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>
32 static void update_pages_handler(struct work_struct *work);
35 * The ring buffer header is special. We must manually up keep it.
37 int ring_buffer_print_entry_header(struct trace_seq *s)
39 trace_seq_puts(s, "# compressed entry header\n");
40 trace_seq_puts(s, "\ttype_len : 5 bits\n");
41 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
42 trace_seq_puts(s, "\tarray : 32 bits\n");
43 trace_seq_putc(s, '\n');
44 trace_seq_printf(s, "\tpadding : type == %d\n",
45 RINGBUF_TYPE_PADDING);
46 trace_seq_printf(s, "\ttime_extend : type == %d\n",
47 RINGBUF_TYPE_TIME_EXTEND);
48 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
49 RINGBUF_TYPE_TIME_STAMP);
50 trace_seq_printf(s, "\tdata max type_len == %d\n",
51 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
53 return !trace_seq_has_overflowed(s);
57 * The ring buffer is made up of a list of pages. A separate list of pages is
58 * allocated for each CPU. A writer may only write to a buffer that is
59 * associated with the CPU it is currently executing on. A reader may read
60 * from any per cpu buffer.
62 * The reader is special. For each per cpu buffer, the reader has its own
63 * reader page. When a reader has read the entire reader page, this reader
64 * page is swapped with another page in the ring buffer.
66 * Now, as long as the writer is off the reader page, the reader can do what
67 * ever it wants with that page. The writer will never write to that page
68 * again (as long as it is out of the ring buffer).
70 * Here's some silly ASCII art.
73 * |reader| RING BUFFER
75 * +------+ +---+ +---+ +---+
84 * |reader| RING BUFFER
85 * |page |------------------v
86 * +------+ +---+ +---+ +---+
95 * |reader| RING BUFFER
96 * |page |------------------v
97 * +------+ +---+ +---+ +---+
102 * +------------------------------+
106 * |buffer| RING BUFFER
107 * |page |------------------v
108 * +------+ +---+ +---+ +---+
110 * | New +---+ +---+ +---+
113 * +------------------------------+
116 * After we make this swap, the reader can hand this page off to the splice
117 * code and be done with it. It can even allocate a new page if it needs to
118 * and swap that into the ring buffer.
120 * We will be using cmpxchg soon to make all this lockless.
124 /* Used for individual buffers (after the counter) */
125 #define RB_BUFFER_OFF (1 << 20)
127 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
129 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
130 #define RB_ALIGNMENT 4U
131 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
132 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
134 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
135 # define RB_FORCE_8BYTE_ALIGNMENT 0
136 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
138 # define RB_FORCE_8BYTE_ALIGNMENT 1
139 # define RB_ARCH_ALIGNMENT 8U
142 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
144 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
145 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
148 RB_LEN_TIME_EXTEND = 8,
149 RB_LEN_TIME_STAMP = 8,
152 #define skip_time_extend(event) \
153 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
155 #define extended_time(event) \
156 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
158 static inline int rb_null_event(struct ring_buffer_event *event)
160 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
163 static void rb_event_set_padding(struct ring_buffer_event *event)
165 /* padding has a NULL time_delta */
166 event->type_len = RINGBUF_TYPE_PADDING;
167 event->time_delta = 0;
171 rb_event_data_length(struct ring_buffer_event *event)
176 length = event->type_len * RB_ALIGNMENT;
178 length = event->array[0];
179 return length + RB_EVNT_HDR_SIZE;
183 * Return the length of the given event. Will return
184 * the length of the time extend if the event is a
187 static inline unsigned
188 rb_event_length(struct ring_buffer_event *event)
190 switch (event->type_len) {
191 case RINGBUF_TYPE_PADDING:
192 if (rb_null_event(event))
195 return event->array[0] + RB_EVNT_HDR_SIZE;
197 case RINGBUF_TYPE_TIME_EXTEND:
198 return RB_LEN_TIME_EXTEND;
200 case RINGBUF_TYPE_TIME_STAMP:
201 return RB_LEN_TIME_STAMP;
203 case RINGBUF_TYPE_DATA:
204 return rb_event_data_length(event);
213 * Return total length of time extend and data,
214 * or just the event length for all other events.
216 static inline unsigned
217 rb_event_ts_length(struct ring_buffer_event *event)
221 if (extended_time(event)) {
222 /* time extends include the data event after it */
223 len = RB_LEN_TIME_EXTEND;
224 event = skip_time_extend(event);
226 return len + rb_event_length(event);
230 * ring_buffer_event_length - return the length of the event
231 * @event: the event to get the length of
233 * Returns the size of the data load of a data event.
234 * If the event is something other than a data event, it
235 * returns the size of the event itself. With the exception
236 * of a TIME EXTEND, where it still returns the size of the
237 * data load of the data event after it.
239 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
243 if (extended_time(event))
244 event = skip_time_extend(event);
246 length = rb_event_length(event);
247 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
249 length -= RB_EVNT_HDR_SIZE;
250 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
251 length -= sizeof(event->array[0]);
254 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
256 /* inline for ring buffer fast paths */
257 static __always_inline void *
258 rb_event_data(struct ring_buffer_event *event)
260 if (extended_time(event))
261 event = skip_time_extend(event);
262 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
263 /* If length is in len field, then array[0] has the data */
265 return (void *)&event->array[0];
266 /* Otherwise length is in array[0] and array[1] has the data */
267 return (void *)&event->array[1];
271 * ring_buffer_event_data - return the data of the event
272 * @event: the event to get the data from
274 void *ring_buffer_event_data(struct ring_buffer_event *event)
276 return rb_event_data(event);
278 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
280 #define for_each_buffer_cpu(buffer, cpu) \
281 for_each_cpu(cpu, buffer->cpumask)
283 #define for_each_online_buffer_cpu(buffer, cpu) \
284 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
287 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
288 #define TS_DELTA_TEST (~TS_MASK)
290 static u64 rb_event_time_stamp(struct ring_buffer_event *event)
294 ts = event->array[0];
296 ts += event->time_delta;
301 /* Flag when events were overwritten */
302 #define RB_MISSED_EVENTS (1 << 31)
303 /* Missed count stored at end */
304 #define RB_MISSED_STORED (1 << 30)
306 struct buffer_data_page {
307 u64 time_stamp; /* page time stamp */
308 local_t commit; /* write committed index */
309 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
313 * Note, the buffer_page list must be first. The buffer pages
314 * are allocated in cache lines, which means that each buffer
315 * page will be at the beginning of a cache line, and thus
316 * the least significant bits will be zero. We use this to
317 * add flags in the list struct pointers, to make the ring buffer
321 struct list_head list; /* list of buffer pages */
322 local_t write; /* index for next write */
323 unsigned read; /* index for next read */
324 local_t entries; /* entries on this page */
325 unsigned long real_end; /* real end of data */
326 struct buffer_data_page *page; /* Actual data page */
330 * The buffer page counters, write and entries, must be reset
331 * atomically when crossing page boundaries. To synchronize this
332 * update, two counters are inserted into the number. One is
333 * the actual counter for the write position or count on the page.
335 * The other is a counter of updaters. Before an update happens
336 * the update partition of the counter is incremented. This will
337 * allow the updater to update the counter atomically.
339 * The counter is 20 bits, and the state data is 12.
341 #define RB_WRITE_MASK 0xfffff
342 #define RB_WRITE_INTCNT (1 << 20)
344 static void rb_init_page(struct buffer_data_page *bpage)
346 local_set(&bpage->commit, 0);
350 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
353 static void free_buffer_page(struct buffer_page *bpage)
355 free_page((unsigned long)bpage->page);
360 * We need to fit the time_stamp delta into 27 bits.
362 static inline int test_time_stamp(u64 delta)
364 if (delta & TS_DELTA_TEST)
369 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
371 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
372 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
374 int ring_buffer_print_page_header(struct trace_seq *s)
376 struct buffer_data_page field;
378 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
379 "offset:0;\tsize:%u;\tsigned:%u;\n",
380 (unsigned int)sizeof(field.time_stamp),
381 (unsigned int)is_signed_type(u64));
383 trace_seq_printf(s, "\tfield: local_t commit;\t"
384 "offset:%u;\tsize:%u;\tsigned:%u;\n",
385 (unsigned int)offsetof(typeof(field), commit),
386 (unsigned int)sizeof(field.commit),
387 (unsigned int)is_signed_type(long));
389 trace_seq_printf(s, "\tfield: int overwrite;\t"
390 "offset:%u;\tsize:%u;\tsigned:%u;\n",
391 (unsigned int)offsetof(typeof(field), commit),
393 (unsigned int)is_signed_type(long));
395 trace_seq_printf(s, "\tfield: char data;\t"
396 "offset:%u;\tsize:%u;\tsigned:%u;\n",
397 (unsigned int)offsetof(typeof(field), data),
398 (unsigned int)BUF_PAGE_SIZE,
399 (unsigned int)is_signed_type(char));
401 return !trace_seq_has_overflowed(s);
405 struct irq_work work;
406 wait_queue_head_t waiters;
407 wait_queue_head_t full_waiters;
408 bool waiters_pending;
409 bool full_waiters_pending;
414 * Structure to hold event state and handle nested events.
416 struct rb_event_info {
421 unsigned long length;
422 struct buffer_page *tail_page;
427 * Used for the add_timestamp
429 * EXTEND - wants a time extend
430 * ABSOLUTE - the buffer requests all events to have absolute time stamps
431 * FORCE - force a full time stamp.
434 RB_ADD_STAMP_NONE = 0,
435 RB_ADD_STAMP_EXTEND = BIT(1),
436 RB_ADD_STAMP_ABSOLUTE = BIT(2),
437 RB_ADD_STAMP_FORCE = BIT(3)
440 * Used for which event context the event is in.
447 * See trace_recursive_lock() comment below for more details.
458 #if BITS_PER_LONG == 32
462 /* To test on 64 bit machines */
467 struct rb_time_struct {
473 #include <asm/local64.h>
474 struct rb_time_struct {
478 typedef struct rb_time_struct rb_time_t;
483 * head_page == tail_page && head == tail then buffer is empty.
485 struct ring_buffer_per_cpu {
487 atomic_t record_disabled;
488 atomic_t resize_disabled;
489 struct trace_buffer *buffer;
490 raw_spinlock_t reader_lock; /* serialize readers */
491 arch_spinlock_t lock;
492 struct lock_class_key lock_key;
493 struct buffer_data_page *free_page;
494 unsigned long nr_pages;
495 unsigned int current_context;
496 struct list_head *pages;
497 struct buffer_page *head_page; /* read from head */
498 struct buffer_page *tail_page; /* write to tail */
499 struct buffer_page *commit_page; /* committed pages */
500 struct buffer_page *reader_page;
501 unsigned long lost_events;
502 unsigned long last_overrun;
504 local_t entries_bytes;
507 local_t commit_overrun;
508 local_t dropped_events;
511 local_t pages_touched;
513 long last_pages_touch;
514 size_t shortest_full;
516 unsigned long read_bytes;
517 rb_time_t write_stamp;
518 rb_time_t before_stamp;
519 u64 event_stamp[MAX_NEST];
521 /* ring buffer pages to update, > 0 to add, < 0 to remove */
522 long nr_pages_to_update;
523 struct list_head new_pages; /* new pages to add */
524 struct work_struct update_pages_work;
525 struct completion update_done;
527 struct rb_irq_work irq_work;
530 struct trace_buffer {
533 atomic_t record_disabled;
534 cpumask_var_t cpumask;
536 struct lock_class_key *reader_lock_key;
540 struct ring_buffer_per_cpu **buffers;
542 struct hlist_node node;
545 struct rb_irq_work irq_work;
549 struct ring_buffer_iter {
550 struct ring_buffer_per_cpu *cpu_buffer;
552 unsigned long next_event;
553 struct buffer_page *head_page;
554 struct buffer_page *cache_reader_page;
555 unsigned long cache_read;
558 struct ring_buffer_event *event;
565 * On 32 bit machines, local64_t is very expensive. As the ring
566 * buffer doesn't need all the features of a true 64 bit atomic,
567 * on 32 bit, it uses these functions (64 still uses local64_t).
569 * For the ring buffer, 64 bit required operations for the time is
572 * - Only need 59 bits (uses 60 to make it even).
573 * - Reads may fail if it interrupted a modification of the time stamp.
574 * It will succeed if it did not interrupt another write even if
575 * the read itself is interrupted by a write.
576 * It returns whether it was successful or not.
578 * - Writes always succeed and will overwrite other writes and writes
579 * that were done by events interrupting the current write.
581 * - A write followed by a read of the same time stamp will always succeed,
582 * but may not contain the same value.
584 * - A cmpxchg will fail if it interrupted another write or cmpxchg.
585 * Other than that, it acts like a normal cmpxchg.
587 * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
588 * (bottom being the least significant 30 bits of the 60 bit time stamp).
590 * The two most significant bits of each half holds a 2 bit counter (0-3).
591 * Each update will increment this counter by one.
592 * When reading the top and bottom, if the two counter bits match then the
593 * top and bottom together make a valid 60 bit number.
595 #define RB_TIME_SHIFT 30
596 #define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
598 static inline int rb_time_cnt(unsigned long val)
600 return (val >> RB_TIME_SHIFT) & 3;
603 static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
607 val = top & RB_TIME_VAL_MASK;
608 val <<= RB_TIME_SHIFT;
609 val |= bottom & RB_TIME_VAL_MASK;
614 static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
616 unsigned long top, bottom;
620 * If the read is interrupted by a write, then the cnt will
621 * be different. Loop until both top and bottom have been read
622 * without interruption.
625 c = local_read(&t->cnt);
626 top = local_read(&t->top);
627 bottom = local_read(&t->bottom);
628 } while (c != local_read(&t->cnt));
630 *cnt = rb_time_cnt(top);
632 /* If top and bottom counts don't match, this interrupted a write */
633 if (*cnt != rb_time_cnt(bottom))
636 *ret = rb_time_val(top, bottom);
640 static bool rb_time_read(rb_time_t *t, u64 *ret)
644 return __rb_time_read(t, ret, &cnt);
647 static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
649 return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
652 static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom)
654 *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
655 *bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
658 static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
660 val = rb_time_val_cnt(val, cnt);
664 static void rb_time_set(rb_time_t *t, u64 val)
666 unsigned long cnt, top, bottom;
668 rb_time_split(val, &top, &bottom);
670 /* Writes always succeed with a valid number even if it gets interrupted. */
672 cnt = local_inc_return(&t->cnt);
673 rb_time_val_set(&t->top, top, cnt);
674 rb_time_val_set(&t->bottom, bottom, cnt);
675 } while (cnt != local_read(&t->cnt));
679 rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
683 ret = local_cmpxchg(l, expect, set);
684 return ret == expect;
687 static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
689 unsigned long cnt, top, bottom;
690 unsigned long cnt2, top2, bottom2;
693 /* The cmpxchg always fails if it interrupted an update */
694 if (!__rb_time_read(t, &val, &cnt2))
700 cnt = local_read(&t->cnt);
701 if ((cnt & 3) != cnt2)
706 rb_time_split(val, &top, &bottom);
707 top = rb_time_val_cnt(top, cnt);
708 bottom = rb_time_val_cnt(bottom, cnt);
710 rb_time_split(set, &top2, &bottom2);
711 top2 = rb_time_val_cnt(top2, cnt2);
712 bottom2 = rb_time_val_cnt(bottom2, cnt2);
714 if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
716 if (!rb_time_read_cmpxchg(&t->top, top, top2))
718 if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
725 /* local64_t always succeeds */
727 static inline bool rb_time_read(rb_time_t *t, u64 *ret)
729 *ret = local64_read(&t->time);
732 static void rb_time_set(rb_time_t *t, u64 val)
734 local64_set(&t->time, val);
737 static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
740 val = local64_cmpxchg(&t->time, expect, set);
741 return val == expect;
746 * Enable this to make sure that the event passed to
747 * ring_buffer_event_time_stamp() is not committed and also
748 * is on the buffer that it passed in.
750 //#define RB_VERIFY_EVENT
751 #ifdef RB_VERIFY_EVENT
752 static struct list_head *rb_list_head(struct list_head *list);
753 static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
756 struct buffer_page *page = cpu_buffer->commit_page;
757 struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
758 struct list_head *next;
760 unsigned long addr = (unsigned long)event;
764 /* Make sure the event exists and is not committed yet */
766 if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
768 commit = local_read(&page->page->commit);
769 write = local_read(&page->write);
770 if (addr >= (unsigned long)&page->page->data[commit] &&
771 addr < (unsigned long)&page->page->data[write])
774 next = rb_list_head(page->list.next);
775 page = list_entry(next, struct buffer_page, list);
780 static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
787 static inline u64 rb_time_stamp(struct trace_buffer *buffer);
790 * ring_buffer_event_time_stamp - return the event's current time stamp
791 * @buffer: The buffer that the event is on
792 * @event: the event to get the time stamp of
794 * Note, this must be called after @event is reserved, and before it is
795 * committed to the ring buffer. And must be called from the same
796 * context where the event was reserved (normal, softirq, irq, etc).
798 * Returns the time stamp associated with the current event.
799 * If the event has an extended time stamp, then that is used as
800 * the time stamp to return.
801 * In the highly unlikely case that the event was nested more than
802 * the max nesting, then the write_stamp of the buffer is returned,
803 * otherwise current time is returned, but that really neither of
804 * the last two cases should ever happen.
806 u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
807 struct ring_buffer_event *event)
809 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
813 /* If the event includes an absolute time, then just use that */
814 if (event->type_len == RINGBUF_TYPE_TIME_STAMP)
815 return rb_event_time_stamp(event);
817 nest = local_read(&cpu_buffer->committing);
818 verify_event(cpu_buffer, event);
819 if (WARN_ON_ONCE(!nest))
822 /* Read the current saved nesting level time stamp */
823 if (likely(--nest < MAX_NEST))
824 return cpu_buffer->event_stamp[nest];
826 /* Shouldn't happen, warn if it does */
827 WARN_ONCE(1, "nest (%d) greater than max", nest);
830 /* Can only fail on 32 bit */
831 if (!rb_time_read(&cpu_buffer->write_stamp, &ts))
832 /* Screw it, just read the current time */
833 ts = rb_time_stamp(cpu_buffer->buffer);
839 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
840 * @buffer: The ring_buffer to get the number of pages from
841 * @cpu: The cpu of the ring_buffer to get the number of pages from
843 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
845 size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
847 return buffer->buffers[cpu]->nr_pages;
851 * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
852 * @buffer: The ring_buffer to get the number of pages from
853 * @cpu: The cpu of the ring_buffer to get the number of pages from
855 * Returns the number of pages that have content in the ring buffer.
857 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
862 read = local_read(&buffer->buffers[cpu]->pages_read);
863 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
864 /* The reader can read an empty page, but not more than that */
866 WARN_ON_ONCE(read > cnt + 1);
874 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
876 * Schedules a delayed work to wake up any task that is blocked on the
877 * ring buffer waiters queue.
879 static void rb_wake_up_waiters(struct irq_work *work)
881 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
883 wake_up_all(&rbwork->waiters);
884 if (rbwork->wakeup_full) {
885 rbwork->wakeup_full = false;
886 wake_up_all(&rbwork->full_waiters);
891 * ring_buffer_wait - wait for input to the ring buffer
892 * @buffer: buffer to wait on
893 * @cpu: the cpu buffer to wait on
894 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
896 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
897 * as data is added to any of the @buffer's cpu buffers. Otherwise
898 * it will wait for data to be added to a specific cpu buffer.
900 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
902 struct ring_buffer_per_cpu *cpu_buffer;
904 struct rb_irq_work *work;
908 * Depending on what the caller is waiting for, either any
909 * data in any cpu buffer, or a specific buffer, put the
910 * caller on the appropriate wait queue.
912 if (cpu == RING_BUFFER_ALL_CPUS) {
913 work = &buffer->irq_work;
914 /* Full only makes sense on per cpu reads */
917 if (!cpumask_test_cpu(cpu, buffer->cpumask))
919 cpu_buffer = buffer->buffers[cpu];
920 work = &cpu_buffer->irq_work;
926 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
928 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
931 * The events can happen in critical sections where
932 * checking a work queue can cause deadlocks.
933 * After adding a task to the queue, this flag is set
934 * only to notify events to try to wake up the queue
937 * We don't clear it even if the buffer is no longer
938 * empty. The flag only causes the next event to run
939 * irq_work to do the work queue wake up. The worse
940 * that can happen if we race with !trace_empty() is that
941 * an event will cause an irq_work to try to wake up
944 * There's no reason to protect this flag either, as
945 * the work queue and irq_work logic will do the necessary
946 * synchronization for the wake ups. The only thing
947 * that is necessary is that the wake up happens after
948 * a task has been queued. It's OK for spurious wake ups.
951 work->full_waiters_pending = true;
953 work->waiters_pending = true;
955 if (signal_pending(current)) {
960 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
963 if (cpu != RING_BUFFER_ALL_CPUS &&
964 !ring_buffer_empty_cpu(buffer, cpu)) {
973 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
974 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
975 nr_pages = cpu_buffer->nr_pages;
976 dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
977 if (!cpu_buffer->shortest_full ||
978 cpu_buffer->shortest_full < full)
979 cpu_buffer->shortest_full = full;
980 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
982 (!nr_pages || (dirty * 100) > full * nr_pages))
990 finish_wait(&work->full_waiters, &wait);
992 finish_wait(&work->waiters, &wait);
998 * ring_buffer_poll_wait - poll on buffer input
999 * @buffer: buffer to wait on
1000 * @cpu: the cpu buffer to wait on
1001 * @filp: the file descriptor
1002 * @poll_table: The poll descriptor
1004 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
1005 * as data is added to any of the @buffer's cpu buffers. Otherwise
1006 * it will wait for data to be added to a specific cpu buffer.
1008 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
1011 __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
1012 struct file *filp, poll_table *poll_table)
1014 struct ring_buffer_per_cpu *cpu_buffer;
1015 struct rb_irq_work *work;
1017 if (cpu == RING_BUFFER_ALL_CPUS)
1018 work = &buffer->irq_work;
1020 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1023 cpu_buffer = buffer->buffers[cpu];
1024 work = &cpu_buffer->irq_work;
1027 poll_wait(filp, &work->waiters, poll_table);
1028 work->waiters_pending = true;
1030 * There's a tight race between setting the waiters_pending and
1031 * checking if the ring buffer is empty. Once the waiters_pending bit
1032 * is set, the next event will wake the task up, but we can get stuck
1033 * if there's only a single event in.
1035 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1036 * but adding a memory barrier to all events will cause too much of a
1037 * performance hit in the fast path. We only need a memory barrier when
1038 * the buffer goes from empty to having content. But as this race is
1039 * extremely small, and it's not a problem if another event comes in, we
1040 * will fix it later.
1044 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1045 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1046 return EPOLLIN | EPOLLRDNORM;
1050 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
1051 #define RB_WARN_ON(b, cond) \
1053 int _____ret = unlikely(cond); \
1055 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1056 struct ring_buffer_per_cpu *__b = \
1058 atomic_inc(&__b->buffer->record_disabled); \
1060 atomic_inc(&b->record_disabled); \
1066 /* Up this if you want to test the TIME_EXTENTS and normalization */
1067 #define DEBUG_SHIFT 0
1069 static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1073 /* Skip retpolines :-( */
1074 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1075 ts = trace_clock_local();
1077 ts = buffer->clock();
1079 /* shift to debug/test normalization and TIME_EXTENTS */
1080 return ts << DEBUG_SHIFT;
1083 u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
1087 preempt_disable_notrace();
1088 time = rb_time_stamp(buffer);
1089 preempt_enable_notrace();
1093 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1095 void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1098 /* Just stupid testing the normalize function and deltas */
1099 *ts >>= DEBUG_SHIFT;
1101 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1104 * Making the ring buffer lockless makes things tricky.
1105 * Although writes only happen on the CPU that they are on,
1106 * and they only need to worry about interrupts. Reads can
1107 * happen on any CPU.
1109 * The reader page is always off the ring buffer, but when the
1110 * reader finishes with a page, it needs to swap its page with
1111 * a new one from the buffer. The reader needs to take from
1112 * the head (writes go to the tail). But if a writer is in overwrite
1113 * mode and wraps, it must push the head page forward.
1115 * Here lies the problem.
1117 * The reader must be careful to replace only the head page, and
1118 * not another one. As described at the top of the file in the
1119 * ASCII art, the reader sets its old page to point to the next
1120 * page after head. It then sets the page after head to point to
1121 * the old reader page. But if the writer moves the head page
1122 * during this operation, the reader could end up with the tail.
1124 * We use cmpxchg to help prevent this race. We also do something
1125 * special with the page before head. We set the LSB to 1.
1127 * When the writer must push the page forward, it will clear the
1128 * bit that points to the head page, move the head, and then set
1129 * the bit that points to the new head page.
1131 * We also don't want an interrupt coming in and moving the head
1132 * page on another writer. Thus we use the second LSB to catch
1135 * head->list->prev->next bit 1 bit 0
1138 * Points to head page 0 1
1141 * Note we can not trust the prev pointer of the head page, because:
1143 * +----+ +-----+ +-----+
1144 * | |------>| T |---X--->| N |
1146 * +----+ +-----+ +-----+
1149 * +----------| R |----------+ |
1153 * Key: ---X--> HEAD flag set in pointer
1158 * (see __rb_reserve_next() to see where this happens)
1160 * What the above shows is that the reader just swapped out
1161 * the reader page with a page in the buffer, but before it
1162 * could make the new header point back to the new page added
1163 * it was preempted by a writer. The writer moved forward onto
1164 * the new page added by the reader and is about to move forward
1167 * You can see, it is legitimate for the previous pointer of
1168 * the head (or any page) not to point back to itself. But only
1172 #define RB_PAGE_NORMAL 0UL
1173 #define RB_PAGE_HEAD 1UL
1174 #define RB_PAGE_UPDATE 2UL
1177 #define RB_FLAG_MASK 3UL
1179 /* PAGE_MOVED is not part of the mask */
1180 #define RB_PAGE_MOVED 4UL
1183 * rb_list_head - remove any bit
1185 static struct list_head *rb_list_head(struct list_head *list)
1187 unsigned long val = (unsigned long)list;
1189 return (struct list_head *)(val & ~RB_FLAG_MASK);
1193 * rb_is_head_page - test if the given page is the head page
1195 * Because the reader may move the head_page pointer, we can
1196 * not trust what the head page is (it may be pointing to
1197 * the reader page). But if the next page is a header page,
1198 * its flags will be non zero.
1201 rb_is_head_page(struct buffer_page *page, struct list_head *list)
1205 val = (unsigned long)list->next;
1207 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1208 return RB_PAGE_MOVED;
1210 return val & RB_FLAG_MASK;
1216 * The unique thing about the reader page, is that, if the
1217 * writer is ever on it, the previous pointer never points
1218 * back to the reader page.
1220 static bool rb_is_reader_page(struct buffer_page *page)
1222 struct list_head *list = page->list.prev;
1224 return rb_list_head(list->next) != &page->list;
1228 * rb_set_list_to_head - set a list_head to be pointing to head.
1230 static void rb_set_list_to_head(struct list_head *list)
1234 ptr = (unsigned long *)&list->next;
1235 *ptr |= RB_PAGE_HEAD;
1236 *ptr &= ~RB_PAGE_UPDATE;
1240 * rb_head_page_activate - sets up head page
1242 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1244 struct buffer_page *head;
1246 head = cpu_buffer->head_page;
1251 * Set the previous list pointer to have the HEAD flag.
1253 rb_set_list_to_head(head->list.prev);
1256 static void rb_list_head_clear(struct list_head *list)
1258 unsigned long *ptr = (unsigned long *)&list->next;
1260 *ptr &= ~RB_FLAG_MASK;
1264 * rb_head_page_deactivate - clears head page ptr (for free list)
1267 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1269 struct list_head *hd;
1271 /* Go through the whole list and clear any pointers found. */
1272 rb_list_head_clear(cpu_buffer->pages);
1274 list_for_each(hd, cpu_buffer->pages)
1275 rb_list_head_clear(hd);
1278 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1279 struct buffer_page *head,
1280 struct buffer_page *prev,
1281 int old_flag, int new_flag)
1283 struct list_head *list;
1284 unsigned long val = (unsigned long)&head->list;
1289 val &= ~RB_FLAG_MASK;
1291 ret = cmpxchg((unsigned long *)&list->next,
1292 val | old_flag, val | new_flag);
1294 /* check if the reader took the page */
1295 if ((ret & ~RB_FLAG_MASK) != val)
1296 return RB_PAGE_MOVED;
1298 return ret & RB_FLAG_MASK;
1301 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1302 struct buffer_page *head,
1303 struct buffer_page *prev,
1306 return rb_head_page_set(cpu_buffer, head, prev,
1307 old_flag, RB_PAGE_UPDATE);
1310 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1311 struct buffer_page *head,
1312 struct buffer_page *prev,
1315 return rb_head_page_set(cpu_buffer, head, prev,
1316 old_flag, RB_PAGE_HEAD);
1319 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1320 struct buffer_page *head,
1321 struct buffer_page *prev,
1324 return rb_head_page_set(cpu_buffer, head, prev,
1325 old_flag, RB_PAGE_NORMAL);
1328 static inline void rb_inc_page(struct buffer_page **bpage)
1330 struct list_head *p = rb_list_head((*bpage)->list.next);
1332 *bpage = list_entry(p, struct buffer_page, list);
1335 static struct buffer_page *
1336 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1338 struct buffer_page *head;
1339 struct buffer_page *page;
1340 struct list_head *list;
1343 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1347 list = cpu_buffer->pages;
1348 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1351 page = head = cpu_buffer->head_page;
1353 * It is possible that the writer moves the header behind
1354 * where we started, and we miss in one loop.
1355 * A second loop should grab the header, but we'll do
1356 * three loops just because I'm paranoid.
1358 for (i = 0; i < 3; i++) {
1360 if (rb_is_head_page(page, page->list.prev)) {
1361 cpu_buffer->head_page = page;
1365 } while (page != head);
1368 RB_WARN_ON(cpu_buffer, 1);
1373 static int rb_head_page_replace(struct buffer_page *old,
1374 struct buffer_page *new)
1376 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1380 val = *ptr & ~RB_FLAG_MASK;
1381 val |= RB_PAGE_HEAD;
1383 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1389 * rb_tail_page_update - move the tail page forward
1391 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1392 struct buffer_page *tail_page,
1393 struct buffer_page *next_page)
1395 unsigned long old_entries;
1396 unsigned long old_write;
1399 * The tail page now needs to be moved forward.
1401 * We need to reset the tail page, but without messing
1402 * with possible erasing of data brought in by interrupts
1403 * that have moved the tail page and are currently on it.
1405 * We add a counter to the write field to denote this.
1407 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1408 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1410 local_inc(&cpu_buffer->pages_touched);
1412 * Just make sure we have seen our old_write and synchronize
1413 * with any interrupts that come in.
1418 * If the tail page is still the same as what we think
1419 * it is, then it is up to us to update the tail
1422 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1423 /* Zero the write counter */
1424 unsigned long val = old_write & ~RB_WRITE_MASK;
1425 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1428 * This will only succeed if an interrupt did
1429 * not come in and change it. In which case, we
1430 * do not want to modify it.
1432 * We add (void) to let the compiler know that we do not care
1433 * about the return value of these functions. We use the
1434 * cmpxchg to only update if an interrupt did not already
1435 * do it for us. If the cmpxchg fails, we don't care.
1437 (void)local_cmpxchg(&next_page->write, old_write, val);
1438 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1441 * No need to worry about races with clearing out the commit.
1442 * it only can increment when a commit takes place. But that
1443 * only happens in the outer most nested commit.
1445 local_set(&next_page->page->commit, 0);
1447 /* Again, either we update tail_page or an interrupt does */
1448 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1452 static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1453 struct buffer_page *bpage)
1455 unsigned long val = (unsigned long)bpage;
1457 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1464 * rb_check_list - make sure a pointer to a list has the last bits zero
1466 static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1467 struct list_head *list)
1469 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1471 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1477 * rb_check_pages - integrity check of buffer pages
1478 * @cpu_buffer: CPU buffer with pages to test
1480 * As a safety measure we check to make sure the data pages have not
1483 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1485 struct list_head *head = cpu_buffer->pages;
1486 struct buffer_page *bpage, *tmp;
1488 /* Reset the head page if it exists */
1489 if (cpu_buffer->head_page)
1490 rb_set_head_page(cpu_buffer);
1492 rb_head_page_deactivate(cpu_buffer);
1494 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1496 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1499 if (rb_check_list(cpu_buffer, head))
1502 list_for_each_entry_safe(bpage, tmp, head, list) {
1503 if (RB_WARN_ON(cpu_buffer,
1504 bpage->list.next->prev != &bpage->list))
1506 if (RB_WARN_ON(cpu_buffer,
1507 bpage->list.prev->next != &bpage->list))
1509 if (rb_check_list(cpu_buffer, &bpage->list))
1513 rb_head_page_activate(cpu_buffer);
1518 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1519 long nr_pages, struct list_head *pages)
1521 struct buffer_page *bpage, *tmp;
1522 bool user_thread = current->mm != NULL;
1527 * Check if the available memory is there first.
1528 * Note, si_mem_available() only gives us a rough estimate of available
1529 * memory. It may not be accurate. But we don't care, we just want
1530 * to prevent doing any allocation when it is obvious that it is
1531 * not going to succeed.
1533 i = si_mem_available();
1538 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1539 * gracefully without invoking oom-killer and the system is not
1542 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1545 * If a user thread allocates too much, and si_mem_available()
1546 * reports there's enough memory, even though there is not.
1547 * Make sure the OOM killer kills this thread. This can happen
1548 * even with RETRY_MAYFAIL because another task may be doing
1549 * an allocation after this task has taken all memory.
1550 * This is the task the OOM killer needs to take out during this
1551 * loop, even if it was triggered by an allocation somewhere else.
1554 set_current_oom_origin();
1555 for (i = 0; i < nr_pages; i++) {
1558 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1559 mflags, cpu_to_node(cpu_buffer->cpu));
1563 rb_check_bpage(cpu_buffer, bpage);
1565 list_add(&bpage->list, pages);
1567 page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0);
1570 bpage->page = page_address(page);
1571 rb_init_page(bpage->page);
1573 if (user_thread && fatal_signal_pending(current))
1577 clear_current_oom_origin();
1582 list_for_each_entry_safe(bpage, tmp, pages, list) {
1583 list_del_init(&bpage->list);
1584 free_buffer_page(bpage);
1587 clear_current_oom_origin();
1592 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1593 unsigned long nr_pages)
1599 if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1603 * The ring buffer page list is a circular list that does not
1604 * start and end with a list head. All page list items point to
1607 cpu_buffer->pages = pages.next;
1610 cpu_buffer->nr_pages = nr_pages;
1612 rb_check_pages(cpu_buffer);
1617 static struct ring_buffer_per_cpu *
1618 rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1620 struct ring_buffer_per_cpu *cpu_buffer;
1621 struct buffer_page *bpage;
1625 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1626 GFP_KERNEL, cpu_to_node(cpu));
1630 cpu_buffer->cpu = cpu;
1631 cpu_buffer->buffer = buffer;
1632 raw_spin_lock_init(&cpu_buffer->reader_lock);
1633 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1634 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1635 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1636 init_completion(&cpu_buffer->update_done);
1637 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1638 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1639 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1641 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1642 GFP_KERNEL, cpu_to_node(cpu));
1644 goto fail_free_buffer;
1646 rb_check_bpage(cpu_buffer, bpage);
1648 cpu_buffer->reader_page = bpage;
1649 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1651 goto fail_free_reader;
1652 bpage->page = page_address(page);
1653 rb_init_page(bpage->page);
1655 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1656 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1658 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1660 goto fail_free_reader;
1662 cpu_buffer->head_page
1663 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1664 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1666 rb_head_page_activate(cpu_buffer);
1671 free_buffer_page(cpu_buffer->reader_page);
1678 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1680 struct list_head *head = cpu_buffer->pages;
1681 struct buffer_page *bpage, *tmp;
1683 free_buffer_page(cpu_buffer->reader_page);
1685 rb_head_page_deactivate(cpu_buffer);
1688 list_for_each_entry_safe(bpage, tmp, head, list) {
1689 list_del_init(&bpage->list);
1690 free_buffer_page(bpage);
1692 bpage = list_entry(head, struct buffer_page, list);
1693 free_buffer_page(bpage);
1700 * __ring_buffer_alloc - allocate a new ring_buffer
1701 * @size: the size in bytes per cpu that is needed.
1702 * @flags: attributes to set for the ring buffer.
1703 * @key: ring buffer reader_lock_key.
1705 * Currently the only flag that is available is the RB_FL_OVERWRITE
1706 * flag. This flag means that the buffer will overwrite old data
1707 * when the buffer wraps. If this flag is not set, the buffer will
1708 * drop data when the tail hits the head.
1710 struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1711 struct lock_class_key *key)
1713 struct trace_buffer *buffer;
1719 /* keep it in its own cache line */
1720 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1725 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1726 goto fail_free_buffer;
1728 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1729 buffer->flags = flags;
1730 buffer->clock = trace_clock_local;
1731 buffer->reader_lock_key = key;
1733 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1734 init_waitqueue_head(&buffer->irq_work.waiters);
1736 /* need at least two pages */
1740 buffer->cpus = nr_cpu_ids;
1742 bsize = sizeof(void *) * nr_cpu_ids;
1743 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1745 if (!buffer->buffers)
1746 goto fail_free_cpumask;
1748 cpu = raw_smp_processor_id();
1749 cpumask_set_cpu(cpu, buffer->cpumask);
1750 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1751 if (!buffer->buffers[cpu])
1752 goto fail_free_buffers;
1754 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1756 goto fail_free_buffers;
1758 mutex_init(&buffer->mutex);
1763 for_each_buffer_cpu(buffer, cpu) {
1764 if (buffer->buffers[cpu])
1765 rb_free_cpu_buffer(buffer->buffers[cpu]);
1767 kfree(buffer->buffers);
1770 free_cpumask_var(buffer->cpumask);
1776 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1779 * ring_buffer_free - free a ring buffer.
1780 * @buffer: the buffer to free.
1783 ring_buffer_free(struct trace_buffer *buffer)
1787 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1789 for_each_buffer_cpu(buffer, cpu)
1790 rb_free_cpu_buffer(buffer->buffers[cpu]);
1792 kfree(buffer->buffers);
1793 free_cpumask_var(buffer->cpumask);
1797 EXPORT_SYMBOL_GPL(ring_buffer_free);
1799 void ring_buffer_set_clock(struct trace_buffer *buffer,
1802 buffer->clock = clock;
1805 void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1807 buffer->time_stamp_abs = abs;
1810 bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1812 return buffer->time_stamp_abs;
1815 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1817 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1819 return local_read(&bpage->entries) & RB_WRITE_MASK;
1822 static inline unsigned long rb_page_write(struct buffer_page *bpage)
1824 return local_read(&bpage->write) & RB_WRITE_MASK;
1828 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1830 struct list_head *tail_page, *to_remove, *next_page;
1831 struct buffer_page *to_remove_page, *tmp_iter_page;
1832 struct buffer_page *last_page, *first_page;
1833 unsigned long nr_removed;
1834 unsigned long head_bit;
1839 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1840 atomic_inc(&cpu_buffer->record_disabled);
1842 * We don't race with the readers since we have acquired the reader
1843 * lock. We also don't race with writers after disabling recording.
1844 * This makes it easy to figure out the first and the last page to be
1845 * removed from the list. We unlink all the pages in between including
1846 * the first and last pages. This is done in a busy loop so that we
1847 * lose the least number of traces.
1848 * The pages are freed after we restart recording and unlock readers.
1850 tail_page = &cpu_buffer->tail_page->list;
1853 * tail page might be on reader page, we remove the next page
1854 * from the ring buffer
1856 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1857 tail_page = rb_list_head(tail_page->next);
1858 to_remove = tail_page;
1860 /* start of pages to remove */
1861 first_page = list_entry(rb_list_head(to_remove->next),
1862 struct buffer_page, list);
1864 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1865 to_remove = rb_list_head(to_remove)->next;
1866 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1869 next_page = rb_list_head(to_remove)->next;
1872 * Now we remove all pages between tail_page and next_page.
1873 * Make sure that we have head_bit value preserved for the
1876 tail_page->next = (struct list_head *)((unsigned long)next_page |
1878 next_page = rb_list_head(next_page);
1879 next_page->prev = tail_page;
1881 /* make sure pages points to a valid page in the ring buffer */
1882 cpu_buffer->pages = next_page;
1884 /* update head page */
1886 cpu_buffer->head_page = list_entry(next_page,
1887 struct buffer_page, list);
1890 * change read pointer to make sure any read iterators reset
1893 cpu_buffer->read = 0;
1895 /* pages are removed, resume tracing and then free the pages */
1896 atomic_dec(&cpu_buffer->record_disabled);
1897 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1899 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1901 /* last buffer page to remove */
1902 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1904 tmp_iter_page = first_page;
1909 to_remove_page = tmp_iter_page;
1910 rb_inc_page(&tmp_iter_page);
1912 /* update the counters */
1913 page_entries = rb_page_entries(to_remove_page);
1916 * If something was added to this page, it was full
1917 * since it is not the tail page. So we deduct the
1918 * bytes consumed in ring buffer from here.
1919 * Increment overrun to account for the lost events.
1921 local_add(page_entries, &cpu_buffer->overrun);
1922 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1926 * We have already removed references to this list item, just
1927 * free up the buffer_page and its page
1929 free_buffer_page(to_remove_page);
1932 } while (to_remove_page != last_page);
1934 RB_WARN_ON(cpu_buffer, nr_removed);
1936 return nr_removed == 0;
1940 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1942 struct list_head *pages = &cpu_buffer->new_pages;
1943 int retries, success;
1945 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1947 * We are holding the reader lock, so the reader page won't be swapped
1948 * in the ring buffer. Now we are racing with the writer trying to
1949 * move head page and the tail page.
1950 * We are going to adapt the reader page update process where:
1951 * 1. We first splice the start and end of list of new pages between
1952 * the head page and its previous page.
1953 * 2. We cmpxchg the prev_page->next to point from head page to the
1954 * start of new pages list.
1955 * 3. Finally, we update the head->prev to the end of new list.
1957 * We will try this process 10 times, to make sure that we don't keep
1963 struct list_head *head_page, *prev_page, *r;
1964 struct list_head *last_page, *first_page;
1965 struct list_head *head_page_with_bit;
1967 head_page = &rb_set_head_page(cpu_buffer)->list;
1970 prev_page = head_page->prev;
1972 first_page = pages->next;
1973 last_page = pages->prev;
1975 head_page_with_bit = (struct list_head *)
1976 ((unsigned long)head_page | RB_PAGE_HEAD);
1978 last_page->next = head_page_with_bit;
1979 first_page->prev = prev_page;
1981 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1983 if (r == head_page_with_bit) {
1985 * yay, we replaced the page pointer to our new list,
1986 * now, we just have to update to head page's prev
1987 * pointer to point to end of list
1989 head_page->prev = last_page;
1996 INIT_LIST_HEAD(pages);
1998 * If we weren't successful in adding in new pages, warn and stop
2001 RB_WARN_ON(cpu_buffer, !success);
2002 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
2004 /* free pages if they weren't inserted */
2006 struct buffer_page *bpage, *tmp;
2007 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2009 list_del_init(&bpage->list);
2010 free_buffer_page(bpage);
2016 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2020 if (cpu_buffer->nr_pages_to_update > 0)
2021 success = rb_insert_pages(cpu_buffer);
2023 success = rb_remove_pages(cpu_buffer,
2024 -cpu_buffer->nr_pages_to_update);
2027 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2030 static void update_pages_handler(struct work_struct *work)
2032 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2033 struct ring_buffer_per_cpu, update_pages_work);
2034 rb_update_pages(cpu_buffer);
2035 complete(&cpu_buffer->update_done);
2039 * ring_buffer_resize - resize the ring buffer
2040 * @buffer: the buffer to resize.
2041 * @size: the new size.
2042 * @cpu_id: the cpu buffer to resize
2044 * Minimum size is 2 * BUF_PAGE_SIZE.
2046 * Returns 0 on success and < 0 on failure.
2048 int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2051 struct ring_buffer_per_cpu *cpu_buffer;
2052 unsigned long nr_pages;
2056 * Always succeed at resizing a non-existent buffer:
2061 /* Make sure the requested buffer exists */
2062 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2063 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2066 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
2068 /* we need a minimum of two pages */
2072 /* prevent another thread from changing buffer sizes */
2073 mutex_lock(&buffer->mutex);
2076 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2078 * Don't succeed if resizing is disabled, as a reader might be
2079 * manipulating the ring buffer and is expecting a sane state while
2082 for_each_buffer_cpu(buffer, cpu) {
2083 cpu_buffer = buffer->buffers[cpu];
2084 if (atomic_read(&cpu_buffer->resize_disabled)) {
2086 goto out_err_unlock;
2090 /* calculate the pages to update */
2091 for_each_buffer_cpu(buffer, cpu) {
2092 cpu_buffer = buffer->buffers[cpu];
2094 cpu_buffer->nr_pages_to_update = nr_pages -
2095 cpu_buffer->nr_pages;
2097 * nothing more to do for removing pages or no update
2099 if (cpu_buffer->nr_pages_to_update <= 0)
2102 * to add pages, make sure all new pages can be
2103 * allocated without receiving ENOMEM
2105 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2106 if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2107 &cpu_buffer->new_pages)) {
2108 /* not enough memory for new pages */
2116 * Fire off all the required work handlers
2117 * We can't schedule on offline CPUs, but it's not necessary
2118 * since we can change their buffer sizes without any race.
2120 for_each_buffer_cpu(buffer, cpu) {
2121 cpu_buffer = buffer->buffers[cpu];
2122 if (!cpu_buffer->nr_pages_to_update)
2125 /* Can't run something on an offline CPU. */
2126 if (!cpu_online(cpu)) {
2127 rb_update_pages(cpu_buffer);
2128 cpu_buffer->nr_pages_to_update = 0;
2130 schedule_work_on(cpu,
2131 &cpu_buffer->update_pages_work);
2135 /* wait for all the updates to complete */
2136 for_each_buffer_cpu(buffer, cpu) {
2137 cpu_buffer = buffer->buffers[cpu];
2138 if (!cpu_buffer->nr_pages_to_update)
2141 if (cpu_online(cpu))
2142 wait_for_completion(&cpu_buffer->update_done);
2143 cpu_buffer->nr_pages_to_update = 0;
2148 cpu_buffer = buffer->buffers[cpu_id];
2150 if (nr_pages == cpu_buffer->nr_pages)
2154 * Don't succeed if resizing is disabled, as a reader might be
2155 * manipulating the ring buffer and is expecting a sane state while
2158 if (atomic_read(&cpu_buffer->resize_disabled)) {
2160 goto out_err_unlock;
2163 cpu_buffer->nr_pages_to_update = nr_pages -
2164 cpu_buffer->nr_pages;
2166 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2167 if (cpu_buffer->nr_pages_to_update > 0 &&
2168 __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2169 &cpu_buffer->new_pages)) {
2176 /* Can't run something on an offline CPU. */
2177 if (!cpu_online(cpu_id))
2178 rb_update_pages(cpu_buffer);
2180 schedule_work_on(cpu_id,
2181 &cpu_buffer->update_pages_work);
2182 wait_for_completion(&cpu_buffer->update_done);
2185 cpu_buffer->nr_pages_to_update = 0;
2191 * The ring buffer resize can happen with the ring buffer
2192 * enabled, so that the update disturbs the tracing as little
2193 * as possible. But if the buffer is disabled, we do not need
2194 * to worry about that, and we can take the time to verify
2195 * that the buffer is not corrupt.
2197 if (atomic_read(&buffer->record_disabled)) {
2198 atomic_inc(&buffer->record_disabled);
2200 * Even though the buffer was disabled, we must make sure
2201 * that it is truly disabled before calling rb_check_pages.
2202 * There could have been a race between checking
2203 * record_disable and incrementing it.
2206 for_each_buffer_cpu(buffer, cpu) {
2207 cpu_buffer = buffer->buffers[cpu];
2208 rb_check_pages(cpu_buffer);
2210 atomic_dec(&buffer->record_disabled);
2213 mutex_unlock(&buffer->mutex);
2217 for_each_buffer_cpu(buffer, cpu) {
2218 struct buffer_page *bpage, *tmp;
2220 cpu_buffer = buffer->buffers[cpu];
2221 cpu_buffer->nr_pages_to_update = 0;
2223 if (list_empty(&cpu_buffer->new_pages))
2226 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2228 list_del_init(&bpage->list);
2229 free_buffer_page(bpage);
2233 mutex_unlock(&buffer->mutex);
2236 EXPORT_SYMBOL_GPL(ring_buffer_resize);
2238 void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2240 mutex_lock(&buffer->mutex);
2242 buffer->flags |= RB_FL_OVERWRITE;
2244 buffer->flags &= ~RB_FL_OVERWRITE;
2245 mutex_unlock(&buffer->mutex);
2247 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2249 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2251 return bpage->page->data + index;
2254 static __always_inline struct ring_buffer_event *
2255 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2257 return __rb_page_index(cpu_buffer->reader_page,
2258 cpu_buffer->reader_page->read);
2261 static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
2263 return local_read(&bpage->page->commit);
2266 static struct ring_buffer_event *
2267 rb_iter_head_event(struct ring_buffer_iter *iter)
2269 struct ring_buffer_event *event;
2270 struct buffer_page *iter_head_page = iter->head_page;
2271 unsigned long commit;
2274 if (iter->head != iter->next_event)
2278 * When the writer goes across pages, it issues a cmpxchg which
2279 * is a mb(), which will synchronize with the rmb here.
2280 * (see rb_tail_page_update() and __rb_reserve_next())
2282 commit = rb_page_commit(iter_head_page);
2284 event = __rb_page_index(iter_head_page, iter->head);
2285 length = rb_event_length(event);
2288 * READ_ONCE() doesn't work on functions and we don't want the
2289 * compiler doing any crazy optimizations with length.
2293 if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
2294 /* Writer corrupted the read? */
2297 memcpy(iter->event, event, length);
2299 * If the page stamp is still the same after this rmb() then the
2300 * event was safely copied without the writer entering the page.
2304 /* Make sure the page didn't change since we read this */
2305 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2306 commit > rb_page_commit(iter_head_page))
2309 iter->next_event = iter->head + length;
2312 /* Reset to the beginning */
2313 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2315 iter->next_event = 0;
2316 iter->missed_events = 1;
2320 /* Size is determined by what has been committed */
2321 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2323 return rb_page_commit(bpage);
2326 static __always_inline unsigned
2327 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2329 return rb_page_commit(cpu_buffer->commit_page);
2332 static __always_inline unsigned
2333 rb_event_index(struct ring_buffer_event *event)
2335 unsigned long addr = (unsigned long)event;
2337 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
2340 static void rb_inc_iter(struct ring_buffer_iter *iter)
2342 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2345 * The iterator could be on the reader page (it starts there).
2346 * But the head could have moved, since the reader was
2347 * found. Check for this case and assign the iterator
2348 * to the head page instead of next.
2350 if (iter->head_page == cpu_buffer->reader_page)
2351 iter->head_page = rb_set_head_page(cpu_buffer);
2353 rb_inc_page(&iter->head_page);
2355 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2357 iter->next_event = 0;
2361 * rb_handle_head_page - writer hit the head page
2363 * Returns: +1 to retry page
2368 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2369 struct buffer_page *tail_page,
2370 struct buffer_page *next_page)
2372 struct buffer_page *new_head;
2377 entries = rb_page_entries(next_page);
2380 * The hard part is here. We need to move the head
2381 * forward, and protect against both readers on
2382 * other CPUs and writers coming in via interrupts.
2384 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2388 * type can be one of four:
2389 * NORMAL - an interrupt already moved it for us
2390 * HEAD - we are the first to get here.
2391 * UPDATE - we are the interrupt interrupting
2393 * MOVED - a reader on another CPU moved the next
2394 * pointer to its reader page. Give up
2401 * We changed the head to UPDATE, thus
2402 * it is our responsibility to update
2405 local_add(entries, &cpu_buffer->overrun);
2406 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2409 * The entries will be zeroed out when we move the
2413 /* still more to do */
2416 case RB_PAGE_UPDATE:
2418 * This is an interrupt that interrupt the
2419 * previous update. Still more to do.
2422 case RB_PAGE_NORMAL:
2424 * An interrupt came in before the update
2425 * and processed this for us.
2426 * Nothing left to do.
2431 * The reader is on another CPU and just did
2432 * a swap with our next_page.
2437 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2442 * Now that we are here, the old head pointer is
2443 * set to UPDATE. This will keep the reader from
2444 * swapping the head page with the reader page.
2445 * The reader (on another CPU) will spin till
2448 * We just need to protect against interrupts
2449 * doing the job. We will set the next pointer
2450 * to HEAD. After that, we set the old pointer
2451 * to NORMAL, but only if it was HEAD before.
2452 * otherwise we are an interrupt, and only
2453 * want the outer most commit to reset it.
2455 new_head = next_page;
2456 rb_inc_page(&new_head);
2458 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2462 * Valid returns are:
2463 * HEAD - an interrupt came in and already set it.
2464 * NORMAL - One of two things:
2465 * 1) We really set it.
2466 * 2) A bunch of interrupts came in and moved
2467 * the page forward again.
2471 case RB_PAGE_NORMAL:
2475 RB_WARN_ON(cpu_buffer, 1);
2480 * It is possible that an interrupt came in,
2481 * set the head up, then more interrupts came in
2482 * and moved it again. When we get back here,
2483 * the page would have been set to NORMAL but we
2484 * just set it back to HEAD.
2486 * How do you detect this? Well, if that happened
2487 * the tail page would have moved.
2489 if (ret == RB_PAGE_NORMAL) {
2490 struct buffer_page *buffer_tail_page;
2492 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2494 * If the tail had moved passed next, then we need
2495 * to reset the pointer.
2497 if (buffer_tail_page != tail_page &&
2498 buffer_tail_page != next_page)
2499 rb_head_page_set_normal(cpu_buffer, new_head,
2505 * If this was the outer most commit (the one that
2506 * changed the original pointer from HEAD to UPDATE),
2507 * then it is up to us to reset it to NORMAL.
2509 if (type == RB_PAGE_HEAD) {
2510 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2513 if (RB_WARN_ON(cpu_buffer,
2514 ret != RB_PAGE_UPDATE))
2522 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2523 unsigned long tail, struct rb_event_info *info)
2525 struct buffer_page *tail_page = info->tail_page;
2526 struct ring_buffer_event *event;
2527 unsigned long length = info->length;
2530 * Only the event that crossed the page boundary
2531 * must fill the old tail_page with padding.
2533 if (tail >= BUF_PAGE_SIZE) {
2535 * If the page was filled, then we still need
2536 * to update the real_end. Reset it to zero
2537 * and the reader will ignore it.
2539 if (tail == BUF_PAGE_SIZE)
2540 tail_page->real_end = 0;
2542 local_sub(length, &tail_page->write);
2546 event = __rb_page_index(tail_page, tail);
2548 /* account for padding bytes */
2549 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2552 * Save the original length to the meta data.
2553 * This will be used by the reader to add lost event
2556 tail_page->real_end = tail;
2559 * If this event is bigger than the minimum size, then
2560 * we need to be careful that we don't subtract the
2561 * write counter enough to allow another writer to slip
2563 * We put in a discarded commit instead, to make sure
2564 * that this space is not used again.
2566 * If we are less than the minimum size, we don't need to
2569 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2570 /* No room for any events */
2572 /* Mark the rest of the page with padding */
2573 rb_event_set_padding(event);
2575 /* Set the write back to the previous setting */
2576 local_sub(length, &tail_page->write);
2580 /* Put in a discarded event */
2581 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2582 event->type_len = RINGBUF_TYPE_PADDING;
2583 /* time delta must be non zero */
2584 event->time_delta = 1;
2586 /* Set write to end of buffer */
2587 length = (tail + length) - BUF_PAGE_SIZE;
2588 local_sub(length, &tail_page->write);
2591 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2594 * This is the slow path, force gcc not to inline it.
2596 static noinline struct ring_buffer_event *
2597 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2598 unsigned long tail, struct rb_event_info *info)
2600 struct buffer_page *tail_page = info->tail_page;
2601 struct buffer_page *commit_page = cpu_buffer->commit_page;
2602 struct trace_buffer *buffer = cpu_buffer->buffer;
2603 struct buffer_page *next_page;
2606 next_page = tail_page;
2608 rb_inc_page(&next_page);
2611 * If for some reason, we had an interrupt storm that made
2612 * it all the way around the buffer, bail, and warn
2615 if (unlikely(next_page == commit_page)) {
2616 local_inc(&cpu_buffer->commit_overrun);
2621 * This is where the fun begins!
2623 * We are fighting against races between a reader that
2624 * could be on another CPU trying to swap its reader
2625 * page with the buffer head.
2627 * We are also fighting against interrupts coming in and
2628 * moving the head or tail on us as well.
2630 * If the next page is the head page then we have filled
2631 * the buffer, unless the commit page is still on the
2634 if (rb_is_head_page(next_page, &tail_page->list)) {
2637 * If the commit is not on the reader page, then
2638 * move the header page.
2640 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2642 * If we are not in overwrite mode,
2643 * this is easy, just stop here.
2645 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2646 local_inc(&cpu_buffer->dropped_events);
2650 ret = rb_handle_head_page(cpu_buffer,
2659 * We need to be careful here too. The
2660 * commit page could still be on the reader
2661 * page. We could have a small buffer, and
2662 * have filled up the buffer with events
2663 * from interrupts and such, and wrapped.
2665 * Note, if the tail page is also on the
2666 * reader_page, we let it move out.
2668 if (unlikely((cpu_buffer->commit_page !=
2669 cpu_buffer->tail_page) &&
2670 (cpu_buffer->commit_page ==
2671 cpu_buffer->reader_page))) {
2672 local_inc(&cpu_buffer->commit_overrun);
2678 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2682 rb_reset_tail(cpu_buffer, tail, info);
2684 /* Commit what we have for now. */
2685 rb_end_commit(cpu_buffer);
2686 /* rb_end_commit() decs committing */
2687 local_inc(&cpu_buffer->committing);
2689 /* fail and let the caller try again */
2690 return ERR_PTR(-EAGAIN);
2694 rb_reset_tail(cpu_buffer, tail, info);
2700 static struct ring_buffer_event *
2701 rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2704 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2706 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2708 /* Not the first event on the page, or not delta? */
2709 if (abs || rb_event_index(event)) {
2710 event->time_delta = delta & TS_MASK;
2711 event->array[0] = delta >> TS_SHIFT;
2713 /* nope, just zero it */
2714 event->time_delta = 0;
2715 event->array[0] = 0;
2718 return skip_time_extend(event);
2721 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2722 static inline bool sched_clock_stable(void)
2729 rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2730 struct rb_event_info *info)
2734 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2735 (unsigned long long)info->delta,
2736 (unsigned long long)info->ts,
2737 (unsigned long long)info->before,
2738 (unsigned long long)info->after,
2739 (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
2740 sched_clock_stable() ? "" :
2741 "If you just came from a suspend/resume,\n"
2742 "please switch to the trace global clock:\n"
2743 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2744 "or add trace_clock=global to the kernel command line\n");
2747 static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2748 struct ring_buffer_event **event,
2749 struct rb_event_info *info,
2751 unsigned int *length)
2753 bool abs = info->add_timestamp &
2754 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2756 if (unlikely(info->delta > (1ULL << 59))) {
2757 /* did the clock go backwards */
2758 if (info->before == info->after && info->before > info->ts) {
2759 /* not interrupted */
2763 * This is possible with a recalibrating of the TSC.
2764 * Do not produce a call stack, but just report it.
2768 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2769 info->before, info->ts);
2772 rb_check_timestamp(cpu_buffer, info);
2776 *event = rb_add_time_stamp(*event, info->delta, abs);
2777 *length -= RB_LEN_TIME_EXTEND;
2782 * rb_update_event - update event type and data
2783 * @cpu_buffer: The per cpu buffer of the @event
2784 * @event: the event to update
2785 * @info: The info to update the @event with (contains length and delta)
2787 * Update the type and data fields of the @event. The length
2788 * is the actual size that is written to the ring buffer,
2789 * and with this, we can determine what to place into the
2793 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2794 struct ring_buffer_event *event,
2795 struct rb_event_info *info)
2797 unsigned length = info->length;
2798 u64 delta = info->delta;
2799 unsigned int nest = local_read(&cpu_buffer->committing) - 1;
2801 if (!WARN_ON_ONCE(nest >= MAX_NEST))
2802 cpu_buffer->event_stamp[nest] = info->ts;
2805 * If we need to add a timestamp, then we
2806 * add it to the start of the reserved space.
2808 if (unlikely(info->add_timestamp))
2809 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2811 event->time_delta = delta;
2812 length -= RB_EVNT_HDR_SIZE;
2813 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2814 event->type_len = 0;
2815 event->array[0] = length;
2817 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2820 static unsigned rb_calculate_event_length(unsigned length)
2822 struct ring_buffer_event event; /* Used only for sizeof array */
2824 /* zero length can cause confusions */
2828 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2829 length += sizeof(event.array[0]);
2831 length += RB_EVNT_HDR_SIZE;
2832 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2835 * In case the time delta is larger than the 27 bits for it
2836 * in the header, we need to add a timestamp. If another
2837 * event comes in when trying to discard this one to increase
2838 * the length, then the timestamp will be added in the allocated
2839 * space of this event. If length is bigger than the size needed
2840 * for the TIME_EXTEND, then padding has to be used. The events
2841 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2842 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2843 * As length is a multiple of 4, we only need to worry if it
2844 * is 12 (RB_LEN_TIME_EXTEND + 4).
2846 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2847 length += RB_ALIGNMENT;
2852 static u64 rb_time_delta(struct ring_buffer_event *event)
2854 switch (event->type_len) {
2855 case RINGBUF_TYPE_PADDING:
2858 case RINGBUF_TYPE_TIME_EXTEND:
2859 return rb_event_time_stamp(event);
2861 case RINGBUF_TYPE_TIME_STAMP:
2864 case RINGBUF_TYPE_DATA:
2865 return event->time_delta;
2872 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2873 struct ring_buffer_event *event)
2875 unsigned long new_index, old_index;
2876 struct buffer_page *bpage;
2877 unsigned long index;
2882 new_index = rb_event_index(event);
2883 old_index = new_index + rb_event_ts_length(event);
2884 addr = (unsigned long)event;
2887 bpage = READ_ONCE(cpu_buffer->tail_page);
2889 delta = rb_time_delta(event);
2891 if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
2894 /* Make sure the write stamp is read before testing the location */
2897 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2898 unsigned long write_mask =
2899 local_read(&bpage->write) & ~RB_WRITE_MASK;
2900 unsigned long event_length = rb_event_length(event);
2902 /* Something came in, can't discard */
2903 if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
2904 write_stamp, write_stamp - delta))
2908 * It's possible that the event time delta is zero
2909 * (has the same time stamp as the previous event)
2910 * in which case write_stamp and before_stamp could
2911 * be the same. In such a case, force before_stamp
2912 * to be different than write_stamp. It doesn't
2913 * matter what it is, as long as its different.
2916 rb_time_set(&cpu_buffer->before_stamp, 0);
2919 * If an event were to come in now, it would see that the
2920 * write_stamp and the before_stamp are different, and assume
2921 * that this event just added itself before updating
2922 * the write stamp. The interrupting event will fix the
2923 * write stamp for us, and use the before stamp as its delta.
2927 * This is on the tail page. It is possible that
2928 * a write could come in and move the tail page
2929 * and write to the next page. That is fine
2930 * because we just shorten what is on this page.
2932 old_index += write_mask;
2933 new_index += write_mask;
2934 index = local_cmpxchg(&bpage->write, old_index, new_index);
2935 if (index == old_index) {
2936 /* update counters */
2937 local_sub(event_length, &cpu_buffer->entries_bytes);
2942 /* could not discard */
2946 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2948 local_inc(&cpu_buffer->committing);
2949 local_inc(&cpu_buffer->commits);
2952 static __always_inline void
2953 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2955 unsigned long max_count;
2958 * We only race with interrupts and NMIs on this CPU.
2959 * If we own the commit event, then we can commit
2960 * all others that interrupted us, since the interruptions
2961 * are in stack format (they finish before they come
2962 * back to us). This allows us to do a simple loop to
2963 * assign the commit to the tail.
2966 max_count = cpu_buffer->nr_pages * 100;
2968 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2969 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2971 if (RB_WARN_ON(cpu_buffer,
2972 rb_is_reader_page(cpu_buffer->tail_page)))
2974 local_set(&cpu_buffer->commit_page->page->commit,
2975 rb_page_write(cpu_buffer->commit_page));
2976 rb_inc_page(&cpu_buffer->commit_page);
2977 /* add barrier to keep gcc from optimizing too much */
2980 while (rb_commit_index(cpu_buffer) !=
2981 rb_page_write(cpu_buffer->commit_page)) {
2983 local_set(&cpu_buffer->commit_page->page->commit,
2984 rb_page_write(cpu_buffer->commit_page));
2985 RB_WARN_ON(cpu_buffer,
2986 local_read(&cpu_buffer->commit_page->page->commit) &
2991 /* again, keep gcc from optimizing */
2995 * If an interrupt came in just after the first while loop
2996 * and pushed the tail page forward, we will be left with
2997 * a dangling commit that will never go forward.
2999 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3003 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3005 unsigned long commits;
3007 if (RB_WARN_ON(cpu_buffer,
3008 !local_read(&cpu_buffer->committing)))
3012 commits = local_read(&cpu_buffer->commits);
3013 /* synchronize with interrupts */
3015 if (local_read(&cpu_buffer->committing) == 1)
3016 rb_set_commit_to_write(cpu_buffer);
3018 local_dec(&cpu_buffer->committing);
3020 /* synchronize with interrupts */
3024 * Need to account for interrupts coming in between the
3025 * updating of the commit page and the clearing of the
3026 * committing counter.
3028 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3029 !local_read(&cpu_buffer->committing)) {
3030 local_inc(&cpu_buffer->committing);
3035 static inline void rb_event_discard(struct ring_buffer_event *event)
3037 if (extended_time(event))
3038 event = skip_time_extend(event);
3040 /* array[0] holds the actual length for the discarded event */
3041 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3042 event->type_len = RINGBUF_TYPE_PADDING;
3043 /* time delta must be non zero */
3044 if (!event->time_delta)
3045 event->time_delta = 1;
3048 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
3049 struct ring_buffer_event *event)
3051 local_inc(&cpu_buffer->entries);
3052 rb_end_commit(cpu_buffer);
3055 static __always_inline void
3056 rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3062 if (buffer->irq_work.waiters_pending) {
3063 buffer->irq_work.waiters_pending = false;
3064 /* irq_work_queue() supplies it's own memory barriers */
3065 irq_work_queue(&buffer->irq_work.work);
3068 if (cpu_buffer->irq_work.waiters_pending) {
3069 cpu_buffer->irq_work.waiters_pending = false;
3070 /* irq_work_queue() supplies it's own memory barriers */
3071 irq_work_queue(&cpu_buffer->irq_work.work);
3074 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3077 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3080 if (!cpu_buffer->irq_work.full_waiters_pending)
3083 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3085 full = cpu_buffer->shortest_full;
3086 nr_pages = cpu_buffer->nr_pages;
3087 dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
3088 if (full && nr_pages && (dirty * 100) <= full * nr_pages)
3091 cpu_buffer->irq_work.wakeup_full = true;
3092 cpu_buffer->irq_work.full_waiters_pending = false;
3093 /* irq_work_queue() supplies it's own memory barriers */
3094 irq_work_queue(&cpu_buffer->irq_work.work);
3097 #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3098 # define do_ring_buffer_record_recursion() \
3099 do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3101 # define do_ring_buffer_record_recursion() do { } while (0)
3105 * The lock and unlock are done within a preempt disable section.
3106 * The current_context per_cpu variable can only be modified
3107 * by the current task between lock and unlock. But it can
3108 * be modified more than once via an interrupt. To pass this
3109 * information from the lock to the unlock without having to
3110 * access the 'in_interrupt()' functions again (which do show
3111 * a bit of overhead in something as critical as function tracing,
3112 * we use a bitmask trick.
3114 * bit 1 = NMI context
3115 * bit 2 = IRQ context
3116 * bit 3 = SoftIRQ context
3117 * bit 4 = normal context.
3119 * This works because this is the order of contexts that can
3120 * preempt other contexts. A SoftIRQ never preempts an IRQ
3123 * When the context is determined, the corresponding bit is
3124 * checked and set (if it was set, then a recursion of that context
3127 * On unlock, we need to clear this bit. To do so, just subtract
3128 * 1 from the current_context and AND it to itself.
3132 * 101 & 100 = 100 (clearing bit zero)
3135 * 1010 & 1001 = 1000 (clearing bit 1)
3137 * The least significant bit can be cleared this way, and it
3138 * just so happens that it is the same bit corresponding to
3139 * the current context.
3141 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3142 * is set when a recursion is detected at the current context, and if
3143 * the TRANSITION bit is already set, it will fail the recursion.
3144 * This is needed because there's a lag between the changing of
3145 * interrupt context and updating the preempt count. In this case,
3146 * a false positive will be found. To handle this, one extra recursion
3147 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3148 * bit is already set, then it is considered a recursion and the function
3149 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3151 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3152 * to be cleared. Even if it wasn't the context that set it. That is,
3153 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3154 * is called before preempt_count() is updated, since the check will
3155 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3156 * NMI then comes in, it will set the NMI bit, but when the NMI code
3157 * does the trace_recursive_unlock() it will clear the TRANSITION bit
3158 * and leave the NMI bit set. But this is fine, because the interrupt
3159 * code that set the TRANSITION bit will then clear the NMI bit when it
3160 * calls trace_recursive_unlock(). If another NMI comes in, it will
3161 * set the TRANSITION bit and continue.
3163 * Note: The TRANSITION bit only handles a single transition between context.
3166 static __always_inline int
3167 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3169 unsigned int val = cpu_buffer->current_context;
3170 unsigned long pc = preempt_count();
3173 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
3174 bit = RB_CTX_NORMAL;
3176 bit = pc & NMI_MASK ? RB_CTX_NMI :
3177 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
3179 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3181 * It is possible that this was called by transitioning
3182 * between interrupt context, and preempt_count() has not
3183 * been updated yet. In this case, use the TRANSITION bit.
3185 bit = RB_CTX_TRANSITION;
3186 if (val & (1 << (bit + cpu_buffer->nest))) {
3187 do_ring_buffer_record_recursion();
3192 val |= (1 << (bit + cpu_buffer->nest));
3193 cpu_buffer->current_context = val;
3198 static __always_inline void
3199 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3201 cpu_buffer->current_context &=
3202 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3205 /* The recursive locking above uses 5 bits */
3206 #define NESTED_BITS 5
3209 * ring_buffer_nest_start - Allow to trace while nested
3210 * @buffer: The ring buffer to modify
3212 * The ring buffer has a safety mechanism to prevent recursion.
3213 * But there may be a case where a trace needs to be done while
3214 * tracing something else. In this case, calling this function
3215 * will allow this function to nest within a currently active
3216 * ring_buffer_lock_reserve().
3218 * Call this function before calling another ring_buffer_lock_reserve() and
3219 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3221 void ring_buffer_nest_start(struct trace_buffer *buffer)
3223 struct ring_buffer_per_cpu *cpu_buffer;
3226 /* Enabled by ring_buffer_nest_end() */
3227 preempt_disable_notrace();
3228 cpu = raw_smp_processor_id();
3229 cpu_buffer = buffer->buffers[cpu];
3230 /* This is the shift value for the above recursive locking */
3231 cpu_buffer->nest += NESTED_BITS;
3235 * ring_buffer_nest_end - Allow to trace while nested
3236 * @buffer: The ring buffer to modify
3238 * Must be called after ring_buffer_nest_start() and after the
3239 * ring_buffer_unlock_commit().
3241 void ring_buffer_nest_end(struct trace_buffer *buffer)
3243 struct ring_buffer_per_cpu *cpu_buffer;
3246 /* disabled by ring_buffer_nest_start() */
3247 cpu = raw_smp_processor_id();
3248 cpu_buffer = buffer->buffers[cpu];
3249 /* This is the shift value for the above recursive locking */
3250 cpu_buffer->nest -= NESTED_BITS;
3251 preempt_enable_notrace();
3255 * ring_buffer_unlock_commit - commit a reserved
3256 * @buffer: The buffer to commit to
3257 * @event: The event pointer to commit.
3259 * This commits the data to the ring buffer, and releases any locks held.
3261 * Must be paired with ring_buffer_lock_reserve.
3263 int ring_buffer_unlock_commit(struct trace_buffer *buffer,
3264 struct ring_buffer_event *event)
3266 struct ring_buffer_per_cpu *cpu_buffer;
3267 int cpu = raw_smp_processor_id();
3269 cpu_buffer = buffer->buffers[cpu];
3271 rb_commit(cpu_buffer, event);
3273 rb_wakeups(buffer, cpu_buffer);
3275 trace_recursive_unlock(cpu_buffer);
3277 preempt_enable_notrace();
3281 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3283 /* Special value to validate all deltas on a page. */
3284 #define CHECK_FULL_PAGE 1L
3286 #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3287 static void dump_buffer_page(struct buffer_data_page *bpage,
3288 struct rb_event_info *info,
3291 struct ring_buffer_event *event;
3295 ts = bpage->time_stamp;
3296 pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3298 for (e = 0; e < tail; e += rb_event_length(event)) {
3300 event = (struct ring_buffer_event *)(bpage->data + e);
3302 switch (event->type_len) {
3304 case RINGBUF_TYPE_TIME_EXTEND:
3305 delta = rb_event_time_stamp(event);
3307 pr_warn(" [%lld] delta:%lld TIME EXTEND\n", ts, delta);
3310 case RINGBUF_TYPE_TIME_STAMP:
3311 delta = rb_event_time_stamp(event);
3313 pr_warn(" [%lld] absolute:%lld TIME STAMP\n", ts, delta);
3316 case RINGBUF_TYPE_PADDING:
3317 ts += event->time_delta;
3318 pr_warn(" [%lld] delta:%d PADDING\n", ts, event->time_delta);
3321 case RINGBUF_TYPE_DATA:
3322 ts += event->time_delta;
3323 pr_warn(" [%lld] delta:%d\n", ts, event->time_delta);
3332 static DEFINE_PER_CPU(atomic_t, checking);
3333 static atomic_t ts_dump;
3336 * Check if the current event time stamp matches the deltas on
3339 static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3340 struct rb_event_info *info,
3343 struct ring_buffer_event *event;
3344 struct buffer_data_page *bpage;
3349 bpage = info->tail_page->page;
3351 if (tail == CHECK_FULL_PAGE) {
3353 tail = local_read(&bpage->commit);
3354 } else if (info->add_timestamp &
3355 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3356 /* Ignore events with absolute time stamps */
3361 * Do not check the first event (skip possible extends too).
3362 * Also do not check if previous events have not been committed.
3364 if (tail <= 8 || tail > local_read(&bpage->commit))
3368 * If this interrupted another event,
3370 if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3373 ts = bpage->time_stamp;
3375 for (e = 0; e < tail; e += rb_event_length(event)) {
3377 event = (struct ring_buffer_event *)(bpage->data + e);
3379 switch (event->type_len) {
3381 case RINGBUF_TYPE_TIME_EXTEND:
3382 delta = rb_event_time_stamp(event);
3386 case RINGBUF_TYPE_TIME_STAMP:
3387 delta = rb_event_time_stamp(event);
3391 case RINGBUF_TYPE_PADDING:
3392 if (event->time_delta == 1)
3395 case RINGBUF_TYPE_DATA:
3396 ts += event->time_delta;
3400 RB_WARN_ON(cpu_buffer, 1);
3403 if ((full && ts > info->ts) ||
3404 (!full && ts + info->delta != info->ts)) {
3405 /* If another report is happening, ignore this one */
3406 if (atomic_inc_return(&ts_dump) != 1) {
3407 atomic_dec(&ts_dump);
3410 atomic_inc(&cpu_buffer->record_disabled);
3411 /* There's some cases in boot up that this can happen */
3412 WARN_ON_ONCE(system_state != SYSTEM_BOOTING);
3413 pr_warn("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s\n",
3415 ts + info->delta, info->ts, info->delta,
3416 info->before, info->after,
3417 full ? " (full)" : "");
3418 dump_buffer_page(bpage, info, tail);
3419 atomic_dec(&ts_dump);
3420 /* Do not re-enable checking */
3424 atomic_dec(this_cpu_ptr(&checking));
3427 static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3428 struct rb_event_info *info,
3432 #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3434 static struct ring_buffer_event *
3435 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3436 struct rb_event_info *info)
3438 struct ring_buffer_event *event;
3439 struct buffer_page *tail_page;
3440 unsigned long tail, write, w;
3444 /* Don't let the compiler play games with cpu_buffer->tail_page */
3445 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3447 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3449 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3450 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3452 info->ts = rb_time_stamp(cpu_buffer->buffer);
3454 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3455 info->delta = info->ts;
3458 * If interrupting an event time update, we may need an
3459 * absolute timestamp.
3460 * Don't bother if this is the start of a new page (w == 0).
3462 if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
3463 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3464 info->length += RB_LEN_TIME_EXTEND;
3466 info->delta = info->ts - info->after;
3467 if (unlikely(test_time_stamp(info->delta))) {
3468 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3469 info->length += RB_LEN_TIME_EXTEND;
3474 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3476 /*C*/ write = local_add_return(info->length, &tail_page->write);
3478 /* set write to only the index of the write */
3479 write &= RB_WRITE_MASK;
3481 tail = write - info->length;
3483 /* See if we shot pass the end of this buffer page */
3484 if (unlikely(write > BUF_PAGE_SIZE)) {
3485 /* before and after may now different, fix it up*/
3486 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3487 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3488 if (a_ok && b_ok && info->before != info->after)
3489 (void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
3490 info->before, info->after);
3492 check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3493 return rb_move_tail(cpu_buffer, tail, info);
3496 if (likely(tail == w)) {
3500 /* Nothing interrupted us between A and C */
3501 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3503 /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
3504 RB_WARN_ON(cpu_buffer, !s_ok);
3505 if (likely(!(info->add_timestamp &
3506 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3507 /* This did not interrupt any time update */
3508 info->delta = info->ts - info->after;
3510 /* Just use full timestamp for interrupting event */
3511 info->delta = info->ts;
3513 check_buffer(cpu_buffer, info, tail);
3514 if (unlikely(info->ts != save_before)) {
3515 /* SLOW PATH - Interrupted between C and E */
3517 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3518 RB_WARN_ON(cpu_buffer, !a_ok);
3520 /* Write stamp must only go forward */
3521 if (save_before > info->after) {
3523 * We do not care about the result, only that
3524 * it gets updated atomically.
3526 (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
3527 info->after, save_before);
3532 /* SLOW PATH - Interrupted between A and C */
3533 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3534 /* Was interrupted before here, write_stamp must be valid */
3535 RB_WARN_ON(cpu_buffer, !a_ok);
3536 ts = rb_time_stamp(cpu_buffer->buffer);
3538 /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3540 rb_time_cmpxchg(&cpu_buffer->write_stamp,
3542 /* Nothing came after this event between C and E */
3543 info->delta = ts - info->after;
3546 * Interrupted between C and E:
3547 * Lost the previous events time stamp. Just set the
3548 * delta to zero, and this will be the same time as
3549 * the event this event interrupted. And the events that
3550 * came after this will still be correct (as they would
3551 * have built their delta on the previous event.
3556 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3560 * If this is the first commit on the page, then it has the same
3561 * timestamp as the page itself.
3563 if (unlikely(!tail && !(info->add_timestamp &
3564 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3567 /* We reserved something on the buffer */
3569 event = __rb_page_index(tail_page, tail);
3570 rb_update_event(cpu_buffer, event, info);
3572 local_inc(&tail_page->entries);
3575 * If this is the first commit on the page, then update
3578 if (unlikely(!tail))
3579 tail_page->page->time_stamp = info->ts;
3581 /* account for these added bytes */
3582 local_add(info->length, &cpu_buffer->entries_bytes);
3587 static __always_inline struct ring_buffer_event *
3588 rb_reserve_next_event(struct trace_buffer *buffer,
3589 struct ring_buffer_per_cpu *cpu_buffer,
3590 unsigned long length)
3592 struct ring_buffer_event *event;
3593 struct rb_event_info info;
3597 rb_start_commit(cpu_buffer);
3598 /* The commit page can not change after this */
3600 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3602 * Due to the ability to swap a cpu buffer from a buffer
3603 * it is possible it was swapped before we committed.
3604 * (committing stops a swap). We check for it here and
3605 * if it happened, we have to fail the write.
3608 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3609 local_dec(&cpu_buffer->committing);
3610 local_dec(&cpu_buffer->commits);
3615 info.length = rb_calculate_event_length(length);
3617 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3618 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3619 info.length += RB_LEN_TIME_EXTEND;
3621 add_ts_default = RB_ADD_STAMP_NONE;
3625 info.add_timestamp = add_ts_default;
3629 * We allow for interrupts to reenter here and do a trace.
3630 * If one does, it will cause this original code to loop
3631 * back here. Even with heavy interrupts happening, this
3632 * should only happen a few times in a row. If this happens
3633 * 1000 times in a row, there must be either an interrupt
3634 * storm or we have something buggy.
3637 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3640 event = __rb_reserve_next(cpu_buffer, &info);
3642 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3643 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3644 info.length -= RB_LEN_TIME_EXTEND;
3651 rb_end_commit(cpu_buffer);
3656 * ring_buffer_lock_reserve - reserve a part of the buffer
3657 * @buffer: the ring buffer to reserve from
3658 * @length: the length of the data to reserve (excluding event header)
3660 * Returns a reserved event on the ring buffer to copy directly to.
3661 * The user of this interface will need to get the body to write into
3662 * and can use the ring_buffer_event_data() interface.
3664 * The length is the length of the data needed, not the event length
3665 * which also includes the event header.
3667 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3668 * If NULL is returned, then nothing has been allocated or locked.
3670 struct ring_buffer_event *
3671 ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3673 struct ring_buffer_per_cpu *cpu_buffer;
3674 struct ring_buffer_event *event;
3677 /* If we are tracing schedule, we don't want to recurse */
3678 preempt_disable_notrace();
3680 if (unlikely(atomic_read(&buffer->record_disabled)))
3683 cpu = raw_smp_processor_id();
3685 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3688 cpu_buffer = buffer->buffers[cpu];
3690 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3693 if (unlikely(length > BUF_MAX_DATA_SIZE))
3696 if (unlikely(trace_recursive_lock(cpu_buffer)))
3699 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3706 trace_recursive_unlock(cpu_buffer);
3708 preempt_enable_notrace();
3711 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3714 * Decrement the entries to the page that an event is on.
3715 * The event does not even need to exist, only the pointer
3716 * to the page it is on. This may only be called before the commit
3720 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3721 struct ring_buffer_event *event)
3723 unsigned long addr = (unsigned long)event;
3724 struct buffer_page *bpage = cpu_buffer->commit_page;
3725 struct buffer_page *start;
3729 /* Do the likely case first */
3730 if (likely(bpage->page == (void *)addr)) {
3731 local_dec(&bpage->entries);
3736 * Because the commit page may be on the reader page we
3737 * start with the next page and check the end loop there.
3739 rb_inc_page(&bpage);
3742 if (bpage->page == (void *)addr) {
3743 local_dec(&bpage->entries);
3746 rb_inc_page(&bpage);
3747 } while (bpage != start);
3749 /* commit not part of this buffer?? */
3750 RB_WARN_ON(cpu_buffer, 1);
3754 * ring_buffer_discard_commit - discard an event that has not been committed
3755 * @buffer: the ring buffer
3756 * @event: non committed event to discard
3758 * Sometimes an event that is in the ring buffer needs to be ignored.
3759 * This function lets the user discard an event in the ring buffer
3760 * and then that event will not be read later.
3762 * This function only works if it is called before the item has been
3763 * committed. It will try to free the event from the ring buffer
3764 * if another event has not been added behind it.
3766 * If another event has been added behind it, it will set the event
3767 * up as discarded, and perform the commit.
3769 * If this function is called, do not call ring_buffer_unlock_commit on
3772 void ring_buffer_discard_commit(struct trace_buffer *buffer,
3773 struct ring_buffer_event *event)
3775 struct ring_buffer_per_cpu *cpu_buffer;
3778 /* The event is discarded regardless */
3779 rb_event_discard(event);
3781 cpu = smp_processor_id();
3782 cpu_buffer = buffer->buffers[cpu];
3785 * This must only be called if the event has not been
3786 * committed yet. Thus we can assume that preemption
3787 * is still disabled.
3789 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3791 rb_decrement_entry(cpu_buffer, event);
3792 if (rb_try_to_discard(cpu_buffer, event))
3796 rb_end_commit(cpu_buffer);
3798 trace_recursive_unlock(cpu_buffer);
3800 preempt_enable_notrace();
3803 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3806 * ring_buffer_write - write data to the buffer without reserving
3807 * @buffer: The ring buffer to write to.
3808 * @length: The length of the data being written (excluding the event header)
3809 * @data: The data to write to the buffer.
3811 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3812 * one function. If you already have the data to write to the buffer, it
3813 * may be easier to simply call this function.
3815 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3816 * and not the length of the event which would hold the header.
3818 int ring_buffer_write(struct trace_buffer *buffer,
3819 unsigned long length,
3822 struct ring_buffer_per_cpu *cpu_buffer;
3823 struct ring_buffer_event *event;
3828 preempt_disable_notrace();
3830 if (atomic_read(&buffer->record_disabled))
3833 cpu = raw_smp_processor_id();
3835 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3838 cpu_buffer = buffer->buffers[cpu];
3840 if (atomic_read(&cpu_buffer->record_disabled))
3843 if (length > BUF_MAX_DATA_SIZE)
3846 if (unlikely(trace_recursive_lock(cpu_buffer)))
3849 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3853 body = rb_event_data(event);
3855 memcpy(body, data, length);
3857 rb_commit(cpu_buffer, event);
3859 rb_wakeups(buffer, cpu_buffer);
3864 trace_recursive_unlock(cpu_buffer);
3867 preempt_enable_notrace();
3871 EXPORT_SYMBOL_GPL(ring_buffer_write);
3873 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3875 struct buffer_page *reader = cpu_buffer->reader_page;
3876 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3877 struct buffer_page *commit = cpu_buffer->commit_page;
3879 /* In case of error, head will be NULL */
3880 if (unlikely(!head))
3883 return reader->read == rb_page_commit(reader) &&
3884 (commit == reader ||
3886 head->read == rb_page_commit(commit)));
3890 * ring_buffer_record_disable - stop all writes into the buffer
3891 * @buffer: The ring buffer to stop writes to.
3893 * This prevents all writes to the buffer. Any attempt to write
3894 * to the buffer after this will fail and return NULL.
3896 * The caller should call synchronize_rcu() after this.
3898 void ring_buffer_record_disable(struct trace_buffer *buffer)
3900 atomic_inc(&buffer->record_disabled);
3902 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3905 * ring_buffer_record_enable - enable writes to the buffer
3906 * @buffer: The ring buffer to enable writes
3908 * Note, multiple disables will need the same number of enables
3909 * to truly enable the writing (much like preempt_disable).
3911 void ring_buffer_record_enable(struct trace_buffer *buffer)
3913 atomic_dec(&buffer->record_disabled);
3915 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3918 * ring_buffer_record_off - stop all writes into the buffer
3919 * @buffer: The ring buffer to stop writes to.
3921 * This prevents all writes to the buffer. Any attempt to write
3922 * to the buffer after this will fail and return NULL.
3924 * This is different than ring_buffer_record_disable() as
3925 * it works like an on/off switch, where as the disable() version
3926 * must be paired with a enable().
3928 void ring_buffer_record_off(struct trace_buffer *buffer)
3931 unsigned int new_rd;
3934 rd = atomic_read(&buffer->record_disabled);
3935 new_rd = rd | RB_BUFFER_OFF;
3936 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3938 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3941 * ring_buffer_record_on - restart writes into the buffer
3942 * @buffer: The ring buffer to start writes to.
3944 * This enables all writes to the buffer that was disabled by
3945 * ring_buffer_record_off().
3947 * This is different than ring_buffer_record_enable() as
3948 * it works like an on/off switch, where as the enable() version
3949 * must be paired with a disable().
3951 void ring_buffer_record_on(struct trace_buffer *buffer)
3954 unsigned int new_rd;
3957 rd = atomic_read(&buffer->record_disabled);
3958 new_rd = rd & ~RB_BUFFER_OFF;
3959 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3961 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3964 * ring_buffer_record_is_on - return true if the ring buffer can write
3965 * @buffer: The ring buffer to see if write is enabled
3967 * Returns true if the ring buffer is in a state that it accepts writes.
3969 bool ring_buffer_record_is_on(struct trace_buffer *buffer)
3971 return !atomic_read(&buffer->record_disabled);
3975 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3976 * @buffer: The ring buffer to see if write is set enabled
3978 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3979 * Note that this does NOT mean it is in a writable state.
3981 * It may return true when the ring buffer has been disabled by
3982 * ring_buffer_record_disable(), as that is a temporary disabling of
3985 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
3987 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
3991 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3992 * @buffer: The ring buffer to stop writes to.
3993 * @cpu: The CPU buffer to stop
3995 * This prevents all writes to the buffer. Any attempt to write
3996 * to the buffer after this will fail and return NULL.
3998 * The caller should call synchronize_rcu() after this.
4000 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
4002 struct ring_buffer_per_cpu *cpu_buffer;
4004 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4007 cpu_buffer = buffer->buffers[cpu];
4008 atomic_inc(&cpu_buffer->record_disabled);
4010 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
4013 * ring_buffer_record_enable_cpu - enable writes to the buffer
4014 * @buffer: The ring buffer to enable writes
4015 * @cpu: The CPU to enable.
4017 * Note, multiple disables will need the same number of enables
4018 * to truly enable the writing (much like preempt_disable).
4020 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
4022 struct ring_buffer_per_cpu *cpu_buffer;
4024 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4027 cpu_buffer = buffer->buffers[cpu];
4028 atomic_dec(&cpu_buffer->record_disabled);
4030 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
4033 * The total entries in the ring buffer is the running counter
4034 * of entries entered into the ring buffer, minus the sum of
4035 * the entries read from the ring buffer and the number of
4036 * entries that were overwritten.
4038 static inline unsigned long
4039 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
4041 return local_read(&cpu_buffer->entries) -
4042 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
4046 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
4047 * @buffer: The ring buffer
4048 * @cpu: The per CPU buffer to read from.
4050 u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
4052 unsigned long flags;
4053 struct ring_buffer_per_cpu *cpu_buffer;
4054 struct buffer_page *bpage;
4057 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4060 cpu_buffer = buffer->buffers[cpu];
4061 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4063 * if the tail is on reader_page, oldest time stamp is on the reader
4066 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
4067 bpage = cpu_buffer->reader_page;
4069 bpage = rb_set_head_page(cpu_buffer);
4071 ret = bpage->page->time_stamp;
4072 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4076 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
4079 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
4080 * @buffer: The ring buffer
4081 * @cpu: The per CPU buffer to read from.
4083 unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
4085 struct ring_buffer_per_cpu *cpu_buffer;
4088 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4091 cpu_buffer = buffer->buffers[cpu];
4092 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4096 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4099 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4100 * @buffer: The ring buffer
4101 * @cpu: The per CPU buffer to get the entries from.
4103 unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4105 struct ring_buffer_per_cpu *cpu_buffer;
4107 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4110 cpu_buffer = buffer->buffers[cpu];
4112 return rb_num_of_entries(cpu_buffer);
4114 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4117 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4118 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4119 * @buffer: The ring buffer
4120 * @cpu: The per CPU buffer to get the number of overruns from
4122 unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4124 struct ring_buffer_per_cpu *cpu_buffer;
4127 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4130 cpu_buffer = buffer->buffers[cpu];
4131 ret = local_read(&cpu_buffer->overrun);
4135 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4138 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4139 * commits failing due to the buffer wrapping around while there are uncommitted
4140 * events, such as during an interrupt storm.
4141 * @buffer: The ring buffer
4142 * @cpu: The per CPU buffer to get the number of overruns from
4145 ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4147 struct ring_buffer_per_cpu *cpu_buffer;
4150 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4153 cpu_buffer = buffer->buffers[cpu];
4154 ret = local_read(&cpu_buffer->commit_overrun);
4158 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4161 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4162 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4163 * @buffer: The ring buffer
4164 * @cpu: The per CPU buffer to get the number of overruns from
4167 ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4169 struct ring_buffer_per_cpu *cpu_buffer;
4172 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4175 cpu_buffer = buffer->buffers[cpu];
4176 ret = local_read(&cpu_buffer->dropped_events);
4180 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4183 * ring_buffer_read_events_cpu - get the number of events successfully read
4184 * @buffer: The ring buffer
4185 * @cpu: The per CPU buffer to get the number of events read
4188 ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4190 struct ring_buffer_per_cpu *cpu_buffer;
4192 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4195 cpu_buffer = buffer->buffers[cpu];
4196 return cpu_buffer->read;
4198 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4201 * ring_buffer_entries - get the number of entries in a buffer
4202 * @buffer: The ring buffer
4204 * Returns the total number of entries in the ring buffer
4207 unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4209 struct ring_buffer_per_cpu *cpu_buffer;
4210 unsigned long entries = 0;
4213 /* if you care about this being correct, lock the buffer */
4214 for_each_buffer_cpu(buffer, cpu) {
4215 cpu_buffer = buffer->buffers[cpu];
4216 entries += rb_num_of_entries(cpu_buffer);
4221 EXPORT_SYMBOL_GPL(ring_buffer_entries);
4224 * ring_buffer_overruns - get the number of overruns in buffer
4225 * @buffer: The ring buffer
4227 * Returns the total number of overruns in the ring buffer
4230 unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4232 struct ring_buffer_per_cpu *cpu_buffer;
4233 unsigned long overruns = 0;
4236 /* if you care about this being correct, lock the buffer */
4237 for_each_buffer_cpu(buffer, cpu) {
4238 cpu_buffer = buffer->buffers[cpu];
4239 overruns += local_read(&cpu_buffer->overrun);
4244 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4246 static void rb_iter_reset(struct ring_buffer_iter *iter)
4248 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4250 /* Iterator usage is expected to have record disabled */
4251 iter->head_page = cpu_buffer->reader_page;
4252 iter->head = cpu_buffer->reader_page->read;
4253 iter->next_event = iter->head;
4255 iter->cache_reader_page = iter->head_page;
4256 iter->cache_read = cpu_buffer->read;
4259 iter->read_stamp = cpu_buffer->read_stamp;
4260 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4262 iter->read_stamp = iter->head_page->page->time_stamp;
4263 iter->page_stamp = iter->read_stamp;
4268 * ring_buffer_iter_reset - reset an iterator
4269 * @iter: The iterator to reset
4271 * Resets the iterator, so that it will start from the beginning
4274 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4276 struct ring_buffer_per_cpu *cpu_buffer;
4277 unsigned long flags;
4282 cpu_buffer = iter->cpu_buffer;
4284 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4285 rb_iter_reset(iter);
4286 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4288 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4291 * ring_buffer_iter_empty - check if an iterator has no more to read
4292 * @iter: The iterator to check
4294 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4296 struct ring_buffer_per_cpu *cpu_buffer;
4297 struct buffer_page *reader;
4298 struct buffer_page *head_page;
4299 struct buffer_page *commit_page;
4300 struct buffer_page *curr_commit_page;
4305 cpu_buffer = iter->cpu_buffer;
4306 reader = cpu_buffer->reader_page;
4307 head_page = cpu_buffer->head_page;
4308 commit_page = cpu_buffer->commit_page;
4309 commit_ts = commit_page->page->time_stamp;
4312 * When the writer goes across pages, it issues a cmpxchg which
4313 * is a mb(), which will synchronize with the rmb here.
4314 * (see rb_tail_page_update())
4317 commit = rb_page_commit(commit_page);
4318 /* We want to make sure that the commit page doesn't change */
4321 /* Make sure commit page didn't change */
4322 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4323 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4325 /* If the commit page changed, then there's more data */
4326 if (curr_commit_page != commit_page ||
4327 curr_commit_ts != commit_ts)
4330 /* Still racy, as it may return a false positive, but that's OK */
4331 return ((iter->head_page == commit_page && iter->head >= commit) ||
4332 (iter->head_page == reader && commit_page == head_page &&
4333 head_page->read == commit &&
4334 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4336 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4339 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4340 struct ring_buffer_event *event)
4344 switch (event->type_len) {
4345 case RINGBUF_TYPE_PADDING:
4348 case RINGBUF_TYPE_TIME_EXTEND:
4349 delta = rb_event_time_stamp(event);
4350 cpu_buffer->read_stamp += delta;
4353 case RINGBUF_TYPE_TIME_STAMP:
4354 delta = rb_event_time_stamp(event);
4355 cpu_buffer->read_stamp = delta;
4358 case RINGBUF_TYPE_DATA:
4359 cpu_buffer->read_stamp += event->time_delta;
4363 RB_WARN_ON(cpu_buffer, 1);
4369 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4370 struct ring_buffer_event *event)
4374 switch (event->type_len) {
4375 case RINGBUF_TYPE_PADDING:
4378 case RINGBUF_TYPE_TIME_EXTEND:
4379 delta = rb_event_time_stamp(event);
4380 iter->read_stamp += delta;
4383 case RINGBUF_TYPE_TIME_STAMP:
4384 delta = rb_event_time_stamp(event);
4385 iter->read_stamp = delta;
4388 case RINGBUF_TYPE_DATA:
4389 iter->read_stamp += event->time_delta;
4393 RB_WARN_ON(iter->cpu_buffer, 1);
4398 static struct buffer_page *
4399 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4401 struct buffer_page *reader = NULL;
4402 unsigned long overwrite;
4403 unsigned long flags;
4407 local_irq_save(flags);
4408 arch_spin_lock(&cpu_buffer->lock);
4412 * This should normally only loop twice. But because the
4413 * start of the reader inserts an empty page, it causes
4414 * a case where we will loop three times. There should be no
4415 * reason to loop four times (that I know of).
4417 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4422 reader = cpu_buffer->reader_page;
4424 /* If there's more to read, return this page */
4425 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4428 /* Never should we have an index greater than the size */
4429 if (RB_WARN_ON(cpu_buffer,
4430 cpu_buffer->reader_page->read > rb_page_size(reader)))
4433 /* check if we caught up to the tail */
4435 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4438 /* Don't bother swapping if the ring buffer is empty */
4439 if (rb_num_of_entries(cpu_buffer) == 0)
4443 * Reset the reader page to size zero.
4445 local_set(&cpu_buffer->reader_page->write, 0);
4446 local_set(&cpu_buffer->reader_page->entries, 0);
4447 local_set(&cpu_buffer->reader_page->page->commit, 0);
4448 cpu_buffer->reader_page->real_end = 0;
4452 * Splice the empty reader page into the list around the head.
4454 reader = rb_set_head_page(cpu_buffer);
4457 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4458 cpu_buffer->reader_page->list.prev = reader->list.prev;
4461 * cpu_buffer->pages just needs to point to the buffer, it
4462 * has no specific buffer page to point to. Lets move it out
4463 * of our way so we don't accidentally swap it.
4465 cpu_buffer->pages = reader->list.prev;
4467 /* The reader page will be pointing to the new head */
4468 rb_set_list_to_head(&cpu_buffer->reader_page->list);
4471 * We want to make sure we read the overruns after we set up our
4472 * pointers to the next object. The writer side does a
4473 * cmpxchg to cross pages which acts as the mb on the writer
4474 * side. Note, the reader will constantly fail the swap
4475 * while the writer is updating the pointers, so this
4476 * guarantees that the overwrite recorded here is the one we
4477 * want to compare with the last_overrun.
4480 overwrite = local_read(&(cpu_buffer->overrun));
4483 * Here's the tricky part.
4485 * We need to move the pointer past the header page.
4486 * But we can only do that if a writer is not currently
4487 * moving it. The page before the header page has the
4488 * flag bit '1' set if it is pointing to the page we want.
4489 * but if the writer is in the process of moving it
4490 * than it will be '2' or already moved '0'.
4493 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4496 * If we did not convert it, then we must try again.
4502 * Yay! We succeeded in replacing the page.
4504 * Now make the new head point back to the reader page.
4506 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4507 rb_inc_page(&cpu_buffer->head_page);
4509 local_inc(&cpu_buffer->pages_read);
4511 /* Finally update the reader page to the new head */
4512 cpu_buffer->reader_page = reader;
4513 cpu_buffer->reader_page->read = 0;
4515 if (overwrite != cpu_buffer->last_overrun) {
4516 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4517 cpu_buffer->last_overrun = overwrite;
4523 /* Update the read_stamp on the first event */
4524 if (reader && reader->read == 0)
4525 cpu_buffer->read_stamp = reader->page->time_stamp;
4527 arch_spin_unlock(&cpu_buffer->lock);
4528 local_irq_restore(flags);
4533 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4535 struct ring_buffer_event *event;
4536 struct buffer_page *reader;
4539 reader = rb_get_reader_page(cpu_buffer);
4541 /* This function should not be called when buffer is empty */
4542 if (RB_WARN_ON(cpu_buffer, !reader))
4545 event = rb_reader_event(cpu_buffer);
4547 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4550 rb_update_read_stamp(cpu_buffer, event);
4552 length = rb_event_length(event);
4553 cpu_buffer->reader_page->read += length;
4556 static void rb_advance_iter(struct ring_buffer_iter *iter)
4558 struct ring_buffer_per_cpu *cpu_buffer;
4560 cpu_buffer = iter->cpu_buffer;
4562 /* If head == next_event then we need to jump to the next event */
4563 if (iter->head == iter->next_event) {
4564 /* If the event gets overwritten again, there's nothing to do */
4565 if (rb_iter_head_event(iter) == NULL)
4569 iter->head = iter->next_event;
4572 * Check if we are at the end of the buffer.
4574 if (iter->next_event >= rb_page_size(iter->head_page)) {
4575 /* discarded commits can make the page empty */
4576 if (iter->head_page == cpu_buffer->commit_page)
4582 rb_update_iter_read_stamp(iter, iter->event);
4585 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4587 return cpu_buffer->lost_events;
4590 static struct ring_buffer_event *
4591 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4592 unsigned long *lost_events)
4594 struct ring_buffer_event *event;
4595 struct buffer_page *reader;
4602 * We repeat when a time extend is encountered.
4603 * Since the time extend is always attached to a data event,
4604 * we should never loop more than once.
4605 * (We never hit the following condition more than twice).
4607 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4610 reader = rb_get_reader_page(cpu_buffer);
4614 event = rb_reader_event(cpu_buffer);
4616 switch (event->type_len) {
4617 case RINGBUF_TYPE_PADDING:
4618 if (rb_null_event(event))
4619 RB_WARN_ON(cpu_buffer, 1);
4621 * Because the writer could be discarding every
4622 * event it creates (which would probably be bad)
4623 * if we were to go back to "again" then we may never
4624 * catch up, and will trigger the warn on, or lock
4625 * the box. Return the padding, and we will release
4626 * the current locks, and try again.
4630 case RINGBUF_TYPE_TIME_EXTEND:
4631 /* Internal data, OK to advance */
4632 rb_advance_reader(cpu_buffer);
4635 case RINGBUF_TYPE_TIME_STAMP:
4637 *ts = rb_event_time_stamp(event);
4638 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4639 cpu_buffer->cpu, ts);
4641 /* Internal data, OK to advance */
4642 rb_advance_reader(cpu_buffer);
4645 case RINGBUF_TYPE_DATA:
4647 *ts = cpu_buffer->read_stamp + event->time_delta;
4648 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4649 cpu_buffer->cpu, ts);
4652 *lost_events = rb_lost_events(cpu_buffer);
4656 RB_WARN_ON(cpu_buffer, 1);
4661 EXPORT_SYMBOL_GPL(ring_buffer_peek);
4663 static struct ring_buffer_event *
4664 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4666 struct trace_buffer *buffer;
4667 struct ring_buffer_per_cpu *cpu_buffer;
4668 struct ring_buffer_event *event;
4674 cpu_buffer = iter->cpu_buffer;
4675 buffer = cpu_buffer->buffer;
4678 * Check if someone performed a consuming read to
4679 * the buffer. A consuming read invalidates the iterator
4680 * and we need to reset the iterator in this case.
4682 if (unlikely(iter->cache_read != cpu_buffer->read ||
4683 iter->cache_reader_page != cpu_buffer->reader_page))
4684 rb_iter_reset(iter);
4687 if (ring_buffer_iter_empty(iter))
4691 * As the writer can mess with what the iterator is trying
4692 * to read, just give up if we fail to get an event after
4693 * three tries. The iterator is not as reliable when reading
4694 * the ring buffer with an active write as the consumer is.
4695 * Do not warn if the three failures is reached.
4700 if (rb_per_cpu_empty(cpu_buffer))
4703 if (iter->head >= rb_page_size(iter->head_page)) {
4708 event = rb_iter_head_event(iter);
4712 switch (event->type_len) {
4713 case RINGBUF_TYPE_PADDING:
4714 if (rb_null_event(event)) {
4718 rb_advance_iter(iter);
4721 case RINGBUF_TYPE_TIME_EXTEND:
4722 /* Internal data, OK to advance */
4723 rb_advance_iter(iter);
4726 case RINGBUF_TYPE_TIME_STAMP:
4728 *ts = rb_event_time_stamp(event);
4729 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4730 cpu_buffer->cpu, ts);
4732 /* Internal data, OK to advance */
4733 rb_advance_iter(iter);
4736 case RINGBUF_TYPE_DATA:
4738 *ts = iter->read_stamp + event->time_delta;
4739 ring_buffer_normalize_time_stamp(buffer,
4740 cpu_buffer->cpu, ts);
4745 RB_WARN_ON(cpu_buffer, 1);
4750 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4752 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4754 if (likely(!in_nmi())) {
4755 raw_spin_lock(&cpu_buffer->reader_lock);
4760 * If an NMI die dumps out the content of the ring buffer
4761 * trylock must be used to prevent a deadlock if the NMI
4762 * preempted a task that holds the ring buffer locks. If
4763 * we get the lock then all is fine, if not, then continue
4764 * to do the read, but this can corrupt the ring buffer,
4765 * so it must be permanently disabled from future writes.
4766 * Reading from NMI is a oneshot deal.
4768 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4771 /* Continue without locking, but disable the ring buffer */
4772 atomic_inc(&cpu_buffer->record_disabled);
4777 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4780 raw_spin_unlock(&cpu_buffer->reader_lock);
4785 * ring_buffer_peek - peek at the next event to be read
4786 * @buffer: The ring buffer to read
4787 * @cpu: The cpu to peak at
4788 * @ts: The timestamp counter of this event.
4789 * @lost_events: a variable to store if events were lost (may be NULL)
4791 * This will return the event that will be read next, but does
4792 * not consume the data.
4794 struct ring_buffer_event *
4795 ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4796 unsigned long *lost_events)
4798 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4799 struct ring_buffer_event *event;
4800 unsigned long flags;
4803 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4807 local_irq_save(flags);
4808 dolock = rb_reader_lock(cpu_buffer);
4809 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4810 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4811 rb_advance_reader(cpu_buffer);
4812 rb_reader_unlock(cpu_buffer, dolock);
4813 local_irq_restore(flags);
4815 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4821 /** ring_buffer_iter_dropped - report if there are dropped events
4822 * @iter: The ring buffer iterator
4824 * Returns true if there was dropped events since the last peek.
4826 bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4828 bool ret = iter->missed_events != 0;
4830 iter->missed_events = 0;
4833 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4836 * ring_buffer_iter_peek - peek at the next event to be read
4837 * @iter: The ring buffer iterator
4838 * @ts: The timestamp counter of this event.
4840 * This will return the event that will be read next, but does
4841 * not increment the iterator.
4843 struct ring_buffer_event *
4844 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4846 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4847 struct ring_buffer_event *event;
4848 unsigned long flags;
4851 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4852 event = rb_iter_peek(iter, ts);
4853 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4855 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4862 * ring_buffer_consume - return an event and consume it
4863 * @buffer: The ring buffer to get the next event from
4864 * @cpu: the cpu to read the buffer from
4865 * @ts: a variable to store the timestamp (may be NULL)
4866 * @lost_events: a variable to store if events were lost (may be NULL)
4868 * Returns the next event in the ring buffer, and that event is consumed.
4869 * Meaning, that sequential reads will keep returning a different event,
4870 * and eventually empty the ring buffer if the producer is slower.
4872 struct ring_buffer_event *
4873 ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4874 unsigned long *lost_events)
4876 struct ring_buffer_per_cpu *cpu_buffer;
4877 struct ring_buffer_event *event = NULL;
4878 unsigned long flags;
4882 /* might be called in atomic */
4885 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4888 cpu_buffer = buffer->buffers[cpu];
4889 local_irq_save(flags);
4890 dolock = rb_reader_lock(cpu_buffer);
4892 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4894 cpu_buffer->lost_events = 0;
4895 rb_advance_reader(cpu_buffer);
4898 rb_reader_unlock(cpu_buffer, dolock);
4899 local_irq_restore(flags);
4904 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4909 EXPORT_SYMBOL_GPL(ring_buffer_consume);
4912 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4913 * @buffer: The ring buffer to read from
4914 * @cpu: The cpu buffer to iterate over
4915 * @flags: gfp flags to use for memory allocation
4917 * This performs the initial preparations necessary to iterate
4918 * through the buffer. Memory is allocated, buffer recording
4919 * is disabled, and the iterator pointer is returned to the caller.
4921 * Disabling buffer recording prevents the reading from being
4922 * corrupted. This is not a consuming read, so a producer is not
4925 * After a sequence of ring_buffer_read_prepare calls, the user is
4926 * expected to make at least one call to ring_buffer_read_prepare_sync.
4927 * Afterwards, ring_buffer_read_start is invoked to get things going
4930 * This overall must be paired with ring_buffer_read_finish.
4932 struct ring_buffer_iter *
4933 ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
4935 struct ring_buffer_per_cpu *cpu_buffer;
4936 struct ring_buffer_iter *iter;
4938 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4941 iter = kzalloc(sizeof(*iter), flags);
4945 iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
4951 cpu_buffer = buffer->buffers[cpu];
4953 iter->cpu_buffer = cpu_buffer;
4955 atomic_inc(&cpu_buffer->resize_disabled);
4959 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4962 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4964 * All previously invoked ring_buffer_read_prepare calls to prepare
4965 * iterators will be synchronized. Afterwards, read_buffer_read_start
4966 * calls on those iterators are allowed.
4969 ring_buffer_read_prepare_sync(void)
4973 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4976 * ring_buffer_read_start - start a non consuming read of the buffer
4977 * @iter: The iterator returned by ring_buffer_read_prepare
4979 * This finalizes the startup of an iteration through the buffer.
4980 * The iterator comes from a call to ring_buffer_read_prepare and
4981 * an intervening ring_buffer_read_prepare_sync must have been
4984 * Must be paired with ring_buffer_read_finish.
4987 ring_buffer_read_start(struct ring_buffer_iter *iter)
4989 struct ring_buffer_per_cpu *cpu_buffer;
4990 unsigned long flags;
4995 cpu_buffer = iter->cpu_buffer;
4997 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4998 arch_spin_lock(&cpu_buffer->lock);
4999 rb_iter_reset(iter);
5000 arch_spin_unlock(&cpu_buffer->lock);
5001 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5003 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
5006 * ring_buffer_read_finish - finish reading the iterator of the buffer
5007 * @iter: The iterator retrieved by ring_buffer_start
5009 * This re-enables the recording to the buffer, and frees the
5013 ring_buffer_read_finish(struct ring_buffer_iter *iter)
5015 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5016 unsigned long flags;
5019 * Ring buffer is disabled from recording, here's a good place
5020 * to check the integrity of the ring buffer.
5021 * Must prevent readers from trying to read, as the check
5022 * clears the HEAD page and readers require it.
5024 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5025 rb_check_pages(cpu_buffer);
5026 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5028 atomic_dec(&cpu_buffer->resize_disabled);
5032 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
5035 * ring_buffer_iter_advance - advance the iterator to the next location
5036 * @iter: The ring buffer iterator
5038 * Move the location of the iterator such that the next read will
5039 * be the next location of the iterator.
5041 void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
5043 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
5044 unsigned long flags;
5046 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5048 rb_advance_iter(iter);
5050 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5052 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
5055 * ring_buffer_size - return the size of the ring buffer (in bytes)
5056 * @buffer: The ring buffer.
5057 * @cpu: The CPU to get ring buffer size from.
5059 unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
5062 * Earlier, this method returned
5063 * BUF_PAGE_SIZE * buffer->nr_pages
5064 * Since the nr_pages field is now removed, we have converted this to
5065 * return the per cpu buffer value.
5067 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5070 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
5072 EXPORT_SYMBOL_GPL(ring_buffer_size);
5075 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
5077 rb_head_page_deactivate(cpu_buffer);
5079 cpu_buffer->head_page
5080 = list_entry(cpu_buffer->pages, struct buffer_page, list);
5081 local_set(&cpu_buffer->head_page->write, 0);
5082 local_set(&cpu_buffer->head_page->entries, 0);
5083 local_set(&cpu_buffer->head_page->page->commit, 0);
5085 cpu_buffer->head_page->read = 0;
5087 cpu_buffer->tail_page = cpu_buffer->head_page;
5088 cpu_buffer->commit_page = cpu_buffer->head_page;
5090 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5091 INIT_LIST_HEAD(&cpu_buffer->new_pages);
5092 local_set(&cpu_buffer->reader_page->write, 0);
5093 local_set(&cpu_buffer->reader_page->entries, 0);
5094 local_set(&cpu_buffer->reader_page->page->commit, 0);
5095 cpu_buffer->reader_page->read = 0;
5097 local_set(&cpu_buffer->entries_bytes, 0);
5098 local_set(&cpu_buffer->overrun, 0);
5099 local_set(&cpu_buffer->commit_overrun, 0);
5100 local_set(&cpu_buffer->dropped_events, 0);
5101 local_set(&cpu_buffer->entries, 0);
5102 local_set(&cpu_buffer->committing, 0);
5103 local_set(&cpu_buffer->commits, 0);
5104 local_set(&cpu_buffer->pages_touched, 0);
5105 local_set(&cpu_buffer->pages_read, 0);
5106 cpu_buffer->last_pages_touch = 0;
5107 cpu_buffer->shortest_full = 0;
5108 cpu_buffer->read = 0;
5109 cpu_buffer->read_bytes = 0;
5111 rb_time_set(&cpu_buffer->write_stamp, 0);
5112 rb_time_set(&cpu_buffer->before_stamp, 0);
5114 memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
5116 cpu_buffer->lost_events = 0;
5117 cpu_buffer->last_overrun = 0;
5119 rb_head_page_activate(cpu_buffer);
5122 /* Must have disabled the cpu buffer then done a synchronize_rcu */
5123 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5125 unsigned long flags;
5127 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5129 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5132 arch_spin_lock(&cpu_buffer->lock);
5134 rb_reset_cpu(cpu_buffer);
5136 arch_spin_unlock(&cpu_buffer->lock);
5139 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5143 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5144 * @buffer: The ring buffer to reset a per cpu buffer of
5145 * @cpu: The CPU buffer to be reset
5147 void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5149 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5151 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5154 /* prevent another thread from changing buffer sizes */
5155 mutex_lock(&buffer->mutex);
5157 atomic_inc(&cpu_buffer->resize_disabled);
5158 atomic_inc(&cpu_buffer->record_disabled);
5160 /* Make sure all commits have finished */
5163 reset_disabled_cpu_buffer(cpu_buffer);
5165 atomic_dec(&cpu_buffer->record_disabled);
5166 atomic_dec(&cpu_buffer->resize_disabled);
5168 mutex_unlock(&buffer->mutex);
5170 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5173 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5174 * @buffer: The ring buffer to reset a per cpu buffer of
5175 * @cpu: The CPU buffer to be reset
5177 void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5179 struct ring_buffer_per_cpu *cpu_buffer;
5182 /* prevent another thread from changing buffer sizes */
5183 mutex_lock(&buffer->mutex);
5185 for_each_online_buffer_cpu(buffer, cpu) {
5186 cpu_buffer = buffer->buffers[cpu];
5188 atomic_inc(&cpu_buffer->resize_disabled);
5189 atomic_inc(&cpu_buffer->record_disabled);
5192 /* Make sure all commits have finished */
5195 for_each_online_buffer_cpu(buffer, cpu) {
5196 cpu_buffer = buffer->buffers[cpu];
5198 reset_disabled_cpu_buffer(cpu_buffer);
5200 atomic_dec(&cpu_buffer->record_disabled);
5201 atomic_dec(&cpu_buffer->resize_disabled);
5204 mutex_unlock(&buffer->mutex);
5208 * ring_buffer_reset - reset a ring buffer
5209 * @buffer: The ring buffer to reset all cpu buffers
5211 void ring_buffer_reset(struct trace_buffer *buffer)
5213 struct ring_buffer_per_cpu *cpu_buffer;
5216 for_each_buffer_cpu(buffer, cpu) {
5217 cpu_buffer = buffer->buffers[cpu];
5219 atomic_inc(&cpu_buffer->resize_disabled);
5220 atomic_inc(&cpu_buffer->record_disabled);
5223 /* Make sure all commits have finished */
5226 for_each_buffer_cpu(buffer, cpu) {
5227 cpu_buffer = buffer->buffers[cpu];
5229 reset_disabled_cpu_buffer(cpu_buffer);
5231 atomic_dec(&cpu_buffer->record_disabled);
5232 atomic_dec(&cpu_buffer->resize_disabled);
5235 EXPORT_SYMBOL_GPL(ring_buffer_reset);
5238 * rind_buffer_empty - is the ring buffer empty?
5239 * @buffer: The ring buffer to test
5241 bool ring_buffer_empty(struct trace_buffer *buffer)
5243 struct ring_buffer_per_cpu *cpu_buffer;
5244 unsigned long flags;
5249 /* yes this is racy, but if you don't like the race, lock the buffer */
5250 for_each_buffer_cpu(buffer, cpu) {
5251 cpu_buffer = buffer->buffers[cpu];
5252 local_irq_save(flags);
5253 dolock = rb_reader_lock(cpu_buffer);
5254 ret = rb_per_cpu_empty(cpu_buffer);
5255 rb_reader_unlock(cpu_buffer, dolock);
5256 local_irq_restore(flags);
5264 EXPORT_SYMBOL_GPL(ring_buffer_empty);
5267 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5268 * @buffer: The ring buffer
5269 * @cpu: The CPU buffer to test
5271 bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5273 struct ring_buffer_per_cpu *cpu_buffer;
5274 unsigned long flags;
5278 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5281 cpu_buffer = buffer->buffers[cpu];
5282 local_irq_save(flags);
5283 dolock = rb_reader_lock(cpu_buffer);
5284 ret = rb_per_cpu_empty(cpu_buffer);
5285 rb_reader_unlock(cpu_buffer, dolock);
5286 local_irq_restore(flags);
5290 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5292 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5294 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5295 * @buffer_a: One buffer to swap with
5296 * @buffer_b: The other buffer to swap with
5297 * @cpu: the CPU of the buffers to swap
5299 * This function is useful for tracers that want to take a "snapshot"
5300 * of a CPU buffer and has another back up buffer lying around.
5301 * it is expected that the tracer handles the cpu buffer not being
5302 * used at the moment.
5304 int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5305 struct trace_buffer *buffer_b, int cpu)
5307 struct ring_buffer_per_cpu *cpu_buffer_a;
5308 struct ring_buffer_per_cpu *cpu_buffer_b;
5311 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5312 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5315 cpu_buffer_a = buffer_a->buffers[cpu];
5316 cpu_buffer_b = buffer_b->buffers[cpu];
5318 /* At least make sure the two buffers are somewhat the same */
5319 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5324 if (atomic_read(&buffer_a->record_disabled))
5327 if (atomic_read(&buffer_b->record_disabled))
5330 if (atomic_read(&cpu_buffer_a->record_disabled))
5333 if (atomic_read(&cpu_buffer_b->record_disabled))
5337 * We can't do a synchronize_rcu here because this
5338 * function can be called in atomic context.
5339 * Normally this will be called from the same CPU as cpu.
5340 * If not it's up to the caller to protect this.
5342 atomic_inc(&cpu_buffer_a->record_disabled);
5343 atomic_inc(&cpu_buffer_b->record_disabled);
5346 if (local_read(&cpu_buffer_a->committing))
5348 if (local_read(&cpu_buffer_b->committing))
5351 buffer_a->buffers[cpu] = cpu_buffer_b;
5352 buffer_b->buffers[cpu] = cpu_buffer_a;
5354 cpu_buffer_b->buffer = buffer_a;
5355 cpu_buffer_a->buffer = buffer_b;
5360 atomic_dec(&cpu_buffer_a->record_disabled);
5361 atomic_dec(&cpu_buffer_b->record_disabled);
5365 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5366 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5369 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5370 * @buffer: the buffer to allocate for.
5371 * @cpu: the cpu buffer to allocate.
5373 * This function is used in conjunction with ring_buffer_read_page.
5374 * When reading a full page from the ring buffer, these functions
5375 * can be used to speed up the process. The calling function should
5376 * allocate a few pages first with this function. Then when it
5377 * needs to get pages from the ring buffer, it passes the result
5378 * of this function into ring_buffer_read_page, which will swap
5379 * the page that was allocated, with the read page of the buffer.
5382 * The page allocated, or ERR_PTR
5384 void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5386 struct ring_buffer_per_cpu *cpu_buffer;
5387 struct buffer_data_page *bpage = NULL;
5388 unsigned long flags;
5391 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5392 return ERR_PTR(-ENODEV);
5394 cpu_buffer = buffer->buffers[cpu];
5395 local_irq_save(flags);
5396 arch_spin_lock(&cpu_buffer->lock);
5398 if (cpu_buffer->free_page) {
5399 bpage = cpu_buffer->free_page;
5400 cpu_buffer->free_page = NULL;
5403 arch_spin_unlock(&cpu_buffer->lock);
5404 local_irq_restore(flags);
5409 page = alloc_pages_node(cpu_to_node(cpu),
5410 GFP_KERNEL | __GFP_NORETRY, 0);
5412 return ERR_PTR(-ENOMEM);
5414 bpage = page_address(page);
5417 rb_init_page(bpage);
5421 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5424 * ring_buffer_free_read_page - free an allocated read page
5425 * @buffer: the buffer the page was allocate for
5426 * @cpu: the cpu buffer the page came from
5427 * @data: the page to free
5429 * Free a page allocated from ring_buffer_alloc_read_page.
5431 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
5433 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5434 struct buffer_data_page *bpage = data;
5435 struct page *page = virt_to_page(bpage);
5436 unsigned long flags;
5438 /* If the page is still in use someplace else, we can't reuse it */
5439 if (page_ref_count(page) > 1)
5442 local_irq_save(flags);
5443 arch_spin_lock(&cpu_buffer->lock);
5445 if (!cpu_buffer->free_page) {
5446 cpu_buffer->free_page = bpage;
5450 arch_spin_unlock(&cpu_buffer->lock);
5451 local_irq_restore(flags);
5454 free_page((unsigned long)bpage);
5456 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5459 * ring_buffer_read_page - extract a page from the ring buffer
5460 * @buffer: buffer to extract from
5461 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5462 * @len: amount to extract
5463 * @cpu: the cpu of the buffer to extract
5464 * @full: should the extraction only happen when the page is full.
5466 * This function will pull out a page from the ring buffer and consume it.
5467 * @data_page must be the address of the variable that was returned
5468 * from ring_buffer_alloc_read_page. This is because the page might be used
5469 * to swap with a page in the ring buffer.
5472 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5473 * if (IS_ERR(rpage))
5474 * return PTR_ERR(rpage);
5475 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5477 * process_page(rpage, ret);
5479 * When @full is set, the function will not return true unless
5480 * the writer is off the reader page.
5482 * Note: it is up to the calling functions to handle sleeps and wakeups.
5483 * The ring buffer can be used anywhere in the kernel and can not
5484 * blindly call wake_up. The layer that uses the ring buffer must be
5485 * responsible for that.
5488 * >=0 if data has been transferred, returns the offset of consumed data.
5489 * <0 if no data has been transferred.
5491 int ring_buffer_read_page(struct trace_buffer *buffer,
5492 void **data_page, size_t len, int cpu, int full)
5494 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5495 struct ring_buffer_event *event;
5496 struct buffer_data_page *bpage;
5497 struct buffer_page *reader;
5498 unsigned long missed_events;
5499 unsigned long flags;
5500 unsigned int commit;
5505 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5509 * If len is not big enough to hold the page header, then
5510 * we can not copy anything.
5512 if (len <= BUF_PAGE_HDR_SIZE)
5515 len -= BUF_PAGE_HDR_SIZE;
5524 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5526 reader = rb_get_reader_page(cpu_buffer);
5530 event = rb_reader_event(cpu_buffer);
5532 read = reader->read;
5533 commit = rb_page_commit(reader);
5535 /* Check if any events were dropped */
5536 missed_events = cpu_buffer->lost_events;
5539 * If this page has been partially read or
5540 * if len is not big enough to read the rest of the page or
5541 * a writer is still on the page, then
5542 * we must copy the data from the page to the buffer.
5543 * Otherwise, we can simply swap the page with the one passed in.
5545 if (read || (len < (commit - read)) ||
5546 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5547 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5548 unsigned int rpos = read;
5549 unsigned int pos = 0;
5555 if (len > (commit - read))
5556 len = (commit - read);
5558 /* Always keep the time extend and data together */
5559 size = rb_event_ts_length(event);
5564 /* save the current timestamp, since the user will need it */
5565 save_timestamp = cpu_buffer->read_stamp;
5567 /* Need to copy one event at a time */
5569 /* We need the size of one event, because
5570 * rb_advance_reader only advances by one event,
5571 * whereas rb_event_ts_length may include the size of
5572 * one or two events.
5573 * We have already ensured there's enough space if this
5574 * is a time extend. */
5575 size = rb_event_length(event);
5576 memcpy(bpage->data + pos, rpage->data + rpos, size);
5580 rb_advance_reader(cpu_buffer);
5581 rpos = reader->read;
5587 event = rb_reader_event(cpu_buffer);
5588 /* Always keep the time extend and data together */
5589 size = rb_event_ts_length(event);
5590 } while (len >= size);
5593 local_set(&bpage->commit, pos);
5594 bpage->time_stamp = save_timestamp;
5596 /* we copied everything to the beginning */
5599 /* update the entry counter */
5600 cpu_buffer->read += rb_page_entries(reader);
5601 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
5603 /* swap the pages */
5604 rb_init_page(bpage);
5605 bpage = reader->page;
5606 reader->page = *data_page;
5607 local_set(&reader->write, 0);
5608 local_set(&reader->entries, 0);
5613 * Use the real_end for the data size,
5614 * This gives us a chance to store the lost events
5617 if (reader->real_end)
5618 local_set(&bpage->commit, reader->real_end);
5622 cpu_buffer->lost_events = 0;
5624 commit = local_read(&bpage->commit);
5626 * Set a flag in the commit field if we lost events
5628 if (missed_events) {
5629 /* If there is room at the end of the page to save the
5630 * missed events, then record it there.
5632 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
5633 memcpy(&bpage->data[commit], &missed_events,
5634 sizeof(missed_events));
5635 local_add(RB_MISSED_STORED, &bpage->commit);
5636 commit += sizeof(missed_events);
5638 local_add(RB_MISSED_EVENTS, &bpage->commit);
5642 * This page may be off to user land. Zero it out here.
5644 if (commit < BUF_PAGE_SIZE)
5645 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
5648 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5653 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5656 * We only allocate new buffers, never free them if the CPU goes down.
5657 * If we were to free the buffer, then the user would lose any trace that was in
5660 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
5662 struct trace_buffer *buffer;
5665 unsigned long nr_pages;
5667 buffer = container_of(node, struct trace_buffer, node);
5668 if (cpumask_test_cpu(cpu, buffer->cpumask))
5673 /* check if all cpu sizes are same */
5674 for_each_buffer_cpu(buffer, cpu_i) {
5675 /* fill in the size from first enabled cpu */
5677 nr_pages = buffer->buffers[cpu_i]->nr_pages;
5678 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
5683 /* allocate minimum pages, user can later expand it */
5686 buffer->buffers[cpu] =
5687 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
5688 if (!buffer->buffers[cpu]) {
5689 WARN(1, "failed to allocate ring buffer on CPU %u\n",
5694 cpumask_set_cpu(cpu, buffer->cpumask);
5698 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5700 * This is a basic integrity check of the ring buffer.
5701 * Late in the boot cycle this test will run when configured in.
5702 * It will kick off a thread per CPU that will go into a loop
5703 * writing to the per cpu ring buffer various sizes of data.
5704 * Some of the data will be large items, some small.
5706 * Another thread is created that goes into a spin, sending out
5707 * IPIs to the other CPUs to also write into the ring buffer.
5708 * this is to test the nesting ability of the buffer.
5710 * Basic stats are recorded and reported. If something in the
5711 * ring buffer should happen that's not expected, a big warning
5712 * is displayed and all ring buffers are disabled.
5714 static struct task_struct *rb_threads[NR_CPUS] __initdata;
5716 struct rb_test_data {
5717 struct trace_buffer *buffer;
5718 unsigned long events;
5719 unsigned long bytes_written;
5720 unsigned long bytes_alloc;
5721 unsigned long bytes_dropped;
5722 unsigned long events_nested;
5723 unsigned long bytes_written_nested;
5724 unsigned long bytes_alloc_nested;
5725 unsigned long bytes_dropped_nested;
5726 int min_size_nested;
5727 int max_size_nested;
5734 static struct rb_test_data rb_data[NR_CPUS] __initdata;
5737 #define RB_TEST_BUFFER_SIZE 1048576
5739 static char rb_string[] __initdata =
5740 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5741 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5742 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5744 static bool rb_test_started __initdata;
5751 static __init int rb_write_something(struct rb_test_data *data, bool nested)
5753 struct ring_buffer_event *event;
5754 struct rb_item *item;
5761 /* Have nested writes different that what is written */
5762 cnt = data->cnt + (nested ? 27 : 0);
5764 /* Multiply cnt by ~e, to make some unique increment */
5765 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
5767 len = size + sizeof(struct rb_item);
5769 started = rb_test_started;
5770 /* read rb_test_started before checking buffer enabled */
5773 event = ring_buffer_lock_reserve(data->buffer, len);
5775 /* Ignore dropped events before test starts. */
5778 data->bytes_dropped += len;
5780 data->bytes_dropped_nested += len;
5785 event_len = ring_buffer_event_length(event);
5787 if (RB_WARN_ON(data->buffer, event_len < len))
5790 item = ring_buffer_event_data(event);
5792 memcpy(item->str, rb_string, size);
5795 data->bytes_alloc_nested += event_len;
5796 data->bytes_written_nested += len;
5797 data->events_nested++;
5798 if (!data->min_size_nested || len < data->min_size_nested)
5799 data->min_size_nested = len;
5800 if (len > data->max_size_nested)
5801 data->max_size_nested = len;
5803 data->bytes_alloc += event_len;
5804 data->bytes_written += len;
5806 if (!data->min_size || len < data->min_size)
5807 data->max_size = len;
5808 if (len > data->max_size)
5809 data->max_size = len;
5813 ring_buffer_unlock_commit(data->buffer, event);
5818 static __init int rb_test(void *arg)
5820 struct rb_test_data *data = arg;
5822 while (!kthread_should_stop()) {
5823 rb_write_something(data, false);
5826 set_current_state(TASK_INTERRUPTIBLE);
5827 /* Now sleep between a min of 100-300us and a max of 1ms */
5828 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
5834 static __init void rb_ipi(void *ignore)
5836 struct rb_test_data *data;
5837 int cpu = smp_processor_id();
5839 data = &rb_data[cpu];
5840 rb_write_something(data, true);
5843 static __init int rb_hammer_test(void *arg)
5845 while (!kthread_should_stop()) {
5847 /* Send an IPI to all cpus to write data! */
5848 smp_call_function(rb_ipi, NULL, 1);
5849 /* No sleep, but for non preempt, let others run */
5856 static __init int test_ringbuffer(void)
5858 struct task_struct *rb_hammer;
5859 struct trace_buffer *buffer;
5863 if (security_locked_down(LOCKDOWN_TRACEFS)) {
5864 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
5868 pr_info("Running ring buffer tests...\n");
5870 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5871 if (WARN_ON(!buffer))
5874 /* Disable buffer so that threads can't write to it yet */
5875 ring_buffer_record_off(buffer);
5877 for_each_online_cpu(cpu) {
5878 rb_data[cpu].buffer = buffer;
5879 rb_data[cpu].cpu = cpu;
5880 rb_data[cpu].cnt = cpu;
5881 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5882 "rbtester/%d", cpu);
5883 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5884 pr_cont("FAILED\n");
5885 ret = PTR_ERR(rb_threads[cpu]);
5889 kthread_bind(rb_threads[cpu], cpu);
5890 wake_up_process(rb_threads[cpu]);
5893 /* Now create the rb hammer! */
5894 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5895 if (WARN_ON(IS_ERR(rb_hammer))) {
5896 pr_cont("FAILED\n");
5897 ret = PTR_ERR(rb_hammer);
5901 ring_buffer_record_on(buffer);
5903 * Show buffer is enabled before setting rb_test_started.
5904 * Yes there's a small race window where events could be
5905 * dropped and the thread wont catch it. But when a ring
5906 * buffer gets enabled, there will always be some kind of
5907 * delay before other CPUs see it. Thus, we don't care about
5908 * those dropped events. We care about events dropped after
5909 * the threads see that the buffer is active.
5912 rb_test_started = true;
5914 set_current_state(TASK_INTERRUPTIBLE);
5915 /* Just run for 10 seconds */;
5916 schedule_timeout(10 * HZ);
5918 kthread_stop(rb_hammer);
5921 for_each_online_cpu(cpu) {
5922 if (!rb_threads[cpu])
5924 kthread_stop(rb_threads[cpu]);
5927 ring_buffer_free(buffer);
5932 pr_info("finished\n");
5933 for_each_online_cpu(cpu) {
5934 struct ring_buffer_event *event;
5935 struct rb_test_data *data = &rb_data[cpu];
5936 struct rb_item *item;
5937 unsigned long total_events;
5938 unsigned long total_dropped;
5939 unsigned long total_written;
5940 unsigned long total_alloc;
5941 unsigned long total_read = 0;
5942 unsigned long total_size = 0;
5943 unsigned long total_len = 0;
5944 unsigned long total_lost = 0;
5947 int small_event_size;
5951 total_events = data->events + data->events_nested;
5952 total_written = data->bytes_written + data->bytes_written_nested;
5953 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5954 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5956 big_event_size = data->max_size + data->max_size_nested;
5957 small_event_size = data->min_size + data->min_size_nested;
5959 pr_info("CPU %d:\n", cpu);
5960 pr_info(" events: %ld\n", total_events);
5961 pr_info(" dropped bytes: %ld\n", total_dropped);
5962 pr_info(" alloced bytes: %ld\n", total_alloc);
5963 pr_info(" written bytes: %ld\n", total_written);
5964 pr_info(" biggest event: %d\n", big_event_size);
5965 pr_info(" smallest event: %d\n", small_event_size);
5967 if (RB_WARN_ON(buffer, total_dropped))
5972 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5974 item = ring_buffer_event_data(event);
5975 total_len += ring_buffer_event_length(event);
5976 total_size += item->size + sizeof(struct rb_item);
5977 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5978 pr_info("FAILED!\n");
5979 pr_info("buffer had: %.*s\n", item->size, item->str);
5980 pr_info("expected: %.*s\n", item->size, rb_string);
5981 RB_WARN_ON(buffer, 1);
5992 pr_info(" read events: %ld\n", total_read);
5993 pr_info(" lost events: %ld\n", total_lost);
5994 pr_info(" total events: %ld\n", total_lost + total_read);
5995 pr_info(" recorded len bytes: %ld\n", total_len);
5996 pr_info(" recorded size bytes: %ld\n", total_size);
5998 pr_info(" With dropped events, record len and size may not match\n"
5999 " alloced and written from above\n");
6001 if (RB_WARN_ON(buffer, total_len != total_alloc ||
6002 total_size != total_written))
6005 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
6011 pr_info("Ring buffer PASSED!\n");
6013 ring_buffer_free(buffer);
6017 late_initcall(test_ringbuffer);
6018 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */