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 struct buffer_data_page
{
323 u64 time_stamp
; /* page time stamp */
324 local_t commit
; /* write committed index */
325 unsigned char data
[]; /* data of buffer page */
329 * Note, the buffer_page list must be first. The buffer pages
330 * are allocated in cache lines, which means that each buffer
331 * page will be at the beginning of a cache line, and thus
332 * the least significant bits will be zero. We use this to
333 * add flags in the list struct pointers, to make the ring buffer
337 struct list_head list
; /* list of buffer pages */
338 local_t write
; /* index for next write */
339 unsigned read
; /* index for next read */
340 local_t entries
; /* entries on this page */
341 struct buffer_data_page
*page
; /* Actual data page */
345 * The buffer page counters, write and entries, must be reset
346 * atomically when crossing page boundaries. To synchronize this
347 * update, two counters are inserted into the number. One is
348 * the actual counter for the write position or count on the page.
350 * The other is a counter of updaters. Before an update happens
351 * the update partition of the counter is incremented. This will
352 * allow the updater to update the counter atomically.
354 * The counter is 20 bits, and the state data is 12.
356 #define RB_WRITE_MASK 0xfffff
357 #define RB_WRITE_INTCNT (1 << 20)
359 static void rb_init_page(struct buffer_data_page
*bpage
)
361 local_set(&bpage
->commit
, 0);
365 * ring_buffer_page_len - the size of data on the page.
366 * @page: The page to read
368 * Returns the amount of data on the page, including buffer page header.
370 size_t ring_buffer_page_len(void *page
)
372 return local_read(&((struct buffer_data_page
*)page
)->commit
)
377 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
380 static void free_buffer_page(struct buffer_page
*bpage
)
382 free_page((unsigned long)bpage
->page
);
387 * We need to fit the time_stamp delta into 27 bits.
389 static inline int test_time_stamp(u64 delta
)
391 if (delta
& TS_DELTA_TEST
)
396 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
398 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
399 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
401 /* Max number of timestamps that can fit on a page */
402 #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP)
404 int ring_buffer_print_page_header(struct trace_seq
*s
)
406 struct buffer_data_page field
;
409 ret
= trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
410 "offset:0;\tsize:%u;\tsigned:%u;\n",
411 (unsigned int)sizeof(field
.time_stamp
),
412 (unsigned int)is_signed_type(u64
));
414 ret
= trace_seq_printf(s
, "\tfield: local_t commit;\t"
415 "offset:%u;\tsize:%u;\tsigned:%u;\n",
416 (unsigned int)offsetof(typeof(field
), commit
),
417 (unsigned int)sizeof(field
.commit
),
418 (unsigned int)is_signed_type(long));
420 ret
= trace_seq_printf(s
, "\tfield: char data;\t"
421 "offset:%u;\tsize:%u;\tsigned:%u;\n",
422 (unsigned int)offsetof(typeof(field
), data
),
423 (unsigned int)BUF_PAGE_SIZE
,
424 (unsigned int)is_signed_type(char));
430 * head_page == tail_page && head == tail then buffer is empty.
432 struct ring_buffer_per_cpu
{
434 struct ring_buffer
*buffer
;
435 spinlock_t reader_lock
; /* serialize readers */
436 arch_spinlock_t lock
;
437 struct lock_class_key lock_key
;
438 struct list_head
*pages
;
439 struct buffer_page
*head_page
; /* read from head */
440 struct buffer_page
*tail_page
; /* write to tail */
441 struct buffer_page
*commit_page
; /* committed pages */
442 struct buffer_page
*reader_page
;
443 local_t commit_overrun
;
451 atomic_t record_disabled
;
458 atomic_t record_disabled
;
459 cpumask_var_t cpumask
;
461 struct lock_class_key
*reader_lock_key
;
465 struct ring_buffer_per_cpu
**buffers
;
467 #ifdef CONFIG_HOTPLUG_CPU
468 struct notifier_block cpu_notify
;
473 struct ring_buffer_iter
{
474 struct ring_buffer_per_cpu
*cpu_buffer
;
476 struct buffer_page
*head_page
;
477 struct buffer_page
*cache_reader_page
;
478 unsigned long cache_read
;
482 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
483 #define RB_WARN_ON(b, cond) \
485 int _____ret = unlikely(cond); \
487 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
488 struct ring_buffer_per_cpu *__b = \
490 atomic_inc(&__b->buffer->record_disabled); \
492 atomic_inc(&b->record_disabled); \
498 /* Up this if you want to test the TIME_EXTENTS and normalization */
499 #define DEBUG_SHIFT 0
501 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
503 /* shift to debug/test normalization and TIME_EXTENTS */
504 return buffer
->clock() << DEBUG_SHIFT
;
507 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
511 preempt_disable_notrace();
512 time
= rb_time_stamp(buffer
);
513 preempt_enable_no_resched_notrace();
517 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
519 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
522 /* Just stupid testing the normalize function and deltas */
525 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
528 * Making the ring buffer lockless makes things tricky.
529 * Although writes only happen on the CPU that they are on,
530 * and they only need to worry about interrupts. Reads can
533 * The reader page is always off the ring buffer, but when the
534 * reader finishes with a page, it needs to swap its page with
535 * a new one from the buffer. The reader needs to take from
536 * the head (writes go to the tail). But if a writer is in overwrite
537 * mode and wraps, it must push the head page forward.
539 * Here lies the problem.
541 * The reader must be careful to replace only the head page, and
542 * not another one. As described at the top of the file in the
543 * ASCII art, the reader sets its old page to point to the next
544 * page after head. It then sets the page after head to point to
545 * the old reader page. But if the writer moves the head page
546 * during this operation, the reader could end up with the tail.
548 * We use cmpxchg to help prevent this race. We also do something
549 * special with the page before head. We set the LSB to 1.
551 * When the writer must push the page forward, it will clear the
552 * bit that points to the head page, move the head, and then set
553 * the bit that points to the new head page.
555 * We also don't want an interrupt coming in and moving the head
556 * page on another writer. Thus we use the second LSB to catch
559 * head->list->prev->next bit 1 bit 0
562 * Points to head page 0 1
565 * Note we can not trust the prev pointer of the head page, because:
567 * +----+ +-----+ +-----+
568 * | |------>| T |---X--->| N |
570 * +----+ +-----+ +-----+
573 * +----------| R |----------+ |
577 * Key: ---X--> HEAD flag set in pointer
582 * (see __rb_reserve_next() to see where this happens)
584 * What the above shows is that the reader just swapped out
585 * the reader page with a page in the buffer, but before it
586 * could make the new header point back to the new page added
587 * it was preempted by a writer. The writer moved forward onto
588 * the new page added by the reader and is about to move forward
591 * You can see, it is legitimate for the previous pointer of
592 * the head (or any page) not to point back to itself. But only
596 #define RB_PAGE_NORMAL 0UL
597 #define RB_PAGE_HEAD 1UL
598 #define RB_PAGE_UPDATE 2UL
601 #define RB_FLAG_MASK 3UL
603 /* PAGE_MOVED is not part of the mask */
604 #define RB_PAGE_MOVED 4UL
607 * rb_list_head - remove any bit
609 static struct list_head
*rb_list_head(struct list_head
*list
)
611 unsigned long val
= (unsigned long)list
;
613 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
617 * rb_is_head_page - test if the given page is the head page
619 * Because the reader may move the head_page pointer, we can
620 * not trust what the head page is (it may be pointing to
621 * the reader page). But if the next page is a header page,
622 * its flags will be non zero.
625 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
626 struct buffer_page
*page
, struct list_head
*list
)
630 val
= (unsigned long)list
->next
;
632 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
633 return RB_PAGE_MOVED
;
635 return val
& RB_FLAG_MASK
;
641 * The unique thing about the reader page, is that, if the
642 * writer is ever on it, the previous pointer never points
643 * back to the reader page.
645 static int rb_is_reader_page(struct buffer_page
*page
)
647 struct list_head
*list
= page
->list
.prev
;
649 return rb_list_head(list
->next
) != &page
->list
;
653 * rb_set_list_to_head - set a list_head to be pointing to head.
655 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
656 struct list_head
*list
)
660 ptr
= (unsigned long *)&list
->next
;
661 *ptr
|= RB_PAGE_HEAD
;
662 *ptr
&= ~RB_PAGE_UPDATE
;
666 * rb_head_page_activate - sets up head page
668 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
670 struct buffer_page
*head
;
672 head
= cpu_buffer
->head_page
;
677 * Set the previous list pointer to have the HEAD flag.
679 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
682 static void rb_list_head_clear(struct list_head
*list
)
684 unsigned long *ptr
= (unsigned long *)&list
->next
;
686 *ptr
&= ~RB_FLAG_MASK
;
690 * rb_head_page_dactivate - clears head page ptr (for free list)
693 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
695 struct list_head
*hd
;
697 /* Go through the whole list and clear any pointers found. */
698 rb_list_head_clear(cpu_buffer
->pages
);
700 list_for_each(hd
, cpu_buffer
->pages
)
701 rb_list_head_clear(hd
);
704 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
705 struct buffer_page
*head
,
706 struct buffer_page
*prev
,
707 int old_flag
, int new_flag
)
709 struct list_head
*list
;
710 unsigned long val
= (unsigned long)&head
->list
;
715 val
&= ~RB_FLAG_MASK
;
717 ret
= cmpxchg((unsigned long *)&list
->next
,
718 val
| old_flag
, val
| new_flag
);
720 /* check if the reader took the page */
721 if ((ret
& ~RB_FLAG_MASK
) != val
)
722 return RB_PAGE_MOVED
;
724 return ret
& RB_FLAG_MASK
;
727 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
728 struct buffer_page
*head
,
729 struct buffer_page
*prev
,
732 return rb_head_page_set(cpu_buffer
, head
, prev
,
733 old_flag
, RB_PAGE_UPDATE
);
736 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
737 struct buffer_page
*head
,
738 struct buffer_page
*prev
,
741 return rb_head_page_set(cpu_buffer
, head
, prev
,
742 old_flag
, RB_PAGE_HEAD
);
745 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
746 struct buffer_page
*head
,
747 struct buffer_page
*prev
,
750 return rb_head_page_set(cpu_buffer
, head
, prev
,
751 old_flag
, RB_PAGE_NORMAL
);
754 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
755 struct buffer_page
**bpage
)
757 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
759 *bpage
= list_entry(p
, struct buffer_page
, list
);
762 static struct buffer_page
*
763 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
765 struct buffer_page
*head
;
766 struct buffer_page
*page
;
767 struct list_head
*list
;
770 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
774 list
= cpu_buffer
->pages
;
775 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
778 page
= head
= cpu_buffer
->head_page
;
780 * It is possible that the writer moves the header behind
781 * where we started, and we miss in one loop.
782 * A second loop should grab the header, but we'll do
783 * three loops just because I'm paranoid.
785 for (i
= 0; i
< 3; i
++) {
787 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
788 cpu_buffer
->head_page
= page
;
791 rb_inc_page(cpu_buffer
, &page
);
792 } while (page
!= head
);
795 RB_WARN_ON(cpu_buffer
, 1);
800 static int rb_head_page_replace(struct buffer_page
*old
,
801 struct buffer_page
*new)
803 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
807 val
= *ptr
& ~RB_FLAG_MASK
;
810 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
816 * rb_tail_page_update - move the tail page forward
818 * Returns 1 if moved tail page, 0 if someone else did.
820 static int rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
821 struct buffer_page
*tail_page
,
822 struct buffer_page
*next_page
)
824 struct buffer_page
*old_tail
;
825 unsigned long old_entries
;
826 unsigned long old_write
;
830 * The tail page now needs to be moved forward.
832 * We need to reset the tail page, but without messing
833 * with possible erasing of data brought in by interrupts
834 * that have moved the tail page and are currently on it.
836 * We add a counter to the write field to denote this.
838 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
839 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
842 * Just make sure we have seen our old_write and synchronize
843 * with any interrupts that come in.
848 * If the tail page is still the same as what we think
849 * it is, then it is up to us to update the tail
852 if (tail_page
== cpu_buffer
->tail_page
) {
853 /* Zero the write counter */
854 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
855 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
858 * This will only succeed if an interrupt did
859 * not come in and change it. In which case, we
860 * do not want to modify it.
862 * We add (void) to let the compiler know that we do not care
863 * about the return value of these functions. We use the
864 * cmpxchg to only update if an interrupt did not already
865 * do it for us. If the cmpxchg fails, we don't care.
867 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
868 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
871 * No need to worry about races with clearing out the commit.
872 * it only can increment when a commit takes place. But that
873 * only happens in the outer most nested commit.
875 local_set(&next_page
->page
->commit
, 0);
877 old_tail
= cmpxchg(&cpu_buffer
->tail_page
,
878 tail_page
, next_page
);
880 if (old_tail
== tail_page
)
887 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
888 struct buffer_page
*bpage
)
890 unsigned long val
= (unsigned long)bpage
;
892 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
899 * rb_check_list - make sure a pointer to a list has the last bits zero
901 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
902 struct list_head
*list
)
904 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
906 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
912 * check_pages - integrity check of buffer pages
913 * @cpu_buffer: CPU buffer with pages to test
915 * As a safety measure we check to make sure the data pages have not
918 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
920 struct list_head
*head
= cpu_buffer
->pages
;
921 struct buffer_page
*bpage
, *tmp
;
923 rb_head_page_deactivate(cpu_buffer
);
925 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
927 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
930 if (rb_check_list(cpu_buffer
, head
))
933 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
934 if (RB_WARN_ON(cpu_buffer
,
935 bpage
->list
.next
->prev
!= &bpage
->list
))
937 if (RB_WARN_ON(cpu_buffer
,
938 bpage
->list
.prev
->next
!= &bpage
->list
))
940 if (rb_check_list(cpu_buffer
, &bpage
->list
))
944 rb_head_page_activate(cpu_buffer
);
949 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
952 struct buffer_page
*bpage
, *tmp
;
959 for (i
= 0; i
< nr_pages
; i
++) {
960 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
961 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
965 rb_check_bpage(cpu_buffer
, bpage
);
967 list_add(&bpage
->list
, &pages
);
969 addr
= __get_free_page(GFP_KERNEL
);
972 bpage
->page
= (void *)addr
;
973 rb_init_page(bpage
->page
);
977 * The ring buffer page list is a circular list that does not
978 * start and end with a list head. All page list items point to
981 cpu_buffer
->pages
= pages
.next
;
984 rb_check_pages(cpu_buffer
);
989 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
990 list_del_init(&bpage
->list
);
991 free_buffer_page(bpage
);
996 static struct ring_buffer_per_cpu
*
997 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
999 struct ring_buffer_per_cpu
*cpu_buffer
;
1000 struct buffer_page
*bpage
;
1004 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1005 GFP_KERNEL
, cpu_to_node(cpu
));
1009 cpu_buffer
->cpu
= cpu
;
1010 cpu_buffer
->buffer
= buffer
;
1011 spin_lock_init(&cpu_buffer
->reader_lock
);
1012 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1013 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1015 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1016 GFP_KERNEL
, cpu_to_node(cpu
));
1018 goto fail_free_buffer
;
1020 rb_check_bpage(cpu_buffer
, bpage
);
1022 cpu_buffer
->reader_page
= bpage
;
1023 addr
= __get_free_page(GFP_KERNEL
);
1025 goto fail_free_reader
;
1026 bpage
->page
= (void *)addr
;
1027 rb_init_page(bpage
->page
);
1029 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1031 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
1033 goto fail_free_reader
;
1035 cpu_buffer
->head_page
1036 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1037 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1039 rb_head_page_activate(cpu_buffer
);
1044 free_buffer_page(cpu_buffer
->reader_page
);
1051 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1053 struct list_head
*head
= cpu_buffer
->pages
;
1054 struct buffer_page
*bpage
, *tmp
;
1056 free_buffer_page(cpu_buffer
->reader_page
);
1058 rb_head_page_deactivate(cpu_buffer
);
1061 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1062 list_del_init(&bpage
->list
);
1063 free_buffer_page(bpage
);
1065 bpage
= list_entry(head
, struct buffer_page
, list
);
1066 free_buffer_page(bpage
);
1072 #ifdef CONFIG_HOTPLUG_CPU
1073 static int rb_cpu_notify(struct notifier_block
*self
,
1074 unsigned long action
, void *hcpu
);
1078 * ring_buffer_alloc - allocate a new ring_buffer
1079 * @size: the size in bytes per cpu that is needed.
1080 * @flags: attributes to set for the ring buffer.
1082 * Currently the only flag that is available is the RB_FL_OVERWRITE
1083 * flag. This flag means that the buffer will overwrite old data
1084 * when the buffer wraps. If this flag is not set, the buffer will
1085 * drop data when the tail hits the head.
1087 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1088 struct lock_class_key
*key
)
1090 struct ring_buffer
*buffer
;
1094 /* keep it in its own cache line */
1095 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1100 if (!alloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1101 goto fail_free_buffer
;
1103 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1104 buffer
->flags
= flags
;
1105 buffer
->clock
= trace_clock_local
;
1106 buffer
->reader_lock_key
= key
;
1108 /* need at least two pages */
1109 if (buffer
->pages
< 2)
1113 * In case of non-hotplug cpu, if the ring-buffer is allocated
1114 * in early initcall, it will not be notified of secondary cpus.
1115 * In that off case, we need to allocate for all possible cpus.
1117 #ifdef CONFIG_HOTPLUG_CPU
1119 cpumask_copy(buffer
->cpumask
, cpu_online_mask
);
1121 cpumask_copy(buffer
->cpumask
, cpu_possible_mask
);
1123 buffer
->cpus
= nr_cpu_ids
;
1125 bsize
= sizeof(void *) * nr_cpu_ids
;
1126 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1128 if (!buffer
->buffers
)
1129 goto fail_free_cpumask
;
1131 for_each_buffer_cpu(buffer
, cpu
) {
1132 buffer
->buffers
[cpu
] =
1133 rb_allocate_cpu_buffer(buffer
, cpu
);
1134 if (!buffer
->buffers
[cpu
])
1135 goto fail_free_buffers
;
1138 #ifdef CONFIG_HOTPLUG_CPU
1139 buffer
->cpu_notify
.notifier_call
= rb_cpu_notify
;
1140 buffer
->cpu_notify
.priority
= 0;
1141 register_cpu_notifier(&buffer
->cpu_notify
);
1145 mutex_init(&buffer
->mutex
);
1150 for_each_buffer_cpu(buffer
, cpu
) {
1151 if (buffer
->buffers
[cpu
])
1152 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1154 kfree(buffer
->buffers
);
1157 free_cpumask_var(buffer
->cpumask
);
1164 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1167 * ring_buffer_free - free a ring buffer.
1168 * @buffer: the buffer to free.
1171 ring_buffer_free(struct ring_buffer
*buffer
)
1177 #ifdef CONFIG_HOTPLUG_CPU
1178 unregister_cpu_notifier(&buffer
->cpu_notify
);
1181 for_each_buffer_cpu(buffer
, cpu
)
1182 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1186 kfree(buffer
->buffers
);
1187 free_cpumask_var(buffer
->cpumask
);
1191 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1193 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1196 buffer
->clock
= clock
;
1199 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1202 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
1204 struct buffer_page
*bpage
;
1205 struct list_head
*p
;
1208 spin_lock_irq(&cpu_buffer
->reader_lock
);
1209 rb_head_page_deactivate(cpu_buffer
);
1211 for (i
= 0; i
< nr_pages
; i
++) {
1212 if (RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
)))
1214 p
= cpu_buffer
->pages
->next
;
1215 bpage
= list_entry(p
, struct buffer_page
, list
);
1216 list_del_init(&bpage
->list
);
1217 free_buffer_page(bpage
);
1219 if (RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
)))
1222 rb_reset_cpu(cpu_buffer
);
1223 rb_check_pages(cpu_buffer
);
1225 spin_unlock_irq(&cpu_buffer
->reader_lock
);
1229 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1230 struct list_head
*pages
, unsigned nr_pages
)
1232 struct buffer_page
*bpage
;
1233 struct list_head
*p
;
1236 spin_lock_irq(&cpu_buffer
->reader_lock
);
1237 rb_head_page_deactivate(cpu_buffer
);
1239 for (i
= 0; i
< nr_pages
; i
++) {
1240 if (RB_WARN_ON(cpu_buffer
, list_empty(pages
)))
1243 bpage
= list_entry(p
, struct buffer_page
, list
);
1244 list_del_init(&bpage
->list
);
1245 list_add_tail(&bpage
->list
, cpu_buffer
->pages
);
1247 rb_reset_cpu(cpu_buffer
);
1248 rb_check_pages(cpu_buffer
);
1250 spin_unlock_irq(&cpu_buffer
->reader_lock
);
1254 * ring_buffer_resize - resize the ring buffer
1255 * @buffer: the buffer to resize.
1256 * @size: the new size.
1258 * Minimum size is 2 * BUF_PAGE_SIZE.
1260 * Returns -1 on failure.
1262 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
1264 struct ring_buffer_per_cpu
*cpu_buffer
;
1265 unsigned nr_pages
, rm_pages
, new_pages
;
1266 struct buffer_page
*bpage
, *tmp
;
1267 unsigned long buffer_size
;
1273 * Always succeed at resizing a non-existent buffer:
1278 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1279 size
*= BUF_PAGE_SIZE
;
1280 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
1282 /* we need a minimum of two pages */
1283 if (size
< BUF_PAGE_SIZE
* 2)
1284 size
= BUF_PAGE_SIZE
* 2;
1286 if (size
== buffer_size
)
1289 atomic_inc(&buffer
->record_disabled
);
1291 /* Make sure all writers are done with this buffer. */
1292 synchronize_sched();
1294 mutex_lock(&buffer
->mutex
);
1297 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1299 if (size
< buffer_size
) {
1301 /* easy case, just free pages */
1302 if (RB_WARN_ON(buffer
, nr_pages
>= buffer
->pages
))
1305 rm_pages
= buffer
->pages
- nr_pages
;
1307 for_each_buffer_cpu(buffer
, cpu
) {
1308 cpu_buffer
= buffer
->buffers
[cpu
];
1309 rb_remove_pages(cpu_buffer
, rm_pages
);
1315 * This is a bit more difficult. We only want to add pages
1316 * when we can allocate enough for all CPUs. We do this
1317 * by allocating all the pages and storing them on a local
1318 * link list. If we succeed in our allocation, then we
1319 * add these pages to the cpu_buffers. Otherwise we just free
1320 * them all and return -ENOMEM;
1322 if (RB_WARN_ON(buffer
, nr_pages
<= buffer
->pages
))
1325 new_pages
= nr_pages
- buffer
->pages
;
1327 for_each_buffer_cpu(buffer
, cpu
) {
1328 for (i
= 0; i
< new_pages
; i
++) {
1329 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
),
1331 GFP_KERNEL
, cpu_to_node(cpu
));
1334 list_add(&bpage
->list
, &pages
);
1335 addr
= __get_free_page(GFP_KERNEL
);
1338 bpage
->page
= (void *)addr
;
1339 rb_init_page(bpage
->page
);
1343 for_each_buffer_cpu(buffer
, cpu
) {
1344 cpu_buffer
= buffer
->buffers
[cpu
];
1345 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
1348 if (RB_WARN_ON(buffer
, !list_empty(&pages
)))
1352 buffer
->pages
= nr_pages
;
1354 mutex_unlock(&buffer
->mutex
);
1356 atomic_dec(&buffer
->record_disabled
);
1361 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
1362 list_del_init(&bpage
->list
);
1363 free_buffer_page(bpage
);
1366 mutex_unlock(&buffer
->mutex
);
1367 atomic_dec(&buffer
->record_disabled
);
1371 * Something went totally wrong, and we are too paranoid
1372 * to even clean up the mess.
1376 mutex_unlock(&buffer
->mutex
);
1377 atomic_dec(&buffer
->record_disabled
);
1380 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1382 static inline void *
1383 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
1385 return bpage
->data
+ index
;
1388 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1390 return bpage
->page
->data
+ index
;
1393 static inline struct ring_buffer_event
*
1394 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1396 return __rb_page_index(cpu_buffer
->reader_page
,
1397 cpu_buffer
->reader_page
->read
);
1400 static inline struct ring_buffer_event
*
1401 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1403 return __rb_page_index(iter
->head_page
, iter
->head
);
1406 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1408 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1411 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
1413 return local_read(&bpage
->page
->commit
);
1416 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1418 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1421 /* Size is determined by what has been commited */
1422 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
1424 return rb_page_commit(bpage
);
1427 static inline unsigned
1428 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1430 return rb_page_commit(cpu_buffer
->commit_page
);
1433 static inline unsigned
1434 rb_event_index(struct ring_buffer_event
*event
)
1436 unsigned long addr
= (unsigned long)event
;
1438 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1442 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1443 struct ring_buffer_event
*event
)
1445 unsigned long addr
= (unsigned long)event
;
1446 unsigned long index
;
1448 index
= rb_event_index(event
);
1451 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
1452 rb_commit_index(cpu_buffer
) == index
;
1456 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
1458 unsigned long max_count
;
1461 * We only race with interrupts and NMIs on this CPU.
1462 * If we own the commit event, then we can commit
1463 * all others that interrupted us, since the interruptions
1464 * are in stack format (they finish before they come
1465 * back to us). This allows us to do a simple loop to
1466 * assign the commit to the tail.
1469 max_count
= cpu_buffer
->buffer
->pages
* 100;
1471 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
1472 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
1474 if (RB_WARN_ON(cpu_buffer
,
1475 rb_is_reader_page(cpu_buffer
->tail_page
)))
1477 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1478 rb_page_write(cpu_buffer
->commit_page
));
1479 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
1480 cpu_buffer
->write_stamp
=
1481 cpu_buffer
->commit_page
->page
->time_stamp
;
1482 /* add barrier to keep gcc from optimizing too much */
1485 while (rb_commit_index(cpu_buffer
) !=
1486 rb_page_write(cpu_buffer
->commit_page
)) {
1488 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1489 rb_page_write(cpu_buffer
->commit_page
));
1490 RB_WARN_ON(cpu_buffer
,
1491 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
1496 /* again, keep gcc from optimizing */
1500 * If an interrupt came in just after the first while loop
1501 * and pushed the tail page forward, we will be left with
1502 * a dangling commit that will never go forward.
1504 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
1508 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1510 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
1511 cpu_buffer
->reader_page
->read
= 0;
1514 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1516 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1519 * The iterator could be on the reader page (it starts there).
1520 * But the head could have moved, since the reader was
1521 * found. Check for this case and assign the iterator
1522 * to the head page instead of next.
1524 if (iter
->head_page
== cpu_buffer
->reader_page
)
1525 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1527 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1529 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1534 * ring_buffer_update_event - update event type and data
1535 * @event: the even to update
1536 * @type: the type of event
1537 * @length: the size of the event field in the ring buffer
1539 * Update the type and data fields of the event. The length
1540 * is the actual size that is written to the ring buffer,
1541 * and with this, we can determine what to place into the
1545 rb_update_event(struct ring_buffer_event
*event
,
1546 unsigned type
, unsigned length
)
1548 event
->type_len
= type
;
1552 case RINGBUF_TYPE_PADDING
:
1553 case RINGBUF_TYPE_TIME_EXTEND
:
1554 case RINGBUF_TYPE_TIME_STAMP
:
1558 length
-= RB_EVNT_HDR_SIZE
;
1559 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
1560 event
->array
[0] = length
;
1562 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
1570 * rb_handle_head_page - writer hit the head page
1572 * Returns: +1 to retry page
1577 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1578 struct buffer_page
*tail_page
,
1579 struct buffer_page
*next_page
)
1581 struct buffer_page
*new_head
;
1586 entries
= rb_page_entries(next_page
);
1589 * The hard part is here. We need to move the head
1590 * forward, and protect against both readers on
1591 * other CPUs and writers coming in via interrupts.
1593 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1597 * type can be one of four:
1598 * NORMAL - an interrupt already moved it for us
1599 * HEAD - we are the first to get here.
1600 * UPDATE - we are the interrupt interrupting
1602 * MOVED - a reader on another CPU moved the next
1603 * pointer to its reader page. Give up
1610 * We changed the head to UPDATE, thus
1611 * it is our responsibility to update
1614 local_add(entries
, &cpu_buffer
->overrun
);
1617 * The entries will be zeroed out when we move the
1621 /* still more to do */
1624 case RB_PAGE_UPDATE
:
1626 * This is an interrupt that interrupt the
1627 * previous update. Still more to do.
1630 case RB_PAGE_NORMAL
:
1632 * An interrupt came in before the update
1633 * and processed this for us.
1634 * Nothing left to do.
1639 * The reader is on another CPU and just did
1640 * a swap with our next_page.
1645 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
1650 * Now that we are here, the old head pointer is
1651 * set to UPDATE. This will keep the reader from
1652 * swapping the head page with the reader page.
1653 * The reader (on another CPU) will spin till
1656 * We just need to protect against interrupts
1657 * doing the job. We will set the next pointer
1658 * to HEAD. After that, we set the old pointer
1659 * to NORMAL, but only if it was HEAD before.
1660 * otherwise we are an interrupt, and only
1661 * want the outer most commit to reset it.
1663 new_head
= next_page
;
1664 rb_inc_page(cpu_buffer
, &new_head
);
1666 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
1670 * Valid returns are:
1671 * HEAD - an interrupt came in and already set it.
1672 * NORMAL - One of two things:
1673 * 1) We really set it.
1674 * 2) A bunch of interrupts came in and moved
1675 * the page forward again.
1679 case RB_PAGE_NORMAL
:
1683 RB_WARN_ON(cpu_buffer
, 1);
1688 * It is possible that an interrupt came in,
1689 * set the head up, then more interrupts came in
1690 * and moved it again. When we get back here,
1691 * the page would have been set to NORMAL but we
1692 * just set it back to HEAD.
1694 * How do you detect this? Well, if that happened
1695 * the tail page would have moved.
1697 if (ret
== RB_PAGE_NORMAL
) {
1699 * If the tail had moved passed next, then we need
1700 * to reset the pointer.
1702 if (cpu_buffer
->tail_page
!= tail_page
&&
1703 cpu_buffer
->tail_page
!= next_page
)
1704 rb_head_page_set_normal(cpu_buffer
, new_head
,
1710 * If this was the outer most commit (the one that
1711 * changed the original pointer from HEAD to UPDATE),
1712 * then it is up to us to reset it to NORMAL.
1714 if (type
== RB_PAGE_HEAD
) {
1715 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
1718 if (RB_WARN_ON(cpu_buffer
,
1719 ret
!= RB_PAGE_UPDATE
))
1726 static unsigned rb_calculate_event_length(unsigned length
)
1728 struct ring_buffer_event event
; /* Used only for sizeof array */
1730 /* zero length can cause confusions */
1734 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
1735 length
+= sizeof(event
.array
[0]);
1737 length
+= RB_EVNT_HDR_SIZE
;
1738 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
1744 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1745 struct buffer_page
*tail_page
,
1746 unsigned long tail
, unsigned long length
)
1748 struct ring_buffer_event
*event
;
1751 * Only the event that crossed the page boundary
1752 * must fill the old tail_page with padding.
1754 if (tail
>= BUF_PAGE_SIZE
) {
1755 local_sub(length
, &tail_page
->write
);
1759 event
= __rb_page_index(tail_page
, tail
);
1760 kmemcheck_annotate_bitfield(event
, bitfield
);
1763 * If this event is bigger than the minimum size, then
1764 * we need to be careful that we don't subtract the
1765 * write counter enough to allow another writer to slip
1767 * We put in a discarded commit instead, to make sure
1768 * that this space is not used again.
1770 * If we are less than the minimum size, we don't need to
1773 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
1774 /* No room for any events */
1776 /* Mark the rest of the page with padding */
1777 rb_event_set_padding(event
);
1779 /* Set the write back to the previous setting */
1780 local_sub(length
, &tail_page
->write
);
1784 /* Put in a discarded event */
1785 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
1786 event
->type_len
= RINGBUF_TYPE_PADDING
;
1787 /* time delta must be non zero */
1788 event
->time_delta
= 1;
1790 /* Set write to end of buffer */
1791 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
1792 local_sub(length
, &tail_page
->write
);
1795 static struct ring_buffer_event
*
1796 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1797 unsigned long length
, unsigned long tail
,
1798 struct buffer_page
*tail_page
, u64
*ts
)
1800 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
1801 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
1802 struct buffer_page
*next_page
;
1805 next_page
= tail_page
;
1807 rb_inc_page(cpu_buffer
, &next_page
);
1810 * If for some reason, we had an interrupt storm that made
1811 * it all the way around the buffer, bail, and warn
1814 if (unlikely(next_page
== commit_page
)) {
1815 local_inc(&cpu_buffer
->commit_overrun
);
1820 * This is where the fun begins!
1822 * We are fighting against races between a reader that
1823 * could be on another CPU trying to swap its reader
1824 * page with the buffer head.
1826 * We are also fighting against interrupts coming in and
1827 * moving the head or tail on us as well.
1829 * If the next page is the head page then we have filled
1830 * the buffer, unless the commit page is still on the
1833 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
1836 * If the commit is not on the reader page, then
1837 * move the header page.
1839 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
1841 * If we are not in overwrite mode,
1842 * this is easy, just stop here.
1844 if (!(buffer
->flags
& RB_FL_OVERWRITE
))
1847 ret
= rb_handle_head_page(cpu_buffer
,
1856 * We need to be careful here too. The
1857 * commit page could still be on the reader
1858 * page. We could have a small buffer, and
1859 * have filled up the buffer with events
1860 * from interrupts and such, and wrapped.
1862 * Note, if the tail page is also the on the
1863 * reader_page, we let it move out.
1865 if (unlikely((cpu_buffer
->commit_page
!=
1866 cpu_buffer
->tail_page
) &&
1867 (cpu_buffer
->commit_page
==
1868 cpu_buffer
->reader_page
))) {
1869 local_inc(&cpu_buffer
->commit_overrun
);
1875 ret
= rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
1878 * Nested commits always have zero deltas, so
1879 * just reread the time stamp
1881 *ts
= rb_time_stamp(buffer
);
1882 next_page
->page
->time_stamp
= *ts
;
1887 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1889 /* fail and let the caller try again */
1890 return ERR_PTR(-EAGAIN
);
1894 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1899 static struct ring_buffer_event
*
1900 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
1901 unsigned type
, unsigned long length
, u64
*ts
)
1903 struct buffer_page
*tail_page
;
1904 struct ring_buffer_event
*event
;
1905 unsigned long tail
, write
;
1907 tail_page
= cpu_buffer
->tail_page
;
1908 write
= local_add_return(length
, &tail_page
->write
);
1910 /* set write to only the index of the write */
1911 write
&= RB_WRITE_MASK
;
1912 tail
= write
- length
;
1914 /* See if we shot pass the end of this buffer page */
1915 if (write
> BUF_PAGE_SIZE
)
1916 return rb_move_tail(cpu_buffer
, length
, tail
,
1919 /* We reserved something on the buffer */
1921 event
= __rb_page_index(tail_page
, tail
);
1922 kmemcheck_annotate_bitfield(event
, bitfield
);
1923 rb_update_event(event
, type
, length
);
1925 /* The passed in type is zero for DATA */
1927 local_inc(&tail_page
->entries
);
1930 * If this is the first commit on the page, then update
1934 tail_page
->page
->time_stamp
= *ts
;
1940 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
1941 struct ring_buffer_event
*event
)
1943 unsigned long new_index
, old_index
;
1944 struct buffer_page
*bpage
;
1945 unsigned long index
;
1948 new_index
= rb_event_index(event
);
1949 old_index
= new_index
+ rb_event_length(event
);
1950 addr
= (unsigned long)event
;
1953 bpage
= cpu_buffer
->tail_page
;
1955 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
1956 unsigned long write_mask
=
1957 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
1959 * This is on the tail page. It is possible that
1960 * a write could come in and move the tail page
1961 * and write to the next page. That is fine
1962 * because we just shorten what is on this page.
1964 old_index
+= write_mask
;
1965 new_index
+= write_mask
;
1966 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
1967 if (index
== old_index
)
1971 /* could not discard */
1976 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1977 u64
*ts
, u64
*delta
)
1979 struct ring_buffer_event
*event
;
1983 if (unlikely(*delta
> (1ULL << 59) && !once
++)) {
1984 printk(KERN_WARNING
"Delta way too big! %llu"
1985 " ts=%llu write stamp = %llu\n",
1986 (unsigned long long)*delta
,
1987 (unsigned long long)*ts
,
1988 (unsigned long long)cpu_buffer
->write_stamp
);
1993 * The delta is too big, we to add a
1996 event
= __rb_reserve_next(cpu_buffer
,
1997 RINGBUF_TYPE_TIME_EXTEND
,
2003 if (PTR_ERR(event
) == -EAGAIN
)
2006 /* Only a commited time event can update the write stamp */
2007 if (rb_event_is_commit(cpu_buffer
, event
)) {
2009 * If this is the first on the page, then it was
2010 * updated with the page itself. Try to discard it
2011 * and if we can't just make it zero.
2013 if (rb_event_index(event
)) {
2014 event
->time_delta
= *delta
& TS_MASK
;
2015 event
->array
[0] = *delta
>> TS_SHIFT
;
2017 /* try to discard, since we do not need this */
2018 if (!rb_try_to_discard(cpu_buffer
, event
)) {
2019 /* nope, just zero it */
2020 event
->time_delta
= 0;
2021 event
->array
[0] = 0;
2024 cpu_buffer
->write_stamp
= *ts
;
2025 /* let the caller know this was the commit */
2028 /* Try to discard the event */
2029 if (!rb_try_to_discard(cpu_buffer
, event
)) {
2030 /* Darn, this is just wasted space */
2031 event
->time_delta
= 0;
2032 event
->array
[0] = 0;
2042 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2044 local_inc(&cpu_buffer
->committing
);
2045 local_inc(&cpu_buffer
->commits
);
2048 static void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2050 unsigned long commits
;
2052 if (RB_WARN_ON(cpu_buffer
,
2053 !local_read(&cpu_buffer
->committing
)))
2057 commits
= local_read(&cpu_buffer
->commits
);
2058 /* synchronize with interrupts */
2060 if (local_read(&cpu_buffer
->committing
) == 1)
2061 rb_set_commit_to_write(cpu_buffer
);
2063 local_dec(&cpu_buffer
->committing
);
2065 /* synchronize with interrupts */
2069 * Need to account for interrupts coming in between the
2070 * updating of the commit page and the clearing of the
2071 * committing counter.
2073 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2074 !local_read(&cpu_buffer
->committing
)) {
2075 local_inc(&cpu_buffer
->committing
);
2080 static struct ring_buffer_event
*
2081 rb_reserve_next_event(struct ring_buffer
*buffer
,
2082 struct ring_buffer_per_cpu
*cpu_buffer
,
2083 unsigned long length
)
2085 struct ring_buffer_event
*event
;
2090 rb_start_commit(cpu_buffer
);
2092 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2094 * Due to the ability to swap a cpu buffer from a buffer
2095 * it is possible it was swapped before we committed.
2096 * (committing stops a swap). We check for it here and
2097 * if it happened, we have to fail the write.
2100 if (unlikely(ACCESS_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2101 local_dec(&cpu_buffer
->committing
);
2102 local_dec(&cpu_buffer
->commits
);
2107 length
= rb_calculate_event_length(length
);
2110 * We allow for interrupts to reenter here and do a trace.
2111 * If one does, it will cause this original code to loop
2112 * back here. Even with heavy interrupts happening, this
2113 * should only happen a few times in a row. If this happens
2114 * 1000 times in a row, there must be either an interrupt
2115 * storm or we have something buggy.
2118 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2121 ts
= rb_time_stamp(cpu_buffer
->buffer
);
2124 * Only the first commit can update the timestamp.
2125 * Yes there is a race here. If an interrupt comes in
2126 * just after the conditional and it traces too, then it
2127 * will also check the deltas. More than one timestamp may
2128 * also be made. But only the entry that did the actual
2129 * commit will be something other than zero.
2131 if (likely(cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
2132 rb_page_write(cpu_buffer
->tail_page
) ==
2133 rb_commit_index(cpu_buffer
))) {
2136 diff
= ts
- cpu_buffer
->write_stamp
;
2138 /* make sure this diff is calculated here */
2141 /* Did the write stamp get updated already? */
2142 if (unlikely(ts
< cpu_buffer
->write_stamp
))
2146 if (unlikely(test_time_stamp(delta
))) {
2148 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
2149 if (commit
== -EBUSY
)
2152 if (commit
== -EAGAIN
)
2155 RB_WARN_ON(cpu_buffer
, commit
< 0);
2160 event
= __rb_reserve_next(cpu_buffer
, 0, length
, &ts
);
2161 if (unlikely(PTR_ERR(event
) == -EAGAIN
))
2167 if (!rb_event_is_commit(cpu_buffer
, event
))
2170 event
->time_delta
= delta
;
2175 rb_end_commit(cpu_buffer
);
2179 #ifdef CONFIG_TRACING
2181 #define TRACE_RECURSIVE_DEPTH 16
2183 static int trace_recursive_lock(void)
2185 current
->trace_recursion
++;
2187 if (likely(current
->trace_recursion
< TRACE_RECURSIVE_DEPTH
))
2190 /* Disable all tracing before we do anything else */
2191 tracing_off_permanent();
2193 printk_once(KERN_WARNING
"Tracing recursion: depth[%ld]:"
2194 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
2195 current
->trace_recursion
,
2196 hardirq_count() >> HARDIRQ_SHIFT
,
2197 softirq_count() >> SOFTIRQ_SHIFT
,
2204 static void trace_recursive_unlock(void)
2206 WARN_ON_ONCE(!current
->trace_recursion
);
2208 current
->trace_recursion
--;
2213 #define trace_recursive_lock() (0)
2214 #define trace_recursive_unlock() do { } while (0)
2218 static DEFINE_PER_CPU(int, rb_need_resched
);
2221 * ring_buffer_lock_reserve - reserve a part of the buffer
2222 * @buffer: the ring buffer to reserve from
2223 * @length: the length of the data to reserve (excluding event header)
2225 * Returns a reseverd event on the ring buffer to copy directly to.
2226 * The user of this interface will need to get the body to write into
2227 * and can use the ring_buffer_event_data() interface.
2229 * The length is the length of the data needed, not the event length
2230 * which also includes the event header.
2232 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2233 * If NULL is returned, then nothing has been allocated or locked.
2235 struct ring_buffer_event
*
2236 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2238 struct ring_buffer_per_cpu
*cpu_buffer
;
2239 struct ring_buffer_event
*event
;
2242 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2245 /* If we are tracing schedule, we don't want to recurse */
2246 resched
= ftrace_preempt_disable();
2248 if (atomic_read(&buffer
->record_disabled
))
2251 if (trace_recursive_lock())
2254 cpu
= raw_smp_processor_id();
2256 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2259 cpu_buffer
= buffer
->buffers
[cpu
];
2261 if (atomic_read(&cpu_buffer
->record_disabled
))
2264 if (length
> BUF_MAX_DATA_SIZE
)
2267 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2272 * Need to store resched state on this cpu.
2273 * Only the first needs to.
2276 if (preempt_count() == 1)
2277 per_cpu(rb_need_resched
, cpu
) = resched
;
2282 trace_recursive_unlock();
2285 ftrace_preempt_enable(resched
);
2288 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2291 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2292 struct ring_buffer_event
*event
)
2295 * The event first in the commit queue updates the
2298 if (rb_event_is_commit(cpu_buffer
, event
))
2299 cpu_buffer
->write_stamp
+= event
->time_delta
;
2302 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2303 struct ring_buffer_event
*event
)
2305 local_inc(&cpu_buffer
->entries
);
2306 rb_update_write_stamp(cpu_buffer
, event
);
2307 rb_end_commit(cpu_buffer
);
2311 * ring_buffer_unlock_commit - commit a reserved
2312 * @buffer: The buffer to commit to
2313 * @event: The event pointer to commit.
2315 * This commits the data to the ring buffer, and releases any locks held.
2317 * Must be paired with ring_buffer_lock_reserve.
2319 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2320 struct ring_buffer_event
*event
)
2322 struct ring_buffer_per_cpu
*cpu_buffer
;
2323 int cpu
= raw_smp_processor_id();
2325 cpu_buffer
= buffer
->buffers
[cpu
];
2327 rb_commit(cpu_buffer
, event
);
2329 trace_recursive_unlock();
2332 * Only the last preempt count needs to restore preemption.
2334 if (preempt_count() == 1)
2335 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
2337 preempt_enable_no_resched_notrace();
2341 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2343 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2345 /* array[0] holds the actual length for the discarded event */
2346 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2347 event
->type_len
= RINGBUF_TYPE_PADDING
;
2348 /* time delta must be non zero */
2349 if (!event
->time_delta
)
2350 event
->time_delta
= 1;
2354 * Decrement the entries to the page that an event is on.
2355 * The event does not even need to exist, only the pointer
2356 * to the page it is on. This may only be called before the commit
2360 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2361 struct ring_buffer_event
*event
)
2363 unsigned long addr
= (unsigned long)event
;
2364 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2365 struct buffer_page
*start
;
2369 /* Do the likely case first */
2370 if (likely(bpage
->page
== (void *)addr
)) {
2371 local_dec(&bpage
->entries
);
2376 * Because the commit page may be on the reader page we
2377 * start with the next page and check the end loop there.
2379 rb_inc_page(cpu_buffer
, &bpage
);
2382 if (bpage
->page
== (void *)addr
) {
2383 local_dec(&bpage
->entries
);
2386 rb_inc_page(cpu_buffer
, &bpage
);
2387 } while (bpage
!= start
);
2389 /* commit not part of this buffer?? */
2390 RB_WARN_ON(cpu_buffer
, 1);
2394 * ring_buffer_commit_discard - discard an event that has not been committed
2395 * @buffer: the ring buffer
2396 * @event: non committed event to discard
2398 * Sometimes an event that is in the ring buffer needs to be ignored.
2399 * This function lets the user discard an event in the ring buffer
2400 * and then that event will not be read later.
2402 * This function only works if it is called before the the item has been
2403 * committed. It will try to free the event from the ring buffer
2404 * if another event has not been added behind it.
2406 * If another event has been added behind it, it will set the event
2407 * up as discarded, and perform the commit.
2409 * If this function is called, do not call ring_buffer_unlock_commit on
2412 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2413 struct ring_buffer_event
*event
)
2415 struct ring_buffer_per_cpu
*cpu_buffer
;
2418 /* The event is discarded regardless */
2419 rb_event_discard(event
);
2421 cpu
= smp_processor_id();
2422 cpu_buffer
= buffer
->buffers
[cpu
];
2425 * This must only be called if the event has not been
2426 * committed yet. Thus we can assume that preemption
2427 * is still disabled.
2429 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2431 rb_decrement_entry(cpu_buffer
, event
);
2432 if (rb_try_to_discard(cpu_buffer
, event
))
2436 * The commit is still visible by the reader, so we
2437 * must still update the timestamp.
2439 rb_update_write_stamp(cpu_buffer
, event
);
2441 rb_end_commit(cpu_buffer
);
2443 trace_recursive_unlock();
2446 * Only the last preempt count needs to restore preemption.
2448 if (preempt_count() == 1)
2449 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
2451 preempt_enable_no_resched_notrace();
2454 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2457 * ring_buffer_write - write data to the buffer without reserving
2458 * @buffer: The ring buffer to write to.
2459 * @length: The length of the data being written (excluding the event header)
2460 * @data: The data to write to the buffer.
2462 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2463 * one function. If you already have the data to write to the buffer, it
2464 * may be easier to simply call this function.
2466 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2467 * and not the length of the event which would hold the header.
2469 int ring_buffer_write(struct ring_buffer
*buffer
,
2470 unsigned long length
,
2473 struct ring_buffer_per_cpu
*cpu_buffer
;
2474 struct ring_buffer_event
*event
;
2479 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2482 resched
= ftrace_preempt_disable();
2484 if (atomic_read(&buffer
->record_disabled
))
2487 cpu
= raw_smp_processor_id();
2489 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2492 cpu_buffer
= buffer
->buffers
[cpu
];
2494 if (atomic_read(&cpu_buffer
->record_disabled
))
2497 if (length
> BUF_MAX_DATA_SIZE
)
2500 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2504 body
= rb_event_data(event
);
2506 memcpy(body
, data
, length
);
2508 rb_commit(cpu_buffer
, event
);
2512 ftrace_preempt_enable(resched
);
2516 EXPORT_SYMBOL_GPL(ring_buffer_write
);
2518 static int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
2520 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
2521 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
2522 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
2524 /* In case of error, head will be NULL */
2525 if (unlikely(!head
))
2528 return reader
->read
== rb_page_commit(reader
) &&
2529 (commit
== reader
||
2531 head
->read
== rb_page_commit(commit
)));
2535 * ring_buffer_record_disable - stop all writes into the buffer
2536 * @buffer: The ring buffer to stop writes to.
2538 * This prevents all writes to the buffer. Any attempt to write
2539 * to the buffer after this will fail and return NULL.
2541 * The caller should call synchronize_sched() after this.
2543 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
2545 atomic_inc(&buffer
->record_disabled
);
2547 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
2550 * ring_buffer_record_enable - enable writes to the buffer
2551 * @buffer: The ring buffer to enable writes
2553 * Note, multiple disables will need the same number of enables
2554 * to truly enable the writing (much like preempt_disable).
2556 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
2558 atomic_dec(&buffer
->record_disabled
);
2560 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
2563 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2564 * @buffer: The ring buffer to stop writes to.
2565 * @cpu: The CPU buffer to stop
2567 * This prevents all writes to the buffer. Any attempt to write
2568 * to the buffer after this will fail and return NULL.
2570 * The caller should call synchronize_sched() after this.
2572 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
2574 struct ring_buffer_per_cpu
*cpu_buffer
;
2576 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2579 cpu_buffer
= buffer
->buffers
[cpu
];
2580 atomic_inc(&cpu_buffer
->record_disabled
);
2582 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
2585 * ring_buffer_record_enable_cpu - enable writes to the buffer
2586 * @buffer: The ring buffer to enable writes
2587 * @cpu: The CPU to enable.
2589 * Note, multiple disables will need the same number of enables
2590 * to truly enable the writing (much like preempt_disable).
2592 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
2594 struct ring_buffer_per_cpu
*cpu_buffer
;
2596 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2599 cpu_buffer
= buffer
->buffers
[cpu
];
2600 atomic_dec(&cpu_buffer
->record_disabled
);
2602 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
2605 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2606 * @buffer: The ring buffer
2607 * @cpu: The per CPU buffer to get the entries from.
2609 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
2611 struct ring_buffer_per_cpu
*cpu_buffer
;
2614 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2617 cpu_buffer
= buffer
->buffers
[cpu
];
2618 ret
= (local_read(&cpu_buffer
->entries
) - local_read(&cpu_buffer
->overrun
))
2623 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
2626 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
2627 * @buffer: The ring buffer
2628 * @cpu: The per CPU buffer to get the number of overruns from
2630 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
2632 struct ring_buffer_per_cpu
*cpu_buffer
;
2635 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2638 cpu_buffer
= buffer
->buffers
[cpu
];
2639 ret
= local_read(&cpu_buffer
->overrun
);
2643 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
2646 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2647 * @buffer: The ring buffer
2648 * @cpu: The per CPU buffer to get the number of overruns from
2651 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
2653 struct ring_buffer_per_cpu
*cpu_buffer
;
2656 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2659 cpu_buffer
= buffer
->buffers
[cpu
];
2660 ret
= local_read(&cpu_buffer
->commit_overrun
);
2664 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
2667 * ring_buffer_entries - get the number of entries in a buffer
2668 * @buffer: The ring buffer
2670 * Returns the total number of entries in the ring buffer
2673 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
2675 struct ring_buffer_per_cpu
*cpu_buffer
;
2676 unsigned long entries
= 0;
2679 /* if you care about this being correct, lock the buffer */
2680 for_each_buffer_cpu(buffer
, cpu
) {
2681 cpu_buffer
= buffer
->buffers
[cpu
];
2682 entries
+= (local_read(&cpu_buffer
->entries
) -
2683 local_read(&cpu_buffer
->overrun
)) - cpu_buffer
->read
;
2688 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
2691 * ring_buffer_overruns - get the number of overruns in buffer
2692 * @buffer: The ring buffer
2694 * Returns the total number of overruns in the ring buffer
2697 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
2699 struct ring_buffer_per_cpu
*cpu_buffer
;
2700 unsigned long overruns
= 0;
2703 /* if you care about this being correct, lock the buffer */
2704 for_each_buffer_cpu(buffer
, cpu
) {
2705 cpu_buffer
= buffer
->buffers
[cpu
];
2706 overruns
+= local_read(&cpu_buffer
->overrun
);
2711 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
2713 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
2715 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2717 /* Iterator usage is expected to have record disabled */
2718 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
2719 iter
->head_page
= rb_set_head_page(cpu_buffer
);
2720 if (unlikely(!iter
->head_page
))
2722 iter
->head
= iter
->head_page
->read
;
2724 iter
->head_page
= cpu_buffer
->reader_page
;
2725 iter
->head
= cpu_buffer
->reader_page
->read
;
2728 iter
->read_stamp
= cpu_buffer
->read_stamp
;
2730 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2731 iter
->cache_reader_page
= cpu_buffer
->reader_page
;
2732 iter
->cache_read
= cpu_buffer
->read
;
2736 * ring_buffer_iter_reset - reset an iterator
2737 * @iter: The iterator to reset
2739 * Resets the iterator, so that it will start from the beginning
2742 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
2744 struct ring_buffer_per_cpu
*cpu_buffer
;
2745 unsigned long flags
;
2750 cpu_buffer
= iter
->cpu_buffer
;
2752 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2753 rb_iter_reset(iter
);
2754 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2756 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
2759 * ring_buffer_iter_empty - check if an iterator has no more to read
2760 * @iter: The iterator to check
2762 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
2764 struct ring_buffer_per_cpu
*cpu_buffer
;
2766 cpu_buffer
= iter
->cpu_buffer
;
2768 return iter
->head_page
== cpu_buffer
->commit_page
&&
2769 iter
->head
== rb_commit_index(cpu_buffer
);
2771 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
2774 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2775 struct ring_buffer_event
*event
)
2779 switch (event
->type_len
) {
2780 case RINGBUF_TYPE_PADDING
:
2783 case RINGBUF_TYPE_TIME_EXTEND
:
2784 delta
= event
->array
[0];
2786 delta
+= event
->time_delta
;
2787 cpu_buffer
->read_stamp
+= delta
;
2790 case RINGBUF_TYPE_TIME_STAMP
:
2791 /* FIXME: not implemented */
2794 case RINGBUF_TYPE_DATA
:
2795 cpu_buffer
->read_stamp
+= event
->time_delta
;
2805 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
2806 struct ring_buffer_event
*event
)
2810 switch (event
->type_len
) {
2811 case RINGBUF_TYPE_PADDING
:
2814 case RINGBUF_TYPE_TIME_EXTEND
:
2815 delta
= event
->array
[0];
2817 delta
+= event
->time_delta
;
2818 iter
->read_stamp
+= delta
;
2821 case RINGBUF_TYPE_TIME_STAMP
:
2822 /* FIXME: not implemented */
2825 case RINGBUF_TYPE_DATA
:
2826 iter
->read_stamp
+= event
->time_delta
;
2835 static struct buffer_page
*
2836 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
2838 struct buffer_page
*reader
= NULL
;
2839 unsigned long flags
;
2843 local_irq_save(flags
);
2844 arch_spin_lock(&cpu_buffer
->lock
);
2848 * This should normally only loop twice. But because the
2849 * start of the reader inserts an empty page, it causes
2850 * a case where we will loop three times. There should be no
2851 * reason to loop four times (that I know of).
2853 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
2858 reader
= cpu_buffer
->reader_page
;
2860 /* If there's more to read, return this page */
2861 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
2864 /* Never should we have an index greater than the size */
2865 if (RB_WARN_ON(cpu_buffer
,
2866 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
2869 /* check if we caught up to the tail */
2871 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
2875 * Reset the reader page to size zero.
2877 local_set(&cpu_buffer
->reader_page
->write
, 0);
2878 local_set(&cpu_buffer
->reader_page
->entries
, 0);
2879 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
2883 * Splice the empty reader page into the list around the head.
2885 reader
= rb_set_head_page(cpu_buffer
);
2886 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
2887 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
2890 * cpu_buffer->pages just needs to point to the buffer, it
2891 * has no specific buffer page to point to. Lets move it out
2892 * of our way so we don't accidently swap it.
2894 cpu_buffer
->pages
= reader
->list
.prev
;
2896 /* The reader page will be pointing to the new head */
2897 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
2900 * Here's the tricky part.
2902 * We need to move the pointer past the header page.
2903 * But we can only do that if a writer is not currently
2904 * moving it. The page before the header page has the
2905 * flag bit '1' set if it is pointing to the page we want.
2906 * but if the writer is in the process of moving it
2907 * than it will be '2' or already moved '0'.
2910 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
2913 * If we did not convert it, then we must try again.
2919 * Yeah! We succeeded in replacing the page.
2921 * Now make the new head point back to the reader page.
2923 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
2924 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
2926 /* Finally update the reader page to the new head */
2927 cpu_buffer
->reader_page
= reader
;
2928 rb_reset_reader_page(cpu_buffer
);
2933 arch_spin_unlock(&cpu_buffer
->lock
);
2934 local_irq_restore(flags
);
2939 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
2941 struct ring_buffer_event
*event
;
2942 struct buffer_page
*reader
;
2945 reader
= rb_get_reader_page(cpu_buffer
);
2947 /* This function should not be called when buffer is empty */
2948 if (RB_WARN_ON(cpu_buffer
, !reader
))
2951 event
= rb_reader_event(cpu_buffer
);
2953 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
2956 rb_update_read_stamp(cpu_buffer
, event
);
2958 length
= rb_event_length(event
);
2959 cpu_buffer
->reader_page
->read
+= length
;
2962 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
2964 struct ring_buffer
*buffer
;
2965 struct ring_buffer_per_cpu
*cpu_buffer
;
2966 struct ring_buffer_event
*event
;
2969 cpu_buffer
= iter
->cpu_buffer
;
2970 buffer
= cpu_buffer
->buffer
;
2973 * Check if we are at the end of the buffer.
2975 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
2976 /* discarded commits can make the page empty */
2977 if (iter
->head_page
== cpu_buffer
->commit_page
)
2983 event
= rb_iter_head_event(iter
);
2985 length
= rb_event_length(event
);
2988 * This should not be called to advance the header if we are
2989 * at the tail of the buffer.
2991 if (RB_WARN_ON(cpu_buffer
,
2992 (iter
->head_page
== cpu_buffer
->commit_page
) &&
2993 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
2996 rb_update_iter_read_stamp(iter
, event
);
2998 iter
->head
+= length
;
3000 /* check for end of page padding */
3001 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3002 (iter
->head_page
!= cpu_buffer
->commit_page
))
3003 rb_advance_iter(iter
);
3006 static struct ring_buffer_event
*
3007 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
)
3009 struct ring_buffer_event
*event
;
3010 struct buffer_page
*reader
;
3015 * We repeat when a timestamp is encountered. It is possible
3016 * to get multiple timestamps from an interrupt entering just
3017 * as one timestamp is about to be written, or from discarded
3018 * commits. The most that we can have is the number on a single page.
3020 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
3023 reader
= rb_get_reader_page(cpu_buffer
);
3027 event
= rb_reader_event(cpu_buffer
);
3029 switch (event
->type_len
) {
3030 case RINGBUF_TYPE_PADDING
:
3031 if (rb_null_event(event
))
3032 RB_WARN_ON(cpu_buffer
, 1);
3034 * Because the writer could be discarding every
3035 * event it creates (which would probably be bad)
3036 * if we were to go back to "again" then we may never
3037 * catch up, and will trigger the warn on, or lock
3038 * the box. Return the padding, and we will release
3039 * the current locks, and try again.
3043 case RINGBUF_TYPE_TIME_EXTEND
:
3044 /* Internal data, OK to advance */
3045 rb_advance_reader(cpu_buffer
);
3048 case RINGBUF_TYPE_TIME_STAMP
:
3049 /* FIXME: not implemented */
3050 rb_advance_reader(cpu_buffer
);
3053 case RINGBUF_TYPE_DATA
:
3055 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3056 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3057 cpu_buffer
->cpu
, ts
);
3067 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3069 static struct ring_buffer_event
*
3070 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3072 struct ring_buffer
*buffer
;
3073 struct ring_buffer_per_cpu
*cpu_buffer
;
3074 struct ring_buffer_event
*event
;
3077 cpu_buffer
= iter
->cpu_buffer
;
3078 buffer
= cpu_buffer
->buffer
;
3081 * Check if someone performed a consuming read to
3082 * the buffer. A consuming read invalidates the iterator
3083 * and we need to reset the iterator in this case.
3085 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3086 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3087 rb_iter_reset(iter
);
3090 if (ring_buffer_iter_empty(iter
))
3094 * We repeat when a timestamp is encountered.
3095 * We can get multiple timestamps by nested interrupts or also
3096 * if filtering is on (discarding commits). Since discarding
3097 * commits can be frequent we can get a lot of timestamps.
3098 * But we limit them by not adding timestamps if they begin
3099 * at the start of a page.
3101 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
3104 if (rb_per_cpu_empty(cpu_buffer
))
3107 if (iter
->head
>= local_read(&iter
->head_page
->page
->commit
)) {
3112 event
= rb_iter_head_event(iter
);
3114 switch (event
->type_len
) {
3115 case RINGBUF_TYPE_PADDING
:
3116 if (rb_null_event(event
)) {
3120 rb_advance_iter(iter
);
3123 case RINGBUF_TYPE_TIME_EXTEND
:
3124 /* Internal data, OK to advance */
3125 rb_advance_iter(iter
);
3128 case RINGBUF_TYPE_TIME_STAMP
:
3129 /* FIXME: not implemented */
3130 rb_advance_iter(iter
);
3133 case RINGBUF_TYPE_DATA
:
3135 *ts
= iter
->read_stamp
+ event
->time_delta
;
3136 ring_buffer_normalize_time_stamp(buffer
,
3137 cpu_buffer
->cpu
, ts
);
3147 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3149 static inline int rb_ok_to_lock(void)
3152 * If an NMI die dumps out the content of the ring buffer
3153 * do not grab locks. We also permanently disable the ring
3154 * buffer too. A one time deal is all you get from reading
3155 * the ring buffer from an NMI.
3157 if (likely(!in_nmi()))
3160 tracing_off_permanent();
3165 * ring_buffer_peek - peek at the next event to be read
3166 * @buffer: The ring buffer to read
3167 * @cpu: The cpu to peak at
3168 * @ts: The timestamp counter of this event.
3170 * This will return the event that will be read next, but does
3171 * not consume the data.
3173 struct ring_buffer_event
*
3174 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
3176 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3177 struct ring_buffer_event
*event
;
3178 unsigned long flags
;
3181 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3184 dolock
= rb_ok_to_lock();
3186 local_irq_save(flags
);
3188 spin_lock(&cpu_buffer
->reader_lock
);
3189 event
= rb_buffer_peek(cpu_buffer
, ts
);
3190 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3191 rb_advance_reader(cpu_buffer
);
3193 spin_unlock(&cpu_buffer
->reader_lock
);
3194 local_irq_restore(flags
);
3196 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3203 * ring_buffer_iter_peek - peek at the next event to be read
3204 * @iter: The ring buffer iterator
3205 * @ts: The timestamp counter of this event.
3207 * This will return the event that will be read next, but does
3208 * not increment the iterator.
3210 struct ring_buffer_event
*
3211 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3213 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3214 struct ring_buffer_event
*event
;
3215 unsigned long flags
;
3218 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3219 event
= rb_iter_peek(iter
, ts
);
3220 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3222 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3229 * ring_buffer_consume - return an event and consume it
3230 * @buffer: The ring buffer to get the next event from
3232 * Returns the next event in the ring buffer, and that event is consumed.
3233 * Meaning, that sequential reads will keep returning a different event,
3234 * and eventually empty the ring buffer if the producer is slower.
3236 struct ring_buffer_event
*
3237 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
3239 struct ring_buffer_per_cpu
*cpu_buffer
;
3240 struct ring_buffer_event
*event
= NULL
;
3241 unsigned long flags
;
3244 dolock
= rb_ok_to_lock();
3247 /* might be called in atomic */
3250 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3253 cpu_buffer
= buffer
->buffers
[cpu
];
3254 local_irq_save(flags
);
3256 spin_lock(&cpu_buffer
->reader_lock
);
3258 event
= rb_buffer_peek(cpu_buffer
, ts
);
3260 rb_advance_reader(cpu_buffer
);
3263 spin_unlock(&cpu_buffer
->reader_lock
);
3264 local_irq_restore(flags
);
3269 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3274 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
3277 * ring_buffer_read_start - start a non consuming read of the buffer
3278 * @buffer: The ring buffer to read from
3279 * @cpu: The cpu buffer to iterate over
3281 * This starts up an iteration through the buffer. It also disables
3282 * the recording to the buffer until the reading is finished.
3283 * This prevents the reading from being corrupted. This is not
3284 * a consuming read, so a producer is not expected.
3286 * Must be paired with ring_buffer_finish.
3288 struct ring_buffer_iter
*
3289 ring_buffer_read_start(struct ring_buffer
*buffer
, int cpu
)
3291 struct ring_buffer_per_cpu
*cpu_buffer
;
3292 struct ring_buffer_iter
*iter
;
3293 unsigned long flags
;
3295 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3298 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
3302 cpu_buffer
= buffer
->buffers
[cpu
];
3304 iter
->cpu_buffer
= cpu_buffer
;
3306 atomic_inc(&cpu_buffer
->record_disabled
);
3307 synchronize_sched();
3309 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3310 arch_spin_lock(&cpu_buffer
->lock
);
3311 rb_iter_reset(iter
);
3312 arch_spin_unlock(&cpu_buffer
->lock
);
3313 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3317 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
3320 * ring_buffer_finish - finish reading the iterator of the buffer
3321 * @iter: The iterator retrieved by ring_buffer_start
3323 * This re-enables the recording to the buffer, and frees the
3327 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
3329 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3331 atomic_dec(&cpu_buffer
->record_disabled
);
3334 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
3337 * ring_buffer_read - read the next item in the ring buffer by the iterator
3338 * @iter: The ring buffer iterator
3339 * @ts: The time stamp of the event read.
3341 * This reads the next event in the ring buffer and increments the iterator.
3343 struct ring_buffer_event
*
3344 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
3346 struct ring_buffer_event
*event
;
3347 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3348 unsigned long flags
;
3350 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3352 event
= rb_iter_peek(iter
, ts
);
3356 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
3359 rb_advance_iter(iter
);
3361 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3365 EXPORT_SYMBOL_GPL(ring_buffer_read
);
3368 * ring_buffer_size - return the size of the ring buffer (in bytes)
3369 * @buffer: The ring buffer.
3371 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
3373 return BUF_PAGE_SIZE
* buffer
->pages
;
3375 EXPORT_SYMBOL_GPL(ring_buffer_size
);
3378 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
3380 rb_head_page_deactivate(cpu_buffer
);
3382 cpu_buffer
->head_page
3383 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
3384 local_set(&cpu_buffer
->head_page
->write
, 0);
3385 local_set(&cpu_buffer
->head_page
->entries
, 0);
3386 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
3388 cpu_buffer
->head_page
->read
= 0;
3390 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
3391 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
3393 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
3394 local_set(&cpu_buffer
->reader_page
->write
, 0);
3395 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3396 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3397 cpu_buffer
->reader_page
->read
= 0;
3399 local_set(&cpu_buffer
->commit_overrun
, 0);
3400 local_set(&cpu_buffer
->overrun
, 0);
3401 local_set(&cpu_buffer
->entries
, 0);
3402 local_set(&cpu_buffer
->committing
, 0);
3403 local_set(&cpu_buffer
->commits
, 0);
3404 cpu_buffer
->read
= 0;
3406 cpu_buffer
->write_stamp
= 0;
3407 cpu_buffer
->read_stamp
= 0;
3409 rb_head_page_activate(cpu_buffer
);
3413 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3414 * @buffer: The ring buffer to reset a per cpu buffer of
3415 * @cpu: The CPU buffer to be reset
3417 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
3419 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3420 unsigned long flags
;
3422 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3425 atomic_inc(&cpu_buffer
->record_disabled
);
3427 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3429 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
3432 arch_spin_lock(&cpu_buffer
->lock
);
3434 rb_reset_cpu(cpu_buffer
);
3436 arch_spin_unlock(&cpu_buffer
->lock
);
3439 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3441 atomic_dec(&cpu_buffer
->record_disabled
);
3443 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
3446 * ring_buffer_reset - reset a ring buffer
3447 * @buffer: The ring buffer to reset all cpu buffers
3449 void ring_buffer_reset(struct ring_buffer
*buffer
)
3453 for_each_buffer_cpu(buffer
, cpu
)
3454 ring_buffer_reset_cpu(buffer
, cpu
);
3456 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
3459 * rind_buffer_empty - is the ring buffer empty?
3460 * @buffer: The ring buffer to test
3462 int ring_buffer_empty(struct ring_buffer
*buffer
)
3464 struct ring_buffer_per_cpu
*cpu_buffer
;
3465 unsigned long flags
;
3470 dolock
= rb_ok_to_lock();
3472 /* yes this is racy, but if you don't like the race, lock the buffer */
3473 for_each_buffer_cpu(buffer
, cpu
) {
3474 cpu_buffer
= buffer
->buffers
[cpu
];
3475 local_irq_save(flags
);
3477 spin_lock(&cpu_buffer
->reader_lock
);
3478 ret
= rb_per_cpu_empty(cpu_buffer
);
3480 spin_unlock(&cpu_buffer
->reader_lock
);
3481 local_irq_restore(flags
);
3489 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
3492 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
3493 * @buffer: The ring buffer
3494 * @cpu: The CPU buffer to test
3496 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
3498 struct ring_buffer_per_cpu
*cpu_buffer
;
3499 unsigned long flags
;
3503 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3506 dolock
= rb_ok_to_lock();
3508 cpu_buffer
= buffer
->buffers
[cpu
];
3509 local_irq_save(flags
);
3511 spin_lock(&cpu_buffer
->reader_lock
);
3512 ret
= rb_per_cpu_empty(cpu_buffer
);
3514 spin_unlock(&cpu_buffer
->reader_lock
);
3515 local_irq_restore(flags
);
3519 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
3521 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3523 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
3524 * @buffer_a: One buffer to swap with
3525 * @buffer_b: The other buffer to swap with
3527 * This function is useful for tracers that want to take a "snapshot"
3528 * of a CPU buffer and has another back up buffer lying around.
3529 * it is expected that the tracer handles the cpu buffer not being
3530 * used at the moment.
3532 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
3533 struct ring_buffer
*buffer_b
, int cpu
)
3535 struct ring_buffer_per_cpu
*cpu_buffer_a
;
3536 struct ring_buffer_per_cpu
*cpu_buffer_b
;
3539 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
3540 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
3543 /* At least make sure the two buffers are somewhat the same */
3544 if (buffer_a
->pages
!= buffer_b
->pages
)
3549 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
3552 if (atomic_read(&buffer_a
->record_disabled
))
3555 if (atomic_read(&buffer_b
->record_disabled
))
3558 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
3559 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
3561 if (atomic_read(&cpu_buffer_a
->record_disabled
))
3564 if (atomic_read(&cpu_buffer_b
->record_disabled
))
3568 * We can't do a synchronize_sched here because this
3569 * function can be called in atomic context.
3570 * Normally this will be called from the same CPU as cpu.
3571 * If not it's up to the caller to protect this.
3573 atomic_inc(&cpu_buffer_a
->record_disabled
);
3574 atomic_inc(&cpu_buffer_b
->record_disabled
);
3577 if (local_read(&cpu_buffer_a
->committing
))
3579 if (local_read(&cpu_buffer_b
->committing
))
3582 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
3583 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
3585 cpu_buffer_b
->buffer
= buffer_a
;
3586 cpu_buffer_a
->buffer
= buffer_b
;
3591 atomic_dec(&cpu_buffer_a
->record_disabled
);
3592 atomic_dec(&cpu_buffer_b
->record_disabled
);
3596 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
3597 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
3600 * ring_buffer_alloc_read_page - allocate a page to read from buffer
3601 * @buffer: the buffer to allocate for.
3603 * This function is used in conjunction with ring_buffer_read_page.
3604 * When reading a full page from the ring buffer, these functions
3605 * can be used to speed up the process. The calling function should
3606 * allocate a few pages first with this function. Then when it
3607 * needs to get pages from the ring buffer, it passes the result
3608 * of this function into ring_buffer_read_page, which will swap
3609 * the page that was allocated, with the read page of the buffer.
3612 * The page allocated, or NULL on error.
3614 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
)
3616 struct buffer_data_page
*bpage
;
3619 addr
= __get_free_page(GFP_KERNEL
);
3623 bpage
= (void *)addr
;
3625 rb_init_page(bpage
);
3629 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
3632 * ring_buffer_free_read_page - free an allocated read page
3633 * @buffer: the buffer the page was allocate for
3634 * @data: the page to free
3636 * Free a page allocated from ring_buffer_alloc_read_page.
3638 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
3640 free_page((unsigned long)data
);
3642 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
3645 * ring_buffer_read_page - extract a page from the ring buffer
3646 * @buffer: buffer to extract from
3647 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
3648 * @len: amount to extract
3649 * @cpu: the cpu of the buffer to extract
3650 * @full: should the extraction only happen when the page is full.
3652 * This function will pull out a page from the ring buffer and consume it.
3653 * @data_page must be the address of the variable that was returned
3654 * from ring_buffer_alloc_read_page. This is because the page might be used
3655 * to swap with a page in the ring buffer.
3658 * rpage = ring_buffer_alloc_read_page(buffer);
3661 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
3663 * process_page(rpage, ret);
3665 * When @full is set, the function will not return true unless
3666 * the writer is off the reader page.
3668 * Note: it is up to the calling functions to handle sleeps and wakeups.
3669 * The ring buffer can be used anywhere in the kernel and can not
3670 * blindly call wake_up. The layer that uses the ring buffer must be
3671 * responsible for that.
3674 * >=0 if data has been transferred, returns the offset of consumed data.
3675 * <0 if no data has been transferred.
3677 int ring_buffer_read_page(struct ring_buffer
*buffer
,
3678 void **data_page
, size_t len
, int cpu
, int full
)
3680 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3681 struct ring_buffer_event
*event
;
3682 struct buffer_data_page
*bpage
;
3683 struct buffer_page
*reader
;
3684 unsigned long flags
;
3685 unsigned int commit
;
3690 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3694 * If len is not big enough to hold the page header, then
3695 * we can not copy anything.
3697 if (len
<= BUF_PAGE_HDR_SIZE
)
3700 len
-= BUF_PAGE_HDR_SIZE
;
3709 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3711 reader
= rb_get_reader_page(cpu_buffer
);
3715 event
= rb_reader_event(cpu_buffer
);
3717 read
= reader
->read
;
3718 commit
= rb_page_commit(reader
);
3721 * If this page has been partially read or
3722 * if len is not big enough to read the rest of the page or
3723 * a writer is still on the page, then
3724 * we must copy the data from the page to the buffer.
3725 * Otherwise, we can simply swap the page with the one passed in.
3727 if (read
|| (len
< (commit
- read
)) ||
3728 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
3729 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
3730 unsigned int rpos
= read
;
3731 unsigned int pos
= 0;
3737 if (len
> (commit
- read
))
3738 len
= (commit
- read
);
3740 size
= rb_event_length(event
);
3745 /* save the current timestamp, since the user will need it */
3746 save_timestamp
= cpu_buffer
->read_stamp
;
3748 /* Need to copy one event at a time */
3750 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
3754 rb_advance_reader(cpu_buffer
);
3755 rpos
= reader
->read
;
3758 event
= rb_reader_event(cpu_buffer
);
3759 size
= rb_event_length(event
);
3760 } while (len
> size
);
3763 local_set(&bpage
->commit
, pos
);
3764 bpage
->time_stamp
= save_timestamp
;
3766 /* we copied everything to the beginning */
3769 /* update the entry counter */
3770 cpu_buffer
->read
+= rb_page_entries(reader
);
3772 /* swap the pages */
3773 rb_init_page(bpage
);
3774 bpage
= reader
->page
;
3775 reader
->page
= *data_page
;
3776 local_set(&reader
->write
, 0);
3777 local_set(&reader
->entries
, 0);
3784 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3789 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
3791 #ifdef CONFIG_TRACING
3793 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
3794 size_t cnt
, loff_t
*ppos
)
3796 unsigned long *p
= filp
->private_data
;
3800 if (test_bit(RB_BUFFERS_DISABLED_BIT
, p
))
3801 r
= sprintf(buf
, "permanently disabled\n");
3803 r
= sprintf(buf
, "%d\n", test_bit(RB_BUFFERS_ON_BIT
, p
));
3805 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
3809 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
3810 size_t cnt
, loff_t
*ppos
)
3812 unsigned long *p
= filp
->private_data
;
3817 if (cnt
>= sizeof(buf
))
3820 if (copy_from_user(&buf
, ubuf
, cnt
))
3825 ret
= strict_strtoul(buf
, 10, &val
);
3830 set_bit(RB_BUFFERS_ON_BIT
, p
);
3832 clear_bit(RB_BUFFERS_ON_BIT
, p
);
3839 static const struct file_operations rb_simple_fops
= {
3840 .open
= tracing_open_generic
,
3841 .read
= rb_simple_read
,
3842 .write
= rb_simple_write
,
3846 static __init
int rb_init_debugfs(void)
3848 struct dentry
*d_tracer
;
3850 d_tracer
= tracing_init_dentry();
3852 trace_create_file("tracing_on", 0644, d_tracer
,
3853 &ring_buffer_flags
, &rb_simple_fops
);
3858 fs_initcall(rb_init_debugfs
);
3861 #ifdef CONFIG_HOTPLUG_CPU
3862 static int rb_cpu_notify(struct notifier_block
*self
,
3863 unsigned long action
, void *hcpu
)
3865 struct ring_buffer
*buffer
=
3866 container_of(self
, struct ring_buffer
, cpu_notify
);
3867 long cpu
= (long)hcpu
;
3870 case CPU_UP_PREPARE
:
3871 case CPU_UP_PREPARE_FROZEN
:
3872 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
3875 buffer
->buffers
[cpu
] =
3876 rb_allocate_cpu_buffer(buffer
, cpu
);
3877 if (!buffer
->buffers
[cpu
]) {
3878 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
3883 cpumask_set_cpu(cpu
, buffer
->cpumask
);
3885 case CPU_DOWN_PREPARE
:
3886 case CPU_DOWN_PREPARE_FROZEN
:
3889 * If we were to free the buffer, then the user would
3890 * lose any trace that was in the buffer.