4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 #include <linux/trace_events.h>
7 #include <linux/ring_buffer.h>
8 #include <linux/trace_clock.h>
9 #include <linux/sched/clock.h>
10 #include <linux/trace_seq.h>
11 #include <linux/spinlock.h>
12 #include <linux/irq_work.h>
13 #include <linux/uaccess.h>
14 #include <linux/hardirq.h>
15 #include <linux/kthread.h> /* for self test */
16 #include <linux/module.h>
17 #include <linux/percpu.h>
18 #include <linux/mutex.h>
19 #include <linux/delay.h>
20 #include <linux/slab.h>
21 #include <linux/init.h>
22 #include <linux/hash.h>
23 #include <linux/list.h>
24 #include <linux/cpu.h>
25 #include <linux/oom.h>
27 #include <asm/local.h>
29 static void update_pages_handler(struct work_struct *work);
32 * The ring buffer header is special. We must manually up keep it.
34 int ring_buffer_print_entry_header(struct trace_seq *s)
36 trace_seq_puts(s, "# compressed entry header\n");
37 trace_seq_puts(s, "\ttype_len : 5 bits\n");
38 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
39 trace_seq_puts(s, "\tarray : 32 bits\n");
40 trace_seq_putc(s, '\n');
41 trace_seq_printf(s, "\tpadding : type == %d\n",
42 RINGBUF_TYPE_PADDING);
43 trace_seq_printf(s, "\ttime_extend : type == %d\n",
44 RINGBUF_TYPE_TIME_EXTEND);
45 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
46 RINGBUF_TYPE_TIME_STAMP);
47 trace_seq_printf(s, "\tdata max type_len == %d\n",
48 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
50 return !trace_seq_has_overflowed(s);
54 * The ring buffer is made up of a list of pages. A separate list of pages is
55 * allocated for each CPU. A writer may only write to a buffer that is
56 * associated with the CPU it is currently executing on. A reader may read
57 * from any per cpu buffer.
59 * The reader is special. For each per cpu buffer, the reader has its own
60 * reader page. When a reader has read the entire reader page, this reader
61 * page is swapped with another page in the ring buffer.
63 * Now, as long as the writer is off the reader page, the reader can do what
64 * ever it wants with that page. The writer will never write to that page
65 * again (as long as it is out of the ring buffer).
67 * Here's some silly ASCII art.
70 * |reader| RING BUFFER
72 * +------+ +---+ +---+ +---+
81 * |reader| RING BUFFER
82 * |page |------------------v
83 * +------+ +---+ +---+ +---+
92 * |reader| RING BUFFER
93 * |page |------------------v
94 * +------+ +---+ +---+ +---+
99 * +------------------------------+
103 * |buffer| RING BUFFER
104 * |page |------------------v
105 * +------+ +---+ +---+ +---+
107 * | New +---+ +---+ +---+
110 * +------------------------------+
113 * After we make this swap, the reader can hand this page off to the splice
114 * code and be done with it. It can even allocate a new page if it needs to
115 * and swap that into the ring buffer.
117 * We will be using cmpxchg soon to make all this lockless.
121 /* Used for individual buffers (after the counter) */
122 #define RB_BUFFER_OFF (1 << 20)
124 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
126 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
127 #define RB_ALIGNMENT 4U
128 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
129 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
131 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
132 # define RB_FORCE_8BYTE_ALIGNMENT 0
133 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
135 # define RB_FORCE_8BYTE_ALIGNMENT 1
136 # define RB_ARCH_ALIGNMENT 8U
139 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
141 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
142 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
145 RB_LEN_TIME_EXTEND = 8,
146 RB_LEN_TIME_STAMP = 8,
149 #define skip_time_extend(event) \
150 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
152 #define extended_time(event) \
153 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
155 static inline int rb_null_event(struct ring_buffer_event *event)
157 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
160 static void rb_event_set_padding(struct ring_buffer_event *event)
162 /* padding has a NULL time_delta */
163 event->type_len = RINGBUF_TYPE_PADDING;
164 event->time_delta = 0;
168 rb_event_data_length(struct ring_buffer_event *event)
173 length = event->type_len * RB_ALIGNMENT;
175 length = event->array[0];
176 return length + RB_EVNT_HDR_SIZE;
180 * Return the length of the given event. Will return
181 * the length of the time extend if the event is a
184 static inline unsigned
185 rb_event_length(struct ring_buffer_event *event)
187 switch (event->type_len) {
188 case RINGBUF_TYPE_PADDING:
189 if (rb_null_event(event))
192 return event->array[0] + RB_EVNT_HDR_SIZE;
194 case RINGBUF_TYPE_TIME_EXTEND:
195 return RB_LEN_TIME_EXTEND;
197 case RINGBUF_TYPE_TIME_STAMP:
198 return RB_LEN_TIME_STAMP;
200 case RINGBUF_TYPE_DATA:
201 return rb_event_data_length(event);
210 * Return total length of time extend and data,
211 * or just the event length for all other events.
213 static inline unsigned
214 rb_event_ts_length(struct ring_buffer_event *event)
218 if (extended_time(event)) {
219 /* time extends include the data event after it */
220 len = RB_LEN_TIME_EXTEND;
221 event = skip_time_extend(event);
223 return len + rb_event_length(event);
227 * ring_buffer_event_length - return the length of the event
228 * @event: the event to get the length of
230 * Returns the size of the data load of a data event.
231 * If the event is something other than a data event, it
232 * returns the size of the event itself. With the exception
233 * of a TIME EXTEND, where it still returns the size of the
234 * data load of the data event after it.
236 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
240 if (extended_time(event))
241 event = skip_time_extend(event);
243 length = rb_event_length(event);
244 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
246 length -= RB_EVNT_HDR_SIZE;
247 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
248 length -= sizeof(event->array[0]);
251 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
253 /* inline for ring buffer fast paths */
254 static __always_inline void *
255 rb_event_data(struct ring_buffer_event *event)
257 if (extended_time(event))
258 event = skip_time_extend(event);
259 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
260 /* If length is in len field, then array[0] has the data */
262 return (void *)&event->array[0];
263 /* Otherwise length is in array[0] and array[1] has the data */
264 return (void *)&event->array[1];
268 * ring_buffer_event_data - return the data of the event
269 * @event: the event to get the data from
271 void *ring_buffer_event_data(struct ring_buffer_event *event)
273 return rb_event_data(event);
275 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
277 #define for_each_buffer_cpu(buffer, cpu) \
278 for_each_cpu(cpu, buffer->cpumask)
281 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
282 #define TS_DELTA_TEST (~TS_MASK)
285 * ring_buffer_event_time_stamp - return the event's extended timestamp
286 * @event: the event to get the timestamp of
288 * Returns the extended timestamp associated with a data event.
289 * An extended time_stamp is a 64-bit timestamp represented
290 * internally in a special way that makes the best use of space
291 * contained within a ring buffer event. This function decodes
292 * it and maps it to a straight u64 value.
294 u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
298 ts = event->array[0];
300 ts += event->time_delta;
305 /* Flag when events were overwritten */
306 #define RB_MISSED_EVENTS (1 << 31)
307 /* Missed count stored at end */
308 #define RB_MISSED_STORED (1 << 30)
310 #define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED)
312 struct buffer_data_page {
313 u64 time_stamp; /* page time stamp */
314 local_t commit; /* write committed index */
315 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
319 * Note, the buffer_page list must be first. The buffer pages
320 * are allocated in cache lines, which means that each buffer
321 * page will be at the beginning of a cache line, and thus
322 * the least significant bits will be zero. We use this to
323 * add flags in the list struct pointers, to make the ring buffer
327 struct list_head list; /* list of buffer pages */
328 local_t write; /* index for next write */
329 unsigned read; /* index for next read */
330 local_t entries; /* entries on this page */
331 unsigned long real_end; /* real end of data */
332 struct buffer_data_page *page; /* Actual data page */
336 * The buffer page counters, write and entries, must be reset
337 * atomically when crossing page boundaries. To synchronize this
338 * update, two counters are inserted into the number. One is
339 * the actual counter for the write position or count on the page.
341 * The other is a counter of updaters. Before an update happens
342 * the update partition of the counter is incremented. This will
343 * allow the updater to update the counter atomically.
345 * The counter is 20 bits, and the state data is 12.
347 #define RB_WRITE_MASK 0xfffff
348 #define RB_WRITE_INTCNT (1 << 20)
350 static void rb_init_page(struct buffer_data_page *bpage)
352 local_set(&bpage->commit, 0);
356 * ring_buffer_page_len - the size of data on the page.
357 * @page: The page to read
359 * Returns the amount of data on the page, including buffer page header.
361 size_t ring_buffer_page_len(void *page)
363 struct buffer_data_page *bpage = page;
365 return (local_read(&bpage->commit) & ~RB_MISSED_FLAGS)
370 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
373 static void free_buffer_page(struct buffer_page *bpage)
375 free_page((unsigned long)bpage->page);
380 * We need to fit the time_stamp delta into 27 bits.
382 static inline int test_time_stamp(u64 delta)
384 if (delta & TS_DELTA_TEST)
389 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
391 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
392 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
394 int ring_buffer_print_page_header(struct trace_seq *s)
396 struct buffer_data_page field;
398 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
399 "offset:0;\tsize:%u;\tsigned:%u;\n",
400 (unsigned int)sizeof(field.time_stamp),
401 (unsigned int)is_signed_type(u64));
403 trace_seq_printf(s, "\tfield: local_t commit;\t"
404 "offset:%u;\tsize:%u;\tsigned:%u;\n",
405 (unsigned int)offsetof(typeof(field), commit),
406 (unsigned int)sizeof(field.commit),
407 (unsigned int)is_signed_type(long));
409 trace_seq_printf(s, "\tfield: int overwrite;\t"
410 "offset:%u;\tsize:%u;\tsigned:%u;\n",
411 (unsigned int)offsetof(typeof(field), commit),
413 (unsigned int)is_signed_type(long));
415 trace_seq_printf(s, "\tfield: char data;\t"
416 "offset:%u;\tsize:%u;\tsigned:%u;\n",
417 (unsigned int)offsetof(typeof(field), data),
418 (unsigned int)BUF_PAGE_SIZE,
419 (unsigned int)is_signed_type(char));
421 return !trace_seq_has_overflowed(s);
425 struct irq_work work;
426 wait_queue_head_t waiters;
427 wait_queue_head_t full_waiters;
428 bool waiters_pending;
429 bool full_waiters_pending;
434 * Structure to hold event state and handle nested events.
436 struct rb_event_info {
439 unsigned long length;
440 struct buffer_page *tail_page;
445 * Used for which event context the event is in.
451 * See trace_recursive_lock() comment below for more details.
462 * head_page == tail_page && head == tail then buffer is empty.
464 struct ring_buffer_per_cpu {
466 atomic_t record_disabled;
467 struct ring_buffer *buffer;
468 raw_spinlock_t reader_lock; /* serialize readers */
469 arch_spinlock_t lock;
470 struct lock_class_key lock_key;
471 struct buffer_data_page *free_page;
472 unsigned long nr_pages;
473 unsigned int current_context;
474 struct list_head *pages;
475 struct buffer_page *head_page; /* read from head */
476 struct buffer_page *tail_page; /* write to tail */
477 struct buffer_page *commit_page; /* committed pages */
478 struct buffer_page *reader_page;
479 unsigned long lost_events;
480 unsigned long last_overrun;
482 local_t entries_bytes;
485 local_t commit_overrun;
486 local_t dropped_events;
490 unsigned long read_bytes;
493 /* ring buffer pages to update, > 0 to add, < 0 to remove */
494 long nr_pages_to_update;
495 struct list_head new_pages; /* new pages to add */
496 struct work_struct update_pages_work;
497 struct completion update_done;
499 struct rb_irq_work irq_work;
505 atomic_t record_disabled;
506 atomic_t resize_disabled;
507 cpumask_var_t cpumask;
509 struct lock_class_key *reader_lock_key;
513 struct ring_buffer_per_cpu **buffers;
515 struct hlist_node node;
518 struct rb_irq_work irq_work;
522 struct ring_buffer_iter {
523 struct ring_buffer_per_cpu *cpu_buffer;
525 struct buffer_page *head_page;
526 struct buffer_page *cache_reader_page;
527 unsigned long cache_read;
532 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
534 * Schedules a delayed work to wake up any task that is blocked on the
535 * ring buffer waiters queue.
537 static void rb_wake_up_waiters(struct irq_work *work)
539 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
541 wake_up_all(&rbwork->waiters);
542 if (rbwork->wakeup_full) {
543 rbwork->wakeup_full = false;
544 wake_up_all(&rbwork->full_waiters);
549 * ring_buffer_wait - wait for input to the ring buffer
550 * @buffer: buffer to wait on
551 * @cpu: the cpu buffer to wait on
552 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
554 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
555 * as data is added to any of the @buffer's cpu buffers. Otherwise
556 * it will wait for data to be added to a specific cpu buffer.
558 int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
560 struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
562 struct rb_irq_work *work;
566 * Depending on what the caller is waiting for, either any
567 * data in any cpu buffer, or a specific buffer, put the
568 * caller on the appropriate wait queue.
570 if (cpu == RING_BUFFER_ALL_CPUS) {
571 work = &buffer->irq_work;
572 /* Full only makes sense on per cpu reads */
575 if (!cpumask_test_cpu(cpu, buffer->cpumask))
577 cpu_buffer = buffer->buffers[cpu];
578 work = &cpu_buffer->irq_work;
584 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
586 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
589 * The events can happen in critical sections where
590 * checking a work queue can cause deadlocks.
591 * After adding a task to the queue, this flag is set
592 * only to notify events to try to wake up the queue
595 * We don't clear it even if the buffer is no longer
596 * empty. The flag only causes the next event to run
597 * irq_work to do the work queue wake up. The worse
598 * that can happen if we race with !trace_empty() is that
599 * an event will cause an irq_work to try to wake up
602 * There's no reason to protect this flag either, as
603 * the work queue and irq_work logic will do the necessary
604 * synchronization for the wake ups. The only thing
605 * that is necessary is that the wake up happens after
606 * a task has been queued. It's OK for spurious wake ups.
609 work->full_waiters_pending = true;
611 work->waiters_pending = true;
613 if (signal_pending(current)) {
618 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
621 if (cpu != RING_BUFFER_ALL_CPUS &&
622 !ring_buffer_empty_cpu(buffer, cpu)) {
629 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
630 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
631 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
641 finish_wait(&work->full_waiters, &wait);
643 finish_wait(&work->waiters, &wait);
649 * ring_buffer_poll_wait - poll on buffer input
650 * @buffer: buffer to wait on
651 * @cpu: the cpu buffer to wait on
652 * @filp: the file descriptor
653 * @poll_table: The poll descriptor
655 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
656 * as data is added to any of the @buffer's cpu buffers. Otherwise
657 * it will wait for data to be added to a specific cpu buffer.
