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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 : 0 : 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 : : event->type_len = RINGBUF_TYPE_PADDING;
157 : : event->time_delta = 0;
158 : : }
159 : :
160 : : static unsigned
161 : 0 : rb_event_data_length(struct ring_buffer_event *event)
162 : : {
163 : 0 : 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 : 0 : 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 : 0 : rb_event_ts_length(struct ring_buffer_event *event)
208 : : {
209 : 0 : unsigned len = 0;
210 : :
211 : 0 : if (extended_time(event)) {
212 : : /* time extends include the data event after it */
213 : 0 : 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 : 0 : 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 : : 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 : 0 : 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 : 0 : 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 : : struct buffer_data_page {
304 : : u64 time_stamp; /* page time stamp */
305 : : local_t commit; /* write committed index */
306 : : unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
307 : : };
308 : :
309 : : /*
310 : : * Note, the buffer_page list must be first. The buffer pages
311 : : * are allocated in cache lines, which means that each buffer
312 : : * page will be at the beginning of a cache line, and thus
313 : : * the least significant bits will be zero. We use this to
314 : : * add flags in the list struct pointers, to make the ring buffer
315 : : * lockless.
316 : : */
317 : : struct buffer_page {
318 : : struct list_head list; /* list of buffer pages */
319 : : local_t write; /* index for next write */
320 : : unsigned read; /* index for next read */
321 : : local_t entries; /* entries on this page */
322 : : unsigned long real_end; /* real end of data */
323 : : struct buffer_data_page *page; /* Actual data page */
324 : : };
325 : :
326 : : /*
327 : : * The buffer page counters, write and entries, must be reset
328 : : * atomically when crossing page boundaries. To synchronize this
329 : : * update, two counters are inserted into the number. One is
330 : : * the actual counter for the write position or count on the page.
331 : : *
332 : : * The other is a counter of updaters. Before an update happens
333 : : * the update partition of the counter is incremented. This will
334 : : * allow the updater to update the counter atomically.
335 : : *
336 : : * The counter is 20 bits, and the state data is 12.
337 : : */
338 : : #define RB_WRITE_MASK 0xfffff
339 : : #define RB_WRITE_INTCNT (1 << 20)
340 : :
341 : 126 : static void rb_init_page(struct buffer_data_page *bpage)
342 : : {
343 : 126 : local_set(&bpage->commit, 0);
344 : : }
345 : :
346 : : /*
347 : : * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
348 : : * this issue out.
349 : : */
350 : 0 : static void free_buffer_page(struct buffer_page *bpage)
351 : : {
352 : 0 : free_page((unsigned long)bpage->page);
353 : 0 : kfree(bpage);
354 : 0 : }
355 : :
356 : : /*
357 : : * We need to fit the time_stamp delta into 27 bits.
358 : : */
359 : 0 : static inline int test_time_stamp(u64 delta)
360 : : {
361 : 0 : if (delta & TS_DELTA_TEST)
362 : 0 : return 1;
363 : : return 0;
364 : : }
365 : :
366 : : #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
367 : :
368 : : /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
369 : : #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
370 : :
371 : 0 : int ring_buffer_print_page_header(struct trace_seq *s)
372 : : {
373 : 0 : struct buffer_data_page field;
374 : :
375 : 0 : trace_seq_printf(s, "\tfield: u64 timestamp;\t"
376 : : "offset:0;\tsize:%u;\tsigned:%u;\n",
377 : : (unsigned int)sizeof(field.time_stamp),
378 : : (unsigned int)is_signed_type(u64));
379 : :
380 : 0 : trace_seq_printf(s, "\tfield: local_t commit;\t"
381 : : "offset:%u;\tsize:%u;\tsigned:%u;\n",
382 : : (unsigned int)offsetof(typeof(field), commit),
383 : : (unsigned int)sizeof(field.commit),
384 : : (unsigned int)is_signed_type(long));
385 : :
386 : 0 : trace_seq_printf(s, "\tfield: int overwrite;\t"
387 : : "offset:%u;\tsize:%u;\tsigned:%u;\n",
388 : : (unsigned int)offsetof(typeof(field), commit),
389 : : 1,
390 : : (unsigned int)is_signed_type(long));
391 : :
392 : 0 : trace_seq_printf(s, "\tfield: char data;\t"
393 : : "offset:%u;\tsize:%u;\tsigned:%u;\n",
394 : : (unsigned int)offsetof(typeof(field), data),
395 : : (unsigned int)BUF_PAGE_SIZE,
396 : : (unsigned int)is_signed_type(char));
397 : :
398 [ # # ]: 0 : return !trace_seq_has_overflowed(s);
399 : : }
400 : :
401 : : struct rb_irq_work {
402 : : struct irq_work work;
403 : : wait_queue_head_t waiters;
404 : : wait_queue_head_t full_waiters;
405 : : bool waiters_pending;
406 : : bool full_waiters_pending;
407 : : bool wakeup_full;
408 : : };
409 : :
410 : : /*
411 : : * Structure to hold event state and handle nested events.
412 : : */
413 : : struct rb_event_info {
414 : : u64 ts;
415 : : u64 delta;
416 : : unsigned long length;
417 : : struct buffer_page *tail_page;
418 : : int add_timestamp;
419 : : };
420 : :
421 : : /*
422 : : * Used for which event context the event is in.
423 : : * NMI = 0
424 : : * IRQ = 1
425 : : * SOFTIRQ = 2
426 : : * NORMAL = 3
427 : : *
428 : : * See trace_recursive_lock() comment below for more details.
429 : : */
430 : : enum {
431 : : RB_CTX_NMI,
432 : : RB_CTX_IRQ,
433 : : RB_CTX_SOFTIRQ,
434 : : RB_CTX_NORMAL,
435 : : RB_CTX_MAX
436 : : };
437 : :
438 : : /*
439 : : * head_page == tail_page && head == tail then buffer is empty.
440 : : */
441 : : struct ring_buffer_per_cpu {
442 : : int cpu;
443 : : atomic_t record_disabled;
444 : : struct trace_buffer *buffer;
445 : : raw_spinlock_t reader_lock; /* serialize readers */
446 : : arch_spinlock_t lock;
447 : : struct lock_class_key lock_key;
448 : : struct buffer_data_page *free_page;
449 : : unsigned long nr_pages;
450 : : unsigned int current_context;
451 : : struct list_head *pages;
452 : : struct buffer_page *head_page; /* read from head */
453 : : struct buffer_page *tail_page; /* write to tail */
454 : : struct buffer_page *commit_page; /* committed pages */
455 : : struct buffer_page *reader_page;
456 : : unsigned long lost_events;
457 : : unsigned long last_overrun;
458 : : unsigned long nest;
459 : : local_t entries_bytes;
460 : : local_t entries;
461 : : local_t overrun;
462 : : local_t commit_overrun;
463 : : local_t dropped_events;
464 : : local_t committing;
465 : : local_t commits;
466 : : local_t pages_touched;
467 : : local_t pages_read;
468 : : long last_pages_touch;
469 : : size_t shortest_full;
470 : : unsigned long read;
471 : : unsigned long read_bytes;
472 : : u64 write_stamp;
473 : : u64 read_stamp;
474 : : /* ring buffer pages to update, > 0 to add, < 0 to remove */
475 : : long nr_pages_to_update;
476 : : struct list_head new_pages; /* new pages to add */
477 : : struct work_struct update_pages_work;
478 : : struct completion update_done;
479 : :
480 : : struct rb_irq_work irq_work;
481 : : };
482 : :
483 : : struct trace_buffer {
484 : : unsigned flags;
485 : : int cpus;
486 : : atomic_t record_disabled;
487 : : atomic_t resize_disabled;
488 : : cpumask_var_t cpumask;
489 : :
490 : : struct lock_class_key *reader_lock_key;
491 : :
492 : : struct mutex mutex;
493 : :
494 : : struct ring_buffer_per_cpu **buffers;
495 : :
496 : : struct hlist_node node;
497 : : u64 (*clock)(void);
498 : :
499 : : struct rb_irq_work irq_work;
500 : : bool time_stamp_abs;
501 : : };
502 : :
503 : : struct ring_buffer_iter {
504 : : struct ring_buffer_per_cpu *cpu_buffer;
505 : : unsigned long head;
506 : : struct buffer_page *head_page;
507 : : struct buffer_page *cache_reader_page;
508 : : unsigned long cache_read;
509 : : u64 read_stamp;
510 : : };
511 : :
512 : : /**
513 : : * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
514 : : * @buffer: The ring_buffer to get the number of pages from
515 : : * @cpu: The cpu of the ring_buffer to get the number of pages from
516 : : *
517 : : * Returns the number of pages used by a per_cpu buffer of the ring buffer.
518 : : */
519 : 0 : size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
520 : : {
521 : 0 : return buffer->buffers[cpu]->nr_pages;
522 : : }
523 : :
524 : : /**
525 : : * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
526 : : * @buffer: The ring_buffer to get the number of pages from
527 : : * @cpu: The cpu of the ring_buffer to get the number of pages from
528 : : *
529 : : * Returns the number of pages that have content in the ring buffer.
530 : : */
531 : 0 : size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
532 : : {
533 : 0 : size_t read;
534 : 0 : size_t cnt;
535 : :
536 : 0 : read = local_read(&buffer->buffers[cpu]->pages_read);
537 : 0 : cnt = local_read(&buffer->buffers[cpu]->pages_touched);
538 : : /* The reader can read an empty page, but not more than that */
539 [ # # ]: 0 : if (cnt < read) {
540 [ # # ]: 0 : WARN_ON_ONCE(read > cnt + 1);
541 : : return 0;
542 : : }
543 : :
544 : 0 : return cnt - read;
545 : : }
546 : :
547 : : /*
548 : : * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
549 : : *
550 : : * Schedules a delayed work to wake up any task that is blocked on the
551 : : * ring buffer waiters queue.
552 : : */
553 : 0 : static void rb_wake_up_waiters(struct irq_work *work)
554 : : {
555 : 0 : struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
556 : :
557 : 0 : wake_up_all(&rbwork->waiters);
558 [ # # ]: 0 : if (rbwork->wakeup_full) {
559 : 0 : rbwork->wakeup_full = false;
560 : 0 : wake_up_all(&rbwork->full_waiters);
561 : : }
562 : 0 : }
563 : :
564 : : /**
565 : : * ring_buffer_wait - wait for input to the ring buffer
566 : : * @buffer: buffer to wait on
567 : : * @cpu: the cpu buffer to wait on
568 : : * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
569 : : *
570 : : * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
571 : : * as data is added to any of the @buffer's cpu buffers. Otherwise
572 : : * it will wait for data to be added to a specific cpu buffer.
573 : : */
574 : 0 : int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
575 : : {
576 : 0 : struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
577 [ # # ]: 0 : DEFINE_WAIT(wait);
578 : 0 : struct rb_irq_work *work;
579 : 0 : int ret = 0;
580 : :
581 : : /*
582 : : * Depending on what the caller is waiting for, either any
583 : : * data in any cpu buffer, or a specific buffer, put the
584 : : * caller on the appropriate wait queue.
585 : : */
586 [ # # ]: 0 : if (cpu == RING_BUFFER_ALL_CPUS) {
587 : 0 : work = &buffer->irq_work;
588 : : /* Full only makes sense on per cpu reads */
589 : 0 : full = 0;
590 : : } else {
591 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
592 : : return -ENODEV;
593 : 0 : cpu_buffer = buffer->buffers[cpu];
594 : 0 : work = &cpu_buffer->irq_work;
595 : : }
596 : :
597 : :
598 : 0 : while (true) {
599 [ # # ]: 0 : if (full)
600 : 0 : prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
601 : : else
602 : 0 : prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
603 : :
604 : : /*
605 : : * The events can happen in critical sections where
606 : : * checking a work queue can cause deadlocks.
607 : : * After adding a task to the queue, this flag is set
608 : : * only to notify events to try to wake up the queue
609 : : * using irq_work.
610 : : *
611 : : * We don't clear it even if the buffer is no longer
612 : : * empty. The flag only causes the next event to run
613 : : * irq_work to do the work queue wake up. The worse
614 : : * that can happen if we race with !trace_empty() is that
615 : : * an event will cause an irq_work to try to wake up
616 : : * an empty queue.
617 : : *
618 : : * There's no reason to protect this flag either, as
619 : : * the work queue and irq_work logic will do the necessary
620 : : * synchronization for the wake ups. The only thing
621 : : * that is necessary is that the wake up happens after
622 : : * a task has been queued. It's OK for spurious wake ups.
623 : : */
624 [ # # ]: 0 : if (full)
625 : 0 : work->full_waiters_pending = true;
626 : : else
627 : 0 : work->waiters_pending = true;
628 : :
629 [ # # ]: 0 : if (signal_pending(current)) {
630 : : ret = -EINTR;
631 : : break;
632 : : }
633 : :
634 [ # # # # ]: 0 : if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
635 : : break;
636 : :
637 [ # # # # ]: 0 : if (cpu != RING_BUFFER_ALL_CPUS &&
638 : 0 : !ring_buffer_empty_cpu(buffer, cpu)) {
639 : 0 : unsigned long flags;
640 : 0 : bool pagebusy;
641 : 0 : size_t nr_pages;
642 : 0 : size_t dirty;
643 : :
644 [ # # ]: 0 : if (!full)
645 : : break;
646 : :
647 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
648 : 0 : pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
649 : 0 : nr_pages = cpu_buffer->nr_pages;
650 : 0 : dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
651 [ # # ]: 0 : if (!cpu_buffer->shortest_full ||
652 [ # # ]: 0 : cpu_buffer->shortest_full < full)
653 : 0 : cpu_buffer->shortest_full = full;
654 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
655 [ # # # # ]: 0 : if (!pagebusy &&
656 [ # # ]: 0 : (!nr_pages || (dirty * 100) > full * nr_pages))
657 : : break;
658 : : }
659 : :
660 : 0 : schedule();
661 : : }
662 : :
663 [ # # ]: 0 : if (full)
664 : 0 : finish_wait(&work->full_waiters, &wait);
665 : : else
666 : 0 : finish_wait(&work->waiters, &wait);
667 : :
668 : : return ret;
669 : : }
670 : :
671 : : /**
672 : : * ring_buffer_poll_wait - poll on buffer input
673 : : * @buffer: buffer to wait on
674 : : * @cpu: the cpu buffer to wait on
675 : : * @filp: the file descriptor
676 : : * @poll_table: The poll descriptor
677 : : *
678 : : * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
679 : : * as data is added to any of the @buffer's cpu buffers. Otherwise
680 : : * it will wait for data to be added to a specific cpu buffer.
681 : : *
682 : : * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
683 : : * zero otherwise.
684 : : */
685 : 0 : __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
686 : : struct file *filp, poll_table *poll_table)
687 : : {
688 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
689 : 0 : struct rb_irq_work *work;
690 : :
691 [ # # ]: 0 : if (cpu == RING_BUFFER_ALL_CPUS)
692 : 0 : work = &buffer->irq_work;
693 : : else {
694 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
695 : : return -EINVAL;
696 : :
697 : 0 : cpu_buffer = buffer->buffers[cpu];
698 : 0 : work = &cpu_buffer->irq_work;
699 : : }
700 : :
701 [ # # ]: 0 : poll_wait(filp, &work->waiters, poll_table);
702 : 0 : work->waiters_pending = true;
703 : : /*
704 : : * There's a tight race between setting the waiters_pending and
705 : : * checking if the ring buffer is empty. Once the waiters_pending bit
706 : : * is set, the next event will wake the task up, but we can get stuck
707 : : * if there's only a single event in.
708 : : *
709 : : * FIXME: Ideally, we need a memory barrier on the writer side as well,
710 : : * but adding a memory barrier to all events will cause too much of a
711 : : * performance hit in the fast path. We only need a memory barrier when
712 : : * the buffer goes from empty to having content. But as this race is
713 : : * extremely small, and it's not a problem if another event comes in, we
714 : : * will fix it later.
715 : : */
716 : 0 : smp_mb();
717 : :
718 [ # # # # : 0 : if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
# # ]
719 [ # # ]: 0 : (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
720 : 0 : return EPOLLIN | EPOLLRDNORM;
721 : : return 0;
722 : : }
723 : :
724 : : /* buffer may be either ring_buffer or ring_buffer_per_cpu */
725 : : #define RB_WARN_ON(b, cond) \
726 : : ({ \
727 : : int _____ret = unlikely(cond); \
728 : : if (_____ret) { \
729 : : if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
730 : : struct ring_buffer_per_cpu *__b = \
731 : : (void *)b; \
732 : : atomic_inc(&__b->buffer->record_disabled); \
733 : : } else \
734 : : atomic_inc(&b->record_disabled); \
735 : : WARN_ON(1); \
736 : : } \
737 : : _____ret; \
738 : : })
739 : :
740 : : /* Up this if you want to test the TIME_EXTENTS and normalization */
741 : : #define DEBUG_SHIFT 0
742 : :
743 : 0 : static inline u64 rb_time_stamp(struct trace_buffer *buffer)
744 : : {
745 : : /* shift to debug/test normalization and TIME_EXTENTS */
746 : 0 : return buffer->clock() << DEBUG_SHIFT;
747 : : }
748 : :
749 : 0 : u64 ring_buffer_time_stamp(struct trace_buffer *buffer, int cpu)
750 : : {
751 : 0 : u64 time;
752 : :
753 : 0 : preempt_disable_notrace();
754 : 0 : time = rb_time_stamp(buffer);
755 : 0 : preempt_enable_notrace();
756 : :
757 : 0 : return time;
758 : : }
759 : : EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
760 : :
761 : 0 : void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
762 : : int cpu, u64 *ts)
763 : : {
764 : : /* Just stupid testing the normalize function and deltas */
765 : 0 : *ts >>= DEBUG_SHIFT;
766 : 0 : }
767 : : EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
768 : :
769 : : /*
770 : : * Making the ring buffer lockless makes things tricky.
771 : : * Although writes only happen on the CPU that they are on,
772 : : * and they only need to worry about interrupts. Reads can
773 : : * happen on any CPU.
774 : : *
775 : : * The reader page is always off the ring buffer, but when the
776 : : * reader finishes with a page, it needs to swap its page with
777 : : * a new one from the buffer. The reader needs to take from
778 : : * the head (writes go to the tail). But if a writer is in overwrite
779 : : * mode and wraps, it must push the head page forward.
780 : : *
781 : : * Here lies the problem.
782 : : *
783 : : * The reader must be careful to replace only the head page, and
784 : : * not another one. As described at the top of the file in the
785 : : * ASCII art, the reader sets its old page to point to the next
786 : : * page after head. It then sets the page after head to point to
787 : : * the old reader page. But if the writer moves the head page
788 : : * during this operation, the reader could end up with the tail.
789 : : *
790 : : * We use cmpxchg to help prevent this race. We also do something
791 : : * special with the page before head. We set the LSB to 1.
792 : : *
793 : : * When the writer must push the page forward, it will clear the
794 : : * bit that points to the head page, move the head, and then set
795 : : * the bit that points to the new head page.
796 : : *
797 : : * We also don't want an interrupt coming in and moving the head
798 : : * page on another writer. Thus we use the second LSB to catch
799 : : * that too. Thus:
800 : : *
801 : : * head->list->prev->next bit 1 bit 0
802 : : * ------- -------
803 : : * Normal page 0 0
804 : : * Points to head page 0 1
805 : : * New head page 1 0
806 : : *
807 : : * Note we can not trust the prev pointer of the head page, because:
808 : : *
809 : : * +----+ +-----+ +-----+
810 : : * | |------>| T |---X--->| N |
811 : : * | |<------| | | |
812 : : * +----+ +-----+ +-----+
813 : : * ^ ^ |
814 : : * | +-----+ | |
815 : : * +----------| R |----------+ |
816 : : * | |<-----------+
817 : : * +-----+
818 : : *
819 : : * Key: ---X--> HEAD flag set in pointer
820 : : * T Tail page
821 : : * R Reader page
822 : : * N Next page
823 : : *
824 : : * (see __rb_reserve_next() to see where this happens)
825 : : *
826 : : * What the above shows is that the reader just swapped out
827 : : * the reader page with a page in the buffer, but before it
828 : : * could make the new header point back to the new page added
829 : : * it was preempted by a writer. The writer moved forward onto
830 : : * the new page added by the reader and is about to move forward
831 : : * again.
832 : : *
833 : : * You can see, it is legitimate for the previous pointer of
834 : : * the head (or any page) not to point back to itself. But only
835 : : * temporarily.
836 : : */
837 : :
838 : : #define RB_PAGE_NORMAL 0UL
839 : : #define RB_PAGE_HEAD 1UL
840 : : #define RB_PAGE_UPDATE 2UL
841 : :
842 : :
843 : : #define RB_FLAG_MASK 3UL
844 : :
845 : : /* PAGE_MOVED is not part of the mask */
846 : : #define RB_PAGE_MOVED 4UL
847 : :
848 : : /*
849 : : * rb_list_head - remove any bit
850 : : */
851 : 0 : static struct list_head *rb_list_head(struct list_head *list)
852 : : {
853 : 0 : unsigned long val = (unsigned long)list;
854 : :
855 : 0 : return (struct list_head *)(val & ~RB_FLAG_MASK);
856 : : }
857 : :
858 : : /*
859 : : * rb_is_head_page - test if the given page is the head page
860 : : *
861 : : * Because the reader may move the head_page pointer, we can
862 : : * not trust what the head page is (it may be pointing to
863 : : * the reader page). But if the next page is a header page,
864 : : * its flags will be non zero.
865 : : */
866 : : static inline int
867 : 0 : rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
868 : : struct buffer_page *page, struct list_head *list)
869 : : {
870 : 0 : unsigned long val;
871 : :
872 : 0 : val = (unsigned long)list->next;
873 : :
874 : 0 : if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
875 : : return RB_PAGE_MOVED;
876 : :
877 : 0 : return val & RB_FLAG_MASK;
878 : : }
879 : :
880 : : /*
881 : : * rb_is_reader_page
882 : : *
883 : : * The unique thing about the reader page, is that, if the
884 : : * writer is ever on it, the previous pointer never points
885 : : * back to the reader page.
886 : : */
887 : 0 : static bool rb_is_reader_page(struct buffer_page *page)
888 : : {
889 : 0 : struct list_head *list = page->list.prev;
890 : :
891 : 0 : return rb_list_head(list->next) != &page->list;
892 : : }
893 : :
894 : : /*
895 : : * rb_set_list_to_head - set a list_head to be pointing to head.
896 : : */
897 : 42 : static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
898 : : struct list_head *list)
899 : : {
900 : 42 : unsigned long *ptr;
901 : :
902 : 42 : ptr = (unsigned long *)&list->next;
903 : 42 : *ptr |= RB_PAGE_HEAD;
904 : 42 : *ptr &= ~RB_PAGE_UPDATE;
905 : 42 : }
906 : :
907 : : /*
908 : : * rb_head_page_activate - sets up head page
909 : : */
910 : 84 : static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
911 : : {
912 : 84 : struct buffer_page *head;
913 : :
914 : 84 : head = cpu_buffer->head_page;
915 : 84 : if (!head)
916 : : return;
917 : :
918 : : /*
919 : : * Set the previous list pointer to have the HEAD flag.
920 : : */
921 : 42 : rb_set_list_to_head(cpu_buffer, head->list.prev);
922 : : }
923 : :
924 : 84 : static void rb_list_head_clear(struct list_head *list)
925 : : {
926 : 84 : unsigned long *ptr = (unsigned long *)&list->next;
927 : :
928 : 84 : *ptr &= ~RB_FLAG_MASK;
929 : : }
930 : :
931 : : /*
932 : : * rb_head_page_deactivate - clears head page ptr (for free list)
933 : : */
934 : : static void
935 : 42 : rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
936 : : {
937 : 42 : struct list_head *hd;
938 : :
939 : : /* Go through the whole list and clear any pointers found. */
940 : 42 : rb_list_head_clear(cpu_buffer->pages);
941 : :
942 [ - - - - : 84 : list_for_each(hd, cpu_buffer->pages)
+ + ]
943 : 42 : rb_list_head_clear(hd);
944 : : }
945 : :
946 : : static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
947 : : struct buffer_page *head,
948 : : struct buffer_page *prev,
949 : : int old_flag, int new_flag)
950 : : {
951 : : struct list_head *list;
952 : : unsigned long val = (unsigned long)&head->list;
953 : : unsigned long ret;
954 : :
955 : : list = &prev->list;
956 : :
957 : : val &= ~RB_FLAG_MASK;
958 : :
959 : : ret = cmpxchg((unsigned long *)&list->next,
960 : : val | old_flag, val | new_flag);
961 : :
962 : : /* check if the reader took the page */
963 : : if ((ret & ~RB_FLAG_MASK) != val)
964 : : return RB_PAGE_MOVED;
965 : :
966 : : return ret & RB_FLAG_MASK;
967 : : }
968 : :
969 : 0 : static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
970 : : struct buffer_page *head,
971 : : struct buffer_page *prev,
972 : : int old_flag)
973 : : {
974 : 0 : return rb_head_page_set(cpu_buffer, head, prev,
975 : : old_flag, RB_PAGE_UPDATE);
976 : : }
977 : :
978 : 0 : static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
979 : : struct buffer_page *head,
980 : : struct buffer_page *prev,
981 : : int old_flag)
982 : : {
983 : 0 : return rb_head_page_set(cpu_buffer, head, prev,
984 : : old_flag, RB_PAGE_HEAD);
985 : : }
986 : :
987 : 0 : static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
988 : : struct buffer_page *head,
989 : : struct buffer_page *prev,
990 : : int old_flag)
991 : : {
992 : 0 : return rb_head_page_set(cpu_buffer, head, prev,
993 : : old_flag, RB_PAGE_NORMAL);
994 : : }
995 : :
996 : 0 : static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
997 : : struct buffer_page **bpage)
998 : : {
999 : 0 : struct list_head *p = rb_list_head((*bpage)->list.next);
1000 : :
1001 : 0 : *bpage = list_entry(p, struct buffer_page, list);
1002 : 0 : }
1003 : :
1004 : : static struct buffer_page *
1005 : 0 : rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1006 : : {
1007 : 0 : struct buffer_page *head;
1008 : 0 : struct buffer_page *page;
1009 : 0 : struct list_head *list;
1010 : 0 : int i;
1011 : :
1012 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1013 : : return NULL;
1014 : :
1015 : : /* sanity check */
1016 : 0 : list = cpu_buffer->pages;
1017 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1018 : : return NULL;
1019 : :
1020 : 0 : page = head = cpu_buffer->head_page;
1021 : : /*
1022 : : * It is possible that the writer moves the header behind
1023 : : * where we started, and we miss in one loop.
1024 : : * A second loop should grab the header, but we'll do
1025 : : * three loops just because I'm paranoid.
1026 : : */
1027 [ # # ]: 0 : for (i = 0; i < 3; i++) {
1028 : 0 : do {
1029 [ # # # # ]: 0 : if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
1030 : 0 : cpu_buffer->head_page = page;
1031 : 0 : return page;
1032 : : }
1033 : 0 : rb_inc_page(cpu_buffer, &page);
1034 [ # # ]: 0 : } while (page != head);
1035 : : }
1036 : :
1037 : 0 : RB_WARN_ON(cpu_buffer, 1);
1038 : :
1039 : 0 : return NULL;
1040 : : }
1041 : :
1042 : : static int rb_head_page_replace(struct buffer_page *old,
1043 : : struct buffer_page *new)
1044 : : {
1045 : : unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1046 : : unsigned long val;
1047 : : unsigned long ret;
1048 : :
1049 : : val = *ptr & ~RB_FLAG_MASK;
1050 : : val |= RB_PAGE_HEAD;
1051 : :
1052 : : ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1053 : :
1054 : : return ret == val;
1055 : : }
1056 : :
1057 : : /*
1058 : : * rb_tail_page_update - move the tail page forward
1059 : : */
1060 : 0 : static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1061 : : struct buffer_page *tail_page,
1062 : : struct buffer_page *next_page)
1063 : : {
1064 : 0 : unsigned long old_entries;
1065 : 0 : unsigned long old_write;
1066 : :
1067 : : /*
1068 : : * The tail page now needs to be moved forward.
1069 : : *
1070 : : * We need to reset the tail page, but without messing
1071 : : * with possible erasing of data brought in by interrupts
1072 : : * that have moved the tail page and are currently on it.
1073 : : *
1074 : : * We add a counter to the write field to denote this.
1075 : : */
1076 : 0 : old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1077 : 0 : old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1078 : :
1079 : 0 : local_inc(&cpu_buffer->pages_touched);
1080 : : /*
1081 : : * Just make sure we have seen our old_write and synchronize
1082 : : * with any interrupts that come in.
1083 : : */
1084 : 0 : barrier();
1085 : :
1086 : : /*
1087 : : * If the tail page is still the same as what we think
1088 : : * it is, then it is up to us to update the tail
1089 : : * pointer.
1090 : : */
1091 [ # # ]: 0 : if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1092 : : /* Zero the write counter */
1093 : 0 : unsigned long val = old_write & ~RB_WRITE_MASK;
1094 : 0 : unsigned long eval = old_entries & ~RB_WRITE_MASK;
1095 : :
1096 : : /*
1097 : : * This will only succeed if an interrupt did
1098 : : * not come in and change it. In which case, we
1099 : : * do not want to modify it.
1100 : : *
1101 : : * We add (void) to let the compiler know that we do not care
1102 : : * about the return value of these functions. We use the
1103 : : * cmpxchg to only update if an interrupt did not already
1104 : : * do it for us. If the cmpxchg fails, we don't care.
1105 : : */
1106 : 0 : (void)local_cmpxchg(&next_page->write, old_write, val);
1107 : 0 : (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1108 : :
1109 : : /*
1110 : : * No need to worry about races with clearing out the commit.
1111 : : * it only can increment when a commit takes place. But that
1112 : : * only happens in the outer most nested commit.
1113 : : */
1114 : 0 : local_set(&next_page->page->commit, 0);
1115 : :
1116 : : /* Again, either we update tail_page or an interrupt does */
1117 : 0 : (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1118 : : }
1119 : 0 : }
1120 : :
1121 : : static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1122 : : struct buffer_page *bpage)
1123 : : {
1124 : : unsigned long val = (unsigned long)bpage;
1125 : :
1126 : : if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1127 : : return 1;
1128 : :
1129 : : return 0;
1130 : : }
1131 : :
1132 : : /**
1133 : : * rb_check_list - make sure a pointer to a list has the last bits zero
1134 : : */
1135 : : static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1136 : : struct list_head *list)
1137 : : {
1138 : : if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1139 : : return 1;
1140 : : if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1141 : : return 1;
1142 : : return 0;
1143 : : }
1144 : :
1145 : : /**
1146 : : * rb_check_pages - integrity check of buffer pages
1147 : : * @cpu_buffer: CPU buffer with pages to test
1148 : : *
1149 : : * As a safety measure we check to make sure the data pages have not
1150 : : * been corrupted.
1151 : : */
1152 : 42 : static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1153 : : {
1154 : 42 : struct list_head *head = cpu_buffer->pages;
1155 : 42 : struct buffer_page *bpage, *tmp;
1156 : :
1157 : : /* Reset the head page if it exists */
1158 [ - + ]: 42 : if (cpu_buffer->head_page)
1159 : 0 : rb_set_head_page(cpu_buffer);
1160 : :
1161 : 42 : rb_head_page_deactivate(cpu_buffer);
1162 : :
1163 [ - + + - ]: 42 : if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1164 : : return -1;
1165 [ - + + - ]: 42 : if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1166 : : return -1;
1167 : :
1168 [ + - ]: 42 : if (rb_check_list(cpu_buffer, head))
1169 : : return -1;
1170 : :
1171 [ + + ]: 84 : list_for_each_entry_safe(bpage, tmp, head, list) {
1172 [ - + + - ]: 42 : if (RB_WARN_ON(cpu_buffer,
1173 : : bpage->list.next->prev != &bpage->list))
1174 : : return -1;
1175 [ - + + - ]: 42 : if (RB_WARN_ON(cpu_buffer,
1176 : : bpage->list.prev->next != &bpage->list))
1177 : : return -1;
1178 [ + - ]: 42 : if (rb_check_list(cpu_buffer, &bpage->list))
1179 : : return -1;
1180 : : }
1181 : :
1182 [ - + ]: 42 : rb_head_page_activate(cpu_buffer);
1183 : :
1184 : : return 0;
1185 : : }
1186 : :
1187 : 42 : static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1188 : : {
1189 : 42 : struct buffer_page *bpage, *tmp;
1190 : 42 : bool user_thread = current->mm != NULL;
1191 : 42 : gfp_t mflags;
1192 : 42 : long i;
1193 : :
1194 : : /*
1195 : : * Check if the available memory is there first.
1196 : : * Note, si_mem_available() only gives us a rough estimate of available
1197 : : * memory. It may not be accurate. But we don't care, we just want
1198 : : * to prevent doing any allocation when it is obvious that it is
1199 : : * not going to succeed.
1200 : : */
1201 : 42 : i = si_mem_available();
1202 [ + - ]: 42 : if (i < nr_pages)
1203 : : return -ENOMEM;
1204 : :
1205 : : /*
1206 : : * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1207 : : * gracefully without invoking oom-killer and the system is not
1208 : : * destabilized.
1209 : : */
1210 : 42 : mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1211 : :
1212 : : /*
1213 : : * If a user thread allocates too much, and si_mem_available()
1214 : : * reports there's enough memory, even though there is not.
1215 : : * Make sure the OOM killer kills this thread. This can happen
1216 : : * even with RETRY_MAYFAIL because another task may be doing
1217 : : * an allocation after this task has taken all memory.
1218 : : * This is the task the OOM killer needs to take out during this
1219 : : * loop, even if it was triggered by an allocation somewhere else.
1220 : : */
1221 [ - + ]: 42 : if (user_thread)
1222 : 0 : set_current_oom_origin();
1223 [ + + ]: 126 : for (i = 0; i < nr_pages; i++) {
1224 : 84 : struct page *page;
1225 : :
1226 : 84 : bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1227 : : mflags, cpu_to_node(cpu));
1228 [ - + ]: 84 : if (!bpage)
1229 : 0 : goto free_pages;
1230 : :
1231 [ - + ]: 84 : list_add(&bpage->list, pages);
1232 : :
1233 [ - + ]: 84 : page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
1234 [ - + ]: 84 : if (!page)
1235 : 0 : goto free_pages;
1236 : 84 : bpage->page = page_address(page);
1237 : 84 : rb_init_page(bpage->page);
1238 : :
1239 [ - + - - ]: 84 : if (user_thread && fatal_signal_pending(current))
1240 : 0 : goto free_pages;
1241 : : }
1242 [ - + ]: 42 : if (user_thread)
1243 : 0 : clear_current_oom_origin();
1244 : :
1245 : : return 0;
1246 : :
1247 : 0 : free_pages:
1248 [ # # ]: 0 : list_for_each_entry_safe(bpage, tmp, pages, list) {
1249 : 0 : list_del_init(&bpage->list);
1250 : 0 : free_buffer_page(bpage);
1251 : : }
1252 [ # # ]: 0 : if (user_thread)
1253 : 0 : clear_current_oom_origin();
1254 : :
1255 : : return -ENOMEM;
1256 : : }
1257 : :
1258 : 42 : static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1259 : : unsigned long nr_pages)
1260 : : {
1261 : 42 : LIST_HEAD(pages);
1262 : :
1263 [ - + ]: 42 : WARN_ON(!nr_pages);
1264 : :
1265 [ + - ]: 42 : if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1266 : : return -ENOMEM;
1267 : :
1268 : : /*
1269 : : * The ring buffer page list is a circular list that does not
1270 : : * start and end with a list head. All page list items point to
1271 : : * other pages.
1272 : : */
1273 : 42 : cpu_buffer->pages = pages.next;
1274 : 42 : list_del(&pages);
1275 : :
1276 : 42 : cpu_buffer->nr_pages = nr_pages;
1277 : :
1278 : 42 : rb_check_pages(cpu_buffer);
1279 : :
1280 : 42 : return 0;
1281 : : }
1282 : :
1283 : : static struct ring_buffer_per_cpu *
1284 : 42 : rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1285 : : {
1286 : 42 : struct ring_buffer_per_cpu *cpu_buffer;
1287 : 42 : struct buffer_page *bpage;
1288 : 42 : struct page *page;
1289 : 42 : int ret;
1290 : :
1291 : 42 : cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1292 : : GFP_KERNEL, cpu_to_node(cpu));
1293 [ + - ]: 42 : if (!cpu_buffer)
1294 : : return NULL;
1295 : :
1296 : 42 : cpu_buffer->cpu = cpu;
1297 : 42 : cpu_buffer->buffer = buffer;
1298 : 42 : raw_spin_lock_init(&cpu_buffer->reader_lock);
1299 : 42 : lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1300 : 42 : cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1301 : 42 : INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1302 : 42 : init_completion(&cpu_buffer->update_done);
1303 : 42 : init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1304 : 42 : init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1305 : 42 : init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1306 : :
1307 : 42 : bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1308 : : GFP_KERNEL, cpu_to_node(cpu));
1309 [ - + ]: 42 : if (!bpage)
1310 : 0 : goto fail_free_buffer;
1311 : :
1312 : 42 : rb_check_bpage(cpu_buffer, bpage);
1313 : :
1314 : 42 : cpu_buffer->reader_page = bpage;
1315 [ - + ]: 42 : page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1316 [ - + ]: 42 : if (!page)
1317 : 0 : goto fail_free_reader;
1318 : 42 : bpage->page = page_address(page);
1319 : 42 : rb_init_page(bpage->page);
1320 : :
1321 : 42 : INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1322 : 42 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
1323 : :
1324 : 42 : ret = rb_allocate_pages(cpu_buffer, nr_pages);
1325 [ - + ]: 42 : if (ret < 0)
1326 : 0 : goto fail_free_reader;
1327 : :
1328 : 42 : cpu_buffer->head_page
1329 : 42 : = list_entry(cpu_buffer->pages, struct buffer_page, list);
1330 : 42 : cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1331 : :
1332 [ + - ]: 42 : rb_head_page_activate(cpu_buffer);
1333 : :
1334 : : return cpu_buffer;
1335 : :
1336 : 0 : fail_free_reader:
1337 : 0 : free_buffer_page(cpu_buffer->reader_page);
1338 : :
1339 : 0 : fail_free_buffer:
1340 : 0 : kfree(cpu_buffer);
1341 : 0 : return NULL;
1342 : : }
1343 : :
1344 : 0 : static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1345 : : {
1346 : 0 : struct list_head *head = cpu_buffer->pages;
1347 : 0 : struct buffer_page *bpage, *tmp;
1348 : :
1349 : 0 : free_buffer_page(cpu_buffer->reader_page);
1350 : :
1351 : 0 : rb_head_page_deactivate(cpu_buffer);
1352 : :
1353 [ # # ]: 0 : if (head) {
1354 [ # # ]: 0 : list_for_each_entry_safe(bpage, tmp, head, list) {
1355 : 0 : list_del_init(&bpage->list);
1356 : 0 : free_buffer_page(bpage);
1357 : : }
1358 : 0 : bpage = list_entry(head, struct buffer_page, list);
1359 : 0 : free_buffer_page(bpage);
1360 : : }
1361 : :
1362 : 0 : kfree(cpu_buffer);
1363 : 0 : }
1364 : :
1365 : : /**
1366 : : * __ring_buffer_alloc - allocate a new ring_buffer
1367 : : * @size: the size in bytes per cpu that is needed.
1368 : : * @flags: attributes to set for the ring buffer.
1369 : : * @key: ring buffer reader_lock_key.
1370 : : *
1371 : : * Currently the only flag that is available is the RB_FL_OVERWRITE
1372 : : * flag. This flag means that the buffer will overwrite old data
1373 : : * when the buffer wraps. If this flag is not set, the buffer will
1374 : : * drop data when the tail hits the head.
1375 : : */
1376 : 42 : struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1377 : : struct lock_class_key *key)
1378 : : {
1379 : 42 : struct trace_buffer *buffer;
1380 : 42 : long nr_pages;
1381 : 42 : int bsize;
1382 : 42 : int cpu;
1383 : 42 : int ret;
1384 : :
1385 : : /* keep it in its own cache line */
1386 : 42 : buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1387 : : GFP_KERNEL);
1388 [ + - ]: 42 : if (!buffer)
1389 : : return NULL;
1390 : :
1391 : 42 : if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1392 : : goto fail_free_buffer;
1393 : :
1394 : 42 : nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1395 : 42 : buffer->flags = flags;
1396 : 42 : buffer->clock = trace_clock_local;
1397 : 42 : buffer->reader_lock_key = key;
1398 : :
1399 : 42 : init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1400 : 42 : init_waitqueue_head(&buffer->irq_work.waiters);
1401 : :
1402 : : /* need at least two pages */
1403 : 42 : if (nr_pages < 2)
1404 : : nr_pages = 2;
1405 : :
1406 : 42 : buffer->cpus = nr_cpu_ids;
1407 : :
1408 : 42 : bsize = sizeof(void *) * nr_cpu_ids;
1409 : 42 : buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1410 : : GFP_KERNEL);
1411 [ - + ]: 42 : if (!buffer->buffers)
1412 : 0 : goto fail_free_cpumask;
1413 : :
1414 : 42 : cpu = raw_smp_processor_id();
1415 : 42 : cpumask_set_cpu(cpu, buffer->cpumask);
1416 : 42 : buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1417 [ - + ]: 42 : if (!buffer->buffers[cpu])
1418 : 0 : goto fail_free_buffers;
1419 : :
1420 : 42 : ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1421 [ - + ]: 42 : if (ret < 0)
1422 : 0 : goto fail_free_buffers;
1423 : :
1424 : 42 : mutex_init(&buffer->mutex);
1425 : :
1426 : 42 : return buffer;
1427 : :
1428 : : fail_free_buffers:
1429 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
1430 [ # # ]: 0 : if (buffer->buffers[cpu])
1431 : 0 : rb_free_cpu_buffer(buffer->buffers[cpu]);
1432 : : }
1433 : 0 : kfree(buffer->buffers);
1434 : :
1435 : 0 : fail_free_cpumask:
1436 : 0 : free_cpumask_var(buffer->cpumask);
1437 : :
1438 : : fail_free_buffer:
1439 : 0 : kfree(buffer);
1440 : 0 : return NULL;
1441 : : }
1442 : : EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1443 : :
1444 : : /**
1445 : : * ring_buffer_free - free a ring buffer.
1446 : : * @buffer: the buffer to free.
1447 : : */
1448 : : void
1449 : 0 : ring_buffer_free(struct trace_buffer *buffer)
1450 : : {
1451 : 0 : int cpu;
1452 : :
1453 : 0 : cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1454 : :
1455 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu)
1456 : 0 : rb_free_cpu_buffer(buffer->buffers[cpu]);
1457 : :
1458 : 0 : kfree(buffer->buffers);
1459 : 0 : free_cpumask_var(buffer->cpumask);
1460 : :
1461 : 0 : kfree(buffer);
1462 : 0 : }
1463 : : EXPORT_SYMBOL_GPL(ring_buffer_free);
1464 : :
1465 : 0 : void ring_buffer_set_clock(struct trace_buffer *buffer,
1466 : : u64 (*clock)(void))
1467 : : {
1468 : 0 : buffer->clock = clock;
1469 : 0 : }
1470 : :
1471 : 0 : void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1472 : : {
1473 : 0 : buffer->time_stamp_abs = abs;
1474 : 0 : }
1475 : :
1476 : 0 : bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1477 : : {
1478 : 0 : return buffer->time_stamp_abs;
1479 : : }
1480 : :
1481 : : static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1482 : :
1483 : 0 : static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1484 : : {
1485 : 0 : return local_read(&bpage->entries) & RB_WRITE_MASK;
1486 : : }
1487 : :
1488 : 0 : static inline unsigned long rb_page_write(struct buffer_page *bpage)
1489 : : {
1490 : 0 : return local_read(&bpage->write) & RB_WRITE_MASK;
1491 : : }
1492 : :
1493 : : static int
1494 : 0 : rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1495 : : {
1496 : 0 : struct list_head *tail_page, *to_remove, *next_page;
1497 : 0 : struct buffer_page *to_remove_page, *tmp_iter_page;
1498 : 0 : struct buffer_page *last_page, *first_page;
1499 : 0 : unsigned long nr_removed;
1500 : 0 : unsigned long head_bit;
1501 : 0 : int page_entries;
1502 : :
1503 : 0 : head_bit = 0;
1504 : :
1505 : 0 : raw_spin_lock_irq(&cpu_buffer->reader_lock);
1506 : 0 : atomic_inc(&cpu_buffer->record_disabled);
1507 : : /*
1508 : : * We don't race with the readers since we have acquired the reader
1509 : : * lock. We also don't race with writers after disabling recording.
1510 : : * This makes it easy to figure out the first and the last page to be
1511 : : * removed from the list. We unlink all the pages in between including
1512 : : * the first and last pages. This is done in a busy loop so that we
1513 : : * lose the least number of traces.
1514 : : * The pages are freed after we restart recording and unlock readers.
1515 : : */
1516 : 0 : tail_page = &cpu_buffer->tail_page->list;
1517 : :
1518 : : /*
1519 : : * tail page might be on reader page, we remove the next page
1520 : : * from the ring buffer
1521 : : */
1522 [ # # ]: 0 : if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1523 : 0 : tail_page = rb_list_head(tail_page->next);
1524 : 0 : to_remove = tail_page;
1525 : :
1526 : : /* start of pages to remove */
1527 : 0 : first_page = list_entry(rb_list_head(to_remove->next),
1528 : : struct buffer_page, list);
1529 : :
1530 [ # # ]: 0 : for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1531 : 0 : to_remove = rb_list_head(to_remove)->next;
1532 : 0 : head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1533 : : }
1534 : :
1535 : 0 : next_page = rb_list_head(to_remove)->next;
1536 : :
1537 : : /*
1538 : : * Now we remove all pages between tail_page and next_page.
