4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 #include <linux/ftrace_event.h>
7 #include <linux/ring_buffer.h>
8 #include <linux/trace_clock.h>
9 #include <linux/trace_seq.h>
10 #include <linux/spinlock.h>
11 #include <linux/irq_work.h>
12 #include <linux/debugfs.h>
13 #include <linux/uaccess.h>
14 #include <linux/hardirq.h>
15 #include <linux/kthread.h> /* for self test */
16 #include <linux/kmemcheck.h>
17 #include <linux/module.h>
18 #include <linux/percpu.h>
19 #include <linux/mutex.h>
20 #include <linux/delay.h>
21 #include <linux/slab.h>
22 #include <linux/init.h>
23 #include <linux/hash.h>
24 #include <linux/list.h>
25 #include <linux/cpu.h>
28 #include <asm/local.h>
30 static void update_pages_handler(struct work_struct
*work
);
33 * The ring buffer header is special. We must manually up keep it.
35 int ring_buffer_print_entry_header(struct trace_seq
*s
)
37 trace_seq_puts(s
, "# compressed entry header\n");
38 trace_seq_puts(s
, "\ttype_len : 5 bits\n");
39 trace_seq_puts(s
, "\ttime_delta : 27 bits\n");
40 trace_seq_puts(s
, "\tarray : 32 bits\n");
41 trace_seq_putc(s
, '\n');
42 trace_seq_printf(s
, "\tpadding : type == %d\n",
43 RINGBUF_TYPE_PADDING
);
44 trace_seq_printf(s
, "\ttime_extend : type == %d\n",
45 RINGBUF_TYPE_TIME_EXTEND
);
46 trace_seq_printf(s
, "\tdata max type_len == %d\n",
47 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
49 return !trace_seq_has_overflowed(s
);
53 * The ring buffer is made up of a list of pages. A separate list of pages is
54 * allocated for each CPU. A writer may only write to a buffer that is
55 * associated with the CPU it is currently executing on. A reader may read
56 * from any per cpu buffer.
58 * The reader is special. For each per cpu buffer, the reader has its own
59 * reader page. When a reader has read the entire reader page, this reader
60 * page is swapped with another page in the ring buffer.
62 * Now, as long as the writer is off the reader page, the reader can do what
63 * ever it wants with that page. The writer will never write to that page
64 * again (as long as it is out of the ring buffer).
66 * Here's some silly ASCII art.
69 * |reader| RING BUFFER
71 * +------+ +---+ +---+ +---+
80 * |reader| RING BUFFER
81 * |page |------------------v
82 * +------+ +---+ +---+ +---+
91 * |reader| RING BUFFER
92 * |page |------------------v
93 * +------+ +---+ +---+ +---+
98 * +------------------------------+
102 * |buffer| RING BUFFER
103 * |page |------------------v
104 * +------+ +---+ +---+ +---+
106 * | New +---+ +---+ +---+
109 * +------------------------------+
112 * After we make this swap, the reader can hand this page off to the splice
113 * code and be done with it. It can even allocate a new page if it needs to
114 * and swap that into the ring buffer.
116 * We will be using cmpxchg soon to make all this lockless.
121 * A fast way to enable or disable all ring buffers is to
122 * call tracing_on or tracing_off. Turning off the ring buffers
123 * prevents all ring buffers from being recorded to.
124 * Turning this switch on, makes it OK to write to the
125 * ring buffer, if the ring buffer is enabled itself.
127 * There's three layers that must be on in order to write
128 * to the ring buffer.
130 * 1) This global flag must be set.
131 * 2) The ring buffer must be enabled for recording.
132 * 3) The per cpu buffer must be enabled for recording.
134 * In case of an anomaly, this global flag has a bit set that
135 * will permantly disable all ring buffers.
139 * Global flag to disable all recording to ring buffers
140 * This has two bits: ON, DISABLED
144 * 0 0 : ring buffers are off
145 * 1 0 : ring buffers are on
146 * X 1 : ring buffers are permanently disabled
150 RB_BUFFERS_ON_BIT
= 0,
151 RB_BUFFERS_DISABLED_BIT
= 1,
155 RB_BUFFERS_ON
= 1 << RB_BUFFERS_ON_BIT
,
156 RB_BUFFERS_DISABLED
= 1 << RB_BUFFERS_DISABLED_BIT
,
159 static unsigned long ring_buffer_flags __read_mostly
= RB_BUFFERS_ON
;
161 /* Used for individual buffers (after the counter) */
162 #define RB_BUFFER_OFF (1 << 20)
164 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
167 * tracing_off_permanent - permanently disable ring buffers
169 * This function, once called, will disable all ring buffers
172 void tracing_off_permanent(void)
174 set_bit(RB_BUFFERS_DISABLED_BIT
, &ring_buffer_flags
);
177 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
178 #define RB_ALIGNMENT 4U
179 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
180 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
182 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
183 # define RB_FORCE_8BYTE_ALIGNMENT 0
184 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
186 # define RB_FORCE_8BYTE_ALIGNMENT 1
187 # define RB_ARCH_ALIGNMENT 8U
190 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
192 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
193 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
196 RB_LEN_TIME_EXTEND
= 8,
197 RB_LEN_TIME_STAMP
= 16,
200 #define skip_time_extend(event) \
201 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
203 static inline int rb_null_event(struct ring_buffer_event
*event
)
205 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
208 static void rb_event_set_padding(struct ring_buffer_event
*event
)
210 /* padding has a NULL time_delta */
211 event
->type_len
= RINGBUF_TYPE_PADDING
;
212 event
->time_delta
= 0;
216 rb_event_data_length(struct ring_buffer_event
*event
)
221 length
= event
->type_len
* RB_ALIGNMENT
;
223 length
= event
->array
[0];
224 return length
+ RB_EVNT_HDR_SIZE
;
228 * Return the length of the given event. Will return
229 * the length of the time extend if the event is a
232 static inline unsigned
233 rb_event_length(struct ring_buffer_event
*event
)
235 switch (event
->type_len
) {
236 case RINGBUF_TYPE_PADDING
:
237 if (rb_null_event(event
))
240 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
242 case RINGBUF_TYPE_TIME_EXTEND
:
243 return RB_LEN_TIME_EXTEND
;
245 case RINGBUF_TYPE_TIME_STAMP
:
246 return RB_LEN_TIME_STAMP
;
248 case RINGBUF_TYPE_DATA
:
249 return rb_event_data_length(event
);
258 * Return total length of time extend and data,
259 * or just the event length for all other events.
261 static inline unsigned
262 rb_event_ts_length(struct ring_buffer_event
*event
)
266 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
267 /* time extends include the data event after it */
268 len
= RB_LEN_TIME_EXTEND
;
269 event
= skip_time_extend(event
);
271 return len
+ rb_event_length(event
);
275 * ring_buffer_event_length - return the length of the event
276 * @event: the event to get the length of
278 * Returns the size of the data load of a data event.
279 * If the event is something other than a data event, it
280 * returns the size of the event itself. With the exception
281 * of a TIME EXTEND, where it still returns the size of the
282 * data load of the data event after it.
284 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
288 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
289 event
= skip_time_extend(event
);
291 length
= rb_event_length(event
);
292 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
294 length
-= RB_EVNT_HDR_SIZE
;
295 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
296 length
-= sizeof(event
->array
[0]);
299 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
301 /* inline for ring buffer fast paths */
303 rb_event_data(struct ring_buffer_event
*event
)
305 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
306 event
= skip_time_extend(event
);
307 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
308 /* If length is in len field, then array[0] has the data */
310 return (void *)&event
->array
[0];
311 /* Otherwise length is in array[0] and array[1] has the data */
312 return (void *)&event
->array
[1];
316 * ring_buffer_event_data - return the data of the event
317 * @event: the event to get the data from
319 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
321 return rb_event_data(event
);
323 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
325 #define for_each_buffer_cpu(buffer, cpu) \
326 for_each_cpu(cpu, buffer->cpumask)
329 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
330 #define TS_DELTA_TEST (~TS_MASK)
332 /* Flag when events were overwritten */
333 #define RB_MISSED_EVENTS (1 << 31)
334 /* Missed count stored at end */
335 #define RB_MISSED_STORED (1 << 30)
337 struct buffer_data_page
{
338 u64 time_stamp
; /* page time stamp */
339 local_t commit
; /* write committed index */
340 unsigned char data
[] RB_ALIGN_DATA
; /* data of buffer page */
344 * Note, the buffer_page list must be first. The buffer pages
345 * are allocated in cache lines, which means that each buffer
346 * page will be at the beginning of a cache line, and thus
347 * the least significant bits will be zero. We use this to
348 * add flags in the list struct pointers, to make the ring buffer
352 struct list_head list
; /* list of buffer pages */
353 local_t write
; /* index for next write */
354 unsigned read
; /* index for next read */
355 local_t entries
; /* entries on this page */
356 unsigned long real_end
; /* real end of data */
357 struct buffer_data_page
*page
; /* Actual data page */
361 * The buffer page counters, write and entries, must be reset
362 * atomically when crossing page boundaries. To synchronize this
363 * update, two counters are inserted into the number. One is
364 * the actual counter for the write position or count on the page.
366 * The other is a counter of updaters. Before an update happens
367 * the update partition of the counter is incremented. This will
368 * allow the updater to update the counter atomically.
370 * The counter is 20 bits, and the state data is 12.
372 #define RB_WRITE_MASK 0xfffff
373 #define RB_WRITE_INTCNT (1 << 20)
375 static void rb_init_page(struct buffer_data_page
*bpage
)
377 local_set(&bpage
->commit
, 0);
381 * ring_buffer_page_len - the size of data on the page.
382 * @page: The page to read
384 * Returns the amount of data on the page, including buffer page header.
386 size_t ring_buffer_page_len(void *page
)
388 return local_read(&((struct buffer_data_page
*)page
)->commit
)
393 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
396 static void free_buffer_page(struct buffer_page
*bpage
)
398 free_page((unsigned long)bpage
->page
);
403 * We need to fit the time_stamp delta into 27 bits.
405 static inline int test_time_stamp(u64 delta
)
407 if (delta
& TS_DELTA_TEST
)
412 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
414 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
415 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
417 int ring_buffer_print_page_header(struct trace_seq
*s
)
419 struct buffer_data_page field
;
421 trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
422 "offset:0;\tsize:%u;\tsigned:%u;\n",
423 (unsigned int)sizeof(field
.time_stamp
),
424 (unsigned int)is_signed_type(u64
));
426 trace_seq_printf(s
, "\tfield: local_t commit;\t"
427 "offset:%u;\tsize:%u;\tsigned:%u;\n",
428 (unsigned int)offsetof(typeof(field
), commit
),
429 (unsigned int)sizeof(field
.commit
),
430 (unsigned int)is_signed_type(long));
432 trace_seq_printf(s
, "\tfield: int overwrite;\t"
433 "offset:%u;\tsize:%u;\tsigned:%u;\n",
434 (unsigned int)offsetof(typeof(field
), commit
),
436 (unsigned int)is_signed_type(long));
438 trace_seq_printf(s
, "\tfield: char data;\t"
439 "offset:%u;\tsize:%u;\tsigned:%u;\n",
440 (unsigned int)offsetof(typeof(field
), data
),
441 (unsigned int)BUF_PAGE_SIZE
,
442 (unsigned int)is_signed_type(char));
444 return !trace_seq_has_overflowed(s
);
448 struct irq_work work
;
449 wait_queue_head_t waiters
;
450 bool waiters_pending
;
454 * head_page == tail_page && head == tail then buffer is empty.
456 struct ring_buffer_per_cpu
{
458 atomic_t record_disabled
;
459 struct ring_buffer
*buffer
;
460 raw_spinlock_t reader_lock
; /* serialize readers */
461 arch_spinlock_t lock
;
462 struct lock_class_key lock_key
;
463 unsigned int nr_pages
;
464 struct list_head
*pages
;
465 struct buffer_page
*head_page
; /* read from head */
466 struct buffer_page
*tail_page
; /* write to tail */
467 struct buffer_page
*commit_page
; /* committed pages */
468 struct buffer_page
*reader_page
;
469 unsigned long lost_events
;
470 unsigned long last_overrun
;
471 local_t entries_bytes
;
474 local_t commit_overrun
;
475 local_t dropped_events
;
479 unsigned long read_bytes
;
482 /* ring buffer pages to update, > 0 to add, < 0 to remove */
483 int nr_pages_to_update
;
484 struct list_head new_pages
; /* new pages to add */
485 struct work_struct update_pages_work
;
486 struct completion update_done
;
488 struct rb_irq_work irq_work
;
494 atomic_t record_disabled
;
495 atomic_t resize_disabled
;
496 cpumask_var_t cpumask
;
498 struct lock_class_key
*reader_lock_key
;
502 struct ring_buffer_per_cpu
**buffers
;
504 #ifdef CONFIG_HOTPLUG_CPU
505 struct notifier_block cpu_notify
;
509 struct rb_irq_work irq_work
;
512 struct ring_buffer_iter
{
513 struct ring_buffer_per_cpu
*cpu_buffer
;
515 struct buffer_page
*head_page
;
516 struct buffer_page
*cache_reader_page
;
517 unsigned long cache_read
;
522 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
524 * Schedules a delayed work to wake up any task that is blocked on the
525 * ring buffer waiters queue.
527 static void rb_wake_up_waiters(struct irq_work
*work
)
529 struct rb_irq_work
*rbwork
= container_of(work
, struct rb_irq_work
, work
);
531 wake_up_all(&rbwork
->waiters
);
535 * ring_buffer_wait - wait for input to the ring buffer
536 * @buffer: buffer to wait on
537 * @cpu: the cpu buffer to wait on
538 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
540 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
541 * as data is added to any of the @buffer's cpu buffers. Otherwise
542 * it will wait for data to be added to a specific cpu buffer.
544 int ring_buffer_wait(struct ring_buffer
*buffer
, int cpu
, bool full
)
546 struct ring_buffer_per_cpu
*uninitialized_var(cpu_buffer
);
548 struct rb_irq_work
*work
;
552 * Depending on what the caller is waiting for, either any
553 * data in any cpu buffer, or a specific buffer, put the
554 * caller on the appropriate wait queue.
556 if (cpu
== RING_BUFFER_ALL_CPUS
)
557 work
= &buffer
->irq_work
;
559 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
561 cpu_buffer
= buffer
->buffers
[cpu
];
562 work
= &cpu_buffer
->irq_work
;
567 prepare_to_wait(&work
->waiters
, &wait
, TASK_INTERRUPTIBLE
);
570 * The events can happen in critical sections where
571 * checking a work queue can cause deadlocks.
572 * After adding a task to the queue, this flag is set
573 * only to notify events to try to wake up the queue
576 * We don't clear it even if the buffer is no longer
577 * empty. The flag only causes the next event to run
578 * irq_work to do the work queue wake up. The worse
579 * that can happen if we race with !trace_empty() is that
580 * an event will cause an irq_work to try to wake up
583 * There's no reason to protect this flag either, as
584 * the work queue and irq_work logic will do the necessary
585 * synchronization for the wake ups. The only thing
586 * that is necessary is that the wake up happens after
587 * a task has been queued. It's OK for spurious wake ups.
589 work
->waiters_pending
= true;
591 if (signal_pending(current
)) {
596 if (cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
))
599 if (cpu
!= RING_BUFFER_ALL_CPUS
&&
600 !ring_buffer_empty_cpu(buffer
, cpu
)) {
607 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
608 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
609 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
618 finish_wait(&work
->waiters
, &wait
);
624 * ring_buffer_poll_wait - poll on buffer input
625 * @buffer: buffer to wait on
626 * @cpu: the cpu buffer to wait on
627 * @filp: the file descriptor
628 * @poll_table: The poll descriptor
630 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
631 * as data is added to any of the @buffer's cpu buffers. Otherwise
632 * it will wait for data to be added to a specific cpu buffer.
634 * Returns POLLIN | POLLRDNORM if data exists in the buffers,
637 int ring_buffer_poll_wait(struct ring_buffer
*buffer
, int cpu
,
638 struct file
*filp
, poll_table
*poll_table
)
640 struct ring_buffer_per_cpu
*cpu_buffer
;
641 struct rb_irq_work
*work
;
643 if (cpu
== RING_BUFFER_ALL_CPUS
)
644 work
= &buffer
->irq_work
;
646 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
649 cpu_buffer
= buffer
->buffers
[cpu
];
650 work
= &cpu_buffer
->irq_work
;
653 poll_wait(filp
, &work
->waiters
, poll_table
);
654 work
->waiters_pending
= true;
656 * There's a tight race between setting the waiters_pending and
657 * checking if the ring buffer is empty. Once the waiters_pending bit
658 * is set, the next event will wake the task up, but we can get stuck
659 * if there's only a single event in.
661 * FIXME: Ideally, we need a memory barrier on the writer side as well,
662 * but adding a memory barrier to all events will cause too much of a
663 * performance hit in the fast path. We only need a memory barrier when
664 * the buffer goes from empty to having content. But as this race is
665 * extremely small, and it's not a problem if another event comes in, we
670 if ((cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
)) ||
671 (cpu
!= RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty_cpu(buffer
, cpu
)))
672 return POLLIN
| POLLRDNORM
;
676 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
677 #define RB_WARN_ON(b, cond) \
679 int _____ret = unlikely(cond); \
681 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
682 struct ring_buffer_per_cpu *__b = \
684 atomic_inc(&__b->buffer->record_disabled); \
686 atomic_inc(&b->record_disabled); \
692 /* Up this if you want to test the TIME_EXTENTS and normalization */
693 #define DEBUG_SHIFT 0
695 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
697 /* shift to debug/test normalization and TIME_EXTENTS */
698 return buffer
->clock() << DEBUG_SHIFT
;
701 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
705 preempt_disable_notrace();
706 time
= rb_time_stamp(buffer
);
707 preempt_enable_no_resched_notrace();
711 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
713 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
716 /* Just stupid testing the normalize function and deltas */
719 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
722 * Making the ring buffer lockless makes things tricky.
723 * Although writes only happen on the CPU that they are on,
724 * and they only need to worry about interrupts. Reads can
727 * The reader page is always off the ring buffer, but when the
728 * reader finishes with a page, it needs to swap its page with
729 * a new one from the buffer. The reader needs to take from
730 * the head (writes go to the tail). But if a writer is in overwrite
731 * mode and wraps, it must push the head page forward.
733 * Here lies the problem.
735 * The reader must be careful to replace only the head page, and
736 * not another one. As described at the top of the file in the
737 * ASCII art, the reader sets its old page to point to the next
738 * page after head. It then sets the page after head to point to
739 * the old reader page. But if the writer moves the head page
740 * during this operation, the reader could end up with the tail.
742 * We use cmpxchg to help prevent this race. We also do something
743 * special with the page before head. We set the LSB to 1.
745 * When the writer must push the page forward, it will clear the
746 * bit that points to the head page, move the head, and then set
747 * the bit that points to the new head page.
749 * We also don't want an interrupt coming in and moving the head
750 * page on another writer. Thus we use the second LSB to catch
753 * head->list->prev->next bit 1 bit 0
756 * Points to head page 0 1
759 * Note we can not trust the prev pointer of the head page, because:
761 * +----+ +-----+ +-----+
762 * | |------>| T |---X--->| N |
764 * +----+ +-----+ +-----+
767 * +----------| R |----------+ |
771 * Key: ---X--> HEAD flag set in pointer
776 * (see __rb_reserve_next() to see where this happens)
778 * What the above shows is that the reader just swapped out
779 * the reader page with a page in the buffer, but before it
780 * could make the new header point back to the new page added
781 * it was preempted by a writer. The writer moved forward onto
782 * the new page added by the reader and is about to move forward
785 * You can see, it is legitimate for the previous pointer of
786 * the head (or any page) not to point back to itself. But only
790 #define RB_PAGE_NORMAL 0UL
791 #define RB_PAGE_HEAD 1UL
792 #define RB_PAGE_UPDATE 2UL
795 #define RB_FLAG_MASK 3UL
797 /* PAGE_MOVED is not part of the mask */
798 #define RB_PAGE_MOVED 4UL
801 * rb_list_head - remove any bit
803 static struct list_head
*rb_list_head(struct list_head
*list
)
805 unsigned long val
= (unsigned long)list
;
807 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
811 * rb_is_head_page - test if the given page is the head page
813 * Because the reader may move the head_page pointer, we can
814 * not trust what the head page is (it may be pointing to
815 * the reader page). But if the next page is a header page,
816 * its flags will be non zero.
819 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
820 struct buffer_page
*page
, struct list_head
*list
)
824 val
= (unsigned long)list
->next
;
826 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
827 return RB_PAGE_MOVED
;
829 return val
& RB_FLAG_MASK
;
835 * The unique thing about the reader page, is that, if the
836 * writer is ever on it, the previous pointer never points
837 * back to the reader page.
839 static int rb_is_reader_page(struct buffer_page
*page
)
841 struct list_head
*list
= page
->list
.prev
;
843 return rb_list_head(list
->next
) != &page
->list
;
847 * rb_set_list_to_head - set a list_head to be pointing to head.
849 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
850 struct list_head
*list
)
854 ptr
= (unsigned long *)&list
->next
;
855 *ptr
|= RB_PAGE_HEAD
;
856 *ptr
&= ~RB_PAGE_UPDATE
;
860 * rb_head_page_activate - sets up head page
862 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
864 struct buffer_page
*head
;
866 head
= cpu_buffer
->head_page
;
871 * Set the previous list pointer to have the HEAD flag.
873 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
876 static void rb_list_head_clear(struct list_head
*list
)
878 unsigned long *ptr
= (unsigned long *)&list
->next
;
880 *ptr
&= ~RB_FLAG_MASK
;
884 * rb_head_page_dactivate - clears head page ptr (for free list)
887 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
889 struct list_head
*hd
;
891 /* Go through the whole list and clear any pointers found. */
892 rb_list_head_clear(cpu_buffer
->pages
);
894 list_for_each(hd
, cpu_buffer
->pages
)
895 rb_list_head_clear(hd
);
898 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
899 struct buffer_page
*head
,
900 struct buffer_page
*prev
,
901 int old_flag
, int new_flag
)
903 struct list_head
*list
;
904 unsigned long val
= (unsigned long)&head
->list
;
909 val
&= ~RB_FLAG_MASK
;
911 ret
= cmpxchg((unsigned long *)&list
->next
,
912 val
| old_flag
, val
| new_flag
);
914 /* check if the reader took the page */
915 if ((ret
& ~RB_FLAG_MASK
) != val
)
916 return RB_PAGE_MOVED
;
918 return ret
& RB_FLAG_MASK
;
921 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
922 struct buffer_page
*head
,
923 struct buffer_page
*prev
,
926 return rb_head_page_set(cpu_buffer
, head
, prev
,
927 old_flag
, RB_PAGE_UPDATE
);
930 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
931 struct buffer_page
*head
,
932 struct buffer_page
*prev
,
935 return rb_head_page_set(cpu_buffer
, head
, prev
,
936 old_flag
, RB_PAGE_HEAD
);
939 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
940 struct buffer_page
*head
,
941 struct buffer_page
*prev
,
944 return rb_head_page_set(cpu_buffer
, head
, prev
,
945 old_flag
, RB_PAGE_NORMAL
);
948 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
949 struct buffer_page
**bpage
)
951 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
953 *bpage
= list_entry(p
, struct buffer_page
, list
);
956 static struct buffer_page
*
957 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
959 struct buffer_page
*head
;
960 struct buffer_page
*page
;
961 struct list_head
*list
;
964 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
968 list
= cpu_buffer
->pages
;
969 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
972 page
= head
= cpu_buffer
->head_page
;
974 * It is possible that the writer moves the header behind
975 * where we started, and we miss in one loop.
976 * A second loop should grab the header, but we'll do
977 * three loops just because I'm paranoid.
979 for (i
= 0; i
< 3; i
++) {
981 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
982 cpu_buffer
->head_page
= page
;
985 rb_inc_page(cpu_buffer
, &page
);
986 } while (page
!= head
);
989 RB_WARN_ON(cpu_buffer
, 1);
994 static int rb_head_page_replace(struct buffer_page
*old
,
995 struct buffer_page
*new)
997 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
1001 val
= *ptr
& ~RB_FLAG_MASK
;
1002 val
|= RB_PAGE_HEAD
;
1004 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
1010 * rb_tail_page_update - move the tail page forward
1012 * Returns 1 if moved tail page, 0 if someone else did.
1014 static int rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1015 struct buffer_page
*tail_page
,
1016 struct buffer_page
*next_page
)
1018 struct buffer_page
*old_tail
;
1019 unsigned long old_entries
;
1020 unsigned long old_write
;
1024 * The tail page now needs to be moved forward.
1026 * We need to reset the tail page, but without messing
1027 * with possible erasing of data brought in by interrupts
1028 * that have moved the tail page and are currently on it.
1030 * We add a counter to the write field to denote this.
1032 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
1033 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
1036 * Just make sure we have seen our old_write and synchronize
1037 * with any interrupts that come in.
1042 * If the tail page is still the same as what we think
1043 * it is, then it is up to us to update the tail
1046 if (tail_page
== cpu_buffer
->tail_page
) {
1047 /* Zero the write counter */
1048 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
1049 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
1052 * This will only succeed if an interrupt did
1053 * not come in and change it. In which case, we
1054 * do not want to modify it.
1056 * We add (void) to let the compiler know that we do not care
1057 * about the return value of these functions. We use the
1058 * cmpxchg to only update if an interrupt did not already
1059 * do it for us. If the cmpxchg fails, we don't care.
1061 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
1062 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
1065 * No need to worry about races with clearing out the commit.
1066 * it only can increment when a commit takes place. But that
1067 * only happens in the outer most nested commit.
1069 local_set(&next_page
->page
->commit
, 0);
1071 old_tail
= cmpxchg(&cpu_buffer
->tail_page
,
1072 tail_page
, next_page
);
1074 if (old_tail
== tail_page
)
1081 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
1082 struct buffer_page
*bpage
)
1084 unsigned long val
= (unsigned long)bpage
;
1086 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
1093 * rb_check_list - make sure a pointer to a list has the last bits zero
1095 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
1096 struct list_head
*list
)
1098 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
1100 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
1106 * rb_check_pages - integrity check of buffer pages
1107 * @cpu_buffer: CPU buffer with pages to test
1109 * As a safety measure we check to make sure the data pages have not
1112 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1114 struct list_head
*head
= cpu_buffer
->pages
;
1115 struct buffer_page
*bpage
, *tmp
;
1117 /* Reset the head page if it exists */
1118 if (cpu_buffer
->head_page
)
1119 rb_set_head_page(cpu_buffer
);
1121 rb_head_page_deactivate(cpu_buffer
);
1123 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
1125 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
1128 if (rb_check_list(cpu_buffer
, head
))
1131 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1132 if (RB_WARN_ON(cpu_buffer
,
1133 bpage
->list
.next
->prev
!= &bpage
->list
))
1135 if (RB_WARN_ON(cpu_buffer
,
1136 bpage
->list
.prev
->next
!= &bpage
->list
))
1138 if (rb_check_list(cpu_buffer
, &bpage
->list
))
1142 rb_head_page_activate(cpu_buffer
);
1147 static int __rb_allocate_pages(int nr_pages
, struct list_head
*pages
, int cpu
)
1150 struct buffer_page
*bpage
, *tmp
;
1152 for (i
= 0; i
< nr_pages
; i
++) {
1155 * __GFP_NORETRY flag makes sure that the allocation fails
1156 * gracefully without invoking oom-killer and the system is
1159 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1160 GFP_KERNEL
| __GFP_NORETRY
,
1165 list_add(&bpage
->list
, pages
);
1167 page
= alloc_pages_node(cpu_to_node(cpu
),
1168 GFP_KERNEL
| __GFP_NORETRY
, 0);
1171 bpage
->page
= page_address(page
);
1172 rb_init_page(bpage
->page
);
1178 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1179 list_del_init(&bpage
->list
);
1180 free_buffer_page(bpage
);
1186 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1193 if (__rb_allocate_pages(nr_pages
, &pages
, cpu_buffer
->cpu
))
1197 * The ring buffer page list is a circular list that does not
1198 * start and end with a list head. All page list items point to
1201 cpu_buffer
->pages
= pages
.next
;
1204 cpu_buffer
->nr_pages
= nr_pages
;
1206 rb_check_pages(cpu_buffer
);
1211 static struct ring_buffer_per_cpu
*
1212 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int nr_pages
, int cpu
)
1214 struct ring_buffer_per_cpu
*cpu_buffer
;
1215 struct buffer_page
*bpage
;
1219 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1220 GFP_KERNEL
, cpu_to_node(cpu
));
1224 cpu_buffer
->cpu
= cpu
;
1225 cpu_buffer
->buffer
= buffer
;
1226 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1227 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1228 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1229 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1230 init_completion(&cpu_buffer
->update_done
);
1231 init_irq_work(&cpu_buffer
->irq_work
.work
, rb_wake_up_waiters
);
1232 init_waitqueue_head(&cpu_buffer
->irq_work
.waiters
);
1234 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1235 GFP_KERNEL
, cpu_to_node(cpu
));
1237 goto fail_free_buffer
;
1239 rb_check_bpage(cpu_buffer
, bpage
);
1241 cpu_buffer
->reader_page
= bpage
;
1242 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, 0);
1244 goto fail_free_reader
;
1245 bpage
->page
= page_address(page
);
1246 rb_init_page(bpage
->page
);
1248 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1249 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1251 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1253 goto fail_free_reader
;
1255 cpu_buffer
->head_page
1256 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1257 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1259 rb_head_page_activate(cpu_buffer
);
1264 free_buffer_page(cpu_buffer
->reader_page
);
1271 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1273 struct list_head
*head
= cpu_buffer
->pages
;
1274 struct buffer_page
*bpage
, *tmp
;
1276 free_buffer_page(cpu_buffer
->reader_page
);
1278 rb_head_page_deactivate(cpu_buffer
);
1281 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1282 list_del_init(&bpage
->list
);
1283 free_buffer_page(bpage
);
1285 bpage
= list_entry(head
, struct buffer_page
, list
);
1286 free_buffer_page(bpage
);
1292 #ifdef CONFIG_HOTPLUG_CPU
1293 static int rb_cpu_notify(struct notifier_block
*self
,
1294 unsigned long action
, void *hcpu
);
1298 * __ring_buffer_alloc - allocate a new ring_buffer
1299 * @size: the size in bytes per cpu that is needed.
1300 * @flags: attributes to set for the ring buffer.
1302 * Currently the only flag that is available is the RB_FL_OVERWRITE
1303 * flag. This flag means that the buffer will overwrite old data
1304 * when the buffer wraps. If this flag is not set, the buffer will
1305 * drop data when the tail hits the head.
1307 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1308 struct lock_class_key
*key
)
1310 struct ring_buffer
*buffer
;
1314 /* keep it in its own cache line */
1315 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1320 if (!alloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1321 goto fail_free_buffer
;
1323 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1324 buffer
->flags
= flags
;
1325 buffer
->clock
= trace_clock_local
;
1326 buffer
->reader_lock_key
= key
;
1328 init_irq_work(&buffer
->irq_work
.work
, rb_wake_up_waiters
);
1329 init_waitqueue_head(&buffer
->irq_work
.waiters
);
1331 /* need at least two pages */
1336 * In case of non-hotplug cpu, if the ring-buffer is allocated
1337 * in early initcall, it will not be notified of secondary cpus.
1338 * In that off case, we need to allocate for all possible cpus.
1340 #ifdef CONFIG_HOTPLUG_CPU
1341 cpu_notifier_register_begin();
1342 cpumask_copy(buffer
->cpumask
, cpu_online_mask
);
1344 cpumask_copy(buffer
->cpumask
, cpu_possible_mask
);
1346 buffer
->cpus
= nr_cpu_ids
;
1348 bsize
= sizeof(void *) * nr_cpu_ids
;
1349 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1351 if (!buffer
->buffers
)
1352 goto fail_free_cpumask
;
1354 for_each_buffer_cpu(buffer
, cpu
) {
1355 buffer
->buffers
[cpu
] =
1356 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1357 if (!buffer
->buffers
[cpu
])
1358 goto fail_free_buffers
;
1361 #ifdef CONFIG_HOTPLUG_CPU
1362 buffer
->cpu_notify
.notifier_call
= rb_cpu_notify
;
1363 buffer
->cpu_notify
.priority
= 0;
1364 __register_cpu_notifier(&buffer
->cpu_notify
);
1365 cpu_notifier_register_done();
1368 mutex_init(&buffer
->mutex
);
1373 for_each_buffer_cpu(buffer
, cpu
) {
1374 if (buffer
->buffers
[cpu
])
1375 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1377 kfree(buffer
->buffers
);
1380 free_cpumask_var(buffer
->cpumask
);
1381 #ifdef CONFIG_HOTPLUG_CPU
1382 cpu_notifier_register_done();
1389 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1392 * ring_buffer_free - free a ring buffer.
1393 * @buffer: the buffer to free.
1396 ring_buffer_free(struct ring_buffer
*buffer
)
1400 #ifdef CONFIG_HOTPLUG_CPU
1401 cpu_notifier_register_begin();
1402 __unregister_cpu_notifier(&buffer
->cpu_notify
);
1405 for_each_buffer_cpu(buffer
, cpu
)
1406 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1408 #ifdef CONFIG_HOTPLUG_CPU
1409 cpu_notifier_register_done();
1412 kfree(buffer
->buffers
);
1413 free_cpumask_var(buffer
->cpumask
);
1417 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1419 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1422 buffer
->clock
= clock
;
1425 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1427 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1429 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1432 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1434 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1438 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned int nr_pages
)
1440 struct list_head
*tail_page
, *to_remove
, *next_page
;
1441 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1442 struct buffer_page
*last_page
, *first_page
;
1443 unsigned int nr_removed
;
1444 unsigned long head_bit
;
1449 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1450 atomic_inc(&cpu_buffer
->record_disabled
);
1452 * We don't race with the readers since we have acquired the reader
1453 * lock. We also don't race with writers after disabling recording.
1454 * This makes it easy to figure out the first and the last page to be
1455 * removed from the list. We unlink all the pages in between including
1456 * the first and last pages. This is done in a busy loop so that we
1457 * lose the least number of traces.
1458 * The pages are freed after we restart recording and unlock readers.
1460 tail_page
= &cpu_buffer
->tail_page
->list
;
1463 * tail page might be on reader page, we remove the next page
1464 * from the ring buffer
1466 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1467 tail_page
= rb_list_head(tail_page
->next
);
1468 to_remove
= tail_page
;
1470 /* start of pages to remove */
1471 first_page
= list_entry(rb_list_head(to_remove
->next
),
1472 struct buffer_page
, list
);
1474 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1475 to_remove
= rb_list_head(to_remove
)->next
;
1476 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1479 next_page
= rb_list_head(to_remove
)->next
;
1482 * Now we remove all pages between tail_page and next_page.
1483 * Make sure that we have head_bit value preserved for the
1486 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1488 next_page
= rb_list_head(next_page
);
1489 next_page
->prev
= tail_page
;
1491 /* make sure pages points to a valid page in the ring buffer */
1492 cpu_buffer
->pages
= next_page
;
1494 /* update head page */
1496 cpu_buffer
->head_page
= list_entry(next_page
,
1497 struct buffer_page
, list
);
1500 * change read pointer to make sure any read iterators reset
1503 cpu_buffer
->read
= 0;
1505 /* pages are removed, resume tracing and then free the pages */
1506 atomic_dec(&cpu_buffer
->record_disabled
);
1507 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1509 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1511 /* last buffer page to remove */
1512 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1514 tmp_iter_page
= first_page
;
1517 to_remove_page
= tmp_iter_page
;
1518 rb_inc_page(cpu_buffer
, &tmp_iter_page
);
1520 /* update the counters */
1521 page_entries
= rb_page_entries(to_remove_page
);
1524 * If something was added to this page, it was full
1525 * since it is not the tail page. So we deduct the
1526 * bytes consumed in ring buffer from here.
1527 * Increment overrun to account for the lost events.
1529 local_add(page_entries
, &cpu_buffer
->overrun
);
1530 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1534 * We have already removed references to this list item, just
1535 * free up the buffer_page and its page
1537 free_buffer_page(to_remove_page
);
1540 } while (to_remove_page
!= last_page
);
1542 RB_WARN_ON(cpu_buffer
, nr_removed
);
1544 return nr_removed
== 0;
1548 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1550 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1551 int retries
, success
;
1553 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1555 * We are holding the reader lock, so the reader page won't be swapped
1556 * in the ring buffer. Now we are racing with the writer trying to
1557 * move head page and the tail page.
1558 * We are going to adapt the reader page update process where:
1559 * 1. We first splice the start and end of list of new pages between
1560 * the head page and its previous page.
1561 * 2. We cmpxchg the prev_page->next to point from head page to the
1562 * start of new pages list.
1563 * 3. Finally, we update the head->prev to the end of new list.
1565 * We will try this process 10 times, to make sure that we don't keep
1571 struct list_head
*head_page
, *prev_page
, *r
;
1572 struct list_head
*last_page
, *first_page
;
1573 struct list_head
*head_page_with_bit
;
1575 head_page
= &rb_set_head_page(cpu_buffer
)->list
;
1578 prev_page
= head_page
->prev
;
1580 first_page
= pages
->next
;
1581 last_page
= pages
->prev
;
1583 head_page_with_bit
= (struct list_head
*)
1584 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1586 last_page
->next
= head_page_with_bit
;
1587 first_page
->prev
= prev_page
;
1589 r
= cmpxchg(&prev_page
->next
, head_page_with_bit
, first_page
);
1591 if (r
== head_page_with_bit
) {
1593 * yay, we replaced the page pointer to our new list,
1594 * now, we just have to update to head page's prev
1595 * pointer to point to end of list
1597 head_page
->prev
= last_page
;
1604 INIT_LIST_HEAD(pages
);
1606 * If we weren't successful in adding in new pages, warn and stop
1609 RB_WARN_ON(cpu_buffer
, !success
);
1610 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1612 /* free pages if they weren't inserted */
1614 struct buffer_page
*bpage
, *tmp
;
1615 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1617 list_del_init(&bpage
->list
);
1618 free_buffer_page(bpage
);
1624 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1628 if (cpu_buffer
->nr_pages_to_update
> 0)
1629 success
= rb_insert_pages(cpu_buffer
);
1631 success
= rb_remove_pages(cpu_buffer
,
1632 -cpu_buffer
->nr_pages_to_update
);
1635 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1638 static void update_pages_handler(struct work_struct
*work
)
1640 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1641 struct ring_buffer_per_cpu
, update_pages_work
);
1642 rb_update_pages(cpu_buffer
);
1643 complete(&cpu_buffer
->update_done
);
1647 * ring_buffer_resize - resize the ring buffer
1648 * @buffer: the buffer to resize.
1649 * @size: the new size.
1650 * @cpu_id: the cpu buffer to resize
1652 * Minimum size is 2 * BUF_PAGE_SIZE.
1654 * Returns 0 on success and < 0 on failure.
1656 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
,
1659 struct ring_buffer_per_cpu
*cpu_buffer
;
1664 * Always succeed at resizing a non-existent buffer:
1669 /* Make sure the requested buffer exists */
1670 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1671 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1674 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1675 size
*= BUF_PAGE_SIZE
;
1677 /* we need a minimum of two pages */
1678 if (size
< BUF_PAGE_SIZE
* 2)
1679 size
= BUF_PAGE_SIZE
* 2;
1681 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1684 * Don't succeed if resizing is disabled, as a reader might be
1685 * manipulating the ring buffer and is expecting a sane state while
1688 if (atomic_read(&buffer
->resize_disabled
))
1691 /* prevent another thread from changing buffer sizes */
1692 mutex_lock(&buffer
->mutex
);
1694 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
1695 /* calculate the pages to update */
1696 for_each_buffer_cpu(buffer
, cpu
) {
1697 cpu_buffer
= buffer
->buffers
[cpu
];
1699 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1700 cpu_buffer
->nr_pages
;
1702 * nothing more to do for removing pages or no update
1704 if (cpu_buffer
->nr_pages_to_update
<= 0)
1707 * to add pages, make sure all new pages can be
1708 * allocated without receiving ENOMEM
1710 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1711 if (__rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1712 &cpu_buffer
->new_pages
, cpu
)) {
1713 /* not enough memory for new pages */
1721 * Fire off all the required work handlers
1722 * We can't schedule on offline CPUs, but it's not necessary
1723 * since we can change their buffer sizes without any race.
1725 for_each_buffer_cpu(buffer
, cpu
) {
1726 cpu_buffer
= buffer
->buffers
[cpu
];
1727 if (!cpu_buffer
->nr_pages_to_update
)
1730 /* Can't run something on an offline CPU. */
1731 if (!cpu_online(cpu
)) {
1732 rb_update_pages(cpu_buffer
);
1733 cpu_buffer
->nr_pages_to_update
= 0;
1735 schedule_work_on(cpu
,
1736 &cpu_buffer
->update_pages_work
);
1740 /* wait for all the updates to complete */
1741 for_each_buffer_cpu(buffer
, cpu
) {
1742 cpu_buffer
= buffer
->buffers
[cpu
];
1743 if (!cpu_buffer
->nr_pages_to_update
)
1746 if (cpu_online(cpu
))
1747 wait_for_completion(&cpu_buffer
->update_done
);
1748 cpu_buffer
->nr_pages_to_update
= 0;
1753 /* Make sure this CPU has been intitialized */
1754 if (!cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1757 cpu_buffer
= buffer
->buffers
[cpu_id
];
1759 if (nr_pages
== cpu_buffer
->nr_pages
)
1762 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1763 cpu_buffer
->nr_pages
;
1765 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1766 if (cpu_buffer
->nr_pages_to_update
> 0 &&
1767 __rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1768 &cpu_buffer
->new_pages
, cpu_id
)) {
1775 /* Can't run something on an offline CPU. */
1776 if (!cpu_online(cpu_id
))
1777 rb_update_pages(cpu_buffer
);
1779 schedule_work_on(cpu_id
,
1780 &cpu_buffer
->update_pages_work
);
1781 wait_for_completion(&cpu_buffer
->update_done
);
1784 cpu_buffer
->nr_pages_to_update
= 0;
1790 * The ring buffer resize can happen with the ring buffer
1791 * enabled, so that the update disturbs the tracing as little
1792 * as possible. But if the buffer is disabled, we do not need
1793 * to worry about that, and we can take the time to verify
1794 * that the buffer is not corrupt.
1796 if (atomic_read(&buffer
->record_disabled
)) {
1797 atomic_inc(&buffer
->record_disabled
);
1799 * Even though the buffer was disabled, we must make sure
1800 * that it is truly disabled before calling rb_check_pages.
1801 * There could have been a race between checking
1802 * record_disable and incrementing it.
1804 synchronize_sched();
1805 for_each_buffer_cpu(buffer
, cpu
) {
1806 cpu_buffer
= buffer
->buffers
[cpu
];
1807 rb_check_pages(cpu_buffer
);
1809 atomic_dec(&buffer
->record_disabled
);
1812 mutex_unlock(&buffer
->mutex
);
1816 for_each_buffer_cpu(buffer
, cpu
) {
1817 struct buffer_page
*bpage
, *tmp
;
1819 cpu_buffer
= buffer
->buffers
[cpu
];
1820 cpu_buffer
->nr_pages_to_update
= 0;
1822 if (list_empty(&cpu_buffer
->new_pages
))
1825 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1827 list_del_init(&bpage
->list
);
1828 free_buffer_page(bpage
);
1831 mutex_unlock(&buffer
->mutex
);
1834 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1836 void ring_buffer_change_overwrite(struct ring_buffer
*buffer
, int val
)
1838 mutex_lock(&buffer
->mutex
);
1840 buffer
->flags
|= RB_FL_OVERWRITE
;
1842 buffer
->flags
&= ~RB_FL_OVERWRITE
;
1843 mutex_unlock(&buffer
->mutex
);
1845 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
1847 static inline void *
1848 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
1850 return bpage
->data
+ index
;
1853 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1855 return bpage
->page
->data
+ index
;
1858 static inline struct ring_buffer_event
*
1859 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1861 return __rb_page_index(cpu_buffer
->reader_page
,
1862 cpu_buffer
->reader_page
->read
);
1865 static inline struct ring_buffer_event
*
1866 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1868 return __rb_page_index(iter
->head_page
, iter
->head
);
1871 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
1873 return local_read(&bpage
->page
->commit
);
1876 /* Size is determined by what has been committed */
1877 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
1879 return rb_page_commit(bpage
);
1882 static inline unsigned
1883 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1885 return rb_page_commit(cpu_buffer
->commit_page
);
1888 static inline unsigned
1889 rb_event_index(struct ring_buffer_event
*event
)
1891 unsigned long addr
= (unsigned long)event
;
1893 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1897 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1898 struct ring_buffer_event
*event
)
1900 unsigned long addr
= (unsigned long)event
;
1901 unsigned long index
;
1903 index
= rb_event_index(event
);
1906 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
1907 rb_commit_index(cpu_buffer
) == index
;
1911 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
1913 unsigned long max_count
;
1916 * We only race with interrupts and NMIs on this CPU.
1917 * If we own the commit event, then we can commit
1918 * all others that interrupted us, since the interruptions
1919 * are in stack format (they finish before they come
1920 * back to us). This allows us to do a simple loop to
1921 * assign the commit to the tail.
1924 max_count
= cpu_buffer
->nr_pages
* 100;
1926 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
1927 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
1929 if (RB_WARN_ON(cpu_buffer
,
1930 rb_is_reader_page(cpu_buffer
->tail_page
)))
1932 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1933 rb_page_write(cpu_buffer
->commit_page
));
1934 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
1935 cpu_buffer
->write_stamp
=
1936 cpu_buffer
->commit_page
->page
->time_stamp
;
1937 /* add barrier to keep gcc from optimizing too much */
1940 while (rb_commit_index(cpu_buffer
) !=
1941 rb_page_write(cpu_buffer
->commit_page
)) {
1943 local_set(&cpu_buffer
->commit_page
->page
->commit
,
1944 rb_page_write(cpu_buffer
->commit_page
));
1945 RB_WARN_ON(cpu_buffer
,
1946 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
1951 /* again, keep gcc from optimizing */
1955 * If an interrupt came in just after the first while loop
1956 * and pushed the tail page forward, we will be left with
1957 * a dangling commit that will never go forward.
1959 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
1963 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1965 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
1966 cpu_buffer
->reader_page
->read
= 0;
1969 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1971 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1974 * The iterator could be on the reader page (it starts there).
1975 * But the head could have moved, since the reader was
1976 * found. Check for this case and assign the iterator
1977 * to the head page instead of next.
1979 if (iter
->head_page
== cpu_buffer
->reader_page
)
1980 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1982 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1984 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1988 /* Slow path, do not inline */
1989 static noinline
struct ring_buffer_event
*
1990 rb_add_time_stamp(struct ring_buffer_event
*event
, u64 delta
)
1992 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
1994 /* Not the first event on the page? */
1995 if (rb_event_index(event
)) {
1996 event
->time_delta
= delta
& TS_MASK
;
1997 event
->array
[0] = delta
>> TS_SHIFT
;
1999 /* nope, just zero it */
2000 event
->time_delta
= 0;
2001 event
->array
[0] = 0;
2004 return skip_time_extend(event
);
2008 * rb_update_event - update event type and data
2009 * @event: the event to update
2010 * @type: the type of event
2011 * @length: the size of the event field in the ring buffer
2013 * Update the type and data fields of the event. The length
2014 * is the actual size that is written to the ring buffer,
2015 * and with this, we can determine what to place into the
2019 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2020 struct ring_buffer_event
*event
, unsigned length
,
2021 int add_timestamp
, u64 delta
)
2023 /* Only a commit updates the timestamp */
2024 if (unlikely(!rb_event_is_commit(cpu_buffer
, event
)))
2028 * If we need to add a timestamp, then we
2029 * add it to the start of the resevered space.
2031 if (unlikely(add_timestamp
)) {
2032 event
= rb_add_time_stamp(event
, delta
);
2033 length
-= RB_LEN_TIME_EXTEND
;
2037 event
->time_delta
= delta
;
2038 length
-= RB_EVNT_HDR_SIZE
;
2039 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
) {
2040 event
->type_len
= 0;
2041 event
->array
[0] = length
;
2043 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
2047 * rb_handle_head_page - writer hit the head page
2049 * Returns: +1 to retry page
2054 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
2055 struct buffer_page
*tail_page
,
2056 struct buffer_page
*next_page
)
2058 struct buffer_page
*new_head
;
2063 entries
= rb_page_entries(next_page
);
2066 * The hard part is here. We need to move the head
2067 * forward, and protect against both readers on
2068 * other CPUs and writers coming in via interrupts.
2070 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
2074 * type can be one of four:
2075 * NORMAL - an interrupt already moved it for us
2076 * HEAD - we are the first to get here.
2077 * UPDATE - we are the interrupt interrupting
2079 * MOVED - a reader on another CPU moved the next
2080 * pointer to its reader page. Give up
2087 * We changed the head to UPDATE, thus
2088 * it is our responsibility to update
2091 local_add(entries
, &cpu_buffer
->overrun
);
2092 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
2095 * The entries will be zeroed out when we move the
2099 /* still more to do */
2102 case RB_PAGE_UPDATE
:
2104 * This is an interrupt that interrupt the
2105 * previous update. Still more to do.
2108 case RB_PAGE_NORMAL
:
2110 * An interrupt came in before the update
2111 * and processed this for us.
2112 * Nothing left to do.
2117 * The reader is on another CPU and just did
2118 * a swap with our next_page.
2123 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
2128 * Now that we are here, the old head pointer is
2129 * set to UPDATE. This will keep the reader from
2130 * swapping the head page with the reader page.
2131 * The reader (on another CPU) will spin till
2134 * We just need to protect against interrupts
2135 * doing the job. We will set the next pointer
2136 * to HEAD. After that, we set the old pointer
2137 * to NORMAL, but only if it was HEAD before.
2138 * otherwise we are an interrupt, and only
2139 * want the outer most commit to reset it.
2141 new_head
= next_page
;
2142 rb_inc_page(cpu_buffer
, &new_head
);
2144 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
2148 * Valid returns are:
2149 * HEAD - an interrupt came in and already set it.
2150 * NORMAL - One of two things:
2151 * 1) We really set it.
2152 * 2) A bunch of interrupts came in and moved
2153 * the page forward again.
2157 case RB_PAGE_NORMAL
:
2161 RB_WARN_ON(cpu_buffer
, 1);
2166 * It is possible that an interrupt came in,
2167 * set the head up, then more interrupts came in
2168 * and moved it again. When we get back here,
2169 * the page would have been set to NORMAL but we
2170 * just set it back to HEAD.
2172 * How do you detect this? Well, if that happened
2173 * the tail page would have moved.
2175 if (ret
== RB_PAGE_NORMAL
) {
2177 * If the tail had moved passed next, then we need
2178 * to reset the pointer.
2180 if (cpu_buffer
->tail_page
!= tail_page
&&
2181 cpu_buffer
->tail_page
!= next_page
)
2182 rb_head_page_set_normal(cpu_buffer
, new_head
,
2188 * If this was the outer most commit (the one that
2189 * changed the original pointer from HEAD to UPDATE),
2190 * then it is up to us to reset it to NORMAL.
2192 if (type
== RB_PAGE_HEAD
) {
2193 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2196 if (RB_WARN_ON(cpu_buffer
,
2197 ret
!= RB_PAGE_UPDATE
))
2204 static unsigned rb_calculate_event_length(unsigned length
)
2206 struct ring_buffer_event event
; /* Used only for sizeof array */
2208 /* zero length can cause confusions */
2212 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
2213 length
+= sizeof(event
.array
[0]);
2215 length
+= RB_EVNT_HDR_SIZE
;
2216 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
2222 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2223 struct buffer_page
*tail_page
,
2224 unsigned long tail
, unsigned long length
)
2226 struct ring_buffer_event
*event
;
2229 * Only the event that crossed the page boundary
2230 * must fill the old tail_page with padding.
2232 if (tail
>= BUF_PAGE_SIZE
) {
2234 * If the page was filled, then we still need
2235 * to update the real_end. Reset it to zero
2236 * and the reader will ignore it.
2238 if (tail
== BUF_PAGE_SIZE
)
2239 tail_page
->real_end
= 0;
2241 local_sub(length
, &tail_page
->write
);
2245 event
= __rb_page_index(tail_page
, tail
);
2246 kmemcheck_annotate_bitfield(event
, bitfield
);
2248 /* account for padding bytes */
2249 local_add(BUF_PAGE_SIZE
- tail
, &cpu_buffer
->entries_bytes
);
2252 * Save the original length to the meta data.
2253 * This will be used by the reader to add lost event
2256 tail_page
->real_end
= tail
;
2259 * If this event is bigger than the minimum size, then
2260 * we need to be careful that we don't subtract the
2261 * write counter enough to allow another writer to slip
2263 * We put in a discarded commit instead, to make sure
2264 * that this space is not used again.
2266 * If we are less than the minimum size, we don't need to
2269 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
2270 /* No room for any events */
2272 /* Mark the rest of the page with padding */
2273 rb_event_set_padding(event
);
2275 /* Set the write back to the previous setting */
2276 local_sub(length
, &tail_page
->write
);
2280 /* Put in a discarded event */
2281 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
2282 event
->type_len
= RINGBUF_TYPE_PADDING
;
2283 /* time delta must be non zero */
2284 event
->time_delta
= 1;
2286 /* Set write to end of buffer */
2287 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
2288 local_sub(length
, &tail_page
->write
);
2292 * This is the slow path, force gcc not to inline it.
2294 static noinline
struct ring_buffer_event
*
2295 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2296 unsigned long length
, unsigned long tail
,
2297 struct buffer_page
*tail_page
, u64 ts
)
2299 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2300 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
2301 struct buffer_page
*next_page
;
2304 next_page
= tail_page
;
2306 rb_inc_page(cpu_buffer
, &next_page
);
2309 * If for some reason, we had an interrupt storm that made
2310 * it all the way around the buffer, bail, and warn
2313 if (unlikely(next_page
== commit_page
)) {
2314 local_inc(&cpu_buffer
->commit_overrun
);
2319 * This is where the fun begins!
2321 * We are fighting against races between a reader that
2322 * could be on another CPU trying to swap its reader
2323 * page with the buffer head.
2325 * We are also fighting against interrupts coming in and
2326 * moving the head or tail on us as well.
2328 * If the next page is the head page then we have filled
2329 * the buffer, unless the commit page is still on the
2332 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
2335 * If the commit is not on the reader page, then
2336 * move the header page.
2338 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2340 * If we are not in overwrite mode,
2341 * this is easy, just stop here.
2343 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2344 local_inc(&cpu_buffer
->dropped_events
);
2348 ret
= rb_handle_head_page(cpu_buffer
,
2357 * We need to be careful here too. The
2358 * commit page could still be on the reader
2359 * page. We could have a small buffer, and
2360 * have filled up the buffer with events
2361 * from interrupts and such, and wrapped.
2363 * Note, if the tail page is also the on the
2364 * reader_page, we let it move out.
2366 if (unlikely((cpu_buffer
->commit_page
!=
2367 cpu_buffer
->tail_page
) &&
2368 (cpu_buffer
->commit_page
==
2369 cpu_buffer
->reader_page
))) {
2370 local_inc(&cpu_buffer
->commit_overrun
);
2376 ret
= rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2379 * Nested commits always have zero deltas, so
2380 * just reread the time stamp
2382 ts
= rb_time_stamp(buffer
);
2383 next_page
->page
->time_stamp
= ts
;
2388 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
2390 /* fail and let the caller try again */
2391 return ERR_PTR(-EAGAIN
);
2395 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
2400 static struct ring_buffer_event
*
2401 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
2402 unsigned long length
, u64 ts
,
2403 u64 delta
, int add_timestamp
)
2405 struct buffer_page
*tail_page
;
2406 struct ring_buffer_event
*event
;
2407 unsigned long tail
, write
;
2410 * If the time delta since the last event is too big to
2411 * hold in the time field of the event, then we append a
2412 * TIME EXTEND event ahead of the data event.
2414 if (unlikely(add_timestamp
))
2415 length
+= RB_LEN_TIME_EXTEND
;
2417 tail_page
= cpu_buffer
->tail_page
;
2418 write
= local_add_return(length
, &tail_page
->write
);
2420 /* set write to only the index of the write */
2421 write
&= RB_WRITE_MASK
;
2422 tail
= write
- length
;
2425 * If this is the first commit on the page, then it has the same
2426 * timestamp as the page itself.
2431 /* See if we shot pass the end of this buffer page */
2432 if (unlikely(write
> BUF_PAGE_SIZE
))
2433 return rb_move_tail(cpu_buffer
, length
, tail
,
2436 /* We reserved something on the buffer */
2438 event
= __rb_page_index(tail_page
, tail
);
2439 kmemcheck_annotate_bitfield(event
, bitfield
);
2440 rb_update_event(cpu_buffer
, event
, length
, add_timestamp
, delta
);
2442 local_inc(&tail_page
->entries
);
2445 * If this is the first commit on the page, then update
2449 tail_page
->page
->time_stamp
= ts
;
2451 /* account for these added bytes */
2452 local_add(length
, &cpu_buffer
->entries_bytes
);
2458 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2459 struct ring_buffer_event
*event
)
2461 unsigned long new_index
, old_index
;
2462 struct buffer_page
*bpage
;
2463 unsigned long index
;
2466 new_index
= rb_event_index(event
);
2467 old_index
= new_index
+ rb_event_ts_length(event
);
2468 addr
= (unsigned long)event
;
2471 bpage
= cpu_buffer
->tail_page
;
2473 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2474 unsigned long write_mask
=
2475 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2476 unsigned long event_length
= rb_event_length(event
);
2478 * This is on the tail page. It is possible that
2479 * a write could come in and move the tail page
2480 * and write to the next page. That is fine
2481 * because we just shorten what is on this page.
2483 old_index
+= write_mask
;
2484 new_index
+= write_mask
;
2485 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2486 if (index
== old_index
) {
2487 /* update counters */
2488 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2493 /* could not discard */
2497 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2499 local_inc(&cpu_buffer
->committing
);
2500 local_inc(&cpu_buffer
->commits
);
2503 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2505 unsigned long commits
;
2507 if (RB_WARN_ON(cpu_buffer
,
2508 !local_read(&cpu_buffer
->committing
)))
2512 commits
= local_read(&cpu_buffer
->commits
);
2513 /* synchronize with interrupts */
2515 if (local_read(&cpu_buffer
->committing
) == 1)
2516 rb_set_commit_to_write(cpu_buffer
);
2518 local_dec(&cpu_buffer
->committing
);
2520 /* synchronize with interrupts */
2524 * Need to account for interrupts coming in between the
2525 * updating of the commit page and the clearing of the
2526 * committing counter.
2528 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2529 !local_read(&cpu_buffer
->committing
)) {
2530 local_inc(&cpu_buffer
->committing
);
2535 static struct ring_buffer_event
*
2536 rb_reserve_next_event(struct ring_buffer
*buffer
,
2537 struct ring_buffer_per_cpu
*cpu_buffer
,
2538 unsigned long length
)
2540 struct ring_buffer_event
*event
;
2546 rb_start_commit(cpu_buffer
);
2548 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2550 * Due to the ability to swap a cpu buffer from a buffer
2551 * it is possible it was swapped before we committed.
2552 * (committing stops a swap). We check for it here and
2553 * if it happened, we have to fail the write.
2556 if (unlikely(ACCESS_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2557 local_dec(&cpu_buffer
->committing
);
2558 local_dec(&cpu_buffer
->commits
);
2563 length
= rb_calculate_event_length(length
);
2569 * We allow for interrupts to reenter here and do a trace.
2570 * If one does, it will cause this original code to loop
2571 * back here. Even with heavy interrupts happening, this
2572 * should only happen a few times in a row. If this happens
2573 * 1000 times in a row, there must be either an interrupt
2574 * storm or we have something buggy.
2577 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2580 ts
= rb_time_stamp(cpu_buffer
->buffer
);
2581 diff
= ts
- cpu_buffer
->write_stamp
;
2583 /* make sure this diff is calculated here */
2586 /* Did the write stamp get updated already? */
2587 if (likely(ts
>= cpu_buffer
->write_stamp
)) {
2589 if (unlikely(test_time_stamp(delta
))) {
2590 int local_clock_stable
= 1;
2591 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2592 local_clock_stable
= sched_clock_stable();
2594 WARN_ONCE(delta
> (1ULL << 59),
2595 KERN_WARNING
"Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2596 (unsigned long long)delta
,
2597 (unsigned long long)ts
,
2598 (unsigned long long)cpu_buffer
->write_stamp
,
2599 local_clock_stable
? "" :
2600 "If you just came from a suspend/resume,\n"
2601 "please switch to the trace global clock:\n"
2602 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2607 event
= __rb_reserve_next(cpu_buffer
, length
, ts
,
2608 delta
, add_timestamp
);
2609 if (unlikely(PTR_ERR(event
) == -EAGAIN
))
2618 rb_end_commit(cpu_buffer
);
2622 #ifdef CONFIG_TRACING
2625 * The lock and unlock are done within a preempt disable section.
2626 * The current_context per_cpu variable can only be modified
2627 * by the current task between lock and unlock. But it can
2628 * be modified more than once via an interrupt. To pass this
2629 * information from the lock to the unlock without having to
2630 * access the 'in_interrupt()' functions again (which do show
2631 * a bit of overhead in something as critical as function tracing,
2632 * we use a bitmask trick.
2634 * bit 0 = NMI context
2635 * bit 1 = IRQ context
2636 * bit 2 = SoftIRQ context
2637 * bit 3 = normal context.
2639 * This works because this is the order of contexts that can
2640 * preempt other contexts. A SoftIRQ never preempts an IRQ
2643 * When the context is determined, the corresponding bit is
2644 * checked and set (if it was set, then a recursion of that context
2647 * On unlock, we need to clear this bit. To do so, just subtract
2648 * 1 from the current_context and AND it to itself.
2652 * 101 & 100 = 100 (clearing bit zero)
2655 * 1010 & 1001 = 1000 (clearing bit 1)
2657 * The least significant bit can be cleared this way, and it
2658 * just so happens that it is the same bit corresponding to
2659 * the current context.
2661 static DEFINE_PER_CPU(unsigned int, current_context
);
2663 static __always_inline
int trace_recursive_lock(void)
2665 unsigned int val
= this_cpu_read(current_context
);
2668 if (in_interrupt()) {
2678 if (unlikely(val
& (1 << bit
)))
2682 this_cpu_write(current_context
, val
);
2687 static __always_inline
void trace_recursive_unlock(void)
2689 unsigned int val
= this_cpu_read(current_context
);
2692 val
&= this_cpu_read(current_context
);
2693 this_cpu_write(current_context
, val
);
2698 #define trace_recursive_lock() (0)
2699 #define trace_recursive_unlock() do { } while (0)
2704 * ring_buffer_lock_reserve - reserve a part of the buffer
2705 * @buffer: the ring buffer to reserve from
2706 * @length: the length of the data to reserve (excluding event header)
2708 * Returns a reseverd event on the ring buffer to copy directly to.
2709 * The user of this interface will need to get the body to write into
2710 * and can use the ring_buffer_event_data() interface.
2712 * The length is the length of the data needed, not the event length
2713 * which also includes the event header.
2715 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2716 * If NULL is returned, then nothing has been allocated or locked.
2718 struct ring_buffer_event
*
2719 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2721 struct ring_buffer_per_cpu
*cpu_buffer
;
2722 struct ring_buffer_event
*event
;
2725 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2728 /* If we are tracing schedule, we don't want to recurse */
2729 preempt_disable_notrace();
2731 if (atomic_read(&buffer
->record_disabled
))
2734 if (trace_recursive_lock())
2737 cpu
= raw_smp_processor_id();
2739 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2742 cpu_buffer
= buffer
->buffers
[cpu
];
2744 if (atomic_read(&cpu_buffer
->record_disabled
))
2747 if (length
> BUF_MAX_DATA_SIZE
)
2750 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2757 trace_recursive_unlock();
2760 preempt_enable_notrace();
2763 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2766 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2767 struct ring_buffer_event
*event
)
2772 * The event first in the commit queue updates the
2775 if (rb_event_is_commit(cpu_buffer
, event
)) {
2777 * A commit event that is first on a page
2778 * updates the write timestamp with the page stamp
2780 if (!rb_event_index(event
))
2781 cpu_buffer
->write_stamp
=
2782 cpu_buffer
->commit_page
->page
->time_stamp
;
2783 else if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
2784 delta
= event
->array
[0];
2786 delta
+= event
->time_delta
;
2787 cpu_buffer
->write_stamp
+= delta
;
2789 cpu_buffer
->write_stamp
+= event
->time_delta
;
2793 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2794 struct ring_buffer_event
*event
)
2796 local_inc(&cpu_buffer
->entries
);
2797 rb_update_write_stamp(cpu_buffer
, event
);
2798 rb_end_commit(cpu_buffer
);
2801 static __always_inline
void
2802 rb_wakeups(struct ring_buffer
*buffer
, struct ring_buffer_per_cpu
*cpu_buffer
)
2804 if (buffer
->irq_work
.waiters_pending
) {
2805 buffer
->irq_work
.waiters_pending
= false;
2806 /* irq_work_queue() supplies it's own memory barriers */
2807 irq_work_queue(&buffer
->irq_work
.work
);
2810 if (cpu_buffer
->irq_work
.waiters_pending
) {
2811 cpu_buffer
->irq_work
.waiters_pending
= false;
2812 /* irq_work_queue() supplies it's own memory barriers */
2813 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2818 * ring_buffer_unlock_commit - commit a reserved
2819 * @buffer: The buffer to commit to
2820 * @event: The event pointer to commit.
2822 * This commits the data to the ring buffer, and releases any locks held.
2824 * Must be paired with ring_buffer_lock_reserve.
2826 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2827 struct ring_buffer_event
*event
)
2829 struct ring_buffer_per_cpu
*cpu_buffer
;
2830 int cpu
= raw_smp_processor_id();
2832 cpu_buffer
= buffer
->buffers
[cpu
];
2834 rb_commit(cpu_buffer
, event
);
2836 rb_wakeups(buffer
, cpu_buffer
);
2838 trace_recursive_unlock();
2840 preempt_enable_notrace();
2844 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2846 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2848 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
2849 event
= skip_time_extend(event
);
2851 /* array[0] holds the actual length for the discarded event */
2852 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2853 event
->type_len
= RINGBUF_TYPE_PADDING
;
2854 /* time delta must be non zero */
2855 if (!event
->time_delta
)
2856 event
->time_delta
= 1;
2860 * Decrement the entries to the page that an event is on.
2861 * The event does not even need to exist, only the pointer
2862 * to the page it is on. This may only be called before the commit
2866 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2867 struct ring_buffer_event
*event
)
2869 unsigned long addr
= (unsigned long)event
;
2870 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2871 struct buffer_page
*start
;
2875 /* Do the likely case first */
2876 if (likely(bpage
->page
== (void *)addr
)) {
2877 local_dec(&bpage
->entries
);
2882 * Because the commit page may be on the reader page we
2883 * start with the next page and check the end loop there.
2885 rb_inc_page(cpu_buffer
, &bpage
);
2888 if (bpage
->page
== (void *)addr
) {
2889 local_dec(&bpage
->entries
);
2892 rb_inc_page(cpu_buffer
, &bpage
);
2893 } while (bpage
!= start
);
2895 /* commit not part of this buffer?? */
2896 RB_WARN_ON(cpu_buffer
, 1);
2900 * ring_buffer_commit_discard - discard an event that has not been committed
2901 * @buffer: the ring buffer
2902 * @event: non committed event to discard
2904 * Sometimes an event that is in the ring buffer needs to be ignored.
2905 * This function lets the user discard an event in the ring buffer
2906 * and then that event will not be read later.
2908 * This function only works if it is called before the the item has been
2909 * committed. It will try to free the event from the ring buffer
2910 * if another event has not been added behind it.
2912 * If another event has been added behind it, it will set the event
2913 * up as discarded, and perform the commit.
2915 * If this function is called, do not call ring_buffer_unlock_commit on
2918 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2919 struct ring_buffer_event
*event
)
2921 struct ring_buffer_per_cpu
*cpu_buffer
;
2924 /* The event is discarded regardless */
2925 rb_event_discard(event
);
2927 cpu
= smp_processor_id();
2928 cpu_buffer
= buffer
->buffers
[cpu
];
2931 * This must only be called if the event has not been
2932 * committed yet. Thus we can assume that preemption
2933 * is still disabled.
2935 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2937 rb_decrement_entry(cpu_buffer
, event
);
2938 if (rb_try_to_discard(cpu_buffer
, event
))
2942 * The commit is still visible by the reader, so we
2943 * must still update the timestamp.
2945 rb_update_write_stamp(cpu_buffer
, event
);
2947 rb_end_commit(cpu_buffer
);
2949 trace_recursive_unlock();
2951 preempt_enable_notrace();
2954 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2957 * ring_buffer_write - write data to the buffer without reserving
2958 * @buffer: The ring buffer to write to.
2959 * @length: The length of the data being written (excluding the event header)
2960 * @data: The data to write to the buffer.
2962 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2963 * one function. If you already have the data to write to the buffer, it
2964 * may be easier to simply call this function.
2966 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2967 * and not the length of the event which would hold the header.
2969 int ring_buffer_write(struct ring_buffer
*buffer
,
2970 unsigned long length
,
2973 struct ring_buffer_per_cpu
*cpu_buffer
;
2974 struct ring_buffer_event
*event
;
2979 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2982 preempt_disable_notrace();
2984 if (atomic_read(&buffer
->record_disabled
))
2987 cpu
= raw_smp_processor_id();
2989 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2992 cpu_buffer
= buffer
->buffers
[cpu
];
2994 if (atomic_read(&cpu_buffer
->record_disabled
))
2997 if (length
> BUF_MAX_DATA_SIZE
)
3000 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
3004 body
= rb_event_data(event
);
3006 memcpy(body
, data
, length
);
3008 rb_commit(cpu_buffer
, event
);
3010 rb_wakeups(buffer
, cpu_buffer
);
3014 preempt_enable_notrace();
3018 EXPORT_SYMBOL_GPL(ring_buffer_write
);
3020 static int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
3022 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
3023 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
3024 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
3026 /* In case of error, head will be NULL */
3027 if (unlikely(!head
))
3030 return reader
->read
== rb_page_commit(reader
) &&
3031 (commit
== reader
||
3033 head
->read
== rb_page_commit(commit
)));
3037 * ring_buffer_record_disable - stop all writes into the buffer
3038 * @buffer: The ring buffer to stop writes to.
3040 * This prevents all writes to the buffer. Any attempt to write
3041 * to the buffer after this will fail and return NULL.
3043 * The caller should call synchronize_sched() after this.
3045 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
3047 atomic_inc(&buffer
->record_disabled
);
3049 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
3052 * ring_buffer_record_enable - enable writes to the buffer
3053 * @buffer: The ring buffer to enable writes
3055 * Note, multiple disables will need the same number of enables
3056 * to truly enable the writing (much like preempt_disable).
3058 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
3060 atomic_dec(&buffer
->record_disabled
);
3062 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
3065 * ring_buffer_record_off - stop all writes into the buffer
3066 * @buffer: The ring buffer to stop writes to.
3068 * This prevents all writes to the buffer. Any attempt to write
3069 * to the buffer after this will fail and return NULL.
3071 * This is different than ring_buffer_record_disable() as
3072 * it works like an on/off switch, where as the disable() version
3073 * must be paired with a enable().
3075 void ring_buffer_record_off(struct ring_buffer
*buffer
)
3078 unsigned int new_rd
;
3081 rd
= atomic_read(&buffer
->record_disabled
);
3082 new_rd
= rd
| RB_BUFFER_OFF
;
3083 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3085 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
3088 * ring_buffer_record_on - restart writes into the buffer
3089 * @buffer: The ring buffer to start writes to.
3091 * This enables all writes to the buffer that was disabled by
3092 * ring_buffer_record_off().
3094 * This is different than ring_buffer_record_enable() as
3095 * it works like an on/off switch, where as the enable() version
3096 * must be paired with a disable().
3098 void ring_buffer_record_on(struct ring_buffer
*buffer
)
3101 unsigned int new_rd
;
3104 rd
= atomic_read(&buffer
->record_disabled
);
3105 new_rd
= rd
& ~RB_BUFFER_OFF
;
3106 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3108 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
3111 * ring_buffer_record_is_on - return true if the ring buffer can write
3112 * @buffer: The ring buffer to see if write is enabled
3114 * Returns true if the ring buffer is in a state that it accepts writes.
3116 int ring_buffer_record_is_on(struct ring_buffer
*buffer
)
3118 return !atomic_read(&buffer
->record_disabled
);
3122 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3123 * @buffer: The ring buffer to stop writes to.
3124 * @cpu: The CPU buffer to stop
3126 * This prevents all writes to the buffer. Any attempt to write
3127 * to the buffer after this will fail and return NULL.
3129 * The caller should call synchronize_sched() after this.
3131 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
3133 struct ring_buffer_per_cpu
*cpu_buffer
;
3135 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3138 cpu_buffer
= buffer
->buffers
[cpu
];
3139 atomic_inc(&cpu_buffer
->record_disabled
);
3141 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
3144 * ring_buffer_record_enable_cpu - enable writes to the buffer
3145 * @buffer: The ring buffer to enable writes
3146 * @cpu: The CPU to enable.
3148 * Note, multiple disables will need the same number of enables
3149 * to truly enable the writing (much like preempt_disable).
3151 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
3153 struct ring_buffer_per_cpu
*cpu_buffer
;
3155 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3158 cpu_buffer
= buffer
->buffers
[cpu
];
3159 atomic_dec(&cpu_buffer
->record_disabled
);
3161 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
3164 * The total entries in the ring buffer is the running counter
3165 * of entries entered into the ring buffer, minus the sum of
3166 * the entries read from the ring buffer and the number of
3167 * entries that were overwritten.
3169 static inline unsigned long
3170 rb_num_of_entries(struct ring_buffer_per_cpu
*cpu_buffer
)
3172 return local_read(&cpu_buffer
->entries
) -
3173 (local_read(&cpu_buffer
->overrun
) + cpu_buffer
->read
);
3177 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3178 * @buffer: The ring buffer
3179 * @cpu: The per CPU buffer to read from.
3181 u64
ring_buffer_oldest_event_ts(struct ring_buffer
*buffer
, int cpu
)
3183 unsigned long flags
;
3184 struct ring_buffer_per_cpu
*cpu_buffer
;
3185 struct buffer_page
*bpage
;
3188 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3191 cpu_buffer
= buffer
->buffers
[cpu
];
3192 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3194 * if the tail is on reader_page, oldest time stamp is on the reader
3197 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
3198 bpage
= cpu_buffer
->reader_page
;
3200 bpage
= rb_set_head_page(cpu_buffer
);
3202 ret
= bpage
->page
->time_stamp
;
3203 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3207 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts
);
3210 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3211 * @buffer: The ring buffer
3212 * @cpu: The per CPU buffer to read from.
3214 unsigned long ring_buffer_bytes_cpu(struct ring_buffer
*buffer
, int cpu
)
3216 struct ring_buffer_per_cpu
*cpu_buffer
;
3219 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3222 cpu_buffer
= buffer
->buffers
[cpu
];
3223 ret
= local_read(&cpu_buffer
->entries_bytes
) - cpu_buffer
->read_bytes
;
3227 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu
);
3230 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3231 * @buffer: The ring buffer
3232 * @cpu: The per CPU buffer to get the entries from.
3234 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
3236 struct ring_buffer_per_cpu
*cpu_buffer
;
3238 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3241 cpu_buffer
= buffer
->buffers
[cpu
];
3243 return rb_num_of_entries(cpu_buffer
);
3245 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
3248 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3249 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3250 * @buffer: The ring buffer
3251 * @cpu: The per CPU buffer to get the number of overruns from
3253 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3255 struct ring_buffer_per_cpu
*cpu_buffer
;
3258 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3261 cpu_buffer
= buffer
->buffers
[cpu
];
3262 ret
= local_read(&cpu_buffer
->overrun
);
3266 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
3269 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3270 * commits failing due to the buffer wrapping around while there are uncommitted
3271 * events, such as during an interrupt storm.
3272 * @buffer: The ring buffer
3273 * @cpu: The per CPU buffer to get the number of overruns from
3276 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3278 struct ring_buffer_per_cpu
*cpu_buffer
;
3281 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3284 cpu_buffer
= buffer
->buffers
[cpu
];
3285 ret
= local_read(&cpu_buffer
->commit_overrun
);
3289 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
3292 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3293 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3294 * @buffer: The ring buffer
3295 * @cpu: The per CPU buffer to get the number of overruns from
3298 ring_buffer_dropped_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3300 struct ring_buffer_per_cpu
*cpu_buffer
;
3303 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3306 cpu_buffer
= buffer
->buffers
[cpu
];
3307 ret
= local_read(&cpu_buffer
->dropped_events
);
3311 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu
);
3314 * ring_buffer_read_events_cpu - get the number of events successfully read
3315 * @buffer: The ring buffer
3316 * @cpu: The per CPU buffer to get the number of events read
3319 ring_buffer_read_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3321 struct ring_buffer_per_cpu
*cpu_buffer
;
3323 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3326 cpu_buffer
= buffer
->buffers
[cpu
];
3327 return cpu_buffer
->read
;
3329 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu
);
3332 * ring_buffer_entries - get the number of entries in a buffer
3333 * @buffer: The ring buffer
3335 * Returns the total number of entries in the ring buffer
3338 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
3340 struct ring_buffer_per_cpu
*cpu_buffer
;
3341 unsigned long entries
= 0;
3344 /* if you care about this being correct, lock the buffer */
3345 for_each_buffer_cpu(buffer
, cpu
) {
3346 cpu_buffer
= buffer
->buffers
[cpu
];
3347 entries
+= rb_num_of_entries(cpu_buffer
);
3352 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
3355 * ring_buffer_overruns - get the number of overruns in buffer
3356 * @buffer: The ring buffer
3358 * Returns the total number of overruns in the ring buffer
3361 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
3363 struct ring_buffer_per_cpu
*cpu_buffer
;
3364 unsigned long overruns
= 0;
3367 /* if you care about this being correct, lock the buffer */
3368 for_each_buffer_cpu(buffer
, cpu
) {
3369 cpu_buffer
= buffer
->buffers
[cpu
];
3370 overruns
+= local_read(&cpu_buffer
->overrun
);
3375 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
3377 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
3379 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3381 /* Iterator usage is expected to have record disabled */
3382 iter
->head_page
= cpu_buffer
->reader_page
;
3383 iter
->head
= cpu_buffer
->reader_page
->read
;
3385 iter
->cache_reader_page
= iter
->head_page
;
3386 iter
->cache_read
= cpu_buffer
->read
;
3389 iter
->read_stamp
= cpu_buffer
->read_stamp
;
3391 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
3395 * ring_buffer_iter_reset - reset an iterator
3396 * @iter: The iterator to reset
3398 * Resets the iterator, so that it will start from the beginning
3401 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
3403 struct ring_buffer_per_cpu
*cpu_buffer
;
3404 unsigned long flags
;
3409 cpu_buffer
= iter
->cpu_buffer
;
3411 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3412 rb_iter_reset(iter
);
3413 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3415 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
3418 * ring_buffer_iter_empty - check if an iterator has no more to read
3419 * @iter: The iterator to check
3421 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
3423 struct ring_buffer_per_cpu
*cpu_buffer
;
3425 cpu_buffer
= iter
->cpu_buffer
;
3427 return iter
->head_page
== cpu_buffer
->commit_page
&&
3428 iter
->head
== rb_commit_index(cpu_buffer
);
3430 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
3433 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
3434 struct ring_buffer_event
*event
)
3438 switch (event
->type_len
) {
3439 case RINGBUF_TYPE_PADDING
:
3442 case RINGBUF_TYPE_TIME_EXTEND
:
3443 delta
= event
->array
[0];
3445 delta
+= event
->time_delta
;
3446 cpu_buffer
->read_stamp
+= delta
;
3449 case RINGBUF_TYPE_TIME_STAMP
:
3450 /* FIXME: not implemented */
3453 case RINGBUF_TYPE_DATA
:
3454 cpu_buffer
->read_stamp
+= event
->time_delta
;
3464 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
3465 struct ring_buffer_event
*event
)
3469 switch (event
->type_len
) {
3470 case RINGBUF_TYPE_PADDING
:
3473 case RINGBUF_TYPE_TIME_EXTEND
:
3474 delta
= event
->array
[0];
3476 delta
+= event
->time_delta
;
3477 iter
->read_stamp
+= delta
;
3480 case RINGBUF_TYPE_TIME_STAMP
:
3481 /* FIXME: not implemented */
3484 case RINGBUF_TYPE_DATA
:
3485 iter
->read_stamp
+= event
->time_delta
;
3494 static struct buffer_page
*
3495 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
3497 struct buffer_page
*reader
= NULL
;
3498 unsigned long overwrite
;
3499 unsigned long flags
;
3503 local_irq_save(flags
);
3504 arch_spin_lock(&cpu_buffer
->lock
);
3508 * This should normally only loop twice. But because the
3509 * start of the reader inserts an empty page, it causes
3510 * a case where we will loop three times. There should be no
3511 * reason to loop four times (that I know of).
3513 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
3518 reader
= cpu_buffer
->reader_page
;
3520 /* If there's more to read, return this page */
3521 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
3524 /* Never should we have an index greater than the size */
3525 if (RB_WARN_ON(cpu_buffer
,
3526 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
3529 /* check if we caught up to the tail */
3531 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
3534 /* Don't bother swapping if the ring buffer is empty */
3535 if (rb_num_of_entries(cpu_buffer
) == 0)
3539 * Reset the reader page to size zero.
3541 local_set(&cpu_buffer
->reader_page
->write
, 0);
3542 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3543 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3544 cpu_buffer
->reader_page
->real_end
= 0;
3548 * Splice the empty reader page into the list around the head.
3550 reader
= rb_set_head_page(cpu_buffer
);
3553 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
3554 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
3557 * cpu_buffer->pages just needs to point to the buffer, it
3558 * has no specific buffer page to point to. Lets move it out
3559 * of our way so we don't accidentally swap it.
3561 cpu_buffer
->pages
= reader
->list
.prev
;
3563 /* The reader page will be pointing to the new head */
3564 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
3567 * We want to make sure we read the overruns after we set up our
3568 * pointers to the next object. The writer side does a
3569 * cmpxchg to cross pages which acts as the mb on the writer
3570 * side. Note, the reader will constantly fail the swap
3571 * while the writer is updating the pointers, so this
3572 * guarantees that the overwrite recorded here is the one we
3573 * want to compare with the last_overrun.
3576 overwrite
= local_read(&(cpu_buffer
->overrun
));
3579 * Here's the tricky part.
3581 * We need to move the pointer past the header page.
3582 * But we can only do that if a writer is not currently
3583 * moving it. The page before the header page has the
3584 * flag bit '1' set if it is pointing to the page we want.
3585 * but if the writer is in the process of moving it
3586 * than it will be '2' or already moved '0'.
3589 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
3592 * If we did not convert it, then we must try again.
3598 * Yeah! We succeeded in replacing the page.
3600 * Now make the new head point back to the reader page.
3602 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
3603 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
3605 /* Finally update the reader page to the new head */
3606 cpu_buffer
->reader_page
= reader
;
3607 rb_reset_reader_page(cpu_buffer
);
3609 if (overwrite
!= cpu_buffer
->last_overrun
) {
3610 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
3611 cpu_buffer
->last_overrun
= overwrite
;
3617 arch_spin_unlock(&cpu_buffer
->lock
);
3618 local_irq_restore(flags
);
3623 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
3625 struct ring_buffer_event
*event
;
3626 struct buffer_page
*reader
;
3629 reader
= rb_get_reader_page(cpu_buffer
);
3631 /* This function should not be called when buffer is empty */
3632 if (RB_WARN_ON(cpu_buffer
, !reader
))
3635 event
= rb_reader_event(cpu_buffer
);
3637 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
3640 rb_update_read_stamp(cpu_buffer
, event
);
3642 length
= rb_event_length(event
);
3643 cpu_buffer
->reader_page
->read
+= length
;
3646 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
3648 struct ring_buffer_per_cpu
*cpu_buffer
;
3649 struct ring_buffer_event
*event
;
3652 cpu_buffer
= iter
->cpu_buffer
;
3655 * Check if we are at the end of the buffer.
3657 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3658 /* discarded commits can make the page empty */
3659 if (iter
->head_page
== cpu_buffer
->commit_page
)
3665 event
= rb_iter_head_event(iter
);
3667 length
= rb_event_length(event
);
3670 * This should not be called to advance the header if we are
3671 * at the tail of the buffer.
3673 if (RB_WARN_ON(cpu_buffer
,
3674 (iter
->head_page
== cpu_buffer
->commit_page
) &&
3675 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
3678 rb_update_iter_read_stamp(iter
, event
);
3680 iter
->head
+= length
;
3682 /* check for end of page padding */
3683 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3684 (iter
->head_page
!= cpu_buffer
->commit_page
))
3688 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
3690 return cpu_buffer
->lost_events
;
3693 static struct ring_buffer_event
*
3694 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
3695 unsigned long *lost_events
)
3697 struct ring_buffer_event
*event
;
3698 struct buffer_page
*reader
;
3703 * We repeat when a time extend is encountered.
3704 * Since the time extend is always attached to a data event,
3705 * we should never loop more than once.
3706 * (We never hit the following condition more than twice).
3708 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
3711 reader
= rb_get_reader_page(cpu_buffer
);
3715 event
= rb_reader_event(cpu_buffer
);
3717 switch (event
->type_len
) {
3718 case RINGBUF_TYPE_PADDING
:
3719 if (rb_null_event(event
))
3720 RB_WARN_ON(cpu_buffer
, 1);
3722 * Because the writer could be discarding every
3723 * event it creates (which would probably be bad)
3724 * if we were to go back to "again" then we may never
3725 * catch up, and will trigger the warn on, or lock
3726 * the box. Return the padding, and we will release
3727 * the current locks, and try again.
3731 case RINGBUF_TYPE_TIME_EXTEND
:
3732 /* Internal data, OK to advance */
3733 rb_advance_reader(cpu_buffer
);
3736 case RINGBUF_TYPE_TIME_STAMP
:
3737 /* FIXME: not implemented */
3738 rb_advance_reader(cpu_buffer
);
3741 case RINGBUF_TYPE_DATA
:
3743 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3744 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3745 cpu_buffer
->cpu
, ts
);
3748 *lost_events
= rb_lost_events(cpu_buffer
);
3757 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3759 static struct ring_buffer_event
*
3760 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3762 struct ring_buffer
*buffer
;
3763 struct ring_buffer_per_cpu
*cpu_buffer
;
3764 struct ring_buffer_event
*event
;
3767 cpu_buffer
= iter
->cpu_buffer
;
3768 buffer
= cpu_buffer
->buffer
;
3771 * Check if someone performed a consuming read to
3772 * the buffer. A consuming read invalidates the iterator
3773 * and we need to reset the iterator in this case.
3775 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3776 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3777 rb_iter_reset(iter
);
3780 if (ring_buffer_iter_empty(iter
))
3784 * We repeat when a time extend is encountered or we hit
3785 * the end of the page. Since the time extend is always attached
3786 * to a data event, we should never loop more than three times.
3787 * Once for going to next page, once on time extend, and
3788 * finally once to get the event.
3789 * (We never hit the following condition more than thrice).
3791 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3))
3794 if (rb_per_cpu_empty(cpu_buffer
))
3797 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3802 event
= rb_iter_head_event(iter
);
3804 switch (event
->type_len
) {
3805 case RINGBUF_TYPE_PADDING
:
3806 if (rb_null_event(event
)) {
3810 rb_advance_iter(iter
);
3813 case RINGBUF_TYPE_TIME_EXTEND
:
3814 /* Internal data, OK to advance */
3815 rb_advance_iter(iter
);
3818 case RINGBUF_TYPE_TIME_STAMP
:
3819 /* FIXME: not implemented */
3820 rb_advance_iter(iter
);
3823 case RINGBUF_TYPE_DATA
:
3825 *ts
= iter
->read_stamp
+ event
->time_delta
;
3826 ring_buffer_normalize_time_stamp(buffer
,
3827 cpu_buffer
->cpu
, ts
);
3837 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3839 static inline int rb_ok_to_lock(void)
3842 * If an NMI die dumps out the content of the ring buffer
3843 * do not grab locks. We also permanently disable the ring
3844 * buffer too. A one time deal is all you get from reading
3845 * the ring buffer from an NMI.
3847 if (likely(!in_nmi()))
3850 tracing_off_permanent();
3855 * ring_buffer_peek - peek at the next event to be read
3856 * @buffer: The ring buffer to read
3857 * @cpu: The cpu to peak at
3858 * @ts: The timestamp counter of this event.
3859 * @lost_events: a variable to store if events were lost (may be NULL)
3861 * This will return the event that will be read next, but does
3862 * not consume the data.
3864 struct ring_buffer_event
*
3865 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3866 unsigned long *lost_events
)
3868 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3869 struct ring_buffer_event
*event
;
3870 unsigned long flags
;
3873 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3876 dolock
= rb_ok_to_lock();
3878 local_irq_save(flags
);
3880 raw_spin_lock(&cpu_buffer
->reader_lock
);
3881 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3882 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3883 rb_advance_reader(cpu_buffer
);
3885 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3886 local_irq_restore(flags
);
3888 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3895 * ring_buffer_iter_peek - peek at the next event to be read
3896 * @iter: The ring buffer iterator
3897 * @ts: The timestamp counter of this event.
3899 * This will return the event that will be read next, but does
3900 * not increment the iterator.
3902 struct ring_buffer_event
*
3903 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3905 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3906 struct ring_buffer_event
*event
;
3907 unsigned long flags
;
3910 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3911 event
= rb_iter_peek(iter
, ts
);
3912 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3914 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3921 * ring_buffer_consume - return an event and consume it
3922 * @buffer: The ring buffer to get the next event from
3923 * @cpu: the cpu to read the buffer from
3924 * @ts: a variable to store the timestamp (may be NULL)
3925 * @lost_events: a variable to store if events were lost (may be NULL)
3927 * Returns the next event in the ring buffer, and that event is consumed.
3928 * Meaning, that sequential reads will keep returning a different event,
3929 * and eventually empty the ring buffer if the producer is slower.
3931 struct ring_buffer_event
*
3932 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3933 unsigned long *lost_events
)
3935 struct ring_buffer_per_cpu
*cpu_buffer
;
3936 struct ring_buffer_event
*event
= NULL
;
3937 unsigned long flags
;
3940 dolock
= rb_ok_to_lock();
3943 /* might be called in atomic */
3946 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3949 cpu_buffer
= buffer
->buffers
[cpu
];
3950 local_irq_save(flags
);
3952 raw_spin_lock(&cpu_buffer
->reader_lock
);
3954 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3956 cpu_buffer
->lost_events
= 0;
3957 rb_advance_reader(cpu_buffer
);
3961 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3962 local_irq_restore(flags
);
3967 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3972 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
3975 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3976 * @buffer: The ring buffer to read from
3977 * @cpu: The cpu buffer to iterate over
3979 * This performs the initial preparations necessary to iterate
3980 * through the buffer. Memory is allocated, buffer recording
3981 * is disabled, and the iterator pointer is returned to the caller.
3983 * Disabling buffer recordng prevents the reading from being
3984 * corrupted. This is not a consuming read, so a producer is not
3987 * After a sequence of ring_buffer_read_prepare calls, the user is
3988 * expected to make at least one call to ring_buffer_read_prepare_sync.
3989 * Afterwards, ring_buffer_read_start is invoked to get things going
3992 * This overall must be paired with ring_buffer_read_finish.
3994 struct ring_buffer_iter
*
3995 ring_buffer_read_prepare(struct ring_buffer
*buffer
, int cpu
)
3997 struct ring_buffer_per_cpu
*cpu_buffer
;
3998 struct ring_buffer_iter
*iter
;
4000 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4003 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
4007 cpu_buffer
= buffer
->buffers
[cpu
];
4009 iter
->cpu_buffer
= cpu_buffer
;
4011 atomic_inc(&buffer
->resize_disabled
);
4012 atomic_inc(&cpu_buffer
->record_disabled
);
4016 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
4019 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4021 * All previously invoked ring_buffer_read_prepare calls to prepare
4022 * iterators will be synchronized. Afterwards, read_buffer_read_start
4023 * calls on those iterators are allowed.
4026 ring_buffer_read_prepare_sync(void)
4028 synchronize_sched();
4030 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
4033 * ring_buffer_read_start - start a non consuming read of the buffer
4034 * @iter: The iterator returned by ring_buffer_read_prepare
4036 * This finalizes the startup of an iteration through the buffer.
4037 * The iterator comes from a call to ring_buffer_read_prepare and
4038 * an intervening ring_buffer_read_prepare_sync must have been
4041 * Must be paired with ring_buffer_read_finish.
4044 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
4046 struct ring_buffer_per_cpu
*cpu_buffer
;
4047 unsigned long flags
;
4052 cpu_buffer
= iter
->cpu_buffer
;
4054 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4055 arch_spin_lock(&cpu_buffer
->lock
);
4056 rb_iter_reset(iter
);
4057 arch_spin_unlock(&cpu_buffer
->lock
);
4058 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4060 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
4063 * ring_buffer_read_finish - finish reading the iterator of the buffer
4064 * @iter: The iterator retrieved by ring_buffer_start
4066 * This re-enables the recording to the buffer, and frees the
4070 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
4072 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4073 unsigned long flags
;
4076 * Ring buffer is disabled from recording, here's a good place
4077 * to check the integrity of the ring buffer.
4078 * Must prevent readers from trying to read, as the check
4079 * clears the HEAD page and readers require it.
4081 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4082 rb_check_pages(cpu_buffer
);
4083 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4085 atomic_dec(&cpu_buffer
->record_disabled
);
4086 atomic_dec(&cpu_buffer
->buffer
->resize_disabled
);
4089 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
4092 * ring_buffer_read - read the next item in the ring buffer by the iterator
4093 * @iter: The ring buffer iterator
4094 * @ts: The time stamp of the event read.
4096 * This reads the next event in the ring buffer and increments the iterator.
4098 struct ring_buffer_event
*
4099 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
4101 struct ring_buffer_event
*event
;
4102 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4103 unsigned long flags
;
4105 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4107 event
= rb_iter_peek(iter
, ts
);
4111 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
4114 rb_advance_iter(iter
);
4116 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4120 EXPORT_SYMBOL_GPL(ring_buffer_read
);
4123 * ring_buffer_size - return the size of the ring buffer (in bytes)
4124 * @buffer: The ring buffer.
4126 unsigned long ring_buffer_size(struct ring_buffer
*buffer
, int cpu
)
4129 * Earlier, this method returned
4130 * BUF_PAGE_SIZE * buffer->nr_pages
4131 * Since the nr_pages field is now removed, we have converted this to
4132 * return the per cpu buffer value.
4134 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4137 return BUF_PAGE_SIZE
* buffer
->buffers
[cpu
]->nr_pages
;
4139 EXPORT_SYMBOL_GPL(ring_buffer_size
);
4142 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
4144 rb_head_page_deactivate(cpu_buffer
);
4146 cpu_buffer
->head_page
4147 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
4148 local_set(&cpu_buffer
->head_page
->write
, 0);
4149 local_set(&cpu_buffer
->head_page
->entries
, 0);
4150 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
4152 cpu_buffer
->head_page
->read
= 0;
4154 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
4155 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
4157 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
4158 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
4159 local_set(&cpu_buffer
->reader_page
->write
, 0);
4160 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4161 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4162 cpu_buffer
->reader_page
->read
= 0;
4164 local_set(&cpu_buffer
->entries_bytes
, 0);
4165 local_set(&cpu_buffer
->overrun
, 0);
4166 local_set(&cpu_buffer
->commit_overrun
, 0);
4167 local_set(&cpu_buffer
->dropped_events
, 0);
4168 local_set(&cpu_buffer
->entries
, 0);
4169 local_set(&cpu_buffer
->committing
, 0);
4170 local_set(&cpu_buffer
->commits
, 0);
4171 cpu_buffer
->read
= 0;
4172 cpu_buffer
->read_bytes
= 0;
4174 cpu_buffer
->write_stamp
= 0;
4175 cpu_buffer
->read_stamp
= 0;
4177 cpu_buffer
->lost_events
= 0;
4178 cpu_buffer
->last_overrun
= 0;
4180 rb_head_page_activate(cpu_buffer
);
4184 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4185 * @buffer: The ring buffer to reset a per cpu buffer of
4186 * @cpu: The CPU buffer to be reset
4188 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
4190 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4191 unsigned long flags
;
4193 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4196 atomic_inc(&buffer
->resize_disabled
);
4197 atomic_inc(&cpu_buffer
->record_disabled
);
4199 /* Make sure all commits have finished */
4200 synchronize_sched();
4202 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4204 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
4207 arch_spin_lock(&cpu_buffer
->lock
);
4209 rb_reset_cpu(cpu_buffer
);
4211 arch_spin_unlock(&cpu_buffer
->lock
);
4214 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4216 atomic_dec(&cpu_buffer
->record_disabled
);
4217 atomic_dec(&buffer
->resize_disabled
);
4219 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
4222 * ring_buffer_reset - reset a ring buffer
4223 * @buffer: The ring buffer to reset all cpu buffers
4225 void ring_buffer_reset(struct ring_buffer
*buffer
)
4229 for_each_buffer_cpu(buffer
, cpu
)
4230 ring_buffer_reset_cpu(buffer
, cpu
);
4232 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
4235 * rind_buffer_empty - is the ring buffer empty?
4236 * @buffer: The ring buffer to test
4238 int ring_buffer_empty(struct ring_buffer
*buffer
)
4240 struct ring_buffer_per_cpu
*cpu_buffer
;
4241 unsigned long flags
;
4246 dolock
= rb_ok_to_lock();
4248 /* yes this is racy, but if you don't like the race, lock the buffer */
4249 for_each_buffer_cpu(buffer
, cpu
) {
4250 cpu_buffer
= buffer
->buffers
[cpu
];
4251 local_irq_save(flags
);
4253 raw_spin_lock(&cpu_buffer
->reader_lock
);
4254 ret
= rb_per_cpu_empty(cpu_buffer
);
4256 raw_spin_unlock(&cpu_buffer
->reader_lock
);
4257 local_irq_restore(flags
);
4265 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
4268 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4269 * @buffer: The ring buffer
4270 * @cpu: The CPU buffer to test
4272 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
4274 struct ring_buffer_per_cpu
*cpu_buffer
;
4275 unsigned long flags
;
4279 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4282 dolock
= rb_ok_to_lock();
4284 cpu_buffer
= buffer
->buffers
[cpu
];
4285 local_irq_save(flags
);
4287 raw_spin_lock(&cpu_buffer
->reader_lock
);
4288 ret
= rb_per_cpu_empty(cpu_buffer
);
4290 raw_spin_unlock(&cpu_buffer
->reader_lock
);
4291 local_irq_restore(flags
);
4295 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
4297 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4299 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4300 * @buffer_a: One buffer to swap with
4301 * @buffer_b: The other buffer to swap with
4303 * This function is useful for tracers that want to take a "snapshot"
4304 * of a CPU buffer and has another back up buffer lying around.
4305 * it is expected that the tracer handles the cpu buffer not being
4306 * used at the moment.
4308 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
4309 struct ring_buffer
*buffer_b
, int cpu
)
4311 struct ring_buffer_per_cpu
*cpu_buffer_a
;
4312 struct ring_buffer_per_cpu
*cpu_buffer_b
;
4315 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
4316 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
4319 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
4320 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
4322 /* At least make sure the two buffers are somewhat the same */
4323 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
4328 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
4331 if (atomic_read(&buffer_a
->record_disabled
))
4334 if (atomic_read(&buffer_b
->record_disabled
))
4337 if (atomic_read(&cpu_buffer_a
->record_disabled
))
4340 if (atomic_read(&cpu_buffer_b
->record_disabled
))
4344 * We can't do a synchronize_sched here because this
4345 * function can be called in atomic context.
4346 * Normally this will be called from the same CPU as cpu.
4347 * If not it's up to the caller to protect this.
4349 atomic_inc(&cpu_buffer_a
->record_disabled
);
4350 atomic_inc(&cpu_buffer_b
->record_disabled
);
4353 if (local_read(&cpu_buffer_a
->committing
))
4355 if (local_read(&cpu_buffer_b
->committing
))
4358 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
4359 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
4361 cpu_buffer_b
->buffer
= buffer_a
;
4362 cpu_buffer_a
->buffer
= buffer_b
;
4367 atomic_dec(&cpu_buffer_a
->record_disabled
);
4368 atomic_dec(&cpu_buffer_b
->record_disabled
);
4372 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
4373 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4376 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4377 * @buffer: the buffer to allocate for.
4378 * @cpu: the cpu buffer to allocate.
4380 * This function is used in conjunction with ring_buffer_read_page.
4381 * When reading a full page from the ring buffer, these functions
4382 * can be used to speed up the process. The calling function should
4383 * allocate a few pages first with this function. Then when it
4384 * needs to get pages from the ring buffer, it passes the result
4385 * of this function into ring_buffer_read_page, which will swap
4386 * the page that was allocated, with the read page of the buffer.
4389 * The page allocated, or NULL on error.
4391 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
, int cpu
)
4393 struct buffer_data_page
*bpage
;
4396 page
= alloc_pages_node(cpu_to_node(cpu
),
4397 GFP_KERNEL
| __GFP_NORETRY
, 0);
4401 bpage
= page_address(page
);
4403 rb_init_page(bpage
);
4407 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
4410 * ring_buffer_free_read_page - free an allocated read page
4411 * @buffer: the buffer the page was allocate for
4412 * @data: the page to free
4414 * Free a page allocated from ring_buffer_alloc_read_page.
4416 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
4418 free_page((unsigned long)data
);
4420 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
4423 * ring_buffer_read_page - extract a page from the ring buffer
4424 * @buffer: buffer to extract from
4425 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4426 * @len: amount to extract
4427 * @cpu: the cpu of the buffer to extract
4428 * @full: should the extraction only happen when the page is full.
4430 * This function will pull out a page from the ring buffer and consume it.
4431 * @data_page must be the address of the variable that was returned
4432 * from ring_buffer_alloc_read_page. This is because the page might be used
4433 * to swap with a page in the ring buffer.
4436 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4439 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4441 * process_page(rpage, ret);
4443 * When @full is set, the function will not return true unless
4444 * the writer is off the reader page.
4446 * Note: it is up to the calling functions to handle sleeps and wakeups.
4447 * The ring buffer can be used anywhere in the kernel and can not
4448 * blindly call wake_up. The layer that uses the ring buffer must be
4449 * responsible for that.
4452 * >=0 if data has been transferred, returns the offset of consumed data.
4453 * <0 if no data has been transferred.
4455 int ring_buffer_read_page(struct ring_buffer
*buffer
,
4456 void **data_page
, size_t len
, int cpu
, int full
)
4458 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4459 struct ring_buffer_event
*event
;
4460 struct buffer_data_page
*bpage
;
4461 struct buffer_page
*reader
;
4462 unsigned long missed_events
;
4463 unsigned long flags
;
4464 unsigned int commit
;
4469 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4473 * If len is not big enough to hold the page header, then
4474 * we can not copy anything.
4476 if (len
<= BUF_PAGE_HDR_SIZE
)
4479 len
-= BUF_PAGE_HDR_SIZE
;
4488 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4490 reader
= rb_get_reader_page(cpu_buffer
);
4494 event
= rb_reader_event(cpu_buffer
);
4496 read
= reader
->read
;
4497 commit
= rb_page_commit(reader
);
4499 /* Check if any events were dropped */
4500 missed_events
= cpu_buffer
->lost_events
;
4503 * If this page has been partially read or
4504 * if len is not big enough to read the rest of the page or
4505 * a writer is still on the page, then
4506 * we must copy the data from the page to the buffer.
4507 * Otherwise, we can simply swap the page with the one passed in.
4509 if (read
|| (len
< (commit
- read
)) ||
4510 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
4511 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
4512 unsigned int rpos
= read
;
4513 unsigned int pos
= 0;
4519 if (len
> (commit
- read
))
4520 len
= (commit
- read
);
4522 /* Always keep the time extend and data together */
4523 size
= rb_event_ts_length(event
);
4528 /* save the current timestamp, since the user will need it */
4529 save_timestamp
= cpu_buffer
->read_stamp
;
4531 /* Need to copy one event at a time */
4533 /* We need the size of one event, because
4534 * rb_advance_reader only advances by one event,
4535 * whereas rb_event_ts_length may include the size of
4536 * one or two events.
4537 * We have already ensured there's enough space if this
4538 * is a time extend. */
4539 size
= rb_event_length(event
);
4540 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
4544 rb_advance_reader(cpu_buffer
);
4545 rpos
= reader
->read
;
4551 event
= rb_reader_event(cpu_buffer
);
4552 /* Always keep the time extend and data together */
4553 size
= rb_event_ts_length(event
);
4554 } while (len
>= size
);
4557 local_set(&bpage
->commit
, pos
);
4558 bpage
->time_stamp
= save_timestamp
;
4560 /* we copied everything to the beginning */
4563 /* update the entry counter */
4564 cpu_buffer
->read
+= rb_page_entries(reader
);
4565 cpu_buffer
->read_bytes
+= BUF_PAGE_SIZE
;
4567 /* swap the pages */
4568 rb_init_page(bpage
);
4569 bpage
= reader
->page
;
4570 reader
->page
= *data_page
;
4571 local_set(&reader
->write
, 0);
4572 local_set(&reader
->entries
, 0);
4577 * Use the real_end for the data size,
4578 * This gives us a chance to store the lost events
4581 if (reader
->real_end
)
4582 local_set(&bpage
->commit
, reader
->real_end
);
4586 cpu_buffer
->lost_events
= 0;
4588 commit
= local_read(&bpage
->commit
);
4590 * Set a flag in the commit field if we lost events
4592 if (missed_events
) {
4593 /* If there is room at the end of the page to save the
4594 * missed events, then record it there.
4596 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
4597 memcpy(&bpage
->data
[commit
], &missed_events
,
4598 sizeof(missed_events
));
4599 local_add(RB_MISSED_STORED
, &bpage
->commit
);
4600 commit
+= sizeof(missed_events
);
4602 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
4606 * This page may be off to user land. Zero it out here.
4608 if (commit
< BUF_PAGE_SIZE
)
4609 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
4612 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4617 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
4619 #ifdef CONFIG_HOTPLUG_CPU
4620 static int rb_cpu_notify(struct notifier_block
*self
,
4621 unsigned long action
, void *hcpu
)
4623 struct ring_buffer
*buffer
=
4624 container_of(self
, struct ring_buffer
, cpu_notify
);
4625 long cpu
= (long)hcpu
;
4626 int cpu_i
, nr_pages_same
;
4627 unsigned int nr_pages
;
4630 case CPU_UP_PREPARE
:
4631 case CPU_UP_PREPARE_FROZEN
:
4632 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
4637 /* check if all cpu sizes are same */
4638 for_each_buffer_cpu(buffer
, cpu_i
) {
4639 /* fill in the size from first enabled cpu */
4641 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
4642 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
4647 /* allocate minimum pages, user can later expand it */
4650 buffer
->buffers
[cpu
] =
4651 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
4652 if (!buffer
->buffers
[cpu
]) {
4653 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4658 cpumask_set_cpu(cpu
, buffer
->cpumask
);
4660 case CPU_DOWN_PREPARE
:
4661 case CPU_DOWN_PREPARE_FROZEN
:
4664 * If we were to free the buffer, then the user would
4665 * lose any trace that was in the buffer.
4675 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4677 * This is a basic integrity check of the ring buffer.
4678 * Late in the boot cycle this test will run when configured in.
4679 * It will kick off a thread per CPU that will go into a loop
4680 * writing to the per cpu ring buffer various sizes of data.
4681 * Some of the data will be large items, some small.
4683 * Another thread is created that goes into a spin, sending out
4684 * IPIs to the other CPUs to also write into the ring buffer.
4685 * this is to test the nesting ability of the buffer.
4687 * Basic stats are recorded and reported. If something in the
4688 * ring buffer should happen that's not expected, a big warning
4689 * is displayed and all ring buffers are disabled.
4691 static struct task_struct
*rb_threads
[NR_CPUS
] __initdata
;
4693 struct rb_test_data
{
4694 struct ring_buffer
*buffer
;
4695 unsigned long events
;
4696 unsigned long bytes_written
;
4697 unsigned long bytes_alloc
;
4698 unsigned long bytes_dropped
;
4699 unsigned long events_nested
;
4700 unsigned long bytes_written_nested
;
4701 unsigned long bytes_alloc_nested
;
4702 unsigned long bytes_dropped_nested
;
4703 int min_size_nested
;
4704 int max_size_nested
;
4711 static struct rb_test_data rb_data
[NR_CPUS
] __initdata
;
4714 #define RB_TEST_BUFFER_SIZE 1048576
4716 static char rb_string
[] __initdata
=
4717 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4718 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4719 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4721 static bool rb_test_started __initdata
;
4728 static __init
int rb_write_something(struct rb_test_data
*data
, bool nested
)
4730 struct ring_buffer_event
*event
;
4731 struct rb_item
*item
;
4738 /* Have nested writes different that what is written */
4739 cnt
= data
->cnt
+ (nested
? 27 : 0);
4741 /* Multiply cnt by ~e, to make some unique increment */
4742 size
= (data
->cnt
* 68 / 25) % (sizeof(rb_string
) - 1);
4744 len
= size
+ sizeof(struct rb_item
);
4746 started
= rb_test_started
;
4747 /* read rb_test_started before checking buffer enabled */
4750 event
= ring_buffer_lock_reserve(data
->buffer
, len
);
4752 /* Ignore dropped events before test starts. */
4755 data
->bytes_dropped
+= len
;
4757 data
->bytes_dropped_nested
+= len
;
4762 event_len
= ring_buffer_event_length(event
);
4764 if (RB_WARN_ON(data
->buffer
, event_len
< len
))
4767 item
= ring_buffer_event_data(event
);
4769 memcpy(item
->str
, rb_string
, size
);
4772 data
->bytes_alloc_nested
+= event_len
;
4773 data
->bytes_written_nested
+= len
;
4774 data
->events_nested
++;
4775 if (!data
->min_size_nested
|| len
< data
->min_size_nested
)
4776 data
->min_size_nested
= len
;
4777 if (len
> data
->max_size_nested
)
4778 data
->max_size_nested
= len
;
4780 data
->bytes_alloc
+= event_len
;
4781 data
->bytes_written
+= len
;
4783 if (!data
->min_size
|| len
< data
->min_size
)
4784 data
->max_size
= len
;
4785 if (len
> data
->max_size
)
4786 data
->max_size
= len
;
4790 ring_buffer_unlock_commit(data
->buffer
, event
);
4795 static __init
int rb_test(void *arg
)
4797 struct rb_test_data
*data
= arg
;
4799 while (!kthread_should_stop()) {
4800 rb_write_something(data
, false);
4803 set_current_state(TASK_INTERRUPTIBLE
);
4804 /* Now sleep between a min of 100-300us and a max of 1ms */
4805 usleep_range(((data
->cnt
% 3) + 1) * 100, 1000);
4811 static __init
void rb_ipi(void *ignore
)
4813 struct rb_test_data
*data
;
4814 int cpu
= smp_processor_id();
4816 data
= &rb_data
[cpu
];
4817 rb_write_something(data
, true);
4820 static __init
int rb_hammer_test(void *arg
)
4822 while (!kthread_should_stop()) {
4824 /* Send an IPI to all cpus to write data! */
4825 smp_call_function(rb_ipi
, NULL
, 1);
4826 /* No sleep, but for non preempt, let others run */
4833 static __init
int test_ringbuffer(void)
4835 struct task_struct
*rb_hammer
;
4836 struct ring_buffer
*buffer
;
4840 pr_info("Running ring buffer tests...\n");
4842 buffer
= ring_buffer_alloc(RB_TEST_BUFFER_SIZE
, RB_FL_OVERWRITE
);
4843 if (WARN_ON(!buffer
))
4846 /* Disable buffer so that threads can't write to it yet */
4847 ring_buffer_record_off(buffer
);
4849 for_each_online_cpu(cpu
) {
4850 rb_data
[cpu
].buffer
= buffer
;
4851 rb_data
[cpu
].cpu
= cpu
;
4852 rb_data
[cpu
].cnt
= cpu
;
4853 rb_threads
[cpu
] = kthread_create(rb_test
, &rb_data
[cpu
],
4854 "rbtester/%d", cpu
);
4855 if (WARN_ON(!rb_threads
[cpu
])) {
4856 pr_cont("FAILED\n");
4861 kthread_bind(rb_threads
[cpu
], cpu
);
4862 wake_up_process(rb_threads
[cpu
]);
4865 /* Now create the rb hammer! */
4866 rb_hammer
= kthread_run(rb_hammer_test
, NULL
, "rbhammer");
4867 if (WARN_ON(!rb_hammer
)) {
4868 pr_cont("FAILED\n");
4873 ring_buffer_record_on(buffer
);
4875 * Show buffer is enabled before setting rb_test_started.
4876 * Yes there's a small race window where events could be
4877 * dropped and the thread wont catch it. But when a ring
4878 * buffer gets enabled, there will always be some kind of
4879 * delay before other CPUs see it. Thus, we don't care about
4880 * those dropped events. We care about events dropped after
4881 * the threads see that the buffer is active.
4884 rb_test_started
= true;
4886 set_current_state(TASK_INTERRUPTIBLE
);
4887 /* Just run for 10 seconds */;
4888 schedule_timeout(10 * HZ
);
4890 kthread_stop(rb_hammer
);
4893 for_each_online_cpu(cpu
) {
4894 if (!rb_threads
[cpu
])
4896 kthread_stop(rb_threads
[cpu
]);
4899 ring_buffer_free(buffer
);
4904 pr_info("finished\n");
4905 for_each_online_cpu(cpu
) {
4906 struct ring_buffer_event
*event
;
4907 struct rb_test_data
*data
= &rb_data
[cpu
];
4908 struct rb_item
*item
;
4909 unsigned long total_events
;
4910 unsigned long total_dropped
;
4911 unsigned long total_written
;
4912 unsigned long total_alloc
;
4913 unsigned long total_read
= 0;
4914 unsigned long total_size
= 0;
4915 unsigned long total_len
= 0;
4916 unsigned long total_lost
= 0;
4919 int small_event_size
;
4923 total_events
= data
->events
+ data
->events_nested
;
4924 total_written
= data
->bytes_written
+ data
->bytes_written_nested
;
4925 total_alloc
= data
->bytes_alloc
+ data
->bytes_alloc_nested
;
4926 total_dropped
= data
->bytes_dropped
+ data
->bytes_dropped_nested
;
4928 big_event_size
= data
->max_size
+ data
->max_size_nested
;
4929 small_event_size
= data
->min_size
+ data
->min_size_nested
;
4931 pr_info("CPU %d:\n", cpu
);
4932 pr_info(" events: %ld\n", total_events
);
4933 pr_info(" dropped bytes: %ld\n", total_dropped
);
4934 pr_info(" alloced bytes: %ld\n", total_alloc
);
4935 pr_info(" written bytes: %ld\n", total_written
);
4936 pr_info(" biggest event: %d\n", big_event_size
);
4937 pr_info(" smallest event: %d\n", small_event_size
);
4939 if (RB_WARN_ON(buffer
, total_dropped
))
4944 while ((event
= ring_buffer_consume(buffer
, cpu
, NULL
, &lost
))) {
4946 item
= ring_buffer_event_data(event
);
4947 total_len
+= ring_buffer_event_length(event
);
4948 total_size
+= item
->size
+ sizeof(struct rb_item
);
4949 if (memcmp(&item
->str
[0], rb_string
, item
->size
) != 0) {
4950 pr_info("FAILED!\n");
4951 pr_info("buffer had: %.*s\n", item
->size
, item
->str
);
4952 pr_info("expected: %.*s\n", item
->size
, rb_string
);
4953 RB_WARN_ON(buffer
, 1);
4964 pr_info(" read events: %ld\n", total_read
);
4965 pr_info(" lost events: %ld\n", total_lost
);
4966 pr_info(" total events: %ld\n", total_lost
+ total_read
);
4967 pr_info(" recorded len bytes: %ld\n", total_len
);
4968 pr_info(" recorded size bytes: %ld\n", total_size
);
4970 pr_info(" With dropped events, record len and size may not match\n"
4971 " alloced and written from above\n");
4973 if (RB_WARN_ON(buffer
, total_len
!= total_alloc
||
4974 total_size
!= total_written
))
4977 if (RB_WARN_ON(buffer
, total_lost
+ total_read
!= total_events
))
4983 pr_info("Ring buffer PASSED!\n");
4985 ring_buffer_free(buffer
);
4989 late_initcall(test_ringbuffer
);
4990 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */