thinkpad-acpi: convert to seq_file
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / trace / ring_buffer.c
bloba330513d96ce321ae0ea50e9fa648d6e9cbfc7e5
1 /*
2 * Generic ring buffer
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
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>
21 #include <linux/fs.h>
23 #include "trace.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)
30 int ret;
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);
44 return ret;
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.
63 * +------+
64 * |reader| RING BUFFER
65 * |page |
66 * +------+ +---+ +---+ +---+
67 * | |-->| |-->| |
68 * +---+ +---+ +---+
69 * ^ |
70 * | |
71 * +---------------+
74 * +------+
75 * |reader| RING BUFFER
76 * |page |------------------v
77 * +------+ +---+ +---+ +---+
78 * | |-->| |-->| |
79 * +---+ +---+ +---+
80 * ^ |
81 * | |
82 * +---------------+
85 * +------+
86 * |reader| RING BUFFER
87 * |page |------------------v
88 * +------+ +---+ +---+ +---+
89 * ^ | |-->| |-->| |
90 * | +---+ +---+ +---+
91 * | |
92 * | |
93 * +------------------------------+
96 * +------+
97 * |buffer| RING BUFFER
98 * |page |------------------v
99 * +------+ +---+ +---+ +---+
100 * ^ | | | |-->| |
101 * | New +---+ +---+ +---+
102 * | Reader------^ |
103 * | page |
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
137 * ON DISABLED
138 * ---- ----------
139 * 0 0 : ring buffers are off
140 * 1 0 : ring buffers are on
141 * X 1 : ring buffers are permanently disabled
144 enum {
145 RB_BUFFERS_ON_BIT = 0,
146 RB_BUFFERS_DISABLED_BIT = 1,
149 enum {
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
188 * permanently.
190 void tracing_off_permanent(void)
192 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
196 * tracing_is_on - show state of ring buffers enabled
198 int tracing_is_on(void)
200 return ring_buffer_flags == RB_BUFFERS_ON;
202 EXPORT_SYMBOL_GPL(tracing_is_on);
204 #include "trace.h"
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
214 enum {
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;
236 static unsigned
237 rb_event_data_length(struct ring_buffer_event *event)
239 unsigned length;
241 if (event->type_len)
242 length = event->type_len * RB_ALIGNMENT;
243 else
244 length = event->array[0];
245 return length + RB_EVNT_HDR_SIZE;
248 /* inline for ring buffer fast paths */
249 static unsigned
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))
255 /* undefined */
256 return -1;
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);
267 default:
268 BUG();
270 /* not hit */
271 return 0;
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)
282 return length;
283 length -= RB_EVNT_HDR_SIZE;
284 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
285 length -= sizeof(event->array[0]);
286 return length;
288 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
290 /* inline for ring buffer fast paths */
291 static void *
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 */
296 if (event->type_len)
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)
315 #define TS_SHIFT 27
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 */
325 struct 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)
347 + BUF_PAGE_HDR_SIZE;
351 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
352 * this issue out.
354 static void free_buffer_page(struct buffer_page *bpage)
356 free_page((unsigned long)bpage->page);
357 kfree(bpage);
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)
366 return 1;
367 return 0;
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;
381 int ret;
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);
397 return ret;
401 * head_page == tail_page && head == tail then buffer is empty.
403 struct ring_buffer_per_cpu {
404 int cpu;
405 struct ring_buffer *buffer;
406 spinlock_t reader_lock; /* serialize readers */
407 raw_spinlock_t lock;
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;
417 unsigned long read;
418 local_t entries;
419 local_t committing;
420 local_t commits;
421 u64 write_stamp;
422 u64 read_stamp;
423 atomic_t record_disabled;
426 struct ring_buffer {
427 unsigned pages;
428 unsigned flags;
429 int cpus;
430 atomic_t record_disabled;
431 cpumask_var_t cpumask;
433 struct lock_class_key *reader_lock_key;
435 struct mutex mutex;
437 struct ring_buffer_per_cpu **buffers;
439 #ifdef CONFIG_HOTPLUG_CPU
440 struct notifier_block cpu_notify;
441 #endif
442 u64 (*clock)(void);
445 struct ring_buffer_iter {
446 struct ring_buffer_per_cpu *cpu_buffer;
447 unsigned long head;
448 struct buffer_page *head_page;
449 u64 read_stamp;
452 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
453 #define RB_WARN_ON(buffer, cond) \
454 ({ \
455 int _____ret = unlikely(cond); \
456 if (_____ret) { \
457 atomic_inc(&buffer->record_disabled); \
458 WARN_ON(1); \
460 _____ret; \
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)
474 u64 time;
476 preempt_disable_notrace();
477 time = rb_time_stamp(buffer, cpu);
478 preempt_enable_no_resched_notrace();
480 return time;
482 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
484 void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
485 int cpu, u64 *ts)
487 /* Just stupid testing the normalize function and deltas */
488 *ts >>= DEBUG_SHIFT;
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
497 * been corrupted.
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))
505 return -1;
506 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
507 return -1;
509 list_for_each_entry_safe(bpage, tmp, head, list) {
510 if (RB_WARN_ON(cpu_buffer,
511 bpage->list.next->prev != &bpage->list))
512 return -1;
513 if (RB_WARN_ON(cpu_buffer,
514 bpage->list.prev->next != &bpage->list))
515 return -1;
518 return 0;
521 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
522 unsigned nr_pages)
524 struct list_head *head = &cpu_buffer->pages;
525 struct buffer_page *bpage, *tmp;
526 unsigned long addr;
527 LIST_HEAD(pages);
528 unsigned i;
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));
533 if (!bpage)
534 goto free_pages;
535 list_add(&bpage->list, &pages);
537 addr = __get_free_page(GFP_KERNEL);
538 if (!addr)
539 goto free_pages;
540 bpage->page = (void *)addr;
541 rb_init_page(bpage->page);
544 list_splice(&pages, head);
546 rb_check_pages(cpu_buffer);
548 return 0;
550 free_pages:
551 list_for_each_entry_safe(bpage, tmp, &pages, list) {
552 list_del_init(&bpage->list);
553 free_buffer_page(bpage);
555 return -ENOMEM;
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;
563 unsigned long addr;
564 int ret;
566 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
567 GFP_KERNEL, cpu_to_node(cpu));
568 if (!cpu_buffer)
569 return NULL;
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));
580 if (!bpage)
581 goto fail_free_buffer;
583 cpu_buffer->reader_page = bpage;
584 addr = __get_free_page(GFP_KERNEL);
585 if (!addr)
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);
593 if (ret < 0)
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;
600 return cpu_buffer;
602 fail_free_reader:
603 free_buffer_page(cpu_buffer->reader_page);
605 fail_free_buffer:
606 kfree(cpu_buffer);
607 return NULL;
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);
621 kfree(cpu_buffer);
624 #ifdef CONFIG_HOTPLUG_CPU
625 static int rb_cpu_notify(struct notifier_block *self,
626 unsigned long action, void *hcpu);
627 #endif
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;
643 int bsize;
644 int cpu;
646 /* keep it in its own cache line */
647 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
648 GFP_KERNEL);
649 if (!buffer)
650 return NULL;
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)
662 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
670 get_online_cpus();
671 cpumask_copy(buffer->cpumask, cpu_online_mask);
672 #else
673 cpumask_copy(buffer->cpumask, cpu_possible_mask);
674 #endif
675 buffer->cpus = nr_cpu_ids;
677 bsize = sizeof(void *) * nr_cpu_ids;
678 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
679 GFP_KERNEL);
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);
694 #endif
696 put_online_cpus();
697 mutex_init(&buffer->mutex);
699 return buffer;
701 fail_free_buffers:
702 for_each_buffer_cpu(buffer, cpu) {
703 if (buffer->buffers[cpu])
704 rb_free_cpu_buffer(buffer->buffers[cpu]);
706 kfree(buffer->buffers);
708 fail_free_cpumask:
709 free_cpumask_var(buffer->cpumask);
710 put_online_cpus();
712 fail_free_buffer:
713 kfree(buffer);
714 return NULL;
716 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
719 * ring_buffer_free - free a ring buffer.
720 * @buffer: the buffer to free.
722 void
723 ring_buffer_free(struct ring_buffer *buffer)
725 int cpu;
727 get_online_cpus();
729 #ifdef CONFIG_HOTPLUG_CPU
730 unregister_cpu_notifier(&buffer->cpu_notify);
731 #endif
733 for_each_buffer_cpu(buffer, cpu)
734 rb_free_cpu_buffer(buffer->buffers[cpu]);
736 put_online_cpus();
738 kfree(buffer->buffers);
739 free_cpumask_var(buffer->cpumask);
741 kfree(buffer);
743 EXPORT_SYMBOL_GPL(ring_buffer_free);
745 void ring_buffer_set_clock(struct ring_buffer *buffer,
746 u64 (*clock)(void))
748 buffer->clock = clock;
751 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
753 static void
754 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
756 struct buffer_page *bpage;
757 struct list_head *p;
758 unsigned i;
760 atomic_inc(&cpu_buffer->record_disabled);
761 synchronize_sched();
763 for (i = 0; i < nr_pages; i++) {
764 if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
765 return;
766 p = cpu_buffer->pages.next;
767 bpage = list_entry(p, struct buffer_page, list);
768 list_del_init(&bpage->list);
769 free_buffer_page(bpage);
771 if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
772 return;
774 rb_reset_cpu(cpu_buffer);
776 rb_check_pages(cpu_buffer);
778 atomic_dec(&cpu_buffer->record_disabled);
782 static void
783 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
784 struct list_head *pages, unsigned nr_pages)
786 struct buffer_page *bpage;
787 struct list_head *p;
788 unsigned i;
790 atomic_inc(&cpu_buffer->record_disabled);
791 synchronize_sched();
793 for (i = 0; i < nr_pages; i++) {
794 if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
795 return;
796 p = pages->next;
797 bpage = list_entry(p, struct buffer_page, list);
798 list_del_init(&bpage->list);
799 list_add_tail(&bpage->list, &cpu_buffer->pages);
801 rb_reset_cpu(cpu_buffer);
803 rb_check_pages(cpu_buffer);
805 atomic_dec(&cpu_buffer->record_disabled);
809 * ring_buffer_resize - resize the ring buffer
810 * @buffer: the buffer to resize.
811 * @size: the new size.
813 * The tracer is responsible for making sure that the buffer is
814 * not being used while changing the size.
815 * Note: We may be able to change the above requirement by using
816 * RCU synchronizations.
818 * Minimum size is 2 * BUF_PAGE_SIZE.
820 * Returns -1 on failure.
822 int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
824 struct ring_buffer_per_cpu *cpu_buffer;
825 unsigned nr_pages, rm_pages, new_pages;
826 struct buffer_page *bpage, *tmp;
827 unsigned long buffer_size;
828 unsigned long addr;
829 LIST_HEAD(pages);
830 int i, cpu;
833 * Always succeed at resizing a non-existent buffer:
835 if (!buffer)
836 return size;
838 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
839 size *= BUF_PAGE_SIZE;
840 buffer_size = buffer->pages * BUF_PAGE_SIZE;
842 /* we need a minimum of two pages */
843 if (size < BUF_PAGE_SIZE * 2)
844 size = BUF_PAGE_SIZE * 2;
846 if (size == buffer_size)
847 return size;
849 mutex_lock(&buffer->mutex);
850 get_online_cpus();
852 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
854 if (size < buffer_size) {
856 /* easy case, just free pages */
857 if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
858 goto out_fail;
860 rm_pages = buffer->pages - nr_pages;
862 for_each_buffer_cpu(buffer, cpu) {
863 cpu_buffer = buffer->buffers[cpu];
864 rb_remove_pages(cpu_buffer, rm_pages);
866 goto out;
870 * This is a bit more difficult. We only want to add pages
871 * when we can allocate enough for all CPUs. We do this
872 * by allocating all the pages and storing them on a local
873 * link list. If we succeed in our allocation, then we
874 * add these pages to the cpu_buffers. Otherwise we just free
875 * them all and return -ENOMEM;
877 if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
878 goto out_fail;
880 new_pages = nr_pages - buffer->pages;
882 for_each_buffer_cpu(buffer, cpu) {
883 for (i = 0; i < new_pages; i++) {
884 bpage = kzalloc_node(ALIGN(sizeof(*bpage),
885 cache_line_size()),
886 GFP_KERNEL, cpu_to_node(cpu));
887 if (!bpage)
888 goto free_pages;
889 list_add(&bpage->list, &pages);
890 addr = __get_free_page(GFP_KERNEL);
891 if (!addr)
892 goto free_pages;
893 bpage->page = (void *)addr;
894 rb_init_page(bpage->page);
898 for_each_buffer_cpu(buffer, cpu) {
899 cpu_buffer = buffer->buffers[cpu];
900 rb_insert_pages(cpu_buffer, &pages, new_pages);
903 if (RB_WARN_ON(buffer, !list_empty(&pages)))
904 goto out_fail;
906 out:
907 buffer->pages = nr_pages;
908 put_online_cpus();
909 mutex_unlock(&buffer->mutex);
911 return size;
913 free_pages:
914 list_for_each_entry_safe(bpage, tmp, &pages, list) {
915 list_del_init(&bpage->list);
916 free_buffer_page(bpage);
918 put_online_cpus();
919 mutex_unlock(&buffer->mutex);
920 return -ENOMEM;
923 * Something went totally wrong, and we are too paranoid
924 * to even clean up the mess.
926 out_fail:
927 put_online_cpus();
928 mutex_unlock(&buffer->mutex);
929 return -1;
931 EXPORT_SYMBOL_GPL(ring_buffer_resize);
933 static inline void *
934 __rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
936 return bpage->data + index;
939 static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
941 return bpage->page->data + index;
944 static inline struct ring_buffer_event *
945 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
947 return __rb_page_index(cpu_buffer->reader_page,
948 cpu_buffer->reader_page->read);
951 static inline struct ring_buffer_event *
952 rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
954 return __rb_page_index(cpu_buffer->head_page,
955 cpu_buffer->head_page->read);
958 static inline struct ring_buffer_event *
959 rb_iter_head_event(struct ring_buffer_iter *iter)
961 return __rb_page_index(iter->head_page, iter->head);
964 static inline unsigned rb_page_write(struct buffer_page *bpage)
966 return local_read(&bpage->write);
969 static inline unsigned rb_page_commit(struct buffer_page *bpage)
971 return local_read(&bpage->page->commit);
974 /* Size is determined by what has been commited */
975 static inline unsigned rb_page_size(struct buffer_page *bpage)
977 return rb_page_commit(bpage);
980 static inline unsigned
981 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
983 return rb_page_commit(cpu_buffer->commit_page);
986 static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
988 return rb_page_commit(cpu_buffer->head_page);
991 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
992 struct buffer_page **bpage)
994 struct list_head *p = (*bpage)->list.next;
996 if (p == &cpu_buffer->pages)
997 p = p->next;
999 *bpage = list_entry(p, struct buffer_page, list);
1002 static inline unsigned
1003 rb_event_index(struct ring_buffer_event *event)
1005 unsigned long addr = (unsigned long)event;
1007 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1010 static inline int
1011 rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1012 struct ring_buffer_event *event)
1014 unsigned long addr = (unsigned long)event;
1015 unsigned long index;
1017 index = rb_event_index(event);
1018 addr &= PAGE_MASK;
1020 return cpu_buffer->commit_page->page == (void *)addr &&
1021 rb_commit_index(cpu_buffer) == index;
1024 static void
1025 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1028 * We only race with interrupts and NMIs on this CPU.
1029 * If we own the commit event, then we can commit
1030 * all others that interrupted us, since the interruptions
1031 * are in stack format (they finish before they come
1032 * back to us). This allows us to do a simple loop to
1033 * assign the commit to the tail.
1035 again:
1036 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
1037 cpu_buffer->commit_page->page->commit =
1038 cpu_buffer->commit_page->write;
1039 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1040 cpu_buffer->write_stamp =
1041 cpu_buffer->commit_page->page->time_stamp;
1042 /* add barrier to keep gcc from optimizing too much */
1043 barrier();
1045 while (rb_commit_index(cpu_buffer) !=
1046 rb_page_write(cpu_buffer->commit_page)) {
1047 cpu_buffer->commit_page->page->commit =
1048 cpu_buffer->commit_page->write;
1049 barrier();
1052 /* again, keep gcc from optimizing */
1053 barrier();
1056 * If an interrupt came in just after the first while loop
1057 * and pushed the tail page forward, we will be left with
1058 * a dangling commit that will never go forward.
1060 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1061 goto again;
1064 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1066 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
1067 cpu_buffer->reader_page->read = 0;
1070 static void rb_inc_iter(struct ring_buffer_iter *iter)
1072 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1075 * The iterator could be on the reader page (it starts there).
1076 * But the head could have moved, since the reader was
1077 * found. Check for this case and assign the iterator
1078 * to the head page instead of next.
1080 if (iter->head_page == cpu_buffer->reader_page)
1081 iter->head_page = cpu_buffer->head_page;
1082 else
1083 rb_inc_page(cpu_buffer, &iter->head_page);
1085 iter->read_stamp = iter->head_page->page->time_stamp;
1086 iter->head = 0;
1090 * ring_buffer_update_event - update event type and data
1091 * @event: the even to update
1092 * @type: the type of event
1093 * @length: the size of the event field in the ring buffer
1095 * Update the type and data fields of the event. The length
1096 * is the actual size that is written to the ring buffer,
1097 * and with this, we can determine what to place into the
1098 * data field.
1100 static void
1101 rb_update_event(struct ring_buffer_event *event,
1102 unsigned type, unsigned length)
1104 event->type_len = type;
1106 switch (type) {
1108 case RINGBUF_TYPE_PADDING:
1109 case RINGBUF_TYPE_TIME_EXTEND:
1110 case RINGBUF_TYPE_TIME_STAMP:
1111 break;
1113 case 0:
1114 length -= RB_EVNT_HDR_SIZE;
1115 if (length > RB_MAX_SMALL_DATA)
1116 event->array[0] = length;
1117 else
1118 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
1119 break;
1120 default:
1121 BUG();
1125 static unsigned rb_calculate_event_length(unsigned length)
1127 struct ring_buffer_event event; /* Used only for sizeof array */
1129 /* zero length can cause confusions */
1130 if (!length)
1131 length = 1;
1133 if (length > RB_MAX_SMALL_DATA)
1134 length += sizeof(event.array[0]);
1136 length += RB_EVNT_HDR_SIZE;
1137 length = ALIGN(length, RB_ALIGNMENT);
1139 return length;
1142 static inline void
1143 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
1144 struct buffer_page *tail_page,
1145 unsigned long tail, unsigned long length)
1147 struct ring_buffer_event *event;
1150 * Only the event that crossed the page boundary
1151 * must fill the old tail_page with padding.
1153 if (tail >= BUF_PAGE_SIZE) {
1154 local_sub(length, &tail_page->write);
1155 return;
1158 event = __rb_page_index(tail_page, tail);
1159 kmemcheck_annotate_bitfield(event, bitfield);
1162 * If this event is bigger than the minimum size, then
1163 * we need to be careful that we don't subtract the
1164 * write counter enough to allow another writer to slip
1165 * in on this page.
1166 * We put in a discarded commit instead, to make sure
1167 * that this space is not used again.
1169 * If we are less than the minimum size, we don't need to
1170 * worry about it.
1172 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
1173 /* No room for any events */
1175 /* Mark the rest of the page with padding */
1176 rb_event_set_padding(event);
1178 /* Set the write back to the previous setting */
1179 local_sub(length, &tail_page->write);
1180 return;
1183 /* Put in a discarded event */
1184 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
1185 event->type_len = RINGBUF_TYPE_PADDING;
1186 /* time delta must be non zero */
1187 event->time_delta = 1;
1188 /* Account for this as an entry */
1189 local_inc(&tail_page->entries);
1190 local_inc(&cpu_buffer->entries);
1192 /* Set write to end of buffer */
1193 length = (tail + length) - BUF_PAGE_SIZE;
1194 local_sub(length, &tail_page->write);
1197 static struct ring_buffer_event *
1198 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
1199 unsigned long length, unsigned long tail,
1200 struct buffer_page *commit_page,
1201 struct buffer_page *tail_page, u64 *ts)
1203 struct buffer_page *next_page, *head_page, *reader_page;
1204 struct ring_buffer *buffer = cpu_buffer->buffer;
1205 bool lock_taken = false;
1206 unsigned long flags;
1208 next_page = tail_page;
1210 local_irq_save(flags);
1212 * Since the write to the buffer is still not
1213 * fully lockless, we must be careful with NMIs.
1214 * The locks in the writers are taken when a write
1215 * crosses to a new page. The locks protect against
1216 * races with the readers (this will soon be fixed
1217 * with a lockless solution).
1219 * Because we can not protect against NMIs, and we
1220 * want to keep traces reentrant, we need to manage
1221 * what happens when we are in an NMI.
1223 * NMIs can happen after we take the lock.
1224 * If we are in an NMI, only take the lock
1225 * if it is not already taken. Otherwise
1226 * simply fail.
1228 if (unlikely(in_nmi())) {
1229 if (!__raw_spin_trylock(&cpu_buffer->lock)) {
1230 cpu_buffer->nmi_dropped++;
1231 goto out_reset;
1233 } else
1234 __raw_spin_lock(&cpu_buffer->lock);
1236 lock_taken = true;
1238 rb_inc_page(cpu_buffer, &next_page);
1240 head_page = cpu_buffer->head_page;
1241 reader_page = cpu_buffer->reader_page;
1243 /* we grabbed the lock before incrementing */
1244 if (RB_WARN_ON(cpu_buffer, next_page == reader_page))
1245 goto out_reset;
1248 * If for some reason, we had an interrupt storm that made
1249 * it all the way around the buffer, bail, and warn
1250 * about it.
1252 if (unlikely(next_page == commit_page)) {
1253 cpu_buffer->commit_overrun++;
1254 goto out_reset;
1257 if (next_page == head_page) {
1258 if (!(buffer->flags & RB_FL_OVERWRITE))
1259 goto out_reset;
1261 /* tail_page has not moved yet? */
1262 if (tail_page == cpu_buffer->tail_page) {
1263 /* count overflows */
1264 cpu_buffer->overrun +=
1265 local_read(&head_page->entries);
1267 rb_inc_page(cpu_buffer, &head_page);
1268 cpu_buffer->head_page = head_page;
1269 cpu_buffer->head_page->read = 0;
1274 * If the tail page is still the same as what we think
1275 * it is, then it is up to us to update the tail
1276 * pointer.
1278 if (tail_page == cpu_buffer->tail_page) {
1279 local_set(&next_page->write, 0);
1280 local_set(&next_page->entries, 0);
1281 local_set(&next_page->page->commit, 0);
1282 cpu_buffer->tail_page = next_page;
1284 /* reread the time stamp */
1285 *ts = rb_time_stamp(buffer, cpu_buffer->cpu);
1286 cpu_buffer->tail_page->page->time_stamp = *ts;
1289 rb_reset_tail(cpu_buffer, tail_page, tail, length);
1291 __raw_spin_unlock(&cpu_buffer->lock);
1292 local_irq_restore(flags);
1294 /* fail and let the caller try again */
1295 return ERR_PTR(-EAGAIN);
1297 out_reset:
1298 /* reset write */
1299 rb_reset_tail(cpu_buffer, tail_page, tail, length);
1301 if (likely(lock_taken))
1302 __raw_spin_unlock(&cpu_buffer->lock);
1303 local_irq_restore(flags);
1304 return NULL;
1307 static struct ring_buffer_event *
1308 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
1309 unsigned type, unsigned long length, u64 *ts)
1311 struct buffer_page *tail_page, *commit_page;
1312 struct ring_buffer_event *event;
1313 unsigned long tail, write;
1315 commit_page = cpu_buffer->commit_page;
1316 /* we just need to protect against interrupts */
1317 barrier();
1318 tail_page = cpu_buffer->tail_page;
1319 write = local_add_return(length, &tail_page->write);
1320 tail = write - length;
1322 /* See if we shot pass the end of this buffer page */
1323 if (write > BUF_PAGE_SIZE)
1324 return rb_move_tail(cpu_buffer, length, tail,
1325 commit_page, tail_page, ts);
1327 /* We reserved something on the buffer */
1329 event = __rb_page_index(tail_page, tail);
1330 kmemcheck_annotate_bitfield(event, bitfield);
1331 rb_update_event(event, type, length);
1333 /* The passed in type is zero for DATA */
1334 if (likely(!type))
1335 local_inc(&tail_page->entries);
1338 * If this is the first commit on the page, then update
1339 * its timestamp.
1341 if (!tail)
1342 tail_page->page->time_stamp = *ts;
1344 return event;
1347 static inline int
1348 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
1349 struct ring_buffer_event *event)
1351 unsigned long new_index, old_index;
1352 struct buffer_page *bpage;
1353 unsigned long index;
1354 unsigned long addr;
1356 new_index = rb_event_index(event);
1357 old_index = new_index + rb_event_length(event);
1358 addr = (unsigned long)event;
1359 addr &= PAGE_MASK;
1361 bpage = cpu_buffer->tail_page;
1363 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
1365 * This is on the tail page. It is possible that
1366 * a write could come in and move the tail page
1367 * and write to the next page. That is fine
1368 * because we just shorten what is on this page.
1370 index = local_cmpxchg(&bpage->write, old_index, new_index);
1371 if (index == old_index)
1372 return 1;
1375 /* could not discard */
1376 return 0;
1379 static int
1380 rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
1381 u64 *ts, u64 *delta)
1383 struct ring_buffer_event *event;
1384 static int once;
1385 int ret;
1387 if (unlikely(*delta > (1ULL << 59) && !once++)) {
1388 printk(KERN_WARNING "Delta way too big! %llu"
1389 " ts=%llu write stamp = %llu\n",
1390 (unsigned long long)*delta,
1391 (unsigned long long)*ts,
1392 (unsigned long long)cpu_buffer->write_stamp);
1393 WARN_ON(1);
1397 * The delta is too big, we to add a
1398 * new timestamp.
1400 event = __rb_reserve_next(cpu_buffer,
1401 RINGBUF_TYPE_TIME_EXTEND,
1402 RB_LEN_TIME_EXTEND,
1403 ts);
1404 if (!event)
1405 return -EBUSY;
1407 if (PTR_ERR(event) == -EAGAIN)
1408 return -EAGAIN;
1410 /* Only a commited time event can update the write stamp */
1411 if (rb_event_is_commit(cpu_buffer, event)) {
1413 * If this is the first on the page, then it was
1414 * updated with the page itself. Try to discard it
1415 * and if we can't just make it zero.
1417 if (rb_event_index(event)) {
1418 event->time_delta = *delta & TS_MASK;
1419 event->array[0] = *delta >> TS_SHIFT;
1420 } else {
1421 /* try to discard, since we do not need this */
1422 if (!rb_try_to_discard(cpu_buffer, event)) {
1423 /* nope, just zero it */
1424 event->time_delta = 0;
1425 event->array[0] = 0;
1428 cpu_buffer->write_stamp = *ts;
1429 /* let the caller know this was the commit */
1430 ret = 1;
1431 } else {
1432 /* Try to discard the event */
1433 if (!rb_try_to_discard(cpu_buffer, event)) {
1434 /* Darn, this is just wasted space */
1435 event->time_delta = 0;
1436 event->array[0] = 0;
1438 ret = 0;
1441 *delta = 0;
1443 return ret;
1446 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
1448 local_inc(&cpu_buffer->committing);
1449 local_inc(&cpu_buffer->commits);
1452 static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
1454 unsigned long commits;
1456 if (RB_WARN_ON(cpu_buffer,
1457 !local_read(&cpu_buffer->committing)))
1458 return;
1460 again:
1461 commits = local_read(&cpu_buffer->commits);
1462 /* synchronize with interrupts */
1463 barrier();
1464 if (local_read(&cpu_buffer->committing) == 1)
1465 rb_set_commit_to_write(cpu_buffer);
1467 local_dec(&cpu_buffer->committing);
1469 /* synchronize with interrupts */
1470 barrier();
1473 * Need to account for interrupts coming in between the
1474 * updating of the commit page and the clearing of the
1475 * committing counter.
1477 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
1478 !local_read(&cpu_buffer->committing)) {
1479 local_inc(&cpu_buffer->committing);
1480 goto again;
1484 static struct ring_buffer_event *
1485 rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
1486 unsigned long length)
1488 struct ring_buffer_event *event;
1489 u64 ts, delta = 0;
1490 int commit = 0;
1491 int nr_loops = 0;
1493 rb_start_commit(cpu_buffer);
1495 length = rb_calculate_event_length(length);
1496 again:
1498 * We allow for interrupts to reenter here and do a trace.
1499 * If one does, it will cause this original code to loop
1500 * back here. Even with heavy interrupts happening, this
1501 * should only happen a few times in a row. If this happens
1502 * 1000 times in a row, there must be either an interrupt
1503 * storm or we have something buggy.
1504 * Bail!
1506 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
1507 goto out_fail;
1509 ts = rb_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);
1512 * Only the first commit can update the timestamp.
1513 * Yes there is a race here. If an interrupt comes in
1514 * just after the conditional and it traces too, then it
1515 * will also check the deltas. More than one timestamp may
1516 * also be made. But only the entry that did the actual
1517 * commit will be something other than zero.
1519 if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
1520 rb_page_write(cpu_buffer->tail_page) ==
1521 rb_commit_index(cpu_buffer))) {
1522 u64 diff;
1524 diff = ts - cpu_buffer->write_stamp;
1526 /* make sure this diff is calculated here */
1527 barrier();
1529 /* Did the write stamp get updated already? */
1530 if (unlikely(ts < cpu_buffer->write_stamp))
1531 goto get_event;
1533 delta = diff;
1534 if (unlikely(test_time_stamp(delta))) {
1536 commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
1537 if (commit == -EBUSY)
1538 goto out_fail;
1540 if (commit == -EAGAIN)
1541 goto again;
1543 RB_WARN_ON(cpu_buffer, commit < 0);
1547 get_event:
1548 event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
1549 if (unlikely(PTR_ERR(event) == -EAGAIN))
1550 goto again;
1552 if (!event)
1553 goto out_fail;
1555 if (!rb_event_is_commit(cpu_buffer, event))
1556 delta = 0;
1558 event->time_delta = delta;
1560 return event;
1562 out_fail:
1563 rb_end_commit(cpu_buffer);
1564 return NULL;
1567 #ifdef CONFIG_TRACING
1569 #define TRACE_RECURSIVE_DEPTH 16
1571 static int trace_recursive_lock(void)
1573 current->trace_recursion++;
1575 if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
1576 return 0;
1578 /* Disable all tracing before we do anything else */
1579 tracing_off_permanent();
1581 printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
1582 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
1583 current->trace_recursion,
1584 hardirq_count() >> HARDIRQ_SHIFT,
1585 softirq_count() >> SOFTIRQ_SHIFT,
1586 in_nmi());
1588 WARN_ON_ONCE(1);
1589 return -1;
1592 static void trace_recursive_unlock(void)
1594 WARN_ON_ONCE(!current->trace_recursion);
1596 current->trace_recursion--;
1599 #else
1601 #define trace_recursive_lock() (0)
1602 #define trace_recursive_unlock() do { } while (0)
1604 #endif
1606 static DEFINE_PER_CPU(int, rb_need_resched);
1609 * ring_buffer_lock_reserve - reserve a part of the buffer
1610 * @buffer: the ring buffer to reserve from
1611 * @length: the length of the data to reserve (excluding event header)
1613 * Returns a reseverd event on the ring buffer to copy directly to.
1614 * The user of this interface will need to get the body to write into
1615 * and can use the ring_buffer_event_data() interface.
1617 * The length is the length of the data needed, not the event length
1618 * which also includes the event header.
1620 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
1621 * If NULL is returned, then nothing has been allocated or locked.
1623 struct ring_buffer_event *
1624 ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
1626 struct ring_buffer_per_cpu *cpu_buffer;
1627 struct ring_buffer_event *event;
1628 int cpu, resched;
1630 if (ring_buffer_flags != RB_BUFFERS_ON)
1631 return NULL;
1633 if (atomic_read(&buffer->record_disabled))
1634 return NULL;
1636 /* If we are tracing schedule, we don't want to recurse */
1637 resched = ftrace_preempt_disable();
1639 if (trace_recursive_lock())
1640 goto out_nocheck;
1642 cpu = raw_smp_processor_id();
1644 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1645 goto out;
1647 cpu_buffer = buffer->buffers[cpu];
1649 if (atomic_read(&cpu_buffer->record_disabled))
1650 goto out;
1652 if (length > BUF_MAX_DATA_SIZE)
1653 goto out;
1655 event = rb_reserve_next_event(cpu_buffer, length);
1656 if (!event)
1657 goto out;
1660 * Need to store resched state on this cpu.
1661 * Only the first needs to.
1664 if (preempt_count() == 1)
1665 per_cpu(rb_need_resched, cpu) = resched;
1667 return event;
1669 out:
1670 trace_recursive_unlock();
1672 out_nocheck:
1673 ftrace_preempt_enable(resched);
1674 return NULL;
1676 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
1678 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
1679 struct ring_buffer_event *event)
1681 local_inc(&cpu_buffer->entries);
1684 * The event first in the commit queue updates the
1685 * time stamp.
1687 if (rb_event_is_commit(cpu_buffer, event))
1688 cpu_buffer->write_stamp += event->time_delta;
1690 rb_end_commit(cpu_buffer);
1694 * ring_buffer_unlock_commit - commit a reserved
1695 * @buffer: The buffer to commit to
1696 * @event: The event pointer to commit.
1698 * This commits the data to the ring buffer, and releases any locks held.
1700 * Must be paired with ring_buffer_lock_reserve.
1702 int ring_buffer_unlock_commit(struct ring_buffer *buffer,
1703 struct ring_buffer_event *event)
1705 struct ring_buffer_per_cpu *cpu_buffer;
1706 int cpu = raw_smp_processor_id();
1708 cpu_buffer = buffer->buffers[cpu];
1710 rb_commit(cpu_buffer, event);
1712 trace_recursive_unlock();
1715 * Only the last preempt count needs to restore preemption.
1717 if (preempt_count() == 1)
1718 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
1719 else
1720 preempt_enable_no_resched_notrace();
1722 return 0;
1724 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
1726 static inline void rb_event_discard(struct ring_buffer_event *event)
1728 /* array[0] holds the actual length for the discarded event */
1729 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
1730 event->type_len = RINGBUF_TYPE_PADDING;
1731 /* time delta must be non zero */
1732 if (!event->time_delta)
1733 event->time_delta = 1;
1737 * ring_buffer_event_discard - discard any event in the ring buffer
1738 * @event: the event to discard
1740 * Sometimes a event that is in the ring buffer needs to be ignored.
1741 * This function lets the user discard an event in the ring buffer
1742 * and then that event will not be read later.
1744 * Note, it is up to the user to be careful with this, and protect
1745 * against races. If the user discards an event that has been consumed
1746 * it is possible that it could corrupt the ring buffer.
1748 void ring_buffer_event_discard(struct ring_buffer_event *event)
1750 rb_event_discard(event);
1752 EXPORT_SYMBOL_GPL(ring_buffer_event_discard);
1755 * ring_buffer_commit_discard - discard an event that has not been committed
1756 * @buffer: the ring buffer
1757 * @event: non committed event to discard
1759 * This is similar to ring_buffer_event_discard but must only be
1760 * performed on an event that has not been committed yet. The difference
1761 * is that this will also try to free the event from the ring buffer
1762 * if another event has not been added behind it.
1764 * If another event has been added behind it, it will set the event
1765 * up as discarded, and perform the commit.
1767 * If this function is called, do not call ring_buffer_unlock_commit on
1768 * the event.
1770 void ring_buffer_discard_commit(struct ring_buffer *buffer,
1771 struct ring_buffer_event *event)
1773 struct ring_buffer_per_cpu *cpu_buffer;
1774 int cpu;
1776 /* The event is discarded regardless */
1777 rb_event_discard(event);
1779 cpu = smp_processor_id();
1780 cpu_buffer = buffer->buffers[cpu];
1783 * This must only be called if the event has not been
1784 * committed yet. Thus we can assume that preemption
1785 * is still disabled.
1787 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
1789 if (rb_try_to_discard(cpu_buffer, event))
1790 goto out;
1793 * The commit is still visible by the reader, so we
1794 * must increment entries.
1796 local_inc(&cpu_buffer->entries);
1797 out:
1798 rb_end_commit(cpu_buffer);
1800 trace_recursive_unlock();
1803 * Only the last preempt count needs to restore preemption.
1805 if (preempt_count() == 1)
1806 ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
1807 else
1808 preempt_enable_no_resched_notrace();
1811 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
1814 * ring_buffer_write - write data to the buffer without reserving
1815 * @buffer: The ring buffer to write to.
1816 * @length: The length of the data being written (excluding the event header)
1817 * @data: The data to write to the buffer.
1819 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
1820 * one function. If you already have the data to write to the buffer, it
1821 * may be easier to simply call this function.
1823 * Note, like ring_buffer_lock_reserve, the length is the length of the data
1824 * and not the length of the event which would hold the header.
1826 int ring_buffer_write(struct ring_buffer *buffer,
1827 unsigned long length,
1828 void *data)
1830 struct ring_buffer_per_cpu *cpu_buffer;
1831 struct ring_buffer_event *event;
1832 void *body;
1833 int ret = -EBUSY;
1834 int cpu, resched;
1836 if (ring_buffer_flags != RB_BUFFERS_ON)
1837 return -EBUSY;
1839 if (atomic_read(&buffer->record_disabled))
1840 return -EBUSY;
1842 resched = ftrace_preempt_disable();
1844 cpu = raw_smp_processor_id();
1846 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1847 goto out;
1849 cpu_buffer = buffer->buffers[cpu];
1851 if (atomic_read(&cpu_buffer->record_disabled))
1852 goto out;
1854 if (length > BUF_MAX_DATA_SIZE)
1855 goto out;
1857 event = rb_reserve_next_event(cpu_buffer, length);
1858 if (!event)
1859 goto out;
1861 body = rb_event_data(event);
1863 memcpy(body, data, length);
1865 rb_commit(cpu_buffer, event);
1867 ret = 0;
1868 out:
1869 ftrace_preempt_enable(resched);
1871 return ret;
1873 EXPORT_SYMBOL_GPL(ring_buffer_write);
1875 static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
1877 struct buffer_page *reader = cpu_buffer->reader_page;
1878 struct buffer_page *head = cpu_buffer->head_page;
1879 struct buffer_page *commit = cpu_buffer->commit_page;
1881 return reader->read == rb_page_commit(reader) &&
1882 (commit == reader ||
1883 (commit == head &&
1884 head->read == rb_page_commit(commit)));
1888 * ring_buffer_record_disable - stop all writes into the buffer
1889 * @buffer: The ring buffer to stop writes to.
1891 * This prevents all writes to the buffer. Any attempt to write
1892 * to the buffer after this will fail and return NULL.
1894 * The caller should call synchronize_sched() after this.
1896 void ring_buffer_record_disable(struct ring_buffer *buffer)
1898 atomic_inc(&buffer->record_disabled);
1900 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
1903 * ring_buffer_record_enable - enable writes to the buffer
1904 * @buffer: The ring buffer to enable writes
1906 * Note, multiple disables will need the same number of enables
1907 * to truely enable the writing (much like preempt_disable).
1909 void ring_buffer_record_enable(struct ring_buffer *buffer)
1911 atomic_dec(&buffer->record_disabled);
1913 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
1916 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
1917 * @buffer: The ring buffer to stop writes to.
1918 * @cpu: The CPU buffer to stop
1920 * This prevents all writes to the buffer. Any attempt to write
1921 * to the buffer after this will fail and return NULL.
1923 * The caller should call synchronize_sched() after this.
1925 void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
1927 struct ring_buffer_per_cpu *cpu_buffer;
1929 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1930 return;
1932 cpu_buffer = buffer->buffers[cpu];
1933 atomic_inc(&cpu_buffer->record_disabled);
1935 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
1938 * ring_buffer_record_enable_cpu - enable writes to the buffer
1939 * @buffer: The ring buffer to enable writes
1940 * @cpu: The CPU to enable.
1942 * Note, multiple disables will need the same number of enables
1943 * to truely enable the writing (much like preempt_disable).
1945 void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
1947 struct ring_buffer_per_cpu *cpu_buffer;
1949 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1950 return;
1952 cpu_buffer = buffer->buffers[cpu];
1953 atomic_dec(&cpu_buffer->record_disabled);
1955 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
1958 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
1959 * @buffer: The ring buffer
1960 * @cpu: The per CPU buffer to get the entries from.
1962 unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
1964 struct ring_buffer_per_cpu *cpu_buffer;
1965 unsigned long ret;
1967 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1968 return 0;
1970 cpu_buffer = buffer->buffers[cpu];
1971 ret = (local_read(&cpu_buffer->entries) - cpu_buffer->overrun)
1972 - cpu_buffer->read;
1974 return ret;
1976 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
1979 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
1980 * @buffer: The ring buffer
1981 * @cpu: The per CPU buffer to get the number of overruns from
1983 unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
1985 struct ring_buffer_per_cpu *cpu_buffer;
1986 unsigned long ret;
1988 if (!cpumask_test_cpu(cpu, buffer->cpumask))
1989 return 0;
1991 cpu_buffer = buffer->buffers[cpu];
1992 ret = cpu_buffer->overrun;
1994 return ret;
1996 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
1999 * ring_buffer_nmi_dropped_cpu - get the number of nmis that were dropped
2000 * @buffer: The ring buffer
2001 * @cpu: The per CPU buffer to get the number of overruns from
2003 unsigned long ring_buffer_nmi_dropped_cpu(struct ring_buffer *buffer, int cpu)
2005 struct ring_buffer_per_cpu *cpu_buffer;
2006 unsigned long ret;
2008 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2009 return 0;
2011 cpu_buffer = buffer->buffers[cpu];
2012 ret = cpu_buffer->nmi_dropped;
2014 return ret;
2016 EXPORT_SYMBOL_GPL(ring_buffer_nmi_dropped_cpu);
2019 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
2020 * @buffer: The ring buffer
2021 * @cpu: The per CPU buffer to get the number of overruns from
2023 unsigned long
2024 ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
2026 struct ring_buffer_per_cpu *cpu_buffer;
2027 unsigned long ret;
2029 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2030 return 0;
2032 cpu_buffer = buffer->buffers[cpu];
2033 ret = cpu_buffer->commit_overrun;
2035 return ret;
2037 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
2040 * ring_buffer_entries - get the number of entries in a buffer
2041 * @buffer: The ring buffer
2043 * Returns the total number of entries in the ring buffer
2044 * (all CPU entries)
2046 unsigned long ring_buffer_entries(struct ring_buffer *buffer)
2048 struct ring_buffer_per_cpu *cpu_buffer;
2049 unsigned long entries = 0;
2050 int cpu;
2052 /* if you care about this being correct, lock the buffer */
2053 for_each_buffer_cpu(buffer, cpu) {
2054 cpu_buffer = buffer->buffers[cpu];
2055 entries += (local_read(&cpu_buffer->entries) -
2056 cpu_buffer->overrun) - cpu_buffer->read;
2059 return entries;
2061 EXPORT_SYMBOL_GPL(ring_buffer_entries);
2064 * ring_buffer_overrun_cpu - get the number of overruns in buffer
2065 * @buffer: The ring buffer
2067 * Returns the total number of overruns in the ring buffer
2068 * (all CPU entries)
2070 unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
2072 struct ring_buffer_per_cpu *cpu_buffer;
2073 unsigned long overruns = 0;
2074 int cpu;
2076 /* if you care about this being correct, lock the buffer */
2077 for_each_buffer_cpu(buffer, cpu) {
2078 cpu_buffer = buffer->buffers[cpu];
2079 overruns += cpu_buffer->overrun;
2082 return overruns;
2084 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
2086 static void rb_iter_reset(struct ring_buffer_iter *iter)
2088 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2090 /* Iterator usage is expected to have record disabled */
2091 if (list_empty(&cpu_buffer->reader_page->list)) {
2092 iter->head_page = cpu_buffer->head_page;
2093 iter->head = cpu_buffer->head_page->read;
2094 } else {
2095 iter->head_page = cpu_buffer->reader_page;
2096 iter->head = cpu_buffer->reader_page->read;
2098 if (iter->head)
2099 iter->read_stamp = cpu_buffer->read_stamp;
2100 else
2101 iter->read_stamp = iter->head_page->page->time_stamp;
2105 * ring_buffer_iter_reset - reset an iterator
2106 * @iter: The iterator to reset
2108 * Resets the iterator, so that it will start from the beginning
2109 * again.
2111 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
2113 struct ring_buffer_per_cpu *cpu_buffer;
2114 unsigned long flags;
2116 if (!iter)
2117 return;
2119 cpu_buffer = iter->cpu_buffer;
2121 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2122 rb_iter_reset(iter);
2123 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2125 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
2128 * ring_buffer_iter_empty - check if an iterator has no more to read
2129 * @iter: The iterator to check
2131 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
2133 struct ring_buffer_per_cpu *cpu_buffer;
2135 cpu_buffer = iter->cpu_buffer;
2137 return iter->head_page == cpu_buffer->commit_page &&
2138 iter->head == rb_commit_index(cpu_buffer);
2140 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
2142 static void
2143 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2144 struct ring_buffer_event *event)
2146 u64 delta;
2148 switch (event->type_len) {
2149 case RINGBUF_TYPE_PADDING:
2150 return;
2152 case RINGBUF_TYPE_TIME_EXTEND:
2153 delta = event->array[0];
2154 delta <<= TS_SHIFT;
2155 delta += event->time_delta;
2156 cpu_buffer->read_stamp += delta;
2157 return;
2159 case RINGBUF_TYPE_TIME_STAMP:
2160 /* FIXME: not implemented */
2161 return;
2163 case RINGBUF_TYPE_DATA:
2164 cpu_buffer->read_stamp += event->time_delta;
2165 return;
2167 default:
2168 BUG();
2170 return;
2173 static void
2174 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
2175 struct ring_buffer_event *event)
2177 u64 delta;
2179 switch (event->type_len) {
2180 case RINGBUF_TYPE_PADDING:
2181 return;
2183 case RINGBUF_TYPE_TIME_EXTEND:
2184 delta = event->array[0];
2185 delta <<= TS_SHIFT;
2186 delta += event->time_delta;
2187 iter->read_stamp += delta;
2188 return;
2190 case RINGBUF_TYPE_TIME_STAMP:
2191 /* FIXME: not implemented */
2192 return;
2194 case RINGBUF_TYPE_DATA:
2195 iter->read_stamp += event->time_delta;
2196 return;
2198 default:
2199 BUG();
2201 return;
2204 static struct buffer_page *
2205 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
2207 struct buffer_page *reader = NULL;
2208 unsigned long flags;
2209 int nr_loops = 0;
2211 local_irq_save(flags);
2212 __raw_spin_lock(&cpu_buffer->lock);
2214 again:
2216 * This should normally only loop twice. But because the
2217 * start of the reader inserts an empty page, it causes
2218 * a case where we will loop three times. There should be no
2219 * reason to loop four times (that I know of).
2221 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
2222 reader = NULL;
2223 goto out;
2226 reader = cpu_buffer->reader_page;
2228 /* If there's more to read, return this page */
2229 if (cpu_buffer->reader_page->read < rb_page_size(reader))
2230 goto out;
2232 /* Never should we have an index greater than the size */
2233 if (RB_WARN_ON(cpu_buffer,
2234 cpu_buffer->reader_page->read > rb_page_size(reader)))
2235 goto out;
2237 /* check if we caught up to the tail */
2238 reader = NULL;
2239 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
2240 goto out;
2243 * Splice the empty reader page into the list around the head.
2244 * Reset the reader page to size zero.
2247 reader = cpu_buffer->head_page;
2248 cpu_buffer->reader_page->list.next = reader->list.next;
2249 cpu_buffer->reader_page->list.prev = reader->list.prev;
2251 local_set(&cpu_buffer->reader_page->write, 0);
2252 local_set(&cpu_buffer->reader_page->entries, 0);
2253 local_set(&cpu_buffer->reader_page->page->commit, 0);
2255 /* Make the reader page now replace the head */
2256 reader->list.prev->next = &cpu_buffer->reader_page->list;
2257 reader->list.next->prev = &cpu_buffer->reader_page->list;
2260 * If the tail is on the reader, then we must set the head
2261 * to the inserted page, otherwise we set it one before.
2263 cpu_buffer->head_page = cpu_buffer->reader_page;
2265 if (cpu_buffer->commit_page != reader)
2266 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
2268 /* Finally update the reader page to the new head */
2269 cpu_buffer->reader_page = reader;
2270 rb_reset_reader_page(cpu_buffer);
2272 goto again;
2274 out:
2275 __raw_spin_unlock(&cpu_buffer->lock);
2276 local_irq_restore(flags);
2278 return reader;
2281 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
2283 struct ring_buffer_event *event;
2284 struct buffer_page *reader;
2285 unsigned length;
2287 reader = rb_get_reader_page(cpu_buffer);
2289 /* This function should not be called when buffer is empty */
2290 if (RB_WARN_ON(cpu_buffer, !reader))
2291 return;
2293 event = rb_reader_event(cpu_buffer);
2295 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX
2296 || rb_discarded_event(event))
2297 cpu_buffer->read++;
2299 rb_update_read_stamp(cpu_buffer, event);
2301 length = rb_event_length(event);
2302 cpu_buffer->reader_page->read += length;
2305 static void rb_advance_iter(struct ring_buffer_iter *iter)
2307 struct ring_buffer *buffer;
2308 struct ring_buffer_per_cpu *cpu_buffer;
2309 struct ring_buffer_event *event;
2310 unsigned length;
2312 cpu_buffer = iter->cpu_buffer;
2313 buffer = cpu_buffer->buffer;
2316 * Check if we are at the end of the buffer.
2318 if (iter->head >= rb_page_size(iter->head_page)) {
2319 /* discarded commits can make the page empty */
2320 if (iter->head_page == cpu_buffer->commit_page)
2321 return;
2322 rb_inc_iter(iter);
2323 return;
2326 event = rb_iter_head_event(iter);
2328 length = rb_event_length(event);
2331 * This should not be called to advance the header if we are
2332 * at the tail of the buffer.
2334 if (RB_WARN_ON(cpu_buffer,
2335 (iter->head_page == cpu_buffer->commit_page) &&
2336 (iter->head + length > rb_commit_index(cpu_buffer))))
2337 return;
2339 rb_update_iter_read_stamp(iter, event);
2341 iter->head += length;
2343 /* check for end of page padding */
2344 if ((iter->head >= rb_page_size(iter->head_page)) &&
2345 (iter->head_page != cpu_buffer->commit_page))
2346 rb_advance_iter(iter);
2349 static struct ring_buffer_event *
2350 rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
2352 struct ring_buffer_per_cpu *cpu_buffer;
2353 struct ring_buffer_event *event;
2354 struct buffer_page *reader;
2355 int nr_loops = 0;
2357 cpu_buffer = buffer->buffers[cpu];
2359 again:
2361 * We repeat when a timestamp is encountered. It is possible
2362 * to get multiple timestamps from an interrupt entering just
2363 * as one timestamp is about to be written, or from discarded
2364 * commits. The most that we can have is the number on a single page.
2366 if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
2367 return NULL;
2369 reader = rb_get_reader_page(cpu_buffer);
2370 if (!reader)
2371 return NULL;
2373 event = rb_reader_event(cpu_buffer);
2375 switch (event->type_len) {
2376 case RINGBUF_TYPE_PADDING:
2377 if (rb_null_event(event))
2378 RB_WARN_ON(cpu_buffer, 1);
2380 * Because the writer could be discarding every
2381 * event it creates (which would probably be bad)
2382 * if we were to go back to "again" then we may never
2383 * catch up, and will trigger the warn on, or lock
2384 * the box. Return the padding, and we will release
2385 * the current locks, and try again.
2387 return event;
2389 case RINGBUF_TYPE_TIME_EXTEND:
2390 /* Internal data, OK to advance */
2391 rb_advance_reader(cpu_buffer);
2392 goto again;
2394 case RINGBUF_TYPE_TIME_STAMP:
2395 /* FIXME: not implemented */
2396 rb_advance_reader(cpu_buffer);
2397 goto again;
2399 case RINGBUF_TYPE_DATA:
2400 if (ts) {
2401 *ts = cpu_buffer->read_stamp + event->time_delta;
2402 ring_buffer_normalize_time_stamp(buffer,
2403 cpu_buffer->cpu, ts);
2405 return event;
2407 default:
2408 BUG();
2411 return NULL;
2413 EXPORT_SYMBOL_GPL(ring_buffer_peek);
2415 static struct ring_buffer_event *
2416 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
2418 struct ring_buffer *buffer;
2419 struct ring_buffer_per_cpu *cpu_buffer;
2420 struct ring_buffer_event *event;
2421 int nr_loops = 0;
2423 if (ring_buffer_iter_empty(iter))
2424 return NULL;
2426 cpu_buffer = iter->cpu_buffer;
2427 buffer = cpu_buffer->buffer;
2429 again:
2431 * We repeat when a timestamp is encountered.
2432 * We can get multiple timestamps by nested interrupts or also
2433 * if filtering is on (discarding commits). Since discarding
2434 * commits can be frequent we can get a lot of timestamps.
2435 * But we limit them by not adding timestamps if they begin
2436 * at the start of a page.
2438 if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
2439 return NULL;
2441 if (rb_per_cpu_empty(cpu_buffer))
2442 return NULL;
2444 event = rb_iter_head_event(iter);
2446 switch (event->type_len) {
2447 case RINGBUF_TYPE_PADDING:
2448 if (rb_null_event(event)) {
2449 rb_inc_iter(iter);
2450 goto again;
2452 rb_advance_iter(iter);
2453 return event;
2455 case RINGBUF_TYPE_TIME_EXTEND:
2456 /* Internal data, OK to advance */
2457 rb_advance_iter(iter);
2458 goto again;
2460 case RINGBUF_TYPE_TIME_STAMP:
2461 /* FIXME: not implemented */
2462 rb_advance_iter(iter);
2463 goto again;
2465 case RINGBUF_TYPE_DATA:
2466 if (ts) {
2467 *ts = iter->read_stamp + event->time_delta;
2468 ring_buffer_normalize_time_stamp(buffer,
2469 cpu_buffer->cpu, ts);
2471 return event;
2473 default:
2474 BUG();
2477 return NULL;
2479 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
2481 static inline int rb_ok_to_lock(void)
2484 * If an NMI die dumps out the content of the ring buffer
2485 * do not grab locks. We also permanently disable the ring
2486 * buffer too. A one time deal is all you get from reading
2487 * the ring buffer from an NMI.
2489 if (likely(!in_nmi()))
2490 return 1;
2492 tracing_off_permanent();
2493 return 0;
2497 * ring_buffer_peek - peek at the next event to be read
2498 * @buffer: The ring buffer to read
2499 * @cpu: The cpu to peak at
2500 * @ts: The timestamp counter of this event.
2502 * This will return the event that will be read next, but does
2503 * not consume the data.
2505 struct ring_buffer_event *
2506 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
2508 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2509 struct ring_buffer_event *event;
2510 unsigned long flags;
2511 int dolock;
2513 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2514 return NULL;
2516 dolock = rb_ok_to_lock();
2517 again:
2518 local_irq_save(flags);
2519 if (dolock)
2520 spin_lock(&cpu_buffer->reader_lock);
2521 event = rb_buffer_peek(buffer, cpu, ts);
2522 if (event && event->type_len == RINGBUF_TYPE_PADDING)
2523 rb_advance_reader(cpu_buffer);
2524 if (dolock)
2525 spin_unlock(&cpu_buffer->reader_lock);
2526 local_irq_restore(flags);
2528 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2529 cpu_relax();
2530 goto again;
2533 return event;
2537 * ring_buffer_iter_peek - peek at the next event to be read
2538 * @iter: The ring buffer iterator
2539 * @ts: The timestamp counter of this event.
2541 * This will return the event that will be read next, but does
2542 * not increment the iterator.
2544 struct ring_buffer_event *
2545 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
2547 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2548 struct ring_buffer_event *event;
2549 unsigned long flags;
2551 again:
2552 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2553 event = rb_iter_peek(iter, ts);
2554 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2556 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2557 cpu_relax();
2558 goto again;
2561 return event;
2565 * ring_buffer_consume - return an event and consume it
2566 * @buffer: The ring buffer to get the next event from
2568 * Returns the next event in the ring buffer, and that event is consumed.
2569 * Meaning, that sequential reads will keep returning a different event,
2570 * and eventually empty the ring buffer if the producer is slower.
2572 struct ring_buffer_event *
2573 ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
2575 struct ring_buffer_per_cpu *cpu_buffer;
2576 struct ring_buffer_event *event = NULL;
2577 unsigned long flags;
2578 int dolock;
2580 dolock = rb_ok_to_lock();
2582 again:
2583 /* might be called in atomic */
2584 preempt_disable();
2586 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2587 goto out;
2589 cpu_buffer = buffer->buffers[cpu];
2590 local_irq_save(flags);
2591 if (dolock)
2592 spin_lock(&cpu_buffer->reader_lock);
2594 event = rb_buffer_peek(buffer, cpu, ts);
2595 if (event)
2596 rb_advance_reader(cpu_buffer);
2598 if (dolock)
2599 spin_unlock(&cpu_buffer->reader_lock);
2600 local_irq_restore(flags);
2602 out:
2603 preempt_enable();
2605 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2606 cpu_relax();
2607 goto again;
2610 return event;
2612 EXPORT_SYMBOL_GPL(ring_buffer_consume);
2615 * ring_buffer_read_start - start a non consuming read of the buffer
2616 * @buffer: The ring buffer to read from
2617 * @cpu: The cpu buffer to iterate over
2619 * This starts up an iteration through the buffer. It also disables
2620 * the recording to the buffer until the reading is finished.
2621 * This prevents the reading from being corrupted. This is not
2622 * a consuming read, so a producer is not expected.
2624 * Must be paired with ring_buffer_finish.
2626 struct ring_buffer_iter *
2627 ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
2629 struct ring_buffer_per_cpu *cpu_buffer;
2630 struct ring_buffer_iter *iter;
2631 unsigned long flags;
2633 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2634 return NULL;
2636 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
2637 if (!iter)
2638 return NULL;
2640 cpu_buffer = buffer->buffers[cpu];
2642 iter->cpu_buffer = cpu_buffer;
2644 atomic_inc(&cpu_buffer->record_disabled);
2645 synchronize_sched();
2647 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2648 __raw_spin_lock(&cpu_buffer->lock);
2649 rb_iter_reset(iter);
2650 __raw_spin_unlock(&cpu_buffer->lock);
2651 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2653 return iter;
2655 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
2658 * ring_buffer_finish - finish reading the iterator of the buffer
2659 * @iter: The iterator retrieved by ring_buffer_start
2661 * This re-enables the recording to the buffer, and frees the
2662 * iterator.
2664 void
2665 ring_buffer_read_finish(struct ring_buffer_iter *iter)
2667 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2669 atomic_dec(&cpu_buffer->record_disabled);
2670 kfree(iter);
2672 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
2675 * ring_buffer_read - read the next item in the ring buffer by the iterator
2676 * @iter: The ring buffer iterator
2677 * @ts: The time stamp of the event read.
2679 * This reads the next event in the ring buffer and increments the iterator.
2681 struct ring_buffer_event *
2682 ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
2684 struct ring_buffer_event *event;
2685 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2686 unsigned long flags;
2688 again:
2689 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2690 event = rb_iter_peek(iter, ts);
2691 if (!event)
2692 goto out;
2694 rb_advance_iter(iter);
2695 out:
2696 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2698 if (event && event->type_len == RINGBUF_TYPE_PADDING) {
2699 cpu_relax();
2700 goto again;
2703 return event;
2705 EXPORT_SYMBOL_GPL(ring_buffer_read);
2708 * ring_buffer_size - return the size of the ring buffer (in bytes)
2709 * @buffer: The ring buffer.
2711 unsigned long ring_buffer_size(struct ring_buffer *buffer)
2713 return BUF_PAGE_SIZE * buffer->pages;
2715 EXPORT_SYMBOL_GPL(ring_buffer_size);
2717 static void
2718 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
2720 cpu_buffer->head_page
2721 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
2722 local_set(&cpu_buffer->head_page->write, 0);
2723 local_set(&cpu_buffer->head_page->entries, 0);
2724 local_set(&cpu_buffer->head_page->page->commit, 0);
2726 cpu_buffer->head_page->read = 0;
2728 cpu_buffer->tail_page = cpu_buffer->head_page;
2729 cpu_buffer->commit_page = cpu_buffer->head_page;
2731 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
2732 local_set(&cpu_buffer->reader_page->write, 0);
2733 local_set(&cpu_buffer->reader_page->entries, 0);
2734 local_set(&cpu_buffer->reader_page->page->commit, 0);
2735 cpu_buffer->reader_page->read = 0;
2737 cpu_buffer->nmi_dropped = 0;
2738 cpu_buffer->commit_overrun = 0;
2739 cpu_buffer->overrun = 0;
2740 cpu_buffer->read = 0;
2741 local_set(&cpu_buffer->entries, 0);
2742 local_set(&cpu_buffer->committing, 0);
2743 local_set(&cpu_buffer->commits, 0);
2745 cpu_buffer->write_stamp = 0;
2746 cpu_buffer->read_stamp = 0;
2750 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
2751 * @buffer: The ring buffer to reset a per cpu buffer of
2752 * @cpu: The CPU buffer to be reset
2754 void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
2756 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
2757 unsigned long flags;
2759 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2760 return;
2762 atomic_inc(&cpu_buffer->record_disabled);
2764 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
2766 __raw_spin_lock(&cpu_buffer->lock);
2768 rb_reset_cpu(cpu_buffer);
2770 __raw_spin_unlock(&cpu_buffer->lock);
2772 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
2774 atomic_dec(&cpu_buffer->record_disabled);
2776 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
2779 * ring_buffer_reset - reset a ring buffer
2780 * @buffer: The ring buffer to reset all cpu buffers
2782 void ring_buffer_reset(struct ring_buffer *buffer)
2784 int cpu;
2786 for_each_buffer_cpu(buffer, cpu)
2787 ring_buffer_reset_cpu(buffer, cpu);
2789 EXPORT_SYMBOL_GPL(ring_buffer_reset);
2792 * rind_buffer_empty - is the ring buffer empty?
2793 * @buffer: The ring buffer to test
2795 int ring_buffer_empty(struct ring_buffer *buffer)
2797 struct ring_buffer_per_cpu *cpu_buffer;
2798 unsigned long flags;
2799 int dolock;
2800 int cpu;
2801 int ret;
2803 dolock = rb_ok_to_lock();
2805 /* yes this is racy, but if you don't like the race, lock the buffer */
2806 for_each_buffer_cpu(buffer, cpu) {
2807 cpu_buffer = buffer->buffers[cpu];
2808 local_irq_save(flags);
2809 if (dolock)
2810 spin_lock(&cpu_buffer->reader_lock);
2811 ret = rb_per_cpu_empty(cpu_buffer);
2812 if (dolock)
2813 spin_unlock(&cpu_buffer->reader_lock);
2814 local_irq_restore(flags);
2816 if (!ret)
2817 return 0;
2820 return 1;
2822 EXPORT_SYMBOL_GPL(ring_buffer_empty);
2825 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
2826 * @buffer: The ring buffer
2827 * @cpu: The CPU buffer to test
2829 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
2831 struct ring_buffer_per_cpu *cpu_buffer;
2832 unsigned long flags;
2833 int dolock;
2834 int ret;
2836 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2837 return 1;
2839 dolock = rb_ok_to_lock();
2841 cpu_buffer = buffer->buffers[cpu];
2842 local_irq_save(flags);
2843 if (dolock)
2844 spin_lock(&cpu_buffer->reader_lock);
2845 ret = rb_per_cpu_empty(cpu_buffer);
2846 if (dolock)
2847 spin_unlock(&cpu_buffer->reader_lock);
2848 local_irq_restore(flags);
2850 return ret;
2852 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
2855 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
2856 * @buffer_a: One buffer to swap with
2857 * @buffer_b: The other buffer to swap with
2859 * This function is useful for tracers that want to take a "snapshot"
2860 * of a CPU buffer and has another back up buffer lying around.
2861 * it is expected that the tracer handles the cpu buffer not being
2862 * used at the moment.
2864 int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
2865 struct ring_buffer *buffer_b, int cpu)
2867 struct ring_buffer_per_cpu *cpu_buffer_a;
2868 struct ring_buffer_per_cpu *cpu_buffer_b;
2869 int ret = -EINVAL;
2871 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
2872 !cpumask_test_cpu(cpu, buffer_b->cpumask))
2873 goto out;
2875 /* At least make sure the two buffers are somewhat the same */
2876 if (buffer_a->pages != buffer_b->pages)
2877 goto out;
2879 ret = -EAGAIN;
2881 if (ring_buffer_flags != RB_BUFFERS_ON)
2882 goto out;
2884 if (atomic_read(&buffer_a->record_disabled))
2885 goto out;
2887 if (atomic_read(&buffer_b->record_disabled))
2888 goto out;
2890 cpu_buffer_a = buffer_a->buffers[cpu];
2891 cpu_buffer_b = buffer_b->buffers[cpu];
2893 if (atomic_read(&cpu_buffer_a->record_disabled))
2894 goto out;
2896 if (atomic_read(&cpu_buffer_b->record_disabled))
2897 goto out;
2900 * We can't do a synchronize_sched here because this
2901 * function can be called in atomic context.
2902 * Normally this will be called from the same CPU as cpu.
2903 * If not it's up to the caller to protect this.
2905 atomic_inc(&cpu_buffer_a->record_disabled);
2906 atomic_inc(&cpu_buffer_b->record_disabled);
2908 buffer_a->buffers[cpu] = cpu_buffer_b;
2909 buffer_b->buffers[cpu] = cpu_buffer_a;
2911 cpu_buffer_b->buffer = buffer_a;
2912 cpu_buffer_a->buffer = buffer_b;
2914 atomic_dec(&cpu_buffer_a->record_disabled);
2915 atomic_dec(&cpu_buffer_b->record_disabled);
2917 ret = 0;
2918 out:
2919 return ret;
2921 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
2924 * ring_buffer_alloc_read_page - allocate a page to read from buffer
2925 * @buffer: the buffer to allocate for.
2927 * This function is used in conjunction with ring_buffer_read_page.
2928 * When reading a full page from the ring buffer, these functions
2929 * can be used to speed up the process. The calling function should
2930 * allocate a few pages first with this function. Then when it
2931 * needs to get pages from the ring buffer, it passes the result
2932 * of this function into ring_buffer_read_page, which will swap
2933 * the page that was allocated, with the read page of the buffer.
2935 * Returns:
2936 * The page allocated, or NULL on error.
2938 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
2940 struct buffer_data_page *bpage;
2941 unsigned long addr;
2943 addr = __get_free_page(GFP_KERNEL);
2944 if (!addr)
2945 return NULL;
2947 bpage = (void *)addr;
2949 rb_init_page(bpage);
2951 return bpage;
2953 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
2956 * ring_buffer_free_read_page - free an allocated read page
2957 * @buffer: the buffer the page was allocate for
2958 * @data: the page to free
2960 * Free a page allocated from ring_buffer_alloc_read_page.
2962 void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
2964 free_page((unsigned long)data);
2966 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
2969 * ring_buffer_read_page - extract a page from the ring buffer
2970 * @buffer: buffer to extract from
2971 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
2972 * @len: amount to extract
2973 * @cpu: the cpu of the buffer to extract
2974 * @full: should the extraction only happen when the page is full.
2976 * This function will pull out a page from the ring buffer and consume it.
2977 * @data_page must be the address of the variable that was returned
2978 * from ring_buffer_alloc_read_page. This is because the page might be used
2979 * to swap with a page in the ring buffer.
2981 * for example:
2982 * rpage = ring_buffer_alloc_read_page(buffer);
2983 * if (!rpage)
2984 * return error;
2985 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
2986 * if (ret >= 0)
2987 * process_page(rpage, ret);
2989 * When @full is set, the function will not return true unless
2990 * the writer is off the reader page.
2992 * Note: it is up to the calling functions to handle sleeps and wakeups.
2993 * The ring buffer can be used anywhere in the kernel and can not
2994 * blindly call wake_up. The layer that uses the ring buffer must be
2995 * responsible for that.
2997 * Returns:
2998 * >=0 if data has been transferred, returns the offset of consumed data.
2999 * <0 if no data has been transferred.
3001 int ring_buffer_read_page(struct ring_buffer *buffer,
3002 void **data_page, size_t len, int cpu, int full)
3004 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3005 struct ring_buffer_event *event;
3006 struct buffer_data_page *bpage;
3007 struct buffer_page *reader;
3008 unsigned long flags;
3009 unsigned int commit;
3010 unsigned int read;
3011 u64 save_timestamp;
3012 int ret = -1;
3014 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3015 goto out;
3018 * If len is not big enough to hold the page header, then
3019 * we can not copy anything.
3021 if (len <= BUF_PAGE_HDR_SIZE)
3022 goto out;
3024 len -= BUF_PAGE_HDR_SIZE;
3026 if (!data_page)
3027 goto out;
3029 bpage = *data_page;
3030 if (!bpage)
3031 goto out;
3033 spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3035 reader = rb_get_reader_page(cpu_buffer);
3036 if (!reader)
3037 goto out_unlock;
3039 event = rb_reader_event(cpu_buffer);
3041 read = reader->read;
3042 commit = rb_page_commit(reader);
3045 * If this page has been partially read or
3046 * if len is not big enough to read the rest of the page or
3047 * a writer is still on the page, then
3048 * we must copy the data from the page to the buffer.
3049 * Otherwise, we can simply swap the page with the one passed in.
3051 if (read || (len < (commit - read)) ||
3052 cpu_buffer->reader_page == cpu_buffer->commit_page) {
3053 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
3054 unsigned int rpos = read;
3055 unsigned int pos = 0;
3056 unsigned int size;
3058 if (full)
3059 goto out_unlock;
3061 if (len > (commit - read))
3062 len = (commit - read);
3064 size = rb_event_length(event);
3066 if (len < size)
3067 goto out_unlock;
3069 /* save the current timestamp, since the user will need it */
3070 save_timestamp = cpu_buffer->read_stamp;
3072 /* Need to copy one event at a time */
3073 do {
3074 memcpy(bpage->data + pos, rpage->data + rpos, size);
3076 len -= size;
3078 rb_advance_reader(cpu_buffer);
3079 rpos = reader->read;
3080 pos += size;
3082 event = rb_reader_event(cpu_buffer);
3083 size = rb_event_length(event);
3084 } while (len > size);
3086 /* update bpage */
3087 local_set(&bpage->commit, pos);
3088 bpage->time_stamp = save_timestamp;
3090 /* we copied everything to the beginning */
3091 read = 0;
3092 } else {
3093 /* update the entry counter */
3094 cpu_buffer->read += local_read(&reader->entries);
3096 /* swap the pages */
3097 rb_init_page(bpage);
3098 bpage = reader->page;
3099 reader->page = *data_page;
3100 local_set(&reader->write, 0);
3101 local_set(&reader->entries, 0);
3102 reader->read = 0;
3103 *data_page = bpage;
3105 ret = read;
3107 out_unlock:
3108 spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3110 out:
3111 return ret;
3113 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
3115 #ifdef CONFIG_TRACING
3116 static ssize_t
3117 rb_simple_read(struct file *filp, char __user *ubuf,
3118 size_t cnt, loff_t *ppos)
3120 unsigned long *p = filp->private_data;
3121 char buf[64];
3122 int r;
3124 if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
3125 r = sprintf(buf, "permanently disabled\n");
3126 else
3127 r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
3129 return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
3132 static ssize_t
3133 rb_simple_write(struct file *filp, const char __user *ubuf,
3134 size_t cnt, loff_t *ppos)
3136 unsigned long *p = filp->private_data;
3137 char buf[64];
3138 unsigned long val;
3139 int ret;
3141 if (cnt >= sizeof(buf))
3142 return -EINVAL;
3144 if (copy_from_user(&buf, ubuf, cnt))
3145 return -EFAULT;
3147 buf[cnt] = 0;
3149 ret = strict_strtoul(buf, 10, &val);
3150 if (ret < 0)
3151 return ret;
3153 if (val)
3154 set_bit(RB_BUFFERS_ON_BIT, p);
3155 else
3156 clear_bit(RB_BUFFERS_ON_BIT, p);
3158 (*ppos)++;
3160 return cnt;
3163 static const struct file_operations rb_simple_fops = {
3164 .open = tracing_open_generic,
3165 .read = rb_simple_read,
3166 .write = rb_simple_write,
3170 static __init int rb_init_debugfs(void)
3172 struct dentry *d_tracer;
3174 d_tracer = tracing_init_dentry();
3176 trace_create_file("tracing_on", 0644, d_tracer,
3177 &ring_buffer_flags, &rb_simple_fops);
3179 return 0;
3182 fs_initcall(rb_init_debugfs);
3183 #endif
3185 #ifdef CONFIG_HOTPLUG_CPU
3186 static int rb_cpu_notify(struct notifier_block *self,
3187 unsigned long action, void *hcpu)
3189 struct ring_buffer *buffer =
3190 container_of(self, struct ring_buffer, cpu_notify);
3191 long cpu = (long)hcpu;
3193 switch (action) {
3194 case CPU_UP_PREPARE:
3195 case CPU_UP_PREPARE_FROZEN:
3196 if (cpumask_test_cpu(cpu, buffer->cpumask))
3197 return NOTIFY_OK;
3199 buffer->buffers[cpu] =
3200 rb_allocate_cpu_buffer(buffer, cpu);
3201 if (!buffer->buffers[cpu]) {
3202 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
3203 cpu);
3204 return NOTIFY_OK;
3206 smp_wmb();
3207 cpumask_set_cpu(cpu, buffer->cpumask);
3208 break;
3209 case CPU_DOWN_PREPARE:
3210 case CPU_DOWN_PREPARE_FROZEN:
3212 * Do nothing.
3213 * If we were to free the buffer, then the user would
3214 * lose any trace that was in the buffer.
3216 break;
3217 default:
3218 break;
3220 return NOTIFY_OK;
3222 #endif