1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
7 #include <linux/trace_recursion.h>
8 #include <linux/trace_events.h>
9 #include <linux/ring_buffer.h>
10 #include <linux/trace_clock.h>
11 #include <linux/sched/clock.h>
12 #include <linux/trace_seq.h>
13 #include <linux/spinlock.h>
14 #include <linux/irq_work.h>
15 #include <linux/security.h>
16 #include <linux/uaccess.h>
17 #include <linux/hardirq.h>
18 #include <linux/kthread.h> /* for self test */
19 #include <linux/module.h>
20 #include <linux/percpu.h>
21 #include <linux/mutex.h>
22 #include <linux/delay.h>
23 #include <linux/slab.h>
24 #include <linux/init.h>
25 #include <linux/hash.h>
26 #include <linux/list.h>
27 #include <linux/cpu.h>
28 #include <linux/oom.h>
30 #include <asm/local64.h>
31 #include <asm/local.h>
34 * The "absolute" timestamp in the buffer is only 59 bits.
35 * If a clock has the 5 MSBs set, it needs to be saved and
38 #define TS_MSB (0xf8ULL << 56)
39 #define ABS_TS_MASK (~TS_MSB)
41 static void update_pages_handler(struct work_struct
*work
);
44 * The ring buffer header is special. We must manually up keep it.
46 int ring_buffer_print_entry_header(struct trace_seq
*s
)
48 trace_seq_puts(s
, "# compressed entry header\n");
49 trace_seq_puts(s
, "\ttype_len : 5 bits\n");
50 trace_seq_puts(s
, "\ttime_delta : 27 bits\n");
51 trace_seq_puts(s
, "\tarray : 32 bits\n");
52 trace_seq_putc(s
, '\n');
53 trace_seq_printf(s
, "\tpadding : type == %d\n",
54 RINGBUF_TYPE_PADDING
);
55 trace_seq_printf(s
, "\ttime_extend : type == %d\n",
56 RINGBUF_TYPE_TIME_EXTEND
);
57 trace_seq_printf(s
, "\ttime_stamp : type == %d\n",
58 RINGBUF_TYPE_TIME_STAMP
);
59 trace_seq_printf(s
, "\tdata max type_len == %d\n",
60 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
62 return !trace_seq_has_overflowed(s
);
66 * The ring buffer is made up of a list of pages. A separate list of pages is
67 * allocated for each CPU. A writer may only write to a buffer that is
68 * associated with the CPU it is currently executing on. A reader may read
69 * from any per cpu buffer.
71 * The reader is special. For each per cpu buffer, the reader has its own
72 * reader page. When a reader has read the entire reader page, this reader
73 * page is swapped with another page in the ring buffer.
75 * Now, as long as the writer is off the reader page, the reader can do what
76 * ever it wants with that page. The writer will never write to that page
77 * again (as long as it is out of the ring buffer).
79 * Here's some silly ASCII art.
82 * |reader| RING BUFFER
84 * +------+ +---+ +---+ +---+
93 * |reader| RING BUFFER
94 * |page |------------------v
95 * +------+ +---+ +---+ +---+
104 * |reader| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
108 * | +---+ +---+ +---+
111 * +------------------------------+
115 * |buffer| RING BUFFER
116 * |page |------------------v
117 * +------+ +---+ +---+ +---+
119 * | New +---+ +---+ +---+
122 * +------------------------------+
125 * After we make this swap, the reader can hand this page off to the splice
126 * code and be done with it. It can even allocate a new page if it needs to
127 * and swap that into the ring buffer.
129 * We will be using cmpxchg soon to make all this lockless.
133 /* Used for individual buffers (after the counter) */
134 #define RB_BUFFER_OFF (1 << 20)
136 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
138 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
139 #define RB_ALIGNMENT 4U
140 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
141 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
143 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
144 # define RB_FORCE_8BYTE_ALIGNMENT 0
145 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
147 # define RB_FORCE_8BYTE_ALIGNMENT 1
148 # define RB_ARCH_ALIGNMENT 8U
151 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
153 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
154 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
157 RB_LEN_TIME_EXTEND
= 8,
158 RB_LEN_TIME_STAMP
= 8,
161 #define skip_time_extend(event) \
162 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
164 #define extended_time(event) \
165 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
167 static inline bool rb_null_event(struct ring_buffer_event
*event
)
169 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
172 static void rb_event_set_padding(struct ring_buffer_event
*event
)
174 /* padding has a NULL time_delta */
175 event
->type_len
= RINGBUF_TYPE_PADDING
;
176 event
->time_delta
= 0;
180 rb_event_data_length(struct ring_buffer_event
*event
)
185 length
= event
->type_len
* RB_ALIGNMENT
;
187 length
= event
->array
[0];
188 return length
+ RB_EVNT_HDR_SIZE
;
192 * Return the length of the given event. Will return
193 * the length of the time extend if the event is a
196 static inline unsigned
197 rb_event_length(struct ring_buffer_event
*event
)
199 switch (event
->type_len
) {
200 case RINGBUF_TYPE_PADDING
:
201 if (rb_null_event(event
))
204 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
206 case RINGBUF_TYPE_TIME_EXTEND
:
207 return RB_LEN_TIME_EXTEND
;
209 case RINGBUF_TYPE_TIME_STAMP
:
210 return RB_LEN_TIME_STAMP
;
212 case RINGBUF_TYPE_DATA
:
213 return rb_event_data_length(event
);
222 * Return total length of time extend and data,
223 * or just the event length for all other events.
225 static inline unsigned
226 rb_event_ts_length(struct ring_buffer_event
*event
)
230 if (extended_time(event
)) {
231 /* time extends include the data event after it */
232 len
= RB_LEN_TIME_EXTEND
;
233 event
= skip_time_extend(event
);
235 return len
+ rb_event_length(event
);
239 * ring_buffer_event_length - return the length of the event
240 * @event: the event to get the length of
242 * Returns the size of the data load of a data event.
243 * If the event is something other than a data event, it
244 * returns the size of the event itself. With the exception
245 * of a TIME EXTEND, where it still returns the size of the
246 * data load of the data event after it.
248 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
252 if (extended_time(event
))
253 event
= skip_time_extend(event
);
255 length
= rb_event_length(event
);
256 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
258 length
-= RB_EVNT_HDR_SIZE
;
259 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
260 length
-= sizeof(event
->array
[0]);
263 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
265 /* inline for ring buffer fast paths */
266 static __always_inline
void *
267 rb_event_data(struct ring_buffer_event
*event
)
269 if (extended_time(event
))
270 event
= skip_time_extend(event
);
271 WARN_ON_ONCE(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
272 /* If length is in len field, then array[0] has the data */
274 return (void *)&event
->array
[0];
275 /* Otherwise length is in array[0] and array[1] has the data */
276 return (void *)&event
->array
[1];
280 * ring_buffer_event_data - return the data of the event
281 * @event: the event to get the data from
283 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
285 return rb_event_data(event
);
287 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
289 #define for_each_buffer_cpu(buffer, cpu) \
290 for_each_cpu(cpu, buffer->cpumask)
292 #define for_each_online_buffer_cpu(buffer, cpu) \
293 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
296 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
297 #define TS_DELTA_TEST (~TS_MASK)
299 static u64
rb_event_time_stamp(struct ring_buffer_event
*event
)
303 ts
= event
->array
[0];
305 ts
+= event
->time_delta
;
310 /* Flag when events were overwritten */
311 #define RB_MISSED_EVENTS (1 << 31)
312 /* Missed count stored at end */
313 #define RB_MISSED_STORED (1 << 30)
315 struct buffer_data_page
{
316 u64 time_stamp
; /* page time stamp */
317 local_t commit
; /* write committed index */
318 unsigned char data
[] RB_ALIGN_DATA
; /* data of buffer page */
321 struct buffer_data_read_page
{
322 unsigned order
; /* order of the page */
323 struct buffer_data_page
*data
; /* actual data, stored in this page */
327 * Note, the buffer_page list must be first. The buffer pages
328 * are allocated in cache lines, which means that each buffer
329 * page will be at the beginning of a cache line, and thus
330 * the least significant bits will be zero. We use this to
331 * add flags in the list struct pointers, to make the ring buffer
335 struct list_head list
; /* list of buffer pages */
336 local_t write
; /* index for next write */
337 unsigned read
; /* index for next read */
338 local_t entries
; /* entries on this page */
339 unsigned long real_end
; /* real end of data */
340 unsigned order
; /* order of the page */
341 struct buffer_data_page
*page
; /* Actual data page */
345 * The buffer page counters, write and entries, must be reset
346 * atomically when crossing page boundaries. To synchronize this
347 * update, two counters are inserted into the number. One is
348 * the actual counter for the write position or count on the page.
350 * The other is a counter of updaters. Before an update happens
351 * the update partition of the counter is incremented. This will
352 * allow the updater to update the counter atomically.
354 * The counter is 20 bits, and the state data is 12.
356 #define RB_WRITE_MASK 0xfffff
357 #define RB_WRITE_INTCNT (1 << 20)
359 static void rb_init_page(struct buffer_data_page
*bpage
)
361 local_set(&bpage
->commit
, 0);
364 static __always_inline
unsigned int rb_page_commit(struct buffer_page
*bpage
)
366 return local_read(&bpage
->page
->commit
);
369 static void free_buffer_page(struct buffer_page
*bpage
)
371 free_pages((unsigned long)bpage
->page
, bpage
->order
);
376 * We need to fit the time_stamp delta into 27 bits.
378 static inline bool test_time_stamp(u64 delta
)
380 return !!(delta
& TS_DELTA_TEST
);
384 struct irq_work work
;
385 wait_queue_head_t waiters
;
386 wait_queue_head_t full_waiters
;
388 bool waiters_pending
;
389 bool full_waiters_pending
;
394 * Structure to hold event state and handle nested events.
396 struct rb_event_info
{
401 unsigned long length
;
402 struct buffer_page
*tail_page
;
407 * Used for the add_timestamp
409 * EXTEND - wants a time extend
410 * ABSOLUTE - the buffer requests all events to have absolute time stamps
411 * FORCE - force a full time stamp.
414 RB_ADD_STAMP_NONE
= 0,
415 RB_ADD_STAMP_EXTEND
= BIT(1),
416 RB_ADD_STAMP_ABSOLUTE
= BIT(2),
417 RB_ADD_STAMP_FORCE
= BIT(3)
420 * Used for which event context the event is in.
427 * See trace_recursive_lock() comment below for more details.
438 struct rb_time_struct
{
441 typedef struct rb_time_struct rb_time_t
;
446 * head_page == tail_page && head == tail then buffer is empty.
448 struct ring_buffer_per_cpu
{
450 atomic_t record_disabled
;
451 atomic_t resize_disabled
;
452 struct trace_buffer
*buffer
;
453 raw_spinlock_t reader_lock
; /* serialize readers */
454 arch_spinlock_t lock
;
455 struct lock_class_key lock_key
;
456 struct buffer_data_page
*free_page
;
457 unsigned long nr_pages
;
458 unsigned int current_context
;
459 struct list_head
*pages
;
460 struct buffer_page
*head_page
; /* read from head */
461 struct buffer_page
*tail_page
; /* write to tail */
462 struct buffer_page
*commit_page
; /* committed pages */
463 struct buffer_page
*reader_page
;
464 unsigned long lost_events
;
465 unsigned long last_overrun
;
467 local_t entries_bytes
;
470 local_t commit_overrun
;
471 local_t dropped_events
;
474 local_t pages_touched
;
477 long last_pages_touch
;
478 size_t shortest_full
;
480 unsigned long read_bytes
;
481 rb_time_t write_stamp
;
482 rb_time_t before_stamp
;
483 u64 event_stamp
[MAX_NEST
];
485 /* pages removed since last reset */
486 unsigned long pages_removed
;
487 /* ring buffer pages to update, > 0 to add, < 0 to remove */
488 long nr_pages_to_update
;
489 struct list_head new_pages
; /* new pages to add */
490 struct work_struct update_pages_work
;
491 struct completion update_done
;
493 struct rb_irq_work irq_work
;
496 struct trace_buffer
{
499 atomic_t record_disabled
;
501 cpumask_var_t cpumask
;
503 struct lock_class_key
*reader_lock_key
;
507 struct ring_buffer_per_cpu
**buffers
;
509 struct hlist_node node
;
512 struct rb_irq_work irq_work
;
515 unsigned int subbuf_size
;
516 unsigned int subbuf_order
;
517 unsigned int max_data_size
;
520 struct ring_buffer_iter
{
521 struct ring_buffer_per_cpu
*cpu_buffer
;
523 unsigned long next_event
;
524 struct buffer_page
*head_page
;
525 struct buffer_page
*cache_reader_page
;
526 unsigned long cache_read
;
527 unsigned long cache_pages_removed
;
530 struct ring_buffer_event
*event
;
535 int ring_buffer_print_page_header(struct trace_buffer
*buffer
, struct trace_seq
*s
)
537 struct buffer_data_page field
;
539 trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
540 "offset:0;\tsize:%u;\tsigned:%u;\n",
541 (unsigned int)sizeof(field
.time_stamp
),
542 (unsigned int)is_signed_type(u64
));
544 trace_seq_printf(s
, "\tfield: local_t commit;\t"
545 "offset:%u;\tsize:%u;\tsigned:%u;\n",
546 (unsigned int)offsetof(typeof(field
), commit
),
547 (unsigned int)sizeof(field
.commit
),
548 (unsigned int)is_signed_type(long));
550 trace_seq_printf(s
, "\tfield: int overwrite;\t"
551 "offset:%u;\tsize:%u;\tsigned:%u;\n",
552 (unsigned int)offsetof(typeof(field
), commit
),
554 (unsigned int)is_signed_type(long));
556 trace_seq_printf(s
, "\tfield: char data;\t"
557 "offset:%u;\tsize:%u;\tsigned:%u;\n",
558 (unsigned int)offsetof(typeof(field
), data
),
559 (unsigned int)buffer
->subbuf_size
,
560 (unsigned int)is_signed_type(char));
562 return !trace_seq_has_overflowed(s
);
565 static inline void rb_time_read(rb_time_t
*t
, u64
*ret
)
567 *ret
= local64_read(&t
->time
);
569 static void rb_time_set(rb_time_t
*t
, u64 val
)
571 local64_set(&t
->time
, val
);
575 * Enable this to make sure that the event passed to
576 * ring_buffer_event_time_stamp() is not committed and also
577 * is on the buffer that it passed in.
579 //#define RB_VERIFY_EVENT
580 #ifdef RB_VERIFY_EVENT
581 static struct list_head
*rb_list_head(struct list_head
*list
);
582 static void verify_event(struct ring_buffer_per_cpu
*cpu_buffer
,
585 struct buffer_page
*page
= cpu_buffer
->commit_page
;
586 struct buffer_page
*tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
587 struct list_head
*next
;
589 unsigned long addr
= (unsigned long)event
;
593 /* Make sure the event exists and is not committed yet */
595 if (page
== tail_page
|| WARN_ON_ONCE(stop
++ > 100))
597 commit
= local_read(&page
->page
->commit
);
598 write
= local_read(&page
->write
);
599 if (addr
>= (unsigned long)&page
->page
->data
[commit
] &&
600 addr
< (unsigned long)&page
->page
->data
[write
])
603 next
= rb_list_head(page
->list
.next
);
604 page
= list_entry(next
, struct buffer_page
, list
);
609 static inline void verify_event(struct ring_buffer_per_cpu
*cpu_buffer
,
616 * The absolute time stamp drops the 5 MSBs and some clocks may
617 * require them. The rb_fix_abs_ts() will take a previous full
618 * time stamp, and add the 5 MSB of that time stamp on to the
619 * saved absolute time stamp. Then they are compared in case of
620 * the unlikely event that the latest time stamp incremented
623 static inline u64
rb_fix_abs_ts(u64 abs
, u64 save_ts
)
625 if (save_ts
& TS_MSB
) {
626 abs
|= save_ts
& TS_MSB
;
627 /* Check for overflow */
628 if (unlikely(abs
< save_ts
))
634 static inline u64
rb_time_stamp(struct trace_buffer
*buffer
);
637 * ring_buffer_event_time_stamp - return the event's current time stamp
638 * @buffer: The buffer that the event is on
639 * @event: the event to get the time stamp of
641 * Note, this must be called after @event is reserved, and before it is
642 * committed to the ring buffer. And must be called from the same
643 * context where the event was reserved (normal, softirq, irq, etc).
645 * Returns the time stamp associated with the current event.
646 * If the event has an extended time stamp, then that is used as
647 * the time stamp to return.
648 * In the highly unlikely case that the event was nested more than
649 * the max nesting, then the write_stamp of the buffer is returned,
650 * otherwise current time is returned, but that really neither of
651 * the last two cases should ever happen.
653 u64
ring_buffer_event_time_stamp(struct trace_buffer
*buffer
,
654 struct ring_buffer_event
*event
)
656 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[smp_processor_id()];
660 /* If the event includes an absolute time, then just use that */
661 if (event
->type_len
== RINGBUF_TYPE_TIME_STAMP
) {
662 ts
= rb_event_time_stamp(event
);
663 return rb_fix_abs_ts(ts
, cpu_buffer
->tail_page
->page
->time_stamp
);
666 nest
= local_read(&cpu_buffer
->committing
);
667 verify_event(cpu_buffer
, event
);
668 if (WARN_ON_ONCE(!nest
))
671 /* Read the current saved nesting level time stamp */
672 if (likely(--nest
< MAX_NEST
))
673 return cpu_buffer
->event_stamp
[nest
];
675 /* Shouldn't happen, warn if it does */
676 WARN_ONCE(1, "nest (%d) greater than max", nest
);
679 rb_time_read(&cpu_buffer
->write_stamp
, &ts
);
685 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
686 * @buffer: The ring_buffer to get the number of pages from
687 * @cpu: The cpu of the ring_buffer to get the number of pages from
689 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
691 size_t ring_buffer_nr_pages(struct trace_buffer
*buffer
, int cpu
)
693 return buffer
->buffers
[cpu
]->nr_pages
;
697 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
698 * @buffer: The ring_buffer to get the number of pages from
699 * @cpu: The cpu of the ring_buffer to get the number of pages from
701 * Returns the number of pages that have content in the ring buffer.
703 size_t ring_buffer_nr_dirty_pages(struct trace_buffer
*buffer
, int cpu
)
709 read
= local_read(&buffer
->buffers
[cpu
]->pages_read
);
710 lost
= local_read(&buffer
->buffers
[cpu
]->pages_lost
);
711 cnt
= local_read(&buffer
->buffers
[cpu
]->pages_touched
);
713 if (WARN_ON_ONCE(cnt
< lost
))
718 /* The reader can read an empty page, but not more than that */
720 WARN_ON_ONCE(read
> cnt
+ 1);
727 static __always_inline
bool full_hit(struct trace_buffer
*buffer
, int cpu
, int full
)
729 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
733 nr_pages
= cpu_buffer
->nr_pages
;
734 if (!nr_pages
|| !full
)
738 * Add one as dirty will never equal nr_pages, as the sub-buffer
739 * that the writer is on is not counted as dirty.
740 * This is needed if "buffer_percent" is set to 100.
742 dirty
= ring_buffer_nr_dirty_pages(buffer
, cpu
) + 1;
744 return (dirty
* 100) >= (full
* nr_pages
);
748 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
750 * Schedules a delayed work to wake up any task that is blocked on the
751 * ring buffer waiters queue.
753 static void rb_wake_up_waiters(struct irq_work
*work
)
755 struct rb_irq_work
*rbwork
= container_of(work
, struct rb_irq_work
, work
);
757 wake_up_all(&rbwork
->waiters
);
758 if (rbwork
->full_waiters_pending
|| rbwork
->wakeup_full
) {
759 rbwork
->wakeup_full
= false;
760 rbwork
->full_waiters_pending
= false;
761 wake_up_all(&rbwork
->full_waiters
);
766 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
767 * @buffer: The ring buffer to wake waiters on
768 * @cpu: The CPU buffer to wake waiters on
770 * In the case of a file that represents a ring buffer is closing,
771 * it is prudent to wake up any waiters that are on this.
773 void ring_buffer_wake_waiters(struct trace_buffer
*buffer
, int cpu
)
775 struct ring_buffer_per_cpu
*cpu_buffer
;
776 struct rb_irq_work
*rbwork
;
781 if (cpu
== RING_BUFFER_ALL_CPUS
) {
783 /* Wake up individual ones too. One level recursion */
784 for_each_buffer_cpu(buffer
, cpu
)
785 ring_buffer_wake_waiters(buffer
, cpu
);
787 rbwork
= &buffer
->irq_work
;
789 if (WARN_ON_ONCE(!buffer
->buffers
))
791 if (WARN_ON_ONCE(cpu
>= nr_cpu_ids
))
794 cpu_buffer
= buffer
->buffers
[cpu
];
795 /* The CPU buffer may not have been initialized yet */
798 rbwork
= &cpu_buffer
->irq_work
;
801 rbwork
->wait_index
++;
802 /* make sure the waiters see the new index */
805 /* This can be called in any context */
806 irq_work_queue(&rbwork
->work
);
810 * ring_buffer_wait - wait for input to the ring buffer
811 * @buffer: buffer to wait on
812 * @cpu: the cpu buffer to wait on
813 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
815 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
816 * as data is added to any of the @buffer's cpu buffers. Otherwise
817 * it will wait for data to be added to a specific cpu buffer.
819 int ring_buffer_wait(struct trace_buffer
*buffer
, int cpu
, int full
)
821 struct ring_buffer_per_cpu
*cpu_buffer
;
823 struct rb_irq_work
*work
;
828 * Depending on what the caller is waiting for, either any
829 * data in any cpu buffer, or a specific buffer, put the
830 * caller on the appropriate wait queue.
832 if (cpu
== RING_BUFFER_ALL_CPUS
) {
833 work
= &buffer
->irq_work
;
834 /* Full only makes sense on per cpu reads */
837 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
839 cpu_buffer
= buffer
->buffers
[cpu
];
840 work
= &cpu_buffer
->irq_work
;
843 wait_index
= READ_ONCE(work
->wait_index
);
847 prepare_to_wait(&work
->full_waiters
, &wait
, TASK_INTERRUPTIBLE
);
849 prepare_to_wait(&work
->waiters
, &wait
, TASK_INTERRUPTIBLE
);
852 * The events can happen in critical sections where
853 * checking a work queue can cause deadlocks.
854 * After adding a task to the queue, this flag is set
855 * only to notify events to try to wake up the queue
858 * We don't clear it even if the buffer is no longer
859 * empty. The flag only causes the next event to run
860 * irq_work to do the work queue wake up. The worse
861 * that can happen if we race with !trace_empty() is that
862 * an event will cause an irq_work to try to wake up
865 * There's no reason to protect this flag either, as
866 * the work queue and irq_work logic will do the necessary
867 * synchronization for the wake ups. The only thing
868 * that is necessary is that the wake up happens after
869 * a task has been queued. It's OK for spurious wake ups.
872 work
->full_waiters_pending
= true;
874 work
->waiters_pending
= true;
876 if (signal_pending(current
)) {
881 if (cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
))
884 if (cpu
!= RING_BUFFER_ALL_CPUS
&&
885 !ring_buffer_empty_cpu(buffer
, cpu
)) {
893 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
894 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
895 done
= !pagebusy
&& full_hit(buffer
, cpu
, full
);
897 if (!cpu_buffer
->shortest_full
||
898 cpu_buffer
->shortest_full
> full
)
899 cpu_buffer
->shortest_full
= full
;
900 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
907 /* Make sure to see the new wait index */
909 if (wait_index
!= work
->wait_index
)
914 finish_wait(&work
->full_waiters
, &wait
);
916 finish_wait(&work
->waiters
, &wait
);
922 * ring_buffer_poll_wait - poll on buffer input
923 * @buffer: buffer to wait on
924 * @cpu: the cpu buffer to wait on
925 * @filp: the file descriptor
926 * @poll_table: The poll descriptor
927 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
929 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
930 * as data is added to any of the @buffer's cpu buffers. Otherwise
931 * it will wait for data to be added to a specific cpu buffer.
933 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
936 __poll_t
ring_buffer_poll_wait(struct trace_buffer
*buffer
, int cpu
,
937 struct file
*filp
, poll_table
*poll_table
, int full
)
939 struct ring_buffer_per_cpu
*cpu_buffer
;
940 struct rb_irq_work
*work
;
942 if (cpu
== RING_BUFFER_ALL_CPUS
) {
943 work
= &buffer
->irq_work
;
946 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
949 cpu_buffer
= buffer
->buffers
[cpu
];
950 work
= &cpu_buffer
->irq_work
;
954 poll_wait(filp
, &work
->full_waiters
, poll_table
);
955 work
->full_waiters_pending
= true;
956 if (!cpu_buffer
->shortest_full
||
957 cpu_buffer
->shortest_full
> full
)
958 cpu_buffer
->shortest_full
= full
;
960 poll_wait(filp
, &work
->waiters
, poll_table
);
961 work
->waiters_pending
= true;
965 * There's a tight race between setting the waiters_pending and
966 * checking if the ring buffer is empty. Once the waiters_pending bit
967 * is set, the next event will wake the task up, but we can get stuck
968 * if there's only a single event in.
970 * FIXME: Ideally, we need a memory barrier on the writer side as well,
971 * but adding a memory barrier to all events will cause too much of a
972 * performance hit in the fast path. We only need a memory barrier when
973 * the buffer goes from empty to having content. But as this race is
974 * extremely small, and it's not a problem if another event comes in, we
980 return full_hit(buffer
, cpu
, full
) ? EPOLLIN
| EPOLLRDNORM
: 0;
982 if ((cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
)) ||
983 (cpu
!= RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty_cpu(buffer
, cpu
)))
984 return EPOLLIN
| EPOLLRDNORM
;
988 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
989 #define RB_WARN_ON(b, cond) \
991 int _____ret = unlikely(cond); \
993 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
994 struct ring_buffer_per_cpu *__b = \
996 atomic_inc(&__b->buffer->record_disabled); \
998 atomic_inc(&b->record_disabled); \
1004 /* Up this if you want to test the TIME_EXTENTS and normalization */
1005 #define DEBUG_SHIFT 0
1007 static inline u64
rb_time_stamp(struct trace_buffer
*buffer
)
1011 /* Skip retpolines :-( */
1012 if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE
) && likely(buffer
->clock
== trace_clock_local
))
1013 ts
= trace_clock_local();
1015 ts
= buffer
->clock();
1017 /* shift to debug/test normalization and TIME_EXTENTS */
1018 return ts
<< DEBUG_SHIFT
;
1021 u64
ring_buffer_time_stamp(struct trace_buffer
*buffer
)
1025 preempt_disable_notrace();
1026 time
= rb_time_stamp(buffer
);
1027 preempt_enable_notrace();
1031 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
1033 void ring_buffer_normalize_time_stamp(struct trace_buffer
*buffer
,
1036 /* Just stupid testing the normalize function and deltas */
1037 *ts
>>= DEBUG_SHIFT
;
1039 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
1042 * Making the ring buffer lockless makes things tricky.
1043 * Although writes only happen on the CPU that they are on,
1044 * and they only need to worry about interrupts. Reads can
1045 * happen on any CPU.
1047 * The reader page is always off the ring buffer, but when the
1048 * reader finishes with a page, it needs to swap its page with
1049 * a new one from the buffer. The reader needs to take from
1050 * the head (writes go to the tail). But if a writer is in overwrite
1051 * mode and wraps, it must push the head page forward.
1053 * Here lies the problem.
1055 * The reader must be careful to replace only the head page, and
1056 * not another one. As described at the top of the file in the
1057 * ASCII art, the reader sets its old page to point to the next
1058 * page after head. It then sets the page after head to point to
1059 * the old reader page. But if the writer moves the head page
1060 * during this operation, the reader could end up with the tail.
1062 * We use cmpxchg to help prevent this race. We also do something
1063 * special with the page before head. We set the LSB to 1.
1065 * When the writer must push the page forward, it will clear the
1066 * bit that points to the head page, move the head, and then set
1067 * the bit that points to the new head page.
1069 * We also don't want an interrupt coming in and moving the head
1070 * page on another writer. Thus we use the second LSB to catch
1073 * head->list->prev->next bit 1 bit 0
1076 * Points to head page 0 1
1079 * Note we can not trust the prev pointer of the head page, because:
1081 * +----+ +-----+ +-----+
1082 * | |------>| T |---X--->| N |
1084 * +----+ +-----+ +-----+
1087 * +----------| R |----------+ |
1091 * Key: ---X--> HEAD flag set in pointer
1096 * (see __rb_reserve_next() to see where this happens)
1098 * What the above shows is that the reader just swapped out
1099 * the reader page with a page in the buffer, but before it
1100 * could make the new header point back to the new page added
1101 * it was preempted by a writer. The writer moved forward onto
1102 * the new page added by the reader and is about to move forward
1105 * You can see, it is legitimate for the previous pointer of
1106 * the head (or any page) not to point back to itself. But only
1110 #define RB_PAGE_NORMAL 0UL
1111 #define RB_PAGE_HEAD 1UL
1112 #define RB_PAGE_UPDATE 2UL
1115 #define RB_FLAG_MASK 3UL
1117 /* PAGE_MOVED is not part of the mask */
1118 #define RB_PAGE_MOVED 4UL
1121 * rb_list_head - remove any bit
1123 static struct list_head
*rb_list_head(struct list_head
*list
)
1125 unsigned long val
= (unsigned long)list
;
1127 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
1131 * rb_is_head_page - test if the given page is the head page
1133 * Because the reader may move the head_page pointer, we can
1134 * not trust what the head page is (it may be pointing to
1135 * the reader page). But if the next page is a header page,
1136 * its flags will be non zero.
1139 rb_is_head_page(struct buffer_page
*page
, struct list_head
*list
)
1143 val
= (unsigned long)list
->next
;
1145 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
1146 return RB_PAGE_MOVED
;
1148 return val
& RB_FLAG_MASK
;
1154 * The unique thing about the reader page, is that, if the
1155 * writer is ever on it, the previous pointer never points
1156 * back to the reader page.
1158 static bool rb_is_reader_page(struct buffer_page
*page
)
1160 struct list_head
*list
= page
->list
.prev
;
1162 return rb_list_head(list
->next
) != &page
->list
;
1166 * rb_set_list_to_head - set a list_head to be pointing to head.
1168 static void rb_set_list_to_head(struct list_head
*list
)
1172 ptr
= (unsigned long *)&list
->next
;
1173 *ptr
|= RB_PAGE_HEAD
;
1174 *ptr
&= ~RB_PAGE_UPDATE
;
1178 * rb_head_page_activate - sets up head page
1180 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
1182 struct buffer_page
*head
;
1184 head
= cpu_buffer
->head_page
;
1189 * Set the previous list pointer to have the HEAD flag.
1191 rb_set_list_to_head(head
->list
.prev
);
1194 static void rb_list_head_clear(struct list_head
*list
)
1196 unsigned long *ptr
= (unsigned long *)&list
->next
;
1198 *ptr
&= ~RB_FLAG_MASK
;
1202 * rb_head_page_deactivate - clears head page ptr (for free list)
1205 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
1207 struct list_head
*hd
;
1209 /* Go through the whole list and clear any pointers found. */
1210 rb_list_head_clear(cpu_buffer
->pages
);
1212 list_for_each(hd
, cpu_buffer
->pages
)
1213 rb_list_head_clear(hd
);
1216 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
1217 struct buffer_page
*head
,
1218 struct buffer_page
*prev
,
1219 int old_flag
, int new_flag
)
1221 struct list_head
*list
;
1222 unsigned long val
= (unsigned long)&head
->list
;
1227 val
&= ~RB_FLAG_MASK
;
1229 ret
= cmpxchg((unsigned long *)&list
->next
,
1230 val
| old_flag
, val
| new_flag
);
1232 /* check if the reader took the page */
1233 if ((ret
& ~RB_FLAG_MASK
) != val
)
1234 return RB_PAGE_MOVED
;
1236 return ret
& RB_FLAG_MASK
;
1239 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1240 struct buffer_page
*head
,
1241 struct buffer_page
*prev
,
1244 return rb_head_page_set(cpu_buffer
, head
, prev
,
1245 old_flag
, RB_PAGE_UPDATE
);
1248 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
1249 struct buffer_page
*head
,
1250 struct buffer_page
*prev
,
1253 return rb_head_page_set(cpu_buffer
, head
, prev
,
1254 old_flag
, RB_PAGE_HEAD
);
1257 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
1258 struct buffer_page
*head
,
1259 struct buffer_page
*prev
,
1262 return rb_head_page_set(cpu_buffer
, head
, prev
,
1263 old_flag
, RB_PAGE_NORMAL
);
1266 static inline void rb_inc_page(struct buffer_page
**bpage
)
1268 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
1270 *bpage
= list_entry(p
, struct buffer_page
, list
);
1273 static struct buffer_page
*
1274 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1276 struct buffer_page
*head
;
1277 struct buffer_page
*page
;
1278 struct list_head
*list
;
1281 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
1285 list
= cpu_buffer
->pages
;
1286 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
1289 page
= head
= cpu_buffer
->head_page
;
1291 * It is possible that the writer moves the header behind
1292 * where we started, and we miss in one loop.
1293 * A second loop should grab the header, but we'll do
1294 * three loops just because I'm paranoid.
1296 for (i
= 0; i
< 3; i
++) {
1298 if (rb_is_head_page(page
, page
->list
.prev
)) {
1299 cpu_buffer
->head_page
= page
;
1303 } while (page
!= head
);
1306 RB_WARN_ON(cpu_buffer
, 1);
1311 static bool rb_head_page_replace(struct buffer_page
*old
,
1312 struct buffer_page
*new)
1314 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
1317 val
= *ptr
& ~RB_FLAG_MASK
;
1318 val
|= RB_PAGE_HEAD
;
1320 return try_cmpxchg(ptr
, &val
, (unsigned long)&new->list
);
1324 * rb_tail_page_update - move the tail page forward
1326 static void rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1327 struct buffer_page
*tail_page
,
1328 struct buffer_page
*next_page
)
1330 unsigned long old_entries
;
1331 unsigned long old_write
;
1334 * The tail page now needs to be moved forward.
1336 * We need to reset the tail page, but without messing
1337 * with possible erasing of data brought in by interrupts
1338 * that have moved the tail page and are currently on it.
1340 * We add a counter to the write field to denote this.
1342 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
1343 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
1345 local_inc(&cpu_buffer
->pages_touched
);
1347 * Just make sure we have seen our old_write and synchronize
1348 * with any interrupts that come in.
1353 * If the tail page is still the same as what we think
1354 * it is, then it is up to us to update the tail
1357 if (tail_page
== READ_ONCE(cpu_buffer
->tail_page
)) {
1358 /* Zero the write counter */
1359 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
1360 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
1363 * This will only succeed if an interrupt did
1364 * not come in and change it. In which case, we
1365 * do not want to modify it.
1367 * We add (void) to let the compiler know that we do not care
1368 * about the return value of these functions. We use the
1369 * cmpxchg to only update if an interrupt did not already
1370 * do it for us. If the cmpxchg fails, we don't care.
1372 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
1373 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
1376 * No need to worry about races with clearing out the commit.
1377 * it only can increment when a commit takes place. But that
1378 * only happens in the outer most nested commit.
1380 local_set(&next_page
->page
->commit
, 0);
1382 /* Again, either we update tail_page or an interrupt does */
1383 (void)cmpxchg(&cpu_buffer
->tail_page
, tail_page
, next_page
);
1387 static void rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
1388 struct buffer_page
*bpage
)
1390 unsigned long val
= (unsigned long)bpage
;
1392 RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
);
1396 * rb_check_pages - integrity check of buffer pages
1397 * @cpu_buffer: CPU buffer with pages to test
1399 * As a safety measure we check to make sure the data pages have not
1402 static void rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1404 struct list_head
*head
= rb_list_head(cpu_buffer
->pages
);
1405 struct list_head
*tmp
;
1407 if (RB_WARN_ON(cpu_buffer
,
1408 rb_list_head(rb_list_head(head
->next
)->prev
) != head
))
1411 if (RB_WARN_ON(cpu_buffer
,
1412 rb_list_head(rb_list_head(head
->prev
)->next
) != head
))
1415 for (tmp
= rb_list_head(head
->next
); tmp
!= head
; tmp
= rb_list_head(tmp
->next
)) {
1416 if (RB_WARN_ON(cpu_buffer
,
1417 rb_list_head(rb_list_head(tmp
->next
)->prev
) != tmp
))
1420 if (RB_WARN_ON(cpu_buffer
,
1421 rb_list_head(rb_list_head(tmp
->prev
)->next
) != tmp
))
1426 static int __rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1427 long nr_pages
, struct list_head
*pages
)
1429 struct buffer_page
*bpage
, *tmp
;
1430 bool user_thread
= current
->mm
!= NULL
;
1435 * Check if the available memory is there first.
1436 * Note, si_mem_available() only gives us a rough estimate of available
1437 * memory. It may not be accurate. But we don't care, we just want
1438 * to prevent doing any allocation when it is obvious that it is
1439 * not going to succeed.
1441 i
= si_mem_available();
1446 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1447 * gracefully without invoking oom-killer and the system is not
1450 mflags
= GFP_KERNEL
| __GFP_RETRY_MAYFAIL
;
1453 * If a user thread allocates too much, and si_mem_available()
1454 * reports there's enough memory, even though there is not.
1455 * Make sure the OOM killer kills this thread. This can happen
1456 * even with RETRY_MAYFAIL because another task may be doing
1457 * an allocation after this task has taken all memory.
1458 * This is the task the OOM killer needs to take out during this
1459 * loop, even if it was triggered by an allocation somewhere else.
1462 set_current_oom_origin();
1463 for (i
= 0; i
< nr_pages
; i
++) {
1466 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1467 mflags
, cpu_to_node(cpu_buffer
->cpu
));
1471 rb_check_bpage(cpu_buffer
, bpage
);
1473 list_add(&bpage
->list
, pages
);
1475 page
= alloc_pages_node(cpu_to_node(cpu_buffer
->cpu
), mflags
,
1476 cpu_buffer
->buffer
->subbuf_order
);
1479 bpage
->page
= page_address(page
);
1480 bpage
->order
= cpu_buffer
->buffer
->subbuf_order
;
1481 rb_init_page(bpage
->page
);
1483 if (user_thread
&& fatal_signal_pending(current
))
1487 clear_current_oom_origin();
1492 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1493 list_del_init(&bpage
->list
);
1494 free_buffer_page(bpage
);
1497 clear_current_oom_origin();
1502 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1503 unsigned long nr_pages
)
1509 if (__rb_allocate_pages(cpu_buffer
, nr_pages
, &pages
))
1513 * The ring buffer page list is a circular list that does not
1514 * start and end with a list head. All page list items point to
1517 cpu_buffer
->pages
= pages
.next
;
1520 cpu_buffer
->nr_pages
= nr_pages
;
1522 rb_check_pages(cpu_buffer
);
1527 static struct ring_buffer_per_cpu
*
1528 rb_allocate_cpu_buffer(struct trace_buffer
*buffer
, long nr_pages
, int cpu
)
1530 struct ring_buffer_per_cpu
*cpu_buffer
;
1531 struct buffer_page
*bpage
;
1535 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1536 GFP_KERNEL
, cpu_to_node(cpu
));
1540 cpu_buffer
->cpu
= cpu
;
1541 cpu_buffer
->buffer
= buffer
;
1542 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1543 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1544 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1545 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1546 init_completion(&cpu_buffer
->update_done
);
1547 init_irq_work(&cpu_buffer
->irq_work
.work
, rb_wake_up_waiters
);
1548 init_waitqueue_head(&cpu_buffer
->irq_work
.waiters
);
1549 init_waitqueue_head(&cpu_buffer
->irq_work
.full_waiters
);
1551 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1552 GFP_KERNEL
, cpu_to_node(cpu
));
1554 goto fail_free_buffer
;
1556 rb_check_bpage(cpu_buffer
, bpage
);
1558 cpu_buffer
->reader_page
= bpage
;
1560 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, cpu_buffer
->buffer
->subbuf_order
);
1562 goto fail_free_reader
;
1563 bpage
->page
= page_address(page
);
1564 rb_init_page(bpage
->page
);
1566 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1567 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1569 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1571 goto fail_free_reader
;
1573 cpu_buffer
->head_page
1574 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1575 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1577 rb_head_page_activate(cpu_buffer
);
1582 free_buffer_page(cpu_buffer
->reader_page
);
1589 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1591 struct list_head
*head
= cpu_buffer
->pages
;
1592 struct buffer_page
*bpage
, *tmp
;
1594 irq_work_sync(&cpu_buffer
->irq_work
.work
);
1596 free_buffer_page(cpu_buffer
->reader_page
);
1599 rb_head_page_deactivate(cpu_buffer
);
1601 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1602 list_del_init(&bpage
->list
);
1603 free_buffer_page(bpage
);
1605 bpage
= list_entry(head
, struct buffer_page
, list
);
1606 free_buffer_page(bpage
);
1609 free_page((unsigned long)cpu_buffer
->free_page
);
1615 * __ring_buffer_alloc - allocate a new ring_buffer
1616 * @size: the size in bytes per cpu that is needed.
1617 * @flags: attributes to set for the ring buffer.
1618 * @key: ring buffer reader_lock_key.
1620 * Currently the only flag that is available is the RB_FL_OVERWRITE
1621 * flag. This flag means that the buffer will overwrite old data
1622 * when the buffer wraps. If this flag is not set, the buffer will
1623 * drop data when the tail hits the head.
1625 struct trace_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1626 struct lock_class_key
*key
)
1628 struct trace_buffer
*buffer
;
1634 /* keep it in its own cache line */
1635 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1640 if (!zalloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1641 goto fail_free_buffer
;
1643 /* Default buffer page size - one system page */
1644 buffer
->subbuf_order
= 0;
1645 buffer
->subbuf_size
= PAGE_SIZE
- BUF_PAGE_HDR_SIZE
;
1647 /* Max payload is buffer page size - header (8bytes) */
1648 buffer
->max_data_size
= buffer
->subbuf_size
- (sizeof(u32
) * 2);
1650 nr_pages
= DIV_ROUND_UP(size
, buffer
->subbuf_size
);
1651 buffer
->flags
= flags
;
1652 buffer
->clock
= trace_clock_local
;
1653 buffer
->reader_lock_key
= key
;
1655 init_irq_work(&buffer
->irq_work
.work
, rb_wake_up_waiters
);
1656 init_waitqueue_head(&buffer
->irq_work
.waiters
);
1658 /* need at least two pages */
1662 buffer
->cpus
= nr_cpu_ids
;
1664 bsize
= sizeof(void *) * nr_cpu_ids
;
1665 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1667 if (!buffer
->buffers
)
1668 goto fail_free_cpumask
;
1670 cpu
= raw_smp_processor_id();
1671 cpumask_set_cpu(cpu
, buffer
->cpumask
);
1672 buffer
->buffers
[cpu
] = rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1673 if (!buffer
->buffers
[cpu
])
1674 goto fail_free_buffers
;
1676 ret
= cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1678 goto fail_free_buffers
;
1680 mutex_init(&buffer
->mutex
);
1685 for_each_buffer_cpu(buffer
, cpu
) {
1686 if (buffer
->buffers
[cpu
])
1687 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1689 kfree(buffer
->buffers
);
1692 free_cpumask_var(buffer
->cpumask
);
1698 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1701 * ring_buffer_free - free a ring buffer.
1702 * @buffer: the buffer to free.
1705 ring_buffer_free(struct trace_buffer
*buffer
)
1709 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1711 irq_work_sync(&buffer
->irq_work
.work
);
1713 for_each_buffer_cpu(buffer
, cpu
)
1714 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1716 kfree(buffer
->buffers
);
1717 free_cpumask_var(buffer
->cpumask
);
1721 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1723 void ring_buffer_set_clock(struct trace_buffer
*buffer
,
1726 buffer
->clock
= clock
;
1729 void ring_buffer_set_time_stamp_abs(struct trace_buffer
*buffer
, bool abs
)
1731 buffer
->time_stamp_abs
= abs
;
1734 bool ring_buffer_time_stamp_abs(struct trace_buffer
*buffer
)
1736 return buffer
->time_stamp_abs
;
1739 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1741 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1743 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1746 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1748 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1752 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned long nr_pages
)
1754 struct list_head
*tail_page
, *to_remove
, *next_page
;
1755 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1756 struct buffer_page
*last_page
, *first_page
;
1757 unsigned long nr_removed
;
1758 unsigned long head_bit
;
1763 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1764 atomic_inc(&cpu_buffer
->record_disabled
);
1766 * We don't race with the readers since we have acquired the reader
1767 * lock. We also don't race with writers after disabling recording.
1768 * This makes it easy to figure out the first and the last page to be
1769 * removed from the list. We unlink all the pages in between including
1770 * the first and last pages. This is done in a busy loop so that we
1771 * lose the least number of traces.
1772 * The pages are freed after we restart recording and unlock readers.
1774 tail_page
= &cpu_buffer
->tail_page
->list
;
1777 * tail page might be on reader page, we remove the next page
1778 * from the ring buffer
1780 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1781 tail_page
= rb_list_head(tail_page
->next
);
1782 to_remove
= tail_page
;
1784 /* start of pages to remove */
1785 first_page
= list_entry(rb_list_head(to_remove
->next
),
1786 struct buffer_page
, list
);
1788 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1789 to_remove
= rb_list_head(to_remove
)->next
;
1790 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1792 /* Read iterators need to reset themselves when some pages removed */
1793 cpu_buffer
->pages_removed
+= nr_removed
;
1795 next_page
= rb_list_head(to_remove
)->next
;
1798 * Now we remove all pages between tail_page and next_page.
1799 * Make sure that we have head_bit value preserved for the
1802 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1804 next_page
= rb_list_head(next_page
);
1805 next_page
->prev
= tail_page
;
1807 /* make sure pages points to a valid page in the ring buffer */
1808 cpu_buffer
->pages
= next_page
;
1810 /* update head page */
1812 cpu_buffer
->head_page
= list_entry(next_page
,
1813 struct buffer_page
, list
);
1815 /* pages are removed, resume tracing and then free the pages */
1816 atomic_dec(&cpu_buffer
->record_disabled
);
1817 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1819 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1821 /* last buffer page to remove */
1822 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1824 tmp_iter_page
= first_page
;
1829 to_remove_page
= tmp_iter_page
;
1830 rb_inc_page(&tmp_iter_page
);
1832 /* update the counters */
1833 page_entries
= rb_page_entries(to_remove_page
);
1836 * If something was added to this page, it was full
1837 * since it is not the tail page. So we deduct the
1838 * bytes consumed in ring buffer from here.
1839 * Increment overrun to account for the lost events.
1841 local_add(page_entries
, &cpu_buffer
->overrun
);
1842 local_sub(rb_page_commit(to_remove_page
), &cpu_buffer
->entries_bytes
);
1843 local_inc(&cpu_buffer
->pages_lost
);
1847 * We have already removed references to this list item, just
1848 * free up the buffer_page and its page
1850 free_buffer_page(to_remove_page
);
1853 } while (to_remove_page
!= last_page
);
1855 RB_WARN_ON(cpu_buffer
, nr_removed
);
1857 return nr_removed
== 0;
1861 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1863 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1864 unsigned long flags
;
1868 /* Can be called at early boot up, where interrupts must not been enabled */
1869 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
1871 * We are holding the reader lock, so the reader page won't be swapped
1872 * in the ring buffer. Now we are racing with the writer trying to
1873 * move head page and the tail page.
1874 * We are going to adapt the reader page update process where:
1875 * 1. We first splice the start and end of list of new pages between
1876 * the head page and its previous page.
1877 * 2. We cmpxchg the prev_page->next to point from head page to the
1878 * start of new pages list.
1879 * 3. Finally, we update the head->prev to the end of new list.
1881 * We will try this process 10 times, to make sure that we don't keep
1887 struct list_head
*head_page
, *prev_page
;
1888 struct list_head
*last_page
, *first_page
;
1889 struct list_head
*head_page_with_bit
;
1890 struct buffer_page
*hpage
= rb_set_head_page(cpu_buffer
);
1894 head_page
= &hpage
->list
;
1895 prev_page
= head_page
->prev
;
1897 first_page
= pages
->next
;
1898 last_page
= pages
->prev
;
1900 head_page_with_bit
= (struct list_head
*)
1901 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1903 last_page
->next
= head_page_with_bit
;
1904 first_page
->prev
= prev_page
;
1906 /* caution: head_page_with_bit gets updated on cmpxchg failure */
1907 if (try_cmpxchg(&prev_page
->next
,
1908 &head_page_with_bit
, first_page
)) {
1910 * yay, we replaced the page pointer to our new list,
1911 * now, we just have to update to head page's prev
1912 * pointer to point to end of list
1914 head_page
->prev
= last_page
;
1921 INIT_LIST_HEAD(pages
);
1923 * If we weren't successful in adding in new pages, warn and stop
1926 RB_WARN_ON(cpu_buffer
, !success
);
1927 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
1929 /* free pages if they weren't inserted */
1931 struct buffer_page
*bpage
, *tmp
;
1932 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1934 list_del_init(&bpage
->list
);
1935 free_buffer_page(bpage
);
1941 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1945 if (cpu_buffer
->nr_pages_to_update
> 0)
1946 success
= rb_insert_pages(cpu_buffer
);
1948 success
= rb_remove_pages(cpu_buffer
,
1949 -cpu_buffer
->nr_pages_to_update
);
1952 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1955 static void update_pages_handler(struct work_struct
*work
)
1957 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1958 struct ring_buffer_per_cpu
, update_pages_work
);
1959 rb_update_pages(cpu_buffer
);
1960 complete(&cpu_buffer
->update_done
);
1964 * ring_buffer_resize - resize the ring buffer
1965 * @buffer: the buffer to resize.
1966 * @size: the new size.
1967 * @cpu_id: the cpu buffer to resize
1969 * Minimum size is 2 * buffer->subbuf_size.
1971 * Returns 0 on success and < 0 on failure.
1973 int ring_buffer_resize(struct trace_buffer
*buffer
, unsigned long size
,
1976 struct ring_buffer_per_cpu
*cpu_buffer
;
1977 unsigned long nr_pages
;
1981 * Always succeed at resizing a non-existent buffer:
1986 /* Make sure the requested buffer exists */
1987 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1988 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1991 nr_pages
= DIV_ROUND_UP(size
, buffer
->subbuf_size
);
1993 /* we need a minimum of two pages */
1997 /* prevent another thread from changing buffer sizes */
1998 mutex_lock(&buffer
->mutex
);
1999 atomic_inc(&buffer
->resizing
);
2001 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
2003 * Don't succeed if resizing is disabled, as a reader might be
2004 * manipulating the ring buffer and is expecting a sane state while
2007 for_each_buffer_cpu(buffer
, cpu
) {
2008 cpu_buffer
= buffer
->buffers
[cpu
];
2009 if (atomic_read(&cpu_buffer
->resize_disabled
)) {
2011 goto out_err_unlock
;
2015 /* calculate the pages to update */
2016 for_each_buffer_cpu(buffer
, cpu
) {
2017 cpu_buffer
= buffer
->buffers
[cpu
];
2019 cpu_buffer
->nr_pages_to_update
= nr_pages
-
2020 cpu_buffer
->nr_pages
;
2022 * nothing more to do for removing pages or no update
2024 if (cpu_buffer
->nr_pages_to_update
<= 0)
2027 * to add pages, make sure all new pages can be
2028 * allocated without receiving ENOMEM
2030 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
2031 if (__rb_allocate_pages(cpu_buffer
, cpu_buffer
->nr_pages_to_update
,
2032 &cpu_buffer
->new_pages
)) {
2033 /* not enough memory for new pages */
2043 * Fire off all the required work handlers
2044 * We can't schedule on offline CPUs, but it's not necessary
2045 * since we can change their buffer sizes without any race.
2047 for_each_buffer_cpu(buffer
, cpu
) {
2048 cpu_buffer
= buffer
->buffers
[cpu
];
2049 if (!cpu_buffer
->nr_pages_to_update
)
2052 /* Can't run something on an offline CPU. */
2053 if (!cpu_online(cpu
)) {
2054 rb_update_pages(cpu_buffer
);
2055 cpu_buffer
->nr_pages_to_update
= 0;
2057 /* Run directly if possible. */
2059 if (cpu
!= smp_processor_id()) {
2061 schedule_work_on(cpu
,
2062 &cpu_buffer
->update_pages_work
);
2064 update_pages_handler(&cpu_buffer
->update_pages_work
);
2070 /* wait for all the updates to complete */
2071 for_each_buffer_cpu(buffer
, cpu
) {
2072 cpu_buffer
= buffer
->buffers
[cpu
];
2073 if (!cpu_buffer
->nr_pages_to_update
)
2076 if (cpu_online(cpu
))
2077 wait_for_completion(&cpu_buffer
->update_done
);
2078 cpu_buffer
->nr_pages_to_update
= 0;
2083 cpu_buffer
= buffer
->buffers
[cpu_id
];
2085 if (nr_pages
== cpu_buffer
->nr_pages
)
2089 * Don't succeed if resizing is disabled, as a reader might be
2090 * manipulating the ring buffer and is expecting a sane state while
2093 if (atomic_read(&cpu_buffer
->resize_disabled
)) {
2095 goto out_err_unlock
;
2098 cpu_buffer
->nr_pages_to_update
= nr_pages
-
2099 cpu_buffer
->nr_pages
;
2101 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
2102 if (cpu_buffer
->nr_pages_to_update
> 0 &&
2103 __rb_allocate_pages(cpu_buffer
, cpu_buffer
->nr_pages_to_update
,
2104 &cpu_buffer
->new_pages
)) {
2111 /* Can't run something on an offline CPU. */
2112 if (!cpu_online(cpu_id
))
2113 rb_update_pages(cpu_buffer
);
2115 /* Run directly if possible. */
2117 if (cpu_id
== smp_processor_id()) {
2118 rb_update_pages(cpu_buffer
);
2122 schedule_work_on(cpu_id
,
2123 &cpu_buffer
->update_pages_work
);
2124 wait_for_completion(&cpu_buffer
->update_done
);
2128 cpu_buffer
->nr_pages_to_update
= 0;
2134 * The ring buffer resize can happen with the ring buffer
2135 * enabled, so that the update disturbs the tracing as little
2136 * as possible. But if the buffer is disabled, we do not need
2137 * to worry about that, and we can take the time to verify
2138 * that the buffer is not corrupt.
2140 if (atomic_read(&buffer
->record_disabled
)) {
2141 atomic_inc(&buffer
->record_disabled
);
2143 * Even though the buffer was disabled, we must make sure
2144 * that it is truly disabled before calling rb_check_pages.
2145 * There could have been a race between checking
2146 * record_disable and incrementing it.
2149 for_each_buffer_cpu(buffer
, cpu
) {
2150 cpu_buffer
= buffer
->buffers
[cpu
];
2151 rb_check_pages(cpu_buffer
);
2153 atomic_dec(&buffer
->record_disabled
);
2156 atomic_dec(&buffer
->resizing
);
2157 mutex_unlock(&buffer
->mutex
);
2161 for_each_buffer_cpu(buffer
, cpu
) {
2162 struct buffer_page
*bpage
, *tmp
;
2164 cpu_buffer
= buffer
->buffers
[cpu
];
2165 cpu_buffer
->nr_pages_to_update
= 0;
2167 if (list_empty(&cpu_buffer
->new_pages
))
2170 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
2172 list_del_init(&bpage
->list
);
2173 free_buffer_page(bpage
);
2177 atomic_dec(&buffer
->resizing
);
2178 mutex_unlock(&buffer
->mutex
);
2181 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
2183 void ring_buffer_change_overwrite(struct trace_buffer
*buffer
, int val
)
2185 mutex_lock(&buffer
->mutex
);
2187 buffer
->flags
|= RB_FL_OVERWRITE
;
2189 buffer
->flags
&= ~RB_FL_OVERWRITE
;
2190 mutex_unlock(&buffer
->mutex
);
2192 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
2194 static __always_inline
void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
2196 return bpage
->page
->data
+ index
;
2199 static __always_inline
struct ring_buffer_event
*
2200 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
2202 return __rb_page_index(cpu_buffer
->reader_page
,
2203 cpu_buffer
->reader_page
->read
);
2206 static struct ring_buffer_event
*
2207 rb_iter_head_event(struct ring_buffer_iter
*iter
)
2209 struct ring_buffer_event
*event
;
2210 struct buffer_page
*iter_head_page
= iter
->head_page
;
2211 unsigned long commit
;
2214 if (iter
->head
!= iter
->next_event
)
2218 * When the writer goes across pages, it issues a cmpxchg which
2219 * is a mb(), which will synchronize with the rmb here.
2220 * (see rb_tail_page_update() and __rb_reserve_next())
2222 commit
= rb_page_commit(iter_head_page
);
2225 /* An event needs to be at least 8 bytes in size */
2226 if (iter
->head
> commit
- 8)
2229 event
= __rb_page_index(iter_head_page
, iter
->head
);
2230 length
= rb_event_length(event
);
2233 * READ_ONCE() doesn't work on functions and we don't want the
2234 * compiler doing any crazy optimizations with length.
2238 if ((iter
->head
+ length
) > commit
|| length
> iter
->event_size
)
2239 /* Writer corrupted the read? */
2242 memcpy(iter
->event
, event
, length
);
2244 * If the page stamp is still the same after this rmb() then the
2245 * event was safely copied without the writer entering the page.
2249 /* Make sure the page didn't change since we read this */
2250 if (iter
->page_stamp
!= iter_head_page
->page
->time_stamp
||
2251 commit
> rb_page_commit(iter_head_page
))
2254 iter
->next_event
= iter
->head
+ length
;
2257 /* Reset to the beginning */
2258 iter
->page_stamp
= iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2260 iter
->next_event
= 0;
2261 iter
->missed_events
= 1;
2265 /* Size is determined by what has been committed */
2266 static __always_inline
unsigned rb_page_size(struct buffer_page
*bpage
)
2268 return rb_page_commit(bpage
);
2271 static __always_inline
unsigned
2272 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
2274 return rb_page_commit(cpu_buffer
->commit_page
);
2277 static __always_inline
unsigned
2278 rb_event_index(struct ring_buffer_per_cpu
*cpu_buffer
, struct ring_buffer_event
*event
)
2280 unsigned long addr
= (unsigned long)event
;
2282 addr
&= (PAGE_SIZE
<< cpu_buffer
->buffer
->subbuf_order
) - 1;
2284 return addr
- BUF_PAGE_HDR_SIZE
;
2287 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
2289 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2292 * The iterator could be on the reader page (it starts there).
2293 * But the head could have moved, since the reader was
2294 * found. Check for this case and assign the iterator
2295 * to the head page instead of next.
2297 if (iter
->head_page
== cpu_buffer
->reader_page
)
2298 iter
->head_page
= rb_set_head_page(cpu_buffer
);
2300 rb_inc_page(&iter
->head_page
);
2302 iter
->page_stamp
= iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2304 iter
->next_event
= 0;
2308 * rb_handle_head_page - writer hit the head page
2310 * Returns: +1 to retry page
2315 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
2316 struct buffer_page
*tail_page
,
2317 struct buffer_page
*next_page
)
2319 struct buffer_page
*new_head
;
2324 entries
= rb_page_entries(next_page
);
2327 * The hard part is here. We need to move the head
2328 * forward, and protect against both readers on
2329 * other CPUs and writers coming in via interrupts.
2331 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
2335 * type can be one of four:
2336 * NORMAL - an interrupt already moved it for us
2337 * HEAD - we are the first to get here.
2338 * UPDATE - we are the interrupt interrupting
2340 * MOVED - a reader on another CPU moved the next
2341 * pointer to its reader page. Give up
2348 * We changed the head to UPDATE, thus
2349 * it is our responsibility to update
2352 local_add(entries
, &cpu_buffer
->overrun
);
2353 local_sub(rb_page_commit(next_page
), &cpu_buffer
->entries_bytes
);
2354 local_inc(&cpu_buffer
->pages_lost
);
2357 * The entries will be zeroed out when we move the
2361 /* still more to do */
2364 case RB_PAGE_UPDATE
:
2366 * This is an interrupt that interrupt the
2367 * previous update. Still more to do.
2370 case RB_PAGE_NORMAL
:
2372 * An interrupt came in before the update
2373 * and processed this for us.
2374 * Nothing left to do.
2379 * The reader is on another CPU and just did
2380 * a swap with our next_page.
2385 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
2390 * Now that we are here, the old head pointer is
2391 * set to UPDATE. This will keep the reader from
2392 * swapping the head page with the reader page.
2393 * The reader (on another CPU) will spin till
2396 * We just need to protect against interrupts
2397 * doing the job. We will set the next pointer
2398 * to HEAD. After that, we set the old pointer
2399 * to NORMAL, but only if it was HEAD before.
2400 * otherwise we are an interrupt, and only
2401 * want the outer most commit to reset it.
2403 new_head
= next_page
;
2404 rb_inc_page(&new_head
);
2406 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
2410 * Valid returns are:
2411 * HEAD - an interrupt came in and already set it.
2412 * NORMAL - One of two things:
2413 * 1) We really set it.
2414 * 2) A bunch of interrupts came in and moved
2415 * the page forward again.
2419 case RB_PAGE_NORMAL
:
2423 RB_WARN_ON(cpu_buffer
, 1);
2428 * It is possible that an interrupt came in,
2429 * set the head up, then more interrupts came in
2430 * and moved it again. When we get back here,
2431 * the page would have been set to NORMAL but we
2432 * just set it back to HEAD.
2434 * How do you detect this? Well, if that happened
2435 * the tail page would have moved.
2437 if (ret
== RB_PAGE_NORMAL
) {
2438 struct buffer_page
*buffer_tail_page
;
2440 buffer_tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2442 * If the tail had moved passed next, then we need
2443 * to reset the pointer.
2445 if (buffer_tail_page
!= tail_page
&&
2446 buffer_tail_page
!= next_page
)
2447 rb_head_page_set_normal(cpu_buffer
, new_head
,
2453 * If this was the outer most commit (the one that
2454 * changed the original pointer from HEAD to UPDATE),
2455 * then it is up to us to reset it to NORMAL.
2457 if (type
== RB_PAGE_HEAD
) {
2458 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2461 if (RB_WARN_ON(cpu_buffer
,
2462 ret
!= RB_PAGE_UPDATE
))
2470 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2471 unsigned long tail
, struct rb_event_info
*info
)
2473 unsigned long bsize
= READ_ONCE(cpu_buffer
->buffer
->subbuf_size
);
2474 struct buffer_page
*tail_page
= info
->tail_page
;
2475 struct ring_buffer_event
*event
;
2476 unsigned long length
= info
->length
;
2479 * Only the event that crossed the page boundary
2480 * must fill the old tail_page with padding.
2482 if (tail
>= bsize
) {
2484 * If the page was filled, then we still need
2485 * to update the real_end. Reset it to zero
2486 * and the reader will ignore it.
2489 tail_page
->real_end
= 0;
2491 local_sub(length
, &tail_page
->write
);
2495 event
= __rb_page_index(tail_page
, tail
);
2498 * Save the original length to the meta data.
2499 * This will be used by the reader to add lost event
2502 tail_page
->real_end
= tail
;
2505 * If this event is bigger than the minimum size, then
2506 * we need to be careful that we don't subtract the
2507 * write counter enough to allow another writer to slip
2509 * We put in a discarded commit instead, to make sure
2510 * that this space is not used again, and this space will
2511 * not be accounted into 'entries_bytes'.
2513 * If we are less than the minimum size, we don't need to
2516 if (tail
> (bsize
- RB_EVNT_MIN_SIZE
)) {
2517 /* No room for any events */
2519 /* Mark the rest of the page with padding */
2520 rb_event_set_padding(event
);
2522 /* Make sure the padding is visible before the write update */
2525 /* Set the write back to the previous setting */
2526 local_sub(length
, &tail_page
->write
);
2530 /* Put in a discarded event */
2531 event
->array
[0] = (bsize
- tail
) - RB_EVNT_HDR_SIZE
;
2532 event
->type_len
= RINGBUF_TYPE_PADDING
;
2533 /* time delta must be non zero */
2534 event
->time_delta
= 1;
2536 /* account for padding bytes */
2537 local_add(bsize
- tail
, &cpu_buffer
->entries_bytes
);
2539 /* Make sure the padding is visible before the tail_page->write update */
2542 /* Set write to end of buffer */
2543 length
= (tail
+ length
) - bsize
;
2544 local_sub(length
, &tail_page
->write
);
2547 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
);
2550 * This is the slow path, force gcc not to inline it.
2552 static noinline
struct ring_buffer_event
*
2553 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2554 unsigned long tail
, struct rb_event_info
*info
)
2556 struct buffer_page
*tail_page
= info
->tail_page
;
2557 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2558 struct trace_buffer
*buffer
= cpu_buffer
->buffer
;
2559 struct buffer_page
*next_page
;
2562 next_page
= tail_page
;
2564 rb_inc_page(&next_page
);
2567 * If for some reason, we had an interrupt storm that made
2568 * it all the way around the buffer, bail, and warn
2571 if (unlikely(next_page
== commit_page
)) {
2572 local_inc(&cpu_buffer
->commit_overrun
);
2577 * This is where the fun begins!
2579 * We are fighting against races between a reader that
2580 * could be on another CPU trying to swap its reader
2581 * page with the buffer head.
2583 * We are also fighting against interrupts coming in and
2584 * moving the head or tail on us as well.
2586 * If the next page is the head page then we have filled
2587 * the buffer, unless the commit page is still on the
2590 if (rb_is_head_page(next_page
, &tail_page
->list
)) {
2593 * If the commit is not on the reader page, then
2594 * move the header page.
2596 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2598 * If we are not in overwrite mode,
2599 * this is easy, just stop here.
2601 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2602 local_inc(&cpu_buffer
->dropped_events
);
2606 ret
= rb_handle_head_page(cpu_buffer
,
2615 * We need to be careful here too. The
2616 * commit page could still be on the reader
2617 * page. We could have a small buffer, and
2618 * have filled up the buffer with events
2619 * from interrupts and such, and wrapped.
2621 * Note, if the tail page is also on the
2622 * reader_page, we let it move out.
2624 if (unlikely((cpu_buffer
->commit_page
!=
2625 cpu_buffer
->tail_page
) &&
2626 (cpu_buffer
->commit_page
==
2627 cpu_buffer
->reader_page
))) {
2628 local_inc(&cpu_buffer
->commit_overrun
);
2634 rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2638 rb_reset_tail(cpu_buffer
, tail
, info
);
2640 /* Commit what we have for now. */
2641 rb_end_commit(cpu_buffer
);
2642 /* rb_end_commit() decs committing */
2643 local_inc(&cpu_buffer
->committing
);
2645 /* fail and let the caller try again */
2646 return ERR_PTR(-EAGAIN
);
2650 rb_reset_tail(cpu_buffer
, tail
, info
);
2656 static struct ring_buffer_event
*
2657 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2658 struct ring_buffer_event
*event
, u64 delta
, bool abs
)
2661 event
->type_len
= RINGBUF_TYPE_TIME_STAMP
;
2663 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
2665 /* Not the first event on the page, or not delta? */
2666 if (abs
|| rb_event_index(cpu_buffer
, event
)) {
2667 event
->time_delta
= delta
& TS_MASK
;
2668 event
->array
[0] = delta
>> TS_SHIFT
;
2670 /* nope, just zero it */
2671 event
->time_delta
= 0;
2672 event
->array
[0] = 0;
2675 return skip_time_extend(event
);
2678 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2679 static inline bool sched_clock_stable(void)
2686 rb_check_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2687 struct rb_event_info
*info
)
2691 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2692 (unsigned long long)info
->delta
,
2693 (unsigned long long)info
->ts
,
2694 (unsigned long long)info
->before
,
2695 (unsigned long long)info
->after
,
2696 (unsigned long long)({rb_time_read(&cpu_buffer
->write_stamp
, &write_stamp
); write_stamp
;}),
2697 sched_clock_stable() ? "" :
2698 "If you just came from a suspend/resume,\n"
2699 "please switch to the trace global clock:\n"
2700 " echo global > /sys/kernel/tracing/trace_clock\n"
2701 "or add trace_clock=global to the kernel command line\n");
2704 static void rb_add_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2705 struct ring_buffer_event
**event
,
2706 struct rb_event_info
*info
,
2708 unsigned int *length
)
2710 bool abs
= info
->add_timestamp
&
2711 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
);
2713 if (unlikely(info
->delta
> (1ULL << 59))) {
2715 * Some timers can use more than 59 bits, and when a timestamp
2716 * is added to the buffer, it will lose those bits.
2718 if (abs
&& (info
->ts
& TS_MSB
)) {
2719 info
->delta
&= ABS_TS_MASK
;
2721 /* did the clock go backwards */
2722 } else if (info
->before
== info
->after
&& info
->before
> info
->ts
) {
2723 /* not interrupted */
2727 * This is possible with a recalibrating of the TSC.
2728 * Do not produce a call stack, but just report it.
2732 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2733 info
->before
, info
->ts
);
2736 rb_check_timestamp(cpu_buffer
, info
);
2740 *event
= rb_add_time_stamp(cpu_buffer
, *event
, info
->delta
, abs
);
2741 *length
-= RB_LEN_TIME_EXTEND
;
2746 * rb_update_event - update event type and data
2747 * @cpu_buffer: The per cpu buffer of the @event
2748 * @event: the event to update
2749 * @info: The info to update the @event with (contains length and delta)
2751 * Update the type and data fields of the @event. The length
2752 * is the actual size that is written to the ring buffer,
2753 * and with this, we can determine what to place into the
2757 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2758 struct ring_buffer_event
*event
,
2759 struct rb_event_info
*info
)
2761 unsigned length
= info
->length
;
2762 u64 delta
= info
->delta
;
2763 unsigned int nest
= local_read(&cpu_buffer
->committing
) - 1;
2765 if (!WARN_ON_ONCE(nest
>= MAX_NEST
))
2766 cpu_buffer
->event_stamp
[nest
] = info
->ts
;
2769 * If we need to add a timestamp, then we
2770 * add it to the start of the reserved space.
2772 if (unlikely(info
->add_timestamp
))
2773 rb_add_timestamp(cpu_buffer
, &event
, info
, &delta
, &length
);
2775 event
->time_delta
= delta
;
2776 length
-= RB_EVNT_HDR_SIZE
;
2777 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
) {
2778 event
->type_len
= 0;
2779 event
->array
[0] = length
;
2781 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
2784 static unsigned rb_calculate_event_length(unsigned length
)
2786 struct ring_buffer_event event
; /* Used only for sizeof array */
2788 /* zero length can cause confusions */
2792 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
2793 length
+= sizeof(event
.array
[0]);
2795 length
+= RB_EVNT_HDR_SIZE
;
2796 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
2799 * In case the time delta is larger than the 27 bits for it
2800 * in the header, we need to add a timestamp. If another
2801 * event comes in when trying to discard this one to increase
2802 * the length, then the timestamp will be added in the allocated
2803 * space of this event. If length is bigger than the size needed
2804 * for the TIME_EXTEND, then padding has to be used. The events
2805 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2806 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2807 * As length is a multiple of 4, we only need to worry if it
2808 * is 12 (RB_LEN_TIME_EXTEND + 4).
2810 if (length
== RB_LEN_TIME_EXTEND
+ RB_ALIGNMENT
)
2811 length
+= RB_ALIGNMENT
;
2817 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2818 struct ring_buffer_event
*event
)
2820 unsigned long new_index
, old_index
;
2821 struct buffer_page
*bpage
;
2824 new_index
= rb_event_index(cpu_buffer
, event
);
2825 old_index
= new_index
+ rb_event_ts_length(event
);
2826 addr
= (unsigned long)event
;
2827 addr
&= ~((PAGE_SIZE
<< cpu_buffer
->buffer
->subbuf_order
) - 1);
2829 bpage
= READ_ONCE(cpu_buffer
->tail_page
);
2832 * Make sure the tail_page is still the same and
2833 * the next write location is the end of this event
2835 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2836 unsigned long write_mask
=
2837 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2838 unsigned long event_length
= rb_event_length(event
);
2841 * For the before_stamp to be different than the write_stamp
2842 * to make sure that the next event adds an absolute
2843 * value and does not rely on the saved write stamp, which
2844 * is now going to be bogus.
2846 * By setting the before_stamp to zero, the next event
2847 * is not going to use the write_stamp and will instead
2848 * create an absolute timestamp. This means there's no
2849 * reason to update the wirte_stamp!
2851 rb_time_set(&cpu_buffer
->before_stamp
, 0);
2854 * If an event were to come in now, it would see that the
2855 * write_stamp and the before_stamp are different, and assume
2856 * that this event just added itself before updating
2857 * the write stamp. The interrupting event will fix the
2858 * write stamp for us, and use an absolute timestamp.
2862 * This is on the tail page. It is possible that
2863 * a write could come in and move the tail page
2864 * and write to the next page. That is fine
2865 * because we just shorten what is on this page.
2867 old_index
+= write_mask
;
2868 new_index
+= write_mask
;
2870 /* caution: old_index gets updated on cmpxchg failure */
2871 if (local_try_cmpxchg(&bpage
->write
, &old_index
, new_index
)) {
2872 /* update counters */
2873 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2878 /* could not discard */
2882 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2884 local_inc(&cpu_buffer
->committing
);
2885 local_inc(&cpu_buffer
->commits
);
2888 static __always_inline
void
2889 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
2891 unsigned long max_count
;
2894 * We only race with interrupts and NMIs on this CPU.
2895 * If we own the commit event, then we can commit
2896 * all others that interrupted us, since the interruptions
2897 * are in stack format (they finish before they come
2898 * back to us). This allows us to do a simple loop to
2899 * assign the commit to the tail.
2902 max_count
= cpu_buffer
->nr_pages
* 100;
2904 while (cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)) {
2905 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
2907 if (RB_WARN_ON(cpu_buffer
,
2908 rb_is_reader_page(cpu_buffer
->tail_page
)))
2911 * No need for a memory barrier here, as the update
2912 * of the tail_page did it for this page.
2914 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2915 rb_page_write(cpu_buffer
->commit_page
));
2916 rb_inc_page(&cpu_buffer
->commit_page
);
2917 /* add barrier to keep gcc from optimizing too much */
2920 while (rb_commit_index(cpu_buffer
) !=
2921 rb_page_write(cpu_buffer
->commit_page
)) {
2923 /* Make sure the readers see the content of what is committed. */
2925 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2926 rb_page_write(cpu_buffer
->commit_page
));
2927 RB_WARN_ON(cpu_buffer
,
2928 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
2933 /* again, keep gcc from optimizing */
2937 * If an interrupt came in just after the first while loop
2938 * and pushed the tail page forward, we will be left with
2939 * a dangling commit that will never go forward.
2941 if (unlikely(cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)))
2945 static __always_inline
void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2947 unsigned long commits
;
2949 if (RB_WARN_ON(cpu_buffer
,
2950 !local_read(&cpu_buffer
->committing
)))
2954 commits
= local_read(&cpu_buffer
->commits
);
2955 /* synchronize with interrupts */
2957 if (local_read(&cpu_buffer
->committing
) == 1)
2958 rb_set_commit_to_write(cpu_buffer
);
2960 local_dec(&cpu_buffer
->committing
);
2962 /* synchronize with interrupts */
2966 * Need to account for interrupts coming in between the
2967 * updating of the commit page and the clearing of the
2968 * committing counter.
2970 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2971 !local_read(&cpu_buffer
->committing
)) {
2972 local_inc(&cpu_buffer
->committing
);
2977 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2979 if (extended_time(event
))
2980 event
= skip_time_extend(event
);
2982 /* array[0] holds the actual length for the discarded event */
2983 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2984 event
->type_len
= RINGBUF_TYPE_PADDING
;
2985 /* time delta must be non zero */
2986 if (!event
->time_delta
)
2987 event
->time_delta
= 1;
2990 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2992 local_inc(&cpu_buffer
->entries
);
2993 rb_end_commit(cpu_buffer
);
2996 static __always_inline
void
2997 rb_wakeups(struct trace_buffer
*buffer
, struct ring_buffer_per_cpu
*cpu_buffer
)
2999 if (buffer
->irq_work
.waiters_pending
) {
3000 buffer
->irq_work
.waiters_pending
= false;
3001 /* irq_work_queue() supplies it's own memory barriers */
3002 irq_work_queue(&buffer
->irq_work
.work
);
3005 if (cpu_buffer
->irq_work
.waiters_pending
) {
3006 cpu_buffer
->irq_work
.waiters_pending
= false;
3007 /* irq_work_queue() supplies it's own memory barriers */
3008 irq_work_queue(&cpu_buffer
->irq_work
.work
);
3011 if (cpu_buffer
->last_pages_touch
== local_read(&cpu_buffer
->pages_touched
))
3014 if (cpu_buffer
->reader_page
== cpu_buffer
->commit_page
)
3017 if (!cpu_buffer
->irq_work
.full_waiters_pending
)
3020 cpu_buffer
->last_pages_touch
= local_read(&cpu_buffer
->pages_touched
);
3022 if (!full_hit(buffer
, cpu_buffer
->cpu
, cpu_buffer
->shortest_full
))
3025 cpu_buffer
->irq_work
.wakeup_full
= true;
3026 cpu_buffer
->irq_work
.full_waiters_pending
= false;
3027 /* irq_work_queue() supplies it's own memory barriers */
3028 irq_work_queue(&cpu_buffer
->irq_work
.work
);
3031 #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3032 # define do_ring_buffer_record_recursion() \
3033 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3035 # define do_ring_buffer_record_recursion() do { } while (0)
3039 * The lock and unlock are done within a preempt disable section.
3040 * The current_context per_cpu variable can only be modified
3041 * by the current task between lock and unlock. But it can
3042 * be modified more than once via an interrupt. To pass this
3043 * information from the lock to the unlock without having to
3044 * access the 'in_interrupt()' functions again (which do show
3045 * a bit of overhead in something as critical as function tracing,
3046 * we use a bitmask trick.
3048 * bit 1 = NMI context
3049 * bit 2 = IRQ context
3050 * bit 3 = SoftIRQ context
3051 * bit 4 = normal context.
3053 * This works because this is the order of contexts that can
3054 * preempt other contexts. A SoftIRQ never preempts an IRQ
3057 * When the context is determined, the corresponding bit is
3058 * checked and set (if it was set, then a recursion of that context
3061 * On unlock, we need to clear this bit. To do so, just subtract
3062 * 1 from the current_context and AND it to itself.
3066 * 101 & 100 = 100 (clearing bit zero)
3069 * 1010 & 1001 = 1000 (clearing bit 1)
3071 * The least significant bit can be cleared this way, and it
3072 * just so happens that it is the same bit corresponding to
3073 * the current context.
3075 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3076 * is set when a recursion is detected at the current context, and if
3077 * the TRANSITION bit is already set, it will fail the recursion.
3078 * This is needed because there's a lag between the changing of
3079 * interrupt context and updating the preempt count. In this case,
3080 * a false positive will be found. To handle this, one extra recursion
3081 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3082 * bit is already set, then it is considered a recursion and the function
3083 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3085 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3086 * to be cleared. Even if it wasn't the context that set it. That is,
3087 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3088 * is called before preempt_count() is updated, since the check will
3089 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3090 * NMI then comes in, it will set the NMI bit, but when the NMI code
3091 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3092 * and leave the NMI bit set. But this is fine, because the interrupt
3093 * code that set the TRANSITION bit will then clear the NMI bit when it
3094 * calls trace_recursive_unlock(). If another NMI comes in, it will
3095 * set the TRANSITION bit and continue.
3097 * Note: The TRANSITION bit only handles a single transition between context.
3100 static __always_inline
bool
3101 trace_recursive_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
3103 unsigned int val
= cpu_buffer
->current_context
;
3104 int bit
= interrupt_context_level();
3106 bit
= RB_CTX_NORMAL
- bit
;
3108 if (unlikely(val
& (1 << (bit
+ cpu_buffer
->nest
)))) {
3110 * It is possible that this was called by transitioning
3111 * between interrupt context, and preempt_count() has not
3112 * been updated yet. In this case, use the TRANSITION bit.
3114 bit
= RB_CTX_TRANSITION
;
3115 if (val
& (1 << (bit
+ cpu_buffer
->nest
))) {
3116 do_ring_buffer_record_recursion();
3121 val
|= (1 << (bit
+ cpu_buffer
->nest
));
3122 cpu_buffer
->current_context
= val
;
3127 static __always_inline
void
3128 trace_recursive_unlock(struct ring_buffer_per_cpu
*cpu_buffer
)
3130 cpu_buffer
->current_context
&=
3131 cpu_buffer
->current_context
- (1 << cpu_buffer
->nest
);
3134 /* The recursive locking above uses 5 bits */
3135 #define NESTED_BITS 5
3138 * ring_buffer_nest_start - Allow to trace while nested
3139 * @buffer: The ring buffer to modify
3141 * The ring buffer has a safety mechanism to prevent recursion.
3142 * But there may be a case where a trace needs to be done while
3143 * tracing something else. In this case, calling this function
3144 * will allow this function to nest within a currently active
3145 * ring_buffer_lock_reserve().
3147 * Call this function before calling another ring_buffer_lock_reserve() and
3148 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3150 void ring_buffer_nest_start(struct trace_buffer
*buffer
)
3152 struct ring_buffer_per_cpu
*cpu_buffer
;
3155 /* Enabled by ring_buffer_nest_end() */
3156 preempt_disable_notrace();
3157 cpu
= raw_smp_processor_id();
3158 cpu_buffer
= buffer
->buffers
[cpu
];
3159 /* This is the shift value for the above recursive locking */
3160 cpu_buffer
->nest
+= NESTED_BITS
;
3164 * ring_buffer_nest_end - Allow to trace while nested
3165 * @buffer: The ring buffer to modify
3167 * Must be called after ring_buffer_nest_start() and after the
3168 * ring_buffer_unlock_commit().
3170 void ring_buffer_nest_end(struct trace_buffer
*buffer
)
3172 struct ring_buffer_per_cpu
*cpu_buffer
;
3175 /* disabled by ring_buffer_nest_start() */
3176 cpu
= raw_smp_processor_id();
3177 cpu_buffer
= buffer
->buffers
[cpu
];
3178 /* This is the shift value for the above recursive locking */
3179 cpu_buffer
->nest
-= NESTED_BITS
;
3180 preempt_enable_notrace();
3184 * ring_buffer_unlock_commit - commit a reserved
3185 * @buffer: The buffer to commit to
3187 * This commits the data to the ring buffer, and releases any locks held.
3189 * Must be paired with ring_buffer_lock_reserve.
3191 int ring_buffer_unlock_commit(struct trace_buffer
*buffer
)
3193 struct ring_buffer_per_cpu
*cpu_buffer
;
3194 int cpu
= raw_smp_processor_id();
3196 cpu_buffer
= buffer
->buffers
[cpu
];
3198 rb_commit(cpu_buffer
);
3200 rb_wakeups(buffer
, cpu_buffer
);
3202 trace_recursive_unlock(cpu_buffer
);
3204 preempt_enable_notrace();
3208 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
3210 /* Special value to validate all deltas on a page. */
3211 #define CHECK_FULL_PAGE 1L
3213 #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3215 static const char *show_irq_str(int bits
)
3217 const char *type
[] = {
3231 /* Assume this is an trace event */
3232 static const char *show_flags(struct ring_buffer_event
*event
)
3234 struct trace_entry
*entry
;
3237 if (rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
< sizeof(*entry
))
3240 entry
= ring_buffer_event_data(event
);
3242 if (entry
->flags
& TRACE_FLAG_SOFTIRQ
)
3245 if (entry
->flags
& TRACE_FLAG_HARDIRQ
)
3248 if (entry
->flags
& TRACE_FLAG_NMI
)
3251 return show_irq_str(bits
);
3254 static const char *show_irq(struct ring_buffer_event
*event
)
3256 struct trace_entry
*entry
;
3258 if (rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
< sizeof(*entry
))
3261 entry
= ring_buffer_event_data(event
);
3262 if (entry
->flags
& TRACE_FLAG_IRQS_OFF
)
3267 static const char *show_interrupt_level(void)
3269 unsigned long pc
= preempt_count();
3270 unsigned char level
= 0;
3272 if (pc
& SOFTIRQ_OFFSET
)
3275 if (pc
& HARDIRQ_MASK
)
3281 return show_irq_str(level
);
3284 static void dump_buffer_page(struct buffer_data_page
*bpage
,
3285 struct rb_event_info
*info
,
3288 struct ring_buffer_event
*event
;
3292 ts
= bpage
->time_stamp
;
3293 pr_warn(" [%lld] PAGE TIME STAMP\n", ts
);
3295 for (e
= 0; e
< tail
; e
+= rb_event_length(event
)) {
3297 event
= (struct ring_buffer_event
*)(bpage
->data
+ e
);
3299 switch (event
->type_len
) {
3301 case RINGBUF_TYPE_TIME_EXTEND
:
3302 delta
= rb_event_time_stamp(event
);
3304 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
3308 case RINGBUF_TYPE_TIME_STAMP
:
3309 delta
= rb_event_time_stamp(event
);
3310 ts
= rb_fix_abs_ts(delta
, ts
);
3311 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
3315 case RINGBUF_TYPE_PADDING
:
3316 ts
+= event
->time_delta
;
3317 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
3318 e
, ts
, event
->time_delta
);
3321 case RINGBUF_TYPE_DATA
:
3322 ts
+= event
->time_delta
;
3323 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
3324 e
, ts
, event
->time_delta
,
3325 show_flags(event
), show_irq(event
));
3332 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail
, e
);
3335 static DEFINE_PER_CPU(atomic_t
, checking
);
3336 static atomic_t ts_dump
;
3338 #define buffer_warn_return(fmt, ...) \
3340 /* If another report is happening, ignore this one */ \
3341 if (atomic_inc_return(&ts_dump) != 1) { \
3342 atomic_dec(&ts_dump); \
3345 atomic_inc(&cpu_buffer->record_disabled); \
3346 pr_warn(fmt, ##__VA_ARGS__); \
3347 dump_buffer_page(bpage, info, tail); \
3348 atomic_dec(&ts_dump); \
3349 /* There's some cases in boot up that this can happen */ \
3350 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
3351 /* Do not re-enable checking */ \
3356 * Check if the current event time stamp matches the deltas on
3359 static void check_buffer(struct ring_buffer_per_cpu
*cpu_buffer
,
3360 struct rb_event_info
*info
,
3363 struct ring_buffer_event
*event
;
3364 struct buffer_data_page
*bpage
;
3369 bpage
= info
->tail_page
->page
;
3371 if (tail
== CHECK_FULL_PAGE
) {
3373 tail
= local_read(&bpage
->commit
);
3374 } else if (info
->add_timestamp
&
3375 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
)) {
3376 /* Ignore events with absolute time stamps */
3381 * Do not check the first event (skip possible extends too).
3382 * Also do not check if previous events have not been committed.
3384 if (tail
<= 8 || tail
> local_read(&bpage
->commit
))
3388 * If this interrupted another event,
3390 if (atomic_inc_return(this_cpu_ptr(&checking
)) != 1)
3393 ts
= bpage
->time_stamp
;
3395 for (e
= 0; e
< tail
; e
+= rb_event_length(event
)) {
3397 event
= (struct ring_buffer_event
*)(bpage
->data
+ e
);
3399 switch (event
->type_len
) {
3401 case RINGBUF_TYPE_TIME_EXTEND
:
3402 delta
= rb_event_time_stamp(event
);
3406 case RINGBUF_TYPE_TIME_STAMP
:
3407 delta
= rb_event_time_stamp(event
);
3408 delta
= rb_fix_abs_ts(delta
, ts
);
3410 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
3411 cpu_buffer
->cpu
, ts
, delta
);
3416 case RINGBUF_TYPE_PADDING
:
3417 if (event
->time_delta
== 1)
3420 case RINGBUF_TYPE_DATA
:
3421 ts
+= event
->time_delta
;
3425 RB_WARN_ON(cpu_buffer
, 1);
3428 if ((full
&& ts
> info
->ts
) ||
3429 (!full
&& ts
+ info
->delta
!= info
->ts
)) {
3430 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
3432 ts
+ info
->delta
, info
->ts
, info
->delta
,
3433 info
->before
, info
->after
,
3434 full
? " (full)" : "", show_interrupt_level());
3437 atomic_dec(this_cpu_ptr(&checking
));
3440 static inline void check_buffer(struct ring_buffer_per_cpu
*cpu_buffer
,
3441 struct rb_event_info
*info
,
3445 #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3447 static struct ring_buffer_event
*
3448 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
3449 struct rb_event_info
*info
)
3451 struct ring_buffer_event
*event
;
3452 struct buffer_page
*tail_page
;
3453 unsigned long tail
, write
, w
;
3455 /* Don't let the compiler play games with cpu_buffer->tail_page */
3456 tail_page
= info
->tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
3458 /*A*/ w
= local_read(&tail_page
->write
) & RB_WRITE_MASK
;
3460 rb_time_read(&cpu_buffer
->before_stamp
, &info
->before
);
3461 rb_time_read(&cpu_buffer
->write_stamp
, &info
->after
);
3463 info
->ts
= rb_time_stamp(cpu_buffer
->buffer
);
3465 if ((info
->add_timestamp
& RB_ADD_STAMP_ABSOLUTE
)) {
3466 info
->delta
= info
->ts
;
3469 * If interrupting an event time update, we may need an
3470 * absolute timestamp.
3471 * Don't bother if this is the start of a new page (w == 0).
3474 /* Use the sub-buffer timestamp */
3476 } else if (unlikely(info
->before
!= info
->after
)) {
3477 info
->add_timestamp
|= RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_EXTEND
;
3478 info
->length
+= RB_LEN_TIME_EXTEND
;
3480 info
->delta
= info
->ts
- info
->after
;
3481 if (unlikely(test_time_stamp(info
->delta
))) {
3482 info
->add_timestamp
|= RB_ADD_STAMP_EXTEND
;
3483 info
->length
+= RB_LEN_TIME_EXTEND
;
3488 /*B*/ rb_time_set(&cpu_buffer
->before_stamp
, info
->ts
);
3490 /*C*/ write
= local_add_return(info
->length
, &tail_page
->write
);
3492 /* set write to only the index of the write */
3493 write
&= RB_WRITE_MASK
;
3495 tail
= write
- info
->length
;
3497 /* See if we shot pass the end of this buffer page */
3498 if (unlikely(write
> cpu_buffer
->buffer
->subbuf_size
)) {
3499 check_buffer(cpu_buffer
, info
, CHECK_FULL_PAGE
);
3500 return rb_move_tail(cpu_buffer
, tail
, info
);
3503 if (likely(tail
== w
)) {
3504 /* Nothing interrupted us between A and C */
3505 /*D*/ rb_time_set(&cpu_buffer
->write_stamp
, info
->ts
);
3507 * If something came in between C and D, the write stamp
3508 * may now not be in sync. But that's fine as the before_stamp
3509 * will be different and then next event will just be forced
3510 * to use an absolute timestamp.
3512 if (likely(!(info
->add_timestamp
&
3513 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
))))
3514 /* This did not interrupt any time update */
3515 info
->delta
= info
->ts
- info
->after
;
3517 /* Just use full timestamp for interrupting event */
3518 info
->delta
= info
->ts
;
3519 check_buffer(cpu_buffer
, info
, tail
);
3522 /* SLOW PATH - Interrupted between A and C */
3524 /* Save the old before_stamp */
3525 rb_time_read(&cpu_buffer
->before_stamp
, &info
->before
);
3528 * Read a new timestamp and update the before_stamp to make
3529 * the next event after this one force using an absolute
3530 * timestamp. This is in case an interrupt were to come in
3533 ts
= rb_time_stamp(cpu_buffer
->buffer
);
3534 rb_time_set(&cpu_buffer
->before_stamp
, ts
);
3537 /*E*/ rb_time_read(&cpu_buffer
->write_stamp
, &info
->after
);
3539 /*F*/ if (write
== (local_read(&tail_page
->write
) & RB_WRITE_MASK
) &&
3540 info
->after
== info
->before
&& info
->after
< ts
) {
3542 * Nothing came after this event between C and F, it is
3543 * safe to use info->after for the delta as it
3544 * matched info->before and is still valid.
3546 info
->delta
= ts
- info
->after
;
3549 * Interrupted between C and F:
3550 * Lost the previous events time stamp. Just set the
3551 * delta to zero, and this will be the same time as
3552 * the event this event interrupted. And the events that
3553 * came after this will still be correct (as they would
3554 * have built their delta on the previous event.
3559 info
->add_timestamp
&= ~RB_ADD_STAMP_FORCE
;
3563 * If this is the first commit on the page, then it has the same
3564 * timestamp as the page itself.
3566 if (unlikely(!tail
&& !(info
->add_timestamp
&
3567 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
))))
3570 /* We reserved something on the buffer */
3572 event
= __rb_page_index(tail_page
, tail
);
3573 rb_update_event(cpu_buffer
, event
, info
);
3575 local_inc(&tail_page
->entries
);
3578 * If this is the first commit on the page, then update
3581 if (unlikely(!tail
))
3582 tail_page
->page
->time_stamp
= info
->ts
;
3584 /* account for these added bytes */
3585 local_add(info
->length
, &cpu_buffer
->entries_bytes
);
3590 static __always_inline
struct ring_buffer_event
*
3591 rb_reserve_next_event(struct trace_buffer
*buffer
,
3592 struct ring_buffer_per_cpu
*cpu_buffer
,
3593 unsigned long length
)
3595 struct ring_buffer_event
*event
;
3596 struct rb_event_info info
;
3600 /* ring buffer does cmpxchg, make sure it is safe in NMI context */
3601 if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
) &&
3602 (unlikely(in_nmi()))) {
3606 rb_start_commit(cpu_buffer
);
3607 /* The commit page can not change after this */
3609 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3611 * Due to the ability to swap a cpu buffer from a buffer
3612 * it is possible it was swapped before we committed.
3613 * (committing stops a swap). We check for it here and
3614 * if it happened, we have to fail the write.
3617 if (unlikely(READ_ONCE(cpu_buffer
->buffer
) != buffer
)) {
3618 local_dec(&cpu_buffer
->committing
);
3619 local_dec(&cpu_buffer
->commits
);
3624 info
.length
= rb_calculate_event_length(length
);
3626 if (ring_buffer_time_stamp_abs(cpu_buffer
->buffer
)) {
3627 add_ts_default
= RB_ADD_STAMP_ABSOLUTE
;
3628 info
.length
+= RB_LEN_TIME_EXTEND
;
3629 if (info
.length
> cpu_buffer
->buffer
->max_data_size
)
3632 add_ts_default
= RB_ADD_STAMP_NONE
;
3636 info
.add_timestamp
= add_ts_default
;
3640 * We allow for interrupts to reenter here and do a trace.
3641 * If one does, it will cause this original code to loop
3642 * back here. Even with heavy interrupts happening, this
3643 * should only happen a few times in a row. If this happens
3644 * 1000 times in a row, there must be either an interrupt
3645 * storm or we have something buggy.
3648 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
3651 event
= __rb_reserve_next(cpu_buffer
, &info
);
3653 if (unlikely(PTR_ERR(event
) == -EAGAIN
)) {
3654 if (info
.add_timestamp
& (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_EXTEND
))
3655 info
.length
-= RB_LEN_TIME_EXTEND
;
3662 rb_end_commit(cpu_buffer
);
3667 * ring_buffer_lock_reserve - reserve a part of the buffer
3668 * @buffer: the ring buffer to reserve from
3669 * @length: the length of the data to reserve (excluding event header)
3671 * Returns a reserved event on the ring buffer to copy directly to.
3672 * The user of this interface will need to get the body to write into
3673 * and can use the ring_buffer_event_data() interface.
3675 * The length is the length of the data needed, not the event length
3676 * which also includes the event header.
3678 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3679 * If NULL is returned, then nothing has been allocated or locked.
3681 struct ring_buffer_event
*
3682 ring_buffer_lock_reserve(struct trace_buffer
*buffer
, unsigned long length
)
3684 struct ring_buffer_per_cpu
*cpu_buffer
;
3685 struct ring_buffer_event
*event
;
3688 /* If we are tracing schedule, we don't want to recurse */
3689 preempt_disable_notrace();
3691 if (unlikely(atomic_read(&buffer
->record_disabled
)))
3694 cpu
= raw_smp_processor_id();
3696 if (unlikely(!cpumask_test_cpu(cpu
, buffer
->cpumask
)))
3699 cpu_buffer
= buffer
->buffers
[cpu
];
3701 if (unlikely(atomic_read(&cpu_buffer
->record_disabled
)))
3704 if (unlikely(length
> buffer
->max_data_size
))
3707 if (unlikely(trace_recursive_lock(cpu_buffer
)))
3710 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
3717 trace_recursive_unlock(cpu_buffer
);
3719 preempt_enable_notrace();
3722 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
3725 * Decrement the entries to the page that an event is on.
3726 * The event does not even need to exist, only the pointer
3727 * to the page it is on. This may only be called before the commit
3731 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
3732 struct ring_buffer_event
*event
)
3734 unsigned long addr
= (unsigned long)event
;
3735 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
3736 struct buffer_page
*start
;
3738 addr
&= ~((PAGE_SIZE
<< cpu_buffer
->buffer
->subbuf_order
) - 1);
3740 /* Do the likely case first */
3741 if (likely(bpage
->page
== (void *)addr
)) {
3742 local_dec(&bpage
->entries
);
3747 * Because the commit page may be on the reader page we
3748 * start with the next page and check the end loop there.
3750 rb_inc_page(&bpage
);
3753 if (bpage
->page
== (void *)addr
) {
3754 local_dec(&bpage
->entries
);
3757 rb_inc_page(&bpage
);
3758 } while (bpage
!= start
);
3760 /* commit not part of this buffer?? */
3761 RB_WARN_ON(cpu_buffer
, 1);
3765 * ring_buffer_discard_commit - discard an event that has not been committed
3766 * @buffer: the ring buffer
3767 * @event: non committed event to discard
3769 * Sometimes an event that is in the ring buffer needs to be ignored.
3770 * This function lets the user discard an event in the ring buffer
3771 * and then that event will not be read later.
3773 * This function only works if it is called before the item has been
3774 * committed. It will try to free the event from the ring buffer
3775 * if another event has not been added behind it.
3777 * If another event has been added behind it, it will set the event
3778 * up as discarded, and perform the commit.
3780 * If this function is called, do not call ring_buffer_unlock_commit on
3783 void ring_buffer_discard_commit(struct trace_buffer
*buffer
,
3784 struct ring_buffer_event
*event
)
3786 struct ring_buffer_per_cpu
*cpu_buffer
;
3789 /* The event is discarded regardless */
3790 rb_event_discard(event
);
3792 cpu
= smp_processor_id();
3793 cpu_buffer
= buffer
->buffers
[cpu
];
3796 * This must only be called if the event has not been
3797 * committed yet. Thus we can assume that preemption
3798 * is still disabled.
3800 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
3802 rb_decrement_entry(cpu_buffer
, event
);
3803 if (rb_try_to_discard(cpu_buffer
, event
))
3807 rb_end_commit(cpu_buffer
);
3809 trace_recursive_unlock(cpu_buffer
);
3811 preempt_enable_notrace();
3814 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
3817 * ring_buffer_write - write data to the buffer without reserving
3818 * @buffer: The ring buffer to write to.
3819 * @length: The length of the data being written (excluding the event header)
3820 * @data: The data to write to the buffer.
3822 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3823 * one function. If you already have the data to write to the buffer, it
3824 * may be easier to simply call this function.
3826 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3827 * and not the length of the event which would hold the header.
3829 int ring_buffer_write(struct trace_buffer
*buffer
,
3830 unsigned long length
,
3833 struct ring_buffer_per_cpu
*cpu_buffer
;
3834 struct ring_buffer_event
*event
;
3839 preempt_disable_notrace();
3841 if (atomic_read(&buffer
->record_disabled
))
3844 cpu
= raw_smp_processor_id();
3846 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3849 cpu_buffer
= buffer
->buffers
[cpu
];
3851 if (atomic_read(&cpu_buffer
->record_disabled
))
3854 if (length
> buffer
->max_data_size
)
3857 if (unlikely(trace_recursive_lock(cpu_buffer
)))
3860 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
3864 body
= rb_event_data(event
);
3866 memcpy(body
, data
, length
);
3868 rb_commit(cpu_buffer
);
3870 rb_wakeups(buffer
, cpu_buffer
);
3875 trace_recursive_unlock(cpu_buffer
);
3878 preempt_enable_notrace();
3882 EXPORT_SYMBOL_GPL(ring_buffer_write
);
3884 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
3886 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
3887 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
3888 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
3890 /* In case of error, head will be NULL */
3891 if (unlikely(!head
))
3894 /* Reader should exhaust content in reader page */
3895 if (reader
->read
!= rb_page_commit(reader
))
3899 * If writers are committing on the reader page, knowing all
3900 * committed content has been read, the ring buffer is empty.
3902 if (commit
== reader
)
3906 * If writers are committing on a page other than reader page
3907 * and head page, there should always be content to read.
3913 * Writers are committing on the head page, we just need
3914 * to care about there're committed data, and the reader will
3915 * swap reader page with head page when it is to read data.
3917 return rb_page_commit(commit
) == 0;
3921 * ring_buffer_record_disable - stop all writes into the buffer
3922 * @buffer: The ring buffer to stop writes to.
3924 * This prevents all writes to the buffer. Any attempt to write
3925 * to the buffer after this will fail and return NULL.
3927 * The caller should call synchronize_rcu() after this.
3929 void ring_buffer_record_disable(struct trace_buffer
*buffer
)
3931 atomic_inc(&buffer
->record_disabled
);
3933 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
3936 * ring_buffer_record_enable - enable writes to the buffer
3937 * @buffer: The ring buffer to enable writes
3939 * Note, multiple disables will need the same number of enables
3940 * to truly enable the writing (much like preempt_disable).
3942 void ring_buffer_record_enable(struct trace_buffer
*buffer
)
3944 atomic_dec(&buffer
->record_disabled
);
3946 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
3949 * ring_buffer_record_off - stop all writes into the buffer
3950 * @buffer: The ring buffer to stop writes to.
3952 * This prevents all writes to the buffer. Any attempt to write
3953 * to the buffer after this will fail and return NULL.
3955 * This is different than ring_buffer_record_disable() as
3956 * it works like an on/off switch, where as the disable() version
3957 * must be paired with a enable().
3959 void ring_buffer_record_off(struct trace_buffer
*buffer
)
3962 unsigned int new_rd
;
3964 rd
= atomic_read(&buffer
->record_disabled
);
3966 new_rd
= rd
| RB_BUFFER_OFF
;
3967 } while (!atomic_try_cmpxchg(&buffer
->record_disabled
, &rd
, new_rd
));
3969 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
3972 * ring_buffer_record_on - restart writes into the buffer
3973 * @buffer: The ring buffer to start writes to.
3975 * This enables all writes to the buffer that was disabled by
3976 * ring_buffer_record_off().
3978 * This is different than ring_buffer_record_enable() as
3979 * it works like an on/off switch, where as the enable() version
3980 * must be paired with a disable().
3982 void ring_buffer_record_on(struct trace_buffer
*buffer
)
3985 unsigned int new_rd
;
3987 rd
= atomic_read(&buffer
->record_disabled
);
3989 new_rd
= rd
& ~RB_BUFFER_OFF
;
3990 } while (!atomic_try_cmpxchg(&buffer
->record_disabled
, &rd
, new_rd
));
3992 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
3995 * ring_buffer_record_is_on - return true if the ring buffer can write
3996 * @buffer: The ring buffer to see if write is enabled
3998 * Returns true if the ring buffer is in a state that it accepts writes.
4000 bool ring_buffer_record_is_on(struct trace_buffer
*buffer
)
4002 return !atomic_read(&buffer
->record_disabled
);
4006 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4007 * @buffer: The ring buffer to see if write is set enabled
4009 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4010 * Note that this does NOT mean it is in a writable state.
4012 * It may return true when the ring buffer has been disabled by
4013 * ring_buffer_record_disable(), as that is a temporary disabling of
4016 bool ring_buffer_record_is_set_on(struct trace_buffer
*buffer
)
4018 return !(atomic_read(&buffer
->record_disabled
) & RB_BUFFER_OFF
);
4022 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4023 * @buffer: The ring buffer to stop writes to.
4024 * @cpu: The CPU buffer to stop
4026 * This prevents all writes to the buffer. Any attempt to write
4027 * to the buffer after this will fail and return NULL.
4029 * The caller should call synchronize_rcu() after this.
4031 void ring_buffer_record_disable_cpu(struct trace_buffer
*buffer
, int cpu
)
4033 struct ring_buffer_per_cpu
*cpu_buffer
;
4035 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4038 cpu_buffer
= buffer
->buffers
[cpu
];
4039 atomic_inc(&cpu_buffer
->record_disabled
);
4041 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
4044 * ring_buffer_record_enable_cpu - enable writes to the buffer
4045 * @buffer: The ring buffer to enable writes
4046 * @cpu: The CPU to enable.
4048 * Note, multiple disables will need the same number of enables
4049 * to truly enable the writing (much like preempt_disable).
4051 void ring_buffer_record_enable_cpu(struct trace_buffer
*buffer
, int cpu
)
4053 struct ring_buffer_per_cpu
*cpu_buffer
;
4055 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4058 cpu_buffer
= buffer
->buffers
[cpu
];
4059 atomic_dec(&cpu_buffer
->record_disabled
);
4061 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
4064 * The total entries in the ring buffer is the running counter
4065 * of entries entered into the ring buffer, minus the sum of
4066 * the entries read from the ring buffer and the number of
4067 * entries that were overwritten.
4069 static inline unsigned long
4070 rb_num_of_entries(struct ring_buffer_per_cpu
*cpu_buffer
)
4072 return local_read(&cpu_buffer
->entries
) -
4073 (local_read(&cpu_buffer
->overrun
) + cpu_buffer
->read
);
4077 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4078 * @buffer: The ring buffer
4079 * @cpu: The per CPU buffer to read from.
4081 u64
ring_buffer_oldest_event_ts(struct trace_buffer
*buffer
, int cpu
)
4083 unsigned long flags
;
4084 struct ring_buffer_per_cpu
*cpu_buffer
;
4085 struct buffer_page
*bpage
;
4088 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4091 cpu_buffer
= buffer
->buffers
[cpu
];
4092 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4094 * if the tail is on reader_page, oldest time stamp is on the reader
4097 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
4098 bpage
= cpu_buffer
->reader_page
;
4100 bpage
= rb_set_head_page(cpu_buffer
);
4102 ret
= bpage
->page
->time_stamp
;
4103 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4107 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts
);
4110 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4111 * @buffer: The ring buffer
4112 * @cpu: The per CPU buffer to read from.
4114 unsigned long ring_buffer_bytes_cpu(struct trace_buffer
*buffer
, int cpu
)
4116 struct ring_buffer_per_cpu
*cpu_buffer
;
4119 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4122 cpu_buffer
= buffer
->buffers
[cpu
];
4123 ret
= local_read(&cpu_buffer
->entries_bytes
) - cpu_buffer
->read_bytes
;
4127 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu
);
4130 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4131 * @buffer: The ring buffer
4132 * @cpu: The per CPU buffer to get the entries from.
4134 unsigned long ring_buffer_entries_cpu(struct trace_buffer
*buffer
, int cpu
)
4136 struct ring_buffer_per_cpu
*cpu_buffer
;
4138 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4141 cpu_buffer
= buffer
->buffers
[cpu
];
4143 return rb_num_of_entries(cpu_buffer
);
4145 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
4148 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4149 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4150 * @buffer: The ring buffer
4151 * @cpu: The per CPU buffer to get the number of overruns from
4153 unsigned long ring_buffer_overrun_cpu(struct trace_buffer
*buffer
, int cpu
)
4155 struct ring_buffer_per_cpu
*cpu_buffer
;
4158 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4161 cpu_buffer
= buffer
->buffers
[cpu
];
4162 ret
= local_read(&cpu_buffer
->overrun
);
4166 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
4169 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4170 * commits failing due to the buffer wrapping around while there are uncommitted
4171 * events, such as during an interrupt storm.
4172 * @buffer: The ring buffer
4173 * @cpu: The per CPU buffer to get the number of overruns from
4176 ring_buffer_commit_overrun_cpu(struct trace_buffer
*buffer
, int cpu
)
4178 struct ring_buffer_per_cpu
*cpu_buffer
;
4181 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4184 cpu_buffer
= buffer
->buffers
[cpu
];
4185 ret
= local_read(&cpu_buffer
->commit_overrun
);
4189 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
4192 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4193 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4194 * @buffer: The ring buffer
4195 * @cpu: The per CPU buffer to get the number of overruns from
4198 ring_buffer_dropped_events_cpu(struct trace_buffer
*buffer
, int cpu
)
4200 struct ring_buffer_per_cpu
*cpu_buffer
;
4203 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4206 cpu_buffer
= buffer
->buffers
[cpu
];
4207 ret
= local_read(&cpu_buffer
->dropped_events
);
4211 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu
);
4214 * ring_buffer_read_events_cpu - get the number of events successfully read
4215 * @buffer: The ring buffer
4216 * @cpu: The per CPU buffer to get the number of events read
4219 ring_buffer_read_events_cpu(struct trace_buffer
*buffer
, int cpu
)
4221 struct ring_buffer_per_cpu
*cpu_buffer
;
4223 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4226 cpu_buffer
= buffer
->buffers
[cpu
];
4227 return cpu_buffer
->read
;
4229 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu
);
4232 * ring_buffer_entries - get the number of entries in a buffer
4233 * @buffer: The ring buffer
4235 * Returns the total number of entries in the ring buffer
4238 unsigned long ring_buffer_entries(struct trace_buffer
*buffer
)
4240 struct ring_buffer_per_cpu
*cpu_buffer
;
4241 unsigned long entries
= 0;
4244 /* if you care about this being correct, lock the buffer */
4245 for_each_buffer_cpu(buffer
, cpu
) {
4246 cpu_buffer
= buffer
->buffers
[cpu
];
4247 entries
+= rb_num_of_entries(cpu_buffer
);
4252 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
4255 * ring_buffer_overruns - get the number of overruns in buffer
4256 * @buffer: The ring buffer
4258 * Returns the total number of overruns in the ring buffer
4261 unsigned long ring_buffer_overruns(struct trace_buffer
*buffer
)
4263 struct ring_buffer_per_cpu
*cpu_buffer
;
4264 unsigned long overruns
= 0;
4267 /* if you care about this being correct, lock the buffer */
4268 for_each_buffer_cpu(buffer
, cpu
) {
4269 cpu_buffer
= buffer
->buffers
[cpu
];
4270 overruns
+= local_read(&cpu_buffer
->overrun
);
4275 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
4277 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
4279 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4281 /* Iterator usage is expected to have record disabled */
4282 iter
->head_page
= cpu_buffer
->reader_page
;
4283 iter
->head
= cpu_buffer
->reader_page
->read
;
4284 iter
->next_event
= iter
->head
;
4286 iter
->cache_reader_page
= iter
->head_page
;
4287 iter
->cache_read
= cpu_buffer
->read
;
4288 iter
->cache_pages_removed
= cpu_buffer
->pages_removed
;
4291 iter
->read_stamp
= cpu_buffer
->read_stamp
;
4292 iter
->page_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
4294 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
4295 iter
->page_stamp
= iter
->read_stamp
;
4300 * ring_buffer_iter_reset - reset an iterator
4301 * @iter: The iterator to reset
4303 * Resets the iterator, so that it will start from the beginning
4306 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
4308 struct ring_buffer_per_cpu
*cpu_buffer
;
4309 unsigned long flags
;
4314 cpu_buffer
= iter
->cpu_buffer
;
4316 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4317 rb_iter_reset(iter
);
4318 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4320 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
4323 * ring_buffer_iter_empty - check if an iterator has no more to read
4324 * @iter: The iterator to check
4326 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
4328 struct ring_buffer_per_cpu
*cpu_buffer
;
4329 struct buffer_page
*reader
;
4330 struct buffer_page
*head_page
;
4331 struct buffer_page
*commit_page
;
4332 struct buffer_page
*curr_commit_page
;
4337 cpu_buffer
= iter
->cpu_buffer
;
4338 reader
= cpu_buffer
->reader_page
;
4339 head_page
= cpu_buffer
->head_page
;
4340 commit_page
= cpu_buffer
->commit_page
;
4341 commit_ts
= commit_page
->page
->time_stamp
;
4344 * When the writer goes across pages, it issues a cmpxchg which
4345 * is a mb(), which will synchronize with the rmb here.
4346 * (see rb_tail_page_update())
4349 commit
= rb_page_commit(commit_page
);
4350 /* We want to make sure that the commit page doesn't change */
4353 /* Make sure commit page didn't change */
4354 curr_commit_page
= READ_ONCE(cpu_buffer
->commit_page
);
4355 curr_commit_ts
= READ_ONCE(curr_commit_page
->page
->time_stamp
);
4357 /* If the commit page changed, then there's more data */
4358 if (curr_commit_page
!= commit_page
||
4359 curr_commit_ts
!= commit_ts
)
4362 /* Still racy, as it may return a false positive, but that's OK */
4363 return ((iter
->head_page
== commit_page
&& iter
->head
>= commit
) ||
4364 (iter
->head_page
== reader
&& commit_page
== head_page
&&
4365 head_page
->read
== commit
&&
4366 iter
->head
== rb_page_commit(cpu_buffer
->reader_page
)));
4368 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
4371 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
4372 struct ring_buffer_event
*event
)
4376 switch (event
->type_len
) {
4377 case RINGBUF_TYPE_PADDING
:
4380 case RINGBUF_TYPE_TIME_EXTEND
:
4381 delta
= rb_event_time_stamp(event
);
4382 cpu_buffer
->read_stamp
+= delta
;
4385 case RINGBUF_TYPE_TIME_STAMP
:
4386 delta
= rb_event_time_stamp(event
);
4387 delta
= rb_fix_abs_ts(delta
, cpu_buffer
->read_stamp
);
4388 cpu_buffer
->read_stamp
= delta
;
4391 case RINGBUF_TYPE_DATA
:
4392 cpu_buffer
->read_stamp
+= event
->time_delta
;
4396 RB_WARN_ON(cpu_buffer
, 1);
4401 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
4402 struct ring_buffer_event
*event
)
4406 switch (event
->type_len
) {
4407 case RINGBUF_TYPE_PADDING
:
4410 case RINGBUF_TYPE_TIME_EXTEND
:
4411 delta
= rb_event_time_stamp(event
);
4412 iter
->read_stamp
+= delta
;
4415 case RINGBUF_TYPE_TIME_STAMP
:
4416 delta
= rb_event_time_stamp(event
);
4417 delta
= rb_fix_abs_ts(delta
, iter
->read_stamp
);
4418 iter
->read_stamp
= delta
;
4421 case RINGBUF_TYPE_DATA
:
4422 iter
->read_stamp
+= event
->time_delta
;
4426 RB_WARN_ON(iter
->cpu_buffer
, 1);
4430 static struct buffer_page
*
4431 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
4433 struct buffer_page
*reader
= NULL
;
4434 unsigned long bsize
= READ_ONCE(cpu_buffer
->buffer
->subbuf_size
);
4435 unsigned long overwrite
;
4436 unsigned long flags
;
4440 local_irq_save(flags
);
4441 arch_spin_lock(&cpu_buffer
->lock
);
4445 * This should normally only loop twice. But because the
4446 * start of the reader inserts an empty page, it causes
4447 * a case where we will loop three times. There should be no
4448 * reason to loop four times (that I know of).
4450 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
4455 reader
= cpu_buffer
->reader_page
;
4457 /* If there's more to read, return this page */
4458 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
4461 /* Never should we have an index greater than the size */
4462 if (RB_WARN_ON(cpu_buffer
,
4463 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
4466 /* check if we caught up to the tail */
4468 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
4471 /* Don't bother swapping if the ring buffer is empty */
4472 if (rb_num_of_entries(cpu_buffer
) == 0)
4476 * Reset the reader page to size zero.
4478 local_set(&cpu_buffer
->reader_page
->write
, 0);
4479 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4480 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4481 cpu_buffer
->reader_page
->real_end
= 0;
4485 * Splice the empty reader page into the list around the head.
4487 reader
= rb_set_head_page(cpu_buffer
);
4490 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
4491 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
4494 * cpu_buffer->pages just needs to point to the buffer, it
4495 * has no specific buffer page to point to. Lets move it out
4496 * of our way so we don't accidentally swap it.
4498 cpu_buffer
->pages
= reader
->list
.prev
;
4500 /* The reader page will be pointing to the new head */
4501 rb_set_list_to_head(&cpu_buffer
->reader_page
->list
);
4504 * We want to make sure we read the overruns after we set up our
4505 * pointers to the next object. The writer side does a
4506 * cmpxchg to cross pages which acts as the mb on the writer
4507 * side. Note, the reader will constantly fail the swap
4508 * while the writer is updating the pointers, so this
4509 * guarantees that the overwrite recorded here is the one we
4510 * want to compare with the last_overrun.
4513 overwrite
= local_read(&(cpu_buffer
->overrun
));
4516 * Here's the tricky part.
4518 * We need to move the pointer past the header page.
4519 * But we can only do that if a writer is not currently
4520 * moving it. The page before the header page has the
4521 * flag bit '1' set if it is pointing to the page we want.
4522 * but if the writer is in the process of moving it
4523 * than it will be '2' or already moved '0'.
4526 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
4529 * If we did not convert it, then we must try again.
4535 * Yay! We succeeded in replacing the page.
4537 * Now make the new head point back to the reader page.
4539 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
4540 rb_inc_page(&cpu_buffer
->head_page
);
4542 local_inc(&cpu_buffer
->pages_read
);
4544 /* Finally update the reader page to the new head */
4545 cpu_buffer
->reader_page
= reader
;
4546 cpu_buffer
->reader_page
->read
= 0;
4548 if (overwrite
!= cpu_buffer
->last_overrun
) {
4549 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
4550 cpu_buffer
->last_overrun
= overwrite
;
4556 /* Update the read_stamp on the first event */
4557 if (reader
&& reader
->read
== 0)
4558 cpu_buffer
->read_stamp
= reader
->page
->time_stamp
;
4560 arch_spin_unlock(&cpu_buffer
->lock
);
4561 local_irq_restore(flags
);
4564 * The writer has preempt disable, wait for it. But not forever
4565 * Although, 1 second is pretty much "forever"
4567 #define USECS_WAIT 1000000
4568 for (nr_loops
= 0; nr_loops
< USECS_WAIT
; nr_loops
++) {
4569 /* If the write is past the end of page, a writer is still updating it */
4570 if (likely(!reader
|| rb_page_write(reader
) <= bsize
))
4575 /* Get the latest version of the reader write value */
4579 /* The writer is not moving forward? Something is wrong */
4580 if (RB_WARN_ON(cpu_buffer
, nr_loops
== USECS_WAIT
))
4584 * Make sure we see any padding after the write update
4585 * (see rb_reset_tail()).
4587 * In addition, a writer may be writing on the reader page
4588 * if the page has not been fully filled, so the read barrier
4589 * is also needed to make sure we see the content of what is
4590 * committed by the writer (see rb_set_commit_to_write()).
4598 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
4600 struct ring_buffer_event
*event
;
4601 struct buffer_page
*reader
;
4604 reader
= rb_get_reader_page(cpu_buffer
);
4606 /* This function should not be called when buffer is empty */
4607 if (RB_WARN_ON(cpu_buffer
, !reader
))
4610 event
= rb_reader_event(cpu_buffer
);
4612 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
4615 rb_update_read_stamp(cpu_buffer
, event
);
4617 length
= rb_event_length(event
);
4618 cpu_buffer
->reader_page
->read
+= length
;
4619 cpu_buffer
->read_bytes
+= length
;
4622 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
4624 struct ring_buffer_per_cpu
*cpu_buffer
;
4626 cpu_buffer
= iter
->cpu_buffer
;
4628 /* If head == next_event then we need to jump to the next event */
4629 if (iter
->head
== iter
->next_event
) {
4630 /* If the event gets overwritten again, there's nothing to do */
4631 if (rb_iter_head_event(iter
) == NULL
)
4635 iter
->head
= iter
->next_event
;
4638 * Check if we are at the end of the buffer.
4640 if (iter
->next_event
>= rb_page_size(iter
->head_page
)) {
4641 /* discarded commits can make the page empty */
4642 if (iter
->head_page
== cpu_buffer
->commit_page
)
4648 rb_update_iter_read_stamp(iter
, iter
->event
);
4651 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
4653 return cpu_buffer
->lost_events
;
4656 static struct ring_buffer_event
*
4657 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
4658 unsigned long *lost_events
)
4660 struct ring_buffer_event
*event
;
4661 struct buffer_page
*reader
;
4668 * We repeat when a time extend is encountered.
4669 * Since the time extend is always attached to a data event,
4670 * we should never loop more than once.
4671 * (We never hit the following condition more than twice).
4673 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
4676 reader
= rb_get_reader_page(cpu_buffer
);
4680 event
= rb_reader_event(cpu_buffer
);
4682 switch (event
->type_len
) {
4683 case RINGBUF_TYPE_PADDING
:
4684 if (rb_null_event(event
))
4685 RB_WARN_ON(cpu_buffer
, 1);
4687 * Because the writer could be discarding every
4688 * event it creates (which would probably be bad)
4689 * if we were to go back to "again" then we may never
4690 * catch up, and will trigger the warn on, or lock
4691 * the box. Return the padding, and we will release
4692 * the current locks, and try again.
4696 case RINGBUF_TYPE_TIME_EXTEND
:
4697 /* Internal data, OK to advance */
4698 rb_advance_reader(cpu_buffer
);
4701 case RINGBUF_TYPE_TIME_STAMP
:
4703 *ts
= rb_event_time_stamp(event
);
4704 *ts
= rb_fix_abs_ts(*ts
, reader
->page
->time_stamp
);
4705 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4706 cpu_buffer
->cpu
, ts
);
4708 /* Internal data, OK to advance */
4709 rb_advance_reader(cpu_buffer
);
4712 case RINGBUF_TYPE_DATA
:
4714 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
4715 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4716 cpu_buffer
->cpu
, ts
);
4719 *lost_events
= rb_lost_events(cpu_buffer
);
4723 RB_WARN_ON(cpu_buffer
, 1);
4728 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
4730 static struct ring_buffer_event
*
4731 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
4733 struct trace_buffer
*buffer
;
4734 struct ring_buffer_per_cpu
*cpu_buffer
;
4735 struct ring_buffer_event
*event
;
4741 cpu_buffer
= iter
->cpu_buffer
;
4742 buffer
= cpu_buffer
->buffer
;
4745 * Check if someone performed a consuming read to the buffer
4746 * or removed some pages from the buffer. In these cases,
4747 * iterator was invalidated and we need to reset it.
4749 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
4750 iter
->cache_reader_page
!= cpu_buffer
->reader_page
||
4751 iter
->cache_pages_removed
!= cpu_buffer
->pages_removed
))
4752 rb_iter_reset(iter
);
4755 if (ring_buffer_iter_empty(iter
))
4759 * As the writer can mess with what the iterator is trying
4760 * to read, just give up if we fail to get an event after
4761 * three tries. The iterator is not as reliable when reading
4762 * the ring buffer with an active write as the consumer is.
4763 * Do not warn if the three failures is reached.
4768 if (rb_per_cpu_empty(cpu_buffer
))
4771 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
4776 event
= rb_iter_head_event(iter
);
4780 switch (event
->type_len
) {
4781 case RINGBUF_TYPE_PADDING
:
4782 if (rb_null_event(event
)) {
4786 rb_advance_iter(iter
);
4789 case RINGBUF_TYPE_TIME_EXTEND
:
4790 /* Internal data, OK to advance */
4791 rb_advance_iter(iter
);
4794 case RINGBUF_TYPE_TIME_STAMP
:
4796 *ts
= rb_event_time_stamp(event
);
4797 *ts
= rb_fix_abs_ts(*ts
, iter
->head_page
->page
->time_stamp
);
4798 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4799 cpu_buffer
->cpu
, ts
);
4801 /* Internal data, OK to advance */
4802 rb_advance_iter(iter
);
4805 case RINGBUF_TYPE_DATA
:
4807 *ts
= iter
->read_stamp
+ event
->time_delta
;
4808 ring_buffer_normalize_time_stamp(buffer
,
4809 cpu_buffer
->cpu
, ts
);
4814 RB_WARN_ON(cpu_buffer
, 1);
4819 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
4821 static inline bool rb_reader_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
4823 if (likely(!in_nmi())) {
4824 raw_spin_lock(&cpu_buffer
->reader_lock
);
4829 * If an NMI die dumps out the content of the ring buffer
4830 * trylock must be used to prevent a deadlock if the NMI
4831 * preempted a task that holds the ring buffer locks. If
4832 * we get the lock then all is fine, if not, then continue
4833 * to do the read, but this can corrupt the ring buffer,
4834 * so it must be permanently disabled from future writes.
4835 * Reading from NMI is a oneshot deal.
4837 if (raw_spin_trylock(&cpu_buffer
->reader_lock
))
4840 /* Continue without locking, but disable the ring buffer */
4841 atomic_inc(&cpu_buffer
->record_disabled
);
4846 rb_reader_unlock(struct ring_buffer_per_cpu
*cpu_buffer
, bool locked
)
4849 raw_spin_unlock(&cpu_buffer
->reader_lock
);
4853 * ring_buffer_peek - peek at the next event to be read
4854 * @buffer: The ring buffer to read
4855 * @cpu: The cpu to peak at
4856 * @ts: The timestamp counter of this event.
4857 * @lost_events: a variable to store if events were lost (may be NULL)
4859 * This will return the event that will be read next, but does
4860 * not consume the data.
4862 struct ring_buffer_event
*
4863 ring_buffer_peek(struct trace_buffer
*buffer
, int cpu
, u64
*ts
,
4864 unsigned long *lost_events
)
4866 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4867 struct ring_buffer_event
*event
;
4868 unsigned long flags
;
4871 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4875 local_irq_save(flags
);
4876 dolock
= rb_reader_lock(cpu_buffer
);
4877 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
4878 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4879 rb_advance_reader(cpu_buffer
);
4880 rb_reader_unlock(cpu_buffer
, dolock
);
4881 local_irq_restore(flags
);
4883 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4889 /** ring_buffer_iter_dropped - report if there are dropped events
4890 * @iter: The ring buffer iterator
4892 * Returns true if there was dropped events since the last peek.
4894 bool ring_buffer_iter_dropped(struct ring_buffer_iter
*iter
)
4896 bool ret
= iter
->missed_events
!= 0;
4898 iter
->missed_events
= 0;
4901 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped
);
4904 * ring_buffer_iter_peek - peek at the next event to be read
4905 * @iter: The ring buffer iterator
4906 * @ts: The timestamp counter of this event.
4908 * This will return the event that will be read next, but does
4909 * not increment the iterator.
4911 struct ring_buffer_event
*
4912 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
4914 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4915 struct ring_buffer_event
*event
;
4916 unsigned long flags
;
4919 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4920 event
= rb_iter_peek(iter
, ts
);
4921 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4923 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4930 * ring_buffer_consume - return an event and consume it
4931 * @buffer: The ring buffer to get the next event from
4932 * @cpu: the cpu to read the buffer from
4933 * @ts: a variable to store the timestamp (may be NULL)
4934 * @lost_events: a variable to store if events were lost (may be NULL)
4936 * Returns the next event in the ring buffer, and that event is consumed.
4937 * Meaning, that sequential reads will keep returning a different event,
4938 * and eventually empty the ring buffer if the producer is slower.
4940 struct ring_buffer_event
*
4941 ring_buffer_consume(struct trace_buffer
*buffer
, int cpu
, u64
*ts
,
4942 unsigned long *lost_events
)
4944 struct ring_buffer_per_cpu
*cpu_buffer
;
4945 struct ring_buffer_event
*event
= NULL
;
4946 unsigned long flags
;
4950 /* might be called in atomic */
4953 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4956 cpu_buffer
= buffer
->buffers
[cpu
];
4957 local_irq_save(flags
);
4958 dolock
= rb_reader_lock(cpu_buffer
);
4960 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
4962 cpu_buffer
->lost_events
= 0;
4963 rb_advance_reader(cpu_buffer
);
4966 rb_reader_unlock(cpu_buffer
, dolock
);
4967 local_irq_restore(flags
);
4972 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4977 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
4980 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4981 * @buffer: The ring buffer to read from
4982 * @cpu: The cpu buffer to iterate over
4983 * @flags: gfp flags to use for memory allocation
4985 * This performs the initial preparations necessary to iterate
4986 * through the buffer. Memory is allocated, buffer recording
4987 * is disabled, and the iterator pointer is returned to the caller.
4989 * Disabling buffer recording prevents the reading from being
4990 * corrupted. This is not a consuming read, so a producer is not
4993 * After a sequence of ring_buffer_read_prepare calls, the user is
4994 * expected to make at least one call to ring_buffer_read_prepare_sync.
4995 * Afterwards, ring_buffer_read_start is invoked to get things going
4998 * This overall must be paired with ring_buffer_read_finish.
5000 struct ring_buffer_iter
*
5001 ring_buffer_read_prepare(struct trace_buffer
*buffer
, int cpu
, gfp_t flags
)
5003 struct ring_buffer_per_cpu
*cpu_buffer
;
5004 struct ring_buffer_iter
*iter
;
5006 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5009 iter
= kzalloc(sizeof(*iter
), flags
);
5013 /* Holds the entire event: data and meta data */
5014 iter
->event_size
= buffer
->subbuf_size
;
5015 iter
->event
= kmalloc(iter
->event_size
, flags
);
5021 cpu_buffer
= buffer
->buffers
[cpu
];
5023 iter
->cpu_buffer
= cpu_buffer
;
5025 atomic_inc(&cpu_buffer
->resize_disabled
);
5029 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
5032 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5034 * All previously invoked ring_buffer_read_prepare calls to prepare
5035 * iterators will be synchronized. Afterwards, read_buffer_read_start
5036 * calls on those iterators are allowed.
5039 ring_buffer_read_prepare_sync(void)
5043 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
5046 * ring_buffer_read_start - start a non consuming read of the buffer
5047 * @iter: The iterator returned by ring_buffer_read_prepare
5049 * This finalizes the startup of an iteration through the buffer.
5050 * The iterator comes from a call to ring_buffer_read_prepare and
5051 * an intervening ring_buffer_read_prepare_sync must have been
5054 * Must be paired with ring_buffer_read_finish.
5057 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
5059 struct ring_buffer_per_cpu
*cpu_buffer
;
5060 unsigned long flags
;
5065 cpu_buffer
= iter
->cpu_buffer
;
5067 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
5068 arch_spin_lock(&cpu_buffer
->lock
);
5069 rb_iter_reset(iter
);
5070 arch_spin_unlock(&cpu_buffer
->lock
);
5071 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
5073 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
5076 * ring_buffer_read_finish - finish reading the iterator of the buffer
5077 * @iter: The iterator retrieved by ring_buffer_start
5079 * This re-enables the recording to the buffer, and frees the
5083 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
5085 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
5086 unsigned long flags
;
5089 * Ring buffer is disabled from recording, here's a good place
5090 * to check the integrity of the ring buffer.
5091 * Must prevent readers from trying to read, as the check
5092 * clears the HEAD page and readers require it.
5094 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
5095 rb_check_pages(cpu_buffer
);
5096 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
5098 atomic_dec(&cpu_buffer
->resize_disabled
);
5102 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
5105 * ring_buffer_iter_advance - advance the iterator to the next location
5106 * @iter: The ring buffer iterator
5108 * Move the location of the iterator such that the next read will
5109 * be the next location of the iterator.
5111 void ring_buffer_iter_advance(struct ring_buffer_iter
*iter
)
5113 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
5114 unsigned long flags
;
5116 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
5118 rb_advance_iter(iter
);
5120 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
5122 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance
);
5125 * ring_buffer_size - return the size of the ring buffer (in bytes)
5126 * @buffer: The ring buffer.
5127 * @cpu: The CPU to get ring buffer size from.
5129 unsigned long ring_buffer_size(struct trace_buffer
*buffer
, int cpu
)
5131 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5134 return buffer
->subbuf_size
* buffer
->buffers
[cpu
]->nr_pages
;
5136 EXPORT_SYMBOL_GPL(ring_buffer_size
);
5139 * ring_buffer_max_event_size - return the max data size of an event
5140 * @buffer: The ring buffer.
5142 * Returns the maximum size an event can be.
5144 unsigned long ring_buffer_max_event_size(struct trace_buffer
*buffer
)
5146 /* If abs timestamp is requested, events have a timestamp too */
5147 if (ring_buffer_time_stamp_abs(buffer
))
5148 return buffer
->max_data_size
- RB_LEN_TIME_EXTEND
;
5149 return buffer
->max_data_size
;
5151 EXPORT_SYMBOL_GPL(ring_buffer_max_event_size
);
5153 static void rb_clear_buffer_page(struct buffer_page
*page
)
5155 local_set(&page
->write
, 0);
5156 local_set(&page
->entries
, 0);
5157 rb_init_page(page
->page
);
5162 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
5164 struct buffer_page
*page
;
5166 rb_head_page_deactivate(cpu_buffer
);
5168 cpu_buffer
->head_page
5169 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
5170 rb_clear_buffer_page(cpu_buffer
->head_page
);
5171 list_for_each_entry(page
, cpu_buffer
->pages
, list
) {
5172 rb_clear_buffer_page(page
);
5175 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
5176 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
5178 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
5179 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
5180 rb_clear_buffer_page(cpu_buffer
->reader_page
);
5182 local_set(&cpu_buffer
->entries_bytes
, 0);
5183 local_set(&cpu_buffer
->overrun
, 0);
5184 local_set(&cpu_buffer
->commit_overrun
, 0);
5185 local_set(&cpu_buffer
->dropped_events
, 0);
5186 local_set(&cpu_buffer
->entries
, 0);
5187 local_set(&cpu_buffer
->committing
, 0);
5188 local_set(&cpu_buffer
->commits
, 0);
5189 local_set(&cpu_buffer
->pages_touched
, 0);
5190 local_set(&cpu_buffer
->pages_lost
, 0);
5191 local_set(&cpu_buffer
->pages_read
, 0);
5192 cpu_buffer
->last_pages_touch
= 0;
5193 cpu_buffer
->shortest_full
= 0;
5194 cpu_buffer
->read
= 0;
5195 cpu_buffer
->read_bytes
= 0;
5197 rb_time_set(&cpu_buffer
->write_stamp
, 0);
5198 rb_time_set(&cpu_buffer
->before_stamp
, 0);
5200 memset(cpu_buffer
->event_stamp
, 0, sizeof(cpu_buffer
->event_stamp
));
5202 cpu_buffer
->lost_events
= 0;
5203 cpu_buffer
->last_overrun
= 0;
5205 rb_head_page_activate(cpu_buffer
);
5206 cpu_buffer
->pages_removed
= 0;
5209 /* Must have disabled the cpu buffer then done a synchronize_rcu */
5210 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
5212 unsigned long flags
;
5214 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
5216 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
5219 arch_spin_lock(&cpu_buffer
->lock
);
5221 rb_reset_cpu(cpu_buffer
);
5223 arch_spin_unlock(&cpu_buffer
->lock
);
5226 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
5230 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5231 * @buffer: The ring buffer to reset a per cpu buffer of
5232 * @cpu: The CPU buffer to be reset
5234 void ring_buffer_reset_cpu(struct trace_buffer
*buffer
, int cpu
)
5236 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
5238 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5241 /* prevent another thread from changing buffer sizes */
5242 mutex_lock(&buffer
->mutex
);
5244 atomic_inc(&cpu_buffer
->resize_disabled
);
5245 atomic_inc(&cpu_buffer
->record_disabled
);
5247 /* Make sure all commits have finished */
5250 reset_disabled_cpu_buffer(cpu_buffer
);
5252 atomic_dec(&cpu_buffer
->record_disabled
);
5253 atomic_dec(&cpu_buffer
->resize_disabled
);
5255 mutex_unlock(&buffer
->mutex
);
5257 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
5259 /* Flag to ensure proper resetting of atomic variables */
5260 #define RESET_BIT (1 << 30)
5263 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5264 * @buffer: The ring buffer to reset a per cpu buffer of
5266 void ring_buffer_reset_online_cpus(struct trace_buffer
*buffer
)
5268 struct ring_buffer_per_cpu
*cpu_buffer
;
5271 /* prevent another thread from changing buffer sizes */
5272 mutex_lock(&buffer
->mutex
);
5274 for_each_online_buffer_cpu(buffer
, cpu
) {
5275 cpu_buffer
= buffer
->buffers
[cpu
];
5277 atomic_add(RESET_BIT
, &cpu_buffer
->resize_disabled
);
5278 atomic_inc(&cpu_buffer
->record_disabled
);
5281 /* Make sure all commits have finished */
5284 for_each_buffer_cpu(buffer
, cpu
) {
5285 cpu_buffer
= buffer
->buffers
[cpu
];
5288 * If a CPU came online during the synchronize_rcu(), then
5291 if (!(atomic_read(&cpu_buffer
->resize_disabled
) & RESET_BIT
))
5294 reset_disabled_cpu_buffer(cpu_buffer
);
5296 atomic_dec(&cpu_buffer
->record_disabled
);
5297 atomic_sub(RESET_BIT
, &cpu_buffer
->resize_disabled
);
5300 mutex_unlock(&buffer
->mutex
);
5304 * ring_buffer_reset - reset a ring buffer
5305 * @buffer: The ring buffer to reset all cpu buffers
5307 void ring_buffer_reset(struct trace_buffer
*buffer
)
5309 struct ring_buffer_per_cpu
*cpu_buffer
;
5312 /* prevent another thread from changing buffer sizes */
5313 mutex_lock(&buffer
->mutex
);
5315 for_each_buffer_cpu(buffer
, cpu
) {
5316 cpu_buffer
= buffer
->buffers
[cpu
];
5318 atomic_inc(&cpu_buffer
->resize_disabled
);
5319 atomic_inc(&cpu_buffer
->record_disabled
);
5322 /* Make sure all commits have finished */
5325 for_each_buffer_cpu(buffer
, cpu
) {
5326 cpu_buffer
= buffer
->buffers
[cpu
];
5328 reset_disabled_cpu_buffer(cpu_buffer
);
5330 atomic_dec(&cpu_buffer
->record_disabled
);
5331 atomic_dec(&cpu_buffer
->resize_disabled
);
5334 mutex_unlock(&buffer
->mutex
);
5336 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
5339 * ring_buffer_empty - is the ring buffer empty?
5340 * @buffer: The ring buffer to test
5342 bool ring_buffer_empty(struct trace_buffer
*buffer
)
5344 struct ring_buffer_per_cpu
*cpu_buffer
;
5345 unsigned long flags
;
5350 /* yes this is racy, but if you don't like the race, lock the buffer */
5351 for_each_buffer_cpu(buffer
, cpu
) {
5352 cpu_buffer
= buffer
->buffers
[cpu
];
5353 local_irq_save(flags
);
5354 dolock
= rb_reader_lock(cpu_buffer
);
5355 ret
= rb_per_cpu_empty(cpu_buffer
);
5356 rb_reader_unlock(cpu_buffer
, dolock
);
5357 local_irq_restore(flags
);
5365 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
5368 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5369 * @buffer: The ring buffer
5370 * @cpu: The CPU buffer to test
5372 bool ring_buffer_empty_cpu(struct trace_buffer
*buffer
, int cpu
)
5374 struct ring_buffer_per_cpu
*cpu_buffer
;
5375 unsigned long flags
;
5379 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5382 cpu_buffer
= buffer
->buffers
[cpu
];
5383 local_irq_save(flags
);
5384 dolock
= rb_reader_lock(cpu_buffer
);
5385 ret
= rb_per_cpu_empty(cpu_buffer
);
5386 rb_reader_unlock(cpu_buffer
, dolock
);
5387 local_irq_restore(flags
);
5391 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
5393 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5395 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5396 * @buffer_a: One buffer to swap with
5397 * @buffer_b: The other buffer to swap with
5398 * @cpu: the CPU of the buffers to swap
5400 * This function is useful for tracers that want to take a "snapshot"
5401 * of a CPU buffer and has another back up buffer lying around.
5402 * it is expected that the tracer handles the cpu buffer not being
5403 * used at the moment.
5405 int ring_buffer_swap_cpu(struct trace_buffer
*buffer_a
,
5406 struct trace_buffer
*buffer_b
, int cpu
)
5408 struct ring_buffer_per_cpu
*cpu_buffer_a
;
5409 struct ring_buffer_per_cpu
*cpu_buffer_b
;
5412 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
5413 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
5416 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
5417 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
5419 /* At least make sure the two buffers are somewhat the same */
5420 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
5423 if (buffer_a
->subbuf_order
!= buffer_b
->subbuf_order
)
5428 if (atomic_read(&buffer_a
->record_disabled
))
5431 if (atomic_read(&buffer_b
->record_disabled
))
5434 if (atomic_read(&cpu_buffer_a
->record_disabled
))
5437 if (atomic_read(&cpu_buffer_b
->record_disabled
))
5441 * We can't do a synchronize_rcu here because this
5442 * function can be called in atomic context.
5443 * Normally this will be called from the same CPU as cpu.
5444 * If not it's up to the caller to protect this.
5446 atomic_inc(&cpu_buffer_a
->record_disabled
);
5447 atomic_inc(&cpu_buffer_b
->record_disabled
);
5450 if (local_read(&cpu_buffer_a
->committing
))
5452 if (local_read(&cpu_buffer_b
->committing
))
5456 * When resize is in progress, we cannot swap it because
5457 * it will mess the state of the cpu buffer.
5459 if (atomic_read(&buffer_a
->resizing
))
5461 if (atomic_read(&buffer_b
->resizing
))
5464 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
5465 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
5467 cpu_buffer_b
->buffer
= buffer_a
;
5468 cpu_buffer_a
->buffer
= buffer_b
;
5473 atomic_dec(&cpu_buffer_a
->record_disabled
);
5474 atomic_dec(&cpu_buffer_b
->record_disabled
);
5478 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
5479 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5482 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5483 * @buffer: the buffer to allocate for.
5484 * @cpu: the cpu buffer to allocate.
5486 * This function is used in conjunction with ring_buffer_read_page.
5487 * When reading a full page from the ring buffer, these functions
5488 * can be used to speed up the process. The calling function should
5489 * allocate a few pages first with this function. Then when it
5490 * needs to get pages from the ring buffer, it passes the result
5491 * of this function into ring_buffer_read_page, which will swap
5492 * the page that was allocated, with the read page of the buffer.
5495 * The page allocated, or ERR_PTR
5497 struct buffer_data_read_page
*
5498 ring_buffer_alloc_read_page(struct trace_buffer
*buffer
, int cpu
)
5500 struct ring_buffer_per_cpu
*cpu_buffer
;
5501 struct buffer_data_read_page
*bpage
= NULL
;
5502 unsigned long flags
;
5505 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5506 return ERR_PTR(-ENODEV
);
5508 bpage
= kzalloc(sizeof(*bpage
), GFP_KERNEL
);
5510 return ERR_PTR(-ENOMEM
);
5512 bpage
->order
= buffer
->subbuf_order
;
5513 cpu_buffer
= buffer
->buffers
[cpu
];
5514 local_irq_save(flags
);
5515 arch_spin_lock(&cpu_buffer
->lock
);
5517 if (cpu_buffer
->free_page
) {
5518 bpage
->data
= cpu_buffer
->free_page
;
5519 cpu_buffer
->free_page
= NULL
;
5522 arch_spin_unlock(&cpu_buffer
->lock
);
5523 local_irq_restore(flags
);
5528 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
| __GFP_NORETRY
,
5529 cpu_buffer
->buffer
->subbuf_order
);
5532 return ERR_PTR(-ENOMEM
);
5535 bpage
->data
= page_address(page
);
5538 rb_init_page(bpage
->data
);
5542 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
5545 * ring_buffer_free_read_page - free an allocated read page
5546 * @buffer: the buffer the page was allocate for
5547 * @cpu: the cpu buffer the page came from
5548 * @data_page: the page to free
5550 * Free a page allocated from ring_buffer_alloc_read_page.
5552 void ring_buffer_free_read_page(struct trace_buffer
*buffer
, int cpu
,
5553 struct buffer_data_read_page
*data_page
)
5555 struct ring_buffer_per_cpu
*cpu_buffer
;
5556 struct buffer_data_page
*bpage
= data_page
->data
;
5557 struct page
*page
= virt_to_page(bpage
);
5558 unsigned long flags
;
5560 if (!buffer
|| !buffer
->buffers
|| !buffer
->buffers
[cpu
])
5563 cpu_buffer
= buffer
->buffers
[cpu
];
5566 * If the page is still in use someplace else, or order of the page
5567 * is different from the subbuffer order of the buffer -
5570 if (page_ref_count(page
) > 1 || data_page
->order
!= buffer
->subbuf_order
)
5573 local_irq_save(flags
);
5574 arch_spin_lock(&cpu_buffer
->lock
);
5576 if (!cpu_buffer
->free_page
) {
5577 cpu_buffer
->free_page
= bpage
;
5581 arch_spin_unlock(&cpu_buffer
->lock
);
5582 local_irq_restore(flags
);
5585 free_pages((unsigned long)bpage
, data_page
->order
);
5588 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
5591 * ring_buffer_read_page - extract a page from the ring buffer
5592 * @buffer: buffer to extract from
5593 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5594 * @len: amount to extract
5595 * @cpu: the cpu of the buffer to extract
5596 * @full: should the extraction only happen when the page is full.
5598 * This function will pull out a page from the ring buffer and consume it.
5599 * @data_page must be the address of the variable that was returned
5600 * from ring_buffer_alloc_read_page. This is because the page might be used
5601 * to swap with a page in the ring buffer.
5604 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5605 * if (IS_ERR(rpage))
5606 * return PTR_ERR(rpage);
5607 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
5609 * process_page(ring_buffer_read_page_data(rpage), ret);
5610 * ring_buffer_free_read_page(buffer, cpu, rpage);
5612 * When @full is set, the function will not return true unless
5613 * the writer is off the reader page.
5615 * Note: it is up to the calling functions to handle sleeps and wakeups.
5616 * The ring buffer can be used anywhere in the kernel and can not
5617 * blindly call wake_up. The layer that uses the ring buffer must be
5618 * responsible for that.
5621 * >=0 if data has been transferred, returns the offset of consumed data.
5622 * <0 if no data has been transferred.
5624 int ring_buffer_read_page(struct trace_buffer
*buffer
,
5625 struct buffer_data_read_page
*data_page
,
5626 size_t len
, int cpu
, int full
)
5628 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
5629 struct ring_buffer_event
*event
;
5630 struct buffer_data_page
*bpage
;
5631 struct buffer_page
*reader
;
5632 unsigned long missed_events
;
5633 unsigned long flags
;
5634 unsigned int commit
;
5639 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5643 * If len is not big enough to hold the page header, then
5644 * we can not copy anything.
5646 if (len
<= BUF_PAGE_HDR_SIZE
)
5649 len
-= BUF_PAGE_HDR_SIZE
;
5651 if (!data_page
|| !data_page
->data
)
5653 if (data_page
->order
!= buffer
->subbuf_order
)
5656 bpage
= data_page
->data
;
5660 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
5662 reader
= rb_get_reader_page(cpu_buffer
);
5666 event
= rb_reader_event(cpu_buffer
);
5668 read
= reader
->read
;
5669 commit
= rb_page_commit(reader
);
5671 /* Check if any events were dropped */
5672 missed_events
= cpu_buffer
->lost_events
;
5675 * If this page has been partially read or
5676 * if len is not big enough to read the rest of the page or
5677 * a writer is still on the page, then
5678 * we must copy the data from the page to the buffer.
5679 * Otherwise, we can simply swap the page with the one passed in.
5681 if (read
|| (len
< (commit
- read
)) ||
5682 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
5683 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
5684 unsigned int rpos
= read
;
5685 unsigned int pos
= 0;
5689 * If a full page is expected, this can still be returned
5690 * if there's been a previous partial read and the
5691 * rest of the page can be read and the commit page is off
5695 (!read
|| (len
< (commit
- read
)) ||
5696 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
))
5699 if (len
> (commit
- read
))
5700 len
= (commit
- read
);
5702 /* Always keep the time extend and data together */
5703 size
= rb_event_ts_length(event
);
5708 /* save the current timestamp, since the user will need it */
5709 save_timestamp
= cpu_buffer
->read_stamp
;
5711 /* Need to copy one event at a time */
5713 /* We need the size of one event, because
5714 * rb_advance_reader only advances by one event,
5715 * whereas rb_event_ts_length may include the size of
5716 * one or two events.
5717 * We have already ensured there's enough space if this
5718 * is a time extend. */
5719 size
= rb_event_length(event
);
5720 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
5724 rb_advance_reader(cpu_buffer
);
5725 rpos
= reader
->read
;
5731 event
= rb_reader_event(cpu_buffer
);
5732 /* Always keep the time extend and data together */
5733 size
= rb_event_ts_length(event
);
5734 } while (len
>= size
);
5737 local_set(&bpage
->commit
, pos
);
5738 bpage
->time_stamp
= save_timestamp
;
5740 /* we copied everything to the beginning */
5743 /* update the entry counter */
5744 cpu_buffer
->read
+= rb_page_entries(reader
);
5745 cpu_buffer
->read_bytes
+= rb_page_commit(reader
);
5747 /* swap the pages */
5748 rb_init_page(bpage
);
5749 bpage
= reader
->page
;
5750 reader
->page
= data_page
->data
;
5751 local_set(&reader
->write
, 0);
5752 local_set(&reader
->entries
, 0);
5754 data_page
->data
= bpage
;
5757 * Use the real_end for the data size,
5758 * This gives us a chance to store the lost events
5761 if (reader
->real_end
)
5762 local_set(&bpage
->commit
, reader
->real_end
);
5766 cpu_buffer
->lost_events
= 0;
5768 commit
= local_read(&bpage
->commit
);
5770 * Set a flag in the commit field if we lost events
5772 if (missed_events
) {
5773 /* If there is room at the end of the page to save the
5774 * missed events, then record it there.
5776 if (buffer
->subbuf_size
- commit
>= sizeof(missed_events
)) {
5777 memcpy(&bpage
->data
[commit
], &missed_events
,
5778 sizeof(missed_events
));
5779 local_add(RB_MISSED_STORED
, &bpage
->commit
);
5780 commit
+= sizeof(missed_events
);
5782 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
5786 * This page may be off to user land. Zero it out here.
5788 if (commit
< buffer
->subbuf_size
)
5789 memset(&bpage
->data
[commit
], 0, buffer
->subbuf_size
- commit
);
5792 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
5797 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
5800 * ring_buffer_read_page_data - get pointer to the data in the page.
5801 * @page: the page to get the data from
5803 * Returns pointer to the actual data in this page.
5805 void *ring_buffer_read_page_data(struct buffer_data_read_page
*page
)
5809 EXPORT_SYMBOL_GPL(ring_buffer_read_page_data
);
5812 * ring_buffer_subbuf_size_get - get size of the sub buffer.
5813 * @buffer: the buffer to get the sub buffer size from
5815 * Returns size of the sub buffer, in bytes.
5817 int ring_buffer_subbuf_size_get(struct trace_buffer
*buffer
)
5819 return buffer
->subbuf_size
+ BUF_PAGE_HDR_SIZE
;
5821 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get
);
5824 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
5825 * @buffer: The ring_buffer to get the system sub page order from
5827 * By default, one ring buffer sub page equals to one system page. This parameter
5828 * is configurable, per ring buffer. The size of the ring buffer sub page can be
5829 * extended, but must be an order of system page size.
5831 * Returns the order of buffer sub page size, in system pages:
5832 * 0 means the sub buffer size is 1 system page and so forth.
5833 * In case of an error < 0 is returned.
5835 int ring_buffer_subbuf_order_get(struct trace_buffer
*buffer
)
5840 return buffer
->subbuf_order
;
5842 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get
);
5845 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
5846 * @buffer: The ring_buffer to set the new page size.
5847 * @order: Order of the system pages in one sub buffer page
5849 * By default, one ring buffer pages equals to one system page. This API can be
5850 * used to set new size of the ring buffer page. The size must be order of
5851 * system page size, that's why the input parameter @order is the order of
5852 * system pages that are allocated for one ring buffer page:
5854 * 1 - 2 system pages
5855 * 3 - 4 system pages
5858 * Returns 0 on success or < 0 in case of an error.
5860 int ring_buffer_subbuf_order_set(struct trace_buffer
*buffer
, int order
)
5862 struct ring_buffer_per_cpu
*cpu_buffer
;
5863 struct buffer_page
*bpage
, *tmp
;
5864 int old_order
, old_size
;
5870 if (!buffer
|| order
< 0)
5873 if (buffer
->subbuf_order
== order
)
5876 psize
= (1 << order
) * PAGE_SIZE
;
5877 if (psize
<= BUF_PAGE_HDR_SIZE
)
5880 old_order
= buffer
->subbuf_order
;
5881 old_size
= buffer
->subbuf_size
;
5883 /* prevent another thread from changing buffer sizes */
5884 mutex_lock(&buffer
->mutex
);
5885 atomic_inc(&buffer
->record_disabled
);
5887 /* Make sure all commits have finished */
5890 buffer
->subbuf_order
= order
;
5891 buffer
->subbuf_size
= psize
- BUF_PAGE_HDR_SIZE
;
5893 /* Make sure all new buffers are allocated, before deleting the old ones */
5894 for_each_buffer_cpu(buffer
, cpu
) {
5896 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5899 cpu_buffer
= buffer
->buffers
[cpu
];
5901 /* Update the number of pages to match the new size */
5902 nr_pages
= old_size
* buffer
->buffers
[cpu
]->nr_pages
;
5903 nr_pages
= DIV_ROUND_UP(nr_pages
, buffer
->subbuf_size
);
5905 /* we need a minimum of two pages */
5909 cpu_buffer
->nr_pages_to_update
= nr_pages
;
5911 /* Include the reader page */
5914 /* Allocate the new size buffer */
5915 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
5916 if (__rb_allocate_pages(cpu_buffer
, nr_pages
,
5917 &cpu_buffer
->new_pages
)) {
5918 /* not enough memory for new pages */
5924 for_each_buffer_cpu(buffer
, cpu
) {
5926 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5929 cpu_buffer
= buffer
->buffers
[cpu
];
5931 /* Clear the head bit to make the link list normal to read */
5932 rb_head_page_deactivate(cpu_buffer
);
5934 /* Now walk the list and free all the old sub buffers */
5935 list_for_each_entry_safe(bpage
, tmp
, cpu_buffer
->pages
, list
) {
5936 list_del_init(&bpage
->list
);
5937 free_buffer_page(bpage
);
5939 /* The above loop stopped an the last page needing to be freed */
5940 bpage
= list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
5941 free_buffer_page(bpage
);
5943 /* Free the current reader page */
5944 free_buffer_page(cpu_buffer
->reader_page
);
5946 /* One page was allocated for the reader page */
5947 cpu_buffer
->reader_page
= list_entry(cpu_buffer
->new_pages
.next
,
5948 struct buffer_page
, list
);
5949 list_del_init(&cpu_buffer
->reader_page
->list
);
5951 /* The cpu_buffer pages are a link list with no head */
5952 cpu_buffer
->pages
= cpu_buffer
->new_pages
.next
;
5953 cpu_buffer
->new_pages
.next
->prev
= cpu_buffer
->new_pages
.prev
;
5954 cpu_buffer
->new_pages
.prev
->next
= cpu_buffer
->new_pages
.next
;
5956 /* Clear the new_pages list */
5957 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
5959 cpu_buffer
->head_page
5960 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
5961 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
5963 cpu_buffer
->nr_pages
= cpu_buffer
->nr_pages_to_update
;
5964 cpu_buffer
->nr_pages_to_update
= 0;
5966 free_pages((unsigned long)cpu_buffer
->free_page
, old_order
);
5967 cpu_buffer
->free_page
= NULL
;
5969 rb_head_page_activate(cpu_buffer
);
5971 rb_check_pages(cpu_buffer
);
5974 atomic_dec(&buffer
->record_disabled
);
5975 mutex_unlock(&buffer
->mutex
);
5980 buffer
->subbuf_order
= old_order
;
5981 buffer
->subbuf_size
= old_size
;
5983 atomic_dec(&buffer
->record_disabled
);
5984 mutex_unlock(&buffer
->mutex
);
5986 for_each_buffer_cpu(buffer
, cpu
) {
5987 cpu_buffer
= buffer
->buffers
[cpu
];
5989 if (!cpu_buffer
->nr_pages_to_update
)
5992 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
, list
) {
5993 list_del_init(&bpage
->list
);
5994 free_buffer_page(bpage
);
6000 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set
);
6003 * We only allocate new buffers, never free them if the CPU goes down.
6004 * If we were to free the buffer, then the user would lose any trace that was in
6007 int trace_rb_cpu_prepare(unsigned int cpu
, struct hlist_node
*node
)
6009 struct trace_buffer
*buffer
;
6012 unsigned long nr_pages
;
6014 buffer
= container_of(node
, struct trace_buffer
, node
);
6015 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
6020 /* check if all cpu sizes are same */
6021 for_each_buffer_cpu(buffer
, cpu_i
) {
6022 /* fill in the size from first enabled cpu */
6024 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
6025 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
6030 /* allocate minimum pages, user can later expand it */
6033 buffer
->buffers
[cpu
] =
6034 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
6035 if (!buffer
->buffers
[cpu
]) {
6036 WARN(1, "failed to allocate ring buffer on CPU %u\n",
6041 cpumask_set_cpu(cpu
, buffer
->cpumask
);
6045 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
6047 * This is a basic integrity check of the ring buffer.
6048 * Late in the boot cycle this test will run when configured in.
6049 * It will kick off a thread per CPU that will go into a loop
6050 * writing to the per cpu ring buffer various sizes of data.
6051 * Some of the data will be large items, some small.
6053 * Another thread is created that goes into a spin, sending out
6054 * IPIs to the other CPUs to also write into the ring buffer.
6055 * this is to test the nesting ability of the buffer.
6057 * Basic stats are recorded and reported. If something in the
6058 * ring buffer should happen that's not expected, a big warning
6059 * is displayed and all ring buffers are disabled.
6061 static struct task_struct
*rb_threads
[NR_CPUS
] __initdata
;
6063 struct rb_test_data
{
6064 struct trace_buffer
*buffer
;
6065 unsigned long events
;
6066 unsigned long bytes_written
;
6067 unsigned long bytes_alloc
;
6068 unsigned long bytes_dropped
;
6069 unsigned long events_nested
;
6070 unsigned long bytes_written_nested
;
6071 unsigned long bytes_alloc_nested
;
6072 unsigned long bytes_dropped_nested
;
6073 int min_size_nested
;
6074 int max_size_nested
;
6081 static struct rb_test_data rb_data
[NR_CPUS
] __initdata
;
6084 #define RB_TEST_BUFFER_SIZE 1048576
6086 static char rb_string
[] __initdata
=
6087 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
6088 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
6089 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
6091 static bool rb_test_started __initdata
;
6098 static __init
int rb_write_something(struct rb_test_data
*data
, bool nested
)
6100 struct ring_buffer_event
*event
;
6101 struct rb_item
*item
;
6108 /* Have nested writes different that what is written */
6109 cnt
= data
->cnt
+ (nested
? 27 : 0);
6111 /* Multiply cnt by ~e, to make some unique increment */
6112 size
= (cnt
* 68 / 25) % (sizeof(rb_string
) - 1);
6114 len
= size
+ sizeof(struct rb_item
);
6116 started
= rb_test_started
;
6117 /* read rb_test_started before checking buffer enabled */
6120 event
= ring_buffer_lock_reserve(data
->buffer
, len
);
6122 /* Ignore dropped events before test starts. */
6125 data
->bytes_dropped
+= len
;
6127 data
->bytes_dropped_nested
+= len
;
6132 event_len
= ring_buffer_event_length(event
);
6134 if (RB_WARN_ON(data
->buffer
, event_len
< len
))
6137 item
= ring_buffer_event_data(event
);
6139 memcpy(item
->str
, rb_string
, size
);
6142 data
->bytes_alloc_nested
+= event_len
;
6143 data
->bytes_written_nested
+= len
;
6144 data
->events_nested
++;
6145 if (!data
->min_size_nested
|| len
< data
->min_size_nested
)
6146 data
->min_size_nested
= len
;
6147 if (len
> data
->max_size_nested
)
6148 data
->max_size_nested
= len
;
6150 data
->bytes_alloc
+= event_len
;
6151 data
->bytes_written
+= len
;
6153 if (!data
->min_size
|| len
< data
->min_size
)
6154 data
->max_size
= len
;
6155 if (len
> data
->max_size
)
6156 data
->max_size
= len
;
6160 ring_buffer_unlock_commit(data
->buffer
);
6165 static __init
int rb_test(void *arg
)
6167 struct rb_test_data
*data
= arg
;
6169 while (!kthread_should_stop()) {
6170 rb_write_something(data
, false);
6173 set_current_state(TASK_INTERRUPTIBLE
);
6174 /* Now sleep between a min of 100-300us and a max of 1ms */
6175 usleep_range(((data
->cnt
% 3) + 1) * 100, 1000);
6181 static __init
void rb_ipi(void *ignore
)
6183 struct rb_test_data
*data
;
6184 int cpu
= smp_processor_id();
6186 data
= &rb_data
[cpu
];
6187 rb_write_something(data
, true);
6190 static __init
int rb_hammer_test(void *arg
)
6192 while (!kthread_should_stop()) {
6194 /* Send an IPI to all cpus to write data! */
6195 smp_call_function(rb_ipi
, NULL
, 1);
6196 /* No sleep, but for non preempt, let others run */
6203 static __init
int test_ringbuffer(void)
6205 struct task_struct
*rb_hammer
;
6206 struct trace_buffer
*buffer
;
6210 if (security_locked_down(LOCKDOWN_TRACEFS
)) {
6211 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6215 pr_info("Running ring buffer tests...\n");
6217 buffer
= ring_buffer_alloc(RB_TEST_BUFFER_SIZE
, RB_FL_OVERWRITE
);
6218 if (WARN_ON(!buffer
))
6221 /* Disable buffer so that threads can't write to it yet */
6222 ring_buffer_record_off(buffer
);
6224 for_each_online_cpu(cpu
) {
6225 rb_data
[cpu
].buffer
= buffer
;
6226 rb_data
[cpu
].cpu
= cpu
;
6227 rb_data
[cpu
].cnt
= cpu
;
6228 rb_threads
[cpu
] = kthread_run_on_cpu(rb_test
, &rb_data
[cpu
],
6229 cpu
, "rbtester/%u");
6230 if (WARN_ON(IS_ERR(rb_threads
[cpu
]))) {
6231 pr_cont("FAILED\n");
6232 ret
= PTR_ERR(rb_threads
[cpu
]);
6237 /* Now create the rb hammer! */
6238 rb_hammer
= kthread_run(rb_hammer_test
, NULL
, "rbhammer");
6239 if (WARN_ON(IS_ERR(rb_hammer
))) {
6240 pr_cont("FAILED\n");
6241 ret
= PTR_ERR(rb_hammer
);
6245 ring_buffer_record_on(buffer
);
6247 * Show buffer is enabled before setting rb_test_started.
6248 * Yes there's a small race window where events could be
6249 * dropped and the thread wont catch it. But when a ring
6250 * buffer gets enabled, there will always be some kind of
6251 * delay before other CPUs see it. Thus, we don't care about
6252 * those dropped events. We care about events dropped after
6253 * the threads see that the buffer is active.
6256 rb_test_started
= true;
6258 set_current_state(TASK_INTERRUPTIBLE
);
6259 /* Just run for 10 seconds */;
6260 schedule_timeout(10 * HZ
);
6262 kthread_stop(rb_hammer
);
6265 for_each_online_cpu(cpu
) {
6266 if (!rb_threads
[cpu
])
6268 kthread_stop(rb_threads
[cpu
]);
6271 ring_buffer_free(buffer
);
6276 pr_info("finished\n");
6277 for_each_online_cpu(cpu
) {
6278 struct ring_buffer_event
*event
;
6279 struct rb_test_data
*data
= &rb_data
[cpu
];
6280 struct rb_item
*item
;
6281 unsigned long total_events
;
6282 unsigned long total_dropped
;
6283 unsigned long total_written
;
6284 unsigned long total_alloc
;
6285 unsigned long total_read
= 0;
6286 unsigned long total_size
= 0;
6287 unsigned long total_len
= 0;
6288 unsigned long total_lost
= 0;
6291 int small_event_size
;
6295 total_events
= data
->events
+ data
->events_nested
;
6296 total_written
= data
->bytes_written
+ data
->bytes_written_nested
;
6297 total_alloc
= data
->bytes_alloc
+ data
->bytes_alloc_nested
;
6298 total_dropped
= data
->bytes_dropped
+ data
->bytes_dropped_nested
;
6300 big_event_size
= data
->max_size
+ data
->max_size_nested
;
6301 small_event_size
= data
->min_size
+ data
->min_size_nested
;
6303 pr_info("CPU %d:\n", cpu
);
6304 pr_info(" events: %ld\n", total_events
);
6305 pr_info(" dropped bytes: %ld\n", total_dropped
);
6306 pr_info(" alloced bytes: %ld\n", total_alloc
);
6307 pr_info(" written bytes: %ld\n", total_written
);
6308 pr_info(" biggest event: %d\n", big_event_size
);
6309 pr_info(" smallest event: %d\n", small_event_size
);
6311 if (RB_WARN_ON(buffer
, total_dropped
))
6316 while ((event
= ring_buffer_consume(buffer
, cpu
, NULL
, &lost
))) {
6318 item
= ring_buffer_event_data(event
);
6319 total_len
+= ring_buffer_event_length(event
);
6320 total_size
+= item
->size
+ sizeof(struct rb_item
);
6321 if (memcmp(&item
->str
[0], rb_string
, item
->size
) != 0) {
6322 pr_info("FAILED!\n");
6323 pr_info("buffer had: %.*s\n", item
->size
, item
->str
);
6324 pr_info("expected: %.*s\n", item
->size
, rb_string
);
6325 RB_WARN_ON(buffer
, 1);
6336 pr_info(" read events: %ld\n", total_read
);
6337 pr_info(" lost events: %ld\n", total_lost
);
6338 pr_info(" total events: %ld\n", total_lost
+ total_read
);
6339 pr_info(" recorded len bytes: %ld\n", total_len
);
6340 pr_info(" recorded size bytes: %ld\n", total_size
);
6342 pr_info(" With dropped events, record len and size may not match\n"
6343 " alloced and written from above\n");
6345 if (RB_WARN_ON(buffer
, total_len
!= total_alloc
||
6346 total_size
!= total_written
))
6349 if (RB_WARN_ON(buffer
, total_lost
+ total_read
!= total_events
))
6355 pr_info("Ring buffer PASSED!\n");
6357 ring_buffer_free(buffer
);
6361 late_initcall(test_ringbuffer
);
6362 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */