 :                         INIT_LIST_HEAD(&cpu_buffer->new_pages);
    1769                 :          0 :                         if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
    1770                 :            :                                                 &cpu_buffer->new_pages, cpu)) {
    1771                 :            :                                 /* not enough memory for new pages */
    1772                 :            :                                 err = -ENOMEM;
    1773                 :            :                                 goto out_err;
    1774                 :            :                         }
    1775                 :            :                 }
    1776                 :            : 
    1777                 :            :                 get_online_cpus();
    1778                 :            :                 /*
    1779                 :            :                  * Fire off all the required work handlers
    1780                 :            :                  * We can't schedule on offline CPUs, but it's not necessary
    1781                 :            :                  * since we can change their buffer sizes without any race.
    1782                 :            :                  */
    1783                 :          0 :                 for_each_buffer_cpu(buffer, cpu) {
    1784                 :          0 :                         cpu_buffer = buffer->buffers[cpu];
    1785                 :          0 :                         if (!cpu_buffer->nr_pages_to_update)
    1786                 :          0 :                                 continue;
    1787                 :            : 
    1788                 :            :                         /* Can't run something on an offline CPU. */
    1789                 :          0 :                         if (!cpu_online(cpu)) {
    1790                 :          0 :                                 rb_update_pages(cpu_buffer);
    1791                 :          0 :                                 cpu_buffer->nr_pages_to_update = 0;
    1792                 :            :                         } else {
    1793                 :          0 :                                 schedule_work_on(cpu,
    1794                 :            :                                                 &cpu_buffer->update_pages_work);
    1795                 :            :                         }
    1796                 :            :                 }
    1797                 :            : 
    1798                 :            :                 /* wait for all the updates to complete */
    1799                 :          0 :                 for_each_buffer_cpu(buffer, cpu) {
    1800                 :          0 :                         cpu_buffer = buffer->buffers[cpu];
    1801                 :          0 :                         if (!cpu_buffer->nr_pages_to_update)
    1802                 :          0 :                                 continue;
    1803                 :            : 
    1804                 :          0 :                         if (cpu_online(cpu))
    1805                 :          0 :                                 wait_for_completion(&cpu_buffer->update_done);
    1806                 :          0 :                         cpu_buffer->nr_pages_to_update = 0;
    1807                 :            :                 }
    1808                 :            : 
    1809                 :            :                 put_online_cpus();
    1810                 :            :         } else {
    1811                 :            :                 /* Make sure this CPU has been initialized */
    1812                 :          0 :                 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
    1813                 :            :                         goto out;
    1814                 :            : 
    1815                 :          0 :                 cpu_buffer = buffer->buffers[cpu_id];
    1816                 :            : 
    1817                 :          0 :                 if (nr_pages == cpu_buffer->nr_pages)
    1818                 :            :                         goto out;
    1819                 :            : 
    1820                 :          0 :                 cpu_buffer->nr_pages_to_update = nr_pages -
    1821                 :            :                                                 cpu_buffer->nr_pages;
    1822                 :            : 
    1823                 :          0 :                 INIT_LIST_HEAD(&cpu_buffer->new_pages);
    1824                 :          0 :                 if (cpu_buffer->nr_pages_to_update > 0 &&
    1825                 :          0 :                         __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
    1826                 :            :                                             &cpu_buffer->new_pages, cpu_id)) {
    1827                 :            :                         err = -ENOMEM;
    1828                 :            :                         goto out_err;
    1829                 :            :                 }
    1830                 :            : 
    1831                 :            :                 get_online_cpus();
    1832                 :            : 
    1833                 :            :                 /* Can't run something on an offline CPU. */
    1834                 :          0 :                 if (!cpu_online(cpu_id))
    1835                 :          0 :                         rb_update_pages(cpu_buffer);
    1836                 :            :                 else {
    1837                 :          0 :                         schedule_work_on(cpu_id,
    1838                 :            :                                          &cpu_buffer->update_pages_work);
    1839                 :          0 :                         wait_for_completion(&cpu_buffer->update_done);
    1840                 :            :                 }
    1841                 :            : 
    1842                 :          0 :                 cpu_buffer->nr_pages_to_update = 0;
    1843                 :            :                 put_online_cpus();
    1844                 :            :         }
    1845                 :            : 
    1846                 :            :  out:
    1847                 :            :         /*
    1848                 :            :          * The ring buffer resize can happen with the ring buffer
    1849                 :            :          * enabled, so that the update disturbs the tracing as little
    1850                 :            :          * as possible. But if the buffer is disabled, we do not need
    1851                 :            :          * to worry about that, and we can take the time to verify
    1852                 :            :          * that the buffer is not corrupt.
    1853                 :            :          */
    1854                 :          0 :         if (atomic_read(&buffer->record_disabled)) {
    1855                 :          0 :                 atomic_inc(&buffer->record_disabled);
    1856                 :            :                 /*
    1857                 :            :                  * Even though the buffer was disabled, we must make sure
    1858                 :            :                  * that it is truly disabled before calling rb_check_pages.
    1859                 :            :                  * There could have been a race between checking
    1860                 :            :                  * record_disable and incrementing it.
    1861                 :            :                  */
    1862                 :          0 :                 synchronize_rcu();
    1863                 :          0 :                 for_each_buffer_cpu(buffer, cpu) {
    1864                 :          0 :                         cpu_buffer = buffer->buffers[cpu];
    1865                 :          0 :                         rb_check_pages(cpu_buffer);
    1866                 :            :                 }
    1867                 :            :                 atomic_dec(&buffer->record_disabled);
    1868                 :            :         }
    1869                 :            : 
    1870                 :          0 :         mutex_unlock(&buffer->mutex);
    1871                 :          0 :         return size;
    1872                 :            : 
    1873                 :            :  out_err:
    1874                 :          0 :         for_each_buffer_cpu(buffer, cpu) {
    1875                 :            :                 struct buffer_page *bpage, *tmp;
    1876                 :            : 
    1877                 :          0 :                 cpu_buffer = buffer->buffers[cpu];
    1878                 :          0 :                 cpu_buffer->nr_pages_to_update = 0;
    1879                 :            : 
    1880                 :          0 :                 if (list_empty(&cpu_buffer->new_pages))
    1881                 :          0 :                         continue;
    1882                 :            : 
    1883                 :          0 :                 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
    1884                 :            :                                         list) {
    1885                 :            :                         list_del_init(&bpage->list);
    1886                 :          0 :                         free_buffer_page(bpage);
    1887                 :            :                 }
    1888                 :            :         }
    1889                 :          0 :         mutex_unlock(&buffer->mutex);
    1890                 :          0 :         return err;
    1891                 :            : }
    1892                 :            : EXPORT_SYMBOL_GPL(ring_buffer_resize);
    1893                 :            : 
    1894                 :          0 : void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
    1895                 :            : {
    1896                 :          0 :         mutex_lock(&buffer->mutex);
    1897                 :          0 :         if (val)
    1898                 :          0 :                 buffer->flags |= RB_FL_OVERWRITE;
    1899                 :            :         else
    1900                 :          0 :                 buffer->flags &= ~RB_FL_OVERWRITE;
    1901                 :          0 :         mutex_unlock(&buffer->mutex);
    1902                 :          0 : }
    1903                 :            : EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
    1904                 :            : 
    1905                 :            : static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
    1906                 :            : {
    1907                 :          0 :         return bpage->page->data + index;
    1908                 :            : }
    1909                 :            : 
    1910                 :            : static __always_inline struct ring_buffer_event *
    1911                 :            : rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
    1912                 :            : {
    1913                 :          0 :         return __rb_page_index(cpu_buffer->reader_page,
    1914                 :          0 :                                cpu_buffer->reader_page->read);
    1915                 :            : }
    1916                 :            : 
    1917                 :            : static __always_inline struct ring_buffer_event *
    1918                 :            : rb_iter_head_event(struct ring_buffer_iter *iter)
    1919                 :            : {
    1920                 :          0 :         return __rb_page_index(iter->head_page, iter->head);
    1921                 :            : }
    1922                 :            : 
    1923                 :            : static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
    1924                 :            : {
    1925                 :          0 :         return local_read(&bpage->page->commit);
    1926                 :            : }
    1927                 :            : 
    1928                 :            : /* Size is determined by what has been committed */
    1929                 :            : static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
    1930                 :            : {
    1931                 :            :         return rb_page_commit(bpage);
    1932                 :            : }
    1933                 :            : 
    1934                 :            : static __always_inline unsigned
    1935                 :            : rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
    1936                 :            : {
    1937                 :          0 :         return rb_page_commit(cpu_buffer->commit_page);
    1938                 :            : }
    1939                 :            : 
    1940                 :            : static __always_inline unsigned
    1941                 :            : rb_event_index(struct ring_buffer_event *event)
    1942                 :            : {
    1943                 :          0 :         unsigned long addr = (unsigned long)event;
    1944                 :            : 
    1945                 :          0 :         return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
    1946                 :            : }
    1947                 :            : 
    1948                 :          0 : static void rb_inc_iter(struct ring_buffer_iter *iter)
    1949                 :            : {
    1950                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
    1951                 :            : 
    1952                 :            :         /*
    1953                 :            :          * The iterator could be on the reader page (it starts there).
    1954                 :            :          * But the head could have moved, since the reader was
    1955                 :            :          * found. Check for this case and assign the iterator
    1956                 :            :          * to the head page instead of next.
    1957                 :            :          */
    1958                 :          0 :         if (iter->head_page == cpu_buffer->reader_page)
    1959                 :          0 :                 iter->head_page = rb_set_head_page(cpu_buffer);
    1960                 :            :         else
    1961                 :            :                 rb_inc_page(cpu_buffer, &iter->head_page);
    1962                 :            : 
    1963                 :          0 :         iter->read_stamp = iter->head_page->page->time_stamp;
    1964                 :          0 :         iter->head = 0;
    1965                 :          0 : }
    1966                 :            : 
    1967                 :            : /*
    1968                 :            :  * rb_handle_head_page - writer hit the head page
    1969                 :            :  *
    1970                 :            :  * Returns: +1 to retry page
    1971                 :            :  *           0 to continue
    1972                 :            :  *          -1 on error
    1973                 :            :  */
    1974                 :            : static int
    1975                 :          0 : rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
    1976                 :            :                     struct buffer_page *tail_page,
    1977                 :            :                     struct buffer_page *next_page)
    1978                 :            : {
    1979                 :            :         struct buffer_page *new_head;
    1980                 :            :         int entries;
    1981                 :            :         int type;
    1982                 :            :         int ret;
    1983                 :            : 
    1984                 :          0 :         entries = rb_page_entries(next_page);
    1985                 :            : 
    1986                 :            :         /*
    1987                 :            :          * The hard part is here. We need to move the head
    1988                 :            :          * forward, and protect against both readers on
    1989                 :            :          * other CPUs and writers coming in via interrupts.
    1990                 :            :          */
    1991                 :            :         type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
    1992                 :            :                                        RB_PAGE_HEAD);
    1993                 :            : 
    1994                 :            :         /*
    1995                 :            :          * type can be one of four:
    1996                 :            :          *  NORMAL - an interrupt already moved it for us
    1997                 :            :          *  HEAD   - we are the first to get here.
    1998                 :            :          *  UPDATE - we are the interrupt interrupting
    1999                 :            :          *           a current move.
    2000                 :            :          *  MOVED  - a reader on another CPU moved the next
    2001                 :            :          *           pointer to its reader page. Give up
    2002                 :            :          *           and try again.
    2003                 :            :          */
    2004                 :            : 
    2005                 :          0 :         switch (type) {
    2006                 :            :         case RB_PAGE_HEAD:
    2007                 :            :                 /*
    2008                 :            :                  * We changed the head to UPDATE, thus
    2009                 :            :                  * it is our responsibility to update
    2010                 :            :                  * the counters.
    2011                 :            :                  */
    2012                 :          0 :                 local_add(entries, &cpu_buffer->overrun);
    2013                 :          0 :                 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
    2014                 :            : 
    2015                 :            :                 /*
    2016                 :            :                  * The entries will be zeroed out when we move the
    2017                 :            :                  * tail page.
    2018                 :            :                  */
    2019                 :            : 
    2020                 :            :                 /* still more to do */
    2021                 :            :                 break;
    2022                 :            : 
    2023                 :            :         case RB_PAGE_UPDATE:
    2024                 :            :                 /*
    2025                 :            :                  * This is an interrupt that interrupt the
    2026                 :            :                  * previous update. Still more to do.
    2027                 :            :                  */
    2028                 :            :                 break;
    2029                 :            :         case RB_PAGE_NORMAL:
    2030                 :            :                 /*
    2031                 :            :                  * An interrupt came in before the update
    2032                 :            :                  * and processed this for us.
    2033                 :            :                  * Nothing left to do.
    2034                 :            :                  */
    2035                 :            :                 return 1;
    2036                 :            :         case RB_PAGE_MOVED:
    2037                 :            :                 /*
    2038                 :            :                  * The reader is on another CPU and just did
    2039                 :            :                  * a swap with our next_page.
    2040                 :            :                  * Try again.
    2041                 :            :                  */
    2042                 :            :                 return 1;
    2043                 :            :         default:
    2044                 :          0 :                 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
    2045                 :          0 :                 return -1;
    2046                 :            :         }
    2047                 :            : 
    2048                 :            :         /*
    2049                 :            :          * Now that we are here, the old head pointer is
    2050                 :            :          * set to UPDATE. This will keep the reader from
    2051                 :            :          * swapping the head page with the reader page.
    2052                 :            :          * The reader (on another CPU) will spin till
    2053                 :            :          * we are finished.
    2054                 :            :          *
    2055                 :            :          * We just need to protect against interrupts
    2056                 :            :          * doing the job. We will set the next pointer
    2057                 :            :          * to HEAD. After that, we set the old pointer
    2058                 :            :          * to NORMAL, but only if it was HEAD before.
    2059                 :            :          * otherwise we are an interrupt, and only
    2060                 :            :          * want the outer most commit to reset it.
    2061                 :            :          */
    2062                 :            :         new_head = next_page;
    2063                 :            :         rb_inc_page(cpu_buffer, &new_head);
    2064                 :            : 
    2065                 :            :         ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
    2066                 :            :                                     RB_PAGE_NORMAL);
    2067                 :            : 
    2068                 :            :         /*
    2069                 :            :          * Valid returns are:
    2070                 :            :          *  HEAD   - an interrupt came in and already set it.
    2071                 :            :          *  NORMAL - One of two things:
    2072                 :            :          *            1) We really set it.
    2073                 :            :          *            2) A bunch of interrupts came in and moved
    2074                 :            :          *               the page forward again.
    2075                 :            :          */
    2076                 :          0 :         switch (ret) {
    2077                 :            :         case RB_PAGE_HEAD:
    2078                 :            :         case RB_PAGE_NORMAL:
    2079                 :            :                 /* OK */
    2080                 :            :                 break;
    2081                 :            :         default:
    2082                 :          0 :                 RB_WARN_ON(cpu_buffer, 1);
    2083                 :          0 :                 return -1;
    2084                 :            :         }
    2085                 :            : 
    2086                 :            :         /*
    2087                 :            :          * It is possible that an interrupt came in,
    2088                 :            :          * set the head up, then more interrupts came in
    2089                 :            :          * and moved it again. When we get back here,
    2090                 :            :          * the page would have been set to NORMAL but we
    2091                 :            :          * just set it back to HEAD.
    2092                 :            :          *
    2093                 :            :          * How do you detect this? Well, if that happened
    2094                 :            :          * the tail page would have moved.
    2095                 :            :          */
    2096                 :          0 :         if (ret == RB_PAGE_NORMAL) {
    2097                 :            :                 struct buffer_page *buffer_tail_page;
    2098                 :            : 
    2099                 :          0 :                 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
    2100                 :            :                 /*
    2101                 :            :                  * If the tail had moved passed next, then we need
    2102                 :            :                  * to reset the pointer.
    2103                 :            :                  */
    2104                 :          0 :                 if (buffer_tail_page != tail_page &&
    2105                 :          0 :                     buffer_tail_page != next_page)
    2106                 :            :                         rb_head_page_set_normal(cpu_buffer, new_head,
    2107                 :            :                                                 next_page,
    2108                 :            :                                                 RB_PAGE_HEAD);
    2109                 :            :         }
    2110                 :            : 
    2111                 :            :         /*
    2112                 :            :          * If this was the outer most commit (the one that
    2113                 :            :          * changed the original pointer from HEAD to UPDATE),
    2114                 :            :          * then it is up to us to reset it to NORMAL.
    2115                 :            :          */
    2116                 :          0 :         if (type == RB_PAGE_HEAD) {
    2117                 :            :                 ret = rb_head_page_set_normal(cpu_buffer, next_page,
    2118                 :            :                                               tail_page,
    2119                 :            :                                               RB_PAGE_UPDATE);
    2120                 :          0 :                 if (RB_WARN_ON(cpu_buffer,
    2121                 :            :                                ret != RB_PAGE_UPDATE))
    2122                 :            :                         return -1;
    2123                 :            :         }
    2124                 :            : 
    2125                 :            :         return 0;
    2126                 :            : }
    2127                 :            : 
    2128                 :            : static inline void
    2129                 :          0 : rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
    2130                 :            :               unsigned long tail, struct rb_event_info *info)
    2131                 :            : {
    2132                 :          0 :         struct buffer_page *tail_page = info->tail_page;
    2133                 :            :         struct ring_buffer_event *event;
    2134                 :          0 :         unsigned long length = info->length;
    2135                 :            : 
    2136                 :            :         /*
    2137                 :            :          * Only the event that crossed the page boundary
    2138                 :            :          * must fill the old tail_page with padding.
    2139                 :            :          */
    2140                 :          0 :         if (tail >= BUF_PAGE_SIZE) {
    2141                 :            :                 /*
    2142                 :            :                  * If the page was filled, then we still need
    2143                 :            :                  * to update the real_end. Reset it to zero
    2144                 :            :                  * and the reader will ignore it.
    2145                 :            :                  */
    2146                 :          0 :                 if (tail == BUF_PAGE_SIZE)
    2147                 :          0 :                         tail_page->real_end = 0;
    2148                 :            : 
    2149                 :          0 :                 local_sub(length, &tail_page->write);
    2150                 :            :                 return;
    2151                 :            :         }
    2152                 :            : 
    2153                 :            :         event = __rb_page_index(tail_page, tail);
    2154                 :            : 
    2155                 :            :         /* account for padding bytes */
    2156                 :          0 :         local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
    2157                 :            : 
    2158                 :            :         /*
    2159                 :            :          * Save the original length to the meta data.
    2160                 :            :          * This will be used by the reader to add lost event
    2161                 :            :          * counter.
    2162                 :            :          */
    2163                 :          0 :         tail_page->real_end = tail;
    2164                 :            : 
    2165                 :            :         /*
    2166                 :            :          * If this event is bigger than the minimum size, then
    2167                 :            :          * we need to be careful that we don't subtract the
    2168                 :            :          * write counter enough to allow another writer to slip
    2169                 :            :          * in on this page.
    2170                 :            :          * We put in a discarded commit instead, to make sure
    2171                 :            :          * that this space is not used again.
    2172                 :            :          *
    2173                 :            :          * If we are less than the minimum size, we don't need to
    2174                 :            :          * worry about it.
    2175                 :            :          */
    2176                 :          0 :         if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
    2177                 :            :                 /* No room for any events */
    2178                 :            : 
    2179                 :            :                 /* Mark the rest of the page with padding */
    2180                 :            :                 rb_event_set_padding(event);
    2181                 :            : 
    2182                 :            :                 /* Set the write back to the previous setting */
    2183                 :          0 :                 local_sub(length, &tail_page->write);
    2184                 :            :                 return;
    2185                 :            :         }
    2186                 :            : 
    2187                 :            :         /* Put in a discarded event */
    2188                 :          0 :         event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
    2189                 :          0 :         event->type_len = RINGBUF_TYPE_PADDING;
    2190                 :            :         /* time delta must be non zero */
    2191                 :          0 :         event->time_delta = 1;
    2192                 :            : 
    2193                 :            :         /* Set write to end of buffer */
    2194                 :          0 :         length = (tail + length) - BUF_PAGE_SIZE;
    2195                 :          0 :         local_sub(length, &tail_page->write);
    2196                 :            : }
    2197                 :            : 
    2198                 :            : static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
    2199                 :            : 
    2200                 :            : /*
    2201                 :            :  * This is the slow path, force gcc not to inline it.
    2202                 :            :  */
    2203                 :            : static noinline struct ring_buffer_event *
    2204                 :          0 : rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
    2205                 :            :              unsigned long tail, struct rb_event_info *info)
    2206                 :            : {
    2207                 :          0 :         struct buffer_page *tail_page = info->tail_page;
    2208                 :          0 :         struct buffer_page *commit_page = cpu_buffer->commit_page;
    2209                 :          0 :         struct ring_buffer *buffer = cpu_buffer->buffer;
    2210                 :            :         struct buffer_page *next_page;
    2211                 :            :         int ret;
    2212                 :            : 
    2213                 :            :         next_page = tail_page;
    2214                 :            : 
    2215                 :            :         rb_inc_page(cpu_buffer, &next_page);
    2216                 :            : 
    2217                 :            :         /*
    2218                 :            :          * If for some reason, we had an interrupt storm that made
    2219                 :            :          * it all the way around the buffer, bail, and warn
    2220                 :            :          * about it.
    2221                 :            :          */
    2222                 :          0 :         if (unlikely(next_page == commit_page)) {
    2223                 :          0 :                 local_inc(&cpu_buffer->commit_overrun);
    2224                 :            :                 goto out_reset;
    2225                 :            :         }
    2226                 :            : 
    2227                 :            :         /*
    2228                 :            :          * This is where the fun begins!
    2229                 :            :          *
    2230                 :            :          * We are fighting against races between a reader that
    2231                 :            :          * could be on another CPU trying to swap its reader
    2232                 :            :          * page with the buffer head.
    2233                 :            :          *
    2234                 :            :          * We are also fighting against interrupts coming in and
    2235                 :            :          * moving the head or tail on us as well.
    2236                 :            :          *
    2237                 :            :          * If the next page is the head page then we have filled
    2238                 :            :          * the buffer, unless the commit page is still on the
    2239                 :            :          * reader page.
    2240                 :            :          */
    2241                 :          0 :         if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
    2242                 :            : 
    2243                 :            :                 /*
    2244                 :            :                  * If the commit is not on the reader page, then
    2245                 :            :                  * move the header page.
    2246                 :            :                  */
    2247                 :          0 :                 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
    2248                 :            :                         /*
    2249                 :            :                          * If we are not in overwrite mode,
    2250                 :            :                          * this is easy, just stop here.
    2251                 :            :                          */
    2252                 :          0 :                         if (!(buffer->flags & RB_FL_OVERWRITE)) {
    2253                 :          0 :                                 local_inc(&cpu_buffer->dropped_events);
    2254                 :            :                                 goto out_reset;
    2255                 :            :                         }
    2256                 :            : 
    2257                 :          0 :                         ret = rb_handle_head_page(cpu_buffer,
    2258                 :            :                                                   tail_page,
    2259                 :            :                                                   next_page);
    2260                 :          0 :                         if (ret < 0)
    2261                 :            :                                 goto out_reset;
    2262                 :          0 :                         if (ret)
    2263                 :            :                                 goto out_again;
    2264                 :            :                 } else {
    2265                 :            :                         /*
    2266                 :            :                          * We need to be careful here too. The
    2267                 :            :                          * commit page could still be on the reader
    2268                 :            :                          * page. We could have a small buffer, and
    2269                 :            :                          * have filled up the buffer with events
    2270                 :            :                          * from interrupts and such, and wrapped.
    2271                 :            :                          *
    2272                 :            :                          * Note, if the tail page is also the on the
    2273                 :            :                          * reader_page, we let it move out.
    2274                 :            :                          */
    2275                 :          0 :                         if (unlikely((cpu_buffer->commit_page !=
    2276                 :            :                                       cpu_buffer->tail_page) &&
    2277                 :            :                                      (cpu_buffer->commit_page ==
    2278                 :            :                                       cpu_buffer->reader_page))) {
    2279                 :          0 :                                 local_inc(&cpu_buffer->commit_overrun);
    2280                 :            :                                 goto out_reset;
    2281                 :            :                         }
    2282                 :            :                 }
    2283                 :            :         }
    2284                 :            : 
    2285                 :          0 :         rb_tail_page_update(cpu_buffer, tail_page, next_page);
    2286                 :            : 
    2287                 :            :  out_again:
    2288                 :            : 
    2289                 :          0 :         rb_reset_tail(cpu_buffer, tail, info);
    2290                 :            : 
    2291                 :            :         /* Commit what we have for now. */
    2292                 :            :         rb_end_commit(cpu_buffer);
    2293                 :            :         /* rb_end_commit() decs committing */
    2294                 :            :         local_inc(&cpu_buffer->committing);
    2295                 :            : 
    2296                 :            :         /* fail and let the caller try again */
    2297                 :          0 :         return ERR_PTR(-EAGAIN);
    2298                 :            : 
    2299                 :            :  out_reset:
    2300                 :            :         /* reset write */
    2301                 :          0 :         rb_reset_tail(cpu_buffer, tail, info);
    2302                 :            : 
    2303                 :          0 :         return NULL;
    2304                 :            : }
    2305                 :            : 
    2306                 :            : /* Slow path, do not inline */
    2307                 :            : static noinline struct ring_buffer_event *
    2308                 :          0 : rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
    2309                 :            : {
    2310                 :          0 :         if (abs)
    2311                 :          0 :                 event->type_len = RINGBUF_TYPE_TIME_STAMP;
    2312                 :            :         else
    2313                 :          0 :                 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
    2314                 :            : 
    2315                 :            :         /* Not the first event on the page, or not delta? */
    2316                 :          0 :         if (abs || rb_event_index(event)) {
    2317                 :          0 :                 event->time_delta = delta & TS_MASK;
    2318                 :          0 :                 event->array[0] = delta >> TS_SHIFT;
    2319                 :            :         } else {
    2320                 :            :                 /* nope, just zero it */
    2321                 :          0 :                 event->time_delta = 0;
    2322                 :          0 :                 event->array[0] = 0;
    2323                 :            :         }
    2324                 :            : 
    2325                 :          0 :         return skip_time_extend(event);
    2326                 :            : }
    2327                 :            : 
    2328                 :            : static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
    2329                 :            :                                      struct ring_buffer_event *event);
    2330                 :            : 
    2331                 :            : /**
    2332                 :            :  * rb_update_event - update event type and data
    2333                 :            :  * @event: the event to update
    2334                 :            :  * @type: the type of event
    2335                 :            :  * @length: the size of the event field in the ring buffer
    2336                 :            :  *
    2337                 :            :  * Update the type and data fields of the event. The length
    2338                 :            :  * is the actual size that is written to the ring buffer,
    2339                 :            :  * and with this, we can determine what to place into the
    2340                 :            :  * data field.
    2341                 :            :  */
    2342                 :            : static void
    2343                 :          0 : rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
    2344                 :            :                 struct ring_buffer_event *event,
    2345                 :            :                 struct rb_event_info *info)
    2346                 :            : {
    2347                 :          0 :         unsigned length = info->length;
    2348                 :          0 :         u64 delta = info->delta;
    2349                 :            : 
    2350                 :            :         /* Only a commit updates the timestamp */
    2351                 :          0 :         if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
    2352                 :            :                 delta = 0;
    2353                 :            : 
    2354                 :            :         /*
    2355                 :            :          * If we need to add a timestamp, then we
    2356                 :            :          * add it to the start of the reserved space.
    2357                 :            :          */
    2358                 :          0 :         if (unlikely(info->add_timestamp)) {
    2359                 :          0 :                 bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer);
    2360                 :            : 
    2361                 :          0 :                 event = rb_add_time_stamp(event, abs ? info->delta : delta, abs);
    2362                 :          0 :                 length -= RB_LEN_TIME_EXTEND;
    2363                 :            :                 delta = 0;
    2364                 :            :         }
    2365                 :            : 
    2366                 :          0 :         event->time_delta = delta;
    2367                 :          0 :         length -= RB_EVNT_HDR_SIZE;
    2368                 :          0 :         if (length > RB_MAX_SMALL_DATA) {
    2369                 :          0 :                 event->type_len = 0;
    2370                 :          0 :                 event->array[0] = length;
    2371                 :            :         } else
    2372                 :          0 :                 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
    2373                 :          0 : }
    2374                 :            : 
    2375                 :          0 : static unsigned rb_calculate_event_length(unsigned length)
    2376                 :            : {
    2377                 :            :         struct ring_buffer_event event; /* Used only for sizeof array */
    2378                 :            : 
    2379                 :            :         /* zero length can cause confusions */
    2380                 :          0 :         if (!length)
    2381                 :          0 :                 length++;
    2382                 :            : 
    2383                 :          0 :         if (length > RB_MAX_SMALL_DATA)
    2384                 :          0 :                 length += sizeof(event.array[0]);
    2385                 :            : 
    2386                 :            :         length += RB_EVNT_HDR_SIZE;
    2387                 :          0 :         length = ALIGN(length, RB_ALIGNMENT);
    2388                 :            : 
    2389                 :            :         /*
    2390                 :            :          * In case the time delta is larger than the 27 bits for it
    2391                 :            :          * in the header, we need to add a timestamp. If another
    2392                 :            :          * event comes in when trying to discard this one to increase
    2393                 :            :          * the length, then the timestamp will be added in the allocated
    2394                 :            :          * space of this event. If length is bigger than the size needed
    2395                 :            :          * for the TIME_EXTEND, then padding has to be used. The events
    2396                 :            :          * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
    2397                 :            :          * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
    2398                 :            :          * As length is a multiple of 4, we only need to worry if it
    2399                 :            :          * is 12 (RB_LEN_TIME_EXTEND + 4).
    2400                 :            :          */
    2401                 :          0 :         if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
    2402                 :          0 :                 length += RB_ALIGNMENT;
    2403                 :            : 
    2404                 :          0 :         return length;
    2405                 :            : }
    2406                 :            : 
    2407                 :            : #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
    2408                 :            : static inline bool sched_clock_stable(void)
    2409                 :            : {
    2410                 :            :         return true;
    2411                 :            : }
    2412                 :            : #endif
    2413                 :            : 
    2414                 :            : static inline int
    2415                 :          0 : rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
    2416                 :            :                   struct ring_buffer_event *event)
    2417                 :            : {
    2418                 :            :         unsigned long new_index, old_index;
    2419                 :            :         struct buffer_page *bpage;
    2420                 :            :         unsigned long index;
    2421                 :            :         unsigned long addr;
    2422                 :            : 
    2423                 :            :         new_index = rb_event_index(event);
    2424                 :          0 :         old_index = new_index + rb_event_ts_length(event);
    2425                 :            :         addr = (unsigned long)event;
    2426                 :          0 :         addr &= PAGE_MASK;
    2427                 :            : 
    2428                 :          0 :         bpage = READ_ONCE(cpu_buffer->tail_page);
    2429                 :            : 
    2430                 :          0 :         if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
    2431                 :          0 :                 unsigned long write_mask =
    2432                 :            :                         local_read(&bpage->write) & ~RB_WRITE_MASK;
    2433                 :          0 :                 unsigned long event_length = rb_event_length(event);
    2434                 :            :                 /*
    2435                 :            :                  * This is on the tail page. It is possible that
    2436                 :            :                  * a write could come in and move the tail page
    2437                 :            :                  * and write to the next page. That is fine
    2438                 :            :                  * because we just shorten what is on this page.
    2439                 :            :                  */
    2440                 :          0 :                 old_index += write_mask;
    2441                 :          0 :                 new_index += write_mask;
    2442                 :          0 :                 index = local_cmpxchg(&bpage->write, old_index, new_index);
    2443                 :          0 :                 if (index == old_index) {
    2444                 :            :                         /* update counters */
    2445                 :          0 :                         local_sub(event_length, &cpu_buffer->entries_bytes);
    2446                 :          0 :                         return 1;
    2447                 :            :                 }
    2448                 :            :         }
    2449                 :            : 
    2450                 :            :         /* could not discard */
    2451                 :            :         return 0;
    2452                 :            : }
    2453                 :            : 
    2454                 :          0 : static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
    2455                 :            : {
    2456                 :          0 :         local_inc(&cpu_buffer->committing);
    2457                 :          0 :         local_inc(&cpu_buffer->commits);
    2458                 :          0 : }
    2459                 :            : 
    2460                 :            : static __always_inline void
    2461                 :            : rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
    2462                 :            : {
    2463                 :            :         unsigned long max_count;
    2464                 :            : 
    2465                 :            :         /*
    2466                 :            :          * We only race with interrupts and NMIs on this CPU.
    2467                 :            :          * If we own the commit event, then we can commit
    2468                 :            :          * all others that interrupted us, since the interruptions
    2469                 :            :          * are in stack format (they finish before they come
    2470                 :            :          * back to us). This allows us to do a simple loop to
    2471                 :            :          * assign the commit to the tail.
    2472                 :            :          */
    2473                 :            :  again:
    2474                 :          0 :         max_count = cpu_buffer->nr_pages * 100;
    2475                 :            : 
    2476                 :          0 :         while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
    2477                 :          0 :                 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
    2478                 :            :                         return;
    2479                 :          0 :                 if (RB_WARN_ON(cpu_buffer,
    2480                 :            :                                rb_is_reader_page(cpu_buffer->tail_page)))
    2481                 :            :                         return;
    2482                 :          0 :                 local_set(&cpu_buffer->commit_page->page->commit,
    2483                 :            :                           rb_page_write(cpu_buffer->commit_page));
    2484                 :          0 :                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
    2485                 :            :                 /* Only update the write stamp if the page has an event */
    2486                 :          0 :                 if (rb_page_write(cpu_buffer->commit_page))
    2487                 :          0 :                         cpu_buffer->write_stamp =
    2488                 :          0 :                                 cpu_buffer->commit_page->page->time_stamp;
    2489                 :            :                 /* add barrier to keep gcc from optimizing too much */
    2490                 :          0 :                 barrier();
    2491                 :            :         }
    2492                 :          0 :         while (rb_commit_index(cpu_buffer) !=
    2493                 :          0 :                rb_page_write(cpu_buffer->commit_page)) {
    2494                 :            : 
    2495                 :          0 :                 local_set(&cpu_buffer->commit_page->page->commit,
    2496                 :            :                           rb_page_write(cpu_buffer->commit_page));
    2497                 :          0 :                 RB_WARN_ON(cpu_buffer,
    2498                 :            :                            local_read(&cpu_buffer->commit_page->page->commit) &
    2499                 :            :                            ~RB_WRITE_MASK);
    2500                 :          0 :                 barrier();
    2501                 :            :         }
    2502                 :            : 
    2503                 :            :         /* again, keep gcc from optimizing */
    2504                 :          0 :         barrier();
    2505                 :            : 
    2506                 :            :         /*
    2507                 :            :          * If an interrupt came in just after the first while loop
    2508                 :            :          * and pushed the tail page forward, we will be left with
    2509                 :            :          * a dangling commit that will never go forward.
    2510                 :            :          */
    2511                 :          0 :         if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
    2512                 :            :                 goto again;
    2513                 :            : }
    2514                 :            : 
    2515                 :            : static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
    2516                 :            : {
    2517                 :            :         unsigned long commits;
    2518                 :            : 
    2519                 :          0 :         if (RB_WARN_ON(cpu_buffer,
    2520                 :            :                        !local_read(&cpu_buffer->committing)))
    2521                 :            :                 return;
    2522                 :            : 
    2523                 :            :  again:
    2524                 :          0 :         commits = local_read(&cpu_buffer->commits);
    2525                 :            :         /* synchronize with interrupts */
    2526                 :          0 :         barrier();
    2527                 :          0 :         if (local_read(&cpu_buffer->committing) == 1)
    2528                 :            :                 rb_set_commit_to_write(cpu_buffer);
    2529                 :            : 
    2530                 :          0 :         local_dec(&cpu_buffer->committing);
    2531                 :            : 
    2532                 :            :         /* synchronize with interrupts */
    2533                 :          0 :         barrier();
    2534                 :            : 
    2535                 :            :         /*
    2536                 :            :          * Need to account for interrupts coming in between the
    2537                 :            :          * updating of the commit page and the clearing of the
    2538                 :            :          * committing counter.
    2539                 :            :          */
    2540                 :          0 :         if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
    2541                 :          0 :             !local_read(&cpu_buffer->committing)) {
    2542                 :          0 :                 local_inc(&cpu_buffer->committing);
    2543                 :            :                 goto again;
    2544                 :            :         }
    2545                 :            : }
    2546                 :            : 
    2547                 :          0 : static inline void rb_event_discard(struct ring_buffer_event *event)
    2548                 :            : {
    2549                 :          0 :         if (extended_time(event))
    2550                 :          0 :                 event = skip_time_extend(event);
    2551                 :            : 
    2552                 :            :         /* array[0] holds the actual length for the discarded event */
    2553                 :          0 :         event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
    2554                 :          0 :         event->type_len = RINGBUF_TYPE_PADDING;
    2555                 :            :         /* time delta must be non zero */
    2556                 :          0 :         if (!event->time_delta)
    2557                 :          0 :                 event->time_delta = 1;
    2558                 :          0 : }
    2559                 :            : 
    2560                 :            : static __always_inline bool
    2561                 :            : rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
    2562                 :            :                    struct ring_buffer_event *event)
    2563                 :            : {
    2564                 :          0 :         unsigned long addr = (unsigned long)event;
    2565                 :            :         unsigned long index;
    2566                 :            : 
    2567                 :            :         index = rb_event_index(event);
    2568                 :          0 :         addr &= PAGE_MASK;
    2569                 :            : 
    2570                 :          0 :         return cpu_buffer->commit_page->page == (void *)addr &&
    2571                 :            :                 rb_commit_index(cpu_buffer) == index;
    2572                 :            : }
    2573                 :            : 
    2574                 :            : static __always_inline void
    2575                 :            : rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
    2576                 :            :                       struct ring_buffer_event *event)
    2577                 :            : {
    2578                 :            :         u64 delta;
    2579                 :            : 
    2580                 :            :         /*
    2581                 :            :          * The event first in the commit queue updates the
    2582                 :            :          * time stamp.
    2583                 :            :          */
    2584                 :          0 :         if (rb_event_is_commit(cpu_buffer, event)) {
    2585                 :            :                 /*
    2586                 :            :                  * A commit event that is first on a page
    2587                 :            :                  * updates the write timestamp with the page stamp
    2588                 :            :                  */
    2589                 :          0 :                 if (!rb_event_index(event))
    2590                 :          0 :                         cpu_buffer->write_stamp =
    2591                 :          0 :                                 cpu_buffer->commit_page->page->time_stamp;
    2592                 :          0 :                 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
    2593                 :          0 :                         delta = ring_buffer_event_time_stamp(event);
    2594                 :          0 :                         cpu_buffer->write_stamp += delta;
    2595                 :          0 :                 } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
    2596                 :          0 :                         delta = ring_buffer_event_time_stamp(event);
    2597                 :          0 :                         cpu_buffer->write_stamp = delta;
    2598                 :            :                 } else
    2599                 :          0 :                         cpu_buffer->write_stamp += event->time_delta;
    2600                 :            :         }
    2601                 :            : }
    2602                 :            : 
    2603                 :          0 : static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
    2604                 :            :                       struct ring_buffer_event *event)
    2605                 :            : {
    2606                 :          0 :         local_inc(&cpu_buffer->entries);
    2607                 :            :         rb_update_write_stamp(cpu_buffer, event);
    2608                 :            :         rb_end_commit(cpu_buffer);
    2609                 :          0 : }
    2610                 :            : 
    2611                 :            : static __always_inline void
    2612                 :            : rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
    2613                 :            : {
    2614                 :            :         size_t nr_pages;
    2615                 :            :         size_t dirty;
    2616                 :            :         size_t full;
    2617                 :            : 
    2618                 :          0 :         if (buffer->irq_work.waiters_pending) {
    2619                 :          0 :                 buffer->irq_work.waiters_pending = false;
    2620                 :            :                 /* irq_work_queue() supplies it's own memory barriers */
    2621                 :          0 :                 irq_work_queue(&buffer->irq_work.work);
    2622                 :            :         }
    2623                 :            : 
    2624                 :          0 :         if (cpu_buffer->irq_work.waiters_pending) {
    2625                 :          0 :                 cpu_buffer->irq_work.waiters_pending = false;
    2626                 :            :                 /* irq_work_queue() supplies it's own memory barriers */
    2627                 :          0 :                 irq_work_queue(&cpu_buffer->irq_work.work);
    2628                 :            :         }
    2629                 :            : 
    2630                 :          0 :         if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
    2631                 :            :                 return;
    2632                 :            : 
    2633                 :          0 :         if (cpu_buffer->reader_page == cpu_buffer->commit_page)
    2634                 :            :                 return;
    2635                 :            : 
    2636                 :          0 :         if (!cpu_buffer->irq_work.full_waiters_pending)
    2637                 :            :                 return;
    2638                 :            : 
    2639                 :          0 :         cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
    2640                 :            : 
    2641                 :          0 :         full = cpu_buffer->shortest_full;
    2642                 :          0 :         nr_pages = cpu_buffer->nr_pages;
    2643                 :          0 :         dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
    2644                 :          0 :         if (full && nr_pages && (dirty * 100) <= full * nr_pages)
    2645                 :            :                 return;
    2646                 :            : 
    2647                 :          0 :         cpu_buffer->irq_work.wakeup_full = true;
    2648                 :          0 :         cpu_buffer->irq_work.full_waiters_pending = false;
    2649                 :            :         /* irq_work_queue() supplies it's own memory barriers */
    2650                 :          0 :         irq_work_queue(&cpu_buffer->irq_work.work);
    2651                 :            : }
    2652                 :            : 
    2653                 :            : /*
    2654                 :            :  * The lock and unlock are done within a preempt disable section.
    2655                 :            :  * The current_context per_cpu variable can only be modified
    2656                 :            :  * by the current task between lock and unlock. But it can
    2657                 :            :  * be modified more than once via an interrupt. To pass this
    2658                 :            :  * information from the lock to the unlock without having to
    2659                 :            :  * access the 'in_interrupt()' functions again (which do show
    2660                 :            :  * a bit of overhead in something as critical as function tracing,
    2661                 :            :  * we use a bitmask trick.
    2662                 :            :  *
    2663                 :            :  *  bit 0 =  NMI context
    2664                 :            :  *  bit 1 =  IRQ context
    2665                 :            :  *  bit 2 =  SoftIRQ context
    2666                 :            :  *  bit 3 =  normal context.
    2667                 :            :  *
    2668                 :            :  * This works because this is the order of contexts that can
    2669                 :            :  * preempt other contexts. A SoftIRQ never preempts an IRQ
    2670                 :            :  * context.
    2671                 :            :  *
    2672                 :            :  * When the context is determined, the corresponding bit is
    2673                 :            :  * checked and set (if it was set, then a recursion of that context
    2674                 :            :  * happened).
    2675                 :            :  *
    2676                 :            :  * On unlock, we need to clear this bit. To do so, just subtract
    2677                 :            :  * 1 from the current_context and AND it to itself.
    2678                 :            :  *
    2679                 :            :  * (binary)
    2680                 :            :  *  101 - 1 = 100
    2681                 :            :  *  101 & 100 = 100 (clearing bit zero)
    2682                 :            :  *
    2683                 :            :  *  1010 - 1 = 1001
    2684                 :            :  *  1010 & 1001 = 1000 (clearing bit 1)
    2685                 :            :  *
    2686                 :            :  * The least significant bit can be cleared this way, and it
    2687                 :            :  * just so happens that it is the same bit corresponding to
    2688                 :            :  * the current context.
    2689                 :            :  */
    2690                 :            : 
    2691                 :            : static __always_inline int
    2692                 :            : trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
    2693                 :            : {
    2694                 :          0 :         unsigned int val = cpu_buffer->current_context;
    2695                 :            :         unsigned long pc = preempt_count();
    2696                 :            :         int bit;
    2697                 :            : 
    2698                 :          0 :         if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
    2699                 :            :                 bit = RB_CTX_NORMAL;
    2700                 :            :         else
    2701                 :          0 :                 bit = pc & NMI_MASK ? RB_CTX_NMI :
    2702                 :          0 :                         pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
    2703                 :            : 
    2704                 :          0 :         if (unlikely(val & (1 << (bit + cpu_buffer->nest))))
    2705                 :            :                 return 1;
    2706                 :            : 
    2707                 :          0 :         val |= (1 << (bit + cpu_buffer->nest));
    2708                 :          0 :         cpu_buffer->current_context = val;
    2709                 :            : 
    2710                 :            :         return 0;
    2711                 :            : }
    2712                 :            : 
    2713                 :            : static __always_inline void
    2714                 :            : trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
    2715                 :            : {
    2716                 :          0 :         cpu_buffer->current_context &=
    2717                 :          0 :                 cpu_buffer->current_context - (1 << cpu_buffer->nest);
    2718                 :            : }
    2719                 :            : 
    2720                 :            : /* The recursive locking above uses 4 bits */
    2721                 :            : #define NESTED_BITS 4
    2722                 :            : 
    2723                 :            : /**
    2724                 :            :  * ring_buffer_nest_start - Allow to trace while nested
    2725                 :            :  * @buffer: The ring buffer to modify
    2726                 :            :  *
    2727                 :            :  * The ring buffer has a safety mechanism to prevent recursion.
    2728                 :            :  * But there may be a case where a trace needs to be done while
    2729                 :            :  * tracing something else. In this case, calling this function
    2730                 :            :  * will allow this function to nest within a currently active
    2731                 :            :  * ring_buffer_lock_reserve().
    2732                 :            :  *
    2733                 :            :  * Call this function before calling another ring_buffer_lock_reserve() and
    2734                 :            :  * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
    2735                 :            :  */
    2736                 :          0 : void ring_buffer_nest_start(struct ring_buffer *buffer)
    2737                 :            : {
    2738                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    2739                 :            :         int cpu;
    2740                 :            : 
    2741                 :            :         /* Enabled by ring_buffer_nest_end() */
    2742                 :          0 :         preempt_disable_notrace();
    2743                 :          0 :         cpu = raw_smp_processor_id();
    2744                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    2745                 :            :         /* This is the shift value for the above recursive locking */
    2746                 :          0 :         cpu_buffer->nest += NESTED_BITS;
    2747                 :          0 : }
    2748                 :            : 
    2749                 :            : /**
    2750                 :            :  * ring_buffer_nest_end - Allow to trace while nested
    2751                 :            :  * @buffer: The ring buffer to modify
    2752                 :            :  *
    2753                 :            :  * Must be called after ring_buffer_nest_start() and after the
    2754                 :            :  * ring_buffer_unlock_commit().
    2755                 :            :  */
    2756                 :          0 : void ring_buffer_nest_end(struct ring_buffer *buffer)
    2757                 :            : {
    2758                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    2759                 :            :         int cpu;
    2760                 :            : 
    2761                 :            :         /* disabled by ring_buffer_nest_start() */
    2762                 :          0 :         cpu = raw_smp_processor_id();
    2763                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    2764                 :            :         /* This is the shift value for the above recursive locking */
    2765                 :          0 :         cpu_buffer->nest -= NESTED_BITS;
    2766                 :          0 :         preempt_enable_notrace();
    2767                 :          0 : }
    2768                 :            : 
    2769                 :            : /**
    2770                 :            :  * ring_buffer_unlock_commit - commit a reserved
    2771                 :            :  * @buffer: The buffer to commit to
    2772                 :            :  * @event: The event pointer to commit.
    2773                 :            :  *
    2774                 :            :  * This commits the data to the ring buffer, and releases any locks held.
    2775                 :            :  *
    2776                 :            :  * Must be paired with ring_buffer_lock_reserve.
    2777                 :            :  */
    2778                 :          0 : int ring_buffer_unlock_commit(struct ring_buffer *buffer,
    2779                 :            :                               struct ring_buffer_event *event)
    2780                 :            : {
    2781                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    2782                 :          0 :         int cpu = raw_smp_processor_id();
    2783                 :            : 
    2784                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    2785                 :            : 
    2786                 :          0 :         rb_commit(cpu_buffer, event);
    2787                 :            : 
    2788                 :            :         rb_wakeups(buffer, cpu_buffer);
    2789                 :            : 
    2790                 :            :         trace_recursive_unlock(cpu_buffer);
    2791                 :            : 
    2792                 :          0 :         preempt_enable_notrace();
    2793                 :            : 
    2794                 :          0 :         return 0;
    2795                 :            : }
    2796                 :            : EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
    2797                 :            : 
    2798                 :            : static noinline void
    2799                 :          0 : rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
    2800                 :            :                     struct rb_event_info *info)
    2801                 :            : {
    2802                 :          0 :         WARN_ONCE(info->delta > (1ULL << 59),
    2803                 :            :                   KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
    2804                 :            :                   (unsigned long long)info->delta,
    2805                 :            :                   (unsigned long long)info->ts,
    2806                 :            :                   (unsigned long long)cpu_buffer->write_stamp,
    2807                 :            :                   sched_clock_stable() ? "" :
    2808                 :            :                   "If you just came from a suspend/resume,\n"
    2809                 :            :                   "please switch to the trace global clock:\n"
    2810                 :            :                   "  echo global > /sys/kernel/debug/tracing/trace_clock\n"
    2811                 :            :                   "or add trace_clock=global to the kernel command line\n");
    2812                 :          0 :         info->add_timestamp = 1;
    2813                 :          0 : }
    2814                 :            : 
    2815                 :            : static struct ring_buffer_event *
    2816                 :          0 : __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
    2817                 :            :                   struct rb_event_info *info)
    2818                 :            : {
    2819                 :            :         struct ring_buffer_event *event;
    2820                 :            :         struct buffer_page *tail_page;
    2821                 :            :         unsigned long tail, write;
    2822                 :            : 
    2823                 :            :         /*
    2824                 :            :          * If the time delta since the last event is too big to
    2825                 :            :          * hold in the time field of the event, then we append a
    2826                 :            :          * TIME EXTEND event ahead of the data event.
    2827                 :            :          */
    2828                 :          0 :         if (unlikely(info->add_timestamp))
    2829                 :          0 :                 info->length += RB_LEN_TIME_EXTEND;
    2830                 :            : 
    2831                 :            :         /* Don't let the compiler play games with cpu_buffer->tail_page */
    2832                 :          0 :         tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
    2833                 :          0 :         write = local_add_return(info->length, &tail_page->write);
    2834                 :            : 
    2835                 :            :         /* set write to only the index of the write */
    2836                 :          0 :         write &= RB_WRITE_MASK;
    2837                 :          0 :         tail = write - info->length;
    2838                 :            : 
    2839                 :            :         /*
    2840                 :            :          * If this is the first commit on the page, then it has the same
    2841                 :            :          * timestamp as the page itself.
    2842                 :            :          */
    2843                 :          0 :         if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
    2844                 :          0 :                 info->delta = 0;
    2845                 :            : 
    2846                 :            :         /* See if we shot pass the end of this buffer page */
    2847                 :          0 :         if (unlikely(write > BUF_PAGE_SIZE))
    2848                 :          0 :                 return rb_move_tail(cpu_buffer, tail, info);
    2849                 :            : 
    2850                 :            :         /* We reserved something on the buffer */
    2851                 :            : 
    2852                 :            :         event = __rb_page_index(tail_page, tail);
    2853                 :          0 :         rb_update_event(cpu_buffer, event, info);
    2854                 :            : 
    2855                 :          0 :         local_inc(&tail_page->entries);
    2856                 :            : 
    2857                 :            :         /*
    2858                 :            :          * If this is the first commit on the page, then update
    2859                 :            :          * its timestamp.
    2860                 :            :          */
    2861                 :          0 :         if (!tail)
    2862                 :          0 :                 tail_page->page->time_stamp = info->ts;
    2863                 :            : 
    2864                 :            :         /* account for these added bytes */
    2865                 :          0 :         local_add(info->length, &cpu_buffer->entries_bytes);
    2866                 :            : 
    2867                 :          0 :         return event;
    2868                 :            : }
    2869                 :            : 
    2870                 :            : static __always_inline struct ring_buffer_event *
    2871                 :            : rb_reserve_next_event(struct ring_buffer *buffer,
    2872                 :            :                       struct ring_buffer_per_cpu *cpu_buffer,
    2873                 :            :                       unsigned long length)
    2874                 :            : {
    2875                 :            :         struct ring_buffer_event *event;
    2876                 :            :         struct rb_event_info info;
    2877                 :            :         int nr_loops = 0;
    2878                 :            :         u64 diff;
    2879                 :            : 
    2880                 :          0 :         rb_start_commit(cpu_buffer);
    2881                 :            : 
    2882                 :            : #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
    2883                 :            :         /*
    2884                 :            :          * Due to the ability to swap a cpu buffer from a buffer
    2885                 :            :          * it is possible it was swapped before we committed.
    2886                 :            :          * (committing stops a swap). We check for it here and
    2887                 :            :          * if it happened, we have to fail the write.
    2888                 :            :          */
    2889                 :          0 :         barrier();
    2890                 :          0 :         if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
    2891                 :          0 :                 local_dec(&cpu_buffer->committing);
    2892                 :          0 :                 local_dec(&cpu_buffer->commits);
    2893                 :            :                 return NULL;
    2894                 :            :         }
    2895                 :            : #endif
    2896                 :            : 
    2897                 :          0 :         info.length = rb_calculate_event_length(length);
    2898                 :            :  again:
    2899                 :          0 :         info.add_timestamp = 0;
    2900                 :          0 :         info.delta = 0;
    2901                 :            : 
    2902                 :            :         /*
    2903                 :            :          * We allow for interrupts to reenter here and do a trace.
    2904                 :            :          * If one does, it will cause this original code to loop
    2905                 :            :          * back here. Even with heavy interrupts happening, this
    2906                 :            :          * should only happen a few times in a row. If this happens
    2907                 :            :          * 1000 times in a row, there must be either an interrupt
    2908                 :            :          * storm or we have something buggy.
    2909                 :            :          * Bail!
    2910                 :            :          */
    2911                 :          0 :         if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
    2912                 :            :                 goto out_fail;
    2913                 :            : 
    2914                 :          0 :         info.ts = rb_time_stamp(cpu_buffer->buffer);
    2915                 :          0 :         diff = info.ts - cpu_buffer->write_stamp;
    2916                 :            : 
    2917                 :            :         /* make sure this diff is calculated here */
    2918                 :          0 :         barrier();
    2919                 :            : 
    2920                 :          0 :         if (ring_buffer_time_stamp_abs(buffer)) {
    2921                 :          0 :                 info.delta = info.ts;
    2922                 :          0 :                 rb_handle_timestamp(cpu_buffer, &info);
    2923                 :            :         } else /* Did the write stamp get updated already? */
    2924                 :          0 :                 if (likely(info.ts >= cpu_buffer->write_stamp)) {
    2925                 :          0 :                 info.delta = diff;
    2926                 :          0 :                 if (unlikely(test_time_stamp(info.delta)))
    2927                 :          0 :                         rb_handle_timestamp(cpu_buffer, &info);
    2928                 :            :         }
    2929                 :            : 
    2930                 :          0 :         event = __rb_reserve_next(cpu_buffer, &info);
    2931                 :            : 
    2932                 :          0 :         if (unlikely(PTR_ERR(event) == -EAGAIN)) {
    2933                 :          0 :                 if (info.add_timestamp)
    2934                 :          0 :                         info.length -= RB_LEN_TIME_EXTEND;
    2935                 :            :                 goto again;
    2936                 :            :         }
    2937                 :            : 
    2938                 :          0 :         if (!event)
    2939                 :            :                 goto out_fail;
    2940                 :            : 
    2941                 :          0 :         return event;
    2942                 :            : 
    2943                 :            :  out_fail:
    2944                 :            :         rb_end_commit(cpu_buffer);
    2945                 :            :         return NULL;
    2946                 :            : }
    2947                 :            : 
    2948                 :            : /**
    2949                 :            :  * ring_buffer_lock_reserve - reserve a part of the buffer
    2950                 :            :  * @buffer: the ring buffer to reserve from
    2951                 :            :  * @length: the length of the data to reserve (excluding event header)
    2952                 :            :  *
    2953                 :            :  * Returns a reserved event on the ring buffer to copy directly to.
    2954                 :            :  * The user of this interface will need to get the body to write into
    2955                 :            :  * and can use the ring_buffer_event_data() interface.
    2956                 :            :  *
    2957                 :            :  * The length is the length of the data needed, not the event length
    2958                 :            :  * which also includes the event header.
    2959                 :            :  *
    2960                 :            :  * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
    2961                 :            :  * If NULL is returned, then nothing has been allocated or locked.
    2962                 :            :  */
    2963                 :            : struct ring_buffer_event *
    2964                 :          0 : ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
    2965                 :            : {
    2966                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    2967                 :            :         struct ring_buffer_event *event;
    2968                 :            :         int cpu;
    2969                 :            : 
    2970                 :            :         /* If we are tracing schedule, we don't want to recurse */
    2971                 :          0 :         preempt_disable_notrace();
    2972                 :            : 
    2973                 :          0 :         if (unlikely(atomic_read(&buffer->record_disabled)))
    2974                 :            :                 goto out;
    2975                 :            : 
    2976                 :          0 :         cpu = raw_smp_processor_id();
    2977                 :            : 
    2978                 :          0 :         if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
    2979                 :            :                 goto out;
    2980                 :            : 
    2981                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    2982                 :            : 
    2983                 :          0 :         if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
    2984                 :            :                 goto out;
    2985                 :            : 
    2986                 :          0 :         if (unlikely(length > BUF_MAX_DATA_SIZE))
    2987                 :            :                 goto out;
    2988                 :            : 
    2989                 :          0 :         if (unlikely(trace_recursive_lock(cpu_buffer)))
    2990                 :            :                 goto out;
    2991                 :            : 
    2992                 :            :         event = rb_reserve_next_event(buffer, cpu_buffer, length);
    2993                 :          0 :         if (!event)
    2994                 :            :                 goto out_unlock;
    2995                 :            : 
    2996                 :            :         return event;
    2997                 :            : 
    2998                 :            :  out_unlock:
    2999                 :            :         trace_recursive_unlock(cpu_buffer);
    3000                 :            :  out:
    3001                 :          0 :         preempt_enable_notrace();
    3002                 :          0 :         return NULL;
    3003                 :            : }
    3004                 :            : EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
    3005                 :            : 
    3006                 :            : /*
    3007                 :            :  * Decrement the entries to the page that an event is on.
    3008                 :            :  * The event does not even need to exist, only the pointer
    3009                 :            :  * to the page it is on. This may only be called before the commit
    3010                 :            :  * takes place.
    3011                 :            :  */
    3012                 :            : static inline void
    3013                 :          0 : rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
    3014                 :            :                    struct ring_buffer_event *event)
    3015                 :            : {
    3016                 :          0 :         unsigned long addr = (unsigned long)event;
    3017                 :          0 :         struct buffer_page *bpage = cpu_buffer->commit_page;
    3018                 :            :         struct buffer_page *start;
    3019                 :            : 
    3020                 :          0 :         addr &= PAGE_MASK;
    3021                 :            : 
    3022                 :            :         /* Do the likely case first */
    3023                 :          0 :         if (likely(bpage->page == (void *)addr)) {
    3024                 :          0 :                 local_dec(&bpage->entries);
    3025                 :            :                 return;
    3026                 :            :         }
    3027                 :            : 
    3028                 :            :         /*
    3029                 :            :          * Because the commit page may be on the reader page we
    3030                 :            :          * start with the next page and check the end loop there.
    3031                 :            :          */
    3032                 :            :         rb_inc_page(cpu_buffer, &bpage);
    3033                 :            :         start = bpage;
    3034                 :            :         do {
    3035                 :          0 :                 if (bpage->page == (void *)addr) {
    3036                 :          0 :                         local_dec(&bpage->entries);
    3037                 :            :                         return;
    3038                 :            :                 }
    3039                 :            :                 rb_inc_page(cpu_buffer, &bpage);
    3040                 :          0 :         } while (bpage != start);
    3041                 :            : 
    3042                 :            :         /* commit not part of this buffer?? */
    3043                 :          0 :         RB_WARN_ON(cpu_buffer, 1);
    3044                 :            : }
    3045                 :            : 
    3046                 :            : /**
    3047                 :            :  * ring_buffer_commit_discard - discard an event that has not been committed
    3048                 :            :  * @buffer: the ring buffer
    3049                 :            :  * @event: non committed event to discard
    3050                 :            :  *
    3051                 :            :  * Sometimes an event that is in the ring buffer needs to be ignored.
    3052                 :            :  * This function lets the user discard an event in the ring buffer
    3053                 :            :  * and then that event will not be read later.
    3054                 :            :  *
    3055                 :            :  * This function only works if it is called before the item has been
    3056                 :            :  * committed. It will try to free the event from the ring buffer
    3057                 :            :  * if another event has not been added behind it.
    3058                 :            :  *
    3059                 :            :  * If another event has been added behind it, it will set the event
    3060                 :            :  * up as discarded, and perform the commit.
    3061                 :            :  *
    3062                 :            :  * If this function is called, do not call ring_buffer_unlock_commit on
    3063                 :            :  * the event.
    3064                 :            :  */
    3065                 :          0 : void ring_buffer_discard_commit(struct ring_buffer *buffer,
    3066                 :            :                                 struct ring_buffer_event *event)
    3067                 :            : {
    3068                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3069                 :            :         int cpu;
    3070                 :            : 
    3071                 :            :         /* The event is discarded regardless */
    3072                 :          0 :         rb_event_discard(event);
    3073                 :            : 
    3074                 :          0 :         cpu = smp_processor_id();
    3075                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3076                 :            : 
    3077                 :            :         /*
    3078                 :            :          * This must only be called if the event has not been
    3079                 :            :          * committed yet. Thus we can assume that preemption
    3080                 :            :          * is still disabled.
    3081                 :            :          */
    3082                 :          0 :         RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
    3083                 :            : 
    3084                 :          0 :         rb_decrement_entry(cpu_buffer, event);
    3085                 :          0 :         if (rb_try_to_discard(cpu_buffer, event))
    3086                 :            :                 goto out;
    3087                 :            : 
    3088                 :            :         /*
    3089                 :            :          * The commit is still visible by the reader, so we
    3090                 :            :          * must still update the timestamp.
    3091                 :            :          */
    3092                 :            :         rb_update_write_stamp(cpu_buffer, event);
    3093                 :            :  out:
    3094                 :            :         rb_end_commit(cpu_buffer);
    3095                 :            : 
    3096                 :            :         trace_recursive_unlock(cpu_buffer);
    3097                 :            : 
    3098                 :          0 :         preempt_enable_notrace();
    3099                 :            : 
    3100                 :          0 : }
    3101                 :            : EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
    3102                 :            : 
    3103                 :            : /**
    3104                 :            :  * ring_buffer_write - write data to the buffer without reserving
    3105                 :            :  * @buffer: The ring buffer to write to.
    3106                 :            :  * @length: The length of the data being written (excluding the event header)
    3107                 :            :  * @data: The data to write to the buffer.
    3108                 :            :  *
    3109                 :            :  * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
    3110                 :            :  * one function. If you already have the data to write to the buffer, it
    3111                 :            :  * may be easier to simply call this function.
    3112                 :            :  *
    3113                 :            :  * Note, like ring_buffer_lock_reserve, the length is the length of the data
    3114                 :            :  * and not the length of the event which would hold the header.
    3115                 :            :  */
    3116                 :          0 : int ring_buffer_write(struct ring_buffer *buffer,
    3117                 :            :                       unsigned long length,
    3118                 :            :                       void *data)
    3119                 :            : {
    3120                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3121                 :            :         struct ring_buffer_event *event;
    3122                 :            :         void *body;
    3123                 :            :         int ret = -EBUSY;
    3124                 :            :         int cpu;
    3125                 :            : 
    3126                 :          0 :         preempt_disable_notrace();
    3127                 :            : 
    3128                 :          0 :         if (atomic_read(&buffer->record_disabled))
    3129                 :            :                 goto out;
    3130                 :            : 
    3131                 :          0 :         cpu = raw_smp_processor_id();
    3132                 :            : 
    3133                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3134                 :            :                 goto out;
    3135                 :            : 
    3136                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3137                 :            : 
    3138                 :          0 :         if (atomic_read(&cpu_buffer->record_disabled))
    3139                 :            :                 goto out;
    3140                 :            : 
    3141                 :          0 :         if (length > BUF_MAX_DATA_SIZE)
    3142                 :            :                 goto out;
    3143                 :            : 
    3144                 :          0 :         if (unlikely(trace_recursive_lock(cpu_buffer)))
    3145                 :            :                 goto out;
    3146                 :            : 
    3147                 :            :         event = rb_reserve_next_event(buffer, cpu_buffer, length);
    3148                 :          0 :         if (!event)
    3149                 :            :                 goto out_unlock;
    3150                 :            : 
    3151                 :            :         body = rb_event_data(event);
    3152                 :            : 
    3153                 :          0 :         memcpy(body, data, length);
    3154                 :            : 
    3155                 :          0 :         rb_commit(cpu_buffer, event);
    3156                 :            : 
    3157                 :            :         rb_wakeups(buffer, cpu_buffer);
    3158                 :            : 
    3159                 :            :         ret = 0;
    3160                 :            : 
    3161                 :            :  out_unlock:
    3162                 :            :         trace_recursive_unlock(cpu_buffer);
    3163                 :            : 
    3164                 :            :  out:
    3165                 :          0 :         preempt_enable_notrace();
    3166                 :            : 
    3167                 :          0 :         return ret;
    3168                 :            : }
    3169                 :            : EXPORT_SYMBOL_GPL(ring_buffer_write);
    3170                 :            : 
    3171                 :          0 : static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
    3172                 :            : {
    3173                 :          0 :         struct buffer_page *reader = cpu_buffer->reader_page;
    3174                 :          0 :         struct buffer_page *head = rb_set_head_page(cpu_buffer);
    3175                 :          0 :         struct buffer_page *commit = cpu_buffer->commit_page;
    3176                 :            : 
    3177                 :            :         /* In case of error, head will be NULL */
    3178                 :          0 :         if (unlikely(!head))
    3179                 :            :                 return true;
    3180                 :            : 
    3181                 :          0 :         return reader->read == rb_page_commit(reader) &&
    3182                 :          0 :                 (commit == reader ||
    3183                 :          0 :                  (commit == head &&
    3184                 :          0 :                   head->read == rb_page_commit(commit)));
    3185                 :            : }
    3186                 :            : 
    3187                 :            : /**
    3188                 :            :  * ring_buffer_record_disable - stop all writes into the buffer
    3189                 :            :  * @buffer: The ring buffer to stop writes to.
    3190                 :            :  *
    3191                 :            :  * This prevents all writes to the buffer. Any attempt to write
    3192                 :            :  * to the buffer after this will fail and return NULL.
    3193                 :            :  *
    3194                 :            :  * The caller should call synchronize_rcu() after this.
    3195                 :            :  */
    3196                 :          0 : void ring_buffer_record_disable(struct ring_buffer *buffer)
    3197                 :            : {
    3198                 :          0 :         atomic_inc(&buffer->record_disabled);
    3199                 :          0 : }
    3200                 :            : EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
    3201                 :            : 
    3202                 :            : /**
    3203                 :            :  * ring_buffer_record_enable - enable writes to the buffer
    3204                 :            :  * @buffer: The ring buffer to enable writes
    3205                 :            :  *
    3206                 :            :  * Note, multiple disables will need the same number of enables
    3207                 :            :  * to truly enable the writing (much like preempt_disable).
    3208                 :            :  */
    3209                 :          0 : void ring_buffer_record_enable(struct ring_buffer *buffer)
    3210                 :            : {
    3211                 :          0 :         atomic_dec(&buffer->record_disabled);
    3212                 :          0 : }
    3213                 :            : EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
    3214                 :            : 
    3215                 :            : /**
    3216                 :            :  * ring_buffer_record_off - stop all writes into the buffer
    3217                 :            :  * @buffer: The ring buffer to stop writes to.
    3218                 :            :  *
    3219                 :            :  * This prevents all writes to the buffer. Any attempt to write
    3220                 :            :  * to the buffer after this will fail and return NULL.
    3221                 :            :  *
    3222                 :            :  * This is different than ring_buffer_record_disable() as
    3223                 :            :  * it works like an on/off switch, where as the disable() version
    3224                 :            :  * must be paired with a enable().
    3225                 :            :  */
    3226                 :          0 : void ring_buffer_record_off(struct ring_buffer *buffer)
    3227                 :            : {
    3228                 :            :         unsigned int rd;
    3229                 :            :         unsigned int new_rd;
    3230                 :            : 
    3231                 :            :         do {
    3232                 :          0 :                 rd = atomic_read(&buffer->record_disabled);
    3233                 :          0 :                 new_rd = rd | RB_BUFFER_OFF;
    3234                 :          0 :         } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
    3235                 :          0 : }
    3236                 :            : EXPORT_SYMBOL_GPL(ring_buffer_record_off);
    3237                 :            : 
    3238                 :            : /**
    3239                 :            :  * ring_buffer_record_on - restart writes into the buffer
    3240                 :            :  * @buffer: The ring buffer to start writes to.
    3241                 :            :  *
    3242                 :            :  * This enables all writes to the buffer that was disabled by
    3243                 :            :  * ring_buffer_record_off().
    3244                 :            :  *
    3245                 :            :  * This is different than ring_buffer_record_enable() as
    3246                 :            :  * it works like an on/off switch, where as the enable() version
    3247                 :            :  * must be paired with a disable().
    3248                 :            :  */
    3249                 :          0 : void ring_buffer_record_on(struct ring_buffer *buffer)
    3250                 :            : {
    3251                 :            :         unsigned int rd;
    3252                 :            :         unsigned int new_rd;
    3253                 :            : 
    3254                 :            :         do {
    3255                 :          0 :                 rd = atomic_read(&buffer->record_disabled);
    3256                 :          0 :                 new_rd = rd & ~RB_BUFFER_OFF;
    3257                 :          0 :         } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
    3258                 :          0 : }
    3259                 :            : EXPORT_SYMBOL_GPL(ring_buffer_record_on);
    3260                 :            : 
    3261                 :            : /**
    3262                 :            :  * ring_buffer_record_is_on - return true if the ring buffer can write
    3263                 :            :  * @buffer: The ring buffer to see if write is enabled
    3264                 :            :  *
    3265                 :            :  * Returns true if the ring buffer is in a state that it accepts writes.
    3266                 :            :  */
    3267                 :          0 : bool ring_buffer_record_is_on(struct ring_buffer *buffer)
    3268                 :            : {
    3269                 :          0 :         return !atomic_read(&buffer->record_disabled);
    3270                 :            : }
    3271                 :            : 
    3272                 :            : /**
    3273                 :            :  * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
    3274                 :            :  * @buffer: The ring buffer to see if write is set enabled
    3275                 :            :  *
    3276                 :            :  * Returns true if the ring buffer is set writable by ring_buffer_record_on().
    3277                 :            :  * Note that this does NOT mean it is in a writable state.
    3278                 :            :  *
    3279                 :            :  * It may return true when the ring buffer has been disabled by
    3280                 :            :  * ring_buffer_record_disable(), as that is a temporary disabling of
    3281                 :            :  * the ring buffer.
    3282                 :            :  */
    3283                 :          0 : bool ring_buffer_record_is_set_on(struct ring_buffer *buffer)
    3284                 :            : {
    3285                 :          0 :         return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
    3286                 :            : }
    3287                 :            : 
    3288                 :            : /**
    3289                 :            :  * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
    3290                 :            :  * @buffer: The ring buffer to stop writes to.
    3291                 :            :  * @cpu: The CPU buffer to stop
    3292                 :            :  *
    3293                 :            :  * This prevents all writes to the buffer. Any attempt to write
    3294                 :            :  * to the buffer after this will fail and return NULL.
    3295                 :            :  *
    3296                 :            :  * The caller should call synchronize_rcu() after this.
    3297                 :            :  */
    3298                 :          0 : void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
    3299                 :            : {
    3300                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3301                 :            : 
    3302                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3303                 :          0 :                 return;
    3304                 :            : 
    3305                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3306                 :          0 :         atomic_inc(&cpu_buffer->record_disabled);
    3307                 :            : }
    3308                 :            : EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
    3309                 :            : 
    3310                 :            : /**
    3311                 :            :  * ring_buffer_record_enable_cpu - enable writes to the buffer
    3312                 :            :  * @buffer: The ring buffer to enable writes
    3313                 :            :  * @cpu: The CPU to enable.
    3314                 :            :  *
    3315                 :            :  * Note, multiple disables will need the same number of enables
    3316                 :            :  * to truly enable the writing (much like preempt_disable).
    3317                 :            :  */
    3318                 :          0 : void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
    3319                 :            : {
    3320                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3321                 :            : 
    3322                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3323                 :          0 :                 return;
    3324                 :            : 
    3325                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3326                 :          0 :         atomic_dec(&cpu_buffer->record_disabled);
    3327                 :            : }
    3328                 :            : EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
    3329                 :            : 
    3330                 :            : /*
    3331                 :            :  * The total entries in the ring buffer is the running counter
    3332                 :            :  * of entries entered into the ring buffer, minus the sum of
    3333                 :            :  * the entries read from the ring buffer and the number of
    3334                 :            :  * entries that were overwritten.
    3335                 :            :  */
    3336                 :            : static inline unsigned long
    3337                 :            : rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
    3338                 :            : {
    3339                 :          0 :         return local_read(&cpu_buffer->entries) -
    3340                 :          0 :                 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
    3341                 :            : }
    3342                 :            : 
    3343                 :            : /**
    3344                 :            :  * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
    3345                 :            :  * @buffer: The ring buffer
    3346                 :            :  * @cpu: The per CPU buffer to read from.
    3347                 :            :  */
    3348                 :          0 : u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
    3349                 :            : {
    3350                 :            :         unsigned long flags;
    3351                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3352                 :            :         struct buffer_page *bpage;
    3353                 :            :         u64 ret = 0;
    3354                 :            : 
    3355                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3356                 :            :                 return 0;
    3357                 :            : 
    3358                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3359                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    3360                 :            :         /*
    3361                 :            :          * if the tail is on reader_page, oldest time stamp is on the reader
    3362                 :            :          * page
    3363                 :            :          */
    3364                 :          0 :         if (cpu_buffer->tail_page == cpu_buffer->reader_page)
    3365                 :            :                 bpage = cpu_buffer->reader_page;
    3366                 :            :         else
    3367                 :          0 :                 bpage = rb_set_head_page(cpu_buffer);
    3368                 :          0 :         if (bpage)
    3369                 :          0 :                 ret = bpage->page->time_stamp;
    3370                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    3371                 :            : 
    3372                 :          0 :         return ret;
    3373                 :            : }
    3374                 :            : EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
    3375                 :            : 
    3376                 :            : /**
    3377                 :            :  * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
    3378                 :            :  * @buffer: The ring buffer
    3379                 :            :  * @cpu: The per CPU buffer to read from.
    3380                 :            :  */
    3381                 :          0 : unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
    3382                 :            : {
    3383                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3384                 :            :         unsigned long ret;
    3385                 :            : 
    3386                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3387                 :            :                 return 0;
    3388                 :            : 
    3389                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3390                 :          0 :         ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
    3391                 :            : 
    3392                 :          0 :         return ret;
    3393                 :            : }
    3394                 :            : EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
    3395                 :            : 
    3396                 :            : /**
    3397                 :            :  * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
    3398                 :            :  * @buffer: The ring buffer
    3399                 :            :  * @cpu: The per CPU buffer to get the entries from.
    3400                 :            :  */
    3401                 :          0 : unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
    3402                 :            : {
    3403                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3404                 :            : 
    3405                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3406                 :            :                 return 0;
    3407                 :            : 
    3408                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3409                 :            : 
    3410                 :          0 :         return rb_num_of_entries(cpu_buffer);
    3411                 :            : }
    3412                 :            : EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
    3413                 :            : 
    3414                 :            : /**
    3415                 :            :  * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
    3416                 :            :  * buffer wrapping around (only if RB_FL_OVERWRITE is on).
    3417                 :            :  * @buffer: The ring buffer
    3418                 :            :  * @cpu: The per CPU buffer to get the number of overruns from
    3419                 :            :  */
    3420                 :          0 : unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
    3421                 :            : {
    3422                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3423                 :            :         unsigned long ret;
    3424                 :            : 
    3425                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3426                 :            :                 return 0;
    3427                 :            : 
    3428                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3429                 :          0 :         ret = local_read(&cpu_buffer->overrun);
    3430                 :            : 
    3431                 :          0 :         return ret;
    3432                 :            : }
    3433                 :            : EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
    3434                 :            : 
    3435                 :            : /**
    3436                 :            :  * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
    3437                 :            :  * commits failing due to the buffer wrapping around while there are uncommitted
    3438                 :            :  * events, such as during an interrupt storm.
    3439                 :            :  * @buffer: The ring buffer
    3440                 :            :  * @cpu: The per CPU buffer to get the number of overruns from
    3441                 :            :  */
    3442                 :            : unsigned long
    3443                 :          0 : ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
    3444                 :            : {
    3445                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3446                 :            :         unsigned long ret;
    3447                 :            : 
    3448                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3449                 :            :                 return 0;
    3450                 :            : 
    3451                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3452                 :          0 :         ret = local_read(&cpu_buffer->commit_overrun);
    3453                 :            : 
    3454                 :          0 :         return ret;
    3455                 :            : }
    3456                 :            : EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
    3457                 :            : 
    3458                 :            : /**
    3459                 :            :  * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
    3460                 :            :  * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
    3461                 :            :  * @buffer: The ring buffer
    3462                 :            :  * @cpu: The per CPU buffer to get the number of overruns from
    3463                 :            :  */
    3464                 :            : unsigned long
    3465                 :          0 : ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
    3466                 :            : {
    3467                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3468                 :            :         unsigned long ret;
    3469                 :            : 
    3470                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3471                 :            :                 return 0;
    3472                 :            : 
    3473                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3474                 :          0 :         ret = local_read(&cpu_buffer->dropped_events);
    3475                 :            : 
    3476                 :          0 :         return ret;
    3477                 :            : }
    3478                 :            : EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
    3479                 :            : 
    3480                 :            : /**
    3481                 :            :  * ring_buffer_read_events_cpu - get the number of events successfully read
    3482                 :            :  * @buffer: The ring buffer
    3483                 :            :  * @cpu: The per CPU buffer to get the number of events read
    3484                 :            :  */
    3485                 :            : unsigned long
    3486                 :          0 : ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
    3487                 :            : {
    3488                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3489                 :            : 
    3490                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    3491                 :            :                 return 0;
    3492                 :            : 
    3493                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    3494                 :          0 :         return cpu_buffer->read;
    3495                 :            : }
    3496                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
    3497                 :            : 
    3498                 :            : /**
    3499                 :            :  * ring_buffer_entries - get the number of entries in a buffer
    3500                 :            :  * @buffer: The ring buffer
    3501                 :            :  *
    3502                 :            :  * Returns the total number of entries in the ring buffer
    3503                 :            :  * (all CPU entries)
    3504                 :            :  */
    3505                 :          0 : unsigned long ring_buffer_entries(struct ring_buffer *buffer)
    3506                 :            : {
    3507                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3508                 :            :         unsigned long entries = 0;
    3509                 :            :         int cpu;
    3510                 :            : 
    3511                 :            :         /* if you care about this being correct, lock the buffer */
    3512                 :          0 :         for_each_buffer_cpu(buffer, cpu) {
    3513                 :          0 :                 cpu_buffer = buffer->buffers[cpu];
    3514                 :          0 :                 entries += rb_num_of_entries(cpu_buffer);
    3515                 :            :         }
    3516                 :            : 
    3517                 :          0 :         return entries;
    3518                 :            : }
    3519                 :            : EXPORT_SYMBOL_GPL(ring_buffer_entries);
    3520                 :            : 
    3521                 :            : /**
    3522                 :            :  * ring_buffer_overruns - get the number of overruns in buffer
    3523                 :            :  * @buffer: The ring buffer
    3524                 :            :  *
    3525                 :            :  * Returns the total number of overruns in the ring buffer
    3526                 :            :  * (all CPU entries)
    3527                 :            :  */
    3528                 :          0 : unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
    3529                 :            : {
    3530                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3531                 :            :         unsigned long overruns = 0;
    3532                 :            :         int cpu;
    3533                 :            : 
    3534                 :            :         /* if you care about this being correct, lock the buffer */
    3535                 :          0 :         for_each_buffer_cpu(buffer, cpu) {
    3536                 :          0 :                 cpu_buffer = buffer->buffers[cpu];
    3537                 :          0 :                 overruns += local_read(&cpu_buffer->overrun);
    3538                 :            :         }
    3539                 :            : 
    3540                 :          0 :         return overruns;
    3541                 :            : }
    3542                 :            : EXPORT_SYMBOL_GPL(ring_buffer_overruns);
    3543                 :            : 
    3544                 :          0 : static void rb_iter_reset(struct ring_buffer_iter *iter)
    3545                 :            : {
    3546                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
    3547                 :            : 
    3548                 :            :         /* Iterator usage is expected to have record disabled */
    3549                 :          0 :         iter->head_page = cpu_buffer->reader_page;
    3550                 :          0 :         iter->head = cpu_buffer->reader_page->read;
    3551                 :            : 
    3552                 :          0 :         iter->cache_reader_page = iter->head_page;
    3553                 :          0 :         iter->cache_read = cpu_buffer->read;
    3554                 :            : 
    3555                 :          0 :         if (iter->head)
    3556                 :          0 :                 iter->read_stamp = cpu_buffer->read_stamp;
    3557                 :            :         else
    3558                 :          0 :                 iter->read_stamp = iter->head_page->page->time_stamp;
    3559                 :          0 : }
    3560                 :            : 
    3561                 :            : /**
    3562                 :            :  * ring_buffer_iter_reset - reset an iterator
    3563                 :            :  * @iter: The iterator to reset
    3564                 :            :  *
    3565                 :            :  * Resets the iterator, so that it will start from the beginning
    3566                 :            :  * again.
    3567                 :            :  */
    3568                 :          0 : void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
    3569                 :            : {
    3570                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3571                 :            :         unsigned long flags;
    3572                 :            : 
    3573                 :          0 :         if (!iter)
    3574                 :          0 :                 return;
    3575                 :            : 
    3576                 :          0 :         cpu_buffer = iter->cpu_buffer;
    3577                 :            : 
    3578                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    3579                 :          0 :         rb_iter_reset(iter);
    3580                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    3581                 :            : }
    3582                 :            : EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
    3583                 :            : 
    3584                 :            : /**
    3585                 :            :  * ring_buffer_iter_empty - check if an iterator has no more to read
    3586                 :            :  * @iter: The iterator to check
    3587                 :            :  */
    3588                 :          0 : int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
    3589                 :            : {
    3590                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3591                 :            :         struct buffer_page *reader;
    3592                 :            :         struct buffer_page *head_page;
    3593                 :            :         struct buffer_page *commit_page;
    3594                 :            :         unsigned commit;
    3595                 :            : 
    3596                 :          0 :         cpu_buffer = iter->cpu_buffer;
    3597                 :            : 
    3598                 :            :         /* Remember, trace recording is off when iterator is in use */
    3599                 :          0 :         reader = cpu_buffer->reader_page;
    3600                 :          0 :         head_page = cpu_buffer->head_page;
    3601                 :          0 :         commit_page = cpu_buffer->commit_page;
    3602                 :            :         commit = rb_page_commit(commit_page);
    3603                 :            : 
    3604                 :          0 :         return ((iter->head_page == commit_page && iter->head == commit) ||
    3605                 :          0 :                 (iter->head_page == reader && commit_page == head_page &&
    3606                 :          0 :                  head_page->read == commit &&
    3607                 :          0 :                  iter->head == rb_page_commit(cpu_buffer->reader_page)));
    3608                 :            : }
    3609                 :            : EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
    3610                 :            : 
    3611                 :            : static void
    3612                 :          0 : rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
    3613                 :            :                      struct ring_buffer_event *event)
    3614                 :            : {
    3615                 :            :         u64 delta;
    3616                 :            : 
    3617                 :          0 :         switch (event->type_len) {
    3618                 :            :         case RINGBUF_TYPE_PADDING:
    3619                 :            :                 return;
    3620                 :            : 
    3621                 :            :         case RINGBUF_TYPE_TIME_EXTEND:
    3622                 :            :                 delta = ring_buffer_event_time_stamp(event);
    3623                 :          0 :                 cpu_buffer->read_stamp += delta;
    3624                 :          0 :                 return;
    3625                 :            : 
    3626                 :            :         case RINGBUF_TYPE_TIME_STAMP:
    3627                 :            :                 delta = ring_buffer_event_time_stamp(event);
    3628                 :          0 :                 cpu_buffer->read_stamp = delta;
    3629                 :          0 :                 return;
    3630                 :            : 
    3631                 :            :         case RINGBUF_TYPE_DATA:
    3632                 :          0 :                 cpu_buffer->read_stamp += event->time_delta;
    3633                 :          0 :                 return;
    3634                 :            : 
    3635                 :            :         default:
    3636                 :          0 :                 BUG();
    3637                 :            :         }
    3638                 :            :         return;
    3639                 :            : }
    3640                 :            : 
    3641                 :            : static void
    3642                 :          0 : rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
    3643                 :            :                           struct ring_buffer_event *event)
    3644                 :            : {
    3645                 :            :         u64 delta;
    3646                 :            : 
    3647                 :          0 :         switch (event->type_len) {
    3648                 :            :         case RINGBUF_TYPE_PADDING:
    3649                 :            :                 return;
    3650                 :            : 
    3651                 :            :         case RINGBUF_TYPE_TIME_EXTEND:
    3652                 :            :                 delta = ring_buffer_event_time_stamp(event);
    3653                 :          0 :                 iter->read_stamp += delta;
    3654                 :          0 :                 return;
    3655                 :            : 
    3656                 :            :         case RINGBUF_TYPE_TIME_STAMP:
    3657                 :            :                 delta = ring_buffer_event_time_stamp(event);
    3658                 :          0 :                 iter->read_stamp = delta;
    3659                 :          0 :                 return;
    3660                 :            : 
    3661                 :            :         case RINGBUF_TYPE_DATA:
    3662                 :          0 :                 iter->read_stamp += event->time_delta;
    3663                 :          0 :                 return;
    3664                 :            : 
    3665                 :            :         default:
    3666                 :          0 :                 BUG();
    3667                 :            :         }
    3668                 :            :         return;
    3669                 :            : }
    3670                 :            : 
    3671                 :            : static struct buffer_page *
    3672                 :          0 : rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
    3673                 :            : {
    3674                 :            :         struct buffer_page *reader = NULL;
    3675                 :            :         unsigned long overwrite;
    3676                 :            :         unsigned long flags;
    3677                 :            :         int nr_loops = 0;
    3678                 :            :         int ret;
    3679                 :            : 
    3680                 :          0 :         local_irq_save(flags);
    3681                 :          0 :         arch_spin_lock(&cpu_buffer->lock);
    3682                 :            : 
    3683                 :            :  again:
    3684                 :            :         /*
    3685                 :            :          * This should normally only loop twice. But because the
    3686                 :            :          * start of the reader inserts an empty page, it causes
    3687                 :            :          * a case where we will loop three times. There should be no
    3688                 :            :          * reason to loop four times (that I know of).
    3689                 :            :          */
    3690                 :          0 :         if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
    3691                 :            :                 reader = NULL;
    3692                 :            :                 goto out;
    3693                 :            :         }
    3694                 :            : 
    3695                 :          0 :         reader = cpu_buffer->reader_page;
    3696                 :            : 
    3697                 :            :         /* If there's more to read, return this page */
    3698                 :          0 :         if (cpu_buffer->reader_page->read < rb_page_size(reader))
    3699                 :            :                 goto out;
    3700                 :            : 
    3701                 :            :         /* Never should we have an index greater than the size */
    3702                 :          0 :         if (RB_WARN_ON(cpu_buffer,
    3703                 :            :                        cpu_buffer->reader_page->read > rb_page_size(reader)))
    3704                 :            :                 goto out;
    3705                 :            : 
    3706                 :            :         /* check if we caught up to the tail */
    3707                 :            :         reader = NULL;
    3708                 :          0 :         if (cpu_buffer->commit_page == cpu_buffer->reader_page)
    3709                 :            :                 goto out;
    3710                 :            : 
    3711                 :            :         /* Don't bother swapping if the ring buffer is empty */
    3712                 :          0 :         if (rb_num_of_entries(cpu_buffer) == 0)
    3713                 :            :                 goto out;
    3714                 :            : 
    3715                 :            :         /*
    3716                 :            :          * Reset the reader page to size zero.
    3717                 :            :          */
    3718                 :            :         local_set(&cpu_buffer->reader_page->write, 0);
    3719                 :          0 :         local_set(&cpu_buffer->reader_page->entries, 0);
    3720                 :          0 :         local_set(&cpu_buffer->reader_page->page->commit, 0);
    3721                 :          0 :         cpu_buffer->reader_page->real_end = 0;
    3722                 :            : 
    3723                 :            :  spin:
    3724                 :            :         /*
    3725                 :            :          * Splice the empty reader page into the list around the head.
    3726                 :            :          */
    3727                 :          0 :         reader = rb_set_head_page(cpu_buffer);
    3728                 :          0 :         if (!reader)
    3729                 :            :                 goto out;
    3730                 :          0 :         cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
    3731                 :          0 :         cpu_buffer->reader_page->list.prev = reader->list.prev;
    3732                 :            : 
    3733                 :            :         /*
    3734                 :            :          * cpu_buffer->pages just needs to point to the buffer, it
    3735                 :            :          *  has no specific buffer page to point to. Lets move it out
    3736                 :            :          *  of our way so we don't accidentally swap it.
    3737                 :            :          */
    3738                 :          0 :         cpu_buffer->pages = reader->list.prev;
    3739                 :            : 
    3740                 :            :         /* The reader page will be pointing to the new head */
    3741                 :          0 :         rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
    3742                 :            : 
    3743                 :            :         /*
    3744                 :            :          * We want to make sure we read the overruns after we set up our
    3745                 :            :          * pointers to the next object. The writer side does a
    3746                 :            :          * cmpxchg to cross pages which acts as the mb on the writer
    3747                 :            :          * side. Note, the reader will constantly fail the swap
    3748                 :            :          * while the writer is updating the pointers, so this
    3749                 :            :          * guarantees that the overwrite recorded here is the one we
    3750                 :            :          * want to compare with the last_overrun.
    3751                 :            :          */
    3752                 :          0 :         smp_mb();
    3753                 :          0 :         overwrite = local_read(&(cpu_buffer->overrun));
    3754                 :            : 
    3755                 :            :         /*
    3756                 :            :          * Here's the tricky part.
    3757                 :            :          *
    3758                 :            :          * We need to move the pointer past the header page.
    3759                 :            :          * But we can only do that if a writer is not currently
    3760                 :            :          * moving it. The page before the header page has the
    3761                 :            :          * flag bit '1' set if it is pointing to the page we want.
    3762                 :            :          * but if the writer is in the process of moving it
    3763                 :            :          * than it will be '2' or already moved '0'.
    3764                 :            :          */
    3765                 :            : 
    3766                 :          0 :         ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
    3767                 :            : 
    3768                 :            :         /*
    3769                 :            :          * If we did not convert it, then we must try again.
    3770                 :            :          */
    3771                 :          0 :         if (!ret)
    3772                 :            :                 goto spin;
    3773                 :            : 
    3774                 :            :         /*
    3775                 :            :          * Yay! We succeeded in replacing the page.
    3776                 :            :          *
    3777                 :            :          * Now make the new head point back to the reader page.
    3778                 :            :          */
    3779                 :          0 :         rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
    3780                 :            :         rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
    3781                 :            : 
    3782                 :          0 :         local_inc(&cpu_buffer->pages_read);
    3783                 :            : 
    3784                 :            :         /* Finally update the reader page to the new head */
    3785                 :          0 :         cpu_buffer->reader_page = reader;
    3786                 :          0 :         cpu_buffer->reader_page->read = 0;
    3787                 :            : 
    3788                 :          0 :         if (overwrite != cpu_buffer->last_overrun) {
    3789                 :          0 :                 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
    3790                 :          0 :                 cpu_buffer->last_overrun = overwrite;
    3791                 :            :         }
    3792                 :            : 
    3793                 :            :         goto again;
    3794                 :            : 
    3795                 :            :  out:
    3796                 :            :         /* Update the read_stamp on the first event */
    3797                 :          0 :         if (reader && reader->read == 0)
    3798                 :          0 :                 cpu_buffer->read_stamp = reader->page->time_stamp;
    3799                 :            : 
    3800                 :            :         arch_spin_unlock(&cpu_buffer->lock);
    3801                 :          0 :         local_irq_restore(flags);
    3802                 :            : 
    3803                 :          0 :         return reader;
    3804                 :            : }
    3805                 :            : 
    3806                 :          0 : static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
    3807                 :            : {
    3808                 :            :         struct ring_buffer_event *event;
    3809                 :            :         struct buffer_page *reader;
    3810                 :            :         unsigned length;
    3811                 :            : 
    3812                 :          0 :         reader = rb_get_reader_page(cpu_buffer);
    3813                 :            : 
    3814                 :            :         /* This function should not be called when buffer is empty */
    3815                 :          0 :         if (RB_WARN_ON(cpu_buffer, !reader))
    3816                 :          0 :                 return;
    3817                 :            : 
    3818                 :            :         event = rb_reader_event(cpu_buffer);
    3819                 :            : 
    3820                 :          0 :         if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
    3821                 :          0 :                 cpu_buffer->read++;
    3822                 :            : 
    3823                 :          0 :         rb_update_read_stamp(cpu_buffer, event);
    3824                 :            : 
    3825                 :          0 :         length = rb_event_length(event);
    3826                 :          0 :         cpu_buffer->reader_page->read += length;
    3827                 :            : }
    3828                 :            : 
    3829                 :          0 : static void rb_advance_iter(struct ring_buffer_iter *iter)
    3830                 :            : {
    3831                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3832                 :            :         struct ring_buffer_event *event;
    3833                 :            :         unsigned length;
    3834                 :            : 
    3835                 :          0 :         cpu_buffer = iter->cpu_buffer;
    3836                 :            : 
    3837                 :            :         /*
    3838                 :            :          * Check if we are at the end of the buffer.
    3839                 :            :          */
    3840                 :          0 :         if (iter->head >= rb_page_size(iter->head_page)) {
    3841                 :            :                 /* discarded commits can make the page empty */
    3842                 :          0 :                 if (iter->head_page == cpu_buffer->commit_page)
    3843                 :            :                         return;
    3844                 :          0 :                 rb_inc_iter(iter);
    3845                 :          0 :                 return;
    3846                 :            :         }
    3847                 :            : 
    3848                 :            :         event = rb_iter_head_event(iter);
    3849                 :            : 
    3850                 :          0 :         length = rb_event_length(event);
    3851                 :            : 
    3852                 :            :         /*
    3853                 :            :          * This should not be called to advance the header if we are
    3854                 :            :          * at the tail of the buffer.
    3855                 :            :          */
    3856                 :          0 :         if (RB_WARN_ON(cpu_buffer,
    3857                 :            :                        (iter->head_page == cpu_buffer->commit_page) &&
    3858                 :            :                        (iter->head + length > rb_commit_index(cpu_buffer))))
    3859                 :            :                 return;
    3860                 :            : 
    3861                 :          0 :         rb_update_iter_read_stamp(iter, event);
    3862                 :            : 
    3863                 :          0 :         iter->head += length;
    3864                 :            : 
    3865                 :            :         /* check for end of page padding */
    3866                 :          0 :         if ((iter->head >= rb_page_size(iter->head_page)) &&
    3867                 :          0 :             (iter->head_page != cpu_buffer->commit_page))
    3868                 :          0 :                 rb_inc_iter(iter);
    3869                 :            : }
    3870                 :            : 
    3871                 :            : static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
    3872                 :            : {
    3873                 :          0 :         return cpu_buffer->lost_events;
    3874                 :            : }
    3875                 :            : 
    3876                 :            : static struct ring_buffer_event *
    3877                 :          0 : rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
    3878                 :            :                unsigned long *lost_events)
    3879                 :            : {
    3880                 :            :         struct ring_buffer_event *event;
    3881                 :            :         struct buffer_page *reader;
    3882                 :            :         int nr_loops = 0;
    3883                 :            : 
    3884                 :          0 :         if (ts)
    3885                 :          0 :                 *ts = 0;
    3886                 :            :  again:
    3887                 :            :         /*
    3888                 :            :          * We repeat when a time extend is encountered.
    3889                 :            :          * Since the time extend is always attached to a data event,
    3890                 :            :          * we should never loop more than once.
    3891                 :            :          * (We never hit the following condition more than twice).
    3892                 :            :          */
    3893                 :          0 :         if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
    3894                 :            :                 return NULL;
    3895                 :            : 
    3896                 :          0 :         reader = rb_get_reader_page(cpu_buffer);
    3897                 :          0 :         if (!reader)
    3898                 :            :                 return NULL;
    3899                 :            : 
    3900                 :            :         event = rb_reader_event(cpu_buffer);
    3901                 :            : 
    3902                 :          0 :         switch (event->type_len) {
    3903                 :            :         case RINGBUF_TYPE_PADDING:
    3904                 :          0 :                 if (rb_null_event(event))
    3905                 :          0 :                         RB_WARN_ON(cpu_buffer, 1);
    3906                 :            :                 /*
    3907                 :            :                  * Because the writer could be discarding every
    3908                 :            :                  * event it creates (which would probably be bad)
    3909                 :            :                  * if we were to go back to "again" then we may never
    3910                 :            :                  * catch up, and will trigger the warn on, or lock
    3911                 :            :                  * the box. Return the padding, and we will release
    3912                 :            :                  * the current locks, and try again.
    3913                 :            :                  */
    3914                 :          0 :                 return event;
    3915                 :            : 
    3916                 :            :         case RINGBUF_TYPE_TIME_EXTEND:
    3917                 :            :                 /* Internal data, OK to advance */
    3918                 :          0 :                 rb_advance_reader(cpu_buffer);
    3919                 :          0 :                 goto again;
    3920                 :            : 
    3921                 :            :         case RINGBUF_TYPE_TIME_STAMP:
    3922                 :          0 :                 if (ts) {
    3923                 :          0 :                         *ts = ring_buffer_event_time_stamp(event);
    3924                 :            :                         ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
    3925                 :            :                                                          cpu_buffer->cpu, ts);
    3926                 :            :                 }
    3927                 :            :                 /* Internal data, OK to advance */
    3928                 :          0 :                 rb_advance_reader(cpu_buffer);
    3929                 :          0 :                 goto again;
    3930                 :            : 
    3931                 :            :         case RINGBUF_TYPE_DATA:
    3932                 :          0 :                 if (ts && !(*ts)) {
    3933                 :          0 :                         *ts = cpu_buffer->read_stamp + event->time_delta;
    3934                 :            :                         ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
    3935                 :            :                                                          cpu_buffer->cpu, ts);
    3936                 :            :                 }
    3937                 :          0 :                 if (lost_events)
    3938                 :          0 :                         *lost_events = rb_lost_events(cpu_buffer);
    3939                 :          0 :                 return event;
    3940                 :            : 
    3941                 :            :         default:
    3942                 :          0 :                 BUG();
    3943                 :            :         }
    3944                 :            : 
    3945                 :            :         return NULL;
    3946                 :            : }
    3947                 :            : EXPORT_SYMBOL_GPL(ring_buffer_peek);
    3948                 :            : 
    3949                 :            : static struct ring_buffer_event *
    3950                 :          0 : rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
    3951                 :            : {
    3952                 :            :         struct ring_buffer *buffer;
    3953                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    3954                 :            :         struct ring_buffer_event *event;
    3955                 :            :         int nr_loops = 0;
    3956                 :            : 
    3957                 :          0 :         if (ts)
    3958                 :          0 :                 *ts = 0;
    3959                 :            : 
    3960                 :          0 :         cpu_buffer = iter->cpu_buffer;
    3961                 :            :         buffer = cpu_buffer->buffer;
    3962                 :            : 
    3963                 :            :         /*
    3964                 :            :          * Check if someone performed a consuming read to
    3965                 :            :          * the buffer. A consuming read invalidates the iterator
    3966                 :            :          * and we need to reset the iterator in this case.
    3967                 :            :          */
    3968                 :          0 :         if (unlikely(iter->cache_read != cpu_buffer->read ||
    3969                 :            :                      iter->cache_reader_page != cpu_buffer->reader_page))
    3970                 :          0 :                 rb_iter_reset(iter);
    3971                 :            : 
    3972                 :            :  again:
    3973                 :          0 :         if (ring_buffer_iter_empty(iter))
    3974                 :            :                 return NULL;
    3975                 :            : 
    3976                 :            :         /*
    3977                 :            :          * We repeat when a time extend is encountered or we hit
    3978                 :            :          * the end of the page. Since the time extend is always attached
    3979                 :            :          * to a data event, we should never loop more than three times.
    3980                 :            :          * Once for going to next page, once on time extend, and
    3981                 :            :          * finally once to get the event.
    3982                 :            :          * (We never hit the following condition more than thrice).
    3983                 :            :          */
    3984                 :          0 :         if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
    3985                 :            :                 return NULL;
    3986                 :            : 
    3987                 :          0 :         if (rb_per_cpu_empty(cpu_buffer))
    3988                 :            :                 return NULL;
    3989                 :            : 
    3990                 :          0 :         if (iter->head >= rb_page_size(iter->head_page)) {
    3991                 :          0 :                 rb_inc_iter(iter);
    3992                 :          0 :                 goto again;
    3993                 :            :         }
    3994                 :            : 
    3995                 :            :         event = rb_iter_head_event(iter);
    3996                 :            : 
    3997                 :          0 :         switch (event->type_len) {
    3998                 :            :         case RINGBUF_TYPE_PADDING:
    3999                 :          0 :                 if (rb_null_event(event)) {
    4000                 :          0 :                         rb_inc_iter(iter);
    4001                 :          0 :                         goto again;
    4002                 :            :                 }
    4003                 :          0 :                 rb_advance_iter(iter);
    4004                 :          0 :                 return event;
    4005                 :            : 
    4006                 :            :         case RINGBUF_TYPE_TIME_EXTEND:
    4007                 :            :                 /* Internal data, OK to advance */
    4008                 :          0 :                 rb_advance_iter(iter);
    4009                 :          0 :                 goto again;
    4010                 :            : 
    4011                 :            :         case RINGBUF_TYPE_TIME_STAMP:
    4012                 :          0 :                 if (ts) {
    4013                 :          0 :                         *ts = ring_buffer_event_time_stamp(event);
    4014                 :            :                         ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
    4015                 :            :                                                          cpu_buffer->cpu, ts);
    4016                 :            :                 }
    4017                 :            :                 /* Internal data, OK to advance */
    4018                 :          0 :                 rb_advance_iter(iter);
    4019                 :          0 :                 goto again;
    4020                 :            : 
    4021                 :            :         case RINGBUF_TYPE_DATA:
    4022                 :          0 :                 if (ts && !(*ts)) {
    4023                 :          0 :                         *ts = iter->read_stamp + event->time_delta;
    4024                 :            :                         ring_buffer_normalize_time_stamp(buffer,
    4025                 :            :                                                          cpu_buffer->cpu, ts);
    4026                 :            :                 }
    4027                 :          0 :                 return event;
    4028                 :            : 
    4029                 :            :         default:
    4030                 :          0 :                 BUG();
    4031                 :            :         }
    4032                 :            : 
    4033                 :            :         return NULL;
    4034                 :            : }
    4035                 :            : EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
    4036                 :            : 
    4037                 :          0 : static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
    4038                 :            : {
    4039                 :          0 :         if (likely(!in_nmi())) {
    4040                 :          0 :                 raw_spin_lock(&cpu_buffer->reader_lock);
    4041                 :          0 :                 return true;
    4042                 :            :         }
    4043                 :            : 
    4044                 :            :         /*
    4045                 :            :          * If an NMI die dumps out the content of the ring buffer
    4046                 :            :          * trylock must be used to prevent a deadlock if the NMI
    4047                 :            :          * preempted a task that holds the ring buffer locks. If
    4048                 :            :          * we get the lock then all is fine, if not, then continue
    4049                 :            :          * to do the read, but this can corrupt the ring buffer,
    4050                 :            :          * so it must be permanently disabled from future writes.
    4051                 :            :          * Reading from NMI is a oneshot deal.
    4052                 :            :          */
    4053                 :          0 :         if (raw_spin_trylock(&cpu_buffer->reader_lock))
    4054                 :            :                 return true;
    4055                 :            : 
    4056                 :            :         /* Continue without locking, but disable the ring buffer */
    4057                 :          0 :         atomic_inc(&cpu_buffer->record_disabled);
    4058                 :          0 :         return false;
    4059                 :            : }
    4060                 :            : 
    4061                 :            : static inline void
    4062                 :            : rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
    4063                 :            : {
    4064                 :          0 :         if (likely(locked))
    4065                 :            :                 raw_spin_unlock(&cpu_buffer->reader_lock);
    4066                 :            :         return;
    4067                 :            : }
    4068                 :            : 
    4069                 :            : /**
    4070                 :            :  * ring_buffer_peek - peek at the next event to be read
    4071                 :            :  * @buffer: The ring buffer to read
    4072                 :            :  * @cpu: The cpu to peak at
    4073                 :            :  * @ts: The timestamp counter of this event.
    4074                 :            :  * @lost_events: a variable to store if events were lost (may be NULL)
    4075                 :            :  *
    4076                 :            :  * This will return the event that will be read next, but does
    4077                 :            :  * not consume the data.
    4078                 :            :  */
    4079                 :            : struct ring_buffer_event *
    4080                 :          0 : ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
    4081                 :            :                  unsigned long *lost_events)
    4082                 :            : {
    4083                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
    4084                 :            :         struct ring_buffer_event *event;
    4085                 :            :         unsigned long flags;
    4086                 :            :         bool dolock;
    4087                 :            : 
    4088                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4089                 :            :                 return NULL;
    4090                 :            : 
    4091                 :            :  again:
    4092                 :          0 :         local_irq_save(flags);
    4093                 :          0 :         dolock = rb_reader_lock(cpu_buffer);
    4094                 :          0 :         event = rb_buffer_peek(cpu_buffer, ts, lost_events);
    4095                 :          0 :         if (event && event->type_len == RINGBUF_TYPE_PADDING)
    4096                 :          0 :                 rb_advance_reader(cpu_buffer);
    4097                 :            :         rb_reader_unlock(cpu_buffer, dolock);
    4098                 :          0 :         local_irq_restore(flags);
    4099                 :            : 
    4100                 :          0 :         if (event && event->type_len == RINGBUF_TYPE_PADDING)
    4101                 :            :                 goto again;
    4102                 :            : 
    4103                 :          0 :         return event;
    4104                 :            : }
    4105                 :            : 
    4106                 :            : /**
    4107                 :            :  * ring_buffer_iter_peek - peek at the next event to be read
    4108                 :            :  * @iter: The ring buffer iterator
    4109                 :            :  * @ts: The timestamp counter of this event.
    4110                 :            :  *
    4111                 :            :  * This will return the event that will be read next, but does
    4112                 :            :  * not increment the iterator.
    4113                 :            :  */
    4114                 :            : struct ring_buffer_event *
    4115                 :          0 : ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
    4116                 :            : {
    4117                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
    4118                 :            :         struct ring_buffer_event *event;
    4119                 :            :         unsigned long flags;
    4120                 :            : 
    4121                 :            :  again:
    4122                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    4123                 :          0 :         event = rb_iter_peek(iter, ts);
    4124                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    4125                 :            : 
    4126                 :          0 :         if (event && event->type_len == RINGBUF_TYPE_PADDING)
    4127                 :            :                 goto again;
    4128                 :            : 
    4129                 :          0 :         return event;
    4130                 :            : }
    4131                 :            : 
    4132                 :            : /**
    4133                 :            :  * ring_buffer_consume - return an event and consume it
    4134                 :            :  * @buffer: The ring buffer to get the next event from
    4135                 :            :  * @cpu: the cpu to read the buffer from
    4136                 :            :  * @ts: a variable to store the timestamp (may be NULL)
    4137                 :            :  * @lost_events: a variable to store if events were lost (may be NULL)
    4138                 :            :  *
    4139                 :            :  * Returns the next event in the ring buffer, and that event is consumed.
    4140                 :            :  * Meaning, that sequential reads will keep returning a different event,
    4141                 :            :  * and eventually empty the ring buffer if the producer is slower.
    4142                 :            :  */
    4143                 :            : struct ring_buffer_event *
    4144                 :          0 : ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
    4145                 :            :                     unsigned long *lost_events)
    4146                 :            : {
    4147                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    4148                 :            :         struct ring_buffer_event *event = NULL;
    4149                 :            :         unsigned long flags;
    4150                 :            :         bool dolock;
    4151                 :            : 
    4152                 :            :  again:
    4153                 :            :         /* might be called in atomic */
    4154                 :          0 :         preempt_disable();
    4155                 :            : 
    4156                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4157                 :            :                 goto out;
    4158                 :            : 
    4159                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    4160                 :          0 :         local_irq_save(flags);
    4161                 :          0 :         dolock = rb_reader_lock(cpu_buffer);
    4162                 :            : 
    4163                 :          0 :         event = rb_buffer_peek(cpu_buffer, ts, lost_events);
    4164                 :          0 :         if (event) {
    4165                 :          0 :                 cpu_buffer->lost_events = 0;
    4166                 :          0 :                 rb_advance_reader(cpu_buffer);
    4167                 :            :         }
    4168                 :            : 
    4169                 :            :         rb_reader_unlock(cpu_buffer, dolock);
    4170                 :          0 :         local_irq_restore(flags);
    4171                 :            : 
    4172                 :            :  out:
    4173                 :          0 :         preempt_enable();
    4174                 :            : 
    4175                 :          0 :         if (event && event->type_len == RINGBUF_TYPE_PADDING)
    4176                 :            :                 goto again;
    4177                 :            : 
    4178                 :          0 :         return event;
    4179                 :            : }
    4180                 :            : EXPORT_SYMBOL_GPL(ring_buffer_consume);
    4181                 :            : 
    4182                 :            : /**
    4183                 :            :  * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
    4184                 :            :  * @buffer: The ring buffer to read from
    4185                 :            :  * @cpu: The cpu buffer to iterate over
    4186                 :            :  * @flags: gfp flags to use for memory allocation
    4187                 :            :  *
    4188                 :            :  * This performs the initial preparations necessary to iterate
    4189                 :            :  * through the buffer.  Memory is allocated, buffer recording
    4190                 :            :  * is disabled, and the iterator pointer is returned to the caller.
    4191                 :            :  *
    4192                 :            :  * Disabling buffer recording prevents the reading from being
    4193                 :            :  * corrupted. This is not a consuming read, so a producer is not
    4194                 :            :  * expected.
    4195                 :            :  *
    4196                 :            :  * After a sequence of ring_buffer_read_prepare calls, the user is
    4197                 :            :  * expected to make at least one call to ring_buffer_read_prepare_sync.
    4198                 :            :  * Afterwards, ring_buffer_read_start is invoked to get things going
    4199                 :            :  * for real.
    4200                 :            :  *
    4201                 :            :  * This overall must be paired with ring_buffer_read_finish.
    4202                 :            :  */
    4203                 :            : struct ring_buffer_iter *
    4204                 :          0 : ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu, gfp_t flags)
    4205                 :            : {
    4206                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    4207                 :            :         struct ring_buffer_iter *iter;
    4208                 :            : 
    4209                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4210                 :            :                 return NULL;
    4211                 :            : 
    4212                 :            :         iter = kmalloc(sizeof(*iter), flags);
    4213                 :          0 :         if (!iter)
    4214                 :            :                 return NULL;
    4215                 :            : 
    4216                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    4217                 :            : 
    4218                 :          0 :         iter->cpu_buffer = cpu_buffer;
    4219                 :            : 
    4220                 :          0 :         atomic_inc(&buffer->resize_disabled);
    4221                 :          0 :         atomic_inc(&cpu_buffer->record_disabled);
    4222                 :            : 
    4223                 :          0 :         return iter;
    4224                 :            : }
    4225                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
    4226                 :            : 
    4227                 :            : /**
    4228                 :            :  * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
    4229                 :            :  *
    4230                 :            :  * All previously invoked ring_buffer_read_prepare calls to prepare
    4231                 :            :  * iterators will be synchronized.  Afterwards, read_buffer_read_start
    4232                 :            :  * calls on those iterators are allowed.
    4233                 :            :  */
    4234                 :            : void
    4235                 :          0 : ring_buffer_read_prepare_sync(void)
    4236                 :            : {
    4237                 :          0 :         synchronize_rcu();
    4238                 :          0 : }
    4239                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
    4240                 :            : 
    4241                 :            : /**
    4242                 :            :  * ring_buffer_read_start - start a non consuming read of the buffer
    4243                 :            :  * @iter: The iterator returned by ring_buffer_read_prepare
    4244                 :            :  *
    4245                 :            :  * This finalizes the startup of an iteration through the buffer.
    4246                 :            :  * The iterator comes from a call to ring_buffer_read_prepare and
    4247                 :            :  * an intervening ring_buffer_read_prepare_sync must have been
    4248                 :            :  * performed.
    4249                 :            :  *
    4250                 :            :  * Must be paired with ring_buffer_read_finish.
    4251                 :            :  */
    4252                 :            : void
    4253                 :          0 : ring_buffer_read_start(struct ring_buffer_iter *iter)
    4254                 :            : {
    4255                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    4256                 :            :         unsigned long flags;
    4257                 :            : 
    4258                 :          0 :         if (!iter)
    4259                 :          0 :                 return;
    4260                 :            : 
    4261                 :          0 :         cpu_buffer = iter->cpu_buffer;
    4262                 :            : 
    4263                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    4264                 :          0 :         arch_spin_lock(&cpu_buffer->lock);
    4265                 :          0 :         rb_iter_reset(iter);
    4266                 :            :         arch_spin_unlock(&cpu_buffer->lock);
    4267                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    4268                 :            : }
    4269                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read_start);
    4270                 :            : 
    4271                 :            : /**
    4272                 :            :  * ring_buffer_read_finish - finish reading the iterator of the buffer
    4273                 :            :  * @iter: The iterator retrieved by ring_buffer_start
    4274                 :            :  *
    4275                 :            :  * This re-enables the recording to the buffer, and frees the
    4276                 :            :  * iterator.
    4277                 :            :  */
    4278                 :            : void
    4279                 :          0 : ring_buffer_read_finish(struct ring_buffer_iter *iter)
    4280                 :            : {
    4281                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
    4282                 :            :         unsigned long flags;
    4283                 :            : 
    4284                 :            :         /*
    4285                 :            :          * Ring buffer is disabled from recording, here's a good place
    4286                 :            :          * to check the integrity of the ring buffer.
    4287                 :            :          * Must prevent readers from trying to read, as the check
    4288                 :            :          * clears the HEAD page and readers require it.
    4289                 :            :          */
    4290                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    4291                 :          0 :         rb_check_pages(cpu_buffer);
    4292                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    4293                 :            : 
    4294                 :          0 :         atomic_dec(&cpu_buffer->record_disabled);
    4295                 :          0 :         atomic_dec(&cpu_buffer->buffer->resize_disabled);
    4296                 :          0 :         kfree(iter);
    4297                 :          0 : }
    4298                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
    4299                 :            : 
    4300                 :            : /**
    4301                 :            :  * ring_buffer_read - read the next item in the ring buffer by the iterator
    4302                 :            :  * @iter: The ring buffer iterator
    4303                 :            :  * @ts: The time stamp of the event read.
    4304                 :            :  *
    4305                 :            :  * This reads the next event in the ring buffer and increments the iterator.
    4306                 :            :  */
    4307                 :            : struct ring_buffer_event *
    4308                 :          0 : ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
    4309                 :            : {
    4310                 :            :         struct ring_buffer_event *event;
    4311                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
    4312                 :            :         unsigned long flags;
    4313                 :            : 
    4314                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    4315                 :            :  again:
    4316                 :          0 :         event = rb_iter_peek(iter, ts);
    4317                 :          0 :         if (!event)
    4318                 :            :                 goto out;
    4319                 :            : 
    4320                 :          0 :         if (event->type_len == RINGBUF_TYPE_PADDING)
    4321                 :            :                 goto again;
    4322                 :            : 
    4323                 :          0 :         rb_advance_iter(iter);
    4324                 :            :  out:
    4325                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    4326                 :            : 
    4327                 :          0 :         return event;
    4328                 :            : }
    4329                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read);
    4330                 :            : 
    4331                 :            : /**
    4332                 :            :  * ring_buffer_size - return the size of the ring buffer (in bytes)
    4333                 :            :  * @buffer: The ring buffer.
    4334                 :            :  */
    4335                 :          3 : unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
    4336                 :            : {
    4337                 :            :         /*
    4338                 :            :          * Earlier, this method returned
    4339                 :            :          *      BUF_PAGE_SIZE * buffer->nr_pages
    4340                 :            :          * Since the nr_pages field is now removed, we have converted this to
    4341                 :            :          * return the per cpu buffer value.
    4342                 :            :          */
    4343                 :          3 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4344                 :            :                 return 0;
    4345                 :            : 
    4346                 :          3 :         return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
    4347                 :            : }
    4348                 :            : EXPORT_SYMBOL_GPL(ring_buffer_size);
    4349                 :            : 
    4350                 :            : static void
    4351                 :          0 : rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
    4352                 :            : {
    4353                 :            :         rb_head_page_deactivate(cpu_buffer);
    4354                 :            : 
    4355                 :            :         cpu_buffer->head_page
    4356                 :          0 :                 = list_entry(cpu_buffer->pages, struct buffer_page, list);
    4357                 :          0 :         local_set(&cpu_buffer->head_page->write, 0);
    4358                 :          0 :         local_set(&cpu_buffer->head_page->entries, 0);
    4359                 :          0 :         local_set(&cpu_buffer->head_page->page->commit, 0);
    4360                 :            : 
    4361                 :          0 :         cpu_buffer->head_page->read = 0;
    4362                 :            : 
    4363                 :          0 :         cpu_buffer->tail_page = cpu_buffer->head_page;
    4364                 :          0 :         cpu_buffer->commit_page = cpu_buffer->head_page;
    4365                 :            : 
    4366                 :          0 :         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
    4367                 :          0 :         INIT_LIST_HEAD(&cpu_buffer->new_pages);
    4368                 :          0 :         local_set(&cpu_buffer->reader_page->write, 0);
    4369                 :          0 :         local_set(&cpu_buffer->reader_page->entries, 0);
    4370                 :          0 :         local_set(&cpu_buffer->reader_page->page->commit, 0);
    4371                 :          0 :         cpu_buffer->reader_page->read = 0;
    4372                 :            : 
    4373                 :            :         local_set(&cpu_buffer->entries_bytes, 0);
    4374                 :            :         local_set(&cpu_buffer->overrun, 0);
    4375                 :            :         local_set(&cpu_buffer->commit_overrun, 0);
    4376                 :            :         local_set(&cpu_buffer->dropped_events, 0);
    4377                 :            :         local_set(&cpu_buffer->entries, 0);
    4378                 :            :         local_set(&cpu_buffer->committing, 0);
    4379                 :            :         local_set(&cpu_buffer->commits, 0);
    4380                 :            :         local_set(&cpu_buffer->pages_touched, 0);
    4381                 :            :         local_set(&cpu_buffer->pages_read, 0);
    4382                 :          0 :         cpu_buffer->last_pages_touch = 0;
    4383                 :          0 :         cpu_buffer->shortest_full = 0;
    4384                 :          0 :         cpu_buffer->read = 0;
    4385                 :          0 :         cpu_buffer->read_bytes = 0;
    4386                 :            : 
    4387                 :          0 :         cpu_buffer->write_stamp = 0;
    4388                 :          0 :         cpu_buffer->read_stamp = 0;
    4389                 :            : 
    4390                 :          0 :         cpu_buffer->lost_events = 0;
    4391                 :          0 :         cpu_buffer->last_overrun = 0;
    4392                 :            : 
    4393                 :            :         rb_head_page_activate(cpu_buffer);
    4394                 :          0 : }
    4395                 :            : 
    4396                 :            : /**
    4397                 :            :  * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
    4398                 :            :  * @buffer: The ring buffer to reset a per cpu buffer of
    4399                 :            :  * @cpu: The CPU buffer to be reset
    4400                 :            :  */
    4401                 :          0 : void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
    4402                 :            : {
    4403                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
    4404                 :            :         unsigned long flags;
    4405                 :            : 
    4406                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4407                 :          0 :                 return;
    4408                 :            : 
    4409                 :          0 :         atomic_inc(&buffer->resize_disabled);
    4410                 :          0 :         atomic_inc(&cpu_buffer->record_disabled);
    4411                 :            : 
    4412                 :            :         /* Make sure all commits have finished */
    4413                 :          0 :         synchronize_rcu();
    4414                 :            : 
    4415                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    4416                 :            : 
    4417                 :          0 :         if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
    4418                 :            :                 goto out;
    4419                 :            : 
    4420                 :          0 :         arch_spin_lock(&cpu_buffer->lock);
    4421                 :            : 
    4422                 :          0 :         rb_reset_cpu(cpu_buffer);
    4423                 :            : 
    4424                 :            :         arch_spin_unlock(&cpu_buffer->lock);
    4425                 :            : 
    4426                 :            :  out:
    4427                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    4428                 :            : 
    4429                 :            :         atomic_dec(&cpu_buffer->record_disabled);
    4430                 :            :         atomic_dec(&buffer->resize_disabled);
    4431                 :            : }
    4432                 :            : EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
    4433                 :            : 
    4434                 :            : /**
    4435                 :            :  * ring_buffer_reset - reset a ring buffer
    4436                 :            :  * @buffer: The ring buffer to reset all cpu buffers
    4437                 :            :  */
    4438                 :          0 : void ring_buffer_reset(struct ring_buffer *buffer)
    4439                 :            : {
    4440                 :            :         int cpu;
    4441                 :            : 
    4442                 :          0 :         for_each_buffer_cpu(buffer, cpu)
    4443                 :          0 :                 ring_buffer_reset_cpu(buffer, cpu);
    4444                 :          0 : }
    4445                 :            : EXPORT_SYMBOL_GPL(ring_buffer_reset);
    4446                 :            : 
    4447                 :            : /**
    4448                 :            :  * rind_buffer_empty - is the ring buffer empty?
    4449                 :            :  * @buffer: The ring buffer to test
    4450                 :            :  */
    4451                 :          0 : bool ring_buffer_empty(struct ring_buffer *buffer)
    4452                 :            : {
    4453                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    4454                 :            :         unsigned long flags;
    4455                 :            :         bool dolock;
    4456                 :            :         int cpu;
    4457                 :            :         int ret;
    4458                 :            : 
    4459                 :            :         /* yes this is racy, but if you don't like the race, lock the buffer */
    4460                 :          0 :         for_each_buffer_cpu(buffer, cpu) {
    4461                 :          0 :                 cpu_buffer = buffer->buffers[cpu];
    4462                 :          0 :                 local_irq_save(flags);
    4463                 :          0 :                 dolock = rb_reader_lock(cpu_buffer);
    4464                 :          0 :                 ret = rb_per_cpu_empty(cpu_buffer);
    4465                 :            :                 rb_reader_unlock(cpu_buffer, dolock);
    4466                 :          0 :                 local_irq_restore(flags);
    4467                 :            : 
    4468                 :          0 :                 if (!ret)
    4469                 :            :                         return false;
    4470                 :            :         }
    4471                 :            : 
    4472                 :            :         return true;
    4473                 :            : }
    4474                 :            : EXPORT_SYMBOL_GPL(ring_buffer_empty);
    4475                 :            : 
    4476                 :            : /**
    4477                 :            :  * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
    4478                 :            :  * @buffer: The ring buffer
    4479                 :            :  * @cpu: The CPU buffer to test
    4480                 :            :  */
    4481                 :          0 : bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
    4482                 :            : {
    4483                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    4484                 :            :         unsigned long flags;
    4485                 :            :         bool dolock;
    4486                 :            :         int ret;
    4487                 :            : 
    4488                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4489                 :            :                 return true;
    4490                 :            : 
    4491                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    4492                 :          0 :         local_irq_save(flags);
    4493                 :          0 :         dolock = rb_reader_lock(cpu_buffer);
    4494                 :          0 :         ret = rb_per_cpu_empty(cpu_buffer);
    4495                 :            :         rb_reader_unlock(cpu_buffer, dolock);
    4496                 :          0 :         local_irq_restore(flags);
    4497                 :            : 
    4498                 :          0 :         return ret;
    4499                 :            : }
    4500                 :            : EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
    4501                 :            : 
    4502                 :            : #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
    4503                 :            : /**
    4504                 :            :  * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
    4505                 :            :  * @buffer_a: One buffer to swap with
    4506                 :            :  * @buffer_b: The other buffer to swap with
    4507                 :            :  *
    4508                 :            :  * This function is useful for tracers that want to take a "snapshot"
    4509                 :            :  * of a CPU buffer and has another back up buffer lying around.
    4510                 :            :  * it is expected that the tracer handles the cpu buffer not being
    4511                 :            :  * used at the moment.
    4512                 :            :  */
    4513                 :          0 : int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
    4514                 :            :                          struct ring_buffer *buffer_b, int cpu)
    4515                 :            : {
    4516                 :            :         struct ring_buffer_per_cpu *cpu_buffer_a;
    4517                 :            :         struct ring_buffer_per_cpu *cpu_buffer_b;
    4518                 :            :         int ret = -EINVAL;
    4519                 :            : 
    4520                 :          0 :         if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
    4521                 :            :             !cpumask_test_cpu(cpu, buffer_b->cpumask))
    4522                 :            :                 goto out;
    4523                 :            : 
    4524                 :          0 :         cpu_buffer_a = buffer_a->buffers[cpu];
    4525                 :          0 :         cpu_buffer_b = buffer_b->buffers[cpu];
    4526                 :            : 
    4527                 :            :         /* At least make sure the two buffers are somewhat the same */
    4528                 :          0 :         if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
    4529                 :            :                 goto out;
    4530                 :            : 
    4531                 :            :         ret = -EAGAIN;
    4532                 :            : 
    4533                 :          0 :         if (atomic_read(&buffer_a->record_disabled))
    4534                 :            :                 goto out;
    4535                 :            : 
    4536                 :          0 :         if (atomic_read(&buffer_b->record_disabled))
    4537                 :            :                 goto out;
    4538                 :            : 
    4539                 :          0 :         if (atomic_read(&cpu_buffer_a->record_disabled))
    4540                 :            :                 goto out;
    4541                 :            : 
    4542                 :          0 :         if (atomic_read(&cpu_buffer_b->record_disabled))
    4543                 :            :                 goto out;
    4544                 :            : 
    4545                 :            :         /*
    4546                 :            :          * We can't do a synchronize_rcu here because this
    4547                 :            :          * function can be called in atomic context.
    4548                 :            :          * Normally this will be called from the same CPU as cpu.
    4549                 :            :          * If not it's up to the caller to protect this.
    4550                 :            :          */
    4551                 :          0 :         atomic_inc(&cpu_buffer_a->record_disabled);
    4552                 :          0 :         atomic_inc(&cpu_buffer_b->record_disabled);
    4553                 :            : 
    4554                 :            :         ret = -EBUSY;
    4555                 :          0 :         if (local_read(&cpu_buffer_a->committing))
    4556                 :            :                 goto out_dec;
    4557                 :          0 :         if (local_read(&cpu_buffer_b->committing))
    4558                 :            :                 goto out_dec;
    4559                 :            : 
    4560                 :          0 :         buffer_a->buffers[cpu] = cpu_buffer_b;
    4561                 :          0 :         buffer_b->buffers[cpu] = cpu_buffer_a;
    4562                 :            : 
    4563                 :          0 :         cpu_buffer_b->buffer = buffer_a;
    4564                 :          0 :         cpu_buffer_a->buffer = buffer_b;
    4565                 :            : 
    4566                 :            :         ret = 0;
    4567                 :            : 
    4568                 :            : out_dec:
    4569                 :            :         atomic_dec(&cpu_buffer_a->record_disabled);
    4570                 :            :         atomic_dec(&cpu_buffer_b->record_disabled);
    4571                 :            : out:
    4572                 :          0 :         return ret;
    4573                 :            : }
    4574                 :            : EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
    4575                 :            : #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
    4576                 :            : 
    4577                 :            : /**
    4578                 :            :  * ring_buffer_alloc_read_page - allocate a page to read from buffer
    4579                 :            :  * @buffer: the buffer to allocate for.
    4580                 :            :  * @cpu: the cpu buffer to allocate.
    4581                 :            :  *
    4582                 :            :  * This function is used in conjunction with ring_buffer_read_page.
    4583                 :            :  * When reading a full page from the ring buffer, these functions
    4584                 :            :  * can be used to speed up the process. The calling function should
    4585                 :            :  * allocate a few pages first with this function. Then when it
    4586                 :            :  * needs to get pages from the ring buffer, it passes the result
    4587                 :            :  * of this function into ring_buffer_read_page, which will swap
    4588                 :            :  * the page that was allocated, with the read page of the buffer.
    4589                 :            :  *
    4590                 :            :  * Returns:
    4591                 :            :  *  The page allocated, or ERR_PTR
    4592                 :            :  */
    4593                 :          0 : void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
    4594                 :            : {
    4595                 :            :         struct ring_buffer_per_cpu *cpu_buffer;
    4596                 :            :         struct buffer_data_page *bpage = NULL;
    4597                 :            :         unsigned long flags;
    4598                 :            :         struct page *page;
    4599                 :            : 
    4600                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4601                 :            :                 return ERR_PTR(-ENODEV);
    4602                 :            : 
    4603                 :          0 :         cpu_buffer = buffer->buffers[cpu];
    4604                 :          0 :         local_irq_save(flags);
    4605                 :          0 :         arch_spin_lock(&cpu_buffer->lock);
    4606                 :            : 
    4607                 :          0 :         if (cpu_buffer->free_page) {
    4608                 :            :                 bpage = cpu_buffer->free_page;
    4609                 :          0 :                 cpu_buffer->free_page = NULL;
    4610                 :            :         }
    4611                 :            : 
    4612                 :            :         arch_spin_unlock(&cpu_buffer->lock);
    4613                 :          0 :         local_irq_restore(flags);
    4614                 :            : 
    4615                 :          0 :         if (bpage)
    4616                 :            :                 goto out;
    4617                 :            : 
    4618                 :            :         page = alloc_pages_node(cpu_to_node(cpu),
    4619                 :            :                                 GFP_KERNEL | __GFP_NORETRY, 0);
    4620                 :          0 :         if (!page)
    4621                 :            :                 return ERR_PTR(-ENOMEM);
    4622                 :            : 
    4623                 :            :         bpage = page_address(page);
    4624                 :            : 
    4625                 :            :  out:
    4626                 :            :         rb_init_page(bpage);
    4627                 :            : 
    4628                 :          0 :         return bpage;
    4629                 :            : }
    4630                 :            : EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
    4631                 :            : 
    4632                 :            : /**
    4633                 :            :  * ring_buffer_free_read_page - free an allocated read page
    4634                 :            :  * @buffer: the buffer the page was allocate for
    4635                 :            :  * @cpu: the cpu buffer the page came from
    4636                 :            :  * @data: the page to free
    4637                 :            :  *
    4638                 :            :  * Free a page allocated from ring_buffer_alloc_read_page.
    4639                 :            :  */
    4640                 :          0 : void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
    4641                 :            : {
    4642                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
    4643                 :            :         struct buffer_data_page *bpage = data;
    4644                 :          0 :         struct page *page = virt_to_page(bpage);
    4645                 :            :         unsigned long flags;
    4646                 :            : 
    4647                 :            :         /* If the page is still in use someplace else, we can't reuse it */
    4648                 :          0 :         if (page_ref_count(page) > 1)
    4649                 :            :                 goto out;
    4650                 :            : 
    4651                 :          0 :         local_irq_save(flags);
    4652                 :          0 :         arch_spin_lock(&cpu_buffer->lock);
    4653                 :            : 
    4654                 :          0 :         if (!cpu_buffer->free_page) {
    4655                 :          0 :                 cpu_buffer->free_page = bpage;
    4656                 :            :                 bpage = NULL;
    4657                 :            :         }
    4658                 :            : 
    4659                 :            :         arch_spin_unlock(&cpu_buffer->lock);
    4660                 :          0 :         local_irq_restore(flags);
    4661                 :            : 
    4662                 :            :  out:
    4663                 :          0 :         free_page((unsigned long)bpage);
    4664                 :          0 : }
    4665                 :            : EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
    4666                 :            : 
    4667                 :            : /**
    4668                 :            :  * ring_buffer_read_page - extract a page from the ring buffer
    4669                 :            :  * @buffer: buffer to extract from
    4670                 :            :  * @data_page: the page to use allocated from ring_buffer_alloc_read_page
    4671                 :            :  * @len: amount to extract
    4672                 :            :  * @cpu: the cpu of the buffer to extract
    4673                 :            :  * @full: should the extraction only happen when the page is full.
    4674                 :            :  *
    4675                 :            :  * This function will pull out a page from the ring buffer and consume it.
    4676                 :            :  * @data_page must be the address of the variable that was returned
    4677                 :            :  * from ring_buffer_alloc_read_page. This is because the page might be used
    4678                 :            :  * to swap with a page in the ring buffer.
    4679                 :            :  *
    4680                 :            :  * for example:
    4681                 :            :  *      rpage = ring_buffer_alloc_read_page(buffer, cpu);
    4682                 :            :  *      if (IS_ERR(rpage))
    4683                 :            :  *              return PTR_ERR(rpage);
    4684                 :            :  *      ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
    4685                 :            :  *      if (ret >= 0)
    4686                 :            :  *              process_page(rpage, ret);
    4687                 :            :  *
    4688                 :            :  * When @full is set, the function will not return true unless
    4689                 :            :  * the writer is off the reader page.
    4690                 :            :  *
    4691                 :            :  * Note: it is up to the calling functions to handle sleeps and wakeups.
    4692                 :            :  *  The ring buffer can be used anywhere in the kernel and can not
    4693                 :            :  *  blindly call wake_up. The layer that uses the ring buffer must be
    4694                 :            :  *  responsible for that.
    4695                 :            :  *
    4696                 :            :  * Returns:
    4697                 :            :  *  >=0 if data has been transferred, returns the offset of consumed data.
    4698                 :            :  *  <0 if no data has been transferred.
    4699                 :            :  */
    4700                 :          0 : int ring_buffer_read_page(struct ring_buffer *buffer,
    4701                 :            :                           void **data_page, size_t len, int cpu, int full)
    4702                 :            : {
    4703                 :          0 :         struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
    4704                 :            :         struct ring_buffer_event *event;
    4705                 :            :         struct buffer_data_page *bpage;
    4706                 :            :         struct buffer_page *reader;
    4707                 :            :         unsigned long missed_events;
    4708                 :            :         unsigned long flags;
    4709                 :            :         unsigned int commit;
    4710                 :            :         unsigned int read;
    4711                 :            :         u64 save_timestamp;
    4712                 :            :         int ret = -1;
    4713                 :            : 
    4714                 :          0 :         if (!cpumask_test_cpu(cpu, buffer->cpumask))
    4715                 :            :                 goto out;
    4716                 :            : 
    4717                 :            :         /*
    4718                 :            :          * If len is not big enough to hold the page header, then
    4719                 :            :          * we can not copy anything.
    4720                 :            :          */
    4721                 :          0 :         if (len <= BUF_PAGE_HDR_SIZE)
    4722                 :            :                 goto out;
    4723                 :            : 
    4724                 :          0 :         len -= BUF_PAGE_HDR_SIZE;
    4725                 :            : 
    4726                 :          0 :         if (!data_page)
    4727                 :            :                 goto out;
    4728                 :            : 
    4729                 :          0 :         bpage = *data_page;
    4730                 :          0 :         if (!bpage)
    4731                 :            :                 goto out;
    4732                 :            : 
    4733                 :          0 :         raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
    4734                 :            : 
    4735                 :          0 :         reader = rb_get_reader_page(cpu_buffer);
    4736                 :          0 :         if (!reader)
    4737                 :            :                 goto out_unlock;
    4738                 :            : 
    4739                 :            :         event = rb_reader_event(cpu_buffer);
    4740                 :            : 
    4741                 :          0 :         read = reader->read;
    4742                 :            :         commit = rb_page_commit(reader);
    4743                 :            : 
    4744                 :            :         /* Check if any events were dropped */
    4745                 :          0 :         missed_events = cpu_buffer->lost_events;
    4746                 :            : 
    4747                 :            :         /*
    4748                 :            :          * If this page has been partially read or
    4749                 :            :          * if len is not big enough to read the rest of the page or
    4750                 :            :          * a writer is still on the page, then
    4751                 :            :          * we must copy the data from the page to the buffer.
    4752                 :            :          * Otherwise, we can simply swap the page with the one passed in.
    4753                 :            :          */
    4754                 :          0 :         if (read || (len < (commit - read)) ||
    4755                 :          0 :             cpu_buffer->reader_page == cpu_buffer->commit_page) {
    4756                 :          0 :                 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
    4757                 :            :                 unsigned int rpos = read;
    4758                 :            :                 unsigned int pos = 0;
    4759                 :            :                 unsigned int size;
    4760                 :            : 
    4761                 :          0 :                 if (full)
    4762                 :            :                         goto out_unlock;
    4763                 :            : 
    4764                 :          0 :                 if (len > (commit - read))
    4765                 :            :                         len = (commit - read);
    4766                 :            : 
    4767                 :            :                 /* Always keep the time extend and data together */
    4768                 :            :                 size = rb_event_ts_length(event);
    4769                 :            : 
    4770                 :          0 :                 if (len < size)
    4771                 :            :                         goto out_unlock;
    4772                 :            : 
    4773                 :            :                 /* save the current timestamp, since the user will need it */
    4774                 :          0 :                 save_timestamp = cpu_buffer->read_stamp;
    4775                 :            : 
    4776                 :            :                 /* Need to copy one event at a time */
    4777                 :            :                 do {
    4778                 :            :                         /* We need the size of one event, because
    4779                 :            :                          * rb_advance_reader only advances by one event,
    4780                 :            :                          * whereas rb_event_ts_length may include the size of
    4781                 :            :                          * one or two events.
    4782                 :            :                          * We have already ensured there's enough space if this
    4783                 :            :                          * is a time extend. */
    4784                 :          0 :                         size = rb_event_length(event);
    4785                 :          0 :                         memcpy(bpage->data + pos, rpage->data + rpos, size);
    4786                 :            : 
    4787                 :          0 :                         len -= size;
    4788                 :            : 
    4789                 :          0 :                         rb_advance_reader(cpu_buffer);
    4790                 :          0 :                         rpos = reader->read;
    4791                 :          0 :                         pos += size;
    4792                 :            : 
    4793                 :          0 :                         if (rpos >= commit)
    4794                 :            :                                 break;
    4795                 :            : 
    4796                 :            :                         event = rb_reader_event(cpu_buffer);
    4797                 :            :                         /* Always keep the time extend and data together */
    4798                 :            :                         size = rb_event_ts_length(event);
    4799                 :          0 :                 } while (len >= size);
    4800                 :            : 
    4801                 :            :                 /* update bpage */
    4802                 :            :                 local_set(&bpage->commit, pos);
    4803                 :          0 :                 bpage->time_stamp = save_timestamp;
    4804                 :            : 
    4805                 :            :                 /* we copied everything to the beginning */
    4806                 :            :                 read = 0;
    4807                 :            :         } else {
    4808                 :            :                 /* update the entry counter */
    4809                 :          0 :                 cpu_buffer->read += rb_page_entries(reader);
    4810                 :          0 :                 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
    4811                 :            : 
    4812                 :            :                 /* swap the pages */
    4813                 :            :                 rb_init_page(bpage);
    4814                 :          0 :                 bpage = reader->page;
    4815                 :          0 :                 reader->page = *data_page;
    4816                 :            :                 local_set(&reader->write, 0);
    4817                 :            :                 local_set(&reader->entries, 0);
    4818                 :          0 :                 reader->read = 0;
    4819                 :          0 :                 *data_page = bpage;
    4820                 :            : 
    4821                 :            :                 /*
    4822                 :            :                  * Use the real_end for the data size,
    4823                 :            :                  * This gives us a chance to store the lost events
    4824                 :            :                  * on the page.
    4825                 :            :                  */
    4826                 :          0 :                 if (reader->real_end)
    4827                 :            :                         local_set(&bpage->commit, reader->real_end);
    4828                 :            :         }
    4829                 :          0 :         ret = read;
    4830                 :            : 
    4831                 :          0 :         cpu_buffer->lost_events = 0;
    4832                 :            : 
    4833                 :          0 :         commit = local_read(&bpage->commit);
    4834                 :            :         /*
    4835                 :            :          * Set a flag in the commit field if we lost events
    4836                 :            :          */
    4837                 :          0 :         if (missed_events) {
    4838                 :            :                 /* If there is room at the end of the page to save the
    4839                 :            :                  * missed events, then record it there.
    4840                 :            :                  */
    4841                 :          0 :                 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
    4842                 :          0 :                         memcpy(&bpage->data[commit], &missed_events,
    4843                 :            :                                sizeof(missed_events));
    4844                 :          0 :                         local_add(RB_MISSED_STORED, &bpage->commit);
    4845                 :          0 :                         commit += sizeof(missed_events);
    4846                 :            :                 }
    4847                 :          0 :                 local_add(RB_MISSED_EVENTS, &bpage->commit);
    4848                 :            :         }
    4849                 :            : 
    4850                 :            :         /*
    4851                 :            :          * This page may be off to user land. Zero it out here.
    4852                 :            :          */
    4853                 :          0 :         if (commit < BUF_PAGE_SIZE)
    4854                 :          0 :                 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
    4855                 :            : 
    4856                 :            :  out_unlock:
    4857                 :          0 :         raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
    4858                 :            : 
    4859                 :            :  out:
    4860                 :          0 :         return ret;
    4861                 :            : }
    4862                 :            : EXPORT_SYMBOL_GPL(ring_buffer_read_page);
    4863                 :            : 
    4864                 :            : /*
    4865                 :            :  * We only allocate new buffers, never free them if the CPU goes down.
    4866                 :            :  * If we were to free the buffer, then the user would lose any trace that was in
    4867                 :            :  * the buffer.
    4868                 :            :  */
    4869                 :          3 : int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
    4870                 :            : {
    4871                 :            :         struct ring_buffer *buffer;
    4872                 :            :         long nr_pages_same;
    4873                 :            :         int cpu_i;
    4874                 :            :         unsigned long nr_pages;
    4875                 :            : 
    4876                 :          3 :         buffer = container_of(node, struct ring_buffer, node);
    4877                 :          3 :         if (cpumask_test_cpu(cpu, buffer->cpumask))
    4878                 :            :                 return 0;
    4879                 :            : 
    4880                 :            :         nr_pages = 0;
    4881                 :            :         nr_pages_same = 1;
    4882                 :            :         /* check if all cpu sizes are same */
    4883                 :          3 :         for_each_buffer_cpu(buffer, cpu_i) {
    4884                 :            :                 /* fill in the size from first enabled cpu */
    4885                 :          3 :                 if (nr_pages == 0)
    4886                 :          3 :                         nr_pages = buffer->buffers[cpu_i]->nr_pages;
    4887                 :          3 :                 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
    4888                 :            :                         nr_pages_same = 0;
    4889                 :            :                         break;
    4890                 :            :                 }
    4891                 :            :         }
    4892                 :            :         /* allocate minimum pages, user can later expand it */
    4893                 :          3 :         if (!nr_pages_same)
    4894                 :            :                 nr_pages = 2;
    4895                 :          3 :         buffer->buffers[cpu] =
    4896                 :          3 :                 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
    4897                 :          3 :         if (!buffer->buffers[cpu]) {
    4898                 :          0 :                 WARN(1, "failed to allocate ring buffer on CPU %u\n",
    4899                 :            :                      cpu);
    4900                 :          0 :                 return -ENOMEM;
    4901                 :            :         }
    4902                 :          3 :         smp_wmb();
    4903                 :            :         cpumask_set_cpu(cpu, buffer->cpumask);
    4904                 :          3 :         return 0;
    4905                 :            : }
    4906                 :            : 
    4907                 :            : #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
    4908                 :            : /*
    4909                 :            :  * This is a basic integrity check of the ring buffer.
    4910                 :            :  * Late in the boot cycle this test will run when configured in.
    4911                 :            :  * It will kick off a thread per CPU that will go into a loop
    4912                 :            :  * writing to the per cpu ring buffer various sizes of data.
    4913                 :            :  * Some of the data will be large items, some small.
    4914                 :            :  *
    4915                 :            :  * Another thread is created that goes into a spin, sending out
    4916                 :            :  * IPIs to the other CPUs to also write into the ring buffer.
    4917                 :            :  * this is to test the nesting ability of the buffer.
    4918                 :            :  *
    4919                 :            :  * Basic stats are recorded and reported. If something in the
    4920                 :            :  * ring buffer should happen that's not expected, a big warning
    4921                 :            :  * is displayed and all ring buffers are disabled.
    4922                 :            :  */
    4923                 :            : static struct task_struct *rb_threads[NR_CPUS] __initdata;
    4924                 :            : 
    4925                 :            : struct rb_test_data {
    4926                 :            :         struct ring_buffer      *buffer;
    4927                 :            :         unsigned long           events;
    4928                 :            :         unsigned long           bytes_written;
    4929                 :            :         unsigned long           bytes_alloc;
    4930                 :            :         unsigned long           bytes_dropped;
    4931                 :            :         unsigned long           events_nested;
    4932                 :            :         unsigned long           bytes_written_nested;
    4933                 :            :         unsigned long           bytes_alloc_nested;
    4934                 :            :         unsigned long           bytes_dropped_nested;
    4935                 :            :         int                     min_size_nested;
    4936                 :            :         int                     max_size_nested;
    4937                 :            :         int                     max_size;
    4938                 :            :         int                     min_size;
    4939                 :            :         int                     cpu;
    4940                 :            :         int                     cnt;
    4941                 :            : };
    4942                 :            : 
    4943                 :            : static struct rb_test_data rb_data[NR_CPUS] __initdata;
    4944                 :            : 
    4945                 :            : /* 1 meg per cpu */
    4946                 :            : #define RB_TEST_BUFFER_SIZE     1048576
    4947                 :            : 
    4948                 :            : static char rb_string[] __initdata =
    4949                 :            :         "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
    4950                 :            :         "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
    4951                 :            :         "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
    4952                 :            : 
    4953                 :            : static bool rb_test_started __initdata;
    4954                 :            : 
    4955                 :            : struct rb_item {
    4956                 :            :         int size;
    4957                 :            :         char str[];
    4958                 :            : };
    4959                 :            : 
    4960                 :            : static __init int rb_write_something(struct rb_test_data *data, bool nested)
    4961                 :            : {
    4962                 :            :         struct ring_buffer_event *event;
    4963                 :            :         struct rb_item *item;
    4964                 :            :         bool started;
    4965                 :            :         int event_len;
    4966                 :            :         int size;
    4967                 :            :         int len;
    4968                 :            :         int cnt;
    4969                 :            : 
    4970                 :            :         /* Have nested writes different that what is written */
    4971                 :            :         cnt = data->cnt + (nested ? 27 : 0);
    4972                 :            : 
    4973                 :            :         /* Multiply cnt by ~e, to make some unique increment */
    4974                 :            :         size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
    4975                 :            : 
    4976                 :            :         len = size + sizeof(struct rb_item);
    4977                 :            : 
    4978                 :            :         started = rb_test_started;
    4979                 :            :         /* read rb_test_started before checking buffer enabled */
    4980                 :            :         smp_rmb();
    4981                 :            : 
    4982                 :            :         event = ring_buffer_lock_reserve(data->buffer, len);
    4983                 :            :         if (!event) {
    4984                 :            :                 /* Ignore dropped events before test starts. */
    4985                 :            :                 if (started) {
    4986                 :            :                         if (nested)
    4987                 :            :                                 data->bytes_dropped += len;
    4988                 :            :                         else
    4989                 :            :                                 data->bytes_dropped_nested += len;
    4990                 :            :                 }
    4991                 :            :                 return len;
    4992                 :            :         }
    4993                 :            : 
    4994                 :            :         event_len = ring_buffer_event_length(event);
    4995                 :            : 
    4996                 :            :         if (RB_WARN_ON(data->buffer, event_len < len))
    4997                 :            :                 goto out;
    4998                 :            : 
    4999                 :            :         item = ring_buffer_event_data(event);
    5000                 :            :         item->size = size;
    5001                 :            :         memcpy(item->str, rb_string, size);
    5002                 :            : 
    5003                 :            :         if (nested) {
    5004                 :            :                 data->bytes_alloc_nested += event_len;
    5005                 :            :                 data->bytes_written_nested += len;
    5006                 :            :                 data->events_nested++;
    5007                 :            :                 if (!data->min_size_nested || len < data->min_size_nested)
    5008                 :            :                         data->min_size_nested = len;
    5009                 :            :                 if (len > data->max_size_nested)
    5010                 :            :                         data->max_size_nested = len;
    5011                 :            :         } else {
    5012                 :            :                 data->bytes_alloc += event_len;
    5013                 :            :                 data->bytes_written += len;
    5014                 :            :                 data->events++;
    5015                 :            :                 if (!data->min_size || len < data->min_size)
    5016                 :            :                         data->max_size = len;
    5017                 :            :                 if (len > data->max_size)
    5018                 :            :                         data->max_size = len;
    5019                 :            :         }
    5020                 :            : 
    5021                 :            :  out:
    5022                 :            :         ring_buffer_unlock_commit(data->buffer, event);
    5023                 :            : 
    5024                 :            :         return 0;
    5025                 :            : }
    5026                 :            : 
    5027                 :            : static __init int rb_test(void *arg)
    5028                 :            : {
    5029                 :            :         struct rb_test_data *data = arg;
    5030                 :            : 
    5031                 :            :         while (!kthread_should_stop()) {
    5032                 :            :                 rb_write_something(data, false);
    5033                 :            :                 data->cnt++;
    5034                 :            : 
    5035                 :            :                 set_current_state(TASK_INTERRUPTIBLE);
    5036                 :            :                 /* Now sleep between a min of 100-300us and a max of 1ms */
    5037                 :            :                 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
    5038                 :            :         }
    5039                 :            : 
    5040                 :            :         return 0;
    5041                 :            : }
    5042                 :            : 
    5043                 :            : static __init void rb_ipi(void *ignore)
    5044                 :            : {
    5045                 :            :         struct rb_test_data *data;
    5046                 :            :         int cpu = smp_processor_id();
    5047                 :            : 
    5048                 :            :         data = &rb_data[cpu];
    5049                 :            :         rb_write_something(data, true);
    5050                 :            : }
    5051                 :            : 
    5052                 :            : static __init int rb_hammer_test(void *arg)
    5053                 :            : {
    5054                 :            :         while (!kthread_should_stop()) {
    5055                 :            : 
    5056                 :            :                 /* Send an IPI to all cpus to write data! */
    5057                 :            :                 smp_call_function(rb_ipi, NULL, 1);
    5058                 :            :                 /* No sleep, but for non preempt, let others run */
    5059                 :            :                 schedule();
    5060                 :            :         }
    5061                 :            : 
    5062                 :            :         return 0;
    5063                 :            : }
    5064                 :            : 
    5065                 :            : static __init int test_ringbuffer(void)
    5066                 :            : {
    5067                 :            :         struct task_struct *rb_hammer;
    5068                 :            :         struct ring_buffer *buffer;
    5069                 :            :         int cpu;
    5070                 :            :         int ret = 0;
    5071                 :            : 
    5072                 :            :         if (security_locked_down(LOCKDOWN_TRACEFS)) {
    5073                 :            :                 pr_warning("Lockdown is enabled, skipping ring buffer tests\n");
    5074                 :            :                 return 0;
    5075                 :            :         }
    5076                 :            : 
    5077                 :            :         pr_info("Running ring buffer tests...\n");
    5078                 :            : 
    5079                 :            :         buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
    5080                 :            :         if (WARN_ON(!buffer))
    5081                 :            :                 return 0;
    5082                 :            : 
    5083                 :            :         /* Disable buffer so that threads can't write to it yet */
    5084                 :            :         ring_buffer_record_off(buffer);
    5085                 :            : 
    5086                 :            :         for_each_online_cpu(cpu) {
    5087                 :            :                 rb_data[cpu].buffer = buffer;
    5088                 :            :                 rb_data[cpu].cpu = cpu;
    5089                 :            :                 rb_data[cpu].cnt = cpu;
    5090                 :            :                 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
    5091                 :            :                                                  "rbtester/%d", cpu);
    5092                 :            :                 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
    5093                 :            :                         pr_cont("FAILED\n");
    5094                 :            :                         ret = PTR_ERR(rb_threads[cpu]);
    5095                 :            :                         goto out_free;
    5096                 :            :                 }
    5097                 :            : 
    5098                 :            :                 kthread_bind(rb_threads[cpu], cpu);
    5099                 :            :                 wake_up_process(rb_threads[cpu]);
    5100                 :            :         }
    5101                 :            : 
    5102                 :            :         /* Now create the rb hammer! */
    5103                 :            :         rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
    5104                 :            :         if (WARN_ON(IS_ERR(rb_hammer))) {
    5105                 :            :                 pr_cont("FAILED\n");
    5106                 :            :                 ret = PTR_ERR(rb_hammer);
    5107                 :            :                 goto out_free;
    5108                 :            :         }
    5109                 :            : 
    5110                 :            :         ring_buffer_record_on(buffer);
    5111                 :            :         /*
    5112                 :            :          * Show buffer is enabled before setting rb_test_started.
    5113                 :            :          * Yes there's a small race window where events could be
    5114                 :            :          * dropped and the thread wont catch it. But when a ring
    5115                 :            :          * buffer gets enabled, there will always be some kind of
    5116                 :            :          * delay before other CPUs see it. Thus, we don't care about
    5117                 :            :          * those dropped events. We care about events dropped after
    5118                 :            :          * the threads see that the buffer is active.
    5119                 :            :          */
    5120                 :            :         smp_wmb();
    5121                 :            :         rb_test_started = true;
    5122                 :            : 
    5123                 :            :         set_current_state(TASK_INTERRUPTIBLE);
    5124                 :            :         /* Just run for 10 seconds */;
    5125                 :            :         schedule_timeout(10 * HZ);
    5126                 :            : 
    5127                 :            :         kthread_stop(rb_hammer);
    5128                 :            : 
    5129                 :            :  out_free:
    5130                 :            :         for_each_online_cpu(cpu) {
    5131                 :            :                 if (!rb_threads[cpu])
    5132                 :            :                         break;
    5133                 :            :                 kthread_stop(rb_threads[cpu]);
    5134                 :            :         }
    5135                 :            :         if (ret) {
    5136                 :            :                 ring_buffer_free(buffer);
    5137                 :            :                 return ret;
    5138                 :            :         }
    5139                 :            : 
    5140                 :            :         /* Report! */
    5141                 :            :         pr_info("finished\n");
    5142                 :            :         for_each_online_cpu(cpu) {
    5143                 :            :                 struct ring_buffer_event *event;
    5144                 :            :                 struct rb_test_data *data = &rb_data[cpu];
    5145                 :            :                 struct rb_item *item;
    5146                 :            :                 unsigned long total_events;
    5147                 :            :                 unsigned long total_dropped;
    5148                 :            :                 unsigned long total_written;
    5149                 :            :                 unsigned long total_alloc;
    5150                 :            :                 unsigned long total_read = 0;
    5151                 :            :                 unsigned long total_size = 0;
    5152                 :            :                 unsigned long total_len = 0;
    5153                 :            :                 unsigned long total_lost = 0;
    5154                 :            :                 unsigned long lost;
    5155                 :            :                 int big_event_size;
    5156                 :            :                 int small_event_size;
    5157                 :            : 
    5158                 :            :                 ret = -1;
    5159                 :            : 
    5160                 :            :                 total_events = data->events + data->events_nested;
    5161                 :            :                 total_written = data->bytes_written + data->bytes_written_nested;
    5162                 :            :                 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
    5163                 :            :                 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
    5164                 :            : 
    5165                 :            :                 big_event_size = data->max_size + data->max_size_nested;
    5166                 :            :                 small_event_size = data->min_size + data->min_size_nested;
    5167                 :            : 
    5168                 :            :                 pr_info("CPU %d:\n", cpu);
    5169                 :            :                 pr_info("              events:    %ld\n", total_events);
    5170                 :            :                 pr_info("       dropped bytes:    %ld\n", total_dropped);
    5171                 :            :                 pr_info("       alloced bytes:    %ld\n", total_alloc);
    5172                 :            :                 pr_info("       written bytes:    %ld\n", total_written);
    5173                 :            :                 pr_info("       biggest event:    %d\n", big_event_size);
    5174                 :            :                 pr_info("      smallest event:    %d\n", small_event_size);
    5175                 :            : 
    5176                 :            :                 if (RB_WARN_ON(buffer, total_dropped))
    5177                 :            :                         break;
    5178                 :            : 
    5179                 :            :                 ret = 0;
    5180                 :            : 
    5181                 :            :                 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
    5182                 :            :                         total_lost += lost;
    5183                 :            :                         item = ring_buffer_event_data(event);
    5184                 :            :                         total_len += ring_buffer_event_length(event);
    5185                 :            :                         total_size += item->size + sizeof(struct rb_item);
    5186                 :            :                         if (memcmp(&item->str[0], rb_string, item->size) != 0) {
    5187                 :            :                                 pr_info("FAILED!\n");
    5188                 :            :                                 pr_info("buffer had: %.*s\n", item->size, item->str);
    5189                 :            :                                 pr_info("expected:   %.*s\n", item->size, rb_string);
    5190                 :            :                                 RB_WARN_ON(buffer, 1);
    5191                 :            :                                 ret = -1;
    5192                 :            :                                 break;
    5193                 :            :                         }
    5194                 :            :                         total_read++;
    5195                 :            :                 }
    5196                 :            :                 if (ret)
    5197                 :            :                         break;
    5198                 :            : 
    5199                 :            :                 ret = -1;
    5200                 :            : 
    5201                 :            :                 pr_info("         read events:   %ld\n", total_read);
    5202                 :            :                 pr_info("         lost events:   %ld\n", total_lost);
    5203                 :            :                 pr_info("        total events:   %ld\n", total_lost + total_read);
    5204                 :            :                 pr_info("  recorded len bytes:   %ld\n", total_len);
    5205                 :            :                 pr_info(" recorded size bytes:   %ld\n", total_size);
    5206                 :            :                 if (total_lost)
    5207                 :            :                         pr_info(" With dropped events, record len and size may not match\n"
    5208                 :            :                                 " alloced and written from above\n");
    5209                 :            :                 if (!total_lost) {
    5210                 :            :                         if (RB_WARN_ON(buffer, total_len != total_alloc ||
    5211                 :            :                                        total_size != total_written))
    5212                 :            :                                 break;
    5213                 :            :                 }
    5214                 :            :                 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
    5215                 :            :                         break;
    5216                 :            : 
    5217                 :            :                 ret = 0;
    5218                 :            :         }
    5219                 :            :         if (!ret)
    5220                 :            :                 pr_info("Ring buffer PASSED!\n");
    5221                 :            : 
    5222                 :            :         ring_buffer_free(buffer);
    5223                 :            :         return 0;
    5224                 :            : }
    5225                 :            : 
    5226                 :            : late_initcall(test_ringbuffer);
    5227                 :            : #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
    

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