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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_recursion.h>
8#include <linux/trace_events.h>
9#include <linux/ring_buffer.h>
10#include <linux/trace_clock.h>
11#include <linux/sched/clock.h>
12#include <linux/trace_seq.h>
13#include <linux/spinlock.h>
14#include <linux/irq_work.h>
15#include <linux/security.h>
16#include <linux/uaccess.h>
17#include <linux/hardirq.h>
18#include <linux/kthread.h> /* for self test */
19#include <linux/module.h>
20#include <linux/percpu.h>
21#include <linux/mutex.h>
22#include <linux/delay.h>
23#include <linux/slab.h>
24#include <linux/init.h>
25#include <linux/hash.h>
26#include <linux/list.h>
27#include <linux/cpu.h>
28#include <linux/oom.h>
29
30#include <asm/local64.h>
31#include <asm/local.h>
32
33/*
34 * The "absolute" timestamp in the buffer is only 59 bits.
35 * If a clock has the 5 MSBs set, it needs to be saved and
36 * reinserted.
37 */
38#define TS_MSB (0xf8ULL << 56)
39#define ABS_TS_MASK (~TS_MSB)
40
41static void update_pages_handler(struct work_struct *work);
42
43/*
44 * The ring buffer header is special. We must manually up keep it.
45 */
46int ring_buffer_print_entry_header(struct trace_seq *s)
47{
48 trace_seq_puts(s, "# compressed entry header\n");
49 trace_seq_puts(s, "\ttype_len : 5 bits\n");
50 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
51 trace_seq_puts(s, "\tarray : 32 bits\n");
52 trace_seq_putc(s, '\n');
53 trace_seq_printf(s, "\tpadding : type == %d\n",
54 RINGBUF_TYPE_PADDING);
55 trace_seq_printf(s, "\ttime_extend : type == %d\n",
56 RINGBUF_TYPE_TIME_EXTEND);
57 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
58 RINGBUF_TYPE_TIME_STAMP);
59 trace_seq_printf(s, "\tdata max type_len == %d\n",
60 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
61
62 return !trace_seq_has_overflowed(s);
63}
64
65/*
66 * The ring buffer is made up of a list of pages. A separate list of pages is
67 * allocated for each CPU. A writer may only write to a buffer that is
68 * associated with the CPU it is currently executing on. A reader may read
69 * from any per cpu buffer.
70 *
71 * The reader is special. For each per cpu buffer, the reader has its own
72 * reader page. When a reader has read the entire reader page, this reader
73 * page is swapped with another page in the ring buffer.
74 *
75 * Now, as long as the writer is off the reader page, the reader can do what
76 * ever it wants with that page. The writer will never write to that page
77 * again (as long as it is out of the ring buffer).
78 *
79 * Here's some silly ASCII art.
80 *
81 * +------+
82 * |reader| RING BUFFER
83 * |page |
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 * |reader| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
107 * ^ | |-->| |-->| |
108 * | +---+ +---+ +---+
109 * | |
110 * | |
111 * +------------------------------+
112 *
113 *
114 * +------+
115 * |buffer| RING BUFFER
116 * |page |------------------v
117 * +------+ +---+ +---+ +---+
118 * ^ | | | |-->| |
119 * | New +---+ +---+ +---+
120 * | Reader------^ |
121 * | page |
122 * +------------------------------+
123 *
124 *
125 * After we make this swap, the reader can hand this page off to the splice
126 * code and be done with it. It can even allocate a new page if it needs to
127 * and swap that into the ring buffer.
128 *
129 * We will be using cmpxchg soon to make all this lockless.
130 *
131 */
132
133/* Used for individual buffers (after the counter) */
134#define RB_BUFFER_OFF (1 << 20)
135
136#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
137
138#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
139#define RB_ALIGNMENT 4U
140#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
141#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
142
143#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
144# define RB_FORCE_8BYTE_ALIGNMENT 0
145# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
146#else
147# define RB_FORCE_8BYTE_ALIGNMENT 1
148# define RB_ARCH_ALIGNMENT 8U
149#endif
150
151#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
152
153/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
154#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
155
156enum {
157 RB_LEN_TIME_EXTEND = 8,
158 RB_LEN_TIME_STAMP = 8,
159};
160
161#define skip_time_extend(event) \
162 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
163
164#define extended_time(event) \
165 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
166
167static inline bool rb_null_event(struct ring_buffer_event *event)
168{
169 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
170}
171
172static void rb_event_set_padding(struct ring_buffer_event *event)
173{
174 /* padding has a NULL time_delta */
175 event->type_len = RINGBUF_TYPE_PADDING;
176 event->time_delta = 0;
177}
178
179static unsigned
180rb_event_data_length(struct ring_buffer_event *event)
181{
182 unsigned length;
183
184 if (event->type_len)
185 length = event->type_len * RB_ALIGNMENT;
186 else
187 length = event->array[0];
188 return length + RB_EVNT_HDR_SIZE;
189}
190
191/*
192 * Return the length of the given event. Will return
193 * the length of the time extend if the event is a
194 * time extend.
195 */
196static inline unsigned
197rb_event_length(struct ring_buffer_event *event)
198{
199 switch (event->type_len) {
200 case RINGBUF_TYPE_PADDING:
201 if (rb_null_event(event))
202 /* undefined */
203 return -1;
204 return event->array[0] + RB_EVNT_HDR_SIZE;
205
206 case RINGBUF_TYPE_TIME_EXTEND:
207 return RB_LEN_TIME_EXTEND;
208
209 case RINGBUF_TYPE_TIME_STAMP:
210 return RB_LEN_TIME_STAMP;
211
212 case RINGBUF_TYPE_DATA:
213 return rb_event_data_length(event);
214 default:
215 WARN_ON_ONCE(1);
216 }
217 /* not hit */
218 return 0;
219}
220
221/*
222 * Return total length of time extend and data,
223 * or just the event length for all other events.
224 */
225static inline unsigned
226rb_event_ts_length(struct ring_buffer_event *event)
227{
228 unsigned len = 0;
229
230 if (extended_time(event)) {
231 /* time extends include the data event after it */
232 len = RB_LEN_TIME_EXTEND;
233 event = skip_time_extend(event);
234 }
235 return len + rb_event_length(event);
236}
237
238/**
239 * ring_buffer_event_length - return the length of the event
240 * @event: the event to get the length of
241 *
242 * Returns the size of the data load of a data event.
243 * If the event is something other than a data event, it
244 * returns the size of the event itself. With the exception
245 * of a TIME EXTEND, where it still returns the size of the
246 * data load of the data event after it.
247 */
248unsigned ring_buffer_event_length(struct ring_buffer_event *event)
249{
250 unsigned length;
251
252 if (extended_time(event))
253 event = skip_time_extend(event);
254
255 length = rb_event_length(event);
256 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
257 return length;
258 length -= RB_EVNT_HDR_SIZE;
259 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
260 length -= sizeof(event->array[0]);
261 return length;
262}
263EXPORT_SYMBOL_GPL(ring_buffer_event_length);
264
265/* inline for ring buffer fast paths */
266static __always_inline void *
267rb_event_data(struct ring_buffer_event *event)
268{
269 if (extended_time(event))
270 event = skip_time_extend(event);
271 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
272 /* If length is in len field, then array[0] has the data */
273 if (event->type_len)
274 return (void *)&event->array[0];
275 /* Otherwise length is in array[0] and array[1] has the data */
276 return (void *)&event->array[1];
277}
278
279/**
280 * ring_buffer_event_data - return the data of the event
281 * @event: the event to get the data from
282 */
283void *ring_buffer_event_data(struct ring_buffer_event *event)
284{
285 return rb_event_data(event);
286}
287EXPORT_SYMBOL_GPL(ring_buffer_event_data);
288
289#define for_each_buffer_cpu(buffer, cpu) \
290 for_each_cpu(cpu, buffer->cpumask)
291
292#define for_each_online_buffer_cpu(buffer, cpu) \
293 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
294
295#define TS_SHIFT 27
296#define TS_MASK ((1ULL << TS_SHIFT) - 1)
297#define TS_DELTA_TEST (~TS_MASK)
298
299static u64 rb_event_time_stamp(struct ring_buffer_event *event)
300{
301 u64 ts;
302
303 ts = event->array[0];
304 ts <<= TS_SHIFT;
305 ts += event->time_delta;
306
307 return ts;
308}
309
310/* Flag when events were overwritten */
311#define RB_MISSED_EVENTS (1 << 31)
312/* Missed count stored at end */
313#define RB_MISSED_STORED (1 << 30)
314
315struct buffer_data_page {
316 u64 time_stamp; /* page time stamp */
317 local_t commit; /* write committed index */
318 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
319};
320
321struct buffer_data_read_page {
322 unsigned order; /* order of the page */
323 struct buffer_data_page *data; /* actual data, stored in this page */
324};
325
326/*
327 * Note, the buffer_page list must be first. The buffer pages
328 * are allocated in cache lines, which means that each buffer
329 * page will be at the beginning of a cache line, and thus
330 * the least significant bits will be zero. We use this to
331 * add flags in the list struct pointers, to make the ring buffer
332 * lockless.
333 */
334struct buffer_page {
335 struct list_head list; /* list of buffer pages */
336 local_t write; /* index for next write */
337 unsigned read; /* index for next read */
338 local_t entries; /* entries on this page */
339 unsigned long real_end; /* real end of data */
340 unsigned order; /* order of the page */
341 struct buffer_data_page *page; /* Actual data page */
342};
343
344/*
345 * The buffer page counters, write and entries, must be reset
346 * atomically when crossing page boundaries. To synchronize this
347 * update, two counters are inserted into the number. One is
348 * the actual counter for the write position or count on the page.
349 *
350 * The other is a counter of updaters. Before an update happens
351 * the update partition of the counter is incremented. This will
352 * allow the updater to update the counter atomically.
353 *
354 * The counter is 20 bits, and the state data is 12.
355 */
356#define RB_WRITE_MASK 0xfffff
357#define RB_WRITE_INTCNT (1 << 20)
358
359static void rb_init_page(struct buffer_data_page *bpage)
360{
361 local_set(&bpage->commit, 0);
362}
363
364static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
365{
366 return local_read(&bpage->page->commit);
367}
368
369static void free_buffer_page(struct buffer_page *bpage)
370{
371 free_pages((unsigned long)bpage->page, bpage->order);
372 kfree(bpage);
373}
374
375/*
376 * We need to fit the time_stamp delta into 27 bits.
377 */
378static inline bool test_time_stamp(u64 delta)
379{
380 return !!(delta & TS_DELTA_TEST);
381}
382
383struct rb_irq_work {
384 struct irq_work work;
385 wait_queue_head_t waiters;
386 wait_queue_head_t full_waiters;
387 bool waiters_pending;
388 bool full_waiters_pending;
389 bool wakeup_full;
390};
391
392/*
393 * Structure to hold event state and handle nested events.
394 */
395struct rb_event_info {
396 u64 ts;
397 u64 delta;
398 u64 before;
399 u64 after;
400 unsigned long length;
401 struct buffer_page *tail_page;
402 int add_timestamp;
403};
404
405/*
406 * Used for the add_timestamp
407 * NONE
408 * EXTEND - wants a time extend
409 * ABSOLUTE - the buffer requests all events to have absolute time stamps
410 * FORCE - force a full time stamp.
411 */
412enum {
413 RB_ADD_STAMP_NONE = 0,
414 RB_ADD_STAMP_EXTEND = BIT(1),
415 RB_ADD_STAMP_ABSOLUTE = BIT(2),
416 RB_ADD_STAMP_FORCE = BIT(3)
417};
418/*
419 * Used for which event context the event is in.
420 * TRANSITION = 0
421 * NMI = 1
422 * IRQ = 2
423 * SOFTIRQ = 3
424 * NORMAL = 4
425 *
426 * See trace_recursive_lock() comment below for more details.
427 */
428enum {
429 RB_CTX_TRANSITION,
430 RB_CTX_NMI,
431 RB_CTX_IRQ,
432 RB_CTX_SOFTIRQ,
433 RB_CTX_NORMAL,
434 RB_CTX_MAX
435};
436
437struct rb_time_struct {
438 local64_t time;
439};
440typedef struct rb_time_struct rb_time_t;
441
442#define MAX_NEST 5
443
444/*
445 * head_page == tail_page && head == tail then buffer is empty.
446 */
447struct ring_buffer_per_cpu {
448 int cpu;
449 atomic_t record_disabled;
450 atomic_t resize_disabled;
451 struct trace_buffer *buffer;
452 raw_spinlock_t reader_lock; /* serialize readers */
453 arch_spinlock_t lock;
454 struct lock_class_key lock_key;
455 struct buffer_data_page *free_page;
456 unsigned long nr_pages;
457 unsigned int current_context;
458 struct list_head *pages;
459 struct buffer_page *head_page; /* read from head */
460 struct buffer_page *tail_page; /* write to tail */
461 struct buffer_page *commit_page; /* committed pages */
462 struct buffer_page *reader_page;
463 unsigned long lost_events;
464 unsigned long last_overrun;
465 unsigned long nest;
466 local_t entries_bytes;
467 local_t entries;
468 local_t overrun;
469 local_t commit_overrun;
470 local_t dropped_events;
471 local_t committing;
472 local_t commits;
473 local_t pages_touched;
474 local_t pages_lost;
475 local_t pages_read;
476 long last_pages_touch;
477 size_t shortest_full;
478 unsigned long read;
479 unsigned long read_bytes;
480 rb_time_t write_stamp;
481 rb_time_t before_stamp;
482 u64 event_stamp[MAX_NEST];
483 u64 read_stamp;
484 /* pages removed since last reset */
485 unsigned long pages_removed;
486 /* ring buffer pages to update, > 0 to add, < 0 to remove */
487 long nr_pages_to_update;
488 struct list_head new_pages; /* new pages to add */
489 struct work_struct update_pages_work;
490 struct completion update_done;
491
492 struct rb_irq_work irq_work;
493};
494
495struct trace_buffer {
496 unsigned flags;
497 int cpus;
498 atomic_t record_disabled;
499 atomic_t resizing;
500 cpumask_var_t cpumask;
501
502 struct lock_class_key *reader_lock_key;
503
504 struct mutex mutex;
505
506 struct ring_buffer_per_cpu **buffers;
507
508 struct hlist_node node;
509 u64 (*clock)(void);
510
511 struct rb_irq_work irq_work;
512 bool time_stamp_abs;
513
514 unsigned int subbuf_size;
515 unsigned int subbuf_order;
516 unsigned int max_data_size;
517};
518
519struct ring_buffer_iter {
520 struct ring_buffer_per_cpu *cpu_buffer;
521 unsigned long head;
522 unsigned long next_event;
523 struct buffer_page *head_page;
524 struct buffer_page *cache_reader_page;
525 unsigned long cache_read;
526 unsigned long cache_pages_removed;
527 u64 read_stamp;
528 u64 page_stamp;
529 struct ring_buffer_event *event;
530 size_t event_size;
531 int missed_events;
532};
533
534int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
535{
536 struct buffer_data_page field;
537
538 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
539 "offset:0;\tsize:%u;\tsigned:%u;\n",
540 (unsigned int)sizeof(field.time_stamp),
541 (unsigned int)is_signed_type(u64));
542
543 trace_seq_printf(s, "\tfield: local_t commit;\t"
544 "offset:%u;\tsize:%u;\tsigned:%u;\n",
545 (unsigned int)offsetof(typeof(field), commit),
546 (unsigned int)sizeof(field.commit),
547 (unsigned int)is_signed_type(long));
548
549 trace_seq_printf(s, "\tfield: int overwrite;\t"
550 "offset:%u;\tsize:%u;\tsigned:%u;\n",
551 (unsigned int)offsetof(typeof(field), commit),
552 1,
553 (unsigned int)is_signed_type(long));
554
555 trace_seq_printf(s, "\tfield: char data;\t"
556 "offset:%u;\tsize:%u;\tsigned:%u;\n",
557 (unsigned int)offsetof(typeof(field), data),
558 (unsigned int)buffer->subbuf_size,
559 (unsigned int)is_signed_type(char));
560
561 return !trace_seq_has_overflowed(s);
562}
563
564static inline void rb_time_read(rb_time_t *t, u64 *ret)
565{
566 *ret = local64_read(&t->time);
567}
568static void rb_time_set(rb_time_t *t, u64 val)
569{
570 local64_set(&t->time, val);
571}
572
573/*
574 * Enable this to make sure that the event passed to
575 * ring_buffer_event_time_stamp() is not committed and also
576 * is on the buffer that it passed in.
577 */
578//#define RB_VERIFY_EVENT
579#ifdef RB_VERIFY_EVENT
580static struct list_head *rb_list_head(struct list_head *list);
581static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
582 void *event)
583{
584 struct buffer_page *page = cpu_buffer->commit_page;
585 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
586 struct list_head *next;
587 long commit, write;
588 unsigned long addr = (unsigned long)event;
589 bool done = false;
590 int stop = 0;
591
592 /* Make sure the event exists and is not committed yet */
593 do {
594 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
595 done = true;
596 commit = local_read(&page->page->commit);
597 write = local_read(&page->write);
598 if (addr >= (unsigned long)&page->page->data[commit] &&
599 addr < (unsigned long)&page->page->data[write])
600 return;
601
602 next = rb_list_head(page->list.next);
603 page = list_entry(next, struct buffer_page, list);
604 } while (!done);
605 WARN_ON_ONCE(1);
606}
607#else
608static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
609 void *event)
610{
611}
612#endif
613
614/*
615 * The absolute time stamp drops the 5 MSBs and some clocks may
616 * require them. The rb_fix_abs_ts() will take a previous full
617 * time stamp, and add the 5 MSB of that time stamp on to the
618 * saved absolute time stamp. Then they are compared in case of
619 * the unlikely event that the latest time stamp incremented
620 * the 5 MSB.
621 */
622static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
623{
624 if (save_ts & TS_MSB) {
625 abs |= save_ts & TS_MSB;
626 /* Check for overflow */
627 if (unlikely(abs < save_ts))
628 abs += 1ULL << 59;
629 }
630 return abs;
631}
632
633static inline u64 rb_time_stamp(struct trace_buffer *buffer);
634
635/**
636 * ring_buffer_event_time_stamp - return the event's current time stamp
637 * @buffer: The buffer that the event is on
638 * @event: the event to get the time stamp of
639 *
640 * Note, this must be called after @event is reserved, and before it is
641 * committed to the ring buffer. And must be called from the same
642 * context where the event was reserved (normal, softirq, irq, etc).
643 *
644 * Returns the time stamp associated with the current event.
645 * If the event has an extended time stamp, then that is used as
646 * the time stamp to return.
647 * In the highly unlikely case that the event was nested more than
648 * the max nesting, then the write_stamp of the buffer is returned,
649 * otherwise current time is returned, but that really neither of
650 * the last two cases should ever happen.
651 */
652u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
653 struct ring_buffer_event *event)
654{
655 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
656 unsigned int nest;
657 u64 ts;
658
659 /* If the event includes an absolute time, then just use that */
660 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
661 ts = rb_event_time_stamp(event);
662 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
663 }
664
665 nest = local_read(&cpu_buffer->committing);
666 verify_event(cpu_buffer, event);
667 if (WARN_ON_ONCE(!nest))
668 goto fail;
669
670 /* Read the current saved nesting level time stamp */
671 if (likely(--nest < MAX_NEST))
672 return cpu_buffer->event_stamp[nest];
673
674 /* Shouldn't happen, warn if it does */
675 WARN_ONCE(1, "nest (%d) greater than max", nest);
676
677 fail:
678 rb_time_read(&cpu_buffer->write_stamp, &ts);
679
680 return ts;
681}
682
683/**
684 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
685 * @buffer: The ring_buffer to get the number of pages from
686 * @cpu: The cpu of the ring_buffer to get the number of pages from
687 *
688 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
689 */
690size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
691{
692 return buffer->buffers[cpu]->nr_pages;
693}
694
695/**
696 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
697 * @buffer: The ring_buffer to get the number of pages from
698 * @cpu: The cpu of the ring_buffer to get the number of pages from
699 *
700 * Returns the number of pages that have content in the ring buffer.
701 */
702size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
703{
704 size_t read;
705 size_t lost;
706 size_t cnt;
707
708 read = local_read(&buffer->buffers[cpu]->pages_read);
709 lost = local_read(&buffer->buffers[cpu]->pages_lost);
710 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
711
712 if (WARN_ON_ONCE(cnt < lost))
713 return 0;
714
715 cnt -= lost;
716
717 /* The reader can read an empty page, but not more than that */
718 if (cnt < read) {
719 WARN_ON_ONCE(read > cnt + 1);
720 return 0;
721 }
722
723 return cnt - read;
724}
725
726static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
727{
728 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
729 size_t nr_pages;
730 size_t dirty;
731
732 nr_pages = cpu_buffer->nr_pages;
733 if (!nr_pages || !full)
734 return true;
735
736 /*
737 * Add one as dirty will never equal nr_pages, as the sub-buffer
738 * that the writer is on is not counted as dirty.
739 * This is needed if "buffer_percent" is set to 100.
740 */
741 dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
742
743 return (dirty * 100) >= (full * nr_pages);
744}
745
746/*
747 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
748 *
749 * Schedules a delayed work to wake up any task that is blocked on the
750 * ring buffer waiters queue.
751 */
752static void rb_wake_up_waiters(struct irq_work *work)
753{
754 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
755
756 wake_up_all(&rbwork->waiters);
757 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
758 /* Only cpu_buffer sets the above flags */
759 struct ring_buffer_per_cpu *cpu_buffer =
760 container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
761
762 /* Called from interrupt context */
763 raw_spin_lock(&cpu_buffer->reader_lock);
764 rbwork->wakeup_full = false;
765 rbwork->full_waiters_pending = false;
766
767 /* Waking up all waiters, they will reset the shortest full */
768 cpu_buffer->shortest_full = 0;
769 raw_spin_unlock(&cpu_buffer->reader_lock);
770
771 wake_up_all(&rbwork->full_waiters);
772 }
773}
774
775/**
776 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
777 * @buffer: The ring buffer to wake waiters on
778 * @cpu: The CPU buffer to wake waiters on
779 *
780 * In the case of a file that represents a ring buffer is closing,
781 * it is prudent to wake up any waiters that are on this.
782 */
783void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
784{
785 struct ring_buffer_per_cpu *cpu_buffer;
786 struct rb_irq_work *rbwork;
787
788 if (!buffer)
789 return;
790
791 if (cpu == RING_BUFFER_ALL_CPUS) {
792
793 /* Wake up individual ones too. One level recursion */
794 for_each_buffer_cpu(buffer, cpu)
795 ring_buffer_wake_waiters(buffer, cpu);
796
797 rbwork = &buffer->irq_work;
798 } else {
799 if (WARN_ON_ONCE(!buffer->buffers))
800 return;
801 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
802 return;
803
804 cpu_buffer = buffer->buffers[cpu];
805 /* The CPU buffer may not have been initialized yet */
806 if (!cpu_buffer)
807 return;
808 rbwork = &cpu_buffer->irq_work;
809 }
810
811 /* This can be called in any context */
812 irq_work_queue(&rbwork->work);
813}
814
815static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
816{
817 struct ring_buffer_per_cpu *cpu_buffer;
818 bool ret = false;
819
820 /* Reads of all CPUs always waits for any data */
821 if (cpu == RING_BUFFER_ALL_CPUS)
822 return !ring_buffer_empty(buffer);
823
824 cpu_buffer = buffer->buffers[cpu];
825
826 if (!ring_buffer_empty_cpu(buffer, cpu)) {
827 unsigned long flags;
828 bool pagebusy;
829
830 if (!full)
831 return true;
832
833 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
834 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
835 ret = !pagebusy && full_hit(buffer, cpu, full);
836
837 if (!cpu_buffer->shortest_full ||
838 cpu_buffer->shortest_full > full)
839 cpu_buffer->shortest_full = full;
840 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
841 }
842 return ret;
843}
844
845/**
846 * ring_buffer_wait - wait for input to the ring buffer
847 * @buffer: buffer to wait on
848 * @cpu: the cpu buffer to wait on
849 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
850 *
851 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
852 * as data is added to any of the @buffer's cpu buffers. Otherwise
853 * it will wait for data to be added to a specific cpu buffer.
854 */
855int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
856{
857 struct ring_buffer_per_cpu *cpu_buffer;
858 DEFINE_WAIT(wait);
859 struct rb_irq_work *work;
860 int ret = 0;
861
862 /*
863 * Depending on what the caller is waiting for, either any
864 * data in any cpu buffer, or a specific buffer, put the
865 * caller on the appropriate wait queue.
866 */
867 if (cpu == RING_BUFFER_ALL_CPUS) {
868 work = &buffer->irq_work;
869 /* Full only makes sense on per cpu reads */
870 full = 0;
871 } else {
872 if (!cpumask_test_cpu(cpu, buffer->cpumask))
873 return -ENODEV;
874 cpu_buffer = buffer->buffers[cpu];
875 work = &cpu_buffer->irq_work;
876 }
877
878 if (full)
879 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
880 else
881 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
882
883 /*
884 * The events can happen in critical sections where
885 * checking a work queue can cause deadlocks.
886 * After adding a task to the queue, this flag is set
887 * only to notify events to try to wake up the queue
888 * using irq_work.
889 *
890 * We don't clear it even if the buffer is no longer
891 * empty. The flag only causes the next event to run
892 * irq_work to do the work queue wake up. The worse
893 * that can happen if we race with !trace_empty() is that
894 * an event will cause an irq_work to try to wake up
895 * an empty queue.
896 *
897 * There's no reason to protect this flag either, as
898 * the work queue and irq_work logic will do the necessary
899 * synchronization for the wake ups. The only thing
900 * that is necessary is that the wake up happens after
901 * a task has been queued. It's OK for spurious wake ups.
902 */
903 if (full)
904 work->full_waiters_pending = true;
905 else
906 work->waiters_pending = true;
907
908 if (rb_watermark_hit(buffer, cpu, full))
909 goto out;
910
911 if (signal_pending(current)) {
912 ret = -EINTR;
913 goto out;
914 }
915
916 schedule();
917 out:
918 if (full)
919 finish_wait(&work->full_waiters, &wait);
920 else
921 finish_wait(&work->waiters, &wait);
922
923 if (!ret && !rb_watermark_hit(buffer, cpu, full) && signal_pending(current))
924 ret = -EINTR;
925
926 return ret;
927}
928
929/**
930 * ring_buffer_poll_wait - poll on buffer input
931 * @buffer: buffer to wait on
932 * @cpu: the cpu buffer to wait on
933 * @filp: the file descriptor
934 * @poll_table: The poll descriptor
935 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
936 *
937 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
938 * as data is added to any of the @buffer's cpu buffers. Otherwise
939 * it will wait for data to be added to a specific cpu buffer.
940 *
941 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
942 * zero otherwise.
943 */
944__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
945 struct file *filp, poll_table *poll_table, int full)
946{
947 struct ring_buffer_per_cpu *cpu_buffer;
948 struct rb_irq_work *rbwork;
949
950 if (cpu == RING_BUFFER_ALL_CPUS) {
951 rbwork = &buffer->irq_work;
952 full = 0;
953 } else {
954 if (!cpumask_test_cpu(cpu, buffer->cpumask))
955 return EPOLLERR;
956
957 cpu_buffer = buffer->buffers[cpu];
958 rbwork = &cpu_buffer->irq_work;
959 }
960
961 if (full) {
962 unsigned long flags;
963
964 poll_wait(filp, &rbwork->full_waiters, poll_table);
965
966 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
967 rbwork->full_waiters_pending = true;
968 if (!cpu_buffer->shortest_full ||
969 cpu_buffer->shortest_full > full)
970 cpu_buffer->shortest_full = full;
971 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
972 } else {
973 poll_wait(filp, &rbwork->waiters, poll_table);
974 rbwork->waiters_pending = true;
975 }
976
977 /*
978 * There's a tight race between setting the waiters_pending and
979 * checking if the ring buffer is empty. Once the waiters_pending bit
980 * is set, the next event will wake the task up, but we can get stuck
981 * if there's only a single event in.
982 *
983 * FIXME: Ideally, we need a memory barrier on the writer side as well,
984 * but adding a memory barrier to all events will cause too much of a
985 * performance hit in the fast path. We only need a memory barrier when
986 * the buffer goes from empty to having content. But as this race is
987 * extremely small, and it's not a problem if another event comes in, we
988 * will fix it later.
989 */
990 smp_mb();
991
992 if (full)
993 return full_hit(buffer, cpu, full) ? EPOLLIN | EPOLLRDNORM : 0;
994
995 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
996 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
997 return EPOLLIN | EPOLLRDNORM;
998 return 0;
999}
1000
1001/* buffer may be either ring_buffer or ring_buffer_per_cpu */
1002#define RB_WARN_ON(b, cond) \
1003 ({ \
1004 int _____ret = unlikely(cond); \
1005 if (_____ret) { \
1006 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1007 struct ring_buffer_per_cpu *__b = \
1008 (void *)b; \
1009 atomic_inc(&__b->buffer->record_disabled); \
1010 } else \
1011 atomic_inc(&b->record_disabled); \
1012 WARN_ON(1); \
1013 } \
1014 _____ret; \
1015 })
1016
1017/* Up this if you want to test the TIME_EXTENTS and normalization */
1018#define DEBUG_SHIFT 0
1019
1020static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1021{
1022 u64 ts;
1023
1024 /* Skip retpolines :-( */
1025 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1026 ts = trace_clock_local();
1027 else
1028 ts = buffer->clock();
1029
1030 /* shift to debug/test normalization and TIME_EXTENTS */
1031 return ts << DEBUG_SHIFT;
1032}
1033
1034u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1035{
1036 u64 time;
1037
1038 preempt_disable_notrace();
1039 time = rb_time_stamp(buffer);
1040 preempt_enable_notrace();
1041
1042 return time;
1043}
1044EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1045
1046void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1047 int cpu, u64 *ts)
1048{
1049 /* Just stupid testing the normalize function and deltas */
1050 *ts >>= DEBUG_SHIFT;
1051}
1052EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1053
1054/*
1055 * Making the ring buffer lockless makes things tricky.
1056 * Although writes only happen on the CPU that they are on,
1057 * and they only need to worry about interrupts. Reads can
1058 * happen on any CPU.
1059 *
1060 * The reader page is always off the ring buffer, but when the
1061 * reader finishes with a page, it needs to swap its page with
1062 * a new one from the buffer. The reader needs to take from
1063 * the head (writes go to the tail). But if a writer is in overwrite
1064 * mode and wraps, it must push the head page forward.
1065 *
1066 * Here lies the problem.
1067 *
1068 * The reader must be careful to replace only the head page, and
1069 * not another one. As described at the top of the file in the
1070 * ASCII art, the reader sets its old page to point to the next
1071 * page after head. It then sets the page after head to point to
1072 * the old reader page. But if the writer moves the head page
1073 * during this operation, the reader could end up with the tail.
1074 *
1075 * We use cmpxchg to help prevent this race. We also do something
1076 * special with the page before head. We set the LSB to 1.
1077 *
1078 * When the writer must push the page forward, it will clear the
1079 * bit that points to the head page, move the head, and then set
1080 * the bit that points to the new head page.
1081 *
1082 * We also don't want an interrupt coming in and moving the head
1083 * page on another writer. Thus we use the second LSB to catch
1084 * that too. Thus:
1085 *
1086 * head->list->prev->next bit 1 bit 0
1087 * ------- -------
1088 * Normal page 0 0
1089 * Points to head page 0 1
1090 * New head page 1 0
1091 *
1092 * Note we can not trust the prev pointer of the head page, because:
1093 *
1094 * +----+ +-----+ +-----+
1095 * | |------>| T |---X--->| N |
1096 * | |<------| | | |
1097 * +----+ +-----+ +-----+
1098 * ^ ^ |
1099 * | +-----+ | |
1100 * +----------| R |----------+ |
1101 * | |<-----------+
1102 * +-----+
1103 *
1104 * Key: ---X--> HEAD flag set in pointer
1105 * T Tail page
1106 * R Reader page
1107 * N Next page
1108 *
1109 * (see __rb_reserve_next() to see where this happens)
1110 *
1111 * What the above shows is that the reader just swapped out
1112 * the reader page with a page in the buffer, but before it
1113 * could make the new header point back to the new page added
1114 * it was preempted by a writer. The writer moved forward onto
1115 * the new page added by the reader and is about to move forward
1116 * again.
1117 *
1118 * You can see, it is legitimate for the previous pointer of
1119 * the head (or any page) not to point back to itself. But only
1120 * temporarily.
1121 */
1122
1123#define RB_PAGE_NORMAL 0UL
1124#define RB_PAGE_HEAD 1UL
1125#define RB_PAGE_UPDATE 2UL
1126
1127
1128#define RB_FLAG_MASK 3UL
1129
1130/* PAGE_MOVED is not part of the mask */
1131#define RB_PAGE_MOVED 4UL
1132
1133/*
1134 * rb_list_head - remove any bit
1135 */
1136static struct list_head *rb_list_head(struct list_head *list)
1137{
1138 unsigned long val = (unsigned long)list;
1139
1140 return (struct list_head *)(val & ~RB_FLAG_MASK);
1141}
1142
1143/*
1144 * rb_is_head_page - test if the given page is the head page
1145 *
1146 * Because the reader may move the head_page pointer, we can
1147 * not trust what the head page is (it may be pointing to
1148 * the reader page). But if the next page is a header page,
1149 * its flags will be non zero.
1150 */
1151static inline int
1152rb_is_head_page(struct buffer_page *page, struct list_head *list)
1153{
1154 unsigned long val;
1155
1156 val = (unsigned long)list->next;
1157
1158 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1159 return RB_PAGE_MOVED;
1160
1161 return val & RB_FLAG_MASK;
1162}
1163
1164/*
1165 * rb_is_reader_page
1166 *
1167 * The unique thing about the reader page, is that, if the
1168 * writer is ever on it, the previous pointer never points
1169 * back to the reader page.
1170 */
1171static bool rb_is_reader_page(struct buffer_page *page)
1172{
1173 struct list_head *list = page->list.prev;
1174
1175 return rb_list_head(list->next) != &page->list;
1176}
1177
1178/*
1179 * rb_set_list_to_head - set a list_head to be pointing to head.
1180 */
1181static void rb_set_list_to_head(struct list_head *list)
1182{
1183 unsigned long *ptr;
1184
1185 ptr = (unsigned long *)&list->next;
1186 *ptr |= RB_PAGE_HEAD;
1187 *ptr &= ~RB_PAGE_UPDATE;
1188}
1189
1190/*
1191 * rb_head_page_activate - sets up head page
1192 */
1193static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1194{
1195 struct buffer_page *head;
1196
1197 head = cpu_buffer->head_page;
1198 if (!head)
1199 return;
1200
1201 /*
1202 * Set the previous list pointer to have the HEAD flag.
1203 */
1204 rb_set_list_to_head(head->list.prev);
1205}
1206
1207static void rb_list_head_clear(struct list_head *list)
1208{
1209 unsigned long *ptr = (unsigned long *)&list->next;
1210
1211 *ptr &= ~RB_FLAG_MASK;
1212}
1213
1214/*
1215 * rb_head_page_deactivate - clears head page ptr (for free list)
1216 */
1217static void
1218rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1219{
1220 struct list_head *hd;
1221
1222 /* Go through the whole list and clear any pointers found. */
1223 rb_list_head_clear(cpu_buffer->pages);
1224
1225 list_for_each(hd, cpu_buffer->pages)
1226 rb_list_head_clear(hd);
1227}
1228
1229static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1230 struct buffer_page *head,
1231 struct buffer_page *prev,
1232 int old_flag, int new_flag)
1233{
1234 struct list_head *list;
1235 unsigned long val = (unsigned long)&head->list;
1236 unsigned long ret;
1237
1238 list = &prev->list;
1239
1240 val &= ~RB_FLAG_MASK;
1241
1242 ret = cmpxchg((unsigned long *)&list->next,
1243 val | old_flag, val | new_flag);
1244
1245 /* check if the reader took the page */
1246 if ((ret & ~RB_FLAG_MASK) != val)
1247 return RB_PAGE_MOVED;
1248
1249 return ret & RB_FLAG_MASK;
1250}
1251
1252static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1253 struct buffer_page *head,
1254 struct buffer_page *prev,
1255 int old_flag)
1256{
1257 return rb_head_page_set(cpu_buffer, head, prev,
1258 old_flag, RB_PAGE_UPDATE);
1259}
1260
1261static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1262 struct buffer_page *head,
1263 struct buffer_page *prev,
1264 int old_flag)
1265{
1266 return rb_head_page_set(cpu_buffer, head, prev,
1267 old_flag, RB_PAGE_HEAD);
1268}
1269
1270static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1271 struct buffer_page *head,
1272 struct buffer_page *prev,
1273 int old_flag)
1274{
1275 return rb_head_page_set(cpu_buffer, head, prev,
1276 old_flag, RB_PAGE_NORMAL);
1277}
1278
1279static inline void rb_inc_page(struct buffer_page **bpage)
1280{
1281 struct list_head *p = rb_list_head((*bpage)->list.next);
1282
1283 *bpage = list_entry(p, struct buffer_page, list);
1284}
1285
1286static struct buffer_page *
1287rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1288{
1289 struct buffer_page *head;
1290 struct buffer_page *page;
1291 struct list_head *list;
1292 int i;
1293
1294 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1295 return NULL;
1296
1297 /* sanity check */
1298 list = cpu_buffer->pages;
1299 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1300 return NULL;
1301
1302 page = head = cpu_buffer->head_page;
1303 /*
1304 * It is possible that the writer moves the header behind
1305 * where we started, and we miss in one loop.
1306 * A second loop should grab the header, but we'll do
1307 * three loops just because I'm paranoid.
1308 */
1309 for (i = 0; i < 3; i++) {
1310 do {
1311 if (rb_is_head_page(page, page->list.prev)) {
1312 cpu_buffer->head_page = page;
1313 return page;
1314 }
1315 rb_inc_page(&page);
1316 } while (page != head);
1317 }
1318
1319 RB_WARN_ON(cpu_buffer, 1);
1320
1321 return NULL;
1322}
1323
1324static bool rb_head_page_replace(struct buffer_page *old,
1325 struct buffer_page *new)
1326{
1327 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1328 unsigned long val;
1329
1330 val = *ptr & ~RB_FLAG_MASK;
1331 val |= RB_PAGE_HEAD;
1332
1333 return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1334}
1335
1336/*
1337 * rb_tail_page_update - move the tail page forward
1338 */
1339static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1340 struct buffer_page *tail_page,
1341 struct buffer_page *next_page)
1342{
1343 unsigned long old_entries;
1344 unsigned long old_write;
1345
1346 /*
1347 * The tail page now needs to be moved forward.
1348 *
1349 * We need to reset the tail page, but without messing
1350 * with possible erasing of data brought in by interrupts
1351 * that have moved the tail page and are currently on it.
1352 *
1353 * We add a counter to the write field to denote this.
1354 */
1355 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1356 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1357
1358 local_inc(&cpu_buffer->pages_touched);
1359 /*
1360 * Just make sure we have seen our old_write and synchronize
1361 * with any interrupts that come in.
1362 */
1363 barrier();
1364
1365 /*
1366 * If the tail page is still the same as what we think
1367 * it is, then it is up to us to update the tail
1368 * pointer.
1369 */
1370 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1371 /* Zero the write counter */
1372 unsigned long val = old_write & ~RB_WRITE_MASK;
1373 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1374
1375 /*
1376 * This will only succeed if an interrupt did
1377 * not come in and change it. In which case, we
1378 * do not want to modify it.
1379 *
1380 * We add (void) to let the compiler know that we do not care
1381 * about the return value of these functions. We use the
1382 * cmpxchg to only update if an interrupt did not already
1383 * do it for us. If the cmpxchg fails, we don't care.
1384 */
1385 (void)local_cmpxchg(&next_page->write, old_write, val);
1386 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1387
1388 /*
1389 * No need to worry about races with clearing out the commit.
1390 * it only can increment when a commit takes place. But that
1391 * only happens in the outer most nested commit.
1392 */
1393 local_set(&next_page->page->commit, 0);
1394
1395 /* Again, either we update tail_page or an interrupt does */
1396 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1397 }
1398}
1399
1400static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1401 struct buffer_page *bpage)
1402{
1403 unsigned long val = (unsigned long)bpage;
1404
1405 RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1406}
1407
1408/**
1409 * rb_check_pages - integrity check of buffer pages
1410 * @cpu_buffer: CPU buffer with pages to test
1411 *
1412 * As a safety measure we check to make sure the data pages have not
1413 * been corrupted.
1414 */
1415static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1416{
1417 struct list_head *head = rb_list_head(cpu_buffer->pages);
1418 struct list_head *tmp;
1419
1420 if (RB_WARN_ON(cpu_buffer,
1421 rb_list_head(rb_list_head(head->next)->prev) != head))
1422 return;
1423
1424 if (RB_WARN_ON(cpu_buffer,
1425 rb_list_head(rb_list_head(head->prev)->next) != head))
1426 return;
1427
1428 for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) {
1429 if (RB_WARN_ON(cpu_buffer,
1430 rb_list_head(rb_list_head(tmp->next)->prev) != tmp))
1431 return;
1432
1433 if (RB_WARN_ON(cpu_buffer,
1434 rb_list_head(rb_list_head(tmp->prev)->next) != tmp))
1435 return;
1436 }
1437}
1438
1439static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1440 long nr_pages, struct list_head *pages)
1441{
1442 struct buffer_page *bpage, *tmp;
1443 bool user_thread = current->mm != NULL;
1444 gfp_t mflags;
1445 long i;
1446
1447 /*
1448 * Check if the available memory is there first.
1449 * Note, si_mem_available() only gives us a rough estimate of available
1450 * memory. It may not be accurate. But we don't care, we just want
1451 * to prevent doing any allocation when it is obvious that it is
1452 * not going to succeed.
1453 */
1454 i = si_mem_available();
1455 if (i < nr_pages)
1456 return -ENOMEM;
1457
1458 /*
1459 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1460 * gracefully without invoking oom-killer and the system is not
1461 * destabilized.
1462 */
1463 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1464
1465 /*
1466 * If a user thread allocates too much, and si_mem_available()
1467 * reports there's enough memory, even though there is not.
1468 * Make sure the OOM killer kills this thread. This can happen
1469 * even with RETRY_MAYFAIL because another task may be doing
1470 * an allocation after this task has taken all memory.
1471 * This is the task the OOM killer needs to take out during this
1472 * loop, even if it was triggered by an allocation somewhere else.
1473 */
1474 if (user_thread)
1475 set_current_oom_origin();
1476 for (i = 0; i < nr_pages; i++) {
1477 struct page *page;
1478
1479 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1480 mflags, cpu_to_node(cpu_buffer->cpu));
1481 if (!bpage)
1482 goto free_pages;
1483
1484 rb_check_bpage(cpu_buffer, bpage);
1485
1486 list_add(&bpage->list, pages);
1487
1488 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags,
1489 cpu_buffer->buffer->subbuf_order);
1490 if (!page)
1491 goto free_pages;
1492 bpage->page = page_address(page);
1493 bpage->order = cpu_buffer->buffer->subbuf_order;
1494 rb_init_page(bpage->page);
1495
1496 if (user_thread && fatal_signal_pending(current))
1497 goto free_pages;
1498 }
1499 if (user_thread)
1500 clear_current_oom_origin();
1501
1502 return 0;
1503
1504free_pages:
1505 list_for_each_entry_safe(bpage, tmp, pages, list) {
1506 list_del_init(&bpage->list);
1507 free_buffer_page(bpage);
1508 }
1509 if (user_thread)
1510 clear_current_oom_origin();
1511
1512 return -ENOMEM;
1513}
1514
1515static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1516 unsigned long nr_pages)
1517{
1518 LIST_HEAD(pages);
1519
1520 WARN_ON(!nr_pages);
1521
1522 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1523 return -ENOMEM;
1524
1525 /*
1526 * The ring buffer page list is a circular list that does not
1527 * start and end with a list head. All page list items point to
1528 * other pages.
1529 */
1530 cpu_buffer->pages = pages.next;
1531 list_del(&pages);
1532
1533 cpu_buffer->nr_pages = nr_pages;
1534
1535 rb_check_pages(cpu_buffer);
1536
1537 return 0;
1538}
1539
1540static struct ring_buffer_per_cpu *
1541rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1542{
1543 struct ring_buffer_per_cpu *cpu_buffer;
1544 struct buffer_page *bpage;
1545 struct page *page;
1546 int ret;
1547
1548 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1549 GFP_KERNEL, cpu_to_node(cpu));
1550 if (!cpu_buffer)
1551 return NULL;
1552
1553 cpu_buffer->cpu = cpu;
1554 cpu_buffer->buffer = buffer;
1555 raw_spin_lock_init(&cpu_buffer->reader_lock);
1556 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1557 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1558 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1559 init_completion(&cpu_buffer->update_done);
1560 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1561 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1562 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1563
1564 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1565 GFP_KERNEL, cpu_to_node(cpu));
1566 if (!bpage)
1567 goto fail_free_buffer;
1568
1569 rb_check_bpage(cpu_buffer, bpage);
1570
1571 cpu_buffer->reader_page = bpage;
1572
1573 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, cpu_buffer->buffer->subbuf_order);
1574 if (!page)
1575 goto fail_free_reader;
1576 bpage->page = page_address(page);
1577 rb_init_page(bpage->page);
1578
1579 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1580 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1581
1582 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1583 if (ret < 0)
1584 goto fail_free_reader;
1585
1586 cpu_buffer->head_page
1587 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1588 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1589
1590 rb_head_page_activate(cpu_buffer);
1591
1592 return cpu_buffer;
1593
1594 fail_free_reader:
1595 free_buffer_page(cpu_buffer->reader_page);
1596
1597 fail_free_buffer:
1598 kfree(cpu_buffer);
1599 return NULL;
1600}
1601
1602static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1603{
1604 struct list_head *head = cpu_buffer->pages;
1605 struct buffer_page *bpage, *tmp;
1606
1607 irq_work_sync(&cpu_buffer->irq_work.work);
1608
1609 free_buffer_page(cpu_buffer->reader_page);
1610
1611 if (head) {
1612 rb_head_page_deactivate(cpu_buffer);
1613
1614 list_for_each_entry_safe(bpage, tmp, head, list) {
1615 list_del_init(&bpage->list);
1616 free_buffer_page(bpage);
1617 }
1618 bpage = list_entry(head, struct buffer_page, list);
1619 free_buffer_page(bpage);
1620 }
1621
1622 free_page((unsigned long)cpu_buffer->free_page);
1623
1624 kfree(cpu_buffer);
1625}
1626
1627/**
1628 * __ring_buffer_alloc - allocate a new ring_buffer
1629 * @size: the size in bytes per cpu that is needed.
1630 * @flags: attributes to set for the ring buffer.
1631 * @key: ring buffer reader_lock_key.
1632 *
1633 * Currently the only flag that is available is the RB_FL_OVERWRITE
1634 * flag. This flag means that the buffer will overwrite old data
1635 * when the buffer wraps. If this flag is not set, the buffer will
1636 * drop data when the tail hits the head.
1637 */
1638struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1639 struct lock_class_key *key)
1640{
1641 struct trace_buffer *buffer;
1642 long nr_pages;
1643 int bsize;
1644 int cpu;
1645 int ret;
1646
1647 /* keep it in its own cache line */
1648 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1649 GFP_KERNEL);
1650 if (!buffer)
1651 return NULL;
1652
1653 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1654 goto fail_free_buffer;
1655
1656 /* Default buffer page size - one system page */
1657 buffer->subbuf_order = 0;
1658 buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE;
1659
1660 /* Max payload is buffer page size - header (8bytes) */
1661 buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
1662
1663 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
1664 buffer->flags = flags;
1665 buffer->clock = trace_clock_local;
1666 buffer->reader_lock_key = key;
1667
1668 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1669 init_waitqueue_head(&buffer->irq_work.waiters);
1670
1671 /* need at least two pages */
1672 if (nr_pages < 2)
1673 nr_pages = 2;
1674
1675 buffer->cpus = nr_cpu_ids;
1676
1677 bsize = sizeof(void *) * nr_cpu_ids;
1678 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1679 GFP_KERNEL);
1680 if (!buffer->buffers)
1681 goto fail_free_cpumask;
1682
1683 cpu = raw_smp_processor_id();
1684 cpumask_set_cpu(cpu, buffer->cpumask);
1685 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1686 if (!buffer->buffers[cpu])
1687 goto fail_free_buffers;
1688
1689 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1690 if (ret < 0)
1691 goto fail_free_buffers;
1692
1693 mutex_init(&buffer->mutex);
1694
1695 return buffer;
1696
1697 fail_free_buffers:
1698 for_each_buffer_cpu(buffer, cpu) {
1699 if (buffer->buffers[cpu])
1700 rb_free_cpu_buffer(buffer->buffers[cpu]);
1701 }
1702 kfree(buffer->buffers);
1703
1704 fail_free_cpumask:
1705 free_cpumask_var(buffer->cpumask);
1706
1707 fail_free_buffer:
1708 kfree(buffer);
1709 return NULL;
1710}
1711EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1712
1713/**
1714 * ring_buffer_free - free a ring buffer.
1715 * @buffer: the buffer to free.
1716 */
1717void
1718ring_buffer_free(struct trace_buffer *buffer)
1719{
1720 int cpu;
1721
1722 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1723
1724 irq_work_sync(&buffer->irq_work.work);
1725
1726 for_each_buffer_cpu(buffer, cpu)
1727 rb_free_cpu_buffer(buffer->buffers[cpu]);
1728
1729 kfree(buffer->buffers);
1730 free_cpumask_var(buffer->cpumask);
1731
1732 kfree(buffer);
1733}
1734EXPORT_SYMBOL_GPL(ring_buffer_free);
1735
1736void ring_buffer_set_clock(struct trace_buffer *buffer,
1737 u64 (*clock)(void))
1738{
1739 buffer->clock = clock;
1740}
1741
1742void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1743{
1744 buffer->time_stamp_abs = abs;
1745}
1746
1747bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1748{
1749 return buffer->time_stamp_abs;
1750}
1751
1752static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1753
1754static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1755{
1756 return local_read(&bpage->entries) & RB_WRITE_MASK;
1757}
1758
1759static inline unsigned long rb_page_write(struct buffer_page *bpage)
1760{
1761 return local_read(&bpage->write) & RB_WRITE_MASK;
1762}
1763
1764static bool
1765rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1766{
1767 struct list_head *tail_page, *to_remove, *next_page;
1768 struct buffer_page *to_remove_page, *tmp_iter_page;
1769 struct buffer_page *last_page, *first_page;
1770 unsigned long nr_removed;
1771 unsigned long head_bit;
1772 int page_entries;
1773
1774 head_bit = 0;
1775
1776 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1777 atomic_inc(&cpu_buffer->record_disabled);
1778 /*
1779 * We don't race with the readers since we have acquired the reader
1780 * lock. We also don't race with writers after disabling recording.
1781 * This makes it easy to figure out the first and the last page to be
1782 * removed from the list. We unlink all the pages in between including
1783 * the first and last pages. This is done in a busy loop so that we
1784 * lose the least number of traces.
1785 * The pages are freed after we restart recording and unlock readers.
1786 */
1787 tail_page = &cpu_buffer->tail_page->list;
1788
1789 /*
1790 * tail page might be on reader page, we remove the next page
1791 * from the ring buffer
1792 */
1793 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1794 tail_page = rb_list_head(tail_page->next);
1795 to_remove = tail_page;
1796
1797 /* start of pages to remove */
1798 first_page = list_entry(rb_list_head(to_remove->next),
1799 struct buffer_page, list);
1800
1801 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1802 to_remove = rb_list_head(to_remove)->next;
1803 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1804 }
1805 /* Read iterators need to reset themselves when some pages removed */
1806 cpu_buffer->pages_removed += nr_removed;
1807
1808 next_page = rb_list_head(to_remove)->next;
1809
1810 /*
1811 * Now we remove all pages between tail_page and next_page.
1812 * Make sure that we have head_bit value preserved for the
1813 * next page
1814 */
1815 tail_page->next = (struct list_head *)((unsigned long)next_page |
1816 head_bit);
1817 next_page = rb_list_head(next_page);
1818 next_page->prev = tail_page;
1819
1820 /* make sure pages points to a valid page in the ring buffer */
1821 cpu_buffer->pages = next_page;
1822
1823 /* update head page */
1824 if (head_bit)
1825 cpu_buffer->head_page = list_entry(next_page,
1826 struct buffer_page, list);
1827
1828 /* pages are removed, resume tracing and then free the pages */
1829 atomic_dec(&cpu_buffer->record_disabled);
1830 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1831
1832 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1833
1834 /* last buffer page to remove */
1835 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1836 list);
1837 tmp_iter_page = first_page;
1838
1839 do {
1840 cond_resched();
1841
1842 to_remove_page = tmp_iter_page;
1843 rb_inc_page(&tmp_iter_page);
1844
1845 /* update the counters */
1846 page_entries = rb_page_entries(to_remove_page);
1847 if (page_entries) {
1848 /*
1849 * If something was added to this page, it was full
1850 * since it is not the tail page. So we deduct the
1851 * bytes consumed in ring buffer from here.
1852 * Increment overrun to account for the lost events.
1853 */
1854 local_add(page_entries, &cpu_buffer->overrun);
1855 local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
1856 local_inc(&cpu_buffer->pages_lost);
1857 }
1858
1859 /*
1860 * We have already removed references to this list item, just
1861 * free up the buffer_page and its page
1862 */
1863 free_buffer_page(to_remove_page);
1864 nr_removed--;
1865
1866 } while (to_remove_page != last_page);
1867
1868 RB_WARN_ON(cpu_buffer, nr_removed);
1869
1870 return nr_removed == 0;
1871}
1872
1873static bool
1874rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1875{
1876 struct list_head *pages = &cpu_buffer->new_pages;
1877 unsigned long flags;
1878 bool success;
1879 int retries;
1880
1881 /* Can be called at early boot up, where interrupts must not been enabled */
1882 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1883 /*
1884 * We are holding the reader lock, so the reader page won't be swapped
1885 * in the ring buffer. Now we are racing with the writer trying to
1886 * move head page and the tail page.
1887 * We are going to adapt the reader page update process where:
1888 * 1. We first splice the start and end of list of new pages between
1889 * the head page and its previous page.
1890 * 2. We cmpxchg the prev_page->next to point from head page to the
1891 * start of new pages list.
1892 * 3. Finally, we update the head->prev to the end of new list.
1893 *
1894 * We will try this process 10 times, to make sure that we don't keep
1895 * spinning.
1896 */
1897 retries = 10;
1898 success = false;
1899 while (retries--) {
1900 struct list_head *head_page, *prev_page;
1901 struct list_head *last_page, *first_page;
1902 struct list_head *head_page_with_bit;
1903 struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
1904
1905 if (!hpage)
1906 break;
1907 head_page = &hpage->list;
1908 prev_page = head_page->prev;
1909
1910 first_page = pages->next;
1911 last_page = pages->prev;
1912
1913 head_page_with_bit = (struct list_head *)
1914 ((unsigned long)head_page | RB_PAGE_HEAD);
1915
1916 last_page->next = head_page_with_bit;
1917 first_page->prev = prev_page;
1918
1919 /* caution: head_page_with_bit gets updated on cmpxchg failure */
1920 if (try_cmpxchg(&prev_page->next,
1921 &head_page_with_bit, first_page)) {
1922 /*
1923 * yay, we replaced the page pointer to our new list,
1924 * now, we just have to update to head page's prev
1925 * pointer to point to end of list
1926 */
1927 head_page->prev = last_page;
1928 success = true;
1929 break;
1930 }
1931 }
1932
1933 if (success)
1934 INIT_LIST_HEAD(pages);
1935 /*
1936 * If we weren't successful in adding in new pages, warn and stop
1937 * tracing
1938 */
1939 RB_WARN_ON(cpu_buffer, !success);
1940 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1941
1942 /* free pages if they weren't inserted */
1943 if (!success) {
1944 struct buffer_page *bpage, *tmp;
1945 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1946 list) {
1947 list_del_init(&bpage->list);
1948 free_buffer_page(bpage);
1949 }
1950 }
1951 return success;
1952}
1953
1954static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1955{
1956 bool success;
1957
1958 if (cpu_buffer->nr_pages_to_update > 0)
1959 success = rb_insert_pages(cpu_buffer);
1960 else
1961 success = rb_remove_pages(cpu_buffer,
1962 -cpu_buffer->nr_pages_to_update);
1963
1964 if (success)
1965 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1966}
1967
1968static void update_pages_handler(struct work_struct *work)
1969{
1970 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1971 struct ring_buffer_per_cpu, update_pages_work);
1972 rb_update_pages(cpu_buffer);
1973 complete(&cpu_buffer->update_done);
1974}
1975
1976/**
1977 * ring_buffer_resize - resize the ring buffer
1978 * @buffer: the buffer to resize.
1979 * @size: the new size.
1980 * @cpu_id: the cpu buffer to resize
1981 *
1982 * Minimum size is 2 * buffer->subbuf_size.
1983 *
1984 * Returns 0 on success and < 0 on failure.
1985 */
1986int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
1987 int cpu_id)
1988{
1989 struct ring_buffer_per_cpu *cpu_buffer;
1990 unsigned long nr_pages;
1991 int cpu, err;
1992
1993 /*
1994 * Always succeed at resizing a non-existent buffer:
1995 */
1996 if (!buffer)
1997 return 0;
1998
1999 /* Make sure the requested buffer exists */
2000 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2001 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2002 return 0;
2003
2004 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2005
2006 /* we need a minimum of two pages */
2007 if (nr_pages < 2)
2008 nr_pages = 2;
2009
2010 /* prevent another thread from changing buffer sizes */
2011 mutex_lock(&buffer->mutex);
2012 atomic_inc(&buffer->resizing);
2013
2014 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2015 /*
2016 * Don't succeed if resizing is disabled, as a reader might be
2017 * manipulating the ring buffer and is expecting a sane state while
2018 * this is true.
2019 */
2020 for_each_buffer_cpu(buffer, cpu) {
2021 cpu_buffer = buffer->buffers[cpu];
2022 if (atomic_read(&cpu_buffer->resize_disabled)) {
2023 err = -EBUSY;
2024 goto out_err_unlock;
2025 }
2026 }
2027
2028 /* calculate the pages to update */
2029 for_each_buffer_cpu(buffer, cpu) {
2030 cpu_buffer = buffer->buffers[cpu];
2031
2032 cpu_buffer->nr_pages_to_update = nr_pages -
2033 cpu_buffer->nr_pages;
2034 /*
2035 * nothing more to do for removing pages or no update
2036 */
2037 if (cpu_buffer->nr_pages_to_update <= 0)
2038 continue;
2039 /*
2040 * to add pages, make sure all new pages can be
2041 * allocated without receiving ENOMEM
2042 */
2043 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2044 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2045 &cpu_buffer->new_pages)) {
2046 /* not enough memory for new pages */
2047 err = -ENOMEM;
2048 goto out_err;
2049 }
2050
2051 cond_resched();
2052 }
2053
2054 cpus_read_lock();
2055 /*
2056 * Fire off all the required work handlers
2057 * We can't schedule on offline CPUs, but it's not necessary
2058 * since we can change their buffer sizes without any race.
2059 */
2060 for_each_buffer_cpu(buffer, cpu) {
2061 cpu_buffer = buffer->buffers[cpu];
2062 if (!cpu_buffer->nr_pages_to_update)
2063 continue;
2064
2065 /* Can't run something on an offline CPU. */
2066 if (!cpu_online(cpu)) {
2067 rb_update_pages(cpu_buffer);
2068 cpu_buffer->nr_pages_to_update = 0;
2069 } else {
2070 /* Run directly if possible. */
2071 migrate_disable();
2072 if (cpu != smp_processor_id()) {
2073 migrate_enable();
2074 schedule_work_on(cpu,
2075 &cpu_buffer->update_pages_work);
2076 } else {
2077 update_pages_handler(&cpu_buffer->update_pages_work);
2078 migrate_enable();
2079 }
2080 }
2081 }
2082
2083 /* wait for all the updates to complete */
2084 for_each_buffer_cpu(buffer, cpu) {
2085 cpu_buffer = buffer->buffers[cpu];
2086 if (!cpu_buffer->nr_pages_to_update)
2087 continue;
2088
2089 if (cpu_online(cpu))
2090 wait_for_completion(&cpu_buffer->update_done);
2091 cpu_buffer->nr_pages_to_update = 0;
2092 }
2093
2094 cpus_read_unlock();
2095 } else {
2096 cpu_buffer = buffer->buffers[cpu_id];
2097
2098 if (nr_pages == cpu_buffer->nr_pages)
2099 goto out;
2100
2101 /*
2102 * Don't succeed if resizing is disabled, as a reader might be
2103 * manipulating the ring buffer and is expecting a sane state while
2104 * this is true.
2105 */
2106 if (atomic_read(&cpu_buffer->resize_disabled)) {
2107 err = -EBUSY;
2108 goto out_err_unlock;
2109 }
2110
2111 cpu_buffer->nr_pages_to_update = nr_pages -
2112 cpu_buffer->nr_pages;
2113
2114 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2115 if (cpu_buffer->nr_pages_to_update > 0 &&
2116 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2117 &cpu_buffer->new_pages)) {
2118 err = -ENOMEM;
2119 goto out_err;
2120 }
2121
2122 cpus_read_lock();
2123
2124 /* Can't run something on an offline CPU. */
2125 if (!cpu_online(cpu_id))
2126 rb_update_pages(cpu_buffer);
2127 else {
2128 /* Run directly if possible. */
2129 migrate_disable();
2130 if (cpu_id == smp_processor_id()) {
2131 rb_update_pages(cpu_buffer);
2132 migrate_enable();
2133 } else {
2134 migrate_enable();
2135 schedule_work_on(cpu_id,
2136 &cpu_buffer->update_pages_work);
2137 wait_for_completion(&cpu_buffer->update_done);
2138 }
2139 }
2140
2141 cpu_buffer->nr_pages_to_update = 0;
2142 cpus_read_unlock();
2143 }
2144
2145 out:
2146 /*
2147 * The ring buffer resize can happen with the ring buffer
2148 * enabled, so that the update disturbs the tracing as little
2149 * as possible. But if the buffer is disabled, we do not need
2150 * to worry about that, and we can take the time to verify
2151 * that the buffer is not corrupt.
2152 */
2153 if (atomic_read(&buffer->record_disabled)) {
2154 atomic_inc(&buffer->record_disabled);
2155 /*
2156 * Even though the buffer was disabled, we must make sure
2157 * that it is truly disabled before calling rb_check_pages.
2158 * There could have been a race between checking
2159 * record_disable and incrementing it.
2160 */
2161 synchronize_rcu();
2162 for_each_buffer_cpu(buffer, cpu) {
2163 cpu_buffer = buffer->buffers[cpu];
2164 rb_check_pages(cpu_buffer);
2165 }
2166 atomic_dec(&buffer->record_disabled);
2167 }
2168
2169 atomic_dec(&buffer->resizing);
2170 mutex_unlock(&buffer->mutex);
2171 return 0;
2172
2173 out_err:
2174 for_each_buffer_cpu(buffer, cpu) {
2175 struct buffer_page *bpage, *tmp;
2176
2177 cpu_buffer = buffer->buffers[cpu];
2178 cpu_buffer->nr_pages_to_update = 0;
2179
2180 if (list_empty(&cpu_buffer->new_pages))
2181 continue;
2182
2183 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2184 list) {
2185 list_del_init(&bpage->list);
2186 free_buffer_page(bpage);
2187 }
2188 }
2189 out_err_unlock:
2190 atomic_dec(&buffer->resizing);
2191 mutex_unlock(&buffer->mutex);
2192 return err;
2193}
2194EXPORT_SYMBOL_GPL(ring_buffer_resize);
2195
2196void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2197{
2198 mutex_lock(&buffer->mutex);
2199 if (val)
2200 buffer->flags |= RB_FL_OVERWRITE;
2201 else
2202 buffer->flags &= ~RB_FL_OVERWRITE;
2203 mutex_unlock(&buffer->mutex);
2204}
2205EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2206
2207static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2208{
2209 return bpage->page->data + index;
2210}
2211
2212static __always_inline struct ring_buffer_event *
2213rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2214{
2215 return __rb_page_index(cpu_buffer->reader_page,
2216 cpu_buffer->reader_page->read);
2217}
2218
2219static struct ring_buffer_event *
2220rb_iter_head_event(struct ring_buffer_iter *iter)
2221{
2222 struct ring_buffer_event *event;
2223 struct buffer_page *iter_head_page = iter->head_page;
2224 unsigned long commit;
2225 unsigned length;
2226
2227 if (iter->head != iter->next_event)
2228 return iter->event;
2229
2230 /*
2231 * When the writer goes across pages, it issues a cmpxchg which
2232 * is a mb(), which will synchronize with the rmb here.
2233 * (see rb_tail_page_update() and __rb_reserve_next())
2234 */
2235 commit = rb_page_commit(iter_head_page);
2236 smp_rmb();
2237
2238 /* An event needs to be at least 8 bytes in size */
2239 if (iter->head > commit - 8)
2240 goto reset;
2241
2242 event = __rb_page_index(iter_head_page, iter->head);
2243 length = rb_event_length(event);
2244
2245 /*
2246 * READ_ONCE() doesn't work on functions and we don't want the
2247 * compiler doing any crazy optimizations with length.
2248 */
2249 barrier();
2250
2251 if ((iter->head + length) > commit || length > iter->event_size)
2252 /* Writer corrupted the read? */
2253 goto reset;
2254
2255 memcpy(iter->event, event, length);
2256 /*
2257 * If the page stamp is still the same after this rmb() then the
2258 * event was safely copied without the writer entering the page.
2259 */
2260 smp_rmb();
2261
2262 /* Make sure the page didn't change since we read this */
2263 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2264 commit > rb_page_commit(iter_head_page))
2265 goto reset;
2266
2267 iter->next_event = iter->head + length;
2268 return iter->event;
2269 reset:
2270 /* Reset to the beginning */
2271 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2272 iter->head = 0;
2273 iter->next_event = 0;
2274 iter->missed_events = 1;
2275 return NULL;
2276}
2277
2278/* Size is determined by what has been committed */
2279static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2280{
2281 return rb_page_commit(bpage);
2282}
2283
2284static __always_inline unsigned
2285rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2286{
2287 return rb_page_commit(cpu_buffer->commit_page);
2288}
2289
2290static __always_inline unsigned
2291rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
2292{
2293 unsigned long addr = (unsigned long)event;
2294
2295 addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
2296
2297 return addr - BUF_PAGE_HDR_SIZE;
2298}
2299
2300static void rb_inc_iter(struct ring_buffer_iter *iter)
2301{
2302 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2303
2304 /*
2305 * The iterator could be on the reader page (it starts there).
2306 * But the head could have moved, since the reader was
2307 * found. Check for this case and assign the iterator
2308 * to the head page instead of next.
2309 */
2310 if (iter->head_page == cpu_buffer->reader_page)
2311 iter->head_page = rb_set_head_page(cpu_buffer);
2312 else
2313 rb_inc_page(&iter->head_page);
2314
2315 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2316 iter->head = 0;
2317 iter->next_event = 0;
2318}
2319
2320/*
2321 * rb_handle_head_page - writer hit the head page
2322 *
2323 * Returns: +1 to retry page
2324 * 0 to continue
2325 * -1 on error
2326 */
2327static int
2328rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2329 struct buffer_page *tail_page,
2330 struct buffer_page *next_page)
2331{
2332 struct buffer_page *new_head;
2333 int entries;
2334 int type;
2335 int ret;
2336
2337 entries = rb_page_entries(next_page);
2338
2339 /*
2340 * The hard part is here. We need to move the head
2341 * forward, and protect against both readers on
2342 * other CPUs and writers coming in via interrupts.
2343 */
2344 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2345 RB_PAGE_HEAD);
2346
2347 /*
2348 * type can be one of four:
2349 * NORMAL - an interrupt already moved it for us
2350 * HEAD - we are the first to get here.
2351 * UPDATE - we are the interrupt interrupting
2352 * a current move.
2353 * MOVED - a reader on another CPU moved the next
2354 * pointer to its reader page. Give up
2355 * and try again.
2356 */
2357
2358 switch (type) {
2359 case RB_PAGE_HEAD:
2360 /*
2361 * We changed the head to UPDATE, thus
2362 * it is our responsibility to update
2363 * the counters.
2364 */
2365 local_add(entries, &cpu_buffer->overrun);
2366 local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
2367 local_inc(&cpu_buffer->pages_lost);
2368
2369 /*
2370 * The entries will be zeroed out when we move the
2371 * tail page.
2372 */
2373
2374 /* still more to do */
2375 break;
2376
2377 case RB_PAGE_UPDATE:
2378 /*
2379 * This is an interrupt that interrupt the
2380 * previous update. Still more to do.
2381 */
2382 break;
2383 case RB_PAGE_NORMAL:
2384 /*
2385 * An interrupt came in before the update
2386 * and processed this for us.
2387 * Nothing left to do.
2388 */
2389 return 1;
2390 case RB_PAGE_MOVED:
2391 /*
2392 * The reader is on another CPU and just did
2393 * a swap with our next_page.
2394 * Try again.
2395 */
2396 return 1;
2397 default:
2398 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2399 return -1;
2400 }
2401
2402 /*
2403 * Now that we are here, the old head pointer is
2404 * set to UPDATE. This will keep the reader from
2405 * swapping the head page with the reader page.
2406 * The reader (on another CPU) will spin till
2407 * we are finished.
2408 *
2409 * We just need to protect against interrupts
2410 * doing the job. We will set the next pointer
2411 * to HEAD. After that, we set the old pointer
2412 * to NORMAL, but only if it was HEAD before.
2413 * otherwise we are an interrupt, and only
2414 * want the outer most commit to reset it.
2415 */
2416 new_head = next_page;
2417 rb_inc_page(&new_head);
2418
2419 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2420 RB_PAGE_NORMAL);
2421
2422 /*
2423 * Valid returns are:
2424 * HEAD - an interrupt came in and already set it.
2425 * NORMAL - One of two things:
2426 * 1) We really set it.
2427 * 2) A bunch of interrupts came in and moved
2428 * the page forward again.
2429 */
2430 switch (ret) {
2431 case RB_PAGE_HEAD:
2432 case RB_PAGE_NORMAL:
2433 /* OK */
2434 break;
2435 default:
2436 RB_WARN_ON(cpu_buffer, 1);
2437 return -1;
2438 }
2439
2440 /*
2441 * It is possible that an interrupt came in,
2442 * set the head up, then more interrupts came in
2443 * and moved it again. When we get back here,
2444 * the page would have been set to NORMAL but we
2445 * just set it back to HEAD.
2446 *
2447 * How do you detect this? Well, if that happened
2448 * the tail page would have moved.
2449 */
2450 if (ret == RB_PAGE_NORMAL) {
2451 struct buffer_page *buffer_tail_page;
2452
2453 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2454 /*
2455 * If the tail had moved passed next, then we need
2456 * to reset the pointer.
2457 */
2458 if (buffer_tail_page != tail_page &&
2459 buffer_tail_page != next_page)
2460 rb_head_page_set_normal(cpu_buffer, new_head,
2461 next_page,
2462 RB_PAGE_HEAD);
2463 }
2464
2465 /*
2466 * If this was the outer most commit (the one that
2467 * changed the original pointer from HEAD to UPDATE),
2468 * then it is up to us to reset it to NORMAL.
2469 */
2470 if (type == RB_PAGE_HEAD) {
2471 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2472 tail_page,
2473 RB_PAGE_UPDATE);
2474 if (RB_WARN_ON(cpu_buffer,
2475 ret != RB_PAGE_UPDATE))
2476 return -1;
2477 }
2478
2479 return 0;
2480}
2481
2482static inline void
2483rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2484 unsigned long tail, struct rb_event_info *info)
2485{
2486 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
2487 struct buffer_page *tail_page = info->tail_page;
2488 struct ring_buffer_event *event;
2489 unsigned long length = info->length;
2490
2491 /*
2492 * Only the event that crossed the page boundary
2493 * must fill the old tail_page with padding.
2494 */
2495 if (tail >= bsize) {
2496 /*
2497 * If the page was filled, then we still need
2498 * to update the real_end. Reset it to zero
2499 * and the reader will ignore it.
2500 */
2501 if (tail == bsize)
2502 tail_page->real_end = 0;
2503
2504 local_sub(length, &tail_page->write);
2505 return;
2506 }
2507
2508 event = __rb_page_index(tail_page, tail);
2509
2510 /*
2511 * Save the original length to the meta data.
2512 * This will be used by the reader to add lost event
2513 * counter.
2514 */
2515 tail_page->real_end = tail;
2516
2517 /*
2518 * If this event is bigger than the minimum size, then
2519 * we need to be careful that we don't subtract the
2520 * write counter enough to allow another writer to slip
2521 * in on this page.
2522 * We put in a discarded commit instead, to make sure
2523 * that this space is not used again, and this space will
2524 * not be accounted into 'entries_bytes'.
2525 *
2526 * If we are less than the minimum size, we don't need to
2527 * worry about it.
2528 */
2529 if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
2530 /* No room for any events */
2531
2532 /* Mark the rest of the page with padding */
2533 rb_event_set_padding(event);
2534
2535 /* Make sure the padding is visible before the write update */
2536 smp_wmb();
2537
2538 /* Set the write back to the previous setting */
2539 local_sub(length, &tail_page->write);
2540 return;
2541 }
2542
2543 /* Put in a discarded event */
2544 event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
2545 event->type_len = RINGBUF_TYPE_PADDING;
2546 /* time delta must be non zero */
2547 event->time_delta = 1;
2548
2549 /* account for padding bytes */
2550 local_add(bsize - tail, &cpu_buffer->entries_bytes);
2551
2552 /* Make sure the padding is visible before the tail_page->write update */
2553 smp_wmb();
2554
2555 /* Set write to end of buffer */
2556 length = (tail + length) - bsize;
2557 local_sub(length, &tail_page->write);
2558}
2559
2560static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2561
2562/*
2563 * This is the slow path, force gcc not to inline it.
2564 */
2565static noinline struct ring_buffer_event *
2566rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2567 unsigned long tail, struct rb_event_info *info)
2568{
2569 struct buffer_page *tail_page = info->tail_page;
2570 struct buffer_page *commit_page = cpu_buffer->commit_page;
2571 struct trace_buffer *buffer = cpu_buffer->buffer;
2572 struct buffer_page *next_page;
2573 int ret;
2574
2575 next_page = tail_page;
2576
2577 rb_inc_page(&next_page);
2578
2579 /*
2580 * If for some reason, we had an interrupt storm that made
2581 * it all the way around the buffer, bail, and warn
2582 * about it.
2583 */
2584 if (unlikely(next_page == commit_page)) {
2585 local_inc(&cpu_buffer->commit_overrun);
2586 goto out_reset;
2587 }
2588
2589 /*
2590 * This is where the fun begins!
2591 *
2592 * We are fighting against races between a reader that
2593 * could be on another CPU trying to swap its reader
2594 * page with the buffer head.
2595 *
2596 * We are also fighting against interrupts coming in and
2597 * moving the head or tail on us as well.
2598 *
2599 * If the next page is the head page then we have filled
2600 * the buffer, unless the commit page is still on the
2601 * reader page.
2602 */
2603 if (rb_is_head_page(next_page, &tail_page->list)) {
2604
2605 /*
2606 * If the commit is not on the reader page, then
2607 * move the header page.
2608 */
2609 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2610 /*
2611 * If we are not in overwrite mode,
2612 * this is easy, just stop here.
2613 */
2614 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2615 local_inc(&cpu_buffer->dropped_events);
2616 goto out_reset;
2617 }
2618
2619 ret = rb_handle_head_page(cpu_buffer,
2620 tail_page,
2621 next_page);
2622 if (ret < 0)
2623 goto out_reset;
2624 if (ret)
2625 goto out_again;
2626 } else {
2627 /*
2628 * We need to be careful here too. The
2629 * commit page could still be on the reader
2630 * page. We could have a small buffer, and
2631 * have filled up the buffer with events
2632 * from interrupts and such, and wrapped.
2633 *
2634 * Note, if the tail page is also on the
2635 * reader_page, we let it move out.
2636 */
2637 if (unlikely((cpu_buffer->commit_page !=
2638 cpu_buffer->tail_page) &&
2639 (cpu_buffer->commit_page ==
2640 cpu_buffer->reader_page))) {
2641 local_inc(&cpu_buffer->commit_overrun);
2642 goto out_reset;
2643 }
2644 }
2645 }
2646
2647 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2648
2649 out_again:
2650
2651 rb_reset_tail(cpu_buffer, tail, info);
2652
2653 /* Commit what we have for now. */
2654 rb_end_commit(cpu_buffer);
2655 /* rb_end_commit() decs committing */
2656 local_inc(&cpu_buffer->committing);
2657
2658 /* fail and let the caller try again */
2659 return ERR_PTR(-EAGAIN);
2660
2661 out_reset:
2662 /* reset write */
2663 rb_reset_tail(cpu_buffer, tail, info);
2664
2665 return NULL;
2666}
2667
2668/* Slow path */
2669static struct ring_buffer_event *
2670rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2671 struct ring_buffer_event *event, u64 delta, bool abs)
2672{
2673 if (abs)
2674 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2675 else
2676 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2677
2678 /* Not the first event on the page, or not delta? */
2679 if (abs || rb_event_index(cpu_buffer, event)) {
2680 event->time_delta = delta & TS_MASK;
2681 event->array[0] = delta >> TS_SHIFT;
2682 } else {
2683 /* nope, just zero it */
2684 event->time_delta = 0;
2685 event->array[0] = 0;
2686 }
2687
2688 return skip_time_extend(event);
2689}
2690
2691#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2692static inline bool sched_clock_stable(void)
2693{
2694 return true;
2695}
2696#endif
2697
2698static void
2699rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2700 struct rb_event_info *info)
2701{
2702 u64 write_stamp;
2703
2704 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2705 (unsigned long long)info->delta,
2706 (unsigned long long)info->ts,
2707 (unsigned long long)info->before,
2708 (unsigned long long)info->after,
2709 (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
2710 sched_clock_stable() ? "" :
2711 "If you just came from a suspend/resume,\n"
2712 "please switch to the trace global clock:\n"
2713 " echo global > /sys/kernel/tracing/trace_clock\n"
2714 "or add trace_clock=global to the kernel command line\n");
2715}
2716
2717static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2718 struct ring_buffer_event **event,
2719 struct rb_event_info *info,
2720 u64 *delta,
2721 unsigned int *length)
2722{
2723 bool abs = info->add_timestamp &
2724 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2725
2726 if (unlikely(info->delta > (1ULL << 59))) {
2727 /*
2728 * Some timers can use more than 59 bits, and when a timestamp
2729 * is added to the buffer, it will lose those bits.
2730 */
2731 if (abs && (info->ts & TS_MSB)) {
2732 info->delta &= ABS_TS_MASK;
2733
2734 /* did the clock go backwards */
2735 } else if (info->before == info->after && info->before > info->ts) {
2736 /* not interrupted */
2737 static int once;
2738
2739 /*
2740 * This is possible with a recalibrating of the TSC.
2741 * Do not produce a call stack, but just report it.
2742 */
2743 if (!once) {
2744 once++;
2745 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2746 info->before, info->ts);
2747 }
2748 } else
2749 rb_check_timestamp(cpu_buffer, info);
2750 if (!abs)
2751 info->delta = 0;
2752 }
2753 *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
2754 *length -= RB_LEN_TIME_EXTEND;
2755 *delta = 0;
2756}
2757
2758/**
2759 * rb_update_event - update event type and data
2760 * @cpu_buffer: The per cpu buffer of the @event
2761 * @event: the event to update
2762 * @info: The info to update the @event with (contains length and delta)
2763 *
2764 * Update the type and data fields of the @event. The length
2765 * is the actual size that is written to the ring buffer,
2766 * and with this, we can determine what to place into the
2767 * data field.
2768 */
2769static void
2770rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2771 struct ring_buffer_event *event,
2772 struct rb_event_info *info)
2773{
2774 unsigned length = info->length;
2775 u64 delta = info->delta;
2776 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2777
2778 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2779 cpu_buffer->event_stamp[nest] = info->ts;
2780
2781 /*
2782 * If we need to add a timestamp, then we
2783 * add it to the start of the reserved space.
2784 */
2785 if (unlikely(info->add_timestamp))
2786 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2787
2788 event->time_delta = delta;
2789 length -= RB_EVNT_HDR_SIZE;
2790 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2791 event->type_len = 0;
2792 event->array[0] = length;
2793 } else
2794 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2795}
2796
2797static unsigned rb_calculate_event_length(unsigned length)
2798{
2799 struct ring_buffer_event event; /* Used only for sizeof array */
2800
2801 /* zero length can cause confusions */
2802 if (!length)
2803 length++;
2804
2805 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2806 length += sizeof(event.array[0]);
2807
2808 length += RB_EVNT_HDR_SIZE;
2809 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2810
2811 /*
2812 * In case the time delta is larger than the 27 bits for it
2813 * in the header, we need to add a timestamp. If another
2814 * event comes in when trying to discard this one to increase
2815 * the length, then the timestamp will be added in the allocated
2816 * space of this event. If length is bigger than the size needed
2817 * for the TIME_EXTEND, then padding has to be used. The events
2818 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2819 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2820 * As length is a multiple of 4, we only need to worry if it
2821 * is 12 (RB_LEN_TIME_EXTEND + 4).
2822 */
2823 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2824 length += RB_ALIGNMENT;
2825
2826 return length;
2827}
2828
2829static inline bool
2830rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2831 struct ring_buffer_event *event)
2832{
2833 unsigned long new_index, old_index;
2834 struct buffer_page *bpage;
2835 unsigned long addr;
2836
2837 new_index = rb_event_index(cpu_buffer, event);
2838 old_index = new_index + rb_event_ts_length(event);
2839 addr = (unsigned long)event;
2840 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
2841
2842 bpage = READ_ONCE(cpu_buffer->tail_page);
2843
2844 /*
2845 * Make sure the tail_page is still the same and
2846 * the next write location is the end of this event
2847 */
2848 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2849 unsigned long write_mask =
2850 local_read(&bpage->write) & ~RB_WRITE_MASK;
2851 unsigned long event_length = rb_event_length(event);
2852
2853 /*
2854 * For the before_stamp to be different than the write_stamp
2855 * to make sure that the next event adds an absolute
2856 * value and does not rely on the saved write stamp, which
2857 * is now going to be bogus.
2858 *
2859 * By setting the before_stamp to zero, the next event
2860 * is not going to use the write_stamp and will instead
2861 * create an absolute timestamp. This means there's no
2862 * reason to update the wirte_stamp!
2863 */
2864 rb_time_set(&cpu_buffer->before_stamp, 0);
2865
2866 /*
2867 * If an event were to come in now, it would see that the
2868 * write_stamp and the before_stamp are different, and assume
2869 * that this event just added itself before updating
2870 * the write stamp. The interrupting event will fix the
2871 * write stamp for us, and use an absolute timestamp.
2872 */
2873
2874 /*
2875 * This is on the tail page. It is possible that
2876 * a write could come in and move the tail page
2877 * and write to the next page. That is fine
2878 * because we just shorten what is on this page.
2879 */
2880 old_index += write_mask;
2881 new_index += write_mask;
2882
2883 /* caution: old_index gets updated on cmpxchg failure */
2884 if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
2885 /* update counters */
2886 local_sub(event_length, &cpu_buffer->entries_bytes);
2887 return true;
2888 }
2889 }
2890
2891 /* could not discard */
2892 return false;
2893}
2894
2895static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2896{
2897 local_inc(&cpu_buffer->committing);
2898 local_inc(&cpu_buffer->commits);
2899}
2900
2901static __always_inline void
2902rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2903{
2904 unsigned long max_count;
2905
2906 /*
2907 * We only race with interrupts and NMIs on this CPU.
2908 * If we own the commit event, then we can commit
2909 * all others that interrupted us, since the interruptions
2910 * are in stack format (they finish before they come
2911 * back to us). This allows us to do a simple loop to
2912 * assign the commit to the tail.
2913 */
2914 again:
2915 max_count = cpu_buffer->nr_pages * 100;
2916
2917 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2918 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2919 return;
2920 if (RB_WARN_ON(cpu_buffer,
2921 rb_is_reader_page(cpu_buffer->tail_page)))
2922 return;
2923 /*
2924 * No need for a memory barrier here, as the update
2925 * of the tail_page did it for this page.
2926 */
2927 local_set(&cpu_buffer->commit_page->page->commit,
2928 rb_page_write(cpu_buffer->commit_page));
2929 rb_inc_page(&cpu_buffer->commit_page);
2930 /* add barrier to keep gcc from optimizing too much */
2931 barrier();
2932 }
2933 while (rb_commit_index(cpu_buffer) !=
2934 rb_page_write(cpu_buffer->commit_page)) {
2935
2936 /* Make sure the readers see the content of what is committed. */
2937 smp_wmb();
2938 local_set(&cpu_buffer->commit_page->page->commit,
2939 rb_page_write(cpu_buffer->commit_page));
2940 RB_WARN_ON(cpu_buffer,
2941 local_read(&cpu_buffer->commit_page->page->commit) &
2942 ~RB_WRITE_MASK);
2943 barrier();
2944 }
2945
2946 /* again, keep gcc from optimizing */
2947 barrier();
2948
2949 /*
2950 * If an interrupt came in just after the first while loop
2951 * and pushed the tail page forward, we will be left with
2952 * a dangling commit that will never go forward.
2953 */
2954 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2955 goto again;
2956}
2957
2958static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2959{
2960 unsigned long commits;
2961
2962 if (RB_WARN_ON(cpu_buffer,
2963 !local_read(&cpu_buffer->committing)))
2964 return;
2965
2966 again:
2967 commits = local_read(&cpu_buffer->commits);
2968 /* synchronize with interrupts */
2969 barrier();
2970 if (local_read(&cpu_buffer->committing) == 1)
2971 rb_set_commit_to_write(cpu_buffer);
2972
2973 local_dec(&cpu_buffer->committing);
2974
2975 /* synchronize with interrupts */
2976 barrier();
2977
2978 /*
2979 * Need to account for interrupts coming in between the
2980 * updating of the commit page and the clearing of the
2981 * committing counter.
2982 */
2983 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2984 !local_read(&cpu_buffer->committing)) {
2985 local_inc(&cpu_buffer->committing);
2986 goto again;
2987 }
2988}
2989
2990static inline void rb_event_discard(struct ring_buffer_event *event)
2991{
2992 if (extended_time(event))
2993 event = skip_time_extend(event);
2994
2995 /* array[0] holds the actual length for the discarded event */
2996 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2997 event->type_len = RINGBUF_TYPE_PADDING;
2998 /* time delta must be non zero */
2999 if (!event->time_delta)
3000 event->time_delta = 1;
3001}
3002
3003static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3004{
3005 local_inc(&cpu_buffer->entries);
3006 rb_end_commit(cpu_buffer);
3007}
3008
3009static __always_inline void
3010rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3011{
3012 if (buffer->irq_work.waiters_pending) {
3013 buffer->irq_work.waiters_pending = false;
3014 /* irq_work_queue() supplies it's own memory barriers */
3015 irq_work_queue(&buffer->irq_work.work);
3016 }
3017
3018 if (cpu_buffer->irq_work.waiters_pending) {
3019 cpu_buffer->irq_work.waiters_pending = false;
3020 /* irq_work_queue() supplies it's own memory barriers */
3021 irq_work_queue(&cpu_buffer->irq_work.work);
3022 }
3023
3024 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3025 return;
3026
3027 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3028 return;
3029
3030 if (!cpu_buffer->irq_work.full_waiters_pending)
3031 return;
3032
3033 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3034
3035 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3036 return;
3037
3038 cpu_buffer->irq_work.wakeup_full = true;
3039 cpu_buffer->irq_work.full_waiters_pending = false;
3040 /* irq_work_queue() supplies it's own memory barriers */
3041 irq_work_queue(&cpu_buffer->irq_work.work);
3042}
3043
3044#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3045# define do_ring_buffer_record_recursion() \
3046 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3047#else
3048# define do_ring_buffer_record_recursion() do { } while (0)
3049#endif
3050
3051/*
3052 * The lock and unlock are done within a preempt disable section.
3053 * The current_context per_cpu variable can only be modified
3054 * by the current task between lock and unlock. But it can
3055 * be modified more than once via an interrupt. To pass this
3056 * information from the lock to the unlock without having to
3057 * access the 'in_interrupt()' functions again (which do show
3058 * a bit of overhead in something as critical as function tracing,
3059 * we use a bitmask trick.
3060 *
3061 * bit 1 = NMI context
3062 * bit 2 = IRQ context
3063 * bit 3 = SoftIRQ context
3064 * bit 4 = normal context.
3065 *
3066 * This works because this is the order of contexts that can
3067 * preempt other contexts. A SoftIRQ never preempts an IRQ
3068 * context.
3069 *
3070 * When the context is determined, the corresponding bit is
3071 * checked and set (if it was set, then a recursion of that context
3072 * happened).
3073 *
3074 * On unlock, we need to clear this bit. To do so, just subtract
3075 * 1 from the current_context and AND it to itself.
3076 *
3077 * (binary)
3078 * 101 - 1 = 100
3079 * 101 & 100 = 100 (clearing bit zero)
3080 *
3081 * 1010 - 1 = 1001
3082 * 1010 & 1001 = 1000 (clearing bit 1)
3083 *
3084 * The least significant bit can be cleared this way, and it
3085 * just so happens that it is the same bit corresponding to
3086 * the current context.
3087 *
3088 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3089 * is set when a recursion is detected at the current context, and if
3090 * the TRANSITION bit is already set, it will fail the recursion.
3091 * This is needed because there's a lag between the changing of
3092 * interrupt context and updating the preempt count. In this case,
3093 * a false positive will be found. To handle this, one extra recursion
3094 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3095 * bit is already set, then it is considered a recursion and the function
3096 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3097 *
3098 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3099 * to be cleared. Even if it wasn't the context that set it. That is,
3100 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3101 * is called before preempt_count() is updated, since the check will
3102 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3103 * NMI then comes in, it will set the NMI bit, but when the NMI code
3104 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3105 * and leave the NMI bit set. But this is fine, because the interrupt
3106 * code that set the TRANSITION bit will then clear the NMI bit when it
3107 * calls trace_recursive_unlock(). If another NMI comes in, it will
3108 * set the TRANSITION bit and continue.
3109 *
3110 * Note: The TRANSITION bit only handles a single transition between context.
3111 */
3112
3113static __always_inline bool
3114trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3115{
3116 unsigned int val = cpu_buffer->current_context;
3117 int bit = interrupt_context_level();
3118
3119 bit = RB_CTX_NORMAL - bit;
3120
3121 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3122 /*
3123 * It is possible that this was called by transitioning
3124 * between interrupt context, and preempt_count() has not
3125 * been updated yet. In this case, use the TRANSITION bit.
3126 */
3127 bit = RB_CTX_TRANSITION;
3128 if (val & (1 << (bit + cpu_buffer->nest))) {
3129 do_ring_buffer_record_recursion();
3130 return true;
3131 }
3132 }
3133
3134 val |= (1 << (bit + cpu_buffer->nest));
3135 cpu_buffer->current_context = val;
3136
3137 return false;
3138}
3139
3140static __always_inline void
3141trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3142{
3143 cpu_buffer->current_context &=
3144 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3145}
3146
3147/* The recursive locking above uses 5 bits */
3148#define NESTED_BITS 5
3149
3150/**
3151 * ring_buffer_nest_start - Allow to trace while nested
3152 * @buffer: The ring buffer to modify
3153 *
3154 * The ring buffer has a safety mechanism to prevent recursion.
3155 * But there may be a case where a trace needs to be done while
3156 * tracing something else. In this case, calling this function
3157 * will allow this function to nest within a currently active
3158 * ring_buffer_lock_reserve().
3159 *
3160 * Call this function before calling another ring_buffer_lock_reserve() and
3161 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3162 */
3163void ring_buffer_nest_start(struct trace_buffer *buffer)
3164{
3165 struct ring_buffer_per_cpu *cpu_buffer;
3166 int cpu;
3167
3168 /* Enabled by ring_buffer_nest_end() */
3169 preempt_disable_notrace();
3170 cpu = raw_smp_processor_id();
3171 cpu_buffer = buffer->buffers[cpu];
3172 /* This is the shift value for the above recursive locking */
3173 cpu_buffer->nest += NESTED_BITS;
3174}
3175
3176/**
3177 * ring_buffer_nest_end - Allow to trace while nested
3178 * @buffer: The ring buffer to modify
3179 *
3180 * Must be called after ring_buffer_nest_start() and after the
3181 * ring_buffer_unlock_commit().
3182 */
3183void ring_buffer_nest_end(struct trace_buffer *buffer)
3184{
3185 struct ring_buffer_per_cpu *cpu_buffer;
3186 int cpu;
3187
3188 /* disabled by ring_buffer_nest_start() */
3189 cpu = raw_smp_processor_id();
3190 cpu_buffer = buffer->buffers[cpu];
3191 /* This is the shift value for the above recursive locking */
3192 cpu_buffer->nest -= NESTED_BITS;
3193 preempt_enable_notrace();
3194}
3195
3196/**
3197 * ring_buffer_unlock_commit - commit a reserved
3198 * @buffer: The buffer to commit to
3199 *
3200 * This commits the data to the ring buffer, and releases any locks held.
3201 *
3202 * Must be paired with ring_buffer_lock_reserve.
3203 */
3204int ring_buffer_unlock_commit(struct trace_buffer *buffer)
3205{
3206 struct ring_buffer_per_cpu *cpu_buffer;
3207 int cpu = raw_smp_processor_id();
3208
3209 cpu_buffer = buffer->buffers[cpu];
3210
3211 rb_commit(cpu_buffer);
3212
3213 rb_wakeups(buffer, cpu_buffer);
3214
3215 trace_recursive_unlock(cpu_buffer);
3216
3217 preempt_enable_notrace();
3218
3219 return 0;
3220}
3221EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3222
3223/* Special value to validate all deltas on a page. */
3224#define CHECK_FULL_PAGE 1L
3225
3226#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3227
3228static const char *show_irq_str(int bits)
3229{
3230 const char *type[] = {
3231 ".", // 0
3232 "s", // 1
3233 "h", // 2
3234 "Hs", // 3
3235 "n", // 4
3236 "Ns", // 5
3237 "Nh", // 6
3238 "NHs", // 7
3239 };
3240
3241 return type[bits];
3242}
3243
3244/* Assume this is an trace event */
3245static const char *show_flags(struct ring_buffer_event *event)
3246{
3247 struct trace_entry *entry;
3248 int bits = 0;
3249
3250 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3251 return "X";
3252
3253 entry = ring_buffer_event_data(event);
3254
3255 if (entry->flags & TRACE_FLAG_SOFTIRQ)
3256 bits |= 1;
3257
3258 if (entry->flags & TRACE_FLAG_HARDIRQ)
3259 bits |= 2;
3260
3261 if (entry->flags & TRACE_FLAG_NMI)
3262 bits |= 4;
3263
3264 return show_irq_str(bits);
3265}
3266
3267static const char *show_irq(struct ring_buffer_event *event)
3268{
3269 struct trace_entry *entry;
3270
3271 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3272 return "";
3273
3274 entry = ring_buffer_event_data(event);
3275 if (entry->flags & TRACE_FLAG_IRQS_OFF)
3276 return "d";
3277 return "";
3278}
3279
3280static const char *show_interrupt_level(void)
3281{
3282 unsigned long pc = preempt_count();
3283 unsigned char level = 0;
3284
3285 if (pc & SOFTIRQ_OFFSET)
3286 level |= 1;
3287
3288 if (pc & HARDIRQ_MASK)
3289 level |= 2;
3290
3291 if (pc & NMI_MASK)
3292 level |= 4;
3293
3294 return show_irq_str(level);
3295}
3296
3297static void dump_buffer_page(struct buffer_data_page *bpage,
3298 struct rb_event_info *info,
3299 unsigned long tail)
3300{
3301 struct ring_buffer_event *event;
3302 u64 ts, delta;
3303 int e;
3304
3305 ts = bpage->time_stamp;
3306 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3307
3308 for (e = 0; e < tail; e += rb_event_length(event)) {
3309
3310 event = (struct ring_buffer_event *)(bpage->data + e);
3311
3312 switch (event->type_len) {
3313
3314 case RINGBUF_TYPE_TIME_EXTEND:
3315 delta = rb_event_time_stamp(event);
3316 ts += delta;
3317 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
3318 e, ts, delta);
3319 break;
3320
3321 case RINGBUF_TYPE_TIME_STAMP:
3322 delta = rb_event_time_stamp(event);
3323 ts = rb_fix_abs_ts(delta, ts);
3324 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
3325 e, ts, delta);
3326 break;
3327
3328 case RINGBUF_TYPE_PADDING:
3329 ts += event->time_delta;
3330 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
3331 e, ts, event->time_delta);
3332 break;
3333
3334 case RINGBUF_TYPE_DATA:
3335 ts += event->time_delta;
3336 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
3337 e, ts, event->time_delta,
3338 show_flags(event), show_irq(event));
3339 break;
3340
3341 default:
3342 break;
3343 }
3344 }
3345 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
3346}
3347
3348static DEFINE_PER_CPU(atomic_t, checking);
3349static atomic_t ts_dump;
3350
3351#define buffer_warn_return(fmt, ...) \
3352 do { \
3353 /* If another report is happening, ignore this one */ \
3354 if (atomic_inc_return(&ts_dump) != 1) { \
3355 atomic_dec(&ts_dump); \
3356 goto out; \
3357 } \
3358 atomic_inc(&cpu_buffer->record_disabled); \
3359 pr_warn(fmt, ##__VA_ARGS__); \
3360 dump_buffer_page(bpage, info, tail); \
3361 atomic_dec(&ts_dump); \
3362 /* There's some cases in boot up that this can happen */ \
3363 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
3364 /* Do not re-enable checking */ \
3365 return; \
3366 } while (0)
3367
3368/*
3369 * Check if the current event time stamp matches the deltas on
3370 * the buffer page.
3371 */
3372static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3373 struct rb_event_info *info,
3374 unsigned long tail)
3375{
3376 struct ring_buffer_event *event;
3377 struct buffer_data_page *bpage;
3378 u64 ts, delta;
3379 bool full = false;
3380 int e;
3381
3382 bpage = info->tail_page->page;
3383
3384 if (tail == CHECK_FULL_PAGE) {
3385 full = true;
3386 tail = local_read(&bpage->commit);
3387 } else if (info->add_timestamp &
3388 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3389 /* Ignore events with absolute time stamps */
3390 return;
3391 }
3392
3393 /*
3394 * Do not check the first event (skip possible extends too).
3395 * Also do not check if previous events have not been committed.
3396 */
3397 if (tail <= 8 || tail > local_read(&bpage->commit))
3398 return;
3399
3400 /*
3401 * If this interrupted another event,
3402 */
3403 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3404 goto out;
3405
3406 ts = bpage->time_stamp;
3407
3408 for (e = 0; e < tail; e += rb_event_length(event)) {
3409
3410 event = (struct ring_buffer_event *)(bpage->data + e);
3411
3412 switch (event->type_len) {
3413
3414 case RINGBUF_TYPE_TIME_EXTEND:
3415 delta = rb_event_time_stamp(event);
3416 ts += delta;
3417 break;
3418
3419 case RINGBUF_TYPE_TIME_STAMP:
3420 delta = rb_event_time_stamp(event);
3421 delta = rb_fix_abs_ts(delta, ts);
3422 if (delta < ts) {
3423 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
3424 cpu_buffer->cpu, ts, delta);
3425 }
3426 ts = delta;
3427 break;
3428
3429 case RINGBUF_TYPE_PADDING:
3430 if (event->time_delta == 1)
3431 break;
3432 fallthrough;
3433 case RINGBUF_TYPE_DATA:
3434 ts += event->time_delta;
3435 break;
3436
3437 default:
3438 RB_WARN_ON(cpu_buffer, 1);
3439 }
3440 }
3441 if ((full && ts > info->ts) ||
3442 (!full && ts + info->delta != info->ts)) {
3443 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
3444 cpu_buffer->cpu,
3445 ts + info->delta, info->ts, info->delta,
3446 info->before, info->after,
3447 full ? " (full)" : "", show_interrupt_level());
3448 }
3449out:
3450 atomic_dec(this_cpu_ptr(&checking));
3451}
3452#else
3453static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3454 struct rb_event_info *info,
3455 unsigned long tail)
3456{
3457}
3458#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3459
3460static struct ring_buffer_event *
3461__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3462 struct rb_event_info *info)
3463{
3464 struct ring_buffer_event *event;
3465 struct buffer_page *tail_page;
3466 unsigned long tail, write, w;
3467
3468 /* Don't let the compiler play games with cpu_buffer->tail_page */
3469 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3470
3471 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3472 barrier();
3473 rb_time_read(&cpu_buffer->before_stamp, &info->before);
3474 rb_time_read(&cpu_buffer->write_stamp, &info->after);
3475 barrier();
3476 info->ts = rb_time_stamp(cpu_buffer->buffer);
3477
3478 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3479 info->delta = info->ts;
3480 } else {
3481 /*
3482 * If interrupting an event time update, we may need an
3483 * absolute timestamp.
3484 * Don't bother if this is the start of a new page (w == 0).
3485 */
3486 if (!w) {
3487 /* Use the sub-buffer timestamp */
3488 info->delta = 0;
3489 } else if (unlikely(info->before != info->after)) {
3490 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3491 info->length += RB_LEN_TIME_EXTEND;
3492 } else {
3493 info->delta = info->ts - info->after;
3494 if (unlikely(test_time_stamp(info->delta))) {
3495 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3496 info->length += RB_LEN_TIME_EXTEND;
3497 }
3498 }
3499 }
3500
3501 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3502
3503 /*C*/ write = local_add_return(info->length, &tail_page->write);
3504
3505 /* set write to only the index of the write */
3506 write &= RB_WRITE_MASK;
3507
3508 tail = write - info->length;
3509
3510 /* See if we shot pass the end of this buffer page */
3511 if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
3512 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3513 return rb_move_tail(cpu_buffer, tail, info);
3514 }
3515
3516 if (likely(tail == w)) {
3517 /* Nothing interrupted us between A and C */
3518 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3519 /*
3520 * If something came in between C and D, the write stamp
3521 * may now not be in sync. But that's fine as the before_stamp
3522 * will be different and then next event will just be forced
3523 * to use an absolute timestamp.
3524 */
3525 if (likely(!(info->add_timestamp &
3526 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3527 /* This did not interrupt any time update */
3528 info->delta = info->ts - info->after;
3529 else
3530 /* Just use full timestamp for interrupting event */
3531 info->delta = info->ts;
3532 check_buffer(cpu_buffer, info, tail);
3533 } else {
3534 u64 ts;
3535 /* SLOW PATH - Interrupted between A and C */
3536
3537 /* Save the old before_stamp */
3538 rb_time_read(&cpu_buffer->before_stamp, &info->before);
3539
3540 /*
3541 * Read a new timestamp and update the before_stamp to make
3542 * the next event after this one force using an absolute
3543 * timestamp. This is in case an interrupt were to come in
3544 * between E and F.
3545 */
3546 ts = rb_time_stamp(cpu_buffer->buffer);
3547 rb_time_set(&cpu_buffer->before_stamp, ts);
3548
3549 barrier();
3550 /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
3551 barrier();
3552 /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3553 info->after == info->before && info->after < ts) {
3554 /*
3555 * Nothing came after this event between C and F, it is
3556 * safe to use info->after for the delta as it
3557 * matched info->before and is still valid.
3558 */
3559 info->delta = ts - info->after;
3560 } else {
3561 /*
3562 * Interrupted between C and F:
3563 * Lost the previous events time stamp. Just set the
3564 * delta to zero, and this will be the same time as
3565 * the event this event interrupted. And the events that
3566 * came after this will still be correct (as they would
3567 * have built their delta on the previous event.
3568 */
3569 info->delta = 0;
3570 }
3571 info->ts = ts;
3572 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3573 }
3574
3575 /*
3576 * If this is the first commit on the page, then it has the same
3577 * timestamp as the page itself.
3578 */
3579 if (unlikely(!tail && !(info->add_timestamp &
3580 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3581 info->delta = 0;
3582
3583 /* We reserved something on the buffer */
3584
3585 event = __rb_page_index(tail_page, tail);
3586 rb_update_event(cpu_buffer, event, info);
3587
3588 local_inc(&tail_page->entries);
3589
3590 /*
3591 * If this is the first commit on the page, then update
3592 * its timestamp.
3593 */
3594 if (unlikely(!tail))
3595 tail_page->page->time_stamp = info->ts;
3596
3597 /* account for these added bytes */
3598 local_add(info->length, &cpu_buffer->entries_bytes);
3599
3600 return event;
3601}
3602
3603static __always_inline struct ring_buffer_event *
3604rb_reserve_next_event(struct trace_buffer *buffer,
3605 struct ring_buffer_per_cpu *cpu_buffer,
3606 unsigned long length)
3607{
3608 struct ring_buffer_event *event;
3609 struct rb_event_info info;
3610 int nr_loops = 0;
3611 int add_ts_default;
3612
3613 /* ring buffer does cmpxchg, make sure it is safe in NMI context */
3614 if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
3615 (unlikely(in_nmi()))) {
3616 return NULL;
3617 }
3618
3619 rb_start_commit(cpu_buffer);
3620 /* The commit page can not change after this */
3621
3622#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3623 /*
3624 * Due to the ability to swap a cpu buffer from a buffer
3625 * it is possible it was swapped before we committed.
3626 * (committing stops a swap). We check for it here and
3627 * if it happened, we have to fail the write.
3628 */
3629 barrier();
3630 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3631 local_dec(&cpu_buffer->committing);
3632 local_dec(&cpu_buffer->commits);
3633 return NULL;
3634 }
3635#endif
3636
3637 info.length = rb_calculate_event_length(length);
3638
3639 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3640 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3641 info.length += RB_LEN_TIME_EXTEND;
3642 if (info.length > cpu_buffer->buffer->max_data_size)
3643 goto out_fail;
3644 } else {
3645 add_ts_default = RB_ADD_STAMP_NONE;
3646 }
3647
3648 again:
3649 info.add_timestamp = add_ts_default;
3650 info.delta = 0;
3651
3652 /*
3653 * We allow for interrupts to reenter here and do a trace.
3654 * If one does, it will cause this original code to loop
3655 * back here. Even with heavy interrupts happening, this
3656 * should only happen a few times in a row. If this happens
3657 * 1000 times in a row, there must be either an interrupt
3658 * storm or we have something buggy.
3659 * Bail!
3660 */
3661 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3662 goto out_fail;
3663
3664 event = __rb_reserve_next(cpu_buffer, &info);
3665
3666 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3667 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3668 info.length -= RB_LEN_TIME_EXTEND;
3669 goto again;
3670 }
3671
3672 if (likely(event))
3673 return event;
3674 out_fail:
3675 rb_end_commit(cpu_buffer);
3676 return NULL;
3677}
3678
3679/**
3680 * ring_buffer_lock_reserve - reserve a part of the buffer
3681 * @buffer: the ring buffer to reserve from
3682 * @length: the length of the data to reserve (excluding event header)
3683 *
3684 * Returns a reserved event on the ring buffer to copy directly to.
3685 * The user of this interface will need to get the body to write into
3686 * and can use the ring_buffer_event_data() interface.
3687 *
3688 * The length is the length of the data needed, not the event length
3689 * which also includes the event header.
3690 *
3691 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3692 * If NULL is returned, then nothing has been allocated or locked.
3693 */
3694struct ring_buffer_event *
3695ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3696{
3697 struct ring_buffer_per_cpu *cpu_buffer;
3698 struct ring_buffer_event *event;
3699 int cpu;
3700
3701 /* If we are tracing schedule, we don't want to recurse */
3702 preempt_disable_notrace();
3703
3704 if (unlikely(atomic_read(&buffer->record_disabled)))
3705 goto out;
3706
3707 cpu = raw_smp_processor_id();
3708
3709 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3710 goto out;
3711
3712 cpu_buffer = buffer->buffers[cpu];
3713
3714 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3715 goto out;
3716
3717 if (unlikely(length > buffer->max_data_size))
3718 goto out;
3719
3720 if (unlikely(trace_recursive_lock(cpu_buffer)))
3721 goto out;
3722
3723 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3724 if (!event)
3725 goto out_unlock;
3726
3727 return event;
3728
3729 out_unlock:
3730 trace_recursive_unlock(cpu_buffer);
3731 out:
3732 preempt_enable_notrace();
3733 return NULL;
3734}
3735EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3736
3737/*
3738 * Decrement the entries to the page that an event is on.
3739 * The event does not even need to exist, only the pointer
3740 * to the page it is on. This may only be called before the commit
3741 * takes place.
3742 */
3743static inline void
3744rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3745 struct ring_buffer_event *event)
3746{
3747 unsigned long addr = (unsigned long)event;
3748 struct buffer_page *bpage = cpu_buffer->commit_page;
3749 struct buffer_page *start;
3750
3751 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3752
3753 /* Do the likely case first */
3754 if (likely(bpage->page == (void *)addr)) {
3755 local_dec(&bpage->entries);
3756 return;
3757 }
3758
3759 /*
3760 * Because the commit page may be on the reader page we
3761 * start with the next page and check the end loop there.
3762 */
3763 rb_inc_page(&bpage);
3764 start = bpage;
3765 do {
3766 if (bpage->page == (void *)addr) {
3767 local_dec(&bpage->entries);
3768 return;
3769 }
3770 rb_inc_page(&bpage);
3771 } while (bpage != start);
3772
3773 /* commit not part of this buffer?? */
3774 RB_WARN_ON(cpu_buffer, 1);
3775}
3776
3777/**
3778 * ring_buffer_discard_commit - discard an event that has not been committed
3779 * @buffer: the ring buffer
3780 * @event: non committed event to discard
3781 *
3782 * Sometimes an event that is in the ring buffer needs to be ignored.
3783 * This function lets the user discard an event in the ring buffer
3784 * and then that event will not be read later.
3785 *
3786 * This function only works if it is called before the item has been
3787 * committed. It will try to free the event from the ring buffer
3788 * if another event has not been added behind it.
3789 *
3790 * If another event has been added behind it, it will set the event
3791 * up as discarded, and perform the commit.
3792 *
3793 * If this function is called, do not call ring_buffer_unlock_commit on
3794 * the event.
3795 */
3796void ring_buffer_discard_commit(struct trace_buffer *buffer,
3797 struct ring_buffer_event *event)
3798{
3799 struct ring_buffer_per_cpu *cpu_buffer;
3800 int cpu;
3801
3802 /* The event is discarded regardless */
3803 rb_event_discard(event);
3804
3805 cpu = smp_processor_id();
3806 cpu_buffer = buffer->buffers[cpu];
3807
3808 /*
3809 * This must only be called if the event has not been
3810 * committed yet. Thus we can assume that preemption
3811 * is still disabled.
3812 */
3813 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3814
3815 rb_decrement_entry(cpu_buffer, event);
3816 if (rb_try_to_discard(cpu_buffer, event))
3817 goto out;
3818
3819 out:
3820 rb_end_commit(cpu_buffer);
3821
3822 trace_recursive_unlock(cpu_buffer);
3823
3824 preempt_enable_notrace();
3825
3826}
3827EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3828
3829/**
3830 * ring_buffer_write - write data to the buffer without reserving
3831 * @buffer: The ring buffer to write to.
3832 * @length: The length of the data being written (excluding the event header)
3833 * @data: The data to write to the buffer.
3834 *
3835 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3836 * one function. If you already have the data to write to the buffer, it
3837 * may be easier to simply call this function.
3838 *
3839 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3840 * and not the length of the event which would hold the header.
3841 */
3842int ring_buffer_write(struct trace_buffer *buffer,
3843 unsigned long length,
3844 void *data)
3845{
3846 struct ring_buffer_per_cpu *cpu_buffer;
3847 struct ring_buffer_event *event;
3848 void *body;
3849 int ret = -EBUSY;
3850 int cpu;
3851
3852 preempt_disable_notrace();
3853
3854 if (atomic_read(&buffer->record_disabled))
3855 goto out;
3856
3857 cpu = raw_smp_processor_id();
3858
3859 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3860 goto out;
3861
3862 cpu_buffer = buffer->buffers[cpu];
3863
3864 if (atomic_read(&cpu_buffer->record_disabled))
3865 goto out;
3866
3867 if (length > buffer->max_data_size)
3868 goto out;
3869
3870 if (unlikely(trace_recursive_lock(cpu_buffer)))
3871 goto out;
3872
3873 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3874 if (!event)
3875 goto out_unlock;
3876
3877 body = rb_event_data(event);
3878
3879 memcpy(body, data, length);
3880
3881 rb_commit(cpu_buffer);
3882
3883 rb_wakeups(buffer, cpu_buffer);
3884
3885 ret = 0;
3886
3887 out_unlock:
3888 trace_recursive_unlock(cpu_buffer);
3889
3890 out:
3891 preempt_enable_notrace();
3892
3893 return ret;
3894}
3895EXPORT_SYMBOL_GPL(ring_buffer_write);
3896
3897static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3898{
3899 struct buffer_page *reader = cpu_buffer->reader_page;
3900 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3901 struct buffer_page *commit = cpu_buffer->commit_page;
3902
3903 /* In case of error, head will be NULL */
3904 if (unlikely(!head))
3905 return true;
3906
3907 /* Reader should exhaust content in reader page */
3908 if (reader->read != rb_page_commit(reader))
3909 return false;
3910
3911 /*
3912 * If writers are committing on the reader page, knowing all
3913 * committed content has been read, the ring buffer is empty.
3914 */
3915 if (commit == reader)
3916 return true;
3917
3918 /*
3919 * If writers are committing on a page other than reader page
3920 * and head page, there should always be content to read.
3921 */
3922 if (commit != head)
3923 return false;
3924
3925 /*
3926 * Writers are committing on the head page, we just need
3927 * to care about there're committed data, and the reader will
3928 * swap reader page with head page when it is to read data.
3929 */
3930 return rb_page_commit(commit) == 0;
3931}
3932
3933/**
3934 * ring_buffer_record_disable - stop all writes into the buffer
3935 * @buffer: The ring buffer to stop writes to.
3936 *
3937 * This prevents all writes to the buffer. Any attempt to write
3938 * to the buffer after this will fail and return NULL.
3939 *
3940 * The caller should call synchronize_rcu() after this.
3941 */
3942void ring_buffer_record_disable(struct trace_buffer *buffer)
3943{
3944 atomic_inc(&buffer->record_disabled);
3945}
3946EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3947
3948/**
3949 * ring_buffer_record_enable - enable writes to the buffer
3950 * @buffer: The ring buffer to enable writes
3951 *
3952 * Note, multiple disables will need the same number of enables
3953 * to truly enable the writing (much like preempt_disable).
3954 */
3955void ring_buffer_record_enable(struct trace_buffer *buffer)
3956{
3957 atomic_dec(&buffer->record_disabled);
3958}
3959EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3960
3961/**
3962 * ring_buffer_record_off - stop all writes into the buffer
3963 * @buffer: The ring buffer to stop writes to.
3964 *
3965 * This prevents all writes to the buffer. Any attempt to write
3966 * to the buffer after this will fail and return NULL.
3967 *
3968 * This is different than ring_buffer_record_disable() as
3969 * it works like an on/off switch, where as the disable() version
3970 * must be paired with a enable().
3971 */
3972void ring_buffer_record_off(struct trace_buffer *buffer)
3973{
3974 unsigned int rd;
3975 unsigned int new_rd;
3976
3977 rd = atomic_read(&buffer->record_disabled);
3978 do {
3979 new_rd = rd | RB_BUFFER_OFF;
3980 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
3981}
3982EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3983
3984/**
3985 * ring_buffer_record_on - restart writes into the buffer
3986 * @buffer: The ring buffer to start writes to.
3987 *
3988 * This enables all writes to the buffer that was disabled by
3989 * ring_buffer_record_off().
3990 *
3991 * This is different than ring_buffer_record_enable() as
3992 * it works like an on/off switch, where as the enable() version
3993 * must be paired with a disable().
3994 */
3995void ring_buffer_record_on(struct trace_buffer *buffer)
3996{
3997 unsigned int rd;
3998 unsigned int new_rd;
3999
4000 rd = atomic_read(&buffer->record_disabled);
4001 do {
4002 new_rd = rd & ~RB_BUFFER_OFF;
4003 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4004}
4005EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4006
4007/**
4008 * ring_buffer_record_is_on - return true if the ring buffer can write
4009 * @buffer: The ring buffer to see if write is enabled
4010 *
4011 * Returns true if the ring buffer is in a state that it accepts writes.
4012 */
4013bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4014{
4015 return !atomic_read(&buffer->record_disabled);
4016}
4017
4018/**
4019 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4020 * @buffer: The ring buffer to see if write is set enabled
4021 *
4022 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4023 * Note that this does NOT mean it is in a writable state.
4024 *
4025 * It may return true when the ring buffer has been disabled by
4026 * ring_buffer_record_disable(), as that is a temporary disabling of
4027 * the ring buffer.
4028 */
4029bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4030{
4031 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4032}
4033
4034/**
4035 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4036 * @buffer: The ring buffer to stop writes to.
4037 * @cpu: The CPU buffer to stop
4038 *
4039 * This prevents all writes to the buffer. Any attempt to write
4040 * to the buffer after this will fail and return NULL.
4041 *
4042 * The caller should call synchronize_rcu() after this.
4043 */
4044void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4045{
4046 struct ring_buffer_per_cpu *cpu_buffer;
4047
4048 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4049 return;
4050
4051 cpu_buffer = buffer->buffers[cpu];
4052 atomic_inc(&cpu_buffer->record_disabled);
4053}
4054EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4055
4056/**
4057 * ring_buffer_record_enable_cpu - enable writes to the buffer
4058 * @buffer: The ring buffer to enable writes
4059 * @cpu: The CPU to enable.
4060 *
4061 * Note, multiple disables will need the same number of enables
4062 * to truly enable the writing (much like preempt_disable).
4063 */
4064void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4065{
4066 struct ring_buffer_per_cpu *cpu_buffer;
4067
4068 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4069 return;
4070
4071 cpu_buffer = buffer->buffers[cpu];
4072 atomic_dec(&cpu_buffer->record_disabled);
4073}
4074EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4075
4076/*
4077 * The total entries in the ring buffer is the running counter
4078 * of entries entered into the ring buffer, minus the sum of
4079 * the entries read from the ring buffer and the number of
4080 * entries that were overwritten.
4081 */
4082static inline unsigned long
4083rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4084{
4085 return local_read(&cpu_buffer->entries) -
4086 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4087}
4088
4089/**
4090 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4091 * @buffer: The ring buffer
4092 * @cpu: The per CPU buffer to read from.
4093 */
4094u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4095{
4096 unsigned long flags;
4097 struct ring_buffer_per_cpu *cpu_buffer;
4098 struct buffer_page *bpage;
4099 u64 ret = 0;
4100
4101 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4102 return 0;
4103
4104 cpu_buffer = buffer->buffers[cpu];
4105 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4106 /*
4107 * if the tail is on reader_page, oldest time stamp is on the reader
4108 * page
4109 */
4110 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4111 bpage = cpu_buffer->reader_page;
4112 else
4113 bpage = rb_set_head_page(cpu_buffer);
4114 if (bpage)
4115 ret = bpage->page->time_stamp;
4116 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4117
4118 return ret;
4119}
4120EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4121
4122/**
4123 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4124 * @buffer: The ring buffer
4125 * @cpu: The per CPU buffer to read from.
4126 */
4127unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4128{
4129 struct ring_buffer_per_cpu *cpu_buffer;
4130 unsigned long ret;
4131
4132 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4133 return 0;
4134
4135 cpu_buffer = buffer->buffers[cpu];
4136 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4137
4138 return ret;
4139}
4140EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4141
4142/**
4143 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4144 * @buffer: The ring buffer
4145 * @cpu: The per CPU buffer to get the entries from.
4146 */
4147unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4148{
4149 struct ring_buffer_per_cpu *cpu_buffer;
4150
4151 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4152 return 0;
4153
4154 cpu_buffer = buffer->buffers[cpu];
4155
4156 return rb_num_of_entries(cpu_buffer);
4157}
4158EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4159
4160/**
4161 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4162 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4163 * @buffer: The ring buffer
4164 * @cpu: The per CPU buffer to get the number of overruns from
4165 */
4166unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4167{
4168 struct ring_buffer_per_cpu *cpu_buffer;
4169 unsigned long ret;
4170
4171 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4172 return 0;
4173
4174 cpu_buffer = buffer->buffers[cpu];
4175 ret = local_read(&cpu_buffer->overrun);
4176
4177 return ret;
4178}
4179EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4180
4181/**
4182 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4183 * commits failing due to the buffer wrapping around while there are uncommitted
4184 * events, such as during an interrupt storm.
4185 * @buffer: The ring buffer
4186 * @cpu: The per CPU buffer to get the number of overruns from
4187 */
4188unsigned long
4189ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4190{
4191 struct ring_buffer_per_cpu *cpu_buffer;
4192 unsigned long ret;
4193
4194 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4195 return 0;
4196
4197 cpu_buffer = buffer->buffers[cpu];
4198 ret = local_read(&cpu_buffer->commit_overrun);
4199
4200 return ret;
4201}
4202EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4203
4204/**
4205 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4206 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4207 * @buffer: The ring buffer
4208 * @cpu: The per CPU buffer to get the number of overruns from
4209 */
4210unsigned long
4211ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4212{
4213 struct ring_buffer_per_cpu *cpu_buffer;
4214 unsigned long ret;
4215
4216 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4217 return 0;
4218
4219 cpu_buffer = buffer->buffers[cpu];
4220 ret = local_read(&cpu_buffer->dropped_events);
4221
4222 return ret;
4223}
4224EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4225
4226/**
4227 * ring_buffer_read_events_cpu - get the number of events successfully read
4228 * @buffer: The ring buffer
4229 * @cpu: The per CPU buffer to get the number of events read
4230 */
4231unsigned long
4232ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4233{
4234 struct ring_buffer_per_cpu *cpu_buffer;
4235
4236 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4237 return 0;
4238
4239 cpu_buffer = buffer->buffers[cpu];
4240 return cpu_buffer->read;
4241}
4242EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4243
4244/**
4245 * ring_buffer_entries - get the number of entries in a buffer
4246 * @buffer: The ring buffer
4247 *
4248 * Returns the total number of entries in the ring buffer
4249 * (all CPU entries)
4250 */
4251unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4252{
4253 struct ring_buffer_per_cpu *cpu_buffer;
4254 unsigned long entries = 0;
4255 int cpu;
4256
4257 /* if you care about this being correct, lock the buffer */
4258 for_each_buffer_cpu(buffer, cpu) {
4259 cpu_buffer = buffer->buffers[cpu];
4260 entries += rb_num_of_entries(cpu_buffer);
4261 }
4262
4263 return entries;
4264}
4265EXPORT_SYMBOL_GPL(ring_buffer_entries);
4266
4267/**
4268 * ring_buffer_overruns - get the number of overruns in buffer
4269 * @buffer: The ring buffer
4270 *
4271 * Returns the total number of overruns in the ring buffer
4272 * (all CPU entries)
4273 */
4274unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4275{
4276 struct ring_buffer_per_cpu *cpu_buffer;
4277 unsigned long overruns = 0;
4278 int cpu;
4279
4280 /* if you care about this being correct, lock the buffer */
4281 for_each_buffer_cpu(buffer, cpu) {
4282 cpu_buffer = buffer->buffers[cpu];
4283 overruns += local_read(&cpu_buffer->overrun);
4284 }
4285
4286 return overruns;
4287}
4288EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4289
4290static void rb_iter_reset(struct ring_buffer_iter *iter)
4291{
4292 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4293
4294 /* Iterator usage is expected to have record disabled */
4295 iter->head_page = cpu_buffer->reader_page;
4296 iter->head = cpu_buffer->reader_page->read;
4297 iter->next_event = iter->head;
4298
4299 iter->cache_reader_page = iter->head_page;
4300 iter->cache_read = cpu_buffer->read;
4301 iter->cache_pages_removed = cpu_buffer->pages_removed;
4302
4303 if (iter->head) {
4304 iter->read_stamp = cpu_buffer->read_stamp;
4305 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4306 } else {
4307 iter->read_stamp = iter->head_page->page->time_stamp;
4308 iter->page_stamp = iter->read_stamp;
4309 }
4310}
4311
4312/**
4313 * ring_buffer_iter_reset - reset an iterator
4314 * @iter: The iterator to reset
4315 *
4316 * Resets the iterator, so that it will start from the beginning
4317 * again.
4318 */
4319void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4320{
4321 struct ring_buffer_per_cpu *cpu_buffer;
4322 unsigned long flags;
4323
4324 if (!iter)
4325 return;
4326
4327 cpu_buffer = iter->cpu_buffer;
4328
4329 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4330 rb_iter_reset(iter);
4331 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4332}
4333EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4334
4335/**
4336 * ring_buffer_iter_empty - check if an iterator has no more to read
4337 * @iter: The iterator to check
4338 */
4339int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4340{
4341 struct ring_buffer_per_cpu *cpu_buffer;
4342 struct buffer_page *reader;
4343 struct buffer_page *head_page;
4344 struct buffer_page *commit_page;
4345 struct buffer_page *curr_commit_page;
4346 unsigned commit;
4347 u64 curr_commit_ts;
4348 u64 commit_ts;
4349
4350 cpu_buffer = iter->cpu_buffer;
4351 reader = cpu_buffer->reader_page;
4352 head_page = cpu_buffer->head_page;
4353 commit_page = cpu_buffer->commit_page;
4354 commit_ts = commit_page->page->time_stamp;
4355
4356 /*
4357 * When the writer goes across pages, it issues a cmpxchg which
4358 * is a mb(), which will synchronize with the rmb here.
4359 * (see rb_tail_page_update())
4360 */
4361 smp_rmb();
4362 commit = rb_page_commit(commit_page);
4363 /* We want to make sure that the commit page doesn't change */
4364 smp_rmb();
4365
4366 /* Make sure commit page didn't change */
4367 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4368 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4369
4370 /* If the commit page changed, then there's more data */
4371 if (curr_commit_page != commit_page ||
4372 curr_commit_ts != commit_ts)
4373 return 0;
4374
4375 /* Still racy, as it may return a false positive, but that's OK */
4376 return ((iter->head_page == commit_page && iter->head >= commit) ||
4377 (iter->head_page == reader && commit_page == head_page &&
4378 head_page->read == commit &&
4379 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4380}
4381EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4382
4383static void
4384rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4385 struct ring_buffer_event *event)
4386{
4387 u64 delta;
4388
4389 switch (event->type_len) {
4390 case RINGBUF_TYPE_PADDING:
4391 return;
4392
4393 case RINGBUF_TYPE_TIME_EXTEND:
4394 delta = rb_event_time_stamp(event);
4395 cpu_buffer->read_stamp += delta;
4396 return;
4397
4398 case RINGBUF_TYPE_TIME_STAMP:
4399 delta = rb_event_time_stamp(event);
4400 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
4401 cpu_buffer->read_stamp = delta;
4402 return;
4403
4404 case RINGBUF_TYPE_DATA:
4405 cpu_buffer->read_stamp += event->time_delta;
4406 return;
4407
4408 default:
4409 RB_WARN_ON(cpu_buffer, 1);
4410 }
4411}
4412
4413static void
4414rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4415 struct ring_buffer_event *event)
4416{
4417 u64 delta;
4418
4419 switch (event->type_len) {
4420 case RINGBUF_TYPE_PADDING:
4421 return;
4422
4423 case RINGBUF_TYPE_TIME_EXTEND:
4424 delta = rb_event_time_stamp(event);
4425 iter->read_stamp += delta;
4426 return;
4427
4428 case RINGBUF_TYPE_TIME_STAMP:
4429 delta = rb_event_time_stamp(event);
4430 delta = rb_fix_abs_ts(delta, iter->read_stamp);
4431 iter->read_stamp = delta;
4432 return;
4433
4434 case RINGBUF_TYPE_DATA:
4435 iter->read_stamp += event->time_delta;
4436 return;
4437
4438 default:
4439 RB_WARN_ON(iter->cpu_buffer, 1);
4440 }
4441}
4442
4443static struct buffer_page *
4444rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4445{
4446 struct buffer_page *reader = NULL;
4447 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
4448 unsigned long overwrite;
4449 unsigned long flags;
4450 int nr_loops = 0;
4451 bool ret;
4452
4453 local_irq_save(flags);
4454 arch_spin_lock(&cpu_buffer->lock);
4455
4456 again:
4457 /*
4458 * This should normally only loop twice. But because the
4459 * start of the reader inserts an empty page, it causes
4460 * a case where we will loop three times. There should be no
4461 * reason to loop four times (that I know of).
4462 */
4463 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4464 reader = NULL;
4465 goto out;
4466 }
4467
4468 reader = cpu_buffer->reader_page;
4469
4470 /* If there's more to read, return this page */
4471 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4472 goto out;
4473
4474 /* Never should we have an index greater than the size */
4475 if (RB_WARN_ON(cpu_buffer,
4476 cpu_buffer->reader_page->read > rb_page_size(reader)))
4477 goto out;
4478
4479 /* check if we caught up to the tail */
4480 reader = NULL;
4481 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4482 goto out;
4483
4484 /* Don't bother swapping if the ring buffer is empty */
4485 if (rb_num_of_entries(cpu_buffer) == 0)
4486 goto out;
4487
4488 /*
4489 * Reset the reader page to size zero.
4490 */
4491 local_set(&cpu_buffer->reader_page->write, 0);
4492 local_set(&cpu_buffer->reader_page->entries, 0);
4493 local_set(&cpu_buffer->reader_page->page->commit, 0);
4494 cpu_buffer->reader_page->real_end = 0;
4495
4496 spin:
4497 /*
4498 * Splice the empty reader page into the list around the head.
4499 */
4500 reader = rb_set_head_page(cpu_buffer);
4501 if (!reader)
4502 goto out;
4503 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4504 cpu_buffer->reader_page->list.prev = reader->list.prev;
4505
4506 /*
4507 * cpu_buffer->pages just needs to point to the buffer, it
4508 * has no specific buffer page to point to. Lets move it out
4509 * of our way so we don't accidentally swap it.
4510 */
4511 cpu_buffer->pages = reader->list.prev;
4512
4513 /* The reader page will be pointing to the new head */
4514 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4515
4516 /*
4517 * We want to make sure we read the overruns after we set up our
4518 * pointers to the next object. The writer side does a
4519 * cmpxchg to cross pages which acts as the mb on the writer
4520 * side. Note, the reader will constantly fail the swap
4521 * while the writer is updating the pointers, so this
4522 * guarantees that the overwrite recorded here is the one we
4523 * want to compare with the last_overrun.
4524 */
4525 smp_mb();
4526 overwrite = local_read(&(cpu_buffer->overrun));
4527
4528 /*
4529 * Here's the tricky part.
4530 *
4531 * We need to move the pointer past the header page.
4532 * But we can only do that if a writer is not currently
4533 * moving it. The page before the header page has the
4534 * flag bit '1' set if it is pointing to the page we want.
4535 * but if the writer is in the process of moving it
4536 * than it will be '2' or already moved '0'.
4537 */
4538
4539 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4540
4541 /*
4542 * If we did not convert it, then we must try again.
4543 */
4544 if (!ret)
4545 goto spin;
4546
4547 /*
4548 * Yay! We succeeded in replacing the page.
4549 *
4550 * Now make the new head point back to the reader page.
4551 */
4552 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4553 rb_inc_page(&cpu_buffer->head_page);
4554
4555 local_inc(&cpu_buffer->pages_read);
4556
4557 /* Finally update the reader page to the new head */
4558 cpu_buffer->reader_page = reader;
4559 cpu_buffer->reader_page->read = 0;
4560
4561 if (overwrite != cpu_buffer->last_overrun) {
4562 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4563 cpu_buffer->last_overrun = overwrite;
4564 }
4565
4566 goto again;
4567
4568 out:
4569 /* Update the read_stamp on the first event */
4570 if (reader && reader->read == 0)
4571 cpu_buffer->read_stamp = reader->page->time_stamp;
4572
4573 arch_spin_unlock(&cpu_buffer->lock);
4574 local_irq_restore(flags);
4575
4576 /*
4577 * The writer has preempt disable, wait for it. But not forever
4578 * Although, 1 second is pretty much "forever"
4579 */
4580#define USECS_WAIT 1000000
4581 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4582 /* If the write is past the end of page, a writer is still updating it */
4583 if (likely(!reader || rb_page_write(reader) <= bsize))
4584 break;
4585
4586 udelay(1);
4587
4588 /* Get the latest version of the reader write value */
4589 smp_rmb();
4590 }
4591
4592 /* The writer is not moving forward? Something is wrong */
4593 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4594 reader = NULL;
4595
4596 /*
4597 * Make sure we see any padding after the write update
4598 * (see rb_reset_tail()).
4599 *
4600 * In addition, a writer may be writing on the reader page
4601 * if the page has not been fully filled, so the read barrier
4602 * is also needed to make sure we see the content of what is
4603 * committed by the writer (see rb_set_commit_to_write()).
4604 */
4605 smp_rmb();
4606
4607
4608 return reader;
4609}
4610
4611static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4612{
4613 struct ring_buffer_event *event;
4614 struct buffer_page *reader;
4615 unsigned length;
4616
4617 reader = rb_get_reader_page(cpu_buffer);
4618
4619 /* This function should not be called when buffer is empty */
4620 if (RB_WARN_ON(cpu_buffer, !reader))
4621 return;
4622
4623 event = rb_reader_event(cpu_buffer);
4624
4625 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4626 cpu_buffer->read++;
4627
4628 rb_update_read_stamp(cpu_buffer, event);
4629
4630 length = rb_event_length(event);
4631 cpu_buffer->reader_page->read += length;
4632 cpu_buffer->read_bytes += length;
4633}
4634
4635static void rb_advance_iter(struct ring_buffer_iter *iter)
4636{
4637 struct ring_buffer_per_cpu *cpu_buffer;
4638
4639 cpu_buffer = iter->cpu_buffer;
4640
4641 /* If head == next_event then we need to jump to the next event */
4642 if (iter->head == iter->next_event) {
4643 /* If the event gets overwritten again, there's nothing to do */
4644 if (rb_iter_head_event(iter) == NULL)
4645 return;
4646 }
4647
4648 iter->head = iter->next_event;
4649
4650 /*
4651 * Check if we are at the end of the buffer.
4652 */
4653 if (iter->next_event >= rb_page_size(iter->head_page)) {
4654 /* discarded commits can make the page empty */
4655 if (iter->head_page == cpu_buffer->commit_page)
4656 return;
4657 rb_inc_iter(iter);
4658 return;
4659 }
4660
4661 rb_update_iter_read_stamp(iter, iter->event);
4662}
4663
4664static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4665{
4666 return cpu_buffer->lost_events;
4667}
4668
4669static struct ring_buffer_event *
4670rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4671 unsigned long *lost_events)
4672{
4673 struct ring_buffer_event *event;
4674 struct buffer_page *reader;
4675 int nr_loops = 0;
4676
4677 if (ts)
4678 *ts = 0;
4679 again:
4680 /*
4681 * We repeat when a time extend is encountered.
4682 * Since the time extend is always attached to a data event,
4683 * we should never loop more than once.
4684 * (We never hit the following condition more than twice).
4685 */
4686 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4687 return NULL;
4688
4689 reader = rb_get_reader_page(cpu_buffer);
4690 if (!reader)
4691 return NULL;
4692
4693 event = rb_reader_event(cpu_buffer);
4694
4695 switch (event->type_len) {
4696 case RINGBUF_TYPE_PADDING:
4697 if (rb_null_event(event))
4698 RB_WARN_ON(cpu_buffer, 1);
4699 /*
4700 * Because the writer could be discarding every
4701 * event it creates (which would probably be bad)
4702 * if we were to go back to "again" then we may never
4703 * catch up, and will trigger the warn on, or lock
4704 * the box. Return the padding, and we will release
4705 * the current locks, and try again.
4706 */
4707 return event;
4708
4709 case RINGBUF_TYPE_TIME_EXTEND:
4710 /* Internal data, OK to advance */
4711 rb_advance_reader(cpu_buffer);
4712 goto again;
4713
4714 case RINGBUF_TYPE_TIME_STAMP:
4715 if (ts) {
4716 *ts = rb_event_time_stamp(event);
4717 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
4718 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4719 cpu_buffer->cpu, ts);
4720 }
4721 /* Internal data, OK to advance */
4722 rb_advance_reader(cpu_buffer);
4723 goto again;
4724
4725 case RINGBUF_TYPE_DATA:
4726 if (ts && !(*ts)) {
4727 *ts = cpu_buffer->read_stamp + event->time_delta;
4728 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4729 cpu_buffer->cpu, ts);
4730 }
4731 if (lost_events)
4732 *lost_events = rb_lost_events(cpu_buffer);
4733 return event;
4734
4735 default:
4736 RB_WARN_ON(cpu_buffer, 1);
4737 }
4738
4739 return NULL;
4740}
4741EXPORT_SYMBOL_GPL(ring_buffer_peek);
4742
4743static struct ring_buffer_event *
4744rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4745{
4746 struct trace_buffer *buffer;
4747 struct ring_buffer_per_cpu *cpu_buffer;
4748 struct ring_buffer_event *event;
4749 int nr_loops = 0;
4750
4751 if (ts)
4752 *ts = 0;
4753
4754 cpu_buffer = iter->cpu_buffer;
4755 buffer = cpu_buffer->buffer;
4756
4757 /*
4758 * Check if someone performed a consuming read to the buffer
4759 * or removed some pages from the buffer. In these cases,
4760 * iterator was invalidated and we need to reset it.
4761 */
4762 if (unlikely(iter->cache_read != cpu_buffer->read ||
4763 iter->cache_reader_page != cpu_buffer->reader_page ||
4764 iter->cache_pages_removed != cpu_buffer->pages_removed))
4765 rb_iter_reset(iter);
4766
4767 again:
4768 if (ring_buffer_iter_empty(iter))
4769 return NULL;
4770
4771 /*
4772 * As the writer can mess with what the iterator is trying
4773 * to read, just give up if we fail to get an event after
4774 * three tries. The iterator is not as reliable when reading
4775 * the ring buffer with an active write as the consumer is.
4776 * Do not warn if the three failures is reached.
4777 */
4778 if (++nr_loops > 3)
4779 return NULL;
4780
4781 if (rb_per_cpu_empty(cpu_buffer))
4782 return NULL;
4783
4784 if (iter->head >= rb_page_size(iter->head_page)) {
4785 rb_inc_iter(iter);
4786 goto again;
4787 }
4788
4789 event = rb_iter_head_event(iter);
4790 if (!event)
4791 goto again;
4792
4793 switch (event->type_len) {
4794 case RINGBUF_TYPE_PADDING:
4795 if (rb_null_event(event)) {
4796 rb_inc_iter(iter);
4797 goto again;
4798 }
4799 rb_advance_iter(iter);
4800 return event;
4801
4802 case RINGBUF_TYPE_TIME_EXTEND:
4803 /* Internal data, OK to advance */
4804 rb_advance_iter(iter);
4805 goto again;
4806
4807 case RINGBUF_TYPE_TIME_STAMP:
4808 if (ts) {
4809 *ts = rb_event_time_stamp(event);
4810 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
4811 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4812 cpu_buffer->cpu, ts);
4813 }
4814 /* Internal data, OK to advance */
4815 rb_advance_iter(iter);
4816 goto again;
4817
4818 case RINGBUF_TYPE_DATA:
4819 if (ts && !(*ts)) {
4820 *ts = iter->read_stamp + event->time_delta;
4821 ring_buffer_normalize_time_stamp(buffer,
4822 cpu_buffer->cpu, ts);
4823 }
4824 return event;
4825
4826 default:
4827 RB_WARN_ON(cpu_buffer, 1);
4828 }
4829
4830 return NULL;
4831}
4832EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4833
4834static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4835{
4836 if (likely(!in_nmi())) {
4837 raw_spin_lock(&cpu_buffer->reader_lock);
4838 return true;
4839 }
4840
4841 /*
4842 * If an NMI die dumps out the content of the ring buffer
4843 * trylock must be used to prevent a deadlock if the NMI
4844 * preempted a task that holds the ring buffer locks. If
4845 * we get the lock then all is fine, if not, then continue
4846 * to do the read, but this can corrupt the ring buffer,
4847 * so it must be permanently disabled from future writes.
4848 * Reading from NMI is a oneshot deal.
4849 */
4850 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4851 return true;
4852
4853 /* Continue without locking, but disable the ring buffer */
4854 atomic_inc(&cpu_buffer->record_disabled);
4855 return false;
4856}
4857
4858static inline void
4859rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4860{
4861 if (likely(locked))
4862 raw_spin_unlock(&cpu_buffer->reader_lock);
4863}
4864
4865/**
4866 * ring_buffer_peek - peek at the next event to be read
4867 * @buffer: The ring buffer to read
4868 * @cpu: The cpu to peak at
4869 * @ts: The timestamp counter of this event.
4870 * @lost_events: a variable to store if events were lost (may be NULL)
4871 *
4872 * This will return the event that will be read next, but does
4873 * not consume the data.
4874 */
4875struct ring_buffer_event *
4876ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4877 unsigned long *lost_events)
4878{
4879 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4880 struct ring_buffer_event *event;
4881 unsigned long flags;
4882 bool dolock;
4883
4884 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4885 return NULL;
4886
4887 again:
4888 local_irq_save(flags);
4889 dolock = rb_reader_lock(cpu_buffer);
4890 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4891 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4892 rb_advance_reader(cpu_buffer);
4893 rb_reader_unlock(cpu_buffer, dolock);
4894 local_irq_restore(flags);
4895
4896 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4897 goto again;
4898
4899 return event;
4900}
4901
4902/** ring_buffer_iter_dropped - report if there are dropped events
4903 * @iter: The ring buffer iterator
4904 *
4905 * Returns true if there was dropped events since the last peek.
4906 */
4907bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4908{
4909 bool ret = iter->missed_events != 0;
4910
4911 iter->missed_events = 0;
4912 return ret;
4913}
4914EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4915
4916/**
4917 * ring_buffer_iter_peek - peek at the next event to be read
4918 * @iter: The ring buffer iterator
4919 * @ts: The timestamp counter of this event.
4920 *
4921 * This will return the event that will be read next, but does
4922 * not increment the iterator.
4923 */
4924struct ring_buffer_event *
4925ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4926{
4927 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4928 struct ring_buffer_event *event;
4929 unsigned long flags;
4930
4931 again:
4932 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4933 event = rb_iter_peek(iter, ts);
4934 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4935
4936 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4937 goto again;
4938
4939 return event;
4940}
4941
4942/**
4943 * ring_buffer_consume - return an event and consume it
4944 * @buffer: The ring buffer to get the next event from
4945 * @cpu: the cpu to read the buffer from
4946 * @ts: a variable to store the timestamp (may be NULL)
4947 * @lost_events: a variable to store if events were lost (may be NULL)
4948 *
4949 * Returns the next event in the ring buffer, and that event is consumed.
4950 * Meaning, that sequential reads will keep returning a different event,
4951 * and eventually empty the ring buffer if the producer is slower.
4952 */
4953struct ring_buffer_event *
4954ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4955 unsigned long *lost_events)
4956{
4957 struct ring_buffer_per_cpu *cpu_buffer;
4958 struct ring_buffer_event *event = NULL;
4959 unsigned long flags;
4960 bool dolock;
4961
4962 again:
4963 /* might be called in atomic */
4964 preempt_disable();
4965
4966 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4967 goto out;
4968
4969 cpu_buffer = buffer->buffers[cpu];
4970 local_irq_save(flags);
4971 dolock = rb_reader_lock(cpu_buffer);
4972
4973 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4974 if (event) {
4975 cpu_buffer->lost_events = 0;
4976 rb_advance_reader(cpu_buffer);
4977 }
4978
4979 rb_reader_unlock(cpu_buffer, dolock);
4980 local_irq_restore(flags);
4981
4982 out:
4983 preempt_enable();
4984
4985 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4986 goto again;
4987
4988 return event;
4989}
4990EXPORT_SYMBOL_GPL(ring_buffer_consume);
4991
4992/**
4993 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4994 * @buffer: The ring buffer to read from
4995 * @cpu: The cpu buffer to iterate over
4996 * @flags: gfp flags to use for memory allocation
4997 *
4998 * This performs the initial preparations necessary to iterate
4999 * through the buffer. Memory is allocated, buffer recording
5000 * is disabled, and the iterator pointer is returned to the caller.
5001 *
5002 * Disabling buffer recording prevents the reading from being
5003 * corrupted. This is not a consuming read, so a producer is not
5004 * expected.
5005 *
5006 * After a sequence of ring_buffer_read_prepare calls, the user is
5007 * expected to make at least one call to ring_buffer_read_prepare_sync.
5008 * Afterwards, ring_buffer_read_start is invoked to get things going
5009 * for real.
5010 *
5011 * This overall must be paired with ring_buffer_read_finish.
5012 */
5013struct ring_buffer_iter *
5014ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5015{
5016 struct ring_buffer_per_cpu *cpu_buffer;
5017 struct ring_buffer_iter *iter;
5018
5019 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5020 return NULL;
5021
5022 iter = kzalloc(sizeof(*iter), flags);
5023 if (!iter)
5024 return NULL;
5025
5026 /* Holds the entire event: data and meta data */
5027 iter->event_size = buffer->subbuf_size;
5028 iter->event = kmalloc(iter->event_size, flags);
5029 if (!iter->event) {
5030 kfree(iter);
5031 return NULL;
5032 }
5033
5034 cpu_buffer = buffer->buffers[cpu];
5035
5036 iter->cpu_buffer = cpu_buffer;
5037
5038 atomic_inc(&cpu_buffer->resize_disabled);
5039
5040 return iter;
5041}
5042EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5043
5044/**
5045 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5046 *
5047 * All previously invoked ring_buffer_read_prepare calls to prepare
5048 * iterators will be synchronized. Afterwards, read_buffer_read_start
5049 * calls on those iterators are allowed.
5050 */
5051void
5052ring_buffer_read_prepare_sync(void)
5053{
5054 synchronize_rcu();
5055}
5056EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5057
5058/**
5059 * ring_buffer_read_start - start a non consuming read of the buffer
5060 * @iter: The iterator returned by ring_buffer_read_prepare
5061 *
5062 * This finalizes the startup of an iteration through the buffer.
5063 * The iterator comes from a call to ring_buffer_read_prepare and
5064 * an intervening ring_buffer_read_prepare_sync must have been
5065 * performed.
5066 *
5067 * Must be paired with ring_buffer_read_finish.
5068 */
5069void
5070ring_buffer_read_start(struct ring_buffer_iter *iter)
5071{
5072 struct ring_buffer_per_cpu *cpu_buffer;
5073 unsigned long flags;
5074
5075 if (!iter)
5076 return;
5077
5078 cpu_buffer = iter->cpu_buffer;
5079
5080 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5081 arch_spin_lock(&cpu_buffer->lock);
5082 rb_iter_reset(iter);
5083 arch_spin_unlock(&cpu_buffer->lock);
5084 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5085}
5086EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5087
5088/**
5089 * ring_buffer_read_finish - finish reading the iterator of the buffer
5090 * @iter: The iterator retrieved by ring_buffer_start
5091 *
5092 * This re-enables the recording to the buffer, and frees the
5093 * iterator.
5094 */
5095void
5096ring_buffer_read_finish(struct ring_buffer_iter *iter)
5097{
5098 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5099 unsigned long flags;
5100
5101 /*
5102 * Ring buffer is disabled from recording, here's a good place
5103 * to check the integrity of the ring buffer.
5104 * Must prevent readers from trying to read, as the check
5105 * clears the HEAD page and readers require it.
5106 */
5107 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5108 rb_check_pages(cpu_buffer);
5109 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5110
5111 atomic_dec(&cpu_buffer->resize_disabled);
5112 kfree(iter->event);
5113 kfree(iter);
5114}
5115EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5116
5117/**
5118 * ring_buffer_iter_advance - advance the iterator to the next location
5119 * @iter: The ring buffer iterator
5120 *
5121 * Move the location of the iterator such that the next read will
5122 * be the next location of the iterator.
5123 */
5124void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5125{
5126 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5127 unsigned long flags;
5128
5129 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5130
5131 rb_advance_iter(iter);
5132
5133 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5134}
5135EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5136
5137/**
5138 * ring_buffer_size - return the size of the ring buffer (in bytes)
5139 * @buffer: The ring buffer.
5140 * @cpu: The CPU to get ring buffer size from.
5141 */
5142unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5143{
5144 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5145 return 0;
5146
5147 return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5148}
5149EXPORT_SYMBOL_GPL(ring_buffer_size);
5150
5151/**
5152 * ring_buffer_max_event_size - return the max data size of an event
5153 * @buffer: The ring buffer.
5154 *
5155 * Returns the maximum size an event can be.
5156 */
5157unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5158{
5159 /* If abs timestamp is requested, events have a timestamp too */
5160 if (ring_buffer_time_stamp_abs(buffer))
5161 return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5162 return buffer->max_data_size;
5163}
5164EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5165
5166static void rb_clear_buffer_page(struct buffer_page *page)
5167{
5168 local_set(&page->write, 0);
5169 local_set(&page->entries, 0);
5170 rb_init_page(page->page);
5171 page->read = 0;
5172}
5173
5174static void
5175rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5176{
5177 struct buffer_page *page;
5178
5179 rb_head_page_deactivate(cpu_buffer);
5180
5181 cpu_buffer->head_page
5182 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5183 rb_clear_buffer_page(cpu_buffer->head_page);
5184 list_for_each_entry(page, cpu_buffer->pages, list) {
5185 rb_clear_buffer_page(page);
5186 }
5187
5188 cpu_buffer->tail_page = cpu_buffer->head_page;
5189 cpu_buffer->commit_page = cpu_buffer->head_page;
5190
5191 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5192 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5193 rb_clear_buffer_page(cpu_buffer->reader_page);
5194
5195 local_set(&cpu_buffer->entries_bytes, 0);
5196 local_set(&cpu_buffer->overrun, 0);
5197 local_set(&cpu_buffer->commit_overrun, 0);
5198 local_set(&cpu_buffer->dropped_events, 0);
5199 local_set(&cpu_buffer->entries, 0);
5200 local_set(&cpu_buffer->committing, 0);
5201 local_set(&cpu_buffer->commits, 0);
5202 local_set(&cpu_buffer->pages_touched, 0);
5203 local_set(&cpu_buffer->pages_lost, 0);
5204 local_set(&cpu_buffer->pages_read, 0);
5205 cpu_buffer->last_pages_touch = 0;
5206 cpu_buffer->shortest_full = 0;
5207 cpu_buffer->read = 0;
5208 cpu_buffer->read_bytes = 0;
5209
5210 rb_time_set(&cpu_buffer->write_stamp, 0);
5211 rb_time_set(&cpu_buffer->before_stamp, 0);
5212
5213 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5214
5215 cpu_buffer->lost_events = 0;
5216 cpu_buffer->last_overrun = 0;
5217
5218 rb_head_page_activate(cpu_buffer);
5219 cpu_buffer->pages_removed = 0;
5220}
5221
5222/* Must have disabled the cpu buffer then done a synchronize_rcu */
5223static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5224{
5225 unsigned long flags;
5226
5227 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5228
5229 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5230 goto out;
5231
5232 arch_spin_lock(&cpu_buffer->lock);
5233
5234 rb_reset_cpu(cpu_buffer);
5235
5236 arch_spin_unlock(&cpu_buffer->lock);
5237
5238 out:
5239 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5240}
5241
5242/**
5243 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5244 * @buffer: The ring buffer to reset a per cpu buffer of
5245 * @cpu: The CPU buffer to be reset
5246 */
5247void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5248{
5249 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5250
5251 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5252 return;
5253
5254 /* prevent another thread from changing buffer sizes */
5255 mutex_lock(&buffer->mutex);
5256
5257 atomic_inc(&cpu_buffer->resize_disabled);
5258 atomic_inc(&cpu_buffer->record_disabled);
5259
5260 /* Make sure all commits have finished */
5261 synchronize_rcu();
5262
5263 reset_disabled_cpu_buffer(cpu_buffer);
5264
5265 atomic_dec(&cpu_buffer->record_disabled);
5266 atomic_dec(&cpu_buffer->resize_disabled);
5267
5268 mutex_unlock(&buffer->mutex);
5269}
5270EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5271
5272/* Flag to ensure proper resetting of atomic variables */
5273#define RESET_BIT (1 << 30)
5274
5275/**
5276 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5277 * @buffer: The ring buffer to reset a per cpu buffer of
5278 */
5279void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5280{
5281 struct ring_buffer_per_cpu *cpu_buffer;
5282 int cpu;
5283
5284 /* prevent another thread from changing buffer sizes */
5285 mutex_lock(&buffer->mutex);
5286
5287 for_each_online_buffer_cpu(buffer, cpu) {
5288 cpu_buffer = buffer->buffers[cpu];
5289
5290 atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
5291 atomic_inc(&cpu_buffer->record_disabled);
5292 }
5293
5294 /* Make sure all commits have finished */
5295 synchronize_rcu();
5296
5297 for_each_buffer_cpu(buffer, cpu) {
5298 cpu_buffer = buffer->buffers[cpu];
5299
5300 /*
5301 * If a CPU came online during the synchronize_rcu(), then
5302 * ignore it.
5303 */
5304 if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
5305 continue;
5306
5307 reset_disabled_cpu_buffer(cpu_buffer);
5308
5309 atomic_dec(&cpu_buffer->record_disabled);
5310 atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
5311 }
5312
5313 mutex_unlock(&buffer->mutex);
5314}
5315
5316/**
5317 * ring_buffer_reset - reset a ring buffer
5318 * @buffer: The ring buffer to reset all cpu buffers
5319 */
5320void ring_buffer_reset(struct trace_buffer *buffer)
5321{
5322 struct ring_buffer_per_cpu *cpu_buffer;
5323 int cpu;
5324
5325 /* prevent another thread from changing buffer sizes */
5326 mutex_lock(&buffer->mutex);
5327
5328 for_each_buffer_cpu(buffer, cpu) {
5329 cpu_buffer = buffer->buffers[cpu];
5330
5331 atomic_inc(&cpu_buffer->resize_disabled);
5332 atomic_inc(&cpu_buffer->record_disabled);
5333 }
5334
5335 /* Make sure all commits have finished */
5336 synchronize_rcu();
5337
5338 for_each_buffer_cpu(buffer, cpu) {
5339 cpu_buffer = buffer->buffers[cpu];
5340
5341 reset_disabled_cpu_buffer(cpu_buffer);
5342
5343 atomic_dec(&cpu_buffer->record_disabled);
5344 atomic_dec(&cpu_buffer->resize_disabled);
5345 }
5346
5347 mutex_unlock(&buffer->mutex);
5348}
5349EXPORT_SYMBOL_GPL(ring_buffer_reset);
5350
5351/**
5352 * ring_buffer_empty - is the ring buffer empty?
5353 * @buffer: The ring buffer to test
5354 */
5355bool ring_buffer_empty(struct trace_buffer *buffer)
5356{
5357 struct ring_buffer_per_cpu *cpu_buffer;
5358 unsigned long flags;
5359 bool dolock;
5360 bool ret;
5361 int cpu;
5362
5363 /* yes this is racy, but if you don't like the race, lock the buffer */
5364 for_each_buffer_cpu(buffer, cpu) {
5365 cpu_buffer = buffer->buffers[cpu];
5366 local_irq_save(flags);
5367 dolock = rb_reader_lock(cpu_buffer);
5368 ret = rb_per_cpu_empty(cpu_buffer);
5369 rb_reader_unlock(cpu_buffer, dolock);
5370 local_irq_restore(flags);
5371
5372 if (!ret)
5373 return false;
5374 }
5375
5376 return true;
5377}
5378EXPORT_SYMBOL_GPL(ring_buffer_empty);
5379
5380/**
5381 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5382 * @buffer: The ring buffer
5383 * @cpu: The CPU buffer to test
5384 */
5385bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5386{
5387 struct ring_buffer_per_cpu *cpu_buffer;
5388 unsigned long flags;
5389 bool dolock;
5390 bool ret;
5391
5392 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5393 return true;
5394
5395 cpu_buffer = buffer->buffers[cpu];
5396 local_irq_save(flags);
5397 dolock = rb_reader_lock(cpu_buffer);
5398 ret = rb_per_cpu_empty(cpu_buffer);
5399 rb_reader_unlock(cpu_buffer, dolock);
5400 local_irq_restore(flags);
5401
5402 return ret;
5403}
5404EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5405
5406#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5407/**
5408 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5409 * @buffer_a: One buffer to swap with
5410 * @buffer_b: The other buffer to swap with
5411 * @cpu: the CPU of the buffers to swap
5412 *
5413 * This function is useful for tracers that want to take a "snapshot"
5414 * of a CPU buffer and has another back up buffer lying around.
5415 * it is expected that the tracer handles the cpu buffer not being
5416 * used at the moment.
5417 */
5418int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5419 struct trace_buffer *buffer_b, int cpu)
5420{
5421 struct ring_buffer_per_cpu *cpu_buffer_a;
5422 struct ring_buffer_per_cpu *cpu_buffer_b;
5423 int ret = -EINVAL;
5424
5425 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5426 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5427 goto out;
5428
5429 cpu_buffer_a = buffer_a->buffers[cpu];
5430 cpu_buffer_b = buffer_b->buffers[cpu];
5431
5432 /* At least make sure the two buffers are somewhat the same */
5433 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5434 goto out;
5435
5436 if (buffer_a->subbuf_order != buffer_b->subbuf_order)
5437 goto out;
5438
5439 ret = -EAGAIN;
5440
5441 if (atomic_read(&buffer_a->record_disabled))
5442 goto out;
5443
5444 if (atomic_read(&buffer_b->record_disabled))
5445 goto out;
5446
5447 if (atomic_read(&cpu_buffer_a->record_disabled))
5448 goto out;
5449
5450 if (atomic_read(&cpu_buffer_b->record_disabled))
5451 goto out;
5452
5453 /*
5454 * We can't do a synchronize_rcu here because this
5455 * function can be called in atomic context.
5456 * Normally this will be called from the same CPU as cpu.
5457 * If not it's up to the caller to protect this.
5458 */
5459 atomic_inc(&cpu_buffer_a->record_disabled);
5460 atomic_inc(&cpu_buffer_b->record_disabled);
5461
5462 ret = -EBUSY;
5463 if (local_read(&cpu_buffer_a->committing))
5464 goto out_dec;
5465 if (local_read(&cpu_buffer_b->committing))
5466 goto out_dec;
5467
5468 /*
5469 * When resize is in progress, we cannot swap it because
5470 * it will mess the state of the cpu buffer.
5471 */
5472 if (atomic_read(&buffer_a->resizing))
5473 goto out_dec;
5474 if (atomic_read(&buffer_b->resizing))
5475 goto out_dec;
5476
5477 buffer_a->buffers[cpu] = cpu_buffer_b;
5478 buffer_b->buffers[cpu] = cpu_buffer_a;
5479
5480 cpu_buffer_b->buffer = buffer_a;
5481 cpu_buffer_a->buffer = buffer_b;
5482
5483 ret = 0;
5484
5485out_dec:
5486 atomic_dec(&cpu_buffer_a->record_disabled);
5487 atomic_dec(&cpu_buffer_b->record_disabled);
5488out:
5489 return ret;
5490}
5491EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5492#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5493
5494/**
5495 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5496 * @buffer: the buffer to allocate for.
5497 * @cpu: the cpu buffer to allocate.
5498 *
5499 * This function is used in conjunction with ring_buffer_read_page.
5500 * When reading a full page from the ring buffer, these functions
5501 * can be used to speed up the process. The calling function should
5502 * allocate a few pages first with this function. Then when it
5503 * needs to get pages from the ring buffer, it passes the result
5504 * of this function into ring_buffer_read_page, which will swap
5505 * the page that was allocated, with the read page of the buffer.
5506 *
5507 * Returns:
5508 * The page allocated, or ERR_PTR
5509 */
5510struct buffer_data_read_page *
5511ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5512{
5513 struct ring_buffer_per_cpu *cpu_buffer;
5514 struct buffer_data_read_page *bpage = NULL;
5515 unsigned long flags;
5516 struct page *page;
5517
5518 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5519 return ERR_PTR(-ENODEV);
5520
5521 bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
5522 if (!bpage)
5523 return ERR_PTR(-ENOMEM);
5524
5525 bpage->order = buffer->subbuf_order;
5526 cpu_buffer = buffer->buffers[cpu];
5527 local_irq_save(flags);
5528 arch_spin_lock(&cpu_buffer->lock);
5529
5530 if (cpu_buffer->free_page) {
5531 bpage->data = cpu_buffer->free_page;
5532 cpu_buffer->free_page = NULL;
5533 }
5534
5535 arch_spin_unlock(&cpu_buffer->lock);
5536 local_irq_restore(flags);
5537
5538 if (bpage->data)
5539 goto out;
5540
5541 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_NORETRY,
5542 cpu_buffer->buffer->subbuf_order);
5543 if (!page) {
5544 kfree(bpage);
5545 return ERR_PTR(-ENOMEM);
5546 }
5547
5548 bpage->data = page_address(page);
5549
5550 out:
5551 rb_init_page(bpage->data);
5552
5553 return bpage;
5554}
5555EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5556
5557/**
5558 * ring_buffer_free_read_page - free an allocated read page
5559 * @buffer: the buffer the page was allocate for
5560 * @cpu: the cpu buffer the page came from
5561 * @data_page: the page to free
5562 *
5563 * Free a page allocated from ring_buffer_alloc_read_page.
5564 */
5565void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
5566 struct buffer_data_read_page *data_page)
5567{
5568 struct ring_buffer_per_cpu *cpu_buffer;
5569 struct buffer_data_page *bpage = data_page->data;
5570 struct page *page = virt_to_page(bpage);
5571 unsigned long flags;
5572
5573 if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
5574 return;
5575
5576 cpu_buffer = buffer->buffers[cpu];
5577
5578 /*
5579 * If the page is still in use someplace else, or order of the page
5580 * is different from the subbuffer order of the buffer -
5581 * we can't reuse it
5582 */
5583 if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
5584 goto out;
5585
5586 local_irq_save(flags);
5587 arch_spin_lock(&cpu_buffer->lock);
5588
5589 if (!cpu_buffer->free_page) {
5590 cpu_buffer->free_page = bpage;
5591 bpage = NULL;
5592 }
5593
5594 arch_spin_unlock(&cpu_buffer->lock);
5595 local_irq_restore(flags);
5596
5597 out:
5598 free_pages((unsigned long)bpage, data_page->order);
5599 kfree(data_page);
5600}
5601EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5602
5603/**
5604 * ring_buffer_read_page - extract a page from the ring buffer
5605 * @buffer: buffer to extract from
5606 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5607 * @len: amount to extract
5608 * @cpu: the cpu of the buffer to extract
5609 * @full: should the extraction only happen when the page is full.
5610 *
5611 * This function will pull out a page from the ring buffer and consume it.
5612 * @data_page must be the address of the variable that was returned
5613 * from ring_buffer_alloc_read_page. This is because the page might be used
5614 * to swap with a page in the ring buffer.
5615 *
5616 * for example:
5617 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5618 * if (IS_ERR(rpage))
5619 * return PTR_ERR(rpage);
5620 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
5621 * if (ret >= 0)
5622 * process_page(ring_buffer_read_page_data(rpage), ret);
5623 * ring_buffer_free_read_page(buffer, cpu, rpage);
5624 *
5625 * When @full is set, the function will not return true unless
5626 * the writer is off the reader page.
5627 *
5628 * Note: it is up to the calling functions to handle sleeps and wakeups.
5629 * The ring buffer can be used anywhere in the kernel and can not
5630 * blindly call wake_up. The layer that uses the ring buffer must be
5631 * responsible for that.
5632 *
5633 * Returns:
5634 * >=0 if data has been transferred, returns the offset of consumed data.
5635 * <0 if no data has been transferred.
5636 */
5637int ring_buffer_read_page(struct trace_buffer *buffer,
5638 struct buffer_data_read_page *data_page,
5639 size_t len, int cpu, int full)
5640{
5641 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5642 struct ring_buffer_event *event;
5643 struct buffer_data_page *bpage;
5644 struct buffer_page *reader;
5645 unsigned long missed_events;
5646 unsigned long flags;
5647 unsigned int commit;
5648 unsigned int read;
5649 u64 save_timestamp;
5650 int ret = -1;
5651
5652 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5653 goto out;
5654
5655 /*
5656 * If len is not big enough to hold the page header, then
5657 * we can not copy anything.
5658 */
5659 if (len <= BUF_PAGE_HDR_SIZE)
5660 goto out;
5661
5662 len -= BUF_PAGE_HDR_SIZE;
5663
5664 if (!data_page || !data_page->data)
5665 goto out;
5666 if (data_page->order != buffer->subbuf_order)
5667 goto out;
5668
5669 bpage = data_page->data;
5670 if (!bpage)
5671 goto out;
5672
5673 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5674
5675 reader = rb_get_reader_page(cpu_buffer);
5676 if (!reader)
5677 goto out_unlock;
5678
5679 event = rb_reader_event(cpu_buffer);
5680
5681 read = reader->read;
5682 commit = rb_page_commit(reader);
5683
5684 /* Check if any events were dropped */
5685 missed_events = cpu_buffer->lost_events;
5686
5687 /*
5688 * If this page has been partially read or
5689 * if len is not big enough to read the rest of the page or
5690 * a writer is still on the page, then
5691 * we must copy the data from the page to the buffer.
5692 * Otherwise, we can simply swap the page with the one passed in.
5693 */
5694 if (read || (len < (commit - read)) ||
5695 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5696 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5697 unsigned int rpos = read;
5698 unsigned int pos = 0;
5699 unsigned int size;
5700
5701 /*
5702 * If a full page is expected, this can still be returned
5703 * if there's been a previous partial read and the
5704 * rest of the page can be read and the commit page is off
5705 * the reader page.
5706 */
5707 if (full &&
5708 (!read || (len < (commit - read)) ||
5709 cpu_buffer->reader_page == cpu_buffer->commit_page))
5710 goto out_unlock;
5711
5712 if (len > (commit - read))
5713 len = (commit - read);
5714
5715 /* Always keep the time extend and data together */
5716 size = rb_event_ts_length(event);
5717
5718 if (len < size)
5719 goto out_unlock;
5720
5721 /* save the current timestamp, since the user will need it */
5722 save_timestamp = cpu_buffer->read_stamp;
5723
5724 /* Need to copy one event at a time */
5725 do {
5726 /* We need the size of one event, because
5727 * rb_advance_reader only advances by one event,
5728 * whereas rb_event_ts_length may include the size of
5729 * one or two events.
5730 * We have already ensured there's enough space if this
5731 * is a time extend. */
5732 size = rb_event_length(event);
5733 memcpy(bpage->data + pos, rpage->data + rpos, size);
5734
5735 len -= size;
5736
5737 rb_advance_reader(cpu_buffer);
5738 rpos = reader->read;
5739 pos += size;
5740
5741 if (rpos >= commit)
5742 break;
5743
5744 event = rb_reader_event(cpu_buffer);
5745 /* Always keep the time extend and data together */
5746 size = rb_event_ts_length(event);
5747 } while (len >= size);
5748
5749 /* update bpage */
5750 local_set(&bpage->commit, pos);
5751 bpage->time_stamp = save_timestamp;
5752
5753 /* we copied everything to the beginning */
5754 read = 0;
5755 } else {
5756 /* update the entry counter */
5757 cpu_buffer->read += rb_page_entries(reader);
5758 cpu_buffer->read_bytes += rb_page_commit(reader);
5759
5760 /* swap the pages */
5761 rb_init_page(bpage);
5762 bpage = reader->page;
5763 reader->page = data_page->data;
5764 local_set(&reader->write, 0);
5765 local_set(&reader->entries, 0);
5766 reader->read = 0;
5767 data_page->data = bpage;
5768
5769 /*
5770 * Use the real_end for the data size,
5771 * This gives us a chance to store the lost events
5772 * on the page.
5773 */
5774 if (reader->real_end)
5775 local_set(&bpage->commit, reader->real_end);
5776 }
5777 ret = read;
5778
5779 cpu_buffer->lost_events = 0;
5780
5781 commit = local_read(&bpage->commit);
5782 /*
5783 * Set a flag in the commit field if we lost events
5784 */
5785 if (missed_events) {
5786 /* If there is room at the end of the page to save the
5787 * missed events, then record it there.
5788 */
5789 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
5790 memcpy(&bpage->data[commit], &missed_events,
5791 sizeof(missed_events));
5792 local_add(RB_MISSED_STORED, &bpage->commit);
5793 commit += sizeof(missed_events);
5794 }
5795 local_add(RB_MISSED_EVENTS, &bpage->commit);
5796 }
5797
5798 /*
5799 * This page may be off to user land. Zero it out here.
5800 */
5801 if (commit < buffer->subbuf_size)
5802 memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
5803
5804 out_unlock:
5805 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5806
5807 out:
5808 return ret;
5809}
5810EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5811
5812/**
5813 * ring_buffer_read_page_data - get pointer to the data in the page.
5814 * @page: the page to get the data from
5815 *
5816 * Returns pointer to the actual data in this page.
5817 */
5818void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
5819{
5820 return page->data;
5821}
5822EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
5823
5824/**
5825 * ring_buffer_subbuf_size_get - get size of the sub buffer.
5826 * @buffer: the buffer to get the sub buffer size from
5827 *
5828 * Returns size of the sub buffer, in bytes.
5829 */
5830int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
5831{
5832 return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
5833}
5834EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
5835
5836/**
5837 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
5838 * @buffer: The ring_buffer to get the system sub page order from
5839 *
5840 * By default, one ring buffer sub page equals to one system page. This parameter
5841 * is configurable, per ring buffer. The size of the ring buffer sub page can be
5842 * extended, but must be an order of system page size.
5843 *
5844 * Returns the order of buffer sub page size, in system pages:
5845 * 0 means the sub buffer size is 1 system page and so forth.
5846 * In case of an error < 0 is returned.
5847 */
5848int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
5849{
5850 if (!buffer)
5851 return -EINVAL;
5852
5853 return buffer->subbuf_order;
5854}
5855EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
5856
5857/**
5858 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
5859 * @buffer: The ring_buffer to set the new page size.
5860 * @order: Order of the system pages in one sub buffer page
5861 *
5862 * By default, one ring buffer pages equals to one system page. This API can be
5863 * used to set new size of the ring buffer page. The size must be order of
5864 * system page size, that's why the input parameter @order is the order of
5865 * system pages that are allocated for one ring buffer page:
5866 * 0 - 1 system page
5867 * 1 - 2 system pages
5868 * 3 - 4 system pages
5869 * ...
5870 *
5871 * Returns 0 on success or < 0 in case of an error.
5872 */
5873int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
5874{
5875 struct ring_buffer_per_cpu *cpu_buffer;
5876 struct buffer_page *bpage, *tmp;
5877 int old_order, old_size;
5878 int nr_pages;
5879 int psize;
5880 int err;
5881 int cpu;
5882
5883 if (!buffer || order < 0)
5884 return -EINVAL;
5885
5886 if (buffer->subbuf_order == order)
5887 return 0;
5888
5889 psize = (1 << order) * PAGE_SIZE;
5890 if (psize <= BUF_PAGE_HDR_SIZE)
5891 return -EINVAL;
5892
5893 /* Size of a subbuf cannot be greater than the write counter */
5894 if (psize > RB_WRITE_MASK + 1)
5895 return -EINVAL;
5896
5897 old_order = buffer->subbuf_order;
5898 old_size = buffer->subbuf_size;
5899
5900 /* prevent another thread from changing buffer sizes */
5901 mutex_lock(&buffer->mutex);
5902 atomic_inc(&buffer->record_disabled);
5903
5904 /* Make sure all commits have finished */
5905 synchronize_rcu();
5906
5907 buffer->subbuf_order = order;
5908 buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
5909
5910 /* Make sure all new buffers are allocated, before deleting the old ones */
5911 for_each_buffer_cpu(buffer, cpu) {
5912
5913 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5914 continue;
5915
5916 cpu_buffer = buffer->buffers[cpu];
5917
5918 /* Update the number of pages to match the new size */
5919 nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
5920 nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
5921
5922 /* we need a minimum of two pages */
5923 if (nr_pages < 2)
5924 nr_pages = 2;
5925
5926 cpu_buffer->nr_pages_to_update = nr_pages;
5927
5928 /* Include the reader page */
5929 nr_pages++;
5930
5931 /* Allocate the new size buffer */
5932 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5933 if (__rb_allocate_pages(cpu_buffer, nr_pages,
5934 &cpu_buffer->new_pages)) {
5935 /* not enough memory for new pages */
5936 err = -ENOMEM;
5937 goto error;
5938 }
5939 }
5940
5941 for_each_buffer_cpu(buffer, cpu) {
5942
5943 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5944 continue;
5945
5946 cpu_buffer = buffer->buffers[cpu];
5947
5948 /* Clear the head bit to make the link list normal to read */
5949 rb_head_page_deactivate(cpu_buffer);
5950
5951 /* Now walk the list and free all the old sub buffers */
5952 list_for_each_entry_safe(bpage, tmp, cpu_buffer->pages, list) {
5953 list_del_init(&bpage->list);
5954 free_buffer_page(bpage);
5955 }
5956 /* The above loop stopped an the last page needing to be freed */
5957 bpage = list_entry(cpu_buffer->pages, struct buffer_page, list);
5958 free_buffer_page(bpage);
5959
5960 /* Free the current reader page */
5961 free_buffer_page(cpu_buffer->reader_page);
5962
5963 /* One page was allocated for the reader page */
5964 cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
5965 struct buffer_page, list);
5966 list_del_init(&cpu_buffer->reader_page->list);
5967
5968 /* The cpu_buffer pages are a link list with no head */
5969 cpu_buffer->pages = cpu_buffer->new_pages.next;
5970 cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev;
5971 cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next;
5972
5973 /* Clear the new_pages list */
5974 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5975
5976 cpu_buffer->head_page
5977 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5978 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
5979
5980 cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
5981 cpu_buffer->nr_pages_to_update = 0;
5982
5983 free_pages((unsigned long)cpu_buffer->free_page, old_order);
5984 cpu_buffer->free_page = NULL;
5985
5986 rb_head_page_activate(cpu_buffer);
5987
5988 rb_check_pages(cpu_buffer);
5989 }
5990
5991 atomic_dec(&buffer->record_disabled);
5992 mutex_unlock(&buffer->mutex);
5993
5994 return 0;
5995
5996error:
5997 buffer->subbuf_order = old_order;
5998 buffer->subbuf_size = old_size;
5999
6000 atomic_dec(&buffer->record_disabled);
6001 mutex_unlock(&buffer->mutex);
6002
6003 for_each_buffer_cpu(buffer, cpu) {
6004 cpu_buffer = buffer->buffers[cpu];
6005
6006 if (!cpu_buffer->nr_pages_to_update)
6007 continue;
6008
6009 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6010 list_del_init(&bpage->list);
6011 free_buffer_page(bpage);
6012 }
6013 }
6014
6015 return err;
6016}
6017EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6018
6019/*
6020 * We only allocate new buffers, never free them if the CPU goes down.
6021 * If we were to free the buffer, then the user would lose any trace that was in
6022 * the buffer.
6023 */
6024int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
6025{
6026 struct trace_buffer *buffer;
6027 long nr_pages_same;
6028 int cpu_i;
6029 unsigned long nr_pages;
6030
6031 buffer = container_of(node, struct trace_buffer, node);
6032 if (cpumask_test_cpu(cpu, buffer->cpumask))
6033 return 0;
6034
6035 nr_pages = 0;
6036 nr_pages_same = 1;
6037 /* check if all cpu sizes are same */
6038 for_each_buffer_cpu(buffer, cpu_i) {
6039 /* fill in the size from first enabled cpu */
6040 if (nr_pages == 0)
6041 nr_pages = buffer->buffers[cpu_i]->nr_pages;
6042 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
6043 nr_pages_same = 0;
6044 break;
6045 }
6046 }
6047 /* allocate minimum pages, user can later expand it */
6048 if (!nr_pages_same)
6049 nr_pages = 2;
6050 buffer->buffers[cpu] =
6051 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
6052 if (!buffer->buffers[cpu]) {
6053 WARN(1, "failed to allocate ring buffer on CPU %u\n",
6054 cpu);
6055 return -ENOMEM;
6056 }
6057 smp_wmb();
6058 cpumask_set_cpu(cpu, buffer->cpumask);
6059 return 0;
6060}
6061
6062#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
6063/*
6064 * This is a basic integrity check of the ring buffer.
6065 * Late in the boot cycle this test will run when configured in.
6066 * It will kick off a thread per CPU that will go into a loop
6067 * writing to the per cpu ring buffer various sizes of data.
6068 * Some of the data will be large items, some small.
6069 *
6070 * Another thread is created that goes into a spin, sending out
6071 * IPIs to the other CPUs to also write into the ring buffer.
6072 * this is to test the nesting ability of the buffer.
6073 *
6074 * Basic stats are recorded and reported. If something in the
6075 * ring buffer should happen that's not expected, a big warning
6076 * is displayed and all ring buffers are disabled.
6077 */
6078static struct task_struct *rb_threads[NR_CPUS] __initdata;
6079
6080struct rb_test_data {
6081 struct trace_buffer *buffer;
6082 unsigned long events;
6083 unsigned long bytes_written;
6084 unsigned long bytes_alloc;
6085 unsigned long bytes_dropped;
6086 unsigned long events_nested;
6087 unsigned long bytes_written_nested;
6088 unsigned long bytes_alloc_nested;
6089 unsigned long bytes_dropped_nested;
6090 int min_size_nested;
6091 int max_size_nested;
6092 int max_size;
6093 int min_size;
6094 int cpu;
6095 int cnt;
6096};
6097
6098static struct rb_test_data rb_data[NR_CPUS] __initdata;
6099
6100/* 1 meg per cpu */
6101#define RB_TEST_BUFFER_SIZE 1048576
6102
6103static char rb_string[] __initdata =
6104 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
6105 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
6106 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
6107
6108static bool rb_test_started __initdata;
6109
6110struct rb_item {
6111 int size;
6112 char str[];
6113};
6114
6115static __init int rb_write_something(struct rb_test_data *data, bool nested)
6116{
6117 struct ring_buffer_event *event;
6118 struct rb_item *item;
6119 bool started;
6120 int event_len;
6121 int size;
6122 int len;
6123 int cnt;
6124
6125 /* Have nested writes different that what is written */
6126 cnt = data->cnt + (nested ? 27 : 0);
6127
6128 /* Multiply cnt by ~e, to make some unique increment */
6129 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
6130
6131 len = size + sizeof(struct rb_item);
6132
6133 started = rb_test_started;
6134 /* read rb_test_started before checking buffer enabled */
6135 smp_rmb();
6136
6137 event = ring_buffer_lock_reserve(data->buffer, len);
6138 if (!event) {
6139 /* Ignore dropped events before test starts. */
6140 if (started) {
6141 if (nested)
6142 data->bytes_dropped += len;
6143 else
6144 data->bytes_dropped_nested += len;
6145 }
6146 return len;
6147 }
6148
6149 event_len = ring_buffer_event_length(event);
6150
6151 if (RB_WARN_ON(data->buffer, event_len < len))
6152 goto out;
6153
6154 item = ring_buffer_event_data(event);
6155 item->size = size;
6156 memcpy(item->str, rb_string, size);
6157
6158 if (nested) {
6159 data->bytes_alloc_nested += event_len;
6160 data->bytes_written_nested += len;
6161 data->events_nested++;
6162 if (!data->min_size_nested || len < data->min_size_nested)
6163 data->min_size_nested = len;
6164 if (len > data->max_size_nested)
6165 data->max_size_nested = len;
6166 } else {
6167 data->bytes_alloc += event_len;
6168 data->bytes_written += len;
6169 data->events++;
6170 if (!data->min_size || len < data->min_size)
6171 data->max_size = len;
6172 if (len > data->max_size)
6173 data->max_size = len;
6174 }
6175
6176 out:
6177 ring_buffer_unlock_commit(data->buffer);
6178
6179 return 0;
6180}
6181
6182static __init int rb_test(void *arg)
6183{
6184 struct rb_test_data *data = arg;
6185
6186 while (!kthread_should_stop()) {
6187 rb_write_something(data, false);
6188 data->cnt++;
6189
6190 set_current_state(TASK_INTERRUPTIBLE);
6191 /* Now sleep between a min of 100-300us and a max of 1ms */
6192 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
6193 }
6194
6195 return 0;
6196}
6197
6198static __init void rb_ipi(void *ignore)
6199{
6200 struct rb_test_data *data;
6201 int cpu = smp_processor_id();
6202
6203 data = &rb_data[cpu];
6204 rb_write_something(data, true);
6205}
6206
6207static __init int rb_hammer_test(void *arg)
6208{
6209 while (!kthread_should_stop()) {
6210
6211 /* Send an IPI to all cpus to write data! */
6212 smp_call_function(rb_ipi, NULL, 1);
6213 /* No sleep, but for non preempt, let others run */
6214 schedule();
6215 }
6216
6217 return 0;
6218}
6219
6220static __init int test_ringbuffer(void)
6221{
6222 struct task_struct *rb_hammer;
6223 struct trace_buffer *buffer;
6224 int cpu;
6225 int ret = 0;
6226
6227 if (security_locked_down(LOCKDOWN_TRACEFS)) {
6228 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6229 return 0;
6230 }
6231
6232 pr_info("Running ring buffer tests...\n");
6233
6234 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
6235 if (WARN_ON(!buffer))
6236 return 0;
6237
6238 /* Disable buffer so that threads can't write to it yet */
6239 ring_buffer_record_off(buffer);
6240
6241 for_each_online_cpu(cpu) {
6242 rb_data[cpu].buffer = buffer;
6243 rb_data[cpu].cpu = cpu;
6244 rb_data[cpu].cnt = cpu;
6245 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
6246 cpu, "rbtester/%u");
6247 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
6248 pr_cont("FAILED\n");
6249 ret = PTR_ERR(rb_threads[cpu]);
6250 goto out_free;
6251 }
6252 }
6253
6254 /* Now create the rb hammer! */
6255 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
6256 if (WARN_ON(IS_ERR(rb_hammer))) {
6257 pr_cont("FAILED\n");
6258 ret = PTR_ERR(rb_hammer);
6259 goto out_free;
6260 }
6261
6262 ring_buffer_record_on(buffer);
6263 /*
6264 * Show buffer is enabled before setting rb_test_started.
6265 * Yes there's a small race window where events could be
6266 * dropped and the thread wont catch it. But when a ring
6267 * buffer gets enabled, there will always be some kind of
6268 * delay before other CPUs see it. Thus, we don't care about
6269 * those dropped events. We care about events dropped after
6270 * the threads see that the buffer is active.
6271 */
6272 smp_wmb();
6273 rb_test_started = true;
6274
6275 set_current_state(TASK_INTERRUPTIBLE);
6276 /* Just run for 10 seconds */;
6277 schedule_timeout(10 * HZ);
6278
6279 kthread_stop(rb_hammer);
6280
6281 out_free:
6282 for_each_online_cpu(cpu) {
6283 if (!rb_threads[cpu])
6284 break;
6285 kthread_stop(rb_threads[cpu]);
6286 }
6287 if (ret) {
6288 ring_buffer_free(buffer);
6289 return ret;
6290 }
6291
6292 /* Report! */
6293 pr_info("finished\n");
6294 for_each_online_cpu(cpu) {
6295 struct ring_buffer_event *event;
6296 struct rb_test_data *data = &rb_data[cpu];
6297 struct rb_item *item;
6298 unsigned long total_events;
6299 unsigned long total_dropped;
6300 unsigned long total_written;
6301 unsigned long total_alloc;
6302 unsigned long total_read = 0;
6303 unsigned long total_size = 0;
6304 unsigned long total_len = 0;
6305 unsigned long total_lost = 0;
6306 unsigned long lost;
6307 int big_event_size;
6308 int small_event_size;
6309
6310 ret = -1;
6311
6312 total_events = data->events + data->events_nested;
6313 total_written = data->bytes_written + data->bytes_written_nested;
6314 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
6315 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
6316
6317 big_event_size = data->max_size + data->max_size_nested;
6318 small_event_size = data->min_size + data->min_size_nested;
6319
6320 pr_info("CPU %d:\n", cpu);
6321 pr_info(" events: %ld\n", total_events);
6322 pr_info(" dropped bytes: %ld\n", total_dropped);
6323 pr_info(" alloced bytes: %ld\n", total_alloc);
6324 pr_info(" written bytes: %ld\n", total_written);
6325 pr_info(" biggest event: %d\n", big_event_size);
6326 pr_info(" smallest event: %d\n", small_event_size);
6327
6328 if (RB_WARN_ON(buffer, total_dropped))
6329 break;
6330
6331 ret = 0;
6332
6333 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
6334 total_lost += lost;
6335 item = ring_buffer_event_data(event);
6336 total_len += ring_buffer_event_length(event);
6337 total_size += item->size + sizeof(struct rb_item);
6338 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
6339 pr_info("FAILED!\n");
6340 pr_info("buffer had: %.*s\n", item->size, item->str);
6341 pr_info("expected: %.*s\n", item->size, rb_string);
6342 RB_WARN_ON(buffer, 1);
6343 ret = -1;
6344 break;
6345 }
6346 total_read++;
6347 }
6348 if (ret)
6349 break;
6350
6351 ret = -1;
6352
6353 pr_info(" read events: %ld\n", total_read);
6354 pr_info(" lost events: %ld\n", total_lost);
6355 pr_info(" total events: %ld\n", total_lost + total_read);
6356 pr_info(" recorded len bytes: %ld\n", total_len);
6357 pr_info(" recorded size bytes: %ld\n", total_size);
6358 if (total_lost) {
6359 pr_info(" With dropped events, record len and size may not match\n"
6360 " alloced and written from above\n");
6361 } else {
6362 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6363 total_size != total_written))
6364 break;
6365 }
6366 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6367 break;
6368
6369 ret = 0;
6370 }
6371 if (!ret)
6372 pr_info("Ring buffer PASSED!\n");
6373
6374 ring_buffer_free(buffer);
6375 return 0;
6376}
6377
6378late_initcall(test_ringbuffer);
6379#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/trace_events.h>
7#include <linux/ring_buffer.h>
8#include <linux/trace_clock.h>
9#include <linux/sched/clock.h>
10#include <linux/trace_seq.h>
11#include <linux/spinlock.h>
12#include <linux/irq_work.h>
13#include <linux/uaccess.h>
14#include <linux/hardirq.h>
15#include <linux/kthread.h> /* for self test */
16#include <linux/module.h>
17#include <linux/percpu.h>
18#include <linux/mutex.h>
19#include <linux/delay.h>
20#include <linux/slab.h>
21#include <linux/init.h>
22#include <linux/hash.h>
23#include <linux/list.h>
24#include <linux/cpu.h>
25#include <linux/oom.h>
26
27#include <asm/local.h>
28
29static void update_pages_handler(struct work_struct *work);
30
31/*
32 * The ring buffer header is special. We must manually up keep it.
33 */
34int ring_buffer_print_entry_header(struct trace_seq *s)
35{
36 trace_seq_puts(s, "# compressed entry header\n");
37 trace_seq_puts(s, "\ttype_len : 5 bits\n");
38 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
39 trace_seq_puts(s, "\tarray : 32 bits\n");
40 trace_seq_putc(s, '\n');
41 trace_seq_printf(s, "\tpadding : type == %d\n",
42 RINGBUF_TYPE_PADDING);
43 trace_seq_printf(s, "\ttime_extend : type == %d\n",
44 RINGBUF_TYPE_TIME_EXTEND);
45 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
46 RINGBUF_TYPE_TIME_STAMP);
47 trace_seq_printf(s, "\tdata max type_len == %d\n",
48 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
49
50 return !trace_seq_has_overflowed(s);
51}
52
53/*
54 * The ring buffer is made up of a list of pages. A separate list of pages is
55 * allocated for each CPU. A writer may only write to a buffer that is
56 * associated with the CPU it is currently executing on. A reader may read
57 * from any per cpu buffer.
58 *
59 * The reader is special. For each per cpu buffer, the reader has its own
60 * reader page. When a reader has read the entire reader page, this reader
61 * page is swapped with another page in the ring buffer.
62 *
63 * Now, as long as the writer is off the reader page, the reader can do what
64 * ever it wants with that page. The writer will never write to that page
65 * again (as long as it is out of the ring buffer).
66 *
67 * Here's some silly ASCII art.
68 *
69 * +------+
70 * |reader| RING BUFFER
71 * |page |
72 * +------+ +---+ +---+ +---+
73 * | |-->| |-->| |
74 * +---+ +---+ +---+
75 * ^ |
76 * | |
77 * +---------------+
78 *
79 *
80 * +------+
81 * |reader| RING BUFFER
82 * |page |------------------v
83 * +------+ +---+ +---+ +---+
84 * | |-->| |-->| |
85 * +---+ +---+ +---+
86 * ^ |
87 * | |
88 * +---------------+
89 *
90 *
91 * +------+
92 * |reader| RING BUFFER
93 * |page |------------------v
94 * +------+ +---+ +---+ +---+
95 * ^ | |-->| |-->| |
96 * | +---+ +---+ +---+
97 * | |
98 * | |
99 * +------------------------------+
100 *
101 *
102 * +------+
103 * |buffer| RING BUFFER
104 * |page |------------------v
105 * +------+ +---+ +---+ +---+
106 * ^ | | | |-->| |
107 * | New +---+ +---+ +---+
108 * | Reader------^ |
109 * | page |
110 * +------------------------------+
111 *
112 *
113 * After we make this swap, the reader can hand this page off to the splice
114 * code and be done with it. It can even allocate a new page if it needs to
115 * and swap that into the ring buffer.
116 *
117 * We will be using cmpxchg soon to make all this lockless.
118 *
119 */
120
121/* Used for individual buffers (after the counter) */
122#define RB_BUFFER_OFF (1 << 20)
123
124#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
125
126#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
127#define RB_ALIGNMENT 4U
128#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
129#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
130
131#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
132# define RB_FORCE_8BYTE_ALIGNMENT 0
133# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
134#else
135# define RB_FORCE_8BYTE_ALIGNMENT 1
136# define RB_ARCH_ALIGNMENT 8U
137#endif
138
139#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
140
141/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
142#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
143
144enum {
145 RB_LEN_TIME_EXTEND = 8,
146 RB_LEN_TIME_STAMP = 8,
147};
148
149#define skip_time_extend(event) \
150 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
151
152#define extended_time(event) \
153 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
154
155static inline int rb_null_event(struct ring_buffer_event *event)
156{
157 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
158}
159
160static void rb_event_set_padding(struct ring_buffer_event *event)
161{
162 /* padding has a NULL time_delta */
163 event->type_len = RINGBUF_TYPE_PADDING;
164 event->time_delta = 0;
165}
166
167static unsigned
168rb_event_data_length(struct ring_buffer_event *event)
169{
170 unsigned length;
171
172 if (event->type_len)
173 length = event->type_len * RB_ALIGNMENT;
174 else
175 length = event->array[0];
176 return length + RB_EVNT_HDR_SIZE;
177}
178
179/*
180 * Return the length of the given event. Will return
181 * the length of the time extend if the event is a
182 * time extend.
183 */
184static inline unsigned
185rb_event_length(struct ring_buffer_event *event)
186{
187 switch (event->type_len) {
188 case RINGBUF_TYPE_PADDING:
189 if (rb_null_event(event))
190 /* undefined */
191 return -1;
192 return event->array[0] + RB_EVNT_HDR_SIZE;
193
194 case RINGBUF_TYPE_TIME_EXTEND:
195 return RB_LEN_TIME_EXTEND;
196
197 case RINGBUF_TYPE_TIME_STAMP:
198 return RB_LEN_TIME_STAMP;
199
200 case RINGBUF_TYPE_DATA:
201 return rb_event_data_length(event);
202 default:
203 BUG();
204 }
205 /* not hit */
206 return 0;
207}
208
209/*
210 * Return total length of time extend and data,
211 * or just the event length for all other events.
212 */
213static inline unsigned
214rb_event_ts_length(struct ring_buffer_event *event)
215{
216 unsigned len = 0;
217
218 if (extended_time(event)) {
219 /* time extends include the data event after it */
220 len = RB_LEN_TIME_EXTEND;
221 event = skip_time_extend(event);
222 }
223 return len + rb_event_length(event);
224}
225
226/**
227 * ring_buffer_event_length - return the length of the event
228 * @event: the event to get the length of
229 *
230 * Returns the size of the data load of a data event.
231 * If the event is something other than a data event, it
232 * returns the size of the event itself. With the exception
233 * of a TIME EXTEND, where it still returns the size of the
234 * data load of the data event after it.
235 */
236unsigned ring_buffer_event_length(struct ring_buffer_event *event)
237{
238 unsigned length;
239
240 if (extended_time(event))
241 event = skip_time_extend(event);
242
243 length = rb_event_length(event);
244 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
245 return length;
246 length -= RB_EVNT_HDR_SIZE;
247 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
248 length -= sizeof(event->array[0]);
249 return length;
250}
251EXPORT_SYMBOL_GPL(ring_buffer_event_length);
252
253/* inline for ring buffer fast paths */
254static __always_inline void *
255rb_event_data(struct ring_buffer_event *event)
256{
257 if (extended_time(event))
258 event = skip_time_extend(event);
259 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
260 /* If length is in len field, then array[0] has the data */
261 if (event->type_len)
262 return (void *)&event->array[0];
263 /* Otherwise length is in array[0] and array[1] has the data */
264 return (void *)&event->array[1];
265}
266
267/**
268 * ring_buffer_event_data - return the data of the event
269 * @event: the event to get the data from
270 */
271void *ring_buffer_event_data(struct ring_buffer_event *event)
272{
273 return rb_event_data(event);
274}
275EXPORT_SYMBOL_GPL(ring_buffer_event_data);
276
277#define for_each_buffer_cpu(buffer, cpu) \
278 for_each_cpu(cpu, buffer->cpumask)
279
280#define TS_SHIFT 27
281#define TS_MASK ((1ULL << TS_SHIFT) - 1)
282#define TS_DELTA_TEST (~TS_MASK)
283
284/**
285 * ring_buffer_event_time_stamp - return the event's extended timestamp
286 * @event: the event to get the timestamp of
287 *
288 * Returns the extended timestamp associated with a data event.
289 * An extended time_stamp is a 64-bit timestamp represented
290 * internally in a special way that makes the best use of space
291 * contained within a ring buffer event. This function decodes
292 * it and maps it to a straight u64 value.
293 */
294u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
295{
296 u64 ts;
297
298 ts = event->array[0];
299 ts <<= TS_SHIFT;
300 ts += event->time_delta;
301
302 return ts;
303}
304
305/* Flag when events were overwritten */
306#define RB_MISSED_EVENTS (1 << 31)
307/* Missed count stored at end */
308#define RB_MISSED_STORED (1 << 30)
309
310#define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED)
311
312struct buffer_data_page {
313 u64 time_stamp; /* page time stamp */
314 local_t commit; /* write committed index */
315 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
316};
317
318/*
319 * Note, the buffer_page list must be first. The buffer pages
320 * are allocated in cache lines, which means that each buffer
321 * page will be at the beginning of a cache line, and thus
322 * the least significant bits will be zero. We use this to
323 * add flags in the list struct pointers, to make the ring buffer
324 * lockless.
325 */
326struct buffer_page {
327 struct list_head list; /* list of buffer pages */
328 local_t write; /* index for next write */
329 unsigned read; /* index for next read */
330 local_t entries; /* entries on this page */
331 unsigned long real_end; /* real end of data */
332 struct buffer_data_page *page; /* Actual data page */
333};
334
335/*
336 * The buffer page counters, write and entries, must be reset
337 * atomically when crossing page boundaries. To synchronize this
338 * update, two counters are inserted into the number. One is
339 * the actual counter for the write position or count on the page.
340 *
341 * The other is a counter of updaters. Before an update happens
342 * the update partition of the counter is incremented. This will
343 * allow the updater to update the counter atomically.
344 *
345 * The counter is 20 bits, and the state data is 12.
346 */
347#define RB_WRITE_MASK 0xfffff
348#define RB_WRITE_INTCNT (1 << 20)
349
350static void rb_init_page(struct buffer_data_page *bpage)
351{
352 local_set(&bpage->commit, 0);
353}
354
355/**
356 * ring_buffer_page_len - the size of data on the page.
357 * @page: The page to read
358 *
359 * Returns the amount of data on the page, including buffer page header.
360 */
361size_t ring_buffer_page_len(void *page)
362{
363 struct buffer_data_page *bpage = page;
364
365 return (local_read(&bpage->commit) & ~RB_MISSED_FLAGS)
366 + BUF_PAGE_HDR_SIZE;
367}
368
369/*
370 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
371 * this issue out.
372 */
373static void free_buffer_page(struct buffer_page *bpage)
374{
375 free_page((unsigned long)bpage->page);
376 kfree(bpage);
377}
378
379/*
380 * We need to fit the time_stamp delta into 27 bits.
381 */
382static inline int test_time_stamp(u64 delta)
383{
384 if (delta & TS_DELTA_TEST)
385 return 1;
386 return 0;
387}
388
389#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
390
391/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
392#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
393
394int ring_buffer_print_page_header(struct trace_seq *s)
395{
396 struct buffer_data_page field;
397
398 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
399 "offset:0;\tsize:%u;\tsigned:%u;\n",
400 (unsigned int)sizeof(field.time_stamp),
401 (unsigned int)is_signed_type(u64));
402
403 trace_seq_printf(s, "\tfield: local_t commit;\t"
404 "offset:%u;\tsize:%u;\tsigned:%u;\n",
405 (unsigned int)offsetof(typeof(field), commit),
406 (unsigned int)sizeof(field.commit),
407 (unsigned int)is_signed_type(long));
408
409 trace_seq_printf(s, "\tfield: int overwrite;\t"
410 "offset:%u;\tsize:%u;\tsigned:%u;\n",
411 (unsigned int)offsetof(typeof(field), commit),
412 1,
413 (unsigned int)is_signed_type(long));
414
415 trace_seq_printf(s, "\tfield: char data;\t"
416 "offset:%u;\tsize:%u;\tsigned:%u;\n",
417 (unsigned int)offsetof(typeof(field), data),
418 (unsigned int)BUF_PAGE_SIZE,
419 (unsigned int)is_signed_type(char));
420
421 return !trace_seq_has_overflowed(s);
422}
423
424struct rb_irq_work {
425 struct irq_work work;
426 wait_queue_head_t waiters;
427 wait_queue_head_t full_waiters;
428 bool waiters_pending;
429 bool full_waiters_pending;
430 bool wakeup_full;
431};
432
433/*
434 * Structure to hold event state and handle nested events.
435 */
436struct rb_event_info {
437 u64 ts;
438 u64 delta;
439 unsigned long length;
440 struct buffer_page *tail_page;
441 int add_timestamp;
442};
443
444/*
445 * Used for which event context the event is in.
446 * NMI = 0
447 * IRQ = 1
448 * SOFTIRQ = 2
449 * NORMAL = 3
450 *
451 * See trace_recursive_lock() comment below for more details.
452 */
453enum {
454 RB_CTX_NMI,
455 RB_CTX_IRQ,
456 RB_CTX_SOFTIRQ,
457 RB_CTX_NORMAL,
458 RB_CTX_MAX
459};
460
461/*
462 * head_page == tail_page && head == tail then buffer is empty.
463 */
464struct ring_buffer_per_cpu {
465 int cpu;
466 atomic_t record_disabled;
467 struct ring_buffer *buffer;
468 raw_spinlock_t reader_lock; /* serialize readers */
469 arch_spinlock_t lock;
470 struct lock_class_key lock_key;
471 struct buffer_data_page *free_page;
472 unsigned long nr_pages;
473 unsigned int current_context;
474 struct list_head *pages;
475 struct buffer_page *head_page; /* read from head */
476 struct buffer_page *tail_page; /* write to tail */
477 struct buffer_page *commit_page; /* committed pages */
478 struct buffer_page *reader_page;
479 unsigned long lost_events;
480 unsigned long last_overrun;
481 unsigned long nest;
482 local_t entries_bytes;
483 local_t entries;
484 local_t overrun;
485 local_t commit_overrun;
486 local_t dropped_events;
487 local_t committing;
488 local_t commits;
489 unsigned long read;
490 unsigned long read_bytes;
491 u64 write_stamp;
492 u64 read_stamp;
493 /* ring buffer pages to update, > 0 to add, < 0 to remove */
494 long nr_pages_to_update;
495 struct list_head new_pages; /* new pages to add */
496 struct work_struct update_pages_work;
497 struct completion update_done;
498
499 struct rb_irq_work irq_work;
500};
501
502struct ring_buffer {
503 unsigned flags;
504 int cpus;
505 atomic_t record_disabled;
506 atomic_t resize_disabled;
507 cpumask_var_t cpumask;
508
509 struct lock_class_key *reader_lock_key;
510
511 struct mutex mutex;
512
513 struct ring_buffer_per_cpu **buffers;
514
515 struct hlist_node node;
516 u64 (*clock)(void);
517
518 struct rb_irq_work irq_work;
519 bool time_stamp_abs;
520};
521
522struct ring_buffer_iter {
523 struct ring_buffer_per_cpu *cpu_buffer;
524 unsigned long head;
525 struct buffer_page *head_page;
526 struct buffer_page *cache_reader_page;
527 unsigned long cache_read;
528 u64 read_stamp;
529};
530
531/*
532 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
533 *
534 * Schedules a delayed work to wake up any task that is blocked on the
535 * ring buffer waiters queue.
536 */
537static void rb_wake_up_waiters(struct irq_work *work)
538{
539 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
540
541 wake_up_all(&rbwork->waiters);
542 if (rbwork->wakeup_full) {
543 rbwork->wakeup_full = false;
544 wake_up_all(&rbwork->full_waiters);
545 }
546}
547
548/**
549 * ring_buffer_wait - wait for input to the ring buffer
550 * @buffer: buffer to wait on
551 * @cpu: the cpu buffer to wait on
552 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
553 *
554 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
555 * as data is added to any of the @buffer's cpu buffers. Otherwise
556 * it will wait for data to be added to a specific cpu buffer.
557 */
558int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
559{
560 struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
561 DEFINE_WAIT(wait);
562 struct rb_irq_work *work;
563 int ret = 0;
564
565 /*
566 * Depending on what the caller is waiting for, either any
567 * data in any cpu buffer, or a specific buffer, put the
568 * caller on the appropriate wait queue.
569 */
570 if (cpu == RING_BUFFER_ALL_CPUS) {
571 work = &buffer->irq_work;
572 /* Full only makes sense on per cpu reads */
573 full = false;
574 } else {
575 if (!cpumask_test_cpu(cpu, buffer->cpumask))
576 return -ENODEV;
577 cpu_buffer = buffer->buffers[cpu];
578 work = &cpu_buffer->irq_work;
579 }
580
581
582 while (true) {
583 if (full)
584 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
585 else
586 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
587
588 /*
589 * The events can happen in critical sections where
590 * checking a work queue can cause deadlocks.
591 * After adding a task to the queue, this flag is set
592 * only to notify events to try to wake up the queue
593 * using irq_work.
594 *
595 * We don't clear it even if the buffer is no longer
596 * empty. The flag only causes the next event to run
597 * irq_work to do the work queue wake up. The worse
598 * that can happen if we race with !trace_empty() is that
599 * an event will cause an irq_work to try to wake up
600 * an empty queue.
601 *
602 * There's no reason to protect this flag either, as
603 * the work queue and irq_work logic will do the necessary
604 * synchronization for the wake ups. The only thing
605 * that is necessary is that the wake up happens after
606 * a task has been queued. It's OK for spurious wake ups.
607 */
608 if (full)
609 work->full_waiters_pending = true;
610 else
611 work->waiters_pending = true;
612
613 if (signal_pending(current)) {
614 ret = -EINTR;
615 break;
616 }
617
618 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
619 break;
620
621 if (cpu != RING_BUFFER_ALL_CPUS &&
622 !ring_buffer_empty_cpu(buffer, cpu)) {
623 unsigned long flags;
624 bool pagebusy;
625
626 if (!full)
627 break;
628
629 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
630 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
631 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
632
633 if (!pagebusy)
634 break;
635 }
636
637 schedule();
638 }
639
640 if (full)
641 finish_wait(&work->full_waiters, &wait);
642 else
643 finish_wait(&work->waiters, &wait);
644
645 return ret;
646}
647
648/**
649 * ring_buffer_poll_wait - poll on buffer input
650 * @buffer: buffer to wait on
651 * @cpu: the cpu buffer to wait on
652 * @filp: the file descriptor
653 * @poll_table: The poll descriptor
654 *
655 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
656 * as data is added to any of the @buffer's cpu buffers. Otherwise
657 * it will wait for data to be added to a specific cpu buffer.
658 *
659 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
660 * zero otherwise.
661 */
662__poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
663 struct file *filp, poll_table *poll_table)
664{
665 struct ring_buffer_per_cpu *cpu_buffer;
666 struct rb_irq_work *work;
667
668 if (cpu == RING_BUFFER_ALL_CPUS)
669 work = &buffer->irq_work;
670 else {
671 if (!cpumask_test_cpu(cpu, buffer->cpumask))
672 return -EINVAL;
673
674 cpu_buffer = buffer->buffers[cpu];
675 work = &cpu_buffer->irq_work;
676 }
677
678 poll_wait(filp, &work->waiters, poll_table);
679 work->waiters_pending = true;
680 /*
681 * There's a tight race between setting the waiters_pending and
682 * checking if the ring buffer is empty. Once the waiters_pending bit
683 * is set, the next event will wake the task up, but we can get stuck
684 * if there's only a single event in.
685 *
686 * FIXME: Ideally, we need a memory barrier on the writer side as well,
687 * but adding a memory barrier to all events will cause too much of a
688 * performance hit in the fast path. We only need a memory barrier when
689 * the buffer goes from empty to having content. But as this race is
690 * extremely small, and it's not a problem if another event comes in, we
691 * will fix it later.
692 */
693 smp_mb();
694
695 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
696 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
697 return EPOLLIN | EPOLLRDNORM;
698 return 0;
699}
700
701/* buffer may be either ring_buffer or ring_buffer_per_cpu */
702#define RB_WARN_ON(b, cond) \
703 ({ \
704 int _____ret = unlikely(cond); \
705 if (_____ret) { \
706 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
707 struct ring_buffer_per_cpu *__b = \
708 (void *)b; \
709 atomic_inc(&__b->buffer->record_disabled); \
710 } else \
711 atomic_inc(&b->record_disabled); \
712 WARN_ON(1); \
713 } \
714 _____ret; \
715 })
716
717/* Up this if you want to test the TIME_EXTENTS and normalization */
718#define DEBUG_SHIFT 0
719
720static inline u64 rb_time_stamp(struct ring_buffer *buffer)
721{
722 /* shift to debug/test normalization and TIME_EXTENTS */
723 return buffer->clock() << DEBUG_SHIFT;
724}
725
726u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
727{
728 u64 time;
729
730 preempt_disable_notrace();
731 time = rb_time_stamp(buffer);
732 preempt_enable_no_resched_notrace();
733
734 return time;
735}
736EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
737
738void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
739 int cpu, u64 *ts)
740{
741 /* Just stupid testing the normalize function and deltas */
742 *ts >>= DEBUG_SHIFT;
743}
744EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
745
746/*
747 * Making the ring buffer lockless makes things tricky.
748 * Although writes only happen on the CPU that they are on,
749 * and they only need to worry about interrupts. Reads can
750 * happen on any CPU.
751 *
752 * The reader page is always off the ring buffer, but when the
753 * reader finishes with a page, it needs to swap its page with
754 * a new one from the buffer. The reader needs to take from
755 * the head (writes go to the tail). But if a writer is in overwrite
756 * mode and wraps, it must push the head page forward.
757 *
758 * Here lies the problem.
759 *
760 * The reader must be careful to replace only the head page, and
761 * not another one. As described at the top of the file in the
762 * ASCII art, the reader sets its old page to point to the next
763 * page after head. It then sets the page after head to point to
764 * the old reader page. But if the writer moves the head page
765 * during this operation, the reader could end up with the tail.
766 *
767 * We use cmpxchg to help prevent this race. We also do something
768 * special with the page before head. We set the LSB to 1.
769 *
770 * When the writer must push the page forward, it will clear the
771 * bit that points to the head page, move the head, and then set
772 * the bit that points to the new head page.
773 *
774 * We also don't want an interrupt coming in and moving the head
775 * page on another writer. Thus we use the second LSB to catch
776 * that too. Thus:
777 *
778 * head->list->prev->next bit 1 bit 0
779 * ------- -------
780 * Normal page 0 0
781 * Points to head page 0 1
782 * New head page 1 0
783 *
784 * Note we can not trust the prev pointer of the head page, because:
785 *
786 * +----+ +-----+ +-----+
787 * | |------>| T |---X--->| N |
788 * | |<------| | | |
789 * +----+ +-----+ +-----+
790 * ^ ^ |
791 * | +-----+ | |
792 * +----------| R |----------+ |
793 * | |<-----------+
794 * +-----+
795 *
796 * Key: ---X--> HEAD flag set in pointer
797 * T Tail page
798 * R Reader page
799 * N Next page
800 *
801 * (see __rb_reserve_next() to see where this happens)
802 *
803 * What the above shows is that the reader just swapped out
804 * the reader page with a page in the buffer, but before it
805 * could make the new header point back to the new page added
806 * it was preempted by a writer. The writer moved forward onto
807 * the new page added by the reader and is about to move forward
808 * again.
809 *
810 * You can see, it is legitimate for the previous pointer of
811 * the head (or any page) not to point back to itself. But only
812 * temporarially.
813 */
814
815#define RB_PAGE_NORMAL 0UL
816#define RB_PAGE_HEAD 1UL
817#define RB_PAGE_UPDATE 2UL
818
819
820#define RB_FLAG_MASK 3UL
821
822/* PAGE_MOVED is not part of the mask */
823#define RB_PAGE_MOVED 4UL
824
825/*
826 * rb_list_head - remove any bit
827 */
828static struct list_head *rb_list_head(struct list_head *list)
829{
830 unsigned long val = (unsigned long)list;
831
832 return (struct list_head *)(val & ~RB_FLAG_MASK);
833}
834
835/*
836 * rb_is_head_page - test if the given page is the head page
837 *
838 * Because the reader may move the head_page pointer, we can
839 * not trust what the head page is (it may be pointing to
840 * the reader page). But if the next page is a header page,
841 * its flags will be non zero.
842 */
843static inline int
844rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
845 struct buffer_page *page, struct list_head *list)
846{
847 unsigned long val;
848
849 val = (unsigned long)list->next;
850
851 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
852 return RB_PAGE_MOVED;
853
854 return val & RB_FLAG_MASK;
855}
856
857/*
858 * rb_is_reader_page
859 *
860 * The unique thing about the reader page, is that, if the
861 * writer is ever on it, the previous pointer never points
862 * back to the reader page.
863 */
864static bool rb_is_reader_page(struct buffer_page *page)
865{
866 struct list_head *list = page->list.prev;
867
868 return rb_list_head(list->next) != &page->list;
869}
870
871/*
872 * rb_set_list_to_head - set a list_head to be pointing to head.
873 */
874static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
875 struct list_head *list)
876{
877 unsigned long *ptr;
878
879 ptr = (unsigned long *)&list->next;
880 *ptr |= RB_PAGE_HEAD;
881 *ptr &= ~RB_PAGE_UPDATE;
882}
883
884/*
885 * rb_head_page_activate - sets up head page
886 */
887static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
888{
889 struct buffer_page *head;
890
891 head = cpu_buffer->head_page;
892 if (!head)
893 return;
894
895 /*
896 * Set the previous list pointer to have the HEAD flag.
897 */
898 rb_set_list_to_head(cpu_buffer, head->list.prev);
899}
900
901static void rb_list_head_clear(struct list_head *list)
902{
903 unsigned long *ptr = (unsigned long *)&list->next;
904
905 *ptr &= ~RB_FLAG_MASK;
906}
907
908/*
909 * rb_head_page_dactivate - clears head page ptr (for free list)
910 */
911static void
912rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
913{
914 struct list_head *hd;
915
916 /* Go through the whole list and clear any pointers found. */
917 rb_list_head_clear(cpu_buffer->pages);
918
919 list_for_each(hd, cpu_buffer->pages)
920 rb_list_head_clear(hd);
921}
922
923static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
924 struct buffer_page *head,
925 struct buffer_page *prev,
926 int old_flag, int new_flag)
927{
928 struct list_head *list;
929 unsigned long val = (unsigned long)&head->list;
930 unsigned long ret;
931
932 list = &prev->list;
933
934 val &= ~RB_FLAG_MASK;
935
936 ret = cmpxchg((unsigned long *)&list->next,
937 val | old_flag, val | new_flag);
938
939 /* check if the reader took the page */
940 if ((ret & ~RB_FLAG_MASK) != val)
941 return RB_PAGE_MOVED;
942
943 return ret & RB_FLAG_MASK;
944}
945
946static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
947 struct buffer_page *head,
948 struct buffer_page *prev,
949 int old_flag)
950{
951 return rb_head_page_set(cpu_buffer, head, prev,
952 old_flag, RB_PAGE_UPDATE);
953}
954
955static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
956 struct buffer_page *head,
957 struct buffer_page *prev,
958 int old_flag)
959{
960 return rb_head_page_set(cpu_buffer, head, prev,
961 old_flag, RB_PAGE_HEAD);
962}
963
964static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
965 struct buffer_page *head,
966 struct buffer_page *prev,
967 int old_flag)
968{
969 return rb_head_page_set(cpu_buffer, head, prev,
970 old_flag, RB_PAGE_NORMAL);
971}
972
973static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
974 struct buffer_page **bpage)
975{
976 struct list_head *p = rb_list_head((*bpage)->list.next);
977
978 *bpage = list_entry(p, struct buffer_page, list);
979}
980
981static struct buffer_page *
982rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
983{
984 struct buffer_page *head;
985 struct buffer_page *page;
986 struct list_head *list;
987 int i;
988
989 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
990 return NULL;
991
992 /* sanity check */
993 list = cpu_buffer->pages;
994 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
995 return NULL;
996
997 page = head = cpu_buffer->head_page;
998 /*
999 * It is possible that the writer moves the header behind
1000 * where we started, and we miss in one loop.
1001 * A second loop should grab the header, but we'll do
1002 * three loops just because I'm paranoid.
1003 */
1004 for (i = 0; i < 3; i++) {
1005 do {
1006 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
1007 cpu_buffer->head_page = page;
1008 return page;
1009 }
1010 rb_inc_page(cpu_buffer, &page);
1011 } while (page != head);
1012 }
1013
1014 RB_WARN_ON(cpu_buffer, 1);
1015
1016 return NULL;
1017}
1018
1019static int rb_head_page_replace(struct buffer_page *old,
1020 struct buffer_page *new)
1021{
1022 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1023 unsigned long val;
1024 unsigned long ret;
1025
1026 val = *ptr & ~RB_FLAG_MASK;
1027 val |= RB_PAGE_HEAD;
1028
1029 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1030
1031 return ret == val;
1032}
1033
1034/*
1035 * rb_tail_page_update - move the tail page forward
1036 */
1037static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1038 struct buffer_page *tail_page,
1039 struct buffer_page *next_page)
1040{
1041 unsigned long old_entries;
1042 unsigned long old_write;
1043
1044 /*
1045 * The tail page now needs to be moved forward.
1046 *
1047 * We need to reset the tail page, but without messing
1048 * with possible erasing of data brought in by interrupts
1049 * that have moved the tail page and are currently on it.
1050 *
1051 * We add a counter to the write field to denote this.
1052 */
1053 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1054 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1055
1056 /*
1057 * Just make sure we have seen our old_write and synchronize
1058 * with any interrupts that come in.
1059 */
1060 barrier();
1061
1062 /*
1063 * If the tail page is still the same as what we think
1064 * it is, then it is up to us to update the tail
1065 * pointer.
1066 */
1067 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1068 /* Zero the write counter */
1069 unsigned long val = old_write & ~RB_WRITE_MASK;
1070 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1071
1072 /*
1073 * This will only succeed if an interrupt did
1074 * not come in and change it. In which case, we
1075 * do not want to modify it.
1076 *
1077 * We add (void) to let the compiler know that we do not care
1078 * about the return value of these functions. We use the
1079 * cmpxchg to only update if an interrupt did not already
1080 * do it for us. If the cmpxchg fails, we don't care.
1081 */
1082 (void)local_cmpxchg(&next_page->write, old_write, val);
1083 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1084
1085 /*
1086 * No need to worry about races with clearing out the commit.
1087 * it only can increment when a commit takes place. But that
1088 * only happens in the outer most nested commit.
1089 */
1090 local_set(&next_page->page->commit, 0);
1091
1092 /* Again, either we update tail_page or an interrupt does */
1093 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1094 }
1095}
1096
1097static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1098 struct buffer_page *bpage)
1099{
1100 unsigned long val = (unsigned long)bpage;
1101
1102 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1103 return 1;
1104
1105 return 0;
1106}
1107
1108/**
1109 * rb_check_list - make sure a pointer to a list has the last bits zero
1110 */
1111static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1112 struct list_head *list)
1113{
1114 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1115 return 1;
1116 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1117 return 1;
1118 return 0;
1119}
1120
1121/**
1122 * rb_check_pages - integrity check of buffer pages
1123 * @cpu_buffer: CPU buffer with pages to test
1124 *
1125 * As a safety measure we check to make sure the data pages have not
1126 * been corrupted.
1127 */
1128static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1129{
1130 struct list_head *head = cpu_buffer->pages;
1131 struct buffer_page *bpage, *tmp;
1132
1133 /* Reset the head page if it exists */
1134 if (cpu_buffer->head_page)
1135 rb_set_head_page(cpu_buffer);
1136
1137 rb_head_page_deactivate(cpu_buffer);
1138
1139 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1140 return -1;
1141 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1142 return -1;
1143
1144 if (rb_check_list(cpu_buffer, head))
1145 return -1;
1146
1147 list_for_each_entry_safe(bpage, tmp, head, list) {
1148 if (RB_WARN_ON(cpu_buffer,
1149 bpage->list.next->prev != &bpage->list))
1150 return -1;
1151 if (RB_WARN_ON(cpu_buffer,
1152 bpage->list.prev->next != &bpage->list))
1153 return -1;
1154 if (rb_check_list(cpu_buffer, &bpage->list))
1155 return -1;
1156 }
1157
1158 rb_head_page_activate(cpu_buffer);
1159
1160 return 0;
1161}
1162
1163static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1164{
1165 struct buffer_page *bpage, *tmp;
1166 bool user_thread = current->mm != NULL;
1167 gfp_t mflags;
1168 long i;
1169
1170 /*
1171 * Check if the available memory is there first.
1172 * Note, si_mem_available() only gives us a rough estimate of available
1173 * memory. It may not be accurate. But we don't care, we just want
1174 * to prevent doing any allocation when it is obvious that it is
1175 * not going to succeed.
1176 */
1177 i = si_mem_available();
1178 if (i < nr_pages)
1179 return -ENOMEM;
1180
1181 /*
1182 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1183 * gracefully without invoking oom-killer and the system is not
1184 * destabilized.
1185 */
1186 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1187
1188 /*
1189 * If a user thread allocates too much, and si_mem_available()
1190 * reports there's enough memory, even though there is not.
1191 * Make sure the OOM killer kills this thread. This can happen
1192 * even with RETRY_MAYFAIL because another task may be doing
1193 * an allocation after this task has taken all memory.
1194 * This is the task the OOM killer needs to take out during this
1195 * loop, even if it was triggered by an allocation somewhere else.
1196 */
1197 if (user_thread)
1198 set_current_oom_origin();
1199 for (i = 0; i < nr_pages; i++) {
1200 struct page *page;
1201
1202 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1203 mflags, cpu_to_node(cpu));
1204 if (!bpage)
1205 goto free_pages;
1206
1207 list_add(&bpage->list, pages);
1208
1209 page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
1210 if (!page)
1211 goto free_pages;
1212 bpage->page = page_address(page);
1213 rb_init_page(bpage->page);
1214
1215 if (user_thread && fatal_signal_pending(current))
1216 goto free_pages;
1217 }
1218 if (user_thread)
1219 clear_current_oom_origin();
1220
1221 return 0;
1222
1223free_pages:
1224 list_for_each_entry_safe(bpage, tmp, pages, list) {
1225 list_del_init(&bpage->list);
1226 free_buffer_page(bpage);
1227 }
1228 if (user_thread)
1229 clear_current_oom_origin();
1230
1231 return -ENOMEM;
1232}
1233
1234static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1235 unsigned long nr_pages)
1236{
1237 LIST_HEAD(pages);
1238
1239 WARN_ON(!nr_pages);
1240
1241 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1242 return -ENOMEM;
1243
1244 /*
1245 * The ring buffer page list is a circular list that does not
1246 * start and end with a list head. All page list items point to
1247 * other pages.
1248 */
1249 cpu_buffer->pages = pages.next;
1250 list_del(&pages);
1251
1252 cpu_buffer->nr_pages = nr_pages;
1253
1254 rb_check_pages(cpu_buffer);
1255
1256 return 0;
1257}
1258
1259static struct ring_buffer_per_cpu *
1260rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
1261{
1262 struct ring_buffer_per_cpu *cpu_buffer;
1263 struct buffer_page *bpage;
1264 struct page *page;
1265 int ret;
1266
1267 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1268 GFP_KERNEL, cpu_to_node(cpu));
1269 if (!cpu_buffer)
1270 return NULL;
1271
1272 cpu_buffer->cpu = cpu;
1273 cpu_buffer->buffer = buffer;
1274 raw_spin_lock_init(&cpu_buffer->reader_lock);
1275 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1276 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1277 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1278 init_completion(&cpu_buffer->update_done);
1279 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1280 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1281 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1282
1283 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1284 GFP_KERNEL, cpu_to_node(cpu));
1285 if (!bpage)
1286 goto fail_free_buffer;
1287
1288 rb_check_bpage(cpu_buffer, bpage);
1289
1290 cpu_buffer->reader_page = bpage;
1291 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1292 if (!page)
1293 goto fail_free_reader;
1294 bpage->page = page_address(page);
1295 rb_init_page(bpage->page);
1296
1297 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1298 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1299
1300 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1301 if (ret < 0)
1302 goto fail_free_reader;
1303
1304 cpu_buffer->head_page
1305 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1306 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1307
1308 rb_head_page_activate(cpu_buffer);
1309
1310 return cpu_buffer;
1311
1312 fail_free_reader:
1313 free_buffer_page(cpu_buffer->reader_page);
1314
1315 fail_free_buffer:
1316 kfree(cpu_buffer);
1317 return NULL;
1318}
1319
1320static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1321{
1322 struct list_head *head = cpu_buffer->pages;
1323 struct buffer_page *bpage, *tmp;
1324
1325 free_buffer_page(cpu_buffer->reader_page);
1326
1327 rb_head_page_deactivate(cpu_buffer);
1328
1329 if (head) {
1330 list_for_each_entry_safe(bpage, tmp, head, list) {
1331 list_del_init(&bpage->list);
1332 free_buffer_page(bpage);
1333 }
1334 bpage = list_entry(head, struct buffer_page, list);
1335 free_buffer_page(bpage);
1336 }
1337
1338 kfree(cpu_buffer);
1339}
1340
1341/**
1342 * __ring_buffer_alloc - allocate a new ring_buffer
1343 * @size: the size in bytes per cpu that is needed.
1344 * @flags: attributes to set for the ring buffer.
1345 *
1346 * Currently the only flag that is available is the RB_FL_OVERWRITE
1347 * flag. This flag means that the buffer will overwrite old data
1348 * when the buffer wraps. If this flag is not set, the buffer will
1349 * drop data when the tail hits the head.
1350 */
1351struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1352 struct lock_class_key *key)
1353{
1354 struct ring_buffer *buffer;
1355 long nr_pages;
1356 int bsize;
1357 int cpu;
1358 int ret;
1359
1360 /* keep it in its own cache line */
1361 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1362 GFP_KERNEL);
1363 if (!buffer)
1364 return NULL;
1365
1366 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1367 goto fail_free_buffer;
1368
1369 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1370 buffer->flags = flags;
1371 buffer->clock = trace_clock_local;
1372 buffer->reader_lock_key = key;
1373
1374 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1375 init_waitqueue_head(&buffer->irq_work.waiters);
1376
1377 /* need at least two pages */
1378 if (nr_pages < 2)
1379 nr_pages = 2;
1380
1381 buffer->cpus = nr_cpu_ids;
1382
1383 bsize = sizeof(void *) * nr_cpu_ids;
1384 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1385 GFP_KERNEL);
1386 if (!buffer->buffers)
1387 goto fail_free_cpumask;
1388
1389 cpu = raw_smp_processor_id();
1390 cpumask_set_cpu(cpu, buffer->cpumask);
1391 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1392 if (!buffer->buffers[cpu])
1393 goto fail_free_buffers;
1394
1395 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1396 if (ret < 0)
1397 goto fail_free_buffers;
1398
1399 mutex_init(&buffer->mutex);
1400
1401 return buffer;
1402
1403 fail_free_buffers:
1404 for_each_buffer_cpu(buffer, cpu) {
1405 if (buffer->buffers[cpu])
1406 rb_free_cpu_buffer(buffer->buffers[cpu]);
1407 }
1408 kfree(buffer->buffers);
1409
1410 fail_free_cpumask:
1411 free_cpumask_var(buffer->cpumask);
1412
1413 fail_free_buffer:
1414 kfree(buffer);
1415 return NULL;
1416}
1417EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1418
1419/**
1420 * ring_buffer_free - free a ring buffer.
1421 * @buffer: the buffer to free.
1422 */
1423void
1424ring_buffer_free(struct ring_buffer *buffer)
1425{
1426 int cpu;
1427
1428 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1429
1430 for_each_buffer_cpu(buffer, cpu)
1431 rb_free_cpu_buffer(buffer->buffers[cpu]);
1432
1433 kfree(buffer->buffers);
1434 free_cpumask_var(buffer->cpumask);
1435
1436 kfree(buffer);
1437}
1438EXPORT_SYMBOL_GPL(ring_buffer_free);
1439
1440void ring_buffer_set_clock(struct ring_buffer *buffer,
1441 u64 (*clock)(void))
1442{
1443 buffer->clock = clock;
1444}
1445
1446void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
1447{
1448 buffer->time_stamp_abs = abs;
1449}
1450
1451bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
1452{
1453 return buffer->time_stamp_abs;
1454}
1455
1456static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1457
1458static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1459{
1460 return local_read(&bpage->entries) & RB_WRITE_MASK;
1461}
1462
1463static inline unsigned long rb_page_write(struct buffer_page *bpage)
1464{
1465 return local_read(&bpage->write) & RB_WRITE_MASK;
1466}
1467
1468static int
1469rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1470{
1471 struct list_head *tail_page, *to_remove, *next_page;
1472 struct buffer_page *to_remove_page, *tmp_iter_page;
1473 struct buffer_page *last_page, *first_page;
1474 unsigned long nr_removed;
1475 unsigned long head_bit;
1476 int page_entries;
1477
1478 head_bit = 0;
1479
1480 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1481 atomic_inc(&cpu_buffer->record_disabled);
1482 /*
1483 * We don't race with the readers since we have acquired the reader
1484 * lock. We also don't race with writers after disabling recording.
1485 * This makes it easy to figure out the first and the last page to be
1486 * removed from the list. We unlink all the pages in between including
1487 * the first and last pages. This is done in a busy loop so that we
1488 * lose the least number of traces.
1489 * The pages are freed after we restart recording and unlock readers.
1490 */
1491 tail_page = &cpu_buffer->tail_page->list;
1492
1493 /*
1494 * tail page might be on reader page, we remove the next page
1495 * from the ring buffer
1496 */
1497 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1498 tail_page = rb_list_head(tail_page->next);
1499 to_remove = tail_page;
1500
1501 /* start of pages to remove */
1502 first_page = list_entry(rb_list_head(to_remove->next),
1503 struct buffer_page, list);
1504
1505 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1506 to_remove = rb_list_head(to_remove)->next;
1507 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1508 }
1509
1510 next_page = rb_list_head(to_remove)->next;
1511
1512 /*
1513 * Now we remove all pages between tail_page and next_page.
1514 * Make sure that we have head_bit value preserved for the
1515 * next page
1516 */
1517 tail_page->next = (struct list_head *)((unsigned long)next_page |
1518 head_bit);
1519 next_page = rb_list_head(next_page);
1520 next_page->prev = tail_page;
1521
1522 /* make sure pages points to a valid page in the ring buffer */
1523 cpu_buffer->pages = next_page;
1524
1525 /* update head page */
1526 if (head_bit)
1527 cpu_buffer->head_page = list_entry(next_page,
1528 struct buffer_page, list);
1529
1530 /*
1531 * change read pointer to make sure any read iterators reset
1532 * themselves
1533 */
1534 cpu_buffer->read = 0;
1535
1536 /* pages are removed, resume tracing and then free the pages */
1537 atomic_dec(&cpu_buffer->record_disabled);
1538 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1539
1540 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1541
1542 /* last buffer page to remove */
1543 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1544 list);
1545 tmp_iter_page = first_page;
1546
1547 do {
1548 to_remove_page = tmp_iter_page;
1549 rb_inc_page(cpu_buffer, &tmp_iter_page);
1550
1551 /* update the counters */
1552 page_entries = rb_page_entries(to_remove_page);
1553 if (page_entries) {
1554 /*
1555 * If something was added to this page, it was full
1556 * since it is not the tail page. So we deduct the
1557 * bytes consumed in ring buffer from here.
1558 * Increment overrun to account for the lost events.
1559 */
1560 local_add(page_entries, &cpu_buffer->overrun);
1561 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1562 }
1563
1564 /*
1565 * We have already removed references to this list item, just
1566 * free up the buffer_page and its page
1567 */
1568 free_buffer_page(to_remove_page);
1569 nr_removed--;
1570
1571 } while (to_remove_page != last_page);
1572
1573 RB_WARN_ON(cpu_buffer, nr_removed);
1574
1575 return nr_removed == 0;
1576}
1577
1578static int
1579rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1580{
1581 struct list_head *pages = &cpu_buffer->new_pages;
1582 int retries, success;
1583
1584 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1585 /*
1586 * We are holding the reader lock, so the reader page won't be swapped
1587 * in the ring buffer. Now we are racing with the writer trying to
1588 * move head page and the tail page.
1589 * We are going to adapt the reader page update process where:
1590 * 1. We first splice the start and end of list of new pages between
1591 * the head page and its previous page.
1592 * 2. We cmpxchg the prev_page->next to point from head page to the
1593 * start of new pages list.
1594 * 3. Finally, we update the head->prev to the end of new list.
1595 *
1596 * We will try this process 10 times, to make sure that we don't keep
1597 * spinning.
1598 */
1599 retries = 10;
1600 success = 0;
1601 while (retries--) {
1602 struct list_head *head_page, *prev_page, *r;
1603 struct list_head *last_page, *first_page;
1604 struct list_head *head_page_with_bit;
1605
1606 head_page = &rb_set_head_page(cpu_buffer)->list;
1607 if (!head_page)
1608 break;
1609 prev_page = head_page->prev;
1610
1611 first_page = pages->next;
1612 last_page = pages->prev;
1613
1614 head_page_with_bit = (struct list_head *)
1615 ((unsigned long)head_page | RB_PAGE_HEAD);
1616
1617 last_page->next = head_page_with_bit;
1618 first_page->prev = prev_page;
1619
1620 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1621
1622 if (r == head_page_with_bit) {
1623 /*
1624 * yay, we replaced the page pointer to our new list,
1625 * now, we just have to update to head page's prev
1626 * pointer to point to end of list
1627 */
1628 head_page->prev = last_page;
1629 success = 1;
1630 break;
1631 }
1632 }
1633
1634 if (success)
1635 INIT_LIST_HEAD(pages);
1636 /*
1637 * If we weren't successful in adding in new pages, warn and stop
1638 * tracing
1639 */
1640 RB_WARN_ON(cpu_buffer, !success);
1641 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1642
1643 /* free pages if they weren't inserted */
1644 if (!success) {
1645 struct buffer_page *bpage, *tmp;
1646 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1647 list) {
1648 list_del_init(&bpage->list);
1649 free_buffer_page(bpage);
1650 }
1651 }
1652 return success;
1653}
1654
1655static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1656{
1657 int success;
1658
1659 if (cpu_buffer->nr_pages_to_update > 0)
1660 success = rb_insert_pages(cpu_buffer);
1661 else
1662 success = rb_remove_pages(cpu_buffer,
1663 -cpu_buffer->nr_pages_to_update);
1664
1665 if (success)
1666 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1667}
1668
1669static void update_pages_handler(struct work_struct *work)
1670{
1671 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1672 struct ring_buffer_per_cpu, update_pages_work);
1673 rb_update_pages(cpu_buffer);
1674 complete(&cpu_buffer->update_done);
1675}
1676
1677/**
1678 * ring_buffer_resize - resize the ring buffer
1679 * @buffer: the buffer to resize.
1680 * @size: the new size.
1681 * @cpu_id: the cpu buffer to resize
1682 *
1683 * Minimum size is 2 * BUF_PAGE_SIZE.
1684 *
1685 * Returns 0 on success and < 0 on failure.
1686 */
1687int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1688 int cpu_id)
1689{
1690 struct ring_buffer_per_cpu *cpu_buffer;
1691 unsigned long nr_pages;
1692 int cpu, err = 0;
1693
1694 /*
1695 * Always succeed at resizing a non-existent buffer:
1696 */
1697 if (!buffer)
1698 return size;
1699
1700 /* Make sure the requested buffer exists */
1701 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1702 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1703 return size;
1704
1705 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1706
1707 /* we need a minimum of two pages */
1708 if (nr_pages < 2)
1709 nr_pages = 2;
1710
1711 size = nr_pages * BUF_PAGE_SIZE;
1712
1713 /*
1714 * Don't succeed if resizing is disabled, as a reader might be
1715 * manipulating the ring buffer and is expecting a sane state while
1716 * this is true.
1717 */
1718 if (atomic_read(&buffer->resize_disabled))
1719 return -EBUSY;
1720
1721 /* prevent another thread from changing buffer sizes */
1722 mutex_lock(&buffer->mutex);
1723
1724 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1725 /* calculate the pages to update */
1726 for_each_buffer_cpu(buffer, cpu) {
1727 cpu_buffer = buffer->buffers[cpu];
1728
1729 cpu_buffer->nr_pages_to_update = nr_pages -
1730 cpu_buffer->nr_pages;
1731 /*
1732 * nothing more to do for removing pages or no update
1733 */
1734 if (cpu_buffer->nr_pages_to_update <= 0)
1735 continue;
1736 /*
1737 * to add pages, make sure all new pages can be
1738 * allocated without receiving ENOMEM
1739 */
1740 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1741 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1742 &cpu_buffer->new_pages, cpu)) {
1743 /* not enough memory for new pages */
1744 err = -ENOMEM;
1745 goto out_err;
1746 }
1747 }
1748
1749 get_online_cpus();
1750 /*
1751 * Fire off all the required work handlers
1752 * We can't schedule on offline CPUs, but it's not necessary
1753 * since we can change their buffer sizes without any race.
1754 */
1755 for_each_buffer_cpu(buffer, cpu) {
1756 cpu_buffer = buffer->buffers[cpu];
1757 if (!cpu_buffer->nr_pages_to_update)
1758 continue;
1759
1760 /* Can't run something on an offline CPU. */
1761 if (!cpu_online(cpu)) {
1762 rb_update_pages(cpu_buffer);
1763 cpu_buffer->nr_pages_to_update = 0;
1764 } else {
1765 schedule_work_on(cpu,
1766 &cpu_buffer->update_pages_work);
1767 }
1768 }
1769
1770 /* wait for all the updates to complete */
1771 for_each_buffer_cpu(buffer, cpu) {
1772 cpu_buffer = buffer->buffers[cpu];
1773 if (!cpu_buffer->nr_pages_to_update)
1774 continue;
1775
1776 if (cpu_online(cpu))
1777 wait_for_completion(&cpu_buffer->update_done);
1778 cpu_buffer->nr_pages_to_update = 0;
1779 }
1780
1781 put_online_cpus();
1782 } else {
1783 /* Make sure this CPU has been intitialized */
1784 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1785 goto out;
1786
1787 cpu_buffer = buffer->buffers[cpu_id];
1788
1789 if (nr_pages == cpu_buffer->nr_pages)
1790 goto out;
1791
1792 cpu_buffer->nr_pages_to_update = nr_pages -
1793 cpu_buffer->nr_pages;
1794
1795 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1796 if (cpu_buffer->nr_pages_to_update > 0 &&
1797 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1798 &cpu_buffer->new_pages, cpu_id)) {
1799 err = -ENOMEM;
1800 goto out_err;
1801 }
1802
1803 get_online_cpus();
1804
1805 /* Can't run something on an offline CPU. */
1806 if (!cpu_online(cpu_id))
1807 rb_update_pages(cpu_buffer);
1808 else {
1809 schedule_work_on(cpu_id,
1810 &cpu_buffer->update_pages_work);
1811 wait_for_completion(&cpu_buffer->update_done);
1812 }
1813
1814 cpu_buffer->nr_pages_to_update = 0;
1815 put_online_cpus();
1816 }
1817
1818 out:
1819 /*
1820 * The ring buffer resize can happen with the ring buffer
1821 * enabled, so that the update disturbs the tracing as little
1822 * as possible. But if the buffer is disabled, we do not need
1823 * to worry about that, and we can take the time to verify
1824 * that the buffer is not corrupt.
1825 */
1826 if (atomic_read(&buffer->record_disabled)) {
1827 atomic_inc(&buffer->record_disabled);
1828 /*
1829 * Even though the buffer was disabled, we must make sure
1830 * that it is truly disabled before calling rb_check_pages.
1831 * There could have been a race between checking
1832 * record_disable and incrementing it.
1833 */
1834 synchronize_sched();
1835 for_each_buffer_cpu(buffer, cpu) {
1836 cpu_buffer = buffer->buffers[cpu];
1837 rb_check_pages(cpu_buffer);
1838 }
1839 atomic_dec(&buffer->record_disabled);
1840 }
1841
1842 mutex_unlock(&buffer->mutex);
1843 return size;
1844
1845 out_err:
1846 for_each_buffer_cpu(buffer, cpu) {
1847 struct buffer_page *bpage, *tmp;
1848
1849 cpu_buffer = buffer->buffers[cpu];
1850 cpu_buffer->nr_pages_to_update = 0;
1851
1852 if (list_empty(&cpu_buffer->new_pages))
1853 continue;
1854
1855 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1856 list) {
1857 list_del_init(&bpage->list);
1858 free_buffer_page(bpage);
1859 }
1860 }
1861 mutex_unlock(&buffer->mutex);
1862 return err;
1863}
1864EXPORT_SYMBOL_GPL(ring_buffer_resize);
1865
1866void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1867{
1868 mutex_lock(&buffer->mutex);
1869 if (val)
1870 buffer->flags |= RB_FL_OVERWRITE;
1871 else
1872 buffer->flags &= ~RB_FL_OVERWRITE;
1873 mutex_unlock(&buffer->mutex);
1874}
1875EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1876
1877static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1878{
1879 return bpage->page->data + index;
1880}
1881
1882static __always_inline struct ring_buffer_event *
1883rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1884{
1885 return __rb_page_index(cpu_buffer->reader_page,
1886 cpu_buffer->reader_page->read);
1887}
1888
1889static __always_inline struct ring_buffer_event *
1890rb_iter_head_event(struct ring_buffer_iter *iter)
1891{
1892 return __rb_page_index(iter->head_page, iter->head);
1893}
1894
1895static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
1896{
1897 return local_read(&bpage->page->commit);
1898}
1899
1900/* Size is determined by what has been committed */
1901static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
1902{
1903 return rb_page_commit(bpage);
1904}
1905
1906static __always_inline unsigned
1907rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1908{
1909 return rb_page_commit(cpu_buffer->commit_page);
1910}
1911
1912static __always_inline unsigned
1913rb_event_index(struct ring_buffer_event *event)
1914{
1915 unsigned long addr = (unsigned long)event;
1916
1917 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1918}
1919
1920static void rb_inc_iter(struct ring_buffer_iter *iter)
1921{
1922 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1923
1924 /*
1925 * The iterator could be on the reader page (it starts there).
1926 * But the head could have moved, since the reader was
1927 * found. Check for this case and assign the iterator
1928 * to the head page instead of next.
1929 */
1930 if (iter->head_page == cpu_buffer->reader_page)
1931 iter->head_page = rb_set_head_page(cpu_buffer);
1932 else
1933 rb_inc_page(cpu_buffer, &iter->head_page);
1934
1935 iter->read_stamp = iter->head_page->page->time_stamp;
1936 iter->head = 0;
1937}
1938
1939/*
1940 * rb_handle_head_page - writer hit the head page
1941 *
1942 * Returns: +1 to retry page
1943 * 0 to continue
1944 * -1 on error
1945 */
1946static int
1947rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1948 struct buffer_page *tail_page,
1949 struct buffer_page *next_page)
1950{
1951 struct buffer_page *new_head;
1952 int entries;
1953 int type;
1954 int ret;
1955
1956 entries = rb_page_entries(next_page);
1957
1958 /*
1959 * The hard part is here. We need to move the head
1960 * forward, and protect against both readers on
1961 * other CPUs and writers coming in via interrupts.
1962 */
1963 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1964 RB_PAGE_HEAD);
1965
1966 /*
1967 * type can be one of four:
1968 * NORMAL - an interrupt already moved it for us
1969 * HEAD - we are the first to get here.
1970 * UPDATE - we are the interrupt interrupting
1971 * a current move.
1972 * MOVED - a reader on another CPU moved the next
1973 * pointer to its reader page. Give up
1974 * and try again.
1975 */
1976
1977 switch (type) {
1978 case RB_PAGE_HEAD:
1979 /*
1980 * We changed the head to UPDATE, thus
1981 * it is our responsibility to update
1982 * the counters.
1983 */
1984 local_add(entries, &cpu_buffer->overrun);
1985 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1986
1987 /*
1988 * The entries will be zeroed out when we move the
1989 * tail page.
1990 */
1991
1992 /* still more to do */
1993 break;
1994
1995 case RB_PAGE_UPDATE:
1996 /*
1997 * This is an interrupt that interrupt the
1998 * previous update. Still more to do.
1999 */
2000 break;
2001 case RB_PAGE_NORMAL:
2002 /*
2003 * An interrupt came in before the update
2004 * and processed this for us.
2005 * Nothing left to do.
2006 */
2007 return 1;
2008 case RB_PAGE_MOVED:
2009 /*
2010 * The reader is on another CPU and just did
2011 * a swap with our next_page.
2012 * Try again.
2013 */
2014 return 1;
2015 default:
2016 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2017 return -1;
2018 }
2019
2020 /*
2021 * Now that we are here, the old head pointer is
2022 * set to UPDATE. This will keep the reader from
2023 * swapping the head page with the reader page.
2024 * The reader (on another CPU) will spin till
2025 * we are finished.
2026 *
2027 * We just need to protect against interrupts
2028 * doing the job. We will set the next pointer
2029 * to HEAD. After that, we set the old pointer
2030 * to NORMAL, but only if it was HEAD before.
2031 * otherwise we are an interrupt, and only
2032 * want the outer most commit to reset it.
2033 */
2034 new_head = next_page;
2035 rb_inc_page(cpu_buffer, &new_head);
2036
2037 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2038 RB_PAGE_NORMAL);
2039
2040 /*
2041 * Valid returns are:
2042 * HEAD - an interrupt came in and already set it.
2043 * NORMAL - One of two things:
2044 * 1) We really set it.
2045 * 2) A bunch of interrupts came in and moved
2046 * the page forward again.
2047 */
2048 switch (ret) {
2049 case RB_PAGE_HEAD:
2050 case RB_PAGE_NORMAL:
2051 /* OK */
2052 break;
2053 default:
2054 RB_WARN_ON(cpu_buffer, 1);
2055 return -1;
2056 }
2057
2058 /*
2059 * It is possible that an interrupt came in,
2060 * set the head up, then more interrupts came in
2061 * and moved it again. When we get back here,
2062 * the page would have been set to NORMAL but we
2063 * just set it back to HEAD.
2064 *
2065 * How do you detect this? Well, if that happened
2066 * the tail page would have moved.
2067 */
2068 if (ret == RB_PAGE_NORMAL) {
2069 struct buffer_page *buffer_tail_page;
2070
2071 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2072 /*
2073 * If the tail had moved passed next, then we need
2074 * to reset the pointer.
2075 */
2076 if (buffer_tail_page != tail_page &&
2077 buffer_tail_page != next_page)
2078 rb_head_page_set_normal(cpu_buffer, new_head,
2079 next_page,
2080 RB_PAGE_HEAD);
2081 }
2082
2083 /*
2084 * If this was the outer most commit (the one that
2085 * changed the original pointer from HEAD to UPDATE),
2086 * then it is up to us to reset it to NORMAL.
2087 */
2088 if (type == RB_PAGE_HEAD) {
2089 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2090 tail_page,
2091 RB_PAGE_UPDATE);
2092 if (RB_WARN_ON(cpu_buffer,
2093 ret != RB_PAGE_UPDATE))
2094 return -1;
2095 }
2096
2097 return 0;
2098}
2099
2100static inline void
2101rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2102 unsigned long tail, struct rb_event_info *info)
2103{
2104 struct buffer_page *tail_page = info->tail_page;
2105 struct ring_buffer_event *event;
2106 unsigned long length = info->length;
2107
2108 /*
2109 * Only the event that crossed the page boundary
2110 * must fill the old tail_page with padding.
2111 */
2112 if (tail >= BUF_PAGE_SIZE) {
2113 /*
2114 * If the page was filled, then we still need
2115 * to update the real_end. Reset it to zero
2116 * and the reader will ignore it.
2117 */
2118 if (tail == BUF_PAGE_SIZE)
2119 tail_page->real_end = 0;
2120
2121 local_sub(length, &tail_page->write);
2122 return;
2123 }
2124
2125 event = __rb_page_index(tail_page, tail);
2126
2127 /* account for padding bytes */
2128 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2129
2130 /*
2131 * Save the original length to the meta data.
2132 * This will be used by the reader to add lost event
2133 * counter.
2134 */
2135 tail_page->real_end = tail;
2136
2137 /*
2138 * If this event is bigger than the minimum size, then
2139 * we need to be careful that we don't subtract the
2140 * write counter enough to allow another writer to slip
2141 * in on this page.
2142 * We put in a discarded commit instead, to make sure
2143 * that this space is not used again.
2144 *
2145 * If we are less than the minimum size, we don't need to
2146 * worry about it.
2147 */
2148 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2149 /* No room for any events */
2150
2151 /* Mark the rest of the page with padding */
2152 rb_event_set_padding(event);
2153
2154 /* Set the write back to the previous setting */
2155 local_sub(length, &tail_page->write);
2156 return;
2157 }
2158
2159 /* Put in a discarded event */
2160 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2161 event->type_len = RINGBUF_TYPE_PADDING;
2162 /* time delta must be non zero */
2163 event->time_delta = 1;
2164
2165 /* Set write to end of buffer */
2166 length = (tail + length) - BUF_PAGE_SIZE;
2167 local_sub(length, &tail_page->write);
2168}
2169
2170static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2171
2172/*
2173 * This is the slow path, force gcc not to inline it.
2174 */
2175static noinline struct ring_buffer_event *
2176rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2177 unsigned long tail, struct rb_event_info *info)
2178{
2179 struct buffer_page *tail_page = info->tail_page;
2180 struct buffer_page *commit_page = cpu_buffer->commit_page;
2181 struct ring_buffer *buffer = cpu_buffer->buffer;
2182 struct buffer_page *next_page;
2183 int ret;
2184
2185 next_page = tail_page;
2186
2187 rb_inc_page(cpu_buffer, &next_page);
2188
2189 /*
2190 * If for some reason, we had an interrupt storm that made
2191 * it all the way around the buffer, bail, and warn
2192 * about it.
2193 */
2194 if (unlikely(next_page == commit_page)) {
2195 local_inc(&cpu_buffer->commit_overrun);
2196 goto out_reset;
2197 }
2198
2199 /*
2200 * This is where the fun begins!
2201 *
2202 * We are fighting against races between a reader that
2203 * could be on another CPU trying to swap its reader
2204 * page with the buffer head.
2205 *
2206 * We are also fighting against interrupts coming in and
2207 * moving the head or tail on us as well.
2208 *
2209 * If the next page is the head page then we have filled
2210 * the buffer, unless the commit page is still on the
2211 * reader page.
2212 */
2213 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2214
2215 /*
2216 * If the commit is not on the reader page, then
2217 * move the header page.
2218 */
2219 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2220 /*
2221 * If we are not in overwrite mode,
2222 * this is easy, just stop here.
2223 */
2224 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2225 local_inc(&cpu_buffer->dropped_events);
2226 goto out_reset;
2227 }
2228
2229 ret = rb_handle_head_page(cpu_buffer,
2230 tail_page,
2231 next_page);
2232 if (ret < 0)
2233 goto out_reset;
2234 if (ret)
2235 goto out_again;
2236 } else {
2237 /*
2238 * We need to be careful here too. The
2239 * commit page could still be on the reader
2240 * page. We could have a small buffer, and
2241 * have filled up the buffer with events
2242 * from interrupts and such, and wrapped.
2243 *
2244 * Note, if the tail page is also the on the
2245 * reader_page, we let it move out.
2246 */
2247 if (unlikely((cpu_buffer->commit_page !=
2248 cpu_buffer->tail_page) &&
2249 (cpu_buffer->commit_page ==
2250 cpu_buffer->reader_page))) {
2251 local_inc(&cpu_buffer->commit_overrun);
2252 goto out_reset;
2253 }
2254 }
2255 }
2256
2257 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2258
2259 out_again:
2260
2261 rb_reset_tail(cpu_buffer, tail, info);
2262
2263 /* Commit what we have for now. */
2264 rb_end_commit(cpu_buffer);
2265 /* rb_end_commit() decs committing */
2266 local_inc(&cpu_buffer->committing);
2267
2268 /* fail and let the caller try again */
2269 return ERR_PTR(-EAGAIN);
2270
2271 out_reset:
2272 /* reset write */
2273 rb_reset_tail(cpu_buffer, tail, info);
2274
2275 return NULL;
2276}
2277
2278/* Slow path, do not inline */
2279static noinline struct ring_buffer_event *
2280rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2281{
2282 if (abs)
2283 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2284 else
2285 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2286
2287 /* Not the first event on the page, or not delta? */
2288 if (abs || rb_event_index(event)) {
2289 event->time_delta = delta & TS_MASK;
2290 event->array[0] = delta >> TS_SHIFT;
2291 } else {
2292 /* nope, just zero it */
2293 event->time_delta = 0;
2294 event->array[0] = 0;
2295 }
2296
2297 return skip_time_extend(event);
2298}
2299
2300static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2301 struct ring_buffer_event *event);
2302
2303/**
2304 * rb_update_event - update event type and data
2305 * @event: the event to update
2306 * @type: the type of event
2307 * @length: the size of the event field in the ring buffer
2308 *
2309 * Update the type and data fields of the event. The length
2310 * is the actual size that is written to the ring buffer,
2311 * and with this, we can determine what to place into the
2312 * data field.
2313 */
2314static void
2315rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2316 struct ring_buffer_event *event,
2317 struct rb_event_info *info)
2318{
2319 unsigned length = info->length;
2320 u64 delta = info->delta;
2321
2322 /* Only a commit updates the timestamp */
2323 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2324 delta = 0;
2325
2326 /*
2327 * If we need to add a timestamp, then we
2328 * add it to the start of the resevered space.
2329 */
2330 if (unlikely(info->add_timestamp)) {
2331 bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer);
2332
2333 event = rb_add_time_stamp(event, info->delta, abs);
2334 length -= RB_LEN_TIME_EXTEND;
2335 delta = 0;
2336 }
2337
2338 event->time_delta = delta;
2339 length -= RB_EVNT_HDR_SIZE;
2340 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2341 event->type_len = 0;
2342 event->array[0] = length;
2343 } else
2344 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2345}
2346
2347static unsigned rb_calculate_event_length(unsigned length)
2348{
2349 struct ring_buffer_event event; /* Used only for sizeof array */
2350
2351 /* zero length can cause confusions */
2352 if (!length)
2353 length++;
2354
2355 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2356 length += sizeof(event.array[0]);
2357
2358 length += RB_EVNT_HDR_SIZE;
2359 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2360
2361 /*
2362 * In case the time delta is larger than the 27 bits for it
2363 * in the header, we need to add a timestamp. If another
2364 * event comes in when trying to discard this one to increase
2365 * the length, then the timestamp will be added in the allocated
2366 * space of this event. If length is bigger than the size needed
2367 * for the TIME_EXTEND, then padding has to be used. The events
2368 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2369 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2370 * As length is a multiple of 4, we only need to worry if it
2371 * is 12 (RB_LEN_TIME_EXTEND + 4).
2372 */
2373 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2374 length += RB_ALIGNMENT;
2375
2376 return length;
2377}
2378
2379#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2380static inline bool sched_clock_stable(void)
2381{
2382 return true;
2383}
2384#endif
2385
2386static inline int
2387rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2388 struct ring_buffer_event *event)
2389{
2390 unsigned long new_index, old_index;
2391 struct buffer_page *bpage;
2392 unsigned long index;
2393 unsigned long addr;
2394
2395 new_index = rb_event_index(event);
2396 old_index = new_index + rb_event_ts_length(event);
2397 addr = (unsigned long)event;
2398 addr &= PAGE_MASK;
2399
2400 bpage = READ_ONCE(cpu_buffer->tail_page);
2401
2402 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2403 unsigned long write_mask =
2404 local_read(&bpage->write) & ~RB_WRITE_MASK;
2405 unsigned long event_length = rb_event_length(event);
2406 /*
2407 * This is on the tail page. It is possible that
2408 * a write could come in and move the tail page
2409 * and write to the next page. That is fine
2410 * because we just shorten what is on this page.
2411 */
2412 old_index += write_mask;
2413 new_index += write_mask;
2414 index = local_cmpxchg(&bpage->write, old_index, new_index);
2415 if (index == old_index) {
2416 /* update counters */
2417 local_sub(event_length, &cpu_buffer->entries_bytes);
2418 return 1;
2419 }
2420 }
2421
2422 /* could not discard */
2423 return 0;
2424}
2425
2426static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2427{
2428 local_inc(&cpu_buffer->committing);
2429 local_inc(&cpu_buffer->commits);
2430}
2431
2432static __always_inline void
2433rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2434{
2435 unsigned long max_count;
2436
2437 /*
2438 * We only race with interrupts and NMIs on this CPU.
2439 * If we own the commit event, then we can commit
2440 * all others that interrupted us, since the interruptions
2441 * are in stack format (they finish before they come
2442 * back to us). This allows us to do a simple loop to
2443 * assign the commit to the tail.
2444 */
2445 again:
2446 max_count = cpu_buffer->nr_pages * 100;
2447
2448 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2449 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2450 return;
2451 if (RB_WARN_ON(cpu_buffer,
2452 rb_is_reader_page(cpu_buffer->tail_page)))
2453 return;
2454 local_set(&cpu_buffer->commit_page->page->commit,
2455 rb_page_write(cpu_buffer->commit_page));
2456 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2457 /* Only update the write stamp if the page has an event */
2458 if (rb_page_write(cpu_buffer->commit_page))
2459 cpu_buffer->write_stamp =
2460 cpu_buffer->commit_page->page->time_stamp;
2461 /* add barrier to keep gcc from optimizing too much */
2462 barrier();
2463 }
2464 while (rb_commit_index(cpu_buffer) !=
2465 rb_page_write(cpu_buffer->commit_page)) {
2466
2467 local_set(&cpu_buffer->commit_page->page->commit,
2468 rb_page_write(cpu_buffer->commit_page));
2469 RB_WARN_ON(cpu_buffer,
2470 local_read(&cpu_buffer->commit_page->page->commit) &
2471 ~RB_WRITE_MASK);
2472 barrier();
2473 }
2474
2475 /* again, keep gcc from optimizing */
2476 barrier();
2477
2478 /*
2479 * If an interrupt came in just after the first while loop
2480 * and pushed the tail page forward, we will be left with
2481 * a dangling commit that will never go forward.
2482 */
2483 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2484 goto again;
2485}
2486
2487static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2488{
2489 unsigned long commits;
2490
2491 if (RB_WARN_ON(cpu_buffer,
2492 !local_read(&cpu_buffer->committing)))
2493 return;
2494
2495 again:
2496 commits = local_read(&cpu_buffer->commits);
2497 /* synchronize with interrupts */
2498 barrier();
2499 if (local_read(&cpu_buffer->committing) == 1)
2500 rb_set_commit_to_write(cpu_buffer);
2501
2502 local_dec(&cpu_buffer->committing);
2503
2504 /* synchronize with interrupts */
2505 barrier();
2506
2507 /*
2508 * Need to account for interrupts coming in between the
2509 * updating of the commit page and the clearing of the
2510 * committing counter.
2511 */
2512 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2513 !local_read(&cpu_buffer->committing)) {
2514 local_inc(&cpu_buffer->committing);
2515 goto again;
2516 }
2517}
2518
2519static inline void rb_event_discard(struct ring_buffer_event *event)
2520{
2521 if (extended_time(event))
2522 event = skip_time_extend(event);
2523
2524 /* array[0] holds the actual length for the discarded event */
2525 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2526 event->type_len = RINGBUF_TYPE_PADDING;
2527 /* time delta must be non zero */
2528 if (!event->time_delta)
2529 event->time_delta = 1;
2530}
2531
2532static __always_inline bool
2533rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2534 struct ring_buffer_event *event)
2535{
2536 unsigned long addr = (unsigned long)event;
2537 unsigned long index;
2538
2539 index = rb_event_index(event);
2540 addr &= PAGE_MASK;
2541
2542 return cpu_buffer->commit_page->page == (void *)addr &&
2543 rb_commit_index(cpu_buffer) == index;
2544}
2545
2546static __always_inline void
2547rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2548 struct ring_buffer_event *event)
2549{
2550 u64 delta;
2551
2552 /*
2553 * The event first in the commit queue updates the
2554 * time stamp.
2555 */
2556 if (rb_event_is_commit(cpu_buffer, event)) {
2557 /*
2558 * A commit event that is first on a page
2559 * updates the write timestamp with the page stamp
2560 */
2561 if (!rb_event_index(event))
2562 cpu_buffer->write_stamp =
2563 cpu_buffer->commit_page->page->time_stamp;
2564 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2565 delta = ring_buffer_event_time_stamp(event);
2566 cpu_buffer->write_stamp += delta;
2567 } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
2568 delta = ring_buffer_event_time_stamp(event);
2569 cpu_buffer->write_stamp = delta;
2570 } else
2571 cpu_buffer->write_stamp += event->time_delta;
2572 }
2573}
2574
2575static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2576 struct ring_buffer_event *event)
2577{
2578 local_inc(&cpu_buffer->entries);
2579 rb_update_write_stamp(cpu_buffer, event);
2580 rb_end_commit(cpu_buffer);
2581}
2582
2583static __always_inline void
2584rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2585{
2586 bool pagebusy;
2587
2588 if (buffer->irq_work.waiters_pending) {
2589 buffer->irq_work.waiters_pending = false;
2590 /* irq_work_queue() supplies it's own memory barriers */
2591 irq_work_queue(&buffer->irq_work.work);
2592 }
2593
2594 if (cpu_buffer->irq_work.waiters_pending) {
2595 cpu_buffer->irq_work.waiters_pending = false;
2596 /* irq_work_queue() supplies it's own memory barriers */
2597 irq_work_queue(&cpu_buffer->irq_work.work);
2598 }
2599
2600 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
2601
2602 if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
2603 cpu_buffer->irq_work.wakeup_full = true;
2604 cpu_buffer->irq_work.full_waiters_pending = false;
2605 /* irq_work_queue() supplies it's own memory barriers */
2606 irq_work_queue(&cpu_buffer->irq_work.work);
2607 }
2608}
2609
2610/*
2611 * The lock and unlock are done within a preempt disable section.
2612 * The current_context per_cpu variable can only be modified
2613 * by the current task between lock and unlock. But it can
2614 * be modified more than once via an interrupt. To pass this
2615 * information from the lock to the unlock without having to
2616 * access the 'in_interrupt()' functions again (which do show
2617 * a bit of overhead in something as critical as function tracing,
2618 * we use a bitmask trick.
2619 *
2620 * bit 0 = NMI context
2621 * bit 1 = IRQ context
2622 * bit 2 = SoftIRQ context
2623 * bit 3 = normal context.
2624 *
2625 * This works because this is the order of contexts that can
2626 * preempt other contexts. A SoftIRQ never preempts an IRQ
2627 * context.
2628 *
2629 * When the context is determined, the corresponding bit is
2630 * checked and set (if it was set, then a recursion of that context
2631 * happened).
2632 *
2633 * On unlock, we need to clear this bit. To do so, just subtract
2634 * 1 from the current_context and AND it to itself.
2635 *
2636 * (binary)
2637 * 101 - 1 = 100
2638 * 101 & 100 = 100 (clearing bit zero)
2639 *
2640 * 1010 - 1 = 1001
2641 * 1010 & 1001 = 1000 (clearing bit 1)
2642 *
2643 * The least significant bit can be cleared this way, and it
2644 * just so happens that it is the same bit corresponding to
2645 * the current context.
2646 */
2647
2648static __always_inline int
2649trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
2650{
2651 unsigned int val = cpu_buffer->current_context;
2652 unsigned long pc = preempt_count();
2653 int bit;
2654
2655 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
2656 bit = RB_CTX_NORMAL;
2657 else
2658 bit = pc & NMI_MASK ? RB_CTX_NMI :
2659 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
2660
2661 if (unlikely(val & (1 << (bit + cpu_buffer->nest))))
2662 return 1;
2663
2664 val |= (1 << (bit + cpu_buffer->nest));
2665 cpu_buffer->current_context = val;
2666
2667 return 0;
2668}
2669
2670static __always_inline void
2671trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
2672{
2673 cpu_buffer->current_context &=
2674 cpu_buffer->current_context - (1 << cpu_buffer->nest);
2675}
2676
2677/* The recursive locking above uses 4 bits */
2678#define NESTED_BITS 4
2679
2680/**
2681 * ring_buffer_nest_start - Allow to trace while nested
2682 * @buffer: The ring buffer to modify
2683 *
2684 * The ring buffer has a safty mechanism to prevent recursion.
2685 * But there may be a case where a trace needs to be done while
2686 * tracing something else. In this case, calling this function
2687 * will allow this function to nest within a currently active
2688 * ring_buffer_lock_reserve().
2689 *
2690 * Call this function before calling another ring_buffer_lock_reserve() and
2691 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
2692 */
2693void ring_buffer_nest_start(struct ring_buffer *buffer)
2694{
2695 struct ring_buffer_per_cpu *cpu_buffer;
2696 int cpu;
2697
2698 /* Enabled by ring_buffer_nest_end() */
2699 preempt_disable_notrace();
2700 cpu = raw_smp_processor_id();
2701 cpu_buffer = buffer->buffers[cpu];
2702 /* This is the shift value for the above recusive locking */
2703 cpu_buffer->nest += NESTED_BITS;
2704}
2705
2706/**
2707 * ring_buffer_nest_end - Allow to trace while nested
2708 * @buffer: The ring buffer to modify
2709 *
2710 * Must be called after ring_buffer_nest_start() and after the
2711 * ring_buffer_unlock_commit().
2712 */
2713void ring_buffer_nest_end(struct ring_buffer *buffer)
2714{
2715 struct ring_buffer_per_cpu *cpu_buffer;
2716 int cpu;
2717
2718 /* disabled by ring_buffer_nest_start() */
2719 cpu = raw_smp_processor_id();
2720 cpu_buffer = buffer->buffers[cpu];
2721 /* This is the shift value for the above recusive locking */
2722 cpu_buffer->nest -= NESTED_BITS;
2723 preempt_enable_notrace();
2724}
2725
2726/**
2727 * ring_buffer_unlock_commit - commit a reserved
2728 * @buffer: The buffer to commit to
2729 * @event: The event pointer to commit.
2730 *
2731 * This commits the data to the ring buffer, and releases any locks held.
2732 *
2733 * Must be paired with ring_buffer_lock_reserve.
2734 */
2735int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2736 struct ring_buffer_event *event)
2737{
2738 struct ring_buffer_per_cpu *cpu_buffer;
2739 int cpu = raw_smp_processor_id();
2740
2741 cpu_buffer = buffer->buffers[cpu];
2742
2743 rb_commit(cpu_buffer, event);
2744
2745 rb_wakeups(buffer, cpu_buffer);
2746
2747 trace_recursive_unlock(cpu_buffer);
2748
2749 preempt_enable_notrace();
2750
2751 return 0;
2752}
2753EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2754
2755static noinline void
2756rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2757 struct rb_event_info *info)
2758{
2759 WARN_ONCE(info->delta > (1ULL << 59),
2760 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2761 (unsigned long long)info->delta,
2762 (unsigned long long)info->ts,
2763 (unsigned long long)cpu_buffer->write_stamp,
2764 sched_clock_stable() ? "" :
2765 "If you just came from a suspend/resume,\n"
2766 "please switch to the trace global clock:\n"
2767 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2768 "or add trace_clock=global to the kernel command line\n");
2769 info->add_timestamp = 1;
2770}
2771
2772static struct ring_buffer_event *
2773__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2774 struct rb_event_info *info)
2775{
2776 struct ring_buffer_event *event;
2777 struct buffer_page *tail_page;
2778 unsigned long tail, write;
2779
2780 /*
2781 * If the time delta since the last event is too big to
2782 * hold in the time field of the event, then we append a
2783 * TIME EXTEND event ahead of the data event.
2784 */
2785 if (unlikely(info->add_timestamp))
2786 info->length += RB_LEN_TIME_EXTEND;
2787
2788 /* Don't let the compiler play games with cpu_buffer->tail_page */
2789 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
2790 write = local_add_return(info->length, &tail_page->write);
2791
2792 /* set write to only the index of the write */
2793 write &= RB_WRITE_MASK;
2794 tail = write - info->length;
2795
2796 /*
2797 * If this is the first commit on the page, then it has the same
2798 * timestamp as the page itself.
2799 */
2800 if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
2801 info->delta = 0;
2802
2803 /* See if we shot pass the end of this buffer page */
2804 if (unlikely(write > BUF_PAGE_SIZE))
2805 return rb_move_tail(cpu_buffer, tail, info);
2806
2807 /* We reserved something on the buffer */
2808
2809 event = __rb_page_index(tail_page, tail);
2810 rb_update_event(cpu_buffer, event, info);
2811
2812 local_inc(&tail_page->entries);
2813
2814 /*
2815 * If this is the first commit on the page, then update
2816 * its timestamp.
2817 */
2818 if (!tail)
2819 tail_page->page->time_stamp = info->ts;
2820
2821 /* account for these added bytes */
2822 local_add(info->length, &cpu_buffer->entries_bytes);
2823
2824 return event;
2825}
2826
2827static __always_inline struct ring_buffer_event *
2828rb_reserve_next_event(struct ring_buffer *buffer,
2829 struct ring_buffer_per_cpu *cpu_buffer,
2830 unsigned long length)
2831{
2832 struct ring_buffer_event *event;
2833 struct rb_event_info info;
2834 int nr_loops = 0;
2835 u64 diff;
2836
2837 rb_start_commit(cpu_buffer);
2838
2839#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2840 /*
2841 * Due to the ability to swap a cpu buffer from a buffer
2842 * it is possible it was swapped before we committed.
2843 * (committing stops a swap). We check for it here and
2844 * if it happened, we have to fail the write.
2845 */
2846 barrier();
2847 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
2848 local_dec(&cpu_buffer->committing);
2849 local_dec(&cpu_buffer->commits);
2850 return NULL;
2851 }
2852#endif
2853
2854 info.length = rb_calculate_event_length(length);
2855 again:
2856 info.add_timestamp = 0;
2857 info.delta = 0;
2858
2859 /*
2860 * We allow for interrupts to reenter here and do a trace.
2861 * If one does, it will cause this original code to loop
2862 * back here. Even with heavy interrupts happening, this
2863 * should only happen a few times in a row. If this happens
2864 * 1000 times in a row, there must be either an interrupt
2865 * storm or we have something buggy.
2866 * Bail!
2867 */
2868 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2869 goto out_fail;
2870
2871 info.ts = rb_time_stamp(cpu_buffer->buffer);
2872 diff = info.ts - cpu_buffer->write_stamp;
2873
2874 /* make sure this diff is calculated here */
2875 barrier();
2876
2877 if (ring_buffer_time_stamp_abs(buffer)) {
2878 info.delta = info.ts;
2879 rb_handle_timestamp(cpu_buffer, &info);
2880 } else /* Did the write stamp get updated already? */
2881 if (likely(info.ts >= cpu_buffer->write_stamp)) {
2882 info.delta = diff;
2883 if (unlikely(test_time_stamp(info.delta)))
2884 rb_handle_timestamp(cpu_buffer, &info);
2885 }
2886
2887 event = __rb_reserve_next(cpu_buffer, &info);
2888
2889 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
2890 if (info.add_timestamp)
2891 info.length -= RB_LEN_TIME_EXTEND;
2892 goto again;
2893 }
2894
2895 if (!event)
2896 goto out_fail;
2897
2898 return event;
2899
2900 out_fail:
2901 rb_end_commit(cpu_buffer);
2902 return NULL;
2903}
2904
2905/**
2906 * ring_buffer_lock_reserve - reserve a part of the buffer
2907 * @buffer: the ring buffer to reserve from
2908 * @length: the length of the data to reserve (excluding event header)
2909 *
2910 * Returns a reseverd event on the ring buffer to copy directly to.
2911 * The user of this interface will need to get the body to write into
2912 * and can use the ring_buffer_event_data() interface.
2913 *
2914 * The length is the length of the data needed, not the event length
2915 * which also includes the event header.
2916 *
2917 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2918 * If NULL is returned, then nothing has been allocated or locked.
2919 */
2920struct ring_buffer_event *
2921ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2922{
2923 struct ring_buffer_per_cpu *cpu_buffer;
2924 struct ring_buffer_event *event;
2925 int cpu;
2926
2927 /* If we are tracing schedule, we don't want to recurse */
2928 preempt_disable_notrace();
2929
2930 if (unlikely(atomic_read(&buffer->record_disabled)))
2931 goto out;
2932
2933 cpu = raw_smp_processor_id();
2934
2935 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
2936 goto out;
2937
2938 cpu_buffer = buffer->buffers[cpu];
2939
2940 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
2941 goto out;
2942
2943 if (unlikely(length > BUF_MAX_DATA_SIZE))
2944 goto out;
2945
2946 if (unlikely(trace_recursive_lock(cpu_buffer)))
2947 goto out;
2948
2949 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2950 if (!event)
2951 goto out_unlock;
2952
2953 return event;
2954
2955 out_unlock:
2956 trace_recursive_unlock(cpu_buffer);
2957 out:
2958 preempt_enable_notrace();
2959 return NULL;
2960}
2961EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2962
2963/*
2964 * Decrement the entries to the page that an event is on.
2965 * The event does not even need to exist, only the pointer
2966 * to the page it is on. This may only be called before the commit
2967 * takes place.
2968 */
2969static inline void
2970rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2971 struct ring_buffer_event *event)
2972{
2973 unsigned long addr = (unsigned long)event;
2974 struct buffer_page *bpage = cpu_buffer->commit_page;
2975 struct buffer_page *start;
2976
2977 addr &= PAGE_MASK;
2978
2979 /* Do the likely case first */
2980 if (likely(bpage->page == (void *)addr)) {
2981 local_dec(&bpage->entries);
2982 return;
2983 }
2984
2985 /*
2986 * Because the commit page may be on the reader page we
2987 * start with the next page and check the end loop there.
2988 */
2989 rb_inc_page(cpu_buffer, &bpage);
2990 start = bpage;
2991 do {
2992 if (bpage->page == (void *)addr) {
2993 local_dec(&bpage->entries);
2994 return;
2995 }
2996 rb_inc_page(cpu_buffer, &bpage);
2997 } while (bpage != start);
2998
2999 /* commit not part of this buffer?? */
3000 RB_WARN_ON(cpu_buffer, 1);
3001}
3002
3003/**
3004 * ring_buffer_commit_discard - discard an event that has not been committed
3005 * @buffer: the ring buffer
3006 * @event: non committed event to discard
3007 *
3008 * Sometimes an event that is in the ring buffer needs to be ignored.
3009 * This function lets the user discard an event in the ring buffer
3010 * and then that event will not be read later.
3011 *
3012 * This function only works if it is called before the the item has been
3013 * committed. It will try to free the event from the ring buffer
3014 * if another event has not been added behind it.
3015 *
3016 * If another event has been added behind it, it will set the event
3017 * up as discarded, and perform the commit.
3018 *
3019 * If this function is called, do not call ring_buffer_unlock_commit on
3020 * the event.
3021 */
3022void ring_buffer_discard_commit(struct ring_buffer *buffer,
3023 struct ring_buffer_event *event)
3024{
3025 struct ring_buffer_per_cpu *cpu_buffer;
3026 int cpu;
3027
3028 /* The event is discarded regardless */
3029 rb_event_discard(event);
3030
3031 cpu = smp_processor_id();
3032 cpu_buffer = buffer->buffers[cpu];
3033
3034 /*
3035 * This must only be called if the event has not been
3036 * committed yet. Thus we can assume that preemption
3037 * is still disabled.
3038 */
3039 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3040
3041 rb_decrement_entry(cpu_buffer, event);
3042 if (rb_try_to_discard(cpu_buffer, event))
3043 goto out;
3044
3045 /*
3046 * The commit is still visible by the reader, so we
3047 * must still update the timestamp.
3048 */
3049 rb_update_write_stamp(cpu_buffer, event);
3050 out:
3051 rb_end_commit(cpu_buffer);
3052
3053 trace_recursive_unlock(cpu_buffer);
3054
3055 preempt_enable_notrace();
3056
3057}
3058EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3059
3060/**
3061 * ring_buffer_write - write data to the buffer without reserving
3062 * @buffer: The ring buffer to write to.
3063 * @length: The length of the data being written (excluding the event header)
3064 * @data: The data to write to the buffer.
3065 *
3066 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3067 * one function. If you already have the data to write to the buffer, it
3068 * may be easier to simply call this function.
3069 *
3070 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3071 * and not the length of the event which would hold the header.
3072 */
3073int ring_buffer_write(struct ring_buffer *buffer,
3074 unsigned long length,
3075 void *data)
3076{
3077 struct ring_buffer_per_cpu *cpu_buffer;
3078 struct ring_buffer_event *event;
3079 void *body;
3080 int ret = -EBUSY;
3081 int cpu;
3082
3083 preempt_disable_notrace();
3084
3085 if (atomic_read(&buffer->record_disabled))
3086 goto out;
3087
3088 cpu = raw_smp_processor_id();
3089
3090 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3091 goto out;
3092
3093 cpu_buffer = buffer->buffers[cpu];
3094
3095 if (atomic_read(&cpu_buffer->record_disabled))
3096 goto out;
3097
3098 if (length > BUF_MAX_DATA_SIZE)
3099 goto out;
3100
3101 if (unlikely(trace_recursive_lock(cpu_buffer)))
3102 goto out;
3103
3104 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3105 if (!event)
3106 goto out_unlock;
3107
3108 body = rb_event_data(event);
3109
3110 memcpy(body, data, length);
3111
3112 rb_commit(cpu_buffer, event);
3113
3114 rb_wakeups(buffer, cpu_buffer);
3115
3116 ret = 0;
3117
3118 out_unlock:
3119 trace_recursive_unlock(cpu_buffer);
3120
3121 out:
3122 preempt_enable_notrace();
3123
3124 return ret;
3125}
3126EXPORT_SYMBOL_GPL(ring_buffer_write);
3127
3128static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3129{
3130 struct buffer_page *reader = cpu_buffer->reader_page;
3131 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3132 struct buffer_page *commit = cpu_buffer->commit_page;
3133
3134 /* In case of error, head will be NULL */
3135 if (unlikely(!head))
3136 return true;
3137
3138 return reader->read == rb_page_commit(reader) &&
3139 (commit == reader ||
3140 (commit == head &&
3141 head->read == rb_page_commit(commit)));
3142}
3143
3144/**
3145 * ring_buffer_record_disable - stop all writes into the buffer
3146 * @buffer: The ring buffer to stop writes to.
3147 *
3148 * This prevents all writes to the buffer. Any attempt to write
3149 * to the buffer after this will fail and return NULL.
3150 *
3151 * The caller should call synchronize_sched() after this.
3152 */
3153void ring_buffer_record_disable(struct ring_buffer *buffer)
3154{
3155 atomic_inc(&buffer->record_disabled);
3156}
3157EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3158
3159/**
3160 * ring_buffer_record_enable - enable writes to the buffer
3161 * @buffer: The ring buffer to enable writes
3162 *
3163 * Note, multiple disables will need the same number of enables
3164 * to truly enable the writing (much like preempt_disable).
3165 */
3166void ring_buffer_record_enable(struct ring_buffer *buffer)
3167{
3168 atomic_dec(&buffer->record_disabled);
3169}
3170EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3171
3172/**
3173 * ring_buffer_record_off - stop all writes into the buffer
3174 * @buffer: The ring buffer to stop writes to.
3175 *
3176 * This prevents all writes to the buffer. Any attempt to write
3177 * to the buffer after this will fail and return NULL.
3178 *
3179 * This is different than ring_buffer_record_disable() as
3180 * it works like an on/off switch, where as the disable() version
3181 * must be paired with a enable().
3182 */
3183void ring_buffer_record_off(struct ring_buffer *buffer)
3184{
3185 unsigned int rd;
3186 unsigned int new_rd;
3187
3188 do {
3189 rd = atomic_read(&buffer->record_disabled);
3190 new_rd = rd | RB_BUFFER_OFF;
3191 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3192}
3193EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3194
3195/**
3196 * ring_buffer_record_on - restart writes into the buffer
3197 * @buffer: The ring buffer to start writes to.
3198 *
3199 * This enables all writes to the buffer that was disabled by
3200 * ring_buffer_record_off().
3201 *
3202 * This is different than ring_buffer_record_enable() as
3203 * it works like an on/off switch, where as the enable() version
3204 * must be paired with a disable().
3205 */
3206void ring_buffer_record_on(struct ring_buffer *buffer)
3207{
3208 unsigned int rd;
3209 unsigned int new_rd;
3210
3211 do {
3212 rd = atomic_read(&buffer->record_disabled);
3213 new_rd = rd & ~RB_BUFFER_OFF;
3214 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3215}
3216EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3217
3218/**
3219 * ring_buffer_record_is_on - return true if the ring buffer can write
3220 * @buffer: The ring buffer to see if write is enabled
3221 *
3222 * Returns true if the ring buffer is in a state that it accepts writes.
3223 */
3224int ring_buffer_record_is_on(struct ring_buffer *buffer)
3225{
3226 return !atomic_read(&buffer->record_disabled);
3227}
3228
3229/**
3230 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3231 * @buffer: The ring buffer to stop writes to.
3232 * @cpu: The CPU buffer to stop
3233 *
3234 * This prevents all writes to the buffer. Any attempt to write
3235 * to the buffer after this will fail and return NULL.
3236 *
3237 * The caller should call synchronize_sched() after this.
3238 */
3239void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3240{
3241 struct ring_buffer_per_cpu *cpu_buffer;
3242
3243 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3244 return;
3245
3246 cpu_buffer = buffer->buffers[cpu];
3247 atomic_inc(&cpu_buffer->record_disabled);
3248}
3249EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3250
3251/**
3252 * ring_buffer_record_enable_cpu - enable writes to the buffer
3253 * @buffer: The ring buffer to enable writes
3254 * @cpu: The CPU to enable.
3255 *
3256 * Note, multiple disables will need the same number of enables
3257 * to truly enable the writing (much like preempt_disable).
3258 */
3259void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3260{
3261 struct ring_buffer_per_cpu *cpu_buffer;
3262
3263 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3264 return;
3265
3266 cpu_buffer = buffer->buffers[cpu];
3267 atomic_dec(&cpu_buffer->record_disabled);
3268}
3269EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3270
3271/*
3272 * The total entries in the ring buffer is the running counter
3273 * of entries entered into the ring buffer, minus the sum of
3274 * the entries read from the ring buffer and the number of
3275 * entries that were overwritten.
3276 */
3277static inline unsigned long
3278rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3279{
3280 return local_read(&cpu_buffer->entries) -
3281 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3282}
3283
3284/**
3285 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3286 * @buffer: The ring buffer
3287 * @cpu: The per CPU buffer to read from.
3288 */
3289u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3290{
3291 unsigned long flags;
3292 struct ring_buffer_per_cpu *cpu_buffer;
3293 struct buffer_page *bpage;
3294 u64 ret = 0;
3295
3296 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3297 return 0;
3298
3299 cpu_buffer = buffer->buffers[cpu];
3300 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3301 /*
3302 * if the tail is on reader_page, oldest time stamp is on the reader
3303 * page
3304 */
3305 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3306 bpage = cpu_buffer->reader_page;
3307 else
3308 bpage = rb_set_head_page(cpu_buffer);
3309 if (bpage)
3310 ret = bpage->page->time_stamp;
3311 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3312
3313 return ret;
3314}
3315EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3316
3317/**
3318 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3319 * @buffer: The ring buffer
3320 * @cpu: The per CPU buffer to read from.
3321 */
3322unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3323{
3324 struct ring_buffer_per_cpu *cpu_buffer;
3325 unsigned long ret;
3326
3327 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3328 return 0;
3329
3330 cpu_buffer = buffer->buffers[cpu];
3331 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3332
3333 return ret;
3334}
3335EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3336
3337/**
3338 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3339 * @buffer: The ring buffer
3340 * @cpu: The per CPU buffer to get the entries from.
3341 */
3342unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3343{
3344 struct ring_buffer_per_cpu *cpu_buffer;
3345
3346 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3347 return 0;
3348
3349 cpu_buffer = buffer->buffers[cpu];
3350
3351 return rb_num_of_entries(cpu_buffer);
3352}
3353EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3354
3355/**
3356 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3357 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3358 * @buffer: The ring buffer
3359 * @cpu: The per CPU buffer to get the number of overruns from
3360 */
3361unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3362{
3363 struct ring_buffer_per_cpu *cpu_buffer;
3364 unsigned long ret;
3365
3366 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3367 return 0;
3368
3369 cpu_buffer = buffer->buffers[cpu];
3370 ret = local_read(&cpu_buffer->overrun);
3371
3372 return ret;
3373}
3374EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3375
3376/**
3377 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3378 * commits failing due to the buffer wrapping around while there are uncommitted
3379 * events, such as during an interrupt storm.
3380 * @buffer: The ring buffer
3381 * @cpu: The per CPU buffer to get the number of overruns from
3382 */
3383unsigned long
3384ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3385{
3386 struct ring_buffer_per_cpu *cpu_buffer;
3387 unsigned long ret;
3388
3389 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3390 return 0;
3391
3392 cpu_buffer = buffer->buffers[cpu];
3393 ret = local_read(&cpu_buffer->commit_overrun);
3394
3395 return ret;
3396}
3397EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3398
3399/**
3400 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3401 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3402 * @buffer: The ring buffer
3403 * @cpu: The per CPU buffer to get the number of overruns from
3404 */
3405unsigned long
3406ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3407{
3408 struct ring_buffer_per_cpu *cpu_buffer;
3409 unsigned long ret;
3410
3411 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3412 return 0;
3413
3414 cpu_buffer = buffer->buffers[cpu];
3415 ret = local_read(&cpu_buffer->dropped_events);
3416
3417 return ret;
3418}
3419EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3420
3421/**
3422 * ring_buffer_read_events_cpu - get the number of events successfully read
3423 * @buffer: The ring buffer
3424 * @cpu: The per CPU buffer to get the number of events read
3425 */
3426unsigned long
3427ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3428{
3429 struct ring_buffer_per_cpu *cpu_buffer;
3430
3431 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3432 return 0;
3433
3434 cpu_buffer = buffer->buffers[cpu];
3435 return cpu_buffer->read;
3436}
3437EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3438
3439/**
3440 * ring_buffer_entries - get the number of entries in a buffer
3441 * @buffer: The ring buffer
3442 *
3443 * Returns the total number of entries in the ring buffer
3444 * (all CPU entries)
3445 */
3446unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3447{
3448 struct ring_buffer_per_cpu *cpu_buffer;
3449 unsigned long entries = 0;
3450 int cpu;
3451
3452 /* if you care about this being correct, lock the buffer */
3453 for_each_buffer_cpu(buffer, cpu) {
3454 cpu_buffer = buffer->buffers[cpu];
3455 entries += rb_num_of_entries(cpu_buffer);
3456 }
3457
3458 return entries;
3459}
3460EXPORT_SYMBOL_GPL(ring_buffer_entries);
3461
3462/**
3463 * ring_buffer_overruns - get the number of overruns in buffer
3464 * @buffer: The ring buffer
3465 *
3466 * Returns the total number of overruns in the ring buffer
3467 * (all CPU entries)
3468 */
3469unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3470{
3471 struct ring_buffer_per_cpu *cpu_buffer;
3472 unsigned long overruns = 0;
3473 int cpu;
3474
3475 /* if you care about this being correct, lock the buffer */
3476 for_each_buffer_cpu(buffer, cpu) {
3477 cpu_buffer = buffer->buffers[cpu];
3478 overruns += local_read(&cpu_buffer->overrun);
3479 }
3480
3481 return overruns;
3482}
3483EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3484
3485static void rb_iter_reset(struct ring_buffer_iter *iter)
3486{
3487 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3488
3489 /* Iterator usage is expected to have record disabled */
3490 iter->head_page = cpu_buffer->reader_page;
3491 iter->head = cpu_buffer->reader_page->read;
3492
3493 iter->cache_reader_page = iter->head_page;
3494 iter->cache_read = cpu_buffer->read;
3495
3496 if (iter->head)
3497 iter->read_stamp = cpu_buffer->read_stamp;
3498 else
3499 iter->read_stamp = iter->head_page->page->time_stamp;
3500}
3501
3502/**
3503 * ring_buffer_iter_reset - reset an iterator
3504 * @iter: The iterator to reset
3505 *
3506 * Resets the iterator, so that it will start from the beginning
3507 * again.
3508 */
3509void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3510{
3511 struct ring_buffer_per_cpu *cpu_buffer;
3512 unsigned long flags;
3513
3514 if (!iter)
3515 return;
3516
3517 cpu_buffer = iter->cpu_buffer;
3518
3519 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3520 rb_iter_reset(iter);
3521 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3522}
3523EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3524
3525/**
3526 * ring_buffer_iter_empty - check if an iterator has no more to read
3527 * @iter: The iterator to check
3528 */
3529int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3530{
3531 struct ring_buffer_per_cpu *cpu_buffer;
3532 struct buffer_page *reader;
3533 struct buffer_page *head_page;
3534 struct buffer_page *commit_page;
3535 unsigned commit;
3536
3537 cpu_buffer = iter->cpu_buffer;
3538
3539 /* Remember, trace recording is off when iterator is in use */
3540 reader = cpu_buffer->reader_page;
3541 head_page = cpu_buffer->head_page;
3542 commit_page = cpu_buffer->commit_page;
3543 commit = rb_page_commit(commit_page);
3544
3545 return ((iter->head_page == commit_page && iter->head == commit) ||
3546 (iter->head_page == reader && commit_page == head_page &&
3547 head_page->read == commit &&
3548 iter->head == rb_page_commit(cpu_buffer->reader_page)));
3549}
3550EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3551
3552static void
3553rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3554 struct ring_buffer_event *event)
3555{
3556 u64 delta;
3557
3558 switch (event->type_len) {
3559 case RINGBUF_TYPE_PADDING:
3560 return;
3561
3562 case RINGBUF_TYPE_TIME_EXTEND:
3563 delta = ring_buffer_event_time_stamp(event);
3564 cpu_buffer->read_stamp += delta;
3565 return;
3566
3567 case RINGBUF_TYPE_TIME_STAMP:
3568 delta = ring_buffer_event_time_stamp(event);
3569 cpu_buffer->read_stamp = delta;
3570 return;
3571
3572 case RINGBUF_TYPE_DATA:
3573 cpu_buffer->read_stamp += event->time_delta;
3574 return;
3575
3576 default:
3577 BUG();
3578 }
3579 return;
3580}
3581
3582static void
3583rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3584 struct ring_buffer_event *event)
3585{
3586 u64 delta;
3587
3588 switch (event->type_len) {
3589 case RINGBUF_TYPE_PADDING:
3590 return;
3591
3592 case RINGBUF_TYPE_TIME_EXTEND:
3593 delta = ring_buffer_event_time_stamp(event);
3594 iter->read_stamp += delta;
3595 return;
3596
3597 case RINGBUF_TYPE_TIME_STAMP:
3598 delta = ring_buffer_event_time_stamp(event);
3599 iter->read_stamp = delta;
3600 return;
3601
3602 case RINGBUF_TYPE_DATA:
3603 iter->read_stamp += event->time_delta;
3604 return;
3605
3606 default:
3607 BUG();
3608 }
3609 return;
3610}
3611
3612static struct buffer_page *
3613rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3614{
3615 struct buffer_page *reader = NULL;
3616 unsigned long overwrite;
3617 unsigned long flags;
3618 int nr_loops = 0;
3619 int ret;
3620
3621 local_irq_save(flags);
3622 arch_spin_lock(&cpu_buffer->lock);
3623
3624 again:
3625 /*
3626 * This should normally only loop twice. But because the
3627 * start of the reader inserts an empty page, it causes
3628 * a case where we will loop three times. There should be no
3629 * reason to loop four times (that I know of).
3630 */
3631 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3632 reader = NULL;
3633 goto out;
3634 }
3635
3636 reader = cpu_buffer->reader_page;
3637
3638 /* If there's more to read, return this page */
3639 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3640 goto out;
3641
3642 /* Never should we have an index greater than the size */
3643 if (RB_WARN_ON(cpu_buffer,
3644 cpu_buffer->reader_page->read > rb_page_size(reader)))
3645 goto out;
3646
3647 /* check if we caught up to the tail */
3648 reader = NULL;
3649 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3650 goto out;
3651
3652 /* Don't bother swapping if the ring buffer is empty */
3653 if (rb_num_of_entries(cpu_buffer) == 0)
3654 goto out;
3655
3656 /*
3657 * Reset the reader page to size zero.
3658 */
3659 local_set(&cpu_buffer->reader_page->write, 0);
3660 local_set(&cpu_buffer->reader_page->entries, 0);
3661 local_set(&cpu_buffer->reader_page->page->commit, 0);
3662 cpu_buffer->reader_page->real_end = 0;
3663
3664 spin:
3665 /*
3666 * Splice the empty reader page into the list around the head.
3667 */
3668 reader = rb_set_head_page(cpu_buffer);
3669 if (!reader)
3670 goto out;
3671 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3672 cpu_buffer->reader_page->list.prev = reader->list.prev;
3673
3674 /*
3675 * cpu_buffer->pages just needs to point to the buffer, it
3676 * has no specific buffer page to point to. Lets move it out
3677 * of our way so we don't accidentally swap it.
3678 */
3679 cpu_buffer->pages = reader->list.prev;
3680
3681 /* The reader page will be pointing to the new head */
3682 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3683
3684 /*
3685 * We want to make sure we read the overruns after we set up our
3686 * pointers to the next object. The writer side does a
3687 * cmpxchg to cross pages which acts as the mb on the writer
3688 * side. Note, the reader will constantly fail the swap
3689 * while the writer is updating the pointers, so this
3690 * guarantees that the overwrite recorded here is the one we
3691 * want to compare with the last_overrun.
3692 */
3693 smp_mb();
3694 overwrite = local_read(&(cpu_buffer->overrun));
3695
3696 /*
3697 * Here's the tricky part.
3698 *
3699 * We need to move the pointer past the header page.
3700 * But we can only do that if a writer is not currently
3701 * moving it. The page before the header page has the
3702 * flag bit '1' set if it is pointing to the page we want.
3703 * but if the writer is in the process of moving it
3704 * than it will be '2' or already moved '0'.
3705 */
3706
3707 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3708
3709 /*
3710 * If we did not convert it, then we must try again.
3711 */
3712 if (!ret)
3713 goto spin;
3714
3715 /*
3716 * Yeah! We succeeded in replacing the page.
3717 *
3718 * Now make the new head point back to the reader page.
3719 */
3720 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3721 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3722
3723 /* Finally update the reader page to the new head */
3724 cpu_buffer->reader_page = reader;
3725 cpu_buffer->reader_page->read = 0;
3726
3727 if (overwrite != cpu_buffer->last_overrun) {
3728 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3729 cpu_buffer->last_overrun = overwrite;
3730 }
3731
3732 goto again;
3733
3734 out:
3735 /* Update the read_stamp on the first event */
3736 if (reader && reader->read == 0)
3737 cpu_buffer->read_stamp = reader->page->time_stamp;
3738
3739 arch_spin_unlock(&cpu_buffer->lock);
3740 local_irq_restore(flags);
3741
3742 return reader;
3743}
3744
3745static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3746{
3747 struct ring_buffer_event *event;
3748 struct buffer_page *reader;
3749 unsigned length;
3750
3751 reader = rb_get_reader_page(cpu_buffer);
3752
3753 /* This function should not be called when buffer is empty */
3754 if (RB_WARN_ON(cpu_buffer, !reader))
3755 return;
3756
3757 event = rb_reader_event(cpu_buffer);
3758
3759 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3760 cpu_buffer->read++;
3761
3762 rb_update_read_stamp(cpu_buffer, event);
3763
3764 length = rb_event_length(event);
3765 cpu_buffer->reader_page->read += length;
3766}
3767
3768static void rb_advance_iter(struct ring_buffer_iter *iter)
3769{
3770 struct ring_buffer_per_cpu *cpu_buffer;
3771 struct ring_buffer_event *event;
3772 unsigned length;
3773
3774 cpu_buffer = iter->cpu_buffer;
3775
3776 /*
3777 * Check if we are at the end of the buffer.
3778 */
3779 if (iter->head >= rb_page_size(iter->head_page)) {
3780 /* discarded commits can make the page empty */
3781 if (iter->head_page == cpu_buffer->commit_page)
3782 return;
3783 rb_inc_iter(iter);
3784 return;
3785 }
3786
3787 event = rb_iter_head_event(iter);
3788
3789 length = rb_event_length(event);
3790
3791 /*
3792 * This should not be called to advance the header if we are
3793 * at the tail of the buffer.
3794 */
3795 if (RB_WARN_ON(cpu_buffer,
3796 (iter->head_page == cpu_buffer->commit_page) &&
3797 (iter->head + length > rb_commit_index(cpu_buffer))))
3798 return;
3799
3800 rb_update_iter_read_stamp(iter, event);
3801
3802 iter->head += length;
3803
3804 /* check for end of page padding */
3805 if ((iter->head >= rb_page_size(iter->head_page)) &&
3806 (iter->head_page != cpu_buffer->commit_page))
3807 rb_inc_iter(iter);
3808}
3809
3810static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3811{
3812 return cpu_buffer->lost_events;
3813}
3814
3815static struct ring_buffer_event *
3816rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3817 unsigned long *lost_events)
3818{
3819 struct ring_buffer_event *event;
3820 struct buffer_page *reader;
3821 int nr_loops = 0;
3822
3823 if (ts)
3824 *ts = 0;
3825 again:
3826 /*
3827 * We repeat when a time extend is encountered.
3828 * Since the time extend is always attached to a data event,
3829 * we should never loop more than once.
3830 * (We never hit the following condition more than twice).
3831 */
3832 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3833 return NULL;
3834
3835 reader = rb_get_reader_page(cpu_buffer);
3836 if (!reader)
3837 return NULL;
3838
3839 event = rb_reader_event(cpu_buffer);
3840
3841 switch (event->type_len) {
3842 case RINGBUF_TYPE_PADDING:
3843 if (rb_null_event(event))
3844 RB_WARN_ON(cpu_buffer, 1);
3845 /*
3846 * Because the writer could be discarding every
3847 * event it creates (which would probably be bad)
3848 * if we were to go back to "again" then we may never
3849 * catch up, and will trigger the warn on, or lock
3850 * the box. Return the padding, and we will release
3851 * the current locks, and try again.
3852 */
3853 return event;
3854
3855 case RINGBUF_TYPE_TIME_EXTEND:
3856 /* Internal data, OK to advance */
3857 rb_advance_reader(cpu_buffer);
3858 goto again;
3859
3860 case RINGBUF_TYPE_TIME_STAMP:
3861 if (ts) {
3862 *ts = ring_buffer_event_time_stamp(event);
3863 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3864 cpu_buffer->cpu, ts);
3865 }
3866 /* Internal data, OK to advance */
3867 rb_advance_reader(cpu_buffer);
3868 goto again;
3869
3870 case RINGBUF_TYPE_DATA:
3871 if (ts && !(*ts)) {
3872 *ts = cpu_buffer->read_stamp + event->time_delta;
3873 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3874 cpu_buffer->cpu, ts);
3875 }
3876 if (lost_events)
3877 *lost_events = rb_lost_events(cpu_buffer);
3878 return event;
3879
3880 default:
3881 BUG();
3882 }
3883
3884 return NULL;
3885}
3886EXPORT_SYMBOL_GPL(ring_buffer_peek);
3887
3888static struct ring_buffer_event *
3889rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3890{
3891 struct ring_buffer *buffer;
3892 struct ring_buffer_per_cpu *cpu_buffer;
3893 struct ring_buffer_event *event;
3894 int nr_loops = 0;
3895
3896 if (ts)
3897 *ts = 0;
3898
3899 cpu_buffer = iter->cpu_buffer;
3900 buffer = cpu_buffer->buffer;
3901
3902 /*
3903 * Check if someone performed a consuming read to
3904 * the buffer. A consuming read invalidates the iterator
3905 * and we need to reset the iterator in this case.
3906 */
3907 if (unlikely(iter->cache_read != cpu_buffer->read ||
3908 iter->cache_reader_page != cpu_buffer->reader_page))
3909 rb_iter_reset(iter);
3910
3911 again:
3912 if (ring_buffer_iter_empty(iter))
3913 return NULL;
3914
3915 /*
3916 * We repeat when a time extend is encountered or we hit
3917 * the end of the page. Since the time extend is always attached
3918 * to a data event, we should never loop more than three times.
3919 * Once for going to next page, once on time extend, and
3920 * finally once to get the event.
3921 * (We never hit the following condition more than thrice).
3922 */
3923 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
3924 return NULL;
3925
3926 if (rb_per_cpu_empty(cpu_buffer))
3927 return NULL;
3928
3929 if (iter->head >= rb_page_size(iter->head_page)) {
3930 rb_inc_iter(iter);
3931 goto again;
3932 }
3933
3934 event = rb_iter_head_event(iter);
3935
3936 switch (event->type_len) {
3937 case RINGBUF_TYPE_PADDING:
3938 if (rb_null_event(event)) {
3939 rb_inc_iter(iter);
3940 goto again;
3941 }
3942 rb_advance_iter(iter);
3943 return event;
3944
3945 case RINGBUF_TYPE_TIME_EXTEND:
3946 /* Internal data, OK to advance */
3947 rb_advance_iter(iter);
3948 goto again;
3949
3950 case RINGBUF_TYPE_TIME_STAMP:
3951 if (ts) {
3952 *ts = ring_buffer_event_time_stamp(event);
3953 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3954 cpu_buffer->cpu, ts);
3955 }
3956 /* Internal data, OK to advance */
3957 rb_advance_iter(iter);
3958 goto again;
3959
3960 case RINGBUF_TYPE_DATA:
3961 if (ts && !(*ts)) {
3962 *ts = iter->read_stamp + event->time_delta;
3963 ring_buffer_normalize_time_stamp(buffer,
3964 cpu_buffer->cpu, ts);
3965 }
3966 return event;
3967
3968 default:
3969 BUG();
3970 }
3971
3972 return NULL;
3973}
3974EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3975
3976static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
3977{
3978 if (likely(!in_nmi())) {
3979 raw_spin_lock(&cpu_buffer->reader_lock);
3980 return true;
3981 }
3982
3983 /*
3984 * If an NMI die dumps out the content of the ring buffer
3985 * trylock must be used to prevent a deadlock if the NMI
3986 * preempted a task that holds the ring buffer locks. If
3987 * we get the lock then all is fine, if not, then continue
3988 * to do the read, but this can corrupt the ring buffer,
3989 * so it must be permanently disabled from future writes.
3990 * Reading from NMI is a oneshot deal.
3991 */
3992 if (raw_spin_trylock(&cpu_buffer->reader_lock))
3993 return true;
3994
3995 /* Continue without locking, but disable the ring buffer */
3996 atomic_inc(&cpu_buffer->record_disabled);
3997 return false;
3998}
3999
4000static inline void
4001rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4002{
4003 if (likely(locked))
4004 raw_spin_unlock(&cpu_buffer->reader_lock);
4005 return;
4006}
4007
4008/**
4009 * ring_buffer_peek - peek at the next event to be read
4010 * @buffer: The ring buffer to read
4011 * @cpu: The cpu to peak at
4012 * @ts: The timestamp counter of this event.
4013 * @lost_events: a variable to store if events were lost (may be NULL)
4014 *
4015 * This will return the event that will be read next, but does
4016 * not consume the data.
4017 */
4018struct ring_buffer_event *
4019ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
4020 unsigned long *lost_events)
4021{
4022 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4023 struct ring_buffer_event *event;
4024 unsigned long flags;
4025 bool dolock;
4026
4027 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4028 return NULL;
4029
4030 again:
4031 local_irq_save(flags);
4032 dolock = rb_reader_lock(cpu_buffer);
4033 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4034 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4035 rb_advance_reader(cpu_buffer);
4036 rb_reader_unlock(cpu_buffer, dolock);
4037 local_irq_restore(flags);
4038
4039 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4040 goto again;
4041
4042 return event;
4043}
4044
4045/**
4046 * ring_buffer_iter_peek - peek at the next event to be read
4047 * @iter: The ring buffer iterator
4048 * @ts: The timestamp counter of this event.
4049 *
4050 * This will return the event that will be read next, but does
4051 * not increment the iterator.
4052 */
4053struct ring_buffer_event *
4054ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4055{
4056 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4057 struct ring_buffer_event *event;
4058 unsigned long flags;
4059
4060 again:
4061 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4062 event = rb_iter_peek(iter, ts);
4063 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4064
4065 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4066 goto again;
4067
4068 return event;
4069}
4070
4071/**
4072 * ring_buffer_consume - return an event and consume it
4073 * @buffer: The ring buffer to get the next event from
4074 * @cpu: the cpu to read the buffer from
4075 * @ts: a variable to store the timestamp (may be NULL)
4076 * @lost_events: a variable to store if events were lost (may be NULL)
4077 *
4078 * Returns the next event in the ring buffer, and that event is consumed.
4079 * Meaning, that sequential reads will keep returning a different event,
4080 * and eventually empty the ring buffer if the producer is slower.
4081 */
4082struct ring_buffer_event *
4083ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
4084 unsigned long *lost_events)
4085{
4086 struct ring_buffer_per_cpu *cpu_buffer;
4087 struct ring_buffer_event *event = NULL;
4088 unsigned long flags;
4089 bool dolock;
4090
4091 again:
4092 /* might be called in atomic */
4093 preempt_disable();
4094
4095 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4096 goto out;
4097
4098 cpu_buffer = buffer->buffers[cpu];
4099 local_irq_save(flags);
4100 dolock = rb_reader_lock(cpu_buffer);
4101
4102 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4103 if (event) {
4104 cpu_buffer->lost_events = 0;
4105 rb_advance_reader(cpu_buffer);
4106 }
4107
4108 rb_reader_unlock(cpu_buffer, dolock);
4109 local_irq_restore(flags);
4110
4111 out:
4112 preempt_enable();
4113
4114 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4115 goto again;
4116
4117 return event;
4118}
4119EXPORT_SYMBOL_GPL(ring_buffer_consume);
4120
4121/**
4122 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4123 * @buffer: The ring buffer to read from
4124 * @cpu: The cpu buffer to iterate over
4125 *
4126 * This performs the initial preparations necessary to iterate
4127 * through the buffer. Memory is allocated, buffer recording
4128 * is disabled, and the iterator pointer is returned to the caller.
4129 *
4130 * Disabling buffer recordng prevents the reading from being
4131 * corrupted. This is not a consuming read, so a producer is not
4132 * expected.
4133 *
4134 * After a sequence of ring_buffer_read_prepare calls, the user is
4135 * expected to make at least one call to ring_buffer_read_prepare_sync.
4136 * Afterwards, ring_buffer_read_start is invoked to get things going
4137 * for real.
4138 *
4139 * This overall must be paired with ring_buffer_read_finish.
4140 */
4141struct ring_buffer_iter *
4142ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
4143{
4144 struct ring_buffer_per_cpu *cpu_buffer;
4145 struct ring_buffer_iter *iter;
4146
4147 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4148 return NULL;
4149
4150 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
4151 if (!iter)
4152 return NULL;
4153
4154 cpu_buffer = buffer->buffers[cpu];
4155
4156 iter->cpu_buffer = cpu_buffer;
4157
4158 atomic_inc(&buffer->resize_disabled);
4159 atomic_inc(&cpu_buffer->record_disabled);
4160
4161 return iter;
4162}
4163EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4164
4165/**
4166 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4167 *
4168 * All previously invoked ring_buffer_read_prepare calls to prepare
4169 * iterators will be synchronized. Afterwards, read_buffer_read_start
4170 * calls on those iterators are allowed.
4171 */
4172void
4173ring_buffer_read_prepare_sync(void)
4174{
4175 synchronize_sched();
4176}
4177EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4178
4179/**
4180 * ring_buffer_read_start - start a non consuming read of the buffer
4181 * @iter: The iterator returned by ring_buffer_read_prepare
4182 *
4183 * This finalizes the startup of an iteration through the buffer.
4184 * The iterator comes from a call to ring_buffer_read_prepare and
4185 * an intervening ring_buffer_read_prepare_sync must have been
4186 * performed.
4187 *
4188 * Must be paired with ring_buffer_read_finish.
4189 */
4190void
4191ring_buffer_read_start(struct ring_buffer_iter *iter)
4192{
4193 struct ring_buffer_per_cpu *cpu_buffer;
4194 unsigned long flags;
4195
4196 if (!iter)
4197 return;
4198
4199 cpu_buffer = iter->cpu_buffer;
4200
4201 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4202 arch_spin_lock(&cpu_buffer->lock);
4203 rb_iter_reset(iter);
4204 arch_spin_unlock(&cpu_buffer->lock);
4205 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4206}
4207EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4208
4209/**
4210 * ring_buffer_read_finish - finish reading the iterator of the buffer
4211 * @iter: The iterator retrieved by ring_buffer_start
4212 *
4213 * This re-enables the recording to the buffer, and frees the
4214 * iterator.
4215 */
4216void
4217ring_buffer_read_finish(struct ring_buffer_iter *iter)
4218{
4219 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4220 unsigned long flags;
4221
4222 /*
4223 * Ring buffer is disabled from recording, here's a good place
4224 * to check the integrity of the ring buffer.
4225 * Must prevent readers from trying to read, as the check
4226 * clears the HEAD page and readers require it.
4227 */
4228 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4229 rb_check_pages(cpu_buffer);
4230 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4231
4232 atomic_dec(&cpu_buffer->record_disabled);
4233 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4234 kfree(iter);
4235}
4236EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4237
4238/**
4239 * ring_buffer_read - read the next item in the ring buffer by the iterator
4240 * @iter: The ring buffer iterator
4241 * @ts: The time stamp of the event read.
4242 *
4243 * This reads the next event in the ring buffer and increments the iterator.
4244 */
4245struct ring_buffer_event *
4246ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4247{
4248 struct ring_buffer_event *event;
4249 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4250 unsigned long flags;
4251
4252 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4253 again:
4254 event = rb_iter_peek(iter, ts);
4255 if (!event)
4256 goto out;
4257
4258 if (event->type_len == RINGBUF_TYPE_PADDING)
4259 goto again;
4260
4261 rb_advance_iter(iter);
4262 out:
4263 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4264
4265 return event;
4266}
4267EXPORT_SYMBOL_GPL(ring_buffer_read);
4268
4269/**
4270 * ring_buffer_size - return the size of the ring buffer (in bytes)
4271 * @buffer: The ring buffer.
4272 */
4273unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4274{
4275 /*
4276 * Earlier, this method returned
4277 * BUF_PAGE_SIZE * buffer->nr_pages
4278 * Since the nr_pages field is now removed, we have converted this to
4279 * return the per cpu buffer value.
4280 */
4281 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4282 return 0;
4283
4284 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4285}
4286EXPORT_SYMBOL_GPL(ring_buffer_size);
4287
4288static void
4289rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4290{
4291 rb_head_page_deactivate(cpu_buffer);
4292
4293 cpu_buffer->head_page
4294 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4295 local_set(&cpu_buffer->head_page->write, 0);
4296 local_set(&cpu_buffer->head_page->entries, 0);
4297 local_set(&cpu_buffer->head_page->page->commit, 0);
4298
4299 cpu_buffer->head_page->read = 0;
4300
4301 cpu_buffer->tail_page = cpu_buffer->head_page;
4302 cpu_buffer->commit_page = cpu_buffer->head_page;
4303
4304 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4305 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4306 local_set(&cpu_buffer->reader_page->write, 0);
4307 local_set(&cpu_buffer->reader_page->entries, 0);
4308 local_set(&cpu_buffer->reader_page->page->commit, 0);
4309 cpu_buffer->reader_page->read = 0;
4310
4311 local_set(&cpu_buffer->entries_bytes, 0);
4312 local_set(&cpu_buffer->overrun, 0);
4313 local_set(&cpu_buffer->commit_overrun, 0);
4314 local_set(&cpu_buffer->dropped_events, 0);
4315 local_set(&cpu_buffer->entries, 0);
4316 local_set(&cpu_buffer->committing, 0);
4317 local_set(&cpu_buffer->commits, 0);
4318 cpu_buffer->read = 0;
4319 cpu_buffer->read_bytes = 0;
4320
4321 cpu_buffer->write_stamp = 0;
4322 cpu_buffer->read_stamp = 0;
4323
4324 cpu_buffer->lost_events = 0;
4325 cpu_buffer->last_overrun = 0;
4326
4327 rb_head_page_activate(cpu_buffer);
4328}
4329
4330/**
4331 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4332 * @buffer: The ring buffer to reset a per cpu buffer of
4333 * @cpu: The CPU buffer to be reset
4334 */
4335void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4336{
4337 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4338 unsigned long flags;
4339
4340 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4341 return;
4342
4343 atomic_inc(&buffer->resize_disabled);
4344 atomic_inc(&cpu_buffer->record_disabled);
4345
4346 /* Make sure all commits have finished */
4347 synchronize_sched();
4348
4349 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4350
4351 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4352 goto out;
4353
4354 arch_spin_lock(&cpu_buffer->lock);
4355
4356 rb_reset_cpu(cpu_buffer);
4357
4358 arch_spin_unlock(&cpu_buffer->lock);
4359
4360 out:
4361 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4362
4363 atomic_dec(&cpu_buffer->record_disabled);
4364 atomic_dec(&buffer->resize_disabled);
4365}
4366EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4367
4368/**
4369 * ring_buffer_reset - reset a ring buffer
4370 * @buffer: The ring buffer to reset all cpu buffers
4371 */
4372void ring_buffer_reset(struct ring_buffer *buffer)
4373{
4374 int cpu;
4375
4376 for_each_buffer_cpu(buffer, cpu)
4377 ring_buffer_reset_cpu(buffer, cpu);
4378}
4379EXPORT_SYMBOL_GPL(ring_buffer_reset);
4380
4381/**
4382 * rind_buffer_empty - is the ring buffer empty?
4383 * @buffer: The ring buffer to test
4384 */
4385bool ring_buffer_empty(struct ring_buffer *buffer)
4386{
4387 struct ring_buffer_per_cpu *cpu_buffer;
4388 unsigned long flags;
4389 bool dolock;
4390 int cpu;
4391 int ret;
4392
4393 /* yes this is racy, but if you don't like the race, lock the buffer */
4394 for_each_buffer_cpu(buffer, cpu) {
4395 cpu_buffer = buffer->buffers[cpu];
4396 local_irq_save(flags);
4397 dolock = rb_reader_lock(cpu_buffer);
4398 ret = rb_per_cpu_empty(cpu_buffer);
4399 rb_reader_unlock(cpu_buffer, dolock);
4400 local_irq_restore(flags);
4401
4402 if (!ret)
4403 return false;
4404 }
4405
4406 return true;
4407}
4408EXPORT_SYMBOL_GPL(ring_buffer_empty);
4409
4410/**
4411 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4412 * @buffer: The ring buffer
4413 * @cpu: The CPU buffer to test
4414 */
4415bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4416{
4417 struct ring_buffer_per_cpu *cpu_buffer;
4418 unsigned long flags;
4419 bool dolock;
4420 int ret;
4421
4422 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4423 return true;
4424
4425 cpu_buffer = buffer->buffers[cpu];
4426 local_irq_save(flags);
4427 dolock = rb_reader_lock(cpu_buffer);
4428 ret = rb_per_cpu_empty(cpu_buffer);
4429 rb_reader_unlock(cpu_buffer, dolock);
4430 local_irq_restore(flags);
4431
4432 return ret;
4433}
4434EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4435
4436#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4437/**
4438 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4439 * @buffer_a: One buffer to swap with
4440 * @buffer_b: The other buffer to swap with
4441 *
4442 * This function is useful for tracers that want to take a "snapshot"
4443 * of a CPU buffer and has another back up buffer lying around.
4444 * it is expected that the tracer handles the cpu buffer not being
4445 * used at the moment.
4446 */
4447int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4448 struct ring_buffer *buffer_b, int cpu)
4449{
4450 struct ring_buffer_per_cpu *cpu_buffer_a;
4451 struct ring_buffer_per_cpu *cpu_buffer_b;
4452 int ret = -EINVAL;
4453
4454 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4455 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4456 goto out;
4457
4458 cpu_buffer_a = buffer_a->buffers[cpu];
4459 cpu_buffer_b = buffer_b->buffers[cpu];
4460
4461 /* At least make sure the two buffers are somewhat the same */
4462 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4463 goto out;
4464
4465 ret = -EAGAIN;
4466
4467 if (atomic_read(&buffer_a->record_disabled))
4468 goto out;
4469
4470 if (atomic_read(&buffer_b->record_disabled))
4471 goto out;
4472
4473 if (atomic_read(&cpu_buffer_a->record_disabled))
4474 goto out;
4475
4476 if (atomic_read(&cpu_buffer_b->record_disabled))
4477 goto out;
4478
4479 /*
4480 * We can't do a synchronize_sched here because this
4481 * function can be called in atomic context.
4482 * Normally this will be called from the same CPU as cpu.
4483 * If not it's up to the caller to protect this.
4484 */
4485 atomic_inc(&cpu_buffer_a->record_disabled);
4486 atomic_inc(&cpu_buffer_b->record_disabled);
4487
4488 ret = -EBUSY;
4489 if (local_read(&cpu_buffer_a->committing))
4490 goto out_dec;
4491 if (local_read(&cpu_buffer_b->committing))
4492 goto out_dec;
4493
4494 buffer_a->buffers[cpu] = cpu_buffer_b;
4495 buffer_b->buffers[cpu] = cpu_buffer_a;
4496
4497 cpu_buffer_b->buffer = buffer_a;
4498 cpu_buffer_a->buffer = buffer_b;
4499
4500 ret = 0;
4501
4502out_dec:
4503 atomic_dec(&cpu_buffer_a->record_disabled);
4504 atomic_dec(&cpu_buffer_b->record_disabled);
4505out:
4506 return ret;
4507}
4508EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4509#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4510
4511/**
4512 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4513 * @buffer: the buffer to allocate for.
4514 * @cpu: the cpu buffer to allocate.
4515 *
4516 * This function is used in conjunction with ring_buffer_read_page.
4517 * When reading a full page from the ring buffer, these functions
4518 * can be used to speed up the process. The calling function should
4519 * allocate a few pages first with this function. Then when it
4520 * needs to get pages from the ring buffer, it passes the result
4521 * of this function into ring_buffer_read_page, which will swap
4522 * the page that was allocated, with the read page of the buffer.
4523 *
4524 * Returns:
4525 * The page allocated, or ERR_PTR
4526 */
4527void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4528{
4529 struct ring_buffer_per_cpu *cpu_buffer;
4530 struct buffer_data_page *bpage = NULL;
4531 unsigned long flags;
4532 struct page *page;
4533
4534 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4535 return ERR_PTR(-ENODEV);
4536
4537 cpu_buffer = buffer->buffers[cpu];
4538 local_irq_save(flags);
4539 arch_spin_lock(&cpu_buffer->lock);
4540
4541 if (cpu_buffer->free_page) {
4542 bpage = cpu_buffer->free_page;
4543 cpu_buffer->free_page = NULL;
4544 }
4545
4546 arch_spin_unlock(&cpu_buffer->lock);
4547 local_irq_restore(flags);
4548
4549 if (bpage)
4550 goto out;
4551
4552 page = alloc_pages_node(cpu_to_node(cpu),
4553 GFP_KERNEL | __GFP_NORETRY, 0);
4554 if (!page)
4555 return ERR_PTR(-ENOMEM);
4556
4557 bpage = page_address(page);
4558
4559 out:
4560 rb_init_page(bpage);
4561
4562 return bpage;
4563}
4564EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4565
4566/**
4567 * ring_buffer_free_read_page - free an allocated read page
4568 * @buffer: the buffer the page was allocate for
4569 * @cpu: the cpu buffer the page came from
4570 * @data: the page to free
4571 *
4572 * Free a page allocated from ring_buffer_alloc_read_page.
4573 */
4574void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
4575{
4576 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4577 struct buffer_data_page *bpage = data;
4578 struct page *page = virt_to_page(bpage);
4579 unsigned long flags;
4580
4581 /* If the page is still in use someplace else, we can't reuse it */
4582 if (page_ref_count(page) > 1)
4583 goto out;
4584
4585 local_irq_save(flags);
4586 arch_spin_lock(&cpu_buffer->lock);
4587
4588 if (!cpu_buffer->free_page) {
4589 cpu_buffer->free_page = bpage;
4590 bpage = NULL;
4591 }
4592
4593 arch_spin_unlock(&cpu_buffer->lock);
4594 local_irq_restore(flags);
4595
4596 out:
4597 free_page((unsigned long)bpage);
4598}
4599EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4600
4601/**
4602 * ring_buffer_read_page - extract a page from the ring buffer
4603 * @buffer: buffer to extract from
4604 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4605 * @len: amount to extract
4606 * @cpu: the cpu of the buffer to extract
4607 * @full: should the extraction only happen when the page is full.
4608 *
4609 * This function will pull out a page from the ring buffer and consume it.
4610 * @data_page must be the address of the variable that was returned
4611 * from ring_buffer_alloc_read_page. This is because the page might be used
4612 * to swap with a page in the ring buffer.
4613 *
4614 * for example:
4615 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4616 * if (IS_ERR(rpage))
4617 * return PTR_ERR(rpage);
4618 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4619 * if (ret >= 0)
4620 * process_page(rpage, ret);
4621 *
4622 * When @full is set, the function will not return true unless
4623 * the writer is off the reader page.
4624 *
4625 * Note: it is up to the calling functions to handle sleeps and wakeups.
4626 * The ring buffer can be used anywhere in the kernel and can not
4627 * blindly call wake_up. The layer that uses the ring buffer must be
4628 * responsible for that.
4629 *
4630 * Returns:
4631 * >=0 if data has been transferred, returns the offset of consumed data.
4632 * <0 if no data has been transferred.
4633 */
4634int ring_buffer_read_page(struct ring_buffer *buffer,
4635 void **data_page, size_t len, int cpu, int full)
4636{
4637 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4638 struct ring_buffer_event *event;
4639 struct buffer_data_page *bpage;
4640 struct buffer_page *reader;
4641 unsigned long missed_events;
4642 unsigned long flags;
4643 unsigned int commit;
4644 unsigned int read;
4645 u64 save_timestamp;
4646 int ret = -1;
4647
4648 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4649 goto out;
4650
4651 /*
4652 * If len is not big enough to hold the page header, then
4653 * we can not copy anything.
4654 */
4655 if (len <= BUF_PAGE_HDR_SIZE)
4656 goto out;
4657
4658 len -= BUF_PAGE_HDR_SIZE;
4659
4660 if (!data_page)
4661 goto out;
4662
4663 bpage = *data_page;
4664 if (!bpage)
4665 goto out;
4666
4667 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4668
4669 reader = rb_get_reader_page(cpu_buffer);
4670 if (!reader)
4671 goto out_unlock;
4672
4673 event = rb_reader_event(cpu_buffer);
4674
4675 read = reader->read;
4676 commit = rb_page_commit(reader);
4677
4678 /* Check if any events were dropped */
4679 missed_events = cpu_buffer->lost_events;
4680
4681 /*
4682 * If this page has been partially read or
4683 * if len is not big enough to read the rest of the page or
4684 * a writer is still on the page, then
4685 * we must copy the data from the page to the buffer.
4686 * Otherwise, we can simply swap the page with the one passed in.
4687 */
4688 if (read || (len < (commit - read)) ||
4689 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4690 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4691 unsigned int rpos = read;
4692 unsigned int pos = 0;
4693 unsigned int size;
4694
4695 if (full)
4696 goto out_unlock;
4697
4698 if (len > (commit - read))
4699 len = (commit - read);
4700
4701 /* Always keep the time extend and data together */
4702 size = rb_event_ts_length(event);
4703
4704 if (len < size)
4705 goto out_unlock;
4706
4707 /* save the current timestamp, since the user will need it */
4708 save_timestamp = cpu_buffer->read_stamp;
4709
4710 /* Need to copy one event at a time */
4711 do {
4712 /* We need the size of one event, because
4713 * rb_advance_reader only advances by one event,
4714 * whereas rb_event_ts_length may include the size of
4715 * one or two events.
4716 * We have already ensured there's enough space if this
4717 * is a time extend. */
4718 size = rb_event_length(event);
4719 memcpy(bpage->data + pos, rpage->data + rpos, size);
4720
4721 len -= size;
4722
4723 rb_advance_reader(cpu_buffer);
4724 rpos = reader->read;
4725 pos += size;
4726
4727 if (rpos >= commit)
4728 break;
4729
4730 event = rb_reader_event(cpu_buffer);
4731 /* Always keep the time extend and data together */
4732 size = rb_event_ts_length(event);
4733 } while (len >= size);
4734
4735 /* update bpage */
4736 local_set(&bpage->commit, pos);
4737 bpage->time_stamp = save_timestamp;
4738
4739 /* we copied everything to the beginning */
4740 read = 0;
4741 } else {
4742 /* update the entry counter */
4743 cpu_buffer->read += rb_page_entries(reader);
4744 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4745
4746 /* swap the pages */
4747 rb_init_page(bpage);
4748 bpage = reader->page;
4749 reader->page = *data_page;
4750 local_set(&reader->write, 0);
4751 local_set(&reader->entries, 0);
4752 reader->read = 0;
4753 *data_page = bpage;
4754
4755 /*
4756 * Use the real_end for the data size,
4757 * This gives us a chance to store the lost events
4758 * on the page.
4759 */
4760 if (reader->real_end)
4761 local_set(&bpage->commit, reader->real_end);
4762 }
4763 ret = read;
4764
4765 cpu_buffer->lost_events = 0;
4766
4767 commit = local_read(&bpage->commit);
4768 /*
4769 * Set a flag in the commit field if we lost events
4770 */
4771 if (missed_events) {
4772 /* If there is room at the end of the page to save the
4773 * missed events, then record it there.
4774 */
4775 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4776 memcpy(&bpage->data[commit], &missed_events,
4777 sizeof(missed_events));
4778 local_add(RB_MISSED_STORED, &bpage->commit);
4779 commit += sizeof(missed_events);
4780 }
4781 local_add(RB_MISSED_EVENTS, &bpage->commit);
4782 }
4783
4784 /*
4785 * This page may be off to user land. Zero it out here.
4786 */
4787 if (commit < BUF_PAGE_SIZE)
4788 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4789
4790 out_unlock:
4791 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4792
4793 out:
4794 return ret;
4795}
4796EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4797
4798/*
4799 * We only allocate new buffers, never free them if the CPU goes down.
4800 * If we were to free the buffer, then the user would lose any trace that was in
4801 * the buffer.
4802 */
4803int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
4804{
4805 struct ring_buffer *buffer;
4806 long nr_pages_same;
4807 int cpu_i;
4808 unsigned long nr_pages;
4809
4810 buffer = container_of(node, struct ring_buffer, node);
4811 if (cpumask_test_cpu(cpu, buffer->cpumask))
4812 return 0;
4813
4814 nr_pages = 0;
4815 nr_pages_same = 1;
4816 /* check if all cpu sizes are same */
4817 for_each_buffer_cpu(buffer, cpu_i) {
4818 /* fill in the size from first enabled cpu */
4819 if (nr_pages == 0)
4820 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4821 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4822 nr_pages_same = 0;
4823 break;
4824 }
4825 }
4826 /* allocate minimum pages, user can later expand it */
4827 if (!nr_pages_same)
4828 nr_pages = 2;
4829 buffer->buffers[cpu] =
4830 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4831 if (!buffer->buffers[cpu]) {
4832 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4833 cpu);
4834 return -ENOMEM;
4835 }
4836 smp_wmb();
4837 cpumask_set_cpu(cpu, buffer->cpumask);
4838 return 0;
4839}
4840
4841#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4842/*
4843 * This is a basic integrity check of the ring buffer.
4844 * Late in the boot cycle this test will run when configured in.
4845 * It will kick off a thread per CPU that will go into a loop
4846 * writing to the per cpu ring buffer various sizes of data.
4847 * Some of the data will be large items, some small.
4848 *
4849 * Another thread is created that goes into a spin, sending out
4850 * IPIs to the other CPUs to also write into the ring buffer.
4851 * this is to test the nesting ability of the buffer.
4852 *
4853 * Basic stats are recorded and reported. If something in the
4854 * ring buffer should happen that's not expected, a big warning
4855 * is displayed and all ring buffers are disabled.
4856 */
4857static struct task_struct *rb_threads[NR_CPUS] __initdata;
4858
4859struct rb_test_data {
4860 struct ring_buffer *buffer;
4861 unsigned long events;
4862 unsigned long bytes_written;
4863 unsigned long bytes_alloc;
4864 unsigned long bytes_dropped;
4865 unsigned long events_nested;
4866 unsigned long bytes_written_nested;
4867 unsigned long bytes_alloc_nested;
4868 unsigned long bytes_dropped_nested;
4869 int min_size_nested;
4870 int max_size_nested;
4871 int max_size;
4872 int min_size;
4873 int cpu;
4874 int cnt;
4875};
4876
4877static struct rb_test_data rb_data[NR_CPUS] __initdata;
4878
4879/* 1 meg per cpu */
4880#define RB_TEST_BUFFER_SIZE 1048576
4881
4882static char rb_string[] __initdata =
4883 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4884 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4885 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4886
4887static bool rb_test_started __initdata;
4888
4889struct rb_item {
4890 int size;
4891 char str[];
4892};
4893
4894static __init int rb_write_something(struct rb_test_data *data, bool nested)
4895{
4896 struct ring_buffer_event *event;
4897 struct rb_item *item;
4898 bool started;
4899 int event_len;
4900 int size;
4901 int len;
4902 int cnt;
4903
4904 /* Have nested writes different that what is written */
4905 cnt = data->cnt + (nested ? 27 : 0);
4906
4907 /* Multiply cnt by ~e, to make some unique increment */
4908 size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
4909
4910 len = size + sizeof(struct rb_item);
4911
4912 started = rb_test_started;
4913 /* read rb_test_started before checking buffer enabled */
4914 smp_rmb();
4915
4916 event = ring_buffer_lock_reserve(data->buffer, len);
4917 if (!event) {
4918 /* Ignore dropped events before test starts. */
4919 if (started) {
4920 if (nested)
4921 data->bytes_dropped += len;
4922 else
4923 data->bytes_dropped_nested += len;
4924 }
4925 return len;
4926 }
4927
4928 event_len = ring_buffer_event_length(event);
4929
4930 if (RB_WARN_ON(data->buffer, event_len < len))
4931 goto out;
4932
4933 item = ring_buffer_event_data(event);
4934 item->size = size;
4935 memcpy(item->str, rb_string, size);
4936
4937 if (nested) {
4938 data->bytes_alloc_nested += event_len;
4939 data->bytes_written_nested += len;
4940 data->events_nested++;
4941 if (!data->min_size_nested || len < data->min_size_nested)
4942 data->min_size_nested = len;
4943 if (len > data->max_size_nested)
4944 data->max_size_nested = len;
4945 } else {
4946 data->bytes_alloc += event_len;
4947 data->bytes_written += len;
4948 data->events++;
4949 if (!data->min_size || len < data->min_size)
4950 data->max_size = len;
4951 if (len > data->max_size)
4952 data->max_size = len;
4953 }
4954
4955 out:
4956 ring_buffer_unlock_commit(data->buffer, event);
4957
4958 return 0;
4959}
4960
4961static __init int rb_test(void *arg)
4962{
4963 struct rb_test_data *data = arg;
4964
4965 while (!kthread_should_stop()) {
4966 rb_write_something(data, false);
4967 data->cnt++;
4968
4969 set_current_state(TASK_INTERRUPTIBLE);
4970 /* Now sleep between a min of 100-300us and a max of 1ms */
4971 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
4972 }
4973
4974 return 0;
4975}
4976
4977static __init void rb_ipi(void *ignore)
4978{
4979 struct rb_test_data *data;
4980 int cpu = smp_processor_id();
4981
4982 data = &rb_data[cpu];
4983 rb_write_something(data, true);
4984}
4985
4986static __init int rb_hammer_test(void *arg)
4987{
4988 while (!kthread_should_stop()) {
4989
4990 /* Send an IPI to all cpus to write data! */
4991 smp_call_function(rb_ipi, NULL, 1);
4992 /* No sleep, but for non preempt, let others run */
4993 schedule();
4994 }
4995
4996 return 0;
4997}
4998
4999static __init int test_ringbuffer(void)
5000{
5001 struct task_struct *rb_hammer;
5002 struct ring_buffer *buffer;
5003 int cpu;
5004 int ret = 0;
5005
5006 pr_info("Running ring buffer tests...\n");
5007
5008 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5009 if (WARN_ON(!buffer))
5010 return 0;
5011
5012 /* Disable buffer so that threads can't write to it yet */
5013 ring_buffer_record_off(buffer);
5014
5015 for_each_online_cpu(cpu) {
5016 rb_data[cpu].buffer = buffer;
5017 rb_data[cpu].cpu = cpu;
5018 rb_data[cpu].cnt = cpu;
5019 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5020 "rbtester/%d", cpu);
5021 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5022 pr_cont("FAILED\n");
5023 ret = PTR_ERR(rb_threads[cpu]);
5024 goto out_free;
5025 }
5026
5027 kthread_bind(rb_threads[cpu], cpu);
5028 wake_up_process(rb_threads[cpu]);
5029 }
5030
5031 /* Now create the rb hammer! */
5032 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5033 if (WARN_ON(IS_ERR(rb_hammer))) {
5034 pr_cont("FAILED\n");
5035 ret = PTR_ERR(rb_hammer);
5036 goto out_free;
5037 }
5038
5039 ring_buffer_record_on(buffer);
5040 /*
5041 * Show buffer is enabled before setting rb_test_started.
5042 * Yes there's a small race window where events could be
5043 * dropped and the thread wont catch it. But when a ring
5044 * buffer gets enabled, there will always be some kind of
5045 * delay before other CPUs see it. Thus, we don't care about
5046 * those dropped events. We care about events dropped after
5047 * the threads see that the buffer is active.
5048 */
5049 smp_wmb();
5050 rb_test_started = true;
5051
5052 set_current_state(TASK_INTERRUPTIBLE);
5053 /* Just run for 10 seconds */;
5054 schedule_timeout(10 * HZ);
5055
5056 kthread_stop(rb_hammer);
5057
5058 out_free:
5059 for_each_online_cpu(cpu) {
5060 if (!rb_threads[cpu])
5061 break;
5062 kthread_stop(rb_threads[cpu]);
5063 }
5064 if (ret) {
5065 ring_buffer_free(buffer);
5066 return ret;
5067 }
5068
5069 /* Report! */
5070 pr_info("finished\n");
5071 for_each_online_cpu(cpu) {
5072 struct ring_buffer_event *event;
5073 struct rb_test_data *data = &rb_data[cpu];
5074 struct rb_item *item;
5075 unsigned long total_events;
5076 unsigned long total_dropped;
5077 unsigned long total_written;
5078 unsigned long total_alloc;
5079 unsigned long total_read = 0;
5080 unsigned long total_size = 0;
5081 unsigned long total_len = 0;
5082 unsigned long total_lost = 0;
5083 unsigned long lost;
5084 int big_event_size;
5085 int small_event_size;
5086
5087 ret = -1;
5088
5089 total_events = data->events + data->events_nested;
5090 total_written = data->bytes_written + data->bytes_written_nested;
5091 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5092 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5093
5094 big_event_size = data->max_size + data->max_size_nested;
5095 small_event_size = data->min_size + data->min_size_nested;
5096
5097 pr_info("CPU %d:\n", cpu);
5098 pr_info(" events: %ld\n", total_events);
5099 pr_info(" dropped bytes: %ld\n", total_dropped);
5100 pr_info(" alloced bytes: %ld\n", total_alloc);
5101 pr_info(" written bytes: %ld\n", total_written);
5102 pr_info(" biggest event: %d\n", big_event_size);
5103 pr_info(" smallest event: %d\n", small_event_size);
5104
5105 if (RB_WARN_ON(buffer, total_dropped))
5106 break;
5107
5108 ret = 0;
5109
5110 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5111 total_lost += lost;
5112 item = ring_buffer_event_data(event);
5113 total_len += ring_buffer_event_length(event);
5114 total_size += item->size + sizeof(struct rb_item);
5115 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5116 pr_info("FAILED!\n");
5117 pr_info("buffer had: %.*s\n", item->size, item->str);
5118 pr_info("expected: %.*s\n", item->size, rb_string);
5119 RB_WARN_ON(buffer, 1);
5120 ret = -1;
5121 break;
5122 }
5123 total_read++;
5124 }
5125 if (ret)
5126 break;
5127
5128 ret = -1;
5129
5130 pr_info(" read events: %ld\n", total_read);
5131 pr_info(" lost events: %ld\n", total_lost);
5132 pr_info(" total events: %ld\n", total_lost + total_read);
5133 pr_info(" recorded len bytes: %ld\n", total_len);
5134 pr_info(" recorded size bytes: %ld\n", total_size);
5135 if (total_lost)
5136 pr_info(" With dropped events, record len and size may not match\n"
5137 " alloced and written from above\n");
5138 if (!total_lost) {
5139 if (RB_WARN_ON(buffer, total_len != total_alloc ||
5140 total_size != total_written))
5141 break;
5142 }
5143 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5144 break;
5145
5146 ret = 0;
5147 }
5148 if (!ret)
5149 pr_info("Ring buffer PASSED!\n");
5150
5151 ring_buffer_free(buffer);
5152 return 0;
5153}
5154
5155late_initcall(test_ringbuffer);
5156#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */