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
);
206 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
207 #define RB_ALIGNMENT 4U
208 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
209 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
211 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
212 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
215 RB_LEN_TIME_EXTEND
= 8,
216 RB_LEN_TIME_STAMP
= 16,
219 static inline int rb_null_event(struct ring_buffer_event
*event
)
221 return event
->type_len
== RINGBUF_TYPE_PADDING
222 && event
->time_delta
== 0;
225 static inline int rb_discarded_event(struct ring_buffer_event
*event
)
227 return event
->type_len
== RINGBUF_TYPE_PADDING
&& event
->time_delta
;
230 static void rb_event_set_padding(struct ring_buffer_event
*event
)
232 event
->type_len
= RINGBUF_TYPE_PADDING
;
233 event
->time_delta
= 0;
237 rb_event_data_length(struct ring_buffer_event
*event
)
242 length
= event
->type_len
* RB_ALIGNMENT
;
244 length
= event
->array
[0];
245 return length
+ RB_EVNT_HDR_SIZE
;
248 /* inline for ring buffer fast paths */
250 rb_event_length(struct ring_buffer_event
*event
)
252 switch (event
->type_len
) {
253 case RINGBUF_TYPE_PADDING
:
254 if (rb_null_event(event
))
257 return event
->array
[0] + RB_EVNT_HDR_SIZE
;
259 case RINGBUF_TYPE_TIME_EXTEND
:
260 return RB_LEN_TIME_EXTEND
;
262 case RINGBUF_TYPE_TIME_STAMP
:
263 return RB_LEN_TIME_STAMP
;
265 case RINGBUF_TYPE_DATA
:
266 return rb_event_data_length(event
);
275 * ring_buffer_event_length - return the length of the event
276 * @event: the event to get the length of
278 unsigned ring_buffer_event_length(struct ring_buffer_event
*event
)
280 unsigned length
= rb_event_length(event
);
281 if (event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
)
283 length
-= RB_EVNT_HDR_SIZE
;
284 if (length
> RB_MAX_SMALL_DATA
+ sizeof(event
->array
[0]))
285 length
-= sizeof(event
->array
[0]);
288 EXPORT_SYMBOL_GPL(ring_buffer_event_length
);
290 /* inline for ring buffer fast paths */
292 rb_event_data(struct ring_buffer_event
*event
)
294 BUG_ON(event
->type_len
> RINGBUF_TYPE_DATA_TYPE_LEN_MAX
);
295 /* If length is in len field, then array[0] has the data */
297 return (void *)&event
->array
[0];
298 /* Otherwise length is in array[0] and array[1] has the data */
299 return (void *)&event
->array
[1];
303 * ring_buffer_event_data - return the data of the event
304 * @event: the event to get the data from
306 void *ring_buffer_event_data(struct ring_buffer_event
*event
)
308 return rb_event_data(event
);
310 EXPORT_SYMBOL_GPL(ring_buffer_event_data
);
312 #define for_each_buffer_cpu(buffer, cpu) \
313 for_each_cpu(cpu, buffer->cpumask)
316 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
317 #define TS_DELTA_TEST (~TS_MASK)
319 struct buffer_data_page
{
320 u64 time_stamp
; /* page time stamp */
321 local_t commit
; /* write committed index */
322 unsigned char data
[]; /* data of buffer page */
326 struct list_head list
; /* list of buffer pages */
327 local_t write
; /* index for next write */
328 unsigned read
; /* index for next read */
329 local_t entries
; /* entries on this page */
330 struct buffer_data_page
*page
; /* Actual data page */
333 static void rb_init_page(struct buffer_data_page
*bpage
)
335 local_set(&bpage
->commit
, 0);
339 * ring_buffer_page_len - the size of data on the page.
340 * @page: The page to read
342 * Returns the amount of data on the page, including buffer page header.
344 size_t ring_buffer_page_len(void *page
)
346 return local_read(&((struct buffer_data_page
*)page
)->commit
)
351 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
354 static void free_buffer_page(struct buffer_page
*bpage
)
356 free_page((unsigned long)bpage
->page
);
361 * We need to fit the time_stamp delta into 27 bits.
363 static inline int test_time_stamp(u64 delta
)
365 if (delta
& TS_DELTA_TEST
)
370 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
372 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
373 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
375 /* Max number of timestamps that can fit on a page */
376 #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP)
378 int ring_buffer_print_page_header(struct trace_seq
*s
)
380 struct buffer_data_page field
;
383 ret
= trace_seq_printf(s
, "\tfield: u64 timestamp;\t"
384 "offset:0;\tsize:%u;\n",
385 (unsigned int)sizeof(field
.time_stamp
));
387 ret
= trace_seq_printf(s
, "\tfield: local_t commit;\t"
388 "offset:%u;\tsize:%u;\n",
389 (unsigned int)offsetof(typeof(field
), commit
),
390 (unsigned int)sizeof(field
.commit
));
392 ret
= trace_seq_printf(s
, "\tfield: char data;\t"
393 "offset:%u;\tsize:%u;\n",
394 (unsigned int)offsetof(typeof(field
), data
),
395 (unsigned int)BUF_PAGE_SIZE
);
401 * head_page == tail_page && head == tail then buffer is empty.
403 struct ring_buffer_per_cpu
{
405 struct ring_buffer
*buffer
;
406 spinlock_t reader_lock
; /* serialize readers */
408 struct lock_class_key lock_key
;
409 struct list_head pages
;
410 struct buffer_page
*head_page
; /* read from head */
411 struct buffer_page
*tail_page
; /* write to tail */
412 struct buffer_page
*commit_page
; /* committed pages */
413 struct buffer_page
*reader_page
;
414 unsigned long nmi_dropped
;
415 unsigned long commit_overrun
;
416 unsigned long overrun
;
423 atomic_t record_disabled
;
430 atomic_t record_disabled
;
431 cpumask_var_t cpumask
;
433 struct lock_class_key
*reader_lock_key
;
437 struct ring_buffer_per_cpu
**buffers
;
439 #ifdef CONFIG_HOTPLUG_CPU
440 struct notifier_block cpu_notify
;
445 struct ring_buffer_iter
{
446 struct ring_buffer_per_cpu
*cpu_buffer
;
448 struct buffer_page
*head_page
;
452 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
453 #define RB_WARN_ON(buffer, cond) \
455 int _____ret = unlikely(cond); \
457 atomic_inc(&buffer->record_disabled); \
463 /* Up this if you want to test the TIME_EXTENTS and normalization */
464 #define DEBUG_SHIFT 0
466 static inline u64
rb_time_stamp(struct ring_buffer
*buffer
, int cpu
)
468 /* shift to debug/test normalization and TIME_EXTENTS */
469 return buffer
->clock() << DEBUG_SHIFT
;
472 u64
ring_buffer_time_stamp(struct ring_buffer
*buffer
, int cpu
)
476 preempt_disable_notrace();
477 time
= rb_time_stamp(buffer
, cpu
);
478 preempt_enable_no_resched_notrace();
482 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp
);
484 void ring_buffer_normalize_time_stamp(struct ring_buffer
*buffer
,
487 /* Just stupid testing the normalize function and deltas */
490 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp
);
493 * check_pages - integrity check of buffer pages
494 * @cpu_buffer: CPU buffer with pages to test
496 * As a safety measure we check to make sure the data pages have not
499 static int rb_check_pages(struct ring_buffer_per_cpu
*cpu_buffer
)
501 struct list_head
*head
= &cpu_buffer
->pages
;
502 struct buffer_page
*bpage
, *tmp
;
504 if (RB_WARN_ON(cpu_buffer
, head
->next
->prev
!= head
))
506 if (RB_WARN_ON(cpu_buffer
, head
->prev
->next
!= head
))
509 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
510 if (RB_WARN_ON(cpu_buffer
,
511 bpage
->list
.next
->prev
!= &bpage
->list
))
513 if (RB_WARN_ON(cpu_buffer
,
514 bpage
->list
.prev
->next
!= &bpage
->list
))
521 static int rb_allocate_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
524 struct list_head
*head
= &cpu_buffer
->pages
;
525 struct buffer_page
*bpage
, *tmp
;
530 for (i
= 0; i
< nr_pages
; i
++) {
531 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
532 GFP_KERNEL
, cpu_to_node(cpu_buffer
->cpu
));
535 list_add(&bpage
->list
, &pages
);
537 addr
= __get_free_page(GFP_KERNEL
);
540 bpage
->page
= (void *)addr
;
541 rb_init_page(bpage
->page
);
544 list_splice(&pages
, head
);
546 rb_check_pages(cpu_buffer
);
551 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
552 list_del_init(&bpage
->list
);
553 free_buffer_page(bpage
);
558 static struct ring_buffer_per_cpu
*
559 rb_allocate_cpu_buffer(struct ring_buffer
*buffer
, int cpu
)
561 struct ring_buffer_per_cpu
*cpu_buffer
;
562 struct buffer_page
*bpage
;
566 cpu_buffer
= kzalloc_node(ALIGN(sizeof(*cpu_buffer
), cache_line_size()),
567 GFP_KERNEL
, cpu_to_node(cpu
));
571 cpu_buffer
->cpu
= cpu
;
572 cpu_buffer
->buffer
= buffer
;
573 spin_lock_init(&cpu_buffer
->reader_lock
);
574 lockdep_set_class(&cpu_buffer
->reader_lock
, buffer
->reader_lock_key
);
575 cpu_buffer
->lock
= (raw_spinlock_t
)__RAW_SPIN_LOCK_UNLOCKED
;
576 INIT_LIST_HEAD(&cpu_buffer
->pages
);
578 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
), cache_line_size()),
579 GFP_KERNEL
, cpu_to_node(cpu
));
581 goto fail_free_buffer
;
583 cpu_buffer
->reader_page
= bpage
;
584 addr
= __get_free_page(GFP_KERNEL
);
586 goto fail_free_reader
;
587 bpage
->page
= (void *)addr
;
588 rb_init_page(bpage
->page
);
590 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
592 ret
= rb_allocate_pages(cpu_buffer
, buffer
->pages
);
594 goto fail_free_reader
;
596 cpu_buffer
->head_page
597 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
598 cpu_buffer
->tail_page
= cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
603 free_buffer_page(cpu_buffer
->reader_page
);
610 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu
*cpu_buffer
)
612 struct list_head
*head
= &cpu_buffer
->pages
;
613 struct buffer_page
*bpage
, *tmp
;
615 free_buffer_page(cpu_buffer
->reader_page
);
617 list_for_each_entry_safe(bpage
, tmp
, head
, list
) {
618 list_del_init(&bpage
->list
);
619 free_buffer_page(bpage
);
624 #ifdef CONFIG_HOTPLUG_CPU
625 static int rb_cpu_notify(struct notifier_block
*self
,
626 unsigned long action
, void *hcpu
);
630 * ring_buffer_alloc - allocate a new ring_buffer
631 * @size: the size in bytes per cpu that is needed.
632 * @flags: attributes to set for the ring buffer.
634 * Currently the only flag that is available is the RB_FL_OVERWRITE
635 * flag. This flag means that the buffer will overwrite old data
636 * when the buffer wraps. If this flag is not set, the buffer will
637 * drop data when the tail hits the head.
639 struct ring_buffer
*__ring_buffer_alloc(unsigned long size
, unsigned flags
,
640 struct lock_class_key
*key
)
642 struct ring_buffer
*buffer
;
646 /* keep it in its own cache line */
647 buffer
= kzalloc(ALIGN(sizeof(*buffer
), cache_line_size()),
652 if (!alloc_cpumask_var(&buffer
->cpumask
, GFP_KERNEL
))
653 goto fail_free_buffer
;
655 buffer
->pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
656 buffer
->flags
= flags
;
657 buffer
->clock
= trace_clock_local
;
658 buffer
->reader_lock_key
= key
;
660 /* need at least two pages */
661 if (buffer
->pages
< 2)
665 * In case of non-hotplug cpu, if the ring-buffer is allocated
666 * in early initcall, it will not be notified of secondary cpus.
667 * In that off case, we need to allocate for all possible cpus.
669 #ifdef CONFIG_HOTPLUG_CPU
671 cpumask_copy(buffer
->cpumask
, cpu_online_mask
);
673 cpumask_copy(buffer
->cpumask
, cpu_possible_mask
);
675 buffer
->cpus
= nr_cpu_ids
;
677 bsize
= sizeof(void *) * nr_cpu_ids
;
678 buffer
->buffers
= kzalloc(ALIGN(bsize
, cache_line_size()),
680 if (!buffer
->buffers
)
681 goto fail_free_cpumask
;
683 for_each_buffer_cpu(buffer
, cpu
) {
684 buffer
->buffers
[cpu
] =
685 rb_allocate_cpu_buffer(buffer
, cpu
);
686 if (!buffer
->buffers
[cpu
])
687 goto fail_free_buffers
;
690 #ifdef CONFIG_HOTPLUG_CPU
691 buffer
->cpu_notify
.notifier_call
= rb_cpu_notify
;
692 buffer
->cpu_notify
.priority
= 0;
693 register_cpu_notifier(&buffer
->cpu_notify
);
697 mutex_init(&buffer
->mutex
);
702 for_each_buffer_cpu(buffer
, cpu
) {
703 if (buffer
->buffers
[cpu
])
704 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
706 kfree(buffer
->buffers
);
709 free_cpumask_var(buffer
->cpumask
);
716 EXPORT_SYMBOL_GPL(__ring_buffer_alloc
);
719 * ring_buffer_free - free a ring buffer.
720 * @buffer: the buffer to free.
723 ring_buffer_free(struct ring_buffer
*buffer
)
729 #ifdef CONFIG_HOTPLUG_CPU
730 unregister_cpu_notifier(&buffer
->cpu_notify
);
733 for_each_buffer_cpu(buffer
, cpu
)
734 rb_free_cpu_buffer(buffer
->buffers
[cpu
]);
738 free_cpumask_var(buffer
->cpumask
);
742 EXPORT_SYMBOL_GPL(ring_buffer_free
);
744 void ring_buffer_set_clock(struct ring_buffer
*buffer
,
747 buffer
->clock
= clock
;
750 static void rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
);
753 rb_remove_pages(struct ring_buffer_per_cpu
*cpu_buffer
, unsigned nr_pages
)
755 struct buffer_page
*bpage
;
759 atomic_inc(&cpu_buffer
->record_disabled
);
762 for (i
= 0; i
< nr_pages
; i
++) {
763 if (RB_WARN_ON(cpu_buffer
, list_empty(&cpu_buffer
->pages
)))
765 p
= cpu_buffer
->pages
.next
;
766 bpage
= list_entry(p
, struct buffer_page
, list
);
767 list_del_init(&bpage
->list
);
768 free_buffer_page(bpage
);
770 if (RB_WARN_ON(cpu_buffer
, list_empty(&cpu_buffer
->pages
)))
773 rb_reset_cpu(cpu_buffer
);
775 rb_check_pages(cpu_buffer
);
777 atomic_dec(&cpu_buffer
->record_disabled
);
782 rb_insert_pages(struct ring_buffer_per_cpu
*cpu_buffer
,
783 struct list_head
*pages
, unsigned nr_pages
)
785 struct buffer_page
*bpage
;
789 atomic_inc(&cpu_buffer
->record_disabled
);
792 for (i
= 0; i
< nr_pages
; i
++) {
793 if (RB_WARN_ON(cpu_buffer
, list_empty(pages
)))
796 bpage
= list_entry(p
, struct buffer_page
, list
);
797 list_del_init(&bpage
->list
);
798 list_add_tail(&bpage
->list
, &cpu_buffer
->pages
);
800 rb_reset_cpu(cpu_buffer
);
802 rb_check_pages(cpu_buffer
);
804 atomic_dec(&cpu_buffer
->record_disabled
);
808 * ring_buffer_resize - resize the ring buffer
809 * @buffer: the buffer to resize.
810 * @size: the new size.
812 * The tracer is responsible for making sure that the buffer is
813 * not being used while changing the size.
814 * Note: We may be able to change the above requirement by using
815 * RCU synchronizations.
817 * Minimum size is 2 * BUF_PAGE_SIZE.
819 * Returns -1 on failure.
821 int ring_buffer_resize(struct ring_buffer
*buffer
, unsigned long size
)
823 struct ring_buffer_per_cpu
*cpu_buffer
;
824 unsigned nr_pages
, rm_pages
, new_pages
;
825 struct buffer_page
*bpage
, *tmp
;
826 unsigned long buffer_size
;
832 * Always succeed at resizing a non-existent buffer:
837 size
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
838 size
*= BUF_PAGE_SIZE
;
839 buffer_size
= buffer
->pages
* BUF_PAGE_SIZE
;
841 /* we need a minimum of two pages */
842 if (size
< BUF_PAGE_SIZE
* 2)
843 size
= BUF_PAGE_SIZE
* 2;
845 if (size
== buffer_size
)
848 mutex_lock(&buffer
->mutex
);
851 nr_pages
= DIV_ROUND_UP(size
, BUF_PAGE_SIZE
);
853 if (size
< buffer_size
) {
855 /* easy case, just free pages */
856 if (RB_WARN_ON(buffer
, nr_pages
>= buffer
->pages
))
859 rm_pages
= buffer
->pages
- nr_pages
;
861 for_each_buffer_cpu(buffer
, cpu
) {
862 cpu_buffer
= buffer
->buffers
[cpu
];
863 rb_remove_pages(cpu_buffer
, rm_pages
);
869 * This is a bit more difficult. We only want to add pages
870 * when we can allocate enough for all CPUs. We do this
871 * by allocating all the pages and storing them on a local
872 * link list. If we succeed in our allocation, then we
873 * add these pages to the cpu_buffers. Otherwise we just free
874 * them all and return -ENOMEM;
876 if (RB_WARN_ON(buffer
, nr_pages
<= buffer
->pages
))
879 new_pages
= nr_pages
- buffer
->pages
;
881 for_each_buffer_cpu(buffer
, cpu
) {
882 for (i
= 0; i
< new_pages
; i
++) {
883 bpage
= kzalloc_node(ALIGN(sizeof(*bpage
),
885 GFP_KERNEL
, cpu_to_node(cpu
));
888 list_add(&bpage
->list
, &pages
);
889 addr
= __get_free_page(GFP_KERNEL
);
892 bpage
->page
= (void *)addr
;
893 rb_init_page(bpage
->page
);
897 for_each_buffer_cpu(buffer
, cpu
) {
898 cpu_buffer
= buffer
->buffers
[cpu
];
899 rb_insert_pages(cpu_buffer
, &pages
, new_pages
);
902 if (RB_WARN_ON(buffer
, !list_empty(&pages
)))
906 buffer
->pages
= nr_pages
;
908 mutex_unlock(&buffer
->mutex
);
913 list_for_each_entry_safe(bpage
, tmp
, &pages
, list
) {
914 list_del_init(&bpage
->list
);
915 free_buffer_page(bpage
);
918 mutex_unlock(&buffer
->mutex
);
922 * Something went totally wrong, and we are too paranoid
923 * to even clean up the mess.
927 mutex_unlock(&buffer
->mutex
);
930 EXPORT_SYMBOL_GPL(ring_buffer_resize
);
933 __rb_data_page_index(struct buffer_data_page
*bpage
, unsigned index
)
935 return bpage
->data
+ index
;
938 static inline void *__rb_page_index(struct buffer_page
*bpage
, unsigned index
)
940 return bpage
->page
->data
+ index
;
943 static inline struct ring_buffer_event
*
944 rb_reader_event(struct ring_buffer_per_cpu
*cpu_buffer
)
946 return __rb_page_index(cpu_buffer
->reader_page
,
947 cpu_buffer
->reader_page
->read
);
950 static inline struct ring_buffer_event
*
951 rb_head_event(struct ring_buffer_per_cpu
*cpu_buffer
)
953 return __rb_page_index(cpu_buffer
->head_page
,
954 cpu_buffer
->head_page
->read
);
957 static inline struct ring_buffer_event
*
958 rb_iter_head_event(struct ring_buffer_iter
*iter
)
960 return __rb_page_index(iter
->head_page
, iter
->head
);
963 static inline unsigned rb_page_write(struct buffer_page
*bpage
)
965 return local_read(&bpage
->write
);
968 static inline unsigned rb_page_commit(struct buffer_page
*bpage
)
970 return local_read(&bpage
->page
->commit
);
973 /* Size is determined by what has been commited */
974 static inline unsigned rb_page_size(struct buffer_page
*bpage
)
976 return rb_page_commit(bpage
);
979 static inline unsigned
980 rb_commit_index(struct ring_buffer_per_cpu
*cpu_buffer
)
982 return rb_page_commit(cpu_buffer
->commit_page
);
985 static inline unsigned rb_head_size(struct ring_buffer_per_cpu
*cpu_buffer
)
987 return rb_page_commit(cpu_buffer
->head_page
);
990 static inline void rb_inc_page(struct ring_buffer_per_cpu
*cpu_buffer
,
991 struct buffer_page
**bpage
)
993 struct list_head
*p
= (*bpage
)->list
.next
;
995 if (p
== &cpu_buffer
->pages
)
998 *bpage
= list_entry(p
, struct buffer_page
, list
);
1001 static inline unsigned
1002 rb_event_index(struct ring_buffer_event
*event
)
1004 unsigned long addr
= (unsigned long)event
;
1006 return (addr
& ~PAGE_MASK
) - BUF_PAGE_HDR_SIZE
;
1010 rb_event_is_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1011 struct ring_buffer_event
*event
)
1013 unsigned long addr
= (unsigned long)event
;
1014 unsigned long index
;
1016 index
= rb_event_index(event
);
1019 return cpu_buffer
->commit_page
->page
== (void *)addr
&&
1020 rb_commit_index(cpu_buffer
) == index
;
1024 rb_set_commit_to_write(struct ring_buffer_per_cpu
*cpu_buffer
)
1027 * We only race with interrupts and NMIs on this CPU.
1028 * If we own the commit event, then we can commit
1029 * all others that interrupted us, since the interruptions
1030 * are in stack format (they finish before they come
1031 * back to us). This allows us to do a simple loop to
1032 * assign the commit to the tail.
1035 while (cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
) {
1036 cpu_buffer
->commit_page
->page
->commit
=
1037 cpu_buffer
->commit_page
->write
;
1038 rb_inc_page(cpu_buffer
, &cpu_buffer
->commit_page
);
1039 cpu_buffer
->write_stamp
=
1040 cpu_buffer
->commit_page
->page
->time_stamp
;
1041 /* add barrier to keep gcc from optimizing too much */
1044 while (rb_commit_index(cpu_buffer
) !=
1045 rb_page_write(cpu_buffer
->commit_page
)) {
1046 cpu_buffer
->commit_page
->page
->commit
=
1047 cpu_buffer
->commit_page
->write
;
1051 /* again, keep gcc from optimizing */
1055 * If an interrupt came in just after the first while loop
1056 * and pushed the tail page forward, we will be left with
1057 * a dangling commit that will never go forward.
1059 if (unlikely(cpu_buffer
->commit_page
!= cpu_buffer
->tail_page
))
1063 static void rb_reset_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
1065 cpu_buffer
->read_stamp
= cpu_buffer
->reader_page
->page
->time_stamp
;
1066 cpu_buffer
->reader_page
->read
= 0;
1069 static void rb_inc_iter(struct ring_buffer_iter
*iter
)
1071 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
1074 * The iterator could be on the reader page (it starts there).
1075 * But the head could have moved, since the reader was
1076 * found. Check for this case and assign the iterator
1077 * to the head page instead of next.
1079 if (iter
->head_page
== cpu_buffer
->reader_page
)
1080 iter
->head_page
= cpu_buffer
->head_page
;
1082 rb_inc_page(cpu_buffer
, &iter
->head_page
);
1084 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
1089 * ring_buffer_update_event - update event type and data
1090 * @event: the even to update
1091 * @type: the type of event
1092 * @length: the size of the event field in the ring buffer
1094 * Update the type and data fields of the event. The length
1095 * is the actual size that is written to the ring buffer,
1096 * and with this, we can determine what to place into the
1100 rb_update_event(struct ring_buffer_event
*event
,
1101 unsigned type
, unsigned length
)
1103 event
->type_len
= type
;
1107 case RINGBUF_TYPE_PADDING
:
1108 case RINGBUF_TYPE_TIME_EXTEND
:
1109 case RINGBUF_TYPE_TIME_STAMP
:
1113 length
-= RB_EVNT_HDR_SIZE
;
1114 if (length
> RB_MAX_SMALL_DATA
)
1115 event
->array
[0] = length
;
1117 event
->type_len
= DIV_ROUND_UP(length
, RB_ALIGNMENT
);
1124 static unsigned rb_calculate_event_length(unsigned length
)
1126 struct ring_buffer_event event
; /* Used only for sizeof array */
1128 /* zero length can cause confusions */
1132 if (length
> RB_MAX_SMALL_DATA
)
1133 length
+= sizeof(event
.array
[0]);
1135 length
+= RB_EVNT_HDR_SIZE
;
1136 length
= ALIGN(length
, RB_ALIGNMENT
);
1142 rb_reset_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1143 struct buffer_page
*tail_page
,
1144 unsigned long tail
, unsigned long length
)
1146 struct ring_buffer_event
*event
;
1149 * Only the event that crossed the page boundary
1150 * must fill the old tail_page with padding.
1152 if (tail
>= BUF_PAGE_SIZE
) {
1153 local_sub(length
, &tail_page
->write
);
1157 event
= __rb_page_index(tail_page
, tail
);
1158 kmemcheck_annotate_bitfield(event
, bitfield
);
1161 * If this event is bigger than the minimum size, then
1162 * we need to be careful that we don't subtract the
1163 * write counter enough to allow another writer to slip
1165 * We put in a discarded commit instead, to make sure
1166 * that this space is not used again.
1168 * If we are less than the minimum size, we don't need to
1171 if (tail
> (BUF_PAGE_SIZE
- RB_EVNT_MIN_SIZE
)) {
1172 /* No room for any events */
1174 /* Mark the rest of the page with padding */
1175 rb_event_set_padding(event
);
1177 /* Set the write back to the previous setting */
1178 local_sub(length
, &tail_page
->write
);
1182 /* Put in a discarded event */
1183 event
->array
[0] = (BUF_PAGE_SIZE
- tail
) - RB_EVNT_HDR_SIZE
;
1184 event
->type_len
= RINGBUF_TYPE_PADDING
;
1185 /* time delta must be non zero */
1186 event
->time_delta
= 1;
1187 /* Account for this as an entry */
1188 local_inc(&tail_page
->entries
);
1189 local_inc(&cpu_buffer
->entries
);
1191 /* Set write to end of buffer */
1192 length
= (tail
+ length
) - BUF_PAGE_SIZE
;
1193 local_sub(length
, &tail_page
->write
);
1196 static struct ring_buffer_event
*
1197 rb_move_tail(struct ring_buffer_per_cpu
*cpu_buffer
,
1198 unsigned long length
, unsigned long tail
,
1199 struct buffer_page
*commit_page
,
1200 struct buffer_page
*tail_page
, u64
*ts
)
1202 struct buffer_page
*next_page
, *head_page
, *reader_page
;
1203 struct ring_buffer
*buffer
= cpu_buffer
->buffer
;
1204 bool lock_taken
= false;
1205 unsigned long flags
;
1207 next_page
= tail_page
;
1209 local_irq_save(flags
);
1211 * Since the write to the buffer is still not
1212 * fully lockless, we must be careful with NMIs.
1213 * The locks in the writers are taken when a write
1214 * crosses to a new page. The locks protect against
1215 * races with the readers (this will soon be fixed
1216 * with a lockless solution).
1218 * Because we can not protect against NMIs, and we
1219 * want to keep traces reentrant, we need to manage
1220 * what happens when we are in an NMI.
1222 * NMIs can happen after we take the lock.
1223 * If we are in an NMI, only take the lock
1224 * if it is not already taken. Otherwise
1227 if (unlikely(in_nmi())) {
1228 if (!__raw_spin_trylock(&cpu_buffer
->lock
)) {
1229 cpu_buffer
->nmi_dropped
++;
1233 __raw_spin_lock(&cpu_buffer
->lock
);
1237 rb_inc_page(cpu_buffer
, &next_page
);
1239 head_page
= cpu_buffer
->head_page
;
1240 reader_page
= cpu_buffer
->reader_page
;
1242 /* we grabbed the lock before incrementing */
1243 if (RB_WARN_ON(cpu_buffer
, next_page
== reader_page
))
1247 * If for some reason, we had an interrupt storm that made
1248 * it all the way around the buffer, bail, and warn
1251 if (unlikely(next_page
== commit_page
)) {
1252 cpu_buffer
->commit_overrun
++;
1256 if (next_page
== head_page
) {
1257 if (!(buffer
->flags
& RB_FL_OVERWRITE
))
1260 /* tail_page has not moved yet? */
1261 if (tail_page
== cpu_buffer
->tail_page
) {
1262 /* count overflows */
1263 cpu_buffer
->overrun
+=
1264 local_read(&head_page
->entries
);
1266 rb_inc_page(cpu_buffer
, &head_page
);
1267 cpu_buffer
->head_page
= head_page
;
1268 cpu_buffer
->head_page
->read
= 0;
1273 * If the tail page is still the same as what we think
1274 * it is, then it is up to us to update the tail
1277 if (tail_page
== cpu_buffer
->tail_page
) {
1278 local_set(&next_page
->write
, 0);
1279 local_set(&next_page
->entries
, 0);
1280 local_set(&next_page
->page
->commit
, 0);
1281 cpu_buffer
->tail_page
= next_page
;
1283 /* reread the time stamp */
1284 *ts
= rb_time_stamp(buffer
, cpu_buffer
->cpu
);
1285 cpu_buffer
->tail_page
->page
->time_stamp
= *ts
;
1288 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1290 __raw_spin_unlock(&cpu_buffer
->lock
);
1291 local_irq_restore(flags
);
1293 /* fail and let the caller try again */
1294 return ERR_PTR(-EAGAIN
);
1298 rb_reset_tail(cpu_buffer
, tail_page
, tail
, length
);
1300 if (likely(lock_taken
))
1301 __raw_spin_unlock(&cpu_buffer
->lock
);
1302 local_irq_restore(flags
);
1306 static struct ring_buffer_event
*
1307 __rb_reserve_next(struct ring_buffer_per_cpu
*cpu_buffer
,
1308 unsigned type
, unsigned long length
, u64
*ts
)
1310 struct buffer_page
*tail_page
, *commit_page
;
1311 struct ring_buffer_event
*event
;
1312 unsigned long tail
, write
;
1314 commit_page
= cpu_buffer
->commit_page
;
1315 /* we just need to protect against interrupts */
1317 tail_page
= cpu_buffer
->tail_page
;
1318 write
= local_add_return(length
, &tail_page
->write
);
1319 tail
= write
- length
;
1321 /* See if we shot pass the end of this buffer page */
1322 if (write
> BUF_PAGE_SIZE
)
1323 return rb_move_tail(cpu_buffer
, length
, tail
,
1324 commit_page
, tail_page
, ts
);
1326 /* We reserved something on the buffer */
1328 event
= __rb_page_index(tail_page
, tail
);
1329 kmemcheck_annotate_bitfield(event
, bitfield
);
1330 rb_update_event(event
, type
, length
);
1332 /* The passed in type is zero for DATA */
1334 local_inc(&tail_page
->entries
);
1337 * If this is the first commit on the page, then update
1341 tail_page
->page
->time_stamp
= *ts
;
1347 rb_try_to_discard(struct ring_buffer_per_cpu
*cpu_buffer
,
1348 struct ring_buffer_event
*event
)
1350 unsigned long new_index
, old_index
;
1351 struct buffer_page
*bpage
;
1352 unsigned long index
;
1355 new_index
= rb_event_index(event
);
1356 old_index
= new_index
+ rb_event_length(event
);
1357 addr
= (unsigned long)event
;
1360 bpage
= cpu_buffer
->tail_page
;
1362 if (bpage
->page
== (void *)addr
&& rb_page_write(bpage
) == old_index
) {
1364 * This is on the tail page. It is possible that
1365 * a write could come in and move the tail page
1366 * and write to the next page. That is fine
1367 * because we just shorten what is on this page.
1369 index
= local_cmpxchg(&bpage
->write
, old_index
, new_index
);
1370 if (index
== old_index
)
1374 /* could not discard */
1379 rb_add_time_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
1380 u64
*ts
, u64
*delta
)
1382 struct ring_buffer_event
*event
;
1386 if (unlikely(*delta
> (1ULL << 59) && !once
++)) {
1387 printk(KERN_WARNING
"Delta way too big! %llu"
1388 " ts=%llu write stamp = %llu\n",
1389 (unsigned long long)*delta
,
1390 (unsigned long long)*ts
,
1391 (unsigned long long)cpu_buffer
->write_stamp
);
1396 * The delta is too big, we to add a
1399 event
= __rb_reserve_next(cpu_buffer
,
1400 RINGBUF_TYPE_TIME_EXTEND
,
1406 if (PTR_ERR(event
) == -EAGAIN
)
1409 /* Only a commited time event can update the write stamp */
1410 if (rb_event_is_commit(cpu_buffer
, event
)) {
1412 * If this is the first on the page, then it was
1413 * updated with the page itself. Try to discard it
1414 * and if we can't just make it zero.
1416 if (rb_event_index(event
)) {
1417 event
->time_delta
= *delta
& TS_MASK
;
1418 event
->array
[0] = *delta
>> TS_SHIFT
;
1420 /* try to discard, since we do not need this */
1421 if (!rb_try_to_discard(cpu_buffer
, event
)) {
1422 /* nope, just zero it */
1423 event
->time_delta
= 0;
1424 event
->array
[0] = 0;
1427 cpu_buffer
->write_stamp
= *ts
;
1428 /* let the caller know this was the commit */
1431 /* Try to discard the event */
1432 if (!rb_try_to_discard(cpu_buffer
, event
)) {
1433 /* Darn, this is just wasted space */
1434 event
->time_delta
= 0;
1435 event
->array
[0] = 0;
1445 static void rb_start_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
1447 local_inc(&cpu_buffer
->committing
);
1448 local_inc(&cpu_buffer
->commits
);
1451 static void rb_end_commit(struct ring_buffer_per_cpu
*cpu_buffer
)
1453 unsigned long commits
;
1455 if (RB_WARN_ON(cpu_buffer
,
1456 !local_read(&cpu_buffer
->committing
)))
1460 commits
= local_read(&cpu_buffer
->commits
);
1461 /* synchronize with interrupts */
1463 if (local_read(&cpu_buffer
->committing
) == 1)
1464 rb_set_commit_to_write(cpu_buffer
);
1466 local_dec(&cpu_buffer
->committing
);
1468 /* synchronize with interrupts */
1472 * Need to account for interrupts coming in between the
1473 * updating of the commit page and the clearing of the
1474 * committing counter.
1476 if (unlikely(local_read(&cpu_buffer
->commits
) != commits
) &&
1477 !local_read(&cpu_buffer
->committing
)) {
1478 local_inc(&cpu_buffer
->committing
);
1483 static struct ring_buffer_event
*
1484 rb_reserve_next_event(struct ring_buffer_per_cpu
*cpu_buffer
,
1485 unsigned long length
)
1487 struct ring_buffer_event
*event
;
1492 rb_start_commit(cpu_buffer
);
1494 length
= rb_calculate_event_length(length
);
1497 * We allow for interrupts to reenter here and do a trace.
1498 * If one does, it will cause this original code to loop
1499 * back here. Even with heavy interrupts happening, this
1500 * should only happen a few times in a row. If this happens
1501 * 1000 times in a row, there must be either an interrupt
1502 * storm or we have something buggy.
1505 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 1000))
1508 ts
= rb_time_stamp(cpu_buffer
->buffer
, cpu_buffer
->cpu
);
1511 * Only the first commit can update the timestamp.
1512 * Yes there is a race here. If an interrupt comes in
1513 * just after the conditional and it traces too, then it
1514 * will also check the deltas. More than one timestamp may
1515 * also be made. But only the entry that did the actual
1516 * commit will be something other than zero.
1518 if (likely(cpu_buffer
->tail_page
== cpu_buffer
->commit_page
&&
1519 rb_page_write(cpu_buffer
->tail_page
) ==
1520 rb_commit_index(cpu_buffer
))) {
1523 diff
= ts
- cpu_buffer
->write_stamp
;
1525 /* make sure this diff is calculated here */
1528 /* Did the write stamp get updated already? */
1529 if (unlikely(ts
< cpu_buffer
->write_stamp
))
1533 if (unlikely(test_time_stamp(delta
))) {
1535 commit
= rb_add_time_stamp(cpu_buffer
, &ts
, &delta
);
1536 if (commit
== -EBUSY
)
1539 if (commit
== -EAGAIN
)
1542 RB_WARN_ON(cpu_buffer
, commit
< 0);
1547 event
= __rb_reserve_next(cpu_buffer
, 0, length
, &ts
);
1548 if (unlikely(PTR_ERR(event
) == -EAGAIN
))
1554 if (!rb_event_is_commit(cpu_buffer
, event
))
1557 event
->time_delta
= delta
;
1562 rb_end_commit(cpu_buffer
);
1566 #define TRACE_RECURSIVE_DEPTH 16
1568 static int trace_recursive_lock(void)
1570 current
->trace_recursion
++;
1572 if (likely(current
->trace_recursion
< TRACE_RECURSIVE_DEPTH
))
1575 /* Disable all tracing before we do anything else */
1576 tracing_off_permanent();
1578 printk_once(KERN_WARNING
"Tracing recursion: depth[%ld]:"
1579 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
1580 current
->trace_recursion
,
1581 hardirq_count() >> HARDIRQ_SHIFT
,
1582 softirq_count() >> SOFTIRQ_SHIFT
,
1589 static void trace_recursive_unlock(void)
1591 WARN_ON_ONCE(!current
->trace_recursion
);
1593 current
->trace_recursion
--;
1596 static DEFINE_PER_CPU(int, rb_need_resched
);
1599 * ring_buffer_lock_reserve - reserve a part of the buffer
1600 * @buffer: the ring buffer to reserve from
1601 * @length: the length of the data to reserve (excluding event header)
1603 * Returns a reseverd event on the ring buffer to copy directly to.
1604 * The user of this interface will need to get the body to write into
1605 * and can use the ring_buffer_event_data() interface.
1607 * The length is the length of the data needed, not the event length
1608 * which also includes the event header.
1610 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1611 * If NULL is returned, then nothing has been allocated or locked.
1613 struct ring_buffer_event
*
1614 ring_buffer_lock_reserve(struct ring_buffer
*buffer
, unsigned long length
)
1616 struct ring_buffer_per_cpu
*cpu_buffer
;
1617 struct ring_buffer_event
*event
;
1620 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
1623 if (atomic_read(&buffer
->record_disabled
))
1626 /* If we are tracing schedule, we don't want to recurse */
1627 resched
= ftrace_preempt_disable();
1629 if (trace_recursive_lock())
1632 cpu
= raw_smp_processor_id();
1634 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
1637 cpu_buffer
= buffer
->buffers
[cpu
];
1639 if (atomic_read(&cpu_buffer
->record_disabled
))
1642 if (length
> BUF_MAX_DATA_SIZE
)
1645 event
= rb_reserve_next_event(cpu_buffer
, length
);
1650 * Need to store resched state on this cpu.
1651 * Only the first needs to.
1654 if (preempt_count() == 1)
1655 per_cpu(rb_need_resched
, cpu
) = resched
;
1660 trace_recursive_unlock();
1663 ftrace_preempt_enable(resched
);
1666 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve
);
1668 static void rb_commit(struct ring_buffer_per_cpu
*cpu_buffer
,
1669 struct ring_buffer_event
*event
)
1671 local_inc(&cpu_buffer
->entries
);
1674 * The event first in the commit queue updates the
1677 if (rb_event_is_commit(cpu_buffer
, event
))
1678 cpu_buffer
->write_stamp
+= event
->time_delta
;
1680 rb_end_commit(cpu_buffer
);
1684 * ring_buffer_unlock_commit - commit a reserved
1685 * @buffer: The buffer to commit to
1686 * @event: The event pointer to commit.
1688 * This commits the data to the ring buffer, and releases any locks held.
1690 * Must be paired with ring_buffer_lock_reserve.
1692 int ring_buffer_unlock_commit(struct ring_buffer
*buffer
,
1693 struct ring_buffer_event
*event
)
1695 struct ring_buffer_per_cpu
*cpu_buffer
;
1696 int cpu
= raw_smp_processor_id();
1698 cpu_buffer
= buffer
->buffers
[cpu
];
1700 rb_commit(cpu_buffer
, event
);
1702 trace_recursive_unlock();
1705 * Only the last preempt count needs to restore preemption.
1707 if (preempt_count() == 1)
1708 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
1710 preempt_enable_no_resched_notrace();
1714 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit
);
1716 static inline void rb_event_discard(struct ring_buffer_event
*event
)
1718 /* array[0] holds the actual length for the discarded event */
1719 event
->array
[0] = rb_event_data_length(event
) - RB_EVNT_HDR_SIZE
;
1720 event
->type_len
= RINGBUF_TYPE_PADDING
;
1721 /* time delta must be non zero */
1722 if (!event
->time_delta
)
1723 event
->time_delta
= 1;
1727 * ring_buffer_event_discard - discard any event in the ring buffer
1728 * @event: the event to discard
1730 * Sometimes a event that is in the ring buffer needs to be ignored.
1731 * This function lets the user discard an event in the ring buffer
1732 * and then that event will not be read later.
1734 * Note, it is up to the user to be careful with this, and protect
1735 * against races. If the user discards an event that has been consumed
1736 * it is possible that it could corrupt the ring buffer.
1738 void ring_buffer_event_discard(struct ring_buffer_event
*event
)
1740 rb_event_discard(event
);
1742 EXPORT_SYMBOL_GPL(ring_buffer_event_discard
);
1745 * ring_buffer_commit_discard - discard an event that has not been committed
1746 * @buffer: the ring buffer
1747 * @event: non committed event to discard
1749 * This is similar to ring_buffer_event_discard but must only be
1750 * performed on an event that has not been committed yet. The difference
1751 * is that this will also try to free the event from the ring buffer
1752 * if another event has not been added behind it.
1754 * If another event has been added behind it, it will set the event
1755 * up as discarded, and perform the commit.
1757 * If this function is called, do not call ring_buffer_unlock_commit on
1760 void ring_buffer_discard_commit(struct ring_buffer
*buffer
,
1761 struct ring_buffer_event
*event
)
1763 struct ring_buffer_per_cpu
*cpu_buffer
;
1766 /* The event is discarded regardless */
1767 rb_event_discard(event
);
1769 cpu
= smp_processor_id();
1770 cpu_buffer
= buffer
->buffers
[cpu
];
1773 * This must only be called if the event has not been
1774 * committed yet. Thus we can assume that preemption
1775 * is still disabled.
1777 RB_WARN_ON(buffer
, !local_read(&cpu_buffer
->committing
));
1779 if (!rb_try_to_discard(cpu_buffer
, event
))
1783 * The commit is still visible by the reader, so we
1784 * must increment entries.
1786 local_inc(&cpu_buffer
->entries
);
1788 rb_end_commit(cpu_buffer
);
1790 trace_recursive_unlock();
1793 * Only the last preempt count needs to restore preemption.
1795 if (preempt_count() == 1)
1796 ftrace_preempt_enable(per_cpu(rb_need_resched
, cpu
));
1798 preempt_enable_no_resched_notrace();
1801 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit
);
1804 * ring_buffer_write - write data to the buffer without reserving
1805 * @buffer: The ring buffer to write to.
1806 * @length: The length of the data being written (excluding the event header)
1807 * @data: The data to write to the buffer.
1809 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1810 * one function. If you already have the data to write to the buffer, it
1811 * may be easier to simply call this function.
1813 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1814 * and not the length of the event which would hold the header.
1816 int ring_buffer_write(struct ring_buffer
*buffer
,
1817 unsigned long length
,
1820 struct ring_buffer_per_cpu
*cpu_buffer
;
1821 struct ring_buffer_event
*event
;
1826 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
1829 if (atomic_read(&buffer
->record_disabled
))
1832 resched
= ftrace_preempt_disable();
1834 cpu
= raw_smp_processor_id();
1836 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
1839 cpu_buffer
= buffer
->buffers
[cpu
];
1841 if (atomic_read(&cpu_buffer
->record_disabled
))
1844 if (length
> BUF_MAX_DATA_SIZE
)
1847 event
= rb_reserve_next_event(cpu_buffer
, length
);
1851 body
= rb_event_data(event
);
1853 memcpy(body
, data
, length
);
1855 rb_commit(cpu_buffer
, event
);
1859 ftrace_preempt_enable(resched
);
1863 EXPORT_SYMBOL_GPL(ring_buffer_write
);
1865 static int rb_per_cpu_empty(struct ring_buffer_per_cpu
*cpu_buffer
)
1867 struct buffer_page
*reader
= cpu_buffer
->reader_page
;
1868 struct buffer_page
*head
= cpu_buffer
->head_page
;
1869 struct buffer_page
*commit
= cpu_buffer
->commit_page
;
1871 return reader
->read
== rb_page_commit(reader
) &&
1872 (commit
== reader
||
1874 head
->read
== rb_page_commit(commit
)));
1878 * ring_buffer_record_disable - stop all writes into the buffer
1879 * @buffer: The ring buffer to stop writes to.
1881 * This prevents all writes to the buffer. Any attempt to write
1882 * to the buffer after this will fail and return NULL.
1884 * The caller should call synchronize_sched() after this.
1886 void ring_buffer_record_disable(struct ring_buffer
*buffer
)
1888 atomic_inc(&buffer
->record_disabled
);
1890 EXPORT_SYMBOL_GPL(ring_buffer_record_disable
);
1893 * ring_buffer_record_enable - enable writes to the buffer
1894 * @buffer: The ring buffer to enable writes
1896 * Note, multiple disables will need the same number of enables
1897 * to truely enable the writing (much like preempt_disable).
1899 void ring_buffer_record_enable(struct ring_buffer
*buffer
)
1901 atomic_dec(&buffer
->record_disabled
);
1903 EXPORT_SYMBOL_GPL(ring_buffer_record_enable
);
1906 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1907 * @buffer: The ring buffer to stop writes to.
1908 * @cpu: The CPU buffer to stop
1910 * This prevents all writes to the buffer. Any attempt to write
1911 * to the buffer after this will fail and return NULL.
1913 * The caller should call synchronize_sched() after this.
1915 void ring_buffer_record_disable_cpu(struct ring_buffer
*buffer
, int cpu
)
1917 struct ring_buffer_per_cpu
*cpu_buffer
;
1919 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
1922 cpu_buffer
= buffer
->buffers
[cpu
];
1923 atomic_inc(&cpu_buffer
->record_disabled
);
1925 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu
);
1928 * ring_buffer_record_enable_cpu - enable writes to the buffer
1929 * @buffer: The ring buffer to enable writes
1930 * @cpu: The CPU to enable.
1932 * Note, multiple disables will need the same number of enables
1933 * to truely enable the writing (much like preempt_disable).
1935 void ring_buffer_record_enable_cpu(struct ring_buffer
*buffer
, int cpu
)
1937 struct ring_buffer_per_cpu
*cpu_buffer
;
1939 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
1942 cpu_buffer
= buffer
->buffers
[cpu
];
1943 atomic_dec(&cpu_buffer
->record_disabled
);
1945 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu
);
1948 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1949 * @buffer: The ring buffer
1950 * @cpu: The per CPU buffer to get the entries from.
1952 unsigned long ring_buffer_entries_cpu(struct ring_buffer
*buffer
, int cpu
)
1954 struct ring_buffer_per_cpu
*cpu_buffer
;
1957 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
1960 cpu_buffer
= buffer
->buffers
[cpu
];
1961 ret
= (local_read(&cpu_buffer
->entries
) - cpu_buffer
->overrun
)
1966 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu
);
1969 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1970 * @buffer: The ring buffer
1971 * @cpu: The per CPU buffer to get the number of overruns from
1973 unsigned long ring_buffer_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
1975 struct ring_buffer_per_cpu
*cpu_buffer
;
1978 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
1981 cpu_buffer
= buffer
->buffers
[cpu
];
1982 ret
= cpu_buffer
->overrun
;
1986 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu
);
1989 * ring_buffer_nmi_dropped_cpu - get the number of nmis that were dropped
1990 * @buffer: The ring buffer
1991 * @cpu: The per CPU buffer to get the number of overruns from
1993 unsigned long ring_buffer_nmi_dropped_cpu(struct ring_buffer
*buffer
, int cpu
)
1995 struct ring_buffer_per_cpu
*cpu_buffer
;
1998 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2001 cpu_buffer
= buffer
->buffers
[cpu
];
2002 ret
= cpu_buffer
->nmi_dropped
;
2006 EXPORT_SYMBOL_GPL(ring_buffer_nmi_dropped_cpu
);
2009 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2010 * @buffer: The ring buffer
2011 * @cpu: The per CPU buffer to get the number of overruns from
2014 ring_buffer_commit_overrun_cpu(struct ring_buffer
*buffer
, int cpu
)
2016 struct ring_buffer_per_cpu
*cpu_buffer
;
2019 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2022 cpu_buffer
= buffer
->buffers
[cpu
];
2023 ret
= cpu_buffer
->commit_overrun
;
2027 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu
);
2030 * ring_buffer_entries - get the number of entries in a buffer
2031 * @buffer: The ring buffer
2033 * Returns the total number of entries in the ring buffer
2036 unsigned long ring_buffer_entries(struct ring_buffer
*buffer
)
2038 struct ring_buffer_per_cpu
*cpu_buffer
;
2039 unsigned long entries
= 0;
2042 /* if you care about this being correct, lock the buffer */
2043 for_each_buffer_cpu(buffer
, cpu
) {
2044 cpu_buffer
= buffer
->buffers
[cpu
];
2045 entries
+= (local_read(&cpu_buffer
->entries
) -
2046 cpu_buffer
->overrun
) - cpu_buffer
->read
;
2051 EXPORT_SYMBOL_GPL(ring_buffer_entries
);
2054 * ring_buffer_overrun_cpu - get the number of overruns in buffer
2055 * @buffer: The ring buffer
2057 * Returns the total number of overruns in the ring buffer
2060 unsigned long ring_buffer_overruns(struct ring_buffer
*buffer
)
2062 struct ring_buffer_per_cpu
*cpu_buffer
;
2063 unsigned long overruns
= 0;
2066 /* if you care about this being correct, lock the buffer */
2067 for_each_buffer_cpu(buffer
, cpu
) {
2068 cpu_buffer
= buffer
->buffers
[cpu
];
2069 overruns
+= cpu_buffer
->overrun
;
2074 EXPORT_SYMBOL_GPL(ring_buffer_overruns
);
2076 static void rb_iter_reset(struct ring_buffer_iter
*iter
)
2078 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2080 /* Iterator usage is expected to have record disabled */
2081 if (list_empty(&cpu_buffer
->reader_page
->list
)) {
2082 iter
->head_page
= cpu_buffer
->head_page
;
2083 iter
->head
= cpu_buffer
->head_page
->read
;
2085 iter
->head_page
= cpu_buffer
->reader_page
;
2086 iter
->head
= cpu_buffer
->reader_page
->read
;
2089 iter
->read_stamp
= cpu_buffer
->read_stamp
;
2091 iter
->read_stamp
= iter
->head_page
->page
->time_stamp
;
2095 * ring_buffer_iter_reset - reset an iterator
2096 * @iter: The iterator to reset
2098 * Resets the iterator, so that it will start from the beginning
2101 void ring_buffer_iter_reset(struct ring_buffer_iter
*iter
)
2103 struct ring_buffer_per_cpu
*cpu_buffer
;
2104 unsigned long flags
;
2109 cpu_buffer
= iter
->cpu_buffer
;
2111 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2112 rb_iter_reset(iter
);
2113 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2115 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset
);
2118 * ring_buffer_iter_empty - check if an iterator has no more to read
2119 * @iter: The iterator to check
2121 int ring_buffer_iter_empty(struct ring_buffer_iter
*iter
)
2123 struct ring_buffer_per_cpu
*cpu_buffer
;
2125 cpu_buffer
= iter
->cpu_buffer
;
2127 return iter
->head_page
== cpu_buffer
->commit_page
&&
2128 iter
->head
== rb_commit_index(cpu_buffer
);
2130 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty
);
2133 rb_update_read_stamp(struct ring_buffer_per_cpu
*cpu_buffer
,
2134 struct ring_buffer_event
*event
)
2138 switch (event
->type_len
) {
2139 case RINGBUF_TYPE_PADDING
:
2142 case RINGBUF_TYPE_TIME_EXTEND
:
2143 delta
= event
->array
[0];
2145 delta
+= event
->time_delta
;
2146 cpu_buffer
->read_stamp
+= delta
;
2149 case RINGBUF_TYPE_TIME_STAMP
:
2150 /* FIXME: not implemented */
2153 case RINGBUF_TYPE_DATA
:
2154 cpu_buffer
->read_stamp
+= event
->time_delta
;
2164 rb_update_iter_read_stamp(struct ring_buffer_iter
*iter
,
2165 struct ring_buffer_event
*event
)
2169 switch (event
->type_len
) {
2170 case RINGBUF_TYPE_PADDING
:
2173 case RINGBUF_TYPE_TIME_EXTEND
:
2174 delta
= event
->array
[0];
2176 delta
+= event
->time_delta
;
2177 iter
->read_stamp
+= delta
;
2180 case RINGBUF_TYPE_TIME_STAMP
:
2181 /* FIXME: not implemented */
2184 case RINGBUF_TYPE_DATA
:
2185 iter
->read_stamp
+= event
->time_delta
;
2194 static struct buffer_page
*
2195 rb_get_reader_page(struct ring_buffer_per_cpu
*cpu_buffer
)
2197 struct buffer_page
*reader
= NULL
;
2198 unsigned long flags
;
2201 local_irq_save(flags
);
2202 __raw_spin_lock(&cpu_buffer
->lock
);
2206 * This should normally only loop twice. But because the
2207 * start of the reader inserts an empty page, it causes
2208 * a case where we will loop three times. There should be no
2209 * reason to loop four times (that I know of).
2211 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> 3)) {
2216 reader
= cpu_buffer
->reader_page
;
2218 /* If there's more to read, return this page */
2219 if (cpu_buffer
->reader_page
->read
< rb_page_size(reader
))
2222 /* Never should we have an index greater than the size */
2223 if (RB_WARN_ON(cpu_buffer
,
2224 cpu_buffer
->reader_page
->read
> rb_page_size(reader
)))
2227 /* check if we caught up to the tail */
2229 if (cpu_buffer
->commit_page
== cpu_buffer
->reader_page
)
2233 * Splice the empty reader page into the list around the head.
2234 * Reset the reader page to size zero.
2237 reader
= cpu_buffer
->head_page
;
2238 cpu_buffer
->reader_page
->list
.next
= reader
->list
.next
;
2239 cpu_buffer
->reader_page
->list
.prev
= reader
->list
.prev
;
2241 local_set(&cpu_buffer
->reader_page
->write
, 0);
2242 local_set(&cpu_buffer
->reader_page
->entries
, 0);
2243 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
2245 /* Make the reader page now replace the head */
2246 reader
->list
.prev
->next
= &cpu_buffer
->reader_page
->list
;
2247 reader
->list
.next
->prev
= &cpu_buffer
->reader_page
->list
;
2250 * If the tail is on the reader, then we must set the head
2251 * to the inserted page, otherwise we set it one before.
2253 cpu_buffer
->head_page
= cpu_buffer
->reader_page
;
2255 if (cpu_buffer
->commit_page
!= reader
)
2256 rb_inc_page(cpu_buffer
, &cpu_buffer
->head_page
);
2258 /* Finally update the reader page to the new head */
2259 cpu_buffer
->reader_page
= reader
;
2260 rb_reset_reader_page(cpu_buffer
);
2265 __raw_spin_unlock(&cpu_buffer
->lock
);
2266 local_irq_restore(flags
);
2271 static void rb_advance_reader(struct ring_buffer_per_cpu
*cpu_buffer
)
2273 struct ring_buffer_event
*event
;
2274 struct buffer_page
*reader
;
2277 reader
= rb_get_reader_page(cpu_buffer
);
2279 /* This function should not be called when buffer is empty */
2280 if (RB_WARN_ON(cpu_buffer
, !reader
))
2283 event
= rb_reader_event(cpu_buffer
);
2285 if (event
->type_len
<= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
2286 || rb_discarded_event(event
))
2289 rb_update_read_stamp(cpu_buffer
, event
);
2291 length
= rb_event_length(event
);
2292 cpu_buffer
->reader_page
->read
+= length
;
2295 static void rb_advance_iter(struct ring_buffer_iter
*iter
)
2297 struct ring_buffer
*buffer
;
2298 struct ring_buffer_per_cpu
*cpu_buffer
;
2299 struct ring_buffer_event
*event
;
2302 cpu_buffer
= iter
->cpu_buffer
;
2303 buffer
= cpu_buffer
->buffer
;
2306 * Check if we are at the end of the buffer.
2308 if (iter
->head
>= rb_page_size(iter
->head_page
)) {
2309 /* discarded commits can make the page empty */
2310 if (iter
->head_page
== cpu_buffer
->commit_page
)
2316 event
= rb_iter_head_event(iter
);
2318 length
= rb_event_length(event
);
2321 * This should not be called to advance the header if we are
2322 * at the tail of the buffer.
2324 if (RB_WARN_ON(cpu_buffer
,
2325 (iter
->head_page
== cpu_buffer
->commit_page
) &&
2326 (iter
->head
+ length
> rb_commit_index(cpu_buffer
))))
2329 rb_update_iter_read_stamp(iter
, event
);
2331 iter
->head
+= length
;
2333 /* check for end of page padding */
2334 if ((iter
->head
>= rb_page_size(iter
->head_page
)) &&
2335 (iter
->head_page
!= cpu_buffer
->commit_page
))
2336 rb_advance_iter(iter
);
2339 static struct ring_buffer_event
*
2340 rb_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
2342 struct ring_buffer_per_cpu
*cpu_buffer
;
2343 struct ring_buffer_event
*event
;
2344 struct buffer_page
*reader
;
2347 cpu_buffer
= buffer
->buffers
[cpu
];
2351 * We repeat when a timestamp is encountered. It is possible
2352 * to get multiple timestamps from an interrupt entering just
2353 * as one timestamp is about to be written, or from discarded
2354 * commits. The most that we can have is the number on a single page.
2356 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
2359 reader
= rb_get_reader_page(cpu_buffer
);
2363 event
= rb_reader_event(cpu_buffer
);
2365 switch (event
->type_len
) {
2366 case RINGBUF_TYPE_PADDING
:
2367 if (rb_null_event(event
))
2368 RB_WARN_ON(cpu_buffer
, 1);
2370 * Because the writer could be discarding every
2371 * event it creates (which would probably be bad)
2372 * if we were to go back to "again" then we may never
2373 * catch up, and will trigger the warn on, or lock
2374 * the box. Return the padding, and we will release
2375 * the current locks, and try again.
2377 rb_advance_reader(cpu_buffer
);
2380 case RINGBUF_TYPE_TIME_EXTEND
:
2381 /* Internal data, OK to advance */
2382 rb_advance_reader(cpu_buffer
);
2385 case RINGBUF_TYPE_TIME_STAMP
:
2386 /* FIXME: not implemented */
2387 rb_advance_reader(cpu_buffer
);
2390 case RINGBUF_TYPE_DATA
:
2392 *ts
= cpu_buffer
->read_stamp
+ event
->time_delta
;
2393 ring_buffer_normalize_time_stamp(buffer
,
2394 cpu_buffer
->cpu
, ts
);
2404 EXPORT_SYMBOL_GPL(ring_buffer_peek
);
2406 static struct ring_buffer_event
*
2407 rb_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
2409 struct ring_buffer
*buffer
;
2410 struct ring_buffer_per_cpu
*cpu_buffer
;
2411 struct ring_buffer_event
*event
;
2414 if (ring_buffer_iter_empty(iter
))
2417 cpu_buffer
= iter
->cpu_buffer
;
2418 buffer
= cpu_buffer
->buffer
;
2422 * We repeat when a timestamp is encountered.
2423 * We can get multiple timestamps by nested interrupts or also
2424 * if filtering is on (discarding commits). Since discarding
2425 * commits can be frequent we can get a lot of timestamps.
2426 * But we limit them by not adding timestamps if they begin
2427 * at the start of a page.
2429 if (RB_WARN_ON(cpu_buffer
, ++nr_loops
> RB_TIMESTAMPS_PER_PAGE
))
2432 if (rb_per_cpu_empty(cpu_buffer
))
2435 event
= rb_iter_head_event(iter
);
2437 switch (event
->type_len
) {
2438 case RINGBUF_TYPE_PADDING
:
2439 if (rb_null_event(event
)) {
2443 rb_advance_iter(iter
);
2446 case RINGBUF_TYPE_TIME_EXTEND
:
2447 /* Internal data, OK to advance */
2448 rb_advance_iter(iter
);
2451 case RINGBUF_TYPE_TIME_STAMP
:
2452 /* FIXME: not implemented */
2453 rb_advance_iter(iter
);
2456 case RINGBUF_TYPE_DATA
:
2458 *ts
= iter
->read_stamp
+ event
->time_delta
;
2459 ring_buffer_normalize_time_stamp(buffer
,
2460 cpu_buffer
->cpu
, ts
);
2470 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek
);
2472 static inline int rb_ok_to_lock(void)
2475 * If an NMI die dumps out the content of the ring buffer
2476 * do not grab locks. We also permanently disable the ring
2477 * buffer too. A one time deal is all you get from reading
2478 * the ring buffer from an NMI.
2480 if (likely(!in_nmi() && !oops_in_progress
))
2483 tracing_off_permanent();
2488 * ring_buffer_peek - peek at the next event to be read
2489 * @buffer: The ring buffer to read
2490 * @cpu: The cpu to peak at
2491 * @ts: The timestamp counter of this event.
2493 * This will return the event that will be read next, but does
2494 * not consume the data.
2496 struct ring_buffer_event
*
2497 ring_buffer_peek(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
2499 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2500 struct ring_buffer_event
*event
;
2501 unsigned long flags
;
2504 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2507 dolock
= rb_ok_to_lock();
2509 local_irq_save(flags
);
2511 spin_lock(&cpu_buffer
->reader_lock
);
2512 event
= rb_buffer_peek(buffer
, cpu
, ts
);
2514 spin_unlock(&cpu_buffer
->reader_lock
);
2515 local_irq_restore(flags
);
2517 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
) {
2526 * ring_buffer_iter_peek - peek at the next event to be read
2527 * @iter: The ring buffer iterator
2528 * @ts: The timestamp counter of this event.
2530 * This will return the event that will be read next, but does
2531 * not increment the iterator.
2533 struct ring_buffer_event
*
2534 ring_buffer_iter_peek(struct ring_buffer_iter
*iter
, u64
*ts
)
2536 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2537 struct ring_buffer_event
*event
;
2538 unsigned long flags
;
2541 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2542 event
= rb_iter_peek(iter
, ts
);
2543 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2545 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
) {
2554 * ring_buffer_consume - return an event and consume it
2555 * @buffer: The ring buffer to get the next event from
2557 * Returns the next event in the ring buffer, and that event is consumed.
2558 * Meaning, that sequential reads will keep returning a different event,
2559 * and eventually empty the ring buffer if the producer is slower.
2561 struct ring_buffer_event
*
2562 ring_buffer_consume(struct ring_buffer
*buffer
, int cpu
, u64
*ts
)
2564 struct ring_buffer_per_cpu
*cpu_buffer
;
2565 struct ring_buffer_event
*event
= NULL
;
2566 unsigned long flags
;
2569 dolock
= rb_ok_to_lock();
2572 /* might be called in atomic */
2575 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2578 cpu_buffer
= buffer
->buffers
[cpu
];
2579 local_irq_save(flags
);
2581 spin_lock(&cpu_buffer
->reader_lock
);
2583 event
= rb_buffer_peek(buffer
, cpu
, ts
);
2587 rb_advance_reader(cpu_buffer
);
2591 spin_unlock(&cpu_buffer
->reader_lock
);
2592 local_irq_restore(flags
);
2597 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
) {
2604 EXPORT_SYMBOL_GPL(ring_buffer_consume
);
2607 * ring_buffer_read_start - start a non consuming read of the buffer
2608 * @buffer: The ring buffer to read from
2609 * @cpu: The cpu buffer to iterate over
2611 * This starts up an iteration through the buffer. It also disables
2612 * the recording to the buffer until the reading is finished.
2613 * This prevents the reading from being corrupted. This is not
2614 * a consuming read, so a producer is not expected.
2616 * Must be paired with ring_buffer_finish.
2618 struct ring_buffer_iter
*
2619 ring_buffer_read_start(struct ring_buffer
*buffer
, int cpu
)
2621 struct ring_buffer_per_cpu
*cpu_buffer
;
2622 struct ring_buffer_iter
*iter
;
2623 unsigned long flags
;
2625 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2628 iter
= kmalloc(sizeof(*iter
), GFP_KERNEL
);
2632 cpu_buffer
= buffer
->buffers
[cpu
];
2634 iter
->cpu_buffer
= cpu_buffer
;
2636 atomic_inc(&cpu_buffer
->record_disabled
);
2637 synchronize_sched();
2639 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2640 __raw_spin_lock(&cpu_buffer
->lock
);
2641 rb_iter_reset(iter
);
2642 __raw_spin_unlock(&cpu_buffer
->lock
);
2643 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2647 EXPORT_SYMBOL_GPL(ring_buffer_read_start
);
2650 * ring_buffer_finish - finish reading the iterator of the buffer
2651 * @iter: The iterator retrieved by ring_buffer_start
2653 * This re-enables the recording to the buffer, and frees the
2657 ring_buffer_read_finish(struct ring_buffer_iter
*iter
)
2659 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2661 atomic_dec(&cpu_buffer
->record_disabled
);
2664 EXPORT_SYMBOL_GPL(ring_buffer_read_finish
);
2667 * ring_buffer_read - read the next item in the ring buffer by the iterator
2668 * @iter: The ring buffer iterator
2669 * @ts: The time stamp of the event read.
2671 * This reads the next event in the ring buffer and increments the iterator.
2673 struct ring_buffer_event
*
2674 ring_buffer_read(struct ring_buffer_iter
*iter
, u64
*ts
)
2676 struct ring_buffer_event
*event
;
2677 struct ring_buffer_per_cpu
*cpu_buffer
= iter
->cpu_buffer
;
2678 unsigned long flags
;
2681 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2682 event
= rb_iter_peek(iter
, ts
);
2686 rb_advance_iter(iter
);
2688 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2690 if (event
&& event
->type_len
== RINGBUF_TYPE_PADDING
) {
2697 EXPORT_SYMBOL_GPL(ring_buffer_read
);
2700 * ring_buffer_size - return the size of the ring buffer (in bytes)
2701 * @buffer: The ring buffer.
2703 unsigned long ring_buffer_size(struct ring_buffer
*buffer
)
2705 return BUF_PAGE_SIZE
* buffer
->pages
;
2707 EXPORT_SYMBOL_GPL(ring_buffer_size
);
2710 rb_reset_cpu(struct ring_buffer_per_cpu
*cpu_buffer
)
2712 cpu_buffer
->head_page
2713 = list_entry(cpu_buffer
->pages
.next
, struct buffer_page
, list
);
2714 local_set(&cpu_buffer
->head_page
->write
, 0);
2715 local_set(&cpu_buffer
->head_page
->entries
, 0);
2716 local_set(&cpu_buffer
->head_page
->page
->commit
, 0);
2718 cpu_buffer
->head_page
->read
= 0;
2720 cpu_buffer
->tail_page
= cpu_buffer
->head_page
;
2721 cpu_buffer
->commit_page
= cpu_buffer
->head_page
;
2723 INIT_LIST_HEAD(&cpu_buffer
->reader_page
->list
);
2724 local_set(&cpu_buffer
->reader_page
->write
, 0);
2725 local_set(&cpu_buffer
->reader_page
->entries
, 0);
2726 local_set(&cpu_buffer
->reader_page
->page
->commit
, 0);
2727 cpu_buffer
->reader_page
->read
= 0;
2729 cpu_buffer
->nmi_dropped
= 0;
2730 cpu_buffer
->commit_overrun
= 0;
2731 cpu_buffer
->overrun
= 0;
2732 cpu_buffer
->read
= 0;
2733 local_set(&cpu_buffer
->entries
, 0);
2734 local_set(&cpu_buffer
->committing
, 0);
2735 local_set(&cpu_buffer
->commits
, 0);
2737 cpu_buffer
->write_stamp
= 0;
2738 cpu_buffer
->read_stamp
= 0;
2742 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2743 * @buffer: The ring buffer to reset a per cpu buffer of
2744 * @cpu: The CPU buffer to be reset
2746 void ring_buffer_reset_cpu(struct ring_buffer
*buffer
, int cpu
)
2748 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2749 unsigned long flags
;
2751 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2754 atomic_inc(&cpu_buffer
->record_disabled
);
2756 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
2758 __raw_spin_lock(&cpu_buffer
->lock
);
2760 rb_reset_cpu(cpu_buffer
);
2762 __raw_spin_unlock(&cpu_buffer
->lock
);
2764 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
2766 atomic_dec(&cpu_buffer
->record_disabled
);
2768 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu
);
2771 * ring_buffer_reset - reset a ring buffer
2772 * @buffer: The ring buffer to reset all cpu buffers
2774 void ring_buffer_reset(struct ring_buffer
*buffer
)
2778 for_each_buffer_cpu(buffer
, cpu
)
2779 ring_buffer_reset_cpu(buffer
, cpu
);
2781 EXPORT_SYMBOL_GPL(ring_buffer_reset
);
2784 * rind_buffer_empty - is the ring buffer empty?
2785 * @buffer: The ring buffer to test
2787 int ring_buffer_empty(struct ring_buffer
*buffer
)
2789 struct ring_buffer_per_cpu
*cpu_buffer
;
2790 unsigned long flags
;
2795 dolock
= rb_ok_to_lock();
2797 /* yes this is racy, but if you don't like the race, lock the buffer */
2798 for_each_buffer_cpu(buffer
, cpu
) {
2799 cpu_buffer
= buffer
->buffers
[cpu
];
2800 local_irq_save(flags
);
2802 spin_lock(&cpu_buffer
->reader_lock
);
2803 ret
= rb_per_cpu_empty(cpu_buffer
);
2805 spin_unlock(&cpu_buffer
->reader_lock
);
2806 local_irq_restore(flags
);
2814 EXPORT_SYMBOL_GPL(ring_buffer_empty
);
2817 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2818 * @buffer: The ring buffer
2819 * @cpu: The CPU buffer to test
2821 int ring_buffer_empty_cpu(struct ring_buffer
*buffer
, int cpu
)
2823 struct ring_buffer_per_cpu
*cpu_buffer
;
2824 unsigned long flags
;
2828 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
2831 dolock
= rb_ok_to_lock();
2833 cpu_buffer
= buffer
->buffers
[cpu
];
2834 local_irq_save(flags
);
2836 spin_lock(&cpu_buffer
->reader_lock
);
2837 ret
= rb_per_cpu_empty(cpu_buffer
);
2839 spin_unlock(&cpu_buffer
->reader_lock
);
2840 local_irq_restore(flags
);
2844 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu
);
2847 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2848 * @buffer_a: One buffer to swap with
2849 * @buffer_b: The other buffer to swap with
2851 * This function is useful for tracers that want to take a "snapshot"
2852 * of a CPU buffer and has another back up buffer lying around.
2853 * it is expected that the tracer handles the cpu buffer not being
2854 * used at the moment.
2856 int ring_buffer_swap_cpu(struct ring_buffer
*buffer_a
,
2857 struct ring_buffer
*buffer_b
, int cpu
)
2859 struct ring_buffer_per_cpu
*cpu_buffer_a
;
2860 struct ring_buffer_per_cpu
*cpu_buffer_b
;
2863 if (!cpumask_test_cpu(cpu
, buffer_a
->cpumask
) ||
2864 !cpumask_test_cpu(cpu
, buffer_b
->cpumask
))
2867 /* At least make sure the two buffers are somewhat the same */
2868 if (buffer_a
->pages
!= buffer_b
->pages
)
2873 if (ring_buffer_flags
!= RB_BUFFERS_ON
)
2876 if (atomic_read(&buffer_a
->record_disabled
))
2879 if (atomic_read(&buffer_b
->record_disabled
))
2882 cpu_buffer_a
= buffer_a
->buffers
[cpu
];
2883 cpu_buffer_b
= buffer_b
->buffers
[cpu
];
2885 if (atomic_read(&cpu_buffer_a
->record_disabled
))
2888 if (atomic_read(&cpu_buffer_b
->record_disabled
))
2892 * We can't do a synchronize_sched here because this
2893 * function can be called in atomic context.
2894 * Normally this will be called from the same CPU as cpu.
2895 * If not it's up to the caller to protect this.
2897 atomic_inc(&cpu_buffer_a
->record_disabled
);
2898 atomic_inc(&cpu_buffer_b
->record_disabled
);
2900 buffer_a
->buffers
[cpu
] = cpu_buffer_b
;
2901 buffer_b
->buffers
[cpu
] = cpu_buffer_a
;
2903 cpu_buffer_b
->buffer
= buffer_a
;
2904 cpu_buffer_a
->buffer
= buffer_b
;
2906 atomic_dec(&cpu_buffer_a
->record_disabled
);
2907 atomic_dec(&cpu_buffer_b
->record_disabled
);
2913 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu
);
2916 * ring_buffer_alloc_read_page - allocate a page to read from buffer
2917 * @buffer: the buffer to allocate for.
2919 * This function is used in conjunction with ring_buffer_read_page.
2920 * When reading a full page from the ring buffer, these functions
2921 * can be used to speed up the process. The calling function should
2922 * allocate a few pages first with this function. Then when it
2923 * needs to get pages from the ring buffer, it passes the result
2924 * of this function into ring_buffer_read_page, which will swap
2925 * the page that was allocated, with the read page of the buffer.
2928 * The page allocated, or NULL on error.
2930 void *ring_buffer_alloc_read_page(struct ring_buffer
*buffer
)
2932 struct buffer_data_page
*bpage
;
2935 addr
= __get_free_page(GFP_KERNEL
);
2939 bpage
= (void *)addr
;
2941 rb_init_page(bpage
);
2945 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page
);
2948 * ring_buffer_free_read_page - free an allocated read page
2949 * @buffer: the buffer the page was allocate for
2950 * @data: the page to free
2952 * Free a page allocated from ring_buffer_alloc_read_page.
2954 void ring_buffer_free_read_page(struct ring_buffer
*buffer
, void *data
)
2956 free_page((unsigned long)data
);
2958 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page
);
2961 * ring_buffer_read_page - extract a page from the ring buffer
2962 * @buffer: buffer to extract from
2963 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
2964 * @len: amount to extract
2965 * @cpu: the cpu of the buffer to extract
2966 * @full: should the extraction only happen when the page is full.
2968 * This function will pull out a page from the ring buffer and consume it.
2969 * @data_page must be the address of the variable that was returned
2970 * from ring_buffer_alloc_read_page. This is because the page might be used
2971 * to swap with a page in the ring buffer.
2974 * rpage = ring_buffer_alloc_read_page(buffer);
2977 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
2979 * process_page(rpage, ret);
2981 * When @full is set, the function will not return true unless
2982 * the writer is off the reader page.
2984 * Note: it is up to the calling functions to handle sleeps and wakeups.
2985 * The ring buffer can be used anywhere in the kernel and can not
2986 * blindly call wake_up. The layer that uses the ring buffer must be
2987 * responsible for that.
2990 * >=0 if data has been transferred, returns the offset of consumed data.
2991 * <0 if no data has been transferred.
2993 int ring_buffer_read_page(struct ring_buffer
*buffer
,
2994 void **data_page
, size_t len
, int cpu
, int full
)
2996 struct ring_buffer_per_cpu
*cpu_buffer
= buffer
->buffers
[cpu
];
2997 struct ring_buffer_event
*event
;
2998 struct buffer_data_page
*bpage
;
2999 struct buffer_page
*reader
;
3000 unsigned long flags
;
3001 unsigned int commit
;
3006 if (!cpumask_test_cpu(cpu
, buffer
->cpumask
))
3010 * If len is not big enough to hold the page header, then
3011 * we can not copy anything.
3013 if (len
<= BUF_PAGE_HDR_SIZE
)
3016 len
-= BUF_PAGE_HDR_SIZE
;
3025 spin_lock_irqsave(&cpu_buffer
->reader_lock
, flags
);
3027 reader
= rb_get_reader_page(cpu_buffer
);
3031 event
= rb_reader_event(cpu_buffer
);
3033 read
= reader
->read
;
3034 commit
= rb_page_commit(reader
);
3037 * If this page has been partially read or
3038 * if len is not big enough to read the rest of the page or
3039 * a writer is still on the page, then
3040 * we must copy the data from the page to the buffer.
3041 * Otherwise, we can simply swap the page with the one passed in.
3043 if (read
|| (len
< (commit
- read
)) ||
3044 cpu_buffer
->reader_page
== cpu_buffer
->commit_page
) {
3045 struct buffer_data_page
*rpage
= cpu_buffer
->reader_page
->page
;
3046 unsigned int rpos
= read
;
3047 unsigned int pos
= 0;
3053 if (len
> (commit
- read
))
3054 len
= (commit
- read
);
3056 size
= rb_event_length(event
);
3061 /* save the current timestamp, since the user will need it */
3062 save_timestamp
= cpu_buffer
->read_stamp
;
3064 /* Need to copy one event at a time */
3066 memcpy(bpage
->data
+ pos
, rpage
->data
+ rpos
, size
);
3070 rb_advance_reader(cpu_buffer
);
3071 rpos
= reader
->read
;
3074 event
= rb_reader_event(cpu_buffer
);
3075 size
= rb_event_length(event
);
3076 } while (len
> size
);
3079 local_set(&bpage
->commit
, pos
);
3080 bpage
->time_stamp
= save_timestamp
;
3082 /* we copied everything to the beginning */
3085 /* update the entry counter */
3086 cpu_buffer
->read
+= local_read(&reader
->entries
);
3088 /* swap the pages */
3089 rb_init_page(bpage
);
3090 bpage
= reader
->page
;
3091 reader
->page
= *data_page
;
3092 local_set(&reader
->write
, 0);
3093 local_set(&reader
->entries
, 0);
3100 spin_unlock_irqrestore(&cpu_buffer
->reader_lock
, flags
);
3105 EXPORT_SYMBOL_GPL(ring_buffer_read_page
);
3108 rb_simple_read(struct file
*filp
, char __user
*ubuf
,
3109 size_t cnt
, loff_t
*ppos
)
3111 unsigned long *p
= filp
->private_data
;
3115 if (test_bit(RB_BUFFERS_DISABLED_BIT
, p
))
3116 r
= sprintf(buf
, "permanently disabled\n");
3118 r
= sprintf(buf
, "%d\n", test_bit(RB_BUFFERS_ON_BIT
, p
));
3120 return simple_read_from_buffer(ubuf
, cnt
, ppos
, buf
, r
);
3124 rb_simple_write(struct file
*filp
, const char __user
*ubuf
,
3125 size_t cnt
, loff_t
*ppos
)
3127 unsigned long *p
= filp
->private_data
;
3132 if (cnt
>= sizeof(buf
))
3135 if (copy_from_user(&buf
, ubuf
, cnt
))
3140 ret
= strict_strtoul(buf
, 10, &val
);
3145 set_bit(RB_BUFFERS_ON_BIT
, p
);
3147 clear_bit(RB_BUFFERS_ON_BIT
, p
);
3154 static const struct file_operations rb_simple_fops
= {
3155 .open
= tracing_open_generic
,
3156 .read
= rb_simple_read
,
3157 .write
= rb_simple_write
,
3161 static __init
int rb_init_debugfs(void)
3163 struct dentry
*d_tracer
;
3165 d_tracer
= tracing_init_dentry();
3167 trace_create_file("tracing_on", 0644, d_tracer
,
3168 &ring_buffer_flags
, &rb_simple_fops
);
3173 fs_initcall(rb_init_debugfs
);
3175 #ifdef CONFIG_HOTPLUG_CPU
3176 static int rb_cpu_notify(struct notifier_block
*self
,
3177 unsigned long action
, void *hcpu
)
3179 struct ring_buffer
*buffer
=
3180 container_of(self
, struct ring_buffer
, cpu_notify
);
3181 long cpu
= (long)hcpu
;
3184 case CPU_UP_PREPARE
:
3185 case CPU_UP_PREPARE_FROZEN
:
3186 if (cpumask_test_cpu(cpu
, buffer
->cpumask
))
3189 buffer
->buffers
[cpu
] =
3190 rb_allocate_cpu_buffer(buffer
, cpu
);
3191 if (!buffer
->buffers
[cpu
]) {
3192 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
3197 cpumask_set_cpu(cpu
, buffer
->cpumask
);
3199 case CPU_DOWN_PREPARE
:
3200 case CPU_DOWN_PREPARE_FROZEN
:
3203 * If we were to free the buffer, then the user would
3204 * lose any trace that was in the buffer.