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1/*
2 * Generic ring buffer
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/ring_buffer.h>
7#include <linux/trace_clock.h>
8#include <linux/spinlock.h>
9#include <linux/debugfs.h>
10#include <linux/uaccess.h>
11#include <linux/hardirq.h>
12#include <linux/kmemcheck.h>
13#include <linux/module.h>
14#include <linux/percpu.h>
15#include <linux/mutex.h>
16#include <linux/slab.h>
17#include <linux/init.h>
18#include <linux/hash.h>
19#include <linux/list.h>
20#include <linux/cpu.h>
21#include <linux/fs.h>
22
23#include <asm/local.h>
24#include "trace.h"
25
26static void update_pages_handler(struct work_struct *work);
27
28/*
29 * The ring buffer header is special. We must manually up keep it.
30 */
31int ring_buffer_print_entry_header(struct trace_seq *s)
32{
33 int ret;
34
35 ret = trace_seq_printf(s, "# compressed entry header\n");
36 ret = trace_seq_printf(s, "\ttype_len : 5 bits\n");
37 ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n");
38 ret = trace_seq_printf(s, "\tarray : 32 bits\n");
39 ret = trace_seq_printf(s, "\n");
40 ret = trace_seq_printf(s, "\tpadding : type == %d\n",
41 RINGBUF_TYPE_PADDING);
42 ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
43 RINGBUF_TYPE_TIME_EXTEND);
44 ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
45 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
46
47 return ret;
48}
49
50/*
51 * The ring buffer is made up of a list of pages. A separate list of pages is
52 * allocated for each CPU. A writer may only write to a buffer that is
53 * associated with the CPU it is currently executing on. A reader may read
54 * from any per cpu buffer.
55 *
56 * The reader is special. For each per cpu buffer, the reader has its own
57 * reader page. When a reader has read the entire reader page, this reader
58 * page is swapped with another page in the ring buffer.
59 *
60 * Now, as long as the writer is off the reader page, the reader can do what
61 * ever it wants with that page. The writer will never write to that page
62 * again (as long as it is out of the ring buffer).
63 *
64 * Here's some silly ASCII art.
65 *
66 * +------+
67 * |reader| RING BUFFER
68 * |page |
69 * +------+ +---+ +---+ +---+
70 * | |-->| |-->| |
71 * +---+ +---+ +---+
72 * ^ |
73 * | |
74 * +---------------+
75 *
76 *
77 * +------+
78 * |reader| RING BUFFER
79 * |page |------------------v
80 * +------+ +---+ +---+ +---+
81 * | |-->| |-->| |
82 * +---+ +---+ +---+
83 * ^ |
84 * | |
85 * +---------------+
86 *
87 *
88 * +------+
89 * |reader| RING BUFFER
90 * |page |------------------v
91 * +------+ +---+ +---+ +---+
92 * ^ | |-->| |-->| |
93 * | +---+ +---+ +---+
94 * | |
95 * | |
96 * +------------------------------+
97 *
98 *
99 * +------+
100 * |buffer| RING BUFFER
101 * |page |------------------v
102 * +------+ +---+ +---+ +---+
103 * ^ | | | |-->| |
104 * | New +---+ +---+ +---+
105 * | Reader------^ |
106 * | page |
107 * +------------------------------+
108 *
109 *
110 * After we make this swap, the reader can hand this page off to the splice
111 * code and be done with it. It can even allocate a new page if it needs to
112 * and swap that into the ring buffer.
113 *
114 * We will be using cmpxchg soon to make all this lockless.
115 *
116 */
117
118/*
119 * A fast way to enable or disable all ring buffers is to
120 * call tracing_on or tracing_off. Turning off the ring buffers
121 * prevents all ring buffers from being recorded to.
122 * Turning this switch on, makes it OK to write to the
123 * ring buffer, if the ring buffer is enabled itself.
124 *
125 * There's three layers that must be on in order to write
126 * to the ring buffer.
127 *
128 * 1) This global flag must be set.
129 * 2) The ring buffer must be enabled for recording.
130 * 3) The per cpu buffer must be enabled for recording.
131 *
132 * In case of an anomaly, this global flag has a bit set that
133 * will permantly disable all ring buffers.
134 */
135
136/*
137 * Global flag to disable all recording to ring buffers
138 * This has two bits: ON, DISABLED
139 *
140 * ON DISABLED
141 * ---- ----------
142 * 0 0 : ring buffers are off
143 * 1 0 : ring buffers are on
144 * X 1 : ring buffers are permanently disabled
145 */
146
147enum {
148 RB_BUFFERS_ON_BIT = 0,
149 RB_BUFFERS_DISABLED_BIT = 1,
150};
151
152enum {
153 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
154 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
155};
156
157static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
158
159/* Used for individual buffers (after the counter) */
160#define RB_BUFFER_OFF (1 << 20)
161
162#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
163
164/**
165 * tracing_off_permanent - permanently disable ring buffers
166 *
167 * This function, once called, will disable all ring buffers
168 * permanently.
169 */
170void tracing_off_permanent(void)
171{
172 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
173}
174
175#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
176#define RB_ALIGNMENT 4U
177#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
178#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
179
180#if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
181# define RB_FORCE_8BYTE_ALIGNMENT 0
182# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
183#else
184# define RB_FORCE_8BYTE_ALIGNMENT 1
185# define RB_ARCH_ALIGNMENT 8U
186#endif
187
188/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
189#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
190
191enum {
192 RB_LEN_TIME_EXTEND = 8,
193 RB_LEN_TIME_STAMP = 16,
194};
195
196#define skip_time_extend(event) \
197 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
198
199static inline int rb_null_event(struct ring_buffer_event *event)
200{
201 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
202}
203
204static void rb_event_set_padding(struct ring_buffer_event *event)
205{
206 /* padding has a NULL time_delta */
207 event->type_len = RINGBUF_TYPE_PADDING;
208 event->time_delta = 0;
209}
210
211static unsigned
212rb_event_data_length(struct ring_buffer_event *event)
213{
214 unsigned length;
215
216 if (event->type_len)
217 length = event->type_len * RB_ALIGNMENT;
218 else
219 length = event->array[0];
220 return length + RB_EVNT_HDR_SIZE;
221}
222
223/*
224 * Return the length of the given event. Will return
225 * the length of the time extend if the event is a
226 * time extend.
227 */
228static inline unsigned
229rb_event_length(struct ring_buffer_event *event)
230{
231 switch (event->type_len) {
232 case RINGBUF_TYPE_PADDING:
233 if (rb_null_event(event))
234 /* undefined */
235 return -1;
236 return event->array[0] + RB_EVNT_HDR_SIZE;
237
238 case RINGBUF_TYPE_TIME_EXTEND:
239 return RB_LEN_TIME_EXTEND;
240
241 case RINGBUF_TYPE_TIME_STAMP:
242 return RB_LEN_TIME_STAMP;
243
244 case RINGBUF_TYPE_DATA:
245 return rb_event_data_length(event);
246 default:
247 BUG();
248 }
249 /* not hit */
250 return 0;
251}
252
253/*
254 * Return total length of time extend and data,
255 * or just the event length for all other events.
256 */
257static inline unsigned
258rb_event_ts_length(struct ring_buffer_event *event)
259{
260 unsigned len = 0;
261
262 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
263 /* time extends include the data event after it */
264 len = RB_LEN_TIME_EXTEND;
265 event = skip_time_extend(event);
266 }
267 return len + rb_event_length(event);
268}
269
270/**
271 * ring_buffer_event_length - return the length of the event
272 * @event: the event to get the length of
273 *
274 * Returns the size of the data load of a data event.
275 * If the event is something other than a data event, it
276 * returns the size of the event itself. With the exception
277 * of a TIME EXTEND, where it still returns the size of the
278 * data load of the data event after it.
279 */
280unsigned ring_buffer_event_length(struct ring_buffer_event *event)
281{
282 unsigned length;
283
284 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
285 event = skip_time_extend(event);
286
287 length = rb_event_length(event);
288 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
289 return length;
290 length -= RB_EVNT_HDR_SIZE;
291 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
292 length -= sizeof(event->array[0]);
293 return length;
294}
295EXPORT_SYMBOL_GPL(ring_buffer_event_length);
296
297/* inline for ring buffer fast paths */
298static void *
299rb_event_data(struct ring_buffer_event *event)
300{
301 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
302 event = skip_time_extend(event);
303 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
304 /* If length is in len field, then array[0] has the data */
305 if (event->type_len)
306 return (void *)&event->array[0];
307 /* Otherwise length is in array[0] and array[1] has the data */
308 return (void *)&event->array[1];
309}
310
311/**
312 * ring_buffer_event_data - return the data of the event
313 * @event: the event to get the data from
314 */
315void *ring_buffer_event_data(struct ring_buffer_event *event)
316{
317 return rb_event_data(event);
318}
319EXPORT_SYMBOL_GPL(ring_buffer_event_data);
320
321#define for_each_buffer_cpu(buffer, cpu) \
322 for_each_cpu(cpu, buffer->cpumask)
323
324#define TS_SHIFT 27
325#define TS_MASK ((1ULL << TS_SHIFT) - 1)
326#define TS_DELTA_TEST (~TS_MASK)
327
328/* Flag when events were overwritten */
329#define RB_MISSED_EVENTS (1 << 31)
330/* Missed count stored at end */
331#define RB_MISSED_STORED (1 << 30)
332
333struct buffer_data_page {
334 u64 time_stamp; /* page time stamp */
335 local_t commit; /* write committed index */
336 unsigned char data[]; /* data of buffer page */
337};
338
339/*
340 * Note, the buffer_page list must be first. The buffer pages
341 * are allocated in cache lines, which means that each buffer
342 * page will be at the beginning of a cache line, and thus
343 * the least significant bits will be zero. We use this to
344 * add flags in the list struct pointers, to make the ring buffer
345 * lockless.
346 */
347struct buffer_page {
348 struct list_head list; /* list of buffer pages */
349 local_t write; /* index for next write */
350 unsigned read; /* index for next read */
351 local_t entries; /* entries on this page */
352 unsigned long real_end; /* real end of data */
353 struct buffer_data_page *page; /* Actual data page */
354};
355
356/*
357 * The buffer page counters, write and entries, must be reset
358 * atomically when crossing page boundaries. To synchronize this
359 * update, two counters are inserted into the number. One is
360 * the actual counter for the write position or count on the page.
361 *
362 * The other is a counter of updaters. Before an update happens
363 * the update partition of the counter is incremented. This will
364 * allow the updater to update the counter atomically.
365 *
366 * The counter is 20 bits, and the state data is 12.
367 */
368#define RB_WRITE_MASK 0xfffff
369#define RB_WRITE_INTCNT (1 << 20)
370
371static void rb_init_page(struct buffer_data_page *bpage)
372{
373 local_set(&bpage->commit, 0);
374}
375
376/**
377 * ring_buffer_page_len - the size of data on the page.
378 * @page: The page to read
379 *
380 * Returns the amount of data on the page, including buffer page header.
381 */
382size_t ring_buffer_page_len(void *page)
383{
384 return local_read(&((struct buffer_data_page *)page)->commit)
385 + BUF_PAGE_HDR_SIZE;
386}
387
388/*
389 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
390 * this issue out.
391 */
392static void free_buffer_page(struct buffer_page *bpage)
393{
394 free_page((unsigned long)bpage->page);
395 kfree(bpage);
396}
397
398/*
399 * We need to fit the time_stamp delta into 27 bits.
400 */
401static inline int test_time_stamp(u64 delta)
402{
403 if (delta & TS_DELTA_TEST)
404 return 1;
405 return 0;
406}
407
408#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
409
410/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
411#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
412
413int ring_buffer_print_page_header(struct trace_seq *s)
414{
415 struct buffer_data_page field;
416 int ret;
417
418 ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
419 "offset:0;\tsize:%u;\tsigned:%u;\n",
420 (unsigned int)sizeof(field.time_stamp),
421 (unsigned int)is_signed_type(u64));
422
423 ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
424 "offset:%u;\tsize:%u;\tsigned:%u;\n",
425 (unsigned int)offsetof(typeof(field), commit),
426 (unsigned int)sizeof(field.commit),
427 (unsigned int)is_signed_type(long));
428
429 ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
430 "offset:%u;\tsize:%u;\tsigned:%u;\n",
431 (unsigned int)offsetof(typeof(field), commit),
432 1,
433 (unsigned int)is_signed_type(long));
434
435 ret = trace_seq_printf(s, "\tfield: char data;\t"
436 "offset:%u;\tsize:%u;\tsigned:%u;\n",
437 (unsigned int)offsetof(typeof(field), data),
438 (unsigned int)BUF_PAGE_SIZE,
439 (unsigned int)is_signed_type(char));
440
441 return ret;
442}
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 struct ring_buffer *buffer;
451 raw_spinlock_t reader_lock; /* serialize readers */
452 arch_spinlock_t lock;
453 struct lock_class_key lock_key;
454 unsigned int nr_pages;
455 struct list_head *pages;
456 struct buffer_page *head_page; /* read from head */
457 struct buffer_page *tail_page; /* write to tail */
458 struct buffer_page *commit_page; /* committed pages */
459 struct buffer_page *reader_page;
460 unsigned long lost_events;
461 unsigned long last_overrun;
462 local_t entries_bytes;
463 local_t commit_overrun;
464 local_t overrun;
465 local_t entries;
466 local_t committing;
467 local_t commits;
468 unsigned long read;
469 unsigned long read_bytes;
470 u64 write_stamp;
471 u64 read_stamp;
472 /* ring buffer pages to update, > 0 to add, < 0 to remove */
473 int nr_pages_to_update;
474 struct list_head new_pages; /* new pages to add */
475 struct work_struct update_pages_work;
476 struct completion update_done;
477};
478
479struct ring_buffer {
480 unsigned flags;
481 int cpus;
482 atomic_t record_disabled;
483 atomic_t resize_disabled;
484 cpumask_var_t cpumask;
485
486 struct lock_class_key *reader_lock_key;
487
488 struct mutex mutex;
489
490 struct ring_buffer_per_cpu **buffers;
491
492#ifdef CONFIG_HOTPLUG_CPU
493 struct notifier_block cpu_notify;
494#endif
495 u64 (*clock)(void);
496};
497
498struct ring_buffer_iter {
499 struct ring_buffer_per_cpu *cpu_buffer;
500 unsigned long head;
501 struct buffer_page *head_page;
502 struct buffer_page *cache_reader_page;
503 unsigned long cache_read;
504 u64 read_stamp;
505};
506
507/* buffer may be either ring_buffer or ring_buffer_per_cpu */
508#define RB_WARN_ON(b, cond) \
509 ({ \
510 int _____ret = unlikely(cond); \
511 if (_____ret) { \
512 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
513 struct ring_buffer_per_cpu *__b = \
514 (void *)b; \
515 atomic_inc(&__b->buffer->record_disabled); \
516 } else \
517 atomic_inc(&b->record_disabled); \
518 WARN_ON(1); \
519 } \
520 _____ret; \
521 })
522
523/* Up this if you want to test the TIME_EXTENTS and normalization */
524#define DEBUG_SHIFT 0
525
526static inline u64 rb_time_stamp(struct ring_buffer *buffer)
527{
528 /* shift to debug/test normalization and TIME_EXTENTS */
529 return buffer->clock() << DEBUG_SHIFT;
530}
531
532u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
533{
534 u64 time;
535
536 preempt_disable_notrace();
537 time = rb_time_stamp(buffer);
538 preempt_enable_no_resched_notrace();
539
540 return time;
541}
542EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
543
544void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
545 int cpu, u64 *ts)
546{
547 /* Just stupid testing the normalize function and deltas */
548 *ts >>= DEBUG_SHIFT;
549}
550EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
551
552/*
553 * Making the ring buffer lockless makes things tricky.
554 * Although writes only happen on the CPU that they are on,
555 * and they only need to worry about interrupts. Reads can
556 * happen on any CPU.
557 *
558 * The reader page is always off the ring buffer, but when the
559 * reader finishes with a page, it needs to swap its page with
560 * a new one from the buffer. The reader needs to take from
561 * the head (writes go to the tail). But if a writer is in overwrite
562 * mode and wraps, it must push the head page forward.
563 *
564 * Here lies the problem.
565 *
566 * The reader must be careful to replace only the head page, and
567 * not another one. As described at the top of the file in the
568 * ASCII art, the reader sets its old page to point to the next
569 * page after head. It then sets the page after head to point to
570 * the old reader page. But if the writer moves the head page
571 * during this operation, the reader could end up with the tail.
572 *
573 * We use cmpxchg to help prevent this race. We also do something
574 * special with the page before head. We set the LSB to 1.
575 *
576 * When the writer must push the page forward, it will clear the
577 * bit that points to the head page, move the head, and then set
578 * the bit that points to the new head page.
579 *
580 * We also don't want an interrupt coming in and moving the head
581 * page on another writer. Thus we use the second LSB to catch
582 * that too. Thus:
583 *
584 * head->list->prev->next bit 1 bit 0
585 * ------- -------
586 * Normal page 0 0
587 * Points to head page 0 1
588 * New head page 1 0
589 *
590 * Note we can not trust the prev pointer of the head page, because:
591 *
592 * +----+ +-----+ +-----+
593 * | |------>| T |---X--->| N |
594 * | |<------| | | |
595 * +----+ +-----+ +-----+
596 * ^ ^ |
597 * | +-----+ | |
598 * +----------| R |----------+ |
599 * | |<-----------+
600 * +-----+
601 *
602 * Key: ---X--> HEAD flag set in pointer
603 * T Tail page
604 * R Reader page
605 * N Next page
606 *
607 * (see __rb_reserve_next() to see where this happens)
608 *
609 * What the above shows is that the reader just swapped out
610 * the reader page with a page in the buffer, but before it
611 * could make the new header point back to the new page added
612 * it was preempted by a writer. The writer moved forward onto
613 * the new page added by the reader and is about to move forward
614 * again.
615 *
616 * You can see, it is legitimate for the previous pointer of
617 * the head (or any page) not to point back to itself. But only
618 * temporarially.
619 */
620
621#define RB_PAGE_NORMAL 0UL
622#define RB_PAGE_HEAD 1UL
623#define RB_PAGE_UPDATE 2UL
624
625
626#define RB_FLAG_MASK 3UL
627
628/* PAGE_MOVED is not part of the mask */
629#define RB_PAGE_MOVED 4UL
630
631/*
632 * rb_list_head - remove any bit
633 */
634static struct list_head *rb_list_head(struct list_head *list)
635{
636 unsigned long val = (unsigned long)list;
637
638 return (struct list_head *)(val & ~RB_FLAG_MASK);
639}
640
641/*
642 * rb_is_head_page - test if the given page is the head page
643 *
644 * Because the reader may move the head_page pointer, we can
645 * not trust what the head page is (it may be pointing to
646 * the reader page). But if the next page is a header page,
647 * its flags will be non zero.
648 */
649static inline int
650rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
651 struct buffer_page *page, struct list_head *list)
652{
653 unsigned long val;
654
655 val = (unsigned long)list->next;
656
657 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
658 return RB_PAGE_MOVED;
659
660 return val & RB_FLAG_MASK;
661}
662
663/*
664 * rb_is_reader_page
665 *
666 * The unique thing about the reader page, is that, if the
667 * writer is ever on it, the previous pointer never points
668 * back to the reader page.
669 */
670static int rb_is_reader_page(struct buffer_page *page)
671{
672 struct list_head *list = page->list.prev;
673
674 return rb_list_head(list->next) != &page->list;
675}
676
677/*
678 * rb_set_list_to_head - set a list_head to be pointing to head.
679 */
680static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
681 struct list_head *list)
682{
683 unsigned long *ptr;
684
685 ptr = (unsigned long *)&list->next;
686 *ptr |= RB_PAGE_HEAD;
687 *ptr &= ~RB_PAGE_UPDATE;
688}
689
690/*
691 * rb_head_page_activate - sets up head page
692 */
693static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
694{
695 struct buffer_page *head;
696
697 head = cpu_buffer->head_page;
698 if (!head)
699 return;
700
701 /*
702 * Set the previous list pointer to have the HEAD flag.
703 */
704 rb_set_list_to_head(cpu_buffer, head->list.prev);
705}
706
707static void rb_list_head_clear(struct list_head *list)
708{
709 unsigned long *ptr = (unsigned long *)&list->next;
710
711 *ptr &= ~RB_FLAG_MASK;
712}
713
714/*
715 * rb_head_page_dactivate - clears head page ptr (for free list)
716 */
717static void
718rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
719{
720 struct list_head *hd;
721
722 /* Go through the whole list and clear any pointers found. */
723 rb_list_head_clear(cpu_buffer->pages);
724
725 list_for_each(hd, cpu_buffer->pages)
726 rb_list_head_clear(hd);
727}
728
729static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
730 struct buffer_page *head,
731 struct buffer_page *prev,
732 int old_flag, int new_flag)
733{
734 struct list_head *list;
735 unsigned long val = (unsigned long)&head->list;
736 unsigned long ret;
737
738 list = &prev->list;
739
740 val &= ~RB_FLAG_MASK;
741
742 ret = cmpxchg((unsigned long *)&list->next,
743 val | old_flag, val | new_flag);
744
745 /* check if the reader took the page */
746 if ((ret & ~RB_FLAG_MASK) != val)
747 return RB_PAGE_MOVED;
748
749 return ret & RB_FLAG_MASK;
750}
751
752static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
753 struct buffer_page *head,
754 struct buffer_page *prev,
755 int old_flag)
756{
757 return rb_head_page_set(cpu_buffer, head, prev,
758 old_flag, RB_PAGE_UPDATE);
759}
760
761static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
762 struct buffer_page *head,
763 struct buffer_page *prev,
764 int old_flag)
765{
766 return rb_head_page_set(cpu_buffer, head, prev,
767 old_flag, RB_PAGE_HEAD);
768}
769
770static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
771 struct buffer_page *head,
772 struct buffer_page *prev,
773 int old_flag)
774{
775 return rb_head_page_set(cpu_buffer, head, prev,
776 old_flag, RB_PAGE_NORMAL);
777}
778
779static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
780 struct buffer_page **bpage)
781{
782 struct list_head *p = rb_list_head((*bpage)->list.next);
783
784 *bpage = list_entry(p, struct buffer_page, list);
785}
786
787static struct buffer_page *
788rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
789{
790 struct buffer_page *head;
791 struct buffer_page *page;
792 struct list_head *list;
793 int i;
794
795 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
796 return NULL;
797
798 /* sanity check */
799 list = cpu_buffer->pages;
800 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
801 return NULL;
802
803 page = head = cpu_buffer->head_page;
804 /*
805 * It is possible that the writer moves the header behind
806 * where we started, and we miss in one loop.
807 * A second loop should grab the header, but we'll do
808 * three loops just because I'm paranoid.
809 */
810 for (i = 0; i < 3; i++) {
811 do {
812 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
813 cpu_buffer->head_page = page;
814 return page;
815 }
816 rb_inc_page(cpu_buffer, &page);
817 } while (page != head);
818 }
819
820 RB_WARN_ON(cpu_buffer, 1);
821
822 return NULL;
823}
824
825static int rb_head_page_replace(struct buffer_page *old,
826 struct buffer_page *new)
827{
828 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
829 unsigned long val;
830 unsigned long ret;
831
832 val = *ptr & ~RB_FLAG_MASK;
833 val |= RB_PAGE_HEAD;
834
835 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
836
837 return ret == val;
838}
839
840/*
841 * rb_tail_page_update - move the tail page forward
842 *
843 * Returns 1 if moved tail page, 0 if someone else did.
844 */
845static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
846 struct buffer_page *tail_page,
847 struct buffer_page *next_page)
848{
849 struct buffer_page *old_tail;
850 unsigned long old_entries;
851 unsigned long old_write;
852 int ret = 0;
853
854 /*
855 * The tail page now needs to be moved forward.
856 *
857 * We need to reset the tail page, but without messing
858 * with possible erasing of data brought in by interrupts
859 * that have moved the tail page and are currently on it.
860 *
861 * We add a counter to the write field to denote this.
862 */
863 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
864 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
865
866 /*
867 * Just make sure we have seen our old_write and synchronize
868 * with any interrupts that come in.
869 */
870 barrier();
871
872 /*
873 * If the tail page is still the same as what we think
874 * it is, then it is up to us to update the tail
875 * pointer.
876 */
877 if (tail_page == cpu_buffer->tail_page) {
878 /* Zero the write counter */
879 unsigned long val = old_write & ~RB_WRITE_MASK;
880 unsigned long eval = old_entries & ~RB_WRITE_MASK;
881
882 /*
883 * This will only succeed if an interrupt did
884 * not come in and change it. In which case, we
885 * do not want to modify it.
886 *
887 * We add (void) to let the compiler know that we do not care
888 * about the return value of these functions. We use the
889 * cmpxchg to only update if an interrupt did not already
890 * do it for us. If the cmpxchg fails, we don't care.
891 */
892 (void)local_cmpxchg(&next_page->write, old_write, val);
893 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
894
895 /*
896 * No need to worry about races with clearing out the commit.
897 * it only can increment when a commit takes place. But that
898 * only happens in the outer most nested commit.
899 */
900 local_set(&next_page->page->commit, 0);
901
902 old_tail = cmpxchg(&cpu_buffer->tail_page,
903 tail_page, next_page);
904
905 if (old_tail == tail_page)
906 ret = 1;
907 }
908
909 return ret;
910}
911
912static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
913 struct buffer_page *bpage)
914{
915 unsigned long val = (unsigned long)bpage;
916
917 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
918 return 1;
919
920 return 0;
921}
922
923/**
924 * rb_check_list - make sure a pointer to a list has the last bits zero
925 */
926static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
927 struct list_head *list)
928{
929 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
930 return 1;
931 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
932 return 1;
933 return 0;
934}
935
936/**
937 * check_pages - integrity check of buffer pages
938 * @cpu_buffer: CPU buffer with pages to test
939 *
940 * As a safety measure we check to make sure the data pages have not
941 * been corrupted.
942 */
943static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
944{
945 struct list_head *head = cpu_buffer->pages;
946 struct buffer_page *bpage, *tmp;
947
948 /* Reset the head page if it exists */
949 if (cpu_buffer->head_page)
950 rb_set_head_page(cpu_buffer);
951
952 rb_head_page_deactivate(cpu_buffer);
953
954 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
955 return -1;
956 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
957 return -1;
958
959 if (rb_check_list(cpu_buffer, head))
960 return -1;
961
962 list_for_each_entry_safe(bpage, tmp, head, list) {
963 if (RB_WARN_ON(cpu_buffer,
964 bpage->list.next->prev != &bpage->list))
965 return -1;
966 if (RB_WARN_ON(cpu_buffer,
967 bpage->list.prev->next != &bpage->list))
968 return -1;
969 if (rb_check_list(cpu_buffer, &bpage->list))
970 return -1;
971 }
972
973 rb_head_page_activate(cpu_buffer);
974
975 return 0;
976}
977
978static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
979{
980 int i;
981 struct buffer_page *bpage, *tmp;
982
983 for (i = 0; i < nr_pages; i++) {
984 struct page *page;
985 /*
986 * __GFP_NORETRY flag makes sure that the allocation fails
987 * gracefully without invoking oom-killer and the system is
988 * not destabilized.
989 */
990 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
991 GFP_KERNEL | __GFP_NORETRY,
992 cpu_to_node(cpu));
993 if (!bpage)
994 goto free_pages;
995
996 list_add(&bpage->list, pages);
997
998 page = alloc_pages_node(cpu_to_node(cpu),
999 GFP_KERNEL | __GFP_NORETRY, 0);
1000 if (!page)
1001 goto free_pages;
1002 bpage->page = page_address(page);
1003 rb_init_page(bpage->page);
1004 }
1005
1006 return 0;
1007
1008free_pages:
1009 list_for_each_entry_safe(bpage, tmp, pages, list) {
1010 list_del_init(&bpage->list);
1011 free_buffer_page(bpage);
1012 }
1013
1014 return -ENOMEM;
1015}
1016
1017static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1018 unsigned nr_pages)
1019{
1020 LIST_HEAD(pages);
1021
1022 WARN_ON(!nr_pages);
1023
1024 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1025 return -ENOMEM;
1026
1027 /*
1028 * The ring buffer page list is a circular list that does not
1029 * start and end with a list head. All page list items point to
1030 * other pages.
1031 */
1032 cpu_buffer->pages = pages.next;
1033 list_del(&pages);
1034
1035 cpu_buffer->nr_pages = nr_pages;
1036
1037 rb_check_pages(cpu_buffer);
1038
1039 return 0;
1040}
1041
1042static struct ring_buffer_per_cpu *
1043rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
1044{
1045 struct ring_buffer_per_cpu *cpu_buffer;
1046 struct buffer_page *bpage;
1047 struct page *page;
1048 int ret;
1049
1050 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1051 GFP_KERNEL, cpu_to_node(cpu));
1052 if (!cpu_buffer)
1053 return NULL;
1054
1055 cpu_buffer->cpu = cpu;
1056 cpu_buffer->buffer = buffer;
1057 raw_spin_lock_init(&cpu_buffer->reader_lock);
1058 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1059 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1060 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1061 init_completion(&cpu_buffer->update_done);
1062
1063 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1064 GFP_KERNEL, cpu_to_node(cpu));
1065 if (!bpage)
1066 goto fail_free_buffer;
1067
1068 rb_check_bpage(cpu_buffer, bpage);
1069
1070 cpu_buffer->reader_page = bpage;
1071 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1072 if (!page)
1073 goto fail_free_reader;
1074 bpage->page = page_address(page);
1075 rb_init_page(bpage->page);
1076
1077 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1078 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1079
1080 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1081 if (ret < 0)
1082 goto fail_free_reader;
1083
1084 cpu_buffer->head_page
1085 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1086 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1087
1088 rb_head_page_activate(cpu_buffer);
1089
1090 return cpu_buffer;
1091
1092 fail_free_reader:
1093 free_buffer_page(cpu_buffer->reader_page);
1094
1095 fail_free_buffer:
1096 kfree(cpu_buffer);
1097 return NULL;
1098}
1099
1100static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1101{
1102 struct list_head *head = cpu_buffer->pages;
1103 struct buffer_page *bpage, *tmp;
1104
1105 free_buffer_page(cpu_buffer->reader_page);
1106
1107 rb_head_page_deactivate(cpu_buffer);
1108
1109 if (head) {
1110 list_for_each_entry_safe(bpage, tmp, head, list) {
1111 list_del_init(&bpage->list);
1112 free_buffer_page(bpage);
1113 }
1114 bpage = list_entry(head, struct buffer_page, list);
1115 free_buffer_page(bpage);
1116 }
1117
1118 kfree(cpu_buffer);
1119}
1120
1121#ifdef CONFIG_HOTPLUG_CPU
1122static int rb_cpu_notify(struct notifier_block *self,
1123 unsigned long action, void *hcpu);
1124#endif
1125
1126/**
1127 * ring_buffer_alloc - allocate a new ring_buffer
1128 * @size: the size in bytes per cpu that is needed.
1129 * @flags: attributes to set for the ring buffer.
1130 *
1131 * Currently the only flag that is available is the RB_FL_OVERWRITE
1132 * flag. This flag means that the buffer will overwrite old data
1133 * when the buffer wraps. If this flag is not set, the buffer will
1134 * drop data when the tail hits the head.
1135 */
1136struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1137 struct lock_class_key *key)
1138{
1139 struct ring_buffer *buffer;
1140 int bsize;
1141 int cpu, nr_pages;
1142
1143 /* keep it in its own cache line */
1144 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1145 GFP_KERNEL);
1146 if (!buffer)
1147 return NULL;
1148
1149 if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1150 goto fail_free_buffer;
1151
1152 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1153 buffer->flags = flags;
1154 buffer->clock = trace_clock_local;
1155 buffer->reader_lock_key = key;
1156
1157 /* need at least two pages */
1158 if (nr_pages < 2)
1159 nr_pages = 2;
1160
1161 /*
1162 * In case of non-hotplug cpu, if the ring-buffer is allocated
1163 * in early initcall, it will not be notified of secondary cpus.
1164 * In that off case, we need to allocate for all possible cpus.
1165 */
1166#ifdef CONFIG_HOTPLUG_CPU
1167 get_online_cpus();
1168 cpumask_copy(buffer->cpumask, cpu_online_mask);
1169#else
1170 cpumask_copy(buffer->cpumask, cpu_possible_mask);
1171#endif
1172 buffer->cpus = nr_cpu_ids;
1173
1174 bsize = sizeof(void *) * nr_cpu_ids;
1175 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1176 GFP_KERNEL);
1177 if (!buffer->buffers)
1178 goto fail_free_cpumask;
1179
1180 for_each_buffer_cpu(buffer, cpu) {
1181 buffer->buffers[cpu] =
1182 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1183 if (!buffer->buffers[cpu])
1184 goto fail_free_buffers;
1185 }
1186
1187#ifdef CONFIG_HOTPLUG_CPU
1188 buffer->cpu_notify.notifier_call = rb_cpu_notify;
1189 buffer->cpu_notify.priority = 0;
1190 register_cpu_notifier(&buffer->cpu_notify);
1191#endif
1192
1193 put_online_cpus();
1194 mutex_init(&buffer->mutex);
1195
1196 return buffer;
1197
1198 fail_free_buffers:
1199 for_each_buffer_cpu(buffer, cpu) {
1200 if (buffer->buffers[cpu])
1201 rb_free_cpu_buffer(buffer->buffers[cpu]);
1202 }
1203 kfree(buffer->buffers);
1204
1205 fail_free_cpumask:
1206 free_cpumask_var(buffer->cpumask);
1207 put_online_cpus();
1208
1209 fail_free_buffer:
1210 kfree(buffer);
1211 return NULL;
1212}
1213EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1214
1215/**
1216 * ring_buffer_free - free a ring buffer.
1217 * @buffer: the buffer to free.
1218 */
1219void
1220ring_buffer_free(struct ring_buffer *buffer)
1221{
1222 int cpu;
1223
1224 get_online_cpus();
1225
1226#ifdef CONFIG_HOTPLUG_CPU
1227 unregister_cpu_notifier(&buffer->cpu_notify);
1228#endif
1229
1230 for_each_buffer_cpu(buffer, cpu)
1231 rb_free_cpu_buffer(buffer->buffers[cpu]);
1232
1233 put_online_cpus();
1234
1235 kfree(buffer->buffers);
1236 free_cpumask_var(buffer->cpumask);
1237
1238 kfree(buffer);
1239}
1240EXPORT_SYMBOL_GPL(ring_buffer_free);
1241
1242void ring_buffer_set_clock(struct ring_buffer *buffer,
1243 u64 (*clock)(void))
1244{
1245 buffer->clock = clock;
1246}
1247
1248static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1249
1250static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1251{
1252 return local_read(&bpage->entries) & RB_WRITE_MASK;
1253}
1254
1255static inline unsigned long rb_page_write(struct buffer_page *bpage)
1256{
1257 return local_read(&bpage->write) & RB_WRITE_MASK;
1258}
1259
1260static int
1261rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
1262{
1263 struct list_head *tail_page, *to_remove, *next_page;
1264 struct buffer_page *to_remove_page, *tmp_iter_page;
1265 struct buffer_page *last_page, *first_page;
1266 unsigned int nr_removed;
1267 unsigned long head_bit;
1268 int page_entries;
1269
1270 head_bit = 0;
1271
1272 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1273 atomic_inc(&cpu_buffer->record_disabled);
1274 /*
1275 * We don't race with the readers since we have acquired the reader
1276 * lock. We also don't race with writers after disabling recording.
1277 * This makes it easy to figure out the first and the last page to be
1278 * removed from the list. We unlink all the pages in between including
1279 * the first and last pages. This is done in a busy loop so that we
1280 * lose the least number of traces.
1281 * The pages are freed after we restart recording and unlock readers.
1282 */
1283 tail_page = &cpu_buffer->tail_page->list;
1284
1285 /*
1286 * tail page might be on reader page, we remove the next page
1287 * from the ring buffer
1288 */
1289 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1290 tail_page = rb_list_head(tail_page->next);
1291 to_remove = tail_page;
1292
1293 /* start of pages to remove */
1294 first_page = list_entry(rb_list_head(to_remove->next),
1295 struct buffer_page, list);
1296
1297 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1298 to_remove = rb_list_head(to_remove)->next;
1299 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1300 }
1301
1302 next_page = rb_list_head(to_remove)->next;
1303
1304 /*
1305 * Now we remove all pages between tail_page and next_page.
1306 * Make sure that we have head_bit value preserved for the
1307 * next page
1308 */
1309 tail_page->next = (struct list_head *)((unsigned long)next_page |
1310 head_bit);
1311 next_page = rb_list_head(next_page);
1312 next_page->prev = tail_page;
1313
1314 /* make sure pages points to a valid page in the ring buffer */
1315 cpu_buffer->pages = next_page;
1316
1317 /* update head page */
1318 if (head_bit)
1319 cpu_buffer->head_page = list_entry(next_page,
1320 struct buffer_page, list);
1321
1322 /*
1323 * change read pointer to make sure any read iterators reset
1324 * themselves
1325 */
1326 cpu_buffer->read = 0;
1327
1328 /* pages are removed, resume tracing and then free the pages */
1329 atomic_dec(&cpu_buffer->record_disabled);
1330 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1331
1332 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1333
1334 /* last buffer page to remove */
1335 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1336 list);
1337 tmp_iter_page = first_page;
1338
1339 do {
1340 to_remove_page = tmp_iter_page;
1341 rb_inc_page(cpu_buffer, &tmp_iter_page);
1342
1343 /* update the counters */
1344 page_entries = rb_page_entries(to_remove_page);
1345 if (page_entries) {
1346 /*
1347 * If something was added to this page, it was full
1348 * since it is not the tail page. So we deduct the
1349 * bytes consumed in ring buffer from here.
1350 * Increment overrun to account for the lost events.
1351 */
1352 local_add(page_entries, &cpu_buffer->overrun);
1353 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1354 }
1355
1356 /*
1357 * We have already removed references to this list item, just
1358 * free up the buffer_page and its page
1359 */
1360 free_buffer_page(to_remove_page);
1361 nr_removed--;
1362
1363 } while (to_remove_page != last_page);
1364
1365 RB_WARN_ON(cpu_buffer, nr_removed);
1366
1367 return nr_removed == 0;
1368}
1369
1370static int
1371rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1372{
1373 struct list_head *pages = &cpu_buffer->new_pages;
1374 int retries, success;
1375
1376 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1377 /*
1378 * We are holding the reader lock, so the reader page won't be swapped
1379 * in the ring buffer. Now we are racing with the writer trying to
1380 * move head page and the tail page.
1381 * We are going to adapt the reader page update process where:
1382 * 1. We first splice the start and end of list of new pages between
1383 * the head page and its previous page.
1384 * 2. We cmpxchg the prev_page->next to point from head page to the
1385 * start of new pages list.
1386 * 3. Finally, we update the head->prev to the end of new list.
1387 *
1388 * We will try this process 10 times, to make sure that we don't keep
1389 * spinning.
1390 */
1391 retries = 10;
1392 success = 0;
1393 while (retries--) {
1394 struct list_head *head_page, *prev_page, *r;
1395 struct list_head *last_page, *first_page;
1396 struct list_head *head_page_with_bit;
1397
1398 head_page = &rb_set_head_page(cpu_buffer)->list;
1399 prev_page = head_page->prev;
1400
1401 first_page = pages->next;
1402 last_page = pages->prev;
1403
1404 head_page_with_bit = (struct list_head *)
1405 ((unsigned long)head_page | RB_PAGE_HEAD);
1406
1407 last_page->next = head_page_with_bit;
1408 first_page->prev = prev_page;
1409
1410 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1411
1412 if (r == head_page_with_bit) {
1413 /*
1414 * yay, we replaced the page pointer to our new list,
1415 * now, we just have to update to head page's prev
1416 * pointer to point to end of list
1417 */
1418 head_page->prev = last_page;
1419 success = 1;
1420 break;
1421 }
1422 }
1423
1424 if (success)
1425 INIT_LIST_HEAD(pages);
1426 /*
1427 * If we weren't successful in adding in new pages, warn and stop
1428 * tracing
1429 */
1430 RB_WARN_ON(cpu_buffer, !success);
1431 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1432
1433 /* free pages if they weren't inserted */
1434 if (!success) {
1435 struct buffer_page *bpage, *tmp;
1436 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1437 list) {
1438 list_del_init(&bpage->list);
1439 free_buffer_page(bpage);
1440 }
1441 }
1442 return success;
1443}
1444
1445static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1446{
1447 int success;
1448
1449 if (cpu_buffer->nr_pages_to_update > 0)
1450 success = rb_insert_pages(cpu_buffer);
1451 else
1452 success = rb_remove_pages(cpu_buffer,
1453 -cpu_buffer->nr_pages_to_update);
1454
1455 if (success)
1456 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1457}
1458
1459static void update_pages_handler(struct work_struct *work)
1460{
1461 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1462 struct ring_buffer_per_cpu, update_pages_work);
1463 rb_update_pages(cpu_buffer);
1464 complete(&cpu_buffer->update_done);
1465}
1466
1467/**
1468 * ring_buffer_resize - resize the ring buffer
1469 * @buffer: the buffer to resize.
1470 * @size: the new size.
1471 *
1472 * Minimum size is 2 * BUF_PAGE_SIZE.
1473 *
1474 * Returns 0 on success and < 0 on failure.
1475 */
1476int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1477 int cpu_id)
1478{
1479 struct ring_buffer_per_cpu *cpu_buffer;
1480 unsigned nr_pages;
1481 int cpu, err = 0;
1482
1483 /*
1484 * Always succeed at resizing a non-existent buffer:
1485 */
1486 if (!buffer)
1487 return size;
1488
1489 /* Make sure the requested buffer exists */
1490 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1491 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1492 return size;
1493
1494 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1495 size *= BUF_PAGE_SIZE;
1496
1497 /* we need a minimum of two pages */
1498 if (size < BUF_PAGE_SIZE * 2)
1499 size = BUF_PAGE_SIZE * 2;
1500
1501 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1502
1503 /*
1504 * Don't succeed if resizing is disabled, as a reader might be
1505 * manipulating the ring buffer and is expecting a sane state while
1506 * this is true.
1507 */
1508 if (atomic_read(&buffer->resize_disabled))
1509 return -EBUSY;
1510
1511 /* prevent another thread from changing buffer sizes */
1512 mutex_lock(&buffer->mutex);
1513
1514 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1515 /* calculate the pages to update */
1516 for_each_buffer_cpu(buffer, cpu) {
1517 cpu_buffer = buffer->buffers[cpu];
1518
1519 cpu_buffer->nr_pages_to_update = nr_pages -
1520 cpu_buffer->nr_pages;
1521 /*
1522 * nothing more to do for removing pages or no update
1523 */
1524 if (cpu_buffer->nr_pages_to_update <= 0)
1525 continue;
1526 /*
1527 * to add pages, make sure all new pages can be
1528 * allocated without receiving ENOMEM
1529 */
1530 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1531 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1532 &cpu_buffer->new_pages, cpu)) {
1533 /* not enough memory for new pages */
1534 err = -ENOMEM;
1535 goto out_err;
1536 }
1537 }
1538
1539 get_online_cpus();
1540 /*
1541 * Fire off all the required work handlers
1542 * We can't schedule on offline CPUs, but it's not necessary
1543 * since we can change their buffer sizes without any race.
1544 */
1545 for_each_buffer_cpu(buffer, cpu) {
1546 cpu_buffer = buffer->buffers[cpu];
1547 if (!cpu_buffer->nr_pages_to_update)
1548 continue;
1549
1550 if (cpu_online(cpu))
1551 schedule_work_on(cpu,
1552 &cpu_buffer->update_pages_work);
1553 else
1554 rb_update_pages(cpu_buffer);
1555 }
1556
1557 /* wait for all the updates to complete */
1558 for_each_buffer_cpu(buffer, cpu) {
1559 cpu_buffer = buffer->buffers[cpu];
1560 if (!cpu_buffer->nr_pages_to_update)
1561 continue;
1562
1563 if (cpu_online(cpu))
1564 wait_for_completion(&cpu_buffer->update_done);
1565 cpu_buffer->nr_pages_to_update = 0;
1566 }
1567
1568 put_online_cpus();
1569 } else {
1570 cpu_buffer = buffer->buffers[cpu_id];
1571
1572 if (nr_pages == cpu_buffer->nr_pages)
1573 goto out;
1574
1575 cpu_buffer->nr_pages_to_update = nr_pages -
1576 cpu_buffer->nr_pages;
1577
1578 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1579 if (cpu_buffer->nr_pages_to_update > 0 &&
1580 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1581 &cpu_buffer->new_pages, cpu_id)) {
1582 err = -ENOMEM;
1583 goto out_err;
1584 }
1585
1586 get_online_cpus();
1587
1588 if (cpu_online(cpu_id)) {
1589 schedule_work_on(cpu_id,
1590 &cpu_buffer->update_pages_work);
1591 wait_for_completion(&cpu_buffer->update_done);
1592 } else
1593 rb_update_pages(cpu_buffer);
1594
1595 cpu_buffer->nr_pages_to_update = 0;
1596 put_online_cpus();
1597 }
1598
1599 out:
1600 /*
1601 * The ring buffer resize can happen with the ring buffer
1602 * enabled, so that the update disturbs the tracing as little
1603 * as possible. But if the buffer is disabled, we do not need
1604 * to worry about that, and we can take the time to verify
1605 * that the buffer is not corrupt.
1606 */
1607 if (atomic_read(&buffer->record_disabled)) {
1608 atomic_inc(&buffer->record_disabled);
1609 /*
1610 * Even though the buffer was disabled, we must make sure
1611 * that it is truly disabled before calling rb_check_pages.
1612 * There could have been a race between checking
1613 * record_disable and incrementing it.
1614 */
1615 synchronize_sched();
1616 for_each_buffer_cpu(buffer, cpu) {
1617 cpu_buffer = buffer->buffers[cpu];
1618 rb_check_pages(cpu_buffer);
1619 }
1620 atomic_dec(&buffer->record_disabled);
1621 }
1622
1623 mutex_unlock(&buffer->mutex);
1624 return size;
1625
1626 out_err:
1627 for_each_buffer_cpu(buffer, cpu) {
1628 struct buffer_page *bpage, *tmp;
1629
1630 cpu_buffer = buffer->buffers[cpu];
1631 cpu_buffer->nr_pages_to_update = 0;
1632
1633 if (list_empty(&cpu_buffer->new_pages))
1634 continue;
1635
1636 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1637 list) {
1638 list_del_init(&bpage->list);
1639 free_buffer_page(bpage);
1640 }
1641 }
1642 mutex_unlock(&buffer->mutex);
1643 return err;
1644}
1645EXPORT_SYMBOL_GPL(ring_buffer_resize);
1646
1647void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1648{
1649 mutex_lock(&buffer->mutex);
1650 if (val)
1651 buffer->flags |= RB_FL_OVERWRITE;
1652 else
1653 buffer->flags &= ~RB_FL_OVERWRITE;
1654 mutex_unlock(&buffer->mutex);
1655}
1656EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1657
1658static inline void *
1659__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
1660{
1661 return bpage->data + index;
1662}
1663
1664static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1665{
1666 return bpage->page->data + index;
1667}
1668
1669static inline struct ring_buffer_event *
1670rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1671{
1672 return __rb_page_index(cpu_buffer->reader_page,
1673 cpu_buffer->reader_page->read);
1674}
1675
1676static inline struct ring_buffer_event *
1677rb_iter_head_event(struct ring_buffer_iter *iter)
1678{
1679 return __rb_page_index(iter->head_page, iter->head);
1680}
1681
1682static inline unsigned rb_page_commit(struct buffer_page *bpage)
1683{
1684 return local_read(&bpage->page->commit);
1685}
1686
1687/* Size is determined by what has been committed */
1688static inline unsigned rb_page_size(struct buffer_page *bpage)
1689{
1690 return rb_page_commit(bpage);
1691}
1692
1693static inline unsigned
1694rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1695{
1696 return rb_page_commit(cpu_buffer->commit_page);
1697}
1698
1699static inline unsigned
1700rb_event_index(struct ring_buffer_event *event)
1701{
1702 unsigned long addr = (unsigned long)event;
1703
1704 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1705}
1706
1707static inline int
1708rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1709 struct ring_buffer_event *event)
1710{
1711 unsigned long addr = (unsigned long)event;
1712 unsigned long index;
1713
1714 index = rb_event_index(event);
1715 addr &= PAGE_MASK;
1716
1717 return cpu_buffer->commit_page->page == (void *)addr &&
1718 rb_commit_index(cpu_buffer) == index;
1719}
1720
1721static void
1722rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1723{
1724 unsigned long max_count;
1725
1726 /*
1727 * We only race with interrupts and NMIs on this CPU.
1728 * If we own the commit event, then we can commit
1729 * all others that interrupted us, since the interruptions
1730 * are in stack format (they finish before they come
1731 * back to us). This allows us to do a simple loop to
1732 * assign the commit to the tail.
1733 */
1734 again:
1735 max_count = cpu_buffer->nr_pages * 100;
1736
1737 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
1738 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
1739 return;
1740 if (RB_WARN_ON(cpu_buffer,
1741 rb_is_reader_page(cpu_buffer->tail_page)))
1742 return;
1743 local_set(&cpu_buffer->commit_page->page->commit,
1744 rb_page_write(cpu_buffer->commit_page));
1745 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1746 cpu_buffer->write_stamp =
1747 cpu_buffer->commit_page->page->time_stamp;
1748 /* add barrier to keep gcc from optimizing too much */
1749 barrier();
1750 }
1751 while (rb_commit_index(cpu_buffer) !=
1752 rb_page_write(cpu_buffer->commit_page)) {
1753
1754 local_set(&cpu_buffer->commit_page->page->commit,
1755 rb_page_write(cpu_buffer->commit_page));
1756 RB_WARN_ON(cpu_buffer,
1757 local_read(&cpu_buffer->commit_page->page->commit) &
1758 ~RB_WRITE_MASK);
1759 barrier();
1760 }
1761
1762 /* again, keep gcc from optimizing */
1763 barrier();
1764
1765 /*
1766 * If an interrupt came in just after the first while loop
1767 * and pushed the tail page forward, we will be left with
1768 * a dangling commit that will never go forward.
1769 */
1770 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1771 goto again;
1772}
1773
1774static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1775{
1776 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
1777 cpu_buffer->reader_page->read = 0;
1778}
1779
1780static void rb_inc_iter(struct ring_buffer_iter *iter)
1781{
1782 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1783
1784 /*
1785 * The iterator could be on the reader page (it starts there).
1786 * But the head could have moved, since the reader was
1787 * found. Check for this case and assign the iterator
1788 * to the head page instead of next.
1789 */
1790 if (iter->head_page == cpu_buffer->reader_page)
1791 iter->head_page = rb_set_head_page(cpu_buffer);
1792 else
1793 rb_inc_page(cpu_buffer, &iter->head_page);
1794
1795 iter->read_stamp = iter->head_page->page->time_stamp;
1796 iter->head = 0;
1797}
1798
1799/* Slow path, do not inline */
1800static noinline struct ring_buffer_event *
1801rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
1802{
1803 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
1804
1805 /* Not the first event on the page? */
1806 if (rb_event_index(event)) {
1807 event->time_delta = delta & TS_MASK;
1808 event->array[0] = delta >> TS_SHIFT;
1809 } else {
1810 /* nope, just zero it */
1811 event->time_delta = 0;
1812 event->array[0] = 0;
1813 }
1814
1815 return skip_time_extend(event);
1816}
1817
1818/**
1819 * ring_buffer_update_event - update event type and data
1820 * @event: the even to update
1821 * @type: the type of event
1822 * @length: the size of the event field in the ring buffer
1823 *
1824 * Update the type and data fields of the event. The length
1825 * is the actual size that is written to the ring buffer,
1826 * and with this, we can determine what to place into the
1827 * data field.
1828 */
1829static void
1830rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
1831 struct ring_buffer_event *event, unsigned length,
1832 int add_timestamp, u64 delta)
1833{
1834 /* Only a commit updates the timestamp */
1835 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
1836 delta = 0;
1837
1838 /*
1839 * If we need to add a timestamp, then we
1840 * add it to the start of the resevered space.
1841 */
1842 if (unlikely(add_timestamp)) {
1843 event = rb_add_time_stamp(event, delta);
1844 length -= RB_LEN_TIME_EXTEND;
1845 delta = 0;
1846 }
1847
1848 event->time_delta = delta;
1849 length -= RB_EVNT_HDR_SIZE;
1850 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
1851 event->type_len = 0;
1852 event->array[0] = length;
1853 } else
1854 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
1855}
1856
1857/*
1858 * rb_handle_head_page - writer hit the head page
1859 *
1860 * Returns: +1 to retry page
1861 * 0 to continue
1862 * -1 on error
1863 */
1864static int
1865rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1866 struct buffer_page *tail_page,
1867 struct buffer_page *next_page)
1868{
1869 struct buffer_page *new_head;
1870 int entries;
1871 int type;
1872 int ret;
1873
1874 entries = rb_page_entries(next_page);
1875
1876 /*
1877 * The hard part is here. We need to move the head
1878 * forward, and protect against both readers on
1879 * other CPUs and writers coming in via interrupts.
1880 */
1881 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1882 RB_PAGE_HEAD);
1883
1884 /*
1885 * type can be one of four:
1886 * NORMAL - an interrupt already moved it for us
1887 * HEAD - we are the first to get here.
1888 * UPDATE - we are the interrupt interrupting
1889 * a current move.
1890 * MOVED - a reader on another CPU moved the next
1891 * pointer to its reader page. Give up
1892 * and try again.
1893 */
1894
1895 switch (type) {
1896 case RB_PAGE_HEAD:
1897 /*
1898 * We changed the head to UPDATE, thus
1899 * it is our responsibility to update
1900 * the counters.
1901 */
1902 local_add(entries, &cpu_buffer->overrun);
1903 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1904
1905 /*
1906 * The entries will be zeroed out when we move the
1907 * tail page.
1908 */
1909
1910 /* still more to do */
1911 break;
1912
1913 case RB_PAGE_UPDATE:
1914 /*
1915 * This is an interrupt that interrupt the
1916 * previous update. Still more to do.
1917 */
1918 break;
1919 case RB_PAGE_NORMAL:
1920 /*
1921 * An interrupt came in before the update
1922 * and processed this for us.
1923 * Nothing left to do.
1924 */
1925 return 1;
1926 case RB_PAGE_MOVED:
1927 /*
1928 * The reader is on another CPU and just did
1929 * a swap with our next_page.
1930 * Try again.
1931 */
1932 return 1;
1933 default:
1934 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
1935 return -1;
1936 }
1937
1938 /*
1939 * Now that we are here, the old head pointer is
1940 * set to UPDATE. This will keep the reader from
1941 * swapping the head page with the reader page.
1942 * The reader (on another CPU) will spin till
1943 * we are finished.
1944 *
1945 * We just need to protect against interrupts
1946 * doing the job. We will set the next pointer
1947 * to HEAD. After that, we set the old pointer
1948 * to NORMAL, but only if it was HEAD before.
1949 * otherwise we are an interrupt, and only
1950 * want the outer most commit to reset it.
1951 */
1952 new_head = next_page;
1953 rb_inc_page(cpu_buffer, &new_head);
1954
1955 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
1956 RB_PAGE_NORMAL);
1957
1958 /*
1959 * Valid returns are:
1960 * HEAD - an interrupt came in and already set it.
1961 * NORMAL - One of two things:
1962 * 1) We really set it.
1963 * 2) A bunch of interrupts came in and moved
1964 * the page forward again.
1965 */
1966 switch (ret) {
1967 case RB_PAGE_HEAD:
1968 case RB_PAGE_NORMAL:
1969 /* OK */
1970 break;
1971 default:
1972 RB_WARN_ON(cpu_buffer, 1);
1973 return -1;
1974 }
1975
1976 /*
1977 * It is possible that an interrupt came in,
1978 * set the head up, then more interrupts came in
1979 * and moved it again. When we get back here,
1980 * the page would have been set to NORMAL but we
1981 * just set it back to HEAD.
1982 *
1983 * How do you detect this? Well, if that happened
1984 * the tail page would have moved.
1985 */
1986 if (ret == RB_PAGE_NORMAL) {
1987 /*
1988 * If the tail had moved passed next, then we need
1989 * to reset the pointer.
1990 */
1991 if (cpu_buffer->tail_page != tail_page &&
1992 cpu_buffer->tail_page != next_page)
1993 rb_head_page_set_normal(cpu_buffer, new_head,
1994 next_page,
1995 RB_PAGE_HEAD);
1996 }
1997
1998 /*
1999 * If this was the outer most commit (the one that
2000 * changed the original pointer from HEAD to UPDATE),
2001 * then it is up to us to reset it to NORMAL.
2002 */
2003 if (type == RB_PAGE_HEAD) {
2004 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2005 tail_page,
2006 RB_PAGE_UPDATE);
2007 if (RB_WARN_ON(cpu_buffer,
2008 ret != RB_PAGE_UPDATE))
2009 return -1;
2010 }
2011
2012 return 0;
2013}
2014
2015static unsigned rb_calculate_event_length(unsigned length)
2016{
2017 struct ring_buffer_event event; /* Used only for sizeof array */
2018
2019 /* zero length can cause confusions */
2020 if (!length)
2021 length = 1;
2022
2023 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2024 length += sizeof(event.array[0]);
2025
2026 length += RB_EVNT_HDR_SIZE;
2027 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2028
2029 return length;
2030}
2031
2032static inline void
2033rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2034 struct buffer_page *tail_page,
2035 unsigned long tail, unsigned long length)
2036{
2037 struct ring_buffer_event *event;
2038
2039 /*
2040 * Only the event that crossed the page boundary
2041 * must fill the old tail_page with padding.
2042 */
2043 if (tail >= BUF_PAGE_SIZE) {
2044 /*
2045 * If the page was filled, then we still need
2046 * to update the real_end. Reset it to zero
2047 * and the reader will ignore it.
2048 */
2049 if (tail == BUF_PAGE_SIZE)
2050 tail_page->real_end = 0;
2051
2052 local_sub(length, &tail_page->write);
2053 return;
2054 }
2055
2056 event = __rb_page_index(tail_page, tail);
2057 kmemcheck_annotate_bitfield(event, bitfield);
2058
2059 /* account for padding bytes */
2060 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2061
2062 /*
2063 * Save the original length to the meta data.
2064 * This will be used by the reader to add lost event
2065 * counter.
2066 */
2067 tail_page->real_end = tail;
2068
2069 /*
2070 * If this event is bigger than the minimum size, then
2071 * we need to be careful that we don't subtract the
2072 * write counter enough to allow another writer to slip
2073 * in on this page.
2074 * We put in a discarded commit instead, to make sure
2075 * that this space is not used again.
2076 *
2077 * If we are less than the minimum size, we don't need to
2078 * worry about it.
2079 */
2080 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2081 /* No room for any events */
2082
2083 /* Mark the rest of the page with padding */
2084 rb_event_set_padding(event);
2085
2086 /* Set the write back to the previous setting */
2087 local_sub(length, &tail_page->write);
2088 return;
2089 }
2090
2091 /* Put in a discarded event */
2092 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2093 event->type_len = RINGBUF_TYPE_PADDING;
2094 /* time delta must be non zero */
2095 event->time_delta = 1;
2096
2097 /* Set write to end of buffer */
2098 length = (tail + length) - BUF_PAGE_SIZE;
2099 local_sub(length, &tail_page->write);
2100}
2101
2102/*
2103 * This is the slow path, force gcc not to inline it.
2104 */
2105static noinline struct ring_buffer_event *
2106rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2107 unsigned long length, unsigned long tail,
2108 struct buffer_page *tail_page, u64 ts)
2109{
2110 struct buffer_page *commit_page = cpu_buffer->commit_page;
2111 struct ring_buffer *buffer = cpu_buffer->buffer;
2112 struct buffer_page *next_page;
2113 int ret;
2114
2115 next_page = tail_page;
2116
2117 rb_inc_page(cpu_buffer, &next_page);
2118
2119 /*
2120 * If for some reason, we had an interrupt storm that made
2121 * it all the way around the buffer, bail, and warn
2122 * about it.
2123 */
2124 if (unlikely(next_page == commit_page)) {
2125 local_inc(&cpu_buffer->commit_overrun);
2126 goto out_reset;
2127 }
2128
2129 /*
2130 * This is where the fun begins!
2131 *
2132 * We are fighting against races between a reader that
2133 * could be on another CPU trying to swap its reader
2134 * page with the buffer head.
2135 *
2136 * We are also fighting against interrupts coming in and
2137 * moving the head or tail on us as well.
2138 *
2139 * If the next page is the head page then we have filled
2140 * the buffer, unless the commit page is still on the
2141 * reader page.
2142 */
2143 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2144
2145 /*
2146 * If the commit is not on the reader page, then
2147 * move the header page.
2148 */
2149 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2150 /*
2151 * If we are not in overwrite mode,
2152 * this is easy, just stop here.
2153 */
2154 if (!(buffer->flags & RB_FL_OVERWRITE))
2155 goto out_reset;
2156
2157 ret = rb_handle_head_page(cpu_buffer,
2158 tail_page,
2159 next_page);
2160 if (ret < 0)
2161 goto out_reset;
2162 if (ret)
2163 goto out_again;
2164 } else {
2165 /*
2166 * We need to be careful here too. The
2167 * commit page could still be on the reader
2168 * page. We could have a small buffer, and
2169 * have filled up the buffer with events
2170 * from interrupts and such, and wrapped.
2171 *
2172 * Note, if the tail page is also the on the
2173 * reader_page, we let it move out.
2174 */
2175 if (unlikely((cpu_buffer->commit_page !=
2176 cpu_buffer->tail_page) &&
2177 (cpu_buffer->commit_page ==
2178 cpu_buffer->reader_page))) {
2179 local_inc(&cpu_buffer->commit_overrun);
2180 goto out_reset;
2181 }
2182 }
2183 }
2184
2185 ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
2186 if (ret) {
2187 /*
2188 * Nested commits always have zero deltas, so
2189 * just reread the time stamp
2190 */
2191 ts = rb_time_stamp(buffer);
2192 next_page->page->time_stamp = ts;
2193 }
2194
2195 out_again:
2196
2197 rb_reset_tail(cpu_buffer, tail_page, tail, length);
2198
2199 /* fail and let the caller try again */
2200 return ERR_PTR(-EAGAIN);
2201
2202 out_reset:
2203 /* reset write */
2204 rb_reset_tail(cpu_buffer, tail_page, tail, length);
2205
2206 return NULL;
2207}
2208
2209static struct ring_buffer_event *
2210__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2211 unsigned long length, u64 ts,
2212 u64 delta, int add_timestamp)
2213{
2214 struct buffer_page *tail_page;
2215 struct ring_buffer_event *event;
2216 unsigned long tail, write;
2217
2218 /*
2219 * If the time delta since the last event is too big to
2220 * hold in the time field of the event, then we append a
2221 * TIME EXTEND event ahead of the data event.
2222 */
2223 if (unlikely(add_timestamp))
2224 length += RB_LEN_TIME_EXTEND;
2225
2226 tail_page = cpu_buffer->tail_page;
2227 write = local_add_return(length, &tail_page->write);
2228
2229 /* set write to only the index of the write */
2230 write &= RB_WRITE_MASK;
2231 tail = write - length;
2232
2233 /* See if we shot pass the end of this buffer page */
2234 if (unlikely(write > BUF_PAGE_SIZE))
2235 return rb_move_tail(cpu_buffer, length, tail,
2236 tail_page, ts);
2237
2238 /* We reserved something on the buffer */
2239
2240 event = __rb_page_index(tail_page, tail);
2241 kmemcheck_annotate_bitfield(event, bitfield);
2242 rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
2243
2244 local_inc(&tail_page->entries);
2245
2246 /*
2247 * If this is the first commit on the page, then update
2248 * its timestamp.
2249 */
2250 if (!tail)
2251 tail_page->page->time_stamp = ts;
2252
2253 /* account for these added bytes */
2254 local_add(length, &cpu_buffer->entries_bytes);
2255
2256 return event;
2257}
2258
2259static inline int
2260rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2261 struct ring_buffer_event *event)
2262{
2263 unsigned long new_index, old_index;
2264 struct buffer_page *bpage;
2265 unsigned long index;
2266 unsigned long addr;
2267
2268 new_index = rb_event_index(event);
2269 old_index = new_index + rb_event_ts_length(event);
2270 addr = (unsigned long)event;
2271 addr &= PAGE_MASK;
2272
2273 bpage = cpu_buffer->tail_page;
2274
2275 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2276 unsigned long write_mask =
2277 local_read(&bpage->write) & ~RB_WRITE_MASK;
2278 unsigned long event_length = rb_event_length(event);
2279 /*
2280 * This is on the tail page. It is possible that
2281 * a write could come in and move the tail page
2282 * and write to the next page. That is fine
2283 * because we just shorten what is on this page.
2284 */
2285 old_index += write_mask;
2286 new_index += write_mask;
2287 index = local_cmpxchg(&bpage->write, old_index, new_index);
2288 if (index == old_index) {
2289 /* update counters */
2290 local_sub(event_length, &cpu_buffer->entries_bytes);
2291 return 1;
2292 }
2293 }
2294
2295 /* could not discard */
2296 return 0;
2297}
2298
2299static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2300{
2301 local_inc(&cpu_buffer->committing);
2302 local_inc(&cpu_buffer->commits);
2303}
2304
2305static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2306{
2307 unsigned long commits;
2308
2309 if (RB_WARN_ON(cpu_buffer,
2310 !local_read(&cpu_buffer->committing)))
2311 return;
2312
2313 again:
2314 commits = local_read(&cpu_buffer->commits);
2315 /* synchronize with interrupts */
2316 barrier();
2317 if (local_read(&cpu_buffer->committing) == 1)
2318 rb_set_commit_to_write(cpu_buffer);
2319
2320 local_dec(&cpu_buffer->committing);
2321
2322 /* synchronize with interrupts */
2323 barrier();
2324
2325 /*
2326 * Need to account for interrupts coming in between the
2327 * updating of the commit page and the clearing of the
2328 * committing counter.
2329 */
2330 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2331 !local_read(&cpu_buffer->committing)) {
2332 local_inc(&cpu_buffer->committing);
2333 goto again;
2334 }
2335}
2336
2337static struct ring_buffer_event *
2338rb_reserve_next_event(struct ring_buffer *buffer,
2339 struct ring_buffer_per_cpu *cpu_buffer,
2340 unsigned long length)
2341{
2342 struct ring_buffer_event *event;
2343 u64 ts, delta;
2344 int nr_loops = 0;
2345 int add_timestamp;
2346 u64 diff;
2347
2348 rb_start_commit(cpu_buffer);
2349
2350#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2351 /*
2352 * Due to the ability to swap a cpu buffer from a buffer
2353 * it is possible it was swapped before we committed.
2354 * (committing stops a swap). We check for it here and
2355 * if it happened, we have to fail the write.
2356 */
2357 barrier();
2358 if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
2359 local_dec(&cpu_buffer->committing);
2360 local_dec(&cpu_buffer->commits);
2361 return NULL;
2362 }
2363#endif
2364
2365 length = rb_calculate_event_length(length);
2366 again:
2367 add_timestamp = 0;
2368 delta = 0;
2369
2370 /*
2371 * We allow for interrupts to reenter here and do a trace.
2372 * If one does, it will cause this original code to loop
2373 * back here. Even with heavy interrupts happening, this
2374 * should only happen a few times in a row. If this happens
2375 * 1000 times in a row, there must be either an interrupt
2376 * storm or we have something buggy.
2377 * Bail!
2378 */
2379 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2380 goto out_fail;
2381
2382 ts = rb_time_stamp(cpu_buffer->buffer);
2383 diff = ts - cpu_buffer->write_stamp;
2384
2385 /* make sure this diff is calculated here */
2386 barrier();
2387
2388 /* Did the write stamp get updated already? */
2389 if (likely(ts >= cpu_buffer->write_stamp)) {
2390 delta = diff;
2391 if (unlikely(test_time_stamp(delta))) {
2392 int local_clock_stable = 1;
2393#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2394 local_clock_stable = sched_clock_stable;
2395#endif
2396 WARN_ONCE(delta > (1ULL << 59),
2397 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2398 (unsigned long long)delta,
2399 (unsigned long long)ts,
2400 (unsigned long long)cpu_buffer->write_stamp,
2401 local_clock_stable ? "" :
2402 "If you just came from a suspend/resume,\n"
2403 "please switch to the trace global clock:\n"
2404 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2405 add_timestamp = 1;
2406 }
2407 }
2408
2409 event = __rb_reserve_next(cpu_buffer, length, ts,
2410 delta, add_timestamp);
2411 if (unlikely(PTR_ERR(event) == -EAGAIN))
2412 goto again;
2413
2414 if (!event)
2415 goto out_fail;
2416
2417 return event;
2418
2419 out_fail:
2420 rb_end_commit(cpu_buffer);
2421 return NULL;
2422}
2423
2424#ifdef CONFIG_TRACING
2425
2426#define TRACE_RECURSIVE_DEPTH 16
2427
2428/* Keep this code out of the fast path cache */
2429static noinline void trace_recursive_fail(void)
2430{
2431 /* Disable all tracing before we do anything else */
2432 tracing_off_permanent();
2433
2434 printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
2435 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
2436 trace_recursion_buffer(),
2437 hardirq_count() >> HARDIRQ_SHIFT,
2438 softirq_count() >> SOFTIRQ_SHIFT,
2439 in_nmi());
2440
2441 WARN_ON_ONCE(1);
2442}
2443
2444static inline int trace_recursive_lock(void)
2445{
2446 trace_recursion_inc();
2447
2448 if (likely(trace_recursion_buffer() < TRACE_RECURSIVE_DEPTH))
2449 return 0;
2450
2451 trace_recursive_fail();
2452
2453 return -1;
2454}
2455
2456static inline void trace_recursive_unlock(void)
2457{
2458 WARN_ON_ONCE(!trace_recursion_buffer());
2459
2460 trace_recursion_dec();
2461}
2462
2463#else
2464
2465#define trace_recursive_lock() (0)
2466#define trace_recursive_unlock() do { } while (0)
2467
2468#endif
2469
2470/**
2471 * ring_buffer_lock_reserve - reserve a part of the buffer
2472 * @buffer: the ring buffer to reserve from
2473 * @length: the length of the data to reserve (excluding event header)
2474 *
2475 * Returns a reseverd event on the ring buffer to copy directly to.
2476 * The user of this interface will need to get the body to write into
2477 * and can use the ring_buffer_event_data() interface.
2478 *
2479 * The length is the length of the data needed, not the event length
2480 * which also includes the event header.
2481 *
2482 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2483 * If NULL is returned, then nothing has been allocated or locked.
2484 */
2485struct ring_buffer_event *
2486ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2487{
2488 struct ring_buffer_per_cpu *cpu_buffer;
2489 struct ring_buffer_event *event;
2490 int cpu;
2491
2492 if (ring_buffer_flags != RB_BUFFERS_ON)
2493 return NULL;
2494
2495 /* If we are tracing schedule, we don't want to recurse */
2496 preempt_disable_notrace();
2497
2498 if (atomic_read(&buffer->record_disabled))
2499 goto out_nocheck;
2500
2501 if (trace_recursive_lock())
2502 goto out_nocheck;
2503
2504 cpu = raw_smp_processor_id();
2505
2506 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2507 goto out;
2508
2509 cpu_buffer = buffer->buffers[cpu];
2510
2511 if (atomic_read(&cpu_buffer->record_disabled))
2512 goto out;
2513
2514 if (length > BUF_MAX_DATA_SIZE)
2515 goto out;
2516
2517 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2518 if (!event)
2519 goto out;
2520
2521 return event;
2522
2523 out:
2524 trace_recursive_unlock();
2525
2526 out_nocheck:
2527 preempt_enable_notrace();
2528 return NULL;
2529}
2530EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2531
2532static void
2533rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2534 struct ring_buffer_event *event)
2535{
2536 u64 delta;
2537
2538 /*
2539 * The event first in the commit queue updates the
2540 * time stamp.
2541 */
2542 if (rb_event_is_commit(cpu_buffer, event)) {
2543 /*
2544 * A commit event that is first on a page
2545 * updates the write timestamp with the page stamp
2546 */
2547 if (!rb_event_index(event))
2548 cpu_buffer->write_stamp =
2549 cpu_buffer->commit_page->page->time_stamp;
2550 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2551 delta = event->array[0];
2552 delta <<= TS_SHIFT;
2553 delta += event->time_delta;
2554 cpu_buffer->write_stamp += delta;
2555 } else
2556 cpu_buffer->write_stamp += event->time_delta;
2557 }
2558}
2559
2560static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2561 struct ring_buffer_event *event)
2562{
2563 local_inc(&cpu_buffer->entries);
2564 rb_update_write_stamp(cpu_buffer, event);
2565 rb_end_commit(cpu_buffer);
2566}
2567
2568/**
2569 * ring_buffer_unlock_commit - commit a reserved
2570 * @buffer: The buffer to commit to
2571 * @event: The event pointer to commit.
2572 *
2573 * This commits the data to the ring buffer, and releases any locks held.
2574 *
2575 * Must be paired with ring_buffer_lock_reserve.
2576 */
2577int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2578 struct ring_buffer_event *event)
2579{
2580 struct ring_buffer_per_cpu *cpu_buffer;
2581 int cpu = raw_smp_processor_id();
2582
2583 cpu_buffer = buffer->buffers[cpu];
2584
2585 rb_commit(cpu_buffer, event);
2586
2587 trace_recursive_unlock();
2588
2589 preempt_enable_notrace();
2590
2591 return 0;
2592}
2593EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2594
2595static inline void rb_event_discard(struct ring_buffer_event *event)
2596{
2597 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
2598 event = skip_time_extend(event);
2599
2600 /* array[0] holds the actual length for the discarded event */
2601 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2602 event->type_len = RINGBUF_TYPE_PADDING;
2603 /* time delta must be non zero */
2604 if (!event->time_delta)
2605 event->time_delta = 1;
2606}
2607
2608/*
2609 * Decrement the entries to the page that an event is on.
2610 * The event does not even need to exist, only the pointer
2611 * to the page it is on. This may only be called before the commit
2612 * takes place.
2613 */
2614static inline void
2615rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2616 struct ring_buffer_event *event)
2617{
2618 unsigned long addr = (unsigned long)event;
2619 struct buffer_page *bpage = cpu_buffer->commit_page;
2620 struct buffer_page *start;
2621
2622 addr &= PAGE_MASK;
2623
2624 /* Do the likely case first */
2625 if (likely(bpage->page == (void *)addr)) {
2626 local_dec(&bpage->entries);
2627 return;
2628 }
2629
2630 /*
2631 * Because the commit page may be on the reader page we
2632 * start with the next page and check the end loop there.
2633 */
2634 rb_inc_page(cpu_buffer, &bpage);
2635 start = bpage;
2636 do {
2637 if (bpage->page == (void *)addr) {
2638 local_dec(&bpage->entries);
2639 return;
2640 }
2641 rb_inc_page(cpu_buffer, &bpage);
2642 } while (bpage != start);
2643
2644 /* commit not part of this buffer?? */
2645 RB_WARN_ON(cpu_buffer, 1);
2646}
2647
2648/**
2649 * ring_buffer_commit_discard - discard an event that has not been committed
2650 * @buffer: the ring buffer
2651 * @event: non committed event to discard
2652 *
2653 * Sometimes an event that is in the ring buffer needs to be ignored.
2654 * This function lets the user discard an event in the ring buffer
2655 * and then that event will not be read later.
2656 *
2657 * This function only works if it is called before the the item has been
2658 * committed. It will try to free the event from the ring buffer
2659 * if another event has not been added behind it.
2660 *
2661 * If another event has been added behind it, it will set the event
2662 * up as discarded, and perform the commit.
2663 *
2664 * If this function is called, do not call ring_buffer_unlock_commit on
2665 * the event.
2666 */
2667void ring_buffer_discard_commit(struct ring_buffer *buffer,
2668 struct ring_buffer_event *event)
2669{
2670 struct ring_buffer_per_cpu *cpu_buffer;
2671 int cpu;
2672
2673 /* The event is discarded regardless */
2674 rb_event_discard(event);
2675
2676 cpu = smp_processor_id();
2677 cpu_buffer = buffer->buffers[cpu];
2678
2679 /*
2680 * This must only be called if the event has not been
2681 * committed yet. Thus we can assume that preemption
2682 * is still disabled.
2683 */
2684 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
2685
2686 rb_decrement_entry(cpu_buffer, event);
2687 if (rb_try_to_discard(cpu_buffer, event))
2688 goto out;
2689
2690 /*
2691 * The commit is still visible by the reader, so we
2692 * must still update the timestamp.
2693 */
2694 rb_update_write_stamp(cpu_buffer, event);
2695 out:
2696 rb_end_commit(cpu_buffer);
2697
2698 trace_recursive_unlock();
2699
2700 preempt_enable_notrace();
2701
2702}
2703EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
2704
2705/**
2706 * ring_buffer_write - write data to the buffer without reserving
2707 * @buffer: The ring buffer to write to.
2708 * @length: The length of the data being written (excluding the event header)
2709 * @data: The data to write to the buffer.
2710 *
2711 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2712 * one function. If you already have the data to write to the buffer, it
2713 * may be easier to simply call this function.
2714 *
2715 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2716 * and not the length of the event which would hold the header.
2717 */
2718int ring_buffer_write(struct ring_buffer *buffer,
2719 unsigned long length,
2720 void *data)
2721{
2722 struct ring_buffer_per_cpu *cpu_buffer;
2723 struct ring_buffer_event *event;
2724 void *body;
2725 int ret = -EBUSY;
2726 int cpu;
2727
2728 if (ring_buffer_flags != RB_BUFFERS_ON)
2729 return -EBUSY;
2730
2731 preempt_disable_notrace();
2732
2733 if (atomic_read(&buffer->record_disabled))
2734 goto out;
2735
2736 cpu = raw_smp_processor_id();
2737
2738 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2739 goto out;
2740
2741 cpu_buffer = buffer->buffers[cpu];
2742
2743 if (atomic_read(&cpu_buffer->record_disabled))
2744 goto out;
2745
2746 if (length > BUF_MAX_DATA_SIZE)
2747 goto out;
2748
2749 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2750 if (!event)
2751 goto out;
2752
2753 body = rb_event_data(event);
2754
2755 memcpy(body, data, length);
2756
2757 rb_commit(cpu_buffer, event);
2758
2759 ret = 0;
2760 out:
2761 preempt_enable_notrace();
2762
2763 return ret;
2764}
2765EXPORT_SYMBOL_GPL(ring_buffer_write);
2766
2767static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
2768{
2769 struct buffer_page *reader = cpu_buffer->reader_page;
2770 struct buffer_page *head = rb_set_head_page(cpu_buffer);
2771 struct buffer_page *commit = cpu_buffer->commit_page;
2772
2773 /* In case of error, head will be NULL */
2774 if (unlikely(!head))
2775 return 1;
2776
2777 return reader->read == rb_page_commit(reader) &&
2778 (commit == reader ||
2779 (commit == head &&
2780 head->read == rb_page_commit(commit)));
2781}
2782
2783/**
2784 * ring_buffer_record_disable - stop all writes into the buffer
2785 * @buffer: The ring buffer to stop writes to.
2786 *
2787 * This prevents all writes to the buffer. Any attempt to write
2788 * to the buffer after this will fail and return NULL.
2789 *
2790 * The caller should call synchronize_sched() after this.
2791 */
2792void ring_buffer_record_disable(struct ring_buffer *buffer)
2793{
2794 atomic_inc(&buffer->record_disabled);
2795}
2796EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
2797
2798/**
2799 * ring_buffer_record_enable - enable writes to the buffer
2800 * @buffer: The ring buffer to enable writes
2801 *
2802 * Note, multiple disables will need the same number of enables
2803 * to truly enable the writing (much like preempt_disable).
2804 */
2805void ring_buffer_record_enable(struct ring_buffer *buffer)
2806{
2807 atomic_dec(&buffer->record_disabled);
2808}
2809EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
2810
2811/**
2812 * ring_buffer_record_off - stop all writes into the buffer
2813 * @buffer: The ring buffer to stop writes to.
2814 *
2815 * This prevents all writes to the buffer. Any attempt to write
2816 * to the buffer after this will fail and return NULL.
2817 *
2818 * This is different than ring_buffer_record_disable() as
2819 * it works like an on/off switch, where as the disable() verison
2820 * must be paired with a enable().
2821 */
2822void ring_buffer_record_off(struct ring_buffer *buffer)
2823{
2824 unsigned int rd;
2825 unsigned int new_rd;
2826
2827 do {
2828 rd = atomic_read(&buffer->record_disabled);
2829 new_rd = rd | RB_BUFFER_OFF;
2830 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
2831}
2832EXPORT_SYMBOL_GPL(ring_buffer_record_off);
2833
2834/**
2835 * ring_buffer_record_on - restart writes into the buffer
2836 * @buffer: The ring buffer to start writes to.
2837 *
2838 * This enables all writes to the buffer that was disabled by
2839 * ring_buffer_record_off().
2840 *
2841 * This is different than ring_buffer_record_enable() as
2842 * it works like an on/off switch, where as the enable() verison
2843 * must be paired with a disable().
2844 */
2845void ring_buffer_record_on(struct ring_buffer *buffer)
2846{
2847 unsigned int rd;
2848 unsigned int new_rd;
2849
2850 do {
2851 rd = atomic_read(&buffer->record_disabled);
2852 new_rd = rd & ~RB_BUFFER_OFF;
2853 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
2854}
2855EXPORT_SYMBOL_GPL(ring_buffer_record_on);
2856
2857/**
2858 * ring_buffer_record_is_on - return true if the ring buffer can write
2859 * @buffer: The ring buffer to see if write is enabled
2860 *
2861 * Returns true if the ring buffer is in a state that it accepts writes.
2862 */
2863int ring_buffer_record_is_on(struct ring_buffer *buffer)
2864{
2865 return !atomic_read(&buffer->record_disabled);
2866}
2867
2868/**
2869 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2870 * @buffer: The ring buffer to stop writes to.
2871 * @cpu: The CPU buffer to stop
2872 *
2873 * This prevents all writes to the buffer. Any attempt to write
2874 * to the buffer after this will fail and return NULL.
2875 *
2876 * The caller should call synchronize_sched() after this.
2877 */
2878void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
2879{
2880 struct ring_buffer_per_cpu *cpu_buffer;
2881
2882 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2883 return;
2884
2885 cpu_buffer = buffer->buffers[cpu];
2886 atomic_inc(&cpu_buffer->record_disabled);
2887}
2888EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
2889
2890/**
2891 * ring_buffer_record_enable_cpu - enable writes to the buffer
2892 * @buffer: The ring buffer to enable writes
2893 * @cpu: The CPU to enable.
2894 *
2895 * Note, multiple disables will need the same number of enables
2896 * to truly enable the writing (much like preempt_disable).
2897 */
2898void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
2899{
2900 struct ring_buffer_per_cpu *cpu_buffer;
2901
2902 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2903 return;
2904
2905 cpu_buffer = buffer->buffers[cpu];
2906 atomic_dec(&cpu_buffer->record_disabled);
2907}
2908EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
2909
2910/*
2911 * The total entries in the ring buffer is the running counter
2912 * of entries entered into the ring buffer, minus the sum of
2913 * the entries read from the ring buffer and the number of
2914 * entries that were overwritten.
2915 */
2916static inline unsigned long
2917rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
2918{
2919 return local_read(&cpu_buffer->entries) -
2920 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
2921}
2922
2923/**
2924 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
2925 * @buffer: The ring buffer
2926 * @cpu: The per CPU buffer to read from.
2927 */
2928unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
2929{
2930 unsigned long flags;
2931 struct ring_buffer_per_cpu *cpu_buffer;
2932 struct buffer_page *bpage;
2933 unsigned long ret;
2934
2935 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2936 return 0;
2937
2938 cpu_buffer = buffer->buffers[cpu];
2939 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2940 /*
2941 * if the tail is on reader_page, oldest time stamp is on the reader
2942 * page
2943 */
2944 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
2945 bpage = cpu_buffer->reader_page;
2946 else
2947 bpage = rb_set_head_page(cpu_buffer);
2948 ret = bpage->page->time_stamp;
2949 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2950
2951 return ret;
2952}
2953EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
2954
2955/**
2956 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
2957 * @buffer: The ring buffer
2958 * @cpu: The per CPU buffer to read from.
2959 */
2960unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
2961{
2962 struct ring_buffer_per_cpu *cpu_buffer;
2963 unsigned long ret;
2964
2965 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2966 return 0;
2967
2968 cpu_buffer = buffer->buffers[cpu];
2969 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
2970
2971 return ret;
2972}
2973EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
2974
2975/**
2976 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2977 * @buffer: The ring buffer
2978 * @cpu: The per CPU buffer to get the entries from.
2979 */
2980unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
2981{
2982 struct ring_buffer_per_cpu *cpu_buffer;
2983
2984 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2985 return 0;
2986
2987 cpu_buffer = buffer->buffers[cpu];
2988
2989 return rb_num_of_entries(cpu_buffer);
2990}
2991EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
2992
2993/**
2994 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
2995 * @buffer: The ring buffer
2996 * @cpu: The per CPU buffer to get the number of overruns from
2997 */
2998unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
2999{
3000 struct ring_buffer_per_cpu *cpu_buffer;
3001 unsigned long ret;
3002
3003 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3004 return 0;
3005
3006 cpu_buffer = buffer->buffers[cpu];
3007 ret = local_read(&cpu_buffer->overrun);
3008
3009 return ret;
3010}
3011EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3012
3013/**
3014 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
3015 * @buffer: The ring buffer
3016 * @cpu: The per CPU buffer to get the number of overruns from
3017 */
3018unsigned long
3019ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3020{
3021 struct ring_buffer_per_cpu *cpu_buffer;
3022 unsigned long ret;
3023
3024 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3025 return 0;
3026
3027 cpu_buffer = buffer->buffers[cpu];
3028 ret = local_read(&cpu_buffer->commit_overrun);
3029
3030 return ret;
3031}
3032EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3033
3034/**
3035 * ring_buffer_entries - get the number of entries in a buffer
3036 * @buffer: The ring buffer
3037 *
3038 * Returns the total number of entries in the ring buffer
3039 * (all CPU entries)
3040 */
3041unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3042{
3043 struct ring_buffer_per_cpu *cpu_buffer;
3044 unsigned long entries = 0;
3045 int cpu;
3046
3047 /* if you care about this being correct, lock the buffer */
3048 for_each_buffer_cpu(buffer, cpu) {
3049 cpu_buffer = buffer->buffers[cpu];
3050 entries += rb_num_of_entries(cpu_buffer);
3051 }
3052
3053 return entries;
3054}
3055EXPORT_SYMBOL_GPL(ring_buffer_entries);
3056
3057/**
3058 * ring_buffer_overruns - get the number of overruns in buffer
3059 * @buffer: The ring buffer
3060 *
3061 * Returns the total number of overruns in the ring buffer
3062 * (all CPU entries)
3063 */
3064unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3065{
3066 struct ring_buffer_per_cpu *cpu_buffer;
3067 unsigned long overruns = 0;
3068 int cpu;
3069
3070 /* if you care about this being correct, lock the buffer */
3071 for_each_buffer_cpu(buffer, cpu) {
3072 cpu_buffer = buffer->buffers[cpu];
3073 overruns += local_read(&cpu_buffer->overrun);
3074 }
3075
3076 return overruns;
3077}
3078EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3079
3080static void rb_iter_reset(struct ring_buffer_iter *iter)
3081{
3082 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3083
3084 /* Iterator usage is expected to have record disabled */
3085 if (list_empty(&cpu_buffer->reader_page->list)) {
3086 iter->head_page = rb_set_head_page(cpu_buffer);
3087 if (unlikely(!iter->head_page))
3088 return;
3089 iter->head = iter->head_page->read;
3090 } else {
3091 iter->head_page = cpu_buffer->reader_page;
3092 iter->head = cpu_buffer->reader_page->read;
3093 }
3094 if (iter->head)
3095 iter->read_stamp = cpu_buffer->read_stamp;
3096 else
3097 iter->read_stamp = iter->head_page->page->time_stamp;
3098 iter->cache_reader_page = cpu_buffer->reader_page;
3099 iter->cache_read = cpu_buffer->read;
3100}
3101
3102/**
3103 * ring_buffer_iter_reset - reset an iterator
3104 * @iter: The iterator to reset
3105 *
3106 * Resets the iterator, so that it will start from the beginning
3107 * again.
3108 */
3109void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3110{
3111 struct ring_buffer_per_cpu *cpu_buffer;
3112 unsigned long flags;
3113
3114 if (!iter)
3115 return;
3116
3117 cpu_buffer = iter->cpu_buffer;
3118
3119 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3120 rb_iter_reset(iter);
3121 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3122}
3123EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3124
3125/**
3126 * ring_buffer_iter_empty - check if an iterator has no more to read
3127 * @iter: The iterator to check
3128 */
3129int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3130{
3131 struct ring_buffer_per_cpu *cpu_buffer;
3132
3133 cpu_buffer = iter->cpu_buffer;
3134
3135 return iter->head_page == cpu_buffer->commit_page &&
3136 iter->head == rb_commit_index(cpu_buffer);
3137}
3138EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3139
3140static void
3141rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3142 struct ring_buffer_event *event)
3143{
3144 u64 delta;
3145
3146 switch (event->type_len) {
3147 case RINGBUF_TYPE_PADDING:
3148 return;
3149
3150 case RINGBUF_TYPE_TIME_EXTEND:
3151 delta = event->array[0];
3152 delta <<= TS_SHIFT;
3153 delta += event->time_delta;
3154 cpu_buffer->read_stamp += delta;
3155 return;
3156
3157 case RINGBUF_TYPE_TIME_STAMP:
3158 /* FIXME: not implemented */
3159 return;
3160
3161 case RINGBUF_TYPE_DATA:
3162 cpu_buffer->read_stamp += event->time_delta;
3163 return;
3164
3165 default:
3166 BUG();
3167 }
3168 return;
3169}
3170
3171static void
3172rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3173 struct ring_buffer_event *event)
3174{
3175 u64 delta;
3176
3177 switch (event->type_len) {
3178 case RINGBUF_TYPE_PADDING:
3179 return;
3180
3181 case RINGBUF_TYPE_TIME_EXTEND:
3182 delta = event->array[0];
3183 delta <<= TS_SHIFT;
3184 delta += event->time_delta;
3185 iter->read_stamp += delta;
3186 return;
3187
3188 case RINGBUF_TYPE_TIME_STAMP:
3189 /* FIXME: not implemented */
3190 return;
3191
3192 case RINGBUF_TYPE_DATA:
3193 iter->read_stamp += event->time_delta;
3194 return;
3195
3196 default:
3197 BUG();
3198 }
3199 return;
3200}
3201
3202static struct buffer_page *
3203rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3204{
3205 struct buffer_page *reader = NULL;
3206 unsigned long overwrite;
3207 unsigned long flags;
3208 int nr_loops = 0;
3209 int ret;
3210
3211 local_irq_save(flags);
3212 arch_spin_lock(&cpu_buffer->lock);
3213
3214 again:
3215 /*
3216 * This should normally only loop twice. But because the
3217 * start of the reader inserts an empty page, it causes
3218 * a case where we will loop three times. There should be no
3219 * reason to loop four times (that I know of).
3220 */
3221 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3222 reader = NULL;
3223 goto out;
3224 }
3225
3226 reader = cpu_buffer->reader_page;
3227
3228 /* If there's more to read, return this page */
3229 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3230 goto out;
3231
3232 /* Never should we have an index greater than the size */
3233 if (RB_WARN_ON(cpu_buffer,
3234 cpu_buffer->reader_page->read > rb_page_size(reader)))
3235 goto out;
3236
3237 /* check if we caught up to the tail */
3238 reader = NULL;
3239 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3240 goto out;
3241
3242 /*
3243 * Reset the reader page to size zero.
3244 */
3245 local_set(&cpu_buffer->reader_page->write, 0);
3246 local_set(&cpu_buffer->reader_page->entries, 0);
3247 local_set(&cpu_buffer->reader_page->page->commit, 0);
3248 cpu_buffer->reader_page->real_end = 0;
3249
3250 spin:
3251 /*
3252 * Splice the empty reader page into the list around the head.
3253 */
3254 reader = rb_set_head_page(cpu_buffer);
3255 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3256 cpu_buffer->reader_page->list.prev = reader->list.prev;
3257
3258 /*
3259 * cpu_buffer->pages just needs to point to the buffer, it
3260 * has no specific buffer page to point to. Lets move it out
3261 * of our way so we don't accidentally swap it.
3262 */
3263 cpu_buffer->pages = reader->list.prev;
3264
3265 /* The reader page will be pointing to the new head */
3266 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3267
3268 /*
3269 * We want to make sure we read the overruns after we set up our
3270 * pointers to the next object. The writer side does a
3271 * cmpxchg to cross pages which acts as the mb on the writer
3272 * side. Note, the reader will constantly fail the swap
3273 * while the writer is updating the pointers, so this
3274 * guarantees that the overwrite recorded here is the one we
3275 * want to compare with the last_overrun.
3276 */
3277 smp_mb();
3278 overwrite = local_read(&(cpu_buffer->overrun));
3279
3280 /*
3281 * Here's the tricky part.
3282 *
3283 * We need to move the pointer past the header page.
3284 * But we can only do that if a writer is not currently
3285 * moving it. The page before the header page has the
3286 * flag bit '1' set if it is pointing to the page we want.
3287 * but if the writer is in the process of moving it
3288 * than it will be '2' or already moved '0'.
3289 */
3290
3291 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3292
3293 /*
3294 * If we did not convert it, then we must try again.
3295 */
3296 if (!ret)
3297 goto spin;
3298
3299 /*
3300 * Yeah! We succeeded in replacing the page.
3301 *
3302 * Now make the new head point back to the reader page.
3303 */
3304 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3305 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3306
3307 /* Finally update the reader page to the new head */
3308 cpu_buffer->reader_page = reader;
3309 rb_reset_reader_page(cpu_buffer);
3310
3311 if (overwrite != cpu_buffer->last_overrun) {
3312 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3313 cpu_buffer->last_overrun = overwrite;
3314 }
3315
3316 goto again;
3317
3318 out:
3319 arch_spin_unlock(&cpu_buffer->lock);
3320 local_irq_restore(flags);
3321
3322 return reader;
3323}
3324
3325static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3326{
3327 struct ring_buffer_event *event;
3328 struct buffer_page *reader;
3329 unsigned length;
3330
3331 reader = rb_get_reader_page(cpu_buffer);
3332
3333 /* This function should not be called when buffer is empty */
3334 if (RB_WARN_ON(cpu_buffer, !reader))
3335 return;
3336
3337 event = rb_reader_event(cpu_buffer);
3338
3339 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3340 cpu_buffer->read++;
3341
3342 rb_update_read_stamp(cpu_buffer, event);
3343
3344 length = rb_event_length(event);
3345 cpu_buffer->reader_page->read += length;
3346}
3347
3348static void rb_advance_iter(struct ring_buffer_iter *iter)
3349{
3350 struct ring_buffer_per_cpu *cpu_buffer;
3351 struct ring_buffer_event *event;
3352 unsigned length;
3353
3354 cpu_buffer = iter->cpu_buffer;
3355
3356 /*
3357 * Check if we are at the end of the buffer.
3358 */
3359 if (iter->head >= rb_page_size(iter->head_page)) {
3360 /* discarded commits can make the page empty */
3361 if (iter->head_page == cpu_buffer->commit_page)
3362 return;
3363 rb_inc_iter(iter);
3364 return;
3365 }
3366
3367 event = rb_iter_head_event(iter);
3368
3369 length = rb_event_length(event);
3370
3371 /*
3372 * This should not be called to advance the header if we are
3373 * at the tail of the buffer.
3374 */
3375 if (RB_WARN_ON(cpu_buffer,
3376 (iter->head_page == cpu_buffer->commit_page) &&
3377 (iter->head + length > rb_commit_index(cpu_buffer))))
3378 return;
3379
3380 rb_update_iter_read_stamp(iter, event);
3381
3382 iter->head += length;
3383
3384 /* check for end of page padding */
3385 if ((iter->head >= rb_page_size(iter->head_page)) &&
3386 (iter->head_page != cpu_buffer->commit_page))
3387 rb_advance_iter(iter);
3388}
3389
3390static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3391{
3392 return cpu_buffer->lost_events;
3393}
3394
3395static struct ring_buffer_event *
3396rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3397 unsigned long *lost_events)
3398{
3399 struct ring_buffer_event *event;
3400 struct buffer_page *reader;
3401 int nr_loops = 0;
3402
3403 again:
3404 /*
3405 * We repeat when a time extend is encountered.
3406 * Since the time extend is always attached to a data event,
3407 * we should never loop more than once.
3408 * (We never hit the following condition more than twice).
3409 */
3410 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3411 return NULL;
3412
3413 reader = rb_get_reader_page(cpu_buffer);
3414 if (!reader)
3415 return NULL;
3416
3417 event = rb_reader_event(cpu_buffer);
3418
3419 switch (event->type_len) {
3420 case RINGBUF_TYPE_PADDING:
3421 if (rb_null_event(event))
3422 RB_WARN_ON(cpu_buffer, 1);
3423 /*
3424 * Because the writer could be discarding every
3425 * event it creates (which would probably be bad)
3426 * if we were to go back to "again" then we may never
3427 * catch up, and will trigger the warn on, or lock
3428 * the box. Return the padding, and we will release
3429 * the current locks, and try again.
3430 */
3431 return event;
3432
3433 case RINGBUF_TYPE_TIME_EXTEND:
3434 /* Internal data, OK to advance */
3435 rb_advance_reader(cpu_buffer);
3436 goto again;
3437
3438 case RINGBUF_TYPE_TIME_STAMP:
3439 /* FIXME: not implemented */
3440 rb_advance_reader(cpu_buffer);
3441 goto again;
3442
3443 case RINGBUF_TYPE_DATA:
3444 if (ts) {
3445 *ts = cpu_buffer->read_stamp + event->time_delta;
3446 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3447 cpu_buffer->cpu, ts);
3448 }
3449 if (lost_events)
3450 *lost_events = rb_lost_events(cpu_buffer);
3451 return event;
3452
3453 default:
3454 BUG();
3455 }
3456
3457 return NULL;
3458}
3459EXPORT_SYMBOL_GPL(ring_buffer_peek);
3460
3461static struct ring_buffer_event *
3462rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3463{
3464 struct ring_buffer *buffer;
3465 struct ring_buffer_per_cpu *cpu_buffer;
3466 struct ring_buffer_event *event;
3467 int nr_loops = 0;
3468
3469 cpu_buffer = iter->cpu_buffer;
3470 buffer = cpu_buffer->buffer;
3471
3472 /*
3473 * Check if someone performed a consuming read to
3474 * the buffer. A consuming read invalidates the iterator
3475 * and we need to reset the iterator in this case.
3476 */
3477 if (unlikely(iter->cache_read != cpu_buffer->read ||
3478 iter->cache_reader_page != cpu_buffer->reader_page))
3479 rb_iter_reset(iter);
3480
3481 again:
3482 if (ring_buffer_iter_empty(iter))
3483 return NULL;
3484
3485 /*
3486 * We repeat when a time extend is encountered.
3487 * Since the time extend is always attached to a data event,
3488 * we should never loop more than once.
3489 * (We never hit the following condition more than twice).
3490 */
3491 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3492 return NULL;
3493
3494 if (rb_per_cpu_empty(cpu_buffer))
3495 return NULL;
3496
3497 if (iter->head >= local_read(&iter->head_page->page->commit)) {
3498 rb_inc_iter(iter);
3499 goto again;
3500 }
3501
3502 event = rb_iter_head_event(iter);
3503
3504 switch (event->type_len) {
3505 case RINGBUF_TYPE_PADDING:
3506 if (rb_null_event(event)) {
3507 rb_inc_iter(iter);
3508 goto again;
3509 }
3510 rb_advance_iter(iter);
3511 return event;
3512
3513 case RINGBUF_TYPE_TIME_EXTEND:
3514 /* Internal data, OK to advance */
3515 rb_advance_iter(iter);
3516 goto again;
3517
3518 case RINGBUF_TYPE_TIME_STAMP:
3519 /* FIXME: not implemented */
3520 rb_advance_iter(iter);
3521 goto again;
3522
3523 case RINGBUF_TYPE_DATA:
3524 if (ts) {
3525 *ts = iter->read_stamp + event->time_delta;
3526 ring_buffer_normalize_time_stamp(buffer,
3527 cpu_buffer->cpu, ts);
3528 }
3529 return event;
3530
3531 default:
3532 BUG();
3533 }
3534
3535 return NULL;
3536}
3537EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3538
3539static inline int rb_ok_to_lock(void)
3540{
3541 /*
3542 * If an NMI die dumps out the content of the ring buffer
3543 * do not grab locks. We also permanently disable the ring
3544 * buffer too. A one time deal is all you get from reading
3545 * the ring buffer from an NMI.
3546 */
3547 if (likely(!in_nmi()))
3548 return 1;
3549
3550 tracing_off_permanent();
3551 return 0;
3552}
3553
3554/**
3555 * ring_buffer_peek - peek at the next event to be read
3556 * @buffer: The ring buffer to read
3557 * @cpu: The cpu to peak at
3558 * @ts: The timestamp counter of this event.
3559 * @lost_events: a variable to store if events were lost (may be NULL)
3560 *
3561 * This will return the event that will be read next, but does
3562 * not consume the data.
3563 */
3564struct ring_buffer_event *
3565ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
3566 unsigned long *lost_events)
3567{
3568 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3569 struct ring_buffer_event *event;
3570 unsigned long flags;
3571 int dolock;
3572
3573 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3574 return NULL;
3575
3576 dolock = rb_ok_to_lock();
3577 again:
3578 local_irq_save(flags);
3579 if (dolock)
3580 raw_spin_lock(&cpu_buffer->reader_lock);
3581 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3582 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3583 rb_advance_reader(cpu_buffer);
3584 if (dolock)
3585 raw_spin_unlock(&cpu_buffer->reader_lock);
3586 local_irq_restore(flags);
3587
3588 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3589 goto again;
3590
3591 return event;
3592}
3593
3594/**
3595 * ring_buffer_iter_peek - peek at the next event to be read
3596 * @iter: The ring buffer iterator
3597 * @ts: The timestamp counter of this event.
3598 *
3599 * This will return the event that will be read next, but does
3600 * not increment the iterator.
3601 */
3602struct ring_buffer_event *
3603ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3604{
3605 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3606 struct ring_buffer_event *event;
3607 unsigned long flags;
3608
3609 again:
3610 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3611 event = rb_iter_peek(iter, ts);
3612 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3613
3614 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3615 goto again;
3616
3617 return event;
3618}
3619
3620/**
3621 * ring_buffer_consume - return an event and consume it
3622 * @buffer: The ring buffer to get the next event from
3623 * @cpu: the cpu to read the buffer from
3624 * @ts: a variable to store the timestamp (may be NULL)
3625 * @lost_events: a variable to store if events were lost (may be NULL)
3626 *
3627 * Returns the next event in the ring buffer, and that event is consumed.
3628 * Meaning, that sequential reads will keep returning a different event,
3629 * and eventually empty the ring buffer if the producer is slower.
3630 */
3631struct ring_buffer_event *
3632ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
3633 unsigned long *lost_events)
3634{
3635 struct ring_buffer_per_cpu *cpu_buffer;
3636 struct ring_buffer_event *event = NULL;
3637 unsigned long flags;
3638 int dolock;
3639
3640 dolock = rb_ok_to_lock();
3641
3642 again:
3643 /* might be called in atomic */
3644 preempt_disable();
3645
3646 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3647 goto out;
3648
3649 cpu_buffer = buffer->buffers[cpu];
3650 local_irq_save(flags);
3651 if (dolock)
3652 raw_spin_lock(&cpu_buffer->reader_lock);
3653
3654 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3655 if (event) {
3656 cpu_buffer->lost_events = 0;
3657 rb_advance_reader(cpu_buffer);
3658 }
3659
3660 if (dolock)
3661 raw_spin_unlock(&cpu_buffer->reader_lock);
3662 local_irq_restore(flags);
3663
3664 out:
3665 preempt_enable();
3666
3667 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3668 goto again;
3669
3670 return event;
3671}
3672EXPORT_SYMBOL_GPL(ring_buffer_consume);
3673
3674/**
3675 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3676 * @buffer: The ring buffer to read from
3677 * @cpu: The cpu buffer to iterate over
3678 *
3679 * This performs the initial preparations necessary to iterate
3680 * through the buffer. Memory is allocated, buffer recording
3681 * is disabled, and the iterator pointer is returned to the caller.
3682 *
3683 * Disabling buffer recordng prevents the reading from being
3684 * corrupted. This is not a consuming read, so a producer is not
3685 * expected.
3686 *
3687 * After a sequence of ring_buffer_read_prepare calls, the user is
3688 * expected to make at least one call to ring_buffer_prepare_sync.
3689 * Afterwards, ring_buffer_read_start is invoked to get things going
3690 * for real.
3691 *
3692 * This overall must be paired with ring_buffer_finish.
3693 */
3694struct ring_buffer_iter *
3695ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
3696{
3697 struct ring_buffer_per_cpu *cpu_buffer;
3698 struct ring_buffer_iter *iter;
3699
3700 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3701 return NULL;
3702
3703 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
3704 if (!iter)
3705 return NULL;
3706
3707 cpu_buffer = buffer->buffers[cpu];
3708
3709 iter->cpu_buffer = cpu_buffer;
3710
3711 atomic_inc(&buffer->resize_disabled);
3712 atomic_inc(&cpu_buffer->record_disabled);
3713
3714 return iter;
3715}
3716EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
3717
3718/**
3719 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
3720 *
3721 * All previously invoked ring_buffer_read_prepare calls to prepare
3722 * iterators will be synchronized. Afterwards, read_buffer_read_start
3723 * calls on those iterators are allowed.
3724 */
3725void
3726ring_buffer_read_prepare_sync(void)
3727{
3728 synchronize_sched();
3729}
3730EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
3731
3732/**
3733 * ring_buffer_read_start - start a non consuming read of the buffer
3734 * @iter: The iterator returned by ring_buffer_read_prepare
3735 *
3736 * This finalizes the startup of an iteration through the buffer.
3737 * The iterator comes from a call to ring_buffer_read_prepare and
3738 * an intervening ring_buffer_read_prepare_sync must have been
3739 * performed.
3740 *
3741 * Must be paired with ring_buffer_finish.
3742 */
3743void
3744ring_buffer_read_start(struct ring_buffer_iter *iter)
3745{
3746 struct ring_buffer_per_cpu *cpu_buffer;
3747 unsigned long flags;
3748
3749 if (!iter)
3750 return;
3751
3752 cpu_buffer = iter->cpu_buffer;
3753
3754 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3755 arch_spin_lock(&cpu_buffer->lock);
3756 rb_iter_reset(iter);
3757 arch_spin_unlock(&cpu_buffer->lock);
3758 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3759}
3760EXPORT_SYMBOL_GPL(ring_buffer_read_start);
3761
3762/**
3763 * ring_buffer_finish - finish reading the iterator of the buffer
3764 * @iter: The iterator retrieved by ring_buffer_start
3765 *
3766 * This re-enables the recording to the buffer, and frees the
3767 * iterator.
3768 */
3769void
3770ring_buffer_read_finish(struct ring_buffer_iter *iter)
3771{
3772 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3773
3774 /*
3775 * Ring buffer is disabled from recording, here's a good place
3776 * to check the integrity of the ring buffer.
3777 */
3778 rb_check_pages(cpu_buffer);
3779
3780 atomic_dec(&cpu_buffer->record_disabled);
3781 atomic_dec(&cpu_buffer->buffer->resize_disabled);
3782 kfree(iter);
3783}
3784EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
3785
3786/**
3787 * ring_buffer_read - read the next item in the ring buffer by the iterator
3788 * @iter: The ring buffer iterator
3789 * @ts: The time stamp of the event read.
3790 *
3791 * This reads the next event in the ring buffer and increments the iterator.
3792 */
3793struct ring_buffer_event *
3794ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
3795{
3796 struct ring_buffer_event *event;
3797 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3798 unsigned long flags;
3799
3800 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3801 again:
3802 event = rb_iter_peek(iter, ts);
3803 if (!event)
3804 goto out;
3805
3806 if (event->type_len == RINGBUF_TYPE_PADDING)
3807 goto again;
3808
3809 rb_advance_iter(iter);
3810 out:
3811 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3812
3813 return event;
3814}
3815EXPORT_SYMBOL_GPL(ring_buffer_read);
3816
3817/**
3818 * ring_buffer_size - return the size of the ring buffer (in bytes)
3819 * @buffer: The ring buffer.
3820 */
3821unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
3822{
3823 /*
3824 * Earlier, this method returned
3825 * BUF_PAGE_SIZE * buffer->nr_pages
3826 * Since the nr_pages field is now removed, we have converted this to
3827 * return the per cpu buffer value.
3828 */
3829 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3830 return 0;
3831
3832 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
3833}
3834EXPORT_SYMBOL_GPL(ring_buffer_size);
3835
3836static void
3837rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
3838{
3839 rb_head_page_deactivate(cpu_buffer);
3840
3841 cpu_buffer->head_page
3842 = list_entry(cpu_buffer->pages, struct buffer_page, list);
3843 local_set(&cpu_buffer->head_page->write, 0);
3844 local_set(&cpu_buffer->head_page->entries, 0);
3845 local_set(&cpu_buffer->head_page->page->commit, 0);
3846
3847 cpu_buffer->head_page->read = 0;
3848
3849 cpu_buffer->tail_page = cpu_buffer->head_page;
3850 cpu_buffer->commit_page = cpu_buffer->head_page;
3851
3852 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
3853 INIT_LIST_HEAD(&cpu_buffer->new_pages);
3854 local_set(&cpu_buffer->reader_page->write, 0);
3855 local_set(&cpu_buffer->reader_page->entries, 0);
3856 local_set(&cpu_buffer->reader_page->page->commit, 0);
3857 cpu_buffer->reader_page->read = 0;
3858
3859 local_set(&cpu_buffer->commit_overrun, 0);
3860 local_set(&cpu_buffer->entries_bytes, 0);
3861 local_set(&cpu_buffer->overrun, 0);
3862 local_set(&cpu_buffer->entries, 0);
3863 local_set(&cpu_buffer->committing, 0);
3864 local_set(&cpu_buffer->commits, 0);
3865 cpu_buffer->read = 0;
3866 cpu_buffer->read_bytes = 0;
3867
3868 cpu_buffer->write_stamp = 0;
3869 cpu_buffer->read_stamp = 0;
3870
3871 cpu_buffer->lost_events = 0;
3872 cpu_buffer->last_overrun = 0;
3873
3874 rb_head_page_activate(cpu_buffer);
3875}
3876
3877/**
3878 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3879 * @buffer: The ring buffer to reset a per cpu buffer of
3880 * @cpu: The CPU buffer to be reset
3881 */
3882void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
3883{
3884 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3885 unsigned long flags;
3886
3887 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3888 return;
3889
3890 atomic_inc(&buffer->resize_disabled);
3891 atomic_inc(&cpu_buffer->record_disabled);
3892
3893 /* Make sure all commits have finished */
3894 synchronize_sched();
3895
3896 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3897
3898 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
3899 goto out;
3900
3901 arch_spin_lock(&cpu_buffer->lock);
3902
3903 rb_reset_cpu(cpu_buffer);
3904
3905 arch_spin_unlock(&cpu_buffer->lock);
3906
3907 out:
3908 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3909
3910 atomic_dec(&cpu_buffer->record_disabled);
3911 atomic_dec(&buffer->resize_disabled);
3912}
3913EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
3914
3915/**
3916 * ring_buffer_reset - reset a ring buffer
3917 * @buffer: The ring buffer to reset all cpu buffers
3918 */
3919void ring_buffer_reset(struct ring_buffer *buffer)
3920{
3921 int cpu;
3922
3923 for_each_buffer_cpu(buffer, cpu)
3924 ring_buffer_reset_cpu(buffer, cpu);
3925}
3926EXPORT_SYMBOL_GPL(ring_buffer_reset);
3927
3928/**
3929 * rind_buffer_empty - is the ring buffer empty?
3930 * @buffer: The ring buffer to test
3931 */
3932int ring_buffer_empty(struct ring_buffer *buffer)
3933{
3934 struct ring_buffer_per_cpu *cpu_buffer;
3935 unsigned long flags;
3936 int dolock;
3937 int cpu;
3938 int ret;
3939
3940 dolock = rb_ok_to_lock();
3941
3942 /* yes this is racy, but if you don't like the race, lock the buffer */
3943 for_each_buffer_cpu(buffer, cpu) {
3944 cpu_buffer = buffer->buffers[cpu];
3945 local_irq_save(flags);
3946 if (dolock)
3947 raw_spin_lock(&cpu_buffer->reader_lock);
3948 ret = rb_per_cpu_empty(cpu_buffer);
3949 if (dolock)
3950 raw_spin_unlock(&cpu_buffer->reader_lock);
3951 local_irq_restore(flags);
3952
3953 if (!ret)
3954 return 0;
3955 }
3956
3957 return 1;
3958}
3959EXPORT_SYMBOL_GPL(ring_buffer_empty);
3960
3961/**
3962 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
3963 * @buffer: The ring buffer
3964 * @cpu: The CPU buffer to test
3965 */
3966int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
3967{
3968 struct ring_buffer_per_cpu *cpu_buffer;
3969 unsigned long flags;
3970 int dolock;
3971 int ret;
3972
3973 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3974 return 1;
3975
3976 dolock = rb_ok_to_lock();
3977
3978 cpu_buffer = buffer->buffers[cpu];
3979 local_irq_save(flags);
3980 if (dolock)
3981 raw_spin_lock(&cpu_buffer->reader_lock);
3982 ret = rb_per_cpu_empty(cpu_buffer);
3983 if (dolock)
3984 raw_spin_unlock(&cpu_buffer->reader_lock);
3985 local_irq_restore(flags);
3986
3987 return ret;
3988}
3989EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
3990
3991#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3992/**
3993 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
3994 * @buffer_a: One buffer to swap with
3995 * @buffer_b: The other buffer to swap with
3996 *
3997 * This function is useful for tracers that want to take a "snapshot"
3998 * of a CPU buffer and has another back up buffer lying around.
3999 * it is expected that the tracer handles the cpu buffer not being
4000 * used at the moment.
4001 */
4002int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4003 struct ring_buffer *buffer_b, int cpu)
4004{
4005 struct ring_buffer_per_cpu *cpu_buffer_a;
4006 struct ring_buffer_per_cpu *cpu_buffer_b;
4007 int ret = -EINVAL;
4008
4009 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4010 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4011 goto out;
4012
4013 cpu_buffer_a = buffer_a->buffers[cpu];
4014 cpu_buffer_b = buffer_b->buffers[cpu];
4015
4016 /* At least make sure the two buffers are somewhat the same */
4017 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4018 goto out;
4019
4020 ret = -EAGAIN;
4021
4022 if (ring_buffer_flags != RB_BUFFERS_ON)
4023 goto out;
4024
4025 if (atomic_read(&buffer_a->record_disabled))
4026 goto out;
4027
4028 if (atomic_read(&buffer_b->record_disabled))
4029 goto out;
4030
4031 if (atomic_read(&cpu_buffer_a->record_disabled))
4032 goto out;
4033
4034 if (atomic_read(&cpu_buffer_b->record_disabled))
4035 goto out;
4036
4037 /*
4038 * We can't do a synchronize_sched here because this
4039 * function can be called in atomic context.
4040 * Normally this will be called from the same CPU as cpu.
4041 * If not it's up to the caller to protect this.
4042 */
4043 atomic_inc(&cpu_buffer_a->record_disabled);
4044 atomic_inc(&cpu_buffer_b->record_disabled);
4045
4046 ret = -EBUSY;
4047 if (local_read(&cpu_buffer_a->committing))
4048 goto out_dec;
4049 if (local_read(&cpu_buffer_b->committing))
4050 goto out_dec;
4051
4052 buffer_a->buffers[cpu] = cpu_buffer_b;
4053 buffer_b->buffers[cpu] = cpu_buffer_a;
4054
4055 cpu_buffer_b->buffer = buffer_a;
4056 cpu_buffer_a->buffer = buffer_b;
4057
4058 ret = 0;
4059
4060out_dec:
4061 atomic_dec(&cpu_buffer_a->record_disabled);
4062 atomic_dec(&cpu_buffer_b->record_disabled);
4063out:
4064 return ret;
4065}
4066EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4067#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4068
4069/**
4070 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4071 * @buffer: the buffer to allocate for.
4072 *
4073 * This function is used in conjunction with ring_buffer_read_page.
4074 * When reading a full page from the ring buffer, these functions
4075 * can be used to speed up the process. The calling function should
4076 * allocate a few pages first with this function. Then when it
4077 * needs to get pages from the ring buffer, it passes the result
4078 * of this function into ring_buffer_read_page, which will swap
4079 * the page that was allocated, with the read page of the buffer.
4080 *
4081 * Returns:
4082 * The page allocated, or NULL on error.
4083 */
4084void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4085{
4086 struct buffer_data_page *bpage;
4087 struct page *page;
4088
4089 page = alloc_pages_node(cpu_to_node(cpu),
4090 GFP_KERNEL | __GFP_NORETRY, 0);
4091 if (!page)
4092 return NULL;
4093
4094 bpage = page_address(page);
4095
4096 rb_init_page(bpage);
4097
4098 return bpage;
4099}
4100EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4101
4102/**
4103 * ring_buffer_free_read_page - free an allocated read page
4104 * @buffer: the buffer the page was allocate for
4105 * @data: the page to free
4106 *
4107 * Free a page allocated from ring_buffer_alloc_read_page.
4108 */
4109void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
4110{
4111 free_page((unsigned long)data);
4112}
4113EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4114
4115/**
4116 * ring_buffer_read_page - extract a page from the ring buffer
4117 * @buffer: buffer to extract from
4118 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4119 * @len: amount to extract
4120 * @cpu: the cpu of the buffer to extract
4121 * @full: should the extraction only happen when the page is full.
4122 *
4123 * This function will pull out a page from the ring buffer and consume it.
4124 * @data_page must be the address of the variable that was returned
4125 * from ring_buffer_alloc_read_page. This is because the page might be used
4126 * to swap with a page in the ring buffer.
4127 *
4128 * for example:
4129 * rpage = ring_buffer_alloc_read_page(buffer);
4130 * if (!rpage)
4131 * return error;
4132 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4133 * if (ret >= 0)
4134 * process_page(rpage, ret);
4135 *
4136 * When @full is set, the function will not return true unless
4137 * the writer is off the reader page.
4138 *
4139 * Note: it is up to the calling functions to handle sleeps and wakeups.
4140 * The ring buffer can be used anywhere in the kernel and can not
4141 * blindly call wake_up. The layer that uses the ring buffer must be
4142 * responsible for that.
4143 *
4144 * Returns:
4145 * >=0 if data has been transferred, returns the offset of consumed data.
4146 * <0 if no data has been transferred.
4147 */
4148int ring_buffer_read_page(struct ring_buffer *buffer,
4149 void **data_page, size_t len, int cpu, int full)
4150{
4151 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4152 struct ring_buffer_event *event;
4153 struct buffer_data_page *bpage;
4154 struct buffer_page *reader;
4155 unsigned long missed_events;
4156 unsigned long flags;
4157 unsigned int commit;
4158 unsigned int read;
4159 u64 save_timestamp;
4160 int ret = -1;
4161
4162 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4163 goto out;
4164
4165 /*
4166 * If len is not big enough to hold the page header, then
4167 * we can not copy anything.
4168 */
4169 if (len <= BUF_PAGE_HDR_SIZE)
4170 goto out;
4171
4172 len -= BUF_PAGE_HDR_SIZE;
4173
4174 if (!data_page)
4175 goto out;
4176
4177 bpage = *data_page;
4178 if (!bpage)
4179 goto out;
4180
4181 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4182
4183 reader = rb_get_reader_page(cpu_buffer);
4184 if (!reader)
4185 goto out_unlock;
4186
4187 event = rb_reader_event(cpu_buffer);
4188
4189 read = reader->read;
4190 commit = rb_page_commit(reader);
4191
4192 /* Check if any events were dropped */
4193 missed_events = cpu_buffer->lost_events;
4194
4195 /*
4196 * If this page has been partially read or
4197 * if len is not big enough to read the rest of the page or
4198 * a writer is still on the page, then
4199 * we must copy the data from the page to the buffer.
4200 * Otherwise, we can simply swap the page with the one passed in.
4201 */
4202 if (read || (len < (commit - read)) ||
4203 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4204 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4205 unsigned int rpos = read;
4206 unsigned int pos = 0;
4207 unsigned int size;
4208
4209 if (full)
4210 goto out_unlock;
4211
4212 if (len > (commit - read))
4213 len = (commit - read);
4214
4215 /* Always keep the time extend and data together */
4216 size = rb_event_ts_length(event);
4217
4218 if (len < size)
4219 goto out_unlock;
4220
4221 /* save the current timestamp, since the user will need it */
4222 save_timestamp = cpu_buffer->read_stamp;
4223
4224 /* Need to copy one event at a time */
4225 do {
4226 /* We need the size of one event, because
4227 * rb_advance_reader only advances by one event,
4228 * whereas rb_event_ts_length may include the size of
4229 * one or two events.
4230 * We have already ensured there's enough space if this
4231 * is a time extend. */
4232 size = rb_event_length(event);
4233 memcpy(bpage->data + pos, rpage->data + rpos, size);
4234
4235 len -= size;
4236
4237 rb_advance_reader(cpu_buffer);
4238 rpos = reader->read;
4239 pos += size;
4240
4241 if (rpos >= commit)
4242 break;
4243
4244 event = rb_reader_event(cpu_buffer);
4245 /* Always keep the time extend and data together */
4246 size = rb_event_ts_length(event);
4247 } while (len >= size);
4248
4249 /* update bpage */
4250 local_set(&bpage->commit, pos);
4251 bpage->time_stamp = save_timestamp;
4252
4253 /* we copied everything to the beginning */
4254 read = 0;
4255 } else {
4256 /* update the entry counter */
4257 cpu_buffer->read += rb_page_entries(reader);
4258 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4259
4260 /* swap the pages */
4261 rb_init_page(bpage);
4262 bpage = reader->page;
4263 reader->page = *data_page;
4264 local_set(&reader->write, 0);
4265 local_set(&reader->entries, 0);
4266 reader->read = 0;
4267 *data_page = bpage;
4268
4269 /*
4270 * Use the real_end for the data size,
4271 * This gives us a chance to store the lost events
4272 * on the page.
4273 */
4274 if (reader->real_end)
4275 local_set(&bpage->commit, reader->real_end);
4276 }
4277 ret = read;
4278
4279 cpu_buffer->lost_events = 0;
4280
4281 commit = local_read(&bpage->commit);
4282 /*
4283 * Set a flag in the commit field if we lost events
4284 */
4285 if (missed_events) {
4286 /* If there is room at the end of the page to save the
4287 * missed events, then record it there.
4288 */
4289 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4290 memcpy(&bpage->data[commit], &missed_events,
4291 sizeof(missed_events));
4292 local_add(RB_MISSED_STORED, &bpage->commit);
4293 commit += sizeof(missed_events);
4294 }
4295 local_add(RB_MISSED_EVENTS, &bpage->commit);
4296 }
4297
4298 /*
4299 * This page may be off to user land. Zero it out here.
4300 */
4301 if (commit < BUF_PAGE_SIZE)
4302 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4303
4304 out_unlock:
4305 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4306
4307 out:
4308 return ret;
4309}
4310EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4311
4312#ifdef CONFIG_HOTPLUG_CPU
4313static int rb_cpu_notify(struct notifier_block *self,
4314 unsigned long action, void *hcpu)
4315{
4316 struct ring_buffer *buffer =
4317 container_of(self, struct ring_buffer, cpu_notify);
4318 long cpu = (long)hcpu;
4319 int cpu_i, nr_pages_same;
4320 unsigned int nr_pages;
4321
4322 switch (action) {
4323 case CPU_UP_PREPARE:
4324 case CPU_UP_PREPARE_FROZEN:
4325 if (cpumask_test_cpu(cpu, buffer->cpumask))
4326 return NOTIFY_OK;
4327
4328 nr_pages = 0;
4329 nr_pages_same = 1;
4330 /* check if all cpu sizes are same */
4331 for_each_buffer_cpu(buffer, cpu_i) {
4332 /* fill in the size from first enabled cpu */
4333 if (nr_pages == 0)
4334 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4335 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4336 nr_pages_same = 0;
4337 break;
4338 }
4339 }
4340 /* allocate minimum pages, user can later expand it */
4341 if (!nr_pages_same)
4342 nr_pages = 2;
4343 buffer->buffers[cpu] =
4344 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4345 if (!buffer->buffers[cpu]) {
4346 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4347 cpu);
4348 return NOTIFY_OK;
4349 }
4350 smp_wmb();
4351 cpumask_set_cpu(cpu, buffer->cpumask);
4352 break;
4353 case CPU_DOWN_PREPARE:
4354 case CPU_DOWN_PREPARE_FROZEN:
4355 /*
4356 * Do nothing.
4357 * If we were to free the buffer, then the user would
4358 * lose any trace that was in the buffer.
4359 */
4360 break;
4361 default:
4362 break;
4363 }
4364 return NOTIFY_OK;
4365}
4366#endif
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 */