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 struct buffer_data_page
{
284 u64 time_stamp
; /* page time stamp */
285 local_t commit
; /* write committed index */
286 unsigned char data
[] RB_ALIGN_DATA
; /* data of buffer page */
290 * Note, the buffer_page list must be first. The buffer pages
291 * are allocated in cache lines, which means that each buffer
292 * page will be at the beginning of a cache line, and thus
293 * the least significant bits will be zero. We use this to
294 * add flags in the list struct pointers, to make the ring buffer
298 struct list_head list
; /* list of buffer pages */
299 local_t write
; /* index for next write */
300 unsigned read
; /* index for next read */
301 local_t entries
; /* entries on this page */
302 unsigned long real_end
; /* real end of data */
303 struct buffer_data_page
*page
; /* Actual data page */
307 * The buffer page counters, write and entries, must be reset
308 * atomically when crossing page boundaries. To synchronize this
309 * update, two counters are inserted into the number. One is
310 * the actual counter for the write position or count on the page.
312 * The other is a counter of updaters. Before an update happens
313 * the update partition of the counter is incremented. This will
314 * allow the updater to update the counter atomically.
316 * The counter is 20 bits, and the state data is 12.
318 #define RB_WRITE_MASK 0xfffff
319 #define RB_WRITE_INTCNT (1 << 20)
321 static void rb_init_page(struct buffer_data_page
*bpage
)
323 local_set(&bpage
->commit
, 0);
327 * ring_buffer_page_len - the size of data on the page.
328 * @page: The page to read
330 * Returns the amount of data on the page, including buffer page header.
332 size_t ring_buffer_page_len(void *page
)
334 return local_read(&((struct buffer_data_page
*)page
)->commit
)
339 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
342 static void free_buffer_page(struct buffer_page
*bpage
)
344 free_page((unsigned long)bpage
->page
);
349 * We need to fit the time_stamp delta into 27 bits.
351 static inline int test_time_stamp(u64 delta
)
353 if (delta
& TS_DELTA_TEST
)
358 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
360 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
361 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
363 int ring_buffer_print_page_header(struct trace_seq
*s
)
365 struct buffer_data_page field
;
367 trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
368 "offset:0;\tsize:%u;\tsigned:%u;\n",
369 (unsigned int)sizeof(field
.time_stamp
),
370 (unsigned int)is_signed_type(u64
));
372 trace_seq_printf(s
, "\tfield: local_t commit;\t"
373 "offset:%u;\tsize:%u;\tsigned:%u;\n",
374 (unsigned int)offsetof(typeof(field
), commit
),
375 (unsigned int)sizeof(field
.commit
),
376 (unsigned int)is_signed_type(long));
378 trace_seq_printf(s
, "\tfield: int overwrite;\t"
379 "offset:%u;\tsize:%u;\tsigned:%u;\n",
380 (unsigned int)offsetof(typeof(field
), commit
),
382 (unsigned int)is_signed_type(long));
384 trace_seq_printf(s
, "\tfield: char data;\t"
385 "offset:%u;\tsize:%u;\tsigned:%u;\n",
386 (unsigned int)offsetof(typeof(field
), data
),
387 (unsigned int)BUF_PAGE_SIZE
,
388 (unsigned int)is_signed_type(char));
390 return !trace_seq_has_overflowed(s
);
394 struct irq_work work
;
395 wait_queue_head_t waiters
;
396 wait_queue_head_t full_waiters
;
397 bool waiters_pending
;
398 bool full_waiters_pending
;
403 * Structure to hold event state and handle nested events.
405 struct rb_event_info
{
408 unsigned long length
;
409 struct buffer_page
*tail_page
;
414 * Used for which event context the event is in.
420 * See trace_recursive_lock() comment below for more details.
431 * head_page == tail_page && head == tail then buffer is empty.
433 struct ring_buffer_per_cpu
{
435 atomic_t record_disabled
;
436 struct ring_buffer
*buffer
;
437 raw_spinlock_t reader_lock
; /* serialize readers */
438 arch_spinlock_t lock
;
439 struct lock_class_key lock_key
;
440 struct buffer_data_page
*free_page
;
441 unsigned long nr_pages
;
442 unsigned int current_context
;
443 struct list_head
*pages
;
444 struct buffer_page
*head_page
; /* read from head */
445 struct buffer_page
*tail_page
; /* write to tail */
446 struct buffer_page
*commit_page
; /* committed pages */
447 struct buffer_page
*reader_page
;
448 unsigned long lost_events
;
449 unsigned long last_overrun
;
450 local_t entries_bytes
;
453 local_t commit_overrun
;
454 local_t dropped_events
;
458 unsigned long read_bytes
;
461 /* ring buffer pages to update, > 0 to add, < 0 to remove */
462 long nr_pages_to_update
;
463 struct list_head new_pages
; /* new pages to add */
464 struct work_struct update_pages_work
;
465 struct completion update_done
;
467 struct rb_irq_work irq_work
;
473 atomic_t record_disabled
;
474 atomic_t resize_disabled
;
475 cpumask_var_t cpumask
;
477 struct lock_class_key
*reader_lock_key
;
481 struct ring_buffer_per_cpu
**buffers
;
483 struct hlist_node node
;
486 struct rb_irq_work irq_work
;
489 struct ring_buffer_iter
{
490 struct ring_buffer_per_cpu
*cpu_buffer
;
492 struct buffer_page
*head_page
;
493 struct buffer_page
*cache_reader_page
;
494 unsigned long cache_read
;
499 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
501 * Schedules a delayed work to wake up any task that is blocked on the
502 * ring buffer waiters queue.
504 static void rb_wake_up_waiters(struct irq_work
*work
)
506 struct rb_irq_work
*rbwork
= container_of(work
, struct rb_irq_work
, work
);
508 wake_up_all(&rbwork
->waiters
);
509 if (rbwork
->wakeup_full
) {
510 rbwork
->wakeup_full
= false;
511 wake_up_all(&rbwork
->full_waiters
);
516 * ring_buffer_wait - wait for input to the ring buffer
517 * @buffer: buffer to wait on
518 * @cpu: the cpu buffer to wait on
519 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
521 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
522 * as data is added to any of the @buffer's cpu buffers. Otherwise
523 * it will wait for data to be added to a specific cpu buffer.
525 int ring_buffer_wait(struct ring_buffer
*buffer
, int cpu
, bool full
)
527 struct ring_buffer_per_cpu
*uninitialized_var(cpu_buffer
);
529 struct rb_irq_work
*work
;
533 * Depending on what the caller is waiting for, either any
534 * data in any cpu buffer, or a specific buffer, put the
535 * caller on the appropriate wait queue.
537 if (cpu
== RING_BUFFER_ALL_CPUS
) {
538 work
= &buffer
->irq_work
;
539 /* Full only makes sense on per cpu reads */
542 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
544 cpu_buffer
= buffer
->buffers
[cpu
];
545 work
= &cpu_buffer
->irq_work
;
551 prepare_to_wait(&work
->full_waiters
, &wait
, TASK_INTERRUPTIBLE
);
553 prepare_to_wait(&work
->waiters
, &wait
, TASK_INTERRUPTIBLE
);
556 * The events can happen in critical sections where
557 * checking a work queue can cause deadlocks.
558 * After adding a task to the queue, this flag is set
559 * only to notify events to try to wake up the queue
562 * We don't clear it even if the buffer is no longer
563 * empty. The flag only causes the next event to run
564 * irq_work to do the work queue wake up. The worse
565 * that can happen if we race with !trace_empty() is that
566 * an event will cause an irq_work to try to wake up
569 * There's no reason to protect this flag either, as
570 * the work queue and irq_work logic will do the necessary
571 * synchronization for the wake ups. The only thing
572 * that is necessary is that the wake up happens after
573 * a task has been queued. It's OK for spurious wake ups.
576 work
->full_waiters_pending
= true;
578 work
->waiters_pending
= true;
580 if (signal_pending(current
)) {
585 if (cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
))
588 if (cpu
!= RING_BUFFER_ALL_CPUS
&&
589 !ring_buffer_empty_cpu(buffer
, cpu
)) {
596 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
597 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
598 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
608 finish_wait(&work
->full_waiters
, &wait
);
610 finish_wait(&work
->waiters
, &wait
);
616 * ring_buffer_poll_wait - poll on buffer input
617 * @buffer: buffer to wait on
618 * @cpu: the cpu buffer to wait on
619 * @filp: the file descriptor
620 * @poll_table: The poll descriptor
622 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
623 * as data is added to any of the @buffer's cpu buffers. Otherwise
624 * it will wait for data to be added to a specific cpu buffer.
626 * Returns POLLIN | POLLRDNORM if data exists in the buffers,
629 int ring_buffer_poll_wait(struct ring_buffer
*buffer
, int cpu
,
630 struct file
*filp
, poll_table
*poll_table
)
632 struct ring_buffer_per_cpu
*cpu_buffer
;
633 struct rb_irq_work
*work
;
635 if (cpu
== RING_BUFFER_ALL_CPUS
)
636 work
= &buffer
->irq_work
;
638 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
641 cpu_buffer
= buffer
->buffers
[cpu
];
642 work
= &cpu_buffer
->irq_work
;
645 poll_wait(filp
, &work
->waiters
, poll_table
);
646 work
->waiters_pending
= true;
648 * There's a tight race between setting the waiters_pending and
649 * checking if the ring buffer is empty. Once the waiters_pending bit
650 * is set, the next event will wake the task up, but we can get stuck
651 * if there's only a single event in.
653 * FIXME: Ideally, we need a memory barrier on the writer side as well,
654 * but adding a memory barrier to all events will cause too much of a
655 * performance hit in the fast path. We only need a memory barrier when
656 * the buffer goes from empty to having content. But as this race is
657 * extremely small, and it's not a problem if another event comes in, we
662 if ((cpu
== RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty(buffer
)) ||
663 (cpu
!= RING_BUFFER_ALL_CPUS
&& !ring_buffer_empty_cpu(buffer
, cpu
)))
664 return POLLIN
| POLLRDNORM
;
668 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
669 #define RB_WARN_ON(b, cond) \
671 int _____ret = unlikely(cond); \
673 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
674 struct ring_buffer_per_cpu *__b = \
676 atomic_inc(&__b->buffer->record_disabled); \
678 atomic_inc(&b->record_disabled); \
684 /* Up this if you want to test the TIME_EXTENTS and normalization */
685 #define DEBUG_SHIFT 0
687 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
)
689 /* shift to debug/test normalization and TIME_EXTENTS */
690 return buffer
->clock() << DEBUG_SHIFT
;
693 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
697 preempt_disable_notrace();
698 time
= rb_time_stamp(buffer
);
699 preempt_enable_no_resched_notrace();
703 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
705 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
708 /* Just stupid testing the normalize function and deltas */
711 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
714 * Making the ring buffer lockless makes things tricky.
715 * Although writes only happen on the CPU that they are on,
716 * and they only need to worry about interrupts. Reads can
719 * The reader page is always off the ring buffer, but when the
720 * reader finishes with a page, it needs to swap its page with
721 * a new one from the buffer. The reader needs to take from
722 * the head (writes go to the tail). But if a writer is in overwrite
723 * mode and wraps, it must push the head page forward.
725 * Here lies the problem.
727 * The reader must be careful to replace only the head page, and
728 * not another one. As described at the top of the file in the
729 * ASCII art, the reader sets its old page to point to the next
730 * page after head. It then sets the page after head to point to
731 * the old reader page. But if the writer moves the head page
732 * during this operation, the reader could end up with the tail.
734 * We use cmpxchg to help prevent this race. We also do something
735 * special with the page before head. We set the LSB to 1.
737 * When the writer must push the page forward, it will clear the
738 * bit that points to the head page, move the head, and then set
739 * the bit that points to the new head page.
741 * We also don't want an interrupt coming in and moving the head
742 * page on another writer. Thus we use the second LSB to catch
745 * head->list->prev->next bit 1 bit 0
748 * Points to head page 0 1
751 * Note we can not trust the prev pointer of the head page, because:
753 * +----+ +-----+ +-----+
754 * | |------>| T |---X--->| N |
756 * +----+ +-----+ +-----+
759 * +----------| R |----------+ |
763 * Key: ---X--> HEAD flag set in pointer
768 * (see __rb_reserve_next() to see where this happens)
770 * What the above shows is that the reader just swapped out
771 * the reader page with a page in the buffer, but before it
772 * could make the new header point back to the new page added
773 * it was preempted by a writer. The writer moved forward onto
774 * the new page added by the reader and is about to move forward
777 * You can see, it is legitimate for the previous pointer of
778 * the head (or any page) not to point back to itself. But only
782 #define RB_PAGE_NORMAL 0UL
783 #define RB_PAGE_HEAD 1UL
784 #define RB_PAGE_UPDATE 2UL
787 #define RB_FLAG_MASK 3UL
789 /* PAGE_MOVED is not part of the mask */
790 #define RB_PAGE_MOVED 4UL
793 * rb_list_head - remove any bit
795 static struct list_head
*rb_list_head(struct list_head
*list
)
797 unsigned long val
= (unsigned long)list
;
799 return (struct list_head
*)(val
& ~RB_FLAG_MASK
);
803 * rb_is_head_page - test if the given page is the head page
805 * Because the reader may move the head_page pointer, we can
806 * not trust what the head page is (it may be pointing to
807 * the reader page). But if the next page is a header page,
808 * its flags will be non zero.
811 rb_is_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
812 struct buffer_page
*page
, struct list_head
*list
)
816 val
= (unsigned long)list
->next
;
818 if ((val
& ~RB_FLAG_MASK
) != (unsigned long)&page
->list
)
819 return RB_PAGE_MOVED
;
821 return val
& RB_FLAG_MASK
;
827 * The unique thing about the reader page, is that, if the
828 * writer is ever on it, the previous pointer never points
829 * back to the reader page.
831 static bool rb_is_reader_page(struct buffer_page
*page
)
833 struct list_head
*list
= page
->list
.prev
;
835 return rb_list_head(list
->next
) != &page
->list
;
839 * rb_set_list_to_head - set a list_head to be pointing to head.
841 static void rb_set_list_to_head(struct ring_buffer_per_cpu
*cpu_buffer
,
842 struct list_head
*list
)
846 ptr
= (unsigned long *)&list
->next
;
847 *ptr
|= RB_PAGE_HEAD
;
848 *ptr
&= ~RB_PAGE_UPDATE
;
852 * rb_head_page_activate - sets up head page
854 static void rb_head_page_activate(struct ring_buffer_per_cpu
*cpu_buffer
)
856 struct buffer_page
*head
;
858 head
= cpu_buffer
->head_page
;
863 * Set the previous list pointer to have the HEAD flag.
865 rb_set_list_to_head(cpu_buffer
, head
->list
.prev
);
868 static void rb_list_head_clear(struct list_head
*list
)
870 unsigned long *ptr
= (unsigned long *)&list
->next
;
872 *ptr
&= ~RB_FLAG_MASK
;
876 * rb_head_page_dactivate - clears head page ptr (for free list)
879 rb_head_page_deactivate(struct ring_buffer_per_cpu
*cpu_buffer
)
881 struct list_head
*hd
;
883 /* Go through the whole list and clear any pointers found. */
884 rb_list_head_clear(cpu_buffer
->pages
);
886 list_for_each(hd
, cpu_buffer
->pages
)
887 rb_list_head_clear(hd
);
890 static int rb_head_page_set(struct ring_buffer_per_cpu
*cpu_buffer
,
891 struct buffer_page
*head
,
892 struct buffer_page
*prev
,
893 int old_flag
, int new_flag
)
895 struct list_head
*list
;
896 unsigned long val
= (unsigned long)&head
->list
;
901 val
&= ~RB_FLAG_MASK
;
903 ret
= cmpxchg((unsigned long *)&list
->next
,
904 val
| old_flag
, val
| new_flag
);
906 /* check if the reader took the page */
907 if ((ret
& ~RB_FLAG_MASK
) != val
)
908 return RB_PAGE_MOVED
;
910 return ret
& RB_FLAG_MASK
;
913 static int rb_head_page_set_update(struct ring_buffer_per_cpu
*cpu_buffer
,
914 struct buffer_page
*head
,
915 struct buffer_page
*prev
,
918 return rb_head_page_set(cpu_buffer
, head
, prev
,
919 old_flag
, RB_PAGE_UPDATE
);
922 static int rb_head_page_set_head(struct ring_buffer_per_cpu
*cpu_buffer
,
923 struct buffer_page
*head
,
924 struct buffer_page
*prev
,
927 return rb_head_page_set(cpu_buffer
, head
, prev
,
928 old_flag
, RB_PAGE_HEAD
);
931 static int rb_head_page_set_normal(struct ring_buffer_per_cpu
*cpu_buffer
,
932 struct buffer_page
*head
,
933 struct buffer_page
*prev
,
936 return rb_head_page_set(cpu_buffer
, head
, prev
,
937 old_flag
, RB_PAGE_NORMAL
);
940 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
941 struct buffer_page
**bpage
)
943 struct list_head
*p
= rb_list_head((*bpage
)->list
.next
);
945 *bpage
= list_entry(p
, struct buffer_page
, list
);
948 static struct buffer_page
*
949 rb_set_head_page(struct ring_buffer_per_cpu
*cpu_buffer
)
951 struct buffer_page
*head
;
952 struct buffer_page
*page
;
953 struct list_head
*list
;
956 if (RB_WARN_ON(cpu_buffer
, !cpu_buffer
->head_page
))
960 list
= cpu_buffer
->pages
;
961 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
->next
) != list
))
964 page
= head
= cpu_buffer
->head_page
;
966 * It is possible that the writer moves the header behind
967 * where we started, and we miss in one loop.
968 * A second loop should grab the header, but we'll do
969 * three loops just because I'm paranoid.
971 for (i
= 0; i
< 3; i
++) {
973 if (rb_is_head_page(cpu_buffer
, page
, page
->list
.prev
)) {
974 cpu_buffer
->head_page
= page
;
977 rb_inc_page(cpu_buffer
, &page
);
978 } while (page
!= head
);
981 RB_WARN_ON(cpu_buffer
, 1);
986 static int rb_head_page_replace(struct buffer_page
*old
,
987 struct buffer_page
*new)
989 unsigned long *ptr
= (unsigned long *)&old
->list
.prev
->next
;
993 val
= *ptr
& ~RB_FLAG_MASK
;
996 ret
= cmpxchg(ptr
, val
, (unsigned long)&new->list
);
1002 * rb_tail_page_update - move the tail page forward
1004 static void rb_tail_page_update(struct ring_buffer_per_cpu
*cpu_buffer
,
1005 struct buffer_page
*tail_page
,
1006 struct buffer_page
*next_page
)
1008 unsigned long old_entries
;
1009 unsigned long old_write
;
1012 * The tail page now needs to be moved forward.
1014 * We need to reset the tail page, but without messing
1015 * with possible erasing of data brought in by interrupts
1016 * that have moved the tail page and are currently on it.
1018 * We add a counter to the write field to denote this.
1020 old_write
= local_add_return(RB_WRITE_INTCNT
, &next_page
->write
);
1021 old_entries
= local_add_return(RB_WRITE_INTCNT
, &next_page
->entries
);
1024 * Just make sure we have seen our old_write and synchronize
1025 * with any interrupts that come in.
1030 * If the tail page is still the same as what we think
1031 * it is, then it is up to us to update the tail
1034 if (tail_page
== READ_ONCE(cpu_buffer
->tail_page
)) {
1035 /* Zero the write counter */
1036 unsigned long val
= old_write
& ~RB_WRITE_MASK
;
1037 unsigned long eval
= old_entries
& ~RB_WRITE_MASK
;
1040 * This will only succeed if an interrupt did
1041 * not come in and change it. In which case, we
1042 * do not want to modify it.
1044 * We add (void) to let the compiler know that we do not care
1045 * about the return value of these functions. We use the
1046 * cmpxchg to only update if an interrupt did not already
1047 * do it for us. If the cmpxchg fails, we don't care.
1049 (void)local_cmpxchg(&next_page
->write
, old_write
, val
);
1050 (void)local_cmpxchg(&next_page
->entries
, old_entries
, eval
);
1053 * No need to worry about races with clearing out the commit.
1054 * it only can increment when a commit takes place. But that
1055 * only happens in the outer most nested commit.
1057 local_set(&next_page
->page
->commit
, 0);
1059 /* Again, either we update tail_page or an interrupt does */
1060 (void)cmpxchg(&cpu_buffer
->tail_page
, tail_page
, next_page
);
1064 static int rb_check_bpage(struct ring_buffer_per_cpu
*cpu_buffer
,
1065 struct buffer_page
*bpage
)
1067 unsigned long val
= (unsigned long)bpage
;
1069 if (RB_WARN_ON(cpu_buffer
, val
& RB_FLAG_MASK
))
1076 * rb_check_list - make sure a pointer to a list has the last bits zero
1078 static int rb_check_list(struct ring_buffer_per_cpu
*cpu_buffer
,
1079 struct list_head
*list
)
1081 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->prev
) != list
->prev
))
1083 if (RB_WARN_ON(cpu_buffer
, rb_list_head(list
->next
) != list
->next
))
1089 * rb_check_pages - integrity check of buffer pages
1090 * @cpu_buffer: CPU buffer with pages to test
1092 * As a safety measure we check to make sure the data pages have not
1095 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1097 struct list_head
*head
= cpu_buffer
->pages
;
1098 struct buffer_page
*bpage
, *tmp
;
1100 /* Reset the head page if it exists */
1101 if (cpu_buffer
->head_page
)
1102 rb_set_head_page(cpu_buffer
);
1104 rb_head_page_deactivate(cpu_buffer
);
1106 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
1108 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
1111 if (rb_check_list(cpu_buffer
, head
))
1114 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1115 if (RB_WARN_ON(cpu_buffer
,
1116 bpage
->list
.next
->prev
!= &bpage
->list
))
1118 if (RB_WARN_ON(cpu_buffer
,
1119 bpage
->list
.prev
->next
!= &bpage
->list
))
1121 if (rb_check_list(cpu_buffer
, &bpage
->list
))
1125 rb_head_page_activate(cpu_buffer
);
1130 static int __rb_allocate_pages(long nr_pages
, struct list_head
*pages
, int cpu
)
1132 struct buffer_page
*bpage
, *tmp
;
1135 for (i
= 0; i
< nr_pages
; i
++) {
1138 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1139 * gracefully without invoking oom-killer and the system is not
1142 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1143 GFP_KERNEL
| __GFP_RETRY_MAYFAIL
,
1148 list_add(&bpage
->list
, pages
);
1150 page
= alloc_pages_node(cpu_to_node(cpu
),
1151 GFP_KERNEL
| __GFP_RETRY_MAYFAIL
, 0);
1154 bpage
->page
= page_address(page
);
1155 rb_init_page(bpage
->page
);
1161 list_for_each_entry_safe(bpage
, tmp
, pages
, list
) {
1162 list_del_init(&bpage
->list
);
1163 free_buffer_page(bpage
);
1169 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
1170 unsigned long nr_pages
)
1176 if (__rb_allocate_pages(nr_pages
, &pages
, cpu_buffer
->cpu
))
1180 * The ring buffer page list is a circular list that does not
1181 * start and end with a list head. All page list items point to
1184 cpu_buffer
->pages
= pages
.next
;
1187 cpu_buffer
->nr_pages
= nr_pages
;
1189 rb_check_pages(cpu_buffer
);
1194 static struct ring_buffer_per_cpu
*
1195 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, long nr_pages
, int cpu
)
1197 struct ring_buffer_per_cpu
*cpu_buffer
;
1198 struct buffer_page
*bpage
;
1202 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
1203 GFP_KERNEL
, cpu_to_node(cpu
));
1207 cpu_buffer
->cpu
= cpu
;
1208 cpu_buffer
->buffer
= buffer
;
1209 raw_spin_lock_init(&cpu_buffer
->reader_lock
);
1210 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
1211 cpu_buffer
->lock
= (arch_spinlock_t
)__ARCH_SPIN_LOCK_UNLOCKED
;
1212 INIT_WORK(&cpu_buffer
->update_pages_work
, update_pages_handler
);
1213 init_completion(&cpu_buffer
->update_done
);
1214 init_irq_work(&cpu_buffer
->irq_work
.work
, rb_wake_up_waiters
);
1215 init_waitqueue_head(&cpu_buffer
->irq_work
.waiters
);
1216 init_waitqueue_head(&cpu_buffer
->irq_work
.full_waiters
);
1218 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
1219 GFP_KERNEL
, cpu_to_node(cpu
));
1221 goto fail_free_buffer
;
1223 rb_check_bpage(cpu_buffer
, bpage
);
1225 cpu_buffer
->reader_page
= bpage
;
1226 page
= alloc_pages_node(cpu_to_node(cpu
), GFP_KERNEL
, 0);
1228 goto fail_free_reader
;
1229 bpage
->page
= page_address(page
);
1230 rb_init_page(bpage
->page
);
1232 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
1233 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1235 ret
= rb_allocate_pages(cpu_buffer
, nr_pages
);
1237 goto fail_free_reader
;
1239 cpu_buffer
->head_page
1240 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
1241 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
1243 rb_head_page_activate(cpu_buffer
);
1248 free_buffer_page(cpu_buffer
->reader_page
);
1255 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
1257 struct list_head
*head
= cpu_buffer
->pages
;
1258 struct buffer_page
*bpage
, *tmp
;
1260 free_buffer_page(cpu_buffer
->reader_page
);
1262 rb_head_page_deactivate(cpu_buffer
);
1265 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
1266 list_del_init(&bpage
->list
);
1267 free_buffer_page(bpage
);
1269 bpage
= list_entry(head
, struct buffer_page
, list
);
1270 free_buffer_page(bpage
);
1277 * __ring_buffer_alloc - allocate a new ring_buffer
1278 * @size: the size in bytes per cpu that is needed.
1279 * @flags: attributes to set for the ring buffer.
1281 * Currently the only flag that is available is the RB_FL_OVERWRITE
1282 * flag. This flag means that the buffer will overwrite old data
1283 * when the buffer wraps. If this flag is not set, the buffer will
1284 * drop data when the tail hits the head.
1286 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
1287 struct lock_class_key
*key
)
1289 struct ring_buffer
*buffer
;
1295 /* keep it in its own cache line */
1296 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
1301 if (!zalloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
1302 goto fail_free_buffer
;
1304 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1305 buffer
->flags
= flags
;
1306 buffer
->clock
= trace_clock_local
;
1307 buffer
->reader_lock_key
= key
;
1309 init_irq_work(&buffer
->irq_work
.work
, rb_wake_up_waiters
);
1310 init_waitqueue_head(&buffer
->irq_work
.waiters
);
1312 /* need at least two pages */
1316 buffer
->cpus
= nr_cpu_ids
;
1318 bsize
= sizeof(void *) * nr_cpu_ids
;
1319 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
1321 if (!buffer
->buffers
)
1322 goto fail_free_cpumask
;
1324 cpu
= raw_smp_processor_id();
1325 cpumask_set_cpu(cpu
, buffer
->cpumask
);
1326 buffer
->buffers
[cpu
] = rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
1327 if (!buffer
->buffers
[cpu
])
1328 goto fail_free_buffers
;
1330 ret
= cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1332 goto fail_free_buffers
;
1334 mutex_init(&buffer
->mutex
);
1339 for_each_buffer_cpu(buffer
, cpu
) {
1340 if (buffer
->buffers
[cpu
])
1341 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1343 kfree(buffer
->buffers
);
1346 free_cpumask_var(buffer
->cpumask
);
1352 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
1355 * ring_buffer_free - free a ring buffer.
1356 * @buffer: the buffer to free.
1359 ring_buffer_free(struct ring_buffer
*buffer
)
1363 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE
, &buffer
->node
);
1365 for_each_buffer_cpu(buffer
, cpu
)
1366 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
1368 kfree(buffer
->buffers
);
1369 free_cpumask_var(buffer
->cpumask
);
1373 EXPORT_SYMBOL_GPL(ring_buffer_free
);
1375 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
1378 buffer
->clock
= clock
;
1381 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
1383 static inline unsigned long rb_page_entries(struct buffer_page
*bpage
)
1385 return local_read(&bpage
->entries
) & RB_WRITE_MASK
;
1388 static inline unsigned long rb_page_write(struct buffer_page
*bpage
)
1390 return local_read(&bpage
->write
) & RB_WRITE_MASK
;
1394 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned long nr_pages
)
1396 struct list_head
*tail_page
, *to_remove
, *next_page
;
1397 struct buffer_page
*to_remove_page
, *tmp_iter_page
;
1398 struct buffer_page
*last_page
, *first_page
;
1399 unsigned long nr_removed
;
1400 unsigned long head_bit
;
1405 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1406 atomic_inc(&cpu_buffer
->record_disabled
);
1408 * We don't race with the readers since we have acquired the reader
1409 * lock. We also don't race with writers after disabling recording.
1410 * This makes it easy to figure out the first and the last page to be
1411 * removed from the list. We unlink all the pages in between including
1412 * the first and last pages. This is done in a busy loop so that we
1413 * lose the least number of traces.
1414 * The pages are freed after we restart recording and unlock readers.
1416 tail_page
= &cpu_buffer
->tail_page
->list
;
1419 * tail page might be on reader page, we remove the next page
1420 * from the ring buffer
1422 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
1423 tail_page
= rb_list_head(tail_page
->next
);
1424 to_remove
= tail_page
;
1426 /* start of pages to remove */
1427 first_page
= list_entry(rb_list_head(to_remove
->next
),
1428 struct buffer_page
, list
);
1430 for (nr_removed
= 0; nr_removed
< nr_pages
; nr_removed
++) {
1431 to_remove
= rb_list_head(to_remove
)->next
;
1432 head_bit
|= (unsigned long)to_remove
& RB_PAGE_HEAD
;
1435 next_page
= rb_list_head(to_remove
)->next
;
1438 * Now we remove all pages between tail_page and next_page.
1439 * Make sure that we have head_bit value preserved for the
1442 tail_page
->next
= (struct list_head
*)((unsigned long)next_page
|
1444 next_page
= rb_list_head(next_page
);
1445 next_page
->prev
= tail_page
;
1447 /* make sure pages points to a valid page in the ring buffer */
1448 cpu_buffer
->pages
= next_page
;
1450 /* update head page */
1452 cpu_buffer
->head_page
= list_entry(next_page
,
1453 struct buffer_page
, list
);
1456 * change read pointer to make sure any read iterators reset
1459 cpu_buffer
->read
= 0;
1461 /* pages are removed, resume tracing and then free the pages */
1462 atomic_dec(&cpu_buffer
->record_disabled
);
1463 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1465 RB_WARN_ON(cpu_buffer
, list_empty(cpu_buffer
->pages
));
1467 /* last buffer page to remove */
1468 last_page
= list_entry(rb_list_head(to_remove
), struct buffer_page
,
1470 tmp_iter_page
= first_page
;
1473 to_remove_page
= tmp_iter_page
;
1474 rb_inc_page(cpu_buffer
, &tmp_iter_page
);
1476 /* update the counters */
1477 page_entries
= rb_page_entries(to_remove_page
);
1480 * If something was added to this page, it was full
1481 * since it is not the tail page. So we deduct the
1482 * bytes consumed in ring buffer from here.
1483 * Increment overrun to account for the lost events.
1485 local_add(page_entries
, &cpu_buffer
->overrun
);
1486 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1490 * We have already removed references to this list item, just
1491 * free up the buffer_page and its page
1493 free_buffer_page(to_remove_page
);
1496 } while (to_remove_page
!= last_page
);
1498 RB_WARN_ON(cpu_buffer
, nr_removed
);
1500 return nr_removed
== 0;
1504 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1506 struct list_head
*pages
= &cpu_buffer
->new_pages
;
1507 int retries
, success
;
1509 raw_spin_lock_irq(&cpu_buffer
->reader_lock
);
1511 * We are holding the reader lock, so the reader page won't be swapped
1512 * in the ring buffer. Now we are racing with the writer trying to
1513 * move head page and the tail page.
1514 * We are going to adapt the reader page update process where:
1515 * 1. We first splice the start and end of list of new pages between
1516 * the head page and its previous page.
1517 * 2. We cmpxchg the prev_page->next to point from head page to the
1518 * start of new pages list.
1519 * 3. Finally, we update the head->prev to the end of new list.
1521 * We will try this process 10 times, to make sure that we don't keep
1527 struct list_head
*head_page
, *prev_page
, *r
;
1528 struct list_head
*last_page
, *first_page
;
1529 struct list_head
*head_page_with_bit
;
1531 head_page
= &rb_set_head_page(cpu_buffer
)->list
;
1534 prev_page
= head_page
->prev
;
1536 first_page
= pages
->next
;
1537 last_page
= pages
->prev
;
1539 head_page_with_bit
= (struct list_head
*)
1540 ((unsigned long)head_page
| RB_PAGE_HEAD
);
1542 last_page
->next
= head_page_with_bit
;
1543 first_page
->prev
= prev_page
;
1545 r
= cmpxchg(&prev_page
->next
, head_page_with_bit
, first_page
);
1547 if (r
== head_page_with_bit
) {
1549 * yay, we replaced the page pointer to our new list,
1550 * now, we just have to update to head page's prev
1551 * pointer to point to end of list
1553 head_page
->prev
= last_page
;
1560 INIT_LIST_HEAD(pages
);
1562 * If we weren't successful in adding in new pages, warn and stop
1565 RB_WARN_ON(cpu_buffer
, !success
);
1566 raw_spin_unlock_irq(&cpu_buffer
->reader_lock
);
1568 /* free pages if they weren't inserted */
1570 struct buffer_page
*bpage
, *tmp
;
1571 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1573 list_del_init(&bpage
->list
);
1574 free_buffer_page(bpage
);
1580 static void rb_update_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
1584 if (cpu_buffer
->nr_pages_to_update
> 0)
1585 success
= rb_insert_pages(cpu_buffer
);
1587 success
= rb_remove_pages(cpu_buffer
,
1588 -cpu_buffer
->nr_pages_to_update
);
1591 cpu_buffer
->nr_pages
+= cpu_buffer
->nr_pages_to_update
;
1594 static void update_pages_handler(struct work_struct
*work
)
1596 struct ring_buffer_per_cpu
*cpu_buffer
= container_of(work
,
1597 struct ring_buffer_per_cpu
, update_pages_work
);
1598 rb_update_pages(cpu_buffer
);
1599 complete(&cpu_buffer
->update_done
);
1603 * ring_buffer_resize - resize the ring buffer
1604 * @buffer: the buffer to resize.
1605 * @size: the new size.
1606 * @cpu_id: the cpu buffer to resize
1608 * Minimum size is 2 * BUF_PAGE_SIZE.
1610 * Returns 0 on success and < 0 on failure.
1612 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
,
1615 struct ring_buffer_per_cpu
*cpu_buffer
;
1616 unsigned long nr_pages
;
1620 * Always succeed at resizing a non-existent buffer:
1625 /* Make sure the requested buffer exists */
1626 if (cpu_id
!= RING_BUFFER_ALL_CPUS
&&
1627 !cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1630 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
1632 /* we need a minimum of two pages */
1636 size
= nr_pages
* BUF_PAGE_SIZE
;
1639 * Don't succeed if resizing is disabled, as a reader might be
1640 * manipulating the ring buffer and is expecting a sane state while
1643 if (atomic_read(&buffer
->resize_disabled
))
1646 /* prevent another thread from changing buffer sizes */
1647 mutex_lock(&buffer
->mutex
);
1649 if (cpu_id
== RING_BUFFER_ALL_CPUS
) {
1650 /* calculate the pages to update */
1651 for_each_buffer_cpu(buffer
, cpu
) {
1652 cpu_buffer
= buffer
->buffers
[cpu
];
1654 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1655 cpu_buffer
->nr_pages
;
1657 * nothing more to do for removing pages or no update
1659 if (cpu_buffer
->nr_pages_to_update
<= 0)
1662 * to add pages, make sure all new pages can be
1663 * allocated without receiving ENOMEM
1665 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1666 if (__rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1667 &cpu_buffer
->new_pages
, cpu
)) {
1668 /* not enough memory for new pages */
1676 * Fire off all the required work handlers
1677 * We can't schedule on offline CPUs, but it's not necessary
1678 * since we can change their buffer sizes without any race.
1680 for_each_buffer_cpu(buffer
, cpu
) {
1681 cpu_buffer
= buffer
->buffers
[cpu
];
1682 if (!cpu_buffer
->nr_pages_to_update
)
1685 /* Can't run something on an offline CPU. */
1686 if (!cpu_online(cpu
)) {
1687 rb_update_pages(cpu_buffer
);
1688 cpu_buffer
->nr_pages_to_update
= 0;
1690 schedule_work_on(cpu
,
1691 &cpu_buffer
->update_pages_work
);
1695 /* wait for all the updates to complete */
1696 for_each_buffer_cpu(buffer
, cpu
) {
1697 cpu_buffer
= buffer
->buffers
[cpu
];
1698 if (!cpu_buffer
->nr_pages_to_update
)
1701 if (cpu_online(cpu
))
1702 wait_for_completion(&cpu_buffer
->update_done
);
1703 cpu_buffer
->nr_pages_to_update
= 0;
1708 /* Make sure this CPU has been intitialized */
1709 if (!cpumask_test_cpu(cpu_id
, buffer
->cpumask
))
1712 cpu_buffer
= buffer
->buffers
[cpu_id
];
1714 if (nr_pages
== cpu_buffer
->nr_pages
)
1717 cpu_buffer
->nr_pages_to_update
= nr_pages
-
1718 cpu_buffer
->nr_pages
;
1720 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
1721 if (cpu_buffer
->nr_pages_to_update
> 0 &&
1722 __rb_allocate_pages(cpu_buffer
->nr_pages_to_update
,
1723 &cpu_buffer
->new_pages
, cpu_id
)) {
1730 /* Can't run something on an offline CPU. */
1731 if (!cpu_online(cpu_id
))
1732 rb_update_pages(cpu_buffer
);
1734 schedule_work_on(cpu_id
,
1735 &cpu_buffer
->update_pages_work
);
1736 wait_for_completion(&cpu_buffer
->update_done
);
1739 cpu_buffer
->nr_pages_to_update
= 0;
1745 * The ring buffer resize can happen with the ring buffer
1746 * enabled, so that the update disturbs the tracing as little
1747 * as possible. But if the buffer is disabled, we do not need
1748 * to worry about that, and we can take the time to verify
1749 * that the buffer is not corrupt.
1751 if (atomic_read(&buffer
->record_disabled
)) {
1752 atomic_inc(&buffer
->record_disabled
);
1754 * Even though the buffer was disabled, we must make sure
1755 * that it is truly disabled before calling rb_check_pages.
1756 * There could have been a race between checking
1757 * record_disable and incrementing it.
1759 synchronize_sched();
1760 for_each_buffer_cpu(buffer
, cpu
) {
1761 cpu_buffer
= buffer
->buffers
[cpu
];
1762 rb_check_pages(cpu_buffer
);
1764 atomic_dec(&buffer
->record_disabled
);
1767 mutex_unlock(&buffer
->mutex
);
1771 for_each_buffer_cpu(buffer
, cpu
) {
1772 struct buffer_page
*bpage
, *tmp
;
1774 cpu_buffer
= buffer
->buffers
[cpu
];
1775 cpu_buffer
->nr_pages_to_update
= 0;
1777 if (list_empty(&cpu_buffer
->new_pages
))
1780 list_for_each_entry_safe(bpage
, tmp
, &cpu_buffer
->new_pages
,
1782 list_del_init(&bpage
->list
);
1783 free_buffer_page(bpage
);
1786 mutex_unlock(&buffer
->mutex
);
1789 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
1791 void ring_buffer_change_overwrite(struct ring_buffer
*buffer
, int val
)
1793 mutex_lock(&buffer
->mutex
);
1795 buffer
->flags
|= RB_FL_OVERWRITE
;
1797 buffer
->flags
&= ~RB_FL_OVERWRITE
;
1798 mutex_unlock(&buffer
->mutex
);
1800 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite
);
1802 static __always_inline
void *
1803 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
1805 return bpage
->data
+ index
;
1808 static __always_inline
void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
1810 return bpage
->page
->data
+ index
;
1813 static __always_inline
struct ring_buffer_event
*
1814 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
1816 return __rb_page_index(cpu_buffer
->reader_page
,
1817 cpu_buffer
->reader_page
->read
);
1820 static __always_inline
struct ring_buffer_event
*
1821 rb_iter_head_event(struct ring_buffer_iter
*iter
)
1823 return __rb_page_index(iter
->head_page
, iter
->head
);
1826 static __always_inline
unsigned rb_page_commit(struct buffer_page
*bpage
)
1828 return local_read(&bpage
->page
->commit
);
1831 /* Size is determined by what has been committed */
1832 static __always_inline
unsigned rb_page_size(struct buffer_page
*bpage
)
1834 return rb_page_commit(bpage
);
1837 static __always_inline
unsigned
1838 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
1840 return rb_page_commit(cpu_buffer
->commit_page
);
1843 static __always_inline
unsigned
1844 rb_event_index(struct ring_buffer_event
*event
)
1846 unsigned long addr
= (unsigned long)event
;
1848 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1851 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1853 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1856 * The iterator could be on the reader page (it starts there).
1857 * But the head could have moved, since the reader was
1858 * found. Check for this case and assign the iterator
1859 * to the head page instead of next.
1861 if (iter
->head_page
== cpu_buffer
->reader_page
)
1862 iter
->head_page
= rb_set_head_page(cpu_buffer
);
1864 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1866 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1871 * rb_handle_head_page - writer hit the head page
1873 * Returns: +1 to retry page
1878 rb_handle_head_page(struct ring_buffer_per_cpu
*cpu_buffer
,
1879 struct buffer_page
*tail_page
,
1880 struct buffer_page
*next_page
)
1882 struct buffer_page
*new_head
;
1887 entries
= rb_page_entries(next_page
);
1890 * The hard part is here. We need to move the head
1891 * forward, and protect against both readers on
1892 * other CPUs and writers coming in via interrupts.
1894 type
= rb_head_page_set_update(cpu_buffer
, next_page
, tail_page
,
1898 * type can be one of four:
1899 * NORMAL - an interrupt already moved it for us
1900 * HEAD - we are the first to get here.
1901 * UPDATE - we are the interrupt interrupting
1903 * MOVED - a reader on another CPU moved the next
1904 * pointer to its reader page. Give up
1911 * We changed the head to UPDATE, thus
1912 * it is our responsibility to update
1915 local_add(entries
, &cpu_buffer
->overrun
);
1916 local_sub(BUF_PAGE_SIZE
, &cpu_buffer
->entries_bytes
);
1919 * The entries will be zeroed out when we move the
1923 /* still more to do */
1926 case RB_PAGE_UPDATE
:
1928 * This is an interrupt that interrupt the
1929 * previous update. Still more to do.
1932 case RB_PAGE_NORMAL
:
1934 * An interrupt came in before the update
1935 * and processed this for us.
1936 * Nothing left to do.
1941 * The reader is on another CPU and just did
1942 * a swap with our next_page.
1947 RB_WARN_ON(cpu_buffer
, 1); /* WTF??? */
1952 * Now that we are here, the old head pointer is
1953 * set to UPDATE. This will keep the reader from
1954 * swapping the head page with the reader page.
1955 * The reader (on another CPU) will spin till
1958 * We just need to protect against interrupts
1959 * doing the job. We will set the next pointer
1960 * to HEAD. After that, we set the old pointer
1961 * to NORMAL, but only if it was HEAD before.
1962 * otherwise we are an interrupt, and only
1963 * want the outer most commit to reset it.
1965 new_head
= next_page
;
1966 rb_inc_page(cpu_buffer
, &new_head
);
1968 ret
= rb_head_page_set_head(cpu_buffer
, new_head
, next_page
,
1972 * Valid returns are:
1973 * HEAD - an interrupt came in and already set it.
1974 * NORMAL - One of two things:
1975 * 1) We really set it.
1976 * 2) A bunch of interrupts came in and moved
1977 * the page forward again.
1981 case RB_PAGE_NORMAL
:
1985 RB_WARN_ON(cpu_buffer
, 1);
1990 * It is possible that an interrupt came in,
1991 * set the head up, then more interrupts came in
1992 * and moved it again. When we get back here,
1993 * the page would have been set to NORMAL but we
1994 * just set it back to HEAD.
1996 * How do you detect this? Well, if that happened
1997 * the tail page would have moved.
1999 if (ret
== RB_PAGE_NORMAL
) {
2000 struct buffer_page
*buffer_tail_page
;
2002 buffer_tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2004 * If the tail had moved passed next, then we need
2005 * to reset the pointer.
2007 if (buffer_tail_page
!= tail_page
&&
2008 buffer_tail_page
!= next_page
)
2009 rb_head_page_set_normal(cpu_buffer
, new_head
,
2015 * If this was the outer most commit (the one that
2016 * changed the original pointer from HEAD to UPDATE),
2017 * then it is up to us to reset it to NORMAL.
2019 if (type
== RB_PAGE_HEAD
) {
2020 ret
= rb_head_page_set_normal(cpu_buffer
, next_page
,
2023 if (RB_WARN_ON(cpu_buffer
,
2024 ret
!= RB_PAGE_UPDATE
))
2032 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2033 unsigned long tail
, struct rb_event_info
*info
)
2035 struct buffer_page
*tail_page
= info
->tail_page
;
2036 struct ring_buffer_event
*event
;
2037 unsigned long length
= info
->length
;
2040 * Only the event that crossed the page boundary
2041 * must fill the old tail_page with padding.
2043 if (tail
>= BUF_PAGE_SIZE
) {
2045 * If the page was filled, then we still need
2046 * to update the real_end. Reset it to zero
2047 * and the reader will ignore it.
2049 if (tail
== BUF_PAGE_SIZE
)
2050 tail_page
->real_end
= 0;
2052 local_sub(length
, &tail_page
->write
);
2056 event
= __rb_page_index(tail_page
, tail
);
2058 /* account for padding bytes */
2059 local_add(BUF_PAGE_SIZE
- tail
, &cpu_buffer
->entries_bytes
);
2062 * Save the original length to the meta data.
2063 * This will be used by the reader to add lost event
2066 tail_page
->real_end
= tail
;
2069 * If this event is bigger than the minimum size, then
2070 * we need to be careful that we don't subtract the
2071 * write counter enough to allow another writer to slip
2073 * We put in a discarded commit instead, to make sure
2074 * that this space is not used again.
2076 * If we are less than the minimum size, we don't need to
2079 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
2080 /* No room for any events */
2082 /* Mark the rest of the page with padding */
2083 rb_event_set_padding(event
);
2085 /* Set the write back to the previous setting */
2086 local_sub(length
, &tail_page
->write
);
2090 /* Put in a discarded event */
2091 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
2092 event
->type_len
= RINGBUF_TYPE_PADDING
;
2093 /* time delta must be non zero */
2094 event
->time_delta
= 1;
2096 /* Set write to end of buffer */
2097 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
2098 local_sub(length
, &tail_page
->write
);
2101 static inline void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
);
2104 * This is the slow path, force gcc not to inline it.
2106 static noinline
struct ring_buffer_event
*
2107 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
2108 unsigned long tail
, struct rb_event_info
*info
)
2110 struct buffer_page
*tail_page
= info
->tail_page
;
2111 struct buffer_page
*commit_page
= cpu_buffer
->commit_page
;
2112 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
2113 struct buffer_page
*next_page
;
2116 next_page
= tail_page
;
2118 rb_inc_page(cpu_buffer
, &next_page
);
2121 * If for some reason, we had an interrupt storm that made
2122 * it all the way around the buffer, bail, and warn
2125 if (unlikely(next_page
== commit_page
)) {
2126 local_inc(&cpu_buffer
->commit_overrun
);
2131 * This is where the fun begins!
2133 * We are fighting against races between a reader that
2134 * could be on another CPU trying to swap its reader
2135 * page with the buffer head.
2137 * We are also fighting against interrupts coming in and
2138 * moving the head or tail on us as well.
2140 * If the next page is the head page then we have filled
2141 * the buffer, unless the commit page is still on the
2144 if (rb_is_head_page(cpu_buffer
, next_page
, &tail_page
->list
)) {
2147 * If the commit is not on the reader page, then
2148 * move the header page.
2150 if (!rb_is_reader_page(cpu_buffer
->commit_page
)) {
2152 * If we are not in overwrite mode,
2153 * this is easy, just stop here.
2155 if (!(buffer
->flags
& RB_FL_OVERWRITE
)) {
2156 local_inc(&cpu_buffer
->dropped_events
);
2160 ret
= rb_handle_head_page(cpu_buffer
,
2169 * We need to be careful here too. The
2170 * commit page could still be on the reader
2171 * page. We could have a small buffer, and
2172 * have filled up the buffer with events
2173 * from interrupts and such, and wrapped.
2175 * Note, if the tail page is also the on the
2176 * reader_page, we let it move out.
2178 if (unlikely((cpu_buffer
->commit_page
!=
2179 cpu_buffer
->tail_page
) &&
2180 (cpu_buffer
->commit_page
==
2181 cpu_buffer
->reader_page
))) {
2182 local_inc(&cpu_buffer
->commit_overrun
);
2188 rb_tail_page_update(cpu_buffer
, tail_page
, next_page
);
2192 rb_reset_tail(cpu_buffer
, tail
, info
);
2194 /* Commit what we have for now. */
2195 rb_end_commit(cpu_buffer
);
2196 /* rb_end_commit() decs committing */
2197 local_inc(&cpu_buffer
->committing
);
2199 /* fail and let the caller try again */
2200 return ERR_PTR(-EAGAIN
);
2204 rb_reset_tail(cpu_buffer
, tail
, info
);
2209 /* Slow path, do not inline */
2210 static noinline
struct ring_buffer_event
*
2211 rb_add_time_stamp(struct ring_buffer_event
*event
, u64 delta
)
2213 event
->type_len
= RINGBUF_TYPE_TIME_EXTEND
;
2215 /* Not the first event on the page? */
2216 if (rb_event_index(event
)) {
2217 event
->time_delta
= delta
& TS_MASK
;
2218 event
->array
[0] = delta
>> TS_SHIFT
;
2220 /* nope, just zero it */
2221 event
->time_delta
= 0;
2222 event
->array
[0] = 0;
2225 return skip_time_extend(event
);
2228 static inline bool rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2229 struct ring_buffer_event
*event
);
2232 * rb_update_event - update event type and data
2233 * @event: the event to update
2234 * @type: the type of event
2235 * @length: the size of the event field in the ring buffer
2237 * Update the type and data fields of the event. The length
2238 * is the actual size that is written to the ring buffer,
2239 * and with this, we can determine what to place into the
2243 rb_update_event(struct ring_buffer_per_cpu
*cpu_buffer
,
2244 struct ring_buffer_event
*event
,
2245 struct rb_event_info
*info
)
2247 unsigned length
= info
->length
;
2248 u64 delta
= info
->delta
;
2250 /* Only a commit updates the timestamp */
2251 if (unlikely(!rb_event_is_commit(cpu_buffer
, event
)))
2255 * If we need to add a timestamp, then we
2256 * add it to the start of the resevered space.
2258 if (unlikely(info
->add_timestamp
)) {
2259 event
= rb_add_time_stamp(event
, delta
);
2260 length
-= RB_LEN_TIME_EXTEND
;
2264 event
->time_delta
= delta
;
2265 length
-= RB_EVNT_HDR_SIZE
;
2266 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
) {
2267 event
->type_len
= 0;
2268 event
->array
[0] = length
;
2270 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
2273 static unsigned rb_calculate_event_length(unsigned length
)
2275 struct ring_buffer_event event
; /* Used only for sizeof array */
2277 /* zero length can cause confusions */
2281 if (length
> RB_MAX_SMALL_DATA
|| RB_FORCE_8BYTE_ALIGNMENT
)
2282 length
+= sizeof(event
.array
[0]);
2284 length
+= RB_EVNT_HDR_SIZE
;
2285 length
= ALIGN(length
, RB_ARCH_ALIGNMENT
);
2288 * In case the time delta is larger than the 27 bits for it
2289 * in the header, we need to add a timestamp. If another
2290 * event comes in when trying to discard this one to increase
2291 * the length, then the timestamp will be added in the allocated
2292 * space of this event. If length is bigger than the size needed
2293 * for the TIME_EXTEND, then padding has to be used. The events
2294 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2295 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2296 * As length is a multiple of 4, we only need to worry if it
2297 * is 12 (RB_LEN_TIME_EXTEND + 4).
2299 if (length
== RB_LEN_TIME_EXTEND
+ RB_ALIGNMENT
)
2300 length
+= RB_ALIGNMENT
;
2305 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2306 static inline bool sched_clock_stable(void)
2313 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
2314 struct ring_buffer_event
*event
)
2316 unsigned long new_index
, old_index
;
2317 struct buffer_page
*bpage
;
2318 unsigned long index
;
2321 new_index
= rb_event_index(event
);
2322 old_index
= new_index
+ rb_event_ts_length(event
);
2323 addr
= (unsigned long)event
;
2326 bpage
= READ_ONCE(cpu_buffer
->tail_page
);
2328 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
2329 unsigned long write_mask
=
2330 local_read(&bpage
->write
) & ~RB_WRITE_MASK
;
2331 unsigned long event_length
= rb_event_length(event
);
2333 * This is on the tail page. It is possible that
2334 * a write could come in and move the tail page
2335 * and write to the next page. That is fine
2336 * because we just shorten what is on this page.
2338 old_index
+= write_mask
;
2339 new_index
+= write_mask
;
2340 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
2341 if (index
== old_index
) {
2342 /* update counters */
2343 local_sub(event_length
, &cpu_buffer
->entries_bytes
);
2348 /* could not discard */
2352 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2354 local_inc(&cpu_buffer
->committing
);
2355 local_inc(&cpu_buffer
->commits
);
2358 static __always_inline
void
2359 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
2361 unsigned long max_count
;
2364 * We only race with interrupts and NMIs on this CPU.
2365 * If we own the commit event, then we can commit
2366 * all others that interrupted us, since the interruptions
2367 * are in stack format (they finish before they come
2368 * back to us). This allows us to do a simple loop to
2369 * assign the commit to the tail.
2372 max_count
= cpu_buffer
->nr_pages
* 100;
2374 while (cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)) {
2375 if (RB_WARN_ON(cpu_buffer
, !(--max_count
)))
2377 if (RB_WARN_ON(cpu_buffer
,
2378 rb_is_reader_page(cpu_buffer
->tail_page
)))
2380 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2381 rb_page_write(cpu_buffer
->commit_page
));
2382 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
2383 /* Only update the write stamp if the page has an event */
2384 if (rb_page_write(cpu_buffer
->commit_page
))
2385 cpu_buffer
->write_stamp
=
2386 cpu_buffer
->commit_page
->page
->time_stamp
;
2387 /* add barrier to keep gcc from optimizing too much */
2390 while (rb_commit_index(cpu_buffer
) !=
2391 rb_page_write(cpu_buffer
->commit_page
)) {
2393 local_set(&cpu_buffer
->commit_page
->page
->commit
,
2394 rb_page_write(cpu_buffer
->commit_page
));
2395 RB_WARN_ON(cpu_buffer
,
2396 local_read(&cpu_buffer
->commit_page
->page
->commit
) &
2401 /* again, keep gcc from optimizing */
2405 * If an interrupt came in just after the first while loop
2406 * and pushed the tail page forward, we will be left with
2407 * a dangling commit that will never go forward.
2409 if (unlikely(cpu_buffer
->commit_page
!= READ_ONCE(cpu_buffer
->tail_page
)))
2413 static __always_inline
void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
2415 unsigned long commits
;
2417 if (RB_WARN_ON(cpu_buffer
,
2418 !local_read(&cpu_buffer
->committing
)))
2422 commits
= local_read(&cpu_buffer
->commits
);
2423 /* synchronize with interrupts */
2425 if (local_read(&cpu_buffer
->committing
) == 1)
2426 rb_set_commit_to_write(cpu_buffer
);
2428 local_dec(&cpu_buffer
->committing
);
2430 /* synchronize with interrupts */
2434 * Need to account for interrupts coming in between the
2435 * updating of the commit page and the clearing of the
2436 * committing counter.
2438 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
2439 !local_read(&cpu_buffer
->committing
)) {
2440 local_inc(&cpu_buffer
->committing
);
2445 static inline void rb_event_discard(struct ring_buffer_event
*event
)
2447 if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
)
2448 event
= skip_time_extend(event
);
2450 /* array[0] holds the actual length for the discarded event */
2451 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
2452 event
->type_len
= RINGBUF_TYPE_PADDING
;
2453 /* time delta must be non zero */
2454 if (!event
->time_delta
)
2455 event
->time_delta
= 1;
2458 static __always_inline
bool
2459 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2460 struct ring_buffer_event
*event
)
2462 unsigned long addr
= (unsigned long)event
;
2463 unsigned long index
;
2465 index
= rb_event_index(event
);
2468 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
2469 rb_commit_index(cpu_buffer
) == index
;
2472 static __always_inline
void
2473 rb_update_write_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2474 struct ring_buffer_event
*event
)
2479 * The event first in the commit queue updates the
2482 if (rb_event_is_commit(cpu_buffer
, event
)) {
2484 * A commit event that is first on a page
2485 * updates the write timestamp with the page stamp
2487 if (!rb_event_index(event
))
2488 cpu_buffer
->write_stamp
=
2489 cpu_buffer
->commit_page
->page
->time_stamp
;
2490 else if (event
->type_len
== RINGBUF_TYPE_TIME_EXTEND
) {
2491 delta
= event
->array
[0];
2493 delta
+= event
->time_delta
;
2494 cpu_buffer
->write_stamp
+= delta
;
2496 cpu_buffer
->write_stamp
+= event
->time_delta
;
2500 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
2501 struct ring_buffer_event
*event
)
2503 local_inc(&cpu_buffer
->entries
);
2504 rb_update_write_stamp(cpu_buffer
, event
);
2505 rb_end_commit(cpu_buffer
);
2508 static __always_inline
void
2509 rb_wakeups(struct ring_buffer
*buffer
, struct ring_buffer_per_cpu
*cpu_buffer
)
2513 if (buffer
->irq_work
.waiters_pending
) {
2514 buffer
->irq_work
.waiters_pending
= false;
2515 /* irq_work_queue() supplies it's own memory barriers */
2516 irq_work_queue(&buffer
->irq_work
.work
);
2519 if (cpu_buffer
->irq_work
.waiters_pending
) {
2520 cpu_buffer
->irq_work
.waiters_pending
= false;
2521 /* irq_work_queue() supplies it's own memory barriers */
2522 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2525 pagebusy
= cpu_buffer
->reader_page
== cpu_buffer
->commit_page
;
2527 if (!pagebusy
&& cpu_buffer
->irq_work
.full_waiters_pending
) {
2528 cpu_buffer
->irq_work
.wakeup_full
= true;
2529 cpu_buffer
->irq_work
.full_waiters_pending
= false;
2530 /* irq_work_queue() supplies it's own memory barriers */
2531 irq_work_queue(&cpu_buffer
->irq_work
.work
);
2536 * The lock and unlock are done within a preempt disable section.
2537 * The current_context per_cpu variable can only be modified
2538 * by the current task between lock and unlock. But it can
2539 * be modified more than once via an interrupt. There are four
2540 * different contexts that we need to consider.
2547 * If for some reason the ring buffer starts to recurse, we
2548 * only allow that to happen at most 4 times (one for each
2549 * context). If it happens 5 times, then we consider this a
2550 * recusive loop and do not let it go further.
2553 static __always_inline
int
2554 trace_recursive_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
2556 if (cpu_buffer
->current_context
>= 4)
2559 cpu_buffer
->current_context
++;
2560 /* Interrupts must see this update */
2566 static __always_inline
void
2567 trace_recursive_unlock(struct ring_buffer_per_cpu
*cpu_buffer
)
2569 /* Don't let the dec leak out */
2571 cpu_buffer
->current_context
--;
2575 * ring_buffer_unlock_commit - commit a reserved
2576 * @buffer: The buffer to commit to
2577 * @event: The event pointer to commit.
2579 * This commits the data to the ring buffer, and releases any locks held.
2581 * Must be paired with ring_buffer_lock_reserve.
2583 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
2584 struct ring_buffer_event
*event
)
2586 struct ring_buffer_per_cpu
*cpu_buffer
;
2587 int cpu
= raw_smp_processor_id();
2589 cpu_buffer
= buffer
->buffers
[cpu
];
2591 rb_commit(cpu_buffer
, event
);
2593 rb_wakeups(buffer
, cpu_buffer
);
2595 trace_recursive_unlock(cpu_buffer
);
2597 preempt_enable_notrace();
2601 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
2603 static noinline
void
2604 rb_handle_timestamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2605 struct rb_event_info
*info
)
2607 WARN_ONCE(info
->delta
> (1ULL << 59),
2608 KERN_WARNING
"Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2609 (unsigned long long)info
->delta
,
2610 (unsigned long long)info
->ts
,
2611 (unsigned long long)cpu_buffer
->write_stamp
,
2612 sched_clock_stable() ? "" :
2613 "If you just came from a suspend/resume,\n"
2614 "please switch to the trace global clock:\n"
2615 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2616 info
->add_timestamp
= 1;
2619 static struct ring_buffer_event
*
2620 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
2621 struct rb_event_info
*info
)
2623 struct ring_buffer_event
*event
;
2624 struct buffer_page
*tail_page
;
2625 unsigned long tail
, write
;
2628 * If the time delta since the last event is too big to
2629 * hold in the time field of the event, then we append a
2630 * TIME EXTEND event ahead of the data event.
2632 if (unlikely(info
->add_timestamp
))
2633 info
->length
+= RB_LEN_TIME_EXTEND
;
2635 /* Don't let the compiler play games with cpu_buffer->tail_page */
2636 tail_page
= info
->tail_page
= READ_ONCE(cpu_buffer
->tail_page
);
2637 write
= local_add_return(info
->length
, &tail_page
->write
);
2639 /* set write to only the index of the write */
2640 write
&= RB_WRITE_MASK
;
2641 tail
= write
- info
->length
;
2644 * If this is the first commit on the page, then it has the same
2645 * timestamp as the page itself.
2650 /* See if we shot pass the end of this buffer page */
2651 if (unlikely(write
> BUF_PAGE_SIZE
))
2652 return rb_move_tail(cpu_buffer
, tail
, info
);
2654 /* We reserved something on the buffer */
2656 event
= __rb_page_index(tail_page
, tail
);
2657 rb_update_event(cpu_buffer
, event
, info
);
2659 local_inc(&tail_page
->entries
);
2662 * If this is the first commit on the page, then update
2666 tail_page
->page
->time_stamp
= info
->ts
;
2668 /* account for these added bytes */
2669 local_add(info
->length
, &cpu_buffer
->entries_bytes
);
2674 static __always_inline
struct ring_buffer_event
*
2675 rb_reserve_next_event(struct ring_buffer
*buffer
,
2676 struct ring_buffer_per_cpu
*cpu_buffer
,
2677 unsigned long length
)
2679 struct ring_buffer_event
*event
;
2680 struct rb_event_info info
;
2684 rb_start_commit(cpu_buffer
);
2686 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2688 * Due to the ability to swap a cpu buffer from a buffer
2689 * it is possible it was swapped before we committed.
2690 * (committing stops a swap). We check for it here and
2691 * if it happened, we have to fail the write.
2694 if (unlikely(READ_ONCE(cpu_buffer
->buffer
) != buffer
)) {
2695 local_dec(&cpu_buffer
->committing
);
2696 local_dec(&cpu_buffer
->commits
);
2701 info
.length
= rb_calculate_event_length(length
);
2703 info
.add_timestamp
= 0;
2707 * We allow for interrupts to reenter here and do a trace.
2708 * If one does, it will cause this original code to loop
2709 * back here. Even with heavy interrupts happening, this
2710 * should only happen a few times in a row. If this happens
2711 * 1000 times in a row, there must be either an interrupt
2712 * storm or we have something buggy.
2715 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
2718 info
.ts
= rb_time_stamp(cpu_buffer
->buffer
);
2719 diff
= info
.ts
- cpu_buffer
->write_stamp
;
2721 /* make sure this diff is calculated here */
2724 /* Did the write stamp get updated already? */
2725 if (likely(info
.ts
>= cpu_buffer
->write_stamp
)) {
2727 if (unlikely(test_time_stamp(info
.delta
)))
2728 rb_handle_timestamp(cpu_buffer
, &info
);
2731 event
= __rb_reserve_next(cpu_buffer
, &info
);
2733 if (unlikely(PTR_ERR(event
) == -EAGAIN
)) {
2734 if (info
.add_timestamp
)
2735 info
.length
-= RB_LEN_TIME_EXTEND
;
2745 rb_end_commit(cpu_buffer
);
2750 * ring_buffer_lock_reserve - reserve a part of the buffer
2751 * @buffer: the ring buffer to reserve from
2752 * @length: the length of the data to reserve (excluding event header)
2754 * Returns a reseverd event on the ring buffer to copy directly to.
2755 * The user of this interface will need to get the body to write into
2756 * and can use the ring_buffer_event_data() interface.
2758 * The length is the length of the data needed, not the event length
2759 * which also includes the event header.
2761 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2762 * If NULL is returned, then nothing has been allocated or locked.
2764 struct ring_buffer_event
*
2765 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
2767 struct ring_buffer_per_cpu
*cpu_buffer
;
2768 struct ring_buffer_event
*event
;
2771 /* If we are tracing schedule, we don't want to recurse */
2772 preempt_disable_notrace();
2774 if (unlikely(atomic_read(&buffer
->record_disabled
)))
2777 cpu
= raw_smp_processor_id();
2779 if (unlikely(!cpumask_test_cpu(cpu
, buffer
->cpumask
)))
2782 cpu_buffer
= buffer
->buffers
[cpu
];
2784 if (unlikely(atomic_read(&cpu_buffer
->record_disabled
)))
2787 if (unlikely(length
> BUF_MAX_DATA_SIZE
))
2790 if (unlikely(trace_recursive_lock(cpu_buffer
)))
2793 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2800 trace_recursive_unlock(cpu_buffer
);
2802 preempt_enable_notrace();
2805 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
2808 * Decrement the entries to the page that an event is on.
2809 * The event does not even need to exist, only the pointer
2810 * to the page it is on. This may only be called before the commit
2814 rb_decrement_entry(struct ring_buffer_per_cpu
*cpu_buffer
,
2815 struct ring_buffer_event
*event
)
2817 unsigned long addr
= (unsigned long)event
;
2818 struct buffer_page
*bpage
= cpu_buffer
->commit_page
;
2819 struct buffer_page
*start
;
2823 /* Do the likely case first */
2824 if (likely(bpage
->page
== (void *)addr
)) {
2825 local_dec(&bpage
->entries
);
2830 * Because the commit page may be on the reader page we
2831 * start with the next page and check the end loop there.
2833 rb_inc_page(cpu_buffer
, &bpage
);
2836 if (bpage
->page
== (void *)addr
) {
2837 local_dec(&bpage
->entries
);
2840 rb_inc_page(cpu_buffer
, &bpage
);
2841 } while (bpage
!= start
);
2843 /* commit not part of this buffer?? */
2844 RB_WARN_ON(cpu_buffer
, 1);
2848 * ring_buffer_commit_discard - discard an event that has not been committed
2849 * @buffer: the ring buffer
2850 * @event: non committed event to discard
2852 * Sometimes an event that is in the ring buffer needs to be ignored.
2853 * This function lets the user discard an event in the ring buffer
2854 * and then that event will not be read later.
2856 * This function only works if it is called before the the item has been
2857 * committed. It will try to free the event from the ring buffer
2858 * if another event has not been added behind it.
2860 * If another event has been added behind it, it will set the event
2861 * up as discarded, and perform the commit.
2863 * If this function is called, do not call ring_buffer_unlock_commit on
2866 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
2867 struct ring_buffer_event
*event
)
2869 struct ring_buffer_per_cpu
*cpu_buffer
;
2872 /* The event is discarded regardless */
2873 rb_event_discard(event
);
2875 cpu
= smp_processor_id();
2876 cpu_buffer
= buffer
->buffers
[cpu
];
2879 * This must only be called if the event has not been
2880 * committed yet. Thus we can assume that preemption
2881 * is still disabled.
2883 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
2885 rb_decrement_entry(cpu_buffer
, event
);
2886 if (rb_try_to_discard(cpu_buffer
, event
))
2890 * The commit is still visible by the reader, so we
2891 * must still update the timestamp.
2893 rb_update_write_stamp(cpu_buffer
, event
);
2895 rb_end_commit(cpu_buffer
);
2897 trace_recursive_unlock(cpu_buffer
);
2899 preempt_enable_notrace();
2902 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
2905 * ring_buffer_write - write data to the buffer without reserving
2906 * @buffer: The ring buffer to write to.
2907 * @length: The length of the data being written (excluding the event header)
2908 * @data: The data to write to the buffer.
2910 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2911 * one function. If you already have the data to write to the buffer, it
2912 * may be easier to simply call this function.
2914 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2915 * and not the length of the event which would hold the header.
2917 int ring_buffer_write(struct ring_buffer
*buffer
,
2918 unsigned long length
,
2921 struct ring_buffer_per_cpu
*cpu_buffer
;
2922 struct ring_buffer_event
*event
;
2927 preempt_disable_notrace();
2929 if (atomic_read(&buffer
->record_disabled
))
2932 cpu
= raw_smp_processor_id();
2934 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2937 cpu_buffer
= buffer
->buffers
[cpu
];
2939 if (atomic_read(&cpu_buffer
->record_disabled
))
2942 if (length
> BUF_MAX_DATA_SIZE
)
2945 if (unlikely(trace_recursive_lock(cpu_buffer
)))
2948 event
= rb_reserve_next_event(buffer
, cpu_buffer
, length
);
2952 body
= rb_event_data(event
);
2954 memcpy(body
, data
, length
);
2956 rb_commit(cpu_buffer
, event
);
2958 rb_wakeups(buffer
, cpu_buffer
);
2963 trace_recursive_unlock(cpu_buffer
);
2966 preempt_enable_notrace();
2970 EXPORT_SYMBOL_GPL(ring_buffer_write
);
2972 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
2974 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
2975 struct buffer_page
*head
= rb_set_head_page(cpu_buffer
);
2976 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
2978 /* In case of error, head will be NULL */
2979 if (unlikely(!head
))
2982 return reader
->read
== rb_page_commit(reader
) &&
2983 (commit
== reader
||
2985 head
->read
== rb_page_commit(commit
)));
2989 * ring_buffer_record_disable - stop all writes into the buffer
2990 * @buffer: The ring buffer to stop writes to.
2992 * This prevents all writes to the buffer. Any attempt to write
2993 * to the buffer after this will fail and return NULL.
2995 * The caller should call synchronize_sched() after this.
2997 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
2999 atomic_inc(&buffer
->record_disabled
);
3001 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
3004 * ring_buffer_record_enable - enable writes to the buffer
3005 * @buffer: The ring buffer to enable writes
3007 * Note, multiple disables will need the same number of enables
3008 * to truly enable the writing (much like preempt_disable).
3010 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
3012 atomic_dec(&buffer
->record_disabled
);
3014 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
3017 * ring_buffer_record_off - stop all writes into the buffer
3018 * @buffer: The ring buffer to stop writes to.
3020 * This prevents all writes to the buffer. Any attempt to write
3021 * to the buffer after this will fail and return NULL.
3023 * This is different than ring_buffer_record_disable() as
3024 * it works like an on/off switch, where as the disable() version
3025 * must be paired with a enable().
3027 void ring_buffer_record_off(struct ring_buffer
*buffer
)
3030 unsigned int new_rd
;
3033 rd
= atomic_read(&buffer
->record_disabled
);
3034 new_rd
= rd
| RB_BUFFER_OFF
;
3035 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3037 EXPORT_SYMBOL_GPL(ring_buffer_record_off
);
3040 * ring_buffer_record_on - restart writes into the buffer
3041 * @buffer: The ring buffer to start writes to.
3043 * This enables all writes to the buffer that was disabled by
3044 * ring_buffer_record_off().
3046 * This is different than ring_buffer_record_enable() as
3047 * it works like an on/off switch, where as the enable() version
3048 * must be paired with a disable().
3050 void ring_buffer_record_on(struct ring_buffer
*buffer
)
3053 unsigned int new_rd
;
3056 rd
= atomic_read(&buffer
->record_disabled
);
3057 new_rd
= rd
& ~RB_BUFFER_OFF
;
3058 } while (atomic_cmpxchg(&buffer
->record_disabled
, rd
, new_rd
) != rd
);
3060 EXPORT_SYMBOL_GPL(ring_buffer_record_on
);
3063 * ring_buffer_record_is_on - return true if the ring buffer can write
3064 * @buffer: The ring buffer to see if write is enabled
3066 * Returns true if the ring buffer is in a state that it accepts writes.
3068 int ring_buffer_record_is_on(struct ring_buffer
*buffer
)
3070 return !atomic_read(&buffer
->record_disabled
);
3074 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3075 * @buffer: The ring buffer to stop writes to.
3076 * @cpu: The CPU buffer to stop
3078 * This prevents all writes to the buffer. Any attempt to write
3079 * to the buffer after this will fail and return NULL.
3081 * The caller should call synchronize_sched() after this.
3083 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
3085 struct ring_buffer_per_cpu
*cpu_buffer
;
3087 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3090 cpu_buffer
= buffer
->buffers
[cpu
];
3091 atomic_inc(&cpu_buffer
->record_disabled
);
3093 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
3096 * ring_buffer_record_enable_cpu - enable writes to the buffer
3097 * @buffer: The ring buffer to enable writes
3098 * @cpu: The CPU to enable.
3100 * Note, multiple disables will need the same number of enables
3101 * to truly enable the writing (much like preempt_disable).
3103 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
3105 struct ring_buffer_per_cpu
*cpu_buffer
;
3107 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3110 cpu_buffer
= buffer
->buffers
[cpu
];
3111 atomic_dec(&cpu_buffer
->record_disabled
);
3113 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
3116 * The total entries in the ring buffer is the running counter
3117 * of entries entered into the ring buffer, minus the sum of
3118 * the entries read from the ring buffer and the number of
3119 * entries that were overwritten.
3121 static inline unsigned long
3122 rb_num_of_entries(struct ring_buffer_per_cpu
*cpu_buffer
)
3124 return local_read(&cpu_buffer
->entries
) -
3125 (local_read(&cpu_buffer
->overrun
) + cpu_buffer
->read
);
3129 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3130 * @buffer: The ring buffer
3131 * @cpu: The per CPU buffer to read from.
3133 u64
ring_buffer_oldest_event_ts(struct ring_buffer
*buffer
, int cpu
)
3135 unsigned long flags
;
3136 struct ring_buffer_per_cpu
*cpu_buffer
;
3137 struct buffer_page
*bpage
;
3140 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3143 cpu_buffer
= buffer
->buffers
[cpu
];
3144 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3146 * if the tail is on reader_page, oldest time stamp is on the reader
3149 if (cpu_buffer
->tail_page
== cpu_buffer
->reader_page
)
3150 bpage
= cpu_buffer
->reader_page
;
3152 bpage
= rb_set_head_page(cpu_buffer
);
3154 ret
= bpage
->page
->time_stamp
;
3155 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3159 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts
);
3162 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3163 * @buffer: The ring buffer
3164 * @cpu: The per CPU buffer to read from.
3166 unsigned long ring_buffer_bytes_cpu(struct ring_buffer
*buffer
, int cpu
)
3168 struct ring_buffer_per_cpu
*cpu_buffer
;
3171 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3174 cpu_buffer
= buffer
->buffers
[cpu
];
3175 ret
= local_read(&cpu_buffer
->entries_bytes
) - cpu_buffer
->read_bytes
;
3179 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu
);
3182 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3183 * @buffer: The ring buffer
3184 * @cpu: The per CPU buffer to get the entries from.
3186 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
3188 struct ring_buffer_per_cpu
*cpu_buffer
;
3190 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3193 cpu_buffer
= buffer
->buffers
[cpu
];
3195 return rb_num_of_entries(cpu_buffer
);
3197 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
3200 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3201 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3202 * @buffer: The ring buffer
3203 * @cpu: The per CPU buffer to get the number of overruns from
3205 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3207 struct ring_buffer_per_cpu
*cpu_buffer
;
3210 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3213 cpu_buffer
= buffer
->buffers
[cpu
];
3214 ret
= local_read(&cpu_buffer
->overrun
);
3218 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
3221 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3222 * commits failing due to the buffer wrapping around while there are uncommitted
3223 * events, such as during an interrupt storm.
3224 * @buffer: The ring buffer
3225 * @cpu: The per CPU buffer to get the number of overruns from
3228 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
3230 struct ring_buffer_per_cpu
*cpu_buffer
;
3233 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3236 cpu_buffer
= buffer
->buffers
[cpu
];
3237 ret
= local_read(&cpu_buffer
->commit_overrun
);
3241 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
3244 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3245 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3246 * @buffer: The ring buffer
3247 * @cpu: The per CPU buffer to get the number of overruns from
3250 ring_buffer_dropped_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3252 struct ring_buffer_per_cpu
*cpu_buffer
;
3255 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3258 cpu_buffer
= buffer
->buffers
[cpu
];
3259 ret
= local_read(&cpu_buffer
->dropped_events
);
3263 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu
);
3266 * ring_buffer_read_events_cpu - get the number of events successfully read
3267 * @buffer: The ring buffer
3268 * @cpu: The per CPU buffer to get the number of events read
3271 ring_buffer_read_events_cpu(struct ring_buffer
*buffer
, int cpu
)
3273 struct ring_buffer_per_cpu
*cpu_buffer
;
3275 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3278 cpu_buffer
= buffer
->buffers
[cpu
];
3279 return cpu_buffer
->read
;
3281 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu
);
3284 * ring_buffer_entries - get the number of entries in a buffer
3285 * @buffer: The ring buffer
3287 * Returns the total number of entries in the ring buffer
3290 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
3292 struct ring_buffer_per_cpu
*cpu_buffer
;
3293 unsigned long entries
= 0;
3296 /* if you care about this being correct, lock the buffer */
3297 for_each_buffer_cpu(buffer
, cpu
) {
3298 cpu_buffer
= buffer
->buffers
[cpu
];
3299 entries
+= rb_num_of_entries(cpu_buffer
);
3304 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
3307 * ring_buffer_overruns - get the number of overruns in buffer
3308 * @buffer: The ring buffer
3310 * Returns the total number of overruns in the ring buffer
3313 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
3315 struct ring_buffer_per_cpu
*cpu_buffer
;
3316 unsigned long overruns
= 0;
3319 /* if you care about this being correct, lock the buffer */
3320 for_each_buffer_cpu(buffer
, cpu
) {
3321 cpu_buffer
= buffer
->buffers
[cpu
];
3322 overruns
+= local_read(&cpu_buffer
->overrun
);
3327 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
3329 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
3331 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3333 /* Iterator usage is expected to have record disabled */
3334 iter
->head_page
= cpu_buffer
->reader_page
;
3335 iter
->head
= cpu_buffer
->reader_page
->read
;
3337 iter
->cache_reader_page
= iter
->head_page
;
3338 iter
->cache_read
= cpu_buffer
->read
;
3341 iter
->read_stamp
= cpu_buffer
->read_stamp
;
3343 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
3347 * ring_buffer_iter_reset - reset an iterator
3348 * @iter: The iterator to reset
3350 * Resets the iterator, so that it will start from the beginning
3353 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
3355 struct ring_buffer_per_cpu
*cpu_buffer
;
3356 unsigned long flags
;
3361 cpu_buffer
= iter
->cpu_buffer
;
3363 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3364 rb_iter_reset(iter
);
3365 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3367 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
3370 * ring_buffer_iter_empty - check if an iterator has no more to read
3371 * @iter: The iterator to check
3373 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
3375 struct ring_buffer_per_cpu
*cpu_buffer
;
3376 struct buffer_page
*reader
;
3377 struct buffer_page
*head_page
;
3378 struct buffer_page
*commit_page
;
3381 cpu_buffer
= iter
->cpu_buffer
;
3383 /* Remember, trace recording is off when iterator is in use */
3384 reader
= cpu_buffer
->reader_page
;
3385 head_page
= cpu_buffer
->head_page
;
3386 commit_page
= cpu_buffer
->commit_page
;
3387 commit
= rb_page_commit(commit_page
);
3389 return ((iter
->head_page
== commit_page
&& iter
->head
== commit
) ||
3390 (iter
->head_page
== reader
&& commit_page
== head_page
&&
3391 head_page
->read
== commit
&&
3392 iter
->head
== rb_page_commit(cpu_buffer
->reader_page
)));
3394 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
3397 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
3398 struct ring_buffer_event
*event
)
3402 switch (event
->type_len
) {
3403 case RINGBUF_TYPE_PADDING
:
3406 case RINGBUF_TYPE_TIME_EXTEND
:
3407 delta
= event
->array
[0];
3409 delta
+= event
->time_delta
;
3410 cpu_buffer
->read_stamp
+= delta
;
3413 case RINGBUF_TYPE_TIME_STAMP
:
3414 /* FIXME: not implemented */
3417 case RINGBUF_TYPE_DATA
:
3418 cpu_buffer
->read_stamp
+= event
->time_delta
;
3428 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
3429 struct ring_buffer_event
*event
)
3433 switch (event
->type_len
) {
3434 case RINGBUF_TYPE_PADDING
:
3437 case RINGBUF_TYPE_TIME_EXTEND
:
3438 delta
= event
->array
[0];
3440 delta
+= event
->time_delta
;
3441 iter
->read_stamp
+= delta
;
3444 case RINGBUF_TYPE_TIME_STAMP
:
3445 /* FIXME: not implemented */
3448 case RINGBUF_TYPE_DATA
:
3449 iter
->read_stamp
+= event
->time_delta
;
3458 static struct buffer_page
*
3459 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
3461 struct buffer_page
*reader
= NULL
;
3462 unsigned long overwrite
;
3463 unsigned long flags
;
3467 local_irq_save(flags
);
3468 arch_spin_lock(&cpu_buffer
->lock
);
3472 * This should normally only loop twice. But because the
3473 * start of the reader inserts an empty page, it causes
3474 * a case where we will loop three times. There should be no
3475 * reason to loop four times (that I know of).
3477 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
3482 reader
= cpu_buffer
->reader_page
;
3484 /* If there's more to read, return this page */
3485 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
3488 /* Never should we have an index greater than the size */
3489 if (RB_WARN_ON(cpu_buffer
,
3490 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
3493 /* check if we caught up to the tail */
3495 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
3498 /* Don't bother swapping if the ring buffer is empty */
3499 if (rb_num_of_entries(cpu_buffer
) == 0)
3503 * Reset the reader page to size zero.
3505 local_set(&cpu_buffer
->reader_page
->write
, 0);
3506 local_set(&cpu_buffer
->reader_page
->entries
, 0);
3507 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
3508 cpu_buffer
->reader_page
->real_end
= 0;
3512 * Splice the empty reader page into the list around the head.
3514 reader
= rb_set_head_page(cpu_buffer
);
3517 cpu_buffer
->reader_page
->list
.next
= rb_list_head(reader
->list
.next
);
3518 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
3521 * cpu_buffer->pages just needs to point to the buffer, it
3522 * has no specific buffer page to point to. Lets move it out
3523 * of our way so we don't accidentally swap it.
3525 cpu_buffer
->pages
= reader
->list
.prev
;
3527 /* The reader page will be pointing to the new head */
3528 rb_set_list_to_head(cpu_buffer
, &cpu_buffer
->reader_page
->list
);
3531 * We want to make sure we read the overruns after we set up our
3532 * pointers to the next object. The writer side does a
3533 * cmpxchg to cross pages which acts as the mb on the writer
3534 * side. Note, the reader will constantly fail the swap
3535 * while the writer is updating the pointers, so this
3536 * guarantees that the overwrite recorded here is the one we
3537 * want to compare with the last_overrun.
3540 overwrite
= local_read(&(cpu_buffer
->overrun
));
3543 * Here's the tricky part.
3545 * We need to move the pointer past the header page.
3546 * But we can only do that if a writer is not currently
3547 * moving it. The page before the header page has the
3548 * flag bit '1' set if it is pointing to the page we want.
3549 * but if the writer is in the process of moving it
3550 * than it will be '2' or already moved '0'.
3553 ret
= rb_head_page_replace(reader
, cpu_buffer
->reader_page
);
3556 * If we did not convert it, then we must try again.
3562 * Yeah! We succeeded in replacing the page.
3564 * Now make the new head point back to the reader page.
3566 rb_list_head(reader
->list
.next
)->prev
= &cpu_buffer
->reader_page
->list
;
3567 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
3569 /* Finally update the reader page to the new head */
3570 cpu_buffer
->reader_page
= reader
;
3571 cpu_buffer
->reader_page
->read
= 0;
3573 if (overwrite
!= cpu_buffer
->last_overrun
) {
3574 cpu_buffer
->lost_events
= overwrite
- cpu_buffer
->last_overrun
;
3575 cpu_buffer
->last_overrun
= overwrite
;
3581 /* Update the read_stamp on the first event */
3582 if (reader
&& reader
->read
== 0)
3583 cpu_buffer
->read_stamp
= reader
->page
->time_stamp
;
3585 arch_spin_unlock(&cpu_buffer
->lock
);
3586 local_irq_restore(flags
);
3591 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
3593 struct ring_buffer_event
*event
;
3594 struct buffer_page
*reader
;
3597 reader
= rb_get_reader_page(cpu_buffer
);
3599 /* This function should not be called when buffer is empty */
3600 if (RB_WARN_ON(cpu_buffer
, !reader
))
3603 event
= rb_reader_event(cpu_buffer
);
3605 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
3608 rb_update_read_stamp(cpu_buffer
, event
);
3610 length
= rb_event_length(event
);
3611 cpu_buffer
->reader_page
->read
+= length
;
3614 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
3616 struct ring_buffer_per_cpu
*cpu_buffer
;
3617 struct ring_buffer_event
*event
;
3620 cpu_buffer
= iter
->cpu_buffer
;
3623 * Check if we are at the end of the buffer.
3625 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3626 /* discarded commits can make the page empty */
3627 if (iter
->head_page
== cpu_buffer
->commit_page
)
3633 event
= rb_iter_head_event(iter
);
3635 length
= rb_event_length(event
);
3638 * This should not be called to advance the header if we are
3639 * at the tail of the buffer.
3641 if (RB_WARN_ON(cpu_buffer
,
3642 (iter
->head_page
== cpu_buffer
->commit_page
) &&
3643 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
3646 rb_update_iter_read_stamp(iter
, event
);
3648 iter
->head
+= length
;
3650 /* check for end of page padding */
3651 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
3652 (iter
->head_page
!= cpu_buffer
->commit_page
))
3656 static int rb_lost_events(struct ring_buffer_per_cpu
*cpu_buffer
)
3658 return cpu_buffer
->lost_events
;
3661 static struct ring_buffer_event
*
3662 rb_buffer_peek(struct ring_buffer_per_cpu
*cpu_buffer
, u64
*ts
,
3663 unsigned long *lost_events
)
3665 struct ring_buffer_event
*event
;
3666 struct buffer_page
*reader
;
3671 * We repeat when a time extend is encountered.
3672 * Since the time extend is always attached to a data event,
3673 * we should never loop more than once.
3674 * (We never hit the following condition more than twice).
3676 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 2))
3679 reader
= rb_get_reader_page(cpu_buffer
);
3683 event
= rb_reader_event(cpu_buffer
);
3685 switch (event
->type_len
) {
3686 case RINGBUF_TYPE_PADDING
:
3687 if (rb_null_event(event
))
3688 RB_WARN_ON(cpu_buffer
, 1);
3690 * Because the writer could be discarding every
3691 * event it creates (which would probably be bad)
3692 * if we were to go back to "again" then we may never
3693 * catch up, and will trigger the warn on, or lock
3694 * the box. Return the padding, and we will release
3695 * the current locks, and try again.
3699 case RINGBUF_TYPE_TIME_EXTEND
:
3700 /* Internal data, OK to advance */
3701 rb_advance_reader(cpu_buffer
);
3704 case RINGBUF_TYPE_TIME_STAMP
:
3705 /* FIXME: not implemented */
3706 rb_advance_reader(cpu_buffer
);
3709 case RINGBUF_TYPE_DATA
:
3711 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
3712 ring_buffer_normalize_time_stamp(cpu_buffer
->buffer
,
3713 cpu_buffer
->cpu
, ts
);
3716 *lost_events
= rb_lost_events(cpu_buffer
);
3725 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
3727 static struct ring_buffer_event
*
3728 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3730 struct ring_buffer
*buffer
;
3731 struct ring_buffer_per_cpu
*cpu_buffer
;
3732 struct ring_buffer_event
*event
;
3735 cpu_buffer
= iter
->cpu_buffer
;
3736 buffer
= cpu_buffer
->buffer
;
3739 * Check if someone performed a consuming read to
3740 * the buffer. A consuming read invalidates the iterator
3741 * and we need to reset the iterator in this case.
3743 if (unlikely(iter
->cache_read
!= cpu_buffer
->read
||
3744 iter
->cache_reader_page
!= cpu_buffer
->reader_page
))
3745 rb_iter_reset(iter
);
3748 if (ring_buffer_iter_empty(iter
))
3752 * We repeat when a time extend is encountered or we hit
3753 * the end of the page. Since the time extend is always attached
3754 * to a data event, we should never loop more than three times.
3755 * Once for going to next page, once on time extend, and
3756 * finally once to get the event.
3757 * (We never hit the following condition more than thrice).
3759 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3))
3762 if (rb_per_cpu_empty(cpu_buffer
))
3765 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
3770 event
= rb_iter_head_event(iter
);
3772 switch (event
->type_len
) {
3773 case RINGBUF_TYPE_PADDING
:
3774 if (rb_null_event(event
)) {
3778 rb_advance_iter(iter
);
3781 case RINGBUF_TYPE_TIME_EXTEND
:
3782 /* Internal data, OK to advance */
3783 rb_advance_iter(iter
);
3786 case RINGBUF_TYPE_TIME_STAMP
:
3787 /* FIXME: not implemented */
3788 rb_advance_iter(iter
);
3791 case RINGBUF_TYPE_DATA
:
3793 *ts
= iter
->read_stamp
+ event
->time_delta
;
3794 ring_buffer_normalize_time_stamp(buffer
,
3795 cpu_buffer
->cpu
, ts
);
3805 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
3807 static inline bool rb_reader_lock(struct ring_buffer_per_cpu
*cpu_buffer
)
3809 if (likely(!in_nmi())) {
3810 raw_spin_lock(&cpu_buffer
->reader_lock
);
3815 * If an NMI die dumps out the content of the ring buffer
3816 * trylock must be used to prevent a deadlock if the NMI
3817 * preempted a task that holds the ring buffer locks. If
3818 * we get the lock then all is fine, if not, then continue
3819 * to do the read, but this can corrupt the ring buffer,
3820 * so it must be permanently disabled from future writes.
3821 * Reading from NMI is a oneshot deal.
3823 if (raw_spin_trylock(&cpu_buffer
->reader_lock
))
3826 /* Continue without locking, but disable the ring buffer */
3827 atomic_inc(&cpu_buffer
->record_disabled
);
3832 rb_reader_unlock(struct ring_buffer_per_cpu
*cpu_buffer
, bool locked
)
3835 raw_spin_unlock(&cpu_buffer
->reader_lock
);
3840 * ring_buffer_peek - peek at the next event to be read
3841 * @buffer: The ring buffer to read
3842 * @cpu: The cpu to peak at
3843 * @ts: The timestamp counter of this event.
3844 * @lost_events: a variable to store if events were lost (may be NULL)
3846 * This will return the event that will be read next, but does
3847 * not consume the data.
3849 struct ring_buffer_event
*
3850 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3851 unsigned long *lost_events
)
3853 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
3854 struct ring_buffer_event
*event
;
3855 unsigned long flags
;
3858 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3862 local_irq_save(flags
);
3863 dolock
= rb_reader_lock(cpu_buffer
);
3864 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3865 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3866 rb_advance_reader(cpu_buffer
);
3867 rb_reader_unlock(cpu_buffer
, dolock
);
3868 local_irq_restore(flags
);
3870 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3877 * ring_buffer_iter_peek - peek at the next event to be read
3878 * @iter: The ring buffer iterator
3879 * @ts: The timestamp counter of this event.
3881 * This will return the event that will be read next, but does
3882 * not increment the iterator.
3884 struct ring_buffer_event
*
3885 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
3887 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
3888 struct ring_buffer_event
*event
;
3889 unsigned long flags
;
3892 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3893 event
= rb_iter_peek(iter
, ts
);
3894 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3896 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3903 * ring_buffer_consume - return an event and consume it
3904 * @buffer: The ring buffer to get the next event from
3905 * @cpu: the cpu to read the buffer from
3906 * @ts: a variable to store the timestamp (may be NULL)
3907 * @lost_events: a variable to store if events were lost (may be NULL)
3909 * Returns the next event in the ring buffer, and that event is consumed.
3910 * Meaning, that sequential reads will keep returning a different event,
3911 * and eventually empty the ring buffer if the producer is slower.
3913 struct ring_buffer_event
*
3914 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
,
3915 unsigned long *lost_events
)
3917 struct ring_buffer_per_cpu
*cpu_buffer
;
3918 struct ring_buffer_event
*event
= NULL
;
3919 unsigned long flags
;
3923 /* might be called in atomic */
3926 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3929 cpu_buffer
= buffer
->buffers
[cpu
];
3930 local_irq_save(flags
);
3931 dolock
= rb_reader_lock(cpu_buffer
);
3933 event
= rb_buffer_peek(cpu_buffer
, ts
, lost_events
);
3935 cpu_buffer
->lost_events
= 0;
3936 rb_advance_reader(cpu_buffer
);
3939 rb_reader_unlock(cpu_buffer
, dolock
);
3940 local_irq_restore(flags
);
3945 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
)
3950 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
3953 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3954 * @buffer: The ring buffer to read from
3955 * @cpu: The cpu buffer to iterate over
3957 * This performs the initial preparations necessary to iterate
3958 * through the buffer. Memory is allocated, buffer recording
3959 * is disabled, and the iterator pointer is returned to the caller.
3961 * Disabling buffer recordng prevents the reading from being
3962 * corrupted. This is not a consuming read, so a producer is not
3965 * After a sequence of ring_buffer_read_prepare calls, the user is
3966 * expected to make at least one call to ring_buffer_read_prepare_sync.
3967 * Afterwards, ring_buffer_read_start is invoked to get things going
3970 * This overall must be paired with ring_buffer_read_finish.
3972 struct ring_buffer_iter
*
3973 ring_buffer_read_prepare(struct ring_buffer
*buffer
, int cpu
)
3975 struct ring_buffer_per_cpu
*cpu_buffer
;
3976 struct ring_buffer_iter
*iter
;
3978 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3981 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
3985 cpu_buffer
= buffer
->buffers
[cpu
];
3987 iter
->cpu_buffer
= cpu_buffer
;
3989 atomic_inc(&buffer
->resize_disabled
);
3990 atomic_inc(&cpu_buffer
->record_disabled
);
3994 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare
);
3997 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
3999 * All previously invoked ring_buffer_read_prepare calls to prepare
4000 * iterators will be synchronized. Afterwards, read_buffer_read_start
4001 * calls on those iterators are allowed.
4004 ring_buffer_read_prepare_sync(void)
4006 synchronize_sched();
4008 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync
);
4011 * ring_buffer_read_start - start a non consuming read of the buffer
4012 * @iter: The iterator returned by ring_buffer_read_prepare
4014 * This finalizes the startup of an iteration through the buffer.
4015 * The iterator comes from a call to ring_buffer_read_prepare and
4016 * an intervening ring_buffer_read_prepare_sync must have been
4019 * Must be paired with ring_buffer_read_finish.
4022 ring_buffer_read_start(struct ring_buffer_iter
*iter
)
4024 struct ring_buffer_per_cpu
*cpu_buffer
;
4025 unsigned long flags
;
4030 cpu_buffer
= iter
->cpu_buffer
;
4032 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4033 arch_spin_lock(&cpu_buffer
->lock
);
4034 rb_iter_reset(iter
);
4035 arch_spin_unlock(&cpu_buffer
->lock
);
4036 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4038 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
4041 * ring_buffer_read_finish - finish reading the iterator of the buffer
4042 * @iter: The iterator retrieved by ring_buffer_start
4044 * This re-enables the recording to the buffer, and frees the
4048 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
4050 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4051 unsigned long flags
;
4054 * Ring buffer is disabled from recording, here's a good place
4055 * to check the integrity of the ring buffer.
4056 * Must prevent readers from trying to read, as the check
4057 * clears the HEAD page and readers require it.
4059 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4060 rb_check_pages(cpu_buffer
);
4061 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4063 atomic_dec(&cpu_buffer
->record_disabled
);
4064 atomic_dec(&cpu_buffer
->buffer
->resize_disabled
);
4067 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
4070 * ring_buffer_read - read the next item in the ring buffer by the iterator
4071 * @iter: The ring buffer iterator
4072 * @ts: The time stamp of the event read.
4074 * This reads the next event in the ring buffer and increments the iterator.
4076 struct ring_buffer_event
*
4077 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
4079 struct ring_buffer_event
*event
;
4080 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
4081 unsigned long flags
;
4083 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4085 event
= rb_iter_peek(iter
, ts
);
4089 if (event
->type_len
== RINGBUF_TYPE_PADDING
)
4092 rb_advance_iter(iter
);
4094 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4098 EXPORT_SYMBOL_GPL(ring_buffer_read
);
4101 * ring_buffer_size - return the size of the ring buffer (in bytes)
4102 * @buffer: The ring buffer.
4104 unsigned long ring_buffer_size(struct ring_buffer
*buffer
, int cpu
)
4107 * Earlier, this method returned
4108 * BUF_PAGE_SIZE * buffer->nr_pages
4109 * Since the nr_pages field is now removed, we have converted this to
4110 * return the per cpu buffer value.
4112 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4115 return BUF_PAGE_SIZE
* buffer
->buffers
[cpu
]->nr_pages
;
4117 EXPORT_SYMBOL_GPL(ring_buffer_size
);
4120 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
4122 rb_head_page_deactivate(cpu_buffer
);
4124 cpu_buffer
->head_page
4125 = list_entry(cpu_buffer
->pages
, struct buffer_page
, list
);
4126 local_set(&cpu_buffer
->head_page
->write
, 0);
4127 local_set(&cpu_buffer
->head_page
->entries
, 0);
4128 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
4130 cpu_buffer
->head_page
->read
= 0;
4132 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
4133 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
4135 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
4136 INIT_LIST_HEAD(&cpu_buffer
->new_pages
);
4137 local_set(&cpu_buffer
->reader_page
->write
, 0);
4138 local_set(&cpu_buffer
->reader_page
->entries
, 0);
4139 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
4140 cpu_buffer
->reader_page
->read
= 0;
4142 local_set(&cpu_buffer
->entries_bytes
, 0);
4143 local_set(&cpu_buffer
->overrun
, 0);
4144 local_set(&cpu_buffer
->commit_overrun
, 0);
4145 local_set(&cpu_buffer
->dropped_events
, 0);
4146 local_set(&cpu_buffer
->entries
, 0);
4147 local_set(&cpu_buffer
->committing
, 0);
4148 local_set(&cpu_buffer
->commits
, 0);
4149 cpu_buffer
->read
= 0;
4150 cpu_buffer
->read_bytes
= 0;
4152 cpu_buffer
->write_stamp
= 0;
4153 cpu_buffer
->read_stamp
= 0;
4155 cpu_buffer
->lost_events
= 0;
4156 cpu_buffer
->last_overrun
= 0;
4158 rb_head_page_activate(cpu_buffer
);
4162 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4163 * @buffer: The ring buffer to reset a per cpu buffer of
4164 * @cpu: The CPU buffer to be reset
4166 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
4168 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4169 unsigned long flags
;
4171 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4174 atomic_inc(&buffer
->resize_disabled
);
4175 atomic_inc(&cpu_buffer
->record_disabled
);
4177 /* Make sure all commits have finished */
4178 synchronize_sched();
4180 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4182 if (RB_WARN_ON(cpu_buffer
, local_read(&cpu_buffer
->committing
)))
4185 arch_spin_lock(&cpu_buffer
->lock
);
4187 rb_reset_cpu(cpu_buffer
);
4189 arch_spin_unlock(&cpu_buffer
->lock
);
4192 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4194 atomic_dec(&cpu_buffer
->record_disabled
);
4195 atomic_dec(&buffer
->resize_disabled
);
4197 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
4200 * ring_buffer_reset - reset a ring buffer
4201 * @buffer: The ring buffer to reset all cpu buffers
4203 void ring_buffer_reset(struct ring_buffer
*buffer
)
4207 for_each_buffer_cpu(buffer
, cpu
)
4208 ring_buffer_reset_cpu(buffer
, cpu
);
4210 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
4213 * rind_buffer_empty - is the ring buffer empty?
4214 * @buffer: The ring buffer to test
4216 bool ring_buffer_empty(struct ring_buffer
*buffer
)
4218 struct ring_buffer_per_cpu
*cpu_buffer
;
4219 unsigned long flags
;
4224 /* yes this is racy, but if you don't like the race, lock the buffer */
4225 for_each_buffer_cpu(buffer
, cpu
) {
4226 cpu_buffer
= buffer
->buffers
[cpu
];
4227 local_irq_save(flags
);
4228 dolock
= rb_reader_lock(cpu_buffer
);
4229 ret
= rb_per_cpu_empty(cpu_buffer
);
4230 rb_reader_unlock(cpu_buffer
, dolock
);
4231 local_irq_restore(flags
);
4239 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
4242 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4243 * @buffer: The ring buffer
4244 * @cpu: The CPU buffer to test
4246 bool ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
4248 struct ring_buffer_per_cpu
*cpu_buffer
;
4249 unsigned long flags
;
4253 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4256 cpu_buffer
= buffer
->buffers
[cpu
];
4257 local_irq_save(flags
);
4258 dolock
= rb_reader_lock(cpu_buffer
);
4259 ret
= rb_per_cpu_empty(cpu_buffer
);
4260 rb_reader_unlock(cpu_buffer
, dolock
);
4261 local_irq_restore(flags
);
4265 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
4267 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4269 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4270 * @buffer_a: One buffer to swap with
4271 * @buffer_b: The other buffer to swap with
4273 * This function is useful for tracers that want to take a "snapshot"
4274 * of a CPU buffer and has another back up buffer lying around.
4275 * it is expected that the tracer handles the cpu buffer not being
4276 * used at the moment.
4278 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
4279 struct ring_buffer
*buffer_b
, int cpu
)
4281 struct ring_buffer_per_cpu
*cpu_buffer_a
;
4282 struct ring_buffer_per_cpu
*cpu_buffer_b
;
4285 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
4286 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
4289 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
4290 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
4292 /* At least make sure the two buffers are somewhat the same */
4293 if (cpu_buffer_a
->nr_pages
!= cpu_buffer_b
->nr_pages
)
4298 if (atomic_read(&buffer_a
->record_disabled
))
4301 if (atomic_read(&buffer_b
->record_disabled
))
4304 if (atomic_read(&cpu_buffer_a
->record_disabled
))
4307 if (atomic_read(&cpu_buffer_b
->record_disabled
))
4311 * We can't do a synchronize_sched here because this
4312 * function can be called in atomic context.
4313 * Normally this will be called from the same CPU as cpu.
4314 * If not it's up to the caller to protect this.
4316 atomic_inc(&cpu_buffer_a
->record_disabled
);
4317 atomic_inc(&cpu_buffer_b
->record_disabled
);
4320 if (local_read(&cpu_buffer_a
->committing
))
4322 if (local_read(&cpu_buffer_b
->committing
))
4325 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
4326 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
4328 cpu_buffer_b
->buffer
= buffer_a
;
4329 cpu_buffer_a
->buffer
= buffer_b
;
4334 atomic_dec(&cpu_buffer_a
->record_disabled
);
4335 atomic_dec(&cpu_buffer_b
->record_disabled
);
4339 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
4340 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4343 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4344 * @buffer: the buffer to allocate for.
4345 * @cpu: the cpu buffer to allocate.
4347 * This function is used in conjunction with ring_buffer_read_page.
4348 * When reading a full page from the ring buffer, these functions
4349 * can be used to speed up the process. The calling function should
4350 * allocate a few pages first with this function. Then when it
4351 * needs to get pages from the ring buffer, it passes the result
4352 * of this function into ring_buffer_read_page, which will swap
4353 * the page that was allocated, with the read page of the buffer.
4356 * The page allocated, or ERR_PTR
4358 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
, int cpu
)
4360 struct ring_buffer_per_cpu
*cpu_buffer
;
4361 struct buffer_data_page
*bpage
= NULL
;
4362 unsigned long flags
;
4365 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4366 return ERR_PTR(-ENODEV
);
4368 cpu_buffer
= buffer
->buffers
[cpu
];
4369 local_irq_save(flags
);
4370 arch_spin_lock(&cpu_buffer
->lock
);
4372 if (cpu_buffer
->free_page
) {
4373 bpage
= cpu_buffer
->free_page
;
4374 cpu_buffer
->free_page
= NULL
;
4377 arch_spin_unlock(&cpu_buffer
->lock
);
4378 local_irq_restore(flags
);
4383 page
= alloc_pages_node(cpu_to_node(cpu
),
4384 GFP_KERNEL
| __GFP_NORETRY
, 0);
4386 return ERR_PTR(-ENOMEM
);
4388 bpage
= page_address(page
);
4391 rb_init_page(bpage
);
4395 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
4398 * ring_buffer_free_read_page - free an allocated read page
4399 * @buffer: the buffer the page was allocate for
4400 * @cpu: the cpu buffer the page came from
4401 * @data: the page to free
4403 * Free a page allocated from ring_buffer_alloc_read_page.
4405 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, int cpu
, void *data
)
4407 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4408 struct buffer_data_page
*bpage
= data
;
4409 unsigned long flags
;
4411 local_irq_save(flags
);
4412 arch_spin_lock(&cpu_buffer
->lock
);
4414 if (!cpu_buffer
->free_page
) {
4415 cpu_buffer
->free_page
= bpage
;
4419 arch_spin_unlock(&cpu_buffer
->lock
);
4420 local_irq_restore(flags
);
4422 free_page((unsigned long)bpage
);
4424 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
4427 * ring_buffer_read_page - extract a page from the ring buffer
4428 * @buffer: buffer to extract from
4429 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4430 * @len: amount to extract
4431 * @cpu: the cpu of the buffer to extract
4432 * @full: should the extraction only happen when the page is full.
4434 * This function will pull out a page from the ring buffer and consume it.
4435 * @data_page must be the address of the variable that was returned
4436 * from ring_buffer_alloc_read_page. This is because the page might be used
4437 * to swap with a page in the ring buffer.
4440 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4441 * if (IS_ERR(rpage))
4442 * return PTR_ERR(rpage);
4443 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4445 * process_page(rpage, ret);
4447 * When @full is set, the function will not return true unless
4448 * the writer is off the reader page.
4450 * Note: it is up to the calling functions to handle sleeps and wakeups.
4451 * The ring buffer can be used anywhere in the kernel and can not
4452 * blindly call wake_up. The layer that uses the ring buffer must be
4453 * responsible for that.
4456 * >=0 if data has been transferred, returns the offset of consumed data.
4457 * <0 if no data has been transferred.
4459 int ring_buffer_read_page(struct ring_buffer
*buffer
,
4460 void **data_page
, size_t len
, int cpu
, int full
)
4462 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
4463 struct ring_buffer_event
*event
;
4464 struct buffer_data_page
*bpage
;
4465 struct buffer_page
*reader
;
4466 unsigned long missed_events
;
4467 unsigned long flags
;
4468 unsigned int commit
;
4473 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
4477 * If len is not big enough to hold the page header, then
4478 * we can not copy anything.
4480 if (len
<= BUF_PAGE_HDR_SIZE
)
4483 len
-= BUF_PAGE_HDR_SIZE
;
4492 raw_spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
4494 reader
= rb_get_reader_page(cpu_buffer
);
4498 event
= rb_reader_event(cpu_buffer
);
4500 read
= reader
->read
;
4501 commit
= rb_page_commit(reader
);
4503 /* Check if any events were dropped */
4504 missed_events
= cpu_buffer
->lost_events
;
4507 * If this page has been partially read or
4508 * if len is not big enough to read the rest of the page or
4509 * a writer is still on the page, then
4510 * we must copy the data from the page to the buffer.
4511 * Otherwise, we can simply swap the page with the one passed in.
4513 if (read
|| (len
< (commit
- read
)) ||
4514 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
4515 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
4516 unsigned int rpos
= read
;
4517 unsigned int pos
= 0;
4523 if (len
> (commit
- read
))
4524 len
= (commit
- read
);
4526 /* Always keep the time extend and data together */
4527 size
= rb_event_ts_length(event
);
4532 /* save the current timestamp, since the user will need it */
4533 save_timestamp
= cpu_buffer
->read_stamp
;
4535 /* Need to copy one event at a time */
4537 /* We need the size of one event, because
4538 * rb_advance_reader only advances by one event,
4539 * whereas rb_event_ts_length may include the size of
4540 * one or two events.
4541 * We have already ensured there's enough space if this
4542 * is a time extend. */
4543 size
= rb_event_length(event
);
4544 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
4548 rb_advance_reader(cpu_buffer
);
4549 rpos
= reader
->read
;
4555 event
= rb_reader_event(cpu_buffer
);
4556 /* Always keep the time extend and data together */
4557 size
= rb_event_ts_length(event
);
4558 } while (len
>= size
);
4561 local_set(&bpage
->commit
, pos
);
4562 bpage
->time_stamp
= save_timestamp
;
4564 /* we copied everything to the beginning */
4567 /* update the entry counter */
4568 cpu_buffer
->read
+= rb_page_entries(reader
);
4569 cpu_buffer
->read_bytes
+= BUF_PAGE_SIZE
;
4571 /* swap the pages */
4572 rb_init_page(bpage
);
4573 bpage
= reader
->page
;
4574 reader
->page
= *data_page
;
4575 local_set(&reader
->write
, 0);
4576 local_set(&reader
->entries
, 0);
4581 * Use the real_end for the data size,
4582 * This gives us a chance to store the lost events
4585 if (reader
->real_end
)
4586 local_set(&bpage
->commit
, reader
->real_end
);
4590 cpu_buffer
->lost_events
= 0;
4592 commit
= local_read(&bpage
->commit
);
4594 * Set a flag in the commit field if we lost events
4596 if (missed_events
) {
4597 /* If there is room at the end of the page to save the
4598 * missed events, then record it there.
4600 if (BUF_PAGE_SIZE
- commit
>= sizeof(missed_events
)) {
4601 memcpy(&bpage
->data
[commit
], &missed_events
,
4602 sizeof(missed_events
));
4603 local_add(RB_MISSED_STORED
, &bpage
->commit
);
4604 commit
+= sizeof(missed_events
);
4606 local_add(RB_MISSED_EVENTS
, &bpage
->commit
);
4610 * This page may be off to user land. Zero it out here.
4612 if (commit
< BUF_PAGE_SIZE
)
4613 memset(&bpage
->data
[commit
], 0, BUF_PAGE_SIZE
- commit
);
4616 raw_spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
4621 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
4624 * We only allocate new buffers, never free them if the CPU goes down.
4625 * If we were to free the buffer, then the user would lose any trace that was in
4628 int trace_rb_cpu_prepare(unsigned int cpu
, struct hlist_node
*node
)
4630 struct ring_buffer
*buffer
;
4633 unsigned long nr_pages
;
4635 buffer
= container_of(node
, struct ring_buffer
, node
);
4636 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
4641 /* check if all cpu sizes are same */
4642 for_each_buffer_cpu(buffer
, cpu_i
) {
4643 /* fill in the size from first enabled cpu */
4645 nr_pages
= buffer
->buffers
[cpu_i
]->nr_pages
;
4646 if (nr_pages
!= buffer
->buffers
[cpu_i
]->nr_pages
) {
4651 /* allocate minimum pages, user can later expand it */
4654 buffer
->buffers
[cpu
] =
4655 rb_allocate_cpu_buffer(buffer
, nr_pages
, cpu
);
4656 if (!buffer
->buffers
[cpu
]) {
4657 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4662 cpumask_set_cpu(cpu
, buffer
->cpumask
);
4666 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4668 * This is a basic integrity check of the ring buffer.
4669 * Late in the boot cycle this test will run when configured in.
4670 * It will kick off a thread per CPU that will go into a loop
4671 * writing to the per cpu ring buffer various sizes of data.
4672 * Some of the data will be large items, some small.
4674 * Another thread is created that goes into a spin, sending out
4675 * IPIs to the other CPUs to also write into the ring buffer.
4676 * this is to test the nesting ability of the buffer.
4678 * Basic stats are recorded and reported. If something in the
4679 * ring buffer should happen that's not expected, a big warning
4680 * is displayed and all ring buffers are disabled.
4682 static struct task_struct
*rb_threads
[NR_CPUS
] __initdata
;
4684 struct rb_test_data
{
4685 struct ring_buffer
*buffer
;
4686 unsigned long events
;
4687 unsigned long bytes_written
;
4688 unsigned long bytes_alloc
;
4689 unsigned long bytes_dropped
;
4690 unsigned long events_nested
;
4691 unsigned long bytes_written_nested
;
4692 unsigned long bytes_alloc_nested
;
4693 unsigned long bytes_dropped_nested
;
4694 int min_size_nested
;
4695 int max_size_nested
;
4702 static struct rb_test_data rb_data
[NR_CPUS
] __initdata
;
4705 #define RB_TEST_BUFFER_SIZE 1048576
4707 static char rb_string
[] __initdata
=
4708 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4709 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4710 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4712 static bool rb_test_started __initdata
;
4719 static __init
int rb_write_something(struct rb_test_data
*data
, bool nested
)
4721 struct ring_buffer_event
*event
;
4722 struct rb_item
*item
;
4729 /* Have nested writes different that what is written */
4730 cnt
= data
->cnt
+ (nested
? 27 : 0);
4732 /* Multiply cnt by ~e, to make some unique increment */
4733 size
= (data
->cnt
* 68 / 25) % (sizeof(rb_string
) - 1);
4735 len
= size
+ sizeof(struct rb_item
);
4737 started
= rb_test_started
;
4738 /* read rb_test_started before checking buffer enabled */
4741 event
= ring_buffer_lock_reserve(data
->buffer
, len
);
4743 /* Ignore dropped events before test starts. */
4746 data
->bytes_dropped
+= len
;
4748 data
->bytes_dropped_nested
+= len
;
4753 event_len
= ring_buffer_event_length(event
);
4755 if (RB_WARN_ON(data
->buffer
, event_len
< len
))
4758 item
= ring_buffer_event_data(event
);
4760 memcpy(item
->str
, rb_string
, size
);
4763 data
->bytes_alloc_nested
+= event_len
;
4764 data
->bytes_written_nested
+= len
;
4765 data
->events_nested
++;
4766 if (!data
->min_size_nested
|| len
< data
->min_size_nested
)
4767 data
->min_size_nested
= len
;
4768 if (len
> data
->max_size_nested
)
4769 data
->max_size_nested
= len
;
4771 data
->bytes_alloc
+= event_len
;
4772 data
->bytes_written
+= len
;
4774 if (!data
->min_size
|| len
< data
->min_size
)
4775 data
->max_size
= len
;
4776 if (len
> data
->max_size
)
4777 data
->max_size
= len
;
4781 ring_buffer_unlock_commit(data
->buffer
, event
);
4786 static __init
int rb_test(void *arg
)
4788 struct rb_test_data
*data
= arg
;
4790 while (!kthread_should_stop()) {
4791 rb_write_something(data
, false);
4794 set_current_state(TASK_INTERRUPTIBLE
);
4795 /* Now sleep between a min of 100-300us and a max of 1ms */
4796 usleep_range(((data
->cnt
% 3) + 1) * 100, 1000);
4802 static __init
void rb_ipi(void *ignore
)
4804 struct rb_test_data
*data
;
4805 int cpu
= smp_processor_id();
4807 data
= &rb_data
[cpu
];
4808 rb_write_something(data
, true);
4811 static __init
int rb_hammer_test(void *arg
)
4813 while (!kthread_should_stop()) {
4815 /* Send an IPI to all cpus to write data! */
4816 smp_call_function(rb_ipi
, NULL
, 1);
4817 /* No sleep, but for non preempt, let others run */
4824 static __init
int test_ringbuffer(void)
4826 struct task_struct
*rb_hammer
;
4827 struct ring_buffer
*buffer
;
4831 pr_info("Running ring buffer tests...\n");
4833 buffer
= ring_buffer_alloc(RB_TEST_BUFFER_SIZE
, RB_FL_OVERWRITE
);
4834 if (WARN_ON(!buffer
))
4837 /* Disable buffer so that threads can't write to it yet */
4838 ring_buffer_record_off(buffer
);
4840 for_each_online_cpu(cpu
) {
4841 rb_data
[cpu
].buffer
= buffer
;
4842 rb_data
[cpu
].cpu
= cpu
;
4843 rb_data
[cpu
].cnt
= cpu
;
4844 rb_threads
[cpu
] = kthread_create(rb_test
, &rb_data
[cpu
],
4845 "rbtester/%d", cpu
);
4846 if (WARN_ON(IS_ERR(rb_threads
[cpu
]))) {
4847 pr_cont("FAILED\n");
4848 ret
= PTR_ERR(rb_threads
[cpu
]);
4852 kthread_bind(rb_threads
[cpu
], cpu
);
4853 wake_up_process(rb_threads
[cpu
]);
4856 /* Now create the rb hammer! */
4857 rb_hammer
= kthread_run(rb_hammer_test
, NULL
, "rbhammer");
4858 if (WARN_ON(IS_ERR(rb_hammer
))) {
4859 pr_cont("FAILED\n");
4860 ret
= PTR_ERR(rb_hammer
);
4864 ring_buffer_record_on(buffer
);
4866 * Show buffer is enabled before setting rb_test_started.
4867 * Yes there's a small race window where events could be
4868 * dropped and the thread wont catch it. But when a ring
4869 * buffer gets enabled, there will always be some kind of
4870 * delay before other CPUs see it. Thus, we don't care about
4871 * those dropped events. We care about events dropped after
4872 * the threads see that the buffer is active.
4875 rb_test_started
= true;
4877 set_current_state(TASK_INTERRUPTIBLE
);
4878 /* Just run for 10 seconds */;
4879 schedule_timeout(10 * HZ
);
4881 kthread_stop(rb_hammer
);
4884 for_each_online_cpu(cpu
) {
4885 if (!rb_threads
[cpu
])
4887 kthread_stop(rb_threads
[cpu
]);
4890 ring_buffer_free(buffer
);
4895 pr_info("finished\n");
4896 for_each_online_cpu(cpu
) {
4897 struct ring_buffer_event
*event
;
4898 struct rb_test_data
*data
= &rb_data
[cpu
];
4899 struct rb_item
*item
;
4900 unsigned long total_events
;
4901 unsigned long total_dropped
;
4902 unsigned long total_written
;
4903 unsigned long total_alloc
;
4904 unsigned long total_read
= 0;
4905 unsigned long total_size
= 0;
4906 unsigned long total_len
= 0;
4907 unsigned long total_lost
= 0;
4910 int small_event_size
;
4914 total_events
= data
->events
+ data
->events_nested
;
4915 total_written
= data
->bytes_written
+ data
->bytes_written_nested
;
4916 total_alloc
= data
->bytes_alloc
+ data
->bytes_alloc_nested
;
4917 total_dropped
= data
->bytes_dropped
+ data
->bytes_dropped_nested
;
4919 big_event_size
= data
->max_size
+ data
->max_size_nested
;
4920 small_event_size
= data
->min_size
+ data
->min_size_nested
;
4922 pr_info("CPU %d:\n", cpu
);
4923 pr_info(" events: %ld\n", total_events
);
4924 pr_info(" dropped bytes: %ld\n", total_dropped
);
4925 pr_info(" alloced bytes: %ld\n", total_alloc
);
4926 pr_info(" written bytes: %ld\n", total_written
);
4927 pr_info(" biggest event: %d\n", big_event_size
);
4928 pr_info(" smallest event: %d\n", small_event_size
);
4930 if (RB_WARN_ON(buffer
, total_dropped
))
4935 while ((event
= ring_buffer_consume(buffer
, cpu
, NULL
, &lost
))) {
4937 item
= ring_buffer_event_data(event
);
4938 total_len
+= ring_buffer_event_length(event
);
4939 total_size
+= item
->size
+ sizeof(struct rb_item
);
4940 if (memcmp(&item
->str
[0], rb_string
, item
->size
) != 0) {
4941 pr_info("FAILED!\n");
4942 pr_info("buffer had: %.*s\n", item
->size
, item
->str
);
4943 pr_info("expected: %.*s\n", item
->size
, rb_string
);
4944 RB_WARN_ON(buffer
, 1);
4955 pr_info(" read events: %ld\n", total_read
);
4956 pr_info(" lost events: %ld\n", total_lost
);
4957 pr_info(" total events: %ld\n", total_lost
+ total_read
);
4958 pr_info(" recorded len bytes: %ld\n", total_len
);
4959 pr_info(" recorded size bytes: %ld\n", total_size
);
4961 pr_info(" With dropped events, record len and size may not match\n"
4962 " alloced and written from above\n");
4964 if (RB_WARN_ON(buffer
, total_len
!= total_alloc
||
4965 total_size
!= total_written
))
4968 if (RB_WARN_ON(buffer
, total_lost
+ total_read
!= total_events
))
4974 pr_info("Ring buffer PASSED!\n");
4976 ring_buffer_free(buffer
);
4980 late_initcall(test_ringbuffer
);
4981 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */