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.
36 * tracing_off - turn off all tracing buffers
38 * This function stops all tracing buffers from recording data.
39 * It does not disable any overhead the tracers themselves may
40 * be causing. This function simply causes all recording to
41 * the ring buffers to fail.
43 void tracing_off(void)
48 /* Up this if you want to test the TIME_EXTENTS and normalization */
52 u64
ring_buffer_time_stamp(int cpu
)
56 preempt_disable_notrace();
57 /* shift to debug/test normalization and TIME_EXTENTS */
58 time
= sched_clock() << DEBUG_SHIFT
;
59 preempt_enable_notrace();
64 void ring_buffer_normalize_time_stamp(int cpu
, u64
*ts
)
66 /* Just stupid testing the normalize function and deltas */
70 #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
71 #define RB_ALIGNMENT_SHIFT 2
72 #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
73 #define RB_MAX_SMALL_DATA 28
76 RB_LEN_TIME_EXTEND
= 8,
77 RB_LEN_TIME_STAMP
= 16,
80 /* inline for ring buffer fast paths */
81 static inline unsigned
82 rb_event_length(struct ring_buffer_event
*event
)
86 switch (event
->type
) {
87 case RINGBUF_TYPE_PADDING
:
91 case RINGBUF_TYPE_TIME_EXTEND
:
92 return RB_LEN_TIME_EXTEND
;
94 case RINGBUF_TYPE_TIME_STAMP
:
95 return RB_LEN_TIME_STAMP
;
97 case RINGBUF_TYPE_DATA
:
99 length
= event
->len
<< RB_ALIGNMENT_SHIFT
;
101 length
= event
->array
[0];
102 return length
+ RB_EVNT_HDR_SIZE
;
111 * ring_buffer_event_length - return the length of the event
112 * @event: the event to get the length of
114 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
116 return rb_event_length(event
);
119 /* inline for ring buffer fast paths */
121 rb_event_data(struct ring_buffer_event
*event
)
123 BUG_ON(event
->type
!= RINGBUF_TYPE_DATA
);
124 /* If length is in len field, then array[0] has the data */
126 return (void *)&event
->array
[0];
127 /* Otherwise length is in array[0] and array[1] has the data */
128 return (void *)&event
->array
[1];
132 * ring_buffer_event_data - return the data of the event
133 * @event: the event to get the data from
135 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
137 return rb_event_data(event
);
140 #define for_each_buffer_cpu(buffer, cpu) \
141 for_each_cpu_mask(cpu, buffer->cpumask)
144 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
145 #define TS_DELTA_TEST (~TS_MASK)
148 * This hack stolen from mm/slob.c.
149 * We can store per page timing information in the page frame of the page.
150 * Thanks to Peter Zijlstra for suggesting this idea.
153 u64 time_stamp
; /* page time stamp */
154 local_t write
; /* index for next write */
155 local_t commit
; /* write commited index */
156 unsigned read
; /* index for next read */
157 struct list_head list
; /* list of free pages */
158 void *page
; /* Actual data page */
162 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
165 static inline void free_buffer_page(struct buffer_page
*bpage
)
168 free_page((unsigned long)bpage
->page
);
173 * We need to fit the time_stamp delta into 27 bits.
175 static inline int test_time_stamp(u64 delta
)
177 if (delta
& TS_DELTA_TEST
)
182 #define BUF_PAGE_SIZE PAGE_SIZE
185 * head_page == tail_page && head == tail then buffer is empty.
187 struct ring_buffer_per_cpu
{
189 struct ring_buffer
*buffer
;
191 struct lock_class_key lock_key
;
192 struct list_head pages
;
193 struct buffer_page
*head_page
; /* read from head */
194 struct buffer_page
*tail_page
; /* write to tail */
195 struct buffer_page
*commit_page
; /* commited pages */
196 struct buffer_page
*reader_page
;
197 unsigned long overrun
;
198 unsigned long entries
;
201 atomic_t record_disabled
;
210 atomic_t record_disabled
;
214 struct ring_buffer_per_cpu
**buffers
;
217 struct ring_buffer_iter
{
218 struct ring_buffer_per_cpu
*cpu_buffer
;
220 struct buffer_page
*head_page
;
224 #define RB_WARN_ON(buffer, cond) \
226 if (unlikely(cond)) { \
227 atomic_inc(&buffer->record_disabled); \
232 #define RB_WARN_ON_RET(buffer, cond) \
234 if (unlikely(cond)) { \
235 atomic_inc(&buffer->record_disabled); \
241 #define RB_WARN_ON_ONCE(buffer, cond) \
244 if (unlikely(cond) && !once) { \
246 atomic_inc(&buffer->record_disabled); \
252 * check_pages - integrity check of buffer pages
253 * @cpu_buffer: CPU buffer with pages to test
255 * As a safty measure we check to make sure the data pages have not
258 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
260 struct list_head
*head
= &cpu_buffer
->pages
;
261 struct buffer_page
*page
, *tmp
;
263 RB_WARN_ON_RET(cpu_buffer
, head
->next
->prev
!= head
);
264 RB_WARN_ON_RET(cpu_buffer
, head
->prev
->next
!= head
);
266 list_for_each_entry_safe(page
, tmp
, head
, list
) {
267 RB_WARN_ON_RET(cpu_buffer
,
268 page
->list
.next
->prev
!= &page
->list
);
269 RB_WARN_ON_RET(cpu_buffer
,
270 page
->list
.prev
->next
!= &page
->list
);
276 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
279 struct list_head
*head
= &cpu_buffer
->pages
;
280 struct buffer_page
*page
, *tmp
;
285 for (i
= 0; i
< nr_pages
; i
++) {
286 page
= kzalloc_node(ALIGN(sizeof(*page
), cache_line_size()),
287 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
290 list_add(&page
->list
, &pages
);
292 addr
= __get_free_page(GFP_KERNEL
);
295 page
->page
= (void *)addr
;
298 list_splice(&pages
, head
);
300 rb_check_pages(cpu_buffer
);
305 list_for_each_entry_safe(page
, tmp
, &pages
, list
) {
306 list_del_init(&page
->list
);
307 free_buffer_page(page
);
312 static struct ring_buffer_per_cpu
*
313 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
315 struct ring_buffer_per_cpu
*cpu_buffer
;
316 struct buffer_page
*page
;
320 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
321 GFP_KERNEL
, cpu_to_node(cpu
));
325 cpu_buffer
->cpu
= cpu
;
326 cpu_buffer
->buffer
= buffer
;
327 spin_lock_init(&cpu_buffer
->lock
);
328 INIT_LIST_HEAD(&cpu_buffer
->pages
);
330 page
= kzalloc_node(ALIGN(sizeof(*page
), cache_line_size()),
331 GFP_KERNEL
, cpu_to_node(cpu
));
333 goto fail_free_buffer
;
335 cpu_buffer
->reader_page
= page
;
336 addr
= __get_free_page(GFP_KERNEL
);
338 goto fail_free_reader
;
339 page
->page
= (void *)addr
;
341 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
343 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
345 goto fail_free_reader
;
347 cpu_buffer
->head_page
348 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
349 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
354 free_buffer_page(cpu_buffer
->reader_page
);
361 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
363 struct list_head
*head
= &cpu_buffer
->pages
;
364 struct buffer_page
*page
, *tmp
;
366 list_del_init(&cpu_buffer
->reader_page
->list
);
367 free_buffer_page(cpu_buffer
->reader_page
);
369 list_for_each_entry_safe(page
, tmp
, head
, list
) {
370 list_del_init(&page
->list
);
371 free_buffer_page(page
);
377 * Causes compile errors if the struct buffer_page gets bigger
378 * than the struct page.
380 extern int ring_buffer_page_too_big(void);
383 * ring_buffer_alloc - allocate a new ring_buffer
384 * @size: the size in bytes per cpu that is needed.
385 * @flags: attributes to set for the ring buffer.
387 * Currently the only flag that is available is the RB_FL_OVERWRITE
388 * flag. This flag means that the buffer will overwrite old data
389 * when the buffer wraps. If this flag is not set, the buffer will
390 * drop data when the tail hits the head.
392 struct ring_buffer
*ring_buffer_alloc(unsigned long size
, unsigned flags
)
394 struct ring_buffer
*buffer
;
398 /* Paranoid! Optimizes out when all is well */
399 if (sizeof(struct buffer_page
) > sizeof(struct page
))
400 ring_buffer_page_too_big();
403 /* keep it in its own cache line */
404 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
409 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
410 buffer
->flags
= flags
;
412 /* need at least two pages */
413 if (buffer
->pages
== 1)
416 buffer
->cpumask
= cpu_possible_map
;
417 buffer
->cpus
= nr_cpu_ids
;
419 bsize
= sizeof(void *) * nr_cpu_ids
;
420 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
422 if (!buffer
->buffers
)
423 goto fail_free_buffer
;
425 for_each_buffer_cpu(buffer
, cpu
) {
426 buffer
->buffers
[cpu
] =
427 rb_allocate_cpu_buffer(buffer
, cpu
);
428 if (!buffer
->buffers
[cpu
])
429 goto fail_free_buffers
;
432 mutex_init(&buffer
->mutex
);
437 for_each_buffer_cpu(buffer
, cpu
) {
438 if (buffer
->buffers
[cpu
])
439 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
441 kfree(buffer
->buffers
);
449 * ring_buffer_free - free a ring buffer.
450 * @buffer: the buffer to free.
453 ring_buffer_free(struct ring_buffer
*buffer
)
457 for_each_buffer_cpu(buffer
, cpu
)
458 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
463 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
466 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
468 struct buffer_page
*page
;
472 atomic_inc(&cpu_buffer
->record_disabled
);
475 for (i
= 0; i
< nr_pages
; i
++) {
476 BUG_ON(list_empty(&cpu_buffer
->pages
));
477 p
= cpu_buffer
->pages
.next
;
478 page
= list_entry(p
, struct buffer_page
, list
);
479 list_del_init(&page
->list
);
480 free_buffer_page(page
);
482 BUG_ON(list_empty(&cpu_buffer
->pages
));
484 rb_reset_cpu(cpu_buffer
);
486 rb_check_pages(cpu_buffer
);
488 atomic_dec(&cpu_buffer
->record_disabled
);
493 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
494 struct list_head
*pages
, unsigned nr_pages
)
496 struct buffer_page
*page
;
500 atomic_inc(&cpu_buffer
->record_disabled
);
503 for (i
= 0; i
< nr_pages
; i
++) {
504 BUG_ON(list_empty(pages
));
506 page
= list_entry(p
, struct buffer_page
, list
);
507 list_del_init(&page
->list
);
508 list_add_tail(&page
->list
, &cpu_buffer
->pages
);
510 rb_reset_cpu(cpu_buffer
);
512 rb_check_pages(cpu_buffer
);
514 atomic_dec(&cpu_buffer
->record_disabled
);
518 * ring_buffer_resize - resize the ring buffer
519 * @buffer: the buffer to resize.
520 * @size: the new size.
522 * The tracer is responsible for making sure that the buffer is
523 * not being used while changing the size.
524 * Note: We may be able to change the above requirement by using
525 * RCU synchronizations.
527 * Minimum size is 2 * BUF_PAGE_SIZE.
529 * Returns -1 on failure.
531 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
533 struct ring_buffer_per_cpu
*cpu_buffer
;
534 unsigned nr_pages
, rm_pages
, new_pages
;
535 struct buffer_page
*page
, *tmp
;
536 unsigned long buffer_size
;
542 * Always succeed at resizing a non-existent buffer:
547 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
548 size
*= BUF_PAGE_SIZE
;
549 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
551 /* we need a minimum of two pages */
552 if (size
< BUF_PAGE_SIZE
* 2)
553 size
= BUF_PAGE_SIZE
* 2;
555 if (size
== buffer_size
)
558 mutex_lock(&buffer
->mutex
);
560 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
562 if (size
< buffer_size
) {
564 /* easy case, just free pages */
565 BUG_ON(nr_pages
>= buffer
->pages
);
567 rm_pages
= buffer
->pages
- nr_pages
;
569 for_each_buffer_cpu(buffer
, cpu
) {
570 cpu_buffer
= buffer
->buffers
[cpu
];
571 rb_remove_pages(cpu_buffer
, rm_pages
);
577 * This is a bit more difficult. We only want to add pages
578 * when we can allocate enough for all CPUs. We do this
579 * by allocating all the pages and storing them on a local
580 * link list. If we succeed in our allocation, then we
581 * add these pages to the cpu_buffers. Otherwise we just free
582 * them all and return -ENOMEM;
584 BUG_ON(nr_pages
<= buffer
->pages
);
585 new_pages
= nr_pages
- buffer
->pages
;
587 for_each_buffer_cpu(buffer
, cpu
) {
588 for (i
= 0; i
< new_pages
; i
++) {
589 page
= kzalloc_node(ALIGN(sizeof(*page
),
591 GFP_KERNEL
, cpu_to_node(cpu
));
594 list_add(&page
->list
, &pages
);
595 addr
= __get_free_page(GFP_KERNEL
);
598 page
->page
= (void *)addr
;
602 for_each_buffer_cpu(buffer
, cpu
) {
603 cpu_buffer
= buffer
->buffers
[cpu
];
604 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
607 BUG_ON(!list_empty(&pages
));
610 buffer
->pages
= nr_pages
;
611 mutex_unlock(&buffer
->mutex
);
616 list_for_each_entry_safe(page
, tmp
, &pages
, list
) {
617 list_del_init(&page
->list
);
618 free_buffer_page(page
);
620 mutex_unlock(&buffer
->mutex
);
624 static inline int rb_null_event(struct ring_buffer_event
*event
)
626 return event
->type
== RINGBUF_TYPE_PADDING
;
629 static inline void *__rb_page_index(struct buffer_page
*page
, unsigned index
)
631 return page
->page
+ index
;
634 static inline struct ring_buffer_event
*
635 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
637 return __rb_page_index(cpu_buffer
->reader_page
,
638 cpu_buffer
->reader_page
->read
);
641 static inline struct ring_buffer_event
*
642 rb_head_event(struct ring_buffer_per_cpu
*cpu_buffer
)
644 return __rb_page_index(cpu_buffer
->head_page
,
645 cpu_buffer
->head_page
->read
);
648 static inline struct ring_buffer_event
*
649 rb_iter_head_event(struct ring_buffer_iter
*iter
)
651 return __rb_page_index(iter
->head_page
, iter
->head
);
654 static inline unsigned rb_page_write(struct buffer_page
*bpage
)
656 return local_read(&bpage
->write
);
659 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
661 return local_read(&bpage
->commit
);
664 /* Size is determined by what has been commited */
665 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
667 return rb_page_commit(bpage
);
670 static inline unsigned
671 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
673 return rb_page_commit(cpu_buffer
->commit_page
);
676 static inline unsigned rb_head_size(struct ring_buffer_per_cpu
*cpu_buffer
)
678 return rb_page_commit(cpu_buffer
->head_page
);
682 * When the tail hits the head and the buffer is in overwrite mode,
683 * the head jumps to the next page and all content on the previous
684 * page is discarded. But before doing so, we update the overrun
685 * variable of the buffer.
687 static void rb_update_overflow(struct ring_buffer_per_cpu
*cpu_buffer
)
689 struct ring_buffer_event
*event
;
692 for (head
= 0; head
< rb_head_size(cpu_buffer
);
693 head
+= rb_event_length(event
)) {
695 event
= __rb_page_index(cpu_buffer
->head_page
, head
);
696 BUG_ON(rb_null_event(event
));
697 /* Only count data entries */
698 if (event
->type
!= RINGBUF_TYPE_DATA
)
700 cpu_buffer
->overrun
++;
701 cpu_buffer
->entries
--;
705 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
706 struct buffer_page
**page
)
708 struct list_head
*p
= (*page
)->list
.next
;
710 if (p
== &cpu_buffer
->pages
)
713 *page
= list_entry(p
, struct buffer_page
, list
);
716 static inline unsigned
717 rb_event_index(struct ring_buffer_event
*event
)
719 unsigned long addr
= (unsigned long)event
;
721 return (addr
& ~PAGE_MASK
) - (PAGE_SIZE
- BUF_PAGE_SIZE
);
725 rb_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
726 struct ring_buffer_event
*event
)
728 unsigned long addr
= (unsigned long)event
;
731 index
= rb_event_index(event
);
734 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
735 rb_commit_index(cpu_buffer
) == index
;
739 rb_set_commit_event(struct ring_buffer_per_cpu
*cpu_buffer
,
740 struct ring_buffer_event
*event
)
742 unsigned long addr
= (unsigned long)event
;
745 index
= rb_event_index(event
);
748 while (cpu_buffer
->commit_page
->page
!= (void *)addr
) {
749 RB_WARN_ON(cpu_buffer
,
750 cpu_buffer
->commit_page
== cpu_buffer
->tail_page
);
751 cpu_buffer
->commit_page
->commit
=
752 cpu_buffer
->commit_page
->write
;
753 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
754 cpu_buffer
->write_stamp
= cpu_buffer
->commit_page
->time_stamp
;
757 /* Now set the commit to the event's index */
758 local_set(&cpu_buffer
->commit_page
->commit
, index
);
762 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
765 * We only race with interrupts and NMIs on this CPU.
766 * If we own the commit event, then we can commit
767 * all others that interrupted us, since the interruptions
768 * are in stack format (they finish before they come
769 * back to us). This allows us to do a simple loop to
770 * assign the commit to the tail.
772 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
773 cpu_buffer
->commit_page
->commit
=
774 cpu_buffer
->commit_page
->write
;
775 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
776 cpu_buffer
->write_stamp
= cpu_buffer
->commit_page
->time_stamp
;
777 /* add barrier to keep gcc from optimizing too much */
780 while (rb_commit_index(cpu_buffer
) !=
781 rb_page_write(cpu_buffer
->commit_page
)) {
782 cpu_buffer
->commit_page
->commit
=
783 cpu_buffer
->commit_page
->write
;
788 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
790 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->time_stamp
;
791 cpu_buffer
->reader_page
->read
= 0;
794 static inline void rb_inc_iter(struct ring_buffer_iter
*iter
)
796 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
799 * The iterator could be on the reader page (it starts there).
800 * But the head could have moved, since the reader was
801 * found. Check for this case and assign the iterator
802 * to the head page instead of next.
804 if (iter
->head_page
== cpu_buffer
->reader_page
)
805 iter
->head_page
= cpu_buffer
->head_page
;
807 rb_inc_page(cpu_buffer
, &iter
->head_page
);
809 iter
->read_stamp
= iter
->head_page
->time_stamp
;
814 * ring_buffer_update_event - update event type and data
815 * @event: the even to update
816 * @type: the type of event
817 * @length: the size of the event field in the ring buffer
819 * Update the type and data fields of the event. The length
820 * is the actual size that is written to the ring buffer,
821 * and with this, we can determine what to place into the
825 rb_update_event(struct ring_buffer_event
*event
,
826 unsigned type
, unsigned length
)
832 case RINGBUF_TYPE_PADDING
:
835 case RINGBUF_TYPE_TIME_EXTEND
:
837 (RB_LEN_TIME_EXTEND
+ (RB_ALIGNMENT
-1))
838 >> RB_ALIGNMENT_SHIFT
;
841 case RINGBUF_TYPE_TIME_STAMP
:
843 (RB_LEN_TIME_STAMP
+ (RB_ALIGNMENT
-1))
844 >> RB_ALIGNMENT_SHIFT
;
847 case RINGBUF_TYPE_DATA
:
848 length
-= RB_EVNT_HDR_SIZE
;
849 if (length
> RB_MAX_SMALL_DATA
) {
851 event
->array
[0] = length
;
854 (length
+ (RB_ALIGNMENT
-1))
855 >> RB_ALIGNMENT_SHIFT
;
862 static inline unsigned rb_calculate_event_length(unsigned length
)
864 struct ring_buffer_event event
; /* Used only for sizeof array */
866 /* zero length can cause confusions */
870 if (length
> RB_MAX_SMALL_DATA
)
871 length
+= sizeof(event
.array
[0]);
873 length
+= RB_EVNT_HDR_SIZE
;
874 length
= ALIGN(length
, RB_ALIGNMENT
);
879 static struct ring_buffer_event
*
880 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
881 unsigned type
, unsigned long length
, u64
*ts
)
883 struct buffer_page
*tail_page
, *head_page
, *reader_page
;
884 unsigned long tail
, write
;
885 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
886 struct ring_buffer_event
*event
;
889 tail_page
= cpu_buffer
->tail_page
;
890 write
= local_add_return(length
, &tail_page
->write
);
891 tail
= write
- length
;
893 /* See if we shot pass the end of this buffer page */
894 if (write
> BUF_PAGE_SIZE
) {
895 struct buffer_page
*next_page
= tail_page
;
897 spin_lock_irqsave(&cpu_buffer
->lock
, flags
);
899 rb_inc_page(cpu_buffer
, &next_page
);
901 head_page
= cpu_buffer
->head_page
;
902 reader_page
= cpu_buffer
->reader_page
;
904 /* we grabbed the lock before incrementing */
905 RB_WARN_ON(cpu_buffer
, next_page
== reader_page
);
908 * If for some reason, we had an interrupt storm that made
909 * it all the way around the buffer, bail, and warn
912 if (unlikely(next_page
== cpu_buffer
->commit_page
)) {
917 if (next_page
== head_page
) {
918 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
920 if (tail
<= BUF_PAGE_SIZE
)
921 local_set(&tail_page
->write
, tail
);
925 /* tail_page has not moved yet? */
926 if (tail_page
== cpu_buffer
->tail_page
) {
927 /* count overflows */
928 rb_update_overflow(cpu_buffer
);
930 rb_inc_page(cpu_buffer
, &head_page
);
931 cpu_buffer
->head_page
= head_page
;
932 cpu_buffer
->head_page
->read
= 0;
937 * If the tail page is still the same as what we think
938 * it is, then it is up to us to update the tail
941 if (tail_page
== cpu_buffer
->tail_page
) {
942 local_set(&next_page
->write
, 0);
943 local_set(&next_page
->commit
, 0);
944 cpu_buffer
->tail_page
= next_page
;
946 /* reread the time stamp */
947 *ts
= ring_buffer_time_stamp(cpu_buffer
->cpu
);
948 cpu_buffer
->tail_page
->time_stamp
= *ts
;
952 * The actual tail page has moved forward.
954 if (tail
< BUF_PAGE_SIZE
) {
955 /* Mark the rest of the page with padding */
956 event
= __rb_page_index(tail_page
, tail
);
957 event
->type
= RINGBUF_TYPE_PADDING
;
960 if (tail
<= BUF_PAGE_SIZE
)
961 /* Set the write back to the previous setting */
962 local_set(&tail_page
->write
, tail
);
965 * If this was a commit entry that failed,
968 if (tail_page
== cpu_buffer
->commit_page
&&
969 tail
== rb_commit_index(cpu_buffer
)) {
970 rb_set_commit_to_write(cpu_buffer
);
973 spin_unlock_irqrestore(&cpu_buffer
->lock
, flags
);
975 /* fail and let the caller try again */
976 return ERR_PTR(-EAGAIN
);
979 /* We reserved something on the buffer */
981 BUG_ON(write
> BUF_PAGE_SIZE
);
983 event
= __rb_page_index(tail_page
, tail
);
984 rb_update_event(event
, type
, length
);
987 * If this is a commit and the tail is zero, then update
988 * this page's time stamp.
990 if (!tail
&& rb_is_commit(cpu_buffer
, event
))
991 cpu_buffer
->commit_page
->time_stamp
= *ts
;
996 spin_unlock_irqrestore(&cpu_buffer
->lock
, flags
);
1001 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1002 u64
*ts
, u64
*delta
)
1004 struct ring_buffer_event
*event
;
1008 if (unlikely(*delta
> (1ULL << 59) && !once
++)) {
1009 printk(KERN_WARNING
"Delta way too big! %llu"
1010 " ts=%llu write stamp = %llu\n",
1011 (unsigned long long)*delta
,
1012 (unsigned long long)*ts
,
1013 (unsigned long long)cpu_buffer
->write_stamp
);
1018 * The delta is too big, we to add a
1021 event
= __rb_reserve_next(cpu_buffer
,
1022 RINGBUF_TYPE_TIME_EXTEND
,
1028 if (PTR_ERR(event
) == -EAGAIN
)
1031 /* Only a commited time event can update the write stamp */
1032 if (rb_is_commit(cpu_buffer
, event
)) {
1034 * If this is the first on the page, then we need to
1035 * update the page itself, and just put in a zero.
1037 if (rb_event_index(event
)) {
1038 event
->time_delta
= *delta
& TS_MASK
;
1039 event
->array
[0] = *delta
>> TS_SHIFT
;
1041 cpu_buffer
->commit_page
->time_stamp
= *ts
;
1042 event
->time_delta
= 0;
1043 event
->array
[0] = 0;
1045 cpu_buffer
->write_stamp
= *ts
;
1046 /* let the caller know this was the commit */
1049 /* Darn, this is just wasted space */
1050 event
->time_delta
= 0;
1051 event
->array
[0] = 0;
1060 static struct ring_buffer_event
*
1061 rb_reserve_next_event(struct ring_buffer_per_cpu
*cpu_buffer
,
1062 unsigned type
, unsigned long length
)
1064 struct ring_buffer_event
*event
;
1071 * We allow for interrupts to reenter here and do a trace.
1072 * If one does, it will cause this original code to loop
1073 * back here. Even with heavy interrupts happening, this
1074 * should only happen a few times in a row. If this happens
1075 * 1000 times in a row, there must be either an interrupt
1076 * storm or we have something buggy.
1079 if (unlikely(++nr_loops
> 1000)) {
1080 RB_WARN_ON(cpu_buffer
, 1);
1084 ts
= ring_buffer_time_stamp(cpu_buffer
->cpu
);
1087 * Only the first commit can update the timestamp.
1088 * Yes there is a race here. If an interrupt comes in
1089 * just after the conditional and it traces too, then it
1090 * will also check the deltas. More than one timestamp may
1091 * also be made. But only the entry that did the actual
1092 * commit will be something other than zero.
1094 if (cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
1095 rb_page_write(cpu_buffer
->tail_page
) ==
1096 rb_commit_index(cpu_buffer
)) {
1098 delta
= ts
- cpu_buffer
->write_stamp
;
1100 /* make sure this delta is calculated here */
1103 /* Did the write stamp get updated already? */
1104 if (unlikely(ts
< cpu_buffer
->write_stamp
))
1107 if (test_time_stamp(delta
)) {
1109 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
1111 if (commit
== -EBUSY
)
1114 if (commit
== -EAGAIN
)
1117 RB_WARN_ON(cpu_buffer
, commit
< 0);
1120 /* Non commits have zero deltas */
1123 event
= __rb_reserve_next(cpu_buffer
, type
, length
, &ts
);
1124 if (PTR_ERR(event
) == -EAGAIN
)
1128 if (unlikely(commit
))
1130 * Ouch! We needed a timestamp and it was commited. But
1131 * we didn't get our event reserved.
1133 rb_set_commit_to_write(cpu_buffer
);
1138 * If the timestamp was commited, make the commit our entry
1139 * now so that we will update it when needed.
1142 rb_set_commit_event(cpu_buffer
, event
);
1143 else if (!rb_is_commit(cpu_buffer
, event
))
1146 event
->time_delta
= delta
;
1151 static DEFINE_PER_CPU(int, rb_need_resched
);
1154 * ring_buffer_lock_reserve - reserve a part of the buffer
1155 * @buffer: the ring buffer to reserve from
1156 * @length: the length of the data to reserve (excluding event header)
1157 * @flags: a pointer to save the interrupt flags
1159 * Returns a reseverd event on the ring buffer to copy directly to.
1160 * The user of this interface will need to get the body to write into
1161 * and can use the ring_buffer_event_data() interface.
1163 * The length is the length of the data needed, not the event length
1164 * which also includes the event header.
1166 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1167 * If NULL is returned, then nothing has been allocated or locked.
1169 struct ring_buffer_event
*
1170 ring_buffer_lock_reserve(struct ring_buffer
*buffer
,
1171 unsigned long length
,
1172 unsigned long *flags
)
1174 struct ring_buffer_per_cpu
*cpu_buffer
;
1175 struct ring_buffer_event
*event
;
1178 if (ring_buffers_off
)
1181 if (atomic_read(&buffer
->record_disabled
))
1184 /* If we are tracing schedule, we don't want to recurse */
1185 resched
= need_resched();
1186 preempt_disable_notrace();
1188 cpu
= raw_smp_processor_id();
1190 if (!cpu_isset(cpu
, buffer
->cpumask
))
1193 cpu_buffer
= buffer
->buffers
[cpu
];
1195 if (atomic_read(&cpu_buffer
->record_disabled
))
1198 length
= rb_calculate_event_length(length
);
1199 if (length
> BUF_PAGE_SIZE
)
1202 event
= rb_reserve_next_event(cpu_buffer
, RINGBUF_TYPE_DATA
, length
);
1207 * Need to store resched state on this cpu.
1208 * Only the first needs to.
1211 if (preempt_count() == 1)
1212 per_cpu(rb_need_resched
, cpu
) = resched
;
1218 preempt_enable_no_resched_notrace();
1220 preempt_enable_notrace();
1224 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1225 struct ring_buffer_event
*event
)
1227 cpu_buffer
->entries
++;
1229 /* Only process further if we own the commit */
1230 if (!rb_is_commit(cpu_buffer
, event
))
1233 cpu_buffer
->write_stamp
+= event
->time_delta
;
1235 rb_set_commit_to_write(cpu_buffer
);
1239 * ring_buffer_unlock_commit - commit a reserved
1240 * @buffer: The buffer to commit to
1241 * @event: The event pointer to commit.
1242 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1244 * This commits the data to the ring buffer, and releases any locks held.
1246 * Must be paired with ring_buffer_lock_reserve.
1248 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
1249 struct ring_buffer_event
*event
,
1250 unsigned long flags
)
1252 struct ring_buffer_per_cpu
*cpu_buffer
;
1253 int cpu
= raw_smp_processor_id();
1255 cpu_buffer
= buffer
->buffers
[cpu
];
1257 rb_commit(cpu_buffer
, event
);
1260 * Only the last preempt count needs to restore preemption.
1262 if (preempt_count() == 1) {
1263 if (per_cpu(rb_need_resched
, cpu
))
1264 preempt_enable_no_resched_notrace();
1266 preempt_enable_notrace();
1268 preempt_enable_no_resched_notrace();
1274 * ring_buffer_write - write data to the buffer without reserving
1275 * @buffer: The ring buffer to write to.
1276 * @length: The length of the data being written (excluding the event header)
1277 * @data: The data to write to the buffer.
1279 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1280 * one function. If you already have the data to write to the buffer, it
1281 * may be easier to simply call this function.
1283 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1284 * and not the length of the event which would hold the header.
1286 int ring_buffer_write(struct ring_buffer
*buffer
,
1287 unsigned long length
,
1290 struct ring_buffer_per_cpu
*cpu_buffer
;
1291 struct ring_buffer_event
*event
;
1292 unsigned long event_length
;
1297 if (ring_buffers_off
)
1300 if (atomic_read(&buffer
->record_disabled
))
1303 resched
= need_resched();
1304 preempt_disable_notrace();
1306 cpu
= raw_smp_processor_id();
1308 if (!cpu_isset(cpu
, buffer
->cpumask
))
1311 cpu_buffer
= buffer
->buffers
[cpu
];
1313 if (atomic_read(&cpu_buffer
->record_disabled
))
1316 event_length
= rb_calculate_event_length(length
);
1317 event
= rb_reserve_next_event(cpu_buffer
,
1318 RINGBUF_TYPE_DATA
, event_length
);
1322 body
= rb_event_data(event
);
1324 memcpy(body
, data
, length
);
1326 rb_commit(cpu_buffer
, event
);
1331 preempt_enable_no_resched_notrace();
1333 preempt_enable_notrace();
1338 static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
1340 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
1341 struct buffer_page
*head
= cpu_buffer
->head_page
;
1342 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
1344 return reader
->read
== rb_page_commit(reader
) &&
1345 (commit
== reader
||
1347 head
->read
== rb_page_commit(commit
)));
1351 * ring_buffer_record_disable - stop all writes into the buffer
1352 * @buffer: The ring buffer to stop writes to.
1354 * This prevents all writes to the buffer. Any attempt to write
1355 * to the buffer after this will fail and return NULL.
1357 * The caller should call synchronize_sched() after this.
1359 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
1361 atomic_inc(&buffer
->record_disabled
);
1365 * ring_buffer_record_enable - enable writes to the buffer
1366 * @buffer: The ring buffer to enable writes
1368 * Note, multiple disables will need the same number of enables
1369 * to truely enable the writing (much like preempt_disable).
1371 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
1373 atomic_dec(&buffer
->record_disabled
);
1377 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1378 * @buffer: The ring buffer to stop writes to.
1379 * @cpu: The CPU buffer to stop
1381 * This prevents all writes to the buffer. Any attempt to write
1382 * to the buffer after this will fail and return NULL.
1384 * The caller should call synchronize_sched() after this.
1386 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
1388 struct ring_buffer_per_cpu
*cpu_buffer
;
1390 if (!cpu_isset(cpu
, buffer
->cpumask
))
1393 cpu_buffer
= buffer
->buffers
[cpu
];
1394 atomic_inc(&cpu_buffer
->record_disabled
);
1398 * ring_buffer_record_enable_cpu - enable writes to the buffer
1399 * @buffer: The ring buffer to enable writes
1400 * @cpu: The CPU to enable.
1402 * Note, multiple disables will need the same number of enables
1403 * to truely enable the writing (much like preempt_disable).
1405 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
1407 struct ring_buffer_per_cpu
*cpu_buffer
;
1409 if (!cpu_isset(cpu
, buffer
->cpumask
))
1412 cpu_buffer
= buffer
->buffers
[cpu
];
1413 atomic_dec(&cpu_buffer
->record_disabled
);
1417 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1418 * @buffer: The ring buffer
1419 * @cpu: The per CPU buffer to get the entries from.
1421 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
1423 struct ring_buffer_per_cpu
*cpu_buffer
;
1425 if (!cpu_isset(cpu
, buffer
->cpumask
))
1428 cpu_buffer
= buffer
->buffers
[cpu
];
1429 return cpu_buffer
->entries
;
1433 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1434 * @buffer: The ring buffer
1435 * @cpu: The per CPU buffer to get the number of overruns from
1437 unsigned long ring_buffer_overrun_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
->overrun
;
1449 * ring_buffer_entries - get the number of entries in a buffer
1450 * @buffer: The ring buffer
1452 * Returns the total number of entries in the ring buffer
1455 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
1457 struct ring_buffer_per_cpu
*cpu_buffer
;
1458 unsigned long entries
= 0;
1461 /* if you care about this being correct, lock the buffer */
1462 for_each_buffer_cpu(buffer
, cpu
) {
1463 cpu_buffer
= buffer
->buffers
[cpu
];
1464 entries
+= cpu_buffer
->entries
;
1471 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1472 * @buffer: The ring buffer
1474 * Returns the total number of overruns in the ring buffer
1477 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
1479 struct ring_buffer_per_cpu
*cpu_buffer
;
1480 unsigned long overruns
= 0;
1483 /* if you care about this being correct, lock the buffer */
1484 for_each_buffer_cpu(buffer
, cpu
) {
1485 cpu_buffer
= buffer
->buffers
[cpu
];
1486 overruns
+= cpu_buffer
->overrun
;
1493 * ring_buffer_iter_reset - reset an iterator
1494 * @iter: The iterator to reset
1496 * Resets the iterator, so that it will start from the beginning
1499 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
1501 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1503 /* Iterator usage is expected to have record disabled */
1504 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
1505 iter
->head_page
= cpu_buffer
->head_page
;
1506 iter
->head
= cpu_buffer
->head_page
->read
;
1508 iter
->head_page
= cpu_buffer
->reader_page
;
1509 iter
->head
= cpu_buffer
->reader_page
->read
;
1512 iter
->read_stamp
= cpu_buffer
->read_stamp
;
1514 iter
->read_stamp
= iter
->head_page
->time_stamp
;
1518 * ring_buffer_iter_empty - check if an iterator has no more to read
1519 * @iter: The iterator to check
1521 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
1523 struct ring_buffer_per_cpu
*cpu_buffer
;
1525 cpu_buffer
= iter
->cpu_buffer
;
1527 return iter
->head_page
== cpu_buffer
->commit_page
&&
1528 iter
->head
== rb_commit_index(cpu_buffer
);
1532 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1533 struct ring_buffer_event
*event
)
1537 switch (event
->type
) {
1538 case RINGBUF_TYPE_PADDING
:
1541 case RINGBUF_TYPE_TIME_EXTEND
:
1542 delta
= event
->array
[0];
1544 delta
+= event
->time_delta
;
1545 cpu_buffer
->read_stamp
+= delta
;
1548 case RINGBUF_TYPE_TIME_STAMP
:
1549 /* FIXME: not implemented */
1552 case RINGBUF_TYPE_DATA
:
1553 cpu_buffer
->read_stamp
+= event
->time_delta
;
1563 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
1564 struct ring_buffer_event
*event
)
1568 switch (event
->type
) {
1569 case RINGBUF_TYPE_PADDING
:
1572 case RINGBUF_TYPE_TIME_EXTEND
:
1573 delta
= event
->array
[0];
1575 delta
+= event
->time_delta
;
1576 iter
->read_stamp
+= delta
;
1579 case RINGBUF_TYPE_TIME_STAMP
:
1580 /* FIXME: not implemented */
1583 case RINGBUF_TYPE_DATA
:
1584 iter
->read_stamp
+= event
->time_delta
;
1593 static struct buffer_page
*
1594 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1596 struct buffer_page
*reader
= NULL
;
1597 unsigned long flags
;
1600 spin_lock_irqsave(&cpu_buffer
->lock
, flags
);
1604 * This should normally only loop twice. But because the
1605 * start of the reader inserts an empty page, it causes
1606 * a case where we will loop three times. There should be no
1607 * reason to loop four times (that I know of).
1609 if (unlikely(++nr_loops
> 3)) {
1610 RB_WARN_ON(cpu_buffer
, 1);
1615 reader
= cpu_buffer
->reader_page
;
1617 /* If there's more to read, return this page */
1618 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
1621 /* Never should we have an index greater than the size */
1622 RB_WARN_ON(cpu_buffer
,
1623 cpu_buffer
->reader_page
->read
> rb_page_size(reader
));
1625 /* check if we caught up to the tail */
1627 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
1631 * Splice the empty reader page into the list around the head.
1632 * Reset the reader page to size zero.
1635 reader
= cpu_buffer
->head_page
;
1636 cpu_buffer
->reader_page
->list
.next
= reader
->list
.next
;
1637 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
1639 local_set(&cpu_buffer
->reader_page
->write
, 0);
1640 local_set(&cpu_buffer
->reader_page
->commit
, 0);
1642 /* Make the reader page now replace the head */
1643 reader
->list
.prev
->next
= &cpu_buffer
->reader_page
->list
;
1644 reader
->list
.next
->prev
= &cpu_buffer
->reader_page
->list
;
1647 * If the tail is on the reader, then we must set the head
1648 * to the inserted page, otherwise we set it one before.
1650 cpu_buffer
->head_page
= cpu_buffer
->reader_page
;
1652 if (cpu_buffer
->commit_page
!= reader
)
1653 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
1655 /* Finally update the reader page to the new head */
1656 cpu_buffer
->reader_page
= reader
;
1657 rb_reset_reader_page(cpu_buffer
);
1662 spin_unlock_irqrestore(&cpu_buffer
->lock
, flags
);
1667 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
1669 struct ring_buffer_event
*event
;
1670 struct buffer_page
*reader
;
1673 reader
= rb_get_reader_page(cpu_buffer
);
1675 /* This function should not be called when buffer is empty */
1678 event
= rb_reader_event(cpu_buffer
);
1680 if (event
->type
== RINGBUF_TYPE_DATA
)
1681 cpu_buffer
->entries
--;
1683 rb_update_read_stamp(cpu_buffer
, event
);
1685 length
= rb_event_length(event
);
1686 cpu_buffer
->reader_page
->read
+= length
;
1689 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
1691 struct ring_buffer
*buffer
;
1692 struct ring_buffer_per_cpu
*cpu_buffer
;
1693 struct ring_buffer_event
*event
;
1696 cpu_buffer
= iter
->cpu_buffer
;
1697 buffer
= cpu_buffer
->buffer
;
1700 * Check if we are at the end of the buffer.
1702 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
1703 BUG_ON(iter
->head_page
== cpu_buffer
->commit_page
);
1708 event
= rb_iter_head_event(iter
);
1710 length
= rb_event_length(event
);
1713 * This should not be called to advance the header if we are
1714 * at the tail of the buffer.
1716 BUG_ON((iter
->head_page
== cpu_buffer
->commit_page
) &&
1717 (iter
->head
+ length
> rb_commit_index(cpu_buffer
)));
1719 rb_update_iter_read_stamp(iter
, event
);
1721 iter
->head
+= length
;
1723 /* check for end of page padding */
1724 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
1725 (iter
->head_page
!= cpu_buffer
->commit_page
))
1726 rb_advance_iter(iter
);
1730 * ring_buffer_peek - peek at the next event to be read
1731 * @buffer: The ring buffer to read
1732 * @cpu: The cpu to peak at
1733 * @ts: The timestamp counter of this event.
1735 * This will return the event that will be read next, but does
1736 * not consume the data.
1738 struct ring_buffer_event
*
1739 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1741 struct ring_buffer_per_cpu
*cpu_buffer
;
1742 struct ring_buffer_event
*event
;
1743 struct buffer_page
*reader
;
1746 if (!cpu_isset(cpu
, buffer
->cpumask
))
1749 cpu_buffer
= buffer
->buffers
[cpu
];
1753 * We repeat when a timestamp is encountered. It is possible
1754 * to get multiple timestamps from an interrupt entering just
1755 * as one timestamp is about to be written. The max times
1756 * that this can happen is the number of nested interrupts we
1757 * can have. Nesting 10 deep of interrupts is clearly
1760 if (unlikely(++nr_loops
> 10)) {
1761 RB_WARN_ON(cpu_buffer
, 1);
1765 reader
= rb_get_reader_page(cpu_buffer
);
1769 event
= rb_reader_event(cpu_buffer
);
1771 switch (event
->type
) {
1772 case RINGBUF_TYPE_PADDING
:
1773 RB_WARN_ON(cpu_buffer
, 1);
1774 rb_advance_reader(cpu_buffer
);
1777 case RINGBUF_TYPE_TIME_EXTEND
:
1778 /* Internal data, OK to advance */
1779 rb_advance_reader(cpu_buffer
);
1782 case RINGBUF_TYPE_TIME_STAMP
:
1783 /* FIXME: not implemented */
1784 rb_advance_reader(cpu_buffer
);
1787 case RINGBUF_TYPE_DATA
:
1789 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
1790 ring_buffer_normalize_time_stamp(cpu_buffer
->cpu
, ts
);
1802 * ring_buffer_iter_peek - peek at the next event to be read
1803 * @iter: The ring buffer iterator
1804 * @ts: The timestamp counter of this event.
1806 * This will return the event that will be read next, but does
1807 * not increment the iterator.
1809 struct ring_buffer_event
*
1810 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
1812 struct ring_buffer
*buffer
;
1813 struct ring_buffer_per_cpu
*cpu_buffer
;
1814 struct ring_buffer_event
*event
;
1817 if (ring_buffer_iter_empty(iter
))
1820 cpu_buffer
= iter
->cpu_buffer
;
1821 buffer
= cpu_buffer
->buffer
;
1825 * We repeat when a timestamp is encountered. It is possible
1826 * to get multiple timestamps from an interrupt entering just
1827 * as one timestamp is about to be written. The max times
1828 * that this can happen is the number of nested interrupts we
1829 * can have. Nesting 10 deep of interrupts is clearly
1832 if (unlikely(++nr_loops
> 10)) {
1833 RB_WARN_ON(cpu_buffer
, 1);
1837 if (rb_per_cpu_empty(cpu_buffer
))
1840 event
= rb_iter_head_event(iter
);
1842 switch (event
->type
) {
1843 case RINGBUF_TYPE_PADDING
:
1847 case RINGBUF_TYPE_TIME_EXTEND
:
1848 /* Internal data, OK to advance */
1849 rb_advance_iter(iter
);
1852 case RINGBUF_TYPE_TIME_STAMP
:
1853 /* FIXME: not implemented */
1854 rb_advance_iter(iter
);
1857 case RINGBUF_TYPE_DATA
:
1859 *ts
= iter
->read_stamp
+ event
->time_delta
;
1860 ring_buffer_normalize_time_stamp(cpu_buffer
->cpu
, ts
);
1872 * ring_buffer_consume - return an event and consume it
1873 * @buffer: The ring buffer to get the next event from
1875 * Returns the next event in the ring buffer, and that event is consumed.
1876 * Meaning, that sequential reads will keep returning a different event,
1877 * and eventually empty the ring buffer if the producer is slower.
1879 struct ring_buffer_event
*
1880 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1882 struct ring_buffer_per_cpu
*cpu_buffer
;
1883 struct ring_buffer_event
*event
;
1885 if (!cpu_isset(cpu
, buffer
->cpumask
))
1888 event
= ring_buffer_peek(buffer
, cpu
, ts
);
1892 cpu_buffer
= buffer
->buffers
[cpu
];
1893 rb_advance_reader(cpu_buffer
);
1899 * ring_buffer_read_start - start a non consuming read of the buffer
1900 * @buffer: The ring buffer to read from
1901 * @cpu: The cpu buffer to iterate over
1903 * This starts up an iteration through the buffer. It also disables
1904 * the recording to the buffer until the reading is finished.
1905 * This prevents the reading from being corrupted. This is not
1906 * a consuming read, so a producer is not expected.
1908 * Must be paired with ring_buffer_finish.
1910 struct ring_buffer_iter
*
1911 ring_buffer_read_start(struct ring_buffer
*buffer
, int cpu
)
1913 struct ring_buffer_per_cpu
*cpu_buffer
;
1914 struct ring_buffer_iter
*iter
;
1915 unsigned long flags
;
1917 if (!cpu_isset(cpu
, buffer
->cpumask
))
1920 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
1924 cpu_buffer
= buffer
->buffers
[cpu
];
1926 iter
->cpu_buffer
= cpu_buffer
;
1928 atomic_inc(&cpu_buffer
->record_disabled
);
1929 synchronize_sched();
1931 spin_lock_irqsave(&cpu_buffer
->lock
, flags
);
1932 ring_buffer_iter_reset(iter
);
1933 spin_unlock_irqrestore(&cpu_buffer
->lock
, flags
);
1939 * ring_buffer_finish - finish reading the iterator of the buffer
1940 * @iter: The iterator retrieved by ring_buffer_start
1942 * This re-enables the recording to the buffer, and frees the
1946 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
1948 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1950 atomic_dec(&cpu_buffer
->record_disabled
);
1955 * ring_buffer_read - read the next item in the ring buffer by the iterator
1956 * @iter: The ring buffer iterator
1957 * @ts: The time stamp of the event read.
1959 * This reads the next event in the ring buffer and increments the iterator.
1961 struct ring_buffer_event
*
1962 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
1964 struct ring_buffer_event
*event
;
1966 event
= ring_buffer_iter_peek(iter
, ts
);
1970 rb_advance_iter(iter
);
1976 * ring_buffer_size - return the size of the ring buffer (in bytes)
1977 * @buffer: The ring buffer.
1979 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
1981 return BUF_PAGE_SIZE
* buffer
->pages
;
1985 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
1987 cpu_buffer
->head_page
1988 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
1989 local_set(&cpu_buffer
->head_page
->write
, 0);
1990 local_set(&cpu_buffer
->head_page
->commit
, 0);
1992 cpu_buffer
->head_page
->read
= 0;
1994 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
1995 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1997 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1998 local_set(&cpu_buffer
->reader_page
->write
, 0);
1999 local_set(&cpu_buffer
->reader_page
->commit
, 0);
2000 cpu_buffer
->reader_page
->read
= 0;
2002 cpu_buffer
->overrun
= 0;
2003 cpu_buffer
->entries
= 0;
2007 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2008 * @buffer: The ring buffer to reset a per cpu buffer of
2009 * @cpu: The CPU buffer to be reset
2011 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
2013 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2014 unsigned long flags
;
2016 if (!cpu_isset(cpu
, buffer
->cpumask
))
2019 spin_lock_irqsave(&cpu_buffer
->lock
, flags
);
2021 rb_reset_cpu(cpu_buffer
);
2023 spin_unlock_irqrestore(&cpu_buffer
->lock
, flags
);
2027 * ring_buffer_reset - reset a ring buffer
2028 * @buffer: The ring buffer to reset all cpu buffers
2030 void ring_buffer_reset(struct ring_buffer
*buffer
)
2034 for_each_buffer_cpu(buffer
, cpu
)
2035 ring_buffer_reset_cpu(buffer
, cpu
);
2039 * rind_buffer_empty - is the ring buffer empty?
2040 * @buffer: The ring buffer to test
2042 int ring_buffer_empty(struct ring_buffer
*buffer
)
2044 struct ring_buffer_per_cpu
*cpu_buffer
;
2047 /* yes this is racy, but if you don't like the race, lock the buffer */
2048 for_each_buffer_cpu(buffer
, cpu
) {
2049 cpu_buffer
= buffer
->buffers
[cpu
];
2050 if (!rb_per_cpu_empty(cpu_buffer
))
2057 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2058 * @buffer: The ring buffer
2059 * @cpu: The CPU buffer to test
2061 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
2063 struct ring_buffer_per_cpu
*cpu_buffer
;
2065 if (!cpu_isset(cpu
, buffer
->cpumask
))
2068 cpu_buffer
= buffer
->buffers
[cpu
];
2069 return rb_per_cpu_empty(cpu_buffer
);
2073 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2074 * @buffer_a: One buffer to swap with
2075 * @buffer_b: The other buffer to swap with
2077 * This function is useful for tracers that want to take a "snapshot"
2078 * of a CPU buffer and has another back up buffer lying around.
2079 * it is expected that the tracer handles the cpu buffer not being
2080 * used at the moment.
2082 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
2083 struct ring_buffer
*buffer_b
, int cpu
)
2085 struct ring_buffer_per_cpu
*cpu_buffer_a
;
2086 struct ring_buffer_per_cpu
*cpu_buffer_b
;
2088 if (!cpu_isset(cpu
, buffer_a
->cpumask
) ||
2089 !cpu_isset(cpu
, buffer_b
->cpumask
))
2092 /* At least make sure the two buffers are somewhat the same */
2093 if (buffer_a
->size
!= buffer_b
->size
||
2094 buffer_a
->pages
!= buffer_b
->pages
)
2097 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
2098 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
2101 * We can't do a synchronize_sched here because this
2102 * function can be called in atomic context.
2103 * Normally this will be called from the same CPU as cpu.
2104 * If not it's up to the caller to protect this.
2106 atomic_inc(&cpu_buffer_a
->record_disabled
);
2107 atomic_inc(&cpu_buffer_b
->record_disabled
);
2109 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
2110 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
2112 cpu_buffer_b
->buffer
= buffer_a
;
2113 cpu_buffer_a
->buffer
= buffer_b
;
2115 atomic_dec(&cpu_buffer_a
->record_disabled
);
2116 atomic_dec(&cpu_buffer_b
->record_disabled
);
2122 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
2123 size_t cnt
, loff_t
*ppos
)
2125 int *p
= filp
->private_data
;
2129 /* !ring_buffers_off == tracing_on */
2130 r
= sprintf(buf
, "%d\n", !*p
);
2132 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
2136 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
2137 size_t cnt
, loff_t
*ppos
)
2139 int *p
= filp
->private_data
;
2144 if (cnt
>= sizeof(buf
))
2147 if (copy_from_user(&buf
, ubuf
, cnt
))
2152 ret
= strict_strtoul(buf
, 10, &val
);
2156 /* !ring_buffers_off == tracing_on */
2164 static struct file_operations rb_simple_fops
= {
2165 .open
= tracing_open_generic
,
2166 .read
= rb_simple_read
,
2167 .write
= rb_simple_write
,
2171 static __init
int rb_init_debugfs(void)
2173 struct dentry
*d_tracer
;
2174 struct dentry
*entry
;
2176 d_tracer
= tracing_init_dentry();
2178 entry
= debugfs_create_file("tracing_on", 0644, d_tracer
,
2179 &ring_buffers_off
, &rb_simple_fops
);
2181 pr_warning("Could not create debugfs 'tracing_on' entry\n");
2186 fs_initcall(rb_init_debugfs
);