4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 #include <linux/ring_buffer.h>
7 #include <linux/trace_clock.h>
8 #include <linux/spinlock.h>
9 #include <linux/debugfs.h>
10 #include <linux/uaccess.h>
11 #include <linux/hardirq.h>
12 #include <linux/kmemcheck.h>
13 #include <linux/module.h>
14 #include <linux/percpu.h>
15 #include <linux/mutex.h>
16 #include <linux/slab.h>
17 #include <linux/init.h>
18 #include <linux/hash.h>
19 #include <linux/list.h>
20 #include <linux/cpu.h>
23 #include <asm/local.h>
26 static void update_pages_handler(struct work_struct
*work
);
29 * The ring buffer header is special. We must manually up keep it.
31 int ring_buffer_print_entry_header(struct trace_seq
*s
)
35 ret
= trace_seq_printf(s
, "# compressed entry header\n");
36 ret
= trace_seq_printf(s
, "\ttype_len : 5 bits\n");
37 ret
= trace_seq_printf(s
, "\ttime_delta : 27 bits\n");
38 ret
= trace_seq_printf(s
, "\tarray : 32 bits\n");
39 ret
= trace_seq_printf(s
, "\n");
40 ret
= trace_seq_printf(s
, "\tpadding : type == %d\n",
41 RINGBUF_TYPE_PADDING
);
42 ret
= trace_seq_printf(s
, "\ttime_extend : type == %d\n",
43 RINGBUF_TYPE_TIME_EXTEND
);
44 ret
= trace_seq_printf(s
, "\tdata max type_len == %d\n",
45 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
51 * The ring buffer is made up of a list of pages. A separate list of pages is
52 * allocated for each CPU. A writer may only write to a buffer that is
53 * associated with the CPU it is currently executing on. A reader may read
54 * from any per cpu buffer.
56 * The reader is special. For each per cpu buffer, the reader has its own
57 * reader page. When a reader has read the entire reader page, this reader
58 * page is swapped with another page in the ring buffer.
60 * Now, as long as the writer is off the reader page, the reader can do what
61 * ever it wants with that page. The writer will never write to that page
62 * again (as long as it is out of the ring buffer).
64 * Here's some silly ASCII art.
67 * |reader| RING BUFFER
69 * +------+ +---+ +---+ +---+
78 * |reader| RING BUFFER
79 * |page |------------------v
80 * +------+ +---+ +---+ +---+
89 * |reader| RING BUFFER
90 * |page |------------------v
91 * +------+ +---+ +---+ +---+
96 * +------------------------------+
100 * |buffer| RING BUFFER
101 * |page |------------------v
102 * +------+ +---+ +---+ +---+
104 * | New +---+ +---+ +---+
107 * +------------------------------+
110 * After we make this swap, the reader can hand this page off to the splice
111 * code and be done with it. It can even allocate a new page if it needs to
112 * and swap that into the ring buffer.
114 * We will be using cmpxchg soon to make all this lockless.
119 * A fast way to enable or disable all ring buffers is to
120 * call tracing_on or tracing_off. Turning off the ring buffers
121 * prevents all ring buffers from being recorded to.
122 * Turning this switch on, makes it OK to write to the
123 * ring buffer, if the ring buffer is enabled itself.
125 * There's three layers that must be on in order to write
126 * to the ring buffer.
128 * 1) This global flag must be set.
129 * 2) The ring buffer must be enabled for recording.
130 * 3) The per cpu buffer must be enabled for recording.
132 * In case of an anomaly, this global flag has a bit set that
133 * will permantly disable all ring buffers.
137 * Global flag to disable all recording to ring buffers
138 * This has two bits: ON, DISABLED
142 * 0 0 : ring buffers are off
143 * 1 0 : ring buffers are on
144 * X 1 : ring buffers are permanently disabled
148 RB_BUFFERS_ON_BIT
= 0,
149 RB_BUFFERS_DISABLED_BIT
= 1,
153 RB_BUFFERS_ON
= 1 << RB_BUFFERS_ON_BIT
,
154 RB_BUFFERS_DISABLED
= 1 << RB_BUFFERS_DISABLED_BIT
,
157 static unsigned long ring_buffer_flags __read_mostly
= RB_BUFFERS_ON
;
159 /* Used for individual buffers (after the counter) */
160 #define RB_BUFFER_OFF (1 << 20)
162 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
165 * tracing_off_permanent - permanently disable ring buffers
167 * This function, once called, will disable all ring buffers
170 void tracing_off_permanent(void)
172 set_bit(RB_BUFFERS_DISABLED_BIT
, &ring_buffer_flags
);
175 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
176 #define RB_ALIGNMENT 4U
177 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
178 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
180 #if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
181 # define RB_FORCE_8BYTE_ALIGNMENT 0
182 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
184 # define RB_FORCE_8BYTE_ALIGNMENT 1
185 # define RB_ARCH_ALIGNMENT 8U
188 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
189 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
192 RB_LEN_TIME_EXTEND
= 8,
193 RB_LEN_TIME_STAMP
= 16,
196 #define skip_time_extend(event) \
197 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
199 static inline int rb_null_event(struct ring_buffer_event
*event
)
201 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
204 static void rb_event_set_padding(struct ring_buffer_event
*event
)
206 /* padding has a NULL time_delta */
207 event
->type_len
= RINGBUF_TYPE_PADDING
;
208 event
->time_delta
= 0;
212 rb_event_data_length(struct ring_buffer_event
*event
)
217 length
= event
->type_len
* RB_ALIGNMENT
;
219 length
= event
->array
[0];
220 return length
+ RB_EVNT_HDR_SIZE
;
224 * Return the length of the given event. Will return
225 * the length of the time extend if the event is a
228 static inline unsigned
229 rb_event_length(struct ring_buffer_event
*event
)
231 switch (event
->type_len
) {
232 case RINGBUF_TYPE_PADDING
:
233 if (rb_null_event(event
))
236 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
238 case RINGBUF_TYPE_TIME_EXTEND
:
239 return RB_LEN_TIME_EXTEND
;
241 case RINGBUF_TYPE_TIME_STAMP
:
242 return RB_LEN_TIME_STAMP
;
244 case RINGBUF_TYPE_DATA
:
245 return rb_event_data_length(event
);
254 * Return total length of time extend and data,
255 * or just the event length for all other events.
257 static inline unsigned
258 rb_event_ts_length(struct ring_buffer_event
*event
)
262 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
263 /* time extends include the data event after it */
264 len
= RB_LEN_TIME_EXTEND
;
265 event
= skip_time_extend(event
);
267 return len
+ rb_event_length(event
);
271 * ring_buffer_event_length - return the length of the event
272 * @event: the event to get the length of
274 * Returns the size of the data load of a data event.
275 * If the event is something other than a data event, it
276 * returns the size of the event itself. With the exception
277 * of a TIME EXTEND, where it still returns the size of the
278 * data load of the data event after it.
280 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
284 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
285 event
= skip_time_extend(event
);
287 length
= rb_event_length(event
);
288 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
290 length
-= RB_EVNT_HDR_SIZE
;
291 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
292 length
-= sizeof(event
->array
[0]);
295 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
297 /* inline for ring buffer fast paths */
299 rb_event_data(struct ring_buffer_event
*event
)
301 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
302 event
= skip_time_extend(event
);
303 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
304 /* If length is in len field, then array[0] has the data */
306 return (void *)&event
->array
[0];
307 /* Otherwise length is in array[0] and array[1] has the data */
308 return (void *)&event
->array
[1];
312 * ring_buffer_event_data - return the data of the event
313 * @event: the event to get the data from
315 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
317 return rb_event_data(event
);
319 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
321 #define for_each_buffer_cpu(buffer, cpu) \
322 for_each_cpu(cpu, buffer->cpumask)
325 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
326 #define TS_DELTA_TEST (~TS_MASK)
328 /* Flag when events were overwritten */
329 #define RB_MISSED_EVENTS (1 << 31)
330 /* Missed count stored at end */
331 #define RB_MISSED_STORED (1 << 30)
333 struct buffer_data_page
{
334 u64 time_stamp
; /* page time stamp */
335 local_t commit
; /* write committed index */
336 unsigned char data
[]; /* data of buffer page */
340 * Note, the buffer_page list must be first. The buffer pages
341 * are allocated in cache lines, which means that each buffer
342 * page will be at the beginning of a cache line, and thus
343 * the least significant bits will be zero. We use this to
344 * add flags in the list struct pointers, to make the ring buffer
348 struct list_head list
; /* list of buffer pages */
349 local_t write
; /* index for next write */
350 unsigned read
; /* index for next read */
351 local_t entries
; /* entries on this page */
352 unsigned long real_end
; /* real end of data */
353 struct buffer_data_page
*page
; /* Actual data page */
357 * The buffer page counters, write and entries, must be reset
358 * atomically when crossing page boundaries. To synchronize this
359 * update, two counters are inserted into the number. One is
360 * the actual counter for the write position or count on the page.
362 * The other is a counter of updaters. Before an update happens
363 * the update partition of the counter is incremented. This will
364 * allow the updater to update the counter atomically.
366 * The counter is 20 bits, and the state data is 12.
368 #define RB_WRITE_MASK 0xfffff
369 #define RB_WRITE_INTCNT (1 << 20)
371 static void rb_init_page(struct buffer_data_page
*bpage
)
373 local_set(&bpage
->commit
, 0);
377 * ring_buffer_page_len - the size of data on the page.
378 * @page: The page to read
380 * Returns the amount of data on the page, including buffer page header.
382 size_t ring_buffer_page_len(void *page
)
384 return local_read(&((struct buffer_data_page
*)page
)->commit
)
389 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
392 static void free_buffer_page(struct buffer_page
*bpage
)
394 free_page((unsigned long)bpage
->page
);
399 * We need to fit the time_stamp delta into 27 bits.
401 static inline int test_time_stamp(u64 delta
)
403 if (delta
& TS_DELTA_TEST
)
408 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
410 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
411 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
413 int ring_buffer_print_page_header(struct trace_seq
*s
)
415 struct buffer_data_page field
;
418 ret
= trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
419 "offset:0;\tsize:%u;\tsigned:%u;\n",
420 (unsigned int)sizeof(field
.time_stamp
),
421 (unsigned int)is_signed_type(u64
));
423 ret
= trace_seq_printf(s
, "\tfield: local_t commit;\t"
424 "offset:%u;\tsize:%u;\tsigned:%u;\n",
425 (unsigned int)offsetof(typeof(field
), commit
),
426 (unsigned int)sizeof(field
.commit
),
427 (unsigned int)is_signed_type(long));
429 ret
= trace_seq_printf(s
, "\tfield: int overwrite;\t"
430 "offset:%u;\tsize:%u;\tsigned:%u;\n",
431 (unsigned int)offsetof(typeof(field
), commit
),
433 (unsigned int)is_signed_type(long));
435 ret
= trace_seq_printf(s
, "\tfield: char data;\t"
436 "offset:%u;\tsize:%u;\tsigned:%u;\n",
437 (unsigned int)offsetof(typeof(field
), data
),
438 (unsigned int)BUF_PAGE_SIZE
,
439 (unsigned int)is_signed_type(char));
445 * head_page == tail_page && head == tail then buffer is empty.
447 struct ring_buffer_per_cpu
{
449 atomic_t record_disabled
;
450 struct ring_buffer
*buffer
;
451 raw_spinlock_t reader_lock
; /* serialize readers */
452 arch_spinlock_t lock
;
453 struct lock_class_key lock_key
;
454 unsigned int nr_pages
;
455 struct list_head
*pages
;
456 struct buffer_page
*head_page
; /* read from head */
457 struct buffer_page
*tail_page
; /* write to tail */
458 struct buffer_page
*commit_page
; /* committed pages */
459 struct buffer_page
*reader_page
;
460 unsigned long lost_events
;
461 unsigned long last_overrun
;
462 local_t entries_bytes
;
465 local_t commit_overrun
;
466 local_t dropped_events
;
470 unsigned long read_bytes
;
473 /* ring buffer pages to update, > 0 to add, < 0 to remove */
474 int nr_pages_to_update
;
475 struct list_head new_pages
; /* new pages to add */
476 struct work_struct update_pages_work
;
477 struct completion update_done
;
483 atomic_t record_disabled
;
484 atomic_t resize_disabled
;
485 cpumask_var_t cpumask
;
487 struct lock_class_key
*reader_lock_key
;
491 struct ring_buffer_per_cpu
**buffers
;
493 #ifdef CONFIG_HOTPLUG_CPU
494 struct notifier_block cpu_notify
;
499 struct ring_buffer_iter
{
500 struct ring_buffer_per_cpu
*cpu_buffer
;
502 struct buffer_page
*head_page
;
503 struct buffer_page
*cache_reader_page
;
504 unsigned long cache_read
;
508 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
509 #define RB_WARN_ON(b, cond) \
511 int _____ret = unlikely(cond); \
513 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
514 struct ring_buffer_per_cpu *__b = \
516 atomic_inc(&__b->buffer->record_disabled); \
518 atomic_inc(&b->record_disabled); \
524 /* Up this if you want to test the TIME_EXTENTS and normalization */
525 #define DEBUG_SHIFT 0
527 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
529 /* shift to debug/test normalization and TIME_EXTENTS */
530 return buffer
->clock() << DEBUG_SHIFT
;
533 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
537 preempt_disable_notrace();
538 time
= rb_time_stamp(buffer
);
539 preempt_enable_no_resched_notrace();
543 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
545 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
548 /* Just stupid testing the normalize function and deltas */
551 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
554 * Making the ring buffer lockless makes things tricky.
555 * Although writes only happen on the CPU that they are on,
556 * and they only need to worry about interrupts. Reads can
559 * The reader page is always off the ring buffer, but when the
560 * reader finishes with a page, it needs to swap its page with
561 * a new one from the buffer. The reader needs to take from
562 * the head (writes go to the tail). But if a writer is in overwrite
563 * mode and wraps, it must push the head page forward.
565 * Here lies the problem.
567 * The reader must be careful to replace only the head page, and
568 * not another one. As described at the top of the file in the
569 * ASCII art, the reader sets its old page to point to the next
570 * page after head. It then sets the page after head to point to
571 * the old reader page. But if the writer moves the head page
572 * during this operation, the reader could end up with the tail.
574 * We use cmpxchg to help prevent this race. We also do something
575 * special with the page before head. We set the LSB to 1.
577 * When the writer must push the page forward, it will clear the
578 * bit that points to the head page, move the head, and then set
579 * the bit that points to the new head page.
581 * We also don't want an interrupt coming in and moving the head
582 * page on another writer. Thus we use the second LSB to catch
585 * head->list->prev->next bit 1 bit 0
588 * Points to head page 0 1
591 * Note we can not trust the prev pointer of the head page, because:
593 * +----+ +-----+ +-----+
594 * | |------>| T |---X--->| N |
596 * +----+ +-----+ +-----+
599 * +----------| R |----------+ |
603 * Key: ---X--> HEAD flag set in pointer
608 * (see __rb_reserve_next() to see where this happens)
610 * What the above shows is that the reader just swapped out
611 * the reader page with a page in the buffer, but before it
612 * could make the new header point back to the new page added
613 * it was preempted by a writer. The writer moved forward onto
614 * the new page added by the reader and is about to move forward
617 * You can see, it is legitimate for the previous pointer of
618 * the head (or any page) not to point back to itself. But only
622 #define RB_PAGE_NORMAL 0UL
623 #define RB_PAGE_HEAD 1UL
624 #define RB_PAGE_UPDATE 2UL
627 #define RB_FLAG_MASK 3UL
629 /* PAGE_MOVED is not part of the mask */
630 #define RB_PAGE_MOVED 4UL
633 * rb_list_head - remove any bit
635 static struct list_head
*rb_list_head(struct list_head
*list
)
637 unsigned long val
= (unsigned long)list
;
639 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
643 * rb_is_head_page - test if the given page is the head page
645 * Because the reader may move the head_page pointer, we can
646 * not trust what the head page is (it may be pointing to
647 * the reader page). But if the next page is a header page,
648 * its flags will be non zero.
651 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
652 struct buffer_page
*page
, struct list_head
*list
)
656 val
= (unsigned long)list
->next
;
658 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
659 return RB_PAGE_MOVED
;
661 return val
& RB_FLAG_MASK
;
667 * The unique thing about the reader page, is that, if the
668 * writer is ever on it, the previous pointer never points
669 * back to the reader page.
671 static int rb_is_reader_page(struct buffer_page
*page
)
673 struct list_head
*list
= page
->list
.prev
;
675 return rb_list_head(list
->next
) != &page
->list
;
679 * rb_set_list_to_head - set a list_head to be pointing to head.
681 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
682 struct list_head
*list
)
686 ptr
= (unsigned long *)&list
->next
;
687 *ptr
|= RB_PAGE_HEAD
;
688 *ptr
&= ~RB_PAGE_UPDATE
;
692 * rb_head_page_activate - sets up head page
694 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
696 struct buffer_page
*head
;
698 head
= cpu_buffer
->head_page
;
703 * Set the previous list pointer to have the HEAD flag.
705 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
708 static void rb_list_head_clear(struct list_head
*list
)
710 unsigned long *ptr
= (unsigned long *)&list
->next
;
712 *ptr
&= ~RB_FLAG_MASK
;
716 * rb_head_page_dactivate - clears head page ptr (for free list)
719 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
721 struct list_head
*hd
;
723 /* Go through the whole list and clear any pointers found. */
724 rb_list_head_clear(cpu_buffer
->pages
);
726 list_for_each(hd
, cpu_buffer
->pages
)
727 rb_list_head_clear(hd
);
730 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
731 struct buffer_page
*head
,
732 struct buffer_page
*prev
,
733 int old_flag
, int new_flag
)
735 struct list_head
*list
;
736 unsigned long val
= (unsigned long)&head
->list
;
741 val
&= ~RB_FLAG_MASK
;
743 ret
= cmpxchg((unsigned long *)&list
->next
,
744 val
| old_flag
, val
| new_flag
);
746 /* check if the reader took the page */
747 if ((ret
& ~RB_FLAG_MASK
) != val
)
748 return RB_PAGE_MOVED
;
750 return ret
& RB_FLAG_MASK
;
753 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
754 struct buffer_page
*head
,
755 struct buffer_page
*prev
,
758 return rb_head_page_set(cpu_buffer
, head
, prev
,
759 old_flag
, RB_PAGE_UPDATE
);
762 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
763 struct buffer_page
*head
,
764 struct buffer_page
*prev
,
767 return rb_head_page_set(cpu_buffer
, head
, prev
,
768 old_flag
, RB_PAGE_HEAD
);
771 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
772 struct buffer_page
*head
,
773 struct buffer_page
*prev
,
776 return rb_head_page_set(cpu_buffer
, head
, prev
,
777 old_flag
, RB_PAGE_NORMAL
);
780 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
781 struct buffer_page
**bpage
)
783 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
785 *bpage
= list_entry(p
, struct buffer_page
, list
);
788 static struct buffer_page
*
789 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
791 struct buffer_page
*head
;
792 struct buffer_page
*page
;
793 struct list_head
*list
;
796 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
800 list
= cpu_buffer
->pages
;
801 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
804 page
= head
= cpu_buffer
->head_page
;
806 * It is possible that the writer moves the header behind
807 * where we started, and we miss in one loop.
808 * A second loop should grab the header, but we'll do
809 * three loops just because I'm paranoid.
811 for (i
= 0; i
< 3; i
++) {
813 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
814 cpu_buffer
->head_page
= page
;
817 rb_inc_page(cpu_buffer
, &page
);
818 } while (page
!= head
);
821 RB_WARN_ON(cpu_buffer
, 1);
826 static int rb_head_page_replace(struct buffer_page
*old
,
827 struct buffer_page
*new)
829 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
833 val
= *ptr
& ~RB_FLAG_MASK
;
836 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
842 * rb_tail_page_update - move the tail page forward
844 * Returns 1 if moved tail page, 0 if someone else did.
846 static int rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
847 struct buffer_page
*tail_page
,
848 struct buffer_page
*next_page
)
850 struct buffer_page
*old_tail
;
851 unsigned long old_entries
;
852 unsigned long old_write
;
856 * The tail page now needs to be moved forward.
858 * We need to reset the tail page, but without messing
859 * with possible erasing of data brought in by interrupts
860 * that have moved the tail page and are currently on it.
862 * We add a counter to the write field to denote this.
864 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
865 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
868 * Just make sure we have seen our old_write and synchronize
869 * with any interrupts that come in.
874 * If the tail page is still the same as what we think
875 * it is, then it is up to us to update the tail
878 if (tail_page
== cpu_buffer
->tail_page
) {
879 /* Zero the write counter */
880 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
881 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
884 * This will only succeed if an interrupt did
885 * not come in and change it. In which case, we
886 * do not want to modify it.
888 * We add (void) to let the compiler know that we do not care
889 * about the return value of these functions. We use the
890 * cmpxchg to only update if an interrupt did not already
891 * do it for us. If the cmpxchg fails, we don't care.
893 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
894 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
897 * No need to worry about races with clearing out the commit.
898 * it only can increment when a commit takes place. But that
899 * only happens in the outer most nested commit.
901 local_set(&next_page
->page
->commit
, 0);
903 old_tail
= cmpxchg(&cpu_buffer
->tail_page
,
904 tail_page
, next_page
);
906 if (old_tail
== tail_page
)
913 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
914 struct buffer_page
*bpage
)
916 unsigned long val
= (unsigned long)bpage
;
918 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
925 * rb_check_list - make sure a pointer to a list has the last bits zero
927 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
928 struct list_head
*list
)
930 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
932 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
938 * check_pages - integrity check of buffer pages
939 * @cpu_buffer: CPU buffer with pages to test
941 * As a safety measure we check to make sure the data pages have not
944 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
946 struct list_head
*head
= cpu_buffer
->pages
;
947 struct buffer_page
*bpage
, *tmp
;
949 /* Reset the head page if it exists */
950 if (cpu_buffer
->head_page
)
951 rb_set_head_page(cpu_buffer
);
953 rb_head_page_deactivate(cpu_buffer
);
955 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
957 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
960 if (rb_check_list(cpu_buffer
, head
))
963 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
964 if (RB_WARN_ON(cpu_buffer
,
965 bpage
->list
.next
->prev
!= &bpage
->list
))
967 if (RB_WARN_ON(cpu_buffer
,
968 bpage
->list
.prev
->next
!= &bpage
->list
))
970 if (rb_check_list(cpu_buffer
, &bpage
->list
))
974 rb_head_page_activate(cpu_buffer
);
979 static int __rb_allocate_pages(int nr_pages
, struct list_head
*pages
, int cpu
)
982 struct buffer_page
*bpage
, *tmp
;
984 for (i
= 0; i
< nr_pages
; i
++) {
987 * __GFP_NORETRY flag makes sure that the allocation fails
988 * gracefully without invoking oom-killer and the system is
991 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
992 GFP_KERNEL
| __GFP_NORETRY
,
997 list_add(&bpage
->list
, pages
);
999 page
= alloc_pages_node(cpu_to_node(cpu
),
1000 GFP_KERNEL
| __GFP_NORETRY
, 0);
1003 bpage
->page
= page_address(page
);
1004 rb_init_page(bpage
->page
);
1010 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1011 list_del_init(&bpage
->list
);
1012 free_buffer_page(bpage
);
1018 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1025 if (__rb_allocate_pages(nr_pages
, &pages
, cpu_buffer
->cpu
))
1029 * The ring buffer page list is a circular list that does not
1030 * start and end with a list head. All page list items point to
1033 cpu_buffer
->pages
= pages
.next
;
1036 cpu_buffer
->nr_pages
= nr_pages
;
1038 rb_check_pages(cpu_buffer
);
1043 static struct ring_buffer_per_cpu
*
1044 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int nr_pages
, int cpu
)
1046 struct ring_buffer_per_cpu
*cpu_buffer
;
1047 struct buffer_page
*bpage
;
1051 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1052 GFP_KERNEL
, cpu_to_node(cpu
));
1056 cpu_buffer
->cpu
= cpu
;
1057 cpu_buffer
->buffer
= buffer
;
1058 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1059 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1060 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1061 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1062 init_completion(&cpu_buffer
->update_done
);
1064 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1065 GFP_KERNEL
, cpu_to_node(cpu
));
1067 goto fail_free_buffer
;
1069 rb_check_bpage(cpu_buffer
, bpage
);
1071 cpu_buffer
->reader_page
= bpage
;
1072 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, 0);
1074 goto fail_free_reader
;
1075 bpage
->page
= page_address(page
);
1076 rb_init_page(bpage
->page
);
1078 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1079 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1081 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1083 goto fail_free_reader
;
1085 cpu_buffer
->head_page
1086 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1087 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1089 rb_head_page_activate(cpu_buffer
);
1094 free_buffer_page(cpu_buffer
->reader_page
);
1101 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1103 struct list_head
*head
= cpu_buffer
->pages
;
1104 struct buffer_page
*bpage
, *tmp
;
1106 free_buffer_page(cpu_buffer
->reader_page
);
1108 rb_head_page_deactivate(cpu_buffer
);
1111 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1112 list_del_init(&bpage
->list
);
1113 free_buffer_page(bpage
);
1115 bpage
= list_entry(head
, struct buffer_page
, list
);
1116 free_buffer_page(bpage
);
1122 #ifdef CONFIG_HOTPLUG_CPU
1123 static int rb_cpu_notify(struct notifier_block
*self
,
1124 unsigned long action
, void *hcpu
);
1128 * ring_buffer_alloc - allocate a new ring_buffer
1129 * @size: the size in bytes per cpu that is needed.
1130 * @flags: attributes to set for the ring buffer.
1132 * Currently the only flag that is available is the RB_FL_OVERWRITE
1133 * flag. This flag means that the buffer will overwrite old data
1134 * when the buffer wraps. If this flag is not set, the buffer will
1135 * drop data when the tail hits the head.
1137 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1138 struct lock_class_key
*key
)
1140 struct ring_buffer
*buffer
;
1144 /* keep it in its own cache line */
1145 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1150 if (!alloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1151 goto fail_free_buffer
;
1153 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1154 buffer
->flags
= flags
;
1155 buffer
->clock
= trace_clock_local
;
1156 buffer
->reader_lock_key
= key
;
1158 /* need at least two pages */
1163 * In case of non-hotplug cpu, if the ring-buffer is allocated
1164 * in early initcall, it will not be notified of secondary cpus.
1165 * In that off case, we need to allocate for all possible cpus.
1167 #ifdef CONFIG_HOTPLUG_CPU
1169 cpumask_copy(buffer
->cpumask
, cpu_online_mask
);
1171 cpumask_copy(buffer
->cpumask
, cpu_possible_mask
);
1173 buffer
->cpus
= nr_cpu_ids
;
1175 bsize
= sizeof(void *) * nr_cpu_ids
;
1176 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1178 if (!buffer
->buffers
)
1179 goto fail_free_cpumask
;
1181 for_each_buffer_cpu(buffer
, cpu
) {
1182 buffer
->buffers
[cpu
] =
1183 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1184 if (!buffer
->buffers
[cpu
])
1185 goto fail_free_buffers
;
1188 #ifdef CONFIG_HOTPLUG_CPU
1189 buffer
->cpu_notify
.notifier_call
= rb_cpu_notify
;
1190 buffer
->cpu_notify
.priority
= 0;
1191 register_cpu_notifier(&buffer
->cpu_notify
);
1195 mutex_init(&buffer
->mutex
);
1200 for_each_buffer_cpu(buffer
, cpu
) {
1201 if (buffer
->buffers
[cpu
])
1202 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1204 kfree(buffer
->buffers
);
1207 free_cpumask_var(buffer
->cpumask
);
1214 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1217 * ring_buffer_free - free a ring buffer.
1218 * @buffer: the buffer to free.
1221 ring_buffer_free(struct ring_buffer
*buffer
)
1227 #ifdef CONFIG_HOTPLUG_CPU
1228 unregister_cpu_notifier(&buffer
->cpu_notify
);
1231 for_each_buffer_cpu(buffer
, cpu
)
1232 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1236 kfree(buffer
->buffers
);
1237 free_cpumask_var(buffer
->cpumask
);
1241 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1243 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1246 buffer
->clock
= clock
;
1249 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1251 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1253 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1256 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1258 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1262 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned int nr_pages
)
1264 struct list_head
*tail_page
, *to_remove
, *next_page
;
1265 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1266 struct buffer_page
*last_page
, *first_page
;
1267 unsigned int nr_removed
;
1268 unsigned long head_bit
;
1273 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1274 atomic_inc(&cpu_buffer
->record_disabled
);
1276 * We don't race with the readers since we have acquired the reader
1277 * lock. We also don't race with writers after disabling recording.
1278 * This makes it easy to figure out the first and the last page to be
1279 * removed from the list. We unlink all the pages in between including
1280 * the first and last pages. This is done in a busy loop so that we
1281 * lose the least number of traces.
1282 * The pages are freed after we restart recording and unlock readers.
1284 tail_page
= &cpu_buffer
->tail_page
->list
;
1287 * tail page might be on reader page, we remove the next page
1288 * from the ring buffer
1290 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1291 tail_page
= rb_list_head(tail_page
->next
);
1292 to_remove
= tail_page
;
1294 /* start of pages to remove */
1295 first_page
= list_entry(rb_list_head(to_remove
->next
),
1296 struct buffer_page
, list
);
1298 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1299 to_remove
= rb_list_head(to_remove
)->next
;
1300 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1303 next_page
= rb_list_head(to_remove
)->next
;
1306 * Now we remove all pages between tail_page and next_page.
1307 * Make sure that we have head_bit value preserved for the
1310 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1312 next_page
= rb_list_head(next_page
);
1313 next_page
->prev
= tail_page
;
1315 /* make sure pages points to a valid page in the ring buffer */
1316 cpu_buffer
->pages
= next_page
;
1318 /* update head page */
1320 cpu_buffer
->head_page
= list_entry(next_page
,
1321 struct buffer_page
, list
);
1324 * change read pointer to make sure any read iterators reset
1327 cpu_buffer
->read
= 0;
1329 /* pages are removed, resume tracing and then free the pages */
1330 atomic_dec(&cpu_buffer
->record_disabled
);
1331 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1333 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1335 /* last buffer page to remove */
1336 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1338 tmp_iter_page
= first_page
;
1341 to_remove_page
= tmp_iter_page
;
1342 rb_inc_page(cpu_buffer
, &tmp_iter_page
);
1344 /* update the counters */
1345 page_entries
= rb_page_entries(to_remove_page
);
1348 * If something was added to this page, it was full
1349 * since it is not the tail page. So we deduct the
1350 * bytes consumed in ring buffer from here.
1351 * Increment overrun to account for the lost events.
1353 local_add(page_entries
, &cpu_buffer
->overrun
);
1354 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1358 * We have already removed references to this list item, just
1359 * free up the buffer_page and its page
1361 free_buffer_page(to_remove_page
);
1364 } while (to_remove_page
!= last_page
);
1366 RB_WARN_ON(cpu_buffer
, nr_removed
);
1368 return nr_removed
== 0;
1372 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1374 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1375 int retries
, success
;
1377 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1379 * We are holding the reader lock, so the reader page won't be swapped
1380 * in the ring buffer. Now we are racing with the writer trying to
1381 * move head page and the tail page.
1382 * We are going to adapt the reader page update process where:
1383 * 1. We first splice the start and end of list of new pages between
1384 * the head page and its previous page.
1385 * 2. We cmpxchg the prev_page->next to point from head page to the
1386 * start of new pages list.
1387 * 3. Finally, we update the head->prev to the end of new list.
1389 * We will try this process 10 times, to make sure that we don't keep
1395 struct list_head
*head_page
, *prev_page
, *r
;
1396 struct list_head
*last_page
, *first_page
;
1397 struct list_head
*head_page_with_bit
;
1399 head_page
= &rb_set_head_page(cpu_buffer
)->list
;
1400 prev_page
= head_page
->prev
;
1402 first_page
= pages
->next
;
1403 last_page
= pages
->prev
;
1405 head_page_with_bit
= (struct list_head
*)
1406 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1408 last_page
->next
= head_page_with_bit
;
1409 first_page
->prev
= prev_page
;
1411 r
= cmpxchg(&prev_page
->next
, head_page_with_bit
, first_page
);
1413 if (r
== head_page_with_bit
) {
1415 * yay, we replaced the page pointer to our new list,
1416 * now, we just have to update to head page's prev
1417 * pointer to point to end of list
1419 head_page
->prev
= last_page
;
1426 INIT_LIST_HEAD(pages
);
1428 * If we weren't successful in adding in new pages, warn and stop
1431 RB_WARN_ON(cpu_buffer
, !success
);
1432 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1434 /* free pages if they weren't inserted */
1436 struct buffer_page
*bpage
, *tmp
;
1437 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1439 list_del_init(&bpage
->list
);
1440 free_buffer_page(bpage
);
1446 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1450 if (cpu_buffer
->nr_pages_to_update
> 0)
1451 success
= rb_insert_pages(cpu_buffer
);
1453 success
= rb_remove_pages(cpu_buffer
,
1454 -cpu_buffer
->nr_pages_to_update
);
1457 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1460 static void update_pages_handler(struct work_struct
*work
)
1462 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1463 struct ring_buffer_per_cpu
, update_pages_work
);
1464 rb_update_pages(cpu_buffer
);
1465 complete(&cpu_buffer
->update_done
);
1469 * ring_buffer_resize - resize the ring buffer
1470 * @buffer: the buffer to resize.
1471 * @size: the new size.
1473 * Minimum size is 2 * BUF_PAGE_SIZE.
1475 * Returns 0 on success and < 0 on failure.
1477 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
,
1480 struct ring_buffer_per_cpu
*cpu_buffer
;
1485 * Always succeed at resizing a non-existent buffer:
1490 /* Make sure the requested buffer exists */
1491 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1492 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1495 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1496 size
*= BUF_PAGE_SIZE
;
1498 /* we need a minimum of two pages */
1499 if (size
< BUF_PAGE_SIZE
* 2)
1500 size
= BUF_PAGE_SIZE
* 2;
1502 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1505 * Don't succeed if resizing is disabled, as a reader might be
1506 * manipulating the ring buffer and is expecting a sane state while
1509 if (atomic_read(&buffer
->resize_disabled
))
1512 /* prevent another thread from changing buffer sizes */
1513 mutex_lock(&buffer
->mutex
);
1515 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
1516 /* calculate the pages to update */
1517 for_each_buffer_cpu(buffer
, cpu
) {
1518 cpu_buffer
= buffer
->buffers
[cpu
];
1520 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1521 cpu_buffer
->nr_pages
;
1523 * nothing more to do for removing pages or no update
1525 if (cpu_buffer
->nr_pages_to_update
<= 0)
1528 * to add pages, make sure all new pages can be
1529 * allocated without receiving ENOMEM
1531 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1532 if (__rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1533 &cpu_buffer
->new_pages
, cpu
)) {
1534 /* not enough memory for new pages */
1542 * Fire off all the required work handlers
1543 * We can't schedule on offline CPUs, but it's not necessary
1544 * since we can change their buffer sizes without any race.
1546 for_each_buffer_cpu(buffer
, cpu
) {
1547 cpu_buffer
= buffer
->buffers
[cpu
];
1548 if (!cpu_buffer
->nr_pages_to_update
)
1551 if (cpu_online(cpu
))
1552 schedule_work_on(cpu
,
1553 &cpu_buffer
->update_pages_work
);
1555 rb_update_pages(cpu_buffer
);
1558 /* wait for all the updates to complete */
1559 for_each_buffer_cpu(buffer
, cpu
) {
1560 cpu_buffer
= buffer
->buffers
[cpu
];
1561 if (!cpu_buffer
->nr_pages_to_update
)
1564 if (cpu_online(cpu
))
1565 wait_for_completion(&cpu_buffer
->update_done
);
1566 cpu_buffer
->nr_pages_to_update
= 0;
1571 /* Make sure this CPU has been intitialized */
1572 if (!cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1575 cpu_buffer
= buffer
->buffers
[cpu_id
];
1577 if (nr_pages
== cpu_buffer
->nr_pages
)
1580 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1581 cpu_buffer
->nr_pages
;
1583 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1584 if (cpu_buffer
->nr_pages_to_update
> 0 &&
1585 __rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1586 &cpu_buffer
->new_pages
, cpu_id
)) {
1593 if (cpu_online(cpu_id
)) {
1594 schedule_work_on(cpu_id
,
1595 &cpu_buffer
->update_pages_work
);
1596 wait_for_completion(&cpu_buffer
->update_done
);
1598 rb_update_pages(cpu_buffer
);
1600 cpu_buffer
->nr_pages_to_update
= 0;
1606 * The ring buffer resize can happen with the ring buffer
1607 * enabled, so that the update disturbs the tracing as little
1608 * as possible. But if the buffer is disabled, we do not need
1609 * to worry about that, and we can take the time to verify
1610 * that the buffer is not corrupt.
1612 if (atomic_read(&buffer
->record_disabled
)) {
1613 atomic_inc(&buffer
->record_disabled
);
1615 * Even though the buffer was disabled, we must make sure
1616 * that it is truly disabled before calling rb_check_pages.
1617 * There could have been a race between checking
1618 * record_disable and incrementing it.
1620 synchronize_sched();
1621 for_each_buffer_cpu(buffer
, cpu
) {
1622 cpu_buffer
= buffer
->buffers
[cpu
];
1623 rb_check_pages(cpu_buffer
);
1625 atomic_dec(&buffer
->record_disabled
);
1628 mutex_unlock(&buffer
->mutex
);
1632 for_each_buffer_cpu(buffer
, cpu
) {
1633 struct buffer_page
*bpage
, *tmp
;
1635 cpu_buffer
= buffer
->buffers
[cpu
];
1636 cpu_buffer
->nr_pages_to_update
= 0;
1638 if (list_empty(&cpu_buffer
->new_pages
))
1641 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1643 list_del_init(&bpage
->list
);
1644 free_buffer_page(bpage
);
1647 mutex_unlock(&buffer
->mutex
);
1650 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1652 void ring_buffer_change_overwrite(struct ring_buffer
*buffer
, int val
)
1654 mutex_lock(&buffer
->mutex
);
1656 buffer
->flags
|= RB_FL_OVERWRITE
;
1658 buffer
->flags
&= ~RB_FL_OVERWRITE
;
1659 mutex_unlock(&buffer
->mutex
);
1661 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
1663 static inline void *
1664 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
1666 return bpage
->data
+ index
;
1669 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1671 return bpage
->page
->data
+ index
;
1674 static inline struct ring_buffer_event
*
1675 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1677 return __rb_page_index(cpu_buffer
->reader_page
,
1678 cpu_buffer
->reader_page
->read
);
1681 static inline struct ring_buffer_event
*
1682 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1684 return __rb_page_index(iter
->head_page
, iter
->head
);
1687 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
1689 return local_read(&bpage
->page
->commit
);
1692 /* Size is determined by what has been committed */
1693 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
1695 return rb_page_commit(bpage
);
1698 static inline unsigned
1699 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1701 return rb_page_commit(cpu_buffer
->commit_page
);
1704 static inline unsigned
1705 rb_event_index(struct ring_buffer_event
*event
)
1707 unsigned long addr
= (unsigned long)event
;
1709 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1713 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1714 struct ring_buffer_event
*event
)
1716 unsigned long addr
= (unsigned long)event
;
1717 unsigned long index
;
1719 index
= rb_event_index(event
);
1722 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
1723 rb_commit_index(cpu_buffer
) == index
;
1727 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
1729 unsigned long max_count
;
1732 * We only race with interrupts and NMIs on this CPU.
1733 * If we own the commit event, then we can commit
1734 * all others that interrupted us, since the interruptions
1735 * are in stack format (they finish before they come
1736 * back to us). This allows us to do a simple loop to
1737 * assign the commit to the tail.
1740 max_count
= cpu_buffer
->nr_pages
* 100;
1742 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
1743 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
1745 if (RB_WARN_ON(cpu_buffer
,
1746 rb_is_reader_page(cpu_buffer
->tail_page
)))
1748 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1749 rb_page_write(cpu_buffer
->commit_page
));
1750 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
1751 cpu_buffer
->write_stamp
=
1752 cpu_buffer
->commit_page
->page
->time_stamp
;
1753 /* add barrier to keep gcc from optimizing too much */
1756 while (rb_commit_index(cpu_buffer
) !=
1757 rb_page_write(cpu_buffer
->commit_page
)) {
1759 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1760 rb_page_write(cpu_buffer
->commit_page
));
1761 RB_WARN_ON(cpu_buffer
,
1762 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
1767 /* again, keep gcc from optimizing */
1771 * If an interrupt came in just after the first while loop
1772 * and pushed the tail page forward, we will be left with
1773 * a dangling commit that will never go forward.
1775 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
1779 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1781 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
1782 cpu_buffer
->reader_page
->read
= 0;
1785 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1787 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1790 * The iterator could be on the reader page (it starts there).
1791 * But the head could have moved, since the reader was
1792 * found. Check for this case and assign the iterator
1793 * to the head page instead of next.
1795 if (iter
->head_page
== cpu_buffer
->reader_page
)
1796 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1798 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1800 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1804 /* Slow path, do not inline */
1805 static noinline
struct ring_buffer_event
*
1806 rb_add_time_stamp(struct ring_buffer_event
*event
, u64 delta
)
1808 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
1810 /* Not the first event on the page? */
1811 if (rb_event_index(event
)) {
1812 event
->time_delta
= delta
& TS_MASK
;
1813 event
->array
[0] = delta
>> TS_SHIFT
;
1815 /* nope, just zero it */
1816 event
->time_delta
= 0;
1817 event
->array
[0] = 0;
1820 return skip_time_extend(event
);
1824 * rb_update_event - update event type and data
1825 * @event: the even to update
1826 * @type: the type of event
1827 * @length: the size of the event field in the ring buffer
1829 * Update the type and data fields of the event. The length
1830 * is the actual size that is written to the ring buffer,
1831 * and with this, we can determine what to place into the
1835 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
1836 struct ring_buffer_event
*event
, unsigned length
,
1837 int add_timestamp
, u64 delta
)
1839 /* Only a commit updates the timestamp */
1840 if (unlikely(!rb_event_is_commit(cpu_buffer
, event
)))
1844 * If we need to add a timestamp, then we
1845 * add it to the start of the resevered space.
1847 if (unlikely(add_timestamp
)) {
1848 event
= rb_add_time_stamp(event
, delta
);
1849 length
-= RB_LEN_TIME_EXTEND
;
1853 event
->time_delta
= delta
;
1854 length
-= RB_EVNT_HDR_SIZE
;
1855 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
) {
1856 event
->type_len
= 0;
1857 event
->array
[0] = length
;
1859 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
1863 * rb_handle_head_page - writer hit the head page
1865 * Returns: +1 to retry page
1870 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1871 struct buffer_page
*tail_page
,
1872 struct buffer_page
*next_page
)
1874 struct buffer_page
*new_head
;
1879 entries
= rb_page_entries(next_page
);
1882 * The hard part is here. We need to move the head
1883 * forward, and protect against both readers on
1884 * other CPUs and writers coming in via interrupts.
1886 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1890 * type can be one of four:
1891 * NORMAL - an interrupt already moved it for us
1892 * HEAD - we are the first to get here.
1893 * UPDATE - we are the interrupt interrupting
1895 * MOVED - a reader on another CPU moved the next
1896 * pointer to its reader page. Give up
1903 * We changed the head to UPDATE, thus
1904 * it is our responsibility to update
1907 local_add(entries
, &cpu_buffer
->overrun
);
1908 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1911 * The entries will be zeroed out when we move the
1915 /* still more to do */
1918 case RB_PAGE_UPDATE
:
1920 * This is an interrupt that interrupt the
1921 * previous update. Still more to do.
1924 case RB_PAGE_NORMAL
:
1926 * An interrupt came in before the update
1927 * and processed this for us.
1928 * Nothing left to do.
1933 * The reader is on another CPU and just did
1934 * a swap with our next_page.
1939 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
1944 * Now that we are here, the old head pointer is
1945 * set to UPDATE. This will keep the reader from
1946 * swapping the head page with the reader page.
1947 * The reader (on another CPU) will spin till
1950 * We just need to protect against interrupts
1951 * doing the job. We will set the next pointer
1952 * to HEAD. After that, we set the old pointer
1953 * to NORMAL, but only if it was HEAD before.
1954 * otherwise we are an interrupt, and only
1955 * want the outer most commit to reset it.
1957 new_head
= next_page
;
1958 rb_inc_page(cpu_buffer
, &new_head
);
1960 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
1964 * Valid returns are:
1965 * HEAD - an interrupt came in and already set it.
1966 * NORMAL - One of two things:
1967 * 1) We really set it.
1968 * 2) A bunch of interrupts came in and moved
1969 * the page forward again.
1973 case RB_PAGE_NORMAL
:
1977 RB_WARN_ON(cpu_buffer
, 1);
1982 * It is possible that an interrupt came in,
1983 * set the head up, then more interrupts came in
1984 * and moved it again. When we get back here,
1985 * the page would have been set to NORMAL but we
1986 * just set it back to HEAD.
1988 * How do you detect this? Well, if that happened
1989 * the tail page would have moved.
1991 if (ret
== RB_PAGE_NORMAL
) {
1993 * If the tail had moved passed next, then we need
1994 * to reset the pointer.
1996 if (cpu_buffer
->tail_page
!= tail_page
&&
1997 cpu_buffer
->tail_page
!= next_page
)
1998 rb_head_page_set_normal(cpu_buffer
, new_head
,
2004 * If this was the outer most commit (the one that
2005 * changed the original pointer from HEAD to UPDATE),
2006 * then it is up to us to reset it to NORMAL.
2008 if (type
== RB_PAGE_HEAD
) {
2009 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2012 if (RB_WARN_ON(cpu_buffer
,
2013 ret
!= RB_PAGE_UPDATE
))
2020 static unsigned rb_calculate_event_length(unsigned length
)
2022 struct ring_buffer_event event
; /* Used only for sizeof array */
2024 /* zero length can cause confusions */
2028 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
2029 length
+= sizeof(event
.array
[0]);
2031 length
+= RB_EVNT_HDR_SIZE
;
2032 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
2038 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2039 struct buffer_page
*tail_page
,
2040 unsigned long tail
, unsigned long length
)
2042 struct ring_buffer_event
*event
;
2045 * Only the event that crossed the page boundary
2046 * must fill the old tail_page with padding.
2048 if (tail
>= BUF_PAGE_SIZE
) {
2050 * If the page was filled, then we still need
2051 * to update the real_end. Reset it to zero
2052 * and the reader will ignore it.
2054 if (tail
== BUF_PAGE_SIZE
)
2055 tail_page
->real_end
= 0;
2057 local_sub(length
, &tail_page
->write
);
2061 event
= __rb_page_index(tail_page
, tail
);
2062 kmemcheck_annotate_bitfield(event
, bitfield
);
2064 /* account for padding bytes */
2065 local_add(BUF_PAGE_SIZE
- tail
, &cpu_buffer
->entries_bytes
);
2068 * Save the original length to the meta data.
2069 * This will be used by the reader to add lost event
2072 tail_page
->real_end
= tail
;
2075 * If this event is bigger than the minimum size, then
2076 * we need to be careful that we don't subtract the
2077 * write counter enough to allow another writer to slip
2079 * We put in a discarded commit instead, to make sure
2080 * that this space is not used again.
2082 * If we are less than the minimum size, we don't need to
2085 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
2086 /* No room for any events */
2088 /* Mark the rest of the page with padding */
2089 rb_event_set_padding(event
);
2091 /* Set the write back to the previous setting */
2092 local_sub(length
, &tail_page
->write
);
2096 /* Put in a discarded event */
2097 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
2098 event
->type_len
= RINGBUF_TYPE_PADDING
;
2099 /* time delta must be non zero */
2100 event
->time_delta
= 1;
2102 /* Set write to end of buffer */
2103 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
2104 local_sub(length
, &tail_page
->write
);
2108 * This is the slow path, force gcc not to inline it.
2110 static noinline
struct ring_buffer_event
*
2111 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2112 unsigned long length
, unsigned long tail
,
2113 struct buffer_page
*tail_page
, u64 ts
)
2115 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2116 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
2117 struct buffer_page
*next_page
;
2120 next_page
= tail_page
;
2122 rb_inc_page(cpu_buffer
, &next_page
);
2125 * If for some reason, we had an interrupt storm that made
2126 * it all the way around the buffer, bail, and warn
2129 if (unlikely(next_page
== commit_page
)) {
2130 local_inc(&cpu_buffer
->commit_overrun
);
2135 * This is where the fun begins!
2137 * We are fighting against races between a reader that
2138 * could be on another CPU trying to swap its reader
2139 * page with the buffer head.
2141 * We are also fighting against interrupts coming in and
2142 * moving the head or tail on us as well.
2144 * If the next page is the head page then we have filled
2145 * the buffer, unless the commit page is still on the
2148 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
2151 * If the commit is not on the reader page, then
2152 * move the header page.
2154 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2156 * If we are not in overwrite mode,
2157 * this is easy, just stop here.
2159 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2160 local_inc(&cpu_buffer
->dropped_events
);
2164 ret
= rb_handle_head_page(cpu_buffer
,
2173 * We need to be careful here too. The
2174 * commit page could still be on the reader
2175 * page. We could have a small buffer, and
2176 * have filled up the buffer with events
2177 * from interrupts and such, and wrapped.
2179 * Note, if the tail page is also the on the
2180 * reader_page, we let it move out.
2182 if (unlikely((cpu_buffer
->commit_page
!=
2183 cpu_buffer
->tail_page
) &&
2184 (cpu_buffer
->commit_page
==
2185 cpu_buffer
->reader_page
))) {
2186 local_inc(&cpu_buffer
->commit_overrun
);
2192 ret
= rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2195 * Nested commits always have zero deltas, so
2196 * just reread the time stamp
2198 ts
= rb_time_stamp(buffer
);
2199 next_page
->page
->time_stamp
= ts
;
2204 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
2206 /* fail and let the caller try again */
2207 return ERR_PTR(-EAGAIN
);
2211 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
2216 static struct ring_buffer_event
*
2217 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
2218 unsigned long length
, u64 ts
,
2219 u64 delta
, int add_timestamp
)
2221 struct buffer_page
*tail_page
;
2222 struct ring_buffer_event
*event
;
2223 unsigned long tail
, write
;
2226 * If the time delta since the last event is too big to
2227 * hold in the time field of the event, then we append a
2228 * TIME EXTEND event ahead of the data event.
2230 if (unlikely(add_timestamp
))
2231 length
+= RB_LEN_TIME_EXTEND
;
2233 tail_page
= cpu_buffer
->tail_page
;
2234 write
= local_add_return(length
, &tail_page
->write
);
2236 /* set write to only the index of the write */
2237 write
&= RB_WRITE_MASK
;
2238 tail
= write
- length
;
2240 /* See if we shot pass the end of this buffer page */
2241 if (unlikely(write
> BUF_PAGE_SIZE
))
2242 return rb_move_tail(cpu_buffer
, length
, tail
,
2245 /* We reserved something on the buffer */
2247 event
= __rb_page_index(tail_page
, tail
);
2248 kmemcheck_annotate_bitfield(event
, bitfield
);
2249 rb_update_event(cpu_buffer
, event
, length
, add_timestamp
, delta
);
2251 local_inc(&tail_page
->entries
);
2254 * If this is the first commit on the page, then update
2258 tail_page
->page
->time_stamp
= ts
;
2260 /* account for these added bytes */
2261 local_add(length
, &cpu_buffer
->entries_bytes
);
2267 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2268 struct ring_buffer_event
*event
)
2270 unsigned long new_index
, old_index
;
2271 struct buffer_page
*bpage
;
2272 unsigned long index
;
2275 new_index
= rb_event_index(event
);
2276 old_index
= new_index
+ rb_event_ts_length(event
);
2277 addr
= (unsigned long)event
;
2280 bpage
= cpu_buffer
->tail_page
;
2282 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2283 unsigned long write_mask
=
2284 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2285 unsigned long event_length
= rb_event_length(event
);
2287 * This is on the tail page. It is possible that
2288 * a write could come in and move the tail page
2289 * and write to the next page. That is fine
2290 * because we just shorten what is on this page.
2292 old_index
+= write_mask
;
2293 new_index
+= write_mask
;
2294 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2295 if (index
== old_index
) {
2296 /* update counters */
2297 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2302 /* could not discard */
2306 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2308 local_inc(&cpu_buffer
->committing
);
2309 local_inc(&cpu_buffer
->commits
);
2312 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2314 unsigned long commits
;
2316 if (RB_WARN_ON(cpu_buffer
,
2317 !local_read(&cpu_buffer
->committing
)))
2321 commits
= local_read(&cpu_buffer
->commits
);
2322 /* synchronize with interrupts */
2324 if (local_read(&cpu_buffer
->committing
) == 1)
2325 rb_set_commit_to_write(cpu_buffer
);
2327 local_dec(&cpu_buffer
->committing
);
2329 /* synchronize with interrupts */
2333 * Need to account for interrupts coming in between the
2334 * updating of the commit page and the clearing of the
2335 * committing counter.
2337 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2338 !local_read(&cpu_buffer
->committing
)) {
2339 local_inc(&cpu_buffer
->committing
);
2344 static struct ring_buffer_event
*
2345 rb_reserve_next_event(struct ring_buffer
*buffer
,
2346 struct ring_buffer_per_cpu
*cpu_buffer
,
2347 unsigned long length
)
2349 struct ring_buffer_event
*event
;
2355 rb_start_commit(cpu_buffer
);
2357 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2359 * Due to the ability to swap a cpu buffer from a buffer
2360 * it is possible it was swapped before we committed.
2361 * (committing stops a swap). We check for it here and
2362 * if it happened, we have to fail the write.
2365 if (unlikely(ACCESS_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2366 local_dec(&cpu_buffer
->committing
);
2367 local_dec(&cpu_buffer
->commits
);
2372 length
= rb_calculate_event_length(length
);
2378 * We allow for interrupts to reenter here and do a trace.
2379 * If one does, it will cause this original code to loop
2380 * back here. Even with heavy interrupts happening, this
2381 * should only happen a few times in a row. If this happens
2382 * 1000 times in a row, there must be either an interrupt
2383 * storm or we have something buggy.
2386 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2389 ts
= rb_time_stamp(cpu_buffer
->buffer
);
2390 diff
= ts
- cpu_buffer
->write_stamp
;
2392 /* make sure this diff is calculated here */
2395 /* Did the write stamp get updated already? */
2396 if (likely(ts
>= cpu_buffer
->write_stamp
)) {
2398 if (unlikely(test_time_stamp(delta
))) {
2399 int local_clock_stable
= 1;
2400 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2401 local_clock_stable
= sched_clock_stable
;
2403 WARN_ONCE(delta
> (1ULL << 59),
2404 KERN_WARNING
"Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2405 (unsigned long long)delta
,
2406 (unsigned long long)ts
,
2407 (unsigned long long)cpu_buffer
->write_stamp
,
2408 local_clock_stable
? "" :
2409 "If you just came from a suspend/resume,\n"
2410 "please switch to the trace global clock:\n"
2411 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2416 event
= __rb_reserve_next(cpu_buffer
, length
, ts
,
2417 delta
, add_timestamp
);
2418 if (unlikely(PTR_ERR(event
) == -EAGAIN
))
2427 rb_end_commit(cpu_buffer
);
2431 #ifdef CONFIG_TRACING
2433 #define TRACE_RECURSIVE_DEPTH 16
2435 /* Keep this code out of the fast path cache */
2436 static noinline
void trace_recursive_fail(void)
2438 /* Disable all tracing before we do anything else */
2439 tracing_off_permanent();
2441 printk_once(KERN_WARNING
"Tracing recursion: depth[%ld]:"
2442 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
2443 trace_recursion_buffer(),
2444 hardirq_count() >> HARDIRQ_SHIFT
,
2445 softirq_count() >> SOFTIRQ_SHIFT
,
2451 static inline int trace_recursive_lock(void)
2453 trace_recursion_inc();
2455 if (likely(trace_recursion_buffer() < TRACE_RECURSIVE_DEPTH
))
2458 trace_recursive_fail();
2463 static inline void trace_recursive_unlock(void)
2465 WARN_ON_ONCE(!trace_recursion_buffer());
2467 trace_recursion_dec();
2472 #define trace_recursive_lock() (0)
2473 #define trace_recursive_unlock() do { } while (0)
2478 * ring_buffer_lock_reserve - reserve a part of the buffer
2479 * @buffer: the ring buffer to reserve from
2480 * @length: the length of the data to reserve (excluding event header)
2482 * Returns a reseverd event on the ring buffer to copy directly to.
2483 * The user of this interface will need to get the body to write into
2484 * and can use the ring_buffer_event_data() interface.
2486 * The length is the length of the data needed, not the event length
2487 * which also includes the event header.
2489 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2490 * If NULL is returned, then nothing has been allocated or locked.
2492 struct ring_buffer_event
*
2493 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2495 struct ring_buffer_per_cpu
*cpu_buffer
;
2496 struct ring_buffer_event
*event
;
2499 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2502 /* If we are tracing schedule, we don't want to recurse */
2503 preempt_disable_notrace();
2505 if (atomic_read(&buffer
->record_disabled
))
2508 if (trace_recursive_lock())
2511 cpu
= raw_smp_processor_id();
2513 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2516 cpu_buffer
= buffer
->buffers
[cpu
];
2518 if (atomic_read(&cpu_buffer
->record_disabled
))
2521 if (length
> BUF_MAX_DATA_SIZE
)
2524 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2531 trace_recursive_unlock();
2534 preempt_enable_notrace();
2537 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2540 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2541 struct ring_buffer_event
*event
)
2546 * The event first in the commit queue updates the
2549 if (rb_event_is_commit(cpu_buffer
, event
)) {
2551 * A commit event that is first on a page
2552 * updates the write timestamp with the page stamp
2554 if (!rb_event_index(event
))
2555 cpu_buffer
->write_stamp
=
2556 cpu_buffer
->commit_page
->page
->time_stamp
;
2557 else if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
2558 delta
= event
->array
[0];
2560 delta
+= event
->time_delta
;
2561 cpu_buffer
->write_stamp
+= delta
;
2563 cpu_buffer
->write_stamp
+= event
->time_delta
;
2567 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2568 struct ring_buffer_event
*event
)
2570 local_inc(&cpu_buffer
->entries
);
2571 rb_update_write_stamp(cpu_buffer
, event
);
2572 rb_end_commit(cpu_buffer
);
2576 * ring_buffer_unlock_commit - commit a reserved
2577 * @buffer: The buffer to commit to
2578 * @event: The event pointer to commit.
2580 * This commits the data to the ring buffer, and releases any locks held.
2582 * Must be paired with ring_buffer_lock_reserve.
2584 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2585 struct ring_buffer_event
*event
)
2587 struct ring_buffer_per_cpu
*cpu_buffer
;
2588 int cpu
= raw_smp_processor_id();
2590 cpu_buffer
= buffer
->buffers
[cpu
];
2592 rb_commit(cpu_buffer
, event
);
2594 trace_recursive_unlock();
2596 preempt_enable_notrace();
2600 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2602 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2604 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
2605 event
= skip_time_extend(event
);
2607 /* array[0] holds the actual length for the discarded event */
2608 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2609 event
->type_len
= RINGBUF_TYPE_PADDING
;
2610 /* time delta must be non zero */
2611 if (!event
->time_delta
)
2612 event
->time_delta
= 1;
2616 * Decrement the entries to the page that an event is on.
2617 * The event does not even need to exist, only the pointer
2618 * to the page it is on. This may only be called before the commit
2622 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2623 struct ring_buffer_event
*event
)
2625 unsigned long addr
= (unsigned long)event
;
2626 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2627 struct buffer_page
*start
;
2631 /* Do the likely case first */
2632 if (likely(bpage
->page
== (void *)addr
)) {
2633 local_dec(&bpage
->entries
);
2638 * Because the commit page may be on the reader page we
2639 * start with the next page and check the end loop there.
2641 rb_inc_page(cpu_buffer
, &bpage
);
2644 if (bpage
->page
== (void *)addr
) {
2645 local_dec(&bpage
->entries
);
2648 rb_inc_page(cpu_buffer
, &bpage
);
2649 } while (bpage
!= start
);
2651 /* commit not part of this buffer?? */
2652 RB_WARN_ON(cpu_buffer
, 1);
2656 * ring_buffer_commit_discard - discard an event that has not been committed
2657 * @buffer: the ring buffer
2658 * @event: non committed event to discard
2660 * Sometimes an event that is in the ring buffer needs to be ignored.
2661 * This function lets the user discard an event in the ring buffer
2662 * and then that event will not be read later.
2664 * This function only works if it is called before the the item has been
2665 * committed. It will try to free the event from the ring buffer
2666 * if another event has not been added behind it.
2668 * If another event has been added behind it, it will set the event
2669 * up as discarded, and perform the commit.
2671 * If this function is called, do not call ring_buffer_unlock_commit on
2674 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2675 struct ring_buffer_event
*event
)
2677 struct ring_buffer_per_cpu
*cpu_buffer
;
2680 /* The event is discarded regardless */
2681 rb_event_discard(event
);
2683 cpu
= smp_processor_id();
2684 cpu_buffer
= buffer
->buffers
[cpu
];
2687 * This must only be called if the event has not been
2688 * committed yet. Thus we can assume that preemption
2689 * is still disabled.
2691 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2693 rb_decrement_entry(cpu_buffer
, event
);
2694 if (rb_try_to_discard(cpu_buffer
, event
))
2698 * The commit is still visible by the reader, so we
2699 * must still update the timestamp.
2701 rb_update_write_stamp(cpu_buffer
, event
);
2703 rb_end_commit(cpu_buffer
);
2705 trace_recursive_unlock();
2707 preempt_enable_notrace();
2710 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2713 * ring_buffer_write - write data to the buffer without reserving
2714 * @buffer: The ring buffer to write to.
2715 * @length: The length of the data being written (excluding the event header)
2716 * @data: The data to write to the buffer.
2718 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2719 * one function. If you already have the data to write to the buffer, it
2720 * may be easier to simply call this function.
2722 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2723 * and not the length of the event which would hold the header.
2725 int ring_buffer_write(struct ring_buffer
*buffer
,
2726 unsigned long length
,
2729 struct ring_buffer_per_cpu
*cpu_buffer
;
2730 struct ring_buffer_event
*event
;
2735 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2738 preempt_disable_notrace();
2740 if (atomic_read(&buffer
->record_disabled
))
2743 cpu
= raw_smp_processor_id();
2745 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2748 cpu_buffer
= buffer
->buffers
[cpu
];
2750 if (atomic_read(&cpu_buffer
->record_disabled
))
2753 if (length
> BUF_MAX_DATA_SIZE
)
2756 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2760 body
= rb_event_data(event
);
2762 memcpy(body
, data
, length
);
2764 rb_commit(cpu_buffer
, event
);
2768 preempt_enable_notrace();
2772 EXPORT_SYMBOL_GPL(ring_buffer_write
);
2774 static int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
2776 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
2777 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
2778 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
2780 /* In case of error, head will be NULL */
2781 if (unlikely(!head
))
2784 return reader
->read
== rb_page_commit(reader
) &&
2785 (commit
== reader
||
2787 head
->read
== rb_page_commit(commit
)));
2791 * ring_buffer_record_disable - stop all writes into the buffer
2792 * @buffer: The ring buffer to stop writes to.
2794 * This prevents all writes to the buffer. Any attempt to write
2795 * to the buffer after this will fail and return NULL.
2797 * The caller should call synchronize_sched() after this.
2799 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
2801 atomic_inc(&buffer
->record_disabled
);
2803 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
2806 * ring_buffer_record_enable - enable writes to the buffer
2807 * @buffer: The ring buffer to enable writes
2809 * Note, multiple disables will need the same number of enables
2810 * to truly enable the writing (much like preempt_disable).
2812 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
2814 atomic_dec(&buffer
->record_disabled
);
2816 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
2819 * ring_buffer_record_off - stop all writes into the buffer
2820 * @buffer: The ring buffer to stop writes to.
2822 * This prevents all writes to the buffer. Any attempt to write
2823 * to the buffer after this will fail and return NULL.
2825 * This is different than ring_buffer_record_disable() as
2826 * it works like an on/off switch, where as the disable() version
2827 * must be paired with a enable().
2829 void ring_buffer_record_off(struct ring_buffer
*buffer
)
2832 unsigned int new_rd
;
2835 rd
= atomic_read(&buffer
->record_disabled
);
2836 new_rd
= rd
| RB_BUFFER_OFF
;
2837 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
2839 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
2842 * ring_buffer_record_on - restart writes into the buffer
2843 * @buffer: The ring buffer to start writes to.
2845 * This enables all writes to the buffer that was disabled by
2846 * ring_buffer_record_off().
2848 * This is different than ring_buffer_record_enable() as
2849 * it works like an on/off switch, where as the enable() version
2850 * must be paired with a disable().
2852 void ring_buffer_record_on(struct ring_buffer
*buffer
)
2855 unsigned int new_rd
;
2858 rd
= atomic_read(&buffer
->record_disabled
);
2859 new_rd
= rd
& ~RB_BUFFER_OFF
;
2860 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
2862 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
2865 * ring_buffer_record_is_on - return true if the ring buffer can write
2866 * @buffer: The ring buffer to see if write is enabled
2868 * Returns true if the ring buffer is in a state that it accepts writes.
2870 int ring_buffer_record_is_on(struct ring_buffer
*buffer
)
2872 return !atomic_read(&buffer
->record_disabled
);
2876 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2877 * @buffer: The ring buffer to stop writes to.
2878 * @cpu: The CPU buffer to stop
2880 * This prevents all writes to the buffer. Any attempt to write
2881 * to the buffer after this will fail and return NULL.
2883 * The caller should call synchronize_sched() after this.
2885 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
2887 struct ring_buffer_per_cpu
*cpu_buffer
;
2889 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2892 cpu_buffer
= buffer
->buffers
[cpu
];
2893 atomic_inc(&cpu_buffer
->record_disabled
);
2895 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
2898 * ring_buffer_record_enable_cpu - enable writes to the buffer
2899 * @buffer: The ring buffer to enable writes
2900 * @cpu: The CPU to enable.
2902 * Note, multiple disables will need the same number of enables
2903 * to truly enable the writing (much like preempt_disable).
2905 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
2907 struct ring_buffer_per_cpu
*cpu_buffer
;
2909 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2912 cpu_buffer
= buffer
->buffers
[cpu
];
2913 atomic_dec(&cpu_buffer
->record_disabled
);
2915 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
2918 * The total entries in the ring buffer is the running counter
2919 * of entries entered into the ring buffer, minus the sum of
2920 * the entries read from the ring buffer and the number of
2921 * entries that were overwritten.
2923 static inline unsigned long
2924 rb_num_of_entries(struct ring_buffer_per_cpu
*cpu_buffer
)
2926 return local_read(&cpu_buffer
->entries
) -
2927 (local_read(&cpu_buffer
->overrun
) + cpu_buffer
->read
);
2931 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
2932 * @buffer: The ring buffer
2933 * @cpu: The per CPU buffer to read from.
2935 u64
ring_buffer_oldest_event_ts(struct ring_buffer
*buffer
, int cpu
)
2937 unsigned long flags
;
2938 struct ring_buffer_per_cpu
*cpu_buffer
;
2939 struct buffer_page
*bpage
;
2942 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2945 cpu_buffer
= buffer
->buffers
[cpu
];
2946 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2948 * if the tail is on reader_page, oldest time stamp is on the reader
2951 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
2952 bpage
= cpu_buffer
->reader_page
;
2954 bpage
= rb_set_head_page(cpu_buffer
);
2955 ret
= bpage
->page
->time_stamp
;
2956 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2960 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts
);
2963 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
2964 * @buffer: The ring buffer
2965 * @cpu: The per CPU buffer to read from.
2967 unsigned long ring_buffer_bytes_cpu(struct ring_buffer
*buffer
, int cpu
)
2969 struct ring_buffer_per_cpu
*cpu_buffer
;
2972 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2975 cpu_buffer
= buffer
->buffers
[cpu
];
2976 ret
= local_read(&cpu_buffer
->entries_bytes
) - cpu_buffer
->read_bytes
;
2980 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu
);
2983 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2984 * @buffer: The ring buffer
2985 * @cpu: The per CPU buffer to get the entries from.
2987 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
2989 struct ring_buffer_per_cpu
*cpu_buffer
;
2991 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2994 cpu_buffer
= buffer
->buffers
[cpu
];
2996 return rb_num_of_entries(cpu_buffer
);
2998 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
3001 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3002 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3003 * @buffer: The ring buffer
3004 * @cpu: The per CPU buffer to get the number of overruns from
3006 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3008 struct ring_buffer_per_cpu
*cpu_buffer
;
3011 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3014 cpu_buffer
= buffer
->buffers
[cpu
];
3015 ret
= local_read(&cpu_buffer
->overrun
);
3019 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
3022 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3023 * commits failing due to the buffer wrapping around while there are uncommitted
3024 * events, such as during an interrupt storm.
3025 * @buffer: The ring buffer
3026 * @cpu: The per CPU buffer to get the number of overruns from
3029 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3031 struct ring_buffer_per_cpu
*cpu_buffer
;
3034 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3037 cpu_buffer
= buffer
->buffers
[cpu
];
3038 ret
= local_read(&cpu_buffer
->commit_overrun
);
3042 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
3045 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3046 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3047 * @buffer: The ring buffer
3048 * @cpu: The per CPU buffer to get the number of overruns from
3051 ring_buffer_dropped_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3053 struct ring_buffer_per_cpu
*cpu_buffer
;
3056 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3059 cpu_buffer
= buffer
->buffers
[cpu
];
3060 ret
= local_read(&cpu_buffer
->dropped_events
);
3064 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu
);
3067 * ring_buffer_entries - get the number of entries in a buffer
3068 * @buffer: The ring buffer
3070 * Returns the total number of entries in the ring buffer
3073 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
3075 struct ring_buffer_per_cpu
*cpu_buffer
;
3076 unsigned long entries
= 0;
3079 /* if you care about this being correct, lock the buffer */
3080 for_each_buffer_cpu(buffer
, cpu
) {
3081 cpu_buffer
= buffer
->buffers
[cpu
];
3082 entries
+= rb_num_of_entries(cpu_buffer
);
3087 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
3090 * ring_buffer_overruns - get the number of overruns in buffer
3091 * @buffer: The ring buffer
3093 * Returns the total number of overruns in the ring buffer
3096 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
3098 struct ring_buffer_per_cpu
*cpu_buffer
;
3099 unsigned long overruns
= 0;
3102 /* if you care about this being correct, lock the buffer */
3103 for_each_buffer_cpu(buffer
, cpu
) {
3104 cpu_buffer
= buffer
->buffers
[cpu
];
3105 overruns
+= local_read(&cpu_buffer
->overrun
);
3110 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
3112 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
3114 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3116 /* Iterator usage is expected to have record disabled */
3117 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
3118 iter
->head_page
= rb_set_head_page(cpu_buffer
);
3119 if (unlikely(!iter
->head_page
))
3121 iter
->head
= iter
->head_page
->read
;
3123 iter
->head_page
= cpu_buffer
->reader_page
;
3124 iter
->head
= cpu_buffer
->reader_page
->read
;
3127 iter
->read_stamp
= cpu_buffer
->read_stamp
;
3129 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
3130 iter
->cache_reader_page
= cpu_buffer
->reader_page
;
3131 iter
->cache_read
= cpu_buffer
->read
;
3135 * ring_buffer_iter_reset - reset an iterator
3136 * @iter: The iterator to reset
3138 * Resets the iterator, so that it will start from the beginning
3141 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
3143 struct ring_buffer_per_cpu
*cpu_buffer
;
3144 unsigned long flags
;
3149 cpu_buffer
= iter
->cpu_buffer
;
3151 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3152 rb_iter_reset(iter
);
3153 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3155 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
3158 * ring_buffer_iter_empty - check if an iterator has no more to read
3159 * @iter: The iterator to check
3161 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
3163 struct ring_buffer_per_cpu
*cpu_buffer
;
3165 cpu_buffer
= iter
->cpu_buffer
;
3167 return iter
->head_page
== cpu_buffer
->commit_page
&&
3168 iter
->head
== rb_commit_index(cpu_buffer
);
3170 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
3173 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
3174 struct ring_buffer_event
*event
)
3178 switch (event
->type_len
) {
3179 case RINGBUF_TYPE_PADDING
:
3182 case RINGBUF_TYPE_TIME_EXTEND
:
3183 delta
= event
->array
[0];
3185 delta
+= event
->time_delta
;
3186 cpu_buffer
->read_stamp
+= delta
;
3189 case RINGBUF_TYPE_TIME_STAMP
:
3190 /* FIXME: not implemented */
3193 case RINGBUF_TYPE_DATA
:
3194 cpu_buffer
->read_stamp
+= event
->time_delta
;
3204 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
3205 struct ring_buffer_event
*event
)
3209 switch (event
->type_len
) {
3210 case RINGBUF_TYPE_PADDING
:
3213 case RINGBUF_TYPE_TIME_EXTEND
:
3214 delta
= event
->array
[0];
3216 delta
+= event
->time_delta
;
3217 iter
->read_stamp
+= delta
;
3220 case RINGBUF_TYPE_TIME_STAMP
:
3221 /* FIXME: not implemented */
3224 case RINGBUF_TYPE_DATA
:
3225 iter
->read_stamp
+= event
->time_delta
;
3234 static struct buffer_page
*
3235 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
3237 struct buffer_page
*reader
= NULL
;
3238 unsigned long overwrite
;
3239 unsigned long flags
;
3243 local_irq_save(flags
);
3244 arch_spin_lock(&cpu_buffer
->lock
);
3248 * This should normally only loop twice. But because the
3249 * start of the reader inserts an empty page, it causes
3250 * a case where we will loop three times. There should be no
3251 * reason to loop four times (that I know of).
3253 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
3258 reader
= cpu_buffer
->reader_page
;
3260 /* If there's more to read, return this page */
3261 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
3264 /* Never should we have an index greater than the size */
3265 if (RB_WARN_ON(cpu_buffer
,
3266 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
3269 /* check if we caught up to the tail */
3271 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
3274 /* Don't bother swapping if the ring buffer is empty */
3275 if (rb_num_of_entries(cpu_buffer
) == 0)
3279 * Reset the reader page to size zero.
3281 local_set(&cpu_buffer
->reader_page
->write
, 0);
3282 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3283 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3284 cpu_buffer
->reader_page
->real_end
= 0;
3288 * Splice the empty reader page into the list around the head.
3290 reader
= rb_set_head_page(cpu_buffer
);
3291 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
3292 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
3295 * cpu_buffer->pages just needs to point to the buffer, it
3296 * has no specific buffer page to point to. Lets move it out
3297 * of our way so we don't accidentally swap it.
3299 cpu_buffer
->pages
= reader
->list
.prev
;
3301 /* The reader page will be pointing to the new head */
3302 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
3305 * We want to make sure we read the overruns after we set up our
3306 * pointers to the next object. The writer side does a
3307 * cmpxchg to cross pages which acts as the mb on the writer
3308 * side. Note, the reader will constantly fail the swap
3309 * while the writer is updating the pointers, so this
3310 * guarantees that the overwrite recorded here is the one we
3311 * want to compare with the last_overrun.
3314 overwrite
= local_read(&(cpu_buffer
->overrun
));
3317 * Here's the tricky part.
3319 * We need to move the pointer past the header page.
3320 * But we can only do that if a writer is not currently
3321 * moving it. The page before the header page has the
3322 * flag bit '1' set if it is pointing to the page we want.
3323 * but if the writer is in the process of moving it
3324 * than it will be '2' or already moved '0'.
3327 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
3330 * If we did not convert it, then we must try again.
3336 * Yeah! We succeeded in replacing the page.
3338 * Now make the new head point back to the reader page.
3340 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
3341 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
3343 /* Finally update the reader page to the new head */
3344 cpu_buffer
->reader_page
= reader
;
3345 rb_reset_reader_page(cpu_buffer
);
3347 if (overwrite
!= cpu_buffer
->last_overrun
) {
3348 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
3349 cpu_buffer
->last_overrun
= overwrite
;
3355 arch_spin_unlock(&cpu_buffer
->lock
);
3356 local_irq_restore(flags
);
3361 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
3363 struct ring_buffer_event
*event
;
3364 struct buffer_page
*reader
;
3367 reader
= rb_get_reader_page(cpu_buffer
);
3369 /* This function should not be called when buffer is empty */
3370 if (RB_WARN_ON(cpu_buffer
, !reader
))
3373 event
= rb_reader_event(cpu_buffer
);
3375 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
3378 rb_update_read_stamp(cpu_buffer
, event
);
3380 length
= rb_event_length(event
);
3381 cpu_buffer
->reader_page
->read
+= length
;
3384 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
3386 struct ring_buffer_per_cpu
*cpu_buffer
;
3387 struct ring_buffer_event
*event
;
3390 cpu_buffer
= iter
->cpu_buffer
;
3393 * Check if we are at the end of the buffer.
3395 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3396 /* discarded commits can make the page empty */
3397 if (iter
->head_page
== cpu_buffer
->commit_page
)
3403 event
= rb_iter_head_event(iter
);
3405 length
= rb_event_length(event
);
3408 * This should not be called to advance the header if we are
3409 * at the tail of the buffer.
3411 if (RB_WARN_ON(cpu_buffer
,
3412 (iter
->head_page
== cpu_buffer
->commit_page
) &&
3413 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
3416 rb_update_iter_read_stamp(iter
, event
);
3418 iter
->head
+= length
;
3420 /* check for end of page padding */
3421 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3422 (iter
->head_page
!= cpu_buffer
->commit_page
))
3423 rb_advance_iter(iter
);
3426 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
3428 return cpu_buffer
->lost_events
;
3431 static struct ring_buffer_event
*
3432 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
3433 unsigned long *lost_events
)
3435 struct ring_buffer_event
*event
;
3436 struct buffer_page
*reader
;
3441 * We repeat when a time extend is encountered.
3442 * Since the time extend is always attached to a data event,
3443 * we should never loop more than once.
3444 * (We never hit the following condition more than twice).
3446 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
3449 reader
= rb_get_reader_page(cpu_buffer
);
3453 event
= rb_reader_event(cpu_buffer
);
3455 switch (event
->type_len
) {
3456 case RINGBUF_TYPE_PADDING
:
3457 if (rb_null_event(event
))
3458 RB_WARN_ON(cpu_buffer
, 1);
3460 * Because the writer could be discarding every
3461 * event it creates (which would probably be bad)
3462 * if we were to go back to "again" then we may never
3463 * catch up, and will trigger the warn on, or lock
3464 * the box. Return the padding, and we will release
3465 * the current locks, and try again.
3469 case RINGBUF_TYPE_TIME_EXTEND
:
3470 /* Internal data, OK to advance */
3471 rb_advance_reader(cpu_buffer
);
3474 case RINGBUF_TYPE_TIME_STAMP
:
3475 /* FIXME: not implemented */
3476 rb_advance_reader(cpu_buffer
);
3479 case RINGBUF_TYPE_DATA
:
3481 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3482 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3483 cpu_buffer
->cpu
, ts
);
3486 *lost_events
= rb_lost_events(cpu_buffer
);
3495 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3497 static struct ring_buffer_event
*
3498 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3500 struct ring_buffer
*buffer
;
3501 struct ring_buffer_per_cpu
*cpu_buffer
;
3502 struct ring_buffer_event
*event
;
3505 cpu_buffer
= iter
->cpu_buffer
;
3506 buffer
= cpu_buffer
->buffer
;
3509 * Check if someone performed a consuming read to
3510 * the buffer. A consuming read invalidates the iterator
3511 * and we need to reset the iterator in this case.
3513 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3514 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3515 rb_iter_reset(iter
);
3518 if (ring_buffer_iter_empty(iter
))
3522 * We repeat when a time extend is encountered.
3523 * Since the time extend is always attached to a data event,
3524 * we should never loop more than once.
3525 * (We never hit the following condition more than twice).
3527 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
3530 if (rb_per_cpu_empty(cpu_buffer
))
3533 if (iter
->head
>= local_read(&iter
->head_page
->page
->commit
)) {
3538 event
= rb_iter_head_event(iter
);
3540 switch (event
->type_len
) {
3541 case RINGBUF_TYPE_PADDING
:
3542 if (rb_null_event(event
)) {
3546 rb_advance_iter(iter
);
3549 case RINGBUF_TYPE_TIME_EXTEND
:
3550 /* Internal data, OK to advance */
3551 rb_advance_iter(iter
);
3554 case RINGBUF_TYPE_TIME_STAMP
:
3555 /* FIXME: not implemented */
3556 rb_advance_iter(iter
);
3559 case RINGBUF_TYPE_DATA
:
3561 *ts
= iter
->read_stamp
+ event
->time_delta
;
3562 ring_buffer_normalize_time_stamp(buffer
,
3563 cpu_buffer
->cpu
, ts
);
3573 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3575 static inline int rb_ok_to_lock(void)
3578 * If an NMI die dumps out the content of the ring buffer
3579 * do not grab locks. We also permanently disable the ring
3580 * buffer too. A one time deal is all you get from reading
3581 * the ring buffer from an NMI.
3583 if (likely(!in_nmi()))
3586 tracing_off_permanent();
3591 * ring_buffer_peek - peek at the next event to be read
3592 * @buffer: The ring buffer to read
3593 * @cpu: The cpu to peak at
3594 * @ts: The timestamp counter of this event.
3595 * @lost_events: a variable to store if events were lost (may be NULL)
3597 * This will return the event that will be read next, but does
3598 * not consume the data.
3600 struct ring_buffer_event
*
3601 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3602 unsigned long *lost_events
)
3604 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3605 struct ring_buffer_event
*event
;
3606 unsigned long flags
;
3609 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3612 dolock
= rb_ok_to_lock();
3614 local_irq_save(flags
);
3616 raw_spin_lock(&cpu_buffer
->reader_lock
);
3617 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3618 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3619 rb_advance_reader(cpu_buffer
);
3621 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3622 local_irq_restore(flags
);
3624 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3631 * ring_buffer_iter_peek - peek at the next event to be read
3632 * @iter: The ring buffer iterator
3633 * @ts: The timestamp counter of this event.
3635 * This will return the event that will be read next, but does
3636 * not increment the iterator.
3638 struct ring_buffer_event
*
3639 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3641 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3642 struct ring_buffer_event
*event
;
3643 unsigned long flags
;
3646 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3647 event
= rb_iter_peek(iter
, ts
);
3648 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3650 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3657 * ring_buffer_consume - return an event and consume it
3658 * @buffer: The ring buffer to get the next event from
3659 * @cpu: the cpu to read the buffer from
3660 * @ts: a variable to store the timestamp (may be NULL)
3661 * @lost_events: a variable to store if events were lost (may be NULL)
3663 * Returns the next event in the ring buffer, and that event is consumed.
3664 * Meaning, that sequential reads will keep returning a different event,
3665 * and eventually empty the ring buffer if the producer is slower.
3667 struct ring_buffer_event
*
3668 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3669 unsigned long *lost_events
)
3671 struct ring_buffer_per_cpu
*cpu_buffer
;
3672 struct ring_buffer_event
*event
= NULL
;
3673 unsigned long flags
;
3676 dolock
= rb_ok_to_lock();
3679 /* might be called in atomic */
3682 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3685 cpu_buffer
= buffer
->buffers
[cpu
];
3686 local_irq_save(flags
);
3688 raw_spin_lock(&cpu_buffer
->reader_lock
);
3690 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3692 cpu_buffer
->lost_events
= 0;
3693 rb_advance_reader(cpu_buffer
);
3697 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3698 local_irq_restore(flags
);
3703 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3708 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
3711 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3712 * @buffer: The ring buffer to read from
3713 * @cpu: The cpu buffer to iterate over
3715 * This performs the initial preparations necessary to iterate
3716 * through the buffer. Memory is allocated, buffer recording
3717 * is disabled, and the iterator pointer is returned to the caller.
3719 * Disabling buffer recordng prevents the reading from being
3720 * corrupted. This is not a consuming read, so a producer is not
3723 * After a sequence of ring_buffer_read_prepare calls, the user is
3724 * expected to make at least one call to ring_buffer_prepare_sync.
3725 * Afterwards, ring_buffer_read_start is invoked to get things going
3728 * This overall must be paired with ring_buffer_finish.
3730 struct ring_buffer_iter
*
3731 ring_buffer_read_prepare(struct ring_buffer
*buffer
, int cpu
)
3733 struct ring_buffer_per_cpu
*cpu_buffer
;
3734 struct ring_buffer_iter
*iter
;
3736 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3739 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
3743 cpu_buffer
= buffer
->buffers
[cpu
];
3745 iter
->cpu_buffer
= cpu_buffer
;
3747 atomic_inc(&buffer
->resize_disabled
);
3748 atomic_inc(&cpu_buffer
->record_disabled
);
3752 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
3755 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
3757 * All previously invoked ring_buffer_read_prepare calls to prepare
3758 * iterators will be synchronized. Afterwards, read_buffer_read_start
3759 * calls on those iterators are allowed.
3762 ring_buffer_read_prepare_sync(void)
3764 synchronize_sched();
3766 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
3769 * ring_buffer_read_start - start a non consuming read of the buffer
3770 * @iter: The iterator returned by ring_buffer_read_prepare
3772 * This finalizes the startup of an iteration through the buffer.
3773 * The iterator comes from a call to ring_buffer_read_prepare and
3774 * an intervening ring_buffer_read_prepare_sync must have been
3777 * Must be paired with ring_buffer_finish.
3780 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
3782 struct ring_buffer_per_cpu
*cpu_buffer
;
3783 unsigned long flags
;
3788 cpu_buffer
= iter
->cpu_buffer
;
3790 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3791 arch_spin_lock(&cpu_buffer
->lock
);
3792 rb_iter_reset(iter
);
3793 arch_spin_unlock(&cpu_buffer
->lock
);
3794 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3796 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
3799 * ring_buffer_finish - finish reading the iterator of the buffer
3800 * @iter: The iterator retrieved by ring_buffer_start
3802 * This re-enables the recording to the buffer, and frees the
3806 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
3808 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3811 * Ring buffer is disabled from recording, here's a good place
3812 * to check the integrity of the ring buffer.
3814 rb_check_pages(cpu_buffer
);
3816 atomic_dec(&cpu_buffer
->record_disabled
);
3817 atomic_dec(&cpu_buffer
->buffer
->resize_disabled
);
3820 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
3823 * ring_buffer_read - read the next item in the ring buffer by the iterator
3824 * @iter: The ring buffer iterator
3825 * @ts: The time stamp of the event read.
3827 * This reads the next event in the ring buffer and increments the iterator.
3829 struct ring_buffer_event
*
3830 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
3832 struct ring_buffer_event
*event
;
3833 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3834 unsigned long flags
;
3836 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3838 event
= rb_iter_peek(iter
, ts
);
3842 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
3845 rb_advance_iter(iter
);
3847 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3851 EXPORT_SYMBOL_GPL(ring_buffer_read
);
3854 * ring_buffer_size - return the size of the ring buffer (in bytes)
3855 * @buffer: The ring buffer.
3857 unsigned long ring_buffer_size(struct ring_buffer
*buffer
, int cpu
)
3860 * Earlier, this method returned
3861 * BUF_PAGE_SIZE * buffer->nr_pages
3862 * Since the nr_pages field is now removed, we have converted this to
3863 * return the per cpu buffer value.
3865 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3868 return BUF_PAGE_SIZE
* buffer
->buffers
[cpu
]->nr_pages
;
3870 EXPORT_SYMBOL_GPL(ring_buffer_size
);
3873 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
3875 rb_head_page_deactivate(cpu_buffer
);
3877 cpu_buffer
->head_page
3878 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
3879 local_set(&cpu_buffer
->head_page
->write
, 0);
3880 local_set(&cpu_buffer
->head_page
->entries
, 0);
3881 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
3883 cpu_buffer
->head_page
->read
= 0;
3885 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
3886 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
3888 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
3889 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
3890 local_set(&cpu_buffer
->reader_page
->write
, 0);
3891 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3892 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3893 cpu_buffer
->reader_page
->read
= 0;
3895 local_set(&cpu_buffer
->entries_bytes
, 0);
3896 local_set(&cpu_buffer
->overrun
, 0);
3897 local_set(&cpu_buffer
->commit_overrun
, 0);
3898 local_set(&cpu_buffer
->dropped_events
, 0);
3899 local_set(&cpu_buffer
->entries
, 0);
3900 local_set(&cpu_buffer
->committing
, 0);
3901 local_set(&cpu_buffer
->commits
, 0);
3902 cpu_buffer
->read
= 0;
3903 cpu_buffer
->read_bytes
= 0;
3905 cpu_buffer
->write_stamp
= 0;
3906 cpu_buffer
->read_stamp
= 0;
3908 cpu_buffer
->lost_events
= 0;
3909 cpu_buffer
->last_overrun
= 0;
3911 rb_head_page_activate(cpu_buffer
);
3915 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3916 * @buffer: The ring buffer to reset a per cpu buffer of
3917 * @cpu: The CPU buffer to be reset
3919 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
3921 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3922 unsigned long flags
;
3924 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3927 atomic_inc(&buffer
->resize_disabled
);
3928 atomic_inc(&cpu_buffer
->record_disabled
);
3930 /* Make sure all commits have finished */
3931 synchronize_sched();
3933 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3935 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
3938 arch_spin_lock(&cpu_buffer
->lock
);
3940 rb_reset_cpu(cpu_buffer
);
3942 arch_spin_unlock(&cpu_buffer
->lock
);
3945 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3947 atomic_dec(&cpu_buffer
->record_disabled
);
3948 atomic_dec(&buffer
->resize_disabled
);
3950 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
3953 * ring_buffer_reset - reset a ring buffer
3954 * @buffer: The ring buffer to reset all cpu buffers
3956 void ring_buffer_reset(struct ring_buffer
*buffer
)
3960 for_each_buffer_cpu(buffer
, cpu
)
3961 ring_buffer_reset_cpu(buffer
, cpu
);
3963 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
3966 * rind_buffer_empty - is the ring buffer empty?
3967 * @buffer: The ring buffer to test
3969 int ring_buffer_empty(struct ring_buffer
*buffer
)
3971 struct ring_buffer_per_cpu
*cpu_buffer
;
3972 unsigned long flags
;
3977 dolock
= rb_ok_to_lock();
3979 /* yes this is racy, but if you don't like the race, lock the buffer */
3980 for_each_buffer_cpu(buffer
, cpu
) {
3981 cpu_buffer
= buffer
->buffers
[cpu
];
3982 local_irq_save(flags
);
3984 raw_spin_lock(&cpu_buffer
->reader_lock
);
3985 ret
= rb_per_cpu_empty(cpu_buffer
);
3987 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3988 local_irq_restore(flags
);
3996 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
3999 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4000 * @buffer: The ring buffer
4001 * @cpu: The CPU buffer to test
4003 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
4005 struct ring_buffer_per_cpu
*cpu_buffer
;
4006 unsigned long flags
;
4010 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4013 dolock
= rb_ok_to_lock();
4015 cpu_buffer
= buffer
->buffers
[cpu
];
4016 local_irq_save(flags
);
4018 raw_spin_lock(&cpu_buffer
->reader_lock
);
4019 ret
= rb_per_cpu_empty(cpu_buffer
);
4021 raw_spin_unlock(&cpu_buffer
->reader_lock
);
4022 local_irq_restore(flags
);
4026 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
4028 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4030 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4031 * @buffer_a: One buffer to swap with
4032 * @buffer_b: The other buffer to swap with
4034 * This function is useful for tracers that want to take a "snapshot"
4035 * of a CPU buffer and has another back up buffer lying around.
4036 * it is expected that the tracer handles the cpu buffer not being
4037 * used at the moment.
4039 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
4040 struct ring_buffer
*buffer_b
, int cpu
)
4042 struct ring_buffer_per_cpu
*cpu_buffer_a
;
4043 struct ring_buffer_per_cpu
*cpu_buffer_b
;
4046 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
4047 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
4050 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
4051 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
4053 /* At least make sure the two buffers are somewhat the same */
4054 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
4059 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
4062 if (atomic_read(&buffer_a
->record_disabled
))
4065 if (atomic_read(&buffer_b
->record_disabled
))
4068 if (atomic_read(&cpu_buffer_a
->record_disabled
))
4071 if (atomic_read(&cpu_buffer_b
->record_disabled
))
4075 * We can't do a synchronize_sched here because this
4076 * function can be called in atomic context.
4077 * Normally this will be called from the same CPU as cpu.
4078 * If not it's up to the caller to protect this.
4080 atomic_inc(&cpu_buffer_a
->record_disabled
);
4081 atomic_inc(&cpu_buffer_b
->record_disabled
);
4084 if (local_read(&cpu_buffer_a
->committing
))
4086 if (local_read(&cpu_buffer_b
->committing
))
4089 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
4090 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
4092 cpu_buffer_b
->buffer
= buffer_a
;
4093 cpu_buffer_a
->buffer
= buffer_b
;
4098 atomic_dec(&cpu_buffer_a
->record_disabled
);
4099 atomic_dec(&cpu_buffer_b
->record_disabled
);
4103 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
4104 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4107 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4108 * @buffer: the buffer to allocate for.
4110 * This function is used in conjunction with ring_buffer_read_page.
4111 * When reading a full page from the ring buffer, these functions
4112 * can be used to speed up the process. The calling function should
4113 * allocate a few pages first with this function. Then when it
4114 * needs to get pages from the ring buffer, it passes the result
4115 * of this function into ring_buffer_read_page, which will swap
4116 * the page that was allocated, with the read page of the buffer.
4119 * The page allocated, or NULL on error.
4121 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
, int cpu
)
4123 struct buffer_data_page
*bpage
;
4126 page
= alloc_pages_node(cpu_to_node(cpu
),
4127 GFP_KERNEL
| __GFP_NORETRY
, 0);
4131 bpage
= page_address(page
);
4133 rb_init_page(bpage
);
4137 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
4140 * ring_buffer_free_read_page - free an allocated read page
4141 * @buffer: the buffer the page was allocate for
4142 * @data: the page to free
4144 * Free a page allocated from ring_buffer_alloc_read_page.
4146 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
4148 free_page((unsigned long)data
);
4150 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
4153 * ring_buffer_read_page - extract a page from the ring buffer
4154 * @buffer: buffer to extract from
4155 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4156 * @len: amount to extract
4157 * @cpu: the cpu of the buffer to extract
4158 * @full: should the extraction only happen when the page is full.
4160 * This function will pull out a page from the ring buffer and consume it.
4161 * @data_page must be the address of the variable that was returned
4162 * from ring_buffer_alloc_read_page. This is because the page might be used
4163 * to swap with a page in the ring buffer.
4166 * rpage = ring_buffer_alloc_read_page(buffer);
4169 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4171 * process_page(rpage, ret);
4173 * When @full is set, the function will not return true unless
4174 * the writer is off the reader page.
4176 * Note: it is up to the calling functions to handle sleeps and wakeups.
4177 * The ring buffer can be used anywhere in the kernel and can not
4178 * blindly call wake_up. The layer that uses the ring buffer must be
4179 * responsible for that.
4182 * >=0 if data has been transferred, returns the offset of consumed data.
4183 * <0 if no data has been transferred.
4185 int ring_buffer_read_page(struct ring_buffer
*buffer
,
4186 void **data_page
, size_t len
, int cpu
, int full
)
4188 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4189 struct ring_buffer_event
*event
;
4190 struct buffer_data_page
*bpage
;
4191 struct buffer_page
*reader
;
4192 unsigned long missed_events
;
4193 unsigned long flags
;
4194 unsigned int commit
;
4199 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4203 * If len is not big enough to hold the page header, then
4204 * we can not copy anything.
4206 if (len
<= BUF_PAGE_HDR_SIZE
)
4209 len
-= BUF_PAGE_HDR_SIZE
;
4218 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4220 reader
= rb_get_reader_page(cpu_buffer
);
4224 event
= rb_reader_event(cpu_buffer
);
4226 read
= reader
->read
;
4227 commit
= rb_page_commit(reader
);
4229 /* Check if any events were dropped */
4230 missed_events
= cpu_buffer
->lost_events
;
4233 * If this page has been partially read or
4234 * if len is not big enough to read the rest of the page or
4235 * a writer is still on the page, then
4236 * we must copy the data from the page to the buffer.
4237 * Otherwise, we can simply swap the page with the one passed in.
4239 if (read
|| (len
< (commit
- read
)) ||
4240 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
4241 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
4242 unsigned int rpos
= read
;
4243 unsigned int pos
= 0;
4249 if (len
> (commit
- read
))
4250 len
= (commit
- read
);
4252 /* Always keep the time extend and data together */
4253 size
= rb_event_ts_length(event
);
4258 /* save the current timestamp, since the user will need it */
4259 save_timestamp
= cpu_buffer
->read_stamp
;
4261 /* Need to copy one event at a time */
4263 /* We need the size of one event, because
4264 * rb_advance_reader only advances by one event,
4265 * whereas rb_event_ts_length may include the size of
4266 * one or two events.
4267 * We have already ensured there's enough space if this
4268 * is a time extend. */
4269 size
= rb_event_length(event
);
4270 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
4274 rb_advance_reader(cpu_buffer
);
4275 rpos
= reader
->read
;
4281 event
= rb_reader_event(cpu_buffer
);
4282 /* Always keep the time extend and data together */
4283 size
= rb_event_ts_length(event
);
4284 } while (len
>= size
);
4287 local_set(&bpage
->commit
, pos
);
4288 bpage
->time_stamp
= save_timestamp
;
4290 /* we copied everything to the beginning */
4293 /* update the entry counter */
4294 cpu_buffer
->read
+= rb_page_entries(reader
);
4295 cpu_buffer
->read_bytes
+= BUF_PAGE_SIZE
;
4297 /* swap the pages */
4298 rb_init_page(bpage
);
4299 bpage
= reader
->page
;
4300 reader
->page
= *data_page
;
4301 local_set(&reader
->write
, 0);
4302 local_set(&reader
->entries
, 0);
4307 * Use the real_end for the data size,
4308 * This gives us a chance to store the lost events
4311 if (reader
->real_end
)
4312 local_set(&bpage
->commit
, reader
->real_end
);
4316 cpu_buffer
->lost_events
= 0;
4318 commit
= local_read(&bpage
->commit
);
4320 * Set a flag in the commit field if we lost events
4322 if (missed_events
) {
4323 /* If there is room at the end of the page to save the
4324 * missed events, then record it there.
4326 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
4327 memcpy(&bpage
->data
[commit
], &missed_events
,
4328 sizeof(missed_events
));
4329 local_add(RB_MISSED_STORED
, &bpage
->commit
);
4330 commit
+= sizeof(missed_events
);
4332 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
4336 * This page may be off to user land. Zero it out here.
4338 if (commit
< BUF_PAGE_SIZE
)
4339 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
4342 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4347 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
4349 #ifdef CONFIG_HOTPLUG_CPU
4350 static int rb_cpu_notify(struct notifier_block
*self
,
4351 unsigned long action
, void *hcpu
)
4353 struct ring_buffer
*buffer
=
4354 container_of(self
, struct ring_buffer
, cpu_notify
);
4355 long cpu
= (long)hcpu
;
4356 int cpu_i
, nr_pages_same
;
4357 unsigned int nr_pages
;
4360 case CPU_UP_PREPARE
:
4361 case CPU_UP_PREPARE_FROZEN
:
4362 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
4367 /* check if all cpu sizes are same */
4368 for_each_buffer_cpu(buffer
, cpu_i
) {
4369 /* fill in the size from first enabled cpu */
4371 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
4372 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
4377 /* allocate minimum pages, user can later expand it */
4380 buffer
->buffers
[cpu
] =
4381 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
4382 if (!buffer
->buffers
[cpu
]) {
4383 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4388 cpumask_set_cpu(cpu
, buffer
->cpumask
);
4390 case CPU_DOWN_PREPARE
:
4391 case CPU_DOWN_PREPARE_FROZEN
:
4394 * If we were to free the buffer, then the user would
4395 * lose any trace that was in the buffer.