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 /* Global flag to disable all recording to ring buffers */
22 static int ring_buffers_off __read_mostly;
25 * tracing_on - enable all tracing buffers
27 * This function enables all tracing buffers that may have been
28 * disabled with tracing_off.
34 EXPORT_SYMBOL_GPL(tracing_on);
37 * tracing_off - turn off all tracing buffers
39 * This function stops all tracing buffers from recording data.
40 * It does not disable any overhead the tracers themselves may
41 * be causing. This function simply causes all recording to
42 * the ring buffers to fail.
44 void tracing_off(void)
48 EXPORT_SYMBOL_GPL(tracing_off);
50 /* Up this if you want to test the TIME_EXTENTS and normalization */
54 u64 ring_buffer_time_stamp(int cpu)
58 preempt_disable_notrace();
59 /* shift to debug/test normalization and TIME_EXTENTS */
60 time = sched_clock() << DEBUG_SHIFT;
61 preempt_enable_notrace();
65 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
67 void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
69 /* Just stupid testing the normalize function and deltas */
72 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
74 #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
75 #define RB_ALIGNMENT_SHIFT 2
76 #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
77 #define RB_MAX_SMALL_DATA 28
80 RB_LEN_TIME_EXTEND = 8,
81 RB_LEN_TIME_STAMP = 16,
84 /* inline for ring buffer fast paths */
85 static inline unsigned
86 rb_event_length(struct ring_buffer_event *event)
90 switch (event->type) {
91 case RINGBUF_TYPE_PADDING:
95 case RINGBUF_TYPE_TIME_EXTEND:
96 return RB_LEN_TIME_EXTEND;
98 case RINGBUF_TYPE_TIME_STAMP:
99 return RB_LEN_TIME_STAMP;
101 case RINGBUF_TYPE_DATA:
103 length = event->len << RB_ALIGNMENT_SHIFT;
105 length = event->array[0];
106 return length + RB_EVNT_HDR_SIZE;
115 * ring_buffer_event_length - return the length of the event
116 * @event: the event to get the length of
118 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
120 return rb_event_length(event);
122 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
124 /* inline for ring buffer fast paths */
126 rb_event_data(struct ring_buffer_event *event)
128 BUG_ON(event->type != RINGBUF_TYPE_DATA);
129 /* If length is in len field, then array[0] has the data */
131 return (void *)&event->array[0];
132 /* Otherwise length is in array[0] and array[1] has the data */
133 return (void *)&event->array[1];
137 * ring_buffer_event_data - return the data of the event
138 * @event: the event to get the data from
140 void *ring_buffer_event_data(struct ring_buffer_event *event)
142 return rb_event_data(event);
144 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
146 #define for_each_buffer_cpu(buffer, cpu) \
147 for_each_cpu_mask(cpu, buffer->cpumask)
150 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
151 #define TS_DELTA_TEST (~TS_MASK)
154 * This hack stolen from mm/slob.c.
155 * We can store per page timing information in the page frame of the page.
156 * Thanks to Peter Zijlstra for suggesting this idea.
159 u64 time_stamp; /* page time stamp */
160 local_t write; /* index for next write */
161 local_t commit; /* write commited index */
162 unsigned read; /* index for next read */
163 struct list_head list; /* list of free pages */
164 void *page; /* Actual data page */
168 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
171 static inline void free_buffer_page(struct buffer_page *bpage)
174 free_page((unsigned long)bpage->page);
179 * We need to fit the time_stamp delta into 27 bits.
181 static inline int test_time_stamp(u64 delta)
183 if (delta & TS_DELTA_TEST)
188 #define BUF_PAGE_SIZE PAGE_SIZE
191 * head_page == tail_page && head == tail then buffer is empty.
193 struct ring_buffer_per_cpu {
195 struct ring_buffer *buffer;
197 struct lock_class_key lock_key;
198 struct list_head pages;
199 struct buffer_page *head_page; /* read from head */
200 struct buffer_page *tail_page; /* write to tail */
201 struct buffer_page *commit_page; /* commited pages */
202 struct buffer_page *reader_page;
203 unsigned long overrun;
204 unsigned long entries;
207 atomic_t record_disabled;
216 atomic_t record_disabled;
220 struct ring_buffer_per_cpu **buffers;
223 struct ring_buffer_iter {
224 struct ring_buffer_per_cpu *cpu_buffer;
226 struct buffer_page *head_page;
230 #define RB_WARN_ON(buffer, cond) \
232 if (unlikely(cond)) { \
233 atomic_inc(&buffer->record_disabled); \
238 #define RB_WARN_ON_RET(buffer, cond) \
240 if (unlikely(cond)) { \
241 atomic_inc(&buffer->record_disabled); \
247 #define RB_WARN_ON_ONCE(buffer, cond) \
250 if (unlikely(cond) && !once) { \
252 atomic_inc(&buffer->record_disabled); \
258 * check_pages - integrity check of buffer pages
259 * @cpu_buffer: CPU buffer with pages to test
261 * As a safty measure we check to make sure the data pages have not
264 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
266 struct list_head *head = &cpu_buffer->pages;
267 struct buffer_page *page, *tmp;
269 RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);
270 RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);
272 list_for_each_entry_safe(page, tmp, head, list) {
273 RB_WARN_ON_RET(cpu_buffer,
274 page->list.next->prev != &page->list);
275 RB_WARN_ON_RET(cpu_buffer,
276 page->list.prev->next != &page->list);
282 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
285 struct list_head *head = &cpu_buffer->pages;
286 struct buffer_page *page, *tmp;
291 for (i = 0; i < nr_pages; i++) {
292 page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
293 GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
296 list_add(&page->list, &pages);
298 addr = __get_free_page(GFP_KERNEL);
301 page->page = (void *)addr;
304 list_splice(&pages, head);
306 rb_check_pages(cpu_buffer);
311 list_for_each_entry_safe(page, tmp, &pages, list) {
312 list_del_init(&page->list);
313 free_buffer_page(page);
318 static struct ring_buffer_per_cpu *
319 rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
321 struct ring_buffer_per_cpu *cpu_buffer;
322 struct buffer_page *page;
326 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
327 GFP_KERNEL, cpu_to_node(cpu));
331 cpu_buffer->cpu = cpu;
332 cpu_buffer->buffer = buffer;
333 spin_lock_init(&cpu_buffer->lock);
334 INIT_LIST_HEAD(&cpu_buffer->pages);
336 page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
337 GFP_KERNEL, cpu_to_node(cpu));
339 goto fail_free_buffer;
341 cpu_buffer->reader_page = page;
342 addr = __get_free_page(GFP_KERNEL);
344 goto fail_free_reader;
345 page->page = (void *)addr;
347 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
349 ret = rb_allocate_pages(cpu_buffer, buffer->pages);
351 goto fail_free_reader;
353 cpu_buffer->head_page
354 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
355 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
360 free_buffer_page(cpu_buffer->reader_page);
367 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
369 struct list_head *head = &cpu_buffer->pages;
370 struct buffer_page *page, *tmp;
372 list_del_init(&cpu_buffer->reader_page->list);
373 free_buffer_page(cpu_buffer->reader_page);
375 list_for_each_entry_safe(page, tmp, head, list) {
376 list_del_init(&page->list);
377 free_buffer_page(page);
383 * Causes compile errors if the struct buffer_page gets bigger
384 * than the struct page.
386 extern int ring_buffer_page_too_big(void);
389 * ring_buffer_alloc - allocate a new ring_buffer
390 * @size: the size in bytes per cpu that is needed.
391 * @flags: attributes to set for the ring buffer.
393 * Currently the only flag that is available is the RB_FL_OVERWRITE
394 * flag. This flag means that the buffer will overwrite old data
395 * when the buffer wraps. If this flag is not set, the buffer will
396 * drop data when the tail hits the head.
398 struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
400 struct ring_buffer *buffer;
404 /* Paranoid! Optimizes out when all is well */
405 if (sizeof(struct buffer_page) > sizeof(struct page))
406 ring_buffer_page_too_big();
409 /* keep it in its own cache line */
410 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
415 buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
416 buffer->flags = flags;
418 /* need at least two pages */
419 if (buffer->pages == 1)
422 buffer->cpumask = cpu_possible_map;
423 buffer->cpus = nr_cpu_ids;
425 bsize = sizeof(void *) * nr_cpu_ids;
426 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
428 if (!buffer->buffers)
429 goto fail_free_buffer;
431 for_each_buffer_cpu(buffer, cpu) {
432 buffer->buffers[cpu] =
433 rb_allocate_cpu_buffer(buffer, cpu);
434 if (!buffer->buffers[cpu])
435 goto fail_free_buffers;
438 mutex_init(&buffer->mutex);
443 for_each_buffer_cpu(buffer, cpu) {
444 if (buffer->buffers[cpu])
445 rb_free_cpu_buffer(buffer->buffers[cpu]);
447 kfree(buffer->buffers);
453 EXPORT_SYMBOL_GPL(ring_buffer_alloc);
456 * ring_buffer_free - free a ring buffer.
457 * @buffer: the buffer to free.
460 ring_buffer_free(struct ring_buffer *buffer)
464 for_each_buffer_cpu(buffer, cpu)
465 rb_free_cpu_buffer(buffer->buffers[cpu]);
469 EXPORT_SYMBOL_GPL(ring_buffer_free);
471 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
474 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
476 struct buffer_page *page;
480 atomic_inc(&cpu_buffer->record_disabled);
483 for (i = 0; i < nr_pages; i++) {
484 BUG_ON(list_empty(&cpu_buffer->pages));
485 p = cpu_buffer->pages.next;
486 page = list_entry(p, struct buffer_page, list);
487 list_del_init(&page->list);
488 free_buffer_page(page);
490 BUG_ON(list_empty(&cpu_buffer->pages));
492 rb_reset_cpu(cpu_buffer);
494 rb_check_pages(cpu_buffer);
496 atomic_dec(&cpu_buffer->record_disabled);
501 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
502 struct list_head *pages, unsigned nr_pages)
504 struct buffer_page *page;
508 atomic_inc(&cpu_buffer->record_disabled);
511 for (i = 0; i < nr_pages; i++) {
512 BUG_ON(list_empty(pages));
514 page = list_entry(p, struct buffer_page, list);
515 list_del_init(&page->list);
516 list_add_tail(&page->list, &cpu_buffer->pages);
518 rb_reset_cpu(cpu_buffer);
520 rb_check_pages(cpu_buffer);
522 atomic_dec(&cpu_buffer->record_disabled);
526 * ring_buffer_resize - resize the ring buffer
527 * @buffer: the buffer to resize.
528 * @size: the new size.
530 * The tracer is responsible for making sure that the buffer is
531 * not being used while changing the size.
532 * Note: We may be able to change the above requirement by using
533 * RCU synchronizations.
535 * Minimum size is 2 * BUF_PAGE_SIZE.
537 * Returns -1 on failure.
539 int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
541 struct ring_buffer_per_cpu *cpu_buffer;
542 unsigned nr_pages, rm_pages, new_pages;
543 struct buffer_page *page, *tmp;
544 unsigned long buffer_size;
550 * Always succeed at resizing a non-existent buffer:
555 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
556 size *= BUF_PAGE_SIZE;
557 buffer_size = buffer->pages * BUF_PAGE_SIZE;
559 /* we need a minimum of two pages */
560 if (size < BUF_PAGE_SIZE * 2)
561 size = BUF_PAGE_SIZE * 2;
563 if (size == buffer_size)
566 mutex_lock(&buffer->mutex);
568 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
570 if (size < buffer_size) {
572 /* easy case, just free pages */
573 BUG_ON(nr_pages >= buffer->pages);
575 rm_pages = buffer->pages - nr_pages;
577 for_each_buffer_cpu(buffer, cpu) {
578 cpu_buffer = buffer->buffers[cpu];
579 rb_remove_pages(cpu_buffer, rm_pages);
585 * This is a bit more difficult. We only want to add pages
586 * when we can allocate enough for all CPUs. We do this
587 * by allocating all the pages and storing them on a local
588 * link list. If we succeed in our allocation, then we
589 * add these pages to the cpu_buffers. Otherwise we just free
590 * them all and return -ENOMEM;
592 BUG_ON(nr_pages <= buffer->pages);
593 new_pages = nr_pages - buffer->pages;
595 for_each_buffer_cpu(buffer, cpu) {
596 for (i = 0; i < new_pages; i++) {
597 page = kzalloc_node(ALIGN(sizeof(*page),
599 GFP_KERNEL, cpu_to_node(cpu));
602 list_add(&page->list, &pages);
603 addr = __get_free_page(GFP_KERNEL);
606 page->page = (void *)addr;
610 for_each_buffer_cpu(buffer, cpu) {
611 cpu_buffer = buffer->buffers[cpu];
612 rb_insert_pages(cpu_buffer, &pages, new_pages);
615 BUG_ON(!list_empty(&pages));
618 buffer->pages = nr_pages;
619 mutex_unlock(&buffer->mutex);
624 list_for_each_entry_safe(page, tmp, &pages, list) {
625 list_del_init(&page->list);
626 free_buffer_page(page);
628 mutex_unlock(&buffer->mutex);
631 EXPORT_SYMBOL_GPL(ring_buffer_resize);
633 static inline int rb_null_event(struct ring_buffer_event *event)
635 return event->type == RINGBUF_TYPE_PADDING;
638 static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
640 return page->page + index;
643 static inline struct ring_buffer_event *
644 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
646 return __rb_page_index(cpu_buffer->reader_page,
647 cpu_buffer->reader_page->read);
650 static inline struct ring_buffer_event *
651 rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
653 return __rb_page_index(cpu_buffer->head_page,
654 cpu_buffer->head_page->read);
657 static inline struct ring_buffer_event *
658 rb_iter_head_event(struct ring_buffer_iter *iter)
660 return __rb_page_index(iter->head_page, iter->head);
663 static inline unsigned rb_page_write(struct buffer_page *bpage)
665 return local_read(&bpage->write);
668 static inline unsigned rb_page_commit(struct buffer_page *bpage)
670 return local_read(&bpage->commit);
673 /* Size is determined by what has been commited */
674 static inline unsigned rb_page_size(struct buffer_page *bpage)
676 return rb_page_commit(bpage);
679 static inline unsigned
680 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
682 return rb_page_commit(cpu_buffer->commit_page);
685 static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
687 return rb_page_commit(cpu_buffer->head_page);
691 * When the tail hits the head and the buffer is in overwrite mode,
692 * the head jumps to the next page and all content on the previous
693 * page is discarded. But before doing so, we update the overrun
694 * variable of the buffer.
696 static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
698 struct ring_buffer_event *event;
701 for (head = 0; head < rb_head_size(cpu_buffer);
702 head += rb_event_length(event)) {
704 event = __rb_page_index(cpu_buffer->head_page, head);
705 BUG_ON(rb_null_event(event));
706 /* Only count data entries */
707 if (event->type != RINGBUF_TYPE_DATA)
709 cpu_buffer->overrun++;
710 cpu_buffer->entries--;
714 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
715 struct buffer_page **page)
717 struct list_head *p = (*page)->list.next;
719 if (p == &cpu_buffer->pages)
722 *page = list_entry(p, struct buffer_page, list);
725 static inline unsigned
726 rb_event_index(struct ring_buffer_event *event)
728 unsigned long addr = (unsigned long)event;
730 return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
734 rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
735 struct ring_buffer_event *event)
737 unsigned long addr = (unsigned long)event;
740 index = rb_event_index(event);
743 return cpu_buffer->commit_page->page == (void *)addr &&
744 rb_commit_index(cpu_buffer) == index;
748 rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
749 struct ring_buffer_event *event)
751 unsigned long addr = (unsigned long)event;
754 index = rb_event_index(event);
757 while (cpu_buffer->commit_page->page != (void *)addr) {
758 RB_WARN_ON(cpu_buffer,
759 cpu_buffer->commit_page == cpu_buffer->tail_page);
760 cpu_buffer->commit_page->commit =
761 cpu_buffer->commit_page->write;
762 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
763 cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
766 /* Now set the commit to the event's index */
767 local_set(&cpu_buffer->commit_page->commit, index);
771 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
774 * We only race with interrupts and NMIs on this CPU.
775 * If we own the commit event, then we can commit
776 * all others that interrupted us, since the interruptions
777 * are in stack format (they finish before they come
778 * back to us). This allows us to do a simple loop to
779 * assign the commit to the tail.
781 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
782 cpu_buffer->commit_page->commit =
783 cpu_buffer->commit_page->write;
784 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
785 cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
786 /* add barrier to keep gcc from optimizing too much */
789 while (rb_commit_index(cpu_buffer) !=
790 rb_page_write(cpu_buffer->commit_page)) {
791 cpu_buffer->commit_page->commit =
792 cpu_buffer->commit_page->write;
797 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
799 cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
800 cpu_buffer->reader_page->read = 0;
803 static inline void rb_inc_iter(struct ring_buffer_iter *iter)
805 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
808 * The iterator could be on the reader page (it starts there).
809 * But the head could have moved, since the reader was
810 * found. Check for this case and assign the iterator
811 * to the head page instead of next.
813 if (iter->head_page == cpu_buffer->reader_page)
814 iter->head_page = cpu_buffer->head_page;
816 rb_inc_page(cpu_buffer, &iter->head_page);
818 iter->read_stamp = iter->head_page->time_stamp;
823 * ring_buffer_update_event - update event type and data
824 * @event: the even to update
825 * @type: the type of event
826 * @length: the size of the event field in the ring buffer
828 * Update the type and data fields of the event. The length
829 * is the actual size that is written to the ring buffer,
830 * and with this, we can determine what to place into the
834 rb_update_event(struct ring_buffer_event *event,
835 unsigned type, unsigned length)
841 case RINGBUF_TYPE_PADDING:
844 case RINGBUF_TYPE_TIME_EXTEND:
846 (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
847 >> RB_ALIGNMENT_SHIFT;
850 case RINGBUF_TYPE_TIME_STAMP:
852 (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
853 >> RB_ALIGNMENT_SHIFT;
856 case RINGBUF_TYPE_DATA:
857 length -= RB_EVNT_HDR_SIZE;
858 if (length > RB_MAX_SMALL_DATA) {
860 event->array[0] = length;
863 (length + (RB_ALIGNMENT-1))
864 >> RB_ALIGNMENT_SHIFT;
871 static inline unsigned rb_calculate_event_length(unsigned length)
873 struct ring_buffer_event event; /* Used only for sizeof array */
875 /* zero length can cause confusions */
879 if (length > RB_MAX_SMALL_DATA)
880 length += sizeof(event.array[0]);
882 length += RB_EVNT_HDR_SIZE;
883 length = ALIGN(length, RB_ALIGNMENT);
888 static struct ring_buffer_event *
889 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
890 unsigned type, unsigned long length, u64 *ts)
892 struct buffer_page *tail_page, *head_page, *reader_page;
893 unsigned long tail, write;
894 struct ring_buffer *buffer = cpu_buffer->buffer;
895 struct ring_buffer_event *event;
898 tail_page = cpu_buffer->tail_page;
899 write = local_add_return(length, &tail_page->write);
900 tail = write - length;
902 /* See if we shot pass the end of this buffer page */
903 if (write > BUF_PAGE_SIZE) {
904 struct buffer_page *next_page = tail_page;
906 spin_lock_irqsave(&cpu_buffer->lock, flags);
908 rb_inc_page(cpu_buffer, &next_page);
910 head_page = cpu_buffer->head_page;
911 reader_page = cpu_buffer->reader_page;
913 /* we grabbed the lock before incrementing */
914 RB_WARN_ON(cpu_buffer, next_page == reader_page);
917 * If for some reason, we had an interrupt storm that made
918 * it all the way around the buffer, bail, and warn
921 if (unlikely(next_page == cpu_buffer->commit_page)) {
926 if (next_page == head_page) {
927 if (!(buffer->flags & RB_FL_OVERWRITE)) {
929 if (tail <= BUF_PAGE_SIZE)
930 local_set(&tail_page->write, tail);
934 /* tail_page has not moved yet? */
935 if (tail_page == cpu_buffer->tail_page) {
936 /* count overflows */
937 rb_update_overflow(cpu_buffer);
939 rb_inc_page(cpu_buffer, &head_page);
940 cpu_buffer->head_page = head_page;
941 cpu_buffer->head_page->read = 0;
946 * If the tail page is still the same as what we think
947 * it is, then it is up to us to update the tail
950 if (tail_page == cpu_buffer->tail_page) {
951 local_set(&next_page->write, 0);
952 local_set(&next_page->commit, 0);
953 cpu_buffer->tail_page = next_page;
955 /* reread the time stamp */
956 *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
957 cpu_buffer->tail_page->time_stamp = *ts;
961 * The actual tail page has moved forward.
963 if (tail < BUF_PAGE_SIZE) {
964 /* Mark the rest of the page with padding */
965 event = __rb_page_index(tail_page, tail);
966 event->type = RINGBUF_TYPE_PADDING;
969 if (tail <= BUF_PAGE_SIZE)
970 /* Set the write back to the previous setting */
971 local_set(&tail_page->write, tail);
974 * If this was a commit entry that failed,
977 if (tail_page == cpu_buffer->commit_page &&
978 tail == rb_commit_index(cpu_buffer)) {
979 rb_set_commit_to_write(cpu_buffer);
982 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
984 /* fail and let the caller try again */
985 return ERR_PTR(-EAGAIN);
988 /* We reserved something on the buffer */
990 BUG_ON(write > BUF_PAGE_SIZE);
992 event = __rb_page_index(tail_page, tail);
993 rb_update_event(event, type, length);
996 * If this is a commit and the tail is zero, then update
997 * this page's time stamp.
999 if (!tail && rb_is_commit(cpu_buffer, event))
1000 cpu_buffer->commit_page->time_stamp = *ts;
1005 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
1010 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1011 u64 *ts, u64 *delta)
1013 struct ring_buffer_event *event;
1017 if (unlikely(*delta > (1ULL << 59) && !once++)) {
1018 printk(KERN_WARNING "Delta way too big! %llu"
1019 " ts=%llu write stamp = %llu\n",
1020 (unsigned long long)*delta,
1021 (unsigned long long)*ts,
1022 (unsigned long long)cpu_buffer->write_stamp);
1027 * The delta is too big, we to add a
1030 event = __rb_reserve_next(cpu_buffer,
1031 RINGBUF_TYPE_TIME_EXTEND,
1037 if (PTR_ERR(event) == -EAGAIN)
1040 /* Only a commited time event can update the write stamp */
1041 if (rb_is_commit(cpu_buffer, event)) {
1043 * If this is the first on the page, then we need to
1044 * update the page itself, and just put in a zero.
1046 if (rb_event_index(event)) {
1047 event->time_delta = *delta & TS_MASK;
1048 event->array[0] = *delta >> TS_SHIFT;
1050 cpu_buffer->commit_page->time_stamp = *ts;
1051 event->time_delta = 0;
1052 event->array[0] = 0;
1054 cpu_buffer->write_stamp = *ts;
1055 /* let the caller know this was the commit */
1058 /* Darn, this is just wasted space */
1059 event->time_delta = 0;
1060 event->array[0] = 0;
1069 static struct ring_buffer_event *
1070 rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
1071 unsigned type, unsigned long length)
1073 struct ring_buffer_event *event;
1080 * We allow for interrupts to reenter here and do a trace.
1081 * If one does, it will cause this original code to loop
1082 * back here. Even with heavy interrupts happening, this
1083 * should only happen a few times in a row. If this happens
1084 * 1000 times in a row, there must be either an interrupt
1085 * storm or we have something buggy.
1088 if (unlikely(++nr_loops > 1000)) {
1089 RB_WARN_ON(cpu_buffer, 1);
1093 ts = ring_buffer_time_stamp(cpu_buffer->cpu);
1096 * Only the first commit can update the timestamp.
1097 * Yes there is a race here. If an interrupt comes in
1098 * just after the conditional and it traces too, then it
1099 * will also check the deltas. More than one timestamp may
1100 * also be made. But only the entry that did the actual
1101 * commit will be something other than zero.
1103 if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
1104 rb_page_write(cpu_buffer->tail_page) ==
1105 rb_commit_index(cpu_buffer)) {
1107 delta = ts - cpu_buffer->write_stamp;
1109 /* make sure this delta is calculated here */
1112 /* Did the write stamp get updated already? */
1113 if (unlikely(ts < cpu_buffer->write_stamp))
1116 if (test_time_stamp(delta)) {
1118 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
1120 if (commit == -EBUSY)
1123 if (commit == -EAGAIN)
1126 RB_WARN_ON(cpu_buffer, commit < 0);
1129 /* Non commits have zero deltas */
1132 event = __rb_reserve_next(cpu_buffer, type, length, &ts);
1133 if (PTR_ERR(event) == -EAGAIN)
1137 if (unlikely(commit))
1139 * Ouch! We needed a timestamp and it was commited. But
1140 * we didn't get our event reserved.
1142 rb_set_commit_to_write(cpu_buffer);
1147 * If the timestamp was commited, make the commit our entry
1148 * now so that we will update it when needed.
1151 rb_set_commit_event(cpu_buffer, event);
1152 else if (!rb_is_commit(cpu_buffer, event))
1155 event->time_delta = delta;
1160 static DEFINE_PER_CPU(int, rb_need_resched);
1163 * ring_buffer_lock_reserve - reserve a part of the buffer
1164 * @buffer: the ring buffer to reserve from
1165 * @length: the length of the data to reserve (excluding event header)
1166 * @flags: a pointer to save the interrupt flags
1168 * Returns a reseverd event on the ring buffer to copy directly to.
1169 * The user of this interface will need to get the body to write into
1170 * and can use the ring_buffer_event_data() interface.
1172 * The length is the length of the data needed, not the event length
1173 * which also includes the event header.
1175 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1176 * If NULL is returned, then nothing has been allocated or locked.
1178 struct ring_buffer_event *
1179 ring_buffer_lock_reserve(struct ring_buffer *buffer,
1180 unsigned long length,
1181 unsigned long *flags)
1183 struct ring_buffer_per_cpu *cpu_buffer;
1184 struct ring_buffer_event *event;
1187 if (ring_buffers_off)
1190 if (atomic_read(&buffer->record_disabled))
1193 /* If we are tracing schedule, we don't want to recurse */
1194 resched = need_resched();
1195 preempt_disable_notrace();
1197 cpu = raw_smp_processor_id();
1199 if (!cpu_isset(cpu, buffer->cpumask))
1202 cpu_buffer = buffer->buffers[cpu];
1204 if (atomic_read(&cpu_buffer->record_disabled))
1207 length = rb_calculate_event_length(length);
1208 if (length > BUF_PAGE_SIZE)
1211 event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
1216 * Need to store resched state on this cpu.
1217 * Only the first needs to.
1220 if (preempt_count() == 1)
1221 per_cpu(rb_need_resched, cpu) = resched;
1227 preempt_enable_no_resched_notrace();
1229 preempt_enable_notrace();
1232 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
1234 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
1235 struct ring_buffer_event *event)
1237 cpu_buffer->entries++;
1239 /* Only process further if we own the commit */
1240 if (!rb_is_commit(cpu_buffer, event))
1243 cpu_buffer->write_stamp += event->time_delta;
1245 rb_set_commit_to_write(cpu_buffer);
1249 * ring_buffer_unlock_commit - commit a reserved
1250 * @buffer: The buffer to commit to
1251 * @event: The event pointer to commit.
1252 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1254 * This commits the data to the ring buffer, and releases any locks held.
1256 * Must be paired with ring_buffer_lock_reserve.
1258 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
1259 struct ring_buffer_event *event,
1260 unsigned long flags)
1262 struct ring_buffer_per_cpu *cpu_buffer;
1263 int cpu = raw_smp_processor_id();
1265 cpu_buffer = buffer->buffers[cpu];
1267 rb_commit(cpu_buffer, event);
1270 * Only the last preempt count needs to restore preemption.
1272 if (preempt_count() == 1) {
1273 if (per_cpu(rb_need_resched, cpu))
1274 preempt_enable_no_resched_notrace();
1276 preempt_enable_notrace();
1278 preempt_enable_no_resched_notrace();
1282 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
1285 * ring_buffer_write - write data to the buffer without reserving
1286 * @buffer: The ring buffer to write to.
1287 * @length: The length of the data being written (excluding the event header)
1288 * @data: The data to write to the buffer.
1290 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1291 * one function. If you already have the data to write to the buffer, it
1292 * may be easier to simply call this function.
1294 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1295 * and not the length of the event which would hold the header.
1297 int ring_buffer_write(struct ring_buffer *buffer,
1298 unsigned long length,
1301 struct ring_buffer_per_cpu *cpu_buffer;
1302 struct ring_buffer_event *event;
1303 unsigned long event_length;
1308 if (ring_buffers_off)
1311 if (atomic_read(&buffer->record_disabled))
1314 resched = need_resched();
1315 preempt_disable_notrace();
1317 cpu = raw_smp_processor_id();
1319 if (!cpu_isset(cpu, buffer->cpumask))
1322 cpu_buffer = buffer->buffers[cpu];
1324 if (atomic_read(&cpu_buffer->record_disabled))
1327 event_length = rb_calculate_event_length(length);
1328 event = rb_reserve_next_event(cpu_buffer,
1329 RINGBUF_TYPE_DATA, event_length);
1333 body = rb_event_data(event);
1335 memcpy(body, data, length);
1337 rb_commit(cpu_buffer, event);
1342 preempt_enable_no_resched_notrace();
1344 preempt_enable_notrace();
1348 EXPORT_SYMBOL_GPL(ring_buffer_write);
1350 static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
1352 struct buffer_page *reader = cpu_buffer->reader_page;
1353 struct buffer_page *head = cpu_buffer->head_page;
1354 struct buffer_page *commit = cpu_buffer->commit_page;
1356 return reader->read == rb_page_commit(reader) &&
1357 (commit == reader ||
1359 head->read == rb_page_commit(commit)));
1363 * ring_buffer_record_disable - stop all writes into the buffer
1364 * @buffer: The ring buffer to stop writes to.
1366 * This prevents all writes to the buffer. Any attempt to write
1367 * to the buffer after this will fail and return NULL.
1369 * The caller should call synchronize_sched() after this.
1371 void ring_buffer_record_disable(struct ring_buffer *buffer)
1373 atomic_inc(&buffer->record_disabled);
1375 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
1378 * ring_buffer_record_enable - enable writes to the buffer
1379 * @buffer: The ring buffer to enable writes
1381 * Note, multiple disables will need the same number of enables
1382 * to truely enable the writing (much like preempt_disable).
1384 void ring_buffer_record_enable(struct ring_buffer *buffer)
1386 atomic_dec(&buffer->record_disabled);
1388 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
1391 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1392 * @buffer: The ring buffer to stop writes to.
1393 * @cpu: The CPU buffer to stop
1395 * This prevents all writes to the buffer. Any attempt to write
1396 * to the buffer after this will fail and return NULL.
1398 * The caller should call synchronize_sched() after this.
1400 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
1402 struct ring_buffer_per_cpu *cpu_buffer;
1404 if (!cpu_isset(cpu, buffer->cpumask))
1407 cpu_buffer = buffer->buffers[cpu];
1408 atomic_inc(&cpu_buffer->record_disabled);
1410 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
1413 * ring_buffer_record_enable_cpu - enable writes to the buffer
1414 * @buffer: The ring buffer to enable writes
1415 * @cpu: The CPU to enable.
1417 * Note, multiple disables will need the same number of enables
1418 * to truely enable the writing (much like preempt_disable).
1420 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
1422 struct ring_buffer_per_cpu *cpu_buffer;
1424 if (!cpu_isset(cpu, buffer->cpumask))
1427 cpu_buffer = buffer->buffers[cpu];
1428 atomic_dec(&cpu_buffer->record_disabled);
1430 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
1433 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1434 * @buffer: The ring buffer
1435 * @cpu: The per CPU buffer to get the entries from.
1437 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
1439 struct ring_buffer_per_cpu *cpu_buffer;
1441 if (!cpu_isset(cpu, buffer->cpumask))
1444 cpu_buffer = buffer->buffers[cpu];
1445 return cpu_buffer->entries;
1447 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
1450 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1451 * @buffer: The ring buffer
1452 * @cpu: The per CPU buffer to get the number of overruns from
1454 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
1456 struct ring_buffer_per_cpu *cpu_buffer;
1458 if (!cpu_isset(cpu, buffer->cpumask))
1461 cpu_buffer = buffer->buffers[cpu];
1462 return cpu_buffer->overrun;
1464 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
1467 * ring_buffer_entries - get the number of entries in a buffer
1468 * @buffer: The ring buffer
1470 * Returns the total number of entries in the ring buffer
1473 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
1475 struct ring_buffer_per_cpu *cpu_buffer;
1476 unsigned long entries = 0;
1479 /* if you care about this being correct, lock the buffer */
1480 for_each_buffer_cpu(buffer, cpu) {
1481 cpu_buffer = buffer->buffers[cpu];
1482 entries += cpu_buffer->entries;
1487 EXPORT_SYMBOL_GPL(ring_buffer_entries);
1490 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1491 * @buffer: The ring buffer
1493 * Returns the total number of overruns in the ring buffer
1496 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
1498 struct ring_buffer_per_cpu *cpu_buffer;
1499 unsigned long overruns = 0;
1502 /* if you care about this being correct, lock the buffer */
1503 for_each_buffer_cpu(buffer, cpu) {
1504 cpu_buffer = buffer->buffers[cpu];
1505 overruns += cpu_buffer->overrun;
1510 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
1513 * ring_buffer_iter_reset - reset an iterator
1514 * @iter: The iterator to reset
1516 * Resets the iterator, so that it will start from the beginning
1519 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
1521 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1523 /* Iterator usage is expected to have record disabled */
1524 if (list_empty(&cpu_buffer->reader_page->list)) {
1525 iter->head_page = cpu_buffer->head_page;
1526 iter->head = cpu_buffer->head_page->read;
1528 iter->head_page = cpu_buffer->reader_page;
1529 iter->head = cpu_buffer->reader_page->read;
1532 iter->read_stamp = cpu_buffer->read_stamp;
1534 iter->read_stamp = iter->head_page->time_stamp;
1536 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
1539 * ring_buffer_iter_empty - check if an iterator has no more to read
1540 * @iter: The iterator to check
1542 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
1544 struct ring_buffer_per_cpu *cpu_buffer;
1546 cpu_buffer = iter->cpu_buffer;
1548 return iter->head_page == cpu_buffer->commit_page &&
1549 iter->head == rb_commit_index(cpu_buffer);
1551 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
1554 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1555 struct ring_buffer_event *event)
1559 switch (event->type) {
1560 case RINGBUF_TYPE_PADDING:
1563 case RINGBUF_TYPE_TIME_EXTEND:
1564 delta = event->array[0];
1566 delta += event->time_delta;
1567 cpu_buffer->read_stamp += delta;
1570 case RINGBUF_TYPE_TIME_STAMP:
1571 /* FIXME: not implemented */
1574 case RINGBUF_TYPE_DATA:
1575 cpu_buffer->read_stamp += event->time_delta;
1585 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
1586 struct ring_buffer_event *event)
1590 switch (event->type) {
1591 case RINGBUF_TYPE_PADDING:
1594 case RINGBUF_TYPE_TIME_EXTEND:
1595 delta = event->array[0];
1597 delta += event->time_delta;
1598 iter->read_stamp += delta;
1601 case RINGBUF_TYPE_TIME_STAMP:
1602 /* FIXME: not implemented */
1605 case RINGBUF_TYPE_DATA:
1606 iter->read_stamp += event->time_delta;
1615 static struct buffer_page *
1616 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1618 struct buffer_page *reader = NULL;
1619 unsigned long flags;
1622 spin_lock_irqsave(&cpu_buffer->lock, flags);
1626 * This should normally only loop twice. But because the
1627 * start of the reader inserts an empty page, it causes
1628 * a case where we will loop three times. There should be no
1629 * reason to loop four times (that I know of).
1631 if (unlikely(++nr_loops > 3)) {
1632 RB_WARN_ON(cpu_buffer, 1);
1637 reader = cpu_buffer->reader_page;
1639 /* If there's more to read, return this page */
1640 if (cpu_buffer->reader_page->read < rb_page_size(reader))
1643 /* Never should we have an index greater than the size */
1644 RB_WARN_ON(cpu_buffer,
1645 cpu_buffer->reader_page->read > rb_page_size(reader));
1647 /* check if we caught up to the tail */
1649 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
1653 * Splice the empty reader page into the list around the head.
1654 * Reset the reader page to size zero.
1657 reader = cpu_buffer->head_page;
1658 cpu_buffer->reader_page->list.next = reader->list.next;
1659 cpu_buffer->reader_page->list.prev = reader->list.prev;
1661 local_set(&cpu_buffer->reader_page->write, 0);
1662 local_set(&cpu_buffer->reader_page->commit, 0);
1664 /* Make the reader page now replace the head */
1665 reader->list.prev->next = &cpu_buffer->reader_page->list;
1666 reader->list.next->prev = &cpu_buffer->reader_page->list;
1669 * If the tail is on the reader, then we must set the head
1670 * to the inserted page, otherwise we set it one before.
1672 cpu_buffer->head_page = cpu_buffer->reader_page;
1674 if (cpu_buffer->commit_page != reader)
1675 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
1677 /* Finally update the reader page to the new head */
1678 cpu_buffer->reader_page = reader;
1679 rb_reset_reader_page(cpu_buffer);
1684 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
1689 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
1691 struct ring_buffer_event *event;
1692 struct buffer_page *reader;
1695 reader = rb_get_reader_page(cpu_buffer);
1697 /* This function should not be called when buffer is empty */
1700 event = rb_reader_event(cpu_buffer);
1702 if (event->type == RINGBUF_TYPE_DATA)
1703 cpu_buffer->entries--;
1705 rb_update_read_stamp(cpu_buffer, event);
1707 length = rb_event_length(event);
1708 cpu_buffer->reader_page->read += length;
1711 static void rb_advance_iter(struct ring_buffer_iter *iter)
1713 struct ring_buffer *buffer;
1714 struct ring_buffer_per_cpu *cpu_buffer;
1715 struct ring_buffer_event *event;
1718 cpu_buffer = iter->cpu_buffer;
1719 buffer = cpu_buffer->buffer;
1722 * Check if we are at the end of the buffer.
1724 if (iter->head >= rb_page_size(iter->head_page)) {
1725 BUG_ON(iter->head_page == cpu_buffer->commit_page);
1730 event = rb_iter_head_event(iter);
1732 length = rb_event_length(event);
1735 * This should not be called to advance the header if we are
1736 * at the tail of the buffer.
1738 BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
1739 (iter->head + length > rb_commit_index(cpu_buffer)));
1741 rb_update_iter_read_stamp(iter, event);
1743 iter->head += length;
1745 /* check for end of page padding */
1746 if ((iter->head >= rb_page_size(iter->head_page)) &&
1747 (iter->head_page != cpu_buffer->commit_page))
1748 rb_advance_iter(iter);
1752 * ring_buffer_peek - peek at the next event to be read
1753 * @buffer: The ring buffer to read
1754 * @cpu: The cpu to peak at
1755 * @ts: The timestamp counter of this event.
1757 * This will return the event that will be read next, but does
1758 * not consume the data.
1760 struct ring_buffer_event *
1761 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
1763 struct ring_buffer_per_cpu *cpu_buffer;
1764 struct ring_buffer_event *event;
1765 struct buffer_page *reader;
1768 if (!cpu_isset(cpu, buffer->cpumask))
1771 cpu_buffer = buffer->buffers[cpu];
1775 * We repeat when a timestamp is encountered. It is possible
1776 * to get multiple timestamps from an interrupt entering just
1777 * as one timestamp is about to be written. The max times
1778 * that this can happen is the number of nested interrupts we
1779 * can have. Nesting 10 deep of interrupts is clearly
1782 if (unlikely(++nr_loops > 10)) {
1783 RB_WARN_ON(cpu_buffer, 1);
1787 reader = rb_get_reader_page(cpu_buffer);
1791 event = rb_reader_event(cpu_buffer);
1793 switch (event->type) {
1794 case RINGBUF_TYPE_PADDING:
1795 RB_WARN_ON(cpu_buffer, 1);
1796 rb_advance_reader(cpu_buffer);
1799 case RINGBUF_TYPE_TIME_EXTEND:
1800 /* Internal data, OK to advance */
1801 rb_advance_reader(cpu_buffer);
1804 case RINGBUF_TYPE_TIME_STAMP:
1805 /* FIXME: not implemented */
1806 rb_advance_reader(cpu_buffer);
1809 case RINGBUF_TYPE_DATA:
1811 *ts = cpu_buffer->read_stamp + event->time_delta;
1812 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1822 EXPORT_SYMBOL_GPL(ring_buffer_peek);
1825 * ring_buffer_iter_peek - peek at the next event to be read
1826 * @iter: The ring buffer iterator
1827 * @ts: The timestamp counter of this event.
1829 * This will return the event that will be read next, but does
1830 * not increment the iterator.
1832 struct ring_buffer_event *
1833 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
1835 struct ring_buffer *buffer;
1836 struct ring_buffer_per_cpu *cpu_buffer;
1837 struct ring_buffer_event *event;
1840 if (ring_buffer_iter_empty(iter))
1843 cpu_buffer = iter->cpu_buffer;
1844 buffer = cpu_buffer->buffer;
1848 * We repeat when a timestamp is encountered. It is possible
1849 * to get multiple timestamps from an interrupt entering just
1850 * as one timestamp is about to be written. The max times
1851 * that this can happen is the number of nested interrupts we
1852 * can have. Nesting 10 deep of interrupts is clearly
1855 if (unlikely(++nr_loops > 10)) {
1856 RB_WARN_ON(cpu_buffer, 1);
1860 if (rb_per_cpu_empty(cpu_buffer))
1863 event = rb_iter_head_event(iter);
1865 switch (event->type) {
1866 case RINGBUF_TYPE_PADDING:
1870 case RINGBUF_TYPE_TIME_EXTEND:
1871 /* Internal data, OK to advance */
1872 rb_advance_iter(iter);
1875 case RINGBUF_TYPE_TIME_STAMP:
1876 /* FIXME: not implemented */
1877 rb_advance_iter(iter);
1880 case RINGBUF_TYPE_DATA:
1882 *ts = iter->read_stamp + event->time_delta;
1883 ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
1893 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
1896 * ring_buffer_consume - return an event and consume it
1897 * @buffer: The ring buffer to get the next event from
1899 * Returns the next event in the ring buffer, and that event is consumed.
1900 * Meaning, that sequential reads will keep returning a different event,
1901 * and eventually empty the ring buffer if the producer is slower.
1903 struct ring_buffer_event *
1904 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
1906 struct ring_buffer_per_cpu *cpu_buffer;
1907 struct ring_buffer_event *event;
1909 if (!cpu_isset(cpu, buffer->cpumask))
1912 event = ring_buffer_peek(buffer, cpu, ts);
1916 cpu_buffer = buffer->buffers[cpu];
1917 rb_advance_reader(cpu_buffer);
1921 EXPORT_SYMBOL_GPL(ring_buffer_consume);
1924 * ring_buffer_read_start - start a non consuming read of the buffer
1925 * @buffer: The ring buffer to read from
1926 * @cpu: The cpu buffer to iterate over
1928 * This starts up an iteration through the buffer. It also disables
1929 * the recording to the buffer until the reading is finished.
1930 * This prevents the reading from being corrupted. This is not
1931 * a consuming read, so a producer is not expected.
1933 * Must be paired with ring_buffer_finish.
1935 struct ring_buffer_iter *
1936 ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
1938 struct ring_buffer_per_cpu *cpu_buffer;
1939 struct ring_buffer_iter *iter;
1940 unsigned long flags;
1942 if (!cpu_isset(cpu, buffer->cpumask))
1945 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
1949 cpu_buffer = buffer->buffers[cpu];
1951 iter->cpu_buffer = cpu_buffer;
1953 atomic_inc(&cpu_buffer->record_disabled);
1954 synchronize_sched();
1956 spin_lock_irqsave(&cpu_buffer->lock, flags);
1957 ring_buffer_iter_reset(iter);
1958 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
1962 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
1965 * ring_buffer_finish - finish reading the iterator of the buffer
1966 * @iter: The iterator retrieved by ring_buffer_start
1968 * This re-enables the recording to the buffer, and frees the
1972 ring_buffer_read_finish(struct ring_buffer_iter *iter)
1974 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1976 atomic_dec(&cpu_buffer->record_disabled);
1979 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
1982 * ring_buffer_read - read the next item in the ring buffer by the iterator
1983 * @iter: The ring buffer iterator
1984 * @ts: The time stamp of the event read.
1986 * This reads the next event in the ring buffer and increments the iterator.
1988 struct ring_buffer_event *
1989 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
1991 struct ring_buffer_event *event;
1993 event = ring_buffer_iter_peek(iter, ts);
1997 rb_advance_iter(iter);
2001 EXPORT_SYMBOL_GPL(ring_buffer_read);
2004 * ring_buffer_size - return the size of the ring buffer (in bytes)
2005 * @buffer: The ring buffer.
2007 unsigned long ring_buffer_size(struct ring_buffer *buffer)
2009 return BUF_PAGE_SIZE * buffer->pages;
2011 EXPORT_SYMBOL_GPL(ring_buffer_size);
2014 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
2016 cpu_buffer->head_page
2017 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
2018 local_set(&cpu_buffer->head_page->write, 0);
2019 local_set(&cpu_buffer->head_page->commit, 0);
2021 cpu_buffer->head_page->read = 0;
2023 cpu_buffer->tail_page = cpu_buffer->head_page;
2024 cpu_buffer->commit_page = cpu_buffer->head_page;
2026 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
2027 local_set(&cpu_buffer->reader_page->write, 0);
2028 local_set(&cpu_buffer->reader_page->commit, 0);
2029 cpu_buffer->reader_page->read = 0;
2031 cpu_buffer->overrun = 0;
2032 cpu_buffer->entries = 0;
2036 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2037 * @buffer: The ring buffer to reset a per cpu buffer of
2038 * @cpu: The CPU buffer to be reset
2040 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
2042 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2043 unsigned long flags;
2045 if (!cpu_isset(cpu, buffer->cpumask))
2048 spin_lock_irqsave(&cpu_buffer->lock, flags);
2050 rb_reset_cpu(cpu_buffer);
2052 spin_unlock_irqrestore(&cpu_buffer->lock, flags);
2054 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
2057 * ring_buffer_reset - reset a ring buffer
2058 * @buffer: The ring buffer to reset all cpu buffers
2060 void ring_buffer_reset(struct ring_buffer *buffer)
2064 for_each_buffer_cpu(buffer, cpu)
2065 ring_buffer_reset_cpu(buffer, cpu);
2067 EXPORT_SYMBOL_GPL(ring_buffer_reset);
2070 * rind_buffer_empty - is the ring buffer empty?
2071 * @buffer: The ring buffer to test
2073 int ring_buffer_empty(struct ring_buffer *buffer)
2075 struct ring_buffer_per_cpu *cpu_buffer;
2078 /* yes this is racy, but if you don't like the race, lock the buffer */
2079 for_each_buffer_cpu(buffer, cpu) {
2080 cpu_buffer = buffer->buffers[cpu];
2081 if (!rb_per_cpu_empty(cpu_buffer))
2086 EXPORT_SYMBOL_GPL(ring_buffer_empty);
2089 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2090 * @buffer: The ring buffer
2091 * @cpu: The CPU buffer to test
2093 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
2095 struct ring_buffer_per_cpu *cpu_buffer;
2097 if (!cpu_isset(cpu, buffer->cpumask))
2100 cpu_buffer = buffer->buffers[cpu];
2101 return rb_per_cpu_empty(cpu_buffer);
2103 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
2106 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2107 * @buffer_a: One buffer to swap with
2108 * @buffer_b: The other buffer to swap with
2110 * This function is useful for tracers that want to take a "snapshot"
2111 * of a CPU buffer and has another back up buffer lying around.
2112 * it is expected that the tracer handles the cpu buffer not being
2113 * used at the moment.
2115 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
2116 struct ring_buffer *buffer_b, int cpu)
2118 struct ring_buffer_per_cpu *cpu_buffer_a;
2119 struct ring_buffer_per_cpu *cpu_buffer_b;
2121 if (!cpu_isset(cpu, buffer_a->cpumask) ||
2122 !cpu_isset(cpu, buffer_b->cpumask))
2125 /* At least make sure the two buffers are somewhat the same */
2126 if (buffer_a->size != buffer_b->size ||
2127 buffer_a->pages != buffer_b->pages)
2130 cpu_buffer_a = buffer_a->buffers[cpu];
2131 cpu_buffer_b = buffer_b->buffers[cpu];
2134 * We can't do a synchronize_sched here because this
2135 * function can be called in atomic context.
2136 * Normally this will be called from the same CPU as cpu.
2137 * If not it's up to the caller to protect this.
2139 atomic_inc(&cpu_buffer_a->record_disabled);
2140 atomic_inc(&cpu_buffer_b->record_disabled);
2142 buffer_a->buffers[cpu] = cpu_buffer_b;
2143 buffer_b->buffers[cpu] = cpu_buffer_a;
2145 cpu_buffer_b->buffer = buffer_a;
2146 cpu_buffer_a->buffer = buffer_b;
2148 atomic_dec(&cpu_buffer_a->record_disabled);
2149 atomic_dec(&cpu_buffer_b->record_disabled);
2153 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
2156 rb_simple_read(struct file *filp, char __user *ubuf,
2157 size_t cnt, loff_t *ppos)
2159 int *p = filp->private_data;
2163 /* !ring_buffers_off == tracing_on */
2164 r = sprintf(buf, "%d\n", !*p);
2166 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
2170 rb_simple_write(struct file *filp, const char __user *ubuf,
2171 size_t cnt, loff_t *ppos)
2173 int *p = filp->private_data;
2178 if (cnt >= sizeof(buf))
2181 if (copy_from_user(&buf, ubuf, cnt))
2186 ret = strict_strtoul(buf, 10, &val);
2190 /* !ring_buffers_off == tracing_on */
2198 static struct file_operations rb_simple_fops = {
2199 .open = tracing_open_generic,
2200 .read = rb_simple_read,
2201 .write = rb_simple_write,
2205 static __init int rb_init_debugfs(void)
2207 struct dentry *d_tracer;
2208 struct dentry *entry;
2210 d_tracer = tracing_init_dentry();
2212 entry = debugfs_create_file("tracing_on", 0644, d_tracer,
2213 &ring_buffers_off, &rb_simple_fops);
2215 pr_warning("Could not create debugfs 'tracing_on' entry\n");
2220 fs_initcall(rb_init_debugfs);