1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
7 #include <linux/trace_events.h>
8 #include <linux/ring_buffer.h>
9 #include <linux/trace_clock.h>
10 #include <linux/sched/clock.h>
11 #include <linux/trace_seq.h>
12 #include <linux/spinlock.h>
13 #include <linux/irq_work.h>
14 #include <linux/security.h>
15 #include <linux/uaccess.h>
16 #include <linux/hardirq.h>
17 #include <linux/kthread.h> /* for self test */
18 #include <linux/module.h>
19 #include <linux/percpu.h>
20 #include <linux/mutex.h>
21 #include <linux/delay.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/list.h>
26 #include <linux/cpu.h>
27 #include <linux/oom.h>
29 #include <asm/local.h>
31 static void update_pages_handler(struct work_struct
*work
);
34 * The ring buffer header is special. We must manually up keep it.
36 int ring_buffer_print_entry_header(struct trace_seq
*s
)
38 trace_seq_puts(s
, "# compressed entry header\n");
39 trace_seq_puts(s
, "\ttype_len : 5 bits\n");
40 trace_seq_puts(s
, "\ttime_delta : 27 bits\n");
41 trace_seq_puts(s
, "\tarray : 32 bits\n");
42 trace_seq_putc(s
, '\n');
43 trace_seq_printf(s
, "\tpadding : type == %d\n",
44 RINGBUF_TYPE_PADDING
);
45 trace_seq_printf(s
, "\ttime_extend : type == %d\n",
46 RINGBUF_TYPE_TIME_EXTEND
);
47 trace_seq_printf(s
, "\ttime_stamp : type == %d\n",
48 RINGBUF_TYPE_TIME_STAMP
);
49 trace_seq_printf(s
, "\tdata max type_len == %d\n",
50 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
52 return !trace_seq_has_overflowed(s
);
56 * The ring buffer is made up of a list of pages. A separate list of pages is
57 * allocated for each CPU. A writer may only write to a buffer that is
58 * associated with the CPU it is currently executing on. A reader may read
59 * from any per cpu buffer.
61 * The reader is special. For each per cpu buffer, the reader has its own
62 * reader page. When a reader has read the entire reader page, this reader
63 * page is swapped with another page in the ring buffer.
65 * Now, as long as the writer is off the reader page, the reader can do what
66 * ever it wants with that page. The writer will never write to that page
67 * again (as long as it is out of the ring buffer).
69 * Here's some silly ASCII art.
72 * |reader| RING BUFFER
74 * +------+ +---+ +---+ +---+
83 * |reader| RING BUFFER
84 * |page |------------------v
85 * +------+ +---+ +---+ +---+
94 * |reader| RING BUFFER
95 * |page |------------------v
96 * +------+ +---+ +---+ +---+
101 * +------------------------------+
105 * |buffer| RING BUFFER
106 * |page |------------------v
107 * +------+ +---+ +---+ +---+
109 * | New +---+ +---+ +---+
112 * +------------------------------+
115 * After we make this swap, the reader can hand this page off to the splice
116 * code and be done with it. It can even allocate a new page if it needs to
117 * and swap that into the ring buffer.
119 * We will be using cmpxchg soon to make all this lockless.
123 /* Used for individual buffers (after the counter) */
124 #define RB_BUFFER_OFF (1 << 20)
126 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
128 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
129 #define RB_ALIGNMENT 4U
130 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
131 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
132 #define RB_ALIGN_DATA __aligned(RB_ALIGNMENT)
134 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
135 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
138 RB_LEN_TIME_EXTEND
= 8,
139 RB_LEN_TIME_STAMP
= 8,
142 #define skip_time_extend(event) \
143 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
145 #define extended_time(event) \
146 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
148 static inline int rb_null_event(struct ring_buffer_event
*event
)
150 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
153 static void rb_event_set_padding(struct ring_buffer_event
*event
)
155 /* padding has a NULL time_delta */
156 event
->type_len
= RINGBUF_TYPE_PADDING
;
157 event
->time_delta
= 0;
161 rb_event_data_length(struct ring_buffer_event
*event
)
166 length
= event
->type_len
* RB_ALIGNMENT
;
168 length
= event
->array
[0];
169 return length
+ RB_EVNT_HDR_SIZE
;
173 * Return the length of the given event. Will return
174 * the length of the time extend if the event is a
177 static inline unsigned
178 rb_event_length(struct ring_buffer_event
*event
)
180 switch (event
->type_len
) {
181 case RINGBUF_TYPE_PADDING
:
182 if (rb_null_event(event
))
185 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
187 case RINGBUF_TYPE_TIME_EXTEND
:
188 return RB_LEN_TIME_EXTEND
;
190 case RINGBUF_TYPE_TIME_STAMP
:
191 return RB_LEN_TIME_STAMP
;
193 case RINGBUF_TYPE_DATA
:
194 return rb_event_data_length(event
);
203 * Return total length of time extend and data,
204 * or just the event length for all other events.
206 static inline unsigned
207 rb_event_ts_length(struct ring_buffer_event
*event
)
211 if (extended_time(event
)) {
212 /* time extends include the data event after it */
213 len
= RB_LEN_TIME_EXTEND
;
214 event
= skip_time_extend(event
);
216 return len
+ rb_event_length(event
);
220 * ring_buffer_event_length - return the length of the event
221 * @event: the event to get the length of
223 * Returns the size of the data load of a data event.
224 * If the event is something other than a data event, it
225 * returns the size of the event itself. With the exception
226 * of a TIME EXTEND, where it still returns the size of the
227 * data load of the data event after it.
229 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
233 if (extended_time(event
))
234 event
= skip_time_extend(event
);
236 length
= rb_event_length(event
);
237 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
239 length
-= RB_EVNT_HDR_SIZE
;
240 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
241 length
-= sizeof(event
->array
[0]);
244 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
246 /* inline for ring buffer fast paths */
247 static __always_inline
void *
248 rb_event_data(struct ring_buffer_event
*event
)
250 if (extended_time(event
))
251 event
= skip_time_extend(event
);
252 WARN_ON_ONCE(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
253 /* If length is in len field, then array[0] has the data */
255 return (void *)&event
->array
[0];
256 /* Otherwise length is in array[0] and array[1] has the data */
257 return (void *)&event
->array
[1];
261 * ring_buffer_event_data - return the data of the event
262 * @event: the event to get the data from
264 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
266 return rb_event_data(event
);
268 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
270 #define for_each_buffer_cpu(buffer, cpu) \
271 for_each_cpu(cpu, buffer->cpumask)
273 #define for_each_online_buffer_cpu(buffer, cpu) \
274 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
277 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
278 #define TS_DELTA_TEST (~TS_MASK)
281 * ring_buffer_event_time_stamp - return the event's extended timestamp
282 * @event: the event to get the timestamp of
284 * Returns the extended timestamp associated with a data event.
285 * An extended time_stamp is a 64-bit timestamp represented
286 * internally in a special way that makes the best use of space
287 * contained within a ring buffer event. This function decodes
288 * it and maps it to a straight u64 value.
290 u64
ring_buffer_event_time_stamp(struct ring_buffer_event
*event
)
294 ts
= event
->array
[0];
296 ts
+= event
->time_delta
;
301 /* Flag when events were overwritten */
302 #define RB_MISSED_EVENTS (1 << 31)
303 /* Missed count stored at end */
304 #define RB_MISSED_STORED (1 << 30)
306 struct buffer_data_page
{
307 u64 time_stamp
; /* page time stamp */
308 local_t commit
; /* write committed index */
309 unsigned char data
[] RB_ALIGN_DATA
; /* data of buffer page */
313 * Note, the buffer_page list must be first. The buffer pages
314 * are allocated in cache lines, which means that each buffer
315 * page will be at the beginning of a cache line, and thus
316 * the least significant bits will be zero. We use this to
317 * add flags in the list struct pointers, to make the ring buffer
321 struct list_head list
; /* list of buffer pages */
322 local_t write
; /* index for next write */
323 unsigned read
; /* index for next read */
324 local_t entries
; /* entries on this page */
325 unsigned long real_end
; /* real end of data */
326 struct buffer_data_page
*page
; /* Actual data page */
330 * The buffer page counters, write and entries, must be reset
331 * atomically when crossing page boundaries. To synchronize this
332 * update, two counters are inserted into the number. One is
333 * the actual counter for the write position or count on the page.
335 * The other is a counter of updaters. Before an update happens
336 * the update partition of the counter is incremented. This will
337 * allow the updater to update the counter atomically.
339 * The counter is 20 bits, and the state data is 12.
341 #define RB_WRITE_MASK 0xfffff
342 #define RB_WRITE_INTCNT (1 << 20)
344 static void rb_init_page(struct buffer_data_page
*bpage
)
346 local_set(&bpage
->commit
, 0);
350 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
353 static void free_buffer_page(struct buffer_page
*bpage
)
355 free_page((unsigned long)bpage
->page
);
360 * We need to fit the time_stamp delta into 27 bits.
362 static inline int test_time_stamp(u64 delta
)
364 if (delta
& TS_DELTA_TEST
)
369 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
371 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
372 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
374 int ring_buffer_print_page_header(struct trace_seq
*s
)
376 struct buffer_data_page field
;
378 trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
379 "offset:0;\tsize:%u;\tsigned:%u;\n",
380 (unsigned int)sizeof(field
.time_stamp
),
381 (unsigned int)is_signed_type(u64
));
383 trace_seq_printf(s
, "\tfield: local_t commit;\t"
384 "offset:%u;\tsize:%u;\tsigned:%u;\n",
385 (unsigned int)offsetof(typeof(field
), commit
),
386 (unsigned int)sizeof(field
.commit
),
387 (unsigned int)is_signed_type(long));
389 trace_seq_printf(s
, "\tfield: int overwrite;\t"
390 "offset:%u;\tsize:%u;\tsigned:%u;\n",
391 (unsigned int)offsetof(typeof(field
), commit
),
393 (unsigned int)is_signed_type(long));
395 trace_seq_printf(s
, "\tfield: char data;\t"
396 "offset:%u;\tsize:%u;\tsigned:%u;\n",
397 (unsigned int)offsetof(typeof(field
), data
),
398 (unsigned int)BUF_PAGE_SIZE
,
399 (unsigned int)is_signed_type(char));
401 return !trace_seq_has_overflowed(s
);
405 struct irq_work work
;
406 wait_queue_head_t waiters
;
407 wait_queue_head_t full_waiters
;
408 bool waiters_pending
;
409 bool full_waiters_pending
;
414 * Structure to hold event state and handle nested events.
416 struct rb_event_info
{
421 unsigned long length
;
422 struct buffer_page
*tail_page
;
427 * Used for the add_timestamp
429 * EXTEND - wants a time extend
430 * ABSOLUTE - the buffer requests all events to have absolute time stamps
431 * FORCE - force a full time stamp.
434 RB_ADD_STAMP_NONE
= 0,
435 RB_ADD_STAMP_EXTEND
= BIT(1),
436 RB_ADD_STAMP_ABSOLUTE
= BIT(2),
437 RB_ADD_STAMP_FORCE
= BIT(3)
440 * Used for which event context the event is in.
447 * See trace_recursive_lock() comment below for more details.
458 #if BITS_PER_LONG == 32
462 /* To test on 64 bit machines */
467 struct rb_time_struct
{
473 #include <asm/local64.h>
474 struct rb_time_struct
{
478 typedef struct rb_time_struct rb_time_t
;
481 * head_page == tail_page && head == tail then buffer is empty.
483 struct ring_buffer_per_cpu
{
485 atomic_t record_disabled
;
486 atomic_t resize_disabled
;
487 struct trace_buffer
*buffer
;
488 raw_spinlock_t reader_lock
; /* serialize readers */
489 arch_spinlock_t lock
;
490 struct lock_class_key lock_key
;
491 struct buffer_data_page
*free_page
;
492 unsigned long nr_pages
;
493 unsigned int current_context
;
494 struct list_head
*pages
;
495 struct buffer_page
*head_page
; /* read from head */
496 struct buffer_page
*tail_page
; /* write to tail */
497 struct buffer_page
*commit_page
; /* committed pages */
498 struct buffer_page
*reader_page
;
499 unsigned long lost_events
;
500 unsigned long last_overrun
;
502 local_t entries_bytes
;
505 local_t commit_overrun
;
506 local_t dropped_events
;
509 local_t pages_touched
;
511 long last_pages_touch
;
512 size_t shortest_full
;
514 unsigned long read_bytes
;
515 rb_time_t write_stamp
;
516 rb_time_t before_stamp
;
518 /* ring buffer pages to update, > 0 to add, < 0 to remove */
519 long nr_pages_to_update
;
520 struct list_head new_pages
; /* new pages to add */
521 struct work_struct update_pages_work
;
522 struct completion update_done
;
524 struct rb_irq_work irq_work
;
527 struct trace_buffer
{
530 atomic_t record_disabled
;
531 cpumask_var_t cpumask
;
533 struct lock_class_key
*reader_lock_key
;
537 struct ring_buffer_per_cpu
**buffers
;
539 struct hlist_node node
;
542 struct rb_irq_work irq_work
;
546 struct ring_buffer_iter
{
547 struct ring_buffer_per_cpu
*cpu_buffer
;
549 unsigned long next_event
;
550 struct buffer_page
*head_page
;
551 struct buffer_page
*cache_reader_page
;
552 unsigned long cache_read
;
555 struct ring_buffer_event
*event
;
562 * On 32 bit machines, local64_t is very expensive. As the ring
563 * buffer doesn't need all the features of a true 64 bit atomic,
564 * on 32 bit, it uses these functions (64 still uses local64_t).
566 * For the ring buffer, 64 bit required operations for the time is
569 * - Only need 59 bits (uses 60 to make it even).
570 * - Reads may fail if it interrupted a modification of the time stamp.
571 * It will succeed if it did not interrupt another write even if
572 * the read itself is interrupted by a write.
573 * It returns whether it was successful or not.
575 * - Writes always succeed and will overwrite other writes and writes
576 * that were done by events interrupting the current write.
578 * - A write followed by a read of the same time stamp will always succeed,
579 * but may not contain the same value.
581 * - A cmpxchg will fail if it interrupted another write or cmpxchg.
582 * Other than that, it acts like a normal cmpxchg.
584 * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
585 * (bottom being the least significant 30 bits of the 60 bit time stamp).
587 * The two most significant bits of each half holds a 2 bit counter (0-3).
588 * Each update will increment this counter by one.
589 * When reading the top and bottom, if the two counter bits match then the
590 * top and bottom together make a valid 60 bit number.
592 #define RB_TIME_SHIFT 30
593 #define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
595 static inline int rb_time_cnt(unsigned long val
)
597 return (val
>> RB_TIME_SHIFT
) & 3;
600 static inline u64
rb_time_val(unsigned long top
, unsigned long bottom
)
604 val
= top
& RB_TIME_VAL_MASK
;
605 val
<<= RB_TIME_SHIFT
;
606 val
|= bottom
& RB_TIME_VAL_MASK
;
611 static inline bool __rb_time_read(rb_time_t
*t
, u64
*ret
, unsigned long *cnt
)
613 unsigned long top
, bottom
;
617 * If the read is interrupted by a write, then the cnt will
618 * be different. Loop until both top and bottom have been read
619 * without interruption.
622 c
= local_read(&t
->cnt
);
623 top
= local_read(&t
->top
);
624 bottom
= local_read(&t
->bottom
);
625 } while (c
!= local_read(&t
->cnt
));
627 *cnt
= rb_time_cnt(top
);
629 /* If top and bottom counts don't match, this interrupted a write */
630 if (*cnt
!= rb_time_cnt(bottom
))
633 *ret
= rb_time_val(top
, bottom
);
637 static bool rb_time_read(rb_time_t
*t
, u64
*ret
)
641 return __rb_time_read(t
, ret
, &cnt
);
644 static inline unsigned long rb_time_val_cnt(unsigned long val
, unsigned long cnt
)
646 return (val
& RB_TIME_VAL_MASK
) | ((cnt
& 3) << RB_TIME_SHIFT
);
649 static inline void rb_time_split(u64 val
, unsigned long *top
, unsigned long *bottom
)
651 *top
= (unsigned long)((val
>> RB_TIME_SHIFT
) & RB_TIME_VAL_MASK
);
652 *bottom
= (unsigned long)(val
& RB_TIME_VAL_MASK
);
655 static inline void rb_time_val_set(local_t
*t
, unsigned long val
, unsigned long cnt
)
657 val
= rb_time_val_cnt(val
, cnt
);
661 static void rb_time_set(rb_time_t
*t
, u64 val
)
663 unsigned long cnt
, top
, bottom
;
665 rb_time_split(val
, &top
, &bottom
);
667 /* Writes always succeed with a valid number even if it gets interrupted. */
669 cnt
= local_inc_return(&t
->cnt
);
670 rb_time_val_set(&t
->top
, top
, cnt
);
671 rb_time_val_set(&t
->bottom
, bottom
, cnt
);
672 } while (cnt
!= local_read(&t
->cnt
));
676 rb_time_read_cmpxchg(local_t
*l
, unsigned long expect
, unsigned long set
)
680 ret
= local_cmpxchg(l
, expect
, set
);
681 return ret
== expect
;
684 static int rb_time_cmpxchg(rb_time_t
*t
, u64 expect
, u64 set
)
686 unsigned long cnt
, top
, bottom
;
687 unsigned long cnt2
, top2
, bottom2
;
690 /* The cmpxchg always fails if it interrupted an update */
691 if (!__rb_time_read(t
, &val
, &cnt2
))
697 cnt
= local_read(&t
->cnt
);
698 if ((cnt
& 3) != cnt2
)
703 rb_time_split(val
, &top
, &bottom
);
704 top
= rb_time_val_cnt(top
, cnt
);
705 bottom
= rb_time_val_cnt(bottom
, cnt
);
707 rb_time_split(set
, &top2
, &bottom2
);
708 top2
= rb_time_val_cnt(top2
, cnt2
);
709 bottom2
= rb_time_val_cnt(bottom2
, cnt2
);
711 if (!rb_time_read_cmpxchg(&t
->cnt
, cnt
, cnt2
))
713 if (!rb_time_read_cmpxchg(&t
->top
, top
, top2
))
715 if (!rb_time_read_cmpxchg(&t
->bottom
, bottom
, bottom2
))
722 /* local64_t always succeeds */
724 static inline bool rb_time_read(rb_time_t
*t
, u64
*ret
)
726 *ret
= local64_read(&t
->time
);
729 static void rb_time_set(rb_time_t
*t
, u64 val
)
731 local64_set(&t
->time
, val
);
734 static bool rb_time_cmpxchg(rb_time_t
*t
, u64 expect
, u64 set
)
737 val
= local64_cmpxchg(&t
->time
, expect
, set
);
738 return val
== expect
;
743 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
744 * @buffer: The ring_buffer to get the number of pages from
745 * @cpu: The cpu of the ring_buffer to get the number of pages from
747 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
749 size_t ring_buffer_nr_pages(struct trace_buffer
*buffer
, int cpu
)
751 return buffer
->buffers
[cpu
]->nr_pages
;
755 * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
756 * @buffer: The ring_buffer to get the number of pages from
757 * @cpu: The cpu of the ring_buffer to get the number of pages from
759 * Returns the number of pages that have content in the ring buffer.
761 size_t ring_buffer_nr_dirty_pages(struct trace_buffer
*buffer
, int cpu
)
766 read
= local_read(&buffer
->buffers
[cpu
]->pages_read
);
767 cnt
= local_read(&buffer
->buffers
[cpu
]->pages_touched
);
768 /* The reader can read an empty page, but not more than that */
770 WARN_ON_ONCE(read
> cnt
+ 1);
778 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
780 * Schedules a delayed work to wake up any task that is blocked on the
781 * ring buffer waiters queue.
783 static void rb_wake_up_waiters(struct irq_work
*work
)
785 struct rb_irq_work
*rbwork
= container_of(work
, struct rb_irq_work
, work
);
787 wake_up_all(&rbwork
->waiters
);
788 if (rbwork
->wakeup_full
) {
789 rbwork
->wakeup_full
= false;
790 wake_up_all(&rbwork
->full_waiters
);
795 * ring_buffer_wait - wait for input to the ring buffer
796 * @buffer: buffer to wait on
797 * @cpu: the cpu buffer to wait on
798 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
800 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
801 * as data is added to any of the @buffer's cpu buffers. Otherwise
802 * it will wait for data to be added to a specific cpu buffer.
804 int ring_buffer_wait(struct trace_buffer
*buffer
, int cpu
, int full
)
806 struct ring_buffer_per_cpu
*cpu_buffer
;
808 struct rb_irq_work
*work
;
812 * Depending on what the caller is waiting for, either any
813 * data in any cpu buffer, or a specific buffer, put the
814 * caller on the appropriate wait queue.
816 if (cpu
== RING_BUFFER_ALL_CPUS
) {
817 work
= &buffer
->irq_work
;
818 /* Full only makes sense on per cpu reads */
821 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
823 cpu_buffer
= buffer
->buffers
[cpu
];
824 work
= &cpu_buffer
->irq_work
;
830 prepare_to_wait(&work
->full_waiters
, &wait
, TASK_INTERRUPTIBLE
);
832 prepare_to_wait(&work
->waiters
, &wait
, TASK_INTERRUPTIBLE
);
835 * The events can happen in critical sections where
836 * checking a work queue can cause deadlocks.
837 * After adding a task to the queue, this flag is set
838 * only to notify events to try to wake up the queue
841 * We don't clear it even if the buffer is no longer
842 * empty. The flag only causes the next event to run
843 * irq_work to do the work queue wake up. The worse
844 * that can happen if we race with !trace_empty() is that
845 * an event will cause an irq_work to try to wake up
848 * There's no reason to protect this flag either, as
849 * the work queue and irq_work logic will do the necessary
850 * synchronization for the wake ups. The only thing
851 * that is necessary is that the wake up happens after
852 * a task has been queued. It's OK for spurious wake ups.
855 work
->full_waiters_pending
= true;
857 work
->waiters_pending
= true;
859 if (signal_pending(current
)) {
864 if (cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
))
867 if (cpu
!= RING_BUFFER_ALL_CPUS
&&
868 !ring_buffer_empty_cpu(buffer
, cpu
)) {
877 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
878 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
879 nr_pages
= cpu_buffer
->nr_pages
;
880 dirty
= ring_buffer_nr_dirty_pages(buffer
, cpu
);
881 if (!cpu_buffer
->shortest_full
||
882 cpu_buffer
->shortest_full
< full
)
883 cpu_buffer
->shortest_full
= full
;
884 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
886 (!nr_pages
|| (dirty
* 100) > full
* nr_pages
))
894 finish_wait(&work
->full_waiters
, &wait
);
896 finish_wait(&work
->waiters
, &wait
);
902 * ring_buffer_poll_wait - poll on buffer input
903 * @buffer: buffer to wait on
904 * @cpu: the cpu buffer to wait on
905 * @filp: the file descriptor
906 * @poll_table: The poll descriptor
908 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
909 * as data is added to any of the @buffer's cpu buffers. Otherwise
910 * it will wait for data to be added to a specific cpu buffer.
912 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
915 __poll_t
ring_buffer_poll_wait(struct trace_buffer
*buffer
, int cpu
,
916 struct file
*filp
, poll_table
*poll_table
)
918 struct ring_buffer_per_cpu
*cpu_buffer
;
919 struct rb_irq_work
*work
;
921 if (cpu
== RING_BUFFER_ALL_CPUS
)
922 work
= &buffer
->irq_work
;
924 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
927 cpu_buffer
= buffer
->buffers
[cpu
];
928 work
= &cpu_buffer
->irq_work
;
931 poll_wait(filp
, &work
->waiters
, poll_table
);
932 work
->waiters_pending
= true;
934 * There's a tight race between setting the waiters_pending and
935 * checking if the ring buffer is empty. Once the waiters_pending bit
936 * is set, the next event will wake the task up, but we can get stuck
937 * if there's only a single event in.
939 * FIXME: Ideally, we need a memory barrier on the writer side as well,
940 * but adding a memory barrier to all events will cause too much of a
941 * performance hit in the fast path. We only need a memory barrier when
942 * the buffer goes from empty to having content. But as this race is
943 * extremely small, and it's not a problem if another event comes in, we
948 if ((cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
)) ||
949 (cpu
!= RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty_cpu(buffer
, cpu
)))
950 return EPOLLIN
| EPOLLRDNORM
;
954 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
955 #define RB_WARN_ON(b, cond) \
957 int _____ret = unlikely(cond); \
959 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
960 struct ring_buffer_per_cpu *__b = \
962 atomic_inc(&__b->buffer->record_disabled); \
964 atomic_inc(&b->record_disabled); \
970 /* Up this if you want to test the TIME_EXTENTS and normalization */
971 #define DEBUG_SHIFT 0
973 static inline u64
rb_time_stamp(struct trace_buffer
*buffer
)
977 /* Skip retpolines :-( */
978 if (IS_ENABLED(CONFIG_RETPOLINE
) && likely(buffer
->clock
== trace_clock_local
))
979 ts
= trace_clock_local();
981 ts
= buffer
->clock();
983 /* shift to debug/test normalization and TIME_EXTENTS */
984 return ts
<< DEBUG_SHIFT
;
987 u64
ring_buffer_time_stamp(struct trace_buffer
*buffer
, int cpu
)
991 preempt_disable_notrace();
992 time
= rb_time_stamp(buffer
);
993 preempt_enable_notrace();
997 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
999 void ring_buffer_normalize_time_stamp(struct trace_buffer
*buffer
,
1002 /* Just stupid testing the normalize function and deltas */
1003 *ts
>>= DEBUG_SHIFT
;
1005 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
1008 * Making the ring buffer lockless makes things tricky.
1009 * Although writes only happen on the CPU that they are on,
1010 * and they only need to worry about interrupts. Reads can
1011 * happen on any CPU.
1013 * The reader page is always off the ring buffer, but when the
1014 * reader finishes with a page, it needs to swap its page with
1015 * a new one from the buffer. The reader needs to take from
1016 * the head (writes go to the tail). But if a writer is in overwrite
1017 * mode and wraps, it must push the head page forward.
1019 * Here lies the problem.
1021 * The reader must be careful to replace only the head page, and
1022 * not another one. As described at the top of the file in the
1023 * ASCII art, the reader sets its old page to point to the next
1024 * page after head. It then sets the page after head to point to
1025 * the old reader page. But if the writer moves the head page
1026 * during this operation, the reader could end up with the tail.
1028 * We use cmpxchg to help prevent this race. We also do something
1029 * special with the page before head. We set the LSB to 1.
1031 * When the writer must push the page forward, it will clear the
1032 * bit that points to the head page, move the head, and then set
1033 * the bit that points to the new head page.
1035 * We also don't want an interrupt coming in and moving the head
1036 * page on another writer. Thus we use the second LSB to catch
1039 * head->list->prev->next bit 1 bit 0
1042 * Points to head page 0 1
1045 * Note we can not trust the prev pointer of the head page, because:
1047 * +----+ +-----+ +-----+
1048 * | |------>| T |---X--->| N |
1050 * +----+ +-----+ +-----+
1053 * +----------| R |----------+ |
1057 * Key: ---X--> HEAD flag set in pointer
1062 * (see __rb_reserve_next() to see where this happens)
1064 * What the above shows is that the reader just swapped out
1065 * the reader page with a page in the buffer, but before it
1066 * could make the new header point back to the new page added
1067 * it was preempted by a writer. The writer moved forward onto
1068 * the new page added by the reader and is about to move forward
1071 * You can see, it is legitimate for the previous pointer of
1072 * the head (or any page) not to point back to itself. But only
1076 #define RB_PAGE_NORMAL 0UL
1077 #define RB_PAGE_HEAD 1UL
1078 #define RB_PAGE_UPDATE 2UL
1081 #define RB_FLAG_MASK 3UL
1083 /* PAGE_MOVED is not part of the mask */
1084 #define RB_PAGE_MOVED 4UL
1087 * rb_list_head - remove any bit
1089 static struct list_head
*rb_list_head(struct list_head
*list
)
1091 unsigned long val
= (unsigned long)list
;
1093 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
1097 * rb_is_head_page - test if the given page is the head page
1099 * Because the reader may move the head_page pointer, we can
1100 * not trust what the head page is (it may be pointing to
1101 * the reader page). But if the next page is a header page,
1102 * its flags will be non zero.
1105 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1106 struct buffer_page
*page
, struct list_head
*list
)
1110 val
= (unsigned long)list
->next
;
1112 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
1113 return RB_PAGE_MOVED
;
1115 return val
& RB_FLAG_MASK
;
1121 * The unique thing about the reader page, is that, if the
1122 * writer is ever on it, the previous pointer never points
1123 * back to the reader page.
1125 static bool rb_is_reader_page(struct buffer_page
*page
)
1127 struct list_head
*list
= page
->list
.prev
;
1129 return rb_list_head(list
->next
) != &page
->list
;
1133 * rb_set_list_to_head - set a list_head to be pointing to head.
1135 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
1136 struct list_head
*list
)
1140 ptr
= (unsigned long *)&list
->next
;
1141 *ptr
|= RB_PAGE_HEAD
;
1142 *ptr
&= ~RB_PAGE_UPDATE
;
1146 * rb_head_page_activate - sets up head page
1148 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
1150 struct buffer_page
*head
;
1152 head
= cpu_buffer
->head_page
;
1157 * Set the previous list pointer to have the HEAD flag.
1159 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
1162 static void rb_list_head_clear(struct list_head
*list
)
1164 unsigned long *ptr
= (unsigned long *)&list
->next
;
1166 *ptr
&= ~RB_FLAG_MASK
;
1170 * rb_head_page_deactivate - clears head page ptr (for free list)
1173 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
1175 struct list_head
*hd
;
1177 /* Go through the whole list and clear any pointers found. */
1178 rb_list_head_clear(cpu_buffer
->pages
);
1180 list_for_each(hd
, cpu_buffer
->pages
)
1181 rb_list_head_clear(hd
);
1184 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
1185 struct buffer_page
*head
,
1186 struct buffer_page
*prev
,
1187 int old_flag
, int new_flag
)
1189 struct list_head
*list
;
1190 unsigned long val
= (unsigned long)&head
->list
;
1195 val
&= ~RB_FLAG_MASK
;
1197 ret
= cmpxchg((unsigned long *)&list
->next
,
1198 val
| old_flag
, val
| new_flag
);
1200 /* check if the reader took the page */
1201 if ((ret
& ~RB_FLAG_MASK
) != val
)
1202 return RB_PAGE_MOVED
;
1204 return ret
& RB_FLAG_MASK
;
1207 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1208 struct buffer_page
*head
,
1209 struct buffer_page
*prev
,
1212 return rb_head_page_set(cpu_buffer
, head
, prev
,
1213 old_flag
, RB_PAGE_UPDATE
);
1216 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
1217 struct buffer_page
*head
,
1218 struct buffer_page
*prev
,
1221 return rb_head_page_set(cpu_buffer
, head
, prev
,
1222 old_flag
, RB_PAGE_HEAD
);
1225 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
1226 struct buffer_page
*head
,
1227 struct buffer_page
*prev
,
1230 return rb_head_page_set(cpu_buffer
, head
, prev
,
1231 old_flag
, RB_PAGE_NORMAL
);
1234 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1235 struct buffer_page
**bpage
)
1237 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
1239 *bpage
= list_entry(p
, struct buffer_page
, list
);
1242 static struct buffer_page
*
1243 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1245 struct buffer_page
*head
;
1246 struct buffer_page
*page
;
1247 struct list_head
*list
;
1250 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
1254 list
= cpu_buffer
->pages
;
1255 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
1258 page
= head
= cpu_buffer
->head_page
;
1260 * It is possible that the writer moves the header behind
1261 * where we started, and we miss in one loop.
1262 * A second loop should grab the header, but we'll do
1263 * three loops just because I'm paranoid.
1265 for (i
= 0; i
< 3; i
++) {
1267 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
1268 cpu_buffer
->head_page
= page
;
1271 rb_inc_page(cpu_buffer
, &page
);
1272 } while (page
!= head
);
1275 RB_WARN_ON(cpu_buffer
, 1);
1280 static int rb_head_page_replace(struct buffer_page
*old
,
1281 struct buffer_page
*new)
1283 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
1287 val
= *ptr
& ~RB_FLAG_MASK
;
1288 val
|= RB_PAGE_HEAD
;
1290 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
1296 * rb_tail_page_update - move the tail page forward
1298 static void rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1299 struct buffer_page
*tail_page
,
1300 struct buffer_page
*next_page
)
1302 unsigned long old_entries
;
1303 unsigned long old_write
;
1306 * The tail page now needs to be moved forward.
1308 * We need to reset the tail page, but without messing
1309 * with possible erasing of data brought in by interrupts
1310 * that have moved the tail page and are currently on it.
1312 * We add a counter to the write field to denote this.
1314 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
1315 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
1317 local_inc(&cpu_buffer
->pages_touched
);
1319 * Just make sure we have seen our old_write and synchronize
1320 * with any interrupts that come in.
1325 * If the tail page is still the same as what we think
1326 * it is, then it is up to us to update the tail
1329 if (tail_page
== READ_ONCE(cpu_buffer
->tail_page
)) {
1330 /* Zero the write counter */
1331 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
1332 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
1335 * This will only succeed if an interrupt did
1336 * not come in and change it. In which case, we
1337 * do not want to modify it.
1339 * We add (void) to let the compiler know that we do not care
1340 * about the return value of these functions. We use the
1341 * cmpxchg to only update if an interrupt did not already
1342 * do it for us. If the cmpxchg fails, we don't care.
1344 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
1345 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
1348 * No need to worry about races with clearing out the commit.
1349 * it only can increment when a commit takes place. But that
1350 * only happens in the outer most nested commit.
1352 local_set(&next_page
->page
->commit
, 0);
1354 /* Again, either we update tail_page or an interrupt does */
1355 (void)cmpxchg(&cpu_buffer
->tail_page
, tail_page
, next_page
);
1359 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
1360 struct buffer_page
*bpage
)
1362 unsigned long val
= (unsigned long)bpage
;
1364 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
1371 * rb_check_list - make sure a pointer to a list has the last bits zero
1373 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
1374 struct list_head
*list
)
1376 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
1378 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
1384 * rb_check_pages - integrity check of buffer pages
1385 * @cpu_buffer: CPU buffer with pages to test
1387 * As a safety measure we check to make sure the data pages have not
1390 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1392 struct list_head
*head
= cpu_buffer
->pages
;
1393 struct buffer_page
*bpage
, *tmp
;
1395 /* Reset the head page if it exists */
1396 if (cpu_buffer
->head_page
)
1397 rb_set_head_page(cpu_buffer
);
1399 rb_head_page_deactivate(cpu_buffer
);
1401 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
1403 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
1406 if (rb_check_list(cpu_buffer
, head
))
1409 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1410 if (RB_WARN_ON(cpu_buffer
,
1411 bpage
->list
.next
->prev
!= &bpage
->list
))
1413 if (RB_WARN_ON(cpu_buffer
,
1414 bpage
->list
.prev
->next
!= &bpage
->list
))
1416 if (rb_check_list(cpu_buffer
, &bpage
->list
))
1420 rb_head_page_activate(cpu_buffer
);
1425 static int __rb_allocate_pages(long nr_pages
, struct list_head
*pages
, int cpu
)
1427 struct buffer_page
*bpage
, *tmp
;
1428 bool user_thread
= current
->mm
!= NULL
;
1433 * Check if the available memory is there first.
1434 * Note, si_mem_available() only gives us a rough estimate of available
1435 * memory. It may not be accurate. But we don't care, we just want
1436 * to prevent doing any allocation when it is obvious that it is
1437 * not going to succeed.
1439 i
= si_mem_available();
1444 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1445 * gracefully without invoking oom-killer and the system is not
1448 mflags
= GFP_KERNEL
| __GFP_RETRY_MAYFAIL
;
1451 * If a user thread allocates too much, and si_mem_available()
1452 * reports there's enough memory, even though there is not.
1453 * Make sure the OOM killer kills this thread. This can happen
1454 * even with RETRY_MAYFAIL because another task may be doing
1455 * an allocation after this task has taken all memory.
1456 * This is the task the OOM killer needs to take out during this
1457 * loop, even if it was triggered by an allocation somewhere else.
1460 set_current_oom_origin();
1461 for (i
= 0; i
< nr_pages
; i
++) {
1464 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1465 mflags
, cpu_to_node(cpu
));
1469 list_add(&bpage
->list
, pages
);
1471 page
= alloc_pages_node(cpu_to_node(cpu
), mflags
, 0);
1474 bpage
->page
= page_address(page
);
1475 rb_init_page(bpage
->page
);
1477 if (user_thread
&& fatal_signal_pending(current
))
1481 clear_current_oom_origin();
1486 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1487 list_del_init(&bpage
->list
);
1488 free_buffer_page(bpage
);
1491 clear_current_oom_origin();
1496 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1497 unsigned long nr_pages
)
1503 if (__rb_allocate_pages(nr_pages
, &pages
, cpu_buffer
->cpu
))
1507 * The ring buffer page list is a circular list that does not
1508 * start and end with a list head. All page list items point to
1511 cpu_buffer
->pages
= pages
.next
;
1514 cpu_buffer
->nr_pages
= nr_pages
;
1516 rb_check_pages(cpu_buffer
);
1521 static struct ring_buffer_per_cpu
*
1522 rb_allocate_cpu_buffer(struct trace_buffer
*buffer
, long nr_pages
, int cpu
)
1524 struct ring_buffer_per_cpu
*cpu_buffer
;
1525 struct buffer_page
*bpage
;
1529 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1530 GFP_KERNEL
, cpu_to_node(cpu
));
1534 cpu_buffer
->cpu
= cpu
;
1535 cpu_buffer
->buffer
= buffer
;
1536 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1537 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1538 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1539 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1540 init_completion(&cpu_buffer
->update_done
);
1541 init_irq_work(&cpu_buffer
->irq_work
.work
, rb_wake_up_waiters
);
1542 init_waitqueue_head(&cpu_buffer
->irq_work
.waiters
);
1543 init_waitqueue_head(&cpu_buffer
->irq_work
.full_waiters
);
1545 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1546 GFP_KERNEL
, cpu_to_node(cpu
));
1548 goto fail_free_buffer
;
1550 rb_check_bpage(cpu_buffer
, bpage
);
1552 cpu_buffer
->reader_page
= bpage
;
1553 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, 0);
1555 goto fail_free_reader
;
1556 bpage
->page
= page_address(page
);
1557 rb_init_page(bpage
->page
);
1559 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1560 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1562 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1564 goto fail_free_reader
;
1566 cpu_buffer
->head_page
1567 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1568 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1570 rb_head_page_activate(cpu_buffer
);
1575 free_buffer_page(cpu_buffer
->reader_page
);
1582 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1584 struct list_head
*head
= cpu_buffer
->pages
;
1585 struct buffer_page
*bpage
, *tmp
;
1587 free_buffer_page(cpu_buffer
->reader_page
);
1589 rb_head_page_deactivate(cpu_buffer
);
1592 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1593 list_del_init(&bpage
->list
);
1594 free_buffer_page(bpage
);
1596 bpage
= list_entry(head
, struct buffer_page
, list
);
1597 free_buffer_page(bpage
);
1604 * __ring_buffer_alloc - allocate a new ring_buffer
1605 * @size: the size in bytes per cpu that is needed.
1606 * @flags: attributes to set for the ring buffer.
1607 * @key: ring buffer reader_lock_key.
1609 * Currently the only flag that is available is the RB_FL_OVERWRITE
1610 * flag. This flag means that the buffer will overwrite old data
1611 * when the buffer wraps. If this flag is not set, the buffer will
1612 * drop data when the tail hits the head.
1614 struct trace_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1615 struct lock_class_key
*key
)
1617 struct trace_buffer
*buffer
;
1623 /* keep it in its own cache line */
1624 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1629 if (!zalloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1630 goto fail_free_buffer
;
1632 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1633 buffer
->flags
= flags
;
1634 buffer
->clock
= trace_clock_local
;
1635 buffer
->reader_lock_key
= key
;
1637 init_irq_work(&buffer
->irq_work
.work
, rb_wake_up_waiters
);
1638 init_waitqueue_head(&buffer
->irq_work
.waiters
);
1640 /* need at least two pages */
1644 buffer
->cpus
= nr_cpu_ids
;
1646 bsize
= sizeof(void *) * nr_cpu_ids
;
1647 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1649 if (!buffer
->buffers
)
1650 goto fail_free_cpumask
;
1652 cpu
= raw_smp_processor_id();
1653 cpumask_set_cpu(cpu
, buffer
->cpumask
);
1654 buffer
->buffers
[cpu
] = rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1655 if (!buffer
->buffers
[cpu
])
1656 goto fail_free_buffers
;
1658 ret
= cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1660 goto fail_free_buffers
;
1662 mutex_init(&buffer
->mutex
);
1667 for_each_buffer_cpu(buffer
, cpu
) {
1668 if (buffer
->buffers
[cpu
])
1669 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1671 kfree(buffer
->buffers
);
1674 free_cpumask_var(buffer
->cpumask
);
1680 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1683 * ring_buffer_free - free a ring buffer.
1684 * @buffer: the buffer to free.
1687 ring_buffer_free(struct trace_buffer
*buffer
)
1691 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1693 for_each_buffer_cpu(buffer
, cpu
)
1694 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1696 kfree(buffer
->buffers
);
1697 free_cpumask_var(buffer
->cpumask
);
1701 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1703 void ring_buffer_set_clock(struct trace_buffer
*buffer
,
1706 buffer
->clock
= clock
;
1709 void ring_buffer_set_time_stamp_abs(struct trace_buffer
*buffer
, bool abs
)
1711 buffer
->time_stamp_abs
= abs
;
1714 bool ring_buffer_time_stamp_abs(struct trace_buffer
*buffer
)
1716 return buffer
->time_stamp_abs
;
1719 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1721 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1723 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1726 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1728 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1732 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned long nr_pages
)
1734 struct list_head
*tail_page
, *to_remove
, *next_page
;
1735 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1736 struct buffer_page
*last_page
, *first_page
;
1737 unsigned long nr_removed
;
1738 unsigned long head_bit
;
1743 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1744 atomic_inc(&cpu_buffer
->record_disabled
);
1746 * We don't race with the readers since we have acquired the reader
1747 * lock. We also don't race with writers after disabling recording.
1748 * This makes it easy to figure out the first and the last page to be
1749 * removed from the list. We unlink all the pages in between including
1750 * the first and last pages. This is done in a busy loop so that we
1751 * lose the least number of traces.
1752 * The pages are freed after we restart recording and unlock readers.
1754 tail_page
= &cpu_buffer
->tail_page
->list
;
1757 * tail page might be on reader page, we remove the next page
1758 * from the ring buffer
1760 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1761 tail_page
= rb_list_head(tail_page
->next
);
1762 to_remove
= tail_page
;
1764 /* start of pages to remove */
1765 first_page
= list_entry(rb_list_head(to_remove
->next
),
1766 struct buffer_page
, list
);
1768 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1769 to_remove
= rb_list_head(to_remove
)->next
;
1770 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1773 next_page
= rb_list_head(to_remove
)->next
;
1776 * Now we remove all pages between tail_page and next_page.
1777 * Make sure that we have head_bit value preserved for the
1780 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1782 next_page
= rb_list_head(next_page
);
1783 next_page
->prev
= tail_page
;
1785 /* make sure pages points to a valid page in the ring buffer */
1786 cpu_buffer
->pages
= next_page
;
1788 /* update head page */
1790 cpu_buffer
->head_page
= list_entry(next_page
,
1791 struct buffer_page
, list
);
1794 * change read pointer to make sure any read iterators reset
1797 cpu_buffer
->read
= 0;
1799 /* pages are removed, resume tracing and then free the pages */
1800 atomic_dec(&cpu_buffer
->record_disabled
);
1801 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1803 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1805 /* last buffer page to remove */
1806 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1808 tmp_iter_page
= first_page
;
1813 to_remove_page
= tmp_iter_page
;
1814 rb_inc_page(cpu_buffer
, &tmp_iter_page
);
1816 /* update the counters */
1817 page_entries
= rb_page_entries(to_remove_page
);
1820 * If something was added to this page, it was full
1821 * since it is not the tail page. So we deduct the
1822 * bytes consumed in ring buffer from here.
1823 * Increment overrun to account for the lost events.
1825 local_add(page_entries
, &cpu_buffer
->overrun
);
1826 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1830 * We have already removed references to this list item, just
1831 * free up the buffer_page and its page
1833 free_buffer_page(to_remove_page
);
1836 } while (to_remove_page
!= last_page
);
1838 RB_WARN_ON(cpu_buffer
, nr_removed
);
1840 return nr_removed
== 0;
1844 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1846 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1847 int retries
, success
;
1849 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1851 * We are holding the reader lock, so the reader page won't be swapped
1852 * in the ring buffer. Now we are racing with the writer trying to
1853 * move head page and the tail page.
1854 * We are going to adapt the reader page update process where:
1855 * 1. We first splice the start and end of list of new pages between
1856 * the head page and its previous page.
1857 * 2. We cmpxchg the prev_page->next to point from head page to the
1858 * start of new pages list.
1859 * 3. Finally, we update the head->prev to the end of new list.
1861 * We will try this process 10 times, to make sure that we don't keep
1867 struct list_head
*head_page
, *prev_page
, *r
;
1868 struct list_head
*last_page
, *first_page
;
1869 struct list_head
*head_page_with_bit
;
1871 head_page
= &rb_set_head_page(cpu_buffer
)->list
;
1874 prev_page
= head_page
->prev
;
1876 first_page
= pages
->next
;
1877 last_page
= pages
->prev
;
1879 head_page_with_bit
= (struct list_head
*)
1880 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1882 last_page
->next
= head_page_with_bit
;
1883 first_page
->prev
= prev_page
;
1885 r
= cmpxchg(&prev_page
->next
, head_page_with_bit
, first_page
);
1887 if (r
== head_page_with_bit
) {
1889 * yay, we replaced the page pointer to our new list,
1890 * now, we just have to update to head page's prev
1891 * pointer to point to end of list
1893 head_page
->prev
= last_page
;
1900 INIT_LIST_HEAD(pages
);
1902 * If we weren't successful in adding in new pages, warn and stop
1905 RB_WARN_ON(cpu_buffer
, !success
);
1906 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1908 /* free pages if they weren't inserted */
1910 struct buffer_page
*bpage
, *tmp
;
1911 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1913 list_del_init(&bpage
->list
);
1914 free_buffer_page(bpage
);
1920 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1924 if (cpu_buffer
->nr_pages_to_update
> 0)
1925 success
= rb_insert_pages(cpu_buffer
);
1927 success
= rb_remove_pages(cpu_buffer
,
1928 -cpu_buffer
->nr_pages_to_update
);
1931 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1934 static void update_pages_handler(struct work_struct
*work
)
1936 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1937 struct ring_buffer_per_cpu
, update_pages_work
);
1938 rb_update_pages(cpu_buffer
);
1939 complete(&cpu_buffer
->update_done
);
1943 * ring_buffer_resize - resize the ring buffer
1944 * @buffer: the buffer to resize.
1945 * @size: the new size.
1946 * @cpu_id: the cpu buffer to resize
1948 * Minimum size is 2 * BUF_PAGE_SIZE.
1950 * Returns 0 on success and < 0 on failure.
1952 int ring_buffer_resize(struct trace_buffer
*buffer
, unsigned long size
,
1955 struct ring_buffer_per_cpu
*cpu_buffer
;
1956 unsigned long nr_pages
;
1960 * Always succeed at resizing a non-existent buffer:
1965 /* Make sure the requested buffer exists */
1966 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1967 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1970 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1972 /* we need a minimum of two pages */
1976 size
= nr_pages
* BUF_PAGE_SIZE
;
1978 /* prevent another thread from changing buffer sizes */
1979 mutex_lock(&buffer
->mutex
);
1982 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
1984 * Don't succeed if resizing is disabled, as a reader might be
1985 * manipulating the ring buffer and is expecting a sane state while
1988 for_each_buffer_cpu(buffer
, cpu
) {
1989 cpu_buffer
= buffer
->buffers
[cpu
];
1990 if (atomic_read(&cpu_buffer
->resize_disabled
)) {
1992 goto out_err_unlock
;
1996 /* calculate the pages to update */
1997 for_each_buffer_cpu(buffer
, cpu
) {
1998 cpu_buffer
= buffer
->buffers
[cpu
];
2000 cpu_buffer
->nr_pages_to_update
= nr_pages
-
2001 cpu_buffer
->nr_pages
;
2003 * nothing more to do for removing pages or no update
2005 if (cpu_buffer
->nr_pages_to_update
<= 0)
2008 * to add pages, make sure all new pages can be
2009 * allocated without receiving ENOMEM
2011 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
2012 if (__rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
2013 &cpu_buffer
->new_pages
, cpu
)) {
2014 /* not enough memory for new pages */
2022 * Fire off all the required work handlers
2023 * We can't schedule on offline CPUs, but it's not necessary
2024 * since we can change their buffer sizes without any race.
2026 for_each_buffer_cpu(buffer
, cpu
) {
2027 cpu_buffer
= buffer
->buffers
[cpu
];
2028 if (!cpu_buffer
->nr_pages_to_update
)
2031 /* Can't run something on an offline CPU. */
2032 if (!cpu_online(cpu
)) {
2033 rb_update_pages(cpu_buffer
);
2034 cpu_buffer
->nr_pages_to_update
= 0;
2036 schedule_work_on(cpu
,
2037 &cpu_buffer
->update_pages_work
);
2041 /* wait for all the updates to complete */
2042 for_each_buffer_cpu(buffer
, cpu
) {
2043 cpu_buffer
= buffer
->buffers
[cpu
];
2044 if (!cpu_buffer
->nr_pages_to_update
)
2047 if (cpu_online(cpu
))
2048 wait_for_completion(&cpu_buffer
->update_done
);
2049 cpu_buffer
->nr_pages_to_update
= 0;
2054 /* Make sure this CPU has been initialized */
2055 if (!cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
2058 cpu_buffer
= buffer
->buffers
[cpu_id
];
2060 if (nr_pages
== cpu_buffer
->nr_pages
)
2064 * Don't succeed if resizing is disabled, as a reader might be
2065 * manipulating the ring buffer and is expecting a sane state while
2068 if (atomic_read(&cpu_buffer
->resize_disabled
)) {
2070 goto out_err_unlock
;
2073 cpu_buffer
->nr_pages_to_update
= nr_pages
-
2074 cpu_buffer
->nr_pages
;
2076 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
2077 if (cpu_buffer
->nr_pages_to_update
> 0 &&
2078 __rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
2079 &cpu_buffer
->new_pages
, cpu_id
)) {
2086 /* Can't run something on an offline CPU. */
2087 if (!cpu_online(cpu_id
))
2088 rb_update_pages(cpu_buffer
);
2090 schedule_work_on(cpu_id
,
2091 &cpu_buffer
->update_pages_work
);
2092 wait_for_completion(&cpu_buffer
->update_done
);
2095 cpu_buffer
->nr_pages_to_update
= 0;
2101 * The ring buffer resize can happen with the ring buffer
2102 * enabled, so that the update disturbs the tracing as little
2103 * as possible. But if the buffer is disabled, we do not need
2104 * to worry about that, and we can take the time to verify
2105 * that the buffer is not corrupt.
2107 if (atomic_read(&buffer
->record_disabled
)) {
2108 atomic_inc(&buffer
->record_disabled
);
2110 * Even though the buffer was disabled, we must make sure
2111 * that it is truly disabled before calling rb_check_pages.
2112 * There could have been a race between checking
2113 * record_disable and incrementing it.
2116 for_each_buffer_cpu(buffer
, cpu
) {
2117 cpu_buffer
= buffer
->buffers
[cpu
];
2118 rb_check_pages(cpu_buffer
);
2120 atomic_dec(&buffer
->record_disabled
);
2123 mutex_unlock(&buffer
->mutex
);
2127 for_each_buffer_cpu(buffer
, cpu
) {
2128 struct buffer_page
*bpage
, *tmp
;
2130 cpu_buffer
= buffer
->buffers
[cpu
];
2131 cpu_buffer
->nr_pages_to_update
= 0;
2133 if (list_empty(&cpu_buffer
->new_pages
))
2136 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
2138 list_del_init(&bpage
->list
);
2139 free_buffer_page(bpage
);
2143 mutex_unlock(&buffer
->mutex
);
2146 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
2148 void ring_buffer_change_overwrite(struct trace_buffer
*buffer
, int val
)
2150 mutex_lock(&buffer
->mutex
);
2152 buffer
->flags
|= RB_FL_OVERWRITE
;
2154 buffer
->flags
&= ~RB_FL_OVERWRITE
;
2155 mutex_unlock(&buffer
->mutex
);
2157 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
2159 static __always_inline
void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
2161 return bpage
->page
->data
+ index
;
2164 static __always_inline
struct ring_buffer_event
*
2165 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
2167 return __rb_page_index(cpu_buffer
->reader_page
,
2168 cpu_buffer
->reader_page
->read
);
2171 static __always_inline
unsigned rb_page_commit(struct buffer_page
*bpage
)
2173 return local_read(&bpage
->page
->commit
);
2176 static struct ring_buffer_event
*
2177 rb_iter_head_event(struct ring_buffer_iter
*iter
)
2179 struct ring_buffer_event
*event
;
2180 struct buffer_page
*iter_head_page
= iter
->head_page
;
2181 unsigned long commit
;
2184 if (iter
->head
!= iter
->next_event
)
2188 * When the writer goes across pages, it issues a cmpxchg which
2189 * is a mb(), which will synchronize with the rmb here.
2190 * (see rb_tail_page_update() and __rb_reserve_next())
2192 commit
= rb_page_commit(iter_head_page
);
2194 event
= __rb_page_index(iter_head_page
, iter
->head
);
2195 length
= rb_event_length(event
);
2198 * READ_ONCE() doesn't work on functions and we don't want the
2199 * compiler doing any crazy optimizations with length.
2203 if ((iter
->head
+ length
) > commit
|| length
> BUF_MAX_DATA_SIZE
)
2204 /* Writer corrupted the read? */
2207 memcpy(iter
->event
, event
, length
);
2209 * If the page stamp is still the same after this rmb() then the
2210 * event was safely copied without the writer entering the page.
2214 /* Make sure the page didn't change since we read this */
2215 if (iter
->page_stamp
!= iter_head_page
->page
->time_stamp
||
2216 commit
> rb_page_commit(iter_head_page
))
2219 iter
->next_event
= iter
->head
+ length
;
2222 /* Reset to the beginning */
2223 iter
->page_stamp
= iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2225 iter
->next_event
= 0;
2226 iter
->missed_events
= 1;
2230 /* Size is determined by what has been committed */
2231 static __always_inline
unsigned rb_page_size(struct buffer_page
*bpage
)
2233 return rb_page_commit(bpage
);
2236 static __always_inline
unsigned
2237 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
2239 return rb_page_commit(cpu_buffer
->commit_page
);
2242 static __always_inline
unsigned
2243 rb_event_index(struct ring_buffer_event
*event
)
2245 unsigned long addr
= (unsigned long)event
;
2247 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
2250 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
2252 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2255 * The iterator could be on the reader page (it starts there).
2256 * But the head could have moved, since the reader was
2257 * found. Check for this case and assign the iterator
2258 * to the head page instead of next.
2260 if (iter
->head_page
== cpu_buffer
->reader_page
)
2261 iter
->head_page
= rb_set_head_page(cpu_buffer
);
2263 rb_inc_page(cpu_buffer
, &iter
->head_page
);
2265 iter
->page_stamp
= iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2267 iter
->next_event
= 0;
2271 * rb_handle_head_page - writer hit the head page
2273 * Returns: +1 to retry page
2278 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
2279 struct buffer_page
*tail_page
,
2280 struct buffer_page
*next_page
)
2282 struct buffer_page
*new_head
;
2287 entries
= rb_page_entries(next_page
);
2290 * The hard part is here. We need to move the head
2291 * forward, and protect against both readers on
2292 * other CPUs and writers coming in via interrupts.
2294 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
2298 * type can be one of four:
2299 * NORMAL - an interrupt already moved it for us
2300 * HEAD - we are the first to get here.
2301 * UPDATE - we are the interrupt interrupting
2303 * MOVED - a reader on another CPU moved the next
2304 * pointer to its reader page. Give up
2311 * We changed the head to UPDATE, thus
2312 * it is our responsibility to update
2315 local_add(entries
, &cpu_buffer
->overrun
);
2316 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
2319 * The entries will be zeroed out when we move the
2323 /* still more to do */
2326 case RB_PAGE_UPDATE
:
2328 * This is an interrupt that interrupt the
2329 * previous update. Still more to do.
2332 case RB_PAGE_NORMAL
:
2334 * An interrupt came in before the update
2335 * and processed this for us.
2336 * Nothing left to do.
2341 * The reader is on another CPU and just did
2342 * a swap with our next_page.
2347 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
2352 * Now that we are here, the old head pointer is
2353 * set to UPDATE. This will keep the reader from
2354 * swapping the head page with the reader page.
2355 * The reader (on another CPU) will spin till
2358 * We just need to protect against interrupts
2359 * doing the job. We will set the next pointer
2360 * to HEAD. After that, we set the old pointer
2361 * to NORMAL, but only if it was HEAD before.
2362 * otherwise we are an interrupt, and only
2363 * want the outer most commit to reset it.
2365 new_head
= next_page
;
2366 rb_inc_page(cpu_buffer
, &new_head
);
2368 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
2372 * Valid returns are:
2373 * HEAD - an interrupt came in and already set it.
2374 * NORMAL - One of two things:
2375 * 1) We really set it.
2376 * 2) A bunch of interrupts came in and moved
2377 * the page forward again.
2381 case RB_PAGE_NORMAL
:
2385 RB_WARN_ON(cpu_buffer
, 1);
2390 * It is possible that an interrupt came in,
2391 * set the head up, then more interrupts came in
2392 * and moved it again. When we get back here,
2393 * the page would have been set to NORMAL but we
2394 * just set it back to HEAD.
2396 * How do you detect this? Well, if that happened
2397 * the tail page would have moved.
2399 if (ret
== RB_PAGE_NORMAL
) {
2400 struct buffer_page
*buffer_tail_page
;
2402 buffer_tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2404 * If the tail had moved passed next, then we need
2405 * to reset the pointer.
2407 if (buffer_tail_page
!= tail_page
&&
2408 buffer_tail_page
!= next_page
)
2409 rb_head_page_set_normal(cpu_buffer
, new_head
,
2415 * If this was the outer most commit (the one that
2416 * changed the original pointer from HEAD to UPDATE),
2417 * then it is up to us to reset it to NORMAL.
2419 if (type
== RB_PAGE_HEAD
) {
2420 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2423 if (RB_WARN_ON(cpu_buffer
,
2424 ret
!= RB_PAGE_UPDATE
))
2432 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2433 unsigned long tail
, struct rb_event_info
*info
)
2435 struct buffer_page
*tail_page
= info
->tail_page
;
2436 struct ring_buffer_event
*event
;
2437 unsigned long length
= info
->length
;
2440 * Only the event that crossed the page boundary
2441 * must fill the old tail_page with padding.
2443 if (tail
>= BUF_PAGE_SIZE
) {
2445 * If the page was filled, then we still need
2446 * to update the real_end. Reset it to zero
2447 * and the reader will ignore it.
2449 if (tail
== BUF_PAGE_SIZE
)
2450 tail_page
->real_end
= 0;
2452 local_sub(length
, &tail_page
->write
);
2456 event
= __rb_page_index(tail_page
, tail
);
2458 /* account for padding bytes */
2459 local_add(BUF_PAGE_SIZE
- tail
, &cpu_buffer
->entries_bytes
);
2462 * Save the original length to the meta data.
2463 * This will be used by the reader to add lost event
2466 tail_page
->real_end
= tail
;
2469 * If this event is bigger than the minimum size, then
2470 * we need to be careful that we don't subtract the
2471 * write counter enough to allow another writer to slip
2473 * We put in a discarded commit instead, to make sure
2474 * that this space is not used again.
2476 * If we are less than the minimum size, we don't need to
2479 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
2480 /* No room for any events */
2482 /* Mark the rest of the page with padding */
2483 rb_event_set_padding(event
);
2485 /* Set the write back to the previous setting */
2486 local_sub(length
, &tail_page
->write
);
2490 /* Put in a discarded event */
2491 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
2492 event
->type_len
= RINGBUF_TYPE_PADDING
;
2493 /* time delta must be non zero */
2494 event
->time_delta
= 1;
2496 /* Set write to end of buffer */
2497 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
2498 local_sub(length
, &tail_page
->write
);
2501 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
);
2504 * This is the slow path, force gcc not to inline it.
2506 static noinline
struct ring_buffer_event
*
2507 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2508 unsigned long tail
, struct rb_event_info
*info
)
2510 struct buffer_page
*tail_page
= info
->tail_page
;
2511 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2512 struct trace_buffer
*buffer
= cpu_buffer
->buffer
;
2513 struct buffer_page
*next_page
;
2516 next_page
= tail_page
;
2518 rb_inc_page(cpu_buffer
, &next_page
);
2521 * If for some reason, we had an interrupt storm that made
2522 * it all the way around the buffer, bail, and warn
2525 if (unlikely(next_page
== commit_page
)) {
2526 local_inc(&cpu_buffer
->commit_overrun
);
2531 * This is where the fun begins!
2533 * We are fighting against races between a reader that
2534 * could be on another CPU trying to swap its reader
2535 * page with the buffer head.
2537 * We are also fighting against interrupts coming in and
2538 * moving the head or tail on us as well.
2540 * If the next page is the head page then we have filled
2541 * the buffer, unless the commit page is still on the
2544 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
2547 * If the commit is not on the reader page, then
2548 * move the header page.
2550 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2552 * If we are not in overwrite mode,
2553 * this is easy, just stop here.
2555 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2556 local_inc(&cpu_buffer
->dropped_events
);
2560 ret
= rb_handle_head_page(cpu_buffer
,
2569 * We need to be careful here too. The
2570 * commit page could still be on the reader
2571 * page. We could have a small buffer, and
2572 * have filled up the buffer with events
2573 * from interrupts and such, and wrapped.
2575 * Note, if the tail page is also the on the
2576 * reader_page, we let it move out.
2578 if (unlikely((cpu_buffer
->commit_page
!=
2579 cpu_buffer
->tail_page
) &&
2580 (cpu_buffer
->commit_page
==
2581 cpu_buffer
->reader_page
))) {
2582 local_inc(&cpu_buffer
->commit_overrun
);
2588 rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2592 rb_reset_tail(cpu_buffer
, tail
, info
);
2594 /* Commit what we have for now. */
2595 rb_end_commit(cpu_buffer
);
2596 /* rb_end_commit() decs committing */
2597 local_inc(&cpu_buffer
->committing
);
2599 /* fail and let the caller try again */
2600 return ERR_PTR(-EAGAIN
);
2604 rb_reset_tail(cpu_buffer
, tail
, info
);
2610 static struct ring_buffer_event
*
2611 rb_add_time_stamp(struct ring_buffer_event
*event
, u64 delta
, bool abs
)
2614 event
->type_len
= RINGBUF_TYPE_TIME_STAMP
;
2616 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
2618 /* Not the first event on the page, or not delta? */
2619 if (abs
|| rb_event_index(event
)) {
2620 event
->time_delta
= delta
& TS_MASK
;
2621 event
->array
[0] = delta
>> TS_SHIFT
;
2623 /* nope, just zero it */
2624 event
->time_delta
= 0;
2625 event
->array
[0] = 0;
2628 return skip_time_extend(event
);
2631 static inline bool rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2632 struct ring_buffer_event
*event
);
2634 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2635 static inline bool sched_clock_stable(void)
2642 rb_check_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2643 struct rb_event_info
*info
)
2647 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2648 (unsigned long long)info
->delta
,
2649 (unsigned long long)info
->ts
,
2650 (unsigned long long)info
->before
,
2651 (unsigned long long)info
->after
,
2652 (unsigned long long)(rb_time_read(&cpu_buffer
->write_stamp
, &write_stamp
) ? write_stamp
: 0),
2653 sched_clock_stable() ? "" :
2654 "If you just came from a suspend/resume,\n"
2655 "please switch to the trace global clock:\n"
2656 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2657 "or add trace_clock=global to the kernel command line\n");
2660 static void rb_add_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2661 struct ring_buffer_event
**event
,
2662 struct rb_event_info
*info
,
2664 unsigned int *length
)
2666 bool abs
= info
->add_timestamp
&
2667 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
);
2669 if (unlikely(info
->delta
> (1ULL << 59))) {
2670 /* did the clock go backwards */
2671 if (info
->before
== info
->after
&& info
->before
> info
->ts
) {
2672 /* not interrupted */
2676 * This is possible with a recalibrating of the TSC.
2677 * Do not produce a call stack, but just report it.
2681 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2682 info
->before
, info
->ts
);
2685 rb_check_timestamp(cpu_buffer
, info
);
2689 *event
= rb_add_time_stamp(*event
, info
->delta
, abs
);
2690 *length
-= RB_LEN_TIME_EXTEND
;
2695 * rb_update_event - update event type and data
2696 * @cpu_buffer: The per cpu buffer of the @event
2697 * @event: the event to update
2698 * @info: The info to update the @event with (contains length and delta)
2700 * Update the type and data fields of the @event. The length
2701 * is the actual size that is written to the ring buffer,
2702 * and with this, we can determine what to place into the
2706 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2707 struct ring_buffer_event
*event
,
2708 struct rb_event_info
*info
)
2710 unsigned length
= info
->length
;
2711 u64 delta
= info
->delta
;
2714 * If we need to add a timestamp, then we
2715 * add it to the start of the reserved space.
2717 if (unlikely(info
->add_timestamp
))
2718 rb_add_timestamp(cpu_buffer
, &event
, info
, &delta
, &length
);
2720 event
->time_delta
= delta
;
2721 length
-= RB_EVNT_HDR_SIZE
;
2722 if (length
> RB_MAX_SMALL_DATA
) {
2723 event
->type_len
= 0;
2724 event
->array
[0] = length
;
2726 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
2729 static unsigned rb_calculate_event_length(unsigned length
)
2731 struct ring_buffer_event event
; /* Used only for sizeof array */
2733 /* zero length can cause confusions */
2737 if (length
> RB_MAX_SMALL_DATA
)
2738 length
+= sizeof(event
.array
[0]);
2740 length
+= RB_EVNT_HDR_SIZE
;
2741 length
= ALIGN(length
, RB_ALIGNMENT
);
2744 * In case the time delta is larger than the 27 bits for it
2745 * in the header, we need to add a timestamp. If another
2746 * event comes in when trying to discard this one to increase
2747 * the length, then the timestamp will be added in the allocated
2748 * space of this event. If length is bigger than the size needed
2749 * for the TIME_EXTEND, then padding has to be used. The events
2750 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2751 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2752 * As length is a multiple of 4, we only need to worry if it
2753 * is 12 (RB_LEN_TIME_EXTEND + 4).
2755 if (length
== RB_LEN_TIME_EXTEND
+ RB_ALIGNMENT
)
2756 length
+= RB_ALIGNMENT
;
2761 static __always_inline
bool
2762 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2763 struct ring_buffer_event
*event
)
2765 unsigned long addr
= (unsigned long)event
;
2766 unsigned long index
;
2768 index
= rb_event_index(event
);
2771 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
2772 rb_commit_index(cpu_buffer
) == index
;
2775 static u64
rb_time_delta(struct ring_buffer_event
*event
)
2777 switch (event
->type_len
) {
2778 case RINGBUF_TYPE_PADDING
:
2781 case RINGBUF_TYPE_TIME_EXTEND
:
2782 return ring_buffer_event_time_stamp(event
);
2784 case RINGBUF_TYPE_TIME_STAMP
:
2787 case RINGBUF_TYPE_DATA
:
2788 return event
->time_delta
;
2795 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2796 struct ring_buffer_event
*event
)
2798 unsigned long new_index
, old_index
;
2799 struct buffer_page
*bpage
;
2800 unsigned long index
;
2805 new_index
= rb_event_index(event
);
2806 old_index
= new_index
+ rb_event_ts_length(event
);
2807 addr
= (unsigned long)event
;
2810 bpage
= READ_ONCE(cpu_buffer
->tail_page
);
2812 delta
= rb_time_delta(event
);
2814 if (!rb_time_read(&cpu_buffer
->write_stamp
, &write_stamp
))
2817 /* Make sure the write stamp is read before testing the location */
2820 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2821 unsigned long write_mask
=
2822 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2823 unsigned long event_length
= rb_event_length(event
);
2825 /* Something came in, can't discard */
2826 if (!rb_time_cmpxchg(&cpu_buffer
->write_stamp
,
2827 write_stamp
, write_stamp
- delta
))
2831 * If an event were to come in now, it would see that the
2832 * write_stamp and the before_stamp are different, and assume
2833 * that this event just added itself before updating
2834 * the write stamp. The interrupting event will fix the
2835 * write stamp for us, and use the before stamp as its delta.
2839 * This is on the tail page. It is possible that
2840 * a write could come in and move the tail page
2841 * and write to the next page. That is fine
2842 * because we just shorten what is on this page.
2844 old_index
+= write_mask
;
2845 new_index
+= write_mask
;
2846 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2847 if (index
== old_index
) {
2848 /* update counters */
2849 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2854 /* could not discard */
2858 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2860 local_inc(&cpu_buffer
->committing
);
2861 local_inc(&cpu_buffer
->commits
);
2864 static __always_inline
void
2865 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
2867 unsigned long max_count
;
2870 * We only race with interrupts and NMIs on this CPU.
2871 * If we own the commit event, then we can commit
2872 * all others that interrupted us, since the interruptions
2873 * are in stack format (they finish before they come
2874 * back to us). This allows us to do a simple loop to
2875 * assign the commit to the tail.
2878 max_count
= cpu_buffer
->nr_pages
* 100;
2880 while (cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)) {
2881 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
2883 if (RB_WARN_ON(cpu_buffer
,
2884 rb_is_reader_page(cpu_buffer
->tail_page
)))
2886 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2887 rb_page_write(cpu_buffer
->commit_page
));
2888 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
2889 /* add barrier to keep gcc from optimizing too much */
2892 while (rb_commit_index(cpu_buffer
) !=
2893 rb_page_write(cpu_buffer
->commit_page
)) {
2895 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2896 rb_page_write(cpu_buffer
->commit_page
));
2897 RB_WARN_ON(cpu_buffer
,
2898 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
2903 /* again, keep gcc from optimizing */
2907 * If an interrupt came in just after the first while loop
2908 * and pushed the tail page forward, we will be left with
2909 * a dangling commit that will never go forward.
2911 if (unlikely(cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)))
2915 static __always_inline
void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2917 unsigned long commits
;
2919 if (RB_WARN_ON(cpu_buffer
,
2920 !local_read(&cpu_buffer
->committing
)))
2924 commits
= local_read(&cpu_buffer
->commits
);
2925 /* synchronize with interrupts */
2927 if (local_read(&cpu_buffer
->committing
) == 1)
2928 rb_set_commit_to_write(cpu_buffer
);
2930 local_dec(&cpu_buffer
->committing
);
2932 /* synchronize with interrupts */
2936 * Need to account for interrupts coming in between the
2937 * updating of the commit page and the clearing of the
2938 * committing counter.
2940 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2941 !local_read(&cpu_buffer
->committing
)) {
2942 local_inc(&cpu_buffer
->committing
);
2947 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2949 if (extended_time(event
))
2950 event
= skip_time_extend(event
);
2952 /* array[0] holds the actual length for the discarded event */
2953 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2954 event
->type_len
= RINGBUF_TYPE_PADDING
;
2955 /* time delta must be non zero */
2956 if (!event
->time_delta
)
2957 event
->time_delta
= 1;
2960 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2961 struct ring_buffer_event
*event
)
2963 local_inc(&cpu_buffer
->entries
);
2964 rb_end_commit(cpu_buffer
);
2967 static __always_inline
void
2968 rb_wakeups(struct trace_buffer
*buffer
, struct ring_buffer_per_cpu
*cpu_buffer
)
2974 if (buffer
->irq_work
.waiters_pending
) {
2975 buffer
->irq_work
.waiters_pending
= false;
2976 /* irq_work_queue() supplies it's own memory barriers */
2977 irq_work_queue(&buffer
->irq_work
.work
);
2980 if (cpu_buffer
->irq_work
.waiters_pending
) {
2981 cpu_buffer
->irq_work
.waiters_pending
= false;
2982 /* irq_work_queue() supplies it's own memory barriers */
2983 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2986 if (cpu_buffer
->last_pages_touch
== local_read(&cpu_buffer
->pages_touched
))
2989 if (cpu_buffer
->reader_page
== cpu_buffer
->commit_page
)
2992 if (!cpu_buffer
->irq_work
.full_waiters_pending
)
2995 cpu_buffer
->last_pages_touch
= local_read(&cpu_buffer
->pages_touched
);
2997 full
= cpu_buffer
->shortest_full
;
2998 nr_pages
= cpu_buffer
->nr_pages
;
2999 dirty
= ring_buffer_nr_dirty_pages(buffer
, cpu_buffer
->cpu
);
3000 if (full
&& nr_pages
&& (dirty
* 100) <= full
* nr_pages
)
3003 cpu_buffer
->irq_work
.wakeup_full
= true;
3004 cpu_buffer
->irq_work
.full_waiters_pending
= false;
3005 /* irq_work_queue() supplies it's own memory barriers */
3006 irq_work_queue(&cpu_buffer
->irq_work
.work
);
3010 * The lock and unlock are done within a preempt disable section.
3011 * The current_context per_cpu variable can only be modified
3012 * by the current task between lock and unlock. But it can
3013 * be modified more than once via an interrupt. To pass this
3014 * information from the lock to the unlock without having to
3015 * access the 'in_interrupt()' functions again (which do show
3016 * a bit of overhead in something as critical as function tracing,
3017 * we use a bitmask trick.
3019 * bit 1 = NMI context
3020 * bit 2 = IRQ context
3021 * bit 3 = SoftIRQ context
3022 * bit 4 = normal context.
3024 * This works because this is the order of contexts that can
3025 * preempt other contexts. A SoftIRQ never preempts an IRQ
3028 * When the context is determined, the corresponding bit is
3029 * checked and set (if it was set, then a recursion of that context
3032 * On unlock, we need to clear this bit. To do so, just subtract
3033 * 1 from the current_context and AND it to itself.
3037 * 101 & 100 = 100 (clearing bit zero)
3040 * 1010 & 1001 = 1000 (clearing bit 1)
3042 * The least significant bit can be cleared this way, and it
3043 * just so happens that it is the same bit corresponding to
3044 * the current context.
3046 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3047 * is set when a recursion is detected at the current context, and if
3048 * the TRANSITION bit is already set, it will fail the recursion.
3049 * This is needed because there's a lag between the changing of
3050 * interrupt context and updating the preempt count. In this case,
3051 * a false positive will be found. To handle this, one extra recursion
3052 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3053 * bit is already set, then it is considered a recursion and the function
3054 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3056 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3057 * to be cleared. Even if it wasn't the context that set it. That is,
3058 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3059 * is called before preempt_count() is updated, since the check will
3060 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3061 * NMI then comes in, it will set the NMI bit, but when the NMI code
3062 * does the trace_recursive_unlock() it will clear the TRANSTION bit
3063 * and leave the NMI bit set. But this is fine, because the interrupt
3064 * code that set the TRANSITION bit will then clear the NMI bit when it
3065 * calls trace_recursive_unlock(). If another NMI comes in, it will
3066 * set the TRANSITION bit and continue.
3068 * Note: The TRANSITION bit only handles a single transition between context.
3071 static __always_inline
int
3072 trace_recursive_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
3074 unsigned int val
= cpu_buffer
->current_context
;
3075 unsigned long pc
= preempt_count();
3078 if (!(pc
& (NMI_MASK
| HARDIRQ_MASK
| SOFTIRQ_OFFSET
)))
3079 bit
= RB_CTX_NORMAL
;
3081 bit
= pc
& NMI_MASK
? RB_CTX_NMI
:
3082 pc
& HARDIRQ_MASK
? RB_CTX_IRQ
: RB_CTX_SOFTIRQ
;
3084 if (unlikely(val
& (1 << (bit
+ cpu_buffer
->nest
)))) {
3086 * It is possible that this was called by transitioning
3087 * between interrupt context, and preempt_count() has not
3088 * been updated yet. In this case, use the TRANSITION bit.
3090 bit
= RB_CTX_TRANSITION
;
3091 if (val
& (1 << (bit
+ cpu_buffer
->nest
)))
3095 val
|= (1 << (bit
+ cpu_buffer
->nest
));
3096 cpu_buffer
->current_context
= val
;
3101 static __always_inline
void
3102 trace_recursive_unlock(struct ring_buffer_per_cpu
*cpu_buffer
)
3104 cpu_buffer
->current_context
&=
3105 cpu_buffer
->current_context
- (1 << cpu_buffer
->nest
);
3108 /* The recursive locking above uses 5 bits */
3109 #define NESTED_BITS 5
3112 * ring_buffer_nest_start - Allow to trace while nested
3113 * @buffer: The ring buffer to modify
3115 * The ring buffer has a safety mechanism to prevent recursion.
3116 * But there may be a case where a trace needs to be done while
3117 * tracing something else. In this case, calling this function
3118 * will allow this function to nest within a currently active
3119 * ring_buffer_lock_reserve().
3121 * Call this function before calling another ring_buffer_lock_reserve() and
3122 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3124 void ring_buffer_nest_start(struct trace_buffer
*buffer
)
3126 struct ring_buffer_per_cpu
*cpu_buffer
;
3129 /* Enabled by ring_buffer_nest_end() */
3130 preempt_disable_notrace();
3131 cpu
= raw_smp_processor_id();
3132 cpu_buffer
= buffer
->buffers
[cpu
];
3133 /* This is the shift value for the above recursive locking */
3134 cpu_buffer
->nest
+= NESTED_BITS
;
3138 * ring_buffer_nest_end - Allow to trace while nested
3139 * @buffer: The ring buffer to modify
3141 * Must be called after ring_buffer_nest_start() and after the
3142 * ring_buffer_unlock_commit().
3144 void ring_buffer_nest_end(struct trace_buffer
*buffer
)
3146 struct ring_buffer_per_cpu
*cpu_buffer
;
3149 /* disabled by ring_buffer_nest_start() */
3150 cpu
= raw_smp_processor_id();
3151 cpu_buffer
= buffer
->buffers
[cpu
];
3152 /* This is the shift value for the above recursive locking */
3153 cpu_buffer
->nest
-= NESTED_BITS
;
3154 preempt_enable_notrace();
3158 * ring_buffer_unlock_commit - commit a reserved
3159 * @buffer: The buffer to commit to
3160 * @event: The event pointer to commit.
3162 * This commits the data to the ring buffer, and releases any locks held.
3164 * Must be paired with ring_buffer_lock_reserve.
3166 int ring_buffer_unlock_commit(struct trace_buffer
*buffer
,
3167 struct ring_buffer_event
*event
)
3169 struct ring_buffer_per_cpu
*cpu_buffer
;
3170 int cpu
= raw_smp_processor_id();
3172 cpu_buffer
= buffer
->buffers
[cpu
];
3174 rb_commit(cpu_buffer
, event
);
3176 rb_wakeups(buffer
, cpu_buffer
);
3178 trace_recursive_unlock(cpu_buffer
);
3180 preempt_enable_notrace();
3184 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
3186 static struct ring_buffer_event
*
3187 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
3188 struct rb_event_info
*info
)
3190 struct ring_buffer_event
*event
;
3191 struct buffer_page
*tail_page
;
3192 unsigned long tail
, write
, w
;
3196 /* Don't let the compiler play games with cpu_buffer->tail_page */
3197 tail_page
= info
->tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
3199 /*A*/ w
= local_read(&tail_page
->write
) & RB_WRITE_MASK
;
3201 b_ok
= rb_time_read(&cpu_buffer
->before_stamp
, &info
->before
);
3202 a_ok
= rb_time_read(&cpu_buffer
->write_stamp
, &info
->after
);
3204 info
->ts
= rb_time_stamp(cpu_buffer
->buffer
);
3206 if ((info
->add_timestamp
& RB_ADD_STAMP_ABSOLUTE
)) {
3207 info
->delta
= info
->ts
;
3210 * If interrupting an event time update, we may need an
3211 * absolute timestamp.
3212 * Don't bother if this is the start of a new page (w == 0).
3214 if (unlikely(!a_ok
|| !b_ok
|| (info
->before
!= info
->after
&& w
))) {
3215 info
->add_timestamp
|= RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_EXTEND
;
3216 info
->length
+= RB_LEN_TIME_EXTEND
;
3218 info
->delta
= info
->ts
- info
->after
;
3219 if (unlikely(test_time_stamp(info
->delta
))) {
3220 info
->add_timestamp
|= RB_ADD_STAMP_EXTEND
;
3221 info
->length
+= RB_LEN_TIME_EXTEND
;
3226 /*B*/ rb_time_set(&cpu_buffer
->before_stamp
, info
->ts
);
3228 /*C*/ write
= local_add_return(info
->length
, &tail_page
->write
);
3230 /* set write to only the index of the write */
3231 write
&= RB_WRITE_MASK
;
3233 tail
= write
- info
->length
;
3235 /* See if we shot pass the end of this buffer page */
3236 if (unlikely(write
> BUF_PAGE_SIZE
)) {
3237 /* before and after may now different, fix it up*/
3238 b_ok
= rb_time_read(&cpu_buffer
->before_stamp
, &info
->before
);
3239 a_ok
= rb_time_read(&cpu_buffer
->write_stamp
, &info
->after
);
3240 if (a_ok
&& b_ok
&& info
->before
!= info
->after
)
3241 (void)rb_time_cmpxchg(&cpu_buffer
->before_stamp
,
3242 info
->before
, info
->after
);
3243 return rb_move_tail(cpu_buffer
, tail
, info
);
3246 if (likely(tail
== w
)) {
3250 /* Nothing interrupted us between A and C */
3251 /*D*/ rb_time_set(&cpu_buffer
->write_stamp
, info
->ts
);
3253 /*E*/ s_ok
= rb_time_read(&cpu_buffer
->before_stamp
, &save_before
);
3254 RB_WARN_ON(cpu_buffer
, !s_ok
);
3255 if (likely(!(info
->add_timestamp
&
3256 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
))))
3257 /* This did not interrupt any time update */
3258 info
->delta
= info
->ts
- info
->after
;
3260 /* Just use full timestamp for inerrupting event */
3261 info
->delta
= info
->ts
;
3263 if (unlikely(info
->ts
!= save_before
)) {
3264 /* SLOW PATH - Interrupted between C and E */
3266 a_ok
= rb_time_read(&cpu_buffer
->write_stamp
, &info
->after
);
3267 RB_WARN_ON(cpu_buffer
, !a_ok
);
3269 /* Write stamp must only go forward */
3270 if (save_before
> info
->after
) {
3272 * We do not care about the result, only that
3273 * it gets updated atomically.
3275 (void)rb_time_cmpxchg(&cpu_buffer
->write_stamp
,
3276 info
->after
, save_before
);
3281 /* SLOW PATH - Interrupted between A and C */
3282 a_ok
= rb_time_read(&cpu_buffer
->write_stamp
, &info
->after
);
3283 /* Was interrupted before here, write_stamp must be valid */
3284 RB_WARN_ON(cpu_buffer
, !a_ok
);
3285 ts
= rb_time_stamp(cpu_buffer
->buffer
);
3287 /*E*/ if (write
== (local_read(&tail_page
->write
) & RB_WRITE_MASK
) &&
3289 rb_time_cmpxchg(&cpu_buffer
->write_stamp
,
3291 /* Nothing came after this event between C and E */
3292 info
->delta
= ts
- info
->after
;
3296 * Interrupted beween C and E:
3297 * Lost the previous events time stamp. Just set the
3298 * delta to zero, and this will be the same time as
3299 * the event this event interrupted. And the events that
3300 * came after this will still be correct (as they would
3301 * have built their delta on the previous event.
3305 info
->add_timestamp
&= ~RB_ADD_STAMP_FORCE
;
3309 * If this is the first commit on the page, then it has the same
3310 * timestamp as the page itself.
3312 if (unlikely(!tail
&& !(info
->add_timestamp
&
3313 (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_ABSOLUTE
))))
3316 /* We reserved something on the buffer */
3318 event
= __rb_page_index(tail_page
, tail
);
3319 rb_update_event(cpu_buffer
, event
, info
);
3321 local_inc(&tail_page
->entries
);
3324 * If this is the first commit on the page, then update
3327 if (unlikely(!tail
))
3328 tail_page
->page
->time_stamp
= info
->ts
;
3330 /* account for these added bytes */
3331 local_add(info
->length
, &cpu_buffer
->entries_bytes
);
3336 static __always_inline
struct ring_buffer_event
*
3337 rb_reserve_next_event(struct trace_buffer
*buffer
,
3338 struct ring_buffer_per_cpu
*cpu_buffer
,
3339 unsigned long length
)
3341 struct ring_buffer_event
*event
;
3342 struct rb_event_info info
;
3346 rb_start_commit(cpu_buffer
);
3347 /* The commit page can not change after this */
3349 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3351 * Due to the ability to swap a cpu buffer from a buffer
3352 * it is possible it was swapped before we committed.
3353 * (committing stops a swap). We check for it here and
3354 * if it happened, we have to fail the write.
3357 if (unlikely(READ_ONCE(cpu_buffer
->buffer
) != buffer
)) {
3358 local_dec(&cpu_buffer
->committing
);
3359 local_dec(&cpu_buffer
->commits
);
3364 info
.length
= rb_calculate_event_length(length
);
3366 if (ring_buffer_time_stamp_abs(cpu_buffer
->buffer
)) {
3367 add_ts_default
= RB_ADD_STAMP_ABSOLUTE
;
3368 info
.length
+= RB_LEN_TIME_EXTEND
;
3370 add_ts_default
= RB_ADD_STAMP_NONE
;
3374 info
.add_timestamp
= add_ts_default
;
3378 * We allow for interrupts to reenter here and do a trace.
3379 * If one does, it will cause this original code to loop
3380 * back here. Even with heavy interrupts happening, this
3381 * should only happen a few times in a row. If this happens
3382 * 1000 times in a row, there must be either an interrupt
3383 * storm or we have something buggy.
3386 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
3389 event
= __rb_reserve_next(cpu_buffer
, &info
);
3391 if (unlikely(PTR_ERR(event
) == -EAGAIN
)) {
3392 if (info
.add_timestamp
& (RB_ADD_STAMP_FORCE
| RB_ADD_STAMP_EXTEND
))
3393 info
.length
-= RB_LEN_TIME_EXTEND
;
3400 rb_end_commit(cpu_buffer
);
3405 * ring_buffer_lock_reserve - reserve a part of the buffer
3406 * @buffer: the ring buffer to reserve from
3407 * @length: the length of the data to reserve (excluding event header)
3409 * Returns a reserved event on the ring buffer to copy directly to.
3410 * The user of this interface will need to get the body to write into
3411 * and can use the ring_buffer_event_data() interface.
3413 * The length is the length of the data needed, not the event length
3414 * which also includes the event header.
3416 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3417 * If NULL is returned, then nothing has been allocated or locked.
3419 struct ring_buffer_event
*
3420 ring_buffer_lock_reserve(struct trace_buffer
*buffer
, unsigned long length
)
3422 struct ring_buffer_per_cpu
*cpu_buffer
;
3423 struct ring_buffer_event
*event
;
3426 /* If we are tracing schedule, we don't want to recurse */
3427 preempt_disable_notrace();
3429 if (unlikely(atomic_read(&buffer
->record_disabled
)))
3432 cpu
= raw_smp_processor_id();
3434 if (unlikely(!cpumask_test_cpu(cpu
, buffer
->cpumask
)))
3437 cpu_buffer
= buffer
->buffers
[cpu
];
3439 if (unlikely(atomic_read(&cpu_buffer
->record_disabled
)))
3442 if (unlikely(length
> BUF_MAX_DATA_SIZE
))
3445 if (unlikely(trace_recursive_lock(cpu_buffer
)))
3448 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
3455 trace_recursive_unlock(cpu_buffer
);
3457 preempt_enable_notrace();
3460 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
3463 * Decrement the entries to the page that an event is on.
3464 * The event does not even need to exist, only the pointer
3465 * to the page it is on. This may only be called before the commit
3469 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
3470 struct ring_buffer_event
*event
)
3472 unsigned long addr
= (unsigned long)event
;
3473 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
3474 struct buffer_page
*start
;
3478 /* Do the likely case first */
3479 if (likely(bpage
->page
== (void *)addr
)) {
3480 local_dec(&bpage
->entries
);
3485 * Because the commit page may be on the reader page we
3486 * start with the next page and check the end loop there.
3488 rb_inc_page(cpu_buffer
, &bpage
);
3491 if (bpage
->page
== (void *)addr
) {
3492 local_dec(&bpage
->entries
);
3495 rb_inc_page(cpu_buffer
, &bpage
);
3496 } while (bpage
!= start
);
3498 /* commit not part of this buffer?? */
3499 RB_WARN_ON(cpu_buffer
, 1);
3503 * ring_buffer_commit_discard - discard an event that has not been committed
3504 * @buffer: the ring buffer
3505 * @event: non committed event to discard
3507 * Sometimes an event that is in the ring buffer needs to be ignored.
3508 * This function lets the user discard an event in the ring buffer
3509 * and then that event will not be read later.
3511 * This function only works if it is called before the item has been
3512 * committed. It will try to free the event from the ring buffer
3513 * if another event has not been added behind it.
3515 * If another event has been added behind it, it will set the event
3516 * up as discarded, and perform the commit.
3518 * If this function is called, do not call ring_buffer_unlock_commit on
3521 void ring_buffer_discard_commit(struct trace_buffer
*buffer
,
3522 struct ring_buffer_event
*event
)
3524 struct ring_buffer_per_cpu
*cpu_buffer
;
3527 /* The event is discarded regardless */
3528 rb_event_discard(event
);
3530 cpu
= smp_processor_id();
3531 cpu_buffer
= buffer
->buffers
[cpu
];
3534 * This must only be called if the event has not been
3535 * committed yet. Thus we can assume that preemption
3536 * is still disabled.
3538 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
3540 rb_decrement_entry(cpu_buffer
, event
);
3541 if (rb_try_to_discard(cpu_buffer
, event
))
3545 rb_end_commit(cpu_buffer
);
3547 trace_recursive_unlock(cpu_buffer
);
3549 preempt_enable_notrace();
3552 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
3555 * ring_buffer_write - write data to the buffer without reserving
3556 * @buffer: The ring buffer to write to.
3557 * @length: The length of the data being written (excluding the event header)
3558 * @data: The data to write to the buffer.
3560 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3561 * one function. If you already have the data to write to the buffer, it
3562 * may be easier to simply call this function.
3564 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3565 * and not the length of the event which would hold the header.
3567 int ring_buffer_write(struct trace_buffer
*buffer
,
3568 unsigned long length
,
3571 struct ring_buffer_per_cpu
*cpu_buffer
;
3572 struct ring_buffer_event
*event
;
3577 preempt_disable_notrace();
3579 if (atomic_read(&buffer
->record_disabled
))
3582 cpu
= raw_smp_processor_id();
3584 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3587 cpu_buffer
= buffer
->buffers
[cpu
];
3589 if (atomic_read(&cpu_buffer
->record_disabled
))
3592 if (length
> BUF_MAX_DATA_SIZE
)
3595 if (unlikely(trace_recursive_lock(cpu_buffer
)))
3598 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
3602 body
= rb_event_data(event
);
3604 memcpy(body
, data
, length
);
3606 rb_commit(cpu_buffer
, event
);
3608 rb_wakeups(buffer
, cpu_buffer
);
3613 trace_recursive_unlock(cpu_buffer
);
3616 preempt_enable_notrace();
3620 EXPORT_SYMBOL_GPL(ring_buffer_write
);
3622 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
3624 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
3625 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
3626 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
3628 /* In case of error, head will be NULL */
3629 if (unlikely(!head
))
3632 return reader
->read
== rb_page_commit(reader
) &&
3633 (commit
== reader
||
3635 head
->read
== rb_page_commit(commit
)));
3639 * ring_buffer_record_disable - stop all writes into the buffer
3640 * @buffer: The ring buffer to stop writes to.
3642 * This prevents all writes to the buffer. Any attempt to write
3643 * to the buffer after this will fail and return NULL.
3645 * The caller should call synchronize_rcu() after this.
3647 void ring_buffer_record_disable(struct trace_buffer
*buffer
)
3649 atomic_inc(&buffer
->record_disabled
);
3651 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
3654 * ring_buffer_record_enable - enable writes to the buffer
3655 * @buffer: The ring buffer to enable writes
3657 * Note, multiple disables will need the same number of enables
3658 * to truly enable the writing (much like preempt_disable).
3660 void ring_buffer_record_enable(struct trace_buffer
*buffer
)
3662 atomic_dec(&buffer
->record_disabled
);
3664 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
3667 * ring_buffer_record_off - stop all writes into the buffer
3668 * @buffer: The ring buffer to stop writes to.
3670 * This prevents all writes to the buffer. Any attempt to write
3671 * to the buffer after this will fail and return NULL.
3673 * This is different than ring_buffer_record_disable() as
3674 * it works like an on/off switch, where as the disable() version
3675 * must be paired with a enable().
3677 void ring_buffer_record_off(struct trace_buffer
*buffer
)
3680 unsigned int new_rd
;
3683 rd
= atomic_read(&buffer
->record_disabled
);
3684 new_rd
= rd
| RB_BUFFER_OFF
;
3685 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3687 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
3690 * ring_buffer_record_on - restart writes into the buffer
3691 * @buffer: The ring buffer to start writes to.
3693 * This enables all writes to the buffer that was disabled by
3694 * ring_buffer_record_off().
3696 * This is different than ring_buffer_record_enable() as
3697 * it works like an on/off switch, where as the enable() version
3698 * must be paired with a disable().
3700 void ring_buffer_record_on(struct trace_buffer
*buffer
)
3703 unsigned int new_rd
;
3706 rd
= atomic_read(&buffer
->record_disabled
);
3707 new_rd
= rd
& ~RB_BUFFER_OFF
;
3708 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3710 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
3713 * ring_buffer_record_is_on - return true if the ring buffer can write
3714 * @buffer: The ring buffer to see if write is enabled
3716 * Returns true if the ring buffer is in a state that it accepts writes.
3718 bool ring_buffer_record_is_on(struct trace_buffer
*buffer
)
3720 return !atomic_read(&buffer
->record_disabled
);
3724 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3725 * @buffer: The ring buffer to see if write is set enabled
3727 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3728 * Note that this does NOT mean it is in a writable state.
3730 * It may return true when the ring buffer has been disabled by
3731 * ring_buffer_record_disable(), as that is a temporary disabling of
3734 bool ring_buffer_record_is_set_on(struct trace_buffer
*buffer
)
3736 return !(atomic_read(&buffer
->record_disabled
) & RB_BUFFER_OFF
);
3740 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3741 * @buffer: The ring buffer to stop writes to.
3742 * @cpu: The CPU buffer to stop
3744 * This prevents all writes to the buffer. Any attempt to write
3745 * to the buffer after this will fail and return NULL.
3747 * The caller should call synchronize_rcu() after this.
3749 void ring_buffer_record_disable_cpu(struct trace_buffer
*buffer
, int cpu
)
3751 struct ring_buffer_per_cpu
*cpu_buffer
;
3753 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3756 cpu_buffer
= buffer
->buffers
[cpu
];
3757 atomic_inc(&cpu_buffer
->record_disabled
);
3759 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
3762 * ring_buffer_record_enable_cpu - enable writes to the buffer
3763 * @buffer: The ring buffer to enable writes
3764 * @cpu: The CPU to enable.
3766 * Note, multiple disables will need the same number of enables
3767 * to truly enable the writing (much like preempt_disable).
3769 void ring_buffer_record_enable_cpu(struct trace_buffer
*buffer
, int cpu
)
3771 struct ring_buffer_per_cpu
*cpu_buffer
;
3773 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3776 cpu_buffer
= buffer
->buffers
[cpu
];
3777 atomic_dec(&cpu_buffer
->record_disabled
);
3779 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
3782 * The total entries in the ring buffer is the running counter
3783 * of entries entered into the ring buffer, minus the sum of
3784 * the entries read from the ring buffer and the number of
3785 * entries that were overwritten.
3787 static inline unsigned long
3788 rb_num_of_entries(struct ring_buffer_per_cpu
*cpu_buffer
)
3790 return local_read(&cpu_buffer
->entries
) -
3791 (local_read(&cpu_buffer
->overrun
) + cpu_buffer
->read
);
3795 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3796 * @buffer: The ring buffer
3797 * @cpu: The per CPU buffer to read from.
3799 u64
ring_buffer_oldest_event_ts(struct trace_buffer
*buffer
, int cpu
)
3801 unsigned long flags
;
3802 struct ring_buffer_per_cpu
*cpu_buffer
;
3803 struct buffer_page
*bpage
;
3806 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3809 cpu_buffer
= buffer
->buffers
[cpu
];
3810 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3812 * if the tail is on reader_page, oldest time stamp is on the reader
3815 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
3816 bpage
= cpu_buffer
->reader_page
;
3818 bpage
= rb_set_head_page(cpu_buffer
);
3820 ret
= bpage
->page
->time_stamp
;
3821 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3825 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts
);
3828 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3829 * @buffer: The ring buffer
3830 * @cpu: The per CPU buffer to read from.
3832 unsigned long ring_buffer_bytes_cpu(struct trace_buffer
*buffer
, int cpu
)
3834 struct ring_buffer_per_cpu
*cpu_buffer
;
3837 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3840 cpu_buffer
= buffer
->buffers
[cpu
];
3841 ret
= local_read(&cpu_buffer
->entries_bytes
) - cpu_buffer
->read_bytes
;
3845 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu
);
3848 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3849 * @buffer: The ring buffer
3850 * @cpu: The per CPU buffer to get the entries from.
3852 unsigned long ring_buffer_entries_cpu(struct trace_buffer
*buffer
, int cpu
)
3854 struct ring_buffer_per_cpu
*cpu_buffer
;
3856 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3859 cpu_buffer
= buffer
->buffers
[cpu
];
3861 return rb_num_of_entries(cpu_buffer
);
3863 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
3866 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3867 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3868 * @buffer: The ring buffer
3869 * @cpu: The per CPU buffer to get the number of overruns from
3871 unsigned long ring_buffer_overrun_cpu(struct trace_buffer
*buffer
, int cpu
)
3873 struct ring_buffer_per_cpu
*cpu_buffer
;
3876 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3879 cpu_buffer
= buffer
->buffers
[cpu
];
3880 ret
= local_read(&cpu_buffer
->overrun
);
3884 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
3887 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3888 * commits failing due to the buffer wrapping around while there are uncommitted
3889 * events, such as during an interrupt storm.
3890 * @buffer: The ring buffer
3891 * @cpu: The per CPU buffer to get the number of overruns from
3894 ring_buffer_commit_overrun_cpu(struct trace_buffer
*buffer
, int cpu
)
3896 struct ring_buffer_per_cpu
*cpu_buffer
;
3899 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3902 cpu_buffer
= buffer
->buffers
[cpu
];
3903 ret
= local_read(&cpu_buffer
->commit_overrun
);
3907 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
3910 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3911 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3912 * @buffer: The ring buffer
3913 * @cpu: The per CPU buffer to get the number of overruns from
3916 ring_buffer_dropped_events_cpu(struct trace_buffer
*buffer
, int cpu
)
3918 struct ring_buffer_per_cpu
*cpu_buffer
;
3921 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3924 cpu_buffer
= buffer
->buffers
[cpu
];
3925 ret
= local_read(&cpu_buffer
->dropped_events
);
3929 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu
);
3932 * ring_buffer_read_events_cpu - get the number of events successfully read
3933 * @buffer: The ring buffer
3934 * @cpu: The per CPU buffer to get the number of events read
3937 ring_buffer_read_events_cpu(struct trace_buffer
*buffer
, int cpu
)
3939 struct ring_buffer_per_cpu
*cpu_buffer
;
3941 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3944 cpu_buffer
= buffer
->buffers
[cpu
];
3945 return cpu_buffer
->read
;
3947 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu
);
3950 * ring_buffer_entries - get the number of entries in a buffer
3951 * @buffer: The ring buffer
3953 * Returns the total number of entries in the ring buffer
3956 unsigned long ring_buffer_entries(struct trace_buffer
*buffer
)
3958 struct ring_buffer_per_cpu
*cpu_buffer
;
3959 unsigned long entries
= 0;
3962 /* if you care about this being correct, lock the buffer */
3963 for_each_buffer_cpu(buffer
, cpu
) {
3964 cpu_buffer
= buffer
->buffers
[cpu
];
3965 entries
+= rb_num_of_entries(cpu_buffer
);
3970 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
3973 * ring_buffer_overruns - get the number of overruns in buffer
3974 * @buffer: The ring buffer
3976 * Returns the total number of overruns in the ring buffer
3979 unsigned long ring_buffer_overruns(struct trace_buffer
*buffer
)
3981 struct ring_buffer_per_cpu
*cpu_buffer
;
3982 unsigned long overruns
= 0;
3985 /* if you care about this being correct, lock the buffer */
3986 for_each_buffer_cpu(buffer
, cpu
) {
3987 cpu_buffer
= buffer
->buffers
[cpu
];
3988 overruns
+= local_read(&cpu_buffer
->overrun
);
3993 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
3995 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
3997 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3999 /* Iterator usage is expected to have record disabled */
4000 iter
->head_page
= cpu_buffer
->reader_page
;
4001 iter
->head
= cpu_buffer
->reader_page
->read
;
4002 iter
->next_event
= iter
->head
;
4004 iter
->cache_reader_page
= iter
->head_page
;
4005 iter
->cache_read
= cpu_buffer
->read
;
4008 iter
->read_stamp
= cpu_buffer
->read_stamp
;
4009 iter
->page_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
4011 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
4012 iter
->page_stamp
= iter
->read_stamp
;
4017 * ring_buffer_iter_reset - reset an iterator
4018 * @iter: The iterator to reset
4020 * Resets the iterator, so that it will start from the beginning
4023 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
4025 struct ring_buffer_per_cpu
*cpu_buffer
;
4026 unsigned long flags
;
4031 cpu_buffer
= iter
->cpu_buffer
;
4033 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4034 rb_iter_reset(iter
);
4035 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4037 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
4040 * ring_buffer_iter_empty - check if an iterator has no more to read
4041 * @iter: The iterator to check
4043 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
4045 struct ring_buffer_per_cpu
*cpu_buffer
;
4046 struct buffer_page
*reader
;
4047 struct buffer_page
*head_page
;
4048 struct buffer_page
*commit_page
;
4049 struct buffer_page
*curr_commit_page
;
4054 cpu_buffer
= iter
->cpu_buffer
;
4055 reader
= cpu_buffer
->reader_page
;
4056 head_page
= cpu_buffer
->head_page
;
4057 commit_page
= cpu_buffer
->commit_page
;
4058 commit_ts
= commit_page
->page
->time_stamp
;
4061 * When the writer goes across pages, it issues a cmpxchg which
4062 * is a mb(), which will synchronize with the rmb here.
4063 * (see rb_tail_page_update())
4066 commit
= rb_page_commit(commit_page
);
4067 /* We want to make sure that the commit page doesn't change */
4070 /* Make sure commit page didn't change */
4071 curr_commit_page
= READ_ONCE(cpu_buffer
->commit_page
);
4072 curr_commit_ts
= READ_ONCE(curr_commit_page
->page
->time_stamp
);
4074 /* If the commit page changed, then there's more data */
4075 if (curr_commit_page
!= commit_page
||
4076 curr_commit_ts
!= commit_ts
)
4079 /* Still racy, as it may return a false positive, but that's OK */
4080 return ((iter
->head_page
== commit_page
&& iter
->head
>= commit
) ||
4081 (iter
->head_page
== reader
&& commit_page
== head_page
&&
4082 head_page
->read
== commit
&&
4083 iter
->head
== rb_page_commit(cpu_buffer
->reader_page
)));
4085 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
4088 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
4089 struct ring_buffer_event
*event
)
4093 switch (event
->type_len
) {
4094 case RINGBUF_TYPE_PADDING
:
4097 case RINGBUF_TYPE_TIME_EXTEND
:
4098 delta
= ring_buffer_event_time_stamp(event
);
4099 cpu_buffer
->read_stamp
+= delta
;
4102 case RINGBUF_TYPE_TIME_STAMP
:
4103 delta
= ring_buffer_event_time_stamp(event
);
4104 cpu_buffer
->read_stamp
= delta
;
4107 case RINGBUF_TYPE_DATA
:
4108 cpu_buffer
->read_stamp
+= event
->time_delta
;
4112 RB_WARN_ON(cpu_buffer
, 1);
4118 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
4119 struct ring_buffer_event
*event
)
4123 switch (event
->type_len
) {
4124 case RINGBUF_TYPE_PADDING
:
4127 case RINGBUF_TYPE_TIME_EXTEND
:
4128 delta
= ring_buffer_event_time_stamp(event
);
4129 iter
->read_stamp
+= delta
;
4132 case RINGBUF_TYPE_TIME_STAMP
:
4133 delta
= ring_buffer_event_time_stamp(event
);
4134 iter
->read_stamp
= delta
;
4137 case RINGBUF_TYPE_DATA
:
4138 iter
->read_stamp
+= event
->time_delta
;
4142 RB_WARN_ON(iter
->cpu_buffer
, 1);
4147 static struct buffer_page
*
4148 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
4150 struct buffer_page
*reader
= NULL
;
4151 unsigned long overwrite
;
4152 unsigned long flags
;
4156 local_irq_save(flags
);
4157 arch_spin_lock(&cpu_buffer
->lock
);
4161 * This should normally only loop twice. But because the
4162 * start of the reader inserts an empty page, it causes
4163 * a case where we will loop three times. There should be no
4164 * reason to loop four times (that I know of).
4166 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
4171 reader
= cpu_buffer
->reader_page
;
4173 /* If there's more to read, return this page */
4174 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
4177 /* Never should we have an index greater than the size */
4178 if (RB_WARN_ON(cpu_buffer
,
4179 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
4182 /* check if we caught up to the tail */
4184 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
4187 /* Don't bother swapping if the ring buffer is empty */
4188 if (rb_num_of_entries(cpu_buffer
) == 0)
4192 * Reset the reader page to size zero.
4194 local_set(&cpu_buffer
->reader_page
->write
, 0);
4195 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4196 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4197 cpu_buffer
->reader_page
->real_end
= 0;
4201 * Splice the empty reader page into the list around the head.
4203 reader
= rb_set_head_page(cpu_buffer
);
4206 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
4207 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
4210 * cpu_buffer->pages just needs to point to the buffer, it
4211 * has no specific buffer page to point to. Lets move it out
4212 * of our way so we don't accidentally swap it.
4214 cpu_buffer
->pages
= reader
->list
.prev
;
4216 /* The reader page will be pointing to the new head */
4217 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
4220 * We want to make sure we read the overruns after we set up our
4221 * pointers to the next object. The writer side does a
4222 * cmpxchg to cross pages which acts as the mb on the writer
4223 * side. Note, the reader will constantly fail the swap
4224 * while the writer is updating the pointers, so this
4225 * guarantees that the overwrite recorded here is the one we
4226 * want to compare with the last_overrun.
4229 overwrite
= local_read(&(cpu_buffer
->overrun
));
4232 * Here's the tricky part.
4234 * We need to move the pointer past the header page.
4235 * But we can only do that if a writer is not currently
4236 * moving it. The page before the header page has the
4237 * flag bit '1' set if it is pointing to the page we want.
4238 * but if the writer is in the process of moving it
4239 * than it will be '2' or already moved '0'.
4242 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
4245 * If we did not convert it, then we must try again.
4251 * Yay! We succeeded in replacing the page.
4253 * Now make the new head point back to the reader page.
4255 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
4256 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
4258 local_inc(&cpu_buffer
->pages_read
);
4260 /* Finally update the reader page to the new head */
4261 cpu_buffer
->reader_page
= reader
;
4262 cpu_buffer
->reader_page
->read
= 0;
4264 if (overwrite
!= cpu_buffer
->last_overrun
) {
4265 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
4266 cpu_buffer
->last_overrun
= overwrite
;
4272 /* Update the read_stamp on the first event */
4273 if (reader
&& reader
->read
== 0)
4274 cpu_buffer
->read_stamp
= reader
->page
->time_stamp
;
4276 arch_spin_unlock(&cpu_buffer
->lock
);
4277 local_irq_restore(flags
);
4282 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
4284 struct ring_buffer_event
*event
;
4285 struct buffer_page
*reader
;
4288 reader
= rb_get_reader_page(cpu_buffer
);
4290 /* This function should not be called when buffer is empty */
4291 if (RB_WARN_ON(cpu_buffer
, !reader
))
4294 event
= rb_reader_event(cpu_buffer
);
4296 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
4299 rb_update_read_stamp(cpu_buffer
, event
);
4301 length
= rb_event_length(event
);
4302 cpu_buffer
->reader_page
->read
+= length
;
4305 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
4307 struct ring_buffer_per_cpu
*cpu_buffer
;
4309 cpu_buffer
= iter
->cpu_buffer
;
4311 /* If head == next_event then we need to jump to the next event */
4312 if (iter
->head
== iter
->next_event
) {
4313 /* If the event gets overwritten again, there's nothing to do */
4314 if (rb_iter_head_event(iter
) == NULL
)
4318 iter
->head
= iter
->next_event
;
4321 * Check if we are at the end of the buffer.
4323 if (iter
->next_event
>= rb_page_size(iter
->head_page
)) {
4324 /* discarded commits can make the page empty */
4325 if (iter
->head_page
== cpu_buffer
->commit_page
)
4331 rb_update_iter_read_stamp(iter
, iter
->event
);
4334 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
4336 return cpu_buffer
->lost_events
;
4339 static struct ring_buffer_event
*
4340 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
4341 unsigned long *lost_events
)
4343 struct ring_buffer_event
*event
;
4344 struct buffer_page
*reader
;
4351 * We repeat when a time extend is encountered.
4352 * Since the time extend is always attached to a data event,
4353 * we should never loop more than once.
4354 * (We never hit the following condition more than twice).
4356 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
4359 reader
= rb_get_reader_page(cpu_buffer
);
4363 event
= rb_reader_event(cpu_buffer
);
4365 switch (event
->type_len
) {
4366 case RINGBUF_TYPE_PADDING
:
4367 if (rb_null_event(event
))
4368 RB_WARN_ON(cpu_buffer
, 1);
4370 * Because the writer could be discarding every
4371 * event it creates (which would probably be bad)
4372 * if we were to go back to "again" then we may never
4373 * catch up, and will trigger the warn on, or lock
4374 * the box. Return the padding, and we will release
4375 * the current locks, and try again.
4379 case RINGBUF_TYPE_TIME_EXTEND
:
4380 /* Internal data, OK to advance */
4381 rb_advance_reader(cpu_buffer
);
4384 case RINGBUF_TYPE_TIME_STAMP
:
4386 *ts
= ring_buffer_event_time_stamp(event
);
4387 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4388 cpu_buffer
->cpu
, ts
);
4390 /* Internal data, OK to advance */
4391 rb_advance_reader(cpu_buffer
);
4394 case RINGBUF_TYPE_DATA
:
4396 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
4397 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4398 cpu_buffer
->cpu
, ts
);
4401 *lost_events
= rb_lost_events(cpu_buffer
);
4405 RB_WARN_ON(cpu_buffer
, 1);
4410 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
4412 static struct ring_buffer_event
*
4413 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
4415 struct trace_buffer
*buffer
;
4416 struct ring_buffer_per_cpu
*cpu_buffer
;
4417 struct ring_buffer_event
*event
;
4423 cpu_buffer
= iter
->cpu_buffer
;
4424 buffer
= cpu_buffer
->buffer
;
4427 * Check if someone performed a consuming read to
4428 * the buffer. A consuming read invalidates the iterator
4429 * and we need to reset the iterator in this case.
4431 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
4432 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
4433 rb_iter_reset(iter
);
4436 if (ring_buffer_iter_empty(iter
))
4440 * As the writer can mess with what the iterator is trying
4441 * to read, just give up if we fail to get an event after
4442 * three tries. The iterator is not as reliable when reading
4443 * the ring buffer with an active write as the consumer is.
4444 * Do not warn if the three failures is reached.
4449 if (rb_per_cpu_empty(cpu_buffer
))
4452 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
4457 event
= rb_iter_head_event(iter
);
4461 switch (event
->type_len
) {
4462 case RINGBUF_TYPE_PADDING
:
4463 if (rb_null_event(event
)) {
4467 rb_advance_iter(iter
);
4470 case RINGBUF_TYPE_TIME_EXTEND
:
4471 /* Internal data, OK to advance */
4472 rb_advance_iter(iter
);
4475 case RINGBUF_TYPE_TIME_STAMP
:
4477 *ts
= ring_buffer_event_time_stamp(event
);
4478 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
4479 cpu_buffer
->cpu
, ts
);
4481 /* Internal data, OK to advance */
4482 rb_advance_iter(iter
);
4485 case RINGBUF_TYPE_DATA
:
4487 *ts
= iter
->read_stamp
+ event
->time_delta
;
4488 ring_buffer_normalize_time_stamp(buffer
,
4489 cpu_buffer
->cpu
, ts
);
4494 RB_WARN_ON(cpu_buffer
, 1);
4499 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
4501 static inline bool rb_reader_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
4503 if (likely(!in_nmi())) {
4504 raw_spin_lock(&cpu_buffer
->reader_lock
);
4509 * If an NMI die dumps out the content of the ring buffer
4510 * trylock must be used to prevent a deadlock if the NMI
4511 * preempted a task that holds the ring buffer locks. If
4512 * we get the lock then all is fine, if not, then continue
4513 * to do the read, but this can corrupt the ring buffer,
4514 * so it must be permanently disabled from future writes.
4515 * Reading from NMI is a oneshot deal.
4517 if (raw_spin_trylock(&cpu_buffer
->reader_lock
))
4520 /* Continue without locking, but disable the ring buffer */
4521 atomic_inc(&cpu_buffer
->record_disabled
);
4526 rb_reader_unlock(struct ring_buffer_per_cpu
*cpu_buffer
, bool locked
)
4529 raw_spin_unlock(&cpu_buffer
->reader_lock
);
4534 * ring_buffer_peek - peek at the next event to be read
4535 * @buffer: The ring buffer to read
4536 * @cpu: The cpu to peak at
4537 * @ts: The timestamp counter of this event.
4538 * @lost_events: a variable to store if events were lost (may be NULL)
4540 * This will return the event that will be read next, but does
4541 * not consume the data.
4543 struct ring_buffer_event
*
4544 ring_buffer_peek(struct trace_buffer
*buffer
, int cpu
, u64
*ts
,
4545 unsigned long *lost_events
)
4547 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4548 struct ring_buffer_event
*event
;
4549 unsigned long flags
;
4552 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4556 local_irq_save(flags
);
4557 dolock
= rb_reader_lock(cpu_buffer
);
4558 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
4559 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4560 rb_advance_reader(cpu_buffer
);
4561 rb_reader_unlock(cpu_buffer
, dolock
);
4562 local_irq_restore(flags
);
4564 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4570 /** ring_buffer_iter_dropped - report if there are dropped events
4571 * @iter: The ring buffer iterator
4573 * Returns true if there was dropped events since the last peek.
4575 bool ring_buffer_iter_dropped(struct ring_buffer_iter
*iter
)
4577 bool ret
= iter
->missed_events
!= 0;
4579 iter
->missed_events
= 0;
4582 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped
);
4585 * ring_buffer_iter_peek - peek at the next event to be read
4586 * @iter: The ring buffer iterator
4587 * @ts: The timestamp counter of this event.
4589 * This will return the event that will be read next, but does
4590 * not increment the iterator.
4592 struct ring_buffer_event
*
4593 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
4595 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4596 struct ring_buffer_event
*event
;
4597 unsigned long flags
;
4600 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4601 event
= rb_iter_peek(iter
, ts
);
4602 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4604 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4611 * ring_buffer_consume - return an event and consume it
4612 * @buffer: The ring buffer to get the next event from
4613 * @cpu: the cpu to read the buffer from
4614 * @ts: a variable to store the timestamp (may be NULL)
4615 * @lost_events: a variable to store if events were lost (may be NULL)
4617 * Returns the next event in the ring buffer, and that event is consumed.
4618 * Meaning, that sequential reads will keep returning a different event,
4619 * and eventually empty the ring buffer if the producer is slower.
4621 struct ring_buffer_event
*
4622 ring_buffer_consume(struct trace_buffer
*buffer
, int cpu
, u64
*ts
,
4623 unsigned long *lost_events
)
4625 struct ring_buffer_per_cpu
*cpu_buffer
;
4626 struct ring_buffer_event
*event
= NULL
;
4627 unsigned long flags
;
4631 /* might be called in atomic */
4634 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4637 cpu_buffer
= buffer
->buffers
[cpu
];
4638 local_irq_save(flags
);
4639 dolock
= rb_reader_lock(cpu_buffer
);
4641 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
4643 cpu_buffer
->lost_events
= 0;
4644 rb_advance_reader(cpu_buffer
);
4647 rb_reader_unlock(cpu_buffer
, dolock
);
4648 local_irq_restore(flags
);
4653 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
4658 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
4661 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4662 * @buffer: The ring buffer to read from
4663 * @cpu: The cpu buffer to iterate over
4664 * @flags: gfp flags to use for memory allocation
4666 * This performs the initial preparations necessary to iterate
4667 * through the buffer. Memory is allocated, buffer recording
4668 * is disabled, and the iterator pointer is returned to the caller.
4670 * Disabling buffer recording prevents the reading from being
4671 * corrupted. This is not a consuming read, so a producer is not
4674 * After a sequence of ring_buffer_read_prepare calls, the user is
4675 * expected to make at least one call to ring_buffer_read_prepare_sync.
4676 * Afterwards, ring_buffer_read_start is invoked to get things going
4679 * This overall must be paired with ring_buffer_read_finish.
4681 struct ring_buffer_iter
*
4682 ring_buffer_read_prepare(struct trace_buffer
*buffer
, int cpu
, gfp_t flags
)
4684 struct ring_buffer_per_cpu
*cpu_buffer
;
4685 struct ring_buffer_iter
*iter
;
4687 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4690 iter
= kzalloc(sizeof(*iter
), flags
);
4694 iter
->event
= kmalloc(BUF_MAX_DATA_SIZE
, flags
);
4700 cpu_buffer
= buffer
->buffers
[cpu
];
4702 iter
->cpu_buffer
= cpu_buffer
;
4704 atomic_inc(&cpu_buffer
->resize_disabled
);
4708 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
4711 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4713 * All previously invoked ring_buffer_read_prepare calls to prepare
4714 * iterators will be synchronized. Afterwards, read_buffer_read_start
4715 * calls on those iterators are allowed.
4718 ring_buffer_read_prepare_sync(void)
4722 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
4725 * ring_buffer_read_start - start a non consuming read of the buffer
4726 * @iter: The iterator returned by ring_buffer_read_prepare
4728 * This finalizes the startup of an iteration through the buffer.
4729 * The iterator comes from a call to ring_buffer_read_prepare and
4730 * an intervening ring_buffer_read_prepare_sync must have been
4733 * Must be paired with ring_buffer_read_finish.
4736 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
4738 struct ring_buffer_per_cpu
*cpu_buffer
;
4739 unsigned long flags
;
4744 cpu_buffer
= iter
->cpu_buffer
;
4746 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4747 arch_spin_lock(&cpu_buffer
->lock
);
4748 rb_iter_reset(iter
);
4749 arch_spin_unlock(&cpu_buffer
->lock
);
4750 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4752 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
4755 * ring_buffer_read_finish - finish reading the iterator of the buffer
4756 * @iter: The iterator retrieved by ring_buffer_start
4758 * This re-enables the recording to the buffer, and frees the
4762 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
4764 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4765 unsigned long flags
;
4768 * Ring buffer is disabled from recording, here's a good place
4769 * to check the integrity of the ring buffer.
4770 * Must prevent readers from trying to read, as the check
4771 * clears the HEAD page and readers require it.
4773 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4774 rb_check_pages(cpu_buffer
);
4775 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4777 atomic_dec(&cpu_buffer
->resize_disabled
);
4781 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
4784 * ring_buffer_iter_advance - advance the iterator to the next location
4785 * @iter: The ring buffer iterator
4787 * Move the location of the iterator such that the next read will
4788 * be the next location of the iterator.
4790 void ring_buffer_iter_advance(struct ring_buffer_iter
*iter
)
4792 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4793 unsigned long flags
;
4795 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4797 rb_advance_iter(iter
);
4799 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4801 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance
);
4804 * ring_buffer_size - return the size of the ring buffer (in bytes)
4805 * @buffer: The ring buffer.
4806 * @cpu: The CPU to get ring buffer size from.
4808 unsigned long ring_buffer_size(struct trace_buffer
*buffer
, int cpu
)
4811 * Earlier, this method returned
4812 * BUF_PAGE_SIZE * buffer->nr_pages
4813 * Since the nr_pages field is now removed, we have converted this to
4814 * return the per cpu buffer value.
4816 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4819 return BUF_PAGE_SIZE
* buffer
->buffers
[cpu
]->nr_pages
;
4821 EXPORT_SYMBOL_GPL(ring_buffer_size
);
4824 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
4826 rb_head_page_deactivate(cpu_buffer
);
4828 cpu_buffer
->head_page
4829 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
4830 local_set(&cpu_buffer
->head_page
->write
, 0);
4831 local_set(&cpu_buffer
->head_page
->entries
, 0);
4832 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
4834 cpu_buffer
->head_page
->read
= 0;
4836 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
4837 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
4839 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
4840 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
4841 local_set(&cpu_buffer
->reader_page
->write
, 0);
4842 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4843 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4844 cpu_buffer
->reader_page
->read
= 0;
4846 local_set(&cpu_buffer
->entries_bytes
, 0);
4847 local_set(&cpu_buffer
->overrun
, 0);
4848 local_set(&cpu_buffer
->commit_overrun
, 0);
4849 local_set(&cpu_buffer
->dropped_events
, 0);
4850 local_set(&cpu_buffer
->entries
, 0);
4851 local_set(&cpu_buffer
->committing
, 0);
4852 local_set(&cpu_buffer
->commits
, 0);
4853 local_set(&cpu_buffer
->pages_touched
, 0);
4854 local_set(&cpu_buffer
->pages_read
, 0);
4855 cpu_buffer
->last_pages_touch
= 0;
4856 cpu_buffer
->shortest_full
= 0;
4857 cpu_buffer
->read
= 0;
4858 cpu_buffer
->read_bytes
= 0;
4860 rb_time_set(&cpu_buffer
->write_stamp
, 0);
4861 rb_time_set(&cpu_buffer
->before_stamp
, 0);
4863 cpu_buffer
->lost_events
= 0;
4864 cpu_buffer
->last_overrun
= 0;
4866 rb_head_page_activate(cpu_buffer
);
4869 /* Must have disabled the cpu buffer then done a synchronize_rcu */
4870 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
4872 unsigned long flags
;
4874 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4876 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
4879 arch_spin_lock(&cpu_buffer
->lock
);
4881 rb_reset_cpu(cpu_buffer
);
4883 arch_spin_unlock(&cpu_buffer
->lock
);
4886 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4890 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4891 * @buffer: The ring buffer to reset a per cpu buffer of
4892 * @cpu: The CPU buffer to be reset
4894 void ring_buffer_reset_cpu(struct trace_buffer
*buffer
, int cpu
)
4896 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4898 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4901 /* prevent another thread from changing buffer sizes */
4902 mutex_lock(&buffer
->mutex
);
4904 atomic_inc(&cpu_buffer
->resize_disabled
);
4905 atomic_inc(&cpu_buffer
->record_disabled
);
4907 /* Make sure all commits have finished */
4910 reset_disabled_cpu_buffer(cpu_buffer
);
4912 atomic_dec(&cpu_buffer
->record_disabled
);
4913 atomic_dec(&cpu_buffer
->resize_disabled
);
4915 mutex_unlock(&buffer
->mutex
);
4917 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
4920 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4921 * @buffer: The ring buffer to reset a per cpu buffer of
4922 * @cpu: The CPU buffer to be reset
4924 void ring_buffer_reset_online_cpus(struct trace_buffer
*buffer
)
4926 struct ring_buffer_per_cpu
*cpu_buffer
;
4929 /* prevent another thread from changing buffer sizes */
4930 mutex_lock(&buffer
->mutex
);
4932 for_each_online_buffer_cpu(buffer
, cpu
) {
4933 cpu_buffer
= buffer
->buffers
[cpu
];
4935 atomic_inc(&cpu_buffer
->resize_disabled
);
4936 atomic_inc(&cpu_buffer
->record_disabled
);
4939 /* Make sure all commits have finished */
4942 for_each_online_buffer_cpu(buffer
, cpu
) {
4943 cpu_buffer
= buffer
->buffers
[cpu
];
4945 reset_disabled_cpu_buffer(cpu_buffer
);
4947 atomic_dec(&cpu_buffer
->record_disabled
);
4948 atomic_dec(&cpu_buffer
->resize_disabled
);
4951 mutex_unlock(&buffer
->mutex
);
4955 * ring_buffer_reset - reset a ring buffer
4956 * @buffer: The ring buffer to reset all cpu buffers
4958 void ring_buffer_reset(struct trace_buffer
*buffer
)
4960 struct ring_buffer_per_cpu
*cpu_buffer
;
4963 for_each_buffer_cpu(buffer
, cpu
) {
4964 cpu_buffer
= buffer
->buffers
[cpu
];
4966 atomic_inc(&cpu_buffer
->resize_disabled
);
4967 atomic_inc(&cpu_buffer
->record_disabled
);
4970 /* Make sure all commits have finished */
4973 for_each_buffer_cpu(buffer
, cpu
) {
4974 cpu_buffer
= buffer
->buffers
[cpu
];
4976 reset_disabled_cpu_buffer(cpu_buffer
);
4978 atomic_dec(&cpu_buffer
->record_disabled
);
4979 atomic_dec(&cpu_buffer
->resize_disabled
);
4982 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
4985 * rind_buffer_empty - is the ring buffer empty?
4986 * @buffer: The ring buffer to test
4988 bool ring_buffer_empty(struct trace_buffer
*buffer
)
4990 struct ring_buffer_per_cpu
*cpu_buffer
;
4991 unsigned long flags
;
4996 /* yes this is racy, but if you don't like the race, lock the buffer */
4997 for_each_buffer_cpu(buffer
, cpu
) {
4998 cpu_buffer
= buffer
->buffers
[cpu
];
4999 local_irq_save(flags
);
5000 dolock
= rb_reader_lock(cpu_buffer
);
5001 ret
= rb_per_cpu_empty(cpu_buffer
);
5002 rb_reader_unlock(cpu_buffer
, dolock
);
5003 local_irq_restore(flags
);
5011 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
5014 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5015 * @buffer: The ring buffer
5016 * @cpu: The CPU buffer to test
5018 bool ring_buffer_empty_cpu(struct trace_buffer
*buffer
, int cpu
)
5020 struct ring_buffer_per_cpu
*cpu_buffer
;
5021 unsigned long flags
;
5025 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5028 cpu_buffer
= buffer
->buffers
[cpu
];
5029 local_irq_save(flags
);
5030 dolock
= rb_reader_lock(cpu_buffer
);
5031 ret
= rb_per_cpu_empty(cpu_buffer
);
5032 rb_reader_unlock(cpu_buffer
, dolock
);
5033 local_irq_restore(flags
);
5037 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
5039 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5041 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5042 * @buffer_a: One buffer to swap with
5043 * @buffer_b: The other buffer to swap with
5044 * @cpu: the CPU of the buffers to swap
5046 * This function is useful for tracers that want to take a "snapshot"
5047 * of a CPU buffer and has another back up buffer lying around.
5048 * it is expected that the tracer handles the cpu buffer not being
5049 * used at the moment.
5051 int ring_buffer_swap_cpu(struct trace_buffer
*buffer_a
,
5052 struct trace_buffer
*buffer_b
, int cpu
)
5054 struct ring_buffer_per_cpu
*cpu_buffer_a
;
5055 struct ring_buffer_per_cpu
*cpu_buffer_b
;
5058 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
5059 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
5062 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
5063 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
5065 /* At least make sure the two buffers are somewhat the same */
5066 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
5071 if (atomic_read(&buffer_a
->record_disabled
))
5074 if (atomic_read(&buffer_b
->record_disabled
))
5077 if (atomic_read(&cpu_buffer_a
->record_disabled
))
5080 if (atomic_read(&cpu_buffer_b
->record_disabled
))
5084 * We can't do a synchronize_rcu here because this
5085 * function can be called in atomic context.
5086 * Normally this will be called from the same CPU as cpu.
5087 * If not it's up to the caller to protect this.
5089 atomic_inc(&cpu_buffer_a
->record_disabled
);
5090 atomic_inc(&cpu_buffer_b
->record_disabled
);
5093 if (local_read(&cpu_buffer_a
->committing
))
5095 if (local_read(&cpu_buffer_b
->committing
))
5098 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
5099 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
5101 cpu_buffer_b
->buffer
= buffer_a
;
5102 cpu_buffer_a
->buffer
= buffer_b
;
5107 atomic_dec(&cpu_buffer_a
->record_disabled
);
5108 atomic_dec(&cpu_buffer_b
->record_disabled
);
5112 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
5113 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5116 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5117 * @buffer: the buffer to allocate for.
5118 * @cpu: the cpu buffer to allocate.
5120 * This function is used in conjunction with ring_buffer_read_page.
5121 * When reading a full page from the ring buffer, these functions
5122 * can be used to speed up the process. The calling function should
5123 * allocate a few pages first with this function. Then when it
5124 * needs to get pages from the ring buffer, it passes the result
5125 * of this function into ring_buffer_read_page, which will swap
5126 * the page that was allocated, with the read page of the buffer.
5129 * The page allocated, or ERR_PTR
5131 void *ring_buffer_alloc_read_page(struct trace_buffer
*buffer
, int cpu
)
5133 struct ring_buffer_per_cpu
*cpu_buffer
;
5134 struct buffer_data_page
*bpage
= NULL
;
5135 unsigned long flags
;
5138 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5139 return ERR_PTR(-ENODEV
);
5141 cpu_buffer
= buffer
->buffers
[cpu
];
5142 local_irq_save(flags
);
5143 arch_spin_lock(&cpu_buffer
->lock
);
5145 if (cpu_buffer
->free_page
) {
5146 bpage
= cpu_buffer
->free_page
;
5147 cpu_buffer
->free_page
= NULL
;
5150 arch_spin_unlock(&cpu_buffer
->lock
);
5151 local_irq_restore(flags
);
5156 page
= alloc_pages_node(cpu_to_node(cpu
),
5157 GFP_KERNEL
| __GFP_NORETRY
, 0);
5159 return ERR_PTR(-ENOMEM
);
5161 bpage
= page_address(page
);
5164 rb_init_page(bpage
);
5168 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
5171 * ring_buffer_free_read_page - free an allocated read page
5172 * @buffer: the buffer the page was allocate for
5173 * @cpu: the cpu buffer the page came from
5174 * @data: the page to free
5176 * Free a page allocated from ring_buffer_alloc_read_page.
5178 void ring_buffer_free_read_page(struct trace_buffer
*buffer
, int cpu
, void *data
)
5180 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
5181 struct buffer_data_page
*bpage
= data
;
5182 struct page
*page
= virt_to_page(bpage
);
5183 unsigned long flags
;
5185 /* If the page is still in use someplace else, we can't reuse it */
5186 if (page_ref_count(page
) > 1)
5189 local_irq_save(flags
);
5190 arch_spin_lock(&cpu_buffer
->lock
);
5192 if (!cpu_buffer
->free_page
) {
5193 cpu_buffer
->free_page
= bpage
;
5197 arch_spin_unlock(&cpu_buffer
->lock
);
5198 local_irq_restore(flags
);
5201 free_page((unsigned long)bpage
);
5203 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
5206 * ring_buffer_read_page - extract a page from the ring buffer
5207 * @buffer: buffer to extract from
5208 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5209 * @len: amount to extract
5210 * @cpu: the cpu of the buffer to extract
5211 * @full: should the extraction only happen when the page is full.
5213 * This function will pull out a page from the ring buffer and consume it.
5214 * @data_page must be the address of the variable that was returned
5215 * from ring_buffer_alloc_read_page. This is because the page might be used
5216 * to swap with a page in the ring buffer.
5219 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5220 * if (IS_ERR(rpage))
5221 * return PTR_ERR(rpage);
5222 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5224 * process_page(rpage, ret);
5226 * When @full is set, the function will not return true unless
5227 * the writer is off the reader page.
5229 * Note: it is up to the calling functions to handle sleeps and wakeups.
5230 * The ring buffer can be used anywhere in the kernel and can not
5231 * blindly call wake_up. The layer that uses the ring buffer must be
5232 * responsible for that.
5235 * >=0 if data has been transferred, returns the offset of consumed data.
5236 * <0 if no data has been transferred.
5238 int ring_buffer_read_page(struct trace_buffer
*buffer
,
5239 void **data_page
, size_t len
, int cpu
, int full
)
5241 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
5242 struct ring_buffer_event
*event
;
5243 struct buffer_data_page
*bpage
;
5244 struct buffer_page
*reader
;
5245 unsigned long missed_events
;
5246 unsigned long flags
;
5247 unsigned int commit
;
5252 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
5256 * If len is not big enough to hold the page header, then
5257 * we can not copy anything.
5259 if (len
<= BUF_PAGE_HDR_SIZE
)
5262 len
-= BUF_PAGE_HDR_SIZE
;
5271 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
5273 reader
= rb_get_reader_page(cpu_buffer
);
5277 event
= rb_reader_event(cpu_buffer
);
5279 read
= reader
->read
;
5280 commit
= rb_page_commit(reader
);
5282 /* Check if any events were dropped */
5283 missed_events
= cpu_buffer
->lost_events
;
5286 * If this page has been partially read or
5287 * if len is not big enough to read the rest of the page or
5288 * a writer is still on the page, then
5289 * we must copy the data from the page to the buffer.
5290 * Otherwise, we can simply swap the page with the one passed in.
5292 if (read
|| (len
< (commit
- read
)) ||
5293 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
5294 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
5295 unsigned int rpos
= read
;
5296 unsigned int pos
= 0;
5302 if (len
> (commit
- read
))
5303 len
= (commit
- read
);
5305 /* Always keep the time extend and data together */
5306 size
= rb_event_ts_length(event
);
5311 /* save the current timestamp, since the user will need it */
5312 save_timestamp
= cpu_buffer
->read_stamp
;
5314 /* Need to copy one event at a time */
5316 /* We need the size of one event, because
5317 * rb_advance_reader only advances by one event,
5318 * whereas rb_event_ts_length may include the size of
5319 * one or two events.
5320 * We have already ensured there's enough space if this
5321 * is a time extend. */
5322 size
= rb_event_length(event
);
5323 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
5327 rb_advance_reader(cpu_buffer
);
5328 rpos
= reader
->read
;
5334 event
= rb_reader_event(cpu_buffer
);
5335 /* Always keep the time extend and data together */
5336 size
= rb_event_ts_length(event
);
5337 } while (len
>= size
);
5340 local_set(&bpage
->commit
, pos
);
5341 bpage
->time_stamp
= save_timestamp
;
5343 /* we copied everything to the beginning */
5346 /* update the entry counter */
5347 cpu_buffer
->read
+= rb_page_entries(reader
);
5348 cpu_buffer
->read_bytes
+= BUF_PAGE_SIZE
;
5350 /* swap the pages */
5351 rb_init_page(bpage
);
5352 bpage
= reader
->page
;
5353 reader
->page
= *data_page
;
5354 local_set(&reader
->write
, 0);
5355 local_set(&reader
->entries
, 0);
5360 * Use the real_end for the data size,
5361 * This gives us a chance to store the lost events
5364 if (reader
->real_end
)
5365 local_set(&bpage
->commit
, reader
->real_end
);
5369 cpu_buffer
->lost_events
= 0;
5371 commit
= local_read(&bpage
->commit
);
5373 * Set a flag in the commit field if we lost events
5375 if (missed_events
) {
5376 /* If there is room at the end of the page to save the
5377 * missed events, then record it there.
5379 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
5380 memcpy(&bpage
->data
[commit
], &missed_events
,
5381 sizeof(missed_events
));
5382 local_add(RB_MISSED_STORED
, &bpage
->commit
);
5383 commit
+= sizeof(missed_events
);
5385 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
5389 * This page may be off to user land. Zero it out here.
5391 if (commit
< BUF_PAGE_SIZE
)
5392 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
5395 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
5400 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
5403 * We only allocate new buffers, never free them if the CPU goes down.
5404 * If we were to free the buffer, then the user would lose any trace that was in
5407 int trace_rb_cpu_prepare(unsigned int cpu
, struct hlist_node
*node
)
5409 struct trace_buffer
*buffer
;
5412 unsigned long nr_pages
;
5414 buffer
= container_of(node
, struct trace_buffer
, node
);
5415 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
5420 /* check if all cpu sizes are same */
5421 for_each_buffer_cpu(buffer
, cpu_i
) {
5422 /* fill in the size from first enabled cpu */
5424 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
5425 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
5430 /* allocate minimum pages, user can later expand it */
5433 buffer
->buffers
[cpu
] =
5434 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
5435 if (!buffer
->buffers
[cpu
]) {
5436 WARN(1, "failed to allocate ring buffer on CPU %u\n",
5441 cpumask_set_cpu(cpu
, buffer
->cpumask
);
5445 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5447 * This is a basic integrity check of the ring buffer.
5448 * Late in the boot cycle this test will run when configured in.
5449 * It will kick off a thread per CPU that will go into a loop
5450 * writing to the per cpu ring buffer various sizes of data.
5451 * Some of the data will be large items, some small.
5453 * Another thread is created that goes into a spin, sending out
5454 * IPIs to the other CPUs to also write into the ring buffer.
5455 * this is to test the nesting ability of the buffer.
5457 * Basic stats are recorded and reported. If something in the
5458 * ring buffer should happen that's not expected, a big warning
5459 * is displayed and all ring buffers are disabled.
5461 static struct task_struct
*rb_threads
[NR_CPUS
] __initdata
;
5463 struct rb_test_data
{
5464 struct trace_buffer
*buffer
;
5465 unsigned long events
;
5466 unsigned long bytes_written
;
5467 unsigned long bytes_alloc
;
5468 unsigned long bytes_dropped
;
5469 unsigned long events_nested
;
5470 unsigned long bytes_written_nested
;
5471 unsigned long bytes_alloc_nested
;
5472 unsigned long bytes_dropped_nested
;
5473 int min_size_nested
;
5474 int max_size_nested
;
5481 static struct rb_test_data rb_data
[NR_CPUS
] __initdata
;
5484 #define RB_TEST_BUFFER_SIZE 1048576
5486 static char rb_string
[] __initdata
=
5487 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5488 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5489 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5491 static bool rb_test_started __initdata
;
5498 static __init
int rb_write_something(struct rb_test_data
*data
, bool nested
)
5500 struct ring_buffer_event
*event
;
5501 struct rb_item
*item
;
5508 /* Have nested writes different that what is written */
5509 cnt
= data
->cnt
+ (nested
? 27 : 0);
5511 /* Multiply cnt by ~e, to make some unique increment */
5512 size
= (cnt
* 68 / 25) % (sizeof(rb_string
) - 1);
5514 len
= size
+ sizeof(struct rb_item
);
5516 started
= rb_test_started
;
5517 /* read rb_test_started before checking buffer enabled */
5520 event
= ring_buffer_lock_reserve(data
->buffer
, len
);
5522 /* Ignore dropped events before test starts. */
5525 data
->bytes_dropped
+= len
;
5527 data
->bytes_dropped_nested
+= len
;
5532 event_len
= ring_buffer_event_length(event
);
5534 if (RB_WARN_ON(data
->buffer
, event_len
< len
))
5537 item
= ring_buffer_event_data(event
);
5539 memcpy(item
->str
, rb_string
, size
);
5542 data
->bytes_alloc_nested
+= event_len
;
5543 data
->bytes_written_nested
+= len
;
5544 data
->events_nested
++;
5545 if (!data
->min_size_nested
|| len
< data
->min_size_nested
)
5546 data
->min_size_nested
= len
;
5547 if (len
> data
->max_size_nested
)
5548 data
->max_size_nested
= len
;
5550 data
->bytes_alloc
+= event_len
;
5551 data
->bytes_written
+= len
;
5553 if (!data
->min_size
|| len
< data
->min_size
)
5554 data
->max_size
= len
;
5555 if (len
> data
->max_size
)
5556 data
->max_size
= len
;
5560 ring_buffer_unlock_commit(data
->buffer
, event
);
5565 static __init
int rb_test(void *arg
)
5567 struct rb_test_data
*data
= arg
;
5569 while (!kthread_should_stop()) {
5570 rb_write_something(data
, false);
5573 set_current_state(TASK_INTERRUPTIBLE
);
5574 /* Now sleep between a min of 100-300us and a max of 1ms */
5575 usleep_range(((data
->cnt
% 3) + 1) * 100, 1000);
5581 static __init
void rb_ipi(void *ignore
)
5583 struct rb_test_data
*data
;
5584 int cpu
= smp_processor_id();
5586 data
= &rb_data
[cpu
];
5587 rb_write_something(data
, true);
5590 static __init
int rb_hammer_test(void *arg
)
5592 while (!kthread_should_stop()) {
5594 /* Send an IPI to all cpus to write data! */
5595 smp_call_function(rb_ipi
, NULL
, 1);
5596 /* No sleep, but for non preempt, let others run */
5603 static __init
int test_ringbuffer(void)
5605 struct task_struct
*rb_hammer
;
5606 struct trace_buffer
*buffer
;
5610 if (security_locked_down(LOCKDOWN_TRACEFS
)) {
5611 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
5615 pr_info("Running ring buffer tests...\n");
5617 buffer
= ring_buffer_alloc(RB_TEST_BUFFER_SIZE
, RB_FL_OVERWRITE
);
5618 if (WARN_ON(!buffer
))
5621 /* Disable buffer so that threads can't write to it yet */
5622 ring_buffer_record_off(buffer
);
5624 for_each_online_cpu(cpu
) {
5625 rb_data
[cpu
].buffer
= buffer
;
5626 rb_data
[cpu
].cpu
= cpu
;
5627 rb_data
[cpu
].cnt
= cpu
;
5628 rb_threads
[cpu
] = kthread_create(rb_test
, &rb_data
[cpu
],
5629 "rbtester/%d", cpu
);
5630 if (WARN_ON(IS_ERR(rb_threads
[cpu
]))) {
5631 pr_cont("FAILED\n");
5632 ret
= PTR_ERR(rb_threads
[cpu
]);
5636 kthread_bind(rb_threads
[cpu
], cpu
);
5637 wake_up_process(rb_threads
[cpu
]);
5640 /* Now create the rb hammer! */
5641 rb_hammer
= kthread_run(rb_hammer_test
, NULL
, "rbhammer");
5642 if (WARN_ON(IS_ERR(rb_hammer
))) {
5643 pr_cont("FAILED\n");
5644 ret
= PTR_ERR(rb_hammer
);
5648 ring_buffer_record_on(buffer
);
5650 * Show buffer is enabled before setting rb_test_started.
5651 * Yes there's a small race window where events could be
5652 * dropped and the thread wont catch it. But when a ring
5653 * buffer gets enabled, there will always be some kind of
5654 * delay before other CPUs see it. Thus, we don't care about
5655 * those dropped events. We care about events dropped after
5656 * the threads see that the buffer is active.
5659 rb_test_started
= true;
5661 set_current_state(TASK_INTERRUPTIBLE
);
5662 /* Just run for 10 seconds */;
5663 schedule_timeout(10 * HZ
);
5665 kthread_stop(rb_hammer
);
5668 for_each_online_cpu(cpu
) {
5669 if (!rb_threads
[cpu
])
5671 kthread_stop(rb_threads
[cpu
]);
5674 ring_buffer_free(buffer
);
5679 pr_info("finished\n");
5680 for_each_online_cpu(cpu
) {
5681 struct ring_buffer_event
*event
;
5682 struct rb_test_data
*data
= &rb_data
[cpu
];
5683 struct rb_item
*item
;
5684 unsigned long total_events
;
5685 unsigned long total_dropped
;
5686 unsigned long total_written
;
5687 unsigned long total_alloc
;
5688 unsigned long total_read
= 0;
5689 unsigned long total_size
= 0;
5690 unsigned long total_len
= 0;
5691 unsigned long total_lost
= 0;
5694 int small_event_size
;
5698 total_events
= data
->events
+ data
->events_nested
;
5699 total_written
= data
->bytes_written
+ data
->bytes_written_nested
;
5700 total_alloc
= data
->bytes_alloc
+ data
->bytes_alloc_nested
;
5701 total_dropped
= data
->bytes_dropped
+ data
->bytes_dropped_nested
;
5703 big_event_size
= data
->max_size
+ data
->max_size_nested
;
5704 small_event_size
= data
->min_size
+ data
->min_size_nested
;
5706 pr_info("CPU %d:\n", cpu
);
5707 pr_info(" events: %ld\n", total_events
);
5708 pr_info(" dropped bytes: %ld\n", total_dropped
);
5709 pr_info(" alloced bytes: %ld\n", total_alloc
);
5710 pr_info(" written bytes: %ld\n", total_written
);
5711 pr_info(" biggest event: %d\n", big_event_size
);
5712 pr_info(" smallest event: %d\n", small_event_size
);
5714 if (RB_WARN_ON(buffer
, total_dropped
))
5719 while ((event
= ring_buffer_consume(buffer
, cpu
, NULL
, &lost
))) {
5721 item
= ring_buffer_event_data(event
);
5722 total_len
+= ring_buffer_event_length(event
);
5723 total_size
+= item
->size
+ sizeof(struct rb_item
);
5724 if (memcmp(&item
->str
[0], rb_string
, item
->size
) != 0) {
5725 pr_info("FAILED!\n");
5726 pr_info("buffer had: %.*s\n", item
->size
, item
->str
);
5727 pr_info("expected: %.*s\n", item
->size
, rb_string
);
5728 RB_WARN_ON(buffer
, 1);
5739 pr_info(" read events: %ld\n", total_read
);
5740 pr_info(" lost events: %ld\n", total_lost
);
5741 pr_info(" total events: %ld\n", total_lost
+ total_read
);
5742 pr_info(" recorded len bytes: %ld\n", total_len
);
5743 pr_info(" recorded size bytes: %ld\n", total_size
);
5745 pr_info(" With dropped events, record len and size may not match\n"
5746 " alloced and written from above\n");
5748 if (RB_WARN_ON(buffer
, total_len
!= total_alloc
||
5749 total_size
!= total_written
))
5752 if (RB_WARN_ON(buffer
, total_lost
+ total_read
!= total_events
))
5758 pr_info("Ring buffer PASSED!\n");
5760 ring_buffer_free(buffer
);
5764 late_initcall(test_ringbuffer
);
5765 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */