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