4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 #include <linux/ring_buffer.h>
7 #include <linux/trace_clock.h>
8 #include <linux/ftrace_irq.h>
9 #include <linux/spinlock.h>
10 #include <linux/debugfs.h>
11 #include <linux/uaccess.h>
12 #include <linux/hardirq.h>
13 #include <linux/kmemcheck.h>
14 #include <linux/module.h>
15 #include <linux/percpu.h>
16 #include <linux/mutex.h>
17 #include <linux/slab.h>
18 #include <linux/init.h>
19 #include <linux/hash.h>
20 #include <linux/list.h>
21 #include <linux/cpu.h>
24 #include <asm/local.h>
28 * The ring buffer header is special. We must manually up keep it.
30 int ring_buffer_print_entry_header(struct trace_seq
*s
)
34 ret
= trace_seq_printf(s
, "# compressed entry header\n");
35 ret
= trace_seq_printf(s
, "\ttype_len : 5 bits\n");
36 ret
= trace_seq_printf(s
, "\ttime_delta : 27 bits\n");
37 ret
= trace_seq_printf(s
, "\tarray : 32 bits\n");
38 ret
= trace_seq_printf(s
, "\n");
39 ret
= trace_seq_printf(s
, "\tpadding : type == %d\n",
40 RINGBUF_TYPE_PADDING
);
41 ret
= trace_seq_printf(s
, "\ttime_extend : type == %d\n",
42 RINGBUF_TYPE_TIME_EXTEND
);
43 ret
= trace_seq_printf(s
, "\tdata max type_len == %d\n",
44 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
50 * The ring buffer is made up of a list of pages. A separate list of pages is
51 * allocated for each CPU. A writer may only write to a buffer that is
52 * associated with the CPU it is currently executing on. A reader may read
53 * from any per cpu buffer.
55 * The reader is special. For each per cpu buffer, the reader has its own
56 * reader page. When a reader has read the entire reader page, this reader
57 * page is swapped with another page in the ring buffer.
59 * Now, as long as the writer is off the reader page, the reader can do what
60 * ever it wants with that page. The writer will never write to that page
61 * again (as long as it is out of the ring buffer).
63 * Here's some silly ASCII art.
66 * |reader| RING BUFFER
68 * +------+ +---+ +---+ +---+
77 * |reader| RING BUFFER
78 * |page |------------------v
79 * +------+ +---+ +---+ +---+
88 * |reader| RING BUFFER
89 * |page |------------------v
90 * +------+ +---+ +---+ +---+
95 * +------------------------------+
99 * |buffer| RING BUFFER
100 * |page |------------------v
101 * +------+ +---+ +---+ +---+
103 * | New +---+ +---+ +---+
106 * +------------------------------+
109 * After we make this swap, the reader can hand this page off to the splice
110 * code and be done with it. It can even allocate a new page if it needs to
111 * and swap that into the ring buffer.
113 * We will be using cmpxchg soon to make all this lockless.
118 * A fast way to enable or disable all ring buffers is to
119 * call tracing_on or tracing_off. Turning off the ring buffers
120 * prevents all ring buffers from being recorded to.
121 * Turning this switch on, makes it OK to write to the
122 * ring buffer, if the ring buffer is enabled itself.
124 * There's three layers that must be on in order to write
125 * to the ring buffer.
127 * 1) This global flag must be set.
128 * 2) The ring buffer must be enabled for recording.
129 * 3) The per cpu buffer must be enabled for recording.
131 * In case of an anomaly, this global flag has a bit set that
132 * will permantly disable all ring buffers.
136 * Global flag to disable all recording to ring buffers
137 * This has two bits: ON, DISABLED
141 * 0 0 : ring buffers are off
142 * 1 0 : ring buffers are on
143 * X 1 : ring buffers are permanently disabled
147 RB_BUFFERS_ON_BIT
= 0,
148 RB_BUFFERS_DISABLED_BIT
= 1,
152 RB_BUFFERS_ON
= 1 << RB_BUFFERS_ON_BIT
,
153 RB_BUFFERS_DISABLED
= 1 << RB_BUFFERS_DISABLED_BIT
,
156 static unsigned long ring_buffer_flags __read_mostly
= RB_BUFFERS_ON
;
158 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
161 * tracing_on - enable all tracing buffers
163 * This function enables all tracing buffers that may have been
164 * disabled with tracing_off.
166 void tracing_on(void)
168 set_bit(RB_BUFFERS_ON_BIT
, &ring_buffer_flags
);
170 EXPORT_SYMBOL_GPL(tracing_on
);
173 * tracing_off - turn off all tracing buffers
175 * This function stops all tracing buffers from recording data.
176 * It does not disable any overhead the tracers themselves may
177 * be causing. This function simply causes all recording to
178 * the ring buffers to fail.
180 void tracing_off(void)
182 clear_bit(RB_BUFFERS_ON_BIT
, &ring_buffer_flags
);
184 EXPORT_SYMBOL_GPL(tracing_off
);
187 * tracing_off_permanent - permanently disable ring buffers
189 * This function, once called, will disable all ring buffers
192 void tracing_off_permanent(void)
194 set_bit(RB_BUFFERS_DISABLED_BIT
, &ring_buffer_flags
);
198 * tracing_is_on - show state of ring buffers enabled
200 int tracing_is_on(void)
202 return ring_buffer_flags
== RB_BUFFERS_ON
;
204 EXPORT_SYMBOL_GPL(tracing_is_on
);
206 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
207 #define RB_ALIGNMENT 4U
208 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
209 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
211 #if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
212 # define RB_FORCE_8BYTE_ALIGNMENT 0
213 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
215 # define RB_FORCE_8BYTE_ALIGNMENT 1
216 # define RB_ARCH_ALIGNMENT 8U
219 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
220 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
223 RB_LEN_TIME_EXTEND
= 8,
224 RB_LEN_TIME_STAMP
= 16,
227 static inline int rb_null_event(struct ring_buffer_event
*event
)
229 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
232 static void rb_event_set_padding(struct ring_buffer_event
*event
)
234 /* padding has a NULL time_delta */
235 event
->type_len
= RINGBUF_TYPE_PADDING
;
236 event
->time_delta
= 0;
240 rb_event_data_length(struct ring_buffer_event
*event
)
245 length
= event
->type_len
* RB_ALIGNMENT
;
247 length
= event
->array
[0];
248 return length
+ RB_EVNT_HDR_SIZE
;
251 /* inline for ring buffer fast paths */
253 rb_event_length(struct ring_buffer_event
*event
)
255 switch (event
->type_len
) {
256 case RINGBUF_TYPE_PADDING
:
257 if (rb_null_event(event
))
260 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
262 case RINGBUF_TYPE_TIME_EXTEND
:
263 return RB_LEN_TIME_EXTEND
;
265 case RINGBUF_TYPE_TIME_STAMP
:
266 return RB_LEN_TIME_STAMP
;
268 case RINGBUF_TYPE_DATA
:
269 return rb_event_data_length(event
);
278 * ring_buffer_event_length - return the length of the event
279 * @event: the event to get the length of
281 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
283 unsigned length
= rb_event_length(event
);
284 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
286 length
-= RB_EVNT_HDR_SIZE
;
287 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
288 length
-= sizeof(event
->array
[0]);
291 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
293 /* inline for ring buffer fast paths */
295 rb_event_data(struct ring_buffer_event
*event
)
297 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
298 /* If length is in len field, then array[0] has the data */
300 return (void *)&event
->array
[0];
301 /* Otherwise length is in array[0] and array[1] has the data */
302 return (void *)&event
->array
[1];
306 * ring_buffer_event_data - return the data of the event
307 * @event: the event to get the data from
309 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
311 return rb_event_data(event
);
313 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
315 #define for_each_buffer_cpu(buffer, cpu) \
316 for_each_cpu(cpu, buffer->cpumask)
319 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
320 #define TS_DELTA_TEST (~TS_MASK)
322 /* Flag when events were overwritten */
323 #define RB_MISSED_EVENTS (1 << 31)
324 /* Missed count stored at end */
325 #define RB_MISSED_STORED (1 << 30)
327 struct buffer_data_page
{
328 u64 time_stamp
; /* page time stamp */
329 local_t commit
; /* write committed index */
330 unsigned char data
[]; /* data of buffer page */
334 * Note, the buffer_page list must be first. The buffer pages
335 * are allocated in cache lines, which means that each buffer
336 * page will be at the beginning of a cache line, and thus
337 * the least significant bits will be zero. We use this to
338 * add flags in the list struct pointers, to make the ring buffer
342 struct list_head list
; /* list of buffer pages */
343 local_t write
; /* index for next write */
344 unsigned read
; /* index for next read */
345 local_t entries
; /* entries on this page */
346 unsigned long real_end
; /* real end of data */
347 struct buffer_data_page
*page
; /* Actual data page */
351 * The buffer page counters, write and entries, must be reset
352 * atomically when crossing page boundaries. To synchronize this
353 * update, two counters are inserted into the number. One is
354 * the actual counter for the write position or count on the page.
356 * The other is a counter of updaters. Before an update happens
357 * the update partition of the counter is incremented. This will
358 * allow the updater to update the counter atomically.
360 * The counter is 20 bits, and the state data is 12.
362 #define RB_WRITE_MASK 0xfffff
363 #define RB_WRITE_INTCNT (1 << 20)
365 static void rb_init_page(struct buffer_data_page
*bpage
)
367 local_set(&bpage
->commit
, 0);
371 * ring_buffer_page_len - the size of data on the page.
372 * @page: The page to read
374 * Returns the amount of data on the page, including buffer page header.
376 size_t ring_buffer_page_len(void *page
)
378 return local_read(&((struct buffer_data_page
*)page
)->commit
)
383 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
386 static void free_buffer_page(struct buffer_page
*bpage
)
388 free_page((unsigned long)bpage
->page
);
393 * We need to fit the time_stamp delta into 27 bits.
395 static inline int test_time_stamp(u64 delta
)
397 if (delta
& TS_DELTA_TEST
)
402 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
404 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
405 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
407 /* Max number of timestamps that can fit on a page */
408 #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_EXTEND)
410 int ring_buffer_print_page_header(struct trace_seq
*s
)
412 struct buffer_data_page field
;
415 ret
= trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
416 "offset:0;\tsize:%u;\tsigned:%u;\n",
417 (unsigned int)sizeof(field
.time_stamp
),
418 (unsigned int)is_signed_type(u64
));
420 ret
= trace_seq_printf(s
, "\tfield: local_t commit;\t"
421 "offset:%u;\tsize:%u;\tsigned:%u;\n",
422 (unsigned int)offsetof(typeof(field
), commit
),
423 (unsigned int)sizeof(field
.commit
),
424 (unsigned int)is_signed_type(long));
426 ret
= trace_seq_printf(s
, "\tfield: int overwrite;\t"
427 "offset:%u;\tsize:%u;\tsigned:%u;\n",
428 (unsigned int)offsetof(typeof(field
), commit
),
430 (unsigned int)is_signed_type(long));
432 ret
= trace_seq_printf(s
, "\tfield: char data;\t"
433 "offset:%u;\tsize:%u;\tsigned:%u;\n",
434 (unsigned int)offsetof(typeof(field
), data
),
435 (unsigned int)BUF_PAGE_SIZE
,
436 (unsigned int)is_signed_type(char));
442 * head_page == tail_page && head == tail then buffer is empty.
444 struct ring_buffer_per_cpu
{
446 atomic_t record_disabled
;
447 struct ring_buffer
*buffer
;
448 spinlock_t reader_lock
; /* serialize readers */
449 arch_spinlock_t lock
;
450 struct lock_class_key lock_key
;
451 struct list_head
*pages
;
452 struct buffer_page
*head_page
; /* read from head */
453 struct buffer_page
*tail_page
; /* write to tail */
454 struct buffer_page
*commit_page
; /* committed pages */
455 struct buffer_page
*reader_page
;
456 unsigned long lost_events
;
457 unsigned long last_overrun
;
458 local_t commit_overrun
;
472 atomic_t record_disabled
;
473 cpumask_var_t cpumask
;
475 struct lock_class_key
*reader_lock_key
;
479 struct ring_buffer_per_cpu
**buffers
;
481 #ifdef CONFIG_HOTPLUG_CPU
482 struct notifier_block cpu_notify
;
487 struct ring_buffer_iter
{
488 struct ring_buffer_per_cpu
*cpu_buffer
;
490 struct buffer_page
*head_page
;
491 struct buffer_page
*cache_reader_page
;
492 unsigned long cache_read
;
496 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
497 #define RB_WARN_ON(b, cond) \
499 int _____ret = unlikely(cond); \
501 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
502 struct ring_buffer_per_cpu *__b = \
504 atomic_inc(&__b->buffer->record_disabled); \
506 atomic_inc(&b->record_disabled); \
512 /* Up this if you want to test the TIME_EXTENTS and normalization */
513 #define DEBUG_SHIFT 0
515 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
517 /* shift to debug/test normalization and TIME_EXTENTS */
518 return buffer
->clock() << DEBUG_SHIFT
;
521 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
525 preempt_disable_notrace();
526 time
= rb_time_stamp(buffer
);
527 preempt_enable_no_resched_notrace();
531 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
533 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
536 /* Just stupid testing the normalize function and deltas */
539 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
542 * Making the ring buffer lockless makes things tricky.
543 * Although writes only happen on the CPU that they are on,
544 * and they only need to worry about interrupts. Reads can
547 * The reader page is always off the ring buffer, but when the
548 * reader finishes with a page, it needs to swap its page with
549 * a new one from the buffer. The reader needs to take from
550 * the head (writes go to the tail). But if a writer is in overwrite
551 * mode and wraps, it must push the head page forward.
553 * Here lies the problem.
555 * The reader must be careful to replace only the head page, and
556 * not another one. As described at the top of the file in the
557 * ASCII art, the reader sets its old page to point to the next
558 * page after head. It then sets the page after head to point to
559 * the old reader page. But if the writer moves the head page
560 * during this operation, the reader could end up with the tail.
562 * We use cmpxchg to help prevent this race. We also do something
563 * special with the page before head. We set the LSB to 1.
565 * When the writer must push the page forward, it will clear the
566 * bit that points to the head page, move the head, and then set
567 * the bit that points to the new head page.
569 * We also don't want an interrupt coming in and moving the head
570 * page on another writer. Thus we use the second LSB to catch
573 * head->list->prev->next bit 1 bit 0
576 * Points to head page 0 1
579 * Note we can not trust the prev pointer of the head page, because:
581 * +----+ +-----+ +-----+
582 * | |------>| T |---X--->| N |
584 * +----+ +-----+ +-----+
587 * +----------| R |----------+ |
591 * Key: ---X--> HEAD flag set in pointer
596 * (see __rb_reserve_next() to see where this happens)
598 * What the above shows is that the reader just swapped out
599 * the reader page with a page in the buffer, but before it
600 * could make the new header point back to the new page added
601 * it was preempted by a writer. The writer moved forward onto
602 * the new page added by the reader and is about to move forward
605 * You can see, it is legitimate for the previous pointer of
606 * the head (or any page) not to point back to itself. But only
610 #define RB_PAGE_NORMAL 0UL
611 #define RB_PAGE_HEAD 1UL
612 #define RB_PAGE_UPDATE 2UL
615 #define RB_FLAG_MASK 3UL
617 /* PAGE_MOVED is not part of the mask */
618 #define RB_PAGE_MOVED 4UL
621 * rb_list_head - remove any bit
623 static struct list_head
*rb_list_head(struct list_head
*list
)
625 unsigned long val
= (unsigned long)list
;
627 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
631 * rb_is_head_page - test if the given page is the head page
633 * Because the reader may move the head_page pointer, we can
634 * not trust what the head page is (it may be pointing to
635 * the reader page). But if the next page is a header page,
636 * its flags will be non zero.
639 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
640 struct buffer_page
*page
, struct list_head
*list
)
644 val
= (unsigned long)list
->next
;
646 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
647 return RB_PAGE_MOVED
;
649 return val
& RB_FLAG_MASK
;
655 * The unique thing about the reader page, is that, if the
656 * writer is ever on it, the previous pointer never points
657 * back to the reader page.
659 static int rb_is_reader_page(struct buffer_page
*page
)
661 struct list_head
*list
= page
->list
.prev
;
663 return rb_list_head(list
->next
) != &page
->list
;
667 * rb_set_list_to_head - set a list_head to be pointing to head.
669 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
670 struct list_head
*list
)
674 ptr
= (unsigned long *)&list
->next
;
675 *ptr
|= RB_PAGE_HEAD
;
676 *ptr
&= ~RB_PAGE_UPDATE
;
680 * rb_head_page_activate - sets up head page
682 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
684 struct buffer_page
*head
;
686 head
= cpu_buffer
->head_page
;
691 * Set the previous list pointer to have the HEAD flag.
693 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
696 static void rb_list_head_clear(struct list_head
*list
)
698 unsigned long *ptr
= (unsigned long *)&list
->next
;
700 *ptr
&= ~RB_FLAG_MASK
;
704 * rb_head_page_dactivate - clears head page ptr (for free list)
707 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
709 struct list_head
*hd
;
711 /* Go through the whole list and clear any pointers found. */
712 rb_list_head_clear(cpu_buffer
->pages
);
714 list_for_each(hd
, cpu_buffer
->pages
)
715 rb_list_head_clear(hd
);
718 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
719 struct buffer_page
*head
,
720 struct buffer_page
*prev
,
721 int old_flag
, int new_flag
)
723 struct list_head
*list
;
724 unsigned long val
= (unsigned long)&head
->list
;
729 val
&= ~RB_FLAG_MASK
;
731 ret
= cmpxchg((unsigned long *)&list
->next
,
732 val
| old_flag
, val
| new_flag
);
734 /* check if the reader took the page */
735 if ((ret
& ~RB_FLAG_MASK
) != val
)
736 return RB_PAGE_MOVED
;
738 return ret
& RB_FLAG_MASK
;
741 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
742 struct buffer_page
*head
,
743 struct buffer_page
*prev
,
746 return rb_head_page_set(cpu_buffer
, head
, prev
,
747 old_flag
, RB_PAGE_UPDATE
);
750 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
751 struct buffer_page
*head
,
752 struct buffer_page
*prev
,
755 return rb_head_page_set(cpu_buffer
, head
, prev
,
756 old_flag
, RB_PAGE_HEAD
);
759 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
760 struct buffer_page
*head
,
761 struct buffer_page
*prev
,
764 return rb_head_page_set(cpu_buffer
, head
, prev
,
765 old_flag
, RB_PAGE_NORMAL
);
768 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
769 struct buffer_page
**bpage
)
771 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
773 *bpage
= list_entry(p
, struct buffer_page
, list
);
776 static struct buffer_page
*
777 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
779 struct buffer_page
*head
;
780 struct buffer_page
*page
;
781 struct list_head
*list
;
784 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
788 list
= cpu_buffer
->pages
;
789 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
792 page
= head
= cpu_buffer
->head_page
;
794 * It is possible that the writer moves the header behind
795 * where we started, and we miss in one loop.
796 * A second loop should grab the header, but we'll do
797 * three loops just because I'm paranoid.
799 for (i
= 0; i
< 3; i
++) {
801 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
802 cpu_buffer
->head_page
= page
;
805 rb_inc_page(cpu_buffer
, &page
);
806 } while (page
!= head
);
809 RB_WARN_ON(cpu_buffer
, 1);
814 static int rb_head_page_replace(struct buffer_page
*old
,
815 struct buffer_page
*new)
817 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
821 val
= *ptr
& ~RB_FLAG_MASK
;
824 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
830 * rb_tail_page_update - move the tail page forward
832 * Returns 1 if moved tail page, 0 if someone else did.
834 static int rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
835 struct buffer_page
*tail_page
,
836 struct buffer_page
*next_page
)
838 struct buffer_page
*old_tail
;
839 unsigned long old_entries
;
840 unsigned long old_write
;
844 * The tail page now needs to be moved forward.
846 * We need to reset the tail page, but without messing
847 * with possible erasing of data brought in by interrupts
848 * that have moved the tail page and are currently on it.
850 * We add a counter to the write field to denote this.
852 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
853 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
856 * Just make sure we have seen our old_write and synchronize
857 * with any interrupts that come in.
862 * If the tail page is still the same as what we think
863 * it is, then it is up to us to update the tail
866 if (tail_page
== cpu_buffer
->tail_page
) {
867 /* Zero the write counter */
868 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
869 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
872 * This will only succeed if an interrupt did
873 * not come in and change it. In which case, we
874 * do not want to modify it.
876 * We add (void) to let the compiler know that we do not care
877 * about the return value of these functions. We use the
878 * cmpxchg to only update if an interrupt did not already
879 * do it for us. If the cmpxchg fails, we don't care.
881 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
882 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
885 * No need to worry about races with clearing out the commit.
886 * it only can increment when a commit takes place. But that
887 * only happens in the outer most nested commit.
889 local_set(&next_page
->page
->commit
, 0);
891 old_tail
= cmpxchg(&cpu_buffer
->tail_page
,
892 tail_page
, next_page
);
894 if (old_tail
== tail_page
)
901 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
902 struct buffer_page
*bpage
)
904 unsigned long val
= (unsigned long)bpage
;
906 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
913 * rb_check_list - make sure a pointer to a list has the last bits zero
915 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
916 struct list_head
*list
)
918 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
920 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
926 * check_pages - integrity check of buffer pages
927 * @cpu_buffer: CPU buffer with pages to test
929 * As a safety measure we check to make sure the data pages have not
932 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
934 struct list_head
*head
= cpu_buffer
->pages
;
935 struct buffer_page
*bpage
, *tmp
;
937 rb_head_page_deactivate(cpu_buffer
);
939 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
941 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
944 if (rb_check_list(cpu_buffer
, head
))
947 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
948 if (RB_WARN_ON(cpu_buffer
,
949 bpage
->list
.next
->prev
!= &bpage
->list
))
951 if (RB_WARN_ON(cpu_buffer
,
952 bpage
->list
.prev
->next
!= &bpage
->list
))
954 if (rb_check_list(cpu_buffer
, &bpage
->list
))
958 rb_head_page_activate(cpu_buffer
);
963 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
966 struct buffer_page
*bpage
, *tmp
;
973 for (i
= 0; i
< nr_pages
; i
++) {
974 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
975 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
979 rb_check_bpage(cpu_buffer
, bpage
);
981 list_add(&bpage
->list
, &pages
);
983 addr
= __get_free_page(GFP_KERNEL
);
986 bpage
->page
= (void *)addr
;
987 rb_init_page(bpage
->page
);
991 * The ring buffer page list is a circular list that does not
992 * start and end with a list head. All page list items point to
995 cpu_buffer
->pages
= pages
.next
;
998 rb_check_pages(cpu_buffer
);
1003 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
1004 list_del_init(&bpage
->list
);
1005 free_buffer_page(bpage
);
1010 static struct ring_buffer_per_cpu
*
1011 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
1013 struct ring_buffer_per_cpu
*cpu_buffer
;
1014 struct buffer_page
*bpage
;
1018 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1019 GFP_KERNEL
, cpu_to_node(cpu
));
1023 cpu_buffer
->cpu
= cpu
;
1024 cpu_buffer
->buffer
= buffer
;
1025 spin_lock_init(&cpu_buffer
->reader_lock
);
1026 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1027 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1029 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1030 GFP_KERNEL
, cpu_to_node(cpu
));
1032 goto fail_free_buffer
;
1034 rb_check_bpage(cpu_buffer
, bpage
);
1036 cpu_buffer
->reader_page
= bpage
;
1037 addr
= __get_free_page(GFP_KERNEL
);
1039 goto fail_free_reader
;
1040 bpage
->page
= (void *)addr
;
1041 rb_init_page(bpage
->page
);
1043 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1045 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
1047 goto fail_free_reader
;
1049 cpu_buffer
->head_page
1050 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1051 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1053 rb_head_page_activate(cpu_buffer
);
1058 free_buffer_page(cpu_buffer
->reader_page
);
1065 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1067 struct list_head
*head
= cpu_buffer
->pages
;
1068 struct buffer_page
*bpage
, *tmp
;
1070 free_buffer_page(cpu_buffer
->reader_page
);
1072 rb_head_page_deactivate(cpu_buffer
);
1075 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1076 list_del_init(&bpage
->list
);
1077 free_buffer_page(bpage
);
1079 bpage
= list_entry(head
, struct buffer_page
, list
);
1080 free_buffer_page(bpage
);
1086 #ifdef CONFIG_HOTPLUG_CPU
1087 static int rb_cpu_notify(struct notifier_block
*self
,
1088 unsigned long action
, void *hcpu
);
1092 * ring_buffer_alloc - allocate a new ring_buffer
1093 * @size: the size in bytes per cpu that is needed.
1094 * @flags: attributes to set for the ring buffer.
1096 * Currently the only flag that is available is the RB_FL_OVERWRITE
1097 * flag. This flag means that the buffer will overwrite old data
1098 * when the buffer wraps. If this flag is not set, the buffer will
1099 * drop data when the tail hits the head.
1101 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1102 struct lock_class_key
*key
)
1104 struct ring_buffer
*buffer
;
1108 /* keep it in its own cache line */
1109 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1114 if (!alloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1115 goto fail_free_buffer
;
1117 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1118 buffer
->flags
= flags
;
1119 buffer
->clock
= trace_clock_local
;
1120 buffer
->reader_lock_key
= key
;
1122 /* need at least two pages */
1123 if (buffer
->pages
< 2)
1127 * In case of non-hotplug cpu, if the ring-buffer is allocated
1128 * in early initcall, it will not be notified of secondary cpus.
1129 * In that off case, we need to allocate for all possible cpus.
1131 #ifdef CONFIG_HOTPLUG_CPU
1133 cpumask_copy(buffer
->cpumask
, cpu_online_mask
);
1135 cpumask_copy(buffer
->cpumask
, cpu_possible_mask
);
1137 buffer
->cpus
= nr_cpu_ids
;
1139 bsize
= sizeof(void *) * nr_cpu_ids
;
1140 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1142 if (!buffer
->buffers
)
1143 goto fail_free_cpumask
;
1145 for_each_buffer_cpu(buffer
, cpu
) {
1146 buffer
->buffers
[cpu
] =
1147 rb_allocate_cpu_buffer(buffer
, cpu
);
1148 if (!buffer
->buffers
[cpu
])
1149 goto fail_free_buffers
;
1152 #ifdef CONFIG_HOTPLUG_CPU
1153 buffer
->cpu_notify
.notifier_call
= rb_cpu_notify
;
1154 buffer
->cpu_notify
.priority
= 0;
1155 register_cpu_notifier(&buffer
->cpu_notify
);
1159 mutex_init(&buffer
->mutex
);
1164 for_each_buffer_cpu(buffer
, cpu
) {
1165 if (buffer
->buffers
[cpu
])
1166 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1168 kfree(buffer
->buffers
);
1171 free_cpumask_var(buffer
->cpumask
);
1178 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1181 * ring_buffer_free - free a ring buffer.
1182 * @buffer: the buffer to free.
1185 ring_buffer_free(struct ring_buffer
*buffer
)
1191 #ifdef CONFIG_HOTPLUG_CPU
1192 unregister_cpu_notifier(&buffer
->cpu_notify
);
1195 for_each_buffer_cpu(buffer
, cpu
)
1196 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1200 kfree(buffer
->buffers
);
1201 free_cpumask_var(buffer
->cpumask
);
1205 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1207 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1210 buffer
->clock
= clock
;
1213 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1216 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
1218 struct buffer_page
*bpage
;
1219 struct list_head
*p
;
1222 spin_lock_irq(&cpu_buffer
->reader_lock
);
1223 rb_head_page_deactivate(cpu_buffer
);
1225 for (i
= 0; i
< nr_pages
; i
++) {
1226 if (RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
)))
1228 p
= cpu_buffer
->pages
->next
;
1229 bpage
= list_entry(p
, struct buffer_page
, list
);
1230 list_del_init(&bpage
->list
);
1231 free_buffer_page(bpage
);
1233 if (RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
)))
1236 rb_reset_cpu(cpu_buffer
);
1237 rb_check_pages(cpu_buffer
);
1240 spin_unlock_irq(&cpu_buffer
->reader_lock
);
1244 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1245 struct list_head
*pages
, unsigned nr_pages
)
1247 struct buffer_page
*bpage
;
1248 struct list_head
*p
;
1251 spin_lock_irq(&cpu_buffer
->reader_lock
);
1252 rb_head_page_deactivate(cpu_buffer
);
1254 for (i
= 0; i
< nr_pages
; i
++) {
1255 if (RB_WARN_ON(cpu_buffer
, list_empty(pages
)))
1258 bpage
= list_entry(p
, struct buffer_page
, list
);
1259 list_del_init(&bpage
->list
);
1260 list_add_tail(&bpage
->list
, cpu_buffer
->pages
);
1262 rb_reset_cpu(cpu_buffer
);
1263 rb_check_pages(cpu_buffer
);
1266 spin_unlock_irq(&cpu_buffer
->reader_lock
);
1270 * ring_buffer_resize - resize the ring buffer
1271 * @buffer: the buffer to resize.
1272 * @size: the new size.
1274 * Minimum size is 2 * BUF_PAGE_SIZE.
1276 * Returns -1 on failure.
1278 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
1280 struct ring_buffer_per_cpu
*cpu_buffer
;
1281 unsigned nr_pages
, rm_pages
, new_pages
;
1282 struct buffer_page
*bpage
, *tmp
;
1283 unsigned long buffer_size
;
1289 * Always succeed at resizing a non-existent buffer:
1294 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1295 size
*= BUF_PAGE_SIZE
;
1296 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
1298 /* we need a minimum of two pages */
1299 if (size
< BUF_PAGE_SIZE
* 2)
1300 size
= BUF_PAGE_SIZE
* 2;
1302 if (size
== buffer_size
)
1305 atomic_inc(&buffer
->record_disabled
);
1307 /* Make sure all writers are done with this buffer. */
1308 synchronize_sched();
1310 mutex_lock(&buffer
->mutex
);
1313 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1315 if (size
< buffer_size
) {
1317 /* easy case, just free pages */
1318 if (RB_WARN_ON(buffer
, nr_pages
>= buffer
->pages
))
1321 rm_pages
= buffer
->pages
- nr_pages
;
1323 for_each_buffer_cpu(buffer
, cpu
) {
1324 cpu_buffer
= buffer
->buffers
[cpu
];
1325 rb_remove_pages(cpu_buffer
, rm_pages
);
1331 * This is a bit more difficult. We only want to add pages
1332 * when we can allocate enough for all CPUs. We do this
1333 * by allocating all the pages and storing them on a local
1334 * link list. If we succeed in our allocation, then we
1335 * add these pages to the cpu_buffers. Otherwise we just free
1336 * them all and return -ENOMEM;
1338 if (RB_WARN_ON(buffer
, nr_pages
<= buffer
->pages
))
1341 new_pages
= nr_pages
- buffer
->pages
;
1343 for_each_buffer_cpu(buffer
, cpu
) {
1344 for (i
= 0; i
< new_pages
; i
++) {
1345 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
),
1347 GFP_KERNEL
, cpu_to_node(cpu
));
1350 list_add(&bpage
->list
, &pages
);
1351 addr
= __get_free_page(GFP_KERNEL
);
1354 bpage
->page
= (void *)addr
;
1355 rb_init_page(bpage
->page
);
1359 for_each_buffer_cpu(buffer
, cpu
) {
1360 cpu_buffer
= buffer
->buffers
[cpu
];
1361 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
1364 if (RB_WARN_ON(buffer
, !list_empty(&pages
)))
1368 buffer
->pages
= nr_pages
;
1370 mutex_unlock(&buffer
->mutex
);
1372 atomic_dec(&buffer
->record_disabled
);
1377 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
1378 list_del_init(&bpage
->list
);
1379 free_buffer_page(bpage
);
1382 mutex_unlock(&buffer
->mutex
);
1383 atomic_dec(&buffer
->record_disabled
);
1387 * Something went totally wrong, and we are too paranoid
1388 * to even clean up the mess.
1392 mutex_unlock(&buffer
->mutex
);
1393 atomic_dec(&buffer
->record_disabled
);
1396 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1398 static inline void *
1399 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
1401 return bpage
->data
+ index
;
1404 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1406 return bpage
->page
->data
+ index
;
1409 static inline struct ring_buffer_event
*
1410 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1412 return __rb_page_index(cpu_buffer
->reader_page
,
1413 cpu_buffer
->reader_page
->read
);
1416 static inline struct ring_buffer_event
*
1417 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1419 return __rb_page_index(iter
->head_page
, iter
->head
);
1422 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1424 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1427 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
1429 return local_read(&bpage
->page
->commit
);
1432 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1434 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1437 /* Size is determined by what has been commited */
1438 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
1440 return rb_page_commit(bpage
);
1443 static inline unsigned
1444 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1446 return rb_page_commit(cpu_buffer
->commit_page
);
1449 static inline unsigned
1450 rb_event_index(struct ring_buffer_event
*event
)
1452 unsigned long addr
= (unsigned long)event
;
1454 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1458 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1459 struct ring_buffer_event
*event
)
1461 unsigned long addr
= (unsigned long)event
;
1462 unsigned long index
;
1464 index
= rb_event_index(event
);
1467 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
1468 rb_commit_index(cpu_buffer
) == index
;
1472 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
1474 unsigned long max_count
;
1477 * We only race with interrupts and NMIs on this CPU.
1478 * If we own the commit event, then we can commit
1479 * all others that interrupted us, since the interruptions
1480 * are in stack format (they finish before they come
1481 * back to us). This allows us to do a simple loop to
1482 * assign the commit to the tail.
1485 max_count
= cpu_buffer
->buffer
->pages
* 100;
1487 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
1488 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
1490 if (RB_WARN_ON(cpu_buffer
,
1491 rb_is_reader_page(cpu_buffer
->tail_page
)))
1493 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1494 rb_page_write(cpu_buffer
->commit_page
));
1495 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
1496 cpu_buffer
->write_stamp
=
1497 cpu_buffer
->commit_page
->page
->time_stamp
;
1498 /* add barrier to keep gcc from optimizing too much */
1501 while (rb_commit_index(cpu_buffer
) !=
1502 rb_page_write(cpu_buffer
->commit_page
)) {
1504 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1505 rb_page_write(cpu_buffer
->commit_page
));
1506 RB_WARN_ON(cpu_buffer
,
1507 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
1512 /* again, keep gcc from optimizing */
1516 * If an interrupt came in just after the first while loop
1517 * and pushed the tail page forward, we will be left with
1518 * a dangling commit that will never go forward.
1520 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
1524 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1526 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
1527 cpu_buffer
->reader_page
->read
= 0;
1530 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1532 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1535 * The iterator could be on the reader page (it starts there).
1536 * But the head could have moved, since the reader was
1537 * found. Check for this case and assign the iterator
1538 * to the head page instead of next.
1540 if (iter
->head_page
== cpu_buffer
->reader_page
)
1541 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1543 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1545 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1550 * ring_buffer_update_event - update event type and data
1551 * @event: the even to update
1552 * @type: the type of event
1553 * @length: the size of the event field in the ring buffer
1555 * Update the type and data fields of the event. The length
1556 * is the actual size that is written to the ring buffer,
1557 * and with this, we can determine what to place into the
1561 rb_update_event(struct ring_buffer_event
*event
,
1562 unsigned type
, unsigned length
)
1564 event
->type_len
= type
;
1568 case RINGBUF_TYPE_PADDING
:
1569 case RINGBUF_TYPE_TIME_EXTEND
:
1570 case RINGBUF_TYPE_TIME_STAMP
:
1574 length
-= RB_EVNT_HDR_SIZE
;
1575 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
1576 event
->array
[0] = length
;
1578 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
1586 * rb_handle_head_page - writer hit the head page
1588 * Returns: +1 to retry page
1593 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1594 struct buffer_page
*tail_page
,
1595 struct buffer_page
*next_page
)
1597 struct buffer_page
*new_head
;
1602 entries
= rb_page_entries(next_page
);
1605 * The hard part is here. We need to move the head
1606 * forward, and protect against both readers on
1607 * other CPUs and writers coming in via interrupts.
1609 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1613 * type can be one of four:
1614 * NORMAL - an interrupt already moved it for us
1615 * HEAD - we are the first to get here.
1616 * UPDATE - we are the interrupt interrupting
1618 * MOVED - a reader on another CPU moved the next
1619 * pointer to its reader page. Give up
1626 * We changed the head to UPDATE, thus
1627 * it is our responsibility to update
1630 local_add(entries
, &cpu_buffer
->overrun
);
1633 * The entries will be zeroed out when we move the
1637 /* still more to do */
1640 case RB_PAGE_UPDATE
:
1642 * This is an interrupt that interrupt the
1643 * previous update. Still more to do.
1646 case RB_PAGE_NORMAL
:
1648 * An interrupt came in before the update
1649 * and processed this for us.
1650 * Nothing left to do.
1655 * The reader is on another CPU and just did
1656 * a swap with our next_page.
1661 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
1666 * Now that we are here, the old head pointer is
1667 * set to UPDATE. This will keep the reader from
1668 * swapping the head page with the reader page.
1669 * The reader (on another CPU) will spin till
1672 * We just need to protect against interrupts
1673 * doing the job. We will set the next pointer
1674 * to HEAD. After that, we set the old pointer
1675 * to NORMAL, but only if it was HEAD before.
1676 * otherwise we are an interrupt, and only
1677 * want the outer most commit to reset it.
1679 new_head
= next_page
;
1680 rb_inc_page(cpu_buffer
, &new_head
);
1682 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
1686 * Valid returns are:
1687 * HEAD - an interrupt came in and already set it.
1688 * NORMAL - One of two things:
1689 * 1) We really set it.
1690 * 2) A bunch of interrupts came in and moved
1691 * the page forward again.
1695 case RB_PAGE_NORMAL
:
1699 RB_WARN_ON(cpu_buffer
, 1);
1704 * It is possible that an interrupt came in,
1705 * set the head up, then more interrupts came in
1706 * and moved it again. When we get back here,
1707 * the page would have been set to NORMAL but we
1708 * just set it back to HEAD.
1710 * How do you detect this? Well, if that happened
1711 * the tail page would have moved.
1713 if (ret
== RB_PAGE_NORMAL
) {
1715 * If the tail had moved passed next, then we need
1716 * to reset the pointer.
1718 if (cpu_buffer
->tail_page
!= tail_page
&&
1719 cpu_buffer
->tail_page
!= next_page
)
1720 rb_head_page_set_normal(cpu_buffer
, new_head
,
1726 * If this was the outer most commit (the one that
1727 * changed the original pointer from HEAD to UPDATE),
1728 * then it is up to us to reset it to NORMAL.
1730 if (type
== RB_PAGE_HEAD
) {
1731 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
1734 if (RB_WARN_ON(cpu_buffer
,
1735 ret
!= RB_PAGE_UPDATE
))
1742 static unsigned rb_calculate_event_length(unsigned length
)
1744 struct ring_buffer_event event
; /* Used only for sizeof array */
1746 /* zero length can cause confusions */
1750 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
1751 length
+= sizeof(event
.array
[0]);
1753 length
+= RB_EVNT_HDR_SIZE
;
1754 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
1760 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1761 struct buffer_page
*tail_page
,
1762 unsigned long tail
, unsigned long length
)
1764 struct ring_buffer_event
*event
;
1767 * Only the event that crossed the page boundary
1768 * must fill the old tail_page with padding.
1770 if (tail
>= BUF_PAGE_SIZE
) {
1772 * If the page was filled, then we still need
1773 * to update the real_end. Reset it to zero
1774 * and the reader will ignore it.
1776 if (tail
== BUF_PAGE_SIZE
)
1777 tail_page
->real_end
= 0;
1779 local_sub(length
, &tail_page
->write
);
1783 event
= __rb_page_index(tail_page
, tail
);
1784 kmemcheck_annotate_bitfield(event
, bitfield
);
1787 * Save the original length to the meta data.
1788 * This will be used by the reader to add lost event
1791 tail_page
->real_end
= tail
;
1794 * If this event is bigger than the minimum size, then
1795 * we need to be careful that we don't subtract the
1796 * write counter enough to allow another writer to slip
1798 * We put in a discarded commit instead, to make sure
1799 * that this space is not used again.
1801 * If we are less than the minimum size, we don't need to
1804 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
1805 /* No room for any events */
1807 /* Mark the rest of the page with padding */
1808 rb_event_set_padding(event
);
1810 /* Set the write back to the previous setting */
1811 local_sub(length
, &tail_page
->write
);
1815 /* Put in a discarded event */
1816 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
1817 event
->type_len
= RINGBUF_TYPE_PADDING
;
1818 /* time delta must be non zero */
1819 event
->time_delta
= 1;
1821 /* Set write to end of buffer */
1822 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
1823 local_sub(length
, &tail_page
->write
);
1827 * This is the slow path, force gcc not to inline it.
1829 static noinline
struct ring_buffer_event
*
1830 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1831 unsigned long length
, unsigned long tail
,
1832 struct buffer_page
*tail_page
, u64
*ts
)
1834 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
1835 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
1836 struct buffer_page
*next_page
;
1839 next_page
= tail_page
;
1841 rb_inc_page(cpu_buffer
, &next_page
);
1844 * If for some reason, we had an interrupt storm that made
1845 * it all the way around the buffer, bail, and warn
1848 if (unlikely(next_page
== commit_page
)) {
1849 local_inc(&cpu_buffer
->commit_overrun
);
1854 * This is where the fun begins!
1856 * We are fighting against races between a reader that
1857 * could be on another CPU trying to swap its reader
1858 * page with the buffer head.
1860 * We are also fighting against interrupts coming in and
1861 * moving the head or tail on us as well.
1863 * If the next page is the head page then we have filled
1864 * the buffer, unless the commit page is still on the
1867 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
1870 * If the commit is not on the reader page, then
1871 * move the header page.
1873 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
1875 * If we are not in overwrite mode,
1876 * this is easy, just stop here.
1878 if (!(buffer
->flags
& RB_FL_OVERWRITE
))
1881 ret
= rb_handle_head_page(cpu_buffer
,
1890 * We need to be careful here too. The
1891 * commit page could still be on the reader
1892 * page. We could have a small buffer, and
1893 * have filled up the buffer with events
1894 * from interrupts and such, and wrapped.
1896 * Note, if the tail page is also the on the
1897 * reader_page, we let it move out.
1899 if (unlikely((cpu_buffer
->commit_page
!=
1900 cpu_buffer
->tail_page
) &&
1901 (cpu_buffer
->commit_page
==
1902 cpu_buffer
->reader_page
))) {
1903 local_inc(&cpu_buffer
->commit_overrun
);
1909 ret
= rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
1912 * Nested commits always have zero deltas, so
1913 * just reread the time stamp
1915 *ts
= rb_time_stamp(buffer
);
1916 next_page
->page
->time_stamp
= *ts
;
1921 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1923 /* fail and let the caller try again */
1924 return ERR_PTR(-EAGAIN
);
1928 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1933 static struct ring_buffer_event
*
1934 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
1935 unsigned type
, unsigned long length
, u64
*ts
)
1937 struct buffer_page
*tail_page
;
1938 struct ring_buffer_event
*event
;
1939 unsigned long tail
, write
;
1941 tail_page
= cpu_buffer
->tail_page
;
1942 write
= local_add_return(length
, &tail_page
->write
);
1944 /* set write to only the index of the write */
1945 write
&= RB_WRITE_MASK
;
1946 tail
= write
- length
;
1948 /* See if we shot pass the end of this buffer page */
1949 if (unlikely(write
> BUF_PAGE_SIZE
))
1950 return rb_move_tail(cpu_buffer
, length
, tail
,
1953 /* We reserved something on the buffer */
1955 event
= __rb_page_index(tail_page
, tail
);
1956 kmemcheck_annotate_bitfield(event
, bitfield
);
1957 rb_update_event(event
, type
, length
);
1959 /* The passed in type is zero for DATA */
1961 local_inc(&tail_page
->entries
);
1964 * If this is the first commit on the page, then update
1968 tail_page
->page
->time_stamp
= *ts
;
1974 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
1975 struct ring_buffer_event
*event
)
1977 unsigned long new_index
, old_index
;
1978 struct buffer_page
*bpage
;
1979 unsigned long index
;
1982 new_index
= rb_event_index(event
);
1983 old_index
= new_index
+ rb_event_length(event
);
1984 addr
= (unsigned long)event
;
1987 bpage
= cpu_buffer
->tail_page
;
1989 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
1990 unsigned long write_mask
=
1991 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
1993 * This is on the tail page. It is possible that
1994 * a write could come in and move the tail page
1995 * and write to the next page. That is fine
1996 * because we just shorten what is on this page.
1998 old_index
+= write_mask
;
1999 new_index
+= write_mask
;
2000 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2001 if (index
== old_index
)
2005 /* could not discard */
2010 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2011 u64
*ts
, u64
*delta
)
2013 struct ring_buffer_event
*event
;
2016 WARN_ONCE(*delta
> (1ULL << 59),
2017 KERN_WARNING
"Delta way too big! %llu ts=%llu write stamp = %llu\n",
2018 (unsigned long long)*delta
,
2019 (unsigned long long)*ts
,
2020 (unsigned long long)cpu_buffer
->write_stamp
);
2023 * The delta is too big, we to add a
2026 event
= __rb_reserve_next(cpu_buffer
,
2027 RINGBUF_TYPE_TIME_EXTEND
,
2033 if (PTR_ERR(event
) == -EAGAIN
)
2036 /* Only a commited time event can update the write stamp */
2037 if (rb_event_is_commit(cpu_buffer
, event
)) {
2039 * If this is the first on the page, then it was
2040 * updated with the page itself. Try to discard it
2041 * and if we can't just make it zero.
2043 if (rb_event_index(event
)) {
2044 event
->time_delta
= *delta
& TS_MASK
;
2045 event
->array
[0] = *delta
>> TS_SHIFT
;
2047 /* try to discard, since we do not need this */
2048 if (!rb_try_to_discard(cpu_buffer
, event
)) {
2049 /* nope, just zero it */
2050 event
->time_delta
= 0;
2051 event
->array
[0] = 0;
2054 cpu_buffer
->write_stamp
= *ts
;
2055 /* let the caller know this was the commit */
2058 /* Try to discard the event */
2059 if (!rb_try_to_discard(cpu_buffer
, event
)) {
2060 /* Darn, this is just wasted space */
2061 event
->time_delta
= 0;
2062 event
->array
[0] = 0;
2072 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2074 local_inc(&cpu_buffer
->committing
);
2075 local_inc(&cpu_buffer
->commits
);
2078 static void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2080 unsigned long commits
;
2082 if (RB_WARN_ON(cpu_buffer
,
2083 !local_read(&cpu_buffer
->committing
)))
2087 commits
= local_read(&cpu_buffer
->commits
);
2088 /* synchronize with interrupts */
2090 if (local_read(&cpu_buffer
->committing
) == 1)
2091 rb_set_commit_to_write(cpu_buffer
);
2093 local_dec(&cpu_buffer
->committing
);
2095 /* synchronize with interrupts */
2099 * Need to account for interrupts coming in between the
2100 * updating of the commit page and the clearing of the
2101 * committing counter.
2103 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2104 !local_read(&cpu_buffer
->committing
)) {
2105 local_inc(&cpu_buffer
->committing
);
2110 static struct ring_buffer_event
*
2111 rb_reserve_next_event(struct ring_buffer
*buffer
,
2112 struct ring_buffer_per_cpu
*cpu_buffer
,
2113 unsigned long length
)
2115 struct ring_buffer_event
*event
;
2120 rb_start_commit(cpu_buffer
);
2122 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2124 * Due to the ability to swap a cpu buffer from a buffer
2125 * it is possible it was swapped before we committed.
2126 * (committing stops a swap). We check for it here and
2127 * if it happened, we have to fail the write.
2130 if (unlikely(ACCESS_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2131 local_dec(&cpu_buffer
->committing
);
2132 local_dec(&cpu_buffer
->commits
);
2137 length
= rb_calculate_event_length(length
);
2140 * We allow for interrupts to reenter here and do a trace.
2141 * If one does, it will cause this original code to loop
2142 * back here. Even with heavy interrupts happening, this
2143 * should only happen a few times in a row. If this happens
2144 * 1000 times in a row, there must be either an interrupt
2145 * storm or we have something buggy.
2148 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2151 ts
= rb_time_stamp(cpu_buffer
->buffer
);
2154 * Only the first commit can update the timestamp.
2155 * Yes there is a race here. If an interrupt comes in
2156 * just after the conditional and it traces too, then it
2157 * will also check the deltas. More than one timestamp may
2158 * also be made. But only the entry that did the actual
2159 * commit will be something other than zero.
2161 if (likely(cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
2162 rb_page_write(cpu_buffer
->tail_page
) ==
2163 rb_commit_index(cpu_buffer
))) {
2166 diff
= ts
- cpu_buffer
->write_stamp
;
2168 /* make sure this diff is calculated here */
2171 /* Did the write stamp get updated already? */
2172 if (unlikely(ts
< cpu_buffer
->write_stamp
))
2176 if (unlikely(test_time_stamp(delta
))) {
2178 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
2179 if (commit
== -EBUSY
)
2182 if (commit
== -EAGAIN
)
2185 RB_WARN_ON(cpu_buffer
, commit
< 0);
2190 event
= __rb_reserve_next(cpu_buffer
, 0, length
, &ts
);
2191 if (unlikely(PTR_ERR(event
) == -EAGAIN
))
2197 if (!rb_event_is_commit(cpu_buffer
, event
))
2200 event
->time_delta
= delta
;
2205 rb_end_commit(cpu_buffer
);
2209 #ifdef CONFIG_TRACING
2211 #define TRACE_RECURSIVE_DEPTH 16
2213 static int trace_recursive_lock(void)
2215 current
->trace_recursion
++;
2217 if (likely(current
->trace_recursion
< TRACE_RECURSIVE_DEPTH
))
2220 /* Disable all tracing before we do anything else */
2221 tracing_off_permanent();
2223 printk_once(KERN_WARNING
"Tracing recursion: depth[%ld]:"
2224 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
2225 current
->trace_recursion
,
2226 hardirq_count() >> HARDIRQ_SHIFT
,
2227 softirq_count() >> SOFTIRQ_SHIFT
,
2234 static void trace_recursive_unlock(void)
2236 WARN_ON_ONCE(!current
->trace_recursion
);
2238 current
->trace_recursion
--;
2243 #define trace_recursive_lock() (0)
2244 #define trace_recursive_unlock() do { } while (0)
2249 * ring_buffer_lock_reserve - reserve a part of the buffer
2250 * @buffer: the ring buffer to reserve from
2251 * @length: the length of the data to reserve (excluding event header)
2253 * Returns a reseverd event on the ring buffer to copy directly to.
2254 * The user of this interface will need to get the body to write into
2255 * and can use the ring_buffer_event_data() interface.
2257 * The length is the length of the data needed, not the event length
2258 * which also includes the event header.
2260 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2261 * If NULL is returned, then nothing has been allocated or locked.
2263 struct ring_buffer_event
*
2264 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2266 struct ring_buffer_per_cpu
*cpu_buffer
;
2267 struct ring_buffer_event
*event
;
2270 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2273 /* If we are tracing schedule, we don't want to recurse */
2274 preempt_disable_notrace();
2276 if (atomic_read(&buffer
->record_disabled
))
2279 if (trace_recursive_lock())
2282 cpu
= raw_smp_processor_id();
2284 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2287 cpu_buffer
= buffer
->buffers
[cpu
];
2289 if (atomic_read(&cpu_buffer
->record_disabled
))
2292 if (length
> BUF_MAX_DATA_SIZE
)
2295 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2302 trace_recursive_unlock();
2305 preempt_enable_notrace();
2308 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2311 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2312 struct ring_buffer_event
*event
)
2315 * The event first in the commit queue updates the
2318 if (rb_event_is_commit(cpu_buffer
, event
))
2319 cpu_buffer
->write_stamp
+= event
->time_delta
;
2322 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2323 struct ring_buffer_event
*event
)
2325 local_inc(&cpu_buffer
->entries
);
2326 rb_update_write_stamp(cpu_buffer
, event
);
2327 rb_end_commit(cpu_buffer
);
2331 * ring_buffer_unlock_commit - commit a reserved
2332 * @buffer: The buffer to commit to
2333 * @event: The event pointer to commit.
2335 * This commits the data to the ring buffer, and releases any locks held.
2337 * Must be paired with ring_buffer_lock_reserve.
2339 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2340 struct ring_buffer_event
*event
)
2342 struct ring_buffer_per_cpu
*cpu_buffer
;
2343 int cpu
= raw_smp_processor_id();
2345 cpu_buffer
= buffer
->buffers
[cpu
];
2347 rb_commit(cpu_buffer
, event
);
2349 trace_recursive_unlock();
2351 preempt_enable_notrace();
2355 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2357 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2359 /* array[0] holds the actual length for the discarded event */
2360 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2361 event
->type_len
= RINGBUF_TYPE_PADDING
;
2362 /* time delta must be non zero */
2363 if (!event
->time_delta
)
2364 event
->time_delta
= 1;
2368 * Decrement the entries to the page that an event is on.
2369 * The event does not even need to exist, only the pointer
2370 * to the page it is on. This may only be called before the commit
2374 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2375 struct ring_buffer_event
*event
)
2377 unsigned long addr
= (unsigned long)event
;
2378 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2379 struct buffer_page
*start
;
2383 /* Do the likely case first */
2384 if (likely(bpage
->page
== (void *)addr
)) {
2385 local_dec(&bpage
->entries
);
2390 * Because the commit page may be on the reader page we
2391 * start with the next page and check the end loop there.
2393 rb_inc_page(cpu_buffer
, &bpage
);
2396 if (bpage
->page
== (void *)addr
) {
2397 local_dec(&bpage
->entries
);
2400 rb_inc_page(cpu_buffer
, &bpage
);
2401 } while (bpage
!= start
);
2403 /* commit not part of this buffer?? */
2404 RB_WARN_ON(cpu_buffer
, 1);
2408 * ring_buffer_commit_discard - discard an event that has not been committed
2409 * @buffer: the ring buffer
2410 * @event: non committed event to discard
2412 * Sometimes an event that is in the ring buffer needs to be ignored.
2413 * This function lets the user discard an event in the ring buffer
2414 * and then that event will not be read later.
2416 * This function only works if it is called before the the item has been
2417 * committed. It will try to free the event from the ring buffer
2418 * if another event has not been added behind it.
2420 * If another event has been added behind it, it will set the event
2421 * up as discarded, and perform the commit.
2423 * If this function is called, do not call ring_buffer_unlock_commit on
2426 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2427 struct ring_buffer_event
*event
)
2429 struct ring_buffer_per_cpu
*cpu_buffer
;
2432 /* The event is discarded regardless */
2433 rb_event_discard(event
);
2435 cpu
= smp_processor_id();
2436 cpu_buffer
= buffer
->buffers
[cpu
];
2439 * This must only be called if the event has not been
2440 * committed yet. Thus we can assume that preemption
2441 * is still disabled.
2443 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2445 rb_decrement_entry(cpu_buffer
, event
);
2446 if (rb_try_to_discard(cpu_buffer
, event
))
2450 * The commit is still visible by the reader, so we
2451 * must still update the timestamp.
2453 rb_update_write_stamp(cpu_buffer
, event
);
2455 rb_end_commit(cpu_buffer
);
2457 trace_recursive_unlock();
2459 preempt_enable_notrace();
2462 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2465 * ring_buffer_write - write data to the buffer without reserving
2466 * @buffer: The ring buffer to write to.
2467 * @length: The length of the data being written (excluding the event header)
2468 * @data: The data to write to the buffer.
2470 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2471 * one function. If you already have the data to write to the buffer, it
2472 * may be easier to simply call this function.
2474 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2475 * and not the length of the event which would hold the header.
2477 int ring_buffer_write(struct ring_buffer
*buffer
,
2478 unsigned long length
,
2481 struct ring_buffer_per_cpu
*cpu_buffer
;
2482 struct ring_buffer_event
*event
;
2487 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2490 preempt_disable_notrace();
2492 if (atomic_read(&buffer
->record_disabled
))
2495 cpu
= raw_smp_processor_id();
2497 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2500 cpu_buffer
= buffer
->buffers
[cpu
];
2502 if (atomic_read(&cpu_buffer
->record_disabled
))
2505 if (length
> BUF_MAX_DATA_SIZE
)
2508 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2512 body
= rb_event_data(event
);
2514 memcpy(body
, data
, length
);
2516 rb_commit(cpu_buffer
, event
);
2520 preempt_enable_notrace();
2524 EXPORT_SYMBOL_GPL(ring_buffer_write
);
2526 static int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
2528 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
2529 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
2530 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
2532 /* In case of error, head will be NULL */
2533 if (unlikely(!head
))
2536 return reader
->read
== rb_page_commit(reader
) &&
2537 (commit
== reader
||
2539 head
->read
== rb_page_commit(commit
)));
2543 * ring_buffer_record_disable - stop all writes into the buffer
2544 * @buffer: The ring buffer to stop writes to.
2546 * This prevents all writes to the buffer. Any attempt to write
2547 * to the buffer after this will fail and return NULL.
2549 * The caller should call synchronize_sched() after this.
2551 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
2553 atomic_inc(&buffer
->record_disabled
);
2555 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
2558 * ring_buffer_record_enable - enable writes to the buffer
2559 * @buffer: The ring buffer to enable writes
2561 * Note, multiple disables will need the same number of enables
2562 * to truly enable the writing (much like preempt_disable).
2564 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
2566 atomic_dec(&buffer
->record_disabled
);
2568 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
2571 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2572 * @buffer: The ring buffer to stop writes to.
2573 * @cpu: The CPU buffer to stop
2575 * This prevents all writes to the buffer. Any attempt to write
2576 * to the buffer after this will fail and return NULL.
2578 * The caller should call synchronize_sched() after this.
2580 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
2582 struct ring_buffer_per_cpu
*cpu_buffer
;
2584 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2587 cpu_buffer
= buffer
->buffers
[cpu
];
2588 atomic_inc(&cpu_buffer
->record_disabled
);
2590 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
2593 * ring_buffer_record_enable_cpu - enable writes to the buffer
2594 * @buffer: The ring buffer to enable writes
2595 * @cpu: The CPU to enable.
2597 * Note, multiple disables will need the same number of enables
2598 * to truly enable the writing (much like preempt_disable).
2600 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
2602 struct ring_buffer_per_cpu
*cpu_buffer
;
2604 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2607 cpu_buffer
= buffer
->buffers
[cpu
];
2608 atomic_dec(&cpu_buffer
->record_disabled
);
2610 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
2613 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2614 * @buffer: The ring buffer
2615 * @cpu: The per CPU buffer to get the entries from.
2617 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
2619 struct ring_buffer_per_cpu
*cpu_buffer
;
2622 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2625 cpu_buffer
= buffer
->buffers
[cpu
];
2626 ret
= (local_read(&cpu_buffer
->entries
) - local_read(&cpu_buffer
->overrun
))
2631 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
2634 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
2635 * @buffer: The ring buffer
2636 * @cpu: The per CPU buffer to get the number of overruns from
2638 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
2640 struct ring_buffer_per_cpu
*cpu_buffer
;
2643 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2646 cpu_buffer
= buffer
->buffers
[cpu
];
2647 ret
= local_read(&cpu_buffer
->overrun
);
2651 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
2654 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2655 * @buffer: The ring buffer
2656 * @cpu: The per CPU buffer to get the number of overruns from
2659 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
2661 struct ring_buffer_per_cpu
*cpu_buffer
;
2664 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2667 cpu_buffer
= buffer
->buffers
[cpu
];
2668 ret
= local_read(&cpu_buffer
->commit_overrun
);
2672 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
2675 * ring_buffer_entries - get the number of entries in a buffer
2676 * @buffer: The ring buffer
2678 * Returns the total number of entries in the ring buffer
2681 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
2683 struct ring_buffer_per_cpu
*cpu_buffer
;
2684 unsigned long entries
= 0;
2687 /* if you care about this being correct, lock the buffer */
2688 for_each_buffer_cpu(buffer
, cpu
) {
2689 cpu_buffer
= buffer
->buffers
[cpu
];
2690 entries
+= (local_read(&cpu_buffer
->entries
) -
2691 local_read(&cpu_buffer
->overrun
)) - cpu_buffer
->read
;
2696 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
2699 * ring_buffer_overruns - get the number of overruns in buffer
2700 * @buffer: The ring buffer
2702 * Returns the total number of overruns in the ring buffer
2705 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
2707 struct ring_buffer_per_cpu
*cpu_buffer
;
2708 unsigned long overruns
= 0;
2711 /* if you care about this being correct, lock the buffer */
2712 for_each_buffer_cpu(buffer
, cpu
) {
2713 cpu_buffer
= buffer
->buffers
[cpu
];
2714 overruns
+= local_read(&cpu_buffer
->overrun
);
2719 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
2721 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
2723 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2725 /* Iterator usage is expected to have record disabled */
2726 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
2727 iter
->head_page
= rb_set_head_page(cpu_buffer
);
2728 if (unlikely(!iter
->head_page
))
2730 iter
->head
= iter
->head_page
->read
;
2732 iter
->head_page
= cpu_buffer
->reader_page
;
2733 iter
->head
= cpu_buffer
->reader_page
->read
;
2736 iter
->read_stamp
= cpu_buffer
->read_stamp
;
2738 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2739 iter
->cache_reader_page
= cpu_buffer
->reader_page
;
2740 iter
->cache_read
= cpu_buffer
->read
;
2744 * ring_buffer_iter_reset - reset an iterator
2745 * @iter: The iterator to reset
2747 * Resets the iterator, so that it will start from the beginning
2750 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
2752 struct ring_buffer_per_cpu
*cpu_buffer
;
2753 unsigned long flags
;
2758 cpu_buffer
= iter
->cpu_buffer
;
2760 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2761 rb_iter_reset(iter
);
2762 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2764 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
2767 * ring_buffer_iter_empty - check if an iterator has no more to read
2768 * @iter: The iterator to check
2770 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
2772 struct ring_buffer_per_cpu
*cpu_buffer
;
2774 cpu_buffer
= iter
->cpu_buffer
;
2776 return iter
->head_page
== cpu_buffer
->commit_page
&&
2777 iter
->head
== rb_commit_index(cpu_buffer
);
2779 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
2782 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2783 struct ring_buffer_event
*event
)
2787 switch (event
->type_len
) {
2788 case RINGBUF_TYPE_PADDING
:
2791 case RINGBUF_TYPE_TIME_EXTEND
:
2792 delta
= event
->array
[0];
2794 delta
+= event
->time_delta
;
2795 cpu_buffer
->read_stamp
+= delta
;
2798 case RINGBUF_TYPE_TIME_STAMP
:
2799 /* FIXME: not implemented */
2802 case RINGBUF_TYPE_DATA
:
2803 cpu_buffer
->read_stamp
+= event
->time_delta
;
2813 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
2814 struct ring_buffer_event
*event
)
2818 switch (event
->type_len
) {
2819 case RINGBUF_TYPE_PADDING
:
2822 case RINGBUF_TYPE_TIME_EXTEND
:
2823 delta
= event
->array
[0];
2825 delta
+= event
->time_delta
;
2826 iter
->read_stamp
+= delta
;
2829 case RINGBUF_TYPE_TIME_STAMP
:
2830 /* FIXME: not implemented */
2833 case RINGBUF_TYPE_DATA
:
2834 iter
->read_stamp
+= event
->time_delta
;
2843 static struct buffer_page
*
2844 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
2846 struct buffer_page
*reader
= NULL
;
2847 unsigned long overwrite
;
2848 unsigned long flags
;
2852 local_irq_save(flags
);
2853 arch_spin_lock(&cpu_buffer
->lock
);
2857 * This should normally only loop twice. But because the
2858 * start of the reader inserts an empty page, it causes
2859 * a case where we will loop three times. There should be no
2860 * reason to loop four times (that I know of).
2862 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
2867 reader
= cpu_buffer
->reader_page
;
2869 /* If there's more to read, return this page */
2870 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
2873 /* Never should we have an index greater than the size */
2874 if (RB_WARN_ON(cpu_buffer
,
2875 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
2878 /* check if we caught up to the tail */
2880 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
2884 * Reset the reader page to size zero.
2886 local_set(&cpu_buffer
->reader_page
->write
, 0);
2887 local_set(&cpu_buffer
->reader_page
->entries
, 0);
2888 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
2889 cpu_buffer
->reader_page
->real_end
= 0;
2893 * Splice the empty reader page into the list around the head.
2895 reader
= rb_set_head_page(cpu_buffer
);
2896 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
2897 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
2900 * cpu_buffer->pages just needs to point to the buffer, it
2901 * has no specific buffer page to point to. Lets move it out
2902 * of our way so we don't accidently swap it.
2904 cpu_buffer
->pages
= reader
->list
.prev
;
2906 /* The reader page will be pointing to the new head */
2907 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
2910 * We want to make sure we read the overruns after we set up our
2911 * pointers to the next object. The writer side does a
2912 * cmpxchg to cross pages which acts as the mb on the writer
2913 * side. Note, the reader will constantly fail the swap
2914 * while the writer is updating the pointers, so this
2915 * guarantees that the overwrite recorded here is the one we
2916 * want to compare with the last_overrun.
2919 overwrite
= local_read(&(cpu_buffer
->overrun
));
2922 * Here's the tricky part.
2924 * We need to move the pointer past the header page.
2925 * But we can only do that if a writer is not currently
2926 * moving it. The page before the header page has the
2927 * flag bit '1' set if it is pointing to the page we want.
2928 * but if the writer is in the process of moving it
2929 * than it will be '2' or already moved '0'.
2932 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
2935 * If we did not convert it, then we must try again.
2941 * Yeah! We succeeded in replacing the page.
2943 * Now make the new head point back to the reader page.
2945 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
2946 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
2948 /* Finally update the reader page to the new head */
2949 cpu_buffer
->reader_page
= reader
;
2950 rb_reset_reader_page(cpu_buffer
);
2952 if (overwrite
!= cpu_buffer
->last_overrun
) {
2953 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
2954 cpu_buffer
->last_overrun
= overwrite
;
2960 arch_spin_unlock(&cpu_buffer
->lock
);
2961 local_irq_restore(flags
);
2966 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
2968 struct ring_buffer_event
*event
;
2969 struct buffer_page
*reader
;
2972 reader
= rb_get_reader_page(cpu_buffer
);
2974 /* This function should not be called when buffer is empty */
2975 if (RB_WARN_ON(cpu_buffer
, !reader
))
2978 event
= rb_reader_event(cpu_buffer
);
2980 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
2983 rb_update_read_stamp(cpu_buffer
, event
);
2985 length
= rb_event_length(event
);
2986 cpu_buffer
->reader_page
->read
+= length
;
2989 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
2991 struct ring_buffer_per_cpu
*cpu_buffer
;
2992 struct ring_buffer_event
*event
;
2995 cpu_buffer
= iter
->cpu_buffer
;
2998 * Check if we are at the end of the buffer.
3000 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3001 /* discarded commits can make the page empty */
3002 if (iter
->head_page
== cpu_buffer
->commit_page
)
3008 event
= rb_iter_head_event(iter
);
3010 length
= rb_event_length(event
);
3013 * This should not be called to advance the header if we are
3014 * at the tail of the buffer.
3016 if (RB_WARN_ON(cpu_buffer
,
3017 (iter
->head_page
== cpu_buffer
->commit_page
) &&
3018 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
3021 rb_update_iter_read_stamp(iter
, event
);
3023 iter
->head
+= length
;
3025 /* check for end of page padding */
3026 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3027 (iter
->head_page
!= cpu_buffer
->commit_page
))
3028 rb_advance_iter(iter
);
3031 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
3033 return cpu_buffer
->lost_events
;
3036 static struct ring_buffer_event
*
3037 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
3038 unsigned long *lost_events
)
3040 struct ring_buffer_event
*event
;
3041 struct buffer_page
*reader
;
3046 * We repeat when a timestamp is encountered. It is possible
3047 * to get multiple timestamps from an interrupt entering just
3048 * as one timestamp is about to be written, or from discarded
3049 * commits. The most that we can have is the number on a single page.
3051 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
3054 reader
= rb_get_reader_page(cpu_buffer
);
3058 event
= rb_reader_event(cpu_buffer
);
3060 switch (event
->type_len
) {
3061 case RINGBUF_TYPE_PADDING
:
3062 if (rb_null_event(event
))
3063 RB_WARN_ON(cpu_buffer
, 1);
3065 * Because the writer could be discarding every
3066 * event it creates (which would probably be bad)
3067 * if we were to go back to "again" then we may never
3068 * catch up, and will trigger the warn on, or lock
3069 * the box. Return the padding, and we will release
3070 * the current locks, and try again.
3074 case RINGBUF_TYPE_TIME_EXTEND
:
3075 /* Internal data, OK to advance */
3076 rb_advance_reader(cpu_buffer
);
3079 case RINGBUF_TYPE_TIME_STAMP
:
3080 /* FIXME: not implemented */
3081 rb_advance_reader(cpu_buffer
);
3084 case RINGBUF_TYPE_DATA
:
3086 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3087 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3088 cpu_buffer
->cpu
, ts
);
3091 *lost_events
= rb_lost_events(cpu_buffer
);
3100 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3102 static struct ring_buffer_event
*
3103 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3105 struct ring_buffer
*buffer
;
3106 struct ring_buffer_per_cpu
*cpu_buffer
;
3107 struct ring_buffer_event
*event
;
3110 cpu_buffer
= iter
->cpu_buffer
;
3111 buffer
= cpu_buffer
->buffer
;
3114 * Check if someone performed a consuming read to
3115 * the buffer. A consuming read invalidates the iterator
3116 * and we need to reset the iterator in this case.
3118 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3119 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3120 rb_iter_reset(iter
);
3123 if (ring_buffer_iter_empty(iter
))
3127 * We repeat when a timestamp is encountered.
3128 * We can get multiple timestamps by nested interrupts or also
3129 * if filtering is on (discarding commits). Since discarding
3130 * commits can be frequent we can get a lot of timestamps.
3131 * But we limit them by not adding timestamps if they begin
3132 * at the start of a page.
3134 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
3137 if (rb_per_cpu_empty(cpu_buffer
))
3140 if (iter
->head
>= local_read(&iter
->head_page
->page
->commit
)) {
3145 event
= rb_iter_head_event(iter
);
3147 switch (event
->type_len
) {
3148 case RINGBUF_TYPE_PADDING
:
3149 if (rb_null_event(event
)) {
3153 rb_advance_iter(iter
);
3156 case RINGBUF_TYPE_TIME_EXTEND
:
3157 /* Internal data, OK to advance */
3158 rb_advance_iter(iter
);
3161 case RINGBUF_TYPE_TIME_STAMP
:
3162 /* FIXME: not implemented */
3163 rb_advance_iter(iter
);
3166 case RINGBUF_TYPE_DATA
:
3168 *ts
= iter
->read_stamp
+ event
->time_delta
;
3169 ring_buffer_normalize_time_stamp(buffer
,
3170 cpu_buffer
->cpu
, ts
);
3180 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3182 static inline int rb_ok_to_lock(void)
3185 * If an NMI die dumps out the content of the ring buffer
3186 * do not grab locks. We also permanently disable the ring
3187 * buffer too. A one time deal is all you get from reading
3188 * the ring buffer from an NMI.
3190 if (likely(!in_nmi()))
3193 tracing_off_permanent();
3198 * ring_buffer_peek - peek at the next event to be read
3199 * @buffer: The ring buffer to read
3200 * @cpu: The cpu to peak at
3201 * @ts: The timestamp counter of this event.
3202 * @lost_events: a variable to store if events were lost (may be NULL)
3204 * This will return the event that will be read next, but does
3205 * not consume the data.
3207 struct ring_buffer_event
*
3208 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3209 unsigned long *lost_events
)
3211 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3212 struct ring_buffer_event
*event
;
3213 unsigned long flags
;
3216 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3219 dolock
= rb_ok_to_lock();
3221 local_irq_save(flags
);
3223 spin_lock(&cpu_buffer
->reader_lock
);
3224 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3225 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3226 rb_advance_reader(cpu_buffer
);
3228 spin_unlock(&cpu_buffer
->reader_lock
);
3229 local_irq_restore(flags
);
3231 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3238 * ring_buffer_iter_peek - peek at the next event to be read
3239 * @iter: The ring buffer iterator
3240 * @ts: The timestamp counter of this event.
3242 * This will return the event that will be read next, but does
3243 * not increment the iterator.
3245 struct ring_buffer_event
*
3246 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3248 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3249 struct ring_buffer_event
*event
;
3250 unsigned long flags
;
3253 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3254 event
= rb_iter_peek(iter
, ts
);
3255 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3257 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3264 * ring_buffer_consume - return an event and consume it
3265 * @buffer: The ring buffer to get the next event from
3266 * @cpu: the cpu to read the buffer from
3267 * @ts: a variable to store the timestamp (may be NULL)
3268 * @lost_events: a variable to store if events were lost (may be NULL)
3270 * Returns the next event in the ring buffer, and that event is consumed.
3271 * Meaning, that sequential reads will keep returning a different event,
3272 * and eventually empty the ring buffer if the producer is slower.
3274 struct ring_buffer_event
*
3275 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3276 unsigned long *lost_events
)
3278 struct ring_buffer_per_cpu
*cpu_buffer
;
3279 struct ring_buffer_event
*event
= NULL
;
3280 unsigned long flags
;
3283 dolock
= rb_ok_to_lock();
3286 /* might be called in atomic */
3289 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3292 cpu_buffer
= buffer
->buffers
[cpu
];
3293 local_irq_save(flags
);
3295 spin_lock(&cpu_buffer
->reader_lock
);
3297 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3299 cpu_buffer
->lost_events
= 0;
3300 rb_advance_reader(cpu_buffer
);
3304 spin_unlock(&cpu_buffer
->reader_lock
);
3305 local_irq_restore(flags
);
3310 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3315 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
3318 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3319 * @buffer: The ring buffer to read from
3320 * @cpu: The cpu buffer to iterate over
3322 * This performs the initial preparations necessary to iterate
3323 * through the buffer. Memory is allocated, buffer recording
3324 * is disabled, and the iterator pointer is returned to the caller.
3326 * Disabling buffer recordng prevents the reading from being
3327 * corrupted. This is not a consuming read, so a producer is not
3330 * After a sequence of ring_buffer_read_prepare calls, the user is
3331 * expected to make at least one call to ring_buffer_prepare_sync.
3332 * Afterwards, ring_buffer_read_start is invoked to get things going
3335 * This overall must be paired with ring_buffer_finish.
3337 struct ring_buffer_iter
*
3338 ring_buffer_read_prepare(struct ring_buffer
*buffer
, int cpu
)
3340 struct ring_buffer_per_cpu
*cpu_buffer
;
3341 struct ring_buffer_iter
*iter
;
3343 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3346 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
3350 cpu_buffer
= buffer
->buffers
[cpu
];
3352 iter
->cpu_buffer
= cpu_buffer
;
3354 atomic_inc(&cpu_buffer
->record_disabled
);
3358 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
3361 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
3363 * All previously invoked ring_buffer_read_prepare calls to prepare
3364 * iterators will be synchronized. Afterwards, read_buffer_read_start
3365 * calls on those iterators are allowed.
3368 ring_buffer_read_prepare_sync(void)
3370 synchronize_sched();
3372 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
3375 * ring_buffer_read_start - start a non consuming read of the buffer
3376 * @iter: The iterator returned by ring_buffer_read_prepare
3378 * This finalizes the startup of an iteration through the buffer.
3379 * The iterator comes from a call to ring_buffer_read_prepare and
3380 * an intervening ring_buffer_read_prepare_sync must have been
3383 * Must be paired with ring_buffer_finish.
3386 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
3388 struct ring_buffer_per_cpu
*cpu_buffer
;
3389 unsigned long flags
;
3394 cpu_buffer
= iter
->cpu_buffer
;
3396 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3397 arch_spin_lock(&cpu_buffer
->lock
);
3398 rb_iter_reset(iter
);
3399 arch_spin_unlock(&cpu_buffer
->lock
);
3400 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3402 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
3405 * ring_buffer_finish - finish reading the iterator of the buffer
3406 * @iter: The iterator retrieved by ring_buffer_start
3408 * This re-enables the recording to the buffer, and frees the
3412 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
3414 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3416 atomic_dec(&cpu_buffer
->record_disabled
);
3419 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
3422 * ring_buffer_read - read the next item in the ring buffer by the iterator
3423 * @iter: The ring buffer iterator
3424 * @ts: The time stamp of the event read.
3426 * This reads the next event in the ring buffer and increments the iterator.
3428 struct ring_buffer_event
*
3429 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
3431 struct ring_buffer_event
*event
;
3432 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3433 unsigned long flags
;
3435 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3437 event
= rb_iter_peek(iter
, ts
);
3441 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
3444 rb_advance_iter(iter
);
3446 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3450 EXPORT_SYMBOL_GPL(ring_buffer_read
);
3453 * ring_buffer_size - return the size of the ring buffer (in bytes)
3454 * @buffer: The ring buffer.
3456 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
3458 return BUF_PAGE_SIZE
* buffer
->pages
;
3460 EXPORT_SYMBOL_GPL(ring_buffer_size
);
3463 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
3465 rb_head_page_deactivate(cpu_buffer
);
3467 cpu_buffer
->head_page
3468 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
3469 local_set(&cpu_buffer
->head_page
->write
, 0);
3470 local_set(&cpu_buffer
->head_page
->entries
, 0);
3471 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
3473 cpu_buffer
->head_page
->read
= 0;
3475 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
3476 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
3478 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
3479 local_set(&cpu_buffer
->reader_page
->write
, 0);
3480 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3481 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3482 cpu_buffer
->reader_page
->read
= 0;
3484 local_set(&cpu_buffer
->commit_overrun
, 0);
3485 local_set(&cpu_buffer
->overrun
, 0);
3486 local_set(&cpu_buffer
->entries
, 0);
3487 local_set(&cpu_buffer
->committing
, 0);
3488 local_set(&cpu_buffer
->commits
, 0);
3489 cpu_buffer
->read
= 0;
3491 cpu_buffer
->write_stamp
= 0;
3492 cpu_buffer
->read_stamp
= 0;
3494 cpu_buffer
->lost_events
= 0;
3495 cpu_buffer
->last_overrun
= 0;
3497 rb_head_page_activate(cpu_buffer
);
3501 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3502 * @buffer: The ring buffer to reset a per cpu buffer of
3503 * @cpu: The CPU buffer to be reset
3505 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
3507 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3508 unsigned long flags
;
3510 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3513 atomic_inc(&cpu_buffer
->record_disabled
);
3515 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3517 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
3520 arch_spin_lock(&cpu_buffer
->lock
);
3522 rb_reset_cpu(cpu_buffer
);
3524 arch_spin_unlock(&cpu_buffer
->lock
);
3527 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3529 atomic_dec(&cpu_buffer
->record_disabled
);
3531 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
3534 * ring_buffer_reset - reset a ring buffer
3535 * @buffer: The ring buffer to reset all cpu buffers
3537 void ring_buffer_reset(struct ring_buffer
*buffer
)
3541 for_each_buffer_cpu(buffer
, cpu
)
3542 ring_buffer_reset_cpu(buffer
, cpu
);
3544 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
3547 * rind_buffer_empty - is the ring buffer empty?
3548 * @buffer: The ring buffer to test
3550 int ring_buffer_empty(struct ring_buffer
*buffer
)
3552 struct ring_buffer_per_cpu
*cpu_buffer
;
3553 unsigned long flags
;
3558 dolock
= rb_ok_to_lock();
3560 /* yes this is racy, but if you don't like the race, lock the buffer */
3561 for_each_buffer_cpu(buffer
, cpu
) {
3562 cpu_buffer
= buffer
->buffers
[cpu
];
3563 local_irq_save(flags
);
3565 spin_lock(&cpu_buffer
->reader_lock
);
3566 ret
= rb_per_cpu_empty(cpu_buffer
);
3568 spin_unlock(&cpu_buffer
->reader_lock
);
3569 local_irq_restore(flags
);
3577 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
3580 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
3581 * @buffer: The ring buffer
3582 * @cpu: The CPU buffer to test
3584 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
3586 struct ring_buffer_per_cpu
*cpu_buffer
;
3587 unsigned long flags
;
3591 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3594 dolock
= rb_ok_to_lock();
3596 cpu_buffer
= buffer
->buffers
[cpu
];
3597 local_irq_save(flags
);
3599 spin_lock(&cpu_buffer
->reader_lock
);
3600 ret
= rb_per_cpu_empty(cpu_buffer
);
3602 spin_unlock(&cpu_buffer
->reader_lock
);
3603 local_irq_restore(flags
);
3607 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
3609 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3611 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
3612 * @buffer_a: One buffer to swap with
3613 * @buffer_b: The other buffer to swap with
3615 * This function is useful for tracers that want to take a "snapshot"
3616 * of a CPU buffer and has another back up buffer lying around.
3617 * it is expected that the tracer handles the cpu buffer not being
3618 * used at the moment.
3620 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
3621 struct ring_buffer
*buffer_b
, int cpu
)
3623 struct ring_buffer_per_cpu
*cpu_buffer_a
;
3624 struct ring_buffer_per_cpu
*cpu_buffer_b
;
3627 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
3628 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
3631 /* At least make sure the two buffers are somewhat the same */
3632 if (buffer_a
->pages
!= buffer_b
->pages
)
3637 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
3640 if (atomic_read(&buffer_a
->record_disabled
))
3643 if (atomic_read(&buffer_b
->record_disabled
))
3646 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
3647 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
3649 if (atomic_read(&cpu_buffer_a
->record_disabled
))
3652 if (atomic_read(&cpu_buffer_b
->record_disabled
))
3656 * We can't do a synchronize_sched here because this
3657 * function can be called in atomic context.
3658 * Normally this will be called from the same CPU as cpu.
3659 * If not it's up to the caller to protect this.
3661 atomic_inc(&cpu_buffer_a
->record_disabled
);
3662 atomic_inc(&cpu_buffer_b
->record_disabled
);
3665 if (local_read(&cpu_buffer_a
->committing
))
3667 if (local_read(&cpu_buffer_b
->committing
))
3670 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
3671 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
3673 cpu_buffer_b
->buffer
= buffer_a
;
3674 cpu_buffer_a
->buffer
= buffer_b
;
3679 atomic_dec(&cpu_buffer_a
->record_disabled
);
3680 atomic_dec(&cpu_buffer_b
->record_disabled
);
3684 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
3685 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
3688 * ring_buffer_alloc_read_page - allocate a page to read from buffer
3689 * @buffer: the buffer to allocate for.
3691 * This function is used in conjunction with ring_buffer_read_page.
3692 * When reading a full page from the ring buffer, these functions
3693 * can be used to speed up the process. The calling function should
3694 * allocate a few pages first with this function. Then when it
3695 * needs to get pages from the ring buffer, it passes the result
3696 * of this function into ring_buffer_read_page, which will swap
3697 * the page that was allocated, with the read page of the buffer.
3700 * The page allocated, or NULL on error.
3702 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
)
3704 struct buffer_data_page
*bpage
;
3707 addr
= __get_free_page(GFP_KERNEL
);
3711 bpage
= (void *)addr
;
3713 rb_init_page(bpage
);
3717 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
3720 * ring_buffer_free_read_page - free an allocated read page
3721 * @buffer: the buffer the page was allocate for
3722 * @data: the page to free
3724 * Free a page allocated from ring_buffer_alloc_read_page.
3726 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
3728 free_page((unsigned long)data
);
3730 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
3733 * ring_buffer_read_page - extract a page from the ring buffer
3734 * @buffer: buffer to extract from
3735 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
3736 * @len: amount to extract
3737 * @cpu: the cpu of the buffer to extract
3738 * @full: should the extraction only happen when the page is full.
3740 * This function will pull out a page from the ring buffer and consume it.
3741 * @data_page must be the address of the variable that was returned
3742 * from ring_buffer_alloc_read_page. This is because the page might be used
3743 * to swap with a page in the ring buffer.
3746 * rpage = ring_buffer_alloc_read_page(buffer);
3749 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
3751 * process_page(rpage, ret);
3753 * When @full is set, the function will not return true unless
3754 * the writer is off the reader page.
3756 * Note: it is up to the calling functions to handle sleeps and wakeups.
3757 * The ring buffer can be used anywhere in the kernel and can not
3758 * blindly call wake_up. The layer that uses the ring buffer must be
3759 * responsible for that.
3762 * >=0 if data has been transferred, returns the offset of consumed data.
3763 * <0 if no data has been transferred.
3765 int ring_buffer_read_page(struct ring_buffer
*buffer
,
3766 void **data_page
, size_t len
, int cpu
, int full
)
3768 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3769 struct ring_buffer_event
*event
;
3770 struct buffer_data_page
*bpage
;
3771 struct buffer_page
*reader
;
3772 unsigned long missed_events
;
3773 unsigned long flags
;
3774 unsigned int commit
;
3779 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3783 * If len is not big enough to hold the page header, then
3784 * we can not copy anything.
3786 if (len
<= BUF_PAGE_HDR_SIZE
)
3789 len
-= BUF_PAGE_HDR_SIZE
;
3798 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3800 reader
= rb_get_reader_page(cpu_buffer
);
3804 event
= rb_reader_event(cpu_buffer
);
3806 read
= reader
->read
;
3807 commit
= rb_page_commit(reader
);
3809 /* Check if any events were dropped */
3810 missed_events
= cpu_buffer
->lost_events
;
3813 * If this page has been partially read or
3814 * if len is not big enough to read the rest of the page or
3815 * a writer is still on the page, then
3816 * we must copy the data from the page to the buffer.
3817 * Otherwise, we can simply swap the page with the one passed in.
3819 if (read
|| (len
< (commit
- read
)) ||
3820 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
3821 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
3822 unsigned int rpos
= read
;
3823 unsigned int pos
= 0;
3829 if (len
> (commit
- read
))
3830 len
= (commit
- read
);
3832 size
= rb_event_length(event
);
3837 /* save the current timestamp, since the user will need it */
3838 save_timestamp
= cpu_buffer
->read_stamp
;
3840 /* Need to copy one event at a time */
3842 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
3846 rb_advance_reader(cpu_buffer
);
3847 rpos
= reader
->read
;
3853 event
= rb_reader_event(cpu_buffer
);
3854 size
= rb_event_length(event
);
3855 } while (len
> size
);
3858 local_set(&bpage
->commit
, pos
);
3859 bpage
->time_stamp
= save_timestamp
;
3861 /* we copied everything to the beginning */
3864 /* update the entry counter */
3865 cpu_buffer
->read
+= rb_page_entries(reader
);
3867 /* swap the pages */
3868 rb_init_page(bpage
);
3869 bpage
= reader
->page
;
3870 reader
->page
= *data_page
;
3871 local_set(&reader
->write
, 0);
3872 local_set(&reader
->entries
, 0);
3877 * Use the real_end for the data size,
3878 * This gives us a chance to store the lost events
3881 if (reader
->real_end
)
3882 local_set(&bpage
->commit
, reader
->real_end
);
3886 cpu_buffer
->lost_events
= 0;
3888 commit
= local_read(&bpage
->commit
);
3890 * Set a flag in the commit field if we lost events
3892 if (missed_events
) {
3893 /* If there is room at the end of the page to save the
3894 * missed events, then record it there.
3896 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
3897 memcpy(&bpage
->data
[commit
], &missed_events
,
3898 sizeof(missed_events
));
3899 local_add(RB_MISSED_STORED
, &bpage
->commit
);
3900 commit
+= sizeof(missed_events
);
3902 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
3906 * This page may be off to user land. Zero it out here.
3908 if (commit
< BUF_PAGE_SIZE
)
3909 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
3912 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3917 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
3919 #ifdef CONFIG_TRACING
3921 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
3922 size_t cnt
, loff_t
*ppos
)
3924 unsigned long *p
= filp
->private_data
;
3928 if (test_bit(RB_BUFFERS_DISABLED_BIT
, p
))
3929 r
= sprintf(buf
, "permanently disabled\n");
3931 r
= sprintf(buf
, "%d\n", test_bit(RB_BUFFERS_ON_BIT
, p
));
3933 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
3937 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
3938 size_t cnt
, loff_t
*ppos
)
3940 unsigned long *p
= filp
->private_data
;
3945 if (cnt
>= sizeof(buf
))
3948 if (copy_from_user(&buf
, ubuf
, cnt
))
3953 ret
= strict_strtoul(buf
, 10, &val
);
3958 set_bit(RB_BUFFERS_ON_BIT
, p
);
3960 clear_bit(RB_BUFFERS_ON_BIT
, p
);
3967 static const struct file_operations rb_simple_fops
= {
3968 .open
= tracing_open_generic
,
3969 .read
= rb_simple_read
,
3970 .write
= rb_simple_write
,
3974 static __init
int rb_init_debugfs(void)
3976 struct dentry
*d_tracer
;
3978 d_tracer
= tracing_init_dentry();
3980 trace_create_file("tracing_on", 0644, d_tracer
,
3981 &ring_buffer_flags
, &rb_simple_fops
);
3986 fs_initcall(rb_init_debugfs
);
3989 #ifdef CONFIG_HOTPLUG_CPU
3990 static int rb_cpu_notify(struct notifier_block
*self
,
3991 unsigned long action
, void *hcpu
)
3993 struct ring_buffer
*buffer
=
3994 container_of(self
, struct ring_buffer
, cpu_notify
);
3995 long cpu
= (long)hcpu
;
3998 case CPU_UP_PREPARE
:
3999 case CPU_UP_PREPARE_FROZEN
:
4000 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
4003 buffer
->buffers
[cpu
] =
4004 rb_allocate_cpu_buffer(buffer
, cpu
);
4005 if (!buffer
->buffers
[cpu
]) {
4006 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4011 cpumask_set_cpu(cpu
, buffer
->cpumask
);
4013 case CPU_DOWN_PREPARE
:
4014 case CPU_DOWN_PREPARE_FROZEN
:
4017 * If we were to free the buffer, then the user would
4018 * lose any trace that was in the buffer.