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/init.h>
18 #include <linux/hash.h>
19 #include <linux/list.h>
20 #include <linux/cpu.h>
26 * The ring buffer header is special. We must manually up keep it.
28 int ring_buffer_print_entry_header(struct trace_seq
*s
)
32 ret
= trace_seq_printf(s
, "# compressed entry header\n");
33 ret
= trace_seq_printf(s
, "\ttype_len : 5 bits\n");
34 ret
= trace_seq_printf(s
, "\ttime_delta : 27 bits\n");
35 ret
= trace_seq_printf(s
, "\tarray : 32 bits\n");
36 ret
= trace_seq_printf(s
, "\n");
37 ret
= trace_seq_printf(s
, "\tpadding : type == %d\n",
38 RINGBUF_TYPE_PADDING
);
39 ret
= trace_seq_printf(s
, "\ttime_extend : type == %d\n",
40 RINGBUF_TYPE_TIME_EXTEND
);
41 ret
= trace_seq_printf(s
, "\tdata max type_len == %d\n",
42 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
48 * The ring buffer is made up of a list of pages. A separate list of pages is
49 * allocated for each CPU. A writer may only write to a buffer that is
50 * associated with the CPU it is currently executing on. A reader may read
51 * from any per cpu buffer.
53 * The reader is special. For each per cpu buffer, the reader has its own
54 * reader page. When a reader has read the entire reader page, this reader
55 * page is swapped with another page in the ring buffer.
57 * Now, as long as the writer is off the reader page, the reader can do what
58 * ever it wants with that page. The writer will never write to that page
59 * again (as long as it is out of the ring buffer).
61 * Here's some silly ASCII art.
64 * |reader| RING BUFFER
66 * +------+ +---+ +---+ +---+
75 * |reader| RING BUFFER
76 * |page |------------------v
77 * +------+ +---+ +---+ +---+
86 * |reader| RING BUFFER
87 * |page |------------------v
88 * +------+ +---+ +---+ +---+
93 * +------------------------------+
97 * |buffer| RING BUFFER
98 * |page |------------------v
99 * +------+ +---+ +---+ +---+
101 * | New +---+ +---+ +---+
104 * +------------------------------+
107 * After we make this swap, the reader can hand this page off to the splice
108 * code and be done with it. It can even allocate a new page if it needs to
109 * and swap that into the ring buffer.
111 * We will be using cmpxchg soon to make all this lockless.
116 * A fast way to enable or disable all ring buffers is to
117 * call tracing_on or tracing_off. Turning off the ring buffers
118 * prevents all ring buffers from being recorded to.
119 * Turning this switch on, makes it OK to write to the
120 * ring buffer, if the ring buffer is enabled itself.
122 * There's three layers that must be on in order to write
123 * to the ring buffer.
125 * 1) This global flag must be set.
126 * 2) The ring buffer must be enabled for recording.
127 * 3) The per cpu buffer must be enabled for recording.
129 * In case of an anomaly, this global flag has a bit set that
130 * will permantly disable all ring buffers.
134 * Global flag to disable all recording to ring buffers
135 * This has two bits: ON, DISABLED
139 * 0 0 : ring buffers are off
140 * 1 0 : ring buffers are on
141 * X 1 : ring buffers are permanently disabled
145 RB_BUFFERS_ON_BIT
= 0,
146 RB_BUFFERS_DISABLED_BIT
= 1,
150 RB_BUFFERS_ON
= 1 << RB_BUFFERS_ON_BIT
,
151 RB_BUFFERS_DISABLED
= 1 << RB_BUFFERS_DISABLED_BIT
,
154 static unsigned long ring_buffer_flags __read_mostly
= RB_BUFFERS_ON
;
156 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
159 * tracing_on - enable all tracing buffers
161 * This function enables all tracing buffers that may have been
162 * disabled with tracing_off.
164 void tracing_on(void)
166 set_bit(RB_BUFFERS_ON_BIT
, &ring_buffer_flags
);
168 EXPORT_SYMBOL_GPL(tracing_on
);
171 * tracing_off - turn off all tracing buffers
173 * This function stops all tracing buffers from recording data.
174 * It does not disable any overhead the tracers themselves may
175 * be causing. This function simply causes all recording to
176 * the ring buffers to fail.
178 void tracing_off(void)
180 clear_bit(RB_BUFFERS_ON_BIT
, &ring_buffer_flags
);
182 EXPORT_SYMBOL_GPL(tracing_off
);
185 * tracing_off_permanent - permanently disable ring buffers
187 * This function, once called, will disable all ring buffers
190 void tracing_off_permanent(void)
192 set_bit(RB_BUFFERS_DISABLED_BIT
, &ring_buffer_flags
);
196 * tracing_is_on - show state of ring buffers enabled
198 int tracing_is_on(void)
200 return ring_buffer_flags
== RB_BUFFERS_ON
;
202 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 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
212 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
215 RB_LEN_TIME_EXTEND
= 8,
216 RB_LEN_TIME_STAMP
= 16,
219 static inline int rb_null_event(struct ring_buffer_event
*event
)
221 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
224 static void rb_event_set_padding(struct ring_buffer_event
*event
)
226 /* padding has a NULL time_delta */
227 event
->type_len
= RINGBUF_TYPE_PADDING
;
228 event
->time_delta
= 0;
232 rb_event_data_length(struct ring_buffer_event
*event
)
237 length
= event
->type_len
* RB_ALIGNMENT
;
239 length
= event
->array
[0];
240 return length
+ RB_EVNT_HDR_SIZE
;
243 /* inline for ring buffer fast paths */
245 rb_event_length(struct ring_buffer_event
*event
)
247 switch (event
->type_len
) {
248 case RINGBUF_TYPE_PADDING
:
249 if (rb_null_event(event
))
252 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
254 case RINGBUF_TYPE_TIME_EXTEND
:
255 return RB_LEN_TIME_EXTEND
;
257 case RINGBUF_TYPE_TIME_STAMP
:
258 return RB_LEN_TIME_STAMP
;
260 case RINGBUF_TYPE_DATA
:
261 return rb_event_data_length(event
);
270 * ring_buffer_event_length - return the length of the event
271 * @event: the event to get the length of
273 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
275 unsigned length
= rb_event_length(event
);
276 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
278 length
-= RB_EVNT_HDR_SIZE
;
279 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
280 length
-= sizeof(event
->array
[0]);
283 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
285 /* inline for ring buffer fast paths */
287 rb_event_data(struct ring_buffer_event
*event
)
289 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
290 /* If length is in len field, then array[0] has the data */
292 return (void *)&event
->array
[0];
293 /* Otherwise length is in array[0] and array[1] has the data */
294 return (void *)&event
->array
[1];
298 * ring_buffer_event_data - return the data of the event
299 * @event: the event to get the data from
301 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
303 return rb_event_data(event
);
305 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
307 #define for_each_buffer_cpu(buffer, cpu) \
308 for_each_cpu(cpu, buffer->cpumask)
311 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
312 #define TS_DELTA_TEST (~TS_MASK)
314 struct buffer_data_page
{
315 u64 time_stamp
; /* page time stamp */
316 local_t commit
; /* write committed index */
317 unsigned char data
[]; /* data of buffer page */
321 * Note, the buffer_page list must be first. The buffer pages
322 * are allocated in cache lines, which means that each buffer
323 * page will be at the beginning of a cache line, and thus
324 * the least significant bits will be zero. We use this to
325 * add flags in the list struct pointers, to make the ring buffer
329 struct list_head list
; /* list of buffer pages */
330 local_t write
; /* index for next write */
331 unsigned read
; /* index for next read */
332 local_t entries
; /* entries on this page */
333 struct buffer_data_page
*page
; /* Actual data page */
337 * The buffer page counters, write and entries, must be reset
338 * atomically when crossing page boundaries. To synchronize this
339 * update, two counters are inserted into the number. One is
340 * the actual counter for the write position or count on the page.
342 * The other is a counter of updaters. Before an update happens
343 * the update partition of the counter is incremented. This will
344 * allow the updater to update the counter atomically.
346 * The counter is 20 bits, and the state data is 12.
348 #define RB_WRITE_MASK 0xfffff
349 #define RB_WRITE_INTCNT (1 << 20)
351 static void rb_init_page(struct buffer_data_page
*bpage
)
353 local_set(&bpage
->commit
, 0);
357 * ring_buffer_page_len - the size of data on the page.
358 * @page: The page to read
360 * Returns the amount of data on the page, including buffer page header.
362 size_t ring_buffer_page_len(void *page
)
364 return local_read(&((struct buffer_data_page
*)page
)->commit
)
369 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
372 static void free_buffer_page(struct buffer_page
*bpage
)
374 free_page((unsigned long)bpage
->page
);
379 * We need to fit the time_stamp delta into 27 bits.
381 static inline int test_time_stamp(u64 delta
)
383 if (delta
& TS_DELTA_TEST
)
388 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
390 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
391 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
393 /* Max number of timestamps that can fit on a page */
394 #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP)
396 int ring_buffer_print_page_header(struct trace_seq
*s
)
398 struct buffer_data_page field
;
401 ret
= trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
402 "offset:0;\tsize:%u;\n",
403 (unsigned int)sizeof(field
.time_stamp
));
405 ret
= trace_seq_printf(s
, "\tfield: local_t commit;\t"
406 "offset:%u;\tsize:%u;\n",
407 (unsigned int)offsetof(typeof(field
), commit
),
408 (unsigned int)sizeof(field
.commit
));
410 ret
= trace_seq_printf(s
, "\tfield: char data;\t"
411 "offset:%u;\tsize:%u;\n",
412 (unsigned int)offsetof(typeof(field
), data
),
413 (unsigned int)BUF_PAGE_SIZE
);
419 * head_page == tail_page && head == tail then buffer is empty.
421 struct ring_buffer_per_cpu
{
423 struct ring_buffer
*buffer
;
424 spinlock_t reader_lock
; /* serialize readers */
426 struct lock_class_key lock_key
;
427 struct list_head
*pages
;
428 struct buffer_page
*head_page
; /* read from head */
429 struct buffer_page
*tail_page
; /* write to tail */
430 struct buffer_page
*commit_page
; /* committed pages */
431 struct buffer_page
*reader_page
;
432 local_t commit_overrun
;
440 atomic_t record_disabled
;
447 atomic_t record_disabled
;
448 cpumask_var_t cpumask
;
450 struct lock_class_key
*reader_lock_key
;
454 struct ring_buffer_per_cpu
**buffers
;
456 #ifdef CONFIG_HOTPLUG_CPU
457 struct notifier_block cpu_notify
;
462 struct ring_buffer_iter
{
463 struct ring_buffer_per_cpu
*cpu_buffer
;
465 struct buffer_page
*head_page
;
469 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
470 #define RB_WARN_ON(b, cond) \
472 int _____ret = unlikely(cond); \
474 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
475 struct ring_buffer_per_cpu *__b = \
477 atomic_inc(&__b->buffer->record_disabled); \
479 atomic_inc(&b->record_disabled); \
485 /* Up this if you want to test the TIME_EXTENTS and normalization */
486 #define DEBUG_SHIFT 0
488 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
, int cpu
)
490 /* shift to debug/test normalization and TIME_EXTENTS */
491 return buffer
->clock() << DEBUG_SHIFT
;
494 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
498 preempt_disable_notrace();
499 time
= rb_time_stamp(buffer
, cpu
);
500 preempt_enable_no_resched_notrace();
504 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
506 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
509 /* Just stupid testing the normalize function and deltas */
512 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
515 * Making the ring buffer lockless makes things tricky.
516 * Although writes only happen on the CPU that they are on,
517 * and they only need to worry about interrupts. Reads can
520 * The reader page is always off the ring buffer, but when the
521 * reader finishes with a page, it needs to swap its page with
522 * a new one from the buffer. The reader needs to take from
523 * the head (writes go to the tail). But if a writer is in overwrite
524 * mode and wraps, it must push the head page forward.
526 * Here lies the problem.
528 * The reader must be careful to replace only the head page, and
529 * not another one. As described at the top of the file in the
530 * ASCII art, the reader sets its old page to point to the next
531 * page after head. It then sets the page after head to point to
532 * the old reader page. But if the writer moves the head page
533 * during this operation, the reader could end up with the tail.
535 * We use cmpxchg to help prevent this race. We also do something
536 * special with the page before head. We set the LSB to 1.
538 * When the writer must push the page forward, it will clear the
539 * bit that points to the head page, move the head, and then set
540 * the bit that points to the new head page.
542 * We also don't want an interrupt coming in and moving the head
543 * page on another writer. Thus we use the second LSB to catch
546 * head->list->prev->next bit 1 bit 0
549 * Points to head page 0 1
552 * Note we can not trust the prev pointer of the head page, because:
554 * +----+ +-----+ +-----+
555 * | |------>| T |---X--->| N |
557 * +----+ +-----+ +-----+
560 * +----------| R |----------+ |
564 * Key: ---X--> HEAD flag set in pointer
569 * (see __rb_reserve_next() to see where this happens)
571 * What the above shows is that the reader just swapped out
572 * the reader page with a page in the buffer, but before it
573 * could make the new header point back to the new page added
574 * it was preempted by a writer. The writer moved forward onto
575 * the new page added by the reader and is about to move forward
578 * You can see, it is legitimate for the previous pointer of
579 * the head (or any page) not to point back to itself. But only
583 #define RB_PAGE_NORMAL 0UL
584 #define RB_PAGE_HEAD 1UL
585 #define RB_PAGE_UPDATE 2UL
588 #define RB_FLAG_MASK 3UL
590 /* PAGE_MOVED is not part of the mask */
591 #define RB_PAGE_MOVED 4UL
594 * rb_list_head - remove any bit
596 static struct list_head
*rb_list_head(struct list_head
*list
)
598 unsigned long val
= (unsigned long)list
;
600 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
604 * rb_is_head_page - test if the give page is the head page
606 * Because the reader may move the head_page pointer, we can
607 * not trust what the head page is (it may be pointing to
608 * the reader page). But if the next page is a header page,
609 * its flags will be non zero.
612 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
613 struct buffer_page
*page
, struct list_head
*list
)
617 val
= (unsigned long)list
->next
;
619 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
620 return RB_PAGE_MOVED
;
622 return val
& RB_FLAG_MASK
;
628 * The unique thing about the reader page, is that, if the
629 * writer is ever on it, the previous pointer never points
630 * back to the reader page.
632 static int rb_is_reader_page(struct buffer_page
*page
)
634 struct list_head
*list
= page
->list
.prev
;
636 return rb_list_head(list
->next
) != &page
->list
;
640 * rb_set_list_to_head - set a list_head to be pointing to head.
642 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
643 struct list_head
*list
)
647 ptr
= (unsigned long *)&list
->next
;
648 *ptr
|= RB_PAGE_HEAD
;
649 *ptr
&= ~RB_PAGE_UPDATE
;
653 * rb_head_page_activate - sets up head page
655 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
657 struct buffer_page
*head
;
659 head
= cpu_buffer
->head_page
;
664 * Set the previous list pointer to have the HEAD flag.
666 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
669 static void rb_list_head_clear(struct list_head
*list
)
671 unsigned long *ptr
= (unsigned long *)&list
->next
;
673 *ptr
&= ~RB_FLAG_MASK
;
677 * rb_head_page_dactivate - clears head page ptr (for free list)
680 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
682 struct list_head
*hd
;
684 /* Go through the whole list and clear any pointers found. */
685 rb_list_head_clear(cpu_buffer
->pages
);
687 list_for_each(hd
, cpu_buffer
->pages
)
688 rb_list_head_clear(hd
);
691 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
692 struct buffer_page
*head
,
693 struct buffer_page
*prev
,
694 int old_flag
, int new_flag
)
696 struct list_head
*list
;
697 unsigned long val
= (unsigned long)&head
->list
;
702 val
&= ~RB_FLAG_MASK
;
704 ret
= (unsigned long)cmpxchg(&list
->next
,
705 val
| old_flag
, val
| new_flag
);
707 /* check if the reader took the page */
708 if ((ret
& ~RB_FLAG_MASK
) != val
)
709 return RB_PAGE_MOVED
;
711 return ret
& RB_FLAG_MASK
;
714 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
715 struct buffer_page
*head
,
716 struct buffer_page
*prev
,
719 return rb_head_page_set(cpu_buffer
, head
, prev
,
720 old_flag
, RB_PAGE_UPDATE
);
723 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
724 struct buffer_page
*head
,
725 struct buffer_page
*prev
,
728 return rb_head_page_set(cpu_buffer
, head
, prev
,
729 old_flag
, RB_PAGE_HEAD
);
732 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
733 struct buffer_page
*head
,
734 struct buffer_page
*prev
,
737 return rb_head_page_set(cpu_buffer
, head
, prev
,
738 old_flag
, RB_PAGE_NORMAL
);
741 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
742 struct buffer_page
**bpage
)
744 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
746 *bpage
= list_entry(p
, struct buffer_page
, list
);
749 static struct buffer_page
*
750 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
752 struct buffer_page
*head
;
753 struct buffer_page
*page
;
754 struct list_head
*list
;
757 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
761 list
= cpu_buffer
->pages
;
762 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
765 page
= head
= cpu_buffer
->head_page
;
767 * It is possible that the writer moves the header behind
768 * where we started, and we miss in one loop.
769 * A second loop should grab the header, but we'll do
770 * three loops just because I'm paranoid.
772 for (i
= 0; i
< 3; i
++) {
774 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
775 cpu_buffer
->head_page
= page
;
778 rb_inc_page(cpu_buffer
, &page
);
779 } while (page
!= head
);
782 RB_WARN_ON(cpu_buffer
, 1);
787 static int rb_head_page_replace(struct buffer_page
*old
,
788 struct buffer_page
*new)
790 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
794 val
= *ptr
& ~RB_FLAG_MASK
;
797 ret
= cmpxchg(ptr
, val
, &new->list
);
803 * rb_tail_page_update - move the tail page forward
805 * Returns 1 if moved tail page, 0 if someone else did.
807 static int rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
808 struct buffer_page
*tail_page
,
809 struct buffer_page
*next_page
)
811 struct buffer_page
*old_tail
;
812 unsigned long old_entries
;
813 unsigned long old_write
;
817 * The tail page now needs to be moved forward.
819 * We need to reset the tail page, but without messing
820 * with possible erasing of data brought in by interrupts
821 * that have moved the tail page and are currently on it.
823 * We add a counter to the write field to denote this.
825 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
826 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
829 * Just make sure we have seen our old_write and synchronize
830 * with any interrupts that come in.
835 * If the tail page is still the same as what we think
836 * it is, then it is up to us to update the tail
839 if (tail_page
== cpu_buffer
->tail_page
) {
840 /* Zero the write counter */
841 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
842 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
845 * This will only succeed if an interrupt did
846 * not come in and change it. In which case, we
847 * do not want to modify it.
849 * We add (void) to let the compiler know that we do not care
850 * about the return value of these functions. We use the
851 * cmpxchg to only update if an interrupt did not already
852 * do it for us. If the cmpxchg fails, we don't care.
854 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
855 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
858 * No need to worry about races with clearing out the commit.
859 * it only can increment when a commit takes place. But that
860 * only happens in the outer most nested commit.
862 local_set(&next_page
->page
->commit
, 0);
864 old_tail
= cmpxchg(&cpu_buffer
->tail_page
,
865 tail_page
, next_page
);
867 if (old_tail
== tail_page
)
874 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
875 struct buffer_page
*bpage
)
877 unsigned long val
= (unsigned long)bpage
;
879 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
886 * rb_check_list - make sure a pointer to a list has the last bits zero
888 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
889 struct list_head
*list
)
891 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
893 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
899 * check_pages - integrity check of buffer pages
900 * @cpu_buffer: CPU buffer with pages to test
902 * As a safety measure we check to make sure the data pages have not
905 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
907 struct list_head
*head
= cpu_buffer
->pages
;
908 struct buffer_page
*bpage
, *tmp
;
910 rb_head_page_deactivate(cpu_buffer
);
912 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
914 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
917 if (rb_check_list(cpu_buffer
, head
))
920 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
921 if (RB_WARN_ON(cpu_buffer
,
922 bpage
->list
.next
->prev
!= &bpage
->list
))
924 if (RB_WARN_ON(cpu_buffer
,
925 bpage
->list
.prev
->next
!= &bpage
->list
))
927 if (rb_check_list(cpu_buffer
, &bpage
->list
))
931 rb_head_page_activate(cpu_buffer
);
936 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
939 struct buffer_page
*bpage
, *tmp
;
946 for (i
= 0; i
< nr_pages
; i
++) {
947 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
948 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
952 rb_check_bpage(cpu_buffer
, bpage
);
954 list_add(&bpage
->list
, &pages
);
956 addr
= __get_free_page(GFP_KERNEL
);
959 bpage
->page
= (void *)addr
;
960 rb_init_page(bpage
->page
);
964 * The ring buffer page list is a circular list that does not
965 * start and end with a list head. All page list items point to
968 cpu_buffer
->pages
= pages
.next
;
971 rb_check_pages(cpu_buffer
);
976 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
977 list_del_init(&bpage
->list
);
978 free_buffer_page(bpage
);
983 static struct ring_buffer_per_cpu
*
984 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
986 struct ring_buffer_per_cpu
*cpu_buffer
;
987 struct buffer_page
*bpage
;
991 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
992 GFP_KERNEL
, cpu_to_node(cpu
));
996 cpu_buffer
->cpu
= cpu
;
997 cpu_buffer
->buffer
= buffer
;
998 spin_lock_init(&cpu_buffer
->reader_lock
);
999 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1000 cpu_buffer
->lock
= (raw_spinlock_t
)__RAW_SPIN_LOCK_UNLOCKED
;
1002 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1003 GFP_KERNEL
, cpu_to_node(cpu
));
1005 goto fail_free_buffer
;
1007 rb_check_bpage(cpu_buffer
, bpage
);
1009 cpu_buffer
->reader_page
= bpage
;
1010 addr
= __get_free_page(GFP_KERNEL
);
1012 goto fail_free_reader
;
1013 bpage
->page
= (void *)addr
;
1014 rb_init_page(bpage
->page
);
1016 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1018 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
1020 goto fail_free_reader
;
1022 cpu_buffer
->head_page
1023 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1024 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1026 rb_head_page_activate(cpu_buffer
);
1031 free_buffer_page(cpu_buffer
->reader_page
);
1038 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1040 struct list_head
*head
= cpu_buffer
->pages
;
1041 struct buffer_page
*bpage
, *tmp
;
1043 free_buffer_page(cpu_buffer
->reader_page
);
1045 rb_head_page_deactivate(cpu_buffer
);
1048 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1049 list_del_init(&bpage
->list
);
1050 free_buffer_page(bpage
);
1052 bpage
= list_entry(head
, struct buffer_page
, list
);
1053 free_buffer_page(bpage
);
1059 #ifdef CONFIG_HOTPLUG_CPU
1060 static int rb_cpu_notify(struct notifier_block
*self
,
1061 unsigned long action
, void *hcpu
);
1065 * ring_buffer_alloc - allocate a new ring_buffer
1066 * @size: the size in bytes per cpu that is needed.
1067 * @flags: attributes to set for the ring buffer.
1069 * Currently the only flag that is available is the RB_FL_OVERWRITE
1070 * flag. This flag means that the buffer will overwrite old data
1071 * when the buffer wraps. If this flag is not set, the buffer will
1072 * drop data when the tail hits the head.
1074 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1075 struct lock_class_key
*key
)
1077 struct ring_buffer
*buffer
;
1081 /* keep it in its own cache line */
1082 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1087 if (!alloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1088 goto fail_free_buffer
;
1090 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1091 buffer
->flags
= flags
;
1092 buffer
->clock
= trace_clock_local
;
1093 buffer
->reader_lock_key
= key
;
1095 /* need at least two pages */
1096 if (buffer
->pages
< 2)
1100 * In case of non-hotplug cpu, if the ring-buffer is allocated
1101 * in early initcall, it will not be notified of secondary cpus.
1102 * In that off case, we need to allocate for all possible cpus.
1104 #ifdef CONFIG_HOTPLUG_CPU
1106 cpumask_copy(buffer
->cpumask
, cpu_online_mask
);
1108 cpumask_copy(buffer
->cpumask
, cpu_possible_mask
);
1110 buffer
->cpus
= nr_cpu_ids
;
1112 bsize
= sizeof(void *) * nr_cpu_ids
;
1113 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1115 if (!buffer
->buffers
)
1116 goto fail_free_cpumask
;
1118 for_each_buffer_cpu(buffer
, cpu
) {
1119 buffer
->buffers
[cpu
] =
1120 rb_allocate_cpu_buffer(buffer
, cpu
);
1121 if (!buffer
->buffers
[cpu
])
1122 goto fail_free_buffers
;
1125 #ifdef CONFIG_HOTPLUG_CPU
1126 buffer
->cpu_notify
.notifier_call
= rb_cpu_notify
;
1127 buffer
->cpu_notify
.priority
= 0;
1128 register_cpu_notifier(&buffer
->cpu_notify
);
1132 mutex_init(&buffer
->mutex
);
1137 for_each_buffer_cpu(buffer
, cpu
) {
1138 if (buffer
->buffers
[cpu
])
1139 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1141 kfree(buffer
->buffers
);
1144 free_cpumask_var(buffer
->cpumask
);
1151 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1154 * ring_buffer_free - free a ring buffer.
1155 * @buffer: the buffer to free.
1158 ring_buffer_free(struct ring_buffer
*buffer
)
1164 #ifdef CONFIG_HOTPLUG_CPU
1165 unregister_cpu_notifier(&buffer
->cpu_notify
);
1168 for_each_buffer_cpu(buffer
, cpu
)
1169 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1173 kfree(buffer
->buffers
);
1174 free_cpumask_var(buffer
->cpumask
);
1178 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1180 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1183 buffer
->clock
= clock
;
1186 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1189 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
1191 struct buffer_page
*bpage
;
1192 struct list_head
*p
;
1195 atomic_inc(&cpu_buffer
->record_disabled
);
1196 synchronize_sched();
1198 rb_head_page_deactivate(cpu_buffer
);
1200 for (i
= 0; i
< nr_pages
; i
++) {
1201 if (RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
)))
1203 p
= cpu_buffer
->pages
->next
;
1204 bpage
= list_entry(p
, struct buffer_page
, list
);
1205 list_del_init(&bpage
->list
);
1206 free_buffer_page(bpage
);
1208 if (RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
)))
1211 rb_reset_cpu(cpu_buffer
);
1213 rb_check_pages(cpu_buffer
);
1215 atomic_dec(&cpu_buffer
->record_disabled
);
1220 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1221 struct list_head
*pages
, unsigned nr_pages
)
1223 struct buffer_page
*bpage
;
1224 struct list_head
*p
;
1227 atomic_inc(&cpu_buffer
->record_disabled
);
1228 synchronize_sched();
1230 spin_lock_irq(&cpu_buffer
->reader_lock
);
1231 rb_head_page_deactivate(cpu_buffer
);
1233 for (i
= 0; i
< nr_pages
; i
++) {
1234 if (RB_WARN_ON(cpu_buffer
, list_empty(pages
)))
1237 bpage
= list_entry(p
, struct buffer_page
, list
);
1238 list_del_init(&bpage
->list
);
1239 list_add_tail(&bpage
->list
, cpu_buffer
->pages
);
1241 rb_reset_cpu(cpu_buffer
);
1242 spin_unlock_irq(&cpu_buffer
->reader_lock
);
1244 rb_check_pages(cpu_buffer
);
1246 atomic_dec(&cpu_buffer
->record_disabled
);
1250 * ring_buffer_resize - resize the ring buffer
1251 * @buffer: the buffer to resize.
1252 * @size: the new size.
1254 * The tracer is responsible for making sure that the buffer is
1255 * not being used while changing the size.
1256 * Note: We may be able to change the above requirement by using
1257 * RCU synchronizations.
1259 * Minimum size is 2 * BUF_PAGE_SIZE.
1261 * Returns -1 on failure.
1263 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
1265 struct ring_buffer_per_cpu
*cpu_buffer
;
1266 unsigned nr_pages
, rm_pages
, new_pages
;
1267 struct buffer_page
*bpage
, *tmp
;
1268 unsigned long buffer_size
;
1274 * Always succeed at resizing a non-existent buffer:
1279 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1280 size
*= BUF_PAGE_SIZE
;
1281 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
1283 /* we need a minimum of two pages */
1284 if (size
< BUF_PAGE_SIZE
* 2)
1285 size
= BUF_PAGE_SIZE
* 2;
1287 if (size
== buffer_size
)
1290 mutex_lock(&buffer
->mutex
);
1293 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1295 if (size
< buffer_size
) {
1297 /* easy case, just free pages */
1298 if (RB_WARN_ON(buffer
, nr_pages
>= buffer
->pages
))
1301 rm_pages
= buffer
->pages
- nr_pages
;
1303 for_each_buffer_cpu(buffer
, cpu
) {
1304 cpu_buffer
= buffer
->buffers
[cpu
];
1305 rb_remove_pages(cpu_buffer
, rm_pages
);
1311 * This is a bit more difficult. We only want to add pages
1312 * when we can allocate enough for all CPUs. We do this
1313 * by allocating all the pages and storing them on a local
1314 * link list. If we succeed in our allocation, then we
1315 * add these pages to the cpu_buffers. Otherwise we just free
1316 * them all and return -ENOMEM;
1318 if (RB_WARN_ON(buffer
, nr_pages
<= buffer
->pages
))
1321 new_pages
= nr_pages
- buffer
->pages
;
1323 for_each_buffer_cpu(buffer
, cpu
) {
1324 for (i
= 0; i
< new_pages
; i
++) {
1325 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
),
1327 GFP_KERNEL
, cpu_to_node(cpu
));
1330 list_add(&bpage
->list
, &pages
);
1331 addr
= __get_free_page(GFP_KERNEL
);
1334 bpage
->page
= (void *)addr
;
1335 rb_init_page(bpage
->page
);
1339 for_each_buffer_cpu(buffer
, cpu
) {
1340 cpu_buffer
= buffer
->buffers
[cpu
];
1341 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
1344 if (RB_WARN_ON(buffer
, !list_empty(&pages
)))
1348 buffer
->pages
= nr_pages
;
1350 mutex_unlock(&buffer
->mutex
);
1355 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
1356 list_del_init(&bpage
->list
);
1357 free_buffer_page(bpage
);
1360 mutex_unlock(&buffer
->mutex
);
1364 * Something went totally wrong, and we are too paranoid
1365 * to even clean up the mess.
1369 mutex_unlock(&buffer
->mutex
);
1372 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1374 static inline void *
1375 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
1377 return bpage
->data
+ index
;
1380 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1382 return bpage
->page
->data
+ index
;
1385 static inline struct ring_buffer_event
*
1386 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1388 return __rb_page_index(cpu_buffer
->reader_page
,
1389 cpu_buffer
->reader_page
->read
);
1392 static inline struct ring_buffer_event
*
1393 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1395 return __rb_page_index(iter
->head_page
, iter
->head
);
1398 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1400 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1403 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
1405 return local_read(&bpage
->page
->commit
);
1408 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1410 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1413 /* Size is determined by what has been commited */
1414 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
1416 return rb_page_commit(bpage
);
1419 static inline unsigned
1420 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1422 return rb_page_commit(cpu_buffer
->commit_page
);
1425 static inline unsigned
1426 rb_event_index(struct ring_buffer_event
*event
)
1428 unsigned long addr
= (unsigned long)event
;
1430 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1434 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1435 struct ring_buffer_event
*event
)
1437 unsigned long addr
= (unsigned long)event
;
1438 unsigned long index
;
1440 index
= rb_event_index(event
);
1443 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
1444 rb_commit_index(cpu_buffer
) == index
;
1448 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
1450 unsigned long max_count
;
1453 * We only race with interrupts and NMIs on this CPU.
1454 * If we own the commit event, then we can commit
1455 * all others that interrupted us, since the interruptions
1456 * are in stack format (they finish before they come
1457 * back to us). This allows us to do a simple loop to
1458 * assign the commit to the tail.
1461 max_count
= cpu_buffer
->buffer
->pages
* 100;
1463 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
1464 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
1466 if (RB_WARN_ON(cpu_buffer
,
1467 rb_is_reader_page(cpu_buffer
->tail_page
)))
1469 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1470 rb_page_write(cpu_buffer
->commit_page
));
1471 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
1472 cpu_buffer
->write_stamp
=
1473 cpu_buffer
->commit_page
->page
->time_stamp
;
1474 /* add barrier to keep gcc from optimizing too much */
1477 while (rb_commit_index(cpu_buffer
) !=
1478 rb_page_write(cpu_buffer
->commit_page
)) {
1480 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1481 rb_page_write(cpu_buffer
->commit_page
));
1482 RB_WARN_ON(cpu_buffer
,
1483 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
1488 /* again, keep gcc from optimizing */
1492 * If an interrupt came in just after the first while loop
1493 * and pushed the tail page forward, we will be left with
1494 * a dangling commit that will never go forward.
1496 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
1500 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1502 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
1503 cpu_buffer
->reader_page
->read
= 0;
1506 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1508 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1511 * The iterator could be on the reader page (it starts there).
1512 * But the head could have moved, since the reader was
1513 * found. Check for this case and assign the iterator
1514 * to the head page instead of next.
1516 if (iter
->head_page
== cpu_buffer
->reader_page
)
1517 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1519 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1521 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1526 * ring_buffer_update_event - update event type and data
1527 * @event: the even to update
1528 * @type: the type of event
1529 * @length: the size of the event field in the ring buffer
1531 * Update the type and data fields of the event. The length
1532 * is the actual size that is written to the ring buffer,
1533 * and with this, we can determine what to place into the
1537 rb_update_event(struct ring_buffer_event
*event
,
1538 unsigned type
, unsigned length
)
1540 event
->type_len
= type
;
1544 case RINGBUF_TYPE_PADDING
:
1545 case RINGBUF_TYPE_TIME_EXTEND
:
1546 case RINGBUF_TYPE_TIME_STAMP
:
1550 length
-= RB_EVNT_HDR_SIZE
;
1551 if (length
> RB_MAX_SMALL_DATA
)
1552 event
->array
[0] = length
;
1554 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
1562 * rb_handle_head_page - writer hit the head page
1564 * Returns: +1 to retry page
1569 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1570 struct buffer_page
*tail_page
,
1571 struct buffer_page
*next_page
)
1573 struct buffer_page
*new_head
;
1578 entries
= rb_page_entries(next_page
);
1581 * The hard part is here. We need to move the head
1582 * forward, and protect against both readers on
1583 * other CPUs and writers coming in via interrupts.
1585 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1589 * type can be one of four:
1590 * NORMAL - an interrupt already moved it for us
1591 * HEAD - we are the first to get here.
1592 * UPDATE - we are the interrupt interrupting
1594 * MOVED - a reader on another CPU moved the next
1595 * pointer to its reader page. Give up
1602 * We changed the head to UPDATE, thus
1603 * it is our responsibility to update
1606 local_add(entries
, &cpu_buffer
->overrun
);
1609 * The entries will be zeroed out when we move the
1613 /* still more to do */
1616 case RB_PAGE_UPDATE
:
1618 * This is an interrupt that interrupt the
1619 * previous update. Still more to do.
1622 case RB_PAGE_NORMAL
:
1624 * An interrupt came in before the update
1625 * and processed this for us.
1626 * Nothing left to do.
1631 * The reader is on another CPU and just did
1632 * a swap with our next_page.
1637 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
1642 * Now that we are here, the old head pointer is
1643 * set to UPDATE. This will keep the reader from
1644 * swapping the head page with the reader page.
1645 * The reader (on another CPU) will spin till
1648 * We just need to protect against interrupts
1649 * doing the job. We will set the next pointer
1650 * to HEAD. After that, we set the old pointer
1651 * to NORMAL, but only if it was HEAD before.
1652 * otherwise we are an interrupt, and only
1653 * want the outer most commit to reset it.
1655 new_head
= next_page
;
1656 rb_inc_page(cpu_buffer
, &new_head
);
1658 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
1662 * Valid returns are:
1663 * HEAD - an interrupt came in and already set it.
1664 * NORMAL - One of two things:
1665 * 1) We really set it.
1666 * 2) A bunch of interrupts came in and moved
1667 * the page forward again.
1671 case RB_PAGE_NORMAL
:
1675 RB_WARN_ON(cpu_buffer
, 1);
1680 * It is possible that an interrupt came in,
1681 * set the head up, then more interrupts came in
1682 * and moved it again. When we get back here,
1683 * the page would have been set to NORMAL but we
1684 * just set it back to HEAD.
1686 * How do you detect this? Well, if that happened
1687 * the tail page would have moved.
1689 if (ret
== RB_PAGE_NORMAL
) {
1691 * If the tail had moved passed next, then we need
1692 * to reset the pointer.
1694 if (cpu_buffer
->tail_page
!= tail_page
&&
1695 cpu_buffer
->tail_page
!= next_page
)
1696 rb_head_page_set_normal(cpu_buffer
, new_head
,
1702 * If this was the outer most commit (the one that
1703 * changed the original pointer from HEAD to UPDATE),
1704 * then it is up to us to reset it to NORMAL.
1706 if (type
== RB_PAGE_HEAD
) {
1707 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
1710 if (RB_WARN_ON(cpu_buffer
,
1711 ret
!= RB_PAGE_UPDATE
))
1718 static unsigned rb_calculate_event_length(unsigned length
)
1720 struct ring_buffer_event event
; /* Used only for sizeof array */
1722 /* zero length can cause confusions */
1726 if (length
> RB_MAX_SMALL_DATA
)
1727 length
+= sizeof(event
.array
[0]);
1729 length
+= RB_EVNT_HDR_SIZE
;
1730 length
= ALIGN(length
, RB_ALIGNMENT
);
1736 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1737 struct buffer_page
*tail_page
,
1738 unsigned long tail
, unsigned long length
)
1740 struct ring_buffer_event
*event
;
1743 * Only the event that crossed the page boundary
1744 * must fill the old tail_page with padding.
1746 if (tail
>= BUF_PAGE_SIZE
) {
1747 local_sub(length
, &tail_page
->write
);
1751 event
= __rb_page_index(tail_page
, tail
);
1752 kmemcheck_annotate_bitfield(event
, bitfield
);
1755 * If this event is bigger than the minimum size, then
1756 * we need to be careful that we don't subtract the
1757 * write counter enough to allow another writer to slip
1759 * We put in a discarded commit instead, to make sure
1760 * that this space is not used again.
1762 * If we are less than the minimum size, we don't need to
1765 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
1766 /* No room for any events */
1768 /* Mark the rest of the page with padding */
1769 rb_event_set_padding(event
);
1771 /* Set the write back to the previous setting */
1772 local_sub(length
, &tail_page
->write
);
1776 /* Put in a discarded event */
1777 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
1778 event
->type_len
= RINGBUF_TYPE_PADDING
;
1779 /* time delta must be non zero */
1780 event
->time_delta
= 1;
1782 /* Set write to end of buffer */
1783 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
1784 local_sub(length
, &tail_page
->write
);
1787 static struct ring_buffer_event
*
1788 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1789 unsigned long length
, unsigned long tail
,
1790 struct buffer_page
*commit_page
,
1791 struct buffer_page
*tail_page
, u64
*ts
)
1793 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
1794 struct buffer_page
*next_page
;
1797 next_page
= tail_page
;
1799 rb_inc_page(cpu_buffer
, &next_page
);
1802 * If for some reason, we had an interrupt storm that made
1803 * it all the way around the buffer, bail, and warn
1806 if (unlikely(next_page
== commit_page
)) {
1807 local_inc(&cpu_buffer
->commit_overrun
);
1812 * This is where the fun begins!
1814 * We are fighting against races between a reader that
1815 * could be on another CPU trying to swap its reader
1816 * page with the buffer head.
1818 * We are also fighting against interrupts coming in and
1819 * moving the head or tail on us as well.
1821 * If the next page is the head page then we have filled
1822 * the buffer, unless the commit page is still on the
1825 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
1828 * If the commit is not on the reader page, then
1829 * move the header page.
1831 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
1833 * If we are not in overwrite mode,
1834 * this is easy, just stop here.
1836 if (!(buffer
->flags
& RB_FL_OVERWRITE
))
1839 ret
= rb_handle_head_page(cpu_buffer
,
1848 * We need to be careful here too. The
1849 * commit page could still be on the reader
1850 * page. We could have a small buffer, and
1851 * have filled up the buffer with events
1852 * from interrupts and such, and wrapped.
1854 * Note, if the tail page is also the on the
1855 * reader_page, we let it move out.
1857 if (unlikely((cpu_buffer
->commit_page
!=
1858 cpu_buffer
->tail_page
) &&
1859 (cpu_buffer
->commit_page
==
1860 cpu_buffer
->reader_page
))) {
1861 local_inc(&cpu_buffer
->commit_overrun
);
1867 ret
= rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
1870 * Nested commits always have zero deltas, so
1871 * just reread the time stamp
1873 *ts
= rb_time_stamp(buffer
, cpu_buffer
->cpu
);
1874 next_page
->page
->time_stamp
= *ts
;
1879 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1881 /* fail and let the caller try again */
1882 return ERR_PTR(-EAGAIN
);
1886 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1891 static struct ring_buffer_event
*
1892 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
1893 unsigned type
, unsigned long length
, u64
*ts
)
1895 struct buffer_page
*tail_page
, *commit_page
;
1896 struct ring_buffer_event
*event
;
1897 unsigned long tail
, write
;
1899 commit_page
= cpu_buffer
->commit_page
;
1900 /* we just need to protect against interrupts */
1902 tail_page
= cpu_buffer
->tail_page
;
1903 write
= local_add_return(length
, &tail_page
->write
);
1905 /* set write to only the index of the write */
1906 write
&= RB_WRITE_MASK
;
1907 tail
= write
- length
;
1909 /* See if we shot pass the end of this buffer page */
1910 if (write
> BUF_PAGE_SIZE
)
1911 return rb_move_tail(cpu_buffer
, length
, tail
,
1912 commit_page
, tail_page
, ts
);
1914 /* We reserved something on the buffer */
1916 event
= __rb_page_index(tail_page
, tail
);
1917 kmemcheck_annotate_bitfield(event
, bitfield
);
1918 rb_update_event(event
, type
, length
);
1920 /* The passed in type is zero for DATA */
1922 local_inc(&tail_page
->entries
);
1925 * If this is the first commit on the page, then update
1929 tail_page
->page
->time_stamp
= *ts
;
1935 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
1936 struct ring_buffer_event
*event
)
1938 unsigned long new_index
, old_index
;
1939 struct buffer_page
*bpage
;
1940 unsigned long index
;
1943 new_index
= rb_event_index(event
);
1944 old_index
= new_index
+ rb_event_length(event
);
1945 addr
= (unsigned long)event
;
1948 bpage
= cpu_buffer
->tail_page
;
1950 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
1951 unsigned long write_mask
=
1952 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
1954 * This is on the tail page. It is possible that
1955 * a write could come in and move the tail page
1956 * and write to the next page. That is fine
1957 * because we just shorten what is on this page.
1959 old_index
+= write_mask
;
1960 new_index
+= write_mask
;
1961 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
1962 if (index
== old_index
)
1966 /* could not discard */
1971 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1972 u64
*ts
, u64
*delta
)
1974 struct ring_buffer_event
*event
;
1978 if (unlikely(*delta
> (1ULL << 59) && !once
++)) {
1979 printk(KERN_WARNING
"Delta way too big! %llu"
1980 " ts=%llu write stamp = %llu\n",
1981 (unsigned long long)*delta
,
1982 (unsigned long long)*ts
,
1983 (unsigned long long)cpu_buffer
->write_stamp
);
1988 * The delta is too big, we to add a
1991 event
= __rb_reserve_next(cpu_buffer
,
1992 RINGBUF_TYPE_TIME_EXTEND
,
1998 if (PTR_ERR(event
) == -EAGAIN
)
2001 /* Only a commited time event can update the write stamp */
2002 if (rb_event_is_commit(cpu_buffer
, event
)) {
2004 * If this is the first on the page, then it was
2005 * updated with the page itself. Try to discard it
2006 * and if we can't just make it zero.
2008 if (rb_event_index(event
)) {
2009 event
->time_delta
= *delta
& TS_MASK
;
2010 event
->array
[0] = *delta
>> TS_SHIFT
;
2012 /* try to discard, since we do not need this */
2013 if (!rb_try_to_discard(cpu_buffer
, event
)) {
2014 /* nope, just zero it */
2015 event
->time_delta
= 0;
2016 event
->array
[0] = 0;
2019 cpu_buffer
->write_stamp
= *ts
;
2020 /* let the caller know this was the commit */
2023 /* Try to discard the event */
2024 if (!rb_try_to_discard(cpu_buffer
, event
)) {
2025 /* Darn, this is just wasted space */
2026 event
->time_delta
= 0;
2027 event
->array
[0] = 0;
2037 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2039 local_inc(&cpu_buffer
->committing
);
2040 local_inc(&cpu_buffer
->commits
);
2043 static void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2045 unsigned long commits
;
2047 if (RB_WARN_ON(cpu_buffer
,
2048 !local_read(&cpu_buffer
->committing
)))
2052 commits
= local_read(&cpu_buffer
->commits
);
2053 /* synchronize with interrupts */
2055 if (local_read(&cpu_buffer
->committing
) == 1)
2056 rb_set_commit_to_write(cpu_buffer
);
2058 local_dec(&cpu_buffer
->committing
);
2060 /* synchronize with interrupts */
2064 * Need to account for interrupts coming in between the
2065 * updating of the commit page and the clearing of the
2066 * committing counter.
2068 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2069 !local_read(&cpu_buffer
->committing
)) {
2070 local_inc(&cpu_buffer
->committing
);
2075 static struct ring_buffer_event
*
2076 rb_reserve_next_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2077 unsigned long length
)
2079 struct ring_buffer_event
*event
;
2084 rb_start_commit(cpu_buffer
);
2086 length
= rb_calculate_event_length(length
);
2089 * We allow for interrupts to reenter here and do a trace.
2090 * If one does, it will cause this original code to loop
2091 * back here. Even with heavy interrupts happening, this
2092 * should only happen a few times in a row. If this happens
2093 * 1000 times in a row, there must be either an interrupt
2094 * storm or we have something buggy.
2097 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2100 ts
= rb_time_stamp(cpu_buffer
->buffer
, cpu_buffer
->cpu
);
2103 * Only the first commit can update the timestamp.
2104 * Yes there is a race here. If an interrupt comes in
2105 * just after the conditional and it traces too, then it
2106 * will also check the deltas. More than one timestamp may
2107 * also be made. But only the entry that did the actual
2108 * commit will be something other than zero.
2110 if (likely(cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
2111 rb_page_write(cpu_buffer
->tail_page
) ==
2112 rb_commit_index(cpu_buffer
))) {
2115 diff
= ts
- cpu_buffer
->write_stamp
;
2117 /* make sure this diff is calculated here */
2120 /* Did the write stamp get updated already? */
2121 if (unlikely(ts
< cpu_buffer
->write_stamp
))
2125 if (unlikely(test_time_stamp(delta
))) {
2127 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
2128 if (commit
== -EBUSY
)
2131 if (commit
== -EAGAIN
)
2134 RB_WARN_ON(cpu_buffer
, commit
< 0);
2139 event
= __rb_reserve_next(cpu_buffer
, 0, length
, &ts
);
2140 if (unlikely(PTR_ERR(event
) == -EAGAIN
))
2146 if (!rb_event_is_commit(cpu_buffer
, event
))
2149 event
->time_delta
= delta
;
2154 rb_end_commit(cpu_buffer
);
2158 #ifdef CONFIG_TRACING
2160 #define TRACE_RECURSIVE_DEPTH 16
2162 static int trace_recursive_lock(void)
2164 current
->trace_recursion
++;
2166 if (likely(current
->trace_recursion
< TRACE_RECURSIVE_DEPTH
))
2169 /* Disable all tracing before we do anything else */
2170 tracing_off_permanent();
2172 printk_once(KERN_WARNING
"Tracing recursion: depth[%ld]:"
2173 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
2174 current
->trace_recursion
,
2175 hardirq_count() >> HARDIRQ_SHIFT
,
2176 softirq_count() >> SOFTIRQ_SHIFT
,
2183 static void trace_recursive_unlock(void)
2185 WARN_ON_ONCE(!current
->trace_recursion
);
2187 current
->trace_recursion
--;
2192 #define trace_recursive_lock() (0)
2193 #define trace_recursive_unlock() do { } while (0)
2197 static DEFINE_PER_CPU(int, rb_need_resched
);
2200 * ring_buffer_lock_reserve - reserve a part of the buffer
2201 * @buffer: the ring buffer to reserve from
2202 * @length: the length of the data to reserve (excluding event header)
2204 * Returns a reseverd event on the ring buffer to copy directly to.
2205 * The user of this interface will need to get the body to write into
2206 * and can use the ring_buffer_event_data() interface.
2208 * The length is the length of the data needed, not the event length
2209 * which also includes the event header.
2211 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2212 * If NULL is returned, then nothing has been allocated or locked.
2214 struct ring_buffer_event
*
2215 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2217 struct ring_buffer_per_cpu
*cpu_buffer
;
2218 struct ring_buffer_event
*event
;
2221 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2224 if (atomic_read(&buffer
->record_disabled
))
2227 /* If we are tracing schedule, we don't want to recurse */
2228 resched
= ftrace_preempt_disable();
2230 if (trace_recursive_lock())
2233 cpu
= raw_smp_processor_id();
2235 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2238 cpu_buffer
= buffer
->buffers
[cpu
];
2240 if (atomic_read(&cpu_buffer
->record_disabled
))
2243 if (length
> BUF_MAX_DATA_SIZE
)
2246 event
= rb_reserve_next_event(cpu_buffer
, length
);
2251 * Need to store resched state on this cpu.
2252 * Only the first needs to.
2255 if (preempt_count() == 1)
2256 per_cpu(rb_need_resched
, cpu
) = resched
;
2261 trace_recursive_unlock();
2264 ftrace_preempt_enable(resched
);
2267 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2270 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2271 struct ring_buffer_event
*event
)
2274 * The event first in the commit queue updates the
2277 if (rb_event_is_commit(cpu_buffer
, event
))
2278 cpu_buffer
->write_stamp
+= event
->time_delta
;
2281 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2282 struct ring_buffer_event
*event
)
2284 local_inc(&cpu_buffer
->entries
);
2285 rb_update_write_stamp(cpu_buffer
, event
);
2286 rb_end_commit(cpu_buffer
);
2290 * ring_buffer_unlock_commit - commit a reserved
2291 * @buffer: The buffer to commit to
2292 * @event: The event pointer to commit.
2294 * This commits the data to the ring buffer, and releases any locks held.
2296 * Must be paired with ring_buffer_lock_reserve.
2298 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2299 struct ring_buffer_event
*event
)
2301 struct ring_buffer_per_cpu
*cpu_buffer
;
2302 int cpu
= raw_smp_processor_id();
2304 cpu_buffer
= buffer
->buffers
[cpu
];
2306 rb_commit(cpu_buffer
, event
);
2308 trace_recursive_unlock();
2311 * Only the last preempt count needs to restore preemption.
2313 if (preempt_count() == 1)
2314 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
2316 preempt_enable_no_resched_notrace();
2320 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2322 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2324 /* array[0] holds the actual length for the discarded event */
2325 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2326 event
->type_len
= RINGBUF_TYPE_PADDING
;
2327 /* time delta must be non zero */
2328 if (!event
->time_delta
)
2329 event
->time_delta
= 1;
2333 * Decrement the entries to the page that an event is on.
2334 * The event does not even need to exist, only the pointer
2335 * to the page it is on. This may only be called before the commit
2339 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2340 struct ring_buffer_event
*event
)
2342 unsigned long addr
= (unsigned long)event
;
2343 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2344 struct buffer_page
*start
;
2348 /* Do the likely case first */
2349 if (likely(bpage
->page
== (void *)addr
)) {
2350 local_dec(&bpage
->entries
);
2355 * Because the commit page may be on the reader page we
2356 * start with the next page and check the end loop there.
2358 rb_inc_page(cpu_buffer
, &bpage
);
2361 if (bpage
->page
== (void *)addr
) {
2362 local_dec(&bpage
->entries
);
2365 rb_inc_page(cpu_buffer
, &bpage
);
2366 } while (bpage
!= start
);
2368 /* commit not part of this buffer?? */
2369 RB_WARN_ON(cpu_buffer
, 1);
2373 * ring_buffer_commit_discard - discard an event that has not been committed
2374 * @buffer: the ring buffer
2375 * @event: non committed event to discard
2377 * Sometimes an event that is in the ring buffer needs to be ignored.
2378 * This function lets the user discard an event in the ring buffer
2379 * and then that event will not be read later.
2381 * This function only works if it is called before the the item has been
2382 * committed. It will try to free the event from the ring buffer
2383 * if another event has not been added behind it.
2385 * If another event has been added behind it, it will set the event
2386 * up as discarded, and perform the commit.
2388 * If this function is called, do not call ring_buffer_unlock_commit on
2391 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2392 struct ring_buffer_event
*event
)
2394 struct ring_buffer_per_cpu
*cpu_buffer
;
2397 /* The event is discarded regardless */
2398 rb_event_discard(event
);
2400 cpu
= smp_processor_id();
2401 cpu_buffer
= buffer
->buffers
[cpu
];
2404 * This must only be called if the event has not been
2405 * committed yet. Thus we can assume that preemption
2406 * is still disabled.
2408 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2410 rb_decrement_entry(cpu_buffer
, event
);
2411 if (rb_try_to_discard(cpu_buffer
, event
))
2415 * The commit is still visible by the reader, so we
2416 * must still update the timestamp.
2418 rb_update_write_stamp(cpu_buffer
, event
);
2420 rb_end_commit(cpu_buffer
);
2422 trace_recursive_unlock();
2425 * Only the last preempt count needs to restore preemption.
2427 if (preempt_count() == 1)
2428 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
2430 preempt_enable_no_resched_notrace();
2433 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2436 * ring_buffer_write - write data to the buffer without reserving
2437 * @buffer: The ring buffer to write to.
2438 * @length: The length of the data being written (excluding the event header)
2439 * @data: The data to write to the buffer.
2441 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2442 * one function. If you already have the data to write to the buffer, it
2443 * may be easier to simply call this function.
2445 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2446 * and not the length of the event which would hold the header.
2448 int ring_buffer_write(struct ring_buffer
*buffer
,
2449 unsigned long length
,
2452 struct ring_buffer_per_cpu
*cpu_buffer
;
2453 struct ring_buffer_event
*event
;
2458 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2461 if (atomic_read(&buffer
->record_disabled
))
2464 resched
= ftrace_preempt_disable();
2466 cpu
= raw_smp_processor_id();
2468 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2471 cpu_buffer
= buffer
->buffers
[cpu
];
2473 if (atomic_read(&cpu_buffer
->record_disabled
))
2476 if (length
> BUF_MAX_DATA_SIZE
)
2479 event
= rb_reserve_next_event(cpu_buffer
, length
);
2483 body
= rb_event_data(event
);
2485 memcpy(body
, data
, length
);
2487 rb_commit(cpu_buffer
, event
);
2491 ftrace_preempt_enable(resched
);
2495 EXPORT_SYMBOL_GPL(ring_buffer_write
);
2497 static int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
2499 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
2500 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
2501 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
2503 /* In case of error, head will be NULL */
2504 if (unlikely(!head
))
2507 return reader
->read
== rb_page_commit(reader
) &&
2508 (commit
== reader
||
2510 head
->read
== rb_page_commit(commit
)));
2514 * ring_buffer_record_disable - stop all writes into the buffer
2515 * @buffer: The ring buffer to stop writes to.
2517 * This prevents all writes to the buffer. Any attempt to write
2518 * to the buffer after this will fail and return NULL.
2520 * The caller should call synchronize_sched() after this.
2522 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
2524 atomic_inc(&buffer
->record_disabled
);
2526 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
2529 * ring_buffer_record_enable - enable writes to the buffer
2530 * @buffer: The ring buffer to enable writes
2532 * Note, multiple disables will need the same number of enables
2533 * to truely enable the writing (much like preempt_disable).
2535 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
2537 atomic_dec(&buffer
->record_disabled
);
2539 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
2542 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2543 * @buffer: The ring buffer to stop writes to.
2544 * @cpu: The CPU buffer to stop
2546 * This prevents all writes to the buffer. Any attempt to write
2547 * to the buffer after this will fail and return NULL.
2549 * The caller should call synchronize_sched() after this.
2551 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
2553 struct ring_buffer_per_cpu
*cpu_buffer
;
2555 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2558 cpu_buffer
= buffer
->buffers
[cpu
];
2559 atomic_inc(&cpu_buffer
->record_disabled
);
2561 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
2564 * ring_buffer_record_enable_cpu - enable writes to the buffer
2565 * @buffer: The ring buffer to enable writes
2566 * @cpu: The CPU to enable.
2568 * Note, multiple disables will need the same number of enables
2569 * to truely enable the writing (much like preempt_disable).
2571 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
2573 struct ring_buffer_per_cpu
*cpu_buffer
;
2575 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2578 cpu_buffer
= buffer
->buffers
[cpu
];
2579 atomic_dec(&cpu_buffer
->record_disabled
);
2581 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
2584 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2585 * @buffer: The ring buffer
2586 * @cpu: The per CPU buffer to get the entries from.
2588 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
2590 struct ring_buffer_per_cpu
*cpu_buffer
;
2593 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2596 cpu_buffer
= buffer
->buffers
[cpu
];
2597 ret
= (local_read(&cpu_buffer
->entries
) - local_read(&cpu_buffer
->overrun
))
2602 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
2605 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
2606 * @buffer: The ring buffer
2607 * @cpu: The per CPU buffer to get the number of overruns from
2609 unsigned long ring_buffer_overrun_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
->overrun
);
2622 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
2625 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2626 * @buffer: The ring buffer
2627 * @cpu: The per CPU buffer to get the number of overruns from
2630 ring_buffer_commit_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
->commit_overrun
);
2643 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
2646 * ring_buffer_entries - get the number of entries in a buffer
2647 * @buffer: The ring buffer
2649 * Returns the total number of entries in the ring buffer
2652 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
2654 struct ring_buffer_per_cpu
*cpu_buffer
;
2655 unsigned long entries
= 0;
2658 /* if you care about this being correct, lock the buffer */
2659 for_each_buffer_cpu(buffer
, cpu
) {
2660 cpu_buffer
= buffer
->buffers
[cpu
];
2661 entries
+= (local_read(&cpu_buffer
->entries
) -
2662 local_read(&cpu_buffer
->overrun
)) - cpu_buffer
->read
;
2667 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
2670 * ring_buffer_overrun_cpu - get the number of overruns in buffer
2671 * @buffer: The ring buffer
2673 * Returns the total number of overruns in the ring buffer
2676 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
2678 struct ring_buffer_per_cpu
*cpu_buffer
;
2679 unsigned long overruns
= 0;
2682 /* if you care about this being correct, lock the buffer */
2683 for_each_buffer_cpu(buffer
, cpu
) {
2684 cpu_buffer
= buffer
->buffers
[cpu
];
2685 overruns
+= local_read(&cpu_buffer
->overrun
);
2690 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
2692 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
2694 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2696 /* Iterator usage is expected to have record disabled */
2697 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
2698 iter
->head_page
= rb_set_head_page(cpu_buffer
);
2699 if (unlikely(!iter
->head_page
))
2701 iter
->head
= iter
->head_page
->read
;
2703 iter
->head_page
= cpu_buffer
->reader_page
;
2704 iter
->head
= cpu_buffer
->reader_page
->read
;
2707 iter
->read_stamp
= cpu_buffer
->read_stamp
;
2709 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2713 * ring_buffer_iter_reset - reset an iterator
2714 * @iter: The iterator to reset
2716 * Resets the iterator, so that it will start from the beginning
2719 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
2721 struct ring_buffer_per_cpu
*cpu_buffer
;
2722 unsigned long flags
;
2727 cpu_buffer
= iter
->cpu_buffer
;
2729 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2730 rb_iter_reset(iter
);
2731 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2733 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
2736 * ring_buffer_iter_empty - check if an iterator has no more to read
2737 * @iter: The iterator to check
2739 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
2741 struct ring_buffer_per_cpu
*cpu_buffer
;
2743 cpu_buffer
= iter
->cpu_buffer
;
2745 return iter
->head_page
== cpu_buffer
->commit_page
&&
2746 iter
->head
== rb_commit_index(cpu_buffer
);
2748 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
2751 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2752 struct ring_buffer_event
*event
)
2756 switch (event
->type_len
) {
2757 case RINGBUF_TYPE_PADDING
:
2760 case RINGBUF_TYPE_TIME_EXTEND
:
2761 delta
= event
->array
[0];
2763 delta
+= event
->time_delta
;
2764 cpu_buffer
->read_stamp
+= delta
;
2767 case RINGBUF_TYPE_TIME_STAMP
:
2768 /* FIXME: not implemented */
2771 case RINGBUF_TYPE_DATA
:
2772 cpu_buffer
->read_stamp
+= event
->time_delta
;
2782 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
2783 struct ring_buffer_event
*event
)
2787 switch (event
->type_len
) {
2788 case RINGBUF_TYPE_PADDING
:
2791 case RINGBUF_TYPE_TIME_EXTEND
:
2792 delta
= event
->array
[0];
2794 delta
+= event
->time_delta
;
2795 iter
->read_stamp
+= delta
;
2798 case RINGBUF_TYPE_TIME_STAMP
:
2799 /* FIXME: not implemented */
2802 case RINGBUF_TYPE_DATA
:
2803 iter
->read_stamp
+= event
->time_delta
;
2812 static struct buffer_page
*
2813 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
2815 struct buffer_page
*reader
= NULL
;
2816 unsigned long flags
;
2820 local_irq_save(flags
);
2821 __raw_spin_lock(&cpu_buffer
->lock
);
2825 * This should normally only loop twice. But because the
2826 * start of the reader inserts an empty page, it causes
2827 * a case where we will loop three times. There should be no
2828 * reason to loop four times (that I know of).
2830 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
2835 reader
= cpu_buffer
->reader_page
;
2837 /* If there's more to read, return this page */
2838 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
2841 /* Never should we have an index greater than the size */
2842 if (RB_WARN_ON(cpu_buffer
,
2843 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
2846 /* check if we caught up to the tail */
2848 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
2852 * Reset the reader page to size zero.
2854 local_set(&cpu_buffer
->reader_page
->write
, 0);
2855 local_set(&cpu_buffer
->reader_page
->entries
, 0);
2856 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
2860 * Splice the empty reader page into the list around the head.
2862 reader
= rb_set_head_page(cpu_buffer
);
2863 cpu_buffer
->reader_page
->list
.next
= reader
->list
.next
;
2864 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
2867 * cpu_buffer->pages just needs to point to the buffer, it
2868 * has no specific buffer page to point to. Lets move it out
2869 * of our way so we don't accidently swap it.
2871 cpu_buffer
->pages
= reader
->list
.prev
;
2873 /* The reader page will be pointing to the new head */
2874 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
2877 * Here's the tricky part.
2879 * We need to move the pointer past the header page.
2880 * But we can only do that if a writer is not currently
2881 * moving it. The page before the header page has the
2882 * flag bit '1' set if it is pointing to the page we want.
2883 * but if the writer is in the process of moving it
2884 * than it will be '2' or already moved '0'.
2887 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
2890 * If we did not convert it, then we must try again.
2896 * Yeah! We succeeded in replacing the page.
2898 * Now make the new head point back to the reader page.
2900 reader
->list
.next
->prev
= &cpu_buffer
->reader_page
->list
;
2901 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
2903 /* Finally update the reader page to the new head */
2904 cpu_buffer
->reader_page
= reader
;
2905 rb_reset_reader_page(cpu_buffer
);
2910 __raw_spin_unlock(&cpu_buffer
->lock
);
2911 local_irq_restore(flags
);
2916 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
2918 struct ring_buffer_event
*event
;
2919 struct buffer_page
*reader
;
2922 reader
= rb_get_reader_page(cpu_buffer
);
2924 /* This function should not be called when buffer is empty */
2925 if (RB_WARN_ON(cpu_buffer
, !reader
))
2928 event
= rb_reader_event(cpu_buffer
);
2930 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
2933 rb_update_read_stamp(cpu_buffer
, event
);
2935 length
= rb_event_length(event
);
2936 cpu_buffer
->reader_page
->read
+= length
;
2939 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
2941 struct ring_buffer
*buffer
;
2942 struct ring_buffer_per_cpu
*cpu_buffer
;
2943 struct ring_buffer_event
*event
;
2946 cpu_buffer
= iter
->cpu_buffer
;
2947 buffer
= cpu_buffer
->buffer
;
2950 * Check if we are at the end of the buffer.
2952 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
2953 /* discarded commits can make the page empty */
2954 if (iter
->head_page
== cpu_buffer
->commit_page
)
2960 event
= rb_iter_head_event(iter
);
2962 length
= rb_event_length(event
);
2965 * This should not be called to advance the header if we are
2966 * at the tail of the buffer.
2968 if (RB_WARN_ON(cpu_buffer
,
2969 (iter
->head_page
== cpu_buffer
->commit_page
) &&
2970 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
2973 rb_update_iter_read_stamp(iter
, event
);
2975 iter
->head
+= length
;
2977 /* check for end of page padding */
2978 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
2979 (iter
->head_page
!= cpu_buffer
->commit_page
))
2980 rb_advance_iter(iter
);
2983 static struct ring_buffer_event
*
2984 rb_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
2986 struct ring_buffer_per_cpu
*cpu_buffer
;
2987 struct ring_buffer_event
*event
;
2988 struct buffer_page
*reader
;
2991 cpu_buffer
= buffer
->buffers
[cpu
];
2995 * We repeat when a timestamp is encountered. It is possible
2996 * to get multiple timestamps from an interrupt entering just
2997 * as one timestamp is about to be written, or from discarded
2998 * commits. The most that we can have is the number on a single page.
3000 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
3003 reader
= rb_get_reader_page(cpu_buffer
);
3007 event
= rb_reader_event(cpu_buffer
);
3009 switch (event
->type_len
) {
3010 case RINGBUF_TYPE_PADDING
:
3011 if (rb_null_event(event
))
3012 RB_WARN_ON(cpu_buffer
, 1);
3014 * Because the writer could be discarding every
3015 * event it creates (which would probably be bad)
3016 * if we were to go back to "again" then we may never
3017 * catch up, and will trigger the warn on, or lock
3018 * the box. Return the padding, and we will release
3019 * the current locks, and try again.
3023 case RINGBUF_TYPE_TIME_EXTEND
:
3024 /* Internal data, OK to advance */
3025 rb_advance_reader(cpu_buffer
);
3028 case RINGBUF_TYPE_TIME_STAMP
:
3029 /* FIXME: not implemented */
3030 rb_advance_reader(cpu_buffer
);
3033 case RINGBUF_TYPE_DATA
:
3035 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3036 ring_buffer_normalize_time_stamp(buffer
,
3037 cpu_buffer
->cpu
, ts
);
3047 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3049 static struct ring_buffer_event
*
3050 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3052 struct ring_buffer
*buffer
;
3053 struct ring_buffer_per_cpu
*cpu_buffer
;
3054 struct ring_buffer_event
*event
;
3057 if (ring_buffer_iter_empty(iter
))
3060 cpu_buffer
= iter
->cpu_buffer
;
3061 buffer
= cpu_buffer
->buffer
;
3065 * We repeat when a timestamp is encountered.
3066 * We can get multiple timestamps by nested interrupts or also
3067 * if filtering is on (discarding commits). Since discarding
3068 * commits can be frequent we can get a lot of timestamps.
3069 * But we limit them by not adding timestamps if they begin
3070 * at the start of a page.
3072 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
3075 if (rb_per_cpu_empty(cpu_buffer
))
3078 event
= rb_iter_head_event(iter
);
3080 switch (event
->type_len
) {
3081 case RINGBUF_TYPE_PADDING
:
3082 if (rb_null_event(event
)) {
3086 rb_advance_iter(iter
);
3089 case RINGBUF_TYPE_TIME_EXTEND
:
3090 /* Internal data, OK to advance */
3091 rb_advance_iter(iter
);
3094 case RINGBUF_TYPE_TIME_STAMP
:
3095 /* FIXME: not implemented */
3096 rb_advance_iter(iter
);
3099 case RINGBUF_TYPE_DATA
:
3101 *ts
= iter
->read_stamp
+ event
->time_delta
;
3102 ring_buffer_normalize_time_stamp(buffer
,
3103 cpu_buffer
->cpu
, ts
);
3113 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3115 static inline int rb_ok_to_lock(void)
3118 * If an NMI die dumps out the content of the ring buffer
3119 * do not grab locks. We also permanently disable the ring
3120 * buffer too. A one time deal is all you get from reading
3121 * the ring buffer from an NMI.
3123 if (likely(!in_nmi()))
3126 tracing_off_permanent();
3131 * ring_buffer_peek - peek at the next event to be read
3132 * @buffer: The ring buffer to read
3133 * @cpu: The cpu to peak at
3134 * @ts: The timestamp counter of this event.
3136 * This will return the event that will be read next, but does
3137 * not consume the data.
3139 struct ring_buffer_event
*
3140 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
3142 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3143 struct ring_buffer_event
*event
;
3144 unsigned long flags
;
3147 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3150 dolock
= rb_ok_to_lock();
3152 local_irq_save(flags
);
3154 spin_lock(&cpu_buffer
->reader_lock
);
3155 event
= rb_buffer_peek(buffer
, cpu
, ts
);
3156 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3157 rb_advance_reader(cpu_buffer
);
3159 spin_unlock(&cpu_buffer
->reader_lock
);
3160 local_irq_restore(flags
);
3162 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3169 * ring_buffer_iter_peek - peek at the next event to be read
3170 * @iter: The ring buffer iterator
3171 * @ts: The timestamp counter of this event.
3173 * This will return the event that will be read next, but does
3174 * not increment the iterator.
3176 struct ring_buffer_event
*
3177 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3179 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3180 struct ring_buffer_event
*event
;
3181 unsigned long flags
;
3184 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3185 event
= rb_iter_peek(iter
, ts
);
3186 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3188 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3195 * ring_buffer_consume - return an event and consume it
3196 * @buffer: The ring buffer to get the next event from
3198 * Returns the next event in the ring buffer, and that event is consumed.
3199 * Meaning, that sequential reads will keep returning a different event,
3200 * and eventually empty the ring buffer if the producer is slower.
3202 struct ring_buffer_event
*
3203 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
3205 struct ring_buffer_per_cpu
*cpu_buffer
;
3206 struct ring_buffer_event
*event
= NULL
;
3207 unsigned long flags
;
3210 dolock
= rb_ok_to_lock();
3213 /* might be called in atomic */
3216 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3219 cpu_buffer
= buffer
->buffers
[cpu
];
3220 local_irq_save(flags
);
3222 spin_lock(&cpu_buffer
->reader_lock
);
3224 event
= rb_buffer_peek(buffer
, cpu
, ts
);
3226 rb_advance_reader(cpu_buffer
);
3229 spin_unlock(&cpu_buffer
->reader_lock
);
3230 local_irq_restore(flags
);
3235 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3240 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
3243 * ring_buffer_read_start - start a non consuming read of the buffer
3244 * @buffer: The ring buffer to read from
3245 * @cpu: The cpu buffer to iterate over
3247 * This starts up an iteration through the buffer. It also disables
3248 * the recording to the buffer until the reading is finished.
3249 * This prevents the reading from being corrupted. This is not
3250 * a consuming read, so a producer is not expected.
3252 * Must be paired with ring_buffer_finish.
3254 struct ring_buffer_iter
*
3255 ring_buffer_read_start(struct ring_buffer
*buffer
, int cpu
)
3257 struct ring_buffer_per_cpu
*cpu_buffer
;
3258 struct ring_buffer_iter
*iter
;
3259 unsigned long flags
;
3261 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3264 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
3268 cpu_buffer
= buffer
->buffers
[cpu
];
3270 iter
->cpu_buffer
= cpu_buffer
;
3272 atomic_inc(&cpu_buffer
->record_disabled
);
3273 synchronize_sched();
3275 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3276 __raw_spin_lock(&cpu_buffer
->lock
);
3277 rb_iter_reset(iter
);
3278 __raw_spin_unlock(&cpu_buffer
->lock
);
3279 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3283 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
3286 * ring_buffer_finish - finish reading the iterator of the buffer
3287 * @iter: The iterator retrieved by ring_buffer_start
3289 * This re-enables the recording to the buffer, and frees the
3293 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
3295 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3297 atomic_dec(&cpu_buffer
->record_disabled
);
3300 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
3303 * ring_buffer_read - read the next item in the ring buffer by the iterator
3304 * @iter: The ring buffer iterator
3305 * @ts: The time stamp of the event read.
3307 * This reads the next event in the ring buffer and increments the iterator.
3309 struct ring_buffer_event
*
3310 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
3312 struct ring_buffer_event
*event
;
3313 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3314 unsigned long flags
;
3316 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3318 event
= rb_iter_peek(iter
, ts
);
3322 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
3325 rb_advance_iter(iter
);
3327 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3331 EXPORT_SYMBOL_GPL(ring_buffer_read
);
3334 * ring_buffer_size - return the size of the ring buffer (in bytes)
3335 * @buffer: The ring buffer.
3337 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
3339 return BUF_PAGE_SIZE
* buffer
->pages
;
3341 EXPORT_SYMBOL_GPL(ring_buffer_size
);
3344 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
3346 rb_head_page_deactivate(cpu_buffer
);
3348 cpu_buffer
->head_page
3349 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
3350 local_set(&cpu_buffer
->head_page
->write
, 0);
3351 local_set(&cpu_buffer
->head_page
->entries
, 0);
3352 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
3354 cpu_buffer
->head_page
->read
= 0;
3356 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
3357 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
3359 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
3360 local_set(&cpu_buffer
->reader_page
->write
, 0);
3361 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3362 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3363 cpu_buffer
->reader_page
->read
= 0;
3365 local_set(&cpu_buffer
->commit_overrun
, 0);
3366 local_set(&cpu_buffer
->overrun
, 0);
3367 local_set(&cpu_buffer
->entries
, 0);
3368 local_set(&cpu_buffer
->committing
, 0);
3369 local_set(&cpu_buffer
->commits
, 0);
3370 cpu_buffer
->read
= 0;
3372 cpu_buffer
->write_stamp
= 0;
3373 cpu_buffer
->read_stamp
= 0;
3375 rb_head_page_activate(cpu_buffer
);
3379 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3380 * @buffer: The ring buffer to reset a per cpu buffer of
3381 * @cpu: The CPU buffer to be reset
3383 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
3385 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3386 unsigned long flags
;
3388 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3391 atomic_inc(&cpu_buffer
->record_disabled
);
3393 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3395 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
3398 __raw_spin_lock(&cpu_buffer
->lock
);
3400 rb_reset_cpu(cpu_buffer
);
3402 __raw_spin_unlock(&cpu_buffer
->lock
);
3405 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3407 atomic_dec(&cpu_buffer
->record_disabled
);
3409 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
3412 * ring_buffer_reset - reset a ring buffer
3413 * @buffer: The ring buffer to reset all cpu buffers
3415 void ring_buffer_reset(struct ring_buffer
*buffer
)
3419 for_each_buffer_cpu(buffer
, cpu
)
3420 ring_buffer_reset_cpu(buffer
, cpu
);
3422 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
3425 * rind_buffer_empty - is the ring buffer empty?
3426 * @buffer: The ring buffer to test
3428 int ring_buffer_empty(struct ring_buffer
*buffer
)
3430 struct ring_buffer_per_cpu
*cpu_buffer
;
3431 unsigned long flags
;
3436 dolock
= rb_ok_to_lock();
3438 /* yes this is racy, but if you don't like the race, lock the buffer */
3439 for_each_buffer_cpu(buffer
, cpu
) {
3440 cpu_buffer
= buffer
->buffers
[cpu
];
3441 local_irq_save(flags
);
3443 spin_lock(&cpu_buffer
->reader_lock
);
3444 ret
= rb_per_cpu_empty(cpu_buffer
);
3446 spin_unlock(&cpu_buffer
->reader_lock
);
3447 local_irq_restore(flags
);
3455 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
3458 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
3459 * @buffer: The ring buffer
3460 * @cpu: The CPU buffer to test
3462 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
3464 struct ring_buffer_per_cpu
*cpu_buffer
;
3465 unsigned long flags
;
3469 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3472 dolock
= rb_ok_to_lock();
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
);
3485 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
3488 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
3489 * @buffer_a: One buffer to swap with
3490 * @buffer_b: The other buffer to swap with
3492 * This function is useful for tracers that want to take a "snapshot"
3493 * of a CPU buffer and has another back up buffer lying around.
3494 * it is expected that the tracer handles the cpu buffer not being
3495 * used at the moment.
3497 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
3498 struct ring_buffer
*buffer_b
, int cpu
)
3500 struct ring_buffer_per_cpu
*cpu_buffer_a
;
3501 struct ring_buffer_per_cpu
*cpu_buffer_b
;
3504 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
3505 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
3508 /* At least make sure the two buffers are somewhat the same */
3509 if (buffer_a
->pages
!= buffer_b
->pages
)
3514 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
3517 if (atomic_read(&buffer_a
->record_disabled
))
3520 if (atomic_read(&buffer_b
->record_disabled
))
3523 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
3524 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
3526 if (atomic_read(&cpu_buffer_a
->record_disabled
))
3529 if (atomic_read(&cpu_buffer_b
->record_disabled
))
3533 * We can't do a synchronize_sched here because this
3534 * function can be called in atomic context.
3535 * Normally this will be called from the same CPU as cpu.
3536 * If not it's up to the caller to protect this.
3538 atomic_inc(&cpu_buffer_a
->record_disabled
);
3539 atomic_inc(&cpu_buffer_b
->record_disabled
);
3542 if (local_read(&cpu_buffer_a
->committing
))
3544 if (local_read(&cpu_buffer_b
->committing
))
3547 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
3548 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
3550 cpu_buffer_b
->buffer
= buffer_a
;
3551 cpu_buffer_a
->buffer
= buffer_b
;
3556 atomic_dec(&cpu_buffer_a
->record_disabled
);
3557 atomic_dec(&cpu_buffer_b
->record_disabled
);
3561 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
3564 * ring_buffer_alloc_read_page - allocate a page to read from buffer
3565 * @buffer: the buffer to allocate for.
3567 * This function is used in conjunction with ring_buffer_read_page.
3568 * When reading a full page from the ring buffer, these functions
3569 * can be used to speed up the process. The calling function should
3570 * allocate a few pages first with this function. Then when it
3571 * needs to get pages from the ring buffer, it passes the result
3572 * of this function into ring_buffer_read_page, which will swap
3573 * the page that was allocated, with the read page of the buffer.
3576 * The page allocated, or NULL on error.
3578 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
)
3580 struct buffer_data_page
*bpage
;
3583 addr
= __get_free_page(GFP_KERNEL
);
3587 bpage
= (void *)addr
;
3589 rb_init_page(bpage
);
3593 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
3596 * ring_buffer_free_read_page - free an allocated read page
3597 * @buffer: the buffer the page was allocate for
3598 * @data: the page to free
3600 * Free a page allocated from ring_buffer_alloc_read_page.
3602 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
3604 free_page((unsigned long)data
);
3606 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
3609 * ring_buffer_read_page - extract a page from the ring buffer
3610 * @buffer: buffer to extract from
3611 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
3612 * @len: amount to extract
3613 * @cpu: the cpu of the buffer to extract
3614 * @full: should the extraction only happen when the page is full.
3616 * This function will pull out a page from the ring buffer and consume it.
3617 * @data_page must be the address of the variable that was returned
3618 * from ring_buffer_alloc_read_page. This is because the page might be used
3619 * to swap with a page in the ring buffer.
3622 * rpage = ring_buffer_alloc_read_page(buffer);
3625 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
3627 * process_page(rpage, ret);
3629 * When @full is set, the function will not return true unless
3630 * the writer is off the reader page.
3632 * Note: it is up to the calling functions to handle sleeps and wakeups.
3633 * The ring buffer can be used anywhere in the kernel and can not
3634 * blindly call wake_up. The layer that uses the ring buffer must be
3635 * responsible for that.
3638 * >=0 if data has been transferred, returns the offset of consumed data.
3639 * <0 if no data has been transferred.
3641 int ring_buffer_read_page(struct ring_buffer
*buffer
,
3642 void **data_page
, size_t len
, int cpu
, int full
)
3644 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3645 struct ring_buffer_event
*event
;
3646 struct buffer_data_page
*bpage
;
3647 struct buffer_page
*reader
;
3648 unsigned long flags
;
3649 unsigned int commit
;
3654 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3658 * If len is not big enough to hold the page header, then
3659 * we can not copy anything.
3661 if (len
<= BUF_PAGE_HDR_SIZE
)
3664 len
-= BUF_PAGE_HDR_SIZE
;
3673 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3675 reader
= rb_get_reader_page(cpu_buffer
);
3679 event
= rb_reader_event(cpu_buffer
);
3681 read
= reader
->read
;
3682 commit
= rb_page_commit(reader
);
3685 * If this page has been partially read or
3686 * if len is not big enough to read the rest of the page or
3687 * a writer is still on the page, then
3688 * we must copy the data from the page to the buffer.
3689 * Otherwise, we can simply swap the page with the one passed in.
3691 if (read
|| (len
< (commit
- read
)) ||
3692 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
3693 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
3694 unsigned int rpos
= read
;
3695 unsigned int pos
= 0;
3701 if (len
> (commit
- read
))
3702 len
= (commit
- read
);
3704 size
= rb_event_length(event
);
3709 /* save the current timestamp, since the user will need it */
3710 save_timestamp
= cpu_buffer
->read_stamp
;
3712 /* Need to copy one event at a time */
3714 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
3718 rb_advance_reader(cpu_buffer
);
3719 rpos
= reader
->read
;
3722 event
= rb_reader_event(cpu_buffer
);
3723 size
= rb_event_length(event
);
3724 } while (len
> size
);
3727 local_set(&bpage
->commit
, pos
);
3728 bpage
->time_stamp
= save_timestamp
;
3730 /* we copied everything to the beginning */
3733 /* update the entry counter */
3734 cpu_buffer
->read
+= rb_page_entries(reader
);
3736 /* swap the pages */
3737 rb_init_page(bpage
);
3738 bpage
= reader
->page
;
3739 reader
->page
= *data_page
;
3740 local_set(&reader
->write
, 0);
3741 local_set(&reader
->entries
, 0);
3748 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3753 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
3755 #ifdef CONFIG_TRACING
3757 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
3758 size_t cnt
, loff_t
*ppos
)
3760 unsigned long *p
= filp
->private_data
;
3764 if (test_bit(RB_BUFFERS_DISABLED_BIT
, p
))
3765 r
= sprintf(buf
, "permanently disabled\n");
3767 r
= sprintf(buf
, "%d\n", test_bit(RB_BUFFERS_ON_BIT
, p
));
3769 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
3773 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
3774 size_t cnt
, loff_t
*ppos
)
3776 unsigned long *p
= filp
->private_data
;
3781 if (cnt
>= sizeof(buf
))
3784 if (copy_from_user(&buf
, ubuf
, cnt
))
3789 ret
= strict_strtoul(buf
, 10, &val
);
3794 set_bit(RB_BUFFERS_ON_BIT
, p
);
3796 clear_bit(RB_BUFFERS_ON_BIT
, p
);
3803 static const struct file_operations rb_simple_fops
= {
3804 .open
= tracing_open_generic
,
3805 .read
= rb_simple_read
,
3806 .write
= rb_simple_write
,
3810 static __init
int rb_init_debugfs(void)
3812 struct dentry
*d_tracer
;
3814 d_tracer
= tracing_init_dentry();
3816 trace_create_file("tracing_on", 0644, d_tracer
,
3817 &ring_buffer_flags
, &rb_simple_fops
);
3822 fs_initcall(rb_init_debugfs
);
3825 #ifdef CONFIG_HOTPLUG_CPU
3826 static int rb_cpu_notify(struct notifier_block
*self
,
3827 unsigned long action
, void *hcpu
)
3829 struct ring_buffer
*buffer
=
3830 container_of(self
, struct ring_buffer
, cpu_notify
);
3831 long cpu
= (long)hcpu
;
3834 case CPU_UP_PREPARE
:
3835 case CPU_UP_PREPARE_FROZEN
:
3836 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
3839 buffer
->buffers
[cpu
] =
3840 rb_allocate_cpu_buffer(buffer
, cpu
);
3841 if (!buffer
->buffers
[cpu
]) {
3842 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
3847 cpumask_set_cpu(cpu
, buffer
->cpumask
);
3849 case CPU_DOWN_PREPARE
:
3850 case CPU_DOWN_PREPARE_FROZEN
:
3853 * If we were to free the buffer, then the user would
3854 * lose any trace that was in the buffer.