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;
1034 * We allow for interrupts to reenter here and do a trace.
1035 * If one does, it will cause this original code to loop
1036 * back here. Even with heavy interrupts happening, this
1037 * should only happen a few times in a row. If this happens
1038 * 1000 times in a row, there must be either an interrupt
1039 * storm or we have something buggy.
1042 if (unlikely(++nr_loops > 1000)) {
1043 RB_WARN_ON(cpu_buffer, 1);
1047 ts = ring_buffer_time_stamp(cpu_buffer->cpu);
1050 * Only the first commit can update the timestamp.
1051 * Yes there is a race here. If an interrupt comes in
1052 * just after the conditional and it traces too, then it
1053 * will also check the deltas. More than one timestamp may
1054 * also be made. But only the entry that did the actual
1055 * commit will be something other than zero.
1057 if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
1058 rb_page_write(cpu_buffer->tail_page) ==
1059 rb_commit_index(cpu_buffer)) {
1061 delta = ts - cpu_buffer->write_stamp;
1063 /* make sure this delta is calculated here */
1066 /* Did the write stamp get updated already? */
1067 if (unlikely(ts < cpu_buffer->write_stamp))
1070 if (test_time_stamp(delta)) {
1072 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
1074 if (commit == -EBUSY)
1077 if (commit == -EAGAIN)
1080 RB_WARN_ON(cpu_buffer, commit < 0);
1083 /* Non commits have zero deltas */
1086 event = __rb_reserve_next(cpu_buffer, type, length, &ts);
1087 if (PTR_ERR(event) == -EAGAIN)
1091 if (unlikely(commit))
1093 * Ouch! We needed a timestamp and it was commited. But
1094 * we didn't get our event reserved.
1096 rb_set_commit_to_write(cpu_buffer);
1101 * If the timestamp was commited, make the commit our entry
1102 * now so that we will update it when needed.
1105 rb_set_commit_event(cpu_buffer, event);
1106 else if (!rb_is_commit(cpu_buffer, event))
1109 event->time_delta = delta;
1114 static DEFINE_PER_CPU(int, rb_need_resched);
1117 * ring_buffer_lock_reserve - reserve a part of the buffer
1118 * @buffer: the ring buffer to reserve from
1119 * @length: the length of the data to reserve (excluding event header)
1120 * @flags: a pointer to save the interrupt flags
1122 * Returns a reseverd event on the ring buffer to copy directly to.
1123 * The user of this interface will need to get the body to write into
1124 * and can use the ring_buffer_event_data() interface.
1126 * The length is the length of the data needed, not the event length
1127 * which also includes the event header.
1129 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1130 * If NULL is returned, then nothing has been allocated or locked.
1132 struct ring_buffer_event *
1133 ring_buffer_lock_reserve(struct ring_buffer *buffer,
1134 unsigned long length,
1135 unsigned long *flags)
1137 struct ring_buffer_per_cpu *cpu_buffer;
1138 struct ring_buffer_event *event;
1141 if (atomic_read(&buffer->record_disabled))
1144 /* If we are tracing schedule, we don't want to recurse */
1145 resched = ftrace_preempt_disable();
1147 cpu = raw_smp_processor_id();
1149 if (!cpu_isset(cpu, buffer->cpumask))
1152 cpu_buffer = buffer->buffers[cpu];
1154 if (atomic_read(&cpu_buffer->record_disabled))
1157 length = rb_calculate_event_length(length);
1158 if (length > BUF_PAGE_SIZE)
1161 event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
1166 * Need to store resched state on this cpu.
1167 * Only the first needs to.
1170 if (preempt_count() == 1)
1171 per_cpu(rb_need_resched, cpu) = resched;
1176 ftrace_preempt_enable(resched);
1180 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
1181 struct ring_buffer_event *event)
1183 cpu_buffer->entries++;
1185 /* Only process further if we own the commit */
1186 if (!rb_is_commit(cpu_buffer, event))
1189 cpu_buffer->write_stamp += event->time_delta;
1191 rb_set_commit_to_write(cpu_buffer);
1195 * ring_buffer_unlock_commit - commit a reserved
1196 * @buffer: The buffer to commit to
1197 * @event: The event pointer to commit.
1198 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1200 * This commits the data to the ring buffer, and releases any locks held.
1202 * Must be paired with ring_buffer_lock_reserve.
1204 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
1205 struct ring_buffer_event *event,
1206 unsigned long flags)
1208 struct ring_buffer_per_cpu *cpu_buffer;
1209 int cpu = raw_smp_processor_id();
1211 cpu_buffer = buffer->buffers[cpu];
1213 rb_commit(cpu_buffer, event);
1216 * Only the last preempt count needs to restore preemption.
1218 if (preempt_count() == 1)
1219 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
1221 preempt_enable_no_resched_notrace();
1227 * ring_buffer_write - write data to the buffer without reserving
1228 * @buffer: The ring buffer to write to.
1229 * @length: The length of the data being written (excluding the event header)
1230 * @data: The data to write to the buffer.
1232 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1233 * one function. If you already have the data to write to the buffer, it
1234 * may be easier to simply call this function.
1236 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1237 * and not the length of the event which would hold the header.
1239 int ring_buffer_write(struct ring_buffer *buffer,
1240 unsigned long length,
1243 struct ring_buffer_per_cpu *cpu_buffer;
1244 struct ring_buffer_event *event;
1245 unsigned long event_length;
1250 if (atomic_read(&buffer->record_disabled))
1253 resched = ftrace_preempt_disable();
1255 cpu = raw_smp_processor_id();
1257 if (!cpu_isset(cpu, buffer->cpumask))
1260 cpu_buffer = buffer->buffers[cpu];
1262 if (atomic_read(&cpu_buffer->record_disabled))
1265 event_length = rb_calculate_event_length(length);
1266 event = rb_reserve_next_event(cpu_buffer,
1267 RINGBUF_TYPE_DATA, event_length);
1271 body = rb_event_data(event);
1273 memcpy(body, data, length);
1275 rb_commit(cpu_buffer, event);
1279 ftrace_preempt_enable(resched);
1284 static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
1286 struct buffer_page *reader = cpu_buffer->reader_page;
1287 struct buffer_page *head = cpu_buffer->head_page;
1288 struct buffer_page *commit = cpu_buffer->commit_page;
1290 return reader->read == rb_page_commit(reader) &&
1291 (commit == reader ||
1293 head->read == rb_page_commit(commit)));
1297 * ring_buffer_record_disable - stop all writes into the buffer
1298 * @buffer: The ring buffer to stop writes to.
1300 * This prevents all writes to the buffer. Any attempt to write
1301 * to the buffer after this will fail and return NULL.
1303 * The caller should call synchronize_sched() after this.
1305 void ring_buffer_record_disable(struct ring_buffer *buffer)
1307 atomic_inc(&buffer->record_disabled);
1311 * ring_buffer_record_enable - enable writes to the buffer
1312 * @buffer: The ring buffer to enable writes
1314 * Note, multiple disables will need the same number of enables
1315 * to truely enable the writing (much like preempt_disable).
1317 void ring_buffer_record_enable(struct ring_buffer *buffer)
1319 atomic_dec(&buffer->record_disabled);
1323 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1324 * @buffer: The ring buffer to stop writes to.
1325 * @cpu: The CPU buffer to stop
1327 * This prevents all writes to the buffer. Any attempt to write
1328 * to the buffer after this will fail and return NULL.
1330 * The caller should call synchronize_sched() after this.
1332 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
1334 struct ring_buffer_per_cpu *cpu_buffer;
1336 if (!cpu_isset(cpu, buffer->cpumask))
1339 cpu_buffer = buffer->buffers[cpu];
1340 atomic_inc(&cpu_buffer->record_disabled);
1344 * ring_buffer_record_enable_cpu - enable writes to the buffer
1345 * @buffer: The ring buffer to enable writes
1346 * @cpu: The CPU to enable.
1348 * Note, multiple disables will need the same number of enables
1349 * to truely enable the writing (much like preempt_disable).
1351 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
1353 struct ring_buffer_per_cpu *cpu_buffer;
1355 if (!cpu_isset(cpu, buffer->cpumask))
1358 cpu_buffer = buffer->buffers[cpu];
1359 atomic_dec(&cpu_buffer->record_disabled);
1363 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1364 * @buffer: The ring buffer
1365 * @cpu: The per CPU buffer to get the entries from.
1367 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
1369 struct ring_buffer_per_cpu *cpu_buffer;
1371 if (!cpu_isset(cpu, buffer->cpumask))
1374 cpu_buffer = buffer->buffers[cpu];
1375 return cpu_buffer->entries;
1379 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1380 * @buffer: The ring buffer
1381 * @cpu: The per CPU buffer to get the number of overruns from
1383 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
1385 struct ring_buffer_per_cpu *cpu_buffer;
1387 if (!cpu_isset(cpu, buffer->cpumask))
1390 cpu_buffer = buffer->buffers[cpu];
1391 return cpu_buffer->overrun;
1395 * ring_buffer_entries - get the number of entries in a buffer
1396 * @buffer: The ring buffer
1398 * Returns the total number of entries in the ring buffer
1401 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
1403 struct ring_buffer_per_cpu *cpu_buffer;
1404 unsigned long entries = 0;
1407 /* if you care about this being correct, lock the buffer */
1408 for_each_buffer_cpu(buffer, cpu) {
1409 cpu_buffer = buffer->buffers[cpu];
1410 entries += cpu_buffer->entries;
1417 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1418 * @buffer: The ring buffer
1420 * Returns the total number of overruns in the ring buffer
1423 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
1425 struct ring_buffer_per_cpu *cpu_buffer;
1426 unsigned long overruns = 0;
1429 /* if you care about this being correct, lock the buffer */
1430 for_each_buffer_cpu(buffer, cpu) {
1431 cpu_buffer = buffer->buffers[cpu];
1432 overruns += cpu_buffer->overrun;
1439 * ring_buffer_iter_reset - reset an iterator
1440 * @iter: The iterator to reset
1442 * Resets the iterator, so that it will start from the beginning
1445 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
1447 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1449 /* Iterator usage is expected to have record disabled */
1450 if (list_empty(&cpu_buffer->reader_page->list)) {
1451 iter->head_page = cpu_buffer->head_page;
1452 iter->head = cpu_buffer->head_page->read;
1454 iter->head_page = cpu_buffer->reader_page;
1455 iter->head = cpu_buffer->reader_page->read;
1458 iter->read_stamp = cpu_buffer->read_stamp;
1460 iter->read_stamp = iter->head_page->time_stamp;
1464 * ring_buffer_iter_empty - check if an iterator has no more to read
1465 * @iter: The iterator to check
1467 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
1469 struct ring_buffer_per_cpu *cpu_buffer;
1471 cpu_buffer = iter->cpu_buffer;
1473 return iter->head_page == cpu_buffer->commit_page &&
1474 iter->head == rb_commit_index(cpu_buffer);
1478 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1479 struct ring_buffer_event *event)
1483 switch (event->type) {
1484 case RINGBUF_TYPE_PADDING:
1487 case RINGBUF_TYPE_TIME_EXTEND:
1488 delta = event->array[0];
1490 delta += event->time_delta;
1491 cpu_buffer->read_stamp += delta;
1494 case RINGBUF_TYPE_TIME_STAMP:
1495 /* FIXME: not implemented */
1498 case RINGBUF_TYPE_DATA:
1499 cpu_buffer->read_stamp += event->time_delta;
1509 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
1510 struct ring_buffer_event *event)
1514 switch (event->type) {
1515 case RINGBUF_TYPE_PADDING:
1518 case RINGBUF_TYPE_TIME_EXTEND:
1519 delta = event->array[0];
1521 delta += event->time_delta;
1522 iter->read_stamp += delta;
1525 case RINGBUF_TYPE_TIME_STAMP:
1526 /* FIXME: not implemented */
1529 case RINGBUF_TYPE_DATA:
1530 iter->read_stamp += event->time_delta;
1539 static struct buffer_page *
1540 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1542 struct buffer_page *reader = NULL;
1543 unsigned long flags;
1546 local_irq_save(flags);
1547 __raw_spin_lock(&cpu_buffer->lock);
1551 * This should normally only loop twice. But because the
1552 * start of the reader inserts an empty page, it causes
1553 * a case where we will loop three times. There should be no
1554 * reason to loop four times (that I know of).
1556 if (unlikely(++nr_loops > 3)) {
1557 RB_WARN_ON(cpu_buffer, 1);
1562 reader = cpu_buffer->reader_page;
1564 /* If there's more to read, return this page */
1565 if (cpu_buffer->reader_page->read < rb_page_size(reader))
1568 /* Never should we have an index greater than the size */
1569 RB_WARN_ON(cpu_buffer,
1570 cpu_buffer->reader_page->read > rb_page_size(reader));
1572 /* check if we caught up to the tail */
1574 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
1578 * Splice the empty reader page into the list around the head.
1579 * Reset the reader page to size zero.
1582 reader = cpu_buffer->head_page;
1583 cpu_buffer->reader_page->list.next = reader->list.next;
1584 cpu_buffer->reader_page->list.prev = reader->list.prev;
1586 local_set(&cpu_buffer->reader_page->write, 0);
1587 local_set(&cpu_buffer->reader_page->commit, 0);
1589 /* Make the reader page now replace the head */
1590 reader->list.prev->next = &cpu_buffer->reader_page->list;
1591 reader->list.next->prev = &cpu_buffer->reader_page->list;
1594 * If the tail is on the reader, then we must set the head
1595 * to the inserted page, otherwise we set it one before.
1597 cpu_buffer->head_page = cpu_buffer->reader_page;
1599 if (cpu_buffer->commit_page != reader)
1600 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
1602 /* Finally update the reader page to the new head */
1603 cpu_buffer->reader_page = reader;
1604 rb_reset_reader_page(cpu_buffer);
1609 __raw_spin_unlock(&cpu_buffer->lock);
1610 local_irq_restore(flags);
1615 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
1617 struct ring_buffer_event *event;
1618 struct buffer_page *reader;
1621 reader = rb_get_reader_page(cpu_buffer);
1623 /* This function should not be called when buffer is empty */
1626 event = rb_reader_event(cpu_buffer);
1628 if (event->type == RINGBUF_TYPE_DATA)
1629 cpu_buffer->entries--;
1631 rb_update_read_stamp(cpu_buffer, event);
1633 length = rb_event_length(event);
1634 cpu_buffer->reader_page->read += length;
1637 static void rb_advance_iter(struct ring_buffer_iter *iter)
1639 struct ring_buffer *buffer;
1640 struct ring_buffer_per_cpu *cpu_buffer;
1641 struct ring_buffer_event *event;
1644 cpu_buffer = iter->cpu_buffer;
1645 buffer = cpu_buffer->buffer;
1648 * Check if we are at the end of the buffer.
1650 if (iter->head >= rb_page_size(iter->head_page)) {
1651 BUG_ON(iter->head_page == cpu_buffer->commit_page);
1656 event = rb_iter_head_event(iter);
1658 length = rb_event_length(event);
1661 * This should not be called to advance the header if we are
1662 * at the tail of the buffer.
1664 BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
1665 (iter->head + length > rb_commit_index(cpu_buffer)));
1667 rb_update_iter_read_stamp(iter, event);
1669 iter->head += length;
1671 /* check for end of page padding */
1672 if ((iter->head >= rb_page_size(iter->head_page)) &&
1673 (iter->head_page != cpu_buffer->commit_page))
1674 rb_advance_iter(iter);
1678 * ring_buffer_peek - peek at the next event to be read
1679 * @buffer: The ring buffer to read
1680 * @cpu: The cpu to peak at
1681 * @ts: The timestamp counter of this event.
1683 * This will return the event that will be read next, but does
1684 * not consume the data.
1686 struct ring_buffer_event *
1687 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
1689 struct ring_buffer_per_cpu *cpu_buffer;
1690 struct ring_buffer_event *event;
1691 struct buffer_page *reader;
1694 if (!cpu_isset(cpu, buffer->cpumask))
1697 cpu_buffer = buffer->buffers[cpu];
1701 * We repeat when a timestamp is encountered. It is possible
1702 * to get multiple timestamps from an interrupt entering just
1703 * as one timestamp is about to be written. The max times
1704 * that this can happen is the number of nested interrupts we
1705 * can have. Nesting 10 deep of interrupts is clearly
1708 if (unlikely(++nr_loops > 10)) {
1709 RB_WARN_ON(cpu_buffer, 1);
1713 reader = rb_get_reader_page(cpu_buffer);
1717 event = rb_reader_event(cpu_buffer);
1719 switch (event->type) {
1720 case RINGBUF_TYPE_PADDING:
1721 RB_WARN_ON(cpu_buffer, 1);
1722 rb_advance_reader(cpu_buffer);
1725 case RINGBUF_TYPE_TIME_EXTEND:
1726 /* Internal data, OK to advance */
1727 rb_advance_reader(cpu_buffer);
1730 case RINGBUF_TYPE_TIME_STAMP:
1731 /* FIXME: not implemented */
1732 rb_advance_reader(cpu_buffer);
1735 case RINGBUF_TYPE_DATA:
1737 *ts = cpu_buffer->read_stamp + event->time_delta;
1738 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1750 * ring_buffer_iter_peek - peek at the next event to be read
1751 * @iter: The ring buffer iterator
1752 * @ts: The timestamp counter of this event.
1754 * This will return the event that will be read next, but does
1755 * not increment the iterator.
1757 struct ring_buffer_event *
1758 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
1760 struct ring_buffer *buffer;
1761 struct ring_buffer_per_cpu *cpu_buffer;
1762 struct ring_buffer_event *event;
1765 if (ring_buffer_iter_empty(iter))
1768 cpu_buffer = iter->cpu_buffer;
1769 buffer = cpu_buffer->buffer;
1773 * We repeat when a timestamp is encountered. It is possible
1774 * to get multiple timestamps from an interrupt entering just
1775 * as one timestamp is about to be written. The max times
1776 * that this can happen is the number of nested interrupts we
1777 * can have. Nesting 10 deep of interrupts is clearly
1780 if (unlikely(++nr_loops > 10)) {
1781 RB_WARN_ON(cpu_buffer, 1);
1785 if (rb_per_cpu_empty(cpu_buffer))
1788 event = rb_iter_head_event(iter);
1790 switch (event->type) {
1791 case RINGBUF_TYPE_PADDING:
1795 case RINGBUF_TYPE_TIME_EXTEND:
1796 /* Internal data, OK to advance */
1797 rb_advance_iter(iter);
1800 case RINGBUF_TYPE_TIME_STAMP:
1801 /* FIXME: not implemented */
1802 rb_advance_iter(iter);
1805 case RINGBUF_TYPE_DATA:
1807 *ts = iter->read_stamp + event->time_delta;
1808 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1820 * ring_buffer_consume - return an event and consume it
1821 * @buffer: The ring buffer to get the next event from
1823 * Returns the next event in the ring buffer, and that event is consumed.
1824 * Meaning, that sequential reads will keep returning a different event,
1825 * and eventually empty the ring buffer if the producer is slower.
1827 struct ring_buffer_event *
1828 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
1830 struct ring_buffer_per_cpu *cpu_buffer;
1831 struct ring_buffer_event *event;
1833 if (!cpu_isset(cpu, buffer->cpumask))
1836 event = ring_buffer_peek(buffer, cpu, ts);
1840 cpu_buffer = buffer->buffers[cpu];
1841 rb_advance_reader(cpu_buffer);
1847 * ring_buffer_read_start - start a non consuming read of the buffer
1848 * @buffer: The ring buffer to read from
1849 * @cpu: The cpu buffer to iterate over
1851 * This starts up an iteration through the buffer. It also disables
1852 * the recording to the buffer until the reading is finished.
1853 * This prevents the reading from being corrupted. This is not
1854 * a consuming read, so a producer is not expected.
1856 * Must be paired with ring_buffer_finish.
1858 struct ring_buffer_iter *
1859 ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
1861 struct ring_buffer_per_cpu *cpu_buffer;
1862 struct ring_buffer_iter *iter;
1863 unsigned long flags;
1865 if (!cpu_isset(cpu, buffer->cpumask))
1868 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
1872 cpu_buffer = buffer->buffers[cpu];
1874 iter->cpu_buffer = cpu_buffer;
1876 atomic_inc(&cpu_buffer->record_disabled);
1877 synchronize_sched();
1879 local_irq_save(flags);
1880 __raw_spin_lock(&cpu_buffer->lock);
1881 ring_buffer_iter_reset(iter);
1882 __raw_spin_unlock(&cpu_buffer->lock);
1883 local_irq_restore(flags);
1889 * ring_buffer_finish - finish reading the iterator of the buffer
1890 * @iter: The iterator retrieved by ring_buffer_start
1892 * This re-enables the recording to the buffer, and frees the
1896 ring_buffer_read_finish(struct ring_buffer_iter *iter)
1898 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1900 atomic_dec(&cpu_buffer->record_disabled);
1905 * ring_buffer_read - read the next item in the ring buffer by the iterator
1906 * @iter: The ring buffer iterator
1907 * @ts: The time stamp of the event read.
1909 * This reads the next event in the ring buffer and increments the iterator.
1911 struct ring_buffer_event *
1912 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
1914 struct ring_buffer_event *event;
1916 event = ring_buffer_iter_peek(iter, ts);
1920 rb_advance_iter(iter);
1926 * ring_buffer_size - return the size of the ring buffer (in bytes)
1927 * @buffer: The ring buffer.
1929 unsigned long ring_buffer_size(struct ring_buffer *buffer)
1931 return BUF_PAGE_SIZE * buffer->pages;
1935 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
1937 cpu_buffer->head_page
1938 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
1939 local_set(&cpu_buffer->head_page->write, 0);
1940 local_set(&cpu_buffer->head_page->commit, 0);
1942 cpu_buffer->head_page->read = 0;
1944 cpu_buffer->tail_page = cpu_buffer->head_page;
1945 cpu_buffer->commit_page = cpu_buffer->head_page;
1947 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1948 local_set(&cpu_buffer->reader_page->write, 0);
1949 local_set(&cpu_buffer->reader_page->commit, 0);
1950 cpu_buffer->reader_page->read = 0;
1952 cpu_buffer->overrun = 0;
1953 cpu_buffer->entries = 0;
1957 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
1958 * @buffer: The ring buffer to reset a per cpu buffer of
1959 * @cpu: The CPU buffer to be reset
1961 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
1963 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
1964 unsigned long flags;
1966 if (!cpu_isset(cpu, buffer->cpumask))
1969 local_irq_save(flags);
1970 __raw_spin_lock(&cpu_buffer->lock);
1972 rb_reset_cpu(cpu_buffer);
1974 __raw_spin_unlock(&cpu_buffer->lock);
1975 local_irq_restore(flags);
1979 * ring_buffer_reset - reset a ring buffer
1980 * @buffer: The ring buffer to reset all cpu buffers
1982 void ring_buffer_reset(struct ring_buffer *buffer)
1986 for_each_buffer_cpu(buffer, cpu)
1987 ring_buffer_reset_cpu(buffer, cpu);
1991 * rind_buffer_empty - is the ring buffer empty?
1992 * @buffer: The ring buffer to test
1994 int ring_buffer_empty(struct ring_buffer *buffer)
1996 struct ring_buffer_per_cpu *cpu_buffer;
1999 /* yes this is racy, but if you don't like the race, lock the buffer */
2000 for_each_buffer_cpu(buffer, cpu) {
2001 cpu_buffer = buffer->buffers[cpu];
2002 if (!rb_per_cpu_empty(cpu_buffer))
2009 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2010 * @buffer: The ring buffer
2011 * @cpu: The CPU buffer to test
2013 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
2015 struct ring_buffer_per_cpu *cpu_buffer;
2017 if (!cpu_isset(cpu, buffer->cpumask))
2020 cpu_buffer = buffer->buffers[cpu];
2021 return rb_per_cpu_empty(cpu_buffer);
2025 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2026 * @buffer_a: One buffer to swap with
2027 * @buffer_b: The other buffer to swap with
2029 * This function is useful for tracers that want to take a "snapshot"
2030 * of a CPU buffer and has another back up buffer lying around.
2031 * it is expected that the tracer handles the cpu buffer not being
2032 * used at the moment.
2034 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
2035 struct ring_buffer *buffer_b, int cpu)
2037 struct ring_buffer_per_cpu *cpu_buffer_a;
2038 struct ring_buffer_per_cpu *cpu_buffer_b;
2040 if (!cpu_isset(cpu, buffer_a->cpumask) ||
2041 !cpu_isset(cpu, buffer_b->cpumask))
2044 /* At least make sure the two buffers are somewhat the same */
2045 if (buffer_a->size != buffer_b->size ||
2046 buffer_a->pages != buffer_b->pages)
2049 cpu_buffer_a = buffer_a->buffers[cpu];
2050 cpu_buffer_b = buffer_b->buffers[cpu];
2053 * We can't do a synchronize_sched here because this
2054 * function can be called in atomic context.
2055 * Normally this will be called from the same CPU as cpu.
2056 * If not it's up to the caller to protect this.
2058 atomic_inc(&cpu_buffer_a->record_disabled);
2059 atomic_inc(&cpu_buffer_b->record_disabled);
2061 buffer_a->buffers[cpu] = cpu_buffer_b;
2062 buffer_b->buffers[cpu] = cpu_buffer_a;
2064 cpu_buffer_b->buffer = buffer_a;
2065 cpu_buffer_a->buffer = buffer_b;
2067 atomic_dec(&cpu_buffer_a->record_disabled);
2068 atomic_dec(&cpu_buffer_b->record_disabled);