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1/*
2 * Generic ring buffer
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/trace_events.h>
7#include <linux/ring_buffer.h>
8#include <linux/trace_clock.h>
9#include <linux/trace_seq.h>
10#include <linux/spinlock.h>
11#include <linux/irq_work.h>
12#include <linux/uaccess.h>
13#include <linux/hardirq.h>
14#include <linux/kthread.h> /* for self test */
15#include <linux/kmemcheck.h>
16#include <linux/module.h>
17#include <linux/percpu.h>
18#include <linux/mutex.h>
19#include <linux/delay.h>
20#include <linux/slab.h>
21#include <linux/init.h>
22#include <linux/hash.h>
23#include <linux/list.h>
24#include <linux/cpu.h>
25
26#include <asm/local.h>
27
28static void update_pages_handler(struct work_struct *work);
29
30/*
31 * The ring buffer header is special. We must manually up keep it.
32 */
33int ring_buffer_print_entry_header(struct trace_seq *s)
34{
35 trace_seq_puts(s, "# compressed entry header\n");
36 trace_seq_puts(s, "\ttype_len : 5 bits\n");
37 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
38 trace_seq_puts(s, "\tarray : 32 bits\n");
39 trace_seq_putc(s, '\n');
40 trace_seq_printf(s, "\tpadding : type == %d\n",
41 RINGBUF_TYPE_PADDING);
42 trace_seq_printf(s, "\ttime_extend : type == %d\n",
43 RINGBUF_TYPE_TIME_EXTEND);
44 trace_seq_printf(s, "\tdata max type_len == %d\n",
45 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
46
47 return !trace_seq_has_overflowed(s);
48}
49
50/*
51 * The ring buffer is made up of a list of pages. A separate list of pages is
52 * allocated for each CPU. A writer may only write to a buffer that is
53 * associated with the CPU it is currently executing on. A reader may read
54 * from any per cpu buffer.
55 *
56 * The reader is special. For each per cpu buffer, the reader has its own
57 * reader page. When a reader has read the entire reader page, this reader
58 * page is swapped with another page in the ring buffer.
59 *
60 * Now, as long as the writer is off the reader page, the reader can do what
61 * ever it wants with that page. The writer will never write to that page
62 * again (as long as it is out of the ring buffer).
63 *
64 * Here's some silly ASCII art.
65 *
66 * +------+
67 * |reader| RING BUFFER
68 * |page |
69 * +------+ +---+ +---+ +---+
70 * | |-->| |-->| |
71 * +---+ +---+ +---+
72 * ^ |
73 * | |
74 * +---------------+
75 *
76 *
77 * +------+
78 * |reader| RING BUFFER
79 * |page |------------------v
80 * +------+ +---+ +---+ +---+
81 * | |-->| |-->| |
82 * +---+ +---+ +---+
83 * ^ |
84 * | |
85 * +---------------+
86 *
87 *
88 * +------+
89 * |reader| RING BUFFER
90 * |page |------------------v
91 * +------+ +---+ +---+ +---+
92 * ^ | |-->| |-->| |
93 * | +---+ +---+ +---+
94 * | |
95 * | |
96 * +------------------------------+
97 *
98 *
99 * +------+
100 * |buffer| RING BUFFER
101 * |page |------------------v
102 * +------+ +---+ +---+ +---+
103 * ^ | | | |-->| |
104 * | New +---+ +---+ +---+
105 * | Reader------^ |
106 * | page |
107 * +------------------------------+
108 *
109 *
110 * After we make this swap, the reader can hand this page off to the splice
111 * code and be done with it. It can even allocate a new page if it needs to
112 * and swap that into the ring buffer.
113 *
114 * We will be using cmpxchg soon to make all this lockless.
115 *
116 */
117
118/* Used for individual buffers (after the counter) */
119#define RB_BUFFER_OFF (1 << 20)
120
121#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
122
123#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
124#define RB_ALIGNMENT 4U
125#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
126#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
127
128#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
129# define RB_FORCE_8BYTE_ALIGNMENT 0
130# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
131#else
132# define RB_FORCE_8BYTE_ALIGNMENT 1
133# define RB_ARCH_ALIGNMENT 8U
134#endif
135
136#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
137
138/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
139#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
140
141enum {
142 RB_LEN_TIME_EXTEND = 8,
143 RB_LEN_TIME_STAMP = 16,
144};
145
146#define skip_time_extend(event) \
147 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
148
149static inline int rb_null_event(struct ring_buffer_event *event)
150{
151 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
152}
153
154static void rb_event_set_padding(struct ring_buffer_event *event)
155{
156 /* padding has a NULL time_delta */
157 event->type_len = RINGBUF_TYPE_PADDING;
158 event->time_delta = 0;
159}
160
161static unsigned
162rb_event_data_length(struct ring_buffer_event *event)
163{
164 unsigned length;
165
166 if (event->type_len)
167 length = event->type_len * RB_ALIGNMENT;
168 else
169 length = event->array[0];
170 return length + RB_EVNT_HDR_SIZE;
171}
172
173/*
174 * Return the length of the given event. Will return
175 * the length of the time extend if the event is a
176 * time extend.
177 */
178static inline unsigned
179rb_event_length(struct ring_buffer_event *event)
180{
181 switch (event->type_len) {
182 case RINGBUF_TYPE_PADDING:
183 if (rb_null_event(event))
184 /* undefined */
185 return -1;
186 return event->array[0] + RB_EVNT_HDR_SIZE;
187
188 case RINGBUF_TYPE_TIME_EXTEND:
189 return RB_LEN_TIME_EXTEND;
190
191 case RINGBUF_TYPE_TIME_STAMP:
192 return RB_LEN_TIME_STAMP;
193
194 case RINGBUF_TYPE_DATA:
195 return rb_event_data_length(event);
196 default:
197 BUG();
198 }
199 /* not hit */
200 return 0;
201}
202
203/*
204 * Return total length of time extend and data,
205 * or just the event length for all other events.
206 */
207static inline unsigned
208rb_event_ts_length(struct ring_buffer_event *event)
209{
210 unsigned len = 0;
211
212 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
213 /* time extends include the data event after it */
214 len = RB_LEN_TIME_EXTEND;
215 event = skip_time_extend(event);
216 }
217 return len + rb_event_length(event);
218}
219
220/**
221 * ring_buffer_event_length - return the length of the event
222 * @event: the event to get the length of
223 *
224 * Returns the size of the data load of a data event.
225 * If the event is something other than a data event, it
226 * returns the size of the event itself. With the exception
227 * of a TIME EXTEND, where it still returns the size of the
228 * data load of the data event after it.
229 */
230unsigned ring_buffer_event_length(struct ring_buffer_event *event)
231{
232 unsigned length;
233
234 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
235 event = skip_time_extend(event);
236
237 length = rb_event_length(event);
238 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
239 return length;
240 length -= RB_EVNT_HDR_SIZE;
241 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
242 length -= sizeof(event->array[0]);
243 return length;
244}
245EXPORT_SYMBOL_GPL(ring_buffer_event_length);
246
247/* inline for ring buffer fast paths */
248static __always_inline void *
249rb_event_data(struct ring_buffer_event *event)
250{
251 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
252 event = skip_time_extend(event);
253 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
254 /* If length is in len field, then array[0] has the data */
255 if (event->type_len)
256 return (void *)&event->array[0];
257 /* Otherwise length is in array[0] and array[1] has the data */
258 return (void *)&event->array[1];
259}
260
261/**
262 * ring_buffer_event_data - return the data of the event
263 * @event: the event to get the data from
264 */
265void *ring_buffer_event_data(struct ring_buffer_event *event)
266{
267 return rb_event_data(event);
268}
269EXPORT_SYMBOL_GPL(ring_buffer_event_data);
270
271#define for_each_buffer_cpu(buffer, cpu) \
272 for_each_cpu(cpu, buffer->cpumask)
273
274#define TS_SHIFT 27
275#define TS_MASK ((1ULL << TS_SHIFT) - 1)
276#define TS_DELTA_TEST (~TS_MASK)
277
278/* Flag when events were overwritten */
279#define RB_MISSED_EVENTS (1 << 31)
280/* Missed count stored at end */
281#define RB_MISSED_STORED (1 << 30)
282
283struct buffer_data_page {
284 u64 time_stamp; /* page time stamp */
285 local_t commit; /* write committed index */
286 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
287};
288
289/*
290 * Note, the buffer_page list must be first. The buffer pages
291 * are allocated in cache lines, which means that each buffer
292 * page will be at the beginning of a cache line, and thus
293 * the least significant bits will be zero. We use this to
294 * add flags in the list struct pointers, to make the ring buffer
295 * lockless.
296 */
297struct buffer_page {
298 struct list_head list; /* list of buffer pages */
299 local_t write; /* index for next write */
300 unsigned read; /* index for next read */
301 local_t entries; /* entries on this page */
302 unsigned long real_end; /* real end of data */
303 struct buffer_data_page *page; /* Actual data page */
304};
305
306/*
307 * The buffer page counters, write and entries, must be reset
308 * atomically when crossing page boundaries. To synchronize this
309 * update, two counters are inserted into the number. One is
310 * the actual counter for the write position or count on the page.
311 *
312 * The other is a counter of updaters. Before an update happens
313 * the update partition of the counter is incremented. This will
314 * allow the updater to update the counter atomically.
315 *
316 * The counter is 20 bits, and the state data is 12.
317 */
318#define RB_WRITE_MASK 0xfffff
319#define RB_WRITE_INTCNT (1 << 20)
320
321static void rb_init_page(struct buffer_data_page *bpage)
322{
323 local_set(&bpage->commit, 0);
324}
325
326/**
327 * ring_buffer_page_len - the size of data on the page.
328 * @page: The page to read
329 *
330 * Returns the amount of data on the page, including buffer page header.
331 */
332size_t ring_buffer_page_len(void *page)
333{
334 return local_read(&((struct buffer_data_page *)page)->commit)
335 + BUF_PAGE_HDR_SIZE;
336}
337
338/*
339 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
340 * this issue out.
341 */
342static void free_buffer_page(struct buffer_page *bpage)
343{
344 free_page((unsigned long)bpage->page);
345 kfree(bpage);
346}
347
348/*
349 * We need to fit the time_stamp delta into 27 bits.
350 */
351static inline int test_time_stamp(u64 delta)
352{
353 if (delta & TS_DELTA_TEST)
354 return 1;
355 return 0;
356}
357
358#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
359
360/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
361#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
362
363int ring_buffer_print_page_header(struct trace_seq *s)
364{
365 struct buffer_data_page field;
366
367 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
368 "offset:0;\tsize:%u;\tsigned:%u;\n",
369 (unsigned int)sizeof(field.time_stamp),
370 (unsigned int)is_signed_type(u64));
371
372 trace_seq_printf(s, "\tfield: local_t commit;\t"
373 "offset:%u;\tsize:%u;\tsigned:%u;\n",
374 (unsigned int)offsetof(typeof(field), commit),
375 (unsigned int)sizeof(field.commit),
376 (unsigned int)is_signed_type(long));
377
378 trace_seq_printf(s, "\tfield: int overwrite;\t"
379 "offset:%u;\tsize:%u;\tsigned:%u;\n",
380 (unsigned int)offsetof(typeof(field), commit),
381 1,
382 (unsigned int)is_signed_type(long));
383
384 trace_seq_printf(s, "\tfield: char data;\t"
385 "offset:%u;\tsize:%u;\tsigned:%u;\n",
386 (unsigned int)offsetof(typeof(field), data),
387 (unsigned int)BUF_PAGE_SIZE,
388 (unsigned int)is_signed_type(char));
389
390 return !trace_seq_has_overflowed(s);
391}
392
393struct rb_irq_work {
394 struct irq_work work;
395 wait_queue_head_t waiters;
396 wait_queue_head_t full_waiters;
397 bool waiters_pending;
398 bool full_waiters_pending;
399 bool wakeup_full;
400};
401
402/*
403 * Structure to hold event state and handle nested events.
404 */
405struct rb_event_info {
406 u64 ts;
407 u64 delta;
408 unsigned long length;
409 struct buffer_page *tail_page;
410 int add_timestamp;
411};
412
413/*
414 * Used for which event context the event is in.
415 * NMI = 0
416 * IRQ = 1
417 * SOFTIRQ = 2
418 * NORMAL = 3
419 *
420 * See trace_recursive_lock() comment below for more details.
421 */
422enum {
423 RB_CTX_NMI,
424 RB_CTX_IRQ,
425 RB_CTX_SOFTIRQ,
426 RB_CTX_NORMAL,
427 RB_CTX_MAX
428};
429
430/*
431 * head_page == tail_page && head == tail then buffer is empty.
432 */
433struct ring_buffer_per_cpu {
434 int cpu;
435 atomic_t record_disabled;
436 struct ring_buffer *buffer;
437 raw_spinlock_t reader_lock; /* serialize readers */
438 arch_spinlock_t lock;
439 struct lock_class_key lock_key;
440 unsigned long nr_pages;
441 unsigned int current_context;
442 struct list_head *pages;
443 struct buffer_page *head_page; /* read from head */
444 struct buffer_page *tail_page; /* write to tail */
445 struct buffer_page *commit_page; /* committed pages */
446 struct buffer_page *reader_page;
447 unsigned long lost_events;
448 unsigned long last_overrun;
449 local_t entries_bytes;
450 local_t entries;
451 local_t overrun;
452 local_t commit_overrun;
453 local_t dropped_events;
454 local_t committing;
455 local_t commits;
456 unsigned long read;
457 unsigned long read_bytes;
458 u64 write_stamp;
459 u64 read_stamp;
460 /* ring buffer pages to update, > 0 to add, < 0 to remove */
461 long nr_pages_to_update;
462 struct list_head new_pages; /* new pages to add */
463 struct work_struct update_pages_work;
464 struct completion update_done;
465
466 struct rb_irq_work irq_work;
467};
468
469struct ring_buffer {
470 unsigned flags;
471 int cpus;
472 atomic_t record_disabled;
473 atomic_t resize_disabled;
474 cpumask_var_t cpumask;
475
476 struct lock_class_key *reader_lock_key;
477
478 struct mutex mutex;
479
480 struct ring_buffer_per_cpu **buffers;
481
482 struct hlist_node node;
483 u64 (*clock)(void);
484
485 struct rb_irq_work irq_work;
486};
487
488struct ring_buffer_iter {
489 struct ring_buffer_per_cpu *cpu_buffer;
490 unsigned long head;
491 struct buffer_page *head_page;
492 struct buffer_page *cache_reader_page;
493 unsigned long cache_read;
494 u64 read_stamp;
495};
496
497/*
498 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
499 *
500 * Schedules a delayed work to wake up any task that is blocked on the
501 * ring buffer waiters queue.
502 */
503static void rb_wake_up_waiters(struct irq_work *work)
504{
505 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
506
507 wake_up_all(&rbwork->waiters);
508 if (rbwork->wakeup_full) {
509 rbwork->wakeup_full = false;
510 wake_up_all(&rbwork->full_waiters);
511 }
512}
513
514/**
515 * ring_buffer_wait - wait for input to the ring buffer
516 * @buffer: buffer to wait on
517 * @cpu: the cpu buffer to wait on
518 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
519 *
520 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
521 * as data is added to any of the @buffer's cpu buffers. Otherwise
522 * it will wait for data to be added to a specific cpu buffer.
523 */
524int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
525{
526 struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
527 DEFINE_WAIT(wait);
528 struct rb_irq_work *work;
529 int ret = 0;
530
531 /*
532 * Depending on what the caller is waiting for, either any
533 * data in any cpu buffer, or a specific buffer, put the
534 * caller on the appropriate wait queue.
535 */
536 if (cpu == RING_BUFFER_ALL_CPUS) {
537 work = &buffer->irq_work;
538 /* Full only makes sense on per cpu reads */
539 full = false;
540 } else {
541 if (!cpumask_test_cpu(cpu, buffer->cpumask))
542 return -ENODEV;
543 cpu_buffer = buffer->buffers[cpu];
544 work = &cpu_buffer->irq_work;
545 }
546
547
548 while (true) {
549 if (full)
550 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
551 else
552 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
553
554 /*
555 * The events can happen in critical sections where
556 * checking a work queue can cause deadlocks.
557 * After adding a task to the queue, this flag is set
558 * only to notify events to try to wake up the queue
559 * using irq_work.
560 *
561 * We don't clear it even if the buffer is no longer
562 * empty. The flag only causes the next event to run
563 * irq_work to do the work queue wake up. The worse
564 * that can happen if we race with !trace_empty() is that
565 * an event will cause an irq_work to try to wake up
566 * an empty queue.
567 *
568 * There's no reason to protect this flag either, as
569 * the work queue and irq_work logic will do the necessary
570 * synchronization for the wake ups. The only thing
571 * that is necessary is that the wake up happens after
572 * a task has been queued. It's OK for spurious wake ups.
573 */
574 if (full)
575 work->full_waiters_pending = true;
576 else
577 work->waiters_pending = true;
578
579 if (signal_pending(current)) {
580 ret = -EINTR;
581 break;
582 }
583
584 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
585 break;
586
587 if (cpu != RING_BUFFER_ALL_CPUS &&
588 !ring_buffer_empty_cpu(buffer, cpu)) {
589 unsigned long flags;
590 bool pagebusy;
591
592 if (!full)
593 break;
594
595 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
596 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
597 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
598
599 if (!pagebusy)
600 break;
601 }
602
603 schedule();
604 }
605
606 if (full)
607 finish_wait(&work->full_waiters, &wait);
608 else
609 finish_wait(&work->waiters, &wait);
610
611 return ret;
612}
613
614/**
615 * ring_buffer_poll_wait - poll on buffer input
616 * @buffer: buffer to wait on
617 * @cpu: the cpu buffer to wait on
618 * @filp: the file descriptor
619 * @poll_table: The poll descriptor
620 *
621 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
622 * as data is added to any of the @buffer's cpu buffers. Otherwise
623 * it will wait for data to be added to a specific cpu buffer.
624 *
625 * Returns POLLIN | POLLRDNORM if data exists in the buffers,
626 * zero otherwise.
627 */
628int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
629 struct file *filp, poll_table *poll_table)
630{
631 struct ring_buffer_per_cpu *cpu_buffer;
632 struct rb_irq_work *work;
633
634 if (cpu == RING_BUFFER_ALL_CPUS)
635 work = &buffer->irq_work;
636 else {
637 if (!cpumask_test_cpu(cpu, buffer->cpumask))
638 return -EINVAL;
639
640 cpu_buffer = buffer->buffers[cpu];
641 work = &cpu_buffer->irq_work;
642 }
643
644 poll_wait(filp, &work->waiters, poll_table);
645 work->waiters_pending = true;
646 /*
647 * There's a tight race between setting the waiters_pending and
648 * checking if the ring buffer is empty. Once the waiters_pending bit
649 * is set, the next event will wake the task up, but we can get stuck
650 * if there's only a single event in.
651 *
652 * FIXME: Ideally, we need a memory barrier on the writer side as well,
653 * but adding a memory barrier to all events will cause too much of a
654 * performance hit in the fast path. We only need a memory barrier when
655 * the buffer goes from empty to having content. But as this race is
656 * extremely small, and it's not a problem if another event comes in, we
657 * will fix it later.
658 */
659 smp_mb();
660
661 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
662 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
663 return POLLIN | POLLRDNORM;
664 return 0;
665}
666
667/* buffer may be either ring_buffer or ring_buffer_per_cpu */
668#define RB_WARN_ON(b, cond) \
669 ({ \
670 int _____ret = unlikely(cond); \
671 if (_____ret) { \
672 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
673 struct ring_buffer_per_cpu *__b = \
674 (void *)b; \
675 atomic_inc(&__b->buffer->record_disabled); \
676 } else \
677 atomic_inc(&b->record_disabled); \
678 WARN_ON(1); \
679 } \
680 _____ret; \
681 })
682
683/* Up this if you want to test the TIME_EXTENTS and normalization */
684#define DEBUG_SHIFT 0
685
686static inline u64 rb_time_stamp(struct ring_buffer *buffer)
687{
688 /* shift to debug/test normalization and TIME_EXTENTS */
689 return buffer->clock() << DEBUG_SHIFT;
690}
691
692u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
693{
694 u64 time;
695
696 preempt_disable_notrace();
697 time = rb_time_stamp(buffer);
698 preempt_enable_no_resched_notrace();
699
700 return time;
701}
702EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
703
704void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
705 int cpu, u64 *ts)
706{
707 /* Just stupid testing the normalize function and deltas */
708 *ts >>= DEBUG_SHIFT;
709}
710EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
711
712/*
713 * Making the ring buffer lockless makes things tricky.
714 * Although writes only happen on the CPU that they are on,
715 * and they only need to worry about interrupts. Reads can
716 * happen on any CPU.
717 *
718 * The reader page is always off the ring buffer, but when the
719 * reader finishes with a page, it needs to swap its page with
720 * a new one from the buffer. The reader needs to take from
721 * the head (writes go to the tail). But if a writer is in overwrite
722 * mode and wraps, it must push the head page forward.
723 *
724 * Here lies the problem.
725 *
726 * The reader must be careful to replace only the head page, and
727 * not another one. As described at the top of the file in the
728 * ASCII art, the reader sets its old page to point to the next
729 * page after head. It then sets the page after head to point to
730 * the old reader page. But if the writer moves the head page
731 * during this operation, the reader could end up with the tail.
732 *
733 * We use cmpxchg to help prevent this race. We also do something
734 * special with the page before head. We set the LSB to 1.
735 *
736 * When the writer must push the page forward, it will clear the
737 * bit that points to the head page, move the head, and then set
738 * the bit that points to the new head page.
739 *
740 * We also don't want an interrupt coming in and moving the head
741 * page on another writer. Thus we use the second LSB to catch
742 * that too. Thus:
743 *
744 * head->list->prev->next bit 1 bit 0
745 * ------- -------
746 * Normal page 0 0
747 * Points to head page 0 1
748 * New head page 1 0
749 *
750 * Note we can not trust the prev pointer of the head page, because:
751 *
752 * +----+ +-----+ +-----+
753 * | |------>| T |---X--->| N |
754 * | |<------| | | |
755 * +----+ +-----+ +-----+
756 * ^ ^ |
757 * | +-----+ | |
758 * +----------| R |----------+ |
759 * | |<-----------+
760 * +-----+
761 *
762 * Key: ---X--> HEAD flag set in pointer
763 * T Tail page
764 * R Reader page
765 * N Next page
766 *
767 * (see __rb_reserve_next() to see where this happens)
768 *
769 * What the above shows is that the reader just swapped out
770 * the reader page with a page in the buffer, but before it
771 * could make the new header point back to the new page added
772 * it was preempted by a writer. The writer moved forward onto
773 * the new page added by the reader and is about to move forward
774 * again.
775 *
776 * You can see, it is legitimate for the previous pointer of
777 * the head (or any page) not to point back to itself. But only
778 * temporarially.
779 */
780
781#define RB_PAGE_NORMAL 0UL
782#define RB_PAGE_HEAD 1UL
783#define RB_PAGE_UPDATE 2UL
784
785
786#define RB_FLAG_MASK 3UL
787
788/* PAGE_MOVED is not part of the mask */
789#define RB_PAGE_MOVED 4UL
790
791/*
792 * rb_list_head - remove any bit
793 */
794static struct list_head *rb_list_head(struct list_head *list)
795{
796 unsigned long val = (unsigned long)list;
797
798 return (struct list_head *)(val & ~RB_FLAG_MASK);
799}
800
801/*
802 * rb_is_head_page - test if the given page is the head page
803 *
804 * Because the reader may move the head_page pointer, we can
805 * not trust what the head page is (it may be pointing to
806 * the reader page). But if the next page is a header page,
807 * its flags will be non zero.
808 */
809static inline int
810rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
811 struct buffer_page *page, struct list_head *list)
812{
813 unsigned long val;
814
815 val = (unsigned long)list->next;
816
817 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
818 return RB_PAGE_MOVED;
819
820 return val & RB_FLAG_MASK;
821}
822
823/*
824 * rb_is_reader_page
825 *
826 * The unique thing about the reader page, is that, if the
827 * writer is ever on it, the previous pointer never points
828 * back to the reader page.
829 */
830static bool rb_is_reader_page(struct buffer_page *page)
831{
832 struct list_head *list = page->list.prev;
833
834 return rb_list_head(list->next) != &page->list;
835}
836
837/*
838 * rb_set_list_to_head - set a list_head to be pointing to head.
839 */
840static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
841 struct list_head *list)
842{
843 unsigned long *ptr;
844
845 ptr = (unsigned long *)&list->next;
846 *ptr |= RB_PAGE_HEAD;
847 *ptr &= ~RB_PAGE_UPDATE;
848}
849
850/*
851 * rb_head_page_activate - sets up head page
852 */
853static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
854{
855 struct buffer_page *head;
856
857 head = cpu_buffer->head_page;
858 if (!head)
859 return;
860
861 /*
862 * Set the previous list pointer to have the HEAD flag.
863 */
864 rb_set_list_to_head(cpu_buffer, head->list.prev);
865}
866
867static void rb_list_head_clear(struct list_head *list)
868{
869 unsigned long *ptr = (unsigned long *)&list->next;
870
871 *ptr &= ~RB_FLAG_MASK;
872}
873
874/*
875 * rb_head_page_dactivate - clears head page ptr (for free list)
876 */
877static void
878rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
879{
880 struct list_head *hd;
881
882 /* Go through the whole list and clear any pointers found. */
883 rb_list_head_clear(cpu_buffer->pages);
884
885 list_for_each(hd, cpu_buffer->pages)
886 rb_list_head_clear(hd);
887}
888
889static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
890 struct buffer_page *head,
891 struct buffer_page *prev,
892 int old_flag, int new_flag)
893{
894 struct list_head *list;
895 unsigned long val = (unsigned long)&head->list;
896 unsigned long ret;
897
898 list = &prev->list;
899
900 val &= ~RB_FLAG_MASK;
901
902 ret = cmpxchg((unsigned long *)&list->next,
903 val | old_flag, val | new_flag);
904
905 /* check if the reader took the page */
906 if ((ret & ~RB_FLAG_MASK) != val)
907 return RB_PAGE_MOVED;
908
909 return ret & RB_FLAG_MASK;
910}
911
912static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
913 struct buffer_page *head,
914 struct buffer_page *prev,
915 int old_flag)
916{
917 return rb_head_page_set(cpu_buffer, head, prev,
918 old_flag, RB_PAGE_UPDATE);
919}
920
921static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
922 struct buffer_page *head,
923 struct buffer_page *prev,
924 int old_flag)
925{
926 return rb_head_page_set(cpu_buffer, head, prev,
927 old_flag, RB_PAGE_HEAD);
928}
929
930static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
931 struct buffer_page *head,
932 struct buffer_page *prev,
933 int old_flag)
934{
935 return rb_head_page_set(cpu_buffer, head, prev,
936 old_flag, RB_PAGE_NORMAL);
937}
938
939static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
940 struct buffer_page **bpage)
941{
942 struct list_head *p = rb_list_head((*bpage)->list.next);
943
944 *bpage = list_entry(p, struct buffer_page, list);
945}
946
947static struct buffer_page *
948rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
949{
950 struct buffer_page *head;
951 struct buffer_page *page;
952 struct list_head *list;
953 int i;
954
955 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
956 return NULL;
957
958 /* sanity check */
959 list = cpu_buffer->pages;
960 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
961 return NULL;
962
963 page = head = cpu_buffer->head_page;
964 /*
965 * It is possible that the writer moves the header behind
966 * where we started, and we miss in one loop.
967 * A second loop should grab the header, but we'll do
968 * three loops just because I'm paranoid.
969 */
970 for (i = 0; i < 3; i++) {
971 do {
972 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
973 cpu_buffer->head_page = page;
974 return page;
975 }
976 rb_inc_page(cpu_buffer, &page);
977 } while (page != head);
978 }
979
980 RB_WARN_ON(cpu_buffer, 1);
981
982 return NULL;
983}
984
985static int rb_head_page_replace(struct buffer_page *old,
986 struct buffer_page *new)
987{
988 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
989 unsigned long val;
990 unsigned long ret;
991
992 val = *ptr & ~RB_FLAG_MASK;
993 val |= RB_PAGE_HEAD;
994
995 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
996
997 return ret == val;
998}
999
1000/*
1001 * rb_tail_page_update - move the tail page forward
1002 */
1003static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1004 struct buffer_page *tail_page,
1005 struct buffer_page *next_page)
1006{
1007 unsigned long old_entries;
1008 unsigned long old_write;
1009
1010 /*
1011 * The tail page now needs to be moved forward.
1012 *
1013 * We need to reset the tail page, but without messing
1014 * with possible erasing of data brought in by interrupts
1015 * that have moved the tail page and are currently on it.
1016 *
1017 * We add a counter to the write field to denote this.
1018 */
1019 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1020 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1021
1022 /*
1023 * Just make sure we have seen our old_write and synchronize
1024 * with any interrupts that come in.
1025 */
1026 barrier();
1027
1028 /*
1029 * If the tail page is still the same as what we think
1030 * it is, then it is up to us to update the tail
1031 * pointer.
1032 */
1033 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1034 /* Zero the write counter */
1035 unsigned long val = old_write & ~RB_WRITE_MASK;
1036 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1037
1038 /*
1039 * This will only succeed if an interrupt did
1040 * not come in and change it. In which case, we
1041 * do not want to modify it.
1042 *
1043 * We add (void) to let the compiler know that we do not care
1044 * about the return value of these functions. We use the
1045 * cmpxchg to only update if an interrupt did not already
1046 * do it for us. If the cmpxchg fails, we don't care.
1047 */
1048 (void)local_cmpxchg(&next_page->write, old_write, val);
1049 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1050
1051 /*
1052 * No need to worry about races with clearing out the commit.
1053 * it only can increment when a commit takes place. But that
1054 * only happens in the outer most nested commit.
1055 */
1056 local_set(&next_page->page->commit, 0);
1057
1058 /* Again, either we update tail_page or an interrupt does */
1059 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1060 }
1061}
1062
1063static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1064 struct buffer_page *bpage)
1065{
1066 unsigned long val = (unsigned long)bpage;
1067
1068 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1069 return 1;
1070
1071 return 0;
1072}
1073
1074/**
1075 * rb_check_list - make sure a pointer to a list has the last bits zero
1076 */
1077static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1078 struct list_head *list)
1079{
1080 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1081 return 1;
1082 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1083 return 1;
1084 return 0;
1085}
1086
1087/**
1088 * rb_check_pages - integrity check of buffer pages
1089 * @cpu_buffer: CPU buffer with pages to test
1090 *
1091 * As a safety measure we check to make sure the data pages have not
1092 * been corrupted.
1093 */
1094static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1095{
1096 struct list_head *head = cpu_buffer->pages;
1097 struct buffer_page *bpage, *tmp;
1098
1099 /* Reset the head page if it exists */
1100 if (cpu_buffer->head_page)
1101 rb_set_head_page(cpu_buffer);
1102
1103 rb_head_page_deactivate(cpu_buffer);
1104
1105 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1106 return -1;
1107 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1108 return -1;
1109
1110 if (rb_check_list(cpu_buffer, head))
1111 return -1;
1112
1113 list_for_each_entry_safe(bpage, tmp, head, list) {
1114 if (RB_WARN_ON(cpu_buffer,
1115 bpage->list.next->prev != &bpage->list))
1116 return -1;
1117 if (RB_WARN_ON(cpu_buffer,
1118 bpage->list.prev->next != &bpage->list))
1119 return -1;
1120 if (rb_check_list(cpu_buffer, &bpage->list))
1121 return -1;
1122 }
1123
1124 rb_head_page_activate(cpu_buffer);
1125
1126 return 0;
1127}
1128
1129static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1130{
1131 struct buffer_page *bpage, *tmp;
1132 long i;
1133
1134 for (i = 0; i < nr_pages; i++) {
1135 struct page *page;
1136 /*
1137 * __GFP_NORETRY flag makes sure that the allocation fails
1138 * gracefully without invoking oom-killer and the system is
1139 * not destabilized.
1140 */
1141 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1142 GFP_KERNEL | __GFP_NORETRY,
1143 cpu_to_node(cpu));
1144 if (!bpage)
1145 goto free_pages;
1146
1147 list_add(&bpage->list, pages);
1148
1149 page = alloc_pages_node(cpu_to_node(cpu),
1150 GFP_KERNEL | __GFP_NORETRY, 0);
1151 if (!page)
1152 goto free_pages;
1153 bpage->page = page_address(page);
1154 rb_init_page(bpage->page);
1155 }
1156
1157 return 0;
1158
1159free_pages:
1160 list_for_each_entry_safe(bpage, tmp, pages, list) {
1161 list_del_init(&bpage->list);
1162 free_buffer_page(bpage);
1163 }
1164
1165 return -ENOMEM;
1166}
1167
1168static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1169 unsigned long nr_pages)
1170{
1171 LIST_HEAD(pages);
1172
1173 WARN_ON(!nr_pages);
1174
1175 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1176 return -ENOMEM;
1177
1178 /*
1179 * The ring buffer page list is a circular list that does not
1180 * start and end with a list head. All page list items point to
1181 * other pages.
1182 */
1183 cpu_buffer->pages = pages.next;
1184 list_del(&pages);
1185
1186 cpu_buffer->nr_pages = nr_pages;
1187
1188 rb_check_pages(cpu_buffer);
1189
1190 return 0;
1191}
1192
1193static struct ring_buffer_per_cpu *
1194rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
1195{
1196 struct ring_buffer_per_cpu *cpu_buffer;
1197 struct buffer_page *bpage;
1198 struct page *page;
1199 int ret;
1200
1201 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1202 GFP_KERNEL, cpu_to_node(cpu));
1203 if (!cpu_buffer)
1204 return NULL;
1205
1206 cpu_buffer->cpu = cpu;
1207 cpu_buffer->buffer = buffer;
1208 raw_spin_lock_init(&cpu_buffer->reader_lock);
1209 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1210 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1211 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1212 init_completion(&cpu_buffer->update_done);
1213 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1214 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1215 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1216
1217 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1218 GFP_KERNEL, cpu_to_node(cpu));
1219 if (!bpage)
1220 goto fail_free_buffer;
1221
1222 rb_check_bpage(cpu_buffer, bpage);
1223
1224 cpu_buffer->reader_page = bpage;
1225 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1226 if (!page)
1227 goto fail_free_reader;
1228 bpage->page = page_address(page);
1229 rb_init_page(bpage->page);
1230
1231 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1232 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1233
1234 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1235 if (ret < 0)
1236 goto fail_free_reader;
1237
1238 cpu_buffer->head_page
1239 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1240 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1241
1242 rb_head_page_activate(cpu_buffer);
1243
1244 return cpu_buffer;
1245
1246 fail_free_reader:
1247 free_buffer_page(cpu_buffer->reader_page);
1248
1249 fail_free_buffer:
1250 kfree(cpu_buffer);
1251 return NULL;
1252}
1253
1254static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1255{
1256 struct list_head *head = cpu_buffer->pages;
1257 struct buffer_page *bpage, *tmp;
1258
1259 free_buffer_page(cpu_buffer->reader_page);
1260
1261 rb_head_page_deactivate(cpu_buffer);
1262
1263 if (head) {
1264 list_for_each_entry_safe(bpage, tmp, head, list) {
1265 list_del_init(&bpage->list);
1266 free_buffer_page(bpage);
1267 }
1268 bpage = list_entry(head, struct buffer_page, list);
1269 free_buffer_page(bpage);
1270 }
1271
1272 kfree(cpu_buffer);
1273}
1274
1275/**
1276 * __ring_buffer_alloc - allocate a new ring_buffer
1277 * @size: the size in bytes per cpu that is needed.
1278 * @flags: attributes to set for the ring buffer.
1279 *
1280 * Currently the only flag that is available is the RB_FL_OVERWRITE
1281 * flag. This flag means that the buffer will overwrite old data
1282 * when the buffer wraps. If this flag is not set, the buffer will
1283 * drop data when the tail hits the head.
1284 */
1285struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1286 struct lock_class_key *key)
1287{
1288 struct ring_buffer *buffer;
1289 long nr_pages;
1290 int bsize;
1291 int cpu;
1292 int ret;
1293
1294 /* keep it in its own cache line */
1295 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1296 GFP_KERNEL);
1297 if (!buffer)
1298 return NULL;
1299
1300 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1301 goto fail_free_buffer;
1302
1303 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1304 buffer->flags = flags;
1305 buffer->clock = trace_clock_local;
1306 buffer->reader_lock_key = key;
1307
1308 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1309 init_waitqueue_head(&buffer->irq_work.waiters);
1310
1311 /* need at least two pages */
1312 if (nr_pages < 2)
1313 nr_pages = 2;
1314
1315 buffer->cpus = nr_cpu_ids;
1316
1317 bsize = sizeof(void *) * nr_cpu_ids;
1318 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1319 GFP_KERNEL);
1320 if (!buffer->buffers)
1321 goto fail_free_cpumask;
1322
1323 cpu = raw_smp_processor_id();
1324 cpumask_set_cpu(cpu, buffer->cpumask);
1325 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1326 if (!buffer->buffers[cpu])
1327 goto fail_free_buffers;
1328
1329 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1330 if (ret < 0)
1331 goto fail_free_buffers;
1332
1333 mutex_init(&buffer->mutex);
1334
1335 return buffer;
1336
1337 fail_free_buffers:
1338 for_each_buffer_cpu(buffer, cpu) {
1339 if (buffer->buffers[cpu])
1340 rb_free_cpu_buffer(buffer->buffers[cpu]);
1341 }
1342 kfree(buffer->buffers);
1343
1344 fail_free_cpumask:
1345 free_cpumask_var(buffer->cpumask);
1346
1347 fail_free_buffer:
1348 kfree(buffer);
1349 return NULL;
1350}
1351EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1352
1353/**
1354 * ring_buffer_free - free a ring buffer.
1355 * @buffer: the buffer to free.
1356 */
1357void
1358ring_buffer_free(struct ring_buffer *buffer)
1359{
1360 int cpu;
1361
1362 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1363
1364 for_each_buffer_cpu(buffer, cpu)
1365 rb_free_cpu_buffer(buffer->buffers[cpu]);
1366
1367 kfree(buffer->buffers);
1368 free_cpumask_var(buffer->cpumask);
1369
1370 kfree(buffer);
1371}
1372EXPORT_SYMBOL_GPL(ring_buffer_free);
1373
1374void ring_buffer_set_clock(struct ring_buffer *buffer,
1375 u64 (*clock)(void))
1376{
1377 buffer->clock = clock;
1378}
1379
1380static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1381
1382static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1383{
1384 return local_read(&bpage->entries) & RB_WRITE_MASK;
1385}
1386
1387static inline unsigned long rb_page_write(struct buffer_page *bpage)
1388{
1389 return local_read(&bpage->write) & RB_WRITE_MASK;
1390}
1391
1392static int
1393rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1394{
1395 struct list_head *tail_page, *to_remove, *next_page;
1396 struct buffer_page *to_remove_page, *tmp_iter_page;
1397 struct buffer_page *last_page, *first_page;
1398 unsigned long nr_removed;
1399 unsigned long head_bit;
1400 int page_entries;
1401
1402 head_bit = 0;
1403
1404 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1405 atomic_inc(&cpu_buffer->record_disabled);
1406 /*
1407 * We don't race with the readers since we have acquired the reader
1408 * lock. We also don't race with writers after disabling recording.
1409 * This makes it easy to figure out the first and the last page to be
1410 * removed from the list. We unlink all the pages in between including
1411 * the first and last pages. This is done in a busy loop so that we
1412 * lose the least number of traces.
1413 * The pages are freed after we restart recording and unlock readers.
1414 */
1415 tail_page = &cpu_buffer->tail_page->list;
1416
1417 /*
1418 * tail page might be on reader page, we remove the next page
1419 * from the ring buffer
1420 */
1421 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1422 tail_page = rb_list_head(tail_page->next);
1423 to_remove = tail_page;
1424
1425 /* start of pages to remove */
1426 first_page = list_entry(rb_list_head(to_remove->next),
1427 struct buffer_page, list);
1428
1429 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1430 to_remove = rb_list_head(to_remove)->next;
1431 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1432 }
1433
1434 next_page = rb_list_head(to_remove)->next;
1435
1436 /*
1437 * Now we remove all pages between tail_page and next_page.
1438 * Make sure that we have head_bit value preserved for the
1439 * next page
1440 */
1441 tail_page->next = (struct list_head *)((unsigned long)next_page |
1442 head_bit);
1443 next_page = rb_list_head(next_page);
1444 next_page->prev = tail_page;
1445
1446 /* make sure pages points to a valid page in the ring buffer */
1447 cpu_buffer->pages = next_page;
1448
1449 /* update head page */
1450 if (head_bit)
1451 cpu_buffer->head_page = list_entry(next_page,
1452 struct buffer_page, list);
1453
1454 /*
1455 * change read pointer to make sure any read iterators reset
1456 * themselves
1457 */
1458 cpu_buffer->read = 0;
1459
1460 /* pages are removed, resume tracing and then free the pages */
1461 atomic_dec(&cpu_buffer->record_disabled);
1462 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1463
1464 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1465
1466 /* last buffer page to remove */
1467 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1468 list);
1469 tmp_iter_page = first_page;
1470
1471 do {
1472 to_remove_page = tmp_iter_page;
1473 rb_inc_page(cpu_buffer, &tmp_iter_page);
1474
1475 /* update the counters */
1476 page_entries = rb_page_entries(to_remove_page);
1477 if (page_entries) {
1478 /*
1479 * If something was added to this page, it was full
1480 * since it is not the tail page. So we deduct the
1481 * bytes consumed in ring buffer from here.
1482 * Increment overrun to account for the lost events.
1483 */
1484 local_add(page_entries, &cpu_buffer->overrun);
1485 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1486 }
1487
1488 /*
1489 * We have already removed references to this list item, just
1490 * free up the buffer_page and its page
1491 */
1492 free_buffer_page(to_remove_page);
1493 nr_removed--;
1494
1495 } while (to_remove_page != last_page);
1496
1497 RB_WARN_ON(cpu_buffer, nr_removed);
1498
1499 return nr_removed == 0;
1500}
1501
1502static int
1503rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1504{
1505 struct list_head *pages = &cpu_buffer->new_pages;
1506 int retries, success;
1507
1508 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1509 /*
1510 * We are holding the reader lock, so the reader page won't be swapped
1511 * in the ring buffer. Now we are racing with the writer trying to
1512 * move head page and the tail page.
1513 * We are going to adapt the reader page update process where:
1514 * 1. We first splice the start and end of list of new pages between
1515 * the head page and its previous page.
1516 * 2. We cmpxchg the prev_page->next to point from head page to the
1517 * start of new pages list.
1518 * 3. Finally, we update the head->prev to the end of new list.
1519 *
1520 * We will try this process 10 times, to make sure that we don't keep
1521 * spinning.
1522 */
1523 retries = 10;
1524 success = 0;
1525 while (retries--) {
1526 struct list_head *head_page, *prev_page, *r;
1527 struct list_head *last_page, *first_page;
1528 struct list_head *head_page_with_bit;
1529
1530 head_page = &rb_set_head_page(cpu_buffer)->list;
1531 if (!head_page)
1532 break;
1533 prev_page = head_page->prev;
1534
1535 first_page = pages->next;
1536 last_page = pages->prev;
1537
1538 head_page_with_bit = (struct list_head *)
1539 ((unsigned long)head_page | RB_PAGE_HEAD);
1540
1541 last_page->next = head_page_with_bit;
1542 first_page->prev = prev_page;
1543
1544 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1545
1546 if (r == head_page_with_bit) {
1547 /*
1548 * yay, we replaced the page pointer to our new list,
1549 * now, we just have to update to head page's prev
1550 * pointer to point to end of list
1551 */
1552 head_page->prev = last_page;
1553 success = 1;
1554 break;
1555 }
1556 }
1557
1558 if (success)
1559 INIT_LIST_HEAD(pages);
1560 /*
1561 * If we weren't successful in adding in new pages, warn and stop
1562 * tracing
1563 */
1564 RB_WARN_ON(cpu_buffer, !success);
1565 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1566
1567 /* free pages if they weren't inserted */
1568 if (!success) {
1569 struct buffer_page *bpage, *tmp;
1570 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1571 list) {
1572 list_del_init(&bpage->list);
1573 free_buffer_page(bpage);
1574 }
1575 }
1576 return success;
1577}
1578
1579static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1580{
1581 int success;
1582
1583 if (cpu_buffer->nr_pages_to_update > 0)
1584 success = rb_insert_pages(cpu_buffer);
1585 else
1586 success = rb_remove_pages(cpu_buffer,
1587 -cpu_buffer->nr_pages_to_update);
1588
1589 if (success)
1590 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1591}
1592
1593static void update_pages_handler(struct work_struct *work)
1594{
1595 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1596 struct ring_buffer_per_cpu, update_pages_work);
1597 rb_update_pages(cpu_buffer);
1598 complete(&cpu_buffer->update_done);
1599}
1600
1601/**
1602 * ring_buffer_resize - resize the ring buffer
1603 * @buffer: the buffer to resize.
1604 * @size: the new size.
1605 * @cpu_id: the cpu buffer to resize
1606 *
1607 * Minimum size is 2 * BUF_PAGE_SIZE.
1608 *
1609 * Returns 0 on success and < 0 on failure.
1610 */
1611int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1612 int cpu_id)
1613{
1614 struct ring_buffer_per_cpu *cpu_buffer;
1615 unsigned long nr_pages;
1616 int cpu, err = 0;
1617
1618 /*
1619 * Always succeed at resizing a non-existent buffer:
1620 */
1621 if (!buffer)
1622 return size;
1623
1624 /* Make sure the requested buffer exists */
1625 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1626 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1627 return size;
1628
1629 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1630
1631 /* we need a minimum of two pages */
1632 if (nr_pages < 2)
1633 nr_pages = 2;
1634
1635 size = nr_pages * BUF_PAGE_SIZE;
1636
1637 /*
1638 * Don't succeed if resizing is disabled, as a reader might be
1639 * manipulating the ring buffer and is expecting a sane state while
1640 * this is true.
1641 */
1642 if (atomic_read(&buffer->resize_disabled))
1643 return -EBUSY;
1644
1645 /* prevent another thread from changing buffer sizes */
1646 mutex_lock(&buffer->mutex);
1647
1648 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1649 /* calculate the pages to update */
1650 for_each_buffer_cpu(buffer, cpu) {
1651 cpu_buffer = buffer->buffers[cpu];
1652
1653 cpu_buffer->nr_pages_to_update = nr_pages -
1654 cpu_buffer->nr_pages;
1655 /*
1656 * nothing more to do for removing pages or no update
1657 */
1658 if (cpu_buffer->nr_pages_to_update <= 0)
1659 continue;
1660 /*
1661 * to add pages, make sure all new pages can be
1662 * allocated without receiving ENOMEM
1663 */
1664 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1665 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1666 &cpu_buffer->new_pages, cpu)) {
1667 /* not enough memory for new pages */
1668 err = -ENOMEM;
1669 goto out_err;
1670 }
1671 }
1672
1673 get_online_cpus();
1674 /*
1675 * Fire off all the required work handlers
1676 * We can't schedule on offline CPUs, but it's not necessary
1677 * since we can change their buffer sizes without any race.
1678 */
1679 for_each_buffer_cpu(buffer, cpu) {
1680 cpu_buffer = buffer->buffers[cpu];
1681 if (!cpu_buffer->nr_pages_to_update)
1682 continue;
1683
1684 /* Can't run something on an offline CPU. */
1685 if (!cpu_online(cpu)) {
1686 rb_update_pages(cpu_buffer);
1687 cpu_buffer->nr_pages_to_update = 0;
1688 } else {
1689 schedule_work_on(cpu,
1690 &cpu_buffer->update_pages_work);
1691 }
1692 }
1693
1694 /* wait for all the updates to complete */
1695 for_each_buffer_cpu(buffer, cpu) {
1696 cpu_buffer = buffer->buffers[cpu];
1697 if (!cpu_buffer->nr_pages_to_update)
1698 continue;
1699
1700 if (cpu_online(cpu))
1701 wait_for_completion(&cpu_buffer->update_done);
1702 cpu_buffer->nr_pages_to_update = 0;
1703 }
1704
1705 put_online_cpus();
1706 } else {
1707 /* Make sure this CPU has been intitialized */
1708 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1709 goto out;
1710
1711 cpu_buffer = buffer->buffers[cpu_id];
1712
1713 if (nr_pages == cpu_buffer->nr_pages)
1714 goto out;
1715
1716 cpu_buffer->nr_pages_to_update = nr_pages -
1717 cpu_buffer->nr_pages;
1718
1719 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1720 if (cpu_buffer->nr_pages_to_update > 0 &&
1721 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1722 &cpu_buffer->new_pages, cpu_id)) {
1723 err = -ENOMEM;
1724 goto out_err;
1725 }
1726
1727 get_online_cpus();
1728
1729 /* Can't run something on an offline CPU. */
1730 if (!cpu_online(cpu_id))
1731 rb_update_pages(cpu_buffer);
1732 else {
1733 schedule_work_on(cpu_id,
1734 &cpu_buffer->update_pages_work);
1735 wait_for_completion(&cpu_buffer->update_done);
1736 }
1737
1738 cpu_buffer->nr_pages_to_update = 0;
1739 put_online_cpus();
1740 }
1741
1742 out:
1743 /*
1744 * The ring buffer resize can happen with the ring buffer
1745 * enabled, so that the update disturbs the tracing as little
1746 * as possible. But if the buffer is disabled, we do not need
1747 * to worry about that, and we can take the time to verify
1748 * that the buffer is not corrupt.
1749 */
1750 if (atomic_read(&buffer->record_disabled)) {
1751 atomic_inc(&buffer->record_disabled);
1752 /*
1753 * Even though the buffer was disabled, we must make sure
1754 * that it is truly disabled before calling rb_check_pages.
1755 * There could have been a race between checking
1756 * record_disable and incrementing it.
1757 */
1758 synchronize_sched();
1759 for_each_buffer_cpu(buffer, cpu) {
1760 cpu_buffer = buffer->buffers[cpu];
1761 rb_check_pages(cpu_buffer);
1762 }
1763 atomic_dec(&buffer->record_disabled);
1764 }
1765
1766 mutex_unlock(&buffer->mutex);
1767 return size;
1768
1769 out_err:
1770 for_each_buffer_cpu(buffer, cpu) {
1771 struct buffer_page *bpage, *tmp;
1772
1773 cpu_buffer = buffer->buffers[cpu];
1774 cpu_buffer->nr_pages_to_update = 0;
1775
1776 if (list_empty(&cpu_buffer->new_pages))
1777 continue;
1778
1779 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1780 list) {
1781 list_del_init(&bpage->list);
1782 free_buffer_page(bpage);
1783 }
1784 }
1785 mutex_unlock(&buffer->mutex);
1786 return err;
1787}
1788EXPORT_SYMBOL_GPL(ring_buffer_resize);
1789
1790void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1791{
1792 mutex_lock(&buffer->mutex);
1793 if (val)
1794 buffer->flags |= RB_FL_OVERWRITE;
1795 else
1796 buffer->flags &= ~RB_FL_OVERWRITE;
1797 mutex_unlock(&buffer->mutex);
1798}
1799EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1800
1801static __always_inline void *
1802__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
1803{
1804 return bpage->data + index;
1805}
1806
1807static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1808{
1809 return bpage->page->data + index;
1810}
1811
1812static __always_inline struct ring_buffer_event *
1813rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1814{
1815 return __rb_page_index(cpu_buffer->reader_page,
1816 cpu_buffer->reader_page->read);
1817}
1818
1819static __always_inline struct ring_buffer_event *
1820rb_iter_head_event(struct ring_buffer_iter *iter)
1821{
1822 return __rb_page_index(iter->head_page, iter->head);
1823}
1824
1825static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
1826{
1827 return local_read(&bpage->page->commit);
1828}
1829
1830/* Size is determined by what has been committed */
1831static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
1832{
1833 return rb_page_commit(bpage);
1834}
1835
1836static __always_inline unsigned
1837rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1838{
1839 return rb_page_commit(cpu_buffer->commit_page);
1840}
1841
1842static __always_inline unsigned
1843rb_event_index(struct ring_buffer_event *event)
1844{
1845 unsigned long addr = (unsigned long)event;
1846
1847 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1848}
1849
1850static void rb_inc_iter(struct ring_buffer_iter *iter)
1851{
1852 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1853
1854 /*
1855 * The iterator could be on the reader page (it starts there).
1856 * But the head could have moved, since the reader was
1857 * found. Check for this case and assign the iterator
1858 * to the head page instead of next.
1859 */
1860 if (iter->head_page == cpu_buffer->reader_page)
1861 iter->head_page = rb_set_head_page(cpu_buffer);
1862 else
1863 rb_inc_page(cpu_buffer, &iter->head_page);
1864
1865 iter->read_stamp = iter->head_page->page->time_stamp;
1866 iter->head = 0;
1867}
1868
1869/*
1870 * rb_handle_head_page - writer hit the head page
1871 *
1872 * Returns: +1 to retry page
1873 * 0 to continue
1874 * -1 on error
1875 */
1876static int
1877rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1878 struct buffer_page *tail_page,
1879 struct buffer_page *next_page)
1880{
1881 struct buffer_page *new_head;
1882 int entries;
1883 int type;
1884 int ret;
1885
1886 entries = rb_page_entries(next_page);
1887
1888 /*
1889 * The hard part is here. We need to move the head
1890 * forward, and protect against both readers on
1891 * other CPUs and writers coming in via interrupts.
1892 */
1893 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1894 RB_PAGE_HEAD);
1895
1896 /*
1897 * type can be one of four:
1898 * NORMAL - an interrupt already moved it for us
1899 * HEAD - we are the first to get here.
1900 * UPDATE - we are the interrupt interrupting
1901 * a current move.
1902 * MOVED - a reader on another CPU moved the next
1903 * pointer to its reader page. Give up
1904 * and try again.
1905 */
1906
1907 switch (type) {
1908 case RB_PAGE_HEAD:
1909 /*
1910 * We changed the head to UPDATE, thus
1911 * it is our responsibility to update
1912 * the counters.
1913 */
1914 local_add(entries, &cpu_buffer->overrun);
1915 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1916
1917 /*
1918 * The entries will be zeroed out when we move the
1919 * tail page.
1920 */
1921
1922 /* still more to do */
1923 break;
1924
1925 case RB_PAGE_UPDATE:
1926 /*
1927 * This is an interrupt that interrupt the
1928 * previous update. Still more to do.
1929 */
1930 break;
1931 case RB_PAGE_NORMAL:
1932 /*
1933 * An interrupt came in before the update
1934 * and processed this for us.
1935 * Nothing left to do.
1936 */
1937 return 1;
1938 case RB_PAGE_MOVED:
1939 /*
1940 * The reader is on another CPU and just did
1941 * a swap with our next_page.
1942 * Try again.
1943 */
1944 return 1;
1945 default:
1946 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
1947 return -1;
1948 }
1949
1950 /*
1951 * Now that we are here, the old head pointer is
1952 * set to UPDATE. This will keep the reader from
1953 * swapping the head page with the reader page.
1954 * The reader (on another CPU) will spin till
1955 * we are finished.
1956 *
1957 * We just need to protect against interrupts
1958 * doing the job. We will set the next pointer
1959 * to HEAD. After that, we set the old pointer
1960 * to NORMAL, but only if it was HEAD before.
1961 * otherwise we are an interrupt, and only
1962 * want the outer most commit to reset it.
1963 */
1964 new_head = next_page;
1965 rb_inc_page(cpu_buffer, &new_head);
1966
1967 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
1968 RB_PAGE_NORMAL);
1969
1970 /*
1971 * Valid returns are:
1972 * HEAD - an interrupt came in and already set it.
1973 * NORMAL - One of two things:
1974 * 1) We really set it.
1975 * 2) A bunch of interrupts came in and moved
1976 * the page forward again.
1977 */
1978 switch (ret) {
1979 case RB_PAGE_HEAD:
1980 case RB_PAGE_NORMAL:
1981 /* OK */
1982 break;
1983 default:
1984 RB_WARN_ON(cpu_buffer, 1);
1985 return -1;
1986 }
1987
1988 /*
1989 * It is possible that an interrupt came in,
1990 * set the head up, then more interrupts came in
1991 * and moved it again. When we get back here,
1992 * the page would have been set to NORMAL but we
1993 * just set it back to HEAD.
1994 *
1995 * How do you detect this? Well, if that happened
1996 * the tail page would have moved.
1997 */
1998 if (ret == RB_PAGE_NORMAL) {
1999 struct buffer_page *buffer_tail_page;
2000
2001 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2002 /*
2003 * If the tail had moved passed next, then we need
2004 * to reset the pointer.
2005 */
2006 if (buffer_tail_page != tail_page &&
2007 buffer_tail_page != next_page)
2008 rb_head_page_set_normal(cpu_buffer, new_head,
2009 next_page,
2010 RB_PAGE_HEAD);
2011 }
2012
2013 /*
2014 * If this was the outer most commit (the one that
2015 * changed the original pointer from HEAD to UPDATE),
2016 * then it is up to us to reset it to NORMAL.
2017 */
2018 if (type == RB_PAGE_HEAD) {
2019 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2020 tail_page,
2021 RB_PAGE_UPDATE);
2022 if (RB_WARN_ON(cpu_buffer,
2023 ret != RB_PAGE_UPDATE))
2024 return -1;
2025 }
2026
2027 return 0;
2028}
2029
2030static inline void
2031rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2032 unsigned long tail, struct rb_event_info *info)
2033{
2034 struct buffer_page *tail_page = info->tail_page;
2035 struct ring_buffer_event *event;
2036 unsigned long length = info->length;
2037
2038 /*
2039 * Only the event that crossed the page boundary
2040 * must fill the old tail_page with padding.
2041 */
2042 if (tail >= BUF_PAGE_SIZE) {
2043 /*
2044 * If the page was filled, then we still need
2045 * to update the real_end. Reset it to zero
2046 * and the reader will ignore it.
2047 */
2048 if (tail == BUF_PAGE_SIZE)
2049 tail_page->real_end = 0;
2050
2051 local_sub(length, &tail_page->write);
2052 return;
2053 }
2054
2055 event = __rb_page_index(tail_page, tail);
2056 kmemcheck_annotate_bitfield(event, bitfield);
2057
2058 /* account for padding bytes */
2059 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2060
2061 /*
2062 * Save the original length to the meta data.
2063 * This will be used by the reader to add lost event
2064 * counter.
2065 */
2066 tail_page->real_end = tail;
2067
2068 /*
2069 * If this event is bigger than the minimum size, then
2070 * we need to be careful that we don't subtract the
2071 * write counter enough to allow another writer to slip
2072 * in on this page.
2073 * We put in a discarded commit instead, to make sure
2074 * that this space is not used again.
2075 *
2076 * If we are less than the minimum size, we don't need to
2077 * worry about it.
2078 */
2079 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2080 /* No room for any events */
2081
2082 /* Mark the rest of the page with padding */
2083 rb_event_set_padding(event);
2084
2085 /* Set the write back to the previous setting */
2086 local_sub(length, &tail_page->write);
2087 return;
2088 }
2089
2090 /* Put in a discarded event */
2091 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2092 event->type_len = RINGBUF_TYPE_PADDING;
2093 /* time delta must be non zero */
2094 event->time_delta = 1;
2095
2096 /* Set write to end of buffer */
2097 length = (tail + length) - BUF_PAGE_SIZE;
2098 local_sub(length, &tail_page->write);
2099}
2100
2101static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2102
2103/*
2104 * This is the slow path, force gcc not to inline it.
2105 */
2106static noinline struct ring_buffer_event *
2107rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2108 unsigned long tail, struct rb_event_info *info)
2109{
2110 struct buffer_page *tail_page = info->tail_page;
2111 struct buffer_page *commit_page = cpu_buffer->commit_page;
2112 struct ring_buffer *buffer = cpu_buffer->buffer;
2113 struct buffer_page *next_page;
2114 int ret;
2115
2116 next_page = tail_page;
2117
2118 rb_inc_page(cpu_buffer, &next_page);
2119
2120 /*
2121 * If for some reason, we had an interrupt storm that made
2122 * it all the way around the buffer, bail, and warn
2123 * about it.
2124 */
2125 if (unlikely(next_page == commit_page)) {
2126 local_inc(&cpu_buffer->commit_overrun);
2127 goto out_reset;
2128 }
2129
2130 /*
2131 * This is where the fun begins!
2132 *
2133 * We are fighting against races between a reader that
2134 * could be on another CPU trying to swap its reader
2135 * page with the buffer head.
2136 *
2137 * We are also fighting against interrupts coming in and
2138 * moving the head or tail on us as well.
2139 *
2140 * If the next page is the head page then we have filled
2141 * the buffer, unless the commit page is still on the
2142 * reader page.
2143 */
2144 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2145
2146 /*
2147 * If the commit is not on the reader page, then
2148 * move the header page.
2149 */
2150 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2151 /*
2152 * If we are not in overwrite mode,
2153 * this is easy, just stop here.
2154 */
2155 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2156 local_inc(&cpu_buffer->dropped_events);
2157 goto out_reset;
2158 }
2159
2160 ret = rb_handle_head_page(cpu_buffer,
2161 tail_page,
2162 next_page);
2163 if (ret < 0)
2164 goto out_reset;
2165 if (ret)
2166 goto out_again;
2167 } else {
2168 /*
2169 * We need to be careful here too. The
2170 * commit page could still be on the reader
2171 * page. We could have a small buffer, and
2172 * have filled up the buffer with events
2173 * from interrupts and such, and wrapped.
2174 *
2175 * Note, if the tail page is also the on the
2176 * reader_page, we let it move out.
2177 */
2178 if (unlikely((cpu_buffer->commit_page !=
2179 cpu_buffer->tail_page) &&
2180 (cpu_buffer->commit_page ==
2181 cpu_buffer->reader_page))) {
2182 local_inc(&cpu_buffer->commit_overrun);
2183 goto out_reset;
2184 }
2185 }
2186 }
2187
2188 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2189
2190 out_again:
2191
2192 rb_reset_tail(cpu_buffer, tail, info);
2193
2194 /* Commit what we have for now. */
2195 rb_end_commit(cpu_buffer);
2196 /* rb_end_commit() decs committing */
2197 local_inc(&cpu_buffer->committing);
2198
2199 /* fail and let the caller try again */
2200 return ERR_PTR(-EAGAIN);
2201
2202 out_reset:
2203 /* reset write */
2204 rb_reset_tail(cpu_buffer, tail, info);
2205
2206 return NULL;
2207}
2208
2209/* Slow path, do not inline */
2210static noinline struct ring_buffer_event *
2211rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
2212{
2213 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2214
2215 /* Not the first event on the page? */
2216 if (rb_event_index(event)) {
2217 event->time_delta = delta & TS_MASK;
2218 event->array[0] = delta >> TS_SHIFT;
2219 } else {
2220 /* nope, just zero it */
2221 event->time_delta = 0;
2222 event->array[0] = 0;
2223 }
2224
2225 return skip_time_extend(event);
2226}
2227
2228static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2229 struct ring_buffer_event *event);
2230
2231/**
2232 * rb_update_event - update event type and data
2233 * @event: the event to update
2234 * @type: the type of event
2235 * @length: the size of the event field in the ring buffer
2236 *
2237 * Update the type and data fields of the event. The length
2238 * is the actual size that is written to the ring buffer,
2239 * and with this, we can determine what to place into the
2240 * data field.
2241 */
2242static void
2243rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2244 struct ring_buffer_event *event,
2245 struct rb_event_info *info)
2246{
2247 unsigned length = info->length;
2248 u64 delta = info->delta;
2249
2250 /* Only a commit updates the timestamp */
2251 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2252 delta = 0;
2253
2254 /*
2255 * If we need to add a timestamp, then we
2256 * add it to the start of the resevered space.
2257 */
2258 if (unlikely(info->add_timestamp)) {
2259 event = rb_add_time_stamp(event, delta);
2260 length -= RB_LEN_TIME_EXTEND;
2261 delta = 0;
2262 }
2263
2264 event->time_delta = delta;
2265 length -= RB_EVNT_HDR_SIZE;
2266 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2267 event->type_len = 0;
2268 event->array[0] = length;
2269 } else
2270 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2271}
2272
2273static unsigned rb_calculate_event_length(unsigned length)
2274{
2275 struct ring_buffer_event event; /* Used only for sizeof array */
2276
2277 /* zero length can cause confusions */
2278 if (!length)
2279 length++;
2280
2281 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2282 length += sizeof(event.array[0]);
2283
2284 length += RB_EVNT_HDR_SIZE;
2285 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2286
2287 /*
2288 * In case the time delta is larger than the 27 bits for it
2289 * in the header, we need to add a timestamp. If another
2290 * event comes in when trying to discard this one to increase
2291 * the length, then the timestamp will be added in the allocated
2292 * space of this event. If length is bigger than the size needed
2293 * for the TIME_EXTEND, then padding has to be used. The events
2294 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2295 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2296 * As length is a multiple of 4, we only need to worry if it
2297 * is 12 (RB_LEN_TIME_EXTEND + 4).
2298 */
2299 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2300 length += RB_ALIGNMENT;
2301
2302 return length;
2303}
2304
2305#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2306static inline bool sched_clock_stable(void)
2307{
2308 return true;
2309}
2310#endif
2311
2312static inline int
2313rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2314 struct ring_buffer_event *event)
2315{
2316 unsigned long new_index, old_index;
2317 struct buffer_page *bpage;
2318 unsigned long index;
2319 unsigned long addr;
2320
2321 new_index = rb_event_index(event);
2322 old_index = new_index + rb_event_ts_length(event);
2323 addr = (unsigned long)event;
2324 addr &= PAGE_MASK;
2325
2326 bpage = READ_ONCE(cpu_buffer->tail_page);
2327
2328 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2329 unsigned long write_mask =
2330 local_read(&bpage->write) & ~RB_WRITE_MASK;
2331 unsigned long event_length = rb_event_length(event);
2332 /*
2333 * This is on the tail page. It is possible that
2334 * a write could come in and move the tail page
2335 * and write to the next page. That is fine
2336 * because we just shorten what is on this page.
2337 */
2338 old_index += write_mask;
2339 new_index += write_mask;
2340 index = local_cmpxchg(&bpage->write, old_index, new_index);
2341 if (index == old_index) {
2342 /* update counters */
2343 local_sub(event_length, &cpu_buffer->entries_bytes);
2344 return 1;
2345 }
2346 }
2347
2348 /* could not discard */
2349 return 0;
2350}
2351
2352static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2353{
2354 local_inc(&cpu_buffer->committing);
2355 local_inc(&cpu_buffer->commits);
2356}
2357
2358static __always_inline void
2359rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2360{
2361 unsigned long max_count;
2362
2363 /*
2364 * We only race with interrupts and NMIs on this CPU.
2365 * If we own the commit event, then we can commit
2366 * all others that interrupted us, since the interruptions
2367 * are in stack format (they finish before they come
2368 * back to us). This allows us to do a simple loop to
2369 * assign the commit to the tail.
2370 */
2371 again:
2372 max_count = cpu_buffer->nr_pages * 100;
2373
2374 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2375 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2376 return;
2377 if (RB_WARN_ON(cpu_buffer,
2378 rb_is_reader_page(cpu_buffer->tail_page)))
2379 return;
2380 local_set(&cpu_buffer->commit_page->page->commit,
2381 rb_page_write(cpu_buffer->commit_page));
2382 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2383 /* Only update the write stamp if the page has an event */
2384 if (rb_page_write(cpu_buffer->commit_page))
2385 cpu_buffer->write_stamp =
2386 cpu_buffer->commit_page->page->time_stamp;
2387 /* add barrier to keep gcc from optimizing too much */
2388 barrier();
2389 }
2390 while (rb_commit_index(cpu_buffer) !=
2391 rb_page_write(cpu_buffer->commit_page)) {
2392
2393 local_set(&cpu_buffer->commit_page->page->commit,
2394 rb_page_write(cpu_buffer->commit_page));
2395 RB_WARN_ON(cpu_buffer,
2396 local_read(&cpu_buffer->commit_page->page->commit) &
2397 ~RB_WRITE_MASK);
2398 barrier();
2399 }
2400
2401 /* again, keep gcc from optimizing */
2402 barrier();
2403
2404 /*
2405 * If an interrupt came in just after the first while loop
2406 * and pushed the tail page forward, we will be left with
2407 * a dangling commit that will never go forward.
2408 */
2409 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2410 goto again;
2411}
2412
2413static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2414{
2415 unsigned long commits;
2416
2417 if (RB_WARN_ON(cpu_buffer,
2418 !local_read(&cpu_buffer->committing)))
2419 return;
2420
2421 again:
2422 commits = local_read(&cpu_buffer->commits);
2423 /* synchronize with interrupts */
2424 barrier();
2425 if (local_read(&cpu_buffer->committing) == 1)
2426 rb_set_commit_to_write(cpu_buffer);
2427
2428 local_dec(&cpu_buffer->committing);
2429
2430 /* synchronize with interrupts */
2431 barrier();
2432
2433 /*
2434 * Need to account for interrupts coming in between the
2435 * updating of the commit page and the clearing of the
2436 * committing counter.
2437 */
2438 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2439 !local_read(&cpu_buffer->committing)) {
2440 local_inc(&cpu_buffer->committing);
2441 goto again;
2442 }
2443}
2444
2445static inline void rb_event_discard(struct ring_buffer_event *event)
2446{
2447 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
2448 event = skip_time_extend(event);
2449
2450 /* array[0] holds the actual length for the discarded event */
2451 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2452 event->type_len = RINGBUF_TYPE_PADDING;
2453 /* time delta must be non zero */
2454 if (!event->time_delta)
2455 event->time_delta = 1;
2456}
2457
2458static __always_inline bool
2459rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2460 struct ring_buffer_event *event)
2461{
2462 unsigned long addr = (unsigned long)event;
2463 unsigned long index;
2464
2465 index = rb_event_index(event);
2466 addr &= PAGE_MASK;
2467
2468 return cpu_buffer->commit_page->page == (void *)addr &&
2469 rb_commit_index(cpu_buffer) == index;
2470}
2471
2472static __always_inline void
2473rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2474 struct ring_buffer_event *event)
2475{
2476 u64 delta;
2477
2478 /*
2479 * The event first in the commit queue updates the
2480 * time stamp.
2481 */
2482 if (rb_event_is_commit(cpu_buffer, event)) {
2483 /*
2484 * A commit event that is first on a page
2485 * updates the write timestamp with the page stamp
2486 */
2487 if (!rb_event_index(event))
2488 cpu_buffer->write_stamp =
2489 cpu_buffer->commit_page->page->time_stamp;
2490 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2491 delta = event->array[0];
2492 delta <<= TS_SHIFT;
2493 delta += event->time_delta;
2494 cpu_buffer->write_stamp += delta;
2495 } else
2496 cpu_buffer->write_stamp += event->time_delta;
2497 }
2498}
2499
2500static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2501 struct ring_buffer_event *event)
2502{
2503 local_inc(&cpu_buffer->entries);
2504 rb_update_write_stamp(cpu_buffer, event);
2505 rb_end_commit(cpu_buffer);
2506}
2507
2508static __always_inline void
2509rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2510{
2511 bool pagebusy;
2512
2513 if (buffer->irq_work.waiters_pending) {
2514 buffer->irq_work.waiters_pending = false;
2515 /* irq_work_queue() supplies it's own memory barriers */
2516 irq_work_queue(&buffer->irq_work.work);
2517 }
2518
2519 if (cpu_buffer->irq_work.waiters_pending) {
2520 cpu_buffer->irq_work.waiters_pending = false;
2521 /* irq_work_queue() supplies it's own memory barriers */
2522 irq_work_queue(&cpu_buffer->irq_work.work);
2523 }
2524
2525 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
2526
2527 if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
2528 cpu_buffer->irq_work.wakeup_full = true;
2529 cpu_buffer->irq_work.full_waiters_pending = false;
2530 /* irq_work_queue() supplies it's own memory barriers */
2531 irq_work_queue(&cpu_buffer->irq_work.work);
2532 }
2533}
2534
2535/*
2536 * The lock and unlock are done within a preempt disable section.
2537 * The current_context per_cpu variable can only be modified
2538 * by the current task between lock and unlock. But it can
2539 * be modified more than once via an interrupt. To pass this
2540 * information from the lock to the unlock without having to
2541 * access the 'in_interrupt()' functions again (which do show
2542 * a bit of overhead in something as critical as function tracing,
2543 * we use a bitmask trick.
2544 *
2545 * bit 0 = NMI context
2546 * bit 1 = IRQ context
2547 * bit 2 = SoftIRQ context
2548 * bit 3 = normal context.
2549 *
2550 * This works because this is the order of contexts that can
2551 * preempt other contexts. A SoftIRQ never preempts an IRQ
2552 * context.
2553 *
2554 * When the context is determined, the corresponding bit is
2555 * checked and set (if it was set, then a recursion of that context
2556 * happened).
2557 *
2558 * On unlock, we need to clear this bit. To do so, just subtract
2559 * 1 from the current_context and AND it to itself.
2560 *
2561 * (binary)
2562 * 101 - 1 = 100
2563 * 101 & 100 = 100 (clearing bit zero)
2564 *
2565 * 1010 - 1 = 1001
2566 * 1010 & 1001 = 1000 (clearing bit 1)
2567 *
2568 * The least significant bit can be cleared this way, and it
2569 * just so happens that it is the same bit corresponding to
2570 * the current context.
2571 */
2572
2573static __always_inline int
2574trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
2575{
2576 unsigned int val = cpu_buffer->current_context;
2577 int bit;
2578
2579 if (in_interrupt()) {
2580 if (in_nmi())
2581 bit = RB_CTX_NMI;
2582 else if (in_irq())
2583 bit = RB_CTX_IRQ;
2584 else
2585 bit = RB_CTX_SOFTIRQ;
2586 } else
2587 bit = RB_CTX_NORMAL;
2588
2589 if (unlikely(val & (1 << bit)))
2590 return 1;
2591
2592 val |= (1 << bit);
2593 cpu_buffer->current_context = val;
2594
2595 return 0;
2596}
2597
2598static __always_inline void
2599trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
2600{
2601 cpu_buffer->current_context &= cpu_buffer->current_context - 1;
2602}
2603
2604/**
2605 * ring_buffer_unlock_commit - commit a reserved
2606 * @buffer: The buffer to commit to
2607 * @event: The event pointer to commit.
2608 *
2609 * This commits the data to the ring buffer, and releases any locks held.
2610 *
2611 * Must be paired with ring_buffer_lock_reserve.
2612 */
2613int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2614 struct ring_buffer_event *event)
2615{
2616 struct ring_buffer_per_cpu *cpu_buffer;
2617 int cpu = raw_smp_processor_id();
2618
2619 cpu_buffer = buffer->buffers[cpu];
2620
2621 rb_commit(cpu_buffer, event);
2622
2623 rb_wakeups(buffer, cpu_buffer);
2624
2625 trace_recursive_unlock(cpu_buffer);
2626
2627 preempt_enable_notrace();
2628
2629 return 0;
2630}
2631EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2632
2633static noinline void
2634rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2635 struct rb_event_info *info)
2636{
2637 WARN_ONCE(info->delta > (1ULL << 59),
2638 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2639 (unsigned long long)info->delta,
2640 (unsigned long long)info->ts,
2641 (unsigned long long)cpu_buffer->write_stamp,
2642 sched_clock_stable() ? "" :
2643 "If you just came from a suspend/resume,\n"
2644 "please switch to the trace global clock:\n"
2645 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2646 info->add_timestamp = 1;
2647}
2648
2649static struct ring_buffer_event *
2650__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2651 struct rb_event_info *info)
2652{
2653 struct ring_buffer_event *event;
2654 struct buffer_page *tail_page;
2655 unsigned long tail, write;
2656
2657 /*
2658 * If the time delta since the last event is too big to
2659 * hold in the time field of the event, then we append a
2660 * TIME EXTEND event ahead of the data event.
2661 */
2662 if (unlikely(info->add_timestamp))
2663 info->length += RB_LEN_TIME_EXTEND;
2664
2665 /* Don't let the compiler play games with cpu_buffer->tail_page */
2666 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
2667 write = local_add_return(info->length, &tail_page->write);
2668
2669 /* set write to only the index of the write */
2670 write &= RB_WRITE_MASK;
2671 tail = write - info->length;
2672
2673 /*
2674 * If this is the first commit on the page, then it has the same
2675 * timestamp as the page itself.
2676 */
2677 if (!tail)
2678 info->delta = 0;
2679
2680 /* See if we shot pass the end of this buffer page */
2681 if (unlikely(write > BUF_PAGE_SIZE))
2682 return rb_move_tail(cpu_buffer, tail, info);
2683
2684 /* We reserved something on the buffer */
2685
2686 event = __rb_page_index(tail_page, tail);
2687 kmemcheck_annotate_bitfield(event, bitfield);
2688 rb_update_event(cpu_buffer, event, info);
2689
2690 local_inc(&tail_page->entries);
2691
2692 /*
2693 * If this is the first commit on the page, then update
2694 * its timestamp.
2695 */
2696 if (!tail)
2697 tail_page->page->time_stamp = info->ts;
2698
2699 /* account for these added bytes */
2700 local_add(info->length, &cpu_buffer->entries_bytes);
2701
2702 return event;
2703}
2704
2705static __always_inline struct ring_buffer_event *
2706rb_reserve_next_event(struct ring_buffer *buffer,
2707 struct ring_buffer_per_cpu *cpu_buffer,
2708 unsigned long length)
2709{
2710 struct ring_buffer_event *event;
2711 struct rb_event_info info;
2712 int nr_loops = 0;
2713 u64 diff;
2714
2715 rb_start_commit(cpu_buffer);
2716
2717#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2718 /*
2719 * Due to the ability to swap a cpu buffer from a buffer
2720 * it is possible it was swapped before we committed.
2721 * (committing stops a swap). We check for it here and
2722 * if it happened, we have to fail the write.
2723 */
2724 barrier();
2725 if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
2726 local_dec(&cpu_buffer->committing);
2727 local_dec(&cpu_buffer->commits);
2728 return NULL;
2729 }
2730#endif
2731
2732 info.length = rb_calculate_event_length(length);
2733 again:
2734 info.add_timestamp = 0;
2735 info.delta = 0;
2736
2737 /*
2738 * We allow for interrupts to reenter here and do a trace.
2739 * If one does, it will cause this original code to loop
2740 * back here. Even with heavy interrupts happening, this
2741 * should only happen a few times in a row. If this happens
2742 * 1000 times in a row, there must be either an interrupt
2743 * storm or we have something buggy.
2744 * Bail!
2745 */
2746 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2747 goto out_fail;
2748
2749 info.ts = rb_time_stamp(cpu_buffer->buffer);
2750 diff = info.ts - cpu_buffer->write_stamp;
2751
2752 /* make sure this diff is calculated here */
2753 barrier();
2754
2755 /* Did the write stamp get updated already? */
2756 if (likely(info.ts >= cpu_buffer->write_stamp)) {
2757 info.delta = diff;
2758 if (unlikely(test_time_stamp(info.delta)))
2759 rb_handle_timestamp(cpu_buffer, &info);
2760 }
2761
2762 event = __rb_reserve_next(cpu_buffer, &info);
2763
2764 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
2765 if (info.add_timestamp)
2766 info.length -= RB_LEN_TIME_EXTEND;
2767 goto again;
2768 }
2769
2770 if (!event)
2771 goto out_fail;
2772
2773 return event;
2774
2775 out_fail:
2776 rb_end_commit(cpu_buffer);
2777 return NULL;
2778}
2779
2780/**
2781 * ring_buffer_lock_reserve - reserve a part of the buffer
2782 * @buffer: the ring buffer to reserve from
2783 * @length: the length of the data to reserve (excluding event header)
2784 *
2785 * Returns a reseverd event on the ring buffer to copy directly to.
2786 * The user of this interface will need to get the body to write into
2787 * and can use the ring_buffer_event_data() interface.
2788 *
2789 * The length is the length of the data needed, not the event length
2790 * which also includes the event header.
2791 *
2792 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2793 * If NULL is returned, then nothing has been allocated or locked.
2794 */
2795struct ring_buffer_event *
2796ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2797{
2798 struct ring_buffer_per_cpu *cpu_buffer;
2799 struct ring_buffer_event *event;
2800 int cpu;
2801
2802 /* If we are tracing schedule, we don't want to recurse */
2803 preempt_disable_notrace();
2804
2805 if (unlikely(atomic_read(&buffer->record_disabled)))
2806 goto out;
2807
2808 cpu = raw_smp_processor_id();
2809
2810 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
2811 goto out;
2812
2813 cpu_buffer = buffer->buffers[cpu];
2814
2815 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
2816 goto out;
2817
2818 if (unlikely(length > BUF_MAX_DATA_SIZE))
2819 goto out;
2820
2821 if (unlikely(trace_recursive_lock(cpu_buffer)))
2822 goto out;
2823
2824 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2825 if (!event)
2826 goto out_unlock;
2827
2828 return event;
2829
2830 out_unlock:
2831 trace_recursive_unlock(cpu_buffer);
2832 out:
2833 preempt_enable_notrace();
2834 return NULL;
2835}
2836EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2837
2838/*
2839 * Decrement the entries to the page that an event is on.
2840 * The event does not even need to exist, only the pointer
2841 * to the page it is on. This may only be called before the commit
2842 * takes place.
2843 */
2844static inline void
2845rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2846 struct ring_buffer_event *event)
2847{
2848 unsigned long addr = (unsigned long)event;
2849 struct buffer_page *bpage = cpu_buffer->commit_page;
2850 struct buffer_page *start;
2851
2852 addr &= PAGE_MASK;
2853
2854 /* Do the likely case first */
2855 if (likely(bpage->page == (void *)addr)) {
2856 local_dec(&bpage->entries);
2857 return;
2858 }
2859
2860 /*
2861 * Because the commit page may be on the reader page we
2862 * start with the next page and check the end loop there.
2863 */
2864 rb_inc_page(cpu_buffer, &bpage);
2865 start = bpage;
2866 do {
2867 if (bpage->page == (void *)addr) {
2868 local_dec(&bpage->entries);
2869 return;
2870 }
2871 rb_inc_page(cpu_buffer, &bpage);
2872 } while (bpage != start);
2873
2874 /* commit not part of this buffer?? */
2875 RB_WARN_ON(cpu_buffer, 1);
2876}
2877
2878/**
2879 * ring_buffer_commit_discard - discard an event that has not been committed
2880 * @buffer: the ring buffer
2881 * @event: non committed event to discard
2882 *
2883 * Sometimes an event that is in the ring buffer needs to be ignored.
2884 * This function lets the user discard an event in the ring buffer
2885 * and then that event will not be read later.
2886 *
2887 * This function only works if it is called before the the item has been
2888 * committed. It will try to free the event from the ring buffer
2889 * if another event has not been added behind it.
2890 *
2891 * If another event has been added behind it, it will set the event
2892 * up as discarded, and perform the commit.
2893 *
2894 * If this function is called, do not call ring_buffer_unlock_commit on
2895 * the event.
2896 */
2897void ring_buffer_discard_commit(struct ring_buffer *buffer,
2898 struct ring_buffer_event *event)
2899{
2900 struct ring_buffer_per_cpu *cpu_buffer;
2901 int cpu;
2902
2903 /* The event is discarded regardless */
2904 rb_event_discard(event);
2905
2906 cpu = smp_processor_id();
2907 cpu_buffer = buffer->buffers[cpu];
2908
2909 /*
2910 * This must only be called if the event has not been
2911 * committed yet. Thus we can assume that preemption
2912 * is still disabled.
2913 */
2914 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
2915
2916 rb_decrement_entry(cpu_buffer, event);
2917 if (rb_try_to_discard(cpu_buffer, event))
2918 goto out;
2919
2920 /*
2921 * The commit is still visible by the reader, so we
2922 * must still update the timestamp.
2923 */
2924 rb_update_write_stamp(cpu_buffer, event);
2925 out:
2926 rb_end_commit(cpu_buffer);
2927
2928 trace_recursive_unlock(cpu_buffer);
2929
2930 preempt_enable_notrace();
2931
2932}
2933EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
2934
2935/**
2936 * ring_buffer_write - write data to the buffer without reserving
2937 * @buffer: The ring buffer to write to.
2938 * @length: The length of the data being written (excluding the event header)
2939 * @data: The data to write to the buffer.
2940 *
2941 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2942 * one function. If you already have the data to write to the buffer, it
2943 * may be easier to simply call this function.
2944 *
2945 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2946 * and not the length of the event which would hold the header.
2947 */
2948int ring_buffer_write(struct ring_buffer *buffer,
2949 unsigned long length,
2950 void *data)
2951{
2952 struct ring_buffer_per_cpu *cpu_buffer;
2953 struct ring_buffer_event *event;
2954 void *body;
2955 int ret = -EBUSY;
2956 int cpu;
2957
2958 preempt_disable_notrace();
2959
2960 if (atomic_read(&buffer->record_disabled))
2961 goto out;
2962
2963 cpu = raw_smp_processor_id();
2964
2965 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2966 goto out;
2967
2968 cpu_buffer = buffer->buffers[cpu];
2969
2970 if (atomic_read(&cpu_buffer->record_disabled))
2971 goto out;
2972
2973 if (length > BUF_MAX_DATA_SIZE)
2974 goto out;
2975
2976 if (unlikely(trace_recursive_lock(cpu_buffer)))
2977 goto out;
2978
2979 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2980 if (!event)
2981 goto out_unlock;
2982
2983 body = rb_event_data(event);
2984
2985 memcpy(body, data, length);
2986
2987 rb_commit(cpu_buffer, event);
2988
2989 rb_wakeups(buffer, cpu_buffer);
2990
2991 ret = 0;
2992
2993 out_unlock:
2994 trace_recursive_unlock(cpu_buffer);
2995
2996 out:
2997 preempt_enable_notrace();
2998
2999 return ret;
3000}
3001EXPORT_SYMBOL_GPL(ring_buffer_write);
3002
3003static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3004{
3005 struct buffer_page *reader = cpu_buffer->reader_page;
3006 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3007 struct buffer_page *commit = cpu_buffer->commit_page;
3008
3009 /* In case of error, head will be NULL */
3010 if (unlikely(!head))
3011 return true;
3012
3013 return reader->read == rb_page_commit(reader) &&
3014 (commit == reader ||
3015 (commit == head &&
3016 head->read == rb_page_commit(commit)));
3017}
3018
3019/**
3020 * ring_buffer_record_disable - stop all writes into the buffer
3021 * @buffer: The ring buffer to stop writes to.
3022 *
3023 * This prevents all writes to the buffer. Any attempt to write
3024 * to the buffer after this will fail and return NULL.
3025 *
3026 * The caller should call synchronize_sched() after this.
3027 */
3028void ring_buffer_record_disable(struct ring_buffer *buffer)
3029{
3030 atomic_inc(&buffer->record_disabled);
3031}
3032EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3033
3034/**
3035 * ring_buffer_record_enable - enable writes to the buffer
3036 * @buffer: The ring buffer to enable writes
3037 *
3038 * Note, multiple disables will need the same number of enables
3039 * to truly enable the writing (much like preempt_disable).
3040 */
3041void ring_buffer_record_enable(struct ring_buffer *buffer)
3042{
3043 atomic_dec(&buffer->record_disabled);
3044}
3045EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3046
3047/**
3048 * ring_buffer_record_off - stop all writes into the buffer
3049 * @buffer: The ring buffer to stop writes to.
3050 *
3051 * This prevents all writes to the buffer. Any attempt to write
3052 * to the buffer after this will fail and return NULL.
3053 *
3054 * This is different than ring_buffer_record_disable() as
3055 * it works like an on/off switch, where as the disable() version
3056 * must be paired with a enable().
3057 */
3058void ring_buffer_record_off(struct ring_buffer *buffer)
3059{
3060 unsigned int rd;
3061 unsigned int new_rd;
3062
3063 do {
3064 rd = atomic_read(&buffer->record_disabled);
3065 new_rd = rd | RB_BUFFER_OFF;
3066 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3067}
3068EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3069
3070/**
3071 * ring_buffer_record_on - restart writes into the buffer
3072 * @buffer: The ring buffer to start writes to.
3073 *
3074 * This enables all writes to the buffer that was disabled by
3075 * ring_buffer_record_off().
3076 *
3077 * This is different than ring_buffer_record_enable() as
3078 * it works like an on/off switch, where as the enable() version
3079 * must be paired with a disable().
3080 */
3081void ring_buffer_record_on(struct ring_buffer *buffer)
3082{
3083 unsigned int rd;
3084 unsigned int new_rd;
3085
3086 do {
3087 rd = atomic_read(&buffer->record_disabled);
3088 new_rd = rd & ~RB_BUFFER_OFF;
3089 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3090}
3091EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3092
3093/**
3094 * ring_buffer_record_is_on - return true if the ring buffer can write
3095 * @buffer: The ring buffer to see if write is enabled
3096 *
3097 * Returns true if the ring buffer is in a state that it accepts writes.
3098 */
3099int ring_buffer_record_is_on(struct ring_buffer *buffer)
3100{
3101 return !atomic_read(&buffer->record_disabled);
3102}
3103
3104/**
3105 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3106 * @buffer: The ring buffer to stop writes to.
3107 * @cpu: The CPU buffer to stop
3108 *
3109 * This prevents all writes to the buffer. Any attempt to write
3110 * to the buffer after this will fail and return NULL.
3111 *
3112 * The caller should call synchronize_sched() after this.
3113 */
3114void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3115{
3116 struct ring_buffer_per_cpu *cpu_buffer;
3117
3118 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3119 return;
3120
3121 cpu_buffer = buffer->buffers[cpu];
3122 atomic_inc(&cpu_buffer->record_disabled);
3123}
3124EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3125
3126/**
3127 * ring_buffer_record_enable_cpu - enable writes to the buffer
3128 * @buffer: The ring buffer to enable writes
3129 * @cpu: The CPU to enable.
3130 *
3131 * Note, multiple disables will need the same number of enables
3132 * to truly enable the writing (much like preempt_disable).
3133 */
3134void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3135{
3136 struct ring_buffer_per_cpu *cpu_buffer;
3137
3138 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3139 return;
3140
3141 cpu_buffer = buffer->buffers[cpu];
3142 atomic_dec(&cpu_buffer->record_disabled);
3143}
3144EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3145
3146/*
3147 * The total entries in the ring buffer is the running counter
3148 * of entries entered into the ring buffer, minus the sum of
3149 * the entries read from the ring buffer and the number of
3150 * entries that were overwritten.
3151 */
3152static inline unsigned long
3153rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3154{
3155 return local_read(&cpu_buffer->entries) -
3156 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3157}
3158
3159/**
3160 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3161 * @buffer: The ring buffer
3162 * @cpu: The per CPU buffer to read from.
3163 */
3164u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3165{
3166 unsigned long flags;
3167 struct ring_buffer_per_cpu *cpu_buffer;
3168 struct buffer_page *bpage;
3169 u64 ret = 0;
3170
3171 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3172 return 0;
3173
3174 cpu_buffer = buffer->buffers[cpu];
3175 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3176 /*
3177 * if the tail is on reader_page, oldest time stamp is on the reader
3178 * page
3179 */
3180 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3181 bpage = cpu_buffer->reader_page;
3182 else
3183 bpage = rb_set_head_page(cpu_buffer);
3184 if (bpage)
3185 ret = bpage->page->time_stamp;
3186 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3187
3188 return ret;
3189}
3190EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3191
3192/**
3193 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3194 * @buffer: The ring buffer
3195 * @cpu: The per CPU buffer to read from.
3196 */
3197unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3198{
3199 struct ring_buffer_per_cpu *cpu_buffer;
3200 unsigned long ret;
3201
3202 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3203 return 0;
3204
3205 cpu_buffer = buffer->buffers[cpu];
3206 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3207
3208 return ret;
3209}
3210EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3211
3212/**
3213 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3214 * @buffer: The ring buffer
3215 * @cpu: The per CPU buffer to get the entries from.
3216 */
3217unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3218{
3219 struct ring_buffer_per_cpu *cpu_buffer;
3220
3221 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3222 return 0;
3223
3224 cpu_buffer = buffer->buffers[cpu];
3225
3226 return rb_num_of_entries(cpu_buffer);
3227}
3228EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3229
3230/**
3231 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3232 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3233 * @buffer: The ring buffer
3234 * @cpu: The per CPU buffer to get the number of overruns from
3235 */
3236unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3237{
3238 struct ring_buffer_per_cpu *cpu_buffer;
3239 unsigned long ret;
3240
3241 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3242 return 0;
3243
3244 cpu_buffer = buffer->buffers[cpu];
3245 ret = local_read(&cpu_buffer->overrun);
3246
3247 return ret;
3248}
3249EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3250
3251/**
3252 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3253 * commits failing due to the buffer wrapping around while there are uncommitted
3254 * events, such as during an interrupt storm.
3255 * @buffer: The ring buffer
3256 * @cpu: The per CPU buffer to get the number of overruns from
3257 */
3258unsigned long
3259ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3260{
3261 struct ring_buffer_per_cpu *cpu_buffer;
3262 unsigned long ret;
3263
3264 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3265 return 0;
3266
3267 cpu_buffer = buffer->buffers[cpu];
3268 ret = local_read(&cpu_buffer->commit_overrun);
3269
3270 return ret;
3271}
3272EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3273
3274/**
3275 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3276 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3277 * @buffer: The ring buffer
3278 * @cpu: The per CPU buffer to get the number of overruns from
3279 */
3280unsigned long
3281ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3282{
3283 struct ring_buffer_per_cpu *cpu_buffer;
3284 unsigned long ret;
3285
3286 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3287 return 0;
3288
3289 cpu_buffer = buffer->buffers[cpu];
3290 ret = local_read(&cpu_buffer->dropped_events);
3291
3292 return ret;
3293}
3294EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3295
3296/**
3297 * ring_buffer_read_events_cpu - get the number of events successfully read
3298 * @buffer: The ring buffer
3299 * @cpu: The per CPU buffer to get the number of events read
3300 */
3301unsigned long
3302ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3303{
3304 struct ring_buffer_per_cpu *cpu_buffer;
3305
3306 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3307 return 0;
3308
3309 cpu_buffer = buffer->buffers[cpu];
3310 return cpu_buffer->read;
3311}
3312EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3313
3314/**
3315 * ring_buffer_entries - get the number of entries in a buffer
3316 * @buffer: The ring buffer
3317 *
3318 * Returns the total number of entries in the ring buffer
3319 * (all CPU entries)
3320 */
3321unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3322{
3323 struct ring_buffer_per_cpu *cpu_buffer;
3324 unsigned long entries = 0;
3325 int cpu;
3326
3327 /* if you care about this being correct, lock the buffer */
3328 for_each_buffer_cpu(buffer, cpu) {
3329 cpu_buffer = buffer->buffers[cpu];
3330 entries += rb_num_of_entries(cpu_buffer);
3331 }
3332
3333 return entries;
3334}
3335EXPORT_SYMBOL_GPL(ring_buffer_entries);
3336
3337/**
3338 * ring_buffer_overruns - get the number of overruns in buffer
3339 * @buffer: The ring buffer
3340 *
3341 * Returns the total number of overruns in the ring buffer
3342 * (all CPU entries)
3343 */
3344unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3345{
3346 struct ring_buffer_per_cpu *cpu_buffer;
3347 unsigned long overruns = 0;
3348 int cpu;
3349
3350 /* if you care about this being correct, lock the buffer */
3351 for_each_buffer_cpu(buffer, cpu) {
3352 cpu_buffer = buffer->buffers[cpu];
3353 overruns += local_read(&cpu_buffer->overrun);
3354 }
3355
3356 return overruns;
3357}
3358EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3359
3360static void rb_iter_reset(struct ring_buffer_iter *iter)
3361{
3362 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3363
3364 /* Iterator usage is expected to have record disabled */
3365 iter->head_page = cpu_buffer->reader_page;
3366 iter->head = cpu_buffer->reader_page->read;
3367
3368 iter->cache_reader_page = iter->head_page;
3369 iter->cache_read = cpu_buffer->read;
3370
3371 if (iter->head)
3372 iter->read_stamp = cpu_buffer->read_stamp;
3373 else
3374 iter->read_stamp = iter->head_page->page->time_stamp;
3375}
3376
3377/**
3378 * ring_buffer_iter_reset - reset an iterator
3379 * @iter: The iterator to reset
3380 *
3381 * Resets the iterator, so that it will start from the beginning
3382 * again.
3383 */
3384void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3385{
3386 struct ring_buffer_per_cpu *cpu_buffer;
3387 unsigned long flags;
3388
3389 if (!iter)
3390 return;
3391
3392 cpu_buffer = iter->cpu_buffer;
3393
3394 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3395 rb_iter_reset(iter);
3396 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3397}
3398EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3399
3400/**
3401 * ring_buffer_iter_empty - check if an iterator has no more to read
3402 * @iter: The iterator to check
3403 */
3404int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3405{
3406 struct ring_buffer_per_cpu *cpu_buffer;
3407
3408 cpu_buffer = iter->cpu_buffer;
3409
3410 return iter->head_page == cpu_buffer->commit_page &&
3411 iter->head == rb_commit_index(cpu_buffer);
3412}
3413EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3414
3415static void
3416rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3417 struct ring_buffer_event *event)
3418{
3419 u64 delta;
3420
3421 switch (event->type_len) {
3422 case RINGBUF_TYPE_PADDING:
3423 return;
3424
3425 case RINGBUF_TYPE_TIME_EXTEND:
3426 delta = event->array[0];
3427 delta <<= TS_SHIFT;
3428 delta += event->time_delta;
3429 cpu_buffer->read_stamp += delta;
3430 return;
3431
3432 case RINGBUF_TYPE_TIME_STAMP:
3433 /* FIXME: not implemented */
3434 return;
3435
3436 case RINGBUF_TYPE_DATA:
3437 cpu_buffer->read_stamp += event->time_delta;
3438 return;
3439
3440 default:
3441 BUG();
3442 }
3443 return;
3444}
3445
3446static void
3447rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3448 struct ring_buffer_event *event)
3449{
3450 u64 delta;
3451
3452 switch (event->type_len) {
3453 case RINGBUF_TYPE_PADDING:
3454 return;
3455
3456 case RINGBUF_TYPE_TIME_EXTEND:
3457 delta = event->array[0];
3458 delta <<= TS_SHIFT;
3459 delta += event->time_delta;
3460 iter->read_stamp += delta;
3461 return;
3462
3463 case RINGBUF_TYPE_TIME_STAMP:
3464 /* FIXME: not implemented */
3465 return;
3466
3467 case RINGBUF_TYPE_DATA:
3468 iter->read_stamp += event->time_delta;
3469 return;
3470
3471 default:
3472 BUG();
3473 }
3474 return;
3475}
3476
3477static struct buffer_page *
3478rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3479{
3480 struct buffer_page *reader = NULL;
3481 unsigned long overwrite;
3482 unsigned long flags;
3483 int nr_loops = 0;
3484 int ret;
3485
3486 local_irq_save(flags);
3487 arch_spin_lock(&cpu_buffer->lock);
3488
3489 again:
3490 /*
3491 * This should normally only loop twice. But because the
3492 * start of the reader inserts an empty page, it causes
3493 * a case where we will loop three times. There should be no
3494 * reason to loop four times (that I know of).
3495 */
3496 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3497 reader = NULL;
3498 goto out;
3499 }
3500
3501 reader = cpu_buffer->reader_page;
3502
3503 /* If there's more to read, return this page */
3504 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3505 goto out;
3506
3507 /* Never should we have an index greater than the size */
3508 if (RB_WARN_ON(cpu_buffer,
3509 cpu_buffer->reader_page->read > rb_page_size(reader)))
3510 goto out;
3511
3512 /* check if we caught up to the tail */
3513 reader = NULL;
3514 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3515 goto out;
3516
3517 /* Don't bother swapping if the ring buffer is empty */
3518 if (rb_num_of_entries(cpu_buffer) == 0)
3519 goto out;
3520
3521 /*
3522 * Reset the reader page to size zero.
3523 */
3524 local_set(&cpu_buffer->reader_page->write, 0);
3525 local_set(&cpu_buffer->reader_page->entries, 0);
3526 local_set(&cpu_buffer->reader_page->page->commit, 0);
3527 cpu_buffer->reader_page->real_end = 0;
3528
3529 spin:
3530 /*
3531 * Splice the empty reader page into the list around the head.
3532 */
3533 reader = rb_set_head_page(cpu_buffer);
3534 if (!reader)
3535 goto out;
3536 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3537 cpu_buffer->reader_page->list.prev = reader->list.prev;
3538
3539 /*
3540 * cpu_buffer->pages just needs to point to the buffer, it
3541 * has no specific buffer page to point to. Lets move it out
3542 * of our way so we don't accidentally swap it.
3543 */
3544 cpu_buffer->pages = reader->list.prev;
3545
3546 /* The reader page will be pointing to the new head */
3547 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3548
3549 /*
3550 * We want to make sure we read the overruns after we set up our
3551 * pointers to the next object. The writer side does a
3552 * cmpxchg to cross pages which acts as the mb on the writer
3553 * side. Note, the reader will constantly fail the swap
3554 * while the writer is updating the pointers, so this
3555 * guarantees that the overwrite recorded here is the one we
3556 * want to compare with the last_overrun.
3557 */
3558 smp_mb();
3559 overwrite = local_read(&(cpu_buffer->overrun));
3560
3561 /*
3562 * Here's the tricky part.
3563 *
3564 * We need to move the pointer past the header page.
3565 * But we can only do that if a writer is not currently
3566 * moving it. The page before the header page has the
3567 * flag bit '1' set if it is pointing to the page we want.
3568 * but if the writer is in the process of moving it
3569 * than it will be '2' or already moved '0'.
3570 */
3571
3572 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3573
3574 /*
3575 * If we did not convert it, then we must try again.
3576 */
3577 if (!ret)
3578 goto spin;
3579
3580 /*
3581 * Yeah! We succeeded in replacing the page.
3582 *
3583 * Now make the new head point back to the reader page.
3584 */
3585 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3586 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3587
3588 /* Finally update the reader page to the new head */
3589 cpu_buffer->reader_page = reader;
3590 cpu_buffer->reader_page->read = 0;
3591
3592 if (overwrite != cpu_buffer->last_overrun) {
3593 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3594 cpu_buffer->last_overrun = overwrite;
3595 }
3596
3597 goto again;
3598
3599 out:
3600 /* Update the read_stamp on the first event */
3601 if (reader && reader->read == 0)
3602 cpu_buffer->read_stamp = reader->page->time_stamp;
3603
3604 arch_spin_unlock(&cpu_buffer->lock);
3605 local_irq_restore(flags);
3606
3607 return reader;
3608}
3609
3610static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3611{
3612 struct ring_buffer_event *event;
3613 struct buffer_page *reader;
3614 unsigned length;
3615
3616 reader = rb_get_reader_page(cpu_buffer);
3617
3618 /* This function should not be called when buffer is empty */
3619 if (RB_WARN_ON(cpu_buffer, !reader))
3620 return;
3621
3622 event = rb_reader_event(cpu_buffer);
3623
3624 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3625 cpu_buffer->read++;
3626
3627 rb_update_read_stamp(cpu_buffer, event);
3628
3629 length = rb_event_length(event);
3630 cpu_buffer->reader_page->read += length;
3631}
3632
3633static void rb_advance_iter(struct ring_buffer_iter *iter)
3634{
3635 struct ring_buffer_per_cpu *cpu_buffer;
3636 struct ring_buffer_event *event;
3637 unsigned length;
3638
3639 cpu_buffer = iter->cpu_buffer;
3640
3641 /*
3642 * Check if we are at the end of the buffer.
3643 */
3644 if (iter->head >= rb_page_size(iter->head_page)) {
3645 /* discarded commits can make the page empty */
3646 if (iter->head_page == cpu_buffer->commit_page)
3647 return;
3648 rb_inc_iter(iter);
3649 return;
3650 }
3651
3652 event = rb_iter_head_event(iter);
3653
3654 length = rb_event_length(event);
3655
3656 /*
3657 * This should not be called to advance the header if we are
3658 * at the tail of the buffer.
3659 */
3660 if (RB_WARN_ON(cpu_buffer,
3661 (iter->head_page == cpu_buffer->commit_page) &&
3662 (iter->head + length > rb_commit_index(cpu_buffer))))
3663 return;
3664
3665 rb_update_iter_read_stamp(iter, event);
3666
3667 iter->head += length;
3668
3669 /* check for end of page padding */
3670 if ((iter->head >= rb_page_size(iter->head_page)) &&
3671 (iter->head_page != cpu_buffer->commit_page))
3672 rb_inc_iter(iter);
3673}
3674
3675static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3676{
3677 return cpu_buffer->lost_events;
3678}
3679
3680static struct ring_buffer_event *
3681rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3682 unsigned long *lost_events)
3683{
3684 struct ring_buffer_event *event;
3685 struct buffer_page *reader;
3686 int nr_loops = 0;
3687
3688 again:
3689 /*
3690 * We repeat when a time extend is encountered.
3691 * Since the time extend is always attached to a data event,
3692 * we should never loop more than once.
3693 * (We never hit the following condition more than twice).
3694 */
3695 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3696 return NULL;
3697
3698 reader = rb_get_reader_page(cpu_buffer);
3699 if (!reader)
3700 return NULL;
3701
3702 event = rb_reader_event(cpu_buffer);
3703
3704 switch (event->type_len) {
3705 case RINGBUF_TYPE_PADDING:
3706 if (rb_null_event(event))
3707 RB_WARN_ON(cpu_buffer, 1);
3708 /*
3709 * Because the writer could be discarding every
3710 * event it creates (which would probably be bad)
3711 * if we were to go back to "again" then we may never
3712 * catch up, and will trigger the warn on, or lock
3713 * the box. Return the padding, and we will release
3714 * the current locks, and try again.
3715 */
3716 return event;
3717
3718 case RINGBUF_TYPE_TIME_EXTEND:
3719 /* Internal data, OK to advance */
3720 rb_advance_reader(cpu_buffer);
3721 goto again;
3722
3723 case RINGBUF_TYPE_TIME_STAMP:
3724 /* FIXME: not implemented */
3725 rb_advance_reader(cpu_buffer);
3726 goto again;
3727
3728 case RINGBUF_TYPE_DATA:
3729 if (ts) {
3730 *ts = cpu_buffer->read_stamp + event->time_delta;
3731 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3732 cpu_buffer->cpu, ts);
3733 }
3734 if (lost_events)
3735 *lost_events = rb_lost_events(cpu_buffer);
3736 return event;
3737
3738 default:
3739 BUG();
3740 }
3741
3742 return NULL;
3743}
3744EXPORT_SYMBOL_GPL(ring_buffer_peek);
3745
3746static struct ring_buffer_event *
3747rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3748{
3749 struct ring_buffer *buffer;
3750 struct ring_buffer_per_cpu *cpu_buffer;
3751 struct ring_buffer_event *event;
3752 int nr_loops = 0;
3753
3754 cpu_buffer = iter->cpu_buffer;
3755 buffer = cpu_buffer->buffer;
3756
3757 /*
3758 * Check if someone performed a consuming read to
3759 * the buffer. A consuming read invalidates the iterator
3760 * and we need to reset the iterator in this case.
3761 */
3762 if (unlikely(iter->cache_read != cpu_buffer->read ||
3763 iter->cache_reader_page != cpu_buffer->reader_page))
3764 rb_iter_reset(iter);
3765
3766 again:
3767 if (ring_buffer_iter_empty(iter))
3768 return NULL;
3769
3770 /*
3771 * We repeat when a time extend is encountered or we hit
3772 * the end of the page. Since the time extend is always attached
3773 * to a data event, we should never loop more than three times.
3774 * Once for going to next page, once on time extend, and
3775 * finally once to get the event.
3776 * (We never hit the following condition more than thrice).
3777 */
3778 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
3779 return NULL;
3780
3781 if (rb_per_cpu_empty(cpu_buffer))
3782 return NULL;
3783
3784 if (iter->head >= rb_page_size(iter->head_page)) {
3785 rb_inc_iter(iter);
3786 goto again;
3787 }
3788
3789 event = rb_iter_head_event(iter);
3790
3791 switch (event->type_len) {
3792 case RINGBUF_TYPE_PADDING:
3793 if (rb_null_event(event)) {
3794 rb_inc_iter(iter);
3795 goto again;
3796 }
3797 rb_advance_iter(iter);
3798 return event;
3799
3800 case RINGBUF_TYPE_TIME_EXTEND:
3801 /* Internal data, OK to advance */
3802 rb_advance_iter(iter);
3803 goto again;
3804
3805 case RINGBUF_TYPE_TIME_STAMP:
3806 /* FIXME: not implemented */
3807 rb_advance_iter(iter);
3808 goto again;
3809
3810 case RINGBUF_TYPE_DATA:
3811 if (ts) {
3812 *ts = iter->read_stamp + event->time_delta;
3813 ring_buffer_normalize_time_stamp(buffer,
3814 cpu_buffer->cpu, ts);
3815 }
3816 return event;
3817
3818 default:
3819 BUG();
3820 }
3821
3822 return NULL;
3823}
3824EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3825
3826static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
3827{
3828 if (likely(!in_nmi())) {
3829 raw_spin_lock(&cpu_buffer->reader_lock);
3830 return true;
3831 }
3832
3833 /*
3834 * If an NMI die dumps out the content of the ring buffer
3835 * trylock must be used to prevent a deadlock if the NMI
3836 * preempted a task that holds the ring buffer locks. If
3837 * we get the lock then all is fine, if not, then continue
3838 * to do the read, but this can corrupt the ring buffer,
3839 * so it must be permanently disabled from future writes.
3840 * Reading from NMI is a oneshot deal.
3841 */
3842 if (raw_spin_trylock(&cpu_buffer->reader_lock))
3843 return true;
3844
3845 /* Continue without locking, but disable the ring buffer */
3846 atomic_inc(&cpu_buffer->record_disabled);
3847 return false;
3848}
3849
3850static inline void
3851rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
3852{
3853 if (likely(locked))
3854 raw_spin_unlock(&cpu_buffer->reader_lock);
3855 return;
3856}
3857
3858/**
3859 * ring_buffer_peek - peek at the next event to be read
3860 * @buffer: The ring buffer to read
3861 * @cpu: The cpu to peak at
3862 * @ts: The timestamp counter of this event.
3863 * @lost_events: a variable to store if events were lost (may be NULL)
3864 *
3865 * This will return the event that will be read next, but does
3866 * not consume the data.
3867 */
3868struct ring_buffer_event *
3869ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
3870 unsigned long *lost_events)
3871{
3872 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3873 struct ring_buffer_event *event;
3874 unsigned long flags;
3875 bool dolock;
3876
3877 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3878 return NULL;
3879
3880 again:
3881 local_irq_save(flags);
3882 dolock = rb_reader_lock(cpu_buffer);
3883 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3884 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3885 rb_advance_reader(cpu_buffer);
3886 rb_reader_unlock(cpu_buffer, dolock);
3887 local_irq_restore(flags);
3888
3889 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3890 goto again;
3891
3892 return event;
3893}
3894
3895/**
3896 * ring_buffer_iter_peek - peek at the next event to be read
3897 * @iter: The ring buffer iterator
3898 * @ts: The timestamp counter of this event.
3899 *
3900 * This will return the event that will be read next, but does
3901 * not increment the iterator.
3902 */
3903struct ring_buffer_event *
3904ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3905{
3906 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3907 struct ring_buffer_event *event;
3908 unsigned long flags;
3909
3910 again:
3911 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3912 event = rb_iter_peek(iter, ts);
3913 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3914
3915 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3916 goto again;
3917
3918 return event;
3919}
3920
3921/**
3922 * ring_buffer_consume - return an event and consume it
3923 * @buffer: The ring buffer to get the next event from
3924 * @cpu: the cpu to read the buffer from
3925 * @ts: a variable to store the timestamp (may be NULL)
3926 * @lost_events: a variable to store if events were lost (may be NULL)
3927 *
3928 * Returns the next event in the ring buffer, and that event is consumed.
3929 * Meaning, that sequential reads will keep returning a different event,
3930 * and eventually empty the ring buffer if the producer is slower.
3931 */
3932struct ring_buffer_event *
3933ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
3934 unsigned long *lost_events)
3935{
3936 struct ring_buffer_per_cpu *cpu_buffer;
3937 struct ring_buffer_event *event = NULL;
3938 unsigned long flags;
3939 bool dolock;
3940
3941 again:
3942 /* might be called in atomic */
3943 preempt_disable();
3944
3945 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3946 goto out;
3947
3948 cpu_buffer = buffer->buffers[cpu];
3949 local_irq_save(flags);
3950 dolock = rb_reader_lock(cpu_buffer);
3951
3952 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3953 if (event) {
3954 cpu_buffer->lost_events = 0;
3955 rb_advance_reader(cpu_buffer);
3956 }
3957
3958 rb_reader_unlock(cpu_buffer, dolock);
3959 local_irq_restore(flags);
3960
3961 out:
3962 preempt_enable();
3963
3964 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3965 goto again;
3966
3967 return event;
3968}
3969EXPORT_SYMBOL_GPL(ring_buffer_consume);
3970
3971/**
3972 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3973 * @buffer: The ring buffer to read from
3974 * @cpu: The cpu buffer to iterate over
3975 *
3976 * This performs the initial preparations necessary to iterate
3977 * through the buffer. Memory is allocated, buffer recording
3978 * is disabled, and the iterator pointer is returned to the caller.
3979 *
3980 * Disabling buffer recordng prevents the reading from being
3981 * corrupted. This is not a consuming read, so a producer is not
3982 * expected.
3983 *
3984 * After a sequence of ring_buffer_read_prepare calls, the user is
3985 * expected to make at least one call to ring_buffer_read_prepare_sync.
3986 * Afterwards, ring_buffer_read_start is invoked to get things going
3987 * for real.
3988 *
3989 * This overall must be paired with ring_buffer_read_finish.
3990 */
3991struct ring_buffer_iter *
3992ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
3993{
3994 struct ring_buffer_per_cpu *cpu_buffer;
3995 struct ring_buffer_iter *iter;
3996
3997 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3998 return NULL;
3999
4000 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
4001 if (!iter)
4002 return NULL;
4003
4004 cpu_buffer = buffer->buffers[cpu];
4005
4006 iter->cpu_buffer = cpu_buffer;
4007
4008 atomic_inc(&buffer->resize_disabled);
4009 atomic_inc(&cpu_buffer->record_disabled);
4010
4011 return iter;
4012}
4013EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4014
4015/**
4016 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4017 *
4018 * All previously invoked ring_buffer_read_prepare calls to prepare
4019 * iterators will be synchronized. Afterwards, read_buffer_read_start
4020 * calls on those iterators are allowed.
4021 */
4022void
4023ring_buffer_read_prepare_sync(void)
4024{
4025 synchronize_sched();
4026}
4027EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4028
4029/**
4030 * ring_buffer_read_start - start a non consuming read of the buffer
4031 * @iter: The iterator returned by ring_buffer_read_prepare
4032 *
4033 * This finalizes the startup of an iteration through the buffer.
4034 * The iterator comes from a call to ring_buffer_read_prepare and
4035 * an intervening ring_buffer_read_prepare_sync must have been
4036 * performed.
4037 *
4038 * Must be paired with ring_buffer_read_finish.
4039 */
4040void
4041ring_buffer_read_start(struct ring_buffer_iter *iter)
4042{
4043 struct ring_buffer_per_cpu *cpu_buffer;
4044 unsigned long flags;
4045
4046 if (!iter)
4047 return;
4048
4049 cpu_buffer = iter->cpu_buffer;
4050
4051 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4052 arch_spin_lock(&cpu_buffer->lock);
4053 rb_iter_reset(iter);
4054 arch_spin_unlock(&cpu_buffer->lock);
4055 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4056}
4057EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4058
4059/**
4060 * ring_buffer_read_finish - finish reading the iterator of the buffer
4061 * @iter: The iterator retrieved by ring_buffer_start
4062 *
4063 * This re-enables the recording to the buffer, and frees the
4064 * iterator.
4065 */
4066void
4067ring_buffer_read_finish(struct ring_buffer_iter *iter)
4068{
4069 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4070 unsigned long flags;
4071
4072 /*
4073 * Ring buffer is disabled from recording, here's a good place
4074 * to check the integrity of the ring buffer.
4075 * Must prevent readers from trying to read, as the check
4076 * clears the HEAD page and readers require it.
4077 */
4078 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4079 rb_check_pages(cpu_buffer);
4080 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4081
4082 atomic_dec(&cpu_buffer->record_disabled);
4083 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4084 kfree(iter);
4085}
4086EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4087
4088/**
4089 * ring_buffer_read - read the next item in the ring buffer by the iterator
4090 * @iter: The ring buffer iterator
4091 * @ts: The time stamp of the event read.
4092 *
4093 * This reads the next event in the ring buffer and increments the iterator.
4094 */
4095struct ring_buffer_event *
4096ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4097{
4098 struct ring_buffer_event *event;
4099 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4100 unsigned long flags;
4101
4102 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4103 again:
4104 event = rb_iter_peek(iter, ts);
4105 if (!event)
4106 goto out;
4107
4108 if (event->type_len == RINGBUF_TYPE_PADDING)
4109 goto again;
4110
4111 rb_advance_iter(iter);
4112 out:
4113 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4114
4115 return event;
4116}
4117EXPORT_SYMBOL_GPL(ring_buffer_read);
4118
4119/**
4120 * ring_buffer_size - return the size of the ring buffer (in bytes)
4121 * @buffer: The ring buffer.
4122 */
4123unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4124{
4125 /*
4126 * Earlier, this method returned
4127 * BUF_PAGE_SIZE * buffer->nr_pages
4128 * Since the nr_pages field is now removed, we have converted this to
4129 * return the per cpu buffer value.
4130 */
4131 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4132 return 0;
4133
4134 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4135}
4136EXPORT_SYMBOL_GPL(ring_buffer_size);
4137
4138static void
4139rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4140{
4141 rb_head_page_deactivate(cpu_buffer);
4142
4143 cpu_buffer->head_page
4144 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4145 local_set(&cpu_buffer->head_page->write, 0);
4146 local_set(&cpu_buffer->head_page->entries, 0);
4147 local_set(&cpu_buffer->head_page->page->commit, 0);
4148
4149 cpu_buffer->head_page->read = 0;
4150
4151 cpu_buffer->tail_page = cpu_buffer->head_page;
4152 cpu_buffer->commit_page = cpu_buffer->head_page;
4153
4154 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4155 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4156 local_set(&cpu_buffer->reader_page->write, 0);
4157 local_set(&cpu_buffer->reader_page->entries, 0);
4158 local_set(&cpu_buffer->reader_page->page->commit, 0);
4159 cpu_buffer->reader_page->read = 0;
4160
4161 local_set(&cpu_buffer->entries_bytes, 0);
4162 local_set(&cpu_buffer->overrun, 0);
4163 local_set(&cpu_buffer->commit_overrun, 0);
4164 local_set(&cpu_buffer->dropped_events, 0);
4165 local_set(&cpu_buffer->entries, 0);
4166 local_set(&cpu_buffer->committing, 0);
4167 local_set(&cpu_buffer->commits, 0);
4168 cpu_buffer->read = 0;
4169 cpu_buffer->read_bytes = 0;
4170
4171 cpu_buffer->write_stamp = 0;
4172 cpu_buffer->read_stamp = 0;
4173
4174 cpu_buffer->lost_events = 0;
4175 cpu_buffer->last_overrun = 0;
4176
4177 rb_head_page_activate(cpu_buffer);
4178}
4179
4180/**
4181 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4182 * @buffer: The ring buffer to reset a per cpu buffer of
4183 * @cpu: The CPU buffer to be reset
4184 */
4185void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4186{
4187 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4188 unsigned long flags;
4189
4190 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4191 return;
4192
4193 atomic_inc(&buffer->resize_disabled);
4194 atomic_inc(&cpu_buffer->record_disabled);
4195
4196 /* Make sure all commits have finished */
4197 synchronize_sched();
4198
4199 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4200
4201 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4202 goto out;
4203
4204 arch_spin_lock(&cpu_buffer->lock);
4205
4206 rb_reset_cpu(cpu_buffer);
4207
4208 arch_spin_unlock(&cpu_buffer->lock);
4209
4210 out:
4211 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4212
4213 atomic_dec(&cpu_buffer->record_disabled);
4214 atomic_dec(&buffer->resize_disabled);
4215}
4216EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4217
4218/**
4219 * ring_buffer_reset - reset a ring buffer
4220 * @buffer: The ring buffer to reset all cpu buffers
4221 */
4222void ring_buffer_reset(struct ring_buffer *buffer)
4223{
4224 int cpu;
4225
4226 for_each_buffer_cpu(buffer, cpu)
4227 ring_buffer_reset_cpu(buffer, cpu);
4228}
4229EXPORT_SYMBOL_GPL(ring_buffer_reset);
4230
4231/**
4232 * rind_buffer_empty - is the ring buffer empty?
4233 * @buffer: The ring buffer to test
4234 */
4235bool ring_buffer_empty(struct ring_buffer *buffer)
4236{
4237 struct ring_buffer_per_cpu *cpu_buffer;
4238 unsigned long flags;
4239 bool dolock;
4240 int cpu;
4241 int ret;
4242
4243 /* yes this is racy, but if you don't like the race, lock the buffer */
4244 for_each_buffer_cpu(buffer, cpu) {
4245 cpu_buffer = buffer->buffers[cpu];
4246 local_irq_save(flags);
4247 dolock = rb_reader_lock(cpu_buffer);
4248 ret = rb_per_cpu_empty(cpu_buffer);
4249 rb_reader_unlock(cpu_buffer, dolock);
4250 local_irq_restore(flags);
4251
4252 if (!ret)
4253 return false;
4254 }
4255
4256 return true;
4257}
4258EXPORT_SYMBOL_GPL(ring_buffer_empty);
4259
4260/**
4261 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4262 * @buffer: The ring buffer
4263 * @cpu: The CPU buffer to test
4264 */
4265bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4266{
4267 struct ring_buffer_per_cpu *cpu_buffer;
4268 unsigned long flags;
4269 bool dolock;
4270 int ret;
4271
4272 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4273 return true;
4274
4275 cpu_buffer = buffer->buffers[cpu];
4276 local_irq_save(flags);
4277 dolock = rb_reader_lock(cpu_buffer);
4278 ret = rb_per_cpu_empty(cpu_buffer);
4279 rb_reader_unlock(cpu_buffer, dolock);
4280 local_irq_restore(flags);
4281
4282 return ret;
4283}
4284EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4285
4286#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4287/**
4288 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4289 * @buffer_a: One buffer to swap with
4290 * @buffer_b: The other buffer to swap with
4291 *
4292 * This function is useful for tracers that want to take a "snapshot"
4293 * of a CPU buffer and has another back up buffer lying around.
4294 * it is expected that the tracer handles the cpu buffer not being
4295 * used at the moment.
4296 */
4297int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4298 struct ring_buffer *buffer_b, int cpu)
4299{
4300 struct ring_buffer_per_cpu *cpu_buffer_a;
4301 struct ring_buffer_per_cpu *cpu_buffer_b;
4302 int ret = -EINVAL;
4303
4304 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4305 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4306 goto out;
4307
4308 cpu_buffer_a = buffer_a->buffers[cpu];
4309 cpu_buffer_b = buffer_b->buffers[cpu];
4310
4311 /* At least make sure the two buffers are somewhat the same */
4312 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4313 goto out;
4314
4315 ret = -EAGAIN;
4316
4317 if (atomic_read(&buffer_a->record_disabled))
4318 goto out;
4319
4320 if (atomic_read(&buffer_b->record_disabled))
4321 goto out;
4322
4323 if (atomic_read(&cpu_buffer_a->record_disabled))
4324 goto out;
4325
4326 if (atomic_read(&cpu_buffer_b->record_disabled))
4327 goto out;
4328
4329 /*
4330 * We can't do a synchronize_sched here because this
4331 * function can be called in atomic context.
4332 * Normally this will be called from the same CPU as cpu.
4333 * If not it's up to the caller to protect this.
4334 */
4335 atomic_inc(&cpu_buffer_a->record_disabled);
4336 atomic_inc(&cpu_buffer_b->record_disabled);
4337
4338 ret = -EBUSY;
4339 if (local_read(&cpu_buffer_a->committing))
4340 goto out_dec;
4341 if (local_read(&cpu_buffer_b->committing))
4342 goto out_dec;
4343
4344 buffer_a->buffers[cpu] = cpu_buffer_b;
4345 buffer_b->buffers[cpu] = cpu_buffer_a;
4346
4347 cpu_buffer_b->buffer = buffer_a;
4348 cpu_buffer_a->buffer = buffer_b;
4349
4350 ret = 0;
4351
4352out_dec:
4353 atomic_dec(&cpu_buffer_a->record_disabled);
4354 atomic_dec(&cpu_buffer_b->record_disabled);
4355out:
4356 return ret;
4357}
4358EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4359#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4360
4361/**
4362 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4363 * @buffer: the buffer to allocate for.
4364 * @cpu: the cpu buffer to allocate.
4365 *
4366 * This function is used in conjunction with ring_buffer_read_page.
4367 * When reading a full page from the ring buffer, these functions
4368 * can be used to speed up the process. The calling function should
4369 * allocate a few pages first with this function. Then when it
4370 * needs to get pages from the ring buffer, it passes the result
4371 * of this function into ring_buffer_read_page, which will swap
4372 * the page that was allocated, with the read page of the buffer.
4373 *
4374 * Returns:
4375 * The page allocated, or NULL on error.
4376 */
4377void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4378{
4379 struct buffer_data_page *bpage;
4380 struct page *page;
4381
4382 page = alloc_pages_node(cpu_to_node(cpu),
4383 GFP_KERNEL | __GFP_NORETRY, 0);
4384 if (!page)
4385 return NULL;
4386
4387 bpage = page_address(page);
4388
4389 rb_init_page(bpage);
4390
4391 return bpage;
4392}
4393EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4394
4395/**
4396 * ring_buffer_free_read_page - free an allocated read page
4397 * @buffer: the buffer the page was allocate for
4398 * @data: the page to free
4399 *
4400 * Free a page allocated from ring_buffer_alloc_read_page.
4401 */
4402void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
4403{
4404 free_page((unsigned long)data);
4405}
4406EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4407
4408/**
4409 * ring_buffer_read_page - extract a page from the ring buffer
4410 * @buffer: buffer to extract from
4411 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4412 * @len: amount to extract
4413 * @cpu: the cpu of the buffer to extract
4414 * @full: should the extraction only happen when the page is full.
4415 *
4416 * This function will pull out a page from the ring buffer and consume it.
4417 * @data_page must be the address of the variable that was returned
4418 * from ring_buffer_alloc_read_page. This is because the page might be used
4419 * to swap with a page in the ring buffer.
4420 *
4421 * for example:
4422 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4423 * if (!rpage)
4424 * return error;
4425 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4426 * if (ret >= 0)
4427 * process_page(rpage, ret);
4428 *
4429 * When @full is set, the function will not return true unless
4430 * the writer is off the reader page.
4431 *
4432 * Note: it is up to the calling functions to handle sleeps and wakeups.
4433 * The ring buffer can be used anywhere in the kernel and can not
4434 * blindly call wake_up. The layer that uses the ring buffer must be
4435 * responsible for that.
4436 *
4437 * Returns:
4438 * >=0 if data has been transferred, returns the offset of consumed data.
4439 * <0 if no data has been transferred.
4440 */
4441int ring_buffer_read_page(struct ring_buffer *buffer,
4442 void **data_page, size_t len, int cpu, int full)
4443{
4444 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4445 struct ring_buffer_event *event;
4446 struct buffer_data_page *bpage;
4447 struct buffer_page *reader;
4448 unsigned long missed_events;
4449 unsigned long flags;
4450 unsigned int commit;
4451 unsigned int read;
4452 u64 save_timestamp;
4453 int ret = -1;
4454
4455 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4456 goto out;
4457
4458 /*
4459 * If len is not big enough to hold the page header, then
4460 * we can not copy anything.
4461 */
4462 if (len <= BUF_PAGE_HDR_SIZE)
4463 goto out;
4464
4465 len -= BUF_PAGE_HDR_SIZE;
4466
4467 if (!data_page)
4468 goto out;
4469
4470 bpage = *data_page;
4471 if (!bpage)
4472 goto out;
4473
4474 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4475
4476 reader = rb_get_reader_page(cpu_buffer);
4477 if (!reader)
4478 goto out_unlock;
4479
4480 event = rb_reader_event(cpu_buffer);
4481
4482 read = reader->read;
4483 commit = rb_page_commit(reader);
4484
4485 /* Check if any events were dropped */
4486 missed_events = cpu_buffer->lost_events;
4487
4488 /*
4489 * If this page has been partially read or
4490 * if len is not big enough to read the rest of the page or
4491 * a writer is still on the page, then
4492 * we must copy the data from the page to the buffer.
4493 * Otherwise, we can simply swap the page with the one passed in.
4494 */
4495 if (read || (len < (commit - read)) ||
4496 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4497 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4498 unsigned int rpos = read;
4499 unsigned int pos = 0;
4500 unsigned int size;
4501
4502 if (full)
4503 goto out_unlock;
4504
4505 if (len > (commit - read))
4506 len = (commit - read);
4507
4508 /* Always keep the time extend and data together */
4509 size = rb_event_ts_length(event);
4510
4511 if (len < size)
4512 goto out_unlock;
4513
4514 /* save the current timestamp, since the user will need it */
4515 save_timestamp = cpu_buffer->read_stamp;
4516
4517 /* Need to copy one event at a time */
4518 do {
4519 /* We need the size of one event, because
4520 * rb_advance_reader only advances by one event,
4521 * whereas rb_event_ts_length may include the size of
4522 * one or two events.
4523 * We have already ensured there's enough space if this
4524 * is a time extend. */
4525 size = rb_event_length(event);
4526 memcpy(bpage->data + pos, rpage->data + rpos, size);
4527
4528 len -= size;
4529
4530 rb_advance_reader(cpu_buffer);
4531 rpos = reader->read;
4532 pos += size;
4533
4534 if (rpos >= commit)
4535 break;
4536
4537 event = rb_reader_event(cpu_buffer);
4538 /* Always keep the time extend and data together */
4539 size = rb_event_ts_length(event);
4540 } while (len >= size);
4541
4542 /* update bpage */
4543 local_set(&bpage->commit, pos);
4544 bpage->time_stamp = save_timestamp;
4545
4546 /* we copied everything to the beginning */
4547 read = 0;
4548 } else {
4549 /* update the entry counter */
4550 cpu_buffer->read += rb_page_entries(reader);
4551 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4552
4553 /* swap the pages */
4554 rb_init_page(bpage);
4555 bpage = reader->page;
4556 reader->page = *data_page;
4557 local_set(&reader->write, 0);
4558 local_set(&reader->entries, 0);
4559 reader->read = 0;
4560 *data_page = bpage;
4561
4562 /*
4563 * Use the real_end for the data size,
4564 * This gives us a chance to store the lost events
4565 * on the page.
4566 */
4567 if (reader->real_end)
4568 local_set(&bpage->commit, reader->real_end);
4569 }
4570 ret = read;
4571
4572 cpu_buffer->lost_events = 0;
4573
4574 commit = local_read(&bpage->commit);
4575 /*
4576 * Set a flag in the commit field if we lost events
4577 */
4578 if (missed_events) {
4579 /* If there is room at the end of the page to save the
4580 * missed events, then record it there.
4581 */
4582 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4583 memcpy(&bpage->data[commit], &missed_events,
4584 sizeof(missed_events));
4585 local_add(RB_MISSED_STORED, &bpage->commit);
4586 commit += sizeof(missed_events);
4587 }
4588 local_add(RB_MISSED_EVENTS, &bpage->commit);
4589 }
4590
4591 /*
4592 * This page may be off to user land. Zero it out here.
4593 */
4594 if (commit < BUF_PAGE_SIZE)
4595 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4596
4597 out_unlock:
4598 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4599
4600 out:
4601 return ret;
4602}
4603EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4604
4605/*
4606 * We only allocate new buffers, never free them if the CPU goes down.
4607 * If we were to free the buffer, then the user would lose any trace that was in
4608 * the buffer.
4609 */
4610int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
4611{
4612 struct ring_buffer *buffer;
4613 long nr_pages_same;
4614 int cpu_i;
4615 unsigned long nr_pages;
4616
4617 buffer = container_of(node, struct ring_buffer, node);
4618 if (cpumask_test_cpu(cpu, buffer->cpumask))
4619 return 0;
4620
4621 nr_pages = 0;
4622 nr_pages_same = 1;
4623 /* check if all cpu sizes are same */
4624 for_each_buffer_cpu(buffer, cpu_i) {
4625 /* fill in the size from first enabled cpu */
4626 if (nr_pages == 0)
4627 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4628 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4629 nr_pages_same = 0;
4630 break;
4631 }
4632 }
4633 /* allocate minimum pages, user can later expand it */
4634 if (!nr_pages_same)
4635 nr_pages = 2;
4636 buffer->buffers[cpu] =
4637 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4638 if (!buffer->buffers[cpu]) {
4639 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4640 cpu);
4641 return -ENOMEM;
4642 }
4643 smp_wmb();
4644 cpumask_set_cpu(cpu, buffer->cpumask);
4645 return 0;
4646}
4647
4648#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4649/*
4650 * This is a basic integrity check of the ring buffer.
4651 * Late in the boot cycle this test will run when configured in.
4652 * It will kick off a thread per CPU that will go into a loop
4653 * writing to the per cpu ring buffer various sizes of data.
4654 * Some of the data will be large items, some small.
4655 *
4656 * Another thread is created that goes into a spin, sending out
4657 * IPIs to the other CPUs to also write into the ring buffer.
4658 * this is to test the nesting ability of the buffer.
4659 *
4660 * Basic stats are recorded and reported. If something in the
4661 * ring buffer should happen that's not expected, a big warning
4662 * is displayed and all ring buffers are disabled.
4663 */
4664static struct task_struct *rb_threads[NR_CPUS] __initdata;
4665
4666struct rb_test_data {
4667 struct ring_buffer *buffer;
4668 unsigned long events;
4669 unsigned long bytes_written;
4670 unsigned long bytes_alloc;
4671 unsigned long bytes_dropped;
4672 unsigned long events_nested;
4673 unsigned long bytes_written_nested;
4674 unsigned long bytes_alloc_nested;
4675 unsigned long bytes_dropped_nested;
4676 int min_size_nested;
4677 int max_size_nested;
4678 int max_size;
4679 int min_size;
4680 int cpu;
4681 int cnt;
4682};
4683
4684static struct rb_test_data rb_data[NR_CPUS] __initdata;
4685
4686/* 1 meg per cpu */
4687#define RB_TEST_BUFFER_SIZE 1048576
4688
4689static char rb_string[] __initdata =
4690 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4691 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4692 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4693
4694static bool rb_test_started __initdata;
4695
4696struct rb_item {
4697 int size;
4698 char str[];
4699};
4700
4701static __init int rb_write_something(struct rb_test_data *data, bool nested)
4702{
4703 struct ring_buffer_event *event;
4704 struct rb_item *item;
4705 bool started;
4706 int event_len;
4707 int size;
4708 int len;
4709 int cnt;
4710
4711 /* Have nested writes different that what is written */
4712 cnt = data->cnt + (nested ? 27 : 0);
4713
4714 /* Multiply cnt by ~e, to make some unique increment */
4715 size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
4716
4717 len = size + sizeof(struct rb_item);
4718
4719 started = rb_test_started;
4720 /* read rb_test_started before checking buffer enabled */
4721 smp_rmb();
4722
4723 event = ring_buffer_lock_reserve(data->buffer, len);
4724 if (!event) {
4725 /* Ignore dropped events before test starts. */
4726 if (started) {
4727 if (nested)
4728 data->bytes_dropped += len;
4729 else
4730 data->bytes_dropped_nested += len;
4731 }
4732 return len;
4733 }
4734
4735 event_len = ring_buffer_event_length(event);
4736
4737 if (RB_WARN_ON(data->buffer, event_len < len))
4738 goto out;
4739
4740 item = ring_buffer_event_data(event);
4741 item->size = size;
4742 memcpy(item->str, rb_string, size);
4743
4744 if (nested) {
4745 data->bytes_alloc_nested += event_len;
4746 data->bytes_written_nested += len;
4747 data->events_nested++;
4748 if (!data->min_size_nested || len < data->min_size_nested)
4749 data->min_size_nested = len;
4750 if (len > data->max_size_nested)
4751 data->max_size_nested = len;
4752 } else {
4753 data->bytes_alloc += event_len;
4754 data->bytes_written += len;
4755 data->events++;
4756 if (!data->min_size || len < data->min_size)
4757 data->max_size = len;
4758 if (len > data->max_size)
4759 data->max_size = len;
4760 }
4761
4762 out:
4763 ring_buffer_unlock_commit(data->buffer, event);
4764
4765 return 0;
4766}
4767
4768static __init int rb_test(void *arg)
4769{
4770 struct rb_test_data *data = arg;
4771
4772 while (!kthread_should_stop()) {
4773 rb_write_something(data, false);
4774 data->cnt++;
4775
4776 set_current_state(TASK_INTERRUPTIBLE);
4777 /* Now sleep between a min of 100-300us and a max of 1ms */
4778 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
4779 }
4780
4781 return 0;
4782}
4783
4784static __init void rb_ipi(void *ignore)
4785{
4786 struct rb_test_data *data;
4787 int cpu = smp_processor_id();
4788
4789 data = &rb_data[cpu];
4790 rb_write_something(data, true);
4791}
4792
4793static __init int rb_hammer_test(void *arg)
4794{
4795 while (!kthread_should_stop()) {
4796
4797 /* Send an IPI to all cpus to write data! */
4798 smp_call_function(rb_ipi, NULL, 1);
4799 /* No sleep, but for non preempt, let others run */
4800 schedule();
4801 }
4802
4803 return 0;
4804}
4805
4806static __init int test_ringbuffer(void)
4807{
4808 struct task_struct *rb_hammer;
4809 struct ring_buffer *buffer;
4810 int cpu;
4811 int ret = 0;
4812
4813 pr_info("Running ring buffer tests...\n");
4814
4815 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
4816 if (WARN_ON(!buffer))
4817 return 0;
4818
4819 /* Disable buffer so that threads can't write to it yet */
4820 ring_buffer_record_off(buffer);
4821
4822 for_each_online_cpu(cpu) {
4823 rb_data[cpu].buffer = buffer;
4824 rb_data[cpu].cpu = cpu;
4825 rb_data[cpu].cnt = cpu;
4826 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
4827 "rbtester/%d", cpu);
4828 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
4829 pr_cont("FAILED\n");
4830 ret = PTR_ERR(rb_threads[cpu]);
4831 goto out_free;
4832 }
4833
4834 kthread_bind(rb_threads[cpu], cpu);
4835 wake_up_process(rb_threads[cpu]);
4836 }
4837
4838 /* Now create the rb hammer! */
4839 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
4840 if (WARN_ON(IS_ERR(rb_hammer))) {
4841 pr_cont("FAILED\n");
4842 ret = PTR_ERR(rb_hammer);
4843 goto out_free;
4844 }
4845
4846 ring_buffer_record_on(buffer);
4847 /*
4848 * Show buffer is enabled before setting rb_test_started.
4849 * Yes there's a small race window where events could be
4850 * dropped and the thread wont catch it. But when a ring
4851 * buffer gets enabled, there will always be some kind of
4852 * delay before other CPUs see it. Thus, we don't care about
4853 * those dropped events. We care about events dropped after
4854 * the threads see that the buffer is active.
4855 */
4856 smp_wmb();
4857 rb_test_started = true;
4858
4859 set_current_state(TASK_INTERRUPTIBLE);
4860 /* Just run for 10 seconds */;
4861 schedule_timeout(10 * HZ);
4862
4863 kthread_stop(rb_hammer);
4864
4865 out_free:
4866 for_each_online_cpu(cpu) {
4867 if (!rb_threads[cpu])
4868 break;
4869 kthread_stop(rb_threads[cpu]);
4870 }
4871 if (ret) {
4872 ring_buffer_free(buffer);
4873 return ret;
4874 }
4875
4876 /* Report! */
4877 pr_info("finished\n");
4878 for_each_online_cpu(cpu) {
4879 struct ring_buffer_event *event;
4880 struct rb_test_data *data = &rb_data[cpu];
4881 struct rb_item *item;
4882 unsigned long total_events;
4883 unsigned long total_dropped;
4884 unsigned long total_written;
4885 unsigned long total_alloc;
4886 unsigned long total_read = 0;
4887 unsigned long total_size = 0;
4888 unsigned long total_len = 0;
4889 unsigned long total_lost = 0;
4890 unsigned long lost;
4891 int big_event_size;
4892 int small_event_size;
4893
4894 ret = -1;
4895
4896 total_events = data->events + data->events_nested;
4897 total_written = data->bytes_written + data->bytes_written_nested;
4898 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
4899 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
4900
4901 big_event_size = data->max_size + data->max_size_nested;
4902 small_event_size = data->min_size + data->min_size_nested;
4903
4904 pr_info("CPU %d:\n", cpu);
4905 pr_info(" events: %ld\n", total_events);
4906 pr_info(" dropped bytes: %ld\n", total_dropped);
4907 pr_info(" alloced bytes: %ld\n", total_alloc);
4908 pr_info(" written bytes: %ld\n", total_written);
4909 pr_info(" biggest event: %d\n", big_event_size);
4910 pr_info(" smallest event: %d\n", small_event_size);
4911
4912 if (RB_WARN_ON(buffer, total_dropped))
4913 break;
4914
4915 ret = 0;
4916
4917 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
4918 total_lost += lost;
4919 item = ring_buffer_event_data(event);
4920 total_len += ring_buffer_event_length(event);
4921 total_size += item->size + sizeof(struct rb_item);
4922 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
4923 pr_info("FAILED!\n");
4924 pr_info("buffer had: %.*s\n", item->size, item->str);
4925 pr_info("expected: %.*s\n", item->size, rb_string);
4926 RB_WARN_ON(buffer, 1);
4927 ret = -1;
4928 break;
4929 }
4930 total_read++;
4931 }
4932 if (ret)
4933 break;
4934
4935 ret = -1;
4936
4937 pr_info(" read events: %ld\n", total_read);
4938 pr_info(" lost events: %ld\n", total_lost);
4939 pr_info(" total events: %ld\n", total_lost + total_read);
4940 pr_info(" recorded len bytes: %ld\n", total_len);
4941 pr_info(" recorded size bytes: %ld\n", total_size);
4942 if (total_lost)
4943 pr_info(" With dropped events, record len and size may not match\n"
4944 " alloced and written from above\n");
4945 if (!total_lost) {
4946 if (RB_WARN_ON(buffer, total_len != total_alloc ||
4947 total_size != total_written))
4948 break;
4949 }
4950 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
4951 break;
4952
4953 ret = 0;
4954 }
4955 if (!ret)
4956 pr_info("Ring buffer PASSED!\n");
4957
4958 ring_buffer_free(buffer);
4959 return 0;
4960}
4961
4962late_initcall(test_ringbuffer);
4963#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
1/*
2 * Generic ring buffer
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/ftrace_event.h>
7#include <linux/ring_buffer.h>
8#include <linux/trace_clock.h>
9#include <linux/trace_seq.h>
10#include <linux/spinlock.h>
11#include <linux/irq_work.h>
12#include <linux/debugfs.h>
13#include <linux/uaccess.h>
14#include <linux/hardirq.h>
15#include <linux/kthread.h> /* for self test */
16#include <linux/kmemcheck.h>
17#include <linux/module.h>
18#include <linux/percpu.h>
19#include <linux/mutex.h>
20#include <linux/delay.h>
21#include <linux/slab.h>
22#include <linux/init.h>
23#include <linux/hash.h>
24#include <linux/list.h>
25#include <linux/cpu.h>
26#include <linux/fs.h>
27
28#include <asm/local.h>
29
30static void update_pages_handler(struct work_struct *work);
31
32/*
33 * The ring buffer header is special. We must manually up keep it.
34 */
35int ring_buffer_print_entry_header(struct trace_seq *s)
36{
37 int ret;
38
39 ret = trace_seq_puts(s, "# compressed entry header\n");
40 ret = trace_seq_puts(s, "\ttype_len : 5 bits\n");
41 ret = trace_seq_puts(s, "\ttime_delta : 27 bits\n");
42 ret = trace_seq_puts(s, "\tarray : 32 bits\n");
43 ret = trace_seq_putc(s, '\n');
44 ret = trace_seq_printf(s, "\tpadding : type == %d\n",
45 RINGBUF_TYPE_PADDING);
46 ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
47 RINGBUF_TYPE_TIME_EXTEND);
48 ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
49 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
50
51 return ret;
52}
53
54/*
55 * The ring buffer is made up of a list of pages. A separate list of pages is
56 * allocated for each CPU. A writer may only write to a buffer that is
57 * associated with the CPU it is currently executing on. A reader may read
58 * from any per cpu buffer.
59 *
60 * The reader is special. For each per cpu buffer, the reader has its own
61 * reader page. When a reader has read the entire reader page, this reader
62 * page is swapped with another page in the ring buffer.
63 *
64 * Now, as long as the writer is off the reader page, the reader can do what
65 * ever it wants with that page. The writer will never write to that page
66 * again (as long as it is out of the ring buffer).
67 *
68 * Here's some silly ASCII art.
69 *
70 * +------+
71 * |reader| RING BUFFER
72 * |page |
73 * +------+ +---+ +---+ +---+
74 * | |-->| |-->| |
75 * +---+ +---+ +---+
76 * ^ |
77 * | |
78 * +---------------+
79 *
80 *
81 * +------+
82 * |reader| RING BUFFER
83 * |page |------------------v
84 * +------+ +---+ +---+ +---+
85 * | |-->| |-->| |
86 * +---+ +---+ +---+
87 * ^ |
88 * | |
89 * +---------------+
90 *
91 *
92 * +------+
93 * |reader| RING BUFFER
94 * |page |------------------v
95 * +------+ +---+ +---+ +---+
96 * ^ | |-->| |-->| |
97 * | +---+ +---+ +---+
98 * | |
99 * | |
100 * +------------------------------+
101 *
102 *
103 * +------+
104 * |buffer| RING BUFFER
105 * |page |------------------v
106 * +------+ +---+ +---+ +---+
107 * ^ | | | |-->| |
108 * | New +---+ +---+ +---+
109 * | Reader------^ |
110 * | page |
111 * +------------------------------+
112 *
113 *
114 * After we make this swap, the reader can hand this page off to the splice
115 * code and be done with it. It can even allocate a new page if it needs to
116 * and swap that into the ring buffer.
117 *
118 * We will be using cmpxchg soon to make all this lockless.
119 *
120 */
121
122/*
123 * A fast way to enable or disable all ring buffers is to
124 * call tracing_on or tracing_off. Turning off the ring buffers
125 * prevents all ring buffers from being recorded to.
126 * Turning this switch on, makes it OK to write to the
127 * ring buffer, if the ring buffer is enabled itself.
128 *
129 * There's three layers that must be on in order to write
130 * to the ring buffer.
131 *
132 * 1) This global flag must be set.
133 * 2) The ring buffer must be enabled for recording.
134 * 3) The per cpu buffer must be enabled for recording.
135 *
136 * In case of an anomaly, this global flag has a bit set that
137 * will permantly disable all ring buffers.
138 */
139
140/*
141 * Global flag to disable all recording to ring buffers
142 * This has two bits: ON, DISABLED
143 *
144 * ON DISABLED
145 * ---- ----------
146 * 0 0 : ring buffers are off
147 * 1 0 : ring buffers are on
148 * X 1 : ring buffers are permanently disabled
149 */
150
151enum {
152 RB_BUFFERS_ON_BIT = 0,
153 RB_BUFFERS_DISABLED_BIT = 1,
154};
155
156enum {
157 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
158 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
159};
160
161static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
162
163/* Used for individual buffers (after the counter) */
164#define RB_BUFFER_OFF (1 << 20)
165
166#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
167
168/**
169 * tracing_off_permanent - permanently disable ring buffers
170 *
171 * This function, once called, will disable all ring buffers
172 * permanently.
173 */
174void tracing_off_permanent(void)
175{
176 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
177}
178
179#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
180#define RB_ALIGNMENT 4U
181#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
182#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
183
184#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
185# define RB_FORCE_8BYTE_ALIGNMENT 0
186# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
187#else
188# define RB_FORCE_8BYTE_ALIGNMENT 1
189# define RB_ARCH_ALIGNMENT 8U
190#endif
191
192#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
193
194/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
195#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
196
197enum {
198 RB_LEN_TIME_EXTEND = 8,
199 RB_LEN_TIME_STAMP = 16,
200};
201
202#define skip_time_extend(event) \
203 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
204
205static inline int rb_null_event(struct ring_buffer_event *event)
206{
207 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
208}
209
210static void rb_event_set_padding(struct ring_buffer_event *event)
211{
212 /* padding has a NULL time_delta */
213 event->type_len = RINGBUF_TYPE_PADDING;
214 event->time_delta = 0;
215}
216
217static unsigned
218rb_event_data_length(struct ring_buffer_event *event)
219{
220 unsigned length;
221
222 if (event->type_len)
223 length = event->type_len * RB_ALIGNMENT;
224 else
225 length = event->array[0];
226 return length + RB_EVNT_HDR_SIZE;
227}
228
229/*
230 * Return the length of the given event. Will return
231 * the length of the time extend if the event is a
232 * time extend.
233 */
234static inline unsigned
235rb_event_length(struct ring_buffer_event *event)
236{
237 switch (event->type_len) {
238 case RINGBUF_TYPE_PADDING:
239 if (rb_null_event(event))
240 /* undefined */
241 return -1;
242 return event->array[0] + RB_EVNT_HDR_SIZE;
243
244 case RINGBUF_TYPE_TIME_EXTEND:
245 return RB_LEN_TIME_EXTEND;
246
247 case RINGBUF_TYPE_TIME_STAMP:
248 return RB_LEN_TIME_STAMP;
249
250 case RINGBUF_TYPE_DATA:
251 return rb_event_data_length(event);
252 default:
253 BUG();
254 }
255 /* not hit */
256 return 0;
257}
258
259/*
260 * Return total length of time extend and data,
261 * or just the event length for all other events.
262 */
263static inline unsigned
264rb_event_ts_length(struct ring_buffer_event *event)
265{
266 unsigned len = 0;
267
268 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
269 /* time extends include the data event after it */
270 len = RB_LEN_TIME_EXTEND;
271 event = skip_time_extend(event);
272 }
273 return len + rb_event_length(event);
274}
275
276/**
277 * ring_buffer_event_length - return the length of the event
278 * @event: the event to get the length of
279 *
280 * Returns the size of the data load of a data event.
281 * If the event is something other than a data event, it
282 * returns the size of the event itself. With the exception
283 * of a TIME EXTEND, where it still returns the size of the
284 * data load of the data event after it.
285 */
286unsigned ring_buffer_event_length(struct ring_buffer_event *event)
287{
288 unsigned length;
289
290 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
291 event = skip_time_extend(event);
292
293 length = rb_event_length(event);
294 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
295 return length;
296 length -= RB_EVNT_HDR_SIZE;
297 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
298 length -= sizeof(event->array[0]);
299 return length;
300}
301EXPORT_SYMBOL_GPL(ring_buffer_event_length);
302
303/* inline for ring buffer fast paths */
304static void *
305rb_event_data(struct ring_buffer_event *event)
306{
307 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
308 event = skip_time_extend(event);
309 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
310 /* If length is in len field, then array[0] has the data */
311 if (event->type_len)
312 return (void *)&event->array[0];
313 /* Otherwise length is in array[0] and array[1] has the data */
314 return (void *)&event->array[1];
315}
316
317/**
318 * ring_buffer_event_data - return the data of the event
319 * @event: the event to get the data from
320 */
321void *ring_buffer_event_data(struct ring_buffer_event *event)
322{
323 return rb_event_data(event);
324}
325EXPORT_SYMBOL_GPL(ring_buffer_event_data);
326
327#define for_each_buffer_cpu(buffer, cpu) \
328 for_each_cpu(cpu, buffer->cpumask)
329
330#define TS_SHIFT 27
331#define TS_MASK ((1ULL << TS_SHIFT) - 1)
332#define TS_DELTA_TEST (~TS_MASK)
333
334/* Flag when events were overwritten */
335#define RB_MISSED_EVENTS (1 << 31)
336/* Missed count stored at end */
337#define RB_MISSED_STORED (1 << 30)
338
339struct buffer_data_page {
340 u64 time_stamp; /* page time stamp */
341 local_t commit; /* write committed index */
342 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
343};
344
345/*
346 * Note, the buffer_page list must be first. The buffer pages
347 * are allocated in cache lines, which means that each buffer
348 * page will be at the beginning of a cache line, and thus
349 * the least significant bits will be zero. We use this to
350 * add flags in the list struct pointers, to make the ring buffer
351 * lockless.
352 */
353struct buffer_page {
354 struct list_head list; /* list of buffer pages */
355 local_t write; /* index for next write */
356 unsigned read; /* index for next read */
357 local_t entries; /* entries on this page */
358 unsigned long real_end; /* real end of data */
359 struct buffer_data_page *page; /* Actual data page */
360};
361
362/*
363 * The buffer page counters, write and entries, must be reset
364 * atomically when crossing page boundaries. To synchronize this
365 * update, two counters are inserted into the number. One is
366 * the actual counter for the write position or count on the page.
367 *
368 * The other is a counter of updaters. Before an update happens
369 * the update partition of the counter is incremented. This will
370 * allow the updater to update the counter atomically.
371 *
372 * The counter is 20 bits, and the state data is 12.
373 */
374#define RB_WRITE_MASK 0xfffff
375#define RB_WRITE_INTCNT (1 << 20)
376
377static void rb_init_page(struct buffer_data_page *bpage)
378{
379 local_set(&bpage->commit, 0);
380}
381
382/**
383 * ring_buffer_page_len - the size of data on the page.
384 * @page: The page to read
385 *
386 * Returns the amount of data on the page, including buffer page header.
387 */
388size_t ring_buffer_page_len(void *page)
389{
390 return local_read(&((struct buffer_data_page *)page)->commit)
391 + BUF_PAGE_HDR_SIZE;
392}
393
394/*
395 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
396 * this issue out.
397 */
398static void free_buffer_page(struct buffer_page *bpage)
399{
400 free_page((unsigned long)bpage->page);
401 kfree(bpage);
402}
403
404/*
405 * We need to fit the time_stamp delta into 27 bits.
406 */
407static inline int test_time_stamp(u64 delta)
408{
409 if (delta & TS_DELTA_TEST)
410 return 1;
411 return 0;
412}
413
414#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
415
416/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
417#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
418
419int ring_buffer_print_page_header(struct trace_seq *s)
420{
421 struct buffer_data_page field;
422 int ret;
423
424 ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
425 "offset:0;\tsize:%u;\tsigned:%u;\n",
426 (unsigned int)sizeof(field.time_stamp),
427 (unsigned int)is_signed_type(u64));
428
429 ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
430 "offset:%u;\tsize:%u;\tsigned:%u;\n",
431 (unsigned int)offsetof(typeof(field), commit),
432 (unsigned int)sizeof(field.commit),
433 (unsigned int)is_signed_type(long));
434
435 ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
436 "offset:%u;\tsize:%u;\tsigned:%u;\n",
437 (unsigned int)offsetof(typeof(field), commit),
438 1,
439 (unsigned int)is_signed_type(long));
440
441 ret = trace_seq_printf(s, "\tfield: char data;\t"
442 "offset:%u;\tsize:%u;\tsigned:%u;\n",
443 (unsigned int)offsetof(typeof(field), data),
444 (unsigned int)BUF_PAGE_SIZE,
445 (unsigned int)is_signed_type(char));
446
447 return ret;
448}
449
450struct rb_irq_work {
451 struct irq_work work;
452 wait_queue_head_t waiters;
453 bool waiters_pending;
454};
455
456/*
457 * head_page == tail_page && head == tail then buffer is empty.
458 */
459struct ring_buffer_per_cpu {
460 int cpu;
461 atomic_t record_disabled;
462 struct ring_buffer *buffer;
463 raw_spinlock_t reader_lock; /* serialize readers */
464 arch_spinlock_t lock;
465 struct lock_class_key lock_key;
466 unsigned int nr_pages;
467 struct list_head *pages;
468 struct buffer_page *head_page; /* read from head */
469 struct buffer_page *tail_page; /* write to tail */
470 struct buffer_page *commit_page; /* committed pages */
471 struct buffer_page *reader_page;
472 unsigned long lost_events;
473 unsigned long last_overrun;
474 local_t entries_bytes;
475 local_t entries;
476 local_t overrun;
477 local_t commit_overrun;
478 local_t dropped_events;
479 local_t committing;
480 local_t commits;
481 unsigned long read;
482 unsigned long read_bytes;
483 u64 write_stamp;
484 u64 read_stamp;
485 /* ring buffer pages to update, > 0 to add, < 0 to remove */
486 int nr_pages_to_update;
487 struct list_head new_pages; /* new pages to add */
488 struct work_struct update_pages_work;
489 struct completion update_done;
490
491 struct rb_irq_work irq_work;
492};
493
494struct ring_buffer {
495 unsigned flags;
496 int cpus;
497 atomic_t record_disabled;
498 atomic_t resize_disabled;
499 cpumask_var_t cpumask;
500
501 struct lock_class_key *reader_lock_key;
502
503 struct mutex mutex;
504
505 struct ring_buffer_per_cpu **buffers;
506
507#ifdef CONFIG_HOTPLUG_CPU
508 struct notifier_block cpu_notify;
509#endif
510 u64 (*clock)(void);
511
512 struct rb_irq_work irq_work;
513};
514
515struct ring_buffer_iter {
516 struct ring_buffer_per_cpu *cpu_buffer;
517 unsigned long head;
518 struct buffer_page *head_page;
519 struct buffer_page *cache_reader_page;
520 unsigned long cache_read;
521 u64 read_stamp;
522};
523
524/*
525 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
526 *
527 * Schedules a delayed work to wake up any task that is blocked on the
528 * ring buffer waiters queue.
529 */
530static void rb_wake_up_waiters(struct irq_work *work)
531{
532 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
533
534 wake_up_all(&rbwork->waiters);
535}
536
537/**
538 * ring_buffer_wait - wait for input to the ring buffer
539 * @buffer: buffer to wait on
540 * @cpu: the cpu buffer to wait on
541 *
542 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
543 * as data is added to any of the @buffer's cpu buffers. Otherwise
544 * it will wait for data to be added to a specific cpu buffer.
545 */
546void ring_buffer_wait(struct ring_buffer *buffer, int cpu)
547{
548 struct ring_buffer_per_cpu *cpu_buffer;
549 DEFINE_WAIT(wait);
550 struct rb_irq_work *work;
551
552 /*
553 * Depending on what the caller is waiting for, either any
554 * data in any cpu buffer, or a specific buffer, put the
555 * caller on the appropriate wait queue.
556 */
557 if (cpu == RING_BUFFER_ALL_CPUS)
558 work = &buffer->irq_work;
559 else {
560 cpu_buffer = buffer->buffers[cpu];
561 work = &cpu_buffer->irq_work;
562 }
563
564
565 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
566
567 /*
568 * The events can happen in critical sections where
569 * checking a work queue can cause deadlocks.
570 * After adding a task to the queue, this flag is set
571 * only to notify events to try to wake up the queue
572 * using irq_work.
573 *
574 * We don't clear it even if the buffer is no longer
575 * empty. The flag only causes the next event to run
576 * irq_work to do the work queue wake up. The worse
577 * that can happen if we race with !trace_empty() is that
578 * an event will cause an irq_work to try to wake up
579 * an empty queue.
580 *
581 * There's no reason to protect this flag either, as
582 * the work queue and irq_work logic will do the necessary
583 * synchronization for the wake ups. The only thing
584 * that is necessary is that the wake up happens after
585 * a task has been queued. It's OK for spurious wake ups.
586 */
587 work->waiters_pending = true;
588
589 if ((cpu == RING_BUFFER_ALL_CPUS && ring_buffer_empty(buffer)) ||
590 (cpu != RING_BUFFER_ALL_CPUS && ring_buffer_empty_cpu(buffer, cpu)))
591 schedule();
592
593 finish_wait(&work->waiters, &wait);
594}
595
596/**
597 * ring_buffer_poll_wait - poll on buffer input
598 * @buffer: buffer to wait on
599 * @cpu: the cpu buffer to wait on
600 * @filp: the file descriptor
601 * @poll_table: The poll descriptor
602 *
603 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
604 * as data is added to any of the @buffer's cpu buffers. Otherwise
605 * it will wait for data to be added to a specific cpu buffer.
606 *
607 * Returns POLLIN | POLLRDNORM if data exists in the buffers,
608 * zero otherwise.
609 */
610int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
611 struct file *filp, poll_table *poll_table)
612{
613 struct ring_buffer_per_cpu *cpu_buffer;
614 struct rb_irq_work *work;
615
616 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
617 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
618 return POLLIN | POLLRDNORM;
619
620 if (cpu == RING_BUFFER_ALL_CPUS)
621 work = &buffer->irq_work;
622 else {
623 if (!cpumask_test_cpu(cpu, buffer->cpumask))
624 return -EINVAL;
625
626 cpu_buffer = buffer->buffers[cpu];
627 work = &cpu_buffer->irq_work;
628 }
629
630 work->waiters_pending = true;
631 poll_wait(filp, &work->waiters, poll_table);
632
633 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
634 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
635 return POLLIN | POLLRDNORM;
636 return 0;
637}
638
639/* buffer may be either ring_buffer or ring_buffer_per_cpu */
640#define RB_WARN_ON(b, cond) \
641 ({ \
642 int _____ret = unlikely(cond); \
643 if (_____ret) { \
644 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
645 struct ring_buffer_per_cpu *__b = \
646 (void *)b; \
647 atomic_inc(&__b->buffer->record_disabled); \
648 } else \
649 atomic_inc(&b->record_disabled); \
650 WARN_ON(1); \
651 } \
652 _____ret; \
653 })
654
655/* Up this if you want to test the TIME_EXTENTS and normalization */
656#define DEBUG_SHIFT 0
657
658static inline u64 rb_time_stamp(struct ring_buffer *buffer)
659{
660 /* shift to debug/test normalization and TIME_EXTENTS */
661 return buffer->clock() << DEBUG_SHIFT;
662}
663
664u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
665{
666 u64 time;
667
668 preempt_disable_notrace();
669 time = rb_time_stamp(buffer);
670 preempt_enable_no_resched_notrace();
671
672 return time;
673}
674EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
675
676void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
677 int cpu, u64 *ts)
678{
679 /* Just stupid testing the normalize function and deltas */
680 *ts >>= DEBUG_SHIFT;
681}
682EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
683
684/*
685 * Making the ring buffer lockless makes things tricky.
686 * Although writes only happen on the CPU that they are on,
687 * and they only need to worry about interrupts. Reads can
688 * happen on any CPU.
689 *
690 * The reader page is always off the ring buffer, but when the
691 * reader finishes with a page, it needs to swap its page with
692 * a new one from the buffer. The reader needs to take from
693 * the head (writes go to the tail). But if a writer is in overwrite
694 * mode and wraps, it must push the head page forward.
695 *
696 * Here lies the problem.
697 *
698 * The reader must be careful to replace only the head page, and
699 * not another one. As described at the top of the file in the
700 * ASCII art, the reader sets its old page to point to the next
701 * page after head. It then sets the page after head to point to
702 * the old reader page. But if the writer moves the head page
703 * during this operation, the reader could end up with the tail.
704 *
705 * We use cmpxchg to help prevent this race. We also do something
706 * special with the page before head. We set the LSB to 1.
707 *
708 * When the writer must push the page forward, it will clear the
709 * bit that points to the head page, move the head, and then set
710 * the bit that points to the new head page.
711 *
712 * We also don't want an interrupt coming in and moving the head
713 * page on another writer. Thus we use the second LSB to catch
714 * that too. Thus:
715 *
716 * head->list->prev->next bit 1 bit 0
717 * ------- -------
718 * Normal page 0 0
719 * Points to head page 0 1
720 * New head page 1 0
721 *
722 * Note we can not trust the prev pointer of the head page, because:
723 *
724 * +----+ +-----+ +-----+
725 * | |------>| T |---X--->| N |
726 * | |<------| | | |
727 * +----+ +-----+ +-----+
728 * ^ ^ |
729 * | +-----+ | |
730 * +----------| R |----------+ |
731 * | |<-----------+
732 * +-----+
733 *
734 * Key: ---X--> HEAD flag set in pointer
735 * T Tail page
736 * R Reader page
737 * N Next page
738 *
739 * (see __rb_reserve_next() to see where this happens)
740 *
741 * What the above shows is that the reader just swapped out
742 * the reader page with a page in the buffer, but before it
743 * could make the new header point back to the new page added
744 * it was preempted by a writer. The writer moved forward onto
745 * the new page added by the reader and is about to move forward
746 * again.
747 *
748 * You can see, it is legitimate for the previous pointer of
749 * the head (or any page) not to point back to itself. But only
750 * temporarially.
751 */
752
753#define RB_PAGE_NORMAL 0UL
754#define RB_PAGE_HEAD 1UL
755#define RB_PAGE_UPDATE 2UL
756
757
758#define RB_FLAG_MASK 3UL
759
760/* PAGE_MOVED is not part of the mask */
761#define RB_PAGE_MOVED 4UL
762
763/*
764 * rb_list_head - remove any bit
765 */
766static struct list_head *rb_list_head(struct list_head *list)
767{
768 unsigned long val = (unsigned long)list;
769
770 return (struct list_head *)(val & ~RB_FLAG_MASK);
771}
772
773/*
774 * rb_is_head_page - test if the given page is the head page
775 *
776 * Because the reader may move the head_page pointer, we can
777 * not trust what the head page is (it may be pointing to
778 * the reader page). But if the next page is a header page,
779 * its flags will be non zero.
780 */
781static inline int
782rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
783 struct buffer_page *page, struct list_head *list)
784{
785 unsigned long val;
786
787 val = (unsigned long)list->next;
788
789 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
790 return RB_PAGE_MOVED;
791
792 return val & RB_FLAG_MASK;
793}
794
795/*
796 * rb_is_reader_page
797 *
798 * The unique thing about the reader page, is that, if the
799 * writer is ever on it, the previous pointer never points
800 * back to the reader page.
801 */
802static int rb_is_reader_page(struct buffer_page *page)
803{
804 struct list_head *list = page->list.prev;
805
806 return rb_list_head(list->next) != &page->list;
807}
808
809/*
810 * rb_set_list_to_head - set a list_head to be pointing to head.
811 */
812static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
813 struct list_head *list)
814{
815 unsigned long *ptr;
816
817 ptr = (unsigned long *)&list->next;
818 *ptr |= RB_PAGE_HEAD;
819 *ptr &= ~RB_PAGE_UPDATE;
820}
821
822/*
823 * rb_head_page_activate - sets up head page
824 */
825static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
826{
827 struct buffer_page *head;
828
829 head = cpu_buffer->head_page;
830 if (!head)
831 return;
832
833 /*
834 * Set the previous list pointer to have the HEAD flag.
835 */
836 rb_set_list_to_head(cpu_buffer, head->list.prev);
837}
838
839static void rb_list_head_clear(struct list_head *list)
840{
841 unsigned long *ptr = (unsigned long *)&list->next;
842
843 *ptr &= ~RB_FLAG_MASK;
844}
845
846/*
847 * rb_head_page_dactivate - clears head page ptr (for free list)
848 */
849static void
850rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
851{
852 struct list_head *hd;
853
854 /* Go through the whole list and clear any pointers found. */
855 rb_list_head_clear(cpu_buffer->pages);
856
857 list_for_each(hd, cpu_buffer->pages)
858 rb_list_head_clear(hd);
859}
860
861static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
862 struct buffer_page *head,
863 struct buffer_page *prev,
864 int old_flag, int new_flag)
865{
866 struct list_head *list;
867 unsigned long val = (unsigned long)&head->list;
868 unsigned long ret;
869
870 list = &prev->list;
871
872 val &= ~RB_FLAG_MASK;
873
874 ret = cmpxchg((unsigned long *)&list->next,
875 val | old_flag, val | new_flag);
876
877 /* check if the reader took the page */
878 if ((ret & ~RB_FLAG_MASK) != val)
879 return RB_PAGE_MOVED;
880
881 return ret & RB_FLAG_MASK;
882}
883
884static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
885 struct buffer_page *head,
886 struct buffer_page *prev,
887 int old_flag)
888{
889 return rb_head_page_set(cpu_buffer, head, prev,
890 old_flag, RB_PAGE_UPDATE);
891}
892
893static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
894 struct buffer_page *head,
895 struct buffer_page *prev,
896 int old_flag)
897{
898 return rb_head_page_set(cpu_buffer, head, prev,
899 old_flag, RB_PAGE_HEAD);
900}
901
902static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
903 struct buffer_page *head,
904 struct buffer_page *prev,
905 int old_flag)
906{
907 return rb_head_page_set(cpu_buffer, head, prev,
908 old_flag, RB_PAGE_NORMAL);
909}
910
911static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
912 struct buffer_page **bpage)
913{
914 struct list_head *p = rb_list_head((*bpage)->list.next);
915
916 *bpage = list_entry(p, struct buffer_page, list);
917}
918
919static struct buffer_page *
920rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
921{
922 struct buffer_page *head;
923 struct buffer_page *page;
924 struct list_head *list;
925 int i;
926
927 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
928 return NULL;
929
930 /* sanity check */
931 list = cpu_buffer->pages;
932 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
933 return NULL;
934
935 page = head = cpu_buffer->head_page;
936 /*
937 * It is possible that the writer moves the header behind
938 * where we started, and we miss in one loop.
939 * A second loop should grab the header, but we'll do
940 * three loops just because I'm paranoid.
941 */
942 for (i = 0; i < 3; i++) {
943 do {
944 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
945 cpu_buffer->head_page = page;
946 return page;
947 }
948 rb_inc_page(cpu_buffer, &page);
949 } while (page != head);
950 }
951
952 RB_WARN_ON(cpu_buffer, 1);
953
954 return NULL;
955}
956
957static int rb_head_page_replace(struct buffer_page *old,
958 struct buffer_page *new)
959{
960 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
961 unsigned long val;
962 unsigned long ret;
963
964 val = *ptr & ~RB_FLAG_MASK;
965 val |= RB_PAGE_HEAD;
966
967 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
968
969 return ret == val;
970}
971
972/*
973 * rb_tail_page_update - move the tail page forward
974 *
975 * Returns 1 if moved tail page, 0 if someone else did.
976 */
977static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
978 struct buffer_page *tail_page,
979 struct buffer_page *next_page)
980{
981 struct buffer_page *old_tail;
982 unsigned long old_entries;
983 unsigned long old_write;
984 int ret = 0;
985
986 /*
987 * The tail page now needs to be moved forward.
988 *
989 * We need to reset the tail page, but without messing
990 * with possible erasing of data brought in by interrupts
991 * that have moved the tail page and are currently on it.
992 *
993 * We add a counter to the write field to denote this.
994 */
995 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
996 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
997
998 /*
999 * Just make sure we have seen our old_write and synchronize
1000 * with any interrupts that come in.
1001 */
1002 barrier();
1003
1004 /*
1005 * If the tail page is still the same as what we think
1006 * it is, then it is up to us to update the tail
1007 * pointer.
1008 */
1009 if (tail_page == cpu_buffer->tail_page) {
1010 /* Zero the write counter */
1011 unsigned long val = old_write & ~RB_WRITE_MASK;
1012 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1013
1014 /*
1015 * This will only succeed if an interrupt did
1016 * not come in and change it. In which case, we
1017 * do not want to modify it.
1018 *
1019 * We add (void) to let the compiler know that we do not care
1020 * about the return value of these functions. We use the
1021 * cmpxchg to only update if an interrupt did not already
1022 * do it for us. If the cmpxchg fails, we don't care.
1023 */
1024 (void)local_cmpxchg(&next_page->write, old_write, val);
1025 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1026
1027 /*
1028 * No need to worry about races with clearing out the commit.
1029 * it only can increment when a commit takes place. But that
1030 * only happens in the outer most nested commit.
1031 */
1032 local_set(&next_page->page->commit, 0);
1033
1034 old_tail = cmpxchg(&cpu_buffer->tail_page,
1035 tail_page, next_page);
1036
1037 if (old_tail == tail_page)
1038 ret = 1;
1039 }
1040
1041 return ret;
1042}
1043
1044static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1045 struct buffer_page *bpage)
1046{
1047 unsigned long val = (unsigned long)bpage;
1048
1049 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1050 return 1;
1051
1052 return 0;
1053}
1054
1055/**
1056 * rb_check_list - make sure a pointer to a list has the last bits zero
1057 */
1058static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1059 struct list_head *list)
1060{
1061 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1062 return 1;
1063 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1064 return 1;
1065 return 0;
1066}
1067
1068/**
1069 * rb_check_pages - integrity check of buffer pages
1070 * @cpu_buffer: CPU buffer with pages to test
1071 *
1072 * As a safety measure we check to make sure the data pages have not
1073 * been corrupted.
1074 */
1075static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1076{
1077 struct list_head *head = cpu_buffer->pages;
1078 struct buffer_page *bpage, *tmp;
1079
1080 /* Reset the head page if it exists */
1081 if (cpu_buffer->head_page)
1082 rb_set_head_page(cpu_buffer);
1083
1084 rb_head_page_deactivate(cpu_buffer);
1085
1086 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1087 return -1;
1088 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1089 return -1;
1090
1091 if (rb_check_list(cpu_buffer, head))
1092 return -1;
1093
1094 list_for_each_entry_safe(bpage, tmp, head, list) {
1095 if (RB_WARN_ON(cpu_buffer,
1096 bpage->list.next->prev != &bpage->list))
1097 return -1;
1098 if (RB_WARN_ON(cpu_buffer,
1099 bpage->list.prev->next != &bpage->list))
1100 return -1;
1101 if (rb_check_list(cpu_buffer, &bpage->list))
1102 return -1;
1103 }
1104
1105 rb_head_page_activate(cpu_buffer);
1106
1107 return 0;
1108}
1109
1110static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
1111{
1112 int i;
1113 struct buffer_page *bpage, *tmp;
1114
1115 for (i = 0; i < nr_pages; i++) {
1116 struct page *page;
1117 /*
1118 * __GFP_NORETRY flag makes sure that the allocation fails
1119 * gracefully without invoking oom-killer and the system is
1120 * not destabilized.
1121 */
1122 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1123 GFP_KERNEL | __GFP_NORETRY,
1124 cpu_to_node(cpu));
1125 if (!bpage)
1126 goto free_pages;
1127
1128 list_add(&bpage->list, pages);
1129
1130 page = alloc_pages_node(cpu_to_node(cpu),
1131 GFP_KERNEL | __GFP_NORETRY, 0);
1132 if (!page)
1133 goto free_pages;
1134 bpage->page = page_address(page);
1135 rb_init_page(bpage->page);
1136 }
1137
1138 return 0;
1139
1140free_pages:
1141 list_for_each_entry_safe(bpage, tmp, pages, list) {
1142 list_del_init(&bpage->list);
1143 free_buffer_page(bpage);
1144 }
1145
1146 return -ENOMEM;
1147}
1148
1149static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1150 unsigned nr_pages)
1151{
1152 LIST_HEAD(pages);
1153
1154 WARN_ON(!nr_pages);
1155
1156 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1157 return -ENOMEM;
1158
1159 /*
1160 * The ring buffer page list is a circular list that does not
1161 * start and end with a list head. All page list items point to
1162 * other pages.
1163 */
1164 cpu_buffer->pages = pages.next;
1165 list_del(&pages);
1166
1167 cpu_buffer->nr_pages = nr_pages;
1168
1169 rb_check_pages(cpu_buffer);
1170
1171 return 0;
1172}
1173
1174static struct ring_buffer_per_cpu *
1175rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
1176{
1177 struct ring_buffer_per_cpu *cpu_buffer;
1178 struct buffer_page *bpage;
1179 struct page *page;
1180 int ret;
1181
1182 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1183 GFP_KERNEL, cpu_to_node(cpu));
1184 if (!cpu_buffer)
1185 return NULL;
1186
1187 cpu_buffer->cpu = cpu;
1188 cpu_buffer->buffer = buffer;
1189 raw_spin_lock_init(&cpu_buffer->reader_lock);
1190 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1191 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1192 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1193 init_completion(&cpu_buffer->update_done);
1194 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1195 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1196
1197 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1198 GFP_KERNEL, cpu_to_node(cpu));
1199 if (!bpage)
1200 goto fail_free_buffer;
1201
1202 rb_check_bpage(cpu_buffer, bpage);
1203
1204 cpu_buffer->reader_page = bpage;
1205 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1206 if (!page)
1207 goto fail_free_reader;
1208 bpage->page = page_address(page);
1209 rb_init_page(bpage->page);
1210
1211 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1212 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1213
1214 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1215 if (ret < 0)
1216 goto fail_free_reader;
1217
1218 cpu_buffer->head_page
1219 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1220 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1221
1222 rb_head_page_activate(cpu_buffer);
1223
1224 return cpu_buffer;
1225
1226 fail_free_reader:
1227 free_buffer_page(cpu_buffer->reader_page);
1228
1229 fail_free_buffer:
1230 kfree(cpu_buffer);
1231 return NULL;
1232}
1233
1234static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1235{
1236 struct list_head *head = cpu_buffer->pages;
1237 struct buffer_page *bpage, *tmp;
1238
1239 free_buffer_page(cpu_buffer->reader_page);
1240
1241 rb_head_page_deactivate(cpu_buffer);
1242
1243 if (head) {
1244 list_for_each_entry_safe(bpage, tmp, head, list) {
1245 list_del_init(&bpage->list);
1246 free_buffer_page(bpage);
1247 }
1248 bpage = list_entry(head, struct buffer_page, list);
1249 free_buffer_page(bpage);
1250 }
1251
1252 kfree(cpu_buffer);
1253}
1254
1255#ifdef CONFIG_HOTPLUG_CPU
1256static int rb_cpu_notify(struct notifier_block *self,
1257 unsigned long action, void *hcpu);
1258#endif
1259
1260/**
1261 * __ring_buffer_alloc - allocate a new ring_buffer
1262 * @size: the size in bytes per cpu that is needed.
1263 * @flags: attributes to set for the ring buffer.
1264 *
1265 * Currently the only flag that is available is the RB_FL_OVERWRITE
1266 * flag. This flag means that the buffer will overwrite old data
1267 * when the buffer wraps. If this flag is not set, the buffer will
1268 * drop data when the tail hits the head.
1269 */
1270struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1271 struct lock_class_key *key)
1272{
1273 struct ring_buffer *buffer;
1274 int bsize;
1275 int cpu, nr_pages;
1276
1277 /* keep it in its own cache line */
1278 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1279 GFP_KERNEL);
1280 if (!buffer)
1281 return NULL;
1282
1283 if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1284 goto fail_free_buffer;
1285
1286 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1287 buffer->flags = flags;
1288 buffer->clock = trace_clock_local;
1289 buffer->reader_lock_key = key;
1290
1291 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1292 init_waitqueue_head(&buffer->irq_work.waiters);
1293
1294 /* need at least two pages */
1295 if (nr_pages < 2)
1296 nr_pages = 2;
1297
1298 /*
1299 * In case of non-hotplug cpu, if the ring-buffer is allocated
1300 * in early initcall, it will not be notified of secondary cpus.
1301 * In that off case, we need to allocate for all possible cpus.
1302 */
1303#ifdef CONFIG_HOTPLUG_CPU
1304 cpu_notifier_register_begin();
1305 cpumask_copy(buffer->cpumask, cpu_online_mask);
1306#else
1307 cpumask_copy(buffer->cpumask, cpu_possible_mask);
1308#endif
1309 buffer->cpus = nr_cpu_ids;
1310
1311 bsize = sizeof(void *) * nr_cpu_ids;
1312 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1313 GFP_KERNEL);
1314 if (!buffer->buffers)
1315 goto fail_free_cpumask;
1316
1317 for_each_buffer_cpu(buffer, cpu) {
1318 buffer->buffers[cpu] =
1319 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1320 if (!buffer->buffers[cpu])
1321 goto fail_free_buffers;
1322 }
1323
1324#ifdef CONFIG_HOTPLUG_CPU
1325 buffer->cpu_notify.notifier_call = rb_cpu_notify;
1326 buffer->cpu_notify.priority = 0;
1327 __register_cpu_notifier(&buffer->cpu_notify);
1328 cpu_notifier_register_done();
1329#endif
1330
1331 mutex_init(&buffer->mutex);
1332
1333 return buffer;
1334
1335 fail_free_buffers:
1336 for_each_buffer_cpu(buffer, cpu) {
1337 if (buffer->buffers[cpu])
1338 rb_free_cpu_buffer(buffer->buffers[cpu]);
1339 }
1340 kfree(buffer->buffers);
1341
1342 fail_free_cpumask:
1343 free_cpumask_var(buffer->cpumask);
1344#ifdef CONFIG_HOTPLUG_CPU
1345 cpu_notifier_register_done();
1346#endif
1347
1348 fail_free_buffer:
1349 kfree(buffer);
1350 return NULL;
1351}
1352EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1353
1354/**
1355 * ring_buffer_free - free a ring buffer.
1356 * @buffer: the buffer to free.
1357 */
1358void
1359ring_buffer_free(struct ring_buffer *buffer)
1360{
1361 int cpu;
1362
1363#ifdef CONFIG_HOTPLUG_CPU
1364 cpu_notifier_register_begin();
1365 __unregister_cpu_notifier(&buffer->cpu_notify);
1366#endif
1367
1368 for_each_buffer_cpu(buffer, cpu)
1369 rb_free_cpu_buffer(buffer->buffers[cpu]);
1370
1371#ifdef CONFIG_HOTPLUG_CPU
1372 cpu_notifier_register_done();
1373#endif
1374
1375 kfree(buffer->buffers);
1376 free_cpumask_var(buffer->cpumask);
1377
1378 kfree(buffer);
1379}
1380EXPORT_SYMBOL_GPL(ring_buffer_free);
1381
1382void ring_buffer_set_clock(struct ring_buffer *buffer,
1383 u64 (*clock)(void))
1384{
1385 buffer->clock = clock;
1386}
1387
1388static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1389
1390static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1391{
1392 return local_read(&bpage->entries) & RB_WRITE_MASK;
1393}
1394
1395static inline unsigned long rb_page_write(struct buffer_page *bpage)
1396{
1397 return local_read(&bpage->write) & RB_WRITE_MASK;
1398}
1399
1400static int
1401rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
1402{
1403 struct list_head *tail_page, *to_remove, *next_page;
1404 struct buffer_page *to_remove_page, *tmp_iter_page;
1405 struct buffer_page *last_page, *first_page;
1406 unsigned int nr_removed;
1407 unsigned long head_bit;
1408 int page_entries;
1409
1410 head_bit = 0;
1411
1412 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1413 atomic_inc(&cpu_buffer->record_disabled);
1414 /*
1415 * We don't race with the readers since we have acquired the reader
1416 * lock. We also don't race with writers after disabling recording.
1417 * This makes it easy to figure out the first and the last page to be
1418 * removed from the list. We unlink all the pages in between including
1419 * the first and last pages. This is done in a busy loop so that we
1420 * lose the least number of traces.
1421 * The pages are freed after we restart recording and unlock readers.
1422 */
1423 tail_page = &cpu_buffer->tail_page->list;
1424
1425 /*
1426 * tail page might be on reader page, we remove the next page
1427 * from the ring buffer
1428 */
1429 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1430 tail_page = rb_list_head(tail_page->next);
1431 to_remove = tail_page;
1432
1433 /* start of pages to remove */
1434 first_page = list_entry(rb_list_head(to_remove->next),
1435 struct buffer_page, list);
1436
1437 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1438 to_remove = rb_list_head(to_remove)->next;
1439 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1440 }
1441
1442 next_page = rb_list_head(to_remove)->next;
1443
1444 /*
1445 * Now we remove all pages between tail_page and next_page.
1446 * Make sure that we have head_bit value preserved for the
1447 * next page
1448 */
1449 tail_page->next = (struct list_head *)((unsigned long)next_page |
1450 head_bit);
1451 next_page = rb_list_head(next_page);
1452 next_page->prev = tail_page;
1453
1454 /* make sure pages points to a valid page in the ring buffer */
1455 cpu_buffer->pages = next_page;
1456
1457 /* update head page */
1458 if (head_bit)
1459 cpu_buffer->head_page = list_entry(next_page,
1460 struct buffer_page, list);
1461
1462 /*
1463 * change read pointer to make sure any read iterators reset
1464 * themselves
1465 */
1466 cpu_buffer->read = 0;
1467
1468 /* pages are removed, resume tracing and then free the pages */
1469 atomic_dec(&cpu_buffer->record_disabled);
1470 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1471
1472 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1473
1474 /* last buffer page to remove */
1475 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1476 list);
1477 tmp_iter_page = first_page;
1478
1479 do {
1480 to_remove_page = tmp_iter_page;
1481 rb_inc_page(cpu_buffer, &tmp_iter_page);
1482
1483 /* update the counters */
1484 page_entries = rb_page_entries(to_remove_page);
1485 if (page_entries) {
1486 /*
1487 * If something was added to this page, it was full
1488 * since it is not the tail page. So we deduct the
1489 * bytes consumed in ring buffer from here.
1490 * Increment overrun to account for the lost events.
1491 */
1492 local_add(page_entries, &cpu_buffer->overrun);
1493 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1494 }
1495
1496 /*
1497 * We have already removed references to this list item, just
1498 * free up the buffer_page and its page
1499 */
1500 free_buffer_page(to_remove_page);
1501 nr_removed--;
1502
1503 } while (to_remove_page != last_page);
1504
1505 RB_WARN_ON(cpu_buffer, nr_removed);
1506
1507 return nr_removed == 0;
1508}
1509
1510static int
1511rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1512{
1513 struct list_head *pages = &cpu_buffer->new_pages;
1514 int retries, success;
1515
1516 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1517 /*
1518 * We are holding the reader lock, so the reader page won't be swapped
1519 * in the ring buffer. Now we are racing with the writer trying to
1520 * move head page and the tail page.
1521 * We are going to adapt the reader page update process where:
1522 * 1. We first splice the start and end of list of new pages between
1523 * the head page and its previous page.
1524 * 2. We cmpxchg the prev_page->next to point from head page to the
1525 * start of new pages list.
1526 * 3. Finally, we update the head->prev to the end of new list.
1527 *
1528 * We will try this process 10 times, to make sure that we don't keep
1529 * spinning.
1530 */
1531 retries = 10;
1532 success = 0;
1533 while (retries--) {
1534 struct list_head *head_page, *prev_page, *r;
1535 struct list_head *last_page, *first_page;
1536 struct list_head *head_page_with_bit;
1537
1538 head_page = &rb_set_head_page(cpu_buffer)->list;
1539 if (!head_page)
1540 break;
1541 prev_page = head_page->prev;
1542
1543 first_page = pages->next;
1544 last_page = pages->prev;
1545
1546 head_page_with_bit = (struct list_head *)
1547 ((unsigned long)head_page | RB_PAGE_HEAD);
1548
1549 last_page->next = head_page_with_bit;
1550 first_page->prev = prev_page;
1551
1552 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1553
1554 if (r == head_page_with_bit) {
1555 /*
1556 * yay, we replaced the page pointer to our new list,
1557 * now, we just have to update to head page's prev
1558 * pointer to point to end of list
1559 */
1560 head_page->prev = last_page;
1561 success = 1;
1562 break;
1563 }
1564 }
1565
1566 if (success)
1567 INIT_LIST_HEAD(pages);
1568 /*
1569 * If we weren't successful in adding in new pages, warn and stop
1570 * tracing
1571 */
1572 RB_WARN_ON(cpu_buffer, !success);
1573 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1574
1575 /* free pages if they weren't inserted */
1576 if (!success) {
1577 struct buffer_page *bpage, *tmp;
1578 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1579 list) {
1580 list_del_init(&bpage->list);
1581 free_buffer_page(bpage);
1582 }
1583 }
1584 return success;
1585}
1586
1587static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1588{
1589 int success;
1590
1591 if (cpu_buffer->nr_pages_to_update > 0)
1592 success = rb_insert_pages(cpu_buffer);
1593 else
1594 success = rb_remove_pages(cpu_buffer,
1595 -cpu_buffer->nr_pages_to_update);
1596
1597 if (success)
1598 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1599}
1600
1601static void update_pages_handler(struct work_struct *work)
1602{
1603 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1604 struct ring_buffer_per_cpu, update_pages_work);
1605 rb_update_pages(cpu_buffer);
1606 complete(&cpu_buffer->update_done);
1607}
1608
1609/**
1610 * ring_buffer_resize - resize the ring buffer
1611 * @buffer: the buffer to resize.
1612 * @size: the new size.
1613 * @cpu_id: the cpu buffer to resize
1614 *
1615 * Minimum size is 2 * BUF_PAGE_SIZE.
1616 *
1617 * Returns 0 on success and < 0 on failure.
1618 */
1619int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1620 int cpu_id)
1621{
1622 struct ring_buffer_per_cpu *cpu_buffer;
1623 unsigned nr_pages;
1624 int cpu, err = 0;
1625
1626 /*
1627 * Always succeed at resizing a non-existent buffer:
1628 */
1629 if (!buffer)
1630 return size;
1631
1632 /* Make sure the requested buffer exists */
1633 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1634 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1635 return size;
1636
1637 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1638 size *= BUF_PAGE_SIZE;
1639
1640 /* we need a minimum of two pages */
1641 if (size < BUF_PAGE_SIZE * 2)
1642 size = BUF_PAGE_SIZE * 2;
1643
1644 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1645
1646 /*
1647 * Don't succeed if resizing is disabled, as a reader might be
1648 * manipulating the ring buffer and is expecting a sane state while
1649 * this is true.
1650 */
1651 if (atomic_read(&buffer->resize_disabled))
1652 return -EBUSY;
1653
1654 /* prevent another thread from changing buffer sizes */
1655 mutex_lock(&buffer->mutex);
1656
1657 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1658 /* calculate the pages to update */
1659 for_each_buffer_cpu(buffer, cpu) {
1660 cpu_buffer = buffer->buffers[cpu];
1661
1662 cpu_buffer->nr_pages_to_update = nr_pages -
1663 cpu_buffer->nr_pages;
1664 /*
1665 * nothing more to do for removing pages or no update
1666 */
1667 if (cpu_buffer->nr_pages_to_update <= 0)
1668 continue;
1669 /*
1670 * to add pages, make sure all new pages can be
1671 * allocated without receiving ENOMEM
1672 */
1673 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1674 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1675 &cpu_buffer->new_pages, cpu)) {
1676 /* not enough memory for new pages */
1677 err = -ENOMEM;
1678 goto out_err;
1679 }
1680 }
1681
1682 get_online_cpus();
1683 /*
1684 * Fire off all the required work handlers
1685 * We can't schedule on offline CPUs, but it's not necessary
1686 * since we can change their buffer sizes without any race.
1687 */
1688 for_each_buffer_cpu(buffer, cpu) {
1689 cpu_buffer = buffer->buffers[cpu];
1690 if (!cpu_buffer->nr_pages_to_update)
1691 continue;
1692
1693 /* The update must run on the CPU that is being updated. */
1694 preempt_disable();
1695 if (cpu == smp_processor_id() || !cpu_online(cpu)) {
1696 rb_update_pages(cpu_buffer);
1697 cpu_buffer->nr_pages_to_update = 0;
1698 } else {
1699 /*
1700 * Can not disable preemption for schedule_work_on()
1701 * on PREEMPT_RT.
1702 */
1703 preempt_enable();
1704 schedule_work_on(cpu,
1705 &cpu_buffer->update_pages_work);
1706 preempt_disable();
1707 }
1708 preempt_enable();
1709 }
1710
1711 /* wait for all the updates to complete */
1712 for_each_buffer_cpu(buffer, cpu) {
1713 cpu_buffer = buffer->buffers[cpu];
1714 if (!cpu_buffer->nr_pages_to_update)
1715 continue;
1716
1717 if (cpu_online(cpu))
1718 wait_for_completion(&cpu_buffer->update_done);
1719 cpu_buffer->nr_pages_to_update = 0;
1720 }
1721
1722 put_online_cpus();
1723 } else {
1724 /* Make sure this CPU has been intitialized */
1725 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1726 goto out;
1727
1728 cpu_buffer = buffer->buffers[cpu_id];
1729
1730 if (nr_pages == cpu_buffer->nr_pages)
1731 goto out;
1732
1733 cpu_buffer->nr_pages_to_update = nr_pages -
1734 cpu_buffer->nr_pages;
1735
1736 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1737 if (cpu_buffer->nr_pages_to_update > 0 &&
1738 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1739 &cpu_buffer->new_pages, cpu_id)) {
1740 err = -ENOMEM;
1741 goto out_err;
1742 }
1743
1744 get_online_cpus();
1745
1746 preempt_disable();
1747 /* The update must run on the CPU that is being updated. */
1748 if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
1749 rb_update_pages(cpu_buffer);
1750 else {
1751 /*
1752 * Can not disable preemption for schedule_work_on()
1753 * on PREEMPT_RT.
1754 */
1755 preempt_enable();
1756 schedule_work_on(cpu_id,
1757 &cpu_buffer->update_pages_work);
1758 wait_for_completion(&cpu_buffer->update_done);
1759 preempt_disable();
1760 }
1761 preempt_enable();
1762
1763 cpu_buffer->nr_pages_to_update = 0;
1764 put_online_cpus();
1765 }
1766
1767 out:
1768 /*
1769 * The ring buffer resize can happen with the ring buffer
1770 * enabled, so that the update disturbs the tracing as little
1771 * as possible. But if the buffer is disabled, we do not need
1772 * to worry about that, and we can take the time to verify
1773 * that the buffer is not corrupt.
1774 */
1775 if (atomic_read(&buffer->record_disabled)) {
1776 atomic_inc(&buffer->record_disabled);
1777 /*
1778 * Even though the buffer was disabled, we must make sure
1779 * that it is truly disabled before calling rb_check_pages.
1780 * There could have been a race between checking
1781 * record_disable and incrementing it.
1782 */
1783 synchronize_sched();
1784 for_each_buffer_cpu(buffer, cpu) {
1785 cpu_buffer = buffer->buffers[cpu];
1786 rb_check_pages(cpu_buffer);
1787 }
1788 atomic_dec(&buffer->record_disabled);
1789 }
1790
1791 mutex_unlock(&buffer->mutex);
1792 return size;
1793
1794 out_err:
1795 for_each_buffer_cpu(buffer, cpu) {
1796 struct buffer_page *bpage, *tmp;
1797
1798 cpu_buffer = buffer->buffers[cpu];
1799 cpu_buffer->nr_pages_to_update = 0;
1800
1801 if (list_empty(&cpu_buffer->new_pages))
1802 continue;
1803
1804 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1805 list) {
1806 list_del_init(&bpage->list);
1807 free_buffer_page(bpage);
1808 }
1809 }
1810 mutex_unlock(&buffer->mutex);
1811 return err;
1812}
1813EXPORT_SYMBOL_GPL(ring_buffer_resize);
1814
1815void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1816{
1817 mutex_lock(&buffer->mutex);
1818 if (val)
1819 buffer->flags |= RB_FL_OVERWRITE;
1820 else
1821 buffer->flags &= ~RB_FL_OVERWRITE;
1822 mutex_unlock(&buffer->mutex);
1823}
1824EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1825
1826static inline void *
1827__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
1828{
1829 return bpage->data + index;
1830}
1831
1832static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1833{
1834 return bpage->page->data + index;
1835}
1836
1837static inline struct ring_buffer_event *
1838rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1839{
1840 return __rb_page_index(cpu_buffer->reader_page,
1841 cpu_buffer->reader_page->read);
1842}
1843
1844static inline struct ring_buffer_event *
1845rb_iter_head_event(struct ring_buffer_iter *iter)
1846{
1847 return __rb_page_index(iter->head_page, iter->head);
1848}
1849
1850static inline unsigned rb_page_commit(struct buffer_page *bpage)
1851{
1852 return local_read(&bpage->page->commit);
1853}
1854
1855/* Size is determined by what has been committed */
1856static inline unsigned rb_page_size(struct buffer_page *bpage)
1857{
1858 return rb_page_commit(bpage);
1859}
1860
1861static inline unsigned
1862rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1863{
1864 return rb_page_commit(cpu_buffer->commit_page);
1865}
1866
1867static inline unsigned
1868rb_event_index(struct ring_buffer_event *event)
1869{
1870 unsigned long addr = (unsigned long)event;
1871
1872 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1873}
1874
1875static inline int
1876rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1877 struct ring_buffer_event *event)
1878{
1879 unsigned long addr = (unsigned long)event;
1880 unsigned long index;
1881
1882 index = rb_event_index(event);
1883 addr &= PAGE_MASK;
1884
1885 return cpu_buffer->commit_page->page == (void *)addr &&
1886 rb_commit_index(cpu_buffer) == index;
1887}
1888
1889static void
1890rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1891{
1892 unsigned long max_count;
1893
1894 /*
1895 * We only race with interrupts and NMIs on this CPU.
1896 * If we own the commit event, then we can commit
1897 * all others that interrupted us, since the interruptions
1898 * are in stack format (they finish before they come
1899 * back to us). This allows us to do a simple loop to
1900 * assign the commit to the tail.
1901 */
1902 again:
1903 max_count = cpu_buffer->nr_pages * 100;
1904
1905 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
1906 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
1907 return;
1908 if (RB_WARN_ON(cpu_buffer,
1909 rb_is_reader_page(cpu_buffer->tail_page)))
1910 return;
1911 local_set(&cpu_buffer->commit_page->page->commit,
1912 rb_page_write(cpu_buffer->commit_page));
1913 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
1914 cpu_buffer->write_stamp =
1915 cpu_buffer->commit_page->page->time_stamp;
1916 /* add barrier to keep gcc from optimizing too much */
1917 barrier();
1918 }
1919 while (rb_commit_index(cpu_buffer) !=
1920 rb_page_write(cpu_buffer->commit_page)) {
1921
1922 local_set(&cpu_buffer->commit_page->page->commit,
1923 rb_page_write(cpu_buffer->commit_page));
1924 RB_WARN_ON(cpu_buffer,
1925 local_read(&cpu_buffer->commit_page->page->commit) &
1926 ~RB_WRITE_MASK);
1927 barrier();
1928 }
1929
1930 /* again, keep gcc from optimizing */
1931 barrier();
1932
1933 /*
1934 * If an interrupt came in just after the first while loop
1935 * and pushed the tail page forward, we will be left with
1936 * a dangling commit that will never go forward.
1937 */
1938 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1939 goto again;
1940}
1941
1942static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
1943{
1944 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
1945 cpu_buffer->reader_page->read = 0;
1946}
1947
1948static void rb_inc_iter(struct ring_buffer_iter *iter)
1949{
1950 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1951
1952 /*
1953 * The iterator could be on the reader page (it starts there).
1954 * But the head could have moved, since the reader was
1955 * found. Check for this case and assign the iterator
1956 * to the head page instead of next.
1957 */
1958 if (iter->head_page == cpu_buffer->reader_page)
1959 iter->head_page = rb_set_head_page(cpu_buffer);
1960 else
1961 rb_inc_page(cpu_buffer, &iter->head_page);
1962
1963 iter->read_stamp = iter->head_page->page->time_stamp;
1964 iter->head = 0;
1965}
1966
1967/* Slow path, do not inline */
1968static noinline struct ring_buffer_event *
1969rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
1970{
1971 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
1972
1973 /* Not the first event on the page? */
1974 if (rb_event_index(event)) {
1975 event->time_delta = delta & TS_MASK;
1976 event->array[0] = delta >> TS_SHIFT;
1977 } else {
1978 /* nope, just zero it */
1979 event->time_delta = 0;
1980 event->array[0] = 0;
1981 }
1982
1983 return skip_time_extend(event);
1984}
1985
1986/**
1987 * rb_update_event - update event type and data
1988 * @event: the even to update
1989 * @type: the type of event
1990 * @length: the size of the event field in the ring buffer
1991 *
1992 * Update the type and data fields of the event. The length
1993 * is the actual size that is written to the ring buffer,
1994 * and with this, we can determine what to place into the
1995 * data field.
1996 */
1997static void
1998rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
1999 struct ring_buffer_event *event, unsigned length,
2000 int add_timestamp, u64 delta)
2001{
2002 /* Only a commit updates the timestamp */
2003 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2004 delta = 0;
2005
2006 /*
2007 * If we need to add a timestamp, then we
2008 * add it to the start of the resevered space.
2009 */
2010 if (unlikely(add_timestamp)) {
2011 event = rb_add_time_stamp(event, delta);
2012 length -= RB_LEN_TIME_EXTEND;
2013 delta = 0;
2014 }
2015
2016 event->time_delta = delta;
2017 length -= RB_EVNT_HDR_SIZE;
2018 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2019 event->type_len = 0;
2020 event->array[0] = length;
2021 } else
2022 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2023}
2024
2025/*
2026 * rb_handle_head_page - writer hit the head page
2027 *
2028 * Returns: +1 to retry page
2029 * 0 to continue
2030 * -1 on error
2031 */
2032static int
2033rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2034 struct buffer_page *tail_page,
2035 struct buffer_page *next_page)
2036{
2037 struct buffer_page *new_head;
2038 int entries;
2039 int type;
2040 int ret;
2041
2042 entries = rb_page_entries(next_page);
2043
2044 /*
2045 * The hard part is here. We need to move the head
2046 * forward, and protect against both readers on
2047 * other CPUs and writers coming in via interrupts.
2048 */
2049 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2050 RB_PAGE_HEAD);
2051
2052 /*
2053 * type can be one of four:
2054 * NORMAL - an interrupt already moved it for us
2055 * HEAD - we are the first to get here.
2056 * UPDATE - we are the interrupt interrupting
2057 * a current move.
2058 * MOVED - a reader on another CPU moved the next
2059 * pointer to its reader page. Give up
2060 * and try again.
2061 */
2062
2063 switch (type) {
2064 case RB_PAGE_HEAD:
2065 /*
2066 * We changed the head to UPDATE, thus
2067 * it is our responsibility to update
2068 * the counters.
2069 */
2070 local_add(entries, &cpu_buffer->overrun);
2071 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2072
2073 /*
2074 * The entries will be zeroed out when we move the
2075 * tail page.
2076 */
2077
2078 /* still more to do */
2079 break;
2080
2081 case RB_PAGE_UPDATE:
2082 /*
2083 * This is an interrupt that interrupt the
2084 * previous update. Still more to do.
2085 */
2086 break;
2087 case RB_PAGE_NORMAL:
2088 /*
2089 * An interrupt came in before the update
2090 * and processed this for us.
2091 * Nothing left to do.
2092 */
2093 return 1;
2094 case RB_PAGE_MOVED:
2095 /*
2096 * The reader is on another CPU and just did
2097 * a swap with our next_page.
2098 * Try again.
2099 */
2100 return 1;
2101 default:
2102 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2103 return -1;
2104 }
2105
2106 /*
2107 * Now that we are here, the old head pointer is
2108 * set to UPDATE. This will keep the reader from
2109 * swapping the head page with the reader page.
2110 * The reader (on another CPU) will spin till
2111 * we are finished.
2112 *
2113 * We just need to protect against interrupts
2114 * doing the job. We will set the next pointer
2115 * to HEAD. After that, we set the old pointer
2116 * to NORMAL, but only if it was HEAD before.
2117 * otherwise we are an interrupt, and only
2118 * want the outer most commit to reset it.
2119 */
2120 new_head = next_page;
2121 rb_inc_page(cpu_buffer, &new_head);
2122
2123 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2124 RB_PAGE_NORMAL);
2125
2126 /*
2127 * Valid returns are:
2128 * HEAD - an interrupt came in and already set it.
2129 * NORMAL - One of two things:
2130 * 1) We really set it.
2131 * 2) A bunch of interrupts came in and moved
2132 * the page forward again.
2133 */
2134 switch (ret) {
2135 case RB_PAGE_HEAD:
2136 case RB_PAGE_NORMAL:
2137 /* OK */
2138 break;
2139 default:
2140 RB_WARN_ON(cpu_buffer, 1);
2141 return -1;
2142 }
2143
2144 /*
2145 * It is possible that an interrupt came in,
2146 * set the head up, then more interrupts came in
2147 * and moved it again. When we get back here,
2148 * the page would have been set to NORMAL but we
2149 * just set it back to HEAD.
2150 *
2151 * How do you detect this? Well, if that happened
2152 * the tail page would have moved.
2153 */
2154 if (ret == RB_PAGE_NORMAL) {
2155 /*
2156 * If the tail had moved passed next, then we need
2157 * to reset the pointer.
2158 */
2159 if (cpu_buffer->tail_page != tail_page &&
2160 cpu_buffer->tail_page != next_page)
2161 rb_head_page_set_normal(cpu_buffer, new_head,
2162 next_page,
2163 RB_PAGE_HEAD);
2164 }
2165
2166 /*
2167 * If this was the outer most commit (the one that
2168 * changed the original pointer from HEAD to UPDATE),
2169 * then it is up to us to reset it to NORMAL.
2170 */
2171 if (type == RB_PAGE_HEAD) {
2172 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2173 tail_page,
2174 RB_PAGE_UPDATE);
2175 if (RB_WARN_ON(cpu_buffer,
2176 ret != RB_PAGE_UPDATE))
2177 return -1;
2178 }
2179
2180 return 0;
2181}
2182
2183static unsigned rb_calculate_event_length(unsigned length)
2184{
2185 struct ring_buffer_event event; /* Used only for sizeof array */
2186
2187 /* zero length can cause confusions */
2188 if (!length)
2189 length = 1;
2190
2191 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2192 length += sizeof(event.array[0]);
2193
2194 length += RB_EVNT_HDR_SIZE;
2195 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2196
2197 return length;
2198}
2199
2200static inline void
2201rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2202 struct buffer_page *tail_page,
2203 unsigned long tail, unsigned long length)
2204{
2205 struct ring_buffer_event *event;
2206
2207 /*
2208 * Only the event that crossed the page boundary
2209 * must fill the old tail_page with padding.
2210 */
2211 if (tail >= BUF_PAGE_SIZE) {
2212 /*
2213 * If the page was filled, then we still need
2214 * to update the real_end. Reset it to zero
2215 * and the reader will ignore it.
2216 */
2217 if (tail == BUF_PAGE_SIZE)
2218 tail_page->real_end = 0;
2219
2220 local_sub(length, &tail_page->write);
2221 return;
2222 }
2223
2224 event = __rb_page_index(tail_page, tail);
2225 kmemcheck_annotate_bitfield(event, bitfield);
2226
2227 /* account for padding bytes */
2228 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2229
2230 /*
2231 * Save the original length to the meta data.
2232 * This will be used by the reader to add lost event
2233 * counter.
2234 */
2235 tail_page->real_end = tail;
2236
2237 /*
2238 * If this event is bigger than the minimum size, then
2239 * we need to be careful that we don't subtract the
2240 * write counter enough to allow another writer to slip
2241 * in on this page.
2242 * We put in a discarded commit instead, to make sure
2243 * that this space is not used again.
2244 *
2245 * If we are less than the minimum size, we don't need to
2246 * worry about it.
2247 */
2248 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2249 /* No room for any events */
2250
2251 /* Mark the rest of the page with padding */
2252 rb_event_set_padding(event);
2253
2254 /* Set the write back to the previous setting */
2255 local_sub(length, &tail_page->write);
2256 return;
2257 }
2258
2259 /* Put in a discarded event */
2260 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2261 event->type_len = RINGBUF_TYPE_PADDING;
2262 /* time delta must be non zero */
2263 event->time_delta = 1;
2264
2265 /* Set write to end of buffer */
2266 length = (tail + length) - BUF_PAGE_SIZE;
2267 local_sub(length, &tail_page->write);
2268}
2269
2270/*
2271 * This is the slow path, force gcc not to inline it.
2272 */
2273static noinline struct ring_buffer_event *
2274rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2275 unsigned long length, unsigned long tail,
2276 struct buffer_page *tail_page, u64 ts)
2277{
2278 struct buffer_page *commit_page = cpu_buffer->commit_page;
2279 struct ring_buffer *buffer = cpu_buffer->buffer;
2280 struct buffer_page *next_page;
2281 int ret;
2282
2283 next_page = tail_page;
2284
2285 rb_inc_page(cpu_buffer, &next_page);
2286
2287 /*
2288 * If for some reason, we had an interrupt storm that made
2289 * it all the way around the buffer, bail, and warn
2290 * about it.
2291 */
2292 if (unlikely(next_page == commit_page)) {
2293 local_inc(&cpu_buffer->commit_overrun);
2294 goto out_reset;
2295 }
2296
2297 /*
2298 * This is where the fun begins!
2299 *
2300 * We are fighting against races between a reader that
2301 * could be on another CPU trying to swap its reader
2302 * page with the buffer head.
2303 *
2304 * We are also fighting against interrupts coming in and
2305 * moving the head or tail on us as well.
2306 *
2307 * If the next page is the head page then we have filled
2308 * the buffer, unless the commit page is still on the
2309 * reader page.
2310 */
2311 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2312
2313 /*
2314 * If the commit is not on the reader page, then
2315 * move the header page.
2316 */
2317 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2318 /*
2319 * If we are not in overwrite mode,
2320 * this is easy, just stop here.
2321 */
2322 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2323 local_inc(&cpu_buffer->dropped_events);
2324 goto out_reset;
2325 }
2326
2327 ret = rb_handle_head_page(cpu_buffer,
2328 tail_page,
2329 next_page);
2330 if (ret < 0)
2331 goto out_reset;
2332 if (ret)
2333 goto out_again;
2334 } else {
2335 /*
2336 * We need to be careful here too. The
2337 * commit page could still be on the reader
2338 * page. We could have a small buffer, and
2339 * have filled up the buffer with events
2340 * from interrupts and such, and wrapped.
2341 *
2342 * Note, if the tail page is also the on the
2343 * reader_page, we let it move out.
2344 */
2345 if (unlikely((cpu_buffer->commit_page !=
2346 cpu_buffer->tail_page) &&
2347 (cpu_buffer->commit_page ==
2348 cpu_buffer->reader_page))) {
2349 local_inc(&cpu_buffer->commit_overrun);
2350 goto out_reset;
2351 }
2352 }
2353 }
2354
2355 ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
2356 if (ret) {
2357 /*
2358 * Nested commits always have zero deltas, so
2359 * just reread the time stamp
2360 */
2361 ts = rb_time_stamp(buffer);
2362 next_page->page->time_stamp = ts;
2363 }
2364
2365 out_again:
2366
2367 rb_reset_tail(cpu_buffer, tail_page, tail, length);
2368
2369 /* fail and let the caller try again */
2370 return ERR_PTR(-EAGAIN);
2371
2372 out_reset:
2373 /* reset write */
2374 rb_reset_tail(cpu_buffer, tail_page, tail, length);
2375
2376 return NULL;
2377}
2378
2379static struct ring_buffer_event *
2380__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2381 unsigned long length, u64 ts,
2382 u64 delta, int add_timestamp)
2383{
2384 struct buffer_page *tail_page;
2385 struct ring_buffer_event *event;
2386 unsigned long tail, write;
2387
2388 /*
2389 * If the time delta since the last event is too big to
2390 * hold in the time field of the event, then we append a
2391 * TIME EXTEND event ahead of the data event.
2392 */
2393 if (unlikely(add_timestamp))
2394 length += RB_LEN_TIME_EXTEND;
2395
2396 tail_page = cpu_buffer->tail_page;
2397 write = local_add_return(length, &tail_page->write);
2398
2399 /* set write to only the index of the write */
2400 write &= RB_WRITE_MASK;
2401 tail = write - length;
2402
2403 /*
2404 * If this is the first commit on the page, then it has the same
2405 * timestamp as the page itself.
2406 */
2407 if (!tail)
2408 delta = 0;
2409
2410 /* See if we shot pass the end of this buffer page */
2411 if (unlikely(write > BUF_PAGE_SIZE))
2412 return rb_move_tail(cpu_buffer, length, tail,
2413 tail_page, ts);
2414
2415 /* We reserved something on the buffer */
2416
2417 event = __rb_page_index(tail_page, tail);
2418 kmemcheck_annotate_bitfield(event, bitfield);
2419 rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
2420
2421 local_inc(&tail_page->entries);
2422
2423 /*
2424 * If this is the first commit on the page, then update
2425 * its timestamp.
2426 */
2427 if (!tail)
2428 tail_page->page->time_stamp = ts;
2429
2430 /* account for these added bytes */
2431 local_add(length, &cpu_buffer->entries_bytes);
2432
2433 return event;
2434}
2435
2436static inline int
2437rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2438 struct ring_buffer_event *event)
2439{
2440 unsigned long new_index, old_index;
2441 struct buffer_page *bpage;
2442 unsigned long index;
2443 unsigned long addr;
2444
2445 new_index = rb_event_index(event);
2446 old_index = new_index + rb_event_ts_length(event);
2447 addr = (unsigned long)event;
2448 addr &= PAGE_MASK;
2449
2450 bpage = cpu_buffer->tail_page;
2451
2452 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2453 unsigned long write_mask =
2454 local_read(&bpage->write) & ~RB_WRITE_MASK;
2455 unsigned long event_length = rb_event_length(event);
2456 /*
2457 * This is on the tail page. It is possible that
2458 * a write could come in and move the tail page
2459 * and write to the next page. That is fine
2460 * because we just shorten what is on this page.
2461 */
2462 old_index += write_mask;
2463 new_index += write_mask;
2464 index = local_cmpxchg(&bpage->write, old_index, new_index);
2465 if (index == old_index) {
2466 /* update counters */
2467 local_sub(event_length, &cpu_buffer->entries_bytes);
2468 return 1;
2469 }
2470 }
2471
2472 /* could not discard */
2473 return 0;
2474}
2475
2476static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2477{
2478 local_inc(&cpu_buffer->committing);
2479 local_inc(&cpu_buffer->commits);
2480}
2481
2482static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2483{
2484 unsigned long commits;
2485
2486 if (RB_WARN_ON(cpu_buffer,
2487 !local_read(&cpu_buffer->committing)))
2488 return;
2489
2490 again:
2491 commits = local_read(&cpu_buffer->commits);
2492 /* synchronize with interrupts */
2493 barrier();
2494 if (local_read(&cpu_buffer->committing) == 1)
2495 rb_set_commit_to_write(cpu_buffer);
2496
2497 local_dec(&cpu_buffer->committing);
2498
2499 /* synchronize with interrupts */
2500 barrier();
2501
2502 /*
2503 * Need to account for interrupts coming in between the
2504 * updating of the commit page and the clearing of the
2505 * committing counter.
2506 */
2507 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2508 !local_read(&cpu_buffer->committing)) {
2509 local_inc(&cpu_buffer->committing);
2510 goto again;
2511 }
2512}
2513
2514static struct ring_buffer_event *
2515rb_reserve_next_event(struct ring_buffer *buffer,
2516 struct ring_buffer_per_cpu *cpu_buffer,
2517 unsigned long length)
2518{
2519 struct ring_buffer_event *event;
2520 u64 ts, delta;
2521 int nr_loops = 0;
2522 int add_timestamp;
2523 u64 diff;
2524
2525 rb_start_commit(cpu_buffer);
2526
2527#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2528 /*
2529 * Due to the ability to swap a cpu buffer from a buffer
2530 * it is possible it was swapped before we committed.
2531 * (committing stops a swap). We check for it here and
2532 * if it happened, we have to fail the write.
2533 */
2534 barrier();
2535 if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
2536 local_dec(&cpu_buffer->committing);
2537 local_dec(&cpu_buffer->commits);
2538 return NULL;
2539 }
2540#endif
2541
2542 length = rb_calculate_event_length(length);
2543 again:
2544 add_timestamp = 0;
2545 delta = 0;
2546
2547 /*
2548 * We allow for interrupts to reenter here and do a trace.
2549 * If one does, it will cause this original code to loop
2550 * back here. Even with heavy interrupts happening, this
2551 * should only happen a few times in a row. If this happens
2552 * 1000 times in a row, there must be either an interrupt
2553 * storm or we have something buggy.
2554 * Bail!
2555 */
2556 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2557 goto out_fail;
2558
2559 ts = rb_time_stamp(cpu_buffer->buffer);
2560 diff = ts - cpu_buffer->write_stamp;
2561
2562 /* make sure this diff is calculated here */
2563 barrier();
2564
2565 /* Did the write stamp get updated already? */
2566 if (likely(ts >= cpu_buffer->write_stamp)) {
2567 delta = diff;
2568 if (unlikely(test_time_stamp(delta))) {
2569 int local_clock_stable = 1;
2570#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2571 local_clock_stable = sched_clock_stable();
2572#endif
2573 WARN_ONCE(delta > (1ULL << 59),
2574 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2575 (unsigned long long)delta,
2576 (unsigned long long)ts,
2577 (unsigned long long)cpu_buffer->write_stamp,
2578 local_clock_stable ? "" :
2579 "If you just came from a suspend/resume,\n"
2580 "please switch to the trace global clock:\n"
2581 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
2582 add_timestamp = 1;
2583 }
2584 }
2585
2586 event = __rb_reserve_next(cpu_buffer, length, ts,
2587 delta, add_timestamp);
2588 if (unlikely(PTR_ERR(event) == -EAGAIN))
2589 goto again;
2590
2591 if (!event)
2592 goto out_fail;
2593
2594 return event;
2595
2596 out_fail:
2597 rb_end_commit(cpu_buffer);
2598 return NULL;
2599}
2600
2601#ifdef CONFIG_TRACING
2602
2603/*
2604 * The lock and unlock are done within a preempt disable section.
2605 * The current_context per_cpu variable can only be modified
2606 * by the current task between lock and unlock. But it can
2607 * be modified more than once via an interrupt. To pass this
2608 * information from the lock to the unlock without having to
2609 * access the 'in_interrupt()' functions again (which do show
2610 * a bit of overhead in something as critical as function tracing,
2611 * we use a bitmask trick.
2612 *
2613 * bit 0 = NMI context
2614 * bit 1 = IRQ context
2615 * bit 2 = SoftIRQ context
2616 * bit 3 = normal context.
2617 *
2618 * This works because this is the order of contexts that can
2619 * preempt other contexts. A SoftIRQ never preempts an IRQ
2620 * context.
2621 *
2622 * When the context is determined, the corresponding bit is
2623 * checked and set (if it was set, then a recursion of that context
2624 * happened).
2625 *
2626 * On unlock, we need to clear this bit. To do so, just subtract
2627 * 1 from the current_context and AND it to itself.
2628 *
2629 * (binary)
2630 * 101 - 1 = 100
2631 * 101 & 100 = 100 (clearing bit zero)
2632 *
2633 * 1010 - 1 = 1001
2634 * 1010 & 1001 = 1000 (clearing bit 1)
2635 *
2636 * The least significant bit can be cleared this way, and it
2637 * just so happens that it is the same bit corresponding to
2638 * the current context.
2639 */
2640static DEFINE_PER_CPU(unsigned int, current_context);
2641
2642static __always_inline int trace_recursive_lock(void)
2643{
2644 unsigned int val = this_cpu_read(current_context);
2645 int bit;
2646
2647 if (in_interrupt()) {
2648 if (in_nmi())
2649 bit = 0;
2650 else if (in_irq())
2651 bit = 1;
2652 else
2653 bit = 2;
2654 } else
2655 bit = 3;
2656
2657 if (unlikely(val & (1 << bit)))
2658 return 1;
2659
2660 val |= (1 << bit);
2661 this_cpu_write(current_context, val);
2662
2663 return 0;
2664}
2665
2666static __always_inline void trace_recursive_unlock(void)
2667{
2668 unsigned int val = this_cpu_read(current_context);
2669
2670 val--;
2671 val &= this_cpu_read(current_context);
2672 this_cpu_write(current_context, val);
2673}
2674
2675#else
2676
2677#define trace_recursive_lock() (0)
2678#define trace_recursive_unlock() do { } while (0)
2679
2680#endif
2681
2682/**
2683 * ring_buffer_lock_reserve - reserve a part of the buffer
2684 * @buffer: the ring buffer to reserve from
2685 * @length: the length of the data to reserve (excluding event header)
2686 *
2687 * Returns a reseverd event on the ring buffer to copy directly to.
2688 * The user of this interface will need to get the body to write into
2689 * and can use the ring_buffer_event_data() interface.
2690 *
2691 * The length is the length of the data needed, not the event length
2692 * which also includes the event header.
2693 *
2694 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2695 * If NULL is returned, then nothing has been allocated or locked.
2696 */
2697struct ring_buffer_event *
2698ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2699{
2700 struct ring_buffer_per_cpu *cpu_buffer;
2701 struct ring_buffer_event *event;
2702 int cpu;
2703
2704 if (ring_buffer_flags != RB_BUFFERS_ON)
2705 return NULL;
2706
2707 /* If we are tracing schedule, we don't want to recurse */
2708 preempt_disable_notrace();
2709
2710 if (atomic_read(&buffer->record_disabled))
2711 goto out_nocheck;
2712
2713 if (trace_recursive_lock())
2714 goto out_nocheck;
2715
2716 cpu = raw_smp_processor_id();
2717
2718 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2719 goto out;
2720
2721 cpu_buffer = buffer->buffers[cpu];
2722
2723 if (atomic_read(&cpu_buffer->record_disabled))
2724 goto out;
2725
2726 if (length > BUF_MAX_DATA_SIZE)
2727 goto out;
2728
2729 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2730 if (!event)
2731 goto out;
2732
2733 return event;
2734
2735 out:
2736 trace_recursive_unlock();
2737
2738 out_nocheck:
2739 preempt_enable_notrace();
2740 return NULL;
2741}
2742EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2743
2744static void
2745rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2746 struct ring_buffer_event *event)
2747{
2748 u64 delta;
2749
2750 /*
2751 * The event first in the commit queue updates the
2752 * time stamp.
2753 */
2754 if (rb_event_is_commit(cpu_buffer, event)) {
2755 /*
2756 * A commit event that is first on a page
2757 * updates the write timestamp with the page stamp
2758 */
2759 if (!rb_event_index(event))
2760 cpu_buffer->write_stamp =
2761 cpu_buffer->commit_page->page->time_stamp;
2762 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2763 delta = event->array[0];
2764 delta <<= TS_SHIFT;
2765 delta += event->time_delta;
2766 cpu_buffer->write_stamp += delta;
2767 } else
2768 cpu_buffer->write_stamp += event->time_delta;
2769 }
2770}
2771
2772static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2773 struct ring_buffer_event *event)
2774{
2775 local_inc(&cpu_buffer->entries);
2776 rb_update_write_stamp(cpu_buffer, event);
2777 rb_end_commit(cpu_buffer);
2778}
2779
2780static __always_inline void
2781rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2782{
2783 if (buffer->irq_work.waiters_pending) {
2784 buffer->irq_work.waiters_pending = false;
2785 /* irq_work_queue() supplies it's own memory barriers */
2786 irq_work_queue(&buffer->irq_work.work);
2787 }
2788
2789 if (cpu_buffer->irq_work.waiters_pending) {
2790 cpu_buffer->irq_work.waiters_pending = false;
2791 /* irq_work_queue() supplies it's own memory barriers */
2792 irq_work_queue(&cpu_buffer->irq_work.work);
2793 }
2794}
2795
2796/**
2797 * ring_buffer_unlock_commit - commit a reserved
2798 * @buffer: The buffer to commit to
2799 * @event: The event pointer to commit.
2800 *
2801 * This commits the data to the ring buffer, and releases any locks held.
2802 *
2803 * Must be paired with ring_buffer_lock_reserve.
2804 */
2805int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2806 struct ring_buffer_event *event)
2807{
2808 struct ring_buffer_per_cpu *cpu_buffer;
2809 int cpu = raw_smp_processor_id();
2810
2811 cpu_buffer = buffer->buffers[cpu];
2812
2813 rb_commit(cpu_buffer, event);
2814
2815 rb_wakeups(buffer, cpu_buffer);
2816
2817 trace_recursive_unlock();
2818
2819 preempt_enable_notrace();
2820
2821 return 0;
2822}
2823EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2824
2825static inline void rb_event_discard(struct ring_buffer_event *event)
2826{
2827 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
2828 event = skip_time_extend(event);
2829
2830 /* array[0] holds the actual length for the discarded event */
2831 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2832 event->type_len = RINGBUF_TYPE_PADDING;
2833 /* time delta must be non zero */
2834 if (!event->time_delta)
2835 event->time_delta = 1;
2836}
2837
2838/*
2839 * Decrement the entries to the page that an event is on.
2840 * The event does not even need to exist, only the pointer
2841 * to the page it is on. This may only be called before the commit
2842 * takes place.
2843 */
2844static inline void
2845rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2846 struct ring_buffer_event *event)
2847{
2848 unsigned long addr = (unsigned long)event;
2849 struct buffer_page *bpage = cpu_buffer->commit_page;
2850 struct buffer_page *start;
2851
2852 addr &= PAGE_MASK;
2853
2854 /* Do the likely case first */
2855 if (likely(bpage->page == (void *)addr)) {
2856 local_dec(&bpage->entries);
2857 return;
2858 }
2859
2860 /*
2861 * Because the commit page may be on the reader page we
2862 * start with the next page and check the end loop there.
2863 */
2864 rb_inc_page(cpu_buffer, &bpage);
2865 start = bpage;
2866 do {
2867 if (bpage->page == (void *)addr) {
2868 local_dec(&bpage->entries);
2869 return;
2870 }
2871 rb_inc_page(cpu_buffer, &bpage);
2872 } while (bpage != start);
2873
2874 /* commit not part of this buffer?? */
2875 RB_WARN_ON(cpu_buffer, 1);
2876}
2877
2878/**
2879 * ring_buffer_commit_discard - discard an event that has not been committed
2880 * @buffer: the ring buffer
2881 * @event: non committed event to discard
2882 *
2883 * Sometimes an event that is in the ring buffer needs to be ignored.
2884 * This function lets the user discard an event in the ring buffer
2885 * and then that event will not be read later.
2886 *
2887 * This function only works if it is called before the the item has been
2888 * committed. It will try to free the event from the ring buffer
2889 * if another event has not been added behind it.
2890 *
2891 * If another event has been added behind it, it will set the event
2892 * up as discarded, and perform the commit.
2893 *
2894 * If this function is called, do not call ring_buffer_unlock_commit on
2895 * the event.
2896 */
2897void ring_buffer_discard_commit(struct ring_buffer *buffer,
2898 struct ring_buffer_event *event)
2899{
2900 struct ring_buffer_per_cpu *cpu_buffer;
2901 int cpu;
2902
2903 /* The event is discarded regardless */
2904 rb_event_discard(event);
2905
2906 cpu = smp_processor_id();
2907 cpu_buffer = buffer->buffers[cpu];
2908
2909 /*
2910 * This must only be called if the event has not been
2911 * committed yet. Thus we can assume that preemption
2912 * is still disabled.
2913 */
2914 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
2915
2916 rb_decrement_entry(cpu_buffer, event);
2917 if (rb_try_to_discard(cpu_buffer, event))
2918 goto out;
2919
2920 /*
2921 * The commit is still visible by the reader, so we
2922 * must still update the timestamp.
2923 */
2924 rb_update_write_stamp(cpu_buffer, event);
2925 out:
2926 rb_end_commit(cpu_buffer);
2927
2928 trace_recursive_unlock();
2929
2930 preempt_enable_notrace();
2931
2932}
2933EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
2934
2935/**
2936 * ring_buffer_write - write data to the buffer without reserving
2937 * @buffer: The ring buffer to write to.
2938 * @length: The length of the data being written (excluding the event header)
2939 * @data: The data to write to the buffer.
2940 *
2941 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2942 * one function. If you already have the data to write to the buffer, it
2943 * may be easier to simply call this function.
2944 *
2945 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2946 * and not the length of the event which would hold the header.
2947 */
2948int ring_buffer_write(struct ring_buffer *buffer,
2949 unsigned long length,
2950 void *data)
2951{
2952 struct ring_buffer_per_cpu *cpu_buffer;
2953 struct ring_buffer_event *event;
2954 void *body;
2955 int ret = -EBUSY;
2956 int cpu;
2957
2958 if (ring_buffer_flags != RB_BUFFERS_ON)
2959 return -EBUSY;
2960
2961 preempt_disable_notrace();
2962
2963 if (atomic_read(&buffer->record_disabled))
2964 goto out;
2965
2966 cpu = raw_smp_processor_id();
2967
2968 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2969 goto out;
2970
2971 cpu_buffer = buffer->buffers[cpu];
2972
2973 if (atomic_read(&cpu_buffer->record_disabled))
2974 goto out;
2975
2976 if (length > BUF_MAX_DATA_SIZE)
2977 goto out;
2978
2979 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2980 if (!event)
2981 goto out;
2982
2983 body = rb_event_data(event);
2984
2985 memcpy(body, data, length);
2986
2987 rb_commit(cpu_buffer, event);
2988
2989 rb_wakeups(buffer, cpu_buffer);
2990
2991 ret = 0;
2992 out:
2993 preempt_enable_notrace();
2994
2995 return ret;
2996}
2997EXPORT_SYMBOL_GPL(ring_buffer_write);
2998
2999static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3000{
3001 struct buffer_page *reader = cpu_buffer->reader_page;
3002 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3003 struct buffer_page *commit = cpu_buffer->commit_page;
3004
3005 /* In case of error, head will be NULL */
3006 if (unlikely(!head))
3007 return 1;
3008
3009 return reader->read == rb_page_commit(reader) &&
3010 (commit == reader ||
3011 (commit == head &&
3012 head->read == rb_page_commit(commit)));
3013}
3014
3015/**
3016 * ring_buffer_record_disable - stop all writes into the buffer
3017 * @buffer: The ring buffer to stop writes to.
3018 *
3019 * This prevents all writes to the buffer. Any attempt to write
3020 * to the buffer after this will fail and return NULL.
3021 *
3022 * The caller should call synchronize_sched() after this.
3023 */
3024void ring_buffer_record_disable(struct ring_buffer *buffer)
3025{
3026 atomic_inc(&buffer->record_disabled);
3027}
3028EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3029
3030/**
3031 * ring_buffer_record_enable - enable writes to the buffer
3032 * @buffer: The ring buffer to enable writes
3033 *
3034 * Note, multiple disables will need the same number of enables
3035 * to truly enable the writing (much like preempt_disable).
3036 */
3037void ring_buffer_record_enable(struct ring_buffer *buffer)
3038{
3039 atomic_dec(&buffer->record_disabled);
3040}
3041EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3042
3043/**
3044 * ring_buffer_record_off - stop all writes into the buffer
3045 * @buffer: The ring buffer to stop writes to.
3046 *
3047 * This prevents all writes to the buffer. Any attempt to write
3048 * to the buffer after this will fail and return NULL.
3049 *
3050 * This is different than ring_buffer_record_disable() as
3051 * it works like an on/off switch, where as the disable() version
3052 * must be paired with a enable().
3053 */
3054void ring_buffer_record_off(struct ring_buffer *buffer)
3055{
3056 unsigned int rd;
3057 unsigned int new_rd;
3058
3059 do {
3060 rd = atomic_read(&buffer->record_disabled);
3061 new_rd = rd | RB_BUFFER_OFF;
3062 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3063}
3064EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3065
3066/**
3067 * ring_buffer_record_on - restart writes into the buffer
3068 * @buffer: The ring buffer to start writes to.
3069 *
3070 * This enables all writes to the buffer that was disabled by
3071 * ring_buffer_record_off().
3072 *
3073 * This is different than ring_buffer_record_enable() as
3074 * it works like an on/off switch, where as the enable() version
3075 * must be paired with a disable().
3076 */
3077void ring_buffer_record_on(struct ring_buffer *buffer)
3078{
3079 unsigned int rd;
3080 unsigned int new_rd;
3081
3082 do {
3083 rd = atomic_read(&buffer->record_disabled);
3084 new_rd = rd & ~RB_BUFFER_OFF;
3085 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3086}
3087EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3088
3089/**
3090 * ring_buffer_record_is_on - return true if the ring buffer can write
3091 * @buffer: The ring buffer to see if write is enabled
3092 *
3093 * Returns true if the ring buffer is in a state that it accepts writes.
3094 */
3095int ring_buffer_record_is_on(struct ring_buffer *buffer)
3096{
3097 return !atomic_read(&buffer->record_disabled);
3098}
3099
3100/**
3101 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3102 * @buffer: The ring buffer to stop writes to.
3103 * @cpu: The CPU buffer to stop
3104 *
3105 * This prevents all writes to the buffer. Any attempt to write
3106 * to the buffer after this will fail and return NULL.
3107 *
3108 * The caller should call synchronize_sched() after this.
3109 */
3110void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3111{
3112 struct ring_buffer_per_cpu *cpu_buffer;
3113
3114 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3115 return;
3116
3117 cpu_buffer = buffer->buffers[cpu];
3118 atomic_inc(&cpu_buffer->record_disabled);
3119}
3120EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3121
3122/**
3123 * ring_buffer_record_enable_cpu - enable writes to the buffer
3124 * @buffer: The ring buffer to enable writes
3125 * @cpu: The CPU to enable.
3126 *
3127 * Note, multiple disables will need the same number of enables
3128 * to truly enable the writing (much like preempt_disable).
3129 */
3130void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3131{
3132 struct ring_buffer_per_cpu *cpu_buffer;
3133
3134 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3135 return;
3136
3137 cpu_buffer = buffer->buffers[cpu];
3138 atomic_dec(&cpu_buffer->record_disabled);
3139}
3140EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3141
3142/*
3143 * The total entries in the ring buffer is the running counter
3144 * of entries entered into the ring buffer, minus the sum of
3145 * the entries read from the ring buffer and the number of
3146 * entries that were overwritten.
3147 */
3148static inline unsigned long
3149rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3150{
3151 return local_read(&cpu_buffer->entries) -
3152 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3153}
3154
3155/**
3156 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3157 * @buffer: The ring buffer
3158 * @cpu: The per CPU buffer to read from.
3159 */
3160u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3161{
3162 unsigned long flags;
3163 struct ring_buffer_per_cpu *cpu_buffer;
3164 struct buffer_page *bpage;
3165 u64 ret = 0;
3166
3167 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3168 return 0;
3169
3170 cpu_buffer = buffer->buffers[cpu];
3171 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3172 /*
3173 * if the tail is on reader_page, oldest time stamp is on the reader
3174 * page
3175 */
3176 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3177 bpage = cpu_buffer->reader_page;
3178 else
3179 bpage = rb_set_head_page(cpu_buffer);
3180 if (bpage)
3181 ret = bpage->page->time_stamp;
3182 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3183
3184 return ret;
3185}
3186EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3187
3188/**
3189 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3190 * @buffer: The ring buffer
3191 * @cpu: The per CPU buffer to read from.
3192 */
3193unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3194{
3195 struct ring_buffer_per_cpu *cpu_buffer;
3196 unsigned long ret;
3197
3198 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3199 return 0;
3200
3201 cpu_buffer = buffer->buffers[cpu];
3202 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3203
3204 return ret;
3205}
3206EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3207
3208/**
3209 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3210 * @buffer: The ring buffer
3211 * @cpu: The per CPU buffer to get the entries from.
3212 */
3213unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3214{
3215 struct ring_buffer_per_cpu *cpu_buffer;
3216
3217 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3218 return 0;
3219
3220 cpu_buffer = buffer->buffers[cpu];
3221
3222 return rb_num_of_entries(cpu_buffer);
3223}
3224EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3225
3226/**
3227 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3228 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3229 * @buffer: The ring buffer
3230 * @cpu: The per CPU buffer to get the number of overruns from
3231 */
3232unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3233{
3234 struct ring_buffer_per_cpu *cpu_buffer;
3235 unsigned long ret;
3236
3237 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3238 return 0;
3239
3240 cpu_buffer = buffer->buffers[cpu];
3241 ret = local_read(&cpu_buffer->overrun);
3242
3243 return ret;
3244}
3245EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3246
3247/**
3248 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3249 * commits failing due to the buffer wrapping around while there are uncommitted
3250 * events, such as during an interrupt storm.
3251 * @buffer: The ring buffer
3252 * @cpu: The per CPU buffer to get the number of overruns from
3253 */
3254unsigned long
3255ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3256{
3257 struct ring_buffer_per_cpu *cpu_buffer;
3258 unsigned long ret;
3259
3260 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3261 return 0;
3262
3263 cpu_buffer = buffer->buffers[cpu];
3264 ret = local_read(&cpu_buffer->commit_overrun);
3265
3266 return ret;
3267}
3268EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3269
3270/**
3271 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3272 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3273 * @buffer: The ring buffer
3274 * @cpu: The per CPU buffer to get the number of overruns from
3275 */
3276unsigned long
3277ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3278{
3279 struct ring_buffer_per_cpu *cpu_buffer;
3280 unsigned long ret;
3281
3282 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3283 return 0;
3284
3285 cpu_buffer = buffer->buffers[cpu];
3286 ret = local_read(&cpu_buffer->dropped_events);
3287
3288 return ret;
3289}
3290EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3291
3292/**
3293 * ring_buffer_read_events_cpu - get the number of events successfully read
3294 * @buffer: The ring buffer
3295 * @cpu: The per CPU buffer to get the number of events read
3296 */
3297unsigned long
3298ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3299{
3300 struct ring_buffer_per_cpu *cpu_buffer;
3301
3302 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3303 return 0;
3304
3305 cpu_buffer = buffer->buffers[cpu];
3306 return cpu_buffer->read;
3307}
3308EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3309
3310/**
3311 * ring_buffer_entries - get the number of entries in a buffer
3312 * @buffer: The ring buffer
3313 *
3314 * Returns the total number of entries in the ring buffer
3315 * (all CPU entries)
3316 */
3317unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3318{
3319 struct ring_buffer_per_cpu *cpu_buffer;
3320 unsigned long entries = 0;
3321 int cpu;
3322
3323 /* if you care about this being correct, lock the buffer */
3324 for_each_buffer_cpu(buffer, cpu) {
3325 cpu_buffer = buffer->buffers[cpu];
3326 entries += rb_num_of_entries(cpu_buffer);
3327 }
3328
3329 return entries;
3330}
3331EXPORT_SYMBOL_GPL(ring_buffer_entries);
3332
3333/**
3334 * ring_buffer_overruns - get the number of overruns in buffer
3335 * @buffer: The ring buffer
3336 *
3337 * Returns the total number of overruns in the ring buffer
3338 * (all CPU entries)
3339 */
3340unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3341{
3342 struct ring_buffer_per_cpu *cpu_buffer;
3343 unsigned long overruns = 0;
3344 int cpu;
3345
3346 /* if you care about this being correct, lock the buffer */
3347 for_each_buffer_cpu(buffer, cpu) {
3348 cpu_buffer = buffer->buffers[cpu];
3349 overruns += local_read(&cpu_buffer->overrun);
3350 }
3351
3352 return overruns;
3353}
3354EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3355
3356static void rb_iter_reset(struct ring_buffer_iter *iter)
3357{
3358 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3359
3360 /* Iterator usage is expected to have record disabled */
3361 if (list_empty(&cpu_buffer->reader_page->list)) {
3362 iter->head_page = rb_set_head_page(cpu_buffer);
3363 if (unlikely(!iter->head_page))
3364 return;
3365 iter->head = iter->head_page->read;
3366 } else {
3367 iter->head_page = cpu_buffer->reader_page;
3368 iter->head = cpu_buffer->reader_page->read;
3369 }
3370 if (iter->head)
3371 iter->read_stamp = cpu_buffer->read_stamp;
3372 else
3373 iter->read_stamp = iter->head_page->page->time_stamp;
3374 iter->cache_reader_page = cpu_buffer->reader_page;
3375 iter->cache_read = cpu_buffer->read;
3376}
3377
3378/**
3379 * ring_buffer_iter_reset - reset an iterator
3380 * @iter: The iterator to reset
3381 *
3382 * Resets the iterator, so that it will start from the beginning
3383 * again.
3384 */
3385void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3386{
3387 struct ring_buffer_per_cpu *cpu_buffer;
3388 unsigned long flags;
3389
3390 if (!iter)
3391 return;
3392
3393 cpu_buffer = iter->cpu_buffer;
3394
3395 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3396 rb_iter_reset(iter);
3397 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3398}
3399EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3400
3401/**
3402 * ring_buffer_iter_empty - check if an iterator has no more to read
3403 * @iter: The iterator to check
3404 */
3405int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3406{
3407 struct ring_buffer_per_cpu *cpu_buffer;
3408
3409 cpu_buffer = iter->cpu_buffer;
3410
3411 return iter->head_page == cpu_buffer->commit_page &&
3412 iter->head == rb_commit_index(cpu_buffer);
3413}
3414EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3415
3416static void
3417rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3418 struct ring_buffer_event *event)
3419{
3420 u64 delta;
3421
3422 switch (event->type_len) {
3423 case RINGBUF_TYPE_PADDING:
3424 return;
3425
3426 case RINGBUF_TYPE_TIME_EXTEND:
3427 delta = event->array[0];
3428 delta <<= TS_SHIFT;
3429 delta += event->time_delta;
3430 cpu_buffer->read_stamp += delta;
3431 return;
3432
3433 case RINGBUF_TYPE_TIME_STAMP:
3434 /* FIXME: not implemented */
3435 return;
3436
3437 case RINGBUF_TYPE_DATA:
3438 cpu_buffer->read_stamp += event->time_delta;
3439 return;
3440
3441 default:
3442 BUG();
3443 }
3444 return;
3445}
3446
3447static void
3448rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3449 struct ring_buffer_event *event)
3450{
3451 u64 delta;
3452
3453 switch (event->type_len) {
3454 case RINGBUF_TYPE_PADDING:
3455 return;
3456
3457 case RINGBUF_TYPE_TIME_EXTEND:
3458 delta = event->array[0];
3459 delta <<= TS_SHIFT;
3460 delta += event->time_delta;
3461 iter->read_stamp += delta;
3462 return;
3463
3464 case RINGBUF_TYPE_TIME_STAMP:
3465 /* FIXME: not implemented */
3466 return;
3467
3468 case RINGBUF_TYPE_DATA:
3469 iter->read_stamp += event->time_delta;
3470 return;
3471
3472 default:
3473 BUG();
3474 }
3475 return;
3476}
3477
3478static struct buffer_page *
3479rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3480{
3481 struct buffer_page *reader = NULL;
3482 unsigned long overwrite;
3483 unsigned long flags;
3484 int nr_loops = 0;
3485 int ret;
3486
3487 local_irq_save(flags);
3488 arch_spin_lock(&cpu_buffer->lock);
3489
3490 again:
3491 /*
3492 * This should normally only loop twice. But because the
3493 * start of the reader inserts an empty page, it causes
3494 * a case where we will loop three times. There should be no
3495 * reason to loop four times (that I know of).
3496 */
3497 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3498 reader = NULL;
3499 goto out;
3500 }
3501
3502 reader = cpu_buffer->reader_page;
3503
3504 /* If there's more to read, return this page */
3505 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3506 goto out;
3507
3508 /* Never should we have an index greater than the size */
3509 if (RB_WARN_ON(cpu_buffer,
3510 cpu_buffer->reader_page->read > rb_page_size(reader)))
3511 goto out;
3512
3513 /* check if we caught up to the tail */
3514 reader = NULL;
3515 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3516 goto out;
3517
3518 /* Don't bother swapping if the ring buffer is empty */
3519 if (rb_num_of_entries(cpu_buffer) == 0)
3520 goto out;
3521
3522 /*
3523 * Reset the reader page to size zero.
3524 */
3525 local_set(&cpu_buffer->reader_page->write, 0);
3526 local_set(&cpu_buffer->reader_page->entries, 0);
3527 local_set(&cpu_buffer->reader_page->page->commit, 0);
3528 cpu_buffer->reader_page->real_end = 0;
3529
3530 spin:
3531 /*
3532 * Splice the empty reader page into the list around the head.
3533 */
3534 reader = rb_set_head_page(cpu_buffer);
3535 if (!reader)
3536 goto out;
3537 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3538 cpu_buffer->reader_page->list.prev = reader->list.prev;
3539
3540 /*
3541 * cpu_buffer->pages just needs to point to the buffer, it
3542 * has no specific buffer page to point to. Lets move it out
3543 * of our way so we don't accidentally swap it.
3544 */
3545 cpu_buffer->pages = reader->list.prev;
3546
3547 /* The reader page will be pointing to the new head */
3548 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3549
3550 /*
3551 * We want to make sure we read the overruns after we set up our
3552 * pointers to the next object. The writer side does a
3553 * cmpxchg to cross pages which acts as the mb on the writer
3554 * side. Note, the reader will constantly fail the swap
3555 * while the writer is updating the pointers, so this
3556 * guarantees that the overwrite recorded here is the one we
3557 * want to compare with the last_overrun.
3558 */
3559 smp_mb();
3560 overwrite = local_read(&(cpu_buffer->overrun));
3561
3562 /*
3563 * Here's the tricky part.
3564 *
3565 * We need to move the pointer past the header page.
3566 * But we can only do that if a writer is not currently
3567 * moving it. The page before the header page has the
3568 * flag bit '1' set if it is pointing to the page we want.
3569 * but if the writer is in the process of moving it
3570 * than it will be '2' or already moved '0'.
3571 */
3572
3573 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3574
3575 /*
3576 * If we did not convert it, then we must try again.
3577 */
3578 if (!ret)
3579 goto spin;
3580
3581 /*
3582 * Yeah! We succeeded in replacing the page.
3583 *
3584 * Now make the new head point back to the reader page.
3585 */
3586 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3587 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3588
3589 /* Finally update the reader page to the new head */
3590 cpu_buffer->reader_page = reader;
3591 rb_reset_reader_page(cpu_buffer);
3592
3593 if (overwrite != cpu_buffer->last_overrun) {
3594 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3595 cpu_buffer->last_overrun = overwrite;
3596 }
3597
3598 goto again;
3599
3600 out:
3601 arch_spin_unlock(&cpu_buffer->lock);
3602 local_irq_restore(flags);
3603
3604 return reader;
3605}
3606
3607static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3608{
3609 struct ring_buffer_event *event;
3610 struct buffer_page *reader;
3611 unsigned length;
3612
3613 reader = rb_get_reader_page(cpu_buffer);
3614
3615 /* This function should not be called when buffer is empty */
3616 if (RB_WARN_ON(cpu_buffer, !reader))
3617 return;
3618
3619 event = rb_reader_event(cpu_buffer);
3620
3621 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3622 cpu_buffer->read++;
3623
3624 rb_update_read_stamp(cpu_buffer, event);
3625
3626 length = rb_event_length(event);
3627 cpu_buffer->reader_page->read += length;
3628}
3629
3630static void rb_advance_iter(struct ring_buffer_iter *iter)
3631{
3632 struct ring_buffer_per_cpu *cpu_buffer;
3633 struct ring_buffer_event *event;
3634 unsigned length;
3635
3636 cpu_buffer = iter->cpu_buffer;
3637
3638 /*
3639 * Check if we are at the end of the buffer.
3640 */
3641 if (iter->head >= rb_page_size(iter->head_page)) {
3642 /* discarded commits can make the page empty */
3643 if (iter->head_page == cpu_buffer->commit_page)
3644 return;
3645 rb_inc_iter(iter);
3646 return;
3647 }
3648
3649 event = rb_iter_head_event(iter);
3650
3651 length = rb_event_length(event);
3652
3653 /*
3654 * This should not be called to advance the header if we are
3655 * at the tail of the buffer.
3656 */
3657 if (RB_WARN_ON(cpu_buffer,
3658 (iter->head_page == cpu_buffer->commit_page) &&
3659 (iter->head + length > rb_commit_index(cpu_buffer))))
3660 return;
3661
3662 rb_update_iter_read_stamp(iter, event);
3663
3664 iter->head += length;
3665
3666 /* check for end of page padding */
3667 if ((iter->head >= rb_page_size(iter->head_page)) &&
3668 (iter->head_page != cpu_buffer->commit_page))
3669 rb_inc_iter(iter);
3670}
3671
3672static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3673{
3674 return cpu_buffer->lost_events;
3675}
3676
3677static struct ring_buffer_event *
3678rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3679 unsigned long *lost_events)
3680{
3681 struct ring_buffer_event *event;
3682 struct buffer_page *reader;
3683 int nr_loops = 0;
3684
3685 again:
3686 /*
3687 * We repeat when a time extend is encountered.
3688 * Since the time extend is always attached to a data event,
3689 * we should never loop more than once.
3690 * (We never hit the following condition more than twice).
3691 */
3692 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3693 return NULL;
3694
3695 reader = rb_get_reader_page(cpu_buffer);
3696 if (!reader)
3697 return NULL;
3698
3699 event = rb_reader_event(cpu_buffer);
3700
3701 switch (event->type_len) {
3702 case RINGBUF_TYPE_PADDING:
3703 if (rb_null_event(event))
3704 RB_WARN_ON(cpu_buffer, 1);
3705 /*
3706 * Because the writer could be discarding every
3707 * event it creates (which would probably be bad)
3708 * if we were to go back to "again" then we may never
3709 * catch up, and will trigger the warn on, or lock
3710 * the box. Return the padding, and we will release
3711 * the current locks, and try again.
3712 */
3713 return event;
3714
3715 case RINGBUF_TYPE_TIME_EXTEND:
3716 /* Internal data, OK to advance */
3717 rb_advance_reader(cpu_buffer);
3718 goto again;
3719
3720 case RINGBUF_TYPE_TIME_STAMP:
3721 /* FIXME: not implemented */
3722 rb_advance_reader(cpu_buffer);
3723 goto again;
3724
3725 case RINGBUF_TYPE_DATA:
3726 if (ts) {
3727 *ts = cpu_buffer->read_stamp + event->time_delta;
3728 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3729 cpu_buffer->cpu, ts);
3730 }
3731 if (lost_events)
3732 *lost_events = rb_lost_events(cpu_buffer);
3733 return event;
3734
3735 default:
3736 BUG();
3737 }
3738
3739 return NULL;
3740}
3741EXPORT_SYMBOL_GPL(ring_buffer_peek);
3742
3743static struct ring_buffer_event *
3744rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3745{
3746 struct ring_buffer *buffer;
3747 struct ring_buffer_per_cpu *cpu_buffer;
3748 struct ring_buffer_event *event;
3749 int nr_loops = 0;
3750
3751 cpu_buffer = iter->cpu_buffer;
3752 buffer = cpu_buffer->buffer;
3753
3754 /*
3755 * Check if someone performed a consuming read to
3756 * the buffer. A consuming read invalidates the iterator
3757 * and we need to reset the iterator in this case.
3758 */
3759 if (unlikely(iter->cache_read != cpu_buffer->read ||
3760 iter->cache_reader_page != cpu_buffer->reader_page))
3761 rb_iter_reset(iter);
3762
3763 again:
3764 if (ring_buffer_iter_empty(iter))
3765 return NULL;
3766
3767 /*
3768 * We repeat when a time extend is encountered.
3769 * Since the time extend is always attached to a data event,
3770 * we should never loop more than once.
3771 * (We never hit the following condition more than twice).
3772 */
3773 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3774 return NULL;
3775
3776 if (rb_per_cpu_empty(cpu_buffer))
3777 return NULL;
3778
3779 if (iter->head >= local_read(&iter->head_page->page->commit)) {
3780 rb_inc_iter(iter);
3781 goto again;
3782 }
3783
3784 event = rb_iter_head_event(iter);
3785
3786 switch (event->type_len) {
3787 case RINGBUF_TYPE_PADDING:
3788 if (rb_null_event(event)) {
3789 rb_inc_iter(iter);
3790 goto again;
3791 }
3792 rb_advance_iter(iter);
3793 return event;
3794
3795 case RINGBUF_TYPE_TIME_EXTEND:
3796 /* Internal data, OK to advance */
3797 rb_advance_iter(iter);
3798 goto again;
3799
3800 case RINGBUF_TYPE_TIME_STAMP:
3801 /* FIXME: not implemented */
3802 rb_advance_iter(iter);
3803 goto again;
3804
3805 case RINGBUF_TYPE_DATA:
3806 if (ts) {
3807 *ts = iter->read_stamp + event->time_delta;
3808 ring_buffer_normalize_time_stamp(buffer,
3809 cpu_buffer->cpu, ts);
3810 }
3811 return event;
3812
3813 default:
3814 BUG();
3815 }
3816
3817 return NULL;
3818}
3819EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3820
3821static inline int rb_ok_to_lock(void)
3822{
3823 /*
3824 * If an NMI die dumps out the content of the ring buffer
3825 * do not grab locks. We also permanently disable the ring
3826 * buffer too. A one time deal is all you get from reading
3827 * the ring buffer from an NMI.
3828 */
3829 if (likely(!in_nmi()))
3830 return 1;
3831
3832 tracing_off_permanent();
3833 return 0;
3834}
3835
3836/**
3837 * ring_buffer_peek - peek at the next event to be read
3838 * @buffer: The ring buffer to read
3839 * @cpu: The cpu to peak at
3840 * @ts: The timestamp counter of this event.
3841 * @lost_events: a variable to store if events were lost (may be NULL)
3842 *
3843 * This will return the event that will be read next, but does
3844 * not consume the data.
3845 */
3846struct ring_buffer_event *
3847ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
3848 unsigned long *lost_events)
3849{
3850 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3851 struct ring_buffer_event *event;
3852 unsigned long flags;
3853 int dolock;
3854
3855 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3856 return NULL;
3857
3858 dolock = rb_ok_to_lock();
3859 again:
3860 local_irq_save(flags);
3861 if (dolock)
3862 raw_spin_lock(&cpu_buffer->reader_lock);
3863 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3864 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3865 rb_advance_reader(cpu_buffer);
3866 if (dolock)
3867 raw_spin_unlock(&cpu_buffer->reader_lock);
3868 local_irq_restore(flags);
3869
3870 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3871 goto again;
3872
3873 return event;
3874}
3875
3876/**
3877 * ring_buffer_iter_peek - peek at the next event to be read
3878 * @iter: The ring buffer iterator
3879 * @ts: The timestamp counter of this event.
3880 *
3881 * This will return the event that will be read next, but does
3882 * not increment the iterator.
3883 */
3884struct ring_buffer_event *
3885ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3886{
3887 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3888 struct ring_buffer_event *event;
3889 unsigned long flags;
3890
3891 again:
3892 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3893 event = rb_iter_peek(iter, ts);
3894 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3895
3896 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3897 goto again;
3898
3899 return event;
3900}
3901
3902/**
3903 * ring_buffer_consume - return an event and consume it
3904 * @buffer: The ring buffer to get the next event from
3905 * @cpu: the cpu to read the buffer from
3906 * @ts: a variable to store the timestamp (may be NULL)
3907 * @lost_events: a variable to store if events were lost (may be NULL)
3908 *
3909 * Returns the next event in the ring buffer, and that event is consumed.
3910 * Meaning, that sequential reads will keep returning a different event,
3911 * and eventually empty the ring buffer if the producer is slower.
3912 */
3913struct ring_buffer_event *
3914ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
3915 unsigned long *lost_events)
3916{
3917 struct ring_buffer_per_cpu *cpu_buffer;
3918 struct ring_buffer_event *event = NULL;
3919 unsigned long flags;
3920 int dolock;
3921
3922 dolock = rb_ok_to_lock();
3923
3924 again:
3925 /* might be called in atomic */
3926 preempt_disable();
3927
3928 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3929 goto out;
3930
3931 cpu_buffer = buffer->buffers[cpu];
3932 local_irq_save(flags);
3933 if (dolock)
3934 raw_spin_lock(&cpu_buffer->reader_lock);
3935
3936 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3937 if (event) {
3938 cpu_buffer->lost_events = 0;
3939 rb_advance_reader(cpu_buffer);
3940 }
3941
3942 if (dolock)
3943 raw_spin_unlock(&cpu_buffer->reader_lock);
3944 local_irq_restore(flags);
3945
3946 out:
3947 preempt_enable();
3948
3949 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3950 goto again;
3951
3952 return event;
3953}
3954EXPORT_SYMBOL_GPL(ring_buffer_consume);
3955
3956/**
3957 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
3958 * @buffer: The ring buffer to read from
3959 * @cpu: The cpu buffer to iterate over
3960 *
3961 * This performs the initial preparations necessary to iterate
3962 * through the buffer. Memory is allocated, buffer recording
3963 * is disabled, and the iterator pointer is returned to the caller.
3964 *
3965 * Disabling buffer recordng prevents the reading from being
3966 * corrupted. This is not a consuming read, so a producer is not
3967 * expected.
3968 *
3969 * After a sequence of ring_buffer_read_prepare calls, the user is
3970 * expected to make at least one call to ring_buffer_read_prepare_sync.
3971 * Afterwards, ring_buffer_read_start is invoked to get things going
3972 * for real.
3973 *
3974 * This overall must be paired with ring_buffer_read_finish.
3975 */
3976struct ring_buffer_iter *
3977ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
3978{
3979 struct ring_buffer_per_cpu *cpu_buffer;
3980 struct ring_buffer_iter *iter;
3981
3982 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3983 return NULL;
3984
3985 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
3986 if (!iter)
3987 return NULL;
3988
3989 cpu_buffer = buffer->buffers[cpu];
3990
3991 iter->cpu_buffer = cpu_buffer;
3992
3993 atomic_inc(&buffer->resize_disabled);
3994 atomic_inc(&cpu_buffer->record_disabled);
3995
3996 return iter;
3997}
3998EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
3999
4000/**
4001 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4002 *
4003 * All previously invoked ring_buffer_read_prepare calls to prepare
4004 * iterators will be synchronized. Afterwards, read_buffer_read_start
4005 * calls on those iterators are allowed.
4006 */
4007void
4008ring_buffer_read_prepare_sync(void)
4009{
4010 synchronize_sched();
4011}
4012EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4013
4014/**
4015 * ring_buffer_read_start - start a non consuming read of the buffer
4016 * @iter: The iterator returned by ring_buffer_read_prepare
4017 *
4018 * This finalizes the startup of an iteration through the buffer.
4019 * The iterator comes from a call to ring_buffer_read_prepare and
4020 * an intervening ring_buffer_read_prepare_sync must have been
4021 * performed.
4022 *
4023 * Must be paired with ring_buffer_read_finish.
4024 */
4025void
4026ring_buffer_read_start(struct ring_buffer_iter *iter)
4027{
4028 struct ring_buffer_per_cpu *cpu_buffer;
4029 unsigned long flags;
4030
4031 if (!iter)
4032 return;
4033
4034 cpu_buffer = iter->cpu_buffer;
4035
4036 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4037 arch_spin_lock(&cpu_buffer->lock);
4038 rb_iter_reset(iter);
4039 arch_spin_unlock(&cpu_buffer->lock);
4040 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4041}
4042EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4043
4044/**
4045 * ring_buffer_read_finish - finish reading the iterator of the buffer
4046 * @iter: The iterator retrieved by ring_buffer_start
4047 *
4048 * This re-enables the recording to the buffer, and frees the
4049 * iterator.
4050 */
4051void
4052ring_buffer_read_finish(struct ring_buffer_iter *iter)
4053{
4054 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4055 unsigned long flags;
4056
4057 /*
4058 * Ring buffer is disabled from recording, here's a good place
4059 * to check the integrity of the ring buffer.
4060 * Must prevent readers from trying to read, as the check
4061 * clears the HEAD page and readers require it.
4062 */
4063 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4064 rb_check_pages(cpu_buffer);
4065 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4066
4067 atomic_dec(&cpu_buffer->record_disabled);
4068 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4069 kfree(iter);
4070}
4071EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4072
4073/**
4074 * ring_buffer_read - read the next item in the ring buffer by the iterator
4075 * @iter: The ring buffer iterator
4076 * @ts: The time stamp of the event read.
4077 *
4078 * This reads the next event in the ring buffer and increments the iterator.
4079 */
4080struct ring_buffer_event *
4081ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4082{
4083 struct ring_buffer_event *event;
4084 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4085 unsigned long flags;
4086
4087 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4088 again:
4089 event = rb_iter_peek(iter, ts);
4090 if (!event)
4091 goto out;
4092
4093 if (event->type_len == RINGBUF_TYPE_PADDING)
4094 goto again;
4095
4096 rb_advance_iter(iter);
4097 out:
4098 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4099
4100 return event;
4101}
4102EXPORT_SYMBOL_GPL(ring_buffer_read);
4103
4104/**
4105 * ring_buffer_size - return the size of the ring buffer (in bytes)
4106 * @buffer: The ring buffer.
4107 */
4108unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4109{
4110 /*
4111 * Earlier, this method returned
4112 * BUF_PAGE_SIZE * buffer->nr_pages
4113 * Since the nr_pages field is now removed, we have converted this to
4114 * return the per cpu buffer value.
4115 */
4116 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4117 return 0;
4118
4119 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4120}
4121EXPORT_SYMBOL_GPL(ring_buffer_size);
4122
4123static void
4124rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4125{
4126 rb_head_page_deactivate(cpu_buffer);
4127
4128 cpu_buffer->head_page
4129 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4130 local_set(&cpu_buffer->head_page->write, 0);
4131 local_set(&cpu_buffer->head_page->entries, 0);
4132 local_set(&cpu_buffer->head_page->page->commit, 0);
4133
4134 cpu_buffer->head_page->read = 0;
4135
4136 cpu_buffer->tail_page = cpu_buffer->head_page;
4137 cpu_buffer->commit_page = cpu_buffer->head_page;
4138
4139 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4140 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4141 local_set(&cpu_buffer->reader_page->write, 0);
4142 local_set(&cpu_buffer->reader_page->entries, 0);
4143 local_set(&cpu_buffer->reader_page->page->commit, 0);
4144 cpu_buffer->reader_page->read = 0;
4145
4146 local_set(&cpu_buffer->entries_bytes, 0);
4147 local_set(&cpu_buffer->overrun, 0);
4148 local_set(&cpu_buffer->commit_overrun, 0);
4149 local_set(&cpu_buffer->dropped_events, 0);
4150 local_set(&cpu_buffer->entries, 0);
4151 local_set(&cpu_buffer->committing, 0);
4152 local_set(&cpu_buffer->commits, 0);
4153 cpu_buffer->read = 0;
4154 cpu_buffer->read_bytes = 0;
4155
4156 cpu_buffer->write_stamp = 0;
4157 cpu_buffer->read_stamp = 0;
4158
4159 cpu_buffer->lost_events = 0;
4160 cpu_buffer->last_overrun = 0;
4161
4162 rb_head_page_activate(cpu_buffer);
4163}
4164
4165/**
4166 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4167 * @buffer: The ring buffer to reset a per cpu buffer of
4168 * @cpu: The CPU buffer to be reset
4169 */
4170void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4171{
4172 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4173 unsigned long flags;
4174
4175 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4176 return;
4177
4178 atomic_inc(&buffer->resize_disabled);
4179 atomic_inc(&cpu_buffer->record_disabled);
4180
4181 /* Make sure all commits have finished */
4182 synchronize_sched();
4183
4184 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4185
4186 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4187 goto out;
4188
4189 arch_spin_lock(&cpu_buffer->lock);
4190
4191 rb_reset_cpu(cpu_buffer);
4192
4193 arch_spin_unlock(&cpu_buffer->lock);
4194
4195 out:
4196 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4197
4198 atomic_dec(&cpu_buffer->record_disabled);
4199 atomic_dec(&buffer->resize_disabled);
4200}
4201EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4202
4203/**
4204 * ring_buffer_reset - reset a ring buffer
4205 * @buffer: The ring buffer to reset all cpu buffers
4206 */
4207void ring_buffer_reset(struct ring_buffer *buffer)
4208{
4209 int cpu;
4210
4211 for_each_buffer_cpu(buffer, cpu)
4212 ring_buffer_reset_cpu(buffer, cpu);
4213}
4214EXPORT_SYMBOL_GPL(ring_buffer_reset);
4215
4216/**
4217 * rind_buffer_empty - is the ring buffer empty?
4218 * @buffer: The ring buffer to test
4219 */
4220int ring_buffer_empty(struct ring_buffer *buffer)
4221{
4222 struct ring_buffer_per_cpu *cpu_buffer;
4223 unsigned long flags;
4224 int dolock;
4225 int cpu;
4226 int ret;
4227
4228 dolock = rb_ok_to_lock();
4229
4230 /* yes this is racy, but if you don't like the race, lock the buffer */
4231 for_each_buffer_cpu(buffer, cpu) {
4232 cpu_buffer = buffer->buffers[cpu];
4233 local_irq_save(flags);
4234 if (dolock)
4235 raw_spin_lock(&cpu_buffer->reader_lock);
4236 ret = rb_per_cpu_empty(cpu_buffer);
4237 if (dolock)
4238 raw_spin_unlock(&cpu_buffer->reader_lock);
4239 local_irq_restore(flags);
4240
4241 if (!ret)
4242 return 0;
4243 }
4244
4245 return 1;
4246}
4247EXPORT_SYMBOL_GPL(ring_buffer_empty);
4248
4249/**
4250 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4251 * @buffer: The ring buffer
4252 * @cpu: The CPU buffer to test
4253 */
4254int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4255{
4256 struct ring_buffer_per_cpu *cpu_buffer;
4257 unsigned long flags;
4258 int dolock;
4259 int ret;
4260
4261 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4262 return 1;
4263
4264 dolock = rb_ok_to_lock();
4265
4266 cpu_buffer = buffer->buffers[cpu];
4267 local_irq_save(flags);
4268 if (dolock)
4269 raw_spin_lock(&cpu_buffer->reader_lock);
4270 ret = rb_per_cpu_empty(cpu_buffer);
4271 if (dolock)
4272 raw_spin_unlock(&cpu_buffer->reader_lock);
4273 local_irq_restore(flags);
4274
4275 return ret;
4276}
4277EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4278
4279#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4280/**
4281 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4282 * @buffer_a: One buffer to swap with
4283 * @buffer_b: The other buffer to swap with
4284 *
4285 * This function is useful for tracers that want to take a "snapshot"
4286 * of a CPU buffer and has another back up buffer lying around.
4287 * it is expected that the tracer handles the cpu buffer not being
4288 * used at the moment.
4289 */
4290int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4291 struct ring_buffer *buffer_b, int cpu)
4292{
4293 struct ring_buffer_per_cpu *cpu_buffer_a;
4294 struct ring_buffer_per_cpu *cpu_buffer_b;
4295 int ret = -EINVAL;
4296
4297 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4298 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4299 goto out;
4300
4301 cpu_buffer_a = buffer_a->buffers[cpu];
4302 cpu_buffer_b = buffer_b->buffers[cpu];
4303
4304 /* At least make sure the two buffers are somewhat the same */
4305 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4306 goto out;
4307
4308 ret = -EAGAIN;
4309
4310 if (ring_buffer_flags != RB_BUFFERS_ON)
4311 goto out;
4312
4313 if (atomic_read(&buffer_a->record_disabled))
4314 goto out;
4315
4316 if (atomic_read(&buffer_b->record_disabled))
4317 goto out;
4318
4319 if (atomic_read(&cpu_buffer_a->record_disabled))
4320 goto out;
4321
4322 if (atomic_read(&cpu_buffer_b->record_disabled))
4323 goto out;
4324
4325 /*
4326 * We can't do a synchronize_sched here because this
4327 * function can be called in atomic context.
4328 * Normally this will be called from the same CPU as cpu.
4329 * If not it's up to the caller to protect this.
4330 */
4331 atomic_inc(&cpu_buffer_a->record_disabled);
4332 atomic_inc(&cpu_buffer_b->record_disabled);
4333
4334 ret = -EBUSY;
4335 if (local_read(&cpu_buffer_a->committing))
4336 goto out_dec;
4337 if (local_read(&cpu_buffer_b->committing))
4338 goto out_dec;
4339
4340 buffer_a->buffers[cpu] = cpu_buffer_b;
4341 buffer_b->buffers[cpu] = cpu_buffer_a;
4342
4343 cpu_buffer_b->buffer = buffer_a;
4344 cpu_buffer_a->buffer = buffer_b;
4345
4346 ret = 0;
4347
4348out_dec:
4349 atomic_dec(&cpu_buffer_a->record_disabled);
4350 atomic_dec(&cpu_buffer_b->record_disabled);
4351out:
4352 return ret;
4353}
4354EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4355#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4356
4357/**
4358 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4359 * @buffer: the buffer to allocate for.
4360 * @cpu: the cpu buffer to allocate.
4361 *
4362 * This function is used in conjunction with ring_buffer_read_page.
4363 * When reading a full page from the ring buffer, these functions
4364 * can be used to speed up the process. The calling function should
4365 * allocate a few pages first with this function. Then when it
4366 * needs to get pages from the ring buffer, it passes the result
4367 * of this function into ring_buffer_read_page, which will swap
4368 * the page that was allocated, with the read page of the buffer.
4369 *
4370 * Returns:
4371 * The page allocated, or NULL on error.
4372 */
4373void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4374{
4375 struct buffer_data_page *bpage;
4376 struct page *page;
4377
4378 page = alloc_pages_node(cpu_to_node(cpu),
4379 GFP_KERNEL | __GFP_NORETRY, 0);
4380 if (!page)
4381 return NULL;
4382
4383 bpage = page_address(page);
4384
4385 rb_init_page(bpage);
4386
4387 return bpage;
4388}
4389EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4390
4391/**
4392 * ring_buffer_free_read_page - free an allocated read page
4393 * @buffer: the buffer the page was allocate for
4394 * @data: the page to free
4395 *
4396 * Free a page allocated from ring_buffer_alloc_read_page.
4397 */
4398void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
4399{
4400 free_page((unsigned long)data);
4401}
4402EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4403
4404/**
4405 * ring_buffer_read_page - extract a page from the ring buffer
4406 * @buffer: buffer to extract from
4407 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4408 * @len: amount to extract
4409 * @cpu: the cpu of the buffer to extract
4410 * @full: should the extraction only happen when the page is full.
4411 *
4412 * This function will pull out a page from the ring buffer and consume it.
4413 * @data_page must be the address of the variable that was returned
4414 * from ring_buffer_alloc_read_page. This is because the page might be used
4415 * to swap with a page in the ring buffer.
4416 *
4417 * for example:
4418 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4419 * if (!rpage)
4420 * return error;
4421 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4422 * if (ret >= 0)
4423 * process_page(rpage, ret);
4424 *
4425 * When @full is set, the function will not return true unless
4426 * the writer is off the reader page.
4427 *
4428 * Note: it is up to the calling functions to handle sleeps and wakeups.
4429 * The ring buffer can be used anywhere in the kernel and can not
4430 * blindly call wake_up. The layer that uses the ring buffer must be
4431 * responsible for that.
4432 *
4433 * Returns:
4434 * >=0 if data has been transferred, returns the offset of consumed data.
4435 * <0 if no data has been transferred.
4436 */
4437int ring_buffer_read_page(struct ring_buffer *buffer,
4438 void **data_page, size_t len, int cpu, int full)
4439{
4440 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4441 struct ring_buffer_event *event;
4442 struct buffer_data_page *bpage;
4443 struct buffer_page *reader;
4444 unsigned long missed_events;
4445 unsigned long flags;
4446 unsigned int commit;
4447 unsigned int read;
4448 u64 save_timestamp;
4449 int ret = -1;
4450
4451 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4452 goto out;
4453
4454 /*
4455 * If len is not big enough to hold the page header, then
4456 * we can not copy anything.
4457 */
4458 if (len <= BUF_PAGE_HDR_SIZE)
4459 goto out;
4460
4461 len -= BUF_PAGE_HDR_SIZE;
4462
4463 if (!data_page)
4464 goto out;
4465
4466 bpage = *data_page;
4467 if (!bpage)
4468 goto out;
4469
4470 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4471
4472 reader = rb_get_reader_page(cpu_buffer);
4473 if (!reader)
4474 goto out_unlock;
4475
4476 event = rb_reader_event(cpu_buffer);
4477
4478 read = reader->read;
4479 commit = rb_page_commit(reader);
4480
4481 /* Check if any events were dropped */
4482 missed_events = cpu_buffer->lost_events;
4483
4484 /*
4485 * If this page has been partially read or
4486 * if len is not big enough to read the rest of the page or
4487 * a writer is still on the page, then
4488 * we must copy the data from the page to the buffer.
4489 * Otherwise, we can simply swap the page with the one passed in.
4490 */
4491 if (read || (len < (commit - read)) ||
4492 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4493 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4494 unsigned int rpos = read;
4495 unsigned int pos = 0;
4496 unsigned int size;
4497
4498 if (full)
4499 goto out_unlock;
4500
4501 if (len > (commit - read))
4502 len = (commit - read);
4503
4504 /* Always keep the time extend and data together */
4505 size = rb_event_ts_length(event);
4506
4507 if (len < size)
4508 goto out_unlock;
4509
4510 /* save the current timestamp, since the user will need it */
4511 save_timestamp = cpu_buffer->read_stamp;
4512
4513 /* Need to copy one event at a time */
4514 do {
4515 /* We need the size of one event, because
4516 * rb_advance_reader only advances by one event,
4517 * whereas rb_event_ts_length may include the size of
4518 * one or two events.
4519 * We have already ensured there's enough space if this
4520 * is a time extend. */
4521 size = rb_event_length(event);
4522 memcpy(bpage->data + pos, rpage->data + rpos, size);
4523
4524 len -= size;
4525
4526 rb_advance_reader(cpu_buffer);
4527 rpos = reader->read;
4528 pos += size;
4529
4530 if (rpos >= commit)
4531 break;
4532
4533 event = rb_reader_event(cpu_buffer);
4534 /* Always keep the time extend and data together */
4535 size = rb_event_ts_length(event);
4536 } while (len >= size);
4537
4538 /* update bpage */
4539 local_set(&bpage->commit, pos);
4540 bpage->time_stamp = save_timestamp;
4541
4542 /* we copied everything to the beginning */
4543 read = 0;
4544 } else {
4545 /* update the entry counter */
4546 cpu_buffer->read += rb_page_entries(reader);
4547 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4548
4549 /* swap the pages */
4550 rb_init_page(bpage);
4551 bpage = reader->page;
4552 reader->page = *data_page;
4553 local_set(&reader->write, 0);
4554 local_set(&reader->entries, 0);
4555 reader->read = 0;
4556 *data_page = bpage;
4557
4558 /*
4559 * Use the real_end for the data size,
4560 * This gives us a chance to store the lost events
4561 * on the page.
4562 */
4563 if (reader->real_end)
4564 local_set(&bpage->commit, reader->real_end);
4565 }
4566 ret = read;
4567
4568 cpu_buffer->lost_events = 0;
4569
4570 commit = local_read(&bpage->commit);
4571 /*
4572 * Set a flag in the commit field if we lost events
4573 */
4574 if (missed_events) {
4575 /* If there is room at the end of the page to save the
4576 * missed events, then record it there.
4577 */
4578 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4579 memcpy(&bpage->data[commit], &missed_events,
4580 sizeof(missed_events));
4581 local_add(RB_MISSED_STORED, &bpage->commit);
4582 commit += sizeof(missed_events);
4583 }
4584 local_add(RB_MISSED_EVENTS, &bpage->commit);
4585 }
4586
4587 /*
4588 * This page may be off to user land. Zero it out here.
4589 */
4590 if (commit < BUF_PAGE_SIZE)
4591 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4592
4593 out_unlock:
4594 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4595
4596 out:
4597 return ret;
4598}
4599EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4600
4601#ifdef CONFIG_HOTPLUG_CPU
4602static int rb_cpu_notify(struct notifier_block *self,
4603 unsigned long action, void *hcpu)
4604{
4605 struct ring_buffer *buffer =
4606 container_of(self, struct ring_buffer, cpu_notify);
4607 long cpu = (long)hcpu;
4608 int cpu_i, nr_pages_same;
4609 unsigned int nr_pages;
4610
4611 switch (action) {
4612 case CPU_UP_PREPARE:
4613 case CPU_UP_PREPARE_FROZEN:
4614 if (cpumask_test_cpu(cpu, buffer->cpumask))
4615 return NOTIFY_OK;
4616
4617 nr_pages = 0;
4618 nr_pages_same = 1;
4619 /* check if all cpu sizes are same */
4620 for_each_buffer_cpu(buffer, cpu_i) {
4621 /* fill in the size from first enabled cpu */
4622 if (nr_pages == 0)
4623 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4624 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4625 nr_pages_same = 0;
4626 break;
4627 }
4628 }
4629 /* allocate minimum pages, user can later expand it */
4630 if (!nr_pages_same)
4631 nr_pages = 2;
4632 buffer->buffers[cpu] =
4633 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4634 if (!buffer->buffers[cpu]) {
4635 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4636 cpu);
4637 return NOTIFY_OK;
4638 }
4639 smp_wmb();
4640 cpumask_set_cpu(cpu, buffer->cpumask);
4641 break;
4642 case CPU_DOWN_PREPARE:
4643 case CPU_DOWN_PREPARE_FROZEN:
4644 /*
4645 * Do nothing.
4646 * If we were to free the buffer, then the user would
4647 * lose any trace that was in the buffer.
4648 */
4649 break;
4650 default:
4651 break;
4652 }
4653 return NOTIFY_OK;
4654}
4655#endif
4656
4657#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4658/*
4659 * This is a basic integrity check of the ring buffer.
4660 * Late in the boot cycle this test will run when configured in.
4661 * It will kick off a thread per CPU that will go into a loop
4662 * writing to the per cpu ring buffer various sizes of data.
4663 * Some of the data will be large items, some small.
4664 *
4665 * Another thread is created that goes into a spin, sending out
4666 * IPIs to the other CPUs to also write into the ring buffer.
4667 * this is to test the nesting ability of the buffer.
4668 *
4669 * Basic stats are recorded and reported. If something in the
4670 * ring buffer should happen that's not expected, a big warning
4671 * is displayed and all ring buffers are disabled.
4672 */
4673static struct task_struct *rb_threads[NR_CPUS] __initdata;
4674
4675struct rb_test_data {
4676 struct ring_buffer *buffer;
4677 unsigned long events;
4678 unsigned long bytes_written;
4679 unsigned long bytes_alloc;
4680 unsigned long bytes_dropped;
4681 unsigned long events_nested;
4682 unsigned long bytes_written_nested;
4683 unsigned long bytes_alloc_nested;
4684 unsigned long bytes_dropped_nested;
4685 int min_size_nested;
4686 int max_size_nested;
4687 int max_size;
4688 int min_size;
4689 int cpu;
4690 int cnt;
4691};
4692
4693static struct rb_test_data rb_data[NR_CPUS] __initdata;
4694
4695/* 1 meg per cpu */
4696#define RB_TEST_BUFFER_SIZE 1048576
4697
4698static char rb_string[] __initdata =
4699 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4700 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4701 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4702
4703static bool rb_test_started __initdata;
4704
4705struct rb_item {
4706 int size;
4707 char str[];
4708};
4709
4710static __init int rb_write_something(struct rb_test_data *data, bool nested)
4711{
4712 struct ring_buffer_event *event;
4713 struct rb_item *item;
4714 bool started;
4715 int event_len;
4716 int size;
4717 int len;
4718 int cnt;
4719
4720 /* Have nested writes different that what is written */
4721 cnt = data->cnt + (nested ? 27 : 0);
4722
4723 /* Multiply cnt by ~e, to make some unique increment */
4724 size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
4725
4726 len = size + sizeof(struct rb_item);
4727
4728 started = rb_test_started;
4729 /* read rb_test_started before checking buffer enabled */
4730 smp_rmb();
4731
4732 event = ring_buffer_lock_reserve(data->buffer, len);
4733 if (!event) {
4734 /* Ignore dropped events before test starts. */
4735 if (started) {
4736 if (nested)
4737 data->bytes_dropped += len;
4738 else
4739 data->bytes_dropped_nested += len;
4740 }
4741 return len;
4742 }
4743
4744 event_len = ring_buffer_event_length(event);
4745
4746 if (RB_WARN_ON(data->buffer, event_len < len))
4747 goto out;
4748
4749 item = ring_buffer_event_data(event);
4750 item->size = size;
4751 memcpy(item->str, rb_string, size);
4752
4753 if (nested) {
4754 data->bytes_alloc_nested += event_len;
4755 data->bytes_written_nested += len;
4756 data->events_nested++;
4757 if (!data->min_size_nested || len < data->min_size_nested)
4758 data->min_size_nested = len;
4759 if (len > data->max_size_nested)
4760 data->max_size_nested = len;
4761 } else {
4762 data->bytes_alloc += event_len;
4763 data->bytes_written += len;
4764 data->events++;
4765 if (!data->min_size || len < data->min_size)
4766 data->max_size = len;
4767 if (len > data->max_size)
4768 data->max_size = len;
4769 }
4770
4771 out:
4772 ring_buffer_unlock_commit(data->buffer, event);
4773
4774 return 0;
4775}
4776
4777static __init int rb_test(void *arg)
4778{
4779 struct rb_test_data *data = arg;
4780
4781 while (!kthread_should_stop()) {
4782 rb_write_something(data, false);
4783 data->cnt++;
4784
4785 set_current_state(TASK_INTERRUPTIBLE);
4786 /* Now sleep between a min of 100-300us and a max of 1ms */
4787 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
4788 }
4789
4790 return 0;
4791}
4792
4793static __init void rb_ipi(void *ignore)
4794{
4795 struct rb_test_data *data;
4796 int cpu = smp_processor_id();
4797
4798 data = &rb_data[cpu];
4799 rb_write_something(data, true);
4800}
4801
4802static __init int rb_hammer_test(void *arg)
4803{
4804 while (!kthread_should_stop()) {
4805
4806 /* Send an IPI to all cpus to write data! */
4807 smp_call_function(rb_ipi, NULL, 1);
4808 /* No sleep, but for non preempt, let others run */
4809 schedule();
4810 }
4811
4812 return 0;
4813}
4814
4815static __init int test_ringbuffer(void)
4816{
4817 struct task_struct *rb_hammer;
4818 struct ring_buffer *buffer;
4819 int cpu;
4820 int ret = 0;
4821
4822 pr_info("Running ring buffer tests...\n");
4823
4824 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
4825 if (WARN_ON(!buffer))
4826 return 0;
4827
4828 /* Disable buffer so that threads can't write to it yet */
4829 ring_buffer_record_off(buffer);
4830
4831 for_each_online_cpu(cpu) {
4832 rb_data[cpu].buffer = buffer;
4833 rb_data[cpu].cpu = cpu;
4834 rb_data[cpu].cnt = cpu;
4835 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
4836 "rbtester/%d", cpu);
4837 if (WARN_ON(!rb_threads[cpu])) {
4838 pr_cont("FAILED\n");
4839 ret = -1;
4840 goto out_free;
4841 }
4842
4843 kthread_bind(rb_threads[cpu], cpu);
4844 wake_up_process(rb_threads[cpu]);
4845 }
4846
4847 /* Now create the rb hammer! */
4848 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
4849 if (WARN_ON(!rb_hammer)) {
4850 pr_cont("FAILED\n");
4851 ret = -1;
4852 goto out_free;
4853 }
4854
4855 ring_buffer_record_on(buffer);
4856 /*
4857 * Show buffer is enabled before setting rb_test_started.
4858 * Yes there's a small race window where events could be
4859 * dropped and the thread wont catch it. But when a ring
4860 * buffer gets enabled, there will always be some kind of
4861 * delay before other CPUs see it. Thus, we don't care about
4862 * those dropped events. We care about events dropped after
4863 * the threads see that the buffer is active.
4864 */
4865 smp_wmb();
4866 rb_test_started = true;
4867
4868 set_current_state(TASK_INTERRUPTIBLE);
4869 /* Just run for 10 seconds */;
4870 schedule_timeout(10 * HZ);
4871
4872 kthread_stop(rb_hammer);
4873
4874 out_free:
4875 for_each_online_cpu(cpu) {
4876 if (!rb_threads[cpu])
4877 break;
4878 kthread_stop(rb_threads[cpu]);
4879 }
4880 if (ret) {
4881 ring_buffer_free(buffer);
4882 return ret;
4883 }
4884
4885 /* Report! */
4886 pr_info("finished\n");
4887 for_each_online_cpu(cpu) {
4888 struct ring_buffer_event *event;
4889 struct rb_test_data *data = &rb_data[cpu];
4890 struct rb_item *item;
4891 unsigned long total_events;
4892 unsigned long total_dropped;
4893 unsigned long total_written;
4894 unsigned long total_alloc;
4895 unsigned long total_read = 0;
4896 unsigned long total_size = 0;
4897 unsigned long total_len = 0;
4898 unsigned long total_lost = 0;
4899 unsigned long lost;
4900 int big_event_size;
4901 int small_event_size;
4902
4903 ret = -1;
4904
4905 total_events = data->events + data->events_nested;
4906 total_written = data->bytes_written + data->bytes_written_nested;
4907 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
4908 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
4909
4910 big_event_size = data->max_size + data->max_size_nested;
4911 small_event_size = data->min_size + data->min_size_nested;
4912
4913 pr_info("CPU %d:\n", cpu);
4914 pr_info(" events: %ld\n", total_events);
4915 pr_info(" dropped bytes: %ld\n", total_dropped);
4916 pr_info(" alloced bytes: %ld\n", total_alloc);
4917 pr_info(" written bytes: %ld\n", total_written);
4918 pr_info(" biggest event: %d\n", big_event_size);
4919 pr_info(" smallest event: %d\n", small_event_size);
4920
4921 if (RB_WARN_ON(buffer, total_dropped))
4922 break;
4923
4924 ret = 0;
4925
4926 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
4927 total_lost += lost;
4928 item = ring_buffer_event_data(event);
4929 total_len += ring_buffer_event_length(event);
4930 total_size += item->size + sizeof(struct rb_item);
4931 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
4932 pr_info("FAILED!\n");
4933 pr_info("buffer had: %.*s\n", item->size, item->str);
4934 pr_info("expected: %.*s\n", item->size, rb_string);
4935 RB_WARN_ON(buffer, 1);
4936 ret = -1;
4937 break;
4938 }
4939 total_read++;
4940 }
4941 if (ret)
4942 break;
4943
4944 ret = -1;
4945
4946 pr_info(" read events: %ld\n", total_read);
4947 pr_info(" lost events: %ld\n", total_lost);
4948 pr_info(" total events: %ld\n", total_lost + total_read);
4949 pr_info(" recorded len bytes: %ld\n", total_len);
4950 pr_info(" recorded size bytes: %ld\n", total_size);
4951 if (total_lost)
4952 pr_info(" With dropped events, record len and size may not match\n"
4953 " alloced and written from above\n");
4954 if (!total_lost) {
4955 if (RB_WARN_ON(buffer, total_len != total_alloc ||
4956 total_size != total_written))
4957 break;
4958 }
4959 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
4960 break;
4961
4962 ret = 0;
4963 }
4964 if (!ret)
4965 pr_info("Ring buffer PASSED!\n");
4966
4967 ring_buffer_free(buffer);
4968 return 0;
4969}
4970
4971late_initcall(test_ringbuffer);
4972#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */