blob: 231db209fa82137461efbd51eb15a8061d6437a6 [file] [log] [blame]
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001/*
2 * Generic ring buffer
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/ring_buffer.h>
7#include <linux/spinlock.h>
8#include <linux/debugfs.h>
9#include <linux/uaccess.h>
10#include <linux/module.h>
11#include <linux/percpu.h>
12#include <linux/mutex.h>
13#include <linux/sched.h> /* used for sched_clock() (for now) */
14#include <linux/init.h>
15#include <linux/hash.h>
16#include <linux/list.h>
17#include <linux/fs.h>
18
Steven Rostedta3583242008-11-11 15:01:42 -050019#include "trace.h"
20
21/* Global flag to disable all recording to ring buffers */
22static int ring_buffers_off __read_mostly;
23
24/**
25 * tracing_on - enable all tracing buffers
26 *
27 * This function enables all tracing buffers that may have been
28 * disabled with tracing_off.
29 */
30void tracing_on(void)
31{
32 ring_buffers_off = 0;
33}
34
35/**
36 * tracing_off - turn off all tracing buffers
37 *
38 * This function stops all tracing buffers from recording data.
39 * It does not disable any overhead the tracers themselves may
40 * be causing. This function simply causes all recording to
41 * the ring buffers to fail.
42 */
43void tracing_off(void)
44{
45 ring_buffers_off = 1;
46}
47
Steven Rostedt7a8e76a2008-09-29 23:02:38 -040048/* Up this if you want to test the TIME_EXTENTS and normalization */
49#define DEBUG_SHIFT 0
50
51/* FIXME!!! */
52u64 ring_buffer_time_stamp(int cpu)
53{
Steven Rostedt47e74f22008-11-12 00:01:27 -050054 u64 time;
55
56 preempt_disable_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -040057 /* shift to debug/test normalization and TIME_EXTENTS */
Steven Rostedt47e74f22008-11-12 00:01:27 -050058 time = sched_clock() << DEBUG_SHIFT;
59 preempt_enable_notrace();
60
61 return time;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -040062}
63
64void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
65{
66 /* Just stupid testing the normalize function and deltas */
67 *ts >>= DEBUG_SHIFT;
68}
69
70#define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
71#define RB_ALIGNMENT_SHIFT 2
72#define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
73#define RB_MAX_SMALL_DATA 28
74
75enum {
76 RB_LEN_TIME_EXTEND = 8,
77 RB_LEN_TIME_STAMP = 16,
78};
79
80/* inline for ring buffer fast paths */
81static inline unsigned
82rb_event_length(struct ring_buffer_event *event)
83{
84 unsigned length;
85
86 switch (event->type) {
87 case RINGBUF_TYPE_PADDING:
88 /* undefined */
89 return -1;
90
91 case RINGBUF_TYPE_TIME_EXTEND:
92 return RB_LEN_TIME_EXTEND;
93
94 case RINGBUF_TYPE_TIME_STAMP:
95 return RB_LEN_TIME_STAMP;
96
97 case RINGBUF_TYPE_DATA:
98 if (event->len)
99 length = event->len << RB_ALIGNMENT_SHIFT;
100 else
101 length = event->array[0];
102 return length + RB_EVNT_HDR_SIZE;
103 default:
104 BUG();
105 }
106 /* not hit */
107 return 0;
108}
109
110/**
111 * ring_buffer_event_length - return the length of the event
112 * @event: the event to get the length of
113 */
114unsigned ring_buffer_event_length(struct ring_buffer_event *event)
115{
116 return rb_event_length(event);
117}
118
119/* inline for ring buffer fast paths */
120static inline void *
121rb_event_data(struct ring_buffer_event *event)
122{
123 BUG_ON(event->type != RINGBUF_TYPE_DATA);
124 /* If length is in len field, then array[0] has the data */
125 if (event->len)
126 return (void *)&event->array[0];
127 /* Otherwise length is in array[0] and array[1] has the data */
128 return (void *)&event->array[1];
129}
130
131/**
132 * ring_buffer_event_data - return the data of the event
133 * @event: the event to get the data from
134 */
135void *ring_buffer_event_data(struct ring_buffer_event *event)
136{
137 return rb_event_data(event);
138}
139
140#define for_each_buffer_cpu(buffer, cpu) \
141 for_each_cpu_mask(cpu, buffer->cpumask)
142
143#define TS_SHIFT 27
144#define TS_MASK ((1ULL << TS_SHIFT) - 1)
145#define TS_DELTA_TEST (~TS_MASK)
146
147/*
148 * This hack stolen from mm/slob.c.
149 * We can store per page timing information in the page frame of the page.
150 * Thanks to Peter Zijlstra for suggesting this idea.
151 */
152struct buffer_page {
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400153 u64 time_stamp; /* page time stamp */
Steven Rostedtbf41a152008-10-04 02:00:59 -0400154 local_t write; /* index for next write */
155 local_t commit; /* write commited index */
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400156 unsigned read; /* index for next read */
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400157 struct list_head list; /* list of free pages */
158 void *page; /* Actual data page */
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400159};
160
161/*
Steven Rostedted568292008-09-29 23:02:40 -0400162 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
163 * this issue out.
164 */
165static inline void free_buffer_page(struct buffer_page *bpage)
166{
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400167 if (bpage->page)
Steven Rostedt6ae2a072008-10-13 10:22:06 -0400168 free_page((unsigned long)bpage->page);
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400169 kfree(bpage);
Steven Rostedted568292008-09-29 23:02:40 -0400170}
171
172/*
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400173 * We need to fit the time_stamp delta into 27 bits.
174 */
175static inline int test_time_stamp(u64 delta)
176{
177 if (delta & TS_DELTA_TEST)
178 return 1;
179 return 0;
180}
181
182#define BUF_PAGE_SIZE PAGE_SIZE
183
184/*
185 * head_page == tail_page && head == tail then buffer is empty.
186 */
187struct ring_buffer_per_cpu {
188 int cpu;
189 struct ring_buffer *buffer;
190 spinlock_t lock;
191 struct lock_class_key lock_key;
192 struct list_head pages;
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400193 struct buffer_page *head_page; /* read from head */
194 struct buffer_page *tail_page; /* write to tail */
Steven Rostedtbf41a152008-10-04 02:00:59 -0400195 struct buffer_page *commit_page; /* commited pages */
Steven Rostedtd7690412008-10-01 00:29:53 -0400196 struct buffer_page *reader_page;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400197 unsigned long overrun;
198 unsigned long entries;
199 u64 write_stamp;
200 u64 read_stamp;
201 atomic_t record_disabled;
202};
203
204struct ring_buffer {
205 unsigned long size;
206 unsigned pages;
207 unsigned flags;
208 int cpus;
209 cpumask_t cpumask;
210 atomic_t record_disabled;
211
212 struct mutex mutex;
213
214 struct ring_buffer_per_cpu **buffers;
215};
216
217struct ring_buffer_iter {
218 struct ring_buffer_per_cpu *cpu_buffer;
219 unsigned long head;
220 struct buffer_page *head_page;
221 u64 read_stamp;
222};
223
Steven Rostedtbf41a152008-10-04 02:00:59 -0400224#define RB_WARN_ON(buffer, cond) \
225 do { \
226 if (unlikely(cond)) { \
227 atomic_inc(&buffer->record_disabled); \
228 WARN_ON(1); \
229 } \
230 } while (0)
231
232#define RB_WARN_ON_RET(buffer, cond) \
233 do { \
234 if (unlikely(cond)) { \
235 atomic_inc(&buffer->record_disabled); \
236 WARN_ON(1); \
237 return -1; \
238 } \
239 } while (0)
240
241#define RB_WARN_ON_ONCE(buffer, cond) \
242 do { \
243 static int once; \
244 if (unlikely(cond) && !once) { \
245 once++; \
246 atomic_inc(&buffer->record_disabled); \
247 WARN_ON(1); \
248 } \
249 } while (0)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400250
251/**
252 * check_pages - integrity check of buffer pages
253 * @cpu_buffer: CPU buffer with pages to test
254 *
255 * As a safty measure we check to make sure the data pages have not
256 * been corrupted.
257 */
258static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
259{
260 struct list_head *head = &cpu_buffer->pages;
261 struct buffer_page *page, *tmp;
262
Steven Rostedtbf41a152008-10-04 02:00:59 -0400263 RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);
264 RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400265
266 list_for_each_entry_safe(page, tmp, head, list) {
Steven Rostedtbf41a152008-10-04 02:00:59 -0400267 RB_WARN_ON_RET(cpu_buffer,
268 page->list.next->prev != &page->list);
269 RB_WARN_ON_RET(cpu_buffer,
270 page->list.prev->next != &page->list);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400271 }
272
273 return 0;
274}
275
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400276static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
277 unsigned nr_pages)
278{
279 struct list_head *head = &cpu_buffer->pages;
280 struct buffer_page *page, *tmp;
281 unsigned long addr;
282 LIST_HEAD(pages);
283 unsigned i;
284
285 for (i = 0; i < nr_pages; i++) {
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400286 page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
Steven Rostedtaa1e0e32008-10-02 19:18:09 -0400287 GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400288 if (!page)
289 goto free_pages;
290 list_add(&page->list, &pages);
291
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400292 addr = __get_free_page(GFP_KERNEL);
293 if (!addr)
294 goto free_pages;
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400295 page->page = (void *)addr;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400296 }
297
298 list_splice(&pages, head);
299
300 rb_check_pages(cpu_buffer);
301
302 return 0;
303
304 free_pages:
305 list_for_each_entry_safe(page, tmp, &pages, list) {
306 list_del_init(&page->list);
Steven Rostedted568292008-09-29 23:02:40 -0400307 free_buffer_page(page);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400308 }
309 return -ENOMEM;
310}
311
312static struct ring_buffer_per_cpu *
313rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
314{
315 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400316 struct buffer_page *page;
Steven Rostedtd7690412008-10-01 00:29:53 -0400317 unsigned long addr;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400318 int ret;
319
320 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
321 GFP_KERNEL, cpu_to_node(cpu));
322 if (!cpu_buffer)
323 return NULL;
324
325 cpu_buffer->cpu = cpu;
326 cpu_buffer->buffer = buffer;
327 spin_lock_init(&cpu_buffer->lock);
328 INIT_LIST_HEAD(&cpu_buffer->pages);
329
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400330 page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
331 GFP_KERNEL, cpu_to_node(cpu));
332 if (!page)
333 goto fail_free_buffer;
334
335 cpu_buffer->reader_page = page;
Steven Rostedtd7690412008-10-01 00:29:53 -0400336 addr = __get_free_page(GFP_KERNEL);
337 if (!addr)
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400338 goto fail_free_reader;
339 page->page = (void *)addr;
340
Steven Rostedtd7690412008-10-01 00:29:53 -0400341 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
Steven Rostedtd7690412008-10-01 00:29:53 -0400342
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400343 ret = rb_allocate_pages(cpu_buffer, buffer->pages);
344 if (ret < 0)
Steven Rostedtd7690412008-10-01 00:29:53 -0400345 goto fail_free_reader;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400346
347 cpu_buffer->head_page
348 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
Steven Rostedtbf41a152008-10-04 02:00:59 -0400349 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400350
351 return cpu_buffer;
352
Steven Rostedtd7690412008-10-01 00:29:53 -0400353 fail_free_reader:
354 free_buffer_page(cpu_buffer->reader_page);
355
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400356 fail_free_buffer:
357 kfree(cpu_buffer);
358 return NULL;
359}
360
361static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
362{
363 struct list_head *head = &cpu_buffer->pages;
364 struct buffer_page *page, *tmp;
365
Steven Rostedtd7690412008-10-01 00:29:53 -0400366 list_del_init(&cpu_buffer->reader_page->list);
367 free_buffer_page(cpu_buffer->reader_page);
368
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400369 list_for_each_entry_safe(page, tmp, head, list) {
370 list_del_init(&page->list);
Steven Rostedted568292008-09-29 23:02:40 -0400371 free_buffer_page(page);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400372 }
373 kfree(cpu_buffer);
374}
375
Steven Rostedta7b13742008-09-29 23:02:39 -0400376/*
377 * Causes compile errors if the struct buffer_page gets bigger
378 * than the struct page.
379 */
380extern int ring_buffer_page_too_big(void);
381
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400382/**
383 * ring_buffer_alloc - allocate a new ring_buffer
384 * @size: the size in bytes that is needed.
385 * @flags: attributes to set for the ring buffer.
386 *
387 * Currently the only flag that is available is the RB_FL_OVERWRITE
388 * flag. This flag means that the buffer will overwrite old data
389 * when the buffer wraps. If this flag is not set, the buffer will
390 * drop data when the tail hits the head.
391 */
392struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
393{
394 struct ring_buffer *buffer;
395 int bsize;
396 int cpu;
397
Steven Rostedta7b13742008-09-29 23:02:39 -0400398 /* Paranoid! Optimizes out when all is well */
399 if (sizeof(struct buffer_page) > sizeof(struct page))
400 ring_buffer_page_too_big();
401
402
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400403 /* keep it in its own cache line */
404 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
405 GFP_KERNEL);
406 if (!buffer)
407 return NULL;
408
409 buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
410 buffer->flags = flags;
411
412 /* need at least two pages */
413 if (buffer->pages == 1)
414 buffer->pages++;
415
416 buffer->cpumask = cpu_possible_map;
417 buffer->cpus = nr_cpu_ids;
418
419 bsize = sizeof(void *) * nr_cpu_ids;
420 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
421 GFP_KERNEL);
422 if (!buffer->buffers)
423 goto fail_free_buffer;
424
425 for_each_buffer_cpu(buffer, cpu) {
426 buffer->buffers[cpu] =
427 rb_allocate_cpu_buffer(buffer, cpu);
428 if (!buffer->buffers[cpu])
429 goto fail_free_buffers;
430 }
431
432 mutex_init(&buffer->mutex);
433
434 return buffer;
435
436 fail_free_buffers:
437 for_each_buffer_cpu(buffer, cpu) {
438 if (buffer->buffers[cpu])
439 rb_free_cpu_buffer(buffer->buffers[cpu]);
440 }
441 kfree(buffer->buffers);
442
443 fail_free_buffer:
444 kfree(buffer);
445 return NULL;
446}
447
448/**
449 * ring_buffer_free - free a ring buffer.
450 * @buffer: the buffer to free.
451 */
452void
453ring_buffer_free(struct ring_buffer *buffer)
454{
455 int cpu;
456
457 for_each_buffer_cpu(buffer, cpu)
458 rb_free_cpu_buffer(buffer->buffers[cpu]);
459
460 kfree(buffer);
461}
462
463static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
464
465static void
466rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
467{
468 struct buffer_page *page;
469 struct list_head *p;
470 unsigned i;
471
472 atomic_inc(&cpu_buffer->record_disabled);
473 synchronize_sched();
474
475 for (i = 0; i < nr_pages; i++) {
476 BUG_ON(list_empty(&cpu_buffer->pages));
477 p = cpu_buffer->pages.next;
478 page = list_entry(p, struct buffer_page, list);
479 list_del_init(&page->list);
Steven Rostedted568292008-09-29 23:02:40 -0400480 free_buffer_page(page);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400481 }
482 BUG_ON(list_empty(&cpu_buffer->pages));
483
484 rb_reset_cpu(cpu_buffer);
485
486 rb_check_pages(cpu_buffer);
487
488 atomic_dec(&cpu_buffer->record_disabled);
489
490}
491
492static void
493rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
494 struct list_head *pages, unsigned nr_pages)
495{
496 struct buffer_page *page;
497 struct list_head *p;
498 unsigned i;
499
500 atomic_inc(&cpu_buffer->record_disabled);
501 synchronize_sched();
502
503 for (i = 0; i < nr_pages; i++) {
504 BUG_ON(list_empty(pages));
505 p = pages->next;
506 page = list_entry(p, struct buffer_page, list);
507 list_del_init(&page->list);
508 list_add_tail(&page->list, &cpu_buffer->pages);
509 }
510 rb_reset_cpu(cpu_buffer);
511
512 rb_check_pages(cpu_buffer);
513
514 atomic_dec(&cpu_buffer->record_disabled);
515}
516
517/**
518 * ring_buffer_resize - resize the ring buffer
519 * @buffer: the buffer to resize.
520 * @size: the new size.
521 *
522 * The tracer is responsible for making sure that the buffer is
523 * not being used while changing the size.
524 * Note: We may be able to change the above requirement by using
525 * RCU synchronizations.
526 *
527 * Minimum size is 2 * BUF_PAGE_SIZE.
528 *
529 * Returns -1 on failure.
530 */
531int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
532{
533 struct ring_buffer_per_cpu *cpu_buffer;
534 unsigned nr_pages, rm_pages, new_pages;
535 struct buffer_page *page, *tmp;
536 unsigned long buffer_size;
537 unsigned long addr;
538 LIST_HEAD(pages);
539 int i, cpu;
540
541 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
542 size *= BUF_PAGE_SIZE;
543 buffer_size = buffer->pages * BUF_PAGE_SIZE;
544
545 /* we need a minimum of two pages */
546 if (size < BUF_PAGE_SIZE * 2)
547 size = BUF_PAGE_SIZE * 2;
548
549 if (size == buffer_size)
550 return size;
551
552 mutex_lock(&buffer->mutex);
553
554 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
555
556 if (size < buffer_size) {
557
558 /* easy case, just free pages */
559 BUG_ON(nr_pages >= buffer->pages);
560
561 rm_pages = buffer->pages - nr_pages;
562
563 for_each_buffer_cpu(buffer, cpu) {
564 cpu_buffer = buffer->buffers[cpu];
565 rb_remove_pages(cpu_buffer, rm_pages);
566 }
567 goto out;
568 }
569
570 /*
571 * This is a bit more difficult. We only want to add pages
572 * when we can allocate enough for all CPUs. We do this
573 * by allocating all the pages and storing them on a local
574 * link list. If we succeed in our allocation, then we
575 * add these pages to the cpu_buffers. Otherwise we just free
576 * them all and return -ENOMEM;
577 */
578 BUG_ON(nr_pages <= buffer->pages);
579 new_pages = nr_pages - buffer->pages;
580
581 for_each_buffer_cpu(buffer, cpu) {
582 for (i = 0; i < new_pages; i++) {
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400583 page = kzalloc_node(ALIGN(sizeof(*page),
584 cache_line_size()),
585 GFP_KERNEL, cpu_to_node(cpu));
586 if (!page)
587 goto free_pages;
588 list_add(&page->list, &pages);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400589 addr = __get_free_page(GFP_KERNEL);
590 if (!addr)
591 goto free_pages;
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400592 page->page = (void *)addr;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400593 }
594 }
595
596 for_each_buffer_cpu(buffer, cpu) {
597 cpu_buffer = buffer->buffers[cpu];
598 rb_insert_pages(cpu_buffer, &pages, new_pages);
599 }
600
601 BUG_ON(!list_empty(&pages));
602
603 out:
604 buffer->pages = nr_pages;
605 mutex_unlock(&buffer->mutex);
606
607 return size;
608
609 free_pages:
610 list_for_each_entry_safe(page, tmp, &pages, list) {
611 list_del_init(&page->list);
Steven Rostedted568292008-09-29 23:02:40 -0400612 free_buffer_page(page);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400613 }
614 return -ENOMEM;
615}
616
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400617static inline int rb_null_event(struct ring_buffer_event *event)
618{
619 return event->type == RINGBUF_TYPE_PADDING;
620}
621
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400622static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400623{
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400624 return page->page + index;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400625}
626
627static inline struct ring_buffer_event *
Steven Rostedtd7690412008-10-01 00:29:53 -0400628rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400629{
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400630 return __rb_page_index(cpu_buffer->reader_page,
631 cpu_buffer->reader_page->read);
632}
633
634static inline struct ring_buffer_event *
635rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
636{
637 return __rb_page_index(cpu_buffer->head_page,
638 cpu_buffer->head_page->read);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400639}
640
641static inline struct ring_buffer_event *
642rb_iter_head_event(struct ring_buffer_iter *iter)
643{
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400644 return __rb_page_index(iter->head_page, iter->head);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400645}
646
Steven Rostedtbf41a152008-10-04 02:00:59 -0400647static inline unsigned rb_page_write(struct buffer_page *bpage)
648{
649 return local_read(&bpage->write);
650}
651
652static inline unsigned rb_page_commit(struct buffer_page *bpage)
653{
654 return local_read(&bpage->commit);
655}
656
657/* Size is determined by what has been commited */
658static inline unsigned rb_page_size(struct buffer_page *bpage)
659{
660 return rb_page_commit(bpage);
661}
662
663static inline unsigned
664rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
665{
666 return rb_page_commit(cpu_buffer->commit_page);
667}
668
669static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
670{
671 return rb_page_commit(cpu_buffer->head_page);
672}
673
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400674/*
675 * When the tail hits the head and the buffer is in overwrite mode,
676 * the head jumps to the next page and all content on the previous
677 * page is discarded. But before doing so, we update the overrun
678 * variable of the buffer.
679 */
680static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
681{
682 struct ring_buffer_event *event;
683 unsigned long head;
684
685 for (head = 0; head < rb_head_size(cpu_buffer);
686 head += rb_event_length(event)) {
687
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400688 event = __rb_page_index(cpu_buffer->head_page, head);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400689 BUG_ON(rb_null_event(event));
690 /* Only count data entries */
691 if (event->type != RINGBUF_TYPE_DATA)
692 continue;
693 cpu_buffer->overrun++;
694 cpu_buffer->entries--;
695 }
696}
697
698static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
699 struct buffer_page **page)
700{
701 struct list_head *p = (*page)->list.next;
702
703 if (p == &cpu_buffer->pages)
704 p = p->next;
705
706 *page = list_entry(p, struct buffer_page, list);
707}
708
Steven Rostedtbf41a152008-10-04 02:00:59 -0400709static inline unsigned
710rb_event_index(struct ring_buffer_event *event)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400711{
Steven Rostedtbf41a152008-10-04 02:00:59 -0400712 unsigned long addr = (unsigned long)event;
713
714 return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400715}
716
Steven Rostedtbf41a152008-10-04 02:00:59 -0400717static inline int
718rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
719 struct ring_buffer_event *event)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400720{
Steven Rostedtbf41a152008-10-04 02:00:59 -0400721 unsigned long addr = (unsigned long)event;
722 unsigned long index;
723
724 index = rb_event_index(event);
725 addr &= PAGE_MASK;
726
727 return cpu_buffer->commit_page->page == (void *)addr &&
728 rb_commit_index(cpu_buffer) == index;
729}
730
731static inline void
732rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
733 struct ring_buffer_event *event)
734{
735 unsigned long addr = (unsigned long)event;
736 unsigned long index;
737
738 index = rb_event_index(event);
739 addr &= PAGE_MASK;
740
741 while (cpu_buffer->commit_page->page != (void *)addr) {
742 RB_WARN_ON(cpu_buffer,
743 cpu_buffer->commit_page == cpu_buffer->tail_page);
744 cpu_buffer->commit_page->commit =
745 cpu_buffer->commit_page->write;
746 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
747 cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
748 }
749
750 /* Now set the commit to the event's index */
751 local_set(&cpu_buffer->commit_page->commit, index);
752}
753
754static inline void
755rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
756{
757 /*
758 * We only race with interrupts and NMIs on this CPU.
759 * If we own the commit event, then we can commit
760 * all others that interrupted us, since the interruptions
761 * are in stack format (they finish before they come
762 * back to us). This allows us to do a simple loop to
763 * assign the commit to the tail.
764 */
765 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
766 cpu_buffer->commit_page->commit =
767 cpu_buffer->commit_page->write;
768 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
769 cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
770 /* add barrier to keep gcc from optimizing too much */
771 barrier();
772 }
773 while (rb_commit_index(cpu_buffer) !=
774 rb_page_write(cpu_buffer->commit_page)) {
775 cpu_buffer->commit_page->commit =
776 cpu_buffer->commit_page->write;
777 barrier();
778 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400779}
780
Steven Rostedtd7690412008-10-01 00:29:53 -0400781static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400782{
Steven Rostedtd7690412008-10-01 00:29:53 -0400783 cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400784 cpu_buffer->reader_page->read = 0;
Steven Rostedtd7690412008-10-01 00:29:53 -0400785}
786
787static inline void rb_inc_iter(struct ring_buffer_iter *iter)
788{
789 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
790
791 /*
792 * The iterator could be on the reader page (it starts there).
793 * But the head could have moved, since the reader was
794 * found. Check for this case and assign the iterator
795 * to the head page instead of next.
796 */
797 if (iter->head_page == cpu_buffer->reader_page)
798 iter->head_page = cpu_buffer->head_page;
799 else
800 rb_inc_page(cpu_buffer, &iter->head_page);
801
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400802 iter->read_stamp = iter->head_page->time_stamp;
803 iter->head = 0;
804}
805
806/**
807 * ring_buffer_update_event - update event type and data
808 * @event: the even to update
809 * @type: the type of event
810 * @length: the size of the event field in the ring buffer
811 *
812 * Update the type and data fields of the event. The length
813 * is the actual size that is written to the ring buffer,
814 * and with this, we can determine what to place into the
815 * data field.
816 */
817static inline void
818rb_update_event(struct ring_buffer_event *event,
819 unsigned type, unsigned length)
820{
821 event->type = type;
822
823 switch (type) {
824
825 case RINGBUF_TYPE_PADDING:
826 break;
827
828 case RINGBUF_TYPE_TIME_EXTEND:
829 event->len =
830 (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
831 >> RB_ALIGNMENT_SHIFT;
832 break;
833
834 case RINGBUF_TYPE_TIME_STAMP:
835 event->len =
836 (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
837 >> RB_ALIGNMENT_SHIFT;
838 break;
839
840 case RINGBUF_TYPE_DATA:
841 length -= RB_EVNT_HDR_SIZE;
842 if (length > RB_MAX_SMALL_DATA) {
843 event->len = 0;
844 event->array[0] = length;
845 } else
846 event->len =
847 (length + (RB_ALIGNMENT-1))
848 >> RB_ALIGNMENT_SHIFT;
849 break;
850 default:
851 BUG();
852 }
853}
854
855static inline unsigned rb_calculate_event_length(unsigned length)
856{
857 struct ring_buffer_event event; /* Used only for sizeof array */
858
859 /* zero length can cause confusions */
860 if (!length)
861 length = 1;
862
863 if (length > RB_MAX_SMALL_DATA)
864 length += sizeof(event.array[0]);
865
866 length += RB_EVNT_HDR_SIZE;
867 length = ALIGN(length, RB_ALIGNMENT);
868
869 return length;
870}
871
872static struct ring_buffer_event *
873__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
874 unsigned type, unsigned long length, u64 *ts)
875{
Steven Rostedtd7690412008-10-01 00:29:53 -0400876 struct buffer_page *tail_page, *head_page, *reader_page;
Steven Rostedtbf41a152008-10-04 02:00:59 -0400877 unsigned long tail, write;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400878 struct ring_buffer *buffer = cpu_buffer->buffer;
879 struct ring_buffer_event *event;
Steven Rostedtbf41a152008-10-04 02:00:59 -0400880 unsigned long flags;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400881
882 tail_page = cpu_buffer->tail_page;
Steven Rostedtbf41a152008-10-04 02:00:59 -0400883 write = local_add_return(length, &tail_page->write);
884 tail = write - length;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400885
Steven Rostedtbf41a152008-10-04 02:00:59 -0400886 /* See if we shot pass the end of this buffer page */
887 if (write > BUF_PAGE_SIZE) {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400888 struct buffer_page *next_page = tail_page;
889
Steven Rostedtbf41a152008-10-04 02:00:59 -0400890 spin_lock_irqsave(&cpu_buffer->lock, flags);
891
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400892 rb_inc_page(cpu_buffer, &next_page);
893
Steven Rostedtd7690412008-10-01 00:29:53 -0400894 head_page = cpu_buffer->head_page;
895 reader_page = cpu_buffer->reader_page;
896
897 /* we grabbed the lock before incrementing */
Steven Rostedtbf41a152008-10-04 02:00:59 -0400898 RB_WARN_ON(cpu_buffer, next_page == reader_page);
899
900 /*
901 * If for some reason, we had an interrupt storm that made
902 * it all the way around the buffer, bail, and warn
903 * about it.
904 */
905 if (unlikely(next_page == cpu_buffer->commit_page)) {
906 WARN_ON_ONCE(1);
907 goto out_unlock;
908 }
Steven Rostedtd7690412008-10-01 00:29:53 -0400909
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400910 if (next_page == head_page) {
Steven Rostedtd7690412008-10-01 00:29:53 -0400911 if (!(buffer->flags & RB_FL_OVERWRITE)) {
Steven Rostedtbf41a152008-10-04 02:00:59 -0400912 /* reset write */
913 if (tail <= BUF_PAGE_SIZE)
914 local_set(&tail_page->write, tail);
915 goto out_unlock;
Steven Rostedtd7690412008-10-01 00:29:53 -0400916 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400917
Steven Rostedtbf41a152008-10-04 02:00:59 -0400918 /* tail_page has not moved yet? */
919 if (tail_page == cpu_buffer->tail_page) {
920 /* count overflows */
921 rb_update_overflow(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400922
Steven Rostedtbf41a152008-10-04 02:00:59 -0400923 rb_inc_page(cpu_buffer, &head_page);
924 cpu_buffer->head_page = head_page;
925 cpu_buffer->head_page->read = 0;
926 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400927 }
928
Steven Rostedtbf41a152008-10-04 02:00:59 -0400929 /*
930 * If the tail page is still the same as what we think
931 * it is, then it is up to us to update the tail
932 * pointer.
933 */
934 if (tail_page == cpu_buffer->tail_page) {
935 local_set(&next_page->write, 0);
936 local_set(&next_page->commit, 0);
937 cpu_buffer->tail_page = next_page;
938
939 /* reread the time stamp */
940 *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
941 cpu_buffer->tail_page->time_stamp = *ts;
942 }
943
944 /*
945 * The actual tail page has moved forward.
946 */
947 if (tail < BUF_PAGE_SIZE) {
948 /* Mark the rest of the page with padding */
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400949 event = __rb_page_index(tail_page, tail);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400950 event->type = RINGBUF_TYPE_PADDING;
951 }
952
Steven Rostedtbf41a152008-10-04 02:00:59 -0400953 if (tail <= BUF_PAGE_SIZE)
954 /* Set the write back to the previous setting */
955 local_set(&tail_page->write, tail);
956
957 /*
958 * If this was a commit entry that failed,
959 * increment that too
960 */
961 if (tail_page == cpu_buffer->commit_page &&
962 tail == rb_commit_index(cpu_buffer)) {
963 rb_set_commit_to_write(cpu_buffer);
964 }
965
966 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
967
968 /* fail and let the caller try again */
969 return ERR_PTR(-EAGAIN);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400970 }
971
Steven Rostedtbf41a152008-10-04 02:00:59 -0400972 /* We reserved something on the buffer */
973
974 BUG_ON(write > BUF_PAGE_SIZE);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400975
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400976 event = __rb_page_index(tail_page, tail);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400977 rb_update_event(event, type, length);
978
Steven Rostedtbf41a152008-10-04 02:00:59 -0400979 /*
980 * If this is a commit and the tail is zero, then update
981 * this page's time stamp.
982 */
983 if (!tail && rb_is_commit(cpu_buffer, event))
984 cpu_buffer->commit_page->time_stamp = *ts;
985
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400986 return event;
Steven Rostedtbf41a152008-10-04 02:00:59 -0400987
988 out_unlock:
989 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
990 return NULL;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400991}
992
993static int
994rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
995 u64 *ts, u64 *delta)
996{
997 struct ring_buffer_event *event;
998 static int once;
Steven Rostedtbf41a152008-10-04 02:00:59 -0400999 int ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001000
1001 if (unlikely(*delta > (1ULL << 59) && !once++)) {
1002 printk(KERN_WARNING "Delta way too big! %llu"
1003 " ts=%llu write stamp = %llu\n",
Stephen Rothwelle2862c92008-10-27 17:43:28 +11001004 (unsigned long long)*delta,
1005 (unsigned long long)*ts,
1006 (unsigned long long)cpu_buffer->write_stamp);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001007 WARN_ON(1);
1008 }
1009
1010 /*
1011 * The delta is too big, we to add a
1012 * new timestamp.
1013 */
1014 event = __rb_reserve_next(cpu_buffer,
1015 RINGBUF_TYPE_TIME_EXTEND,
1016 RB_LEN_TIME_EXTEND,
1017 ts);
1018 if (!event)
Steven Rostedtbf41a152008-10-04 02:00:59 -04001019 return -EBUSY;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001020
Steven Rostedtbf41a152008-10-04 02:00:59 -04001021 if (PTR_ERR(event) == -EAGAIN)
1022 return -EAGAIN;
1023
1024 /* Only a commited time event can update the write stamp */
1025 if (rb_is_commit(cpu_buffer, event)) {
1026 /*
1027 * If this is the first on the page, then we need to
1028 * update the page itself, and just put in a zero.
1029 */
1030 if (rb_event_index(event)) {
1031 event->time_delta = *delta & TS_MASK;
1032 event->array[0] = *delta >> TS_SHIFT;
1033 } else {
1034 cpu_buffer->commit_page->time_stamp = *ts;
1035 event->time_delta = 0;
1036 event->array[0] = 0;
1037 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001038 cpu_buffer->write_stamp = *ts;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001039 /* let the caller know this was the commit */
1040 ret = 1;
1041 } else {
1042 /* Darn, this is just wasted space */
1043 event->time_delta = 0;
1044 event->array[0] = 0;
1045 ret = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001046 }
1047
Steven Rostedtbf41a152008-10-04 02:00:59 -04001048 *delta = 0;
1049
1050 return ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001051}
1052
1053static struct ring_buffer_event *
1054rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
1055 unsigned type, unsigned long length)
1056{
1057 struct ring_buffer_event *event;
1058 u64 ts, delta;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001059 int commit = 0;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001060 int nr_loops = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001061
Steven Rostedtbf41a152008-10-04 02:00:59 -04001062 again:
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001063 /*
1064 * We allow for interrupts to reenter here and do a trace.
1065 * If one does, it will cause this original code to loop
1066 * back here. Even with heavy interrupts happening, this
1067 * should only happen a few times in a row. If this happens
1068 * 1000 times in a row, there must be either an interrupt
1069 * storm or we have something buggy.
1070 * Bail!
1071 */
1072 if (unlikely(++nr_loops > 1000)) {
1073 RB_WARN_ON(cpu_buffer, 1);
1074 return NULL;
1075 }
1076
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001077 ts = ring_buffer_time_stamp(cpu_buffer->cpu);
1078
Steven Rostedtbf41a152008-10-04 02:00:59 -04001079 /*
1080 * Only the first commit can update the timestamp.
1081 * Yes there is a race here. If an interrupt comes in
1082 * just after the conditional and it traces too, then it
1083 * will also check the deltas. More than one timestamp may
1084 * also be made. But only the entry that did the actual
1085 * commit will be something other than zero.
1086 */
1087 if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
1088 rb_page_write(cpu_buffer->tail_page) ==
1089 rb_commit_index(cpu_buffer)) {
1090
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001091 delta = ts - cpu_buffer->write_stamp;
1092
Steven Rostedtbf41a152008-10-04 02:00:59 -04001093 /* make sure this delta is calculated here */
1094 barrier();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001095
Steven Rostedtbf41a152008-10-04 02:00:59 -04001096 /* Did the write stamp get updated already? */
1097 if (unlikely(ts < cpu_buffer->write_stamp))
Steven Rostedt4143c5c2008-11-10 21:46:01 -05001098 delta = 0;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001099
1100 if (test_time_stamp(delta)) {
1101
1102 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
1103
1104 if (commit == -EBUSY)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001105 return NULL;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001106
1107 if (commit == -EAGAIN)
1108 goto again;
1109
1110 RB_WARN_ON(cpu_buffer, commit < 0);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001111 }
Steven Rostedtbf41a152008-10-04 02:00:59 -04001112 } else
1113 /* Non commits have zero deltas */
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001114 delta = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001115
1116 event = __rb_reserve_next(cpu_buffer, type, length, &ts);
Steven Rostedtbf41a152008-10-04 02:00:59 -04001117 if (PTR_ERR(event) == -EAGAIN)
1118 goto again;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001119
Steven Rostedtbf41a152008-10-04 02:00:59 -04001120 if (!event) {
1121 if (unlikely(commit))
1122 /*
1123 * Ouch! We needed a timestamp and it was commited. But
1124 * we didn't get our event reserved.
1125 */
1126 rb_set_commit_to_write(cpu_buffer);
1127 return NULL;
1128 }
1129
1130 /*
1131 * If the timestamp was commited, make the commit our entry
1132 * now so that we will update it when needed.
1133 */
1134 if (commit)
1135 rb_set_commit_event(cpu_buffer, event);
1136 else if (!rb_is_commit(cpu_buffer, event))
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001137 delta = 0;
1138
1139 event->time_delta = delta;
1140
1141 return event;
1142}
1143
Steven Rostedtbf41a152008-10-04 02:00:59 -04001144static DEFINE_PER_CPU(int, rb_need_resched);
1145
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001146/**
1147 * ring_buffer_lock_reserve - reserve a part of the buffer
1148 * @buffer: the ring buffer to reserve from
1149 * @length: the length of the data to reserve (excluding event header)
1150 * @flags: a pointer to save the interrupt flags
1151 *
1152 * Returns a reseverd event on the ring buffer to copy directly to.
1153 * The user of this interface will need to get the body to write into
1154 * and can use the ring_buffer_event_data() interface.
1155 *
1156 * The length is the length of the data needed, not the event length
1157 * which also includes the event header.
1158 *
1159 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1160 * If NULL is returned, then nothing has been allocated or locked.
1161 */
1162struct ring_buffer_event *
1163ring_buffer_lock_reserve(struct ring_buffer *buffer,
1164 unsigned long length,
1165 unsigned long *flags)
1166{
1167 struct ring_buffer_per_cpu *cpu_buffer;
1168 struct ring_buffer_event *event;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001169 int cpu, resched;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001170
Steven Rostedta3583242008-11-11 15:01:42 -05001171 if (ring_buffers_off)
1172 return NULL;
1173
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001174 if (atomic_read(&buffer->record_disabled))
1175 return NULL;
1176
Steven Rostedtbf41a152008-10-04 02:00:59 -04001177 /* If we are tracing schedule, we don't want to recurse */
1178 resched = need_resched();
1179 preempt_disable_notrace();
1180
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001181 cpu = raw_smp_processor_id();
1182
1183 if (!cpu_isset(cpu, buffer->cpumask))
Steven Rostedtd7690412008-10-01 00:29:53 -04001184 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001185
1186 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001187
1188 if (atomic_read(&cpu_buffer->record_disabled))
Steven Rostedtd7690412008-10-01 00:29:53 -04001189 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001190
1191 length = rb_calculate_event_length(length);
1192 if (length > BUF_PAGE_SIZE)
Steven Rostedtbf41a152008-10-04 02:00:59 -04001193 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001194
1195 event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
1196 if (!event)
Steven Rostedtd7690412008-10-01 00:29:53 -04001197 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001198
Steven Rostedtbf41a152008-10-04 02:00:59 -04001199 /*
1200 * Need to store resched state on this cpu.
1201 * Only the first needs to.
1202 */
1203
1204 if (preempt_count() == 1)
1205 per_cpu(rb_need_resched, cpu) = resched;
1206
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001207 return event;
1208
Steven Rostedtd7690412008-10-01 00:29:53 -04001209 out:
Steven Rostedtbf41a152008-10-04 02:00:59 -04001210 if (resched)
1211 preempt_enable_notrace();
1212 else
1213 preempt_enable_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001214 return NULL;
1215}
1216
1217static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
1218 struct ring_buffer_event *event)
1219{
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001220 cpu_buffer->entries++;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001221
1222 /* Only process further if we own the commit */
1223 if (!rb_is_commit(cpu_buffer, event))
1224 return;
1225
1226 cpu_buffer->write_stamp += event->time_delta;
1227
1228 rb_set_commit_to_write(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001229}
1230
1231/**
1232 * ring_buffer_unlock_commit - commit a reserved
1233 * @buffer: The buffer to commit to
1234 * @event: The event pointer to commit.
1235 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1236 *
1237 * This commits the data to the ring buffer, and releases any locks held.
1238 *
1239 * Must be paired with ring_buffer_lock_reserve.
1240 */
1241int ring_buffer_unlock_commit(struct ring_buffer *buffer,
1242 struct ring_buffer_event *event,
1243 unsigned long flags)
1244{
1245 struct ring_buffer_per_cpu *cpu_buffer;
1246 int cpu = raw_smp_processor_id();
1247
1248 cpu_buffer = buffer->buffers[cpu];
1249
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001250 rb_commit(cpu_buffer, event);
1251
Steven Rostedtbf41a152008-10-04 02:00:59 -04001252 /*
1253 * Only the last preempt count needs to restore preemption.
1254 */
1255 if (preempt_count() == 1) {
1256 if (per_cpu(rb_need_resched, cpu))
1257 preempt_enable_no_resched_notrace();
1258 else
1259 preempt_enable_notrace();
1260 } else
1261 preempt_enable_no_resched_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001262
1263 return 0;
1264}
1265
1266/**
1267 * ring_buffer_write - write data to the buffer without reserving
1268 * @buffer: The ring buffer to write to.
1269 * @length: The length of the data being written (excluding the event header)
1270 * @data: The data to write to the buffer.
1271 *
1272 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1273 * one function. If you already have the data to write to the buffer, it
1274 * may be easier to simply call this function.
1275 *
1276 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1277 * and not the length of the event which would hold the header.
1278 */
1279int ring_buffer_write(struct ring_buffer *buffer,
1280 unsigned long length,
1281 void *data)
1282{
1283 struct ring_buffer_per_cpu *cpu_buffer;
1284 struct ring_buffer_event *event;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001285 unsigned long event_length;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001286 void *body;
1287 int ret = -EBUSY;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001288 int cpu, resched;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001289
Steven Rostedta3583242008-11-11 15:01:42 -05001290 if (ring_buffers_off)
1291 return -EBUSY;
1292
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001293 if (atomic_read(&buffer->record_disabled))
1294 return -EBUSY;
1295
Steven Rostedtbf41a152008-10-04 02:00:59 -04001296 resched = need_resched();
1297 preempt_disable_notrace();
1298
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001299 cpu = raw_smp_processor_id();
1300
1301 if (!cpu_isset(cpu, buffer->cpumask))
Steven Rostedtd7690412008-10-01 00:29:53 -04001302 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001303
1304 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001305
1306 if (atomic_read(&cpu_buffer->record_disabled))
1307 goto out;
1308
1309 event_length = rb_calculate_event_length(length);
1310 event = rb_reserve_next_event(cpu_buffer,
1311 RINGBUF_TYPE_DATA, event_length);
1312 if (!event)
1313 goto out;
1314
1315 body = rb_event_data(event);
1316
1317 memcpy(body, data, length);
1318
1319 rb_commit(cpu_buffer, event);
1320
1321 ret = 0;
1322 out:
Steven Rostedtbf41a152008-10-04 02:00:59 -04001323 if (resched)
1324 preempt_enable_no_resched_notrace();
1325 else
1326 preempt_enable_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001327
1328 return ret;
1329}
1330
Steven Rostedtbf41a152008-10-04 02:00:59 -04001331static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
1332{
1333 struct buffer_page *reader = cpu_buffer->reader_page;
1334 struct buffer_page *head = cpu_buffer->head_page;
1335 struct buffer_page *commit = cpu_buffer->commit_page;
1336
1337 return reader->read == rb_page_commit(reader) &&
1338 (commit == reader ||
1339 (commit == head &&
1340 head->read == rb_page_commit(commit)));
1341}
1342
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001343/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001344 * ring_buffer_record_disable - stop all writes into the buffer
1345 * @buffer: The ring buffer to stop writes to.
1346 *
1347 * This prevents all writes to the buffer. Any attempt to write
1348 * to the buffer after this will fail and return NULL.
1349 *
1350 * The caller should call synchronize_sched() after this.
1351 */
1352void ring_buffer_record_disable(struct ring_buffer *buffer)
1353{
1354 atomic_inc(&buffer->record_disabled);
1355}
1356
1357/**
1358 * ring_buffer_record_enable - enable writes to the buffer
1359 * @buffer: The ring buffer to enable writes
1360 *
1361 * Note, multiple disables will need the same number of enables
1362 * to truely enable the writing (much like preempt_disable).
1363 */
1364void ring_buffer_record_enable(struct ring_buffer *buffer)
1365{
1366 atomic_dec(&buffer->record_disabled);
1367}
1368
1369/**
1370 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1371 * @buffer: The ring buffer to stop writes to.
1372 * @cpu: The CPU buffer to stop
1373 *
1374 * This prevents all writes to the buffer. Any attempt to write
1375 * to the buffer after this will fail and return NULL.
1376 *
1377 * The caller should call synchronize_sched() after this.
1378 */
1379void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
1380{
1381 struct ring_buffer_per_cpu *cpu_buffer;
1382
1383 if (!cpu_isset(cpu, buffer->cpumask))
1384 return;
1385
1386 cpu_buffer = buffer->buffers[cpu];
1387 atomic_inc(&cpu_buffer->record_disabled);
1388}
1389
1390/**
1391 * ring_buffer_record_enable_cpu - enable writes to the buffer
1392 * @buffer: The ring buffer to enable writes
1393 * @cpu: The CPU to enable.
1394 *
1395 * Note, multiple disables will need the same number of enables
1396 * to truely enable the writing (much like preempt_disable).
1397 */
1398void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
1399{
1400 struct ring_buffer_per_cpu *cpu_buffer;
1401
1402 if (!cpu_isset(cpu, buffer->cpumask))
1403 return;
1404
1405 cpu_buffer = buffer->buffers[cpu];
1406 atomic_dec(&cpu_buffer->record_disabled);
1407}
1408
1409/**
1410 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1411 * @buffer: The ring buffer
1412 * @cpu: The per CPU buffer to get the entries from.
1413 */
1414unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
1415{
1416 struct ring_buffer_per_cpu *cpu_buffer;
1417
1418 if (!cpu_isset(cpu, buffer->cpumask))
1419 return 0;
1420
1421 cpu_buffer = buffer->buffers[cpu];
1422 return cpu_buffer->entries;
1423}
1424
1425/**
1426 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1427 * @buffer: The ring buffer
1428 * @cpu: The per CPU buffer to get the number of overruns from
1429 */
1430unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
1431{
1432 struct ring_buffer_per_cpu *cpu_buffer;
1433
1434 if (!cpu_isset(cpu, buffer->cpumask))
1435 return 0;
1436
1437 cpu_buffer = buffer->buffers[cpu];
1438 return cpu_buffer->overrun;
1439}
1440
1441/**
1442 * ring_buffer_entries - get the number of entries in a buffer
1443 * @buffer: The ring buffer
1444 *
1445 * Returns the total number of entries in the ring buffer
1446 * (all CPU entries)
1447 */
1448unsigned long ring_buffer_entries(struct ring_buffer *buffer)
1449{
1450 struct ring_buffer_per_cpu *cpu_buffer;
1451 unsigned long entries = 0;
1452 int cpu;
1453
1454 /* if you care about this being correct, lock the buffer */
1455 for_each_buffer_cpu(buffer, cpu) {
1456 cpu_buffer = buffer->buffers[cpu];
1457 entries += cpu_buffer->entries;
1458 }
1459
1460 return entries;
1461}
1462
1463/**
1464 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1465 * @buffer: The ring buffer
1466 *
1467 * Returns the total number of overruns in the ring buffer
1468 * (all CPU entries)
1469 */
1470unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
1471{
1472 struct ring_buffer_per_cpu *cpu_buffer;
1473 unsigned long overruns = 0;
1474 int cpu;
1475
1476 /* if you care about this being correct, lock the buffer */
1477 for_each_buffer_cpu(buffer, cpu) {
1478 cpu_buffer = buffer->buffers[cpu];
1479 overruns += cpu_buffer->overrun;
1480 }
1481
1482 return overruns;
1483}
1484
1485/**
1486 * ring_buffer_iter_reset - reset an iterator
1487 * @iter: The iterator to reset
1488 *
1489 * Resets the iterator, so that it will start from the beginning
1490 * again.
1491 */
1492void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
1493{
1494 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1495
Steven Rostedtd7690412008-10-01 00:29:53 -04001496 /* Iterator usage is expected to have record disabled */
1497 if (list_empty(&cpu_buffer->reader_page->list)) {
1498 iter->head_page = cpu_buffer->head_page;
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001499 iter->head = cpu_buffer->head_page->read;
Steven Rostedtd7690412008-10-01 00:29:53 -04001500 } else {
1501 iter->head_page = cpu_buffer->reader_page;
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001502 iter->head = cpu_buffer->reader_page->read;
Steven Rostedtd7690412008-10-01 00:29:53 -04001503 }
1504 if (iter->head)
1505 iter->read_stamp = cpu_buffer->read_stamp;
1506 else
1507 iter->read_stamp = iter->head_page->time_stamp;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001508}
1509
1510/**
1511 * ring_buffer_iter_empty - check if an iterator has no more to read
1512 * @iter: The iterator to check
1513 */
1514int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
1515{
1516 struct ring_buffer_per_cpu *cpu_buffer;
1517
1518 cpu_buffer = iter->cpu_buffer;
1519
Steven Rostedtbf41a152008-10-04 02:00:59 -04001520 return iter->head_page == cpu_buffer->commit_page &&
1521 iter->head == rb_commit_index(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001522}
1523
1524static void
1525rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1526 struct ring_buffer_event *event)
1527{
1528 u64 delta;
1529
1530 switch (event->type) {
1531 case RINGBUF_TYPE_PADDING:
1532 return;
1533
1534 case RINGBUF_TYPE_TIME_EXTEND:
1535 delta = event->array[0];
1536 delta <<= TS_SHIFT;
1537 delta += event->time_delta;
1538 cpu_buffer->read_stamp += delta;
1539 return;
1540
1541 case RINGBUF_TYPE_TIME_STAMP:
1542 /* FIXME: not implemented */
1543 return;
1544
1545 case RINGBUF_TYPE_DATA:
1546 cpu_buffer->read_stamp += event->time_delta;
1547 return;
1548
1549 default:
1550 BUG();
1551 }
1552 return;
1553}
1554
1555static void
1556rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
1557 struct ring_buffer_event *event)
1558{
1559 u64 delta;
1560
1561 switch (event->type) {
1562 case RINGBUF_TYPE_PADDING:
1563 return;
1564
1565 case RINGBUF_TYPE_TIME_EXTEND:
1566 delta = event->array[0];
1567 delta <<= TS_SHIFT;
1568 delta += event->time_delta;
1569 iter->read_stamp += delta;
1570 return;
1571
1572 case RINGBUF_TYPE_TIME_STAMP:
1573 /* FIXME: not implemented */
1574 return;
1575
1576 case RINGBUF_TYPE_DATA:
1577 iter->read_stamp += event->time_delta;
1578 return;
1579
1580 default:
1581 BUG();
1582 }
1583 return;
1584}
1585
Steven Rostedtd7690412008-10-01 00:29:53 -04001586static struct buffer_page *
1587rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001588{
Steven Rostedtd7690412008-10-01 00:29:53 -04001589 struct buffer_page *reader = NULL;
1590 unsigned long flags;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001591 int nr_loops = 0;
Steven Rostedtd7690412008-10-01 00:29:53 -04001592
1593 spin_lock_irqsave(&cpu_buffer->lock, flags);
1594
1595 again:
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001596 /*
1597 * This should normally only loop twice. But because the
1598 * start of the reader inserts an empty page, it causes
1599 * a case where we will loop three times. There should be no
1600 * reason to loop four times (that I know of).
1601 */
1602 if (unlikely(++nr_loops > 3)) {
1603 RB_WARN_ON(cpu_buffer, 1);
1604 reader = NULL;
1605 goto out;
1606 }
1607
Steven Rostedtd7690412008-10-01 00:29:53 -04001608 reader = cpu_buffer->reader_page;
1609
1610 /* If there's more to read, return this page */
Steven Rostedtbf41a152008-10-04 02:00:59 -04001611 if (cpu_buffer->reader_page->read < rb_page_size(reader))
Steven Rostedtd7690412008-10-01 00:29:53 -04001612 goto out;
1613
1614 /* Never should we have an index greater than the size */
Steven Rostedtbf41a152008-10-04 02:00:59 -04001615 RB_WARN_ON(cpu_buffer,
1616 cpu_buffer->reader_page->read > rb_page_size(reader));
Steven Rostedtd7690412008-10-01 00:29:53 -04001617
1618 /* check if we caught up to the tail */
1619 reader = NULL;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001620 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
Steven Rostedtd7690412008-10-01 00:29:53 -04001621 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001622
1623 /*
Steven Rostedtd7690412008-10-01 00:29:53 -04001624 * Splice the empty reader page into the list around the head.
1625 * Reset the reader page to size zero.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001626 */
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001627
Steven Rostedtd7690412008-10-01 00:29:53 -04001628 reader = cpu_buffer->head_page;
1629 cpu_buffer->reader_page->list.next = reader->list.next;
1630 cpu_buffer->reader_page->list.prev = reader->list.prev;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001631
1632 local_set(&cpu_buffer->reader_page->write, 0);
1633 local_set(&cpu_buffer->reader_page->commit, 0);
Steven Rostedtd7690412008-10-01 00:29:53 -04001634
1635 /* Make the reader page now replace the head */
1636 reader->list.prev->next = &cpu_buffer->reader_page->list;
1637 reader->list.next->prev = &cpu_buffer->reader_page->list;
1638
1639 /*
1640 * If the tail is on the reader, then we must set the head
1641 * to the inserted page, otherwise we set it one before.
1642 */
1643 cpu_buffer->head_page = cpu_buffer->reader_page;
1644
Steven Rostedtbf41a152008-10-04 02:00:59 -04001645 if (cpu_buffer->commit_page != reader)
Steven Rostedtd7690412008-10-01 00:29:53 -04001646 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
1647
1648 /* Finally update the reader page to the new head */
1649 cpu_buffer->reader_page = reader;
1650 rb_reset_reader_page(cpu_buffer);
1651
1652 goto again;
1653
1654 out:
1655 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
1656
1657 return reader;
1658}
1659
1660static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
1661{
1662 struct ring_buffer_event *event;
1663 struct buffer_page *reader;
1664 unsigned length;
1665
1666 reader = rb_get_reader_page(cpu_buffer);
1667
1668 /* This function should not be called when buffer is empty */
1669 BUG_ON(!reader);
1670
1671 event = rb_reader_event(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001672
1673 if (event->type == RINGBUF_TYPE_DATA)
1674 cpu_buffer->entries--;
1675
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001676 rb_update_read_stamp(cpu_buffer, event);
1677
Steven Rostedtd7690412008-10-01 00:29:53 -04001678 length = rb_event_length(event);
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001679 cpu_buffer->reader_page->read += length;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001680}
1681
1682static void rb_advance_iter(struct ring_buffer_iter *iter)
1683{
1684 struct ring_buffer *buffer;
1685 struct ring_buffer_per_cpu *cpu_buffer;
1686 struct ring_buffer_event *event;
1687 unsigned length;
1688
1689 cpu_buffer = iter->cpu_buffer;
1690 buffer = cpu_buffer->buffer;
1691
1692 /*
1693 * Check if we are at the end of the buffer.
1694 */
Steven Rostedtbf41a152008-10-04 02:00:59 -04001695 if (iter->head >= rb_page_size(iter->head_page)) {
1696 BUG_ON(iter->head_page == cpu_buffer->commit_page);
Steven Rostedtd7690412008-10-01 00:29:53 -04001697 rb_inc_iter(iter);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001698 return;
1699 }
1700
1701 event = rb_iter_head_event(iter);
1702
1703 length = rb_event_length(event);
1704
1705 /*
1706 * This should not be called to advance the header if we are
1707 * at the tail of the buffer.
1708 */
Steven Rostedtbf41a152008-10-04 02:00:59 -04001709 BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
1710 (iter->head + length > rb_commit_index(cpu_buffer)));
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001711
1712 rb_update_iter_read_stamp(iter, event);
1713
1714 iter->head += length;
1715
1716 /* check for end of page padding */
Steven Rostedtbf41a152008-10-04 02:00:59 -04001717 if ((iter->head >= rb_page_size(iter->head_page)) &&
1718 (iter->head_page != cpu_buffer->commit_page))
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001719 rb_advance_iter(iter);
1720}
1721
1722/**
1723 * ring_buffer_peek - peek at the next event to be read
1724 * @buffer: The ring buffer to read
1725 * @cpu: The cpu to peak at
1726 * @ts: The timestamp counter of this event.
1727 *
1728 * This will return the event that will be read next, but does
1729 * not consume the data.
1730 */
1731struct ring_buffer_event *
1732ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
1733{
1734 struct ring_buffer_per_cpu *cpu_buffer;
1735 struct ring_buffer_event *event;
Steven Rostedtd7690412008-10-01 00:29:53 -04001736 struct buffer_page *reader;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001737 int nr_loops = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001738
1739 if (!cpu_isset(cpu, buffer->cpumask))
1740 return NULL;
1741
1742 cpu_buffer = buffer->buffers[cpu];
1743
1744 again:
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001745 /*
1746 * We repeat when a timestamp is encountered. It is possible
1747 * to get multiple timestamps from an interrupt entering just
1748 * as one timestamp is about to be written. The max times
1749 * that this can happen is the number of nested interrupts we
1750 * can have. Nesting 10 deep of interrupts is clearly
1751 * an anomaly.
1752 */
1753 if (unlikely(++nr_loops > 10)) {
1754 RB_WARN_ON(cpu_buffer, 1);
1755 return NULL;
1756 }
1757
Steven Rostedtd7690412008-10-01 00:29:53 -04001758 reader = rb_get_reader_page(cpu_buffer);
1759 if (!reader)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001760 return NULL;
1761
Steven Rostedtd7690412008-10-01 00:29:53 -04001762 event = rb_reader_event(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001763
1764 switch (event->type) {
1765 case RINGBUF_TYPE_PADDING:
Steven Rostedtbf41a152008-10-04 02:00:59 -04001766 RB_WARN_ON(cpu_buffer, 1);
Steven Rostedtd7690412008-10-01 00:29:53 -04001767 rb_advance_reader(cpu_buffer);
1768 return NULL;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001769
1770 case RINGBUF_TYPE_TIME_EXTEND:
1771 /* Internal data, OK to advance */
Steven Rostedtd7690412008-10-01 00:29:53 -04001772 rb_advance_reader(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001773 goto again;
1774
1775 case RINGBUF_TYPE_TIME_STAMP:
1776 /* FIXME: not implemented */
Steven Rostedtd7690412008-10-01 00:29:53 -04001777 rb_advance_reader(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001778 goto again;
1779
1780 case RINGBUF_TYPE_DATA:
1781 if (ts) {
1782 *ts = cpu_buffer->read_stamp + event->time_delta;
1783 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1784 }
1785 return event;
1786
1787 default:
1788 BUG();
1789 }
1790
1791 return NULL;
1792}
1793
1794/**
1795 * ring_buffer_iter_peek - peek at the next event to be read
1796 * @iter: The ring buffer iterator
1797 * @ts: The timestamp counter of this event.
1798 *
1799 * This will return the event that will be read next, but does
1800 * not increment the iterator.
1801 */
1802struct ring_buffer_event *
1803ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
1804{
1805 struct ring_buffer *buffer;
1806 struct ring_buffer_per_cpu *cpu_buffer;
1807 struct ring_buffer_event *event;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001808 int nr_loops = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001809
1810 if (ring_buffer_iter_empty(iter))
1811 return NULL;
1812
1813 cpu_buffer = iter->cpu_buffer;
1814 buffer = cpu_buffer->buffer;
1815
1816 again:
Steven Rostedt818e3dd2008-10-31 09:58:35 -04001817 /*
1818 * We repeat when a timestamp is encountered. It is possible
1819 * to get multiple timestamps from an interrupt entering just
1820 * as one timestamp is about to be written. The max times
1821 * that this can happen is the number of nested interrupts we
1822 * can have. Nesting 10 deep of interrupts is clearly
1823 * an anomaly.
1824 */
1825 if (unlikely(++nr_loops > 10)) {
1826 RB_WARN_ON(cpu_buffer, 1);
1827 return NULL;
1828 }
1829
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001830 if (rb_per_cpu_empty(cpu_buffer))
1831 return NULL;
1832
1833 event = rb_iter_head_event(iter);
1834
1835 switch (event->type) {
1836 case RINGBUF_TYPE_PADDING:
Steven Rostedtd7690412008-10-01 00:29:53 -04001837 rb_inc_iter(iter);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001838 goto again;
1839
1840 case RINGBUF_TYPE_TIME_EXTEND:
1841 /* Internal data, OK to advance */
1842 rb_advance_iter(iter);
1843 goto again;
1844
1845 case RINGBUF_TYPE_TIME_STAMP:
1846 /* FIXME: not implemented */
1847 rb_advance_iter(iter);
1848 goto again;
1849
1850 case RINGBUF_TYPE_DATA:
1851 if (ts) {
1852 *ts = iter->read_stamp + event->time_delta;
1853 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1854 }
1855 return event;
1856
1857 default:
1858 BUG();
1859 }
1860
1861 return NULL;
1862}
1863
1864/**
1865 * ring_buffer_consume - return an event and consume it
1866 * @buffer: The ring buffer to get the next event from
1867 *
1868 * Returns the next event in the ring buffer, and that event is consumed.
1869 * Meaning, that sequential reads will keep returning a different event,
1870 * and eventually empty the ring buffer if the producer is slower.
1871 */
1872struct ring_buffer_event *
1873ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
1874{
1875 struct ring_buffer_per_cpu *cpu_buffer;
1876 struct ring_buffer_event *event;
1877
1878 if (!cpu_isset(cpu, buffer->cpumask))
1879 return NULL;
1880
1881 event = ring_buffer_peek(buffer, cpu, ts);
1882 if (!event)
1883 return NULL;
1884
1885 cpu_buffer = buffer->buffers[cpu];
Steven Rostedtd7690412008-10-01 00:29:53 -04001886 rb_advance_reader(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001887
1888 return event;
1889}
1890
1891/**
1892 * ring_buffer_read_start - start a non consuming read of the buffer
1893 * @buffer: The ring buffer to read from
1894 * @cpu: The cpu buffer to iterate over
1895 *
1896 * This starts up an iteration through the buffer. It also disables
1897 * the recording to the buffer until the reading is finished.
1898 * This prevents the reading from being corrupted. This is not
1899 * a consuming read, so a producer is not expected.
1900 *
1901 * Must be paired with ring_buffer_finish.
1902 */
1903struct ring_buffer_iter *
1904ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
1905{
1906 struct ring_buffer_per_cpu *cpu_buffer;
1907 struct ring_buffer_iter *iter;
Steven Rostedtd7690412008-10-01 00:29:53 -04001908 unsigned long flags;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001909
1910 if (!cpu_isset(cpu, buffer->cpumask))
1911 return NULL;
1912
1913 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
1914 if (!iter)
1915 return NULL;
1916
1917 cpu_buffer = buffer->buffers[cpu];
1918
1919 iter->cpu_buffer = cpu_buffer;
1920
1921 atomic_inc(&cpu_buffer->record_disabled);
1922 synchronize_sched();
1923
Steven Rostedtd7690412008-10-01 00:29:53 -04001924 spin_lock_irqsave(&cpu_buffer->lock, flags);
1925 ring_buffer_iter_reset(iter);
1926 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001927
1928 return iter;
1929}
1930
1931/**
1932 * ring_buffer_finish - finish reading the iterator of the buffer
1933 * @iter: The iterator retrieved by ring_buffer_start
1934 *
1935 * This re-enables the recording to the buffer, and frees the
1936 * iterator.
1937 */
1938void
1939ring_buffer_read_finish(struct ring_buffer_iter *iter)
1940{
1941 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1942
1943 atomic_dec(&cpu_buffer->record_disabled);
1944 kfree(iter);
1945}
1946
1947/**
1948 * ring_buffer_read - read the next item in the ring buffer by the iterator
1949 * @iter: The ring buffer iterator
1950 * @ts: The time stamp of the event read.
1951 *
1952 * This reads the next event in the ring buffer and increments the iterator.
1953 */
1954struct ring_buffer_event *
1955ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
1956{
1957 struct ring_buffer_event *event;
1958
1959 event = ring_buffer_iter_peek(iter, ts);
1960 if (!event)
1961 return NULL;
1962
1963 rb_advance_iter(iter);
1964
1965 return event;
1966}
1967
1968/**
1969 * ring_buffer_size - return the size of the ring buffer (in bytes)
1970 * @buffer: The ring buffer.
1971 */
1972unsigned long ring_buffer_size(struct ring_buffer *buffer)
1973{
1974 return BUF_PAGE_SIZE * buffer->pages;
1975}
1976
1977static void
1978rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
1979{
1980 cpu_buffer->head_page
1981 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
Steven Rostedtbf41a152008-10-04 02:00:59 -04001982 local_set(&cpu_buffer->head_page->write, 0);
1983 local_set(&cpu_buffer->head_page->commit, 0);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001984
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001985 cpu_buffer->head_page->read = 0;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001986
1987 cpu_buffer->tail_page = cpu_buffer->head_page;
1988 cpu_buffer->commit_page = cpu_buffer->head_page;
1989
1990 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1991 local_set(&cpu_buffer->reader_page->write, 0);
1992 local_set(&cpu_buffer->reader_page->commit, 0);
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001993 cpu_buffer->reader_page->read = 0;
Steven Rostedtd7690412008-10-01 00:29:53 -04001994
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001995 cpu_buffer->overrun = 0;
1996 cpu_buffer->entries = 0;
1997}
1998
1999/**
2000 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2001 * @buffer: The ring buffer to reset a per cpu buffer of
2002 * @cpu: The CPU buffer to be reset
2003 */
2004void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
2005{
2006 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2007 unsigned long flags;
2008
2009 if (!cpu_isset(cpu, buffer->cpumask))
2010 return;
2011
Steven Rostedtd7690412008-10-01 00:29:53 -04002012 spin_lock_irqsave(&cpu_buffer->lock, flags);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002013
2014 rb_reset_cpu(cpu_buffer);
2015
Steven Rostedtd7690412008-10-01 00:29:53 -04002016 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002017}
2018
2019/**
2020 * ring_buffer_reset - reset a ring buffer
2021 * @buffer: The ring buffer to reset all cpu buffers
2022 */
2023void ring_buffer_reset(struct ring_buffer *buffer)
2024{
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002025 int cpu;
2026
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002027 for_each_buffer_cpu(buffer, cpu)
Steven Rostedtd7690412008-10-01 00:29:53 -04002028 ring_buffer_reset_cpu(buffer, cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002029}
2030
2031/**
2032 * rind_buffer_empty - is the ring buffer empty?
2033 * @buffer: The ring buffer to test
2034 */
2035int ring_buffer_empty(struct ring_buffer *buffer)
2036{
2037 struct ring_buffer_per_cpu *cpu_buffer;
2038 int cpu;
2039
2040 /* yes this is racy, but if you don't like the race, lock the buffer */
2041 for_each_buffer_cpu(buffer, cpu) {
2042 cpu_buffer = buffer->buffers[cpu];
2043 if (!rb_per_cpu_empty(cpu_buffer))
2044 return 0;
2045 }
2046 return 1;
2047}
2048
2049/**
2050 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2051 * @buffer: The ring buffer
2052 * @cpu: The CPU buffer to test
2053 */
2054int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
2055{
2056 struct ring_buffer_per_cpu *cpu_buffer;
2057
2058 if (!cpu_isset(cpu, buffer->cpumask))
2059 return 1;
2060
2061 cpu_buffer = buffer->buffers[cpu];
2062 return rb_per_cpu_empty(cpu_buffer);
2063}
2064
2065/**
2066 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2067 * @buffer_a: One buffer to swap with
2068 * @buffer_b: The other buffer to swap with
2069 *
2070 * This function is useful for tracers that want to take a "snapshot"
2071 * of a CPU buffer and has another back up buffer lying around.
2072 * it is expected that the tracer handles the cpu buffer not being
2073 * used at the moment.
2074 */
2075int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
2076 struct ring_buffer *buffer_b, int cpu)
2077{
2078 struct ring_buffer_per_cpu *cpu_buffer_a;
2079 struct ring_buffer_per_cpu *cpu_buffer_b;
2080
2081 if (!cpu_isset(cpu, buffer_a->cpumask) ||
2082 !cpu_isset(cpu, buffer_b->cpumask))
2083 return -EINVAL;
2084
2085 /* At least make sure the two buffers are somewhat the same */
2086 if (buffer_a->size != buffer_b->size ||
2087 buffer_a->pages != buffer_b->pages)
2088 return -EINVAL;
2089
2090 cpu_buffer_a = buffer_a->buffers[cpu];
2091 cpu_buffer_b = buffer_b->buffers[cpu];
2092
2093 /*
2094 * We can't do a synchronize_sched here because this
2095 * function can be called in atomic context.
2096 * Normally this will be called from the same CPU as cpu.
2097 * If not it's up to the caller to protect this.
2098 */
2099 atomic_inc(&cpu_buffer_a->record_disabled);
2100 atomic_inc(&cpu_buffer_b->record_disabled);
2101
2102 buffer_a->buffers[cpu] = cpu_buffer_b;
2103 buffer_b->buffers[cpu] = cpu_buffer_a;
2104
2105 cpu_buffer_b->buffer = buffer_a;
2106 cpu_buffer_a->buffer = buffer_b;
2107
2108 atomic_dec(&cpu_buffer_a->record_disabled);
2109 atomic_dec(&cpu_buffer_b->record_disabled);
2110
2111 return 0;
2112}
2113
Steven Rostedta3583242008-11-11 15:01:42 -05002114static ssize_t
2115rb_simple_read(struct file *filp, char __user *ubuf,
2116 size_t cnt, loff_t *ppos)
2117{
2118 int *p = filp->private_data;
2119 char buf[64];
2120 int r;
2121
2122 /* !ring_buffers_off == tracing_on */
2123 r = sprintf(buf, "%d\n", !*p);
2124
2125 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
2126}
2127
2128static ssize_t
2129rb_simple_write(struct file *filp, const char __user *ubuf,
2130 size_t cnt, loff_t *ppos)
2131{
2132 int *p = filp->private_data;
2133 char buf[64];
2134 long val;
2135 int ret;
2136
2137 if (cnt >= sizeof(buf))
2138 return -EINVAL;
2139
2140 if (copy_from_user(&buf, ubuf, cnt))
2141 return -EFAULT;
2142
2143 buf[cnt] = 0;
2144
2145 ret = strict_strtoul(buf, 10, &val);
2146 if (ret < 0)
2147 return ret;
2148
2149 /* !ring_buffers_off == tracing_on */
2150 *p = !val;
2151
2152 (*ppos)++;
2153
2154 return cnt;
2155}
2156
2157static struct file_operations rb_simple_fops = {
2158 .open = tracing_open_generic,
2159 .read = rb_simple_read,
2160 .write = rb_simple_write,
2161};
2162
2163
2164static __init int rb_init_debugfs(void)
2165{
2166 struct dentry *d_tracer;
2167 struct dentry *entry;
2168
2169 d_tracer = tracing_init_dentry();
2170
2171 entry = debugfs_create_file("tracing_on", 0644, d_tracer,
2172 &ring_buffers_off, &rb_simple_fops);
2173 if (!entry)
2174 pr_warning("Could not create debugfs 'tracing_on' entry\n");
2175
2176 return 0;
2177}
2178
2179fs_initcall(rb_init_debugfs);