1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
7 #include <linux/trace_events.h>
8 #include <linux/ring_buffer.h>
9 #include <linux/trace_clock.h>
10 #include <linux/sched/clock.h>
11 #include <linux/trace_seq.h>
12 #include <linux/spinlock.h>
13 #include <linux/irq_work.h>
14 #include <linux/security.h>
15 #include <linux/uaccess.h>
16 #include <linux/hardirq.h>
17 #include <linux/kthread.h> /* for self test */
18 #include <linux/module.h>
19 #include <linux/percpu.h>
20 #include <linux/mutex.h>
21 #include <linux/delay.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/list.h>
26 #include <linux/cpu.h>
27 #include <linux/oom.h>
29 #include <asm/local.h>
31 static void update_pages_handler(struct work_struct
*work
);
34 * The ring buffer header is special. We must manually up keep it.
36 int ring_buffer_print_entry_header(struct trace_seq
*s
)
38 trace_seq_puts(s
, "# compressed entry header\n");
39 trace_seq_puts(s
, "\ttype_len : 5 bits\n");
40 trace_seq_puts(s
, "\ttime_delta : 27 bits\n");
41 trace_seq_puts(s
, "\tarray : 32 bits\n");
42 trace_seq_putc(s
, '\n');
43 trace_seq_printf(s
, "\tpadding : type == %d\n",
44 RINGBUF_TYPE_PADDING
);
45 trace_seq_printf(s
, "\ttime_extend : type == %d\n",
46 RINGBUF_TYPE_TIME_EXTEND
);
47 trace_seq_printf(s
, "\ttime_stamp : type == %d\n",
48 RINGBUF_TYPE_TIME_STAMP
);
49 trace_seq_printf(s
, "\tdata max type_len == %d\n",
50 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
52 return !trace_seq_has_overflowed(s
);
56 * The ring buffer is made up of a list of pages. A separate list of pages is
57 * allocated for each CPU. A writer may only write to a buffer that is
58 * associated with the CPU it is currently executing on. A reader may read
59 * from any per cpu buffer.
61 * The reader is special. For each per cpu buffer, the reader has its own
62 * reader page. When a reader has read the entire reader page, this reader
63 * page is swapped with another page in the ring buffer.
65 * Now, as long as the writer is off the reader page, the reader can do what
66 * ever it wants with that page. The writer will never write to that page
67 * again (as long as it is out of the ring buffer).
69 * Here's some silly ASCII art.
72 * |reader| RING BUFFER
74 * +------+ +---+ +---+ +---+
83 * |reader| RING BUFFER
84 * |page |------------------v
85 * +------+ +---+ +---+ +---+
94 * |reader| RING BUFFER
95 * |page |------------------v
96 * +------+ +---+ +---+ +---+
101 * +------------------------------+
105 * |buffer| RING BUFFER
106 * |page |------------------v
107 * +------+ +---+ +---+ +---+
109 * | New +---+ +---+ +---+
112 * +------------------------------+
115 * After we make this swap, the reader can hand this page off to the splice
116 * code and be done with it. It can even allocate a new page if it needs to
117 * and swap that into the ring buffer.
119 * We will be using cmpxchg soon to make all this lockless.
123 /* Used for individual buffers (after the counter) */
124 #define RB_BUFFER_OFF (1 << 20)
126 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
128 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
129 #define RB_ALIGNMENT 4U
130 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
131 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
132 #define RB_ALIGN_DATA __aligned(RB_ALIGNMENT)
134 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
135 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
138 RB_LEN_TIME_EXTEND
= 8,
139 RB_LEN_TIME_STAMP
= 8,
142 #define skip_time_extend(event) \
143 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
145 #define extended_time(event) \
146 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
148 static inline int rb_null_event(struct ring_buffer_event
*event
)
150 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
153 static void rb_event_set_padding(struct ring_buffer_event
*event
)
155 /* padding has a NULL time_delta */
156 event
->type_len
= RINGBUF_TYPE_PADDING
;
157 event
->time_delta
= 0;
161 rb_event_data_length(struct ring_buffer_event
*event
)
166 length
= event
->type_len
* RB_ALIGNMENT
;
168 length
= event
->array
[0];
169 return length
+ RB_EVNT_HDR_SIZE
;
173 * Return the length of the given event. Will return
174 * the length of the time extend if the event is a
177 static inline unsigned
178 rb_event_length(struct ring_buffer_event
*event
)
180 switch (event
->type_len
) {
181 case RINGBUF_TYPE_PADDING
:
182 if (rb_null_event(event
))
185 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
187 case RINGBUF_TYPE_TIME_EXTEND
:
188 return RB_LEN_TIME_EXTEND
;
190 case RINGBUF_TYPE_TIME_STAMP
:
191 return RB_LEN_TIME_STAMP
;
193 case RINGBUF_TYPE_DATA
:
194 return rb_event_data_length(event
);
203 * Return total length of time extend and data,
204 * or just the event length for all other events.
206 static inline unsigned
207 rb_event_ts_length(struct ring_buffer_event
*event
)
211 if (extended_time(event
)) {
212 /* time extends include the data event after it */
213 len
= RB_LEN_TIME_EXTEND
;
214 event
= skip_time_extend(event
);
216 return len
+ rb_event_length(event
);
220 * ring_buffer_event_length - return the length of the event
221 * @event: the event to get the length of
223 * Returns the size of the data load of a data event.
224 * If the event is something other than a data event, it
225 * returns the size of the event itself. With the exception
226 * of a TIME EXTEND, where it still returns the size of the
227 * data load of the data event after it.
229 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
233 if (extended_time(event
))
234 event
= skip_time_extend(event
);
236 length
= rb_event_length(event
);
237 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
239 length
-= RB_EVNT_HDR_SIZE
;
240 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
241 length
-= sizeof(event
->array
[0]);
244 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
246 /* inline for ring buffer fast paths */
247 static __always_inline
void *
248 rb_event_data(struct ring_buffer_event
*event
)
250 if (extended_time(event
))
251 event
= skip_time_extend(event
);
252 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
253 /* If length is in len field, then array[0] has the data */
255 return (void *)&event
->array
[0];
256 /* Otherwise length is in array[0] and array[1] has the data */
257 return (void *)&event
->array
[1];
261 * ring_buffer_event_data - return the data of the event
262 * @event: the event to get the data from
264 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
266 return rb_event_data(event
);
268 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
270 #define for_each_buffer_cpu(buffer, cpu) \
271 for_each_cpu(cpu, buffer->cpumask)
274 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
275 #define TS_DELTA_TEST (~TS_MASK)
278 * ring_buffer_event_time_stamp - return the event's extended timestamp
279 * @event: the event to get the timestamp of
281 * Returns the extended timestamp associated with a data event.
282 * An extended time_stamp is a 64-bit timestamp represented
283 * internally in a special way that makes the best use of space
284 * contained within a ring buffer event. This function decodes
285 * it and maps it to a straight u64 value.
287 u64
ring_buffer_event_time_stamp(struct ring_buffer_event
*event
)
291 ts
= event
->array
[0];
293 ts
+= event
->time_delta
;
298 /* Flag when events were overwritten */
299 #define RB_MISSED_EVENTS (1 << 31)
300 /* Missed count stored at end */
301 #define RB_MISSED_STORED (1 << 30)
303 #define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED)
305 struct buffer_data_page
{
306 u64 time_stamp
; /* page time stamp */
307 local_t commit
; /* write committed index */
308 unsigned char data
[] RB_ALIGN_DATA
; /* data of buffer page */
312 * Note, the buffer_page list must be first. The buffer pages
313 * are allocated in cache lines, which means that each buffer
314 * page will be at the beginning of a cache line, and thus
315 * the least significant bits will be zero. We use this to
316 * add flags in the list struct pointers, to make the ring buffer
320 struct list_head list
; /* list of buffer pages */
321 local_t write
; /* index for next write */
322 unsigned read
; /* index for next read */
323 local_t entries
; /* entries on this page */
324 unsigned long real_end
; /* real end of data */
325 struct buffer_data_page
*page
; /* Actual data page */
329 * The buffer page counters, write and entries, must be reset
330 * atomically when crossing page boundaries. To synchronize this
331 * update, two counters are inserted into the number. One is
332 * the actual counter for the write position or count on the page.
334 * The other is a counter of updaters. Before an update happens
335 * the update partition of the counter is incremented. This will
336 * allow the updater to update the counter atomically.
338 * The counter is 20 bits, and the state data is 12.
340 #define RB_WRITE_MASK 0xfffff
341 #define RB_WRITE_INTCNT (1 << 20)
343 static void rb_init_page(struct buffer_data_page
*bpage
)
345 local_set(&bpage
->commit
, 0);
349 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
352 static void free_buffer_page(struct buffer_page
*bpage
)
354 free_page((unsigned long)bpage
->page
);
359 * We need to fit the time_stamp delta into 27 bits.
361 static inline int test_time_stamp(u64 delta
)
363 if (delta
& TS_DELTA_TEST
)
368 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
370 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
371 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
373 int ring_buffer_print_page_header(struct trace_seq
*s
)
375 struct buffer_data_page field
;
377 trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
378 "offset:0;\tsize:%u;\tsigned:%u;\n",
379 (unsigned int)sizeof(field
.time_stamp
),
380 (unsigned int)is_signed_type(u64
));
382 trace_seq_printf(s
, "\tfield: local_t commit;\t"
383 "offset:%u;\tsize:%u;\tsigned:%u;\n",
384 (unsigned int)offsetof(typeof(field
), commit
),
385 (unsigned int)sizeof(field
.commit
),
386 (unsigned int)is_signed_type(long));
388 trace_seq_printf(s
, "\tfield: int overwrite;\t"
389 "offset:%u;\tsize:%u;\tsigned:%u;\n",
390 (unsigned int)offsetof(typeof(field
), commit
),
392 (unsigned int)is_signed_type(long));
394 trace_seq_printf(s
, "\tfield: char data;\t"
395 "offset:%u;\tsize:%u;\tsigned:%u;\n",
396 (unsigned int)offsetof(typeof(field
), data
),
397 (unsigned int)BUF_PAGE_SIZE
,
398 (unsigned int)is_signed_type(char));
400 return !trace_seq_has_overflowed(s
);
404 struct irq_work work
;
405 wait_queue_head_t waiters
;
406 wait_queue_head_t full_waiters
;
407 bool waiters_pending
;
408 bool full_waiters_pending
;
413 * Structure to hold event state and handle nested events.
415 struct rb_event_info
{
418 unsigned long length
;
419 struct buffer_page
*tail_page
;
424 * Used for which event context the event is in.
430 * See trace_recursive_lock() comment below for more details.
441 * head_page == tail_page && head == tail then buffer is empty.
443 struct ring_buffer_per_cpu
{
445 atomic_t record_disabled
;
446 struct ring_buffer
*buffer
;
447 raw_spinlock_t reader_lock
; /* serialize readers */
448 arch_spinlock_t lock
;
449 struct lock_class_key lock_key
;
450 struct buffer_data_page
*free_page
;
451 unsigned long nr_pages
;
452 unsigned int current_context
;
453 struct list_head
*pages
;
454 struct buffer_page
*head_page
; /* read from head */
455 struct buffer_page
*tail_page
; /* write to tail */
456 struct buffer_page
*commit_page
; /* committed pages */
457 struct buffer_page
*reader_page
;
458 unsigned long lost_events
;
459 unsigned long last_overrun
;
461 local_t entries_bytes
;
464 local_t commit_overrun
;
465 local_t dropped_events
;
468 local_t pages_touched
;
470 long last_pages_touch
;
471 size_t shortest_full
;
473 unsigned long read_bytes
;
476 /* ring buffer pages to update, > 0 to add, < 0 to remove */
477 long nr_pages_to_update
;
478 struct list_head new_pages
; /* new pages to add */
479 struct work_struct update_pages_work
;
480 struct completion update_done
;
482 struct rb_irq_work irq_work
;
488 atomic_t record_disabled
;
489 atomic_t resize_disabled
;
490 cpumask_var_t cpumask
;
492 struct lock_class_key
*reader_lock_key
;
496 struct ring_buffer_per_cpu
**buffers
;
498 struct hlist_node node
;
501 struct rb_irq_work irq_work
;
505 struct ring_buffer_iter
{
506 struct ring_buffer_per_cpu
*cpu_buffer
;
508 struct buffer_page
*head_page
;
509 struct buffer_page
*cache_reader_page
;
510 unsigned long cache_read
;
515 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
516 * @buffer: The ring_buffer to get the number of pages from
517 * @cpu: The cpu of the ring_buffer to get the number of pages from
519 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
521 size_t ring_buffer_nr_pages(struct ring_buffer
*buffer
, int cpu
)
523 return buffer
->buffers
[cpu
]->nr_pages
;
527 * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
528 * @buffer: The ring_buffer to get the number of pages from
529 * @cpu: The cpu of the ring_buffer to get the number of pages from
531 * Returns the number of pages that have content in the ring buffer.
533 size_t ring_buffer_nr_dirty_pages(struct ring_buffer
*buffer
, int cpu
)
538 read
= local_read(&buffer
->buffers
[cpu
]->pages_read
);
539 cnt
= local_read(&buffer
->buffers
[cpu
]->pages_touched
);
540 /* The reader can read an empty page, but not more than that */
542 WARN_ON_ONCE(read
> cnt
+ 1);
550 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
552 * Schedules a delayed work to wake up any task that is blocked on the
553 * ring buffer waiters queue.
555 static void rb_wake_up_waiters(struct irq_work
*work
)
557 struct rb_irq_work
*rbwork
= container_of(work
, struct rb_irq_work
, work
);
559 wake_up_all(&rbwork
->waiters
);
560 if (rbwork
->wakeup_full
) {
561 rbwork
->wakeup_full
= false;
562 wake_up_all(&rbwork
->full_waiters
);
567 * ring_buffer_wait - wait for input to the ring buffer
568 * @buffer: buffer to wait on
569 * @cpu: the cpu buffer to wait on
570 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
572 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
573 * as data is added to any of the @buffer's cpu buffers. Otherwise
574 * it will wait for data to be added to a specific cpu buffer.
576 int ring_buffer_wait(struct ring_buffer
*buffer
, int cpu
, int full
)
578 struct ring_buffer_per_cpu
*uninitialized_var(cpu_buffer
);
580 struct rb_irq_work
*work
;
584 * Depending on what the caller is waiting for, either any
585 * data in any cpu buffer, or a specific buffer, put the
586 * caller on the appropriate wait queue.
588 if (cpu
== RING_BUFFER_ALL_CPUS
) {
589 work
= &buffer
->irq_work
;
590 /* Full only makes sense on per cpu reads */
593 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
595 cpu_buffer
= buffer
->buffers
[cpu
];
596 work
= &cpu_buffer
->irq_work
;
602 prepare_to_wait(&work
->full_waiters
, &wait
, TASK_INTERRUPTIBLE
);
604 prepare_to_wait(&work
->waiters
, &wait
, TASK_INTERRUPTIBLE
);
607 * The events can happen in critical sections where
608 * checking a work queue can cause deadlocks.
609 * After adding a task to the queue, this flag is set
610 * only to notify events to try to wake up the queue
613 * We don't clear it even if the buffer is no longer
614 * empty. The flag only causes the next event to run
615 * irq_work to do the work queue wake up. The worse
616 * that can happen if we race with !trace_empty() is that
617 * an event will cause an irq_work to try to wake up
620 * There's no reason to protect this flag either, as
621 * the work queue and irq_work logic will do the necessary
622 * synchronization for the wake ups. The only thing
623 * that is necessary is that the wake up happens after
624 * a task has been queued. It's OK for spurious wake ups.
627 work
->full_waiters_pending
= true;
629 work
->waiters_pending
= true;
631 if (signal_pending(current
)) {
636 if (cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
))
639 if (cpu
!= RING_BUFFER_ALL_CPUS
&&
640 !ring_buffer_empty_cpu(buffer
, cpu
)) {
649 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
650 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
651 nr_pages
= cpu_buffer
->nr_pages
;
652 dirty
= ring_buffer_nr_dirty_pages(buffer
, cpu
);
653 if (!cpu_buffer
->shortest_full
||
654 cpu_buffer
->shortest_full
< full
)
655 cpu_buffer
->shortest_full
= full
;
656 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
658 (!nr_pages
|| (dirty
* 100) > full
* nr_pages
))
666 finish_wait(&work
->full_waiters
, &wait
);
668 finish_wait(&work
->waiters
, &wait
);
674 * ring_buffer_poll_wait - poll on buffer input
675 * @buffer: buffer to wait on
676 * @cpu: the cpu buffer to wait on
677 * @filp: the file descriptor
678 * @poll_table: The poll descriptor
680 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
681 * as data is added to any of the @buffer's cpu buffers. Otherwise
682 * it will wait for data to be added to a specific cpu buffer.
684 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
687 __poll_t
ring_buffer_poll_wait(struct ring_buffer
*buffer
, int cpu
,
688 struct file
*filp
, poll_table
*poll_table
)
690 struct ring_buffer_per_cpu
*cpu_buffer
;
691 struct rb_irq_work
*work
;
693 if (cpu
== RING_BUFFER_ALL_CPUS
)
694 work
= &buffer
->irq_work
;
696 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
699 cpu_buffer
= buffer
->buffers
[cpu
];
700 work
= &cpu_buffer
->irq_work
;
703 poll_wait(filp
, &work
->waiters
, poll_table
);
704 work
->waiters_pending
= true;
706 * There's a tight race between setting the waiters_pending and
707 * checking if the ring buffer is empty. Once the waiters_pending bit
708 * is set, the next event will wake the task up, but we can get stuck
709 * if there's only a single event in.
711 * FIXME: Ideally, we need a memory barrier on the writer side as well,
712 * but adding a memory barrier to all events will cause too much of a
713 * performance hit in the fast path. We only need a memory barrier when
714 * the buffer goes from empty to having content. But as this race is
715 * extremely small, and it's not a problem if another event comes in, we
720 if ((cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
)) ||
721 (cpu
!= RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty_cpu(buffer
, cpu
)))
722 return EPOLLIN
| EPOLLRDNORM
;
726 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
727 #define RB_WARN_ON(b, cond) \
729 int _____ret = unlikely(cond); \
731 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
732 struct ring_buffer_per_cpu *__b = \
734 atomic_inc(&__b->buffer->record_disabled); \
736 atomic_inc(&b->record_disabled); \
742 /* Up this if you want to test the TIME_EXTENTS and normalization */
743 #define DEBUG_SHIFT 0
745 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
747 /* shift to debug/test normalization and TIME_EXTENTS */
748 return buffer
->clock() << DEBUG_SHIFT
;
751 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
755 preempt_disable_notrace();
756 time
= rb_time_stamp(buffer
);
757 preempt_enable_notrace();
761 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
763 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
766 /* Just stupid testing the normalize function and deltas */
769 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
772 * Making the ring buffer lockless makes things tricky.
773 * Although writes only happen on the CPU that they are on,
774 * and they only need to worry about interrupts. Reads can
777 * The reader page is always off the ring buffer, but when the
778 * reader finishes with a page, it needs to swap its page with
779 * a new one from the buffer. The reader needs to take from
780 * the head (writes go to the tail). But if a writer is in overwrite
781 * mode and wraps, it must push the head page forward.
783 * Here lies the problem.
785 * The reader must be careful to replace only the head page, and
786 * not another one. As described at the top of the file in the
787 * ASCII art, the reader sets its old page to point to the next
788 * page after head. It then sets the page after head to point to
789 * the old reader page. But if the writer moves the head page
790 * during this operation, the reader could end up with the tail.
792 * We use cmpxchg to help prevent this race. We also do something
793 * special with the page before head. We set the LSB to 1.
795 * When the writer must push the page forward, it will clear the
796 * bit that points to the head page, move the head, and then set
797 * the bit that points to the new head page.
799 * We also don't want an interrupt coming in and moving the head
800 * page on another writer. Thus we use the second LSB to catch
803 * head->list->prev->next bit 1 bit 0
806 * Points to head page 0 1
809 * Note we can not trust the prev pointer of the head page, because:
811 * +----+ +-----+ +-----+
812 * | |------>| T |---X--->| N |
814 * +----+ +-----+ +-----+
817 * +----------| R |----------+ |
821 * Key: ---X--> HEAD flag set in pointer
826 * (see __rb_reserve_next() to see where this happens)
828 * What the above shows is that the reader just swapped out
829 * the reader page with a page in the buffer, but before it
830 * could make the new header point back to the new page added
831 * it was preempted by a writer. The writer moved forward onto
832 * the new page added by the reader and is about to move forward
835 * You can see, it is legitimate for the previous pointer of
836 * the head (or any page) not to point back to itself. But only
840 #define RB_PAGE_NORMAL 0UL
841 #define RB_PAGE_HEAD 1UL
842 #define RB_PAGE_UPDATE 2UL
845 #define RB_FLAG_MASK 3UL
847 /* PAGE_MOVED is not part of the mask */
848 #define RB_PAGE_MOVED 4UL
851 * rb_list_head - remove any bit
853 static struct list_head
*rb_list_head(struct list_head
*list
)
855 unsigned long val
= (unsigned long)list
;
857 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
861 * rb_is_head_page - test if the given page is the head page
863 * Because the reader may move the head_page pointer, we can
864 * not trust what the head page is (it may be pointing to
865 * the reader page). But if the next page is a header page,
866 * its flags will be non zero.
869 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
870 struct buffer_page
*page
, struct list_head
*list
)
874 val
= (unsigned long)list
->next
;
876 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
877 return RB_PAGE_MOVED
;
879 return val
& RB_FLAG_MASK
;
885 * The unique thing about the reader page, is that, if the
886 * writer is ever on it, the previous pointer never points
887 * back to the reader page.
889 static bool rb_is_reader_page(struct buffer_page
*page
)
891 struct list_head
*list
= page
->list
.prev
;
893 return rb_list_head(list
->next
) != &page
->list
;
897 * rb_set_list_to_head - set a list_head to be pointing to head.
899 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
900 struct list_head
*list
)
904 ptr
= (unsigned long *)&list
->next
;
905 *ptr
|= RB_PAGE_HEAD
;
906 *ptr
&= ~RB_PAGE_UPDATE
;
910 * rb_head_page_activate - sets up head page
912 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
914 struct buffer_page
*head
;
916 head
= cpu_buffer
->head_page
;
921 * Set the previous list pointer to have the HEAD flag.
923 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
926 static void rb_list_head_clear(struct list_head
*list
)
928 unsigned long *ptr
= (unsigned long *)&list
->next
;
930 *ptr
&= ~RB_FLAG_MASK
;
934 * rb_head_page_deactivate - clears head page ptr (for free list)
937 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
939 struct list_head
*hd
;
941 /* Go through the whole list and clear any pointers found. */
942 rb_list_head_clear(cpu_buffer
->pages
);
944 list_for_each(hd
, cpu_buffer
->pages
)
945 rb_list_head_clear(hd
);
948 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
949 struct buffer_page
*head
,
950 struct buffer_page
*prev
,
951 int old_flag
, int new_flag
)
953 struct list_head
*list
;
954 unsigned long val
= (unsigned long)&head
->list
;
959 val
&= ~RB_FLAG_MASK
;
961 ret
= cmpxchg((unsigned long *)&list
->next
,
962 val
| old_flag
, val
| new_flag
);
964 /* check if the reader took the page */
965 if ((ret
& ~RB_FLAG_MASK
) != val
)
966 return RB_PAGE_MOVED
;
968 return ret
& RB_FLAG_MASK
;
971 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
972 struct buffer_page
*head
,
973 struct buffer_page
*prev
,
976 return rb_head_page_set(cpu_buffer
, head
, prev
,
977 old_flag
, RB_PAGE_UPDATE
);
980 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
981 struct buffer_page
*head
,
982 struct buffer_page
*prev
,
985 return rb_head_page_set(cpu_buffer
, head
, prev
,
986 old_flag
, RB_PAGE_HEAD
);
989 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
990 struct buffer_page
*head
,
991 struct buffer_page
*prev
,
994 return rb_head_page_set(cpu_buffer
, head
, prev
,
995 old_flag
, RB_PAGE_NORMAL
);
998 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
999 struct buffer_page
**bpage
)
1001 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
1003 *bpage
= list_entry(p
, struct buffer_page
, list
);
1006 static struct buffer_page
*
1007 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1009 struct buffer_page
*head
;
1010 struct buffer_page
*page
;
1011 struct list_head
*list
;
1014 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
1018 list
= cpu_buffer
->pages
;
1019 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
1022 page
= head
= cpu_buffer
->head_page
;
1024 * It is possible that the writer moves the header behind
1025 * where we started, and we miss in one loop.
1026 * A second loop should grab the header, but we'll do
1027 * three loops just because I'm paranoid.
1029 for (i
= 0; i
< 3; i
++) {
1031 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
1032 cpu_buffer
->head_page
= page
;
1035 rb_inc_page(cpu_buffer
, &page
);
1036 } while (page
!= head
);
1039 RB_WARN_ON(cpu_buffer
, 1);
1044 static int rb_head_page_replace(struct buffer_page
*old
,
1045 struct buffer_page
*new)
1047 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
1051 val
= *ptr
& ~RB_FLAG_MASK
;
1052 val
|= RB_PAGE_HEAD
;
1054 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
1060 * rb_tail_page_update - move the tail page forward
1062 static void rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1063 struct buffer_page
*tail_page
,
1064 struct buffer_page
*next_page
)
1066 unsigned long old_entries
;
1067 unsigned long old_write
;
1070 * The tail page now needs to be moved forward.
1072 * We need to reset the tail page, but without messing
1073 * with possible erasing of data brought in by interrupts
1074 * that have moved the tail page and are currently on it.
1076 * We add a counter to the write field to denote this.
1078 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
1079 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
1081 local_inc(&cpu_buffer
->pages_touched
);
1083 * Just make sure we have seen our old_write and synchronize
1084 * with any interrupts that come in.
1089 * If the tail page is still the same as what we think
1090 * it is, then it is up to us to update the tail
1093 if (tail_page
== READ_ONCE(cpu_buffer
->tail_page
)) {
1094 /* Zero the write counter */
1095 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
1096 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
1099 * This will only succeed if an interrupt did
1100 * not come in and change it. In which case, we
1101 * do not want to modify it.
1103 * We add (void) to let the compiler know that we do not care
1104 * about the return value of these functions. We use the
1105 * cmpxchg to only update if an interrupt did not already
1106 * do it for us. If the cmpxchg fails, we don't care.
1108 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
1109 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
1112 * No need to worry about races with clearing out the commit.
1113 * it only can increment when a commit takes place. But that
1114 * only happens in the outer most nested commit.
1116 local_set(&next_page
->page
->commit
, 0);
1118 /* Again, either we update tail_page or an interrupt does */
1119 (void)cmpxchg(&cpu_buffer
->tail_page
, tail_page
, next_page
);
1123 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
1124 struct buffer_page
*bpage
)
1126 unsigned long val
= (unsigned long)bpage
;
1128 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
1135 * rb_check_list - make sure a pointer to a list has the last bits zero
1137 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
1138 struct list_head
*list
)
1140 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
1142 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
1148 * rb_check_pages - integrity check of buffer pages
1149 * @cpu_buffer: CPU buffer with pages to test
1151 * As a safety measure we check to make sure the data pages have not
1154 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1156 struct list_head
*head
= cpu_buffer
->pages
;
1157 struct buffer_page
*bpage
, *tmp
;
1159 /* Reset the head page if it exists */
1160 if (cpu_buffer
->head_page
)
1161 rb_set_head_page(cpu_buffer
);
1163 rb_head_page_deactivate(cpu_buffer
);
1165 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
1167 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
1170 if (rb_check_list(cpu_buffer
, head
))
1173 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1174 if (RB_WARN_ON(cpu_buffer
,
1175 bpage
->list
.next
->prev
!= &bpage
->list
))
1177 if (RB_WARN_ON(cpu_buffer
,
1178 bpage
->list
.prev
->next
!= &bpage
->list
))
1180 if (rb_check_list(cpu_buffer
, &bpage
->list
))
1184 rb_head_page_activate(cpu_buffer
);
1189 static int __rb_allocate_pages(long nr_pages
, struct list_head
*pages
, int cpu
)
1191 struct buffer_page
*bpage
, *tmp
;
1192 bool user_thread
= current
->mm
!= NULL
;
1197 * Check if the available memory is there first.
1198 * Note, si_mem_available() only gives us a rough estimate of available
1199 * memory. It may not be accurate. But we don't care, we just want
1200 * to prevent doing any allocation when it is obvious that it is
1201 * not going to succeed.
1203 i
= si_mem_available();
1208 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1209 * gracefully without invoking oom-killer and the system is not
1212 mflags
= GFP_KERNEL
| __GFP_RETRY_MAYFAIL
;
1215 * If a user thread allocates too much, and si_mem_available()
1216 * reports there's enough memory, even though there is not.
1217 * Make sure the OOM killer kills this thread. This can happen
1218 * even with RETRY_MAYFAIL because another task may be doing
1219 * an allocation after this task has taken all memory.
1220 * This is the task the OOM killer needs to take out during this
1221 * loop, even if it was triggered by an allocation somewhere else.
1224 set_current_oom_origin();
1225 for (i
= 0; i
< nr_pages
; i
++) {
1228 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1229 mflags
, cpu_to_node(cpu
));
1233 list_add(&bpage
->list
, pages
);
1235 page
= alloc_pages_node(cpu_to_node(cpu
), mflags
, 0);
1238 bpage
->page
= page_address(page
);
1239 rb_init_page(bpage
->page
);
1241 if (user_thread
&& fatal_signal_pending(current
))
1245 clear_current_oom_origin();
1250 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1251 list_del_init(&bpage
->list
);
1252 free_buffer_page(bpage
);
1255 clear_current_oom_origin();
1260 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1261 unsigned long nr_pages
)
1267 if (__rb_allocate_pages(nr_pages
, &pages
, cpu_buffer
->cpu
))
1271 * The ring buffer page list is a circular list that does not
1272 * start and end with a list head. All page list items point to
1275 cpu_buffer
->pages
= pages
.next
;
1278 cpu_buffer
->nr_pages
= nr_pages
;
1280 rb_check_pages(cpu_buffer
);
1285 static struct ring_buffer_per_cpu
*
1286 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, long nr_pages
, int cpu
)
1288 struct ring_buffer_per_cpu
*cpu_buffer
;
1289 struct buffer_page
*bpage
;
1293 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1294 GFP_KERNEL
, cpu_to_node(cpu
));
1298 cpu_buffer
->cpu
= cpu
;
1299 cpu_buffer
->buffer
= buffer
;
1300 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1301 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1302 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1303 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1304 init_completion(&cpu_buffer
->update_done
);
1305 init_irq_work(&cpu_buffer
->irq_work
.work
, rb_wake_up_waiters
);
1306 init_waitqueue_head(&cpu_buffer
->irq_work
.waiters
);
1307 init_waitqueue_head(&cpu_buffer
->irq_work
.full_waiters
);
1309 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1310 GFP_KERNEL
, cpu_to_node(cpu
));
1312 goto fail_free_buffer
;
1314 rb_check_bpage(cpu_buffer
, bpage
);
1316 cpu_buffer
->reader_page
= bpage
;
1317 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, 0);
1319 goto fail_free_reader
;
1320 bpage
->page
= page_address(page
);
1321 rb_init_page(bpage
->page
);
1323 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1324 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1326 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1328 goto fail_free_reader
;
1330 cpu_buffer
->head_page
1331 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1332 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1334 rb_head_page_activate(cpu_buffer
);
1339 free_buffer_page(cpu_buffer
->reader_page
);
1346 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1348 struct list_head
*head
= cpu_buffer
->pages
;
1349 struct buffer_page
*bpage
, *tmp
;
1351 free_buffer_page(cpu_buffer
->reader_page
);
1353 rb_head_page_deactivate(cpu_buffer
);
1356 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1357 list_del_init(&bpage
->list
);
1358 free_buffer_page(bpage
);
1360 bpage
= list_entry(head
, struct buffer_page
, list
);
1361 free_buffer_page(bpage
);
1368 * __ring_buffer_alloc - allocate a new ring_buffer
1369 * @size: the size in bytes per cpu that is needed.
1370 * @flags: attributes to set for the ring buffer.
1372 * Currently the only flag that is available is the RB_FL_OVERWRITE
1373 * flag. This flag means that the buffer will overwrite old data
1374 * when the buffer wraps. If this flag is not set, the buffer will
1375 * drop data when the tail hits the head.
1377 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1378 struct lock_class_key
*key
)
1380 struct ring_buffer
*buffer
;
1386 /* keep it in its own cache line */
1387 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1392 if (!zalloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1393 goto fail_free_buffer
;
1395 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1396 buffer
->flags
= flags
;
1397 buffer
->clock
= trace_clock_local
;
1398 buffer
->reader_lock_key
= key
;
1400 init_irq_work(&buffer
->irq_work
.work
, rb_wake_up_waiters
);
1401 init_waitqueue_head(&buffer
->irq_work
.waiters
);
1403 /* need at least two pages */
1407 buffer
->cpus
= nr_cpu_ids
;
1409 bsize
= sizeof(void *) * nr_cpu_ids
;
1410 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1412 if (!buffer
->buffers
)
1413 goto fail_free_cpumask
;
1415 cpu
= raw_smp_processor_id();
1416 cpumask_set_cpu(cpu
, buffer
->cpumask
);
1417 buffer
->buffers
[cpu
] = rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1418 if (!buffer
->buffers
[cpu
])
1419 goto fail_free_buffers
;
1421 ret
= cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1423 goto fail_free_buffers
;
1425 mutex_init(&buffer
->mutex
);
1430 for_each_buffer_cpu(buffer
, cpu
) {
1431 if (buffer
->buffers
[cpu
])
1432 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1434 kfree(buffer
->buffers
);
1437 free_cpumask_var(buffer
->cpumask
);
1443 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1446 * ring_buffer_free - free a ring buffer.
1447 * @buffer: the buffer to free.
1450 ring_buffer_free(struct ring_buffer
*buffer
)
1454 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1456 for_each_buffer_cpu(buffer
, cpu
)
1457 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1459 kfree(buffer
->buffers
);
1460 free_cpumask_var(buffer
->cpumask
);
1464 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1466 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1469 buffer
->clock
= clock
;
1472 void ring_buffer_set_time_stamp_abs(struct ring_buffer
*buffer
, bool abs
)
1474 buffer
->time_stamp_abs
= abs
;
1477 bool ring_buffer_time_stamp_abs(struct ring_buffer
*buffer
)
1479 return buffer
->time_stamp_abs
;
1482 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1484 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1486 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1489 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1491 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1495 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned long nr_pages
)
1497 struct list_head
*tail_page
, *to_remove
, *next_page
;
1498 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1499 struct buffer_page
*last_page
, *first_page
;
1500 unsigned long nr_removed
;
1501 unsigned long head_bit
;
1506 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1507 atomic_inc(&cpu_buffer
->record_disabled
);
1509 * We don't race with the readers since we have acquired the reader
1510 * lock. We also don't race with writers after disabling recording.
1511 * This makes it easy to figure out the first and the last page to be
1512 * removed from the list. We unlink all the pages in between including
1513 * the first and last pages. This is done in a busy loop so that we
1514 * lose the least number of traces.
1515 * The pages are freed after we restart recording and unlock readers.
1517 tail_page
= &cpu_buffer
->tail_page
->list
;
1520 * tail page might be on reader page, we remove the next page
1521 * from the ring buffer
1523 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1524 tail_page
= rb_list_head(tail_page
->next
);
1525 to_remove
= tail_page
;
1527 /* start of pages to remove */
1528 first_page
= list_entry(rb_list_head(to_remove
->next
),
1529 struct buffer_page
, list
);
1531 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1532 to_remove
= rb_list_head(to_remove
)->next
;
1533 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1536 next_page
= rb_list_head(to_remove
)->next
;
1539 * Now we remove all pages between tail_page and next_page.
1540 * Make sure that we have head_bit value preserved for the
1543 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1545 next_page
= rb_list_head(next_page
);
1546 next_page
->prev
= tail_page
;
1548 /* make sure pages points to a valid page in the ring buffer */
1549 cpu_buffer
->pages
= next_page
;
1551 /* update head page */
1553 cpu_buffer
->head_page
= list_entry(next_page
,
1554 struct buffer_page
, list
);
1557 * change read pointer to make sure any read iterators reset
1560 cpu_buffer
->read
= 0;
1562 /* pages are removed, resume tracing and then free the pages */
1563 atomic_dec(&cpu_buffer
->record_disabled
);
1564 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1566 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1568 /* last buffer page to remove */
1569 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1571 tmp_iter_page
= first_page
;
1576 to_remove_page
= tmp_iter_page
;
1577 rb_inc_page(cpu_buffer
, &tmp_iter_page
);
1579 /* update the counters */
1580 page_entries
= rb_page_entries(to_remove_page
);
1583 * If something was added to this page, it was full
1584 * since it is not the tail page. So we deduct the
1585 * bytes consumed in ring buffer from here.
1586 * Increment overrun to account for the lost events.
1588 local_add(page_entries
, &cpu_buffer
->overrun
);
1589 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1593 * We have already removed references to this list item, just
1594 * free up the buffer_page and its page
1596 free_buffer_page(to_remove_page
);
1599 } while (to_remove_page
!= last_page
);
1601 RB_WARN_ON(cpu_buffer
, nr_removed
);
1603 return nr_removed
== 0;
1607 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1609 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1610 int retries
, success
;
1612 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1614 * We are holding the reader lock, so the reader page won't be swapped
1615 * in the ring buffer. Now we are racing with the writer trying to
1616 * move head page and the tail page.
1617 * We are going to adapt the reader page update process where:
1618 * 1. We first splice the start and end of list of new pages between
1619 * the head page and its previous page.
1620 * 2. We cmpxchg the prev_page->next to point from head page to the
1621 * start of new pages list.
1622 * 3. Finally, we update the head->prev to the end of new list.
1624 * We will try this process 10 times, to make sure that we don't keep
1630 struct list_head
*head_page
, *prev_page
, *r
;
1631 struct list_head
*last_page
, *first_page
;
1632 struct list_head
*head_page_with_bit
;
1634 head_page
= &rb_set_head_page(cpu_buffer
)->list
;
1637 prev_page
= head_page
->prev
;
1639 first_page
= pages
->next
;
1640 last_page
= pages
->prev
;
1642 head_page_with_bit
= (struct list_head
*)
1643 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1645 last_page
->next
= head_page_with_bit
;
1646 first_page
->prev
= prev_page
;
1648 r
= cmpxchg(&prev_page
->next
, head_page_with_bit
, first_page
);
1650 if (r
== head_page_with_bit
) {
1652 * yay, we replaced the page pointer to our new list,
1653 * now, we just have to update to head page's prev
1654 * pointer to point to end of list
1656 head_page
->prev
= last_page
;
1663 INIT_LIST_HEAD(pages
);
1665 * If we weren't successful in adding in new pages, warn and stop
1668 RB_WARN_ON(cpu_buffer
, !success
);
1669 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1671 /* free pages if they weren't inserted */
1673 struct buffer_page
*bpage
, *tmp
;
1674 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1676 list_del_init(&bpage
->list
);
1677 free_buffer_page(bpage
);
1683 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1687 if (cpu_buffer
->nr_pages_to_update
> 0)
1688 success
= rb_insert_pages(cpu_buffer
);
1690 success
= rb_remove_pages(cpu_buffer
,
1691 -cpu_buffer
->nr_pages_to_update
);
1694 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1697 static void update_pages_handler(struct work_struct
*work
)
1699 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1700 struct ring_buffer_per_cpu
, update_pages_work
);
1701 rb_update_pages(cpu_buffer
);
1702 complete(&cpu_buffer
->update_done
);
1706 * ring_buffer_resize - resize the ring buffer
1707 * @buffer: the buffer to resize.
1708 * @size: the new size.
1709 * @cpu_id: the cpu buffer to resize
1711 * Minimum size is 2 * BUF_PAGE_SIZE.
1713 * Returns 0 on success and < 0 on failure.
1715 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
,
1718 struct ring_buffer_per_cpu
*cpu_buffer
;
1719 unsigned long nr_pages
;
1723 * Always succeed at resizing a non-existent buffer:
1728 /* Make sure the requested buffer exists */
1729 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1730 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1733 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1735 /* we need a minimum of two pages */
1739 size
= nr_pages
* BUF_PAGE_SIZE
;
1742 * Don't succeed if resizing is disabled, as a reader might be
1743 * manipulating the ring buffer and is expecting a sane state while
1746 if (atomic_read(&buffer
->resize_disabled
))
1749 /* prevent another thread from changing buffer sizes */
1750 mutex_lock(&buffer
->mutex
);
1752 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
1753 /* calculate the pages to update */
1754 for_each_buffer_cpu(buffer
, cpu
) {
1755 cpu_buffer
= buffer
->buffers
[cpu
];
1757 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1758 cpu_buffer
->nr_pages
;
1760 * nothing more to do for removing pages or no update
1762 if (cpu_buffer
->nr_pages_to_update
<= 0)
1765 * to add pages, make sure all new pages can be
1766 * allocated without receiving ENOMEM
1768 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1769 if (__rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1770 &cpu_buffer
->new_pages
, cpu
)) {
1771 /* not enough memory for new pages */
1779 * Fire off all the required work handlers
1780 * We can't schedule on offline CPUs, but it's not necessary
1781 * since we can change their buffer sizes without any race.
1783 for_each_buffer_cpu(buffer
, cpu
) {
1784 cpu_buffer
= buffer
->buffers
[cpu
];
1785 if (!cpu_buffer
->nr_pages_to_update
)
1788 /* Can't run something on an offline CPU. */
1789 if (!cpu_online(cpu
)) {
1790 rb_update_pages(cpu_buffer
);
1791 cpu_buffer
->nr_pages_to_update
= 0;
1793 schedule_work_on(cpu
,
1794 &cpu_buffer
->update_pages_work
);
1798 /* wait for all the updates to complete */
1799 for_each_buffer_cpu(buffer
, cpu
) {
1800 cpu_buffer
= buffer
->buffers
[cpu
];
1801 if (!cpu_buffer
->nr_pages_to_update
)
1804 if (cpu_online(cpu
))
1805 wait_for_completion(&cpu_buffer
->update_done
);
1806 cpu_buffer
->nr_pages_to_update
= 0;
1811 /* Make sure this CPU has been initialized */
1812 if (!cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1815 cpu_buffer
= buffer
->buffers
[cpu_id
];
1817 if (nr_pages
== cpu_buffer
->nr_pages
)
1820 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1821 cpu_buffer
->nr_pages
;
1823 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1824 if (cpu_buffer
->nr_pages_to_update
> 0 &&
1825 __rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1826 &cpu_buffer
->new_pages
, cpu_id
)) {
1833 /* Can't run something on an offline CPU. */
1834 if (!cpu_online(cpu_id
))
1835 rb_update_pages(cpu_buffer
);
1837 schedule_work_on(cpu_id
,
1838 &cpu_buffer
->update_pages_work
);
1839 wait_for_completion(&cpu_buffer
->update_done
);
1842 cpu_buffer
->nr_pages_to_update
= 0;
1848 * The ring buffer resize can happen with the ring buffer
1849 * enabled, so that the update disturbs the tracing as little
1850 * as possible. But if the buffer is disabled, we do not need
1851 * to worry about that, and we can take the time to verify
1852 * that the buffer is not corrupt.
1854 if (atomic_read(&buffer
->record_disabled
)) {
1855 atomic_inc(&buffer
->record_disabled
);
1857 * Even though the buffer was disabled, we must make sure
1858 * that it is truly disabled before calling rb_check_pages.
1859 * There could have been a race between checking
1860 * record_disable and incrementing it.
1863 for_each_buffer_cpu(buffer
, cpu
) {
1864 cpu_buffer
= buffer
->buffers
[cpu
];
1865 rb_check_pages(cpu_buffer
);
1867 atomic_dec(&buffer
->record_disabled
);
1870 mutex_unlock(&buffer
->mutex
);
1874 for_each_buffer_cpu(buffer
, cpu
) {
1875 struct buffer_page
*bpage
, *tmp
;
1877 cpu_buffer
= buffer
->buffers
[cpu
];
1878 cpu_buffer
->nr_pages_to_update
= 0;
1880 if (list_empty(&cpu_buffer
->new_pages
))
1883 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1885 list_del_init(&bpage
->list
);
1886 free_buffer_page(bpage
);
1889 mutex_unlock(&buffer
->mutex
);
1892 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1894 void ring_buffer_change_overwrite(struct ring_buffer
*buffer
, int val
)
1896 mutex_lock(&buffer
->mutex
);
1898 buffer
->flags
|= RB_FL_OVERWRITE
;
1900 buffer
->flags
&= ~RB_FL_OVERWRITE
;
1901 mutex_unlock(&buffer
->mutex
);
1903 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
1905 static __always_inline
void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1907 return bpage
->page
->data
+ index
;
1910 static __always_inline
struct ring_buffer_event
*
1911 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1913 return __rb_page_index(cpu_buffer
->reader_page
,
1914 cpu_buffer
->reader_page
->read
);
1917 static __always_inline
struct ring_buffer_event
*
1918 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1920 return __rb_page_index(iter
->head_page
, iter
->head
);
1923 static __always_inline
unsigned rb_page_commit(struct buffer_page
*bpage
)
1925 return local_read(&bpage
->page
->commit
);
1928 /* Size is determined by what has been committed */
1929 static __always_inline
unsigned rb_page_size(struct buffer_page
*bpage
)
1931 return rb_page_commit(bpage
);
1934 static __always_inline
unsigned
1935 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1937 return rb_page_commit(cpu_buffer
->commit_page
);
1940 static __always_inline
unsigned
1941 rb_event_index(struct ring_buffer_event
*event
)
1943 unsigned long addr
= (unsigned long)event
;
1945 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1948 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1950 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1953 * The iterator could be on the reader page (it starts there).
1954 * But the head could have moved, since the reader was
1955 * found. Check for this case and assign the iterator
1956 * to the head page instead of next.
1958 if (iter
->head_page
== cpu_buffer
->reader_page
)
1959 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1961 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1963 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1968 * rb_handle_head_page - writer hit the head page
1970 * Returns: +1 to retry page
1975 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1976 struct buffer_page
*tail_page
,
1977 struct buffer_page
*next_page
)
1979 struct buffer_page
*new_head
;
1984 entries
= rb_page_entries(next_page
);
1987 * The hard part is here. We need to move the head
1988 * forward, and protect against both readers on
1989 * other CPUs and writers coming in via interrupts.
1991 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1995 * type can be one of four:
1996 * NORMAL - an interrupt already moved it for us
1997 * HEAD - we are the first to get here.
1998 * UPDATE - we are the interrupt interrupting
2000 * MOVED - a reader on another CPU moved the next
2001 * pointer to its reader page. Give up
2008 * We changed the head to UPDATE, thus
2009 * it is our responsibility to update
2012 local_add(entries
, &cpu_buffer
->overrun
);
2013 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
2016 * The entries will be zeroed out when we move the
2020 /* still more to do */
2023 case RB_PAGE_UPDATE
:
2025 * This is an interrupt that interrupt the
2026 * previous update. Still more to do.
2029 case RB_PAGE_NORMAL
:
2031 * An interrupt came in before the update
2032 * and processed this for us.
2033 * Nothing left to do.
2038 * The reader is on another CPU and just did
2039 * a swap with our next_page.
2044 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
2049 * Now that we are here, the old head pointer is
2050 * set to UPDATE. This will keep the reader from
2051 * swapping the head page with the reader page.
2052 * The reader (on another CPU) will spin till
2055 * We just need to protect against interrupts
2056 * doing the job. We will set the next pointer
2057 * to HEAD. After that, we set the old pointer
2058 * to NORMAL, but only if it was HEAD before.
2059 * otherwise we are an interrupt, and only
2060 * want the outer most commit to reset it.
2062 new_head
= next_page
;
2063 rb_inc_page(cpu_buffer
, &new_head
);
2065 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
2069 * Valid returns are:
2070 * HEAD - an interrupt came in and already set it.
2071 * NORMAL - One of two things:
2072 * 1) We really set it.
2073 * 2) A bunch of interrupts came in and moved
2074 * the page forward again.
2078 case RB_PAGE_NORMAL
:
2082 RB_WARN_ON(cpu_buffer
, 1);
2087 * It is possible that an interrupt came in,
2088 * set the head up, then more interrupts came in
2089 * and moved it again. When we get back here,
2090 * the page would have been set to NORMAL but we
2091 * just set it back to HEAD.
2093 * How do you detect this? Well, if that happened
2094 * the tail page would have moved.
2096 if (ret
== RB_PAGE_NORMAL
) {
2097 struct buffer_page
*buffer_tail_page
;
2099 buffer_tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2101 * If the tail had moved passed next, then we need
2102 * to reset the pointer.
2104 if (buffer_tail_page
!= tail_page
&&
2105 buffer_tail_page
!= next_page
)
2106 rb_head_page_set_normal(cpu_buffer
, new_head
,
2112 * If this was the outer most commit (the one that
2113 * changed the original pointer from HEAD to UPDATE),
2114 * then it is up to us to reset it to NORMAL.
2116 if (type
== RB_PAGE_HEAD
) {
2117 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2120 if (RB_WARN_ON(cpu_buffer
,
2121 ret
!= RB_PAGE_UPDATE
))
2129 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2130 unsigned long tail
, struct rb_event_info
*info
)
2132 struct buffer_page
*tail_page
= info
->tail_page
;
2133 struct ring_buffer_event
*event
;
2134 unsigned long length
= info
->length
;
2137 * Only the event that crossed the page boundary
2138 * must fill the old tail_page with padding.
2140 if (tail
>= BUF_PAGE_SIZE
) {
2142 * If the page was filled, then we still need
2143 * to update the real_end. Reset it to zero
2144 * and the reader will ignore it.
2146 if (tail
== BUF_PAGE_SIZE
)
2147 tail_page
->real_end
= 0;
2149 local_sub(length
, &tail_page
->write
);
2153 event
= __rb_page_index(tail_page
, tail
);
2155 /* account for padding bytes */
2156 local_add(BUF_PAGE_SIZE
- tail
, &cpu_buffer
->entries_bytes
);
2159 * Save the original length to the meta data.
2160 * This will be used by the reader to add lost event
2163 tail_page
->real_end
= tail
;
2166 * If this event is bigger than the minimum size, then
2167 * we need to be careful that we don't subtract the
2168 * write counter enough to allow another writer to slip
2170 * We put in a discarded commit instead, to make sure
2171 * that this space is not used again.
2173 * If we are less than the minimum size, we don't need to
2176 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
2177 /* No room for any events */
2179 /* Mark the rest of the page with padding */
2180 rb_event_set_padding(event
);
2182 /* Set the write back to the previous setting */
2183 local_sub(length
, &tail_page
->write
);
2187 /* Put in a discarded event */
2188 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
2189 event
->type_len
= RINGBUF_TYPE_PADDING
;
2190 /* time delta must be non zero */
2191 event
->time_delta
= 1;
2193 /* Set write to end of buffer */
2194 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
2195 local_sub(length
, &tail_page
->write
);
2198 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
);
2201 * This is the slow path, force gcc not to inline it.
2203 static noinline
struct ring_buffer_event
*
2204 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2205 unsigned long tail
, struct rb_event_info
*info
)
2207 struct buffer_page
*tail_page
= info
->tail_page
;
2208 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2209 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
2210 struct buffer_page
*next_page
;
2213 next_page
= tail_page
;
2215 rb_inc_page(cpu_buffer
, &next_page
);
2218 * If for some reason, we had an interrupt storm that made
2219 * it all the way around the buffer, bail, and warn
2222 if (unlikely(next_page
== commit_page
)) {
2223 local_inc(&cpu_buffer
->commit_overrun
);
2228 * This is where the fun begins!
2230 * We are fighting against races between a reader that
2231 * could be on another CPU trying to swap its reader
2232 * page with the buffer head.
2234 * We are also fighting against interrupts coming in and
2235 * moving the head or tail on us as well.
2237 * If the next page is the head page then we have filled
2238 * the buffer, unless the commit page is still on the
2241 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
2244 * If the commit is not on the reader page, then
2245 * move the header page.
2247 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2249 * If we are not in overwrite mode,
2250 * this is easy, just stop here.
2252 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2253 local_inc(&cpu_buffer
->dropped_events
);
2257 ret
= rb_handle_head_page(cpu_buffer
,
2266 * We need to be careful here too. The
2267 * commit page could still be on the reader
2268 * page. We could have a small buffer, and
2269 * have filled up the buffer with events
2270 * from interrupts and such, and wrapped.
2272 * Note, if the tail page is also the on the
2273 * reader_page, we let it move out.
2275 if (unlikely((cpu_buffer
->commit_page
!=
2276 cpu_buffer
->tail_page
) &&
2277 (cpu_buffer
->commit_page
==
2278 cpu_buffer
->reader_page
))) {
2279 local_inc(&cpu_buffer
->commit_overrun
);
2285 rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2289 rb_reset_tail(cpu_buffer
, tail
, info
);
2291 /* Commit what we have for now. */
2292 rb_end_commit(cpu_buffer
);
2293 /* rb_end_commit() decs committing */
2294 local_inc(&cpu_buffer
->committing
);
2296 /* fail and let the caller try again */
2297 return ERR_PTR(-EAGAIN
);
2301 rb_reset_tail(cpu_buffer
, tail
, info
);
2306 /* Slow path, do not inline */
2307 static noinline
struct ring_buffer_event
*
2308 rb_add_time_stamp(struct ring_buffer_event
*event
, u64 delta
, bool abs
)
2311 event
->type_len
= RINGBUF_TYPE_TIME_STAMP
;
2313 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
2315 /* Not the first event on the page, or not delta? */
2316 if (abs
|| rb_event_index(event
)) {
2317 event
->time_delta
= delta
& TS_MASK
;
2318 event
->array
[0] = delta
>> TS_SHIFT
;
2320 /* nope, just zero it */
2321 event
->time_delta
= 0;
2322 event
->array
[0] = 0;
2325 return skip_time_extend(event
);
2328 static inline bool rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2329 struct ring_buffer_event
*event
);
2332 * rb_update_event - update event type and data
2333 * @event: the event to update
2334 * @type: the type of event
2335 * @length: the size of the event field in the ring buffer
2337 * Update the type and data fields of the event. The length
2338 * is the actual size that is written to the ring buffer,
2339 * and with this, we can determine what to place into the
2343 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2344 struct ring_buffer_event
*event
,
2345 struct rb_event_info
*info
)
2347 unsigned length
= info
->length
;
2348 u64 delta
= info
->delta
;
2350 /* Only a commit updates the timestamp */
2351 if (unlikely(!rb_event_is_commit(cpu_buffer
, event
)))
2355 * If we need to add a timestamp, then we
2356 * add it to the start of the reserved space.
2358 if (unlikely(info
->add_timestamp
)) {
2359 bool abs
= ring_buffer_time_stamp_abs(cpu_buffer
->buffer
);
2361 event
= rb_add_time_stamp(event
, info
->delta
, abs
);
2362 length
-= RB_LEN_TIME_EXTEND
;
2366 event
->time_delta
= delta
;
2367 length
-= RB_EVNT_HDR_SIZE
;
2368 if (length
> RB_MAX_SMALL_DATA
) {
2369 event
->type_len
= 0;
2370 event
->array
[0] = length
;
2372 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
2375 static unsigned rb_calculate_event_length(unsigned length
)
2377 struct ring_buffer_event event
; /* Used only for sizeof array */
2379 /* zero length can cause confusions */
2383 if (length
> RB_MAX_SMALL_DATA
)
2384 length
+= sizeof(event
.array
[0]);
2386 length
+= RB_EVNT_HDR_SIZE
;
2387 length
= ALIGN(length
, RB_ALIGNMENT
);
2390 * In case the time delta is larger than the 27 bits for it
2391 * in the header, we need to add a timestamp. If another
2392 * event comes in when trying to discard this one to increase
2393 * the length, then the timestamp will be added in the allocated
2394 * space of this event. If length is bigger than the size needed
2395 * for the TIME_EXTEND, then padding has to be used. The events
2396 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2397 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2398 * As length is a multiple of 4, we only need to worry if it
2399 * is 12 (RB_LEN_TIME_EXTEND + 4).
2401 if (length
== RB_LEN_TIME_EXTEND
+ RB_ALIGNMENT
)
2402 length
+= RB_ALIGNMENT
;
2407 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2408 static inline bool sched_clock_stable(void)
2415 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2416 struct ring_buffer_event
*event
)
2418 unsigned long new_index
, old_index
;
2419 struct buffer_page
*bpage
;
2420 unsigned long index
;
2423 new_index
= rb_event_index(event
);
2424 old_index
= new_index
+ rb_event_ts_length(event
);
2425 addr
= (unsigned long)event
;
2428 bpage
= READ_ONCE(cpu_buffer
->tail_page
);
2430 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2431 unsigned long write_mask
=
2432 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2433 unsigned long event_length
= rb_event_length(event
);
2435 * This is on the tail page. It is possible that
2436 * a write could come in and move the tail page
2437 * and write to the next page. That is fine
2438 * because we just shorten what is on this page.
2440 old_index
+= write_mask
;
2441 new_index
+= write_mask
;
2442 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2443 if (index
== old_index
) {
2444 /* update counters */
2445 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2450 /* could not discard */
2454 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2456 local_inc(&cpu_buffer
->committing
);
2457 local_inc(&cpu_buffer
->commits
);
2460 static __always_inline
void
2461 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
2463 unsigned long max_count
;
2466 * We only race with interrupts and NMIs on this CPU.
2467 * If we own the commit event, then we can commit
2468 * all others that interrupted us, since the interruptions
2469 * are in stack format (they finish before they come
2470 * back to us). This allows us to do a simple loop to
2471 * assign the commit to the tail.
2474 max_count
= cpu_buffer
->nr_pages
* 100;
2476 while (cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)) {
2477 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
2479 if (RB_WARN_ON(cpu_buffer
,
2480 rb_is_reader_page(cpu_buffer
->tail_page
)))
2482 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2483 rb_page_write(cpu_buffer
->commit_page
));
2484 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
2485 /* Only update the write stamp if the page has an event */
2486 if (rb_page_write(cpu_buffer
->commit_page
))
2487 cpu_buffer
->write_stamp
=
2488 cpu_buffer
->commit_page
->page
->time_stamp
;
2489 /* add barrier to keep gcc from optimizing too much */
2492 while (rb_commit_index(cpu_buffer
) !=
2493 rb_page_write(cpu_buffer
->commit_page
)) {
2495 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2496 rb_page_write(cpu_buffer
->commit_page
));
2497 RB_WARN_ON(cpu_buffer
,
2498 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
2503 /* again, keep gcc from optimizing */
2507 * If an interrupt came in just after the first while loop
2508 * and pushed the tail page forward, we will be left with
2509 * a dangling commit that will never go forward.
2511 if (unlikely(cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)))
2515 static __always_inline
void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2517 unsigned long commits
;
2519 if (RB_WARN_ON(cpu_buffer
,
2520 !local_read(&cpu_buffer
->committing
)))
2524 commits
= local_read(&cpu_buffer
->commits
);
2525 /* synchronize with interrupts */
2527 if (local_read(&cpu_buffer
->committing
) == 1)
2528 rb_set_commit_to_write(cpu_buffer
);
2530 local_dec(&cpu_buffer
->committing
);
2532 /* synchronize with interrupts */
2536 * Need to account for interrupts coming in between the
2537 * updating of the commit page and the clearing of the
2538 * committing counter.
2540 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2541 !local_read(&cpu_buffer
->committing
)) {
2542 local_inc(&cpu_buffer
->committing
);
2547 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2549 if (extended_time(event
))
2550 event
= skip_time_extend(event
);
2552 /* array[0] holds the actual length for the discarded event */
2553 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2554 event
->type_len
= RINGBUF_TYPE_PADDING
;
2555 /* time delta must be non zero */
2556 if (!event
->time_delta
)
2557 event
->time_delta
= 1;
2560 static __always_inline
bool
2561 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2562 struct ring_buffer_event
*event
)
2564 unsigned long addr
= (unsigned long)event
;
2565 unsigned long index
;
2567 index
= rb_event_index(event
);
2570 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
2571 rb_commit_index(cpu_buffer
) == index
;
2574 static __always_inline
void
2575 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2576 struct ring_buffer_event
*event
)
2581 * The event first in the commit queue updates the
2584 if (rb_event_is_commit(cpu_buffer
, event
)) {
2586 * A commit event that is first on a page
2587 * updates the write timestamp with the page stamp
2589 if (!rb_event_index(event
))
2590 cpu_buffer
->write_stamp
=
2591 cpu_buffer
->commit_page
->page
->time_stamp
;
2592 else if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
2593 delta
= ring_buffer_event_time_stamp(event
);
2594 cpu_buffer
->write_stamp
+= delta
;
2595 } else if (event
->type_len
== RINGBUF_TYPE_TIME_STAMP
) {
2596 delta
= ring_buffer_event_time_stamp(event
);
2597 cpu_buffer
->write_stamp
= delta
;
2599 cpu_buffer
->write_stamp
+= event
->time_delta
;
2603 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2604 struct ring_buffer_event
*event
)
2606 local_inc(&cpu_buffer
->entries
);
2607 rb_update_write_stamp(cpu_buffer
, event
);
2608 rb_end_commit(cpu_buffer
);
2611 static __always_inline
void
2612 rb_wakeups(struct ring_buffer
*buffer
, struct ring_buffer_per_cpu
*cpu_buffer
)
2618 if (buffer
->irq_work
.waiters_pending
) {
2619 buffer
->irq_work
.waiters_pending
= false;
2620 /* irq_work_queue() supplies it's own memory barriers */
2621 irq_work_queue(&buffer
->irq_work
.work
);
2624 if (cpu_buffer
->irq_work
.waiters_pending
) {
2625 cpu_buffer
->irq_work
.waiters_pending
= false;
2626 /* irq_work_queue() supplies it's own memory barriers */
2627 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2630 if (cpu_buffer
->last_pages_touch
== local_read(&cpu_buffer
->pages_touched
))
2633 if (cpu_buffer
->reader_page
== cpu_buffer
->commit_page
)
2636 if (!cpu_buffer
->irq_work
.full_waiters_pending
)
2639 cpu_buffer
->last_pages_touch
= local_read(&cpu_buffer
->pages_touched
);
2641 full
= cpu_buffer
->shortest_full
;
2642 nr_pages
= cpu_buffer
->nr_pages
;
2643 dirty
= ring_buffer_nr_dirty_pages(buffer
, cpu_buffer
->cpu
);
2644 if (full
&& nr_pages
&& (dirty
* 100) <= full
* nr_pages
)
2647 cpu_buffer
->irq_work
.wakeup_full
= true;
2648 cpu_buffer
->irq_work
.full_waiters_pending
= false;
2649 /* irq_work_queue() supplies it's own memory barriers */
2650 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2654 * The lock and unlock are done within a preempt disable section.
2655 * The current_context per_cpu variable can only be modified
2656 * by the current task between lock and unlock. But it can
2657 * be modified more than once via an interrupt. To pass this
2658 * information from the lock to the unlock without having to
2659 * access the 'in_interrupt()' functions again (which do show
2660 * a bit of overhead in something as critical as function tracing,
2661 * we use a bitmask trick.
2663 * bit 0 = NMI context
2664 * bit 1 = IRQ context
2665 * bit 2 = SoftIRQ context
2666 * bit 3 = normal context.
2668 * This works because this is the order of contexts that can
2669 * preempt other contexts. A SoftIRQ never preempts an IRQ
2672 * When the context is determined, the corresponding bit is
2673 * checked and set (if it was set, then a recursion of that context
2676 * On unlock, we need to clear this bit. To do so, just subtract
2677 * 1 from the current_context and AND it to itself.
2681 * 101 & 100 = 100 (clearing bit zero)
2684 * 1010 & 1001 = 1000 (clearing bit 1)
2686 * The least significant bit can be cleared this way, and it
2687 * just so happens that it is the same bit corresponding to
2688 * the current context.
2691 static __always_inline
int
2692 trace_recursive_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
2694 unsigned int val
= cpu_buffer
->current_context
;
2695 unsigned long pc
= preempt_count();
2698 if (!(pc
& (NMI_MASK
| HARDIRQ_MASK
| SOFTIRQ_OFFSET
)))
2699 bit
= RB_CTX_NORMAL
;
2701 bit
= pc
& NMI_MASK
? RB_CTX_NMI
:
2702 pc
& HARDIRQ_MASK
? RB_CTX_IRQ
: RB_CTX_SOFTIRQ
;
2704 if (unlikely(val
& (1 << (bit
+ cpu_buffer
->nest
))))
2707 val
|= (1 << (bit
+ cpu_buffer
->nest
));
2708 cpu_buffer
->current_context
= val
;
2713 static __always_inline
void
2714 trace_recursive_unlock(struct ring_buffer_per_cpu
*cpu_buffer
)
2716 cpu_buffer
->current_context
&=
2717 cpu_buffer
->current_context
- (1 << cpu_buffer
->nest
);
2720 /* The recursive locking above uses 4 bits */
2721 #define NESTED_BITS 4
2724 * ring_buffer_nest_start - Allow to trace while nested
2725 * @buffer: The ring buffer to modify
2727 * The ring buffer has a safety mechanism to prevent recursion.
2728 * But there may be a case where a trace needs to be done while
2729 * tracing something else. In this case, calling this function
2730 * will allow this function to nest within a currently active
2731 * ring_buffer_lock_reserve().
2733 * Call this function before calling another ring_buffer_lock_reserve() and
2734 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
2736 void ring_buffer_nest_start(struct ring_buffer
*buffer
)
2738 struct ring_buffer_per_cpu
*cpu_buffer
;
2741 /* Enabled by ring_buffer_nest_end() */
2742 preempt_disable_notrace();
2743 cpu
= raw_smp_processor_id();
2744 cpu_buffer
= buffer
->buffers
[cpu
];
2745 /* This is the shift value for the above recursive locking */
2746 cpu_buffer
->nest
+= NESTED_BITS
;
2750 * ring_buffer_nest_end - Allow to trace while nested
2751 * @buffer: The ring buffer to modify
2753 * Must be called after ring_buffer_nest_start() and after the
2754 * ring_buffer_unlock_commit().
2756 void ring_buffer_nest_end(struct ring_buffer
*buffer
)
2758 struct ring_buffer_per_cpu
*cpu_buffer
;
2761 /* disabled by ring_buffer_nest_start() */
2762 cpu
= raw_smp_processor_id();
2763 cpu_buffer
= buffer
->buffers
[cpu
];
2764 /* This is the shift value for the above recursive locking */
2765 cpu_buffer
->nest
-= NESTED_BITS
;
2766 preempt_enable_notrace();
2770 * ring_buffer_unlock_commit - commit a reserved
2771 * @buffer: The buffer to commit to
2772 * @event: The event pointer to commit.
2774 * This commits the data to the ring buffer, and releases any locks held.
2776 * Must be paired with ring_buffer_lock_reserve.
2778 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2779 struct ring_buffer_event
*event
)
2781 struct ring_buffer_per_cpu
*cpu_buffer
;
2782 int cpu
= raw_smp_processor_id();
2784 cpu_buffer
= buffer
->buffers
[cpu
];
2786 rb_commit(cpu_buffer
, event
);
2788 rb_wakeups(buffer
, cpu_buffer
);
2790 trace_recursive_unlock(cpu_buffer
);
2792 preempt_enable_notrace();
2796 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2798 static noinline
void
2799 rb_handle_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2800 struct rb_event_info
*info
)
2802 WARN_ONCE(info
->delta
> (1ULL << 59),
2803 KERN_WARNING
"Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2804 (unsigned long long)info
->delta
,
2805 (unsigned long long)info
->ts
,
2806 (unsigned long long)cpu_buffer
->write_stamp
,
2807 sched_clock_stable() ? "" :
2808 "If you just came from a suspend/resume,\n"
2809 "please switch to the trace global clock:\n"
2810 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2811 "or add trace_clock=global to the kernel command line\n");
2812 info
->add_timestamp
= 1;
2815 static struct ring_buffer_event
*
2816 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
2817 struct rb_event_info
*info
)
2819 struct ring_buffer_event
*event
;
2820 struct buffer_page
*tail_page
;
2821 unsigned long tail
, write
;
2824 * If the time delta since the last event is too big to
2825 * hold in the time field of the event, then we append a
2826 * TIME EXTEND event ahead of the data event.
2828 if (unlikely(info
->add_timestamp
))
2829 info
->length
+= RB_LEN_TIME_EXTEND
;
2831 /* Don't let the compiler play games with cpu_buffer->tail_page */
2832 tail_page
= info
->tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2833 write
= local_add_return(info
->length
, &tail_page
->write
);
2835 /* set write to only the index of the write */
2836 write
&= RB_WRITE_MASK
;
2837 tail
= write
- info
->length
;
2840 * If this is the first commit on the page, then it has the same
2841 * timestamp as the page itself.
2843 if (!tail
&& !ring_buffer_time_stamp_abs(cpu_buffer
->buffer
))
2846 /* See if we shot pass the end of this buffer page */
2847 if (unlikely(write
> BUF_PAGE_SIZE
))
2848 return rb_move_tail(cpu_buffer
, tail
, info
);
2850 /* We reserved something on the buffer */
2852 event
= __rb_page_index(tail_page
, tail
);
2853 rb_update_event(cpu_buffer
, event
, info
);
2855 local_inc(&tail_page
->entries
);
2858 * If this is the first commit on the page, then update
2862 tail_page
->page
->time_stamp
= info
->ts
;
2864 /* account for these added bytes */
2865 local_add(info
->length
, &cpu_buffer
->entries_bytes
);
2870 static __always_inline
struct ring_buffer_event
*
2871 rb_reserve_next_event(struct ring_buffer
*buffer
,
2872 struct ring_buffer_per_cpu
*cpu_buffer
,
2873 unsigned long length
)
2875 struct ring_buffer_event
*event
;
2876 struct rb_event_info info
;
2880 rb_start_commit(cpu_buffer
);
2882 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2884 * Due to the ability to swap a cpu buffer from a buffer
2885 * it is possible it was swapped before we committed.
2886 * (committing stops a swap). We check for it here and
2887 * if it happened, we have to fail the write.
2890 if (unlikely(READ_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2891 local_dec(&cpu_buffer
->committing
);
2892 local_dec(&cpu_buffer
->commits
);
2897 info
.length
= rb_calculate_event_length(length
);
2899 info
.add_timestamp
= 0;
2903 * We allow for interrupts to reenter here and do a trace.
2904 * If one does, it will cause this original code to loop
2905 * back here. Even with heavy interrupts happening, this
2906 * should only happen a few times in a row. If this happens
2907 * 1000 times in a row, there must be either an interrupt
2908 * storm or we have something buggy.
2911 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2914 info
.ts
= rb_time_stamp(cpu_buffer
->buffer
);
2915 diff
= info
.ts
- cpu_buffer
->write_stamp
;
2917 /* make sure this diff is calculated here */
2920 if (ring_buffer_time_stamp_abs(buffer
)) {
2921 info
.delta
= info
.ts
;
2922 rb_handle_timestamp(cpu_buffer
, &info
);
2923 } else /* Did the write stamp get updated already? */
2924 if (likely(info
.ts
>= cpu_buffer
->write_stamp
)) {
2926 if (unlikely(test_time_stamp(info
.delta
)))
2927 rb_handle_timestamp(cpu_buffer
, &info
);
2930 event
= __rb_reserve_next(cpu_buffer
, &info
);
2932 if (unlikely(PTR_ERR(event
) == -EAGAIN
)) {
2933 if (info
.add_timestamp
)
2934 info
.length
-= RB_LEN_TIME_EXTEND
;
2944 rb_end_commit(cpu_buffer
);
2949 * ring_buffer_lock_reserve - reserve a part of the buffer
2950 * @buffer: the ring buffer to reserve from
2951 * @length: the length of the data to reserve (excluding event header)
2953 * Returns a reserved event on the ring buffer to copy directly to.
2954 * The user of this interface will need to get the body to write into
2955 * and can use the ring_buffer_event_data() interface.
2957 * The length is the length of the data needed, not the event length
2958 * which also includes the event header.
2960 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2961 * If NULL is returned, then nothing has been allocated or locked.
2963 struct ring_buffer_event
*
2964 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2966 struct ring_buffer_per_cpu
*cpu_buffer
;
2967 struct ring_buffer_event
*event
;
2970 /* If we are tracing schedule, we don't want to recurse */
2971 preempt_disable_notrace();
2973 if (unlikely(atomic_read(&buffer
->record_disabled
)))
2976 cpu
= raw_smp_processor_id();
2978 if (unlikely(!cpumask_test_cpu(cpu
, buffer
->cpumask
)))
2981 cpu_buffer
= buffer
->buffers
[cpu
];
2983 if (unlikely(atomic_read(&cpu_buffer
->record_disabled
)))
2986 if (unlikely(length
> BUF_MAX_DATA_SIZE
))
2989 if (unlikely(trace_recursive_lock(cpu_buffer
)))
2992 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2999 trace_recursive_unlock(cpu_buffer
);
3001 preempt_enable_notrace();
3004 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
3007 * Decrement the entries to the page that an event is on.
3008 * The event does not even need to exist, only the pointer
3009 * to the page it is on. This may only be called before the commit
3013 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
3014 struct ring_buffer_event
*event
)
3016 unsigned long addr
= (unsigned long)event
;
3017 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
3018 struct buffer_page
*start
;
3022 /* Do the likely case first */
3023 if (likely(bpage
->page
== (void *)addr
)) {
3024 local_dec(&bpage
->entries
);
3029 * Because the commit page may be on the reader page we
3030 * start with the next page and check the end loop there.
3032 rb_inc_page(cpu_buffer
, &bpage
);
3035 if (bpage
->page
== (void *)addr
) {
3036 local_dec(&bpage
->entries
);
3039 rb_inc_page(cpu_buffer
, &bpage
);
3040 } while (bpage
!= start
);
3042 /* commit not part of this buffer?? */
3043 RB_WARN_ON(cpu_buffer
, 1);
3047 * ring_buffer_commit_discard - discard an event that has not been committed
3048 * @buffer: the ring buffer
3049 * @event: non committed event to discard
3051 * Sometimes an event that is in the ring buffer needs to be ignored.
3052 * This function lets the user discard an event in the ring buffer
3053 * and then that event will not be read later.
3055 * This function only works if it is called before the item has been
3056 * committed. It will try to free the event from the ring buffer
3057 * if another event has not been added behind it.
3059 * If another event has been added behind it, it will set the event
3060 * up as discarded, and perform the commit.
3062 * If this function is called, do not call ring_buffer_unlock_commit on
3065 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
3066 struct ring_buffer_event
*event
)
3068 struct ring_buffer_per_cpu
*cpu_buffer
;
3071 /* The event is discarded regardless */
3072 rb_event_discard(event
);
3074 cpu
= smp_processor_id();
3075 cpu_buffer
= buffer
->buffers
[cpu
];
3078 * This must only be called if the event has not been
3079 * committed yet. Thus we can assume that preemption
3080 * is still disabled.
3082 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
3084 rb_decrement_entry(cpu_buffer
, event
);
3085 if (rb_try_to_discard(cpu_buffer
, event
))
3089 * The commit is still visible by the reader, so we
3090 * must still update the timestamp.
3092 rb_update_write_stamp(cpu_buffer
, event
);
3094 rb_end_commit(cpu_buffer
);
3096 trace_recursive_unlock(cpu_buffer
);
3098 preempt_enable_notrace();
3101 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
3104 * ring_buffer_write - write data to the buffer without reserving
3105 * @buffer: The ring buffer to write to.
3106 * @length: The length of the data being written (excluding the event header)
3107 * @data: The data to write to the buffer.
3109 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3110 * one function. If you already have the data to write to the buffer, it
3111 * may be easier to simply call this function.
3113 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3114 * and not the length of the event which would hold the header.
3116 int ring_buffer_write(struct ring_buffer
*buffer
,
3117 unsigned long length
,
3120 struct ring_buffer_per_cpu
*cpu_buffer
;
3121 struct ring_buffer_event
*event
;
3126 preempt_disable_notrace();
3128 if (atomic_read(&buffer
->record_disabled
))
3131 cpu
= raw_smp_processor_id();
3133 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3136 cpu_buffer
= buffer
->buffers
[cpu
];
3138 if (atomic_read(&cpu_buffer
->record_disabled
))
3141 if (length
> BUF_MAX_DATA_SIZE
)
3144 if (unlikely(trace_recursive_lock(cpu_buffer
)))
3147 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
3151 body
= rb_event_data(event
);
3153 memcpy(body
, data
, length
);
3155 rb_commit(cpu_buffer
, event
);
3157 rb_wakeups(buffer
, cpu_buffer
);
3162 trace_recursive_unlock(cpu_buffer
);
3165 preempt_enable_notrace();
3169 EXPORT_SYMBOL_GPL(ring_buffer_write
);
3171 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
3173 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
3174 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
3175 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
3177 /* In case of error, head will be NULL */
3178 if (unlikely(!head
))
3181 return reader
->read
== rb_page_commit(reader
) &&
3182 (commit
== reader
||
3184 head
->read
== rb_page_commit(commit
)));
3188 * ring_buffer_record_disable - stop all writes into the buffer
3189 * @buffer: The ring buffer to stop writes to.
3191 * This prevents all writes to the buffer. Any attempt to write
3192 * to the buffer after this will fail and return NULL.
3194 * The caller should call synchronize_rcu() after this.
3196 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
3198 atomic_inc(&buffer
->record_disabled
);
3200 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
3203 * ring_buffer_record_enable - enable writes to the buffer
3204 * @buffer: The ring buffer to enable writes
3206 * Note, multiple disables will need the same number of enables
3207 * to truly enable the writing (much like preempt_disable).
3209 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
3211 atomic_dec(&buffer
->record_disabled
);
3213 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
3216 * ring_buffer_record_off - stop all writes into the buffer
3217 * @buffer: The ring buffer to stop writes to.
3219 * This prevents all writes to the buffer. Any attempt to write
3220 * to the buffer after this will fail and return NULL.
3222 * This is different than ring_buffer_record_disable() as
3223 * it works like an on/off switch, where as the disable() version
3224 * must be paired with a enable().
3226 void ring_buffer_record_off(struct ring_buffer
*buffer
)
3229 unsigned int new_rd
;
3232 rd
= atomic_read(&buffer
->record_disabled
);
3233 new_rd
= rd
| RB_BUFFER_OFF
;
3234 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3236 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
3239 * ring_buffer_record_on - restart writes into the buffer
3240 * @buffer: The ring buffer to start writes to.
3242 * This enables all writes to the buffer that was disabled by
3243 * ring_buffer_record_off().
3245 * This is different than ring_buffer_record_enable() as
3246 * it works like an on/off switch, where as the enable() version
3247 * must be paired with a disable().
3249 void ring_buffer_record_on(struct ring_buffer
*buffer
)
3252 unsigned int new_rd
;
3255 rd
= atomic_read(&buffer
->record_disabled
);
3256 new_rd
= rd
& ~RB_BUFFER_OFF
;
3257 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3259 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
3262 * ring_buffer_record_is_on - return true if the ring buffer can write
3263 * @buffer: The ring buffer to see if write is enabled
3265 * Returns true if the ring buffer is in a state that it accepts writes.
3267 bool ring_buffer_record_is_on(struct ring_buffer
*buffer
)
3269 return !atomic_read(&buffer
->record_disabled
);
3273 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3274 * @buffer: The ring buffer to see if write is set enabled
3276 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3277 * Note that this does NOT mean it is in a writable state.
3279 * It may return true when the ring buffer has been disabled by
3280 * ring_buffer_record_disable(), as that is a temporary disabling of
3283 bool ring_buffer_record_is_set_on(struct ring_buffer
*buffer
)
3285 return !(atomic_read(&buffer
->record_disabled
) & RB_BUFFER_OFF
);
3289 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3290 * @buffer: The ring buffer to stop writes to.
3291 * @cpu: The CPU buffer to stop
3293 * This prevents all writes to the buffer. Any attempt to write
3294 * to the buffer after this will fail and return NULL.
3296 * The caller should call synchronize_rcu() after this.
3298 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
3300 struct ring_buffer_per_cpu
*cpu_buffer
;
3302 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3305 cpu_buffer
= buffer
->buffers
[cpu
];
3306 atomic_inc(&cpu_buffer
->record_disabled
);
3308 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
3311 * ring_buffer_record_enable_cpu - enable writes to the buffer
3312 * @buffer: The ring buffer to enable writes
3313 * @cpu: The CPU to enable.
3315 * Note, multiple disables will need the same number of enables
3316 * to truly enable the writing (much like preempt_disable).
3318 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
3320 struct ring_buffer_per_cpu
*cpu_buffer
;
3322 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3325 cpu_buffer
= buffer
->buffers
[cpu
];
3326 atomic_dec(&cpu_buffer
->record_disabled
);
3328 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
3331 * The total entries in the ring buffer is the running counter
3332 * of entries entered into the ring buffer, minus the sum of
3333 * the entries read from the ring buffer and the number of
3334 * entries that were overwritten.
3336 static inline unsigned long
3337 rb_num_of_entries(struct ring_buffer_per_cpu
*cpu_buffer
)
3339 return local_read(&cpu_buffer
->entries
) -
3340 (local_read(&cpu_buffer
->overrun
) + cpu_buffer
->read
);
3344 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3345 * @buffer: The ring buffer
3346 * @cpu: The per CPU buffer to read from.
3348 u64
ring_buffer_oldest_event_ts(struct ring_buffer
*buffer
, int cpu
)
3350 unsigned long flags
;
3351 struct ring_buffer_per_cpu
*cpu_buffer
;
3352 struct buffer_page
*bpage
;
3355 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3358 cpu_buffer
= buffer
->buffers
[cpu
];
3359 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3361 * if the tail is on reader_page, oldest time stamp is on the reader
3364 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
3365 bpage
= cpu_buffer
->reader_page
;
3367 bpage
= rb_set_head_page(cpu_buffer
);
3369 ret
= bpage
->page
->time_stamp
;
3370 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3374 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts
);
3377 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3378 * @buffer: The ring buffer
3379 * @cpu: The per CPU buffer to read from.
3381 unsigned long ring_buffer_bytes_cpu(struct ring_buffer
*buffer
, int cpu
)
3383 struct ring_buffer_per_cpu
*cpu_buffer
;
3386 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3389 cpu_buffer
= buffer
->buffers
[cpu
];
3390 ret
= local_read(&cpu_buffer
->entries_bytes
) - cpu_buffer
->read_bytes
;
3394 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu
);
3397 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3398 * @buffer: The ring buffer
3399 * @cpu: The per CPU buffer to get the entries from.
3401 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
3403 struct ring_buffer_per_cpu
*cpu_buffer
;
3405 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3408 cpu_buffer
= buffer
->buffers
[cpu
];
3410 return rb_num_of_entries(cpu_buffer
);
3412 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
3415 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3416 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3417 * @buffer: The ring buffer
3418 * @cpu: The per CPU buffer to get the number of overruns from
3420 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3422 struct ring_buffer_per_cpu
*cpu_buffer
;
3425 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3428 cpu_buffer
= buffer
->buffers
[cpu
];
3429 ret
= local_read(&cpu_buffer
->overrun
);
3433 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
3436 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3437 * commits failing due to the buffer wrapping around while there are uncommitted
3438 * events, such as during an interrupt storm.
3439 * @buffer: The ring buffer
3440 * @cpu: The per CPU buffer to get the number of overruns from
3443 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3445 struct ring_buffer_per_cpu
*cpu_buffer
;
3448 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3451 cpu_buffer
= buffer
->buffers
[cpu
];
3452 ret
= local_read(&cpu_buffer
->commit_overrun
);
3456 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
3459 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3460 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3461 * @buffer: The ring buffer
3462 * @cpu: The per CPU buffer to get the number of overruns from
3465 ring_buffer_dropped_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3467 struct ring_buffer_per_cpu
*cpu_buffer
;
3470 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3473 cpu_buffer
= buffer
->buffers
[cpu
];
3474 ret
= local_read(&cpu_buffer
->dropped_events
);
3478 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu
);
3481 * ring_buffer_read_events_cpu - get the number of events successfully read
3482 * @buffer: The ring buffer
3483 * @cpu: The per CPU buffer to get the number of events read
3486 ring_buffer_read_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3488 struct ring_buffer_per_cpu
*cpu_buffer
;
3490 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3493 cpu_buffer
= buffer
->buffers
[cpu
];
3494 return cpu_buffer
->read
;
3496 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu
);
3499 * ring_buffer_entries - get the number of entries in a buffer
3500 * @buffer: The ring buffer
3502 * Returns the total number of entries in the ring buffer
3505 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
3507 struct ring_buffer_per_cpu
*cpu_buffer
;
3508 unsigned long entries
= 0;
3511 /* if you care about this being correct, lock the buffer */
3512 for_each_buffer_cpu(buffer
, cpu
) {
3513 cpu_buffer
= buffer
->buffers
[cpu
];
3514 entries
+= rb_num_of_entries(cpu_buffer
);
3519 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
3522 * ring_buffer_overruns - get the number of overruns in buffer
3523 * @buffer: The ring buffer
3525 * Returns the total number of overruns in the ring buffer
3528 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
3530 struct ring_buffer_per_cpu
*cpu_buffer
;
3531 unsigned long overruns
= 0;
3534 /* if you care about this being correct, lock the buffer */
3535 for_each_buffer_cpu(buffer
, cpu
) {
3536 cpu_buffer
= buffer
->buffers
[cpu
];
3537 overruns
+= local_read(&cpu_buffer
->overrun
);
3542 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
3544 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
3546 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3548 /* Iterator usage is expected to have record disabled */
3549 iter
->head_page
= cpu_buffer
->reader_page
;
3550 iter
->head
= cpu_buffer
->reader_page
->read
;
3552 iter
->cache_reader_page
= iter
->head_page
;
3553 iter
->cache_read
= cpu_buffer
->read
;
3556 iter
->read_stamp
= cpu_buffer
->read_stamp
;
3558 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
3562 * ring_buffer_iter_reset - reset an iterator
3563 * @iter: The iterator to reset
3565 * Resets the iterator, so that it will start from the beginning
3568 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
3570 struct ring_buffer_per_cpu
*cpu_buffer
;
3571 unsigned long flags
;
3576 cpu_buffer
= iter
->cpu_buffer
;
3578 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3579 rb_iter_reset(iter
);
3580 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3582 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
3585 * ring_buffer_iter_empty - check if an iterator has no more to read
3586 * @iter: The iterator to check
3588 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
3590 struct ring_buffer_per_cpu
*cpu_buffer
;
3591 struct buffer_page
*reader
;
3592 struct buffer_page
*head_page
;
3593 struct buffer_page
*commit_page
;
3596 cpu_buffer
= iter
->cpu_buffer
;
3598 /* Remember, trace recording is off when iterator is in use */
3599 reader
= cpu_buffer
->reader_page
;
3600 head_page
= cpu_buffer
->head_page
;
3601 commit_page
= cpu_buffer
->commit_page
;
3602 commit
= rb_page_commit(commit_page
);
3604 return ((iter
->head_page
== commit_page
&& iter
->head
== commit
) ||
3605 (iter
->head_page
== reader
&& commit_page
== head_page
&&
3606 head_page
->read
== commit
&&
3607 iter
->head
== rb_page_commit(cpu_buffer
->reader_page
)));
3609 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
3612 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
3613 struct ring_buffer_event
*event
)
3617 switch (event
->type_len
) {
3618 case RINGBUF_TYPE_PADDING
:
3621 case RINGBUF_TYPE_TIME_EXTEND
:
3622 delta
= ring_buffer_event_time_stamp(event
);
3623 cpu_buffer
->read_stamp
+= delta
;
3626 case RINGBUF_TYPE_TIME_STAMP
:
3627 delta
= ring_buffer_event_time_stamp(event
);
3628 cpu_buffer
->read_stamp
= delta
;
3631 case RINGBUF_TYPE_DATA
:
3632 cpu_buffer
->read_stamp
+= event
->time_delta
;
3642 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
3643 struct ring_buffer_event
*event
)
3647 switch (event
->type_len
) {
3648 case RINGBUF_TYPE_PADDING
:
3651 case RINGBUF_TYPE_TIME_EXTEND
:
3652 delta
= ring_buffer_event_time_stamp(event
);
3653 iter
->read_stamp
+= delta
;
3656 case RINGBUF_TYPE_TIME_STAMP
:
3657 delta
= ring_buffer_event_time_stamp(event
);
3658 iter
->read_stamp
= delta
;
3661 case RINGBUF_TYPE_DATA
:
3662 iter
->read_stamp
+= event
->time_delta
;
3671 static struct buffer_page
*
3672 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
3674 struct buffer_page
*reader
= NULL
;
3675 unsigned long overwrite
;
3676 unsigned long flags
;
3680 local_irq_save(flags
);
3681 arch_spin_lock(&cpu_buffer
->lock
);
3685 * This should normally only loop twice. But because the
3686 * start of the reader inserts an empty page, it causes
3687 * a case where we will loop three times. There should be no
3688 * reason to loop four times (that I know of).
3690 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
3695 reader
= cpu_buffer
->reader_page
;
3697 /* If there's more to read, return this page */
3698 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
3701 /* Never should we have an index greater than the size */
3702 if (RB_WARN_ON(cpu_buffer
,
3703 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
3706 /* check if we caught up to the tail */
3708 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
3711 /* Don't bother swapping if the ring buffer is empty */
3712 if (rb_num_of_entries(cpu_buffer
) == 0)
3716 * Reset the reader page to size zero.
3718 local_set(&cpu_buffer
->reader_page
->write
, 0);
3719 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3720 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3721 cpu_buffer
->reader_page
->real_end
= 0;
3725 * Splice the empty reader page into the list around the head.
3727 reader
= rb_set_head_page(cpu_buffer
);
3730 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
3731 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
3734 * cpu_buffer->pages just needs to point to the buffer, it
3735 * has no specific buffer page to point to. Lets move it out
3736 * of our way so we don't accidentally swap it.
3738 cpu_buffer
->pages
= reader
->list
.prev
;
3740 /* The reader page will be pointing to the new head */
3741 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
3744 * We want to make sure we read the overruns after we set up our
3745 * pointers to the next object. The writer side does a
3746 * cmpxchg to cross pages which acts as the mb on the writer
3747 * side. Note, the reader will constantly fail the swap
3748 * while the writer is updating the pointers, so this
3749 * guarantees that the overwrite recorded here is the one we
3750 * want to compare with the last_overrun.
3753 overwrite
= local_read(&(cpu_buffer
->overrun
));
3756 * Here's the tricky part.
3758 * We need to move the pointer past the header page.
3759 * But we can only do that if a writer is not currently
3760 * moving it. The page before the header page has the
3761 * flag bit '1' set if it is pointing to the page we want.
3762 * but if the writer is in the process of moving it
3763 * than it will be '2' or already moved '0'.
3766 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
3769 * If we did not convert it, then we must try again.
3775 * Yay! We succeeded in replacing the page.
3777 * Now make the new head point back to the reader page.
3779 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
3780 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
3782 local_inc(&cpu_buffer
->pages_read
);
3784 /* Finally update the reader page to the new head */
3785 cpu_buffer
->reader_page
= reader
;
3786 cpu_buffer
->reader_page
->read
= 0;
3788 if (overwrite
!= cpu_buffer
->last_overrun
) {
3789 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
3790 cpu_buffer
->last_overrun
= overwrite
;
3796 /* Update the read_stamp on the first event */
3797 if (reader
&& reader
->read
== 0)
3798 cpu_buffer
->read_stamp
= reader
->page
->time_stamp
;
3800 arch_spin_unlock(&cpu_buffer
->lock
);
3801 local_irq_restore(flags
);
3806 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
3808 struct ring_buffer_event
*event
;
3809 struct buffer_page
*reader
;
3812 reader
= rb_get_reader_page(cpu_buffer
);
3814 /* This function should not be called when buffer is empty */
3815 if (RB_WARN_ON(cpu_buffer
, !reader
))
3818 event
= rb_reader_event(cpu_buffer
);
3820 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
3823 rb_update_read_stamp(cpu_buffer
, event
);
3825 length
= rb_event_length(event
);
3826 cpu_buffer
->reader_page
->read
+= length
;
3829 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
3831 struct ring_buffer_per_cpu
*cpu_buffer
;
3832 struct ring_buffer_event
*event
;
3835 cpu_buffer
= iter
->cpu_buffer
;
3838 * Check if we are at the end of the buffer.
3840 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3841 /* discarded commits can make the page empty */
3842 if (iter
->head_page
== cpu_buffer
->commit_page
)
3848 event
= rb_iter_head_event(iter
);
3850 length
= rb_event_length(event
);
3853 * This should not be called to advance the header if we are
3854 * at the tail of the buffer.
3856 if (RB_WARN_ON(cpu_buffer
,
3857 (iter
->head_page
== cpu_buffer
->commit_page
) &&
3858 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
3861 rb_update_iter_read_stamp(iter
, event
);
3863 iter
->head
+= length
;
3865 /* check for end of page padding */
3866 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3867 (iter
->head_page
!= cpu_buffer
->commit_page
))
3871 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
3873 return cpu_buffer
->lost_events
;
3876 static struct ring_buffer_event
*
3877 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
3878 unsigned long *lost_events
)
3880 struct ring_buffer_event
*event
;
3881 struct buffer_page
*reader
;
3888 * We repeat when a time extend is encountered.
3889 * Since the time extend is always attached to a data event,
3890 * we should never loop more than once.
3891 * (We never hit the following condition more than twice).
3893 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
3896 reader
= rb_get_reader_page(cpu_buffer
);
3900 event
= rb_reader_event(cpu_buffer
);
3902 switch (event
->type_len
) {
3903 case RINGBUF_TYPE_PADDING
:
3904 if (rb_null_event(event
))
3905 RB_WARN_ON(cpu_buffer
, 1);
3907 * Because the writer could be discarding every
3908 * event it creates (which would probably be bad)
3909 * if we were to go back to "again" then we may never
3910 * catch up, and will trigger the warn on, or lock
3911 * the box. Return the padding, and we will release
3912 * the current locks, and try again.
3916 case RINGBUF_TYPE_TIME_EXTEND
:
3917 /* Internal data, OK to advance */
3918 rb_advance_reader(cpu_buffer
);
3921 case RINGBUF_TYPE_TIME_STAMP
:
3923 *ts
= ring_buffer_event_time_stamp(event
);
3924 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3925 cpu_buffer
->cpu
, ts
);
3927 /* Internal data, OK to advance */
3928 rb_advance_reader(cpu_buffer
);
3931 case RINGBUF_TYPE_DATA
:
3933 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3934 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3935 cpu_buffer
->cpu
, ts
);
3938 *lost_events
= rb_lost_events(cpu_buffer
);
3947 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3949 static struct ring_buffer_event
*
3950 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3952 struct ring_buffer
*buffer
;
3953 struct ring_buffer_per_cpu
*cpu_buffer
;
3954 struct ring_buffer_event
*event
;
3960 cpu_buffer
= iter
->cpu_buffer
;
3961 buffer
= cpu_buffer
->buffer
;
3964 * Check if someone performed a consuming read to
3965 * the buffer. A consuming read invalidates the iterator
3966 * and we need to reset the iterator in this case.
3968 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3969 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3970 rb_iter_reset(iter
);
3973 if (ring_buffer_iter_empty(iter
))
3977 * We repeat when a time extend is encountered or we hit
3978 * the end of the page. Since the time extend is always attached
3979 * to a data event, we should never loop more than three times.
3980 * Once for going to next page, once on time extend, and
3981 * finally once to get the event.
3982 * (We never hit the following condition more than thrice).
3984 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3))
3987 if (rb_per_cpu_empty(cpu_buffer
))
3990 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3995 event
= rb_iter_head_event(iter
);
3997 switch (event
->type_len
) {
3998 case RINGBUF_TYPE_PADDING
:
3999 if (rb_null_event(event
)) {
4003 rb_advance_iter(iter
);
4006 case RINGBUF_TYPE_TIME_EXTEND
:
4007 /* Internal data, OK to advance */
4008 rb_advance_iter(iter
);
4011 case RINGBUF_TYPE_TIME_STAMP
:
4013 *ts
= ring_buffer_event_time_stamp(event
);
4014 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4015 cpu_buffer
->cpu
, ts
);
4017 /* Internal data, OK to advance */
4018 rb_advance_iter(iter
);
4021 case RINGBUF_TYPE_DATA
:
4023 *ts
= iter
->read_stamp
+ event
->time_delta
;
4024 ring_buffer_normalize_time_stamp(buffer
,
4025 cpu_buffer
->cpu
, ts
);
4035 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
4037 static inline bool rb_reader_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
4039 if (likely(!in_nmi())) {
4040 raw_spin_lock(&cpu_buffer
->reader_lock
);
4045 * If an NMI die dumps out the content of the ring buffer
4046 * trylock must be used to prevent a deadlock if the NMI
4047 * preempted a task that holds the ring buffer locks. If
4048 * we get the lock then all is fine, if not, then continue
4049 * to do the read, but this can corrupt the ring buffer,
4050 * so it must be permanently disabled from future writes.
4051 * Reading from NMI is a oneshot deal.
4053 if (raw_spin_trylock(&cpu_buffer
->reader_lock
))
4056 /* Continue without locking, but disable the ring buffer */
4057 atomic_inc(&cpu_buffer
->record_disabled
);
4062 rb_reader_unlock(struct ring_buffer_per_cpu
*cpu_buffer
, bool locked
)
4065 raw_spin_unlock(&cpu_buffer
->reader_lock
);
4070 * ring_buffer_peek - peek at the next event to be read
4071 * @buffer: The ring buffer to read
4072 * @cpu: The cpu to peak at
4073 * @ts: The timestamp counter of this event.
4074 * @lost_events: a variable to store if events were lost (may be NULL)
4076 * This will return the event that will be read next, but does
4077 * not consume the data.
4079 struct ring_buffer_event
*
4080 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
4081 unsigned long *lost_events
)
4083 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4084 struct ring_buffer_event
*event
;
4085 unsigned long flags
;
4088 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4092 local_irq_save(flags
);
4093 dolock
= rb_reader_lock(cpu_buffer
);
4094 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
4095 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4096 rb_advance_reader(cpu_buffer
);
4097 rb_reader_unlock(cpu_buffer
, dolock
);
4098 local_irq_restore(flags
);
4100 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4107 * ring_buffer_iter_peek - peek at the next event to be read
4108 * @iter: The ring buffer iterator
4109 * @ts: The timestamp counter of this event.
4111 * This will return the event that will be read next, but does
4112 * not increment the iterator.
4114 struct ring_buffer_event
*
4115 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
4117 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4118 struct ring_buffer_event
*event
;
4119 unsigned long flags
;
4122 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4123 event
= rb_iter_peek(iter
, ts
);
4124 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4126 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4133 * ring_buffer_consume - return an event and consume it
4134 * @buffer: The ring buffer to get the next event from
4135 * @cpu: the cpu to read the buffer from
4136 * @ts: a variable to store the timestamp (may be NULL)
4137 * @lost_events: a variable to store if events were lost (may be NULL)
4139 * Returns the next event in the ring buffer, and that event is consumed.
4140 * Meaning, that sequential reads will keep returning a different event,
4141 * and eventually empty the ring buffer if the producer is slower.
4143 struct ring_buffer_event
*
4144 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
4145 unsigned long *lost_events
)
4147 struct ring_buffer_per_cpu
*cpu_buffer
;
4148 struct ring_buffer_event
*event
= NULL
;
4149 unsigned long flags
;
4153 /* might be called in atomic */
4156 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4159 cpu_buffer
= buffer
->buffers
[cpu
];
4160 local_irq_save(flags
);
4161 dolock
= rb_reader_lock(cpu_buffer
);
4163 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
4165 cpu_buffer
->lost_events
= 0;
4166 rb_advance_reader(cpu_buffer
);
4169 rb_reader_unlock(cpu_buffer
, dolock
);
4170 local_irq_restore(flags
);
4175 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4180 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
4183 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4184 * @buffer: The ring buffer to read from
4185 * @cpu: The cpu buffer to iterate over
4186 * @flags: gfp flags to use for memory allocation
4188 * This performs the initial preparations necessary to iterate
4189 * through the buffer. Memory is allocated, buffer recording
4190 * is disabled, and the iterator pointer is returned to the caller.
4192 * Disabling buffer recording prevents the reading from being
4193 * corrupted. This is not a consuming read, so a producer is not
4196 * After a sequence of ring_buffer_read_prepare calls, the user is
4197 * expected to make at least one call to ring_buffer_read_prepare_sync.
4198 * Afterwards, ring_buffer_read_start is invoked to get things going
4201 * This overall must be paired with ring_buffer_read_finish.
4203 struct ring_buffer_iter
*
4204 ring_buffer_read_prepare(struct ring_buffer
*buffer
, int cpu
, gfp_t flags
)
4206 struct ring_buffer_per_cpu
*cpu_buffer
;
4207 struct ring_buffer_iter
*iter
;
4209 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4212 iter
= kmalloc(sizeof(*iter
), flags
);
4216 cpu_buffer
= buffer
->buffers
[cpu
];
4218 iter
->cpu_buffer
= cpu_buffer
;
4220 atomic_inc(&buffer
->resize_disabled
);
4221 atomic_inc(&cpu_buffer
->record_disabled
);
4225 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
4228 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4230 * All previously invoked ring_buffer_read_prepare calls to prepare
4231 * iterators will be synchronized. Afterwards, read_buffer_read_start
4232 * calls on those iterators are allowed.
4235 ring_buffer_read_prepare_sync(void)
4239 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
4242 * ring_buffer_read_start - start a non consuming read of the buffer
4243 * @iter: The iterator returned by ring_buffer_read_prepare
4245 * This finalizes the startup of an iteration through the buffer.
4246 * The iterator comes from a call to ring_buffer_read_prepare and
4247 * an intervening ring_buffer_read_prepare_sync must have been
4250 * Must be paired with ring_buffer_read_finish.
4253 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
4255 struct ring_buffer_per_cpu
*cpu_buffer
;
4256 unsigned long flags
;
4261 cpu_buffer
= iter
->cpu_buffer
;
4263 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4264 arch_spin_lock(&cpu_buffer
->lock
);
4265 rb_iter_reset(iter
);
4266 arch_spin_unlock(&cpu_buffer
->lock
);
4267 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4269 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
4272 * ring_buffer_read_finish - finish reading the iterator of the buffer
4273 * @iter: The iterator retrieved by ring_buffer_start
4275 * This re-enables the recording to the buffer, and frees the
4279 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
4281 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4282 unsigned long flags
;
4285 * Ring buffer is disabled from recording, here's a good place
4286 * to check the integrity of the ring buffer.
4287 * Must prevent readers from trying to read, as the check
4288 * clears the HEAD page and readers require it.
4290 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4291 rb_check_pages(cpu_buffer
);
4292 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4294 atomic_dec(&cpu_buffer
->record_disabled
);
4295 atomic_dec(&cpu_buffer
->buffer
->resize_disabled
);
4298 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
4301 * ring_buffer_read - read the next item in the ring buffer by the iterator
4302 * @iter: The ring buffer iterator
4303 * @ts: The time stamp of the event read.
4305 * This reads the next event in the ring buffer and increments the iterator.
4307 struct ring_buffer_event
*
4308 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
4310 struct ring_buffer_event
*event
;
4311 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4312 unsigned long flags
;
4314 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4316 event
= rb_iter_peek(iter
, ts
);
4320 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
4323 rb_advance_iter(iter
);
4325 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4329 EXPORT_SYMBOL_GPL(ring_buffer_read
);
4332 * ring_buffer_size - return the size of the ring buffer (in bytes)
4333 * @buffer: The ring buffer.
4335 unsigned long ring_buffer_size(struct ring_buffer
*buffer
, int cpu
)
4338 * Earlier, this method returned
4339 * BUF_PAGE_SIZE * buffer->nr_pages
4340 * Since the nr_pages field is now removed, we have converted this to
4341 * return the per cpu buffer value.
4343 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4346 return BUF_PAGE_SIZE
* buffer
->buffers
[cpu
]->nr_pages
;
4348 EXPORT_SYMBOL_GPL(ring_buffer_size
);
4351 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
4353 rb_head_page_deactivate(cpu_buffer
);
4355 cpu_buffer
->head_page
4356 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
4357 local_set(&cpu_buffer
->head_page
->write
, 0);
4358 local_set(&cpu_buffer
->head_page
->entries
, 0);
4359 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
4361 cpu_buffer
->head_page
->read
= 0;
4363 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
4364 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
4366 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
4367 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
4368 local_set(&cpu_buffer
->reader_page
->write
, 0);
4369 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4370 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4371 cpu_buffer
->reader_page
->read
= 0;
4373 local_set(&cpu_buffer
->entries_bytes
, 0);
4374 local_set(&cpu_buffer
->overrun
, 0);
4375 local_set(&cpu_buffer
->commit_overrun
, 0);
4376 local_set(&cpu_buffer
->dropped_events
, 0);
4377 local_set(&cpu_buffer
->entries
, 0);
4378 local_set(&cpu_buffer
->committing
, 0);
4379 local_set(&cpu_buffer
->commits
, 0);
4380 local_set(&cpu_buffer
->pages_touched
, 0);
4381 local_set(&cpu_buffer
->pages_read
, 0);
4382 cpu_buffer
->last_pages_touch
= 0;
4383 cpu_buffer
->shortest_full
= 0;
4384 cpu_buffer
->read
= 0;
4385 cpu_buffer
->read_bytes
= 0;
4387 cpu_buffer
->write_stamp
= 0;
4388 cpu_buffer
->read_stamp
= 0;
4390 cpu_buffer
->lost_events
= 0;
4391 cpu_buffer
->last_overrun
= 0;
4393 rb_head_page_activate(cpu_buffer
);
4397 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4398 * @buffer: The ring buffer to reset a per cpu buffer of
4399 * @cpu: The CPU buffer to be reset
4401 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
4403 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4404 unsigned long flags
;
4406 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4409 atomic_inc(&buffer
->resize_disabled
);
4410 atomic_inc(&cpu_buffer
->record_disabled
);
4412 /* Make sure all commits have finished */
4415 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4417 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
4420 arch_spin_lock(&cpu_buffer
->lock
);
4422 rb_reset_cpu(cpu_buffer
);
4424 arch_spin_unlock(&cpu_buffer
->lock
);
4427 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4429 atomic_dec(&cpu_buffer
->record_disabled
);
4430 atomic_dec(&buffer
->resize_disabled
);
4432 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
4435 * ring_buffer_reset - reset a ring buffer
4436 * @buffer: The ring buffer to reset all cpu buffers
4438 void ring_buffer_reset(struct ring_buffer
*buffer
)
4442 for_each_buffer_cpu(buffer
, cpu
)
4443 ring_buffer_reset_cpu(buffer
, cpu
);
4445 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
4448 * rind_buffer_empty - is the ring buffer empty?
4449 * @buffer: The ring buffer to test
4451 bool ring_buffer_empty(struct ring_buffer
*buffer
)
4453 struct ring_buffer_per_cpu
*cpu_buffer
;
4454 unsigned long flags
;
4459 /* yes this is racy, but if you don't like the race, lock the buffer */
4460 for_each_buffer_cpu(buffer
, cpu
) {
4461 cpu_buffer
= buffer
->buffers
[cpu
];
4462 local_irq_save(flags
);
4463 dolock
= rb_reader_lock(cpu_buffer
);
4464 ret
= rb_per_cpu_empty(cpu_buffer
);
4465 rb_reader_unlock(cpu_buffer
, dolock
);
4466 local_irq_restore(flags
);
4474 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
4477 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4478 * @buffer: The ring buffer
4479 * @cpu: The CPU buffer to test
4481 bool ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
4483 struct ring_buffer_per_cpu
*cpu_buffer
;
4484 unsigned long flags
;
4488 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4491 cpu_buffer
= buffer
->buffers
[cpu
];
4492 local_irq_save(flags
);
4493 dolock
= rb_reader_lock(cpu_buffer
);
4494 ret
= rb_per_cpu_empty(cpu_buffer
);
4495 rb_reader_unlock(cpu_buffer
, dolock
);
4496 local_irq_restore(flags
);
4500 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
4502 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4504 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4505 * @buffer_a: One buffer to swap with
4506 * @buffer_b: The other buffer to swap with
4508 * This function is useful for tracers that want to take a "snapshot"
4509 * of a CPU buffer and has another back up buffer lying around.
4510 * it is expected that the tracer handles the cpu buffer not being
4511 * used at the moment.
4513 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
4514 struct ring_buffer
*buffer_b
, int cpu
)
4516 struct ring_buffer_per_cpu
*cpu_buffer_a
;
4517 struct ring_buffer_per_cpu
*cpu_buffer_b
;
4520 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
4521 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
4524 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
4525 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
4527 /* At least make sure the two buffers are somewhat the same */
4528 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
4533 if (atomic_read(&buffer_a
->record_disabled
))
4536 if (atomic_read(&buffer_b
->record_disabled
))
4539 if (atomic_read(&cpu_buffer_a
->record_disabled
))
4542 if (atomic_read(&cpu_buffer_b
->record_disabled
))
4546 * We can't do a synchronize_rcu here because this
4547 * function can be called in atomic context.
4548 * Normally this will be called from the same CPU as cpu.
4549 * If not it's up to the caller to protect this.
4551 atomic_inc(&cpu_buffer_a
->record_disabled
);
4552 atomic_inc(&cpu_buffer_b
->record_disabled
);
4555 if (local_read(&cpu_buffer_a
->committing
))
4557 if (local_read(&cpu_buffer_b
->committing
))
4560 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
4561 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
4563 cpu_buffer_b
->buffer
= buffer_a
;
4564 cpu_buffer_a
->buffer
= buffer_b
;
4569 atomic_dec(&cpu_buffer_a
->record_disabled
);
4570 atomic_dec(&cpu_buffer_b
->record_disabled
);
4574 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
4575 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4578 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4579 * @buffer: the buffer to allocate for.
4580 * @cpu: the cpu buffer to allocate.
4582 * This function is used in conjunction with ring_buffer_read_page.
4583 * When reading a full page from the ring buffer, these functions
4584 * can be used to speed up the process. The calling function should
4585 * allocate a few pages first with this function. Then when it
4586 * needs to get pages from the ring buffer, it passes the result
4587 * of this function into ring_buffer_read_page, which will swap
4588 * the page that was allocated, with the read page of the buffer.
4591 * The page allocated, or ERR_PTR
4593 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
, int cpu
)
4595 struct ring_buffer_per_cpu
*cpu_buffer
;
4596 struct buffer_data_page
*bpage
= NULL
;
4597 unsigned long flags
;
4600 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4601 return ERR_PTR(-ENODEV
);
4603 cpu_buffer
= buffer
->buffers
[cpu
];
4604 local_irq_save(flags
);
4605 arch_spin_lock(&cpu_buffer
->lock
);
4607 if (cpu_buffer
->free_page
) {
4608 bpage
= cpu_buffer
->free_page
;
4609 cpu_buffer
->free_page
= NULL
;
4612 arch_spin_unlock(&cpu_buffer
->lock
);
4613 local_irq_restore(flags
);
4618 page
= alloc_pages_node(cpu_to_node(cpu
),
4619 GFP_KERNEL
| __GFP_NORETRY
, 0);
4621 return ERR_PTR(-ENOMEM
);
4623 bpage
= page_address(page
);
4626 rb_init_page(bpage
);
4630 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
4633 * ring_buffer_free_read_page - free an allocated read page
4634 * @buffer: the buffer the page was allocate for
4635 * @cpu: the cpu buffer the page came from
4636 * @data: the page to free
4638 * Free a page allocated from ring_buffer_alloc_read_page.
4640 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, int cpu
, void *data
)
4642 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4643 struct buffer_data_page
*bpage
= data
;
4644 struct page
*page
= virt_to_page(bpage
);
4645 unsigned long flags
;
4647 /* If the page is still in use someplace else, we can't reuse it */
4648 if (page_ref_count(page
) > 1)
4651 local_irq_save(flags
);
4652 arch_spin_lock(&cpu_buffer
->lock
);
4654 if (!cpu_buffer
->free_page
) {
4655 cpu_buffer
->free_page
= bpage
;
4659 arch_spin_unlock(&cpu_buffer
->lock
);
4660 local_irq_restore(flags
);
4663 free_page((unsigned long)bpage
);
4665 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
4668 * ring_buffer_read_page - extract a page from the ring buffer
4669 * @buffer: buffer to extract from
4670 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4671 * @len: amount to extract
4672 * @cpu: the cpu of the buffer to extract
4673 * @full: should the extraction only happen when the page is full.
4675 * This function will pull out a page from the ring buffer and consume it.
4676 * @data_page must be the address of the variable that was returned
4677 * from ring_buffer_alloc_read_page. This is because the page might be used
4678 * to swap with a page in the ring buffer.
4681 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4682 * if (IS_ERR(rpage))
4683 * return PTR_ERR(rpage);
4684 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4686 * process_page(rpage, ret);
4688 * When @full is set, the function will not return true unless
4689 * the writer is off the reader page.
4691 * Note: it is up to the calling functions to handle sleeps and wakeups.
4692 * The ring buffer can be used anywhere in the kernel and can not
4693 * blindly call wake_up. The layer that uses the ring buffer must be
4694 * responsible for that.
4697 * >=0 if data has been transferred, returns the offset of consumed data.
4698 * <0 if no data has been transferred.
4700 int ring_buffer_read_page(struct ring_buffer
*buffer
,
4701 void **data_page
, size_t len
, int cpu
, int full
)
4703 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4704 struct ring_buffer_event
*event
;
4705 struct buffer_data_page
*bpage
;
4706 struct buffer_page
*reader
;
4707 unsigned long missed_events
;
4708 unsigned long flags
;
4709 unsigned int commit
;
4714 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4718 * If len is not big enough to hold the page header, then
4719 * we can not copy anything.
4721 if (len
<= BUF_PAGE_HDR_SIZE
)
4724 len
-= BUF_PAGE_HDR_SIZE
;
4733 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4735 reader
= rb_get_reader_page(cpu_buffer
);
4739 event
= rb_reader_event(cpu_buffer
);
4741 read
= reader
->read
;
4742 commit
= rb_page_commit(reader
);
4744 /* Check if any events were dropped */
4745 missed_events
= cpu_buffer
->lost_events
;
4748 * If this page has been partially read or
4749 * if len is not big enough to read the rest of the page or
4750 * a writer is still on the page, then
4751 * we must copy the data from the page to the buffer.
4752 * Otherwise, we can simply swap the page with the one passed in.
4754 if (read
|| (len
< (commit
- read
)) ||
4755 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
4756 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
4757 unsigned int rpos
= read
;
4758 unsigned int pos
= 0;
4764 if (len
> (commit
- read
))
4765 len
= (commit
- read
);
4767 /* Always keep the time extend and data together */
4768 size
= rb_event_ts_length(event
);
4773 /* save the current timestamp, since the user will need it */
4774 save_timestamp
= cpu_buffer
->read_stamp
;
4776 /* Need to copy one event at a time */
4778 /* We need the size of one event, because
4779 * rb_advance_reader only advances by one event,
4780 * whereas rb_event_ts_length may include the size of
4781 * one or two events.
4782 * We have already ensured there's enough space if this
4783 * is a time extend. */
4784 size
= rb_event_length(event
);
4785 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
4789 rb_advance_reader(cpu_buffer
);
4790 rpos
= reader
->read
;
4796 event
= rb_reader_event(cpu_buffer
);
4797 /* Always keep the time extend and data together */
4798 size
= rb_event_ts_length(event
);
4799 } while (len
>= size
);
4802 local_set(&bpage
->commit
, pos
);
4803 bpage
->time_stamp
= save_timestamp
;
4805 /* we copied everything to the beginning */
4808 /* update the entry counter */
4809 cpu_buffer
->read
+= rb_page_entries(reader
);
4810 cpu_buffer
->read_bytes
+= BUF_PAGE_SIZE
;
4812 /* swap the pages */
4813 rb_init_page(bpage
);
4814 bpage
= reader
->page
;
4815 reader
->page
= *data_page
;
4816 local_set(&reader
->write
, 0);
4817 local_set(&reader
->entries
, 0);
4822 * Use the real_end for the data size,
4823 * This gives us a chance to store the lost events
4826 if (reader
->real_end
)
4827 local_set(&bpage
->commit
, reader
->real_end
);
4831 cpu_buffer
->lost_events
= 0;
4833 commit
= local_read(&bpage
->commit
);
4835 * Set a flag in the commit field if we lost events
4837 if (missed_events
) {
4838 /* If there is room at the end of the page to save the
4839 * missed events, then record it there.
4841 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
4842 memcpy(&bpage
->data
[commit
], &missed_events
,
4843 sizeof(missed_events
));
4844 local_add(RB_MISSED_STORED
, &bpage
->commit
);
4845 commit
+= sizeof(missed_events
);
4847 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
4851 * This page may be off to user land. Zero it out here.
4853 if (commit
< BUF_PAGE_SIZE
)
4854 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
4857 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4862 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
4865 * We only allocate new buffers, never free them if the CPU goes down.
4866 * If we were to free the buffer, then the user would lose any trace that was in
4869 int trace_rb_cpu_prepare(unsigned int cpu
, struct hlist_node
*node
)
4871 struct ring_buffer
*buffer
;
4874 unsigned long nr_pages
;
4876 buffer
= container_of(node
, struct ring_buffer
, node
);
4877 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
4882 /* check if all cpu sizes are same */
4883 for_each_buffer_cpu(buffer
, cpu_i
) {
4884 /* fill in the size from first enabled cpu */
4886 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
4887 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
4892 /* allocate minimum pages, user can later expand it */
4895 buffer
->buffers
[cpu
] =
4896 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
4897 if (!buffer
->buffers
[cpu
]) {
4898 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4903 cpumask_set_cpu(cpu
, buffer
->cpumask
);
4907 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4909 * This is a basic integrity check of the ring buffer.
4910 * Late in the boot cycle this test will run when configured in.
4911 * It will kick off a thread per CPU that will go into a loop
4912 * writing to the per cpu ring buffer various sizes of data.
4913 * Some of the data will be large items, some small.
4915 * Another thread is created that goes into a spin, sending out
4916 * IPIs to the other CPUs to also write into the ring buffer.
4917 * this is to test the nesting ability of the buffer.
4919 * Basic stats are recorded and reported. If something in the
4920 * ring buffer should happen that's not expected, a big warning
4921 * is displayed and all ring buffers are disabled.
4923 static struct task_struct
*rb_threads
[NR_CPUS
] __initdata
;
4925 struct rb_test_data
{
4926 struct ring_buffer
*buffer
;
4927 unsigned long events
;
4928 unsigned long bytes_written
;
4929 unsigned long bytes_alloc
;
4930 unsigned long bytes_dropped
;
4931 unsigned long events_nested
;
4932 unsigned long bytes_written_nested
;
4933 unsigned long bytes_alloc_nested
;
4934 unsigned long bytes_dropped_nested
;
4935 int min_size_nested
;
4936 int max_size_nested
;
4943 static struct rb_test_data rb_data
[NR_CPUS
] __initdata
;
4946 #define RB_TEST_BUFFER_SIZE 1048576
4948 static char rb_string
[] __initdata
=
4949 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4950 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4951 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4953 static bool rb_test_started __initdata
;
4960 static __init
int rb_write_something(struct rb_test_data
*data
, bool nested
)
4962 struct ring_buffer_event
*event
;
4963 struct rb_item
*item
;
4970 /* Have nested writes different that what is written */
4971 cnt
= data
->cnt
+ (nested
? 27 : 0);
4973 /* Multiply cnt by ~e, to make some unique increment */
4974 size
= (cnt
* 68 / 25) % (sizeof(rb_string
) - 1);
4976 len
= size
+ sizeof(struct rb_item
);
4978 started
= rb_test_started
;
4979 /* read rb_test_started before checking buffer enabled */
4982 event
= ring_buffer_lock_reserve(data
->buffer
, len
);
4984 /* Ignore dropped events before test starts. */
4987 data
->bytes_dropped
+= len
;
4989 data
->bytes_dropped_nested
+= len
;
4994 event_len
= ring_buffer_event_length(event
);
4996 if (RB_WARN_ON(data
->buffer
, event_len
< len
))
4999 item
= ring_buffer_event_data(event
);
5001 memcpy(item
->str
, rb_string
, size
);
5004 data
->bytes_alloc_nested
+= event_len
;
5005 data
->bytes_written_nested
+= len
;
5006 data
->events_nested
++;
5007 if (!data
->min_size_nested
|| len
< data
->min_size_nested
)
5008 data
->min_size_nested
= len
;
5009 if (len
> data
->max_size_nested
)
5010 data
->max_size_nested
= len
;
5012 data
->bytes_alloc
+= event_len
;
5013 data
->bytes_written
+= len
;
5015 if (!data
->min_size
|| len
< data
->min_size
)
5016 data
->max_size
= len
;
5017 if (len
> data
->max_size
)
5018 data
->max_size
= len
;
5022 ring_buffer_unlock_commit(data
->buffer
, event
);
5027 static __init
int rb_test(void *arg
)
5029 struct rb_test_data
*data
= arg
;
5031 while (!kthread_should_stop()) {
5032 rb_write_something(data
, false);
5035 set_current_state(TASK_INTERRUPTIBLE
);
5036 /* Now sleep between a min of 100-300us and a max of 1ms */
5037 usleep_range(((data
->cnt
% 3) + 1) * 100, 1000);
5043 static __init
void rb_ipi(void *ignore
)
5045 struct rb_test_data
*data
;
5046 int cpu
= smp_processor_id();
5048 data
= &rb_data
[cpu
];
5049 rb_write_something(data
, true);
5052 static __init
int rb_hammer_test(void *arg
)
5054 while (!kthread_should_stop()) {
5056 /* Send an IPI to all cpus to write data! */
5057 smp_call_function(rb_ipi
, NULL
, 1);
5058 /* No sleep, but for non preempt, let others run */
5065 static __init
int test_ringbuffer(void)
5067 struct task_struct
*rb_hammer
;
5068 struct ring_buffer
*buffer
;
5072 if (security_locked_down(LOCKDOWN_TRACEFS
)) {
5073 pr_warning("Lockdown is enabled, skipping ring buffer tests\n");
5077 pr_info("Running ring buffer tests...\n");
5079 buffer
= ring_buffer_alloc(RB_TEST_BUFFER_SIZE
, RB_FL_OVERWRITE
);
5080 if (WARN_ON(!buffer
))
5083 /* Disable buffer so that threads can't write to it yet */
5084 ring_buffer_record_off(buffer
);
5086 for_each_online_cpu(cpu
) {
5087 rb_data
[cpu
].buffer
= buffer
;
5088 rb_data
[cpu
].cpu
= cpu
;
5089 rb_data
[cpu
].cnt
= cpu
;
5090 rb_threads
[cpu
] = kthread_create(rb_test
, &rb_data
[cpu
],
5091 "rbtester/%d", cpu
);
5092 if (WARN_ON(IS_ERR(rb_threads
[cpu
]))) {
5093 pr_cont("FAILED\n");
5094 ret
= PTR_ERR(rb_threads
[cpu
]);
5098 kthread_bind(rb_threads
[cpu
], cpu
);
5099 wake_up_process(rb_threads
[cpu
]);
5102 /* Now create the rb hammer! */
5103 rb_hammer
= kthread_run(rb_hammer_test
, NULL
, "rbhammer");
5104 if (WARN_ON(IS_ERR(rb_hammer
))) {
5105 pr_cont("FAILED\n");
5106 ret
= PTR_ERR(rb_hammer
);
5110 ring_buffer_record_on(buffer
);
5112 * Show buffer is enabled before setting rb_test_started.
5113 * Yes there's a small race window where events could be
5114 * dropped and the thread wont catch it. But when a ring
5115 * buffer gets enabled, there will always be some kind of
5116 * delay before other CPUs see it. Thus, we don't care about
5117 * those dropped events. We care about events dropped after
5118 * the threads see that the buffer is active.
5121 rb_test_started
= true;
5123 set_current_state(TASK_INTERRUPTIBLE
);
5124 /* Just run for 10 seconds */;
5125 schedule_timeout(10 * HZ
);
5127 kthread_stop(rb_hammer
);
5130 for_each_online_cpu(cpu
) {
5131 if (!rb_threads
[cpu
])
5133 kthread_stop(rb_threads
[cpu
]);
5136 ring_buffer_free(buffer
);
5141 pr_info("finished\n");
5142 for_each_online_cpu(cpu
) {
5143 struct ring_buffer_event
*event
;
5144 struct rb_test_data
*data
= &rb_data
[cpu
];
5145 struct rb_item
*item
;
5146 unsigned long total_events
;
5147 unsigned long total_dropped
;
5148 unsigned long total_written
;
5149 unsigned long total_alloc
;
5150 unsigned long total_read
= 0;
5151 unsigned long total_size
= 0;
5152 unsigned long total_len
= 0;
5153 unsigned long total_lost
= 0;
5156 int small_event_size
;
5160 total_events
= data
->events
+ data
->events_nested
;
5161 total_written
= data
->bytes_written
+ data
->bytes_written_nested
;
5162 total_alloc
= data
->bytes_alloc
+ data
->bytes_alloc_nested
;
5163 total_dropped
= data
->bytes_dropped
+ data
->bytes_dropped_nested
;
5165 big_event_size
= data
->max_size
+ data
->max_size_nested
;
5166 small_event_size
= data
->min_size
+ data
->min_size_nested
;
5168 pr_info("CPU %d:\n", cpu
);
5169 pr_info(" events: %ld\n", total_events
);
5170 pr_info(" dropped bytes: %ld\n", total_dropped
);
5171 pr_info(" alloced bytes: %ld\n", total_alloc
);
5172 pr_info(" written bytes: %ld\n", total_written
);
5173 pr_info(" biggest event: %d\n", big_event_size
);
5174 pr_info(" smallest event: %d\n", small_event_size
);
5176 if (RB_WARN_ON(buffer
, total_dropped
))
5181 while ((event
= ring_buffer_consume(buffer
, cpu
, NULL
, &lost
))) {
5183 item
= ring_buffer_event_data(event
);
5184 total_len
+= ring_buffer_event_length(event
);
5185 total_size
+= item
->size
+ sizeof(struct rb_item
);
5186 if (memcmp(&item
->str
[0], rb_string
, item
->size
) != 0) {
5187 pr_info("FAILED!\n");
5188 pr_info("buffer had: %.*s\n", item
->size
, item
->str
);
5189 pr_info("expected: %.*s\n", item
->size
, rb_string
);
5190 RB_WARN_ON(buffer
, 1);
5201 pr_info(" read events: %ld\n", total_read
);
5202 pr_info(" lost events: %ld\n", total_lost
);
5203 pr_info(" total events: %ld\n", total_lost
+ total_read
);
5204 pr_info(" recorded len bytes: %ld\n", total_len
);
5205 pr_info(" recorded size bytes: %ld\n", total_size
);
5207 pr_info(" With dropped events, record len and size may not match\n"
5208 " alloced and written from above\n");
5210 if (RB_WARN_ON(buffer
, total_len
!= total_alloc
||
5211 total_size
!= total_written
))
5214 if (RB_WARN_ON(buffer
, total_lost
+ total_read
!= total_events
))
5220 pr_info("Ring buffer PASSED!\n");
5222 ring_buffer_free(buffer
);
5226 late_initcall(test_ringbuffer
);
5227 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */