4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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>
21 /* Up this if you want to test the TIME_EXTENTS and normalization */
25 u64 ring_buffer_time_stamp(int cpu)
27 /* shift to debug/test normalization and TIME_EXTENTS */
28 return sched_clock() << DEBUG_SHIFT;
31 void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
33 /* Just stupid testing the normalize function and deltas */
37 #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
38 #define RB_ALIGNMENT_SHIFT 2
39 #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
40 #define RB_MAX_SMALL_DATA 28
43 RB_LEN_TIME_EXTEND = 8,
44 RB_LEN_TIME_STAMP = 16,
47 /* inline for ring buffer fast paths */
48 static inline unsigned
49 rb_event_length(struct ring_buffer_event *event)
53 switch (event->type) {
54 case RINGBUF_TYPE_PADDING:
58 case RINGBUF_TYPE_TIME_EXTEND:
59 return RB_LEN_TIME_EXTEND;
61 case RINGBUF_TYPE_TIME_STAMP:
62 return RB_LEN_TIME_STAMP;
64 case RINGBUF_TYPE_DATA:
66 length = event->len << RB_ALIGNMENT_SHIFT;
68 length = event->array[0];
69 return length + RB_EVNT_HDR_SIZE;
78 * ring_buffer_event_length - return the length of the event
79 * @event: the event to get the length of
81 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
83 return rb_event_length(event);
86 /* inline for ring buffer fast paths */
88 rb_event_data(struct ring_buffer_event *event)
90 BUG_ON(event->type != RINGBUF_TYPE_DATA);
91 /* If length is in len field, then array[0] has the data */
93 return (void *)&event->array[0];
94 /* Otherwise length is in array[0] and array[1] has the data */
95 return (void *)&event->array[1];
99 * ring_buffer_event_data - return the data of the event
100 * @event: the event to get the data from
102 void *ring_buffer_event_data(struct ring_buffer_event *event)
104 return rb_event_data(event);
107 #define for_each_buffer_cpu(buffer, cpu) \
108 for_each_cpu_mask(cpu, buffer->cpumask)
111 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
112 #define TS_DELTA_TEST (~TS_MASK)
115 * This hack stolen from mm/slob.c.
116 * We can store per page timing information in the page frame of the page.
117 * Thanks to Peter Zijlstra for suggesting this idea.
120 u64 time_stamp; /* page time stamp */
121 local_t write; /* index for next write */
122 local_t commit; /* write commited index */
123 unsigned read; /* index for next read */
124 struct list_head list; /* list of free pages */
125 void *page; /* Actual data page */
129 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
132 static inline void free_buffer_page(struct buffer_page *bpage)
135 free_page((unsigned long)bpage->page);
140 * We need to fit the time_stamp delta into 27 bits.
142 static inline int test_time_stamp(u64 delta)
144 if (delta & TS_DELTA_TEST)
149 #define BUF_PAGE_SIZE PAGE_SIZE
152 * head_page == tail_page && head == tail then buffer is empty.
154 struct ring_buffer_per_cpu {
156 struct ring_buffer *buffer;
158 struct lock_class_key lock_key;
159 struct list_head pages;
160 struct buffer_page *head_page; /* read from head */
161 struct buffer_page *tail_page; /* write to tail */
162 struct buffer_page *commit_page; /* commited pages */
163 struct buffer_page *reader_page;
164 unsigned long overrun;
165 unsigned long entries;
168 atomic_t record_disabled;
177 atomic_t record_disabled;
181 struct ring_buffer_per_cpu **buffers;
184 struct ring_buffer_iter {
185 struct ring_buffer_per_cpu *cpu_buffer;
187 struct buffer_page *head_page;
191 #define RB_WARN_ON(buffer, cond) \
193 if (unlikely(cond)) { \
194 atomic_inc(&buffer->record_disabled); \
199 #define RB_WARN_ON_RET(buffer, cond) \
201 if (unlikely(cond)) { \
202 atomic_inc(&buffer->record_disabled); \
208 #define RB_WARN_ON_ONCE(buffer, cond) \
211 if (unlikely(cond) && !once) { \
213 atomic_inc(&buffer->record_disabled); \
219 * check_pages - integrity check of buffer pages
220 * @cpu_buffer: CPU buffer with pages to test
222 * As a safty measure we check to make sure the data pages have not
225 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
227 struct list_head *head = &cpu_buffer->pages;
228 struct buffer_page *page, *tmp;
230 RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);
231 RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);
233 list_for_each_entry_safe(page, tmp, head, list) {
234 RB_WARN_ON_RET(cpu_buffer,
235 page->list.next->prev != &page->list);
236 RB_WARN_ON_RET(cpu_buffer,
237 page->list.prev->next != &page->list);
243 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
246 struct list_head *head = &cpu_buffer->pages;
247 struct buffer_page *page, *tmp;
252 for (i = 0; i < nr_pages; i++) {
253 page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
254 GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
257 list_add(&page->list, &pages);
259 addr = __get_free_page(GFP_KERNEL);
262 page->page = (void *)addr;
265 list_splice(&pages, head);
267 rb_check_pages(cpu_buffer);
272 list_for_each_entry_safe(page, tmp, &pages, list) {
273 list_del_init(&page->list);
274 free_buffer_page(page);
279 static struct ring_buffer_per_cpu *
280 rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
282 struct ring_buffer_per_cpu *cpu_buffer;
283 struct buffer_page *page;
287 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
288 GFP_KERNEL, cpu_to_node(cpu));
292 cpu_buffer->cpu = cpu;
293 cpu_buffer->buffer = buffer;
294 cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
295 INIT_LIST_HEAD(&cpu_buffer->pages);
297 page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
298 GFP_KERNEL, cpu_to_node(cpu));
300 goto fail_free_buffer;
302 cpu_buffer->reader_page = page;
303 addr = __get_free_page(GFP_KERNEL);
305 goto fail_free_reader;
306 page->page = (void *)addr;
308 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
310 ret = rb_allocate_pages(cpu_buffer, buffer->pages);
312 goto fail_free_reader;
314 cpu_buffer->head_page
315 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
316 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
321 free_buffer_page(cpu_buffer->reader_page);
328 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
330 struct list_head *head = &cpu_buffer->pages;
331 struct buffer_page *page, *tmp;
333 list_del_init(&cpu_buffer->reader_page->list);
334 free_buffer_page(cpu_buffer->reader_page);
336 list_for_each_entry_safe(page, tmp, head, list) {
337 list_del_init(&page->list);
338 free_buffer_page(page);
344 * Causes compile errors if the struct buffer_page gets bigger
345 * than the struct page.
347 extern int ring_buffer_page_too_big(void);
350 * ring_buffer_alloc - allocate a new ring_buffer
351 * @size: the size in bytes that is needed.
352 * @flags: attributes to set for the ring buffer.
354 * Currently the only flag that is available is the RB_FL_OVERWRITE
355 * flag. This flag means that the buffer will overwrite old data
356 * when the buffer wraps. If this flag is not set, the buffer will
357 * drop data when the tail hits the head.
359 struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
361 struct ring_buffer *buffer;
365 /* Paranoid! Optimizes out when all is well */
366 if (sizeof(struct buffer_page) > sizeof(struct page))
367 ring_buffer_page_too_big();
370 /* keep it in its own cache line */
371 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
376 buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
377 buffer->flags = flags;
379 /* need at least two pages */
380 if (buffer->pages == 1)
383 buffer->cpumask = cpu_possible_map;
384 buffer->cpus = nr_cpu_ids;
386 bsize = sizeof(void *) * nr_cpu_ids;
387 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
389 if (!buffer->buffers)
390 goto fail_free_buffer;
392 for_each_buffer_cpu(buffer, cpu) {
393 buffer->buffers[cpu] =
394 rb_allocate_cpu_buffer(buffer, cpu);
395 if (!buffer->buffers[cpu])
396 goto fail_free_buffers;
399 mutex_init(&buffer->mutex);
404 for_each_buffer_cpu(buffer, cpu) {
405 if (buffer->buffers[cpu])
406 rb_free_cpu_buffer(buffer->buffers[cpu]);
408 kfree(buffer->buffers);
416 * ring_buffer_free - free a ring buffer.
417 * @buffer: the buffer to free.
420 ring_buffer_free(struct ring_buffer *buffer)
424 for_each_buffer_cpu(buffer, cpu)
425 rb_free_cpu_buffer(buffer->buffers[cpu]);
430 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
433 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
435 struct buffer_page *page;
439 atomic_inc(&cpu_buffer->record_disabled);
442 for (i = 0; i < nr_pages; i++) {
443 BUG_ON(list_empty(&cpu_buffer->pages));
444 p = cpu_buffer->pages.next;
445 page = list_entry(p, struct buffer_page, list);
446 list_del_init(&page->list);
447 free_buffer_page(page);
449 BUG_ON(list_empty(&cpu_buffer->pages));
451 rb_reset_cpu(cpu_buffer);
453 rb_check_pages(cpu_buffer);
455 atomic_dec(&cpu_buffer->record_disabled);
460 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
461 struct list_head *pages, unsigned nr_pages)
463 struct buffer_page *page;
467 atomic_inc(&cpu_buffer->record_disabled);
470 for (i = 0; i < nr_pages; i++) {
471 BUG_ON(list_empty(pages));
473 page = list_entry(p, struct buffer_page, list);
474 list_del_init(&page->list);
475 list_add_tail(&page->list, &cpu_buffer->pages);
477 rb_reset_cpu(cpu_buffer);
479 rb_check_pages(cpu_buffer);
481 atomic_dec(&cpu_buffer->record_disabled);
485 * ring_buffer_resize - resize the ring buffer
486 * @buffer: the buffer to resize.
487 * @size: the new size.
489 * The tracer is responsible for making sure that the buffer is
490 * not being used while changing the size.
491 * Note: We may be able to change the above requirement by using
492 * RCU synchronizations.
494 * Minimum size is 2 * BUF_PAGE_SIZE.
496 * Returns -1 on failure.
498 int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
500 struct ring_buffer_per_cpu *cpu_buffer;
501 unsigned nr_pages, rm_pages, new_pages;
502 struct buffer_page *page, *tmp;
503 unsigned long buffer_size;
508 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
509 size *= BUF_PAGE_SIZE;
510 buffer_size = buffer->pages * BUF_PAGE_SIZE;
512 /* we need a minimum of two pages */
513 if (size < BUF_PAGE_SIZE * 2)
514 size = BUF_PAGE_SIZE * 2;
516 if (size == buffer_size)
519 mutex_lock(&buffer->mutex);
521 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
523 if (size < buffer_size) {
525 /* easy case, just free pages */
526 BUG_ON(nr_pages >= buffer->pages);
528 rm_pages = buffer->pages - nr_pages;
530 for_each_buffer_cpu(buffer, cpu) {
531 cpu_buffer = buffer->buffers[cpu];
532 rb_remove_pages(cpu_buffer, rm_pages);
538 * This is a bit more difficult. We only want to add pages
539 * when we can allocate enough for all CPUs. We do this
540 * by allocating all the pages and storing them on a local
541 * link list. If we succeed in our allocation, then we
542 * add these pages to the cpu_buffers. Otherwise we just free
543 * them all and return -ENOMEM;
545 BUG_ON(nr_pages <= buffer->pages);
546 new_pages = nr_pages - buffer->pages;
548 for_each_buffer_cpu(buffer, cpu) {
549 for (i = 0; i < new_pages; i++) {
550 page = kzalloc_node(ALIGN(sizeof(*page),
552 GFP_KERNEL, cpu_to_node(cpu));
555 list_add(&page->list, &pages);
556 addr = __get_free_page(GFP_KERNEL);
559 page->page = (void *)addr;
563 for_each_buffer_cpu(buffer, cpu) {
564 cpu_buffer = buffer->buffers[cpu];
565 rb_insert_pages(cpu_buffer, &pages, new_pages);
568 BUG_ON(!list_empty(&pages));
571 buffer->pages = nr_pages;
572 mutex_unlock(&buffer->mutex);
577 list_for_each_entry_safe(page, tmp, &pages, list) {
578 list_del_init(&page->list);
579 free_buffer_page(page);
584 static inline int rb_null_event(struct ring_buffer_event *event)
586 return event->type == RINGBUF_TYPE_PADDING;
589 static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
591 return page->page + index;
594 static inline struct ring_buffer_event *
595 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
597 return __rb_page_index(cpu_buffer->reader_page,
598 cpu_buffer->reader_page->read);
601 static inline struct ring_buffer_event *
602 rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
604 return __rb_page_index(cpu_buffer->head_page,
605 cpu_buffer->head_page->read);
608 static inline struct ring_buffer_event *
609 rb_iter_head_event(struct ring_buffer_iter *iter)
611 return __rb_page_index(iter->head_page, iter->head);
614 static inline unsigned rb_page_write(struct buffer_page *bpage)
616 return local_read(&bpage->write);
619 static inline unsigned rb_page_commit(struct buffer_page *bpage)
621 return local_read(&bpage->commit);
624 /* Size is determined by what has been commited */
625 static inline unsigned rb_page_size(struct buffer_page *bpage)
627 return rb_page_commit(bpage);
630 static inline unsigned
631 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
633 return rb_page_commit(cpu_buffer->commit_page);
636 static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
638 return rb_page_commit(cpu_buffer->head_page);
642 * When the tail hits the head and the buffer is in overwrite mode,
643 * the head jumps to the next page and all content on the previous
644 * page is discarded. But before doing so, we update the overrun
645 * variable of the buffer.
647 static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
649 struct ring_buffer_event *event;
652 for (head = 0; head < rb_head_size(cpu_buffer);
653 head += rb_event_length(event)) {
655 event = __rb_page_index(cpu_buffer->head_page, head);
656 BUG_ON(rb_null_event(event));
657 /* Only count data entries */
658 if (event->type != RINGBUF_TYPE_DATA)
660 cpu_buffer->overrun++;
661 cpu_buffer->entries--;
665 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
666 struct buffer_page **page)
668 struct list_head *p = (*page)->list.next;
670 if (p == &cpu_buffer->pages)
673 *page = list_entry(p, struct buffer_page, list);
676 static inline unsigned
677 rb_event_index(struct ring_buffer_event *event)
679 unsigned long addr = (unsigned long)event;
681 return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
685 rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
686 struct ring_buffer_event *event)
688 unsigned long addr = (unsigned long)event;
691 index = rb_event_index(event);
694 return cpu_buffer->commit_page->page == (void *)addr &&
695 rb_commit_index(cpu_buffer) == index;
699 rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
700 struct ring_buffer_event *event)
702 unsigned long addr = (unsigned long)event;
705 index = rb_event_index(event);
708 while (cpu_buffer->commit_page->page != (void *)addr) {
709 RB_WARN_ON(cpu_buffer,
710 cpu_buffer->commit_page == cpu_buffer->tail_page);
711 cpu_buffer->commit_page->commit =
712 cpu_buffer->commit_page->write;
713 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
714 cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
717 /* Now set the commit to the event's index */
718 local_set(&cpu_buffer->commit_page->commit, index);
722 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
725 * We only race with interrupts and NMIs on this CPU.
726 * If we own the commit event, then we can commit
727 * all others that interrupted us, since the interruptions
728 * are in stack format (they finish before they come
729 * back to us). This allows us to do a simple loop to
730 * assign the commit to the tail.
732 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
733 cpu_buffer->commit_page->commit =
734 cpu_buffer->commit_page->write;
735 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
736 cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
737 /* add barrier to keep gcc from optimizing too much */
740 while (rb_commit_index(cpu_buffer) !=
741 rb_page_write(cpu_buffer->commit_page)) {
742 cpu_buffer->commit_page->commit =
743 cpu_buffer->commit_page->write;
748 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
750 cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
751 cpu_buffer->reader_page->read = 0;
754 static inline void rb_inc_iter(struct ring_buffer_iter *iter)
756 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
759 * The iterator could be on the reader page (it starts there).
760 * But the head could have moved, since the reader was
761 * found. Check for this case and assign the iterator
762 * to the head page instead of next.
764 if (iter->head_page == cpu_buffer->reader_page)
765 iter->head_page = cpu_buffer->head_page;
767 rb_inc_page(cpu_buffer, &iter->head_page);
769 iter->read_stamp = iter->head_page->time_stamp;
774 * ring_buffer_update_event - update event type and data
775 * @event: the even to update
776 * @type: the type of event
777 * @length: the size of the event field in the ring buffer
779 * Update the type and data fields of the event. The length
780 * is the actual size that is written to the ring buffer,
781 * and with this, we can determine what to place into the
785 rb_update_event(struct ring_buffer_event *event,
786 unsigned type, unsigned length)
792 case RINGBUF_TYPE_PADDING:
795 case RINGBUF_TYPE_TIME_EXTEND:
797 (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
798 >> RB_ALIGNMENT_SHIFT;
801 case RINGBUF_TYPE_TIME_STAMP:
803 (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
804 >> RB_ALIGNMENT_SHIFT;
807 case RINGBUF_TYPE_DATA:
808 length -= RB_EVNT_HDR_SIZE;
809 if (length > RB_MAX_SMALL_DATA) {
811 event->array[0] = length;
814 (length + (RB_ALIGNMENT-1))
815 >> RB_ALIGNMENT_SHIFT;
822 static inline unsigned rb_calculate_event_length(unsigned length)
824 struct ring_buffer_event event; /* Used only for sizeof array */
826 /* zero length can cause confusions */
830 if (length > RB_MAX_SMALL_DATA)
831 length += sizeof(event.array[0]);
833 length += RB_EVNT_HDR_SIZE;
834 length = ALIGN(length, RB_ALIGNMENT);
839 static struct ring_buffer_event *
840 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
841 unsigned type, unsigned long length, u64 *ts)
843 struct buffer_page *tail_page, *head_page, *reader_page;
844 unsigned long tail, write;
845 struct ring_buffer *buffer = cpu_buffer->buffer;
846 struct ring_buffer_event *event;
849 tail_page = cpu_buffer->tail_page;
850 write = local_add_return(length, &tail_page->write);
851 tail = write - length;
853 /* See if we shot pass the end of this buffer page */
854 if (write > BUF_PAGE_SIZE) {
855 struct buffer_page *next_page = tail_page;
857 local_irq_save(flags);
858 __raw_spin_lock(&cpu_buffer->lock);
860 rb_inc_page(cpu_buffer, &next_page);
862 head_page = cpu_buffer->head_page;
863 reader_page = cpu_buffer->reader_page;
865 /* we grabbed the lock before incrementing */
866 RB_WARN_ON(cpu_buffer, next_page == reader_page);
869 * If for some reason, we had an interrupt storm that made
870 * it all the way around the buffer, bail, and warn
873 if (unlikely(next_page == cpu_buffer->commit_page)) {
878 if (next_page == head_page) {
879 if (!(buffer->flags & RB_FL_OVERWRITE)) {
881 if (tail <= BUF_PAGE_SIZE)
882 local_set(&tail_page->write, tail);
886 /* tail_page has not moved yet? */
887 if (tail_page == cpu_buffer->tail_page) {
888 /* count overflows */
889 rb_update_overflow(cpu_buffer);
891 rb_inc_page(cpu_buffer, &head_page);
892 cpu_buffer->head_page = head_page;
893 cpu_buffer->head_page->read = 0;
898 * If the tail page is still the same as what we think
899 * it is, then it is up to us to update the tail
902 if (tail_page == cpu_buffer->tail_page) {
903 local_set(&next_page->write, 0);
904 local_set(&next_page->commit, 0);
905 cpu_buffer->tail_page = next_page;
907 /* reread the time stamp */
908 *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
909 cpu_buffer->tail_page->time_stamp = *ts;
913 * The actual tail page has moved forward.
915 if (tail < BUF_PAGE_SIZE) {
916 /* Mark the rest of the page with padding */
917 event = __rb_page_index(tail_page, tail);
918 event->type = RINGBUF_TYPE_PADDING;
921 if (tail <= BUF_PAGE_SIZE)
922 /* Set the write back to the previous setting */
923 local_set(&tail_page->write, tail);
926 * If this was a commit entry that failed,
929 if (tail_page == cpu_buffer->commit_page &&
930 tail == rb_commit_index(cpu_buffer)) {
931 rb_set_commit_to_write(cpu_buffer);
934 __raw_spin_unlock(&cpu_buffer->lock);
935 local_irq_restore(flags);
937 /* fail and let the caller try again */
938 return ERR_PTR(-EAGAIN);
941 /* We reserved something on the buffer */
943 BUG_ON(write > BUF_PAGE_SIZE);
945 event = __rb_page_index(tail_page, tail);
946 rb_update_event(event, type, length);
949 * If this is a commit and the tail is zero, then update
950 * this page's time stamp.
952 if (!tail && rb_is_commit(cpu_buffer, event))
953 cpu_buffer->commit_page->time_stamp = *ts;
958 __raw_spin_unlock(&cpu_buffer->lock);
959 local_irq_restore(flags);
964 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
967 struct ring_buffer_event *event;
971 if (unlikely(*delta > (1ULL << 59) && !once++)) {
972 printk(KERN_WARNING "Delta way too big! %llu"
973 " ts=%llu write stamp = %llu\n",
974 (unsigned long long)*delta,
975 (unsigned long long)*ts,
976 (unsigned long long)cpu_buffer->write_stamp);
981 * The delta is too big, we to add a
984 event = __rb_reserve_next(cpu_buffer,
985 RINGBUF_TYPE_TIME_EXTEND,
991 if (PTR_ERR(event) == -EAGAIN)
994 /* Only a commited time event can update the write stamp */
995 if (rb_is_commit(cpu_buffer, event)) {
997 * If this is the first on the page, then we need to
998 * update the page itself, and just put in a zero.
1000 if (rb_event_index(event)) {
1001 event->time_delta = *delta & TS_MASK;
1002 event->array[0] = *delta >> TS_SHIFT;
1004 cpu_buffer->commit_page->time_stamp = *ts;
1005 event->time_delta = 0;
1006 event->array[0] = 0;
1008 cpu_buffer->write_stamp = *ts;
1009 /* let the caller know this was the commit */
1012 /* Darn, this is just wasted space */
1013 event->time_delta = 0;
1014 event->array[0] = 0;
1023 static struct ring_buffer_event *
1024 rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
1025 unsigned type, unsigned long length)
1027 struct ring_buffer_event *event;
1032 ts = ring_buffer_time_stamp(cpu_buffer->cpu);
1035 * Only the first commit can update the timestamp.
1036 * Yes there is a race here. If an interrupt comes in
1037 * just after the conditional and it traces too, then it
1038 * will also check the deltas. More than one timestamp may
1039 * also be made. But only the entry that did the actual
1040 * commit will be something other than zero.
1042 if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
1043 rb_page_write(cpu_buffer->tail_page) ==
1044 rb_commit_index(cpu_buffer)) {
1046 delta = ts - cpu_buffer->write_stamp;
1048 /* make sure this delta is calculated here */
1051 /* Did the write stamp get updated already? */
1052 if (unlikely(ts < cpu_buffer->write_stamp))
1055 if (test_time_stamp(delta)) {
1057 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
1059 if (commit == -EBUSY)
1062 if (commit == -EAGAIN)
1065 RB_WARN_ON(cpu_buffer, commit < 0);
1068 /* Non commits have zero deltas */
1071 event = __rb_reserve_next(cpu_buffer, type, length, &ts);
1072 if (PTR_ERR(event) == -EAGAIN)
1076 if (unlikely(commit))
1078 * Ouch! We needed a timestamp and it was commited. But
1079 * we didn't get our event reserved.
1081 rb_set_commit_to_write(cpu_buffer);
1086 * If the timestamp was commited, make the commit our entry
1087 * now so that we will update it when needed.
1090 rb_set_commit_event(cpu_buffer, event);
1091 else if (!rb_is_commit(cpu_buffer, event))
1094 event->time_delta = delta;
1099 static DEFINE_PER_CPU(int, rb_need_resched);
1102 * ring_buffer_lock_reserve - reserve a part of the buffer
1103 * @buffer: the ring buffer to reserve from
1104 * @length: the length of the data to reserve (excluding event header)
1105 * @flags: a pointer to save the interrupt flags
1107 * Returns a reseverd event on the ring buffer to copy directly to.
1108 * The user of this interface will need to get the body to write into
1109 * and can use the ring_buffer_event_data() interface.
1111 * The length is the length of the data needed, not the event length
1112 * which also includes the event header.
1114 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1115 * If NULL is returned, then nothing has been allocated or locked.
1117 struct ring_buffer_event *
1118 ring_buffer_lock_reserve(struct ring_buffer *buffer,
1119 unsigned long length,
1120 unsigned long *flags)
1122 struct ring_buffer_per_cpu *cpu_buffer;
1123 struct ring_buffer_event *event;
1126 if (atomic_read(&buffer->record_disabled))
1129 /* If we are tracing schedule, we don't want to recurse */
1130 resched = ftrace_preempt_disable();
1132 cpu = raw_smp_processor_id();
1134 if (!cpu_isset(cpu, buffer->cpumask))
1137 cpu_buffer = buffer->buffers[cpu];
1139 if (atomic_read(&cpu_buffer->record_disabled))
1142 length = rb_calculate_event_length(length);
1143 if (length > BUF_PAGE_SIZE)
1146 event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
1151 * Need to store resched state on this cpu.
1152 * Only the first needs to.
1155 if (preempt_count() == 1)
1156 per_cpu(rb_need_resched, cpu) = resched;
1161 ftrace_preempt_enable(resched);
1165 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
1166 struct ring_buffer_event *event)
1168 cpu_buffer->entries++;
1170 /* Only process further if we own the commit */
1171 if (!rb_is_commit(cpu_buffer, event))
1174 cpu_buffer->write_stamp += event->time_delta;
1176 rb_set_commit_to_write(cpu_buffer);
1180 * ring_buffer_unlock_commit - commit a reserved
1181 * @buffer: The buffer to commit to
1182 * @event: The event pointer to commit.
1183 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1185 * This commits the data to the ring buffer, and releases any locks held.
1187 * Must be paired with ring_buffer_lock_reserve.
1189 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
1190 struct ring_buffer_event *event,
1191 unsigned long flags)
1193 struct ring_buffer_per_cpu *cpu_buffer;
1194 int cpu = raw_smp_processor_id();
1196 cpu_buffer = buffer->buffers[cpu];
1198 rb_commit(cpu_buffer, event);
1201 * Only the last preempt count needs to restore preemption.
1203 if (preempt_count() == 1)
1204 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
1206 preempt_enable_no_resched_notrace();
1212 * ring_buffer_write - write data to the buffer without reserving
1213 * @buffer: The ring buffer to write to.
1214 * @length: The length of the data being written (excluding the event header)
1215 * @data: The data to write to the buffer.
1217 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1218 * one function. If you already have the data to write to the buffer, it
1219 * may be easier to simply call this function.
1221 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1222 * and not the length of the event which would hold the header.
1224 int ring_buffer_write(struct ring_buffer *buffer,
1225 unsigned long length,
1228 struct ring_buffer_per_cpu *cpu_buffer;
1229 struct ring_buffer_event *event;
1230 unsigned long event_length;
1235 if (atomic_read(&buffer->record_disabled))
1238 resched = ftrace_preempt_disable();
1240 cpu = raw_smp_processor_id();
1242 if (!cpu_isset(cpu, buffer->cpumask))
1245 cpu_buffer = buffer->buffers[cpu];
1247 if (atomic_read(&cpu_buffer->record_disabled))
1250 event_length = rb_calculate_event_length(length);
1251 event = rb_reserve_next_event(cpu_buffer,
1252 RINGBUF_TYPE_DATA, event_length);
1256 body = rb_event_data(event);
1258 memcpy(body, data, length);
1260 rb_commit(cpu_buffer, event);
1264 ftrace_preempt_enable(resched);
1269 static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
1271 struct buffer_page *reader = cpu_buffer->reader_page;
1272 struct buffer_page *head = cpu_buffer->head_page;
1273 struct buffer_page *commit = cpu_buffer->commit_page;
1275 return reader->read == rb_page_commit(reader) &&
1276 (commit == reader ||
1278 head->read == rb_page_commit(commit)));
1282 * ring_buffer_record_disable - stop all writes into the buffer
1283 * @buffer: The ring buffer to stop writes to.
1285 * This prevents all writes to the buffer. Any attempt to write
1286 * to the buffer after this will fail and return NULL.
1288 * The caller should call synchronize_sched() after this.
1290 void ring_buffer_record_disable(struct ring_buffer *buffer)
1292 atomic_inc(&buffer->record_disabled);
1296 * ring_buffer_record_enable - enable writes to the buffer
1297 * @buffer: The ring buffer to enable writes
1299 * Note, multiple disables will need the same number of enables
1300 * to truely enable the writing (much like preempt_disable).
1302 void ring_buffer_record_enable(struct ring_buffer *buffer)
1304 atomic_dec(&buffer->record_disabled);
1308 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1309 * @buffer: The ring buffer to stop writes to.
1310 * @cpu: The CPU buffer to stop
1312 * This prevents all writes to the buffer. Any attempt to write
1313 * to the buffer after this will fail and return NULL.
1315 * The caller should call synchronize_sched() after this.
1317 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
1319 struct ring_buffer_per_cpu *cpu_buffer;
1321 if (!cpu_isset(cpu, buffer->cpumask))
1324 cpu_buffer = buffer->buffers[cpu];
1325 atomic_inc(&cpu_buffer->record_disabled);
1329 * ring_buffer_record_enable_cpu - enable writes to the buffer
1330 * @buffer: The ring buffer to enable writes
1331 * @cpu: The CPU to enable.
1333 * Note, multiple disables will need the same number of enables
1334 * to truely enable the writing (much like preempt_disable).
1336 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
1338 struct ring_buffer_per_cpu *cpu_buffer;
1340 if (!cpu_isset(cpu, buffer->cpumask))
1343 cpu_buffer = buffer->buffers[cpu];
1344 atomic_dec(&cpu_buffer->record_disabled);
1348 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1349 * @buffer: The ring buffer
1350 * @cpu: The per CPU buffer to get the entries from.
1352 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
1354 struct ring_buffer_per_cpu *cpu_buffer;
1356 if (!cpu_isset(cpu, buffer->cpumask))
1359 cpu_buffer = buffer->buffers[cpu];
1360 return cpu_buffer->entries;
1364 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1365 * @buffer: The ring buffer
1366 * @cpu: The per CPU buffer to get the number of overruns from
1368 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
1370 struct ring_buffer_per_cpu *cpu_buffer;
1372 if (!cpu_isset(cpu, buffer->cpumask))
1375 cpu_buffer = buffer->buffers[cpu];
1376 return cpu_buffer->overrun;
1380 * ring_buffer_entries - get the number of entries in a buffer
1381 * @buffer: The ring buffer
1383 * Returns the total number of entries in the ring buffer
1386 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
1388 struct ring_buffer_per_cpu *cpu_buffer;
1389 unsigned long entries = 0;
1392 /* if you care about this being correct, lock the buffer */
1393 for_each_buffer_cpu(buffer, cpu) {
1394 cpu_buffer = buffer->buffers[cpu];
1395 entries += cpu_buffer->entries;
1402 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1403 * @buffer: The ring buffer
1405 * Returns the total number of overruns in the ring buffer
1408 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
1410 struct ring_buffer_per_cpu *cpu_buffer;
1411 unsigned long overruns = 0;
1414 /* if you care about this being correct, lock the buffer */
1415 for_each_buffer_cpu(buffer, cpu) {
1416 cpu_buffer = buffer->buffers[cpu];
1417 overruns += cpu_buffer->overrun;
1424 * ring_buffer_iter_reset - reset an iterator
1425 * @iter: The iterator to reset
1427 * Resets the iterator, so that it will start from the beginning
1430 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
1432 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1434 /* Iterator usage is expected to have record disabled */
1435 if (list_empty(&cpu_buffer->reader_page->list)) {
1436 iter->head_page = cpu_buffer->head_page;
1437 iter->head = cpu_buffer->head_page->read;
1439 iter->head_page = cpu_buffer->reader_page;
1440 iter->head = cpu_buffer->reader_page->read;
1443 iter->read_stamp = cpu_buffer->read_stamp;
1445 iter->read_stamp = iter->head_page->time_stamp;
1449 * ring_buffer_iter_empty - check if an iterator has no more to read
1450 * @iter: The iterator to check
1452 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
1454 struct ring_buffer_per_cpu *cpu_buffer;
1456 cpu_buffer = iter->cpu_buffer;
1458 return iter->head_page == cpu_buffer->commit_page &&
1459 iter->head == rb_commit_index(cpu_buffer);
1463 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1464 struct ring_buffer_event *event)
1468 switch (event->type) {
1469 case RINGBUF_TYPE_PADDING:
1472 case RINGBUF_TYPE_TIME_EXTEND:
1473 delta = event->array[0];
1475 delta += event->time_delta;
1476 cpu_buffer->read_stamp += delta;
1479 case RINGBUF_TYPE_TIME_STAMP:
1480 /* FIXME: not implemented */
1483 case RINGBUF_TYPE_DATA:
1484 cpu_buffer->read_stamp += event->time_delta;
1494 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
1495 struct ring_buffer_event *event)
1499 switch (event->type) {
1500 case RINGBUF_TYPE_PADDING:
1503 case RINGBUF_TYPE_TIME_EXTEND:
1504 delta = event->array[0];
1506 delta += event->time_delta;
1507 iter->read_stamp += delta;
1510 case RINGBUF_TYPE_TIME_STAMP:
1511 /* FIXME: not implemented */
1514 case RINGBUF_TYPE_DATA:
1515 iter->read_stamp += event->time_delta;
1524 static struct buffer_page *
1525 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1527 struct buffer_page *reader = NULL;
1528 unsigned long flags;
1530 local_irq_save(flags);
1531 __raw_spin_lock(&cpu_buffer->lock);
1534 reader = cpu_buffer->reader_page;
1536 /* If there's more to read, return this page */
1537 if (cpu_buffer->reader_page->read < rb_page_size(reader))
1540 /* Never should we have an index greater than the size */
1541 RB_WARN_ON(cpu_buffer,
1542 cpu_buffer->reader_page->read > rb_page_size(reader));
1544 /* check if we caught up to the tail */
1546 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
1550 * Splice the empty reader page into the list around the head.
1551 * Reset the reader page to size zero.
1554 reader = cpu_buffer->head_page;
1555 cpu_buffer->reader_page->list.next = reader->list.next;
1556 cpu_buffer->reader_page->list.prev = reader->list.prev;
1558 local_set(&cpu_buffer->reader_page->write, 0);
1559 local_set(&cpu_buffer->reader_page->commit, 0);
1561 /* Make the reader page now replace the head */
1562 reader->list.prev->next = &cpu_buffer->reader_page->list;
1563 reader->list.next->prev = &cpu_buffer->reader_page->list;
1566 * If the tail is on the reader, then we must set the head
1567 * to the inserted page, otherwise we set it one before.
1569 cpu_buffer->head_page = cpu_buffer->reader_page;
1571 if (cpu_buffer->commit_page != reader)
1572 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
1574 /* Finally update the reader page to the new head */
1575 cpu_buffer->reader_page = reader;
1576 rb_reset_reader_page(cpu_buffer);
1581 __raw_spin_unlock(&cpu_buffer->lock);
1582 local_irq_restore(flags);
1587 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
1589 struct ring_buffer_event *event;
1590 struct buffer_page *reader;
1593 reader = rb_get_reader_page(cpu_buffer);
1595 /* This function should not be called when buffer is empty */
1598 event = rb_reader_event(cpu_buffer);
1600 if (event->type == RINGBUF_TYPE_DATA)
1601 cpu_buffer->entries--;
1603 rb_update_read_stamp(cpu_buffer, event);
1605 length = rb_event_length(event);
1606 cpu_buffer->reader_page->read += length;
1609 static void rb_advance_iter(struct ring_buffer_iter *iter)
1611 struct ring_buffer *buffer;
1612 struct ring_buffer_per_cpu *cpu_buffer;
1613 struct ring_buffer_event *event;
1616 cpu_buffer = iter->cpu_buffer;
1617 buffer = cpu_buffer->buffer;
1620 * Check if we are at the end of the buffer.
1622 if (iter->head >= rb_page_size(iter->head_page)) {
1623 BUG_ON(iter->head_page == cpu_buffer->commit_page);
1628 event = rb_iter_head_event(iter);
1630 length = rb_event_length(event);
1633 * This should not be called to advance the header if we are
1634 * at the tail of the buffer.
1636 BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
1637 (iter->head + length > rb_commit_index(cpu_buffer)));
1639 rb_update_iter_read_stamp(iter, event);
1641 iter->head += length;
1643 /* check for end of page padding */
1644 if ((iter->head >= rb_page_size(iter->head_page)) &&
1645 (iter->head_page != cpu_buffer->commit_page))
1646 rb_advance_iter(iter);
1650 * ring_buffer_peek - peek at the next event to be read
1651 * @buffer: The ring buffer to read
1652 * @cpu: The cpu to peak at
1653 * @ts: The timestamp counter of this event.
1655 * This will return the event that will be read next, but does
1656 * not consume the data.
1658 struct ring_buffer_event *
1659 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
1661 struct ring_buffer_per_cpu *cpu_buffer;
1662 struct ring_buffer_event *event;
1663 struct buffer_page *reader;
1665 if (!cpu_isset(cpu, buffer->cpumask))
1668 cpu_buffer = buffer->buffers[cpu];
1671 reader = rb_get_reader_page(cpu_buffer);
1675 event = rb_reader_event(cpu_buffer);
1677 switch (event->type) {
1678 case RINGBUF_TYPE_PADDING:
1679 RB_WARN_ON(cpu_buffer, 1);
1680 rb_advance_reader(cpu_buffer);
1683 case RINGBUF_TYPE_TIME_EXTEND:
1684 /* Internal data, OK to advance */
1685 rb_advance_reader(cpu_buffer);
1688 case RINGBUF_TYPE_TIME_STAMP:
1689 /* FIXME: not implemented */
1690 rb_advance_reader(cpu_buffer);
1693 case RINGBUF_TYPE_DATA:
1695 *ts = cpu_buffer->read_stamp + event->time_delta;
1696 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1708 * ring_buffer_iter_peek - peek at the next event to be read
1709 * @iter: The ring buffer iterator
1710 * @ts: The timestamp counter of this event.
1712 * This will return the event that will be read next, but does
1713 * not increment the iterator.
1715 struct ring_buffer_event *
1716 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
1718 struct ring_buffer *buffer;
1719 struct ring_buffer_per_cpu *cpu_buffer;
1720 struct ring_buffer_event *event;
1722 if (ring_buffer_iter_empty(iter))
1725 cpu_buffer = iter->cpu_buffer;
1726 buffer = cpu_buffer->buffer;
1729 if (rb_per_cpu_empty(cpu_buffer))
1732 event = rb_iter_head_event(iter);
1734 switch (event->type) {
1735 case RINGBUF_TYPE_PADDING:
1739 case RINGBUF_TYPE_TIME_EXTEND:
1740 /* Internal data, OK to advance */
1741 rb_advance_iter(iter);
1744 case RINGBUF_TYPE_TIME_STAMP:
1745 /* FIXME: not implemented */
1746 rb_advance_iter(iter);
1749 case RINGBUF_TYPE_DATA:
1751 *ts = iter->read_stamp + event->time_delta;
1752 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1764 * ring_buffer_consume - return an event and consume it
1765 * @buffer: The ring buffer to get the next event from
1767 * Returns the next event in the ring buffer, and that event is consumed.
1768 * Meaning, that sequential reads will keep returning a different event,
1769 * and eventually empty the ring buffer if the producer is slower.
1771 struct ring_buffer_event *
1772 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
1774 struct ring_buffer_per_cpu *cpu_buffer;
1775 struct ring_buffer_event *event;
1777 if (!cpu_isset(cpu, buffer->cpumask))
1780 event = ring_buffer_peek(buffer, cpu, ts);
1784 cpu_buffer = buffer->buffers[cpu];
1785 rb_advance_reader(cpu_buffer);
1791 * ring_buffer_read_start - start a non consuming read of the buffer
1792 * @buffer: The ring buffer to read from
1793 * @cpu: The cpu buffer to iterate over
1795 * This starts up an iteration through the buffer. It also disables
1796 * the recording to the buffer until the reading is finished.
1797 * This prevents the reading from being corrupted. This is not
1798 * a consuming read, so a producer is not expected.
1800 * Must be paired with ring_buffer_finish.
1802 struct ring_buffer_iter *
1803 ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
1805 struct ring_buffer_per_cpu *cpu_buffer;
1806 struct ring_buffer_iter *iter;
1807 unsigned long flags;
1809 if (!cpu_isset(cpu, buffer->cpumask))
1812 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
1816 cpu_buffer = buffer->buffers[cpu];
1818 iter->cpu_buffer = cpu_buffer;
1820 atomic_inc(&cpu_buffer->record_disabled);
1821 synchronize_sched();
1823 local_irq_save(flags);
1824 __raw_spin_lock(&cpu_buffer->lock);
1825 ring_buffer_iter_reset(iter);
1826 __raw_spin_unlock(&cpu_buffer->lock);
1827 local_irq_restore(flags);
1833 * ring_buffer_finish - finish reading the iterator of the buffer
1834 * @iter: The iterator retrieved by ring_buffer_start
1836 * This re-enables the recording to the buffer, and frees the
1840 ring_buffer_read_finish(struct ring_buffer_iter *iter)
1842 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1844 atomic_dec(&cpu_buffer->record_disabled);
1849 * ring_buffer_read - read the next item in the ring buffer by the iterator
1850 * @iter: The ring buffer iterator
1851 * @ts: The time stamp of the event read.
1853 * This reads the next event in the ring buffer and increments the iterator.
1855 struct ring_buffer_event *
1856 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
1858 struct ring_buffer_event *event;
1860 event = ring_buffer_iter_peek(iter, ts);
1864 rb_advance_iter(iter);
1870 * ring_buffer_size - return the size of the ring buffer (in bytes)
1871 * @buffer: The ring buffer.
1873 unsigned long ring_buffer_size(struct ring_buffer *buffer)
1875 return BUF_PAGE_SIZE * buffer->pages;
1879 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
1881 cpu_buffer->head_page
1882 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
1883 local_set(&cpu_buffer->head_page->write, 0);
1884 local_set(&cpu_buffer->head_page->commit, 0);
1886 cpu_buffer->head_page->read = 0;
1888 cpu_buffer->tail_page = cpu_buffer->head_page;
1889 cpu_buffer->commit_page = cpu_buffer->head_page;
1891 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1892 local_set(&cpu_buffer->reader_page->write, 0);
1893 local_set(&cpu_buffer->reader_page->commit, 0);
1894 cpu_buffer->reader_page->read = 0;
1896 cpu_buffer->overrun = 0;
1897 cpu_buffer->entries = 0;
1901 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
1902 * @buffer: The ring buffer to reset a per cpu buffer of
1903 * @cpu: The CPU buffer to be reset
1905 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
1907 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
1908 unsigned long flags;
1910 if (!cpu_isset(cpu, buffer->cpumask))
1913 local_irq_save(flags);
1914 __raw_spin_lock(&cpu_buffer->lock);
1916 rb_reset_cpu(cpu_buffer);
1918 __raw_spin_unlock(&cpu_buffer->lock);
1919 local_irq_restore(flags);
1923 * ring_buffer_reset - reset a ring buffer
1924 * @buffer: The ring buffer to reset all cpu buffers
1926 void ring_buffer_reset(struct ring_buffer *buffer)
1930 for_each_buffer_cpu(buffer, cpu)
1931 ring_buffer_reset_cpu(buffer, cpu);
1935 * rind_buffer_empty - is the ring buffer empty?
1936 * @buffer: The ring buffer to test
1938 int ring_buffer_empty(struct ring_buffer *buffer)
1940 struct ring_buffer_per_cpu *cpu_buffer;
1943 /* yes this is racy, but if you don't like the race, lock the buffer */
1944 for_each_buffer_cpu(buffer, cpu) {
1945 cpu_buffer = buffer->buffers[cpu];
1946 if (!rb_per_cpu_empty(cpu_buffer))
1953 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
1954 * @buffer: The ring buffer
1955 * @cpu: The CPU buffer to test
1957 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
1959 struct ring_buffer_per_cpu *cpu_buffer;
1961 if (!cpu_isset(cpu, buffer->cpumask))
1964 cpu_buffer = buffer->buffers[cpu];
1965 return rb_per_cpu_empty(cpu_buffer);
1969 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
1970 * @buffer_a: One buffer to swap with
1971 * @buffer_b: The other buffer to swap with
1973 * This function is useful for tracers that want to take a "snapshot"
1974 * of a CPU buffer and has another back up buffer lying around.
1975 * it is expected that the tracer handles the cpu buffer not being
1976 * used at the moment.
1978 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
1979 struct ring_buffer *buffer_b, int cpu)
1981 struct ring_buffer_per_cpu *cpu_buffer_a;
1982 struct ring_buffer_per_cpu *cpu_buffer_b;
1984 if (!cpu_isset(cpu, buffer_a->cpumask) ||
1985 !cpu_isset(cpu, buffer_b->cpumask))
1988 /* At least make sure the two buffers are somewhat the same */
1989 if (buffer_a->size != buffer_b->size ||
1990 buffer_a->pages != buffer_b->pages)
1993 cpu_buffer_a = buffer_a->buffers[cpu];
1994 cpu_buffer_b = buffer_b->buffers[cpu];
1997 * We can't do a synchronize_sched here because this
1998 * function can be called in atomic context.
1999 * Normally this will be called from the same CPU as cpu.
2000 * If not it's up to the caller to protect this.
2002 atomic_inc(&cpu_buffer_a->record_disabled);
2003 atomic_inc(&cpu_buffer_b->record_disabled);
2005 buffer_a->buffers[cpu] = cpu_buffer_b;
2006 buffer_b->buffers[cpu] = cpu_buffer_a;
2008 cpu_buffer_b->buffer = buffer_a;
2009 cpu_buffer_a->buffer = buffer_b;
2011 atomic_dec(&cpu_buffer_a->record_disabled);
2012 atomic_dec(&cpu_buffer_b->record_disabled);