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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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