1539 : : * Make sure that we have head_bit value preserved for the
1540 : : * next page
1541 : : */
1542 : 0 : tail_page->next = (struct list_head *)((unsigned long)next_page |
1543 : : head_bit);
1544 : 0 : next_page = rb_list_head(next_page);
1545 : 0 : next_page->prev = tail_page;
1546 : :
1547 : : /* make sure pages points to a valid page in the ring buffer */
1548 : 0 : cpu_buffer->pages = next_page;
1549 : :
1550 : : /* update head page */
1551 [ # # ]: 0 : if (head_bit)
1552 : 0 : cpu_buffer->head_page = list_entry(next_page,
1553 : : struct buffer_page, list);
1554 : :
1555 : : /*
1556 : : * change read pointer to make sure any read iterators reset
1557 : : * themselves
1558 : : */
1559 : 0 : cpu_buffer->read = 0;
1560 : :
1561 : : /* pages are removed, resume tracing and then free the pages */
1562 : 0 : atomic_dec(&cpu_buffer->record_disabled);
1563 : 0 : raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1564 : :
1565 [ # # ]: 0 : RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1566 : :
1567 : : /* last buffer page to remove */
1568 : : last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1569 : : list);
1570 : : tmp_iter_page = first_page;
1571 : :
1572 : 0 : do {
1573 : 0 : cond_resched();
1574 : :
1575 : 0 : to_remove_page = tmp_iter_page;
1576 : 0 : rb_inc_page(cpu_buffer, &tmp_iter_page);
1577 : :
1578 : : /* update the counters */
1579 : 0 : page_entries = rb_page_entries(to_remove_page);
1580 [ # # ]: 0 : if (page_entries) {
1581 : : /*
1582 : : * If something was added to this page, it was full
1583 : : * since it is not the tail page. So we deduct the
1584 : : * bytes consumed in ring buffer from here.
1585 : : * Increment overrun to account for the lost events.
1586 : : */
1587 : 0 : local_add(page_entries, &cpu_buffer->overrun);
1588 : 0 : local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1589 : : }
1590 : :
1591 : : /*
1592 : : * We have already removed references to this list item, just
1593 : : * free up the buffer_page and its page
1594 : : */
1595 : 0 : free_buffer_page(to_remove_page);
1596 : 0 : nr_removed--;
1597 : :
1598 [ # # ]: 0 : } while (to_remove_page != last_page);
1599 : :
1600 [ # # ]: 0 : RB_WARN_ON(cpu_buffer, nr_removed);
1601 : :
1602 : 0 : return nr_removed == 0;
1603 : : }
1604 : :
1605 : : static int
1606 : 0 : rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1607 : : {
1608 : 0 : struct list_head *pages = &cpu_buffer->new_pages;
1609 : 0 : int retries, success;
1610 : :
1611 : 0 : raw_spin_lock_irq(&cpu_buffer->reader_lock);
1612 : : /*
1613 : : * We are holding the reader lock, so the reader page won't be swapped
1614 : : * in the ring buffer. Now we are racing with the writer trying to
1615 : : * move head page and the tail page.
1616 : : * We are going to adapt the reader page update process where:
1617 : : * 1. We first splice the start and end of list of new pages between
1618 : : * the head page and its previous page.
1619 : : * 2. We cmpxchg the prev_page->next to point from head page to the
1620 : : * start of new pages list.
1621 : : * 3. Finally, we update the head->prev to the end of new list.
1622 : : *
1623 : : * We will try this process 10 times, to make sure that we don't keep
1624 : : * spinning.
1625 : : */
1626 : 0 : retries = 10;
1627 : 0 : success = 0;
1628 [ # # ]: 0 : while (retries--) {
1629 : 0 : struct list_head *head_page, *prev_page, *r;
1630 : 0 : struct list_head *last_page, *first_page;
1631 : 0 : struct list_head *head_page_with_bit;
1632 : :
1633 : 0 : head_page = &rb_set_head_page(cpu_buffer)->list;
1634 [ # # ]: 0 : if (!head_page)
1635 : : break;
1636 : 0 : prev_page = head_page->prev;
1637 : :
1638 : 0 : first_page = pages->next;
1639 : 0 : last_page = pages->prev;
1640 : :
1641 : 0 : head_page_with_bit = (struct list_head *)
1642 : 0 : ((unsigned long)head_page | RB_PAGE_HEAD);
1643 : :
1644 : 0 : last_page->next = head_page_with_bit;
1645 : 0 : first_page->prev = prev_page;
1646 : :
1647 : 0 : r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1648 : :
1649 [ # # ]: 0 : if (r == head_page_with_bit) {
1650 : : /*
1651 : : * yay, we replaced the page pointer to our new list,
1652 : : * now, we just have to update to head page's prev
1653 : : * pointer to point to end of list
1654 : : */
1655 : 0 : head_page->prev = last_page;
1656 : 0 : success = 1;
1657 : 0 : break;
1658 : : }
1659 : : }
1660 : :
1661 : 0 : if (success)
1662 : 0 : INIT_LIST_HEAD(pages);
1663 : : /*
1664 : : * If we weren't successful in adding in new pages, warn and stop
1665 : : * tracing
1666 : : */
1667 [ # # ]: 0 : RB_WARN_ON(cpu_buffer, !success);
1668 : 0 : raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1669 : :
1670 : : /* free pages if they weren't inserted */
1671 [ # # ]: 0 : if (!success) {
1672 : 0 : struct buffer_page *bpage, *tmp;
1673 [ # # ]: 0 : list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1674 : : list) {
1675 : 0 : list_del_init(&bpage->list);
1676 : 0 : free_buffer_page(bpage);
1677 : : }
1678 : : }
1679 : 0 : return success;
1680 : : }
1681 : :
1682 : 0 : static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1683 : : {
1684 : 0 : int success;
1685 : :
1686 [ # # ]: 0 : if (cpu_buffer->nr_pages_to_update > 0)
1687 : 0 : success = rb_insert_pages(cpu_buffer);
1688 : : else
1689 : 0 : success = rb_remove_pages(cpu_buffer,
1690 : 0 : -cpu_buffer->nr_pages_to_update);
1691 : :
1692 [ # # ]: 0 : if (success)
1693 : 0 : cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1694 : 0 : }
1695 : :
1696 : 0 : static void update_pages_handler(struct work_struct *work)
1697 : : {
1698 : 0 : struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1699 : : struct ring_buffer_per_cpu, update_pages_work);
1700 : 0 : rb_update_pages(cpu_buffer);
1701 : 0 : complete(&cpu_buffer->update_done);
1702 : 0 : }
1703 : :
1704 : : /**
1705 : : * ring_buffer_resize - resize the ring buffer
1706 : : * @buffer: the buffer to resize.
1707 : : * @size: the new size.
1708 : : * @cpu_id: the cpu buffer to resize
1709 : : *
1710 : : * Minimum size is 2 * BUF_PAGE_SIZE.
1711 : : *
1712 : : * Returns 0 on success and < 0 on failure.
1713 : : */
1714 : 0 : int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
1715 : : int cpu_id)
1716 : : {
1717 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
1718 : 0 : unsigned long nr_pages;
1719 : 0 : int cpu, err = 0;
1720 : :
1721 : : /*
1722 : : * Always succeed at resizing a non-existent buffer:
1723 : : */
1724 [ # # ]: 0 : if (!buffer)
1725 : 0 : return size;
1726 : :
1727 : : /* Make sure the requested buffer exists */
1728 [ # # # # ]: 0 : if (cpu_id != RING_BUFFER_ALL_CPUS &&
1729 : : !cpumask_test_cpu(cpu_id, buffer->cpumask))
1730 : 0 : return size;
1731 : :
1732 : 0 : nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1733 : :
1734 : : /* we need a minimum of two pages */
1735 [ # # ]: 0 : if (nr_pages < 2)
1736 : 0 : nr_pages = 2;
1737 : :
1738 : 0 : size = nr_pages * BUF_PAGE_SIZE;
1739 : :
1740 : : /*
1741 : : * Don't succeed if resizing is disabled, as a reader might be
1742 : : * manipulating the ring buffer and is expecting a sane state while
1743 : : * this is true.
1744 : : */
1745 [ # # ]: 0 : if (atomic_read(&buffer->resize_disabled))
1746 : : return -EBUSY;
1747 : :
1748 : : /* prevent another thread from changing buffer sizes */
1749 : 0 : mutex_lock(&buffer->mutex);
1750 : :
1751 [ # # ]: 0 : if (cpu_id == RING_BUFFER_ALL_CPUS) {
1752 : : /* calculate the pages to update */
1753 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
1754 : 0 : cpu_buffer = buffer->buffers[cpu];
1755 : :
1756 : 0 : cpu_buffer->nr_pages_to_update = nr_pages -
1757 : 0 : cpu_buffer->nr_pages;
1758 : : /*
1759 : : * nothing more to do for removing pages or no update
1760 : : */
1761 [ # # ]: 0 : if (cpu_buffer->nr_pages_to_update <= 0)
1762 : 0 : continue;
1763 : : /*
1764 : : * to add pages, make sure all new pages can be
1765 : : * allocated without receiving ENOMEM
1766 : : */
1767 : 0 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
1768 [ # # ]: 0 : if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1769 : : &cpu_buffer->new_pages, cpu)) {
1770 : : /* not enough memory for new pages */
1771 : 0 : err = -ENOMEM;
1772 : 0 : goto out_err;
1773 : : }
1774 : : }
1775 : :
1776 : 0 : get_online_cpus();
1777 : : /*
1778 : : * Fire off all the required work handlers
1779 : : * We can't schedule on offline CPUs, but it's not necessary
1780 : : * since we can change their buffer sizes without any race.
1781 : : */
1782 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
1783 : 0 : cpu_buffer = buffer->buffers[cpu];
1784 [ # # ]: 0 : if (!cpu_buffer->nr_pages_to_update)
1785 : 0 : continue;
1786 : :
1787 : : /* Can't run something on an offline CPU. */
1788 [ # # ]: 0 : if (!cpu_online(cpu)) {
1789 : 0 : rb_update_pages(cpu_buffer);
1790 : 0 : cpu_buffer->nr_pages_to_update = 0;
1791 : : } else {
1792 : 0 : schedule_work_on(cpu,
1793 : : &cpu_buffer->update_pages_work);
1794 : : }
1795 : : }
1796 : :
1797 : : /* wait for all the updates to complete */
1798 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
1799 : 0 : cpu_buffer = buffer->buffers[cpu];
1800 [ # # ]: 0 : if (!cpu_buffer->nr_pages_to_update)
1801 : 0 : continue;
1802 : :
1803 [ # # ]: 0 : if (cpu_online(cpu))
1804 : 0 : wait_for_completion(&cpu_buffer->update_done);
1805 : 0 : cpu_buffer->nr_pages_to_update = 0;
1806 : : }
1807 : :
1808 : 0 : put_online_cpus();
1809 : : } else {
1810 : : /* Make sure this CPU has been initialized */
1811 [ # # ]: 0 : if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1812 : 0 : goto out;
1813 : :
1814 : 0 : cpu_buffer = buffer->buffers[cpu_id];
1815 : :
1816 [ # # ]: 0 : if (nr_pages == cpu_buffer->nr_pages)
1817 : 0 : goto out;
1818 : :
1819 : 0 : cpu_buffer->nr_pages_to_update = nr_pages -
1820 : : cpu_buffer->nr_pages;
1821 : :
1822 [ # # ]: 0 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
1823 [ # # # # ]: 0 : if (cpu_buffer->nr_pages_to_update > 0 &&
1824 : 0 : __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1825 : : &cpu_buffer->new_pages, cpu_id)) {
1826 : 0 : err = -ENOMEM;
1827 : 0 : goto out_err;
1828 : : }
1829 : :
1830 : 0 : get_online_cpus();
1831 : :
1832 : : /* Can't run something on an offline CPU. */
1833 [ # # ]: 0 : if (!cpu_online(cpu_id))
1834 : 0 : rb_update_pages(cpu_buffer);
1835 : : else {
1836 : 0 : schedule_work_on(cpu_id,
1837 : : &cpu_buffer->update_pages_work);
1838 : 0 : wait_for_completion(&cpu_buffer->update_done);
1839 : : }
1840 : :
1841 : 0 : cpu_buffer->nr_pages_to_update = 0;
1842 : 0 : put_online_cpus();
1843 : : }
1844 : :
1845 : 0 : out:
1846 : : /*
1847 : : * The ring buffer resize can happen with the ring buffer
1848 : : * enabled, so that the update disturbs the tracing as little
1849 : : * as possible. But if the buffer is disabled, we do not need
1850 : : * to worry about that, and we can take the time to verify
1851 : : * that the buffer is not corrupt.
1852 : : */
1853 [ # # ]: 0 : if (atomic_read(&buffer->record_disabled)) {
1854 : 0 : atomic_inc(&buffer->record_disabled);
1855 : : /*
1856 : : * Even though the buffer was disabled, we must make sure
1857 : : * that it is truly disabled before calling rb_check_pages.
1858 : : * There could have been a race between checking
1859 : : * record_disable and incrementing it.
1860 : : */
1861 : 0 : synchronize_rcu();
1862 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
1863 : 0 : cpu_buffer = buffer->buffers[cpu];
1864 : 0 : rb_check_pages(cpu_buffer);
1865 : : }
1866 : 0 : atomic_dec(&buffer->record_disabled);
1867 : : }
1868 : :
1869 : 0 : mutex_unlock(&buffer->mutex);
1870 : 0 : return size;
1871 : :
1872 : : out_err:
1873 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
1874 : 0 : struct buffer_page *bpage, *tmp;
1875 : :
1876 : 0 : cpu_buffer = buffer->buffers[cpu];
1877 : 0 : cpu_buffer->nr_pages_to_update = 0;
1878 : :
1879 [ # # ]: 0 : if (list_empty(&cpu_buffer->new_pages))
1880 : 0 : continue;
1881 : :
1882 [ # # ]: 0 : list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1883 : : list) {
1884 : 0 : list_del_init(&bpage->list);
1885 : 0 : free_buffer_page(bpage);
1886 : : }
1887 : : }
1888 : 0 : mutex_unlock(&buffer->mutex);
1889 : 0 : return err;
1890 : : }
1891 : : EXPORT_SYMBOL_GPL(ring_buffer_resize);
1892 : :
1893 : 0 : void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
1894 : : {
1895 : 0 : mutex_lock(&buffer->mutex);
1896 [ # # ]: 0 : if (val)
1897 : 0 : buffer->flags |= RB_FL_OVERWRITE;
1898 : : else
1899 : 0 : buffer->flags &= ~RB_FL_OVERWRITE;
1900 : 0 : mutex_unlock(&buffer->mutex);
1901 : 0 : }
1902 : : EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1903 : :
1904 : 0 : static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1905 : : {
1906 : 0 : return bpage->page->data + index;
1907 : : }
1908 : :
1909 : : static __always_inline struct ring_buffer_event *
1910 : 0 : rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1911 : : {
1912 : 0 : return __rb_page_index(cpu_buffer->reader_page,
1913 : 0 : cpu_buffer->reader_page->read);
1914 : : }
1915 : :
1916 : : static __always_inline struct ring_buffer_event *
1917 : 0 : rb_iter_head_event(struct ring_buffer_iter *iter)
1918 : : {
1919 : 0 : return __rb_page_index(iter->head_page, iter->head);
1920 : : }
1921 : :
1922 : 0 : static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
1923 : : {
1924 : 0 : return local_read(&bpage->page->commit);
1925 : : }
1926 : :
1927 : : /* Size is determined by what has been committed */
1928 : 0 : static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
1929 : : {
1930 : 0 : return rb_page_commit(bpage);
1931 : : }
1932 : :
1933 : : static __always_inline unsigned
1934 : 0 : rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1935 : : {
1936 : 0 : return rb_page_commit(cpu_buffer->commit_page);
1937 : : }
1938 : :
1939 : : static __always_inline unsigned
1940 : 0 : rb_event_index(struct ring_buffer_event *event)
1941 : : {
1942 : 0 : unsigned long addr = (unsigned long)event;
1943 : :
1944 : 0 : return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1945 : : }
1946 : :
1947 : 0 : static void rb_inc_iter(struct ring_buffer_iter *iter)
1948 : : {
1949 : 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1950 : :
1951 : : /*
1952 : : * The iterator could be on the reader page (it starts there).
1953 : : * But the head could have moved, since the reader was
1954 : : * found. Check for this case and assign the iterator
1955 : : * to the head page instead of next.
1956 : : */
1957 [ # # ]: 0 : if (iter->head_page == cpu_buffer->reader_page)
1958 : 0 : iter->head_page = rb_set_head_page(cpu_buffer);
1959 : : else
1960 : 0 : rb_inc_page(cpu_buffer, &iter->head_page);
1961 : :
1962 : 0 : iter->read_stamp = iter->head_page->page->time_stamp;
1963 : 0 : iter->head = 0;
1964 : 0 : }
1965 : :
1966 : : /*
1967 : : * rb_handle_head_page - writer hit the head page
1968 : : *
1969 : : * Returns: +1 to retry page
1970 : : * 0 to continue
1971 : : * -1 on error
1972 : : */
1973 : : static int
1974 : 0 : rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1975 : : struct buffer_page *tail_page,
1976 : : struct buffer_page *next_page)
1977 : : {
1978 : 0 : struct buffer_page *new_head;
1979 : 0 : int entries;
1980 : 0 : int type;
1981 : 0 : int ret;
1982 : :
1983 : 0 : entries = rb_page_entries(next_page);
1984 : :
1985 : : /*
1986 : : * The hard part is here. We need to move the head
1987 : : * forward, and protect against both readers on
1988 : : * other CPUs and writers coming in via interrupts.
1989 : : */
1990 : 0 : type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1991 : : RB_PAGE_HEAD);
1992 : :
1993 : : /*
1994 : : * type can be one of four:
1995 : : * NORMAL - an interrupt already moved it for us
1996 : : * HEAD - we are the first to get here.
1997 : : * UPDATE - we are the interrupt interrupting
1998 : : * a current move.
1999 : : * MOVED - a reader on another CPU moved the next
2000 : : * pointer to its reader page. Give up
2001 : : * and try again.
2002 : : */
2003 : :
2004 [ # # # # ]: 0 : switch (type) {
2005 : 0 : case RB_PAGE_HEAD:
2006 : : /*
2007 : : * We changed the head to UPDATE, thus
2008 : : * it is our responsibility to update
2009 : : * the counters.
2010 : : */
2011 : 0 : local_add(entries, &cpu_buffer->overrun);
2012 : 0 : local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2013 : :
2014 : : /*
2015 : : * The entries will be zeroed out when we move the
2016 : : * tail page.
2017 : : */
2018 : :
2019 : : /* still more to do */
2020 : : break;
2021 : :
2022 : : case RB_PAGE_UPDATE:
2023 : : /*
2024 : : * This is an interrupt that interrupt the
2025 : : * previous update. Still more to do.
2026 : : */
2027 : : break;
2028 : : case RB_PAGE_NORMAL:
2029 : : /*
2030 : : * An interrupt came in before the update
2031 : : * and processed this for us.
2032 : : * Nothing left to do.
2033 : : */
2034 : : return 1;
2035 : : case RB_PAGE_MOVED:
2036 : : /*
2037 : : * The reader is on another CPU and just did
2038 : : * a swap with our next_page.
2039 : : * Try again.
2040 : : */
2041 : : return 1;
2042 : : default:
2043 : 0 : RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2044 : 0 : return -1;
2045 : : }
2046 : :
2047 : : /*
2048 : : * Now that we are here, the old head pointer is
2049 : : * set to UPDATE. This will keep the reader from
2050 : : * swapping the head page with the reader page.
2051 : : * The reader (on another CPU) will spin till
2052 : : * we are finished.
2053 : : *
2054 : : * We just need to protect against interrupts
2055 : : * doing the job. We will set the next pointer
2056 : : * to HEAD. After that, we set the old pointer
2057 : : * to NORMAL, but only if it was HEAD before.
2058 : : * otherwise we are an interrupt, and only
2059 : : * want the outer most commit to reset it.
2060 : : */
2061 : 0 : new_head = next_page;
2062 : 0 : rb_inc_page(cpu_buffer, &new_head);
2063 : :
2064 : 0 : ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2065 : : RB_PAGE_NORMAL);
2066 : :
2067 : : /*
2068 : : * Valid returns are:
2069 : : * HEAD - an interrupt came in and already set it.
2070 : : * NORMAL - One of two things:
2071 : : * 1) We really set it.
2072 : : * 2) A bunch of interrupts came in and moved
2073 : : * the page forward again.
2074 : : */
2075 [ # # ]: 0 : switch (ret) {
2076 : : case RB_PAGE_HEAD:
2077 : : case RB_PAGE_NORMAL:
2078 : : /* OK */
2079 : 0 : break;
2080 : : default:
2081 : 0 : RB_WARN_ON(cpu_buffer, 1);
2082 : 0 : return -1;
2083 : : }
2084 : :
2085 : : /*
2086 : : * It is possible that an interrupt came in,
2087 : : * set the head up, then more interrupts came in
2088 : : * and moved it again. When we get back here,
2089 : : * the page would have been set to NORMAL but we
2090 : : * just set it back to HEAD.
2091 : : *
2092 : : * How do you detect this? Well, if that happened
2093 : : * the tail page would have moved.
2094 : : */
2095 [ # # ]: 0 : if (ret == RB_PAGE_NORMAL) {
2096 : 0 : struct buffer_page *buffer_tail_page;
2097 : :
2098 [ # # ]: 0 : buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2099 : : /*
2100 : : * If the tail had moved passed next, then we need
2101 : : * to reset the pointer.
2102 : : */
2103 : 0 : if (buffer_tail_page != tail_page &&
2104 [ # # ]: 0 : buffer_tail_page != next_page)
2105 : 0 : rb_head_page_set_normal(cpu_buffer, new_head,
2106 : : next_page,
2107 : : RB_PAGE_HEAD);
2108 : : }
2109 : :
2110 : : /*
2111 : : * If this was the outer most commit (the one that
2112 : : * changed the original pointer from HEAD to UPDATE),
2113 : : * then it is up to us to reset it to NORMAL.
2114 : : */
2115 [ # # ]: 0 : if (type == RB_PAGE_HEAD) {
2116 : 0 : ret = rb_head_page_set_normal(cpu_buffer, next_page,
2117 : : tail_page,
2118 : : RB_PAGE_UPDATE);
2119 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer,
2120 : : ret != RB_PAGE_UPDATE))
2121 : 0 : return -1;
2122 : : }
2123 : :
2124 : : return 0;
2125 : : }
2126 : :
2127 : : static inline void
2128 : : rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2129 : : unsigned long tail, struct rb_event_info *info)
2130 : : {
2131 : : struct buffer_page *tail_page = info->tail_page;
2132 : : struct ring_buffer_event *event;
2133 : : unsigned long length = info->length;
2134 : :
2135 : : /*
2136 : : * Only the event that crossed the page boundary
2137 : : * must fill the old tail_page with padding.
2138 : : */
2139 : : if (tail >= BUF_PAGE_SIZE) {
2140 : : /*
2141 : : * If the page was filled, then we still need
2142 : : * to update the real_end. Reset it to zero
2143 : : * and the reader will ignore it.
2144 : : */
2145 : : if (tail == BUF_PAGE_SIZE)
2146 : : tail_page->real_end = 0;
2147 : :
2148 : : local_sub(length, &tail_page->write);
2149 : : return;
2150 : : }
2151 : :
2152 : : event = __rb_page_index(tail_page, tail);
2153 : :
2154 : : /* account for padding bytes */
2155 : : local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2156 : :
2157 : : /*
2158 : : * Save the original length to the meta data.
2159 : : * This will be used by the reader to add lost event
2160 : : * counter.
2161 : : */
2162 : : tail_page->real_end = tail;
2163 : :
2164 : : /*
2165 : : * If this event is bigger than the minimum size, then
2166 : : * we need to be careful that we don't subtract the
2167 : : * write counter enough to allow another writer to slip
2168 : : * in on this page.
2169 : : * We put in a discarded commit instead, to make sure
2170 : : * that this space is not used again.
2171 : : *
2172 : : * If we are less than the minimum size, we don't need to
2173 : : * worry about it.
2174 : : */
2175 : : if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2176 : : /* No room for any events */
2177 : :
2178 : : /* Mark the rest of the page with padding */
2179 : : rb_event_set_padding(event);
2180 : :
2181 : : /* Set the write back to the previous setting */
2182 : : local_sub(length, &tail_page->write);
2183 : : return;
2184 : : }
2185 : :
2186 : : /* Put in a discarded event */
2187 : : event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2188 : : event->type_len = RINGBUF_TYPE_PADDING;
2189 : : /* time delta must be non zero */
2190 : : event->time_delta = 1;
2191 : :
2192 : : /* Set write to end of buffer */
2193 : : length = (tail + length) - BUF_PAGE_SIZE;
2194 : : local_sub(length, &tail_page->write);
2195 : : }
2196 : :
2197 : : static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2198 : :
2199 : : /*
2200 : : * This is the slow path, force gcc not to inline it.
2201 : : */
2202 : : static noinline struct ring_buffer_event *
2203 : 0 : rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2204 : : unsigned long tail, struct rb_event_info *info)
2205 : : {
2206 : 0 : struct buffer_page *tail_page = info->tail_page;
2207 : 0 : struct buffer_page *commit_page = cpu_buffer->commit_page;
2208 : 0 : struct trace_buffer *buffer = cpu_buffer->buffer;
2209 : 0 : struct buffer_page *next_page;
2210 : 0 : int ret;
2211 : :
2212 : 0 : next_page = tail_page;
2213 : :
2214 : 0 : rb_inc_page(cpu_buffer, &next_page);
2215 : :
2216 : : /*
2217 : : * If for some reason, we had an interrupt storm that made
2218 : : * it all the way around the buffer, bail, and warn
2219 : : * about it.
2220 : : */
2221 [ # # ]: 0 : if (unlikely(next_page == commit_page)) {
2222 : 0 : local_inc(&cpu_buffer->commit_overrun);
2223 : 0 : goto out_reset;
2224 : : }
2225 : :
2226 : : /*
2227 : : * This is where the fun begins!
2228 : : *
2229 : : * We are fighting against races between a reader that
2230 : : * could be on another CPU trying to swap its reader
2231 : : * page with the buffer head.
2232 : : *
2233 : : * We are also fighting against interrupts coming in and
2234 : : * moving the head or tail on us as well.
2235 : : *
2236 : : * If the next page is the head page then we have filled
2237 : : * the buffer, unless the commit page is still on the
2238 : : * reader page.
2239 : : */
2240 [ # # # # ]: 0 : if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2241 : :
2242 : : /*
2243 : : * If the commit is not on the reader page, then
2244 : : * move the header page.
2245 : : */
2246 [ # # ]: 0 : if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2247 : : /*
2248 : : * If we are not in overwrite mode,
2249 : : * this is easy, just stop here.
2250 : : */
2251 [ # # ]: 0 : if (!(buffer->flags & RB_FL_OVERWRITE)) {
2252 : 0 : local_inc(&cpu_buffer->dropped_events);
2253 : 0 : goto out_reset;
2254 : : }
2255 : :
2256 : 0 : ret = rb_handle_head_page(cpu_buffer,
2257 : : tail_page,
2258 : : next_page);
2259 [ # # ]: 0 : if (ret < 0)
2260 : 0 : goto out_reset;
2261 [ # # ]: 0 : if (ret)
2262 : 0 : goto out_again;
2263 : : } else {
2264 : : /*
2265 : : * We need to be careful here too. The
2266 : : * commit page could still be on the reader
2267 : : * page. We could have a small buffer, and
2268 : : * have filled up the buffer with events
2269 : : * from interrupts and such, and wrapped.
2270 : : *
2271 : : * Note, if the tail page is also the on the
2272 : : * reader_page, we let it move out.
2273 : : */
2274 [ # # # # ]: 0 : if (unlikely((cpu_buffer->commit_page !=
2275 : : cpu_buffer->tail_page) &&
2276 : : (cpu_buffer->commit_page ==
2277 : : cpu_buffer->reader_page))) {
2278 : 0 : local_inc(&cpu_buffer->commit_overrun);
2279 : 0 : goto out_reset;
2280 : : }
2281 : : }
2282 : : }
2283 : :
2284 : 0 : rb_tail_page_update(cpu_buffer, tail_page, next_page);
2285 : :
2286 : 0 : out_again:
2287 : :
2288 : 0 : rb_reset_tail(cpu_buffer, tail, info);
2289 : :
2290 : : /* Commit what we have for now. */
2291 : 0 : rb_end_commit(cpu_buffer);
2292 : : /* rb_end_commit() decs committing */
2293 : 0 : local_inc(&cpu_buffer->committing);
2294 : :
2295 : : /* fail and let the caller try again */
2296 : 0 : return ERR_PTR(-EAGAIN);
2297 : :
2298 : 0 : out_reset:
2299 : : /* reset write */
2300 : 0 : rb_reset_tail(cpu_buffer, tail, info);
2301 : :
2302 : 0 : return NULL;
2303 : : }
2304 : :
2305 : : /* Slow path, do not inline */
2306 : : static noinline struct ring_buffer_event *
2307 : 0 : rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2308 : : {
2309 [ # # ]: 0 : if (abs)
2310 : 0 : event->type_len = RINGBUF_TYPE_TIME_STAMP;
2311 : : else
2312 : 0 : event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2313 : :
2314 : : /* Not the first event on the page, or not delta? */
2315 [ # # # # ]: 0 : if (abs || rb_event_index(event)) {
2316 : 0 : event->time_delta = delta & TS_MASK;
2317 : 0 : event->array[0] = delta >> TS_SHIFT;
2318 : : } else {
2319 : : /* nope, just zero it */
2320 : 0 : event->time_delta = 0;
2321 : 0 : event->array[0] = 0;
2322 : : }
2323 : :
2324 : 0 : return skip_time_extend(event);
2325 : : }
2326 : :
2327 : : static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2328 : : struct ring_buffer_event *event);
2329 : :
2330 : : /**
2331 : : * rb_update_event - update event type and data
2332 : : * @cpu_buffer: The per cpu buffer of the @event
2333 : : * @event: the event to update
2334 : : * @info: The info to update the @event with (contains length and delta)
2335 : : *
2336 : : * Update the type and data fields of the @event. The length
2337 : : * is the actual size that is written to the ring buffer,
2338 : : * and with this, we can determine what to place into the
2339 : : * data field.
2340 : : */
2341 : : static void
2342 : : rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2343 : : struct ring_buffer_event *event,
2344 : : struct rb_event_info *info)
2345 : : {
2346 : : unsigned length = info->length;
2347 : : u64 delta = info->delta;
2348 : :
2349 : : /* Only a commit updates the timestamp */
2350 : : if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2351 : : delta = 0;
2352 : :
2353 : : /*
2354 : : * If we need to add a timestamp, then we
2355 : : * add it to the start of the reserved space.
2356 : : */
2357 : : if (unlikely(info->add_timestamp)) {
2358 : : bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer);
2359 : :
2360 : : event = rb_add_time_stamp(event, info->delta, abs);
2361 : : length -= RB_LEN_TIME_EXTEND;
2362 : : delta = 0;
2363 : : }
2364 : :
2365 : : event->time_delta = delta;
2366 : : length -= RB_EVNT_HDR_SIZE;
2367 : : if (length > RB_MAX_SMALL_DATA) {
2368 : : event->type_len = 0;
2369 : : event->array[0] = length;
2370 : : } else
2371 : : event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2372 : : }
2373 : :
2374 : 0 : static unsigned rb_calculate_event_length(unsigned length)
2375 : : {
2376 : 0 : struct ring_buffer_event event; /* Used only for sizeof array */
2377 : :
2378 : : /* zero length can cause confusions */
2379 : 0 : if (!length)
2380 : : length++;
2381 : :
2382 : 0 : if (length > RB_MAX_SMALL_DATA)
2383 : 0 : length += sizeof(event.array[0]);
2384 : :
2385 : 0 : length += RB_EVNT_HDR_SIZE;
2386 : 0 : length = ALIGN(length, RB_ALIGNMENT);
2387 : :
2388 : : /*
2389 : : * In case the time delta is larger than the 27 bits for it
2390 : : * in the header, we need to add a timestamp. If another
2391 : : * event comes in when trying to discard this one to increase
2392 : : * the length, then the timestamp will be added in the allocated
2393 : : * space of this event. If length is bigger than the size needed
2394 : : * for the TIME_EXTEND, then padding has to be used. The events
2395 : : * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2396 : : * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2397 : : * As length is a multiple of 4, we only need to worry if it
2398 : : * is 12 (RB_LEN_TIME_EXTEND + 4).
2399 : : */
2400 [ # # # # ]: 0 : if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2401 : 0 : length += RB_ALIGNMENT;
2402 : :
2403 : 0 : return length;
2404 : : }
2405 : :
2406 : : #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2407 : : static inline bool sched_clock_stable(void)
2408 : : {
2409 : : return true;
2410 : : }
2411 : : #endif
2412 : :
2413 : : static inline int
2414 : 0 : rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2415 : : struct ring_buffer_event *event)
2416 : : {
2417 : 0 : unsigned long new_index, old_index;
2418 : 0 : struct buffer_page *bpage;
2419 : 0 : unsigned long index;
2420 : 0 : unsigned long addr;
2421 : :
2422 : 0 : new_index = rb_event_index(event);
2423 [ # # ]: 0 : old_index = new_index + rb_event_ts_length(event);
2424 : 0 : addr = (unsigned long)event;
2425 : 0 : addr &= PAGE_MASK;
2426 : :
2427 [ # # ]: 0 : bpage = READ_ONCE(cpu_buffer->tail_page);
2428 : :
2429 [ # # # # ]: 0 : if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2430 : 0 : unsigned long write_mask =
2431 : : local_read(&bpage->write) & ~RB_WRITE_MASK;
2432 : 0 : unsigned long event_length = rb_event_length(event);
2433 : : /*
2434 : : * This is on the tail page. It is possible that
2435 : : * a write could come in and move the tail page
2436 : : * and write to the next page. That is fine
2437 : : * because we just shorten what is on this page.
2438 : : */
2439 : 0 : old_index += write_mask;
2440 : 0 : new_index += write_mask;
2441 : 0 : index = local_cmpxchg(&bpage->write, old_index, new_index);
2442 [ # # ]: 0 : if (index == old_index) {
2443 : : /* update counters */
2444 : 0 : local_sub(event_length, &cpu_buffer->entries_bytes);
2445 : 0 : return 1;
2446 : : }
2447 : : }
2448 : :
2449 : : /* could not discard */
2450 : : return 0;
2451 : : }
2452 : :
2453 : 0 : static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2454 : : {
2455 : 0 : local_inc(&cpu_buffer->committing);
2456 : 0 : local_inc(&cpu_buffer->commits);
2457 : : }
2458 : :
2459 : : static __always_inline void
2460 : : rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2461 : : {
2462 : 0 : unsigned long max_count;
2463 : :
2464 : : /*
2465 : : * We only race with interrupts and NMIs on this CPU.
2466 : : * If we own the commit event, then we can commit
2467 : : * all others that interrupted us, since the interruptions
2468 : : * are in stack format (they finish before they come
2469 : : * back to us). This allows us to do a simple loop to
2470 : : * assign the commit to the tail.
2471 : : */
2472 : 0 : again:
2473 : 0 : max_count = cpu_buffer->nr_pages * 100;
2474 : :
2475 [ # # # # : 0 : while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
# # # # #
# ]
2476 [ # # # # : 0 : if (RB_WARN_ON(cpu_buffer, !(--max_count)))
# # # # #
# # # # #
# # # # #
# ]
2477 : : return;
2478 [ # # # # : 0 : if (RB_WARN_ON(cpu_buffer,
# # # # #
# # # # #
# # # # #
# ]
2479 : : rb_is_reader_page(cpu_buffer->tail_page)))
2480 : : return;
2481 : 0 : local_set(&cpu_buffer->commit_page->page->commit,
2482 : : rb_page_write(cpu_buffer->commit_page));
2483 : 0 : rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2484 : : /* Only update the write stamp if the page has an event */
2485 [ # # # # : 0 : if (rb_page_write(cpu_buffer->commit_page))
# # # # #
# ]
2486 : 0 : cpu_buffer->write_stamp =
2487 : 0 : cpu_buffer->commit_page->page->time_stamp;
2488 : : /* add barrier to keep gcc from optimizing too much */
2489 : 0 : barrier();
2490 : : }
2491 [ # # # # : 0 : while (rb_commit_index(cpu_buffer) !=
# # # # #
# ]
2492 : 0 : rb_page_write(cpu_buffer->commit_page)) {
2493 : :
2494 : 0 : local_set(&cpu_buffer->commit_page->page->commit,
2495 : : rb_page_write(cpu_buffer->commit_page));
2496 [ # # # # : 0 : RB_WARN_ON(cpu_buffer,
# # # # #
# ]
2497 : : local_read(&cpu_buffer->commit_page->page->commit) &
2498 : : ~RB_WRITE_MASK);
2499 : 0 : barrier();
2500 : : }
2501 : :
2502 : : /* again, keep gcc from optimizing */
2503 : 0 : barrier();
2504 : :
2505 : : /*
2506 : : * If an interrupt came in just after the first while loop
2507 : : * and pushed the tail page forward, we will be left with
2508 : : * a dangling commit that will never go forward.
2509 : : */
2510 [ # # # # : 0 : if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
# # # # #
# ]
2511 : 0 : goto again;
2512 : : }
2513 : :
2514 : 0 : static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2515 : : {
2516 : 0 : unsigned long commits;
2517 : :
2518 [ # # # # : 0 : if (RB_WARN_ON(cpu_buffer,
# # # # #
# # # # #
# # # # #
# ]
2519 : : !local_read(&cpu_buffer->committing)))
2520 : : return;
2521 : :
2522 : 0 : again:
2523 : 0 : commits = local_read(&cpu_buffer->commits);
2524 : : /* synchronize with interrupts */
2525 : 0 : barrier();
2526 [ # # # # : 0 : if (local_read(&cpu_buffer->committing) == 1)
# # # # #
# ]
2527 : : rb_set_commit_to_write(cpu_buffer);
2528 : :
2529 : 0 : local_dec(&cpu_buffer->committing);
2530 : :
2531 : : /* synchronize with interrupts */
2532 : 0 : barrier();
2533 : :
2534 : : /*
2535 : : * Need to account for interrupts coming in between the
2536 : : * updating of the commit page and the clearing of the
2537 : : * committing counter.
2538 : : */
2539 [ # # # # : 0 : if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
# # # # #
# # # # #
# # # # #
# ]
2540 : 0 : !local_read(&cpu_buffer->committing)) {
2541 : 0 : local_inc(&cpu_buffer->committing);
2542 : 0 : goto again;
2543 : : }
2544 : : }
2545 : :
2546 : 0 : static inline void rb_event_discard(struct ring_buffer_event *event)
2547 : : {
2548 [ # # ]: 0 : if (extended_time(event))
2549 : 0 : event = skip_time_extend(event);
2550 : :
2551 : : /* array[0] holds the actual length for the discarded event */
2552 [ # # ]: 0 : event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2553 : 0 : event->type_len = RINGBUF_TYPE_PADDING;
2554 : : /* time delta must be non zero */
2555 [ # # ]: 0 : if (!event->time_delta)
2556 : 0 : event->time_delta = 1;
2557 : 0 : }
2558 : :
2559 : : static __always_inline bool
2560 : 0 : rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2561 : : struct ring_buffer_event *event)
2562 : : {
2563 : 0 : unsigned long addr = (unsigned long)event;
2564 : 0 : unsigned long index;
2565 : :
2566 : 0 : index = rb_event_index(event);
2567 : 0 : addr &= PAGE_MASK;
2568 : :
2569 [ # # # # ]: 0 : return cpu_buffer->commit_page->page == (void *)addr &&
2570 : : rb_commit_index(cpu_buffer) == index;
2571 : : }
2572 : :
2573 : : static __always_inline void
2574 : 0 : rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2575 : : struct ring_buffer_event *event)
2576 : : {
2577 : 0 : u64 delta;
2578 : :
2579 : : /*
2580 : : * The event first in the commit queue updates the
2581 : : * time stamp.
2582 : : */
2583 [ # # # # ]: 0 : if (rb_event_is_commit(cpu_buffer, event)) {
2584 : : /*
2585 : : * A commit event that is first on a page
2586 : : * updates the write timestamp with the page stamp
2587 : : */
2588 [ # # # # ]: 0 : if (!rb_event_index(event))
2589 : 0 : cpu_buffer->write_stamp =
2590 : 0 : cpu_buffer->commit_page->page->time_stamp;
2591 [ # # # # ]: 0 : else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2592 : 0 : delta = ring_buffer_event_time_stamp(event);
2593 : 0 : cpu_buffer->write_stamp += delta;
2594 [ # # # # ]: 0 : } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
2595 : 0 : delta = ring_buffer_event_time_stamp(event);
2596 : 0 : cpu_buffer->write_stamp = delta;
2597 : : } else
2598 : 0 : cpu_buffer->write_stamp += event->time_delta;
2599 : : }
2600 : : }
2601 : :
2602 : 0 : static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2603 : : struct ring_buffer_event *event)
2604 : : {
2605 : 0 : local_inc(&cpu_buffer->entries);
2606 [ # # ]: 0 : rb_update_write_stamp(cpu_buffer, event);
2607 : 0 : rb_end_commit(cpu_buffer);
2608 : 0 : }
2609 : :
2610 : : static __always_inline void
2611 : 0 : rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2612 : : {
2613 : 0 : size_t nr_pages;
2614 : 0 : size_t dirty;
2615 : 0 : size_t full;
2616 : :
2617 : 0 : if (buffer->irq_work.waiters_pending) {
2618 : 0 : buffer->irq_work.waiters_pending = false;
2619 : : /* irq_work_queue() supplies it's own memory barriers */
2620 : 0 : irq_work_queue(&buffer->irq_work.work);
2621 : : }
2622 : :
2623 [ # # # # ]: 0 : if (cpu_buffer->irq_work.waiters_pending) {
2624 : 0 : cpu_buffer->irq_work.waiters_pending = false;
2625 : : /* irq_work_queue() supplies it's own memory barriers */
2626 : 0 : irq_work_queue(&cpu_buffer->irq_work.work);
2627 : : }
2628 : :
2629 [ # # # # ]: 0 : if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
2630 : : return;
2631 : :
2632 [ # # # # ]: 0 : if (cpu_buffer->reader_page == cpu_buffer->commit_page)
2633 : : return;
2634 : :
2635 [ # # # # ]: 0 : if (!cpu_buffer->irq_work.full_waiters_pending)
2636 : : return;
2637 : :
2638 : 0 : cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
2639 : :
2640 : 0 : full = cpu_buffer->shortest_full;
2641 : 0 : nr_pages = cpu_buffer->nr_pages;
2642 : 0 : dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
2643 [ # # # # : 0 : if (full && nr_pages && (dirty * 100) <= full * nr_pages)
# # # # ]
2644 : : return;
2645 : :
2646 : 0 : cpu_buffer->irq_work.wakeup_full = true;
2647 : 0 : cpu_buffer->irq_work.full_waiters_pending = false;
2648 : : /* irq_work_queue() supplies it's own memory barriers */
2649 : 0 : irq_work_queue(&cpu_buffer->irq_work.work);
2650 : : }
2651 : :
2652 : : /*
2653 : : * The lock and unlock are done within a preempt disable section.
2654 : : * The current_context per_cpu variable can only be modified
2655 : : * by the current task between lock and unlock. But it can
2656 : : * be modified more than once via an interrupt. To pass this
2657 : : * information from the lock to the unlock without having to
2658 : : * access the 'in_interrupt()' functions again (which do show
2659 : : * a bit of overhead in something as critical as function tracing,
2660 : : * we use a bitmask trick.
2661 : : *
2662 : : * bit 0 = NMI context
2663 : : * bit 1 = IRQ context
2664 : : * bit 2 = SoftIRQ context
2665 : : * bit 3 = normal context.
2666 : : *
2667 : : * This works because this is the order of contexts that can
2668 : : * preempt other contexts. A SoftIRQ never preempts an IRQ
2669 : : * context.
2670 : : *
2671 : : * When the context is determined, the corresponding bit is
2672 : : * checked and set (if it was set, then a recursion of that context
2673 : : * happened).
2674 : : *
2675 : : * On unlock, we need to clear this bit. To do so, just subtract
2676 : : * 1 from the current_context and AND it to itself.
2677 : : *
2678 : : * (binary)
2679 : : * 101 - 1 = 100
2680 : : * 101 & 100 = 100 (clearing bit zero)
2681 : : *
2682 : : * 1010 - 1 = 1001
2683 : : * 1010 & 1001 = 1000 (clearing bit 1)
2684 : : *
2685 : : * The least significant bit can be cleared this way, and it
2686 : : * just so happens that it is the same bit corresponding to
2687 : : * the current context.
2688 : : */
2689 : :
2690 : : static __always_inline int
2691 : 0 : trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
2692 : : {
2693 : 0 : unsigned int val = cpu_buffer->current_context;
2694 : 0 : unsigned long pc = preempt_count();
2695 : 0 : int bit;
2696 : :
2697 [ # # # # ]: 0 : if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
2698 : : bit = RB_CTX_NORMAL;
2699 : : else
2700 [ # # # # ]: 0 : bit = pc & NMI_MASK ? RB_CTX_NMI :
2701 [ # # # # ]: 0 : pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
2702 : :
2703 [ # # # # ]: 0 : if (unlikely(val & (1 << (bit + cpu_buffer->nest))))
2704 : : return 1;
2705 : :
2706 : 0 : val |= (1 << (bit + cpu_buffer->nest));
2707 : 0 : cpu_buffer->current_context = val;
2708 : :
2709 : 0 : return 0;
2710 : : }
2711 : :
2712 : : static __always_inline void
2713 : 0 : trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
2714 : : {
2715 : 0 : cpu_buffer->current_context &=
2716 : 0 : cpu_buffer->current_context - (1 << cpu_buffer->nest);
2717 : 0 : }
2718 : :
2719 : : /* The recursive locking above uses 4 bits */
2720 : : #define NESTED_BITS 4
2721 : :
2722 : : /**
2723 : : * ring_buffer_nest_start - Allow to trace while nested
2724 : : * @buffer: The ring buffer to modify
2725 : : *
2726 : : * The ring buffer has a safety mechanism to prevent recursion.
2727 : : * But there may be a case where a trace needs to be done while
2728 : : * tracing something else. In this case, calling this function
2729 : : * will allow this function to nest within a currently active
2730 : : * ring_buffer_lock_reserve().
2731 : : *
2732 : : * Call this function before calling another ring_buffer_lock_reserve() and
2733 : : * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
2734 : : */
2735 : 0 : void ring_buffer_nest_start(struct trace_buffer *buffer)
2736 : : {
2737 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
2738 : 0 : int cpu;
2739 : :
2740 : : /* Enabled by ring_buffer_nest_end() */
2741 : 0 : preempt_disable_notrace();
2742 : 0 : cpu = raw_smp_processor_id();
2743 : 0 : cpu_buffer = buffer->buffers[cpu];
2744 : : /* This is the shift value for the above recursive locking */
2745 : 0 : cpu_buffer->nest += NESTED_BITS;
2746 : 0 : }
2747 : :
2748 : : /**
2749 : : * ring_buffer_nest_end - Allow to trace while nested
2750 : : * @buffer: The ring buffer to modify
2751 : : *
2752 : : * Must be called after ring_buffer_nest_start() and after the
2753 : : * ring_buffer_unlock_commit().
2754 : : */
2755 : 0 : void ring_buffer_nest_end(struct trace_buffer *buffer)
2756 : : {
2757 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
2758 : 0 : int cpu;
2759 : :
2760 : : /* disabled by ring_buffer_nest_start() */
2761 : 0 : cpu = raw_smp_processor_id();
2762 : 0 : cpu_buffer = buffer->buffers[cpu];
2763 : : /* This is the shift value for the above recursive locking */
2764 : 0 : cpu_buffer->nest -= NESTED_BITS;
2765 : 0 : preempt_enable_notrace();
2766 : 0 : }
2767 : :
2768 : : /**
2769 : : * ring_buffer_unlock_commit - commit a reserved
2770 : : * @buffer: The buffer to commit to
2771 : : * @event: The event pointer to commit.
2772 : : *
2773 : : * This commits the data to the ring buffer, and releases any locks held.
2774 : : *
2775 : : * Must be paired with ring_buffer_lock_reserve.
2776 : : */
2777 : 0 : int ring_buffer_unlock_commit(struct trace_buffer *buffer,
2778 : : struct ring_buffer_event *event)
2779 : : {
2780 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
2781 : 0 : int cpu = raw_smp_processor_id();
2782 : :
2783 : 0 : cpu_buffer = buffer->buffers[cpu];
2784 : :
2785 : 0 : rb_commit(cpu_buffer, event);
2786 : :
2787 [ # # ]: 0 : rb_wakeups(buffer, cpu_buffer);
2788 : :
2789 : 0 : trace_recursive_unlock(cpu_buffer);
2790 : :
2791 : 0 : preempt_enable_notrace();
2792 : :
2793 : 0 : return 0;
2794 : : }
2795 : : EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2796 : :
2797 : : static noinline void
2798 : : rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2799 : : struct rb_event_info *info)
2800 : : {
2801 : : WARN_ONCE(info->delta > (1ULL << 59),
2802 : : KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2803 : : (unsigned long long)info->delta,
2804 : : (unsigned long long)info->ts,
2805 : : (unsigned long long)cpu_buffer->write_stamp,
2806 : : sched_clock_stable() ? "" :
2807 : : "If you just came from a suspend/resume,\n"
2808 : : "please switch to the trace global clock:\n"
2809 : : " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2810 : : "or add trace_clock=global to the kernel command line\n");
2811 : : info->add_timestamp = 1;
2812 : : }
2813 : :
2814 : : static struct ring_buffer_event *
2815 : 0 : __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2816 : : struct rb_event_info *info)
2817 : : {
2818 : 0 : struct ring_buffer_event *event;
2819 : 0 : struct buffer_page *tail_page;
2820 : 0 : unsigned long tail, write;
2821 : :
2822 : : /*
2823 : : * If the time delta since the last event is too big to
2824 : : * hold in the time field of the event, then we append a
2825 : : * TIME EXTEND event ahead of the data event.
2826 : : */
2827 [ # # ]: 0 : if (unlikely(info->add_timestamp))
2828 : 0 : info->length += RB_LEN_TIME_EXTEND;
2829 : :
2830 : : /* Don't let the compiler play games with cpu_buffer->tail_page */
2831 : 0 : tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
2832 : 0 : write = local_add_return(info->length, &tail_page->write);
2833 : :
2834 : : /* set write to only the index of the write */
2835 : 0 : write &= RB_WRITE_MASK;
2836 : 0 : tail = write - info->length;
2837 : :
2838 : : /*
2839 : : * If this is the first commit on the page, then it has the same
2840 : : * timestamp as the page itself.
2841 : : */
2842 [ # # # # ]: 0 : if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
2843 : 0 : info->delta = 0;
2844 : :
2845 : : /* See if we shot pass the end of this buffer page */
2846 [ # # ]: 0 : if (unlikely(write > BUF_PAGE_SIZE))
2847 : 0 : return rb_move_tail(cpu_buffer, tail, info);
2848 : :
2849 : : /* We reserved something on the buffer */
2850 : :
2851 : 0 : event = __rb_page_index(tail_page, tail);
2852 : 0 : rb_update_event(cpu_buffer, event, info);
2853 : :
2854 : 0 : local_inc(&tail_page->entries);
2855 : :
2856 : : /*
2857 : : * If this is the first commit on the page, then update
2858 : : * its timestamp.
2859 : : */
2860 [ # # ]: 0 : if (!tail)
2861 : 0 : tail_page->page->time_stamp = info->ts;
2862 : :
2863 : : /* account for these added bytes */
2864 : 0 : local_add(info->length, &cpu_buffer->entries_bytes);
2865 : :
2866 : 0 : return event;
2867 : : }
2868 : :
2869 : : static __always_inline struct ring_buffer_event *
2870 : 0 : rb_reserve_next_event(struct trace_buffer *buffer,
2871 : : struct ring_buffer_per_cpu *cpu_buffer,
2872 : : unsigned long length)
2873 : : {
2874 : 0 : struct ring_buffer_event *event;
2875 : 0 : struct rb_event_info info;
2876 : 0 : int nr_loops = 0;
2877 : 0 : u64 diff;
2878 : :
2879 : 0 : rb_start_commit(cpu_buffer);
2880 : :
2881 : : #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2882 : : /*
2883 : : * Due to the ability to swap a cpu buffer from a buffer
2884 : : * it is possible it was swapped before we committed.
2885 : : * (committing stops a swap). We check for it here and
2886 : : * if it happened, we have to fail the write.
2887 : : */
2888 : : barrier();
2889 : : if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
2890 : : local_dec(&cpu_buffer->committing);
2891 : : local_dec(&cpu_buffer->commits);
2892 : : return NULL;
2893 : : }
2894 : : #endif
2895 : :
2896 [ # # # # ]: 0 : info.length = rb_calculate_event_length(length);
2897 : 0 : again:
2898 : 0 : info.add_timestamp = 0;
2899 : 0 : info.delta = 0;
2900 : :
2901 : : /*
2902 : : * We allow for interrupts to reenter here and do a trace.
2903 : : * If one does, it will cause this original code to loop
2904 : : * back here. Even with heavy interrupts happening, this
2905 : : * should only happen a few times in a row. If this happens
2906 : : * 1000 times in a row, there must be either an interrupt
2907 : : * storm or we have something buggy.
2908 : : * Bail!
2909 : : */
2910 [ # # # # : 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
# # # # ]
2911 : 0 : goto out_fail;
2912 : :
2913 : 0 : info.ts = rb_time_stamp(cpu_buffer->buffer);
2914 : 0 : diff = info.ts - cpu_buffer->write_stamp;
2915 : :
2916 : : /* make sure this diff is calculated here */
2917 : 0 : barrier();
2918 : :
2919 [ # # # # ]: 0 : if (ring_buffer_time_stamp_abs(buffer)) {
2920 : 0 : info.delta = info.ts;
2921 : 0 : rb_handle_timestamp(cpu_buffer, &info);
2922 : : } else /* Did the write stamp get updated already? */
2923 [ # # # # ]: 0 : if (likely(info.ts >= cpu_buffer->write_stamp)) {
2924 : 0 : info.delta = diff;
2925 [ # # # # : 0 : if (unlikely(test_time_stamp(info.delta)))
# # # # ]
2926 : 0 : rb_handle_timestamp(cpu_buffer, &info);
2927 : : }
2928 : :
2929 : 0 : event = __rb_reserve_next(cpu_buffer, &info);
2930 : :
2931 [ # # # # ]: 0 : if (unlikely(PTR_ERR(event) == -EAGAIN)) {
2932 [ # # # # ]: 0 : if (info.add_timestamp)
2933 : 0 : info.length -= RB_LEN_TIME_EXTEND;
2934 : 0 : goto again;
2935 : : }
2936 : :
2937 [ # # # # ]: 0 : if (!event)
2938 : 0 : goto out_fail;
2939 : :
2940 : : return event;
2941 : :
2942 : 0 : out_fail:
2943 : 0 : rb_end_commit(cpu_buffer);
2944 : : return NULL;
2945 : : }
2946 : :
2947 : : /**
2948 : : * ring_buffer_lock_reserve - reserve a part of the buffer
2949 : : * @buffer: the ring buffer to reserve from
2950 : : * @length: the length of the data to reserve (excluding event header)
2951 : : *
2952 : : * Returns a reserved event on the ring buffer to copy directly to.
2953 : : * The user of this interface will need to get the body to write into
2954 : : * and can use the ring_buffer_event_data() interface.
2955 : : *
2956 : : * The length is the length of the data needed, not the event length
2957 : : * which also includes the event header.
2958 : : *
2959 : : * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2960 : : * If NULL is returned, then nothing has been allocated or locked.
2961 : : */
2962 : : struct ring_buffer_event *
2963 : 0 : ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
2964 : : {
2965 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
2966 : 0 : struct ring_buffer_event *event;
2967 : 0 : int cpu;
2968 : :
2969 : : /* If we are tracing schedule, we don't want to recurse */
2970 : 0 : preempt_disable_notrace();
2971 : :
2972 [ # # ]: 0 : if (unlikely(atomic_read(&buffer->record_disabled)))
2973 : 0 : goto out;
2974 : :
2975 : 0 : cpu = raw_smp_processor_id();
2976 : :
2977 [ # # ]: 0 : if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
2978 : 0 : goto out;
2979 : :
2980 : 0 : cpu_buffer = buffer->buffers[cpu];
2981 : :
2982 [ # # ]: 0 : if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
2983 : 0 : goto out;
2984 : :
2985 [ # # ]: 0 : if (unlikely(length > BUF_MAX_DATA_SIZE))
2986 : 0 : goto out;
2987 : :
2988 [ # # # # ]: 0 : if (unlikely(trace_recursive_lock(cpu_buffer)))
2989 : 0 : goto out;
2990 : :
2991 : 0 : event = rb_reserve_next_event(buffer, cpu_buffer, length);
2992 [ # # ]: 0 : if (!event)
2993 : 0 : goto out_unlock;
2994 : :
2995 : : return event;
2996 : :
2997 : : out_unlock:
2998 : 0 : trace_recursive_unlock(cpu_buffer);
2999 : 0 : out:
3000 : 0 : preempt_enable_notrace();
3001 : 0 : return NULL;
3002 : : }
3003 : : EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3004 : :
3005 : : /*
3006 : : * Decrement the entries to the page that an event is on.
3007 : : * The event does not even need to exist, only the pointer
3008 : : * to the page it is on. This may only be called before the commit
3009 : : * takes place.
3010 : : */
3011 : : static inline void
3012 : : rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3013 : : struct ring_buffer_event *event)
3014 : : {
3015 : : unsigned long addr = (unsigned long)event;
3016 : : struct buffer_page *bpage = cpu_buffer->commit_page;
3017 : : struct buffer_page *start;
3018 : :
3019 : : addr &= PAGE_MASK;
3020 : :
3021 : : /* Do the likely case first */
3022 : : if (likely(bpage->page == (void *)addr)) {
3023 : : local_dec(&bpage->entries);
3024 : : return;
3025 : : }
3026 : :
3027 : : /*
3028 : : * Because the commit page may be on the reader page we
3029 : : * start with the next page and check the end loop there.
3030 : : */
3031 : : rb_inc_page(cpu_buffer, &bpage);
3032 : : start = bpage;
3033 : : do {
3034 : : if (bpage->page == (void *)addr) {
3035 : : local_dec(&bpage->entries);
3036 : : return;
3037 : : }
3038 : : rb_inc_page(cpu_buffer, &bpage);
3039 : : } while (bpage != start);
3040 : :
3041 : : /* commit not part of this buffer?? */
3042 : : RB_WARN_ON(cpu_buffer, 1);
3043 : : }
3044 : :
3045 : : /**
3046 : : * ring_buffer_commit_discard - discard an event that has not been committed
3047 : : * @buffer: the ring buffer
3048 : : * @event: non committed event to discard
3049 : : *
3050 : : * Sometimes an event that is in the ring buffer needs to be ignored.
3051 : : * This function lets the user discard an event in the ring buffer
3052 : : * and then that event will not be read later.
3053 : : *
3054 : : * This function only works if it is called before the item has been
3055 : : * committed. It will try to free the event from the ring buffer
3056 : : * if another event has not been added behind it.
3057 : : *
3058 : : * If another event has been added behind it, it will set the event
3059 : : * up as discarded, and perform the commit.
3060 : : *
3061 : : * If this function is called, do not call ring_buffer_unlock_commit on
3062 : : * the event.
3063 : : */
3064 : 0 : void ring_buffer_discard_commit(struct trace_buffer *buffer,
3065 : : struct ring_buffer_event *event)
3066 : : {
3067 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3068 : 0 : int cpu;
3069 : :
3070 : : /* The event is discarded regardless */
3071 : 0 : rb_event_discard(event);
3072 : :
3073 : 0 : cpu = smp_processor_id();
3074 : 0 : cpu_buffer = buffer->buffers[cpu];
3075 : :
3076 : : /*
3077 : : * This must only be called if the event has not been
3078 : : * committed yet. Thus we can assume that preemption
3079 : : * is still disabled.
3080 : : */
3081 [ # # ]: 0 : RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3082 : :
3083 : 0 : rb_decrement_entry(cpu_buffer, event);
3084 [ # # ]: 0 : if (rb_try_to_discard(cpu_buffer, event))
3085 : 0 : goto out;
3086 : :
3087 : : /*
3088 : : * The commit is still visible by the reader, so we
3089 : : * must still update the timestamp.
3090 : : */
3091 [ # # ]: 0 : rb_update_write_stamp(cpu_buffer, event);
3092 : 0 : out:
3093 : 0 : rb_end_commit(cpu_buffer);
3094 : :
3095 : 0 : trace_recursive_unlock(cpu_buffer);
3096 : :
3097 : 0 : preempt_enable_notrace();
3098 : :
3099 : 0 : }
3100 : : EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3101 : :
3102 : : /**
3103 : : * ring_buffer_write - write data to the buffer without reserving
3104 : : * @buffer: The ring buffer to write to.
3105 : : * @length: The length of the data being written (excluding the event header)
3106 : : * @data: The data to write to the buffer.
3107 : : *
3108 : : * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3109 : : * one function. If you already have the data to write to the buffer, it
3110 : : * may be easier to simply call this function.
3111 : : *
3112 : : * Note, like ring_buffer_lock_reserve, the length is the length of the data
3113 : : * and not the length of the event which would hold the header.
3114 : : */
3115 : 0 : int ring_buffer_write(struct trace_buffer *buffer,
3116 : : unsigned long length,
3117 : : void *data)
3118 : : {
3119 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3120 : 0 : struct ring_buffer_event *event;
3121 : 0 : void *body;
3122 : 0 : int ret = -EBUSY;
3123 : 0 : int cpu;
3124 : :
3125 : 0 : preempt_disable_notrace();
3126 : :
3127 [ # # ]: 0 : if (atomic_read(&buffer->record_disabled))
3128 : 0 : goto out;
3129 : :
3130 : 0 : cpu = raw_smp_processor_id();
3131 : :
3132 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3133 : 0 : goto out;
3134 : :
3135 : 0 : cpu_buffer = buffer->buffers[cpu];
3136 : :
3137 [ # # ]: 0 : if (atomic_read(&cpu_buffer->record_disabled))
3138 : 0 : goto out;
3139 : :
3140 [ # # ]: 0 : if (length > BUF_MAX_DATA_SIZE)
3141 : 0 : goto out;
3142 : :
3143 [ # # # # ]: 0 : if (unlikely(trace_recursive_lock(cpu_buffer)))
3144 : 0 : goto out;
3145 : :
3146 : 0 : event = rb_reserve_next_event(buffer, cpu_buffer, length);
3147 [ # # ]: 0 : if (!event)
3148 : 0 : goto out_unlock;
3149 : :
3150 [ # # ]: 0 : body = rb_event_data(event);
3151 : :
3152 : 0 : memcpy(body, data, length);
3153 : :
3154 : 0 : rb_commit(cpu_buffer, event);
3155 : :
3156 [ # # ]: 0 : rb_wakeups(buffer, cpu_buffer);
3157 : :
3158 : : ret = 0;
3159 : :
3160 : 0 : out_unlock:
3161 : 0 : trace_recursive_unlock(cpu_buffer);
3162 : :
3163 : 0 : out:
3164 : 0 : preempt_enable_notrace();
3165 : :
3166 : 0 : return ret;
3167 : : }
3168 : : EXPORT_SYMBOL_GPL(ring_buffer_write);
3169 : :
3170 : 0 : static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3171 : : {
3172 : 0 : struct buffer_page *reader = cpu_buffer->reader_page;
3173 : 0 : struct buffer_page *head = rb_set_head_page(cpu_buffer);
3174 : 0 : struct buffer_page *commit = cpu_buffer->commit_page;
3175 : :
3176 : : /* In case of error, head will be NULL */
3177 [ # # ]: 0 : if (unlikely(!head))
3178 : : return true;
3179 : :
3180 [ # # # # ]: 0 : return reader->read == rb_page_commit(reader) &&
3181 [ # # ]: 0 : (commit == reader ||
3182 [ # # ]: 0 : (commit == head &&
3183 : 0 : head->read == rb_page_commit(commit)));
3184 : : }
3185 : :
3186 : : /**
3187 : : * ring_buffer_record_disable - stop all writes into the buffer
3188 : : * @buffer: The ring buffer to stop writes to.
3189 : : *
3190 : : * This prevents all writes to the buffer. Any attempt to write
3191 : : * to the buffer after this will fail and return NULL.
3192 : : *
3193 : : * The caller should call synchronize_rcu() after this.
3194 : : */
3195 : 0 : void ring_buffer_record_disable(struct trace_buffer *buffer)
3196 : : {
3197 : 0 : atomic_inc(&buffer->record_disabled);
3198 : 0 : }
3199 : : EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3200 : :
3201 : : /**
3202 : : * ring_buffer_record_enable - enable writes to the buffer
3203 : : * @buffer: The ring buffer to enable writes
3204 : : *
3205 : : * Note, multiple disables will need the same number of enables
3206 : : * to truly enable the writing (much like preempt_disable).
3207 : : */
3208 : 0 : void ring_buffer_record_enable(struct trace_buffer *buffer)
3209 : : {
3210 : 0 : atomic_dec(&buffer->record_disabled);
3211 : 0 : }
3212 : : EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3213 : :
3214 : : /**
3215 : : * ring_buffer_record_off - stop all writes into the buffer
3216 : : * @buffer: The ring buffer to stop writes to.
3217 : : *
3218 : : * This prevents all writes to the buffer. Any attempt to write
3219 : : * to the buffer after this will fail and return NULL.
3220 : : *
3221 : : * This is different than ring_buffer_record_disable() as
3222 : : * it works like an on/off switch, where as the disable() version
3223 : : * must be paired with a enable().
3224 : : */
3225 : 0 : void ring_buffer_record_off(struct trace_buffer *buffer)
3226 : : {
3227 : 0 : unsigned int rd;
3228 : 0 : unsigned int new_rd;
3229 : :
3230 : 0 : do {
3231 : 0 : rd = atomic_read(&buffer->record_disabled);
3232 : 0 : new_rd = rd | RB_BUFFER_OFF;
3233 [ # # ]: 0 : } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3234 : 0 : }
3235 : : EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3236 : :
3237 : : /**
3238 : : * ring_buffer_record_on - restart writes into the buffer
3239 : : * @buffer: The ring buffer to start writes to.
3240 : : *
3241 : : * This enables all writes to the buffer that was disabled by
3242 : : * ring_buffer_record_off().
3243 : : *
3244 : : * This is different than ring_buffer_record_enable() as
3245 : : * it works like an on/off switch, where as the enable() version
3246 : : * must be paired with a disable().
3247 : : */
3248 : 0 : void ring_buffer_record_on(struct trace_buffer *buffer)
3249 : : {
3250 : 0 : unsigned int rd;
3251 : 0 : unsigned int new_rd;
3252 : :
3253 : 0 : do {
3254 : 0 : rd = atomic_read(&buffer->record_disabled);
3255 : 0 : new_rd = rd & ~RB_BUFFER_OFF;
3256 [ # # ]: 0 : } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3257 : 0 : }
3258 : : EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3259 : :
3260 : : /**
3261 : : * ring_buffer_record_is_on - return true if the ring buffer can write
3262 : : * @buffer: The ring buffer to see if write is enabled
3263 : : *
3264 : : * Returns true if the ring buffer is in a state that it accepts writes.
3265 : : */
3266 : 0 : bool ring_buffer_record_is_on(struct trace_buffer *buffer)
3267 : : {
3268 : 0 : return !atomic_read(&buffer->record_disabled);
3269 : : }
3270 : :
3271 : : /**
3272 : : * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3273 : : * @buffer: The ring buffer to see if write is set enabled
3274 : : *
3275 : : * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3276 : : * Note that this does NOT mean it is in a writable state.
3277 : : *
3278 : : * It may return true when the ring buffer has been disabled by
3279 : : * ring_buffer_record_disable(), as that is a temporary disabling of
3280 : : * the ring buffer.
3281 : : */
3282 : 0 : bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
3283 : : {
3284 : 0 : return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
3285 : : }
3286 : :
3287 : : /**
3288 : : * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3289 : : * @buffer: The ring buffer to stop writes to.
3290 : : * @cpu: The CPU buffer to stop
3291 : : *
3292 : : * This prevents all writes to the buffer. Any attempt to write
3293 : : * to the buffer after this will fail and return NULL.
3294 : : *
3295 : : * The caller should call synchronize_rcu() after this.
3296 : : */
3297 : 0 : void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
3298 : : {
3299 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3300 : :
3301 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3302 : : return;
3303 : :
3304 : 0 : cpu_buffer = buffer->buffers[cpu];
3305 : 0 : atomic_inc(&cpu_buffer->record_disabled);
3306 : : }
3307 : : EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3308 : :
3309 : : /**
3310 : : * ring_buffer_record_enable_cpu - enable writes to the buffer
3311 : : * @buffer: The ring buffer to enable writes
3312 : : * @cpu: The CPU to enable.
3313 : : *
3314 : : * Note, multiple disables will need the same number of enables
3315 : : * to truly enable the writing (much like preempt_disable).
3316 : : */
3317 : 0 : void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
3318 : : {
3319 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3320 : :
3321 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3322 : : return;
3323 : :
3324 : 0 : cpu_buffer = buffer->buffers[cpu];
3325 : 0 : atomic_dec(&cpu_buffer->record_disabled);
3326 : : }
3327 : : EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3328 : :
3329 : : /*
3330 : : * The total entries in the ring buffer is the running counter
3331 : : * of entries entered into the ring buffer, minus the sum of
3332 : : * the entries read from the ring buffer and the number of
3333 : : * entries that were overwritten.
3334 : : */
3335 : : static inline unsigned long
3336 : 0 : rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3337 : : {
3338 : 0 : return local_read(&cpu_buffer->entries) -
3339 : 0 : (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3340 : : }
3341 : :
3342 : : /**
3343 : : * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3344 : : * @buffer: The ring buffer
3345 : : * @cpu: The per CPU buffer to read from.
3346 : : */
3347 : 0 : u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
3348 : : {
3349 : 0 : unsigned long flags;
3350 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3351 : 0 : struct buffer_page *bpage;
3352 : 0 : u64 ret = 0;
3353 : :
3354 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3355 : : return 0;
3356 : :
3357 : 0 : cpu_buffer = buffer->buffers[cpu];
3358 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3359 : : /*
3360 : : * if the tail is on reader_page, oldest time stamp is on the reader
3361 : : * page
3362 : : */
3363 [ # # ]: 0 : if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3364 : : bpage = cpu_buffer->reader_page;
3365 : : else
3366 : 0 : bpage = rb_set_head_page(cpu_buffer);
3367 [ # # ]: 0 : if (bpage)
3368 : 0 : ret = bpage->page->time_stamp;
3369 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3370 : :
3371 : 0 : return ret;
3372 : : }
3373 : : EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3374 : :
3375 : : /**
3376 : : * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3377 : : * @buffer: The ring buffer
3378 : : * @cpu: The per CPU buffer to read from.
3379 : : */
3380 : 0 : unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
3381 : : {
3382 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3383 : 0 : unsigned long ret;
3384 : :
3385 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3386 : : return 0;
3387 : :
3388 : 0 : cpu_buffer = buffer->buffers[cpu];
3389 : 0 : ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3390 : :
3391 : 0 : return ret;
3392 : : }
3393 : : EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3394 : :
3395 : : /**
3396 : : * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3397 : : * @buffer: The ring buffer
3398 : : * @cpu: The per CPU buffer to get the entries from.
3399 : : */
3400 : 0 : unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
3401 : : {
3402 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3403 : :
3404 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3405 : : return 0;
3406 : :
3407 : 0 : cpu_buffer = buffer->buffers[cpu];
3408 : :
3409 : 0 : return rb_num_of_entries(cpu_buffer);
3410 : : }
3411 : : EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3412 : :
3413 : : /**
3414 : : * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3415 : : * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3416 : : * @buffer: The ring buffer
3417 : : * @cpu: The per CPU buffer to get the number of overruns from
3418 : : */
3419 : 0 : unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
3420 : : {
3421 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3422 : 0 : unsigned long ret;
3423 : :
3424 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3425 : : return 0;
3426 : :
3427 : 0 : cpu_buffer = buffer->buffers[cpu];
3428 : 0 : ret = local_read(&cpu_buffer->overrun);
3429 : :
3430 : 0 : return ret;
3431 : : }
3432 : : EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3433 : :
3434 : : /**
3435 : : * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3436 : : * commits failing due to the buffer wrapping around while there are uncommitted
3437 : : * events, such as during an interrupt storm.
3438 : : * @buffer: The ring buffer
3439 : : * @cpu: The per CPU buffer to get the number of overruns from
3440 : : */
3441 : : unsigned long
3442 : 0 : ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
3443 : : {
3444 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3445 : 0 : unsigned long ret;
3446 : :
3447 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3448 : : return 0;
3449 : :
3450 : 0 : cpu_buffer = buffer->buffers[cpu];
3451 : 0 : ret = local_read(&cpu_buffer->commit_overrun);
3452 : :
3453 : 0 : return ret;
3454 : : }
3455 : : EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3456 : :
3457 : : /**
3458 : : * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3459 : : * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3460 : : * @buffer: The ring buffer
3461 : : * @cpu: The per CPU buffer to get the number of overruns from
3462 : : */
3463 : : unsigned long
3464 : 0 : ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
3465 : : {
3466 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3467 : 0 : unsigned long ret;
3468 : :
3469 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3470 : : return 0;
3471 : :
3472 : 0 : cpu_buffer = buffer->buffers[cpu];
3473 : 0 : ret = local_read(&cpu_buffer->dropped_events);
3474 : :
3475 : 0 : return ret;
3476 : : }
3477 : : EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3478 : :
3479 : : /**
3480 : : * ring_buffer_read_events_cpu - get the number of events successfully read
3481 : : * @buffer: The ring buffer
3482 : : * @cpu: The per CPU buffer to get the number of events read
3483 : : */
3484 : : unsigned long
3485 : 0 : ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
3486 : : {
3487 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3488 : :
3489 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3490 : : return 0;
3491 : :
3492 : 0 : cpu_buffer = buffer->buffers[cpu];
3493 : 0 : return cpu_buffer->read;
3494 : : }
3495 : : EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3496 : :
3497 : : /**
3498 : : * ring_buffer_entries - get the number of entries in a buffer
3499 : : * @buffer: The ring buffer
3500 : : *
3501 : : * Returns the total number of entries in the ring buffer
3502 : : * (all CPU entries)
3503 : : */
3504 : 0 : unsigned long ring_buffer_entries(struct trace_buffer *buffer)
3505 : : {
3506 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3507 : 0 : unsigned long entries = 0;
3508 : 0 : int cpu;
3509 : :
3510 : : /* if you care about this being correct, lock the buffer */
3511 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
3512 : 0 : cpu_buffer = buffer->buffers[cpu];
3513 : 0 : entries += rb_num_of_entries(cpu_buffer);
3514 : : }
3515 : :
3516 : 0 : return entries;
3517 : : }
3518 : : EXPORT_SYMBOL_GPL(ring_buffer_entries);
3519 : :
3520 : : /**
3521 : : * ring_buffer_overruns - get the number of overruns in buffer
3522 : : * @buffer: The ring buffer
3523 : : *
3524 : : * Returns the total number of overruns in the ring buffer
3525 : : * (all CPU entries)
3526 : : */
3527 : 0 : unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
3528 : : {
3529 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3530 : 0 : unsigned long overruns = 0;
3531 : 0 : int cpu;
3532 : :
3533 : : /* if you care about this being correct, lock the buffer */
3534 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu) {
3535 : 0 : cpu_buffer = buffer->buffers[cpu];
3536 : 0 : overruns += local_read(&cpu_buffer->overrun);
3537 : : }
3538 : :
3539 : 0 : return overruns;
3540 : : }
3541 : : EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3542 : :
3543 : 0 : static void rb_iter_reset(struct ring_buffer_iter *iter)
3544 : : {
3545 : 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3546 : :
3547 : : /* Iterator usage is expected to have record disabled */
3548 : 0 : iter->head_page = cpu_buffer->reader_page;
3549 : 0 : iter->head = cpu_buffer->reader_page->read;
3550 : :
3551 : 0 : iter->cache_reader_page = iter->head_page;
3552 : 0 : iter->cache_read = cpu_buffer->read;
3553 : :
3554 : 0 : if (iter->head)
3555 : 0 : iter->read_stamp = cpu_buffer->read_stamp;
3556 : : else
3557 : 0 : iter->read_stamp = iter->head_page->page->time_stamp;
3558 : : }
3559 : :
3560 : : /**
3561 : : * ring_buffer_iter_reset - reset an iterator
3562 : : * @iter: The iterator to reset
3563 : : *
3564 : : * Resets the iterator, so that it will start from the beginning
3565 : : * again.
3566 : : */
3567 : 0 : void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3568 : : {
3569 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3570 : 0 : unsigned long flags;
3571 : :
3572 [ # # ]: 0 : if (!iter)
3573 : : return;
3574 : :
3575 : 0 : cpu_buffer = iter->cpu_buffer;
3576 : :
3577 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3578 [ # # ]: 0 : rb_iter_reset(iter);
3579 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3580 : : }
3581 : : EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3582 : :
3583 : : /**
3584 : : * ring_buffer_iter_empty - check if an iterator has no more to read
3585 : : * @iter: The iterator to check
3586 : : */
3587 : 0 : int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3588 : : {
3589 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3590 : 0 : struct buffer_page *reader;
3591 : 0 : struct buffer_page *head_page;
3592 : 0 : struct buffer_page *commit_page;
3593 : 0 : unsigned commit;
3594 : :
3595 : 0 : cpu_buffer = iter->cpu_buffer;
3596 : :
3597 : : /* Remember, trace recording is off when iterator is in use */
3598 : 0 : reader = cpu_buffer->reader_page;
3599 : 0 : head_page = cpu_buffer->head_page;
3600 : 0 : commit_page = cpu_buffer->commit_page;
3601 : 0 : commit = rb_page_commit(commit_page);
3602 : :
3603 [ # # # # : 0 : return ((iter->head_page == commit_page && iter->head == commit) ||
# # ]
3604 [ # # ]: 0 : (iter->head_page == reader && commit_page == head_page &&
3605 [ # # ]: 0 : head_page->read == commit &&
3606 [ # # ]: 0 : iter->head == rb_page_commit(cpu_buffer->reader_page)));
3607 : : }
3608 : : EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3609 : :
3610 : : static void
3611 : : rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3612 : : struct ring_buffer_event *event)
3613 : : {
3614 : : u64 delta;
3615 : :
3616 : : switch (event->type_len) {
3617 : : case RINGBUF_TYPE_PADDING:
3618 : : return;
3619 : :
3620 : : case RINGBUF_TYPE_TIME_EXTEND:
3621 : : delta = ring_buffer_event_time_stamp(event);
3622 : : cpu_buffer->read_stamp += delta;
3623 : : return;
3624 : :
3625 : : case RINGBUF_TYPE_TIME_STAMP:
3626 : : delta = ring_buffer_event_time_stamp(event);
3627 : : cpu_buffer->read_stamp = delta;
3628 : : return;
3629 : :
3630 : : case RINGBUF_TYPE_DATA:
3631 : : cpu_buffer->read_stamp += event->time_delta;
3632 : : return;
3633 : :
3634 : : default:
3635 : : BUG();
3636 : : }
3637 : : return;
3638 : : }
3639 : :
3640 : : static void
3641 : : rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3642 : : struct ring_buffer_event *event)
3643 : : {
3644 : : u64 delta;
3645 : :
3646 : : switch (event->type_len) {
3647 : : case RINGBUF_TYPE_PADDING:
3648 : : return;
3649 : :
3650 : : case RINGBUF_TYPE_TIME_EXTEND:
3651 : : delta = ring_buffer_event_time_stamp(event);
3652 : : iter->read_stamp += delta;
3653 : : return;
3654 : :
3655 : : case RINGBUF_TYPE_TIME_STAMP:
3656 : : delta = ring_buffer_event_time_stamp(event);
3657 : : iter->read_stamp = delta;
3658 : : return;
3659 : :
3660 : : case RINGBUF_TYPE_DATA:
3661 : : iter->read_stamp += event->time_delta;
3662 : : return;
3663 : :
3664 : : default:
3665 : : BUG();
3666 : : }
3667 : : return;
3668 : : }
3669 : :
3670 : : static struct buffer_page *
3671 : 0 : rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3672 : : {
3673 : 0 : struct buffer_page *reader = NULL;
3674 : 0 : unsigned long overwrite;
3675 : 0 : unsigned long flags;
3676 : 0 : int nr_loops = 0;
3677 : 0 : int ret;
3678 : :
3679 : 0 : local_irq_save(flags);
3680 : 0 : arch_spin_lock(&cpu_buffer->lock);
3681 : :
3682 : 0 : again:
3683 : : /*
3684 : : * This should normally only loop twice. But because the
3685 : : * start of the reader inserts an empty page, it causes
3686 : : * a case where we will loop three times. There should be no
3687 : : * reason to loop four times (that I know of).
3688 : : */
3689 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3690 : 0 : reader = NULL;
3691 : 0 : goto out;
3692 : : }
3693 : :
3694 : 0 : reader = cpu_buffer->reader_page;
3695 : :
3696 : : /* If there's more to read, return this page */
3697 [ # # ]: 0 : if (cpu_buffer->reader_page->read < rb_page_size(reader))
3698 : 0 : goto out;
3699 : :
3700 : : /* Never should we have an index greater than the size */
3701 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer,
3702 : : cpu_buffer->reader_page->read > rb_page_size(reader)))
3703 : 0 : goto out;
3704 : :
3705 : : /* check if we caught up to the tail */
3706 : 0 : reader = NULL;
3707 [ # # ]: 0 : if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3708 : 0 : goto out;
3709 : :
3710 : : /* Don't bother swapping if the ring buffer is empty */
3711 [ # # ]: 0 : if (rb_num_of_entries(cpu_buffer) == 0)
3712 : 0 : goto out;
3713 : :
3714 : : /*
3715 : : * Reset the reader page to size zero.
3716 : : */
3717 : 0 : local_set(&cpu_buffer->reader_page->write, 0);
3718 : 0 : local_set(&cpu_buffer->reader_page->entries, 0);
3719 : 0 : local_set(&cpu_buffer->reader_page->page->commit, 0);
3720 : 0 : cpu_buffer->reader_page->real_end = 0;
3721 : :
3722 : 0 : spin:
3723 : : /*
3724 : : * Splice the empty reader page into the list around the head.
3725 : : */
3726 : 0 : reader = rb_set_head_page(cpu_buffer);
3727 [ # # ]: 0 : if (!reader)
3728 : 0 : goto out;
3729 : 0 : cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3730 : 0 : cpu_buffer->reader_page->list.prev = reader->list.prev;
3731 : :
3732 : : /*
3733 : : * cpu_buffer->pages just needs to point to the buffer, it
3734 : : * has no specific buffer page to point to. Lets move it out
3735 : : * of our way so we don't accidentally swap it.
3736 : : */
3737 : 0 : cpu_buffer->pages = reader->list.prev;
3738 : :
3739 : : /* The reader page will be pointing to the new head */
3740 : 0 : rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3741 : :
3742 : : /*
3743 : : * We want to make sure we read the overruns after we set up our
3744 : : * pointers to the next object. The writer side does a
3745 : : * cmpxchg to cross pages which acts as the mb on the writer
3746 : : * side. Note, the reader will constantly fail the swap
3747 : : * while the writer is updating the pointers, so this
3748 : : * guarantees that the overwrite recorded here is the one we
3749 : : * want to compare with the last_overrun.
3750 : : */
3751 : 0 : smp_mb();
3752 : 0 : overwrite = local_read(&(cpu_buffer->overrun));
3753 : :
3754 : : /*
3755 : : * Here's the tricky part.
3756 : : *
3757 : : * We need to move the pointer past the header page.
3758 : : * But we can only do that if a writer is not currently
3759 : : * moving it. The page before the header page has the
3760 : : * flag bit '1' set if it is pointing to the page we want.
3761 : : * but if the writer is in the process of moving it
3762 : : * than it will be '2' or already moved '0'.
3763 : : */
3764 : :
3765 : 0 : ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3766 : :
3767 : : /*
3768 : : * If we did not convert it, then we must try again.
3769 : : */
3770 [ # # ]: 0 : if (!ret)
3771 : 0 : goto spin;
3772 : :
3773 : : /*
3774 : : * Yay! We succeeded in replacing the page.
3775 : : *
3776 : : * Now make the new head point back to the reader page.
3777 : : */
3778 : 0 : rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3779 : 0 : rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3780 : :
3781 : 0 : local_inc(&cpu_buffer->pages_read);
3782 : :
3783 : : /* Finally update the reader page to the new head */
3784 : 0 : cpu_buffer->reader_page = reader;
3785 : 0 : cpu_buffer->reader_page->read = 0;
3786 : :
3787 [ # # ]: 0 : if (overwrite != cpu_buffer->last_overrun) {
3788 : 0 : cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3789 : 0 : cpu_buffer->last_overrun = overwrite;
3790 : : }
3791 : :
3792 : 0 : goto again;
3793 : :
3794 : 0 : out:
3795 : : /* Update the read_stamp on the first event */
3796 [ # # # # ]: 0 : if (reader && reader->read == 0)
3797 : 0 : cpu_buffer->read_stamp = reader->page->time_stamp;
3798 : :
3799 : 0 : arch_spin_unlock(&cpu_buffer->lock);
3800 : 0 : local_irq_restore(flags);
3801 : :
3802 : 0 : return reader;
3803 : : }
3804 : :
3805 : 0 : static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3806 : : {
3807 : 0 : struct ring_buffer_event *event;
3808 : 0 : struct buffer_page *reader;
3809 : 0 : unsigned length;
3810 : :
3811 : 0 : reader = rb_get_reader_page(cpu_buffer);
3812 : :
3813 : : /* This function should not be called when buffer is empty */
3814 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer, !reader))
3815 : : return;
3816 : :
3817 : 0 : event = rb_reader_event(cpu_buffer);
3818 : :
3819 [ # # ]: 0 : if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3820 : 0 : cpu_buffer->read++;
3821 : :
3822 : 0 : rb_update_read_stamp(cpu_buffer, event);
3823 : :
3824 : 0 : length = rb_event_length(event);
3825 : 0 : cpu_buffer->reader_page->read += length;
3826 : : }
3827 : :
3828 : 0 : static void rb_advance_iter(struct ring_buffer_iter *iter)
3829 : : {
3830 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3831 : 0 : struct ring_buffer_event *event;
3832 : 0 : unsigned length;
3833 : :
3834 : 0 : cpu_buffer = iter->cpu_buffer;
3835 : :
3836 : : /*
3837 : : * Check if we are at the end of the buffer.
3838 : : */
3839 [ # # ]: 0 : if (iter->head >= rb_page_size(iter->head_page)) {
3840 : : /* discarded commits can make the page empty */
3841 [ # # ]: 0 : if (iter->head_page == cpu_buffer->commit_page)
3842 : : return;
3843 : 0 : rb_inc_iter(iter);
3844 : 0 : return;
3845 : : }
3846 : :
3847 : 0 : event = rb_iter_head_event(iter);
3848 : :
3849 : 0 : length = rb_event_length(event);
3850 : :
3851 : : /*
3852 : : * This should not be called to advance the header if we are
3853 : : * at the tail of the buffer.
3854 : : */
3855 [ # # # # : 0 : if (RB_WARN_ON(cpu_buffer,
# # ]
3856 : : (iter->head_page == cpu_buffer->commit_page) &&
3857 : : (iter->head + length > rb_commit_index(cpu_buffer))))
3858 : : return;
3859 : :
3860 : 0 : rb_update_iter_read_stamp(iter, event);
3861 : :
3862 : 0 : iter->head += length;
3863 : :
3864 : : /* check for end of page padding */
3865 [ # # ]: 0 : if ((iter->head >= rb_page_size(iter->head_page)) &&
3866 [ # # ]: 0 : (iter->head_page != cpu_buffer->commit_page))
3867 : 0 : rb_inc_iter(iter);
3868 : : }
3869 : :
3870 : 0 : static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3871 : : {
3872 : 0 : return cpu_buffer->lost_events;
3873 : : }
3874 : :
3875 : : static struct ring_buffer_event *
3876 : 0 : rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3877 : : unsigned long *lost_events)
3878 : : {
3879 : 0 : struct ring_buffer_event *event;
3880 : 0 : struct buffer_page *reader;
3881 : 0 : int nr_loops = 0;
3882 : :
3883 [ # # ]: 0 : if (ts)
3884 : 0 : *ts = 0;
3885 : 0 : again:
3886 : : /*
3887 : : * We repeat when a time extend is encountered.
3888 : : * Since the time extend is always attached to a data event,
3889 : : * we should never loop more than once.
3890 : : * (We never hit the following condition more than twice).
3891 : : */
3892 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3893 : : return NULL;
3894 : :
3895 : 0 : reader = rb_get_reader_page(cpu_buffer);
3896 [ # # ]: 0 : if (!reader)
3897 : : return NULL;
3898 : :
3899 : 0 : event = rb_reader_event(cpu_buffer);
3900 : :
3901 [ # # # # : 0 : switch (event->type_len) {
# ]
3902 : : case RINGBUF_TYPE_PADDING:
3903 [ # # ]: 0 : if (rb_null_event(event))
3904 : 0 : RB_WARN_ON(cpu_buffer, 1);
3905 : : /*
3906 : : * Because the writer could be discarding every
3907 : : * event it creates (which would probably be bad)
3908 : : * if we were to go back to "again" then we may never
3909 : : * catch up, and will trigger the warn on, or lock
3910 : : * the box. Return the padding, and we will release
3911 : : * the current locks, and try again.
3912 : : */
3913 : : return event;
3914 : :
3915 : 0 : case RINGBUF_TYPE_TIME_EXTEND:
3916 : : /* Internal data, OK to advance */
3917 : 0 : rb_advance_reader(cpu_buffer);
3918 : 0 : goto again;
3919 : :
3920 : 0 : case RINGBUF_TYPE_TIME_STAMP:
3921 [ # # ]: 0 : if (ts) {
3922 : 0 : *ts = ring_buffer_event_time_stamp(event);
3923 : 0 : ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3924 : : cpu_buffer->cpu, ts);
3925 : : }
3926 : : /* Internal data, OK to advance */
3927 : 0 : rb_advance_reader(cpu_buffer);
3928 : 0 : goto again;
3929 : :
3930 : 0 : case RINGBUF_TYPE_DATA:
3931 [ # # # # ]: 0 : if (ts && !(*ts)) {
3932 : 0 : *ts = cpu_buffer->read_stamp + event->time_delta;
3933 : 0 : ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3934 : : cpu_buffer->cpu, ts);
3935 : : }
3936 [ # # ]: 0 : if (lost_events)
3937 : 0 : *lost_events = rb_lost_events(cpu_buffer);
3938 : : return event;
3939 : :
3940 : 0 : default:
3941 : 0 : BUG();
3942 : : }
3943 : :
3944 : : return NULL;
3945 : : }
3946 : : EXPORT_SYMBOL_GPL(ring_buffer_peek);
3947 : :
3948 : : static struct ring_buffer_event *
3949 : 0 : rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3950 : : {
3951 : 0 : struct trace_buffer *buffer;
3952 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
3953 : 0 : struct ring_buffer_event *event;
3954 : 0 : int nr_loops = 0;
3955 : :
3956 [ # # ]: 0 : if (ts)
3957 : 0 : *ts = 0;
3958 : :
3959 : 0 : cpu_buffer = iter->cpu_buffer;
3960 : 0 : buffer = cpu_buffer->buffer;
3961 : :
3962 : : /*
3963 : : * Check if someone performed a consuming read to
3964 : : * the buffer. A consuming read invalidates the iterator
3965 : : * and we need to reset the iterator in this case.
3966 : : */
3967 [ # # # # ]: 0 : if (unlikely(iter->cache_read != cpu_buffer->read ||
3968 : : iter->cache_reader_page != cpu_buffer->reader_page))
3969 [ # # ]: 0 : rb_iter_reset(iter);
3970 : :
3971 : 0 : again:
3972 [ # # ]: 0 : if (ring_buffer_iter_empty(iter))
3973 : : return NULL;
3974 : :
3975 : : /*
3976 : : * We repeat when a time extend is encountered or we hit
3977 : : * the end of the page. Since the time extend is always attached
3978 : : * to a data event, we should never loop more than three times.
3979 : : * Once for going to next page, once on time extend, and
3980 : : * finally once to get the event.
3981 : : * (We never hit the following condition more than thrice).
3982 : : */
3983 [ # # # # ]: 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
3984 : : return NULL;
3985 : :
3986 [ # # ]: 0 : if (rb_per_cpu_empty(cpu_buffer))
3987 : : return NULL;
3988 : :
3989 [ # # ]: 0 : if (iter->head >= rb_page_size(iter->head_page)) {
3990 : 0 : rb_inc_iter(iter);
3991 : 0 : goto again;
3992 : : }
3993 : :
3994 : 0 : event = rb_iter_head_event(iter);
3995 : :
3996 [ # # # # : 0 : switch (event->type_len) {
# ]
3997 : : case RINGBUF_TYPE_PADDING:
3998 [ # # ]: 0 : if (rb_null_event(event)) {
3999 : 0 : rb_inc_iter(iter);
4000 : 0 : goto again;
4001 : : }
4002 : 0 : rb_advance_iter(iter);
4003 : 0 : return event;
4004 : :
4005 : 0 : case RINGBUF_TYPE_TIME_EXTEND:
4006 : : /* Internal data, OK to advance */
4007 : 0 : rb_advance_iter(iter);
4008 : 0 : goto again;
4009 : :
4010 : 0 : case RINGBUF_TYPE_TIME_STAMP:
4011 [ # # ]: 0 : if (ts) {
4012 : 0 : *ts = ring_buffer_event_time_stamp(event);
4013 : 0 : ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4014 : : cpu_buffer->cpu, ts);
4015 : : }
4016 : : /* Internal data, OK to advance */
4017 : 0 : rb_advance_iter(iter);
4018 : 0 : goto again;
4019 : :
4020 : 0 : case RINGBUF_TYPE_DATA:
4021 [ # # # # ]: 0 : if (ts && !(*ts)) {
4022 : 0 : *ts = iter->read_stamp + event->time_delta;
4023 : 0 : ring_buffer_normalize_time_stamp(buffer,
4024 : : cpu_buffer->cpu, ts);
4025 : : }
4026 : : return event;
4027 : :
4028 : 0 : default:
4029 : 0 : BUG();
4030 : : }
4031 : :
4032 : : return NULL;
4033 : : }
4034 : : EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4035 : :
4036 : 0 : static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4037 : : {
4038 [ # # ]: 0 : if (likely(!in_nmi())) {
4039 : 0 : raw_spin_lock(&cpu_buffer->reader_lock);
4040 : 0 : return true;
4041 : : }
4042 : :
4043 : : /*
4044 : : * If an NMI die dumps out the content of the ring buffer
4045 : : * trylock must be used to prevent a deadlock if the NMI
4046 : : * preempted a task that holds the ring buffer locks. If
4047 : : * we get the lock then all is fine, if not, then continue
4048 : : * to do the read, but this can corrupt the ring buffer,
4049 : : * so it must be permanently disabled from future writes.
4050 : : * Reading from NMI is a oneshot deal.
4051 : : */
4052 [ # # ]: 0 : if (raw_spin_trylock(&cpu_buffer->reader_lock))
4053 : : return true;
4054 : :
4055 : : /* Continue without locking, but disable the ring buffer */
4056 : 0 : atomic_inc(&cpu_buffer->record_disabled);
4057 : 0 : return false;
4058 : : }
4059 : :
4060 : : static inline void
4061 : 0 : rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4062 : : {
4063 : 0 : if (likely(locked))
4064 : 0 : raw_spin_unlock(&cpu_buffer->reader_lock);
4065 : 0 : return;
4066 : : }
4067 : :
4068 : : /**
4069 : : * ring_buffer_peek - peek at the next event to be read
4070 : : * @buffer: The ring buffer to read
4071 : : * @cpu: The cpu to peak at
4072 : : * @ts: The timestamp counter of this event.
4073 : : * @lost_events: a variable to store if events were lost (may be NULL)
4074 : : *
4075 : : * This will return the event that will be read next, but does
4076 : : * not consume the data.
4077 : : */
4078 : : struct ring_buffer_event *
4079 : 0 : ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4080 : : unsigned long *lost_events)
4081 : : {
4082 : 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4083 : 0 : struct ring_buffer_event *event;
4084 : 0 : unsigned long flags;
4085 : 0 : bool dolock;
4086 : :
4087 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4088 : : return NULL;
4089 : :
4090 : 0 : again:
4091 : 0 : local_irq_save(flags);
4092 : 0 : dolock = rb_reader_lock(cpu_buffer);
4093 : 0 : event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4094 [ # # # # ]: 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4095 : 0 : rb_advance_reader(cpu_buffer);
4096 [ # # ]: 0 : rb_reader_unlock(cpu_buffer, dolock);
4097 : 0 : local_irq_restore(flags);
4098 : :
4099 [ # # # # ]: 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4100 : 0 : goto again;
4101 : :
4102 : : return event;
4103 : : }
4104 : :
4105 : : /**
4106 : : * ring_buffer_iter_peek - peek at the next event to be read
4107 : : * @iter: The ring buffer iterator
4108 : : * @ts: The timestamp counter of this event.
4109 : : *
4110 : : * This will return the event that will be read next, but does
4111 : : * not increment the iterator.
4112 : : */
4113 : : struct ring_buffer_event *
4114 : 0 : ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4115 : : {
4116 : 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4117 : 0 : struct ring_buffer_event *event;
4118 : 0 : unsigned long flags;
4119 : :
4120 : 0 : again:
4121 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4122 : 0 : event = rb_iter_peek(iter, ts);
4123 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4124 : :
4125 [ # # # # ]: 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4126 : 0 : goto again;
4127 : :
4128 : 0 : return event;
4129 : : }
4130 : :
4131 : : /**
4132 : : * ring_buffer_consume - return an event and consume it
4133 : : * @buffer: The ring buffer to get the next event from
4134 : : * @cpu: the cpu to read the buffer from
4135 : : * @ts: a variable to store the timestamp (may be NULL)
4136 : : * @lost_events: a variable to store if events were lost (may be NULL)
4137 : : *
4138 : : * Returns the next event in the ring buffer, and that event is consumed.
4139 : : * Meaning, that sequential reads will keep returning a different event,
4140 : : * and eventually empty the ring buffer if the producer is slower.
4141 : : */
4142 : : struct ring_buffer_event *
4143 : 0 : ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4144 : : unsigned long *lost_events)
4145 : : {
4146 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
4147 : 0 : struct ring_buffer_event *event = NULL;
4148 : 0 : unsigned long flags;
4149 : 0 : bool dolock;
4150 : :
4151 : 0 : again:
4152 : : /* might be called in atomic */
4153 : 0 : preempt_disable();
4154 : :
4155 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4156 : 0 : goto out;
4157 : :
4158 : 0 : cpu_buffer = buffer->buffers[cpu];
4159 : 0 : local_irq_save(flags);
4160 : 0 : dolock = rb_reader_lock(cpu_buffer);
4161 : :
4162 : 0 : event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4163 [ # # ]: 0 : if (event) {
4164 : 0 : cpu_buffer->lost_events = 0;
4165 : 0 : rb_advance_reader(cpu_buffer);
4166 : : }
4167 : :
4168 [ # # ]: 0 : rb_reader_unlock(cpu_buffer, dolock);
4169 : 0 : local_irq_restore(flags);
4170 : :
4171 : 0 : out:
4172 : 0 : preempt_enable();
4173 : :
4174 [ # # # # ]: 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4175 : 0 : goto again;
4176 : :
4177 : 0 : return event;
4178 : : }
4179 : : EXPORT_SYMBOL_GPL(ring_buffer_consume);
4180 : :
4181 : : /**
4182 : : * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4183 : : * @buffer: The ring buffer to read from
4184 : : * @cpu: The cpu buffer to iterate over
4185 : : * @flags: gfp flags to use for memory allocation
4186 : : *
4187 : : * This performs the initial preparations necessary to iterate
4188 : : * through the buffer. Memory is allocated, buffer recording
4189 : : * is disabled, and the iterator pointer is returned to the caller.
4190 : : *
4191 : : * Disabling buffer recording prevents the reading from being
4192 : : * corrupted. This is not a consuming read, so a producer is not
4193 : : * expected.
4194 : : *
4195 : : * After a sequence of ring_buffer_read_prepare calls, the user is
4196 : : * expected to make at least one call to ring_buffer_read_prepare_sync.
4197 : : * Afterwards, ring_buffer_read_start is invoked to get things going
4198 : : * for real.
4199 : : *
4200 : : * This overall must be paired with ring_buffer_read_finish.
4201 : : */
4202 : : struct ring_buffer_iter *
4203 : 0 : ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
4204 : : {
4205 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
4206 : 0 : struct ring_buffer_iter *iter;
4207 : :
4208 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4209 : : return NULL;
4210 : :
4211 [ # # ]: 0 : iter = kmalloc(sizeof(*iter), flags);
4212 [ # # ]: 0 : if (!iter)
4213 : : return NULL;
4214 : :
4215 : 0 : cpu_buffer = buffer->buffers[cpu];
4216 : :
4217 : 0 : iter->cpu_buffer = cpu_buffer;
4218 : :
4219 : 0 : atomic_inc(&buffer->resize_disabled);
4220 : 0 : atomic_inc(&cpu_buffer->record_disabled);
4221 : :
4222 : 0 : return iter;
4223 : : }
4224 : : EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4225 : :
4226 : : /**
4227 : : * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4228 : : *
4229 : : * All previously invoked ring_buffer_read_prepare calls to prepare
4230 : : * iterators will be synchronized. Afterwards, read_buffer_read_start
4231 : : * calls on those iterators are allowed.
4232 : : */
4233 : : void
4234 : 0 : ring_buffer_read_prepare_sync(void)
4235 : : {
4236 : 0 : synchronize_rcu();
4237 : 0 : }
4238 : : EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4239 : :
4240 : : /**
4241 : : * ring_buffer_read_start - start a non consuming read of the buffer
4242 : : * @iter: The iterator returned by ring_buffer_read_prepare
4243 : : *
4244 : : * This finalizes the startup of an iteration through the buffer.
4245 : : * The iterator comes from a call to ring_buffer_read_prepare and
4246 : : * an intervening ring_buffer_read_prepare_sync must have been
4247 : : * performed.
4248 : : *
4249 : : * Must be paired with ring_buffer_read_finish.
4250 : : */
4251 : : void
4252 : 0 : ring_buffer_read_start(struct ring_buffer_iter *iter)
4253 : : {
4254 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
4255 : 0 : unsigned long flags;
4256 : :
4257 [ # # ]: 0 : if (!iter)
4258 : : return;
4259 : :
4260 : 0 : cpu_buffer = iter->cpu_buffer;
4261 : :
4262 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4263 : 0 : arch_spin_lock(&cpu_buffer->lock);
4264 [ # # ]: 0 : rb_iter_reset(iter);
4265 : 0 : arch_spin_unlock(&cpu_buffer->lock);
4266 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4267 : : }
4268 : : EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4269 : :
4270 : : /**
4271 : : * ring_buffer_read_finish - finish reading the iterator of the buffer
4272 : : * @iter: The iterator retrieved by ring_buffer_start
4273 : : *
4274 : : * This re-enables the recording to the buffer, and frees the
4275 : : * iterator.
4276 : : */
4277 : : void
4278 : 0 : ring_buffer_read_finish(struct ring_buffer_iter *iter)
4279 : : {
4280 : 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4281 : 0 : unsigned long flags;
4282 : :
4283 : : /*
4284 : : * Ring buffer is disabled from recording, here's a good place
4285 : : * to check the integrity of the ring buffer.
4286 : : * Must prevent readers from trying to read, as the check
4287 : : * clears the HEAD page and readers require it.
4288 : : */
4289 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4290 : 0 : rb_check_pages(cpu_buffer);
4291 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4292 : :
4293 : 0 : atomic_dec(&cpu_buffer->record_disabled);
4294 : 0 : atomic_dec(&cpu_buffer->buffer->resize_disabled);
4295 : 0 : kfree(iter);
4296 : 0 : }
4297 : : EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4298 : :
4299 : : /**
4300 : : * ring_buffer_read - read the next item in the ring buffer by the iterator
4301 : : * @iter: The ring buffer iterator
4302 : : * @ts: The time stamp of the event read.
4303 : : *
4304 : : * This reads the next event in the ring buffer and increments the iterator.
4305 : : */
4306 : : struct ring_buffer_event *
4307 : 0 : ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4308 : : {
4309 : 0 : struct ring_buffer_event *event;
4310 : 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4311 : 0 : unsigned long flags;
4312 : :
4313 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4314 : 0 : again:
4315 : 0 : event = rb_iter_peek(iter, ts);
4316 [ # # ]: 0 : if (!event)
4317 : 0 : goto out;
4318 : :
4319 [ # # ]: 0 : if (event->type_len == RINGBUF_TYPE_PADDING)
4320 : 0 : goto again;
4321 : :
4322 : 0 : rb_advance_iter(iter);
4323 : 0 : out:
4324 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4325 : :
4326 : 0 : return event;
4327 : : }
4328 : : EXPORT_SYMBOL_GPL(ring_buffer_read);
4329 : :
4330 : : /**
4331 : : * ring_buffer_size - return the size of the ring buffer (in bytes)
4332 : : * @buffer: The ring buffer.
4333 : : * @cpu: The CPU to get ring buffer size from.
4334 : : */
4335 : 21 : unsigned long ring_buffer_size(struct trace_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 [ + - ]: 21 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4344 : : return 0;
4345 : :
4346 : 21 : 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 : 0 : rb_head_page_deactivate(cpu_buffer);
4354 : :
4355 : 0 : 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 : 0 : local_set(&cpu_buffer->entries_bytes, 0);
4374 : 0 : local_set(&cpu_buffer->overrun, 0);
4375 : 0 : local_set(&cpu_buffer->commit_overrun, 0);
4376 : 0 : local_set(&cpu_buffer->dropped_events, 0);
4377 : 0 : local_set(&cpu_buffer->entries, 0);
4378 : 0 : local_set(&cpu_buffer->committing, 0);
4379 : 0 : local_set(&cpu_buffer->commits, 0);
4380 : 0 : local_set(&cpu_buffer->pages_touched, 0);
4381 : 0 : 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 [ # # ]: 0 : 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 trace_buffer *buffer, int cpu)
4402 : : {
4403 : 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4404 : 0 : unsigned long flags;
4405 : :
4406 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4407 : : 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 : 0 : goto out;
4419 : :
4420 : 0 : arch_spin_lock(&cpu_buffer->lock);
4421 : :
4422 : 0 : rb_reset_cpu(cpu_buffer);
4423 : :
4424 : 0 : arch_spin_unlock(&cpu_buffer->lock);
4425 : :
4426 : 0 : out:
4427 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4428 : :
4429 : 0 : atomic_dec(&cpu_buffer->record_disabled);
4430 : 0 : 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 trace_buffer *buffer)
4439 : : {
4440 : 0 : 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 trace_buffer *buffer)
4452 : : {
4453 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
4454 : 0 : unsigned long flags;
4455 : 0 : bool dolock;
4456 : 0 : int cpu;
4457 : 0 : 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 [ # # ]: 0 : 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 trace_buffer *buffer, int cpu)
4482 : : {
4483 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
4484 : 0 : unsigned long flags;
4485 : 0 : bool dolock;
4486 : 0 : 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 [ # # ]: 0 : 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 : : * @cpu: the CPU of the buffers to swap
4508 : : *
4509 : : * This function is useful for tracers that want to take a "snapshot"
4510 : : * of a CPU buffer and has another back up buffer lying around.
4511 : : * it is expected that the tracer handles the cpu buffer not being
4512 : : * used at the moment.
4513 : : */
4514 : : int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
4515 : : struct trace_buffer *buffer_b, int cpu)
4516 : : {
4517 : : struct ring_buffer_per_cpu *cpu_buffer_a;
4518 : : struct ring_buffer_per_cpu *cpu_buffer_b;
4519 : : int ret = -EINVAL;
4520 : :
4521 : : if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4522 : : !cpumask_test_cpu(cpu, buffer_b->cpumask))
4523 : : goto out;
4524 : :
4525 : : cpu_buffer_a = buffer_a->buffers[cpu];
4526 : : cpu_buffer_b = buffer_b->buffers[cpu];
4527 : :
4528 : : /* At least make sure the two buffers are somewhat the same */
4529 : : if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4530 : : goto out;
4531 : :
4532 : : ret = -EAGAIN;
4533 : :
4534 : : if (atomic_read(&buffer_a->record_disabled))
4535 : : goto out;
4536 : :
4537 : : if (atomic_read(&buffer_b->record_disabled))
4538 : : goto out;
4539 : :
4540 : : if (atomic_read(&cpu_buffer_a->record_disabled))
4541 : : goto out;
4542 : :
4543 : : if (atomic_read(&cpu_buffer_b->record_disabled))
4544 : : goto out;
4545 : :
4546 : : /*
4547 : : * We can't do a synchronize_rcu here because this
4548 : : * function can be called in atomic context.
4549 : : * Normally this will be called from the same CPU as cpu.
4550 : : * If not it's up to the caller to protect this.
4551 : : */
4552 : : atomic_inc(&cpu_buffer_a->record_disabled);
4553 : : atomic_inc(&cpu_buffer_b->record_disabled);
4554 : :
4555 : : ret = -EBUSY;
4556 : : if (local_read(&cpu_buffer_a->committing))
4557 : : goto out_dec;
4558 : : if (local_read(&cpu_buffer_b->committing))
4559 : : goto out_dec;
4560 : :
4561 : : buffer_a->buffers[cpu] = cpu_buffer_b;
4562 : : buffer_b->buffers[cpu] = cpu_buffer_a;
4563 : :
4564 : : cpu_buffer_b->buffer = buffer_a;
4565 : : cpu_buffer_a->buffer = buffer_b;
4566 : :
4567 : : ret = 0;
4568 : :
4569 : : out_dec:
4570 : : atomic_dec(&cpu_buffer_a->record_disabled);
4571 : : atomic_dec(&cpu_buffer_b->record_disabled);
4572 : : out:
4573 : : return ret;
4574 : : }
4575 : : EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4576 : : #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4577 : :
4578 : : /**
4579 : : * ring_buffer_alloc_read_page - allocate a page to read from buffer
4580 : : * @buffer: the buffer to allocate for.
4581 : : * @cpu: the cpu buffer to allocate.
4582 : : *
4583 : : * This function is used in conjunction with ring_buffer_read_page.
4584 : : * When reading a full page from the ring buffer, these functions
4585 : : * can be used to speed up the process. The calling function should
4586 : : * allocate a few pages first with this function. Then when it
4587 : : * needs to get pages from the ring buffer, it passes the result
4588 : : * of this function into ring_buffer_read_page, which will swap
4589 : : * the page that was allocated, with the read page of the buffer.
4590 : : *
4591 : : * Returns:
4592 : : * The page allocated, or ERR_PTR
4593 : : */
4594 : 0 : void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
4595 : : {
4596 : 0 : struct ring_buffer_per_cpu *cpu_buffer;
4597 : 0 : struct buffer_data_page *bpage = NULL;
4598 : 0 : unsigned long flags;
4599 : 0 : struct page *page;
4600 : :
4601 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4602 : : return ERR_PTR(-ENODEV);
4603 : :
4604 : 0 : cpu_buffer = buffer->buffers[cpu];
4605 : 0 : local_irq_save(flags);
4606 : 0 : arch_spin_lock(&cpu_buffer->lock);
4607 : :
4608 [ # # ]: 0 : if (cpu_buffer->free_page) {
4609 : 0 : bpage = cpu_buffer->free_page;
4610 : 0 : cpu_buffer->free_page = NULL;
4611 : : }
4612 : :
4613 : 0 : arch_spin_unlock(&cpu_buffer->lock);
4614 : 0 : local_irq_restore(flags);
4615 : :
4616 [ # # ]: 0 : if (bpage)
4617 : 0 : goto out;
4618 : :
4619 [ # # ]: 0 : page = alloc_pages_node(cpu_to_node(cpu),
4620 : : GFP_KERNEL | __GFP_NORETRY, 0);
4621 [ # # ]: 0 : if (!page)
4622 : : return ERR_PTR(-ENOMEM);
4623 : :
4624 : 0 : bpage = page_address(page);
4625 : :
4626 : 0 : out:
4627 : 0 : rb_init_page(bpage);
4628 : :
4629 : 0 : return bpage;
4630 : : }
4631 : : EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4632 : :
4633 : : /**
4634 : : * ring_buffer_free_read_page - free an allocated read page
4635 : : * @buffer: the buffer the page was allocate for
4636 : : * @cpu: the cpu buffer the page came from
4637 : : * @data: the page to free
4638 : : *
4639 : : * Free a page allocated from ring_buffer_alloc_read_page.
4640 : : */
4641 : 0 : void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
4642 : : {
4643 : 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4644 : 0 : struct buffer_data_page *bpage = data;
4645 [ # # ]: 0 : struct page *page = virt_to_page(bpage);
4646 : 0 : unsigned long flags;
4647 : :
4648 : : /* If the page is still in use someplace else, we can't reuse it */
4649 [ # # ]: 0 : if (page_ref_count(page) > 1)
4650 : 0 : goto out;
4651 : :
4652 : 0 : local_irq_save(flags);
4653 : 0 : arch_spin_lock(&cpu_buffer->lock);
4654 : :
4655 [ # # ]: 0 : if (!cpu_buffer->free_page) {
4656 : 0 : cpu_buffer->free_page = bpage;
4657 : 0 : bpage = NULL;
4658 : : }
4659 : :
4660 : 0 : arch_spin_unlock(&cpu_buffer->lock);
4661 : 0 : local_irq_restore(flags);
4662 : :
4663 : 0 : out:
4664 : 0 : free_page((unsigned long)bpage);
4665 : 0 : }
4666 : : EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4667 : :
4668 : : /**
4669 : : * ring_buffer_read_page - extract a page from the ring buffer
4670 : : * @buffer: buffer to extract from
4671 : : * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4672 : : * @len: amount to extract
4673 : : * @cpu: the cpu of the buffer to extract
4674 : : * @full: should the extraction only happen when the page is full.
4675 : : *
4676 : : * This function will pull out a page from the ring buffer and consume it.
4677 : : * @data_page must be the address of the variable that was returned
4678 : : * from ring_buffer_alloc_read_page. This is because the page might be used
4679 : : * to swap with a page in the ring buffer.
4680 : : *
4681 : : * for example:
4682 : : * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4683 : : * if (IS_ERR(rpage))
4684 : : * return PTR_ERR(rpage);
4685 : : * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4686 : : * if (ret >= 0)
4687 : : * process_page(rpage, ret);
4688 : : *
4689 : : * When @full is set, the function will not return true unless
4690 : : * the writer is off the reader page.
4691 : : *
4692 : : * Note: it is up to the calling functions to handle sleeps and wakeups.
4693 : : * The ring buffer can be used anywhere in the kernel and can not
4694 : : * blindly call wake_up. The layer that uses the ring buffer must be
4695 : : * responsible for that.
4696 : : *
4697 : : * Returns:
4698 : : * >=0 if data has been transferred, returns the offset of consumed data.
4699 : : * <0 if no data has been transferred.
4700 : : */
4701 : 0 : int ring_buffer_read_page(struct trace_buffer *buffer,
4702 : : void **data_page, size_t len, int cpu, int full)
4703 : : {
4704 : 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4705 : 0 : struct ring_buffer_event *event;
4706 : 0 : struct buffer_data_page *bpage;
4707 : 0 : struct buffer_page *reader;
4708 : 0 : unsigned long missed_events;
4709 : 0 : unsigned long flags;
4710 : 0 : unsigned int commit;
4711 : 0 : unsigned int read;
4712 : 0 : u64 save_timestamp;
4713 : 0 : int ret = -1;
4714 : :
4715 [ # # ]: 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4716 : 0 : goto out;
4717 : :
4718 : : /*
4719 : : * If len is not big enough to hold the page header, then
4720 : : * we can not copy anything.
4721 : : */
4722 [ # # ]: 0 : if (len <= BUF_PAGE_HDR_SIZE)
4723 : 0 : goto out;
4724 : :
4725 : 0 : len -= BUF_PAGE_HDR_SIZE;
4726 : :
4727 [ # # ]: 0 : if (!data_page)
4728 : 0 : goto out;
4729 : :
4730 : 0 : bpage = *data_page;
4731 [ # # ]: 0 : if (!bpage)
4732 : 0 : goto out;
4733 : :
4734 : 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4735 : :
4736 : 0 : reader = rb_get_reader_page(cpu_buffer);
4737 [ # # ]: 0 : if (!reader)
4738 : 0 : goto out_unlock;
4739 : :
4740 : 0 : event = rb_reader_event(cpu_buffer);
4741 : :
4742 : 0 : read = reader->read;
4743 : 0 : commit = rb_page_commit(reader);
4744 : :
4745 : : /* Check if any events were dropped */
4746 : 0 : missed_events = cpu_buffer->lost_events;
4747 : :
4748 : : /*
4749 : : * If this page has been partially read or
4750 : : * if len is not big enough to read the rest of the page or
4751 : : * a writer is still on the page, then
4752 : : * we must copy the data from the page to the buffer.
4753 : : * Otherwise, we can simply swap the page with the one passed in.
4754 : : */
4755 [ # # # # ]: 0 : if (read || (len < (commit - read)) ||
4756 [ # # ]: 0 : cpu_buffer->reader_page == cpu_buffer->commit_page) {
4757 : 0 : struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4758 : 0 : unsigned int rpos = read;
4759 : 0 : unsigned int pos = 0;
4760 : 0 : unsigned int size;
4761 : :
4762 [ # # ]: 0 : if (full)
4763 : 0 : goto out_unlock;
4764 : :
4765 : 0 : if (len > (commit - read))
4766 : : len = (commit - read);
4767 : :
4768 : : /* Always keep the time extend and data together */
4769 [ # # ]: 0 : size = rb_event_ts_length(event);
4770 : :
4771 [ # # ]: 0 : if (len < size)
4772 : 0 : goto out_unlock;
4773 : :
4774 : : /* save the current timestamp, since the user will need it */
4775 : 0 : save_timestamp = cpu_buffer->read_stamp;
4776 : :
4777 : : /* Need to copy one event at a time */
4778 : 0 : do {
4779 : : /* We need the size of one event, because
4780 : : * rb_advance_reader only advances by one event,
4781 : : * whereas rb_event_ts_length may include the size of
4782 : : * one or two events.
4783 : : * We have already ensured there's enough space if this
4784 : : * is a time extend. */
4785 : 0 : size = rb_event_length(event);
4786 : 0 : memcpy(bpage->data + pos, rpage->data + rpos, size);
4787 : :
4788 : 0 : len -= size;
4789 : :
4790 : 0 : rb_advance_reader(cpu_buffer);
4791 : 0 : rpos = reader->read;
4792 : 0 : pos += size;
4793 : :
4794 [ # # ]: 0 : if (rpos >= commit)
4795 : : break;
4796 : :
4797 : 0 : event = rb_reader_event(cpu_buffer);
4798 : : /* Always keep the time extend and data together */
4799 [ # # ]: 0 : size = rb_event_ts_length(event);
4800 [ # # ]: 0 : } while (len >= size);
4801 : :
4802 : : /* update bpage */
4803 : 0 : local_set(&bpage->commit, pos);
4804 : 0 : bpage->time_stamp = save_timestamp;
4805 : :
4806 : : /* we copied everything to the beginning */
4807 : 0 : read = 0;
4808 : : } else {
4809 : : /* update the entry counter */
4810 : 0 : cpu_buffer->read += rb_page_entries(reader);
4811 : 0 : cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4812 : :
4813 : : /* swap the pages */
4814 : 0 : rb_init_page(bpage);
4815 : 0 : bpage = reader->page;
4816 : 0 : reader->page = *data_page;
4817 : 0 : local_set(&reader->write, 0);
4818 : 0 : local_set(&reader->entries, 0);
4819 : 0 : reader->read = 0;
4820 : 0 : *data_page = bpage;
4821 : :
4822 : : /*
4823 : : * Use the real_end for the data size,
4824 : : * This gives us a chance to store the lost events
4825 : : * on the page.
4826 : : */
4827 [ # # ]: 0 : if (reader->real_end)
4828 : 0 : local_set(&bpage->commit, reader->real_end);
4829 : : }
4830 : 0 : ret = read;
4831 : :
4832 : 0 : cpu_buffer->lost_events = 0;
4833 : :
4834 : 0 : commit = local_read(&bpage->commit);
4835 : : /*
4836 : : * Set a flag in the commit field if we lost events
4837 : : */
4838 [ # # ]: 0 : if (missed_events) {
4839 : : /* If there is room at the end of the page to save the
4840 : : * missed events, then record it there.
4841 : : */
4842 [ # # ]: 0 : if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4843 : 0 : memcpy(&bpage->data[commit], &missed_events,
4844 : : sizeof(missed_events));
4845 : 0 : local_add(RB_MISSED_STORED, &bpage->commit);
4846 : 0 : commit += sizeof(missed_events);
4847 : : }
4848 : 0 : local_add(RB_MISSED_EVENTS, &bpage->commit);
4849 : : }
4850 : :
4851 : : /*
4852 : : * This page may be off to user land. Zero it out here.
4853 : : */
4854 [ # # ]: 0 : if (commit < BUF_PAGE_SIZE)
4855 : 0 : memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4856 : :
4857 : 0 : out_unlock:
4858 : 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4859 : :
4860 : 0 : out:
4861 : 0 : return ret;
4862 : : }
4863 : : EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4864 : :
4865 : : /*
4866 : : * We only allocate new buffers, never free them if the CPU goes down.
4867 : : * If we were to free the buffer, then the user would lose any trace that was in
4868 : : * the buffer.
4869 : : */
4870 : 42 : int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
4871 : : {
4872 : 42 : struct trace_buffer *buffer;
4873 : 42 : long nr_pages_same;
4874 : 42 : int cpu_i;
4875 : 42 : unsigned long nr_pages;
4876 : :
4877 : 42 : buffer = container_of(node, struct trace_buffer, node);
4878 [ - + ]: 42 : if (cpumask_test_cpu(cpu, buffer->cpumask))
4879 : : return 0;
4880 : :
4881 : : nr_pages = 0;
4882 : : nr_pages_same = 1;
4883 : : /* check if all cpu sizes are same */
4884 [ # # ]: 0 : for_each_buffer_cpu(buffer, cpu_i) {
4885 : : /* fill in the size from first enabled cpu */
4886 [ # # ]: 0 : if (nr_pages == 0)
4887 : 0 : nr_pages = buffer->buffers[cpu_i]->nr_pages;
4888 [ # # ]: 0 : if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4889 : : nr_pages_same = 0;
4890 : : break;
4891 : : }
4892 : : }
4893 : : /* allocate minimum pages, user can later expand it */
4894 [ # # ]: 0 : if (!nr_pages_same)
4895 : 0 : nr_pages = 2;
4896 : 0 : buffer->buffers[cpu] =
4897 : 0 : rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4898 [ # # ]: 0 : if (!buffer->buffers[cpu]) {
4899 : 0 : WARN(1, "failed to allocate ring buffer on CPU %u\n",
4900 : : cpu);
4901 : 0 : return -ENOMEM;
4902 : : }
4903 : 0 : smp_wmb();
4904 : 0 : cpumask_set_cpu(cpu, buffer->cpumask);
4905 : 0 : return 0;
4906 : : }
4907 : :
4908 : : #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4909 : : /*
4910 : : * This is a basic integrity check of the ring buffer.
4911 : : * Late in the boot cycle this test will run when configured in.
4912 : : * It will kick off a thread per CPU that will go into a loop
4913 : : * writing to the per cpu ring buffer various sizes of data.
4914 : : * Some of the data will be large items, some small.
4915 : : *
4916 : : * Another thread is created that goes into a spin, sending out
4917 : : * IPIs to the other CPUs to also write into the ring buffer.
4918 : : * this is to test the nesting ability of the buffer.
4919 : : *
4920 : : * Basic stats are recorded and reported. If something in the
4921 : : * ring buffer should happen that's not expected, a big warning
4922 : : * is displayed and all ring buffers are disabled.
4923 : : */
4924 : : static struct task_struct *rb_threads[NR_CPUS] __initdata;
4925 : :
4926 : : struct rb_test_data {
4927 : : struct trace_buffer *buffer;
4928 : : unsigned long events;
4929 : : unsigned long bytes_written;
4930 : : unsigned long bytes_alloc;
4931 : : unsigned long bytes_dropped;
4932 : : unsigned long events_nested;
4933 : : unsigned long bytes_written_nested;
4934 : : unsigned long bytes_alloc_nested;
4935 : : unsigned long bytes_dropped_nested;
4936 : : int min_size_nested;
4937 : : int max_size_nested;
4938 : : int max_size;
4939 : : int min_size;
4940 : : int cpu;
4941 : : int cnt;
4942 : : };
4943 : :
4944 : : static struct rb_test_data rb_data[NR_CPUS] __initdata;
4945 : :
4946 : : /* 1 meg per cpu */
4947 : : #define RB_TEST_BUFFER_SIZE 1048576
4948 : :
4949 : : static char rb_string[] __initdata =
4950 : : "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4951 : : "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4952 : : "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4953 : :
4954 : : static bool rb_test_started __initdata;
4955 : :
4956 : : struct rb_item {
4957 : : int size;
4958 : : char str[];
4959 : : };
4960 : :
4961 : : static __init int rb_write_something(struct rb_test_data *data, bool nested)
4962 : : {
4963 : : struct ring_buffer_event *event;
4964 : : struct rb_item *item;
4965 : : bool started;
4966 : : int event_len;
4967 : : int size;
4968 : : int len;
4969 : : int cnt;
4970 : :
4971 : : /* Have nested writes different that what is written */
4972 : : cnt = data->cnt + (nested ? 27 : 0);
4973 : :
4974 : : /* Multiply cnt by ~e, to make some unique increment */
4975 : : size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
4976 : :
4977 : : len = size + sizeof(struct rb_item);
4978 : :
4979 : : started = rb_test_started;
4980 : : /* read rb_test_started before checking buffer enabled */
4981 : : smp_rmb();
4982 : :
4983 : : event = ring_buffer_lock_reserve(data->buffer, len);
4984 : : if (!event) {
4985 : : /* Ignore dropped events before test starts. */
4986 : : if (started) {
4987 : : if (nested)
4988 : : data->bytes_dropped += len;
4989 : : else
4990 : : data->bytes_dropped_nested += len;
4991 : : }
4992 : : return len;
4993 : : }
4994 : :
4995 : : event_len = ring_buffer_event_length(event);
4996 : :
4997 : : if (RB_WARN_ON(data->buffer, event_len < len))
4998 : : goto out;
4999 : :
5000 : : item = ring_buffer_event_data(event);
5001 : : item->size = size;
5002 : : memcpy(item->str, rb_string, size);
5003 : :
5004 : : if (nested) {
5005 : : data->bytes_alloc_nested += event_len;
5006 : : data->bytes_written_nested += len;
5007 : : data->events_nested++;
5008 : : if (!data->min_size_nested || len < data->min_size_nested)
5009 : : data->min_size_nested = len;
5010 : : if (len > data->max_size_nested)
5011 : : data->max_size_nested = len;
5012 : : } else {
5013 : : data->bytes_alloc += event_len;
5014 : : data->bytes_written += len;
5015 : : data->events++;
5016 : : if (!data->min_size || len < data->min_size)
5017 : : data->max_size = len;
5018 : : if (len > data->max_size)
5019 : : data->max_size = len;
5020 : : }
5021 : :
5022 : : out:
5023 : : ring_buffer_unlock_commit(data->buffer, event);
5024 : :
5025 : : return 0;
5026 : : }
5027 : :
5028 : : static __init int rb_test(void *arg)
5029 : : {
5030 : : struct rb_test_data *data = arg;
5031 : :
5032 : : while (!kthread_should_stop()) {
5033 : : rb_write_something(data, false);
5034 : : data->cnt++;
5035 : :
5036 : : set_current_state(TASK_INTERRUPTIBLE);
5037 : : /* Now sleep between a min of 100-300us and a max of 1ms */
5038 : : usleep_range(((data->cnt % 3) + 1) * 100, 1000);
5039 : : }
5040 : :
5041 : : return 0;
5042 : : }
5043 : :
5044 : : static __init void rb_ipi(void *ignore)
5045 : : {
5046 : : struct rb_test_data *data;
5047 : : int cpu = smp_processor_id();
5048 : :
5049 : : data = &rb_data[cpu];
5050 : : rb_write_something(data, true);
5051 : : }
5052 : :
5053 : : static __init int rb_hammer_test(void *arg)
5054 : : {
5055 : : while (!kthread_should_stop()) {
5056 : :
5057 : : /* Send an IPI to all cpus to write data! */
5058 : : smp_call_function(rb_ipi, NULL, 1);
5059 : : /* No sleep, but for non preempt, let others run */
5060 : : schedule();
5061 : : }
5062 : :
5063 : : return 0;
5064 : : }
5065 : :
5066 : : static __init int test_ringbuffer(void)
5067 : : {
5068 : : struct task_struct *rb_hammer;
5069 : : struct trace_buffer *buffer;
5070 : : int cpu;
5071 : : int ret = 0;
5072 : :
5073 : : if (security_locked_down(LOCKDOWN_TRACEFS)) {
5074 : : pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
5075 : : return 0;
5076 : : }
5077 : :
5078 : : pr_info("Running ring buffer tests...\n");
5079 : :
5080 : : buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5081 : : if (WARN_ON(!buffer))
5082 : : return 0;
5083 : :
5084 : : /* Disable buffer so that threads can't write to it yet */
5085 : : ring_buffer_record_off(buffer);
5086 : :
5087 : : for_each_online_cpu(cpu) {
5088 : : rb_data[cpu].buffer = buffer;
5089 : : rb_data[cpu].cpu = cpu;
5090 : : rb_data[cpu].cnt = cpu;
5091 : : rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5092 : : "rbtester/%d", cpu);
5093 : : if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5094 : : pr_cont("FAILED\n");
5095 : : ret = PTR_ERR(rb_threads[cpu]);
5096 : : goto out_free;
5097 : : }
5098 : :
5099 : : kthread_bind(rb_threads[cpu], cpu);
5100 : : wake_up_process(rb_threads[cpu]);
5101 : : }
5102 : :
5103 : : /* Now create the rb hammer! */
5104 : : rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5105 : : if (WARN_ON(IS_ERR(rb_hammer))) {
5106 : : pr_cont("FAILED\n");
5107 : : ret = PTR_ERR(rb_hammer);
5108 : : goto out_free;
5109 : : }
5110 : :
5111 : : ring_buffer_record_on(buffer);
5112 : : /*
5113 : : * Show buffer is enabled before setting rb_test_started.
5114 : : * Yes there's a small race window where events could be
5115 : : * dropped and the thread wont catch it. But when a ring
5116 : : * buffer gets enabled, there will always be some kind of
5117 : : * delay before other CPUs see it. Thus, we don't care about
5118 : : * those dropped events. We care about events dropped after
5119 : : * the threads see that the buffer is active.
5120 : : */
5121 : : smp_wmb();
5122 : : rb_test_started = true;
5123 : :
5124 : : set_current_state(TASK_INTERRUPTIBLE);
5125 : : /* Just run for 10 seconds */;
5126 : : schedule_timeout(10 * HZ);
5127 : :
5128 : : kthread_stop(rb_hammer);
5129 : :
5130 : : out_free:
5131 : : for_each_online_cpu(cpu) {
5132 : : if (!rb_threads[cpu])
5133 : : break;
5134 : : kthread_stop(rb_threads[cpu]);
5135 : : }
5136 : : if (ret) {
5137 : : ring_buffer_free(buffer);
5138 : : return ret;
5139 : : }
5140 : :
5141 : : /* Report! */
5142 : : pr_info("finished\n");
5143 : : for_each_online_cpu(cpu) {
5144 : : struct ring_buffer_event *event;
5145 : : struct rb_test_data *data = &rb_data[cpu];
5146 : : struct rb_item *item;
5147 : : unsigned long total_events;
5148 : : unsigned long total_dropped;
5149 : : unsigned long total_written;
5150 : : unsigned long total_alloc;
5151 : : unsigned long total_read = 0;
5152 : : unsigned long total_size = 0;
5153 : : unsigned long total_len = 0;
5154 : : unsigned long total_lost = 0;
5155 : : unsigned long lost;
5156 : : int big_event_size;
5157 : : int small_event_size;
5158 : :
5159 : : ret = -1;
5160 : :
5161 : : total_events = data->events + data->events_nested;
5162 : : total_written = data->bytes_written + data->bytes_written_nested;
5163 : : total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5164 : : total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5165 : :
5166 : : big_event_size = data->max_size + data->max_size_nested;
5167 : : small_event_size = data->min_size + data->min_size_nested;
5168 : :
5169 : : pr_info("CPU %d:\n", cpu);
5170 : : pr_info(" events: %ld\n", total_events);
5171 : : pr_info(" dropped bytes: %ld\n", total_dropped);
5172 : : pr_info(" alloced bytes: %ld\n", total_alloc);
5173 : : pr_info(" written bytes: %ld\n", total_written);
5174 : : pr_info(" biggest event: %d\n", big_event_size);
5175 : : pr_info(" smallest event: %d\n", small_event_size);
5176 : :
5177 : : if (RB_WARN_ON(buffer, total_dropped))
5178 : : break;
5179 : :
5180 : : ret = 0;
5181 : :
5182 : : while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5183 : : total_lost += lost;
5184 : : item = ring_buffer_event_data(event);
5185 : : total_len += ring_buffer_event_length(event);
5186 : : total_size += item->size + sizeof(struct rb_item);
5187 : : if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5188 : : pr_info("FAILED!\n");
5189 : : pr_info("buffer had: %.*s\n", item->size, item->str);
5190 : : pr_info("expected: %.*s\n", item->size, rb_string);
5191 : : RB_WARN_ON(buffer, 1);
5192 : : ret = -1;
5193 : : break;
5194 : : }
5195 : : total_read++;
5196 : : }
5197 : : if (ret)
5198 : : break;
5199 : :
5200 : : ret = -1;
5201 : :
5202 : : pr_info(" read events: %ld\n", total_read);
5203 : : pr_info(" lost events: %ld\n", total_lost);
5204 : : pr_info(" total events: %ld\n", total_lost + total_read);
5205 : : pr_info(" recorded len bytes: %ld\n", total_len);
5206 : : pr_info(" recorded size bytes: %ld\n", total_size);
5207 : : if (total_lost)
5208 : : pr_info(" With dropped events, record len and size may not match\n"
5209 : : " alloced and written from above\n");
5210 : : if (!total_lost) {
5211 : : if (RB_WARN_ON(buffer, total_len != total_alloc ||
5212 : : total_size != total_written))
5213 : : break;
5214 : : }
5215 : : if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5216 : : break;
5217 : :
5218 : : ret = 0;
5219 : : }
5220 : : if (!ret)
5221 : : pr_info("Ring buffer PASSED!\n");
5222 : :
5223 : : ring_buffer_free(buffer);
5224 : : return 0;
5225 : : }
5226 : :
5227 : : late_initcall(test_ringbuffer);
5228 : : #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
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