659 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
662 __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
663 struct file *filp, poll_table *poll_table)
665 struct ring_buffer_per_cpu *cpu_buffer;
666 struct rb_irq_work *work;
668 if (cpu == RING_BUFFER_ALL_CPUS)
669 work = &buffer->irq_work;
671 if (!cpumask_test_cpu(cpu, buffer->cpumask))
674 cpu_buffer = buffer->buffers[cpu];
675 work = &cpu_buffer->irq_work;
678 poll_wait(filp, &work->waiters, poll_table);
679 work->waiters_pending = true;
681 * There's a tight race between setting the waiters_pending and
682 * checking if the ring buffer is empty. Once the waiters_pending bit
683 * is set, the next event will wake the task up, but we can get stuck
684 * if there's only a single event in.
686 * FIXME: Ideally, we need a memory barrier on the writer side as well,
687 * but adding a memory barrier to all events will cause too much of a
688 * performance hit in the fast path. We only need a memory barrier when
689 * the buffer goes from empty to having content. But as this race is
690 * extremely small, and it's not a problem if another event comes in, we
695 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
696 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
697 return EPOLLIN | EPOLLRDNORM;
701 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
702 #define RB_WARN_ON(b, cond) \
704 int _____ret = unlikely(cond); \
706 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
707 struct ring_buffer_per_cpu *__b = \
709 atomic_inc(&__b->buffer->record_disabled); \
711 atomic_inc(&b->record_disabled); \
717 /* Up this if you want to test the TIME_EXTENTS and normalization */
718 #define DEBUG_SHIFT 0
720 static inline u64 rb_time_stamp(struct ring_buffer *buffer)
722 /* shift to debug/test normalization and TIME_EXTENTS */
723 return buffer->clock() << DEBUG_SHIFT;
726 u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
730 preempt_disable_notrace();
731 time = rb_time_stamp(buffer);
732 preempt_enable_no_resched_notrace();
736 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
738 void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
741 /* Just stupid testing the normalize function and deltas */
744 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
747 * Making the ring buffer lockless makes things tricky.
748 * Although writes only happen on the CPU that they are on,
749 * and they only need to worry about interrupts. Reads can
752 * The reader page is always off the ring buffer, but when the
753 * reader finishes with a page, it needs to swap its page with
754 * a new one from the buffer. The reader needs to take from
755 * the head (writes go to the tail). But if a writer is in overwrite
756 * mode and wraps, it must push the head page forward.
758 * Here lies the problem.
760 * The reader must be careful to replace only the head page, and
761 * not another one. As described at the top of the file in the
762 * ASCII art, the reader sets its old page to point to the next
763 * page after head. It then sets the page after head to point to
764 * the old reader page. But if the writer moves the head page
765 * during this operation, the reader could end up with the tail.
767 * We use cmpxchg to help prevent this race. We also do something
768 * special with the page before head. We set the LSB to 1.
770 * When the writer must push the page forward, it will clear the
771 * bit that points to the head page, move the head, and then set
772 * the bit that points to the new head page.
774 * We also don't want an interrupt coming in and moving the head
775 * page on another writer. Thus we use the second LSB to catch
778 * head->list->prev->next bit 1 bit 0
781 * Points to head page 0 1
784 * Note we can not trust the prev pointer of the head page, because:
786 * +----+ +-----+ +-----+
787 * | |------>| T |---X--->| N |
789 * +----+ +-----+ +-----+
792 * +----------| R |----------+ |
796 * Key: ---X--> HEAD flag set in pointer
801 * (see __rb_reserve_next() to see where this happens)
803 * What the above shows is that the reader just swapped out
804 * the reader page with a page in the buffer, but before it
805 * could make the new header point back to the new page added
806 * it was preempted by a writer. The writer moved forward onto
807 * the new page added by the reader and is about to move forward
810 * You can see, it is legitimate for the previous pointer of
811 * the head (or any page) not to point back to itself. But only
815 #define RB_PAGE_NORMAL 0UL
816 #define RB_PAGE_HEAD 1UL
817 #define RB_PAGE_UPDATE 2UL
820 #define RB_FLAG_MASK 3UL
822 /* PAGE_MOVED is not part of the mask */
823 #define RB_PAGE_MOVED 4UL
826 * rb_list_head - remove any bit
828 static struct list_head *rb_list_head(struct list_head *list)
830 unsigned long val = (unsigned long)list;
832 return (struct list_head *)(val & ~RB_FLAG_MASK);
836 * rb_is_head_page - test if the given page is the head page
838 * Because the reader may move the head_page pointer, we can
839 * not trust what the head page is (it may be pointing to
840 * the reader page). But if the next page is a header page,
841 * its flags will be non zero.
844 rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
845 struct buffer_page *page, struct list_head *list)
849 val = (unsigned long)list->next;
851 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
852 return RB_PAGE_MOVED;
854 return val & RB_FLAG_MASK;
860 * The unique thing about the reader page, is that, if the
861 * writer is ever on it, the previous pointer never points
862 * back to the reader page.
864 static bool rb_is_reader_page(struct buffer_page *page)
866 struct list_head *list = page->list.prev;
868 return rb_list_head(list->next) != &page->list;
872 * rb_set_list_to_head - set a list_head to be pointing to head.
874 static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
875 struct list_head *list)
879 ptr = (unsigned long *)&list->next;
880 *ptr |= RB_PAGE_HEAD;
881 *ptr &= ~RB_PAGE_UPDATE;
885 * rb_head_page_activate - sets up head page
887 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
889 struct buffer_page *head;
891 head = cpu_buffer->head_page;
896 * Set the previous list pointer to have the HEAD flag.
898 rb_set_list_to_head(cpu_buffer, head->list.prev);
901 static void rb_list_head_clear(struct list_head *list)
903 unsigned long *ptr = (unsigned long *)&list->next;
905 *ptr &= ~RB_FLAG_MASK;
909 * rb_head_page_deactivate - clears head page ptr (for free list)
912 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
914 struct list_head *hd;
916 /* Go through the whole list and clear any pointers found. */
917 rb_list_head_clear(cpu_buffer->pages);
919 list_for_each(hd, cpu_buffer->pages)
920 rb_list_head_clear(hd);
923 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
924 struct buffer_page *head,
925 struct buffer_page *prev,
926 int old_flag, int new_flag)
928 struct list_head *list;
929 unsigned long val = (unsigned long)&head->list;
934 val &= ~RB_FLAG_MASK;
936 ret = cmpxchg((unsigned long *)&list->next,
937 val | old_flag, val | new_flag);
939 /* check if the reader took the page */
940 if ((ret & ~RB_FLAG_MASK) != val)
941 return RB_PAGE_MOVED;
943 return ret & RB_FLAG_MASK;
946 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
947 struct buffer_page *head,
948 struct buffer_page *prev,
951 return rb_head_page_set(cpu_buffer, head, prev,
952 old_flag, RB_PAGE_UPDATE);
955 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
956 struct buffer_page *head,
957 struct buffer_page *prev,
960 return rb_head_page_set(cpu_buffer, head, prev,
961 old_flag, RB_PAGE_HEAD);
964 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
965 struct buffer_page *head,
966 struct buffer_page *prev,
969 return rb_head_page_set(cpu_buffer, head, prev,
970 old_flag, RB_PAGE_NORMAL);
973 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
974 struct buffer_page **bpage)
976 struct list_head *p = rb_list_head((*bpage)->list.next);
978 *bpage = list_entry(p, struct buffer_page, list);
981 static struct buffer_page *
982 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
984 struct buffer_page *head;
985 struct buffer_page *page;
986 struct list_head *list;
989 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
993 list = cpu_buffer->pages;
994 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
997 page = head = cpu_buffer->head_page;
999 * It is possible that the writer moves the header behind
1000 * where we started, and we miss in one loop.
1001 * A second loop should grab the header, but we'll do
1002 * three loops just because I'm paranoid.
1004 for (i = 0; i < 3; i++) {
1006 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
1007 cpu_buffer->head_page = page;
1010 rb_inc_page(cpu_buffer, &page);
1011 } while (page != head);
1014 RB_WARN_ON(cpu_buffer, 1);
1019 static int rb_head_page_replace(struct buffer_page *old,
1020 struct buffer_page *new)
1022 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1026 val = *ptr & ~RB_FLAG_MASK;
1027 val |= RB_PAGE_HEAD;
1029 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1035 * rb_tail_page_update - move the tail page forward
1037 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1038 struct buffer_page *tail_page,
1039 struct buffer_page *next_page)
1041 unsigned long old_entries;
1042 unsigned long old_write;
1045 * The tail page now needs to be moved forward.
1047 * We need to reset the tail page, but without messing
1048 * with possible erasing of data brought in by interrupts
1049 * that have moved the tail page and are currently on it.
1051 * We add a counter to the write field to denote this.
1053 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1054 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1057 * Just make sure we have seen our old_write and synchronize
1058 * with any interrupts that come in.
1063 * If the tail page is still the same as what we think
1064 * it is, then it is up to us to update the tail
1067 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1068 /* Zero the write counter */
1069 unsigned long val = old_write & ~RB_WRITE_MASK;
1070 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1073 * This will only succeed if an interrupt did
1074 * not come in and change it. In which case, we
1075 * do not want to modify it.
1077 * We add (void) to let the compiler know that we do not care
1078 * about the return value of these functions. We use the
1079 * cmpxchg to only update if an interrupt did not already
1080 * do it for us. If the cmpxchg fails, we don't care.
1082 (void)local_cmpxchg(&next_page->write, old_write, val);
1083 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1086 * No need to worry about races with clearing out the commit.
1087 * it only can increment when a commit takes place. But that
1088 * only happens in the outer most nested commit.
1090 local_set(&next_page->page->commit, 0);
1092 /* Again, either we update tail_page or an interrupt does */
1093 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1097 static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1098 struct buffer_page *bpage)
1100 unsigned long val = (unsigned long)bpage;
1102 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1109 * rb_check_list - make sure a pointer to a list has the last bits zero
1111 static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1112 struct list_head *list)
1114 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1116 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1122 * rb_check_pages - integrity check of buffer pages
1123 * @cpu_buffer: CPU buffer with pages to test
1125 * As a safety measure we check to make sure the data pages have not
1128 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1130 struct list_head *head = cpu_buffer->pages;
1131 struct buffer_page *bpage, *tmp;
1133 /* Reset the head page if it exists */
1134 if (cpu_buffer->head_page)
1135 rb_set_head_page(cpu_buffer);
1137 rb_head_page_deactivate(cpu_buffer);
1139 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1141 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1144 if (rb_check_list(cpu_buffer, head))
1147 list_for_each_entry_safe(bpage, tmp, head, list) {
1148 if (RB_WARN_ON(cpu_buffer,
1149 bpage->list.next->prev != &bpage->list))
1151 if (RB_WARN_ON(cpu_buffer,
1152 bpage->list.prev->next != &bpage->list))
1154 if (rb_check_list(cpu_buffer, &bpage->list))
1158 rb_head_page_activate(cpu_buffer);
1163 static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1165 struct buffer_page *bpage, *tmp;
1166 bool user_thread = current->mm != NULL;
1171 * Check if the available memory is there first.
1172 * Note, si_mem_available() only gives us a rough estimate of available
1173 * memory. It may not be accurate. But we don't care, we just want
1174 * to prevent doing any allocation when it is obvious that it is
1175 * not going to succeed.
1177 i = si_mem_available();
1182 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1183 * gracefully without invoking oom-killer and the system is not
1186 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1189 * If a user thread allocates too much, and si_mem_available()
1190 * reports there's enough memory, even though there is not.
1191 * Make sure the OOM killer kills this thread. This can happen
1192 * even with RETRY_MAYFAIL because another task may be doing
1193 * an allocation after this task has taken all memory.
1194 * This is the task the OOM killer needs to take out during this
1195 * loop, even if it was triggered by an allocation somewhere else.
1198 set_current_oom_origin();
1199 for (i = 0; i < nr_pages; i++) {
1202 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1203 mflags, cpu_to_node(cpu));
1207 list_add(&bpage->list, pages);
1209 page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
1212 bpage->page = page_address(page);
1213 rb_init_page(bpage->page);
1215 if (user_thread && fatal_signal_pending(current))
1219 clear_current_oom_origin();
1224 list_for_each_entry_safe(bpage, tmp, pages, list) {
1225 list_del_init(&bpage->list);
1226 free_buffer_page(bpage);
1229 clear_current_oom_origin();
1234 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1235 unsigned long nr_pages)
1241 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1245 * The ring buffer page list is a circular list that does not
1246 * start and end with a list head. All page list items point to
1249 cpu_buffer->pages = pages.next;
1252 cpu_buffer->nr_pages = nr_pages;
1254 rb_check_pages(cpu_buffer);
1259 static struct ring_buffer_per_cpu *
1260 rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
1262 struct ring_buffer_per_cpu *cpu_buffer;
1263 struct buffer_page *bpage;
1267 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1268 GFP_KERNEL, cpu_to_node(cpu));
1272 cpu_buffer->cpu = cpu;
1273 cpu_buffer->buffer = buffer;
1274 raw_spin_lock_init(&cpu_buffer->reader_lock);
1275 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1276 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1277 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1278 init_completion(&cpu_buffer->update_done);
1279 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1280 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1281 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1283 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1284 GFP_KERNEL, cpu_to_node(cpu));
1286 goto fail_free_buffer;
1288 rb_check_bpage(cpu_buffer, bpage);
1290 cpu_buffer->reader_page = bpage;
1291 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1293 goto fail_free_reader;
1294 bpage->page = page_address(page);
1295 rb_init_page(bpage->page);
1297 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1298 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1300 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1302 goto fail_free_reader;
1304 cpu_buffer->head_page
1305 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1306 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1308 rb_head_page_activate(cpu_buffer);
1313 free_buffer_page(cpu_buffer->reader_page);
1320 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1322 struct list_head *head = cpu_buffer->pages;
1323 struct buffer_page *bpage, *tmp;
1325 free_buffer_page(cpu_buffer->reader_page);
1327 rb_head_page_deactivate(cpu_buffer);
1330 list_for_each_entry_safe(bpage, tmp, head, list) {
1331 list_del_init(&bpage->list);
1332 free_buffer_page(bpage);
1334 bpage = list_entry(head, struct buffer_page, list);
1335 free_buffer_page(bpage);
1342 * __ring_buffer_alloc - allocate a new ring_buffer
1343 * @size: the size in bytes per cpu that is needed.
1344 * @flags: attributes to set for the ring buffer.
1346 * Currently the only flag that is available is the RB_FL_OVERWRITE
1347 * flag. This flag means that the buffer will overwrite old data
1348 * when the buffer wraps. If this flag is not set, the buffer will
1349 * drop data when the tail hits the head.
1351 struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1352 struct lock_class_key *key)
1354 struct ring_buffer *buffer;
1360 /* keep it in its own cache line */
1361 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1366 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1367 goto fail_free_buffer;
1369 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1370 buffer->flags = flags;
1371 buffer->clock = trace_clock_local;
1372 buffer->reader_lock_key = key;
1374 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1375 init_waitqueue_head(&buffer->irq_work.waiters);
1377 /* need at least two pages */
1381 buffer->cpus = nr_cpu_ids;
1383 bsize = sizeof(void *) * nr_cpu_ids;
1384 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1386 if (!buffer->buffers)
1387 goto fail_free_cpumask;
1389 cpu = raw_smp_processor_id();
1390 cpumask_set_cpu(cpu, buffer->cpumask);
1391 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1392 if (!buffer->buffers[cpu])
1393 goto fail_free_buffers;
1395 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1397 goto fail_free_buffers;
1399 mutex_init(&buffer->mutex);
1404 for_each_buffer_cpu(buffer, cpu) {
1405 if (buffer->buffers[cpu])
1406 rb_free_cpu_buffer(buffer->buffers[cpu]);
1408 kfree(buffer->buffers);
1411 free_cpumask_var(buffer->cpumask);
1417 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1420 * ring_buffer_free - free a ring buffer.
1421 * @buffer: the buffer to free.
1424 ring_buffer_free(struct ring_buffer *buffer)
1428 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1430 for_each_buffer_cpu(buffer, cpu)
1431 rb_free_cpu_buffer(buffer->buffers[cpu]);
1433 kfree(buffer->buffers);
1434 free_cpumask_var(buffer->cpumask);
1438 EXPORT_SYMBOL_GPL(ring_buffer_free);
1440 void ring_buffer_set_clock(struct ring_buffer *buffer,
1443 buffer->clock = clock;
1446 void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
1448 buffer->time_stamp_abs = abs;
1451 bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
1453 return buffer->time_stamp_abs;
1456 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1458 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1460 return local_read(&bpage->entries) & RB_WRITE_MASK;
1463 static inline unsigned long rb_page_write(struct buffer_page *bpage)
1465 return local_read(&bpage->write) & RB_WRITE_MASK;
1469 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1471 struct list_head *tail_page, *to_remove, *next_page;
1472 struct buffer_page *to_remove_page, *tmp_iter_page;
1473 struct buffer_page *last_page, *first_page;
1474 unsigned long nr_removed;
1475 unsigned long head_bit;
1480 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1481 atomic_inc(&cpu_buffer->record_disabled);
1483 * We don't race with the readers since we have acquired the reader
1484 * lock. We also don't race with writers after disabling recording.
1485 * This makes it easy to figure out the first and the last page to be
1486 * removed from the list. We unlink all the pages in between including
1487 * the first and last pages. This is done in a busy loop so that we
1488 * lose the least number of traces.
1489 * The pages are freed after we restart recording and unlock readers.
1491 tail_page = &cpu_buffer->tail_page->list;
1494 * tail page might be on reader page, we remove the next page
1495 * from the ring buffer
1497 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1498 tail_page = rb_list_head(tail_page->next);
1499 to_remove = tail_page;
1501 /* start of pages to remove */
1502 first_page = list_entry(rb_list_head(to_remove->next),
1503 struct buffer_page, list);
1505 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1506 to_remove = rb_list_head(to_remove)->next;
1507 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1510 next_page = rb_list_head(to_remove)->next;
1513 * Now we remove all pages between tail_page and next_page.
1514 * Make sure that we have head_bit value preserved for the
1517 tail_page->next = (struct list_head *)((unsigned long)next_page |
1519 next_page = rb_list_head(next_page);
1520 next_page->prev = tail_page;
1522 /* make sure pages points to a valid page in the ring buffer */
1523 cpu_buffer->pages = next_page;
1525 /* update head page */
1527 cpu_buffer->head_page = list_entry(next_page,
1528 struct buffer_page, list);
1531 * change read pointer to make sure any read iterators reset
1534 cpu_buffer->read = 0;
1536 /* pages are removed, resume tracing and then free the pages */
1537 atomic_dec(&cpu_buffer->record_disabled);
1538 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1540 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1542 /* last buffer page to remove */
1543 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1545 tmp_iter_page = first_page;
1548 to_remove_page = tmp_iter_page;
1549 rb_inc_page(cpu_buffer, &tmp_iter_page);
1551 /* update the counters */
1552 page_entries = rb_page_entries(to_remove_page);
1555 * If something was added to this page, it was full
1556 * since it is not the tail page. So we deduct the
1557 * bytes consumed in ring buffer from here.
1558 * Increment overrun to account for the lost events.
1560 local_add(page_entries, &cpu_buffer->overrun);
1561 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1565 * We have already removed references to this list item, just
1566 * free up the buffer_page and its page
1568 free_buffer_page(to_remove_page);
1571 } while (to_remove_page != last_page);
1573 RB_WARN_ON(cpu_buffer, nr_removed);
1575 return nr_removed == 0;
1579 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1581 struct list_head *pages = &cpu_buffer->new_pages;
1582 int retries, success;
1584 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1586 * We are holding the reader lock, so the reader page won't be swapped
1587 * in the ring buffer. Now we are racing with the writer trying to
1588 * move head page and the tail page.
1589 * We are going to adapt the reader page update process where:
1590 * 1. We first splice the start and end of list of new pages between
1591 * the head page and its previous page.
1592 * 2. We cmpxchg the prev_page->next to point from head page to the
1593 * start of new pages list.
1594 * 3. Finally, we update the head->prev to the end of new list.
1596 * We will try this process 10 times, to make sure that we don't keep
1602 struct list_head *head_page, *prev_page, *r;
1603 struct list_head *last_page, *first_page;
1604 struct list_head *head_page_with_bit;
1606 head_page = &rb_set_head_page(cpu_buffer)->list;
1609 prev_page = head_page->prev;
1611 first_page = pages->next;
1612 last_page = pages->prev;
1614 head_page_with_bit = (struct list_head *)
1615 ((unsigned long)head_page | RB_PAGE_HEAD);
1617 last_page->next = head_page_with_bit;
1618 first_page->prev = prev_page;
1620 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1622 if (r == head_page_with_bit) {
1624 * yay, we replaced the page pointer to our new list,
1625 * now, we just have to update to head page's prev
1626 * pointer to point to end of list
1628 head_page->prev = last_page;
1635 INIT_LIST_HEAD(pages);
1637 * If we weren't successful in adding in new pages, warn and stop
1640 RB_WARN_ON(cpu_buffer, !success);
1641 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1643 /* free pages if they weren't inserted */
1645 struct buffer_page *bpage, *tmp;
1646 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1648 list_del_init(&bpage->list);
1649 free_buffer_page(bpage);
1655 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1659 if (cpu_buffer->nr_pages_to_update > 0)
1660 success = rb_insert_pages(cpu_buffer);
1662 success = rb_remove_pages(cpu_buffer,
1663 -cpu_buffer->nr_pages_to_update);
1666 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1669 static void update_pages_handler(struct work_struct *work)
1671 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1672 struct ring_buffer_per_cpu, update_pages_work);
1673 rb_update_pages(cpu_buffer);
1674 complete(&cpu_buffer->update_done);
1678 * ring_buffer_resize - resize the ring buffer
1679 * @buffer: the buffer to resize.
1680 * @size: the new size.
1681 * @cpu_id: the cpu buffer to resize
1683 * Minimum size is 2 * BUF_PAGE_SIZE.
1685 * Returns 0 on success and < 0 on failure.
1687 int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1690 struct ring_buffer_per_cpu *cpu_buffer;
1691 unsigned long nr_pages;
1695 * Always succeed at resizing a non-existent buffer:
1700 /* Make sure the requested buffer exists */
1701 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1702 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1705 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1707 /* we need a minimum of two pages */
1711 size = nr_pages * BUF_PAGE_SIZE;
1714 * Don't succeed if resizing is disabled, as a reader might be
1715 * manipulating the ring buffer and is expecting a sane state while
1718 if (atomic_read(&buffer->resize_disabled))
1721 /* prevent another thread from changing buffer sizes */
1722 mutex_lock(&buffer->mutex);
1724 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1725 /* calculate the pages to update */
1726 for_each_buffer_cpu(buffer, cpu) {
1727 cpu_buffer = buffer->buffers[cpu];
1729 cpu_buffer->nr_pages_to_update = nr_pages -
1730 cpu_buffer->nr_pages;
1732 * nothing more to do for removing pages or no update
1734 if (cpu_buffer->nr_pages_to_update <= 0)
1737 * to add pages, make sure all new pages can be
1738 * allocated without receiving ENOMEM
1740 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1741 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1742 &cpu_buffer->new_pages, cpu)) {
1743 /* not enough memory for new pages */
1751 * Fire off all the required work handlers
1752 * We can't schedule on offline CPUs, but it's not necessary
1753 * since we can change their buffer sizes without any race.
1755 for_each_buffer_cpu(buffer, cpu) {
1756 cpu_buffer = buffer->buffers[cpu];
1757 if (!cpu_buffer->nr_pages_to_update)
1760 /* Can't run something on an offline CPU. */
1761 if (!cpu_online(cpu)) {
1762 rb_update_pages(cpu_buffer);
1763 cpu_buffer->nr_pages_to_update = 0;
1765 schedule_work_on(cpu,
1766 &cpu_buffer->update_pages_work);
1770 /* wait for all the updates to complete */
1771 for_each_buffer_cpu(buffer, cpu) {
1772 cpu_buffer = buffer->buffers[cpu];
1773 if (!cpu_buffer->nr_pages_to_update)
1776 if (cpu_online(cpu))
1777 wait_for_completion(&cpu_buffer->update_done);
1778 cpu_buffer->nr_pages_to_update = 0;
1783 /* Make sure this CPU has been initialized */
1784 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1787 cpu_buffer = buffer->buffers[cpu_id];
1789 if (nr_pages == cpu_buffer->nr_pages)
1792 cpu_buffer->nr_pages_to_update = nr_pages -
1793 cpu_buffer->nr_pages;
1795 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1796 if (cpu_buffer->nr_pages_to_update > 0 &&
1797 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1798 &cpu_buffer->new_pages, cpu_id)) {
1805 /* Can't run something on an offline CPU. */
1806 if (!cpu_online(cpu_id))
1807 rb_update_pages(cpu_buffer);
1809 schedule_work_on(cpu_id,
1810 &cpu_buffer->update_pages_work);
1811 wait_for_completion(&cpu_buffer->update_done);
1814 cpu_buffer->nr_pages_to_update = 0;
1820 * The ring buffer resize can happen with the ring buffer
1821 * enabled, so that the update disturbs the tracing as little
1822 * as possible. But if the buffer is disabled, we do not need
1823 * to worry about that, and we can take the time to verify
1824 * that the buffer is not corrupt.
1826 if (atomic_read(&buffer->record_disabled)) {
1827 atomic_inc(&buffer->record_disabled);
1829 * Even though the buffer was disabled, we must make sure
1830 * that it is truly disabled before calling rb_check_pages.
1831 * There could have been a race between checking
1832 * record_disable and incrementing it.
1834 synchronize_sched();
1835 for_each_buffer_cpu(buffer, cpu) {
1836 cpu_buffer = buffer->buffers[cpu];
1837 rb_check_pages(cpu_buffer);
1839 atomic_dec(&buffer->record_disabled);
1842 mutex_unlock(&buffer->mutex);
1846 for_each_buffer_cpu(buffer, cpu) {
1847 struct buffer_page *bpage, *tmp;
1849 cpu_buffer = buffer->buffers[cpu];
1850 cpu_buffer->nr_pages_to_update = 0;
1852 if (list_empty(&cpu_buffer->new_pages))
1855 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1857 list_del_init(&bpage->list);
1858 free_buffer_page(bpage);
1861 mutex_unlock(&buffer->mutex);
1864 EXPORT_SYMBOL_GPL(ring_buffer_resize);
1866 void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1868 mutex_lock(&buffer->mutex);
1870 buffer->flags |= RB_FL_OVERWRITE;
1872 buffer->flags &= ~RB_FL_OVERWRITE;
1873 mutex_unlock(&buffer->mutex);
1875 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1877 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1879 return bpage->page->data + index;
1882 static __always_inline struct ring_buffer_event *
1883 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1885 return __rb_page_index(cpu_buffer->reader_page,
1886 cpu_buffer->reader_page->read);
1889 static __always_inline struct ring_buffer_event *
1890 rb_iter_head_event(struct ring_buffer_iter *iter)
1892 return __rb_page_index(iter->head_page, iter->head);
1895 static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
1897 return local_read(&bpage->page->commit);
1900 /* Size is determined by what has been committed */
1901 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
1903 return rb_page_commit(bpage);
1906 static __always_inline unsigned
1907 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1909 return rb_page_commit(cpu_buffer->commit_page);
1912 static __always_inline unsigned
1913 rb_event_index(struct ring_buffer_event *event)
1915 unsigned long addr = (unsigned long)event;
1917 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1920 static void rb_inc_iter(struct ring_buffer_iter *iter)
1922 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1925 * The iterator could be on the reader page (it starts there).
1926 * But the head could have moved, since the reader was
1927 * found. Check for this case and assign the iterator
1928 * to the head page instead of next.
1930 if (iter->head_page == cpu_buffer->reader_page)
1931 iter->head_page = rb_set_head_page(cpu_buffer);
1933 rb_inc_page(cpu_buffer, &iter->head_page);
1935 iter->read_stamp = iter->head_page->page->time_stamp;
1940 * rb_handle_head_page - writer hit the head page
1942 * Returns: +1 to retry page
1947 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1948 struct buffer_page *tail_page,
1949 struct buffer_page *next_page)
1951 struct buffer_page *new_head;
1956 entries = rb_page_entries(next_page);
1959 * The hard part is here. We need to move the head
1960 * forward, and protect against both readers on
1961 * other CPUs and writers coming in via interrupts.
1963 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1967 * type can be one of four:
1968 * NORMAL - an interrupt already moved it for us
1969 * HEAD - we are the first to get here.
1970 * UPDATE - we are the interrupt interrupting
1972 * MOVED - a reader on another CPU moved the next
1973 * pointer to its reader page. Give up
1980 * We changed the head to UPDATE, thus
1981 * it is our responsibility to update
1984 local_add(entries, &cpu_buffer->overrun);
1985 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1988 * The entries will be zeroed out when we move the
1992 /* still more to do */
1995 case RB_PAGE_UPDATE:
1997 * This is an interrupt that interrupt the
1998 * previous update. Still more to do.
2001 case RB_PAGE_NORMAL:
2003 * An interrupt came in before the update
2004 * and processed this for us.
2005 * Nothing left to do.
2010 * The reader is on another CPU and just did
2011 * a swap with our next_page.
2016 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2021 * Now that we are here, the old head pointer is
2022 * set to UPDATE. This will keep the reader from
2023 * swapping the head page with the reader page.
2024 * The reader (on another CPU) will spin till
2027 * We just need to protect against interrupts
2028 * doing the job. We will set the next pointer
2029 * to HEAD. After that, we set the old pointer
2030 * to NORMAL, but only if it was HEAD before.
2031 * otherwise we are an interrupt, and only
2032 * want the outer most commit to reset it.
2034 new_head = next_page;
2035 rb_inc_page(cpu_buffer, &new_head);
2037 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2041 * Valid returns are:
2042 * HEAD - an interrupt came in and already set it.
2043 * NORMAL - One of two things:
2044 * 1) We really set it.
2045 * 2) A bunch of interrupts came in and moved
2046 * the page forward again.
2050 case RB_PAGE_NORMAL:
2054 RB_WARN_ON(cpu_buffer, 1);
2059 * It is possible that an interrupt came in,
2060 * set the head up, then more interrupts came in
2061 * and moved it again. When we get back here,
2062 * the page would have been set to NORMAL but we
2063 * just set it back to HEAD.
2065 * How do you detect this? Well, if that happened
2066 * the tail page would have moved.
2068 if (ret == RB_PAGE_NORMAL) {
2069 struct buffer_page *buffer_tail_page;
2071 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2073 * If the tail had moved passed next, then we need
2074 * to reset the pointer.
2076 if (buffer_tail_page != tail_page &&
2077 buffer_tail_page != next_page)
2078 rb_head_page_set_normal(cpu_buffer, new_head,
2084 * If this was the outer most commit (the one that
2085 * changed the original pointer from HEAD to UPDATE),
2086 * then it is up to us to reset it to NORMAL.
2088 if (type == RB_PAGE_HEAD) {
2089 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2092 if (RB_WARN_ON(cpu_buffer,
2093 ret != RB_PAGE_UPDATE))
2101 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2102 unsigned long tail, struct rb_event_info *info)
2104 struct buffer_page *tail_page = info->tail_page;
2105 struct ring_buffer_event *event;
2106 unsigned long length = info->length;
2109 * Only the event that crossed the page boundary
2110 * must fill the old tail_page with padding.
2112 if (tail >= BUF_PAGE_SIZE) {
2114 * If the page was filled, then we still need
2115 * to update the real_end. Reset it to zero
2116 * and the reader will ignore it.
2118 if (tail == BUF_PAGE_SIZE)
2119 tail_page->real_end = 0;
2121 local_sub(length, &tail_page->write);
2125 event = __rb_page_index(tail_page, tail);
2127 /* account for padding bytes */
2128 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2131 * Save the original length to the meta data.
2132 * This will be used by the reader to add lost event
2135 tail_page->real_end = tail;
2138 * If this event is bigger than the minimum size, then
2139 * we need to be careful that we don't subtract the
2140 * write counter enough to allow another writer to slip
2142 * We put in a discarded commit instead, to make sure
2143 * that this space is not used again.
2145 * If we are less than the minimum size, we don't need to
2148 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2149 /* No room for any events */
2151 /* Mark the rest of the page with padding */
2152 rb_event_set_padding(event);
2154 /* Set the write back to the previous setting */
2155 local_sub(length, &tail_page->write);
2159 /* Put in a discarded event */
2160 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2161 event->type_len = RINGBUF_TYPE_PADDING;
2162 /* time delta must be non zero */
2163 event->time_delta = 1;
2165 /* Set write to end of buffer */
2166 length = (tail + length) - BUF_PAGE_SIZE;
2167 local_sub(length, &tail_page->write);
2170 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2173 * This is the slow path, force gcc not to inline it.
2175 static noinline struct ring_buffer_event *
2176 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2177 unsigned long tail, struct rb_event_info *info)
2179 struct buffer_page *tail_page = info->tail_page;
2180 struct buffer_page *commit_page = cpu_buffer->commit_page;
2181 struct ring_buffer *buffer = cpu_buffer->buffer;
2182 struct buffer_page *next_page;
2185 next_page = tail_page;
2187 rb_inc_page(cpu_buffer, &next_page);
2190 * If for some reason, we had an interrupt storm that made
2191 * it all the way around the buffer, bail, and warn
2194 if (unlikely(next_page == commit_page)) {
2195 local_inc(&cpu_buffer->commit_overrun);
2200 * This is where the fun begins!
2202 * We are fighting against races between a reader that
2203 * could be on another CPU trying to swap its reader
2204 * page with the buffer head.
2206 * We are also fighting against interrupts coming in and
2207 * moving the head or tail on us as well.
2209 * If the next page is the head page then we have filled
2210 * the buffer, unless the commit page is still on the
2213 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2216 * If the commit is not on the reader page, then
2217 * move the header page.
2219 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2221 * If we are not in overwrite mode,
2222 * this is easy, just stop here.
2224 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2225 local_inc(&cpu_buffer->dropped_events);
2229 ret = rb_handle_head_page(cpu_buffer,
2238 * We need to be careful here too. The
2239 * commit page could still be on the reader
2240 * page. We could have a small buffer, and
2241 * have filled up the buffer with events
2242 * from interrupts and such, and wrapped.
2244 * Note, if the tail page is also the on the
2245 * reader_page, we let it move out.
2247 if (unlikely((cpu_buffer->commit_page !=
2248 cpu_buffer->tail_page) &&
2249 (cpu_buffer->commit_page ==
2250 cpu_buffer->reader_page))) {
2251 local_inc(&cpu_buffer->commit_overrun);
2257 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2261 rb_reset_tail(cpu_buffer, tail, info);
2263 /* Commit what we have for now. */
2264 rb_end_commit(cpu_buffer);
2265 /* rb_end_commit() decs committing */
2266 local_inc(&cpu_buffer->committing);
2268 /* fail and let the caller try again */
2269 return ERR_PTR(-EAGAIN);
2273 rb_reset_tail(cpu_buffer, tail, info);
2278 /* Slow path, do not inline */
2279 static noinline struct ring_buffer_event *
2280 rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2283 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2285 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2287 /* Not the first event on the page, or not delta? */
2288 if (abs || rb_event_index(event)) {
2289 event->time_delta = delta & TS_MASK;
2290 event->array[0] = delta >> TS_SHIFT;
2292 /* nope, just zero it */
2293 event->time_delta = 0;
2294 event->array[0] = 0;
2297 return skip_time_extend(event);
2300 static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2301 struct ring_buffer_event *event);
2304 * rb_update_event - update event type and data
2305 * @event: the event to update
2306 * @type: the type of event
2307 * @length: the size of the event field in the ring buffer
2309 * Update the type and data fields of the event. The length
2310 * is the actual size that is written to the ring buffer,
2311 * and with this, we can determine what to place into the
2315 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2316 struct ring_buffer_event *event,
2317 struct rb_event_info *info)
2319 unsigned length = info->length;
2320 u64 delta = info->delta;
2322 /* Only a commit updates the timestamp */
2323 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2327 * If we need to add a timestamp, then we
2328 * add it to the start of the reserved space.
2330 if (unlikely(info->add_timestamp)) {
2331 bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer);
2333 event = rb_add_time_stamp(event, info->delta, abs);
2334 length -= RB_LEN_TIME_EXTEND;
2338 event->time_delta = delta;
2339 length -= RB_EVNT_HDR_SIZE;
2340 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2341 event->type_len = 0;
2342 event->array[0] = length;
2344 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2347 static unsigned rb_calculate_event_length(unsigned length)
2349 struct ring_buffer_event event; /* Used only for sizeof array */
2351 /* zero length can cause confusions */
2355 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2356 length += sizeof(event.array[0]);
2358 length += RB_EVNT_HDR_SIZE;
2359 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2362 * In case the time delta is larger than the 27 bits for it
2363 * in the header, we need to add a timestamp. If another
2364 * event comes in when trying to discard this one to increase
2365 * the length, then the timestamp will be added in the allocated
2366 * space of this event. If length is bigger than the size needed
2367 * for the TIME_EXTEND, then padding has to be used. The events
2368 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2369 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2370 * As length is a multiple of 4, we only need to worry if it
2371 * is 12 (RB_LEN_TIME_EXTEND + 4).
2373 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2374 length += RB_ALIGNMENT;
2379 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2380 static inline bool sched_clock_stable(void)
2387 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2388 struct ring_buffer_event *event)
2390 unsigned long new_index, old_index;
2391 struct buffer_page *bpage;
2392 unsigned long index;
2395 new_index = rb_event_index(event);
2396 old_index = new_index + rb_event_ts_length(event);
2397 addr = (unsigned long)event;
2400 bpage = READ_ONCE(cpu_buffer->tail_page);
2402 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2403 unsigned long write_mask =
2404 local_read(&bpage->write) & ~RB_WRITE_MASK;
2405 unsigned long event_length = rb_event_length(event);
2407 * This is on the tail page. It is possible that
2408 * a write could come in and move the tail page
2409 * and write to the next page. That is fine
2410 * because we just shorten what is on this page.
2412 old_index += write_mask;
2413 new_index += write_mask;
2414 index = local_cmpxchg(&bpage->write, old_index, new_index);
2415 if (index == old_index) {
2416 /* update counters */
2417 local_sub(event_length, &cpu_buffer->entries_bytes);
2422 /* could not discard */
2426 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2428 local_inc(&cpu_buffer->committing);
2429 local_inc(&cpu_buffer->commits);
2432 static __always_inline void
2433 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2435 unsigned long max_count;
2438 * We only race with interrupts and NMIs on this CPU.
2439 * If we own the commit event, then we can commit
2440 * all others that interrupted us, since the interruptions
2441 * are in stack format (they finish before they come
2442 * back to us). This allows us to do a simple loop to
2443 * assign the commit to the tail.
2446 max_count = cpu_buffer->nr_pages * 100;
2448 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2449 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2451 if (RB_WARN_ON(cpu_buffer,
2452 rb_is_reader_page(cpu_buffer->tail_page)))
2454 local_set(&cpu_buffer->commit_page->page->commit,
2455 rb_page_write(cpu_buffer->commit_page));
2456 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2457 /* Only update the write stamp if the page has an event */
2458 if (rb_page_write(cpu_buffer->commit_page))
2459 cpu_buffer->write_stamp =
2460 cpu_buffer->commit_page->page->time_stamp;
2461 /* add barrier to keep gcc from optimizing too much */
2464 while (rb_commit_index(cpu_buffer) !=
2465 rb_page_write(cpu_buffer->commit_page)) {
2467 local_set(&cpu_buffer->commit_page->page->commit,
2468 rb_page_write(cpu_buffer->commit_page));
2469 RB_WARN_ON(cpu_buffer,
2470 local_read(&cpu_buffer->commit_page->page->commit) &
2475 /* again, keep gcc from optimizing */
2479 * If an interrupt came in just after the first while loop
2480 * and pushed the tail page forward, we will be left with
2481 * a dangling commit that will never go forward.
2483 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2487 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2489 unsigned long commits;
2491 if (RB_WARN_ON(cpu_buffer,
2492 !local_read(&cpu_buffer->committing)))
2496 commits = local_read(&cpu_buffer->commits);
2497 /* synchronize with interrupts */
2499 if (local_read(&cpu_buffer->committing) == 1)
2500 rb_set_commit_to_write(cpu_buffer);
2502 local_dec(&cpu_buffer->committing);
2504 /* synchronize with interrupts */
2508 * Need to account for interrupts coming in between the
2509 * updating of the commit page and the clearing of the
2510 * committing counter.
2512 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2513 !local_read(&cpu_buffer->committing)) {
2514 local_inc(&cpu_buffer->committing);
2519 static inline void rb_event_discard(struct ring_buffer_event *event)
2521 if (extended_time(event))
2522 event = skip_time_extend(event);
2524 /* array[0] holds the actual length for the discarded event */
2525 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2526 event->type_len = RINGBUF_TYPE_PADDING;
2527 /* time delta must be non zero */
2528 if (!event->time_delta)
2529 event->time_delta = 1;
2532 static __always_inline bool
2533 rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2534 struct ring_buffer_event *event)
2536 unsigned long addr = (unsigned long)event;
2537 unsigned long index;
2539 index = rb_event_index(event);
2542 return cpu_buffer->commit_page->page == (void *)addr &&
2543 rb_commit_index(cpu_buffer) == index;
2546 static __always_inline void
2547 rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2548 struct ring_buffer_event *event)
2553 * The event first in the commit queue updates the
2556 if (rb_event_is_commit(cpu_buffer, event)) {
2558 * A commit event that is first on a page
2559 * updates the write timestamp with the page stamp
2561 if (!rb_event_index(event))
2562 cpu_buffer->write_stamp =
2563 cpu_buffer->commit_page->page->time_stamp;
2564 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2565 delta = ring_buffer_event_time_stamp(event);
2566 cpu_buffer->write_stamp += delta;
2567 } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
2568 delta = ring_buffer_event_time_stamp(event);
2569 cpu_buffer->write_stamp = delta;
2571 cpu_buffer->write_stamp += event->time_delta;
2575 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2576 struct ring_buffer_event *event)
2578 local_inc(&cpu_buffer->entries);
2579 rb_update_write_stamp(cpu_buffer, event);
2580 rb_end_commit(cpu_buffer);
2583 static __always_inline void
2584 rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2588 if (buffer->irq_work.waiters_pending) {
2589 buffer->irq_work.waiters_pending = false;
2590 /* irq_work_queue() supplies it's own memory barriers */
2591 irq_work_queue(&buffer->irq_work.work);
2594 if (cpu_buffer->irq_work.waiters_pending) {
2595 cpu_buffer->irq_work.waiters_pending = false;
2596 /* irq_work_queue() supplies it's own memory barriers */
2597 irq_work_queue(&cpu_buffer->irq_work.work);
2600 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
2602 if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
2603 cpu_buffer->irq_work.wakeup_full = true;
2604 cpu_buffer->irq_work.full_waiters_pending = false;
2605 /* irq_work_queue() supplies it's own memory barriers */
2606 irq_work_queue(&cpu_buffer->irq_work.work);
2611 * The lock and unlock are done within a preempt disable section.
2612 * The current_context per_cpu variable can only be modified
2613 * by the current task between lock and unlock. But it can
2614 * be modified more than once via an interrupt. To pass this
2615 * information from the lock to the unlock without having to
2616 * access the 'in_interrupt()' functions again (which do show
2617 * a bit of overhead in something as critical as function tracing,
2618 * we use a bitmask trick.
2620 * bit 0 = NMI context
2621 * bit 1 = IRQ context
2622 * bit 2 = SoftIRQ context
2623 * bit 3 = normal context.
2625 * This works because this is the order of contexts that can
2626 * preempt other contexts. A SoftIRQ never preempts an IRQ
2629 * When the context is determined, the corresponding bit is
2630 * checked and set (if it was set, then a recursion of that context
2633 * On unlock, we need to clear this bit. To do so, just subtract
2634 * 1 from the current_context and AND it to itself.
2638 * 101 & 100 = 100 (clearing bit zero)
2641 * 1010 & 1001 = 1000 (clearing bit 1)
2643 * The least significant bit can be cleared this way, and it
2644 * just so happens that it is the same bit corresponding to
2645 * the current context.
2648 static __always_inline int
2649 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
2651 unsigned int val = cpu_buffer->current_context;
2652 unsigned long pc = preempt_count();
2655 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
2656 bit = RB_CTX_NORMAL;
2658 bit = pc & NMI_MASK ? RB_CTX_NMI :
2659 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
2661 if (unlikely(val & (1 << (bit + cpu_buffer->nest))))
2664 val |= (1 << (bit + cpu_buffer->nest));
2665 cpu_buffer->current_context = val;
2670 static __always_inline void
2671 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
2673 cpu_buffer->current_context &=
2674 cpu_buffer->current_context - (1 << cpu_buffer->nest);
2677 /* The recursive locking above uses 4 bits */
2678 #define NESTED_BITS 4
2681 * ring_buffer_nest_start - Allow to trace while nested
2682 * @buffer: The ring buffer to modify
2684 * The ring buffer has a safety mechanism to prevent recursion.
2685 * But there may be a case where a trace needs to be done while
2686 * tracing something else. In this case, calling this function
2687 * will allow this function to nest within a currently active
2688 * ring_buffer_lock_reserve().
2690 * Call this function before calling another ring_buffer_lock_reserve() and
2691 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
2693 void ring_buffer_nest_start(struct ring_buffer *buffer)
2695 struct ring_buffer_per_cpu *cpu_buffer;
2698 /* Enabled by ring_buffer_nest_end() */
2699 preempt_disable_notrace();
2700 cpu = raw_smp_processor_id();
2701 cpu_buffer = buffer->buffers[cpu];
2702 /* This is the shift value for the above recursive locking */
2703 cpu_buffer->nest += NESTED_BITS;
2707 * ring_buffer_nest_end - Allow to trace while nested
2708 * @buffer: The ring buffer to modify
2710 * Must be called after ring_buffer_nest_start() and after the
2711 * ring_buffer_unlock_commit().
2713 void ring_buffer_nest_end(struct ring_buffer *buffer)
2715 struct ring_buffer_per_cpu *cpu_buffer;
2718 /* disabled by ring_buffer_nest_start() */
2719 cpu = raw_smp_processor_id();
2720 cpu_buffer = buffer->buffers[cpu];
2721 /* This is the shift value for the above recursive locking */
2722 cpu_buffer->nest -= NESTED_BITS;
2723 preempt_enable_notrace();
2727 * ring_buffer_unlock_commit - commit a reserved
2728 * @buffer: The buffer to commit to
2729 * @event: The event pointer to commit.
2731 * This commits the data to the ring buffer, and releases any locks held.
2733 * Must be paired with ring_buffer_lock_reserve.
2735 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2736 struct ring_buffer_event *event)
2738 struct ring_buffer_per_cpu *cpu_buffer;
2739 int cpu = raw_smp_processor_id();
2741 cpu_buffer = buffer->buffers[cpu];
2743 rb_commit(cpu_buffer, event);
2745 rb_wakeups(buffer, cpu_buffer);
2747 trace_recursive_unlock(cpu_buffer);
2749 preempt_enable_notrace();
2753 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2755 static noinline void
2756 rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2757 struct rb_event_info *info)
2759 WARN_ONCE(info->delta > (1ULL << 59),
2760 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2761 (unsigned long long)info->delta,
2762 (unsigned long long)info->ts,
2763 (unsigned long long)cpu_buffer->write_stamp,
2764 sched_clock_stable() ? "" :
2765 "If you just came from a suspend/resume,\n"
2766 "please switch to the trace global clock:\n"
2767 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2768 "or add trace_clock=global to the kernel command line\n");
2769 info->add_timestamp = 1;
2772 static struct ring_buffer_event *
2773 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2774 struct rb_event_info *info)
2776 struct ring_buffer_event *event;
2777 struct buffer_page *tail_page;
2778 unsigned long tail, write;
2781 * If the time delta since the last event is too big to
2782 * hold in the time field of the event, then we append a
2783 * TIME EXTEND event ahead of the data event.
2785 if (unlikely(info->add_timestamp))
2786 info->length += RB_LEN_TIME_EXTEND;
2788 /* Don't let the compiler play games with cpu_buffer->tail_page */
2789 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
2790 write = local_add_return(info->length, &tail_page->write);
2792 /* set write to only the index of the write */
2793 write &= RB_WRITE_MASK;
2794 tail = write - info->length;
2797 * If this is the first commit on the page, then it has the same
2798 * timestamp as the page itself.
2800 if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
2803 /* See if we shot pass the end of this buffer page */
2804 if (unlikely(write > BUF_PAGE_SIZE))
2805 return rb_move_tail(cpu_buffer, tail, info);
2807 /* We reserved something on the buffer */
2809 event = __rb_page_index(tail_page, tail);
2810 rb_update_event(cpu_buffer, event, info);
2812 local_inc(&tail_page->entries);
2815 * If this is the first commit on the page, then update
2819 tail_page->page->time_stamp = info->ts;
2821 /* account for these added bytes */
2822 local_add(info->length, &cpu_buffer->entries_bytes);
2827 static __always_inline struct ring_buffer_event *
2828 rb_reserve_next_event(struct ring_buffer *buffer,
2829 struct ring_buffer_per_cpu *cpu_buffer,
2830 unsigned long length)
2832 struct ring_buffer_event *event;
2833 struct rb_event_info info;
2837 rb_start_commit(cpu_buffer);
2839 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2841 * Due to the ability to swap a cpu buffer from a buffer
2842 * it is possible it was swapped before we committed.
2843 * (committing stops a swap). We check for it here and
2844 * if it happened, we have to fail the write.
2847 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
2848 local_dec(&cpu_buffer->committing);
2849 local_dec(&cpu_buffer->commits);
2854 info.length = rb_calculate_event_length(length);
2856 info.add_timestamp = 0;
2860 * We allow for interrupts to reenter here and do a trace.
2861 * If one does, it will cause this original code to loop
2862 * back here. Even with heavy interrupts happening, this
2863 * should only happen a few times in a row. If this happens
2864 * 1000 times in a row, there must be either an interrupt
2865 * storm or we have something buggy.
2868 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2871 info.ts = rb_time_stamp(cpu_buffer->buffer);
2872 diff = info.ts - cpu_buffer->write_stamp;
2874 /* make sure this diff is calculated here */
2877 if (ring_buffer_time_stamp_abs(buffer)) {
2878 info.delta = info.ts;
2879 rb_handle_timestamp(cpu_buffer, &info);
2880 } else /* Did the write stamp get updated already? */
2881 if (likely(info.ts >= cpu_buffer->write_stamp)) {
2883 if (unlikely(test_time_stamp(info.delta)))
2884 rb_handle_timestamp(cpu_buffer, &info);
2887 event = __rb_reserve_next(cpu_buffer, &info);
2889 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
2890 if (info.add_timestamp)
2891 info.length -= RB_LEN_TIME_EXTEND;
2901 rb_end_commit(cpu_buffer);
2906 * ring_buffer_lock_reserve - reserve a part of the buffer
2907 * @buffer: the ring buffer to reserve from
2908 * @length: the length of the data to reserve (excluding event header)
2910 * Returns a reserved event on the ring buffer to copy directly to.
2911 * The user of this interface will need to get the body to write into
2912 * and can use the ring_buffer_event_data() interface.
2914 * The length is the length of the data needed, not the event length
2915 * which also includes the event header.
2917 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2918 * If NULL is returned, then nothing has been allocated or locked.
2920 struct ring_buffer_event *
2921 ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2923 struct ring_buffer_per_cpu *cpu_buffer;
2924 struct ring_buffer_event *event;
2927 /* If we are tracing schedule, we don't want to recurse */
2928 preempt_disable_notrace();
2930 if (unlikely(atomic_read(&buffer->record_disabled)))
2933 cpu = raw_smp_processor_id();
2935 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
2938 cpu_buffer = buffer->buffers[cpu];
2940 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
2943 if (unlikely(length > BUF_MAX_DATA_SIZE))
2946 if (unlikely(trace_recursive_lock(cpu_buffer)))
2949 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2956 trace_recursive_unlock(cpu_buffer);
2958 preempt_enable_notrace();
2961 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2964 * Decrement the entries to the page that an event is on.
2965 * The event does not even need to exist, only the pointer
2966 * to the page it is on. This may only be called before the commit
2970 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2971 struct ring_buffer_event *event)
2973 unsigned long addr = (unsigned long)event;
2974 struct buffer_page *bpage = cpu_buffer->commit_page;
2975 struct buffer_page *start;
2979 /* Do the likely case first */
2980 if (likely(bpage->page == (void *)addr)) {
2981 local_dec(&bpage->entries);
2986 * Because the commit page may be on the reader page we
2987 * start with the next page and check the end loop there.
2989 rb_inc_page(cpu_buffer, &bpage);
2992 if (bpage->page == (void *)addr) {
2993 local_dec(&bpage->entries);
2996 rb_inc_page(cpu_buffer, &bpage);
2997 } while (bpage != start);
2999 /* commit not part of this buffer?? */
3000 RB_WARN_ON(cpu_buffer, 1);
3004 * ring_buffer_commit_discard - discard an event that has not been committed
3005 * @buffer: the ring buffer
3006 * @event: non committed event to discard
3008 * Sometimes an event that is in the ring buffer needs to be ignored.
3009 * This function lets the user discard an event in the ring buffer
3010 * and then that event will not be read later.
3012 * This function only works if it is called before the item has been
3013 * committed. It will try to free the event from the ring buffer
3014 * if another event has not been added behind it.
3016 * If another event has been added behind it, it will set the event
3017 * up as discarded, and perform the commit.
3019 * If this function is called, do not call ring_buffer_unlock_commit on
3022 void ring_buffer_discard_commit(struct ring_buffer *buffer,
3023 struct ring_buffer_event *event)
3025 struct ring_buffer_per_cpu *cpu_buffer;
3028 /* The event is discarded regardless */
3029 rb_event_discard(event);
3031 cpu = smp_processor_id();
3032 cpu_buffer = buffer->buffers[cpu];
3035 * This must only be called if the event has not been
3036 * committed yet. Thus we can assume that preemption
3037 * is still disabled.
3039 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3041 rb_decrement_entry(cpu_buffer, event);
3042 if (rb_try_to_discard(cpu_buffer, event))
3046 * The commit is still visible by the reader, so we
3047 * must still update the timestamp.
3049 rb_update_write_stamp(cpu_buffer, event);
3051 rb_end_commit(cpu_buffer);
3053 trace_recursive_unlock(cpu_buffer);
3055 preempt_enable_notrace();
3058 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3061 * ring_buffer_write - write data to the buffer without reserving
3062 * @buffer: The ring buffer to write to.
3063 * @length: The length of the data being written (excluding the event header)
3064 * @data: The data to write to the buffer.
3066 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3067 * one function. If you already have the data to write to the buffer, it
3068 * may be easier to simply call this function.
3070 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3071 * and not the length of the event which would hold the header.
3073 int ring_buffer_write(struct ring_buffer *buffer,
3074 unsigned long length,
3077 struct ring_buffer_per_cpu *cpu_buffer;
3078 struct ring_buffer_event *event;
3083 preempt_disable_notrace();
3085 if (atomic_read(&buffer->record_disabled))
3088 cpu = raw_smp_processor_id();
3090 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3093 cpu_buffer = buffer->buffers[cpu];
3095 if (atomic_read(&cpu_buffer->record_disabled))
3098 if (length > BUF_MAX_DATA_SIZE)
3101 if (unlikely(trace_recursive_lock(cpu_buffer)))
3104 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3108 body = rb_event_data(event);
3110 memcpy(body, data, length);
3112 rb_commit(cpu_buffer, event);
3114 rb_wakeups(buffer, cpu_buffer);
3119 trace_recursive_unlock(cpu_buffer);
3122 preempt_enable_notrace();
3126 EXPORT_SYMBOL_GPL(ring_buffer_write);
3128 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3130 struct buffer_page *reader = cpu_buffer->reader_page;
3131 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3132 struct buffer_page *commit = cpu_buffer->commit_page;
3134 /* In case of error, head will be NULL */
3135 if (unlikely(!head))
3138 return reader->read == rb_page_commit(reader) &&
3139 (commit == reader ||
3141 head->read == rb_page_commit(commit)));
3145 * ring_buffer_record_disable - stop all writes into the buffer
3146 * @buffer: The ring buffer to stop writes to.
3148 * This prevents all writes to the buffer. Any attempt to write
3149 * to the buffer after this will fail and return NULL.
3151 * The caller should call synchronize_sched() after this.
3153 void ring_buffer_record_disable(struct ring_buffer *buffer)
3155 atomic_inc(&buffer->record_disabled);
3157 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3160 * ring_buffer_record_enable - enable writes to the buffer
3161 * @buffer: The ring buffer to enable writes
3163 * Note, multiple disables will need the same number of enables
3164 * to truly enable the writing (much like preempt_disable).
3166 void ring_buffer_record_enable(struct ring_buffer *buffer)
3168 atomic_dec(&buffer->record_disabled);
3170 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3173 * ring_buffer_record_off - stop all writes into the buffer
3174 * @buffer: The ring buffer to stop writes to.
3176 * This prevents all writes to the buffer. Any attempt to write
3177 * to the buffer after this will fail and return NULL.
3179 * This is different than ring_buffer_record_disable() as
3180 * it works like an on/off switch, where as the disable() version
3181 * must be paired with a enable().
3183 void ring_buffer_record_off(struct ring_buffer *buffer)
3186 unsigned int new_rd;
3189 rd = atomic_read(&buffer->record_disabled);
3190 new_rd = rd | RB_BUFFER_OFF;
3191 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3193 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3196 * ring_buffer_record_on - restart writes into the buffer
3197 * @buffer: The ring buffer to start writes to.
3199 * This enables all writes to the buffer that was disabled by
3200 * ring_buffer_record_off().
3202 * This is different than ring_buffer_record_enable() as
3203 * it works like an on/off switch, where as the enable() version
3204 * must be paired with a disable().
3206 void ring_buffer_record_on(struct ring_buffer *buffer)
3209 unsigned int new_rd;
3212 rd = atomic_read(&buffer->record_disabled);
3213 new_rd = rd & ~RB_BUFFER_OFF;
3214 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3216 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3219 * ring_buffer_record_is_on - return true if the ring buffer can write
3220 * @buffer: The ring buffer to see if write is enabled
3222 * Returns true if the ring buffer is in a state that it accepts writes.
3224 int ring_buffer_record_is_on(struct ring_buffer *buffer)
3226 return !atomic_read(&buffer->record_disabled);
3230 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3231 * @buffer: The ring buffer to see if write is set enabled
3233 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3234 * Note that this does NOT mean it is in a writable state.
3236 * It may return true when the ring buffer has been disabled by
3237 * ring_buffer_record_disable(), as that is a temporary disabling of
3240 int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
3242 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
3246 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3247 * @buffer: The ring buffer to stop writes to.
3248 * @cpu: The CPU buffer to stop
3250 * This prevents all writes to the buffer. Any attempt to write
3251 * to the buffer after this will fail and return NULL.
3253 * The caller should call synchronize_sched() after this.
3255 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3257 struct ring_buffer_per_cpu *cpu_buffer;
3259 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3262 cpu_buffer = buffer->buffers[cpu];
3263 atomic_inc(&cpu_buffer->record_disabled);
3265 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3268 * ring_buffer_record_enable_cpu - enable writes to the buffer
3269 * @buffer: The ring buffer to enable writes
3270 * @cpu: The CPU to enable.
3272 * Note, multiple disables will need the same number of enables
3273 * to truly enable the writing (much like preempt_disable).
3275 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3277 struct ring_buffer_per_cpu *cpu_buffer;
3279 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3282 cpu_buffer = buffer->buffers[cpu];
3283 atomic_dec(&cpu_buffer->record_disabled);
3285 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3288 * The total entries in the ring buffer is the running counter
3289 * of entries entered into the ring buffer, minus the sum of
3290 * the entries read from the ring buffer and the number of
3291 * entries that were overwritten.
3293 static inline unsigned long
3294 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3296 return local_read(&cpu_buffer->entries) -
3297 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3301 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3302 * @buffer: The ring buffer
3303 * @cpu: The per CPU buffer to read from.
3305 u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3307 unsigned long flags;
3308 struct ring_buffer_per_cpu *cpu_buffer;
3309 struct buffer_page *bpage;
3312 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3315 cpu_buffer = buffer->buffers[cpu];
3316 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3318 * if the tail is on reader_page, oldest time stamp is on the reader
3321 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3322 bpage = cpu_buffer->reader_page;
3324 bpage = rb_set_head_page(cpu_buffer);
3326 ret = bpage->page->time_stamp;
3327 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3331 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3334 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3335 * @buffer: The ring buffer
3336 * @cpu: The per CPU buffer to read from.
3338 unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3340 struct ring_buffer_per_cpu *cpu_buffer;
3343 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3346 cpu_buffer = buffer->buffers[cpu];
3347 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3351 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3354 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3355 * @buffer: The ring buffer
3356 * @cpu: The per CPU buffer to get the entries from.
3358 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3360 struct ring_buffer_per_cpu *cpu_buffer;
3362 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3365 cpu_buffer = buffer->buffers[cpu];
3367 return rb_num_of_entries(cpu_buffer);
3369 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3372 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3373 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3374 * @buffer: The ring buffer
3375 * @cpu: The per CPU buffer to get the number of overruns from
3377 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3379 struct ring_buffer_per_cpu *cpu_buffer;
3382 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3385 cpu_buffer = buffer->buffers[cpu];
3386 ret = local_read(&cpu_buffer->overrun);
3390 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3393 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3394 * commits failing due to the buffer wrapping around while there are uncommitted
3395 * events, such as during an interrupt storm.
3396 * @buffer: The ring buffer
3397 * @cpu: The per CPU buffer to get the number of overruns from
3400 ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3402 struct ring_buffer_per_cpu *cpu_buffer;
3405 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3408 cpu_buffer = buffer->buffers[cpu];
3409 ret = local_read(&cpu_buffer->commit_overrun);
3413 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3416 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3417 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3418 * @buffer: The ring buffer
3419 * @cpu: The per CPU buffer to get the number of overruns from
3422 ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3424 struct ring_buffer_per_cpu *cpu_buffer;
3427 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3430 cpu_buffer = buffer->buffers[cpu];
3431 ret = local_read(&cpu_buffer->dropped_events);
3435 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3438 * ring_buffer_read_events_cpu - get the number of events successfully read
3439 * @buffer: The ring buffer
3440 * @cpu: The per CPU buffer to get the number of events read
3443 ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3445 struct ring_buffer_per_cpu *cpu_buffer;
3447 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3450 cpu_buffer = buffer->buffers[cpu];
3451 return cpu_buffer->read;
3453 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3456 * ring_buffer_entries - get the number of entries in a buffer
3457 * @buffer: The ring buffer
3459 * Returns the total number of entries in the ring buffer
3462 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3464 struct ring_buffer_per_cpu *cpu_buffer;
3465 unsigned long entries = 0;
3468 /* if you care about this being correct, lock the buffer */
3469 for_each_buffer_cpu(buffer, cpu) {
3470 cpu_buffer = buffer->buffers[cpu];
3471 entries += rb_num_of_entries(cpu_buffer);
3476 EXPORT_SYMBOL_GPL(ring_buffer_entries);
3479 * ring_buffer_overruns - get the number of overruns in buffer
3480 * @buffer: The ring buffer
3482 * Returns the total number of overruns in the ring buffer
3485 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3487 struct ring_buffer_per_cpu *cpu_buffer;
3488 unsigned long overruns = 0;
3491 /* if you care about this being correct, lock the buffer */
3492 for_each_buffer_cpu(buffer, cpu) {
3493 cpu_buffer = buffer->buffers[cpu];
3494 overruns += local_read(&cpu_buffer->overrun);
3499 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3501 static void rb_iter_reset(struct ring_buffer_iter *iter)
3503 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3505 /* Iterator usage is expected to have record disabled */
3506 iter->head_page = cpu_buffer->reader_page;
3507 iter->head = cpu_buffer->reader_page->read;
3509 iter->cache_reader_page = iter->head_page;
3510 iter->cache_read = cpu_buffer->read;
3513 iter->read_stamp = cpu_buffer->read_stamp;
3515 iter->read_stamp = iter->head_page->page->time_stamp;
3519 * ring_buffer_iter_reset - reset an iterator
3520 * @iter: The iterator to reset
3522 * Resets the iterator, so that it will start from the beginning
3525 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3527 struct ring_buffer_per_cpu *cpu_buffer;
3528 unsigned long flags;
3533 cpu_buffer = iter->cpu_buffer;
3535 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3536 rb_iter_reset(iter);
3537 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3539 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3542 * ring_buffer_iter_empty - check if an iterator has no more to read
3543 * @iter: The iterator to check
3545 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3547 struct ring_buffer_per_cpu *cpu_buffer;
3548 struct buffer_page *reader;
3549 struct buffer_page *head_page;
3550 struct buffer_page *commit_page;
3553 cpu_buffer = iter->cpu_buffer;
3555 /* Remember, trace recording is off when iterator is in use */
3556 reader = cpu_buffer->reader_page;
3557 head_page = cpu_buffer->head_page;
3558 commit_page = cpu_buffer->commit_page;
3559 commit = rb_page_commit(commit_page);
3561 return ((iter->head_page == commit_page && iter->head == commit) ||
3562 (iter->head_page == reader && commit_page == head_page &&
3563 head_page->read == commit &&
3564 iter->head == rb_page_commit(cpu_buffer->reader_page)));
3566 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3569 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3570 struct ring_buffer_event *event)
3574 switch (event->type_len) {
3575 case RINGBUF_TYPE_PADDING:
3578 case RINGBUF_TYPE_TIME_EXTEND:
3579 delta = ring_buffer_event_time_stamp(event);
3580 cpu_buffer->read_stamp += delta;
3583 case RINGBUF_TYPE_TIME_STAMP:
3584 delta = ring_buffer_event_time_stamp(event);
3585 cpu_buffer->read_stamp = delta;
3588 case RINGBUF_TYPE_DATA:
3589 cpu_buffer->read_stamp += event->time_delta;
3599 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3600 struct ring_buffer_event *event)
3604 switch (event->type_len) {
3605 case RINGBUF_TYPE_PADDING:
3608 case RINGBUF_TYPE_TIME_EXTEND:
3609 delta = ring_buffer_event_time_stamp(event);
3610 iter->read_stamp += delta;
3613 case RINGBUF_TYPE_TIME_STAMP:
3614 delta = ring_buffer_event_time_stamp(event);
3615 iter->read_stamp = delta;
3618 case RINGBUF_TYPE_DATA:
3619 iter->read_stamp += event->time_delta;
3628 static struct buffer_page *
3629 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3631 struct buffer_page *reader = NULL;
3632 unsigned long overwrite;
3633 unsigned long flags;
3637 local_irq_save(flags);
3638 arch_spin_lock(&cpu_buffer->lock);
3642 * This should normally only loop twice. But because the
3643 * start of the reader inserts an empty page, it causes
3644 * a case where we will loop three times. There should be no
3645 * reason to loop four times (that I know of).
3647 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3652 reader = cpu_buffer->reader_page;
3654 /* If there's more to read, return this page */
3655 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3658 /* Never should we have an index greater than the size */
3659 if (RB_WARN_ON(cpu_buffer,
3660 cpu_buffer->reader_page->read > rb_page_size(reader)))
3663 /* check if we caught up to the tail */
3665 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3668 /* Don't bother swapping if the ring buffer is empty */
3669 if (rb_num_of_entries(cpu_buffer) == 0)
3673 * Reset the reader page to size zero.
3675 local_set(&cpu_buffer->reader_page->write, 0);
3676 local_set(&cpu_buffer->reader_page->entries, 0);
3677 local_set(&cpu_buffer->reader_page->page->commit, 0);
3678 cpu_buffer->reader_page->real_end = 0;
3682 * Splice the empty reader page into the list around the head.
3684 reader = rb_set_head_page(cpu_buffer);
3687 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3688 cpu_buffer->reader_page->list.prev = reader->list.prev;
3691 * cpu_buffer->pages just needs to point to the buffer, it
3692 * has no specific buffer page to point to. Lets move it out
3693 * of our way so we don't accidentally swap it.
3695 cpu_buffer->pages = reader->list.prev;
3697 /* The reader page will be pointing to the new head */
3698 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3701 * We want to make sure we read the overruns after we set up our
3702 * pointers to the next object. The writer side does a
3703 * cmpxchg to cross pages which acts as the mb on the writer
3704 * side. Note, the reader will constantly fail the swap
3705 * while the writer is updating the pointers, so this
3706 * guarantees that the overwrite recorded here is the one we
3707 * want to compare with the last_overrun.
3710 overwrite = local_read(&(cpu_buffer->overrun));
3713 * Here's the tricky part.
3715 * We need to move the pointer past the header page.
3716 * But we can only do that if a writer is not currently
3717 * moving it. The page before the header page has the
3718 * flag bit '1' set if it is pointing to the page we want.
3719 * but if the writer is in the process of moving it
3720 * than it will be '2' or already moved '0'.
3723 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3726 * If we did not convert it, then we must try again.
3732 * Yeah! We succeeded in replacing the page.
3734 * Now make the new head point back to the reader page.
3736 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3737 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3739 /* Finally update the reader page to the new head */
3740 cpu_buffer->reader_page = reader;
3741 cpu_buffer->reader_page->read = 0;
3743 if (overwrite != cpu_buffer->last_overrun) {
3744 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3745 cpu_buffer->last_overrun = overwrite;
3751 /* Update the read_stamp on the first event */
3752 if (reader && reader->read == 0)
3753 cpu_buffer->read_stamp = reader->page->time_stamp;
3755 arch_spin_unlock(&cpu_buffer->lock);
3756 local_irq_restore(flags);
3761 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3763 struct ring_buffer_event *event;
3764 struct buffer_page *reader;
3767 reader = rb_get_reader_page(cpu_buffer);
3769 /* This function should not be called when buffer is empty */
3770 if (RB_WARN_ON(cpu_buffer, !reader))
3773 event = rb_reader_event(cpu_buffer);
3775 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3778 rb_update_read_stamp(cpu_buffer, event);
3780 length = rb_event_length(event);
3781 cpu_buffer->reader_page->read += length;
3784 static void rb_advance_iter(struct ring_buffer_iter *iter)
3786 struct ring_buffer_per_cpu *cpu_buffer;
3787 struct ring_buffer_event *event;
3790 cpu_buffer = iter->cpu_buffer;
3793 * Check if we are at the end of the buffer.
3795 if (iter->head >= rb_page_size(iter->head_page)) {
3796 /* discarded commits can make the page empty */
3797 if (iter->head_page == cpu_buffer->commit_page)
3803 event = rb_iter_head_event(iter);
3805 length = rb_event_length(event);
3808 * This should not be called to advance the header if we are
3809 * at the tail of the buffer.
3811 if (RB_WARN_ON(cpu_buffer,
3812 (iter->head_page == cpu_buffer->commit_page) &&
3813 (iter->head + length > rb_commit_index(cpu_buffer))))
3816 rb_update_iter_read_stamp(iter, event);
3818 iter->head += length;
3820 /* check for end of page padding */
3821 if ((iter->head >= rb_page_size(iter->head_page)) &&
3822 (iter->head_page != cpu_buffer->commit_page))
3826 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3828 return cpu_buffer->lost_events;
3831 static struct ring_buffer_event *
3832 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3833 unsigned long *lost_events)
3835 struct ring_buffer_event *event;
3836 struct buffer_page *reader;
3843 * We repeat when a time extend is encountered.
3844 * Since the time extend is always attached to a data event,
3845 * we should never loop more than once.
3846 * (We never hit the following condition more than twice).
3848 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3851 reader = rb_get_reader_page(cpu_buffer);
3855 event = rb_reader_event(cpu_buffer);
3857 switch (event->type_len) {
3858 case RINGBUF_TYPE_PADDING:
3859 if (rb_null_event(event))
3860 RB_WARN_ON(cpu_buffer, 1);
3862 * Because the writer could be discarding every
3863 * event it creates (which would probably be bad)
3864 * if we were to go back to "again" then we may never
3865 * catch up, and will trigger the warn on, or lock
3866 * the box. Return the padding, and we will release
3867 * the current locks, and try again.
3871 case RINGBUF_TYPE_TIME_EXTEND:
3872 /* Internal data, OK to advance */
3873 rb_advance_reader(cpu_buffer);
3876 case RINGBUF_TYPE_TIME_STAMP:
3878 *ts = ring_buffer_event_time_stamp(event);
3879 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3880 cpu_buffer->cpu, ts);
3882 /* Internal data, OK to advance */
3883 rb_advance_reader(cpu_buffer);
3886 case RINGBUF_TYPE_DATA:
3888 *ts = cpu_buffer->read_stamp + event->time_delta;
3889 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3890 cpu_buffer->cpu, ts);
3893 *lost_events = rb_lost_events(cpu_buffer);
3902 EXPORT_SYMBOL_GPL(ring_buffer_peek);
3904 static struct ring_buffer_event *
3905 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3907 struct ring_buffer *buffer;
3908 struct ring_buffer_per_cpu *cpu_buffer;
3909 struct ring_buffer_event *event;
3915 cpu_buffer = iter->cpu_buffer;
3916 buffer = cpu_buffer->buffer;
3919 * Check if someone performed a consuming read to
3920 * the buffer. A consuming read invalidates the iterator
3921 * and we need to reset the iterator in this case.
3923 if (unlikely(iter->cache_read != cpu_buffer->read ||
3924 iter->cache_reader_page != cpu_buffer->reader_page))
3925 rb_iter_reset(iter);
3928 if (ring_buffer_iter_empty(iter))
3932 * We repeat when a time extend is encountered or we hit
3933 * the end of the page. Since the time extend is always attached
3934 * to a data event, we should never loop more than three times.
3935 * Once for going to next page, once on time extend, and
3936 * finally once to get the event.
3937 * (We never hit the following condition more than thrice).
3939 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
3942 if (rb_per_cpu_empty(cpu_buffer))
3945 if (iter->head >= rb_page_size(iter->head_page)) {
3950 event = rb_iter_head_event(iter);
3952 switch (event->type_len) {
3953 case RINGBUF_TYPE_PADDING:
3954 if (rb_null_event(event)) {
3958 rb_advance_iter(iter);
3961 case RINGBUF_TYPE_TIME_EXTEND:
3962 /* Internal data, OK to advance */
3963 rb_advance_iter(iter);
3966 case RINGBUF_TYPE_TIME_STAMP:
3968 *ts = ring_buffer_event_time_stamp(event);
3969 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3970 cpu_buffer->cpu, ts);
3972 /* Internal data, OK to advance */
3973 rb_advance_iter(iter);
3976 case RINGBUF_TYPE_DATA:
3978 *ts = iter->read_stamp + event->time_delta;
3979 ring_buffer_normalize_time_stamp(buffer,
3980 cpu_buffer->cpu, ts);
3990 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3992 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
3994 if (likely(!in_nmi())) {
3995 raw_spin_lock(&cpu_buffer->reader_lock);
4000 * If an NMI die dumps out the content of the ring buffer
4001 * trylock must be used to prevent a deadlock if the NMI
4002 * preempted a task that holds the ring buffer locks. If
4003 * we get the lock then all is fine, if not, then continue
4004 * to do the read, but this can corrupt the ring buffer,
4005 * so it must be permanently disabled from future writes.
4006 * Reading from NMI is a oneshot deal.
4008 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4011 /* Continue without locking, but disable the ring buffer */
4012 atomic_inc(&cpu_buffer->record_disabled);
4017 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4020 raw_spin_unlock(&cpu_buffer->reader_lock);
4025 * ring_buffer_peek - peek at the next event to be read
4026 * @buffer: The ring buffer to read
4027 * @cpu: The cpu to peak at
4028 * @ts: The timestamp counter of this event.
4029 * @lost_events: a variable to store if events were lost (may be NULL)
4031 * This will return the event that will be read next, but does
4032 * not consume the data.
4034 struct ring_buffer_event *
4035 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
4036 unsigned long *lost_events)
4038 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4039 struct ring_buffer_event *event;
4040 unsigned long flags;
4043 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4047 local_irq_save(flags);
4048 dolock = rb_reader_lock(cpu_buffer);
4049 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4050 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4051 rb_advance_reader(cpu_buffer);
4052 rb_reader_unlock(cpu_buffer, dolock);
4053 local_irq_restore(flags);
4055 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4062 * ring_buffer_iter_peek - peek at the next event to be read
4063 * @iter: The ring buffer iterator
4064 * @ts: The timestamp counter of this event.
4066 * This will return the event that will be read next, but does
4067 * not increment the iterator.
4069 struct ring_buffer_event *
4070 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4072 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4073 struct ring_buffer_event *event;
4074 unsigned long flags;
4077 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4078 event = rb_iter_peek(iter, ts);
4079 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4081 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4088 * ring_buffer_consume - return an event and consume it
4089 * @buffer: The ring buffer to get the next event from
4090 * @cpu: the cpu to read the buffer from
4091 * @ts: a variable to store the timestamp (may be NULL)
4092 * @lost_events: a variable to store if events were lost (may be NULL)
4094 * Returns the next event in the ring buffer, and that event is consumed.
4095 * Meaning, that sequential reads will keep returning a different event,
4096 * and eventually empty the ring buffer if the producer is slower.
4098 struct ring_buffer_event *
4099 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
4100 unsigned long *lost_events)
4102 struct ring_buffer_per_cpu *cpu_buffer;
4103 struct ring_buffer_event *event = NULL;
4104 unsigned long flags;
4108 /* might be called in atomic */
4111 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4114 cpu_buffer = buffer->buffers[cpu];
4115 local_irq_save(flags);
4116 dolock = rb_reader_lock(cpu_buffer);
4118 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4120 cpu_buffer->lost_events = 0;
4121 rb_advance_reader(cpu_buffer);
4124 rb_reader_unlock(cpu_buffer, dolock);
4125 local_irq_restore(flags);
4130 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4135 EXPORT_SYMBOL_GPL(ring_buffer_consume);
4138 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4139 * @buffer: The ring buffer to read from
4140 * @cpu: The cpu buffer to iterate over
4142 * This performs the initial preparations necessary to iterate
4143 * through the buffer. Memory is allocated, buffer recording
4144 * is disabled, and the iterator pointer is returned to the caller.
4146 * Disabling buffer recording prevents the reading from being
4147 * corrupted. This is not a consuming read, so a producer is not
4150 * After a sequence of ring_buffer_read_prepare calls, the user is
4151 * expected to make at least one call to ring_buffer_read_prepare_sync.
4152 * Afterwards, ring_buffer_read_start is invoked to get things going
4155 * This overall must be paired with ring_buffer_read_finish.
4157 struct ring_buffer_iter *
4158 ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
4160 struct ring_buffer_per_cpu *cpu_buffer;
4161 struct ring_buffer_iter *iter;
4163 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4166 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
4170 cpu_buffer = buffer->buffers[cpu];
4172 iter->cpu_buffer = cpu_buffer;
4174 atomic_inc(&buffer->resize_disabled);
4175 atomic_inc(&cpu_buffer->record_disabled);
4179 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4182 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4184 * All previously invoked ring_buffer_read_prepare calls to prepare
4185 * iterators will be synchronized. Afterwards, read_buffer_read_start
4186 * calls on those iterators are allowed.
4189 ring_buffer_read_prepare_sync(void)
4191 synchronize_sched();
4193 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4196 * ring_buffer_read_start - start a non consuming read of the buffer
4197 * @iter: The iterator returned by ring_buffer_read_prepare
4199 * This finalizes the startup of an iteration through the buffer.
4200 * The iterator comes from a call to ring_buffer_read_prepare and
4201 * an intervening ring_buffer_read_prepare_sync must have been
4204 * Must be paired with ring_buffer_read_finish.
4207 ring_buffer_read_start(struct ring_buffer_iter *iter)
4209 struct ring_buffer_per_cpu *cpu_buffer;
4210 unsigned long flags;
4215 cpu_buffer = iter->cpu_buffer;
4217 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4218 arch_spin_lock(&cpu_buffer->lock);
4219 rb_iter_reset(iter);
4220 arch_spin_unlock(&cpu_buffer->lock);
4221 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4223 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4226 * ring_buffer_read_finish - finish reading the iterator of the buffer
4227 * @iter: The iterator retrieved by ring_buffer_start
4229 * This re-enables the recording to the buffer, and frees the
4233 ring_buffer_read_finish(struct ring_buffer_iter *iter)
4235 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4236 unsigned long flags;
4239 * Ring buffer is disabled from recording, here's a good place
4240 * to check the integrity of the ring buffer.
4241 * Must prevent readers from trying to read, as the check
4242 * clears the HEAD page and readers require it.
4244 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4245 rb_check_pages(cpu_buffer);
4246 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4248 atomic_dec(&cpu_buffer->record_disabled);
4249 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4252 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4255 * ring_buffer_read - read the next item in the ring buffer by the iterator
4256 * @iter: The ring buffer iterator
4257 * @ts: The time stamp of the event read.
4259 * This reads the next event in the ring buffer and increments the iterator.
4261 struct ring_buffer_event *
4262 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4264 struct ring_buffer_event *event;
4265 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4266 unsigned long flags;
4268 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4270 event = rb_iter_peek(iter, ts);
4274 if (event->type_len == RINGBUF_TYPE_PADDING)
4277 rb_advance_iter(iter);
4279 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4283 EXPORT_SYMBOL_GPL(ring_buffer_read);
4286 * ring_buffer_size - return the size of the ring buffer (in bytes)
4287 * @buffer: The ring buffer.
4289 unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4292 * Earlier, this method returned
4293 * BUF_PAGE_SIZE * buffer->nr_pages
4294 * Since the nr_pages field is now removed, we have converted this to
4295 * return the per cpu buffer value.
4297 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4300 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4302 EXPORT_SYMBOL_GPL(ring_buffer_size);
4305 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4307 rb_head_page_deactivate(cpu_buffer);
4309 cpu_buffer->head_page
4310 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4311 local_set(&cpu_buffer->head_page->write, 0);
4312 local_set(&cpu_buffer->head_page->entries, 0);
4313 local_set(&cpu_buffer->head_page->page->commit, 0);
4315 cpu_buffer->head_page->read = 0;
4317 cpu_buffer->tail_page = cpu_buffer->head_page;
4318 cpu_buffer->commit_page = cpu_buffer->head_page;
4320 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4321 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4322 local_set(&cpu_buffer->reader_page->write, 0);
4323 local_set(&cpu_buffer->reader_page->entries, 0);
4324 local_set(&cpu_buffer->reader_page->page->commit, 0);
4325 cpu_buffer->reader_page->read = 0;
4327 local_set(&cpu_buffer->entries_bytes, 0);
4328 local_set(&cpu_buffer->overrun, 0);
4329 local_set(&cpu_buffer->commit_overrun, 0);
4330 local_set(&cpu_buffer->dropped_events, 0);
4331 local_set(&cpu_buffer->entries, 0);
4332 local_set(&cpu_buffer->committing, 0);
4333 local_set(&cpu_buffer->commits, 0);
4334 cpu_buffer->read = 0;
4335 cpu_buffer->read_bytes = 0;
4337 cpu_buffer->write_stamp = 0;
4338 cpu_buffer->read_stamp = 0;
4340 cpu_buffer->lost_events = 0;
4341 cpu_buffer->last_overrun = 0;
4343 rb_head_page_activate(cpu_buffer);
4347 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4348 * @buffer: The ring buffer to reset a per cpu buffer of
4349 * @cpu: The CPU buffer to be reset
4351 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4353 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4354 unsigned long flags;
4356 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4359 atomic_inc(&buffer->resize_disabled);
4360 atomic_inc(&cpu_buffer->record_disabled);
4362 /* Make sure all commits have finished */
4363 synchronize_sched();
4365 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4367 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4370 arch_spin_lock(&cpu_buffer->lock);
4372 rb_reset_cpu(cpu_buffer);
4374 arch_spin_unlock(&cpu_buffer->lock);
4377 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4379 atomic_dec(&cpu_buffer->record_disabled);
4380 atomic_dec(&buffer->resize_disabled);
4382 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4385 * ring_buffer_reset - reset a ring buffer
4386 * @buffer: The ring buffer to reset all cpu buffers
4388 void ring_buffer_reset(struct ring_buffer *buffer)
4392 for_each_buffer_cpu(buffer, cpu)
4393 ring_buffer_reset_cpu(buffer, cpu);
4395 EXPORT_SYMBOL_GPL(ring_buffer_reset);
4398 * rind_buffer_empty - is the ring buffer empty?
4399 * @buffer: The ring buffer to test
4401 bool ring_buffer_empty(struct ring_buffer *buffer)
4403 struct ring_buffer_per_cpu *cpu_buffer;
4404 unsigned long flags;
4409 /* yes this is racy, but if you don't like the race, lock the buffer */
4410 for_each_buffer_cpu(buffer, cpu) {
4411 cpu_buffer = buffer->buffers[cpu];
4412 local_irq_save(flags);
4413 dolock = rb_reader_lock(cpu_buffer);
4414 ret = rb_per_cpu_empty(cpu_buffer);
4415 rb_reader_unlock(cpu_buffer, dolock);
4416 local_irq_restore(flags);
4424 EXPORT_SYMBOL_GPL(ring_buffer_empty);
4427 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4428 * @buffer: The ring buffer
4429 * @cpu: The CPU buffer to test
4431 bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4433 struct ring_buffer_per_cpu *cpu_buffer;
4434 unsigned long flags;
4438 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4441 cpu_buffer = buffer->buffers[cpu];
4442 local_irq_save(flags);
4443 dolock = rb_reader_lock(cpu_buffer);
4444 ret = rb_per_cpu_empty(cpu_buffer);
4445 rb_reader_unlock(cpu_buffer, dolock);
4446 local_irq_restore(flags);
4450 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4452 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4454 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4455 * @buffer_a: One buffer to swap with
4456 * @buffer_b: The other buffer to swap with
4458 * This function is useful for tracers that want to take a "snapshot"
4459 * of a CPU buffer and has another back up buffer lying around.
4460 * it is expected that the tracer handles the cpu buffer not being
4461 * used at the moment.
4463 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4464 struct ring_buffer *buffer_b, int cpu)
4466 struct ring_buffer_per_cpu *cpu_buffer_a;
4467 struct ring_buffer_per_cpu *cpu_buffer_b;
4470 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4471 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4474 cpu_buffer_a = buffer_a->buffers[cpu];
4475 cpu_buffer_b = buffer_b->buffers[cpu];
4477 /* At least make sure the two buffers are somewhat the same */
4478 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4483 if (atomic_read(&buffer_a->record_disabled))
4486 if (atomic_read(&buffer_b->record_disabled))
4489 if (atomic_read(&cpu_buffer_a->record_disabled))
4492 if (atomic_read(&cpu_buffer_b->record_disabled))
4496 * We can't do a synchronize_sched here because this
4497 * function can be called in atomic context.
4498 * Normally this will be called from the same CPU as cpu.
4499 * If not it's up to the caller to protect this.
4501 atomic_inc(&cpu_buffer_a->record_disabled);
4502 atomic_inc(&cpu_buffer_b->record_disabled);
4505 if (local_read(&cpu_buffer_a->committing))
4507 if (local_read(&cpu_buffer_b->committing))
4510 buffer_a->buffers[cpu] = cpu_buffer_b;
4511 buffer_b->buffers[cpu] = cpu_buffer_a;
4513 cpu_buffer_b->buffer = buffer_a;
4514 cpu_buffer_a->buffer = buffer_b;
4519 atomic_dec(&cpu_buffer_a->record_disabled);
4520 atomic_dec(&cpu_buffer_b->record_disabled);
4524 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4525 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4528 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4529 * @buffer: the buffer to allocate for.
4530 * @cpu: the cpu buffer to allocate.
4532 * This function is used in conjunction with ring_buffer_read_page.
4533 * When reading a full page from the ring buffer, these functions
4534 * can be used to speed up the process. The calling function should
4535 * allocate a few pages first with this function. Then when it
4536 * needs to get pages from the ring buffer, it passes the result
4537 * of this function into ring_buffer_read_page, which will swap
4538 * the page that was allocated, with the read page of the buffer.
4541 * The page allocated, or ERR_PTR
4543 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4545 struct ring_buffer_per_cpu *cpu_buffer;
4546 struct buffer_data_page *bpage = NULL;
4547 unsigned long flags;
4550 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4551 return ERR_PTR(-ENODEV);
4553 cpu_buffer = buffer->buffers[cpu];
4554 local_irq_save(flags);
4555 arch_spin_lock(&cpu_buffer->lock);
4557 if (cpu_buffer->free_page) {
4558 bpage = cpu_buffer->free_page;
4559 cpu_buffer->free_page = NULL;
4562 arch_spin_unlock(&cpu_buffer->lock);
4563 local_irq_restore(flags);
4568 page = alloc_pages_node(cpu_to_node(cpu),
4569 GFP_KERNEL | __GFP_NORETRY, 0);
4571 return ERR_PTR(-ENOMEM);
4573 bpage = page_address(page);
4576 rb_init_page(bpage);
4580 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4583 * ring_buffer_free_read_page - free an allocated read page
4584 * @buffer: the buffer the page was allocate for
4585 * @cpu: the cpu buffer the page came from
4586 * @data: the page to free
4588 * Free a page allocated from ring_buffer_alloc_read_page.
4590 void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
4592 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4593 struct buffer_data_page *bpage = data;
4594 struct page *page = virt_to_page(bpage);
4595 unsigned long flags;
4597 /* If the page is still in use someplace else, we can't reuse it */
4598 if (page_ref_count(page) > 1)
4601 local_irq_save(flags);
4602 arch_spin_lock(&cpu_buffer->lock);
4604 if (!cpu_buffer->free_page) {
4605 cpu_buffer->free_page = bpage;
4609 arch_spin_unlock(&cpu_buffer->lock);
4610 local_irq_restore(flags);
4613 free_page((unsigned long)bpage);
4615 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4618 * ring_buffer_read_page - extract a page from the ring buffer
4619 * @buffer: buffer to extract from
4620 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4621 * @len: amount to extract
4622 * @cpu: the cpu of the buffer to extract
4623 * @full: should the extraction only happen when the page is full.
4625 * This function will pull out a page from the ring buffer and consume it.
4626 * @data_page must be the address of the variable that was returned
4627 * from ring_buffer_alloc_read_page. This is because the page might be used
4628 * to swap with a page in the ring buffer.
4631 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4632 * if (IS_ERR(rpage))
4633 * return PTR_ERR(rpage);
4634 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4636 * process_page(rpage, ret);
4638 * When @full is set, the function will not return true unless
4639 * the writer is off the reader page.
4641 * Note: it is up to the calling functions to handle sleeps and wakeups.
4642 * The ring buffer can be used anywhere in the kernel and can not
4643 * blindly call wake_up. The layer that uses the ring buffer must be
4644 * responsible for that.
4647 * >=0 if data has been transferred, returns the offset of consumed data.
4648 * <0 if no data has been transferred.
4650 int ring_buffer_read_page(struct ring_buffer *buffer,
4651 void **data_page, size_t len, int cpu, int full)
4653 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4654 struct ring_buffer_event *event;
4655 struct buffer_data_page *bpage;
4656 struct buffer_page *reader;
4657 unsigned long missed_events;
4658 unsigned long flags;
4659 unsigned int commit;
4664 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4668 * If len is not big enough to hold the page header, then
4669 * we can not copy anything.
4671 if (len <= BUF_PAGE_HDR_SIZE)
4674 len -= BUF_PAGE_HDR_SIZE;
4683 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4685 reader = rb_get_reader_page(cpu_buffer);
4689 event = rb_reader_event(cpu_buffer);
4691 read = reader->read;
4692 commit = rb_page_commit(reader);
4694 /* Check if any events were dropped */
4695 missed_events = cpu_buffer->lost_events;
4698 * If this page has been partially read or
4699 * if len is not big enough to read the rest of the page or
4700 * a writer is still on the page, then
4701 * we must copy the data from the page to the buffer.
4702 * Otherwise, we can simply swap the page with the one passed in.
4704 if (read || (len < (commit - read)) ||
4705 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4706 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4707 unsigned int rpos = read;
4708 unsigned int pos = 0;
4714 if (len > (commit - read))
4715 len = (commit - read);
4717 /* Always keep the time extend and data together */
4718 size = rb_event_ts_length(event);
4723 /* save the current timestamp, since the user will need it */
4724 save_timestamp = cpu_buffer->read_stamp;
4726 /* Need to copy one event at a time */
4728 /* We need the size of one event, because
4729 * rb_advance_reader only advances by one event,
4730 * whereas rb_event_ts_length may include the size of
4731 * one or two events.
4732 * We have already ensured there's enough space if this
4733 * is a time extend. */
4734 size = rb_event_length(event);
4735 memcpy(bpage->data + pos, rpage->data + rpos, size);
4739 rb_advance_reader(cpu_buffer);
4740 rpos = reader->read;
4746 event = rb_reader_event(cpu_buffer);
4747 /* Always keep the time extend and data together */
4748 size = rb_event_ts_length(event);
4749 } while (len >= size);
4752 local_set(&bpage->commit, pos);
4753 bpage->time_stamp = save_timestamp;
4755 /* we copied everything to the beginning */
4758 /* update the entry counter */
4759 cpu_buffer->read += rb_page_entries(reader);
4760 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4762 /* swap the pages */
4763 rb_init_page(bpage);
4764 bpage = reader->page;
4765 reader->page = *data_page;
4766 local_set(&reader->write, 0);
4767 local_set(&reader->entries, 0);
4772 * Use the real_end for the data size,
4773 * This gives us a chance to store the lost events
4776 if (reader->real_end)
4777 local_set(&bpage->commit, reader->real_end);
4781 cpu_buffer->lost_events = 0;
4783 commit = local_read(&bpage->commit);
4785 * Set a flag in the commit field if we lost events
4787 if (missed_events) {
4788 /* If there is room at the end of the page to save the
4789 * missed events, then record it there.
4791 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4792 memcpy(&bpage->data[commit], &missed_events,
4793 sizeof(missed_events));
4794 local_add(RB_MISSED_STORED, &bpage->commit);
4795 commit += sizeof(missed_events);
4797 local_add(RB_MISSED_EVENTS, &bpage->commit);
4801 * This page may be off to user land. Zero it out here.
4803 if (commit < BUF_PAGE_SIZE)
4804 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4807 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4812 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4815 * We only allocate new buffers, never free them if the CPU goes down.
4816 * If we were to free the buffer, then the user would lose any trace that was in
4819 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
4821 struct ring_buffer *buffer;
4824 unsigned long nr_pages;
4826 buffer = container_of(node, struct ring_buffer, node);
4827 if (cpumask_test_cpu(cpu, buffer->cpumask))
4832 /* check if all cpu sizes are same */
4833 for_each_buffer_cpu(buffer, cpu_i) {
4834 /* fill in the size from first enabled cpu */
4836 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4837 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4842 /* allocate minimum pages, user can later expand it */
4845 buffer->buffers[cpu] =
4846 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4847 if (!buffer->buffers[cpu]) {
4848 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4853 cpumask_set_cpu(cpu, buffer->cpumask);
4857 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4859 * This is a basic integrity check of the ring buffer.
4860 * Late in the boot cycle this test will run when configured in.
4861 * It will kick off a thread per CPU that will go into a loop
4862 * writing to the per cpu ring buffer various sizes of data.
4863 * Some of the data will be large items, some small.
4865 * Another thread is created that goes into a spin, sending out
4866 * IPIs to the other CPUs to also write into the ring buffer.
4867 * this is to test the nesting ability of the buffer.
4869 * Basic stats are recorded and reported. If something in the
4870 * ring buffer should happen that's not expected, a big warning
4871 * is displayed and all ring buffers are disabled.
4873 static struct task_struct *rb_threads[NR_CPUS] __initdata;
4875 struct rb_test_data {
4876 struct ring_buffer *buffer;
4877 unsigned long events;
4878 unsigned long bytes_written;
4879 unsigned long bytes_alloc;
4880 unsigned long bytes_dropped;
4881 unsigned long events_nested;
4882 unsigned long bytes_written_nested;
4883 unsigned long bytes_alloc_nested;
4884 unsigned long bytes_dropped_nested;
4885 int min_size_nested;
4886 int max_size_nested;
4893 static struct rb_test_data rb_data[NR_CPUS] __initdata;
4896 #define RB_TEST_BUFFER_SIZE 1048576
4898 static char rb_string[] __initdata =
4899 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4900 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4901 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4903 static bool rb_test_started __initdata;
4910 static __init int rb_write_something(struct rb_test_data *data, bool nested)
4912 struct ring_buffer_event *event;
4913 struct rb_item *item;
4920 /* Have nested writes different that what is written */
4921 cnt = data->cnt + (nested ? 27 : 0);
4923 /* Multiply cnt by ~e, to make some unique increment */
4924 size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
4926 len = size + sizeof(struct rb_item);
4928 started = rb_test_started;
4929 /* read rb_test_started before checking buffer enabled */
4932 event = ring_buffer_lock_reserve(data->buffer, len);
4934 /* Ignore dropped events before test starts. */
4937 data->bytes_dropped += len;
4939 data->bytes_dropped_nested += len;
4944 event_len = ring_buffer_event_length(event);
4946 if (RB_WARN_ON(data->buffer, event_len < len))
4949 item = ring_buffer_event_data(event);
4951 memcpy(item->str, rb_string, size);
4954 data->bytes_alloc_nested += event_len;
4955 data->bytes_written_nested += len;
4956 data->events_nested++;
4957 if (!data->min_size_nested || len < data->min_size_nested)
4958 data->min_size_nested = len;
4959 if (len > data->max_size_nested)
4960 data->max_size_nested = len;
4962 data->bytes_alloc += event_len;
4963 data->bytes_written += len;
4965 if (!data->min_size || len < data->min_size)
4966 data->max_size = len;
4967 if (len > data->max_size)
4968 data->max_size = len;
4972 ring_buffer_unlock_commit(data->buffer, event);
4977 static __init int rb_test(void *arg)
4979 struct rb_test_data *data = arg;
4981 while (!kthread_should_stop()) {
4982 rb_write_something(data, false);
4985 set_current_state(TASK_INTERRUPTIBLE);
4986 /* Now sleep between a min of 100-300us and a max of 1ms */
4987 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
4993 static __init void rb_ipi(void *ignore)
4995 struct rb_test_data *data;
4996 int cpu = smp_processor_id();
4998 data = &rb_data[cpu];
4999 rb_write_something(data, true);
5002 static __init int rb_hammer_test(void *arg)
5004 while (!kthread_should_stop()) {
5006 /* Send an IPI to all cpus to write data! */
5007 smp_call_function(rb_ipi, NULL, 1);
5008 /* No sleep, but for non preempt, let others run */
5015 static __init int test_ringbuffer(void)
5017 struct task_struct *rb_hammer;
5018 struct ring_buffer *buffer;
5022 pr_info("Running ring buffer tests...\n");
5024 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5025 if (WARN_ON(!buffer))
5028 /* Disable buffer so that threads can't write to it yet */
5029 ring_buffer_record_off(buffer);
5031 for_each_online_cpu(cpu) {
5032 rb_data[cpu].buffer = buffer;
5033 rb_data[cpu].cpu = cpu;
5034 rb_data[cpu].cnt = cpu;
5035 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5036 "rbtester/%d", cpu);
5037 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5038 pr_cont("FAILED\n");
5039 ret = PTR_ERR(rb_threads[cpu]);
5043 kthread_bind(rb_threads[cpu], cpu);
5044 wake_up_process(rb_threads[cpu]);
5047 /* Now create the rb hammer! */
5048 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5049 if (WARN_ON(IS_ERR(rb_hammer))) {
5050 pr_cont("FAILED\n");
5051 ret = PTR_ERR(rb_hammer);
5055 ring_buffer_record_on(buffer);
5057 * Show buffer is enabled before setting rb_test_started.
5058 * Yes there's a small race window where events could be
5059 * dropped and the thread wont catch it. But when a ring
5060 * buffer gets enabled, there will always be some kind of
5061 * delay before other CPUs see it. Thus, we don't care about
5062 * those dropped events. We care about events dropped after
5063 * the threads see that the buffer is active.
5066 rb_test_started = true;
5068 set_current_state(TASK_INTERRUPTIBLE);
5069 /* Just run for 10 seconds */;
5070 schedule_timeout(10 * HZ);
5072 kthread_stop(rb_hammer);
5075 for_each_online_cpu(cpu) {
5076 if (!rb_threads[cpu])
5078 kthread_stop(rb_threads[cpu]);
5081 ring_buffer_free(buffer);
5086 pr_info("finished\n");
5087 for_each_online_cpu(cpu) {
5088 struct ring_buffer_event *event;
5089 struct rb_test_data *data = &rb_data[cpu];
5090 struct rb_item *item;
5091 unsigned long total_events;
5092 unsigned long total_dropped;
5093 unsigned long total_written;
5094 unsigned long total_alloc;
5095 unsigned long total_read = 0;
5096 unsigned long total_size = 0;
5097 unsigned long total_len = 0;
5098 unsigned long total_lost = 0;
5101 int small_event_size;
5105 total_events = data->events + data->events_nested;
5106 total_written = data->bytes_written + data->bytes_written_nested;
5107 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5108 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5110 big_event_size = data->max_size + data->max_size_nested;
5111 small_event_size = data->min_size + data->min_size_nested;
5113 pr_info("CPU %d:\n", cpu);
5114 pr_info(" events: %ld\n", total_events);
5115 pr_info(" dropped bytes: %ld\n", total_dropped);
5116 pr_info(" alloced bytes: %ld\n", total_alloc);
5117 pr_info(" written bytes: %ld\n", total_written);
5118 pr_info(" biggest event: %d\n", big_event_size);
5119 pr_info(" smallest event: %d\n", small_event_size);
5121 if (RB_WARN_ON(buffer, total_dropped))
5126 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5128 item = ring_buffer_event_data(event);
5129 total_len += ring_buffer_event_length(event);
5130 total_size += item->size + sizeof(struct rb_item);
5131 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5132 pr_info("FAILED!\n");
5133 pr_info("buffer had: %.*s\n", item->size, item->str);
5134 pr_info("expected: %.*s\n", item->size, rb_string);
5135 RB_WARN_ON(buffer, 1);
5146 pr_info(" read events: %ld\n", total_read);
5147 pr_info(" lost events: %ld\n", total_lost);
5148 pr_info(" total events: %ld\n", total_lost + total_read);
5149 pr_info(" recorded len bytes: %ld\n", total_len);
5150 pr_info(" recorded size bytes: %ld\n", total_size);
5152 pr_info(" With dropped events, record len and size may not match\n"
5153 " alloced and written from above\n");
5155 if (RB_WARN_ON(buffer, total_len != total_alloc ||
5156 total_size != total_written))
5159 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5165 pr_info("Ring buffer PASSED!\n");
5167 ring_buffer_free(buffer);
5171 late_initcall(test_ringbuffer);
5172 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */