4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 #include <linux/ring_buffer.h>
7 #include <linux/trace_clock.h>
8 #include <linux/ftrace_irq.h>
9 #include <linux/spinlock.h>
10 #include <linux/debugfs.h>
11 #include <linux/uaccess.h>
12 #include <linux/hardirq.h>
13 #include <linux/kmemcheck.h>
14 #include <linux/module.h>
15 #include <linux/percpu.h>
16 #include <linux/mutex.h>
17 #include <linux/init.h>
18 #include <linux/hash.h>
19 #include <linux/list.h>
20 #include <linux/cpu.h>
26 * The ring buffer header is special. We must manually up keep it.
28 int ring_buffer_print_entry_header(struct trace_seq *s)
32 ret = trace_seq_printf(s, "# compressed entry header\n");
33 ret = trace_seq_printf(s, "\ttype_len : 5 bits\n");
34 ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n");
35 ret = trace_seq_printf(s, "\tarray : 32 bits\n");
36 ret = trace_seq_printf(s, "\n");
37 ret = trace_seq_printf(s, "\tpadding : type == %d\n",
38 RINGBUF_TYPE_PADDING);
39 ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
40 RINGBUF_TYPE_TIME_EXTEND);
41 ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
42 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
48 * The ring buffer is made up of a list of pages. A separate list of pages is
49 * allocated for each CPU. A writer may only write to a buffer that is
50 * associated with the CPU it is currently executing on. A reader may read
51 * from any per cpu buffer.
53 * The reader is special. For each per cpu buffer, the reader has its own
54 * reader page. When a reader has read the entire reader page, this reader
55 * page is swapped with another page in the ring buffer.
57 * Now, as long as the writer is off the reader page, the reader can do what
58 * ever it wants with that page. The writer will never write to that page
59 * again (as long as it is out of the ring buffer).
61 * Here's some silly ASCII art.
64 * |reader| RING BUFFER
66 * +------+ +---+ +---+ +---+
75 * |reader| RING BUFFER
76 * |page |------------------v
77 * +------+ +---+ +---+ +---+
86 * |reader| RING BUFFER
87 * |page |------------------v
88 * +------+ +---+ +---+ +---+
93 * +------------------------------+
97 * |buffer| RING BUFFER
98 * |page |------------------v
99 * +------+ +---+ +---+ +---+
101 * | New +---+ +---+ +---+
104 * +------------------------------+
107 * After we make this swap, the reader can hand this page off to the splice
108 * code and be done with it. It can even allocate a new page if it needs to
109 * and swap that into the ring buffer.
111 * We will be using cmpxchg soon to make all this lockless.
116 * A fast way to enable or disable all ring buffers is to
117 * call tracing_on or tracing_off. Turning off the ring buffers
118 * prevents all ring buffers from being recorded to.
119 * Turning this switch on, makes it OK to write to the
120 * ring buffer, if the ring buffer is enabled itself.
122 * There's three layers that must be on in order to write
123 * to the ring buffer.
125 * 1) This global flag must be set.
126 * 2) The ring buffer must be enabled for recording.
127 * 3) The per cpu buffer must be enabled for recording.
129 * In case of an anomaly, this global flag has a bit set that
130 * will permantly disable all ring buffers.
134 * Global flag to disable all recording to ring buffers
135 * This has two bits: ON, DISABLED
139 * 0 0 : ring buffers are off
140 * 1 0 : ring buffers are on
141 * X 1 : ring buffers are permanently disabled
145 RB_BUFFERS_ON_BIT = 0,
146 RB_BUFFERS_DISABLED_BIT = 1,
150 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
151 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
154 static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
156 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
159 * tracing_on - enable all tracing buffers
161 * This function enables all tracing buffers that may have been
162 * disabled with tracing_off.
164 void tracing_on(void)
166 set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
168 EXPORT_SYMBOL_GPL(tracing_on);
171 * tracing_off - turn off all tracing buffers
173 * This function stops all tracing buffers from recording data.
174 * It does not disable any overhead the tracers themselves may
175 * be causing. This function simply causes all recording to
176 * the ring buffers to fail.
178 void tracing_off(void)
180 clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
182 EXPORT_SYMBOL_GPL(tracing_off);
185 * tracing_off_permanent - permanently disable ring buffers
187 * This function, once called, will disable all ring buffers
190 void tracing_off_permanent(void)
192 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
196 * tracing_is_on - show state of ring buffers enabled
198 int tracing_is_on(void)
200 return ring_buffer_flags == RB_BUFFERS_ON;
202 EXPORT_SYMBOL_GPL(tracing_is_on);
204 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
205 #define RB_ALIGNMENT 4U
206 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
207 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
209 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
210 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
213 RB_LEN_TIME_EXTEND = 8,
214 RB_LEN_TIME_STAMP = 16,
217 static inline int rb_null_event(struct ring_buffer_event *event)
219 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
222 static void rb_event_set_padding(struct ring_buffer_event *event)
224 /* padding has a NULL time_delta */
225 event->type_len = RINGBUF_TYPE_PADDING;
226 event->time_delta = 0;
230 rb_event_data_length(struct ring_buffer_event *event)
235 length = event->type_len * RB_ALIGNMENT;
237 length = event->array[0];
238 return length + RB_EVNT_HDR_SIZE;
241 /* inline for ring buffer fast paths */
243 rb_event_length(struct ring_buffer_event *event)
245 switch (event->type_len) {
246 case RINGBUF_TYPE_PADDING:
247 if (rb_null_event(event))
250 return event->array[0] + RB_EVNT_HDR_SIZE;
252 case RINGBUF_TYPE_TIME_EXTEND:
253 return RB_LEN_TIME_EXTEND;
255 case RINGBUF_TYPE_TIME_STAMP:
256 return RB_LEN_TIME_STAMP;
258 case RINGBUF_TYPE_DATA:
259 return rb_event_data_length(event);
268 * ring_buffer_event_length - return the length of the event
269 * @event: the event to get the length of
271 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
273 unsigned length = rb_event_length(event);
274 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
276 length -= RB_EVNT_HDR_SIZE;
277 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
278 length -= sizeof(event->array[0]);
281 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
283 /* inline for ring buffer fast paths */
285 rb_event_data(struct ring_buffer_event *event)
287 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
288 /* If length is in len field, then array[0] has the data */
290 return (void *)&event->array[0];
291 /* Otherwise length is in array[0] and array[1] has the data */
292 return (void *)&event->array[1];
296 * ring_buffer_event_data - return the data of the event
297 * @event: the event to get the data from
299 void *ring_buffer_event_data(struct ring_buffer_event *event)
301 return rb_event_data(event);
303 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
305 #define for_each_buffer_cpu(buffer, cpu) \
306 for_each_cpu(cpu, buffer->cpumask)
309 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
310 #define TS_DELTA_TEST (~TS_MASK)
312 struct buffer_data_page {
313 u64 time_stamp; /* page time stamp */
314 local_t commit; /* write committed index */
315 unsigned char data[]; /* data of buffer page */
319 * Note, the buffer_page list must be first. The buffer pages
320 * are allocated in cache lines, which means that each buffer
321 * page will be at the beginning of a cache line, and thus
322 * the least significant bits will be zero. We use this to
323 * add flags in the list struct pointers, to make the ring buffer
327 struct list_head list; /* list of buffer pages */
328 local_t write; /* index for next write */
329 unsigned read; /* index for next read */
330 local_t entries; /* entries on this page */
331 struct buffer_data_page *page; /* Actual data page */
335 * The buffer page counters, write and entries, must be reset
336 * atomically when crossing page boundaries. To synchronize this
337 * update, two counters are inserted into the number. One is
338 * the actual counter for the write position or count on the page.
340 * The other is a counter of updaters. Before an update happens
341 * the update partition of the counter is incremented. This will
342 * allow the updater to update the counter atomically.
344 * The counter is 20 bits, and the state data is 12.
346 #define RB_WRITE_MASK 0xfffff
347 #define RB_WRITE_INTCNT (1 << 20)
349 static void rb_init_page(struct buffer_data_page *bpage)
351 local_set(&bpage->commit, 0);
355 * ring_buffer_page_len - the size of data on the page.
356 * @page: The page to read
358 * Returns the amount of data on the page, including buffer page header.
360 size_t ring_buffer_page_len(void *page)
362 return local_read(&((struct buffer_data_page *)page)->commit)
367 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
370 static void free_buffer_page(struct buffer_page *bpage)
372 free_page((unsigned long)bpage->page);
377 * We need to fit the time_stamp delta into 27 bits.
379 static inline int test_time_stamp(u64 delta)
381 if (delta & TS_DELTA_TEST)
386 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
388 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
389 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
391 /* Max number of timestamps that can fit on a page */
392 #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP)
394 int ring_buffer_print_page_header(struct trace_seq *s)
396 struct buffer_data_page field;
399 ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
400 "offset:0;\tsize:%u;\n",
401 (unsigned int)sizeof(field.time_stamp));
403 ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
404 "offset:%u;\tsize:%u;\n",
405 (unsigned int)offsetof(typeof(field), commit),
406 (unsigned int)sizeof(field.commit));
408 ret = trace_seq_printf(s, "\tfield: char data;\t"
409 "offset:%u;\tsize:%u;\n",
410 (unsigned int)offsetof(typeof(field), data),
411 (unsigned int)BUF_PAGE_SIZE);
417 * head_page == tail_page && head == tail then buffer is empty.
419 struct ring_buffer_per_cpu {
421 struct ring_buffer *buffer;
422 spinlock_t reader_lock; /* serialize readers */
424 struct lock_class_key lock_key;
425 struct list_head *pages;
426 struct buffer_page *head_page; /* read from head */
427 struct buffer_page *tail_page; /* write to tail */
428 struct buffer_page *commit_page; /* committed pages */
429 struct buffer_page *reader_page;
430 local_t commit_overrun;
438 atomic_t record_disabled;
445 atomic_t record_disabled;
446 cpumask_var_t cpumask;
448 struct lock_class_key *reader_lock_key;
452 struct ring_buffer_per_cpu **buffers;
454 #ifdef CONFIG_HOTPLUG_CPU
455 struct notifier_block cpu_notify;
460 struct ring_buffer_iter {
461 struct ring_buffer_per_cpu *cpu_buffer;
463 struct buffer_page *head_page;
467 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
468 #define RB_WARN_ON(b, cond) \
470 int _____ret = unlikely(cond); \
472 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
473 struct ring_buffer_per_cpu *__b = \
475 atomic_inc(&__b->buffer->record_disabled); \
477 atomic_inc(&b->record_disabled); \
483 /* Up this if you want to test the TIME_EXTENTS and normalization */
484 #define DEBUG_SHIFT 0
486 static inline u64 rb_time_stamp(struct ring_buffer *buffer)
488 /* shift to debug/test normalization and TIME_EXTENTS */
489 return buffer->clock() << DEBUG_SHIFT;
492 u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
496 preempt_disable_notrace();
497 time = rb_time_stamp(buffer);
498 preempt_enable_no_resched_notrace();
502 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
504 void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
507 /* Just stupid testing the normalize function and deltas */
510 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
513 * Making the ring buffer lockless makes things tricky.
514 * Although writes only happen on the CPU that they are on,
515 * and they only need to worry about interrupts. Reads can
518 * The reader page is always off the ring buffer, but when the
519 * reader finishes with a page, it needs to swap its page with
520 * a new one from the buffer. The reader needs to take from
521 * the head (writes go to the tail). But if a writer is in overwrite
522 * mode and wraps, it must push the head page forward.
524 * Here lies the problem.
526 * The reader must be careful to replace only the head page, and
527 * not another one. As described at the top of the file in the
528 * ASCII art, the reader sets its old page to point to the next
529 * page after head. It then sets the page after head to point to
530 * the old reader page. But if the writer moves the head page
531 * during this operation, the reader could end up with the tail.
533 * We use cmpxchg to help prevent this race. We also do something
534 * special with the page before head. We set the LSB to 1.
536 * When the writer must push the page forward, it will clear the
537 * bit that points to the head page, move the head, and then set
538 * the bit that points to the new head page.
540 * We also don't want an interrupt coming in and moving the head
541 * page on another writer. Thus we use the second LSB to catch
544 * head->list->prev->next bit 1 bit 0
547 * Points to head page 0 1
550 * Note we can not trust the prev pointer of the head page, because:
552 * +----+ +-----+ +-----+
553 * | |------>| T |---X--->| N |
555 * +----+ +-----+ +-----+
558 * +----------| R |----------+ |
562 * Key: ---X--> HEAD flag set in pointer
567 * (see __rb_reserve_next() to see where this happens)
569 * What the above shows is that the reader just swapped out
570 * the reader page with a page in the buffer, but before it
571 * could make the new header point back to the new page added
572 * it was preempted by a writer. The writer moved forward onto
573 * the new page added by the reader and is about to move forward
576 * You can see, it is legitimate for the previous pointer of
577 * the head (or any page) not to point back to itself. But only
581 #define RB_PAGE_NORMAL 0UL
582 #define RB_PAGE_HEAD 1UL
583 #define RB_PAGE_UPDATE 2UL
586 #define RB_FLAG_MASK 3UL
588 /* PAGE_MOVED is not part of the mask */
589 #define RB_PAGE_MOVED 4UL
592 * rb_list_head - remove any bit
594 static struct list_head *rb_list_head(struct list_head *list)
596 unsigned long val = (unsigned long)list;
598 return (struct list_head *)(val & ~RB_FLAG_MASK);
602 * rb_is_head_page - test if the given page is the head page
604 * Because the reader may move the head_page pointer, we can
605 * not trust what the head page is (it may be pointing to
606 * the reader page). But if the next page is a header page,
607 * its flags will be non zero.
610 rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
611 struct buffer_page *page, struct list_head *list)
615 val = (unsigned long)list->next;
617 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
618 return RB_PAGE_MOVED;
620 return val & RB_FLAG_MASK;
626 * The unique thing about the reader page, is that, if the
627 * writer is ever on it, the previous pointer never points
628 * back to the reader page.
630 static int rb_is_reader_page(struct buffer_page *page)
632 struct list_head *list = page->list.prev;
634 return rb_list_head(list->next) != &page->list;
638 * rb_set_list_to_head - set a list_head to be pointing to head.
640 static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
641 struct list_head *list)
645 ptr = (unsigned long *)&list->next;
646 *ptr |= RB_PAGE_HEAD;
647 *ptr &= ~RB_PAGE_UPDATE;
651 * rb_head_page_activate - sets up head page
653 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
655 struct buffer_page *head;
657 head = cpu_buffer->head_page;
662 * Set the previous list pointer to have the HEAD flag.
664 rb_set_list_to_head(cpu_buffer, head->list.prev);
667 static void rb_list_head_clear(struct list_head *list)
669 unsigned long *ptr = (unsigned long *)&list->next;
671 *ptr &= ~RB_FLAG_MASK;
675 * rb_head_page_dactivate - clears head page ptr (for free list)
678 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
680 struct list_head *hd;
682 /* Go through the whole list and clear any pointers found. */
683 rb_list_head_clear(cpu_buffer->pages);
685 list_for_each(hd, cpu_buffer->pages)
686 rb_list_head_clear(hd);
689 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
690 struct buffer_page *head,
691 struct buffer_page *prev,
692 int old_flag, int new_flag)
694 struct list_head *list;
695 unsigned long val = (unsigned long)&head->list;
700 val &= ~RB_FLAG_MASK;
702 ret = cmpxchg((unsigned long *)&list->next,
703 val | old_flag, val | new_flag);
705 /* check if the reader took the page */
706 if ((ret & ~RB_FLAG_MASK) != val)
707 return RB_PAGE_MOVED;
709 return ret & RB_FLAG_MASK;
712 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
713 struct buffer_page *head,
714 struct buffer_page *prev,
717 return rb_head_page_set(cpu_buffer, head, prev,
718 old_flag, RB_PAGE_UPDATE);
721 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
722 struct buffer_page *head,
723 struct buffer_page *prev,
726 return rb_head_page_set(cpu_buffer, head, prev,
727 old_flag, RB_PAGE_HEAD);
730 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
731 struct buffer_page *head,
732 struct buffer_page *prev,
735 return rb_head_page_set(cpu_buffer, head, prev,
736 old_flag, RB_PAGE_NORMAL);
739 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
740 struct buffer_page **bpage)
742 struct list_head *p = rb_list_head((*bpage)->list.next);
744 *bpage = list_entry(p, struct buffer_page, list);
747 static struct buffer_page *
748 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
750 struct buffer_page *head;
751 struct buffer_page *page;
752 struct list_head *list;
755 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
759 list = cpu_buffer->pages;
760 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
763 page = head = cpu_buffer->head_page;
765 * It is possible that the writer moves the header behind
766 * where we started, and we miss in one loop.
767 * A second loop should grab the header, but we'll do
768 * three loops just because I'm paranoid.
770 for (i = 0; i < 3; i++) {
772 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
773 cpu_buffer->head_page = page;
776 rb_inc_page(cpu_buffer, &page);
777 } while (page != head);
780 RB_WARN_ON(cpu_buffer, 1);
785 static int rb_head_page_replace(struct buffer_page *old,
786 struct buffer_page *new)
788 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
792 val = *ptr & ~RB_FLAG_MASK;
795 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
801 * rb_tail_page_update - move the tail page forward
803 * Returns 1 if moved tail page, 0 if someone else did.
805 static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
806 struct buffer_page *tail_page,
807 struct buffer_page *next_page)
809 struct buffer_page *old_tail;
810 unsigned long old_entries;
811 unsigned long old_write;
815 * The tail page now needs to be moved forward.
817 * We need to reset the tail page, but without messing
818 * with possible erasing of data brought in by interrupts
819 * that have moved the tail page and are currently on it.
821 * We add a counter to the write field to denote this.
823 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
824 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
827 * Just make sure we have seen our old_write and synchronize
828 * with any interrupts that come in.
833 * If the tail page is still the same as what we think
834 * it is, then it is up to us to update the tail
837 if (tail_page == cpu_buffer->tail_page) {
838 /* Zero the write counter */
839 unsigned long val = old_write & ~RB_WRITE_MASK;
840 unsigned long eval = old_entries & ~RB_WRITE_MASK;
843 * This will only succeed if an interrupt did
844 * not come in and change it. In which case, we
845 * do not want to modify it.
847 * We add (void) to let the compiler know that we do not care
848 * about the return value of these functions. We use the
849 * cmpxchg to only update if an interrupt did not already
850 * do it for us. If the cmpxchg fails, we don't care.
852 (void)local_cmpxchg(&next_page->write, old_write, val);
853 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
856 * No need to worry about races with clearing out the commit.
857 * it only can increment when a commit takes place. But that
858 * only happens in the outer most nested commit.
860 local_set(&next_page->page->commit, 0);
862 old_tail = cmpxchg(&cpu_buffer->tail_page,
863 tail_page, next_page);
865 if (old_tail == tail_page)
872 static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
873 struct buffer_page *bpage)
875 unsigned long val = (unsigned long)bpage;
877 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
884 * rb_check_list - make sure a pointer to a list has the last bits zero
886 static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
887 struct list_head *list)
889 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
891 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
897 * check_pages - integrity check of buffer pages
898 * @cpu_buffer: CPU buffer with pages to test
900 * As a safety measure we check to make sure the data pages have not
903 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
905 struct list_head *head = cpu_buffer->pages;
906 struct buffer_page *bpage, *tmp;
908 rb_head_page_deactivate(cpu_buffer);
910 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
912 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
915 if (rb_check_list(cpu_buffer, head))
918 list_for_each_entry_safe(bpage, tmp, head, list) {
919 if (RB_WARN_ON(cpu_buffer,
920 bpage->list.next->prev != &bpage->list))
922 if (RB_WARN_ON(cpu_buffer,
923 bpage->list.prev->next != &bpage->list))
925 if (rb_check_list(cpu_buffer, &bpage->list))
929 rb_head_page_activate(cpu_buffer);
934 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
937 struct buffer_page *bpage, *tmp;
944 for (i = 0; i < nr_pages; i++) {
945 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
946 GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
950 rb_check_bpage(cpu_buffer, bpage);
952 list_add(&bpage->list, &pages);
954 addr = __get_free_page(GFP_KERNEL);
957 bpage->page = (void *)addr;
958 rb_init_page(bpage->page);
962 * The ring buffer page list is a circular list that does not
963 * start and end with a list head. All page list items point to
966 cpu_buffer->pages = pages.next;
969 rb_check_pages(cpu_buffer);
974 list_for_each_entry_safe(bpage, tmp, &pages, list) {
975 list_del_init(&bpage->list);
976 free_buffer_page(bpage);
981 static struct ring_buffer_per_cpu *
982 rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
984 struct ring_buffer_per_cpu *cpu_buffer;
985 struct buffer_page *bpage;
989 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
990 GFP_KERNEL, cpu_to_node(cpu));
994 cpu_buffer->cpu = cpu;
995 cpu_buffer->buffer = buffer;
996 spin_lock_init(&cpu_buffer->reader_lock);
997 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
998 cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
1000 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1001 GFP_KERNEL, cpu_to_node(cpu));
1003 goto fail_free_buffer;
1005 rb_check_bpage(cpu_buffer, bpage);
1007 cpu_buffer->reader_page = bpage;
1008 addr = __get_free_page(GFP_KERNEL);
1010 goto fail_free_reader;
1011 bpage->page = (void *)addr;
1012 rb_init_page(bpage->page);
1014 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1016 ret = rb_allocate_pages(cpu_buffer, buffer->pages);
1018 goto fail_free_reader;
1020 cpu_buffer->head_page
1021 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1022 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1024 rb_head_page_activate(cpu_buffer);
1029 free_buffer_page(cpu_buffer->reader_page);
1036 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1038 struct list_head *head = cpu_buffer->pages;
1039 struct buffer_page *bpage, *tmp;
1041 free_buffer_page(cpu_buffer->reader_page);
1043 rb_head_page_deactivate(cpu_buffer);
1046 list_for_each_entry_safe(bpage, tmp, head, list) {
1047 list_del_init(&bpage->list);
1048 free_buffer_page(bpage);
1050 bpage = list_entry(head, struct buffer_page, list);
1051 free_buffer_page(bpage);
1057 #ifdef CONFIG_HOTPLUG_CPU
1058 static int rb_cpu_notify(struct notifier_block *self,
1059 unsigned long action, void *hcpu);
1063 * ring_buffer_alloc - allocate a new ring_buffer
1064 * @size: the size in bytes per cpu that is needed.
1065 * @flags: attributes to set for the ring buffer.
1067 * Currently the only flag that is available is the RB_FL_OVERWRITE
1068 * flag. This flag means that the buffer will overwrite old data
1069 * when the buffer wraps. If this flag is not set, the buffer will
1070 * drop data when the tail hits the head.
1072 struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1073 struct lock_class_key *key)
1075 struct ring_buffer *buffer;
1079 /* keep it in its own cache line */
1080 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1085 if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1086 goto fail_free_buffer;
1088 buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1089 buffer->flags = flags;
1090 buffer->clock = trace_clock_local;
1091 buffer->reader_lock_key = key;
1093 /* need at least two pages */
1094 if (buffer->pages < 2)
1098 * In case of non-hotplug cpu, if the ring-buffer is allocated
1099 * in early initcall, it will not be notified of secondary cpus.
1100 * In that off case, we need to allocate for all possible cpus.
1102 #ifdef CONFIG_HOTPLUG_CPU
1104 cpumask_copy(buffer->cpumask, cpu_online_mask);
1106 cpumask_copy(buffer->cpumask, cpu_possible_mask);
1108 buffer->cpus = nr_cpu_ids;
1110 bsize = sizeof(void *) * nr_cpu_ids;
1111 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1113 if (!buffer->buffers)
1114 goto fail_free_cpumask;
1116 for_each_buffer_cpu(buffer, cpu) {
1117 buffer->buffers[cpu] =
1118 rb_allocate_cpu_buffer(buffer, cpu);
1119 if (!buffer->buffers[cpu])
1120 goto fail_free_buffers;
1123 #ifdef CONFIG_HOTPLUG_CPU
1124 buffer->cpu_notify.notifier_call = rb_cpu_notify;
1125 buffer->cpu_notify.priority = 0;
1126 register_cpu_notifier(&buffer->cpu_notify);
1130 mutex_init(&buffer->mutex);
1135 for_each_buffer_cpu(buffer, cpu) {
1136 if (buffer->buffers[cpu])
1137 rb_free_cpu_buffer(buffer->buffers[cpu]);
1139 kfree(buffer->buffers);
1142 free_cpumask_var(buffer->cpumask);
1149 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1152 * ring_buffer_free - free a ring buffer.
1153 * @buffer: the buffer to free.
1156 ring_buffer_free(struct ring_buffer *buffer)
1162 #ifdef CONFIG_HOTPLUG_CPU
1163 unregister_cpu_notifier(&buffer->cpu_notify);
1166 for_each_buffer_cpu(buffer, cpu)
1167 rb_free_cpu_buffer(buffer->buffers[cpu]);
1171 kfree(buffer->buffers);
1172 free_cpumask_var(buffer->cpumask);
1176 EXPORT_SYMBOL_GPL(ring_buffer_free);
1178 void ring_buffer_set_clock(struct ring_buffer *buffer,
1181 buffer->clock = clock;
1184 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1187 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
1189 struct buffer_page *bpage;
1190 struct list_head *p;
1193 atomic_inc(&cpu_buffer->record_disabled);
1194 synchronize_sched();
1196 spin_lock_irq(&cpu_buffer->reader_lock);
1197 rb_head_page_deactivate(cpu_buffer);
1199 for (i = 0; i < nr_pages; i++) {
1200 if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
1202 p = cpu_buffer->pages->next;
1203 bpage = list_entry(p, struct buffer_page, list);
1204 list_del_init(&bpage->list);
1205 free_buffer_page(bpage);
1207 if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
1210 rb_reset_cpu(cpu_buffer);
1211 spin_unlock_irq(&cpu_buffer->reader_lock);
1213 rb_check_pages(cpu_buffer);
1215 atomic_dec(&cpu_buffer->record_disabled);
1220 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
1221 struct list_head *pages, unsigned nr_pages)
1223 struct buffer_page *bpage;
1224 struct list_head *p;
1227 atomic_inc(&cpu_buffer->record_disabled);
1228 synchronize_sched();
1230 spin_lock_irq(&cpu_buffer->reader_lock);
1231 rb_head_page_deactivate(cpu_buffer);
1233 for (i = 0; i < nr_pages; i++) {
1234 if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
1237 bpage = list_entry(p, struct buffer_page, list);
1238 list_del_init(&bpage->list);
1239 list_add_tail(&bpage->list, cpu_buffer->pages);
1241 rb_reset_cpu(cpu_buffer);
1242 spin_unlock_irq(&cpu_buffer->reader_lock);
1244 rb_check_pages(cpu_buffer);
1246 atomic_dec(&cpu_buffer->record_disabled);
1250 * ring_buffer_resize - resize the ring buffer
1251 * @buffer: the buffer to resize.
1252 * @size: the new size.
1254 * The tracer is responsible for making sure that the buffer is
1255 * not being used while changing the size.
1256 * Note: We may be able to change the above requirement by using
1257 * RCU synchronizations.
1259 * Minimum size is 2 * BUF_PAGE_SIZE.
1261 * Returns -1 on failure.
1263 int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
1265 struct ring_buffer_per_cpu *cpu_buffer;
1266 unsigned nr_pages, rm_pages, new_pages;
1267 struct buffer_page *bpage, *tmp;
1268 unsigned long buffer_size;
1274 * Always succeed at resizing a non-existent buffer:
1279 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1280 size *= BUF_PAGE_SIZE;
1281 buffer_size = buffer->pages * BUF_PAGE_SIZE;
1283 /* we need a minimum of two pages */
1284 if (size < BUF_PAGE_SIZE * 2)
1285 size = BUF_PAGE_SIZE * 2;
1287 if (size == buffer_size)
1290 mutex_lock(&buffer->mutex);
1293 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1295 if (size < buffer_size) {
1297 /* easy case, just free pages */
1298 if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
1301 rm_pages = buffer->pages - nr_pages;
1303 for_each_buffer_cpu(buffer, cpu) {
1304 cpu_buffer = buffer->buffers[cpu];
1305 rb_remove_pages(cpu_buffer, rm_pages);
1311 * This is a bit more difficult. We only want to add pages
1312 * when we can allocate enough for all CPUs. We do this
1313 * by allocating all the pages and storing them on a local
1314 * link list. If we succeed in our allocation, then we
1315 * add these pages to the cpu_buffers. Otherwise we just free
1316 * them all and return -ENOMEM;
1318 if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
1321 new_pages = nr_pages - buffer->pages;
1323 for_each_buffer_cpu(buffer, cpu) {
1324 for (i = 0; i < new_pages; i++) {
1325 bpage = kzalloc_node(ALIGN(sizeof(*bpage),
1327 GFP_KERNEL, cpu_to_node(cpu));
1330 list_add(&bpage->list, &pages);
1331 addr = __get_free_page(GFP_KERNEL);
1334 bpage->page = (void *)addr;
1335 rb_init_page(bpage->page);
1339 for_each_buffer_cpu(buffer, cpu) {
1340 cpu_buffer = buffer->buffers[cpu];
1341 rb_insert_pages(cpu_buffer, &pages, new_pages);
1344 if (RB_WARN_ON(buffer, !list_empty(&pages)))
1348 buffer->pages = nr_pages;
1350 mutex_unlock(&buffer->mutex);
1355 list_for_each_entry_safe(bpage, tmp, &pages, list) {
1356 list_del_init(&bpage->list);
1357 free_buffer_page(bpage);
1360 mutex_unlock(&buffer->mutex);
1364 * Something went totally wrong, and we are too paranoid
1365 * to even clean up the mess.
1369 mutex_unlock(&buffer->mutex);
1372 EXPORT_SYMBOL_GPL(ring_buffer_resize);
1374 static inline void *
1375 __rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
1377 return bpage->data + index;
1380 static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1382 return bpage->page->data + index;
1385 static inline struct ring_buffer_event *
1386 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1388 return __rb_page_index(cpu_buffer->reader_page,
1389 cpu_buffer->reader_page->read);
1392 static inline struct ring_buffer_event *
1393 rb_iter_head_event(struct ring_buffer_iter *iter)
1395 return __rb_page_index(iter->head_page, iter->head);
1398 static inline unsigned long rb_page_write(struct buffer_page *bpage)
1400 return local_read(&bpage->write) & RB_WRITE_MASK;
1403 static inline unsigned rb_page_commit(struct buffer_page *bpage)
1405 return local_read(&bpage->page->commit);
1408 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1410 return local_read(&bpage->entries) & RB_WRITE_MASK;
1413 /* Size is determined by what has been commited */
1414 static inline unsigned rb_page_size(struct buffer_page *bpage)
1416 return rb_page_commit(bpage);
1419 static inline unsigned
1420 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1422 return rb_page_commit(cpu_buffer->commit_page);
1425 static inline unsigned
1426 rb_event_index(struct ring_buffer_event *event)
1428 unsigned long addr = (unsigned long)event;
1430 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1434 rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1435 struct ring_buffer_event *event)
1437 unsigned long addr = (unsigned long)event;
1438 unsigned long index;
1440 index = rb_event_index(event);
1443 return cpu_buffer->commit_page->page == (void *)addr &&
1444 rb_commit_index(cpu_buffer) == index;
1448 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1450 unsigned long max_count;
1453 * We only race with interrupts and NMIs on this CPU.
1454 * If we own the commit event, then we can commit
1455 * all others that interrupted us, since the interruptions
1456 * are in stack format (they finish before they come
1457 * back to us). This allows us to do a simple loop to
1458 * assign the commit to the tail.
1461 max_count = cpu_buffer->buffer->pages * 100;
1463 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
1464 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
1466 if (RB_WARN_ON(cpu_buffer,
1467 rb_is_reader_page(cpu_buffer->tail_page)))
1469 local_set(&cpu_buffer->commit_page->page->commit,
1470 rb_page_write(cpu_buffer->commit_page));
1471 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1472 cpu_buffer->write_stamp =
1473 cpu_buffer->commit_page->page->time_stamp;
1474 /* add barrier to keep gcc from optimizing too much */
1477 while (rb_commit_index(cpu_buffer) !=
1478 rb_page_write(cpu_buffer->commit_page)) {
1480 local_set(&cpu_buffer->commit_page->page->commit,
1481 rb_page_write(cpu_buffer->commit_page));
1482 RB_WARN_ON(cpu_buffer,
1483 local_read(&cpu_buffer->commit_page->page->commit) &
1488 /* again, keep gcc from optimizing */
1492 * If an interrupt came in just after the first while loop
1493 * and pushed the tail page forward, we will be left with
1494 * a dangling commit that will never go forward.
1496 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1500 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1502 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
1503 cpu_buffer->reader_page->read = 0;
1506 static void rb_inc_iter(struct ring_buffer_iter *iter)
1508 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1511 * The iterator could be on the reader page (it starts there).
1512 * But the head could have moved, since the reader was
1513 * found. Check for this case and assign the iterator
1514 * to the head page instead of next.
1516 if (iter->head_page == cpu_buffer->reader_page)
1517 iter->head_page = rb_set_head_page(cpu_buffer);
1519 rb_inc_page(cpu_buffer, &iter->head_page);
1521 iter->read_stamp = iter->head_page->page->time_stamp;
1526 * ring_buffer_update_event - update event type and data
1527 * @event: the even to update
1528 * @type: the type of event
1529 * @length: the size of the event field in the ring buffer
1531 * Update the type and data fields of the event. The length
1532 * is the actual size that is written to the ring buffer,
1533 * and with this, we can determine what to place into the
1537 rb_update_event(struct ring_buffer_event *event,
1538 unsigned type, unsigned length)
1540 event->type_len = type;
1544 case RINGBUF_TYPE_PADDING:
1545 case RINGBUF_TYPE_TIME_EXTEND:
1546 case RINGBUF_TYPE_TIME_STAMP:
1550 length -= RB_EVNT_HDR_SIZE;
1551 if (length > RB_MAX_SMALL_DATA)
1552 event->array[0] = length;
1554 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
1562 * rb_handle_head_page - writer hit the head page
1564 * Returns: +1 to retry page
1569 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1570 struct buffer_page *tail_page,
1571 struct buffer_page *next_page)
1573 struct buffer_page *new_head;
1578 entries = rb_page_entries(next_page);
1581 * The hard part is here. We need to move the head
1582 * forward, and protect against both readers on
1583 * other CPUs and writers coming in via interrupts.
1585 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1589 * type can be one of four:
1590 * NORMAL - an interrupt already moved it for us
1591 * HEAD - we are the first to get here.
1592 * UPDATE - we are the interrupt interrupting
1594 * MOVED - a reader on another CPU moved the next
1595 * pointer to its reader page. Give up
1602 * We changed the head to UPDATE, thus
1603 * it is our responsibility to update
1606 local_add(entries, &cpu_buffer->overrun);
1609 * The entries will be zeroed out when we move the
1613 /* still more to do */
1616 case RB_PAGE_UPDATE:
1618 * This is an interrupt that interrupt the
1619 * previous update. Still more to do.
1622 case RB_PAGE_NORMAL:
1624 * An interrupt came in before the update
1625 * and processed this for us.
1626 * Nothing left to do.
1631 * The reader is on another CPU and just did
1632 * a swap with our next_page.
1637 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
1642 * Now that we are here, the old head pointer is
1643 * set to UPDATE. This will keep the reader from
1644 * swapping the head page with the reader page.
1645 * The reader (on another CPU) will spin till
1648 * We just need to protect against interrupts
1649 * doing the job. We will set the next pointer
1650 * to HEAD. After that, we set the old pointer
1651 * to NORMAL, but only if it was HEAD before.
1652 * otherwise we are an interrupt, and only
1653 * want the outer most commit to reset it.
1655 new_head = next_page;
1656 rb_inc_page(cpu_buffer, &new_head);
1658 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
1662 * Valid returns are:
1663 * HEAD - an interrupt came in and already set it.
1664 * NORMAL - One of two things:
1665 * 1) We really set it.
1666 * 2) A bunch of interrupts came in and moved
1667 * the page forward again.
1671 case RB_PAGE_NORMAL:
1675 RB_WARN_ON(cpu_buffer, 1);
1680 * It is possible that an interrupt came in,
1681 * set the head up, then more interrupts came in
1682 * and moved it again. When we get back here,
1683 * the page would have been set to NORMAL but we
1684 * just set it back to HEAD.
1686 * How do you detect this? Well, if that happened
1687 * the tail page would have moved.
1689 if (ret == RB_PAGE_NORMAL) {
1691 * If the tail had moved passed next, then we need
1692 * to reset the pointer.
1694 if (cpu_buffer->tail_page != tail_page &&
1695 cpu_buffer->tail_page != next_page)
1696 rb_head_page_set_normal(cpu_buffer, new_head,
1702 * If this was the outer most commit (the one that
1703 * changed the original pointer from HEAD to UPDATE),
1704 * then it is up to us to reset it to NORMAL.
1706 if (type == RB_PAGE_HEAD) {
1707 ret = rb_head_page_set_normal(cpu_buffer, next_page,
1710 if (RB_WARN_ON(cpu_buffer,
1711 ret != RB_PAGE_UPDATE))
1718 static unsigned rb_calculate_event_length(unsigned length)
1720 struct ring_buffer_event event; /* Used only for sizeof array */
1722 /* zero length can cause confusions */
1726 if (length > RB_MAX_SMALL_DATA)
1727 length += sizeof(event.array[0]);
1729 length += RB_EVNT_HDR_SIZE;
1730 length = ALIGN(length, RB_ALIGNMENT);
1736 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
1737 struct buffer_page *tail_page,
1738 unsigned long tail, unsigned long length)
1740 struct ring_buffer_event *event;
1743 * Only the event that crossed the page boundary
1744 * must fill the old tail_page with padding.
1746 if (tail >= BUF_PAGE_SIZE) {
1747 local_sub(length, &tail_page->write);
1751 event = __rb_page_index(tail_page, tail);
1752 kmemcheck_annotate_bitfield(event, bitfield);
1755 * If this event is bigger than the minimum size, then
1756 * we need to be careful that we don't subtract the
1757 * write counter enough to allow another writer to slip
1759 * We put in a discarded commit instead, to make sure
1760 * that this space is not used again.
1762 * If we are less than the minimum size, we don't need to
1765 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
1766 /* No room for any events */
1768 /* Mark the rest of the page with padding */
1769 rb_event_set_padding(event);
1771 /* Set the write back to the previous setting */
1772 local_sub(length, &tail_page->write);
1776 /* Put in a discarded event */
1777 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
1778 event->type_len = RINGBUF_TYPE_PADDING;
1779 /* time delta must be non zero */
1780 event->time_delta = 1;
1782 /* Set write to end of buffer */
1783 length = (tail + length) - BUF_PAGE_SIZE;
1784 local_sub(length, &tail_page->write);
1787 static struct ring_buffer_event *
1788 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
1789 unsigned long length, unsigned long tail,
1790 struct buffer_page *tail_page, u64 *ts)
1792 struct buffer_page *commit_page = cpu_buffer->commit_page;
1793 struct ring_buffer *buffer = cpu_buffer->buffer;
1794 struct buffer_page *next_page;
1797 next_page = tail_page;
1799 rb_inc_page(cpu_buffer, &next_page);
1802 * If for some reason, we had an interrupt storm that made
1803 * it all the way around the buffer, bail, and warn
1806 if (unlikely(next_page == commit_page)) {
1807 local_inc(&cpu_buffer->commit_overrun);
1812 * This is where the fun begins!
1814 * We are fighting against races between a reader that
1815 * could be on another CPU trying to swap its reader
1816 * page with the buffer head.
1818 * We are also fighting against interrupts coming in and
1819 * moving the head or tail on us as well.
1821 * If the next page is the head page then we have filled
1822 * the buffer, unless the commit page is still on the
1825 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
1828 * If the commit is not on the reader page, then
1829 * move the header page.
1831 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
1833 * If we are not in overwrite mode,
1834 * this is easy, just stop here.
1836 if (!(buffer->flags & RB_FL_OVERWRITE))
1839 ret = rb_handle_head_page(cpu_buffer,
1848 * We need to be careful here too. The
1849 * commit page could still be on the reader
1850 * page. We could have a small buffer, and
1851 * have filled up the buffer with events
1852 * from interrupts and such, and wrapped.
1854 * Note, if the tail page is also the on the
1855 * reader_page, we let it move out.
1857 if (unlikely((cpu_buffer->commit_page !=
1858 cpu_buffer->tail_page) &&
1859 (cpu_buffer->commit_page ==
1860 cpu_buffer->reader_page))) {
1861 local_inc(&cpu_buffer->commit_overrun);
1867 ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
1870 * Nested commits always have zero deltas, so
1871 * just reread the time stamp
1873 *ts = rb_time_stamp(buffer);
1874 next_page->page->time_stamp = *ts;
1879 rb_reset_tail(cpu_buffer, tail_page, tail, length);
1881 /* fail and let the caller try again */
1882 return ERR_PTR(-EAGAIN);
1886 rb_reset_tail(cpu_buffer, tail_page, tail, length);
1891 static struct ring_buffer_event *
1892 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
1893 unsigned type, unsigned long length, u64 *ts)
1895 struct buffer_page *tail_page;
1896 struct ring_buffer_event *event;
1897 unsigned long tail, write;
1899 tail_page = cpu_buffer->tail_page;
1900 write = local_add_return(length, &tail_page->write);
1902 /* set write to only the index of the write */
1903 write &= RB_WRITE_MASK;
1904 tail = write - length;
1906 /* See if we shot pass the end of this buffer page */
1907 if (write > BUF_PAGE_SIZE)
1908 return rb_move_tail(cpu_buffer, length, tail,
1911 /* We reserved something on the buffer */
1913 event = __rb_page_index(tail_page, tail);
1914 kmemcheck_annotate_bitfield(event, bitfield);
1915 rb_update_event(event, type, length);
1917 /* The passed in type is zero for DATA */
1919 local_inc(&tail_page->entries);
1922 * If this is the first commit on the page, then update
1926 tail_page->page->time_stamp = *ts;
1932 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
1933 struct ring_buffer_event *event)
1935 unsigned long new_index, old_index;
1936 struct buffer_page *bpage;
1937 unsigned long index;
1940 new_index = rb_event_index(event);
1941 old_index = new_index + rb_event_length(event);
1942 addr = (unsigned long)event;
1945 bpage = cpu_buffer->tail_page;
1947 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
1948 unsigned long write_mask =
1949 local_read(&bpage->write) & ~RB_WRITE_MASK;
1951 * This is on the tail page. It is possible that
1952 * a write could come in and move the tail page
1953 * and write to the next page. That is fine
1954 * because we just shorten what is on this page.
1956 old_index += write_mask;
1957 new_index += write_mask;
1958 index = local_cmpxchg(&bpage->write, old_index, new_index);
1959 if (index == old_index)
1963 /* could not discard */
1968 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1969 u64 *ts, u64 *delta)
1971 struct ring_buffer_event *event;
1975 if (unlikely(*delta > (1ULL << 59) && !once++)) {
1976 printk(KERN_WARNING "Delta way too big! %llu"
1977 " ts=%llu write stamp = %llu\n",
1978 (unsigned long long)*delta,
1979 (unsigned long long)*ts,
1980 (unsigned long long)cpu_buffer->write_stamp);
1985 * The delta is too big, we to add a
1988 event = __rb_reserve_next(cpu_buffer,
1989 RINGBUF_TYPE_TIME_EXTEND,
1995 if (PTR_ERR(event) == -EAGAIN)
1998 /* Only a commited time event can update the write stamp */
1999 if (rb_event_is_commit(cpu_buffer, event)) {
2001 * If this is the first on the page, then it was
2002 * updated with the page itself. Try to discard it
2003 * and if we can't just make it zero.
2005 if (rb_event_index(event)) {
2006 event->time_delta = *delta & TS_MASK;
2007 event->array[0] = *delta >> TS_SHIFT;
2009 /* try to discard, since we do not need this */
2010 if (!rb_try_to_discard(cpu_buffer, event)) {
2011 /* nope, just zero it */
2012 event->time_delta = 0;
2013 event->array[0] = 0;
2016 cpu_buffer->write_stamp = *ts;
2017 /* let the caller know this was the commit */
2020 /* Try to discard the event */
2021 if (!rb_try_to_discard(cpu_buffer, event)) {
2022 /* Darn, this is just wasted space */
2023 event->time_delta = 0;
2024 event->array[0] = 0;
2034 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2036 local_inc(&cpu_buffer->committing);
2037 local_inc(&cpu_buffer->commits);
2040 static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2042 unsigned long commits;
2044 if (RB_WARN_ON(cpu_buffer,
2045 !local_read(&cpu_buffer->committing)))
2049 commits = local_read(&cpu_buffer->commits);
2050 /* synchronize with interrupts */
2052 if (local_read(&cpu_buffer->committing) == 1)
2053 rb_set_commit_to_write(cpu_buffer);
2055 local_dec(&cpu_buffer->committing);
2057 /* synchronize with interrupts */
2061 * Need to account for interrupts coming in between the
2062 * updating of the commit page and the clearing of the
2063 * committing counter.
2065 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2066 !local_read(&cpu_buffer->committing)) {
2067 local_inc(&cpu_buffer->committing);
2072 static struct ring_buffer_event *
2073 rb_reserve_next_event(struct ring_buffer *buffer,
2074 struct ring_buffer_per_cpu *cpu_buffer,
2075 unsigned long length)
2077 struct ring_buffer_event *event;
2082 rb_start_commit(cpu_buffer);
2084 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2086 * Due to the ability to swap a cpu buffer from a buffer
2087 * it is possible it was swapped before we committed.
2088 * (committing stops a swap). We check for it here and
2089 * if it happened, we have to fail the write.
2092 if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
2093 local_dec(&cpu_buffer->committing);
2094 local_dec(&cpu_buffer->commits);
2099 length = rb_calculate_event_length(length);
2102 * We allow for interrupts to reenter here and do a trace.
2103 * If one does, it will cause this original code to loop
2104 * back here. Even with heavy interrupts happening, this
2105 * should only happen a few times in a row. If this happens
2106 * 1000 times in a row, there must be either an interrupt
2107 * storm or we have something buggy.
2110 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2113 ts = rb_time_stamp(cpu_buffer->buffer);
2116 * Only the first commit can update the timestamp.
2117 * Yes there is a race here. If an interrupt comes in
2118 * just after the conditional and it traces too, then it
2119 * will also check the deltas. More than one timestamp may
2120 * also be made. But only the entry that did the actual
2121 * commit will be something other than zero.
2123 if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
2124 rb_page_write(cpu_buffer->tail_page) ==
2125 rb_commit_index(cpu_buffer))) {
2128 diff = ts - cpu_buffer->write_stamp;
2130 /* make sure this diff is calculated here */
2133 /* Did the write stamp get updated already? */
2134 if (unlikely(ts < cpu_buffer->write_stamp))
2138 if (unlikely(test_time_stamp(delta))) {
2140 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
2141 if (commit == -EBUSY)
2144 if (commit == -EAGAIN)
2147 RB_WARN_ON(cpu_buffer, commit < 0);
2152 event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
2153 if (unlikely(PTR_ERR(event) == -EAGAIN))
2159 if (!rb_event_is_commit(cpu_buffer, event))
2162 event->time_delta = delta;
2167 rb_end_commit(cpu_buffer);
2171 #ifdef CONFIG_TRACING
2173 #define TRACE_RECURSIVE_DEPTH 16
2175 static int trace_recursive_lock(void)
2177 current->trace_recursion++;
2179 if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
2182 /* Disable all tracing before we do anything else */
2183 tracing_off_permanent();
2185 printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
2186 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
2187 current->trace_recursion,
2188 hardirq_count() >> HARDIRQ_SHIFT,
2189 softirq_count() >> SOFTIRQ_SHIFT,
2196 static void trace_recursive_unlock(void)
2198 WARN_ON_ONCE(!current->trace_recursion);
2200 current->trace_recursion--;
2205 #define trace_recursive_lock() (0)
2206 #define trace_recursive_unlock() do { } while (0)
2210 static DEFINE_PER_CPU(int, rb_need_resched);
2213 * ring_buffer_lock_reserve - reserve a part of the buffer
2214 * @buffer: the ring buffer to reserve from
2215 * @length: the length of the data to reserve (excluding event header)
2217 * Returns a reseverd event on the ring buffer to copy directly to.
2218 * The user of this interface will need to get the body to write into
2219 * and can use the ring_buffer_event_data() interface.
2221 * The length is the length of the data needed, not the event length
2222 * which also includes the event header.
2224 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2225 * If NULL is returned, then nothing has been allocated or locked.
2227 struct ring_buffer_event *
2228 ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2230 struct ring_buffer_per_cpu *cpu_buffer;
2231 struct ring_buffer_event *event;
2234 if (ring_buffer_flags != RB_BUFFERS_ON)
2237 if (atomic_read(&buffer->record_disabled))
2240 /* If we are tracing schedule, we don't want to recurse */
2241 resched = ftrace_preempt_disable();
2243 if (trace_recursive_lock())
2246 cpu = raw_smp_processor_id();
2248 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2251 cpu_buffer = buffer->buffers[cpu];
2253 if (atomic_read(&cpu_buffer->record_disabled))
2256 if (length > BUF_MAX_DATA_SIZE)
2259 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2264 * Need to store resched state on this cpu.
2265 * Only the first needs to.
2268 if (preempt_count() == 1)
2269 per_cpu(rb_need_resched, cpu) = resched;
2274 trace_recursive_unlock();
2277 ftrace_preempt_enable(resched);
2280 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2283 rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2284 struct ring_buffer_event *event)
2287 * The event first in the commit queue updates the
2290 if (rb_event_is_commit(cpu_buffer, event))
2291 cpu_buffer->write_stamp += event->time_delta;
2294 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2295 struct ring_buffer_event *event)
2297 local_inc(&cpu_buffer->entries);
2298 rb_update_write_stamp(cpu_buffer, event);
2299 rb_end_commit(cpu_buffer);
2303 * ring_buffer_unlock_commit - commit a reserved
2304 * @buffer: The buffer to commit to
2305 * @event: The event pointer to commit.
2307 * This commits the data to the ring buffer, and releases any locks held.
2309 * Must be paired with ring_buffer_lock_reserve.
2311 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2312 struct ring_buffer_event *event)
2314 struct ring_buffer_per_cpu *cpu_buffer;
2315 int cpu = raw_smp_processor_id();
2317 cpu_buffer = buffer->buffers[cpu];
2319 rb_commit(cpu_buffer, event);
2321 trace_recursive_unlock();
2324 * Only the last preempt count needs to restore preemption.
2326 if (preempt_count() == 1)
2327 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
2329 preempt_enable_no_resched_notrace();
2333 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2335 static inline void rb_event_discard(struct ring_buffer_event *event)
2337 /* array[0] holds the actual length for the discarded event */
2338 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2339 event->type_len = RINGBUF_TYPE_PADDING;
2340 /* time delta must be non zero */
2341 if (!event->time_delta)
2342 event->time_delta = 1;
2346 * Decrement the entries to the page that an event is on.
2347 * The event does not even need to exist, only the pointer
2348 * to the page it is on. This may only be called before the commit
2352 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2353 struct ring_buffer_event *event)
2355 unsigned long addr = (unsigned long)event;
2356 struct buffer_page *bpage = cpu_buffer->commit_page;
2357 struct buffer_page *start;
2361 /* Do the likely case first */
2362 if (likely(bpage->page == (void *)addr)) {
2363 local_dec(&bpage->entries);
2368 * Because the commit page may be on the reader page we
2369 * start with the next page and check the end loop there.
2371 rb_inc_page(cpu_buffer, &bpage);
2374 if (bpage->page == (void *)addr) {
2375 local_dec(&bpage->entries);
2378 rb_inc_page(cpu_buffer, &bpage);
2379 } while (bpage != start);
2381 /* commit not part of this buffer?? */
2382 RB_WARN_ON(cpu_buffer, 1);
2386 * ring_buffer_commit_discard - discard an event that has not been committed
2387 * @buffer: the ring buffer
2388 * @event: non committed event to discard
2390 * Sometimes an event that is in the ring buffer needs to be ignored.
2391 * This function lets the user discard an event in the ring buffer
2392 * and then that event will not be read later.
2394 * This function only works if it is called before the the item has been
2395 * committed. It will try to free the event from the ring buffer
2396 * if another event has not been added behind it.
2398 * If another event has been added behind it, it will set the event
2399 * up as discarded, and perform the commit.
2401 * If this function is called, do not call ring_buffer_unlock_commit on
2404 void ring_buffer_discard_commit(struct ring_buffer *buffer,
2405 struct ring_buffer_event *event)
2407 struct ring_buffer_per_cpu *cpu_buffer;
2410 /* The event is discarded regardless */
2411 rb_event_discard(event);
2413 cpu = smp_processor_id();
2414 cpu_buffer = buffer->buffers[cpu];
2417 * This must only be called if the event has not been
2418 * committed yet. Thus we can assume that preemption
2419 * is still disabled.
2421 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
2423 rb_decrement_entry(cpu_buffer, event);
2424 if (rb_try_to_discard(cpu_buffer, event))
2428 * The commit is still visible by the reader, so we
2429 * must still update the timestamp.
2431 rb_update_write_stamp(cpu_buffer, event);
2433 rb_end_commit(cpu_buffer);
2435 trace_recursive_unlock();
2438 * Only the last preempt count needs to restore preemption.
2440 if (preempt_count() == 1)
2441 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
2443 preempt_enable_no_resched_notrace();
2446 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
2449 * ring_buffer_write - write data to the buffer without reserving
2450 * @buffer: The ring buffer to write to.
2451 * @length: The length of the data being written (excluding the event header)
2452 * @data: The data to write to the buffer.
2454 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2455 * one function. If you already have the data to write to the buffer, it
2456 * may be easier to simply call this function.
2458 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2459 * and not the length of the event which would hold the header.
2461 int ring_buffer_write(struct ring_buffer *buffer,
2462 unsigned long length,
2465 struct ring_buffer_per_cpu *cpu_buffer;
2466 struct ring_buffer_event *event;
2471 if (ring_buffer_flags != RB_BUFFERS_ON)
2474 if (atomic_read(&buffer->record_disabled))
2477 resched = ftrace_preempt_disable();
2479 cpu = raw_smp_processor_id();
2481 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2484 cpu_buffer = buffer->buffers[cpu];
2486 if (atomic_read(&cpu_buffer->record_disabled))
2489 if (length > BUF_MAX_DATA_SIZE)
2492 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2496 body = rb_event_data(event);
2498 memcpy(body, data, length);
2500 rb_commit(cpu_buffer, event);
2504 ftrace_preempt_enable(resched);
2508 EXPORT_SYMBOL_GPL(ring_buffer_write);
2510 static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
2512 struct buffer_page *reader = cpu_buffer->reader_page;
2513 struct buffer_page *head = rb_set_head_page(cpu_buffer);
2514 struct buffer_page *commit = cpu_buffer->commit_page;
2516 /* In case of error, head will be NULL */
2517 if (unlikely(!head))
2520 return reader->read == rb_page_commit(reader) &&
2521 (commit == reader ||
2523 head->read == rb_page_commit(commit)));
2527 * ring_buffer_record_disable - stop all writes into the buffer
2528 * @buffer: The ring buffer to stop writes to.
2530 * This prevents all writes to the buffer. Any attempt to write
2531 * to the buffer after this will fail and return NULL.
2533 * The caller should call synchronize_sched() after this.
2535 void ring_buffer_record_disable(struct ring_buffer *buffer)
2537 atomic_inc(&buffer->record_disabled);
2539 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
2542 * ring_buffer_record_enable - enable writes to the buffer
2543 * @buffer: The ring buffer to enable writes
2545 * Note, multiple disables will need the same number of enables
2546 * to truely enable the writing (much like preempt_disable).
2548 void ring_buffer_record_enable(struct ring_buffer *buffer)
2550 atomic_dec(&buffer->record_disabled);
2552 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
2555 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2556 * @buffer: The ring buffer to stop writes to.
2557 * @cpu: The CPU buffer to stop
2559 * This prevents all writes to the buffer. Any attempt to write
2560 * to the buffer after this will fail and return NULL.
2562 * The caller should call synchronize_sched() after this.
2564 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
2566 struct ring_buffer_per_cpu *cpu_buffer;
2568 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2571 cpu_buffer = buffer->buffers[cpu];
2572 atomic_inc(&cpu_buffer->record_disabled);
2574 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
2577 * ring_buffer_record_enable_cpu - enable writes to the buffer
2578 * @buffer: The ring buffer to enable writes
2579 * @cpu: The CPU to enable.
2581 * Note, multiple disables will need the same number of enables
2582 * to truely enable the writing (much like preempt_disable).
2584 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
2586 struct ring_buffer_per_cpu *cpu_buffer;
2588 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2591 cpu_buffer = buffer->buffers[cpu];
2592 atomic_dec(&cpu_buffer->record_disabled);
2594 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
2597 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2598 * @buffer: The ring buffer
2599 * @cpu: The per CPU buffer to get the entries from.
2601 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
2603 struct ring_buffer_per_cpu *cpu_buffer;
2606 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2609 cpu_buffer = buffer->buffers[cpu];
2610 ret = (local_read(&cpu_buffer->entries) - local_read(&cpu_buffer->overrun))
2615 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
2618 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
2619 * @buffer: The ring buffer
2620 * @cpu: The per CPU buffer to get the number of overruns from
2622 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
2624 struct ring_buffer_per_cpu *cpu_buffer;
2627 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2630 cpu_buffer = buffer->buffers[cpu];
2631 ret = local_read(&cpu_buffer->overrun);
2635 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
2638 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2639 * @buffer: The ring buffer
2640 * @cpu: The per CPU buffer to get the number of overruns from
2643 ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
2645 struct ring_buffer_per_cpu *cpu_buffer;
2648 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2651 cpu_buffer = buffer->buffers[cpu];
2652 ret = local_read(&cpu_buffer->commit_overrun);
2656 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
2659 * ring_buffer_entries - get the number of entries in a buffer
2660 * @buffer: The ring buffer
2662 * Returns the total number of entries in the ring buffer
2665 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
2667 struct ring_buffer_per_cpu *cpu_buffer;
2668 unsigned long entries = 0;
2671 /* if you care about this being correct, lock the buffer */
2672 for_each_buffer_cpu(buffer, cpu) {
2673 cpu_buffer = buffer->buffers[cpu];
2674 entries += (local_read(&cpu_buffer->entries) -
2675 local_read(&cpu_buffer->overrun)) - cpu_buffer->read;
2680 EXPORT_SYMBOL_GPL(ring_buffer_entries);
2683 * ring_buffer_overruns - get the number of overruns in buffer
2684 * @buffer: The ring buffer
2686 * Returns the total number of overruns in the ring buffer
2689 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
2691 struct ring_buffer_per_cpu *cpu_buffer;
2692 unsigned long overruns = 0;
2695 /* if you care about this being correct, lock the buffer */
2696 for_each_buffer_cpu(buffer, cpu) {
2697 cpu_buffer = buffer->buffers[cpu];
2698 overruns += local_read(&cpu_buffer->overrun);
2703 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
2705 static void rb_iter_reset(struct ring_buffer_iter *iter)
2707 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2709 /* Iterator usage is expected to have record disabled */
2710 if (list_empty(&cpu_buffer->reader_page->list)) {
2711 iter->head_page = rb_set_head_page(cpu_buffer);
2712 if (unlikely(!iter->head_page))
2714 iter->head = iter->head_page->read;
2716 iter->head_page = cpu_buffer->reader_page;
2717 iter->head = cpu_buffer->reader_page->read;
2720 iter->read_stamp = cpu_buffer->read_stamp;
2722 iter->read_stamp = iter->head_page->page->time_stamp;
2726 * ring_buffer_iter_reset - reset an iterator
2727 * @iter: The iterator to reset
2729 * Resets the iterator, so that it will start from the beginning
2732 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
2734 struct ring_buffer_per_cpu *cpu_buffer;
2735 unsigned long flags;
2740 cpu_buffer = iter->cpu_buffer;
2742 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2743 rb_iter_reset(iter);
2744 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2746 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
2749 * ring_buffer_iter_empty - check if an iterator has no more to read
2750 * @iter: The iterator to check
2752 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
2754 struct ring_buffer_per_cpu *cpu_buffer;
2756 cpu_buffer = iter->cpu_buffer;
2758 return iter->head_page == cpu_buffer->commit_page &&
2759 iter->head == rb_commit_index(cpu_buffer);
2761 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
2764 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2765 struct ring_buffer_event *event)
2769 switch (event->type_len) {
2770 case RINGBUF_TYPE_PADDING:
2773 case RINGBUF_TYPE_TIME_EXTEND:
2774 delta = event->array[0];
2776 delta += event->time_delta;
2777 cpu_buffer->read_stamp += delta;
2780 case RINGBUF_TYPE_TIME_STAMP:
2781 /* FIXME: not implemented */
2784 case RINGBUF_TYPE_DATA:
2785 cpu_buffer->read_stamp += event->time_delta;
2795 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
2796 struct ring_buffer_event *event)
2800 switch (event->type_len) {
2801 case RINGBUF_TYPE_PADDING:
2804 case RINGBUF_TYPE_TIME_EXTEND:
2805 delta = event->array[0];
2807 delta += event->time_delta;
2808 iter->read_stamp += delta;
2811 case RINGBUF_TYPE_TIME_STAMP:
2812 /* FIXME: not implemented */
2815 case RINGBUF_TYPE_DATA:
2816 iter->read_stamp += event->time_delta;
2825 static struct buffer_page *
2826 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
2828 struct buffer_page *reader = NULL;
2829 unsigned long flags;
2833 local_irq_save(flags);
2834 __raw_spin_lock(&cpu_buffer->lock);
2838 * This should normally only loop twice. But because the
2839 * start of the reader inserts an empty page, it causes
2840 * a case where we will loop three times. There should be no
2841 * reason to loop four times (that I know of).
2843 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
2848 reader = cpu_buffer->reader_page;
2850 /* If there's more to read, return this page */
2851 if (cpu_buffer->reader_page->read < rb_page_size(reader))
2854 /* Never should we have an index greater than the size */
2855 if (RB_WARN_ON(cpu_buffer,
2856 cpu_buffer->reader_page->read > rb_page_size(reader)))
2859 /* check if we caught up to the tail */
2861 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
2865 * Reset the reader page to size zero.
2867 local_set(&cpu_buffer->reader_page->write, 0);
2868 local_set(&cpu_buffer->reader_page->entries, 0);
2869 local_set(&cpu_buffer->reader_page->page->commit, 0);
2873 * Splice the empty reader page into the list around the head.
2875 reader = rb_set_head_page(cpu_buffer);
2876 cpu_buffer->reader_page->list.next = reader->list.next;
2877 cpu_buffer->reader_page->list.prev = reader->list.prev;
2880 * cpu_buffer->pages just needs to point to the buffer, it
2881 * has no specific buffer page to point to. Lets move it out
2882 * of our way so we don't accidently swap it.
2884 cpu_buffer->pages = reader->list.prev;
2886 /* The reader page will be pointing to the new head */
2887 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
2890 * Here's the tricky part.
2892 * We need to move the pointer past the header page.
2893 * But we can only do that if a writer is not currently
2894 * moving it. The page before the header page has the
2895 * flag bit '1' set if it is pointing to the page we want.
2896 * but if the writer is in the process of moving it
2897 * than it will be '2' or already moved '0'.
2900 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
2903 * If we did not convert it, then we must try again.
2909 * Yeah! We succeeded in replacing the page.
2911 * Now make the new head point back to the reader page.
2913 reader->list.next->prev = &cpu_buffer->reader_page->list;
2914 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
2916 /* Finally update the reader page to the new head */
2917 cpu_buffer->reader_page = reader;
2918 rb_reset_reader_page(cpu_buffer);
2923 __raw_spin_unlock(&cpu_buffer->lock);
2924 local_irq_restore(flags);
2929 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
2931 struct ring_buffer_event *event;
2932 struct buffer_page *reader;
2935 reader = rb_get_reader_page(cpu_buffer);
2937 /* This function should not be called when buffer is empty */
2938 if (RB_WARN_ON(cpu_buffer, !reader))
2941 event = rb_reader_event(cpu_buffer);
2943 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
2946 rb_update_read_stamp(cpu_buffer, event);
2948 length = rb_event_length(event);
2949 cpu_buffer->reader_page->read += length;
2952 static void rb_advance_iter(struct ring_buffer_iter *iter)
2954 struct ring_buffer *buffer;
2955 struct ring_buffer_per_cpu *cpu_buffer;
2956 struct ring_buffer_event *event;
2959 cpu_buffer = iter->cpu_buffer;
2960 buffer = cpu_buffer->buffer;
2963 * Check if we are at the end of the buffer.
2965 if (iter->head >= rb_page_size(iter->head_page)) {
2966 /* discarded commits can make the page empty */
2967 if (iter->head_page == cpu_buffer->commit_page)
2973 event = rb_iter_head_event(iter);
2975 length = rb_event_length(event);
2978 * This should not be called to advance the header if we are
2979 * at the tail of the buffer.
2981 if (RB_WARN_ON(cpu_buffer,
2982 (iter->head_page == cpu_buffer->commit_page) &&
2983 (iter->head + length > rb_commit_index(cpu_buffer))))
2986 rb_update_iter_read_stamp(iter, event);
2988 iter->head += length;
2990 /* check for end of page padding */
2991 if ((iter->head >= rb_page_size(iter->head_page)) &&
2992 (iter->head_page != cpu_buffer->commit_page))
2993 rb_advance_iter(iter);
2996 static struct ring_buffer_event *
2997 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts)
2999 struct ring_buffer_event *event;
3000 struct buffer_page *reader;
3005 * We repeat when a timestamp is encountered. It is possible
3006 * to get multiple timestamps from an interrupt entering just
3007 * as one timestamp is about to be written, or from discarded
3008 * commits. The most that we can have is the number on a single page.
3010 if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
3013 reader = rb_get_reader_page(cpu_buffer);
3017 event = rb_reader_event(cpu_buffer);
3019 switch (event->type_len) {
3020 case RINGBUF_TYPE_PADDING:
3021 if (rb_null_event(event))
3022 RB_WARN_ON(cpu_buffer, 1);
3024 * Because the writer could be discarding every
3025 * event it creates (which would probably be bad)
3026 * if we were to go back to "again" then we may never
3027 * catch up, and will trigger the warn on, or lock
3028 * the box. Return the padding, and we will release
3029 * the current locks, and try again.
3033 case RINGBUF_TYPE_TIME_EXTEND:
3034 /* Internal data, OK to advance */
3035 rb_advance_reader(cpu_buffer);
3038 case RINGBUF_TYPE_TIME_STAMP:
3039 /* FIXME: not implemented */
3040 rb_advance_reader(cpu_buffer);
3043 case RINGBUF_TYPE_DATA:
3045 *ts = cpu_buffer->read_stamp + event->time_delta;
3046 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3047 cpu_buffer->cpu, ts);
3057 EXPORT_SYMBOL_GPL(ring_buffer_peek);
3059 static struct ring_buffer_event *
3060 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3062 struct ring_buffer *buffer;
3063 struct ring_buffer_per_cpu *cpu_buffer;
3064 struct ring_buffer_event *event;
3067 if (ring_buffer_iter_empty(iter))
3070 cpu_buffer = iter->cpu_buffer;
3071 buffer = cpu_buffer->buffer;
3075 * We repeat when a timestamp is encountered.
3076 * We can get multiple timestamps by nested interrupts or also
3077 * if filtering is on (discarding commits). Since discarding
3078 * commits can be frequent we can get a lot of timestamps.
3079 * But we limit them by not adding timestamps if they begin
3080 * at the start of a page.
3082 if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
3085 if (rb_per_cpu_empty(cpu_buffer))
3088 event = rb_iter_head_event(iter);
3090 switch (event->type_len) {
3091 case RINGBUF_TYPE_PADDING:
3092 if (rb_null_event(event)) {
3096 rb_advance_iter(iter);
3099 case RINGBUF_TYPE_TIME_EXTEND:
3100 /* Internal data, OK to advance */
3101 rb_advance_iter(iter);
3104 case RINGBUF_TYPE_TIME_STAMP:
3105 /* FIXME: not implemented */
3106 rb_advance_iter(iter);
3109 case RINGBUF_TYPE_DATA:
3111 *ts = iter->read_stamp + event->time_delta;
3112 ring_buffer_normalize_time_stamp(buffer,
3113 cpu_buffer->cpu, ts);
3123 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3125 static inline int rb_ok_to_lock(void)
3128 * If an NMI die dumps out the content of the ring buffer
3129 * do not grab locks. We also permanently disable the ring
3130 * buffer too. A one time deal is all you get from reading
3131 * the ring buffer from an NMI.
3133 if (likely(!in_nmi()))
3136 tracing_off_permanent();
3141 * ring_buffer_peek - peek at the next event to be read
3142 * @buffer: The ring buffer to read
3143 * @cpu: The cpu to peak at
3144 * @ts: The timestamp counter of this event.
3146 * This will return the event that will be read next, but does
3147 * not consume the data.
3149 struct ring_buffer_event *
3150 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
3152 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3153 struct ring_buffer_event *event;
3154 unsigned long flags;
3157 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3160 dolock = rb_ok_to_lock();
3162 local_irq_save(flags);
3164 spin_lock(&cpu_buffer->reader_lock);
3165 event = rb_buffer_peek(cpu_buffer, ts);
3166 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3167 rb_advance_reader(cpu_buffer);
3169 spin_unlock(&cpu_buffer->reader_lock);
3170 local_irq_restore(flags);
3172 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3179 * ring_buffer_iter_peek - peek at the next event to be read
3180 * @iter: The ring buffer iterator
3181 * @ts: The timestamp counter of this event.
3183 * This will return the event that will be read next, but does
3184 * not increment the iterator.
3186 struct ring_buffer_event *
3187 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3189 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3190 struct ring_buffer_event *event;
3191 unsigned long flags;
3194 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3195 event = rb_iter_peek(iter, ts);
3196 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3198 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3205 * ring_buffer_consume - return an event and consume it
3206 * @buffer: The ring buffer to get the next event from
3208 * Returns the next event in the ring buffer, and that event is consumed.
3209 * Meaning, that sequential reads will keep returning a different event,
3210 * and eventually empty the ring buffer if the producer is slower.
3212 struct ring_buffer_event *
3213 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
3215 struct ring_buffer_per_cpu *cpu_buffer;
3216 struct ring_buffer_event *event = NULL;
3217 unsigned long flags;
3220 dolock = rb_ok_to_lock();
3223 /* might be called in atomic */
3226 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3229 cpu_buffer = buffer->buffers[cpu];
3230 local_irq_save(flags);
3232 spin_lock(&cpu_buffer->reader_lock);
3234 event = rb_buffer_peek(cpu_buffer, ts);
3236 rb_advance_reader(cpu_buffer);
3239 spin_unlock(&cpu_buffer->reader_lock);
3240 local_irq_restore(flags);
3245 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3250 EXPORT_SYMBOL_GPL(ring_buffer_consume);
3253 * ring_buffer_read_start - start a non consuming read of the buffer
3254 * @buffer: The ring buffer to read from
3255 * @cpu: The cpu buffer to iterate over
3257 * This starts up an iteration through the buffer. It also disables
3258 * the recording to the buffer until the reading is finished.
3259 * This prevents the reading from being corrupted. This is not
3260 * a consuming read, so a producer is not expected.
3262 * Must be paired with ring_buffer_finish.
3264 struct ring_buffer_iter *
3265 ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
3267 struct ring_buffer_per_cpu *cpu_buffer;
3268 struct ring_buffer_iter *iter;
3269 unsigned long flags;
3271 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3274 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
3278 cpu_buffer = buffer->buffers[cpu];
3280 iter->cpu_buffer = cpu_buffer;
3282 atomic_inc(&cpu_buffer->record_disabled);
3283 synchronize_sched();
3285 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3286 __raw_spin_lock(&cpu_buffer->lock);
3287 rb_iter_reset(iter);
3288 __raw_spin_unlock(&cpu_buffer->lock);
3289 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3293 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
3296 * ring_buffer_finish - finish reading the iterator of the buffer
3297 * @iter: The iterator retrieved by ring_buffer_start
3299 * This re-enables the recording to the buffer, and frees the
3303 ring_buffer_read_finish(struct ring_buffer_iter *iter)
3305 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3307 atomic_dec(&cpu_buffer->record_disabled);
3310 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
3313 * ring_buffer_read - read the next item in the ring buffer by the iterator
3314 * @iter: The ring buffer iterator
3315 * @ts: The time stamp of the event read.
3317 * This reads the next event in the ring buffer and increments the iterator.
3319 struct ring_buffer_event *
3320 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
3322 struct ring_buffer_event *event;
3323 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3324 unsigned long flags;
3326 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3328 event = rb_iter_peek(iter, ts);
3332 if (event->type_len == RINGBUF_TYPE_PADDING)
3335 rb_advance_iter(iter);
3337 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3341 EXPORT_SYMBOL_GPL(ring_buffer_read);
3344 * ring_buffer_size - return the size of the ring buffer (in bytes)
3345 * @buffer: The ring buffer.
3347 unsigned long ring_buffer_size(struct ring_buffer *buffer)
3349 return BUF_PAGE_SIZE * buffer->pages;
3351 EXPORT_SYMBOL_GPL(ring_buffer_size);
3354 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
3356 rb_head_page_deactivate(cpu_buffer);
3358 cpu_buffer->head_page
3359 = list_entry(cpu_buffer->pages, struct buffer_page, list);
3360 local_set(&cpu_buffer->head_page->write, 0);
3361 local_set(&cpu_buffer->head_page->entries, 0);
3362 local_set(&cpu_buffer->head_page->page->commit, 0);
3364 cpu_buffer->head_page->read = 0;
3366 cpu_buffer->tail_page = cpu_buffer->head_page;
3367 cpu_buffer->commit_page = cpu_buffer->head_page;
3369 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
3370 local_set(&cpu_buffer->reader_page->write, 0);
3371 local_set(&cpu_buffer->reader_page->entries, 0);
3372 local_set(&cpu_buffer->reader_page->page->commit, 0);
3373 cpu_buffer->reader_page->read = 0;
3375 local_set(&cpu_buffer->commit_overrun, 0);
3376 local_set(&cpu_buffer->overrun, 0);
3377 local_set(&cpu_buffer->entries, 0);
3378 local_set(&cpu_buffer->committing, 0);
3379 local_set(&cpu_buffer->commits, 0);
3380 cpu_buffer->read = 0;
3382 cpu_buffer->write_stamp = 0;
3383 cpu_buffer->read_stamp = 0;
3385 rb_head_page_activate(cpu_buffer);
3389 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3390 * @buffer: The ring buffer to reset a per cpu buffer of
3391 * @cpu: The CPU buffer to be reset
3393 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
3395 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3396 unsigned long flags;
3398 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3401 atomic_inc(&cpu_buffer->record_disabled);
3403 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3405 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
3408 __raw_spin_lock(&cpu_buffer->lock);
3410 rb_reset_cpu(cpu_buffer);
3412 __raw_spin_unlock(&cpu_buffer->lock);
3415 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3417 atomic_dec(&cpu_buffer->record_disabled);
3419 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
3422 * ring_buffer_reset - reset a ring buffer
3423 * @buffer: The ring buffer to reset all cpu buffers
3425 void ring_buffer_reset(struct ring_buffer *buffer)
3429 for_each_buffer_cpu(buffer, cpu)
3430 ring_buffer_reset_cpu(buffer, cpu);
3432 EXPORT_SYMBOL_GPL(ring_buffer_reset);
3435 * rind_buffer_empty - is the ring buffer empty?
3436 * @buffer: The ring buffer to test
3438 int ring_buffer_empty(struct ring_buffer *buffer)
3440 struct ring_buffer_per_cpu *cpu_buffer;
3441 unsigned long flags;
3446 dolock = rb_ok_to_lock();
3448 /* yes this is racy, but if you don't like the race, lock the buffer */
3449 for_each_buffer_cpu(buffer, cpu) {
3450 cpu_buffer = buffer->buffers[cpu];
3451 local_irq_save(flags);
3453 spin_lock(&cpu_buffer->reader_lock);
3454 ret = rb_per_cpu_empty(cpu_buffer);
3456 spin_unlock(&cpu_buffer->reader_lock);
3457 local_irq_restore(flags);
3465 EXPORT_SYMBOL_GPL(ring_buffer_empty);
3468 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
3469 * @buffer: The ring buffer
3470 * @cpu: The CPU buffer to test
3472 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
3474 struct ring_buffer_per_cpu *cpu_buffer;
3475 unsigned long flags;
3479 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3482 dolock = rb_ok_to_lock();
3484 cpu_buffer = buffer->buffers[cpu];
3485 local_irq_save(flags);
3487 spin_lock(&cpu_buffer->reader_lock);
3488 ret = rb_per_cpu_empty(cpu_buffer);
3490 spin_unlock(&cpu_buffer->reader_lock);
3491 local_irq_restore(flags);
3495 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
3497 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3499 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
3500 * @buffer_a: One buffer to swap with
3501 * @buffer_b: The other buffer to swap with
3503 * This function is useful for tracers that want to take a "snapshot"
3504 * of a CPU buffer and has another back up buffer lying around.
3505 * it is expected that the tracer handles the cpu buffer not being
3506 * used at the moment.
3508 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
3509 struct ring_buffer *buffer_b, int cpu)
3511 struct ring_buffer_per_cpu *cpu_buffer_a;
3512 struct ring_buffer_per_cpu *cpu_buffer_b;
3515 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
3516 !cpumask_test_cpu(cpu, buffer_b->cpumask))
3519 /* At least make sure the two buffers are somewhat the same */
3520 if (buffer_a->pages != buffer_b->pages)
3525 if (ring_buffer_flags != RB_BUFFERS_ON)
3528 if (atomic_read(&buffer_a->record_disabled))
3531 if (atomic_read(&buffer_b->record_disabled))
3534 cpu_buffer_a = buffer_a->buffers[cpu];
3535 cpu_buffer_b = buffer_b->buffers[cpu];
3537 if (atomic_read(&cpu_buffer_a->record_disabled))
3540 if (atomic_read(&cpu_buffer_b->record_disabled))
3544 * We can't do a synchronize_sched here because this
3545 * function can be called in atomic context.
3546 * Normally this will be called from the same CPU as cpu.
3547 * If not it's up to the caller to protect this.
3549 atomic_inc(&cpu_buffer_a->record_disabled);
3550 atomic_inc(&cpu_buffer_b->record_disabled);
3553 if (local_read(&cpu_buffer_a->committing))
3555 if (local_read(&cpu_buffer_b->committing))
3558 buffer_a->buffers[cpu] = cpu_buffer_b;
3559 buffer_b->buffers[cpu] = cpu_buffer_a;
3561 cpu_buffer_b->buffer = buffer_a;
3562 cpu_buffer_a->buffer = buffer_b;
3567 atomic_dec(&cpu_buffer_a->record_disabled);
3568 atomic_dec(&cpu_buffer_b->record_disabled);
3572 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
3573 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
3576 * ring_buffer_alloc_read_page - allocate a page to read from buffer
3577 * @buffer: the buffer to allocate for.
3579 * This function is used in conjunction with ring_buffer_read_page.
3580 * When reading a full page from the ring buffer, these functions
3581 * can be used to speed up the process. The calling function should
3582 * allocate a few pages first with this function. Then when it
3583 * needs to get pages from the ring buffer, it passes the result
3584 * of this function into ring_buffer_read_page, which will swap
3585 * the page that was allocated, with the read page of the buffer.
3588 * The page allocated, or NULL on error.
3590 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
3592 struct buffer_data_page *bpage;
3595 addr = __get_free_page(GFP_KERNEL);
3599 bpage = (void *)addr;
3601 rb_init_page(bpage);
3605 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
3608 * ring_buffer_free_read_page - free an allocated read page
3609 * @buffer: the buffer the page was allocate for
3610 * @data: the page to free
3612 * Free a page allocated from ring_buffer_alloc_read_page.
3614 void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
3616 free_page((unsigned long)data);
3618 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
3621 * ring_buffer_read_page - extract a page from the ring buffer
3622 * @buffer: buffer to extract from
3623 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
3624 * @len: amount to extract
3625 * @cpu: the cpu of the buffer to extract
3626 * @full: should the extraction only happen when the page is full.
3628 * This function will pull out a page from the ring buffer and consume it.
3629 * @data_page must be the address of the variable that was returned
3630 * from ring_buffer_alloc_read_page. This is because the page might be used
3631 * to swap with a page in the ring buffer.
3634 * rpage = ring_buffer_alloc_read_page(buffer);
3637 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
3639 * process_page(rpage, ret);
3641 * When @full is set, the function will not return true unless
3642 * the writer is off the reader page.
3644 * Note: it is up to the calling functions to handle sleeps and wakeups.
3645 * The ring buffer can be used anywhere in the kernel and can not
3646 * blindly call wake_up. The layer that uses the ring buffer must be
3647 * responsible for that.
3650 * >=0 if data has been transferred, returns the offset of consumed data.
3651 * <0 if no data has been transferred.
3653 int ring_buffer_read_page(struct ring_buffer *buffer,
3654 void **data_page, size_t len, int cpu, int full)
3656 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3657 struct ring_buffer_event *event;
3658 struct buffer_data_page *bpage;
3659 struct buffer_page *reader;
3660 unsigned long flags;
3661 unsigned int commit;
3666 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3670 * If len is not big enough to hold the page header, then
3671 * we can not copy anything.
3673 if (len <= BUF_PAGE_HDR_SIZE)
3676 len -= BUF_PAGE_HDR_SIZE;
3685 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3687 reader = rb_get_reader_page(cpu_buffer);
3691 event = rb_reader_event(cpu_buffer);
3693 read = reader->read;
3694 commit = rb_page_commit(reader);
3697 * If this page has been partially read or
3698 * if len is not big enough to read the rest of the page or
3699 * a writer is still on the page, then
3700 * we must copy the data from the page to the buffer.
3701 * Otherwise, we can simply swap the page with the one passed in.
3703 if (read || (len < (commit - read)) ||
3704 cpu_buffer->reader_page == cpu_buffer->commit_page) {
3705 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
3706 unsigned int rpos = read;
3707 unsigned int pos = 0;
3713 if (len > (commit - read))
3714 len = (commit - read);
3716 size = rb_event_length(event);
3721 /* save the current timestamp, since the user will need it */
3722 save_timestamp = cpu_buffer->read_stamp;
3724 /* Need to copy one event at a time */
3726 memcpy(bpage->data + pos, rpage->data + rpos, size);
3730 rb_advance_reader(cpu_buffer);
3731 rpos = reader->read;
3734 event = rb_reader_event(cpu_buffer);
3735 size = rb_event_length(event);
3736 } while (len > size);
3739 local_set(&bpage->commit, pos);
3740 bpage->time_stamp = save_timestamp;
3742 /* we copied everything to the beginning */
3745 /* update the entry counter */
3746 cpu_buffer->read += rb_page_entries(reader);
3748 /* swap the pages */
3749 rb_init_page(bpage);
3750 bpage = reader->page;
3751 reader->page = *data_page;
3752 local_set(&reader->write, 0);
3753 local_set(&reader->entries, 0);
3760 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3765 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
3767 #ifdef CONFIG_TRACING
3769 rb_simple_read(struct file *filp, char __user *ubuf,
3770 size_t cnt, loff_t *ppos)
3772 unsigned long *p = filp->private_data;
3776 if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
3777 r = sprintf(buf, "permanently disabled\n");
3779 r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
3781 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
3785 rb_simple_write(struct file *filp, const char __user *ubuf,
3786 size_t cnt, loff_t *ppos)
3788 unsigned long *p = filp->private_data;
3793 if (cnt >= sizeof(buf))
3796 if (copy_from_user(&buf, ubuf, cnt))
3801 ret = strict_strtoul(buf, 10, &val);
3806 set_bit(RB_BUFFERS_ON_BIT, p);
3808 clear_bit(RB_BUFFERS_ON_BIT, p);
3815 static const struct file_operations rb_simple_fops = {
3816 .open = tracing_open_generic,
3817 .read = rb_simple_read,
3818 .write = rb_simple_write,
3822 static __init int rb_init_debugfs(void)
3824 struct dentry *d_tracer;
3826 d_tracer = tracing_init_dentry();
3828 trace_create_file("tracing_on", 0644, d_tracer,
3829 &ring_buffer_flags, &rb_simple_fops);
3834 fs_initcall(rb_init_debugfs);
3837 #ifdef CONFIG_HOTPLUG_CPU
3838 static int rb_cpu_notify(struct notifier_block *self,
3839 unsigned long action, void *hcpu)
3841 struct ring_buffer *buffer =
3842 container_of(self, struct ring_buffer, cpu_notify);
3843 long cpu = (long)hcpu;
3846 case CPU_UP_PREPARE:
3847 case CPU_UP_PREPARE_FROZEN:
3848 if (cpumask_test_cpu(cpu, buffer->cpumask))
3851 buffer->buffers[cpu] =
3852 rb_allocate_cpu_buffer(buffer, cpu);
3853 if (!buffer->buffers[cpu]) {
3854 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
3859 cpumask_set_cpu(cpu, buffer->cpumask);
3861 case CPU_DOWN_PREPARE:
3862 case CPU_DOWN_PREPARE_FROZEN:
3865 * If we were to free the buffer, then the user would
3866 * lose any trace that was in the buffer.