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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/uaccess.h>
15#include <linux/hardirq.h>
16#include <linux/kthread.h> /* for self test */
17#include <linux/module.h>
18#include <linux/percpu.h>
19#include <linux/mutex.h>
20#include <linux/delay.h>
21#include <linux/slab.h>
22#include <linux/init.h>
23#include <linux/hash.h>
24#include <linux/list.h>
25#include <linux/cpu.h>
26#include <linux/oom.h>
27
28#include <asm/local.h>
29
30static void update_pages_handler(struct work_struct *work);
31
32/*
33 * The ring buffer header is special. We must manually up keep it.
34 */
35int ring_buffer_print_entry_header(struct trace_seq *s)
36{
37 trace_seq_puts(s, "# compressed entry header\n");
38 trace_seq_puts(s, "\ttype_len : 5 bits\n");
39 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
40 trace_seq_puts(s, "\tarray : 32 bits\n");
41 trace_seq_putc(s, '\n');
42 trace_seq_printf(s, "\tpadding : type == %d\n",
43 RINGBUF_TYPE_PADDING);
44 trace_seq_printf(s, "\ttime_extend : type == %d\n",
45 RINGBUF_TYPE_TIME_EXTEND);
46 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
47 RINGBUF_TYPE_TIME_STAMP);
48 trace_seq_printf(s, "\tdata max type_len == %d\n",
49 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
50
51 return !trace_seq_has_overflowed(s);
52}
53
54/*
55 * The ring buffer is made up of a list of pages. A separate list of pages is
56 * allocated for each CPU. A writer may only write to a buffer that is
57 * associated with the CPU it is currently executing on. A reader may read
58 * from any per cpu buffer.
59 *
60 * The reader is special. For each per cpu buffer, the reader has its own
61 * reader page. When a reader has read the entire reader page, this reader
62 * page is swapped with another page in the ring buffer.
63 *
64 * Now, as long as the writer is off the reader page, the reader can do what
65 * ever it wants with that page. The writer will never write to that page
66 * again (as long as it is out of the ring buffer).
67 *
68 * Here's some silly ASCII art.
69 *
70 * +------+
71 * |reader| RING BUFFER
72 * |page |
73 * +------+ +---+ +---+ +---+
74 * | |-->| |-->| |
75 * +---+ +---+ +---+
76 * ^ |
77 * | |
78 * +---------------+
79 *
80 *
81 * +------+
82 * |reader| RING BUFFER
83 * |page |------------------v
84 * +------+ +---+ +---+ +---+
85 * | |-->| |-->| |
86 * +---+ +---+ +---+
87 * ^ |
88 * | |
89 * +---------------+
90 *
91 *
92 * +------+
93 * |reader| RING BUFFER
94 * |page |------------------v
95 * +------+ +---+ +---+ +---+
96 * ^ | |-->| |-->| |
97 * | +---+ +---+ +---+
98 * | |
99 * | |
100 * +------------------------------+
101 *
102 *
103 * +------+
104 * |buffer| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
107 * ^ | | | |-->| |
108 * | New +---+ +---+ +---+
109 * | Reader------^ |
110 * | page |
111 * +------------------------------+
112 *
113 *
114 * After we make this swap, the reader can hand this page off to the splice
115 * code and be done with it. It can even allocate a new page if it needs to
116 * and swap that into the ring buffer.
117 *
118 * We will be using cmpxchg soon to make all this lockless.
119 *
120 */
121
122/* Used for individual buffers (after the counter) */
123#define RB_BUFFER_OFF (1 << 20)
124
125#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
126
127#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
128#define RB_ALIGNMENT 4U
129#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
130#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
131#define RB_ALIGN_DATA __aligned(RB_ALIGNMENT)
132
133/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
134#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
135
136enum {
137 RB_LEN_TIME_EXTEND = 8,
138 RB_LEN_TIME_STAMP = 8,
139};
140
141#define skip_time_extend(event) \
142 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
143
144#define extended_time(event) \
145 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
146
147static inline int rb_null_event(struct ring_buffer_event *event)
148{
149 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
150}
151
152static void rb_event_set_padding(struct ring_buffer_event *event)
153{
154 /* padding has a NULL time_delta */
155 event->type_len = RINGBUF_TYPE_PADDING;
156 event->time_delta = 0;
157}
158
159static unsigned
160rb_event_data_length(struct ring_buffer_event *event)
161{
162 unsigned length;
163
164 if (event->type_len)
165 length = event->type_len * RB_ALIGNMENT;
166 else
167 length = event->array[0];
168 return length + RB_EVNT_HDR_SIZE;
169}
170
171/*
172 * Return the length of the given event. Will return
173 * the length of the time extend if the event is a
174 * time extend.
175 */
176static inline unsigned
177rb_event_length(struct ring_buffer_event *event)
178{
179 switch (event->type_len) {
180 case RINGBUF_TYPE_PADDING:
181 if (rb_null_event(event))
182 /* undefined */
183 return -1;
184 return event->array[0] + RB_EVNT_HDR_SIZE;
185
186 case RINGBUF_TYPE_TIME_EXTEND:
187 return RB_LEN_TIME_EXTEND;
188
189 case RINGBUF_TYPE_TIME_STAMP:
190 return RB_LEN_TIME_STAMP;
191
192 case RINGBUF_TYPE_DATA:
193 return rb_event_data_length(event);
194 default:
195 BUG();
196 }
197 /* not hit */
198 return 0;
199}
200
201/*
202 * Return total length of time extend and data,
203 * or just the event length for all other events.
204 */
205static inline unsigned
206rb_event_ts_length(struct ring_buffer_event *event)
207{
208 unsigned len = 0;
209
210 if (extended_time(event)) {
211 /* time extends include the data event after it */
212 len = RB_LEN_TIME_EXTEND;
213 event = skip_time_extend(event);
214 }
215 return len + rb_event_length(event);
216}
217
218/**
219 * ring_buffer_event_length - return the length of the event
220 * @event: the event to get the length of
221 *
222 * Returns the size of the data load of a data event.
223 * If the event is something other than a data event, it
224 * returns the size of the event itself. With the exception
225 * of a TIME EXTEND, where it still returns the size of the
226 * data load of the data event after it.
227 */
228unsigned ring_buffer_event_length(struct ring_buffer_event *event)
229{
230 unsigned length;
231
232 if (extended_time(event))
233 event = skip_time_extend(event);
234
235 length = rb_event_length(event);
236 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
237 return length;
238 length -= RB_EVNT_HDR_SIZE;
239 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
240 length -= sizeof(event->array[0]);
241 return length;
242}
243EXPORT_SYMBOL_GPL(ring_buffer_event_length);
244
245/* inline for ring buffer fast paths */
246static __always_inline void *
247rb_event_data(struct ring_buffer_event *event)
248{
249 if (extended_time(event))
250 event = skip_time_extend(event);
251 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
252 /* If length is in len field, then array[0] has the data */
253 if (event->type_len)
254 return (void *)&event->array[0];
255 /* Otherwise length is in array[0] and array[1] has the data */
256 return (void *)&event->array[1];
257}
258
259/**
260 * ring_buffer_event_data - return the data of the event
261 * @event: the event to get the data from
262 */
263void *ring_buffer_event_data(struct ring_buffer_event *event)
264{
265 return rb_event_data(event);
266}
267EXPORT_SYMBOL_GPL(ring_buffer_event_data);
268
269#define for_each_buffer_cpu(buffer, cpu) \
270 for_each_cpu(cpu, buffer->cpumask)
271
272#define TS_SHIFT 27
273#define TS_MASK ((1ULL << TS_SHIFT) - 1)
274#define TS_DELTA_TEST (~TS_MASK)
275
276/**
277 * ring_buffer_event_time_stamp - return the event's extended timestamp
278 * @event: the event to get the timestamp of
279 *
280 * Returns the extended timestamp associated with a data event.
281 * An extended time_stamp is a 64-bit timestamp represented
282 * internally in a special way that makes the best use of space
283 * contained within a ring buffer event. This function decodes
284 * it and maps it to a straight u64 value.
285 */
286u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
287{
288 u64 ts;
289
290 ts = event->array[0];
291 ts <<= TS_SHIFT;
292 ts += event->time_delta;
293
294 return ts;
295}
296
297/* Flag when events were overwritten */
298#define RB_MISSED_EVENTS (1 << 31)
299/* Missed count stored at end */
300#define RB_MISSED_STORED (1 << 30)
301
302#define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED)
303
304struct buffer_data_page {
305 u64 time_stamp; /* page time stamp */
306 local_t commit; /* write committed index */
307 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
308};
309
310/*
311 * Note, the buffer_page list must be first. The buffer pages
312 * are allocated in cache lines, which means that each buffer
313 * page will be at the beginning of a cache line, and thus
314 * the least significant bits will be zero. We use this to
315 * add flags in the list struct pointers, to make the ring buffer
316 * lockless.
317 */
318struct buffer_page {
319 struct list_head list; /* list of buffer pages */
320 local_t write; /* index for next write */
321 unsigned read; /* index for next read */
322 local_t entries; /* entries on this page */
323 unsigned long real_end; /* real end of data */
324 struct buffer_data_page *page; /* Actual data page */
325};
326
327/*
328 * The buffer page counters, write and entries, must be reset
329 * atomically when crossing page boundaries. To synchronize this
330 * update, two counters are inserted into the number. One is
331 * the actual counter for the write position or count on the page.
332 *
333 * The other is a counter of updaters. Before an update happens
334 * the update partition of the counter is incremented. This will
335 * allow the updater to update the counter atomically.
336 *
337 * The counter is 20 bits, and the state data is 12.
338 */
339#define RB_WRITE_MASK 0xfffff
340#define RB_WRITE_INTCNT (1 << 20)
341
342static void rb_init_page(struct buffer_data_page *bpage)
343{
344 local_set(&bpage->commit, 0);
345}
346
347/*
348 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
349 * this issue out.
350 */
351static void free_buffer_page(struct buffer_page *bpage)
352{
353 free_page((unsigned long)bpage->page);
354 kfree(bpage);
355}
356
357/*
358 * We need to fit the time_stamp delta into 27 bits.
359 */
360static inline int test_time_stamp(u64 delta)
361{
362 if (delta & TS_DELTA_TEST)
363 return 1;
364 return 0;
365}
366
367#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
368
369/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
370#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
371
372int ring_buffer_print_page_header(struct trace_seq *s)
373{
374 struct buffer_data_page field;
375
376 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
377 "offset:0;\tsize:%u;\tsigned:%u;\n",
378 (unsigned int)sizeof(field.time_stamp),
379 (unsigned int)is_signed_type(u64));
380
381 trace_seq_printf(s, "\tfield: local_t commit;\t"
382 "offset:%u;\tsize:%u;\tsigned:%u;\n",
383 (unsigned int)offsetof(typeof(field), commit),
384 (unsigned int)sizeof(field.commit),
385 (unsigned int)is_signed_type(long));
386
387 trace_seq_printf(s, "\tfield: int overwrite;\t"
388 "offset:%u;\tsize:%u;\tsigned:%u;\n",
389 (unsigned int)offsetof(typeof(field), commit),
390 1,
391 (unsigned int)is_signed_type(long));
392
393 trace_seq_printf(s, "\tfield: char data;\t"
394 "offset:%u;\tsize:%u;\tsigned:%u;\n",
395 (unsigned int)offsetof(typeof(field), data),
396 (unsigned int)BUF_PAGE_SIZE,
397 (unsigned int)is_signed_type(char));
398
399 return !trace_seq_has_overflowed(s);
400}
401
402struct rb_irq_work {
403 struct irq_work work;
404 wait_queue_head_t waiters;
405 wait_queue_head_t full_waiters;
406 bool waiters_pending;
407 bool full_waiters_pending;
408 bool wakeup_full;
409};
410
411/*
412 * Structure to hold event state and handle nested events.
413 */
414struct rb_event_info {
415 u64 ts;
416 u64 delta;
417 unsigned long length;
418 struct buffer_page *tail_page;
419 int add_timestamp;
420};
421
422/*
423 * Used for which event context the event is in.
424 * NMI = 0
425 * IRQ = 1
426 * SOFTIRQ = 2
427 * NORMAL = 3
428 *
429 * See trace_recursive_lock() comment below for more details.
430 */
431enum {
432 RB_CTX_NMI,
433 RB_CTX_IRQ,
434 RB_CTX_SOFTIRQ,
435 RB_CTX_NORMAL,
436 RB_CTX_MAX
437};
438
439/*
440 * head_page == tail_page && head == tail then buffer is empty.
441 */
442struct ring_buffer_per_cpu {
443 int cpu;
444 atomic_t record_disabled;
445 struct ring_buffer *buffer;
446 raw_spinlock_t reader_lock; /* serialize readers */
447 arch_spinlock_t lock;
448 struct lock_class_key lock_key;
449 struct buffer_data_page *free_page;
450 unsigned long nr_pages;
451 unsigned int current_context;
452 struct list_head *pages;
453 struct buffer_page *head_page; /* read from head */
454 struct buffer_page *tail_page; /* write to tail */
455 struct buffer_page *commit_page; /* committed pages */
456 struct buffer_page *reader_page;
457 unsigned long lost_events;
458 unsigned long last_overrun;
459 unsigned long nest;
460 local_t entries_bytes;
461 local_t entries;
462 local_t overrun;
463 local_t commit_overrun;
464 local_t dropped_events;
465 local_t committing;
466 local_t commits;
467 local_t pages_touched;
468 local_t pages_read;
469 long last_pages_touch;
470 size_t shortest_full;
471 unsigned long read;
472 unsigned long read_bytes;
473 u64 write_stamp;
474 u64 read_stamp;
475 /* ring buffer pages to update, > 0 to add, < 0 to remove */
476 long nr_pages_to_update;
477 struct list_head new_pages; /* new pages to add */
478 struct work_struct update_pages_work;
479 struct completion update_done;
480
481 struct rb_irq_work irq_work;
482};
483
484struct ring_buffer {
485 unsigned flags;
486 int cpus;
487 atomic_t record_disabled;
488 atomic_t resize_disabled;
489 cpumask_var_t cpumask;
490
491 struct lock_class_key *reader_lock_key;
492
493 struct mutex mutex;
494
495 struct ring_buffer_per_cpu **buffers;
496
497 struct hlist_node node;
498 u64 (*clock)(void);
499
500 struct rb_irq_work irq_work;
501 bool time_stamp_abs;
502};
503
504struct ring_buffer_iter {
505 struct ring_buffer_per_cpu *cpu_buffer;
506 unsigned long head;
507 struct buffer_page *head_page;
508 struct buffer_page *cache_reader_page;
509 unsigned long cache_read;
510 u64 read_stamp;
511};
512
513/**
514 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
515 * @buffer: The ring_buffer to get the number of pages from
516 * @cpu: The cpu of the ring_buffer to get the number of pages from
517 *
518 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
519 */
520size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu)
521{
522 return buffer->buffers[cpu]->nr_pages;
523}
524
525/**
526 * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
527 * @buffer: The ring_buffer to get the number of pages from
528 * @cpu: The cpu of the ring_buffer to get the number of pages from
529 *
530 * Returns the number of pages that have content in the ring buffer.
531 */
532size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu)
533{
534 size_t read;
535 size_t cnt;
536
537 read = local_read(&buffer->buffers[cpu]->pages_read);
538 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
539 /* The reader can read an empty page, but not more than that */
540 if (cnt < read) {
541 WARN_ON_ONCE(read > cnt + 1);
542 return 0;
543 }
544
545 return cnt - read;
546}
547
548/*
549 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
550 *
551 * Schedules a delayed work to wake up any task that is blocked on the
552 * ring buffer waiters queue.
553 */
554static void rb_wake_up_waiters(struct irq_work *work)
555{
556 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
557
558 wake_up_all(&rbwork->waiters);
559 if (rbwork->wakeup_full) {
560 rbwork->wakeup_full = false;
561 wake_up_all(&rbwork->full_waiters);
562 }
563}
564
565/**
566 * ring_buffer_wait - wait for input to the ring buffer
567 * @buffer: buffer to wait on
568 * @cpu: the cpu buffer to wait on
569 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
570 *
571 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
572 * as data is added to any of the @buffer's cpu buffers. Otherwise
573 * it will wait for data to be added to a specific cpu buffer.
574 */
575int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full)
576{
577 struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
578 DEFINE_WAIT(wait);
579 struct rb_irq_work *work;
580 int ret = 0;
581
582 /*
583 * Depending on what the caller is waiting for, either any
584 * data in any cpu buffer, or a specific buffer, put the
585 * caller on the appropriate wait queue.
586 */
587 if (cpu == RING_BUFFER_ALL_CPUS) {
588 work = &buffer->irq_work;
589 /* Full only makes sense on per cpu reads */
590 full = 0;
591 } else {
592 if (!cpumask_test_cpu(cpu, buffer->cpumask))
593 return -ENODEV;
594 cpu_buffer = buffer->buffers[cpu];
595 work = &cpu_buffer->irq_work;
596 }
597
598
599 while (true) {
600 if (full)
601 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
602 else
603 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
604
605 /*
606 * The events can happen in critical sections where
607 * checking a work queue can cause deadlocks.
608 * After adding a task to the queue, this flag is set
609 * only to notify events to try to wake up the queue
610 * using irq_work.
611 *
612 * We don't clear it even if the buffer is no longer
613 * empty. The flag only causes the next event to run
614 * irq_work to do the work queue wake up. The worse
615 * that can happen if we race with !trace_empty() is that
616 * an event will cause an irq_work to try to wake up
617 * an empty queue.
618 *
619 * There's no reason to protect this flag either, as
620 * the work queue and irq_work logic will do the necessary
621 * synchronization for the wake ups. The only thing
622 * that is necessary is that the wake up happens after
623 * a task has been queued. It's OK for spurious wake ups.
624 */
625 if (full)
626 work->full_waiters_pending = true;
627 else
628 work->waiters_pending = true;
629
630 if (signal_pending(current)) {
631 ret = -EINTR;
632 break;
633 }
634
635 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
636 break;
637
638 if (cpu != RING_BUFFER_ALL_CPUS &&
639 !ring_buffer_empty_cpu(buffer, cpu)) {
640 unsigned long flags;
641 bool pagebusy;
642 size_t nr_pages;
643 size_t dirty;
644
645 if (!full)
646 break;
647
648 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
649 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
650 nr_pages = cpu_buffer->nr_pages;
651 dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
652 if (!cpu_buffer->shortest_full ||
653 cpu_buffer->shortest_full < full)
654 cpu_buffer->shortest_full = full;
655 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
656 if (!pagebusy &&
657 (!nr_pages || (dirty * 100) > full * nr_pages))
658 break;
659 }
660
661 schedule();
662 }
663
664 if (full)
665 finish_wait(&work->full_waiters, &wait);
666 else
667 finish_wait(&work->waiters, &wait);
668
669 return ret;
670}
671
672/**
673 * ring_buffer_poll_wait - poll on buffer input
674 * @buffer: buffer to wait on
675 * @cpu: the cpu buffer to wait on
676 * @filp: the file descriptor
677 * @poll_table: The poll descriptor
678 *
679 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
680 * as data is added to any of the @buffer's cpu buffers. Otherwise
681 * it will wait for data to be added to a specific cpu buffer.
682 *
683 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
684 * zero otherwise.
685 */
686__poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
687 struct file *filp, poll_table *poll_table)
688{
689 struct ring_buffer_per_cpu *cpu_buffer;
690 struct rb_irq_work *work;
691
692 if (cpu == RING_BUFFER_ALL_CPUS)
693 work = &buffer->irq_work;
694 else {
695 if (!cpumask_test_cpu(cpu, buffer->cpumask))
696 return -EINVAL;
697
698 cpu_buffer = buffer->buffers[cpu];
699 work = &cpu_buffer->irq_work;
700 }
701
702 poll_wait(filp, &work->waiters, poll_table);
703 work->waiters_pending = true;
704 /*
705 * There's a tight race between setting the waiters_pending and
706 * checking if the ring buffer is empty. Once the waiters_pending bit
707 * is set, the next event will wake the task up, but we can get stuck
708 * if there's only a single event in.
709 *
710 * FIXME: Ideally, we need a memory barrier on the writer side as well,
711 * but adding a memory barrier to all events will cause too much of a
712 * performance hit in the fast path. We only need a memory barrier when
713 * the buffer goes from empty to having content. But as this race is
714 * extremely small, and it's not a problem if another event comes in, we
715 * will fix it later.
716 */
717 smp_mb();
718
719 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
720 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
721 return EPOLLIN | EPOLLRDNORM;
722 return 0;
723}
724
725/* buffer may be either ring_buffer or ring_buffer_per_cpu */
726#define RB_WARN_ON(b, cond) \
727 ({ \
728 int _____ret = unlikely(cond); \
729 if (_____ret) { \
730 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
731 struct ring_buffer_per_cpu *__b = \
732 (void *)b; \
733 atomic_inc(&__b->buffer->record_disabled); \
734 } else \
735 atomic_inc(&b->record_disabled); \
736 WARN_ON(1); \
737 } \
738 _____ret; \
739 })
740
741/* Up this if you want to test the TIME_EXTENTS and normalization */
742#define DEBUG_SHIFT 0
743
744static inline u64 rb_time_stamp(struct ring_buffer *buffer)
745{
746 /* shift to debug/test normalization and TIME_EXTENTS */
747 return buffer->clock() << DEBUG_SHIFT;
748}
749
750u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
751{
752 u64 time;
753
754 preempt_disable_notrace();
755 time = rb_time_stamp(buffer);
756 preempt_enable_notrace();
757
758 return time;
759}
760EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
761
762void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
763 int cpu, u64 *ts)
764{
765 /* Just stupid testing the normalize function and deltas */
766 *ts >>= DEBUG_SHIFT;
767}
768EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
769
770/*
771 * Making the ring buffer lockless makes things tricky.
772 * Although writes only happen on the CPU that they are on,
773 * and they only need to worry about interrupts. Reads can
774 * happen on any CPU.
775 *
776 * The reader page is always off the ring buffer, but when the
777 * reader finishes with a page, it needs to swap its page with
778 * a new one from the buffer. The reader needs to take from
779 * the head (writes go to the tail). But if a writer is in overwrite
780 * mode and wraps, it must push the head page forward.
781 *
782 * Here lies the problem.
783 *
784 * The reader must be careful to replace only the head page, and
785 * not another one. As described at the top of the file in the
786 * ASCII art, the reader sets its old page to point to the next
787 * page after head. It then sets the page after head to point to
788 * the old reader page. But if the writer moves the head page
789 * during this operation, the reader could end up with the tail.
790 *
791 * We use cmpxchg to help prevent this race. We also do something
792 * special with the page before head. We set the LSB to 1.
793 *
794 * When the writer must push the page forward, it will clear the
795 * bit that points to the head page, move the head, and then set
796 * the bit that points to the new head page.
797 *
798 * We also don't want an interrupt coming in and moving the head
799 * page on another writer. Thus we use the second LSB to catch
800 * that too. Thus:
801 *
802 * head->list->prev->next bit 1 bit 0
803 * ------- -------
804 * Normal page 0 0
805 * Points to head page 0 1
806 * New head page 1 0
807 *
808 * Note we can not trust the prev pointer of the head page, because:
809 *
810 * +----+ +-----+ +-----+
811 * | |------>| T |---X--->| N |
812 * | |<------| | | |
813 * +----+ +-----+ +-----+
814 * ^ ^ |
815 * | +-----+ | |
816 * +----------| R |----------+ |
817 * | |<-----------+
818 * +-----+
819 *
820 * Key: ---X--> HEAD flag set in pointer
821 * T Tail page
822 * R Reader page
823 * N Next page
824 *
825 * (see __rb_reserve_next() to see where this happens)
826 *
827 * What the above shows is that the reader just swapped out
828 * the reader page with a page in the buffer, but before it
829 * could make the new header point back to the new page added
830 * it was preempted by a writer. The writer moved forward onto
831 * the new page added by the reader and is about to move forward
832 * again.
833 *
834 * You can see, it is legitimate for the previous pointer of
835 * the head (or any page) not to point back to itself. But only
836 * temporarily.
837 */
838
839#define RB_PAGE_NORMAL 0UL
840#define RB_PAGE_HEAD 1UL
841#define RB_PAGE_UPDATE 2UL
842
843
844#define RB_FLAG_MASK 3UL
845
846/* PAGE_MOVED is not part of the mask */
847#define RB_PAGE_MOVED 4UL
848
849/*
850 * rb_list_head - remove any bit
851 */
852static struct list_head *rb_list_head(struct list_head *list)
853{
854 unsigned long val = (unsigned long)list;
855
856 return (struct list_head *)(val & ~RB_FLAG_MASK);
857}
858
859/*
860 * rb_is_head_page - test if the given page is the head page
861 *
862 * Because the reader may move the head_page pointer, we can
863 * not trust what the head page is (it may be pointing to
864 * the reader page). But if the next page is a header page,
865 * its flags will be non zero.
866 */
867static inline int
868rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
869 struct buffer_page *page, struct list_head *list)
870{
871 unsigned long val;
872
873 val = (unsigned long)list->next;
874
875 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
876 return RB_PAGE_MOVED;
877
878 return val & RB_FLAG_MASK;
879}
880
881/*
882 * rb_is_reader_page
883 *
884 * The unique thing about the reader page, is that, if the
885 * writer is ever on it, the previous pointer never points
886 * back to the reader page.
887 */
888static bool rb_is_reader_page(struct buffer_page *page)
889{
890 struct list_head *list = page->list.prev;
891
892 return rb_list_head(list->next) != &page->list;
893}
894
895/*
896 * rb_set_list_to_head - set a list_head to be pointing to head.
897 */
898static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
899 struct list_head *list)
900{
901 unsigned long *ptr;
902
903 ptr = (unsigned long *)&list->next;
904 *ptr |= RB_PAGE_HEAD;
905 *ptr &= ~RB_PAGE_UPDATE;
906}
907
908/*
909 * rb_head_page_activate - sets up head page
910 */
911static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
912{
913 struct buffer_page *head;
914
915 head = cpu_buffer->head_page;
916 if (!head)
917 return;
918
919 /*
920 * Set the previous list pointer to have the HEAD flag.
921 */
922 rb_set_list_to_head(cpu_buffer, head->list.prev);
923}
924
925static void rb_list_head_clear(struct list_head *list)
926{
927 unsigned long *ptr = (unsigned long *)&list->next;
928
929 *ptr &= ~RB_FLAG_MASK;
930}
931
932/*
933 * rb_head_page_deactivate - clears head page ptr (for free list)
934 */
935static void
936rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
937{
938 struct list_head *hd;
939
940 /* Go through the whole list and clear any pointers found. */
941 rb_list_head_clear(cpu_buffer->pages);
942
943 list_for_each(hd, cpu_buffer->pages)
944 rb_list_head_clear(hd);
945}
946
947static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
948 struct buffer_page *head,
949 struct buffer_page *prev,
950 int old_flag, int new_flag)
951{
952 struct list_head *list;
953 unsigned long val = (unsigned long)&head->list;
954 unsigned long ret;
955
956 list = &prev->list;
957
958 val &= ~RB_FLAG_MASK;
959
960 ret = cmpxchg((unsigned long *)&list->next,
961 val | old_flag, val | new_flag);
962
963 /* check if the reader took the page */
964 if ((ret & ~RB_FLAG_MASK) != val)
965 return RB_PAGE_MOVED;
966
967 return ret & RB_FLAG_MASK;
968}
969
970static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
971 struct buffer_page *head,
972 struct buffer_page *prev,
973 int old_flag)
974{
975 return rb_head_page_set(cpu_buffer, head, prev,
976 old_flag, RB_PAGE_UPDATE);
977}
978
979static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
980 struct buffer_page *head,
981 struct buffer_page *prev,
982 int old_flag)
983{
984 return rb_head_page_set(cpu_buffer, head, prev,
985 old_flag, RB_PAGE_HEAD);
986}
987
988static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
989 struct buffer_page *head,
990 struct buffer_page *prev,
991 int old_flag)
992{
993 return rb_head_page_set(cpu_buffer, head, prev,
994 old_flag, RB_PAGE_NORMAL);
995}
996
997static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
998 struct buffer_page **bpage)
999{
1000 struct list_head *p = rb_list_head((*bpage)->list.next);
1001
1002 *bpage = list_entry(p, struct buffer_page, list);
1003}
1004
1005static struct buffer_page *
1006rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1007{
1008 struct buffer_page *head;
1009 struct buffer_page *page;
1010 struct list_head *list;
1011 int i;
1012
1013 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1014 return NULL;
1015
1016 /* sanity check */
1017 list = cpu_buffer->pages;
1018 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1019 return NULL;
1020
1021 page = head = cpu_buffer->head_page;
1022 /*
1023 * It is possible that the writer moves the header behind
1024 * where we started, and we miss in one loop.
1025 * A second loop should grab the header, but we'll do
1026 * three loops just because I'm paranoid.
1027 */
1028 for (i = 0; i < 3; i++) {
1029 do {
1030 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
1031 cpu_buffer->head_page = page;
1032 return page;
1033 }
1034 rb_inc_page(cpu_buffer, &page);
1035 } while (page != head);
1036 }
1037
1038 RB_WARN_ON(cpu_buffer, 1);
1039
1040 return NULL;
1041}
1042
1043static int rb_head_page_replace(struct buffer_page *old,
1044 struct buffer_page *new)
1045{
1046 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1047 unsigned long val;
1048 unsigned long ret;
1049
1050 val = *ptr & ~RB_FLAG_MASK;
1051 val |= RB_PAGE_HEAD;
1052
1053 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1054
1055 return ret == val;
1056}
1057
1058/*
1059 * rb_tail_page_update - move the tail page forward
1060 */
1061static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1062 struct buffer_page *tail_page,
1063 struct buffer_page *next_page)
1064{
1065 unsigned long old_entries;
1066 unsigned long old_write;
1067
1068 /*
1069 * The tail page now needs to be moved forward.
1070 *
1071 * We need to reset the tail page, but without messing
1072 * with possible erasing of data brought in by interrupts
1073 * that have moved the tail page and are currently on it.
1074 *
1075 * We add a counter to the write field to denote this.
1076 */
1077 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1078 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1079
1080 local_inc(&cpu_buffer->pages_touched);
1081 /*
1082 * Just make sure we have seen our old_write and synchronize
1083 * with any interrupts that come in.
1084 */
1085 barrier();
1086
1087 /*
1088 * If the tail page is still the same as what we think
1089 * it is, then it is up to us to update the tail
1090 * pointer.
1091 */
1092 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1093 /* Zero the write counter */
1094 unsigned long val = old_write & ~RB_WRITE_MASK;
1095 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1096
1097 /*
1098 * This will only succeed if an interrupt did
1099 * not come in and change it. In which case, we
1100 * do not want to modify it.
1101 *
1102 * We add (void) to let the compiler know that we do not care
1103 * about the return value of these functions. We use the
1104 * cmpxchg to only update if an interrupt did not already
1105 * do it for us. If the cmpxchg fails, we don't care.
1106 */
1107 (void)local_cmpxchg(&next_page->write, old_write, val);
1108 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1109
1110 /*
1111 * No need to worry about races with clearing out the commit.
1112 * it only can increment when a commit takes place. But that
1113 * only happens in the outer most nested commit.
1114 */
1115 local_set(&next_page->page->commit, 0);
1116
1117 /* Again, either we update tail_page or an interrupt does */
1118 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1119 }
1120}
1121
1122static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1123 struct buffer_page *bpage)
1124{
1125 unsigned long val = (unsigned long)bpage;
1126
1127 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1128 return 1;
1129
1130 return 0;
1131}
1132
1133/**
1134 * rb_check_list - make sure a pointer to a list has the last bits zero
1135 */
1136static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1137 struct list_head *list)
1138{
1139 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1140 return 1;
1141 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1142 return 1;
1143 return 0;
1144}
1145
1146/**
1147 * rb_check_pages - integrity check of buffer pages
1148 * @cpu_buffer: CPU buffer with pages to test
1149 *
1150 * As a safety measure we check to make sure the data pages have not
1151 * been corrupted.
1152 */
1153static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1154{
1155 struct list_head *head = cpu_buffer->pages;
1156 struct buffer_page *bpage, *tmp;
1157
1158 /* Reset the head page if it exists */
1159 if (cpu_buffer->head_page)
1160 rb_set_head_page(cpu_buffer);
1161
1162 rb_head_page_deactivate(cpu_buffer);
1163
1164 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1165 return -1;
1166 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1167 return -1;
1168
1169 if (rb_check_list(cpu_buffer, head))
1170 return -1;
1171
1172 list_for_each_entry_safe(bpage, tmp, head, list) {
1173 if (RB_WARN_ON(cpu_buffer,
1174 bpage->list.next->prev != &bpage->list))
1175 return -1;
1176 if (RB_WARN_ON(cpu_buffer,
1177 bpage->list.prev->next != &bpage->list))
1178 return -1;
1179 if (rb_check_list(cpu_buffer, &bpage->list))
1180 return -1;
1181 }
1182
1183 rb_head_page_activate(cpu_buffer);
1184
1185 return 0;
1186}
1187
1188static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1189{
1190 struct buffer_page *bpage, *tmp;
1191 bool user_thread = current->mm != NULL;
1192 gfp_t mflags;
1193 long i;
1194
1195 /*
1196 * Check if the available memory is there first.
1197 * Note, si_mem_available() only gives us a rough estimate of available
1198 * memory. It may not be accurate. But we don't care, we just want
1199 * to prevent doing any allocation when it is obvious that it is
1200 * not going to succeed.
1201 */
1202 i = si_mem_available();
1203 if (i < nr_pages)
1204 return -ENOMEM;
1205
1206 /*
1207 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1208 * gracefully without invoking oom-killer and the system is not
1209 * destabilized.
1210 */
1211 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1212
1213 /*
1214 * If a user thread allocates too much, and si_mem_available()
1215 * reports there's enough memory, even though there is not.
1216 * Make sure the OOM killer kills this thread. This can happen
1217 * even with RETRY_MAYFAIL because another task may be doing
1218 * an allocation after this task has taken all memory.
1219 * This is the task the OOM killer needs to take out during this
1220 * loop, even if it was triggered by an allocation somewhere else.
1221 */
1222 if (user_thread)
1223 set_current_oom_origin();
1224 for (i = 0; i < nr_pages; i++) {
1225 struct page *page;
1226
1227 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1228 mflags, cpu_to_node(cpu));
1229 if (!bpage)
1230 goto free_pages;
1231
1232 list_add(&bpage->list, pages);
1233
1234 page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
1235 if (!page)
1236 goto free_pages;
1237 bpage->page = page_address(page);
1238 rb_init_page(bpage->page);
1239
1240 if (user_thread && fatal_signal_pending(current))
1241 goto free_pages;
1242 }
1243 if (user_thread)
1244 clear_current_oom_origin();
1245
1246 return 0;
1247
1248free_pages:
1249 list_for_each_entry_safe(bpage, tmp, pages, list) {
1250 list_del_init(&bpage->list);
1251 free_buffer_page(bpage);
1252 }
1253 if (user_thread)
1254 clear_current_oom_origin();
1255
1256 return -ENOMEM;
1257}
1258
1259static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1260 unsigned long nr_pages)
1261{
1262 LIST_HEAD(pages);
1263
1264 WARN_ON(!nr_pages);
1265
1266 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1267 return -ENOMEM;
1268
1269 /*
1270 * The ring buffer page list is a circular list that does not
1271 * start and end with a list head. All page list items point to
1272 * other pages.
1273 */
1274 cpu_buffer->pages = pages.next;
1275 list_del(&pages);
1276
1277 cpu_buffer->nr_pages = nr_pages;
1278
1279 rb_check_pages(cpu_buffer);
1280
1281 return 0;
1282}
1283
1284static struct ring_buffer_per_cpu *
1285rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
1286{
1287 struct ring_buffer_per_cpu *cpu_buffer;
1288 struct buffer_page *bpage;
1289 struct page *page;
1290 int ret;
1291
1292 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1293 GFP_KERNEL, cpu_to_node(cpu));
1294 if (!cpu_buffer)
1295 return NULL;
1296
1297 cpu_buffer->cpu = cpu;
1298 cpu_buffer->buffer = buffer;
1299 raw_spin_lock_init(&cpu_buffer->reader_lock);
1300 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1301 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1302 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1303 init_completion(&cpu_buffer->update_done);
1304 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1305 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1306 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1307
1308 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1309 GFP_KERNEL, cpu_to_node(cpu));
1310 if (!bpage)
1311 goto fail_free_buffer;
1312
1313 rb_check_bpage(cpu_buffer, bpage);
1314
1315 cpu_buffer->reader_page = bpage;
1316 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1317 if (!page)
1318 goto fail_free_reader;
1319 bpage->page = page_address(page);
1320 rb_init_page(bpage->page);
1321
1322 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1323 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1324
1325 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1326 if (ret < 0)
1327 goto fail_free_reader;
1328
1329 cpu_buffer->head_page
1330 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1331 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1332
1333 rb_head_page_activate(cpu_buffer);
1334
1335 return cpu_buffer;
1336
1337 fail_free_reader:
1338 free_buffer_page(cpu_buffer->reader_page);
1339
1340 fail_free_buffer:
1341 kfree(cpu_buffer);
1342 return NULL;
1343}
1344
1345static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1346{
1347 struct list_head *head = cpu_buffer->pages;
1348 struct buffer_page *bpage, *tmp;
1349
1350 free_buffer_page(cpu_buffer->reader_page);
1351
1352 rb_head_page_deactivate(cpu_buffer);
1353
1354 if (head) {
1355 list_for_each_entry_safe(bpage, tmp, head, list) {
1356 list_del_init(&bpage->list);
1357 free_buffer_page(bpage);
1358 }
1359 bpage = list_entry(head, struct buffer_page, list);
1360 free_buffer_page(bpage);
1361 }
1362
1363 kfree(cpu_buffer);
1364}
1365
1366/**
1367 * __ring_buffer_alloc - allocate a new ring_buffer
1368 * @size: the size in bytes per cpu that is needed.
1369 * @flags: attributes to set for the ring buffer.
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 */
1376struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1377 struct lock_class_key *key)
1378{
1379 struct ring_buffer *buffer;
1380 long nr_pages;
1381 int bsize;
1382 int cpu;
1383 int ret;
1384
1385 /* keep it in its own cache line */
1386 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1387 GFP_KERNEL);
1388 if (!buffer)
1389 return NULL;
1390
1391 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1392 goto fail_free_buffer;
1393
1394 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1395 buffer->flags = flags;
1396 buffer->clock = trace_clock_local;
1397 buffer->reader_lock_key = key;
1398
1399 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1400 init_waitqueue_head(&buffer->irq_work.waiters);
1401
1402 /* need at least two pages */
1403 if (nr_pages < 2)
1404 nr_pages = 2;
1405
1406 buffer->cpus = nr_cpu_ids;
1407
1408 bsize = sizeof(void *) * nr_cpu_ids;
1409 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1410 GFP_KERNEL);
1411 if (!buffer->buffers)
1412 goto fail_free_cpumask;
1413
1414 cpu = raw_smp_processor_id();
1415 cpumask_set_cpu(cpu, buffer->cpumask);
1416 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1417 if (!buffer->buffers[cpu])
1418 goto fail_free_buffers;
1419
1420 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1421 if (ret < 0)
1422 goto fail_free_buffers;
1423
1424 mutex_init(&buffer->mutex);
1425
1426 return buffer;
1427
1428 fail_free_buffers:
1429 for_each_buffer_cpu(buffer, cpu) {
1430 if (buffer->buffers[cpu])
1431 rb_free_cpu_buffer(buffer->buffers[cpu]);
1432 }
1433 kfree(buffer->buffers);
1434
1435 fail_free_cpumask:
1436 free_cpumask_var(buffer->cpumask);
1437
1438 fail_free_buffer:
1439 kfree(buffer);
1440 return NULL;
1441}
1442EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1443
1444/**
1445 * ring_buffer_free - free a ring buffer.
1446 * @buffer: the buffer to free.
1447 */
1448void
1449ring_buffer_free(struct ring_buffer *buffer)
1450{
1451 int cpu;
1452
1453 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1454
1455 for_each_buffer_cpu(buffer, cpu)
1456 rb_free_cpu_buffer(buffer->buffers[cpu]);
1457
1458 kfree(buffer->buffers);
1459 free_cpumask_var(buffer->cpumask);
1460
1461 kfree(buffer);
1462}
1463EXPORT_SYMBOL_GPL(ring_buffer_free);
1464
1465void ring_buffer_set_clock(struct ring_buffer *buffer,
1466 u64 (*clock)(void))
1467{
1468 buffer->clock = clock;
1469}
1470
1471void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
1472{
1473 buffer->time_stamp_abs = abs;
1474}
1475
1476bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
1477{
1478 return buffer->time_stamp_abs;
1479}
1480
1481static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1482
1483static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1484{
1485 return local_read(&bpage->entries) & RB_WRITE_MASK;
1486}
1487
1488static inline unsigned long rb_page_write(struct buffer_page *bpage)
1489{
1490 return local_read(&bpage->write) & RB_WRITE_MASK;
1491}
1492
1493static int
1494rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1495{
1496 struct list_head *tail_page, *to_remove, *next_page;
1497 struct buffer_page *to_remove_page, *tmp_iter_page;
1498 struct buffer_page *last_page, *first_page;
1499 unsigned long nr_removed;
1500 unsigned long head_bit;
1501 int page_entries;
1502
1503 head_bit = 0;
1504
1505 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1506 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 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 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1523 tail_page = rb_list_head(tail_page->next);
1524 to_remove = tail_page;
1525
1526 /* start of pages to remove */
1527 first_page = list_entry(rb_list_head(to_remove->next),
1528 struct buffer_page, list);
1529
1530 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1531 to_remove = rb_list_head(to_remove)->next;
1532 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1533 }
1534
1535 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 tail_page->next = (struct list_head *)((unsigned long)next_page |
1543 head_bit);
1544 next_page = rb_list_head(next_page);
1545 next_page->prev = tail_page;
1546
1547 /* make sure pages points to a valid page in the ring buffer */
1548 cpu_buffer->pages = next_page;
1549
1550 /* update head page */
1551 if (head_bit)
1552 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 cpu_buffer->read = 0;
1560
1561 /* pages are removed, resume tracing and then free the pages */
1562 atomic_dec(&cpu_buffer->record_disabled);
1563 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1564
1565 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 do {
1573 cond_resched();
1574
1575 to_remove_page = tmp_iter_page;
1576 rb_inc_page(cpu_buffer, &tmp_iter_page);
1577
1578 /* update the counters */
1579 page_entries = rb_page_entries(to_remove_page);
1580 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 local_add(page_entries, &cpu_buffer->overrun);
1588 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 free_buffer_page(to_remove_page);
1596 nr_removed--;
1597
1598 } while (to_remove_page != last_page);
1599
1600 RB_WARN_ON(cpu_buffer, nr_removed);
1601
1602 return nr_removed == 0;
1603}
1604
1605static int
1606rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1607{
1608 struct list_head *pages = &cpu_buffer->new_pages;
1609 int retries, success;
1610
1611 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 retries = 10;
1627 success = 0;
1628 while (retries--) {
1629 struct list_head *head_page, *prev_page, *r;
1630 struct list_head *last_page, *first_page;
1631 struct list_head *head_page_with_bit;
1632
1633 head_page = &rb_set_head_page(cpu_buffer)->list;
1634 if (!head_page)
1635 break;
1636 prev_page = head_page->prev;
1637
1638 first_page = pages->next;
1639 last_page = pages->prev;
1640
1641 head_page_with_bit = (struct list_head *)
1642 ((unsigned long)head_page | RB_PAGE_HEAD);
1643
1644 last_page->next = head_page_with_bit;
1645 first_page->prev = prev_page;
1646
1647 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1648
1649 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 head_page->prev = last_page;
1656 success = 1;
1657 break;
1658 }
1659 }
1660
1661 if (success)
1662 INIT_LIST_HEAD(pages);
1663 /*
1664 * If we weren't successful in adding in new pages, warn and stop
1665 * tracing
1666 */
1667 RB_WARN_ON(cpu_buffer, !success);
1668 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1669
1670 /* free pages if they weren't inserted */
1671 if (!success) {
1672 struct buffer_page *bpage, *tmp;
1673 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1674 list) {
1675 list_del_init(&bpage->list);
1676 free_buffer_page(bpage);
1677 }
1678 }
1679 return success;
1680}
1681
1682static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1683{
1684 int success;
1685
1686 if (cpu_buffer->nr_pages_to_update > 0)
1687 success = rb_insert_pages(cpu_buffer);
1688 else
1689 success = rb_remove_pages(cpu_buffer,
1690 -cpu_buffer->nr_pages_to_update);
1691
1692 if (success)
1693 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1694}
1695
1696static void update_pages_handler(struct work_struct *work)
1697{
1698 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1699 struct ring_buffer_per_cpu, update_pages_work);
1700 rb_update_pages(cpu_buffer);
1701 complete(&cpu_buffer->update_done);
1702}
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 */
1714int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1715 int cpu_id)
1716{
1717 struct ring_buffer_per_cpu *cpu_buffer;
1718 unsigned long nr_pages;
1719 int cpu, err = 0;
1720
1721 /*
1722 * Always succeed at resizing a non-existent buffer:
1723 */
1724 if (!buffer)
1725 return size;
1726
1727 /* Make sure the requested buffer exists */
1728 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1729 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1730 return size;
1731
1732 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1733
1734 /* we need a minimum of two pages */
1735 if (nr_pages < 2)
1736 nr_pages = 2;
1737
1738 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 if (atomic_read(&buffer->resize_disabled))
1746 return -EBUSY;
1747
1748 /* prevent another thread from changing buffer sizes */
1749 mutex_lock(&buffer->mutex);
1750
1751 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1752 /* calculate the pages to update */
1753 for_each_buffer_cpu(buffer, cpu) {
1754 cpu_buffer = buffer->buffers[cpu];
1755
1756 cpu_buffer->nr_pages_to_update = nr_pages -
1757 cpu_buffer->nr_pages;
1758 /*
1759 * nothing more to do for removing pages or no update
1760 */
1761 if (cpu_buffer->nr_pages_to_update <= 0)
1762 continue;
1763 /*
1764 * to add pages, make sure all new pages can be
1765 * allocated without receiving ENOMEM
1766 */
1767 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1768 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1769 &cpu_buffer->new_pages, cpu)) {
1770 /* not enough memory for new pages */
1771 err = -ENOMEM;
1772 goto out_err;
1773 }
1774 }
1775
1776 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 for_each_buffer_cpu(buffer, cpu) {
1783 cpu_buffer = buffer->buffers[cpu];
1784 if (!cpu_buffer->nr_pages_to_update)
1785 continue;
1786
1787 /* Can't run something on an offline CPU. */
1788 if (!cpu_online(cpu)) {
1789 rb_update_pages(cpu_buffer);
1790 cpu_buffer->nr_pages_to_update = 0;
1791 } else {
1792 schedule_work_on(cpu,
1793 &cpu_buffer->update_pages_work);
1794 }
1795 }
1796
1797 /* wait for all the updates to complete */
1798 for_each_buffer_cpu(buffer, cpu) {
1799 cpu_buffer = buffer->buffers[cpu];
1800 if (!cpu_buffer->nr_pages_to_update)
1801 continue;
1802
1803 if (cpu_online(cpu))
1804 wait_for_completion(&cpu_buffer->update_done);
1805 cpu_buffer->nr_pages_to_update = 0;
1806 }
1807
1808 put_online_cpus();
1809 } else {
1810 /* Make sure this CPU has been initialized */
1811 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1812 goto out;
1813
1814 cpu_buffer = buffer->buffers[cpu_id];
1815
1816 if (nr_pages == cpu_buffer->nr_pages)
1817 goto out;
1818
1819 cpu_buffer->nr_pages_to_update = nr_pages -
1820 cpu_buffer->nr_pages;
1821
1822 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1823 if (cpu_buffer->nr_pages_to_update > 0 &&
1824 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1825 &cpu_buffer->new_pages, cpu_id)) {
1826 err = -ENOMEM;
1827 goto out_err;
1828 }
1829
1830 get_online_cpus();
1831
1832 /* Can't run something on an offline CPU. */
1833 if (!cpu_online(cpu_id))
1834 rb_update_pages(cpu_buffer);
1835 else {
1836 schedule_work_on(cpu_id,
1837 &cpu_buffer->update_pages_work);
1838 wait_for_completion(&cpu_buffer->update_done);
1839 }
1840
1841 cpu_buffer->nr_pages_to_update = 0;
1842 put_online_cpus();
1843 }
1844
1845 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 if (atomic_read(&buffer->record_disabled)) {
1854 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 synchronize_rcu();
1862 for_each_buffer_cpu(buffer, cpu) {
1863 cpu_buffer = buffer->buffers[cpu];
1864 rb_check_pages(cpu_buffer);
1865 }
1866 atomic_dec(&buffer->record_disabled);
1867 }
1868
1869 mutex_unlock(&buffer->mutex);
1870 return size;
1871
1872 out_err:
1873 for_each_buffer_cpu(buffer, cpu) {
1874 struct buffer_page *bpage, *tmp;
1875
1876 cpu_buffer = buffer->buffers[cpu];
1877 cpu_buffer->nr_pages_to_update = 0;
1878
1879 if (list_empty(&cpu_buffer->new_pages))
1880 continue;
1881
1882 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1883 list) {
1884 list_del_init(&bpage->list);
1885 free_buffer_page(bpage);
1886 }
1887 }
1888 mutex_unlock(&buffer->mutex);
1889 return err;
1890}
1891EXPORT_SYMBOL_GPL(ring_buffer_resize);
1892
1893void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1894{
1895 mutex_lock(&buffer->mutex);
1896 if (val)
1897 buffer->flags |= RB_FL_OVERWRITE;
1898 else
1899 buffer->flags &= ~RB_FL_OVERWRITE;
1900 mutex_unlock(&buffer->mutex);
1901}
1902EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1903
1904static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1905{
1906 return bpage->page->data + index;
1907}
1908
1909static __always_inline struct ring_buffer_event *
1910rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1911{
1912 return __rb_page_index(cpu_buffer->reader_page,
1913 cpu_buffer->reader_page->read);
1914}
1915
1916static __always_inline struct ring_buffer_event *
1917rb_iter_head_event(struct ring_buffer_iter *iter)
1918{
1919 return __rb_page_index(iter->head_page, iter->head);
1920}
1921
1922static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
1923{
1924 return local_read(&bpage->page->commit);
1925}
1926
1927/* Size is determined by what has been committed */
1928static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
1929{
1930 return rb_page_commit(bpage);
1931}
1932
1933static __always_inline unsigned
1934rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1935{
1936 return rb_page_commit(cpu_buffer->commit_page);
1937}
1938
1939static __always_inline unsigned
1940rb_event_index(struct ring_buffer_event *event)
1941{
1942 unsigned long addr = (unsigned long)event;
1943
1944 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1945}
1946
1947static void rb_inc_iter(struct ring_buffer_iter *iter)
1948{
1949 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 if (iter->head_page == cpu_buffer->reader_page)
1958 iter->head_page = rb_set_head_page(cpu_buffer);
1959 else
1960 rb_inc_page(cpu_buffer, &iter->head_page);
1961
1962 iter->read_stamp = iter->head_page->page->time_stamp;
1963 iter->head = 0;
1964}
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 */
1973static int
1974rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1975 struct buffer_page *tail_page,
1976 struct buffer_page *next_page)
1977{
1978 struct buffer_page *new_head;
1979 int entries;
1980 int type;
1981 int ret;
1982
1983 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 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 switch (type) {
2005 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 local_add(entries, &cpu_buffer->overrun);
2012 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 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2044 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 new_head = next_page;
2062 rb_inc_page(cpu_buffer, &new_head);
2063
2064 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 switch (ret) {
2076 case RB_PAGE_HEAD:
2077 case RB_PAGE_NORMAL:
2078 /* OK */
2079 break;
2080 default:
2081 RB_WARN_ON(cpu_buffer, 1);
2082 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 if (ret == RB_PAGE_NORMAL) {
2096 struct buffer_page *buffer_tail_page;
2097
2098 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 if (buffer_tail_page != tail_page &&
2104 buffer_tail_page != next_page)
2105 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 if (type == RB_PAGE_HEAD) {
2116 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2117 tail_page,
2118 RB_PAGE_UPDATE);
2119 if (RB_WARN_ON(cpu_buffer,
2120 ret != RB_PAGE_UPDATE))
2121 return -1;
2122 }
2123
2124 return 0;
2125}
2126
2127static inline void
2128rb_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
2197static 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 */
2202static noinline struct ring_buffer_event *
2203rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2204 unsigned long tail, struct rb_event_info *info)
2205{
2206 struct buffer_page *tail_page = info->tail_page;
2207 struct buffer_page *commit_page = cpu_buffer->commit_page;
2208 struct ring_buffer *buffer = cpu_buffer->buffer;
2209 struct buffer_page *next_page;
2210 int ret;
2211
2212 next_page = tail_page;
2213
2214 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 if (unlikely(next_page == commit_page)) {
2222 local_inc(&cpu_buffer->commit_overrun);
2223 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 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 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 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2252 local_inc(&cpu_buffer->dropped_events);
2253 goto out_reset;
2254 }
2255
2256 ret = rb_handle_head_page(cpu_buffer,
2257 tail_page,
2258 next_page);
2259 if (ret < 0)
2260 goto out_reset;
2261 if (ret)
2262 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 if (unlikely((cpu_buffer->commit_page !=
2275 cpu_buffer->tail_page) &&
2276 (cpu_buffer->commit_page ==
2277 cpu_buffer->reader_page))) {
2278 local_inc(&cpu_buffer->commit_overrun);
2279 goto out_reset;
2280 }
2281 }
2282 }
2283
2284 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2285
2286 out_again:
2287
2288 rb_reset_tail(cpu_buffer, tail, info);
2289
2290 /* Commit what we have for now. */
2291 rb_end_commit(cpu_buffer);
2292 /* rb_end_commit() decs committing */
2293 local_inc(&cpu_buffer->committing);
2294
2295 /* fail and let the caller try again */
2296 return ERR_PTR(-EAGAIN);
2297
2298 out_reset:
2299 /* reset write */
2300 rb_reset_tail(cpu_buffer, tail, info);
2301
2302 return NULL;
2303}
2304
2305/* Slow path, do not inline */
2306static noinline struct ring_buffer_event *
2307rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2308{
2309 if (abs)
2310 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2311 else
2312 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2313
2314 /* Not the first event on the page, or not delta? */
2315 if (abs || rb_event_index(event)) {
2316 event->time_delta = delta & TS_MASK;
2317 event->array[0] = delta >> TS_SHIFT;
2318 } else {
2319 /* nope, just zero it */
2320 event->time_delta = 0;
2321 event->array[0] = 0;
2322 }
2323
2324 return skip_time_extend(event);
2325}
2326
2327static 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 * @event: the event to update
2333 * @type: the type of event
2334 * @length: the size of the event field in the ring buffer
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 */
2341static void
2342rb_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
2374static unsigned rb_calculate_event_length(unsigned length)
2375{
2376 struct ring_buffer_event event; /* Used only for sizeof array */
2377
2378 /* zero length can cause confusions */
2379 if (!length)
2380 length++;
2381
2382 if (length > RB_MAX_SMALL_DATA)
2383 length += sizeof(event.array[0]);
2384
2385 length += RB_EVNT_HDR_SIZE;
2386 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 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2401 length += RB_ALIGNMENT;
2402
2403 return length;
2404}
2405
2406#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2407static inline bool sched_clock_stable(void)
2408{
2409 return true;
2410}
2411#endif
2412
2413static inline int
2414rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2415 struct ring_buffer_event *event)
2416{
2417 unsigned long new_index, old_index;
2418 struct buffer_page *bpage;
2419 unsigned long index;
2420 unsigned long addr;
2421
2422 new_index = rb_event_index(event);
2423 old_index = new_index + rb_event_ts_length(event);
2424 addr = (unsigned long)event;
2425 addr &= PAGE_MASK;
2426
2427 bpage = READ_ONCE(cpu_buffer->tail_page);
2428
2429 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2430 unsigned long write_mask =
2431 local_read(&bpage->write) & ~RB_WRITE_MASK;
2432 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 old_index += write_mask;
2440 new_index += write_mask;
2441 index = local_cmpxchg(&bpage->write, old_index, new_index);
2442 if (index == old_index) {
2443 /* update counters */
2444 local_sub(event_length, &cpu_buffer->entries_bytes);
2445 return 1;
2446 }
2447 }
2448
2449 /* could not discard */
2450 return 0;
2451}
2452
2453static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2454{
2455 local_inc(&cpu_buffer->committing);
2456 local_inc(&cpu_buffer->commits);
2457}
2458
2459static __always_inline void
2460rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2461{
2462 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 again:
2473 max_count = cpu_buffer->nr_pages * 100;
2474
2475 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2476 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2477 return;
2478 if (RB_WARN_ON(cpu_buffer,
2479 rb_is_reader_page(cpu_buffer->tail_page)))
2480 return;
2481 local_set(&cpu_buffer->commit_page->page->commit,
2482 rb_page_write(cpu_buffer->commit_page));
2483 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2484 /* Only update the write stamp if the page has an event */
2485 if (rb_page_write(cpu_buffer->commit_page))
2486 cpu_buffer->write_stamp =
2487 cpu_buffer->commit_page->page->time_stamp;
2488 /* add barrier to keep gcc from optimizing too much */
2489 barrier();
2490 }
2491 while (rb_commit_index(cpu_buffer) !=
2492 rb_page_write(cpu_buffer->commit_page)) {
2493
2494 local_set(&cpu_buffer->commit_page->page->commit,
2495 rb_page_write(cpu_buffer->commit_page));
2496 RB_WARN_ON(cpu_buffer,
2497 local_read(&cpu_buffer->commit_page->page->commit) &
2498 ~RB_WRITE_MASK);
2499 barrier();
2500 }
2501
2502 /* again, keep gcc from optimizing */
2503 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 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2511 goto again;
2512}
2513
2514static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2515{
2516 unsigned long commits;
2517
2518 if (RB_WARN_ON(cpu_buffer,
2519 !local_read(&cpu_buffer->committing)))
2520 return;
2521
2522 again:
2523 commits = local_read(&cpu_buffer->commits);
2524 /* synchronize with interrupts */
2525 barrier();
2526 if (local_read(&cpu_buffer->committing) == 1)
2527 rb_set_commit_to_write(cpu_buffer);
2528
2529 local_dec(&cpu_buffer->committing);
2530
2531 /* synchronize with interrupts */
2532 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 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2540 !local_read(&cpu_buffer->committing)) {
2541 local_inc(&cpu_buffer->committing);
2542 goto again;
2543 }
2544}
2545
2546static inline void rb_event_discard(struct ring_buffer_event *event)
2547{
2548 if (extended_time(event))
2549 event = skip_time_extend(event);
2550
2551 /* array[0] holds the actual length for the discarded event */
2552 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2553 event->type_len = RINGBUF_TYPE_PADDING;
2554 /* time delta must be non zero */
2555 if (!event->time_delta)
2556 event->time_delta = 1;
2557}
2558
2559static __always_inline bool
2560rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2561 struct ring_buffer_event *event)
2562{
2563 unsigned long addr = (unsigned long)event;
2564 unsigned long index;
2565
2566 index = rb_event_index(event);
2567 addr &= PAGE_MASK;
2568
2569 return cpu_buffer->commit_page->page == (void *)addr &&
2570 rb_commit_index(cpu_buffer) == index;
2571}
2572
2573static __always_inline void
2574rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2575 struct ring_buffer_event *event)
2576{
2577 u64 delta;
2578
2579 /*
2580 * The event first in the commit queue updates the
2581 * time stamp.
2582 */
2583 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 if (!rb_event_index(event))
2589 cpu_buffer->write_stamp =
2590 cpu_buffer->commit_page->page->time_stamp;
2591 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2592 delta = ring_buffer_event_time_stamp(event);
2593 cpu_buffer->write_stamp += delta;
2594 } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
2595 delta = ring_buffer_event_time_stamp(event);
2596 cpu_buffer->write_stamp = delta;
2597 } else
2598 cpu_buffer->write_stamp += event->time_delta;
2599 }
2600}
2601
2602static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2603 struct ring_buffer_event *event)
2604{
2605 local_inc(&cpu_buffer->entries);
2606 rb_update_write_stamp(cpu_buffer, event);
2607 rb_end_commit(cpu_buffer);
2608}
2609
2610static __always_inline void
2611rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2612{
2613 size_t nr_pages;
2614 size_t dirty;
2615 size_t full;
2616
2617 if (buffer->irq_work.waiters_pending) {
2618 buffer->irq_work.waiters_pending = false;
2619 /* irq_work_queue() supplies it's own memory barriers */
2620 irq_work_queue(&buffer->irq_work.work);
2621 }
2622
2623 if (cpu_buffer->irq_work.waiters_pending) {
2624 cpu_buffer->irq_work.waiters_pending = false;
2625 /* irq_work_queue() supplies it's own memory barriers */
2626 irq_work_queue(&cpu_buffer->irq_work.work);
2627 }
2628
2629 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
2630 return;
2631
2632 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
2633 return;
2634
2635 if (!cpu_buffer->irq_work.full_waiters_pending)
2636 return;
2637
2638 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
2639
2640 full = cpu_buffer->shortest_full;
2641 nr_pages = cpu_buffer->nr_pages;
2642 dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
2643 if (full && nr_pages && (dirty * 100) <= full * nr_pages)
2644 return;
2645
2646 cpu_buffer->irq_work.wakeup_full = true;
2647 cpu_buffer->irq_work.full_waiters_pending = false;
2648 /* irq_work_queue() supplies it's own memory barriers */
2649 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
2690static __always_inline int
2691trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
2692{
2693 unsigned int val = cpu_buffer->current_context;
2694 unsigned long pc = preempt_count();
2695 int bit;
2696
2697 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
2698 bit = RB_CTX_NORMAL;
2699 else
2700 bit = pc & NMI_MASK ? RB_CTX_NMI :
2701 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
2702
2703 if (unlikely(val & (1 << (bit + cpu_buffer->nest))))
2704 return 1;
2705
2706 val |= (1 << (bit + cpu_buffer->nest));
2707 cpu_buffer->current_context = val;
2708
2709 return 0;
2710}
2711
2712static __always_inline void
2713trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
2714{
2715 cpu_buffer->current_context &=
2716 cpu_buffer->current_context - (1 << cpu_buffer->nest);
2717}
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 */
2735void ring_buffer_nest_start(struct ring_buffer *buffer)
2736{
2737 struct ring_buffer_per_cpu *cpu_buffer;
2738 int cpu;
2739
2740 /* Enabled by ring_buffer_nest_end() */
2741 preempt_disable_notrace();
2742 cpu = raw_smp_processor_id();
2743 cpu_buffer = buffer->buffers[cpu];
2744 /* This is the shift value for the above recursive locking */
2745 cpu_buffer->nest += NESTED_BITS;
2746}
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 */
2755void ring_buffer_nest_end(struct ring_buffer *buffer)
2756{
2757 struct ring_buffer_per_cpu *cpu_buffer;
2758 int cpu;
2759
2760 /* disabled by ring_buffer_nest_start() */
2761 cpu = raw_smp_processor_id();
2762 cpu_buffer = buffer->buffers[cpu];
2763 /* This is the shift value for the above recursive locking */
2764 cpu_buffer->nest -= NESTED_BITS;
2765 preempt_enable_notrace();
2766}
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 */
2777int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2778 struct ring_buffer_event *event)
2779{
2780 struct ring_buffer_per_cpu *cpu_buffer;
2781 int cpu = raw_smp_processor_id();
2782
2783 cpu_buffer = buffer->buffers[cpu];
2784
2785 rb_commit(cpu_buffer, event);
2786
2787 rb_wakeups(buffer, cpu_buffer);
2788
2789 trace_recursive_unlock(cpu_buffer);
2790
2791 preempt_enable_notrace();
2792
2793 return 0;
2794}
2795EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2796
2797static noinline void
2798rb_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
2814static struct ring_buffer_event *
2815__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2816 struct rb_event_info *info)
2817{
2818 struct ring_buffer_event *event;
2819 struct buffer_page *tail_page;
2820 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 if (unlikely(info->add_timestamp))
2828 info->length += RB_LEN_TIME_EXTEND;
2829
2830 /* Don't let the compiler play games with cpu_buffer->tail_page */
2831 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
2832 write = local_add_return(info->length, &tail_page->write);
2833
2834 /* set write to only the index of the write */
2835 write &= RB_WRITE_MASK;
2836 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 if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
2843 info->delta = 0;
2844
2845 /* See if we shot pass the end of this buffer page */
2846 if (unlikely(write > BUF_PAGE_SIZE))
2847 return rb_move_tail(cpu_buffer, tail, info);
2848
2849 /* We reserved something on the buffer */
2850
2851 event = __rb_page_index(tail_page, tail);
2852 rb_update_event(cpu_buffer, event, info);
2853
2854 local_inc(&tail_page->entries);
2855
2856 /*
2857 * If this is the first commit on the page, then update
2858 * its timestamp.
2859 */
2860 if (!tail)
2861 tail_page->page->time_stamp = info->ts;
2862
2863 /* account for these added bytes */
2864 local_add(info->length, &cpu_buffer->entries_bytes);
2865
2866 return event;
2867}
2868
2869static __always_inline struct ring_buffer_event *
2870rb_reserve_next_event(struct ring_buffer *buffer,
2871 struct ring_buffer_per_cpu *cpu_buffer,
2872 unsigned long length)
2873{
2874 struct ring_buffer_event *event;
2875 struct rb_event_info info;
2876 int nr_loops = 0;
2877 u64 diff;
2878
2879 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 info.length = rb_calculate_event_length(length);
2897 again:
2898 info.add_timestamp = 0;
2899 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 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2911 goto out_fail;
2912
2913 info.ts = rb_time_stamp(cpu_buffer->buffer);
2914 diff = info.ts - cpu_buffer->write_stamp;
2915
2916 /* make sure this diff is calculated here */
2917 barrier();
2918
2919 if (ring_buffer_time_stamp_abs(buffer)) {
2920 info.delta = info.ts;
2921 rb_handle_timestamp(cpu_buffer, &info);
2922 } else /* Did the write stamp get updated already? */
2923 if (likely(info.ts >= cpu_buffer->write_stamp)) {
2924 info.delta = diff;
2925 if (unlikely(test_time_stamp(info.delta)))
2926 rb_handle_timestamp(cpu_buffer, &info);
2927 }
2928
2929 event = __rb_reserve_next(cpu_buffer, &info);
2930
2931 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
2932 if (info.add_timestamp)
2933 info.length -= RB_LEN_TIME_EXTEND;
2934 goto again;
2935 }
2936
2937 if (!event)
2938 goto out_fail;
2939
2940 return event;
2941
2942 out_fail:
2943 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 */
2962struct ring_buffer_event *
2963ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2964{
2965 struct ring_buffer_per_cpu *cpu_buffer;
2966 struct ring_buffer_event *event;
2967 int cpu;
2968
2969 /* If we are tracing schedule, we don't want to recurse */
2970 preempt_disable_notrace();
2971
2972 if (unlikely(atomic_read(&buffer->record_disabled)))
2973 goto out;
2974
2975 cpu = raw_smp_processor_id();
2976
2977 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
2978 goto out;
2979
2980 cpu_buffer = buffer->buffers[cpu];
2981
2982 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
2983 goto out;
2984
2985 if (unlikely(length > BUF_MAX_DATA_SIZE))
2986 goto out;
2987
2988 if (unlikely(trace_recursive_lock(cpu_buffer)))
2989 goto out;
2990
2991 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2992 if (!event)
2993 goto out_unlock;
2994
2995 return event;
2996
2997 out_unlock:
2998 trace_recursive_unlock(cpu_buffer);
2999 out:
3000 preempt_enable_notrace();
3001 return NULL;
3002}
3003EXPORT_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 */
3011static inline void
3012rb_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 */
3064void ring_buffer_discard_commit(struct ring_buffer *buffer,
3065 struct ring_buffer_event *event)
3066{
3067 struct ring_buffer_per_cpu *cpu_buffer;
3068 int cpu;
3069
3070 /* The event is discarded regardless */
3071 rb_event_discard(event);
3072
3073 cpu = smp_processor_id();
3074 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 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3082
3083 rb_decrement_entry(cpu_buffer, event);
3084 if (rb_try_to_discard(cpu_buffer, event))
3085 goto out;
3086
3087 /*
3088 * The commit is still visible by the reader, so we
3089 * must still update the timestamp.
3090 */
3091 rb_update_write_stamp(cpu_buffer, event);
3092 out:
3093 rb_end_commit(cpu_buffer);
3094
3095 trace_recursive_unlock(cpu_buffer);
3096
3097 preempt_enable_notrace();
3098
3099}
3100EXPORT_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 */
3115int ring_buffer_write(struct ring_buffer *buffer,
3116 unsigned long length,
3117 void *data)
3118{
3119 struct ring_buffer_per_cpu *cpu_buffer;
3120 struct ring_buffer_event *event;
3121 void *body;
3122 int ret = -EBUSY;
3123 int cpu;
3124
3125 preempt_disable_notrace();
3126
3127 if (atomic_read(&buffer->record_disabled))
3128 goto out;
3129
3130 cpu = raw_smp_processor_id();
3131
3132 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3133 goto out;
3134
3135 cpu_buffer = buffer->buffers[cpu];
3136
3137 if (atomic_read(&cpu_buffer->record_disabled))
3138 goto out;
3139
3140 if (length > BUF_MAX_DATA_SIZE)
3141 goto out;
3142
3143 if (unlikely(trace_recursive_lock(cpu_buffer)))
3144 goto out;
3145
3146 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3147 if (!event)
3148 goto out_unlock;
3149
3150 body = rb_event_data(event);
3151
3152 memcpy(body, data, length);
3153
3154 rb_commit(cpu_buffer, event);
3155
3156 rb_wakeups(buffer, cpu_buffer);
3157
3158 ret = 0;
3159
3160 out_unlock:
3161 trace_recursive_unlock(cpu_buffer);
3162
3163 out:
3164 preempt_enable_notrace();
3165
3166 return ret;
3167}
3168EXPORT_SYMBOL_GPL(ring_buffer_write);
3169
3170static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3171{
3172 struct buffer_page *reader = cpu_buffer->reader_page;
3173 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3174 struct buffer_page *commit = cpu_buffer->commit_page;
3175
3176 /* In case of error, head will be NULL */
3177 if (unlikely(!head))
3178 return true;
3179
3180 return reader->read == rb_page_commit(reader) &&
3181 (commit == reader ||
3182 (commit == head &&
3183 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 */
3195void ring_buffer_record_disable(struct ring_buffer *buffer)
3196{
3197 atomic_inc(&buffer->record_disabled);
3198}
3199EXPORT_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 */
3208void ring_buffer_record_enable(struct ring_buffer *buffer)
3209{
3210 atomic_dec(&buffer->record_disabled);
3211}
3212EXPORT_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 */
3225void ring_buffer_record_off(struct ring_buffer *buffer)
3226{
3227 unsigned int rd;
3228 unsigned int new_rd;
3229
3230 do {
3231 rd = atomic_read(&buffer->record_disabled);
3232 new_rd = rd | RB_BUFFER_OFF;
3233 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3234}
3235EXPORT_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 */
3248void ring_buffer_record_on(struct ring_buffer *buffer)
3249{
3250 unsigned int rd;
3251 unsigned int new_rd;
3252
3253 do {
3254 rd = atomic_read(&buffer->record_disabled);
3255 new_rd = rd & ~RB_BUFFER_OFF;
3256 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3257}
3258EXPORT_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 */
3266bool ring_buffer_record_is_on(struct ring_buffer *buffer)
3267{
3268 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 */
3282bool ring_buffer_record_is_set_on(struct ring_buffer *buffer)
3283{
3284 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 */
3297void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3298{
3299 struct ring_buffer_per_cpu *cpu_buffer;
3300
3301 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3302 return;
3303
3304 cpu_buffer = buffer->buffers[cpu];
3305 atomic_inc(&cpu_buffer->record_disabled);
3306}
3307EXPORT_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 */
3317void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3318{
3319 struct ring_buffer_per_cpu *cpu_buffer;
3320
3321 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3322 return;
3323
3324 cpu_buffer = buffer->buffers[cpu];
3325 atomic_dec(&cpu_buffer->record_disabled);
3326}
3327EXPORT_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 */
3335static inline unsigned long
3336rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3337{
3338 return local_read(&cpu_buffer->entries) -
3339 (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 */
3347u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3348{
3349 unsigned long flags;
3350 struct ring_buffer_per_cpu *cpu_buffer;
3351 struct buffer_page *bpage;
3352 u64 ret = 0;
3353
3354 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3355 return 0;
3356
3357 cpu_buffer = buffer->buffers[cpu];
3358 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 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3364 bpage = cpu_buffer->reader_page;
3365 else
3366 bpage = rb_set_head_page(cpu_buffer);
3367 if (bpage)
3368 ret = bpage->page->time_stamp;
3369 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3370
3371 return ret;
3372}
3373EXPORT_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 */
3380unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3381{
3382 struct ring_buffer_per_cpu *cpu_buffer;
3383 unsigned long ret;
3384
3385 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3386 return 0;
3387
3388 cpu_buffer = buffer->buffers[cpu];
3389 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3390
3391 return ret;
3392}
3393EXPORT_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 */
3400unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3401{
3402 struct ring_buffer_per_cpu *cpu_buffer;
3403
3404 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3405 return 0;
3406
3407 cpu_buffer = buffer->buffers[cpu];
3408
3409 return rb_num_of_entries(cpu_buffer);
3410}
3411EXPORT_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 */
3419unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3420{
3421 struct ring_buffer_per_cpu *cpu_buffer;
3422 unsigned long ret;
3423
3424 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3425 return 0;
3426
3427 cpu_buffer = buffer->buffers[cpu];
3428 ret = local_read(&cpu_buffer->overrun);
3429
3430 return ret;
3431}
3432EXPORT_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 */
3441unsigned long
3442ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3443{
3444 struct ring_buffer_per_cpu *cpu_buffer;
3445 unsigned long ret;
3446
3447 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3448 return 0;
3449
3450 cpu_buffer = buffer->buffers[cpu];
3451 ret = local_read(&cpu_buffer->commit_overrun);
3452
3453 return ret;
3454}
3455EXPORT_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 */
3463unsigned long
3464ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3465{
3466 struct ring_buffer_per_cpu *cpu_buffer;
3467 unsigned long ret;
3468
3469 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3470 return 0;
3471
3472 cpu_buffer = buffer->buffers[cpu];
3473 ret = local_read(&cpu_buffer->dropped_events);
3474
3475 return ret;
3476}
3477EXPORT_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 */
3484unsigned long
3485ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3486{
3487 struct ring_buffer_per_cpu *cpu_buffer;
3488
3489 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3490 return 0;
3491
3492 cpu_buffer = buffer->buffers[cpu];
3493 return cpu_buffer->read;
3494}
3495EXPORT_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 */
3504unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3505{
3506 struct ring_buffer_per_cpu *cpu_buffer;
3507 unsigned long entries = 0;
3508 int cpu;
3509
3510 /* if you care about this being correct, lock the buffer */
3511 for_each_buffer_cpu(buffer, cpu) {
3512 cpu_buffer = buffer->buffers[cpu];
3513 entries += rb_num_of_entries(cpu_buffer);
3514 }
3515
3516 return entries;
3517}
3518EXPORT_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 */
3527unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3528{
3529 struct ring_buffer_per_cpu *cpu_buffer;
3530 unsigned long overruns = 0;
3531 int cpu;
3532
3533 /* if you care about this being correct, lock the buffer */
3534 for_each_buffer_cpu(buffer, cpu) {
3535 cpu_buffer = buffer->buffers[cpu];
3536 overruns += local_read(&cpu_buffer->overrun);
3537 }
3538
3539 return overruns;
3540}
3541EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3542
3543static void rb_iter_reset(struct ring_buffer_iter *iter)
3544{
3545 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3546
3547 /* Iterator usage is expected to have record disabled */
3548 iter->head_page = cpu_buffer->reader_page;
3549 iter->head = cpu_buffer->reader_page->read;
3550
3551 iter->cache_reader_page = iter->head_page;
3552 iter->cache_read = cpu_buffer->read;
3553
3554 if (iter->head)
3555 iter->read_stamp = cpu_buffer->read_stamp;
3556 else
3557 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 */
3567void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3568{
3569 struct ring_buffer_per_cpu *cpu_buffer;
3570 unsigned long flags;
3571
3572 if (!iter)
3573 return;
3574
3575 cpu_buffer = iter->cpu_buffer;
3576
3577 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3578 rb_iter_reset(iter);
3579 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3580}
3581EXPORT_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 */
3587int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3588{
3589 struct ring_buffer_per_cpu *cpu_buffer;
3590 struct buffer_page *reader;
3591 struct buffer_page *head_page;
3592 struct buffer_page *commit_page;
3593 unsigned commit;
3594
3595 cpu_buffer = iter->cpu_buffer;
3596
3597 /* Remember, trace recording is off when iterator is in use */
3598 reader = cpu_buffer->reader_page;
3599 head_page = cpu_buffer->head_page;
3600 commit_page = cpu_buffer->commit_page;
3601 commit = rb_page_commit(commit_page);
3602
3603 return ((iter->head_page == commit_page && iter->head == commit) ||
3604 (iter->head_page == reader && commit_page == head_page &&
3605 head_page->read == commit &&
3606 iter->head == rb_page_commit(cpu_buffer->reader_page)));
3607}
3608EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3609
3610static void
3611rb_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
3640static void
3641rb_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
3670static struct buffer_page *
3671rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3672{
3673 struct buffer_page *reader = NULL;
3674 unsigned long overwrite;
3675 unsigned long flags;
3676 int nr_loops = 0;
3677 int ret;
3678
3679 local_irq_save(flags);
3680 arch_spin_lock(&cpu_buffer->lock);
3681
3682 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 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3690 reader = NULL;
3691 goto out;
3692 }
3693
3694 reader = cpu_buffer->reader_page;
3695
3696 /* If there's more to read, return this page */
3697 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3698 goto out;
3699
3700 /* Never should we have an index greater than the size */
3701 if (RB_WARN_ON(cpu_buffer,
3702 cpu_buffer->reader_page->read > rb_page_size(reader)))
3703 goto out;
3704
3705 /* check if we caught up to the tail */
3706 reader = NULL;
3707 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3708 goto out;
3709
3710 /* Don't bother swapping if the ring buffer is empty */
3711 if (rb_num_of_entries(cpu_buffer) == 0)
3712 goto out;
3713
3714 /*
3715 * Reset the reader page to size zero.
3716 */
3717 local_set(&cpu_buffer->reader_page->write, 0);
3718 local_set(&cpu_buffer->reader_page->entries, 0);
3719 local_set(&cpu_buffer->reader_page->page->commit, 0);
3720 cpu_buffer->reader_page->real_end = 0;
3721
3722 spin:
3723 /*
3724 * Splice the empty reader page into the list around the head.
3725 */
3726 reader = rb_set_head_page(cpu_buffer);
3727 if (!reader)
3728 goto out;
3729 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3730 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 cpu_buffer->pages = reader->list.prev;
3738
3739 /* The reader page will be pointing to the new head */
3740 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 smp_mb();
3752 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 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 if (!ret)
3771 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 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3779 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3780
3781 local_inc(&cpu_buffer->pages_read);
3782
3783 /* Finally update the reader page to the new head */
3784 cpu_buffer->reader_page = reader;
3785 cpu_buffer->reader_page->read = 0;
3786
3787 if (overwrite != cpu_buffer->last_overrun) {
3788 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3789 cpu_buffer->last_overrun = overwrite;
3790 }
3791
3792 goto again;
3793
3794 out:
3795 /* Update the read_stamp on the first event */
3796 if (reader && reader->read == 0)
3797 cpu_buffer->read_stamp = reader->page->time_stamp;
3798
3799 arch_spin_unlock(&cpu_buffer->lock);
3800 local_irq_restore(flags);
3801
3802 return reader;
3803}
3804
3805static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3806{
3807 struct ring_buffer_event *event;
3808 struct buffer_page *reader;
3809 unsigned length;
3810
3811 reader = rb_get_reader_page(cpu_buffer);
3812
3813 /* This function should not be called when buffer is empty */
3814 if (RB_WARN_ON(cpu_buffer, !reader))
3815 return;
3816
3817 event = rb_reader_event(cpu_buffer);
3818
3819 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3820 cpu_buffer->read++;
3821
3822 rb_update_read_stamp(cpu_buffer, event);
3823
3824 length = rb_event_length(event);
3825 cpu_buffer->reader_page->read += length;
3826}
3827
3828static void rb_advance_iter(struct ring_buffer_iter *iter)
3829{
3830 struct ring_buffer_per_cpu *cpu_buffer;
3831 struct ring_buffer_event *event;
3832 unsigned length;
3833
3834 cpu_buffer = iter->cpu_buffer;
3835
3836 /*
3837 * Check if we are at the end of the buffer.
3838 */
3839 if (iter->head >= rb_page_size(iter->head_page)) {
3840 /* discarded commits can make the page empty */
3841 if (iter->head_page == cpu_buffer->commit_page)
3842 return;
3843 rb_inc_iter(iter);
3844 return;
3845 }
3846
3847 event = rb_iter_head_event(iter);
3848
3849 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 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 rb_update_iter_read_stamp(iter, event);
3861
3862 iter->head += length;
3863
3864 /* check for end of page padding */
3865 if ((iter->head >= rb_page_size(iter->head_page)) &&
3866 (iter->head_page != cpu_buffer->commit_page))
3867 rb_inc_iter(iter);
3868}
3869
3870static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3871{
3872 return cpu_buffer->lost_events;
3873}
3874
3875static struct ring_buffer_event *
3876rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3877 unsigned long *lost_events)
3878{
3879 struct ring_buffer_event *event;
3880 struct buffer_page *reader;
3881 int nr_loops = 0;
3882
3883 if (ts)
3884 *ts = 0;
3885 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 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3893 return NULL;
3894
3895 reader = rb_get_reader_page(cpu_buffer);
3896 if (!reader)
3897 return NULL;
3898
3899 event = rb_reader_event(cpu_buffer);
3900
3901 switch (event->type_len) {
3902 case RINGBUF_TYPE_PADDING:
3903 if (rb_null_event(event))
3904 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 case RINGBUF_TYPE_TIME_EXTEND:
3916 /* Internal data, OK to advance */
3917 rb_advance_reader(cpu_buffer);
3918 goto again;
3919
3920 case RINGBUF_TYPE_TIME_STAMP:
3921 if (ts) {
3922 *ts = ring_buffer_event_time_stamp(event);
3923 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3924 cpu_buffer->cpu, ts);
3925 }
3926 /* Internal data, OK to advance */
3927 rb_advance_reader(cpu_buffer);
3928 goto again;
3929
3930 case RINGBUF_TYPE_DATA:
3931 if (ts && !(*ts)) {
3932 *ts = cpu_buffer->read_stamp + event->time_delta;
3933 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3934 cpu_buffer->cpu, ts);
3935 }
3936 if (lost_events)
3937 *lost_events = rb_lost_events(cpu_buffer);
3938 return event;
3939
3940 default:
3941 BUG();
3942 }
3943
3944 return NULL;
3945}
3946EXPORT_SYMBOL_GPL(ring_buffer_peek);
3947
3948static struct ring_buffer_event *
3949rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3950{
3951 struct ring_buffer *buffer;
3952 struct ring_buffer_per_cpu *cpu_buffer;
3953 struct ring_buffer_event *event;
3954 int nr_loops = 0;
3955
3956 if (ts)
3957 *ts = 0;
3958
3959 cpu_buffer = iter->cpu_buffer;
3960 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 if (unlikely(iter->cache_read != cpu_buffer->read ||
3968 iter->cache_reader_page != cpu_buffer->reader_page))
3969 rb_iter_reset(iter);
3970
3971 again:
3972 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 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
3984 return NULL;
3985
3986 if (rb_per_cpu_empty(cpu_buffer))
3987 return NULL;
3988
3989 if (iter->head >= rb_page_size(iter->head_page)) {
3990 rb_inc_iter(iter);
3991 goto again;
3992 }
3993
3994 event = rb_iter_head_event(iter);
3995
3996 switch (event->type_len) {
3997 case RINGBUF_TYPE_PADDING:
3998 if (rb_null_event(event)) {
3999 rb_inc_iter(iter);
4000 goto again;
4001 }
4002 rb_advance_iter(iter);
4003 return event;
4004
4005 case RINGBUF_TYPE_TIME_EXTEND:
4006 /* Internal data, OK to advance */
4007 rb_advance_iter(iter);
4008 goto again;
4009
4010 case RINGBUF_TYPE_TIME_STAMP:
4011 if (ts) {
4012 *ts = ring_buffer_event_time_stamp(event);
4013 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4014 cpu_buffer->cpu, ts);
4015 }
4016 /* Internal data, OK to advance */
4017 rb_advance_iter(iter);
4018 goto again;
4019
4020 case RINGBUF_TYPE_DATA:
4021 if (ts && !(*ts)) {
4022 *ts = iter->read_stamp + event->time_delta;
4023 ring_buffer_normalize_time_stamp(buffer,
4024 cpu_buffer->cpu, ts);
4025 }
4026 return event;
4027
4028 default:
4029 BUG();
4030 }
4031
4032 return NULL;
4033}
4034EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4035
4036static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4037{
4038 if (likely(!in_nmi())) {
4039 raw_spin_lock(&cpu_buffer->reader_lock);
4040 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 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4053 return true;
4054
4055 /* Continue without locking, but disable the ring buffer */
4056 atomic_inc(&cpu_buffer->record_disabled);
4057 return false;
4058}
4059
4060static inline void
4061rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4062{
4063 if (likely(locked))
4064 raw_spin_unlock(&cpu_buffer->reader_lock);
4065 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 */
4078struct ring_buffer_event *
4079ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
4080 unsigned long *lost_events)
4081{
4082 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4083 struct ring_buffer_event *event;
4084 unsigned long flags;
4085 bool dolock;
4086
4087 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4088 return NULL;
4089
4090 again:
4091 local_irq_save(flags);
4092 dolock = rb_reader_lock(cpu_buffer);
4093 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4094 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4095 rb_advance_reader(cpu_buffer);
4096 rb_reader_unlock(cpu_buffer, dolock);
4097 local_irq_restore(flags);
4098
4099 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4100 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 */
4113struct ring_buffer_event *
4114ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4115{
4116 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4117 struct ring_buffer_event *event;
4118 unsigned long flags;
4119
4120 again:
4121 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4122 event = rb_iter_peek(iter, ts);
4123 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4124
4125 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4126 goto again;
4127
4128 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 */
4142struct ring_buffer_event *
4143ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
4144 unsigned long *lost_events)
4145{
4146 struct ring_buffer_per_cpu *cpu_buffer;
4147 struct ring_buffer_event *event = NULL;
4148 unsigned long flags;
4149 bool dolock;
4150
4151 again:
4152 /* might be called in atomic */
4153 preempt_disable();
4154
4155 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4156 goto out;
4157
4158 cpu_buffer = buffer->buffers[cpu];
4159 local_irq_save(flags);
4160 dolock = rb_reader_lock(cpu_buffer);
4161
4162 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4163 if (event) {
4164 cpu_buffer->lost_events = 0;
4165 rb_advance_reader(cpu_buffer);
4166 }
4167
4168 rb_reader_unlock(cpu_buffer, dolock);
4169 local_irq_restore(flags);
4170
4171 out:
4172 preempt_enable();
4173
4174 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4175 goto again;
4176
4177 return event;
4178}
4179EXPORT_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 */
4202struct ring_buffer_iter *
4203ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu, gfp_t flags)
4204{
4205 struct ring_buffer_per_cpu *cpu_buffer;
4206 struct ring_buffer_iter *iter;
4207
4208 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4209 return NULL;
4210
4211 iter = kmalloc(sizeof(*iter), flags);
4212 if (!iter)
4213 return NULL;
4214
4215 cpu_buffer = buffer->buffers[cpu];
4216
4217 iter->cpu_buffer = cpu_buffer;
4218
4219 atomic_inc(&buffer->resize_disabled);
4220 atomic_inc(&cpu_buffer->record_disabled);
4221
4222 return iter;
4223}
4224EXPORT_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 */
4233void
4234ring_buffer_read_prepare_sync(void)
4235{
4236 synchronize_rcu();
4237}
4238EXPORT_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 */
4251void
4252ring_buffer_read_start(struct ring_buffer_iter *iter)
4253{
4254 struct ring_buffer_per_cpu *cpu_buffer;
4255 unsigned long flags;
4256
4257 if (!iter)
4258 return;
4259
4260 cpu_buffer = iter->cpu_buffer;
4261
4262 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4263 arch_spin_lock(&cpu_buffer->lock);
4264 rb_iter_reset(iter);
4265 arch_spin_unlock(&cpu_buffer->lock);
4266 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4267}
4268EXPORT_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 */
4277void
4278ring_buffer_read_finish(struct ring_buffer_iter *iter)
4279{
4280 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4281 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 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4290 rb_check_pages(cpu_buffer);
4291 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4292
4293 atomic_dec(&cpu_buffer->record_disabled);
4294 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4295 kfree(iter);
4296}
4297EXPORT_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 */
4306struct ring_buffer_event *
4307ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4308{
4309 struct ring_buffer_event *event;
4310 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4311 unsigned long flags;
4312
4313 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4314 again:
4315 event = rb_iter_peek(iter, ts);
4316 if (!event)
4317 goto out;
4318
4319 if (event->type_len == RINGBUF_TYPE_PADDING)
4320 goto again;
4321
4322 rb_advance_iter(iter);
4323 out:
4324 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4325
4326 return event;
4327}
4328EXPORT_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 */
4334unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4335{
4336 /*
4337 * Earlier, this method returned
4338 * BUF_PAGE_SIZE * buffer->nr_pages
4339 * Since the nr_pages field is now removed, we have converted this to
4340 * return the per cpu buffer value.
4341 */
4342 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4343 return 0;
4344
4345 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4346}
4347EXPORT_SYMBOL_GPL(ring_buffer_size);
4348
4349static void
4350rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4351{
4352 rb_head_page_deactivate(cpu_buffer);
4353
4354 cpu_buffer->head_page
4355 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4356 local_set(&cpu_buffer->head_page->write, 0);
4357 local_set(&cpu_buffer->head_page->entries, 0);
4358 local_set(&cpu_buffer->head_page->page->commit, 0);
4359
4360 cpu_buffer->head_page->read = 0;
4361
4362 cpu_buffer->tail_page = cpu_buffer->head_page;
4363 cpu_buffer->commit_page = cpu_buffer->head_page;
4364
4365 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4366 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4367 local_set(&cpu_buffer->reader_page->write, 0);
4368 local_set(&cpu_buffer->reader_page->entries, 0);
4369 local_set(&cpu_buffer->reader_page->page->commit, 0);
4370 cpu_buffer->reader_page->read = 0;
4371
4372 local_set(&cpu_buffer->entries_bytes, 0);
4373 local_set(&cpu_buffer->overrun, 0);
4374 local_set(&cpu_buffer->commit_overrun, 0);
4375 local_set(&cpu_buffer->dropped_events, 0);
4376 local_set(&cpu_buffer->entries, 0);
4377 local_set(&cpu_buffer->committing, 0);
4378 local_set(&cpu_buffer->commits, 0);
4379 local_set(&cpu_buffer->pages_touched, 0);
4380 local_set(&cpu_buffer->pages_read, 0);
4381 cpu_buffer->last_pages_touch = 0;
4382 cpu_buffer->shortest_full = 0;
4383 cpu_buffer->read = 0;
4384 cpu_buffer->read_bytes = 0;
4385
4386 cpu_buffer->write_stamp = 0;
4387 cpu_buffer->read_stamp = 0;
4388
4389 cpu_buffer->lost_events = 0;
4390 cpu_buffer->last_overrun = 0;
4391
4392 rb_head_page_activate(cpu_buffer);
4393}
4394
4395/**
4396 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4397 * @buffer: The ring buffer to reset a per cpu buffer of
4398 * @cpu: The CPU buffer to be reset
4399 */
4400void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4401{
4402 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4403 unsigned long flags;
4404
4405 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4406 return;
4407
4408 atomic_inc(&buffer->resize_disabled);
4409 atomic_inc(&cpu_buffer->record_disabled);
4410
4411 /* Make sure all commits have finished */
4412 synchronize_rcu();
4413
4414 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4415
4416 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4417 goto out;
4418
4419 arch_spin_lock(&cpu_buffer->lock);
4420
4421 rb_reset_cpu(cpu_buffer);
4422
4423 arch_spin_unlock(&cpu_buffer->lock);
4424
4425 out:
4426 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4427
4428 atomic_dec(&cpu_buffer->record_disabled);
4429 atomic_dec(&buffer->resize_disabled);
4430}
4431EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4432
4433/**
4434 * ring_buffer_reset - reset a ring buffer
4435 * @buffer: The ring buffer to reset all cpu buffers
4436 */
4437void ring_buffer_reset(struct ring_buffer *buffer)
4438{
4439 int cpu;
4440
4441 for_each_buffer_cpu(buffer, cpu)
4442 ring_buffer_reset_cpu(buffer, cpu);
4443}
4444EXPORT_SYMBOL_GPL(ring_buffer_reset);
4445
4446/**
4447 * rind_buffer_empty - is the ring buffer empty?
4448 * @buffer: The ring buffer to test
4449 */
4450bool ring_buffer_empty(struct ring_buffer *buffer)
4451{
4452 struct ring_buffer_per_cpu *cpu_buffer;
4453 unsigned long flags;
4454 bool dolock;
4455 int cpu;
4456 int ret;
4457
4458 /* yes this is racy, but if you don't like the race, lock the buffer */
4459 for_each_buffer_cpu(buffer, cpu) {
4460 cpu_buffer = buffer->buffers[cpu];
4461 local_irq_save(flags);
4462 dolock = rb_reader_lock(cpu_buffer);
4463 ret = rb_per_cpu_empty(cpu_buffer);
4464 rb_reader_unlock(cpu_buffer, dolock);
4465 local_irq_restore(flags);
4466
4467 if (!ret)
4468 return false;
4469 }
4470
4471 return true;
4472}
4473EXPORT_SYMBOL_GPL(ring_buffer_empty);
4474
4475/**
4476 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4477 * @buffer: The ring buffer
4478 * @cpu: The CPU buffer to test
4479 */
4480bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4481{
4482 struct ring_buffer_per_cpu *cpu_buffer;
4483 unsigned long flags;
4484 bool dolock;
4485 int ret;
4486
4487 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4488 return true;
4489
4490 cpu_buffer = buffer->buffers[cpu];
4491 local_irq_save(flags);
4492 dolock = rb_reader_lock(cpu_buffer);
4493 ret = rb_per_cpu_empty(cpu_buffer);
4494 rb_reader_unlock(cpu_buffer, dolock);
4495 local_irq_restore(flags);
4496
4497 return ret;
4498}
4499EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4500
4501#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4502/**
4503 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4504 * @buffer_a: One buffer to swap with
4505 * @buffer_b: The other buffer to swap with
4506 *
4507 * This function is useful for tracers that want to take a "snapshot"
4508 * of a CPU buffer and has another back up buffer lying around.
4509 * it is expected that the tracer handles the cpu buffer not being
4510 * used at the moment.
4511 */
4512int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4513 struct ring_buffer *buffer_b, int cpu)
4514{
4515 struct ring_buffer_per_cpu *cpu_buffer_a;
4516 struct ring_buffer_per_cpu *cpu_buffer_b;
4517 int ret = -EINVAL;
4518
4519 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4520 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4521 goto out;
4522
4523 cpu_buffer_a = buffer_a->buffers[cpu];
4524 cpu_buffer_b = buffer_b->buffers[cpu];
4525
4526 /* At least make sure the two buffers are somewhat the same */
4527 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4528 goto out;
4529
4530 ret = -EAGAIN;
4531
4532 if (atomic_read(&buffer_a->record_disabled))
4533 goto out;
4534
4535 if (atomic_read(&buffer_b->record_disabled))
4536 goto out;
4537
4538 if (atomic_read(&cpu_buffer_a->record_disabled))
4539 goto out;
4540
4541 if (atomic_read(&cpu_buffer_b->record_disabled))
4542 goto out;
4543
4544 /*
4545 * We can't do a synchronize_rcu here because this
4546 * function can be called in atomic context.
4547 * Normally this will be called from the same CPU as cpu.
4548 * If not it's up to the caller to protect this.
4549 */
4550 atomic_inc(&cpu_buffer_a->record_disabled);
4551 atomic_inc(&cpu_buffer_b->record_disabled);
4552
4553 ret = -EBUSY;
4554 if (local_read(&cpu_buffer_a->committing))
4555 goto out_dec;
4556 if (local_read(&cpu_buffer_b->committing))
4557 goto out_dec;
4558
4559 buffer_a->buffers[cpu] = cpu_buffer_b;
4560 buffer_b->buffers[cpu] = cpu_buffer_a;
4561
4562 cpu_buffer_b->buffer = buffer_a;
4563 cpu_buffer_a->buffer = buffer_b;
4564
4565 ret = 0;
4566
4567out_dec:
4568 atomic_dec(&cpu_buffer_a->record_disabled);
4569 atomic_dec(&cpu_buffer_b->record_disabled);
4570out:
4571 return ret;
4572}
4573EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4574#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4575
4576/**
4577 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4578 * @buffer: the buffer to allocate for.
4579 * @cpu: the cpu buffer to allocate.
4580 *
4581 * This function is used in conjunction with ring_buffer_read_page.
4582 * When reading a full page from the ring buffer, these functions
4583 * can be used to speed up the process. The calling function should
4584 * allocate a few pages first with this function. Then when it
4585 * needs to get pages from the ring buffer, it passes the result
4586 * of this function into ring_buffer_read_page, which will swap
4587 * the page that was allocated, with the read page of the buffer.
4588 *
4589 * Returns:
4590 * The page allocated, or ERR_PTR
4591 */
4592void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4593{
4594 struct ring_buffer_per_cpu *cpu_buffer;
4595 struct buffer_data_page *bpage = NULL;
4596 unsigned long flags;
4597 struct page *page;
4598
4599 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4600 return ERR_PTR(-ENODEV);
4601
4602 cpu_buffer = buffer->buffers[cpu];
4603 local_irq_save(flags);
4604 arch_spin_lock(&cpu_buffer->lock);
4605
4606 if (cpu_buffer->free_page) {
4607 bpage = cpu_buffer->free_page;
4608 cpu_buffer->free_page = NULL;
4609 }
4610
4611 arch_spin_unlock(&cpu_buffer->lock);
4612 local_irq_restore(flags);
4613
4614 if (bpage)
4615 goto out;
4616
4617 page = alloc_pages_node(cpu_to_node(cpu),
4618 GFP_KERNEL | __GFP_NORETRY, 0);
4619 if (!page)
4620 return ERR_PTR(-ENOMEM);
4621
4622 bpage = page_address(page);
4623
4624 out:
4625 rb_init_page(bpage);
4626
4627 return bpage;
4628}
4629EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4630
4631/**
4632 * ring_buffer_free_read_page - free an allocated read page
4633 * @buffer: the buffer the page was allocate for
4634 * @cpu: the cpu buffer the page came from
4635 * @data: the page to free
4636 *
4637 * Free a page allocated from ring_buffer_alloc_read_page.
4638 */
4639void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
4640{
4641 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4642 struct buffer_data_page *bpage = data;
4643 struct page *page = virt_to_page(bpage);
4644 unsigned long flags;
4645
4646 /* If the page is still in use someplace else, we can't reuse it */
4647 if (page_ref_count(page) > 1)
4648 goto out;
4649
4650 local_irq_save(flags);
4651 arch_spin_lock(&cpu_buffer->lock);
4652
4653 if (!cpu_buffer->free_page) {
4654 cpu_buffer->free_page = bpage;
4655 bpage = NULL;
4656 }
4657
4658 arch_spin_unlock(&cpu_buffer->lock);
4659 local_irq_restore(flags);
4660
4661 out:
4662 free_page((unsigned long)bpage);
4663}
4664EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4665
4666/**
4667 * ring_buffer_read_page - extract a page from the ring buffer
4668 * @buffer: buffer to extract from
4669 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4670 * @len: amount to extract
4671 * @cpu: the cpu of the buffer to extract
4672 * @full: should the extraction only happen when the page is full.
4673 *
4674 * This function will pull out a page from the ring buffer and consume it.
4675 * @data_page must be the address of the variable that was returned
4676 * from ring_buffer_alloc_read_page. This is because the page might be used
4677 * to swap with a page in the ring buffer.
4678 *
4679 * for example:
4680 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4681 * if (IS_ERR(rpage))
4682 * return PTR_ERR(rpage);
4683 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4684 * if (ret >= 0)
4685 * process_page(rpage, ret);
4686 *
4687 * When @full is set, the function will not return true unless
4688 * the writer is off the reader page.
4689 *
4690 * Note: it is up to the calling functions to handle sleeps and wakeups.
4691 * The ring buffer can be used anywhere in the kernel and can not
4692 * blindly call wake_up. The layer that uses the ring buffer must be
4693 * responsible for that.
4694 *
4695 * Returns:
4696 * >=0 if data has been transferred, returns the offset of consumed data.
4697 * <0 if no data has been transferred.
4698 */
4699int ring_buffer_read_page(struct ring_buffer *buffer,
4700 void **data_page, size_t len, int cpu, int full)
4701{
4702 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4703 struct ring_buffer_event *event;
4704 struct buffer_data_page *bpage;
4705 struct buffer_page *reader;
4706 unsigned long missed_events;
4707 unsigned long flags;
4708 unsigned int commit;
4709 unsigned int read;
4710 u64 save_timestamp;
4711 int ret = -1;
4712
4713 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4714 goto out;
4715
4716 /*
4717 * If len is not big enough to hold the page header, then
4718 * we can not copy anything.
4719 */
4720 if (len <= BUF_PAGE_HDR_SIZE)
4721 goto out;
4722
4723 len -= BUF_PAGE_HDR_SIZE;
4724
4725 if (!data_page)
4726 goto out;
4727
4728 bpage = *data_page;
4729 if (!bpage)
4730 goto out;
4731
4732 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4733
4734 reader = rb_get_reader_page(cpu_buffer);
4735 if (!reader)
4736 goto out_unlock;
4737
4738 event = rb_reader_event(cpu_buffer);
4739
4740 read = reader->read;
4741 commit = rb_page_commit(reader);
4742
4743 /* Check if any events were dropped */
4744 missed_events = cpu_buffer->lost_events;
4745
4746 /*
4747 * If this page has been partially read or
4748 * if len is not big enough to read the rest of the page or
4749 * a writer is still on the page, then
4750 * we must copy the data from the page to the buffer.
4751 * Otherwise, we can simply swap the page with the one passed in.
4752 */
4753 if (read || (len < (commit - read)) ||
4754 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4755 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4756 unsigned int rpos = read;
4757 unsigned int pos = 0;
4758 unsigned int size;
4759
4760 if (full)
4761 goto out_unlock;
4762
4763 if (len > (commit - read))
4764 len = (commit - read);
4765
4766 /* Always keep the time extend and data together */
4767 size = rb_event_ts_length(event);
4768
4769 if (len < size)
4770 goto out_unlock;
4771
4772 /* save the current timestamp, since the user will need it */
4773 save_timestamp = cpu_buffer->read_stamp;
4774
4775 /* Need to copy one event at a time */
4776 do {
4777 /* We need the size of one event, because
4778 * rb_advance_reader only advances by one event,
4779 * whereas rb_event_ts_length may include the size of
4780 * one or two events.
4781 * We have already ensured there's enough space if this
4782 * is a time extend. */
4783 size = rb_event_length(event);
4784 memcpy(bpage->data + pos, rpage->data + rpos, size);
4785
4786 len -= size;
4787
4788 rb_advance_reader(cpu_buffer);
4789 rpos = reader->read;
4790 pos += size;
4791
4792 if (rpos >= commit)
4793 break;
4794
4795 event = rb_reader_event(cpu_buffer);
4796 /* Always keep the time extend and data together */
4797 size = rb_event_ts_length(event);
4798 } while (len >= size);
4799
4800 /* update bpage */
4801 local_set(&bpage->commit, pos);
4802 bpage->time_stamp = save_timestamp;
4803
4804 /* we copied everything to the beginning */
4805 read = 0;
4806 } else {
4807 /* update the entry counter */
4808 cpu_buffer->read += rb_page_entries(reader);
4809 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4810
4811 /* swap the pages */
4812 rb_init_page(bpage);
4813 bpage = reader->page;
4814 reader->page = *data_page;
4815 local_set(&reader->write, 0);
4816 local_set(&reader->entries, 0);
4817 reader->read = 0;
4818 *data_page = bpage;
4819
4820 /*
4821 * Use the real_end for the data size,
4822 * This gives us a chance to store the lost events
4823 * on the page.
4824 */
4825 if (reader->real_end)
4826 local_set(&bpage->commit, reader->real_end);
4827 }
4828 ret = read;
4829
4830 cpu_buffer->lost_events = 0;
4831
4832 commit = local_read(&bpage->commit);
4833 /*
4834 * Set a flag in the commit field if we lost events
4835 */
4836 if (missed_events) {
4837 /* If there is room at the end of the page to save the
4838 * missed events, then record it there.
4839 */
4840 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4841 memcpy(&bpage->data[commit], &missed_events,
4842 sizeof(missed_events));
4843 local_add(RB_MISSED_STORED, &bpage->commit);
4844 commit += sizeof(missed_events);
4845 }
4846 local_add(RB_MISSED_EVENTS, &bpage->commit);
4847 }
4848
4849 /*
4850 * This page may be off to user land. Zero it out here.
4851 */
4852 if (commit < BUF_PAGE_SIZE)
4853 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4854
4855 out_unlock:
4856 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4857
4858 out:
4859 return ret;
4860}
4861EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4862
4863/*
4864 * We only allocate new buffers, never free them if the CPU goes down.
4865 * If we were to free the buffer, then the user would lose any trace that was in
4866 * the buffer.
4867 */
4868int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
4869{
4870 struct ring_buffer *buffer;
4871 long nr_pages_same;
4872 int cpu_i;
4873 unsigned long nr_pages;
4874
4875 buffer = container_of(node, struct ring_buffer, node);
4876 if (cpumask_test_cpu(cpu, buffer->cpumask))
4877 return 0;
4878
4879 nr_pages = 0;
4880 nr_pages_same = 1;
4881 /* check if all cpu sizes are same */
4882 for_each_buffer_cpu(buffer, cpu_i) {
4883 /* fill in the size from first enabled cpu */
4884 if (nr_pages == 0)
4885 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4886 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4887 nr_pages_same = 0;
4888 break;
4889 }
4890 }
4891 /* allocate minimum pages, user can later expand it */
4892 if (!nr_pages_same)
4893 nr_pages = 2;
4894 buffer->buffers[cpu] =
4895 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4896 if (!buffer->buffers[cpu]) {
4897 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4898 cpu);
4899 return -ENOMEM;
4900 }
4901 smp_wmb();
4902 cpumask_set_cpu(cpu, buffer->cpumask);
4903 return 0;
4904}
4905
4906#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4907/*
4908 * This is a basic integrity check of the ring buffer.
4909 * Late in the boot cycle this test will run when configured in.
4910 * It will kick off a thread per CPU that will go into a loop
4911 * writing to the per cpu ring buffer various sizes of data.
4912 * Some of the data will be large items, some small.
4913 *
4914 * Another thread is created that goes into a spin, sending out
4915 * IPIs to the other CPUs to also write into the ring buffer.
4916 * this is to test the nesting ability of the buffer.
4917 *
4918 * Basic stats are recorded and reported. If something in the
4919 * ring buffer should happen that's not expected, a big warning
4920 * is displayed and all ring buffers are disabled.
4921 */
4922static struct task_struct *rb_threads[NR_CPUS] __initdata;
4923
4924struct rb_test_data {
4925 struct ring_buffer *buffer;
4926 unsigned long events;
4927 unsigned long bytes_written;
4928 unsigned long bytes_alloc;
4929 unsigned long bytes_dropped;
4930 unsigned long events_nested;
4931 unsigned long bytes_written_nested;
4932 unsigned long bytes_alloc_nested;
4933 unsigned long bytes_dropped_nested;
4934 int min_size_nested;
4935 int max_size_nested;
4936 int max_size;
4937 int min_size;
4938 int cpu;
4939 int cnt;
4940};
4941
4942static struct rb_test_data rb_data[NR_CPUS] __initdata;
4943
4944/* 1 meg per cpu */
4945#define RB_TEST_BUFFER_SIZE 1048576
4946
4947static char rb_string[] __initdata =
4948 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4949 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4950 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4951
4952static bool rb_test_started __initdata;
4953
4954struct rb_item {
4955 int size;
4956 char str[];
4957};
4958
4959static __init int rb_write_something(struct rb_test_data *data, bool nested)
4960{
4961 struct ring_buffer_event *event;
4962 struct rb_item *item;
4963 bool started;
4964 int event_len;
4965 int size;
4966 int len;
4967 int cnt;
4968
4969 /* Have nested writes different that what is written */
4970 cnt = data->cnt + (nested ? 27 : 0);
4971
4972 /* Multiply cnt by ~e, to make some unique increment */
4973 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
4974
4975 len = size + sizeof(struct rb_item);
4976
4977 started = rb_test_started;
4978 /* read rb_test_started before checking buffer enabled */
4979 smp_rmb();
4980
4981 event = ring_buffer_lock_reserve(data->buffer, len);
4982 if (!event) {
4983 /* Ignore dropped events before test starts. */
4984 if (started) {
4985 if (nested)
4986 data->bytes_dropped += len;
4987 else
4988 data->bytes_dropped_nested += len;
4989 }
4990 return len;
4991 }
4992
4993 event_len = ring_buffer_event_length(event);
4994
4995 if (RB_WARN_ON(data->buffer, event_len < len))
4996 goto out;
4997
4998 item = ring_buffer_event_data(event);
4999 item->size = size;
5000 memcpy(item->str, rb_string, size);
5001
5002 if (nested) {
5003 data->bytes_alloc_nested += event_len;
5004 data->bytes_written_nested += len;
5005 data->events_nested++;
5006 if (!data->min_size_nested || len < data->min_size_nested)
5007 data->min_size_nested = len;
5008 if (len > data->max_size_nested)
5009 data->max_size_nested = len;
5010 } else {
5011 data->bytes_alloc += event_len;
5012 data->bytes_written += len;
5013 data->events++;
5014 if (!data->min_size || len < data->min_size)
5015 data->max_size = len;
5016 if (len > data->max_size)
5017 data->max_size = len;
5018 }
5019
5020 out:
5021 ring_buffer_unlock_commit(data->buffer, event);
5022
5023 return 0;
5024}
5025
5026static __init int rb_test(void *arg)
5027{
5028 struct rb_test_data *data = arg;
5029
5030 while (!kthread_should_stop()) {
5031 rb_write_something(data, false);
5032 data->cnt++;
5033
5034 set_current_state(TASK_INTERRUPTIBLE);
5035 /* Now sleep between a min of 100-300us and a max of 1ms */
5036 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
5037 }
5038
5039 return 0;
5040}
5041
5042static __init void rb_ipi(void *ignore)
5043{
5044 struct rb_test_data *data;
5045 int cpu = smp_processor_id();
5046
5047 data = &rb_data[cpu];
5048 rb_write_something(data, true);
5049}
5050
5051static __init int rb_hammer_test(void *arg)
5052{
5053 while (!kthread_should_stop()) {
5054
5055 /* Send an IPI to all cpus to write data! */
5056 smp_call_function(rb_ipi, NULL, 1);
5057 /* No sleep, but for non preempt, let others run */
5058 schedule();
5059 }
5060
5061 return 0;
5062}
5063
5064static __init int test_ringbuffer(void)
5065{
5066 struct task_struct *rb_hammer;
5067 struct ring_buffer *buffer;
5068 int cpu;
5069 int ret = 0;
5070
5071 pr_info("Running ring buffer tests...\n");
5072
5073 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5074 if (WARN_ON(!buffer))
5075 return 0;
5076
5077 /* Disable buffer so that threads can't write to it yet */
5078 ring_buffer_record_off(buffer);
5079
5080 for_each_online_cpu(cpu) {
5081 rb_data[cpu].buffer = buffer;
5082 rb_data[cpu].cpu = cpu;
5083 rb_data[cpu].cnt = cpu;
5084 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5085 "rbtester/%d", cpu);
5086 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5087 pr_cont("FAILED\n");
5088 ret = PTR_ERR(rb_threads[cpu]);
5089 goto out_free;
5090 }
5091
5092 kthread_bind(rb_threads[cpu], cpu);
5093 wake_up_process(rb_threads[cpu]);
5094 }
5095
5096 /* Now create the rb hammer! */
5097 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5098 if (WARN_ON(IS_ERR(rb_hammer))) {
5099 pr_cont("FAILED\n");
5100 ret = PTR_ERR(rb_hammer);
5101 goto out_free;
5102 }
5103
5104 ring_buffer_record_on(buffer);
5105 /*
5106 * Show buffer is enabled before setting rb_test_started.
5107 * Yes there's a small race window where events could be
5108 * dropped and the thread wont catch it. But when a ring
5109 * buffer gets enabled, there will always be some kind of
5110 * delay before other CPUs see it. Thus, we don't care about
5111 * those dropped events. We care about events dropped after
5112 * the threads see that the buffer is active.
5113 */
5114 smp_wmb();
5115 rb_test_started = true;
5116
5117 set_current_state(TASK_INTERRUPTIBLE);
5118 /* Just run for 10 seconds */;
5119 schedule_timeout(10 * HZ);
5120
5121 kthread_stop(rb_hammer);
5122
5123 out_free:
5124 for_each_online_cpu(cpu) {
5125 if (!rb_threads[cpu])
5126 break;
5127 kthread_stop(rb_threads[cpu]);
5128 }
5129 if (ret) {
5130 ring_buffer_free(buffer);
5131 return ret;
5132 }
5133
5134 /* Report! */
5135 pr_info("finished\n");
5136 for_each_online_cpu(cpu) {
5137 struct ring_buffer_event *event;
5138 struct rb_test_data *data = &rb_data[cpu];
5139 struct rb_item *item;
5140 unsigned long total_events;
5141 unsigned long total_dropped;
5142 unsigned long total_written;
5143 unsigned long total_alloc;
5144 unsigned long total_read = 0;
5145 unsigned long total_size = 0;
5146 unsigned long total_len = 0;
5147 unsigned long total_lost = 0;
5148 unsigned long lost;
5149 int big_event_size;
5150 int small_event_size;
5151
5152 ret = -1;
5153
5154 total_events = data->events + data->events_nested;
5155 total_written = data->bytes_written + data->bytes_written_nested;
5156 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5157 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5158
5159 big_event_size = data->max_size + data->max_size_nested;
5160 small_event_size = data->min_size + data->min_size_nested;
5161
5162 pr_info("CPU %d:\n", cpu);
5163 pr_info(" events: %ld\n", total_events);
5164 pr_info(" dropped bytes: %ld\n", total_dropped);
5165 pr_info(" alloced bytes: %ld\n", total_alloc);
5166 pr_info(" written bytes: %ld\n", total_written);
5167 pr_info(" biggest event: %d\n", big_event_size);
5168 pr_info(" smallest event: %d\n", small_event_size);
5169
5170 if (RB_WARN_ON(buffer, total_dropped))
5171 break;
5172
5173 ret = 0;
5174
5175 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5176 total_lost += lost;
5177 item = ring_buffer_event_data(event);
5178 total_len += ring_buffer_event_length(event);
5179 total_size += item->size + sizeof(struct rb_item);
5180 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5181 pr_info("FAILED!\n");
5182 pr_info("buffer had: %.*s\n", item->size, item->str);
5183 pr_info("expected: %.*s\n", item->size, rb_string);
5184 RB_WARN_ON(buffer, 1);
5185 ret = -1;
5186 break;
5187 }
5188 total_read++;
5189 }
5190 if (ret)
5191 break;
5192
5193 ret = -1;
5194
5195 pr_info(" read events: %ld\n", total_read);
5196 pr_info(" lost events: %ld\n", total_lost);
5197 pr_info(" total events: %ld\n", total_lost + total_read);
5198 pr_info(" recorded len bytes: %ld\n", total_len);
5199 pr_info(" recorded size bytes: %ld\n", total_size);
5200 if (total_lost)
5201 pr_info(" With dropped events, record len and size may not match\n"
5202 " alloced and written from above\n");
5203 if (!total_lost) {
5204 if (RB_WARN_ON(buffer, total_len != total_alloc ||
5205 total_size != total_written))
5206 break;
5207 }
5208 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5209 break;
5210
5211 ret = 0;
5212 }
5213 if (!ret)
5214 pr_info("Ring buffer PASSED!\n");
5215
5216 ring_buffer_free(buffer);
5217 return 0;
5218}
5219
5220late_initcall(test_ringbuffer);
5221#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
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_recursion.h>
8#include <linux/trace_events.h>
9#include <linux/ring_buffer.h>
10#include <linux/trace_clock.h>
11#include <linux/sched/clock.h>
12#include <linux/trace_seq.h>
13#include <linux/spinlock.h>
14#include <linux/irq_work.h>
15#include <linux/security.h>
16#include <linux/uaccess.h>
17#include <linux/hardirq.h>
18#include <linux/kthread.h> /* for self test */
19#include <linux/module.h>
20#include <linux/percpu.h>
21#include <linux/mutex.h>
22#include <linux/delay.h>
23#include <linux/slab.h>
24#include <linux/init.h>
25#include <linux/hash.h>
26#include <linux/list.h>
27#include <linux/cpu.h>
28#include <linux/oom.h>
29
30#include <asm/local.h>
31
32static void update_pages_handler(struct work_struct *work);
33
34/*
35 * The ring buffer header is special. We must manually up keep it.
36 */
37int ring_buffer_print_entry_header(struct trace_seq *s)
38{
39 trace_seq_puts(s, "# compressed entry header\n");
40 trace_seq_puts(s, "\ttype_len : 5 bits\n");
41 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
42 trace_seq_puts(s, "\tarray : 32 bits\n");
43 trace_seq_putc(s, '\n');
44 trace_seq_printf(s, "\tpadding : type == %d\n",
45 RINGBUF_TYPE_PADDING);
46 trace_seq_printf(s, "\ttime_extend : type == %d\n",
47 RINGBUF_TYPE_TIME_EXTEND);
48 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
49 RINGBUF_TYPE_TIME_STAMP);
50 trace_seq_printf(s, "\tdata max type_len == %d\n",
51 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
52
53 return !trace_seq_has_overflowed(s);
54}
55
56/*
57 * The ring buffer is made up of a list of pages. A separate list of pages is
58 * allocated for each CPU. A writer may only write to a buffer that is
59 * associated with the CPU it is currently executing on. A reader may read
60 * from any per cpu buffer.
61 *
62 * The reader is special. For each per cpu buffer, the reader has its own
63 * reader page. When a reader has read the entire reader page, this reader
64 * page is swapped with another page in the ring buffer.
65 *
66 * Now, as long as the writer is off the reader page, the reader can do what
67 * ever it wants with that page. The writer will never write to that page
68 * again (as long as it is out of the ring buffer).
69 *
70 * Here's some silly ASCII art.
71 *
72 * +------+
73 * |reader| RING BUFFER
74 * |page |
75 * +------+ +---+ +---+ +---+
76 * | |-->| |-->| |
77 * +---+ +---+ +---+
78 * ^ |
79 * | |
80 * +---------------+
81 *
82 *
83 * +------+
84 * |reader| RING BUFFER
85 * |page |------------------v
86 * +------+ +---+ +---+ +---+
87 * | |-->| |-->| |
88 * +---+ +---+ +---+
89 * ^ |
90 * | |
91 * +---------------+
92 *
93 *
94 * +------+
95 * |reader| RING BUFFER
96 * |page |------------------v
97 * +------+ +---+ +---+ +---+
98 * ^ | |-->| |-->| |
99 * | +---+ +---+ +---+
100 * | |
101 * | |
102 * +------------------------------+
103 *
104 *
105 * +------+
106 * |buffer| RING BUFFER
107 * |page |------------------v
108 * +------+ +---+ +---+ +---+
109 * ^ | | | |-->| |
110 * | New +---+ +---+ +---+
111 * | Reader------^ |
112 * | page |
113 * +------------------------------+
114 *
115 *
116 * After we make this swap, the reader can hand this page off to the splice
117 * code and be done with it. It can even allocate a new page if it needs to
118 * and swap that into the ring buffer.
119 *
120 * We will be using cmpxchg soon to make all this lockless.
121 *
122 */
123
124/* Used for individual buffers (after the counter) */
125#define RB_BUFFER_OFF (1 << 20)
126
127#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
128
129#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
130#define RB_ALIGNMENT 4U
131#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
132#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
133
134#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
135# define RB_FORCE_8BYTE_ALIGNMENT 0
136# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
137#else
138# define RB_FORCE_8BYTE_ALIGNMENT 1
139# define RB_ARCH_ALIGNMENT 8U
140#endif
141
142#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
143
144/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
145#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
146
147enum {
148 RB_LEN_TIME_EXTEND = 8,
149 RB_LEN_TIME_STAMP = 8,
150};
151
152#define skip_time_extend(event) \
153 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
154
155#define extended_time(event) \
156 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
157
158static inline int rb_null_event(struct ring_buffer_event *event)
159{
160 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
161}
162
163static void rb_event_set_padding(struct ring_buffer_event *event)
164{
165 /* padding has a NULL time_delta */
166 event->type_len = RINGBUF_TYPE_PADDING;
167 event->time_delta = 0;
168}
169
170static unsigned
171rb_event_data_length(struct ring_buffer_event *event)
172{
173 unsigned length;
174
175 if (event->type_len)
176 length = event->type_len * RB_ALIGNMENT;
177 else
178 length = event->array[0];
179 return length + RB_EVNT_HDR_SIZE;
180}
181
182/*
183 * Return the length of the given event. Will return
184 * the length of the time extend if the event is a
185 * time extend.
186 */
187static inline unsigned
188rb_event_length(struct ring_buffer_event *event)
189{
190 switch (event->type_len) {
191 case RINGBUF_TYPE_PADDING:
192 if (rb_null_event(event))
193 /* undefined */
194 return -1;
195 return event->array[0] + RB_EVNT_HDR_SIZE;
196
197 case RINGBUF_TYPE_TIME_EXTEND:
198 return RB_LEN_TIME_EXTEND;
199
200 case RINGBUF_TYPE_TIME_STAMP:
201 return RB_LEN_TIME_STAMP;
202
203 case RINGBUF_TYPE_DATA:
204 return rb_event_data_length(event);
205 default:
206 WARN_ON_ONCE(1);
207 }
208 /* not hit */
209 return 0;
210}
211
212/*
213 * Return total length of time extend and data,
214 * or just the event length for all other events.
215 */
216static inline unsigned
217rb_event_ts_length(struct ring_buffer_event *event)
218{
219 unsigned len = 0;
220
221 if (extended_time(event)) {
222 /* time extends include the data event after it */
223 len = RB_LEN_TIME_EXTEND;
224 event = skip_time_extend(event);
225 }
226 return len + rb_event_length(event);
227}
228
229/**
230 * ring_buffer_event_length - return the length of the event
231 * @event: the event to get the length of
232 *
233 * Returns the size of the data load of a data event.
234 * If the event is something other than a data event, it
235 * returns the size of the event itself. With the exception
236 * of a TIME EXTEND, where it still returns the size of the
237 * data load of the data event after it.
238 */
239unsigned ring_buffer_event_length(struct ring_buffer_event *event)
240{
241 unsigned length;
242
243 if (extended_time(event))
244 event = skip_time_extend(event);
245
246 length = rb_event_length(event);
247 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
248 return length;
249 length -= RB_EVNT_HDR_SIZE;
250 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
251 length -= sizeof(event->array[0]);
252 return length;
253}
254EXPORT_SYMBOL_GPL(ring_buffer_event_length);
255
256/* inline for ring buffer fast paths */
257static __always_inline void *
258rb_event_data(struct ring_buffer_event *event)
259{
260 if (extended_time(event))
261 event = skip_time_extend(event);
262 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
263 /* If length is in len field, then array[0] has the data */
264 if (event->type_len)
265 return (void *)&event->array[0];
266 /* Otherwise length is in array[0] and array[1] has the data */
267 return (void *)&event->array[1];
268}
269
270/**
271 * ring_buffer_event_data - return the data of the event
272 * @event: the event to get the data from
273 */
274void *ring_buffer_event_data(struct ring_buffer_event *event)
275{
276 return rb_event_data(event);
277}
278EXPORT_SYMBOL_GPL(ring_buffer_event_data);
279
280#define for_each_buffer_cpu(buffer, cpu) \
281 for_each_cpu(cpu, buffer->cpumask)
282
283#define for_each_online_buffer_cpu(buffer, cpu) \
284 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
285
286#define TS_SHIFT 27
287#define TS_MASK ((1ULL << TS_SHIFT) - 1)
288#define TS_DELTA_TEST (~TS_MASK)
289
290static u64 rb_event_time_stamp(struct ring_buffer_event *event)
291{
292 u64 ts;
293
294 ts = event->array[0];
295 ts <<= TS_SHIFT;
296 ts += event->time_delta;
297
298 return ts;
299}
300
301/* Flag when events were overwritten */
302#define RB_MISSED_EVENTS (1 << 31)
303/* Missed count stored at end */
304#define RB_MISSED_STORED (1 << 30)
305
306struct buffer_data_page {
307 u64 time_stamp; /* page time stamp */
308 local_t commit; /* write committed index */
309 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
310};
311
312/*
313 * Note, the buffer_page list must be first. The buffer pages
314 * are allocated in cache lines, which means that each buffer
315 * page will be at the beginning of a cache line, and thus
316 * the least significant bits will be zero. We use this to
317 * add flags in the list struct pointers, to make the ring buffer
318 * lockless.
319 */
320struct buffer_page {
321 struct list_head list; /* list of buffer pages */
322 local_t write; /* index for next write */
323 unsigned read; /* index for next read */
324 local_t entries; /* entries on this page */
325 unsigned long real_end; /* real end of data */
326 struct buffer_data_page *page; /* Actual data page */
327};
328
329/*
330 * The buffer page counters, write and entries, must be reset
331 * atomically when crossing page boundaries. To synchronize this
332 * update, two counters are inserted into the number. One is
333 * the actual counter for the write position or count on the page.
334 *
335 * The other is a counter of updaters. Before an update happens
336 * the update partition of the counter is incremented. This will
337 * allow the updater to update the counter atomically.
338 *
339 * The counter is 20 bits, and the state data is 12.
340 */
341#define RB_WRITE_MASK 0xfffff
342#define RB_WRITE_INTCNT (1 << 20)
343
344static void rb_init_page(struct buffer_data_page *bpage)
345{
346 local_set(&bpage->commit, 0);
347}
348
349/*
350 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
351 * this issue out.
352 */
353static void free_buffer_page(struct buffer_page *bpage)
354{
355 free_page((unsigned long)bpage->page);
356 kfree(bpage);
357}
358
359/*
360 * We need to fit the time_stamp delta into 27 bits.
361 */
362static inline int test_time_stamp(u64 delta)
363{
364 if (delta & TS_DELTA_TEST)
365 return 1;
366 return 0;
367}
368
369#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
370
371/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
372#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
373
374int ring_buffer_print_page_header(struct trace_seq *s)
375{
376 struct buffer_data_page field;
377
378 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
379 "offset:0;\tsize:%u;\tsigned:%u;\n",
380 (unsigned int)sizeof(field.time_stamp),
381 (unsigned int)is_signed_type(u64));
382
383 trace_seq_printf(s, "\tfield: local_t commit;\t"
384 "offset:%u;\tsize:%u;\tsigned:%u;\n",
385 (unsigned int)offsetof(typeof(field), commit),
386 (unsigned int)sizeof(field.commit),
387 (unsigned int)is_signed_type(long));
388
389 trace_seq_printf(s, "\tfield: int overwrite;\t"
390 "offset:%u;\tsize:%u;\tsigned:%u;\n",
391 (unsigned int)offsetof(typeof(field), commit),
392 1,
393 (unsigned int)is_signed_type(long));
394
395 trace_seq_printf(s, "\tfield: char data;\t"
396 "offset:%u;\tsize:%u;\tsigned:%u;\n",
397 (unsigned int)offsetof(typeof(field), data),
398 (unsigned int)BUF_PAGE_SIZE,
399 (unsigned int)is_signed_type(char));
400
401 return !trace_seq_has_overflowed(s);
402}
403
404struct rb_irq_work {
405 struct irq_work work;
406 wait_queue_head_t waiters;
407 wait_queue_head_t full_waiters;
408 bool waiters_pending;
409 bool full_waiters_pending;
410 bool wakeup_full;
411};
412
413/*
414 * Structure to hold event state and handle nested events.
415 */
416struct rb_event_info {
417 u64 ts;
418 u64 delta;
419 u64 before;
420 u64 after;
421 unsigned long length;
422 struct buffer_page *tail_page;
423 int add_timestamp;
424};
425
426/*
427 * Used for the add_timestamp
428 * NONE
429 * EXTEND - wants a time extend
430 * ABSOLUTE - the buffer requests all events to have absolute time stamps
431 * FORCE - force a full time stamp.
432 */
433enum {
434 RB_ADD_STAMP_NONE = 0,
435 RB_ADD_STAMP_EXTEND = BIT(1),
436 RB_ADD_STAMP_ABSOLUTE = BIT(2),
437 RB_ADD_STAMP_FORCE = BIT(3)
438};
439/*
440 * Used for which event context the event is in.
441 * TRANSITION = 0
442 * NMI = 1
443 * IRQ = 2
444 * SOFTIRQ = 3
445 * NORMAL = 4
446 *
447 * See trace_recursive_lock() comment below for more details.
448 */
449enum {
450 RB_CTX_TRANSITION,
451 RB_CTX_NMI,
452 RB_CTX_IRQ,
453 RB_CTX_SOFTIRQ,
454 RB_CTX_NORMAL,
455 RB_CTX_MAX
456};
457
458#if BITS_PER_LONG == 32
459#define RB_TIME_32
460#endif
461
462/* To test on 64 bit machines */
463//#define RB_TIME_32
464
465#ifdef RB_TIME_32
466
467struct rb_time_struct {
468 local_t cnt;
469 local_t top;
470 local_t bottom;
471};
472#else
473#include <asm/local64.h>
474struct rb_time_struct {
475 local64_t time;
476};
477#endif
478typedef struct rb_time_struct rb_time_t;
479
480#define MAX_NEST 5
481
482/*
483 * head_page == tail_page && head == tail then buffer is empty.
484 */
485struct ring_buffer_per_cpu {
486 int cpu;
487 atomic_t record_disabled;
488 atomic_t resize_disabled;
489 struct trace_buffer *buffer;
490 raw_spinlock_t reader_lock; /* serialize readers */
491 arch_spinlock_t lock;
492 struct lock_class_key lock_key;
493 struct buffer_data_page *free_page;
494 unsigned long nr_pages;
495 unsigned int current_context;
496 struct list_head *pages;
497 struct buffer_page *head_page; /* read from head */
498 struct buffer_page *tail_page; /* write to tail */
499 struct buffer_page *commit_page; /* committed pages */
500 struct buffer_page *reader_page;
501 unsigned long lost_events;
502 unsigned long last_overrun;
503 unsigned long nest;
504 local_t entries_bytes;
505 local_t entries;
506 local_t overrun;
507 local_t commit_overrun;
508 local_t dropped_events;
509 local_t committing;
510 local_t commits;
511 local_t pages_touched;
512 local_t pages_read;
513 long last_pages_touch;
514 size_t shortest_full;
515 unsigned long read;
516 unsigned long read_bytes;
517 rb_time_t write_stamp;
518 rb_time_t before_stamp;
519 u64 event_stamp[MAX_NEST];
520 u64 read_stamp;
521 /* ring buffer pages to update, > 0 to add, < 0 to remove */
522 long nr_pages_to_update;
523 struct list_head new_pages; /* new pages to add */
524 struct work_struct update_pages_work;
525 struct completion update_done;
526
527 struct rb_irq_work irq_work;
528};
529
530struct trace_buffer {
531 unsigned flags;
532 int cpus;
533 atomic_t record_disabled;
534 cpumask_var_t cpumask;
535
536 struct lock_class_key *reader_lock_key;
537
538 struct mutex mutex;
539
540 struct ring_buffer_per_cpu **buffers;
541
542 struct hlist_node node;
543 u64 (*clock)(void);
544
545 struct rb_irq_work irq_work;
546 bool time_stamp_abs;
547};
548
549struct ring_buffer_iter {
550 struct ring_buffer_per_cpu *cpu_buffer;
551 unsigned long head;
552 unsigned long next_event;
553 struct buffer_page *head_page;
554 struct buffer_page *cache_reader_page;
555 unsigned long cache_read;
556 u64 read_stamp;
557 u64 page_stamp;
558 struct ring_buffer_event *event;
559 int missed_events;
560};
561
562#ifdef RB_TIME_32
563
564/*
565 * On 32 bit machines, local64_t is very expensive. As the ring
566 * buffer doesn't need all the features of a true 64 bit atomic,
567 * on 32 bit, it uses these functions (64 still uses local64_t).
568 *
569 * For the ring buffer, 64 bit required operations for the time is
570 * the following:
571 *
572 * - Only need 59 bits (uses 60 to make it even).
573 * - Reads may fail if it interrupted a modification of the time stamp.
574 * It will succeed if it did not interrupt another write even if
575 * the read itself is interrupted by a write.
576 * It returns whether it was successful or not.
577 *
578 * - Writes always succeed and will overwrite other writes and writes
579 * that were done by events interrupting the current write.
580 *
581 * - A write followed by a read of the same time stamp will always succeed,
582 * but may not contain the same value.
583 *
584 * - A cmpxchg will fail if it interrupted another write or cmpxchg.
585 * Other than that, it acts like a normal cmpxchg.
586 *
587 * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
588 * (bottom being the least significant 30 bits of the 60 bit time stamp).
589 *
590 * The two most significant bits of each half holds a 2 bit counter (0-3).
591 * Each update will increment this counter by one.
592 * When reading the top and bottom, if the two counter bits match then the
593 * top and bottom together make a valid 60 bit number.
594 */
595#define RB_TIME_SHIFT 30
596#define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
597
598static inline int rb_time_cnt(unsigned long val)
599{
600 return (val >> RB_TIME_SHIFT) & 3;
601}
602
603static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
604{
605 u64 val;
606
607 val = top & RB_TIME_VAL_MASK;
608 val <<= RB_TIME_SHIFT;
609 val |= bottom & RB_TIME_VAL_MASK;
610
611 return val;
612}
613
614static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
615{
616 unsigned long top, bottom;
617 unsigned long c;
618
619 /*
620 * If the read is interrupted by a write, then the cnt will
621 * be different. Loop until both top and bottom have been read
622 * without interruption.
623 */
624 do {
625 c = local_read(&t->cnt);
626 top = local_read(&t->top);
627 bottom = local_read(&t->bottom);
628 } while (c != local_read(&t->cnt));
629
630 *cnt = rb_time_cnt(top);
631
632 /* If top and bottom counts don't match, this interrupted a write */
633 if (*cnt != rb_time_cnt(bottom))
634 return false;
635
636 *ret = rb_time_val(top, bottom);
637 return true;
638}
639
640static bool rb_time_read(rb_time_t *t, u64 *ret)
641{
642 unsigned long cnt;
643
644 return __rb_time_read(t, ret, &cnt);
645}
646
647static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
648{
649 return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
650}
651
652static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom)
653{
654 *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
655 *bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
656}
657
658static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
659{
660 val = rb_time_val_cnt(val, cnt);
661 local_set(t, val);
662}
663
664static void rb_time_set(rb_time_t *t, u64 val)
665{
666 unsigned long cnt, top, bottom;
667
668 rb_time_split(val, &top, &bottom);
669
670 /* Writes always succeed with a valid number even if it gets interrupted. */
671 do {
672 cnt = local_inc_return(&t->cnt);
673 rb_time_val_set(&t->top, top, cnt);
674 rb_time_val_set(&t->bottom, bottom, cnt);
675 } while (cnt != local_read(&t->cnt));
676}
677
678static inline bool
679rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
680{
681 unsigned long ret;
682
683 ret = local_cmpxchg(l, expect, set);
684 return ret == expect;
685}
686
687static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
688{
689 unsigned long cnt, top, bottom;
690 unsigned long cnt2, top2, bottom2;
691 u64 val;
692
693 /* The cmpxchg always fails if it interrupted an update */
694 if (!__rb_time_read(t, &val, &cnt2))
695 return false;
696
697 if (val != expect)
698 return false;
699
700 cnt = local_read(&t->cnt);
701 if ((cnt & 3) != cnt2)
702 return false;
703
704 cnt2 = cnt + 1;
705
706 rb_time_split(val, &top, &bottom);
707 top = rb_time_val_cnt(top, cnt);
708 bottom = rb_time_val_cnt(bottom, cnt);
709
710 rb_time_split(set, &top2, &bottom2);
711 top2 = rb_time_val_cnt(top2, cnt2);
712 bottom2 = rb_time_val_cnt(bottom2, cnt2);
713
714 if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
715 return false;
716 if (!rb_time_read_cmpxchg(&t->top, top, top2))
717 return false;
718 if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
719 return false;
720 return true;
721}
722
723#else /* 64 bits */
724
725/* local64_t always succeeds */
726
727static inline bool rb_time_read(rb_time_t *t, u64 *ret)
728{
729 *ret = local64_read(&t->time);
730 return true;
731}
732static void rb_time_set(rb_time_t *t, u64 val)
733{
734 local64_set(&t->time, val);
735}
736
737static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
738{
739 u64 val;
740 val = local64_cmpxchg(&t->time, expect, set);
741 return val == expect;
742}
743#endif
744
745/*
746 * Enable this to make sure that the event passed to
747 * ring_buffer_event_time_stamp() is not committed and also
748 * is on the buffer that it passed in.
749 */
750//#define RB_VERIFY_EVENT
751#ifdef RB_VERIFY_EVENT
752static struct list_head *rb_list_head(struct list_head *list);
753static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
754 void *event)
755{
756 struct buffer_page *page = cpu_buffer->commit_page;
757 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
758 struct list_head *next;
759 long commit, write;
760 unsigned long addr = (unsigned long)event;
761 bool done = false;
762 int stop = 0;
763
764 /* Make sure the event exists and is not committed yet */
765 do {
766 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
767 done = true;
768 commit = local_read(&page->page->commit);
769 write = local_read(&page->write);
770 if (addr >= (unsigned long)&page->page->data[commit] &&
771 addr < (unsigned long)&page->page->data[write])
772 return;
773
774 next = rb_list_head(page->list.next);
775 page = list_entry(next, struct buffer_page, list);
776 } while (!done);
777 WARN_ON_ONCE(1);
778}
779#else
780static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
781 void *event)
782{
783}
784#endif
785
786
787static inline u64 rb_time_stamp(struct trace_buffer *buffer);
788
789/**
790 * ring_buffer_event_time_stamp - return the event's current time stamp
791 * @buffer: The buffer that the event is on
792 * @event: the event to get the time stamp of
793 *
794 * Note, this must be called after @event is reserved, and before it is
795 * committed to the ring buffer. And must be called from the same
796 * context where the event was reserved (normal, softirq, irq, etc).
797 *
798 * Returns the time stamp associated with the current event.
799 * If the event has an extended time stamp, then that is used as
800 * the time stamp to return.
801 * In the highly unlikely case that the event was nested more than
802 * the max nesting, then the write_stamp of the buffer is returned,
803 * otherwise current time is returned, but that really neither of
804 * the last two cases should ever happen.
805 */
806u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
807 struct ring_buffer_event *event)
808{
809 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
810 unsigned int nest;
811 u64 ts;
812
813 /* If the event includes an absolute time, then just use that */
814 if (event->type_len == RINGBUF_TYPE_TIME_STAMP)
815 return rb_event_time_stamp(event);
816
817 nest = local_read(&cpu_buffer->committing);
818 verify_event(cpu_buffer, event);
819 if (WARN_ON_ONCE(!nest))
820 goto fail;
821
822 /* Read the current saved nesting level time stamp */
823 if (likely(--nest < MAX_NEST))
824 return cpu_buffer->event_stamp[nest];
825
826 /* Shouldn't happen, warn if it does */
827 WARN_ONCE(1, "nest (%d) greater than max", nest);
828
829 fail:
830 /* Can only fail on 32 bit */
831 if (!rb_time_read(&cpu_buffer->write_stamp, &ts))
832 /* Screw it, just read the current time */
833 ts = rb_time_stamp(cpu_buffer->buffer);
834
835 return ts;
836}
837
838/**
839 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
840 * @buffer: The ring_buffer to get the number of pages from
841 * @cpu: The cpu of the ring_buffer to get the number of pages from
842 *
843 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
844 */
845size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
846{
847 return buffer->buffers[cpu]->nr_pages;
848}
849
850/**
851 * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
852 * @buffer: The ring_buffer to get the number of pages from
853 * @cpu: The cpu of the ring_buffer to get the number of pages from
854 *
855 * Returns the number of pages that have content in the ring buffer.
856 */
857size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
858{
859 size_t read;
860 size_t cnt;
861
862 read = local_read(&buffer->buffers[cpu]->pages_read);
863 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
864 /* The reader can read an empty page, but not more than that */
865 if (cnt < read) {
866 WARN_ON_ONCE(read > cnt + 1);
867 return 0;
868 }
869
870 return cnt - read;
871}
872
873/*
874 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
875 *
876 * Schedules a delayed work to wake up any task that is blocked on the
877 * ring buffer waiters queue.
878 */
879static void rb_wake_up_waiters(struct irq_work *work)
880{
881 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
882
883 wake_up_all(&rbwork->waiters);
884 if (rbwork->wakeup_full) {
885 rbwork->wakeup_full = false;
886 wake_up_all(&rbwork->full_waiters);
887 }
888}
889
890/**
891 * ring_buffer_wait - wait for input to the ring buffer
892 * @buffer: buffer to wait on
893 * @cpu: the cpu buffer to wait on
894 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
895 *
896 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
897 * as data is added to any of the @buffer's cpu buffers. Otherwise
898 * it will wait for data to be added to a specific cpu buffer.
899 */
900int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
901{
902 struct ring_buffer_per_cpu *cpu_buffer;
903 DEFINE_WAIT(wait);
904 struct rb_irq_work *work;
905 int ret = 0;
906
907 /*
908 * Depending on what the caller is waiting for, either any
909 * data in any cpu buffer, or a specific buffer, put the
910 * caller on the appropriate wait queue.
911 */
912 if (cpu == RING_BUFFER_ALL_CPUS) {
913 work = &buffer->irq_work;
914 /* Full only makes sense on per cpu reads */
915 full = 0;
916 } else {
917 if (!cpumask_test_cpu(cpu, buffer->cpumask))
918 return -ENODEV;
919 cpu_buffer = buffer->buffers[cpu];
920 work = &cpu_buffer->irq_work;
921 }
922
923
924 while (true) {
925 if (full)
926 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
927 else
928 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
929
930 /*
931 * The events can happen in critical sections where
932 * checking a work queue can cause deadlocks.
933 * After adding a task to the queue, this flag is set
934 * only to notify events to try to wake up the queue
935 * using irq_work.
936 *
937 * We don't clear it even if the buffer is no longer
938 * empty. The flag only causes the next event to run
939 * irq_work to do the work queue wake up. The worse
940 * that can happen if we race with !trace_empty() is that
941 * an event will cause an irq_work to try to wake up
942 * an empty queue.
943 *
944 * There's no reason to protect this flag either, as
945 * the work queue and irq_work logic will do the necessary
946 * synchronization for the wake ups. The only thing
947 * that is necessary is that the wake up happens after
948 * a task has been queued. It's OK for spurious wake ups.
949 */
950 if (full)
951 work->full_waiters_pending = true;
952 else
953 work->waiters_pending = true;
954
955 if (signal_pending(current)) {
956 ret = -EINTR;
957 break;
958 }
959
960 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
961 break;
962
963 if (cpu != RING_BUFFER_ALL_CPUS &&
964 !ring_buffer_empty_cpu(buffer, cpu)) {
965 unsigned long flags;
966 bool pagebusy;
967 size_t nr_pages;
968 size_t dirty;
969
970 if (!full)
971 break;
972
973 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
974 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
975 nr_pages = cpu_buffer->nr_pages;
976 dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
977 if (!cpu_buffer->shortest_full ||
978 cpu_buffer->shortest_full < full)
979 cpu_buffer->shortest_full = full;
980 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
981 if (!pagebusy &&
982 (!nr_pages || (dirty * 100) > full * nr_pages))
983 break;
984 }
985
986 schedule();
987 }
988
989 if (full)
990 finish_wait(&work->full_waiters, &wait);
991 else
992 finish_wait(&work->waiters, &wait);
993
994 return ret;
995}
996
997/**
998 * ring_buffer_poll_wait - poll on buffer input
999 * @buffer: buffer to wait on
1000 * @cpu: the cpu buffer to wait on
1001 * @filp: the file descriptor
1002 * @poll_table: The poll descriptor
1003 *
1004 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1005 * as data is added to any of the @buffer's cpu buffers. Otherwise
1006 * it will wait for data to be added to a specific cpu buffer.
1007 *
1008 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1009 * zero otherwise.
1010 */
1011__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1012 struct file *filp, poll_table *poll_table)
1013{
1014 struct ring_buffer_per_cpu *cpu_buffer;
1015 struct rb_irq_work *work;
1016
1017 if (cpu == RING_BUFFER_ALL_CPUS)
1018 work = &buffer->irq_work;
1019 else {
1020 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1021 return -EINVAL;
1022
1023 cpu_buffer = buffer->buffers[cpu];
1024 work = &cpu_buffer->irq_work;
1025 }
1026
1027 poll_wait(filp, &work->waiters, poll_table);
1028 work->waiters_pending = true;
1029 /*
1030 * There's a tight race between setting the waiters_pending and
1031 * checking if the ring buffer is empty. Once the waiters_pending bit
1032 * is set, the next event will wake the task up, but we can get stuck
1033 * if there's only a single event in.
1034 *
1035 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1036 * but adding a memory barrier to all events will cause too much of a
1037 * performance hit in the fast path. We only need a memory barrier when
1038 * the buffer goes from empty to having content. But as this race is
1039 * extremely small, and it's not a problem if another event comes in, we
1040 * will fix it later.
1041 */
1042 smp_mb();
1043
1044 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1045 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1046 return EPOLLIN | EPOLLRDNORM;
1047 return 0;
1048}
1049
1050/* buffer may be either ring_buffer or ring_buffer_per_cpu */
1051#define RB_WARN_ON(b, cond) \
1052 ({ \
1053 int _____ret = unlikely(cond); \
1054 if (_____ret) { \
1055 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1056 struct ring_buffer_per_cpu *__b = \
1057 (void *)b; \
1058 atomic_inc(&__b->buffer->record_disabled); \
1059 } else \
1060 atomic_inc(&b->record_disabled); \
1061 WARN_ON(1); \
1062 } \
1063 _____ret; \
1064 })
1065
1066/* Up this if you want to test the TIME_EXTENTS and normalization */
1067#define DEBUG_SHIFT 0
1068
1069static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1070{
1071 u64 ts;
1072
1073 /* Skip retpolines :-( */
1074 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1075 ts = trace_clock_local();
1076 else
1077 ts = buffer->clock();
1078
1079 /* shift to debug/test normalization and TIME_EXTENTS */
1080 return ts << DEBUG_SHIFT;
1081}
1082
1083u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1084{
1085 u64 time;
1086
1087 preempt_disable_notrace();
1088 time = rb_time_stamp(buffer);
1089 preempt_enable_notrace();
1090
1091 return time;
1092}
1093EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1094
1095void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1096 int cpu, u64 *ts)
1097{
1098 /* Just stupid testing the normalize function and deltas */
1099 *ts >>= DEBUG_SHIFT;
1100}
1101EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1102
1103/*
1104 * Making the ring buffer lockless makes things tricky.
1105 * Although writes only happen on the CPU that they are on,
1106 * and they only need to worry about interrupts. Reads can
1107 * happen on any CPU.
1108 *
1109 * The reader page is always off the ring buffer, but when the
1110 * reader finishes with a page, it needs to swap its page with
1111 * a new one from the buffer. The reader needs to take from
1112 * the head (writes go to the tail). But if a writer is in overwrite
1113 * mode and wraps, it must push the head page forward.
1114 *
1115 * Here lies the problem.
1116 *
1117 * The reader must be careful to replace only the head page, and
1118 * not another one. As described at the top of the file in the
1119 * ASCII art, the reader sets its old page to point to the next
1120 * page after head. It then sets the page after head to point to
1121 * the old reader page. But if the writer moves the head page
1122 * during this operation, the reader could end up with the tail.
1123 *
1124 * We use cmpxchg to help prevent this race. We also do something
1125 * special with the page before head. We set the LSB to 1.
1126 *
1127 * When the writer must push the page forward, it will clear the
1128 * bit that points to the head page, move the head, and then set
1129 * the bit that points to the new head page.
1130 *
1131 * We also don't want an interrupt coming in and moving the head
1132 * page on another writer. Thus we use the second LSB to catch
1133 * that too. Thus:
1134 *
1135 * head->list->prev->next bit 1 bit 0
1136 * ------- -------
1137 * Normal page 0 0
1138 * Points to head page 0 1
1139 * New head page 1 0
1140 *
1141 * Note we can not trust the prev pointer of the head page, because:
1142 *
1143 * +----+ +-----+ +-----+
1144 * | |------>| T |---X--->| N |
1145 * | |<------| | | |
1146 * +----+ +-----+ +-----+
1147 * ^ ^ |
1148 * | +-----+ | |
1149 * +----------| R |----------+ |
1150 * | |<-----------+
1151 * +-----+
1152 *
1153 * Key: ---X--> HEAD flag set in pointer
1154 * T Tail page
1155 * R Reader page
1156 * N Next page
1157 *
1158 * (see __rb_reserve_next() to see where this happens)
1159 *
1160 * What the above shows is that the reader just swapped out
1161 * the reader page with a page in the buffer, but before it
1162 * could make the new header point back to the new page added
1163 * it was preempted by a writer. The writer moved forward onto
1164 * the new page added by the reader and is about to move forward
1165 * again.
1166 *
1167 * You can see, it is legitimate for the previous pointer of
1168 * the head (or any page) not to point back to itself. But only
1169 * temporarily.
1170 */
1171
1172#define RB_PAGE_NORMAL 0UL
1173#define RB_PAGE_HEAD 1UL
1174#define RB_PAGE_UPDATE 2UL
1175
1176
1177#define RB_FLAG_MASK 3UL
1178
1179/* PAGE_MOVED is not part of the mask */
1180#define RB_PAGE_MOVED 4UL
1181
1182/*
1183 * rb_list_head - remove any bit
1184 */
1185static struct list_head *rb_list_head(struct list_head *list)
1186{
1187 unsigned long val = (unsigned long)list;
1188
1189 return (struct list_head *)(val & ~RB_FLAG_MASK);
1190}
1191
1192/*
1193 * rb_is_head_page - test if the given page is the head page
1194 *
1195 * Because the reader may move the head_page pointer, we can
1196 * not trust what the head page is (it may be pointing to
1197 * the reader page). But if the next page is a header page,
1198 * its flags will be non zero.
1199 */
1200static inline int
1201rb_is_head_page(struct buffer_page *page, struct list_head *list)
1202{
1203 unsigned long val;
1204
1205 val = (unsigned long)list->next;
1206
1207 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1208 return RB_PAGE_MOVED;
1209
1210 return val & RB_FLAG_MASK;
1211}
1212
1213/*
1214 * rb_is_reader_page
1215 *
1216 * The unique thing about the reader page, is that, if the
1217 * writer is ever on it, the previous pointer never points
1218 * back to the reader page.
1219 */
1220static bool rb_is_reader_page(struct buffer_page *page)
1221{
1222 struct list_head *list = page->list.prev;
1223
1224 return rb_list_head(list->next) != &page->list;
1225}
1226
1227/*
1228 * rb_set_list_to_head - set a list_head to be pointing to head.
1229 */
1230static void rb_set_list_to_head(struct list_head *list)
1231{
1232 unsigned long *ptr;
1233
1234 ptr = (unsigned long *)&list->next;
1235 *ptr |= RB_PAGE_HEAD;
1236 *ptr &= ~RB_PAGE_UPDATE;
1237}
1238
1239/*
1240 * rb_head_page_activate - sets up head page
1241 */
1242static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1243{
1244 struct buffer_page *head;
1245
1246 head = cpu_buffer->head_page;
1247 if (!head)
1248 return;
1249
1250 /*
1251 * Set the previous list pointer to have the HEAD flag.
1252 */
1253 rb_set_list_to_head(head->list.prev);
1254}
1255
1256static void rb_list_head_clear(struct list_head *list)
1257{
1258 unsigned long *ptr = (unsigned long *)&list->next;
1259
1260 *ptr &= ~RB_FLAG_MASK;
1261}
1262
1263/*
1264 * rb_head_page_deactivate - clears head page ptr (for free list)
1265 */
1266static void
1267rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1268{
1269 struct list_head *hd;
1270
1271 /* Go through the whole list and clear any pointers found. */
1272 rb_list_head_clear(cpu_buffer->pages);
1273
1274 list_for_each(hd, cpu_buffer->pages)
1275 rb_list_head_clear(hd);
1276}
1277
1278static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1279 struct buffer_page *head,
1280 struct buffer_page *prev,
1281 int old_flag, int new_flag)
1282{
1283 struct list_head *list;
1284 unsigned long val = (unsigned long)&head->list;
1285 unsigned long ret;
1286
1287 list = &prev->list;
1288
1289 val &= ~RB_FLAG_MASK;
1290
1291 ret = cmpxchg((unsigned long *)&list->next,
1292 val | old_flag, val | new_flag);
1293
1294 /* check if the reader took the page */
1295 if ((ret & ~RB_FLAG_MASK) != val)
1296 return RB_PAGE_MOVED;
1297
1298 return ret & RB_FLAG_MASK;
1299}
1300
1301static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1302 struct buffer_page *head,
1303 struct buffer_page *prev,
1304 int old_flag)
1305{
1306 return rb_head_page_set(cpu_buffer, head, prev,
1307 old_flag, RB_PAGE_UPDATE);
1308}
1309
1310static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1311 struct buffer_page *head,
1312 struct buffer_page *prev,
1313 int old_flag)
1314{
1315 return rb_head_page_set(cpu_buffer, head, prev,
1316 old_flag, RB_PAGE_HEAD);
1317}
1318
1319static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1320 struct buffer_page *head,
1321 struct buffer_page *prev,
1322 int old_flag)
1323{
1324 return rb_head_page_set(cpu_buffer, head, prev,
1325 old_flag, RB_PAGE_NORMAL);
1326}
1327
1328static inline void rb_inc_page(struct buffer_page **bpage)
1329{
1330 struct list_head *p = rb_list_head((*bpage)->list.next);
1331
1332 *bpage = list_entry(p, struct buffer_page, list);
1333}
1334
1335static struct buffer_page *
1336rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1337{
1338 struct buffer_page *head;
1339 struct buffer_page *page;
1340 struct list_head *list;
1341 int i;
1342
1343 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1344 return NULL;
1345
1346 /* sanity check */
1347 list = cpu_buffer->pages;
1348 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1349 return NULL;
1350
1351 page = head = cpu_buffer->head_page;
1352 /*
1353 * It is possible that the writer moves the header behind
1354 * where we started, and we miss in one loop.
1355 * A second loop should grab the header, but we'll do
1356 * three loops just because I'm paranoid.
1357 */
1358 for (i = 0; i < 3; i++) {
1359 do {
1360 if (rb_is_head_page(page, page->list.prev)) {
1361 cpu_buffer->head_page = page;
1362 return page;
1363 }
1364 rb_inc_page(&page);
1365 } while (page != head);
1366 }
1367
1368 RB_WARN_ON(cpu_buffer, 1);
1369
1370 return NULL;
1371}
1372
1373static int rb_head_page_replace(struct buffer_page *old,
1374 struct buffer_page *new)
1375{
1376 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1377 unsigned long val;
1378 unsigned long ret;
1379
1380 val = *ptr & ~RB_FLAG_MASK;
1381 val |= RB_PAGE_HEAD;
1382
1383 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1384
1385 return ret == val;
1386}
1387
1388/*
1389 * rb_tail_page_update - move the tail page forward
1390 */
1391static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1392 struct buffer_page *tail_page,
1393 struct buffer_page *next_page)
1394{
1395 unsigned long old_entries;
1396 unsigned long old_write;
1397
1398 /*
1399 * The tail page now needs to be moved forward.
1400 *
1401 * We need to reset the tail page, but without messing
1402 * with possible erasing of data brought in by interrupts
1403 * that have moved the tail page and are currently on it.
1404 *
1405 * We add a counter to the write field to denote this.
1406 */
1407 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1408 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1409
1410 local_inc(&cpu_buffer->pages_touched);
1411 /*
1412 * Just make sure we have seen our old_write and synchronize
1413 * with any interrupts that come in.
1414 */
1415 barrier();
1416
1417 /*
1418 * If the tail page is still the same as what we think
1419 * it is, then it is up to us to update the tail
1420 * pointer.
1421 */
1422 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1423 /* Zero the write counter */
1424 unsigned long val = old_write & ~RB_WRITE_MASK;
1425 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1426
1427 /*
1428 * This will only succeed if an interrupt did
1429 * not come in and change it. In which case, we
1430 * do not want to modify it.
1431 *
1432 * We add (void) to let the compiler know that we do not care
1433 * about the return value of these functions. We use the
1434 * cmpxchg to only update if an interrupt did not already
1435 * do it for us. If the cmpxchg fails, we don't care.
1436 */
1437 (void)local_cmpxchg(&next_page->write, old_write, val);
1438 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1439
1440 /*
1441 * No need to worry about races with clearing out the commit.
1442 * it only can increment when a commit takes place. But that
1443 * only happens in the outer most nested commit.
1444 */
1445 local_set(&next_page->page->commit, 0);
1446
1447 /* Again, either we update tail_page or an interrupt does */
1448 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1449 }
1450}
1451
1452static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1453 struct buffer_page *bpage)
1454{
1455 unsigned long val = (unsigned long)bpage;
1456
1457 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1458 return 1;
1459
1460 return 0;
1461}
1462
1463/**
1464 * rb_check_list - make sure a pointer to a list has the last bits zero
1465 */
1466static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1467 struct list_head *list)
1468{
1469 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1470 return 1;
1471 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1472 return 1;
1473 return 0;
1474}
1475
1476/**
1477 * rb_check_pages - integrity check of buffer pages
1478 * @cpu_buffer: CPU buffer with pages to test
1479 *
1480 * As a safety measure we check to make sure the data pages have not
1481 * been corrupted.
1482 */
1483static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1484{
1485 struct list_head *head = cpu_buffer->pages;
1486 struct buffer_page *bpage, *tmp;
1487
1488 /* Reset the head page if it exists */
1489 if (cpu_buffer->head_page)
1490 rb_set_head_page(cpu_buffer);
1491
1492 rb_head_page_deactivate(cpu_buffer);
1493
1494 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1495 return -1;
1496 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1497 return -1;
1498
1499 if (rb_check_list(cpu_buffer, head))
1500 return -1;
1501
1502 list_for_each_entry_safe(bpage, tmp, head, list) {
1503 if (RB_WARN_ON(cpu_buffer,
1504 bpage->list.next->prev != &bpage->list))
1505 return -1;
1506 if (RB_WARN_ON(cpu_buffer,
1507 bpage->list.prev->next != &bpage->list))
1508 return -1;
1509 if (rb_check_list(cpu_buffer, &bpage->list))
1510 return -1;
1511 }
1512
1513 rb_head_page_activate(cpu_buffer);
1514
1515 return 0;
1516}
1517
1518static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1519 long nr_pages, struct list_head *pages)
1520{
1521 struct buffer_page *bpage, *tmp;
1522 bool user_thread = current->mm != NULL;
1523 gfp_t mflags;
1524 long i;
1525
1526 /*
1527 * Check if the available memory is there first.
1528 * Note, si_mem_available() only gives us a rough estimate of available
1529 * memory. It may not be accurate. But we don't care, we just want
1530 * to prevent doing any allocation when it is obvious that it is
1531 * not going to succeed.
1532 */
1533 i = si_mem_available();
1534 if (i < nr_pages)
1535 return -ENOMEM;
1536
1537 /*
1538 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1539 * gracefully without invoking oom-killer and the system is not
1540 * destabilized.
1541 */
1542 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1543
1544 /*
1545 * If a user thread allocates too much, and si_mem_available()
1546 * reports there's enough memory, even though there is not.
1547 * Make sure the OOM killer kills this thread. This can happen
1548 * even with RETRY_MAYFAIL because another task may be doing
1549 * an allocation after this task has taken all memory.
1550 * This is the task the OOM killer needs to take out during this
1551 * loop, even if it was triggered by an allocation somewhere else.
1552 */
1553 if (user_thread)
1554 set_current_oom_origin();
1555 for (i = 0; i < nr_pages; i++) {
1556 struct page *page;
1557
1558 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1559 mflags, cpu_to_node(cpu_buffer->cpu));
1560 if (!bpage)
1561 goto free_pages;
1562
1563 rb_check_bpage(cpu_buffer, bpage);
1564
1565 list_add(&bpage->list, pages);
1566
1567 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0);
1568 if (!page)
1569 goto free_pages;
1570 bpage->page = page_address(page);
1571 rb_init_page(bpage->page);
1572
1573 if (user_thread && fatal_signal_pending(current))
1574 goto free_pages;
1575 }
1576 if (user_thread)
1577 clear_current_oom_origin();
1578
1579 return 0;
1580
1581free_pages:
1582 list_for_each_entry_safe(bpage, tmp, pages, list) {
1583 list_del_init(&bpage->list);
1584 free_buffer_page(bpage);
1585 }
1586 if (user_thread)
1587 clear_current_oom_origin();
1588
1589 return -ENOMEM;
1590}
1591
1592static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1593 unsigned long nr_pages)
1594{
1595 LIST_HEAD(pages);
1596
1597 WARN_ON(!nr_pages);
1598
1599 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1600 return -ENOMEM;
1601
1602 /*
1603 * The ring buffer page list is a circular list that does not
1604 * start and end with a list head. All page list items point to
1605 * other pages.
1606 */
1607 cpu_buffer->pages = pages.next;
1608 list_del(&pages);
1609
1610 cpu_buffer->nr_pages = nr_pages;
1611
1612 rb_check_pages(cpu_buffer);
1613
1614 return 0;
1615}
1616
1617static struct ring_buffer_per_cpu *
1618rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1619{
1620 struct ring_buffer_per_cpu *cpu_buffer;
1621 struct buffer_page *bpage;
1622 struct page *page;
1623 int ret;
1624
1625 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1626 GFP_KERNEL, cpu_to_node(cpu));
1627 if (!cpu_buffer)
1628 return NULL;
1629
1630 cpu_buffer->cpu = cpu;
1631 cpu_buffer->buffer = buffer;
1632 raw_spin_lock_init(&cpu_buffer->reader_lock);
1633 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1634 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1635 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1636 init_completion(&cpu_buffer->update_done);
1637 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1638 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1639 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1640
1641 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1642 GFP_KERNEL, cpu_to_node(cpu));
1643 if (!bpage)
1644 goto fail_free_buffer;
1645
1646 rb_check_bpage(cpu_buffer, bpage);
1647
1648 cpu_buffer->reader_page = bpage;
1649 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1650 if (!page)
1651 goto fail_free_reader;
1652 bpage->page = page_address(page);
1653 rb_init_page(bpage->page);
1654
1655 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1656 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1657
1658 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1659 if (ret < 0)
1660 goto fail_free_reader;
1661
1662 cpu_buffer->head_page
1663 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1664 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1665
1666 rb_head_page_activate(cpu_buffer);
1667
1668 return cpu_buffer;
1669
1670 fail_free_reader:
1671 free_buffer_page(cpu_buffer->reader_page);
1672
1673 fail_free_buffer:
1674 kfree(cpu_buffer);
1675 return NULL;
1676}
1677
1678static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1679{
1680 struct list_head *head = cpu_buffer->pages;
1681 struct buffer_page *bpage, *tmp;
1682
1683 free_buffer_page(cpu_buffer->reader_page);
1684
1685 rb_head_page_deactivate(cpu_buffer);
1686
1687 if (head) {
1688 list_for_each_entry_safe(bpage, tmp, head, list) {
1689 list_del_init(&bpage->list);
1690 free_buffer_page(bpage);
1691 }
1692 bpage = list_entry(head, struct buffer_page, list);
1693 free_buffer_page(bpage);
1694 }
1695
1696 kfree(cpu_buffer);
1697}
1698
1699/**
1700 * __ring_buffer_alloc - allocate a new ring_buffer
1701 * @size: the size in bytes per cpu that is needed.
1702 * @flags: attributes to set for the ring buffer.
1703 * @key: ring buffer reader_lock_key.
1704 *
1705 * Currently the only flag that is available is the RB_FL_OVERWRITE
1706 * flag. This flag means that the buffer will overwrite old data
1707 * when the buffer wraps. If this flag is not set, the buffer will
1708 * drop data when the tail hits the head.
1709 */
1710struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1711 struct lock_class_key *key)
1712{
1713 struct trace_buffer *buffer;
1714 long nr_pages;
1715 int bsize;
1716 int cpu;
1717 int ret;
1718
1719 /* keep it in its own cache line */
1720 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1721 GFP_KERNEL);
1722 if (!buffer)
1723 return NULL;
1724
1725 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1726 goto fail_free_buffer;
1727
1728 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1729 buffer->flags = flags;
1730 buffer->clock = trace_clock_local;
1731 buffer->reader_lock_key = key;
1732
1733 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1734 init_waitqueue_head(&buffer->irq_work.waiters);
1735
1736 /* need at least two pages */
1737 if (nr_pages < 2)
1738 nr_pages = 2;
1739
1740 buffer->cpus = nr_cpu_ids;
1741
1742 bsize = sizeof(void *) * nr_cpu_ids;
1743 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1744 GFP_KERNEL);
1745 if (!buffer->buffers)
1746 goto fail_free_cpumask;
1747
1748 cpu = raw_smp_processor_id();
1749 cpumask_set_cpu(cpu, buffer->cpumask);
1750 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1751 if (!buffer->buffers[cpu])
1752 goto fail_free_buffers;
1753
1754 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1755 if (ret < 0)
1756 goto fail_free_buffers;
1757
1758 mutex_init(&buffer->mutex);
1759
1760 return buffer;
1761
1762 fail_free_buffers:
1763 for_each_buffer_cpu(buffer, cpu) {
1764 if (buffer->buffers[cpu])
1765 rb_free_cpu_buffer(buffer->buffers[cpu]);
1766 }
1767 kfree(buffer->buffers);
1768
1769 fail_free_cpumask:
1770 free_cpumask_var(buffer->cpumask);
1771
1772 fail_free_buffer:
1773 kfree(buffer);
1774 return NULL;
1775}
1776EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1777
1778/**
1779 * ring_buffer_free - free a ring buffer.
1780 * @buffer: the buffer to free.
1781 */
1782void
1783ring_buffer_free(struct trace_buffer *buffer)
1784{
1785 int cpu;
1786
1787 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1788
1789 for_each_buffer_cpu(buffer, cpu)
1790 rb_free_cpu_buffer(buffer->buffers[cpu]);
1791
1792 kfree(buffer->buffers);
1793 free_cpumask_var(buffer->cpumask);
1794
1795 kfree(buffer);
1796}
1797EXPORT_SYMBOL_GPL(ring_buffer_free);
1798
1799void ring_buffer_set_clock(struct trace_buffer *buffer,
1800 u64 (*clock)(void))
1801{
1802 buffer->clock = clock;
1803}
1804
1805void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1806{
1807 buffer->time_stamp_abs = abs;
1808}
1809
1810bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1811{
1812 return buffer->time_stamp_abs;
1813}
1814
1815static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1816
1817static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1818{
1819 return local_read(&bpage->entries) & RB_WRITE_MASK;
1820}
1821
1822static inline unsigned long rb_page_write(struct buffer_page *bpage)
1823{
1824 return local_read(&bpage->write) & RB_WRITE_MASK;
1825}
1826
1827static int
1828rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1829{
1830 struct list_head *tail_page, *to_remove, *next_page;
1831 struct buffer_page *to_remove_page, *tmp_iter_page;
1832 struct buffer_page *last_page, *first_page;
1833 unsigned long nr_removed;
1834 unsigned long head_bit;
1835 int page_entries;
1836
1837 head_bit = 0;
1838
1839 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1840 atomic_inc(&cpu_buffer->record_disabled);
1841 /*
1842 * We don't race with the readers since we have acquired the reader
1843 * lock. We also don't race with writers after disabling recording.
1844 * This makes it easy to figure out the first and the last page to be
1845 * removed from the list. We unlink all the pages in between including
1846 * the first and last pages. This is done in a busy loop so that we
1847 * lose the least number of traces.
1848 * The pages are freed after we restart recording and unlock readers.
1849 */
1850 tail_page = &cpu_buffer->tail_page->list;
1851
1852 /*
1853 * tail page might be on reader page, we remove the next page
1854 * from the ring buffer
1855 */
1856 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1857 tail_page = rb_list_head(tail_page->next);
1858 to_remove = tail_page;
1859
1860 /* start of pages to remove */
1861 first_page = list_entry(rb_list_head(to_remove->next),
1862 struct buffer_page, list);
1863
1864 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1865 to_remove = rb_list_head(to_remove)->next;
1866 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1867 }
1868
1869 next_page = rb_list_head(to_remove)->next;
1870
1871 /*
1872 * Now we remove all pages between tail_page and next_page.
1873 * Make sure that we have head_bit value preserved for the
1874 * next page
1875 */
1876 tail_page->next = (struct list_head *)((unsigned long)next_page |
1877 head_bit);
1878 next_page = rb_list_head(next_page);
1879 next_page->prev = tail_page;
1880
1881 /* make sure pages points to a valid page in the ring buffer */
1882 cpu_buffer->pages = next_page;
1883
1884 /* update head page */
1885 if (head_bit)
1886 cpu_buffer->head_page = list_entry(next_page,
1887 struct buffer_page, list);
1888
1889 /*
1890 * change read pointer to make sure any read iterators reset
1891 * themselves
1892 */
1893 cpu_buffer->read = 0;
1894
1895 /* pages are removed, resume tracing and then free the pages */
1896 atomic_dec(&cpu_buffer->record_disabled);
1897 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1898
1899 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1900
1901 /* last buffer page to remove */
1902 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1903 list);
1904 tmp_iter_page = first_page;
1905
1906 do {
1907 cond_resched();
1908
1909 to_remove_page = tmp_iter_page;
1910 rb_inc_page(&tmp_iter_page);
1911
1912 /* update the counters */
1913 page_entries = rb_page_entries(to_remove_page);
1914 if (page_entries) {
1915 /*
1916 * If something was added to this page, it was full
1917 * since it is not the tail page. So we deduct the
1918 * bytes consumed in ring buffer from here.
1919 * Increment overrun to account for the lost events.
1920 */
1921 local_add(page_entries, &cpu_buffer->overrun);
1922 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1923 }
1924
1925 /*
1926 * We have already removed references to this list item, just
1927 * free up the buffer_page and its page
1928 */
1929 free_buffer_page(to_remove_page);
1930 nr_removed--;
1931
1932 } while (to_remove_page != last_page);
1933
1934 RB_WARN_ON(cpu_buffer, nr_removed);
1935
1936 return nr_removed == 0;
1937}
1938
1939static int
1940rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1941{
1942 struct list_head *pages = &cpu_buffer->new_pages;
1943 int retries, success;
1944
1945 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1946 /*
1947 * We are holding the reader lock, so the reader page won't be swapped
1948 * in the ring buffer. Now we are racing with the writer trying to
1949 * move head page and the tail page.
1950 * We are going to adapt the reader page update process where:
1951 * 1. We first splice the start and end of list of new pages between
1952 * the head page and its previous page.
1953 * 2. We cmpxchg the prev_page->next to point from head page to the
1954 * start of new pages list.
1955 * 3. Finally, we update the head->prev to the end of new list.
1956 *
1957 * We will try this process 10 times, to make sure that we don't keep
1958 * spinning.
1959 */
1960 retries = 10;
1961 success = 0;
1962 while (retries--) {
1963 struct list_head *head_page, *prev_page, *r;
1964 struct list_head *last_page, *first_page;
1965 struct list_head *head_page_with_bit;
1966
1967 head_page = &rb_set_head_page(cpu_buffer)->list;
1968 if (!head_page)
1969 break;
1970 prev_page = head_page->prev;
1971
1972 first_page = pages->next;
1973 last_page = pages->prev;
1974
1975 head_page_with_bit = (struct list_head *)
1976 ((unsigned long)head_page | RB_PAGE_HEAD);
1977
1978 last_page->next = head_page_with_bit;
1979 first_page->prev = prev_page;
1980
1981 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1982
1983 if (r == head_page_with_bit) {
1984 /*
1985 * yay, we replaced the page pointer to our new list,
1986 * now, we just have to update to head page's prev
1987 * pointer to point to end of list
1988 */
1989 head_page->prev = last_page;
1990 success = 1;
1991 break;
1992 }
1993 }
1994
1995 if (success)
1996 INIT_LIST_HEAD(pages);
1997 /*
1998 * If we weren't successful in adding in new pages, warn and stop
1999 * tracing
2000 */
2001 RB_WARN_ON(cpu_buffer, !success);
2002 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2003
2004 /* free pages if they weren't inserted */
2005 if (!success) {
2006 struct buffer_page *bpage, *tmp;
2007 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2008 list) {
2009 list_del_init(&bpage->list);
2010 free_buffer_page(bpage);
2011 }
2012 }
2013 return success;
2014}
2015
2016static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2017{
2018 int success;
2019
2020 if (cpu_buffer->nr_pages_to_update > 0)
2021 success = rb_insert_pages(cpu_buffer);
2022 else
2023 success = rb_remove_pages(cpu_buffer,
2024 -cpu_buffer->nr_pages_to_update);
2025
2026 if (success)
2027 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2028}
2029
2030static void update_pages_handler(struct work_struct *work)
2031{
2032 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2033 struct ring_buffer_per_cpu, update_pages_work);
2034 rb_update_pages(cpu_buffer);
2035 complete(&cpu_buffer->update_done);
2036}
2037
2038/**
2039 * ring_buffer_resize - resize the ring buffer
2040 * @buffer: the buffer to resize.
2041 * @size: the new size.
2042 * @cpu_id: the cpu buffer to resize
2043 *
2044 * Minimum size is 2 * BUF_PAGE_SIZE.
2045 *
2046 * Returns 0 on success and < 0 on failure.
2047 */
2048int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2049 int cpu_id)
2050{
2051 struct ring_buffer_per_cpu *cpu_buffer;
2052 unsigned long nr_pages;
2053 int cpu, err;
2054
2055 /*
2056 * Always succeed at resizing a non-existent buffer:
2057 */
2058 if (!buffer)
2059 return 0;
2060
2061 /* Make sure the requested buffer exists */
2062 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2063 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2064 return 0;
2065
2066 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
2067
2068 /* we need a minimum of two pages */
2069 if (nr_pages < 2)
2070 nr_pages = 2;
2071
2072 /* prevent another thread from changing buffer sizes */
2073 mutex_lock(&buffer->mutex);
2074
2075
2076 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2077 /*
2078 * Don't succeed if resizing is disabled, as a reader might be
2079 * manipulating the ring buffer and is expecting a sane state while
2080 * this is true.
2081 */
2082 for_each_buffer_cpu(buffer, cpu) {
2083 cpu_buffer = buffer->buffers[cpu];
2084 if (atomic_read(&cpu_buffer->resize_disabled)) {
2085 err = -EBUSY;
2086 goto out_err_unlock;
2087 }
2088 }
2089
2090 /* calculate the pages to update */
2091 for_each_buffer_cpu(buffer, cpu) {
2092 cpu_buffer = buffer->buffers[cpu];
2093
2094 cpu_buffer->nr_pages_to_update = nr_pages -
2095 cpu_buffer->nr_pages;
2096 /*
2097 * nothing more to do for removing pages or no update
2098 */
2099 if (cpu_buffer->nr_pages_to_update <= 0)
2100 continue;
2101 /*
2102 * to add pages, make sure all new pages can be
2103 * allocated without receiving ENOMEM
2104 */
2105 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2106 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2107 &cpu_buffer->new_pages)) {
2108 /* not enough memory for new pages */
2109 err = -ENOMEM;
2110 goto out_err;
2111 }
2112 }
2113
2114 get_online_cpus();
2115 /*
2116 * Fire off all the required work handlers
2117 * We can't schedule on offline CPUs, but it's not necessary
2118 * since we can change their buffer sizes without any race.
2119 */
2120 for_each_buffer_cpu(buffer, cpu) {
2121 cpu_buffer = buffer->buffers[cpu];
2122 if (!cpu_buffer->nr_pages_to_update)
2123 continue;
2124
2125 /* Can't run something on an offline CPU. */
2126 if (!cpu_online(cpu)) {
2127 rb_update_pages(cpu_buffer);
2128 cpu_buffer->nr_pages_to_update = 0;
2129 } else {
2130 schedule_work_on(cpu,
2131 &cpu_buffer->update_pages_work);
2132 }
2133 }
2134
2135 /* wait for all the updates to complete */
2136 for_each_buffer_cpu(buffer, cpu) {
2137 cpu_buffer = buffer->buffers[cpu];
2138 if (!cpu_buffer->nr_pages_to_update)
2139 continue;
2140
2141 if (cpu_online(cpu))
2142 wait_for_completion(&cpu_buffer->update_done);
2143 cpu_buffer->nr_pages_to_update = 0;
2144 }
2145
2146 put_online_cpus();
2147 } else {
2148 cpu_buffer = buffer->buffers[cpu_id];
2149
2150 if (nr_pages == cpu_buffer->nr_pages)
2151 goto out;
2152
2153 /*
2154 * Don't succeed if resizing is disabled, as a reader might be
2155 * manipulating the ring buffer and is expecting a sane state while
2156 * this is true.
2157 */
2158 if (atomic_read(&cpu_buffer->resize_disabled)) {
2159 err = -EBUSY;
2160 goto out_err_unlock;
2161 }
2162
2163 cpu_buffer->nr_pages_to_update = nr_pages -
2164 cpu_buffer->nr_pages;
2165
2166 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2167 if (cpu_buffer->nr_pages_to_update > 0 &&
2168 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2169 &cpu_buffer->new_pages)) {
2170 err = -ENOMEM;
2171 goto out_err;
2172 }
2173
2174 get_online_cpus();
2175
2176 /* Can't run something on an offline CPU. */
2177 if (!cpu_online(cpu_id))
2178 rb_update_pages(cpu_buffer);
2179 else {
2180 schedule_work_on(cpu_id,
2181 &cpu_buffer->update_pages_work);
2182 wait_for_completion(&cpu_buffer->update_done);
2183 }
2184
2185 cpu_buffer->nr_pages_to_update = 0;
2186 put_online_cpus();
2187 }
2188
2189 out:
2190 /*
2191 * The ring buffer resize can happen with the ring buffer
2192 * enabled, so that the update disturbs the tracing as little
2193 * as possible. But if the buffer is disabled, we do not need
2194 * to worry about that, and we can take the time to verify
2195 * that the buffer is not corrupt.
2196 */
2197 if (atomic_read(&buffer->record_disabled)) {
2198 atomic_inc(&buffer->record_disabled);
2199 /*
2200 * Even though the buffer was disabled, we must make sure
2201 * that it is truly disabled before calling rb_check_pages.
2202 * There could have been a race between checking
2203 * record_disable and incrementing it.
2204 */
2205 synchronize_rcu();
2206 for_each_buffer_cpu(buffer, cpu) {
2207 cpu_buffer = buffer->buffers[cpu];
2208 rb_check_pages(cpu_buffer);
2209 }
2210 atomic_dec(&buffer->record_disabled);
2211 }
2212
2213 mutex_unlock(&buffer->mutex);
2214 return 0;
2215
2216 out_err:
2217 for_each_buffer_cpu(buffer, cpu) {
2218 struct buffer_page *bpage, *tmp;
2219
2220 cpu_buffer = buffer->buffers[cpu];
2221 cpu_buffer->nr_pages_to_update = 0;
2222
2223 if (list_empty(&cpu_buffer->new_pages))
2224 continue;
2225
2226 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2227 list) {
2228 list_del_init(&bpage->list);
2229 free_buffer_page(bpage);
2230 }
2231 }
2232 out_err_unlock:
2233 mutex_unlock(&buffer->mutex);
2234 return err;
2235}
2236EXPORT_SYMBOL_GPL(ring_buffer_resize);
2237
2238void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2239{
2240 mutex_lock(&buffer->mutex);
2241 if (val)
2242 buffer->flags |= RB_FL_OVERWRITE;
2243 else
2244 buffer->flags &= ~RB_FL_OVERWRITE;
2245 mutex_unlock(&buffer->mutex);
2246}
2247EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2248
2249static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2250{
2251 return bpage->page->data + index;
2252}
2253
2254static __always_inline struct ring_buffer_event *
2255rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2256{
2257 return __rb_page_index(cpu_buffer->reader_page,
2258 cpu_buffer->reader_page->read);
2259}
2260
2261static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
2262{
2263 return local_read(&bpage->page->commit);
2264}
2265
2266static struct ring_buffer_event *
2267rb_iter_head_event(struct ring_buffer_iter *iter)
2268{
2269 struct ring_buffer_event *event;
2270 struct buffer_page *iter_head_page = iter->head_page;
2271 unsigned long commit;
2272 unsigned length;
2273
2274 if (iter->head != iter->next_event)
2275 return iter->event;
2276
2277 /*
2278 * When the writer goes across pages, it issues a cmpxchg which
2279 * is a mb(), which will synchronize with the rmb here.
2280 * (see rb_tail_page_update() and __rb_reserve_next())
2281 */
2282 commit = rb_page_commit(iter_head_page);
2283 smp_rmb();
2284 event = __rb_page_index(iter_head_page, iter->head);
2285 length = rb_event_length(event);
2286
2287 /*
2288 * READ_ONCE() doesn't work on functions and we don't want the
2289 * compiler doing any crazy optimizations with length.
2290 */
2291 barrier();
2292
2293 if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
2294 /* Writer corrupted the read? */
2295 goto reset;
2296
2297 memcpy(iter->event, event, length);
2298 /*
2299 * If the page stamp is still the same after this rmb() then the
2300 * event was safely copied without the writer entering the page.
2301 */
2302 smp_rmb();
2303
2304 /* Make sure the page didn't change since we read this */
2305 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2306 commit > rb_page_commit(iter_head_page))
2307 goto reset;
2308
2309 iter->next_event = iter->head + length;
2310 return iter->event;
2311 reset:
2312 /* Reset to the beginning */
2313 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2314 iter->head = 0;
2315 iter->next_event = 0;
2316 iter->missed_events = 1;
2317 return NULL;
2318}
2319
2320/* Size is determined by what has been committed */
2321static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2322{
2323 return rb_page_commit(bpage);
2324}
2325
2326static __always_inline unsigned
2327rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2328{
2329 return rb_page_commit(cpu_buffer->commit_page);
2330}
2331
2332static __always_inline unsigned
2333rb_event_index(struct ring_buffer_event *event)
2334{
2335 unsigned long addr = (unsigned long)event;
2336
2337 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
2338}
2339
2340static void rb_inc_iter(struct ring_buffer_iter *iter)
2341{
2342 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2343
2344 /*
2345 * The iterator could be on the reader page (it starts there).
2346 * But the head could have moved, since the reader was
2347 * found. Check for this case and assign the iterator
2348 * to the head page instead of next.
2349 */
2350 if (iter->head_page == cpu_buffer->reader_page)
2351 iter->head_page = rb_set_head_page(cpu_buffer);
2352 else
2353 rb_inc_page(&iter->head_page);
2354
2355 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2356 iter->head = 0;
2357 iter->next_event = 0;
2358}
2359
2360/*
2361 * rb_handle_head_page - writer hit the head page
2362 *
2363 * Returns: +1 to retry page
2364 * 0 to continue
2365 * -1 on error
2366 */
2367static int
2368rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2369 struct buffer_page *tail_page,
2370 struct buffer_page *next_page)
2371{
2372 struct buffer_page *new_head;
2373 int entries;
2374 int type;
2375 int ret;
2376
2377 entries = rb_page_entries(next_page);
2378
2379 /*
2380 * The hard part is here. We need to move the head
2381 * forward, and protect against both readers on
2382 * other CPUs and writers coming in via interrupts.
2383 */
2384 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2385 RB_PAGE_HEAD);
2386
2387 /*
2388 * type can be one of four:
2389 * NORMAL - an interrupt already moved it for us
2390 * HEAD - we are the first to get here.
2391 * UPDATE - we are the interrupt interrupting
2392 * a current move.
2393 * MOVED - a reader on another CPU moved the next
2394 * pointer to its reader page. Give up
2395 * and try again.
2396 */
2397
2398 switch (type) {
2399 case RB_PAGE_HEAD:
2400 /*
2401 * We changed the head to UPDATE, thus
2402 * it is our responsibility to update
2403 * the counters.
2404 */
2405 local_add(entries, &cpu_buffer->overrun);
2406 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2407
2408 /*
2409 * The entries will be zeroed out when we move the
2410 * tail page.
2411 */
2412
2413 /* still more to do */
2414 break;
2415
2416 case RB_PAGE_UPDATE:
2417 /*
2418 * This is an interrupt that interrupt the
2419 * previous update. Still more to do.
2420 */
2421 break;
2422 case RB_PAGE_NORMAL:
2423 /*
2424 * An interrupt came in before the update
2425 * and processed this for us.
2426 * Nothing left to do.
2427 */
2428 return 1;
2429 case RB_PAGE_MOVED:
2430 /*
2431 * The reader is on another CPU and just did
2432 * a swap with our next_page.
2433 * Try again.
2434 */
2435 return 1;
2436 default:
2437 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2438 return -1;
2439 }
2440
2441 /*
2442 * Now that we are here, the old head pointer is
2443 * set to UPDATE. This will keep the reader from
2444 * swapping the head page with the reader page.
2445 * The reader (on another CPU) will spin till
2446 * we are finished.
2447 *
2448 * We just need to protect against interrupts
2449 * doing the job. We will set the next pointer
2450 * to HEAD. After that, we set the old pointer
2451 * to NORMAL, but only if it was HEAD before.
2452 * otherwise we are an interrupt, and only
2453 * want the outer most commit to reset it.
2454 */
2455 new_head = next_page;
2456 rb_inc_page(&new_head);
2457
2458 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2459 RB_PAGE_NORMAL);
2460
2461 /*
2462 * Valid returns are:
2463 * HEAD - an interrupt came in and already set it.
2464 * NORMAL - One of two things:
2465 * 1) We really set it.
2466 * 2) A bunch of interrupts came in and moved
2467 * the page forward again.
2468 */
2469 switch (ret) {
2470 case RB_PAGE_HEAD:
2471 case RB_PAGE_NORMAL:
2472 /* OK */
2473 break;
2474 default:
2475 RB_WARN_ON(cpu_buffer, 1);
2476 return -1;
2477 }
2478
2479 /*
2480 * It is possible that an interrupt came in,
2481 * set the head up, then more interrupts came in
2482 * and moved it again. When we get back here,
2483 * the page would have been set to NORMAL but we
2484 * just set it back to HEAD.
2485 *
2486 * How do you detect this? Well, if that happened
2487 * the tail page would have moved.
2488 */
2489 if (ret == RB_PAGE_NORMAL) {
2490 struct buffer_page *buffer_tail_page;
2491
2492 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2493 /*
2494 * If the tail had moved passed next, then we need
2495 * to reset the pointer.
2496 */
2497 if (buffer_tail_page != tail_page &&
2498 buffer_tail_page != next_page)
2499 rb_head_page_set_normal(cpu_buffer, new_head,
2500 next_page,
2501 RB_PAGE_HEAD);
2502 }
2503
2504 /*
2505 * If this was the outer most commit (the one that
2506 * changed the original pointer from HEAD to UPDATE),
2507 * then it is up to us to reset it to NORMAL.
2508 */
2509 if (type == RB_PAGE_HEAD) {
2510 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2511 tail_page,
2512 RB_PAGE_UPDATE);
2513 if (RB_WARN_ON(cpu_buffer,
2514 ret != RB_PAGE_UPDATE))
2515 return -1;
2516 }
2517
2518 return 0;
2519}
2520
2521static inline void
2522rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2523 unsigned long tail, struct rb_event_info *info)
2524{
2525 struct buffer_page *tail_page = info->tail_page;
2526 struct ring_buffer_event *event;
2527 unsigned long length = info->length;
2528
2529 /*
2530 * Only the event that crossed the page boundary
2531 * must fill the old tail_page with padding.
2532 */
2533 if (tail >= BUF_PAGE_SIZE) {
2534 /*
2535 * If the page was filled, then we still need
2536 * to update the real_end. Reset it to zero
2537 * and the reader will ignore it.
2538 */
2539 if (tail == BUF_PAGE_SIZE)
2540 tail_page->real_end = 0;
2541
2542 local_sub(length, &tail_page->write);
2543 return;
2544 }
2545
2546 event = __rb_page_index(tail_page, tail);
2547
2548 /* account for padding bytes */
2549 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2550
2551 /*
2552 * Save the original length to the meta data.
2553 * This will be used by the reader to add lost event
2554 * counter.
2555 */
2556 tail_page->real_end = tail;
2557
2558 /*
2559 * If this event is bigger than the minimum size, then
2560 * we need to be careful that we don't subtract the
2561 * write counter enough to allow another writer to slip
2562 * in on this page.
2563 * We put in a discarded commit instead, to make sure
2564 * that this space is not used again.
2565 *
2566 * If we are less than the minimum size, we don't need to
2567 * worry about it.
2568 */
2569 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2570 /* No room for any events */
2571
2572 /* Mark the rest of the page with padding */
2573 rb_event_set_padding(event);
2574
2575 /* Set the write back to the previous setting */
2576 local_sub(length, &tail_page->write);
2577 return;
2578 }
2579
2580 /* Put in a discarded event */
2581 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2582 event->type_len = RINGBUF_TYPE_PADDING;
2583 /* time delta must be non zero */
2584 event->time_delta = 1;
2585
2586 /* Set write to end of buffer */
2587 length = (tail + length) - BUF_PAGE_SIZE;
2588 local_sub(length, &tail_page->write);
2589}
2590
2591static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2592
2593/*
2594 * This is the slow path, force gcc not to inline it.
2595 */
2596static noinline struct ring_buffer_event *
2597rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2598 unsigned long tail, struct rb_event_info *info)
2599{
2600 struct buffer_page *tail_page = info->tail_page;
2601 struct buffer_page *commit_page = cpu_buffer->commit_page;
2602 struct trace_buffer *buffer = cpu_buffer->buffer;
2603 struct buffer_page *next_page;
2604 int ret;
2605
2606 next_page = tail_page;
2607
2608 rb_inc_page(&next_page);
2609
2610 /*
2611 * If for some reason, we had an interrupt storm that made
2612 * it all the way around the buffer, bail, and warn
2613 * about it.
2614 */
2615 if (unlikely(next_page == commit_page)) {
2616 local_inc(&cpu_buffer->commit_overrun);
2617 goto out_reset;
2618 }
2619
2620 /*
2621 * This is where the fun begins!
2622 *
2623 * We are fighting against races between a reader that
2624 * could be on another CPU trying to swap its reader
2625 * page with the buffer head.
2626 *
2627 * We are also fighting against interrupts coming in and
2628 * moving the head or tail on us as well.
2629 *
2630 * If the next page is the head page then we have filled
2631 * the buffer, unless the commit page is still on the
2632 * reader page.
2633 */
2634 if (rb_is_head_page(next_page, &tail_page->list)) {
2635
2636 /*
2637 * If the commit is not on the reader page, then
2638 * move the header page.
2639 */
2640 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2641 /*
2642 * If we are not in overwrite mode,
2643 * this is easy, just stop here.
2644 */
2645 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2646 local_inc(&cpu_buffer->dropped_events);
2647 goto out_reset;
2648 }
2649
2650 ret = rb_handle_head_page(cpu_buffer,
2651 tail_page,
2652 next_page);
2653 if (ret < 0)
2654 goto out_reset;
2655 if (ret)
2656 goto out_again;
2657 } else {
2658 /*
2659 * We need to be careful here too. The
2660 * commit page could still be on the reader
2661 * page. We could have a small buffer, and
2662 * have filled up the buffer with events
2663 * from interrupts and such, and wrapped.
2664 *
2665 * Note, if the tail page is also on the
2666 * reader_page, we let it move out.
2667 */
2668 if (unlikely((cpu_buffer->commit_page !=
2669 cpu_buffer->tail_page) &&
2670 (cpu_buffer->commit_page ==
2671 cpu_buffer->reader_page))) {
2672 local_inc(&cpu_buffer->commit_overrun);
2673 goto out_reset;
2674 }
2675 }
2676 }
2677
2678 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2679
2680 out_again:
2681
2682 rb_reset_tail(cpu_buffer, tail, info);
2683
2684 /* Commit what we have for now. */
2685 rb_end_commit(cpu_buffer);
2686 /* rb_end_commit() decs committing */
2687 local_inc(&cpu_buffer->committing);
2688
2689 /* fail and let the caller try again */
2690 return ERR_PTR(-EAGAIN);
2691
2692 out_reset:
2693 /* reset write */
2694 rb_reset_tail(cpu_buffer, tail, info);
2695
2696 return NULL;
2697}
2698
2699/* Slow path */
2700static struct ring_buffer_event *
2701rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2702{
2703 if (abs)
2704 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2705 else
2706 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2707
2708 /* Not the first event on the page, or not delta? */
2709 if (abs || rb_event_index(event)) {
2710 event->time_delta = delta & TS_MASK;
2711 event->array[0] = delta >> TS_SHIFT;
2712 } else {
2713 /* nope, just zero it */
2714 event->time_delta = 0;
2715 event->array[0] = 0;
2716 }
2717
2718 return skip_time_extend(event);
2719}
2720
2721#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2722static inline bool sched_clock_stable(void)
2723{
2724 return true;
2725}
2726#endif
2727
2728static void
2729rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2730 struct rb_event_info *info)
2731{
2732 u64 write_stamp;
2733
2734 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2735 (unsigned long long)info->delta,
2736 (unsigned long long)info->ts,
2737 (unsigned long long)info->before,
2738 (unsigned long long)info->after,
2739 (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
2740 sched_clock_stable() ? "" :
2741 "If you just came from a suspend/resume,\n"
2742 "please switch to the trace global clock:\n"
2743 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2744 "or add trace_clock=global to the kernel command line\n");
2745}
2746
2747static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2748 struct ring_buffer_event **event,
2749 struct rb_event_info *info,
2750 u64 *delta,
2751 unsigned int *length)
2752{
2753 bool abs = info->add_timestamp &
2754 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2755
2756 if (unlikely(info->delta > (1ULL << 59))) {
2757 /* did the clock go backwards */
2758 if (info->before == info->after && info->before > info->ts) {
2759 /* not interrupted */
2760 static int once;
2761
2762 /*
2763 * This is possible with a recalibrating of the TSC.
2764 * Do not produce a call stack, but just report it.
2765 */
2766 if (!once) {
2767 once++;
2768 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2769 info->before, info->ts);
2770 }
2771 } else
2772 rb_check_timestamp(cpu_buffer, info);
2773 if (!abs)
2774 info->delta = 0;
2775 }
2776 *event = rb_add_time_stamp(*event, info->delta, abs);
2777 *length -= RB_LEN_TIME_EXTEND;
2778 *delta = 0;
2779}
2780
2781/**
2782 * rb_update_event - update event type and data
2783 * @cpu_buffer: The per cpu buffer of the @event
2784 * @event: the event to update
2785 * @info: The info to update the @event with (contains length and delta)
2786 *
2787 * Update the type and data fields of the @event. The length
2788 * is the actual size that is written to the ring buffer,
2789 * and with this, we can determine what to place into the
2790 * data field.
2791 */
2792static void
2793rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2794 struct ring_buffer_event *event,
2795 struct rb_event_info *info)
2796{
2797 unsigned length = info->length;
2798 u64 delta = info->delta;
2799 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2800
2801 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2802 cpu_buffer->event_stamp[nest] = info->ts;
2803
2804 /*
2805 * If we need to add a timestamp, then we
2806 * add it to the start of the reserved space.
2807 */
2808 if (unlikely(info->add_timestamp))
2809 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2810
2811 event->time_delta = delta;
2812 length -= RB_EVNT_HDR_SIZE;
2813 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2814 event->type_len = 0;
2815 event->array[0] = length;
2816 } else
2817 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2818}
2819
2820static unsigned rb_calculate_event_length(unsigned length)
2821{
2822 struct ring_buffer_event event; /* Used only for sizeof array */
2823
2824 /* zero length can cause confusions */
2825 if (!length)
2826 length++;
2827
2828 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2829 length += sizeof(event.array[0]);
2830
2831 length += RB_EVNT_HDR_SIZE;
2832 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2833
2834 /*
2835 * In case the time delta is larger than the 27 bits for it
2836 * in the header, we need to add a timestamp. If another
2837 * event comes in when trying to discard this one to increase
2838 * the length, then the timestamp will be added in the allocated
2839 * space of this event. If length is bigger than the size needed
2840 * for the TIME_EXTEND, then padding has to be used. The events
2841 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2842 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2843 * As length is a multiple of 4, we only need to worry if it
2844 * is 12 (RB_LEN_TIME_EXTEND + 4).
2845 */
2846 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2847 length += RB_ALIGNMENT;
2848
2849 return length;
2850}
2851
2852static u64 rb_time_delta(struct ring_buffer_event *event)
2853{
2854 switch (event->type_len) {
2855 case RINGBUF_TYPE_PADDING:
2856 return 0;
2857
2858 case RINGBUF_TYPE_TIME_EXTEND:
2859 return rb_event_time_stamp(event);
2860
2861 case RINGBUF_TYPE_TIME_STAMP:
2862 return 0;
2863
2864 case RINGBUF_TYPE_DATA:
2865 return event->time_delta;
2866 default:
2867 return 0;
2868 }
2869}
2870
2871static inline int
2872rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2873 struct ring_buffer_event *event)
2874{
2875 unsigned long new_index, old_index;
2876 struct buffer_page *bpage;
2877 unsigned long index;
2878 unsigned long addr;
2879 u64 write_stamp;
2880 u64 delta;
2881
2882 new_index = rb_event_index(event);
2883 old_index = new_index + rb_event_ts_length(event);
2884 addr = (unsigned long)event;
2885 addr &= PAGE_MASK;
2886
2887 bpage = READ_ONCE(cpu_buffer->tail_page);
2888
2889 delta = rb_time_delta(event);
2890
2891 if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
2892 return 0;
2893
2894 /* Make sure the write stamp is read before testing the location */
2895 barrier();
2896
2897 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2898 unsigned long write_mask =
2899 local_read(&bpage->write) & ~RB_WRITE_MASK;
2900 unsigned long event_length = rb_event_length(event);
2901
2902 /* Something came in, can't discard */
2903 if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
2904 write_stamp, write_stamp - delta))
2905 return 0;
2906
2907 /*
2908 * It's possible that the event time delta is zero
2909 * (has the same time stamp as the previous event)
2910 * in which case write_stamp and before_stamp could
2911 * be the same. In such a case, force before_stamp
2912 * to be different than write_stamp. It doesn't
2913 * matter what it is, as long as its different.
2914 */
2915 if (!delta)
2916 rb_time_set(&cpu_buffer->before_stamp, 0);
2917
2918 /*
2919 * If an event were to come in now, it would see that the
2920 * write_stamp and the before_stamp are different, and assume
2921 * that this event just added itself before updating
2922 * the write stamp. The interrupting event will fix the
2923 * write stamp for us, and use the before stamp as its delta.
2924 */
2925
2926 /*
2927 * This is on the tail page. It is possible that
2928 * a write could come in and move the tail page
2929 * and write to the next page. That is fine
2930 * because we just shorten what is on this page.
2931 */
2932 old_index += write_mask;
2933 new_index += write_mask;
2934 index = local_cmpxchg(&bpage->write, old_index, new_index);
2935 if (index == old_index) {
2936 /* update counters */
2937 local_sub(event_length, &cpu_buffer->entries_bytes);
2938 return 1;
2939 }
2940 }
2941
2942 /* could not discard */
2943 return 0;
2944}
2945
2946static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2947{
2948 local_inc(&cpu_buffer->committing);
2949 local_inc(&cpu_buffer->commits);
2950}
2951
2952static __always_inline void
2953rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2954{
2955 unsigned long max_count;
2956
2957 /*
2958 * We only race with interrupts and NMIs on this CPU.
2959 * If we own the commit event, then we can commit
2960 * all others that interrupted us, since the interruptions
2961 * are in stack format (they finish before they come
2962 * back to us). This allows us to do a simple loop to
2963 * assign the commit to the tail.
2964 */
2965 again:
2966 max_count = cpu_buffer->nr_pages * 100;
2967
2968 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2969 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2970 return;
2971 if (RB_WARN_ON(cpu_buffer,
2972 rb_is_reader_page(cpu_buffer->tail_page)))
2973 return;
2974 local_set(&cpu_buffer->commit_page->page->commit,
2975 rb_page_write(cpu_buffer->commit_page));
2976 rb_inc_page(&cpu_buffer->commit_page);
2977 /* add barrier to keep gcc from optimizing too much */
2978 barrier();
2979 }
2980 while (rb_commit_index(cpu_buffer) !=
2981 rb_page_write(cpu_buffer->commit_page)) {
2982
2983 local_set(&cpu_buffer->commit_page->page->commit,
2984 rb_page_write(cpu_buffer->commit_page));
2985 RB_WARN_ON(cpu_buffer,
2986 local_read(&cpu_buffer->commit_page->page->commit) &
2987 ~RB_WRITE_MASK);
2988 barrier();
2989 }
2990
2991 /* again, keep gcc from optimizing */
2992 barrier();
2993
2994 /*
2995 * If an interrupt came in just after the first while loop
2996 * and pushed the tail page forward, we will be left with
2997 * a dangling commit that will never go forward.
2998 */
2999 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3000 goto again;
3001}
3002
3003static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3004{
3005 unsigned long commits;
3006
3007 if (RB_WARN_ON(cpu_buffer,
3008 !local_read(&cpu_buffer->committing)))
3009 return;
3010
3011 again:
3012 commits = local_read(&cpu_buffer->commits);
3013 /* synchronize with interrupts */
3014 barrier();
3015 if (local_read(&cpu_buffer->committing) == 1)
3016 rb_set_commit_to_write(cpu_buffer);
3017
3018 local_dec(&cpu_buffer->committing);
3019
3020 /* synchronize with interrupts */
3021 barrier();
3022
3023 /*
3024 * Need to account for interrupts coming in between the
3025 * updating of the commit page and the clearing of the
3026 * committing counter.
3027 */
3028 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3029 !local_read(&cpu_buffer->committing)) {
3030 local_inc(&cpu_buffer->committing);
3031 goto again;
3032 }
3033}
3034
3035static inline void rb_event_discard(struct ring_buffer_event *event)
3036{
3037 if (extended_time(event))
3038 event = skip_time_extend(event);
3039
3040 /* array[0] holds the actual length for the discarded event */
3041 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3042 event->type_len = RINGBUF_TYPE_PADDING;
3043 /* time delta must be non zero */
3044 if (!event->time_delta)
3045 event->time_delta = 1;
3046}
3047
3048static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
3049 struct ring_buffer_event *event)
3050{
3051 local_inc(&cpu_buffer->entries);
3052 rb_end_commit(cpu_buffer);
3053}
3054
3055static __always_inline void
3056rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3057{
3058 size_t nr_pages;
3059 size_t dirty;
3060 size_t full;
3061
3062 if (buffer->irq_work.waiters_pending) {
3063 buffer->irq_work.waiters_pending = false;
3064 /* irq_work_queue() supplies it's own memory barriers */
3065 irq_work_queue(&buffer->irq_work.work);
3066 }
3067
3068 if (cpu_buffer->irq_work.waiters_pending) {
3069 cpu_buffer->irq_work.waiters_pending = false;
3070 /* irq_work_queue() supplies it's own memory barriers */
3071 irq_work_queue(&cpu_buffer->irq_work.work);
3072 }
3073
3074 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3075 return;
3076
3077 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3078 return;
3079
3080 if (!cpu_buffer->irq_work.full_waiters_pending)
3081 return;
3082
3083 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3084
3085 full = cpu_buffer->shortest_full;
3086 nr_pages = cpu_buffer->nr_pages;
3087 dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
3088 if (full && nr_pages && (dirty * 100) <= full * nr_pages)
3089 return;
3090
3091 cpu_buffer->irq_work.wakeup_full = true;
3092 cpu_buffer->irq_work.full_waiters_pending = false;
3093 /* irq_work_queue() supplies it's own memory barriers */
3094 irq_work_queue(&cpu_buffer->irq_work.work);
3095}
3096
3097#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3098# define do_ring_buffer_record_recursion() \
3099 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3100#else
3101# define do_ring_buffer_record_recursion() do { } while (0)
3102#endif
3103
3104/*
3105 * The lock and unlock are done within a preempt disable section.
3106 * The current_context per_cpu variable can only be modified
3107 * by the current task between lock and unlock. But it can
3108 * be modified more than once via an interrupt. To pass this
3109 * information from the lock to the unlock without having to
3110 * access the 'in_interrupt()' functions again (which do show
3111 * a bit of overhead in something as critical as function tracing,
3112 * we use a bitmask trick.
3113 *
3114 * bit 1 = NMI context
3115 * bit 2 = IRQ context
3116 * bit 3 = SoftIRQ context
3117 * bit 4 = normal context.
3118 *
3119 * This works because this is the order of contexts that can
3120 * preempt other contexts. A SoftIRQ never preempts an IRQ
3121 * context.
3122 *
3123 * When the context is determined, the corresponding bit is
3124 * checked and set (if it was set, then a recursion of that context
3125 * happened).
3126 *
3127 * On unlock, we need to clear this bit. To do so, just subtract
3128 * 1 from the current_context and AND it to itself.
3129 *
3130 * (binary)
3131 * 101 - 1 = 100
3132 * 101 & 100 = 100 (clearing bit zero)
3133 *
3134 * 1010 - 1 = 1001
3135 * 1010 & 1001 = 1000 (clearing bit 1)
3136 *
3137 * The least significant bit can be cleared this way, and it
3138 * just so happens that it is the same bit corresponding to
3139 * the current context.
3140 *
3141 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3142 * is set when a recursion is detected at the current context, and if
3143 * the TRANSITION bit is already set, it will fail the recursion.
3144 * This is needed because there's a lag between the changing of
3145 * interrupt context and updating the preempt count. In this case,
3146 * a false positive will be found. To handle this, one extra recursion
3147 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3148 * bit is already set, then it is considered a recursion and the function
3149 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3150 *
3151 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3152 * to be cleared. Even if it wasn't the context that set it. That is,
3153 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3154 * is called before preempt_count() is updated, since the check will
3155 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3156 * NMI then comes in, it will set the NMI bit, but when the NMI code
3157 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3158 * and leave the NMI bit set. But this is fine, because the interrupt
3159 * code that set the TRANSITION bit will then clear the NMI bit when it
3160 * calls trace_recursive_unlock(). If another NMI comes in, it will
3161 * set the TRANSITION bit and continue.
3162 *
3163 * Note: The TRANSITION bit only handles a single transition between context.
3164 */
3165
3166static __always_inline int
3167trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3168{
3169 unsigned int val = cpu_buffer->current_context;
3170 unsigned long pc = preempt_count();
3171 int bit;
3172
3173 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
3174 bit = RB_CTX_NORMAL;
3175 else
3176 bit = pc & NMI_MASK ? RB_CTX_NMI :
3177 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
3178
3179 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3180 /*
3181 * It is possible that this was called by transitioning
3182 * between interrupt context, and preempt_count() has not
3183 * been updated yet. In this case, use the TRANSITION bit.
3184 */
3185 bit = RB_CTX_TRANSITION;
3186 if (val & (1 << (bit + cpu_buffer->nest))) {
3187 do_ring_buffer_record_recursion();
3188 return 1;
3189 }
3190 }
3191
3192 val |= (1 << (bit + cpu_buffer->nest));
3193 cpu_buffer->current_context = val;
3194
3195 return 0;
3196}
3197
3198static __always_inline void
3199trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3200{
3201 cpu_buffer->current_context &=
3202 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3203}
3204
3205/* The recursive locking above uses 5 bits */
3206#define NESTED_BITS 5
3207
3208/**
3209 * ring_buffer_nest_start - Allow to trace while nested
3210 * @buffer: The ring buffer to modify
3211 *
3212 * The ring buffer has a safety mechanism to prevent recursion.
3213 * But there may be a case where a trace needs to be done while
3214 * tracing something else. In this case, calling this function
3215 * will allow this function to nest within a currently active
3216 * ring_buffer_lock_reserve().
3217 *
3218 * Call this function before calling another ring_buffer_lock_reserve() and
3219 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3220 */
3221void ring_buffer_nest_start(struct trace_buffer *buffer)
3222{
3223 struct ring_buffer_per_cpu *cpu_buffer;
3224 int cpu;
3225
3226 /* Enabled by ring_buffer_nest_end() */
3227 preempt_disable_notrace();
3228 cpu = raw_smp_processor_id();
3229 cpu_buffer = buffer->buffers[cpu];
3230 /* This is the shift value for the above recursive locking */
3231 cpu_buffer->nest += NESTED_BITS;
3232}
3233
3234/**
3235 * ring_buffer_nest_end - Allow to trace while nested
3236 * @buffer: The ring buffer to modify
3237 *
3238 * Must be called after ring_buffer_nest_start() and after the
3239 * ring_buffer_unlock_commit().
3240 */
3241void ring_buffer_nest_end(struct trace_buffer *buffer)
3242{
3243 struct ring_buffer_per_cpu *cpu_buffer;
3244 int cpu;
3245
3246 /* disabled by ring_buffer_nest_start() */
3247 cpu = raw_smp_processor_id();
3248 cpu_buffer = buffer->buffers[cpu];
3249 /* This is the shift value for the above recursive locking */
3250 cpu_buffer->nest -= NESTED_BITS;
3251 preempt_enable_notrace();
3252}
3253
3254/**
3255 * ring_buffer_unlock_commit - commit a reserved
3256 * @buffer: The buffer to commit to
3257 * @event: The event pointer to commit.
3258 *
3259 * This commits the data to the ring buffer, and releases any locks held.
3260 *
3261 * Must be paired with ring_buffer_lock_reserve.
3262 */
3263int ring_buffer_unlock_commit(struct trace_buffer *buffer,
3264 struct ring_buffer_event *event)
3265{
3266 struct ring_buffer_per_cpu *cpu_buffer;
3267 int cpu = raw_smp_processor_id();
3268
3269 cpu_buffer = buffer->buffers[cpu];
3270
3271 rb_commit(cpu_buffer, event);
3272
3273 rb_wakeups(buffer, cpu_buffer);
3274
3275 trace_recursive_unlock(cpu_buffer);
3276
3277 preempt_enable_notrace();
3278
3279 return 0;
3280}
3281EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3282
3283/* Special value to validate all deltas on a page. */
3284#define CHECK_FULL_PAGE 1L
3285
3286#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3287static void dump_buffer_page(struct buffer_data_page *bpage,
3288 struct rb_event_info *info,
3289 unsigned long tail)
3290{
3291 struct ring_buffer_event *event;
3292 u64 ts, delta;
3293 int e;
3294
3295 ts = bpage->time_stamp;
3296 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3297
3298 for (e = 0; e < tail; e += rb_event_length(event)) {
3299
3300 event = (struct ring_buffer_event *)(bpage->data + e);
3301
3302 switch (event->type_len) {
3303
3304 case RINGBUF_TYPE_TIME_EXTEND:
3305 delta = rb_event_time_stamp(event);
3306 ts += delta;
3307 pr_warn(" [%lld] delta:%lld TIME EXTEND\n", ts, delta);
3308 break;
3309
3310 case RINGBUF_TYPE_TIME_STAMP:
3311 delta = rb_event_time_stamp(event);
3312 ts = delta;
3313 pr_warn(" [%lld] absolute:%lld TIME STAMP\n", ts, delta);
3314 break;
3315
3316 case RINGBUF_TYPE_PADDING:
3317 ts += event->time_delta;
3318 pr_warn(" [%lld] delta:%d PADDING\n", ts, event->time_delta);
3319 break;
3320
3321 case RINGBUF_TYPE_DATA:
3322 ts += event->time_delta;
3323 pr_warn(" [%lld] delta:%d\n", ts, event->time_delta);
3324 break;
3325
3326 default:
3327 break;
3328 }
3329 }
3330}
3331
3332static DEFINE_PER_CPU(atomic_t, checking);
3333static atomic_t ts_dump;
3334
3335/*
3336 * Check if the current event time stamp matches the deltas on
3337 * the buffer page.
3338 */
3339static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3340 struct rb_event_info *info,
3341 unsigned long tail)
3342{
3343 struct ring_buffer_event *event;
3344 struct buffer_data_page *bpage;
3345 u64 ts, delta;
3346 bool full = false;
3347 int e;
3348
3349 bpage = info->tail_page->page;
3350
3351 if (tail == CHECK_FULL_PAGE) {
3352 full = true;
3353 tail = local_read(&bpage->commit);
3354 } else if (info->add_timestamp &
3355 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3356 /* Ignore events with absolute time stamps */
3357 return;
3358 }
3359
3360 /*
3361 * Do not check the first event (skip possible extends too).
3362 * Also do not check if previous events have not been committed.
3363 */
3364 if (tail <= 8 || tail > local_read(&bpage->commit))
3365 return;
3366
3367 /*
3368 * If this interrupted another event,
3369 */
3370 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3371 goto out;
3372
3373 ts = bpage->time_stamp;
3374
3375 for (e = 0; e < tail; e += rb_event_length(event)) {
3376
3377 event = (struct ring_buffer_event *)(bpage->data + e);
3378
3379 switch (event->type_len) {
3380
3381 case RINGBUF_TYPE_TIME_EXTEND:
3382 delta = rb_event_time_stamp(event);
3383 ts += delta;
3384 break;
3385
3386 case RINGBUF_TYPE_TIME_STAMP:
3387 delta = rb_event_time_stamp(event);
3388 ts = delta;
3389 break;
3390
3391 case RINGBUF_TYPE_PADDING:
3392 if (event->time_delta == 1)
3393 break;
3394 fallthrough;
3395 case RINGBUF_TYPE_DATA:
3396 ts += event->time_delta;
3397 break;
3398
3399 default:
3400 RB_WARN_ON(cpu_buffer, 1);
3401 }
3402 }
3403 if ((full && ts > info->ts) ||
3404 (!full && ts + info->delta != info->ts)) {
3405 /* If another report is happening, ignore this one */
3406 if (atomic_inc_return(&ts_dump) != 1) {
3407 atomic_dec(&ts_dump);
3408 goto out;
3409 }
3410 atomic_inc(&cpu_buffer->record_disabled);
3411 /* There's some cases in boot up that this can happen */
3412 WARN_ON_ONCE(system_state != SYSTEM_BOOTING);
3413 pr_warn("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s\n",
3414 cpu_buffer->cpu,
3415 ts + info->delta, info->ts, info->delta,
3416 info->before, info->after,
3417 full ? " (full)" : "");
3418 dump_buffer_page(bpage, info, tail);
3419 atomic_dec(&ts_dump);
3420 /* Do not re-enable checking */
3421 return;
3422 }
3423out:
3424 atomic_dec(this_cpu_ptr(&checking));
3425}
3426#else
3427static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3428 struct rb_event_info *info,
3429 unsigned long tail)
3430{
3431}
3432#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3433
3434static struct ring_buffer_event *
3435__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3436 struct rb_event_info *info)
3437{
3438 struct ring_buffer_event *event;
3439 struct buffer_page *tail_page;
3440 unsigned long tail, write, w;
3441 bool a_ok;
3442 bool b_ok;
3443
3444 /* Don't let the compiler play games with cpu_buffer->tail_page */
3445 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3446
3447 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3448 barrier();
3449 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3450 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3451 barrier();
3452 info->ts = rb_time_stamp(cpu_buffer->buffer);
3453
3454 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3455 info->delta = info->ts;
3456 } else {
3457 /*
3458 * If interrupting an event time update, we may need an
3459 * absolute timestamp.
3460 * Don't bother if this is the start of a new page (w == 0).
3461 */
3462 if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
3463 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3464 info->length += RB_LEN_TIME_EXTEND;
3465 } else {
3466 info->delta = info->ts - info->after;
3467 if (unlikely(test_time_stamp(info->delta))) {
3468 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3469 info->length += RB_LEN_TIME_EXTEND;
3470 }
3471 }
3472 }
3473
3474 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3475
3476 /*C*/ write = local_add_return(info->length, &tail_page->write);
3477
3478 /* set write to only the index of the write */
3479 write &= RB_WRITE_MASK;
3480
3481 tail = write - info->length;
3482
3483 /* See if we shot pass the end of this buffer page */
3484 if (unlikely(write > BUF_PAGE_SIZE)) {
3485 /* before and after may now different, fix it up*/
3486 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3487 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3488 if (a_ok && b_ok && info->before != info->after)
3489 (void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
3490 info->before, info->after);
3491 if (a_ok && b_ok)
3492 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3493 return rb_move_tail(cpu_buffer, tail, info);
3494 }
3495
3496 if (likely(tail == w)) {
3497 u64 save_before;
3498 bool s_ok;
3499
3500 /* Nothing interrupted us between A and C */
3501 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3502 barrier();
3503 /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
3504 RB_WARN_ON(cpu_buffer, !s_ok);
3505 if (likely(!(info->add_timestamp &
3506 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3507 /* This did not interrupt any time update */
3508 info->delta = info->ts - info->after;
3509 else
3510 /* Just use full timestamp for interrupting event */
3511 info->delta = info->ts;
3512 barrier();
3513 check_buffer(cpu_buffer, info, tail);
3514 if (unlikely(info->ts != save_before)) {
3515 /* SLOW PATH - Interrupted between C and E */
3516
3517 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3518 RB_WARN_ON(cpu_buffer, !a_ok);
3519
3520 /* Write stamp must only go forward */
3521 if (save_before > info->after) {
3522 /*
3523 * We do not care about the result, only that
3524 * it gets updated atomically.
3525 */
3526 (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
3527 info->after, save_before);
3528 }
3529 }
3530 } else {
3531 u64 ts;
3532 /* SLOW PATH - Interrupted between A and C */
3533 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3534 /* Was interrupted before here, write_stamp must be valid */
3535 RB_WARN_ON(cpu_buffer, !a_ok);
3536 ts = rb_time_stamp(cpu_buffer->buffer);
3537 barrier();
3538 /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3539 info->after < ts &&
3540 rb_time_cmpxchg(&cpu_buffer->write_stamp,
3541 info->after, ts)) {
3542 /* Nothing came after this event between C and E */
3543 info->delta = ts - info->after;
3544 } else {
3545 /*
3546 * Interrupted between C and E:
3547 * Lost the previous events time stamp. Just set the
3548 * delta to zero, and this will be the same time as
3549 * the event this event interrupted. And the events that
3550 * came after this will still be correct (as they would
3551 * have built their delta on the previous event.
3552 */
3553 info->delta = 0;
3554 }
3555 info->ts = ts;
3556 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3557 }
3558
3559 /*
3560 * If this is the first commit on the page, then it has the same
3561 * timestamp as the page itself.
3562 */
3563 if (unlikely(!tail && !(info->add_timestamp &
3564 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3565 info->delta = 0;
3566
3567 /* We reserved something on the buffer */
3568
3569 event = __rb_page_index(tail_page, tail);
3570 rb_update_event(cpu_buffer, event, info);
3571
3572 local_inc(&tail_page->entries);
3573
3574 /*
3575 * If this is the first commit on the page, then update
3576 * its timestamp.
3577 */
3578 if (unlikely(!tail))
3579 tail_page->page->time_stamp = info->ts;
3580
3581 /* account for these added bytes */
3582 local_add(info->length, &cpu_buffer->entries_bytes);
3583
3584 return event;
3585}
3586
3587static __always_inline struct ring_buffer_event *
3588rb_reserve_next_event(struct trace_buffer *buffer,
3589 struct ring_buffer_per_cpu *cpu_buffer,
3590 unsigned long length)
3591{
3592 struct ring_buffer_event *event;
3593 struct rb_event_info info;
3594 int nr_loops = 0;
3595 int add_ts_default;
3596
3597 rb_start_commit(cpu_buffer);
3598 /* The commit page can not change after this */
3599
3600#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3601 /*
3602 * Due to the ability to swap a cpu buffer from a buffer
3603 * it is possible it was swapped before we committed.
3604 * (committing stops a swap). We check for it here and
3605 * if it happened, we have to fail the write.
3606 */
3607 barrier();
3608 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3609 local_dec(&cpu_buffer->committing);
3610 local_dec(&cpu_buffer->commits);
3611 return NULL;
3612 }
3613#endif
3614
3615 info.length = rb_calculate_event_length(length);
3616
3617 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3618 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3619 info.length += RB_LEN_TIME_EXTEND;
3620 } else {
3621 add_ts_default = RB_ADD_STAMP_NONE;
3622 }
3623
3624 again:
3625 info.add_timestamp = add_ts_default;
3626 info.delta = 0;
3627
3628 /*
3629 * We allow for interrupts to reenter here and do a trace.
3630 * If one does, it will cause this original code to loop
3631 * back here. Even with heavy interrupts happening, this
3632 * should only happen a few times in a row. If this happens
3633 * 1000 times in a row, there must be either an interrupt
3634 * storm or we have something buggy.
3635 * Bail!
3636 */
3637 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3638 goto out_fail;
3639
3640 event = __rb_reserve_next(cpu_buffer, &info);
3641
3642 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3643 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3644 info.length -= RB_LEN_TIME_EXTEND;
3645 goto again;
3646 }
3647
3648 if (likely(event))
3649 return event;
3650 out_fail:
3651 rb_end_commit(cpu_buffer);
3652 return NULL;
3653}
3654
3655/**
3656 * ring_buffer_lock_reserve - reserve a part of the buffer
3657 * @buffer: the ring buffer to reserve from
3658 * @length: the length of the data to reserve (excluding event header)
3659 *
3660 * Returns a reserved event on the ring buffer to copy directly to.
3661 * The user of this interface will need to get the body to write into
3662 * and can use the ring_buffer_event_data() interface.
3663 *
3664 * The length is the length of the data needed, not the event length
3665 * which also includes the event header.
3666 *
3667 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3668 * If NULL is returned, then nothing has been allocated or locked.
3669 */
3670struct ring_buffer_event *
3671ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3672{
3673 struct ring_buffer_per_cpu *cpu_buffer;
3674 struct ring_buffer_event *event;
3675 int cpu;
3676
3677 /* If we are tracing schedule, we don't want to recurse */
3678 preempt_disable_notrace();
3679
3680 if (unlikely(atomic_read(&buffer->record_disabled)))
3681 goto out;
3682
3683 cpu = raw_smp_processor_id();
3684
3685 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3686 goto out;
3687
3688 cpu_buffer = buffer->buffers[cpu];
3689
3690 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3691 goto out;
3692
3693 if (unlikely(length > BUF_MAX_DATA_SIZE))
3694 goto out;
3695
3696 if (unlikely(trace_recursive_lock(cpu_buffer)))
3697 goto out;
3698
3699 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3700 if (!event)
3701 goto out_unlock;
3702
3703 return event;
3704
3705 out_unlock:
3706 trace_recursive_unlock(cpu_buffer);
3707 out:
3708 preempt_enable_notrace();
3709 return NULL;
3710}
3711EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3712
3713/*
3714 * Decrement the entries to the page that an event is on.
3715 * The event does not even need to exist, only the pointer
3716 * to the page it is on. This may only be called before the commit
3717 * takes place.
3718 */
3719static inline void
3720rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3721 struct ring_buffer_event *event)
3722{
3723 unsigned long addr = (unsigned long)event;
3724 struct buffer_page *bpage = cpu_buffer->commit_page;
3725 struct buffer_page *start;
3726
3727 addr &= PAGE_MASK;
3728
3729 /* Do the likely case first */
3730 if (likely(bpage->page == (void *)addr)) {
3731 local_dec(&bpage->entries);
3732 return;
3733 }
3734
3735 /*
3736 * Because the commit page may be on the reader page we
3737 * start with the next page and check the end loop there.
3738 */
3739 rb_inc_page(&bpage);
3740 start = bpage;
3741 do {
3742 if (bpage->page == (void *)addr) {
3743 local_dec(&bpage->entries);
3744 return;
3745 }
3746 rb_inc_page(&bpage);
3747 } while (bpage != start);
3748
3749 /* commit not part of this buffer?? */
3750 RB_WARN_ON(cpu_buffer, 1);
3751}
3752
3753/**
3754 * ring_buffer_discard_commit - discard an event that has not been committed
3755 * @buffer: the ring buffer
3756 * @event: non committed event to discard
3757 *
3758 * Sometimes an event that is in the ring buffer needs to be ignored.
3759 * This function lets the user discard an event in the ring buffer
3760 * and then that event will not be read later.
3761 *
3762 * This function only works if it is called before the item has been
3763 * committed. It will try to free the event from the ring buffer
3764 * if another event has not been added behind it.
3765 *
3766 * If another event has been added behind it, it will set the event
3767 * up as discarded, and perform the commit.
3768 *
3769 * If this function is called, do not call ring_buffer_unlock_commit on
3770 * the event.
3771 */
3772void ring_buffer_discard_commit(struct trace_buffer *buffer,
3773 struct ring_buffer_event *event)
3774{
3775 struct ring_buffer_per_cpu *cpu_buffer;
3776 int cpu;
3777
3778 /* The event is discarded regardless */
3779 rb_event_discard(event);
3780
3781 cpu = smp_processor_id();
3782 cpu_buffer = buffer->buffers[cpu];
3783
3784 /*
3785 * This must only be called if the event has not been
3786 * committed yet. Thus we can assume that preemption
3787 * is still disabled.
3788 */
3789 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3790
3791 rb_decrement_entry(cpu_buffer, event);
3792 if (rb_try_to_discard(cpu_buffer, event))
3793 goto out;
3794
3795 out:
3796 rb_end_commit(cpu_buffer);
3797
3798 trace_recursive_unlock(cpu_buffer);
3799
3800 preempt_enable_notrace();
3801
3802}
3803EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3804
3805/**
3806 * ring_buffer_write - write data to the buffer without reserving
3807 * @buffer: The ring buffer to write to.
3808 * @length: The length of the data being written (excluding the event header)
3809 * @data: The data to write to the buffer.
3810 *
3811 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3812 * one function. If you already have the data to write to the buffer, it
3813 * may be easier to simply call this function.
3814 *
3815 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3816 * and not the length of the event which would hold the header.
3817 */
3818int ring_buffer_write(struct trace_buffer *buffer,
3819 unsigned long length,
3820 void *data)
3821{
3822 struct ring_buffer_per_cpu *cpu_buffer;
3823 struct ring_buffer_event *event;
3824 void *body;
3825 int ret = -EBUSY;
3826 int cpu;
3827
3828 preempt_disable_notrace();
3829
3830 if (atomic_read(&buffer->record_disabled))
3831 goto out;
3832
3833 cpu = raw_smp_processor_id();
3834
3835 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3836 goto out;
3837
3838 cpu_buffer = buffer->buffers[cpu];
3839
3840 if (atomic_read(&cpu_buffer->record_disabled))
3841 goto out;
3842
3843 if (length > BUF_MAX_DATA_SIZE)
3844 goto out;
3845
3846 if (unlikely(trace_recursive_lock(cpu_buffer)))
3847 goto out;
3848
3849 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3850 if (!event)
3851 goto out_unlock;
3852
3853 body = rb_event_data(event);
3854
3855 memcpy(body, data, length);
3856
3857 rb_commit(cpu_buffer, event);
3858
3859 rb_wakeups(buffer, cpu_buffer);
3860
3861 ret = 0;
3862
3863 out_unlock:
3864 trace_recursive_unlock(cpu_buffer);
3865
3866 out:
3867 preempt_enable_notrace();
3868
3869 return ret;
3870}
3871EXPORT_SYMBOL_GPL(ring_buffer_write);
3872
3873static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3874{
3875 struct buffer_page *reader = cpu_buffer->reader_page;
3876 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3877 struct buffer_page *commit = cpu_buffer->commit_page;
3878
3879 /* In case of error, head will be NULL */
3880 if (unlikely(!head))
3881 return true;
3882
3883 /* Reader should exhaust content in reader page */
3884 if (reader->read != rb_page_commit(reader))
3885 return false;
3886
3887 /*
3888 * If writers are committing on the reader page, knowing all
3889 * committed content has been read, the ring buffer is empty.
3890 */
3891 if (commit == reader)
3892 return true;
3893
3894 /*
3895 * If writers are committing on a page other than reader page
3896 * and head page, there should always be content to read.
3897 */
3898 if (commit != head)
3899 return false;
3900
3901 /*
3902 * Writers are committing on the head page, we just need
3903 * to care about there're committed data, and the reader will
3904 * swap reader page with head page when it is to read data.
3905 */
3906 return rb_page_commit(commit) == 0;
3907}
3908
3909/**
3910 * ring_buffer_record_disable - stop all writes into the buffer
3911 * @buffer: The ring buffer to stop writes to.
3912 *
3913 * This prevents all writes to the buffer. Any attempt to write
3914 * to the buffer after this will fail and return NULL.
3915 *
3916 * The caller should call synchronize_rcu() after this.
3917 */
3918void ring_buffer_record_disable(struct trace_buffer *buffer)
3919{
3920 atomic_inc(&buffer->record_disabled);
3921}
3922EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3923
3924/**
3925 * ring_buffer_record_enable - enable writes to the buffer
3926 * @buffer: The ring buffer to enable writes
3927 *
3928 * Note, multiple disables will need the same number of enables
3929 * to truly enable the writing (much like preempt_disable).
3930 */
3931void ring_buffer_record_enable(struct trace_buffer *buffer)
3932{
3933 atomic_dec(&buffer->record_disabled);
3934}
3935EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3936
3937/**
3938 * ring_buffer_record_off - stop all writes into the buffer
3939 * @buffer: The ring buffer to stop writes to.
3940 *
3941 * This prevents all writes to the buffer. Any attempt to write
3942 * to the buffer after this will fail and return NULL.
3943 *
3944 * This is different than ring_buffer_record_disable() as
3945 * it works like an on/off switch, where as the disable() version
3946 * must be paired with a enable().
3947 */
3948void ring_buffer_record_off(struct trace_buffer *buffer)
3949{
3950 unsigned int rd;
3951 unsigned int new_rd;
3952
3953 do {
3954 rd = atomic_read(&buffer->record_disabled);
3955 new_rd = rd | RB_BUFFER_OFF;
3956 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3957}
3958EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3959
3960/**
3961 * ring_buffer_record_on - restart writes into the buffer
3962 * @buffer: The ring buffer to start writes to.
3963 *
3964 * This enables all writes to the buffer that was disabled by
3965 * ring_buffer_record_off().
3966 *
3967 * This is different than ring_buffer_record_enable() as
3968 * it works like an on/off switch, where as the enable() version
3969 * must be paired with a disable().
3970 */
3971void ring_buffer_record_on(struct trace_buffer *buffer)
3972{
3973 unsigned int rd;
3974 unsigned int new_rd;
3975
3976 do {
3977 rd = atomic_read(&buffer->record_disabled);
3978 new_rd = rd & ~RB_BUFFER_OFF;
3979 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3980}
3981EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3982
3983/**
3984 * ring_buffer_record_is_on - return true if the ring buffer can write
3985 * @buffer: The ring buffer to see if write is enabled
3986 *
3987 * Returns true if the ring buffer is in a state that it accepts writes.
3988 */
3989bool ring_buffer_record_is_on(struct trace_buffer *buffer)
3990{
3991 return !atomic_read(&buffer->record_disabled);
3992}
3993
3994/**
3995 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3996 * @buffer: The ring buffer to see if write is set enabled
3997 *
3998 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3999 * Note that this does NOT mean it is in a writable state.
4000 *
4001 * It may return true when the ring buffer has been disabled by
4002 * ring_buffer_record_disable(), as that is a temporary disabling of
4003 * the ring buffer.
4004 */
4005bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4006{
4007 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4008}
4009
4010/**
4011 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4012 * @buffer: The ring buffer to stop writes to.
4013 * @cpu: The CPU buffer to stop
4014 *
4015 * This prevents all writes to the buffer. Any attempt to write
4016 * to the buffer after this will fail and return NULL.
4017 *
4018 * The caller should call synchronize_rcu() after this.
4019 */
4020void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4021{
4022 struct ring_buffer_per_cpu *cpu_buffer;
4023
4024 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4025 return;
4026
4027 cpu_buffer = buffer->buffers[cpu];
4028 atomic_inc(&cpu_buffer->record_disabled);
4029}
4030EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4031
4032/**
4033 * ring_buffer_record_enable_cpu - enable writes to the buffer
4034 * @buffer: The ring buffer to enable writes
4035 * @cpu: The CPU to enable.
4036 *
4037 * Note, multiple disables will need the same number of enables
4038 * to truly enable the writing (much like preempt_disable).
4039 */
4040void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4041{
4042 struct ring_buffer_per_cpu *cpu_buffer;
4043
4044 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4045 return;
4046
4047 cpu_buffer = buffer->buffers[cpu];
4048 atomic_dec(&cpu_buffer->record_disabled);
4049}
4050EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4051
4052/*
4053 * The total entries in the ring buffer is the running counter
4054 * of entries entered into the ring buffer, minus the sum of
4055 * the entries read from the ring buffer and the number of
4056 * entries that were overwritten.
4057 */
4058static inline unsigned long
4059rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4060{
4061 return local_read(&cpu_buffer->entries) -
4062 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4063}
4064
4065/**
4066 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4067 * @buffer: The ring buffer
4068 * @cpu: The per CPU buffer to read from.
4069 */
4070u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4071{
4072 unsigned long flags;
4073 struct ring_buffer_per_cpu *cpu_buffer;
4074 struct buffer_page *bpage;
4075 u64 ret = 0;
4076
4077 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4078 return 0;
4079
4080 cpu_buffer = buffer->buffers[cpu];
4081 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4082 /*
4083 * if the tail is on reader_page, oldest time stamp is on the reader
4084 * page
4085 */
4086 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4087 bpage = cpu_buffer->reader_page;
4088 else
4089 bpage = rb_set_head_page(cpu_buffer);
4090 if (bpage)
4091 ret = bpage->page->time_stamp;
4092 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4093
4094 return ret;
4095}
4096EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4097
4098/**
4099 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
4100 * @buffer: The ring buffer
4101 * @cpu: The per CPU buffer to read from.
4102 */
4103unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4104{
4105 struct ring_buffer_per_cpu *cpu_buffer;
4106 unsigned long ret;
4107
4108 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4109 return 0;
4110
4111 cpu_buffer = buffer->buffers[cpu];
4112 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4113
4114 return ret;
4115}
4116EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4117
4118/**
4119 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4120 * @buffer: The ring buffer
4121 * @cpu: The per CPU buffer to get the entries from.
4122 */
4123unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4124{
4125 struct ring_buffer_per_cpu *cpu_buffer;
4126
4127 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4128 return 0;
4129
4130 cpu_buffer = buffer->buffers[cpu];
4131
4132 return rb_num_of_entries(cpu_buffer);
4133}
4134EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4135
4136/**
4137 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4138 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4139 * @buffer: The ring buffer
4140 * @cpu: The per CPU buffer to get the number of overruns from
4141 */
4142unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4143{
4144 struct ring_buffer_per_cpu *cpu_buffer;
4145 unsigned long ret;
4146
4147 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4148 return 0;
4149
4150 cpu_buffer = buffer->buffers[cpu];
4151 ret = local_read(&cpu_buffer->overrun);
4152
4153 return ret;
4154}
4155EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4156
4157/**
4158 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4159 * commits failing due to the buffer wrapping around while there are uncommitted
4160 * events, such as during an interrupt storm.
4161 * @buffer: The ring buffer
4162 * @cpu: The per CPU buffer to get the number of overruns from
4163 */
4164unsigned long
4165ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4166{
4167 struct ring_buffer_per_cpu *cpu_buffer;
4168 unsigned long ret;
4169
4170 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4171 return 0;
4172
4173 cpu_buffer = buffer->buffers[cpu];
4174 ret = local_read(&cpu_buffer->commit_overrun);
4175
4176 return ret;
4177}
4178EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4179
4180/**
4181 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4182 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4183 * @buffer: The ring buffer
4184 * @cpu: The per CPU buffer to get the number of overruns from
4185 */
4186unsigned long
4187ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4188{
4189 struct ring_buffer_per_cpu *cpu_buffer;
4190 unsigned long ret;
4191
4192 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4193 return 0;
4194
4195 cpu_buffer = buffer->buffers[cpu];
4196 ret = local_read(&cpu_buffer->dropped_events);
4197
4198 return ret;
4199}
4200EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4201
4202/**
4203 * ring_buffer_read_events_cpu - get the number of events successfully read
4204 * @buffer: The ring buffer
4205 * @cpu: The per CPU buffer to get the number of events read
4206 */
4207unsigned long
4208ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4209{
4210 struct ring_buffer_per_cpu *cpu_buffer;
4211
4212 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4213 return 0;
4214
4215 cpu_buffer = buffer->buffers[cpu];
4216 return cpu_buffer->read;
4217}
4218EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4219
4220/**
4221 * ring_buffer_entries - get the number of entries in a buffer
4222 * @buffer: The ring buffer
4223 *
4224 * Returns the total number of entries in the ring buffer
4225 * (all CPU entries)
4226 */
4227unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4228{
4229 struct ring_buffer_per_cpu *cpu_buffer;
4230 unsigned long entries = 0;
4231 int cpu;
4232
4233 /* if you care about this being correct, lock the buffer */
4234 for_each_buffer_cpu(buffer, cpu) {
4235 cpu_buffer = buffer->buffers[cpu];
4236 entries += rb_num_of_entries(cpu_buffer);
4237 }
4238
4239 return entries;
4240}
4241EXPORT_SYMBOL_GPL(ring_buffer_entries);
4242
4243/**
4244 * ring_buffer_overruns - get the number of overruns in buffer
4245 * @buffer: The ring buffer
4246 *
4247 * Returns the total number of overruns in the ring buffer
4248 * (all CPU entries)
4249 */
4250unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4251{
4252 struct ring_buffer_per_cpu *cpu_buffer;
4253 unsigned long overruns = 0;
4254 int cpu;
4255
4256 /* if you care about this being correct, lock the buffer */
4257 for_each_buffer_cpu(buffer, cpu) {
4258 cpu_buffer = buffer->buffers[cpu];
4259 overruns += local_read(&cpu_buffer->overrun);
4260 }
4261
4262 return overruns;
4263}
4264EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4265
4266static void rb_iter_reset(struct ring_buffer_iter *iter)
4267{
4268 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4269
4270 /* Iterator usage is expected to have record disabled */
4271 iter->head_page = cpu_buffer->reader_page;
4272 iter->head = cpu_buffer->reader_page->read;
4273 iter->next_event = iter->head;
4274
4275 iter->cache_reader_page = iter->head_page;
4276 iter->cache_read = cpu_buffer->read;
4277
4278 if (iter->head) {
4279 iter->read_stamp = cpu_buffer->read_stamp;
4280 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4281 } else {
4282 iter->read_stamp = iter->head_page->page->time_stamp;
4283 iter->page_stamp = iter->read_stamp;
4284 }
4285}
4286
4287/**
4288 * ring_buffer_iter_reset - reset an iterator
4289 * @iter: The iterator to reset
4290 *
4291 * Resets the iterator, so that it will start from the beginning
4292 * again.
4293 */
4294void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4295{
4296 struct ring_buffer_per_cpu *cpu_buffer;
4297 unsigned long flags;
4298
4299 if (!iter)
4300 return;
4301
4302 cpu_buffer = iter->cpu_buffer;
4303
4304 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4305 rb_iter_reset(iter);
4306 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4307}
4308EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4309
4310/**
4311 * ring_buffer_iter_empty - check if an iterator has no more to read
4312 * @iter: The iterator to check
4313 */
4314int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4315{
4316 struct ring_buffer_per_cpu *cpu_buffer;
4317 struct buffer_page *reader;
4318 struct buffer_page *head_page;
4319 struct buffer_page *commit_page;
4320 struct buffer_page *curr_commit_page;
4321 unsigned commit;
4322 u64 curr_commit_ts;
4323 u64 commit_ts;
4324
4325 cpu_buffer = iter->cpu_buffer;
4326 reader = cpu_buffer->reader_page;
4327 head_page = cpu_buffer->head_page;
4328 commit_page = cpu_buffer->commit_page;
4329 commit_ts = commit_page->page->time_stamp;
4330
4331 /*
4332 * When the writer goes across pages, it issues a cmpxchg which
4333 * is a mb(), which will synchronize with the rmb here.
4334 * (see rb_tail_page_update())
4335 */
4336 smp_rmb();
4337 commit = rb_page_commit(commit_page);
4338 /* We want to make sure that the commit page doesn't change */
4339 smp_rmb();
4340
4341 /* Make sure commit page didn't change */
4342 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4343 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4344
4345 /* If the commit page changed, then there's more data */
4346 if (curr_commit_page != commit_page ||
4347 curr_commit_ts != commit_ts)
4348 return 0;
4349
4350 /* Still racy, as it may return a false positive, but that's OK */
4351 return ((iter->head_page == commit_page && iter->head >= commit) ||
4352 (iter->head_page == reader && commit_page == head_page &&
4353 head_page->read == commit &&
4354 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4355}
4356EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4357
4358static void
4359rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4360 struct ring_buffer_event *event)
4361{
4362 u64 delta;
4363
4364 switch (event->type_len) {
4365 case RINGBUF_TYPE_PADDING:
4366 return;
4367
4368 case RINGBUF_TYPE_TIME_EXTEND:
4369 delta = rb_event_time_stamp(event);
4370 cpu_buffer->read_stamp += delta;
4371 return;
4372
4373 case RINGBUF_TYPE_TIME_STAMP:
4374 delta = rb_event_time_stamp(event);
4375 cpu_buffer->read_stamp = delta;
4376 return;
4377
4378 case RINGBUF_TYPE_DATA:
4379 cpu_buffer->read_stamp += event->time_delta;
4380 return;
4381
4382 default:
4383 RB_WARN_ON(cpu_buffer, 1);
4384 }
4385 return;
4386}
4387
4388static void
4389rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4390 struct ring_buffer_event *event)
4391{
4392 u64 delta;
4393
4394 switch (event->type_len) {
4395 case RINGBUF_TYPE_PADDING:
4396 return;
4397
4398 case RINGBUF_TYPE_TIME_EXTEND:
4399 delta = rb_event_time_stamp(event);
4400 iter->read_stamp += delta;
4401 return;
4402
4403 case RINGBUF_TYPE_TIME_STAMP:
4404 delta = rb_event_time_stamp(event);
4405 iter->read_stamp = delta;
4406 return;
4407
4408 case RINGBUF_TYPE_DATA:
4409 iter->read_stamp += event->time_delta;
4410 return;
4411
4412 default:
4413 RB_WARN_ON(iter->cpu_buffer, 1);
4414 }
4415 return;
4416}
4417
4418static struct buffer_page *
4419rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4420{
4421 struct buffer_page *reader = NULL;
4422 unsigned long overwrite;
4423 unsigned long flags;
4424 int nr_loops = 0;
4425 int ret;
4426
4427 local_irq_save(flags);
4428 arch_spin_lock(&cpu_buffer->lock);
4429
4430 again:
4431 /*
4432 * This should normally only loop twice. But because the
4433 * start of the reader inserts an empty page, it causes
4434 * a case where we will loop three times. There should be no
4435 * reason to loop four times (that I know of).
4436 */
4437 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4438 reader = NULL;
4439 goto out;
4440 }
4441
4442 reader = cpu_buffer->reader_page;
4443
4444 /* If there's more to read, return this page */
4445 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4446 goto out;
4447
4448 /* Never should we have an index greater than the size */
4449 if (RB_WARN_ON(cpu_buffer,
4450 cpu_buffer->reader_page->read > rb_page_size(reader)))
4451 goto out;
4452
4453 /* check if we caught up to the tail */
4454 reader = NULL;
4455 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4456 goto out;
4457
4458 /* Don't bother swapping if the ring buffer is empty */
4459 if (rb_num_of_entries(cpu_buffer) == 0)
4460 goto out;
4461
4462 /*
4463 * Reset the reader page to size zero.
4464 */
4465 local_set(&cpu_buffer->reader_page->write, 0);
4466 local_set(&cpu_buffer->reader_page->entries, 0);
4467 local_set(&cpu_buffer->reader_page->page->commit, 0);
4468 cpu_buffer->reader_page->real_end = 0;
4469
4470 spin:
4471 /*
4472 * Splice the empty reader page into the list around the head.
4473 */
4474 reader = rb_set_head_page(cpu_buffer);
4475 if (!reader)
4476 goto out;
4477 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4478 cpu_buffer->reader_page->list.prev = reader->list.prev;
4479
4480 /*
4481 * cpu_buffer->pages just needs to point to the buffer, it
4482 * has no specific buffer page to point to. Lets move it out
4483 * of our way so we don't accidentally swap it.
4484 */
4485 cpu_buffer->pages = reader->list.prev;
4486
4487 /* The reader page will be pointing to the new head */
4488 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4489
4490 /*
4491 * We want to make sure we read the overruns after we set up our
4492 * pointers to the next object. The writer side does a
4493 * cmpxchg to cross pages which acts as the mb on the writer
4494 * side. Note, the reader will constantly fail the swap
4495 * while the writer is updating the pointers, so this
4496 * guarantees that the overwrite recorded here is the one we
4497 * want to compare with the last_overrun.
4498 */
4499 smp_mb();
4500 overwrite = local_read(&(cpu_buffer->overrun));
4501
4502 /*
4503 * Here's the tricky part.
4504 *
4505 * We need to move the pointer past the header page.
4506 * But we can only do that if a writer is not currently
4507 * moving it. The page before the header page has the
4508 * flag bit '1' set if it is pointing to the page we want.
4509 * but if the writer is in the process of moving it
4510 * than it will be '2' or already moved '0'.
4511 */
4512
4513 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4514
4515 /*
4516 * If we did not convert it, then we must try again.
4517 */
4518 if (!ret)
4519 goto spin;
4520
4521 /*
4522 * Yay! We succeeded in replacing the page.
4523 *
4524 * Now make the new head point back to the reader page.
4525 */
4526 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4527 rb_inc_page(&cpu_buffer->head_page);
4528
4529 local_inc(&cpu_buffer->pages_read);
4530
4531 /* Finally update the reader page to the new head */
4532 cpu_buffer->reader_page = reader;
4533 cpu_buffer->reader_page->read = 0;
4534
4535 if (overwrite != cpu_buffer->last_overrun) {
4536 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4537 cpu_buffer->last_overrun = overwrite;
4538 }
4539
4540 goto again;
4541
4542 out:
4543 /* Update the read_stamp on the first event */
4544 if (reader && reader->read == 0)
4545 cpu_buffer->read_stamp = reader->page->time_stamp;
4546
4547 arch_spin_unlock(&cpu_buffer->lock);
4548 local_irq_restore(flags);
4549
4550 return reader;
4551}
4552
4553static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4554{
4555 struct ring_buffer_event *event;
4556 struct buffer_page *reader;
4557 unsigned length;
4558
4559 reader = rb_get_reader_page(cpu_buffer);
4560
4561 /* This function should not be called when buffer is empty */
4562 if (RB_WARN_ON(cpu_buffer, !reader))
4563 return;
4564
4565 event = rb_reader_event(cpu_buffer);
4566
4567 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4568 cpu_buffer->read++;
4569
4570 rb_update_read_stamp(cpu_buffer, event);
4571
4572 length = rb_event_length(event);
4573 cpu_buffer->reader_page->read += length;
4574}
4575
4576static void rb_advance_iter(struct ring_buffer_iter *iter)
4577{
4578 struct ring_buffer_per_cpu *cpu_buffer;
4579
4580 cpu_buffer = iter->cpu_buffer;
4581
4582 /* If head == next_event then we need to jump to the next event */
4583 if (iter->head == iter->next_event) {
4584 /* If the event gets overwritten again, there's nothing to do */
4585 if (rb_iter_head_event(iter) == NULL)
4586 return;
4587 }
4588
4589 iter->head = iter->next_event;
4590
4591 /*
4592 * Check if we are at the end of the buffer.
4593 */
4594 if (iter->next_event >= rb_page_size(iter->head_page)) {
4595 /* discarded commits can make the page empty */
4596 if (iter->head_page == cpu_buffer->commit_page)
4597 return;
4598 rb_inc_iter(iter);
4599 return;
4600 }
4601
4602 rb_update_iter_read_stamp(iter, iter->event);
4603}
4604
4605static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4606{
4607 return cpu_buffer->lost_events;
4608}
4609
4610static struct ring_buffer_event *
4611rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4612 unsigned long *lost_events)
4613{
4614 struct ring_buffer_event *event;
4615 struct buffer_page *reader;
4616 int nr_loops = 0;
4617
4618 if (ts)
4619 *ts = 0;
4620 again:
4621 /*
4622 * We repeat when a time extend is encountered.
4623 * Since the time extend is always attached to a data event,
4624 * we should never loop more than once.
4625 * (We never hit the following condition more than twice).
4626 */
4627 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4628 return NULL;
4629
4630 reader = rb_get_reader_page(cpu_buffer);
4631 if (!reader)
4632 return NULL;
4633
4634 event = rb_reader_event(cpu_buffer);
4635
4636 switch (event->type_len) {
4637 case RINGBUF_TYPE_PADDING:
4638 if (rb_null_event(event))
4639 RB_WARN_ON(cpu_buffer, 1);
4640 /*
4641 * Because the writer could be discarding every
4642 * event it creates (which would probably be bad)
4643 * if we were to go back to "again" then we may never
4644 * catch up, and will trigger the warn on, or lock
4645 * the box. Return the padding, and we will release
4646 * the current locks, and try again.
4647 */
4648 return event;
4649
4650 case RINGBUF_TYPE_TIME_EXTEND:
4651 /* Internal data, OK to advance */
4652 rb_advance_reader(cpu_buffer);
4653 goto again;
4654
4655 case RINGBUF_TYPE_TIME_STAMP:
4656 if (ts) {
4657 *ts = rb_event_time_stamp(event);
4658 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4659 cpu_buffer->cpu, ts);
4660 }
4661 /* Internal data, OK to advance */
4662 rb_advance_reader(cpu_buffer);
4663 goto again;
4664
4665 case RINGBUF_TYPE_DATA:
4666 if (ts && !(*ts)) {
4667 *ts = cpu_buffer->read_stamp + event->time_delta;
4668 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4669 cpu_buffer->cpu, ts);
4670 }
4671 if (lost_events)
4672 *lost_events = rb_lost_events(cpu_buffer);
4673 return event;
4674
4675 default:
4676 RB_WARN_ON(cpu_buffer, 1);
4677 }
4678
4679 return NULL;
4680}
4681EXPORT_SYMBOL_GPL(ring_buffer_peek);
4682
4683static struct ring_buffer_event *
4684rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4685{
4686 struct trace_buffer *buffer;
4687 struct ring_buffer_per_cpu *cpu_buffer;
4688 struct ring_buffer_event *event;
4689 int nr_loops = 0;
4690
4691 if (ts)
4692 *ts = 0;
4693
4694 cpu_buffer = iter->cpu_buffer;
4695 buffer = cpu_buffer->buffer;
4696
4697 /*
4698 * Check if someone performed a consuming read to
4699 * the buffer. A consuming read invalidates the iterator
4700 * and we need to reset the iterator in this case.
4701 */
4702 if (unlikely(iter->cache_read != cpu_buffer->read ||
4703 iter->cache_reader_page != cpu_buffer->reader_page))
4704 rb_iter_reset(iter);
4705
4706 again:
4707 if (ring_buffer_iter_empty(iter))
4708 return NULL;
4709
4710 /*
4711 * As the writer can mess with what the iterator is trying
4712 * to read, just give up if we fail to get an event after
4713 * three tries. The iterator is not as reliable when reading
4714 * the ring buffer with an active write as the consumer is.
4715 * Do not warn if the three failures is reached.
4716 */
4717 if (++nr_loops > 3)
4718 return NULL;
4719
4720 if (rb_per_cpu_empty(cpu_buffer))
4721 return NULL;
4722
4723 if (iter->head >= rb_page_size(iter->head_page)) {
4724 rb_inc_iter(iter);
4725 goto again;
4726 }
4727
4728 event = rb_iter_head_event(iter);
4729 if (!event)
4730 goto again;
4731
4732 switch (event->type_len) {
4733 case RINGBUF_TYPE_PADDING:
4734 if (rb_null_event(event)) {
4735 rb_inc_iter(iter);
4736 goto again;
4737 }
4738 rb_advance_iter(iter);
4739 return event;
4740
4741 case RINGBUF_TYPE_TIME_EXTEND:
4742 /* Internal data, OK to advance */
4743 rb_advance_iter(iter);
4744 goto again;
4745
4746 case RINGBUF_TYPE_TIME_STAMP:
4747 if (ts) {
4748 *ts = rb_event_time_stamp(event);
4749 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4750 cpu_buffer->cpu, ts);
4751 }
4752 /* Internal data, OK to advance */
4753 rb_advance_iter(iter);
4754 goto again;
4755
4756 case RINGBUF_TYPE_DATA:
4757 if (ts && !(*ts)) {
4758 *ts = iter->read_stamp + event->time_delta;
4759 ring_buffer_normalize_time_stamp(buffer,
4760 cpu_buffer->cpu, ts);
4761 }
4762 return event;
4763
4764 default:
4765 RB_WARN_ON(cpu_buffer, 1);
4766 }
4767
4768 return NULL;
4769}
4770EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4771
4772static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4773{
4774 if (likely(!in_nmi())) {
4775 raw_spin_lock(&cpu_buffer->reader_lock);
4776 return true;
4777 }
4778
4779 /*
4780 * If an NMI die dumps out the content of the ring buffer
4781 * trylock must be used to prevent a deadlock if the NMI
4782 * preempted a task that holds the ring buffer locks. If
4783 * we get the lock then all is fine, if not, then continue
4784 * to do the read, but this can corrupt the ring buffer,
4785 * so it must be permanently disabled from future writes.
4786 * Reading from NMI is a oneshot deal.
4787 */
4788 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4789 return true;
4790
4791 /* Continue without locking, but disable the ring buffer */
4792 atomic_inc(&cpu_buffer->record_disabled);
4793 return false;
4794}
4795
4796static inline void
4797rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4798{
4799 if (likely(locked))
4800 raw_spin_unlock(&cpu_buffer->reader_lock);
4801 return;
4802}
4803
4804/**
4805 * ring_buffer_peek - peek at the next event to be read
4806 * @buffer: The ring buffer to read
4807 * @cpu: The cpu to peak at
4808 * @ts: The timestamp counter of this event.
4809 * @lost_events: a variable to store if events were lost (may be NULL)
4810 *
4811 * This will return the event that will be read next, but does
4812 * not consume the data.
4813 */
4814struct ring_buffer_event *
4815ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4816 unsigned long *lost_events)
4817{
4818 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4819 struct ring_buffer_event *event;
4820 unsigned long flags;
4821 bool dolock;
4822
4823 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4824 return NULL;
4825
4826 again:
4827 local_irq_save(flags);
4828 dolock = rb_reader_lock(cpu_buffer);
4829 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4830 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4831 rb_advance_reader(cpu_buffer);
4832 rb_reader_unlock(cpu_buffer, dolock);
4833 local_irq_restore(flags);
4834
4835 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4836 goto again;
4837
4838 return event;
4839}
4840
4841/** ring_buffer_iter_dropped - report if there are dropped events
4842 * @iter: The ring buffer iterator
4843 *
4844 * Returns true if there was dropped events since the last peek.
4845 */
4846bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4847{
4848 bool ret = iter->missed_events != 0;
4849
4850 iter->missed_events = 0;
4851 return ret;
4852}
4853EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4854
4855/**
4856 * ring_buffer_iter_peek - peek at the next event to be read
4857 * @iter: The ring buffer iterator
4858 * @ts: The timestamp counter of this event.
4859 *
4860 * This will return the event that will be read next, but does
4861 * not increment the iterator.
4862 */
4863struct ring_buffer_event *
4864ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4865{
4866 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4867 struct ring_buffer_event *event;
4868 unsigned long flags;
4869
4870 again:
4871 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4872 event = rb_iter_peek(iter, ts);
4873 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4874
4875 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4876 goto again;
4877
4878 return event;
4879}
4880
4881/**
4882 * ring_buffer_consume - return an event and consume it
4883 * @buffer: The ring buffer to get the next event from
4884 * @cpu: the cpu to read the buffer from
4885 * @ts: a variable to store the timestamp (may be NULL)
4886 * @lost_events: a variable to store if events were lost (may be NULL)
4887 *
4888 * Returns the next event in the ring buffer, and that event is consumed.
4889 * Meaning, that sequential reads will keep returning a different event,
4890 * and eventually empty the ring buffer if the producer is slower.
4891 */
4892struct ring_buffer_event *
4893ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4894 unsigned long *lost_events)
4895{
4896 struct ring_buffer_per_cpu *cpu_buffer;
4897 struct ring_buffer_event *event = NULL;
4898 unsigned long flags;
4899 bool dolock;
4900
4901 again:
4902 /* might be called in atomic */
4903 preempt_disable();
4904
4905 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4906 goto out;
4907
4908 cpu_buffer = buffer->buffers[cpu];
4909 local_irq_save(flags);
4910 dolock = rb_reader_lock(cpu_buffer);
4911
4912 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4913 if (event) {
4914 cpu_buffer->lost_events = 0;
4915 rb_advance_reader(cpu_buffer);
4916 }
4917
4918 rb_reader_unlock(cpu_buffer, dolock);
4919 local_irq_restore(flags);
4920
4921 out:
4922 preempt_enable();
4923
4924 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4925 goto again;
4926
4927 return event;
4928}
4929EXPORT_SYMBOL_GPL(ring_buffer_consume);
4930
4931/**
4932 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4933 * @buffer: The ring buffer to read from
4934 * @cpu: The cpu buffer to iterate over
4935 * @flags: gfp flags to use for memory allocation
4936 *
4937 * This performs the initial preparations necessary to iterate
4938 * through the buffer. Memory is allocated, buffer recording
4939 * is disabled, and the iterator pointer is returned to the caller.
4940 *
4941 * Disabling buffer recording prevents the reading from being
4942 * corrupted. This is not a consuming read, so a producer is not
4943 * expected.
4944 *
4945 * After a sequence of ring_buffer_read_prepare calls, the user is
4946 * expected to make at least one call to ring_buffer_read_prepare_sync.
4947 * Afterwards, ring_buffer_read_start is invoked to get things going
4948 * for real.
4949 *
4950 * This overall must be paired with ring_buffer_read_finish.
4951 */
4952struct ring_buffer_iter *
4953ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
4954{
4955 struct ring_buffer_per_cpu *cpu_buffer;
4956 struct ring_buffer_iter *iter;
4957
4958 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4959 return NULL;
4960
4961 iter = kzalloc(sizeof(*iter), flags);
4962 if (!iter)
4963 return NULL;
4964
4965 iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
4966 if (!iter->event) {
4967 kfree(iter);
4968 return NULL;
4969 }
4970
4971 cpu_buffer = buffer->buffers[cpu];
4972
4973 iter->cpu_buffer = cpu_buffer;
4974
4975 atomic_inc(&cpu_buffer->resize_disabled);
4976
4977 return iter;
4978}
4979EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4980
4981/**
4982 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4983 *
4984 * All previously invoked ring_buffer_read_prepare calls to prepare
4985 * iterators will be synchronized. Afterwards, read_buffer_read_start
4986 * calls on those iterators are allowed.
4987 */
4988void
4989ring_buffer_read_prepare_sync(void)
4990{
4991 synchronize_rcu();
4992}
4993EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4994
4995/**
4996 * ring_buffer_read_start - start a non consuming read of the buffer
4997 * @iter: The iterator returned by ring_buffer_read_prepare
4998 *
4999 * This finalizes the startup of an iteration through the buffer.
5000 * The iterator comes from a call to ring_buffer_read_prepare and
5001 * an intervening ring_buffer_read_prepare_sync must have been
5002 * performed.
5003 *
5004 * Must be paired with ring_buffer_read_finish.
5005 */
5006void
5007ring_buffer_read_start(struct ring_buffer_iter *iter)
5008{
5009 struct ring_buffer_per_cpu *cpu_buffer;
5010 unsigned long flags;
5011
5012 if (!iter)
5013 return;
5014
5015 cpu_buffer = iter->cpu_buffer;
5016
5017 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5018 arch_spin_lock(&cpu_buffer->lock);
5019 rb_iter_reset(iter);
5020 arch_spin_unlock(&cpu_buffer->lock);
5021 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5022}
5023EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5024
5025/**
5026 * ring_buffer_read_finish - finish reading the iterator of the buffer
5027 * @iter: The iterator retrieved by ring_buffer_start
5028 *
5029 * This re-enables the recording to the buffer, and frees the
5030 * iterator.
5031 */
5032void
5033ring_buffer_read_finish(struct ring_buffer_iter *iter)
5034{
5035 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5036 unsigned long flags;
5037
5038 /*
5039 * Ring buffer is disabled from recording, here's a good place
5040 * to check the integrity of the ring buffer.
5041 * Must prevent readers from trying to read, as the check
5042 * clears the HEAD page and readers require it.
5043 */
5044 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5045 rb_check_pages(cpu_buffer);
5046 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5047
5048 atomic_dec(&cpu_buffer->resize_disabled);
5049 kfree(iter->event);
5050 kfree(iter);
5051}
5052EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5053
5054/**
5055 * ring_buffer_iter_advance - advance the iterator to the next location
5056 * @iter: The ring buffer iterator
5057 *
5058 * Move the location of the iterator such that the next read will
5059 * be the next location of the iterator.
5060 */
5061void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5062{
5063 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5064 unsigned long flags;
5065
5066 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5067
5068 rb_advance_iter(iter);
5069
5070 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5071}
5072EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5073
5074/**
5075 * ring_buffer_size - return the size of the ring buffer (in bytes)
5076 * @buffer: The ring buffer.
5077 * @cpu: The CPU to get ring buffer size from.
5078 */
5079unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5080{
5081 /*
5082 * Earlier, this method returned
5083 * BUF_PAGE_SIZE * buffer->nr_pages
5084 * Since the nr_pages field is now removed, we have converted this to
5085 * return the per cpu buffer value.
5086 */
5087 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5088 return 0;
5089
5090 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
5091}
5092EXPORT_SYMBOL_GPL(ring_buffer_size);
5093
5094static void
5095rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5096{
5097 rb_head_page_deactivate(cpu_buffer);
5098
5099 cpu_buffer->head_page
5100 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5101 local_set(&cpu_buffer->head_page->write, 0);
5102 local_set(&cpu_buffer->head_page->entries, 0);
5103 local_set(&cpu_buffer->head_page->page->commit, 0);
5104
5105 cpu_buffer->head_page->read = 0;
5106
5107 cpu_buffer->tail_page = cpu_buffer->head_page;
5108 cpu_buffer->commit_page = cpu_buffer->head_page;
5109
5110 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5111 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5112 local_set(&cpu_buffer->reader_page->write, 0);
5113 local_set(&cpu_buffer->reader_page->entries, 0);
5114 local_set(&cpu_buffer->reader_page->page->commit, 0);
5115 cpu_buffer->reader_page->read = 0;
5116
5117 local_set(&cpu_buffer->entries_bytes, 0);
5118 local_set(&cpu_buffer->overrun, 0);
5119 local_set(&cpu_buffer->commit_overrun, 0);
5120 local_set(&cpu_buffer->dropped_events, 0);
5121 local_set(&cpu_buffer->entries, 0);
5122 local_set(&cpu_buffer->committing, 0);
5123 local_set(&cpu_buffer->commits, 0);
5124 local_set(&cpu_buffer->pages_touched, 0);
5125 local_set(&cpu_buffer->pages_read, 0);
5126 cpu_buffer->last_pages_touch = 0;
5127 cpu_buffer->shortest_full = 0;
5128 cpu_buffer->read = 0;
5129 cpu_buffer->read_bytes = 0;
5130
5131 rb_time_set(&cpu_buffer->write_stamp, 0);
5132 rb_time_set(&cpu_buffer->before_stamp, 0);
5133
5134 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5135
5136 cpu_buffer->lost_events = 0;
5137 cpu_buffer->last_overrun = 0;
5138
5139 rb_head_page_activate(cpu_buffer);
5140}
5141
5142/* Must have disabled the cpu buffer then done a synchronize_rcu */
5143static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5144{
5145 unsigned long flags;
5146
5147 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5148
5149 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5150 goto out;
5151
5152 arch_spin_lock(&cpu_buffer->lock);
5153
5154 rb_reset_cpu(cpu_buffer);
5155
5156 arch_spin_unlock(&cpu_buffer->lock);
5157
5158 out:
5159 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5160}
5161
5162/**
5163 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5164 * @buffer: The ring buffer to reset a per cpu buffer of
5165 * @cpu: The CPU buffer to be reset
5166 */
5167void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5168{
5169 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5170
5171 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5172 return;
5173
5174 /* prevent another thread from changing buffer sizes */
5175 mutex_lock(&buffer->mutex);
5176
5177 atomic_inc(&cpu_buffer->resize_disabled);
5178 atomic_inc(&cpu_buffer->record_disabled);
5179
5180 /* Make sure all commits have finished */
5181 synchronize_rcu();
5182
5183 reset_disabled_cpu_buffer(cpu_buffer);
5184
5185 atomic_dec(&cpu_buffer->record_disabled);
5186 atomic_dec(&cpu_buffer->resize_disabled);
5187
5188 mutex_unlock(&buffer->mutex);
5189}
5190EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5191
5192/**
5193 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5194 * @buffer: The ring buffer to reset a per cpu buffer of
5195 * @cpu: The CPU buffer to be reset
5196 */
5197void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5198{
5199 struct ring_buffer_per_cpu *cpu_buffer;
5200 int cpu;
5201
5202 /* prevent another thread from changing buffer sizes */
5203 mutex_lock(&buffer->mutex);
5204
5205 for_each_online_buffer_cpu(buffer, cpu) {
5206 cpu_buffer = buffer->buffers[cpu];
5207
5208 atomic_inc(&cpu_buffer->resize_disabled);
5209 atomic_inc(&cpu_buffer->record_disabled);
5210 }
5211
5212 /* Make sure all commits have finished */
5213 synchronize_rcu();
5214
5215 for_each_online_buffer_cpu(buffer, cpu) {
5216 cpu_buffer = buffer->buffers[cpu];
5217
5218 reset_disabled_cpu_buffer(cpu_buffer);
5219
5220 atomic_dec(&cpu_buffer->record_disabled);
5221 atomic_dec(&cpu_buffer->resize_disabled);
5222 }
5223
5224 mutex_unlock(&buffer->mutex);
5225}
5226
5227/**
5228 * ring_buffer_reset - reset a ring buffer
5229 * @buffer: The ring buffer to reset all cpu buffers
5230 */
5231void ring_buffer_reset(struct trace_buffer *buffer)
5232{
5233 struct ring_buffer_per_cpu *cpu_buffer;
5234 int cpu;
5235
5236 for_each_buffer_cpu(buffer, cpu) {
5237 cpu_buffer = buffer->buffers[cpu];
5238
5239 atomic_inc(&cpu_buffer->resize_disabled);
5240 atomic_inc(&cpu_buffer->record_disabled);
5241 }
5242
5243 /* Make sure all commits have finished */
5244 synchronize_rcu();
5245
5246 for_each_buffer_cpu(buffer, cpu) {
5247 cpu_buffer = buffer->buffers[cpu];
5248
5249 reset_disabled_cpu_buffer(cpu_buffer);
5250
5251 atomic_dec(&cpu_buffer->record_disabled);
5252 atomic_dec(&cpu_buffer->resize_disabled);
5253 }
5254}
5255EXPORT_SYMBOL_GPL(ring_buffer_reset);
5256
5257/**
5258 * rind_buffer_empty - is the ring buffer empty?
5259 * @buffer: The ring buffer to test
5260 */
5261bool ring_buffer_empty(struct trace_buffer *buffer)
5262{
5263 struct ring_buffer_per_cpu *cpu_buffer;
5264 unsigned long flags;
5265 bool dolock;
5266 int cpu;
5267 int ret;
5268
5269 /* yes this is racy, but if you don't like the race, lock the buffer */
5270 for_each_buffer_cpu(buffer, cpu) {
5271 cpu_buffer = buffer->buffers[cpu];
5272 local_irq_save(flags);
5273 dolock = rb_reader_lock(cpu_buffer);
5274 ret = rb_per_cpu_empty(cpu_buffer);
5275 rb_reader_unlock(cpu_buffer, dolock);
5276 local_irq_restore(flags);
5277
5278 if (!ret)
5279 return false;
5280 }
5281
5282 return true;
5283}
5284EXPORT_SYMBOL_GPL(ring_buffer_empty);
5285
5286/**
5287 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5288 * @buffer: The ring buffer
5289 * @cpu: The CPU buffer to test
5290 */
5291bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5292{
5293 struct ring_buffer_per_cpu *cpu_buffer;
5294 unsigned long flags;
5295 bool dolock;
5296 int ret;
5297
5298 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5299 return true;
5300
5301 cpu_buffer = buffer->buffers[cpu];
5302 local_irq_save(flags);
5303 dolock = rb_reader_lock(cpu_buffer);
5304 ret = rb_per_cpu_empty(cpu_buffer);
5305 rb_reader_unlock(cpu_buffer, dolock);
5306 local_irq_restore(flags);
5307
5308 return ret;
5309}
5310EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5311
5312#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5313/**
5314 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5315 * @buffer_a: One buffer to swap with
5316 * @buffer_b: The other buffer to swap with
5317 * @cpu: the CPU of the buffers to swap
5318 *
5319 * This function is useful for tracers that want to take a "snapshot"
5320 * of a CPU buffer and has another back up buffer lying around.
5321 * it is expected that the tracer handles the cpu buffer not being
5322 * used at the moment.
5323 */
5324int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5325 struct trace_buffer *buffer_b, int cpu)
5326{
5327 struct ring_buffer_per_cpu *cpu_buffer_a;
5328 struct ring_buffer_per_cpu *cpu_buffer_b;
5329 int ret = -EINVAL;
5330
5331 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5332 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5333 goto out;
5334
5335 cpu_buffer_a = buffer_a->buffers[cpu];
5336 cpu_buffer_b = buffer_b->buffers[cpu];
5337
5338 /* At least make sure the two buffers are somewhat the same */
5339 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5340 goto out;
5341
5342 ret = -EAGAIN;
5343
5344 if (atomic_read(&buffer_a->record_disabled))
5345 goto out;
5346
5347 if (atomic_read(&buffer_b->record_disabled))
5348 goto out;
5349
5350 if (atomic_read(&cpu_buffer_a->record_disabled))
5351 goto out;
5352
5353 if (atomic_read(&cpu_buffer_b->record_disabled))
5354 goto out;
5355
5356 /*
5357 * We can't do a synchronize_rcu here because this
5358 * function can be called in atomic context.
5359 * Normally this will be called from the same CPU as cpu.
5360 * If not it's up to the caller to protect this.
5361 */
5362 atomic_inc(&cpu_buffer_a->record_disabled);
5363 atomic_inc(&cpu_buffer_b->record_disabled);
5364
5365 ret = -EBUSY;
5366 if (local_read(&cpu_buffer_a->committing))
5367 goto out_dec;
5368 if (local_read(&cpu_buffer_b->committing))
5369 goto out_dec;
5370
5371 buffer_a->buffers[cpu] = cpu_buffer_b;
5372 buffer_b->buffers[cpu] = cpu_buffer_a;
5373
5374 cpu_buffer_b->buffer = buffer_a;
5375 cpu_buffer_a->buffer = buffer_b;
5376
5377 ret = 0;
5378
5379out_dec:
5380 atomic_dec(&cpu_buffer_a->record_disabled);
5381 atomic_dec(&cpu_buffer_b->record_disabled);
5382out:
5383 return ret;
5384}
5385EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5386#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5387
5388/**
5389 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5390 * @buffer: the buffer to allocate for.
5391 * @cpu: the cpu buffer to allocate.
5392 *
5393 * This function is used in conjunction with ring_buffer_read_page.
5394 * When reading a full page from the ring buffer, these functions
5395 * can be used to speed up the process. The calling function should
5396 * allocate a few pages first with this function. Then when it
5397 * needs to get pages from the ring buffer, it passes the result
5398 * of this function into ring_buffer_read_page, which will swap
5399 * the page that was allocated, with the read page of the buffer.
5400 *
5401 * Returns:
5402 * The page allocated, or ERR_PTR
5403 */
5404void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5405{
5406 struct ring_buffer_per_cpu *cpu_buffer;
5407 struct buffer_data_page *bpage = NULL;
5408 unsigned long flags;
5409 struct page *page;
5410
5411 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5412 return ERR_PTR(-ENODEV);
5413
5414 cpu_buffer = buffer->buffers[cpu];
5415 local_irq_save(flags);
5416 arch_spin_lock(&cpu_buffer->lock);
5417
5418 if (cpu_buffer->free_page) {
5419 bpage = cpu_buffer->free_page;
5420 cpu_buffer->free_page = NULL;
5421 }
5422
5423 arch_spin_unlock(&cpu_buffer->lock);
5424 local_irq_restore(flags);
5425
5426 if (bpage)
5427 goto out;
5428
5429 page = alloc_pages_node(cpu_to_node(cpu),
5430 GFP_KERNEL | __GFP_NORETRY, 0);
5431 if (!page)
5432 return ERR_PTR(-ENOMEM);
5433
5434 bpage = page_address(page);
5435
5436 out:
5437 rb_init_page(bpage);
5438
5439 return bpage;
5440}
5441EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5442
5443/**
5444 * ring_buffer_free_read_page - free an allocated read page
5445 * @buffer: the buffer the page was allocate for
5446 * @cpu: the cpu buffer the page came from
5447 * @data: the page to free
5448 *
5449 * Free a page allocated from ring_buffer_alloc_read_page.
5450 */
5451void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
5452{
5453 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5454 struct buffer_data_page *bpage = data;
5455 struct page *page = virt_to_page(bpage);
5456 unsigned long flags;
5457
5458 /* If the page is still in use someplace else, we can't reuse it */
5459 if (page_ref_count(page) > 1)
5460 goto out;
5461
5462 local_irq_save(flags);
5463 arch_spin_lock(&cpu_buffer->lock);
5464
5465 if (!cpu_buffer->free_page) {
5466 cpu_buffer->free_page = bpage;
5467 bpage = NULL;
5468 }
5469
5470 arch_spin_unlock(&cpu_buffer->lock);
5471 local_irq_restore(flags);
5472
5473 out:
5474 free_page((unsigned long)bpage);
5475}
5476EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5477
5478/**
5479 * ring_buffer_read_page - extract a page from the ring buffer
5480 * @buffer: buffer to extract from
5481 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5482 * @len: amount to extract
5483 * @cpu: the cpu of the buffer to extract
5484 * @full: should the extraction only happen when the page is full.
5485 *
5486 * This function will pull out a page from the ring buffer and consume it.
5487 * @data_page must be the address of the variable that was returned
5488 * from ring_buffer_alloc_read_page. This is because the page might be used
5489 * to swap with a page in the ring buffer.
5490 *
5491 * for example:
5492 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5493 * if (IS_ERR(rpage))
5494 * return PTR_ERR(rpage);
5495 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5496 * if (ret >= 0)
5497 * process_page(rpage, ret);
5498 *
5499 * When @full is set, the function will not return true unless
5500 * the writer is off the reader page.
5501 *
5502 * Note: it is up to the calling functions to handle sleeps and wakeups.
5503 * The ring buffer can be used anywhere in the kernel and can not
5504 * blindly call wake_up. The layer that uses the ring buffer must be
5505 * responsible for that.
5506 *
5507 * Returns:
5508 * >=0 if data has been transferred, returns the offset of consumed data.
5509 * <0 if no data has been transferred.
5510 */
5511int ring_buffer_read_page(struct trace_buffer *buffer,
5512 void **data_page, size_t len, int cpu, int full)
5513{
5514 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5515 struct ring_buffer_event *event;
5516 struct buffer_data_page *bpage;
5517 struct buffer_page *reader;
5518 unsigned long missed_events;
5519 unsigned long flags;
5520 unsigned int commit;
5521 unsigned int read;
5522 u64 save_timestamp;
5523 int ret = -1;
5524
5525 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5526 goto out;
5527
5528 /*
5529 * If len is not big enough to hold the page header, then
5530 * we can not copy anything.
5531 */
5532 if (len <= BUF_PAGE_HDR_SIZE)
5533 goto out;
5534
5535 len -= BUF_PAGE_HDR_SIZE;
5536
5537 if (!data_page)
5538 goto out;
5539
5540 bpage = *data_page;
5541 if (!bpage)
5542 goto out;
5543
5544 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5545
5546 reader = rb_get_reader_page(cpu_buffer);
5547 if (!reader)
5548 goto out_unlock;
5549
5550 event = rb_reader_event(cpu_buffer);
5551
5552 read = reader->read;
5553 commit = rb_page_commit(reader);
5554
5555 /* Check if any events were dropped */
5556 missed_events = cpu_buffer->lost_events;
5557
5558 /*
5559 * If this page has been partially read or
5560 * if len is not big enough to read the rest of the page or
5561 * a writer is still on the page, then
5562 * we must copy the data from the page to the buffer.
5563 * Otherwise, we can simply swap the page with the one passed in.
5564 */
5565 if (read || (len < (commit - read)) ||
5566 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5567 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5568 unsigned int rpos = read;
5569 unsigned int pos = 0;
5570 unsigned int size;
5571
5572 if (full)
5573 goto out_unlock;
5574
5575 if (len > (commit - read))
5576 len = (commit - read);
5577
5578 /* Always keep the time extend and data together */
5579 size = rb_event_ts_length(event);
5580
5581 if (len < size)
5582 goto out_unlock;
5583
5584 /* save the current timestamp, since the user will need it */
5585 save_timestamp = cpu_buffer->read_stamp;
5586
5587 /* Need to copy one event at a time */
5588 do {
5589 /* We need the size of one event, because
5590 * rb_advance_reader only advances by one event,
5591 * whereas rb_event_ts_length may include the size of
5592 * one or two events.
5593 * We have already ensured there's enough space if this
5594 * is a time extend. */
5595 size = rb_event_length(event);
5596 memcpy(bpage->data + pos, rpage->data + rpos, size);
5597
5598 len -= size;
5599
5600 rb_advance_reader(cpu_buffer);
5601 rpos = reader->read;
5602 pos += size;
5603
5604 if (rpos >= commit)
5605 break;
5606
5607 event = rb_reader_event(cpu_buffer);
5608 /* Always keep the time extend and data together */
5609 size = rb_event_ts_length(event);
5610 } while (len >= size);
5611
5612 /* update bpage */
5613 local_set(&bpage->commit, pos);
5614 bpage->time_stamp = save_timestamp;
5615
5616 /* we copied everything to the beginning */
5617 read = 0;
5618 } else {
5619 /* update the entry counter */
5620 cpu_buffer->read += rb_page_entries(reader);
5621 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
5622
5623 /* swap the pages */
5624 rb_init_page(bpage);
5625 bpage = reader->page;
5626 reader->page = *data_page;
5627 local_set(&reader->write, 0);
5628 local_set(&reader->entries, 0);
5629 reader->read = 0;
5630 *data_page = bpage;
5631
5632 /*
5633 * Use the real_end for the data size,
5634 * This gives us a chance to store the lost events
5635 * on the page.
5636 */
5637 if (reader->real_end)
5638 local_set(&bpage->commit, reader->real_end);
5639 }
5640 ret = read;
5641
5642 cpu_buffer->lost_events = 0;
5643
5644 commit = local_read(&bpage->commit);
5645 /*
5646 * Set a flag in the commit field if we lost events
5647 */
5648 if (missed_events) {
5649 /* If there is room at the end of the page to save the
5650 * missed events, then record it there.
5651 */
5652 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
5653 memcpy(&bpage->data[commit], &missed_events,
5654 sizeof(missed_events));
5655 local_add(RB_MISSED_STORED, &bpage->commit);
5656 commit += sizeof(missed_events);
5657 }
5658 local_add(RB_MISSED_EVENTS, &bpage->commit);
5659 }
5660
5661 /*
5662 * This page may be off to user land. Zero it out here.
5663 */
5664 if (commit < BUF_PAGE_SIZE)
5665 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
5666
5667 out_unlock:
5668 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5669
5670 out:
5671 return ret;
5672}
5673EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5674
5675/*
5676 * We only allocate new buffers, never free them if the CPU goes down.
5677 * If we were to free the buffer, then the user would lose any trace that was in
5678 * the buffer.
5679 */
5680int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
5681{
5682 struct trace_buffer *buffer;
5683 long nr_pages_same;
5684 int cpu_i;
5685 unsigned long nr_pages;
5686
5687 buffer = container_of(node, struct trace_buffer, node);
5688 if (cpumask_test_cpu(cpu, buffer->cpumask))
5689 return 0;
5690
5691 nr_pages = 0;
5692 nr_pages_same = 1;
5693 /* check if all cpu sizes are same */
5694 for_each_buffer_cpu(buffer, cpu_i) {
5695 /* fill in the size from first enabled cpu */
5696 if (nr_pages == 0)
5697 nr_pages = buffer->buffers[cpu_i]->nr_pages;
5698 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
5699 nr_pages_same = 0;
5700 break;
5701 }
5702 }
5703 /* allocate minimum pages, user can later expand it */
5704 if (!nr_pages_same)
5705 nr_pages = 2;
5706 buffer->buffers[cpu] =
5707 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
5708 if (!buffer->buffers[cpu]) {
5709 WARN(1, "failed to allocate ring buffer on CPU %u\n",
5710 cpu);
5711 return -ENOMEM;
5712 }
5713 smp_wmb();
5714 cpumask_set_cpu(cpu, buffer->cpumask);
5715 return 0;
5716}
5717
5718#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5719/*
5720 * This is a basic integrity check of the ring buffer.
5721 * Late in the boot cycle this test will run when configured in.
5722 * It will kick off a thread per CPU that will go into a loop
5723 * writing to the per cpu ring buffer various sizes of data.
5724 * Some of the data will be large items, some small.
5725 *
5726 * Another thread is created that goes into a spin, sending out
5727 * IPIs to the other CPUs to also write into the ring buffer.
5728 * this is to test the nesting ability of the buffer.
5729 *
5730 * Basic stats are recorded and reported. If something in the
5731 * ring buffer should happen that's not expected, a big warning
5732 * is displayed and all ring buffers are disabled.
5733 */
5734static struct task_struct *rb_threads[NR_CPUS] __initdata;
5735
5736struct rb_test_data {
5737 struct trace_buffer *buffer;
5738 unsigned long events;
5739 unsigned long bytes_written;
5740 unsigned long bytes_alloc;
5741 unsigned long bytes_dropped;
5742 unsigned long events_nested;
5743 unsigned long bytes_written_nested;
5744 unsigned long bytes_alloc_nested;
5745 unsigned long bytes_dropped_nested;
5746 int min_size_nested;
5747 int max_size_nested;
5748 int max_size;
5749 int min_size;
5750 int cpu;
5751 int cnt;
5752};
5753
5754static struct rb_test_data rb_data[NR_CPUS] __initdata;
5755
5756/* 1 meg per cpu */
5757#define RB_TEST_BUFFER_SIZE 1048576
5758
5759static char rb_string[] __initdata =
5760 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5761 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5762 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5763
5764static bool rb_test_started __initdata;
5765
5766struct rb_item {
5767 int size;
5768 char str[];
5769};
5770
5771static __init int rb_write_something(struct rb_test_data *data, bool nested)
5772{
5773 struct ring_buffer_event *event;
5774 struct rb_item *item;
5775 bool started;
5776 int event_len;
5777 int size;
5778 int len;
5779 int cnt;
5780
5781 /* Have nested writes different that what is written */
5782 cnt = data->cnt + (nested ? 27 : 0);
5783
5784 /* Multiply cnt by ~e, to make some unique increment */
5785 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
5786
5787 len = size + sizeof(struct rb_item);
5788
5789 started = rb_test_started;
5790 /* read rb_test_started before checking buffer enabled */
5791 smp_rmb();
5792
5793 event = ring_buffer_lock_reserve(data->buffer, len);
5794 if (!event) {
5795 /* Ignore dropped events before test starts. */
5796 if (started) {
5797 if (nested)
5798 data->bytes_dropped += len;
5799 else
5800 data->bytes_dropped_nested += len;
5801 }
5802 return len;
5803 }
5804
5805 event_len = ring_buffer_event_length(event);
5806
5807 if (RB_WARN_ON(data->buffer, event_len < len))
5808 goto out;
5809
5810 item = ring_buffer_event_data(event);
5811 item->size = size;
5812 memcpy(item->str, rb_string, size);
5813
5814 if (nested) {
5815 data->bytes_alloc_nested += event_len;
5816 data->bytes_written_nested += len;
5817 data->events_nested++;
5818 if (!data->min_size_nested || len < data->min_size_nested)
5819 data->min_size_nested = len;
5820 if (len > data->max_size_nested)
5821 data->max_size_nested = len;
5822 } else {
5823 data->bytes_alloc += event_len;
5824 data->bytes_written += len;
5825 data->events++;
5826 if (!data->min_size || len < data->min_size)
5827 data->max_size = len;
5828 if (len > data->max_size)
5829 data->max_size = len;
5830 }
5831
5832 out:
5833 ring_buffer_unlock_commit(data->buffer, event);
5834
5835 return 0;
5836}
5837
5838static __init int rb_test(void *arg)
5839{
5840 struct rb_test_data *data = arg;
5841
5842 while (!kthread_should_stop()) {
5843 rb_write_something(data, false);
5844 data->cnt++;
5845
5846 set_current_state(TASK_INTERRUPTIBLE);
5847 /* Now sleep between a min of 100-300us and a max of 1ms */
5848 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
5849 }
5850
5851 return 0;
5852}
5853
5854static __init void rb_ipi(void *ignore)
5855{
5856 struct rb_test_data *data;
5857 int cpu = smp_processor_id();
5858
5859 data = &rb_data[cpu];
5860 rb_write_something(data, true);
5861}
5862
5863static __init int rb_hammer_test(void *arg)
5864{
5865 while (!kthread_should_stop()) {
5866
5867 /* Send an IPI to all cpus to write data! */
5868 smp_call_function(rb_ipi, NULL, 1);
5869 /* No sleep, but for non preempt, let others run */
5870 schedule();
5871 }
5872
5873 return 0;
5874}
5875
5876static __init int test_ringbuffer(void)
5877{
5878 struct task_struct *rb_hammer;
5879 struct trace_buffer *buffer;
5880 int cpu;
5881 int ret = 0;
5882
5883 if (security_locked_down(LOCKDOWN_TRACEFS)) {
5884 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
5885 return 0;
5886 }
5887
5888 pr_info("Running ring buffer tests...\n");
5889
5890 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5891 if (WARN_ON(!buffer))
5892 return 0;
5893
5894 /* Disable buffer so that threads can't write to it yet */
5895 ring_buffer_record_off(buffer);
5896
5897 for_each_online_cpu(cpu) {
5898 rb_data[cpu].buffer = buffer;
5899 rb_data[cpu].cpu = cpu;
5900 rb_data[cpu].cnt = cpu;
5901 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5902 "rbtester/%d", cpu);
5903 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5904 pr_cont("FAILED\n");
5905 ret = PTR_ERR(rb_threads[cpu]);
5906 goto out_free;
5907 }
5908
5909 kthread_bind(rb_threads[cpu], cpu);
5910 wake_up_process(rb_threads[cpu]);
5911 }
5912
5913 /* Now create the rb hammer! */
5914 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5915 if (WARN_ON(IS_ERR(rb_hammer))) {
5916 pr_cont("FAILED\n");
5917 ret = PTR_ERR(rb_hammer);
5918 goto out_free;
5919 }
5920
5921 ring_buffer_record_on(buffer);
5922 /*
5923 * Show buffer is enabled before setting rb_test_started.
5924 * Yes there's a small race window where events could be
5925 * dropped and the thread wont catch it. But when a ring
5926 * buffer gets enabled, there will always be some kind of
5927 * delay before other CPUs see it. Thus, we don't care about
5928 * those dropped events. We care about events dropped after
5929 * the threads see that the buffer is active.
5930 */
5931 smp_wmb();
5932 rb_test_started = true;
5933
5934 set_current_state(TASK_INTERRUPTIBLE);
5935 /* Just run for 10 seconds */;
5936 schedule_timeout(10 * HZ);
5937
5938 kthread_stop(rb_hammer);
5939
5940 out_free:
5941 for_each_online_cpu(cpu) {
5942 if (!rb_threads[cpu])
5943 break;
5944 kthread_stop(rb_threads[cpu]);
5945 }
5946 if (ret) {
5947 ring_buffer_free(buffer);
5948 return ret;
5949 }
5950
5951 /* Report! */
5952 pr_info("finished\n");
5953 for_each_online_cpu(cpu) {
5954 struct ring_buffer_event *event;
5955 struct rb_test_data *data = &rb_data[cpu];
5956 struct rb_item *item;
5957 unsigned long total_events;
5958 unsigned long total_dropped;
5959 unsigned long total_written;
5960 unsigned long total_alloc;
5961 unsigned long total_read = 0;
5962 unsigned long total_size = 0;
5963 unsigned long total_len = 0;
5964 unsigned long total_lost = 0;
5965 unsigned long lost;
5966 int big_event_size;
5967 int small_event_size;
5968
5969 ret = -1;
5970
5971 total_events = data->events + data->events_nested;
5972 total_written = data->bytes_written + data->bytes_written_nested;
5973 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5974 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5975
5976 big_event_size = data->max_size + data->max_size_nested;
5977 small_event_size = data->min_size + data->min_size_nested;
5978
5979 pr_info("CPU %d:\n", cpu);
5980 pr_info(" events: %ld\n", total_events);
5981 pr_info(" dropped bytes: %ld\n", total_dropped);
5982 pr_info(" alloced bytes: %ld\n", total_alloc);
5983 pr_info(" written bytes: %ld\n", total_written);
5984 pr_info(" biggest event: %d\n", big_event_size);
5985 pr_info(" smallest event: %d\n", small_event_size);
5986
5987 if (RB_WARN_ON(buffer, total_dropped))
5988 break;
5989
5990 ret = 0;
5991
5992 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5993 total_lost += lost;
5994 item = ring_buffer_event_data(event);
5995 total_len += ring_buffer_event_length(event);
5996 total_size += item->size + sizeof(struct rb_item);
5997 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5998 pr_info("FAILED!\n");
5999 pr_info("buffer had: %.*s\n", item->size, item->str);
6000 pr_info("expected: %.*s\n", item->size, rb_string);
6001 RB_WARN_ON(buffer, 1);
6002 ret = -1;
6003 break;
6004 }
6005 total_read++;
6006 }
6007 if (ret)
6008 break;
6009
6010 ret = -1;
6011
6012 pr_info(" read events: %ld\n", total_read);
6013 pr_info(" lost events: %ld\n", total_lost);
6014 pr_info(" total events: %ld\n", total_lost + total_read);
6015 pr_info(" recorded len bytes: %ld\n", total_len);
6016 pr_info(" recorded size bytes: %ld\n", total_size);
6017 if (total_lost)
6018 pr_info(" With dropped events, record len and size may not match\n"
6019 " alloced and written from above\n");
6020 if (!total_lost) {
6021 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6022 total_size != total_written))
6023 break;
6024 }
6025 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6026 break;
6027
6028 ret = 0;
6029 }
6030 if (!ret)
6031 pr_info("Ring buffer PASSED!\n");
6032
6033 ring_buffer_free(buffer);
6034 return 0;
6035}
6036
6037late_initcall(test_ringbuffer);
6038#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */