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/module.h>
14 #include <linux/percpu.h>
15 #include <linux/mutex.h>
16 #include <linux/init.h>
17 #include <linux/hash.h>
18 #include <linux/list.h>
19 #include <linux/cpu.h>
25 * The ring buffer header is special. We must manually up keep it.
27 int ring_buffer_print_entry_header(struct trace_seq *s)
31 ret = trace_seq_printf(s, "# compressed entry header\n");
32 ret = trace_seq_printf(s, "\ttype_len : 5 bits\n");
33 ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n");
34 ret = trace_seq_printf(s, "\tarray : 32 bits\n");
35 ret = trace_seq_printf(s, "\n");
36 ret = trace_seq_printf(s, "\tpadding : type == %d\n",
37 RINGBUF_TYPE_PADDING);
38 ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
39 RINGBUF_TYPE_TIME_EXTEND);
40 ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
41 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
47 * The ring buffer is made up of a list of pages. A separate list of pages is
48 * allocated for each CPU. A writer may only write to a buffer that is
49 * associated with the CPU it is currently executing on. A reader may read
50 * from any per cpu buffer.
52 * The reader is special. For each per cpu buffer, the reader has its own
53 * reader page. When a reader has read the entire reader page, this reader
54 * page is swapped with another page in the ring buffer.
56 * Now, as long as the writer is off the reader page, the reader can do what
57 * ever it wants with that page. The writer will never write to that page
58 * again (as long as it is out of the ring buffer).
60 * Here's some silly ASCII art.
63 * |reader| RING BUFFER
65 * +------+ +---+ +---+ +---+
74 * |reader| RING BUFFER
75 * |page |------------------v
76 * +------+ +---+ +---+ +---+
85 * |reader| RING BUFFER
86 * |page |------------------v
87 * +------+ +---+ +---+ +---+
92 * +------------------------------+
96 * |buffer| RING BUFFER
97 * |page |------------------v
98 * +------+ +---+ +---+ +---+
100 * | New +---+ +---+ +---+
103 * +------------------------------+
106 * After we make this swap, the reader can hand this page off to the splice
107 * code and be done with it. It can even allocate a new page if it needs to
108 * and swap that into the ring buffer.
110 * We will be using cmpxchg soon to make all this lockless.
115 * A fast way to enable or disable all ring buffers is to
116 * call tracing_on or tracing_off. Turning off the ring buffers
117 * prevents all ring buffers from being recorded to.
118 * Turning this switch on, makes it OK to write to the
119 * ring buffer, if the ring buffer is enabled itself.
121 * There's three layers that must be on in order to write
122 * to the ring buffer.
124 * 1) This global flag must be set.
125 * 2) The ring buffer must be enabled for recording.
126 * 3) The per cpu buffer must be enabled for recording.
128 * In case of an anomaly, this global flag has a bit set that
129 * will permantly disable all ring buffers.
133 * Global flag to disable all recording to ring buffers
134 * This has two bits: ON, DISABLED
138 * 0 0 : ring buffers are off
139 * 1 0 : ring buffers are on
140 * X 1 : ring buffers are permanently disabled
144 RB_BUFFERS_ON_BIT = 0,
145 RB_BUFFERS_DISABLED_BIT = 1,
149 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
150 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
153 static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
155 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
158 * tracing_on - enable all tracing buffers
160 * This function enables all tracing buffers that may have been
161 * disabled with tracing_off.
163 void tracing_on(void)
165 set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
167 EXPORT_SYMBOL_GPL(tracing_on);
170 * tracing_off - turn off all tracing buffers
172 * This function stops all tracing buffers from recording data.
173 * It does not disable any overhead the tracers themselves may
174 * be causing. This function simply causes all recording to
175 * the ring buffers to fail.
177 void tracing_off(void)
179 clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
181 EXPORT_SYMBOL_GPL(tracing_off);
184 * tracing_off_permanent - permanently disable ring buffers
186 * This function, once called, will disable all ring buffers
189 void tracing_off_permanent(void)
191 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
195 * tracing_is_on - show state of ring buffers enabled
197 int tracing_is_on(void)
199 return ring_buffer_flags == RB_BUFFERS_ON;
201 EXPORT_SYMBOL_GPL(tracing_is_on);
205 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
206 #define RB_ALIGNMENT 4U
207 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
208 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
210 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
211 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
214 RB_LEN_TIME_EXTEND = 8,
215 RB_LEN_TIME_STAMP = 16,
218 static inline int rb_null_event(struct ring_buffer_event *event)
220 return event->type_len == RINGBUF_TYPE_PADDING
221 && event->time_delta == 0;
224 static inline int rb_discarded_event(struct ring_buffer_event *event)
226 return event->type_len == RINGBUF_TYPE_PADDING && event->time_delta;
229 static void rb_event_set_padding(struct ring_buffer_event *event)
231 event->type_len = RINGBUF_TYPE_PADDING;
232 event->time_delta = 0;
236 rb_event_data_length(struct ring_buffer_event *event)
241 length = event->type_len * RB_ALIGNMENT;
243 length = event->array[0];
244 return length + RB_EVNT_HDR_SIZE;
247 /* inline for ring buffer fast paths */
249 rb_event_length(struct ring_buffer_event *event)
251 switch (event->type_len) {
252 case RINGBUF_TYPE_PADDING:
253 if (rb_null_event(event))
256 return event->array[0] + RB_EVNT_HDR_SIZE;
258 case RINGBUF_TYPE_TIME_EXTEND:
259 return RB_LEN_TIME_EXTEND;
261 case RINGBUF_TYPE_TIME_STAMP:
262 return RB_LEN_TIME_STAMP;
264 case RINGBUF_TYPE_DATA:
265 return rb_event_data_length(event);
274 * ring_buffer_event_length - return the length of the event
275 * @event: the event to get the length of
277 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
279 unsigned length = rb_event_length(event);
280 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
282 length -= RB_EVNT_HDR_SIZE;
283 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
284 length -= sizeof(event->array[0]);
287 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
289 /* inline for ring buffer fast paths */
291 rb_event_data(struct ring_buffer_event *event)
293 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
294 /* If length is in len field, then array[0] has the data */
296 return (void *)&event->array[0];
297 /* Otherwise length is in array[0] and array[1] has the data */
298 return (void *)&event->array[1];
302 * ring_buffer_event_data - return the data of the event
303 * @event: the event to get the data from
305 void *ring_buffer_event_data(struct ring_buffer_event *event)
307 return rb_event_data(event);
309 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
311 #define for_each_buffer_cpu(buffer, cpu) \
312 for_each_cpu(cpu, buffer->cpumask)
315 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
316 #define TS_DELTA_TEST (~TS_MASK)
318 struct buffer_data_page {
319 u64 time_stamp; /* page time stamp */
320 local_t commit; /* write committed index */
321 unsigned char data[]; /* data of buffer page */
325 struct list_head list; /* list of buffer pages */
326 local_t write; /* index for next write */
327 unsigned read; /* index for next read */
328 local_t entries; /* entries on this page */
329 struct buffer_data_page *page; /* Actual data page */
332 static void rb_init_page(struct buffer_data_page *bpage)
334 local_set(&bpage->commit, 0);
338 * ring_buffer_page_len - the size of data on the page.
339 * @page: The page to read
341 * Returns the amount of data on the page, including buffer page header.
343 size_t ring_buffer_page_len(void *page)
345 return local_read(&((struct buffer_data_page *)page)->commit)
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 /* Max number of timestamps that can fit on a page */
375 #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP)
377 int ring_buffer_print_page_header(struct trace_seq *s)
379 struct buffer_data_page field;
382 ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
383 "offset:0;\tsize:%u;\n",
384 (unsigned int)sizeof(field.time_stamp));
386 ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
387 "offset:%u;\tsize:%u;\n",
388 (unsigned int)offsetof(typeof(field), commit),
389 (unsigned int)sizeof(field.commit));
391 ret = trace_seq_printf(s, "\tfield: char data;\t"
392 "offset:%u;\tsize:%u;\n",
393 (unsigned int)offsetof(typeof(field), data),
394 (unsigned int)BUF_PAGE_SIZE);
400 * head_page == tail_page && head == tail then buffer is empty.
402 struct ring_buffer_per_cpu {
404 struct ring_buffer *buffer;
405 spinlock_t reader_lock; /* serialize readers */
407 struct lock_class_key lock_key;
408 struct list_head pages;
409 struct buffer_page *head_page; /* read from head */
410 struct buffer_page *tail_page; /* write to tail */
411 struct buffer_page *commit_page; /* committed pages */
412 struct buffer_page *reader_page;
413 unsigned long nmi_dropped;
414 unsigned long commit_overrun;
415 unsigned long overrun;
420 atomic_t record_disabled;
427 atomic_t record_disabled;
428 cpumask_var_t cpumask;
430 struct lock_class_key *reader_lock_key;
434 struct ring_buffer_per_cpu **buffers;
436 #ifdef CONFIG_HOTPLUG_CPU
437 struct notifier_block cpu_notify;
442 struct ring_buffer_iter {
443 struct ring_buffer_per_cpu *cpu_buffer;
445 struct buffer_page *head_page;
449 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
450 #define RB_WARN_ON(buffer, cond) \
452 int _____ret = unlikely(cond); \
454 atomic_inc(&buffer->record_disabled); \
460 /* Up this if you want to test the TIME_EXTENTS and normalization */
461 #define DEBUG_SHIFT 0
463 static inline u64 rb_time_stamp(struct ring_buffer *buffer, int cpu)
465 /* shift to debug/test normalization and TIME_EXTENTS */
466 return buffer->clock() << DEBUG_SHIFT;
469 u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
473 preempt_disable_notrace();
474 time = rb_time_stamp(buffer, cpu);
475 preempt_enable_no_resched_notrace();
479 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
481 void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
484 /* Just stupid testing the normalize function and deltas */
487 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
490 * check_pages - integrity check of buffer pages
491 * @cpu_buffer: CPU buffer with pages to test
493 * As a safety measure we check to make sure the data pages have not
496 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
498 struct list_head *head = &cpu_buffer->pages;
499 struct buffer_page *bpage, *tmp;
501 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
503 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
506 list_for_each_entry_safe(bpage, tmp, head, list) {
507 if (RB_WARN_ON(cpu_buffer,
508 bpage->list.next->prev != &bpage->list))
510 if (RB_WARN_ON(cpu_buffer,
511 bpage->list.prev->next != &bpage->list))
518 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
521 struct list_head *head = &cpu_buffer->pages;
522 struct buffer_page *bpage, *tmp;
527 for (i = 0; i < nr_pages; i++) {
528 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
529 GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
532 list_add(&bpage->list, &pages);
534 addr = __get_free_page(GFP_KERNEL);
537 bpage->page = (void *)addr;
538 rb_init_page(bpage->page);
541 list_splice(&pages, head);
543 rb_check_pages(cpu_buffer);
548 list_for_each_entry_safe(bpage, tmp, &pages, list) {
549 list_del_init(&bpage->list);
550 free_buffer_page(bpage);
555 static struct ring_buffer_per_cpu *
556 rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
558 struct ring_buffer_per_cpu *cpu_buffer;
559 struct buffer_page *bpage;
563 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
564 GFP_KERNEL, cpu_to_node(cpu));
568 cpu_buffer->cpu = cpu;
569 cpu_buffer->buffer = buffer;
570 spin_lock_init(&cpu_buffer->reader_lock);
571 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
572 cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
573 INIT_LIST_HEAD(&cpu_buffer->pages);
575 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
576 GFP_KERNEL, cpu_to_node(cpu));
578 goto fail_free_buffer;
580 cpu_buffer->reader_page = bpage;
581 addr = __get_free_page(GFP_KERNEL);
583 goto fail_free_reader;
584 bpage->page = (void *)addr;
585 rb_init_page(bpage->page);
587 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
589 ret = rb_allocate_pages(cpu_buffer, buffer->pages);
591 goto fail_free_reader;
593 cpu_buffer->head_page
594 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
595 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
600 free_buffer_page(cpu_buffer->reader_page);
607 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
609 struct list_head *head = &cpu_buffer->pages;
610 struct buffer_page *bpage, *tmp;
612 free_buffer_page(cpu_buffer->reader_page);
614 list_for_each_entry_safe(bpage, tmp, head, list) {
615 list_del_init(&bpage->list);
616 free_buffer_page(bpage);
622 * Causes compile errors if the struct buffer_page gets bigger
623 * than the struct page.
625 extern int ring_buffer_page_too_big(void);
627 #ifdef CONFIG_HOTPLUG_CPU
628 static int rb_cpu_notify(struct notifier_block *self,
629 unsigned long action, void *hcpu);
633 * ring_buffer_alloc - allocate a new ring_buffer
634 * @size: the size in bytes per cpu that is needed.
635 * @flags: attributes to set for the ring buffer.
637 * Currently the only flag that is available is the RB_FL_OVERWRITE
638 * flag. This flag means that the buffer will overwrite old data
639 * when the buffer wraps. If this flag is not set, the buffer will
640 * drop data when the tail hits the head.
642 struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
643 struct lock_class_key *key)
645 struct ring_buffer *buffer;
649 /* Paranoid! Optimizes out when all is well */
650 if (sizeof(struct buffer_page) > sizeof(struct page))
651 ring_buffer_page_too_big();
654 /* keep it in its own cache line */
655 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
660 if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
661 goto fail_free_buffer;
663 buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
664 buffer->flags = flags;
665 buffer->clock = trace_clock_local;
666 buffer->reader_lock_key = key;
668 /* need at least two pages */
669 if (buffer->pages == 1)
673 * In case of non-hotplug cpu, if the ring-buffer is allocated
674 * in early initcall, it will not be notified of secondary cpus.
675 * In that off case, we need to allocate for all possible cpus.
677 #ifdef CONFIG_HOTPLUG_CPU
679 cpumask_copy(buffer->cpumask, cpu_online_mask);
681 cpumask_copy(buffer->cpumask, cpu_possible_mask);
683 buffer->cpus = nr_cpu_ids;
685 bsize = sizeof(void *) * nr_cpu_ids;
686 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
688 if (!buffer->buffers)
689 goto fail_free_cpumask;
691 for_each_buffer_cpu(buffer, cpu) {
692 buffer->buffers[cpu] =
693 rb_allocate_cpu_buffer(buffer, cpu);
694 if (!buffer->buffers[cpu])
695 goto fail_free_buffers;
698 #ifdef CONFIG_HOTPLUG_CPU
699 buffer->cpu_notify.notifier_call = rb_cpu_notify;
700 buffer->cpu_notify.priority = 0;
701 register_cpu_notifier(&buffer->cpu_notify);
705 mutex_init(&buffer->mutex);
710 for_each_buffer_cpu(buffer, cpu) {
711 if (buffer->buffers[cpu])
712 rb_free_cpu_buffer(buffer->buffers[cpu]);
714 kfree(buffer->buffers);
717 free_cpumask_var(buffer->cpumask);
724 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
727 * ring_buffer_free - free a ring buffer.
728 * @buffer: the buffer to free.
731 ring_buffer_free(struct ring_buffer *buffer)
737 #ifdef CONFIG_HOTPLUG_CPU
738 unregister_cpu_notifier(&buffer->cpu_notify);
741 for_each_buffer_cpu(buffer, cpu)
742 rb_free_cpu_buffer(buffer->buffers[cpu]);
746 free_cpumask_var(buffer->cpumask);
750 EXPORT_SYMBOL_GPL(ring_buffer_free);
752 void ring_buffer_set_clock(struct ring_buffer *buffer,
755 buffer->clock = clock;
758 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
761 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
763 struct buffer_page *bpage;
767 atomic_inc(&cpu_buffer->record_disabled);
770 for (i = 0; i < nr_pages; i++) {
771 if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
773 p = cpu_buffer->pages.next;
774 bpage = list_entry(p, struct buffer_page, list);
775 list_del_init(&bpage->list);
776 free_buffer_page(bpage);
778 if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
781 rb_reset_cpu(cpu_buffer);
783 rb_check_pages(cpu_buffer);
785 atomic_dec(&cpu_buffer->record_disabled);
790 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
791 struct list_head *pages, unsigned nr_pages)
793 struct buffer_page *bpage;
797 atomic_inc(&cpu_buffer->record_disabled);
800 for (i = 0; i < nr_pages; i++) {
801 if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
804 bpage = list_entry(p, struct buffer_page, list);
805 list_del_init(&bpage->list);
806 list_add_tail(&bpage->list, &cpu_buffer->pages);
808 rb_reset_cpu(cpu_buffer);
810 rb_check_pages(cpu_buffer);
812 atomic_dec(&cpu_buffer->record_disabled);
816 * ring_buffer_resize - resize the ring buffer
817 * @buffer: the buffer to resize.
818 * @size: the new size.
820 * The tracer is responsible for making sure that the buffer is
821 * not being used while changing the size.
822 * Note: We may be able to change the above requirement by using
823 * RCU synchronizations.
825 * Minimum size is 2 * BUF_PAGE_SIZE.
827 * Returns -1 on failure.
829 int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
831 struct ring_buffer_per_cpu *cpu_buffer;
832 unsigned nr_pages, rm_pages, new_pages;
833 struct buffer_page *bpage, *tmp;
834 unsigned long buffer_size;
840 * Always succeed at resizing a non-existent buffer:
845 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
846 size *= BUF_PAGE_SIZE;
847 buffer_size = buffer->pages * BUF_PAGE_SIZE;
849 /* we need a minimum of two pages */
850 if (size < BUF_PAGE_SIZE * 2)
851 size = BUF_PAGE_SIZE * 2;
853 if (size == buffer_size)
856 mutex_lock(&buffer->mutex);
859 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
861 if (size < buffer_size) {
863 /* easy case, just free pages */
864 if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
867 rm_pages = buffer->pages - nr_pages;
869 for_each_buffer_cpu(buffer, cpu) {
870 cpu_buffer = buffer->buffers[cpu];
871 rb_remove_pages(cpu_buffer, rm_pages);
877 * This is a bit more difficult. We only want to add pages
878 * when we can allocate enough for all CPUs. We do this
879 * by allocating all the pages and storing them on a local
880 * link list. If we succeed in our allocation, then we
881 * add these pages to the cpu_buffers. Otherwise we just free
882 * them all and return -ENOMEM;
884 if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
887 new_pages = nr_pages - buffer->pages;
889 for_each_buffer_cpu(buffer, cpu) {
890 for (i = 0; i < new_pages; i++) {
891 bpage = kzalloc_node(ALIGN(sizeof(*bpage),
893 GFP_KERNEL, cpu_to_node(cpu));
896 list_add(&bpage->list, &pages);
897 addr = __get_free_page(GFP_KERNEL);
900 bpage->page = (void *)addr;
901 rb_init_page(bpage->page);
905 for_each_buffer_cpu(buffer, cpu) {
906 cpu_buffer = buffer->buffers[cpu];
907 rb_insert_pages(cpu_buffer, &pages, new_pages);
910 if (RB_WARN_ON(buffer, !list_empty(&pages)))
914 buffer->pages = nr_pages;
916 mutex_unlock(&buffer->mutex);
921 list_for_each_entry_safe(bpage, tmp, &pages, list) {
922 list_del_init(&bpage->list);
923 free_buffer_page(bpage);
926 mutex_unlock(&buffer->mutex);
930 * Something went totally wrong, and we are too paranoid
931 * to even clean up the mess.
935 mutex_unlock(&buffer->mutex);
938 EXPORT_SYMBOL_GPL(ring_buffer_resize);
941 __rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
943 return bpage->data + index;
946 static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
948 return bpage->page->data + index;
951 static inline struct ring_buffer_event *
952 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
954 return __rb_page_index(cpu_buffer->reader_page,
955 cpu_buffer->reader_page->read);
958 static inline struct ring_buffer_event *
959 rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
961 return __rb_page_index(cpu_buffer->head_page,
962 cpu_buffer->head_page->read);
965 static inline struct ring_buffer_event *
966 rb_iter_head_event(struct ring_buffer_iter *iter)
968 return __rb_page_index(iter->head_page, iter->head);
971 static inline unsigned rb_page_write(struct buffer_page *bpage)
973 return local_read(&bpage->write);
976 static inline unsigned rb_page_commit(struct buffer_page *bpage)
978 return local_read(&bpage->page->commit);
981 /* Size is determined by what has been commited */
982 static inline unsigned rb_page_size(struct buffer_page *bpage)
984 return rb_page_commit(bpage);
987 static inline unsigned
988 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
990 return rb_page_commit(cpu_buffer->commit_page);
993 static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
995 return rb_page_commit(cpu_buffer->head_page);
998 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
999 struct buffer_page **bpage)
1001 struct list_head *p = (*bpage)->list.next;
1003 if (p == &cpu_buffer->pages)
1006 *bpage = list_entry(p, struct buffer_page, list);
1009 static inline unsigned
1010 rb_event_index(struct ring_buffer_event *event)
1012 unsigned long addr = (unsigned long)event;
1014 return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
1018 rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1019 struct ring_buffer_event *event)
1021 unsigned long addr = (unsigned long)event;
1022 unsigned long index;
1024 index = rb_event_index(event);
1027 return cpu_buffer->commit_page->page == (void *)addr &&
1028 rb_commit_index(cpu_buffer) == index;
1032 rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
1033 struct ring_buffer_event *event)
1035 unsigned long addr = (unsigned long)event;
1036 unsigned long index;
1038 index = rb_event_index(event);
1041 while (cpu_buffer->commit_page->page != (void *)addr) {
1042 if (RB_WARN_ON(cpu_buffer,
1043 cpu_buffer->commit_page == cpu_buffer->tail_page))
1045 cpu_buffer->commit_page->page->commit =
1046 cpu_buffer->commit_page->write;
1047 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1048 cpu_buffer->write_stamp =
1049 cpu_buffer->commit_page->page->time_stamp;
1052 /* Now set the commit to the event's index */
1053 local_set(&cpu_buffer->commit_page->page->commit, index);
1057 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1060 * We only race with interrupts and NMIs on this CPU.
1061 * If we own the commit event, then we can commit
1062 * all others that interrupted us, since the interruptions
1063 * are in stack format (they finish before they come
1064 * back to us). This allows us to do a simple loop to
1065 * assign the commit to the tail.
1068 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
1069 cpu_buffer->commit_page->page->commit =
1070 cpu_buffer->commit_page->write;
1071 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1072 cpu_buffer->write_stamp =
1073 cpu_buffer->commit_page->page->time_stamp;
1074 /* add barrier to keep gcc from optimizing too much */
1077 while (rb_commit_index(cpu_buffer) !=
1078 rb_page_write(cpu_buffer->commit_page)) {
1079 cpu_buffer->commit_page->page->commit =
1080 cpu_buffer->commit_page->write;
1084 /* again, keep gcc from optimizing */
1088 * If an interrupt came in just after the first while loop
1089 * and pushed the tail page forward, we will be left with
1090 * a dangling commit that will never go forward.
1092 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1096 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1098 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
1099 cpu_buffer->reader_page->read = 0;
1102 static void rb_inc_iter(struct ring_buffer_iter *iter)
1104 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1107 * The iterator could be on the reader page (it starts there).
1108 * But the head could have moved, since the reader was
1109 * found. Check for this case and assign the iterator
1110 * to the head page instead of next.
1112 if (iter->head_page == cpu_buffer->reader_page)
1113 iter->head_page = cpu_buffer->head_page;
1115 rb_inc_page(cpu_buffer, &iter->head_page);
1117 iter->read_stamp = iter->head_page->page->time_stamp;
1122 * ring_buffer_update_event - update event type and data
1123 * @event: the even to update
1124 * @type: the type of event
1125 * @length: the size of the event field in the ring buffer
1127 * Update the type and data fields of the event. The length
1128 * is the actual size that is written to the ring buffer,
1129 * and with this, we can determine what to place into the
1133 rb_update_event(struct ring_buffer_event *event,
1134 unsigned type, unsigned length)
1136 event->type_len = type;
1140 case RINGBUF_TYPE_PADDING:
1141 case RINGBUF_TYPE_TIME_EXTEND:
1142 case RINGBUF_TYPE_TIME_STAMP:
1146 length -= RB_EVNT_HDR_SIZE;
1147 if (length > RB_MAX_SMALL_DATA)
1148 event->array[0] = length;
1150 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
1157 static unsigned rb_calculate_event_length(unsigned length)
1159 struct ring_buffer_event event; /* Used only for sizeof array */
1161 /* zero length can cause confusions */
1165 if (length > RB_MAX_SMALL_DATA)
1166 length += sizeof(event.array[0]);
1168 length += RB_EVNT_HDR_SIZE;
1169 length = ALIGN(length, RB_ALIGNMENT);
1175 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
1176 struct buffer_page *tail_page,
1177 unsigned long tail, unsigned long length)
1179 struct ring_buffer_event *event;
1182 * Only the event that crossed the page boundary
1183 * must fill the old tail_page with padding.
1185 if (tail >= BUF_PAGE_SIZE) {
1186 local_sub(length, &tail_page->write);
1190 event = __rb_page_index(tail_page, tail);
1193 * If this event is bigger than the minimum size, then
1194 * we need to be careful that we don't subtract the
1195 * write counter enough to allow another writer to slip
1197 * We put in a discarded commit instead, to make sure
1198 * that this space is not used again.
1200 * If we are less than the minimum size, we don't need to
1203 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
1204 /* No room for any events */
1206 /* Mark the rest of the page with padding */
1207 rb_event_set_padding(event);
1209 /* Set the write back to the previous setting */
1210 local_sub(length, &tail_page->write);
1214 /* Put in a discarded event */
1215 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
1216 event->type_len = RINGBUF_TYPE_PADDING;
1217 /* time delta must be non zero */
1218 event->time_delta = 1;
1219 /* Account for this as an entry */
1220 local_inc(&tail_page->entries);
1221 local_inc(&cpu_buffer->entries);
1223 /* Set write to end of buffer */
1224 length = (tail + length) - BUF_PAGE_SIZE;
1225 local_sub(length, &tail_page->write);
1228 static struct ring_buffer_event *
1229 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
1230 unsigned long length, unsigned long tail,
1231 struct buffer_page *commit_page,
1232 struct buffer_page *tail_page, u64 *ts)
1234 struct buffer_page *next_page, *head_page, *reader_page;
1235 struct ring_buffer *buffer = cpu_buffer->buffer;
1236 bool lock_taken = false;
1237 unsigned long flags;
1239 next_page = tail_page;
1241 local_irq_save(flags);
1243 * Since the write to the buffer is still not
1244 * fully lockless, we must be careful with NMIs.
1245 * The locks in the writers are taken when a write
1246 * crosses to a new page. The locks protect against
1247 * races with the readers (this will soon be fixed
1248 * with a lockless solution).
1250 * Because we can not protect against NMIs, and we
1251 * want to keep traces reentrant, we need to manage
1252 * what happens when we are in an NMI.
1254 * NMIs can happen after we take the lock.
1255 * If we are in an NMI, only take the lock
1256 * if it is not already taken. Otherwise
1259 if (unlikely(in_nmi())) {
1260 if (!__raw_spin_trylock(&cpu_buffer->lock)) {
1261 cpu_buffer->nmi_dropped++;
1265 __raw_spin_lock(&cpu_buffer->lock);
1269 rb_inc_page(cpu_buffer, &next_page);
1271 head_page = cpu_buffer->head_page;
1272 reader_page = cpu_buffer->reader_page;
1274 /* we grabbed the lock before incrementing */
1275 if (RB_WARN_ON(cpu_buffer, next_page == reader_page))
1279 * If for some reason, we had an interrupt storm that made
1280 * it all the way around the buffer, bail, and warn
1283 if (unlikely(next_page == commit_page)) {
1284 cpu_buffer->commit_overrun++;
1288 if (next_page == head_page) {
1289 if (!(buffer->flags & RB_FL_OVERWRITE))
1292 /* tail_page has not moved yet? */
1293 if (tail_page == cpu_buffer->tail_page) {
1294 /* count overflows */
1295 cpu_buffer->overrun +=
1296 local_read(&head_page->entries);
1298 rb_inc_page(cpu_buffer, &head_page);
1299 cpu_buffer->head_page = head_page;
1300 cpu_buffer->head_page->read = 0;
1305 * If the tail page is still the same as what we think
1306 * it is, then it is up to us to update the tail
1309 if (tail_page == cpu_buffer->tail_page) {
1310 local_set(&next_page->write, 0);
1311 local_set(&next_page->entries, 0);
1312 local_set(&next_page->page->commit, 0);
1313 cpu_buffer->tail_page = next_page;
1315 /* reread the time stamp */
1316 *ts = rb_time_stamp(buffer, cpu_buffer->cpu);
1317 cpu_buffer->tail_page->page->time_stamp = *ts;
1320 rb_reset_tail(cpu_buffer, tail_page, tail, length);
1323 * If this was a commit entry that failed,
1324 * increment that too
1326 if (tail_page == cpu_buffer->commit_page &&
1327 tail == rb_commit_index(cpu_buffer)) {
1328 rb_set_commit_to_write(cpu_buffer);
1331 __raw_spin_unlock(&cpu_buffer->lock);
1332 local_irq_restore(flags);
1334 /* fail and let the caller try again */
1335 return ERR_PTR(-EAGAIN);
1339 rb_reset_tail(cpu_buffer, tail_page, tail, length);
1341 if (likely(lock_taken))
1342 __raw_spin_unlock(&cpu_buffer->lock);
1343 local_irq_restore(flags);
1347 static struct ring_buffer_event *
1348 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
1349 unsigned type, unsigned long length, u64 *ts)
1351 struct buffer_page *tail_page, *commit_page;
1352 struct ring_buffer_event *event;
1353 unsigned long tail, write;
1355 commit_page = cpu_buffer->commit_page;
1356 /* we just need to protect against interrupts */
1358 tail_page = cpu_buffer->tail_page;
1359 write = local_add_return(length, &tail_page->write);
1360 tail = write - length;
1362 /* See if we shot pass the end of this buffer page */
1363 if (write > BUF_PAGE_SIZE)
1364 return rb_move_tail(cpu_buffer, length, tail,
1365 commit_page, tail_page, ts);
1367 /* We reserved something on the buffer */
1369 if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
1372 event = __rb_page_index(tail_page, tail);
1373 rb_update_event(event, type, length);
1375 /* The passed in type is zero for DATA */
1377 local_inc(&tail_page->entries);
1380 * If this is a commit and the tail is zero, then update
1381 * this page's time stamp.
1383 if (!tail && rb_is_commit(cpu_buffer, event))
1384 cpu_buffer->commit_page->page->time_stamp = *ts;
1390 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
1391 struct ring_buffer_event *event)
1393 unsigned long new_index, old_index;
1394 struct buffer_page *bpage;
1395 unsigned long index;
1398 new_index = rb_event_index(event);
1399 old_index = new_index + rb_event_length(event);
1400 addr = (unsigned long)event;
1403 bpage = cpu_buffer->tail_page;
1405 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
1407 * This is on the tail page. It is possible that
1408 * a write could come in and move the tail page
1409 * and write to the next page. That is fine
1410 * because we just shorten what is on this page.
1412 index = local_cmpxchg(&bpage->write, old_index, new_index);
1413 if (index == old_index)
1417 /* could not discard */
1422 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1423 u64 *ts, u64 *delta)
1425 struct ring_buffer_event *event;
1429 if (unlikely(*delta > (1ULL << 59) && !once++)) {
1430 printk(KERN_WARNING "Delta way too big! %llu"
1431 " ts=%llu write stamp = %llu\n",
1432 (unsigned long long)*delta,
1433 (unsigned long long)*ts,
1434 (unsigned long long)cpu_buffer->write_stamp);
1439 * The delta is too big, we to add a
1442 event = __rb_reserve_next(cpu_buffer,
1443 RINGBUF_TYPE_TIME_EXTEND,
1449 if (PTR_ERR(event) == -EAGAIN)
1452 /* Only a commited time event can update the write stamp */
1453 if (rb_is_commit(cpu_buffer, event)) {
1455 * If this is the first on the page, then we need to
1456 * update the page itself, and just put in a zero.
1458 if (rb_event_index(event)) {
1459 event->time_delta = *delta & TS_MASK;
1460 event->array[0] = *delta >> TS_SHIFT;
1462 cpu_buffer->commit_page->page->time_stamp = *ts;
1463 /* try to discard, since we do not need this */
1464 if (!rb_try_to_discard(cpu_buffer, event)) {
1465 /* nope, just zero it */
1466 event->time_delta = 0;
1467 event->array[0] = 0;
1470 cpu_buffer->write_stamp = *ts;
1471 /* let the caller know this was the commit */
1474 /* Try to discard the event */
1475 if (!rb_try_to_discard(cpu_buffer, event)) {
1476 /* Darn, this is just wasted space */
1477 event->time_delta = 0;
1478 event->array[0] = 0;
1488 static struct ring_buffer_event *
1489 rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
1490 unsigned long length)
1492 struct ring_buffer_event *event;
1497 length = rb_calculate_event_length(length);
1500 * We allow for interrupts to reenter here and do a trace.
1501 * If one does, it will cause this original code to loop
1502 * back here. Even with heavy interrupts happening, this
1503 * should only happen a few times in a row. If this happens
1504 * 1000 times in a row, there must be either an interrupt
1505 * storm or we have something buggy.
1508 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
1511 ts = rb_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);
1514 * Only the first commit can update the timestamp.
1515 * Yes there is a race here. If an interrupt comes in
1516 * just after the conditional and it traces too, then it
1517 * will also check the deltas. More than one timestamp may
1518 * also be made. But only the entry that did the actual
1519 * commit will be something other than zero.
1521 if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
1522 rb_page_write(cpu_buffer->tail_page) ==
1523 rb_commit_index(cpu_buffer))) {
1526 diff = ts - cpu_buffer->write_stamp;
1528 /* make sure this diff is calculated here */
1531 /* Did the write stamp get updated already? */
1532 if (unlikely(ts < cpu_buffer->write_stamp))
1536 if (unlikely(test_time_stamp(delta))) {
1538 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
1539 if (commit == -EBUSY)
1542 if (commit == -EAGAIN)
1545 RB_WARN_ON(cpu_buffer, commit < 0);
1550 event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
1551 if (unlikely(PTR_ERR(event) == -EAGAIN))
1555 if (unlikely(commit))
1557 * Ouch! We needed a timestamp and it was commited. But
1558 * we didn't get our event reserved.
1560 rb_set_commit_to_write(cpu_buffer);
1565 * If the timestamp was commited, make the commit our entry
1566 * now so that we will update it when needed.
1568 if (unlikely(commit))
1569 rb_set_commit_event(cpu_buffer, event);
1570 else if (!rb_is_commit(cpu_buffer, event))
1573 event->time_delta = delta;
1578 #define TRACE_RECURSIVE_DEPTH 16
1580 static int trace_recursive_lock(void)
1582 current->trace_recursion++;
1584 if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
1587 /* Disable all tracing before we do anything else */
1588 tracing_off_permanent();
1590 printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
1591 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
1592 current->trace_recursion,
1593 hardirq_count() >> HARDIRQ_SHIFT,
1594 softirq_count() >> SOFTIRQ_SHIFT,
1601 static void trace_recursive_unlock(void)
1603 WARN_ON_ONCE(!current->trace_recursion);
1605 current->trace_recursion--;
1608 static DEFINE_PER_CPU(int, rb_need_resched);
1611 * ring_buffer_lock_reserve - reserve a part of the buffer
1612 * @buffer: the ring buffer to reserve from
1613 * @length: the length of the data to reserve (excluding event header)
1615 * Returns a reseverd event on the ring buffer to copy directly to.
1616 * The user of this interface will need to get the body to write into
1617 * and can use the ring_buffer_event_data() interface.
1619 * The length is the length of the data needed, not the event length
1620 * which also includes the event header.
1622 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1623 * If NULL is returned, then nothing has been allocated or locked.
1625 struct ring_buffer_event *
1626 ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
1628 struct ring_buffer_per_cpu *cpu_buffer;
1629 struct ring_buffer_event *event;
1632 if (ring_buffer_flags != RB_BUFFERS_ON)
1635 if (atomic_read(&buffer->record_disabled))
1638 /* If we are tracing schedule, we don't want to recurse */
1639 resched = ftrace_preempt_disable();
1641 if (trace_recursive_lock())
1644 cpu = raw_smp_processor_id();
1646 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1649 cpu_buffer = buffer->buffers[cpu];
1651 if (atomic_read(&cpu_buffer->record_disabled))
1654 if (length > BUF_MAX_DATA_SIZE)
1657 event = rb_reserve_next_event(cpu_buffer, length);
1662 * Need to store resched state on this cpu.
1663 * Only the first needs to.
1666 if (preempt_count() == 1)
1667 per_cpu(rb_need_resched, cpu) = resched;
1672 trace_recursive_unlock();
1675 ftrace_preempt_enable(resched);
1678 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
1680 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
1681 struct ring_buffer_event *event)
1683 local_inc(&cpu_buffer->entries);
1685 /* Only process further if we own the commit */
1686 if (!rb_is_commit(cpu_buffer, event))
1689 cpu_buffer->write_stamp += event->time_delta;
1691 rb_set_commit_to_write(cpu_buffer);
1695 * ring_buffer_unlock_commit - commit a reserved
1696 * @buffer: The buffer to commit to
1697 * @event: The event pointer to commit.
1699 * This commits the data to the ring buffer, and releases any locks held.
1701 * Must be paired with ring_buffer_lock_reserve.
1703 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
1704 struct ring_buffer_event *event)
1706 struct ring_buffer_per_cpu *cpu_buffer;
1707 int cpu = raw_smp_processor_id();
1709 cpu_buffer = buffer->buffers[cpu];
1711 rb_commit(cpu_buffer, event);
1713 trace_recursive_unlock();
1716 * Only the last preempt count needs to restore preemption.
1718 if (preempt_count() == 1)
1719 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
1721 preempt_enable_no_resched_notrace();
1725 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
1727 static inline void rb_event_discard(struct ring_buffer_event *event)
1729 /* array[0] holds the actual length for the discarded event */
1730 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
1731 event->type_len = RINGBUF_TYPE_PADDING;
1732 /* time delta must be non zero */
1733 if (!event->time_delta)
1734 event->time_delta = 1;
1738 * ring_buffer_event_discard - discard any event in the ring buffer
1739 * @event: the event to discard
1741 * Sometimes a event that is in the ring buffer needs to be ignored.
1742 * This function lets the user discard an event in the ring buffer
1743 * and then that event will not be read later.
1745 * Note, it is up to the user to be careful with this, and protect
1746 * against races. If the user discards an event that has been consumed
1747 * it is possible that it could corrupt the ring buffer.
1749 void ring_buffer_event_discard(struct ring_buffer_event *event)
1751 rb_event_discard(event);
1753 EXPORT_SYMBOL_GPL(ring_buffer_event_discard);
1756 * ring_buffer_commit_discard - discard an event that has not been committed
1757 * @buffer: the ring buffer
1758 * @event: non committed event to discard
1760 * This is similar to ring_buffer_event_discard but must only be
1761 * performed on an event that has not been committed yet. The difference
1762 * is that this will also try to free the event from the ring buffer
1763 * if another event has not been added behind it.
1765 * If another event has been added behind it, it will set the event
1766 * up as discarded, and perform the commit.
1768 * If this function is called, do not call ring_buffer_unlock_commit on
1771 void ring_buffer_discard_commit(struct ring_buffer *buffer,
1772 struct ring_buffer_event *event)
1774 struct ring_buffer_per_cpu *cpu_buffer;
1777 /* The event is discarded regardless */
1778 rb_event_discard(event);
1781 * This must only be called if the event has not been
1782 * committed yet. Thus we can assume that preemption
1783 * is still disabled.
1785 RB_WARN_ON(buffer, preemptible());
1787 cpu = smp_processor_id();
1788 cpu_buffer = buffer->buffers[cpu];
1790 if (!rb_try_to_discard(cpu_buffer, event))
1794 * The commit is still visible by the reader, so we
1795 * must increment entries.
1797 local_inc(&cpu_buffer->entries);
1800 * If a write came in and pushed the tail page
1801 * we still need to update the commit pointer
1802 * if we were the commit.
1804 if (rb_is_commit(cpu_buffer, event))
1805 rb_set_commit_to_write(cpu_buffer);
1807 trace_recursive_unlock();
1810 * Only the last preempt count needs to restore preemption.
1812 if (preempt_count() == 1)
1813 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
1815 preempt_enable_no_resched_notrace();
1818 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
1821 * ring_buffer_write - write data to the buffer without reserving
1822 * @buffer: The ring buffer to write to.
1823 * @length: The length of the data being written (excluding the event header)
1824 * @data: The data to write to the buffer.
1826 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1827 * one function. If you already have the data to write to the buffer, it
1828 * may be easier to simply call this function.
1830 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1831 * and not the length of the event which would hold the header.
1833 int ring_buffer_write(struct ring_buffer *buffer,
1834 unsigned long length,
1837 struct ring_buffer_per_cpu *cpu_buffer;
1838 struct ring_buffer_event *event;
1843 if (ring_buffer_flags != RB_BUFFERS_ON)
1846 if (atomic_read(&buffer->record_disabled))
1849 resched = ftrace_preempt_disable();
1851 cpu = raw_smp_processor_id();
1853 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1856 cpu_buffer = buffer->buffers[cpu];
1858 if (atomic_read(&cpu_buffer->record_disabled))
1861 if (length > BUF_MAX_DATA_SIZE)
1864 event = rb_reserve_next_event(cpu_buffer, length);
1868 body = rb_event_data(event);
1870 memcpy(body, data, length);
1872 rb_commit(cpu_buffer, event);
1876 ftrace_preempt_enable(resched);
1880 EXPORT_SYMBOL_GPL(ring_buffer_write);
1882 static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
1884 struct buffer_page *reader = cpu_buffer->reader_page;
1885 struct buffer_page *head = cpu_buffer->head_page;
1886 struct buffer_page *commit = cpu_buffer->commit_page;
1888 return reader->read == rb_page_commit(reader) &&
1889 (commit == reader ||
1891 head->read == rb_page_commit(commit)));
1895 * ring_buffer_record_disable - stop all writes into the buffer
1896 * @buffer: The ring buffer to stop writes to.
1898 * This prevents all writes to the buffer. Any attempt to write
1899 * to the buffer after this will fail and return NULL.
1901 * The caller should call synchronize_sched() after this.
1903 void ring_buffer_record_disable(struct ring_buffer *buffer)
1905 atomic_inc(&buffer->record_disabled);
1907 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
1910 * ring_buffer_record_enable - enable writes to the buffer
1911 * @buffer: The ring buffer to enable writes
1913 * Note, multiple disables will need the same number of enables
1914 * to truely enable the writing (much like preempt_disable).
1916 void ring_buffer_record_enable(struct ring_buffer *buffer)
1918 atomic_dec(&buffer->record_disabled);
1920 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
1923 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1924 * @buffer: The ring buffer to stop writes to.
1925 * @cpu: The CPU buffer to stop
1927 * This prevents all writes to the buffer. Any attempt to write
1928 * to the buffer after this will fail and return NULL.
1930 * The caller should call synchronize_sched() after this.
1932 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
1934 struct ring_buffer_per_cpu *cpu_buffer;
1936 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1939 cpu_buffer = buffer->buffers[cpu];
1940 atomic_inc(&cpu_buffer->record_disabled);
1942 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
1945 * ring_buffer_record_enable_cpu - enable writes to the buffer
1946 * @buffer: The ring buffer to enable writes
1947 * @cpu: The CPU to enable.
1949 * Note, multiple disables will need the same number of enables
1950 * to truely enable the writing (much like preempt_disable).
1952 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
1954 struct ring_buffer_per_cpu *cpu_buffer;
1956 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1959 cpu_buffer = buffer->buffers[cpu];
1960 atomic_dec(&cpu_buffer->record_disabled);
1962 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
1965 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1966 * @buffer: The ring buffer
1967 * @cpu: The per CPU buffer to get the entries from.
1969 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
1971 struct ring_buffer_per_cpu *cpu_buffer;
1974 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1977 cpu_buffer = buffer->buffers[cpu];
1978 ret = (local_read(&cpu_buffer->entries) - cpu_buffer->overrun)
1983 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
1986 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1987 * @buffer: The ring buffer
1988 * @cpu: The per CPU buffer to get the number of overruns from
1990 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
1992 struct ring_buffer_per_cpu *cpu_buffer;
1995 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1998 cpu_buffer = buffer->buffers[cpu];
1999 ret = cpu_buffer->overrun;
2003 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
2006 * ring_buffer_nmi_dropped_cpu - get the number of nmis that were dropped
2007 * @buffer: The ring buffer
2008 * @cpu: The per CPU buffer to get the number of overruns from
2010 unsigned long ring_buffer_nmi_dropped_cpu(struct ring_buffer *buffer, int cpu)
2012 struct ring_buffer_per_cpu *cpu_buffer;
2015 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2018 cpu_buffer = buffer->buffers[cpu];
2019 ret = cpu_buffer->nmi_dropped;
2023 EXPORT_SYMBOL_GPL(ring_buffer_nmi_dropped_cpu);
2026 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2027 * @buffer: The ring buffer
2028 * @cpu: The per CPU buffer to get the number of overruns from
2031 ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
2033 struct ring_buffer_per_cpu *cpu_buffer;
2036 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2039 cpu_buffer = buffer->buffers[cpu];
2040 ret = cpu_buffer->commit_overrun;
2044 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
2047 * ring_buffer_entries - get the number of entries in a buffer
2048 * @buffer: The ring buffer
2050 * Returns the total number of entries in the ring buffer
2053 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
2055 struct ring_buffer_per_cpu *cpu_buffer;
2056 unsigned long entries = 0;
2059 /* if you care about this being correct, lock the buffer */
2060 for_each_buffer_cpu(buffer, cpu) {
2061 cpu_buffer = buffer->buffers[cpu];
2062 entries += (local_read(&cpu_buffer->entries) -
2063 cpu_buffer->overrun) - cpu_buffer->read;
2068 EXPORT_SYMBOL_GPL(ring_buffer_entries);
2071 * ring_buffer_overrun_cpu - get the number of overruns in buffer
2072 * @buffer: The ring buffer
2074 * Returns the total number of overruns in the ring buffer
2077 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
2079 struct ring_buffer_per_cpu *cpu_buffer;
2080 unsigned long overruns = 0;
2083 /* if you care about this being correct, lock the buffer */
2084 for_each_buffer_cpu(buffer, cpu) {
2085 cpu_buffer = buffer->buffers[cpu];
2086 overruns += cpu_buffer->overrun;
2091 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
2093 static void rb_iter_reset(struct ring_buffer_iter *iter)
2095 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2097 /* Iterator usage is expected to have record disabled */
2098 if (list_empty(&cpu_buffer->reader_page->list)) {
2099 iter->head_page = cpu_buffer->head_page;
2100 iter->head = cpu_buffer->head_page->read;
2102 iter->head_page = cpu_buffer->reader_page;
2103 iter->head = cpu_buffer->reader_page->read;
2106 iter->read_stamp = cpu_buffer->read_stamp;
2108 iter->read_stamp = iter->head_page->page->time_stamp;
2112 * ring_buffer_iter_reset - reset an iterator
2113 * @iter: The iterator to reset
2115 * Resets the iterator, so that it will start from the beginning
2118 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
2120 struct ring_buffer_per_cpu *cpu_buffer;
2121 unsigned long flags;
2126 cpu_buffer = iter->cpu_buffer;
2128 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2129 rb_iter_reset(iter);
2130 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2132 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
2135 * ring_buffer_iter_empty - check if an iterator has no more to read
2136 * @iter: The iterator to check
2138 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
2140 struct ring_buffer_per_cpu *cpu_buffer;
2142 cpu_buffer = iter->cpu_buffer;
2144 return iter->head_page == cpu_buffer->commit_page &&
2145 iter->head == rb_commit_index(cpu_buffer);
2147 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
2150 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2151 struct ring_buffer_event *event)
2155 switch (event->type_len) {
2156 case RINGBUF_TYPE_PADDING:
2159 case RINGBUF_TYPE_TIME_EXTEND:
2160 delta = event->array[0];
2162 delta += event->time_delta;
2163 cpu_buffer->read_stamp += delta;
2166 case RINGBUF_TYPE_TIME_STAMP:
2167 /* FIXME: not implemented */
2170 case RINGBUF_TYPE_DATA:
2171 cpu_buffer->read_stamp += event->time_delta;
2181 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
2182 struct ring_buffer_event *event)
2186 switch (event->type_len) {
2187 case RINGBUF_TYPE_PADDING:
2190 case RINGBUF_TYPE_TIME_EXTEND:
2191 delta = event->array[0];
2193 delta += event->time_delta;
2194 iter->read_stamp += delta;
2197 case RINGBUF_TYPE_TIME_STAMP:
2198 /* FIXME: not implemented */
2201 case RINGBUF_TYPE_DATA:
2202 iter->read_stamp += event->time_delta;
2211 static struct buffer_page *
2212 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
2214 struct buffer_page *reader = NULL;
2215 unsigned long flags;
2218 local_irq_save(flags);
2219 __raw_spin_lock(&cpu_buffer->lock);
2223 * This should normally only loop twice. But because the
2224 * start of the reader inserts an empty page, it causes
2225 * a case where we will loop three times. There should be no
2226 * reason to loop four times (that I know of).
2228 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
2233 reader = cpu_buffer->reader_page;
2235 /* If there's more to read, return this page */
2236 if (cpu_buffer->reader_page->read < rb_page_size(reader))
2239 /* Never should we have an index greater than the size */
2240 if (RB_WARN_ON(cpu_buffer,
2241 cpu_buffer->reader_page->read > rb_page_size(reader)))
2244 /* check if we caught up to the tail */
2246 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
2250 * Splice the empty reader page into the list around the head.
2251 * Reset the reader page to size zero.
2254 reader = cpu_buffer->head_page;
2255 cpu_buffer->reader_page->list.next = reader->list.next;
2256 cpu_buffer->reader_page->list.prev = reader->list.prev;
2258 local_set(&cpu_buffer->reader_page->write, 0);
2259 local_set(&cpu_buffer->reader_page->entries, 0);
2260 local_set(&cpu_buffer->reader_page->page->commit, 0);
2262 /* Make the reader page now replace the head */
2263 reader->list.prev->next = &cpu_buffer->reader_page->list;
2264 reader->list.next->prev = &cpu_buffer->reader_page->list;
2267 * If the tail is on the reader, then we must set the head
2268 * to the inserted page, otherwise we set it one before.
2270 cpu_buffer->head_page = cpu_buffer->reader_page;
2272 if (cpu_buffer->commit_page != reader)
2273 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
2275 /* Finally update the reader page to the new head */
2276 cpu_buffer->reader_page = reader;
2277 rb_reset_reader_page(cpu_buffer);
2282 __raw_spin_unlock(&cpu_buffer->lock);
2283 local_irq_restore(flags);
2288 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
2290 struct ring_buffer_event *event;
2291 struct buffer_page *reader;
2294 reader = rb_get_reader_page(cpu_buffer);
2296 /* This function should not be called when buffer is empty */
2297 if (RB_WARN_ON(cpu_buffer, !reader))
2300 event = rb_reader_event(cpu_buffer);
2302 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
2303 || rb_discarded_event(event))
2306 rb_update_read_stamp(cpu_buffer, event);
2308 length = rb_event_length(event);
2309 cpu_buffer->reader_page->read += length;
2312 static void rb_advance_iter(struct ring_buffer_iter *iter)
2314 struct ring_buffer *buffer;
2315 struct ring_buffer_per_cpu *cpu_buffer;
2316 struct ring_buffer_event *event;
2319 cpu_buffer = iter->cpu_buffer;
2320 buffer = cpu_buffer->buffer;
2323 * Check if we are at the end of the buffer.
2325 if (iter->head >= rb_page_size(iter->head_page)) {
2326 /* discarded commits can make the page empty */
2327 if (iter->head_page == cpu_buffer->commit_page)
2333 event = rb_iter_head_event(iter);
2335 length = rb_event_length(event);
2338 * This should not be called to advance the header if we are
2339 * at the tail of the buffer.
2341 if (RB_WARN_ON(cpu_buffer,
2342 (iter->head_page == cpu_buffer->commit_page) &&
2343 (iter->head + length > rb_commit_index(cpu_buffer))))
2346 rb_update_iter_read_stamp(iter, event);
2348 iter->head += length;
2350 /* check for end of page padding */
2351 if ((iter->head >= rb_page_size(iter->head_page)) &&
2352 (iter->head_page != cpu_buffer->commit_page))
2353 rb_advance_iter(iter);
2356 static struct ring_buffer_event *
2357 rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
2359 struct ring_buffer_per_cpu *cpu_buffer;
2360 struct ring_buffer_event *event;
2361 struct buffer_page *reader;
2364 cpu_buffer = buffer->buffers[cpu];
2368 * We repeat when a timestamp is encountered. It is possible
2369 * to get multiple timestamps from an interrupt entering just
2370 * as one timestamp is about to be written, or from discarded
2371 * commits. The most that we can have is the number on a single page.
2373 if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
2376 reader = rb_get_reader_page(cpu_buffer);
2380 event = rb_reader_event(cpu_buffer);
2382 switch (event->type_len) {
2383 case RINGBUF_TYPE_PADDING:
2384 if (rb_null_event(event))
2385 RB_WARN_ON(cpu_buffer, 1);
2387 * Because the writer could be discarding every
2388 * event it creates (which would probably be bad)
2389 * if we were to go back to "again" then we may never
2390 * catch up, and will trigger the warn on, or lock
2391 * the box. Return the padding, and we will release
2392 * the current locks, and try again.
2394 rb_advance_reader(cpu_buffer);
2397 case RINGBUF_TYPE_TIME_EXTEND:
2398 /* Internal data, OK to advance */
2399 rb_advance_reader(cpu_buffer);
2402 case RINGBUF_TYPE_TIME_STAMP:
2403 /* FIXME: not implemented */
2404 rb_advance_reader(cpu_buffer);
2407 case RINGBUF_TYPE_DATA:
2409 *ts = cpu_buffer->read_stamp + event->time_delta;
2410 ring_buffer_normalize_time_stamp(buffer,
2411 cpu_buffer->cpu, ts);
2421 EXPORT_SYMBOL_GPL(ring_buffer_peek);
2423 static struct ring_buffer_event *
2424 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
2426 struct ring_buffer *buffer;
2427 struct ring_buffer_per_cpu *cpu_buffer;
2428 struct ring_buffer_event *event;
2431 if (ring_buffer_iter_empty(iter))
2434 cpu_buffer = iter->cpu_buffer;
2435 buffer = cpu_buffer->buffer;
2439 * We repeat when a timestamp is encountered.
2440 * We can get multiple timestamps by nested interrupts or also
2441 * if filtering is on (discarding commits). Since discarding
2442 * commits can be frequent we can get a lot of timestamps.
2443 * But we limit them by not adding timestamps if they begin
2444 * at the start of a page.
2446 if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
2449 if (rb_per_cpu_empty(cpu_buffer))
2452 event = rb_iter_head_event(iter);
2454 switch (event->type_len) {
2455 case RINGBUF_TYPE_PADDING:
2456 if (rb_null_event(event)) {
2460 rb_advance_iter(iter);
2463 case RINGBUF_TYPE_TIME_EXTEND:
2464 /* Internal data, OK to advance */
2465 rb_advance_iter(iter);
2468 case RINGBUF_TYPE_TIME_STAMP:
2469 /* FIXME: not implemented */
2470 rb_advance_iter(iter);
2473 case RINGBUF_TYPE_DATA:
2475 *ts = iter->read_stamp + event->time_delta;
2476 ring_buffer_normalize_time_stamp(buffer,
2477 cpu_buffer->cpu, ts);
2487 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
2490 * ring_buffer_peek - peek at the next event to be read
2491 * @buffer: The ring buffer to read
2492 * @cpu: The cpu to peak at
2493 * @ts: The timestamp counter of this event.
2495 * This will return the event that will be read next, but does
2496 * not consume the data.
2498 struct ring_buffer_event *
2499 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
2501 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2502 struct ring_buffer_event *event;
2503 unsigned long flags;
2505 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2509 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2510 event = rb_buffer_peek(buffer, cpu, ts);
2511 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2513 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2522 * ring_buffer_iter_peek - peek at the next event to be read
2523 * @iter: The ring buffer iterator
2524 * @ts: The timestamp counter of this event.
2526 * This will return the event that will be read next, but does
2527 * not increment the iterator.
2529 struct ring_buffer_event *
2530 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
2532 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2533 struct ring_buffer_event *event;
2534 unsigned long flags;
2537 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2538 event = rb_iter_peek(iter, ts);
2539 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2541 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2550 * ring_buffer_consume - return an event and consume it
2551 * @buffer: The ring buffer to get the next event from
2553 * Returns the next event in the ring buffer, and that event is consumed.
2554 * Meaning, that sequential reads will keep returning a different event,
2555 * and eventually empty the ring buffer if the producer is slower.
2557 struct ring_buffer_event *
2558 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
2560 struct ring_buffer_per_cpu *cpu_buffer;
2561 struct ring_buffer_event *event = NULL;
2562 unsigned long flags;
2565 /* might be called in atomic */
2568 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2571 cpu_buffer = buffer->buffers[cpu];
2572 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2574 event = rb_buffer_peek(buffer, cpu, ts);
2578 rb_advance_reader(cpu_buffer);
2581 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2586 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2593 EXPORT_SYMBOL_GPL(ring_buffer_consume);
2596 * ring_buffer_read_start - start a non consuming read of the buffer
2597 * @buffer: The ring buffer to read from
2598 * @cpu: The cpu buffer to iterate over
2600 * This starts up an iteration through the buffer. It also disables
2601 * the recording to the buffer until the reading is finished.
2602 * This prevents the reading from being corrupted. This is not
2603 * a consuming read, so a producer is not expected.
2605 * Must be paired with ring_buffer_finish.
2607 struct ring_buffer_iter *
2608 ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
2610 struct ring_buffer_per_cpu *cpu_buffer;
2611 struct ring_buffer_iter *iter;
2612 unsigned long flags;
2614 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2617 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
2621 cpu_buffer = buffer->buffers[cpu];
2623 iter->cpu_buffer = cpu_buffer;
2625 atomic_inc(&cpu_buffer->record_disabled);
2626 synchronize_sched();
2628 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2629 __raw_spin_lock(&cpu_buffer->lock);
2630 rb_iter_reset(iter);
2631 __raw_spin_unlock(&cpu_buffer->lock);
2632 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2636 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
2639 * ring_buffer_finish - finish reading the iterator of the buffer
2640 * @iter: The iterator retrieved by ring_buffer_start
2642 * This re-enables the recording to the buffer, and frees the
2646 ring_buffer_read_finish(struct ring_buffer_iter *iter)
2648 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2650 atomic_dec(&cpu_buffer->record_disabled);
2653 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
2656 * ring_buffer_read - read the next item in the ring buffer by the iterator
2657 * @iter: The ring buffer iterator
2658 * @ts: The time stamp of the event read.
2660 * This reads the next event in the ring buffer and increments the iterator.
2662 struct ring_buffer_event *
2663 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
2665 struct ring_buffer_event *event;
2666 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2667 unsigned long flags;
2670 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2671 event = rb_iter_peek(iter, ts);
2675 rb_advance_iter(iter);
2677 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2679 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2686 EXPORT_SYMBOL_GPL(ring_buffer_read);
2689 * ring_buffer_size - return the size of the ring buffer (in bytes)
2690 * @buffer: The ring buffer.
2692 unsigned long ring_buffer_size(struct ring_buffer *buffer)
2694 return BUF_PAGE_SIZE * buffer->pages;
2696 EXPORT_SYMBOL_GPL(ring_buffer_size);
2699 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
2701 cpu_buffer->head_page
2702 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
2703 local_set(&cpu_buffer->head_page->write, 0);
2704 local_set(&cpu_buffer->head_page->entries, 0);
2705 local_set(&cpu_buffer->head_page->page->commit, 0);
2707 cpu_buffer->head_page->read = 0;
2709 cpu_buffer->tail_page = cpu_buffer->head_page;
2710 cpu_buffer->commit_page = cpu_buffer->head_page;
2712 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
2713 local_set(&cpu_buffer->reader_page->write, 0);
2714 local_set(&cpu_buffer->reader_page->entries, 0);
2715 local_set(&cpu_buffer->reader_page->page->commit, 0);
2716 cpu_buffer->reader_page->read = 0;
2718 cpu_buffer->nmi_dropped = 0;
2719 cpu_buffer->commit_overrun = 0;
2720 cpu_buffer->overrun = 0;
2721 cpu_buffer->read = 0;
2722 local_set(&cpu_buffer->entries, 0);
2724 cpu_buffer->write_stamp = 0;
2725 cpu_buffer->read_stamp = 0;
2729 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2730 * @buffer: The ring buffer to reset a per cpu buffer of
2731 * @cpu: The CPU buffer to be reset
2733 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
2735 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2736 unsigned long flags;
2738 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2741 atomic_inc(&cpu_buffer->record_disabled);
2743 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2745 __raw_spin_lock(&cpu_buffer->lock);
2747 rb_reset_cpu(cpu_buffer);
2749 __raw_spin_unlock(&cpu_buffer->lock);
2751 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2753 atomic_dec(&cpu_buffer->record_disabled);
2755 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
2758 * ring_buffer_reset - reset a ring buffer
2759 * @buffer: The ring buffer to reset all cpu buffers
2761 void ring_buffer_reset(struct ring_buffer *buffer)
2765 for_each_buffer_cpu(buffer, cpu)
2766 ring_buffer_reset_cpu(buffer, cpu);
2768 EXPORT_SYMBOL_GPL(ring_buffer_reset);
2771 * rind_buffer_empty - is the ring buffer empty?
2772 * @buffer: The ring buffer to test
2774 int ring_buffer_empty(struct ring_buffer *buffer)
2776 struct ring_buffer_per_cpu *cpu_buffer;
2779 /* yes this is racy, but if you don't like the race, lock the buffer */
2780 for_each_buffer_cpu(buffer, cpu) {
2781 cpu_buffer = buffer->buffers[cpu];
2782 if (!rb_per_cpu_empty(cpu_buffer))
2788 EXPORT_SYMBOL_GPL(ring_buffer_empty);
2791 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2792 * @buffer: The ring buffer
2793 * @cpu: The CPU buffer to test
2795 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
2797 struct ring_buffer_per_cpu *cpu_buffer;
2800 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2803 cpu_buffer = buffer->buffers[cpu];
2804 ret = rb_per_cpu_empty(cpu_buffer);
2809 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
2812 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2813 * @buffer_a: One buffer to swap with
2814 * @buffer_b: The other buffer to swap with
2816 * This function is useful for tracers that want to take a "snapshot"
2817 * of a CPU buffer and has another back up buffer lying around.
2818 * it is expected that the tracer handles the cpu buffer not being
2819 * used at the moment.
2821 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
2822 struct ring_buffer *buffer_b, int cpu)
2824 struct ring_buffer_per_cpu *cpu_buffer_a;
2825 struct ring_buffer_per_cpu *cpu_buffer_b;
2828 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
2829 !cpumask_test_cpu(cpu, buffer_b->cpumask))
2832 /* At least make sure the two buffers are somewhat the same */
2833 if (buffer_a->pages != buffer_b->pages)
2838 if (ring_buffer_flags != RB_BUFFERS_ON)
2841 if (atomic_read(&buffer_a->record_disabled))
2844 if (atomic_read(&buffer_b->record_disabled))
2847 cpu_buffer_a = buffer_a->buffers[cpu];
2848 cpu_buffer_b = buffer_b->buffers[cpu];
2850 if (atomic_read(&cpu_buffer_a->record_disabled))
2853 if (atomic_read(&cpu_buffer_b->record_disabled))
2857 * We can't do a synchronize_sched here because this
2858 * function can be called in atomic context.
2859 * Normally this will be called from the same CPU as cpu.
2860 * If not it's up to the caller to protect this.
2862 atomic_inc(&cpu_buffer_a->record_disabled);
2863 atomic_inc(&cpu_buffer_b->record_disabled);
2865 buffer_a->buffers[cpu] = cpu_buffer_b;
2866 buffer_b->buffers[cpu] = cpu_buffer_a;
2868 cpu_buffer_b->buffer = buffer_a;
2869 cpu_buffer_a->buffer = buffer_b;
2871 atomic_dec(&cpu_buffer_a->record_disabled);
2872 atomic_dec(&cpu_buffer_b->record_disabled);
2878 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
2881 * ring_buffer_alloc_read_page - allocate a page to read from buffer
2882 * @buffer: the buffer to allocate for.
2884 * This function is used in conjunction with ring_buffer_read_page.
2885 * When reading a full page from the ring buffer, these functions
2886 * can be used to speed up the process. The calling function should
2887 * allocate a few pages first with this function. Then when it
2888 * needs to get pages from the ring buffer, it passes the result
2889 * of this function into ring_buffer_read_page, which will swap
2890 * the page that was allocated, with the read page of the buffer.
2893 * The page allocated, or NULL on error.
2895 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
2897 struct buffer_data_page *bpage;
2900 addr = __get_free_page(GFP_KERNEL);
2904 bpage = (void *)addr;
2906 rb_init_page(bpage);
2910 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
2913 * ring_buffer_free_read_page - free an allocated read page
2914 * @buffer: the buffer the page was allocate for
2915 * @data: the page to free
2917 * Free a page allocated from ring_buffer_alloc_read_page.
2919 void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
2921 free_page((unsigned long)data);
2923 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
2926 * ring_buffer_read_page - extract a page from the ring buffer
2927 * @buffer: buffer to extract from
2928 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
2929 * @len: amount to extract
2930 * @cpu: the cpu of the buffer to extract
2931 * @full: should the extraction only happen when the page is full.
2933 * This function will pull out a page from the ring buffer and consume it.
2934 * @data_page must be the address of the variable that was returned
2935 * from ring_buffer_alloc_read_page. This is because the page might be used
2936 * to swap with a page in the ring buffer.
2939 * rpage = ring_buffer_alloc_read_page(buffer);
2942 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
2944 * process_page(rpage, ret);
2946 * When @full is set, the function will not return true unless
2947 * the writer is off the reader page.
2949 * Note: it is up to the calling functions to handle sleeps and wakeups.
2950 * The ring buffer can be used anywhere in the kernel and can not
2951 * blindly call wake_up. The layer that uses the ring buffer must be
2952 * responsible for that.
2955 * >=0 if data has been transferred, returns the offset of consumed data.
2956 * <0 if no data has been transferred.
2958 int ring_buffer_read_page(struct ring_buffer *buffer,
2959 void **data_page, size_t len, int cpu, int full)
2961 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2962 struct ring_buffer_event *event;
2963 struct buffer_data_page *bpage;
2964 struct buffer_page *reader;
2965 unsigned long flags;
2966 unsigned int commit;
2971 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2975 * If len is not big enough to hold the page header, then
2976 * we can not copy anything.
2978 if (len <= BUF_PAGE_HDR_SIZE)
2981 len -= BUF_PAGE_HDR_SIZE;
2990 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2992 reader = rb_get_reader_page(cpu_buffer);
2996 event = rb_reader_event(cpu_buffer);
2998 read = reader->read;
2999 commit = rb_page_commit(reader);
3002 * If this page has been partially read or
3003 * if len is not big enough to read the rest of the page or
3004 * a writer is still on the page, then
3005 * we must copy the data from the page to the buffer.
3006 * Otherwise, we can simply swap the page with the one passed in.
3008 if (read || (len < (commit - read)) ||
3009 cpu_buffer->reader_page == cpu_buffer->commit_page) {
3010 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
3011 unsigned int rpos = read;
3012 unsigned int pos = 0;
3018 if (len > (commit - read))
3019 len = (commit - read);
3021 size = rb_event_length(event);
3026 /* save the current timestamp, since the user will need it */
3027 save_timestamp = cpu_buffer->read_stamp;
3029 /* Need to copy one event at a time */
3031 memcpy(bpage->data + pos, rpage->data + rpos, size);
3035 rb_advance_reader(cpu_buffer);
3036 rpos = reader->read;
3039 event = rb_reader_event(cpu_buffer);
3040 size = rb_event_length(event);
3041 } while (len > size);
3044 local_set(&bpage->commit, pos);
3045 bpage->time_stamp = save_timestamp;
3047 /* we copied everything to the beginning */
3050 /* update the entry counter */
3051 cpu_buffer->read += local_read(&reader->entries);
3053 /* swap the pages */
3054 rb_init_page(bpage);
3055 bpage = reader->page;
3056 reader->page = *data_page;
3057 local_set(&reader->write, 0);
3058 local_set(&reader->entries, 0);
3065 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3070 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
3073 rb_simple_read(struct file *filp, char __user *ubuf,
3074 size_t cnt, loff_t *ppos)
3076 unsigned long *p = filp->private_data;
3080 if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
3081 r = sprintf(buf, "permanently disabled\n");
3083 r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
3085 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
3089 rb_simple_write(struct file *filp, const char __user *ubuf,
3090 size_t cnt, loff_t *ppos)
3092 unsigned long *p = filp->private_data;
3097 if (cnt >= sizeof(buf))
3100 if (copy_from_user(&buf, ubuf, cnt))
3105 ret = strict_strtoul(buf, 10, &val);
3110 set_bit(RB_BUFFERS_ON_BIT, p);
3112 clear_bit(RB_BUFFERS_ON_BIT, p);
3119 static const struct file_operations rb_simple_fops = {
3120 .open = tracing_open_generic,
3121 .read = rb_simple_read,
3122 .write = rb_simple_write,
3126 static __init int rb_init_debugfs(void)
3128 struct dentry *d_tracer;
3130 d_tracer = tracing_init_dentry();
3132 trace_create_file("tracing_on", 0644, d_tracer,
3133 &ring_buffer_flags, &rb_simple_fops);
3138 fs_initcall(rb_init_debugfs);
3140 #ifdef CONFIG_HOTPLUG_CPU
3141 static int rb_cpu_notify(struct notifier_block *self,
3142 unsigned long action, void *hcpu)
3144 struct ring_buffer *buffer =
3145 container_of(self, struct ring_buffer, cpu_notify);
3146 long cpu = (long)hcpu;
3149 case CPU_UP_PREPARE:
3150 case CPU_UP_PREPARE_FROZEN:
3151 if (cpumask_test_cpu(cpu, buffer->cpumask))
3154 buffer->buffers[cpu] =
3155 rb_allocate_cpu_buffer(buffer, cpu);
3156 if (!buffer->buffers[cpu]) {
3157 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
3162 cpumask_set_cpu(cpu, buffer->cpumask);
3164 case CPU_DOWN_PREPARE:
3165 case CPU_DOWN_PREPARE_FROZEN:
3168 * If we were to free the buffer, then the user would
3169 * lose any trace that was in the buffer.