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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/sched/clock.h>
10#include <linux/trace_seq.h>
11#include <linux/spinlock.h>
12#include <linux/irq_work.h>
13#include <linux/uaccess.h>
14#include <linux/hardirq.h>
15#include <linux/kthread.h> /* for self test */
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#include <linux/oom.h>
26
27#include <asm/local.h>
28
29static void update_pages_handler(struct work_struct *work);
30
31/*
32 * The ring buffer header is special. We must manually up keep it.
33 */
34int ring_buffer_print_entry_header(struct trace_seq *s)
35{
36 trace_seq_puts(s, "# compressed entry header\n");
37 trace_seq_puts(s, "\ttype_len : 5 bits\n");
38 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
39 trace_seq_puts(s, "\tarray : 32 bits\n");
40 trace_seq_putc(s, '\n');
41 trace_seq_printf(s, "\tpadding : type == %d\n",
42 RINGBUF_TYPE_PADDING);
43 trace_seq_printf(s, "\ttime_extend : type == %d\n",
44 RINGBUF_TYPE_TIME_EXTEND);
45 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
46 RINGBUF_TYPE_TIME_STAMP);
47 trace_seq_printf(s, "\tdata max type_len == %d\n",
48 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
49
50 return !trace_seq_has_overflowed(s);
51}
52
53/*
54 * The ring buffer is made up of a list of pages. A separate list of pages is
55 * allocated for each CPU. A writer may only write to a buffer that is
56 * associated with the CPU it is currently executing on. A reader may read
57 * from any per cpu buffer.
58 *
59 * The reader is special. For each per cpu buffer, the reader has its own
60 * reader page. When a reader has read the entire reader page, this reader
61 * page is swapped with another page in the ring buffer.
62 *
63 * Now, as long as the writer is off the reader page, the reader can do what
64 * ever it wants with that page. The writer will never write to that page
65 * again (as long as it is out of the ring buffer).
66 *
67 * Here's some silly ASCII art.
68 *
69 * +------+
70 * |reader| RING BUFFER
71 * |page |
72 * +------+ +---+ +---+ +---+
73 * | |-->| |-->| |
74 * +---+ +---+ +---+
75 * ^ |
76 * | |
77 * +---------------+
78 *
79 *
80 * +------+
81 * |reader| RING BUFFER
82 * |page |------------------v
83 * +------+ +---+ +---+ +---+
84 * | |-->| |-->| |
85 * +---+ +---+ +---+
86 * ^ |
87 * | |
88 * +---------------+
89 *
90 *
91 * +------+
92 * |reader| RING BUFFER
93 * |page |------------------v
94 * +------+ +---+ +---+ +---+
95 * ^ | |-->| |-->| |
96 * | +---+ +---+ +---+
97 * | |
98 * | |
99 * +------------------------------+
100 *
101 *
102 * +------+
103 * |buffer| RING BUFFER
104 * |page |------------------v
105 * +------+ +---+ +---+ +---+
106 * ^ | | | |-->| |
107 * | New +---+ +---+ +---+
108 * | Reader------^ |
109 * | page |
110 * +------------------------------+
111 *
112 *
113 * After we make this swap, the reader can hand this page off to the splice
114 * code and be done with it. It can even allocate a new page if it needs to
115 * and swap that into the ring buffer.
116 *
117 * We will be using cmpxchg soon to make all this lockless.
118 *
119 */
120
121/* Used for individual buffers (after the counter) */
122#define RB_BUFFER_OFF (1 << 20)
123
124#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
125
126#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
127#define RB_ALIGNMENT 4U
128#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
129#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
130
131#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
132# define RB_FORCE_8BYTE_ALIGNMENT 0
133# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
134#else
135# define RB_FORCE_8BYTE_ALIGNMENT 1
136# define RB_ARCH_ALIGNMENT 8U
137#endif
138
139#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
140
141/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
142#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
143
144enum {
145 RB_LEN_TIME_EXTEND = 8,
146 RB_LEN_TIME_STAMP = 8,
147};
148
149#define skip_time_extend(event) \
150 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
151
152#define extended_time(event) \
153 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
154
155static inline int rb_null_event(struct ring_buffer_event *event)
156{
157 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
158}
159
160static void rb_event_set_padding(struct ring_buffer_event *event)
161{
162 /* padding has a NULL time_delta */
163 event->type_len = RINGBUF_TYPE_PADDING;
164 event->time_delta = 0;
165}
166
167static unsigned
168rb_event_data_length(struct ring_buffer_event *event)
169{
170 unsigned length;
171
172 if (event->type_len)
173 length = event->type_len * RB_ALIGNMENT;
174 else
175 length = event->array[0];
176 return length + RB_EVNT_HDR_SIZE;
177}
178
179/*
180 * Return the length of the given event. Will return
181 * the length of the time extend if the event is a
182 * time extend.
183 */
184static inline unsigned
185rb_event_length(struct ring_buffer_event *event)
186{
187 switch (event->type_len) {
188 case RINGBUF_TYPE_PADDING:
189 if (rb_null_event(event))
190 /* undefined */
191 return -1;
192 return event->array[0] + RB_EVNT_HDR_SIZE;
193
194 case RINGBUF_TYPE_TIME_EXTEND:
195 return RB_LEN_TIME_EXTEND;
196
197 case RINGBUF_TYPE_TIME_STAMP:
198 return RB_LEN_TIME_STAMP;
199
200 case RINGBUF_TYPE_DATA:
201 return rb_event_data_length(event);
202 default:
203 BUG();
204 }
205 /* not hit */
206 return 0;
207}
208
209/*
210 * Return total length of time extend and data,
211 * or just the event length for all other events.
212 */
213static inline unsigned
214rb_event_ts_length(struct ring_buffer_event *event)
215{
216 unsigned len = 0;
217
218 if (extended_time(event)) {
219 /* time extends include the data event after it */
220 len = RB_LEN_TIME_EXTEND;
221 event = skip_time_extend(event);
222 }
223 return len + rb_event_length(event);
224}
225
226/**
227 * ring_buffer_event_length - return the length of the event
228 * @event: the event to get the length of
229 *
230 * Returns the size of the data load of a data event.
231 * If the event is something other than a data event, it
232 * returns the size of the event itself. With the exception
233 * of a TIME EXTEND, where it still returns the size of the
234 * data load of the data event after it.
235 */
236unsigned ring_buffer_event_length(struct ring_buffer_event *event)
237{
238 unsigned length;
239
240 if (extended_time(event))
241 event = skip_time_extend(event);
242
243 length = rb_event_length(event);
244 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
245 return length;
246 length -= RB_EVNT_HDR_SIZE;
247 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
248 length -= sizeof(event->array[0]);
249 return length;
250}
251EXPORT_SYMBOL_GPL(ring_buffer_event_length);
252
253/* inline for ring buffer fast paths */
254static __always_inline void *
255rb_event_data(struct ring_buffer_event *event)
256{
257 if (extended_time(event))
258 event = skip_time_extend(event);
259 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
260 /* If length is in len field, then array[0] has the data */
261 if (event->type_len)
262 return (void *)&event->array[0];
263 /* Otherwise length is in array[0] and array[1] has the data */
264 return (void *)&event->array[1];
265}
266
267/**
268 * ring_buffer_event_data - return the data of the event
269 * @event: the event to get the data from
270 */
271void *ring_buffer_event_data(struct ring_buffer_event *event)
272{
273 return rb_event_data(event);
274}
275EXPORT_SYMBOL_GPL(ring_buffer_event_data);
276
277#define for_each_buffer_cpu(buffer, cpu) \
278 for_each_cpu(cpu, buffer->cpumask)
279
280#define TS_SHIFT 27
281#define TS_MASK ((1ULL << TS_SHIFT) - 1)
282#define TS_DELTA_TEST (~TS_MASK)
283
284/**
285 * ring_buffer_event_time_stamp - return the event's extended timestamp
286 * @event: the event to get the timestamp of
287 *
288 * Returns the extended timestamp associated with a data event.
289 * An extended time_stamp is a 64-bit timestamp represented
290 * internally in a special way that makes the best use of space
291 * contained within a ring buffer event. This function decodes
292 * it and maps it to a straight u64 value.
293 */
294u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
295{
296 u64 ts;
297
298 ts = event->array[0];
299 ts <<= TS_SHIFT;
300 ts += event->time_delta;
301
302 return ts;
303}
304
305/* Flag when events were overwritten */
306#define RB_MISSED_EVENTS (1 << 31)
307/* Missed count stored at end */
308#define RB_MISSED_STORED (1 << 30)
309
310#define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED)
311
312struct buffer_data_page {
313 u64 time_stamp; /* page time stamp */
314 local_t commit; /* write committed index */
315 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
316};
317
318/*
319 * Note, the buffer_page list must be first. The buffer pages
320 * are allocated in cache lines, which means that each buffer
321 * page will be at the beginning of a cache line, and thus
322 * the least significant bits will be zero. We use this to
323 * add flags in the list struct pointers, to make the ring buffer
324 * lockless.
325 */
326struct buffer_page {
327 struct list_head list; /* list of buffer pages */
328 local_t write; /* index for next write */
329 unsigned read; /* index for next read */
330 local_t entries; /* entries on this page */
331 unsigned long real_end; /* real end of data */
332 struct buffer_data_page *page; /* Actual data page */
333};
334
335/*
336 * The buffer page counters, write and entries, must be reset
337 * atomically when crossing page boundaries. To synchronize this
338 * update, two counters are inserted into the number. One is
339 * the actual counter for the write position or count on the page.
340 *
341 * The other is a counter of updaters. Before an update happens
342 * the update partition of the counter is incremented. This will
343 * allow the updater to update the counter atomically.
344 *
345 * The counter is 20 bits, and the state data is 12.
346 */
347#define RB_WRITE_MASK 0xfffff
348#define RB_WRITE_INTCNT (1 << 20)
349
350static void rb_init_page(struct buffer_data_page *bpage)
351{
352 local_set(&bpage->commit, 0);
353}
354
355/**
356 * ring_buffer_page_len - the size of data on the page.
357 * @page: The page to read
358 *
359 * Returns the amount of data on the page, including buffer page header.
360 */
361size_t ring_buffer_page_len(void *page)
362{
363 struct buffer_data_page *bpage = page;
364
365 return (local_read(&bpage->commit) & ~RB_MISSED_FLAGS)
366 + BUF_PAGE_HDR_SIZE;
367}
368
369/*
370 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
371 * this issue out.
372 */
373static void free_buffer_page(struct buffer_page *bpage)
374{
375 free_page((unsigned long)bpage->page);
376 kfree(bpage);
377}
378
379/*
380 * We need to fit the time_stamp delta into 27 bits.
381 */
382static inline int test_time_stamp(u64 delta)
383{
384 if (delta & TS_DELTA_TEST)
385 return 1;
386 return 0;
387}
388
389#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
390
391/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
392#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
393
394int ring_buffer_print_page_header(struct trace_seq *s)
395{
396 struct buffer_data_page field;
397
398 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
399 "offset:0;\tsize:%u;\tsigned:%u;\n",
400 (unsigned int)sizeof(field.time_stamp),
401 (unsigned int)is_signed_type(u64));
402
403 trace_seq_printf(s, "\tfield: local_t commit;\t"
404 "offset:%u;\tsize:%u;\tsigned:%u;\n",
405 (unsigned int)offsetof(typeof(field), commit),
406 (unsigned int)sizeof(field.commit),
407 (unsigned int)is_signed_type(long));
408
409 trace_seq_printf(s, "\tfield: int overwrite;\t"
410 "offset:%u;\tsize:%u;\tsigned:%u;\n",
411 (unsigned int)offsetof(typeof(field), commit),
412 1,
413 (unsigned int)is_signed_type(long));
414
415 trace_seq_printf(s, "\tfield: char data;\t"
416 "offset:%u;\tsize:%u;\tsigned:%u;\n",
417 (unsigned int)offsetof(typeof(field), data),
418 (unsigned int)BUF_PAGE_SIZE,
419 (unsigned int)is_signed_type(char));
420
421 return !trace_seq_has_overflowed(s);
422}
423
424struct rb_irq_work {
425 struct irq_work work;
426 wait_queue_head_t waiters;
427 wait_queue_head_t full_waiters;
428 bool waiters_pending;
429 bool full_waiters_pending;
430 bool wakeup_full;
431};
432
433/*
434 * Structure to hold event state and handle nested events.
435 */
436struct rb_event_info {
437 u64 ts;
438 u64 delta;
439 unsigned long length;
440 struct buffer_page *tail_page;
441 int add_timestamp;
442};
443
444/*
445 * Used for which event context the event is in.
446 * NMI = 0
447 * IRQ = 1
448 * SOFTIRQ = 2
449 * NORMAL = 3
450 *
451 * See trace_recursive_lock() comment below for more details.
452 */
453enum {
454 RB_CTX_NMI,
455 RB_CTX_IRQ,
456 RB_CTX_SOFTIRQ,
457 RB_CTX_NORMAL,
458 RB_CTX_MAX
459};
460
461/*
462 * head_page == tail_page && head == tail then buffer is empty.
463 */
464struct ring_buffer_per_cpu {
465 int cpu;
466 atomic_t record_disabled;
467 struct ring_buffer *buffer;
468 raw_spinlock_t reader_lock; /* serialize readers */
469 arch_spinlock_t lock;
470 struct lock_class_key lock_key;
471 struct buffer_data_page *free_page;
472 unsigned long nr_pages;
473 unsigned int current_context;
474 struct list_head *pages;
475 struct buffer_page *head_page; /* read from head */
476 struct buffer_page *tail_page; /* write to tail */
477 struct buffer_page *commit_page; /* committed pages */
478 struct buffer_page *reader_page;
479 unsigned long lost_events;
480 unsigned long last_overrun;
481 unsigned long nest;
482 local_t entries_bytes;
483 local_t entries;
484 local_t overrun;
485 local_t commit_overrun;
486 local_t dropped_events;
487 local_t committing;
488 local_t commits;
489 unsigned long read;
490 unsigned long read_bytes;
491 u64 write_stamp;
492 u64 read_stamp;
493 /* ring buffer pages to update, > 0 to add, < 0 to remove */
494 long nr_pages_to_update;
495 struct list_head new_pages; /* new pages to add */
496 struct work_struct update_pages_work;
497 struct completion update_done;
498
499 struct rb_irq_work irq_work;
500};
501
502struct ring_buffer {
503 unsigned flags;
504 int cpus;
505 atomic_t record_disabled;
506 atomic_t resize_disabled;
507 cpumask_var_t cpumask;
508
509 struct lock_class_key *reader_lock_key;
510
511 struct mutex mutex;
512
513 struct ring_buffer_per_cpu **buffers;
514
515 struct hlist_node node;
516 u64 (*clock)(void);
517
518 struct rb_irq_work irq_work;
519 bool time_stamp_abs;
520};
521
522struct ring_buffer_iter {
523 struct ring_buffer_per_cpu *cpu_buffer;
524 unsigned long head;
525 struct buffer_page *head_page;
526 struct buffer_page *cache_reader_page;
527 unsigned long cache_read;
528 u64 read_stamp;
529};
530
531/*
532 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
533 *
534 * Schedules a delayed work to wake up any task that is blocked on the
535 * ring buffer waiters queue.
536 */
537static void rb_wake_up_waiters(struct irq_work *work)
538{
539 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
540
541 wake_up_all(&rbwork->waiters);
542 if (rbwork->wakeup_full) {
543 rbwork->wakeup_full = false;
544 wake_up_all(&rbwork->full_waiters);
545 }
546}
547
548/**
549 * ring_buffer_wait - wait for input to the ring buffer
550 * @buffer: buffer to wait on
551 * @cpu: the cpu buffer to wait on
552 * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS
553 *
554 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
555 * as data is added to any of the @buffer's cpu buffers. Otherwise
556 * it will wait for data to be added to a specific cpu buffer.
557 */
558int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full)
559{
560 struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer);
561 DEFINE_WAIT(wait);
562 struct rb_irq_work *work;
563 int ret = 0;
564
565 /*
566 * Depending on what the caller is waiting for, either any
567 * data in any cpu buffer, or a specific buffer, put the
568 * caller on the appropriate wait queue.
569 */
570 if (cpu == RING_BUFFER_ALL_CPUS) {
571 work = &buffer->irq_work;
572 /* Full only makes sense on per cpu reads */
573 full = false;
574 } else {
575 if (!cpumask_test_cpu(cpu, buffer->cpumask))
576 return -ENODEV;
577 cpu_buffer = buffer->buffers[cpu];
578 work = &cpu_buffer->irq_work;
579 }
580
581
582 while (true) {
583 if (full)
584 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
585 else
586 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
587
588 /*
589 * The events can happen in critical sections where
590 * checking a work queue can cause deadlocks.
591 * After adding a task to the queue, this flag is set
592 * only to notify events to try to wake up the queue
593 * using irq_work.
594 *
595 * We don't clear it even if the buffer is no longer
596 * empty. The flag only causes the next event to run
597 * irq_work to do the work queue wake up. The worse
598 * that can happen if we race with !trace_empty() is that
599 * an event will cause an irq_work to try to wake up
600 * an empty queue.
601 *
602 * There's no reason to protect this flag either, as
603 * the work queue and irq_work logic will do the necessary
604 * synchronization for the wake ups. The only thing
605 * that is necessary is that the wake up happens after
606 * a task has been queued. It's OK for spurious wake ups.
607 */
608 if (full)
609 work->full_waiters_pending = true;
610 else
611 work->waiters_pending = true;
612
613 if (signal_pending(current)) {
614 ret = -EINTR;
615 break;
616 }
617
618 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
619 break;
620
621 if (cpu != RING_BUFFER_ALL_CPUS &&
622 !ring_buffer_empty_cpu(buffer, cpu)) {
623 unsigned long flags;
624 bool pagebusy;
625
626 if (!full)
627 break;
628
629 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
630 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
631 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
632
633 if (!pagebusy)
634 break;
635 }
636
637 schedule();
638 }
639
640 if (full)
641 finish_wait(&work->full_waiters, &wait);
642 else
643 finish_wait(&work->waiters, &wait);
644
645 return ret;
646}
647
648/**
649 * ring_buffer_poll_wait - poll on buffer input
650 * @buffer: buffer to wait on
651 * @cpu: the cpu buffer to wait on
652 * @filp: the file descriptor
653 * @poll_table: The poll descriptor
654 *
655 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
656 * as data is added to any of the @buffer's cpu buffers. Otherwise
657 * it will wait for data to be added to a specific cpu buffer.
658 *
659 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
660 * zero otherwise.
661 */
662__poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
663 struct file *filp, poll_table *poll_table)
664{
665 struct ring_buffer_per_cpu *cpu_buffer;
666 struct rb_irq_work *work;
667
668 if (cpu == RING_BUFFER_ALL_CPUS)
669 work = &buffer->irq_work;
670 else {
671 if (!cpumask_test_cpu(cpu, buffer->cpumask))
672 return -EINVAL;
673
674 cpu_buffer = buffer->buffers[cpu];
675 work = &cpu_buffer->irq_work;
676 }
677
678 poll_wait(filp, &work->waiters, poll_table);
679 work->waiters_pending = true;
680 /*
681 * There's a tight race between setting the waiters_pending and
682 * checking if the ring buffer is empty. Once the waiters_pending bit
683 * is set, the next event will wake the task up, but we can get stuck
684 * if there's only a single event in.
685 *
686 * FIXME: Ideally, we need a memory barrier on the writer side as well,
687 * but adding a memory barrier to all events will cause too much of a
688 * performance hit in the fast path. We only need a memory barrier when
689 * the buffer goes from empty to having content. But as this race is
690 * extremely small, and it's not a problem if another event comes in, we
691 * will fix it later.
692 */
693 smp_mb();
694
695 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
696 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
697 return EPOLLIN | EPOLLRDNORM;
698 return 0;
699}
700
701/* buffer may be either ring_buffer or ring_buffer_per_cpu */
702#define RB_WARN_ON(b, cond) \
703 ({ \
704 int _____ret = unlikely(cond); \
705 if (_____ret) { \
706 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
707 struct ring_buffer_per_cpu *__b = \
708 (void *)b; \
709 atomic_inc(&__b->buffer->record_disabled); \
710 } else \
711 atomic_inc(&b->record_disabled); \
712 WARN_ON(1); \
713 } \
714 _____ret; \
715 })
716
717/* Up this if you want to test the TIME_EXTENTS and normalization */
718#define DEBUG_SHIFT 0
719
720static inline u64 rb_time_stamp(struct ring_buffer *buffer)
721{
722 /* shift to debug/test normalization and TIME_EXTENTS */
723 return buffer->clock() << DEBUG_SHIFT;
724}
725
726u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
727{
728 u64 time;
729
730 preempt_disable_notrace();
731 time = rb_time_stamp(buffer);
732 preempt_enable_no_resched_notrace();
733
734 return time;
735}
736EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
737
738void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
739 int cpu, u64 *ts)
740{
741 /* Just stupid testing the normalize function and deltas */
742 *ts >>= DEBUG_SHIFT;
743}
744EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
745
746/*
747 * Making the ring buffer lockless makes things tricky.
748 * Although writes only happen on the CPU that they are on,
749 * and they only need to worry about interrupts. Reads can
750 * happen on any CPU.
751 *
752 * The reader page is always off the ring buffer, but when the
753 * reader finishes with a page, it needs to swap its page with
754 * a new one from the buffer. The reader needs to take from
755 * the head (writes go to the tail). But if a writer is in overwrite
756 * mode and wraps, it must push the head page forward.
757 *
758 * Here lies the problem.
759 *
760 * The reader must be careful to replace only the head page, and
761 * not another one. As described at the top of the file in the
762 * ASCII art, the reader sets its old page to point to the next
763 * page after head. It then sets the page after head to point to
764 * the old reader page. But if the writer moves the head page
765 * during this operation, the reader could end up with the tail.
766 *
767 * We use cmpxchg to help prevent this race. We also do something
768 * special with the page before head. We set the LSB to 1.
769 *
770 * When the writer must push the page forward, it will clear the
771 * bit that points to the head page, move the head, and then set
772 * the bit that points to the new head page.
773 *
774 * We also don't want an interrupt coming in and moving the head
775 * page on another writer. Thus we use the second LSB to catch
776 * that too. Thus:
777 *
778 * head->list->prev->next bit 1 bit 0
779 * ------- -------
780 * Normal page 0 0
781 * Points to head page 0 1
782 * New head page 1 0
783 *
784 * Note we can not trust the prev pointer of the head page, because:
785 *
786 * +----+ +-----+ +-----+
787 * | |------>| T |---X--->| N |
788 * | |<------| | | |
789 * +----+ +-----+ +-----+
790 * ^ ^ |
791 * | +-----+ | |
792 * +----------| R |----------+ |
793 * | |<-----------+
794 * +-----+
795 *
796 * Key: ---X--> HEAD flag set in pointer
797 * T Tail page
798 * R Reader page
799 * N Next page
800 *
801 * (see __rb_reserve_next() to see where this happens)
802 *
803 * What the above shows is that the reader just swapped out
804 * the reader page with a page in the buffer, but before it
805 * could make the new header point back to the new page added
806 * it was preempted by a writer. The writer moved forward onto
807 * the new page added by the reader and is about to move forward
808 * again.
809 *
810 * You can see, it is legitimate for the previous pointer of
811 * the head (or any page) not to point back to itself. But only
812 * temporarially.
813 */
814
815#define RB_PAGE_NORMAL 0UL
816#define RB_PAGE_HEAD 1UL
817#define RB_PAGE_UPDATE 2UL
818
819
820#define RB_FLAG_MASK 3UL
821
822/* PAGE_MOVED is not part of the mask */
823#define RB_PAGE_MOVED 4UL
824
825/*
826 * rb_list_head - remove any bit
827 */
828static struct list_head *rb_list_head(struct list_head *list)
829{
830 unsigned long val = (unsigned long)list;
831
832 return (struct list_head *)(val & ~RB_FLAG_MASK);
833}
834
835/*
836 * rb_is_head_page - test if the given page is the head page
837 *
838 * Because the reader may move the head_page pointer, we can
839 * not trust what the head page is (it may be pointing to
840 * the reader page). But if the next page is a header page,
841 * its flags will be non zero.
842 */
843static inline int
844rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
845 struct buffer_page *page, struct list_head *list)
846{
847 unsigned long val;
848
849 val = (unsigned long)list->next;
850
851 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
852 return RB_PAGE_MOVED;
853
854 return val & RB_FLAG_MASK;
855}
856
857/*
858 * rb_is_reader_page
859 *
860 * The unique thing about the reader page, is that, if the
861 * writer is ever on it, the previous pointer never points
862 * back to the reader page.
863 */
864static bool rb_is_reader_page(struct buffer_page *page)
865{
866 struct list_head *list = page->list.prev;
867
868 return rb_list_head(list->next) != &page->list;
869}
870
871/*
872 * rb_set_list_to_head - set a list_head to be pointing to head.
873 */
874static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
875 struct list_head *list)
876{
877 unsigned long *ptr;
878
879 ptr = (unsigned long *)&list->next;
880 *ptr |= RB_PAGE_HEAD;
881 *ptr &= ~RB_PAGE_UPDATE;
882}
883
884/*
885 * rb_head_page_activate - sets up head page
886 */
887static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
888{
889 struct buffer_page *head;
890
891 head = cpu_buffer->head_page;
892 if (!head)
893 return;
894
895 /*
896 * Set the previous list pointer to have the HEAD flag.
897 */
898 rb_set_list_to_head(cpu_buffer, head->list.prev);
899}
900
901static void rb_list_head_clear(struct list_head *list)
902{
903 unsigned long *ptr = (unsigned long *)&list->next;
904
905 *ptr &= ~RB_FLAG_MASK;
906}
907
908/*
909 * rb_head_page_dactivate - clears head page ptr (for free list)
910 */
911static void
912rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
913{
914 struct list_head *hd;
915
916 /* Go through the whole list and clear any pointers found. */
917 rb_list_head_clear(cpu_buffer->pages);
918
919 list_for_each(hd, cpu_buffer->pages)
920 rb_list_head_clear(hd);
921}
922
923static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
924 struct buffer_page *head,
925 struct buffer_page *prev,
926 int old_flag, int new_flag)
927{
928 struct list_head *list;
929 unsigned long val = (unsigned long)&head->list;
930 unsigned long ret;
931
932 list = &prev->list;
933
934 val &= ~RB_FLAG_MASK;
935
936 ret = cmpxchg((unsigned long *)&list->next,
937 val | old_flag, val | new_flag);
938
939 /* check if the reader took the page */
940 if ((ret & ~RB_FLAG_MASK) != val)
941 return RB_PAGE_MOVED;
942
943 return ret & RB_FLAG_MASK;
944}
945
946static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
947 struct buffer_page *head,
948 struct buffer_page *prev,
949 int old_flag)
950{
951 return rb_head_page_set(cpu_buffer, head, prev,
952 old_flag, RB_PAGE_UPDATE);
953}
954
955static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
956 struct buffer_page *head,
957 struct buffer_page *prev,
958 int old_flag)
959{
960 return rb_head_page_set(cpu_buffer, head, prev,
961 old_flag, RB_PAGE_HEAD);
962}
963
964static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
965 struct buffer_page *head,
966 struct buffer_page *prev,
967 int old_flag)
968{
969 return rb_head_page_set(cpu_buffer, head, prev,
970 old_flag, RB_PAGE_NORMAL);
971}
972
973static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
974 struct buffer_page **bpage)
975{
976 struct list_head *p = rb_list_head((*bpage)->list.next);
977
978 *bpage = list_entry(p, struct buffer_page, list);
979}
980
981static struct buffer_page *
982rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
983{
984 struct buffer_page *head;
985 struct buffer_page *page;
986 struct list_head *list;
987 int i;
988
989 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
990 return NULL;
991
992 /* sanity check */
993 list = cpu_buffer->pages;
994 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
995 return NULL;
996
997 page = head = cpu_buffer->head_page;
998 /*
999 * It is possible that the writer moves the header behind
1000 * where we started, and we miss in one loop.
1001 * A second loop should grab the header, but we'll do
1002 * three loops just because I'm paranoid.
1003 */
1004 for (i = 0; i < 3; i++) {
1005 do {
1006 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
1007 cpu_buffer->head_page = page;
1008 return page;
1009 }
1010 rb_inc_page(cpu_buffer, &page);
1011 } while (page != head);
1012 }
1013
1014 RB_WARN_ON(cpu_buffer, 1);
1015
1016 return NULL;
1017}
1018
1019static int rb_head_page_replace(struct buffer_page *old,
1020 struct buffer_page *new)
1021{
1022 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1023 unsigned long val;
1024 unsigned long ret;
1025
1026 val = *ptr & ~RB_FLAG_MASK;
1027 val |= RB_PAGE_HEAD;
1028
1029 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1030
1031 return ret == val;
1032}
1033
1034/*
1035 * rb_tail_page_update - move the tail page forward
1036 */
1037static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1038 struct buffer_page *tail_page,
1039 struct buffer_page *next_page)
1040{
1041 unsigned long old_entries;
1042 unsigned long old_write;
1043
1044 /*
1045 * The tail page now needs to be moved forward.
1046 *
1047 * We need to reset the tail page, but without messing
1048 * with possible erasing of data brought in by interrupts
1049 * that have moved the tail page and are currently on it.
1050 *
1051 * We add a counter to the write field to denote this.
1052 */
1053 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1054 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1055
1056 /*
1057 * Just make sure we have seen our old_write and synchronize
1058 * with any interrupts that come in.
1059 */
1060 barrier();
1061
1062 /*
1063 * If the tail page is still the same as what we think
1064 * it is, then it is up to us to update the tail
1065 * pointer.
1066 */
1067 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1068 /* Zero the write counter */
1069 unsigned long val = old_write & ~RB_WRITE_MASK;
1070 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1071
1072 /*
1073 * This will only succeed if an interrupt did
1074 * not come in and change it. In which case, we
1075 * do not want to modify it.
1076 *
1077 * We add (void) to let the compiler know that we do not care
1078 * about the return value of these functions. We use the
1079 * cmpxchg to only update if an interrupt did not already
1080 * do it for us. If the cmpxchg fails, we don't care.
1081 */
1082 (void)local_cmpxchg(&next_page->write, old_write, val);
1083 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1084
1085 /*
1086 * No need to worry about races with clearing out the commit.
1087 * it only can increment when a commit takes place. But that
1088 * only happens in the outer most nested commit.
1089 */
1090 local_set(&next_page->page->commit, 0);
1091
1092 /* Again, either we update tail_page or an interrupt does */
1093 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1094 }
1095}
1096
1097static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1098 struct buffer_page *bpage)
1099{
1100 unsigned long val = (unsigned long)bpage;
1101
1102 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1103 return 1;
1104
1105 return 0;
1106}
1107
1108/**
1109 * rb_check_list - make sure a pointer to a list has the last bits zero
1110 */
1111static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1112 struct list_head *list)
1113{
1114 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1115 return 1;
1116 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1117 return 1;
1118 return 0;
1119}
1120
1121/**
1122 * rb_check_pages - integrity check of buffer pages
1123 * @cpu_buffer: CPU buffer with pages to test
1124 *
1125 * As a safety measure we check to make sure the data pages have not
1126 * been corrupted.
1127 */
1128static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1129{
1130 struct list_head *head = cpu_buffer->pages;
1131 struct buffer_page *bpage, *tmp;
1132
1133 /* Reset the head page if it exists */
1134 if (cpu_buffer->head_page)
1135 rb_set_head_page(cpu_buffer);
1136
1137 rb_head_page_deactivate(cpu_buffer);
1138
1139 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1140 return -1;
1141 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1142 return -1;
1143
1144 if (rb_check_list(cpu_buffer, head))
1145 return -1;
1146
1147 list_for_each_entry_safe(bpage, tmp, head, list) {
1148 if (RB_WARN_ON(cpu_buffer,
1149 bpage->list.next->prev != &bpage->list))
1150 return -1;
1151 if (RB_WARN_ON(cpu_buffer,
1152 bpage->list.prev->next != &bpage->list))
1153 return -1;
1154 if (rb_check_list(cpu_buffer, &bpage->list))
1155 return -1;
1156 }
1157
1158 rb_head_page_activate(cpu_buffer);
1159
1160 return 0;
1161}
1162
1163static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1164{
1165 struct buffer_page *bpage, *tmp;
1166 bool user_thread = current->mm != NULL;
1167 gfp_t mflags;
1168 long i;
1169
1170 /*
1171 * Check if the available memory is there first.
1172 * Note, si_mem_available() only gives us a rough estimate of available
1173 * memory. It may not be accurate. But we don't care, we just want
1174 * to prevent doing any allocation when it is obvious that it is
1175 * not going to succeed.
1176 */
1177 i = si_mem_available();
1178 if (i < nr_pages)
1179 return -ENOMEM;
1180
1181 /*
1182 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1183 * gracefully without invoking oom-killer and the system is not
1184 * destabilized.
1185 */
1186 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1187
1188 /*
1189 * If a user thread allocates too much, and si_mem_available()
1190 * reports there's enough memory, even though there is not.
1191 * Make sure the OOM killer kills this thread. This can happen
1192 * even with RETRY_MAYFAIL because another task may be doing
1193 * an allocation after this task has taken all memory.
1194 * This is the task the OOM killer needs to take out during this
1195 * loop, even if it was triggered by an allocation somewhere else.
1196 */
1197 if (user_thread)
1198 set_current_oom_origin();
1199 for (i = 0; i < nr_pages; i++) {
1200 struct page *page;
1201
1202 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1203 mflags, cpu_to_node(cpu));
1204 if (!bpage)
1205 goto free_pages;
1206
1207 list_add(&bpage->list, pages);
1208
1209 page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
1210 if (!page)
1211 goto free_pages;
1212 bpage->page = page_address(page);
1213 rb_init_page(bpage->page);
1214
1215 if (user_thread && fatal_signal_pending(current))
1216 goto free_pages;
1217 }
1218 if (user_thread)
1219 clear_current_oom_origin();
1220
1221 return 0;
1222
1223free_pages:
1224 list_for_each_entry_safe(bpage, tmp, pages, list) {
1225 list_del_init(&bpage->list);
1226 free_buffer_page(bpage);
1227 }
1228 if (user_thread)
1229 clear_current_oom_origin();
1230
1231 return -ENOMEM;
1232}
1233
1234static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1235 unsigned long nr_pages)
1236{
1237 LIST_HEAD(pages);
1238
1239 WARN_ON(!nr_pages);
1240
1241 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1242 return -ENOMEM;
1243
1244 /*
1245 * The ring buffer page list is a circular list that does not
1246 * start and end with a list head. All page list items point to
1247 * other pages.
1248 */
1249 cpu_buffer->pages = pages.next;
1250 list_del(&pages);
1251
1252 cpu_buffer->nr_pages = nr_pages;
1253
1254 rb_check_pages(cpu_buffer);
1255
1256 return 0;
1257}
1258
1259static struct ring_buffer_per_cpu *
1260rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu)
1261{
1262 struct ring_buffer_per_cpu *cpu_buffer;
1263 struct buffer_page *bpage;
1264 struct page *page;
1265 int ret;
1266
1267 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1268 GFP_KERNEL, cpu_to_node(cpu));
1269 if (!cpu_buffer)
1270 return NULL;
1271
1272 cpu_buffer->cpu = cpu;
1273 cpu_buffer->buffer = buffer;
1274 raw_spin_lock_init(&cpu_buffer->reader_lock);
1275 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1276 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1277 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1278 init_completion(&cpu_buffer->update_done);
1279 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1280 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1281 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1282
1283 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1284 GFP_KERNEL, cpu_to_node(cpu));
1285 if (!bpage)
1286 goto fail_free_buffer;
1287
1288 rb_check_bpage(cpu_buffer, bpage);
1289
1290 cpu_buffer->reader_page = bpage;
1291 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1292 if (!page)
1293 goto fail_free_reader;
1294 bpage->page = page_address(page);
1295 rb_init_page(bpage->page);
1296
1297 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1298 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1299
1300 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1301 if (ret < 0)
1302 goto fail_free_reader;
1303
1304 cpu_buffer->head_page
1305 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1306 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1307
1308 rb_head_page_activate(cpu_buffer);
1309
1310 return cpu_buffer;
1311
1312 fail_free_reader:
1313 free_buffer_page(cpu_buffer->reader_page);
1314
1315 fail_free_buffer:
1316 kfree(cpu_buffer);
1317 return NULL;
1318}
1319
1320static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1321{
1322 struct list_head *head = cpu_buffer->pages;
1323 struct buffer_page *bpage, *tmp;
1324
1325 free_buffer_page(cpu_buffer->reader_page);
1326
1327 rb_head_page_deactivate(cpu_buffer);
1328
1329 if (head) {
1330 list_for_each_entry_safe(bpage, tmp, head, list) {
1331 list_del_init(&bpage->list);
1332 free_buffer_page(bpage);
1333 }
1334 bpage = list_entry(head, struct buffer_page, list);
1335 free_buffer_page(bpage);
1336 }
1337
1338 kfree(cpu_buffer);
1339}
1340
1341/**
1342 * __ring_buffer_alloc - allocate a new ring_buffer
1343 * @size: the size in bytes per cpu that is needed.
1344 * @flags: attributes to set for the ring buffer.
1345 *
1346 * Currently the only flag that is available is the RB_FL_OVERWRITE
1347 * flag. This flag means that the buffer will overwrite old data
1348 * when the buffer wraps. If this flag is not set, the buffer will
1349 * drop data when the tail hits the head.
1350 */
1351struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1352 struct lock_class_key *key)
1353{
1354 struct ring_buffer *buffer;
1355 long nr_pages;
1356 int bsize;
1357 int cpu;
1358 int ret;
1359
1360 /* keep it in its own cache line */
1361 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1362 GFP_KERNEL);
1363 if (!buffer)
1364 return NULL;
1365
1366 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1367 goto fail_free_buffer;
1368
1369 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1370 buffer->flags = flags;
1371 buffer->clock = trace_clock_local;
1372 buffer->reader_lock_key = key;
1373
1374 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1375 init_waitqueue_head(&buffer->irq_work.waiters);
1376
1377 /* need at least two pages */
1378 if (nr_pages < 2)
1379 nr_pages = 2;
1380
1381 buffer->cpus = nr_cpu_ids;
1382
1383 bsize = sizeof(void *) * nr_cpu_ids;
1384 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1385 GFP_KERNEL);
1386 if (!buffer->buffers)
1387 goto fail_free_cpumask;
1388
1389 cpu = raw_smp_processor_id();
1390 cpumask_set_cpu(cpu, buffer->cpumask);
1391 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1392 if (!buffer->buffers[cpu])
1393 goto fail_free_buffers;
1394
1395 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1396 if (ret < 0)
1397 goto fail_free_buffers;
1398
1399 mutex_init(&buffer->mutex);
1400
1401 return buffer;
1402
1403 fail_free_buffers:
1404 for_each_buffer_cpu(buffer, cpu) {
1405 if (buffer->buffers[cpu])
1406 rb_free_cpu_buffer(buffer->buffers[cpu]);
1407 }
1408 kfree(buffer->buffers);
1409
1410 fail_free_cpumask:
1411 free_cpumask_var(buffer->cpumask);
1412
1413 fail_free_buffer:
1414 kfree(buffer);
1415 return NULL;
1416}
1417EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1418
1419/**
1420 * ring_buffer_free - free a ring buffer.
1421 * @buffer: the buffer to free.
1422 */
1423void
1424ring_buffer_free(struct ring_buffer *buffer)
1425{
1426 int cpu;
1427
1428 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1429
1430 for_each_buffer_cpu(buffer, cpu)
1431 rb_free_cpu_buffer(buffer->buffers[cpu]);
1432
1433 kfree(buffer->buffers);
1434 free_cpumask_var(buffer->cpumask);
1435
1436 kfree(buffer);
1437}
1438EXPORT_SYMBOL_GPL(ring_buffer_free);
1439
1440void ring_buffer_set_clock(struct ring_buffer *buffer,
1441 u64 (*clock)(void))
1442{
1443 buffer->clock = clock;
1444}
1445
1446void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
1447{
1448 buffer->time_stamp_abs = abs;
1449}
1450
1451bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
1452{
1453 return buffer->time_stamp_abs;
1454}
1455
1456static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1457
1458static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1459{
1460 return local_read(&bpage->entries) & RB_WRITE_MASK;
1461}
1462
1463static inline unsigned long rb_page_write(struct buffer_page *bpage)
1464{
1465 return local_read(&bpage->write) & RB_WRITE_MASK;
1466}
1467
1468static int
1469rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1470{
1471 struct list_head *tail_page, *to_remove, *next_page;
1472 struct buffer_page *to_remove_page, *tmp_iter_page;
1473 struct buffer_page *last_page, *first_page;
1474 unsigned long nr_removed;
1475 unsigned long head_bit;
1476 int page_entries;
1477
1478 head_bit = 0;
1479
1480 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1481 atomic_inc(&cpu_buffer->record_disabled);
1482 /*
1483 * We don't race with the readers since we have acquired the reader
1484 * lock. We also don't race with writers after disabling recording.
1485 * This makes it easy to figure out the first and the last page to be
1486 * removed from the list. We unlink all the pages in between including
1487 * the first and last pages. This is done in a busy loop so that we
1488 * lose the least number of traces.
1489 * The pages are freed after we restart recording and unlock readers.
1490 */
1491 tail_page = &cpu_buffer->tail_page->list;
1492
1493 /*
1494 * tail page might be on reader page, we remove the next page
1495 * from the ring buffer
1496 */
1497 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1498 tail_page = rb_list_head(tail_page->next);
1499 to_remove = tail_page;
1500
1501 /* start of pages to remove */
1502 first_page = list_entry(rb_list_head(to_remove->next),
1503 struct buffer_page, list);
1504
1505 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1506 to_remove = rb_list_head(to_remove)->next;
1507 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1508 }
1509
1510 next_page = rb_list_head(to_remove)->next;
1511
1512 /*
1513 * Now we remove all pages between tail_page and next_page.
1514 * Make sure that we have head_bit value preserved for the
1515 * next page
1516 */
1517 tail_page->next = (struct list_head *)((unsigned long)next_page |
1518 head_bit);
1519 next_page = rb_list_head(next_page);
1520 next_page->prev = tail_page;
1521
1522 /* make sure pages points to a valid page in the ring buffer */
1523 cpu_buffer->pages = next_page;
1524
1525 /* update head page */
1526 if (head_bit)
1527 cpu_buffer->head_page = list_entry(next_page,
1528 struct buffer_page, list);
1529
1530 /*
1531 * change read pointer to make sure any read iterators reset
1532 * themselves
1533 */
1534 cpu_buffer->read = 0;
1535
1536 /* pages are removed, resume tracing and then free the pages */
1537 atomic_dec(&cpu_buffer->record_disabled);
1538 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1539
1540 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1541
1542 /* last buffer page to remove */
1543 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1544 list);
1545 tmp_iter_page = first_page;
1546
1547 do {
1548 to_remove_page = tmp_iter_page;
1549 rb_inc_page(cpu_buffer, &tmp_iter_page);
1550
1551 /* update the counters */
1552 page_entries = rb_page_entries(to_remove_page);
1553 if (page_entries) {
1554 /*
1555 * If something was added to this page, it was full
1556 * since it is not the tail page. So we deduct the
1557 * bytes consumed in ring buffer from here.
1558 * Increment overrun to account for the lost events.
1559 */
1560 local_add(page_entries, &cpu_buffer->overrun);
1561 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1562 }
1563
1564 /*
1565 * We have already removed references to this list item, just
1566 * free up the buffer_page and its page
1567 */
1568 free_buffer_page(to_remove_page);
1569 nr_removed--;
1570
1571 } while (to_remove_page != last_page);
1572
1573 RB_WARN_ON(cpu_buffer, nr_removed);
1574
1575 return nr_removed == 0;
1576}
1577
1578static int
1579rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1580{
1581 struct list_head *pages = &cpu_buffer->new_pages;
1582 int retries, success;
1583
1584 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1585 /*
1586 * We are holding the reader lock, so the reader page won't be swapped
1587 * in the ring buffer. Now we are racing with the writer trying to
1588 * move head page and the tail page.
1589 * We are going to adapt the reader page update process where:
1590 * 1. We first splice the start and end of list of new pages between
1591 * the head page and its previous page.
1592 * 2. We cmpxchg the prev_page->next to point from head page to the
1593 * start of new pages list.
1594 * 3. Finally, we update the head->prev to the end of new list.
1595 *
1596 * We will try this process 10 times, to make sure that we don't keep
1597 * spinning.
1598 */
1599 retries = 10;
1600 success = 0;
1601 while (retries--) {
1602 struct list_head *head_page, *prev_page, *r;
1603 struct list_head *last_page, *first_page;
1604 struct list_head *head_page_with_bit;
1605
1606 head_page = &rb_set_head_page(cpu_buffer)->list;
1607 if (!head_page)
1608 break;
1609 prev_page = head_page->prev;
1610
1611 first_page = pages->next;
1612 last_page = pages->prev;
1613
1614 head_page_with_bit = (struct list_head *)
1615 ((unsigned long)head_page | RB_PAGE_HEAD);
1616
1617 last_page->next = head_page_with_bit;
1618 first_page->prev = prev_page;
1619
1620 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1621
1622 if (r == head_page_with_bit) {
1623 /*
1624 * yay, we replaced the page pointer to our new list,
1625 * now, we just have to update to head page's prev
1626 * pointer to point to end of list
1627 */
1628 head_page->prev = last_page;
1629 success = 1;
1630 break;
1631 }
1632 }
1633
1634 if (success)
1635 INIT_LIST_HEAD(pages);
1636 /*
1637 * If we weren't successful in adding in new pages, warn and stop
1638 * tracing
1639 */
1640 RB_WARN_ON(cpu_buffer, !success);
1641 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1642
1643 /* free pages if they weren't inserted */
1644 if (!success) {
1645 struct buffer_page *bpage, *tmp;
1646 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1647 list) {
1648 list_del_init(&bpage->list);
1649 free_buffer_page(bpage);
1650 }
1651 }
1652 return success;
1653}
1654
1655static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1656{
1657 int success;
1658
1659 if (cpu_buffer->nr_pages_to_update > 0)
1660 success = rb_insert_pages(cpu_buffer);
1661 else
1662 success = rb_remove_pages(cpu_buffer,
1663 -cpu_buffer->nr_pages_to_update);
1664
1665 if (success)
1666 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1667}
1668
1669static void update_pages_handler(struct work_struct *work)
1670{
1671 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1672 struct ring_buffer_per_cpu, update_pages_work);
1673 rb_update_pages(cpu_buffer);
1674 complete(&cpu_buffer->update_done);
1675}
1676
1677/**
1678 * ring_buffer_resize - resize the ring buffer
1679 * @buffer: the buffer to resize.
1680 * @size: the new size.
1681 * @cpu_id: the cpu buffer to resize
1682 *
1683 * Minimum size is 2 * BUF_PAGE_SIZE.
1684 *
1685 * Returns 0 on success and < 0 on failure.
1686 */
1687int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1688 int cpu_id)
1689{
1690 struct ring_buffer_per_cpu *cpu_buffer;
1691 unsigned long nr_pages;
1692 int cpu, err = 0;
1693
1694 /*
1695 * Always succeed at resizing a non-existent buffer:
1696 */
1697 if (!buffer)
1698 return size;
1699
1700 /* Make sure the requested buffer exists */
1701 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1702 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1703 return size;
1704
1705 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1706
1707 /* we need a minimum of two pages */
1708 if (nr_pages < 2)
1709 nr_pages = 2;
1710
1711 size = nr_pages * BUF_PAGE_SIZE;
1712
1713 /*
1714 * Don't succeed if resizing is disabled, as a reader might be
1715 * manipulating the ring buffer and is expecting a sane state while
1716 * this is true.
1717 */
1718 if (atomic_read(&buffer->resize_disabled))
1719 return -EBUSY;
1720
1721 /* prevent another thread from changing buffer sizes */
1722 mutex_lock(&buffer->mutex);
1723
1724 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1725 /* calculate the pages to update */
1726 for_each_buffer_cpu(buffer, cpu) {
1727 cpu_buffer = buffer->buffers[cpu];
1728
1729 cpu_buffer->nr_pages_to_update = nr_pages -
1730 cpu_buffer->nr_pages;
1731 /*
1732 * nothing more to do for removing pages or no update
1733 */
1734 if (cpu_buffer->nr_pages_to_update <= 0)
1735 continue;
1736 /*
1737 * to add pages, make sure all new pages can be
1738 * allocated without receiving ENOMEM
1739 */
1740 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1741 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1742 &cpu_buffer->new_pages, cpu)) {
1743 /* not enough memory for new pages */
1744 err = -ENOMEM;
1745 goto out_err;
1746 }
1747 }
1748
1749 get_online_cpus();
1750 /*
1751 * Fire off all the required work handlers
1752 * We can't schedule on offline CPUs, but it's not necessary
1753 * since we can change their buffer sizes without any race.
1754 */
1755 for_each_buffer_cpu(buffer, cpu) {
1756 cpu_buffer = buffer->buffers[cpu];
1757 if (!cpu_buffer->nr_pages_to_update)
1758 continue;
1759
1760 /* Can't run something on an offline CPU. */
1761 if (!cpu_online(cpu)) {
1762 rb_update_pages(cpu_buffer);
1763 cpu_buffer->nr_pages_to_update = 0;
1764 } else {
1765 schedule_work_on(cpu,
1766 &cpu_buffer->update_pages_work);
1767 }
1768 }
1769
1770 /* wait for all the updates to complete */
1771 for_each_buffer_cpu(buffer, cpu) {
1772 cpu_buffer = buffer->buffers[cpu];
1773 if (!cpu_buffer->nr_pages_to_update)
1774 continue;
1775
1776 if (cpu_online(cpu))
1777 wait_for_completion(&cpu_buffer->update_done);
1778 cpu_buffer->nr_pages_to_update = 0;
1779 }
1780
1781 put_online_cpus();
1782 } else {
1783 /* Make sure this CPU has been intitialized */
1784 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1785 goto out;
1786
1787 cpu_buffer = buffer->buffers[cpu_id];
1788
1789 if (nr_pages == cpu_buffer->nr_pages)
1790 goto out;
1791
1792 cpu_buffer->nr_pages_to_update = nr_pages -
1793 cpu_buffer->nr_pages;
1794
1795 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1796 if (cpu_buffer->nr_pages_to_update > 0 &&
1797 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
1798 &cpu_buffer->new_pages, cpu_id)) {
1799 err = -ENOMEM;
1800 goto out_err;
1801 }
1802
1803 get_online_cpus();
1804
1805 /* Can't run something on an offline CPU. */
1806 if (!cpu_online(cpu_id))
1807 rb_update_pages(cpu_buffer);
1808 else {
1809 schedule_work_on(cpu_id,
1810 &cpu_buffer->update_pages_work);
1811 wait_for_completion(&cpu_buffer->update_done);
1812 }
1813
1814 cpu_buffer->nr_pages_to_update = 0;
1815 put_online_cpus();
1816 }
1817
1818 out:
1819 /*
1820 * The ring buffer resize can happen with the ring buffer
1821 * enabled, so that the update disturbs the tracing as little
1822 * as possible. But if the buffer is disabled, we do not need
1823 * to worry about that, and we can take the time to verify
1824 * that the buffer is not corrupt.
1825 */
1826 if (atomic_read(&buffer->record_disabled)) {
1827 atomic_inc(&buffer->record_disabled);
1828 /*
1829 * Even though the buffer was disabled, we must make sure
1830 * that it is truly disabled before calling rb_check_pages.
1831 * There could have been a race between checking
1832 * record_disable and incrementing it.
1833 */
1834 synchronize_sched();
1835 for_each_buffer_cpu(buffer, cpu) {
1836 cpu_buffer = buffer->buffers[cpu];
1837 rb_check_pages(cpu_buffer);
1838 }
1839 atomic_dec(&buffer->record_disabled);
1840 }
1841
1842 mutex_unlock(&buffer->mutex);
1843 return size;
1844
1845 out_err:
1846 for_each_buffer_cpu(buffer, cpu) {
1847 struct buffer_page *bpage, *tmp;
1848
1849 cpu_buffer = buffer->buffers[cpu];
1850 cpu_buffer->nr_pages_to_update = 0;
1851
1852 if (list_empty(&cpu_buffer->new_pages))
1853 continue;
1854
1855 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1856 list) {
1857 list_del_init(&bpage->list);
1858 free_buffer_page(bpage);
1859 }
1860 }
1861 mutex_unlock(&buffer->mutex);
1862 return err;
1863}
1864EXPORT_SYMBOL_GPL(ring_buffer_resize);
1865
1866void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1867{
1868 mutex_lock(&buffer->mutex);
1869 if (val)
1870 buffer->flags |= RB_FL_OVERWRITE;
1871 else
1872 buffer->flags &= ~RB_FL_OVERWRITE;
1873 mutex_unlock(&buffer->mutex);
1874}
1875EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1876
1877static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
1878{
1879 return bpage->page->data + index;
1880}
1881
1882static __always_inline struct ring_buffer_event *
1883rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
1884{
1885 return __rb_page_index(cpu_buffer->reader_page,
1886 cpu_buffer->reader_page->read);
1887}
1888
1889static __always_inline struct ring_buffer_event *
1890rb_iter_head_event(struct ring_buffer_iter *iter)
1891{
1892 return __rb_page_index(iter->head_page, iter->head);
1893}
1894
1895static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
1896{
1897 return local_read(&bpage->page->commit);
1898}
1899
1900/* Size is determined by what has been committed */
1901static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
1902{
1903 return rb_page_commit(bpage);
1904}
1905
1906static __always_inline unsigned
1907rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1908{
1909 return rb_page_commit(cpu_buffer->commit_page);
1910}
1911
1912static __always_inline unsigned
1913rb_event_index(struct ring_buffer_event *event)
1914{
1915 unsigned long addr = (unsigned long)event;
1916
1917 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
1918}
1919
1920static void rb_inc_iter(struct ring_buffer_iter *iter)
1921{
1922 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1923
1924 /*
1925 * The iterator could be on the reader page (it starts there).
1926 * But the head could have moved, since the reader was
1927 * found. Check for this case and assign the iterator
1928 * to the head page instead of next.
1929 */
1930 if (iter->head_page == cpu_buffer->reader_page)
1931 iter->head_page = rb_set_head_page(cpu_buffer);
1932 else
1933 rb_inc_page(cpu_buffer, &iter->head_page);
1934
1935 iter->read_stamp = iter->head_page->page->time_stamp;
1936 iter->head = 0;
1937}
1938
1939/*
1940 * rb_handle_head_page - writer hit the head page
1941 *
1942 * Returns: +1 to retry page
1943 * 0 to continue
1944 * -1 on error
1945 */
1946static int
1947rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1948 struct buffer_page *tail_page,
1949 struct buffer_page *next_page)
1950{
1951 struct buffer_page *new_head;
1952 int entries;
1953 int type;
1954 int ret;
1955
1956 entries = rb_page_entries(next_page);
1957
1958 /*
1959 * The hard part is here. We need to move the head
1960 * forward, and protect against both readers on
1961 * other CPUs and writers coming in via interrupts.
1962 */
1963 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1964 RB_PAGE_HEAD);
1965
1966 /*
1967 * type can be one of four:
1968 * NORMAL - an interrupt already moved it for us
1969 * HEAD - we are the first to get here.
1970 * UPDATE - we are the interrupt interrupting
1971 * a current move.
1972 * MOVED - a reader on another CPU moved the next
1973 * pointer to its reader page. Give up
1974 * and try again.
1975 */
1976
1977 switch (type) {
1978 case RB_PAGE_HEAD:
1979 /*
1980 * We changed the head to UPDATE, thus
1981 * it is our responsibility to update
1982 * the counters.
1983 */
1984 local_add(entries, &cpu_buffer->overrun);
1985 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1986
1987 /*
1988 * The entries will be zeroed out when we move the
1989 * tail page.
1990 */
1991
1992 /* still more to do */
1993 break;
1994
1995 case RB_PAGE_UPDATE:
1996 /*
1997 * This is an interrupt that interrupt the
1998 * previous update. Still more to do.
1999 */
2000 break;
2001 case RB_PAGE_NORMAL:
2002 /*
2003 * An interrupt came in before the update
2004 * and processed this for us.
2005 * Nothing left to do.
2006 */
2007 return 1;
2008 case RB_PAGE_MOVED:
2009 /*
2010 * The reader is on another CPU and just did
2011 * a swap with our next_page.
2012 * Try again.
2013 */
2014 return 1;
2015 default:
2016 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2017 return -1;
2018 }
2019
2020 /*
2021 * Now that we are here, the old head pointer is
2022 * set to UPDATE. This will keep the reader from
2023 * swapping the head page with the reader page.
2024 * The reader (on another CPU) will spin till
2025 * we are finished.
2026 *
2027 * We just need to protect against interrupts
2028 * doing the job. We will set the next pointer
2029 * to HEAD. After that, we set the old pointer
2030 * to NORMAL, but only if it was HEAD before.
2031 * otherwise we are an interrupt, and only
2032 * want the outer most commit to reset it.
2033 */
2034 new_head = next_page;
2035 rb_inc_page(cpu_buffer, &new_head);
2036
2037 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2038 RB_PAGE_NORMAL);
2039
2040 /*
2041 * Valid returns are:
2042 * HEAD - an interrupt came in and already set it.
2043 * NORMAL - One of two things:
2044 * 1) We really set it.
2045 * 2) A bunch of interrupts came in and moved
2046 * the page forward again.
2047 */
2048 switch (ret) {
2049 case RB_PAGE_HEAD:
2050 case RB_PAGE_NORMAL:
2051 /* OK */
2052 break;
2053 default:
2054 RB_WARN_ON(cpu_buffer, 1);
2055 return -1;
2056 }
2057
2058 /*
2059 * It is possible that an interrupt came in,
2060 * set the head up, then more interrupts came in
2061 * and moved it again. When we get back here,
2062 * the page would have been set to NORMAL but we
2063 * just set it back to HEAD.
2064 *
2065 * How do you detect this? Well, if that happened
2066 * the tail page would have moved.
2067 */
2068 if (ret == RB_PAGE_NORMAL) {
2069 struct buffer_page *buffer_tail_page;
2070
2071 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2072 /*
2073 * If the tail had moved passed next, then we need
2074 * to reset the pointer.
2075 */
2076 if (buffer_tail_page != tail_page &&
2077 buffer_tail_page != next_page)
2078 rb_head_page_set_normal(cpu_buffer, new_head,
2079 next_page,
2080 RB_PAGE_HEAD);
2081 }
2082
2083 /*
2084 * If this was the outer most commit (the one that
2085 * changed the original pointer from HEAD to UPDATE),
2086 * then it is up to us to reset it to NORMAL.
2087 */
2088 if (type == RB_PAGE_HEAD) {
2089 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2090 tail_page,
2091 RB_PAGE_UPDATE);
2092 if (RB_WARN_ON(cpu_buffer,
2093 ret != RB_PAGE_UPDATE))
2094 return -1;
2095 }
2096
2097 return 0;
2098}
2099
2100static inline void
2101rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2102 unsigned long tail, struct rb_event_info *info)
2103{
2104 struct buffer_page *tail_page = info->tail_page;
2105 struct ring_buffer_event *event;
2106 unsigned long length = info->length;
2107
2108 /*
2109 * Only the event that crossed the page boundary
2110 * must fill the old tail_page with padding.
2111 */
2112 if (tail >= BUF_PAGE_SIZE) {
2113 /*
2114 * If the page was filled, then we still need
2115 * to update the real_end. Reset it to zero
2116 * and the reader will ignore it.
2117 */
2118 if (tail == BUF_PAGE_SIZE)
2119 tail_page->real_end = 0;
2120
2121 local_sub(length, &tail_page->write);
2122 return;
2123 }
2124
2125 event = __rb_page_index(tail_page, tail);
2126
2127 /* account for padding bytes */
2128 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2129
2130 /*
2131 * Save the original length to the meta data.
2132 * This will be used by the reader to add lost event
2133 * counter.
2134 */
2135 tail_page->real_end = tail;
2136
2137 /*
2138 * If this event is bigger than the minimum size, then
2139 * we need to be careful that we don't subtract the
2140 * write counter enough to allow another writer to slip
2141 * in on this page.
2142 * We put in a discarded commit instead, to make sure
2143 * that this space is not used again.
2144 *
2145 * If we are less than the minimum size, we don't need to
2146 * worry about it.
2147 */
2148 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2149 /* No room for any events */
2150
2151 /* Mark the rest of the page with padding */
2152 rb_event_set_padding(event);
2153
2154 /* Set the write back to the previous setting */
2155 local_sub(length, &tail_page->write);
2156 return;
2157 }
2158
2159 /* Put in a discarded event */
2160 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2161 event->type_len = RINGBUF_TYPE_PADDING;
2162 /* time delta must be non zero */
2163 event->time_delta = 1;
2164
2165 /* Set write to end of buffer */
2166 length = (tail + length) - BUF_PAGE_SIZE;
2167 local_sub(length, &tail_page->write);
2168}
2169
2170static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2171
2172/*
2173 * This is the slow path, force gcc not to inline it.
2174 */
2175static noinline struct ring_buffer_event *
2176rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2177 unsigned long tail, struct rb_event_info *info)
2178{
2179 struct buffer_page *tail_page = info->tail_page;
2180 struct buffer_page *commit_page = cpu_buffer->commit_page;
2181 struct ring_buffer *buffer = cpu_buffer->buffer;
2182 struct buffer_page *next_page;
2183 int ret;
2184
2185 next_page = tail_page;
2186
2187 rb_inc_page(cpu_buffer, &next_page);
2188
2189 /*
2190 * If for some reason, we had an interrupt storm that made
2191 * it all the way around the buffer, bail, and warn
2192 * about it.
2193 */
2194 if (unlikely(next_page == commit_page)) {
2195 local_inc(&cpu_buffer->commit_overrun);
2196 goto out_reset;
2197 }
2198
2199 /*
2200 * This is where the fun begins!
2201 *
2202 * We are fighting against races between a reader that
2203 * could be on another CPU trying to swap its reader
2204 * page with the buffer head.
2205 *
2206 * We are also fighting against interrupts coming in and
2207 * moving the head or tail on us as well.
2208 *
2209 * If the next page is the head page then we have filled
2210 * the buffer, unless the commit page is still on the
2211 * reader page.
2212 */
2213 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2214
2215 /*
2216 * If the commit is not on the reader page, then
2217 * move the header page.
2218 */
2219 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2220 /*
2221 * If we are not in overwrite mode,
2222 * this is easy, just stop here.
2223 */
2224 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2225 local_inc(&cpu_buffer->dropped_events);
2226 goto out_reset;
2227 }
2228
2229 ret = rb_handle_head_page(cpu_buffer,
2230 tail_page,
2231 next_page);
2232 if (ret < 0)
2233 goto out_reset;
2234 if (ret)
2235 goto out_again;
2236 } else {
2237 /*
2238 * We need to be careful here too. The
2239 * commit page could still be on the reader
2240 * page. We could have a small buffer, and
2241 * have filled up the buffer with events
2242 * from interrupts and such, and wrapped.
2243 *
2244 * Note, if the tail page is also the on the
2245 * reader_page, we let it move out.
2246 */
2247 if (unlikely((cpu_buffer->commit_page !=
2248 cpu_buffer->tail_page) &&
2249 (cpu_buffer->commit_page ==
2250 cpu_buffer->reader_page))) {
2251 local_inc(&cpu_buffer->commit_overrun);
2252 goto out_reset;
2253 }
2254 }
2255 }
2256
2257 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2258
2259 out_again:
2260
2261 rb_reset_tail(cpu_buffer, tail, info);
2262
2263 /* Commit what we have for now. */
2264 rb_end_commit(cpu_buffer);
2265 /* rb_end_commit() decs committing */
2266 local_inc(&cpu_buffer->committing);
2267
2268 /* fail and let the caller try again */
2269 return ERR_PTR(-EAGAIN);
2270
2271 out_reset:
2272 /* reset write */
2273 rb_reset_tail(cpu_buffer, tail, info);
2274
2275 return NULL;
2276}
2277
2278/* Slow path, do not inline */
2279static noinline struct ring_buffer_event *
2280rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2281{
2282 if (abs)
2283 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2284 else
2285 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2286
2287 /* Not the first event on the page, or not delta? */
2288 if (abs || rb_event_index(event)) {
2289 event->time_delta = delta & TS_MASK;
2290 event->array[0] = delta >> TS_SHIFT;
2291 } else {
2292 /* nope, just zero it */
2293 event->time_delta = 0;
2294 event->array[0] = 0;
2295 }
2296
2297 return skip_time_extend(event);
2298}
2299
2300static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2301 struct ring_buffer_event *event);
2302
2303/**
2304 * rb_update_event - update event type and data
2305 * @event: the event to update
2306 * @type: the type of event
2307 * @length: the size of the event field in the ring buffer
2308 *
2309 * Update the type and data fields of the event. The length
2310 * is the actual size that is written to the ring buffer,
2311 * and with this, we can determine what to place into the
2312 * data field.
2313 */
2314static void
2315rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2316 struct ring_buffer_event *event,
2317 struct rb_event_info *info)
2318{
2319 unsigned length = info->length;
2320 u64 delta = info->delta;
2321
2322 /* Only a commit updates the timestamp */
2323 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
2324 delta = 0;
2325
2326 /*
2327 * If we need to add a timestamp, then we
2328 * add it to the start of the resevered space.
2329 */
2330 if (unlikely(info->add_timestamp)) {
2331 bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer);
2332
2333 event = rb_add_time_stamp(event, info->delta, abs);
2334 length -= RB_LEN_TIME_EXTEND;
2335 delta = 0;
2336 }
2337
2338 event->time_delta = delta;
2339 length -= RB_EVNT_HDR_SIZE;
2340 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2341 event->type_len = 0;
2342 event->array[0] = length;
2343 } else
2344 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2345}
2346
2347static unsigned rb_calculate_event_length(unsigned length)
2348{
2349 struct ring_buffer_event event; /* Used only for sizeof array */
2350
2351 /* zero length can cause confusions */
2352 if (!length)
2353 length++;
2354
2355 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2356 length += sizeof(event.array[0]);
2357
2358 length += RB_EVNT_HDR_SIZE;
2359 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2360
2361 /*
2362 * In case the time delta is larger than the 27 bits for it
2363 * in the header, we need to add a timestamp. If another
2364 * event comes in when trying to discard this one to increase
2365 * the length, then the timestamp will be added in the allocated
2366 * space of this event. If length is bigger than the size needed
2367 * for the TIME_EXTEND, then padding has to be used. The events
2368 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2369 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2370 * As length is a multiple of 4, we only need to worry if it
2371 * is 12 (RB_LEN_TIME_EXTEND + 4).
2372 */
2373 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2374 length += RB_ALIGNMENT;
2375
2376 return length;
2377}
2378
2379#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2380static inline bool sched_clock_stable(void)
2381{
2382 return true;
2383}
2384#endif
2385
2386static inline int
2387rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2388 struct ring_buffer_event *event)
2389{
2390 unsigned long new_index, old_index;
2391 struct buffer_page *bpage;
2392 unsigned long index;
2393 unsigned long addr;
2394
2395 new_index = rb_event_index(event);
2396 old_index = new_index + rb_event_ts_length(event);
2397 addr = (unsigned long)event;
2398 addr &= PAGE_MASK;
2399
2400 bpage = READ_ONCE(cpu_buffer->tail_page);
2401
2402 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2403 unsigned long write_mask =
2404 local_read(&bpage->write) & ~RB_WRITE_MASK;
2405 unsigned long event_length = rb_event_length(event);
2406 /*
2407 * This is on the tail page. It is possible that
2408 * a write could come in and move the tail page
2409 * and write to the next page. That is fine
2410 * because we just shorten what is on this page.
2411 */
2412 old_index += write_mask;
2413 new_index += write_mask;
2414 index = local_cmpxchg(&bpage->write, old_index, new_index);
2415 if (index == old_index) {
2416 /* update counters */
2417 local_sub(event_length, &cpu_buffer->entries_bytes);
2418 return 1;
2419 }
2420 }
2421
2422 /* could not discard */
2423 return 0;
2424}
2425
2426static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2427{
2428 local_inc(&cpu_buffer->committing);
2429 local_inc(&cpu_buffer->commits);
2430}
2431
2432static __always_inline void
2433rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2434{
2435 unsigned long max_count;
2436
2437 /*
2438 * We only race with interrupts and NMIs on this CPU.
2439 * If we own the commit event, then we can commit
2440 * all others that interrupted us, since the interruptions
2441 * are in stack format (they finish before they come
2442 * back to us). This allows us to do a simple loop to
2443 * assign the commit to the tail.
2444 */
2445 again:
2446 max_count = cpu_buffer->nr_pages * 100;
2447
2448 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2449 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2450 return;
2451 if (RB_WARN_ON(cpu_buffer,
2452 rb_is_reader_page(cpu_buffer->tail_page)))
2453 return;
2454 local_set(&cpu_buffer->commit_page->page->commit,
2455 rb_page_write(cpu_buffer->commit_page));
2456 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2457 /* Only update the write stamp if the page has an event */
2458 if (rb_page_write(cpu_buffer->commit_page))
2459 cpu_buffer->write_stamp =
2460 cpu_buffer->commit_page->page->time_stamp;
2461 /* add barrier to keep gcc from optimizing too much */
2462 barrier();
2463 }
2464 while (rb_commit_index(cpu_buffer) !=
2465 rb_page_write(cpu_buffer->commit_page)) {
2466
2467 local_set(&cpu_buffer->commit_page->page->commit,
2468 rb_page_write(cpu_buffer->commit_page));
2469 RB_WARN_ON(cpu_buffer,
2470 local_read(&cpu_buffer->commit_page->page->commit) &
2471 ~RB_WRITE_MASK);
2472 barrier();
2473 }
2474
2475 /* again, keep gcc from optimizing */
2476 barrier();
2477
2478 /*
2479 * If an interrupt came in just after the first while loop
2480 * and pushed the tail page forward, we will be left with
2481 * a dangling commit that will never go forward.
2482 */
2483 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2484 goto again;
2485}
2486
2487static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2488{
2489 unsigned long commits;
2490
2491 if (RB_WARN_ON(cpu_buffer,
2492 !local_read(&cpu_buffer->committing)))
2493 return;
2494
2495 again:
2496 commits = local_read(&cpu_buffer->commits);
2497 /* synchronize with interrupts */
2498 barrier();
2499 if (local_read(&cpu_buffer->committing) == 1)
2500 rb_set_commit_to_write(cpu_buffer);
2501
2502 local_dec(&cpu_buffer->committing);
2503
2504 /* synchronize with interrupts */
2505 barrier();
2506
2507 /*
2508 * Need to account for interrupts coming in between the
2509 * updating of the commit page and the clearing of the
2510 * committing counter.
2511 */
2512 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2513 !local_read(&cpu_buffer->committing)) {
2514 local_inc(&cpu_buffer->committing);
2515 goto again;
2516 }
2517}
2518
2519static inline void rb_event_discard(struct ring_buffer_event *event)
2520{
2521 if (extended_time(event))
2522 event = skip_time_extend(event);
2523
2524 /* array[0] holds the actual length for the discarded event */
2525 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2526 event->type_len = RINGBUF_TYPE_PADDING;
2527 /* time delta must be non zero */
2528 if (!event->time_delta)
2529 event->time_delta = 1;
2530}
2531
2532static __always_inline bool
2533rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2534 struct ring_buffer_event *event)
2535{
2536 unsigned long addr = (unsigned long)event;
2537 unsigned long index;
2538
2539 index = rb_event_index(event);
2540 addr &= PAGE_MASK;
2541
2542 return cpu_buffer->commit_page->page == (void *)addr &&
2543 rb_commit_index(cpu_buffer) == index;
2544}
2545
2546static __always_inline void
2547rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
2548 struct ring_buffer_event *event)
2549{
2550 u64 delta;
2551
2552 /*
2553 * The event first in the commit queue updates the
2554 * time stamp.
2555 */
2556 if (rb_event_is_commit(cpu_buffer, event)) {
2557 /*
2558 * A commit event that is first on a page
2559 * updates the write timestamp with the page stamp
2560 */
2561 if (!rb_event_index(event))
2562 cpu_buffer->write_stamp =
2563 cpu_buffer->commit_page->page->time_stamp;
2564 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2565 delta = ring_buffer_event_time_stamp(event);
2566 cpu_buffer->write_stamp += delta;
2567 } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
2568 delta = ring_buffer_event_time_stamp(event);
2569 cpu_buffer->write_stamp = delta;
2570 } else
2571 cpu_buffer->write_stamp += event->time_delta;
2572 }
2573}
2574
2575static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2576 struct ring_buffer_event *event)
2577{
2578 local_inc(&cpu_buffer->entries);
2579 rb_update_write_stamp(cpu_buffer, event);
2580 rb_end_commit(cpu_buffer);
2581}
2582
2583static __always_inline void
2584rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2585{
2586 bool pagebusy;
2587
2588 if (buffer->irq_work.waiters_pending) {
2589 buffer->irq_work.waiters_pending = false;
2590 /* irq_work_queue() supplies it's own memory barriers */
2591 irq_work_queue(&buffer->irq_work.work);
2592 }
2593
2594 if (cpu_buffer->irq_work.waiters_pending) {
2595 cpu_buffer->irq_work.waiters_pending = false;
2596 /* irq_work_queue() supplies it's own memory barriers */
2597 irq_work_queue(&cpu_buffer->irq_work.work);
2598 }
2599
2600 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
2601
2602 if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) {
2603 cpu_buffer->irq_work.wakeup_full = true;
2604 cpu_buffer->irq_work.full_waiters_pending = false;
2605 /* irq_work_queue() supplies it's own memory barriers */
2606 irq_work_queue(&cpu_buffer->irq_work.work);
2607 }
2608}
2609
2610/*
2611 * The lock and unlock are done within a preempt disable section.
2612 * The current_context per_cpu variable can only be modified
2613 * by the current task between lock and unlock. But it can
2614 * be modified more than once via an interrupt. To pass this
2615 * information from the lock to the unlock without having to
2616 * access the 'in_interrupt()' functions again (which do show
2617 * a bit of overhead in something as critical as function tracing,
2618 * we use a bitmask trick.
2619 *
2620 * bit 0 = NMI context
2621 * bit 1 = IRQ context
2622 * bit 2 = SoftIRQ context
2623 * bit 3 = normal context.
2624 *
2625 * This works because this is the order of contexts that can
2626 * preempt other contexts. A SoftIRQ never preempts an IRQ
2627 * context.
2628 *
2629 * When the context is determined, the corresponding bit is
2630 * checked and set (if it was set, then a recursion of that context
2631 * happened).
2632 *
2633 * On unlock, we need to clear this bit. To do so, just subtract
2634 * 1 from the current_context and AND it to itself.
2635 *
2636 * (binary)
2637 * 101 - 1 = 100
2638 * 101 & 100 = 100 (clearing bit zero)
2639 *
2640 * 1010 - 1 = 1001
2641 * 1010 & 1001 = 1000 (clearing bit 1)
2642 *
2643 * The least significant bit can be cleared this way, and it
2644 * just so happens that it is the same bit corresponding to
2645 * the current context.
2646 */
2647
2648static __always_inline int
2649trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
2650{
2651 unsigned int val = cpu_buffer->current_context;
2652 unsigned long pc = preempt_count();
2653 int bit;
2654
2655 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
2656 bit = RB_CTX_NORMAL;
2657 else
2658 bit = pc & NMI_MASK ? RB_CTX_NMI :
2659 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
2660
2661 if (unlikely(val & (1 << (bit + cpu_buffer->nest))))
2662 return 1;
2663
2664 val |= (1 << (bit + cpu_buffer->nest));
2665 cpu_buffer->current_context = val;
2666
2667 return 0;
2668}
2669
2670static __always_inline void
2671trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
2672{
2673 cpu_buffer->current_context &=
2674 cpu_buffer->current_context - (1 << cpu_buffer->nest);
2675}
2676
2677/* The recursive locking above uses 4 bits */
2678#define NESTED_BITS 4
2679
2680/**
2681 * ring_buffer_nest_start - Allow to trace while nested
2682 * @buffer: The ring buffer to modify
2683 *
2684 * The ring buffer has a safty mechanism to prevent recursion.
2685 * But there may be a case where a trace needs to be done while
2686 * tracing something else. In this case, calling this function
2687 * will allow this function to nest within a currently active
2688 * ring_buffer_lock_reserve().
2689 *
2690 * Call this function before calling another ring_buffer_lock_reserve() and
2691 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
2692 */
2693void ring_buffer_nest_start(struct ring_buffer *buffer)
2694{
2695 struct ring_buffer_per_cpu *cpu_buffer;
2696 int cpu;
2697
2698 /* Enabled by ring_buffer_nest_end() */
2699 preempt_disable_notrace();
2700 cpu = raw_smp_processor_id();
2701 cpu_buffer = buffer->buffers[cpu];
2702 /* This is the shift value for the above recusive locking */
2703 cpu_buffer->nest += NESTED_BITS;
2704}
2705
2706/**
2707 * ring_buffer_nest_end - Allow to trace while nested
2708 * @buffer: The ring buffer to modify
2709 *
2710 * Must be called after ring_buffer_nest_start() and after the
2711 * ring_buffer_unlock_commit().
2712 */
2713void ring_buffer_nest_end(struct ring_buffer *buffer)
2714{
2715 struct ring_buffer_per_cpu *cpu_buffer;
2716 int cpu;
2717
2718 /* disabled by ring_buffer_nest_start() */
2719 cpu = raw_smp_processor_id();
2720 cpu_buffer = buffer->buffers[cpu];
2721 /* This is the shift value for the above recusive locking */
2722 cpu_buffer->nest -= NESTED_BITS;
2723 preempt_enable_notrace();
2724}
2725
2726/**
2727 * ring_buffer_unlock_commit - commit a reserved
2728 * @buffer: The buffer to commit to
2729 * @event: The event pointer to commit.
2730 *
2731 * This commits the data to the ring buffer, and releases any locks held.
2732 *
2733 * Must be paired with ring_buffer_lock_reserve.
2734 */
2735int ring_buffer_unlock_commit(struct ring_buffer *buffer,
2736 struct ring_buffer_event *event)
2737{
2738 struct ring_buffer_per_cpu *cpu_buffer;
2739 int cpu = raw_smp_processor_id();
2740
2741 cpu_buffer = buffer->buffers[cpu];
2742
2743 rb_commit(cpu_buffer, event);
2744
2745 rb_wakeups(buffer, cpu_buffer);
2746
2747 trace_recursive_unlock(cpu_buffer);
2748
2749 preempt_enable_notrace();
2750
2751 return 0;
2752}
2753EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
2754
2755static noinline void
2756rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2757 struct rb_event_info *info)
2758{
2759 WARN_ONCE(info->delta > (1ULL << 59),
2760 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
2761 (unsigned long long)info->delta,
2762 (unsigned long long)info->ts,
2763 (unsigned long long)cpu_buffer->write_stamp,
2764 sched_clock_stable() ? "" :
2765 "If you just came from a suspend/resume,\n"
2766 "please switch to the trace global clock:\n"
2767 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2768 "or add trace_clock=global to the kernel command line\n");
2769 info->add_timestamp = 1;
2770}
2771
2772static struct ring_buffer_event *
2773__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
2774 struct rb_event_info *info)
2775{
2776 struct ring_buffer_event *event;
2777 struct buffer_page *tail_page;
2778 unsigned long tail, write;
2779
2780 /*
2781 * If the time delta since the last event is too big to
2782 * hold in the time field of the event, then we append a
2783 * TIME EXTEND event ahead of the data event.
2784 */
2785 if (unlikely(info->add_timestamp))
2786 info->length += RB_LEN_TIME_EXTEND;
2787
2788 /* Don't let the compiler play games with cpu_buffer->tail_page */
2789 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
2790 write = local_add_return(info->length, &tail_page->write);
2791
2792 /* set write to only the index of the write */
2793 write &= RB_WRITE_MASK;
2794 tail = write - info->length;
2795
2796 /*
2797 * If this is the first commit on the page, then it has the same
2798 * timestamp as the page itself.
2799 */
2800 if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer))
2801 info->delta = 0;
2802
2803 /* See if we shot pass the end of this buffer page */
2804 if (unlikely(write > BUF_PAGE_SIZE))
2805 return rb_move_tail(cpu_buffer, tail, info);
2806
2807 /* We reserved something on the buffer */
2808
2809 event = __rb_page_index(tail_page, tail);
2810 rb_update_event(cpu_buffer, event, info);
2811
2812 local_inc(&tail_page->entries);
2813
2814 /*
2815 * If this is the first commit on the page, then update
2816 * its timestamp.
2817 */
2818 if (!tail)
2819 tail_page->page->time_stamp = info->ts;
2820
2821 /* account for these added bytes */
2822 local_add(info->length, &cpu_buffer->entries_bytes);
2823
2824 return event;
2825}
2826
2827static __always_inline struct ring_buffer_event *
2828rb_reserve_next_event(struct ring_buffer *buffer,
2829 struct ring_buffer_per_cpu *cpu_buffer,
2830 unsigned long length)
2831{
2832 struct ring_buffer_event *event;
2833 struct rb_event_info info;
2834 int nr_loops = 0;
2835 u64 diff;
2836
2837 rb_start_commit(cpu_buffer);
2838
2839#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
2840 /*
2841 * Due to the ability to swap a cpu buffer from a buffer
2842 * it is possible it was swapped before we committed.
2843 * (committing stops a swap). We check for it here and
2844 * if it happened, we have to fail the write.
2845 */
2846 barrier();
2847 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
2848 local_dec(&cpu_buffer->committing);
2849 local_dec(&cpu_buffer->commits);
2850 return NULL;
2851 }
2852#endif
2853
2854 info.length = rb_calculate_event_length(length);
2855 again:
2856 info.add_timestamp = 0;
2857 info.delta = 0;
2858
2859 /*
2860 * We allow for interrupts to reenter here and do a trace.
2861 * If one does, it will cause this original code to loop
2862 * back here. Even with heavy interrupts happening, this
2863 * should only happen a few times in a row. If this happens
2864 * 1000 times in a row, there must be either an interrupt
2865 * storm or we have something buggy.
2866 * Bail!
2867 */
2868 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
2869 goto out_fail;
2870
2871 info.ts = rb_time_stamp(cpu_buffer->buffer);
2872 diff = info.ts - cpu_buffer->write_stamp;
2873
2874 /* make sure this diff is calculated here */
2875 barrier();
2876
2877 if (ring_buffer_time_stamp_abs(buffer)) {
2878 info.delta = info.ts;
2879 rb_handle_timestamp(cpu_buffer, &info);
2880 } else /* Did the write stamp get updated already? */
2881 if (likely(info.ts >= cpu_buffer->write_stamp)) {
2882 info.delta = diff;
2883 if (unlikely(test_time_stamp(info.delta)))
2884 rb_handle_timestamp(cpu_buffer, &info);
2885 }
2886
2887 event = __rb_reserve_next(cpu_buffer, &info);
2888
2889 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
2890 if (info.add_timestamp)
2891 info.length -= RB_LEN_TIME_EXTEND;
2892 goto again;
2893 }
2894
2895 if (!event)
2896 goto out_fail;
2897
2898 return event;
2899
2900 out_fail:
2901 rb_end_commit(cpu_buffer);
2902 return NULL;
2903}
2904
2905/**
2906 * ring_buffer_lock_reserve - reserve a part of the buffer
2907 * @buffer: the ring buffer to reserve from
2908 * @length: the length of the data to reserve (excluding event header)
2909 *
2910 * Returns a reseverd event on the ring buffer to copy directly to.
2911 * The user of this interface will need to get the body to write into
2912 * and can use the ring_buffer_event_data() interface.
2913 *
2914 * The length is the length of the data needed, not the event length
2915 * which also includes the event header.
2916 *
2917 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2918 * If NULL is returned, then nothing has been allocated or locked.
2919 */
2920struct ring_buffer_event *
2921ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
2922{
2923 struct ring_buffer_per_cpu *cpu_buffer;
2924 struct ring_buffer_event *event;
2925 int cpu;
2926
2927 /* If we are tracing schedule, we don't want to recurse */
2928 preempt_disable_notrace();
2929
2930 if (unlikely(atomic_read(&buffer->record_disabled)))
2931 goto out;
2932
2933 cpu = raw_smp_processor_id();
2934
2935 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
2936 goto out;
2937
2938 cpu_buffer = buffer->buffers[cpu];
2939
2940 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
2941 goto out;
2942
2943 if (unlikely(length > BUF_MAX_DATA_SIZE))
2944 goto out;
2945
2946 if (unlikely(trace_recursive_lock(cpu_buffer)))
2947 goto out;
2948
2949 event = rb_reserve_next_event(buffer, cpu_buffer, length);
2950 if (!event)
2951 goto out_unlock;
2952
2953 return event;
2954
2955 out_unlock:
2956 trace_recursive_unlock(cpu_buffer);
2957 out:
2958 preempt_enable_notrace();
2959 return NULL;
2960}
2961EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
2962
2963/*
2964 * Decrement the entries to the page that an event is on.
2965 * The event does not even need to exist, only the pointer
2966 * to the page it is on. This may only be called before the commit
2967 * takes place.
2968 */
2969static inline void
2970rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2971 struct ring_buffer_event *event)
2972{
2973 unsigned long addr = (unsigned long)event;
2974 struct buffer_page *bpage = cpu_buffer->commit_page;
2975 struct buffer_page *start;
2976
2977 addr &= PAGE_MASK;
2978
2979 /* Do the likely case first */
2980 if (likely(bpage->page == (void *)addr)) {
2981 local_dec(&bpage->entries);
2982 return;
2983 }
2984
2985 /*
2986 * Because the commit page may be on the reader page we
2987 * start with the next page and check the end loop there.
2988 */
2989 rb_inc_page(cpu_buffer, &bpage);
2990 start = bpage;
2991 do {
2992 if (bpage->page == (void *)addr) {
2993 local_dec(&bpage->entries);
2994 return;
2995 }
2996 rb_inc_page(cpu_buffer, &bpage);
2997 } while (bpage != start);
2998
2999 /* commit not part of this buffer?? */
3000 RB_WARN_ON(cpu_buffer, 1);
3001}
3002
3003/**
3004 * ring_buffer_commit_discard - discard an event that has not been committed
3005 * @buffer: the ring buffer
3006 * @event: non committed event to discard
3007 *
3008 * Sometimes an event that is in the ring buffer needs to be ignored.
3009 * This function lets the user discard an event in the ring buffer
3010 * and then that event will not be read later.
3011 *
3012 * This function only works if it is called before the the item has been
3013 * committed. It will try to free the event from the ring buffer
3014 * if another event has not been added behind it.
3015 *
3016 * If another event has been added behind it, it will set the event
3017 * up as discarded, and perform the commit.
3018 *
3019 * If this function is called, do not call ring_buffer_unlock_commit on
3020 * the event.
3021 */
3022void ring_buffer_discard_commit(struct ring_buffer *buffer,
3023 struct ring_buffer_event *event)
3024{
3025 struct ring_buffer_per_cpu *cpu_buffer;
3026 int cpu;
3027
3028 /* The event is discarded regardless */
3029 rb_event_discard(event);
3030
3031 cpu = smp_processor_id();
3032 cpu_buffer = buffer->buffers[cpu];
3033
3034 /*
3035 * This must only be called if the event has not been
3036 * committed yet. Thus we can assume that preemption
3037 * is still disabled.
3038 */
3039 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3040
3041 rb_decrement_entry(cpu_buffer, event);
3042 if (rb_try_to_discard(cpu_buffer, event))
3043 goto out;
3044
3045 /*
3046 * The commit is still visible by the reader, so we
3047 * must still update the timestamp.
3048 */
3049 rb_update_write_stamp(cpu_buffer, event);
3050 out:
3051 rb_end_commit(cpu_buffer);
3052
3053 trace_recursive_unlock(cpu_buffer);
3054
3055 preempt_enable_notrace();
3056
3057}
3058EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3059
3060/**
3061 * ring_buffer_write - write data to the buffer without reserving
3062 * @buffer: The ring buffer to write to.
3063 * @length: The length of the data being written (excluding the event header)
3064 * @data: The data to write to the buffer.
3065 *
3066 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3067 * one function. If you already have the data to write to the buffer, it
3068 * may be easier to simply call this function.
3069 *
3070 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3071 * and not the length of the event which would hold the header.
3072 */
3073int ring_buffer_write(struct ring_buffer *buffer,
3074 unsigned long length,
3075 void *data)
3076{
3077 struct ring_buffer_per_cpu *cpu_buffer;
3078 struct ring_buffer_event *event;
3079 void *body;
3080 int ret = -EBUSY;
3081 int cpu;
3082
3083 preempt_disable_notrace();
3084
3085 if (atomic_read(&buffer->record_disabled))
3086 goto out;
3087
3088 cpu = raw_smp_processor_id();
3089
3090 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3091 goto out;
3092
3093 cpu_buffer = buffer->buffers[cpu];
3094
3095 if (atomic_read(&cpu_buffer->record_disabled))
3096 goto out;
3097
3098 if (length > BUF_MAX_DATA_SIZE)
3099 goto out;
3100
3101 if (unlikely(trace_recursive_lock(cpu_buffer)))
3102 goto out;
3103
3104 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3105 if (!event)
3106 goto out_unlock;
3107
3108 body = rb_event_data(event);
3109
3110 memcpy(body, data, length);
3111
3112 rb_commit(cpu_buffer, event);
3113
3114 rb_wakeups(buffer, cpu_buffer);
3115
3116 ret = 0;
3117
3118 out_unlock:
3119 trace_recursive_unlock(cpu_buffer);
3120
3121 out:
3122 preempt_enable_notrace();
3123
3124 return ret;
3125}
3126EXPORT_SYMBOL_GPL(ring_buffer_write);
3127
3128static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3129{
3130 struct buffer_page *reader = cpu_buffer->reader_page;
3131 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3132 struct buffer_page *commit = cpu_buffer->commit_page;
3133
3134 /* In case of error, head will be NULL */
3135 if (unlikely(!head))
3136 return true;
3137
3138 return reader->read == rb_page_commit(reader) &&
3139 (commit == reader ||
3140 (commit == head &&
3141 head->read == rb_page_commit(commit)));
3142}
3143
3144/**
3145 * ring_buffer_record_disable - stop all writes into the buffer
3146 * @buffer: The ring buffer to stop writes to.
3147 *
3148 * This prevents all writes to the buffer. Any attempt to write
3149 * to the buffer after this will fail and return NULL.
3150 *
3151 * The caller should call synchronize_sched() after this.
3152 */
3153void ring_buffer_record_disable(struct ring_buffer *buffer)
3154{
3155 atomic_inc(&buffer->record_disabled);
3156}
3157EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3158
3159/**
3160 * ring_buffer_record_enable - enable writes to the buffer
3161 * @buffer: The ring buffer to enable writes
3162 *
3163 * Note, multiple disables will need the same number of enables
3164 * to truly enable the writing (much like preempt_disable).
3165 */
3166void ring_buffer_record_enable(struct ring_buffer *buffer)
3167{
3168 atomic_dec(&buffer->record_disabled);
3169}
3170EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3171
3172/**
3173 * ring_buffer_record_off - stop all writes into the buffer
3174 * @buffer: The ring buffer to stop writes to.
3175 *
3176 * This prevents all writes to the buffer. Any attempt to write
3177 * to the buffer after this will fail and return NULL.
3178 *
3179 * This is different than ring_buffer_record_disable() as
3180 * it works like an on/off switch, where as the disable() version
3181 * must be paired with a enable().
3182 */
3183void ring_buffer_record_off(struct ring_buffer *buffer)
3184{
3185 unsigned int rd;
3186 unsigned int new_rd;
3187
3188 do {
3189 rd = atomic_read(&buffer->record_disabled);
3190 new_rd = rd | RB_BUFFER_OFF;
3191 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3192}
3193EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3194
3195/**
3196 * ring_buffer_record_on - restart writes into the buffer
3197 * @buffer: The ring buffer to start writes to.
3198 *
3199 * This enables all writes to the buffer that was disabled by
3200 * ring_buffer_record_off().
3201 *
3202 * This is different than ring_buffer_record_enable() as
3203 * it works like an on/off switch, where as the enable() version
3204 * must be paired with a disable().
3205 */
3206void ring_buffer_record_on(struct ring_buffer *buffer)
3207{
3208 unsigned int rd;
3209 unsigned int new_rd;
3210
3211 do {
3212 rd = atomic_read(&buffer->record_disabled);
3213 new_rd = rd & ~RB_BUFFER_OFF;
3214 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3215}
3216EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3217
3218/**
3219 * ring_buffer_record_is_on - return true if the ring buffer can write
3220 * @buffer: The ring buffer to see if write is enabled
3221 *
3222 * Returns true if the ring buffer is in a state that it accepts writes.
3223 */
3224int ring_buffer_record_is_on(struct ring_buffer *buffer)
3225{
3226 return !atomic_read(&buffer->record_disabled);
3227}
3228
3229/**
3230 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3231 * @buffer: The ring buffer to stop writes to.
3232 * @cpu: The CPU buffer to stop
3233 *
3234 * This prevents all writes to the buffer. Any attempt to write
3235 * to the buffer after this will fail and return NULL.
3236 *
3237 * The caller should call synchronize_sched() after this.
3238 */
3239void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
3240{
3241 struct ring_buffer_per_cpu *cpu_buffer;
3242
3243 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3244 return;
3245
3246 cpu_buffer = buffer->buffers[cpu];
3247 atomic_inc(&cpu_buffer->record_disabled);
3248}
3249EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3250
3251/**
3252 * ring_buffer_record_enable_cpu - enable writes to the buffer
3253 * @buffer: The ring buffer to enable writes
3254 * @cpu: The CPU to enable.
3255 *
3256 * Note, multiple disables will need the same number of enables
3257 * to truly enable the writing (much like preempt_disable).
3258 */
3259void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
3260{
3261 struct ring_buffer_per_cpu *cpu_buffer;
3262
3263 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3264 return;
3265
3266 cpu_buffer = buffer->buffers[cpu];
3267 atomic_dec(&cpu_buffer->record_disabled);
3268}
3269EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3270
3271/*
3272 * The total entries in the ring buffer is the running counter
3273 * of entries entered into the ring buffer, minus the sum of
3274 * the entries read from the ring buffer and the number of
3275 * entries that were overwritten.
3276 */
3277static inline unsigned long
3278rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3279{
3280 return local_read(&cpu_buffer->entries) -
3281 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3282}
3283
3284/**
3285 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3286 * @buffer: The ring buffer
3287 * @cpu: The per CPU buffer to read from.
3288 */
3289u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
3290{
3291 unsigned long flags;
3292 struct ring_buffer_per_cpu *cpu_buffer;
3293 struct buffer_page *bpage;
3294 u64 ret = 0;
3295
3296 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3297 return 0;
3298
3299 cpu_buffer = buffer->buffers[cpu];
3300 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3301 /*
3302 * if the tail is on reader_page, oldest time stamp is on the reader
3303 * page
3304 */
3305 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3306 bpage = cpu_buffer->reader_page;
3307 else
3308 bpage = rb_set_head_page(cpu_buffer);
3309 if (bpage)
3310 ret = bpage->page->time_stamp;
3311 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3312
3313 return ret;
3314}
3315EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3316
3317/**
3318 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3319 * @buffer: The ring buffer
3320 * @cpu: The per CPU buffer to read from.
3321 */
3322unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
3323{
3324 struct ring_buffer_per_cpu *cpu_buffer;
3325 unsigned long ret;
3326
3327 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3328 return 0;
3329
3330 cpu_buffer = buffer->buffers[cpu];
3331 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3332
3333 return ret;
3334}
3335EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3336
3337/**
3338 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3339 * @buffer: The ring buffer
3340 * @cpu: The per CPU buffer to get the entries from.
3341 */
3342unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
3343{
3344 struct ring_buffer_per_cpu *cpu_buffer;
3345
3346 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3347 return 0;
3348
3349 cpu_buffer = buffer->buffers[cpu];
3350
3351 return rb_num_of_entries(cpu_buffer);
3352}
3353EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3354
3355/**
3356 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3357 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3358 * @buffer: The ring buffer
3359 * @cpu: The per CPU buffer to get the number of overruns from
3360 */
3361unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3362{
3363 struct ring_buffer_per_cpu *cpu_buffer;
3364 unsigned long ret;
3365
3366 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3367 return 0;
3368
3369 cpu_buffer = buffer->buffers[cpu];
3370 ret = local_read(&cpu_buffer->overrun);
3371
3372 return ret;
3373}
3374EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3375
3376/**
3377 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
3378 * commits failing due to the buffer wrapping around while there are uncommitted
3379 * events, such as during an interrupt storm.
3380 * @buffer: The ring buffer
3381 * @cpu: The per CPU buffer to get the number of overruns from
3382 */
3383unsigned long
3384ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3385{
3386 struct ring_buffer_per_cpu *cpu_buffer;
3387 unsigned long ret;
3388
3389 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3390 return 0;
3391
3392 cpu_buffer = buffer->buffers[cpu];
3393 ret = local_read(&cpu_buffer->commit_overrun);
3394
3395 return ret;
3396}
3397EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3398
3399/**
3400 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
3401 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
3402 * @buffer: The ring buffer
3403 * @cpu: The per CPU buffer to get the number of overruns from
3404 */
3405unsigned long
3406ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu)
3407{
3408 struct ring_buffer_per_cpu *cpu_buffer;
3409 unsigned long ret;
3410
3411 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3412 return 0;
3413
3414 cpu_buffer = buffer->buffers[cpu];
3415 ret = local_read(&cpu_buffer->dropped_events);
3416
3417 return ret;
3418}
3419EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
3420
3421/**
3422 * ring_buffer_read_events_cpu - get the number of events successfully read
3423 * @buffer: The ring buffer
3424 * @cpu: The per CPU buffer to get the number of events read
3425 */
3426unsigned long
3427ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu)
3428{
3429 struct ring_buffer_per_cpu *cpu_buffer;
3430
3431 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3432 return 0;
3433
3434 cpu_buffer = buffer->buffers[cpu];
3435 return cpu_buffer->read;
3436}
3437EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
3438
3439/**
3440 * ring_buffer_entries - get the number of entries in a buffer
3441 * @buffer: The ring buffer
3442 *
3443 * Returns the total number of entries in the ring buffer
3444 * (all CPU entries)
3445 */
3446unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3447{
3448 struct ring_buffer_per_cpu *cpu_buffer;
3449 unsigned long entries = 0;
3450 int cpu;
3451
3452 /* if you care about this being correct, lock the buffer */
3453 for_each_buffer_cpu(buffer, cpu) {
3454 cpu_buffer = buffer->buffers[cpu];
3455 entries += rb_num_of_entries(cpu_buffer);
3456 }
3457
3458 return entries;
3459}
3460EXPORT_SYMBOL_GPL(ring_buffer_entries);
3461
3462/**
3463 * ring_buffer_overruns - get the number of overruns in buffer
3464 * @buffer: The ring buffer
3465 *
3466 * Returns the total number of overruns in the ring buffer
3467 * (all CPU entries)
3468 */
3469unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3470{
3471 struct ring_buffer_per_cpu *cpu_buffer;
3472 unsigned long overruns = 0;
3473 int cpu;
3474
3475 /* if you care about this being correct, lock the buffer */
3476 for_each_buffer_cpu(buffer, cpu) {
3477 cpu_buffer = buffer->buffers[cpu];
3478 overruns += local_read(&cpu_buffer->overrun);
3479 }
3480
3481 return overruns;
3482}
3483EXPORT_SYMBOL_GPL(ring_buffer_overruns);
3484
3485static void rb_iter_reset(struct ring_buffer_iter *iter)
3486{
3487 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3488
3489 /* Iterator usage is expected to have record disabled */
3490 iter->head_page = cpu_buffer->reader_page;
3491 iter->head = cpu_buffer->reader_page->read;
3492
3493 iter->cache_reader_page = iter->head_page;
3494 iter->cache_read = cpu_buffer->read;
3495
3496 if (iter->head)
3497 iter->read_stamp = cpu_buffer->read_stamp;
3498 else
3499 iter->read_stamp = iter->head_page->page->time_stamp;
3500}
3501
3502/**
3503 * ring_buffer_iter_reset - reset an iterator
3504 * @iter: The iterator to reset
3505 *
3506 * Resets the iterator, so that it will start from the beginning
3507 * again.
3508 */
3509void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3510{
3511 struct ring_buffer_per_cpu *cpu_buffer;
3512 unsigned long flags;
3513
3514 if (!iter)
3515 return;
3516
3517 cpu_buffer = iter->cpu_buffer;
3518
3519 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3520 rb_iter_reset(iter);
3521 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3522}
3523EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
3524
3525/**
3526 * ring_buffer_iter_empty - check if an iterator has no more to read
3527 * @iter: The iterator to check
3528 */
3529int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3530{
3531 struct ring_buffer_per_cpu *cpu_buffer;
3532 struct buffer_page *reader;
3533 struct buffer_page *head_page;
3534 struct buffer_page *commit_page;
3535 unsigned commit;
3536
3537 cpu_buffer = iter->cpu_buffer;
3538
3539 /* Remember, trace recording is off when iterator is in use */
3540 reader = cpu_buffer->reader_page;
3541 head_page = cpu_buffer->head_page;
3542 commit_page = cpu_buffer->commit_page;
3543 commit = rb_page_commit(commit_page);
3544
3545 return ((iter->head_page == commit_page && iter->head == commit) ||
3546 (iter->head_page == reader && commit_page == head_page &&
3547 head_page->read == commit &&
3548 iter->head == rb_page_commit(cpu_buffer->reader_page)));
3549}
3550EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
3551
3552static void
3553rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3554 struct ring_buffer_event *event)
3555{
3556 u64 delta;
3557
3558 switch (event->type_len) {
3559 case RINGBUF_TYPE_PADDING:
3560 return;
3561
3562 case RINGBUF_TYPE_TIME_EXTEND:
3563 delta = ring_buffer_event_time_stamp(event);
3564 cpu_buffer->read_stamp += delta;
3565 return;
3566
3567 case RINGBUF_TYPE_TIME_STAMP:
3568 delta = ring_buffer_event_time_stamp(event);
3569 cpu_buffer->read_stamp = delta;
3570 return;
3571
3572 case RINGBUF_TYPE_DATA:
3573 cpu_buffer->read_stamp += event->time_delta;
3574 return;
3575
3576 default:
3577 BUG();
3578 }
3579 return;
3580}
3581
3582static void
3583rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3584 struct ring_buffer_event *event)
3585{
3586 u64 delta;
3587
3588 switch (event->type_len) {
3589 case RINGBUF_TYPE_PADDING:
3590 return;
3591
3592 case RINGBUF_TYPE_TIME_EXTEND:
3593 delta = ring_buffer_event_time_stamp(event);
3594 iter->read_stamp += delta;
3595 return;
3596
3597 case RINGBUF_TYPE_TIME_STAMP:
3598 delta = ring_buffer_event_time_stamp(event);
3599 iter->read_stamp = delta;
3600 return;
3601
3602 case RINGBUF_TYPE_DATA:
3603 iter->read_stamp += event->time_delta;
3604 return;
3605
3606 default:
3607 BUG();
3608 }
3609 return;
3610}
3611
3612static struct buffer_page *
3613rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
3614{
3615 struct buffer_page *reader = NULL;
3616 unsigned long overwrite;
3617 unsigned long flags;
3618 int nr_loops = 0;
3619 int ret;
3620
3621 local_irq_save(flags);
3622 arch_spin_lock(&cpu_buffer->lock);
3623
3624 again:
3625 /*
3626 * This should normally only loop twice. But because the
3627 * start of the reader inserts an empty page, it causes
3628 * a case where we will loop three times. There should be no
3629 * reason to loop four times (that I know of).
3630 */
3631 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
3632 reader = NULL;
3633 goto out;
3634 }
3635
3636 reader = cpu_buffer->reader_page;
3637
3638 /* If there's more to read, return this page */
3639 if (cpu_buffer->reader_page->read < rb_page_size(reader))
3640 goto out;
3641
3642 /* Never should we have an index greater than the size */
3643 if (RB_WARN_ON(cpu_buffer,
3644 cpu_buffer->reader_page->read > rb_page_size(reader)))
3645 goto out;
3646
3647 /* check if we caught up to the tail */
3648 reader = NULL;
3649 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
3650 goto out;
3651
3652 /* Don't bother swapping if the ring buffer is empty */
3653 if (rb_num_of_entries(cpu_buffer) == 0)
3654 goto out;
3655
3656 /*
3657 * Reset the reader page to size zero.
3658 */
3659 local_set(&cpu_buffer->reader_page->write, 0);
3660 local_set(&cpu_buffer->reader_page->entries, 0);
3661 local_set(&cpu_buffer->reader_page->page->commit, 0);
3662 cpu_buffer->reader_page->real_end = 0;
3663
3664 spin:
3665 /*
3666 * Splice the empty reader page into the list around the head.
3667 */
3668 reader = rb_set_head_page(cpu_buffer);
3669 if (!reader)
3670 goto out;
3671 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
3672 cpu_buffer->reader_page->list.prev = reader->list.prev;
3673
3674 /*
3675 * cpu_buffer->pages just needs to point to the buffer, it
3676 * has no specific buffer page to point to. Lets move it out
3677 * of our way so we don't accidentally swap it.
3678 */
3679 cpu_buffer->pages = reader->list.prev;
3680
3681 /* The reader page will be pointing to the new head */
3682 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
3683
3684 /*
3685 * We want to make sure we read the overruns after we set up our
3686 * pointers to the next object. The writer side does a
3687 * cmpxchg to cross pages which acts as the mb on the writer
3688 * side. Note, the reader will constantly fail the swap
3689 * while the writer is updating the pointers, so this
3690 * guarantees that the overwrite recorded here is the one we
3691 * want to compare with the last_overrun.
3692 */
3693 smp_mb();
3694 overwrite = local_read(&(cpu_buffer->overrun));
3695
3696 /*
3697 * Here's the tricky part.
3698 *
3699 * We need to move the pointer past the header page.
3700 * But we can only do that if a writer is not currently
3701 * moving it. The page before the header page has the
3702 * flag bit '1' set if it is pointing to the page we want.
3703 * but if the writer is in the process of moving it
3704 * than it will be '2' or already moved '0'.
3705 */
3706
3707 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3708
3709 /*
3710 * If we did not convert it, then we must try again.
3711 */
3712 if (!ret)
3713 goto spin;
3714
3715 /*
3716 * Yeah! We succeeded in replacing the page.
3717 *
3718 * Now make the new head point back to the reader page.
3719 */
3720 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
3721 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
3722
3723 /* Finally update the reader page to the new head */
3724 cpu_buffer->reader_page = reader;
3725 cpu_buffer->reader_page->read = 0;
3726
3727 if (overwrite != cpu_buffer->last_overrun) {
3728 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3729 cpu_buffer->last_overrun = overwrite;
3730 }
3731
3732 goto again;
3733
3734 out:
3735 /* Update the read_stamp on the first event */
3736 if (reader && reader->read == 0)
3737 cpu_buffer->read_stamp = reader->page->time_stamp;
3738
3739 arch_spin_unlock(&cpu_buffer->lock);
3740 local_irq_restore(flags);
3741
3742 return reader;
3743}
3744
3745static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3746{
3747 struct ring_buffer_event *event;
3748 struct buffer_page *reader;
3749 unsigned length;
3750
3751 reader = rb_get_reader_page(cpu_buffer);
3752
3753 /* This function should not be called when buffer is empty */
3754 if (RB_WARN_ON(cpu_buffer, !reader))
3755 return;
3756
3757 event = rb_reader_event(cpu_buffer);
3758
3759 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
3760 cpu_buffer->read++;
3761
3762 rb_update_read_stamp(cpu_buffer, event);
3763
3764 length = rb_event_length(event);
3765 cpu_buffer->reader_page->read += length;
3766}
3767
3768static void rb_advance_iter(struct ring_buffer_iter *iter)
3769{
3770 struct ring_buffer_per_cpu *cpu_buffer;
3771 struct ring_buffer_event *event;
3772 unsigned length;
3773
3774 cpu_buffer = iter->cpu_buffer;
3775
3776 /*
3777 * Check if we are at the end of the buffer.
3778 */
3779 if (iter->head >= rb_page_size(iter->head_page)) {
3780 /* discarded commits can make the page empty */
3781 if (iter->head_page == cpu_buffer->commit_page)
3782 return;
3783 rb_inc_iter(iter);
3784 return;
3785 }
3786
3787 event = rb_iter_head_event(iter);
3788
3789 length = rb_event_length(event);
3790
3791 /*
3792 * This should not be called to advance the header if we are
3793 * at the tail of the buffer.
3794 */
3795 if (RB_WARN_ON(cpu_buffer,
3796 (iter->head_page == cpu_buffer->commit_page) &&
3797 (iter->head + length > rb_commit_index(cpu_buffer))))
3798 return;
3799
3800 rb_update_iter_read_stamp(iter, event);
3801
3802 iter->head += length;
3803
3804 /* check for end of page padding */
3805 if ((iter->head >= rb_page_size(iter->head_page)) &&
3806 (iter->head_page != cpu_buffer->commit_page))
3807 rb_inc_iter(iter);
3808}
3809
3810static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3811{
3812 return cpu_buffer->lost_events;
3813}
3814
3815static struct ring_buffer_event *
3816rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3817 unsigned long *lost_events)
3818{
3819 struct ring_buffer_event *event;
3820 struct buffer_page *reader;
3821 int nr_loops = 0;
3822
3823 if (ts)
3824 *ts = 0;
3825 again:
3826 /*
3827 * We repeat when a time extend is encountered.
3828 * Since the time extend is always attached to a data event,
3829 * we should never loop more than once.
3830 * (We never hit the following condition more than twice).
3831 */
3832 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
3833 return NULL;
3834
3835 reader = rb_get_reader_page(cpu_buffer);
3836 if (!reader)
3837 return NULL;
3838
3839 event = rb_reader_event(cpu_buffer);
3840
3841 switch (event->type_len) {
3842 case RINGBUF_TYPE_PADDING:
3843 if (rb_null_event(event))
3844 RB_WARN_ON(cpu_buffer, 1);
3845 /*
3846 * Because the writer could be discarding every
3847 * event it creates (which would probably be bad)
3848 * if we were to go back to "again" then we may never
3849 * catch up, and will trigger the warn on, or lock
3850 * the box. Return the padding, and we will release
3851 * the current locks, and try again.
3852 */
3853 return event;
3854
3855 case RINGBUF_TYPE_TIME_EXTEND:
3856 /* Internal data, OK to advance */
3857 rb_advance_reader(cpu_buffer);
3858 goto again;
3859
3860 case RINGBUF_TYPE_TIME_STAMP:
3861 if (ts) {
3862 *ts = ring_buffer_event_time_stamp(event);
3863 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3864 cpu_buffer->cpu, ts);
3865 }
3866 /* Internal data, OK to advance */
3867 rb_advance_reader(cpu_buffer);
3868 goto again;
3869
3870 case RINGBUF_TYPE_DATA:
3871 if (ts && !(*ts)) {
3872 *ts = cpu_buffer->read_stamp + event->time_delta;
3873 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3874 cpu_buffer->cpu, ts);
3875 }
3876 if (lost_events)
3877 *lost_events = rb_lost_events(cpu_buffer);
3878 return event;
3879
3880 default:
3881 BUG();
3882 }
3883
3884 return NULL;
3885}
3886EXPORT_SYMBOL_GPL(ring_buffer_peek);
3887
3888static struct ring_buffer_event *
3889rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3890{
3891 struct ring_buffer *buffer;
3892 struct ring_buffer_per_cpu *cpu_buffer;
3893 struct ring_buffer_event *event;
3894 int nr_loops = 0;
3895
3896 if (ts)
3897 *ts = 0;
3898
3899 cpu_buffer = iter->cpu_buffer;
3900 buffer = cpu_buffer->buffer;
3901
3902 /*
3903 * Check if someone performed a consuming read to
3904 * the buffer. A consuming read invalidates the iterator
3905 * and we need to reset the iterator in this case.
3906 */
3907 if (unlikely(iter->cache_read != cpu_buffer->read ||
3908 iter->cache_reader_page != cpu_buffer->reader_page))
3909 rb_iter_reset(iter);
3910
3911 again:
3912 if (ring_buffer_iter_empty(iter))
3913 return NULL;
3914
3915 /*
3916 * We repeat when a time extend is encountered or we hit
3917 * the end of the page. Since the time extend is always attached
3918 * to a data event, we should never loop more than three times.
3919 * Once for going to next page, once on time extend, and
3920 * finally once to get the event.
3921 * (We never hit the following condition more than thrice).
3922 */
3923 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3))
3924 return NULL;
3925
3926 if (rb_per_cpu_empty(cpu_buffer))
3927 return NULL;
3928
3929 if (iter->head >= rb_page_size(iter->head_page)) {
3930 rb_inc_iter(iter);
3931 goto again;
3932 }
3933
3934 event = rb_iter_head_event(iter);
3935
3936 switch (event->type_len) {
3937 case RINGBUF_TYPE_PADDING:
3938 if (rb_null_event(event)) {
3939 rb_inc_iter(iter);
3940 goto again;
3941 }
3942 rb_advance_iter(iter);
3943 return event;
3944
3945 case RINGBUF_TYPE_TIME_EXTEND:
3946 /* Internal data, OK to advance */
3947 rb_advance_iter(iter);
3948 goto again;
3949
3950 case RINGBUF_TYPE_TIME_STAMP:
3951 if (ts) {
3952 *ts = ring_buffer_event_time_stamp(event);
3953 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
3954 cpu_buffer->cpu, ts);
3955 }
3956 /* Internal data, OK to advance */
3957 rb_advance_iter(iter);
3958 goto again;
3959
3960 case RINGBUF_TYPE_DATA:
3961 if (ts && !(*ts)) {
3962 *ts = iter->read_stamp + event->time_delta;
3963 ring_buffer_normalize_time_stamp(buffer,
3964 cpu_buffer->cpu, ts);
3965 }
3966 return event;
3967
3968 default:
3969 BUG();
3970 }
3971
3972 return NULL;
3973}
3974EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
3975
3976static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
3977{
3978 if (likely(!in_nmi())) {
3979 raw_spin_lock(&cpu_buffer->reader_lock);
3980 return true;
3981 }
3982
3983 /*
3984 * If an NMI die dumps out the content of the ring buffer
3985 * trylock must be used to prevent a deadlock if the NMI
3986 * preempted a task that holds the ring buffer locks. If
3987 * we get the lock then all is fine, if not, then continue
3988 * to do the read, but this can corrupt the ring buffer,
3989 * so it must be permanently disabled from future writes.
3990 * Reading from NMI is a oneshot deal.
3991 */
3992 if (raw_spin_trylock(&cpu_buffer->reader_lock))
3993 return true;
3994
3995 /* Continue without locking, but disable the ring buffer */
3996 atomic_inc(&cpu_buffer->record_disabled);
3997 return false;
3998}
3999
4000static inline void
4001rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4002{
4003 if (likely(locked))
4004 raw_spin_unlock(&cpu_buffer->reader_lock);
4005 return;
4006}
4007
4008/**
4009 * ring_buffer_peek - peek at the next event to be read
4010 * @buffer: The ring buffer to read
4011 * @cpu: The cpu to peak at
4012 * @ts: The timestamp counter of this event.
4013 * @lost_events: a variable to store if events were lost (may be NULL)
4014 *
4015 * This will return the event that will be read next, but does
4016 * not consume the data.
4017 */
4018struct ring_buffer_event *
4019ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
4020 unsigned long *lost_events)
4021{
4022 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4023 struct ring_buffer_event *event;
4024 unsigned long flags;
4025 bool dolock;
4026
4027 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4028 return NULL;
4029
4030 again:
4031 local_irq_save(flags);
4032 dolock = rb_reader_lock(cpu_buffer);
4033 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4034 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4035 rb_advance_reader(cpu_buffer);
4036 rb_reader_unlock(cpu_buffer, dolock);
4037 local_irq_restore(flags);
4038
4039 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4040 goto again;
4041
4042 return event;
4043}
4044
4045/**
4046 * ring_buffer_iter_peek - peek at the next event to be read
4047 * @iter: The ring buffer iterator
4048 * @ts: The timestamp counter of this event.
4049 *
4050 * This will return the event that will be read next, but does
4051 * not increment the iterator.
4052 */
4053struct ring_buffer_event *
4054ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4055{
4056 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4057 struct ring_buffer_event *event;
4058 unsigned long flags;
4059
4060 again:
4061 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4062 event = rb_iter_peek(iter, ts);
4063 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4064
4065 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4066 goto again;
4067
4068 return event;
4069}
4070
4071/**
4072 * ring_buffer_consume - return an event and consume it
4073 * @buffer: The ring buffer to get the next event from
4074 * @cpu: the cpu to read the buffer from
4075 * @ts: a variable to store the timestamp (may be NULL)
4076 * @lost_events: a variable to store if events were lost (may be NULL)
4077 *
4078 * Returns the next event in the ring buffer, and that event is consumed.
4079 * Meaning, that sequential reads will keep returning a different event,
4080 * and eventually empty the ring buffer if the producer is slower.
4081 */
4082struct ring_buffer_event *
4083ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
4084 unsigned long *lost_events)
4085{
4086 struct ring_buffer_per_cpu *cpu_buffer;
4087 struct ring_buffer_event *event = NULL;
4088 unsigned long flags;
4089 bool dolock;
4090
4091 again:
4092 /* might be called in atomic */
4093 preempt_disable();
4094
4095 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4096 goto out;
4097
4098 cpu_buffer = buffer->buffers[cpu];
4099 local_irq_save(flags);
4100 dolock = rb_reader_lock(cpu_buffer);
4101
4102 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4103 if (event) {
4104 cpu_buffer->lost_events = 0;
4105 rb_advance_reader(cpu_buffer);
4106 }
4107
4108 rb_reader_unlock(cpu_buffer, dolock);
4109 local_irq_restore(flags);
4110
4111 out:
4112 preempt_enable();
4113
4114 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4115 goto again;
4116
4117 return event;
4118}
4119EXPORT_SYMBOL_GPL(ring_buffer_consume);
4120
4121/**
4122 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4123 * @buffer: The ring buffer to read from
4124 * @cpu: The cpu buffer to iterate over
4125 *
4126 * This performs the initial preparations necessary to iterate
4127 * through the buffer. Memory is allocated, buffer recording
4128 * is disabled, and the iterator pointer is returned to the caller.
4129 *
4130 * Disabling buffer recordng prevents the reading from being
4131 * corrupted. This is not a consuming read, so a producer is not
4132 * expected.
4133 *
4134 * After a sequence of ring_buffer_read_prepare calls, the user is
4135 * expected to make at least one call to ring_buffer_read_prepare_sync.
4136 * Afterwards, ring_buffer_read_start is invoked to get things going
4137 * for real.
4138 *
4139 * This overall must be paired with ring_buffer_read_finish.
4140 */
4141struct ring_buffer_iter *
4142ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
4143{
4144 struct ring_buffer_per_cpu *cpu_buffer;
4145 struct ring_buffer_iter *iter;
4146
4147 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4148 return NULL;
4149
4150 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
4151 if (!iter)
4152 return NULL;
4153
4154 cpu_buffer = buffer->buffers[cpu];
4155
4156 iter->cpu_buffer = cpu_buffer;
4157
4158 atomic_inc(&buffer->resize_disabled);
4159 atomic_inc(&cpu_buffer->record_disabled);
4160
4161 return iter;
4162}
4163EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4164
4165/**
4166 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4167 *
4168 * All previously invoked ring_buffer_read_prepare calls to prepare
4169 * iterators will be synchronized. Afterwards, read_buffer_read_start
4170 * calls on those iterators are allowed.
4171 */
4172void
4173ring_buffer_read_prepare_sync(void)
4174{
4175 synchronize_sched();
4176}
4177EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4178
4179/**
4180 * ring_buffer_read_start - start a non consuming read of the buffer
4181 * @iter: The iterator returned by ring_buffer_read_prepare
4182 *
4183 * This finalizes the startup of an iteration through the buffer.
4184 * The iterator comes from a call to ring_buffer_read_prepare and
4185 * an intervening ring_buffer_read_prepare_sync must have been
4186 * performed.
4187 *
4188 * Must be paired with ring_buffer_read_finish.
4189 */
4190void
4191ring_buffer_read_start(struct ring_buffer_iter *iter)
4192{
4193 struct ring_buffer_per_cpu *cpu_buffer;
4194 unsigned long flags;
4195
4196 if (!iter)
4197 return;
4198
4199 cpu_buffer = iter->cpu_buffer;
4200
4201 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4202 arch_spin_lock(&cpu_buffer->lock);
4203 rb_iter_reset(iter);
4204 arch_spin_unlock(&cpu_buffer->lock);
4205 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4206}
4207EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4208
4209/**
4210 * ring_buffer_read_finish - finish reading the iterator of the buffer
4211 * @iter: The iterator retrieved by ring_buffer_start
4212 *
4213 * This re-enables the recording to the buffer, and frees the
4214 * iterator.
4215 */
4216void
4217ring_buffer_read_finish(struct ring_buffer_iter *iter)
4218{
4219 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4220 unsigned long flags;
4221
4222 /*
4223 * Ring buffer is disabled from recording, here's a good place
4224 * to check the integrity of the ring buffer.
4225 * Must prevent readers from trying to read, as the check
4226 * clears the HEAD page and readers require it.
4227 */
4228 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4229 rb_check_pages(cpu_buffer);
4230 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4231
4232 atomic_dec(&cpu_buffer->record_disabled);
4233 atomic_dec(&cpu_buffer->buffer->resize_disabled);
4234 kfree(iter);
4235}
4236EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4237
4238/**
4239 * ring_buffer_read - read the next item in the ring buffer by the iterator
4240 * @iter: The ring buffer iterator
4241 * @ts: The time stamp of the event read.
4242 *
4243 * This reads the next event in the ring buffer and increments the iterator.
4244 */
4245struct ring_buffer_event *
4246ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
4247{
4248 struct ring_buffer_event *event;
4249 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4250 unsigned long flags;
4251
4252 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4253 again:
4254 event = rb_iter_peek(iter, ts);
4255 if (!event)
4256 goto out;
4257
4258 if (event->type_len == RINGBUF_TYPE_PADDING)
4259 goto again;
4260
4261 rb_advance_iter(iter);
4262 out:
4263 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4264
4265 return event;
4266}
4267EXPORT_SYMBOL_GPL(ring_buffer_read);
4268
4269/**
4270 * ring_buffer_size - return the size of the ring buffer (in bytes)
4271 * @buffer: The ring buffer.
4272 */
4273unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
4274{
4275 /*
4276 * Earlier, this method returned
4277 * BUF_PAGE_SIZE * buffer->nr_pages
4278 * Since the nr_pages field is now removed, we have converted this to
4279 * return the per cpu buffer value.
4280 */
4281 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4282 return 0;
4283
4284 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4285}
4286EXPORT_SYMBOL_GPL(ring_buffer_size);
4287
4288static void
4289rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4290{
4291 rb_head_page_deactivate(cpu_buffer);
4292
4293 cpu_buffer->head_page
4294 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4295 local_set(&cpu_buffer->head_page->write, 0);
4296 local_set(&cpu_buffer->head_page->entries, 0);
4297 local_set(&cpu_buffer->head_page->page->commit, 0);
4298
4299 cpu_buffer->head_page->read = 0;
4300
4301 cpu_buffer->tail_page = cpu_buffer->head_page;
4302 cpu_buffer->commit_page = cpu_buffer->head_page;
4303
4304 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4305 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4306 local_set(&cpu_buffer->reader_page->write, 0);
4307 local_set(&cpu_buffer->reader_page->entries, 0);
4308 local_set(&cpu_buffer->reader_page->page->commit, 0);
4309 cpu_buffer->reader_page->read = 0;
4310
4311 local_set(&cpu_buffer->entries_bytes, 0);
4312 local_set(&cpu_buffer->overrun, 0);
4313 local_set(&cpu_buffer->commit_overrun, 0);
4314 local_set(&cpu_buffer->dropped_events, 0);
4315 local_set(&cpu_buffer->entries, 0);
4316 local_set(&cpu_buffer->committing, 0);
4317 local_set(&cpu_buffer->commits, 0);
4318 cpu_buffer->read = 0;
4319 cpu_buffer->read_bytes = 0;
4320
4321 cpu_buffer->write_stamp = 0;
4322 cpu_buffer->read_stamp = 0;
4323
4324 cpu_buffer->lost_events = 0;
4325 cpu_buffer->last_overrun = 0;
4326
4327 rb_head_page_activate(cpu_buffer);
4328}
4329
4330/**
4331 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
4332 * @buffer: The ring buffer to reset a per cpu buffer of
4333 * @cpu: The CPU buffer to be reset
4334 */
4335void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
4336{
4337 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4338 unsigned long flags;
4339
4340 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4341 return;
4342
4343 atomic_inc(&buffer->resize_disabled);
4344 atomic_inc(&cpu_buffer->record_disabled);
4345
4346 /* Make sure all commits have finished */
4347 synchronize_sched();
4348
4349 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4350
4351 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
4352 goto out;
4353
4354 arch_spin_lock(&cpu_buffer->lock);
4355
4356 rb_reset_cpu(cpu_buffer);
4357
4358 arch_spin_unlock(&cpu_buffer->lock);
4359
4360 out:
4361 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4362
4363 atomic_dec(&cpu_buffer->record_disabled);
4364 atomic_dec(&buffer->resize_disabled);
4365}
4366EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
4367
4368/**
4369 * ring_buffer_reset - reset a ring buffer
4370 * @buffer: The ring buffer to reset all cpu buffers
4371 */
4372void ring_buffer_reset(struct ring_buffer *buffer)
4373{
4374 int cpu;
4375
4376 for_each_buffer_cpu(buffer, cpu)
4377 ring_buffer_reset_cpu(buffer, cpu);
4378}
4379EXPORT_SYMBOL_GPL(ring_buffer_reset);
4380
4381/**
4382 * rind_buffer_empty - is the ring buffer empty?
4383 * @buffer: The ring buffer to test
4384 */
4385bool ring_buffer_empty(struct ring_buffer *buffer)
4386{
4387 struct ring_buffer_per_cpu *cpu_buffer;
4388 unsigned long flags;
4389 bool dolock;
4390 int cpu;
4391 int ret;
4392
4393 /* yes this is racy, but if you don't like the race, lock the buffer */
4394 for_each_buffer_cpu(buffer, cpu) {
4395 cpu_buffer = buffer->buffers[cpu];
4396 local_irq_save(flags);
4397 dolock = rb_reader_lock(cpu_buffer);
4398 ret = rb_per_cpu_empty(cpu_buffer);
4399 rb_reader_unlock(cpu_buffer, dolock);
4400 local_irq_restore(flags);
4401
4402 if (!ret)
4403 return false;
4404 }
4405
4406 return true;
4407}
4408EXPORT_SYMBOL_GPL(ring_buffer_empty);
4409
4410/**
4411 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
4412 * @buffer: The ring buffer
4413 * @cpu: The CPU buffer to test
4414 */
4415bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
4416{
4417 struct ring_buffer_per_cpu *cpu_buffer;
4418 unsigned long flags;
4419 bool dolock;
4420 int ret;
4421
4422 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4423 return true;
4424
4425 cpu_buffer = buffer->buffers[cpu];
4426 local_irq_save(flags);
4427 dolock = rb_reader_lock(cpu_buffer);
4428 ret = rb_per_cpu_empty(cpu_buffer);
4429 rb_reader_unlock(cpu_buffer, dolock);
4430 local_irq_restore(flags);
4431
4432 return ret;
4433}
4434EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
4435
4436#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
4437/**
4438 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4439 * @buffer_a: One buffer to swap with
4440 * @buffer_b: The other buffer to swap with
4441 *
4442 * This function is useful for tracers that want to take a "snapshot"
4443 * of a CPU buffer and has another back up buffer lying around.
4444 * it is expected that the tracer handles the cpu buffer not being
4445 * used at the moment.
4446 */
4447int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4448 struct ring_buffer *buffer_b, int cpu)
4449{
4450 struct ring_buffer_per_cpu *cpu_buffer_a;
4451 struct ring_buffer_per_cpu *cpu_buffer_b;
4452 int ret = -EINVAL;
4453
4454 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4455 !cpumask_test_cpu(cpu, buffer_b->cpumask))
4456 goto out;
4457
4458 cpu_buffer_a = buffer_a->buffers[cpu];
4459 cpu_buffer_b = buffer_b->buffers[cpu];
4460
4461 /* At least make sure the two buffers are somewhat the same */
4462 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
4463 goto out;
4464
4465 ret = -EAGAIN;
4466
4467 if (atomic_read(&buffer_a->record_disabled))
4468 goto out;
4469
4470 if (atomic_read(&buffer_b->record_disabled))
4471 goto out;
4472
4473 if (atomic_read(&cpu_buffer_a->record_disabled))
4474 goto out;
4475
4476 if (atomic_read(&cpu_buffer_b->record_disabled))
4477 goto out;
4478
4479 /*
4480 * We can't do a synchronize_sched here because this
4481 * function can be called in atomic context.
4482 * Normally this will be called from the same CPU as cpu.
4483 * If not it's up to the caller to protect this.
4484 */
4485 atomic_inc(&cpu_buffer_a->record_disabled);
4486 atomic_inc(&cpu_buffer_b->record_disabled);
4487
4488 ret = -EBUSY;
4489 if (local_read(&cpu_buffer_a->committing))
4490 goto out_dec;
4491 if (local_read(&cpu_buffer_b->committing))
4492 goto out_dec;
4493
4494 buffer_a->buffers[cpu] = cpu_buffer_b;
4495 buffer_b->buffers[cpu] = cpu_buffer_a;
4496
4497 cpu_buffer_b->buffer = buffer_a;
4498 cpu_buffer_a->buffer = buffer_b;
4499
4500 ret = 0;
4501
4502out_dec:
4503 atomic_dec(&cpu_buffer_a->record_disabled);
4504 atomic_dec(&cpu_buffer_b->record_disabled);
4505out:
4506 return ret;
4507}
4508EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
4509#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
4510
4511/**
4512 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4513 * @buffer: the buffer to allocate for.
4514 * @cpu: the cpu buffer to allocate.
4515 *
4516 * This function is used in conjunction with ring_buffer_read_page.
4517 * When reading a full page from the ring buffer, these functions
4518 * can be used to speed up the process. The calling function should
4519 * allocate a few pages first with this function. Then when it
4520 * needs to get pages from the ring buffer, it passes the result
4521 * of this function into ring_buffer_read_page, which will swap
4522 * the page that was allocated, with the read page of the buffer.
4523 *
4524 * Returns:
4525 * The page allocated, or ERR_PTR
4526 */
4527void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
4528{
4529 struct ring_buffer_per_cpu *cpu_buffer;
4530 struct buffer_data_page *bpage = NULL;
4531 unsigned long flags;
4532 struct page *page;
4533
4534 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4535 return ERR_PTR(-ENODEV);
4536
4537 cpu_buffer = buffer->buffers[cpu];
4538 local_irq_save(flags);
4539 arch_spin_lock(&cpu_buffer->lock);
4540
4541 if (cpu_buffer->free_page) {
4542 bpage = cpu_buffer->free_page;
4543 cpu_buffer->free_page = NULL;
4544 }
4545
4546 arch_spin_unlock(&cpu_buffer->lock);
4547 local_irq_restore(flags);
4548
4549 if (bpage)
4550 goto out;
4551
4552 page = alloc_pages_node(cpu_to_node(cpu),
4553 GFP_KERNEL | __GFP_NORETRY, 0);
4554 if (!page)
4555 return ERR_PTR(-ENOMEM);
4556
4557 bpage = page_address(page);
4558
4559 out:
4560 rb_init_page(bpage);
4561
4562 return bpage;
4563}
4564EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
4565
4566/**
4567 * ring_buffer_free_read_page - free an allocated read page
4568 * @buffer: the buffer the page was allocate for
4569 * @cpu: the cpu buffer the page came from
4570 * @data: the page to free
4571 *
4572 * Free a page allocated from ring_buffer_alloc_read_page.
4573 */
4574void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data)
4575{
4576 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4577 struct buffer_data_page *bpage = data;
4578 struct page *page = virt_to_page(bpage);
4579 unsigned long flags;
4580
4581 /* If the page is still in use someplace else, we can't reuse it */
4582 if (page_ref_count(page) > 1)
4583 goto out;
4584
4585 local_irq_save(flags);
4586 arch_spin_lock(&cpu_buffer->lock);
4587
4588 if (!cpu_buffer->free_page) {
4589 cpu_buffer->free_page = bpage;
4590 bpage = NULL;
4591 }
4592
4593 arch_spin_unlock(&cpu_buffer->lock);
4594 local_irq_restore(flags);
4595
4596 out:
4597 free_page((unsigned long)bpage);
4598}
4599EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
4600
4601/**
4602 * ring_buffer_read_page - extract a page from the ring buffer
4603 * @buffer: buffer to extract from
4604 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
4605 * @len: amount to extract
4606 * @cpu: the cpu of the buffer to extract
4607 * @full: should the extraction only happen when the page is full.
4608 *
4609 * This function will pull out a page from the ring buffer and consume it.
4610 * @data_page must be the address of the variable that was returned
4611 * from ring_buffer_alloc_read_page. This is because the page might be used
4612 * to swap with a page in the ring buffer.
4613 *
4614 * for example:
4615 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
4616 * if (IS_ERR(rpage))
4617 * return PTR_ERR(rpage);
4618 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
4619 * if (ret >= 0)
4620 * process_page(rpage, ret);
4621 *
4622 * When @full is set, the function will not return true unless
4623 * the writer is off the reader page.
4624 *
4625 * Note: it is up to the calling functions to handle sleeps and wakeups.
4626 * The ring buffer can be used anywhere in the kernel and can not
4627 * blindly call wake_up. The layer that uses the ring buffer must be
4628 * responsible for that.
4629 *
4630 * Returns:
4631 * >=0 if data has been transferred, returns the offset of consumed data.
4632 * <0 if no data has been transferred.
4633 */
4634int ring_buffer_read_page(struct ring_buffer *buffer,
4635 void **data_page, size_t len, int cpu, int full)
4636{
4637 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4638 struct ring_buffer_event *event;
4639 struct buffer_data_page *bpage;
4640 struct buffer_page *reader;
4641 unsigned long missed_events;
4642 unsigned long flags;
4643 unsigned int commit;
4644 unsigned int read;
4645 u64 save_timestamp;
4646 int ret = -1;
4647
4648 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4649 goto out;
4650
4651 /*
4652 * If len is not big enough to hold the page header, then
4653 * we can not copy anything.
4654 */
4655 if (len <= BUF_PAGE_HDR_SIZE)
4656 goto out;
4657
4658 len -= BUF_PAGE_HDR_SIZE;
4659
4660 if (!data_page)
4661 goto out;
4662
4663 bpage = *data_page;
4664 if (!bpage)
4665 goto out;
4666
4667 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4668
4669 reader = rb_get_reader_page(cpu_buffer);
4670 if (!reader)
4671 goto out_unlock;
4672
4673 event = rb_reader_event(cpu_buffer);
4674
4675 read = reader->read;
4676 commit = rb_page_commit(reader);
4677
4678 /* Check if any events were dropped */
4679 missed_events = cpu_buffer->lost_events;
4680
4681 /*
4682 * If this page has been partially read or
4683 * if len is not big enough to read the rest of the page or
4684 * a writer is still on the page, then
4685 * we must copy the data from the page to the buffer.
4686 * Otherwise, we can simply swap the page with the one passed in.
4687 */
4688 if (read || (len < (commit - read)) ||
4689 cpu_buffer->reader_page == cpu_buffer->commit_page) {
4690 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
4691 unsigned int rpos = read;
4692 unsigned int pos = 0;
4693 unsigned int size;
4694
4695 if (full)
4696 goto out_unlock;
4697
4698 if (len > (commit - read))
4699 len = (commit - read);
4700
4701 /* Always keep the time extend and data together */
4702 size = rb_event_ts_length(event);
4703
4704 if (len < size)
4705 goto out_unlock;
4706
4707 /* save the current timestamp, since the user will need it */
4708 save_timestamp = cpu_buffer->read_stamp;
4709
4710 /* Need to copy one event at a time */
4711 do {
4712 /* We need the size of one event, because
4713 * rb_advance_reader only advances by one event,
4714 * whereas rb_event_ts_length may include the size of
4715 * one or two events.
4716 * We have already ensured there's enough space if this
4717 * is a time extend. */
4718 size = rb_event_length(event);
4719 memcpy(bpage->data + pos, rpage->data + rpos, size);
4720
4721 len -= size;
4722
4723 rb_advance_reader(cpu_buffer);
4724 rpos = reader->read;
4725 pos += size;
4726
4727 if (rpos >= commit)
4728 break;
4729
4730 event = rb_reader_event(cpu_buffer);
4731 /* Always keep the time extend and data together */
4732 size = rb_event_ts_length(event);
4733 } while (len >= size);
4734
4735 /* update bpage */
4736 local_set(&bpage->commit, pos);
4737 bpage->time_stamp = save_timestamp;
4738
4739 /* we copied everything to the beginning */
4740 read = 0;
4741 } else {
4742 /* update the entry counter */
4743 cpu_buffer->read += rb_page_entries(reader);
4744 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
4745
4746 /* swap the pages */
4747 rb_init_page(bpage);
4748 bpage = reader->page;
4749 reader->page = *data_page;
4750 local_set(&reader->write, 0);
4751 local_set(&reader->entries, 0);
4752 reader->read = 0;
4753 *data_page = bpage;
4754
4755 /*
4756 * Use the real_end for the data size,
4757 * This gives us a chance to store the lost events
4758 * on the page.
4759 */
4760 if (reader->real_end)
4761 local_set(&bpage->commit, reader->real_end);
4762 }
4763 ret = read;
4764
4765 cpu_buffer->lost_events = 0;
4766
4767 commit = local_read(&bpage->commit);
4768 /*
4769 * Set a flag in the commit field if we lost events
4770 */
4771 if (missed_events) {
4772 /* If there is room at the end of the page to save the
4773 * missed events, then record it there.
4774 */
4775 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4776 memcpy(&bpage->data[commit], &missed_events,
4777 sizeof(missed_events));
4778 local_add(RB_MISSED_STORED, &bpage->commit);
4779 commit += sizeof(missed_events);
4780 }
4781 local_add(RB_MISSED_EVENTS, &bpage->commit);
4782 }
4783
4784 /*
4785 * This page may be off to user land. Zero it out here.
4786 */
4787 if (commit < BUF_PAGE_SIZE)
4788 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4789
4790 out_unlock:
4791 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4792
4793 out:
4794 return ret;
4795}
4796EXPORT_SYMBOL_GPL(ring_buffer_read_page);
4797
4798/*
4799 * We only allocate new buffers, never free them if the CPU goes down.
4800 * If we were to free the buffer, then the user would lose any trace that was in
4801 * the buffer.
4802 */
4803int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
4804{
4805 struct ring_buffer *buffer;
4806 long nr_pages_same;
4807 int cpu_i;
4808 unsigned long nr_pages;
4809
4810 buffer = container_of(node, struct ring_buffer, node);
4811 if (cpumask_test_cpu(cpu, buffer->cpumask))
4812 return 0;
4813
4814 nr_pages = 0;
4815 nr_pages_same = 1;
4816 /* check if all cpu sizes are same */
4817 for_each_buffer_cpu(buffer, cpu_i) {
4818 /* fill in the size from first enabled cpu */
4819 if (nr_pages == 0)
4820 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4821 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4822 nr_pages_same = 0;
4823 break;
4824 }
4825 }
4826 /* allocate minimum pages, user can later expand it */
4827 if (!nr_pages_same)
4828 nr_pages = 2;
4829 buffer->buffers[cpu] =
4830 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
4831 if (!buffer->buffers[cpu]) {
4832 WARN(1, "failed to allocate ring buffer on CPU %u\n",
4833 cpu);
4834 return -ENOMEM;
4835 }
4836 smp_wmb();
4837 cpumask_set_cpu(cpu, buffer->cpumask);
4838 return 0;
4839}
4840
4841#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
4842/*
4843 * This is a basic integrity check of the ring buffer.
4844 * Late in the boot cycle this test will run when configured in.
4845 * It will kick off a thread per CPU that will go into a loop
4846 * writing to the per cpu ring buffer various sizes of data.
4847 * Some of the data will be large items, some small.
4848 *
4849 * Another thread is created that goes into a spin, sending out
4850 * IPIs to the other CPUs to also write into the ring buffer.
4851 * this is to test the nesting ability of the buffer.
4852 *
4853 * Basic stats are recorded and reported. If something in the
4854 * ring buffer should happen that's not expected, a big warning
4855 * is displayed and all ring buffers are disabled.
4856 */
4857static struct task_struct *rb_threads[NR_CPUS] __initdata;
4858
4859struct rb_test_data {
4860 struct ring_buffer *buffer;
4861 unsigned long events;
4862 unsigned long bytes_written;
4863 unsigned long bytes_alloc;
4864 unsigned long bytes_dropped;
4865 unsigned long events_nested;
4866 unsigned long bytes_written_nested;
4867 unsigned long bytes_alloc_nested;
4868 unsigned long bytes_dropped_nested;
4869 int min_size_nested;
4870 int max_size_nested;
4871 int max_size;
4872 int min_size;
4873 int cpu;
4874 int cnt;
4875};
4876
4877static struct rb_test_data rb_data[NR_CPUS] __initdata;
4878
4879/* 1 meg per cpu */
4880#define RB_TEST_BUFFER_SIZE 1048576
4881
4882static char rb_string[] __initdata =
4883 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
4884 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
4885 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
4886
4887static bool rb_test_started __initdata;
4888
4889struct rb_item {
4890 int size;
4891 char str[];
4892};
4893
4894static __init int rb_write_something(struct rb_test_data *data, bool nested)
4895{
4896 struct ring_buffer_event *event;
4897 struct rb_item *item;
4898 bool started;
4899 int event_len;
4900 int size;
4901 int len;
4902 int cnt;
4903
4904 /* Have nested writes different that what is written */
4905 cnt = data->cnt + (nested ? 27 : 0);
4906
4907 /* Multiply cnt by ~e, to make some unique increment */
4908 size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1);
4909
4910 len = size + sizeof(struct rb_item);
4911
4912 started = rb_test_started;
4913 /* read rb_test_started before checking buffer enabled */
4914 smp_rmb();
4915
4916 event = ring_buffer_lock_reserve(data->buffer, len);
4917 if (!event) {
4918 /* Ignore dropped events before test starts. */
4919 if (started) {
4920 if (nested)
4921 data->bytes_dropped += len;
4922 else
4923 data->bytes_dropped_nested += len;
4924 }
4925 return len;
4926 }
4927
4928 event_len = ring_buffer_event_length(event);
4929
4930 if (RB_WARN_ON(data->buffer, event_len < len))
4931 goto out;
4932
4933 item = ring_buffer_event_data(event);
4934 item->size = size;
4935 memcpy(item->str, rb_string, size);
4936
4937 if (nested) {
4938 data->bytes_alloc_nested += event_len;
4939 data->bytes_written_nested += len;
4940 data->events_nested++;
4941 if (!data->min_size_nested || len < data->min_size_nested)
4942 data->min_size_nested = len;
4943 if (len > data->max_size_nested)
4944 data->max_size_nested = len;
4945 } else {
4946 data->bytes_alloc += event_len;
4947 data->bytes_written += len;
4948 data->events++;
4949 if (!data->min_size || len < data->min_size)
4950 data->max_size = len;
4951 if (len > data->max_size)
4952 data->max_size = len;
4953 }
4954
4955 out:
4956 ring_buffer_unlock_commit(data->buffer, event);
4957
4958 return 0;
4959}
4960
4961static __init int rb_test(void *arg)
4962{
4963 struct rb_test_data *data = arg;
4964
4965 while (!kthread_should_stop()) {
4966 rb_write_something(data, false);
4967 data->cnt++;
4968
4969 set_current_state(TASK_INTERRUPTIBLE);
4970 /* Now sleep between a min of 100-300us and a max of 1ms */
4971 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
4972 }
4973
4974 return 0;
4975}
4976
4977static __init void rb_ipi(void *ignore)
4978{
4979 struct rb_test_data *data;
4980 int cpu = smp_processor_id();
4981
4982 data = &rb_data[cpu];
4983 rb_write_something(data, true);
4984}
4985
4986static __init int rb_hammer_test(void *arg)
4987{
4988 while (!kthread_should_stop()) {
4989
4990 /* Send an IPI to all cpus to write data! */
4991 smp_call_function(rb_ipi, NULL, 1);
4992 /* No sleep, but for non preempt, let others run */
4993 schedule();
4994 }
4995
4996 return 0;
4997}
4998
4999static __init int test_ringbuffer(void)
5000{
5001 struct task_struct *rb_hammer;
5002 struct ring_buffer *buffer;
5003 int cpu;
5004 int ret = 0;
5005
5006 pr_info("Running ring buffer tests...\n");
5007
5008 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5009 if (WARN_ON(!buffer))
5010 return 0;
5011
5012 /* Disable buffer so that threads can't write to it yet */
5013 ring_buffer_record_off(buffer);
5014
5015 for_each_online_cpu(cpu) {
5016 rb_data[cpu].buffer = buffer;
5017 rb_data[cpu].cpu = cpu;
5018 rb_data[cpu].cnt = cpu;
5019 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5020 "rbtester/%d", cpu);
5021 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5022 pr_cont("FAILED\n");
5023 ret = PTR_ERR(rb_threads[cpu]);
5024 goto out_free;
5025 }
5026
5027 kthread_bind(rb_threads[cpu], cpu);
5028 wake_up_process(rb_threads[cpu]);
5029 }
5030
5031 /* Now create the rb hammer! */
5032 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5033 if (WARN_ON(IS_ERR(rb_hammer))) {
5034 pr_cont("FAILED\n");
5035 ret = PTR_ERR(rb_hammer);
5036 goto out_free;
5037 }
5038
5039 ring_buffer_record_on(buffer);
5040 /*
5041 * Show buffer is enabled before setting rb_test_started.
5042 * Yes there's a small race window where events could be
5043 * dropped and the thread wont catch it. But when a ring
5044 * buffer gets enabled, there will always be some kind of
5045 * delay before other CPUs see it. Thus, we don't care about
5046 * those dropped events. We care about events dropped after
5047 * the threads see that the buffer is active.
5048 */
5049 smp_wmb();
5050 rb_test_started = true;
5051
5052 set_current_state(TASK_INTERRUPTIBLE);
5053 /* Just run for 10 seconds */;
5054 schedule_timeout(10 * HZ);
5055
5056 kthread_stop(rb_hammer);
5057
5058 out_free:
5059 for_each_online_cpu(cpu) {
5060 if (!rb_threads[cpu])
5061 break;
5062 kthread_stop(rb_threads[cpu]);
5063 }
5064 if (ret) {
5065 ring_buffer_free(buffer);
5066 return ret;
5067 }
5068
5069 /* Report! */
5070 pr_info("finished\n");
5071 for_each_online_cpu(cpu) {
5072 struct ring_buffer_event *event;
5073 struct rb_test_data *data = &rb_data[cpu];
5074 struct rb_item *item;
5075 unsigned long total_events;
5076 unsigned long total_dropped;
5077 unsigned long total_written;
5078 unsigned long total_alloc;
5079 unsigned long total_read = 0;
5080 unsigned long total_size = 0;
5081 unsigned long total_len = 0;
5082 unsigned long total_lost = 0;
5083 unsigned long lost;
5084 int big_event_size;
5085 int small_event_size;
5086
5087 ret = -1;
5088
5089 total_events = data->events + data->events_nested;
5090 total_written = data->bytes_written + data->bytes_written_nested;
5091 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5092 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5093
5094 big_event_size = data->max_size + data->max_size_nested;
5095 small_event_size = data->min_size + data->min_size_nested;
5096
5097 pr_info("CPU %d:\n", cpu);
5098 pr_info(" events: %ld\n", total_events);
5099 pr_info(" dropped bytes: %ld\n", total_dropped);
5100 pr_info(" alloced bytes: %ld\n", total_alloc);
5101 pr_info(" written bytes: %ld\n", total_written);
5102 pr_info(" biggest event: %d\n", big_event_size);
5103 pr_info(" smallest event: %d\n", small_event_size);
5104
5105 if (RB_WARN_ON(buffer, total_dropped))
5106 break;
5107
5108 ret = 0;
5109
5110 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5111 total_lost += lost;
5112 item = ring_buffer_event_data(event);
5113 total_len += ring_buffer_event_length(event);
5114 total_size += item->size + sizeof(struct rb_item);
5115 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5116 pr_info("FAILED!\n");
5117 pr_info("buffer had: %.*s\n", item->size, item->str);
5118 pr_info("expected: %.*s\n", item->size, rb_string);
5119 RB_WARN_ON(buffer, 1);
5120 ret = -1;
5121 break;
5122 }
5123 total_read++;
5124 }
5125 if (ret)
5126 break;
5127
5128 ret = -1;
5129
5130 pr_info(" read events: %ld\n", total_read);
5131 pr_info(" lost events: %ld\n", total_lost);
5132 pr_info(" total events: %ld\n", total_lost + total_read);
5133 pr_info(" recorded len bytes: %ld\n", total_len);
5134 pr_info(" recorded size bytes: %ld\n", total_size);
5135 if (total_lost)
5136 pr_info(" With dropped events, record len and size may not match\n"
5137 " alloced and written from above\n");
5138 if (!total_lost) {
5139 if (RB_WARN_ON(buffer, total_len != total_alloc ||
5140 total_size != total_written))
5141 break;
5142 }
5143 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5144 break;
5145
5146 ret = 0;
5147 }
5148 if (!ret)
5149 pr_info("Ring buffer PASSED!\n");
5150
5151 ring_buffer_free(buffer);
5152 return 0;
5153}
5154
5155late_initcall(test_ringbuffer);
5156#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 */