1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
7 #include <linux/trace_recursion.h>
8 #include <linux/trace_events.h>
9 #include <linux/ring_buffer.h>
10 #include <linux/trace_clock.h>
11 #include <linux/sched/clock.h>
12 #include <linux/trace_seq.h>
13 #include <linux/spinlock.h>
14 #include <linux/irq_work.h>
15 #include <linux/security.h>
16 #include <linux/uaccess.h>
17 #include <linux/hardirq.h>
18 #include <linux/kthread.h> /* for self test */
19 #include <linux/module.h>
20 #include <linux/percpu.h>
21 #include <linux/mutex.h>
22 #include <linux/delay.h>
23 #include <linux/slab.h>
24 #include <linux/init.h>
25 #include <linux/hash.h>
26 #include <linux/list.h>
27 #include <linux/cpu.h>
28 #include <linux/oom.h>
30 #include <asm/local.h>
33 * The "absolute" timestamp in the buffer is only 59 bits.
34 * If a clock has the 5 MSBs set, it needs to be saved and
37 #define TS_MSB (0xf8ULL << 56)
38 #define ABS_TS_MASK (~TS_MSB)
40 static void update_pages_handler(struct work_struct *work);
43 * The ring buffer header is special. We must manually up keep it.
45 int ring_buffer_print_entry_header(struct trace_seq *s)
47 trace_seq_puts(s, "# compressed entry header\n");
48 trace_seq_puts(s, "\ttype_len : 5 bits\n");
49 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
50 trace_seq_puts(s, "\tarray : 32 bits\n");
51 trace_seq_putc(s, '\n');
52 trace_seq_printf(s, "\tpadding : type == %d\n",
53 RINGBUF_TYPE_PADDING);
54 trace_seq_printf(s, "\ttime_extend : type == %d\n",
55 RINGBUF_TYPE_TIME_EXTEND);
56 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
57 RINGBUF_TYPE_TIME_STAMP);
58 trace_seq_printf(s, "\tdata max type_len == %d\n",
59 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
61 return !trace_seq_has_overflowed(s);
65 * The ring buffer is made up of a list of pages. A separate list of pages is
66 * allocated for each CPU. A writer may only write to a buffer that is
67 * associated with the CPU it is currently executing on. A reader may read
68 * from any per cpu buffer.
70 * The reader is special. For each per cpu buffer, the reader has its own
71 * reader page. When a reader has read the entire reader page, this reader
72 * page is swapped with another page in the ring buffer.
74 * Now, as long as the writer is off the reader page, the reader can do what
75 * ever it wants with that page. The writer will never write to that page
76 * again (as long as it is out of the ring buffer).
78 * Here's some silly ASCII art.
81 * |reader| RING BUFFER
83 * +------+ +---+ +---+ +---+
92 * |reader| RING BUFFER
93 * |page |------------------v
94 * +------+ +---+ +---+ +---+
103 * |reader| RING BUFFER
104 * |page |------------------v
105 * +------+ +---+ +---+ +---+
107 * | +---+ +---+ +---+
110 * +------------------------------+
114 * |buffer| RING BUFFER
115 * |page |------------------v
116 * +------+ +---+ +---+ +---+
118 * | New +---+ +---+ +---+
121 * +------------------------------+
124 * After we make this swap, the reader can hand this page off to the splice
125 * code and be done with it. It can even allocate a new page if it needs to
126 * and swap that into the ring buffer.
128 * We will be using cmpxchg soon to make all this lockless.
132 /* Used for individual buffers (after the counter) */
133 #define RB_BUFFER_OFF (1 << 20)
135 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
137 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
138 #define RB_ALIGNMENT 4U
139 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
140 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
142 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
143 # define RB_FORCE_8BYTE_ALIGNMENT 0
144 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
146 # define RB_FORCE_8BYTE_ALIGNMENT 1
147 # define RB_ARCH_ALIGNMENT 8U
150 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
152 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
153 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
156 RB_LEN_TIME_EXTEND = 8,
157 RB_LEN_TIME_STAMP = 8,
160 #define skip_time_extend(event) \
161 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
163 #define extended_time(event) \
164 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
166 static inline int rb_null_event(struct ring_buffer_event *event)
168 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
171 static void rb_event_set_padding(struct ring_buffer_event *event)
173 /* padding has a NULL time_delta */
174 event->type_len = RINGBUF_TYPE_PADDING;
175 event->time_delta = 0;
179 rb_event_data_length(struct ring_buffer_event *event)
184 length = event->type_len * RB_ALIGNMENT;
186 length = event->array[0];
187 return length + RB_EVNT_HDR_SIZE;
191 * Return the length of the given event. Will return
192 * the length of the time extend if the event is a
195 static inline unsigned
196 rb_event_length(struct ring_buffer_event *event)
198 switch (event->type_len) {
199 case RINGBUF_TYPE_PADDING:
200 if (rb_null_event(event))
203 return event->array[0] + RB_EVNT_HDR_SIZE;
205 case RINGBUF_TYPE_TIME_EXTEND:
206 return RB_LEN_TIME_EXTEND;
208 case RINGBUF_TYPE_TIME_STAMP:
209 return RB_LEN_TIME_STAMP;
211 case RINGBUF_TYPE_DATA:
212 return rb_event_data_length(event);
221 * Return total length of time extend and data,
222 * or just the event length for all other events.
224 static inline unsigned
225 rb_event_ts_length(struct ring_buffer_event *event)
229 if (extended_time(event)) {
230 /* time extends include the data event after it */
231 len = RB_LEN_TIME_EXTEND;
232 event = skip_time_extend(event);
234 return len + rb_event_length(event);
238 * ring_buffer_event_length - return the length of the event
239 * @event: the event to get the length of
241 * Returns the size of the data load of a data event.
242 * If the event is something other than a data event, it
243 * returns the size of the event itself. With the exception
244 * of a TIME EXTEND, where it still returns the size of the
245 * data load of the data event after it.
247 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
251 if (extended_time(event))
252 event = skip_time_extend(event);
254 length = rb_event_length(event);
255 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
257 length -= RB_EVNT_HDR_SIZE;
258 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
259 length -= sizeof(event->array[0]);
262 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
264 /* inline for ring buffer fast paths */
265 static __always_inline void *
266 rb_event_data(struct ring_buffer_event *event)
268 if (extended_time(event))
269 event = skip_time_extend(event);
270 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
271 /* If length is in len field, then array[0] has the data */
273 return (void *)&event->array[0];
274 /* Otherwise length is in array[0] and array[1] has the data */
275 return (void *)&event->array[1];
279 * ring_buffer_event_data - return the data of the event
280 * @event: the event to get the data from
282 void *ring_buffer_event_data(struct ring_buffer_event *event)
284 return rb_event_data(event);
286 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
288 #define for_each_buffer_cpu(buffer, cpu) \
289 for_each_cpu(cpu, buffer->cpumask)
291 #define for_each_online_buffer_cpu(buffer, cpu) \
292 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
295 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
296 #define TS_DELTA_TEST (~TS_MASK)
298 static u64 rb_event_time_stamp(struct ring_buffer_event *event)
302 ts = event->array[0];
304 ts += event->time_delta;
309 /* Flag when events were overwritten */
310 #define RB_MISSED_EVENTS (1 << 31)
311 /* Missed count stored at end */
312 #define RB_MISSED_STORED (1 << 30)
314 struct buffer_data_page {
315 u64 time_stamp; /* page time stamp */
316 local_t commit; /* write committed index */
317 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
321 * Note, the buffer_page list must be first. The buffer pages
322 * are allocated in cache lines, which means that each buffer
323 * page will be at the beginning of a cache line, and thus
324 * the least significant bits will be zero. We use this to
325 * add flags in the list struct pointers, to make the ring buffer
329 struct list_head list; /* list of buffer pages */
330 local_t write; /* index for next write */
331 unsigned read; /* index for next read */
332 local_t entries; /* entries on this page */
333 unsigned long real_end; /* real end of data */
334 struct buffer_data_page *page; /* Actual data page */
338 * The buffer page counters, write and entries, must be reset
339 * atomically when crossing page boundaries. To synchronize this
340 * update, two counters are inserted into the number. One is
341 * the actual counter for the write position or count on the page.
343 * The other is a counter of updaters. Before an update happens
344 * the update partition of the counter is incremented. This will
345 * allow the updater to update the counter atomically.
347 * The counter is 20 bits, and the state data is 12.
349 #define RB_WRITE_MASK 0xfffff
350 #define RB_WRITE_INTCNT (1 << 20)
352 static void rb_init_page(struct buffer_data_page *bpage)
354 local_set(&bpage->commit, 0);
358 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
361 static void free_buffer_page(struct buffer_page *bpage)
363 free_page((unsigned long)bpage->page);
368 * We need to fit the time_stamp delta into 27 bits.
370 static inline int test_time_stamp(u64 delta)
372 if (delta & TS_DELTA_TEST)
377 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
379 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
380 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
382 int ring_buffer_print_page_header(struct trace_seq *s)
384 struct buffer_data_page field;
386 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
387 "offset:0;\tsize:%u;\tsigned:%u;\n",
388 (unsigned int)sizeof(field.time_stamp),
389 (unsigned int)is_signed_type(u64));
391 trace_seq_printf(s, "\tfield: local_t commit;\t"
392 "offset:%u;\tsize:%u;\tsigned:%u;\n",
393 (unsigned int)offsetof(typeof(field), commit),
394 (unsigned int)sizeof(field.commit),
395 (unsigned int)is_signed_type(long));
397 trace_seq_printf(s, "\tfield: int overwrite;\t"
398 "offset:%u;\tsize:%u;\tsigned:%u;\n",
399 (unsigned int)offsetof(typeof(field), commit),
401 (unsigned int)is_signed_type(long));
403 trace_seq_printf(s, "\tfield: char data;\t"
404 "offset:%u;\tsize:%u;\tsigned:%u;\n",
405 (unsigned int)offsetof(typeof(field), data),
406 (unsigned int)BUF_PAGE_SIZE,
407 (unsigned int)is_signed_type(char));
409 return !trace_seq_has_overflowed(s);
413 struct irq_work work;
414 wait_queue_head_t waiters;
415 wait_queue_head_t full_waiters;
417 bool waiters_pending;
418 bool full_waiters_pending;
423 * Structure to hold event state and handle nested events.
425 struct rb_event_info {
430 unsigned long length;
431 struct buffer_page *tail_page;
436 * Used for the add_timestamp
438 * EXTEND - wants a time extend
439 * ABSOLUTE - the buffer requests all events to have absolute time stamps
440 * FORCE - force a full time stamp.
443 RB_ADD_STAMP_NONE = 0,
444 RB_ADD_STAMP_EXTEND = BIT(1),
445 RB_ADD_STAMP_ABSOLUTE = BIT(2),
446 RB_ADD_STAMP_FORCE = BIT(3)
449 * Used for which event context the event is in.
456 * See trace_recursive_lock() comment below for more details.
467 #if BITS_PER_LONG == 32
471 /* To test on 64 bit machines */
476 struct rb_time_struct {
483 #include <asm/local64.h>
484 struct rb_time_struct {
488 typedef struct rb_time_struct rb_time_t;
493 * head_page == tail_page && head == tail then buffer is empty.
495 struct ring_buffer_per_cpu {
497 atomic_t record_disabled;
498 atomic_t resize_disabled;
499 struct trace_buffer *buffer;
500 raw_spinlock_t reader_lock; /* serialize readers */
501 arch_spinlock_t lock;
502 struct lock_class_key lock_key;
503 struct buffer_data_page *free_page;
504 unsigned long nr_pages;
505 unsigned int current_context;
506 struct list_head *pages;
507 struct buffer_page *head_page; /* read from head */
508 struct buffer_page *tail_page; /* write to tail */
509 struct buffer_page *commit_page; /* committed pages */
510 struct buffer_page *reader_page;
511 unsigned long lost_events;
512 unsigned long last_overrun;
514 local_t entries_bytes;
517 local_t commit_overrun;
518 local_t dropped_events;
521 local_t pages_touched;
524 long last_pages_touch;
525 size_t shortest_full;
527 unsigned long read_bytes;
528 rb_time_t write_stamp;
529 rb_time_t before_stamp;
530 u64 event_stamp[MAX_NEST];
532 /* ring buffer pages to update, > 0 to add, < 0 to remove */
533 long nr_pages_to_update;
534 struct list_head new_pages; /* new pages to add */
535 struct work_struct update_pages_work;
536 struct completion update_done;
538 struct rb_irq_work irq_work;
541 struct trace_buffer {
544 atomic_t record_disabled;
545 cpumask_var_t cpumask;
547 struct lock_class_key *reader_lock_key;
551 struct ring_buffer_per_cpu **buffers;
553 struct hlist_node node;
556 struct rb_irq_work irq_work;
560 struct ring_buffer_iter {
561 struct ring_buffer_per_cpu *cpu_buffer;
563 unsigned long next_event;
564 struct buffer_page *head_page;
565 struct buffer_page *cache_reader_page;
566 unsigned long cache_read;
569 struct ring_buffer_event *event;
576 * On 32 bit machines, local64_t is very expensive. As the ring
577 * buffer doesn't need all the features of a true 64 bit atomic,
578 * on 32 bit, it uses these functions (64 still uses local64_t).
580 * For the ring buffer, 64 bit required operations for the time is
583 * - Reads may fail if it interrupted a modification of the time stamp.
584 * It will succeed if it did not interrupt another write even if
585 * the read itself is interrupted by a write.
586 * It returns whether it was successful or not.
588 * - Writes always succeed and will overwrite other writes and writes
589 * that were done by events interrupting the current write.
591 * - A write followed by a read of the same time stamp will always succeed,
592 * but may not contain the same value.
594 * - A cmpxchg will fail if it interrupted another write or cmpxchg.
595 * Other than that, it acts like a normal cmpxchg.
597 * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
598 * (bottom being the least significant 30 bits of the 60 bit time stamp).
600 * The two most significant bits of each half holds a 2 bit counter (0-3).
601 * Each update will increment this counter by one.
602 * When reading the top and bottom, if the two counter bits match then the
603 * top and bottom together make a valid 60 bit number.
605 #define RB_TIME_SHIFT 30
606 #define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
607 #define RB_TIME_MSB_SHIFT 60
609 static inline int rb_time_cnt(unsigned long val)
611 return (val >> RB_TIME_SHIFT) & 3;
614 static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
618 val = top & RB_TIME_VAL_MASK;
619 val <<= RB_TIME_SHIFT;
620 val |= bottom & RB_TIME_VAL_MASK;
625 static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
627 unsigned long top, bottom, msb;
631 * If the read is interrupted by a write, then the cnt will
632 * be different. Loop until both top and bottom have been read
633 * without interruption.
636 c = local_read(&t->cnt);
637 top = local_read(&t->top);
638 bottom = local_read(&t->bottom);
639 msb = local_read(&t->msb);
640 } while (c != local_read(&t->cnt));
642 *cnt = rb_time_cnt(top);
644 /* If top and bottom counts don't match, this interrupted a write */
645 if (*cnt != rb_time_cnt(bottom))
648 /* The shift to msb will lose its cnt bits */
649 *ret = rb_time_val(top, bottom) | ((u64)msb << RB_TIME_MSB_SHIFT);
653 static bool rb_time_read(rb_time_t *t, u64 *ret)
657 return __rb_time_read(t, ret, &cnt);
660 static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
662 return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
665 static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom,
668 *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
669 *bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
670 *msb = (unsigned long)(val >> RB_TIME_MSB_SHIFT);
673 static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
675 val = rb_time_val_cnt(val, cnt);
679 static void rb_time_set(rb_time_t *t, u64 val)
681 unsigned long cnt, top, bottom, msb;
683 rb_time_split(val, &top, &bottom, &msb);
685 /* Writes always succeed with a valid number even if it gets interrupted. */
687 cnt = local_inc_return(&t->cnt);
688 rb_time_val_set(&t->top, top, cnt);
689 rb_time_val_set(&t->bottom, bottom, cnt);
690 rb_time_val_set(&t->msb, val >> RB_TIME_MSB_SHIFT, cnt);
691 } while (cnt != local_read(&t->cnt));
695 rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
699 ret = local_cmpxchg(l, expect, set);
700 return ret == expect;
703 static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
705 unsigned long cnt, top, bottom, msb;
706 unsigned long cnt2, top2, bottom2, msb2;
709 /* The cmpxchg always fails if it interrupted an update */
710 if (!__rb_time_read(t, &val, &cnt2))
716 cnt = local_read(&t->cnt);
717 if ((cnt & 3) != cnt2)
722 rb_time_split(val, &top, &bottom, &msb);
723 top = rb_time_val_cnt(top, cnt);
724 bottom = rb_time_val_cnt(bottom, cnt);
726 rb_time_split(set, &top2, &bottom2, &msb2);
727 top2 = rb_time_val_cnt(top2, cnt2);
728 bottom2 = rb_time_val_cnt(bottom2, cnt2);
730 if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
732 if (!rb_time_read_cmpxchg(&t->msb, msb, msb2))
734 if (!rb_time_read_cmpxchg(&t->top, top, top2))
736 if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
743 /* local64_t always succeeds */
745 static inline bool rb_time_read(rb_time_t *t, u64 *ret)
747 *ret = local64_read(&t->time);
750 static void rb_time_set(rb_time_t *t, u64 val)
752 local64_set(&t->time, val);
755 static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
758 val = local64_cmpxchg(&t->time, expect, set);
759 return val == expect;
764 * Enable this to make sure that the event passed to
765 * ring_buffer_event_time_stamp() is not committed and also
766 * is on the buffer that it passed in.
768 //#define RB_VERIFY_EVENT
769 #ifdef RB_VERIFY_EVENT
770 static struct list_head *rb_list_head(struct list_head *list);
771 static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
774 struct buffer_page *page = cpu_buffer->commit_page;
775 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
776 struct list_head *next;
778 unsigned long addr = (unsigned long)event;
782 /* Make sure the event exists and is not committed yet */
784 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
786 commit = local_read(&page->page->commit);
787 write = local_read(&page->write);
788 if (addr >= (unsigned long)&page->page->data[commit] &&
789 addr < (unsigned long)&page->page->data[write])
792 next = rb_list_head(page->list.next);
793 page = list_entry(next, struct buffer_page, list);
798 static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
805 * The absolute time stamp drops the 5 MSBs and some clocks may
806 * require them. The rb_fix_abs_ts() will take a previous full
807 * time stamp, and add the 5 MSB of that time stamp on to the
808 * saved absolute time stamp. Then they are compared in case of
809 * the unlikely event that the latest time stamp incremented
812 static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
814 if (save_ts & TS_MSB) {
815 abs |= save_ts & TS_MSB;
816 /* Check for overflow */
817 if (unlikely(abs < save_ts))
823 static inline u64 rb_time_stamp(struct trace_buffer *buffer);
826 * ring_buffer_event_time_stamp - return the event's current time stamp
827 * @buffer: The buffer that the event is on
828 * @event: the event to get the time stamp of
830 * Note, this must be called after @event is reserved, and before it is
831 * committed to the ring buffer. And must be called from the same
832 * context where the event was reserved (normal, softirq, irq, etc).
834 * Returns the time stamp associated with the current event.
835 * If the event has an extended time stamp, then that is used as
836 * the time stamp to return.
837 * In the highly unlikely case that the event was nested more than
838 * the max nesting, then the write_stamp of the buffer is returned,
839 * otherwise current time is returned, but that really neither of
840 * the last two cases should ever happen.
842 u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
843 struct ring_buffer_event *event)
845 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
849 /* If the event includes an absolute time, then just use that */
850 if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
851 ts = rb_event_time_stamp(event);
852 return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
855 nest = local_read(&cpu_buffer->committing);
856 verify_event(cpu_buffer, event);
857 if (WARN_ON_ONCE(!nest))
860 /* Read the current saved nesting level time stamp */
861 if (likely(--nest < MAX_NEST))
862 return cpu_buffer->event_stamp[nest];
864 /* Shouldn't happen, warn if it does */
865 WARN_ONCE(1, "nest (%d) greater than max", nest);
868 /* Can only fail on 32 bit */
869 if (!rb_time_read(&cpu_buffer->write_stamp, &ts))
870 /* Screw it, just read the current time */
871 ts = rb_time_stamp(cpu_buffer->buffer);
877 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
878 * @buffer: The ring_buffer to get the number of pages from
879 * @cpu: The cpu of the ring_buffer to get the number of pages from
881 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
883 size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
885 return buffer->buffers[cpu]->nr_pages;
889 * ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
890 * @buffer: The ring_buffer to get the number of pages from
891 * @cpu: The cpu of the ring_buffer to get the number of pages from
893 * Returns the number of pages that have content in the ring buffer.
895 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
901 read = local_read(&buffer->buffers[cpu]->pages_read);
902 lost = local_read(&buffer->buffers[cpu]->pages_lost);
903 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
905 if (WARN_ON_ONCE(cnt < lost))
910 /* The reader can read an empty page, but not more than that */
912 WARN_ON_ONCE(read > cnt + 1);
919 static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
921 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
925 nr_pages = cpu_buffer->nr_pages;
926 if (!nr_pages || !full)
929 dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
931 return (dirty * 100) > (full * nr_pages);
935 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
937 * Schedules a delayed work to wake up any task that is blocked on the
938 * ring buffer waiters queue.
940 static void rb_wake_up_waiters(struct irq_work *work)
942 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
944 wake_up_all(&rbwork->waiters);
945 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
946 rbwork->wakeup_full = false;
947 rbwork->full_waiters_pending = false;
948 wake_up_all(&rbwork->full_waiters);
953 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
954 * @buffer: The ring buffer to wake waiters on
956 * In the case of a file that represents a ring buffer is closing,
957 * it is prudent to wake up any waiters that are on this.
959 void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
961 struct ring_buffer_per_cpu *cpu_buffer;
962 struct rb_irq_work *rbwork;
967 if (cpu == RING_BUFFER_ALL_CPUS) {
969 /* Wake up individual ones too. One level recursion */
970 for_each_buffer_cpu(buffer, cpu)
971 ring_buffer_wake_waiters(buffer, cpu);
973 rbwork = &buffer->irq_work;
975 if (WARN_ON_ONCE(!buffer->buffers))
977 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
980 cpu_buffer = buffer->buffers[cpu];
981 /* The CPU buffer may not have been initialized yet */
984 rbwork = &cpu_buffer->irq_work;
987 rbwork->wait_index++;
988 /* make sure the waiters see the new index */
991 rb_wake_up_waiters(&rbwork->work);
995 * ring_buffer_wait - wait for input to the ring buffer
996 * @buffer: buffer to wait on
997 * @cpu: the cpu buffer to wait on
998 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
1000 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1001 * as data is added to any of the @buffer's cpu buffers. Otherwise
1002 * it will wait for data to be added to a specific cpu buffer.
1004 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
1006 struct ring_buffer_per_cpu *cpu_buffer;
1008 struct rb_irq_work *work;
1013 * Depending on what the caller is waiting for, either any
1014 * data in any cpu buffer, or a specific buffer, put the
1015 * caller on the appropriate wait queue.
1017 if (cpu == RING_BUFFER_ALL_CPUS) {
1018 work = &buffer->irq_work;
1019 /* Full only makes sense on per cpu reads */
1022 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1024 cpu_buffer = buffer->buffers[cpu];
1025 work = &cpu_buffer->irq_work;
1028 wait_index = READ_ONCE(work->wait_index);
1032 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
1034 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
1037 * The events can happen in critical sections where
1038 * checking a work queue can cause deadlocks.
1039 * After adding a task to the queue, this flag is set
1040 * only to notify events to try to wake up the queue
1043 * We don't clear it even if the buffer is no longer
1044 * empty. The flag only causes the next event to run
1045 * irq_work to do the work queue wake up. The worse
1046 * that can happen if we race with !trace_empty() is that
1047 * an event will cause an irq_work to try to wake up
1050 * There's no reason to protect this flag either, as
1051 * the work queue and irq_work logic will do the necessary
1052 * synchronization for the wake ups. The only thing
1053 * that is necessary is that the wake up happens after
1054 * a task has been queued. It's OK for spurious wake ups.
1057 work->full_waiters_pending = true;
1059 work->waiters_pending = true;
1061 if (signal_pending(current)) {
1066 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
1069 if (cpu != RING_BUFFER_ALL_CPUS &&
1070 !ring_buffer_empty_cpu(buffer, cpu)) {
1071 unsigned long flags;
1078 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
1079 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
1080 done = !pagebusy && full_hit(buffer, cpu, full);
1082 if (!cpu_buffer->shortest_full ||
1083 cpu_buffer->shortest_full > full)
1084 cpu_buffer->shortest_full = full;
1085 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
1092 /* Make sure to see the new wait index */
1094 if (wait_index != work->wait_index)
1099 finish_wait(&work->full_waiters, &wait);
1101 finish_wait(&work->waiters, &wait);
1107 * ring_buffer_poll_wait - poll on buffer input
1108 * @buffer: buffer to wait on
1109 * @cpu: the cpu buffer to wait on
1110 * @filp: the file descriptor
1111 * @poll_table: The poll descriptor
1112 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
1114 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1115 * as data is added to any of the @buffer's cpu buffers. Otherwise
1116 * it will wait for data to be added to a specific cpu buffer.
1118 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1121 __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1122 struct file *filp, poll_table *poll_table, int full)
1124 struct ring_buffer_per_cpu *cpu_buffer;
1125 struct rb_irq_work *work;
1127 if (cpu == RING_BUFFER_ALL_CPUS) {
1128 work = &buffer->irq_work;
1131 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1134 cpu_buffer = buffer->buffers[cpu];
1135 work = &cpu_buffer->irq_work;
1139 poll_wait(filp, &work->full_waiters, poll_table);
1140 work->full_waiters_pending = true;
1142 poll_wait(filp, &work->waiters, poll_table);
1143 work->waiters_pending = true;
1147 * There's a tight race between setting the waiters_pending and
1148 * checking if the ring buffer is empty. Once the waiters_pending bit
1149 * is set, the next event will wake the task up, but we can get stuck
1150 * if there's only a single event in.
1152 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1153 * but adding a memory barrier to all events will cause too much of a
1154 * performance hit in the fast path. We only need a memory barrier when
1155 * the buffer goes from empty to having content. But as this race is
1156 * extremely small, and it's not a problem if another event comes in, we
1157 * will fix it later.
1162 return full_hit(buffer, cpu, full) ? EPOLLIN | EPOLLRDNORM : 0;
1164 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1165 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1166 return EPOLLIN | EPOLLRDNORM;
1170 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
1171 #define RB_WARN_ON(b, cond) \
1173 int _____ret = unlikely(cond); \
1175 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1176 struct ring_buffer_per_cpu *__b = \
1178 atomic_inc(&__b->buffer->record_disabled); \
1180 atomic_inc(&b->record_disabled); \
1186 /* Up this if you want to test the TIME_EXTENTS and normalization */
1187 #define DEBUG_SHIFT 0
1189 static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1193 /* Skip retpolines :-( */
1194 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1195 ts = trace_clock_local();
1197 ts = buffer->clock();
1199 /* shift to debug/test normalization and TIME_EXTENTS */
1200 return ts << DEBUG_SHIFT;
1203 u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1207 preempt_disable_notrace();
1208 time = rb_time_stamp(buffer);
1209 preempt_enable_notrace();
1213 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1215 void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1218 /* Just stupid testing the normalize function and deltas */
1219 *ts >>= DEBUG_SHIFT;
1221 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1224 * Making the ring buffer lockless makes things tricky.
1225 * Although writes only happen on the CPU that they are on,
1226 * and they only need to worry about interrupts. Reads can
1227 * happen on any CPU.
1229 * The reader page is always off the ring buffer, but when the
1230 * reader finishes with a page, it needs to swap its page with
1231 * a new one from the buffer. The reader needs to take from
1232 * the head (writes go to the tail). But if a writer is in overwrite
1233 * mode and wraps, it must push the head page forward.
1235 * Here lies the problem.
1237 * The reader must be careful to replace only the head page, and
1238 * not another one. As described at the top of the file in the
1239 * ASCII art, the reader sets its old page to point to the next
1240 * page after head. It then sets the page after head to point to
1241 * the old reader page. But if the writer moves the head page
1242 * during this operation, the reader could end up with the tail.
1244 * We use cmpxchg to help prevent this race. We also do something
1245 * special with the page before head. We set the LSB to 1.
1247 * When the writer must push the page forward, it will clear the
1248 * bit that points to the head page, move the head, and then set
1249 * the bit that points to the new head page.
1251 * We also don't want an interrupt coming in and moving the head
1252 * page on another writer. Thus we use the second LSB to catch
1255 * head->list->prev->next bit 1 bit 0
1258 * Points to head page 0 1
1261 * Note we can not trust the prev pointer of the head page, because:
1263 * +----+ +-----+ +-----+
1264 * | |------>| T |---X--->| N |
1266 * +----+ +-----+ +-----+
1269 * +----------| R |----------+ |
1273 * Key: ---X--> HEAD flag set in pointer
1278 * (see __rb_reserve_next() to see where this happens)
1280 * What the above shows is that the reader just swapped out
1281 * the reader page with a page in the buffer, but before it
1282 * could make the new header point back to the new page added
1283 * it was preempted by a writer. The writer moved forward onto
1284 * the new page added by the reader and is about to move forward
1287 * You can see, it is legitimate for the previous pointer of
1288 * the head (or any page) not to point back to itself. But only
1292 #define RB_PAGE_NORMAL 0UL
1293 #define RB_PAGE_HEAD 1UL
1294 #define RB_PAGE_UPDATE 2UL
1297 #define RB_FLAG_MASK 3UL
1299 /* PAGE_MOVED is not part of the mask */
1300 #define RB_PAGE_MOVED 4UL
1303 * rb_list_head - remove any bit
1305 static struct list_head *rb_list_head(struct list_head *list)
1307 unsigned long val = (unsigned long)list;
1309 return (struct list_head *)(val & ~RB_FLAG_MASK);
1313 * rb_is_head_page - test if the given page is the head page
1315 * Because the reader may move the head_page pointer, we can
1316 * not trust what the head page is (it may be pointing to
1317 * the reader page). But if the next page is a header page,
1318 * its flags will be non zero.
1321 rb_is_head_page(struct buffer_page *page, struct list_head *list)
1325 val = (unsigned long)list->next;
1327 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1328 return RB_PAGE_MOVED;
1330 return val & RB_FLAG_MASK;
1336 * The unique thing about the reader page, is that, if the
1337 * writer is ever on it, the previous pointer never points
1338 * back to the reader page.
1340 static bool rb_is_reader_page(struct buffer_page *page)
1342 struct list_head *list = page->list.prev;
1344 return rb_list_head(list->next) != &page->list;
1348 * rb_set_list_to_head - set a list_head to be pointing to head.
1350 static void rb_set_list_to_head(struct list_head *list)
1354 ptr = (unsigned long *)&list->next;
1355 *ptr |= RB_PAGE_HEAD;
1356 *ptr &= ~RB_PAGE_UPDATE;
1360 * rb_head_page_activate - sets up head page
1362 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1364 struct buffer_page *head;
1366 head = cpu_buffer->head_page;
1371 * Set the previous list pointer to have the HEAD flag.
1373 rb_set_list_to_head(head->list.prev);
1376 static void rb_list_head_clear(struct list_head *list)
1378 unsigned long *ptr = (unsigned long *)&list->next;
1380 *ptr &= ~RB_FLAG_MASK;
1384 * rb_head_page_deactivate - clears head page ptr (for free list)
1387 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1389 struct list_head *hd;
1391 /* Go through the whole list and clear any pointers found. */
1392 rb_list_head_clear(cpu_buffer->pages);
1394 list_for_each(hd, cpu_buffer->pages)
1395 rb_list_head_clear(hd);
1398 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1399 struct buffer_page *head,
1400 struct buffer_page *prev,
1401 int old_flag, int new_flag)
1403 struct list_head *list;
1404 unsigned long val = (unsigned long)&head->list;
1409 val &= ~RB_FLAG_MASK;
1411 ret = cmpxchg((unsigned long *)&list->next,
1412 val | old_flag, val | new_flag);
1414 /* check if the reader took the page */
1415 if ((ret & ~RB_FLAG_MASK) != val)
1416 return RB_PAGE_MOVED;
1418 return ret & RB_FLAG_MASK;
1421 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1422 struct buffer_page *head,
1423 struct buffer_page *prev,
1426 return rb_head_page_set(cpu_buffer, head, prev,
1427 old_flag, RB_PAGE_UPDATE);
1430 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1431 struct buffer_page *head,
1432 struct buffer_page *prev,
1435 return rb_head_page_set(cpu_buffer, head, prev,
1436 old_flag, RB_PAGE_HEAD);
1439 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1440 struct buffer_page *head,
1441 struct buffer_page *prev,
1444 return rb_head_page_set(cpu_buffer, head, prev,
1445 old_flag, RB_PAGE_NORMAL);
1448 static inline void rb_inc_page(struct buffer_page **bpage)
1450 struct list_head *p = rb_list_head((*bpage)->list.next);
1452 *bpage = list_entry(p, struct buffer_page, list);
1455 static struct buffer_page *
1456 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1458 struct buffer_page *head;
1459 struct buffer_page *page;
1460 struct list_head *list;
1463 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1467 list = cpu_buffer->pages;
1468 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1471 page = head = cpu_buffer->head_page;
1473 * It is possible that the writer moves the header behind
1474 * where we started, and we miss in one loop.
1475 * A second loop should grab the header, but we'll do
1476 * three loops just because I'm paranoid.
1478 for (i = 0; i < 3; i++) {
1480 if (rb_is_head_page(page, page->list.prev)) {
1481 cpu_buffer->head_page = page;
1485 } while (page != head);
1488 RB_WARN_ON(cpu_buffer, 1);
1493 static int rb_head_page_replace(struct buffer_page *old,
1494 struct buffer_page *new)
1496 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1500 val = *ptr & ~RB_FLAG_MASK;
1501 val |= RB_PAGE_HEAD;
1503 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1509 * rb_tail_page_update - move the tail page forward
1511 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1512 struct buffer_page *tail_page,
1513 struct buffer_page *next_page)
1515 unsigned long old_entries;
1516 unsigned long old_write;
1519 * The tail page now needs to be moved forward.
1521 * We need to reset the tail page, but without messing
1522 * with possible erasing of data brought in by interrupts
1523 * that have moved the tail page and are currently on it.
1525 * We add a counter to the write field to denote this.
1527 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1528 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1530 local_inc(&cpu_buffer->pages_touched);
1532 * Just make sure we have seen our old_write and synchronize
1533 * with any interrupts that come in.
1538 * If the tail page is still the same as what we think
1539 * it is, then it is up to us to update the tail
1542 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1543 /* Zero the write counter */
1544 unsigned long val = old_write & ~RB_WRITE_MASK;
1545 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1548 * This will only succeed if an interrupt did
1549 * not come in and change it. In which case, we
1550 * do not want to modify it.
1552 * We add (void) to let the compiler know that we do not care
1553 * about the return value of these functions. We use the
1554 * cmpxchg to only update if an interrupt did not already
1555 * do it for us. If the cmpxchg fails, we don't care.
1557 (void)local_cmpxchg(&next_page->write, old_write, val);
1558 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1561 * No need to worry about races with clearing out the commit.
1562 * it only can increment when a commit takes place. But that
1563 * only happens in the outer most nested commit.
1565 local_set(&next_page->page->commit, 0);
1567 /* Again, either we update tail_page or an interrupt does */
1568 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1572 static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1573 struct buffer_page *bpage)
1575 unsigned long val = (unsigned long)bpage;
1577 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1584 * rb_check_list - make sure a pointer to a list has the last bits zero
1586 static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1587 struct list_head *list)
1589 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1591 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1597 * rb_check_pages - integrity check of buffer pages
1598 * @cpu_buffer: CPU buffer with pages to test
1600 * As a safety measure we check to make sure the data pages have not
1603 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1605 struct list_head *head = cpu_buffer->pages;
1606 struct buffer_page *bpage, *tmp;
1608 /* Reset the head page if it exists */
1609 if (cpu_buffer->head_page)
1610 rb_set_head_page(cpu_buffer);
1612 rb_head_page_deactivate(cpu_buffer);
1614 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1616 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1619 if (rb_check_list(cpu_buffer, head))
1622 list_for_each_entry_safe(bpage, tmp, head, list) {
1623 if (RB_WARN_ON(cpu_buffer,
1624 bpage->list.next->prev != &bpage->list))
1626 if (RB_WARN_ON(cpu_buffer,
1627 bpage->list.prev->next != &bpage->list))
1629 if (rb_check_list(cpu_buffer, &bpage->list))
1633 rb_head_page_activate(cpu_buffer);
1638 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1639 long nr_pages, struct list_head *pages)
1641 struct buffer_page *bpage, *tmp;
1642 bool user_thread = current->mm != NULL;
1647 * Check if the available memory is there first.
1648 * Note, si_mem_available() only gives us a rough estimate of available
1649 * memory. It may not be accurate. But we don't care, we just want
1650 * to prevent doing any allocation when it is obvious that it is
1651 * not going to succeed.
1653 i = si_mem_available();
1658 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1659 * gracefully without invoking oom-killer and the system is not
1662 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1665 * If a user thread allocates too much, and si_mem_available()
1666 * reports there's enough memory, even though there is not.
1667 * Make sure the OOM killer kills this thread. This can happen
1668 * even with RETRY_MAYFAIL because another task may be doing
1669 * an allocation after this task has taken all memory.
1670 * This is the task the OOM killer needs to take out during this
1671 * loop, even if it was triggered by an allocation somewhere else.
1674 set_current_oom_origin();
1675 for (i = 0; i < nr_pages; i++) {
1678 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1679 mflags, cpu_to_node(cpu_buffer->cpu));
1683 rb_check_bpage(cpu_buffer, bpage);
1685 list_add(&bpage->list, pages);
1687 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0);
1690 bpage->page = page_address(page);
1691 rb_init_page(bpage->page);
1693 if (user_thread && fatal_signal_pending(current))
1697 clear_current_oom_origin();
1702 list_for_each_entry_safe(bpage, tmp, pages, list) {
1703 list_del_init(&bpage->list);
1704 free_buffer_page(bpage);
1707 clear_current_oom_origin();
1712 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1713 unsigned long nr_pages)
1719 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1723 * The ring buffer page list is a circular list that does not
1724 * start and end with a list head. All page list items point to
1727 cpu_buffer->pages = pages.next;
1730 cpu_buffer->nr_pages = nr_pages;
1732 rb_check_pages(cpu_buffer);
1737 static struct ring_buffer_per_cpu *
1738 rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1740 struct ring_buffer_per_cpu *cpu_buffer;
1741 struct buffer_page *bpage;
1745 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1746 GFP_KERNEL, cpu_to_node(cpu));
1750 cpu_buffer->cpu = cpu;
1751 cpu_buffer->buffer = buffer;
1752 raw_spin_lock_init(&cpu_buffer->reader_lock);
1753 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1754 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1755 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1756 init_completion(&cpu_buffer->update_done);
1757 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1758 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1759 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1761 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1762 GFP_KERNEL, cpu_to_node(cpu));
1764 goto fail_free_buffer;
1766 rb_check_bpage(cpu_buffer, bpage);
1768 cpu_buffer->reader_page = bpage;
1769 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1771 goto fail_free_reader;
1772 bpage->page = page_address(page);
1773 rb_init_page(bpage->page);
1775 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1776 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1778 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1780 goto fail_free_reader;
1782 cpu_buffer->head_page
1783 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1784 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1786 rb_head_page_activate(cpu_buffer);
1791 free_buffer_page(cpu_buffer->reader_page);
1798 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1800 struct list_head *head = cpu_buffer->pages;
1801 struct buffer_page *bpage, *tmp;
1803 free_buffer_page(cpu_buffer->reader_page);
1806 rb_head_page_deactivate(cpu_buffer);
1808 list_for_each_entry_safe(bpage, tmp, head, list) {
1809 list_del_init(&bpage->list);
1810 free_buffer_page(bpage);
1812 bpage = list_entry(head, struct buffer_page, list);
1813 free_buffer_page(bpage);
1820 * __ring_buffer_alloc - allocate a new ring_buffer
1821 * @size: the size in bytes per cpu that is needed.
1822 * @flags: attributes to set for the ring buffer.
1823 * @key: ring buffer reader_lock_key.
1825 * Currently the only flag that is available is the RB_FL_OVERWRITE
1826 * flag. This flag means that the buffer will overwrite old data
1827 * when the buffer wraps. If this flag is not set, the buffer will
1828 * drop data when the tail hits the head.
1830 struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1831 struct lock_class_key *key)
1833 struct trace_buffer *buffer;
1839 /* keep it in its own cache line */
1840 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1845 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1846 goto fail_free_buffer;
1848 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1849 buffer->flags = flags;
1850 buffer->clock = trace_clock_local;
1851 buffer->reader_lock_key = key;
1853 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1854 init_waitqueue_head(&buffer->irq_work.waiters);
1856 /* need at least two pages */
1860 buffer->cpus = nr_cpu_ids;
1862 bsize = sizeof(void *) * nr_cpu_ids;
1863 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1865 if (!buffer->buffers)
1866 goto fail_free_cpumask;
1868 cpu = raw_smp_processor_id();
1869 cpumask_set_cpu(cpu, buffer->cpumask);
1870 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1871 if (!buffer->buffers[cpu])
1872 goto fail_free_buffers;
1874 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1876 goto fail_free_buffers;
1878 mutex_init(&buffer->mutex);
1883 for_each_buffer_cpu(buffer, cpu) {
1884 if (buffer->buffers[cpu])
1885 rb_free_cpu_buffer(buffer->buffers[cpu]);
1887 kfree(buffer->buffers);
1890 free_cpumask_var(buffer->cpumask);
1896 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1899 * ring_buffer_free - free a ring buffer.
1900 * @buffer: the buffer to free.
1903 ring_buffer_free(struct trace_buffer *buffer)
1907 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1909 for_each_buffer_cpu(buffer, cpu)
1910 rb_free_cpu_buffer(buffer->buffers[cpu]);
1912 kfree(buffer->buffers);
1913 free_cpumask_var(buffer->cpumask);
1917 EXPORT_SYMBOL_GPL(ring_buffer_free);
1919 void ring_buffer_set_clock(struct trace_buffer *buffer,
1922 buffer->clock = clock;
1925 void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1927 buffer->time_stamp_abs = abs;
1930 bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1932 return buffer->time_stamp_abs;
1935 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1937 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1939 return local_read(&bpage->entries) & RB_WRITE_MASK;
1942 static inline unsigned long rb_page_write(struct buffer_page *bpage)
1944 return local_read(&bpage->write) & RB_WRITE_MASK;
1948 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1950 struct list_head *tail_page, *to_remove, *next_page;
1951 struct buffer_page *to_remove_page, *tmp_iter_page;
1952 struct buffer_page *last_page, *first_page;
1953 unsigned long nr_removed;
1954 unsigned long head_bit;
1959 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1960 atomic_inc(&cpu_buffer->record_disabled);
1962 * We don't race with the readers since we have acquired the reader
1963 * lock. We also don't race with writers after disabling recording.
1964 * This makes it easy to figure out the first and the last page to be
1965 * removed from the list. We unlink all the pages in between including
1966 * the first and last pages. This is done in a busy loop so that we
1967 * lose the least number of traces.
1968 * The pages are freed after we restart recording and unlock readers.
1970 tail_page = &cpu_buffer->tail_page->list;
1973 * tail page might be on reader page, we remove the next page
1974 * from the ring buffer
1976 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1977 tail_page = rb_list_head(tail_page->next);
1978 to_remove = tail_page;
1980 /* start of pages to remove */
1981 first_page = list_entry(rb_list_head(to_remove->next),
1982 struct buffer_page, list);
1984 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1985 to_remove = rb_list_head(to_remove)->next;
1986 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1989 next_page = rb_list_head(to_remove)->next;
1992 * Now we remove all pages between tail_page and next_page.
1993 * Make sure that we have head_bit value preserved for the
1996 tail_page->next = (struct list_head *)((unsigned long)next_page |
1998 next_page = rb_list_head(next_page);
1999 next_page->prev = tail_page;
2001 /* make sure pages points to a valid page in the ring buffer */
2002 cpu_buffer->pages = next_page;
2004 /* update head page */
2006 cpu_buffer->head_page = list_entry(next_page,
2007 struct buffer_page, list);
2010 * change read pointer to make sure any read iterators reset
2013 cpu_buffer->read = 0;
2015 /* pages are removed, resume tracing and then free the pages */
2016 atomic_dec(&cpu_buffer->record_disabled);
2017 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2019 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
2021 /* last buffer page to remove */
2022 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
2024 tmp_iter_page = first_page;
2029 to_remove_page = tmp_iter_page;
2030 rb_inc_page(&tmp_iter_page);
2032 /* update the counters */
2033 page_entries = rb_page_entries(to_remove_page);
2036 * If something was added to this page, it was full
2037 * since it is not the tail page. So we deduct the
2038 * bytes consumed in ring buffer from here.
2039 * Increment overrun to account for the lost events.
2041 local_add(page_entries, &cpu_buffer->overrun);
2042 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2043 local_inc(&cpu_buffer->pages_lost);
2047 * We have already removed references to this list item, just
2048 * free up the buffer_page and its page
2050 free_buffer_page(to_remove_page);
2053 } while (to_remove_page != last_page);
2055 RB_WARN_ON(cpu_buffer, nr_removed);
2057 return nr_removed == 0;
2061 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
2063 struct list_head *pages = &cpu_buffer->new_pages;
2064 int retries, success;
2066 raw_spin_lock_irq(&cpu_buffer->reader_lock);
2068 * We are holding the reader lock, so the reader page won't be swapped
2069 * in the ring buffer. Now we are racing with the writer trying to
2070 * move head page and the tail page.
2071 * We are going to adapt the reader page update process where:
2072 * 1. We first splice the start and end of list of new pages between
2073 * the head page and its previous page.
2074 * 2. We cmpxchg the prev_page->next to point from head page to the
2075 * start of new pages list.
2076 * 3. Finally, we update the head->prev to the end of new list.
2078 * We will try this process 10 times, to make sure that we don't keep
2084 struct list_head *head_page, *prev_page, *r;
2085 struct list_head *last_page, *first_page;
2086 struct list_head *head_page_with_bit;
2088 head_page = &rb_set_head_page(cpu_buffer)->list;
2091 prev_page = head_page->prev;
2093 first_page = pages->next;
2094 last_page = pages->prev;
2096 head_page_with_bit = (struct list_head *)
2097 ((unsigned long)head_page | RB_PAGE_HEAD);
2099 last_page->next = head_page_with_bit;
2100 first_page->prev = prev_page;
2102 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
2104 if (r == head_page_with_bit) {
2106 * yay, we replaced the page pointer to our new list,
2107 * now, we just have to update to head page's prev
2108 * pointer to point to end of list
2110 head_page->prev = last_page;
2117 INIT_LIST_HEAD(pages);
2119 * If we weren't successful in adding in new pages, warn and stop
2122 RB_WARN_ON(cpu_buffer, !success);
2123 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2125 /* free pages if they weren't inserted */
2127 struct buffer_page *bpage, *tmp;
2128 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2130 list_del_init(&bpage->list);
2131 free_buffer_page(bpage);
2137 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2141 if (cpu_buffer->nr_pages_to_update > 0)
2142 success = rb_insert_pages(cpu_buffer);
2144 success = rb_remove_pages(cpu_buffer,
2145 -cpu_buffer->nr_pages_to_update);
2148 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2151 static void update_pages_handler(struct work_struct *work)
2153 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2154 struct ring_buffer_per_cpu, update_pages_work);
2155 rb_update_pages(cpu_buffer);
2156 complete(&cpu_buffer->update_done);
2160 * ring_buffer_resize - resize the ring buffer
2161 * @buffer: the buffer to resize.
2162 * @size: the new size.
2163 * @cpu_id: the cpu buffer to resize
2165 * Minimum size is 2 * BUF_PAGE_SIZE.
2167 * Returns 0 on success and < 0 on failure.
2169 int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2172 struct ring_buffer_per_cpu *cpu_buffer;
2173 unsigned long nr_pages;
2177 * Always succeed at resizing a non-existent buffer:
2182 /* Make sure the requested buffer exists */
2183 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2184 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2187 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
2189 /* we need a minimum of two pages */
2193 /* prevent another thread from changing buffer sizes */
2194 mutex_lock(&buffer->mutex);
2197 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2199 * Don't succeed if resizing is disabled, as a reader might be
2200 * manipulating the ring buffer and is expecting a sane state while
2203 for_each_buffer_cpu(buffer, cpu) {
2204 cpu_buffer = buffer->buffers[cpu];
2205 if (atomic_read(&cpu_buffer->resize_disabled)) {
2207 goto out_err_unlock;
2211 /* calculate the pages to update */
2212 for_each_buffer_cpu(buffer, cpu) {
2213 cpu_buffer = buffer->buffers[cpu];
2215 cpu_buffer->nr_pages_to_update = nr_pages -
2216 cpu_buffer->nr_pages;
2218 * nothing more to do for removing pages or no update
2220 if (cpu_buffer->nr_pages_to_update <= 0)
2223 * to add pages, make sure all new pages can be
2224 * allocated without receiving ENOMEM
2226 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2227 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2228 &cpu_buffer->new_pages)) {
2229 /* not enough memory for new pages */
2237 * Fire off all the required work handlers
2238 * We can't schedule on offline CPUs, but it's not necessary
2239 * since we can change their buffer sizes without any race.
2241 for_each_buffer_cpu(buffer, cpu) {
2242 cpu_buffer = buffer->buffers[cpu];
2243 if (!cpu_buffer->nr_pages_to_update)
2246 /* Can't run something on an offline CPU. */
2247 if (!cpu_online(cpu)) {
2248 rb_update_pages(cpu_buffer);
2249 cpu_buffer->nr_pages_to_update = 0;
2251 schedule_work_on(cpu,
2252 &cpu_buffer->update_pages_work);
2256 /* wait for all the updates to complete */
2257 for_each_buffer_cpu(buffer, cpu) {
2258 cpu_buffer = buffer->buffers[cpu];
2259 if (!cpu_buffer->nr_pages_to_update)
2262 if (cpu_online(cpu))
2263 wait_for_completion(&cpu_buffer->update_done);
2264 cpu_buffer->nr_pages_to_update = 0;
2269 cpu_buffer = buffer->buffers[cpu_id];
2271 if (nr_pages == cpu_buffer->nr_pages)
2275 * Don't succeed if resizing is disabled, as a reader might be
2276 * manipulating the ring buffer and is expecting a sane state while
2279 if (atomic_read(&cpu_buffer->resize_disabled)) {
2281 goto out_err_unlock;
2284 cpu_buffer->nr_pages_to_update = nr_pages -
2285 cpu_buffer->nr_pages;
2287 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2288 if (cpu_buffer->nr_pages_to_update > 0 &&
2289 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2290 &cpu_buffer->new_pages)) {
2297 /* Can't run something on an offline CPU. */
2298 if (!cpu_online(cpu_id))
2299 rb_update_pages(cpu_buffer);
2301 schedule_work_on(cpu_id,
2302 &cpu_buffer->update_pages_work);
2303 wait_for_completion(&cpu_buffer->update_done);
2306 cpu_buffer->nr_pages_to_update = 0;
2312 * The ring buffer resize can happen with the ring buffer
2313 * enabled, so that the update disturbs the tracing as little
2314 * as possible. But if the buffer is disabled, we do not need
2315 * to worry about that, and we can take the time to verify
2316 * that the buffer is not corrupt.
2318 if (atomic_read(&buffer->record_disabled)) {
2319 atomic_inc(&buffer->record_disabled);
2321 * Even though the buffer was disabled, we must make sure
2322 * that it is truly disabled before calling rb_check_pages.
2323 * There could have been a race between checking
2324 * record_disable and incrementing it.
2327 for_each_buffer_cpu(buffer, cpu) {
2328 cpu_buffer = buffer->buffers[cpu];
2329 rb_check_pages(cpu_buffer);
2331 atomic_dec(&buffer->record_disabled);
2334 mutex_unlock(&buffer->mutex);
2338 for_each_buffer_cpu(buffer, cpu) {
2339 struct buffer_page *bpage, *tmp;
2341 cpu_buffer = buffer->buffers[cpu];
2342 cpu_buffer->nr_pages_to_update = 0;
2344 if (list_empty(&cpu_buffer->new_pages))
2347 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2349 list_del_init(&bpage->list);
2350 free_buffer_page(bpage);
2354 mutex_unlock(&buffer->mutex);
2357 EXPORT_SYMBOL_GPL(ring_buffer_resize);
2359 void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2361 mutex_lock(&buffer->mutex);
2363 buffer->flags |= RB_FL_OVERWRITE;
2365 buffer->flags &= ~RB_FL_OVERWRITE;
2366 mutex_unlock(&buffer->mutex);
2368 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2370 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2372 return bpage->page->data + index;
2375 static __always_inline struct ring_buffer_event *
2376 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2378 return __rb_page_index(cpu_buffer->reader_page,
2379 cpu_buffer->reader_page->read);
2382 static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
2384 return local_read(&bpage->page->commit);
2387 static struct ring_buffer_event *
2388 rb_iter_head_event(struct ring_buffer_iter *iter)
2390 struct ring_buffer_event *event;
2391 struct buffer_page *iter_head_page = iter->head_page;
2392 unsigned long commit;
2395 if (iter->head != iter->next_event)
2399 * When the writer goes across pages, it issues a cmpxchg which
2400 * is a mb(), which will synchronize with the rmb here.
2401 * (see rb_tail_page_update() and __rb_reserve_next())
2403 commit = rb_page_commit(iter_head_page);
2405 event = __rb_page_index(iter_head_page, iter->head);
2406 length = rb_event_length(event);
2409 * READ_ONCE() doesn't work on functions and we don't want the
2410 * compiler doing any crazy optimizations with length.
2414 if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
2415 /* Writer corrupted the read? */
2418 memcpy(iter->event, event, length);
2420 * If the page stamp is still the same after this rmb() then the
2421 * event was safely copied without the writer entering the page.
2425 /* Make sure the page didn't change since we read this */
2426 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2427 commit > rb_page_commit(iter_head_page))
2430 iter->next_event = iter->head + length;
2433 /* Reset to the beginning */
2434 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2436 iter->next_event = 0;
2437 iter->missed_events = 1;
2441 /* Size is determined by what has been committed */
2442 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2444 return rb_page_commit(bpage);
2447 static __always_inline unsigned
2448 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2450 return rb_page_commit(cpu_buffer->commit_page);
2453 static __always_inline unsigned
2454 rb_event_index(struct ring_buffer_event *event)
2456 unsigned long addr = (unsigned long)event;
2458 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
2461 static void rb_inc_iter(struct ring_buffer_iter *iter)
2463 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2466 * The iterator could be on the reader page (it starts there).
2467 * But the head could have moved, since the reader was
2468 * found. Check for this case and assign the iterator
2469 * to the head page instead of next.
2471 if (iter->head_page == cpu_buffer->reader_page)
2472 iter->head_page = rb_set_head_page(cpu_buffer);
2474 rb_inc_page(&iter->head_page);
2476 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2478 iter->next_event = 0;
2482 * rb_handle_head_page - writer hit the head page
2484 * Returns: +1 to retry page
2489 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2490 struct buffer_page *tail_page,
2491 struct buffer_page *next_page)
2493 struct buffer_page *new_head;
2498 entries = rb_page_entries(next_page);
2501 * The hard part is here. We need to move the head
2502 * forward, and protect against both readers on
2503 * other CPUs and writers coming in via interrupts.
2505 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2509 * type can be one of four:
2510 * NORMAL - an interrupt already moved it for us
2511 * HEAD - we are the first to get here.
2512 * UPDATE - we are the interrupt interrupting
2514 * MOVED - a reader on another CPU moved the next
2515 * pointer to its reader page. Give up
2522 * We changed the head to UPDATE, thus
2523 * it is our responsibility to update
2526 local_add(entries, &cpu_buffer->overrun);
2527 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2528 local_inc(&cpu_buffer->pages_lost);
2531 * The entries will be zeroed out when we move the
2535 /* still more to do */
2538 case RB_PAGE_UPDATE:
2540 * This is an interrupt that interrupt the
2541 * previous update. Still more to do.
2544 case RB_PAGE_NORMAL:
2546 * An interrupt came in before the update
2547 * and processed this for us.
2548 * Nothing left to do.
2553 * The reader is on another CPU and just did
2554 * a swap with our next_page.
2559 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2564 * Now that we are here, the old head pointer is
2565 * set to UPDATE. This will keep the reader from
2566 * swapping the head page with the reader page.
2567 * The reader (on another CPU) will spin till
2570 * We just need to protect against interrupts
2571 * doing the job. We will set the next pointer
2572 * to HEAD. After that, we set the old pointer
2573 * to NORMAL, but only if it was HEAD before.
2574 * otherwise we are an interrupt, and only
2575 * want the outer most commit to reset it.
2577 new_head = next_page;
2578 rb_inc_page(&new_head);
2580 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2584 * Valid returns are:
2585 * HEAD - an interrupt came in and already set it.
2586 * NORMAL - One of two things:
2587 * 1) We really set it.
2588 * 2) A bunch of interrupts came in and moved
2589 * the page forward again.
2593 case RB_PAGE_NORMAL:
2597 RB_WARN_ON(cpu_buffer, 1);
2602 * It is possible that an interrupt came in,
2603 * set the head up, then more interrupts came in
2604 * and moved it again. When we get back here,
2605 * the page would have been set to NORMAL but we
2606 * just set it back to HEAD.
2608 * How do you detect this? Well, if that happened
2609 * the tail page would have moved.
2611 if (ret == RB_PAGE_NORMAL) {
2612 struct buffer_page *buffer_tail_page;
2614 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2616 * If the tail had moved passed next, then we need
2617 * to reset the pointer.
2619 if (buffer_tail_page != tail_page &&
2620 buffer_tail_page != next_page)
2621 rb_head_page_set_normal(cpu_buffer, new_head,
2627 * If this was the outer most commit (the one that
2628 * changed the original pointer from HEAD to UPDATE),
2629 * then it is up to us to reset it to NORMAL.
2631 if (type == RB_PAGE_HEAD) {
2632 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2635 if (RB_WARN_ON(cpu_buffer,
2636 ret != RB_PAGE_UPDATE))
2644 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2645 unsigned long tail, struct rb_event_info *info)
2647 struct buffer_page *tail_page = info->tail_page;
2648 struct ring_buffer_event *event;
2649 unsigned long length = info->length;
2652 * Only the event that crossed the page boundary
2653 * must fill the old tail_page with padding.
2655 if (tail >= BUF_PAGE_SIZE) {
2657 * If the page was filled, then we still need
2658 * to update the real_end. Reset it to zero
2659 * and the reader will ignore it.
2661 if (tail == BUF_PAGE_SIZE)
2662 tail_page->real_end = 0;
2664 local_sub(length, &tail_page->write);
2668 event = __rb_page_index(tail_page, tail);
2670 /* account for padding bytes */
2671 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2674 * Save the original length to the meta data.
2675 * This will be used by the reader to add lost event
2678 tail_page->real_end = tail;
2681 * If this event is bigger than the minimum size, then
2682 * we need to be careful that we don't subtract the
2683 * write counter enough to allow another writer to slip
2685 * We put in a discarded commit instead, to make sure
2686 * that this space is not used again.
2688 * If we are less than the minimum size, we don't need to
2691 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2692 /* No room for any events */
2694 /* Mark the rest of the page with padding */
2695 rb_event_set_padding(event);
2697 /* Make sure the padding is visible before the write update */
2700 /* Set the write back to the previous setting */
2701 local_sub(length, &tail_page->write);
2705 /* Put in a discarded event */
2706 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2707 event->type_len = RINGBUF_TYPE_PADDING;
2708 /* time delta must be non zero */
2709 event->time_delta = 1;
2711 /* Make sure the padding is visible before the tail_page->write update */
2714 /* Set write to end of buffer */
2715 length = (tail + length) - BUF_PAGE_SIZE;
2716 local_sub(length, &tail_page->write);
2719 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2722 * This is the slow path, force gcc not to inline it.
2724 static noinline struct ring_buffer_event *
2725 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2726 unsigned long tail, struct rb_event_info *info)
2728 struct buffer_page *tail_page = info->tail_page;
2729 struct buffer_page *commit_page = cpu_buffer->commit_page;
2730 struct trace_buffer *buffer = cpu_buffer->buffer;
2731 struct buffer_page *next_page;
2734 next_page = tail_page;
2736 rb_inc_page(&next_page);
2739 * If for some reason, we had an interrupt storm that made
2740 * it all the way around the buffer, bail, and warn
2743 if (unlikely(next_page == commit_page)) {
2744 local_inc(&cpu_buffer->commit_overrun);
2749 * This is where the fun begins!
2751 * We are fighting against races between a reader that
2752 * could be on another CPU trying to swap its reader
2753 * page with the buffer head.
2755 * We are also fighting against interrupts coming in and
2756 * moving the head or tail on us as well.
2758 * If the next page is the head page then we have filled
2759 * the buffer, unless the commit page is still on the
2762 if (rb_is_head_page(next_page, &tail_page->list)) {
2765 * If the commit is not on the reader page, then
2766 * move the header page.
2768 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2770 * If we are not in overwrite mode,
2771 * this is easy, just stop here.
2773 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2774 local_inc(&cpu_buffer->dropped_events);
2778 ret = rb_handle_head_page(cpu_buffer,
2787 * We need to be careful here too. The
2788 * commit page could still be on the reader
2789 * page. We could have a small buffer, and
2790 * have filled up the buffer with events
2791 * from interrupts and such, and wrapped.
2793 * Note, if the tail page is also on the
2794 * reader_page, we let it move out.
2796 if (unlikely((cpu_buffer->commit_page !=
2797 cpu_buffer->tail_page) &&
2798 (cpu_buffer->commit_page ==
2799 cpu_buffer->reader_page))) {
2800 local_inc(&cpu_buffer->commit_overrun);
2806 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2810 rb_reset_tail(cpu_buffer, tail, info);
2812 /* Commit what we have for now. */
2813 rb_end_commit(cpu_buffer);
2814 /* rb_end_commit() decs committing */
2815 local_inc(&cpu_buffer->committing);
2817 /* fail and let the caller try again */
2818 return ERR_PTR(-EAGAIN);
2822 rb_reset_tail(cpu_buffer, tail, info);
2828 static struct ring_buffer_event *
2829 rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2832 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2834 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2836 /* Not the first event on the page, or not delta? */
2837 if (abs || rb_event_index(event)) {
2838 event->time_delta = delta & TS_MASK;
2839 event->array[0] = delta >> TS_SHIFT;
2841 /* nope, just zero it */
2842 event->time_delta = 0;
2843 event->array[0] = 0;
2846 return skip_time_extend(event);
2849 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2850 static inline bool sched_clock_stable(void)
2857 rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2858 struct rb_event_info *info)
2862 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2863 (unsigned long long)info->delta,
2864 (unsigned long long)info->ts,
2865 (unsigned long long)info->before,
2866 (unsigned long long)info->after,
2867 (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
2868 sched_clock_stable() ? "" :
2869 "If you just came from a suspend/resume,\n"
2870 "please switch to the trace global clock:\n"
2871 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2872 "or add trace_clock=global to the kernel command line\n");
2875 static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2876 struct ring_buffer_event **event,
2877 struct rb_event_info *info,
2879 unsigned int *length)
2881 bool abs = info->add_timestamp &
2882 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2884 if (unlikely(info->delta > (1ULL << 59))) {
2886 * Some timers can use more than 59 bits, and when a timestamp
2887 * is added to the buffer, it will lose those bits.
2889 if (abs && (info->ts & TS_MSB)) {
2890 info->delta &= ABS_TS_MASK;
2892 /* did the clock go backwards */
2893 } else if (info->before == info->after && info->before > info->ts) {
2894 /* not interrupted */
2898 * This is possible with a recalibrating of the TSC.
2899 * Do not produce a call stack, but just report it.
2903 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2904 info->before, info->ts);
2907 rb_check_timestamp(cpu_buffer, info);
2911 *event = rb_add_time_stamp(*event, info->delta, abs);
2912 *length -= RB_LEN_TIME_EXTEND;
2917 * rb_update_event - update event type and data
2918 * @cpu_buffer: The per cpu buffer of the @event
2919 * @event: the event to update
2920 * @info: The info to update the @event with (contains length and delta)
2922 * Update the type and data fields of the @event. The length
2923 * is the actual size that is written to the ring buffer,
2924 * and with this, we can determine what to place into the
2928 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2929 struct ring_buffer_event *event,
2930 struct rb_event_info *info)
2932 unsigned length = info->length;
2933 u64 delta = info->delta;
2934 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2936 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2937 cpu_buffer->event_stamp[nest] = info->ts;
2940 * If we need to add a timestamp, then we
2941 * add it to the start of the reserved space.
2943 if (unlikely(info->add_timestamp))
2944 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2946 event->time_delta = delta;
2947 length -= RB_EVNT_HDR_SIZE;
2948 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2949 event->type_len = 0;
2950 event->array[0] = length;
2952 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2955 static unsigned rb_calculate_event_length(unsigned length)
2957 struct ring_buffer_event event; /* Used only for sizeof array */
2959 /* zero length can cause confusions */
2963 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2964 length += sizeof(event.array[0]);
2966 length += RB_EVNT_HDR_SIZE;
2967 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2970 * In case the time delta is larger than the 27 bits for it
2971 * in the header, we need to add a timestamp. If another
2972 * event comes in when trying to discard this one to increase
2973 * the length, then the timestamp will be added in the allocated
2974 * space of this event. If length is bigger than the size needed
2975 * for the TIME_EXTEND, then padding has to be used. The events
2976 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2977 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2978 * As length is a multiple of 4, we only need to worry if it
2979 * is 12 (RB_LEN_TIME_EXTEND + 4).
2981 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2982 length += RB_ALIGNMENT;
2987 static u64 rb_time_delta(struct ring_buffer_event *event)
2989 switch (event->type_len) {
2990 case RINGBUF_TYPE_PADDING:
2993 case RINGBUF_TYPE_TIME_EXTEND:
2994 return rb_event_time_stamp(event);
2996 case RINGBUF_TYPE_TIME_STAMP:
2999 case RINGBUF_TYPE_DATA:
3000 return event->time_delta;
3007 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
3008 struct ring_buffer_event *event)
3010 unsigned long new_index, old_index;
3011 struct buffer_page *bpage;
3012 unsigned long index;
3017 new_index = rb_event_index(event);
3018 old_index = new_index + rb_event_ts_length(event);
3019 addr = (unsigned long)event;
3022 bpage = READ_ONCE(cpu_buffer->tail_page);
3024 delta = rb_time_delta(event);
3026 if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
3029 /* Make sure the write stamp is read before testing the location */
3032 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
3033 unsigned long write_mask =
3034 local_read(&bpage->write) & ~RB_WRITE_MASK;
3035 unsigned long event_length = rb_event_length(event);
3037 /* Something came in, can't discard */
3038 if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
3039 write_stamp, write_stamp - delta))
3043 * It's possible that the event time delta is zero
3044 * (has the same time stamp as the previous event)
3045 * in which case write_stamp and before_stamp could
3046 * be the same. In such a case, force before_stamp
3047 * to be different than write_stamp. It doesn't
3048 * matter what it is, as long as its different.
3051 rb_time_set(&cpu_buffer->before_stamp, 0);
3054 * If an event were to come in now, it would see that the
3055 * write_stamp and the before_stamp are different, and assume
3056 * that this event just added itself before updating
3057 * the write stamp. The interrupting event will fix the
3058 * write stamp for us, and use the before stamp as its delta.
3062 * This is on the tail page. It is possible that
3063 * a write could come in and move the tail page
3064 * and write to the next page. That is fine
3065 * because we just shorten what is on this page.
3067 old_index += write_mask;
3068 new_index += write_mask;
3069 index = local_cmpxchg(&bpage->write, old_index, new_index);
3070 if (index == old_index) {
3071 /* update counters */
3072 local_sub(event_length, &cpu_buffer->entries_bytes);
3077 /* could not discard */
3081 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
3083 local_inc(&cpu_buffer->committing);
3084 local_inc(&cpu_buffer->commits);
3087 static __always_inline void
3088 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
3090 unsigned long max_count;
3093 * We only race with interrupts and NMIs on this CPU.
3094 * If we own the commit event, then we can commit
3095 * all others that interrupted us, since the interruptions
3096 * are in stack format (they finish before they come
3097 * back to us). This allows us to do a simple loop to
3098 * assign the commit to the tail.
3101 max_count = cpu_buffer->nr_pages * 100;
3103 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
3104 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
3106 if (RB_WARN_ON(cpu_buffer,
3107 rb_is_reader_page(cpu_buffer->tail_page)))
3109 local_set(&cpu_buffer->commit_page->page->commit,
3110 rb_page_write(cpu_buffer->commit_page));
3111 rb_inc_page(&cpu_buffer->commit_page);
3112 /* add barrier to keep gcc from optimizing too much */
3115 while (rb_commit_index(cpu_buffer) !=
3116 rb_page_write(cpu_buffer->commit_page)) {
3118 local_set(&cpu_buffer->commit_page->page->commit,
3119 rb_page_write(cpu_buffer->commit_page));
3120 RB_WARN_ON(cpu_buffer,
3121 local_read(&cpu_buffer->commit_page->page->commit) &
3126 /* again, keep gcc from optimizing */
3130 * If an interrupt came in just after the first while loop
3131 * and pushed the tail page forward, we will be left with
3132 * a dangling commit that will never go forward.
3134 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3138 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3140 unsigned long commits;
3142 if (RB_WARN_ON(cpu_buffer,
3143 !local_read(&cpu_buffer->committing)))
3147 commits = local_read(&cpu_buffer->commits);
3148 /* synchronize with interrupts */
3150 if (local_read(&cpu_buffer->committing) == 1)
3151 rb_set_commit_to_write(cpu_buffer);
3153 local_dec(&cpu_buffer->committing);
3155 /* synchronize with interrupts */
3159 * Need to account for interrupts coming in between the
3160 * updating of the commit page and the clearing of the
3161 * committing counter.
3163 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3164 !local_read(&cpu_buffer->committing)) {
3165 local_inc(&cpu_buffer->committing);
3170 static inline void rb_event_discard(struct ring_buffer_event *event)
3172 if (extended_time(event))
3173 event = skip_time_extend(event);
3175 /* array[0] holds the actual length for the discarded event */
3176 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3177 event->type_len = RINGBUF_TYPE_PADDING;
3178 /* time delta must be non zero */
3179 if (!event->time_delta)
3180 event->time_delta = 1;
3183 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
3184 struct ring_buffer_event *event)
3186 local_inc(&cpu_buffer->entries);
3187 rb_end_commit(cpu_buffer);
3190 static __always_inline void
3191 rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3193 if (buffer->irq_work.waiters_pending) {
3194 buffer->irq_work.waiters_pending = false;
3195 /* irq_work_queue() supplies it's own memory barriers */
3196 irq_work_queue(&buffer->irq_work.work);
3199 if (cpu_buffer->irq_work.waiters_pending) {
3200 cpu_buffer->irq_work.waiters_pending = false;
3201 /* irq_work_queue() supplies it's own memory barriers */
3202 irq_work_queue(&cpu_buffer->irq_work.work);
3205 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3208 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3211 if (!cpu_buffer->irq_work.full_waiters_pending)
3214 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3216 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3219 cpu_buffer->irq_work.wakeup_full = true;
3220 cpu_buffer->irq_work.full_waiters_pending = false;
3221 /* irq_work_queue() supplies it's own memory barriers */
3222 irq_work_queue(&cpu_buffer->irq_work.work);
3225 #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3226 # define do_ring_buffer_record_recursion() \
3227 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3229 # define do_ring_buffer_record_recursion() do { } while (0)
3233 * The lock and unlock are done within a preempt disable section.
3234 * The current_context per_cpu variable can only be modified
3235 * by the current task between lock and unlock. But it can
3236 * be modified more than once via an interrupt. To pass this
3237 * information from the lock to the unlock without having to
3238 * access the 'in_interrupt()' functions again (which do show
3239 * a bit of overhead in something as critical as function tracing,
3240 * we use a bitmask trick.
3242 * bit 1 = NMI context
3243 * bit 2 = IRQ context
3244 * bit 3 = SoftIRQ context
3245 * bit 4 = normal context.
3247 * This works because this is the order of contexts that can
3248 * preempt other contexts. A SoftIRQ never preempts an IRQ
3251 * When the context is determined, the corresponding bit is
3252 * checked and set (if it was set, then a recursion of that context
3255 * On unlock, we need to clear this bit. To do so, just subtract
3256 * 1 from the current_context and AND it to itself.
3260 * 101 & 100 = 100 (clearing bit zero)
3263 * 1010 & 1001 = 1000 (clearing bit 1)
3265 * The least significant bit can be cleared this way, and it
3266 * just so happens that it is the same bit corresponding to
3267 * the current context.
3269 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3270 * is set when a recursion is detected at the current context, and if
3271 * the TRANSITION bit is already set, it will fail the recursion.
3272 * This is needed because there's a lag between the changing of
3273 * interrupt context and updating the preempt count. In this case,
3274 * a false positive will be found. To handle this, one extra recursion
3275 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3276 * bit is already set, then it is considered a recursion and the function
3277 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3279 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3280 * to be cleared. Even if it wasn't the context that set it. That is,
3281 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3282 * is called before preempt_count() is updated, since the check will
3283 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3284 * NMI then comes in, it will set the NMI bit, but when the NMI code
3285 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3286 * and leave the NMI bit set. But this is fine, because the interrupt
3287 * code that set the TRANSITION bit will then clear the NMI bit when it
3288 * calls trace_recursive_unlock(). If another NMI comes in, it will
3289 * set the TRANSITION bit and continue.
3291 * Note: The TRANSITION bit only handles a single transition between context.
3294 static __always_inline int
3295 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3297 unsigned int val = cpu_buffer->current_context;
3298 int bit = interrupt_context_level();
3300 bit = RB_CTX_NORMAL - bit;
3302 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3304 * It is possible that this was called by transitioning
3305 * between interrupt context, and preempt_count() has not
3306 * been updated yet. In this case, use the TRANSITION bit.
3308 bit = RB_CTX_TRANSITION;
3309 if (val & (1 << (bit + cpu_buffer->nest))) {
3310 do_ring_buffer_record_recursion();
3315 val |= (1 << (bit + cpu_buffer->nest));
3316 cpu_buffer->current_context = val;
3321 static __always_inline void
3322 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3324 cpu_buffer->current_context &=
3325 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3328 /* The recursive locking above uses 5 bits */
3329 #define NESTED_BITS 5
3332 * ring_buffer_nest_start - Allow to trace while nested
3333 * @buffer: The ring buffer to modify
3335 * The ring buffer has a safety mechanism to prevent recursion.
3336 * But there may be a case where a trace needs to be done while
3337 * tracing something else. In this case, calling this function
3338 * will allow this function to nest within a currently active
3339 * ring_buffer_lock_reserve().
3341 * Call this function before calling another ring_buffer_lock_reserve() and
3342 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3344 void ring_buffer_nest_start(struct trace_buffer *buffer)
3346 struct ring_buffer_per_cpu *cpu_buffer;
3349 /* Enabled by ring_buffer_nest_end() */
3350 preempt_disable_notrace();
3351 cpu = raw_smp_processor_id();
3352 cpu_buffer = buffer->buffers[cpu];
3353 /* This is the shift value for the above recursive locking */
3354 cpu_buffer->nest += NESTED_BITS;
3358 * ring_buffer_nest_end - Allow to trace while nested
3359 * @buffer: The ring buffer to modify
3361 * Must be called after ring_buffer_nest_start() and after the
3362 * ring_buffer_unlock_commit().
3364 void ring_buffer_nest_end(struct trace_buffer *buffer)
3366 struct ring_buffer_per_cpu *cpu_buffer;
3369 /* disabled by ring_buffer_nest_start() */
3370 cpu = raw_smp_processor_id();
3371 cpu_buffer = buffer->buffers[cpu];
3372 /* This is the shift value for the above recursive locking */
3373 cpu_buffer->nest -= NESTED_BITS;
3374 preempt_enable_notrace();
3378 * ring_buffer_unlock_commit - commit a reserved
3379 * @buffer: The buffer to commit to
3380 * @event: The event pointer to commit.
3382 * This commits the data to the ring buffer, and releases any locks held.
3384 * Must be paired with ring_buffer_lock_reserve.
3386 int ring_buffer_unlock_commit(struct trace_buffer *buffer,
3387 struct ring_buffer_event *event)
3389 struct ring_buffer_per_cpu *cpu_buffer;
3390 int cpu = raw_smp_processor_id();
3392 cpu_buffer = buffer->buffers[cpu];
3394 rb_commit(cpu_buffer, event);
3396 rb_wakeups(buffer, cpu_buffer);
3398 trace_recursive_unlock(cpu_buffer);
3400 preempt_enable_notrace();
3404 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3406 /* Special value to validate all deltas on a page. */
3407 #define CHECK_FULL_PAGE 1L
3409 #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3410 static void dump_buffer_page(struct buffer_data_page *bpage,
3411 struct rb_event_info *info,
3414 struct ring_buffer_event *event;
3418 ts = bpage->time_stamp;
3419 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3421 for (e = 0; e < tail; e += rb_event_length(event)) {
3423 event = (struct ring_buffer_event *)(bpage->data + e);
3425 switch (event->type_len) {
3427 case RINGBUF_TYPE_TIME_EXTEND:
3428 delta = rb_event_time_stamp(event);
3430 pr_warn(" [%lld] delta:%lld TIME EXTEND\n", ts, delta);
3433 case RINGBUF_TYPE_TIME_STAMP:
3434 delta = rb_event_time_stamp(event);
3435 ts = rb_fix_abs_ts(delta, ts);
3436 pr_warn(" [%lld] absolute:%lld TIME STAMP\n", ts, delta);
3439 case RINGBUF_TYPE_PADDING:
3440 ts += event->time_delta;
3441 pr_warn(" [%lld] delta:%d PADDING\n", ts, event->time_delta);
3444 case RINGBUF_TYPE_DATA:
3445 ts += event->time_delta;
3446 pr_warn(" [%lld] delta:%d\n", ts, event->time_delta);
3455 static DEFINE_PER_CPU(atomic_t, checking);
3456 static atomic_t ts_dump;
3459 * Check if the current event time stamp matches the deltas on
3462 static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3463 struct rb_event_info *info,
3466 struct ring_buffer_event *event;
3467 struct buffer_data_page *bpage;
3472 bpage = info->tail_page->page;
3474 if (tail == CHECK_FULL_PAGE) {
3476 tail = local_read(&bpage->commit);
3477 } else if (info->add_timestamp &
3478 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3479 /* Ignore events with absolute time stamps */
3484 * Do not check the first event (skip possible extends too).
3485 * Also do not check if previous events have not been committed.
3487 if (tail <= 8 || tail > local_read(&bpage->commit))
3491 * If this interrupted another event,
3493 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3496 ts = bpage->time_stamp;
3498 for (e = 0; e < tail; e += rb_event_length(event)) {
3500 event = (struct ring_buffer_event *)(bpage->data + e);
3502 switch (event->type_len) {
3504 case RINGBUF_TYPE_TIME_EXTEND:
3505 delta = rb_event_time_stamp(event);
3509 case RINGBUF_TYPE_TIME_STAMP:
3510 delta = rb_event_time_stamp(event);
3511 ts = rb_fix_abs_ts(delta, ts);
3514 case RINGBUF_TYPE_PADDING:
3515 if (event->time_delta == 1)
3518 case RINGBUF_TYPE_DATA:
3519 ts += event->time_delta;
3523 RB_WARN_ON(cpu_buffer, 1);
3526 if ((full && ts > info->ts) ||
3527 (!full && ts + info->delta != info->ts)) {
3528 /* If another report is happening, ignore this one */
3529 if (atomic_inc_return(&ts_dump) != 1) {
3530 atomic_dec(&ts_dump);
3533 atomic_inc(&cpu_buffer->record_disabled);
3534 /* There's some cases in boot up that this can happen */
3535 WARN_ON_ONCE(system_state != SYSTEM_BOOTING);
3536 pr_warn("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s\n",
3538 ts + info->delta, info->ts, info->delta,
3539 info->before, info->after,
3540 full ? " (full)" : "");
3541 dump_buffer_page(bpage, info, tail);
3542 atomic_dec(&ts_dump);
3543 /* Do not re-enable checking */
3547 atomic_dec(this_cpu_ptr(&checking));
3550 static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3551 struct rb_event_info *info,
3555 #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3557 static struct ring_buffer_event *
3558 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3559 struct rb_event_info *info)
3561 struct ring_buffer_event *event;
3562 struct buffer_page *tail_page;
3563 unsigned long tail, write, w;
3567 /* Don't let the compiler play games with cpu_buffer->tail_page */
3568 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3570 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3572 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3573 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3575 info->ts = rb_time_stamp(cpu_buffer->buffer);
3577 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3578 info->delta = info->ts;
3581 * If interrupting an event time update, we may need an
3582 * absolute timestamp.
3583 * Don't bother if this is the start of a new page (w == 0).
3585 if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
3586 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3587 info->length += RB_LEN_TIME_EXTEND;
3589 info->delta = info->ts - info->after;
3590 if (unlikely(test_time_stamp(info->delta))) {
3591 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3592 info->length += RB_LEN_TIME_EXTEND;
3597 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3599 /*C*/ write = local_add_return(info->length, &tail_page->write);
3601 /* set write to only the index of the write */
3602 write &= RB_WRITE_MASK;
3604 tail = write - info->length;
3606 /* See if we shot pass the end of this buffer page */
3607 if (unlikely(write > BUF_PAGE_SIZE)) {
3608 /* before and after may now different, fix it up*/
3609 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3610 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3611 if (a_ok && b_ok && info->before != info->after)
3612 (void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
3613 info->before, info->after);
3615 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3616 return rb_move_tail(cpu_buffer, tail, info);
3619 if (likely(tail == w)) {
3623 /* Nothing interrupted us between A and C */
3624 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3626 /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
3627 RB_WARN_ON(cpu_buffer, !s_ok);
3628 if (likely(!(info->add_timestamp &
3629 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3630 /* This did not interrupt any time update */
3631 info->delta = info->ts - info->after;
3633 /* Just use full timestamp for interrupting event */
3634 info->delta = info->ts;
3636 check_buffer(cpu_buffer, info, tail);
3637 if (unlikely(info->ts != save_before)) {
3638 /* SLOW PATH - Interrupted between C and E */
3640 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3641 RB_WARN_ON(cpu_buffer, !a_ok);
3643 /* Write stamp must only go forward */
3644 if (save_before > info->after) {
3646 * We do not care about the result, only that
3647 * it gets updated atomically.
3649 (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
3650 info->after, save_before);
3655 /* SLOW PATH - Interrupted between A and C */
3656 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3657 /* Was interrupted before here, write_stamp must be valid */
3658 RB_WARN_ON(cpu_buffer, !a_ok);
3659 ts = rb_time_stamp(cpu_buffer->buffer);
3661 /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3663 rb_time_cmpxchg(&cpu_buffer->write_stamp,
3665 /* Nothing came after this event between C and E */
3666 info->delta = ts - info->after;
3669 * Interrupted between C and E:
3670 * Lost the previous events time stamp. Just set the
3671 * delta to zero, and this will be the same time as
3672 * the event this event interrupted. And the events that
3673 * came after this will still be correct (as they would
3674 * have built their delta on the previous event.
3679 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3683 * If this is the first commit on the page, then it has the same
3684 * timestamp as the page itself.
3686 if (unlikely(!tail && !(info->add_timestamp &
3687 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3690 /* We reserved something on the buffer */
3692 event = __rb_page_index(tail_page, tail);
3693 rb_update_event(cpu_buffer, event, info);
3695 local_inc(&tail_page->entries);
3698 * If this is the first commit on the page, then update
3701 if (unlikely(!tail))
3702 tail_page->page->time_stamp = info->ts;
3704 /* account for these added bytes */
3705 local_add(info->length, &cpu_buffer->entries_bytes);
3710 static __always_inline struct ring_buffer_event *
3711 rb_reserve_next_event(struct trace_buffer *buffer,
3712 struct ring_buffer_per_cpu *cpu_buffer,
3713 unsigned long length)
3715 struct ring_buffer_event *event;
3716 struct rb_event_info info;
3720 rb_start_commit(cpu_buffer);
3721 /* The commit page can not change after this */
3723 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3725 * Due to the ability to swap a cpu buffer from a buffer
3726 * it is possible it was swapped before we committed.
3727 * (committing stops a swap). We check for it here and
3728 * if it happened, we have to fail the write.
3731 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3732 local_dec(&cpu_buffer->committing);
3733 local_dec(&cpu_buffer->commits);
3738 info.length = rb_calculate_event_length(length);
3740 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3741 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3742 info.length += RB_LEN_TIME_EXTEND;
3744 add_ts_default = RB_ADD_STAMP_NONE;
3748 info.add_timestamp = add_ts_default;
3752 * We allow for interrupts to reenter here and do a trace.
3753 * If one does, it will cause this original code to loop
3754 * back here. Even with heavy interrupts happening, this
3755 * should only happen a few times in a row. If this happens
3756 * 1000 times in a row, there must be either an interrupt
3757 * storm or we have something buggy.
3760 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3763 event = __rb_reserve_next(cpu_buffer, &info);
3765 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3766 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3767 info.length -= RB_LEN_TIME_EXTEND;
3774 rb_end_commit(cpu_buffer);
3779 * ring_buffer_lock_reserve - reserve a part of the buffer
3780 * @buffer: the ring buffer to reserve from
3781 * @length: the length of the data to reserve (excluding event header)
3783 * Returns a reserved event on the ring buffer to copy directly to.
3784 * The user of this interface will need to get the body to write into
3785 * and can use the ring_buffer_event_data() interface.
3787 * The length is the length of the data needed, not the event length
3788 * which also includes the event header.
3790 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3791 * If NULL is returned, then nothing has been allocated or locked.
3793 struct ring_buffer_event *
3794 ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3796 struct ring_buffer_per_cpu *cpu_buffer;
3797 struct ring_buffer_event *event;
3800 /* If we are tracing schedule, we don't want to recurse */
3801 preempt_disable_notrace();
3803 if (unlikely(atomic_read(&buffer->record_disabled)))
3806 cpu = raw_smp_processor_id();
3808 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3811 cpu_buffer = buffer->buffers[cpu];
3813 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3816 if (unlikely(length > BUF_MAX_DATA_SIZE))
3819 if (unlikely(trace_recursive_lock(cpu_buffer)))
3822 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3829 trace_recursive_unlock(cpu_buffer);
3831 preempt_enable_notrace();
3834 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3837 * Decrement the entries to the page that an event is on.
3838 * The event does not even need to exist, only the pointer
3839 * to the page it is on. This may only be called before the commit
3843 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3844 struct ring_buffer_event *event)
3846 unsigned long addr = (unsigned long)event;
3847 struct buffer_page *bpage = cpu_buffer->commit_page;
3848 struct buffer_page *start;
3852 /* Do the likely case first */
3853 if (likely(bpage->page == (void *)addr)) {
3854 local_dec(&bpage->entries);
3859 * Because the commit page may be on the reader page we
3860 * start with the next page and check the end loop there.
3862 rb_inc_page(&bpage);
3865 if (bpage->page == (void *)addr) {
3866 local_dec(&bpage->entries);
3869 rb_inc_page(&bpage);
3870 } while (bpage != start);
3872 /* commit not part of this buffer?? */
3873 RB_WARN_ON(cpu_buffer, 1);
3877 * ring_buffer_discard_commit - discard an event that has not been committed
3878 * @buffer: the ring buffer
3879 * @event: non committed event to discard
3881 * Sometimes an event that is in the ring buffer needs to be ignored.
3882 * This function lets the user discard an event in the ring buffer
3883 * and then that event will not be read later.
3885 * This function only works if it is called before the item has been
3886 * committed. It will try to free the event from the ring buffer
3887 * if another event has not been added behind it.
3889 * If another event has been added behind it, it will set the event
3890 * up as discarded, and perform the commit.
3892 * If this function is called, do not call ring_buffer_unlock_commit on
3895 void ring_buffer_discard_commit(struct trace_buffer *buffer,
3896 struct ring_buffer_event *event)
3898 struct ring_buffer_per_cpu *cpu_buffer;
3901 /* The event is discarded regardless */
3902 rb_event_discard(event);
3904 cpu = smp_processor_id();
3905 cpu_buffer = buffer->buffers[cpu];
3908 * This must only be called if the event has not been
3909 * committed yet. Thus we can assume that preemption
3910 * is still disabled.
3912 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3914 rb_decrement_entry(cpu_buffer, event);
3915 if (rb_try_to_discard(cpu_buffer, event))
3919 rb_end_commit(cpu_buffer);
3921 trace_recursive_unlock(cpu_buffer);
3923 preempt_enable_notrace();
3926 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3929 * ring_buffer_write - write data to the buffer without reserving
3930 * @buffer: The ring buffer to write to.
3931 * @length: The length of the data being written (excluding the event header)
3932 * @data: The data to write to the buffer.
3934 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3935 * one function. If you already have the data to write to the buffer, it
3936 * may be easier to simply call this function.
3938 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3939 * and not the length of the event which would hold the header.
3941 int ring_buffer_write(struct trace_buffer *buffer,
3942 unsigned long length,
3945 struct ring_buffer_per_cpu *cpu_buffer;
3946 struct ring_buffer_event *event;
3951 preempt_disable_notrace();
3953 if (atomic_read(&buffer->record_disabled))
3956 cpu = raw_smp_processor_id();
3958 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3961 cpu_buffer = buffer->buffers[cpu];
3963 if (atomic_read(&cpu_buffer->record_disabled))
3966 if (length > BUF_MAX_DATA_SIZE)
3969 if (unlikely(trace_recursive_lock(cpu_buffer)))
3972 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3976 body = rb_event_data(event);
3978 memcpy(body, data, length);
3980 rb_commit(cpu_buffer, event);
3982 rb_wakeups(buffer, cpu_buffer);
3987 trace_recursive_unlock(cpu_buffer);
3990 preempt_enable_notrace();
3994 EXPORT_SYMBOL_GPL(ring_buffer_write);
3996 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3998 struct buffer_page *reader = cpu_buffer->reader_page;
3999 struct buffer_page *head = rb_set_head_page(cpu_buffer);
4000 struct buffer_page *commit = cpu_buffer->commit_page;
4002 /* In case of error, head will be NULL */
4003 if (unlikely(!head))
4006 /* Reader should exhaust content in reader page */
4007 if (reader->read != rb_page_commit(reader))
4011 * If writers are committing on the reader page, knowing all
4012 * committed content has been read, the ring buffer is empty.
4014 if (commit == reader)
4018 * If writers are committing on a page other than reader page
4019 * and head page, there should always be content to read.
4025 * Writers are committing on the head page, we just need
4026 * to care about there're committed data, and the reader will
4027 * swap reader page with head page when it is to read data.
4029 return rb_page_commit(commit) == 0;
4033 * ring_buffer_record_disable - stop all writes into the buffer
4034 * @buffer: The ring buffer to stop writes to.
4036 * This prevents all writes to the buffer. Any attempt to write
4037 * to the buffer after this will fail and return NULL.
4039 * The caller should call synchronize_rcu() after this.
4041 void ring_buffer_record_disable(struct trace_buffer *buffer)
4043 atomic_inc(&buffer->record_disabled);
4045 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
4048 * ring_buffer_record_enable - enable writes to the buffer
4049 * @buffer: The ring buffer to enable writes
4051 * Note, multiple disables will need the same number of enables
4052 * to truly enable the writing (much like preempt_disable).
4054 void ring_buffer_record_enable(struct trace_buffer *buffer)
4056 atomic_dec(&buffer->record_disabled);
4058 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
4061 * ring_buffer_record_off - stop all writes into the buffer
4062 * @buffer: The ring buffer to stop writes to.
4064 * This prevents all writes to the buffer. Any attempt to write
4065 * to the buffer after this will fail and return NULL.
4067 * This is different than ring_buffer_record_disable() as
4068 * it works like an on/off switch, where as the disable() version
4069 * must be paired with a enable().
4071 void ring_buffer_record_off(struct trace_buffer *buffer)
4074 unsigned int new_rd;
4077 rd = atomic_read(&buffer->record_disabled);
4078 new_rd = rd | RB_BUFFER_OFF;
4079 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
4081 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
4084 * ring_buffer_record_on - restart writes into the buffer
4085 * @buffer: The ring buffer to start writes to.
4087 * This enables all writes to the buffer that was disabled by
4088 * ring_buffer_record_off().
4090 * This is different than ring_buffer_record_enable() as
4091 * it works like an on/off switch, where as the enable() version
4092 * must be paired with a disable().
4094 void ring_buffer_record_on(struct trace_buffer *buffer)
4097 unsigned int new_rd;
4100 rd = atomic_read(&buffer->record_disabled);
4101 new_rd = rd & ~RB_BUFFER_OFF;
4102 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
4104 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
4107 * ring_buffer_record_is_on - return true if the ring buffer can write
4108 * @buffer: The ring buffer to see if write is enabled
4110 * Returns true if the ring buffer is in a state that it accepts writes.
4112 bool ring_buffer_record_is_on(struct trace_buffer *buffer)
4114 return !atomic_read(&buffer->record_disabled);
4118 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
4119 * @buffer: The ring buffer to see if write is set enabled
4121 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
4122 * Note that this does NOT mean it is in a writable state.
4124 * It may return true when the ring buffer has been disabled by
4125 * ring_buffer_record_disable(), as that is a temporary disabling of
4128 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
4130 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
4134 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
4135 * @buffer: The ring buffer to stop writes to.
4136 * @cpu: The CPU buffer to stop
4138 * This prevents all writes to the buffer. Any attempt to write
4139 * to the buffer after this will fail and return NULL.
4141 * The caller should call synchronize_rcu() after this.
4143 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4145 struct ring_buffer_per_cpu *cpu_buffer;
4147 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4150 cpu_buffer = buffer->buffers[cpu];
4151 atomic_inc(&cpu_buffer->record_disabled);
4153 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4156 * ring_buffer_record_enable_cpu - enable writes to the buffer
4157 * @buffer: The ring buffer to enable writes
4158 * @cpu: The CPU to enable.
4160 * Note, multiple disables will need the same number of enables
4161 * to truly enable the writing (much like preempt_disable).
4163 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4165 struct ring_buffer_per_cpu *cpu_buffer;
4167 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4170 cpu_buffer = buffer->buffers[cpu];
4171 atomic_dec(&cpu_buffer->record_disabled);
4173 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4176 * The total entries in the ring buffer is the running counter
4177 * of entries entered into the ring buffer, minus the sum of
4178 * the entries read from the ring buffer and the number of
4179 * entries that were overwritten.
4181 static inline unsigned long
4182 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4184 return local_read(&cpu_buffer->entries) -
4185 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4189 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4190 * @buffer: The ring buffer
4191 * @cpu: The per CPU buffer to read from.
4193 u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4195 unsigned long flags;
4196 struct ring_buffer_per_cpu *cpu_buffer;
4197 struct buffer_page *bpage;
4200 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4203 cpu_buffer = buffer->buffers[cpu];
4204 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4206 * if the tail is on reader_page, oldest time stamp is on the reader
4209 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4210 bpage = cpu_buffer->reader_page;
4212 bpage = rb_set_head_page(cpu_buffer);
4214 ret = bpage->page->time_stamp;
4215 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4219 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4222 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
4223 * @buffer: The ring buffer
4224 * @cpu: The per CPU buffer to read from.
4226 unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4228 struct ring_buffer_per_cpu *cpu_buffer;
4231 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4234 cpu_buffer = buffer->buffers[cpu];
4235 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4239 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4242 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4243 * @buffer: The ring buffer
4244 * @cpu: The per CPU buffer to get the entries from.
4246 unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4248 struct ring_buffer_per_cpu *cpu_buffer;
4250 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4253 cpu_buffer = buffer->buffers[cpu];
4255 return rb_num_of_entries(cpu_buffer);
4257 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4260 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4261 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4262 * @buffer: The ring buffer
4263 * @cpu: The per CPU buffer to get the number of overruns from
4265 unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4267 struct ring_buffer_per_cpu *cpu_buffer;
4270 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4273 cpu_buffer = buffer->buffers[cpu];
4274 ret = local_read(&cpu_buffer->overrun);
4278 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4281 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4282 * commits failing due to the buffer wrapping around while there are uncommitted
4283 * events, such as during an interrupt storm.
4284 * @buffer: The ring buffer
4285 * @cpu: The per CPU buffer to get the number of overruns from
4288 ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4290 struct ring_buffer_per_cpu *cpu_buffer;
4293 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4296 cpu_buffer = buffer->buffers[cpu];
4297 ret = local_read(&cpu_buffer->commit_overrun);
4301 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4304 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4305 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4306 * @buffer: The ring buffer
4307 * @cpu: The per CPU buffer to get the number of overruns from
4310 ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4312 struct ring_buffer_per_cpu *cpu_buffer;
4315 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4318 cpu_buffer = buffer->buffers[cpu];
4319 ret = local_read(&cpu_buffer->dropped_events);
4323 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4326 * ring_buffer_read_events_cpu - get the number of events successfully read
4327 * @buffer: The ring buffer
4328 * @cpu: The per CPU buffer to get the number of events read
4331 ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4333 struct ring_buffer_per_cpu *cpu_buffer;
4335 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4338 cpu_buffer = buffer->buffers[cpu];
4339 return cpu_buffer->read;
4341 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4344 * ring_buffer_entries - get the number of entries in a buffer
4345 * @buffer: The ring buffer
4347 * Returns the total number of entries in the ring buffer
4350 unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4352 struct ring_buffer_per_cpu *cpu_buffer;
4353 unsigned long entries = 0;
4356 /* if you care about this being correct, lock the buffer */
4357 for_each_buffer_cpu(buffer, cpu) {
4358 cpu_buffer = buffer->buffers[cpu];
4359 entries += rb_num_of_entries(cpu_buffer);
4364 EXPORT_SYMBOL_GPL(ring_buffer_entries);
4367 * ring_buffer_overruns - get the number of overruns in buffer
4368 * @buffer: The ring buffer
4370 * Returns the total number of overruns in the ring buffer
4373 unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4375 struct ring_buffer_per_cpu *cpu_buffer;
4376 unsigned long overruns = 0;
4379 /* if you care about this being correct, lock the buffer */
4380 for_each_buffer_cpu(buffer, cpu) {
4381 cpu_buffer = buffer->buffers[cpu];
4382 overruns += local_read(&cpu_buffer->overrun);
4387 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4389 static void rb_iter_reset(struct ring_buffer_iter *iter)
4391 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4393 /* Iterator usage is expected to have record disabled */
4394 iter->head_page = cpu_buffer->reader_page;
4395 iter->head = cpu_buffer->reader_page->read;
4396 iter->next_event = iter->head;
4398 iter->cache_reader_page = iter->head_page;
4399 iter->cache_read = cpu_buffer->read;
4402 iter->read_stamp = cpu_buffer->read_stamp;
4403 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4405 iter->read_stamp = iter->head_page->page->time_stamp;
4406 iter->page_stamp = iter->read_stamp;
4411 * ring_buffer_iter_reset - reset an iterator
4412 * @iter: The iterator to reset
4414 * Resets the iterator, so that it will start from the beginning
4417 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4419 struct ring_buffer_per_cpu *cpu_buffer;
4420 unsigned long flags;
4425 cpu_buffer = iter->cpu_buffer;
4427 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4428 rb_iter_reset(iter);
4429 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4431 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4434 * ring_buffer_iter_empty - check if an iterator has no more to read
4435 * @iter: The iterator to check
4437 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4439 struct ring_buffer_per_cpu *cpu_buffer;
4440 struct buffer_page *reader;
4441 struct buffer_page *head_page;
4442 struct buffer_page *commit_page;
4443 struct buffer_page *curr_commit_page;
4448 cpu_buffer = iter->cpu_buffer;
4449 reader = cpu_buffer->reader_page;
4450 head_page = cpu_buffer->head_page;
4451 commit_page = cpu_buffer->commit_page;
4452 commit_ts = commit_page->page->time_stamp;
4455 * When the writer goes across pages, it issues a cmpxchg which
4456 * is a mb(), which will synchronize with the rmb here.
4457 * (see rb_tail_page_update())
4460 commit = rb_page_commit(commit_page);
4461 /* We want to make sure that the commit page doesn't change */
4464 /* Make sure commit page didn't change */
4465 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4466 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4468 /* If the commit page changed, then there's more data */
4469 if (curr_commit_page != commit_page ||
4470 curr_commit_ts != commit_ts)
4473 /* Still racy, as it may return a false positive, but that's OK */
4474 return ((iter->head_page == commit_page && iter->head >= commit) ||
4475 (iter->head_page == reader && commit_page == head_page &&
4476 head_page->read == commit &&
4477 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4479 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4482 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4483 struct ring_buffer_event *event)
4487 switch (event->type_len) {
4488 case RINGBUF_TYPE_PADDING:
4491 case RINGBUF_TYPE_TIME_EXTEND:
4492 delta = rb_event_time_stamp(event);
4493 cpu_buffer->read_stamp += delta;
4496 case RINGBUF_TYPE_TIME_STAMP:
4497 delta = rb_event_time_stamp(event);
4498 delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
4499 cpu_buffer->read_stamp = delta;
4502 case RINGBUF_TYPE_DATA:
4503 cpu_buffer->read_stamp += event->time_delta;
4507 RB_WARN_ON(cpu_buffer, 1);
4513 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4514 struct ring_buffer_event *event)
4518 switch (event->type_len) {
4519 case RINGBUF_TYPE_PADDING:
4522 case RINGBUF_TYPE_TIME_EXTEND:
4523 delta = rb_event_time_stamp(event);
4524 iter->read_stamp += delta;
4527 case RINGBUF_TYPE_TIME_STAMP:
4528 delta = rb_event_time_stamp(event);
4529 delta = rb_fix_abs_ts(delta, iter->read_stamp);
4530 iter->read_stamp = delta;
4533 case RINGBUF_TYPE_DATA:
4534 iter->read_stamp += event->time_delta;
4538 RB_WARN_ON(iter->cpu_buffer, 1);
4543 static struct buffer_page *
4544 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4546 struct buffer_page *reader = NULL;
4547 unsigned long overwrite;
4548 unsigned long flags;
4552 local_irq_save(flags);
4553 arch_spin_lock(&cpu_buffer->lock);
4557 * This should normally only loop twice. But because the
4558 * start of the reader inserts an empty page, it causes
4559 * a case where we will loop three times. There should be no
4560 * reason to loop four times (that I know of).
4562 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4567 reader = cpu_buffer->reader_page;
4569 /* If there's more to read, return this page */
4570 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4573 /* Never should we have an index greater than the size */
4574 if (RB_WARN_ON(cpu_buffer,
4575 cpu_buffer->reader_page->read > rb_page_size(reader)))
4578 /* check if we caught up to the tail */
4580 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4583 /* Don't bother swapping if the ring buffer is empty */
4584 if (rb_num_of_entries(cpu_buffer) == 0)
4588 * Reset the reader page to size zero.
4590 local_set(&cpu_buffer->reader_page->write, 0);
4591 local_set(&cpu_buffer->reader_page->entries, 0);
4592 local_set(&cpu_buffer->reader_page->page->commit, 0);
4593 cpu_buffer->reader_page->real_end = 0;
4597 * Splice the empty reader page into the list around the head.
4599 reader = rb_set_head_page(cpu_buffer);
4602 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4603 cpu_buffer->reader_page->list.prev = reader->list.prev;
4606 * cpu_buffer->pages just needs to point to the buffer, it
4607 * has no specific buffer page to point to. Lets move it out
4608 * of our way so we don't accidentally swap it.
4610 cpu_buffer->pages = reader->list.prev;
4612 /* The reader page will be pointing to the new head */
4613 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4616 * We want to make sure we read the overruns after we set up our
4617 * pointers to the next object. The writer side does a
4618 * cmpxchg to cross pages which acts as the mb on the writer
4619 * side. Note, the reader will constantly fail the swap
4620 * while the writer is updating the pointers, so this
4621 * guarantees that the overwrite recorded here is the one we
4622 * want to compare with the last_overrun.
4625 overwrite = local_read(&(cpu_buffer->overrun));
4628 * Here's the tricky part.
4630 * We need to move the pointer past the header page.
4631 * But we can only do that if a writer is not currently
4632 * moving it. The page before the header page has the
4633 * flag bit '1' set if it is pointing to the page we want.
4634 * but if the writer is in the process of moving it
4635 * than it will be '2' or already moved '0'.
4638 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4641 * If we did not convert it, then we must try again.
4647 * Yay! We succeeded in replacing the page.
4649 * Now make the new head point back to the reader page.
4651 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4652 rb_inc_page(&cpu_buffer->head_page);
4654 local_inc(&cpu_buffer->pages_read);
4656 /* Finally update the reader page to the new head */
4657 cpu_buffer->reader_page = reader;
4658 cpu_buffer->reader_page->read = 0;
4660 if (overwrite != cpu_buffer->last_overrun) {
4661 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4662 cpu_buffer->last_overrun = overwrite;
4668 /* Update the read_stamp on the first event */
4669 if (reader && reader->read == 0)
4670 cpu_buffer->read_stamp = reader->page->time_stamp;
4672 arch_spin_unlock(&cpu_buffer->lock);
4673 local_irq_restore(flags);
4676 * The writer has preempt disable, wait for it. But not forever
4677 * Although, 1 second is pretty much "forever"
4679 #define USECS_WAIT 1000000
4680 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4681 /* If the write is past the end of page, a writer is still updating it */
4682 if (likely(!reader || rb_page_write(reader) <= BUF_PAGE_SIZE))
4687 /* Get the latest version of the reader write value */
4691 /* The writer is not moving forward? Something is wrong */
4692 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4696 * Make sure we see any padding after the write update
4697 * (see rb_reset_tail())
4705 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4707 struct ring_buffer_event *event;
4708 struct buffer_page *reader;
4711 reader = rb_get_reader_page(cpu_buffer);
4713 /* This function should not be called when buffer is empty */
4714 if (RB_WARN_ON(cpu_buffer, !reader))
4717 event = rb_reader_event(cpu_buffer);
4719 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4722 rb_update_read_stamp(cpu_buffer, event);
4724 length = rb_event_length(event);
4725 cpu_buffer->reader_page->read += length;
4728 static void rb_advance_iter(struct ring_buffer_iter *iter)
4730 struct ring_buffer_per_cpu *cpu_buffer;
4732 cpu_buffer = iter->cpu_buffer;
4734 /* If head == next_event then we need to jump to the next event */
4735 if (iter->head == iter->next_event) {
4736 /* If the event gets overwritten again, there's nothing to do */
4737 if (rb_iter_head_event(iter) == NULL)
4741 iter->head = iter->next_event;
4744 * Check if we are at the end of the buffer.
4746 if (iter->next_event >= rb_page_size(iter->head_page)) {
4747 /* discarded commits can make the page empty */
4748 if (iter->head_page == cpu_buffer->commit_page)
4754 rb_update_iter_read_stamp(iter, iter->event);
4757 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4759 return cpu_buffer->lost_events;
4762 static struct ring_buffer_event *
4763 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4764 unsigned long *lost_events)
4766 struct ring_buffer_event *event;
4767 struct buffer_page *reader;
4774 * We repeat when a time extend is encountered.
4775 * Since the time extend is always attached to a data event,
4776 * we should never loop more than once.
4777 * (We never hit the following condition more than twice).
4779 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4782 reader = rb_get_reader_page(cpu_buffer);
4786 event = rb_reader_event(cpu_buffer);
4788 switch (event->type_len) {
4789 case RINGBUF_TYPE_PADDING:
4790 if (rb_null_event(event))
4791 RB_WARN_ON(cpu_buffer, 1);
4793 * Because the writer could be discarding every
4794 * event it creates (which would probably be bad)
4795 * if we were to go back to "again" then we may never
4796 * catch up, and will trigger the warn on, or lock
4797 * the box. Return the padding, and we will release
4798 * the current locks, and try again.
4802 case RINGBUF_TYPE_TIME_EXTEND:
4803 /* Internal data, OK to advance */
4804 rb_advance_reader(cpu_buffer);
4807 case RINGBUF_TYPE_TIME_STAMP:
4809 *ts = rb_event_time_stamp(event);
4810 *ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
4811 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4812 cpu_buffer->cpu, ts);
4814 /* Internal data, OK to advance */
4815 rb_advance_reader(cpu_buffer);
4818 case RINGBUF_TYPE_DATA:
4820 *ts = cpu_buffer->read_stamp + event->time_delta;
4821 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4822 cpu_buffer->cpu, ts);
4825 *lost_events = rb_lost_events(cpu_buffer);
4829 RB_WARN_ON(cpu_buffer, 1);
4834 EXPORT_SYMBOL_GPL(ring_buffer_peek);
4836 static struct ring_buffer_event *
4837 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4839 struct trace_buffer *buffer;
4840 struct ring_buffer_per_cpu *cpu_buffer;
4841 struct ring_buffer_event *event;
4847 cpu_buffer = iter->cpu_buffer;
4848 buffer = cpu_buffer->buffer;
4851 * Check if someone performed a consuming read to
4852 * the buffer. A consuming read invalidates the iterator
4853 * and we need to reset the iterator in this case.
4855 if (unlikely(iter->cache_read != cpu_buffer->read ||
4856 iter->cache_reader_page != cpu_buffer->reader_page))
4857 rb_iter_reset(iter);
4860 if (ring_buffer_iter_empty(iter))
4864 * As the writer can mess with what the iterator is trying
4865 * to read, just give up if we fail to get an event after
4866 * three tries. The iterator is not as reliable when reading
4867 * the ring buffer with an active write as the consumer is.
4868 * Do not warn if the three failures is reached.
4873 if (rb_per_cpu_empty(cpu_buffer))
4876 if (iter->head >= rb_page_size(iter->head_page)) {
4881 event = rb_iter_head_event(iter);
4885 switch (event->type_len) {
4886 case RINGBUF_TYPE_PADDING:
4887 if (rb_null_event(event)) {
4891 rb_advance_iter(iter);
4894 case RINGBUF_TYPE_TIME_EXTEND:
4895 /* Internal data, OK to advance */
4896 rb_advance_iter(iter);
4899 case RINGBUF_TYPE_TIME_STAMP:
4901 *ts = rb_event_time_stamp(event);
4902 *ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
4903 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4904 cpu_buffer->cpu, ts);
4906 /* Internal data, OK to advance */
4907 rb_advance_iter(iter);
4910 case RINGBUF_TYPE_DATA:
4912 *ts = iter->read_stamp + event->time_delta;
4913 ring_buffer_normalize_time_stamp(buffer,
4914 cpu_buffer->cpu, ts);
4919 RB_WARN_ON(cpu_buffer, 1);
4924 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4926 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4928 if (likely(!in_nmi())) {
4929 raw_spin_lock(&cpu_buffer->reader_lock);
4934 * If an NMI die dumps out the content of the ring buffer
4935 * trylock must be used to prevent a deadlock if the NMI
4936 * preempted a task that holds the ring buffer locks. If
4937 * we get the lock then all is fine, if not, then continue
4938 * to do the read, but this can corrupt the ring buffer,
4939 * so it must be permanently disabled from future writes.
4940 * Reading from NMI is a oneshot deal.
4942 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4945 /* Continue without locking, but disable the ring buffer */
4946 atomic_inc(&cpu_buffer->record_disabled);
4951 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4954 raw_spin_unlock(&cpu_buffer->reader_lock);
4959 * ring_buffer_peek - peek at the next event to be read
4960 * @buffer: The ring buffer to read
4961 * @cpu: The cpu to peak at
4962 * @ts: The timestamp counter of this event.
4963 * @lost_events: a variable to store if events were lost (may be NULL)
4965 * This will return the event that will be read next, but does
4966 * not consume the data.
4968 struct ring_buffer_event *
4969 ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4970 unsigned long *lost_events)
4972 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4973 struct ring_buffer_event *event;
4974 unsigned long flags;
4977 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4981 local_irq_save(flags);
4982 dolock = rb_reader_lock(cpu_buffer);
4983 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4984 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4985 rb_advance_reader(cpu_buffer);
4986 rb_reader_unlock(cpu_buffer, dolock);
4987 local_irq_restore(flags);
4989 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4995 /** ring_buffer_iter_dropped - report if there are dropped events
4996 * @iter: The ring buffer iterator
4998 * Returns true if there was dropped events since the last peek.
5000 bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
5002 bool ret = iter->missed_events != 0;
5004 iter->missed_events = 0;
5007 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
5010 * ring_buffer_iter_peek - peek at the next event to be read
5011 * @iter: The ring buffer iterator
5012 * @ts: The timestamp counter of this event.
5014 * This will return the event that will be read next, but does
5015 * not increment the iterator.
5017 struct ring_buffer_event *
5018 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
5020 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5021 struct ring_buffer_event *event;
5022 unsigned long flags;
5025 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5026 event = rb_iter_peek(iter, ts);
5027 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5029 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5036 * ring_buffer_consume - return an event and consume it
5037 * @buffer: The ring buffer to get the next event from
5038 * @cpu: the cpu to read the buffer from
5039 * @ts: a variable to store the timestamp (may be NULL)
5040 * @lost_events: a variable to store if events were lost (may be NULL)
5042 * Returns the next event in the ring buffer, and that event is consumed.
5043 * Meaning, that sequential reads will keep returning a different event,
5044 * and eventually empty the ring buffer if the producer is slower.
5046 struct ring_buffer_event *
5047 ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
5048 unsigned long *lost_events)
5050 struct ring_buffer_per_cpu *cpu_buffer;
5051 struct ring_buffer_event *event = NULL;
5052 unsigned long flags;
5056 /* might be called in atomic */
5059 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5062 cpu_buffer = buffer->buffers[cpu];
5063 local_irq_save(flags);
5064 dolock = rb_reader_lock(cpu_buffer);
5066 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
5068 cpu_buffer->lost_events = 0;
5069 rb_advance_reader(cpu_buffer);
5072 rb_reader_unlock(cpu_buffer, dolock);
5073 local_irq_restore(flags);
5078 if (event && event->type_len == RINGBUF_TYPE_PADDING)
5083 EXPORT_SYMBOL_GPL(ring_buffer_consume);
5086 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
5087 * @buffer: The ring buffer to read from
5088 * @cpu: The cpu buffer to iterate over
5089 * @flags: gfp flags to use for memory allocation
5091 * This performs the initial preparations necessary to iterate
5092 * through the buffer. Memory is allocated, buffer recording
5093 * is disabled, and the iterator pointer is returned to the caller.
5095 * Disabling buffer recording prevents the reading from being
5096 * corrupted. This is not a consuming read, so a producer is not
5099 * After a sequence of ring_buffer_read_prepare calls, the user is
5100 * expected to make at least one call to ring_buffer_read_prepare_sync.
5101 * Afterwards, ring_buffer_read_start is invoked to get things going
5104 * This overall must be paired with ring_buffer_read_finish.
5106 struct ring_buffer_iter *
5107 ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
5109 struct ring_buffer_per_cpu *cpu_buffer;
5110 struct ring_buffer_iter *iter;
5112 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5115 iter = kzalloc(sizeof(*iter), flags);
5119 iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
5125 cpu_buffer = buffer->buffers[cpu];
5127 iter->cpu_buffer = cpu_buffer;
5129 atomic_inc(&cpu_buffer->resize_disabled);
5133 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
5136 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
5138 * All previously invoked ring_buffer_read_prepare calls to prepare
5139 * iterators will be synchronized. Afterwards, read_buffer_read_start
5140 * calls on those iterators are allowed.
5143 ring_buffer_read_prepare_sync(void)
5147 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
5150 * ring_buffer_read_start - start a non consuming read of the buffer
5151 * @iter: The iterator returned by ring_buffer_read_prepare
5153 * This finalizes the startup of an iteration through the buffer.
5154 * The iterator comes from a call to ring_buffer_read_prepare and
5155 * an intervening ring_buffer_read_prepare_sync must have been
5158 * Must be paired with ring_buffer_read_finish.
5161 ring_buffer_read_start(struct ring_buffer_iter *iter)
5163 struct ring_buffer_per_cpu *cpu_buffer;
5164 unsigned long flags;
5169 cpu_buffer = iter->cpu_buffer;
5171 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5172 arch_spin_lock(&cpu_buffer->lock);
5173 rb_iter_reset(iter);
5174 arch_spin_unlock(&cpu_buffer->lock);
5175 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5177 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5180 * ring_buffer_read_finish - finish reading the iterator of the buffer
5181 * @iter: The iterator retrieved by ring_buffer_start
5183 * This re-enables the recording to the buffer, and frees the
5187 ring_buffer_read_finish(struct ring_buffer_iter *iter)
5189 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5190 unsigned long flags;
5193 * Ring buffer is disabled from recording, here's a good place
5194 * to check the integrity of the ring buffer.
5195 * Must prevent readers from trying to read, as the check
5196 * clears the HEAD page and readers require it.
5198 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5199 rb_check_pages(cpu_buffer);
5200 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5202 atomic_dec(&cpu_buffer->resize_disabled);
5206 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5209 * ring_buffer_iter_advance - advance the iterator to the next location
5210 * @iter: The ring buffer iterator
5212 * Move the location of the iterator such that the next read will
5213 * be the next location of the iterator.
5215 void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5217 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5218 unsigned long flags;
5220 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5222 rb_advance_iter(iter);
5224 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5226 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5229 * ring_buffer_size - return the size of the ring buffer (in bytes)
5230 * @buffer: The ring buffer.
5231 * @cpu: The CPU to get ring buffer size from.
5233 unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5236 * Earlier, this method returned
5237 * BUF_PAGE_SIZE * buffer->nr_pages
5238 * Since the nr_pages field is now removed, we have converted this to
5239 * return the per cpu buffer value.
5241 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5244 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
5246 EXPORT_SYMBOL_GPL(ring_buffer_size);
5249 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5251 rb_head_page_deactivate(cpu_buffer);
5253 cpu_buffer->head_page
5254 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5255 local_set(&cpu_buffer->head_page->write, 0);
5256 local_set(&cpu_buffer->head_page->entries, 0);
5257 local_set(&cpu_buffer->head_page->page->commit, 0);
5259 cpu_buffer->head_page->read = 0;
5261 cpu_buffer->tail_page = cpu_buffer->head_page;
5262 cpu_buffer->commit_page = cpu_buffer->head_page;
5264 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5265 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5266 local_set(&cpu_buffer->reader_page->write, 0);
5267 local_set(&cpu_buffer->reader_page->entries, 0);
5268 local_set(&cpu_buffer->reader_page->page->commit, 0);
5269 cpu_buffer->reader_page->read = 0;
5271 local_set(&cpu_buffer->entries_bytes, 0);
5272 local_set(&cpu_buffer->overrun, 0);
5273 local_set(&cpu_buffer->commit_overrun, 0);
5274 local_set(&cpu_buffer->dropped_events, 0);
5275 local_set(&cpu_buffer->entries, 0);
5276 local_set(&cpu_buffer->committing, 0);
5277 local_set(&cpu_buffer->commits, 0);
5278 local_set(&cpu_buffer->pages_touched, 0);
5279 local_set(&cpu_buffer->pages_lost, 0);
5280 local_set(&cpu_buffer->pages_read, 0);
5281 cpu_buffer->last_pages_touch = 0;
5282 cpu_buffer->shortest_full = 0;
5283 cpu_buffer->read = 0;
5284 cpu_buffer->read_bytes = 0;
5286 rb_time_set(&cpu_buffer->write_stamp, 0);
5287 rb_time_set(&cpu_buffer->before_stamp, 0);
5289 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5291 cpu_buffer->lost_events = 0;
5292 cpu_buffer->last_overrun = 0;
5294 rb_head_page_activate(cpu_buffer);
5297 /* Must have disabled the cpu buffer then done a synchronize_rcu */
5298 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5300 unsigned long flags;
5302 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5304 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5307 arch_spin_lock(&cpu_buffer->lock);
5309 rb_reset_cpu(cpu_buffer);
5311 arch_spin_unlock(&cpu_buffer->lock);
5314 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5318 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5319 * @buffer: The ring buffer to reset a per cpu buffer of
5320 * @cpu: The CPU buffer to be reset
5322 void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5324 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5326 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5329 /* prevent another thread from changing buffer sizes */
5330 mutex_lock(&buffer->mutex);
5332 atomic_inc(&cpu_buffer->resize_disabled);
5333 atomic_inc(&cpu_buffer->record_disabled);
5335 /* Make sure all commits have finished */
5338 reset_disabled_cpu_buffer(cpu_buffer);
5340 atomic_dec(&cpu_buffer->record_disabled);
5341 atomic_dec(&cpu_buffer->resize_disabled);
5343 mutex_unlock(&buffer->mutex);
5345 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5348 * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
5349 * @buffer: The ring buffer to reset a per cpu buffer of
5350 * @cpu: The CPU buffer to be reset
5352 void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5354 struct ring_buffer_per_cpu *cpu_buffer;
5357 /* prevent another thread from changing buffer sizes */
5358 mutex_lock(&buffer->mutex);
5360 for_each_online_buffer_cpu(buffer, cpu) {
5361 cpu_buffer = buffer->buffers[cpu];
5363 atomic_inc(&cpu_buffer->resize_disabled);
5364 atomic_inc(&cpu_buffer->record_disabled);
5367 /* Make sure all commits have finished */
5370 for_each_online_buffer_cpu(buffer, cpu) {
5371 cpu_buffer = buffer->buffers[cpu];
5373 reset_disabled_cpu_buffer(cpu_buffer);
5375 atomic_dec(&cpu_buffer->record_disabled);
5376 atomic_dec(&cpu_buffer->resize_disabled);
5379 mutex_unlock(&buffer->mutex);
5383 * ring_buffer_reset - reset a ring buffer
5384 * @buffer: The ring buffer to reset all cpu buffers
5386 void ring_buffer_reset(struct trace_buffer *buffer)
5388 struct ring_buffer_per_cpu *cpu_buffer;
5391 /* prevent another thread from changing buffer sizes */
5392 mutex_lock(&buffer->mutex);
5394 for_each_buffer_cpu(buffer, cpu) {
5395 cpu_buffer = buffer->buffers[cpu];
5397 atomic_inc(&cpu_buffer->resize_disabled);
5398 atomic_inc(&cpu_buffer->record_disabled);
5401 /* Make sure all commits have finished */
5404 for_each_buffer_cpu(buffer, cpu) {
5405 cpu_buffer = buffer->buffers[cpu];
5407 reset_disabled_cpu_buffer(cpu_buffer);
5409 atomic_dec(&cpu_buffer->record_disabled);
5410 atomic_dec(&cpu_buffer->resize_disabled);
5413 mutex_unlock(&buffer->mutex);
5415 EXPORT_SYMBOL_GPL(ring_buffer_reset);
5418 * ring_buffer_empty - is the ring buffer empty?
5419 * @buffer: The ring buffer to test
5421 bool ring_buffer_empty(struct trace_buffer *buffer)
5423 struct ring_buffer_per_cpu *cpu_buffer;
5424 unsigned long flags;
5429 /* yes this is racy, but if you don't like the race, lock the buffer */
5430 for_each_buffer_cpu(buffer, cpu) {
5431 cpu_buffer = buffer->buffers[cpu];
5432 local_irq_save(flags);
5433 dolock = rb_reader_lock(cpu_buffer);
5434 ret = rb_per_cpu_empty(cpu_buffer);
5435 rb_reader_unlock(cpu_buffer, dolock);
5436 local_irq_restore(flags);
5444 EXPORT_SYMBOL_GPL(ring_buffer_empty);
5447 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5448 * @buffer: The ring buffer
5449 * @cpu: The CPU buffer to test
5451 bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5453 struct ring_buffer_per_cpu *cpu_buffer;
5454 unsigned long flags;
5458 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5461 cpu_buffer = buffer->buffers[cpu];
5462 local_irq_save(flags);
5463 dolock = rb_reader_lock(cpu_buffer);
5464 ret = rb_per_cpu_empty(cpu_buffer);
5465 rb_reader_unlock(cpu_buffer, dolock);
5466 local_irq_restore(flags);
5470 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5472 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5474 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5475 * @buffer_a: One buffer to swap with
5476 * @buffer_b: The other buffer to swap with
5477 * @cpu: the CPU of the buffers to swap
5479 * This function is useful for tracers that want to take a "snapshot"
5480 * of a CPU buffer and has another back up buffer lying around.
5481 * it is expected that the tracer handles the cpu buffer not being
5482 * used at the moment.
5484 int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5485 struct trace_buffer *buffer_b, int cpu)
5487 struct ring_buffer_per_cpu *cpu_buffer_a;
5488 struct ring_buffer_per_cpu *cpu_buffer_b;
5491 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5492 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5495 cpu_buffer_a = buffer_a->buffers[cpu];
5496 cpu_buffer_b = buffer_b->buffers[cpu];
5498 /* At least make sure the two buffers are somewhat the same */
5499 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5504 if (atomic_read(&buffer_a->record_disabled))
5507 if (atomic_read(&buffer_b->record_disabled))
5510 if (atomic_read(&cpu_buffer_a->record_disabled))
5513 if (atomic_read(&cpu_buffer_b->record_disabled))
5517 * We can't do a synchronize_rcu here because this
5518 * function can be called in atomic context.
5519 * Normally this will be called from the same CPU as cpu.
5520 * If not it's up to the caller to protect this.
5522 atomic_inc(&cpu_buffer_a->record_disabled);
5523 atomic_inc(&cpu_buffer_b->record_disabled);
5526 if (local_read(&cpu_buffer_a->committing))
5528 if (local_read(&cpu_buffer_b->committing))
5531 buffer_a->buffers[cpu] = cpu_buffer_b;
5532 buffer_b->buffers[cpu] = cpu_buffer_a;
5534 cpu_buffer_b->buffer = buffer_a;
5535 cpu_buffer_a->buffer = buffer_b;
5540 atomic_dec(&cpu_buffer_a->record_disabled);
5541 atomic_dec(&cpu_buffer_b->record_disabled);
5545 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5546 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5549 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5550 * @buffer: the buffer to allocate for.
5551 * @cpu: the cpu buffer to allocate.
5553 * This function is used in conjunction with ring_buffer_read_page.
5554 * When reading a full page from the ring buffer, these functions
5555 * can be used to speed up the process. The calling function should
5556 * allocate a few pages first with this function. Then when it
5557 * needs to get pages from the ring buffer, it passes the result
5558 * of this function into ring_buffer_read_page, which will swap
5559 * the page that was allocated, with the read page of the buffer.
5562 * The page allocated, or ERR_PTR
5564 void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5566 struct ring_buffer_per_cpu *cpu_buffer;
5567 struct buffer_data_page *bpage = NULL;
5568 unsigned long flags;
5571 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5572 return ERR_PTR(-ENODEV);
5574 cpu_buffer = buffer->buffers[cpu];
5575 local_irq_save(flags);
5576 arch_spin_lock(&cpu_buffer->lock);
5578 if (cpu_buffer->free_page) {
5579 bpage = cpu_buffer->free_page;
5580 cpu_buffer->free_page = NULL;
5583 arch_spin_unlock(&cpu_buffer->lock);
5584 local_irq_restore(flags);
5589 page = alloc_pages_node(cpu_to_node(cpu),
5590 GFP_KERNEL | __GFP_NORETRY, 0);
5592 return ERR_PTR(-ENOMEM);
5594 bpage = page_address(page);
5597 rb_init_page(bpage);
5601 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5604 * ring_buffer_free_read_page - free an allocated read page
5605 * @buffer: the buffer the page was allocate for
5606 * @cpu: the cpu buffer the page came from
5607 * @data: the page to free
5609 * Free a page allocated from ring_buffer_alloc_read_page.
5611 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
5613 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5614 struct buffer_data_page *bpage = data;
5615 struct page *page = virt_to_page(bpage);
5616 unsigned long flags;
5618 /* If the page is still in use someplace else, we can't reuse it */
5619 if (page_ref_count(page) > 1)
5622 local_irq_save(flags);
5623 arch_spin_lock(&cpu_buffer->lock);
5625 if (!cpu_buffer->free_page) {
5626 cpu_buffer->free_page = bpage;
5630 arch_spin_unlock(&cpu_buffer->lock);
5631 local_irq_restore(flags);
5634 free_page((unsigned long)bpage);
5636 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5639 * ring_buffer_read_page - extract a page from the ring buffer
5640 * @buffer: buffer to extract from
5641 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5642 * @len: amount to extract
5643 * @cpu: the cpu of the buffer to extract
5644 * @full: should the extraction only happen when the page is full.
5646 * This function will pull out a page from the ring buffer and consume it.
5647 * @data_page must be the address of the variable that was returned
5648 * from ring_buffer_alloc_read_page. This is because the page might be used
5649 * to swap with a page in the ring buffer.
5652 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5653 * if (IS_ERR(rpage))
5654 * return PTR_ERR(rpage);
5655 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5657 * process_page(rpage, ret);
5659 * When @full is set, the function will not return true unless
5660 * the writer is off the reader page.
5662 * Note: it is up to the calling functions to handle sleeps and wakeups.
5663 * The ring buffer can be used anywhere in the kernel and can not
5664 * blindly call wake_up. The layer that uses the ring buffer must be
5665 * responsible for that.
5668 * >=0 if data has been transferred, returns the offset of consumed data.
5669 * <0 if no data has been transferred.
5671 int ring_buffer_read_page(struct trace_buffer *buffer,
5672 void **data_page, size_t len, int cpu, int full)
5674 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5675 struct ring_buffer_event *event;
5676 struct buffer_data_page *bpage;
5677 struct buffer_page *reader;
5678 unsigned long missed_events;
5679 unsigned long flags;
5680 unsigned int commit;
5685 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5689 * If len is not big enough to hold the page header, then
5690 * we can not copy anything.
5692 if (len <= BUF_PAGE_HDR_SIZE)
5695 len -= BUF_PAGE_HDR_SIZE;
5704 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5706 reader = rb_get_reader_page(cpu_buffer);
5710 event = rb_reader_event(cpu_buffer);
5712 read = reader->read;
5713 commit = rb_page_commit(reader);
5715 /* Check if any events were dropped */
5716 missed_events = cpu_buffer->lost_events;
5719 * If this page has been partially read or
5720 * if len is not big enough to read the rest of the page or
5721 * a writer is still on the page, then
5722 * we must copy the data from the page to the buffer.
5723 * Otherwise, we can simply swap the page with the one passed in.
5725 if (read || (len < (commit - read)) ||
5726 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5727 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5728 unsigned int rpos = read;
5729 unsigned int pos = 0;
5733 * If a full page is expected, this can still be returned
5734 * if there's been a previous partial read and the
5735 * rest of the page can be read and the commit page is off
5739 (!read || (len < (commit - read)) ||
5740 cpu_buffer->reader_page == cpu_buffer->commit_page))
5743 if (len > (commit - read))
5744 len = (commit - read);
5746 /* Always keep the time extend and data together */
5747 size = rb_event_ts_length(event);
5752 /* save the current timestamp, since the user will need it */
5753 save_timestamp = cpu_buffer->read_stamp;
5755 /* Need to copy one event at a time */
5757 /* We need the size of one event, because
5758 * rb_advance_reader only advances by one event,
5759 * whereas rb_event_ts_length may include the size of
5760 * one or two events.
5761 * We have already ensured there's enough space if this
5762 * is a time extend. */
5763 size = rb_event_length(event);
5764 memcpy(bpage->data + pos, rpage->data + rpos, size);
5768 rb_advance_reader(cpu_buffer);
5769 rpos = reader->read;
5775 event = rb_reader_event(cpu_buffer);
5776 /* Always keep the time extend and data together */
5777 size = rb_event_ts_length(event);
5778 } while (len >= size);
5781 local_set(&bpage->commit, pos);
5782 bpage->time_stamp = save_timestamp;
5784 /* we copied everything to the beginning */
5787 /* update the entry counter */
5788 cpu_buffer->read += rb_page_entries(reader);
5789 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
5791 /* swap the pages */
5792 rb_init_page(bpage);
5793 bpage = reader->page;
5794 reader->page = *data_page;
5795 local_set(&reader->write, 0);
5796 local_set(&reader->entries, 0);
5801 * Use the real_end for the data size,
5802 * This gives us a chance to store the lost events
5805 if (reader->real_end)
5806 local_set(&bpage->commit, reader->real_end);
5810 cpu_buffer->lost_events = 0;
5812 commit = local_read(&bpage->commit);
5814 * Set a flag in the commit field if we lost events
5816 if (missed_events) {
5817 /* If there is room at the end of the page to save the
5818 * missed events, then record it there.
5820 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
5821 memcpy(&bpage->data[commit], &missed_events,
5822 sizeof(missed_events));
5823 local_add(RB_MISSED_STORED, &bpage->commit);
5824 commit += sizeof(missed_events);
5826 local_add(RB_MISSED_EVENTS, &bpage->commit);
5830 * This page may be off to user land. Zero it out here.
5832 if (commit < BUF_PAGE_SIZE)
5833 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
5836 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5841 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5844 * We only allocate new buffers, never free them if the CPU goes down.
5845 * If we were to free the buffer, then the user would lose any trace that was in
5848 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
5850 struct trace_buffer *buffer;
5853 unsigned long nr_pages;
5855 buffer = container_of(node, struct trace_buffer, node);
5856 if (cpumask_test_cpu(cpu, buffer->cpumask))
5861 /* check if all cpu sizes are same */
5862 for_each_buffer_cpu(buffer, cpu_i) {
5863 /* fill in the size from first enabled cpu */
5865 nr_pages = buffer->buffers[cpu_i]->nr_pages;
5866 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
5871 /* allocate minimum pages, user can later expand it */
5874 buffer->buffers[cpu] =
5875 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
5876 if (!buffer->buffers[cpu]) {
5877 WARN(1, "failed to allocate ring buffer on CPU %u\n",
5882 cpumask_set_cpu(cpu, buffer->cpumask);
5886 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5888 * This is a basic integrity check of the ring buffer.
5889 * Late in the boot cycle this test will run when configured in.
5890 * It will kick off a thread per CPU that will go into a loop
5891 * writing to the per cpu ring buffer various sizes of data.
5892 * Some of the data will be large items, some small.
5894 * Another thread is created that goes into a spin, sending out
5895 * IPIs to the other CPUs to also write into the ring buffer.
5896 * this is to test the nesting ability of the buffer.
5898 * Basic stats are recorded and reported. If something in the
5899 * ring buffer should happen that's not expected, a big warning
5900 * is displayed and all ring buffers are disabled.
5902 static struct task_struct *rb_threads[NR_CPUS] __initdata;
5904 struct rb_test_data {
5905 struct trace_buffer *buffer;
5906 unsigned long events;
5907 unsigned long bytes_written;
5908 unsigned long bytes_alloc;
5909 unsigned long bytes_dropped;
5910 unsigned long events_nested;
5911 unsigned long bytes_written_nested;
5912 unsigned long bytes_alloc_nested;
5913 unsigned long bytes_dropped_nested;
5914 int min_size_nested;
5915 int max_size_nested;
5922 static struct rb_test_data rb_data[NR_CPUS] __initdata;
5925 #define RB_TEST_BUFFER_SIZE 1048576
5927 static char rb_string[] __initdata =
5928 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5929 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5930 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5932 static bool rb_test_started __initdata;
5939 static __init int rb_write_something(struct rb_test_data *data, bool nested)
5941 struct ring_buffer_event *event;
5942 struct rb_item *item;
5949 /* Have nested writes different that what is written */
5950 cnt = data->cnt + (nested ? 27 : 0);
5952 /* Multiply cnt by ~e, to make some unique increment */
5953 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
5955 len = size + sizeof(struct rb_item);
5957 started = rb_test_started;
5958 /* read rb_test_started before checking buffer enabled */
5961 event = ring_buffer_lock_reserve(data->buffer, len);
5963 /* Ignore dropped events before test starts. */
5966 data->bytes_dropped += len;
5968 data->bytes_dropped_nested += len;
5973 event_len = ring_buffer_event_length(event);
5975 if (RB_WARN_ON(data->buffer, event_len < len))
5978 item = ring_buffer_event_data(event);
5980 memcpy(item->str, rb_string, size);
5983 data->bytes_alloc_nested += event_len;
5984 data->bytes_written_nested += len;
5985 data->events_nested++;
5986 if (!data->min_size_nested || len < data->min_size_nested)
5987 data->min_size_nested = len;
5988 if (len > data->max_size_nested)
5989 data->max_size_nested = len;
5991 data->bytes_alloc += event_len;
5992 data->bytes_written += len;
5994 if (!data->min_size || len < data->min_size)
5995 data->max_size = len;
5996 if (len > data->max_size)
5997 data->max_size = len;
6001 ring_buffer_unlock_commit(data->buffer, event);
6006 static __init int rb_test(void *arg)
6008 struct rb_test_data *data = arg;
6010 while (!kthread_should_stop()) {
6011 rb_write_something(data, false);
6014 set_current_state(TASK_INTERRUPTIBLE);
6015 /* Now sleep between a min of 100-300us and a max of 1ms */
6016 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
6022 static __init void rb_ipi(void *ignore)
6024 struct rb_test_data *data;
6025 int cpu = smp_processor_id();
6027 data = &rb_data[cpu];
6028 rb_write_something(data, true);
6031 static __init int rb_hammer_test(void *arg)
6033 while (!kthread_should_stop()) {
6035 /* Send an IPI to all cpus to write data! */
6036 smp_call_function(rb_ipi, NULL, 1);
6037 /* No sleep, but for non preempt, let others run */
6044 static __init int test_ringbuffer(void)
6046 struct task_struct *rb_hammer;
6047 struct trace_buffer *buffer;
6051 if (security_locked_down(LOCKDOWN_TRACEFS)) {
6052 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
6056 pr_info("Running ring buffer tests...\n");
6058 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
6059 if (WARN_ON(!buffer))
6062 /* Disable buffer so that threads can't write to it yet */
6063 ring_buffer_record_off(buffer);
6065 for_each_online_cpu(cpu) {
6066 rb_data[cpu].buffer = buffer;
6067 rb_data[cpu].cpu = cpu;
6068 rb_data[cpu].cnt = cpu;
6069 rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
6070 cpu, "rbtester/%u");
6071 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
6072 pr_cont("FAILED\n");
6073 ret = PTR_ERR(rb_threads[cpu]);
6078 /* Now create the rb hammer! */
6079 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
6080 if (WARN_ON(IS_ERR(rb_hammer))) {
6081 pr_cont("FAILED\n");
6082 ret = PTR_ERR(rb_hammer);
6086 ring_buffer_record_on(buffer);
6088 * Show buffer is enabled before setting rb_test_started.
6089 * Yes there's a small race window where events could be
6090 * dropped and the thread wont catch it. But when a ring
6091 * buffer gets enabled, there will always be some kind of
6092 * delay before other CPUs see it. Thus, we don't care about
6093 * those dropped events. We care about events dropped after
6094 * the threads see that the buffer is active.
6097 rb_test_started = true;
6099 set_current_state(TASK_INTERRUPTIBLE);
6100 /* Just run for 10 seconds */;
6101 schedule_timeout(10 * HZ);
6103 kthread_stop(rb_hammer);
6106 for_each_online_cpu(cpu) {
6107 if (!rb_threads[cpu])
6109 kthread_stop(rb_threads[cpu]);
6112 ring_buffer_free(buffer);
6117 pr_info("finished\n");
6118 for_each_online_cpu(cpu) {
6119 struct ring_buffer_event *event;
6120 struct rb_test_data *data = &rb_data[cpu];
6121 struct rb_item *item;
6122 unsigned long total_events;
6123 unsigned long total_dropped;
6124 unsigned long total_written;
6125 unsigned long total_alloc;
6126 unsigned long total_read = 0;
6127 unsigned long total_size = 0;
6128 unsigned long total_len = 0;
6129 unsigned long total_lost = 0;
6132 int small_event_size;
6136 total_events = data->events + data->events_nested;
6137 total_written = data->bytes_written + data->bytes_written_nested;
6138 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
6139 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
6141 big_event_size = data->max_size + data->max_size_nested;
6142 small_event_size = data->min_size + data->min_size_nested;
6144 pr_info("CPU %d:\n", cpu);
6145 pr_info(" events: %ld\n", total_events);
6146 pr_info(" dropped bytes: %ld\n", total_dropped);
6147 pr_info(" alloced bytes: %ld\n", total_alloc);
6148 pr_info(" written bytes: %ld\n", total_written);
6149 pr_info(" biggest event: %d\n", big_event_size);
6150 pr_info(" smallest event: %d\n", small_event_size);
6152 if (RB_WARN_ON(buffer, total_dropped))
6157 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
6159 item = ring_buffer_event_data(event);
6160 total_len += ring_buffer_event_length(event);
6161 total_size += item->size + sizeof(struct rb_item);
6162 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
6163 pr_info("FAILED!\n");
6164 pr_info("buffer had: %.*s\n", item->size, item->str);
6165 pr_info("expected: %.*s\n", item->size, rb_string);
6166 RB_WARN_ON(buffer, 1);
6177 pr_info(" read events: %ld\n", total_read);
6178 pr_info(" lost events: %ld\n", total_lost);
6179 pr_info(" total events: %ld\n", total_lost + total_read);
6180 pr_info(" recorded len bytes: %ld\n", total_len);
6181 pr_info(" recorded size bytes: %ld\n", total_size);
6183 pr_info(" With dropped events, record len and size may not match\n"
6184 " alloced and written from above\n");
6186 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6187 total_size != total_written))
6190 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6196 pr_info("Ring buffer PASSED!\n");
6198 ring_buffer_free(buffer);
6202 late_initcall(test_ringbuffer);
6203 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */