4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 #include <linux/trace_events.h>
7 #include <linux/ring_buffer.h>
8 #include <linux/trace_clock.h>
9 #include <linux/sched/clock.h>
10 #include <linux/trace_seq.h>
11 #include <linux/spinlock.h>
12 #include <linux/irq_work.h>
13 #include <linux/uaccess.h>
14 #include <linux/hardirq.h>
15 #include <linux/kthread.h> /* for self test */
16 #include <linux/module.h>
17 #include <linux/percpu.h>
18 #include <linux/mutex.h>
19 #include <linux/delay.h>
20 #include <linux/slab.h>
21 #include <linux/init.h>
22 #include <linux/hash.h>
23 #include <linux/list.h>
24 #include <linux/cpu.h>
26 #include <asm/local.h>
28 static void update_pages_handler(struct work_struct
*work
);
31 * The ring buffer header is special. We must manually up keep it.
33 int ring_buffer_print_entry_header(struct trace_seq
*s
)
35 trace_seq_puts(s
, "# compressed entry header\n");
36 trace_seq_puts(s
, "\ttype_len : 5 bits\n");
37 trace_seq_puts(s
, "\ttime_delta : 27 bits\n");
38 trace_seq_puts(s
, "\tarray : 32 bits\n");
39 trace_seq_putc(s
, '\n');
40 trace_seq_printf(s
, "\tpadding : type == %d\n",
41 RINGBUF_TYPE_PADDING
);
42 trace_seq_printf(s
, "\ttime_extend : type == %d\n",
43 RINGBUF_TYPE_TIME_EXTEND
);
44 trace_seq_printf(s
, "\tdata max type_len == %d\n",
45 RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
47 return !trace_seq_has_overflowed(s
);
51 * The ring buffer is made up of a list of pages. A separate list of pages is
52 * allocated for each CPU. A writer may only write to a buffer that is
53 * associated with the CPU it is currently executing on. A reader may read
54 * from any per cpu buffer.
56 * The reader is special. For each per cpu buffer, the reader has its own
57 * reader page. When a reader has read the entire reader page, this reader
58 * page is swapped with another page in the ring buffer.
60 * Now, as long as the writer is off the reader page, the reader can do what
61 * ever it wants with that page. The writer will never write to that page
62 * again (as long as it is out of the ring buffer).
64 * Here's some silly ASCII art.
67 * |reader| RING BUFFER
69 * +------+ +---+ +---+ +---+
78 * |reader| RING BUFFER
79 * |page |------------------v
80 * +------+ +---+ +---+ +---+
89 * |reader| RING BUFFER
90 * |page |------------------v
91 * +------+ +---+ +---+ +---+
96 * +------------------------------+
100 * |buffer| RING BUFFER
101 * |page |------------------v
102 * +------+ +---+ +---+ +---+
104 * | New +---+ +---+ +---+
107 * +------------------------------+
110 * After we make this swap, the reader can hand this page off to the splice
111 * code and be done with it. It can even allocate a new page if it needs to
112 * and swap that into the ring buffer.
114 * We will be using cmpxchg soon to make all this lockless.
118 /* Used for individual buffers (after the counter) */
119 #define RB_BUFFER_OFF (1 << 20)
121 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
123 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
124 #define RB_ALIGNMENT 4U
125 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
126 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
128 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
129 # define RB_FORCE_8BYTE_ALIGNMENT 0
130 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
132 # define RB_FORCE_8BYTE_ALIGNMENT 1
133 # define RB_ARCH_ALIGNMENT 8U
136 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
138 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
139 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
142 RB_LEN_TIME_EXTEND
= 8,
143 RB_LEN_TIME_STAMP
= 16,
146 #define skip_time_extend(event) \
147 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
149 static inline int rb_null_event(struct ring_buffer_event
*event
)
151 return event
->type_len
== RINGBUF_TYPE_PADDING
&& !event
->time_delta
;
154 static void rb_event_set_padding(struct ring_buffer_event
*event
)
156 /* padding has a NULL time_delta */
157 event
->type_len
= RINGBUF_TYPE_PADDING
;
158 event
->time_delta
= 0;
162 rb_event_data_length(struct ring_buffer_event
*event
)
167 length
= event
->type_len
* RB_ALIGNMENT
;
169 length
= event
->array
[0];
170 return length
+ RB_EVNT_HDR_SIZE
;
174 * Return the length of the given event. Will return
175 * the length of the time extend if the event is a
178 static inline unsigned
179 rb_event_length(struct ring_buffer_event
*event
)
181 switch (event
->type_len
) {
182 case RINGBUF_TYPE_PADDING
:
183 if (rb_null_event(event
))
186 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
188 case RINGBUF_TYPE_TIME_EXTEND
:
189 return RB_LEN_TIME_EXTEND
;
191 case RINGBUF_TYPE_TIME_STAMP
:
192 return RB_LEN_TIME_STAMP
;
194 case RINGBUF_TYPE_DATA
:
195 return rb_event_data_length(event
);
204 * Return total length of time extend and data,
205 * or just the event length for all other events.
207 static inline unsigned
208 rb_event_ts_length(struct ring_buffer_event
*event
)
212 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
213 /* time extends include the data event after it */
214 len
= RB_LEN_TIME_EXTEND
;
215 event
= skip_time_extend(event
);
217 return len
+ rb_event_length(event
);
221 * ring_buffer_event_length - return the length of the event
222 * @event: the event to get the length of
224 * Returns the size of the data load of a data event.
225 * If the event is something other than a data event, it
226 * returns the size of the event itself. With the exception
227 * of a TIME EXTEND, where it still returns the size of the
228 * data load of the data event after it.
230 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
234 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
235 event
= skip_time_extend(event
);
237 length
= rb_event_length(event
);
238 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
240 length
-= RB_EVNT_HDR_SIZE
;
241 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
242 length
-= sizeof(event
->array
[0]);
245 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
247 /* inline for ring buffer fast paths */
248 static __always_inline
void *
249 rb_event_data(struct ring_buffer_event
*event
)
251 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
252 event
= skip_time_extend(event
);
253 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
254 /* If length is in len field, then array[0] has the data */
256 return (void *)&event
->array
[0];
257 /* Otherwise length is in array[0] and array[1] has the data */
258 return (void *)&event
->array
[1];
262 * ring_buffer_event_data - return the data of the event
263 * @event: the event to get the data from
265 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
267 return rb_event_data(event
);
269 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
271 #define for_each_buffer_cpu(buffer, cpu) \
272 for_each_cpu(cpu, buffer->cpumask)
275 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
276 #define TS_DELTA_TEST (~TS_MASK)
278 /* Flag when events were overwritten */
279 #define RB_MISSED_EVENTS (1 << 31)
280 /* Missed count stored at end */
281 #define RB_MISSED_STORED (1 << 30)
283 #define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED)
285 struct buffer_data_page
{
286 u64 time_stamp
; /* page time stamp */
287 local_t commit
; /* write committed index */
288 unsigned char data
[] RB_ALIGN_DATA
; /* data of buffer page */
292 * Note, the buffer_page list must be first. The buffer pages
293 * are allocated in cache lines, which means that each buffer
294 * page will be at the beginning of a cache line, and thus
295 * the least significant bits will be zero. We use this to
296 * add flags in the list struct pointers, to make the ring buffer
300 struct list_head list
; /* list of buffer pages */
301 local_t write
; /* index for next write */
302 unsigned read
; /* index for next read */
303 local_t entries
; /* entries on this page */
304 unsigned long real_end
; /* real end of data */
305 struct buffer_data_page
*page
; /* Actual data page */
309 * The buffer page counters, write and entries, must be reset
310 * atomically when crossing page boundaries. To synchronize this
311 * update, two counters are inserted into the number. One is
312 * the actual counter for the write position or count on the page.
314 * The other is a counter of updaters. Before an update happens
315 * the update partition of the counter is incremented. This will
316 * allow the updater to update the counter atomically.
318 * The counter is 20 bits, and the state data is 12.
320 #define RB_WRITE_MASK 0xfffff
321 #define RB_WRITE_INTCNT (1 << 20)
323 static void rb_init_page(struct buffer_data_page
*bpage
)
325 local_set(&bpage
->commit
, 0);
329 * ring_buffer_page_len - the size of data on the page.
330 * @page: The page to read
332 * Returns the amount of data on the page, including buffer page header.
334 size_t ring_buffer_page_len(void *page
)
336 struct buffer_data_page
*bpage
= page
;
338 return (local_read(&bpage
->commit
) & ~RB_MISSED_FLAGS
)
343 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
346 static void free_buffer_page(struct buffer_page
*bpage
)
348 free_page((unsigned long)bpage
->page
);
353 * We need to fit the time_stamp delta into 27 bits.
355 static inline int test_time_stamp(u64 delta
)
357 if (delta
& TS_DELTA_TEST
)
362 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
364 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
365 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
367 int ring_buffer_print_page_header(struct trace_seq
*s
)
369 struct buffer_data_page field
;
371 trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
372 "offset:0;\tsize:%u;\tsigned:%u;\n",
373 (unsigned int)sizeof(field
.time_stamp
),
374 (unsigned int)is_signed_type(u64
));
376 trace_seq_printf(s
, "\tfield: local_t commit;\t"
377 "offset:%u;\tsize:%u;\tsigned:%u;\n",
378 (unsigned int)offsetof(typeof(field
), commit
),
379 (unsigned int)sizeof(field
.commit
),
380 (unsigned int)is_signed_type(long));
382 trace_seq_printf(s
, "\tfield: int overwrite;\t"
383 "offset:%u;\tsize:%u;\tsigned:%u;\n",
384 (unsigned int)offsetof(typeof(field
), commit
),
386 (unsigned int)is_signed_type(long));
388 trace_seq_printf(s
, "\tfield: char data;\t"
389 "offset:%u;\tsize:%u;\tsigned:%u;\n",
390 (unsigned int)offsetof(typeof(field
), data
),
391 (unsigned int)BUF_PAGE_SIZE
,
392 (unsigned int)is_signed_type(char));
394 return !trace_seq_has_overflowed(s
);
398 struct irq_work work
;
399 wait_queue_head_t waiters
;
400 wait_queue_head_t full_waiters
;
401 bool waiters_pending
;
402 bool full_waiters_pending
;
407 * Structure to hold event state and handle nested events.
409 struct rb_event_info
{
412 unsigned long length
;
413 struct buffer_page
*tail_page
;
418 * Used for which event context the event is in.
424 * See trace_recursive_lock() comment below for more details.
435 * head_page == tail_page && head == tail then buffer is empty.
437 struct ring_buffer_per_cpu
{
439 atomic_t record_disabled
;
440 struct ring_buffer
*buffer
;
441 raw_spinlock_t reader_lock
; /* serialize readers */
442 arch_spinlock_t lock
;
443 struct lock_class_key lock_key
;
444 struct buffer_data_page
*free_page
;
445 unsigned long nr_pages
;
446 unsigned int current_context
;
447 struct list_head
*pages
;
448 struct buffer_page
*head_page
; /* read from head */
449 struct buffer_page
*tail_page
; /* write to tail */
450 struct buffer_page
*commit_page
; /* committed pages */
451 struct buffer_page
*reader_page
;
452 unsigned long lost_events
;
453 unsigned long last_overrun
;
454 local_t entries_bytes
;
457 local_t commit_overrun
;
458 local_t dropped_events
;
462 unsigned long read_bytes
;
465 /* ring buffer pages to update, > 0 to add, < 0 to remove */
466 long nr_pages_to_update
;
467 struct list_head new_pages
; /* new pages to add */
468 struct work_struct update_pages_work
;
469 struct completion update_done
;
471 struct rb_irq_work irq_work
;
477 atomic_t record_disabled
;
478 atomic_t resize_disabled
;
479 cpumask_var_t cpumask
;
481 struct lock_class_key
*reader_lock_key
;
485 struct ring_buffer_per_cpu
**buffers
;
487 struct hlist_node node
;
490 struct rb_irq_work irq_work
;
493 struct ring_buffer_iter
{
494 struct ring_buffer_per_cpu
*cpu_buffer
;
496 struct buffer_page
*head_page
;
497 struct buffer_page
*cache_reader_page
;
498 unsigned long cache_read
;
503 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
505 * Schedules a delayed work to wake up any task that is blocked on the
506 * ring buffer waiters queue.
508 static void rb_wake_up_waiters(struct irq_work
*work
)
510 struct rb_irq_work
*rbwork
= container_of(work
, struct rb_irq_work
, work
);
512 wake_up_all(&rbwork
->waiters
);
513 if (rbwork
->wakeup_full
) {
514 rbwork
->wakeup_full
= false;
515 wake_up_all(&rbwork
->full_waiters
);
520 * ring_buffer_wait - wait for input to the ring buffer
521 * @buffer: buffer to wait on
522 * @cpu: the cpu buffer to wait on
523 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
525 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
526 * as data is added to any of the @buffer's cpu buffers. Otherwise
527 * it will wait for data to be added to a specific cpu buffer.
529 int ring_buffer_wait(struct ring_buffer
*buffer
, int cpu
, bool full
)
531 struct ring_buffer_per_cpu
*uninitialized_var(cpu_buffer
);
533 struct rb_irq_work
*work
;
537 * Depending on what the caller is waiting for, either any
538 * data in any cpu buffer, or a specific buffer, put the
539 * caller on the appropriate wait queue.
541 if (cpu
== RING_BUFFER_ALL_CPUS
) {
542 work
= &buffer
->irq_work
;
543 /* Full only makes sense on per cpu reads */
546 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
548 cpu_buffer
= buffer
->buffers
[cpu
];
549 work
= &cpu_buffer
->irq_work
;
555 prepare_to_wait(&work
->full_waiters
, &wait
, TASK_INTERRUPTIBLE
);
557 prepare_to_wait(&work
->waiters
, &wait
, TASK_INTERRUPTIBLE
);
560 * The events can happen in critical sections where
561 * checking a work queue can cause deadlocks.
562 * After adding a task to the queue, this flag is set
563 * only to notify events to try to wake up the queue
566 * We don't clear it even if the buffer is no longer
567 * empty. The flag only causes the next event to run
568 * irq_work to do the work queue wake up. The worse
569 * that can happen if we race with !trace_empty() is that
570 * an event will cause an irq_work to try to wake up
573 * There's no reason to protect this flag either, as
574 * the work queue and irq_work logic will do the necessary
575 * synchronization for the wake ups. The only thing
576 * that is necessary is that the wake up happens after
577 * a task has been queued. It's OK for spurious wake ups.
580 work
->full_waiters_pending
= true;
582 work
->waiters_pending
= true;
584 if (signal_pending(current
)) {
589 if (cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
))
592 if (cpu
!= RING_BUFFER_ALL_CPUS
&&
593 !ring_buffer_empty_cpu(buffer
, cpu
)) {
600 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
601 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
602 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
612 finish_wait(&work
->full_waiters
, &wait
);
614 finish_wait(&work
->waiters
, &wait
);
620 * ring_buffer_poll_wait - poll on buffer input
621 * @buffer: buffer to wait on
622 * @cpu: the cpu buffer to wait on
623 * @filp: the file descriptor
624 * @poll_table: The poll descriptor
626 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
627 * as data is added to any of the @buffer's cpu buffers. Otherwise
628 * it will wait for data to be added to a specific cpu buffer.
630 * Returns POLLIN | POLLRDNORM if data exists in the buffers,
633 int ring_buffer_poll_wait(struct ring_buffer
*buffer
, int cpu
,
634 struct file
*filp
, poll_table
*poll_table
)
636 struct ring_buffer_per_cpu
*cpu_buffer
;
637 struct rb_irq_work
*work
;
639 if (cpu
== RING_BUFFER_ALL_CPUS
)
640 work
= &buffer
->irq_work
;
642 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
645 cpu_buffer
= buffer
->buffers
[cpu
];
646 work
= &cpu_buffer
->irq_work
;
649 poll_wait(filp
, &work
->waiters
, poll_table
);
650 work
->waiters_pending
= true;
652 * There's a tight race between setting the waiters_pending and
653 * checking if the ring buffer is empty. Once the waiters_pending bit
654 * is set, the next event will wake the task up, but we can get stuck
655 * if there's only a single event in.
657 * FIXME: Ideally, we need a memory barrier on the writer side as well,
658 * but adding a memory barrier to all events will cause too much of a
659 * performance hit in the fast path. We only need a memory barrier when
660 * the buffer goes from empty to having content. But as this race is
661 * extremely small, and it's not a problem if another event comes in, we
666 if ((cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
)) ||
667 (cpu
!= RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty_cpu(buffer
, cpu
)))
668 return POLLIN
| POLLRDNORM
;
672 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
673 #define RB_WARN_ON(b, cond) \
675 int _____ret = unlikely(cond); \
677 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
678 struct ring_buffer_per_cpu *__b = \
680 atomic_inc(&__b->buffer->record_disabled); \
682 atomic_inc(&b->record_disabled); \
688 /* Up this if you want to test the TIME_EXTENTS and normalization */
689 #define DEBUG_SHIFT 0
691 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
693 /* shift to debug/test normalization and TIME_EXTENTS */
694 return buffer
->clock() << DEBUG_SHIFT
;
697 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
701 preempt_disable_notrace();
702 time
= rb_time_stamp(buffer
);
703 preempt_enable_no_resched_notrace();
707 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
709 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
712 /* Just stupid testing the normalize function and deltas */
715 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
718 * Making the ring buffer lockless makes things tricky.
719 * Although writes only happen on the CPU that they are on,
720 * and they only need to worry about interrupts. Reads can
723 * The reader page is always off the ring buffer, but when the
724 * reader finishes with a page, it needs to swap its page with
725 * a new one from the buffer. The reader needs to take from
726 * the head (writes go to the tail). But if a writer is in overwrite
727 * mode and wraps, it must push the head page forward.
729 * Here lies the problem.
731 * The reader must be careful to replace only the head page, and
732 * not another one. As described at the top of the file in the
733 * ASCII art, the reader sets its old page to point to the next
734 * page after head. It then sets the page after head to point to
735 * the old reader page. But if the writer moves the head page
736 * during this operation, the reader could end up with the tail.
738 * We use cmpxchg to help prevent this race. We also do something
739 * special with the page before head. We set the LSB to 1.
741 * When the writer must push the page forward, it will clear the
742 * bit that points to the head page, move the head, and then set
743 * the bit that points to the new head page.
745 * We also don't want an interrupt coming in and moving the head
746 * page on another writer. Thus we use the second LSB to catch
749 * head->list->prev->next bit 1 bit 0
752 * Points to head page 0 1
755 * Note we can not trust the prev pointer of the head page, because:
757 * +----+ +-----+ +-----+
758 * | |------>| T |---X--->| N |
760 * +----+ +-----+ +-----+
763 * +----------| R |----------+ |
767 * Key: ---X--> HEAD flag set in pointer
772 * (see __rb_reserve_next() to see where this happens)
774 * What the above shows is that the reader just swapped out
775 * the reader page with a page in the buffer, but before it
776 * could make the new header point back to the new page added
777 * it was preempted by a writer. The writer moved forward onto
778 * the new page added by the reader and is about to move forward
781 * You can see, it is legitimate for the previous pointer of
782 * the head (or any page) not to point back to itself. But only
786 #define RB_PAGE_NORMAL 0UL
787 #define RB_PAGE_HEAD 1UL
788 #define RB_PAGE_UPDATE 2UL
791 #define RB_FLAG_MASK 3UL
793 /* PAGE_MOVED is not part of the mask */
794 #define RB_PAGE_MOVED 4UL
797 * rb_list_head - remove any bit
799 static struct list_head
*rb_list_head(struct list_head
*list
)
801 unsigned long val
= (unsigned long)list
;
803 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
807 * rb_is_head_page - test if the given page is the head page
809 * Because the reader may move the head_page pointer, we can
810 * not trust what the head page is (it may be pointing to
811 * the reader page). But if the next page is a header page,
812 * its flags will be non zero.
815 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
816 struct buffer_page
*page
, struct list_head
*list
)
820 val
= (unsigned long)list
->next
;
822 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
823 return RB_PAGE_MOVED
;
825 return val
& RB_FLAG_MASK
;
831 * The unique thing about the reader page, is that, if the
832 * writer is ever on it, the previous pointer never points
833 * back to the reader page.
835 static bool rb_is_reader_page(struct buffer_page
*page
)
837 struct list_head
*list
= page
->list
.prev
;
839 return rb_list_head(list
->next
) != &page
->list
;
843 * rb_set_list_to_head - set a list_head to be pointing to head.
845 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
846 struct list_head
*list
)
850 ptr
= (unsigned long *)&list
->next
;
851 *ptr
|= RB_PAGE_HEAD
;
852 *ptr
&= ~RB_PAGE_UPDATE
;
856 * rb_head_page_activate - sets up head page
858 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
860 struct buffer_page
*head
;
862 head
= cpu_buffer
->head_page
;
867 * Set the previous list pointer to have the HEAD flag.
869 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
872 static void rb_list_head_clear(struct list_head
*list
)
874 unsigned long *ptr
= (unsigned long *)&list
->next
;
876 *ptr
&= ~RB_FLAG_MASK
;
880 * rb_head_page_dactivate - clears head page ptr (for free list)
883 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
885 struct list_head
*hd
;
887 /* Go through the whole list and clear any pointers found. */
888 rb_list_head_clear(cpu_buffer
->pages
);
890 list_for_each(hd
, cpu_buffer
->pages
)
891 rb_list_head_clear(hd
);
894 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
895 struct buffer_page
*head
,
896 struct buffer_page
*prev
,
897 int old_flag
, int new_flag
)
899 struct list_head
*list
;
900 unsigned long val
= (unsigned long)&head
->list
;
905 val
&= ~RB_FLAG_MASK
;
907 ret
= cmpxchg((unsigned long *)&list
->next
,
908 val
| old_flag
, val
| new_flag
);
910 /* check if the reader took the page */
911 if ((ret
& ~RB_FLAG_MASK
) != val
)
912 return RB_PAGE_MOVED
;
914 return ret
& RB_FLAG_MASK
;
917 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
918 struct buffer_page
*head
,
919 struct buffer_page
*prev
,
922 return rb_head_page_set(cpu_buffer
, head
, prev
,
923 old_flag
, RB_PAGE_UPDATE
);
926 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
927 struct buffer_page
*head
,
928 struct buffer_page
*prev
,
931 return rb_head_page_set(cpu_buffer
, head
, prev
,
932 old_flag
, RB_PAGE_HEAD
);
935 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
936 struct buffer_page
*head
,
937 struct buffer_page
*prev
,
940 return rb_head_page_set(cpu_buffer
, head
, prev
,
941 old_flag
, RB_PAGE_NORMAL
);
944 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
945 struct buffer_page
**bpage
)
947 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
949 *bpage
= list_entry(p
, struct buffer_page
, list
);
952 static struct buffer_page
*
953 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
955 struct buffer_page
*head
;
956 struct buffer_page
*page
;
957 struct list_head
*list
;
960 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
964 list
= cpu_buffer
->pages
;
965 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
968 page
= head
= cpu_buffer
->head_page
;
970 * It is possible that the writer moves the header behind
971 * where we started, and we miss in one loop.
972 * A second loop should grab the header, but we'll do
973 * three loops just because I'm paranoid.
975 for (i
= 0; i
< 3; i
++) {
977 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
978 cpu_buffer
->head_page
= page
;
981 rb_inc_page(cpu_buffer
, &page
);
982 } while (page
!= head
);
985 RB_WARN_ON(cpu_buffer
, 1);
990 static int rb_head_page_replace(struct buffer_page
*old
,
991 struct buffer_page
*new)
993 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
997 val
= *ptr
& ~RB_FLAG_MASK
;
1000 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
1006 * rb_tail_page_update - move the tail page forward
1008 static void rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1009 struct buffer_page
*tail_page
,
1010 struct buffer_page
*next_page
)
1012 unsigned long old_entries
;
1013 unsigned long old_write
;
1016 * The tail page now needs to be moved forward.
1018 * We need to reset the tail page, but without messing
1019 * with possible erasing of data brought in by interrupts
1020 * that have moved the tail page and are currently on it.
1022 * We add a counter to the write field to denote this.
1024 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
1025 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
1028 * Just make sure we have seen our old_write and synchronize
1029 * with any interrupts that come in.
1034 * If the tail page is still the same as what we think
1035 * it is, then it is up to us to update the tail
1038 if (tail_page
== READ_ONCE(cpu_buffer
->tail_page
)) {
1039 /* Zero the write counter */
1040 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
1041 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
1044 * This will only succeed if an interrupt did
1045 * not come in and change it. In which case, we
1046 * do not want to modify it.
1048 * We add (void) to let the compiler know that we do not care
1049 * about the return value of these functions. We use the
1050 * cmpxchg to only update if an interrupt did not already
1051 * do it for us. If the cmpxchg fails, we don't care.
1053 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
1054 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
1057 * No need to worry about races with clearing out the commit.
1058 * it only can increment when a commit takes place. But that
1059 * only happens in the outer most nested commit.
1061 local_set(&next_page
->page
->commit
, 0);
1063 /* Again, either we update tail_page or an interrupt does */
1064 (void)cmpxchg(&cpu_buffer
->tail_page
, tail_page
, next_page
);
1068 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
1069 struct buffer_page
*bpage
)
1071 unsigned long val
= (unsigned long)bpage
;
1073 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
1080 * rb_check_list - make sure a pointer to a list has the last bits zero
1082 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
1083 struct list_head
*list
)
1085 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
1087 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
1093 * rb_check_pages - integrity check of buffer pages
1094 * @cpu_buffer: CPU buffer with pages to test
1096 * As a safety measure we check to make sure the data pages have not
1099 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1101 struct list_head
*head
= cpu_buffer
->pages
;
1102 struct buffer_page
*bpage
, *tmp
;
1104 /* Reset the head page if it exists */
1105 if (cpu_buffer
->head_page
)
1106 rb_set_head_page(cpu_buffer
);
1108 rb_head_page_deactivate(cpu_buffer
);
1110 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
1112 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
1115 if (rb_check_list(cpu_buffer
, head
))
1118 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1119 if (RB_WARN_ON(cpu_buffer
,
1120 bpage
->list
.next
->prev
!= &bpage
->list
))
1122 if (RB_WARN_ON(cpu_buffer
,
1123 bpage
->list
.prev
->next
!= &bpage
->list
))
1125 if (rb_check_list(cpu_buffer
, &bpage
->list
))
1129 rb_head_page_activate(cpu_buffer
);
1134 static int __rb_allocate_pages(long nr_pages
, struct list_head
*pages
, int cpu
)
1136 struct buffer_page
*bpage
, *tmp
;
1139 /* Check if the available memory is there first */
1140 i
= si_mem_available();
1144 for (i
= 0; i
< nr_pages
; i
++) {
1147 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1148 * gracefully without invoking oom-killer and the system is not
1151 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1152 GFP_KERNEL
| __GFP_RETRY_MAYFAIL
,
1157 list_add(&bpage
->list
, pages
);
1159 page
= alloc_pages_node(cpu_to_node(cpu
),
1160 GFP_KERNEL
| __GFP_RETRY_MAYFAIL
, 0);
1163 bpage
->page
= page_address(page
);
1164 rb_init_page(bpage
->page
);
1170 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1171 list_del_init(&bpage
->list
);
1172 free_buffer_page(bpage
);
1178 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1179 unsigned long nr_pages
)
1185 if (__rb_allocate_pages(nr_pages
, &pages
, cpu_buffer
->cpu
))
1189 * The ring buffer page list is a circular list that does not
1190 * start and end with a list head. All page list items point to
1193 cpu_buffer
->pages
= pages
.next
;
1196 cpu_buffer
->nr_pages
= nr_pages
;
1198 rb_check_pages(cpu_buffer
);
1203 static struct ring_buffer_per_cpu
*
1204 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, long nr_pages
, int cpu
)
1206 struct ring_buffer_per_cpu
*cpu_buffer
;
1207 struct buffer_page
*bpage
;
1211 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1212 GFP_KERNEL
, cpu_to_node(cpu
));
1216 cpu_buffer
->cpu
= cpu
;
1217 cpu_buffer
->buffer
= buffer
;
1218 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1219 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1220 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1221 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1222 init_completion(&cpu_buffer
->update_done
);
1223 init_irq_work(&cpu_buffer
->irq_work
.work
, rb_wake_up_waiters
);
1224 init_waitqueue_head(&cpu_buffer
->irq_work
.waiters
);
1225 init_waitqueue_head(&cpu_buffer
->irq_work
.full_waiters
);
1227 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1228 GFP_KERNEL
, cpu_to_node(cpu
));
1230 goto fail_free_buffer
;
1232 rb_check_bpage(cpu_buffer
, bpage
);
1234 cpu_buffer
->reader_page
= bpage
;
1235 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, 0);
1237 goto fail_free_reader
;
1238 bpage
->page
= page_address(page
);
1239 rb_init_page(bpage
->page
);
1241 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1242 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1244 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1246 goto fail_free_reader
;
1248 cpu_buffer
->head_page
1249 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1250 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1252 rb_head_page_activate(cpu_buffer
);
1257 free_buffer_page(cpu_buffer
->reader_page
);
1264 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1266 struct list_head
*head
= cpu_buffer
->pages
;
1267 struct buffer_page
*bpage
, *tmp
;
1269 free_buffer_page(cpu_buffer
->reader_page
);
1271 rb_head_page_deactivate(cpu_buffer
);
1274 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1275 list_del_init(&bpage
->list
);
1276 free_buffer_page(bpage
);
1278 bpage
= list_entry(head
, struct buffer_page
, list
);
1279 free_buffer_page(bpage
);
1286 * __ring_buffer_alloc - allocate a new ring_buffer
1287 * @size: the size in bytes per cpu that is needed.
1288 * @flags: attributes to set for the ring buffer.
1290 * Currently the only flag that is available is the RB_FL_OVERWRITE
1291 * flag. This flag means that the buffer will overwrite old data
1292 * when the buffer wraps. If this flag is not set, the buffer will
1293 * drop data when the tail hits the head.
1295 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1296 struct lock_class_key
*key
)
1298 struct ring_buffer
*buffer
;
1304 /* keep it in its own cache line */
1305 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1310 if (!zalloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1311 goto fail_free_buffer
;
1313 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1314 buffer
->flags
= flags
;
1315 buffer
->clock
= trace_clock_local
;
1316 buffer
->reader_lock_key
= key
;
1318 init_irq_work(&buffer
->irq_work
.work
, rb_wake_up_waiters
);
1319 init_waitqueue_head(&buffer
->irq_work
.waiters
);
1321 /* need at least two pages */
1325 buffer
->cpus
= nr_cpu_ids
;
1327 bsize
= sizeof(void *) * nr_cpu_ids
;
1328 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1330 if (!buffer
->buffers
)
1331 goto fail_free_cpumask
;
1333 cpu
= raw_smp_processor_id();
1334 cpumask_set_cpu(cpu
, buffer
->cpumask
);
1335 buffer
->buffers
[cpu
] = rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1336 if (!buffer
->buffers
[cpu
])
1337 goto fail_free_buffers
;
1339 ret
= cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1341 goto fail_free_buffers
;
1343 mutex_init(&buffer
->mutex
);
1348 for_each_buffer_cpu(buffer
, cpu
) {
1349 if (buffer
->buffers
[cpu
])
1350 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1352 kfree(buffer
->buffers
);
1355 free_cpumask_var(buffer
->cpumask
);
1361 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1364 * ring_buffer_free - free a ring buffer.
1365 * @buffer: the buffer to free.
1368 ring_buffer_free(struct ring_buffer
*buffer
)
1372 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1374 for_each_buffer_cpu(buffer
, cpu
)
1375 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1377 kfree(buffer
->buffers
);
1378 free_cpumask_var(buffer
->cpumask
);
1382 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1384 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1387 buffer
->clock
= clock
;
1390 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1392 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1394 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1397 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1399 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1403 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned long nr_pages
)
1405 struct list_head
*tail_page
, *to_remove
, *next_page
;
1406 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1407 struct buffer_page
*last_page
, *first_page
;
1408 unsigned long nr_removed
;
1409 unsigned long head_bit
;
1414 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1415 atomic_inc(&cpu_buffer
->record_disabled
);
1417 * We don't race with the readers since we have acquired the reader
1418 * lock. We also don't race with writers after disabling recording.
1419 * This makes it easy to figure out the first and the last page to be
1420 * removed from the list. We unlink all the pages in between including
1421 * the first and last pages. This is done in a busy loop so that we
1422 * lose the least number of traces.
1423 * The pages are freed after we restart recording and unlock readers.
1425 tail_page
= &cpu_buffer
->tail_page
->list
;
1428 * tail page might be on reader page, we remove the next page
1429 * from the ring buffer
1431 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1432 tail_page
= rb_list_head(tail_page
->next
);
1433 to_remove
= tail_page
;
1435 /* start of pages to remove */
1436 first_page
= list_entry(rb_list_head(to_remove
->next
),
1437 struct buffer_page
, list
);
1439 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1440 to_remove
= rb_list_head(to_remove
)->next
;
1441 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1444 next_page
= rb_list_head(to_remove
)->next
;
1447 * Now we remove all pages between tail_page and next_page.
1448 * Make sure that we have head_bit value preserved for the
1451 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1453 next_page
= rb_list_head(next_page
);
1454 next_page
->prev
= tail_page
;
1456 /* make sure pages points to a valid page in the ring buffer */
1457 cpu_buffer
->pages
= next_page
;
1459 /* update head page */
1461 cpu_buffer
->head_page
= list_entry(next_page
,
1462 struct buffer_page
, list
);
1465 * change read pointer to make sure any read iterators reset
1468 cpu_buffer
->read
= 0;
1470 /* pages are removed, resume tracing and then free the pages */
1471 atomic_dec(&cpu_buffer
->record_disabled
);
1472 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1474 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1476 /* last buffer page to remove */
1477 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1479 tmp_iter_page
= first_page
;
1484 to_remove_page
= tmp_iter_page
;
1485 rb_inc_page(cpu_buffer
, &tmp_iter_page
);
1487 /* update the counters */
1488 page_entries
= rb_page_entries(to_remove_page
);
1491 * If something was added to this page, it was full
1492 * since it is not the tail page. So we deduct the
1493 * bytes consumed in ring buffer from here.
1494 * Increment overrun to account for the lost events.
1496 local_add(page_entries
, &cpu_buffer
->overrun
);
1497 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1501 * We have already removed references to this list item, just
1502 * free up the buffer_page and its page
1504 free_buffer_page(to_remove_page
);
1507 } while (to_remove_page
!= last_page
);
1509 RB_WARN_ON(cpu_buffer
, nr_removed
);
1511 return nr_removed
== 0;
1515 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1517 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1518 int retries
, success
;
1520 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1522 * We are holding the reader lock, so the reader page won't be swapped
1523 * in the ring buffer. Now we are racing with the writer trying to
1524 * move head page and the tail page.
1525 * We are going to adapt the reader page update process where:
1526 * 1. We first splice the start and end of list of new pages between
1527 * the head page and its previous page.
1528 * 2. We cmpxchg the prev_page->next to point from head page to the
1529 * start of new pages list.
1530 * 3. Finally, we update the head->prev to the end of new list.
1532 * We will try this process 10 times, to make sure that we don't keep
1538 struct list_head
*head_page
, *prev_page
, *r
;
1539 struct list_head
*last_page
, *first_page
;
1540 struct list_head
*head_page_with_bit
;
1542 head_page
= &rb_set_head_page(cpu_buffer
)->list
;
1545 prev_page
= head_page
->prev
;
1547 first_page
= pages
->next
;
1548 last_page
= pages
->prev
;
1550 head_page_with_bit
= (struct list_head
*)
1551 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1553 last_page
->next
= head_page_with_bit
;
1554 first_page
->prev
= prev_page
;
1556 r
= cmpxchg(&prev_page
->next
, head_page_with_bit
, first_page
);
1558 if (r
== head_page_with_bit
) {
1560 * yay, we replaced the page pointer to our new list,
1561 * now, we just have to update to head page's prev
1562 * pointer to point to end of list
1564 head_page
->prev
= last_page
;
1571 INIT_LIST_HEAD(pages
);
1573 * If we weren't successful in adding in new pages, warn and stop
1576 RB_WARN_ON(cpu_buffer
, !success
);
1577 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1579 /* free pages if they weren't inserted */
1581 struct buffer_page
*bpage
, *tmp
;
1582 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1584 list_del_init(&bpage
->list
);
1585 free_buffer_page(bpage
);
1591 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1595 if (cpu_buffer
->nr_pages_to_update
> 0)
1596 success
= rb_insert_pages(cpu_buffer
);
1598 success
= rb_remove_pages(cpu_buffer
,
1599 -cpu_buffer
->nr_pages_to_update
);
1602 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1605 static void update_pages_handler(struct work_struct
*work
)
1607 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1608 struct ring_buffer_per_cpu
, update_pages_work
);
1609 rb_update_pages(cpu_buffer
);
1610 complete(&cpu_buffer
->update_done
);
1614 * ring_buffer_resize - resize the ring buffer
1615 * @buffer: the buffer to resize.
1616 * @size: the new size.
1617 * @cpu_id: the cpu buffer to resize
1619 * Minimum size is 2 * BUF_PAGE_SIZE.
1621 * Returns 0 on success and < 0 on failure.
1623 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
,
1626 struct ring_buffer_per_cpu
*cpu_buffer
;
1627 unsigned long nr_pages
;
1631 * Always succeed at resizing a non-existent buffer:
1636 /* Make sure the requested buffer exists */
1637 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1638 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1641 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1643 /* we need a minimum of two pages */
1647 size
= nr_pages
* BUF_PAGE_SIZE
;
1650 * Don't succeed if resizing is disabled, as a reader might be
1651 * manipulating the ring buffer and is expecting a sane state while
1654 if (atomic_read(&buffer
->resize_disabled
))
1657 /* prevent another thread from changing buffer sizes */
1658 mutex_lock(&buffer
->mutex
);
1660 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
1661 /* calculate the pages to update */
1662 for_each_buffer_cpu(buffer
, cpu
) {
1663 cpu_buffer
= buffer
->buffers
[cpu
];
1665 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1666 cpu_buffer
->nr_pages
;
1668 * nothing more to do for removing pages or no update
1670 if (cpu_buffer
->nr_pages_to_update
<= 0)
1673 * to add pages, make sure all new pages can be
1674 * allocated without receiving ENOMEM
1676 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1677 if (__rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1678 &cpu_buffer
->new_pages
, cpu
)) {
1679 /* not enough memory for new pages */
1687 * Fire off all the required work handlers
1688 * We can't schedule on offline CPUs, but it's not necessary
1689 * since we can change their buffer sizes without any race.
1691 for_each_buffer_cpu(buffer
, cpu
) {
1692 cpu_buffer
= buffer
->buffers
[cpu
];
1693 if (!cpu_buffer
->nr_pages_to_update
)
1696 /* Can't run something on an offline CPU. */
1697 if (!cpu_online(cpu
)) {
1698 rb_update_pages(cpu_buffer
);
1699 cpu_buffer
->nr_pages_to_update
= 0;
1701 schedule_work_on(cpu
,
1702 &cpu_buffer
->update_pages_work
);
1706 /* wait for all the updates to complete */
1707 for_each_buffer_cpu(buffer
, cpu
) {
1708 cpu_buffer
= buffer
->buffers
[cpu
];
1709 if (!cpu_buffer
->nr_pages_to_update
)
1712 if (cpu_online(cpu
))
1713 wait_for_completion(&cpu_buffer
->update_done
);
1714 cpu_buffer
->nr_pages_to_update
= 0;
1719 /* Make sure this CPU has been intitialized */
1720 if (!cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1723 cpu_buffer
= buffer
->buffers
[cpu_id
];
1725 if (nr_pages
== cpu_buffer
->nr_pages
)
1728 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1729 cpu_buffer
->nr_pages
;
1731 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1732 if (cpu_buffer
->nr_pages_to_update
> 0 &&
1733 __rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1734 &cpu_buffer
->new_pages
, cpu_id
)) {
1741 /* Can't run something on an offline CPU. */
1742 if (!cpu_online(cpu_id
))
1743 rb_update_pages(cpu_buffer
);
1745 schedule_work_on(cpu_id
,
1746 &cpu_buffer
->update_pages_work
);
1747 wait_for_completion(&cpu_buffer
->update_done
);
1750 cpu_buffer
->nr_pages_to_update
= 0;
1756 * The ring buffer resize can happen with the ring buffer
1757 * enabled, so that the update disturbs the tracing as little
1758 * as possible. But if the buffer is disabled, we do not need
1759 * to worry about that, and we can take the time to verify
1760 * that the buffer is not corrupt.
1762 if (atomic_read(&buffer
->record_disabled
)) {
1763 atomic_inc(&buffer
->record_disabled
);
1765 * Even though the buffer was disabled, we must make sure
1766 * that it is truly disabled before calling rb_check_pages.
1767 * There could have been a race between checking
1768 * record_disable and incrementing it.
1770 synchronize_sched();
1771 for_each_buffer_cpu(buffer
, cpu
) {
1772 cpu_buffer
= buffer
->buffers
[cpu
];
1773 rb_check_pages(cpu_buffer
);
1775 atomic_dec(&buffer
->record_disabled
);
1778 mutex_unlock(&buffer
->mutex
);
1782 for_each_buffer_cpu(buffer
, cpu
) {
1783 struct buffer_page
*bpage
, *tmp
;
1785 cpu_buffer
= buffer
->buffers
[cpu
];
1786 cpu_buffer
->nr_pages_to_update
= 0;
1788 if (list_empty(&cpu_buffer
->new_pages
))
1791 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1793 list_del_init(&bpage
->list
);
1794 free_buffer_page(bpage
);
1797 mutex_unlock(&buffer
->mutex
);
1800 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1802 void ring_buffer_change_overwrite(struct ring_buffer
*buffer
, int val
)
1804 mutex_lock(&buffer
->mutex
);
1806 buffer
->flags
|= RB_FL_OVERWRITE
;
1808 buffer
->flags
&= ~RB_FL_OVERWRITE
;
1809 mutex_unlock(&buffer
->mutex
);
1811 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
1813 static __always_inline
void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1815 return bpage
->page
->data
+ index
;
1818 static __always_inline
struct ring_buffer_event
*
1819 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1821 return __rb_page_index(cpu_buffer
->reader_page
,
1822 cpu_buffer
->reader_page
->read
);
1825 static __always_inline
struct ring_buffer_event
*
1826 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1828 return __rb_page_index(iter
->head_page
, iter
->head
);
1831 static __always_inline
unsigned rb_page_commit(struct buffer_page
*bpage
)
1833 return local_read(&bpage
->page
->commit
);
1836 /* Size is determined by what has been committed */
1837 static __always_inline
unsigned rb_page_size(struct buffer_page
*bpage
)
1839 return rb_page_commit(bpage
);
1842 static __always_inline
unsigned
1843 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1845 return rb_page_commit(cpu_buffer
->commit_page
);
1848 static __always_inline
unsigned
1849 rb_event_index(struct ring_buffer_event
*event
)
1851 unsigned long addr
= (unsigned long)event
;
1853 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1856 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1858 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1861 * The iterator could be on the reader page (it starts there).
1862 * But the head could have moved, since the reader was
1863 * found. Check for this case and assign the iterator
1864 * to the head page instead of next.
1866 if (iter
->head_page
== cpu_buffer
->reader_page
)
1867 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1869 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1871 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1876 * rb_handle_head_page - writer hit the head page
1878 * Returns: +1 to retry page
1883 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1884 struct buffer_page
*tail_page
,
1885 struct buffer_page
*next_page
)
1887 struct buffer_page
*new_head
;
1892 entries
= rb_page_entries(next_page
);
1895 * The hard part is here. We need to move the head
1896 * forward, and protect against both readers on
1897 * other CPUs and writers coming in via interrupts.
1899 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1903 * type can be one of four:
1904 * NORMAL - an interrupt already moved it for us
1905 * HEAD - we are the first to get here.
1906 * UPDATE - we are the interrupt interrupting
1908 * MOVED - a reader on another CPU moved the next
1909 * pointer to its reader page. Give up
1916 * We changed the head to UPDATE, thus
1917 * it is our responsibility to update
1920 local_add(entries
, &cpu_buffer
->overrun
);
1921 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1924 * The entries will be zeroed out when we move the
1928 /* still more to do */
1931 case RB_PAGE_UPDATE
:
1933 * This is an interrupt that interrupt the
1934 * previous update. Still more to do.
1937 case RB_PAGE_NORMAL
:
1939 * An interrupt came in before the update
1940 * and processed this for us.
1941 * Nothing left to do.
1946 * The reader is on another CPU and just did
1947 * a swap with our next_page.
1952 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
1957 * Now that we are here, the old head pointer is
1958 * set to UPDATE. This will keep the reader from
1959 * swapping the head page with the reader page.
1960 * The reader (on another CPU) will spin till
1963 * We just need to protect against interrupts
1964 * doing the job. We will set the next pointer
1965 * to HEAD. After that, we set the old pointer
1966 * to NORMAL, but only if it was HEAD before.
1967 * otherwise we are an interrupt, and only
1968 * want the outer most commit to reset it.
1970 new_head
= next_page
;
1971 rb_inc_page(cpu_buffer
, &new_head
);
1973 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
1977 * Valid returns are:
1978 * HEAD - an interrupt came in and already set it.
1979 * NORMAL - One of two things:
1980 * 1) We really set it.
1981 * 2) A bunch of interrupts came in and moved
1982 * the page forward again.
1986 case RB_PAGE_NORMAL
:
1990 RB_WARN_ON(cpu_buffer
, 1);
1995 * It is possible that an interrupt came in,
1996 * set the head up, then more interrupts came in
1997 * and moved it again. When we get back here,
1998 * the page would have been set to NORMAL but we
1999 * just set it back to HEAD.
2001 * How do you detect this? Well, if that happened
2002 * the tail page would have moved.
2004 if (ret
== RB_PAGE_NORMAL
) {
2005 struct buffer_page
*buffer_tail_page
;
2007 buffer_tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2009 * If the tail had moved passed next, then we need
2010 * to reset the pointer.
2012 if (buffer_tail_page
!= tail_page
&&
2013 buffer_tail_page
!= next_page
)
2014 rb_head_page_set_normal(cpu_buffer
, new_head
,
2020 * If this was the outer most commit (the one that
2021 * changed the original pointer from HEAD to UPDATE),
2022 * then it is up to us to reset it to NORMAL.
2024 if (type
== RB_PAGE_HEAD
) {
2025 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2028 if (RB_WARN_ON(cpu_buffer
,
2029 ret
!= RB_PAGE_UPDATE
))
2037 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2038 unsigned long tail
, struct rb_event_info
*info
)
2040 struct buffer_page
*tail_page
= info
->tail_page
;
2041 struct ring_buffer_event
*event
;
2042 unsigned long length
= info
->length
;
2045 * Only the event that crossed the page boundary
2046 * must fill the old tail_page with padding.
2048 if (tail
>= BUF_PAGE_SIZE
) {
2050 * If the page was filled, then we still need
2051 * to update the real_end. Reset it to zero
2052 * and the reader will ignore it.
2054 if (tail
== BUF_PAGE_SIZE
)
2055 tail_page
->real_end
= 0;
2057 local_sub(length
, &tail_page
->write
);
2061 event
= __rb_page_index(tail_page
, tail
);
2063 /* account for padding bytes */
2064 local_add(BUF_PAGE_SIZE
- tail
, &cpu_buffer
->entries_bytes
);
2067 * Save the original length to the meta data.
2068 * This will be used by the reader to add lost event
2071 tail_page
->real_end
= tail
;
2074 * If this event is bigger than the minimum size, then
2075 * we need to be careful that we don't subtract the
2076 * write counter enough to allow another writer to slip
2078 * We put in a discarded commit instead, to make sure
2079 * that this space is not used again.
2081 * If we are less than the minimum size, we don't need to
2084 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
2085 /* No room for any events */
2087 /* Mark the rest of the page with padding */
2088 rb_event_set_padding(event
);
2090 /* Set the write back to the previous setting */
2091 local_sub(length
, &tail_page
->write
);
2095 /* Put in a discarded event */
2096 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
2097 event
->type_len
= RINGBUF_TYPE_PADDING
;
2098 /* time delta must be non zero */
2099 event
->time_delta
= 1;
2101 /* Set write to end of buffer */
2102 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
2103 local_sub(length
, &tail_page
->write
);
2106 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
);
2109 * This is the slow path, force gcc not to inline it.
2111 static noinline
struct ring_buffer_event
*
2112 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2113 unsigned long tail
, struct rb_event_info
*info
)
2115 struct buffer_page
*tail_page
= info
->tail_page
;
2116 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2117 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
2118 struct buffer_page
*next_page
;
2121 next_page
= tail_page
;
2123 rb_inc_page(cpu_buffer
, &next_page
);
2126 * If for some reason, we had an interrupt storm that made
2127 * it all the way around the buffer, bail, and warn
2130 if (unlikely(next_page
== commit_page
)) {
2131 local_inc(&cpu_buffer
->commit_overrun
);
2136 * This is where the fun begins!
2138 * We are fighting against races between a reader that
2139 * could be on another CPU trying to swap its reader
2140 * page with the buffer head.
2142 * We are also fighting against interrupts coming in and
2143 * moving the head or tail on us as well.
2145 * If the next page is the head page then we have filled
2146 * the buffer, unless the commit page is still on the
2149 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
2152 * If the commit is not on the reader page, then
2153 * move the header page.
2155 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2157 * If we are not in overwrite mode,
2158 * this is easy, just stop here.
2160 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2161 local_inc(&cpu_buffer
->dropped_events
);
2165 ret
= rb_handle_head_page(cpu_buffer
,
2174 * We need to be careful here too. The
2175 * commit page could still be on the reader
2176 * page. We could have a small buffer, and
2177 * have filled up the buffer with events
2178 * from interrupts and such, and wrapped.
2180 * Note, if the tail page is also the on the
2181 * reader_page, we let it move out.
2183 if (unlikely((cpu_buffer
->commit_page
!=
2184 cpu_buffer
->tail_page
) &&
2185 (cpu_buffer
->commit_page
==
2186 cpu_buffer
->reader_page
))) {
2187 local_inc(&cpu_buffer
->commit_overrun
);
2193 rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2197 rb_reset_tail(cpu_buffer
, tail
, info
);
2199 /* Commit what we have for now. */
2200 rb_end_commit(cpu_buffer
);
2201 /* rb_end_commit() decs committing */
2202 local_inc(&cpu_buffer
->committing
);
2204 /* fail and let the caller try again */
2205 return ERR_PTR(-EAGAIN
);
2209 rb_reset_tail(cpu_buffer
, tail
, info
);
2214 /* Slow path, do not inline */
2215 static noinline
struct ring_buffer_event
*
2216 rb_add_time_stamp(struct ring_buffer_event
*event
, u64 delta
)
2218 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
2220 /* Not the first event on the page? */
2221 if (rb_event_index(event
)) {
2222 event
->time_delta
= delta
& TS_MASK
;
2223 event
->array
[0] = delta
>> TS_SHIFT
;
2225 /* nope, just zero it */
2226 event
->time_delta
= 0;
2227 event
->array
[0] = 0;
2230 return skip_time_extend(event
);
2233 static inline bool rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2234 struct ring_buffer_event
*event
);
2237 * rb_update_event - update event type and data
2238 * @event: the event to update
2239 * @type: the type of event
2240 * @length: the size of the event field in the ring buffer
2242 * Update the type and data fields of the event. The length
2243 * is the actual size that is written to the ring buffer,
2244 * and with this, we can determine what to place into the
2248 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2249 struct ring_buffer_event
*event
,
2250 struct rb_event_info
*info
)
2252 unsigned length
= info
->length
;
2253 u64 delta
= info
->delta
;
2255 /* Only a commit updates the timestamp */
2256 if (unlikely(!rb_event_is_commit(cpu_buffer
, event
)))
2260 * If we need to add a timestamp, then we
2261 * add it to the start of the resevered space.
2263 if (unlikely(info
->add_timestamp
)) {
2264 event
= rb_add_time_stamp(event
, delta
);
2265 length
-= RB_LEN_TIME_EXTEND
;
2269 event
->time_delta
= delta
;
2270 length
-= RB_EVNT_HDR_SIZE
;
2271 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
) {
2272 event
->type_len
= 0;
2273 event
->array
[0] = length
;
2275 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
2278 static unsigned rb_calculate_event_length(unsigned length
)
2280 struct ring_buffer_event event
; /* Used only for sizeof array */
2282 /* zero length can cause confusions */
2286 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
2287 length
+= sizeof(event
.array
[0]);
2289 length
+= RB_EVNT_HDR_SIZE
;
2290 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
2293 * In case the time delta is larger than the 27 bits for it
2294 * in the header, we need to add a timestamp. If another
2295 * event comes in when trying to discard this one to increase
2296 * the length, then the timestamp will be added in the allocated
2297 * space of this event. If length is bigger than the size needed
2298 * for the TIME_EXTEND, then padding has to be used. The events
2299 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2300 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2301 * As length is a multiple of 4, we only need to worry if it
2302 * is 12 (RB_LEN_TIME_EXTEND + 4).
2304 if (length
== RB_LEN_TIME_EXTEND
+ RB_ALIGNMENT
)
2305 length
+= RB_ALIGNMENT
;
2310 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2311 static inline bool sched_clock_stable(void)
2318 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2319 struct ring_buffer_event
*event
)
2321 unsigned long new_index
, old_index
;
2322 struct buffer_page
*bpage
;
2323 unsigned long index
;
2326 new_index
= rb_event_index(event
);
2327 old_index
= new_index
+ rb_event_ts_length(event
);
2328 addr
= (unsigned long)event
;
2331 bpage
= READ_ONCE(cpu_buffer
->tail_page
);
2333 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2334 unsigned long write_mask
=
2335 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2336 unsigned long event_length
= rb_event_length(event
);
2338 * This is on the tail page. It is possible that
2339 * a write could come in and move the tail page
2340 * and write to the next page. That is fine
2341 * because we just shorten what is on this page.
2343 old_index
+= write_mask
;
2344 new_index
+= write_mask
;
2345 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2346 if (index
== old_index
) {
2347 /* update counters */
2348 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2353 /* could not discard */
2357 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2359 local_inc(&cpu_buffer
->committing
);
2360 local_inc(&cpu_buffer
->commits
);
2363 static __always_inline
void
2364 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
2366 unsigned long max_count
;
2369 * We only race with interrupts and NMIs on this CPU.
2370 * If we own the commit event, then we can commit
2371 * all others that interrupted us, since the interruptions
2372 * are in stack format (they finish before they come
2373 * back to us). This allows us to do a simple loop to
2374 * assign the commit to the tail.
2377 max_count
= cpu_buffer
->nr_pages
* 100;
2379 while (cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)) {
2380 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
2382 if (RB_WARN_ON(cpu_buffer
,
2383 rb_is_reader_page(cpu_buffer
->tail_page
)))
2385 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2386 rb_page_write(cpu_buffer
->commit_page
));
2387 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
2388 /* Only update the write stamp if the page has an event */
2389 if (rb_page_write(cpu_buffer
->commit_page
))
2390 cpu_buffer
->write_stamp
=
2391 cpu_buffer
->commit_page
->page
->time_stamp
;
2392 /* add barrier to keep gcc from optimizing too much */
2395 while (rb_commit_index(cpu_buffer
) !=
2396 rb_page_write(cpu_buffer
->commit_page
)) {
2398 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2399 rb_page_write(cpu_buffer
->commit_page
));
2400 RB_WARN_ON(cpu_buffer
,
2401 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
2406 /* again, keep gcc from optimizing */
2410 * If an interrupt came in just after the first while loop
2411 * and pushed the tail page forward, we will be left with
2412 * a dangling commit that will never go forward.
2414 if (unlikely(cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)))
2418 static __always_inline
void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2420 unsigned long commits
;
2422 if (RB_WARN_ON(cpu_buffer
,
2423 !local_read(&cpu_buffer
->committing
)))
2427 commits
= local_read(&cpu_buffer
->commits
);
2428 /* synchronize with interrupts */
2430 if (local_read(&cpu_buffer
->committing
) == 1)
2431 rb_set_commit_to_write(cpu_buffer
);
2433 local_dec(&cpu_buffer
->committing
);
2435 /* synchronize with interrupts */
2439 * Need to account for interrupts coming in between the
2440 * updating of the commit page and the clearing of the
2441 * committing counter.
2443 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2444 !local_read(&cpu_buffer
->committing
)) {
2445 local_inc(&cpu_buffer
->committing
);
2450 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2452 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
2453 event
= skip_time_extend(event
);
2455 /* array[0] holds the actual length for the discarded event */
2456 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2457 event
->type_len
= RINGBUF_TYPE_PADDING
;
2458 /* time delta must be non zero */
2459 if (!event
->time_delta
)
2460 event
->time_delta
= 1;
2463 static __always_inline
bool
2464 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2465 struct ring_buffer_event
*event
)
2467 unsigned long addr
= (unsigned long)event
;
2468 unsigned long index
;
2470 index
= rb_event_index(event
);
2473 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
2474 rb_commit_index(cpu_buffer
) == index
;
2477 static __always_inline
void
2478 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2479 struct ring_buffer_event
*event
)
2484 * The event first in the commit queue updates the
2487 if (rb_event_is_commit(cpu_buffer
, event
)) {
2489 * A commit event that is first on a page
2490 * updates the write timestamp with the page stamp
2492 if (!rb_event_index(event
))
2493 cpu_buffer
->write_stamp
=
2494 cpu_buffer
->commit_page
->page
->time_stamp
;
2495 else if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
2496 delta
= event
->array
[0];
2498 delta
+= event
->time_delta
;
2499 cpu_buffer
->write_stamp
+= delta
;
2501 cpu_buffer
->write_stamp
+= event
->time_delta
;
2505 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2506 struct ring_buffer_event
*event
)
2508 local_inc(&cpu_buffer
->entries
);
2509 rb_update_write_stamp(cpu_buffer
, event
);
2510 rb_end_commit(cpu_buffer
);
2513 static __always_inline
void
2514 rb_wakeups(struct ring_buffer
*buffer
, struct ring_buffer_per_cpu
*cpu_buffer
)
2518 if (buffer
->irq_work
.waiters_pending
) {
2519 buffer
->irq_work
.waiters_pending
= false;
2520 /* irq_work_queue() supplies it's own memory barriers */
2521 irq_work_queue(&buffer
->irq_work
.work
);
2524 if (cpu_buffer
->irq_work
.waiters_pending
) {
2525 cpu_buffer
->irq_work
.waiters_pending
= false;
2526 /* irq_work_queue() supplies it's own memory barriers */
2527 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2530 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
2532 if (!pagebusy
&& cpu_buffer
->irq_work
.full_waiters_pending
) {
2533 cpu_buffer
->irq_work
.wakeup_full
= true;
2534 cpu_buffer
->irq_work
.full_waiters_pending
= false;
2535 /* irq_work_queue() supplies it's own memory barriers */
2536 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2541 * The lock and unlock are done within a preempt disable section.
2542 * The current_context per_cpu variable can only be modified
2543 * by the current task between lock and unlock. But it can
2544 * be modified more than once via an interrupt. To pass this
2545 * information from the lock to the unlock without having to
2546 * access the 'in_interrupt()' functions again (which do show
2547 * a bit of overhead in something as critical as function tracing,
2548 * we use a bitmask trick.
2550 * bit 0 = NMI context
2551 * bit 1 = IRQ context
2552 * bit 2 = SoftIRQ context
2553 * bit 3 = normal context.
2555 * This works because this is the order of contexts that can
2556 * preempt other contexts. A SoftIRQ never preempts an IRQ
2559 * When the context is determined, the corresponding bit is
2560 * checked and set (if it was set, then a recursion of that context
2563 * On unlock, we need to clear this bit. To do so, just subtract
2564 * 1 from the current_context and AND it to itself.
2568 * 101 & 100 = 100 (clearing bit zero)
2571 * 1010 & 1001 = 1000 (clearing bit 1)
2573 * The least significant bit can be cleared this way, and it
2574 * just so happens that it is the same bit corresponding to
2575 * the current context.
2578 static __always_inline
int
2579 trace_recursive_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
2581 unsigned int val
= cpu_buffer
->current_context
;
2582 unsigned long pc
= preempt_count();
2585 if (!(pc
& (NMI_MASK
| HARDIRQ_MASK
| SOFTIRQ_OFFSET
)))
2586 bit
= RB_CTX_NORMAL
;
2588 bit
= pc
& NMI_MASK
? RB_CTX_NMI
:
2589 pc
& HARDIRQ_MASK
? RB_CTX_IRQ
: RB_CTX_SOFTIRQ
;
2591 if (unlikely(val
& (1 << bit
)))
2595 cpu_buffer
->current_context
= val
;
2600 static __always_inline
void
2601 trace_recursive_unlock(struct ring_buffer_per_cpu
*cpu_buffer
)
2603 cpu_buffer
->current_context
&= cpu_buffer
->current_context
- 1;
2607 * ring_buffer_unlock_commit - commit a reserved
2608 * @buffer: The buffer to commit to
2609 * @event: The event pointer to commit.
2611 * This commits the data to the ring buffer, and releases any locks held.
2613 * Must be paired with ring_buffer_lock_reserve.
2615 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2616 struct ring_buffer_event
*event
)
2618 struct ring_buffer_per_cpu
*cpu_buffer
;
2619 int cpu
= raw_smp_processor_id();
2621 cpu_buffer
= buffer
->buffers
[cpu
];
2623 rb_commit(cpu_buffer
, event
);
2625 rb_wakeups(buffer
, cpu_buffer
);
2627 trace_recursive_unlock(cpu_buffer
);
2629 preempt_enable_notrace();
2633 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2635 static noinline
void
2636 rb_handle_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2637 struct rb_event_info
*info
)
2639 WARN_ONCE(info
->delta
> (1ULL << 59),
2640 KERN_WARNING
"Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2641 (unsigned long long)info
->delta
,
2642 (unsigned long long)info
->ts
,
2643 (unsigned long long)cpu_buffer
->write_stamp
,
2644 sched_clock_stable() ? "" :
2645 "If you just came from a suspend/resume,\n"
2646 "please switch to the trace global clock:\n"
2647 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2648 info
->add_timestamp
= 1;
2651 static struct ring_buffer_event
*
2652 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
2653 struct rb_event_info
*info
)
2655 struct ring_buffer_event
*event
;
2656 struct buffer_page
*tail_page
;
2657 unsigned long tail
, write
;
2660 * If the time delta since the last event is too big to
2661 * hold in the time field of the event, then we append a
2662 * TIME EXTEND event ahead of the data event.
2664 if (unlikely(info
->add_timestamp
))
2665 info
->length
+= RB_LEN_TIME_EXTEND
;
2667 /* Don't let the compiler play games with cpu_buffer->tail_page */
2668 tail_page
= info
->tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2669 write
= local_add_return(info
->length
, &tail_page
->write
);
2671 /* set write to only the index of the write */
2672 write
&= RB_WRITE_MASK
;
2673 tail
= write
- info
->length
;
2676 * If this is the first commit on the page, then it has the same
2677 * timestamp as the page itself.
2682 /* See if we shot pass the end of this buffer page */
2683 if (unlikely(write
> BUF_PAGE_SIZE
))
2684 return rb_move_tail(cpu_buffer
, tail
, info
);
2686 /* We reserved something on the buffer */
2688 event
= __rb_page_index(tail_page
, tail
);
2689 rb_update_event(cpu_buffer
, event
, info
);
2691 local_inc(&tail_page
->entries
);
2694 * If this is the first commit on the page, then update
2698 tail_page
->page
->time_stamp
= info
->ts
;
2700 /* account for these added bytes */
2701 local_add(info
->length
, &cpu_buffer
->entries_bytes
);
2706 static __always_inline
struct ring_buffer_event
*
2707 rb_reserve_next_event(struct ring_buffer
*buffer
,
2708 struct ring_buffer_per_cpu
*cpu_buffer
,
2709 unsigned long length
)
2711 struct ring_buffer_event
*event
;
2712 struct rb_event_info info
;
2716 rb_start_commit(cpu_buffer
);
2718 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2720 * Due to the ability to swap a cpu buffer from a buffer
2721 * it is possible it was swapped before we committed.
2722 * (committing stops a swap). We check for it here and
2723 * if it happened, we have to fail the write.
2726 if (unlikely(READ_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2727 local_dec(&cpu_buffer
->committing
);
2728 local_dec(&cpu_buffer
->commits
);
2733 info
.length
= rb_calculate_event_length(length
);
2735 info
.add_timestamp
= 0;
2739 * We allow for interrupts to reenter here and do a trace.
2740 * If one does, it will cause this original code to loop
2741 * back here. Even with heavy interrupts happening, this
2742 * should only happen a few times in a row. If this happens
2743 * 1000 times in a row, there must be either an interrupt
2744 * storm or we have something buggy.
2747 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2750 info
.ts
= rb_time_stamp(cpu_buffer
->buffer
);
2751 diff
= info
.ts
- cpu_buffer
->write_stamp
;
2753 /* make sure this diff is calculated here */
2756 /* Did the write stamp get updated already? */
2757 if (likely(info
.ts
>= cpu_buffer
->write_stamp
)) {
2759 if (unlikely(test_time_stamp(info
.delta
)))
2760 rb_handle_timestamp(cpu_buffer
, &info
);
2763 event
= __rb_reserve_next(cpu_buffer
, &info
);
2765 if (unlikely(PTR_ERR(event
) == -EAGAIN
)) {
2766 if (info
.add_timestamp
)
2767 info
.length
-= RB_LEN_TIME_EXTEND
;
2777 rb_end_commit(cpu_buffer
);
2782 * ring_buffer_lock_reserve - reserve a part of the buffer
2783 * @buffer: the ring buffer to reserve from
2784 * @length: the length of the data to reserve (excluding event header)
2786 * Returns a reseverd event on the ring buffer to copy directly to.
2787 * The user of this interface will need to get the body to write into
2788 * and can use the ring_buffer_event_data() interface.
2790 * The length is the length of the data needed, not the event length
2791 * which also includes the event header.
2793 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2794 * If NULL is returned, then nothing has been allocated or locked.
2796 struct ring_buffer_event
*
2797 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2799 struct ring_buffer_per_cpu
*cpu_buffer
;
2800 struct ring_buffer_event
*event
;
2803 /* If we are tracing schedule, we don't want to recurse */
2804 preempt_disable_notrace();
2806 if (unlikely(atomic_read(&buffer
->record_disabled
)))
2809 cpu
= raw_smp_processor_id();
2811 if (unlikely(!cpumask_test_cpu(cpu
, buffer
->cpumask
)))
2814 cpu_buffer
= buffer
->buffers
[cpu
];
2816 if (unlikely(atomic_read(&cpu_buffer
->record_disabled
)))
2819 if (unlikely(length
> BUF_MAX_DATA_SIZE
))
2822 if (unlikely(trace_recursive_lock(cpu_buffer
)))
2825 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2832 trace_recursive_unlock(cpu_buffer
);
2834 preempt_enable_notrace();
2837 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2840 * Decrement the entries to the page that an event is on.
2841 * The event does not even need to exist, only the pointer
2842 * to the page it is on. This may only be called before the commit
2846 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2847 struct ring_buffer_event
*event
)
2849 unsigned long addr
= (unsigned long)event
;
2850 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2851 struct buffer_page
*start
;
2855 /* Do the likely case first */
2856 if (likely(bpage
->page
== (void *)addr
)) {
2857 local_dec(&bpage
->entries
);
2862 * Because the commit page may be on the reader page we
2863 * start with the next page and check the end loop there.
2865 rb_inc_page(cpu_buffer
, &bpage
);
2868 if (bpage
->page
== (void *)addr
) {
2869 local_dec(&bpage
->entries
);
2872 rb_inc_page(cpu_buffer
, &bpage
);
2873 } while (bpage
!= start
);
2875 /* commit not part of this buffer?? */
2876 RB_WARN_ON(cpu_buffer
, 1);
2880 * ring_buffer_commit_discard - discard an event that has not been committed
2881 * @buffer: the ring buffer
2882 * @event: non committed event to discard
2884 * Sometimes an event that is in the ring buffer needs to be ignored.
2885 * This function lets the user discard an event in the ring buffer
2886 * and then that event will not be read later.
2888 * This function only works if it is called before the the item has been
2889 * committed. It will try to free the event from the ring buffer
2890 * if another event has not been added behind it.
2892 * If another event has been added behind it, it will set the event
2893 * up as discarded, and perform the commit.
2895 * If this function is called, do not call ring_buffer_unlock_commit on
2898 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2899 struct ring_buffer_event
*event
)
2901 struct ring_buffer_per_cpu
*cpu_buffer
;
2904 /* The event is discarded regardless */
2905 rb_event_discard(event
);
2907 cpu
= smp_processor_id();
2908 cpu_buffer
= buffer
->buffers
[cpu
];
2911 * This must only be called if the event has not been
2912 * committed yet. Thus we can assume that preemption
2913 * is still disabled.
2915 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2917 rb_decrement_entry(cpu_buffer
, event
);
2918 if (rb_try_to_discard(cpu_buffer
, event
))
2922 * The commit is still visible by the reader, so we
2923 * must still update the timestamp.
2925 rb_update_write_stamp(cpu_buffer
, event
);
2927 rb_end_commit(cpu_buffer
);
2929 trace_recursive_unlock(cpu_buffer
);
2931 preempt_enable_notrace();
2934 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2937 * ring_buffer_write - write data to the buffer without reserving
2938 * @buffer: The ring buffer to write to.
2939 * @length: The length of the data being written (excluding the event header)
2940 * @data: The data to write to the buffer.
2942 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2943 * one function. If you already have the data to write to the buffer, it
2944 * may be easier to simply call this function.
2946 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2947 * and not the length of the event which would hold the header.
2949 int ring_buffer_write(struct ring_buffer
*buffer
,
2950 unsigned long length
,
2953 struct ring_buffer_per_cpu
*cpu_buffer
;
2954 struct ring_buffer_event
*event
;
2959 preempt_disable_notrace();
2961 if (atomic_read(&buffer
->record_disabled
))
2964 cpu
= raw_smp_processor_id();
2966 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2969 cpu_buffer
= buffer
->buffers
[cpu
];
2971 if (atomic_read(&cpu_buffer
->record_disabled
))
2974 if (length
> BUF_MAX_DATA_SIZE
)
2977 if (unlikely(trace_recursive_lock(cpu_buffer
)))
2980 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2984 body
= rb_event_data(event
);
2986 memcpy(body
, data
, length
);
2988 rb_commit(cpu_buffer
, event
);
2990 rb_wakeups(buffer
, cpu_buffer
);
2995 trace_recursive_unlock(cpu_buffer
);
2998 preempt_enable_notrace();
3002 EXPORT_SYMBOL_GPL(ring_buffer_write
);
3004 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
3006 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
3007 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
3008 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
3010 /* In case of error, head will be NULL */
3011 if (unlikely(!head
))
3014 return reader
->read
== rb_page_commit(reader
) &&
3015 (commit
== reader
||
3017 head
->read
== rb_page_commit(commit
)));
3021 * ring_buffer_record_disable - stop all writes into the buffer
3022 * @buffer: The ring buffer to stop writes to.
3024 * This prevents all writes to the buffer. Any attempt to write
3025 * to the buffer after this will fail and return NULL.
3027 * The caller should call synchronize_sched() after this.
3029 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
3031 atomic_inc(&buffer
->record_disabled
);
3033 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
3036 * ring_buffer_record_enable - enable writes to the buffer
3037 * @buffer: The ring buffer to enable writes
3039 * Note, multiple disables will need the same number of enables
3040 * to truly enable the writing (much like preempt_disable).
3042 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
3044 atomic_dec(&buffer
->record_disabled
);
3046 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
3049 * ring_buffer_record_off - stop all writes into the buffer
3050 * @buffer: The ring buffer to stop writes to.
3052 * This prevents all writes to the buffer. Any attempt to write
3053 * to the buffer after this will fail and return NULL.
3055 * This is different than ring_buffer_record_disable() as
3056 * it works like an on/off switch, where as the disable() version
3057 * must be paired with a enable().
3059 void ring_buffer_record_off(struct ring_buffer
*buffer
)
3062 unsigned int new_rd
;
3065 rd
= atomic_read(&buffer
->record_disabled
);
3066 new_rd
= rd
| RB_BUFFER_OFF
;
3067 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3069 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
3072 * ring_buffer_record_on - restart writes into the buffer
3073 * @buffer: The ring buffer to start writes to.
3075 * This enables all writes to the buffer that was disabled by
3076 * ring_buffer_record_off().
3078 * This is different than ring_buffer_record_enable() as
3079 * it works like an on/off switch, where as the enable() version
3080 * must be paired with a disable().
3082 void ring_buffer_record_on(struct ring_buffer
*buffer
)
3085 unsigned int new_rd
;
3088 rd
= atomic_read(&buffer
->record_disabled
);
3089 new_rd
= rd
& ~RB_BUFFER_OFF
;
3090 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3092 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
3095 * ring_buffer_record_is_on - return true if the ring buffer can write
3096 * @buffer: The ring buffer to see if write is enabled
3098 * Returns true if the ring buffer is in a state that it accepts writes.
3100 int ring_buffer_record_is_on(struct ring_buffer
*buffer
)
3102 return !atomic_read(&buffer
->record_disabled
);
3106 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3107 * @buffer: The ring buffer to see if write is set enabled
3109 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3110 * Note that this does NOT mean it is in a writable state.
3112 * It may return true when the ring buffer has been disabled by
3113 * ring_buffer_record_disable(), as that is a temporary disabling of
3116 int ring_buffer_record_is_set_on(struct ring_buffer
*buffer
)
3118 return !(atomic_read(&buffer
->record_disabled
) & RB_BUFFER_OFF
);
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
;
3424 struct buffer_page
*reader
;
3425 struct buffer_page
*head_page
;
3426 struct buffer_page
*commit_page
;
3429 cpu_buffer
= iter
->cpu_buffer
;
3431 /* Remember, trace recording is off when iterator is in use */
3432 reader
= cpu_buffer
->reader_page
;
3433 head_page
= cpu_buffer
->head_page
;
3434 commit_page
= cpu_buffer
->commit_page
;
3435 commit
= rb_page_commit(commit_page
);
3437 return ((iter
->head_page
== commit_page
&& iter
->head
== commit
) ||
3438 (iter
->head_page
== reader
&& commit_page
== head_page
&&
3439 head_page
->read
== commit
&&
3440 iter
->head
== rb_page_commit(cpu_buffer
->reader_page
)));
3442 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
3445 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
3446 struct ring_buffer_event
*event
)
3450 switch (event
->type_len
) {
3451 case RINGBUF_TYPE_PADDING
:
3454 case RINGBUF_TYPE_TIME_EXTEND
:
3455 delta
= event
->array
[0];
3457 delta
+= event
->time_delta
;
3458 cpu_buffer
->read_stamp
+= delta
;
3461 case RINGBUF_TYPE_TIME_STAMP
:
3462 /* FIXME: not implemented */
3465 case RINGBUF_TYPE_DATA
:
3466 cpu_buffer
->read_stamp
+= event
->time_delta
;
3476 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
3477 struct ring_buffer_event
*event
)
3481 switch (event
->type_len
) {
3482 case RINGBUF_TYPE_PADDING
:
3485 case RINGBUF_TYPE_TIME_EXTEND
:
3486 delta
= event
->array
[0];
3488 delta
+= event
->time_delta
;
3489 iter
->read_stamp
+= delta
;
3492 case RINGBUF_TYPE_TIME_STAMP
:
3493 /* FIXME: not implemented */
3496 case RINGBUF_TYPE_DATA
:
3497 iter
->read_stamp
+= event
->time_delta
;
3506 static struct buffer_page
*
3507 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
3509 struct buffer_page
*reader
= NULL
;
3510 unsigned long overwrite
;
3511 unsigned long flags
;
3515 local_irq_save(flags
);
3516 arch_spin_lock(&cpu_buffer
->lock
);
3520 * This should normally only loop twice. But because the
3521 * start of the reader inserts an empty page, it causes
3522 * a case where we will loop three times. There should be no
3523 * reason to loop four times (that I know of).
3525 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
3530 reader
= cpu_buffer
->reader_page
;
3532 /* If there's more to read, return this page */
3533 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
3536 /* Never should we have an index greater than the size */
3537 if (RB_WARN_ON(cpu_buffer
,
3538 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
3541 /* check if we caught up to the tail */
3543 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
3546 /* Don't bother swapping if the ring buffer is empty */
3547 if (rb_num_of_entries(cpu_buffer
) == 0)
3551 * Reset the reader page to size zero.
3553 local_set(&cpu_buffer
->reader_page
->write
, 0);
3554 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3555 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3556 cpu_buffer
->reader_page
->real_end
= 0;
3560 * Splice the empty reader page into the list around the head.
3562 reader
= rb_set_head_page(cpu_buffer
);
3565 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
3566 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
3569 * cpu_buffer->pages just needs to point to the buffer, it
3570 * has no specific buffer page to point to. Lets move it out
3571 * of our way so we don't accidentally swap it.
3573 cpu_buffer
->pages
= reader
->list
.prev
;
3575 /* The reader page will be pointing to the new head */
3576 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
3579 * We want to make sure we read the overruns after we set up our
3580 * pointers to the next object. The writer side does a
3581 * cmpxchg to cross pages which acts as the mb on the writer
3582 * side. Note, the reader will constantly fail the swap
3583 * while the writer is updating the pointers, so this
3584 * guarantees that the overwrite recorded here is the one we
3585 * want to compare with the last_overrun.
3588 overwrite
= local_read(&(cpu_buffer
->overrun
));
3591 * Here's the tricky part.
3593 * We need to move the pointer past the header page.
3594 * But we can only do that if a writer is not currently
3595 * moving it. The page before the header page has the
3596 * flag bit '1' set if it is pointing to the page we want.
3597 * but if the writer is in the process of moving it
3598 * than it will be '2' or already moved '0'.
3601 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
3604 * If we did not convert it, then we must try again.
3610 * Yeah! We succeeded in replacing the page.
3612 * Now make the new head point back to the reader page.
3614 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
3615 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
3617 /* Finally update the reader page to the new head */
3618 cpu_buffer
->reader_page
= reader
;
3619 cpu_buffer
->reader_page
->read
= 0;
3621 if (overwrite
!= cpu_buffer
->last_overrun
) {
3622 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
3623 cpu_buffer
->last_overrun
= overwrite
;
3629 /* Update the read_stamp on the first event */
3630 if (reader
&& reader
->read
== 0)
3631 cpu_buffer
->read_stamp
= reader
->page
->time_stamp
;
3633 arch_spin_unlock(&cpu_buffer
->lock
);
3634 local_irq_restore(flags
);
3639 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
3641 struct ring_buffer_event
*event
;
3642 struct buffer_page
*reader
;
3645 reader
= rb_get_reader_page(cpu_buffer
);
3647 /* This function should not be called when buffer is empty */
3648 if (RB_WARN_ON(cpu_buffer
, !reader
))
3651 event
= rb_reader_event(cpu_buffer
);
3653 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
3656 rb_update_read_stamp(cpu_buffer
, event
);
3658 length
= rb_event_length(event
);
3659 cpu_buffer
->reader_page
->read
+= length
;
3662 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
3664 struct ring_buffer_per_cpu
*cpu_buffer
;
3665 struct ring_buffer_event
*event
;
3668 cpu_buffer
= iter
->cpu_buffer
;
3671 * Check if we are at the end of the buffer.
3673 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3674 /* discarded commits can make the page empty */
3675 if (iter
->head_page
== cpu_buffer
->commit_page
)
3681 event
= rb_iter_head_event(iter
);
3683 length
= rb_event_length(event
);
3686 * This should not be called to advance the header if we are
3687 * at the tail of the buffer.
3689 if (RB_WARN_ON(cpu_buffer
,
3690 (iter
->head_page
== cpu_buffer
->commit_page
) &&
3691 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
3694 rb_update_iter_read_stamp(iter
, event
);
3696 iter
->head
+= length
;
3698 /* check for end of page padding */
3699 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3700 (iter
->head_page
!= cpu_buffer
->commit_page
))
3704 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
3706 return cpu_buffer
->lost_events
;
3709 static struct ring_buffer_event
*
3710 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
3711 unsigned long *lost_events
)
3713 struct ring_buffer_event
*event
;
3714 struct buffer_page
*reader
;
3719 * We repeat when a time extend is encountered.
3720 * Since the time extend is always attached to a data event,
3721 * we should never loop more than once.
3722 * (We never hit the following condition more than twice).
3724 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
3727 reader
= rb_get_reader_page(cpu_buffer
);
3731 event
= rb_reader_event(cpu_buffer
);
3733 switch (event
->type_len
) {
3734 case RINGBUF_TYPE_PADDING
:
3735 if (rb_null_event(event
))
3736 RB_WARN_ON(cpu_buffer
, 1);
3738 * Because the writer could be discarding every
3739 * event it creates (which would probably be bad)
3740 * if we were to go back to "again" then we may never
3741 * catch up, and will trigger the warn on, or lock
3742 * the box. Return the padding, and we will release
3743 * the current locks, and try again.
3747 case RINGBUF_TYPE_TIME_EXTEND
:
3748 /* Internal data, OK to advance */
3749 rb_advance_reader(cpu_buffer
);
3752 case RINGBUF_TYPE_TIME_STAMP
:
3753 /* FIXME: not implemented */
3754 rb_advance_reader(cpu_buffer
);
3757 case RINGBUF_TYPE_DATA
:
3759 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3760 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3761 cpu_buffer
->cpu
, ts
);
3764 *lost_events
= rb_lost_events(cpu_buffer
);
3773 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3775 static struct ring_buffer_event
*
3776 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3778 struct ring_buffer
*buffer
;
3779 struct ring_buffer_per_cpu
*cpu_buffer
;
3780 struct ring_buffer_event
*event
;
3783 cpu_buffer
= iter
->cpu_buffer
;
3784 buffer
= cpu_buffer
->buffer
;
3787 * Check if someone performed a consuming read to
3788 * the buffer. A consuming read invalidates the iterator
3789 * and we need to reset the iterator in this case.
3791 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3792 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3793 rb_iter_reset(iter
);
3796 if (ring_buffer_iter_empty(iter
))
3800 * We repeat when a time extend is encountered or we hit
3801 * the end of the page. Since the time extend is always attached
3802 * to a data event, we should never loop more than three times.
3803 * Once for going to next page, once on time extend, and
3804 * finally once to get the event.
3805 * (We never hit the following condition more than thrice).
3807 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3))
3810 if (rb_per_cpu_empty(cpu_buffer
))
3813 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3818 event
= rb_iter_head_event(iter
);
3820 switch (event
->type_len
) {
3821 case RINGBUF_TYPE_PADDING
:
3822 if (rb_null_event(event
)) {
3826 rb_advance_iter(iter
);
3829 case RINGBUF_TYPE_TIME_EXTEND
:
3830 /* Internal data, OK to advance */
3831 rb_advance_iter(iter
);
3834 case RINGBUF_TYPE_TIME_STAMP
:
3835 /* FIXME: not implemented */
3836 rb_advance_iter(iter
);
3839 case RINGBUF_TYPE_DATA
:
3841 *ts
= iter
->read_stamp
+ event
->time_delta
;
3842 ring_buffer_normalize_time_stamp(buffer
,
3843 cpu_buffer
->cpu
, ts
);
3853 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3855 static inline bool rb_reader_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
3857 if (likely(!in_nmi())) {
3858 raw_spin_lock(&cpu_buffer
->reader_lock
);
3863 * If an NMI die dumps out the content of the ring buffer
3864 * trylock must be used to prevent a deadlock if the NMI
3865 * preempted a task that holds the ring buffer locks. If
3866 * we get the lock then all is fine, if not, then continue
3867 * to do the read, but this can corrupt the ring buffer,
3868 * so it must be permanently disabled from future writes.
3869 * Reading from NMI is a oneshot deal.
3871 if (raw_spin_trylock(&cpu_buffer
->reader_lock
))
3874 /* Continue without locking, but disable the ring buffer */
3875 atomic_inc(&cpu_buffer
->record_disabled
);
3880 rb_reader_unlock(struct ring_buffer_per_cpu
*cpu_buffer
, bool locked
)
3883 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3888 * ring_buffer_peek - peek at the next event to be read
3889 * @buffer: The ring buffer to read
3890 * @cpu: The cpu to peak at
3891 * @ts: The timestamp counter of this event.
3892 * @lost_events: a variable to store if events were lost (may be NULL)
3894 * This will return the event that will be read next, but does
3895 * not consume the data.
3897 struct ring_buffer_event
*
3898 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3899 unsigned long *lost_events
)
3901 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3902 struct ring_buffer_event
*event
;
3903 unsigned long flags
;
3906 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3910 local_irq_save(flags
);
3911 dolock
= rb_reader_lock(cpu_buffer
);
3912 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3913 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3914 rb_advance_reader(cpu_buffer
);
3915 rb_reader_unlock(cpu_buffer
, dolock
);
3916 local_irq_restore(flags
);
3918 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3925 * ring_buffer_iter_peek - peek at the next event to be read
3926 * @iter: The ring buffer iterator
3927 * @ts: The timestamp counter of this event.
3929 * This will return the event that will be read next, but does
3930 * not increment the iterator.
3932 struct ring_buffer_event
*
3933 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3935 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3936 struct ring_buffer_event
*event
;
3937 unsigned long flags
;
3940 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3941 event
= rb_iter_peek(iter
, ts
);
3942 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3944 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3951 * ring_buffer_consume - return an event and consume it
3952 * @buffer: The ring buffer to get the next event from
3953 * @cpu: the cpu to read the buffer from
3954 * @ts: a variable to store the timestamp (may be NULL)
3955 * @lost_events: a variable to store if events were lost (may be NULL)
3957 * Returns the next event in the ring buffer, and that event is consumed.
3958 * Meaning, that sequential reads will keep returning a different event,
3959 * and eventually empty the ring buffer if the producer is slower.
3961 struct ring_buffer_event
*
3962 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3963 unsigned long *lost_events
)
3965 struct ring_buffer_per_cpu
*cpu_buffer
;
3966 struct ring_buffer_event
*event
= NULL
;
3967 unsigned long flags
;
3971 /* might be called in atomic */
3974 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3977 cpu_buffer
= buffer
->buffers
[cpu
];
3978 local_irq_save(flags
);
3979 dolock
= rb_reader_lock(cpu_buffer
);
3981 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3983 cpu_buffer
->lost_events
= 0;
3984 rb_advance_reader(cpu_buffer
);
3987 rb_reader_unlock(cpu_buffer
, dolock
);
3988 local_irq_restore(flags
);
3993 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3998 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
4001 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4002 * @buffer: The ring buffer to read from
4003 * @cpu: The cpu buffer to iterate over
4004 * @flags: gfp flags to use for memory allocation
4006 * This performs the initial preparations necessary to iterate
4007 * through the buffer. Memory is allocated, buffer recording
4008 * is disabled, and the iterator pointer is returned to the caller.
4010 * Disabling buffer recordng prevents the reading from being
4011 * corrupted. This is not a consuming read, so a producer is not
4014 * After a sequence of ring_buffer_read_prepare calls, the user is
4015 * expected to make at least one call to ring_buffer_read_prepare_sync.
4016 * Afterwards, ring_buffer_read_start is invoked to get things going
4019 * This overall must be paired with ring_buffer_read_finish.
4021 struct ring_buffer_iter
*
4022 ring_buffer_read_prepare(struct ring_buffer
*buffer
, int cpu
, gfp_t flags
)
4024 struct ring_buffer_per_cpu
*cpu_buffer
;
4025 struct ring_buffer_iter
*iter
;
4027 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4030 iter
= kmalloc(sizeof(*iter
), flags
);
4034 cpu_buffer
= buffer
->buffers
[cpu
];
4036 iter
->cpu_buffer
= cpu_buffer
;
4038 atomic_inc(&buffer
->resize_disabled
);
4039 atomic_inc(&cpu_buffer
->record_disabled
);
4043 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
4046 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4048 * All previously invoked ring_buffer_read_prepare calls to prepare
4049 * iterators will be synchronized. Afterwards, read_buffer_read_start
4050 * calls on those iterators are allowed.
4053 ring_buffer_read_prepare_sync(void)
4055 synchronize_sched();
4057 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
4060 * ring_buffer_read_start - start a non consuming read of the buffer
4061 * @iter: The iterator returned by ring_buffer_read_prepare
4063 * This finalizes the startup of an iteration through the buffer.
4064 * The iterator comes from a call to ring_buffer_read_prepare and
4065 * an intervening ring_buffer_read_prepare_sync must have been
4068 * Must be paired with ring_buffer_read_finish.
4071 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
4073 struct ring_buffer_per_cpu
*cpu_buffer
;
4074 unsigned long flags
;
4079 cpu_buffer
= iter
->cpu_buffer
;
4081 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4082 arch_spin_lock(&cpu_buffer
->lock
);
4083 rb_iter_reset(iter
);
4084 arch_spin_unlock(&cpu_buffer
->lock
);
4085 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4087 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
4090 * ring_buffer_read_finish - finish reading the iterator of the buffer
4091 * @iter: The iterator retrieved by ring_buffer_start
4093 * This re-enables the recording to the buffer, and frees the
4097 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
4099 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4100 unsigned long flags
;
4103 * Ring buffer is disabled from recording, here's a good place
4104 * to check the integrity of the ring buffer.
4105 * Must prevent readers from trying to read, as the check
4106 * clears the HEAD page and readers require it.
4108 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4109 rb_check_pages(cpu_buffer
);
4110 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4112 atomic_dec(&cpu_buffer
->record_disabled
);
4113 atomic_dec(&cpu_buffer
->buffer
->resize_disabled
);
4116 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
4119 * ring_buffer_read - read the next item in the ring buffer by the iterator
4120 * @iter: The ring buffer iterator
4121 * @ts: The time stamp of the event read.
4123 * This reads the next event in the ring buffer and increments the iterator.
4125 struct ring_buffer_event
*
4126 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
4128 struct ring_buffer_event
*event
;
4129 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4130 unsigned long flags
;
4132 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4134 event
= rb_iter_peek(iter
, ts
);
4138 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
4141 rb_advance_iter(iter
);
4143 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4147 EXPORT_SYMBOL_GPL(ring_buffer_read
);
4150 * ring_buffer_size - return the size of the ring buffer (in bytes)
4151 * @buffer: The ring buffer.
4153 unsigned long ring_buffer_size(struct ring_buffer
*buffer
, int cpu
)
4156 * Earlier, this method returned
4157 * BUF_PAGE_SIZE * buffer->nr_pages
4158 * Since the nr_pages field is now removed, we have converted this to
4159 * return the per cpu buffer value.
4161 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4164 return BUF_PAGE_SIZE
* buffer
->buffers
[cpu
]->nr_pages
;
4166 EXPORT_SYMBOL_GPL(ring_buffer_size
);
4169 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
4171 rb_head_page_deactivate(cpu_buffer
);
4173 cpu_buffer
->head_page
4174 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
4175 local_set(&cpu_buffer
->head_page
->write
, 0);
4176 local_set(&cpu_buffer
->head_page
->entries
, 0);
4177 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
4179 cpu_buffer
->head_page
->read
= 0;
4181 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
4182 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
4184 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
4185 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
4186 local_set(&cpu_buffer
->reader_page
->write
, 0);
4187 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4188 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4189 cpu_buffer
->reader_page
->read
= 0;
4191 local_set(&cpu_buffer
->entries_bytes
, 0);
4192 local_set(&cpu_buffer
->overrun
, 0);
4193 local_set(&cpu_buffer
->commit_overrun
, 0);
4194 local_set(&cpu_buffer
->dropped_events
, 0);
4195 local_set(&cpu_buffer
->entries
, 0);
4196 local_set(&cpu_buffer
->committing
, 0);
4197 local_set(&cpu_buffer
->commits
, 0);
4198 cpu_buffer
->read
= 0;
4199 cpu_buffer
->read_bytes
= 0;
4201 cpu_buffer
->write_stamp
= 0;
4202 cpu_buffer
->read_stamp
= 0;
4204 cpu_buffer
->lost_events
= 0;
4205 cpu_buffer
->last_overrun
= 0;
4207 rb_head_page_activate(cpu_buffer
);
4211 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4212 * @buffer: The ring buffer to reset a per cpu buffer of
4213 * @cpu: The CPU buffer to be reset
4215 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
4217 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4218 unsigned long flags
;
4220 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4223 atomic_inc(&buffer
->resize_disabled
);
4224 atomic_inc(&cpu_buffer
->record_disabled
);
4226 /* Make sure all commits have finished */
4227 synchronize_sched();
4229 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4231 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
4234 arch_spin_lock(&cpu_buffer
->lock
);
4236 rb_reset_cpu(cpu_buffer
);
4238 arch_spin_unlock(&cpu_buffer
->lock
);
4241 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4243 atomic_dec(&cpu_buffer
->record_disabled
);
4244 atomic_dec(&buffer
->resize_disabled
);
4246 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
4249 * ring_buffer_reset - reset a ring buffer
4250 * @buffer: The ring buffer to reset all cpu buffers
4252 void ring_buffer_reset(struct ring_buffer
*buffer
)
4256 for_each_buffer_cpu(buffer
, cpu
)
4257 ring_buffer_reset_cpu(buffer
, cpu
);
4259 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
4262 * rind_buffer_empty - is the ring buffer empty?
4263 * @buffer: The ring buffer to test
4265 bool ring_buffer_empty(struct ring_buffer
*buffer
)
4267 struct ring_buffer_per_cpu
*cpu_buffer
;
4268 unsigned long flags
;
4273 /* yes this is racy, but if you don't like the race, lock the buffer */
4274 for_each_buffer_cpu(buffer
, cpu
) {
4275 cpu_buffer
= buffer
->buffers
[cpu
];
4276 local_irq_save(flags
);
4277 dolock
= rb_reader_lock(cpu_buffer
);
4278 ret
= rb_per_cpu_empty(cpu_buffer
);
4279 rb_reader_unlock(cpu_buffer
, dolock
);
4280 local_irq_restore(flags
);
4288 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
4291 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4292 * @buffer: The ring buffer
4293 * @cpu: The CPU buffer to test
4295 bool ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
4297 struct ring_buffer_per_cpu
*cpu_buffer
;
4298 unsigned long flags
;
4302 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4305 cpu_buffer
= buffer
->buffers
[cpu
];
4306 local_irq_save(flags
);
4307 dolock
= rb_reader_lock(cpu_buffer
);
4308 ret
= rb_per_cpu_empty(cpu_buffer
);
4309 rb_reader_unlock(cpu_buffer
, dolock
);
4310 local_irq_restore(flags
);
4314 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
4316 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4318 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4319 * @buffer_a: One buffer to swap with
4320 * @buffer_b: The other buffer to swap with
4322 * This function is useful for tracers that want to take a "snapshot"
4323 * of a CPU buffer and has another back up buffer lying around.
4324 * it is expected that the tracer handles the cpu buffer not being
4325 * used at the moment.
4327 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
4328 struct ring_buffer
*buffer_b
, int cpu
)
4330 struct ring_buffer_per_cpu
*cpu_buffer_a
;
4331 struct ring_buffer_per_cpu
*cpu_buffer_b
;
4334 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
4335 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
4338 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
4339 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
4341 /* At least make sure the two buffers are somewhat the same */
4342 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
4347 if (atomic_read(&buffer_a
->record_disabled
))
4350 if (atomic_read(&buffer_b
->record_disabled
))
4353 if (atomic_read(&cpu_buffer_a
->record_disabled
))
4356 if (atomic_read(&cpu_buffer_b
->record_disabled
))
4360 * We can't do a synchronize_sched here because this
4361 * function can be called in atomic context.
4362 * Normally this will be called from the same CPU as cpu.
4363 * If not it's up to the caller to protect this.
4365 atomic_inc(&cpu_buffer_a
->record_disabled
);
4366 atomic_inc(&cpu_buffer_b
->record_disabled
);
4369 if (local_read(&cpu_buffer_a
->committing
))
4371 if (local_read(&cpu_buffer_b
->committing
))
4374 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
4375 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
4377 cpu_buffer_b
->buffer
= buffer_a
;
4378 cpu_buffer_a
->buffer
= buffer_b
;
4383 atomic_dec(&cpu_buffer_a
->record_disabled
);
4384 atomic_dec(&cpu_buffer_b
->record_disabled
);
4388 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
4389 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4392 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4393 * @buffer: the buffer to allocate for.
4394 * @cpu: the cpu buffer to allocate.
4396 * This function is used in conjunction with ring_buffer_read_page.
4397 * When reading a full page from the ring buffer, these functions
4398 * can be used to speed up the process. The calling function should
4399 * allocate a few pages first with this function. Then when it
4400 * needs to get pages from the ring buffer, it passes the result
4401 * of this function into ring_buffer_read_page, which will swap
4402 * the page that was allocated, with the read page of the buffer.
4405 * The page allocated, or ERR_PTR
4407 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
, int cpu
)
4409 struct ring_buffer_per_cpu
*cpu_buffer
;
4410 struct buffer_data_page
*bpage
= NULL
;
4411 unsigned long flags
;
4414 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4415 return ERR_PTR(-ENODEV
);
4417 cpu_buffer
= buffer
->buffers
[cpu
];
4418 local_irq_save(flags
);
4419 arch_spin_lock(&cpu_buffer
->lock
);
4421 if (cpu_buffer
->free_page
) {
4422 bpage
= cpu_buffer
->free_page
;
4423 cpu_buffer
->free_page
= NULL
;
4426 arch_spin_unlock(&cpu_buffer
->lock
);
4427 local_irq_restore(flags
);
4432 page
= alloc_pages_node(cpu_to_node(cpu
),
4433 GFP_KERNEL
| __GFP_NORETRY
, 0);
4435 return ERR_PTR(-ENOMEM
);
4437 bpage
= page_address(page
);
4440 rb_init_page(bpage
);
4444 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
4447 * ring_buffer_free_read_page - free an allocated read page
4448 * @buffer: the buffer the page was allocate for
4449 * @cpu: the cpu buffer the page came from
4450 * @data: the page to free
4452 * Free a page allocated from ring_buffer_alloc_read_page.
4454 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, int cpu
, void *data
)
4456 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4457 struct buffer_data_page
*bpage
= data
;
4458 struct page
*page
= virt_to_page(bpage
);
4459 unsigned long flags
;
4461 /* If the page is still in use someplace else, we can't reuse it */
4462 if (page_ref_count(page
) > 1)
4465 local_irq_save(flags
);
4466 arch_spin_lock(&cpu_buffer
->lock
);
4468 if (!cpu_buffer
->free_page
) {
4469 cpu_buffer
->free_page
= bpage
;
4473 arch_spin_unlock(&cpu_buffer
->lock
);
4474 local_irq_restore(flags
);
4477 free_page((unsigned long)bpage
);
4479 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
4482 * ring_buffer_read_page - extract a page from the ring buffer
4483 * @buffer: buffer to extract from
4484 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4485 * @len: amount to extract
4486 * @cpu: the cpu of the buffer to extract
4487 * @full: should the extraction only happen when the page is full.
4489 * This function will pull out a page from the ring buffer and consume it.
4490 * @data_page must be the address of the variable that was returned
4491 * from ring_buffer_alloc_read_page. This is because the page might be used
4492 * to swap with a page in the ring buffer.
4495 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4496 * if (IS_ERR(rpage))
4497 * return PTR_ERR(rpage);
4498 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4500 * process_page(rpage, ret);
4502 * When @full is set, the function will not return true unless
4503 * the writer is off the reader page.
4505 * Note: it is up to the calling functions to handle sleeps and wakeups.
4506 * The ring buffer can be used anywhere in the kernel and can not
4507 * blindly call wake_up. The layer that uses the ring buffer must be
4508 * responsible for that.
4511 * >=0 if data has been transferred, returns the offset of consumed data.
4512 * <0 if no data has been transferred.
4514 int ring_buffer_read_page(struct ring_buffer
*buffer
,
4515 void **data_page
, size_t len
, int cpu
, int full
)
4517 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4518 struct ring_buffer_event
*event
;
4519 struct buffer_data_page
*bpage
;
4520 struct buffer_page
*reader
;
4521 unsigned long missed_events
;
4522 unsigned long flags
;
4523 unsigned int commit
;
4528 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4532 * If len is not big enough to hold the page header, then
4533 * we can not copy anything.
4535 if (len
<= BUF_PAGE_HDR_SIZE
)
4538 len
-= BUF_PAGE_HDR_SIZE
;
4547 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4549 reader
= rb_get_reader_page(cpu_buffer
);
4553 event
= rb_reader_event(cpu_buffer
);
4555 read
= reader
->read
;
4556 commit
= rb_page_commit(reader
);
4558 /* Check if any events were dropped */
4559 missed_events
= cpu_buffer
->lost_events
;
4562 * If this page has been partially read or
4563 * if len is not big enough to read the rest of the page or
4564 * a writer is still on the page, then
4565 * we must copy the data from the page to the buffer.
4566 * Otherwise, we can simply swap the page with the one passed in.
4568 if (read
|| (len
< (commit
- read
)) ||
4569 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
4570 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
4571 unsigned int rpos
= read
;
4572 unsigned int pos
= 0;
4578 if (len
> (commit
- read
))
4579 len
= (commit
- read
);
4581 /* Always keep the time extend and data together */
4582 size
= rb_event_ts_length(event
);
4587 /* save the current timestamp, since the user will need it */
4588 save_timestamp
= cpu_buffer
->read_stamp
;
4590 /* Need to copy one event at a time */
4592 /* We need the size of one event, because
4593 * rb_advance_reader only advances by one event,
4594 * whereas rb_event_ts_length may include the size of
4595 * one or two events.
4596 * We have already ensured there's enough space if this
4597 * is a time extend. */
4598 size
= rb_event_length(event
);
4599 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
4603 rb_advance_reader(cpu_buffer
);
4604 rpos
= reader
->read
;
4610 event
= rb_reader_event(cpu_buffer
);
4611 /* Always keep the time extend and data together */
4612 size
= rb_event_ts_length(event
);
4613 } while (len
>= size
);
4616 local_set(&bpage
->commit
, pos
);
4617 bpage
->time_stamp
= save_timestamp
;
4619 /* we copied everything to the beginning */
4622 /* update the entry counter */
4623 cpu_buffer
->read
+= rb_page_entries(reader
);
4624 cpu_buffer
->read_bytes
+= BUF_PAGE_SIZE
;
4626 /* swap the pages */
4627 rb_init_page(bpage
);
4628 bpage
= reader
->page
;
4629 reader
->page
= *data_page
;
4630 local_set(&reader
->write
, 0);
4631 local_set(&reader
->entries
, 0);
4636 * Use the real_end for the data size,
4637 * This gives us a chance to store the lost events
4640 if (reader
->real_end
)
4641 local_set(&bpage
->commit
, reader
->real_end
);
4645 cpu_buffer
->lost_events
= 0;
4647 commit
= local_read(&bpage
->commit
);
4649 * Set a flag in the commit field if we lost events
4651 if (missed_events
) {
4652 /* If there is room at the end of the page to save the
4653 * missed events, then record it there.
4655 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
4656 memcpy(&bpage
->data
[commit
], &missed_events
,
4657 sizeof(missed_events
));
4658 local_add(RB_MISSED_STORED
, &bpage
->commit
);
4659 commit
+= sizeof(missed_events
);
4661 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
4665 * This page may be off to user land. Zero it out here.
4667 if (commit
< BUF_PAGE_SIZE
)
4668 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
4671 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4676 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
4679 * We only allocate new buffers, never free them if the CPU goes down.
4680 * If we were to free the buffer, then the user would lose any trace that was in
4683 int trace_rb_cpu_prepare(unsigned int cpu
, struct hlist_node
*node
)
4685 struct ring_buffer
*buffer
;
4688 unsigned long nr_pages
;
4690 buffer
= container_of(node
, struct ring_buffer
, node
);
4691 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
4696 /* check if all cpu sizes are same */
4697 for_each_buffer_cpu(buffer
, cpu_i
) {
4698 /* fill in the size from first enabled cpu */
4700 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
4701 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
4706 /* allocate minimum pages, user can later expand it */
4709 buffer
->buffers
[cpu
] =
4710 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
4711 if (!buffer
->buffers
[cpu
]) {
4712 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4717 cpumask_set_cpu(cpu
, buffer
->cpumask
);
4721 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4723 * This is a basic integrity check of the ring buffer.
4724 * Late in the boot cycle this test will run when configured in.
4725 * It will kick off a thread per CPU that will go into a loop
4726 * writing to the per cpu ring buffer various sizes of data.
4727 * Some of the data will be large items, some small.
4729 * Another thread is created that goes into a spin, sending out
4730 * IPIs to the other CPUs to also write into the ring buffer.
4731 * this is to test the nesting ability of the buffer.
4733 * Basic stats are recorded and reported. If something in the
4734 * ring buffer should happen that's not expected, a big warning
4735 * is displayed and all ring buffers are disabled.
4737 static struct task_struct
*rb_threads
[NR_CPUS
] __initdata
;
4739 struct rb_test_data
{
4740 struct ring_buffer
*buffer
;
4741 unsigned long events
;
4742 unsigned long bytes_written
;
4743 unsigned long bytes_alloc
;
4744 unsigned long bytes_dropped
;
4745 unsigned long events_nested
;
4746 unsigned long bytes_written_nested
;
4747 unsigned long bytes_alloc_nested
;
4748 unsigned long bytes_dropped_nested
;
4749 int min_size_nested
;
4750 int max_size_nested
;
4757 static struct rb_test_data rb_data
[NR_CPUS
] __initdata
;
4760 #define RB_TEST_BUFFER_SIZE 1048576
4762 static char rb_string
[] __initdata
=
4763 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4764 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4765 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4767 static bool rb_test_started __initdata
;
4774 static __init
int rb_write_something(struct rb_test_data
*data
, bool nested
)
4776 struct ring_buffer_event
*event
;
4777 struct rb_item
*item
;
4784 /* Have nested writes different that what is written */
4785 cnt
= data
->cnt
+ (nested
? 27 : 0);
4787 /* Multiply cnt by ~e, to make some unique increment */
4788 size
= (data
->cnt
* 68 / 25) % (sizeof(rb_string
) - 1);
4790 len
= size
+ sizeof(struct rb_item
);
4792 started
= rb_test_started
;
4793 /* read rb_test_started before checking buffer enabled */
4796 event
= ring_buffer_lock_reserve(data
->buffer
, len
);
4798 /* Ignore dropped events before test starts. */
4801 data
->bytes_dropped
+= len
;
4803 data
->bytes_dropped_nested
+= len
;
4808 event_len
= ring_buffer_event_length(event
);
4810 if (RB_WARN_ON(data
->buffer
, event_len
< len
))
4813 item
= ring_buffer_event_data(event
);
4815 memcpy(item
->str
, rb_string
, size
);
4818 data
->bytes_alloc_nested
+= event_len
;
4819 data
->bytes_written_nested
+= len
;
4820 data
->events_nested
++;
4821 if (!data
->min_size_nested
|| len
< data
->min_size_nested
)
4822 data
->min_size_nested
= len
;
4823 if (len
> data
->max_size_nested
)
4824 data
->max_size_nested
= len
;
4826 data
->bytes_alloc
+= event_len
;
4827 data
->bytes_written
+= len
;
4829 if (!data
->min_size
|| len
< data
->min_size
)
4830 data
->max_size
= len
;
4831 if (len
> data
->max_size
)
4832 data
->max_size
= len
;
4836 ring_buffer_unlock_commit(data
->buffer
, event
);
4841 static __init
int rb_test(void *arg
)
4843 struct rb_test_data
*data
= arg
;
4845 while (!kthread_should_stop()) {
4846 rb_write_something(data
, false);
4849 set_current_state(TASK_INTERRUPTIBLE
);
4850 /* Now sleep between a min of 100-300us and a max of 1ms */
4851 usleep_range(((data
->cnt
% 3) + 1) * 100, 1000);
4857 static __init
void rb_ipi(void *ignore
)
4859 struct rb_test_data
*data
;
4860 int cpu
= smp_processor_id();
4862 data
= &rb_data
[cpu
];
4863 rb_write_something(data
, true);
4866 static __init
int rb_hammer_test(void *arg
)
4868 while (!kthread_should_stop()) {
4870 /* Send an IPI to all cpus to write data! */
4871 smp_call_function(rb_ipi
, NULL
, 1);
4872 /* No sleep, but for non preempt, let others run */
4879 static __init
int test_ringbuffer(void)
4881 struct task_struct
*rb_hammer
;
4882 struct ring_buffer
*buffer
;
4886 pr_info("Running ring buffer tests...\n");
4888 buffer
= ring_buffer_alloc(RB_TEST_BUFFER_SIZE
, RB_FL_OVERWRITE
);
4889 if (WARN_ON(!buffer
))
4892 /* Disable buffer so that threads can't write to it yet */
4893 ring_buffer_record_off(buffer
);
4895 for_each_online_cpu(cpu
) {
4896 rb_data
[cpu
].buffer
= buffer
;
4897 rb_data
[cpu
].cpu
= cpu
;
4898 rb_data
[cpu
].cnt
= cpu
;
4899 rb_threads
[cpu
] = kthread_create(rb_test
, &rb_data
[cpu
],
4900 "rbtester/%d", cpu
);
4901 if (WARN_ON(IS_ERR(rb_threads
[cpu
]))) {
4902 pr_cont("FAILED\n");
4903 ret
= PTR_ERR(rb_threads
[cpu
]);
4907 kthread_bind(rb_threads
[cpu
], cpu
);
4908 wake_up_process(rb_threads
[cpu
]);
4911 /* Now create the rb hammer! */
4912 rb_hammer
= kthread_run(rb_hammer_test
, NULL
, "rbhammer");
4913 if (WARN_ON(IS_ERR(rb_hammer
))) {
4914 pr_cont("FAILED\n");
4915 ret
= PTR_ERR(rb_hammer
);
4919 ring_buffer_record_on(buffer
);
4921 * Show buffer is enabled before setting rb_test_started.
4922 * Yes there's a small race window where events could be
4923 * dropped and the thread wont catch it. But when a ring
4924 * buffer gets enabled, there will always be some kind of
4925 * delay before other CPUs see it. Thus, we don't care about
4926 * those dropped events. We care about events dropped after
4927 * the threads see that the buffer is active.
4930 rb_test_started
= true;
4932 set_current_state(TASK_INTERRUPTIBLE
);
4933 /* Just run for 10 seconds */;
4934 schedule_timeout(10 * HZ
);
4936 kthread_stop(rb_hammer
);
4939 for_each_online_cpu(cpu
) {
4940 if (!rb_threads
[cpu
])
4942 kthread_stop(rb_threads
[cpu
]);
4945 ring_buffer_free(buffer
);
4950 pr_info("finished\n");
4951 for_each_online_cpu(cpu
) {
4952 struct ring_buffer_event
*event
;
4953 struct rb_test_data
*data
= &rb_data
[cpu
];
4954 struct rb_item
*item
;
4955 unsigned long total_events
;
4956 unsigned long total_dropped
;
4957 unsigned long total_written
;
4958 unsigned long total_alloc
;
4959 unsigned long total_read
= 0;
4960 unsigned long total_size
= 0;
4961 unsigned long total_len
= 0;
4962 unsigned long total_lost
= 0;
4965 int small_event_size
;
4969 total_events
= data
->events
+ data
->events_nested
;
4970 total_written
= data
->bytes_written
+ data
->bytes_written_nested
;
4971 total_alloc
= data
->bytes_alloc
+ data
->bytes_alloc_nested
;
4972 total_dropped
= data
->bytes_dropped
+ data
->bytes_dropped_nested
;
4974 big_event_size
= data
->max_size
+ data
->max_size_nested
;
4975 small_event_size
= data
->min_size
+ data
->min_size_nested
;
4977 pr_info("CPU %d:\n", cpu
);
4978 pr_info(" events: %ld\n", total_events
);
4979 pr_info(" dropped bytes: %ld\n", total_dropped
);
4980 pr_info(" alloced bytes: %ld\n", total_alloc
);
4981 pr_info(" written bytes: %ld\n", total_written
);
4982 pr_info(" biggest event: %d\n", big_event_size
);
4983 pr_info(" smallest event: %d\n", small_event_size
);
4985 if (RB_WARN_ON(buffer
, total_dropped
))
4990 while ((event
= ring_buffer_consume(buffer
, cpu
, NULL
, &lost
))) {
4992 item
= ring_buffer_event_data(event
);
4993 total_len
+= ring_buffer_event_length(event
);
4994 total_size
+= item
->size
+ sizeof(struct rb_item
);
4995 if (memcmp(&item
->str
[0], rb_string
, item
->size
) != 0) {
4996 pr_info("FAILED!\n");
4997 pr_info("buffer had: %.*s\n", item
->size
, item
->str
);
4998 pr_info("expected: %.*s\n", item
->size
, rb_string
);
4999 RB_WARN_ON(buffer
, 1);
5010 pr_info(" read events: %ld\n", total_read
);
5011 pr_info(" lost events: %ld\n", total_lost
);
5012 pr_info(" total events: %ld\n", total_lost
+ total_read
);
5013 pr_info(" recorded len bytes: %ld\n", total_len
);
5014 pr_info(" recorded size bytes: %ld\n", total_size
);
5016 pr_info(" With dropped events, record len and size may not match\n"
5017 " alloced and written from above\n");
5019 if (RB_WARN_ON(buffer
, total_len
!= total_alloc
||
5020 total_size
!= total_written
))
5023 if (RB_WARN_ON(buffer
, total_lost
+ total_read
!= total_events
))
5029 pr_info("Ring buffer PASSED!\n");
5031 ring_buffer_free(buffer
);
5035 late_initcall(test_ringbuffer
);
5036 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */