1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
7 #include <linux/trace_recursion.h>
8 #include <linux/trace_events.h>
9 #include <linux/ring_buffer.h>
10 #include <linux/trace_clock.h>
11 #include <linux/sched/clock.h>
12 #include <linux/trace_seq.h>
13 #include <linux/spinlock.h>
14 #include <linux/irq_work.h>
15 #include <linux/security.h>
16 #include <linux/uaccess.h>
17 #include <linux/hardirq.h>
18 #include <linux/kthread.h> /* for self test */
19 #include <linux/module.h>
20 #include <linux/percpu.h>
21 #include <linux/mutex.h>
22 #include <linux/delay.h>
23 #include <linux/slab.h>
24 #include <linux/init.h>
25 #include <linux/hash.h>
26 #include <linux/list.h>
27 #include <linux/cpu.h>
28 #include <linux/oom.h>
30 #include <asm/local64.h>
31 #include <asm/local.h>
34 * The "absolute" timestamp in the buffer is only 59 bits.
35 * If a clock has the 5 MSBs set, it needs to be saved and
38 #define TS_MSB (0xf8ULL << 56)
39 #define ABS_TS_MASK (~TS_MSB)
41 static void update_pages_handler(struct work_struct *work);
44 * The ring buffer header is special. We must manually up keep it.
46 int ring_buffer_print_entry_header(struct trace_seq *s)
48 trace_seq_puts(s, "# compressed entry header\n");
49 trace_seq_puts(s, "\ttype_len : 5 bits\n");
50 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
51 trace_seq_puts(s, "\tarray : 32 bits\n");
52 trace_seq_putc(s, '\n');
53 trace_seq_printf(s, "\tpadding : type == %d\n",
54 RINGBUF_TYPE_PADDING);
55 trace_seq_printf(s, "\ttime_extend : type == %d\n",
56 RINGBUF_TYPE_TIME_EXTEND);
57 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
58 RINGBUF_TYPE_TIME_STAMP);
59 trace_seq_printf(s, "\tdata max type_len == %d\n",
60 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
62 return !trace_seq_has_overflowed(s);
66 * The ring buffer is made up of a list of pages. A separate list of pages is
67 * allocated for each CPU. A writer may only write to a buffer that is
68 * associated with the CPU it is currently executing on. A reader may read
69 * from any per cpu buffer.
71 * The reader is special. For each per cpu buffer, the reader has its own
72 * reader page. When a reader has read the entire reader page, this reader
73 * page is swapped with another page in the ring buffer.
75 * Now, as long as the writer is off the reader page, the reader can do what
76 * ever it wants with that page. The writer will never write to that page
77 * again (as long as it is out of the ring buffer).
79 * Here's some silly ASCII art.
82 * |reader| RING BUFFER
84 * +------+ +---+ +---+ +---+
93 * |reader| RING BUFFER
94 * |page |------------------v
95 * +------+ +---+ +---+ +---+
104 * |reader| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
108 * | +---+ +---+ +---+
111 * +------------------------------+
115 * |buffer| RING BUFFER
116 * |page |------------------v
117 * +------+ +---+ +---+ +---+
119 * | New +---+ +---+ +---+
122 * +------------------------------+
125 * After we make this swap, the reader can hand this page off to the splice
126 * code and be done with it. It can even allocate a new page if it needs to
127 * and swap that into the ring buffer.
129 * We will be using cmpxchg soon to make all this lockless.
133 /* Used for individual buffers (after the counter) */
134 #define RB_BUFFER_OFF (1 << 20)
136 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
138 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
139 #define RB_ALIGNMENT 4U
140 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
141 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
143 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
144 # define RB_FORCE_8BYTE_ALIGNMENT 0
145 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
147 # define RB_FORCE_8BYTE_ALIGNMENT 1
148 # define RB_ARCH_ALIGNMENT 8U
151 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
153 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
154 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
157 RB_LEN_TIME_EXTEND = 8,
158 RB_LEN_TIME_STAMP = 8,
161 #define skip_time_extend(event) \
162 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
164 #define extended_time(event) \
165 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
167 static inline bool rb_null_event(struct ring_buffer_event *event)
169 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
172 static void rb_event_set_padding(struct ring_buffer_event *event)
174 /* padding has a NULL time_delta */
175 event->type_len = RINGBUF_TYPE_PADDING;
176 event->time_delta = 0;
180 rb_event_data_length(struct ring_buffer_event *event)
185 length = event->type_len * RB_ALIGNMENT;
187 length = event->array[0];
188 return length + RB_EVNT_HDR_SIZE;
192 * Return the length of the given event. Will return
193 * the length of the time extend if the event is a
196 static inline unsigned
197 rb_event_length(struct ring_buffer_event *event)
199 switch (event->type_len) {
200 case RINGBUF_TYPE_PADDING:
201 if (rb_null_event(event))
204 return event->array[0] + RB_EVNT_HDR_SIZE;
206 case RINGBUF_TYPE_TIME_EXTEND:
207 return RB_LEN_TIME_EXTEND;
209 case RINGBUF_TYPE_TIME_STAMP:
210 return RB_LEN_TIME_STAMP;
212 case RINGBUF_TYPE_DATA:
213 return rb_event_data_length(event);
222 * Return total length of time extend and data,
223 * or just the event length for all other events.
225 static inline unsigned
226 rb_event_ts_length(struct ring_buffer_event *event)
230 if (extended_time(event)) {
231 /* time extends include the data event after it */
232 len = RB_LEN_TIME_EXTEND;
233 event = skip_time_extend(event);
235 return len + rb_event_length(event);
239 * ring_buffer_event_length - return the length of the event
240 * @event: the event to get the length of
242 * Returns the size of the data load of a data event.
243 * If the event is something other than a data event, it
244 * returns the size of the event itself. With the exception
245 * of a TIME EXTEND, where it still returns the size of the
246 * data load of the data event after it.
248 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
252 if (extended_time(event))
253 event = skip_time_extend(event);
255 length = rb_event_length(event);
256 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
258 length -= RB_EVNT_HDR_SIZE;
259 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
260 length -= sizeof(event->array[0]);
263 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
265 /* inline for ring buffer fast paths */
266 static __always_inline void *
267 rb_event_data(struct ring_buffer_event *event)
269 if (extended_time(event))
270 event = skip_time_extend(event);
271 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
272 /* If length is in len field, then array[0] has the data */
274 return (void *)&event->array[0];
275 /* Otherwise length is in array[0] and array[1] has the data */
276 return (void *)&event->array[1];
280 * ring_buffer_event_data - return the data of the event
281 * @event: the event to get the data from
283 void *ring_buffer_event_data(struct ring_buffer_event *event)
285 return rb_event_data(event);
287 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
289 #define for_each_buffer_cpu(buffer, cpu) \
290 for_each_cpu(cpu, buffer->cpumask)
292 #define for_each_online_buffer_cpu(buffer, cpu) \
293 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
296 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
297 #define TS_DELTA_TEST (~TS_MASK)
299 static u64 rb_event_time_stamp(struct ring_buffer_event *event)
303 ts = event->array[0];
305 ts += event->time_delta;
310 /* Flag when events were overwritten */
311 #define RB_MISSED_EVENTS (1 << 31)
312 /* Missed count stored at end */
313 #define RB_MISSED_STORED (1 << 30)
315 struct buffer_data_page {
316 u64 time_stamp; /* page time stamp */
317 local_t commit; /* write committed index */
318 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
321 struct buffer_data_read_page {
322 unsigned order; /* order of the page */
323 struct buffer_data_page *data; /* actual data, stored in this page */
327 * Note, the buffer_page list must be first. The buffer pages
328 * are allocated in cache lines, which means that each buffer
329 * page will be at the beginning of a cache line, and thus
330 * the least significant bits will be zero. We use this to
331 * add flags in the list struct pointers, to make the ring buffer
335 struct list_head list; /* list of buffer pages */
336 local_t write; /* index for next write */
337 unsigned read; /* index for next read */
338 local_t entries; /* entries on this page */
339 unsigned long real_end; /* real end of data */
340 unsigned order; /* order of the page */
341 struct buffer_data_page *page; /* Actual data page */
345 * The buffer page counters, write and entries, must be reset
346 * atomically when crossing page boundaries. To synchronize this
347 * update, two counters are inserted into the number. One is
348 * the actual counter for the write position or count on the page.
350 * The other is a counter of updaters. Before an update happens
351 * the update partition of the counter is incremented. This will
352 * allow the updater to update the counter atomically.
354 * The counter is 20 bits, and the state data is 12.
356 #define RB_WRITE_MASK 0xfffff
357 #define RB_WRITE_INTCNT (1 << 20)
359 static void rb_init_page(struct buffer_data_page *bpage)
361 local_set(&bpage->commit, 0);
364 static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
366 return local_read(&bpage->page->commit);
369 static void free_buffer_page(struct buffer_page *bpage)
371 free_pages((unsigned long)bpage->page, bpage->order);
376 * We need to fit the time_stamp delta into 27 bits.
378 static inline bool test_time_stamp(u64 delta)
380 return !!(delta & TS_DELTA_TEST);
384 struct irq_work work;
385 wait_queue_head_t waiters;
386 wait_queue_head_t full_waiters;
388 bool waiters_pending;
389 bool full_waiters_pending;
394 * Structure to hold event state and handle nested events.
396 struct rb_event_info {
401 unsigned long length;
402 struct buffer_page *tail_page;
407 * Used for the add_timestamp
409 * EXTEND - wants a time extend
410 * ABSOLUTE - the buffer requests all events to have absolute time stamps
411 * FORCE - force a full time stamp.
414 RB_ADD_STAMP_NONE = 0,
415 RB_ADD_STAMP_EXTEND = BIT(1),
416 RB_ADD_STAMP_ABSOLUTE = BIT(2),
417 RB_ADD_STAMP_FORCE = BIT(3)
420 * Used for which event context the event is in.
427 * See trace_recursive_lock() comment below for more details.
438 struct rb_time_struct {
441 typedef struct rb_time_struct rb_time_t;
446 * head_page == tail_page && head == tail then buffer is empty.
448 struct ring_buffer_per_cpu {
450 atomic_t record_disabled;
451 atomic_t resize_disabled;
452 struct trace_buffer *buffer;
453 raw_spinlock_t reader_lock; /* serialize readers */
454 arch_spinlock_t lock;
455 struct lock_class_key lock_key;
456 struct buffer_data_page *free_page;
457 unsigned long nr_pages;
458 unsigned int current_context;
459 struct list_head *pages;
460 struct buffer_page *head_page; /* read from head */
461 struct buffer_page *tail_page; /* write to tail */
462 struct buffer_page *commit_page; /* committed pages */
463 struct buffer_page *reader_page;
464 unsigned long lost_events;
465 unsigned long last_overrun;
467 local_t entries_bytes;
470 local_t commit_overrun;
471 local_t dropped_events;
474 local_t pages_touched;
477 long last_pages_touch;
478 size_t shortest_full;
480 unsigned long read_bytes;
481 rb_time_t write_stamp;
482 rb_time_t before_stamp;
483 u64 event_stamp[MAX_NEST];
485 /* pages removed since last reset */
486 unsigned long pages_removed;
487 /* ring buffer pages to update, > 0 to add, < 0 to remove */
488 long nr_pages_to_update;
489 struct list_head new_pages; /* new pages to add */
490 struct work_struct update_pages_work;
491 struct completion update_done;
493 struct rb_irq_work irq_work;
496 struct trace_buffer {
499 atomic_t record_disabled;
501 cpumask_var_t cpumask;
503 struct lock_class_key *reader_lock_key;
507 struct ring_buffer_per_cpu **buffers;
509 struct hlist_node node;
512 struct rb_irq_work irq_work;
515 unsigned int subbuf_size;
516 unsigned int subbuf_order;
517 unsigned int max_data_size;
520 struct ring_buffer_iter {
521 struct ring_buffer_per_cpu *cpu_buffer;
523 unsigned long next_event;
524 struct buffer_page *head_page;
525 struct buffer_page *cache_reader_page;
526 unsigned long cache_read;
527 unsigned long cache_pages_removed;
530 struct ring_buffer_event *event;
535 int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
537 struct buffer_data_page field;
539 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
540 "offset:0;\tsize:%u;\tsigned:%u;\n",
541 (unsigned int)sizeof(field.time_stamp),
542 (unsigned int)is_signed_type(u64));
544 trace_seq_printf(s, "\tfield: local_t commit;\t"
545 "offset:%u;\tsize:%u;\tsigned:%u;\n",
546 (unsigned int)offsetof(typeof(field), commit),
547 (unsigned int)sizeof(field.commit),
548 (unsigned int)is_signed_type(long));
550 trace_seq_printf(s, "\tfield: int overwrite;\t"
551 "offset:%u;\tsize:%u;\tsigned:%u;\n",
552 (unsigned int)offsetof(typeof(field), commit),
554 (unsigned int)is_signed_type(long));
556 trace_seq_printf(s, "\tfield: char data;\t"
557 "offset:%u;\tsize:%u;\tsigned:%u;\n",
558 (unsigned int)offsetof(typeof(field), data),
559 (unsigned int)buffer->subbuf_size,
560 (unsigned int)is_signed_type(char));
562 return !trace_seq_has_overflowed(s);
565 static inline void rb_time_read(rb_time_t *t, u64 *ret)
567 *ret = local64_read(&t->time);
569 static void rb_time_set(rb_time_t *t, u64 val)
571 local64_set(&t->time, val);
575 * Enable this to make sure that the event passed to
576 * ring_buffer_event_time_stamp() is not committed and also
577 * is on the buffer that it passed in.
579 //#define RB_VERIFY_EVENT
580 #ifdef RB_VERIFY_EVENT
581 static struct list_head *rb_list_head(struct list_head *list);
582 static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
585 struct buffer_page *page = cpu_buffer->commit_page;
586 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
587 struct list_head *next;
589 unsigned long addr = (unsigned long)event;
593 /* Make sure the event exists and is not committed yet */
595 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
597 commit = local_read(&page->page->commit);
598 write = local_read(&page->write);
599 if (addr >= (unsigned long)&page->page->data[commit] &&
600 addr < (unsigned long)&page->page->data[write])
603 next = rb_list_head(page->list.next);
604 page = list_entry(next, struct buffer_page, list);
609 static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
616 * The absolute time stamp drops the 5 MSBs and some clocks may
617 * require them. The rb_fix_abs_ts() will take a previous full
618 * time stamp, and add the 5 MSB of that time stamp on to the
619 * saved absolute time stamp. Then they are compared in case of
620 * the unlikely event that the latest time stamp incremented
623 static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
625 if (save_ts & TS_MSB) {
626 abs |= save_ts & TS_MSB;
627 /* Check for overflow */
628 if (unlikely(abs < save_ts))
634 static inline u64 rb_time_stamp(struct trace_buffer *buffer);
637 * ring_buffer_event_time_stamp - return the event's current time stamp
638 * @buffer: The buffer that the event is on
639 * @event: the event to get the time stamp of
641 * Note, this must be called after @event is reserved, and before it is
642 * committed to the ring buffer. And must be called from the same
643 * context where the event was reserved (normal, softirq, irq, etc).
645 * Returns the time stamp associated with the current event.
646 * If the event has an extended time stamp, then that is used as
647 * the time stamp to return.
648 * In the highly unlikely case that the event was nested more than
649 * the max nesting, then the write_stamp of the buffer is returned,
650 * otherwise current time is returned, but that really neither of
651 * the last two cases should ever happen.
653 u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
654 struct ring_buffer_event *event)
656 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
660 /* If the event includes an absolute time, then just use that */
661 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
662 ts = rb_event_time_stamp(event);
663 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
666 nest = local_read(&cpu_buffer->committing);
667 verify_event(cpu_buffer, event);
668 if (WARN_ON_ONCE(!nest))
671 /* Read the current saved nesting level time stamp */
672 if (likely(--nest < MAX_NEST))
673 return cpu_buffer->event_stamp[nest];
675 /* Shouldn't happen, warn if it does */
676 WARN_ONCE(1, "nest (%d) greater than max", nest);
679 rb_time_read(&cpu_buffer->write_stamp, &ts);
685 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
686 * @buffer: The ring_buffer to get the number of pages from
687 * @cpu: The cpu of the ring_buffer to get the number of pages from
689 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
691 size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
693 return buffer->buffers[cpu]->nr_pages;
697 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
698 * @buffer: The ring_buffer to get the number of pages from
699 * @cpu: The cpu of the ring_buffer to get the number of pages from
701 * Returns the number of pages that have content in the ring buffer.
703 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
709 read = local_read(&buffer->buffers[cpu]->pages_read);
710 lost = local_read(&buffer->buffers[cpu]->pages_lost);
711 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
713 if (WARN_ON_ONCE(cnt < lost))
718 /* The reader can read an empty page, but not more than that */
720 WARN_ON_ONCE(read > cnt + 1);
727 static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
729 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
733 nr_pages = cpu_buffer->nr_pages;
734 if (!nr_pages || !full)
738 * Add one as dirty will never equal nr_pages, as the sub-buffer
739 * that the writer is on is not counted as dirty.
740 * This is needed if "buffer_percent" is set to 100.
742 dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
744 return (dirty * 100) >= (full * nr_pages);
748 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
750 * Schedules a delayed work to wake up any task that is blocked on the
751 * ring buffer waiters queue.
753 static void rb_wake_up_waiters(struct irq_work *work)
755 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
757 /* For waiters waiting for the first wake up */
758 (void)atomic_fetch_inc_release(&rbwork->seq);
760 wake_up_all(&rbwork->waiters);
761 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
762 /* Only cpu_buffer sets the above flags */
763 struct ring_buffer_per_cpu *cpu_buffer =
764 container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
766 /* Called from interrupt context */
767 raw_spin_lock(&cpu_buffer->reader_lock);
768 rbwork->wakeup_full = false;
769 rbwork->full_waiters_pending = false;
771 /* Waking up all waiters, they will reset the shortest full */
772 cpu_buffer->shortest_full = 0;
773 raw_spin_unlock(&cpu_buffer->reader_lock);
775 wake_up_all(&rbwork->full_waiters);
780 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
781 * @buffer: The ring buffer to wake waiters on
782 * @cpu: The CPU buffer to wake waiters on
784 * In the case of a file that represents a ring buffer is closing,
785 * it is prudent to wake up any waiters that are on this.
787 void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
789 struct ring_buffer_per_cpu *cpu_buffer;
790 struct rb_irq_work *rbwork;
795 if (cpu == RING_BUFFER_ALL_CPUS) {
797 /* Wake up individual ones too. One level recursion */
798 for_each_buffer_cpu(buffer, cpu)
799 ring_buffer_wake_waiters(buffer, cpu);
801 rbwork = &buffer->irq_work;
803 if (WARN_ON_ONCE(!buffer->buffers))
805 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
808 cpu_buffer = buffer->buffers[cpu];
809 /* The CPU buffer may not have been initialized yet */
812 rbwork = &cpu_buffer->irq_work;
815 /* This can be called in any context */
816 irq_work_queue(&rbwork->work);
819 static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
821 struct ring_buffer_per_cpu *cpu_buffer;
824 /* Reads of all CPUs always waits for any data */
825 if (cpu == RING_BUFFER_ALL_CPUS)
826 return !ring_buffer_empty(buffer);
828 cpu_buffer = buffer->buffers[cpu];
830 if (!ring_buffer_empty_cpu(buffer, cpu)) {
837 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
838 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
839 ret = !pagebusy && full_hit(buffer, cpu, full);
841 if (!ret && (!cpu_buffer->shortest_full ||
842 cpu_buffer->shortest_full > full)) {
843 cpu_buffer->shortest_full = full;
845 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
851 rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
852 int cpu, int full, ring_buffer_cond_fn cond, void *data)
854 if (rb_watermark_hit(buffer, cpu, full))
861 * The events can happen in critical sections where
862 * checking a work queue can cause deadlocks.
863 * After adding a task to the queue, this flag is set
864 * only to notify events to try to wake up the queue
867 * We don't clear it even if the buffer is no longer
868 * empty. The flag only causes the next event to run
869 * irq_work to do the work queue wake up. The worse
870 * that can happen if we race with !trace_empty() is that
871 * an event will cause an irq_work to try to wake up
874 * There's no reason to protect this flag either, as
875 * the work queue and irq_work logic will do the necessary
876 * synchronization for the wake ups. The only thing
877 * that is necessary is that the wake up happens after
878 * a task has been queued. It's OK for spurious wake ups.
881 rbwork->full_waiters_pending = true;
883 rbwork->waiters_pending = true;
888 struct rb_wait_data {
889 struct rb_irq_work *irq_work;
894 * The default wait condition for ring_buffer_wait() is to just to exit the
895 * wait loop the first time it is woken up.
897 static bool rb_wait_once(void *data)
899 struct rb_wait_data *rdata = data;
900 struct rb_irq_work *rbwork = rdata->irq_work;
902 return atomic_read_acquire(&rbwork->seq) != rdata->seq;
906 * ring_buffer_wait - wait for input to the ring buffer
907 * @buffer: buffer to wait on
908 * @cpu: the cpu buffer to wait on
909 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
910 * @cond: condition function to break out of wait (NULL to run once)
911 * @data: the data to pass to @cond.
913 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
914 * as data is added to any of the @buffer's cpu buffers. Otherwise
915 * it will wait for data to be added to a specific cpu buffer.
917 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
918 ring_buffer_cond_fn cond, void *data)
920 struct ring_buffer_per_cpu *cpu_buffer;
921 struct wait_queue_head *waitq;
922 struct rb_irq_work *rbwork;
923 struct rb_wait_data rdata;
927 * Depending on what the caller is waiting for, either any
928 * data in any cpu buffer, or a specific buffer, put the
929 * caller on the appropriate wait queue.
931 if (cpu == RING_BUFFER_ALL_CPUS) {
932 rbwork = &buffer->irq_work;
933 /* Full only makes sense on per cpu reads */
936 if (!cpumask_test_cpu(cpu, buffer->cpumask))
938 cpu_buffer = buffer->buffers[cpu];
939 rbwork = &cpu_buffer->irq_work;
943 waitq = &rbwork->full_waiters;
945 waitq = &rbwork->waiters;
947 /* Set up to exit loop as soon as it is woken */
950 rdata.irq_work = rbwork;
951 rdata.seq = atomic_read_acquire(&rbwork->seq);
955 ret = wait_event_interruptible((*waitq),
956 rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
962 * ring_buffer_poll_wait - poll on buffer input
963 * @buffer: buffer to wait on
964 * @cpu: the cpu buffer to wait on
965 * @filp: the file descriptor
966 * @poll_table: The poll descriptor
967 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
969 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
970 * as data is added to any of the @buffer's cpu buffers. Otherwise
971 * it will wait for data to be added to a specific cpu buffer.
973 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
976 __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
977 struct file *filp, poll_table *poll_table, int full)
979 struct ring_buffer_per_cpu *cpu_buffer;
980 struct rb_irq_work *rbwork;
982 if (cpu == RING_BUFFER_ALL_CPUS) {
983 rbwork = &buffer->irq_work;
986 if (!cpumask_test_cpu(cpu, buffer->cpumask))
989 cpu_buffer = buffer->buffers[cpu];
990 rbwork = &cpu_buffer->irq_work;
996 poll_wait(filp, &rbwork->full_waiters, poll_table);
998 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
999 if (!cpu_buffer->shortest_full ||
1000 cpu_buffer->shortest_full > full)
1001 cpu_buffer->shortest_full = full;
1002 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1003 if (full_hit(buffer, cpu, full))
1004 return EPOLLIN | EPOLLRDNORM;
1006 * Only allow full_waiters_pending update to be seen after
1007 * the shortest_full is set. If the writer sees the
1008 * full_waiters_pending flag set, it will compare the
1009 * amount in the ring buffer to shortest_full. If the amount
1010 * in the ring buffer is greater than the shortest_full
1011 * percent, it will call the irq_work handler to wake up
1012 * this list. The irq_handler will reset shortest_full
1013 * back to zero. That's done under the reader_lock, but
1014 * the below smp_mb() makes sure that the update to
1015 * full_waiters_pending doesn't leak up into the above.
1018 rbwork->full_waiters_pending = true;
1022 poll_wait(filp, &rbwork->waiters, poll_table);
1023 rbwork->waiters_pending = true;
1026 * There's a tight race between setting the waiters_pending and
1027 * checking if the ring buffer is empty. Once the waiters_pending bit
1028 * is set, the next event will wake the task up, but we can get stuck
1029 * if there's only a single event in.
1031 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1032 * but adding a memory barrier to all events will cause too much of a
1033 * performance hit in the fast path. We only need a memory barrier when
1034 * the buffer goes from empty to having content. But as this race is
1035 * extremely small, and it's not a problem if another event comes in, we
1036 * will fix it later.
1040 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1041 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1042 return EPOLLIN | EPOLLRDNORM;
1046 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
1047 #define RB_WARN_ON(b, cond) \
1049 int _____ret = unlikely(cond); \
1051 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1052 struct ring_buffer_per_cpu *__b = \
1054 atomic_inc(&__b->buffer->record_disabled); \
1056 atomic_inc(&b->record_disabled); \
1062 /* Up this if you want to test the TIME_EXTENTS and normalization */
1063 #define DEBUG_SHIFT 0
1065 static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1069 /* Skip retpolines :-( */
1070 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1071 ts = trace_clock_local();
1073 ts = buffer->clock();
1075 /* shift to debug/test normalization and TIME_EXTENTS */
1076 return ts << DEBUG_SHIFT;
1079 u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1083 preempt_disable_notrace();
1084 time = rb_time_stamp(buffer);
1085 preempt_enable_notrace();
1089 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1091 void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1094 /* Just stupid testing the normalize function and deltas */
1095 *ts >>= DEBUG_SHIFT;
1097 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1100 * Making the ring buffer lockless makes things tricky.
1101 * Although writes only happen on the CPU that they are on,
1102 * and they only need to worry about interrupts. Reads can
1103 * happen on any CPU.
1105 * The reader page is always off the ring buffer, but when the
1106 * reader finishes with a page, it needs to swap its page with
1107 * a new one from the buffer. The reader needs to take from
1108 * the head (writes go to the tail). But if a writer is in overwrite
1109 * mode and wraps, it must push the head page forward.
1111 * Here lies the problem.
1113 * The reader must be careful to replace only the head page, and
1114 * not another one. As described at the top of the file in the
1115 * ASCII art, the reader sets its old page to point to the next
1116 * page after head. It then sets the page after head to point to
1117 * the old reader page. But if the writer moves the head page
1118 * during this operation, the reader could end up with the tail.
1120 * We use cmpxchg to help prevent this race. We also do something
1121 * special with the page before head. We set the LSB to 1.
1123 * When the writer must push the page forward, it will clear the
1124 * bit that points to the head page, move the head, and then set
1125 * the bit that points to the new head page.
1127 * We also don't want an interrupt coming in and moving the head
1128 * page on another writer. Thus we use the second LSB to catch
1131 * head->list->prev->next bit 1 bit 0
1134 * Points to head page 0 1
1137 * Note we can not trust the prev pointer of the head page, because:
1139 * +----+ +-----+ +-----+
1140 * | |------>| T |---X--->| N |
1142 * +----+ +-----+ +-----+
1145 * +----------| R |----------+ |
1149 * Key: ---X--> HEAD flag set in pointer
1154 * (see __rb_reserve_next() to see where this happens)
1156 * What the above shows is that the reader just swapped out
1157 * the reader page with a page in the buffer, but before it
1158 * could make the new header point back to the new page added
1159 * it was preempted by a writer. The writer moved forward onto
1160 * the new page added by the reader and is about to move forward
1163 * You can see, it is legitimate for the previous pointer of
1164 * the head (or any page) not to point back to itself. But only
1168 #define RB_PAGE_NORMAL 0UL
1169 #define RB_PAGE_HEAD 1UL
1170 #define RB_PAGE_UPDATE 2UL
1173 #define RB_FLAG_MASK 3UL
1175 /* PAGE_MOVED is not part of the mask */
1176 #define RB_PAGE_MOVED 4UL
1179 * rb_list_head - remove any bit
1181 static struct list_head *rb_list_head(struct list_head *list)
1183 unsigned long val = (unsigned long)list;
1185 return (struct list_head *)(val & ~RB_FLAG_MASK);
1189 * rb_is_head_page - test if the given page is the head page
1191 * Because the reader may move the head_page pointer, we can
1192 * not trust what the head page is (it may be pointing to
1193 * the reader page). But if the next page is a header page,
1194 * its flags will be non zero.
1197 rb_is_head_page(struct buffer_page *page, struct list_head *list)
1201 val = (unsigned long)list->next;
1203 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1204 return RB_PAGE_MOVED;
1206 return val & RB_FLAG_MASK;
1212 * The unique thing about the reader page, is that, if the
1213 * writer is ever on it, the previous pointer never points
1214 * back to the reader page.
1216 static bool rb_is_reader_page(struct buffer_page *page)
1218 struct list_head *list = page->list.prev;
1220 return rb_list_head(list->next) != &page->list;
1224 * rb_set_list_to_head - set a list_head to be pointing to head.
1226 static void rb_set_list_to_head(struct list_head *list)
1230 ptr = (unsigned long *)&list->next;
1231 *ptr |= RB_PAGE_HEAD;
1232 *ptr &= ~RB_PAGE_UPDATE;
1236 * rb_head_page_activate - sets up head page
1238 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1240 struct buffer_page *head;
1242 head = cpu_buffer->head_page;
1247 * Set the previous list pointer to have the HEAD flag.
1249 rb_set_list_to_head(head->list.prev);
1252 static void rb_list_head_clear(struct list_head *list)
1254 unsigned long *ptr = (unsigned long *)&list->next;
1256 *ptr &= ~RB_FLAG_MASK;
1260 * rb_head_page_deactivate - clears head page ptr (for free list)
1263 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1265 struct list_head *hd;
1267 /* Go through the whole list and clear any pointers found. */
1268 rb_list_head_clear(cpu_buffer->pages);
1270 list_for_each(hd, cpu_buffer->pages)
1271 rb_list_head_clear(hd);
1274 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1275 struct buffer_page *head,
1276 struct buffer_page *prev,
1277 int old_flag, int new_flag)
1279 struct list_head *list;
1280 unsigned long val = (unsigned long)&head->list;
1285 val &= ~RB_FLAG_MASK;
1287 ret = cmpxchg((unsigned long *)&list->next,
1288 val | old_flag, val | new_flag);
1290 /* check if the reader took the page */
1291 if ((ret & ~RB_FLAG_MASK) != val)
1292 return RB_PAGE_MOVED;
1294 return ret & RB_FLAG_MASK;
1297 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1298 struct buffer_page *head,
1299 struct buffer_page *prev,
1302 return rb_head_page_set(cpu_buffer, head, prev,
1303 old_flag, RB_PAGE_UPDATE);
1306 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1307 struct buffer_page *head,
1308 struct buffer_page *prev,
1311 return rb_head_page_set(cpu_buffer, head, prev,
1312 old_flag, RB_PAGE_HEAD);
1315 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1316 struct buffer_page *head,
1317 struct buffer_page *prev,
1320 return rb_head_page_set(cpu_buffer, head, prev,
1321 old_flag, RB_PAGE_NORMAL);
1324 static inline void rb_inc_page(struct buffer_page **bpage)
1326 struct list_head *p = rb_list_head((*bpage)->list.next);
1328 *bpage = list_entry(p, struct buffer_page, list);
1331 static struct buffer_page *
1332 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1334 struct buffer_page *head;
1335 struct buffer_page *page;
1336 struct list_head *list;
1339 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1343 list = cpu_buffer->pages;
1344 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1347 page = head = cpu_buffer->head_page;
1349 * It is possible that the writer moves the header behind
1350 * where we started, and we miss in one loop.
1351 * A second loop should grab the header, but we'll do
1352 * three loops just because I'm paranoid.
1354 for (i = 0; i < 3; i++) {
1356 if (rb_is_head_page(page, page->list.prev)) {
1357 cpu_buffer->head_page = page;
1361 } while (page != head);
1364 RB_WARN_ON(cpu_buffer, 1);
1369 static bool rb_head_page_replace(struct buffer_page *old,
1370 struct buffer_page *new)
1372 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1375 val = *ptr & ~RB_FLAG_MASK;
1376 val |= RB_PAGE_HEAD;
1378 return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1382 * rb_tail_page_update - move the tail page forward
1384 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1385 struct buffer_page *tail_page,
1386 struct buffer_page *next_page)
1388 unsigned long old_entries;
1389 unsigned long old_write;
1392 * The tail page now needs to be moved forward.
1394 * We need to reset the tail page, but without messing
1395 * with possible erasing of data brought in by interrupts
1396 * that have moved the tail page and are currently on it.
1398 * We add a counter to the write field to denote this.
1400 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1401 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1404 * Just make sure we have seen our old_write and synchronize
1405 * with any interrupts that come in.
1410 * If the tail page is still the same as what we think
1411 * it is, then it is up to us to update the tail
1414 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1415 /* Zero the write counter */
1416 unsigned long val = old_write & ~RB_WRITE_MASK;
1417 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1420 * This will only succeed if an interrupt did
1421 * not come in and change it. In which case, we
1422 * do not want to modify it.
1424 * We add (void) to let the compiler know that we do not care
1425 * about the return value of these functions. We use the
1426 * cmpxchg to only update if an interrupt did not already
1427 * do it for us. If the cmpxchg fails, we don't care.
1429 (void)local_cmpxchg(&next_page->write, old_write, val);
1430 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1433 * No need to worry about races with clearing out the commit.
1434 * it only can increment when a commit takes place. But that
1435 * only happens in the outer most nested commit.
1437 local_set(&next_page->page->commit, 0);
1439 /* Either we update tail_page or an interrupt does */
1440 if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
1441 local_inc(&cpu_buffer->pages_touched);
1445 static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1446 struct buffer_page *bpage)
1448 unsigned long val = (unsigned long)bpage;
1450 RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1454 * rb_check_pages - integrity check of buffer pages
1455 * @cpu_buffer: CPU buffer with pages to test
1457 * As a safety measure we check to make sure the data pages have not
1460 static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1462 struct list_head *head = rb_list_head(cpu_buffer->pages);
1463 struct list_head *tmp;
1465 if (RB_WARN_ON(cpu_buffer,
1466 rb_list_head(rb_list_head(head->next)->prev) != head))
1469 if (RB_WARN_ON(cpu_buffer,
1470 rb_list_head(rb_list_head(head->prev)->next) != head))
1473 for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) {
1474 if (RB_WARN_ON(cpu_buffer,
1475 rb_list_head(rb_list_head(tmp->next)->prev) != tmp))
1478 if (RB_WARN_ON(cpu_buffer,
1479 rb_list_head(rb_list_head(tmp->prev)->next) != tmp))
1484 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1485 long nr_pages, struct list_head *pages)
1487 struct buffer_page *bpage, *tmp;
1488 bool user_thread = current->mm != NULL;
1493 * Check if the available memory is there first.
1494 * Note, si_mem_available() only gives us a rough estimate of available
1495 * memory. It may not be accurate. But we don't care, we just want
1496 * to prevent doing any allocation when it is obvious that it is
1497 * not going to succeed.
1499 i = si_mem_available();
1504 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1505 * gracefully without invoking oom-killer and the system is not
1508 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1511 * If a user thread allocates too much, and si_mem_available()
1512 * reports there's enough memory, even though there is not.
1513 * Make sure the OOM killer kills this thread. This can happen
1514 * even with RETRY_MAYFAIL because another task may be doing
1515 * an allocation after this task has taken all memory.
1516 * This is the task the OOM killer needs to take out during this
1517 * loop, even if it was triggered by an allocation somewhere else.
1520 set_current_oom_origin();
1521 for (i = 0; i < nr_pages; i++) {
1524 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1525 mflags, cpu_to_node(cpu_buffer->cpu));
1529 rb_check_bpage(cpu_buffer, bpage);
1531 list_add(&bpage->list, pages);
1533 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags,
1534 cpu_buffer->buffer->subbuf_order);
1537 bpage->page = page_address(page);
1538 bpage->order = cpu_buffer->buffer->subbuf_order;
1539 rb_init_page(bpage->page);
1541 if (user_thread && fatal_signal_pending(current))
1545 clear_current_oom_origin();
1550 list_for_each_entry_safe(bpage, tmp, pages, list) {
1551 list_del_init(&bpage->list);
1552 free_buffer_page(bpage);
1555 clear_current_oom_origin();
1560 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1561 unsigned long nr_pages)
1567 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1571 * The ring buffer page list is a circular list that does not
1572 * start and end with a list head. All page list items point to
1575 cpu_buffer->pages = pages.next;
1578 cpu_buffer->nr_pages = nr_pages;
1580 rb_check_pages(cpu_buffer);
1585 static struct ring_buffer_per_cpu *
1586 rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1588 struct ring_buffer_per_cpu *cpu_buffer;
1589 struct buffer_page *bpage;
1593 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1594 GFP_KERNEL, cpu_to_node(cpu));
1598 cpu_buffer->cpu = cpu;
1599 cpu_buffer->buffer = buffer;
1600 raw_spin_lock_init(&cpu_buffer->reader_lock);
1601 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1602 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1603 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1604 init_completion(&cpu_buffer->update_done);
1605 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1606 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1607 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1609 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1610 GFP_KERNEL, cpu_to_node(cpu));
1612 goto fail_free_buffer;
1614 rb_check_bpage(cpu_buffer, bpage);
1616 cpu_buffer->reader_page = bpage;
1618 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, cpu_buffer->buffer->subbuf_order);
1620 goto fail_free_reader;
1621 bpage->page = page_address(page);
1622 rb_init_page(bpage->page);
1624 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1625 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1627 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1629 goto fail_free_reader;
1631 cpu_buffer->head_page
1632 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1633 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1635 rb_head_page_activate(cpu_buffer);
1640 free_buffer_page(cpu_buffer->reader_page);
1647 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1649 struct list_head *head = cpu_buffer->pages;
1650 struct buffer_page *bpage, *tmp;
1652 irq_work_sync(&cpu_buffer->irq_work.work);
1654 free_buffer_page(cpu_buffer->reader_page);
1657 rb_head_page_deactivate(cpu_buffer);
1659 list_for_each_entry_safe(bpage, tmp, head, list) {
1660 list_del_init(&bpage->list);
1661 free_buffer_page(bpage);
1663 bpage = list_entry(head, struct buffer_page, list);
1664 free_buffer_page(bpage);
1667 free_page((unsigned long)cpu_buffer->free_page);
1673 * __ring_buffer_alloc - allocate a new ring_buffer
1674 * @size: the size in bytes per cpu that is needed.
1675 * @flags: attributes to set for the ring buffer.
1676 * @key: ring buffer reader_lock_key.
1678 * Currently the only flag that is available is the RB_FL_OVERWRITE
1679 * flag. This flag means that the buffer will overwrite old data
1680 * when the buffer wraps. If this flag is not set, the buffer will
1681 * drop data when the tail hits the head.
1683 struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1684 struct lock_class_key *key)
1686 struct trace_buffer *buffer;
1692 /* keep it in its own cache line */
1693 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1698 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1699 goto fail_free_buffer;
1701 /* Default buffer page size - one system page */
1702 buffer->subbuf_order = 0;
1703 buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE;
1705 /* Max payload is buffer page size - header (8bytes) */
1706 buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
1708 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
1709 buffer->flags = flags;
1710 buffer->clock = trace_clock_local;
1711 buffer->reader_lock_key = key;
1713 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1714 init_waitqueue_head(&buffer->irq_work.waiters);
1716 /* need at least two pages */
1720 buffer->cpus = nr_cpu_ids;
1722 bsize = sizeof(void *) * nr_cpu_ids;
1723 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1725 if (!buffer->buffers)
1726 goto fail_free_cpumask;
1728 cpu = raw_smp_processor_id();
1729 cpumask_set_cpu(cpu, buffer->cpumask);
1730 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1731 if (!buffer->buffers[cpu])
1732 goto fail_free_buffers;
1734 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1736 goto fail_free_buffers;
1738 mutex_init(&buffer->mutex);
1743 for_each_buffer_cpu(buffer, cpu) {
1744 if (buffer->buffers[cpu])
1745 rb_free_cpu_buffer(buffer->buffers[cpu]);
1747 kfree(buffer->buffers);
1750 free_cpumask_var(buffer->cpumask);
1756 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1759 * ring_buffer_free - free a ring buffer.
1760 * @buffer: the buffer to free.
1763 ring_buffer_free(struct trace_buffer *buffer)
1767 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1769 irq_work_sync(&buffer->irq_work.work);
1771 for_each_buffer_cpu(buffer, cpu)
1772 rb_free_cpu_buffer(buffer->buffers[cpu]);
1774 kfree(buffer->buffers);
1775 free_cpumask_var(buffer->cpumask);
1779 EXPORT_SYMBOL_GPL(ring_buffer_free);
1781 void ring_buffer_set_clock(struct trace_buffer *buffer,
1784 buffer->clock = clock;
1787 void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1789 buffer->time_stamp_abs = abs;
1792 bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1794 return buffer->time_stamp_abs;
1797 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1799 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1801 return local_read(&bpage->entries) & RB_WRITE_MASK;
1804 static inline unsigned long rb_page_write(struct buffer_page *bpage)
1806 return local_read(&bpage->write) & RB_WRITE_MASK;
1810 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1812 struct list_head *tail_page, *to_remove, *next_page;
1813 struct buffer_page *to_remove_page, *tmp_iter_page;
1814 struct buffer_page *last_page, *first_page;
1815 unsigned long nr_removed;
1816 unsigned long head_bit;
1821 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1822 atomic_inc(&cpu_buffer->record_disabled);
1824 * We don't race with the readers since we have acquired the reader
1825 * lock. We also don't race with writers after disabling recording.
1826 * This makes it easy to figure out the first and the last page to be
1827 * removed from the list. We unlink all the pages in between including
1828 * the first and last pages. This is done in a busy loop so that we
1829 * lose the least number of traces.
1830 * The pages are freed after we restart recording and unlock readers.
1832 tail_page = &cpu_buffer->tail_page->list;
1835 * tail page might be on reader page, we remove the next page
1836 * from the ring buffer
1838 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1839 tail_page = rb_list_head(tail_page->next);
1840 to_remove = tail_page;
1842 /* start of pages to remove */
1843 first_page = list_entry(rb_list_head(to_remove->next),
1844 struct buffer_page, list);
1846 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1847 to_remove = rb_list_head(to_remove)->next;
1848 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1850 /* Read iterators need to reset themselves when some pages removed */
1851 cpu_buffer->pages_removed += nr_removed;
1853 next_page = rb_list_head(to_remove)->next;
1856 * Now we remove all pages between tail_page and next_page.
1857 * Make sure that we have head_bit value preserved for the
1860 tail_page->next = (struct list_head *)((unsigned long)next_page |
1862 next_page = rb_list_head(next_page);
1863 next_page->prev = tail_page;
1865 /* make sure pages points to a valid page in the ring buffer */
1866 cpu_buffer->pages = next_page;
1868 /* update head page */
1870 cpu_buffer->head_page = list_entry(next_page,
1871 struct buffer_page, list);
1873 /* pages are removed, resume tracing and then free the pages */
1874 atomic_dec(&cpu_buffer->record_disabled);
1875 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1877 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1879 /* last buffer page to remove */
1880 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1882 tmp_iter_page = first_page;
1887 to_remove_page = tmp_iter_page;
1888 rb_inc_page(&tmp_iter_page);
1890 /* update the counters */
1891 page_entries = rb_page_entries(to_remove_page);
1894 * If something was added to this page, it was full
1895 * since it is not the tail page. So we deduct the
1896 * bytes consumed in ring buffer from here.
1897 * Increment overrun to account for the lost events.
1899 local_add(page_entries, &cpu_buffer->overrun);
1900 local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
1901 local_inc(&cpu_buffer->pages_lost);
1905 * We have already removed references to this list item, just
1906 * free up the buffer_page and its page
1908 free_buffer_page(to_remove_page);
1911 } while (to_remove_page != last_page);
1913 RB_WARN_ON(cpu_buffer, nr_removed);
1915 return nr_removed == 0;
1919 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1921 struct list_head *pages = &cpu_buffer->new_pages;
1922 unsigned long flags;
1926 /* Can be called at early boot up, where interrupts must not been enabled */
1927 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1929 * We are holding the reader lock, so the reader page won't be swapped
1930 * in the ring buffer. Now we are racing with the writer trying to
1931 * move head page and the tail page.
1932 * We are going to adapt the reader page update process where:
1933 * 1. We first splice the start and end of list of new pages between
1934 * the head page and its previous page.
1935 * 2. We cmpxchg the prev_page->next to point from head page to the
1936 * start of new pages list.
1937 * 3. Finally, we update the head->prev to the end of new list.
1939 * We will try this process 10 times, to make sure that we don't keep
1945 struct list_head *head_page, *prev_page;
1946 struct list_head *last_page, *first_page;
1947 struct list_head *head_page_with_bit;
1948 struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
1952 head_page = &hpage->list;
1953 prev_page = head_page->prev;
1955 first_page = pages->next;
1956 last_page = pages->prev;
1958 head_page_with_bit = (struct list_head *)
1959 ((unsigned long)head_page | RB_PAGE_HEAD);
1961 last_page->next = head_page_with_bit;
1962 first_page->prev = prev_page;
1964 /* caution: head_page_with_bit gets updated on cmpxchg failure */
1965 if (try_cmpxchg(&prev_page->next,
1966 &head_page_with_bit, first_page)) {
1968 * yay, we replaced the page pointer to our new list,
1969 * now, we just have to update to head page's prev
1970 * pointer to point to end of list
1972 head_page->prev = last_page;
1979 INIT_LIST_HEAD(pages);
1981 * If we weren't successful in adding in new pages, warn and stop
1984 RB_WARN_ON(cpu_buffer, !success);
1985 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1987 /* free pages if they weren't inserted */
1989 struct buffer_page *bpage, *tmp;
1990 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1992 list_del_init(&bpage->list);
1993 free_buffer_page(bpage);
1999 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2003 if (cpu_buffer->nr_pages_to_update > 0)
2004 success = rb_insert_pages(cpu_buffer);
2006 success = rb_remove_pages(cpu_buffer,
2007 -cpu_buffer->nr_pages_to_update);
2010 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2013 static void update_pages_handler(struct work_struct *work)
2015 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2016 struct ring_buffer_per_cpu, update_pages_work);
2017 rb_update_pages(cpu_buffer);
2018 complete(&cpu_buffer->update_done);
2022 * ring_buffer_resize - resize the ring buffer
2023 * @buffer: the buffer to resize.
2024 * @size: the new size.
2025 * @cpu_id: the cpu buffer to resize
2027 * Minimum size is 2 * buffer->subbuf_size.
2029 * Returns 0 on success and < 0 on failure.
2031 int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2034 struct ring_buffer_per_cpu *cpu_buffer;
2035 unsigned long nr_pages;
2039 * Always succeed at resizing a non-existent buffer:
2044 /* Make sure the requested buffer exists */
2045 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2046 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2049 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2051 /* we need a minimum of two pages */
2055 /* prevent another thread from changing buffer sizes */
2056 mutex_lock(&buffer->mutex);
2057 atomic_inc(&buffer->resizing);
2059 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2061 * Don't succeed if resizing is disabled, as a reader might be
2062 * manipulating the ring buffer and is expecting a sane state while
2065 for_each_buffer_cpu(buffer, cpu) {
2066 cpu_buffer = buffer->buffers[cpu];
2067 if (atomic_read(&cpu_buffer->resize_disabled)) {
2069 goto out_err_unlock;
2073 /* calculate the pages to update */
2074 for_each_buffer_cpu(buffer, cpu) {
2075 cpu_buffer = buffer->buffers[cpu];
2077 cpu_buffer->nr_pages_to_update = nr_pages -
2078 cpu_buffer->nr_pages;
2080 * nothing more to do for removing pages or no update
2082 if (cpu_buffer->nr_pages_to_update <= 0)
2085 * to add pages, make sure all new pages can be
2086 * allocated without receiving ENOMEM
2088 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2089 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2090 &cpu_buffer->new_pages)) {
2091 /* not enough memory for new pages */
2101 * Fire off all the required work handlers
2102 * We can't schedule on offline CPUs, but it's not necessary
2103 * since we can change their buffer sizes without any race.
2105 for_each_buffer_cpu(buffer, cpu) {
2106 cpu_buffer = buffer->buffers[cpu];
2107 if (!cpu_buffer->nr_pages_to_update)
2110 /* Can't run something on an offline CPU. */
2111 if (!cpu_online(cpu)) {
2112 rb_update_pages(cpu_buffer);
2113 cpu_buffer->nr_pages_to_update = 0;
2115 /* Run directly if possible. */
2117 if (cpu != smp_processor_id()) {
2119 schedule_work_on(cpu,
2120 &cpu_buffer->update_pages_work);
2122 update_pages_handler(&cpu_buffer->update_pages_work);
2128 /* wait for all the updates to complete */
2129 for_each_buffer_cpu(buffer, cpu) {
2130 cpu_buffer = buffer->buffers[cpu];
2131 if (!cpu_buffer->nr_pages_to_update)
2134 if (cpu_online(cpu))
2135 wait_for_completion(&cpu_buffer->update_done);
2136 cpu_buffer->nr_pages_to_update = 0;
2141 cpu_buffer = buffer->buffers[cpu_id];
2143 if (nr_pages == cpu_buffer->nr_pages)
2147 * Don't succeed if resizing is disabled, as a reader might be
2148 * manipulating the ring buffer and is expecting a sane state while
2151 if (atomic_read(&cpu_buffer->resize_disabled)) {
2153 goto out_err_unlock;
2156 cpu_buffer->nr_pages_to_update = nr_pages -
2157 cpu_buffer->nr_pages;
2159 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2160 if (cpu_buffer->nr_pages_to_update > 0 &&
2161 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2162 &cpu_buffer->new_pages)) {
2169 /* Can't run something on an offline CPU. */
2170 if (!cpu_online(cpu_id))
2171 rb_update_pages(cpu_buffer);
2173 /* Run directly if possible. */
2175 if (cpu_id == smp_processor_id()) {
2176 rb_update_pages(cpu_buffer);
2180 schedule_work_on(cpu_id,
2181 &cpu_buffer->update_pages_work);
2182 wait_for_completion(&cpu_buffer->update_done);
2186 cpu_buffer->nr_pages_to_update = 0;
2192 * The ring buffer resize can happen with the ring buffer
2193 * enabled, so that the update disturbs the tracing as little
2194 * as possible. But if the buffer is disabled, we do not need
2195 * to worry about that, and we can take the time to verify
2196 * that the buffer is not corrupt.
2198 if (atomic_read(&buffer->record_disabled)) {
2199 atomic_inc(&buffer->record_disabled);
2201 * Even though the buffer was disabled, we must make sure
2202 * that it is truly disabled before calling rb_check_pages.
2203 * There could have been a race between checking
2204 * record_disable and incrementing it.
2207 for_each_buffer_cpu(buffer, cpu) {
2208 cpu_buffer = buffer->buffers[cpu];
2209 rb_check_pages(cpu_buffer);
2211 atomic_dec(&buffer->record_disabled);
2214 atomic_dec(&buffer->resizing);
2215 mutex_unlock(&buffer->mutex);
2219 for_each_buffer_cpu(buffer, cpu) {
2220 struct buffer_page *bpage, *tmp;
2222 cpu_buffer = buffer->buffers[cpu];
2223 cpu_buffer->nr_pages_to_update = 0;
2225 if (list_empty(&cpu_buffer->new_pages))
2228 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2230 list_del_init(&bpage->list);
2231 free_buffer_page(bpage);
2235 atomic_dec(&buffer->resizing);
2236 mutex_unlock(&buffer->mutex);
2239 EXPORT_SYMBOL_GPL(ring_buffer_resize);
2241 void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2243 mutex_lock(&buffer->mutex);
2245 buffer->flags |= RB_FL_OVERWRITE;
2247 buffer->flags &= ~RB_FL_OVERWRITE;
2248 mutex_unlock(&buffer->mutex);
2250 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2252 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2254 return bpage->page->data + index;
2257 static __always_inline struct ring_buffer_event *
2258 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2260 return __rb_page_index(cpu_buffer->reader_page,
2261 cpu_buffer->reader_page->read);
2264 static struct ring_buffer_event *
2265 rb_iter_head_event(struct ring_buffer_iter *iter)
2267 struct ring_buffer_event *event;
2268 struct buffer_page *iter_head_page = iter->head_page;
2269 unsigned long commit;
2272 if (iter->head != iter->next_event)
2276 * When the writer goes across pages, it issues a cmpxchg which
2277 * is a mb(), which will synchronize with the rmb here.
2278 * (see rb_tail_page_update() and __rb_reserve_next())
2280 commit = rb_page_commit(iter_head_page);
2283 /* An event needs to be at least 8 bytes in size */
2284 if (iter->head > commit - 8)
2287 event = __rb_page_index(iter_head_page, iter->head);
2288 length = rb_event_length(event);
2291 * READ_ONCE() doesn't work on functions and we don't want the
2292 * compiler doing any crazy optimizations with length.
2296 if ((iter->head + length) > commit || length > iter->event_size)
2297 /* Writer corrupted the read? */
2300 memcpy(iter->event, event, length);
2302 * If the page stamp is still the same after this rmb() then the
2303 * event was safely copied without the writer entering the page.
2307 /* Make sure the page didn't change since we read this */
2308 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2309 commit > rb_page_commit(iter_head_page))
2312 iter->next_event = iter->head + length;
2315 /* Reset to the beginning */
2316 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2318 iter->next_event = 0;
2319 iter->missed_events = 1;
2323 /* Size is determined by what has been committed */
2324 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2326 return rb_page_commit(bpage);
2329 static __always_inline unsigned
2330 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2332 return rb_page_commit(cpu_buffer->commit_page);
2335 static __always_inline unsigned
2336 rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
2338 unsigned long addr = (unsigned long)event;
2340 addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
2342 return addr - BUF_PAGE_HDR_SIZE;
2345 static void rb_inc_iter(struct ring_buffer_iter *iter)
2347 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2350 * The iterator could be on the reader page (it starts there).
2351 * But the head could have moved, since the reader was
2352 * found. Check for this case and assign the iterator
2353 * to the head page instead of next.
2355 if (iter->head_page == cpu_buffer->reader_page)
2356 iter->head_page = rb_set_head_page(cpu_buffer);
2358 rb_inc_page(&iter->head_page);
2360 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2362 iter->next_event = 0;
2366 * rb_handle_head_page - writer hit the head page
2368 * Returns: +1 to retry page
2373 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2374 struct buffer_page *tail_page,
2375 struct buffer_page *next_page)
2377 struct buffer_page *new_head;
2382 entries = rb_page_entries(next_page);
2385 * The hard part is here. We need to move the head
2386 * forward, and protect against both readers on
2387 * other CPUs and writers coming in via interrupts.
2389 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2393 * type can be one of four:
2394 * NORMAL - an interrupt already moved it for us
2395 * HEAD - we are the first to get here.
2396 * UPDATE - we are the interrupt interrupting
2398 * MOVED - a reader on another CPU moved the next
2399 * pointer to its reader page. Give up
2406 * We changed the head to UPDATE, thus
2407 * it is our responsibility to update
2410 local_add(entries, &cpu_buffer->overrun);
2411 local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
2412 local_inc(&cpu_buffer->pages_lost);
2415 * The entries will be zeroed out when we move the
2419 /* still more to do */
2422 case RB_PAGE_UPDATE:
2424 * This is an interrupt that interrupt the
2425 * previous update. Still more to do.
2428 case RB_PAGE_NORMAL:
2430 * An interrupt came in before the update
2431 * and processed this for us.
2432 * Nothing left to do.
2437 * The reader is on another CPU and just did
2438 * a swap with our next_page.
2443 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2448 * Now that we are here, the old head pointer is
2449 * set to UPDATE. This will keep the reader from
2450 * swapping the head page with the reader page.
2451 * The reader (on another CPU) will spin till
2454 * We just need to protect against interrupts
2455 * doing the job. We will set the next pointer
2456 * to HEAD. After that, we set the old pointer
2457 * to NORMAL, but only if it was HEAD before.
2458 * otherwise we are an interrupt, and only
2459 * want the outer most commit to reset it.
2461 new_head = next_page;
2462 rb_inc_page(&new_head);
2464 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2468 * Valid returns are:
2469 * HEAD - an interrupt came in and already set it.
2470 * NORMAL - One of two things:
2471 * 1) We really set it.
2472 * 2) A bunch of interrupts came in and moved
2473 * the page forward again.
2477 case RB_PAGE_NORMAL:
2481 RB_WARN_ON(cpu_buffer, 1);
2486 * It is possible that an interrupt came in,
2487 * set the head up, then more interrupts came in
2488 * and moved it again. When we get back here,
2489 * the page would have been set to NORMAL but we
2490 * just set it back to HEAD.
2492 * How do you detect this? Well, if that happened
2493 * the tail page would have moved.
2495 if (ret == RB_PAGE_NORMAL) {
2496 struct buffer_page *buffer_tail_page;
2498 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2500 * If the tail had moved passed next, then we need
2501 * to reset the pointer.
2503 if (buffer_tail_page != tail_page &&
2504 buffer_tail_page != next_page)
2505 rb_head_page_set_normal(cpu_buffer, new_head,
2511 * If this was the outer most commit (the one that
2512 * changed the original pointer from HEAD to UPDATE),
2513 * then it is up to us to reset it to NORMAL.
2515 if (type == RB_PAGE_HEAD) {
2516 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2519 if (RB_WARN_ON(cpu_buffer,
2520 ret != RB_PAGE_UPDATE))
2528 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2529 unsigned long tail, struct rb_event_info *info)
2531 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
2532 struct buffer_page *tail_page = info->tail_page;
2533 struct ring_buffer_event *event;
2534 unsigned long length = info->length;
2537 * Only the event that crossed the page boundary
2538 * must fill the old tail_page with padding.
2540 if (tail >= bsize) {
2542 * If the page was filled, then we still need
2543 * to update the real_end. Reset it to zero
2544 * and the reader will ignore it.
2547 tail_page->real_end = 0;
2549 local_sub(length, &tail_page->write);
2553 event = __rb_page_index(tail_page, tail);
2556 * Save the original length to the meta data.
2557 * This will be used by the reader to add lost event
2560 tail_page->real_end = tail;
2563 * If this event is bigger than the minimum size, then
2564 * we need to be careful that we don't subtract the
2565 * write counter enough to allow another writer to slip
2567 * We put in a discarded commit instead, to make sure
2568 * that this space is not used again, and this space will
2569 * not be accounted into 'entries_bytes'.
2571 * If we are less than the minimum size, we don't need to
2574 if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
2575 /* No room for any events */
2577 /* Mark the rest of the page with padding */
2578 rb_event_set_padding(event);
2580 /* Make sure the padding is visible before the write update */
2583 /* Set the write back to the previous setting */
2584 local_sub(length, &tail_page->write);
2588 /* Put in a discarded event */
2589 event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
2590 event->type_len = RINGBUF_TYPE_PADDING;
2591 /* time delta must be non zero */
2592 event->time_delta = 1;
2594 /* account for padding bytes */
2595 local_add(bsize - tail, &cpu_buffer->entries_bytes);
2597 /* Make sure the padding is visible before the tail_page->write update */
2600 /* Set write to end of buffer */
2601 length = (tail + length) - bsize;
2602 local_sub(length, &tail_page->write);
2605 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2608 * This is the slow path, force gcc not to inline it.
2610 static noinline struct ring_buffer_event *
2611 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2612 unsigned long tail, struct rb_event_info *info)
2614 struct buffer_page *tail_page = info->tail_page;
2615 struct buffer_page *commit_page = cpu_buffer->commit_page;
2616 struct trace_buffer *buffer = cpu_buffer->buffer;
2617 struct buffer_page *next_page;
2620 next_page = tail_page;
2622 rb_inc_page(&next_page);
2625 * If for some reason, we had an interrupt storm that made
2626 * it all the way around the buffer, bail, and warn
2629 if (unlikely(next_page == commit_page)) {
2630 local_inc(&cpu_buffer->commit_overrun);
2635 * This is where the fun begins!
2637 * We are fighting against races between a reader that
2638 * could be on another CPU trying to swap its reader
2639 * page with the buffer head.
2641 * We are also fighting against interrupts coming in and
2642 * moving the head or tail on us as well.
2644 * If the next page is the head page then we have filled
2645 * the buffer, unless the commit page is still on the
2648 if (rb_is_head_page(next_page, &tail_page->list)) {
2651 * If the commit is not on the reader page, then
2652 * move the header page.
2654 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2656 * If we are not in overwrite mode,
2657 * this is easy, just stop here.
2659 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2660 local_inc(&cpu_buffer->dropped_events);
2664 ret = rb_handle_head_page(cpu_buffer,
2673 * We need to be careful here too. The
2674 * commit page could still be on the reader
2675 * page. We could have a small buffer, and
2676 * have filled up the buffer with events
2677 * from interrupts and such, and wrapped.
2679 * Note, if the tail page is also on the
2680 * reader_page, we let it move out.
2682 if (unlikely((cpu_buffer->commit_page !=
2683 cpu_buffer->tail_page) &&
2684 (cpu_buffer->commit_page ==
2685 cpu_buffer->reader_page))) {
2686 local_inc(&cpu_buffer->commit_overrun);
2692 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2696 rb_reset_tail(cpu_buffer, tail, info);
2698 /* Commit what we have for now. */
2699 rb_end_commit(cpu_buffer);
2700 /* rb_end_commit() decs committing */
2701 local_inc(&cpu_buffer->committing);
2703 /* fail and let the caller try again */
2704 return ERR_PTR(-EAGAIN);
2708 rb_reset_tail(cpu_buffer, tail, info);
2714 static struct ring_buffer_event *
2715 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2716 struct ring_buffer_event *event, u64 delta, bool abs)
2719 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2721 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2723 /* Not the first event on the page, or not delta? */
2724 if (abs || rb_event_index(cpu_buffer, event)) {
2725 event->time_delta = delta & TS_MASK;
2726 event->array[0] = delta >> TS_SHIFT;
2728 /* nope, just zero it */
2729 event->time_delta = 0;
2730 event->array[0] = 0;
2733 return skip_time_extend(event);
2736 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2737 static inline bool sched_clock_stable(void)
2744 rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2745 struct rb_event_info *info)
2749 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2750 (unsigned long long)info->delta,
2751 (unsigned long long)info->ts,
2752 (unsigned long long)info->before,
2753 (unsigned long long)info->after,
2754 (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
2755 sched_clock_stable() ? "" :
2756 "If you just came from a suspend/resume,\n"
2757 "please switch to the trace global clock:\n"
2758 " echo global > /sys/kernel/tracing/trace_clock\n"
2759 "or add trace_clock=global to the kernel command line\n");
2762 static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2763 struct ring_buffer_event **event,
2764 struct rb_event_info *info,
2766 unsigned int *length)
2768 bool abs = info->add_timestamp &
2769 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2771 if (unlikely(info->delta > (1ULL << 59))) {
2773 * Some timers can use more than 59 bits, and when a timestamp
2774 * is added to the buffer, it will lose those bits.
2776 if (abs && (info->ts & TS_MSB)) {
2777 info->delta &= ABS_TS_MASK;
2779 /* did the clock go backwards */
2780 } else if (info->before == info->after && info->before > info->ts) {
2781 /* not interrupted */
2785 * This is possible with a recalibrating of the TSC.
2786 * Do not produce a call stack, but just report it.
2790 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2791 info->before, info->ts);
2794 rb_check_timestamp(cpu_buffer, info);
2798 *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
2799 *length -= RB_LEN_TIME_EXTEND;
2804 * rb_update_event - update event type and data
2805 * @cpu_buffer: The per cpu buffer of the @event
2806 * @event: the event to update
2807 * @info: The info to update the @event with (contains length and delta)
2809 * Update the type and data fields of the @event. The length
2810 * is the actual size that is written to the ring buffer,
2811 * and with this, we can determine what to place into the
2815 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2816 struct ring_buffer_event *event,
2817 struct rb_event_info *info)
2819 unsigned length = info->length;
2820 u64 delta = info->delta;
2821 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2823 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2824 cpu_buffer->event_stamp[nest] = info->ts;
2827 * If we need to add a timestamp, then we
2828 * add it to the start of the reserved space.
2830 if (unlikely(info->add_timestamp))
2831 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2833 event->time_delta = delta;
2834 length -= RB_EVNT_HDR_SIZE;
2835 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2836 event->type_len = 0;
2837 event->array[0] = length;
2839 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2842 static unsigned rb_calculate_event_length(unsigned length)
2844 struct ring_buffer_event event; /* Used only for sizeof array */
2846 /* zero length can cause confusions */
2850 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2851 length += sizeof(event.array[0]);
2853 length += RB_EVNT_HDR_SIZE;
2854 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2857 * In case the time delta is larger than the 27 bits for it
2858 * in the header, we need to add a timestamp. If another
2859 * event comes in when trying to discard this one to increase
2860 * the length, then the timestamp will be added in the allocated
2861 * space of this event. If length is bigger than the size needed
2862 * for the TIME_EXTEND, then padding has to be used. The events
2863 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2864 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2865 * As length is a multiple of 4, we only need to worry if it
2866 * is 12 (RB_LEN_TIME_EXTEND + 4).
2868 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2869 length += RB_ALIGNMENT;
2875 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2876 struct ring_buffer_event *event)
2878 unsigned long new_index, old_index;
2879 struct buffer_page *bpage;
2882 new_index = rb_event_index(cpu_buffer, event);
2883 old_index = new_index + rb_event_ts_length(event);
2884 addr = (unsigned long)event;
2885 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
2887 bpage = READ_ONCE(cpu_buffer->tail_page);
2890 * Make sure the tail_page is still the same and
2891 * the next write location is the end of this event
2893 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2894 unsigned long write_mask =
2895 local_read(&bpage->write) & ~RB_WRITE_MASK;
2896 unsigned long event_length = rb_event_length(event);
2899 * For the before_stamp to be different than the write_stamp
2900 * to make sure that the next event adds an absolute
2901 * value and does not rely on the saved write stamp, which
2902 * is now going to be bogus.
2904 * By setting the before_stamp to zero, the next event
2905 * is not going to use the write_stamp and will instead
2906 * create an absolute timestamp. This means there's no
2907 * reason to update the wirte_stamp!
2909 rb_time_set(&cpu_buffer->before_stamp, 0);
2912 * If an event were to come in now, it would see that the
2913 * write_stamp and the before_stamp are different, and assume
2914 * that this event just added itself before updating
2915 * the write stamp. The interrupting event will fix the
2916 * write stamp for us, and use an absolute timestamp.
2920 * This is on the tail page. It is possible that
2921 * a write could come in and move the tail page
2922 * and write to the next page. That is fine
2923 * because we just shorten what is on this page.
2925 old_index += write_mask;
2926 new_index += write_mask;
2928 /* caution: old_index gets updated on cmpxchg failure */
2929 if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
2930 /* update counters */
2931 local_sub(event_length, &cpu_buffer->entries_bytes);
2936 /* could not discard */
2940 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2942 local_inc(&cpu_buffer->committing);
2943 local_inc(&cpu_buffer->commits);
2946 static __always_inline void
2947 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2949 unsigned long max_count;
2952 * We only race with interrupts and NMIs on this CPU.
2953 * If we own the commit event, then we can commit
2954 * all others that interrupted us, since the interruptions
2955 * are in stack format (they finish before they come
2956 * back to us). This allows us to do a simple loop to
2957 * assign the commit to the tail.
2960 max_count = cpu_buffer->nr_pages * 100;
2962 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2963 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2965 if (RB_WARN_ON(cpu_buffer,
2966 rb_is_reader_page(cpu_buffer->tail_page)))
2969 * No need for a memory barrier here, as the update
2970 * of the tail_page did it for this page.
2972 local_set(&cpu_buffer->commit_page->page->commit,
2973 rb_page_write(cpu_buffer->commit_page));
2974 rb_inc_page(&cpu_buffer->commit_page);
2975 /* add barrier to keep gcc from optimizing too much */
2978 while (rb_commit_index(cpu_buffer) !=
2979 rb_page_write(cpu_buffer->commit_page)) {
2981 /* Make sure the readers see the content of what is committed. */
2983 local_set(&cpu_buffer->commit_page->page->commit,
2984 rb_page_write(cpu_buffer->commit_page));
2985 RB_WARN_ON(cpu_buffer,
2986 local_read(&cpu_buffer->commit_page->page->commit) &
2991 /* again, keep gcc from optimizing */
2995 * If an interrupt came in just after the first while loop
2996 * and pushed the tail page forward, we will be left with
2997 * a dangling commit that will never go forward.
2999 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3003 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3005 unsigned long commits;
3007 if (RB_WARN_ON(cpu_buffer,
3008 !local_read(&cpu_buffer->committing)))
3012 commits = local_read(&cpu_buffer->commits);
3013 /* synchronize with interrupts */
3015 if (local_read(&cpu_buffer->committing) == 1)
3016 rb_set_commit_to_write(cpu_buffer);
3018 local_dec(&cpu_buffer->committing);
3020 /* synchronize with interrupts */
3024 * Need to account for interrupts coming in between the
3025 * updating of the commit page and the clearing of the
3026 * committing counter.
3028 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3029 !local_read(&cpu_buffer->committing)) {
3030 local_inc(&cpu_buffer->committing);
3035 static inline void rb_event_discard(struct ring_buffer_event *event)
3037 if (extended_time(event))
3038 event = skip_time_extend(event);
3040 /* array[0] holds the actual length for the discarded event */
3041 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3042 event->type_len = RINGBUF_TYPE_PADDING;
3043 /* time delta must be non zero */
3044 if (!event->time_delta)
3045 event->time_delta = 1;
3048 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3050 local_inc(&cpu_buffer->entries);
3051 rb_end_commit(cpu_buffer);
3054 static __always_inline void
3055 rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3057 if (buffer->irq_work.waiters_pending) {
3058 buffer->irq_work.waiters_pending = false;
3059 /* irq_work_queue() supplies it's own memory barriers */
3060 irq_work_queue(&buffer->irq_work.work);
3063 if (cpu_buffer->irq_work.waiters_pending) {
3064 cpu_buffer->irq_work.waiters_pending = false;
3065 /* irq_work_queue() supplies it's own memory barriers */
3066 irq_work_queue(&cpu_buffer->irq_work.work);
3069 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3072 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3075 if (!cpu_buffer->irq_work.full_waiters_pending)
3078 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3080 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3083 cpu_buffer->irq_work.wakeup_full = true;
3084 cpu_buffer->irq_work.full_waiters_pending = false;
3085 /* irq_work_queue() supplies it's own memory barriers */
3086 irq_work_queue(&cpu_buffer->irq_work.work);
3089 #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3090 # define do_ring_buffer_record_recursion() \
3091 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3093 # define do_ring_buffer_record_recursion() do { } while (0)
3097 * The lock and unlock are done within a preempt disable section.
3098 * The current_context per_cpu variable can only be modified
3099 * by the current task between lock and unlock. But it can
3100 * be modified more than once via an interrupt. To pass this
3101 * information from the lock to the unlock without having to
3102 * access the 'in_interrupt()' functions again (which do show
3103 * a bit of overhead in something as critical as function tracing,
3104 * we use a bitmask trick.
3106 * bit 1 = NMI context
3107 * bit 2 = IRQ context
3108 * bit 3 = SoftIRQ context
3109 * bit 4 = normal context.
3111 * This works because this is the order of contexts that can
3112 * preempt other contexts. A SoftIRQ never preempts an IRQ
3115 * When the context is determined, the corresponding bit is
3116 * checked and set (if it was set, then a recursion of that context
3119 * On unlock, we need to clear this bit. To do so, just subtract
3120 * 1 from the current_context and AND it to itself.
3124 * 101 & 100 = 100 (clearing bit zero)
3127 * 1010 & 1001 = 1000 (clearing bit 1)
3129 * The least significant bit can be cleared this way, and it
3130 * just so happens that it is the same bit corresponding to
3131 * the current context.
3133 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3134 * is set when a recursion is detected at the current context, and if
3135 * the TRANSITION bit is already set, it will fail the recursion.
3136 * This is needed because there's a lag between the changing of
3137 * interrupt context and updating the preempt count. In this case,
3138 * a false positive will be found. To handle this, one extra recursion
3139 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3140 * bit is already set, then it is considered a recursion and the function
3141 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3143 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3144 * to be cleared. Even if it wasn't the context that set it. That is,
3145 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3146 * is called before preempt_count() is updated, since the check will
3147 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3148 * NMI then comes in, it will set the NMI bit, but when the NMI code
3149 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3150 * and leave the NMI bit set. But this is fine, because the interrupt
3151 * code that set the TRANSITION bit will then clear the NMI bit when it
3152 * calls trace_recursive_unlock(). If another NMI comes in, it will
3153 * set the TRANSITION bit and continue.
3155 * Note: The TRANSITION bit only handles a single transition between context.
3158 static __always_inline bool
3159 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3161 unsigned int val = cpu_buffer->current_context;
3162 int bit = interrupt_context_level();
3164 bit = RB_CTX_NORMAL - bit;
3166 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3168 * It is possible that this was called by transitioning
3169 * between interrupt context, and preempt_count() has not
3170 * been updated yet. In this case, use the TRANSITION bit.
3172 bit = RB_CTX_TRANSITION;
3173 if (val & (1 << (bit + cpu_buffer->nest))) {
3174 do_ring_buffer_record_recursion();
3179 val |= (1 << (bit + cpu_buffer->nest));
3180 cpu_buffer->current_context = val;
3185 static __always_inline void
3186 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3188 cpu_buffer->current_context &=
3189 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3192 /* The recursive locking above uses 5 bits */
3193 #define NESTED_BITS 5
3196 * ring_buffer_nest_start - Allow to trace while nested
3197 * @buffer: The ring buffer to modify
3199 * The ring buffer has a safety mechanism to prevent recursion.
3200 * But there may be a case where a trace needs to be done while
3201 * tracing something else. In this case, calling this function
3202 * will allow this function to nest within a currently active
3203 * ring_buffer_lock_reserve().
3205 * Call this function before calling another ring_buffer_lock_reserve() and
3206 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3208 void ring_buffer_nest_start(struct trace_buffer *buffer)
3210 struct ring_buffer_per_cpu *cpu_buffer;
3213 /* Enabled by ring_buffer_nest_end() */
3214 preempt_disable_notrace();
3215 cpu = raw_smp_processor_id();
3216 cpu_buffer = buffer->buffers[cpu];
3217 /* This is the shift value for the above recursive locking */
3218 cpu_buffer->nest += NESTED_BITS;
3222 * ring_buffer_nest_end - Allow to trace while nested
3223 * @buffer: The ring buffer to modify
3225 * Must be called after ring_buffer_nest_start() and after the
3226 * ring_buffer_unlock_commit().
3228 void ring_buffer_nest_end(struct trace_buffer *buffer)
3230 struct ring_buffer_per_cpu *cpu_buffer;
3233 /* disabled by ring_buffer_nest_start() */
3234 cpu = raw_smp_processor_id();
3235 cpu_buffer = buffer->buffers[cpu];
3236 /* This is the shift value for the above recursive locking */
3237 cpu_buffer->nest -= NESTED_BITS;
3238 preempt_enable_notrace();
3242 * ring_buffer_unlock_commit - commit a reserved
3243 * @buffer: The buffer to commit to
3245 * This commits the data to the ring buffer, and releases any locks held.
3247 * Must be paired with ring_buffer_lock_reserve.
3249 int ring_buffer_unlock_commit(struct trace_buffer *buffer)
3251 struct ring_buffer_per_cpu *cpu_buffer;
3252 int cpu = raw_smp_processor_id();
3254 cpu_buffer = buffer->buffers[cpu];
3256 rb_commit(cpu_buffer);
3258 rb_wakeups(buffer, cpu_buffer);
3260 trace_recursive_unlock(cpu_buffer);
3262 preempt_enable_notrace();
3266 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3268 /* Special value to validate all deltas on a page. */
3269 #define CHECK_FULL_PAGE 1L
3271 #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3273 static const char *show_irq_str(int bits)
3275 const char *type[] = {
3289 /* Assume this is an trace event */
3290 static const char *show_flags(struct ring_buffer_event *event)
3292 struct trace_entry *entry;
3295 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3298 entry = ring_buffer_event_data(event);
3300 if (entry->flags & TRACE_FLAG_SOFTIRQ)
3303 if (entry->flags & TRACE_FLAG_HARDIRQ)
3306 if (entry->flags & TRACE_FLAG_NMI)
3309 return show_irq_str(bits);
3312 static const char *show_irq(struct ring_buffer_event *event)
3314 struct trace_entry *entry;
3316 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
3319 entry = ring_buffer_event_data(event);
3320 if (entry->flags & TRACE_FLAG_IRQS_OFF)
3325 static const char *show_interrupt_level(void)
3327 unsigned long pc = preempt_count();
3328 unsigned char level = 0;
3330 if (pc & SOFTIRQ_OFFSET)
3333 if (pc & HARDIRQ_MASK)
3339 return show_irq_str(level);
3342 static void dump_buffer_page(struct buffer_data_page *bpage,
3343 struct rb_event_info *info,
3346 struct ring_buffer_event *event;
3350 ts = bpage->time_stamp;
3351 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3353 for (e = 0; e < tail; e += rb_event_length(event)) {
3355 event = (struct ring_buffer_event *)(bpage->data + e);
3357 switch (event->type_len) {
3359 case RINGBUF_TYPE_TIME_EXTEND:
3360 delta = rb_event_time_stamp(event);
3362 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
3366 case RINGBUF_TYPE_TIME_STAMP:
3367 delta = rb_event_time_stamp(event);
3368 ts = rb_fix_abs_ts(delta, ts);
3369 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
3373 case RINGBUF_TYPE_PADDING:
3374 ts += event->time_delta;
3375 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
3376 e, ts, event->time_delta);
3379 case RINGBUF_TYPE_DATA:
3380 ts += event->time_delta;
3381 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
3382 e, ts, event->time_delta,
3383 show_flags(event), show_irq(event));
3390 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
3393 static DEFINE_PER_CPU(atomic_t, checking);
3394 static atomic_t ts_dump;
3396 #define buffer_warn_return(fmt, ...) \
3398 /* If another report is happening, ignore this one */ \
3399 if (atomic_inc_return(&ts_dump) != 1) { \
3400 atomic_dec(&ts_dump); \
3403 atomic_inc(&cpu_buffer->record_disabled); \
3404 pr_warn(fmt, ##__VA_ARGS__); \
3405 dump_buffer_page(bpage, info, tail); \
3406 atomic_dec(&ts_dump); \
3407 /* There's some cases in boot up that this can happen */ \
3408 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
3409 /* Do not re-enable checking */ \
3414 * Check if the current event time stamp matches the deltas on
3417 static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3418 struct rb_event_info *info,
3421 struct ring_buffer_event *event;
3422 struct buffer_data_page *bpage;
3427 bpage = info->tail_page->page;
3429 if (tail == CHECK_FULL_PAGE) {
3431 tail = local_read(&bpage->commit);
3432 } else if (info->add_timestamp &
3433 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3434 /* Ignore events with absolute time stamps */
3439 * Do not check the first event (skip possible extends too).
3440 * Also do not check if previous events have not been committed.
3442 if (tail <= 8 || tail > local_read(&bpage->commit))
3446 * If this interrupted another event,
3448 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3451 ts = bpage->time_stamp;
3453 for (e = 0; e < tail; e += rb_event_length(event)) {
3455 event = (struct ring_buffer_event *)(bpage->data + e);
3457 switch (event->type_len) {
3459 case RINGBUF_TYPE_TIME_EXTEND:
3460 delta = rb_event_time_stamp(event);
3464 case RINGBUF_TYPE_TIME_STAMP:
3465 delta = rb_event_time_stamp(event);
3466 delta = rb_fix_abs_ts(delta, ts);
3468 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
3469 cpu_buffer->cpu, ts, delta);
3474 case RINGBUF_TYPE_PADDING:
3475 if (event->time_delta == 1)
3478 case RINGBUF_TYPE_DATA:
3479 ts += event->time_delta;
3483 RB_WARN_ON(cpu_buffer, 1);
3486 if ((full && ts > info->ts) ||
3487 (!full && ts + info->delta != info->ts)) {
3488 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
3490 ts + info->delta, info->ts, info->delta,
3491 info->before, info->after,
3492 full ? " (full)" : "", show_interrupt_level());
3495 atomic_dec(this_cpu_ptr(&checking));
3498 static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3499 struct rb_event_info *info,
3503 #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3505 static struct ring_buffer_event *
3506 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3507 struct rb_event_info *info)
3509 struct ring_buffer_event *event;
3510 struct buffer_page *tail_page;
3511 unsigned long tail, write, w;
3513 /* Don't let the compiler play games with cpu_buffer->tail_page */
3514 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3516 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3518 rb_time_read(&cpu_buffer->before_stamp, &info->before);
3519 rb_time_read(&cpu_buffer->write_stamp, &info->after);
3521 info->ts = rb_time_stamp(cpu_buffer->buffer);
3523 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3524 info->delta = info->ts;
3527 * If interrupting an event time update, we may need an
3528 * absolute timestamp.
3529 * Don't bother if this is the start of a new page (w == 0).
3532 /* Use the sub-buffer timestamp */
3534 } else if (unlikely(info->before != info->after)) {
3535 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3536 info->length += RB_LEN_TIME_EXTEND;
3538 info->delta = info->ts - info->after;
3539 if (unlikely(test_time_stamp(info->delta))) {
3540 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3541 info->length += RB_LEN_TIME_EXTEND;
3546 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3548 /*C*/ write = local_add_return(info->length, &tail_page->write);
3550 /* set write to only the index of the write */
3551 write &= RB_WRITE_MASK;
3553 tail = write - info->length;
3555 /* See if we shot pass the end of this buffer page */
3556 if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
3557 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3558 return rb_move_tail(cpu_buffer, tail, info);
3561 if (likely(tail == w)) {
3562 /* Nothing interrupted us between A and C */
3563 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3565 * If something came in between C and D, the write stamp
3566 * may now not be in sync. But that's fine as the before_stamp
3567 * will be different and then next event will just be forced
3568 * to use an absolute timestamp.
3570 if (likely(!(info->add_timestamp &
3571 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3572 /* This did not interrupt any time update */
3573 info->delta = info->ts - info->after;
3575 /* Just use full timestamp for interrupting event */
3576 info->delta = info->ts;
3577 check_buffer(cpu_buffer, info, tail);
3580 /* SLOW PATH - Interrupted between A and C */
3582 /* Save the old before_stamp */
3583 rb_time_read(&cpu_buffer->before_stamp, &info->before);
3586 * Read a new timestamp and update the before_stamp to make
3587 * the next event after this one force using an absolute
3588 * timestamp. This is in case an interrupt were to come in
3591 ts = rb_time_stamp(cpu_buffer->buffer);
3592 rb_time_set(&cpu_buffer->before_stamp, ts);
3595 /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
3597 /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3598 info->after == info->before && info->after < ts) {
3600 * Nothing came after this event between C and F, it is
3601 * safe to use info->after for the delta as it
3602 * matched info->before and is still valid.
3604 info->delta = ts - info->after;
3607 * Interrupted between C and F:
3608 * Lost the previous events time stamp. Just set the
3609 * delta to zero, and this will be the same time as
3610 * the event this event interrupted. And the events that
3611 * came after this will still be correct (as they would
3612 * have built their delta on the previous event.
3617 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3621 * If this is the first commit on the page, then it has the same
3622 * timestamp as the page itself.
3624 if (unlikely(!tail && !(info->add_timestamp &
3625 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3628 /* We reserved something on the buffer */
3630 event = __rb_page_index(tail_page, tail);
3631 rb_update_event(cpu_buffer, event, info);
3633 local_inc(&tail_page->entries);
3636 * If this is the first commit on the page, then update
3639 if (unlikely(!tail))
3640 tail_page->page->time_stamp = info->ts;
3642 /* account for these added bytes */
3643 local_add(info->length, &cpu_buffer->entries_bytes);
3648 static __always_inline struct ring_buffer_event *
3649 rb_reserve_next_event(struct trace_buffer *buffer,
3650 struct ring_buffer_per_cpu *cpu_buffer,
3651 unsigned long length)
3653 struct ring_buffer_event *event;
3654 struct rb_event_info info;
3658 /* ring buffer does cmpxchg, make sure it is safe in NMI context */
3659 if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
3660 (unlikely(in_nmi()))) {
3664 rb_start_commit(cpu_buffer);
3665 /* The commit page can not change after this */
3667 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3669 * Due to the ability to swap a cpu buffer from a buffer
3670 * it is possible it was swapped before we committed.
3671 * (committing stops a swap). We check for it here and
3672 * if it happened, we have to fail the write.
3675 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3676 local_dec(&cpu_buffer->committing);
3677 local_dec(&cpu_buffer->commits);
3682 info.length = rb_calculate_event_length(length);
3684 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3685 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3686 info.length += RB_LEN_TIME_EXTEND;
3687 if (info.length > cpu_buffer->buffer->max_data_size)
3690 add_ts_default = RB_ADD_STAMP_NONE;
3694 info.add_timestamp = add_ts_default;
3698 * We allow for interrupts to reenter here and do a trace.
3699 * If one does, it will cause this original code to loop
3700 * back here. Even with heavy interrupts happening, this
3701 * should only happen a few times in a row. If this happens
3702 * 1000 times in a row, there must be either an interrupt
3703 * storm or we have something buggy.
3706 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3709 event = __rb_reserve_next(cpu_buffer, &info);
3711 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3712 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3713 info.length -= RB_LEN_TIME_EXTEND;
3720 rb_end_commit(cpu_buffer);
3725 * ring_buffer_lock_reserve - reserve a part of the buffer
3726 * @buffer: the ring buffer to reserve from
3727 * @length: the length of the data to reserve (excluding event header)
3729 * Returns a reserved event on the ring buffer to copy directly to.
3730 * The user of this interface will need to get the body to write into
3731 * and can use the ring_buffer_event_data() interface.
3733 * The length is the length of the data needed, not the event length
3734 * which also includes the event header.
3736 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3737 * If NULL is returned, then nothing has been allocated or locked.
3739 struct ring_buffer_event *
3740 ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3742 struct ring_buffer_per_cpu *cpu_buffer;
3743 struct ring_buffer_event *event;
3746 /* If we are tracing schedule, we don't want to recurse */
3747 preempt_disable_notrace();
3749 if (unlikely(atomic_read(&buffer->record_disabled)))
3752 cpu = raw_smp_processor_id();
3754 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3757 cpu_buffer = buffer->buffers[cpu];
3759 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3762 if (unlikely(length > buffer->max_data_size))
3765 if (unlikely(trace_recursive_lock(cpu_buffer)))
3768 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3775 trace_recursive_unlock(cpu_buffer);
3777 preempt_enable_notrace();
3780 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3783 * Decrement the entries to the page that an event is on.
3784 * The event does not even need to exist, only the pointer
3785 * to the page it is on. This may only be called before the commit
3789 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3790 struct ring_buffer_event *event)
3792 unsigned long addr = (unsigned long)event;
3793 struct buffer_page *bpage = cpu_buffer->commit_page;
3794 struct buffer_page *start;
3796 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3798 /* Do the likely case first */
3799 if (likely(bpage->page == (void *)addr)) {
3800 local_dec(&bpage->entries);
3805 * Because the commit page may be on the reader page we
3806 * start with the next page and check the end loop there.
3808 rb_inc_page(&bpage);
3811 if (bpage->page == (void *)addr) {
3812 local_dec(&bpage->entries);
3815 rb_inc_page(&bpage);
3816 } while (bpage != start);
3818 /* commit not part of this buffer?? */
3819 RB_WARN_ON(cpu_buffer, 1);
3823 * ring_buffer_discard_commit - discard an event that has not been committed
3824 * @buffer: the ring buffer
3825 * @event: non committed event to discard
3827 * Sometimes an event that is in the ring buffer needs to be ignored.
3828 * This function lets the user discard an event in the ring buffer
3829 * and then that event will not be read later.
3831 * This function only works if it is called before the item has been
3832 * committed. It will try to free the event from the ring buffer
3833 * if another event has not been added behind it.
3835 * If another event has been added behind it, it will set the event
3836 * up as discarded, and perform the commit.
3838 * If this function is called, do not call ring_buffer_unlock_commit on
3841 void ring_buffer_discard_commit(struct trace_buffer *buffer,
3842 struct ring_buffer_event *event)
3844 struct ring_buffer_per_cpu *cpu_buffer;
3847 /* The event is discarded regardless */
3848 rb_event_discard(event);
3850 cpu = smp_processor_id();
3851 cpu_buffer = buffer->buffers[cpu];
3854 * This must only be called if the event has not been
3855 * committed yet. Thus we can assume that preemption
3856 * is still disabled.
3858 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3860 rb_decrement_entry(cpu_buffer, event);
3861 if (rb_try_to_discard(cpu_buffer, event))
3865 rb_end_commit(cpu_buffer);
3867 trace_recursive_unlock(cpu_buffer);
3869 preempt_enable_notrace();
3872 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3875 * ring_buffer_write - write data to the buffer without reserving
3876 * @buffer: The ring buffer to write to.
3877 * @length: The length of the data being written (excluding the event header)
3878 * @data: The data to write to the buffer.
3880 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3881 * one function. If you already have the data to write to the buffer, it
3882 * may be easier to simply call this function.
3884 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3885 * and not the length of the event which would hold the header.
3887 int ring_buffer_write(struct trace_buffer *buffer,
3888 unsigned long length,
3891 struct ring_buffer_per_cpu *cpu_buffer;
3892 struct ring_buffer_event *event;
3897 preempt_disable_notrace();
3899 if (atomic_read(&buffer->record_disabled))
3902 cpu = raw_smp_processor_id();
3904 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3907 cpu_buffer = buffer->buffers[cpu];
3909 if (atomic_read(&cpu_buffer->record_disabled))
3912 if (length > buffer->max_data_size)
3915 if (unlikely(trace_recursive_lock(cpu_buffer)))
3918 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3922 body = rb_event_data(event);
3924 memcpy(body, data, length);
3926 rb_commit(cpu_buffer);
3928 rb_wakeups(buffer, cpu_buffer);
3933 trace_recursive_unlock(cpu_buffer);
3936 preempt_enable_notrace();
3940 EXPORT_SYMBOL_GPL(ring_buffer_write);
3942 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3944 struct buffer_page *reader = cpu_buffer->reader_page;
3945 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3946 struct buffer_page *commit = cpu_buffer->commit_page;
3948 /* In case of error, head will be NULL */
3949 if (unlikely(!head))
3952 /* Reader should exhaust content in reader page */
3953 if (reader->read != rb_page_commit(reader))
3957 * If writers are committing on the reader page, knowing all
3958 * committed content has been read, the ring buffer is empty.
3960 if (commit == reader)
3964 * If writers are committing on a page other than reader page
3965 * and head page, there should always be content to read.
3971 * Writers are committing on the head page, we just need
3972 * to care about there're committed data, and the reader will
3973 * swap reader page with head page when it is to read data.
3975 return rb_page_commit(commit) == 0;
3979 * ring_buffer_record_disable - stop all writes into the buffer
3980 * @buffer: The ring buffer to stop writes to.
3982 * This prevents all writes to the buffer. Any attempt to write
3983 * to the buffer after this will fail and return NULL.
3985 * The caller should call synchronize_rcu() after this.
3987 void ring_buffer_record_disable(struct trace_buffer *buffer)
3989 atomic_inc(&buffer->record_disabled);
3991 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3994 * ring_buffer_record_enable - enable writes to the buffer
3995 * @buffer: The ring buffer to enable writes
3997 * Note, multiple disables will need the same number of enables
3998 * to truly enable the writing (much like preempt_disable).
4000 void ring_buffer_record_enable(struct trace_buffer *buffer)
4002 atomic_dec(&buffer->record_disabled);
4004 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4007 * ring_buffer_record_off - stop all writes into the buffer
4008 * @buffer: The ring buffer to stop writes to.
4010 * This prevents all writes to the buffer. Any attempt to write
4011 * to the buffer after this will fail and return NULL.
4013 * This is different than ring_buffer_record_disable() as
4014 * it works like an on/off switch, where as the disable() version
4015 * must be paired with a enable().
4017 void ring_buffer_record_off(struct trace_buffer *buffer)
4020 unsigned int new_rd;
4022 rd = atomic_read(&buffer->record_disabled);
4024 new_rd = rd | RB_BUFFER_OFF;
4025 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4027 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4030 * ring_buffer_record_on - restart writes into the buffer
4031 * @buffer: The ring buffer to start writes to.
4033 * This enables all writes to the buffer that was disabled by
4034 * ring_buffer_record_off().
4036 * This is different than ring_buffer_record_enable() as
4037 * it works like an on/off switch, where as the enable() version
4038 * must be paired with a disable().
4040 void ring_buffer_record_on(struct trace_buffer *buffer)
4043 unsigned int new_rd;
4045 rd = atomic_read(&buffer->record_disabled);
4047 new_rd = rd & ~RB_BUFFER_OFF;
4048 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4050 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4053 * ring_buffer_record_is_on - return true if the ring buffer can write
4054 * @buffer: The ring buffer to see if write is enabled
4056 * Returns true if the ring buffer is in a state that it accepts writes.
4058 bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4060 return !atomic_read(&buffer->record_disabled);
4064 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4065 * @buffer: The ring buffer to see if write is set enabled
4067 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4068 * Note that this does NOT mean it is in a writable state.
4070 * It may return true when the ring buffer has been disabled by
4071 * ring_buffer_record_disable(), as that is a temporary disabling of
4074 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4076 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4080 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4081 * @buffer: The ring buffer to stop writes to.
4082 * @cpu: The CPU buffer to stop
4084 * This prevents all writes to the buffer. Any attempt to write
4085 * to the buffer after this will fail and return NULL.
4087 * The caller should call synchronize_rcu() after this.
4089 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4091 struct ring_buffer_per_cpu *cpu_buffer;
4093 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4096 cpu_buffer = buffer->buffers[cpu];
4097 atomic_inc(&cpu_buffer->record_disabled);
4099 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4102 * ring_buffer_record_enable_cpu - enable writes to the buffer
4103 * @buffer: The ring buffer to enable writes
4104 * @cpu: The CPU to enable.
4106 * Note, multiple disables will need the same number of enables
4107 * to truly enable the writing (much like preempt_disable).
4109 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4111 struct ring_buffer_per_cpu *cpu_buffer;
4113 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4116 cpu_buffer = buffer->buffers[cpu];
4117 atomic_dec(&cpu_buffer->record_disabled);
4119 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4122 * The total entries in the ring buffer is the running counter
4123 * of entries entered into the ring buffer, minus the sum of
4124 * the entries read from the ring buffer and the number of
4125 * entries that were overwritten.
4127 static inline unsigned long
4128 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4130 return local_read(&cpu_buffer->entries) -
4131 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4135 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4136 * @buffer: The ring buffer
4137 * @cpu: The per CPU buffer to read from.
4139 u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4141 unsigned long flags;
4142 struct ring_buffer_per_cpu *cpu_buffer;
4143 struct buffer_page *bpage;
4146 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4149 cpu_buffer = buffer->buffers[cpu];
4150 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4152 * if the tail is on reader_page, oldest time stamp is on the reader
4155 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4156 bpage = cpu_buffer->reader_page;
4158 bpage = rb_set_head_page(cpu_buffer);
4160 ret = bpage->page->time_stamp;
4161 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4165 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4168 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4169 * @buffer: The ring buffer
4170 * @cpu: The per CPU buffer to read from.
4172 unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4174 struct ring_buffer_per_cpu *cpu_buffer;
4177 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4180 cpu_buffer = buffer->buffers[cpu];
4181 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4185 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4188 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4189 * @buffer: The ring buffer
4190 * @cpu: The per CPU buffer to get the entries from.
4192 unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4194 struct ring_buffer_per_cpu *cpu_buffer;
4196 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4199 cpu_buffer = buffer->buffers[cpu];
4201 return rb_num_of_entries(cpu_buffer);
4203 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4206 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4207 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4208 * @buffer: The ring buffer
4209 * @cpu: The per CPU buffer to get the number of overruns from
4211 unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4213 struct ring_buffer_per_cpu *cpu_buffer;
4216 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4219 cpu_buffer = buffer->buffers[cpu];
4220 ret = local_read(&cpu_buffer->overrun);
4224 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4227 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4228 * commits failing due to the buffer wrapping around while there are uncommitted
4229 * events, such as during an interrupt storm.
4230 * @buffer: The ring buffer
4231 * @cpu: The per CPU buffer to get the number of overruns from
4234 ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4236 struct ring_buffer_per_cpu *cpu_buffer;
4239 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4242 cpu_buffer = buffer->buffers[cpu];
4243 ret = local_read(&cpu_buffer->commit_overrun);
4247 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4250 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4251 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4252 * @buffer: The ring buffer
4253 * @cpu: The per CPU buffer to get the number of overruns from
4256 ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4258 struct ring_buffer_per_cpu *cpu_buffer;
4261 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4264 cpu_buffer = buffer->buffers[cpu];
4265 ret = local_read(&cpu_buffer->dropped_events);
4269 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4272 * ring_buffer_read_events_cpu - get the number of events successfully read
4273 * @buffer: The ring buffer
4274 * @cpu: The per CPU buffer to get the number of events read
4277 ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4279 struct ring_buffer_per_cpu *cpu_buffer;
4281 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4284 cpu_buffer = buffer->buffers[cpu];
4285 return cpu_buffer->read;
4287 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4290 * ring_buffer_entries - get the number of entries in a buffer
4291 * @buffer: The ring buffer
4293 * Returns the total number of entries in the ring buffer
4296 unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4298 struct ring_buffer_per_cpu *cpu_buffer;
4299 unsigned long entries = 0;
4302 /* if you care about this being correct, lock the buffer */
4303 for_each_buffer_cpu(buffer, cpu) {
4304 cpu_buffer = buffer->buffers[cpu];
4305 entries += rb_num_of_entries(cpu_buffer);
4310 EXPORT_SYMBOL_GPL(ring_buffer_entries);
4313 * ring_buffer_overruns - get the number of overruns in buffer
4314 * @buffer: The ring buffer
4316 * Returns the total number of overruns in the ring buffer
4319 unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4321 struct ring_buffer_per_cpu *cpu_buffer;
4322 unsigned long overruns = 0;
4325 /* if you care about this being correct, lock the buffer */
4326 for_each_buffer_cpu(buffer, cpu) {
4327 cpu_buffer = buffer->buffers[cpu];
4328 overruns += local_read(&cpu_buffer->overrun);
4333 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4335 static void rb_iter_reset(struct ring_buffer_iter *iter)
4337 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4339 /* Iterator usage is expected to have record disabled */
4340 iter->head_page = cpu_buffer->reader_page;
4341 iter->head = cpu_buffer->reader_page->read;
4342 iter->next_event = iter->head;
4344 iter->cache_reader_page = iter->head_page;
4345 iter->cache_read = cpu_buffer->read;
4346 iter->cache_pages_removed = cpu_buffer->pages_removed;
4349 iter->read_stamp = cpu_buffer->read_stamp;
4350 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4352 iter->read_stamp = iter->head_page->page->time_stamp;
4353 iter->page_stamp = iter->read_stamp;
4358 * ring_buffer_iter_reset - reset an iterator
4359 * @iter: The iterator to reset
4361 * Resets the iterator, so that it will start from the beginning
4364 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4366 struct ring_buffer_per_cpu *cpu_buffer;
4367 unsigned long flags;
4372 cpu_buffer = iter->cpu_buffer;
4374 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4375 rb_iter_reset(iter);
4376 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4378 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4381 * ring_buffer_iter_empty - check if an iterator has no more to read
4382 * @iter: The iterator to check
4384 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4386 struct ring_buffer_per_cpu *cpu_buffer;
4387 struct buffer_page *reader;
4388 struct buffer_page *head_page;
4389 struct buffer_page *commit_page;
4390 struct buffer_page *curr_commit_page;
4395 cpu_buffer = iter->cpu_buffer;
4396 reader = cpu_buffer->reader_page;
4397 head_page = cpu_buffer->head_page;
4398 commit_page = READ_ONCE(cpu_buffer->commit_page);
4399 commit_ts = commit_page->page->time_stamp;
4402 * When the writer goes across pages, it issues a cmpxchg which
4403 * is a mb(), which will synchronize with the rmb here.
4404 * (see rb_tail_page_update())
4407 commit = rb_page_commit(commit_page);
4408 /* We want to make sure that the commit page doesn't change */
4411 /* Make sure commit page didn't change */
4412 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4413 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4415 /* If the commit page changed, then there's more data */
4416 if (curr_commit_page != commit_page ||
4417 curr_commit_ts != commit_ts)
4420 /* Still racy, as it may return a false positive, but that's OK */
4421 return ((iter->head_page == commit_page && iter->head >= commit) ||
4422 (iter->head_page == reader && commit_page == head_page &&
4423 head_page->read == commit &&
4424 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4426 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4429 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4430 struct ring_buffer_event *event)
4434 switch (event->type_len) {
4435 case RINGBUF_TYPE_PADDING:
4438 case RINGBUF_TYPE_TIME_EXTEND:
4439 delta = rb_event_time_stamp(event);
4440 cpu_buffer->read_stamp += delta;
4443 case RINGBUF_TYPE_TIME_STAMP:
4444 delta = rb_event_time_stamp(event);
4445 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
4446 cpu_buffer->read_stamp = delta;
4449 case RINGBUF_TYPE_DATA:
4450 cpu_buffer->read_stamp += event->time_delta;
4454 RB_WARN_ON(cpu_buffer, 1);
4459 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4460 struct ring_buffer_event *event)
4464 switch (event->type_len) {
4465 case RINGBUF_TYPE_PADDING:
4468 case RINGBUF_TYPE_TIME_EXTEND:
4469 delta = rb_event_time_stamp(event);
4470 iter->read_stamp += delta;
4473 case RINGBUF_TYPE_TIME_STAMP:
4474 delta = rb_event_time_stamp(event);
4475 delta = rb_fix_abs_ts(delta, iter->read_stamp);
4476 iter->read_stamp = delta;
4479 case RINGBUF_TYPE_DATA:
4480 iter->read_stamp += event->time_delta;
4484 RB_WARN_ON(iter->cpu_buffer, 1);
4488 static struct buffer_page *
4489 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4491 struct buffer_page *reader = NULL;
4492 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
4493 unsigned long overwrite;
4494 unsigned long flags;
4498 local_irq_save(flags);
4499 arch_spin_lock(&cpu_buffer->lock);
4503 * This should normally only loop twice. But because the
4504 * start of the reader inserts an empty page, it causes
4505 * a case where we will loop three times. There should be no
4506 * reason to loop four times (that I know of).
4508 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4513 reader = cpu_buffer->reader_page;
4515 /* If there's more to read, return this page */
4516 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4519 /* Never should we have an index greater than the size */
4520 if (RB_WARN_ON(cpu_buffer,
4521 cpu_buffer->reader_page->read > rb_page_size(reader)))
4524 /* check if we caught up to the tail */
4526 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4529 /* Don't bother swapping if the ring buffer is empty */
4530 if (rb_num_of_entries(cpu_buffer) == 0)
4534 * Reset the reader page to size zero.
4536 local_set(&cpu_buffer->reader_page->write, 0);
4537 local_set(&cpu_buffer->reader_page->entries, 0);
4538 local_set(&cpu_buffer->reader_page->page->commit, 0);
4539 cpu_buffer->reader_page->real_end = 0;
4543 * Splice the empty reader page into the list around the head.
4545 reader = rb_set_head_page(cpu_buffer);
4548 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4549 cpu_buffer->reader_page->list.prev = reader->list.prev;
4552 * cpu_buffer->pages just needs to point to the buffer, it
4553 * has no specific buffer page to point to. Lets move it out
4554 * of our way so we don't accidentally swap it.
4556 cpu_buffer->pages = reader->list.prev;
4558 /* The reader page will be pointing to the new head */
4559 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4562 * We want to make sure we read the overruns after we set up our
4563 * pointers to the next object. The writer side does a
4564 * cmpxchg to cross pages which acts as the mb on the writer
4565 * side. Note, the reader will constantly fail the swap
4566 * while the writer is updating the pointers, so this
4567 * guarantees that the overwrite recorded here is the one we
4568 * want to compare with the last_overrun.
4571 overwrite = local_read(&(cpu_buffer->overrun));
4574 * Here's the tricky part.
4576 * We need to move the pointer past the header page.
4577 * But we can only do that if a writer is not currently
4578 * moving it. The page before the header page has the
4579 * flag bit '1' set if it is pointing to the page we want.
4580 * but if the writer is in the process of moving it
4581 * than it will be '2' or already moved '0'.
4584 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4587 * If we did not convert it, then we must try again.
4593 * Yay! We succeeded in replacing the page.
4595 * Now make the new head point back to the reader page.
4597 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4598 rb_inc_page(&cpu_buffer->head_page);
4600 local_inc(&cpu_buffer->pages_read);
4602 /* Finally update the reader page to the new head */
4603 cpu_buffer->reader_page = reader;
4604 cpu_buffer->reader_page->read = 0;
4606 if (overwrite != cpu_buffer->last_overrun) {
4607 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4608 cpu_buffer->last_overrun = overwrite;
4614 /* Update the read_stamp on the first event */
4615 if (reader && reader->read == 0)
4616 cpu_buffer->read_stamp = reader->page->time_stamp;
4618 arch_spin_unlock(&cpu_buffer->lock);
4619 local_irq_restore(flags);
4622 * The writer has preempt disable, wait for it. But not forever
4623 * Although, 1 second is pretty much "forever"
4625 #define USECS_WAIT 1000000
4626 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4627 /* If the write is past the end of page, a writer is still updating it */
4628 if (likely(!reader || rb_page_write(reader) <= bsize))
4633 /* Get the latest version of the reader write value */
4637 /* The writer is not moving forward? Something is wrong */
4638 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4642 * Make sure we see any padding after the write update
4643 * (see rb_reset_tail()).
4645 * In addition, a writer may be writing on the reader page
4646 * if the page has not been fully filled, so the read barrier
4647 * is also needed to make sure we see the content of what is
4648 * committed by the writer (see rb_set_commit_to_write()).
4656 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4658 struct ring_buffer_event *event;
4659 struct buffer_page *reader;
4662 reader = rb_get_reader_page(cpu_buffer);
4664 /* This function should not be called when buffer is empty */
4665 if (RB_WARN_ON(cpu_buffer, !reader))
4668 event = rb_reader_event(cpu_buffer);
4670 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4673 rb_update_read_stamp(cpu_buffer, event);
4675 length = rb_event_length(event);
4676 cpu_buffer->reader_page->read += length;
4677 cpu_buffer->read_bytes += length;
4680 static void rb_advance_iter(struct ring_buffer_iter *iter)
4682 struct ring_buffer_per_cpu *cpu_buffer;
4684 cpu_buffer = iter->cpu_buffer;
4686 /* If head == next_event then we need to jump to the next event */
4687 if (iter->head == iter->next_event) {
4688 /* If the event gets overwritten again, there's nothing to do */
4689 if (rb_iter_head_event(iter) == NULL)
4693 iter->head = iter->next_event;
4696 * Check if we are at the end of the buffer.
4698 if (iter->next_event >= rb_page_size(iter->head_page)) {
4699 /* discarded commits can make the page empty */
4700 if (iter->head_page == cpu_buffer->commit_page)
4706 rb_update_iter_read_stamp(iter, iter->event);
4709 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4711 return cpu_buffer->lost_events;
4714 static struct ring_buffer_event *
4715 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4716 unsigned long *lost_events)
4718 struct ring_buffer_event *event;
4719 struct buffer_page *reader;
4726 * We repeat when a time extend is encountered.
4727 * Since the time extend is always attached to a data event,
4728 * we should never loop more than once.
4729 * (We never hit the following condition more than twice).
4731 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4734 reader = rb_get_reader_page(cpu_buffer);
4738 event = rb_reader_event(cpu_buffer);
4740 switch (event->type_len) {
4741 case RINGBUF_TYPE_PADDING:
4742 if (rb_null_event(event))
4743 RB_WARN_ON(cpu_buffer, 1);
4745 * Because the writer could be discarding every
4746 * event it creates (which would probably be bad)
4747 * if we were to go back to "again" then we may never
4748 * catch up, and will trigger the warn on, or lock
4749 * the box. Return the padding, and we will release
4750 * the current locks, and try again.
4754 case RINGBUF_TYPE_TIME_EXTEND:
4755 /* Internal data, OK to advance */
4756 rb_advance_reader(cpu_buffer);
4759 case RINGBUF_TYPE_TIME_STAMP:
4761 *ts = rb_event_time_stamp(event);
4762 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
4763 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4764 cpu_buffer->cpu, ts);
4766 /* Internal data, OK to advance */
4767 rb_advance_reader(cpu_buffer);
4770 case RINGBUF_TYPE_DATA:
4772 *ts = cpu_buffer->read_stamp + event->time_delta;
4773 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4774 cpu_buffer->cpu, ts);
4777 *lost_events = rb_lost_events(cpu_buffer);
4781 RB_WARN_ON(cpu_buffer, 1);
4786 EXPORT_SYMBOL_GPL(ring_buffer_peek);
4788 static struct ring_buffer_event *
4789 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4791 struct trace_buffer *buffer;
4792 struct ring_buffer_per_cpu *cpu_buffer;
4793 struct ring_buffer_event *event;
4799 cpu_buffer = iter->cpu_buffer;
4800 buffer = cpu_buffer->buffer;
4803 * Check if someone performed a consuming read to the buffer
4804 * or removed some pages from the buffer. In these cases,
4805 * iterator was invalidated and we need to reset it.
4807 if (unlikely(iter->cache_read != cpu_buffer->read ||
4808 iter->cache_reader_page != cpu_buffer->reader_page ||
4809 iter->cache_pages_removed != cpu_buffer->pages_removed))
4810 rb_iter_reset(iter);
4813 if (ring_buffer_iter_empty(iter))
4817 * As the writer can mess with what the iterator is trying
4818 * to read, just give up if we fail to get an event after
4819 * three tries. The iterator is not as reliable when reading
4820 * the ring buffer with an active write as the consumer is.
4821 * Do not warn if the three failures is reached.
4826 if (rb_per_cpu_empty(cpu_buffer))
4829 if (iter->head >= rb_page_size(iter->head_page)) {
4834 event = rb_iter_head_event(iter);
4838 switch (event->type_len) {
4839 case RINGBUF_TYPE_PADDING:
4840 if (rb_null_event(event)) {
4844 rb_advance_iter(iter);
4847 case RINGBUF_TYPE_TIME_EXTEND:
4848 /* Internal data, OK to advance */
4849 rb_advance_iter(iter);
4852 case RINGBUF_TYPE_TIME_STAMP:
4854 *ts = rb_event_time_stamp(event);
4855 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
4856 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4857 cpu_buffer->cpu, ts);
4859 /* Internal data, OK to advance */
4860 rb_advance_iter(iter);
4863 case RINGBUF_TYPE_DATA:
4865 *ts = iter->read_stamp + event->time_delta;
4866 ring_buffer_normalize_time_stamp(buffer,
4867 cpu_buffer->cpu, ts);
4872 RB_WARN_ON(cpu_buffer, 1);
4877 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4879 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4881 if (likely(!in_nmi())) {
4882 raw_spin_lock(&cpu_buffer->reader_lock);
4887 * If an NMI die dumps out the content of the ring buffer
4888 * trylock must be used to prevent a deadlock if the NMI
4889 * preempted a task that holds the ring buffer locks. If
4890 * we get the lock then all is fine, if not, then continue
4891 * to do the read, but this can corrupt the ring buffer,
4892 * so it must be permanently disabled from future writes.
4893 * Reading from NMI is a oneshot deal.
4895 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4898 /* Continue without locking, but disable the ring buffer */
4899 atomic_inc(&cpu_buffer->record_disabled);
4904 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4907 raw_spin_unlock(&cpu_buffer->reader_lock);
4911 * ring_buffer_peek - peek at the next event to be read
4912 * @buffer: The ring buffer to read
4913 * @cpu: The cpu to peak at
4914 * @ts: The timestamp counter of this event.
4915 * @lost_events: a variable to store if events were lost (may be NULL)
4917 * This will return the event that will be read next, but does
4918 * not consume the data.
4920 struct ring_buffer_event *
4921 ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4922 unsigned long *lost_events)
4924 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4925 struct ring_buffer_event *event;
4926 unsigned long flags;
4929 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4933 local_irq_save(flags);
4934 dolock = rb_reader_lock(cpu_buffer);
4935 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4936 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4937 rb_advance_reader(cpu_buffer);
4938 rb_reader_unlock(cpu_buffer, dolock);
4939 local_irq_restore(flags);
4941 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4947 /** ring_buffer_iter_dropped - report if there are dropped events
4948 * @iter: The ring buffer iterator
4950 * Returns true if there was dropped events since the last peek.
4952 bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4954 bool ret = iter->missed_events != 0;
4956 iter->missed_events = 0;
4959 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4962 * ring_buffer_iter_peek - peek at the next event to be read
4963 * @iter: The ring buffer iterator
4964 * @ts: The timestamp counter of this event.
4966 * This will return the event that will be read next, but does
4967 * not increment the iterator.
4969 struct ring_buffer_event *
4970 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4972 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4973 struct ring_buffer_event *event;
4974 unsigned long flags;
4977 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4978 event = rb_iter_peek(iter, ts);
4979 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4981 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4988 * ring_buffer_consume - return an event and consume it
4989 * @buffer: The ring buffer to get the next event from
4990 * @cpu: the cpu to read the buffer from
4991 * @ts: a variable to store the timestamp (may be NULL)
4992 * @lost_events: a variable to store if events were lost (may be NULL)
4994 * Returns the next event in the ring buffer, and that event is consumed.
4995 * Meaning, that sequential reads will keep returning a different event,
4996 * and eventually empty the ring buffer if the producer is slower.
4998 struct ring_buffer_event *
4999 ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5000 unsigned long *lost_events)
5002 struct ring_buffer_per_cpu *cpu_buffer;
5003 struct ring_buffer_event *event = NULL;
5004 unsigned long flags;
5008 /* might be called in atomic */
5011 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5014 cpu_buffer = buffer->buffers[cpu];
5015 local_irq_save(flags);
5016 dolock = rb_reader_lock(cpu_buffer);
5018 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5020 cpu_buffer->lost_events = 0;
5021 rb_advance_reader(cpu_buffer);
5024 rb_reader_unlock(cpu_buffer, dolock);
5025 local_irq_restore(flags);
5030 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5035 EXPORT_SYMBOL_GPL(ring_buffer_consume);
5038 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5039 * @buffer: The ring buffer to read from
5040 * @cpu: The cpu buffer to iterate over
5041 * @flags: gfp flags to use for memory allocation
5043 * This performs the initial preparations necessary to iterate
5044 * through the buffer. Memory is allocated, buffer recording
5045 * is disabled, and the iterator pointer is returned to the caller.
5047 * Disabling buffer recording prevents the reading from being
5048 * corrupted. This is not a consuming read, so a producer is not
5051 * After a sequence of ring_buffer_read_prepare calls, the user is
5052 * expected to make at least one call to ring_buffer_read_prepare_sync.
5053 * Afterwards, ring_buffer_read_start is invoked to get things going
5056 * This overall must be paired with ring_buffer_read_finish.
5058 struct ring_buffer_iter *
5059 ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5061 struct ring_buffer_per_cpu *cpu_buffer;
5062 struct ring_buffer_iter *iter;
5064 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5067 iter = kzalloc(sizeof(*iter), flags);
5071 /* Holds the entire event: data and meta data */
5072 iter->event_size = buffer->subbuf_size;
5073 iter->event = kmalloc(iter->event_size, flags);
5079 cpu_buffer = buffer->buffers[cpu];
5081 iter->cpu_buffer = cpu_buffer;
5083 atomic_inc(&cpu_buffer->resize_disabled);
5087 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5090 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5092 * All previously invoked ring_buffer_read_prepare calls to prepare
5093 * iterators will be synchronized. Afterwards, read_buffer_read_start
5094 * calls on those iterators are allowed.
5097 ring_buffer_read_prepare_sync(void)
5101 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5104 * ring_buffer_read_start - start a non consuming read of the buffer
5105 * @iter: The iterator returned by ring_buffer_read_prepare
5107 * This finalizes the startup of an iteration through the buffer.
5108 * The iterator comes from a call to ring_buffer_read_prepare and
5109 * an intervening ring_buffer_read_prepare_sync must have been
5112 * Must be paired with ring_buffer_read_finish.
5115 ring_buffer_read_start(struct ring_buffer_iter *iter)
5117 struct ring_buffer_per_cpu *cpu_buffer;
5118 unsigned long flags;
5123 cpu_buffer = iter->cpu_buffer;
5125 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5126 arch_spin_lock(&cpu_buffer->lock);
5127 rb_iter_reset(iter);
5128 arch_spin_unlock(&cpu_buffer->lock);
5129 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5131 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5134 * ring_buffer_read_finish - finish reading the iterator of the buffer
5135 * @iter: The iterator retrieved by ring_buffer_start
5137 * This re-enables the recording to the buffer, and frees the
5141 ring_buffer_read_finish(struct ring_buffer_iter *iter)
5143 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5144 unsigned long flags;
5147 * Ring buffer is disabled from recording, here's a good place
5148 * to check the integrity of the ring buffer.
5149 * Must prevent readers from trying to read, as the check
5150 * clears the HEAD page and readers require it.
5152 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5153 rb_check_pages(cpu_buffer);
5154 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5156 atomic_dec(&cpu_buffer->resize_disabled);
5160 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5163 * ring_buffer_iter_advance - advance the iterator to the next location
5164 * @iter: The ring buffer iterator
5166 * Move the location of the iterator such that the next read will
5167 * be the next location of the iterator.
5169 void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5171 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5172 unsigned long flags;
5174 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5176 rb_advance_iter(iter);
5178 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5180 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5183 * ring_buffer_size - return the size of the ring buffer (in bytes)
5184 * @buffer: The ring buffer.
5185 * @cpu: The CPU to get ring buffer size from.
5187 unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5189 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5192 return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5194 EXPORT_SYMBOL_GPL(ring_buffer_size);
5197 * ring_buffer_max_event_size - return the max data size of an event
5198 * @buffer: The ring buffer.
5200 * Returns the maximum size an event can be.
5202 unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5204 /* If abs timestamp is requested, events have a timestamp too */
5205 if (ring_buffer_time_stamp_abs(buffer))
5206 return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5207 return buffer->max_data_size;
5209 EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5211 static void rb_clear_buffer_page(struct buffer_page *page)
5213 local_set(&page->write, 0);
5214 local_set(&page->entries, 0);
5215 rb_init_page(page->page);
5220 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5222 struct buffer_page *page;
5224 rb_head_page_deactivate(cpu_buffer);
5226 cpu_buffer->head_page
5227 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5228 rb_clear_buffer_page(cpu_buffer->head_page);
5229 list_for_each_entry(page, cpu_buffer->pages, list) {
5230 rb_clear_buffer_page(page);
5233 cpu_buffer->tail_page = cpu_buffer->head_page;
5234 cpu_buffer->commit_page = cpu_buffer->head_page;
5236 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5237 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5238 rb_clear_buffer_page(cpu_buffer->reader_page);
5240 local_set(&cpu_buffer->entries_bytes, 0);
5241 local_set(&cpu_buffer->overrun, 0);
5242 local_set(&cpu_buffer->commit_overrun, 0);
5243 local_set(&cpu_buffer->dropped_events, 0);
5244 local_set(&cpu_buffer->entries, 0);
5245 local_set(&cpu_buffer->committing, 0);
5246 local_set(&cpu_buffer->commits, 0);
5247 local_set(&cpu_buffer->pages_touched, 0);
5248 local_set(&cpu_buffer->pages_lost, 0);
5249 local_set(&cpu_buffer->pages_read, 0);
5250 cpu_buffer->last_pages_touch = 0;
5251 cpu_buffer->shortest_full = 0;
5252 cpu_buffer->read = 0;
5253 cpu_buffer->read_bytes = 0;
5255 rb_time_set(&cpu_buffer->write_stamp, 0);
5256 rb_time_set(&cpu_buffer->before_stamp, 0);
5258 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5260 cpu_buffer->lost_events = 0;
5261 cpu_buffer->last_overrun = 0;
5263 rb_head_page_activate(cpu_buffer);
5264 cpu_buffer->pages_removed = 0;
5267 /* Must have disabled the cpu buffer then done a synchronize_rcu */
5268 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5270 unsigned long flags;
5272 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5274 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5277 arch_spin_lock(&cpu_buffer->lock);
5279 rb_reset_cpu(cpu_buffer);
5281 arch_spin_unlock(&cpu_buffer->lock);
5284 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5288 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5289 * @buffer: The ring buffer to reset a per cpu buffer of
5290 * @cpu: The CPU buffer to be reset
5292 void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5294 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5296 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5299 /* prevent another thread from changing buffer sizes */
5300 mutex_lock(&buffer->mutex);
5302 atomic_inc(&cpu_buffer->resize_disabled);
5303 atomic_inc(&cpu_buffer->record_disabled);
5305 /* Make sure all commits have finished */
5308 reset_disabled_cpu_buffer(cpu_buffer);
5310 atomic_dec(&cpu_buffer->record_disabled);
5311 atomic_dec(&cpu_buffer->resize_disabled);
5313 mutex_unlock(&buffer->mutex);
5315 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5317 /* Flag to ensure proper resetting of atomic variables */
5318 #define RESET_BIT (1 << 30)
5321 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5322 * @buffer: The ring buffer to reset a per cpu buffer of
5324 void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5326 struct ring_buffer_per_cpu *cpu_buffer;
5329 /* prevent another thread from changing buffer sizes */
5330 mutex_lock(&buffer->mutex);
5332 for_each_online_buffer_cpu(buffer, cpu) {
5333 cpu_buffer = buffer->buffers[cpu];
5335 atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
5336 atomic_inc(&cpu_buffer->record_disabled);
5339 /* Make sure all commits have finished */
5342 for_each_buffer_cpu(buffer, cpu) {
5343 cpu_buffer = buffer->buffers[cpu];
5346 * If a CPU came online during the synchronize_rcu(), then
5349 if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
5352 reset_disabled_cpu_buffer(cpu_buffer);
5354 atomic_dec(&cpu_buffer->record_disabled);
5355 atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
5358 mutex_unlock(&buffer->mutex);
5362 * ring_buffer_reset - reset a ring buffer
5363 * @buffer: The ring buffer to reset all cpu buffers
5365 void ring_buffer_reset(struct trace_buffer *buffer)
5367 struct ring_buffer_per_cpu *cpu_buffer;
5370 /* prevent another thread from changing buffer sizes */
5371 mutex_lock(&buffer->mutex);
5373 for_each_buffer_cpu(buffer, cpu) {
5374 cpu_buffer = buffer->buffers[cpu];
5376 atomic_inc(&cpu_buffer->resize_disabled);
5377 atomic_inc(&cpu_buffer->record_disabled);
5380 /* Make sure all commits have finished */
5383 for_each_buffer_cpu(buffer, cpu) {
5384 cpu_buffer = buffer->buffers[cpu];
5386 reset_disabled_cpu_buffer(cpu_buffer);
5388 atomic_dec(&cpu_buffer->record_disabled);
5389 atomic_dec(&cpu_buffer->resize_disabled);
5392 mutex_unlock(&buffer->mutex);
5394 EXPORT_SYMBOL_GPL(ring_buffer_reset);
5397 * ring_buffer_empty - is the ring buffer empty?
5398 * @buffer: The ring buffer to test
5400 bool ring_buffer_empty(struct trace_buffer *buffer)
5402 struct ring_buffer_per_cpu *cpu_buffer;
5403 unsigned long flags;
5408 /* yes this is racy, but if you don't like the race, lock the buffer */
5409 for_each_buffer_cpu(buffer, cpu) {
5410 cpu_buffer = buffer->buffers[cpu];
5411 local_irq_save(flags);
5412 dolock = rb_reader_lock(cpu_buffer);
5413 ret = rb_per_cpu_empty(cpu_buffer);
5414 rb_reader_unlock(cpu_buffer, dolock);
5415 local_irq_restore(flags);
5423 EXPORT_SYMBOL_GPL(ring_buffer_empty);
5426 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5427 * @buffer: The ring buffer
5428 * @cpu: The CPU buffer to test
5430 bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5432 struct ring_buffer_per_cpu *cpu_buffer;
5433 unsigned long flags;
5437 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5440 cpu_buffer = buffer->buffers[cpu];
5441 local_irq_save(flags);
5442 dolock = rb_reader_lock(cpu_buffer);
5443 ret = rb_per_cpu_empty(cpu_buffer);
5444 rb_reader_unlock(cpu_buffer, dolock);
5445 local_irq_restore(flags);
5449 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5451 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5453 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5454 * @buffer_a: One buffer to swap with
5455 * @buffer_b: The other buffer to swap with
5456 * @cpu: the CPU of the buffers to swap
5458 * This function is useful for tracers that want to take a "snapshot"
5459 * of a CPU buffer and has another back up buffer lying around.
5460 * it is expected that the tracer handles the cpu buffer not being
5461 * used at the moment.
5463 int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5464 struct trace_buffer *buffer_b, int cpu)
5466 struct ring_buffer_per_cpu *cpu_buffer_a;
5467 struct ring_buffer_per_cpu *cpu_buffer_b;
5470 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5471 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5474 cpu_buffer_a = buffer_a->buffers[cpu];
5475 cpu_buffer_b = buffer_b->buffers[cpu];
5477 /* At least make sure the two buffers are somewhat the same */
5478 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5481 if (buffer_a->subbuf_order != buffer_b->subbuf_order)
5486 if (atomic_read(&buffer_a->record_disabled))
5489 if (atomic_read(&buffer_b->record_disabled))
5492 if (atomic_read(&cpu_buffer_a->record_disabled))
5495 if (atomic_read(&cpu_buffer_b->record_disabled))
5499 * We can't do a synchronize_rcu here because this
5500 * function can be called in atomic context.
5501 * Normally this will be called from the same CPU as cpu.
5502 * If not it's up to the caller to protect this.
5504 atomic_inc(&cpu_buffer_a->record_disabled);
5505 atomic_inc(&cpu_buffer_b->record_disabled);
5508 if (local_read(&cpu_buffer_a->committing))
5510 if (local_read(&cpu_buffer_b->committing))
5514 * When resize is in progress, we cannot swap it because
5515 * it will mess the state of the cpu buffer.
5517 if (atomic_read(&buffer_a->resizing))
5519 if (atomic_read(&buffer_b->resizing))
5522 buffer_a->buffers[cpu] = cpu_buffer_b;
5523 buffer_b->buffers[cpu] = cpu_buffer_a;
5525 cpu_buffer_b->buffer = buffer_a;
5526 cpu_buffer_a->buffer = buffer_b;
5531 atomic_dec(&cpu_buffer_a->record_disabled);
5532 atomic_dec(&cpu_buffer_b->record_disabled);
5536 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5537 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5540 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5541 * @buffer: the buffer to allocate for.
5542 * @cpu: the cpu buffer to allocate.
5544 * This function is used in conjunction with ring_buffer_read_page.
5545 * When reading a full page from the ring buffer, these functions
5546 * can be used to speed up the process. The calling function should
5547 * allocate a few pages first with this function. Then when it
5548 * needs to get pages from the ring buffer, it passes the result
5549 * of this function into ring_buffer_read_page, which will swap
5550 * the page that was allocated, with the read page of the buffer.
5553 * The page allocated, or ERR_PTR
5555 struct buffer_data_read_page *
5556 ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5558 struct ring_buffer_per_cpu *cpu_buffer;
5559 struct buffer_data_read_page *bpage = NULL;
5560 unsigned long flags;
5563 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5564 return ERR_PTR(-ENODEV);
5566 bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
5568 return ERR_PTR(-ENOMEM);
5570 bpage->order = buffer->subbuf_order;
5571 cpu_buffer = buffer->buffers[cpu];
5572 local_irq_save(flags);
5573 arch_spin_lock(&cpu_buffer->lock);
5575 if (cpu_buffer->free_page) {
5576 bpage->data = cpu_buffer->free_page;
5577 cpu_buffer->free_page = NULL;
5580 arch_spin_unlock(&cpu_buffer->lock);
5581 local_irq_restore(flags);
5586 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_NORETRY,
5587 cpu_buffer->buffer->subbuf_order);
5590 return ERR_PTR(-ENOMEM);
5593 bpage->data = page_address(page);
5596 rb_init_page(bpage->data);
5600 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5603 * ring_buffer_free_read_page - free an allocated read page
5604 * @buffer: the buffer the page was allocate for
5605 * @cpu: the cpu buffer the page came from
5606 * @data_page: the page to free
5608 * Free a page allocated from ring_buffer_alloc_read_page.
5610 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
5611 struct buffer_data_read_page *data_page)
5613 struct ring_buffer_per_cpu *cpu_buffer;
5614 struct buffer_data_page *bpage = data_page->data;
5615 struct page *page = virt_to_page(bpage);
5616 unsigned long flags;
5618 if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
5621 cpu_buffer = buffer->buffers[cpu];
5624 * If the page is still in use someplace else, or order of the page
5625 * is different from the subbuffer order of the buffer -
5628 if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
5631 local_irq_save(flags);
5632 arch_spin_lock(&cpu_buffer->lock);
5634 if (!cpu_buffer->free_page) {
5635 cpu_buffer->free_page = bpage;
5639 arch_spin_unlock(&cpu_buffer->lock);
5640 local_irq_restore(flags);
5643 free_pages((unsigned long)bpage, data_page->order);
5646 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5649 * ring_buffer_read_page - extract a page from the ring buffer
5650 * @buffer: buffer to extract from
5651 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5652 * @len: amount to extract
5653 * @cpu: the cpu of the buffer to extract
5654 * @full: should the extraction only happen when the page is full.
5656 * This function will pull out a page from the ring buffer and consume it.
5657 * @data_page must be the address of the variable that was returned
5658 * from ring_buffer_alloc_read_page. This is because the page might be used
5659 * to swap with a page in the ring buffer.
5662 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5663 * if (IS_ERR(rpage))
5664 * return PTR_ERR(rpage);
5665 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
5667 * process_page(ring_buffer_read_page_data(rpage), ret);
5668 * ring_buffer_free_read_page(buffer, cpu, rpage);
5670 * When @full is set, the function will not return true unless
5671 * the writer is off the reader page.
5673 * Note: it is up to the calling functions to handle sleeps and wakeups.
5674 * The ring buffer can be used anywhere in the kernel and can not
5675 * blindly call wake_up. The layer that uses the ring buffer must be
5676 * responsible for that.
5679 * >=0 if data has been transferred, returns the offset of consumed data.
5680 * <0 if no data has been transferred.
5682 int ring_buffer_read_page(struct trace_buffer *buffer,
5683 struct buffer_data_read_page *data_page,
5684 size_t len, int cpu, int full)
5686 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5687 struct ring_buffer_event *event;
5688 struct buffer_data_page *bpage;
5689 struct buffer_page *reader;
5690 unsigned long missed_events;
5691 unsigned long flags;
5692 unsigned int commit;
5697 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5701 * If len is not big enough to hold the page header, then
5702 * we can not copy anything.
5704 if (len <= BUF_PAGE_HDR_SIZE)
5707 len -= BUF_PAGE_HDR_SIZE;
5709 if (!data_page || !data_page->data)
5711 if (data_page->order != buffer->subbuf_order)
5714 bpage = data_page->data;
5718 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5720 reader = rb_get_reader_page(cpu_buffer);
5724 event = rb_reader_event(cpu_buffer);
5726 read = reader->read;
5727 commit = rb_page_commit(reader);
5729 /* Check if any events were dropped */
5730 missed_events = cpu_buffer->lost_events;
5733 * If this page has been partially read or
5734 * if len is not big enough to read the rest of the page or
5735 * a writer is still on the page, then
5736 * we must copy the data from the page to the buffer.
5737 * Otherwise, we can simply swap the page with the one passed in.
5739 if (read || (len < (commit - read)) ||
5740 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5741 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5742 unsigned int rpos = read;
5743 unsigned int pos = 0;
5747 * If a full page is expected, this can still be returned
5748 * if there's been a previous partial read and the
5749 * rest of the page can be read and the commit page is off
5753 (!read || (len < (commit - read)) ||
5754 cpu_buffer->reader_page == cpu_buffer->commit_page))
5757 if (len > (commit - read))
5758 len = (commit - read);
5760 /* Always keep the time extend and data together */
5761 size = rb_event_ts_length(event);
5766 /* save the current timestamp, since the user will need it */
5767 save_timestamp = cpu_buffer->read_stamp;
5769 /* Need to copy one event at a time */
5771 /* We need the size of one event, because
5772 * rb_advance_reader only advances by one event,
5773 * whereas rb_event_ts_length may include the size of
5774 * one or two events.
5775 * We have already ensured there's enough space if this
5776 * is a time extend. */
5777 size = rb_event_length(event);
5778 memcpy(bpage->data + pos, rpage->data + rpos, size);
5782 rb_advance_reader(cpu_buffer);
5783 rpos = reader->read;
5789 event = rb_reader_event(cpu_buffer);
5790 /* Always keep the time extend and data together */
5791 size = rb_event_ts_length(event);
5792 } while (len >= size);
5795 local_set(&bpage->commit, pos);
5796 bpage->time_stamp = save_timestamp;
5798 /* we copied everything to the beginning */
5801 /* update the entry counter */
5802 cpu_buffer->read += rb_page_entries(reader);
5803 cpu_buffer->read_bytes += rb_page_commit(reader);
5805 /* swap the pages */
5806 rb_init_page(bpage);
5807 bpage = reader->page;
5808 reader->page = data_page->data;
5809 local_set(&reader->write, 0);
5810 local_set(&reader->entries, 0);
5812 data_page->data = bpage;
5815 * Use the real_end for the data size,
5816 * This gives us a chance to store the lost events
5819 if (reader->real_end)
5820 local_set(&bpage->commit, reader->real_end);
5824 cpu_buffer->lost_events = 0;
5826 commit = local_read(&bpage->commit);
5828 * Set a flag in the commit field if we lost events
5830 if (missed_events) {
5831 /* If there is room at the end of the page to save the
5832 * missed events, then record it there.
5834 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
5835 memcpy(&bpage->data[commit], &missed_events,
5836 sizeof(missed_events));
5837 local_add(RB_MISSED_STORED, &bpage->commit);
5838 commit += sizeof(missed_events);
5840 local_add(RB_MISSED_EVENTS, &bpage->commit);
5844 * This page may be off to user land. Zero it out here.
5846 if (commit < buffer->subbuf_size)
5847 memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
5850 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5855 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5858 * ring_buffer_read_page_data - get pointer to the data in the page.
5859 * @page: the page to get the data from
5861 * Returns pointer to the actual data in this page.
5863 void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
5867 EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
5870 * ring_buffer_subbuf_size_get - get size of the sub buffer.
5871 * @buffer: the buffer to get the sub buffer size from
5873 * Returns size of the sub buffer, in bytes.
5875 int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
5877 return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
5879 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
5882 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
5883 * @buffer: The ring_buffer to get the system sub page order from
5885 * By default, one ring buffer sub page equals to one system page. This parameter
5886 * is configurable, per ring buffer. The size of the ring buffer sub page can be
5887 * extended, but must be an order of system page size.
5889 * Returns the order of buffer sub page size, in system pages:
5890 * 0 means the sub buffer size is 1 system page and so forth.
5891 * In case of an error < 0 is returned.
5893 int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
5898 return buffer->subbuf_order;
5900 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
5903 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
5904 * @buffer: The ring_buffer to set the new page size.
5905 * @order: Order of the system pages in one sub buffer page
5907 * By default, one ring buffer pages equals to one system page. This API can be
5908 * used to set new size of the ring buffer page. The size must be order of
5909 * system page size, that's why the input parameter @order is the order of
5910 * system pages that are allocated for one ring buffer page:
5912 * 1 - 2 system pages
5913 * 3 - 4 system pages
5916 * Returns 0 on success or < 0 in case of an error.
5918 int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
5920 struct ring_buffer_per_cpu *cpu_buffer;
5921 struct buffer_page *bpage, *tmp;
5922 int old_order, old_size;
5928 if (!buffer || order < 0)
5931 if (buffer->subbuf_order == order)
5934 psize = (1 << order) * PAGE_SIZE;
5935 if (psize <= BUF_PAGE_HDR_SIZE)
5938 /* Size of a subbuf cannot be greater than the write counter */
5939 if (psize > RB_WRITE_MASK + 1)
5942 old_order = buffer->subbuf_order;
5943 old_size = buffer->subbuf_size;
5945 /* prevent another thread from changing buffer sizes */
5946 mutex_lock(&buffer->mutex);
5947 atomic_inc(&buffer->record_disabled);
5949 /* Make sure all commits have finished */
5952 buffer->subbuf_order = order;
5953 buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
5955 /* Make sure all new buffers are allocated, before deleting the old ones */
5956 for_each_buffer_cpu(buffer, cpu) {
5958 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5961 cpu_buffer = buffer->buffers[cpu];
5963 /* Update the number of pages to match the new size */
5964 nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
5965 nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
5967 /* we need a minimum of two pages */
5971 cpu_buffer->nr_pages_to_update = nr_pages;
5973 /* Include the reader page */
5976 /* Allocate the new size buffer */
5977 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5978 if (__rb_allocate_pages(cpu_buffer, nr_pages,
5979 &cpu_buffer->new_pages)) {
5980 /* not enough memory for new pages */
5986 for_each_buffer_cpu(buffer, cpu) {
5988 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5991 cpu_buffer = buffer->buffers[cpu];
5993 /* Clear the head bit to make the link list normal to read */
5994 rb_head_page_deactivate(cpu_buffer);
5996 /* Now walk the list and free all the old sub buffers */
5997 list_for_each_entry_safe(bpage, tmp, cpu_buffer->pages, list) {
5998 list_del_init(&bpage->list);
5999 free_buffer_page(bpage);
6001 /* The above loop stopped an the last page needing to be freed */
6002 bpage = list_entry(cpu_buffer->pages, struct buffer_page, list);
6003 free_buffer_page(bpage);
6005 /* Free the current reader page */
6006 free_buffer_page(cpu_buffer->reader_page);
6008 /* One page was allocated for the reader page */
6009 cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
6010 struct buffer_page, list);
6011 list_del_init(&cpu_buffer->reader_page->list);
6013 /* The cpu_buffer pages are a link list with no head */
6014 cpu_buffer->pages = cpu_buffer->new_pages.next;
6015 cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev;
6016 cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next;
6018 /* Clear the new_pages list */
6019 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6021 cpu_buffer->head_page
6022 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6023 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
6025 cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
6026 cpu_buffer->nr_pages_to_update = 0;
6028 free_pages((unsigned long)cpu_buffer->free_page, old_order);
6029 cpu_buffer->free_page = NULL;
6031 rb_head_page_activate(cpu_buffer);
6033 rb_check_pages(cpu_buffer);
6036 atomic_dec(&buffer->record_disabled);
6037 mutex_unlock(&buffer->mutex);
6042 buffer->subbuf_order = old_order;
6043 buffer->subbuf_size = old_size;
6045 atomic_dec(&buffer->record_disabled);
6046 mutex_unlock(&buffer->mutex);
6048 for_each_buffer_cpu(buffer, cpu) {
6049 cpu_buffer = buffer->buffers[cpu];
6051 if (!cpu_buffer->nr_pages_to_update)
6054 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6055 list_del_init(&bpage->list);
6056 free_buffer_page(bpage);
6062 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6065 * We only allocate new buffers, never free them if the CPU goes down.
6066 * If we were to free the buffer, then the user would lose any trace that was in
6069 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
6071 struct trace_buffer *buffer;
6074 unsigned long nr_pages;
6076 buffer = container_of(node, struct trace_buffer, node);
6077 if (cpumask_test_cpu(cpu, buffer->cpumask))
6082 /* check if all cpu sizes are same */
6083 for_each_buffer_cpu(buffer, cpu_i) {
6084 /* fill in the size from first enabled cpu */
6086 nr_pages = buffer->buffers[cpu_i]->nr_pages;
6087 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
6092 /* allocate minimum pages, user can later expand it */
6095 buffer->buffers[cpu] =
6096 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
6097 if (!buffer->buffers[cpu]) {
6098 WARN(1, "failed to allocate ring buffer on CPU %u\n",
6103 cpumask_set_cpu(cpu, buffer->cpumask);
6107 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
6109 * This is a basic integrity check of the ring buffer.
6110 * Late in the boot cycle this test will run when configured in.
6111 * It will kick off a thread per CPU that will go into a loop
6112 * writing to the per cpu ring buffer various sizes of data.
6113 * Some of the data will be large items, some small.
6115 * Another thread is created that goes into a spin, sending out
6116 * IPIs to the other CPUs to also write into the ring buffer.
6117 * this is to test the nesting ability of the buffer.
6119 * Basic stats are recorded and reported. If something in the
6120 * ring buffer should happen that's not expected, a big warning
6121 * is displayed and all ring buffers are disabled.
6123 static struct task_struct *rb_threads[NR_CPUS] __initdata;
6125 struct rb_test_data {
6126 struct trace_buffer *buffer;
6127 unsigned long events;
6128 unsigned long bytes_written;
6129 unsigned long bytes_alloc;
6130 unsigned long bytes_dropped;
6131 unsigned long events_nested;
6132 unsigned long bytes_written_nested;
6133 unsigned long bytes_alloc_nested;
6134 unsigned long bytes_dropped_nested;
6135 int min_size_nested;
6136 int max_size_nested;
6143 static struct rb_test_data rb_data[NR_CPUS] __initdata;
6146 #define RB_TEST_BUFFER_SIZE 1048576
6148 static char rb_string[] __initdata =
6149 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
6150 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
6151 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
6153 static bool rb_test_started __initdata;
6160 static __init int rb_write_something(struct rb_test_data *data, bool nested)
6162 struct ring_buffer_event *event;
6163 struct rb_item *item;
6170 /* Have nested writes different that what is written */
6171 cnt = data->cnt + (nested ? 27 : 0);
6173 /* Multiply cnt by ~e, to make some unique increment */
6174 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
6176 len = size + sizeof(struct rb_item);
6178 started = rb_test_started;
6179 /* read rb_test_started before checking buffer enabled */
6182 event = ring_buffer_lock_reserve(data->buffer, len);
6184 /* Ignore dropped events before test starts. */
6187 data->bytes_dropped += len;
6189 data->bytes_dropped_nested += len;
6194 event_len = ring_buffer_event_length(event);
6196 if (RB_WARN_ON(data->buffer, event_len < len))
6199 item = ring_buffer_event_data(event);
6201 memcpy(item->str, rb_string, size);
6204 data->bytes_alloc_nested += event_len;
6205 data->bytes_written_nested += len;
6206 data->events_nested++;
6207 if (!data->min_size_nested || len < data->min_size_nested)
6208 data->min_size_nested = len;
6209 if (len > data->max_size_nested)
6210 data->max_size_nested = len;
6212 data->bytes_alloc += event_len;
6213 data->bytes_written += len;
6215 if (!data->min_size || len < data->min_size)
6216 data->max_size = len;
6217 if (len > data->max_size)
6218 data->max_size = len;
6222 ring_buffer_unlock_commit(data->buffer);
6227 static __init int rb_test(void *arg)
6229 struct rb_test_data *data = arg;
6231 while (!kthread_should_stop()) {
6232 rb_write_something(data, false);
6235 set_current_state(TASK_INTERRUPTIBLE);
6236 /* Now sleep between a min of 100-300us and a max of 1ms */
6237 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
6243 static __init void rb_ipi(void *ignore)
6245 struct rb_test_data *data;
6246 int cpu = smp_processor_id();
6248 data = &rb_data[cpu];
6249 rb_write_something(data, true);
6252 static __init int rb_hammer_test(void *arg)
6254 while (!kthread_should_stop()) {
6256 /* Send an IPI to all cpus to write data! */
6257 smp_call_function(rb_ipi, NULL, 1);
6258 /* No sleep, but for non preempt, let others run */
6265 static __init int test_ringbuffer(void)
6267 struct task_struct *rb_hammer;
6268 struct trace_buffer *buffer;
6272 if (security_locked_down(LOCKDOWN_TRACEFS)) {
6273 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6277 pr_info("Running ring buffer tests...\n");
6279 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
6280 if (WARN_ON(!buffer))
6283 /* Disable buffer so that threads can't write to it yet */
6284 ring_buffer_record_off(buffer);
6286 for_each_online_cpu(cpu) {
6287 rb_data[cpu].buffer = buffer;
6288 rb_data[cpu].cpu = cpu;
6289 rb_data[cpu].cnt = cpu;
6290 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
6291 cpu, "rbtester/%u");
6292 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
6293 pr_cont("FAILED\n");
6294 ret = PTR_ERR(rb_threads[cpu]);
6299 /* Now create the rb hammer! */
6300 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
6301 if (WARN_ON(IS_ERR(rb_hammer))) {
6302 pr_cont("FAILED\n");
6303 ret = PTR_ERR(rb_hammer);
6307 ring_buffer_record_on(buffer);
6309 * Show buffer is enabled before setting rb_test_started.
6310 * Yes there's a small race window where events could be
6311 * dropped and the thread wont catch it. But when a ring
6312 * buffer gets enabled, there will always be some kind of
6313 * delay before other CPUs see it. Thus, we don't care about
6314 * those dropped events. We care about events dropped after
6315 * the threads see that the buffer is active.
6318 rb_test_started = true;
6320 set_current_state(TASK_INTERRUPTIBLE);
6321 /* Just run for 10 seconds */;
6322 schedule_timeout(10 * HZ);
6324 kthread_stop(rb_hammer);
6327 for_each_online_cpu(cpu) {
6328 if (!rb_threads[cpu])
6330 kthread_stop(rb_threads[cpu]);
6333 ring_buffer_free(buffer);
6338 pr_info("finished\n");
6339 for_each_online_cpu(cpu) {
6340 struct ring_buffer_event *event;
6341 struct rb_test_data *data = &rb_data[cpu];
6342 struct rb_item *item;
6343 unsigned long total_events;
6344 unsigned long total_dropped;
6345 unsigned long total_written;
6346 unsigned long total_alloc;
6347 unsigned long total_read = 0;
6348 unsigned long total_size = 0;
6349 unsigned long total_len = 0;
6350 unsigned long total_lost = 0;
6353 int small_event_size;
6357 total_events = data->events + data->events_nested;
6358 total_written = data->bytes_written + data->bytes_written_nested;
6359 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
6360 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
6362 big_event_size = data->max_size + data->max_size_nested;
6363 small_event_size = data->min_size + data->min_size_nested;
6365 pr_info("CPU %d:\n", cpu);
6366 pr_info(" events: %ld\n", total_events);
6367 pr_info(" dropped bytes: %ld\n", total_dropped);
6368 pr_info(" alloced bytes: %ld\n", total_alloc);
6369 pr_info(" written bytes: %ld\n", total_written);
6370 pr_info(" biggest event: %d\n", big_event_size);
6371 pr_info(" smallest event: %d\n", small_event_size);
6373 if (RB_WARN_ON(buffer, total_dropped))
6378 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
6380 item = ring_buffer_event_data(event);
6381 total_len += ring_buffer_event_length(event);
6382 total_size += item->size + sizeof(struct rb_item);
6383 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
6384 pr_info("FAILED!\n");
6385 pr_info("buffer had: %.*s\n", item->size, item->str);
6386 pr_info("expected: %.*s\n", item->size, rb_string);
6387 RB_WARN_ON(buffer, 1);
6398 pr_info(" read events: %ld\n", total_read);
6399 pr_info(" lost events: %ld\n", total_lost);
6400 pr_info(" total events: %ld\n", total_lost + total_read);
6401 pr_info(" recorded len bytes: %ld\n", total_len);
6402 pr_info(" recorded size bytes: %ld\n", total_size);
6404 pr_info(" With dropped events, record len and size may not match\n"
6405 " alloced and written from above\n");
6407 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6408 total_size != total_written))
6411 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6417 pr_info("Ring buffer PASSED!\n");
6419 ring_buffer_free(buffer);
6423 late_initcall(test_ringbuffer);
6424 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */