1 // SPDX-License-Identifier: GPL-2.0
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/cacheflush.h>
13 #include <linux/trace_seq.h>
14 #include <linux/spinlock.h>
15 #include <linux/irq_work.h>
16 #include <linux/security.h>
17 #include <linux/uaccess.h>
18 #include <linux/hardirq.h>
19 #include <linux/kthread.h> /* for self test */
20 #include <linux/module.h>
21 #include <linux/percpu.h>
22 #include <linux/mutex.h>
23 #include <linux/delay.h>
24 #include <linux/slab.h>
25 #include <linux/init.h>
26 #include <linux/hash.h>
27 #include <linux/list.h>
28 #include <linux/cpu.h>
29 #include <linux/oom.h>
32 #include <asm/local64.h>
33 #include <asm/local.h>
38 * The "absolute" timestamp in the buffer is only 59 bits.
39 * If a clock has the 5 MSBs set, it needs to be saved and
42 #define TS_MSB (0xf8ULL << 56)
43 #define ABS_TS_MASK (~TS_MSB)
45 static void update_pages_handler(struct work_struct *work);
47 #define RING_BUFFER_META_MAGIC 0xBADFEED
49 struct ring_buffer_meta {
52 unsigned long text_addr;
53 unsigned long data_addr;
54 unsigned long first_buffer;
55 unsigned long head_buffer;
56 unsigned long commit_buffer;
63 * The ring buffer header is special. We must manually up keep it.
65 int ring_buffer_print_entry_header(struct trace_seq *s)
67 trace_seq_puts(s, "# compressed entry header\n");
68 trace_seq_puts(s, "\ttype_len : 5 bits\n");
69 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
70 trace_seq_puts(s, "\tarray : 32 bits\n");
71 trace_seq_putc(s, '\n');
72 trace_seq_printf(s, "\tpadding : type == %d\n",
73 RINGBUF_TYPE_PADDING);
74 trace_seq_printf(s, "\ttime_extend : type == %d\n",
75 RINGBUF_TYPE_TIME_EXTEND);
76 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
77 RINGBUF_TYPE_TIME_STAMP);
78 trace_seq_printf(s, "\tdata max type_len == %d\n",
79 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
81 return !trace_seq_has_overflowed(s);
85 * The ring buffer is made up of a list of pages. A separate list of pages is
86 * allocated for each CPU. A writer may only write to a buffer that is
87 * associated with the CPU it is currently executing on. A reader may read
88 * from any per cpu buffer.
90 * The reader is special. For each per cpu buffer, the reader has its own
91 * reader page. When a reader has read the entire reader page, this reader
92 * page is swapped with another page in the ring buffer.
94 * Now, as long as the writer is off the reader page, the reader can do what
95 * ever it wants with that page. The writer will never write to that page
96 * again (as long as it is out of the ring buffer).
98 * Here's some silly ASCII art.
101 * |reader| RING BUFFER
103 * +------+ +---+ +---+ +---+
112 * |reader| RING BUFFER
113 * |page |------------------v
114 * +------+ +---+ +---+ +---+
123 * |reader| RING BUFFER
124 * |page |------------------v
125 * +------+ +---+ +---+ +---+
127 * | +---+ +---+ +---+
130 * +------------------------------+
134 * |buffer| RING BUFFER
135 * |page |------------------v
136 * +------+ +---+ +---+ +---+
138 * | New +---+ +---+ +---+
141 * +------------------------------+
144 * After we make this swap, the reader can hand this page off to the splice
145 * code and be done with it. It can even allocate a new page if it needs to
146 * and swap that into the ring buffer.
148 * We will be using cmpxchg soon to make all this lockless.
152 /* Used for individual buffers (after the counter) */
153 #define RB_BUFFER_OFF (1 << 20)
155 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
157 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
158 #define RB_ALIGNMENT 4U
159 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
160 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
162 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
163 # define RB_FORCE_8BYTE_ALIGNMENT 0
164 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
166 # define RB_FORCE_8BYTE_ALIGNMENT 1
167 # define RB_ARCH_ALIGNMENT 8U
170 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
172 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
173 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
176 RB_LEN_TIME_EXTEND = 8,
177 RB_LEN_TIME_STAMP = 8,
180 #define skip_time_extend(event) \
181 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
183 #define extended_time(event) \
184 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
186 static inline bool rb_null_event(struct ring_buffer_event *event)
188 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
191 static void rb_event_set_padding(struct ring_buffer_event *event)
193 /* padding has a NULL time_delta */
194 event->type_len = RINGBUF_TYPE_PADDING;
195 event->time_delta = 0;
199 rb_event_data_length(struct ring_buffer_event *event)
204 length = event->type_len * RB_ALIGNMENT;
206 length = event->array[0];
207 return length + RB_EVNT_HDR_SIZE;
211 * Return the length of the given event. Will return
212 * the length of the time extend if the event is a
215 static inline unsigned
216 rb_event_length(struct ring_buffer_event *event)
218 switch (event->type_len) {
219 case RINGBUF_TYPE_PADDING:
220 if (rb_null_event(event))
223 return event->array[0] + RB_EVNT_HDR_SIZE;
225 case RINGBUF_TYPE_TIME_EXTEND:
226 return RB_LEN_TIME_EXTEND;
228 case RINGBUF_TYPE_TIME_STAMP:
229 return RB_LEN_TIME_STAMP;
231 case RINGBUF_TYPE_DATA:
232 return rb_event_data_length(event);
241 * Return total length of time extend and data,
242 * or just the event length for all other events.
244 static inline unsigned
245 rb_event_ts_length(struct ring_buffer_event *event)
249 if (extended_time(event)) {
250 /* time extends include the data event after it */
251 len = RB_LEN_TIME_EXTEND;
252 event = skip_time_extend(event);
254 return len + rb_event_length(event);
258 * ring_buffer_event_length - return the length of the event
259 * @event: the event to get the length of
261 * Returns the size of the data load of a data event.
262 * If the event is something other than a data event, it
263 * returns the size of the event itself. With the exception
264 * of a TIME EXTEND, where it still returns the size of the
265 * data load of the data event after it.
267 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
271 if (extended_time(event))
272 event = skip_time_extend(event);
274 length = rb_event_length(event);
275 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
277 length -= RB_EVNT_HDR_SIZE;
278 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
279 length -= sizeof(event->array[0]);
282 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
284 /* inline for ring buffer fast paths */
285 static __always_inline void *
286 rb_event_data(struct ring_buffer_event *event)
288 if (extended_time(event))
289 event = skip_time_extend(event);
290 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
291 /* If length is in len field, then array[0] has the data */
293 return (void *)&event->array[0];
294 /* Otherwise length is in array[0] and array[1] has the data */
295 return (void *)&event->array[1];
299 * ring_buffer_event_data - return the data of the event
300 * @event: the event to get the data from
302 void *ring_buffer_event_data(struct ring_buffer_event *event)
304 return rb_event_data(event);
306 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
308 #define for_each_buffer_cpu(buffer, cpu) \
309 for_each_cpu(cpu, buffer->cpumask)
311 #define for_each_online_buffer_cpu(buffer, cpu) \
312 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
315 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
316 #define TS_DELTA_TEST (~TS_MASK)
318 static u64 rb_event_time_stamp(struct ring_buffer_event *event)
322 ts = event->array[0];
324 ts += event->time_delta;
329 /* Flag when events were overwritten */
330 #define RB_MISSED_EVENTS (1 << 31)
331 /* Missed count stored at end */
332 #define RB_MISSED_STORED (1 << 30)
334 #define RB_MISSED_MASK (3 << 30)
336 struct buffer_data_page {
337 u64 time_stamp; /* page time stamp */
338 local_t commit; /* write committed index */
339 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
342 struct buffer_data_read_page {
343 unsigned order; /* order of the page */
344 struct buffer_data_page *data; /* actual data, stored in this page */
348 * Note, the buffer_page list must be first. The buffer pages
349 * are allocated in cache lines, which means that each buffer
350 * page will be at the beginning of a cache line, and thus
351 * the least significant bits will be zero. We use this to
352 * add flags in the list struct pointers, to make the ring buffer
356 struct list_head list; /* list of buffer pages */
357 local_t write; /* index for next write */
358 unsigned read; /* index for next read */
359 local_t entries; /* entries on this page */
360 unsigned long real_end; /* real end of data */
361 unsigned order; /* order of the page */
362 u32 id:30; /* ID for external mapping */
363 u32 range:1; /* Mapped via a range */
364 struct buffer_data_page *page; /* Actual data page */
368 * The buffer page counters, write and entries, must be reset
369 * atomically when crossing page boundaries. To synchronize this
370 * update, two counters are inserted into the number. One is
371 * the actual counter for the write position or count on the page.
373 * The other is a counter of updaters. Before an update happens
374 * the update partition of the counter is incremented. This will
375 * allow the updater to update the counter atomically.
377 * The counter is 20 bits, and the state data is 12.
379 #define RB_WRITE_MASK 0xfffff
380 #define RB_WRITE_INTCNT (1 << 20)
382 static void rb_init_page(struct buffer_data_page *bpage)
384 local_set(&bpage->commit, 0);
387 static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
389 return local_read(&bpage->page->commit);
392 static void free_buffer_page(struct buffer_page *bpage)
394 /* Range pages are not to be freed */
396 free_pages((unsigned long)bpage->page, bpage->order);
401 * We need to fit the time_stamp delta into 27 bits.
403 static inline bool test_time_stamp(u64 delta)
405 return !!(delta & TS_DELTA_TEST);
409 struct irq_work work;
410 wait_queue_head_t waiters;
411 wait_queue_head_t full_waiters;
413 bool waiters_pending;
414 bool full_waiters_pending;
419 * Structure to hold event state and handle nested events.
421 struct rb_event_info {
426 unsigned long length;
427 struct buffer_page *tail_page;
432 * Used for the add_timestamp
434 * EXTEND - wants a time extend
435 * ABSOLUTE - the buffer requests all events to have absolute time stamps
436 * FORCE - force a full time stamp.
439 RB_ADD_STAMP_NONE = 0,
440 RB_ADD_STAMP_EXTEND = BIT(1),
441 RB_ADD_STAMP_ABSOLUTE = BIT(2),
442 RB_ADD_STAMP_FORCE = BIT(3)
445 * Used for which event context the event is in.
452 * See trace_recursive_lock() comment below for more details.
463 struct rb_time_struct {
466 typedef struct rb_time_struct rb_time_t;
471 * head_page == tail_page && head == tail then buffer is empty.
473 struct ring_buffer_per_cpu {
475 atomic_t record_disabled;
476 atomic_t resize_disabled;
477 struct trace_buffer *buffer;
478 raw_spinlock_t reader_lock; /* serialize readers */
479 arch_spinlock_t lock;
480 struct lock_class_key lock_key;
481 struct buffer_data_page *free_page;
482 unsigned long nr_pages;
483 unsigned int current_context;
484 struct list_head *pages;
485 /* pages generation counter, incremented when the list changes */
487 struct buffer_page *head_page; /* read from head */
488 struct buffer_page *tail_page; /* write to tail */
489 struct buffer_page *commit_page; /* committed pages */
490 struct buffer_page *reader_page;
491 unsigned long lost_events;
492 unsigned long last_overrun;
494 local_t entries_bytes;
497 local_t commit_overrun;
498 local_t dropped_events;
501 local_t pages_touched;
504 long last_pages_touch;
505 size_t shortest_full;
507 unsigned long read_bytes;
508 rb_time_t write_stamp;
509 rb_time_t before_stamp;
510 u64 event_stamp[MAX_NEST];
512 /* pages removed since last reset */
513 unsigned long pages_removed;
516 unsigned int user_mapped; /* user space mapping */
517 struct mutex mapping_lock;
518 unsigned long *subbuf_ids; /* ID to subbuf VA */
519 struct trace_buffer_meta *meta_page;
520 struct ring_buffer_meta *ring_meta;
522 /* ring buffer pages to update, > 0 to add, < 0 to remove */
523 long nr_pages_to_update;
524 struct list_head new_pages; /* new pages to add */
525 struct work_struct update_pages_work;
526 struct completion update_done;
528 struct rb_irq_work irq_work;
531 struct trace_buffer {
534 atomic_t record_disabled;
536 cpumask_var_t cpumask;
538 struct lock_class_key *reader_lock_key;
542 struct ring_buffer_per_cpu **buffers;
544 struct hlist_node node;
547 struct rb_irq_work irq_work;
550 unsigned long range_addr_start;
551 unsigned long range_addr_end;
553 long last_text_delta;
554 long last_data_delta;
556 unsigned int subbuf_size;
557 unsigned int subbuf_order;
558 unsigned int max_data_size;
561 struct ring_buffer_iter {
562 struct ring_buffer_per_cpu *cpu_buffer;
564 unsigned long next_event;
565 struct buffer_page *head_page;
566 struct buffer_page *cache_reader_page;
567 unsigned long cache_read;
568 unsigned long cache_pages_removed;
571 struct ring_buffer_event *event;
576 int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
578 struct buffer_data_page field;
580 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
581 "offset:0;\tsize:%u;\tsigned:%u;\n",
582 (unsigned int)sizeof(field.time_stamp),
583 (unsigned int)is_signed_type(u64));
585 trace_seq_printf(s, "\tfield: local_t commit;\t"
586 "offset:%u;\tsize:%u;\tsigned:%u;\n",
587 (unsigned int)offsetof(typeof(field), commit),
588 (unsigned int)sizeof(field.commit),
589 (unsigned int)is_signed_type(long));
591 trace_seq_printf(s, "\tfield: int overwrite;\t"
592 "offset:%u;\tsize:%u;\tsigned:%u;\n",
593 (unsigned int)offsetof(typeof(field), commit),
595 (unsigned int)is_signed_type(long));
597 trace_seq_printf(s, "\tfield: char data;\t"
598 "offset:%u;\tsize:%u;\tsigned:%u;\n",
599 (unsigned int)offsetof(typeof(field), data),
600 (unsigned int)buffer->subbuf_size,
601 (unsigned int)is_signed_type(char));
603 return !trace_seq_has_overflowed(s);
606 static inline void rb_time_read(rb_time_t *t, u64 *ret)
608 *ret = local64_read(&t->time);
610 static void rb_time_set(rb_time_t *t, u64 val)
612 local64_set(&t->time, val);
616 * Enable this to make sure that the event passed to
617 * ring_buffer_event_time_stamp() is not committed and also
618 * is on the buffer that it passed in.
620 //#define RB_VERIFY_EVENT
621 #ifdef RB_VERIFY_EVENT
622 static struct list_head *rb_list_head(struct list_head *list);
623 static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
626 struct buffer_page *page = cpu_buffer->commit_page;
627 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
628 struct list_head *next;
630 unsigned long addr = (unsigned long)event;
634 /* Make sure the event exists and is not committed yet */
636 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
638 commit = local_read(&page->page->commit);
639 write = local_read(&page->write);
640 if (addr >= (unsigned long)&page->page->data[commit] &&
641 addr < (unsigned long)&page->page->data[write])
644 next = rb_list_head(page->list.next);
645 page = list_entry(next, struct buffer_page, list);
650 static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
657 * The absolute time stamp drops the 5 MSBs and some clocks may
658 * require them. The rb_fix_abs_ts() will take a previous full
659 * time stamp, and add the 5 MSB of that time stamp on to the
660 * saved absolute time stamp. Then they are compared in case of
661 * the unlikely event that the latest time stamp incremented
664 static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
666 if (save_ts & TS_MSB) {
667 abs |= save_ts & TS_MSB;
668 /* Check for overflow */
669 if (unlikely(abs < save_ts))
675 static inline u64 rb_time_stamp(struct trace_buffer *buffer);
678 * ring_buffer_event_time_stamp - return the event's current time stamp
679 * @buffer: The buffer that the event is on
680 * @event: the event to get the time stamp of
682 * Note, this must be called after @event is reserved, and before it is
683 * committed to the ring buffer. And must be called from the same
684 * context where the event was reserved (normal, softirq, irq, etc).
686 * Returns the time stamp associated with the current event.
687 * If the event has an extended time stamp, then that is used as
688 * the time stamp to return.
689 * In the highly unlikely case that the event was nested more than
690 * the max nesting, then the write_stamp of the buffer is returned,
691 * otherwise current time is returned, but that really neither of
692 * the last two cases should ever happen.
694 u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
695 struct ring_buffer_event *event)
697 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
701 /* If the event includes an absolute time, then just use that */
702 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
703 ts = rb_event_time_stamp(event);
704 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
707 nest = local_read(&cpu_buffer->committing);
708 verify_event(cpu_buffer, event);
709 if (WARN_ON_ONCE(!nest))
712 /* Read the current saved nesting level time stamp */
713 if (likely(--nest < MAX_NEST))
714 return cpu_buffer->event_stamp[nest];
716 /* Shouldn't happen, warn if it does */
717 WARN_ONCE(1, "nest (%d) greater than max", nest);
720 rb_time_read(&cpu_buffer->write_stamp, &ts);
726 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
727 * @buffer: The ring_buffer to get the number of pages from
728 * @cpu: The cpu of the ring_buffer to get the number of pages from
730 * Returns the number of pages that have content in the ring buffer.
732 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
738 read = local_read(&buffer->buffers[cpu]->pages_read);
739 lost = local_read(&buffer->buffers[cpu]->pages_lost);
740 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
742 if (WARN_ON_ONCE(cnt < lost))
747 /* The reader can read an empty page, but not more than that */
749 WARN_ON_ONCE(read > cnt + 1);
756 static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
758 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
762 nr_pages = cpu_buffer->nr_pages;
763 if (!nr_pages || !full)
767 * Add one as dirty will never equal nr_pages, as the sub-buffer
768 * that the writer is on is not counted as dirty.
769 * This is needed if "buffer_percent" is set to 100.
771 dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
773 return (dirty * 100) >= (full * nr_pages);
777 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
779 * Schedules a delayed work to wake up any task that is blocked on the
780 * ring buffer waiters queue.
782 static void rb_wake_up_waiters(struct irq_work *work)
784 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
786 /* For waiters waiting for the first wake up */
787 (void)atomic_fetch_inc_release(&rbwork->seq);
789 wake_up_all(&rbwork->waiters);
790 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
791 /* Only cpu_buffer sets the above flags */
792 struct ring_buffer_per_cpu *cpu_buffer =
793 container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
795 /* Called from interrupt context */
796 raw_spin_lock(&cpu_buffer->reader_lock);
797 rbwork->wakeup_full = false;
798 rbwork->full_waiters_pending = false;
800 /* Waking up all waiters, they will reset the shortest full */
801 cpu_buffer->shortest_full = 0;
802 raw_spin_unlock(&cpu_buffer->reader_lock);
804 wake_up_all(&rbwork->full_waiters);
809 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
810 * @buffer: The ring buffer to wake waiters on
811 * @cpu: The CPU buffer to wake waiters on
813 * In the case of a file that represents a ring buffer is closing,
814 * it is prudent to wake up any waiters that are on this.
816 void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
818 struct ring_buffer_per_cpu *cpu_buffer;
819 struct rb_irq_work *rbwork;
824 if (cpu == RING_BUFFER_ALL_CPUS) {
826 /* Wake up individual ones too. One level recursion */
827 for_each_buffer_cpu(buffer, cpu)
828 ring_buffer_wake_waiters(buffer, cpu);
830 rbwork = &buffer->irq_work;
832 if (WARN_ON_ONCE(!buffer->buffers))
834 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
837 cpu_buffer = buffer->buffers[cpu];
838 /* The CPU buffer may not have been initialized yet */
841 rbwork = &cpu_buffer->irq_work;
844 /* This can be called in any context */
845 irq_work_queue(&rbwork->work);
848 static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
850 struct ring_buffer_per_cpu *cpu_buffer;
853 /* Reads of all CPUs always waits for any data */
854 if (cpu == RING_BUFFER_ALL_CPUS)
855 return !ring_buffer_empty(buffer);
857 cpu_buffer = buffer->buffers[cpu];
859 if (!ring_buffer_empty_cpu(buffer, cpu)) {
866 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
867 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
868 ret = !pagebusy && full_hit(buffer, cpu, full);
870 if (!ret && (!cpu_buffer->shortest_full ||
871 cpu_buffer->shortest_full > full)) {
872 cpu_buffer->shortest_full = full;
874 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
880 rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
881 int cpu, int full, ring_buffer_cond_fn cond, void *data)
883 if (rb_watermark_hit(buffer, cpu, full))
890 * The events can happen in critical sections where
891 * checking a work queue can cause deadlocks.
892 * After adding a task to the queue, this flag is set
893 * only to notify events to try to wake up the queue
896 * We don't clear it even if the buffer is no longer
897 * empty. The flag only causes the next event to run
898 * irq_work to do the work queue wake up. The worse
899 * that can happen if we race with !trace_empty() is that
900 * an event will cause an irq_work to try to wake up
903 * There's no reason to protect this flag either, as
904 * the work queue and irq_work logic will do the necessary
905 * synchronization for the wake ups. The only thing
906 * that is necessary is that the wake up happens after
907 * a task has been queued. It's OK for spurious wake ups.
910 rbwork->full_waiters_pending = true;
912 rbwork->waiters_pending = true;
917 struct rb_wait_data {
918 struct rb_irq_work *irq_work;
923 * The default wait condition for ring_buffer_wait() is to just to exit the
924 * wait loop the first time it is woken up.
926 static bool rb_wait_once(void *data)
928 struct rb_wait_data *rdata = data;
929 struct rb_irq_work *rbwork = rdata->irq_work;
931 return atomic_read_acquire(&rbwork->seq) != rdata->seq;
935 * ring_buffer_wait - wait for input to the ring buffer
936 * @buffer: buffer to wait on
937 * @cpu: the cpu buffer to wait on
938 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
939 * @cond: condition function to break out of wait (NULL to run once)
940 * @data: the data to pass to @cond.
942 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
943 * as data is added to any of the @buffer's cpu buffers. Otherwise
944 * it will wait for data to be added to a specific cpu buffer.
946 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
947 ring_buffer_cond_fn cond, void *data)
949 struct ring_buffer_per_cpu *cpu_buffer;
950 struct wait_queue_head *waitq;
951 struct rb_irq_work *rbwork;
952 struct rb_wait_data rdata;
956 * Depending on what the caller is waiting for, either any
957 * data in any cpu buffer, or a specific buffer, put the
958 * caller on the appropriate wait queue.
960 if (cpu == RING_BUFFER_ALL_CPUS) {
961 rbwork = &buffer->irq_work;
962 /* Full only makes sense on per cpu reads */
965 if (!cpumask_test_cpu(cpu, buffer->cpumask))
967 cpu_buffer = buffer->buffers[cpu];
968 rbwork = &cpu_buffer->irq_work;
972 waitq = &rbwork->full_waiters;
974 waitq = &rbwork->waiters;
976 /* Set up to exit loop as soon as it is woken */
979 rdata.irq_work = rbwork;
980 rdata.seq = atomic_read_acquire(&rbwork->seq);
984 ret = wait_event_interruptible((*waitq),
985 rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
991 * ring_buffer_poll_wait - poll on buffer input
992 * @buffer: buffer to wait on
993 * @cpu: the cpu buffer to wait on
994 * @filp: the file descriptor
995 * @poll_table: The poll descriptor
996 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
998 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
999 * as data is added to any of the @buffer's cpu buffers. Otherwise
1000 * it will wait for data to be added to a specific cpu buffer.
1002 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1005 __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1006 struct file *filp, poll_table *poll_table, int full)
1008 struct ring_buffer_per_cpu *cpu_buffer;
1009 struct rb_irq_work *rbwork;
1011 if (cpu == RING_BUFFER_ALL_CPUS) {
1012 rbwork = &buffer->irq_work;
1015 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1018 cpu_buffer = buffer->buffers[cpu];
1019 rbwork = &cpu_buffer->irq_work;
1023 poll_wait(filp, &rbwork->full_waiters, poll_table);
1025 if (rb_watermark_hit(buffer, cpu, full))
1026 return EPOLLIN | EPOLLRDNORM;
1028 * Only allow full_waiters_pending update to be seen after
1029 * the shortest_full is set (in rb_watermark_hit). If the
1030 * writer sees the full_waiters_pending flag set, it will
1031 * compare the amount in the ring buffer to shortest_full.
1032 * If the amount in the ring buffer is greater than the
1033 * shortest_full percent, it will call the irq_work handler
1034 * to wake up this list. The irq_handler will reset shortest_full
1035 * back to zero. That's done under the reader_lock, but
1036 * the below smp_mb() makes sure that the update to
1037 * full_waiters_pending doesn't leak up into the above.
1040 rbwork->full_waiters_pending = true;
1044 poll_wait(filp, &rbwork->waiters, poll_table);
1045 rbwork->waiters_pending = true;
1048 * There's a tight race between setting the waiters_pending and
1049 * checking if the ring buffer is empty. Once the waiters_pending bit
1050 * is set, the next event will wake the task up, but we can get stuck
1051 * if there's only a single event in.
1053 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1054 * but adding a memory barrier to all events will cause too much of a
1055 * performance hit in the fast path. We only need a memory barrier when
1056 * the buffer goes from empty to having content. But as this race is
1057 * extremely small, and it's not a problem if another event comes in, we
1058 * will fix it later.
1062 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1063 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1064 return EPOLLIN | EPOLLRDNORM;
1068 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
1069 #define RB_WARN_ON(b, cond) \
1071 int _____ret = unlikely(cond); \
1073 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1074 struct ring_buffer_per_cpu *__b = \
1076 atomic_inc(&__b->buffer->record_disabled); \
1078 atomic_inc(&b->record_disabled); \
1084 /* Up this if you want to test the TIME_EXTENTS and normalization */
1085 #define DEBUG_SHIFT 0
1087 static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1091 /* Skip retpolines :-( */
1092 if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1093 ts = trace_clock_local();
1095 ts = buffer->clock();
1097 /* shift to debug/test normalization and TIME_EXTENTS */
1098 return ts << DEBUG_SHIFT;
1101 u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1105 preempt_disable_notrace();
1106 time = rb_time_stamp(buffer);
1107 preempt_enable_notrace();
1111 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1113 void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1116 /* Just stupid testing the normalize function and deltas */
1117 *ts >>= DEBUG_SHIFT;
1119 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1122 * Making the ring buffer lockless makes things tricky.
1123 * Although writes only happen on the CPU that they are on,
1124 * and they only need to worry about interrupts. Reads can
1125 * happen on any CPU.
1127 * The reader page is always off the ring buffer, but when the
1128 * reader finishes with a page, it needs to swap its page with
1129 * a new one from the buffer. The reader needs to take from
1130 * the head (writes go to the tail). But if a writer is in overwrite
1131 * mode and wraps, it must push the head page forward.
1133 * Here lies the problem.
1135 * The reader must be careful to replace only the head page, and
1136 * not another one. As described at the top of the file in the
1137 * ASCII art, the reader sets its old page to point to the next
1138 * page after head. It then sets the page after head to point to
1139 * the old reader page. But if the writer moves the head page
1140 * during this operation, the reader could end up with the tail.
1142 * We use cmpxchg to help prevent this race. We also do something
1143 * special with the page before head. We set the LSB to 1.
1145 * When the writer must push the page forward, it will clear the
1146 * bit that points to the head page, move the head, and then set
1147 * the bit that points to the new head page.
1149 * We also don't want an interrupt coming in and moving the head
1150 * page on another writer. Thus we use the second LSB to catch
1153 * head->list->prev->next bit 1 bit 0
1156 * Points to head page 0 1
1159 * Note we can not trust the prev pointer of the head page, because:
1161 * +----+ +-----+ +-----+
1162 * | |------>| T |---X--->| N |
1164 * +----+ +-----+ +-----+
1167 * +----------| R |----------+ |
1171 * Key: ---X--> HEAD flag set in pointer
1176 * (see __rb_reserve_next() to see where this happens)
1178 * What the above shows is that the reader just swapped out
1179 * the reader page with a page in the buffer, but before it
1180 * could make the new header point back to the new page added
1181 * it was preempted by a writer. The writer moved forward onto
1182 * the new page added by the reader and is about to move forward
1185 * You can see, it is legitimate for the previous pointer of
1186 * the head (or any page) not to point back to itself. But only
1190 #define RB_PAGE_NORMAL 0UL
1191 #define RB_PAGE_HEAD 1UL
1192 #define RB_PAGE_UPDATE 2UL
1195 #define RB_FLAG_MASK 3UL
1197 /* PAGE_MOVED is not part of the mask */
1198 #define RB_PAGE_MOVED 4UL
1201 * rb_list_head - remove any bit
1203 static struct list_head *rb_list_head(struct list_head *list)
1205 unsigned long val = (unsigned long)list;
1207 return (struct list_head *)(val & ~RB_FLAG_MASK);
1211 * rb_is_head_page - test if the given page is the head page
1213 * Because the reader may move the head_page pointer, we can
1214 * not trust what the head page is (it may be pointing to
1215 * the reader page). But if the next page is a header page,
1216 * its flags will be non zero.
1219 rb_is_head_page(struct buffer_page *page, struct list_head *list)
1223 val = (unsigned long)list->next;
1225 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1226 return RB_PAGE_MOVED;
1228 return val & RB_FLAG_MASK;
1234 * The unique thing about the reader page, is that, if the
1235 * writer is ever on it, the previous pointer never points
1236 * back to the reader page.
1238 static bool rb_is_reader_page(struct buffer_page *page)
1240 struct list_head *list = page->list.prev;
1242 return rb_list_head(list->next) != &page->list;
1246 * rb_set_list_to_head - set a list_head to be pointing to head.
1248 static void rb_set_list_to_head(struct list_head *list)
1252 ptr = (unsigned long *)&list->next;
1253 *ptr |= RB_PAGE_HEAD;
1254 *ptr &= ~RB_PAGE_UPDATE;
1258 * rb_head_page_activate - sets up head page
1260 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1262 struct buffer_page *head;
1264 head = cpu_buffer->head_page;
1269 * Set the previous list pointer to have the HEAD flag.
1271 rb_set_list_to_head(head->list.prev);
1273 if (cpu_buffer->ring_meta) {
1274 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
1275 meta->head_buffer = (unsigned long)head->page;
1279 static void rb_list_head_clear(struct list_head *list)
1281 unsigned long *ptr = (unsigned long *)&list->next;
1283 *ptr &= ~RB_FLAG_MASK;
1287 * rb_head_page_deactivate - clears head page ptr (for free list)
1290 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1292 struct list_head *hd;
1294 /* Go through the whole list and clear any pointers found. */
1295 rb_list_head_clear(cpu_buffer->pages);
1297 list_for_each(hd, cpu_buffer->pages)
1298 rb_list_head_clear(hd);
1301 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1302 struct buffer_page *head,
1303 struct buffer_page *prev,
1304 int old_flag, int new_flag)
1306 struct list_head *list;
1307 unsigned long val = (unsigned long)&head->list;
1312 val &= ~RB_FLAG_MASK;
1314 ret = cmpxchg((unsigned long *)&list->next,
1315 val | old_flag, val | new_flag);
1317 /* check if the reader took the page */
1318 if ((ret & ~RB_FLAG_MASK) != val)
1319 return RB_PAGE_MOVED;
1321 return ret & RB_FLAG_MASK;
1324 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1325 struct buffer_page *head,
1326 struct buffer_page *prev,
1329 return rb_head_page_set(cpu_buffer, head, prev,
1330 old_flag, RB_PAGE_UPDATE);
1333 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1334 struct buffer_page *head,
1335 struct buffer_page *prev,
1338 return rb_head_page_set(cpu_buffer, head, prev,
1339 old_flag, RB_PAGE_HEAD);
1342 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1343 struct buffer_page *head,
1344 struct buffer_page *prev,
1347 return rb_head_page_set(cpu_buffer, head, prev,
1348 old_flag, RB_PAGE_NORMAL);
1351 static inline void rb_inc_page(struct buffer_page **bpage)
1353 struct list_head *p = rb_list_head((*bpage)->list.next);
1355 *bpage = list_entry(p, struct buffer_page, list);
1358 static struct buffer_page *
1359 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1361 struct buffer_page *head;
1362 struct buffer_page *page;
1363 struct list_head *list;
1366 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1370 list = cpu_buffer->pages;
1371 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1374 page = head = cpu_buffer->head_page;
1376 * It is possible that the writer moves the header behind
1377 * where we started, and we miss in one loop.
1378 * A second loop should grab the header, but we'll do
1379 * three loops just because I'm paranoid.
1381 for (i = 0; i < 3; i++) {
1383 if (rb_is_head_page(page, page->list.prev)) {
1384 cpu_buffer->head_page = page;
1388 } while (page != head);
1391 RB_WARN_ON(cpu_buffer, 1);
1396 static bool rb_head_page_replace(struct buffer_page *old,
1397 struct buffer_page *new)
1399 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1402 val = *ptr & ~RB_FLAG_MASK;
1403 val |= RB_PAGE_HEAD;
1405 return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
1409 * rb_tail_page_update - move the tail page forward
1411 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1412 struct buffer_page *tail_page,
1413 struct buffer_page *next_page)
1415 unsigned long old_entries;
1416 unsigned long old_write;
1419 * The tail page now needs to be moved forward.
1421 * We need to reset the tail page, but without messing
1422 * with possible erasing of data brought in by interrupts
1423 * that have moved the tail page and are currently on it.
1425 * We add a counter to the write field to denote this.
1427 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1428 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1431 * Just make sure we have seen our old_write and synchronize
1432 * with any interrupts that come in.
1437 * If the tail page is still the same as what we think
1438 * it is, then it is up to us to update the tail
1441 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1442 /* Zero the write counter */
1443 unsigned long val = old_write & ~RB_WRITE_MASK;
1444 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1447 * This will only succeed if an interrupt did
1448 * not come in and change it. In which case, we
1449 * do not want to modify it.
1451 * We add (void) to let the compiler know that we do not care
1452 * about the return value of these functions. We use the
1453 * cmpxchg to only update if an interrupt did not already
1454 * do it for us. If the cmpxchg fails, we don't care.
1456 (void)local_cmpxchg(&next_page->write, old_write, val);
1457 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1460 * No need to worry about races with clearing out the commit.
1461 * it only can increment when a commit takes place. But that
1462 * only happens in the outer most nested commit.
1464 local_set(&next_page->page->commit, 0);
1466 /* Either we update tail_page or an interrupt does */
1467 if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
1468 local_inc(&cpu_buffer->pages_touched);
1472 static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1473 struct buffer_page *bpage)
1475 unsigned long val = (unsigned long)bpage;
1477 RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
1480 static bool rb_check_links(struct ring_buffer_per_cpu *cpu_buffer,
1481 struct list_head *list)
1483 if (RB_WARN_ON(cpu_buffer,
1484 rb_list_head(rb_list_head(list->next)->prev) != list))
1487 if (RB_WARN_ON(cpu_buffer,
1488 rb_list_head(rb_list_head(list->prev)->next) != list))
1495 * rb_check_pages - integrity check of buffer pages
1496 * @cpu_buffer: CPU buffer with pages to test
1498 * As a safety measure we check to make sure the data pages have not
1501 static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1503 struct list_head *head, *tmp;
1504 unsigned long buffer_cnt;
1505 unsigned long flags;
1509 * Walk the linked list underpinning the ring buffer and validate all
1510 * its next and prev links.
1512 * The check acquires the reader_lock to avoid concurrent processing
1513 * with code that could be modifying the list. However, the lock cannot
1514 * be held for the entire duration of the walk, as this would make the
1515 * time when interrupts are disabled non-deterministic, dependent on the
1516 * ring buffer size. Therefore, the code releases and re-acquires the
1517 * lock after checking each page. The ring_buffer_per_cpu.cnt variable
1518 * is then used to detect if the list was modified while the lock was
1519 * not held, in which case the check needs to be restarted.
1521 * The code attempts to perform the check at most three times before
1522 * giving up. This is acceptable because this is only a self-validation
1523 * to detect problems early on. In practice, the list modification
1524 * operations are fairly spaced, and so this check typically succeeds at
1525 * most on the second try.
1531 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1532 head = rb_list_head(cpu_buffer->pages);
1533 if (!rb_check_links(cpu_buffer, head))
1535 buffer_cnt = cpu_buffer->cnt;
1537 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1540 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1542 if (buffer_cnt != cpu_buffer->cnt) {
1543 /* The list was updated, try again. */
1544 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1548 tmp = rb_list_head(tmp->next);
1550 /* The iteration circled back, all is done. */
1553 if (!rb_check_links(cpu_buffer, tmp))
1556 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1560 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1564 * Take an address, add the meta data size as well as the array of
1565 * array subbuffer indexes, then align it to a subbuffer size.
1567 * This is used to help find the next per cpu subbuffer within a mapped range.
1569 static unsigned long
1570 rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
1572 addr += sizeof(struct ring_buffer_meta) +
1573 sizeof(int) * nr_subbufs;
1574 return ALIGN(addr, subbuf_size);
1578 * Return the ring_buffer_meta for a given @cpu.
1580 static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu)
1582 int subbuf_size = buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
1583 unsigned long ptr = buffer->range_addr_start;
1584 struct ring_buffer_meta *meta;
1590 /* When nr_pages passed in is zero, the first meta has already been initialized */
1592 meta = (struct ring_buffer_meta *)ptr;
1593 nr_subbufs = meta->nr_subbufs;
1596 /* Include the reader page */
1597 nr_subbufs = nr_pages + 1;
1601 * The first chunk may not be subbuffer aligned, where as
1602 * the rest of the chunks are.
1605 ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
1606 ptr += subbuf_size * nr_subbufs;
1608 /* We can use multiplication to find chunks greater than 1 */
1613 /* Save the beginning of this CPU chunk */
1615 ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
1616 ptr += subbuf_size * nr_subbufs;
1618 /* Now all chunks after this are the same size */
1620 ptr += size * (cpu - 2);
1626 /* Return the start of subbufs given the meta pointer */
1627 static void *rb_subbufs_from_meta(struct ring_buffer_meta *meta)
1629 int subbuf_size = meta->subbuf_size;
1632 ptr = (unsigned long)meta;
1633 ptr = rb_range_align_subbuf(ptr, subbuf_size, meta->nr_subbufs);
1639 * Return a specific sub-buffer for a given @cpu defined by @idx.
1641 static void *rb_range_buffer(struct ring_buffer_per_cpu *cpu_buffer, int idx)
1643 struct ring_buffer_meta *meta;
1647 meta = rb_range_meta(cpu_buffer->buffer, 0, cpu_buffer->cpu);
1651 if (WARN_ON_ONCE(idx >= meta->nr_subbufs))
1654 subbuf_size = meta->subbuf_size;
1656 /* Map this buffer to the order that's in meta->buffers[] */
1657 idx = meta->buffers[idx];
1659 ptr = (unsigned long)rb_subbufs_from_meta(meta);
1661 ptr += subbuf_size * idx;
1662 if (ptr + subbuf_size > cpu_buffer->buffer->range_addr_end)
1669 * See if the existing memory contains valid ring buffer data.
1670 * As the previous kernel must be the same as this kernel, all
1671 * the calculations (size of buffers and number of buffers)
1674 static bool rb_meta_valid(struct ring_buffer_meta *meta, int cpu,
1675 struct trace_buffer *buffer, int nr_pages,
1676 unsigned long *subbuf_mask)
1678 int subbuf_size = PAGE_SIZE;
1679 struct buffer_data_page *subbuf;
1680 unsigned long buffers_start;
1681 unsigned long buffers_end;
1687 /* Check the meta magic and meta struct size */
1688 if (meta->magic != RING_BUFFER_META_MAGIC ||
1689 meta->struct_size != sizeof(*meta)) {
1690 pr_info("Ring buffer boot meta[%d] mismatch of magic or struct size\n", cpu);
1694 /* The subbuffer's size and number of subbuffers must match */
1695 if (meta->subbuf_size != subbuf_size ||
1696 meta->nr_subbufs != nr_pages + 1) {
1697 pr_info("Ring buffer boot meta [%d] mismatch of subbuf_size/nr_pages\n", cpu);
1701 buffers_start = meta->first_buffer;
1702 buffers_end = meta->first_buffer + (subbuf_size * meta->nr_subbufs);
1704 /* Is the head and commit buffers within the range of buffers? */
1705 if (meta->head_buffer < buffers_start ||
1706 meta->head_buffer >= buffers_end) {
1707 pr_info("Ring buffer boot meta [%d] head buffer out of range\n", cpu);
1711 if (meta->commit_buffer < buffers_start ||
1712 meta->commit_buffer >= buffers_end) {
1713 pr_info("Ring buffer boot meta [%d] commit buffer out of range\n", cpu);
1717 subbuf = rb_subbufs_from_meta(meta);
1719 bitmap_clear(subbuf_mask, 0, meta->nr_subbufs);
1721 /* Is the meta buffers and the subbufs themselves have correct data? */
1722 for (i = 0; i < meta->nr_subbufs; i++) {
1723 if (meta->buffers[i] < 0 ||
1724 meta->buffers[i] >= meta->nr_subbufs) {
1725 pr_info("Ring buffer boot meta [%d] array out of range\n", cpu);
1729 if ((unsigned)local_read(&subbuf->commit) > subbuf_size) {
1730 pr_info("Ring buffer boot meta [%d] buffer invalid commit\n", cpu);
1734 if (test_bit(meta->buffers[i], subbuf_mask)) {
1735 pr_info("Ring buffer boot meta [%d] array has duplicates\n", cpu);
1739 set_bit(meta->buffers[i], subbuf_mask);
1740 subbuf = (void *)subbuf + subbuf_size;
1746 static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf);
1748 static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu,
1749 unsigned long long *timestamp, u64 *delta_ptr)
1751 struct ring_buffer_event *event;
1759 ts = dpage->time_stamp;
1761 for (e = 0; e < tail; e += rb_event_length(event)) {
1763 event = (struct ring_buffer_event *)(dpage->data + e);
1765 switch (event->type_len) {
1767 case RINGBUF_TYPE_TIME_EXTEND:
1768 delta = rb_event_time_stamp(event);
1772 case RINGBUF_TYPE_TIME_STAMP:
1773 delta = rb_event_time_stamp(event);
1774 delta = rb_fix_abs_ts(delta, ts);
1783 case RINGBUF_TYPE_PADDING:
1784 if (event->time_delta == 1)
1787 case RINGBUF_TYPE_DATA:
1789 ts += event->time_delta;
1800 static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu)
1802 unsigned long long ts;
1806 tail = local_read(&dpage->commit);
1807 return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
1810 /* If the meta data has been validated, now validate the events */
1811 static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
1813 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
1814 struct buffer_page *head_page;
1815 unsigned long entry_bytes = 0;
1816 unsigned long entries = 0;
1820 if (!meta || !meta->head_buffer)
1823 /* Do the reader page first */
1824 ret = rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu);
1826 pr_info("Ring buffer reader page is invalid\n");
1830 entry_bytes += local_read(&cpu_buffer->reader_page->page->commit);
1831 local_set(&cpu_buffer->reader_page->entries, ret);
1833 head_page = cpu_buffer->head_page;
1835 /* If both the head and commit are on the reader_page then we are done. */
1836 if (head_page == cpu_buffer->reader_page &&
1837 head_page == cpu_buffer->commit_page)
1840 /* Iterate until finding the commit page */
1841 for (i = 0; i < meta->nr_subbufs + 1; i++, rb_inc_page(&head_page)) {
1843 /* Reader page has already been done */
1844 if (head_page == cpu_buffer->reader_page)
1847 ret = rb_validate_buffer(head_page->page, cpu_buffer->cpu);
1849 pr_info("Ring buffer meta [%d] invalid buffer page\n",
1854 /* If the buffer has content, update pages_touched */
1856 local_inc(&cpu_buffer->pages_touched);
1859 entry_bytes += local_read(&head_page->page->commit);
1860 local_set(&cpu_buffer->head_page->entries, ret);
1862 if (head_page == cpu_buffer->commit_page)
1866 if (head_page != cpu_buffer->commit_page) {
1867 pr_info("Ring buffer meta [%d] commit page not found\n",
1872 local_set(&cpu_buffer->entries, entries);
1873 local_set(&cpu_buffer->entries_bytes, entry_bytes);
1875 pr_info("Ring buffer meta [%d] is from previous boot!\n", cpu_buffer->cpu);
1879 /* The content of the buffers are invalid, reset the meta data */
1880 meta->head_buffer = 0;
1881 meta->commit_buffer = 0;
1883 /* Reset the reader page */
1884 local_set(&cpu_buffer->reader_page->entries, 0);
1885 local_set(&cpu_buffer->reader_page->page->commit, 0);
1887 /* Reset all the subbuffers */
1888 for (i = 0; i < meta->nr_subbufs - 1; i++, rb_inc_page(&head_page)) {
1889 local_set(&head_page->entries, 0);
1890 local_set(&head_page->page->commit, 0);
1894 /* Used to calculate data delta */
1895 static char rb_data_ptr[] = "";
1897 #define THIS_TEXT_PTR ((unsigned long)rb_meta_init_text_addr)
1898 #define THIS_DATA_PTR ((unsigned long)rb_data_ptr)
1900 static void rb_meta_init_text_addr(struct ring_buffer_meta *meta)
1902 meta->text_addr = THIS_TEXT_PTR;
1903 meta->data_addr = THIS_DATA_PTR;
1906 static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
1908 struct ring_buffer_meta *meta;
1909 unsigned long *subbuf_mask;
1910 unsigned long delta;
1915 /* Create a mask to test the subbuf array */
1916 subbuf_mask = bitmap_alloc(nr_pages + 1, GFP_KERNEL);
1917 /* If subbuf_mask fails to allocate, then rb_meta_valid() will return false */
1919 for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
1922 meta = rb_range_meta(buffer, nr_pages, cpu);
1924 if (rb_meta_valid(meta, cpu, buffer, nr_pages, subbuf_mask)) {
1925 /* Make the mappings match the current address */
1926 subbuf = rb_subbufs_from_meta(meta);
1927 delta = (unsigned long)subbuf - meta->first_buffer;
1928 meta->first_buffer += delta;
1929 meta->head_buffer += delta;
1930 meta->commit_buffer += delta;
1931 buffer->last_text_delta = THIS_TEXT_PTR - meta->text_addr;
1932 buffer->last_data_delta = THIS_DATA_PTR - meta->data_addr;
1936 if (cpu < nr_cpu_ids - 1)
1937 next_meta = rb_range_meta(buffer, nr_pages, cpu + 1);
1939 next_meta = (void *)buffer->range_addr_end;
1941 memset(meta, 0, next_meta - (void *)meta);
1943 meta->magic = RING_BUFFER_META_MAGIC;
1944 meta->struct_size = sizeof(*meta);
1946 meta->nr_subbufs = nr_pages + 1;
1947 meta->subbuf_size = PAGE_SIZE;
1949 subbuf = rb_subbufs_from_meta(meta);
1951 meta->first_buffer = (unsigned long)subbuf;
1952 rb_meta_init_text_addr(meta);
1955 * The buffers[] array holds the order of the sub-buffers
1956 * that are after the meta data. The sub-buffers may
1957 * be swapped out when read and inserted into a different
1958 * location of the ring buffer. Although their addresses
1959 * remain the same, the buffers[] array contains the
1960 * index into the sub-buffers holding their actual order.
1962 for (i = 0; i < meta->nr_subbufs; i++) {
1963 meta->buffers[i] = i;
1964 rb_init_page(subbuf);
1965 subbuf += meta->subbuf_size;
1968 bitmap_free(subbuf_mask);
1971 static void *rbm_start(struct seq_file *m, loff_t *pos)
1973 struct ring_buffer_per_cpu *cpu_buffer = m->private;
1974 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
1980 if (*pos > meta->nr_subbufs)
1989 static void *rbm_next(struct seq_file *m, void *v, loff_t *pos)
1993 return rbm_start(m, pos);
1996 static int rbm_show(struct seq_file *m, void *v)
1998 struct ring_buffer_per_cpu *cpu_buffer = m->private;
1999 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
2000 unsigned long val = (unsigned long)v;
2003 seq_printf(m, "head_buffer: %d\n",
2004 rb_meta_subbuf_idx(meta, (void *)meta->head_buffer));
2005 seq_printf(m, "commit_buffer: %d\n",
2006 rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer));
2007 seq_printf(m, "subbuf_size: %d\n", meta->subbuf_size);
2008 seq_printf(m, "nr_subbufs: %d\n", meta->nr_subbufs);
2013 seq_printf(m, "buffer[%ld]: %d\n", val, meta->buffers[val]);
2018 static void rbm_stop(struct seq_file *m, void *p)
2022 static const struct seq_operations rb_meta_seq_ops = {
2029 int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buffer, int cpu)
2034 ret = seq_open(file, &rb_meta_seq_ops);
2038 m = file->private_data;
2039 m->private = buffer->buffers[cpu];
2044 /* Map the buffer_pages to the previous head and commit pages */
2045 static void rb_meta_buffer_update(struct ring_buffer_per_cpu *cpu_buffer,
2046 struct buffer_page *bpage)
2048 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
2050 if (meta->head_buffer == (unsigned long)bpage->page)
2051 cpu_buffer->head_page = bpage;
2053 if (meta->commit_buffer == (unsigned long)bpage->page) {
2054 cpu_buffer->commit_page = bpage;
2055 cpu_buffer->tail_page = bpage;
2059 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
2060 long nr_pages, struct list_head *pages)
2062 struct trace_buffer *buffer = cpu_buffer->buffer;
2063 struct ring_buffer_meta *meta = NULL;
2064 struct buffer_page *bpage, *tmp;
2065 bool user_thread = current->mm != NULL;
2070 * Check if the available memory is there first.
2071 * Note, si_mem_available() only gives us a rough estimate of available
2072 * memory. It may not be accurate. But we don't care, we just want
2073 * to prevent doing any allocation when it is obvious that it is
2074 * not going to succeed.
2076 i = si_mem_available();
2081 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
2082 * gracefully without invoking oom-killer and the system is not
2085 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
2088 * If a user thread allocates too much, and si_mem_available()
2089 * reports there's enough memory, even though there is not.
2090 * Make sure the OOM killer kills this thread. This can happen
2091 * even with RETRY_MAYFAIL because another task may be doing
2092 * an allocation after this task has taken all memory.
2093 * This is the task the OOM killer needs to take out during this
2094 * loop, even if it was triggered by an allocation somewhere else.
2097 set_current_oom_origin();
2099 if (buffer->range_addr_start)
2100 meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
2102 for (i = 0; i < nr_pages; i++) {
2105 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
2106 mflags, cpu_to_node(cpu_buffer->cpu));
2110 rb_check_bpage(cpu_buffer, bpage);
2113 * Append the pages as for mapped buffers we want to keep
2116 list_add_tail(&bpage->list, pages);
2119 /* A range was given. Use that for the buffer page */
2120 bpage->page = rb_range_buffer(cpu_buffer, i + 1);
2123 /* If this is valid from a previous boot */
2124 if (meta->head_buffer)
2125 rb_meta_buffer_update(cpu_buffer, bpage);
2129 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
2130 mflags | __GFP_COMP | __GFP_ZERO,
2131 cpu_buffer->buffer->subbuf_order);
2134 bpage->page = page_address(page);
2135 rb_init_page(bpage->page);
2137 bpage->order = cpu_buffer->buffer->subbuf_order;
2139 if (user_thread && fatal_signal_pending(current))
2143 clear_current_oom_origin();
2148 list_for_each_entry_safe(bpage, tmp, pages, list) {
2149 list_del_init(&bpage->list);
2150 free_buffer_page(bpage);
2153 clear_current_oom_origin();
2158 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
2159 unsigned long nr_pages)
2165 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
2169 * The ring buffer page list is a circular list that does not
2170 * start and end with a list head. All page list items point to
2173 cpu_buffer->pages = pages.next;
2176 cpu_buffer->nr_pages = nr_pages;
2178 rb_check_pages(cpu_buffer);
2183 static struct ring_buffer_per_cpu *
2184 rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
2186 struct ring_buffer_per_cpu *cpu_buffer;
2187 struct ring_buffer_meta *meta;
2188 struct buffer_page *bpage;
2192 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
2193 GFP_KERNEL, cpu_to_node(cpu));
2197 cpu_buffer->cpu = cpu;
2198 cpu_buffer->buffer = buffer;
2199 raw_spin_lock_init(&cpu_buffer->reader_lock);
2200 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
2201 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
2202 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
2203 init_completion(&cpu_buffer->update_done);
2204 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
2205 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
2206 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
2207 mutex_init(&cpu_buffer->mapping_lock);
2209 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
2210 GFP_KERNEL, cpu_to_node(cpu));
2212 goto fail_free_buffer;
2214 rb_check_bpage(cpu_buffer, bpage);
2216 cpu_buffer->reader_page = bpage;
2218 if (buffer->range_addr_start) {
2220 * Range mapped buffers have the same restrictions as memory
2223 cpu_buffer->mapped = 1;
2224 cpu_buffer->ring_meta = rb_range_meta(buffer, nr_pages, cpu);
2225 bpage->page = rb_range_buffer(cpu_buffer, 0);
2227 goto fail_free_reader;
2228 if (cpu_buffer->ring_meta->head_buffer)
2229 rb_meta_buffer_update(cpu_buffer, bpage);
2232 page = alloc_pages_node(cpu_to_node(cpu),
2233 GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
2234 cpu_buffer->buffer->subbuf_order);
2236 goto fail_free_reader;
2237 bpage->page = page_address(page);
2238 rb_init_page(bpage->page);
2241 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
2242 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2244 ret = rb_allocate_pages(cpu_buffer, nr_pages);
2246 goto fail_free_reader;
2248 rb_meta_validate_events(cpu_buffer);
2250 /* If the boot meta was valid then this has already been updated */
2251 meta = cpu_buffer->ring_meta;
2252 if (!meta || !meta->head_buffer ||
2253 !cpu_buffer->head_page || !cpu_buffer->commit_page || !cpu_buffer->tail_page) {
2254 if (meta && meta->head_buffer &&
2255 (cpu_buffer->head_page || cpu_buffer->commit_page || cpu_buffer->tail_page)) {
2256 pr_warn("Ring buffer meta buffers not all mapped\n");
2257 if (!cpu_buffer->head_page)
2258 pr_warn(" Missing head_page\n");
2259 if (!cpu_buffer->commit_page)
2260 pr_warn(" Missing commit_page\n");
2261 if (!cpu_buffer->tail_page)
2262 pr_warn(" Missing tail_page\n");
2265 cpu_buffer->head_page
2266 = list_entry(cpu_buffer->pages, struct buffer_page, list);
2267 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
2269 rb_head_page_activate(cpu_buffer);
2271 if (cpu_buffer->ring_meta)
2272 meta->commit_buffer = meta->head_buffer;
2274 /* The valid meta buffer still needs to activate the head page */
2275 rb_head_page_activate(cpu_buffer);
2281 free_buffer_page(cpu_buffer->reader_page);
2288 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
2290 struct list_head *head = cpu_buffer->pages;
2291 struct buffer_page *bpage, *tmp;
2293 irq_work_sync(&cpu_buffer->irq_work.work);
2295 free_buffer_page(cpu_buffer->reader_page);
2298 rb_head_page_deactivate(cpu_buffer);
2300 list_for_each_entry_safe(bpage, tmp, head, list) {
2301 list_del_init(&bpage->list);
2302 free_buffer_page(bpage);
2304 bpage = list_entry(head, struct buffer_page, list);
2305 free_buffer_page(bpage);
2308 free_page((unsigned long)cpu_buffer->free_page);
2313 static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags,
2314 int order, unsigned long start,
2316 struct lock_class_key *key)
2318 struct trace_buffer *buffer;
2325 /* keep it in its own cache line */
2326 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
2331 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
2332 goto fail_free_buffer;
2334 buffer->subbuf_order = order;
2335 subbuf_size = (PAGE_SIZE << order);
2336 buffer->subbuf_size = subbuf_size - BUF_PAGE_HDR_SIZE;
2338 /* Max payload is buffer page size - header (8bytes) */
2339 buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
2341 buffer->flags = flags;
2342 buffer->clock = trace_clock_local;
2343 buffer->reader_lock_key = key;
2345 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
2346 init_waitqueue_head(&buffer->irq_work.waiters);
2348 buffer->cpus = nr_cpu_ids;
2350 bsize = sizeof(void *) * nr_cpu_ids;
2351 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
2353 if (!buffer->buffers)
2354 goto fail_free_cpumask;
2356 /* If start/end are specified, then that overrides size */
2362 size = size / nr_cpu_ids;
2365 * The number of sub-buffers (nr_pages) is determined by the
2366 * total size allocated minus the meta data size.
2367 * Then that is divided by the number of per CPU buffers
2368 * needed, plus account for the integer array index that
2369 * will be appended to the meta data.
2371 nr_pages = (size - sizeof(struct ring_buffer_meta)) /
2372 (subbuf_size + sizeof(int));
2373 /* Need at least two pages plus the reader page */
2375 goto fail_free_buffers;
2378 /* Make sure that the size fits aligned */
2379 for (n = 0, ptr = start; n < nr_cpu_ids; n++) {
2380 ptr += sizeof(struct ring_buffer_meta) +
2381 sizeof(int) * nr_pages;
2382 ptr = ALIGN(ptr, subbuf_size);
2383 ptr += subbuf_size * nr_pages;
2387 goto fail_free_buffers;
2392 /* nr_pages should not count the reader page */
2394 buffer->range_addr_start = start;
2395 buffer->range_addr_end = end;
2397 rb_range_meta_init(buffer, nr_pages);
2400 /* need at least two pages */
2401 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2406 cpu = raw_smp_processor_id();
2407 cpumask_set_cpu(cpu, buffer->cpumask);
2408 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
2409 if (!buffer->buffers[cpu])
2410 goto fail_free_buffers;
2412 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
2414 goto fail_free_buffers;
2416 mutex_init(&buffer->mutex);
2421 for_each_buffer_cpu(buffer, cpu) {
2422 if (buffer->buffers[cpu])
2423 rb_free_cpu_buffer(buffer->buffers[cpu]);
2425 kfree(buffer->buffers);
2428 free_cpumask_var(buffer->cpumask);
2436 * __ring_buffer_alloc - allocate a new ring_buffer
2437 * @size: the size in bytes per cpu that is needed.
2438 * @flags: attributes to set for the ring buffer.
2439 * @key: ring buffer reader_lock_key.
2441 * Currently the only flag that is available is the RB_FL_OVERWRITE
2442 * flag. This flag means that the buffer will overwrite old data
2443 * when the buffer wraps. If this flag is not set, the buffer will
2444 * drop data when the tail hits the head.
2446 struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
2447 struct lock_class_key *key)
2449 /* Default buffer page size - one system page */
2450 return alloc_buffer(size, flags, 0, 0, 0,key);
2453 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
2456 * __ring_buffer_alloc_range - allocate a new ring_buffer from existing memory
2457 * @size: the size in bytes per cpu that is needed.
2458 * @flags: attributes to set for the ring buffer.
2459 * @order: sub-buffer order
2460 * @start: start of allocated range
2461 * @range_size: size of allocated range
2462 * @key: ring buffer reader_lock_key.
2464 * Currently the only flag that is available is the RB_FL_OVERWRITE
2465 * flag. This flag means that the buffer will overwrite old data
2466 * when the buffer wraps. If this flag is not set, the buffer will
2467 * drop data when the tail hits the head.
2469 struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags,
2470 int order, unsigned long start,
2471 unsigned long range_size,
2472 struct lock_class_key *key)
2474 return alloc_buffer(size, flags, order, start, start + range_size, key);
2478 * ring_buffer_last_boot_delta - return the delta offset from last boot
2479 * @buffer: The buffer to return the delta from
2480 * @text: Return text delta
2481 * @data: Return data delta
2483 * Returns: The true if the delta is non zero
2485 bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, long *text,
2491 if (!buffer->last_text_delta)
2494 *text = buffer->last_text_delta;
2495 *data = buffer->last_data_delta;
2501 * ring_buffer_free - free a ring buffer.
2502 * @buffer: the buffer to free.
2505 ring_buffer_free(struct trace_buffer *buffer)
2509 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
2511 irq_work_sync(&buffer->irq_work.work);
2513 for_each_buffer_cpu(buffer, cpu)
2514 rb_free_cpu_buffer(buffer->buffers[cpu]);
2516 kfree(buffer->buffers);
2517 free_cpumask_var(buffer->cpumask);
2521 EXPORT_SYMBOL_GPL(ring_buffer_free);
2523 void ring_buffer_set_clock(struct trace_buffer *buffer,
2526 buffer->clock = clock;
2529 void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
2531 buffer->time_stamp_abs = abs;
2534 bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
2536 return buffer->time_stamp_abs;
2539 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
2541 return local_read(&bpage->entries) & RB_WRITE_MASK;
2544 static inline unsigned long rb_page_write(struct buffer_page *bpage)
2546 return local_read(&bpage->write) & RB_WRITE_MASK;
2550 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
2552 struct list_head *tail_page, *to_remove, *next_page;
2553 struct buffer_page *to_remove_page, *tmp_iter_page;
2554 struct buffer_page *last_page, *first_page;
2555 unsigned long nr_removed;
2556 unsigned long head_bit;
2561 raw_spin_lock_irq(&cpu_buffer->reader_lock);
2562 atomic_inc(&cpu_buffer->record_disabled);
2564 * We don't race with the readers since we have acquired the reader
2565 * lock. We also don't race with writers after disabling recording.
2566 * This makes it easy to figure out the first and the last page to be
2567 * removed from the list. We unlink all the pages in between including
2568 * the first and last pages. This is done in a busy loop so that we
2569 * lose the least number of traces.
2570 * The pages are freed after we restart recording and unlock readers.
2572 tail_page = &cpu_buffer->tail_page->list;
2575 * tail page might be on reader page, we remove the next page
2576 * from the ring buffer
2578 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
2579 tail_page = rb_list_head(tail_page->next);
2580 to_remove = tail_page;
2582 /* start of pages to remove */
2583 first_page = list_entry(rb_list_head(to_remove->next),
2584 struct buffer_page, list);
2586 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
2587 to_remove = rb_list_head(to_remove)->next;
2588 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
2590 /* Read iterators need to reset themselves when some pages removed */
2591 cpu_buffer->pages_removed += nr_removed;
2593 next_page = rb_list_head(to_remove)->next;
2596 * Now we remove all pages between tail_page and next_page.
2597 * Make sure that we have head_bit value preserved for the
2600 tail_page->next = (struct list_head *)((unsigned long)next_page |
2602 next_page = rb_list_head(next_page);
2603 next_page->prev = tail_page;
2605 /* make sure pages points to a valid page in the ring buffer */
2606 cpu_buffer->pages = next_page;
2609 /* update head page */
2611 cpu_buffer->head_page = list_entry(next_page,
2612 struct buffer_page, list);
2614 /* pages are removed, resume tracing and then free the pages */
2615 atomic_dec(&cpu_buffer->record_disabled);
2616 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2618 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
2620 /* last buffer page to remove */
2621 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
2623 tmp_iter_page = first_page;
2628 to_remove_page = tmp_iter_page;
2629 rb_inc_page(&tmp_iter_page);
2631 /* update the counters */
2632 page_entries = rb_page_entries(to_remove_page);
2635 * If something was added to this page, it was full
2636 * since it is not the tail page. So we deduct the
2637 * bytes consumed in ring buffer from here.
2638 * Increment overrun to account for the lost events.
2640 local_add(page_entries, &cpu_buffer->overrun);
2641 local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
2642 local_inc(&cpu_buffer->pages_lost);
2646 * We have already removed references to this list item, just
2647 * free up the buffer_page and its page
2649 free_buffer_page(to_remove_page);
2652 } while (to_remove_page != last_page);
2654 RB_WARN_ON(cpu_buffer, nr_removed);
2656 return nr_removed == 0;
2660 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
2662 struct list_head *pages = &cpu_buffer->new_pages;
2663 unsigned long flags;
2667 /* Can be called at early boot up, where interrupts must not been enabled */
2668 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2670 * We are holding the reader lock, so the reader page won't be swapped
2671 * in the ring buffer. Now we are racing with the writer trying to
2672 * move head page and the tail page.
2673 * We are going to adapt the reader page update process where:
2674 * 1. We first splice the start and end of list of new pages between
2675 * the head page and its previous page.
2676 * 2. We cmpxchg the prev_page->next to point from head page to the
2677 * start of new pages list.
2678 * 3. Finally, we update the head->prev to the end of new list.
2680 * We will try this process 10 times, to make sure that we don't keep
2686 struct list_head *head_page, *prev_page;
2687 struct list_head *last_page, *first_page;
2688 struct list_head *head_page_with_bit;
2689 struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
2693 head_page = &hpage->list;
2694 prev_page = head_page->prev;
2696 first_page = pages->next;
2697 last_page = pages->prev;
2699 head_page_with_bit = (struct list_head *)
2700 ((unsigned long)head_page | RB_PAGE_HEAD);
2702 last_page->next = head_page_with_bit;
2703 first_page->prev = prev_page;
2705 /* caution: head_page_with_bit gets updated on cmpxchg failure */
2706 if (try_cmpxchg(&prev_page->next,
2707 &head_page_with_bit, first_page)) {
2709 * yay, we replaced the page pointer to our new list,
2710 * now, we just have to update to head page's prev
2711 * pointer to point to end of list
2713 head_page->prev = last_page;
2721 INIT_LIST_HEAD(pages);
2723 * If we weren't successful in adding in new pages, warn and stop
2726 RB_WARN_ON(cpu_buffer, !success);
2727 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2729 /* free pages if they weren't inserted */
2731 struct buffer_page *bpage, *tmp;
2732 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2734 list_del_init(&bpage->list);
2735 free_buffer_page(bpage);
2741 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2745 if (cpu_buffer->nr_pages_to_update > 0)
2746 success = rb_insert_pages(cpu_buffer);
2748 success = rb_remove_pages(cpu_buffer,
2749 -cpu_buffer->nr_pages_to_update);
2752 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2755 static void update_pages_handler(struct work_struct *work)
2757 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2758 struct ring_buffer_per_cpu, update_pages_work);
2759 rb_update_pages(cpu_buffer);
2760 complete(&cpu_buffer->update_done);
2764 * ring_buffer_resize - resize the ring buffer
2765 * @buffer: the buffer to resize.
2766 * @size: the new size.
2767 * @cpu_id: the cpu buffer to resize
2769 * Minimum size is 2 * buffer->subbuf_size.
2771 * Returns 0 on success and < 0 on failure.
2773 int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2776 struct ring_buffer_per_cpu *cpu_buffer;
2777 unsigned long nr_pages;
2781 * Always succeed at resizing a non-existent buffer:
2786 /* Make sure the requested buffer exists */
2787 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2788 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2791 nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
2793 /* we need a minimum of two pages */
2797 /* prevent another thread from changing buffer sizes */
2798 mutex_lock(&buffer->mutex);
2799 atomic_inc(&buffer->resizing);
2801 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2803 * Don't succeed if resizing is disabled, as a reader might be
2804 * manipulating the ring buffer and is expecting a sane state while
2807 for_each_buffer_cpu(buffer, cpu) {
2808 cpu_buffer = buffer->buffers[cpu];
2809 if (atomic_read(&cpu_buffer->resize_disabled)) {
2811 goto out_err_unlock;
2815 /* calculate the pages to update */
2816 for_each_buffer_cpu(buffer, cpu) {
2817 cpu_buffer = buffer->buffers[cpu];
2819 cpu_buffer->nr_pages_to_update = nr_pages -
2820 cpu_buffer->nr_pages;
2822 * nothing more to do for removing pages or no update
2824 if (cpu_buffer->nr_pages_to_update <= 0)
2827 * to add pages, make sure all new pages can be
2828 * allocated without receiving ENOMEM
2830 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2831 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2832 &cpu_buffer->new_pages)) {
2833 /* not enough memory for new pages */
2843 * Fire off all the required work handlers
2844 * We can't schedule on offline CPUs, but it's not necessary
2845 * since we can change their buffer sizes without any race.
2847 for_each_buffer_cpu(buffer, cpu) {
2848 cpu_buffer = buffer->buffers[cpu];
2849 if (!cpu_buffer->nr_pages_to_update)
2852 /* Can't run something on an offline CPU. */
2853 if (!cpu_online(cpu)) {
2854 rb_update_pages(cpu_buffer);
2855 cpu_buffer->nr_pages_to_update = 0;
2857 /* Run directly if possible. */
2859 if (cpu != smp_processor_id()) {
2861 schedule_work_on(cpu,
2862 &cpu_buffer->update_pages_work);
2864 update_pages_handler(&cpu_buffer->update_pages_work);
2870 /* wait for all the updates to complete */
2871 for_each_buffer_cpu(buffer, cpu) {
2872 cpu_buffer = buffer->buffers[cpu];
2873 if (!cpu_buffer->nr_pages_to_update)
2876 if (cpu_online(cpu))
2877 wait_for_completion(&cpu_buffer->update_done);
2878 cpu_buffer->nr_pages_to_update = 0;
2883 cpu_buffer = buffer->buffers[cpu_id];
2885 if (nr_pages == cpu_buffer->nr_pages)
2889 * Don't succeed if resizing is disabled, as a reader might be
2890 * manipulating the ring buffer and is expecting a sane state while
2893 if (atomic_read(&cpu_buffer->resize_disabled)) {
2895 goto out_err_unlock;
2898 cpu_buffer->nr_pages_to_update = nr_pages -
2899 cpu_buffer->nr_pages;
2901 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2902 if (cpu_buffer->nr_pages_to_update > 0 &&
2903 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2904 &cpu_buffer->new_pages)) {
2911 /* Can't run something on an offline CPU. */
2912 if (!cpu_online(cpu_id))
2913 rb_update_pages(cpu_buffer);
2915 /* Run directly if possible. */
2917 if (cpu_id == smp_processor_id()) {
2918 rb_update_pages(cpu_buffer);
2922 schedule_work_on(cpu_id,
2923 &cpu_buffer->update_pages_work);
2924 wait_for_completion(&cpu_buffer->update_done);
2928 cpu_buffer->nr_pages_to_update = 0;
2934 * The ring buffer resize can happen with the ring buffer
2935 * enabled, so that the update disturbs the tracing as little
2936 * as possible. But if the buffer is disabled, we do not need
2937 * to worry about that, and we can take the time to verify
2938 * that the buffer is not corrupt.
2940 if (atomic_read(&buffer->record_disabled)) {
2941 atomic_inc(&buffer->record_disabled);
2943 * Even though the buffer was disabled, we must make sure
2944 * that it is truly disabled before calling rb_check_pages.
2945 * There could have been a race between checking
2946 * record_disable and incrementing it.
2949 for_each_buffer_cpu(buffer, cpu) {
2950 cpu_buffer = buffer->buffers[cpu];
2951 rb_check_pages(cpu_buffer);
2953 atomic_dec(&buffer->record_disabled);
2956 atomic_dec(&buffer->resizing);
2957 mutex_unlock(&buffer->mutex);
2961 for_each_buffer_cpu(buffer, cpu) {
2962 struct buffer_page *bpage, *tmp;
2964 cpu_buffer = buffer->buffers[cpu];
2965 cpu_buffer->nr_pages_to_update = 0;
2967 if (list_empty(&cpu_buffer->new_pages))
2970 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2972 list_del_init(&bpage->list);
2973 free_buffer_page(bpage);
2977 atomic_dec(&buffer->resizing);
2978 mutex_unlock(&buffer->mutex);
2981 EXPORT_SYMBOL_GPL(ring_buffer_resize);
2983 void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2985 mutex_lock(&buffer->mutex);
2987 buffer->flags |= RB_FL_OVERWRITE;
2989 buffer->flags &= ~RB_FL_OVERWRITE;
2990 mutex_unlock(&buffer->mutex);
2992 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2994 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2996 return bpage->page->data + index;
2999 static __always_inline struct ring_buffer_event *
3000 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
3002 return __rb_page_index(cpu_buffer->reader_page,
3003 cpu_buffer->reader_page->read);
3006 static struct ring_buffer_event *
3007 rb_iter_head_event(struct ring_buffer_iter *iter)
3009 struct ring_buffer_event *event;
3010 struct buffer_page *iter_head_page = iter->head_page;
3011 unsigned long commit;
3014 if (iter->head != iter->next_event)
3018 * When the writer goes across pages, it issues a cmpxchg which
3019 * is a mb(), which will synchronize with the rmb here.
3020 * (see rb_tail_page_update() and __rb_reserve_next())
3022 commit = rb_page_commit(iter_head_page);
3025 /* An event needs to be at least 8 bytes in size */
3026 if (iter->head > commit - 8)
3029 event = __rb_page_index(iter_head_page, iter->head);
3030 length = rb_event_length(event);
3033 * READ_ONCE() doesn't work on functions and we don't want the
3034 * compiler doing any crazy optimizations with length.
3038 if ((iter->head + length) > commit || length > iter->event_size)
3039 /* Writer corrupted the read? */
3042 memcpy(iter->event, event, length);
3044 * If the page stamp is still the same after this rmb() then the
3045 * event was safely copied without the writer entering the page.
3049 /* Make sure the page didn't change since we read this */
3050 if (iter->page_stamp != iter_head_page->page->time_stamp ||
3051 commit > rb_page_commit(iter_head_page))
3054 iter->next_event = iter->head + length;
3057 /* Reset to the beginning */
3058 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
3060 iter->next_event = 0;
3061 iter->missed_events = 1;
3065 /* Size is determined by what has been committed */
3066 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
3068 return rb_page_commit(bpage) & ~RB_MISSED_MASK;
3071 static __always_inline unsigned
3072 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
3074 return rb_page_commit(cpu_buffer->commit_page);
3077 static __always_inline unsigned
3078 rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
3080 unsigned long addr = (unsigned long)event;
3082 addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
3084 return addr - BUF_PAGE_HDR_SIZE;
3087 static void rb_inc_iter(struct ring_buffer_iter *iter)
3089 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3092 * The iterator could be on the reader page (it starts there).
3093 * But the head could have moved, since the reader was
3094 * found. Check for this case and assign the iterator
3095 * to the head page instead of next.
3097 if (iter->head_page == cpu_buffer->reader_page)
3098 iter->head_page = rb_set_head_page(cpu_buffer);
3100 rb_inc_page(&iter->head_page);
3102 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
3104 iter->next_event = 0;
3107 /* Return the index into the sub-buffers for a given sub-buffer */
3108 static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf)
3112 subbuf_array = (void *)meta + sizeof(int) * meta->nr_subbufs;
3113 subbuf_array = (void *)ALIGN((unsigned long)subbuf_array, meta->subbuf_size);
3114 return (subbuf - subbuf_array) / meta->subbuf_size;
3117 static void rb_update_meta_head(struct ring_buffer_per_cpu *cpu_buffer,
3118 struct buffer_page *next_page)
3120 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
3121 unsigned long old_head = (unsigned long)next_page->page;
3122 unsigned long new_head;
3124 rb_inc_page(&next_page);
3125 new_head = (unsigned long)next_page->page;
3128 * Only move it forward once, if something else came in and
3129 * moved it forward, then we don't want to touch it.
3131 (void)cmpxchg(&meta->head_buffer, old_head, new_head);
3134 static void rb_update_meta_reader(struct ring_buffer_per_cpu *cpu_buffer,
3135 struct buffer_page *reader)
3137 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
3138 void *old_reader = cpu_buffer->reader_page->page;
3139 void *new_reader = reader->page;
3143 cpu_buffer->reader_page->id = id;
3146 meta->buffers[0] = rb_meta_subbuf_idx(meta, new_reader);
3147 meta->buffers[id] = rb_meta_subbuf_idx(meta, old_reader);
3149 /* The head pointer is the one after the reader */
3150 rb_update_meta_head(cpu_buffer, reader);
3154 * rb_handle_head_page - writer hit the head page
3156 * Returns: +1 to retry page
3161 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
3162 struct buffer_page *tail_page,
3163 struct buffer_page *next_page)
3165 struct buffer_page *new_head;
3170 entries = rb_page_entries(next_page);
3173 * The hard part is here. We need to move the head
3174 * forward, and protect against both readers on
3175 * other CPUs and writers coming in via interrupts.
3177 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
3181 * type can be one of four:
3182 * NORMAL - an interrupt already moved it for us
3183 * HEAD - we are the first to get here.
3184 * UPDATE - we are the interrupt interrupting
3186 * MOVED - a reader on another CPU moved the next
3187 * pointer to its reader page. Give up
3194 * We changed the head to UPDATE, thus
3195 * it is our responsibility to update
3198 local_add(entries, &cpu_buffer->overrun);
3199 local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
3200 local_inc(&cpu_buffer->pages_lost);
3202 if (cpu_buffer->ring_meta)
3203 rb_update_meta_head(cpu_buffer, next_page);
3205 * The entries will be zeroed out when we move the
3209 /* still more to do */
3212 case RB_PAGE_UPDATE:
3214 * This is an interrupt that interrupt the
3215 * previous update. Still more to do.
3218 case RB_PAGE_NORMAL:
3220 * An interrupt came in before the update
3221 * and processed this for us.
3222 * Nothing left to do.
3227 * The reader is on another CPU and just did
3228 * a swap with our next_page.
3233 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
3238 * Now that we are here, the old head pointer is
3239 * set to UPDATE. This will keep the reader from
3240 * swapping the head page with the reader page.
3241 * The reader (on another CPU) will spin till
3244 * We just need to protect against interrupts
3245 * doing the job. We will set the next pointer
3246 * to HEAD. After that, we set the old pointer
3247 * to NORMAL, but only if it was HEAD before.
3248 * otherwise we are an interrupt, and only
3249 * want the outer most commit to reset it.
3251 new_head = next_page;
3252 rb_inc_page(&new_head);
3254 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
3258 * Valid returns are:
3259 * HEAD - an interrupt came in and already set it.
3260 * NORMAL - One of two things:
3261 * 1) We really set it.
3262 * 2) A bunch of interrupts came in and moved
3263 * the page forward again.
3267 case RB_PAGE_NORMAL:
3271 RB_WARN_ON(cpu_buffer, 1);
3276 * It is possible that an interrupt came in,
3277 * set the head up, then more interrupts came in
3278 * and moved it again. When we get back here,
3279 * the page would have been set to NORMAL but we
3280 * just set it back to HEAD.
3282 * How do you detect this? Well, if that happened
3283 * the tail page would have moved.
3285 if (ret == RB_PAGE_NORMAL) {
3286 struct buffer_page *buffer_tail_page;
3288 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
3290 * If the tail had moved passed next, then we need
3291 * to reset the pointer.
3293 if (buffer_tail_page != tail_page &&
3294 buffer_tail_page != next_page)
3295 rb_head_page_set_normal(cpu_buffer, new_head,
3301 * If this was the outer most commit (the one that
3302 * changed the original pointer from HEAD to UPDATE),
3303 * then it is up to us to reset it to NORMAL.
3305 if (type == RB_PAGE_HEAD) {
3306 ret = rb_head_page_set_normal(cpu_buffer, next_page,
3309 if (RB_WARN_ON(cpu_buffer,
3310 ret != RB_PAGE_UPDATE))
3318 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
3319 unsigned long tail, struct rb_event_info *info)
3321 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
3322 struct buffer_page *tail_page = info->tail_page;
3323 struct ring_buffer_event *event;
3324 unsigned long length = info->length;
3327 * Only the event that crossed the page boundary
3328 * must fill the old tail_page with padding.
3330 if (tail >= bsize) {
3332 * If the page was filled, then we still need
3333 * to update the real_end. Reset it to zero
3334 * and the reader will ignore it.
3337 tail_page->real_end = 0;
3339 local_sub(length, &tail_page->write);
3343 event = __rb_page_index(tail_page, tail);
3346 * Save the original length to the meta data.
3347 * This will be used by the reader to add lost event
3350 tail_page->real_end = tail;
3353 * If this event is bigger than the minimum size, then
3354 * we need to be careful that we don't subtract the
3355 * write counter enough to allow another writer to slip
3357 * We put in a discarded commit instead, to make sure
3358 * that this space is not used again, and this space will
3359 * not be accounted into 'entries_bytes'.
3361 * If we are less than the minimum size, we don't need to
3364 if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
3365 /* No room for any events */
3367 /* Mark the rest of the page with padding */
3368 rb_event_set_padding(event);
3370 /* Make sure the padding is visible before the write update */
3373 /* Set the write back to the previous setting */
3374 local_sub(length, &tail_page->write);
3378 /* Put in a discarded event */
3379 event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
3380 event->type_len = RINGBUF_TYPE_PADDING;
3381 /* time delta must be non zero */
3382 event->time_delta = 1;
3384 /* account for padding bytes */
3385 local_add(bsize - tail, &cpu_buffer->entries_bytes);
3387 /* Make sure the padding is visible before the tail_page->write update */
3390 /* Set write to end of buffer */
3391 length = (tail + length) - bsize;
3392 local_sub(length, &tail_page->write);
3395 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
3398 * This is the slow path, force gcc not to inline it.
3400 static noinline struct ring_buffer_event *
3401 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
3402 unsigned long tail, struct rb_event_info *info)
3404 struct buffer_page *tail_page = info->tail_page;
3405 struct buffer_page *commit_page = cpu_buffer->commit_page;
3406 struct trace_buffer *buffer = cpu_buffer->buffer;
3407 struct buffer_page *next_page;
3410 next_page = tail_page;
3412 rb_inc_page(&next_page);
3415 * If for some reason, we had an interrupt storm that made
3416 * it all the way around the buffer, bail, and warn
3419 if (unlikely(next_page == commit_page)) {
3420 local_inc(&cpu_buffer->commit_overrun);
3425 * This is where the fun begins!
3427 * We are fighting against races between a reader that
3428 * could be on another CPU trying to swap its reader
3429 * page with the buffer head.
3431 * We are also fighting against interrupts coming in and
3432 * moving the head or tail on us as well.
3434 * If the next page is the head page then we have filled
3435 * the buffer, unless the commit page is still on the
3438 if (rb_is_head_page(next_page, &tail_page->list)) {
3441 * If the commit is not on the reader page, then
3442 * move the header page.
3444 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
3446 * If we are not in overwrite mode,
3447 * this is easy, just stop here.
3449 if (!(buffer->flags & RB_FL_OVERWRITE)) {
3450 local_inc(&cpu_buffer->dropped_events);
3454 ret = rb_handle_head_page(cpu_buffer,
3463 * We need to be careful here too. The
3464 * commit page could still be on the reader
3465 * page. We could have a small buffer, and
3466 * have filled up the buffer with events
3467 * from interrupts and such, and wrapped.
3469 * Note, if the tail page is also on the
3470 * reader_page, we let it move out.
3472 if (unlikely((cpu_buffer->commit_page !=
3473 cpu_buffer->tail_page) &&
3474 (cpu_buffer->commit_page ==
3475 cpu_buffer->reader_page))) {
3476 local_inc(&cpu_buffer->commit_overrun);
3482 rb_tail_page_update(cpu_buffer, tail_page, next_page);
3486 rb_reset_tail(cpu_buffer, tail, info);
3488 /* Commit what we have for now. */
3489 rb_end_commit(cpu_buffer);
3490 /* rb_end_commit() decs committing */
3491 local_inc(&cpu_buffer->committing);
3493 /* fail and let the caller try again */
3494 return ERR_PTR(-EAGAIN);
3498 rb_reset_tail(cpu_buffer, tail, info);
3504 static struct ring_buffer_event *
3505 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3506 struct ring_buffer_event *event, u64 delta, bool abs)
3509 event->type_len = RINGBUF_TYPE_TIME_STAMP;
3511 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
3513 /* Not the first event on the page, or not delta? */
3514 if (abs || rb_event_index(cpu_buffer, event)) {
3515 event->time_delta = delta & TS_MASK;
3516 event->array[0] = delta >> TS_SHIFT;
3518 /* nope, just zero it */
3519 event->time_delta = 0;
3520 event->array[0] = 0;
3523 return skip_time_extend(event);
3526 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
3527 static inline bool sched_clock_stable(void)
3534 rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
3535 struct rb_event_info *info)
3539 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
3540 (unsigned long long)info->delta,
3541 (unsigned long long)info->ts,
3542 (unsigned long long)info->before,
3543 (unsigned long long)info->after,
3544 (unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
3545 sched_clock_stable() ? "" :
3546 "If you just came from a suspend/resume,\n"
3547 "please switch to the trace global clock:\n"
3548 " echo global > /sys/kernel/tracing/trace_clock\n"
3549 "or add trace_clock=global to the kernel command line\n");
3552 static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
3553 struct ring_buffer_event **event,
3554 struct rb_event_info *info,
3556 unsigned int *length)
3558 bool abs = info->add_timestamp &
3559 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
3561 if (unlikely(info->delta > (1ULL << 59))) {
3563 * Some timers can use more than 59 bits, and when a timestamp
3564 * is added to the buffer, it will lose those bits.
3566 if (abs && (info->ts & TS_MSB)) {
3567 info->delta &= ABS_TS_MASK;
3569 /* did the clock go backwards */
3570 } else if (info->before == info->after && info->before > info->ts) {
3571 /* not interrupted */
3575 * This is possible with a recalibrating of the TSC.
3576 * Do not produce a call stack, but just report it.
3580 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
3581 info->before, info->ts);
3584 rb_check_timestamp(cpu_buffer, info);
3588 *event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
3589 *length -= RB_LEN_TIME_EXTEND;
3594 * rb_update_event - update event type and data
3595 * @cpu_buffer: The per cpu buffer of the @event
3596 * @event: the event to update
3597 * @info: The info to update the @event with (contains length and delta)
3599 * Update the type and data fields of the @event. The length
3600 * is the actual size that is written to the ring buffer,
3601 * and with this, we can determine what to place into the
3605 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
3606 struct ring_buffer_event *event,
3607 struct rb_event_info *info)
3609 unsigned length = info->length;
3610 u64 delta = info->delta;
3611 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
3613 if (!WARN_ON_ONCE(nest >= MAX_NEST))
3614 cpu_buffer->event_stamp[nest] = info->ts;
3617 * If we need to add a timestamp, then we
3618 * add it to the start of the reserved space.
3620 if (unlikely(info->add_timestamp))
3621 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
3623 event->time_delta = delta;
3624 length -= RB_EVNT_HDR_SIZE;
3625 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
3626 event->type_len = 0;
3627 event->array[0] = length;
3629 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
3632 static unsigned rb_calculate_event_length(unsigned length)
3634 struct ring_buffer_event event; /* Used only for sizeof array */
3636 /* zero length can cause confusions */
3640 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
3641 length += sizeof(event.array[0]);
3643 length += RB_EVNT_HDR_SIZE;
3644 length = ALIGN(length, RB_ARCH_ALIGNMENT);
3647 * In case the time delta is larger than the 27 bits for it
3648 * in the header, we need to add a timestamp. If another
3649 * event comes in when trying to discard this one to increase
3650 * the length, then the timestamp will be added in the allocated
3651 * space of this event. If length is bigger than the size needed
3652 * for the TIME_EXTEND, then padding has to be used. The events
3653 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
3654 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
3655 * As length is a multiple of 4, we only need to worry if it
3656 * is 12 (RB_LEN_TIME_EXTEND + 4).
3658 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
3659 length += RB_ALIGNMENT;
3665 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
3666 struct ring_buffer_event *event)
3668 unsigned long new_index, old_index;
3669 struct buffer_page *bpage;
3672 new_index = rb_event_index(cpu_buffer, event);
3673 old_index = new_index + rb_event_ts_length(event);
3674 addr = (unsigned long)event;
3675 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
3677 bpage = READ_ONCE(cpu_buffer->tail_page);
3680 * Make sure the tail_page is still the same and
3681 * the next write location is the end of this event
3683 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
3684 unsigned long write_mask =
3685 local_read(&bpage->write) & ~RB_WRITE_MASK;
3686 unsigned long event_length = rb_event_length(event);
3689 * For the before_stamp to be different than the write_stamp
3690 * to make sure that the next event adds an absolute
3691 * value and does not rely on the saved write stamp, which
3692 * is now going to be bogus.
3694 * By setting the before_stamp to zero, the next event
3695 * is not going to use the write_stamp and will instead
3696 * create an absolute timestamp. This means there's no
3697 * reason to update the wirte_stamp!
3699 rb_time_set(&cpu_buffer->before_stamp, 0);
3702 * If an event were to come in now, it would see that the
3703 * write_stamp and the before_stamp are different, and assume
3704 * that this event just added itself before updating
3705 * the write stamp. The interrupting event will fix the
3706 * write stamp for us, and use an absolute timestamp.
3710 * This is on the tail page. It is possible that
3711 * a write could come in and move the tail page
3712 * and write to the next page. That is fine
3713 * because we just shorten what is on this page.
3715 old_index += write_mask;
3716 new_index += write_mask;
3718 /* caution: old_index gets updated on cmpxchg failure */
3719 if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
3720 /* update counters */
3721 local_sub(event_length, &cpu_buffer->entries_bytes);
3726 /* could not discard */
3730 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
3732 local_inc(&cpu_buffer->committing);
3733 local_inc(&cpu_buffer->commits);
3736 static __always_inline void
3737 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
3739 unsigned long max_count;
3742 * We only race with interrupts and NMIs on this CPU.
3743 * If we own the commit event, then we can commit
3744 * all others that interrupted us, since the interruptions
3745 * are in stack format (they finish before they come
3746 * back to us). This allows us to do a simple loop to
3747 * assign the commit to the tail.
3750 max_count = cpu_buffer->nr_pages * 100;
3752 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
3753 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
3755 if (RB_WARN_ON(cpu_buffer,
3756 rb_is_reader_page(cpu_buffer->tail_page)))
3759 * No need for a memory barrier here, as the update
3760 * of the tail_page did it for this page.
3762 local_set(&cpu_buffer->commit_page->page->commit,
3763 rb_page_write(cpu_buffer->commit_page));
3764 rb_inc_page(&cpu_buffer->commit_page);
3765 if (cpu_buffer->ring_meta) {
3766 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
3767 meta->commit_buffer = (unsigned long)cpu_buffer->commit_page->page;
3769 /* add barrier to keep gcc from optimizing too much */
3772 while (rb_commit_index(cpu_buffer) !=
3773 rb_page_write(cpu_buffer->commit_page)) {
3775 /* Make sure the readers see the content of what is committed. */
3777 local_set(&cpu_buffer->commit_page->page->commit,
3778 rb_page_write(cpu_buffer->commit_page));
3779 RB_WARN_ON(cpu_buffer,
3780 local_read(&cpu_buffer->commit_page->page->commit) &
3785 /* again, keep gcc from optimizing */
3789 * If an interrupt came in just after the first while loop
3790 * and pushed the tail page forward, we will be left with
3791 * a dangling commit that will never go forward.
3793 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3797 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3799 unsigned long commits;
3801 if (RB_WARN_ON(cpu_buffer,
3802 !local_read(&cpu_buffer->committing)))
3806 commits = local_read(&cpu_buffer->commits);
3807 /* synchronize with interrupts */
3809 if (local_read(&cpu_buffer->committing) == 1)
3810 rb_set_commit_to_write(cpu_buffer);
3812 local_dec(&cpu_buffer->committing);
3814 /* synchronize with interrupts */
3818 * Need to account for interrupts coming in between the
3819 * updating of the commit page and the clearing of the
3820 * committing counter.
3822 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3823 !local_read(&cpu_buffer->committing)) {
3824 local_inc(&cpu_buffer->committing);
3829 static inline void rb_event_discard(struct ring_buffer_event *event)
3831 if (extended_time(event))
3832 event = skip_time_extend(event);
3834 /* array[0] holds the actual length for the discarded event */
3835 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3836 event->type_len = RINGBUF_TYPE_PADDING;
3837 /* time delta must be non zero */
3838 if (!event->time_delta)
3839 event->time_delta = 1;
3842 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
3844 local_inc(&cpu_buffer->entries);
3845 rb_end_commit(cpu_buffer);
3848 static __always_inline void
3849 rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3851 if (buffer->irq_work.waiters_pending) {
3852 buffer->irq_work.waiters_pending = false;
3853 /* irq_work_queue() supplies it's own memory barriers */
3854 irq_work_queue(&buffer->irq_work.work);
3857 if (cpu_buffer->irq_work.waiters_pending) {
3858 cpu_buffer->irq_work.waiters_pending = false;
3859 /* irq_work_queue() supplies it's own memory barriers */
3860 irq_work_queue(&cpu_buffer->irq_work.work);
3863 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3866 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3869 if (!cpu_buffer->irq_work.full_waiters_pending)
3872 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3874 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3877 cpu_buffer->irq_work.wakeup_full = true;
3878 cpu_buffer->irq_work.full_waiters_pending = false;
3879 /* irq_work_queue() supplies it's own memory barriers */
3880 irq_work_queue(&cpu_buffer->irq_work.work);
3883 #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3884 # define do_ring_buffer_record_recursion() \
3885 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3887 # define do_ring_buffer_record_recursion() do { } while (0)
3891 * The lock and unlock are done within a preempt disable section.
3892 * The current_context per_cpu variable can only be modified
3893 * by the current task between lock and unlock. But it can
3894 * be modified more than once via an interrupt. To pass this
3895 * information from the lock to the unlock without having to
3896 * access the 'in_interrupt()' functions again (which do show
3897 * a bit of overhead in something as critical as function tracing,
3898 * we use a bitmask trick.
3900 * bit 1 = NMI context
3901 * bit 2 = IRQ context
3902 * bit 3 = SoftIRQ context
3903 * bit 4 = normal context.
3905 * This works because this is the order of contexts that can
3906 * preempt other contexts. A SoftIRQ never preempts an IRQ
3909 * When the context is determined, the corresponding bit is
3910 * checked and set (if it was set, then a recursion of that context
3913 * On unlock, we need to clear this bit. To do so, just subtract
3914 * 1 from the current_context and AND it to itself.
3918 * 101 & 100 = 100 (clearing bit zero)
3921 * 1010 & 1001 = 1000 (clearing bit 1)
3923 * The least significant bit can be cleared this way, and it
3924 * just so happens that it is the same bit corresponding to
3925 * the current context.
3927 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3928 * is set when a recursion is detected at the current context, and if
3929 * the TRANSITION bit is already set, it will fail the recursion.
3930 * This is needed because there's a lag between the changing of
3931 * interrupt context and updating the preempt count. In this case,
3932 * a false positive will be found. To handle this, one extra recursion
3933 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3934 * bit is already set, then it is considered a recursion and the function
3935 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3937 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3938 * to be cleared. Even if it wasn't the context that set it. That is,
3939 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3940 * is called before preempt_count() is updated, since the check will
3941 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3942 * NMI then comes in, it will set the NMI bit, but when the NMI code
3943 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3944 * and leave the NMI bit set. But this is fine, because the interrupt
3945 * code that set the TRANSITION bit will then clear the NMI bit when it
3946 * calls trace_recursive_unlock(). If another NMI comes in, it will
3947 * set the TRANSITION bit and continue.
3949 * Note: The TRANSITION bit only handles a single transition between context.
3952 static __always_inline bool
3953 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3955 unsigned int val = cpu_buffer->current_context;
3956 int bit = interrupt_context_level();
3958 bit = RB_CTX_NORMAL - bit;
3960 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3962 * It is possible that this was called by transitioning
3963 * between interrupt context, and preempt_count() has not
3964 * been updated yet. In this case, use the TRANSITION bit.
3966 bit = RB_CTX_TRANSITION;
3967 if (val & (1 << (bit + cpu_buffer->nest))) {
3968 do_ring_buffer_record_recursion();
3973 val |= (1 << (bit + cpu_buffer->nest));
3974 cpu_buffer->current_context = val;
3979 static __always_inline void
3980 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3982 cpu_buffer->current_context &=
3983 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3986 /* The recursive locking above uses 5 bits */
3987 #define NESTED_BITS 5
3990 * ring_buffer_nest_start - Allow to trace while nested
3991 * @buffer: The ring buffer to modify
3993 * The ring buffer has a safety mechanism to prevent recursion.
3994 * But there may be a case where a trace needs to be done while
3995 * tracing something else. In this case, calling this function
3996 * will allow this function to nest within a currently active
3997 * ring_buffer_lock_reserve().
3999 * Call this function before calling another ring_buffer_lock_reserve() and
4000 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
4002 void ring_buffer_nest_start(struct trace_buffer *buffer)
4004 struct ring_buffer_per_cpu *cpu_buffer;
4007 /* Enabled by ring_buffer_nest_end() */
4008 preempt_disable_notrace();
4009 cpu = raw_smp_processor_id();
4010 cpu_buffer = buffer->buffers[cpu];
4011 /* This is the shift value for the above recursive locking */
4012 cpu_buffer->nest += NESTED_BITS;
4016 * ring_buffer_nest_end - Allow to trace while nested
4017 * @buffer: The ring buffer to modify
4019 * Must be called after ring_buffer_nest_start() and after the
4020 * ring_buffer_unlock_commit().
4022 void ring_buffer_nest_end(struct trace_buffer *buffer)
4024 struct ring_buffer_per_cpu *cpu_buffer;
4027 /* disabled by ring_buffer_nest_start() */
4028 cpu = raw_smp_processor_id();
4029 cpu_buffer = buffer->buffers[cpu];
4030 /* This is the shift value for the above recursive locking */
4031 cpu_buffer->nest -= NESTED_BITS;
4032 preempt_enable_notrace();
4036 * ring_buffer_unlock_commit - commit a reserved
4037 * @buffer: The buffer to commit to
4039 * This commits the data to the ring buffer, and releases any locks held.
4041 * Must be paired with ring_buffer_lock_reserve.
4043 int ring_buffer_unlock_commit(struct trace_buffer *buffer)
4045 struct ring_buffer_per_cpu *cpu_buffer;
4046 int cpu = raw_smp_processor_id();
4048 cpu_buffer = buffer->buffers[cpu];
4050 rb_commit(cpu_buffer);
4052 rb_wakeups(buffer, cpu_buffer);
4054 trace_recursive_unlock(cpu_buffer);
4056 preempt_enable_notrace();
4060 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
4062 /* Special value to validate all deltas on a page. */
4063 #define CHECK_FULL_PAGE 1L
4065 #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
4067 static const char *show_irq_str(int bits)
4069 const char *type[] = {
4083 /* Assume this is a trace event */
4084 static const char *show_flags(struct ring_buffer_event *event)
4086 struct trace_entry *entry;
4089 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
4092 entry = ring_buffer_event_data(event);
4094 if (entry->flags & TRACE_FLAG_SOFTIRQ)
4097 if (entry->flags & TRACE_FLAG_HARDIRQ)
4100 if (entry->flags & TRACE_FLAG_NMI)
4103 return show_irq_str(bits);
4106 static const char *show_irq(struct ring_buffer_event *event)
4108 struct trace_entry *entry;
4110 if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
4113 entry = ring_buffer_event_data(event);
4114 if (entry->flags & TRACE_FLAG_IRQS_OFF)
4119 static const char *show_interrupt_level(void)
4121 unsigned long pc = preempt_count();
4122 unsigned char level = 0;
4124 if (pc & SOFTIRQ_OFFSET)
4127 if (pc & HARDIRQ_MASK)
4133 return show_irq_str(level);
4136 static void dump_buffer_page(struct buffer_data_page *bpage,
4137 struct rb_event_info *info,
4140 struct ring_buffer_event *event;
4144 ts = bpage->time_stamp;
4145 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
4147 for (e = 0; e < tail; e += rb_event_length(event)) {
4149 event = (struct ring_buffer_event *)(bpage->data + e);
4151 switch (event->type_len) {
4153 case RINGBUF_TYPE_TIME_EXTEND:
4154 delta = rb_event_time_stamp(event);
4156 pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
4160 case RINGBUF_TYPE_TIME_STAMP:
4161 delta = rb_event_time_stamp(event);
4162 ts = rb_fix_abs_ts(delta, ts);
4163 pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
4167 case RINGBUF_TYPE_PADDING:
4168 ts += event->time_delta;
4169 pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
4170 e, ts, event->time_delta);
4173 case RINGBUF_TYPE_DATA:
4174 ts += event->time_delta;
4175 pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
4176 e, ts, event->time_delta,
4177 show_flags(event), show_irq(event));
4184 pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
4187 static DEFINE_PER_CPU(atomic_t, checking);
4188 static atomic_t ts_dump;
4190 #define buffer_warn_return(fmt, ...) \
4192 /* If another report is happening, ignore this one */ \
4193 if (atomic_inc_return(&ts_dump) != 1) { \
4194 atomic_dec(&ts_dump); \
4197 atomic_inc(&cpu_buffer->record_disabled); \
4198 pr_warn(fmt, ##__VA_ARGS__); \
4199 dump_buffer_page(bpage, info, tail); \
4200 atomic_dec(&ts_dump); \
4201 /* There's some cases in boot up that this can happen */ \
4202 if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
4203 /* Do not re-enable checking */ \
4208 * Check if the current event time stamp matches the deltas on
4211 static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
4212 struct rb_event_info *info,
4215 struct buffer_data_page *bpage;
4220 bpage = info->tail_page->page;
4222 if (tail == CHECK_FULL_PAGE) {
4224 tail = local_read(&bpage->commit);
4225 } else if (info->add_timestamp &
4226 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
4227 /* Ignore events with absolute time stamps */
4232 * Do not check the first event (skip possible extends too).
4233 * Also do not check if previous events have not been committed.
4235 if (tail <= 8 || tail > local_read(&bpage->commit))
4239 * If this interrupted another event,
4241 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
4244 ret = rb_read_data_buffer(bpage, tail, cpu_buffer->cpu, &ts, &delta);
4247 buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
4248 cpu_buffer->cpu, ts, delta);
4252 if ((full && ts > info->ts) ||
4253 (!full && ts + info->delta != info->ts)) {
4254 buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
4256 ts + info->delta, info->ts, info->delta,
4257 info->before, info->after,
4258 full ? " (full)" : "", show_interrupt_level());
4261 atomic_dec(this_cpu_ptr(&checking));
4264 static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
4265 struct rb_event_info *info,
4269 #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
4271 static struct ring_buffer_event *
4272 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
4273 struct rb_event_info *info)
4275 struct ring_buffer_event *event;
4276 struct buffer_page *tail_page;
4277 unsigned long tail, write, w;
4279 /* Don't let the compiler play games with cpu_buffer->tail_page */
4280 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
4282 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
4284 rb_time_read(&cpu_buffer->before_stamp, &info->before);
4285 rb_time_read(&cpu_buffer->write_stamp, &info->after);
4287 info->ts = rb_time_stamp(cpu_buffer->buffer);
4289 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
4290 info->delta = info->ts;
4293 * If interrupting an event time update, we may need an
4294 * absolute timestamp.
4295 * Don't bother if this is the start of a new page (w == 0).
4298 /* Use the sub-buffer timestamp */
4300 } else if (unlikely(info->before != info->after)) {
4301 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
4302 info->length += RB_LEN_TIME_EXTEND;
4304 info->delta = info->ts - info->after;
4305 if (unlikely(test_time_stamp(info->delta))) {
4306 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
4307 info->length += RB_LEN_TIME_EXTEND;
4312 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
4314 /*C*/ write = local_add_return(info->length, &tail_page->write);
4316 /* set write to only the index of the write */
4317 write &= RB_WRITE_MASK;
4319 tail = write - info->length;
4321 /* See if we shot pass the end of this buffer page */
4322 if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
4323 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
4324 return rb_move_tail(cpu_buffer, tail, info);
4327 if (likely(tail == w)) {
4328 /* Nothing interrupted us between A and C */
4329 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
4331 * If something came in between C and D, the write stamp
4332 * may now not be in sync. But that's fine as the before_stamp
4333 * will be different and then next event will just be forced
4334 * to use an absolute timestamp.
4336 if (likely(!(info->add_timestamp &
4337 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
4338 /* This did not interrupt any time update */
4339 info->delta = info->ts - info->after;
4341 /* Just use full timestamp for interrupting event */
4342 info->delta = info->ts;
4343 check_buffer(cpu_buffer, info, tail);
4346 /* SLOW PATH - Interrupted between A and C */
4348 /* Save the old before_stamp */
4349 rb_time_read(&cpu_buffer->before_stamp, &info->before);
4352 * Read a new timestamp and update the before_stamp to make
4353 * the next event after this one force using an absolute
4354 * timestamp. This is in case an interrupt were to come in
4357 ts = rb_time_stamp(cpu_buffer->buffer);
4358 rb_time_set(&cpu_buffer->before_stamp, ts);
4361 /*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
4363 /*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
4364 info->after == info->before && info->after < ts) {
4366 * Nothing came after this event between C and F, it is
4367 * safe to use info->after for the delta as it
4368 * matched info->before and is still valid.
4370 info->delta = ts - info->after;
4373 * Interrupted between C and F:
4374 * Lost the previous events time stamp. Just set the
4375 * delta to zero, and this will be the same time as
4376 * the event this event interrupted. And the events that
4377 * came after this will still be correct (as they would
4378 * have built their delta on the previous event.
4383 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
4387 * If this is the first commit on the page, then it has the same
4388 * timestamp as the page itself.
4390 if (unlikely(!tail && !(info->add_timestamp &
4391 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
4394 /* We reserved something on the buffer */
4396 event = __rb_page_index(tail_page, tail);
4397 rb_update_event(cpu_buffer, event, info);
4399 local_inc(&tail_page->entries);
4402 * If this is the first commit on the page, then update
4405 if (unlikely(!tail))
4406 tail_page->page->time_stamp = info->ts;
4408 /* account for these added bytes */
4409 local_add(info->length, &cpu_buffer->entries_bytes);
4414 static __always_inline struct ring_buffer_event *
4415 rb_reserve_next_event(struct trace_buffer *buffer,
4416 struct ring_buffer_per_cpu *cpu_buffer,
4417 unsigned long length)
4419 struct ring_buffer_event *event;
4420 struct rb_event_info info;
4425 * ring buffer does cmpxchg as well as atomic64 operations
4426 * (which some archs use locking for atomic64), make sure this
4427 * is safe in NMI context
4429 if ((!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) ||
4430 IS_ENABLED(CONFIG_GENERIC_ATOMIC64)) &&
4431 (unlikely(in_nmi()))) {
4435 rb_start_commit(cpu_buffer);
4436 /* The commit page can not change after this */
4438 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4440 * Due to the ability to swap a cpu buffer from a buffer
4441 * it is possible it was swapped before we committed.
4442 * (committing stops a swap). We check for it here and
4443 * if it happened, we have to fail the write.
4446 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
4447 local_dec(&cpu_buffer->committing);
4448 local_dec(&cpu_buffer->commits);
4453 info.length = rb_calculate_event_length(length);
4455 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
4456 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
4457 info.length += RB_LEN_TIME_EXTEND;
4458 if (info.length > cpu_buffer->buffer->max_data_size)
4461 add_ts_default = RB_ADD_STAMP_NONE;
4465 info.add_timestamp = add_ts_default;
4469 * We allow for interrupts to reenter here and do a trace.
4470 * If one does, it will cause this original code to loop
4471 * back here. Even with heavy interrupts happening, this
4472 * should only happen a few times in a row. If this happens
4473 * 1000 times in a row, there must be either an interrupt
4474 * storm or we have something buggy.
4477 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
4480 event = __rb_reserve_next(cpu_buffer, &info);
4482 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
4483 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
4484 info.length -= RB_LEN_TIME_EXTEND;
4491 rb_end_commit(cpu_buffer);
4496 * ring_buffer_lock_reserve - reserve a part of the buffer
4497 * @buffer: the ring buffer to reserve from
4498 * @length: the length of the data to reserve (excluding event header)
4500 * Returns a reserved event on the ring buffer to copy directly to.
4501 * The user of this interface will need to get the body to write into
4502 * and can use the ring_buffer_event_data() interface.
4504 * The length is the length of the data needed, not the event length
4505 * which also includes the event header.
4507 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
4508 * If NULL is returned, then nothing has been allocated or locked.
4510 struct ring_buffer_event *
4511 ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
4513 struct ring_buffer_per_cpu *cpu_buffer;
4514 struct ring_buffer_event *event;
4517 /* If we are tracing schedule, we don't want to recurse */
4518 preempt_disable_notrace();
4520 if (unlikely(atomic_read(&buffer->record_disabled)))
4523 cpu = raw_smp_processor_id();
4525 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
4528 cpu_buffer = buffer->buffers[cpu];
4530 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
4533 if (unlikely(length > buffer->max_data_size))
4536 if (unlikely(trace_recursive_lock(cpu_buffer)))
4539 event = rb_reserve_next_event(buffer, cpu_buffer, length);
4546 trace_recursive_unlock(cpu_buffer);
4548 preempt_enable_notrace();
4551 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
4554 * Decrement the entries to the page that an event is on.
4555 * The event does not even need to exist, only the pointer
4556 * to the page it is on. This may only be called before the commit
4560 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
4561 struct ring_buffer_event *event)
4563 unsigned long addr = (unsigned long)event;
4564 struct buffer_page *bpage = cpu_buffer->commit_page;
4565 struct buffer_page *start;
4567 addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
4569 /* Do the likely case first */
4570 if (likely(bpage->page == (void *)addr)) {
4571 local_dec(&bpage->entries);
4576 * Because the commit page may be on the reader page we
4577 * start with the next page and check the end loop there.
4579 rb_inc_page(&bpage);
4582 if (bpage->page == (void *)addr) {
4583 local_dec(&bpage->entries);
4586 rb_inc_page(&bpage);
4587 } while (bpage != start);
4589 /* commit not part of this buffer?? */
4590 RB_WARN_ON(cpu_buffer, 1);
4594 * ring_buffer_discard_commit - discard an event that has not been committed
4595 * @buffer: the ring buffer
4596 * @event: non committed event to discard
4598 * Sometimes an event that is in the ring buffer needs to be ignored.
4599 * This function lets the user discard an event in the ring buffer
4600 * and then that event will not be read later.
4602 * This function only works if it is called before the item has been
4603 * committed. It will try to free the event from the ring buffer
4604 * if another event has not been added behind it.
4606 * If another event has been added behind it, it will set the event
4607 * up as discarded, and perform the commit.
4609 * If this function is called, do not call ring_buffer_unlock_commit on
4612 void ring_buffer_discard_commit(struct trace_buffer *buffer,
4613 struct ring_buffer_event *event)
4615 struct ring_buffer_per_cpu *cpu_buffer;
4618 /* The event is discarded regardless */
4619 rb_event_discard(event);
4621 cpu = smp_processor_id();
4622 cpu_buffer = buffer->buffers[cpu];
4625 * This must only be called if the event has not been
4626 * committed yet. Thus we can assume that preemption
4627 * is still disabled.
4629 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
4631 rb_decrement_entry(cpu_buffer, event);
4632 if (rb_try_to_discard(cpu_buffer, event))
4636 rb_end_commit(cpu_buffer);
4638 trace_recursive_unlock(cpu_buffer);
4640 preempt_enable_notrace();
4643 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
4646 * ring_buffer_write - write data to the buffer without reserving
4647 * @buffer: The ring buffer to write to.
4648 * @length: The length of the data being written (excluding the event header)
4649 * @data: The data to write to the buffer.
4651 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
4652 * one function. If you already have the data to write to the buffer, it
4653 * may be easier to simply call this function.
4655 * Note, like ring_buffer_lock_reserve, the length is the length of the data
4656 * and not the length of the event which would hold the header.
4658 int ring_buffer_write(struct trace_buffer *buffer,
4659 unsigned long length,
4662 struct ring_buffer_per_cpu *cpu_buffer;
4663 struct ring_buffer_event *event;
4668 preempt_disable_notrace();
4670 if (atomic_read(&buffer->record_disabled))
4673 cpu = raw_smp_processor_id();
4675 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4678 cpu_buffer = buffer->buffers[cpu];
4680 if (atomic_read(&cpu_buffer->record_disabled))
4683 if (length > buffer->max_data_size)
4686 if (unlikely(trace_recursive_lock(cpu_buffer)))
4689 event = rb_reserve_next_event(buffer, cpu_buffer, length);
4693 body = rb_event_data(event);
4695 memcpy(body, data, length);
4697 rb_commit(cpu_buffer);
4699 rb_wakeups(buffer, cpu_buffer);
4704 trace_recursive_unlock(cpu_buffer);
4707 preempt_enable_notrace();
4711 EXPORT_SYMBOL_GPL(ring_buffer_write);
4714 * The total entries in the ring buffer is the running counter
4715 * of entries entered into the ring buffer, minus the sum of
4716 * the entries read from the ring buffer and the number of
4717 * entries that were overwritten.
4719 static inline unsigned long
4720 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4722 return local_read(&cpu_buffer->entries) -
4723 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4726 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
4728 return !rb_num_of_entries(cpu_buffer);
4732 * ring_buffer_record_disable - stop all writes into the buffer
4733 * @buffer: The ring buffer to stop writes to.
4735 * This prevents all writes to the buffer. Any attempt to write
4736 * to the buffer after this will fail and return NULL.
4738 * The caller should call synchronize_rcu() after this.
4740 void ring_buffer_record_disable(struct trace_buffer *buffer)
4742 atomic_inc(&buffer->record_disabled);
4744 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
4747 * ring_buffer_record_enable - enable writes to the buffer
4748 * @buffer: The ring buffer to enable writes
4750 * Note, multiple disables will need the same number of enables
4751 * to truly enable the writing (much like preempt_disable).
4753 void ring_buffer_record_enable(struct trace_buffer *buffer)
4755 atomic_dec(&buffer->record_disabled);
4757 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4760 * ring_buffer_record_off - stop all writes into the buffer
4761 * @buffer: The ring buffer to stop writes to.
4763 * This prevents all writes to the buffer. Any attempt to write
4764 * to the buffer after this will fail and return NULL.
4766 * This is different than ring_buffer_record_disable() as
4767 * it works like an on/off switch, where as the disable() version
4768 * must be paired with a enable().
4770 void ring_buffer_record_off(struct trace_buffer *buffer)
4773 unsigned int new_rd;
4775 rd = atomic_read(&buffer->record_disabled);
4777 new_rd = rd | RB_BUFFER_OFF;
4778 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4780 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4783 * ring_buffer_record_on - restart writes into the buffer
4784 * @buffer: The ring buffer to start writes to.
4786 * This enables all writes to the buffer that was disabled by
4787 * ring_buffer_record_off().
4789 * This is different than ring_buffer_record_enable() as
4790 * it works like an on/off switch, where as the enable() version
4791 * must be paired with a disable().
4793 void ring_buffer_record_on(struct trace_buffer *buffer)
4796 unsigned int new_rd;
4798 rd = atomic_read(&buffer->record_disabled);
4800 new_rd = rd & ~RB_BUFFER_OFF;
4801 } while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
4803 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4806 * ring_buffer_record_is_on - return true if the ring buffer can write
4807 * @buffer: The ring buffer to see if write is enabled
4809 * Returns true if the ring buffer is in a state that it accepts writes.
4811 bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4813 return !atomic_read(&buffer->record_disabled);
4817 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4818 * @buffer: The ring buffer to see if write is set enabled
4820 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4821 * Note that this does NOT mean it is in a writable state.
4823 * It may return true when the ring buffer has been disabled by
4824 * ring_buffer_record_disable(), as that is a temporary disabling of
4827 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4829 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4833 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4834 * @buffer: The ring buffer to stop writes to.
4835 * @cpu: The CPU buffer to stop
4837 * This prevents all writes to the buffer. Any attempt to write
4838 * to the buffer after this will fail and return NULL.
4840 * The caller should call synchronize_rcu() after this.
4842 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4844 struct ring_buffer_per_cpu *cpu_buffer;
4846 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4849 cpu_buffer = buffer->buffers[cpu];
4850 atomic_inc(&cpu_buffer->record_disabled);
4852 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4855 * ring_buffer_record_enable_cpu - enable writes to the buffer
4856 * @buffer: The ring buffer to enable writes
4857 * @cpu: The CPU to enable.
4859 * Note, multiple disables will need the same number of enables
4860 * to truly enable the writing (much like preempt_disable).
4862 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4864 struct ring_buffer_per_cpu *cpu_buffer;
4866 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4869 cpu_buffer = buffer->buffers[cpu];
4870 atomic_dec(&cpu_buffer->record_disabled);
4872 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4875 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4876 * @buffer: The ring buffer
4877 * @cpu: The per CPU buffer to read from.
4879 u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4881 unsigned long flags;
4882 struct ring_buffer_per_cpu *cpu_buffer;
4883 struct buffer_page *bpage;
4886 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4889 cpu_buffer = buffer->buffers[cpu];
4890 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4892 * if the tail is on reader_page, oldest time stamp is on the reader
4895 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4896 bpage = cpu_buffer->reader_page;
4898 bpage = rb_set_head_page(cpu_buffer);
4900 ret = bpage->page->time_stamp;
4901 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4905 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4908 * ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
4909 * @buffer: The ring buffer
4910 * @cpu: The per CPU buffer to read from.
4912 unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4914 struct ring_buffer_per_cpu *cpu_buffer;
4917 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4920 cpu_buffer = buffer->buffers[cpu];
4921 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4925 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4928 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4929 * @buffer: The ring buffer
4930 * @cpu: The per CPU buffer to get the entries from.
4932 unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4934 struct ring_buffer_per_cpu *cpu_buffer;
4936 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4939 cpu_buffer = buffer->buffers[cpu];
4941 return rb_num_of_entries(cpu_buffer);
4943 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4946 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4947 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4948 * @buffer: The ring buffer
4949 * @cpu: The per CPU buffer to get the number of overruns from
4951 unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4953 struct ring_buffer_per_cpu *cpu_buffer;
4956 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4959 cpu_buffer = buffer->buffers[cpu];
4960 ret = local_read(&cpu_buffer->overrun);
4964 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4967 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4968 * commits failing due to the buffer wrapping around while there are uncommitted
4969 * events, such as during an interrupt storm.
4970 * @buffer: The ring buffer
4971 * @cpu: The per CPU buffer to get the number of overruns from
4974 ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4976 struct ring_buffer_per_cpu *cpu_buffer;
4979 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4982 cpu_buffer = buffer->buffers[cpu];
4983 ret = local_read(&cpu_buffer->commit_overrun);
4987 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4990 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4991 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4992 * @buffer: The ring buffer
4993 * @cpu: The per CPU buffer to get the number of overruns from
4996 ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4998 struct ring_buffer_per_cpu *cpu_buffer;
5001 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5004 cpu_buffer = buffer->buffers[cpu];
5005 ret = local_read(&cpu_buffer->dropped_events);
5009 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
5012 * ring_buffer_read_events_cpu - get the number of events successfully read
5013 * @buffer: The ring buffer
5014 * @cpu: The per CPU buffer to get the number of events read
5017 ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
5019 struct ring_buffer_per_cpu *cpu_buffer;
5021 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5024 cpu_buffer = buffer->buffers[cpu];
5025 return cpu_buffer->read;
5027 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
5030 * ring_buffer_entries - get the number of entries in a buffer
5031 * @buffer: The ring buffer
5033 * Returns the total number of entries in the ring buffer
5036 unsigned long ring_buffer_entries(struct trace_buffer *buffer)
5038 struct ring_buffer_per_cpu *cpu_buffer;
5039 unsigned long entries = 0;
5042 /* if you care about this being correct, lock the buffer */
5043 for_each_buffer_cpu(buffer, cpu) {
5044 cpu_buffer = buffer->buffers[cpu];
5045 entries += rb_num_of_entries(cpu_buffer);
5050 EXPORT_SYMBOL_GPL(ring_buffer_entries);
5053 * ring_buffer_overruns - get the number of overruns in buffer
5054 * @buffer: The ring buffer
5056 * Returns the total number of overruns in the ring buffer
5059 unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
5061 struct ring_buffer_per_cpu *cpu_buffer;
5062 unsigned long overruns = 0;
5065 /* if you care about this being correct, lock the buffer */
5066 for_each_buffer_cpu(buffer, cpu) {
5067 cpu_buffer = buffer->buffers[cpu];
5068 overruns += local_read(&cpu_buffer->overrun);
5073 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
5075 static void rb_iter_reset(struct ring_buffer_iter *iter)
5077 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5079 /* Iterator usage is expected to have record disabled */
5080 iter->head_page = cpu_buffer->reader_page;
5081 iter->head = cpu_buffer->reader_page->read;
5082 iter->next_event = iter->head;
5084 iter->cache_reader_page = iter->head_page;
5085 iter->cache_read = cpu_buffer->read;
5086 iter->cache_pages_removed = cpu_buffer->pages_removed;
5089 iter->read_stamp = cpu_buffer->read_stamp;
5090 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
5092 iter->read_stamp = iter->head_page->page->time_stamp;
5093 iter->page_stamp = iter->read_stamp;
5098 * ring_buffer_iter_reset - reset an iterator
5099 * @iter: The iterator to reset
5101 * Resets the iterator, so that it will start from the beginning
5104 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
5106 struct ring_buffer_per_cpu *cpu_buffer;
5107 unsigned long flags;
5112 cpu_buffer = iter->cpu_buffer;
5114 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5115 rb_iter_reset(iter);
5116 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5118 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
5121 * ring_buffer_iter_empty - check if an iterator has no more to read
5122 * @iter: The iterator to check
5124 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
5126 struct ring_buffer_per_cpu *cpu_buffer;
5127 struct buffer_page *reader;
5128 struct buffer_page *head_page;
5129 struct buffer_page *commit_page;
5130 struct buffer_page *curr_commit_page;
5135 cpu_buffer = iter->cpu_buffer;
5136 reader = cpu_buffer->reader_page;
5137 head_page = cpu_buffer->head_page;
5138 commit_page = READ_ONCE(cpu_buffer->commit_page);
5139 commit_ts = commit_page->page->time_stamp;
5142 * When the writer goes across pages, it issues a cmpxchg which
5143 * is a mb(), which will synchronize with the rmb here.
5144 * (see rb_tail_page_update())
5147 commit = rb_page_commit(commit_page);
5148 /* We want to make sure that the commit page doesn't change */
5151 /* Make sure commit page didn't change */
5152 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
5153 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
5155 /* If the commit page changed, then there's more data */
5156 if (curr_commit_page != commit_page ||
5157 curr_commit_ts != commit_ts)
5160 /* Still racy, as it may return a false positive, but that's OK */
5161 return ((iter->head_page == commit_page && iter->head >= commit) ||
5162 (iter->head_page == reader && commit_page == head_page &&
5163 head_page->read == commit &&
5164 iter->head == rb_page_size(cpu_buffer->reader_page)));
5166 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
5169 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
5170 struct ring_buffer_event *event)
5174 switch (event->type_len) {
5175 case RINGBUF_TYPE_PADDING:
5178 case RINGBUF_TYPE_TIME_EXTEND:
5179 delta = rb_event_time_stamp(event);
5180 cpu_buffer->read_stamp += delta;
5183 case RINGBUF_TYPE_TIME_STAMP:
5184 delta = rb_event_time_stamp(event);
5185 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
5186 cpu_buffer->read_stamp = delta;
5189 case RINGBUF_TYPE_DATA:
5190 cpu_buffer->read_stamp += event->time_delta;
5194 RB_WARN_ON(cpu_buffer, 1);
5199 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
5200 struct ring_buffer_event *event)
5204 switch (event->type_len) {
5205 case RINGBUF_TYPE_PADDING:
5208 case RINGBUF_TYPE_TIME_EXTEND:
5209 delta = rb_event_time_stamp(event);
5210 iter->read_stamp += delta;
5213 case RINGBUF_TYPE_TIME_STAMP:
5214 delta = rb_event_time_stamp(event);
5215 delta = rb_fix_abs_ts(delta, iter->read_stamp);
5216 iter->read_stamp = delta;
5219 case RINGBUF_TYPE_DATA:
5220 iter->read_stamp += event->time_delta;
5224 RB_WARN_ON(iter->cpu_buffer, 1);
5228 static struct buffer_page *
5229 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
5231 struct buffer_page *reader = NULL;
5232 unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
5233 unsigned long overwrite;
5234 unsigned long flags;
5238 local_irq_save(flags);
5239 arch_spin_lock(&cpu_buffer->lock);
5243 * This should normally only loop twice. But because the
5244 * start of the reader inserts an empty page, it causes
5245 * a case where we will loop three times. There should be no
5246 * reason to loop four times (that I know of).
5248 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
5253 reader = cpu_buffer->reader_page;
5255 /* If there's more to read, return this page */
5256 if (cpu_buffer->reader_page->read < rb_page_size(reader))
5259 /* Never should we have an index greater than the size */
5260 if (RB_WARN_ON(cpu_buffer,
5261 cpu_buffer->reader_page->read > rb_page_size(reader)))
5264 /* check if we caught up to the tail */
5266 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
5269 /* Don't bother swapping if the ring buffer is empty */
5270 if (rb_num_of_entries(cpu_buffer) == 0)
5274 * Reset the reader page to size zero.
5276 local_set(&cpu_buffer->reader_page->write, 0);
5277 local_set(&cpu_buffer->reader_page->entries, 0);
5278 local_set(&cpu_buffer->reader_page->page->commit, 0);
5279 cpu_buffer->reader_page->real_end = 0;
5283 * Splice the empty reader page into the list around the head.
5285 reader = rb_set_head_page(cpu_buffer);
5288 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
5289 cpu_buffer->reader_page->list.prev = reader->list.prev;
5292 * cpu_buffer->pages just needs to point to the buffer, it
5293 * has no specific buffer page to point to. Lets move it out
5294 * of our way so we don't accidentally swap it.
5296 cpu_buffer->pages = reader->list.prev;
5298 /* The reader page will be pointing to the new head */
5299 rb_set_list_to_head(&cpu_buffer->reader_page->list);
5302 * We want to make sure we read the overruns after we set up our
5303 * pointers to the next object. The writer side does a
5304 * cmpxchg to cross pages which acts as the mb on the writer
5305 * side. Note, the reader will constantly fail the swap
5306 * while the writer is updating the pointers, so this
5307 * guarantees that the overwrite recorded here is the one we
5308 * want to compare with the last_overrun.
5311 overwrite = local_read(&(cpu_buffer->overrun));
5314 * Here's the tricky part.
5316 * We need to move the pointer past the header page.
5317 * But we can only do that if a writer is not currently
5318 * moving it. The page before the header page has the
5319 * flag bit '1' set if it is pointing to the page we want.
5320 * but if the writer is in the process of moving it
5321 * than it will be '2' or already moved '0'.
5324 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
5327 * If we did not convert it, then we must try again.
5332 if (cpu_buffer->ring_meta)
5333 rb_update_meta_reader(cpu_buffer, reader);
5336 * Yay! We succeeded in replacing the page.
5338 * Now make the new head point back to the reader page.
5340 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
5341 rb_inc_page(&cpu_buffer->head_page);
5344 local_inc(&cpu_buffer->pages_read);
5346 /* Finally update the reader page to the new head */
5347 cpu_buffer->reader_page = reader;
5348 cpu_buffer->reader_page->read = 0;
5350 if (overwrite != cpu_buffer->last_overrun) {
5351 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
5352 cpu_buffer->last_overrun = overwrite;
5358 /* Update the read_stamp on the first event */
5359 if (reader && reader->read == 0)
5360 cpu_buffer->read_stamp = reader->page->time_stamp;
5362 arch_spin_unlock(&cpu_buffer->lock);
5363 local_irq_restore(flags);
5366 * The writer has preempt disable, wait for it. But not forever
5367 * Although, 1 second is pretty much "forever"
5369 #define USECS_WAIT 1000000
5370 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
5371 /* If the write is past the end of page, a writer is still updating it */
5372 if (likely(!reader || rb_page_write(reader) <= bsize))
5377 /* Get the latest version of the reader write value */
5381 /* The writer is not moving forward? Something is wrong */
5382 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
5386 * Make sure we see any padding after the write update
5387 * (see rb_reset_tail()).
5389 * In addition, a writer may be writing on the reader page
5390 * if the page has not been fully filled, so the read barrier
5391 * is also needed to make sure we see the content of what is
5392 * committed by the writer (see rb_set_commit_to_write()).
5400 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
5402 struct ring_buffer_event *event;
5403 struct buffer_page *reader;
5406 reader = rb_get_reader_page(cpu_buffer);
5408 /* This function should not be called when buffer is empty */
5409 if (RB_WARN_ON(cpu_buffer, !reader))
5412 event = rb_reader_event(cpu_buffer);
5414 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
5417 rb_update_read_stamp(cpu_buffer, event);
5419 length = rb_event_length(event);
5420 cpu_buffer->reader_page->read += length;
5421 cpu_buffer->read_bytes += length;
5424 static void rb_advance_iter(struct ring_buffer_iter *iter)
5426 struct ring_buffer_per_cpu *cpu_buffer;
5428 cpu_buffer = iter->cpu_buffer;
5430 /* If head == next_event then we need to jump to the next event */
5431 if (iter->head == iter->next_event) {
5432 /* If the event gets overwritten again, there's nothing to do */
5433 if (rb_iter_head_event(iter) == NULL)
5437 iter->head = iter->next_event;
5440 * Check if we are at the end of the buffer.
5442 if (iter->next_event >= rb_page_size(iter->head_page)) {
5443 /* discarded commits can make the page empty */
5444 if (iter->head_page == cpu_buffer->commit_page)
5450 rb_update_iter_read_stamp(iter, iter->event);
5453 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
5455 return cpu_buffer->lost_events;
5458 static struct ring_buffer_event *
5459 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
5460 unsigned long *lost_events)
5462 struct ring_buffer_event *event;
5463 struct buffer_page *reader;
5470 * We repeat when a time extend is encountered.
5471 * Since the time extend is always attached to a data event,
5472 * we should never loop more than once.
5473 * (We never hit the following condition more than twice).
5475 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
5478 reader = rb_get_reader_page(cpu_buffer);
5482 event = rb_reader_event(cpu_buffer);
5484 switch (event->type_len) {
5485 case RINGBUF_TYPE_PADDING:
5486 if (rb_null_event(event))
5487 RB_WARN_ON(cpu_buffer, 1);
5489 * Because the writer could be discarding every
5490 * event it creates (which would probably be bad)
5491 * if we were to go back to "again" then we may never
5492 * catch up, and will trigger the warn on, or lock
5493 * the box. Return the padding, and we will release
5494 * the current locks, and try again.
5498 case RINGBUF_TYPE_TIME_EXTEND:
5499 /* Internal data, OK to advance */
5500 rb_advance_reader(cpu_buffer);
5503 case RINGBUF_TYPE_TIME_STAMP:
5505 *ts = rb_event_time_stamp(event);
5506 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
5507 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5508 cpu_buffer->cpu, ts);
5510 /* Internal data, OK to advance */
5511 rb_advance_reader(cpu_buffer);
5514 case RINGBUF_TYPE_DATA:
5516 *ts = cpu_buffer->read_stamp + event->time_delta;
5517 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5518 cpu_buffer->cpu, ts);
5521 *lost_events = rb_lost_events(cpu_buffer);
5525 RB_WARN_ON(cpu_buffer, 1);
5530 EXPORT_SYMBOL_GPL(ring_buffer_peek);
5532 static struct ring_buffer_event *
5533 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5535 struct trace_buffer *buffer;
5536 struct ring_buffer_per_cpu *cpu_buffer;
5537 struct ring_buffer_event *event;
5543 cpu_buffer = iter->cpu_buffer;
5544 buffer = cpu_buffer->buffer;
5547 * Check if someone performed a consuming read to the buffer
5548 * or removed some pages from the buffer. In these cases,
5549 * iterator was invalidated and we need to reset it.
5551 if (unlikely(iter->cache_read != cpu_buffer->read ||
5552 iter->cache_reader_page != cpu_buffer->reader_page ||
5553 iter->cache_pages_removed != cpu_buffer->pages_removed))
5554 rb_iter_reset(iter);
5557 if (ring_buffer_iter_empty(iter))
5561 * As the writer can mess with what the iterator is trying
5562 * to read, just give up if we fail to get an event after
5563 * three tries. The iterator is not as reliable when reading
5564 * the ring buffer with an active write as the consumer is.
5565 * Do not warn if the three failures is reached.
5570 if (rb_per_cpu_empty(cpu_buffer))
5573 if (iter->head >= rb_page_size(iter->head_page)) {
5578 event = rb_iter_head_event(iter);
5582 switch (event->type_len) {
5583 case RINGBUF_TYPE_PADDING:
5584 if (rb_null_event(event)) {
5588 rb_advance_iter(iter);
5591 case RINGBUF_TYPE_TIME_EXTEND:
5592 /* Internal data, OK to advance */
5593 rb_advance_iter(iter);
5596 case RINGBUF_TYPE_TIME_STAMP:
5598 *ts = rb_event_time_stamp(event);
5599 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
5600 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
5601 cpu_buffer->cpu, ts);
5603 /* Internal data, OK to advance */
5604 rb_advance_iter(iter);
5607 case RINGBUF_TYPE_DATA:
5609 *ts = iter->read_stamp + event->time_delta;
5610 ring_buffer_normalize_time_stamp(buffer,
5611 cpu_buffer->cpu, ts);
5616 RB_WARN_ON(cpu_buffer, 1);
5621 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
5623 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
5625 if (likely(!in_nmi())) {
5626 raw_spin_lock(&cpu_buffer->reader_lock);
5631 * If an NMI die dumps out the content of the ring buffer
5632 * trylock must be used to prevent a deadlock if the NMI
5633 * preempted a task that holds the ring buffer locks. If
5634 * we get the lock then all is fine, if not, then continue
5635 * to do the read, but this can corrupt the ring buffer,
5636 * so it must be permanently disabled from future writes.
5637 * Reading from NMI is a oneshot deal.
5639 if (raw_spin_trylock(&cpu_buffer->reader_lock))
5642 /* Continue without locking, but disable the ring buffer */
5643 atomic_inc(&cpu_buffer->record_disabled);
5648 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
5651 raw_spin_unlock(&cpu_buffer->reader_lock);
5655 * ring_buffer_peek - peek at the next event to be read
5656 * @buffer: The ring buffer to read
5657 * @cpu: The cpu to peak at
5658 * @ts: The timestamp counter of this event.
5659 * @lost_events: a variable to store if events were lost (may be NULL)
5661 * This will return the event that will be read next, but does
5662 * not consume the data.
5664 struct ring_buffer_event *
5665 ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
5666 unsigned long *lost_events)
5668 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5669 struct ring_buffer_event *event;
5670 unsigned long flags;
5673 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5677 local_irq_save(flags);
5678 dolock = rb_reader_lock(cpu_buffer);
5679 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5680 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5681 rb_advance_reader(cpu_buffer);
5682 rb_reader_unlock(cpu_buffer, dolock);
5683 local_irq_restore(flags);
5685 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5691 /** ring_buffer_iter_dropped - report if there are dropped events
5692 * @iter: The ring buffer iterator
5694 * Returns true if there was dropped events since the last peek.
5696 bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
5698 bool ret = iter->missed_events != 0;
5700 iter->missed_events = 0;
5703 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
5706 * ring_buffer_iter_peek - peek at the next event to be read
5707 * @iter: The ring buffer iterator
5708 * @ts: The timestamp counter of this event.
5710 * This will return the event that will be read next, but does
5711 * not increment the iterator.
5713 struct ring_buffer_event *
5714 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5716 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5717 struct ring_buffer_event *event;
5718 unsigned long flags;
5721 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5722 event = rb_iter_peek(iter, ts);
5723 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5725 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5732 * ring_buffer_consume - return an event and consume it
5733 * @buffer: The ring buffer to get the next event from
5734 * @cpu: the cpu to read the buffer from
5735 * @ts: a variable to store the timestamp (may be NULL)
5736 * @lost_events: a variable to store if events were lost (may be NULL)
5738 * Returns the next event in the ring buffer, and that event is consumed.
5739 * Meaning, that sequential reads will keep returning a different event,
5740 * and eventually empty the ring buffer if the producer is slower.
5742 struct ring_buffer_event *
5743 ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5744 unsigned long *lost_events)
5746 struct ring_buffer_per_cpu *cpu_buffer;
5747 struct ring_buffer_event *event = NULL;
5748 unsigned long flags;
5752 /* might be called in atomic */
5755 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5758 cpu_buffer = buffer->buffers[cpu];
5759 local_irq_save(flags);
5760 dolock = rb_reader_lock(cpu_buffer);
5762 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5764 cpu_buffer->lost_events = 0;
5765 rb_advance_reader(cpu_buffer);
5768 rb_reader_unlock(cpu_buffer, dolock);
5769 local_irq_restore(flags);
5774 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5779 EXPORT_SYMBOL_GPL(ring_buffer_consume);
5782 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5783 * @buffer: The ring buffer to read from
5784 * @cpu: The cpu buffer to iterate over
5785 * @flags: gfp flags to use for memory allocation
5787 * This performs the initial preparations necessary to iterate
5788 * through the buffer. Memory is allocated, buffer resizing
5789 * is disabled, and the iterator pointer is returned to the caller.
5791 * After a sequence of ring_buffer_read_prepare calls, the user is
5792 * expected to make at least one call to ring_buffer_read_prepare_sync.
5793 * Afterwards, ring_buffer_read_start is invoked to get things going
5796 * This overall must be paired with ring_buffer_read_finish.
5798 struct ring_buffer_iter *
5799 ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5801 struct ring_buffer_per_cpu *cpu_buffer;
5802 struct ring_buffer_iter *iter;
5804 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5807 iter = kzalloc(sizeof(*iter), flags);
5811 /* Holds the entire event: data and meta data */
5812 iter->event_size = buffer->subbuf_size;
5813 iter->event = kmalloc(iter->event_size, flags);
5819 cpu_buffer = buffer->buffers[cpu];
5821 iter->cpu_buffer = cpu_buffer;
5823 atomic_inc(&cpu_buffer->resize_disabled);
5827 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5830 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5832 * All previously invoked ring_buffer_read_prepare calls to prepare
5833 * iterators will be synchronized. Afterwards, read_buffer_read_start
5834 * calls on those iterators are allowed.
5837 ring_buffer_read_prepare_sync(void)
5841 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5844 * ring_buffer_read_start - start a non consuming read of the buffer
5845 * @iter: The iterator returned by ring_buffer_read_prepare
5847 * This finalizes the startup of an iteration through the buffer.
5848 * The iterator comes from a call to ring_buffer_read_prepare and
5849 * an intervening ring_buffer_read_prepare_sync must have been
5852 * Must be paired with ring_buffer_read_finish.
5855 ring_buffer_read_start(struct ring_buffer_iter *iter)
5857 struct ring_buffer_per_cpu *cpu_buffer;
5858 unsigned long flags;
5863 cpu_buffer = iter->cpu_buffer;
5865 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5866 arch_spin_lock(&cpu_buffer->lock);
5867 rb_iter_reset(iter);
5868 arch_spin_unlock(&cpu_buffer->lock);
5869 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5871 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5874 * ring_buffer_read_finish - finish reading the iterator of the buffer
5875 * @iter: The iterator retrieved by ring_buffer_start
5877 * This re-enables resizing of the buffer, and frees the iterator.
5880 ring_buffer_read_finish(struct ring_buffer_iter *iter)
5882 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5884 /* Use this opportunity to check the integrity of the ring buffer. */
5885 rb_check_pages(cpu_buffer);
5887 atomic_dec(&cpu_buffer->resize_disabled);
5891 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5894 * ring_buffer_iter_advance - advance the iterator to the next location
5895 * @iter: The ring buffer iterator
5897 * Move the location of the iterator such that the next read will
5898 * be the next location of the iterator.
5900 void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5902 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5903 unsigned long flags;
5905 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5907 rb_advance_iter(iter);
5909 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5911 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5914 * ring_buffer_size - return the size of the ring buffer (in bytes)
5915 * @buffer: The ring buffer.
5916 * @cpu: The CPU to get ring buffer size from.
5918 unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5920 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5923 return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
5925 EXPORT_SYMBOL_GPL(ring_buffer_size);
5928 * ring_buffer_max_event_size - return the max data size of an event
5929 * @buffer: The ring buffer.
5931 * Returns the maximum size an event can be.
5933 unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
5935 /* If abs timestamp is requested, events have a timestamp too */
5936 if (ring_buffer_time_stamp_abs(buffer))
5937 return buffer->max_data_size - RB_LEN_TIME_EXTEND;
5938 return buffer->max_data_size;
5940 EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
5942 static void rb_clear_buffer_page(struct buffer_page *page)
5944 local_set(&page->write, 0);
5945 local_set(&page->entries, 0);
5946 rb_init_page(page->page);
5950 static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
5952 struct trace_buffer_meta *meta = cpu_buffer->meta_page;
5957 meta->reader.read = cpu_buffer->reader_page->read;
5958 meta->reader.id = cpu_buffer->reader_page->id;
5959 meta->reader.lost_events = cpu_buffer->lost_events;
5961 meta->entries = local_read(&cpu_buffer->entries);
5962 meta->overrun = local_read(&cpu_buffer->overrun);
5963 meta->read = cpu_buffer->read;
5965 /* Some archs do not have data cache coherency between kernel and user-space */
5966 flush_dcache_folio(virt_to_folio(cpu_buffer->meta_page));
5970 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5972 struct buffer_page *page;
5974 rb_head_page_deactivate(cpu_buffer);
5976 cpu_buffer->head_page
5977 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5978 rb_clear_buffer_page(cpu_buffer->head_page);
5979 list_for_each_entry(page, cpu_buffer->pages, list) {
5980 rb_clear_buffer_page(page);
5983 cpu_buffer->tail_page = cpu_buffer->head_page;
5984 cpu_buffer->commit_page = cpu_buffer->head_page;
5986 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5987 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5988 rb_clear_buffer_page(cpu_buffer->reader_page);
5990 local_set(&cpu_buffer->entries_bytes, 0);
5991 local_set(&cpu_buffer->overrun, 0);
5992 local_set(&cpu_buffer->commit_overrun, 0);
5993 local_set(&cpu_buffer->dropped_events, 0);
5994 local_set(&cpu_buffer->entries, 0);
5995 local_set(&cpu_buffer->committing, 0);
5996 local_set(&cpu_buffer->commits, 0);
5997 local_set(&cpu_buffer->pages_touched, 0);
5998 local_set(&cpu_buffer->pages_lost, 0);
5999 local_set(&cpu_buffer->pages_read, 0);
6000 cpu_buffer->last_pages_touch = 0;
6001 cpu_buffer->shortest_full = 0;
6002 cpu_buffer->read = 0;
6003 cpu_buffer->read_bytes = 0;
6005 rb_time_set(&cpu_buffer->write_stamp, 0);
6006 rb_time_set(&cpu_buffer->before_stamp, 0);
6008 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
6010 cpu_buffer->lost_events = 0;
6011 cpu_buffer->last_overrun = 0;
6013 rb_head_page_activate(cpu_buffer);
6014 cpu_buffer->pages_removed = 0;
6016 if (cpu_buffer->mapped) {
6017 rb_update_meta_page(cpu_buffer);
6018 if (cpu_buffer->ring_meta) {
6019 struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
6020 meta->commit_buffer = meta->head_buffer;
6025 /* Must have disabled the cpu buffer then done a synchronize_rcu */
6026 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
6028 unsigned long flags;
6030 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6032 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
6035 arch_spin_lock(&cpu_buffer->lock);
6037 rb_reset_cpu(cpu_buffer);
6039 arch_spin_unlock(&cpu_buffer->lock);
6042 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6046 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
6047 * @buffer: The ring buffer to reset a per cpu buffer of
6048 * @cpu: The CPU buffer to be reset
6050 void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
6052 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
6053 struct ring_buffer_meta *meta;
6055 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6058 /* prevent another thread from changing buffer sizes */
6059 mutex_lock(&buffer->mutex);
6061 atomic_inc(&cpu_buffer->resize_disabled);
6062 atomic_inc(&cpu_buffer->record_disabled);
6064 /* Make sure all commits have finished */
6067 reset_disabled_cpu_buffer(cpu_buffer);
6069 atomic_dec(&cpu_buffer->record_disabled);
6070 atomic_dec(&cpu_buffer->resize_disabled);
6072 /* Make sure persistent meta now uses this buffer's addresses */
6073 meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
6075 rb_meta_init_text_addr(meta);
6077 mutex_unlock(&buffer->mutex);
6079 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
6081 /* Flag to ensure proper resetting of atomic variables */
6082 #define RESET_BIT (1 << 30)
6085 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
6086 * @buffer: The ring buffer to reset a per cpu buffer of
6088 void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
6090 struct ring_buffer_per_cpu *cpu_buffer;
6091 struct ring_buffer_meta *meta;
6094 /* prevent another thread from changing buffer sizes */
6095 mutex_lock(&buffer->mutex);
6097 for_each_online_buffer_cpu(buffer, cpu) {
6098 cpu_buffer = buffer->buffers[cpu];
6100 atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
6101 atomic_inc(&cpu_buffer->record_disabled);
6104 /* Make sure all commits have finished */
6107 for_each_buffer_cpu(buffer, cpu) {
6108 cpu_buffer = buffer->buffers[cpu];
6111 * If a CPU came online during the synchronize_rcu(), then
6114 if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
6117 reset_disabled_cpu_buffer(cpu_buffer);
6119 /* Make sure persistent meta now uses this buffer's addresses */
6120 meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
6122 rb_meta_init_text_addr(meta);
6124 atomic_dec(&cpu_buffer->record_disabled);
6125 atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
6128 mutex_unlock(&buffer->mutex);
6132 * ring_buffer_reset - reset a ring buffer
6133 * @buffer: The ring buffer to reset all cpu buffers
6135 void ring_buffer_reset(struct trace_buffer *buffer)
6137 struct ring_buffer_per_cpu *cpu_buffer;
6140 /* prevent another thread from changing buffer sizes */
6141 mutex_lock(&buffer->mutex);
6143 for_each_buffer_cpu(buffer, cpu) {
6144 cpu_buffer = buffer->buffers[cpu];
6146 atomic_inc(&cpu_buffer->resize_disabled);
6147 atomic_inc(&cpu_buffer->record_disabled);
6150 /* Make sure all commits have finished */
6153 for_each_buffer_cpu(buffer, cpu) {
6154 cpu_buffer = buffer->buffers[cpu];
6156 reset_disabled_cpu_buffer(cpu_buffer);
6158 atomic_dec(&cpu_buffer->record_disabled);
6159 atomic_dec(&cpu_buffer->resize_disabled);
6162 mutex_unlock(&buffer->mutex);
6164 EXPORT_SYMBOL_GPL(ring_buffer_reset);
6167 * ring_buffer_empty - is the ring buffer empty?
6168 * @buffer: The ring buffer to test
6170 bool ring_buffer_empty(struct trace_buffer *buffer)
6172 struct ring_buffer_per_cpu *cpu_buffer;
6173 unsigned long flags;
6178 /* yes this is racy, but if you don't like the race, lock the buffer */
6179 for_each_buffer_cpu(buffer, cpu) {
6180 cpu_buffer = buffer->buffers[cpu];
6181 local_irq_save(flags);
6182 dolock = rb_reader_lock(cpu_buffer);
6183 ret = rb_per_cpu_empty(cpu_buffer);
6184 rb_reader_unlock(cpu_buffer, dolock);
6185 local_irq_restore(flags);
6193 EXPORT_SYMBOL_GPL(ring_buffer_empty);
6196 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
6197 * @buffer: The ring buffer
6198 * @cpu: The CPU buffer to test
6200 bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
6202 struct ring_buffer_per_cpu *cpu_buffer;
6203 unsigned long flags;
6207 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6210 cpu_buffer = buffer->buffers[cpu];
6211 local_irq_save(flags);
6212 dolock = rb_reader_lock(cpu_buffer);
6213 ret = rb_per_cpu_empty(cpu_buffer);
6214 rb_reader_unlock(cpu_buffer, dolock);
6215 local_irq_restore(flags);
6219 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
6221 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
6223 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
6224 * @buffer_a: One buffer to swap with
6225 * @buffer_b: The other buffer to swap with
6226 * @cpu: the CPU of the buffers to swap
6228 * This function is useful for tracers that want to take a "snapshot"
6229 * of a CPU buffer and has another back up buffer lying around.
6230 * it is expected that the tracer handles the cpu buffer not being
6231 * used at the moment.
6233 int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
6234 struct trace_buffer *buffer_b, int cpu)
6236 struct ring_buffer_per_cpu *cpu_buffer_a;
6237 struct ring_buffer_per_cpu *cpu_buffer_b;
6240 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
6241 !cpumask_test_cpu(cpu, buffer_b->cpumask))
6244 cpu_buffer_a = buffer_a->buffers[cpu];
6245 cpu_buffer_b = buffer_b->buffers[cpu];
6247 /* It's up to the callers to not try to swap mapped buffers */
6248 if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) {
6253 /* At least make sure the two buffers are somewhat the same */
6254 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
6257 if (buffer_a->subbuf_order != buffer_b->subbuf_order)
6262 if (atomic_read(&buffer_a->record_disabled))
6265 if (atomic_read(&buffer_b->record_disabled))
6268 if (atomic_read(&cpu_buffer_a->record_disabled))
6271 if (atomic_read(&cpu_buffer_b->record_disabled))
6275 * We can't do a synchronize_rcu here because this
6276 * function can be called in atomic context.
6277 * Normally this will be called from the same CPU as cpu.
6278 * If not it's up to the caller to protect this.
6280 atomic_inc(&cpu_buffer_a->record_disabled);
6281 atomic_inc(&cpu_buffer_b->record_disabled);
6284 if (local_read(&cpu_buffer_a->committing))
6286 if (local_read(&cpu_buffer_b->committing))
6290 * When resize is in progress, we cannot swap it because
6291 * it will mess the state of the cpu buffer.
6293 if (atomic_read(&buffer_a->resizing))
6295 if (atomic_read(&buffer_b->resizing))
6298 buffer_a->buffers[cpu] = cpu_buffer_b;
6299 buffer_b->buffers[cpu] = cpu_buffer_a;
6301 cpu_buffer_b->buffer = buffer_a;
6302 cpu_buffer_a->buffer = buffer_b;
6307 atomic_dec(&cpu_buffer_a->record_disabled);
6308 atomic_dec(&cpu_buffer_b->record_disabled);
6312 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
6313 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
6316 * ring_buffer_alloc_read_page - allocate a page to read from buffer
6317 * @buffer: the buffer to allocate for.
6318 * @cpu: the cpu buffer to allocate.
6320 * This function is used in conjunction with ring_buffer_read_page.
6321 * When reading a full page from the ring buffer, these functions
6322 * can be used to speed up the process. The calling function should
6323 * allocate a few pages first with this function. Then when it
6324 * needs to get pages from the ring buffer, it passes the result
6325 * of this function into ring_buffer_read_page, which will swap
6326 * the page that was allocated, with the read page of the buffer.
6329 * The page allocated, or ERR_PTR
6331 struct buffer_data_read_page *
6332 ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
6334 struct ring_buffer_per_cpu *cpu_buffer;
6335 struct buffer_data_read_page *bpage = NULL;
6336 unsigned long flags;
6339 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6340 return ERR_PTR(-ENODEV);
6342 bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
6344 return ERR_PTR(-ENOMEM);
6346 bpage->order = buffer->subbuf_order;
6347 cpu_buffer = buffer->buffers[cpu];
6348 local_irq_save(flags);
6349 arch_spin_lock(&cpu_buffer->lock);
6351 if (cpu_buffer->free_page) {
6352 bpage->data = cpu_buffer->free_page;
6353 cpu_buffer->free_page = NULL;
6356 arch_spin_unlock(&cpu_buffer->lock);
6357 local_irq_restore(flags);
6362 page = alloc_pages_node(cpu_to_node(cpu),
6363 GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO,
6364 cpu_buffer->buffer->subbuf_order);
6367 return ERR_PTR(-ENOMEM);
6370 bpage->data = page_address(page);
6373 rb_init_page(bpage->data);
6377 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
6380 * ring_buffer_free_read_page - free an allocated read page
6381 * @buffer: the buffer the page was allocate for
6382 * @cpu: the cpu buffer the page came from
6383 * @data_page: the page to free
6385 * Free a page allocated from ring_buffer_alloc_read_page.
6387 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
6388 struct buffer_data_read_page *data_page)
6390 struct ring_buffer_per_cpu *cpu_buffer;
6391 struct buffer_data_page *bpage = data_page->data;
6392 struct page *page = virt_to_page(bpage);
6393 unsigned long flags;
6395 if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
6398 cpu_buffer = buffer->buffers[cpu];
6401 * If the page is still in use someplace else, or order of the page
6402 * is different from the subbuffer order of the buffer -
6405 if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
6408 local_irq_save(flags);
6409 arch_spin_lock(&cpu_buffer->lock);
6411 if (!cpu_buffer->free_page) {
6412 cpu_buffer->free_page = bpage;
6416 arch_spin_unlock(&cpu_buffer->lock);
6417 local_irq_restore(flags);
6420 free_pages((unsigned long)bpage, data_page->order);
6423 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
6426 * ring_buffer_read_page - extract a page from the ring buffer
6427 * @buffer: buffer to extract from
6428 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
6429 * @len: amount to extract
6430 * @cpu: the cpu of the buffer to extract
6431 * @full: should the extraction only happen when the page is full.
6433 * This function will pull out a page from the ring buffer and consume it.
6434 * @data_page must be the address of the variable that was returned
6435 * from ring_buffer_alloc_read_page. This is because the page might be used
6436 * to swap with a page in the ring buffer.
6439 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
6440 * if (IS_ERR(rpage))
6441 * return PTR_ERR(rpage);
6442 * ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
6444 * process_page(ring_buffer_read_page_data(rpage), ret);
6445 * ring_buffer_free_read_page(buffer, cpu, rpage);
6447 * When @full is set, the function will not return true unless
6448 * the writer is off the reader page.
6450 * Note: it is up to the calling functions to handle sleeps and wakeups.
6451 * The ring buffer can be used anywhere in the kernel and can not
6452 * blindly call wake_up. The layer that uses the ring buffer must be
6453 * responsible for that.
6456 * >=0 if data has been transferred, returns the offset of consumed data.
6457 * <0 if no data has been transferred.
6459 int ring_buffer_read_page(struct trace_buffer *buffer,
6460 struct buffer_data_read_page *data_page,
6461 size_t len, int cpu, int full)
6463 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
6464 struct ring_buffer_event *event;
6465 struct buffer_data_page *bpage;
6466 struct buffer_page *reader;
6467 unsigned long missed_events;
6468 unsigned long flags;
6469 unsigned int commit;
6474 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6478 * If len is not big enough to hold the page header, then
6479 * we can not copy anything.
6481 if (len <= BUF_PAGE_HDR_SIZE)
6484 len -= BUF_PAGE_HDR_SIZE;
6486 if (!data_page || !data_page->data)
6488 if (data_page->order != buffer->subbuf_order)
6491 bpage = data_page->data;
6495 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6497 reader = rb_get_reader_page(cpu_buffer);
6501 event = rb_reader_event(cpu_buffer);
6503 read = reader->read;
6504 commit = rb_page_size(reader);
6506 /* Check if any events were dropped */
6507 missed_events = cpu_buffer->lost_events;
6510 * If this page has been partially read or
6511 * if len is not big enough to read the rest of the page or
6512 * a writer is still on the page, then
6513 * we must copy the data from the page to the buffer.
6514 * Otherwise, we can simply swap the page with the one passed in.
6516 if (read || (len < (commit - read)) ||
6517 cpu_buffer->reader_page == cpu_buffer->commit_page ||
6518 cpu_buffer->mapped) {
6519 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
6520 unsigned int rpos = read;
6521 unsigned int pos = 0;
6525 * If a full page is expected, this can still be returned
6526 * if there's been a previous partial read and the
6527 * rest of the page can be read and the commit page is off
6531 (!read || (len < (commit - read)) ||
6532 cpu_buffer->reader_page == cpu_buffer->commit_page))
6535 if (len > (commit - read))
6536 len = (commit - read);
6538 /* Always keep the time extend and data together */
6539 size = rb_event_ts_length(event);
6544 /* save the current timestamp, since the user will need it */
6545 save_timestamp = cpu_buffer->read_stamp;
6547 /* Need to copy one event at a time */
6549 /* We need the size of one event, because
6550 * rb_advance_reader only advances by one event,
6551 * whereas rb_event_ts_length may include the size of
6552 * one or two events.
6553 * We have already ensured there's enough space if this
6554 * is a time extend. */
6555 size = rb_event_length(event);
6556 memcpy(bpage->data + pos, rpage->data + rpos, size);
6560 rb_advance_reader(cpu_buffer);
6561 rpos = reader->read;
6567 event = rb_reader_event(cpu_buffer);
6568 /* Always keep the time extend and data together */
6569 size = rb_event_ts_length(event);
6570 } while (len >= size);
6573 local_set(&bpage->commit, pos);
6574 bpage->time_stamp = save_timestamp;
6576 /* we copied everything to the beginning */
6579 /* update the entry counter */
6580 cpu_buffer->read += rb_page_entries(reader);
6581 cpu_buffer->read_bytes += rb_page_size(reader);
6583 /* swap the pages */
6584 rb_init_page(bpage);
6585 bpage = reader->page;
6586 reader->page = data_page->data;
6587 local_set(&reader->write, 0);
6588 local_set(&reader->entries, 0);
6590 data_page->data = bpage;
6593 * Use the real_end for the data size,
6594 * This gives us a chance to store the lost events
6597 if (reader->real_end)
6598 local_set(&bpage->commit, reader->real_end);
6602 cpu_buffer->lost_events = 0;
6604 commit = local_read(&bpage->commit);
6606 * Set a flag in the commit field if we lost events
6608 if (missed_events) {
6609 /* If there is room at the end of the page to save the
6610 * missed events, then record it there.
6612 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
6613 memcpy(&bpage->data[commit], &missed_events,
6614 sizeof(missed_events));
6615 local_add(RB_MISSED_STORED, &bpage->commit);
6616 commit += sizeof(missed_events);
6618 local_add(RB_MISSED_EVENTS, &bpage->commit);
6622 * This page may be off to user land. Zero it out here.
6624 if (commit < buffer->subbuf_size)
6625 memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
6628 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6633 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
6636 * ring_buffer_read_page_data - get pointer to the data in the page.
6637 * @page: the page to get the data from
6639 * Returns pointer to the actual data in this page.
6641 void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
6645 EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
6648 * ring_buffer_subbuf_size_get - get size of the sub buffer.
6649 * @buffer: the buffer to get the sub buffer size from
6651 * Returns size of the sub buffer, in bytes.
6653 int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
6655 return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
6657 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
6660 * ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
6661 * @buffer: The ring_buffer to get the system sub page order from
6663 * By default, one ring buffer sub page equals to one system page. This parameter
6664 * is configurable, per ring buffer. The size of the ring buffer sub page can be
6665 * extended, but must be an order of system page size.
6667 * Returns the order of buffer sub page size, in system pages:
6668 * 0 means the sub buffer size is 1 system page and so forth.
6669 * In case of an error < 0 is returned.
6671 int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
6676 return buffer->subbuf_order;
6678 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
6681 * ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
6682 * @buffer: The ring_buffer to set the new page size.
6683 * @order: Order of the system pages in one sub buffer page
6685 * By default, one ring buffer pages equals to one system page. This API can be
6686 * used to set new size of the ring buffer page. The size must be order of
6687 * system page size, that's why the input parameter @order is the order of
6688 * system pages that are allocated for one ring buffer page:
6690 * 1 - 2 system pages
6691 * 3 - 4 system pages
6694 * Returns 0 on success or < 0 in case of an error.
6696 int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
6698 struct ring_buffer_per_cpu *cpu_buffer;
6699 struct buffer_page *bpage, *tmp;
6700 int old_order, old_size;
6706 if (!buffer || order < 0)
6709 if (buffer->subbuf_order == order)
6712 psize = (1 << order) * PAGE_SIZE;
6713 if (psize <= BUF_PAGE_HDR_SIZE)
6716 /* Size of a subbuf cannot be greater than the write counter */
6717 if (psize > RB_WRITE_MASK + 1)
6720 old_order = buffer->subbuf_order;
6721 old_size = buffer->subbuf_size;
6723 /* prevent another thread from changing buffer sizes */
6724 mutex_lock(&buffer->mutex);
6725 atomic_inc(&buffer->record_disabled);
6727 /* Make sure all commits have finished */
6730 buffer->subbuf_order = order;
6731 buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
6733 /* Make sure all new buffers are allocated, before deleting the old ones */
6734 for_each_buffer_cpu(buffer, cpu) {
6736 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6739 cpu_buffer = buffer->buffers[cpu];
6741 if (cpu_buffer->mapped) {
6746 /* Update the number of pages to match the new size */
6747 nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
6748 nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
6750 /* we need a minimum of two pages */
6754 cpu_buffer->nr_pages_to_update = nr_pages;
6756 /* Include the reader page */
6759 /* Allocate the new size buffer */
6760 INIT_LIST_HEAD(&cpu_buffer->new_pages);
6761 if (__rb_allocate_pages(cpu_buffer, nr_pages,
6762 &cpu_buffer->new_pages)) {
6763 /* not enough memory for new pages */
6769 for_each_buffer_cpu(buffer, cpu) {
6770 struct buffer_data_page *old_free_data_page;
6771 struct list_head old_pages;
6772 unsigned long flags;
6774 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6777 cpu_buffer = buffer->buffers[cpu];
6779 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6781 /* Clear the head bit to make the link list normal to read */
6782 rb_head_page_deactivate(cpu_buffer);
6785 * Collect buffers from the cpu_buffer pages list and the
6786 * reader_page on old_pages, so they can be freed later when not
6787 * under a spinlock. The pages list is a linked list with no
6788 * head, adding old_pages turns it into a regular list with
6789 * old_pages being the head.
6791 list_add(&old_pages, cpu_buffer->pages);
6792 list_add(&cpu_buffer->reader_page->list, &old_pages);
6794 /* One page was allocated for the reader page */
6795 cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
6796 struct buffer_page, list);
6797 list_del_init(&cpu_buffer->reader_page->list);
6799 /* Install the new pages, remove the head from the list */
6800 cpu_buffer->pages = cpu_buffer->new_pages.next;
6801 list_del_init(&cpu_buffer->new_pages);
6804 cpu_buffer->head_page
6805 = list_entry(cpu_buffer->pages, struct buffer_page, list);
6806 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
6808 cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
6809 cpu_buffer->nr_pages_to_update = 0;
6811 old_free_data_page = cpu_buffer->free_page;
6812 cpu_buffer->free_page = NULL;
6814 rb_head_page_activate(cpu_buffer);
6816 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6818 /* Free old sub buffers */
6819 list_for_each_entry_safe(bpage, tmp, &old_pages, list) {
6820 list_del_init(&bpage->list);
6821 free_buffer_page(bpage);
6823 free_pages((unsigned long)old_free_data_page, old_order);
6825 rb_check_pages(cpu_buffer);
6828 atomic_dec(&buffer->record_disabled);
6829 mutex_unlock(&buffer->mutex);
6834 buffer->subbuf_order = old_order;
6835 buffer->subbuf_size = old_size;
6837 atomic_dec(&buffer->record_disabled);
6838 mutex_unlock(&buffer->mutex);
6840 for_each_buffer_cpu(buffer, cpu) {
6841 cpu_buffer = buffer->buffers[cpu];
6843 if (!cpu_buffer->nr_pages_to_update)
6846 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
6847 list_del_init(&bpage->list);
6848 free_buffer_page(bpage);
6854 EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
6856 static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6860 if (cpu_buffer->meta_page)
6863 page = alloc_page(GFP_USER | __GFP_ZERO);
6867 cpu_buffer->meta_page = page_to_virt(page);
6872 static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
6874 unsigned long addr = (unsigned long)cpu_buffer->meta_page;
6877 cpu_buffer->meta_page = NULL;
6880 static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer,
6881 unsigned long *subbuf_ids)
6883 struct trace_buffer_meta *meta = cpu_buffer->meta_page;
6884 unsigned int nr_subbufs = cpu_buffer->nr_pages + 1;
6885 struct buffer_page *first_subbuf, *subbuf;
6888 subbuf_ids[id] = (unsigned long)cpu_buffer->reader_page->page;
6889 cpu_buffer->reader_page->id = id++;
6891 first_subbuf = subbuf = rb_set_head_page(cpu_buffer);
6893 if (WARN_ON(id >= nr_subbufs))
6896 subbuf_ids[id] = (unsigned long)subbuf->page;
6899 rb_inc_page(&subbuf);
6901 } while (subbuf != first_subbuf);
6903 /* install subbuf ID to kern VA translation */
6904 cpu_buffer->subbuf_ids = subbuf_ids;
6906 meta->meta_struct_len = sizeof(*meta);
6907 meta->nr_subbufs = nr_subbufs;
6908 meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
6909 meta->meta_page_size = meta->subbuf_size;
6911 rb_update_meta_page(cpu_buffer);
6914 static struct ring_buffer_per_cpu *
6915 rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu)
6917 struct ring_buffer_per_cpu *cpu_buffer;
6919 if (!cpumask_test_cpu(cpu, buffer->cpumask))
6920 return ERR_PTR(-EINVAL);
6922 cpu_buffer = buffer->buffers[cpu];
6924 mutex_lock(&cpu_buffer->mapping_lock);
6926 if (!cpu_buffer->user_mapped) {
6927 mutex_unlock(&cpu_buffer->mapping_lock);
6928 return ERR_PTR(-ENODEV);
6934 static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer)
6936 mutex_unlock(&cpu_buffer->mapping_lock);
6940 * Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need
6941 * to be set-up or torn-down.
6943 static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
6946 unsigned long flags;
6948 lockdep_assert_held(&cpu_buffer->mapping_lock);
6950 /* mapped is always greater or equal to user_mapped */
6951 if (WARN_ON(cpu_buffer->mapped < cpu_buffer->user_mapped))
6954 if (inc && cpu_buffer->mapped == UINT_MAX)
6957 if (WARN_ON(!inc && cpu_buffer->user_mapped == 0))
6960 mutex_lock(&cpu_buffer->buffer->mutex);
6961 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
6964 cpu_buffer->user_mapped++;
6965 cpu_buffer->mapped++;
6967 cpu_buffer->user_mapped--;
6968 cpu_buffer->mapped--;
6971 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
6972 mutex_unlock(&cpu_buffer->buffer->mutex);
6978 * +--------------+ pgoff == 0
6980 * +--------------+ pgoff == 1
6983 * +--------------+ pgoff == (1 + (1 << subbuf_order))
6989 static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
6990 struct vm_area_struct *vma)
6992 unsigned long nr_subbufs, nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff;
6993 unsigned int subbuf_pages, subbuf_order;
6994 struct page **pages;
6998 /* Refuse MP_PRIVATE or writable mappings */
6999 if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC ||
7000 !(vma->vm_flags & VM_MAYSHARE))
7003 subbuf_order = cpu_buffer->buffer->subbuf_order;
7004 subbuf_pages = 1 << subbuf_order;
7006 if (subbuf_order && pgoff % subbuf_pages)
7010 * Make sure the mapping cannot become writable later. Also tell the VM
7011 * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND).
7013 vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP,
7016 lockdep_assert_held(&cpu_buffer->mapping_lock);
7018 nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
7019 nr_pages = ((nr_subbufs + 1) << subbuf_order); /* + meta-page */
7020 if (nr_pages <= pgoff)
7025 nr_vma_pages = vma_pages(vma);
7026 if (!nr_vma_pages || nr_vma_pages > nr_pages)
7029 nr_pages = nr_vma_pages;
7031 pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
7036 unsigned long meta_page_padding;
7038 pages[p++] = virt_to_page(cpu_buffer->meta_page);
7041 * Pad with the zero-page to align the meta-page with the
7044 meta_page_padding = subbuf_pages - 1;
7045 while (meta_page_padding-- && p < nr_pages) {
7046 unsigned long __maybe_unused zero_addr =
7047 vma->vm_start + (PAGE_SIZE * p);
7049 pages[p++] = ZERO_PAGE(zero_addr);
7052 /* Skip the meta-page */
7053 pgoff -= subbuf_pages;
7055 s += pgoff / subbuf_pages;
7058 while (p < nr_pages) {
7062 if (WARN_ON_ONCE(s >= nr_subbufs)) {
7067 page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
7069 for (; off < (1 << (subbuf_order)); off++, page++) {
7078 err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
7086 static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
7087 struct vm_area_struct *vma)
7093 int ring_buffer_map(struct trace_buffer *buffer, int cpu,
7094 struct vm_area_struct *vma)
7096 struct ring_buffer_per_cpu *cpu_buffer;
7097 unsigned long flags, *subbuf_ids;
7100 if (!cpumask_test_cpu(cpu, buffer->cpumask))
7103 cpu_buffer = buffer->buffers[cpu];
7105 mutex_lock(&cpu_buffer->mapping_lock);
7107 if (cpu_buffer->user_mapped) {
7108 err = __rb_map_vma(cpu_buffer, vma);
7110 err = __rb_inc_dec_mapped(cpu_buffer, true);
7111 mutex_unlock(&cpu_buffer->mapping_lock);
7115 /* prevent another thread from changing buffer/sub-buffer sizes */
7116 mutex_lock(&buffer->mutex);
7118 err = rb_alloc_meta_page(cpu_buffer);
7122 /* subbuf_ids include the reader while nr_pages does not */
7123 subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL);
7125 rb_free_meta_page(cpu_buffer);
7130 atomic_inc(&cpu_buffer->resize_disabled);
7133 * Lock all readers to block any subbuf swap until the subbuf IDs are
7136 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7137 rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
7139 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7141 err = __rb_map_vma(cpu_buffer, vma);
7143 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7144 /* This is the first time it is mapped by user */
7145 cpu_buffer->mapped++;
7146 cpu_buffer->user_mapped = 1;
7147 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7149 kfree(cpu_buffer->subbuf_ids);
7150 cpu_buffer->subbuf_ids = NULL;
7151 rb_free_meta_page(cpu_buffer);
7152 atomic_dec(&cpu_buffer->resize_disabled);
7156 mutex_unlock(&buffer->mutex);
7157 mutex_unlock(&cpu_buffer->mapping_lock);
7162 int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
7164 struct ring_buffer_per_cpu *cpu_buffer;
7165 unsigned long flags;
7168 if (!cpumask_test_cpu(cpu, buffer->cpumask))
7171 cpu_buffer = buffer->buffers[cpu];
7173 mutex_lock(&cpu_buffer->mapping_lock);
7175 if (!cpu_buffer->user_mapped) {
7178 } else if (cpu_buffer->user_mapped > 1) {
7179 __rb_inc_dec_mapped(cpu_buffer, false);
7183 mutex_lock(&buffer->mutex);
7184 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7186 /* This is the last user space mapping */
7187 if (!WARN_ON_ONCE(cpu_buffer->mapped < cpu_buffer->user_mapped))
7188 cpu_buffer->mapped--;
7189 cpu_buffer->user_mapped = 0;
7191 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7193 kfree(cpu_buffer->subbuf_ids);
7194 cpu_buffer->subbuf_ids = NULL;
7195 rb_free_meta_page(cpu_buffer);
7196 atomic_dec(&cpu_buffer->resize_disabled);
7198 mutex_unlock(&buffer->mutex);
7201 mutex_unlock(&cpu_buffer->mapping_lock);
7206 int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu)
7208 struct ring_buffer_per_cpu *cpu_buffer;
7209 struct buffer_page *reader;
7210 unsigned long missed_events;
7211 unsigned long reader_size;
7212 unsigned long flags;
7214 cpu_buffer = rb_get_mapped_buffer(buffer, cpu);
7215 if (IS_ERR(cpu_buffer))
7216 return (int)PTR_ERR(cpu_buffer);
7218 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
7221 if (rb_per_cpu_empty(cpu_buffer))
7224 reader_size = rb_page_size(cpu_buffer->reader_page);
7227 * There are data to be read on the current reader page, we can
7228 * return to the caller. But before that, we assume the latter will read
7229 * everything. Let's update the kernel reader accordingly.
7231 if (cpu_buffer->reader_page->read < reader_size) {
7232 while (cpu_buffer->reader_page->read < reader_size)
7233 rb_advance_reader(cpu_buffer);
7237 reader = rb_get_reader_page(cpu_buffer);
7238 if (WARN_ON(!reader))
7241 /* Check if any events were dropped */
7242 missed_events = cpu_buffer->lost_events;
7244 if (cpu_buffer->reader_page != cpu_buffer->commit_page) {
7245 if (missed_events) {
7246 struct buffer_data_page *bpage = reader->page;
7247 unsigned int commit;
7249 * Use the real_end for the data size,
7250 * This gives us a chance to store the lost events
7253 if (reader->real_end)
7254 local_set(&bpage->commit, reader->real_end);
7256 * If there is room at the end of the page to save the
7257 * missed events, then record it there.
7259 commit = rb_page_size(reader);
7260 if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
7261 memcpy(&bpage->data[commit], &missed_events,
7262 sizeof(missed_events));
7263 local_add(RB_MISSED_STORED, &bpage->commit);
7265 local_add(RB_MISSED_EVENTS, &bpage->commit);
7269 * There really shouldn't be any missed events if the commit
7270 * is on the reader page.
7272 WARN_ON_ONCE(missed_events);
7275 cpu_buffer->lost_events = 0;
7280 /* Some archs do not have data cache coherency between kernel and user-space */
7281 flush_dcache_folio(virt_to_folio(cpu_buffer->reader_page->page));
7283 rb_update_meta_page(cpu_buffer);
7285 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
7286 rb_put_mapped_buffer(cpu_buffer);
7292 * We only allocate new buffers, never free them if the CPU goes down.
7293 * If we were to free the buffer, then the user would lose any trace that was in
7296 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
7298 struct trace_buffer *buffer;
7301 unsigned long nr_pages;
7303 buffer = container_of(node, struct trace_buffer, node);
7304 if (cpumask_test_cpu(cpu, buffer->cpumask))
7309 /* check if all cpu sizes are same */
7310 for_each_buffer_cpu(buffer, cpu_i) {
7311 /* fill in the size from first enabled cpu */
7313 nr_pages = buffer->buffers[cpu_i]->nr_pages;
7314 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
7319 /* allocate minimum pages, user can later expand it */
7322 buffer->buffers[cpu] =
7323 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
7324 if (!buffer->buffers[cpu]) {
7325 WARN(1, "failed to allocate ring buffer on CPU %u\n",
7330 cpumask_set_cpu(cpu, buffer->cpumask);
7334 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
7336 * This is a basic integrity check of the ring buffer.
7337 * Late in the boot cycle this test will run when configured in.
7338 * It will kick off a thread per CPU that will go into a loop
7339 * writing to the per cpu ring buffer various sizes of data.
7340 * Some of the data will be large items, some small.
7342 * Another thread is created that goes into a spin, sending out
7343 * IPIs to the other CPUs to also write into the ring buffer.
7344 * this is to test the nesting ability of the buffer.
7346 * Basic stats are recorded and reported. If something in the
7347 * ring buffer should happen that's not expected, a big warning
7348 * is displayed and all ring buffers are disabled.
7350 static struct task_struct *rb_threads[NR_CPUS] __initdata;
7352 struct rb_test_data {
7353 struct trace_buffer *buffer;
7354 unsigned long events;
7355 unsigned long bytes_written;
7356 unsigned long bytes_alloc;
7357 unsigned long bytes_dropped;
7358 unsigned long events_nested;
7359 unsigned long bytes_written_nested;
7360 unsigned long bytes_alloc_nested;
7361 unsigned long bytes_dropped_nested;
7362 int min_size_nested;
7363 int max_size_nested;
7370 static struct rb_test_data rb_data[NR_CPUS] __initdata;
7373 #define RB_TEST_BUFFER_SIZE 1048576
7375 static char rb_string[] __initdata =
7376 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
7377 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
7378 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
7380 static bool rb_test_started __initdata;
7387 static __init int rb_write_something(struct rb_test_data *data, bool nested)
7389 struct ring_buffer_event *event;
7390 struct rb_item *item;
7397 /* Have nested writes different that what is written */
7398 cnt = data->cnt + (nested ? 27 : 0);
7400 /* Multiply cnt by ~e, to make some unique increment */
7401 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
7403 len = size + sizeof(struct rb_item);
7405 started = rb_test_started;
7406 /* read rb_test_started before checking buffer enabled */
7409 event = ring_buffer_lock_reserve(data->buffer, len);
7411 /* Ignore dropped events before test starts. */
7414 data->bytes_dropped += len;
7416 data->bytes_dropped_nested += len;
7421 event_len = ring_buffer_event_length(event);
7423 if (RB_WARN_ON(data->buffer, event_len < len))
7426 item = ring_buffer_event_data(event);
7428 memcpy(item->str, rb_string, size);
7431 data->bytes_alloc_nested += event_len;
7432 data->bytes_written_nested += len;
7433 data->events_nested++;
7434 if (!data->min_size_nested || len < data->min_size_nested)
7435 data->min_size_nested = len;
7436 if (len > data->max_size_nested)
7437 data->max_size_nested = len;
7439 data->bytes_alloc += event_len;
7440 data->bytes_written += len;
7442 if (!data->min_size || len < data->min_size)
7443 data->max_size = len;
7444 if (len > data->max_size)
7445 data->max_size = len;
7449 ring_buffer_unlock_commit(data->buffer);
7454 static __init int rb_test(void *arg)
7456 struct rb_test_data *data = arg;
7458 while (!kthread_should_stop()) {
7459 rb_write_something(data, false);
7462 set_current_state(TASK_INTERRUPTIBLE);
7463 /* Now sleep between a min of 100-300us and a max of 1ms */
7464 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
7470 static __init void rb_ipi(void *ignore)
7472 struct rb_test_data *data;
7473 int cpu = smp_processor_id();
7475 data = &rb_data[cpu];
7476 rb_write_something(data, true);
7479 static __init int rb_hammer_test(void *arg)
7481 while (!kthread_should_stop()) {
7483 /* Send an IPI to all cpus to write data! */
7484 smp_call_function(rb_ipi, NULL, 1);
7485 /* No sleep, but for non preempt, let others run */
7492 static __init int test_ringbuffer(void)
7494 struct task_struct *rb_hammer;
7495 struct trace_buffer *buffer;
7499 if (security_locked_down(LOCKDOWN_TRACEFS)) {
7500 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
7504 pr_info("Running ring buffer tests...\n");
7506 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
7507 if (WARN_ON(!buffer))
7510 /* Disable buffer so that threads can't write to it yet */
7511 ring_buffer_record_off(buffer);
7513 for_each_online_cpu(cpu) {
7514 rb_data[cpu].buffer = buffer;
7515 rb_data[cpu].cpu = cpu;
7516 rb_data[cpu].cnt = cpu;
7517 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
7518 cpu, "rbtester/%u");
7519 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
7520 pr_cont("FAILED\n");
7521 ret = PTR_ERR(rb_threads[cpu]);
7526 /* Now create the rb hammer! */
7527 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
7528 if (WARN_ON(IS_ERR(rb_hammer))) {
7529 pr_cont("FAILED\n");
7530 ret = PTR_ERR(rb_hammer);
7534 ring_buffer_record_on(buffer);
7536 * Show buffer is enabled before setting rb_test_started.
7537 * Yes there's a small race window where events could be
7538 * dropped and the thread wont catch it. But when a ring
7539 * buffer gets enabled, there will always be some kind of
7540 * delay before other CPUs see it. Thus, we don't care about
7541 * those dropped events. We care about events dropped after
7542 * the threads see that the buffer is active.
7545 rb_test_started = true;
7547 set_current_state(TASK_INTERRUPTIBLE);
7548 /* Just run for 10 seconds */;
7549 schedule_timeout(10 * HZ);
7551 kthread_stop(rb_hammer);
7554 for_each_online_cpu(cpu) {
7555 if (!rb_threads[cpu])
7557 kthread_stop(rb_threads[cpu]);
7560 ring_buffer_free(buffer);
7565 pr_info("finished\n");
7566 for_each_online_cpu(cpu) {
7567 struct ring_buffer_event *event;
7568 struct rb_test_data *data = &rb_data[cpu];
7569 struct rb_item *item;
7570 unsigned long total_events;
7571 unsigned long total_dropped;
7572 unsigned long total_written;
7573 unsigned long total_alloc;
7574 unsigned long total_read = 0;
7575 unsigned long total_size = 0;
7576 unsigned long total_len = 0;
7577 unsigned long total_lost = 0;
7580 int small_event_size;
7584 total_events = data->events + data->events_nested;
7585 total_written = data->bytes_written + data->bytes_written_nested;
7586 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
7587 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
7589 big_event_size = data->max_size + data->max_size_nested;
7590 small_event_size = data->min_size + data->min_size_nested;
7592 pr_info("CPU %d:\n", cpu);
7593 pr_info(" events: %ld\n", total_events);
7594 pr_info(" dropped bytes: %ld\n", total_dropped);
7595 pr_info(" alloced bytes: %ld\n", total_alloc);
7596 pr_info(" written bytes: %ld\n", total_written);
7597 pr_info(" biggest event: %d\n", big_event_size);
7598 pr_info(" smallest event: %d\n", small_event_size);
7600 if (RB_WARN_ON(buffer, total_dropped))
7605 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
7607 item = ring_buffer_event_data(event);
7608 total_len += ring_buffer_event_length(event);
7609 total_size += item->size + sizeof(struct rb_item);
7610 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
7611 pr_info("FAILED!\n");
7612 pr_info("buffer had: %.*s\n", item->size, item->str);
7613 pr_info("expected: %.*s\n", item->size, rb_string);
7614 RB_WARN_ON(buffer, 1);
7625 pr_info(" read events: %ld\n", total_read);
7626 pr_info(" lost events: %ld\n", total_lost);
7627 pr_info(" total events: %ld\n", total_lost + total_read);
7628 pr_info(" recorded len bytes: %ld\n", total_len);
7629 pr_info(" recorded size bytes: %ld\n", total_size);
7631 pr_info(" With dropped events, record len and size may not match\n"
7632 " alloced and written from above\n");
7634 if (RB_WARN_ON(buffer, total_len != total_alloc ||
7635 total_size != total_written))
7638 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
7644 pr_info("Ring buffer PASSED!\n");
7646 ring_buffer_free(buffer);
7650 late_initcall(test_ringbuffer);
7651 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */