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)
50 /* Up this if you want to test the TIME_EXTENTS and normalization */
54 u64
ring_buffer_time_stamp(int cpu
)
56 /* shift to debug/test normalization and TIME_EXTENTS */
57 return sched_clock() << DEBUG_SHIFT
;
60 void ring_buffer_normalize_time_stamp(int cpu
, u64
*ts
)
62 /* Just stupid testing the normalize function and deltas */
66 #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
67 #define RB_ALIGNMENT_SHIFT 2
68 #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
69 #define RB_MAX_SMALL_DATA 28
72 RB_LEN_TIME_EXTEND
= 8,
73 RB_LEN_TIME_STAMP
= 16,
76 /* inline for ring buffer fast paths */
77 static inline unsigned
78 rb_event_length(struct ring_buffer_event
*event
)
82 switch (event
->type
) {
83 case RINGBUF_TYPE_PADDING
:
87 case RINGBUF_TYPE_TIME_EXTEND
:
88 return RB_LEN_TIME_EXTEND
;
90 case RINGBUF_TYPE_TIME_STAMP
:
91 return RB_LEN_TIME_STAMP
;
93 case RINGBUF_TYPE_DATA
:
95 length
= event
->len
<< RB_ALIGNMENT_SHIFT
;
97 length
= event
->array
[0];
98 return length
+ RB_EVNT_HDR_SIZE
;
107 * ring_buffer_event_length - return the length of the event
108 * @event: the event to get the length of
110 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
112 return rb_event_length(event
);
115 /* inline for ring buffer fast paths */
117 rb_event_data(struct ring_buffer_event
*event
)
119 BUG_ON(event
->type
!= RINGBUF_TYPE_DATA
);
120 /* If length is in len field, then array[0] has the data */
122 return (void *)&event
->array
[0];
123 /* Otherwise length is in array[0] and array[1] has the data */
124 return (void *)&event
->array
[1];
128 * ring_buffer_event_data - return the data of the event
129 * @event: the event to get the data from
131 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
133 return rb_event_data(event
);
136 #define for_each_buffer_cpu(buffer, cpu) \
137 for_each_cpu_mask(cpu, buffer->cpumask)
140 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
141 #define TS_DELTA_TEST (~TS_MASK)
144 * This hack stolen from mm/slob.c.
145 * We can store per page timing information in the page frame of the page.
146 * Thanks to Peter Zijlstra for suggesting this idea.
149 u64 time_stamp
; /* page time stamp */
150 local_t write
; /* index for next write */
151 local_t commit
; /* write commited index */
152 unsigned read
; /* index for next read */
153 struct list_head list
; /* list of free pages */
154 void *page
; /* Actual data page */
158 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
161 static inline void free_buffer_page(struct buffer_page
*bpage
)
164 free_page((unsigned long)bpage
->page
);
169 * We need to fit the time_stamp delta into 27 bits.
171 static inline int test_time_stamp(u64 delta
)
173 if (delta
& TS_DELTA_TEST
)
178 #define BUF_PAGE_SIZE PAGE_SIZE
181 * head_page == tail_page && head == tail then buffer is empty.
183 struct ring_buffer_per_cpu
{
185 struct ring_buffer
*buffer
;
186 spinlock_t reader_lock
; /* serialize readers */
188 struct lock_class_key lock_key
;
189 struct list_head pages
;
190 struct buffer_page
*head_page
; /* read from head */
191 struct buffer_page
*tail_page
; /* write to tail */
192 struct buffer_page
*commit_page
; /* commited pages */
193 struct buffer_page
*reader_page
;
194 unsigned long overrun
;
195 unsigned long entries
;
198 atomic_t record_disabled
;
207 atomic_t record_disabled
;
211 struct ring_buffer_per_cpu
**buffers
;
214 struct ring_buffer_iter
{
215 struct ring_buffer_per_cpu
*cpu_buffer
;
217 struct buffer_page
*head_page
;
221 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
222 #define RB_WARN_ON(buffer, cond) \
224 int _____ret = unlikely(cond); \
226 atomic_inc(&buffer->record_disabled); \
233 * check_pages - integrity check of buffer pages
234 * @cpu_buffer: CPU buffer with pages to test
236 * As a safty measure we check to make sure the data pages have not
239 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
241 struct list_head
*head
= &cpu_buffer
->pages
;
242 struct buffer_page
*page
, *tmp
;
244 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
246 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
249 list_for_each_entry_safe(page
, tmp
, head
, list
) {
250 if (RB_WARN_ON(cpu_buffer
,
251 page
->list
.next
->prev
!= &page
->list
))
253 if (RB_WARN_ON(cpu_buffer
,
254 page
->list
.prev
->next
!= &page
->list
))
261 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
264 struct list_head
*head
= &cpu_buffer
->pages
;
265 struct buffer_page
*page
, *tmp
;
270 for (i
= 0; i
< nr_pages
; i
++) {
271 page
= kzalloc_node(ALIGN(sizeof(*page
), cache_line_size()),
272 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
275 list_add(&page
->list
, &pages
);
277 addr
= __get_free_page(GFP_KERNEL
);
280 page
->page
= (void *)addr
;
283 list_splice(&pages
, head
);
285 rb_check_pages(cpu_buffer
);
290 list_for_each_entry_safe(page
, tmp
, &pages
, list
) {
291 list_del_init(&page
->list
);
292 free_buffer_page(page
);
297 static struct ring_buffer_per_cpu
*
298 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
300 struct ring_buffer_per_cpu
*cpu_buffer
;
301 struct buffer_page
*page
;
305 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
306 GFP_KERNEL
, cpu_to_node(cpu
));
310 cpu_buffer
->cpu
= cpu
;
311 cpu_buffer
->buffer
= buffer
;
312 spin_lock_init(&cpu_buffer
->reader_lock
);
313 cpu_buffer
->lock
= (raw_spinlock_t
)__RAW_SPIN_LOCK_UNLOCKED
;
314 INIT_LIST_HEAD(&cpu_buffer
->pages
);
316 page
= kzalloc_node(ALIGN(sizeof(*page
), cache_line_size()),
317 GFP_KERNEL
, cpu_to_node(cpu
));
319 goto fail_free_buffer
;
321 cpu_buffer
->reader_page
= page
;
322 addr
= __get_free_page(GFP_KERNEL
);
324 goto fail_free_reader
;
325 page
->page
= (void *)addr
;
327 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
329 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
331 goto fail_free_reader
;
333 cpu_buffer
->head_page
334 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
335 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
340 free_buffer_page(cpu_buffer
->reader_page
);
347 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
349 struct list_head
*head
= &cpu_buffer
->pages
;
350 struct buffer_page
*page
, *tmp
;
352 list_del_init(&cpu_buffer
->reader_page
->list
);
353 free_buffer_page(cpu_buffer
->reader_page
);
355 list_for_each_entry_safe(page
, tmp
, head
, list
) {
356 list_del_init(&page
->list
);
357 free_buffer_page(page
);
363 * Causes compile errors if the struct buffer_page gets bigger
364 * than the struct page.
366 extern int ring_buffer_page_too_big(void);
369 * ring_buffer_alloc - allocate a new ring_buffer
370 * @size: the size in bytes that is needed.
371 * @flags: attributes to set for the ring buffer.
373 * Currently the only flag that is available is the RB_FL_OVERWRITE
374 * flag. This flag means that the buffer will overwrite old data
375 * when the buffer wraps. If this flag is not set, the buffer will
376 * drop data when the tail hits the head.
378 struct ring_buffer
*ring_buffer_alloc(unsigned long size
, unsigned flags
)
380 struct ring_buffer
*buffer
;
384 /* Paranoid! Optimizes out when all is well */
385 if (sizeof(struct buffer_page
) > sizeof(struct page
))
386 ring_buffer_page_too_big();
389 /* keep it in its own cache line */
390 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
395 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
396 buffer
->flags
= flags
;
398 /* need at least two pages */
399 if (buffer
->pages
== 1)
402 buffer
->cpumask
= cpu_possible_map
;
403 buffer
->cpus
= nr_cpu_ids
;
405 bsize
= sizeof(void *) * nr_cpu_ids
;
406 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
408 if (!buffer
->buffers
)
409 goto fail_free_buffer
;
411 for_each_buffer_cpu(buffer
, cpu
) {
412 buffer
->buffers
[cpu
] =
413 rb_allocate_cpu_buffer(buffer
, cpu
);
414 if (!buffer
->buffers
[cpu
])
415 goto fail_free_buffers
;
418 mutex_init(&buffer
->mutex
);
423 for_each_buffer_cpu(buffer
, cpu
) {
424 if (buffer
->buffers
[cpu
])
425 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
427 kfree(buffer
->buffers
);
435 * ring_buffer_free - free a ring buffer.
436 * @buffer: the buffer to free.
439 ring_buffer_free(struct ring_buffer
*buffer
)
443 for_each_buffer_cpu(buffer
, cpu
)
444 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
449 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
452 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
454 struct buffer_page
*page
;
458 atomic_inc(&cpu_buffer
->record_disabled
);
461 for (i
= 0; i
< nr_pages
; i
++) {
462 if (RB_WARN_ON(cpu_buffer
, list_empty(&cpu_buffer
->pages
)))
464 p
= cpu_buffer
->pages
.next
;
465 page
= list_entry(p
, struct buffer_page
, list
);
466 list_del_init(&page
->list
);
467 free_buffer_page(page
);
469 if (RB_WARN_ON(cpu_buffer
, list_empty(&cpu_buffer
->pages
)))
472 rb_reset_cpu(cpu_buffer
);
474 rb_check_pages(cpu_buffer
);
476 atomic_dec(&cpu_buffer
->record_disabled
);
481 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
482 struct list_head
*pages
, unsigned nr_pages
)
484 struct buffer_page
*page
;
488 atomic_inc(&cpu_buffer
->record_disabled
);
491 for (i
= 0; i
< nr_pages
; i
++) {
492 if (RB_WARN_ON(cpu_buffer
, list_empty(pages
)))
495 page
= list_entry(p
, struct buffer_page
, list
);
496 list_del_init(&page
->list
);
497 list_add_tail(&page
->list
, &cpu_buffer
->pages
);
499 rb_reset_cpu(cpu_buffer
);
501 rb_check_pages(cpu_buffer
);
503 atomic_dec(&cpu_buffer
->record_disabled
);
507 * ring_buffer_resize - resize the ring buffer
508 * @buffer: the buffer to resize.
509 * @size: the new size.
511 * The tracer is responsible for making sure that the buffer is
512 * not being used while changing the size.
513 * Note: We may be able to change the above requirement by using
514 * RCU synchronizations.
516 * Minimum size is 2 * BUF_PAGE_SIZE.
518 * Returns -1 on failure.
520 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
522 struct ring_buffer_per_cpu
*cpu_buffer
;
523 unsigned nr_pages
, rm_pages
, new_pages
;
524 struct buffer_page
*page
, *tmp
;
525 unsigned long buffer_size
;
530 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
531 size
*= BUF_PAGE_SIZE
;
532 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
534 /* we need a minimum of two pages */
535 if (size
< BUF_PAGE_SIZE
* 2)
536 size
= BUF_PAGE_SIZE
* 2;
538 if (size
== buffer_size
)
541 mutex_lock(&buffer
->mutex
);
543 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
545 if (size
< buffer_size
) {
547 /* easy case, just free pages */
548 if (RB_WARN_ON(buffer
, nr_pages
>= buffer
->pages
)) {
549 mutex_unlock(&buffer
->mutex
);
553 rm_pages
= buffer
->pages
- nr_pages
;
555 for_each_buffer_cpu(buffer
, cpu
) {
556 cpu_buffer
= buffer
->buffers
[cpu
];
557 rb_remove_pages(cpu_buffer
, rm_pages
);
563 * This is a bit more difficult. We only want to add pages
564 * when we can allocate enough for all CPUs. We do this
565 * by allocating all the pages and storing them on a local
566 * link list. If we succeed in our allocation, then we
567 * add these pages to the cpu_buffers. Otherwise we just free
568 * them all and return -ENOMEM;
570 if (RB_WARN_ON(buffer
, nr_pages
<= buffer
->pages
)) {
571 mutex_unlock(&buffer
->mutex
);
575 new_pages
= nr_pages
- buffer
->pages
;
577 for_each_buffer_cpu(buffer
, cpu
) {
578 for (i
= 0; i
< new_pages
; i
++) {
579 page
= kzalloc_node(ALIGN(sizeof(*page
),
581 GFP_KERNEL
, cpu_to_node(cpu
));
584 list_add(&page
->list
, &pages
);
585 addr
= __get_free_page(GFP_KERNEL
);
588 page
->page
= (void *)addr
;
592 for_each_buffer_cpu(buffer
, cpu
) {
593 cpu_buffer
= buffer
->buffers
[cpu
];
594 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
597 if (RB_WARN_ON(buffer
, !list_empty(&pages
))) {
598 mutex_unlock(&buffer
->mutex
);
603 buffer
->pages
= nr_pages
;
604 mutex_unlock(&buffer
->mutex
);
609 list_for_each_entry_safe(page
, tmp
, &pages
, list
) {
610 list_del_init(&page
->list
);
611 free_buffer_page(page
);
616 static inline int rb_null_event(struct ring_buffer_event
*event
)
618 return event
->type
== RINGBUF_TYPE_PADDING
;
621 static inline void *__rb_page_index(struct buffer_page
*page
, unsigned index
)
623 return page
->page
+ index
;
626 static inline struct ring_buffer_event
*
627 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
629 return __rb_page_index(cpu_buffer
->reader_page
,
630 cpu_buffer
->reader_page
->read
);
633 static inline struct ring_buffer_event
*
634 rb_head_event(struct ring_buffer_per_cpu
*cpu_buffer
)
636 return __rb_page_index(cpu_buffer
->head_page
,
637 cpu_buffer
->head_page
->read
);
640 static inline struct ring_buffer_event
*
641 rb_iter_head_event(struct ring_buffer_iter
*iter
)
643 return __rb_page_index(iter
->head_page
, iter
->head
);
646 static inline unsigned rb_page_write(struct buffer_page
*bpage
)
648 return local_read(&bpage
->write
);
651 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
653 return local_read(&bpage
->commit
);
656 /* Size is determined by what has been commited */
657 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
659 return rb_page_commit(bpage
);
662 static inline unsigned
663 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
665 return rb_page_commit(cpu_buffer
->commit_page
);
668 static inline unsigned rb_head_size(struct ring_buffer_per_cpu
*cpu_buffer
)
670 return rb_page_commit(cpu_buffer
->head_page
);
674 * When the tail hits the head and the buffer is in overwrite mode,
675 * the head jumps to the next page and all content on the previous
676 * page is discarded. But before doing so, we update the overrun
677 * variable of the buffer.
679 static void rb_update_overflow(struct ring_buffer_per_cpu
*cpu_buffer
)
681 struct ring_buffer_event
*event
;
684 for (head
= 0; head
< rb_head_size(cpu_buffer
);
685 head
+= rb_event_length(event
)) {
687 event
= __rb_page_index(cpu_buffer
->head_page
, head
);
688 if (RB_WARN_ON(cpu_buffer
, rb_null_event(event
)))
690 /* Only count data entries */
691 if (event
->type
!= RINGBUF_TYPE_DATA
)
693 cpu_buffer
->overrun
++;
694 cpu_buffer
->entries
--;
698 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
699 struct buffer_page
**page
)
701 struct list_head
*p
= (*page
)->list
.next
;
703 if (p
== &cpu_buffer
->pages
)
706 *page
= list_entry(p
, struct buffer_page
, list
);
709 static inline unsigned
710 rb_event_index(struct ring_buffer_event
*event
)
712 unsigned long addr
= (unsigned long)event
;
714 return (addr
& ~PAGE_MASK
) - (PAGE_SIZE
- BUF_PAGE_SIZE
);
718 rb_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
719 struct ring_buffer_event
*event
)
721 unsigned long addr
= (unsigned long)event
;
724 index
= rb_event_index(event
);
727 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
728 rb_commit_index(cpu_buffer
) == index
;
732 rb_set_commit_event(struct ring_buffer_per_cpu
*cpu_buffer
,
733 struct ring_buffer_event
*event
)
735 unsigned long addr
= (unsigned long)event
;
738 index
= rb_event_index(event
);
741 while (cpu_buffer
->commit_page
->page
!= (void *)addr
) {
742 if (RB_WARN_ON(cpu_buffer
,
743 cpu_buffer
->commit_page
== cpu_buffer
->tail_page
))
745 cpu_buffer
->commit_page
->commit
=
746 cpu_buffer
->commit_page
->write
;
747 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
748 cpu_buffer
->write_stamp
= cpu_buffer
->commit_page
->time_stamp
;
751 /* Now set the commit to the event's index */
752 local_set(&cpu_buffer
->commit_page
->commit
, index
);
756 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
759 * We only race with interrupts and NMIs on this CPU.
760 * If we own the commit event, then we can commit
761 * all others that interrupted us, since the interruptions
762 * are in stack format (they finish before they come
763 * back to us). This allows us to do a simple loop to
764 * assign the commit to the tail.
766 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
767 cpu_buffer
->commit_page
->commit
=
768 cpu_buffer
->commit_page
->write
;
769 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
770 cpu_buffer
->write_stamp
= cpu_buffer
->commit_page
->time_stamp
;
771 /* add barrier to keep gcc from optimizing too much */
774 while (rb_commit_index(cpu_buffer
) !=
775 rb_page_write(cpu_buffer
->commit_page
)) {
776 cpu_buffer
->commit_page
->commit
=
777 cpu_buffer
->commit_page
->write
;
782 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
784 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->time_stamp
;
785 cpu_buffer
->reader_page
->read
= 0;
788 static inline void rb_inc_iter(struct ring_buffer_iter
*iter
)
790 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
793 * The iterator could be on the reader page (it starts there).
794 * But the head could have moved, since the reader was
795 * found. Check for this case and assign the iterator
796 * to the head page instead of next.
798 if (iter
->head_page
== cpu_buffer
->reader_page
)
799 iter
->head_page
= cpu_buffer
->head_page
;
801 rb_inc_page(cpu_buffer
, &iter
->head_page
);
803 iter
->read_stamp
= iter
->head_page
->time_stamp
;
808 * ring_buffer_update_event - update event type and data
809 * @event: the even to update
810 * @type: the type of event
811 * @length: the size of the event field in the ring buffer
813 * Update the type and data fields of the event. The length
814 * is the actual size that is written to the ring buffer,
815 * and with this, we can determine what to place into the
819 rb_update_event(struct ring_buffer_event
*event
,
820 unsigned type
, unsigned length
)
826 case RINGBUF_TYPE_PADDING
:
829 case RINGBUF_TYPE_TIME_EXTEND
:
831 (RB_LEN_TIME_EXTEND
+ (RB_ALIGNMENT
-1))
832 >> RB_ALIGNMENT_SHIFT
;
835 case RINGBUF_TYPE_TIME_STAMP
:
837 (RB_LEN_TIME_STAMP
+ (RB_ALIGNMENT
-1))
838 >> RB_ALIGNMENT_SHIFT
;
841 case RINGBUF_TYPE_DATA
:
842 length
-= RB_EVNT_HDR_SIZE
;
843 if (length
> RB_MAX_SMALL_DATA
) {
845 event
->array
[0] = length
;
848 (length
+ (RB_ALIGNMENT
-1))
849 >> RB_ALIGNMENT_SHIFT
;
856 static inline unsigned rb_calculate_event_length(unsigned length
)
858 struct ring_buffer_event event
; /* Used only for sizeof array */
860 /* zero length can cause confusions */
864 if (length
> RB_MAX_SMALL_DATA
)
865 length
+= sizeof(event
.array
[0]);
867 length
+= RB_EVNT_HDR_SIZE
;
868 length
= ALIGN(length
, RB_ALIGNMENT
);
873 static struct ring_buffer_event
*
874 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
875 unsigned type
, unsigned long length
, u64
*ts
)
877 struct buffer_page
*tail_page
, *head_page
, *reader_page
;
878 unsigned long tail
, write
;
879 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
880 struct ring_buffer_event
*event
;
883 tail_page
= cpu_buffer
->tail_page
;
884 write
= local_add_return(length
, &tail_page
->write
);
885 tail
= write
- length
;
887 /* See if we shot pass the end of this buffer page */
888 if (write
> BUF_PAGE_SIZE
) {
889 struct buffer_page
*next_page
= tail_page
;
891 local_irq_save(flags
);
892 __raw_spin_lock(&cpu_buffer
->lock
);
894 rb_inc_page(cpu_buffer
, &next_page
);
896 head_page
= cpu_buffer
->head_page
;
897 reader_page
= cpu_buffer
->reader_page
;
899 /* we grabbed the lock before incrementing */
900 if (RB_WARN_ON(cpu_buffer
, next_page
== reader_page
))
904 * If for some reason, we had an interrupt storm that made
905 * it all the way around the buffer, bail, and warn
908 if (unlikely(next_page
== cpu_buffer
->commit_page
)) {
913 if (next_page
== head_page
) {
914 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
916 if (tail
<= BUF_PAGE_SIZE
)
917 local_set(&tail_page
->write
, tail
);
921 /* tail_page has not moved yet? */
922 if (tail_page
== cpu_buffer
->tail_page
) {
923 /* count overflows */
924 rb_update_overflow(cpu_buffer
);
926 rb_inc_page(cpu_buffer
, &head_page
);
927 cpu_buffer
->head_page
= head_page
;
928 cpu_buffer
->head_page
->read
= 0;
933 * If the tail page is still the same as what we think
934 * it is, then it is up to us to update the tail
937 if (tail_page
== cpu_buffer
->tail_page
) {
938 local_set(&next_page
->write
, 0);
939 local_set(&next_page
->commit
, 0);
940 cpu_buffer
->tail_page
= next_page
;
942 /* reread the time stamp */
943 *ts
= ring_buffer_time_stamp(cpu_buffer
->cpu
);
944 cpu_buffer
->tail_page
->time_stamp
= *ts
;
948 * The actual tail page has moved forward.
950 if (tail
< BUF_PAGE_SIZE
) {
951 /* Mark the rest of the page with padding */
952 event
= __rb_page_index(tail_page
, tail
);
953 event
->type
= RINGBUF_TYPE_PADDING
;
956 if (tail
<= BUF_PAGE_SIZE
)
957 /* Set the write back to the previous setting */
958 local_set(&tail_page
->write
, tail
);
961 * If this was a commit entry that failed,
964 if (tail_page
== cpu_buffer
->commit_page
&&
965 tail
== rb_commit_index(cpu_buffer
)) {
966 rb_set_commit_to_write(cpu_buffer
);
969 __raw_spin_unlock(&cpu_buffer
->lock
);
970 local_irq_restore(flags
);
972 /* fail and let the caller try again */
973 return ERR_PTR(-EAGAIN
);
976 /* We reserved something on the buffer */
978 if (RB_WARN_ON(cpu_buffer
, write
> BUF_PAGE_SIZE
))
981 event
= __rb_page_index(tail_page
, tail
);
982 rb_update_event(event
, type
, length
);
985 * If this is a commit and the tail is zero, then update
986 * this page's time stamp.
988 if (!tail
&& rb_is_commit(cpu_buffer
, event
))
989 cpu_buffer
->commit_page
->time_stamp
= *ts
;
994 __raw_spin_unlock(&cpu_buffer
->lock
);
995 local_irq_restore(flags
);
1000 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1001 u64
*ts
, u64
*delta
)
1003 struct ring_buffer_event
*event
;
1007 if (unlikely(*delta
> (1ULL << 59) && !once
++)) {
1008 printk(KERN_WARNING
"Delta way too big! %llu"
1009 " ts=%llu write stamp = %llu\n",
1010 (unsigned long long)*delta
,
1011 (unsigned long long)*ts
,
1012 (unsigned long long)cpu_buffer
->write_stamp
);
1017 * The delta is too big, we to add a
1020 event
= __rb_reserve_next(cpu_buffer
,
1021 RINGBUF_TYPE_TIME_EXTEND
,
1027 if (PTR_ERR(event
) == -EAGAIN
)
1030 /* Only a commited time event can update the write stamp */
1031 if (rb_is_commit(cpu_buffer
, event
)) {
1033 * If this is the first on the page, then we need to
1034 * update the page itself, and just put in a zero.
1036 if (rb_event_index(event
)) {
1037 event
->time_delta
= *delta
& TS_MASK
;
1038 event
->array
[0] = *delta
>> TS_SHIFT
;
1040 cpu_buffer
->commit_page
->time_stamp
= *ts
;
1041 event
->time_delta
= 0;
1042 event
->array
[0] = 0;
1044 cpu_buffer
->write_stamp
= *ts
;
1045 /* let the caller know this was the commit */
1048 /* Darn, this is just wasted space */
1049 event
->time_delta
= 0;
1050 event
->array
[0] = 0;
1059 static struct ring_buffer_event
*
1060 rb_reserve_next_event(struct ring_buffer_per_cpu
*cpu_buffer
,
1061 unsigned type
, unsigned long length
)
1063 struct ring_buffer_event
*event
;
1070 * We allow for interrupts to reenter here and do a trace.
1071 * If one does, it will cause this original code to loop
1072 * back here. Even with heavy interrupts happening, this
1073 * should only happen a few times in a row. If this happens
1074 * 1000 times in a row, there must be either an interrupt
1075 * storm or we have something buggy.
1078 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
1081 ts
= ring_buffer_time_stamp(cpu_buffer
->cpu
);
1084 * Only the first commit can update the timestamp.
1085 * Yes there is a race here. If an interrupt comes in
1086 * just after the conditional and it traces too, then it
1087 * will also check the deltas. More than one timestamp may
1088 * also be made. But only the entry that did the actual
1089 * commit will be something other than zero.
1091 if (cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
1092 rb_page_write(cpu_buffer
->tail_page
) ==
1093 rb_commit_index(cpu_buffer
)) {
1095 delta
= ts
- cpu_buffer
->write_stamp
;
1097 /* make sure this delta is calculated here */
1100 /* Did the write stamp get updated already? */
1101 if (unlikely(ts
< cpu_buffer
->write_stamp
))
1104 if (test_time_stamp(delta
)) {
1106 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
1108 if (commit
== -EBUSY
)
1111 if (commit
== -EAGAIN
)
1114 RB_WARN_ON(cpu_buffer
, commit
< 0);
1117 /* Non commits have zero deltas */
1120 event
= __rb_reserve_next(cpu_buffer
, type
, length
, &ts
);
1121 if (PTR_ERR(event
) == -EAGAIN
)
1125 if (unlikely(commit
))
1127 * Ouch! We needed a timestamp and it was commited. But
1128 * we didn't get our event reserved.
1130 rb_set_commit_to_write(cpu_buffer
);
1135 * If the timestamp was commited, make the commit our entry
1136 * now so that we will update it when needed.
1139 rb_set_commit_event(cpu_buffer
, event
);
1140 else if (!rb_is_commit(cpu_buffer
, event
))
1143 event
->time_delta
= delta
;
1148 static DEFINE_PER_CPU(int, rb_need_resched
);
1151 * ring_buffer_lock_reserve - reserve a part of the buffer
1152 * @buffer: the ring buffer to reserve from
1153 * @length: the length of the data to reserve (excluding event header)
1154 * @flags: a pointer to save the interrupt flags
1156 * Returns a reseverd event on the ring buffer to copy directly to.
1157 * The user of this interface will need to get the body to write into
1158 * and can use the ring_buffer_event_data() interface.
1160 * The length is the length of the data needed, not the event length
1161 * which also includes the event header.
1163 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1164 * If NULL is returned, then nothing has been allocated or locked.
1166 struct ring_buffer_event
*
1167 ring_buffer_lock_reserve(struct ring_buffer
*buffer
,
1168 unsigned long length
,
1169 unsigned long *flags
)
1171 struct ring_buffer_per_cpu
*cpu_buffer
;
1172 struct ring_buffer_event
*event
;
1175 if (ring_buffers_off
)
1178 if (atomic_read(&buffer
->record_disabled
))
1181 /* If we are tracing schedule, we don't want to recurse */
1182 resched
= ftrace_preempt_disable();
1184 cpu
= raw_smp_processor_id();
1186 if (!cpu_isset(cpu
, buffer
->cpumask
))
1189 cpu_buffer
= buffer
->buffers
[cpu
];
1191 if (atomic_read(&cpu_buffer
->record_disabled
))
1194 length
= rb_calculate_event_length(length
);
1195 if (length
> BUF_PAGE_SIZE
)
1198 event
= rb_reserve_next_event(cpu_buffer
, RINGBUF_TYPE_DATA
, length
);
1203 * Need to store resched state on this cpu.
1204 * Only the first needs to.
1207 if (preempt_count() == 1)
1208 per_cpu(rb_need_resched
, cpu
) = resched
;
1213 ftrace_preempt_enable(resched
);
1217 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1218 struct ring_buffer_event
*event
)
1220 cpu_buffer
->entries
++;
1222 /* Only process further if we own the commit */
1223 if (!rb_is_commit(cpu_buffer
, event
))
1226 cpu_buffer
->write_stamp
+= event
->time_delta
;
1228 rb_set_commit_to_write(cpu_buffer
);
1232 * ring_buffer_unlock_commit - commit a reserved
1233 * @buffer: The buffer to commit to
1234 * @event: The event pointer to commit.
1235 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1237 * This commits the data to the ring buffer, and releases any locks held.
1239 * Must be paired with ring_buffer_lock_reserve.
1241 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
1242 struct ring_buffer_event
*event
,
1243 unsigned long flags
)
1245 struct ring_buffer_per_cpu
*cpu_buffer
;
1246 int cpu
= raw_smp_processor_id();
1248 cpu_buffer
= buffer
->buffers
[cpu
];
1250 rb_commit(cpu_buffer
, event
);
1253 * Only the last preempt count needs to restore preemption.
1255 if (preempt_count() == 1)
1256 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
1258 preempt_enable_no_resched_notrace();
1264 * ring_buffer_write - write data to the buffer without reserving
1265 * @buffer: The ring buffer to write to.
1266 * @length: The length of the data being written (excluding the event header)
1267 * @data: The data to write to the buffer.
1269 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1270 * one function. If you already have the data to write to the buffer, it
1271 * may be easier to simply call this function.
1273 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1274 * and not the length of the event which would hold the header.
1276 int ring_buffer_write(struct ring_buffer
*buffer
,
1277 unsigned long length
,
1280 struct ring_buffer_per_cpu
*cpu_buffer
;
1281 struct ring_buffer_event
*event
;
1282 unsigned long event_length
;
1287 if (ring_buffers_off
)
1290 if (atomic_read(&buffer
->record_disabled
))
1293 resched
= ftrace_preempt_disable();
1295 cpu
= raw_smp_processor_id();
1297 if (!cpu_isset(cpu
, buffer
->cpumask
))
1300 cpu_buffer
= buffer
->buffers
[cpu
];
1302 if (atomic_read(&cpu_buffer
->record_disabled
))
1305 event_length
= rb_calculate_event_length(length
);
1306 event
= rb_reserve_next_event(cpu_buffer
,
1307 RINGBUF_TYPE_DATA
, event_length
);
1311 body
= rb_event_data(event
);
1313 memcpy(body
, data
, length
);
1315 rb_commit(cpu_buffer
, event
);
1319 ftrace_preempt_enable(resched
);
1324 static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
1326 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
1327 struct buffer_page
*head
= cpu_buffer
->head_page
;
1328 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
1330 return reader
->read
== rb_page_commit(reader
) &&
1331 (commit
== reader
||
1333 head
->read
== rb_page_commit(commit
)));
1337 * ring_buffer_record_disable - stop all writes into the buffer
1338 * @buffer: The ring buffer to stop writes to.
1340 * This prevents all writes to the buffer. Any attempt to write
1341 * to the buffer after this will fail and return NULL.
1343 * The caller should call synchronize_sched() after this.
1345 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
1347 atomic_inc(&buffer
->record_disabled
);
1351 * ring_buffer_record_enable - enable writes to the buffer
1352 * @buffer: The ring buffer to enable writes
1354 * Note, multiple disables will need the same number of enables
1355 * to truely enable the writing (much like preempt_disable).
1357 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
1359 atomic_dec(&buffer
->record_disabled
);
1363 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1364 * @buffer: The ring buffer to stop writes to.
1365 * @cpu: The CPU buffer to stop
1367 * This prevents all writes to the buffer. Any attempt to write
1368 * to the buffer after this will fail and return NULL.
1370 * The caller should call synchronize_sched() after this.
1372 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
1374 struct ring_buffer_per_cpu
*cpu_buffer
;
1376 if (!cpu_isset(cpu
, buffer
->cpumask
))
1379 cpu_buffer
= buffer
->buffers
[cpu
];
1380 atomic_inc(&cpu_buffer
->record_disabled
);
1384 * ring_buffer_record_enable_cpu - enable writes to the buffer
1385 * @buffer: The ring buffer to enable writes
1386 * @cpu: The CPU to enable.
1388 * Note, multiple disables will need the same number of enables
1389 * to truely enable the writing (much like preempt_disable).
1391 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
1393 struct ring_buffer_per_cpu
*cpu_buffer
;
1395 if (!cpu_isset(cpu
, buffer
->cpumask
))
1398 cpu_buffer
= buffer
->buffers
[cpu
];
1399 atomic_dec(&cpu_buffer
->record_disabled
);
1403 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1404 * @buffer: The ring buffer
1405 * @cpu: The per CPU buffer to get the entries from.
1407 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
1409 struct ring_buffer_per_cpu
*cpu_buffer
;
1411 if (!cpu_isset(cpu
, buffer
->cpumask
))
1414 cpu_buffer
= buffer
->buffers
[cpu
];
1415 return cpu_buffer
->entries
;
1419 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1420 * @buffer: The ring buffer
1421 * @cpu: The per CPU buffer to get the number of overruns from
1423 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
1425 struct ring_buffer_per_cpu
*cpu_buffer
;
1427 if (!cpu_isset(cpu
, buffer
->cpumask
))
1430 cpu_buffer
= buffer
->buffers
[cpu
];
1431 return cpu_buffer
->overrun
;
1435 * ring_buffer_entries - get the number of entries in a buffer
1436 * @buffer: The ring buffer
1438 * Returns the total number of entries in the ring buffer
1441 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
1443 struct ring_buffer_per_cpu
*cpu_buffer
;
1444 unsigned long entries
= 0;
1447 /* if you care about this being correct, lock the buffer */
1448 for_each_buffer_cpu(buffer
, cpu
) {
1449 cpu_buffer
= buffer
->buffers
[cpu
];
1450 entries
+= cpu_buffer
->entries
;
1457 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1458 * @buffer: The ring buffer
1460 * Returns the total number of overruns in the ring buffer
1463 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
1465 struct ring_buffer_per_cpu
*cpu_buffer
;
1466 unsigned long overruns
= 0;
1469 /* if you care about this being correct, lock the buffer */
1470 for_each_buffer_cpu(buffer
, cpu
) {
1471 cpu_buffer
= buffer
->buffers
[cpu
];
1472 overruns
+= cpu_buffer
->overrun
;
1478 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
1480 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1482 /* Iterator usage is expected to have record disabled */
1483 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
1484 iter
->head_page
= cpu_buffer
->head_page
;
1485 iter
->head
= cpu_buffer
->head_page
->read
;
1487 iter
->head_page
= cpu_buffer
->reader_page
;
1488 iter
->head
= cpu_buffer
->reader_page
->read
;
1491 iter
->read_stamp
= cpu_buffer
->read_stamp
;
1493 iter
->read_stamp
= iter
->head_page
->time_stamp
;
1497 * ring_buffer_iter_reset - reset an iterator
1498 * @iter: The iterator to reset
1500 * Resets the iterator, so that it will start from the beginning
1503 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
1505 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1506 unsigned long flags
;
1508 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1509 rb_iter_reset(iter
);
1510 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1514 * ring_buffer_iter_empty - check if an iterator has no more to read
1515 * @iter: The iterator to check
1517 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
1519 struct ring_buffer_per_cpu
*cpu_buffer
;
1521 cpu_buffer
= iter
->cpu_buffer
;
1523 return iter
->head_page
== cpu_buffer
->commit_page
&&
1524 iter
->head
== rb_commit_index(cpu_buffer
);
1528 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1529 struct ring_buffer_event
*event
)
1533 switch (event
->type
) {
1534 case RINGBUF_TYPE_PADDING
:
1537 case RINGBUF_TYPE_TIME_EXTEND
:
1538 delta
= event
->array
[0];
1540 delta
+= event
->time_delta
;
1541 cpu_buffer
->read_stamp
+= delta
;
1544 case RINGBUF_TYPE_TIME_STAMP
:
1545 /* FIXME: not implemented */
1548 case RINGBUF_TYPE_DATA
:
1549 cpu_buffer
->read_stamp
+= event
->time_delta
;
1559 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
1560 struct ring_buffer_event
*event
)
1564 switch (event
->type
) {
1565 case RINGBUF_TYPE_PADDING
:
1568 case RINGBUF_TYPE_TIME_EXTEND
:
1569 delta
= event
->array
[0];
1571 delta
+= event
->time_delta
;
1572 iter
->read_stamp
+= delta
;
1575 case RINGBUF_TYPE_TIME_STAMP
:
1576 /* FIXME: not implemented */
1579 case RINGBUF_TYPE_DATA
:
1580 iter
->read_stamp
+= event
->time_delta
;
1589 static struct buffer_page
*
1590 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1592 struct buffer_page
*reader
= NULL
;
1593 unsigned long flags
;
1596 local_irq_save(flags
);
1597 __raw_spin_lock(&cpu_buffer
->lock
);
1601 * This should normally only loop twice. But because the
1602 * start of the reader inserts an empty page, it causes
1603 * a case where we will loop three times. There should be no
1604 * reason to loop four times (that I know of).
1606 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
1611 reader
= cpu_buffer
->reader_page
;
1613 /* If there's more to read, return this page */
1614 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
1617 /* Never should we have an index greater than the size */
1618 if (RB_WARN_ON(cpu_buffer
,
1619 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
1622 /* check if we caught up to the tail */
1624 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
1628 * Splice the empty reader page into the list around the head.
1629 * Reset the reader page to size zero.
1632 reader
= cpu_buffer
->head_page
;
1633 cpu_buffer
->reader_page
->list
.next
= reader
->list
.next
;
1634 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
1636 local_set(&cpu_buffer
->reader_page
->write
, 0);
1637 local_set(&cpu_buffer
->reader_page
->commit
, 0);
1639 /* Make the reader page now replace the head */
1640 reader
->list
.prev
->next
= &cpu_buffer
->reader_page
->list
;
1641 reader
->list
.next
->prev
= &cpu_buffer
->reader_page
->list
;
1644 * If the tail is on the reader, then we must set the head
1645 * to the inserted page, otherwise we set it one before.
1647 cpu_buffer
->head_page
= cpu_buffer
->reader_page
;
1649 if (cpu_buffer
->commit_page
!= reader
)
1650 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
1652 /* Finally update the reader page to the new head */
1653 cpu_buffer
->reader_page
= reader
;
1654 rb_reset_reader_page(cpu_buffer
);
1659 __raw_spin_unlock(&cpu_buffer
->lock
);
1660 local_irq_restore(flags
);
1665 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
1667 struct ring_buffer_event
*event
;
1668 struct buffer_page
*reader
;
1671 reader
= rb_get_reader_page(cpu_buffer
);
1673 /* This function should not be called when buffer is empty */
1674 if (RB_WARN_ON(cpu_buffer
, !reader
))
1677 event
= rb_reader_event(cpu_buffer
);
1679 if (event
->type
== RINGBUF_TYPE_DATA
)
1680 cpu_buffer
->entries
--;
1682 rb_update_read_stamp(cpu_buffer
, event
);
1684 length
= rb_event_length(event
);
1685 cpu_buffer
->reader_page
->read
+= length
;
1688 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
1690 struct ring_buffer
*buffer
;
1691 struct ring_buffer_per_cpu
*cpu_buffer
;
1692 struct ring_buffer_event
*event
;
1695 cpu_buffer
= iter
->cpu_buffer
;
1696 buffer
= cpu_buffer
->buffer
;
1699 * Check if we are at the end of the buffer.
1701 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
1702 if (RB_WARN_ON(buffer
,
1703 iter
->head_page
== cpu_buffer
->commit_page
))
1709 event
= rb_iter_head_event(iter
);
1711 length
= rb_event_length(event
);
1714 * This should not be called to advance the header if we are
1715 * at the tail of the buffer.
1717 if (RB_WARN_ON(cpu_buffer
,
1718 (iter
->head_page
== cpu_buffer
->commit_page
) &&
1719 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
1722 rb_update_iter_read_stamp(iter
, event
);
1724 iter
->head
+= length
;
1726 /* check for end of page padding */
1727 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
1728 (iter
->head_page
!= cpu_buffer
->commit_page
))
1729 rb_advance_iter(iter
);
1732 static struct ring_buffer_event
*
1733 rb_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1735 struct ring_buffer_per_cpu
*cpu_buffer
;
1736 struct ring_buffer_event
*event
;
1737 struct buffer_page
*reader
;
1740 if (!cpu_isset(cpu
, buffer
->cpumask
))
1743 cpu_buffer
= buffer
->buffers
[cpu
];
1747 * We repeat when a timestamp is encountered. It is possible
1748 * to get multiple timestamps from an interrupt entering just
1749 * as one timestamp is about to be written. The max times
1750 * that this can happen is the number of nested interrupts we
1751 * can have. Nesting 10 deep of interrupts is clearly
1754 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 10))
1757 reader
= rb_get_reader_page(cpu_buffer
);
1761 event
= rb_reader_event(cpu_buffer
);
1763 switch (event
->type
) {
1764 case RINGBUF_TYPE_PADDING
:
1765 RB_WARN_ON(cpu_buffer
, 1);
1766 rb_advance_reader(cpu_buffer
);
1769 case RINGBUF_TYPE_TIME_EXTEND
:
1770 /* Internal data, OK to advance */
1771 rb_advance_reader(cpu_buffer
);
1774 case RINGBUF_TYPE_TIME_STAMP
:
1775 /* FIXME: not implemented */
1776 rb_advance_reader(cpu_buffer
);
1779 case RINGBUF_TYPE_DATA
:
1781 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
1782 ring_buffer_normalize_time_stamp(cpu_buffer
->cpu
, ts
);
1793 static struct ring_buffer_event
*
1794 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
1796 struct ring_buffer
*buffer
;
1797 struct ring_buffer_per_cpu
*cpu_buffer
;
1798 struct ring_buffer_event
*event
;
1801 if (ring_buffer_iter_empty(iter
))
1804 cpu_buffer
= iter
->cpu_buffer
;
1805 buffer
= cpu_buffer
->buffer
;
1809 * We repeat when a timestamp is encountered. It is possible
1810 * to get multiple timestamps from an interrupt entering just
1811 * as one timestamp is about to be written. The max times
1812 * that this can happen is the number of nested interrupts we
1813 * can have. Nesting 10 deep of interrupts is clearly
1816 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 10))
1819 if (rb_per_cpu_empty(cpu_buffer
))
1822 event
= rb_iter_head_event(iter
);
1824 switch (event
->type
) {
1825 case RINGBUF_TYPE_PADDING
:
1829 case RINGBUF_TYPE_TIME_EXTEND
:
1830 /* Internal data, OK to advance */
1831 rb_advance_iter(iter
);
1834 case RINGBUF_TYPE_TIME_STAMP
:
1835 /* FIXME: not implemented */
1836 rb_advance_iter(iter
);
1839 case RINGBUF_TYPE_DATA
:
1841 *ts
= iter
->read_stamp
+ event
->time_delta
;
1842 ring_buffer_normalize_time_stamp(cpu_buffer
->cpu
, ts
);
1854 * ring_buffer_peek - peek at the next event to be read
1855 * @buffer: The ring buffer to read
1856 * @cpu: The cpu to peak at
1857 * @ts: The timestamp counter of this event.
1859 * This will return the event that will be read next, but does
1860 * not consume the data.
1862 struct ring_buffer_event
*
1863 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1865 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
1866 struct ring_buffer_event
*event
;
1867 unsigned long flags
;
1869 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1870 event
= rb_buffer_peek(buffer
, cpu
, ts
);
1871 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1877 * ring_buffer_iter_peek - peek at the next event to be read
1878 * @iter: The ring buffer iterator
1879 * @ts: The timestamp counter of this event.
1881 * This will return the event that will be read next, but does
1882 * not increment the iterator.
1884 struct ring_buffer_event
*
1885 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
1887 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1888 struct ring_buffer_event
*event
;
1889 unsigned long flags
;
1891 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1892 event
= rb_iter_peek(iter
, ts
);
1893 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1899 * ring_buffer_consume - return an event and consume it
1900 * @buffer: The ring buffer to get the next event from
1902 * Returns the next event in the ring buffer, and that event is consumed.
1903 * Meaning, that sequential reads will keep returning a different event,
1904 * and eventually empty the ring buffer if the producer is slower.
1906 struct ring_buffer_event
*
1907 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1909 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
1910 struct ring_buffer_event
*event
;
1911 unsigned long flags
;
1913 if (!cpu_isset(cpu
, buffer
->cpumask
))
1916 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1918 event
= rb_buffer_peek(buffer
, cpu
, ts
);
1922 rb_advance_reader(cpu_buffer
);
1925 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1931 * ring_buffer_read_start - start a non consuming read of the buffer
1932 * @buffer: The ring buffer to read from
1933 * @cpu: The cpu buffer to iterate over
1935 * This starts up an iteration through the buffer. It also disables
1936 * the recording to the buffer until the reading is finished.
1937 * This prevents the reading from being corrupted. This is not
1938 * a consuming read, so a producer is not expected.
1940 * Must be paired with ring_buffer_finish.
1942 struct ring_buffer_iter
*
1943 ring_buffer_read_start(struct ring_buffer
*buffer
, int cpu
)
1945 struct ring_buffer_per_cpu
*cpu_buffer
;
1946 struct ring_buffer_iter
*iter
;
1947 unsigned long flags
;
1949 if (!cpu_isset(cpu
, buffer
->cpumask
))
1952 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
1956 cpu_buffer
= buffer
->buffers
[cpu
];
1958 iter
->cpu_buffer
= cpu_buffer
;
1960 atomic_inc(&cpu_buffer
->record_disabled
);
1961 synchronize_sched();
1963 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1964 __raw_spin_lock(&cpu_buffer
->lock
);
1965 rb_iter_reset(iter
);
1966 __raw_spin_unlock(&cpu_buffer
->lock
);
1967 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1973 * ring_buffer_finish - finish reading the iterator of the buffer
1974 * @iter: The iterator retrieved by ring_buffer_start
1976 * This re-enables the recording to the buffer, and frees the
1980 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
1982 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1984 atomic_dec(&cpu_buffer
->record_disabled
);
1989 * ring_buffer_read - read the next item in the ring buffer by the iterator
1990 * @iter: The ring buffer iterator
1991 * @ts: The time stamp of the event read.
1993 * This reads the next event in the ring buffer and increments the iterator.
1995 struct ring_buffer_event
*
1996 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
1998 struct ring_buffer_event
*event
;
1999 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2000 unsigned long flags
;
2002 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2003 event
= rb_iter_peek(iter
, ts
);
2007 rb_advance_iter(iter
);
2009 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2015 * ring_buffer_size - return the size of the ring buffer (in bytes)
2016 * @buffer: The ring buffer.
2018 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
2020 return BUF_PAGE_SIZE
* buffer
->pages
;
2024 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
2026 cpu_buffer
->head_page
2027 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
2028 local_set(&cpu_buffer
->head_page
->write
, 0);
2029 local_set(&cpu_buffer
->head_page
->commit
, 0);
2031 cpu_buffer
->head_page
->read
= 0;
2033 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
2034 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
2036 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
2037 local_set(&cpu_buffer
->reader_page
->write
, 0);
2038 local_set(&cpu_buffer
->reader_page
->commit
, 0);
2039 cpu_buffer
->reader_page
->read
= 0;
2041 cpu_buffer
->overrun
= 0;
2042 cpu_buffer
->entries
= 0;
2046 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2047 * @buffer: The ring buffer to reset a per cpu buffer of
2048 * @cpu: The CPU buffer to be reset
2050 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
2052 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2053 unsigned long flags
;
2055 if (!cpu_isset(cpu
, buffer
->cpumask
))
2058 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2060 __raw_spin_lock(&cpu_buffer
->lock
);
2062 rb_reset_cpu(cpu_buffer
);
2064 __raw_spin_unlock(&cpu_buffer
->lock
);
2066 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2070 * ring_buffer_reset - reset a ring buffer
2071 * @buffer: The ring buffer to reset all cpu buffers
2073 void ring_buffer_reset(struct ring_buffer
*buffer
)
2077 for_each_buffer_cpu(buffer
, cpu
)
2078 ring_buffer_reset_cpu(buffer
, cpu
);
2082 * rind_buffer_empty - is the ring buffer empty?
2083 * @buffer: The ring buffer to test
2085 int ring_buffer_empty(struct ring_buffer
*buffer
)
2087 struct ring_buffer_per_cpu
*cpu_buffer
;
2090 /* yes this is racy, but if you don't like the race, lock the buffer */
2091 for_each_buffer_cpu(buffer
, cpu
) {
2092 cpu_buffer
= buffer
->buffers
[cpu
];
2093 if (!rb_per_cpu_empty(cpu_buffer
))
2100 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2101 * @buffer: The ring buffer
2102 * @cpu: The CPU buffer to test
2104 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
2106 struct ring_buffer_per_cpu
*cpu_buffer
;
2108 if (!cpu_isset(cpu
, buffer
->cpumask
))
2111 cpu_buffer
= buffer
->buffers
[cpu
];
2112 return rb_per_cpu_empty(cpu_buffer
);
2116 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2117 * @buffer_a: One buffer to swap with
2118 * @buffer_b: The other buffer to swap with
2120 * This function is useful for tracers that want to take a "snapshot"
2121 * of a CPU buffer and has another back up buffer lying around.
2122 * it is expected that the tracer handles the cpu buffer not being
2123 * used at the moment.
2125 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
2126 struct ring_buffer
*buffer_b
, int cpu
)
2128 struct ring_buffer_per_cpu
*cpu_buffer_a
;
2129 struct ring_buffer_per_cpu
*cpu_buffer_b
;
2131 if (!cpu_isset(cpu
, buffer_a
->cpumask
) ||
2132 !cpu_isset(cpu
, buffer_b
->cpumask
))
2135 /* At least make sure the two buffers are somewhat the same */
2136 if (buffer_a
->size
!= buffer_b
->size
||
2137 buffer_a
->pages
!= buffer_b
->pages
)
2140 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
2141 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
2144 * We can't do a synchronize_sched here because this
2145 * function can be called in atomic context.
2146 * Normally this will be called from the same CPU as cpu.
2147 * If not it's up to the caller to protect this.
2149 atomic_inc(&cpu_buffer_a
->record_disabled
);
2150 atomic_inc(&cpu_buffer_b
->record_disabled
);
2152 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
2153 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
2155 cpu_buffer_b
->buffer
= buffer_a
;
2156 cpu_buffer_a
->buffer
= buffer_b
;
2158 atomic_dec(&cpu_buffer_a
->record_disabled
);
2159 atomic_dec(&cpu_buffer_b
->record_disabled
);
2165 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
2166 size_t cnt
, loff_t
*ppos
)
2168 int *p
= filp
->private_data
;
2172 /* !ring_buffers_off == tracing_on */
2173 r
= sprintf(buf
, "%d\n", !*p
);
2175 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
2179 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
2180 size_t cnt
, loff_t
*ppos
)
2182 int *p
= filp
->private_data
;
2187 if (cnt
>= sizeof(buf
))
2190 if (copy_from_user(&buf
, ubuf
, cnt
))
2195 ret
= strict_strtoul(buf
, 10, &val
);
2199 /* !ring_buffers_off == tracing_on */
2207 static struct file_operations rb_simple_fops
= {
2208 .open
= tracing_open_generic
,
2209 .read
= rb_simple_read
,
2210 .write
= rb_simple_write
,
2214 static __init
int rb_init_debugfs(void)
2216 struct dentry
*d_tracer
;
2217 struct dentry
*entry
;
2219 d_tracer
= tracing_init_dentry();
2221 entry
= debugfs_create_file("tracing_on", 0644, d_tracer
,
2222 &ring_buffers_off
, &rb_simple_fops
);
2224 pr_warning("Could not create debugfs 'tracing_on' entry\n");
2229 fs_initcall(rb_init_debugfs
);