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>
22 * A fast way to enable or disable all ring buffers is to
23 * call tracing_on or tracing_off. Turning off the ring buffers
24 * prevents all ring buffers from being recorded to.
25 * Turning this switch on, makes it OK to write to the
26 * ring buffer, if the ring buffer is enabled itself.
28 * There's three layers that must be on in order to write
31 * 1) This global flag must be set.
32 * 2) The ring buffer must be enabled for recording.
33 * 3) The per cpu buffer must be enabled for recording.
35 * In case of an anomaly, this global flag has a bit set that
36 * will permantly disable all ring buffers.
40 * Global flag to disable all recording to ring buffers
41 * This has two bits: ON, DISABLED
45 * 0 0 : ring buffers are off
46 * 1 0 : ring buffers are on
47 * X 1 : ring buffers are permanently disabled
51 RB_BUFFERS_ON_BIT
= 0,
52 RB_BUFFERS_DISABLED_BIT
= 1,
56 RB_BUFFERS_ON
= 1 << RB_BUFFERS_ON_BIT
,
57 RB_BUFFERS_DISABLED
= 1 << RB_BUFFERS_DISABLED_BIT
,
60 static long ring_buffer_flags __read_mostly
= RB_BUFFERS_ON
;
63 * tracing_on - enable all tracing buffers
65 * This function enables all tracing buffers that may have been
66 * disabled with tracing_off.
70 set_bit(RB_BUFFERS_ON_BIT
, &ring_buffer_flags
);
72 EXPORT_SYMBOL_GPL(tracing_on
);
75 * tracing_off - turn off all tracing buffers
77 * This function stops all tracing buffers from recording data.
78 * It does not disable any overhead the tracers themselves may
79 * be causing. This function simply causes all recording to
80 * the ring buffers to fail.
82 void tracing_off(void)
84 clear_bit(RB_BUFFERS_ON_BIT
, &ring_buffer_flags
);
86 EXPORT_SYMBOL_GPL(tracing_off
);
89 * tracing_off_permanent - permanently disable ring buffers
91 * This function, once called, will disable all ring buffers
94 void tracing_off_permanent(void)
96 set_bit(RB_BUFFERS_DISABLED_BIT
, &ring_buffer_flags
);
101 /* Up this if you want to test the TIME_EXTENTS and normalization */
102 #define DEBUG_SHIFT 0
105 u64
ring_buffer_time_stamp(int cpu
)
109 preempt_disable_notrace();
110 /* shift to debug/test normalization and TIME_EXTENTS */
111 time
= sched_clock() << DEBUG_SHIFT
;
112 preempt_enable_no_resched_notrace();
116 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
118 void ring_buffer_normalize_time_stamp(int cpu
, u64
*ts
)
120 /* Just stupid testing the normalize function and deltas */
123 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
125 #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
126 #define RB_ALIGNMENT_SHIFT 2
127 #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
128 #define RB_MAX_SMALL_DATA 28
131 RB_LEN_TIME_EXTEND
= 8,
132 RB_LEN_TIME_STAMP
= 16,
135 /* inline for ring buffer fast paths */
136 static inline unsigned
137 rb_event_length(struct ring_buffer_event
*event
)
141 switch (event
->type
) {
142 case RINGBUF_TYPE_PADDING
:
146 case RINGBUF_TYPE_TIME_EXTEND
:
147 return RB_LEN_TIME_EXTEND
;
149 case RINGBUF_TYPE_TIME_STAMP
:
150 return RB_LEN_TIME_STAMP
;
152 case RINGBUF_TYPE_DATA
:
154 length
= event
->len
<< RB_ALIGNMENT_SHIFT
;
156 length
= event
->array
[0];
157 return length
+ RB_EVNT_HDR_SIZE
;
166 * ring_buffer_event_length - return the length of the event
167 * @event: the event to get the length of
169 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
171 return rb_event_length(event
);
173 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
175 /* inline for ring buffer fast paths */
177 rb_event_data(struct ring_buffer_event
*event
)
179 BUG_ON(event
->type
!= RINGBUF_TYPE_DATA
);
180 /* If length is in len field, then array[0] has the data */
182 return (void *)&event
->array
[0];
183 /* Otherwise length is in array[0] and array[1] has the data */
184 return (void *)&event
->array
[1];
188 * ring_buffer_event_data - return the data of the event
189 * @event: the event to get the data from
191 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
193 return rb_event_data(event
);
195 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
197 #define for_each_buffer_cpu(buffer, cpu) \
198 for_each_cpu_mask(cpu, buffer->cpumask)
201 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
202 #define TS_DELTA_TEST (~TS_MASK)
204 struct buffer_data_page
{
205 u64 time_stamp
; /* page time stamp */
206 local_t commit
; /* write commited index */
207 unsigned char data
[]; /* data of buffer page */
211 local_t write
; /* index for next write */
212 unsigned read
; /* index for next read */
213 struct list_head list
; /* list of free pages */
214 struct buffer_data_page
*page
; /* Actual data page */
217 static void rb_init_page(struct buffer_data_page
*bpage
)
219 local_set(&bpage
->commit
, 0);
223 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
226 static inline void free_buffer_page(struct buffer_page
*bpage
)
229 free_page((unsigned long)bpage
->page
);
234 * We need to fit the time_stamp delta into 27 bits.
236 static inline int test_time_stamp(u64 delta
)
238 if (delta
& TS_DELTA_TEST
)
243 #define BUF_PAGE_SIZE (PAGE_SIZE - sizeof(struct buffer_data_page))
246 * head_page == tail_page && head == tail then buffer is empty.
248 struct ring_buffer_per_cpu
{
250 struct ring_buffer
*buffer
;
251 spinlock_t reader_lock
; /* serialize readers */
253 struct lock_class_key lock_key
;
254 struct list_head pages
;
255 struct buffer_page
*head_page
; /* read from head */
256 struct buffer_page
*tail_page
; /* write to tail */
257 struct buffer_page
*commit_page
; /* commited pages */
258 struct buffer_page
*reader_page
;
259 unsigned long overrun
;
260 unsigned long entries
;
263 atomic_t record_disabled
;
271 atomic_t record_disabled
;
275 struct ring_buffer_per_cpu
**buffers
;
278 struct ring_buffer_iter
{
279 struct ring_buffer_per_cpu
*cpu_buffer
;
281 struct buffer_page
*head_page
;
285 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
286 #define RB_WARN_ON(buffer, cond) \
288 int _____ret = unlikely(cond); \
290 atomic_inc(&buffer->record_disabled); \
297 * check_pages - integrity check of buffer pages
298 * @cpu_buffer: CPU buffer with pages to test
300 * As a safty measure we check to make sure the data pages have not
303 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
305 struct list_head
*head
= &cpu_buffer
->pages
;
306 struct buffer_page
*bpage
, *tmp
;
308 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
310 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
313 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
314 if (RB_WARN_ON(cpu_buffer
,
315 bpage
->list
.next
->prev
!= &bpage
->list
))
317 if (RB_WARN_ON(cpu_buffer
,
318 bpage
->list
.prev
->next
!= &bpage
->list
))
325 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
328 struct list_head
*head
= &cpu_buffer
->pages
;
329 struct buffer_page
*bpage
, *tmp
;
334 for (i
= 0; i
< nr_pages
; i
++) {
335 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
336 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
339 list_add(&bpage
->list
, &pages
);
341 addr
= __get_free_page(GFP_KERNEL
);
344 bpage
->page
= (void *)addr
;
345 rb_init_page(bpage
->page
);
348 list_splice(&pages
, head
);
350 rb_check_pages(cpu_buffer
);
355 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
356 list_del_init(&bpage
->list
);
357 free_buffer_page(bpage
);
362 static struct ring_buffer_per_cpu
*
363 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
365 struct ring_buffer_per_cpu
*cpu_buffer
;
366 struct buffer_page
*bpage
;
370 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
371 GFP_KERNEL
, cpu_to_node(cpu
));
375 cpu_buffer
->cpu
= cpu
;
376 cpu_buffer
->buffer
= buffer
;
377 spin_lock_init(&cpu_buffer
->reader_lock
);
378 cpu_buffer
->lock
= (raw_spinlock_t
)__RAW_SPIN_LOCK_UNLOCKED
;
379 INIT_LIST_HEAD(&cpu_buffer
->pages
);
381 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
382 GFP_KERNEL
, cpu_to_node(cpu
));
384 goto fail_free_buffer
;
386 cpu_buffer
->reader_page
= bpage
;
387 addr
= __get_free_page(GFP_KERNEL
);
389 goto fail_free_reader
;
390 bpage
->page
= (void *)addr
;
391 rb_init_page(bpage
->page
);
393 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
395 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
397 goto fail_free_reader
;
399 cpu_buffer
->head_page
400 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
401 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
406 free_buffer_page(cpu_buffer
->reader_page
);
413 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
415 struct list_head
*head
= &cpu_buffer
->pages
;
416 struct buffer_page
*bpage
, *tmp
;
418 list_del_init(&cpu_buffer
->reader_page
->list
);
419 free_buffer_page(cpu_buffer
->reader_page
);
421 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
422 list_del_init(&bpage
->list
);
423 free_buffer_page(bpage
);
429 * Causes compile errors if the struct buffer_page gets bigger
430 * than the struct page.
432 extern int ring_buffer_page_too_big(void);
435 * ring_buffer_alloc - allocate a new ring_buffer
436 * @size: the size in bytes per cpu that is needed.
437 * @flags: attributes to set for the ring buffer.
439 * Currently the only flag that is available is the RB_FL_OVERWRITE
440 * flag. This flag means that the buffer will overwrite old data
441 * when the buffer wraps. If this flag is not set, the buffer will
442 * drop data when the tail hits the head.
444 struct ring_buffer
*ring_buffer_alloc(unsigned long size
, unsigned flags
)
446 struct ring_buffer
*buffer
;
450 /* Paranoid! Optimizes out when all is well */
451 if (sizeof(struct buffer_page
) > sizeof(struct page
))
452 ring_buffer_page_too_big();
455 /* keep it in its own cache line */
456 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
461 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
462 buffer
->flags
= flags
;
464 /* need at least two pages */
465 if (buffer
->pages
== 1)
468 buffer
->cpumask
= cpu_possible_map
;
469 buffer
->cpus
= nr_cpu_ids
;
471 bsize
= sizeof(void *) * nr_cpu_ids
;
472 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
474 if (!buffer
->buffers
)
475 goto fail_free_buffer
;
477 for_each_buffer_cpu(buffer
, cpu
) {
478 buffer
->buffers
[cpu
] =
479 rb_allocate_cpu_buffer(buffer
, cpu
);
480 if (!buffer
->buffers
[cpu
])
481 goto fail_free_buffers
;
484 mutex_init(&buffer
->mutex
);
489 for_each_buffer_cpu(buffer
, cpu
) {
490 if (buffer
->buffers
[cpu
])
491 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
493 kfree(buffer
->buffers
);
499 EXPORT_SYMBOL_GPL(ring_buffer_alloc
);
502 * ring_buffer_free - free a ring buffer.
503 * @buffer: the buffer to free.
506 ring_buffer_free(struct ring_buffer
*buffer
)
510 for_each_buffer_cpu(buffer
, cpu
)
511 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
515 EXPORT_SYMBOL_GPL(ring_buffer_free
);
517 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
520 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
522 struct buffer_page
*bpage
;
526 atomic_inc(&cpu_buffer
->record_disabled
);
529 for (i
= 0; i
< nr_pages
; i
++) {
530 if (RB_WARN_ON(cpu_buffer
, list_empty(&cpu_buffer
->pages
)))
532 p
= cpu_buffer
->pages
.next
;
533 bpage
= list_entry(p
, struct buffer_page
, list
);
534 list_del_init(&bpage
->list
);
535 free_buffer_page(bpage
);
537 if (RB_WARN_ON(cpu_buffer
, list_empty(&cpu_buffer
->pages
)))
540 rb_reset_cpu(cpu_buffer
);
542 rb_check_pages(cpu_buffer
);
544 atomic_dec(&cpu_buffer
->record_disabled
);
549 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
550 struct list_head
*pages
, unsigned nr_pages
)
552 struct buffer_page
*bpage
;
556 atomic_inc(&cpu_buffer
->record_disabled
);
559 for (i
= 0; i
< nr_pages
; i
++) {
560 if (RB_WARN_ON(cpu_buffer
, list_empty(pages
)))
563 bpage
= list_entry(p
, struct buffer_page
, list
);
564 list_del_init(&bpage
->list
);
565 list_add_tail(&bpage
->list
, &cpu_buffer
->pages
);
567 rb_reset_cpu(cpu_buffer
);
569 rb_check_pages(cpu_buffer
);
571 atomic_dec(&cpu_buffer
->record_disabled
);
575 * ring_buffer_resize - resize the ring buffer
576 * @buffer: the buffer to resize.
577 * @size: the new size.
579 * The tracer is responsible for making sure that the buffer is
580 * not being used while changing the size.
581 * Note: We may be able to change the above requirement by using
582 * RCU synchronizations.
584 * Minimum size is 2 * BUF_PAGE_SIZE.
586 * Returns -1 on failure.
588 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
590 struct ring_buffer_per_cpu
*cpu_buffer
;
591 unsigned nr_pages
, rm_pages
, new_pages
;
592 struct buffer_page
*bpage
, *tmp
;
593 unsigned long buffer_size
;
599 * Always succeed at resizing a non-existent buffer:
604 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
605 size
*= BUF_PAGE_SIZE
;
606 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
608 /* we need a minimum of two pages */
609 if (size
< BUF_PAGE_SIZE
* 2)
610 size
= BUF_PAGE_SIZE
* 2;
612 if (size
== buffer_size
)
615 mutex_lock(&buffer
->mutex
);
617 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
619 if (size
< buffer_size
) {
621 /* easy case, just free pages */
622 if (RB_WARN_ON(buffer
, nr_pages
>= buffer
->pages
)) {
623 mutex_unlock(&buffer
->mutex
);
627 rm_pages
= buffer
->pages
- nr_pages
;
629 for_each_buffer_cpu(buffer
, cpu
) {
630 cpu_buffer
= buffer
->buffers
[cpu
];
631 rb_remove_pages(cpu_buffer
, rm_pages
);
637 * This is a bit more difficult. We only want to add pages
638 * when we can allocate enough for all CPUs. We do this
639 * by allocating all the pages and storing them on a local
640 * link list. If we succeed in our allocation, then we
641 * add these pages to the cpu_buffers. Otherwise we just free
642 * them all and return -ENOMEM;
644 if (RB_WARN_ON(buffer
, nr_pages
<= buffer
->pages
)) {
645 mutex_unlock(&buffer
->mutex
);
649 new_pages
= nr_pages
- buffer
->pages
;
651 for_each_buffer_cpu(buffer
, cpu
) {
652 for (i
= 0; i
< new_pages
; i
++) {
653 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
),
655 GFP_KERNEL
, cpu_to_node(cpu
));
658 list_add(&bpage
->list
, &pages
);
659 addr
= __get_free_page(GFP_KERNEL
);
662 bpage
->page
= (void *)addr
;
663 rb_init_page(bpage
->page
);
667 for_each_buffer_cpu(buffer
, cpu
) {
668 cpu_buffer
= buffer
->buffers
[cpu
];
669 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
672 if (RB_WARN_ON(buffer
, !list_empty(&pages
))) {
673 mutex_unlock(&buffer
->mutex
);
678 buffer
->pages
= nr_pages
;
679 mutex_unlock(&buffer
->mutex
);
684 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
685 list_del_init(&bpage
->list
);
686 free_buffer_page(bpage
);
688 mutex_unlock(&buffer
->mutex
);
691 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
693 static inline int rb_null_event(struct ring_buffer_event
*event
)
695 return event
->type
== RINGBUF_TYPE_PADDING
;
699 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
701 return bpage
->data
+ index
;
704 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
706 return bpage
->page
->data
+ index
;
709 static inline struct ring_buffer_event
*
710 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
712 return __rb_page_index(cpu_buffer
->reader_page
,
713 cpu_buffer
->reader_page
->read
);
716 static inline struct ring_buffer_event
*
717 rb_head_event(struct ring_buffer_per_cpu
*cpu_buffer
)
719 return __rb_page_index(cpu_buffer
->head_page
,
720 cpu_buffer
->head_page
->read
);
723 static inline struct ring_buffer_event
*
724 rb_iter_head_event(struct ring_buffer_iter
*iter
)
726 return __rb_page_index(iter
->head_page
, iter
->head
);
729 static inline unsigned rb_page_write(struct buffer_page
*bpage
)
731 return local_read(&bpage
->write
);
734 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
736 return local_read(&bpage
->page
->commit
);
739 /* Size is determined by what has been commited */
740 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
742 return rb_page_commit(bpage
);
745 static inline unsigned
746 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
748 return rb_page_commit(cpu_buffer
->commit_page
);
751 static inline unsigned rb_head_size(struct ring_buffer_per_cpu
*cpu_buffer
)
753 return rb_page_commit(cpu_buffer
->head_page
);
757 * When the tail hits the head and the buffer is in overwrite mode,
758 * the head jumps to the next page and all content on the previous
759 * page is discarded. But before doing so, we update the overrun
760 * variable of the buffer.
762 static void rb_update_overflow(struct ring_buffer_per_cpu
*cpu_buffer
)
764 struct ring_buffer_event
*event
;
767 for (head
= 0; head
< rb_head_size(cpu_buffer
);
768 head
+= rb_event_length(event
)) {
770 event
= __rb_page_index(cpu_buffer
->head_page
, head
);
771 if (RB_WARN_ON(cpu_buffer
, rb_null_event(event
)))
773 /* Only count data entries */
774 if (event
->type
!= RINGBUF_TYPE_DATA
)
776 cpu_buffer
->overrun
++;
777 cpu_buffer
->entries
--;
781 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
782 struct buffer_page
**bpage
)
784 struct list_head
*p
= (*bpage
)->list
.next
;
786 if (p
== &cpu_buffer
->pages
)
789 *bpage
= list_entry(p
, struct buffer_page
, list
);
792 static inline unsigned
793 rb_event_index(struct ring_buffer_event
*event
)
795 unsigned long addr
= (unsigned long)event
;
797 return (addr
& ~PAGE_MASK
) - (PAGE_SIZE
- BUF_PAGE_SIZE
);
801 rb_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
802 struct ring_buffer_event
*event
)
804 unsigned long addr
= (unsigned long)event
;
807 index
= rb_event_index(event
);
810 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
811 rb_commit_index(cpu_buffer
) == index
;
815 rb_set_commit_event(struct ring_buffer_per_cpu
*cpu_buffer
,
816 struct ring_buffer_event
*event
)
818 unsigned long addr
= (unsigned long)event
;
821 index
= rb_event_index(event
);
824 while (cpu_buffer
->commit_page
->page
!= (void *)addr
) {
825 if (RB_WARN_ON(cpu_buffer
,
826 cpu_buffer
->commit_page
== cpu_buffer
->tail_page
))
828 cpu_buffer
->commit_page
->page
->commit
=
829 cpu_buffer
->commit_page
->write
;
830 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
831 cpu_buffer
->write_stamp
=
832 cpu_buffer
->commit_page
->page
->time_stamp
;
835 /* Now set the commit to the event's index */
836 local_set(&cpu_buffer
->commit_page
->page
->commit
, index
);
840 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
843 * We only race with interrupts and NMIs on this CPU.
844 * If we own the commit event, then we can commit
845 * all others that interrupted us, since the interruptions
846 * are in stack format (they finish before they come
847 * back to us). This allows us to do a simple loop to
848 * assign the commit to the tail.
851 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
852 cpu_buffer
->commit_page
->page
->commit
=
853 cpu_buffer
->commit_page
->write
;
854 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
855 cpu_buffer
->write_stamp
=
856 cpu_buffer
->commit_page
->page
->time_stamp
;
857 /* add barrier to keep gcc from optimizing too much */
860 while (rb_commit_index(cpu_buffer
) !=
861 rb_page_write(cpu_buffer
->commit_page
)) {
862 cpu_buffer
->commit_page
->page
->commit
=
863 cpu_buffer
->commit_page
->write
;
867 /* again, keep gcc from optimizing */
871 * If an interrupt came in just after the first while loop
872 * and pushed the tail page forward, we will be left with
873 * a dangling commit that will never go forward.
875 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
879 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
881 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
882 cpu_buffer
->reader_page
->read
= 0;
885 static inline void rb_inc_iter(struct ring_buffer_iter
*iter
)
887 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
890 * The iterator could be on the reader page (it starts there).
891 * But the head could have moved, since the reader was
892 * found. Check for this case and assign the iterator
893 * to the head page instead of next.
895 if (iter
->head_page
== cpu_buffer
->reader_page
)
896 iter
->head_page
= cpu_buffer
->head_page
;
898 rb_inc_page(cpu_buffer
, &iter
->head_page
);
900 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
905 * ring_buffer_update_event - update event type and data
906 * @event: the even to update
907 * @type: the type of event
908 * @length: the size of the event field in the ring buffer
910 * Update the type and data fields of the event. The length
911 * is the actual size that is written to the ring buffer,
912 * and with this, we can determine what to place into the
916 rb_update_event(struct ring_buffer_event
*event
,
917 unsigned type
, unsigned length
)
923 case RINGBUF_TYPE_PADDING
:
926 case RINGBUF_TYPE_TIME_EXTEND
:
928 (RB_LEN_TIME_EXTEND
+ (RB_ALIGNMENT
-1))
929 >> RB_ALIGNMENT_SHIFT
;
932 case RINGBUF_TYPE_TIME_STAMP
:
934 (RB_LEN_TIME_STAMP
+ (RB_ALIGNMENT
-1))
935 >> RB_ALIGNMENT_SHIFT
;
938 case RINGBUF_TYPE_DATA
:
939 length
-= RB_EVNT_HDR_SIZE
;
940 if (length
> RB_MAX_SMALL_DATA
) {
942 event
->array
[0] = length
;
945 (length
+ (RB_ALIGNMENT
-1))
946 >> RB_ALIGNMENT_SHIFT
;
953 static inline unsigned rb_calculate_event_length(unsigned length
)
955 struct ring_buffer_event event
; /* Used only for sizeof array */
957 /* zero length can cause confusions */
961 if (length
> RB_MAX_SMALL_DATA
)
962 length
+= sizeof(event
.array
[0]);
964 length
+= RB_EVNT_HDR_SIZE
;
965 length
= ALIGN(length
, RB_ALIGNMENT
);
970 static struct ring_buffer_event
*
971 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
972 unsigned type
, unsigned long length
, u64
*ts
)
974 struct buffer_page
*tail_page
, *head_page
, *reader_page
, *commit_page
;
975 unsigned long tail
, write
;
976 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
977 struct ring_buffer_event
*event
;
980 commit_page
= cpu_buffer
->commit_page
;
981 /* we just need to protect against interrupts */
983 tail_page
= cpu_buffer
->tail_page
;
984 write
= local_add_return(length
, &tail_page
->write
);
985 tail
= write
- length
;
987 /* See if we shot pass the end of this buffer page */
988 if (write
> BUF_PAGE_SIZE
) {
989 struct buffer_page
*next_page
= tail_page
;
991 local_irq_save(flags
);
992 __raw_spin_lock(&cpu_buffer
->lock
);
994 rb_inc_page(cpu_buffer
, &next_page
);
996 head_page
= cpu_buffer
->head_page
;
997 reader_page
= cpu_buffer
->reader_page
;
999 /* we grabbed the lock before incrementing */
1000 if (RB_WARN_ON(cpu_buffer
, next_page
== reader_page
))
1004 * If for some reason, we had an interrupt storm that made
1005 * it all the way around the buffer, bail, and warn
1008 if (unlikely(next_page
== commit_page
)) {
1013 if (next_page
== head_page
) {
1014 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
1016 if (tail
<= BUF_PAGE_SIZE
)
1017 local_set(&tail_page
->write
, tail
);
1021 /* tail_page has not moved yet? */
1022 if (tail_page
== cpu_buffer
->tail_page
) {
1023 /* count overflows */
1024 rb_update_overflow(cpu_buffer
);
1026 rb_inc_page(cpu_buffer
, &head_page
);
1027 cpu_buffer
->head_page
= head_page
;
1028 cpu_buffer
->head_page
->read
= 0;
1033 * If the tail page is still the same as what we think
1034 * it is, then it is up to us to update the tail
1037 if (tail_page
== cpu_buffer
->tail_page
) {
1038 local_set(&next_page
->write
, 0);
1039 local_set(&next_page
->page
->commit
, 0);
1040 cpu_buffer
->tail_page
= next_page
;
1042 /* reread the time stamp */
1043 *ts
= ring_buffer_time_stamp(cpu_buffer
->cpu
);
1044 cpu_buffer
->tail_page
->page
->time_stamp
= *ts
;
1048 * The actual tail page has moved forward.
1050 if (tail
< BUF_PAGE_SIZE
) {
1051 /* Mark the rest of the page with padding */
1052 event
= __rb_page_index(tail_page
, tail
);
1053 event
->type
= RINGBUF_TYPE_PADDING
;
1056 if (tail
<= BUF_PAGE_SIZE
)
1057 /* Set the write back to the previous setting */
1058 local_set(&tail_page
->write
, tail
);
1061 * If this was a commit entry that failed,
1062 * increment that too
1064 if (tail_page
== cpu_buffer
->commit_page
&&
1065 tail
== rb_commit_index(cpu_buffer
)) {
1066 rb_set_commit_to_write(cpu_buffer
);
1069 __raw_spin_unlock(&cpu_buffer
->lock
);
1070 local_irq_restore(flags
);
1072 /* fail and let the caller try again */
1073 return ERR_PTR(-EAGAIN
);
1076 /* We reserved something on the buffer */
1078 if (RB_WARN_ON(cpu_buffer
, write
> BUF_PAGE_SIZE
))
1081 event
= __rb_page_index(tail_page
, tail
);
1082 rb_update_event(event
, type
, length
);
1085 * If this is a commit and the tail is zero, then update
1086 * this page's time stamp.
1088 if (!tail
&& rb_is_commit(cpu_buffer
, event
))
1089 cpu_buffer
->commit_page
->page
->time_stamp
= *ts
;
1094 __raw_spin_unlock(&cpu_buffer
->lock
);
1095 local_irq_restore(flags
);
1100 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1101 u64
*ts
, u64
*delta
)
1103 struct ring_buffer_event
*event
;
1107 if (unlikely(*delta
> (1ULL << 59) && !once
++)) {
1108 printk(KERN_WARNING
"Delta way too big! %llu"
1109 " ts=%llu write stamp = %llu\n",
1110 (unsigned long long)*delta
,
1111 (unsigned long long)*ts
,
1112 (unsigned long long)cpu_buffer
->write_stamp
);
1117 * The delta is too big, we to add a
1120 event
= __rb_reserve_next(cpu_buffer
,
1121 RINGBUF_TYPE_TIME_EXTEND
,
1127 if (PTR_ERR(event
) == -EAGAIN
)
1130 /* Only a commited time event can update the write stamp */
1131 if (rb_is_commit(cpu_buffer
, event
)) {
1133 * If this is the first on the page, then we need to
1134 * update the page itself, and just put in a zero.
1136 if (rb_event_index(event
)) {
1137 event
->time_delta
= *delta
& TS_MASK
;
1138 event
->array
[0] = *delta
>> TS_SHIFT
;
1140 cpu_buffer
->commit_page
->page
->time_stamp
= *ts
;
1141 event
->time_delta
= 0;
1142 event
->array
[0] = 0;
1144 cpu_buffer
->write_stamp
= *ts
;
1145 /* let the caller know this was the commit */
1148 /* Darn, this is just wasted space */
1149 event
->time_delta
= 0;
1150 event
->array
[0] = 0;
1159 static struct ring_buffer_event
*
1160 rb_reserve_next_event(struct ring_buffer_per_cpu
*cpu_buffer
,
1161 unsigned type
, unsigned long length
)
1163 struct ring_buffer_event
*event
;
1170 * We allow for interrupts to reenter here and do a trace.
1171 * If one does, it will cause this original code to loop
1172 * back here. Even with heavy interrupts happening, this
1173 * should only happen a few times in a row. If this happens
1174 * 1000 times in a row, there must be either an interrupt
1175 * storm or we have something buggy.
1178 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
1181 ts
= ring_buffer_time_stamp(cpu_buffer
->cpu
);
1184 * Only the first commit can update the timestamp.
1185 * Yes there is a race here. If an interrupt comes in
1186 * just after the conditional and it traces too, then it
1187 * will also check the deltas. More than one timestamp may
1188 * also be made. But only the entry that did the actual
1189 * commit will be something other than zero.
1191 if (cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
1192 rb_page_write(cpu_buffer
->tail_page
) ==
1193 rb_commit_index(cpu_buffer
)) {
1195 delta
= ts
- cpu_buffer
->write_stamp
;
1197 /* make sure this delta is calculated here */
1200 /* Did the write stamp get updated already? */
1201 if (unlikely(ts
< cpu_buffer
->write_stamp
))
1204 if (test_time_stamp(delta
)) {
1206 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
1208 if (commit
== -EBUSY
)
1211 if (commit
== -EAGAIN
)
1214 RB_WARN_ON(cpu_buffer
, commit
< 0);
1217 /* Non commits have zero deltas */
1220 event
= __rb_reserve_next(cpu_buffer
, type
, length
, &ts
);
1221 if (PTR_ERR(event
) == -EAGAIN
)
1225 if (unlikely(commit
))
1227 * Ouch! We needed a timestamp and it was commited. But
1228 * we didn't get our event reserved.
1230 rb_set_commit_to_write(cpu_buffer
);
1235 * If the timestamp was commited, make the commit our entry
1236 * now so that we will update it when needed.
1239 rb_set_commit_event(cpu_buffer
, event
);
1240 else if (!rb_is_commit(cpu_buffer
, event
))
1243 event
->time_delta
= delta
;
1248 static DEFINE_PER_CPU(int, rb_need_resched
);
1251 * ring_buffer_lock_reserve - reserve a part of the buffer
1252 * @buffer: the ring buffer to reserve from
1253 * @length: the length of the data to reserve (excluding event header)
1254 * @flags: a pointer to save the interrupt flags
1256 * Returns a reseverd event on the ring buffer to copy directly to.
1257 * The user of this interface will need to get the body to write into
1258 * and can use the ring_buffer_event_data() interface.
1260 * The length is the length of the data needed, not the event length
1261 * which also includes the event header.
1263 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1264 * If NULL is returned, then nothing has been allocated or locked.
1266 struct ring_buffer_event
*
1267 ring_buffer_lock_reserve(struct ring_buffer
*buffer
,
1268 unsigned long length
,
1269 unsigned long *flags
)
1271 struct ring_buffer_per_cpu
*cpu_buffer
;
1272 struct ring_buffer_event
*event
;
1275 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
1278 if (atomic_read(&buffer
->record_disabled
))
1281 /* If we are tracing schedule, we don't want to recurse */
1282 resched
= ftrace_preempt_disable();
1284 cpu
= raw_smp_processor_id();
1286 if (!cpu_isset(cpu
, buffer
->cpumask
))
1289 cpu_buffer
= buffer
->buffers
[cpu
];
1291 if (atomic_read(&cpu_buffer
->record_disabled
))
1294 length
= rb_calculate_event_length(length
);
1295 if (length
> BUF_PAGE_SIZE
)
1298 event
= rb_reserve_next_event(cpu_buffer
, RINGBUF_TYPE_DATA
, length
);
1303 * Need to store resched state on this cpu.
1304 * Only the first needs to.
1307 if (preempt_count() == 1)
1308 per_cpu(rb_need_resched
, cpu
) = resched
;
1313 ftrace_preempt_enable(resched
);
1316 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
1318 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1319 struct ring_buffer_event
*event
)
1321 cpu_buffer
->entries
++;
1323 /* Only process further if we own the commit */
1324 if (!rb_is_commit(cpu_buffer
, event
))
1327 cpu_buffer
->write_stamp
+= event
->time_delta
;
1329 rb_set_commit_to_write(cpu_buffer
);
1333 * ring_buffer_unlock_commit - commit a reserved
1334 * @buffer: The buffer to commit to
1335 * @event: The event pointer to commit.
1336 * @flags: the interrupt flags received from ring_buffer_lock_reserve.
1338 * This commits the data to the ring buffer, and releases any locks held.
1340 * Must be paired with ring_buffer_lock_reserve.
1342 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
1343 struct ring_buffer_event
*event
,
1344 unsigned long flags
)
1346 struct ring_buffer_per_cpu
*cpu_buffer
;
1347 int cpu
= raw_smp_processor_id();
1349 cpu_buffer
= buffer
->buffers
[cpu
];
1351 rb_commit(cpu_buffer
, event
);
1354 * Only the last preempt count needs to restore preemption.
1356 if (preempt_count() == 1)
1357 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
1359 preempt_enable_no_resched_notrace();
1363 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
1366 * ring_buffer_write - write data to the buffer without reserving
1367 * @buffer: The ring buffer to write to.
1368 * @length: The length of the data being written (excluding the event header)
1369 * @data: The data to write to the buffer.
1371 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1372 * one function. If you already have the data to write to the buffer, it
1373 * may be easier to simply call this function.
1375 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1376 * and not the length of the event which would hold the header.
1378 int ring_buffer_write(struct ring_buffer
*buffer
,
1379 unsigned long length
,
1382 struct ring_buffer_per_cpu
*cpu_buffer
;
1383 struct ring_buffer_event
*event
;
1384 unsigned long event_length
;
1389 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
1392 if (atomic_read(&buffer
->record_disabled
))
1395 resched
= ftrace_preempt_disable();
1397 cpu
= raw_smp_processor_id();
1399 if (!cpu_isset(cpu
, buffer
->cpumask
))
1402 cpu_buffer
= buffer
->buffers
[cpu
];
1404 if (atomic_read(&cpu_buffer
->record_disabled
))
1407 event_length
= rb_calculate_event_length(length
);
1408 event
= rb_reserve_next_event(cpu_buffer
,
1409 RINGBUF_TYPE_DATA
, event_length
);
1413 body
= rb_event_data(event
);
1415 memcpy(body
, data
, length
);
1417 rb_commit(cpu_buffer
, event
);
1421 ftrace_preempt_enable(resched
);
1425 EXPORT_SYMBOL_GPL(ring_buffer_write
);
1427 static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
1429 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
1430 struct buffer_page
*head
= cpu_buffer
->head_page
;
1431 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
1433 return reader
->read
== rb_page_commit(reader
) &&
1434 (commit
== reader
||
1436 head
->read
== rb_page_commit(commit
)));
1440 * ring_buffer_record_disable - stop all writes into the buffer
1441 * @buffer: The ring buffer to stop writes to.
1443 * This prevents all writes to the buffer. Any attempt to write
1444 * to the buffer after this will fail and return NULL.
1446 * The caller should call synchronize_sched() after this.
1448 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
1450 atomic_inc(&buffer
->record_disabled
);
1452 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
1455 * ring_buffer_record_enable - enable writes to the buffer
1456 * @buffer: The ring buffer to enable writes
1458 * Note, multiple disables will need the same number of enables
1459 * to truely enable the writing (much like preempt_disable).
1461 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
1463 atomic_dec(&buffer
->record_disabled
);
1465 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
1468 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1469 * @buffer: The ring buffer to stop writes to.
1470 * @cpu: The CPU buffer to stop
1472 * This prevents all writes to the buffer. Any attempt to write
1473 * to the buffer after this will fail and return NULL.
1475 * The caller should call synchronize_sched() after this.
1477 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
1479 struct ring_buffer_per_cpu
*cpu_buffer
;
1481 if (!cpu_isset(cpu
, buffer
->cpumask
))
1484 cpu_buffer
= buffer
->buffers
[cpu
];
1485 atomic_inc(&cpu_buffer
->record_disabled
);
1487 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
1490 * ring_buffer_record_enable_cpu - enable writes to the buffer
1491 * @buffer: The ring buffer to enable writes
1492 * @cpu: The CPU to enable.
1494 * Note, multiple disables will need the same number of enables
1495 * to truely enable the writing (much like preempt_disable).
1497 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
1499 struct ring_buffer_per_cpu
*cpu_buffer
;
1501 if (!cpu_isset(cpu
, buffer
->cpumask
))
1504 cpu_buffer
= buffer
->buffers
[cpu
];
1505 atomic_dec(&cpu_buffer
->record_disabled
);
1507 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
1510 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1511 * @buffer: The ring buffer
1512 * @cpu: The per CPU buffer to get the entries from.
1514 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
1516 struct ring_buffer_per_cpu
*cpu_buffer
;
1518 if (!cpu_isset(cpu
, buffer
->cpumask
))
1521 cpu_buffer
= buffer
->buffers
[cpu
];
1522 return cpu_buffer
->entries
;
1524 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
1527 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1528 * @buffer: The ring buffer
1529 * @cpu: The per CPU buffer to get the number of overruns from
1531 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
1533 struct ring_buffer_per_cpu
*cpu_buffer
;
1535 if (!cpu_isset(cpu
, buffer
->cpumask
))
1538 cpu_buffer
= buffer
->buffers
[cpu
];
1539 return cpu_buffer
->overrun
;
1541 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
1544 * ring_buffer_entries - get the number of entries in a buffer
1545 * @buffer: The ring buffer
1547 * Returns the total number of entries in the ring buffer
1550 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
1552 struct ring_buffer_per_cpu
*cpu_buffer
;
1553 unsigned long entries
= 0;
1556 /* if you care about this being correct, lock the buffer */
1557 for_each_buffer_cpu(buffer
, cpu
) {
1558 cpu_buffer
= buffer
->buffers
[cpu
];
1559 entries
+= cpu_buffer
->entries
;
1564 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
1567 * ring_buffer_overrun_cpu - get the number of overruns in buffer
1568 * @buffer: The ring buffer
1570 * Returns the total number of overruns in the ring buffer
1573 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
1575 struct ring_buffer_per_cpu
*cpu_buffer
;
1576 unsigned long overruns
= 0;
1579 /* if you care about this being correct, lock the buffer */
1580 for_each_buffer_cpu(buffer
, cpu
) {
1581 cpu_buffer
= buffer
->buffers
[cpu
];
1582 overruns
+= cpu_buffer
->overrun
;
1587 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
1589 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
1591 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1593 /* Iterator usage is expected to have record disabled */
1594 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
1595 iter
->head_page
= cpu_buffer
->head_page
;
1596 iter
->head
= cpu_buffer
->head_page
->read
;
1598 iter
->head_page
= cpu_buffer
->reader_page
;
1599 iter
->head
= cpu_buffer
->reader_page
->read
;
1602 iter
->read_stamp
= cpu_buffer
->read_stamp
;
1604 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1608 * ring_buffer_iter_reset - reset an iterator
1609 * @iter: The iterator to reset
1611 * Resets the iterator, so that it will start from the beginning
1614 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
1616 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1617 unsigned long flags
;
1619 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1620 rb_iter_reset(iter
);
1621 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1623 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
1626 * ring_buffer_iter_empty - check if an iterator has no more to read
1627 * @iter: The iterator to check
1629 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
1631 struct ring_buffer_per_cpu
*cpu_buffer
;
1633 cpu_buffer
= iter
->cpu_buffer
;
1635 return iter
->head_page
== cpu_buffer
->commit_page
&&
1636 iter
->head
== rb_commit_index(cpu_buffer
);
1638 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
1641 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1642 struct ring_buffer_event
*event
)
1646 switch (event
->type
) {
1647 case RINGBUF_TYPE_PADDING
:
1650 case RINGBUF_TYPE_TIME_EXTEND
:
1651 delta
= event
->array
[0];
1653 delta
+= event
->time_delta
;
1654 cpu_buffer
->read_stamp
+= delta
;
1657 case RINGBUF_TYPE_TIME_STAMP
:
1658 /* FIXME: not implemented */
1661 case RINGBUF_TYPE_DATA
:
1662 cpu_buffer
->read_stamp
+= event
->time_delta
;
1672 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
1673 struct ring_buffer_event
*event
)
1677 switch (event
->type
) {
1678 case RINGBUF_TYPE_PADDING
:
1681 case RINGBUF_TYPE_TIME_EXTEND
:
1682 delta
= event
->array
[0];
1684 delta
+= event
->time_delta
;
1685 iter
->read_stamp
+= delta
;
1688 case RINGBUF_TYPE_TIME_STAMP
:
1689 /* FIXME: not implemented */
1692 case RINGBUF_TYPE_DATA
:
1693 iter
->read_stamp
+= event
->time_delta
;
1702 static struct buffer_page
*
1703 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1705 struct buffer_page
*reader
= NULL
;
1706 unsigned long flags
;
1709 local_irq_save(flags
);
1710 __raw_spin_lock(&cpu_buffer
->lock
);
1714 * This should normally only loop twice. But because the
1715 * start of the reader inserts an empty page, it causes
1716 * a case where we will loop three times. There should be no
1717 * reason to loop four times (that I know of).
1719 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
1724 reader
= cpu_buffer
->reader_page
;
1726 /* If there's more to read, return this page */
1727 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
1730 /* Never should we have an index greater than the size */
1731 if (RB_WARN_ON(cpu_buffer
,
1732 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
1735 /* check if we caught up to the tail */
1737 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
1741 * Splice the empty reader page into the list around the head.
1742 * Reset the reader page to size zero.
1745 reader
= cpu_buffer
->head_page
;
1746 cpu_buffer
->reader_page
->list
.next
= reader
->list
.next
;
1747 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
1749 local_set(&cpu_buffer
->reader_page
->write
, 0);
1750 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
1752 /* Make the reader page now replace the head */
1753 reader
->list
.prev
->next
= &cpu_buffer
->reader_page
->list
;
1754 reader
->list
.next
->prev
= &cpu_buffer
->reader_page
->list
;
1757 * If the tail is on the reader, then we must set the head
1758 * to the inserted page, otherwise we set it one before.
1760 cpu_buffer
->head_page
= cpu_buffer
->reader_page
;
1762 if (cpu_buffer
->commit_page
!= reader
)
1763 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
1765 /* Finally update the reader page to the new head */
1766 cpu_buffer
->reader_page
= reader
;
1767 rb_reset_reader_page(cpu_buffer
);
1772 __raw_spin_unlock(&cpu_buffer
->lock
);
1773 local_irq_restore(flags
);
1778 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
1780 struct ring_buffer_event
*event
;
1781 struct buffer_page
*reader
;
1784 reader
= rb_get_reader_page(cpu_buffer
);
1786 /* This function should not be called when buffer is empty */
1787 if (RB_WARN_ON(cpu_buffer
, !reader
))
1790 event
= rb_reader_event(cpu_buffer
);
1792 if (event
->type
== RINGBUF_TYPE_DATA
)
1793 cpu_buffer
->entries
--;
1795 rb_update_read_stamp(cpu_buffer
, event
);
1797 length
= rb_event_length(event
);
1798 cpu_buffer
->reader_page
->read
+= length
;
1801 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
1803 struct ring_buffer
*buffer
;
1804 struct ring_buffer_per_cpu
*cpu_buffer
;
1805 struct ring_buffer_event
*event
;
1808 cpu_buffer
= iter
->cpu_buffer
;
1809 buffer
= cpu_buffer
->buffer
;
1812 * Check if we are at the end of the buffer.
1814 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
1815 if (RB_WARN_ON(buffer
,
1816 iter
->head_page
== cpu_buffer
->commit_page
))
1822 event
= rb_iter_head_event(iter
);
1824 length
= rb_event_length(event
);
1827 * This should not be called to advance the header if we are
1828 * at the tail of the buffer.
1830 if (RB_WARN_ON(cpu_buffer
,
1831 (iter
->head_page
== cpu_buffer
->commit_page
) &&
1832 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
1835 rb_update_iter_read_stamp(iter
, event
);
1837 iter
->head
+= length
;
1839 /* check for end of page padding */
1840 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
1841 (iter
->head_page
!= cpu_buffer
->commit_page
))
1842 rb_advance_iter(iter
);
1845 static struct ring_buffer_event
*
1846 rb_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1848 struct ring_buffer_per_cpu
*cpu_buffer
;
1849 struct ring_buffer_event
*event
;
1850 struct buffer_page
*reader
;
1853 if (!cpu_isset(cpu
, buffer
->cpumask
))
1856 cpu_buffer
= buffer
->buffers
[cpu
];
1860 * We repeat when a timestamp is encountered. It is possible
1861 * to get multiple timestamps from an interrupt entering just
1862 * as one timestamp is about to be written. The max times
1863 * that this can happen is the number of nested interrupts we
1864 * can have. Nesting 10 deep of interrupts is clearly
1867 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 10))
1870 reader
= rb_get_reader_page(cpu_buffer
);
1874 event
= rb_reader_event(cpu_buffer
);
1876 switch (event
->type
) {
1877 case RINGBUF_TYPE_PADDING
:
1878 RB_WARN_ON(cpu_buffer
, 1);
1879 rb_advance_reader(cpu_buffer
);
1882 case RINGBUF_TYPE_TIME_EXTEND
:
1883 /* Internal data, OK to advance */
1884 rb_advance_reader(cpu_buffer
);
1887 case RINGBUF_TYPE_TIME_STAMP
:
1888 /* FIXME: not implemented */
1889 rb_advance_reader(cpu_buffer
);
1892 case RINGBUF_TYPE_DATA
:
1894 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
1895 ring_buffer_normalize_time_stamp(cpu_buffer
->cpu
, ts
);
1905 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
1907 static struct ring_buffer_event
*
1908 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
1910 struct ring_buffer
*buffer
;
1911 struct ring_buffer_per_cpu
*cpu_buffer
;
1912 struct ring_buffer_event
*event
;
1915 if (ring_buffer_iter_empty(iter
))
1918 cpu_buffer
= iter
->cpu_buffer
;
1919 buffer
= cpu_buffer
->buffer
;
1923 * We repeat when a timestamp is encountered. It is possible
1924 * to get multiple timestamps from an interrupt entering just
1925 * as one timestamp is about to be written. The max times
1926 * that this can happen is the number of nested interrupts we
1927 * can have. Nesting 10 deep of interrupts is clearly
1930 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 10))
1933 if (rb_per_cpu_empty(cpu_buffer
))
1936 event
= rb_iter_head_event(iter
);
1938 switch (event
->type
) {
1939 case RINGBUF_TYPE_PADDING
:
1943 case RINGBUF_TYPE_TIME_EXTEND
:
1944 /* Internal data, OK to advance */
1945 rb_advance_iter(iter
);
1948 case RINGBUF_TYPE_TIME_STAMP
:
1949 /* FIXME: not implemented */
1950 rb_advance_iter(iter
);
1953 case RINGBUF_TYPE_DATA
:
1955 *ts
= iter
->read_stamp
+ event
->time_delta
;
1956 ring_buffer_normalize_time_stamp(cpu_buffer
->cpu
, ts
);
1966 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
1969 * ring_buffer_peek - peek at the next event to be read
1970 * @buffer: The ring buffer to read
1971 * @cpu: The cpu to peak at
1972 * @ts: The timestamp counter of this event.
1974 * This will return the event that will be read next, but does
1975 * not consume the data.
1977 struct ring_buffer_event
*
1978 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
1980 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
1981 struct ring_buffer_event
*event
;
1982 unsigned long flags
;
1984 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1985 event
= rb_buffer_peek(buffer
, cpu
, ts
);
1986 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1992 * ring_buffer_iter_peek - peek at the next event to be read
1993 * @iter: The ring buffer iterator
1994 * @ts: The timestamp counter of this event.
1996 * This will return the event that will be read next, but does
1997 * not increment the iterator.
1999 struct ring_buffer_event
*
2000 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
2002 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2003 struct ring_buffer_event
*event
;
2004 unsigned long flags
;
2006 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2007 event
= rb_iter_peek(iter
, ts
);
2008 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2014 * ring_buffer_consume - return an event and consume it
2015 * @buffer: The ring buffer to get the next event from
2017 * Returns the next event in the ring buffer, and that event is consumed.
2018 * Meaning, that sequential reads will keep returning a different event,
2019 * and eventually empty the ring buffer if the producer is slower.
2021 struct ring_buffer_event
*
2022 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
2024 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2025 struct ring_buffer_event
*event
;
2026 unsigned long flags
;
2028 if (!cpu_isset(cpu
, buffer
->cpumask
))
2031 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2033 event
= rb_buffer_peek(buffer
, cpu
, ts
);
2037 rb_advance_reader(cpu_buffer
);
2040 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2044 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
2047 * ring_buffer_read_start - start a non consuming read of the buffer
2048 * @buffer: The ring buffer to read from
2049 * @cpu: The cpu buffer to iterate over
2051 * This starts up an iteration through the buffer. It also disables
2052 * the recording to the buffer until the reading is finished.
2053 * This prevents the reading from being corrupted. This is not
2054 * a consuming read, so a producer is not expected.
2056 * Must be paired with ring_buffer_finish.
2058 struct ring_buffer_iter
*
2059 ring_buffer_read_start(struct ring_buffer
*buffer
, int cpu
)
2061 struct ring_buffer_per_cpu
*cpu_buffer
;
2062 struct ring_buffer_iter
*iter
;
2063 unsigned long flags
;
2065 if (!cpu_isset(cpu
, buffer
->cpumask
))
2068 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
2072 cpu_buffer
= buffer
->buffers
[cpu
];
2074 iter
->cpu_buffer
= cpu_buffer
;
2076 atomic_inc(&cpu_buffer
->record_disabled
);
2077 synchronize_sched();
2079 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2080 __raw_spin_lock(&cpu_buffer
->lock
);
2081 rb_iter_reset(iter
);
2082 __raw_spin_unlock(&cpu_buffer
->lock
);
2083 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2087 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
2090 * ring_buffer_finish - finish reading the iterator of the buffer
2091 * @iter: The iterator retrieved by ring_buffer_start
2093 * This re-enables the recording to the buffer, and frees the
2097 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
2099 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2101 atomic_dec(&cpu_buffer
->record_disabled
);
2104 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
2107 * ring_buffer_read - read the next item in the ring buffer by the iterator
2108 * @iter: The ring buffer iterator
2109 * @ts: The time stamp of the event read.
2111 * This reads the next event in the ring buffer and increments the iterator.
2113 struct ring_buffer_event
*
2114 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
2116 struct ring_buffer_event
*event
;
2117 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2118 unsigned long flags
;
2120 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2121 event
= rb_iter_peek(iter
, ts
);
2125 rb_advance_iter(iter
);
2127 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2131 EXPORT_SYMBOL_GPL(ring_buffer_read
);
2134 * ring_buffer_size - return the size of the ring buffer (in bytes)
2135 * @buffer: The ring buffer.
2137 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
2139 return BUF_PAGE_SIZE
* buffer
->pages
;
2141 EXPORT_SYMBOL_GPL(ring_buffer_size
);
2144 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
2146 cpu_buffer
->head_page
2147 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
2148 local_set(&cpu_buffer
->head_page
->write
, 0);
2149 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
2151 cpu_buffer
->head_page
->read
= 0;
2153 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
2154 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
2156 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
2157 local_set(&cpu_buffer
->reader_page
->write
, 0);
2158 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
2159 cpu_buffer
->reader_page
->read
= 0;
2161 cpu_buffer
->overrun
= 0;
2162 cpu_buffer
->entries
= 0;
2166 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2167 * @buffer: The ring buffer to reset a per cpu buffer of
2168 * @cpu: The CPU buffer to be reset
2170 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
2172 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2173 unsigned long flags
;
2175 if (!cpu_isset(cpu
, buffer
->cpumask
))
2178 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2180 __raw_spin_lock(&cpu_buffer
->lock
);
2182 rb_reset_cpu(cpu_buffer
);
2184 __raw_spin_unlock(&cpu_buffer
->lock
);
2186 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2188 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
2191 * ring_buffer_reset - reset a ring buffer
2192 * @buffer: The ring buffer to reset all cpu buffers
2194 void ring_buffer_reset(struct ring_buffer
*buffer
)
2198 for_each_buffer_cpu(buffer
, cpu
)
2199 ring_buffer_reset_cpu(buffer
, cpu
);
2201 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
2204 * rind_buffer_empty - is the ring buffer empty?
2205 * @buffer: The ring buffer to test
2207 int ring_buffer_empty(struct ring_buffer
*buffer
)
2209 struct ring_buffer_per_cpu
*cpu_buffer
;
2212 /* yes this is racy, but if you don't like the race, lock the buffer */
2213 for_each_buffer_cpu(buffer
, cpu
) {
2214 cpu_buffer
= buffer
->buffers
[cpu
];
2215 if (!rb_per_cpu_empty(cpu_buffer
))
2220 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
2223 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2224 * @buffer: The ring buffer
2225 * @cpu: The CPU buffer to test
2227 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
2229 struct ring_buffer_per_cpu
*cpu_buffer
;
2231 if (!cpu_isset(cpu
, buffer
->cpumask
))
2234 cpu_buffer
= buffer
->buffers
[cpu
];
2235 return rb_per_cpu_empty(cpu_buffer
);
2237 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
2240 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2241 * @buffer_a: One buffer to swap with
2242 * @buffer_b: The other buffer to swap with
2244 * This function is useful for tracers that want to take a "snapshot"
2245 * of a CPU buffer and has another back up buffer lying around.
2246 * it is expected that the tracer handles the cpu buffer not being
2247 * used at the moment.
2249 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
2250 struct ring_buffer
*buffer_b
, int cpu
)
2252 struct ring_buffer_per_cpu
*cpu_buffer_a
;
2253 struct ring_buffer_per_cpu
*cpu_buffer_b
;
2255 if (!cpu_isset(cpu
, buffer_a
->cpumask
) ||
2256 !cpu_isset(cpu
, buffer_b
->cpumask
))
2259 /* At least make sure the two buffers are somewhat the same */
2260 if (buffer_a
->pages
!= buffer_b
->pages
)
2263 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
2264 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
2267 * We can't do a synchronize_sched here because this
2268 * function can be called in atomic context.
2269 * Normally this will be called from the same CPU as cpu.
2270 * If not it's up to the caller to protect this.
2272 atomic_inc(&cpu_buffer_a
->record_disabled
);
2273 atomic_inc(&cpu_buffer_b
->record_disabled
);
2275 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
2276 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
2278 cpu_buffer_b
->buffer
= buffer_a
;
2279 cpu_buffer_a
->buffer
= buffer_b
;
2281 atomic_dec(&cpu_buffer_a
->record_disabled
);
2282 atomic_dec(&cpu_buffer_b
->record_disabled
);
2286 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
2288 static void rb_remove_entries(struct ring_buffer_per_cpu
*cpu_buffer
,
2289 struct buffer_data_page
*bpage
)
2291 struct ring_buffer_event
*event
;
2294 __raw_spin_lock(&cpu_buffer
->lock
);
2295 for (head
= 0; head
< local_read(&bpage
->commit
);
2296 head
+= rb_event_length(event
)) {
2298 event
= __rb_data_page_index(bpage
, head
);
2299 if (RB_WARN_ON(cpu_buffer
, rb_null_event(event
)))
2301 /* Only count data entries */
2302 if (event
->type
!= RINGBUF_TYPE_DATA
)
2304 cpu_buffer
->entries
--;
2306 __raw_spin_unlock(&cpu_buffer
->lock
);
2310 * ring_buffer_alloc_read_page - allocate a page to read from buffer
2311 * @buffer: the buffer to allocate for.
2313 * This function is used in conjunction with ring_buffer_read_page.
2314 * When reading a full page from the ring buffer, these functions
2315 * can be used to speed up the process. The calling function should
2316 * allocate a few pages first with this function. Then when it
2317 * needs to get pages from the ring buffer, it passes the result
2318 * of this function into ring_buffer_read_page, which will swap
2319 * the page that was allocated, with the read page of the buffer.
2322 * The page allocated, or NULL on error.
2324 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
)
2327 struct buffer_data_page
*bpage
;
2329 addr
= __get_free_page(GFP_KERNEL
);
2333 bpage
= (void *)addr
;
2339 * ring_buffer_free_read_page - free an allocated read page
2340 * @buffer: the buffer the page was allocate for
2341 * @data: the page to free
2343 * Free a page allocated from ring_buffer_alloc_read_page.
2345 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
2347 free_page((unsigned long)data
);
2351 * ring_buffer_read_page - extract a page from the ring buffer
2352 * @buffer: buffer to extract from
2353 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
2354 * @cpu: the cpu of the buffer to extract
2355 * @full: should the extraction only happen when the page is full.
2357 * This function will pull out a page from the ring buffer and consume it.
2358 * @data_page must be the address of the variable that was returned
2359 * from ring_buffer_alloc_read_page. This is because the page might be used
2360 * to swap with a page in the ring buffer.
2363 * rpage = ring_buffer_alloc_page(buffer);
2366 * ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
2368 * process_page(rpage);
2370 * When @full is set, the function will not return true unless
2371 * the writer is off the reader page.
2373 * Note: it is up to the calling functions to handle sleeps and wakeups.
2374 * The ring buffer can be used anywhere in the kernel and can not
2375 * blindly call wake_up. The layer that uses the ring buffer must be
2376 * responsible for that.
2379 * 1 if data has been transferred
2380 * 0 if no data has been transferred.
2382 int ring_buffer_read_page(struct ring_buffer
*buffer
,
2383 void **data_page
, int cpu
, int full
)
2385 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2386 struct ring_buffer_event
*event
;
2387 struct buffer_data_page
*bpage
;
2388 unsigned long flags
;
2398 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2401 * rb_buffer_peek will get the next ring buffer if
2402 * the current reader page is empty.
2404 event
= rb_buffer_peek(buffer
, cpu
, NULL
);
2408 /* check for data */
2409 if (!local_read(&cpu_buffer
->reader_page
->page
->commit
))
2412 * If the writer is already off of the read page, then simply
2413 * switch the read page with the given page. Otherwise
2414 * we need to copy the data from the reader to the writer.
2416 if (cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
2417 unsigned int read
= cpu_buffer
->reader_page
->read
;
2421 /* The writer is still on the reader page, we must copy */
2422 bpage
= cpu_buffer
->reader_page
->page
;
2424 cpu_buffer
->reader_page
->page
->data
+ read
,
2425 local_read(&bpage
->commit
) - read
);
2427 /* consume what was read */
2428 cpu_buffer
->reader_page
+= read
;
2431 /* swap the pages */
2432 rb_init_page(bpage
);
2433 bpage
= cpu_buffer
->reader_page
->page
;
2434 cpu_buffer
->reader_page
->page
= *data_page
;
2435 cpu_buffer
->reader_page
->read
= 0;
2440 /* update the entry counter */
2441 rb_remove_entries(cpu_buffer
, bpage
);
2443 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2449 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
2450 size_t cnt
, loff_t
*ppos
)
2452 long *p
= filp
->private_data
;
2456 if (test_bit(RB_BUFFERS_DISABLED_BIT
, p
))
2457 r
= sprintf(buf
, "permanently disabled\n");
2459 r
= sprintf(buf
, "%d\n", test_bit(RB_BUFFERS_ON_BIT
, p
));
2461 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
2465 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
2466 size_t cnt
, loff_t
*ppos
)
2468 long *p
= filp
->private_data
;
2473 if (cnt
>= sizeof(buf
))
2476 if (copy_from_user(&buf
, ubuf
, cnt
))
2481 ret
= strict_strtoul(buf
, 10, &val
);
2486 set_bit(RB_BUFFERS_ON_BIT
, p
);
2488 clear_bit(RB_BUFFERS_ON_BIT
, p
);
2495 static struct file_operations rb_simple_fops
= {
2496 .open
= tracing_open_generic
,
2497 .read
= rb_simple_read
,
2498 .write
= rb_simple_write
,
2502 static __init
int rb_init_debugfs(void)
2504 struct dentry
*d_tracer
;
2505 struct dentry
*entry
;
2507 d_tracer
= tracing_init_dentry();
2509 entry
= debugfs_create_file("tracing_on", 0644, d_tracer
,
2510 &ring_buffer_flags
, &rb_simple_fops
);
2512 pr_warning("Could not create debugfs 'tracing_on' entry\n");
2517 fs_initcall(rb_init_debugfs
);