1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Generic ring buffer
4 *
5 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
6 */
7 #include <linux/trace_events.h>
8 #include <linux/ring_buffer.h>
9 #include <linux/trace_clock.h>
10 #include <linux/sched/clock.h>
11 #include <linux/trace_seq.h>
12 #include <linux/spinlock.h>
13 #include <linux/irq_work.h>
14 #include <linux/security.h>
15 #include <linux/uaccess.h>
16 #include <linux/hardirq.h>
17 #include <linux/kthread.h> /* for self test */
18 #include <linux/module.h>
19 #include <linux/percpu.h>
20 #include <linux/mutex.h>
21 #include <linux/delay.h>
22 #include <linux/slab.h>
23 #include <linux/init.h>
24 #include <linux/hash.h>
25 #include <linux/list.h>
26 #include <linux/cpu.h>
27 #include <linux/oom.h>
28
29 #include <asm/local.h>
30
31 static void update_pages_handler(struct work_struct *work);
32
33 /*
34 * The ring buffer header is special. We must manually up keep it.
35 */
ring_buffer_print_entry_header(struct trace_seq * s)36 int ring_buffer_print_entry_header(struct trace_seq *s)
37 {
38 trace_seq_puts(s, "# compressed entry header\n");
39 trace_seq_puts(s, "\ttype_len : 5 bits\n");
40 trace_seq_puts(s, "\ttime_delta : 27 bits\n");
41 trace_seq_puts(s, "\tarray : 32 bits\n");
42 trace_seq_putc(s, '\n');
43 trace_seq_printf(s, "\tpadding : type == %d\n",
44 RINGBUF_TYPE_PADDING);
45 trace_seq_printf(s, "\ttime_extend : type == %d\n",
46 RINGBUF_TYPE_TIME_EXTEND);
47 trace_seq_printf(s, "\ttime_stamp : type == %d\n",
48 RINGBUF_TYPE_TIME_STAMP);
49 trace_seq_printf(s, "\tdata max type_len == %d\n",
50 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
51
52 return !trace_seq_has_overflowed(s);
53 }
54
55 /*
56 * The ring buffer is made up of a list of pages. A separate list of pages is
57 * allocated for each CPU. A writer may only write to a buffer that is
58 * associated with the CPU it is currently executing on. A reader may read
59 * from any per cpu buffer.
60 *
61 * The reader is special. For each per cpu buffer, the reader has its own
62 * reader page. When a reader has read the entire reader page, this reader
63 * page is swapped with another page in the ring buffer.
64 *
65 * Now, as long as the writer is off the reader page, the reader can do what
66 * ever it wants with that page. The writer will never write to that page
67 * again (as long as it is out of the ring buffer).
68 *
69 * Here's some silly ASCII art.
70 *
71 * +------+
72 * |reader| RING BUFFER
73 * |page |
74 * +------+ +---+ +---+ +---+
75 * | |-->| |-->| |
76 * +---+ +---+ +---+
77 * ^ |
78 * | |
79 * +---------------+
80 *
81 *
82 * +------+
83 * |reader| RING BUFFER
84 * |page |------------------v
85 * +------+ +---+ +---+ +---+
86 * | |-->| |-->| |
87 * +---+ +---+ +---+
88 * ^ |
89 * | |
90 * +---------------+
91 *
92 *
93 * +------+
94 * |reader| RING BUFFER
95 * |page |------------------v
96 * +------+ +---+ +---+ +---+
97 * ^ | |-->| |-->| |
98 * | +---+ +---+ +---+
99 * | |
100 * | |
101 * +------------------------------+
102 *
103 *
104 * +------+
105 * |buffer| RING BUFFER
106 * |page |------------------v
107 * +------+ +---+ +---+ +---+
108 * ^ | | | |-->| |
109 * | New +---+ +---+ +---+
110 * | Reader------^ |
111 * | page |
112 * +------------------------------+
113 *
114 *
115 * After we make this swap, the reader can hand this page off to the splice
116 * code and be done with it. It can even allocate a new page if it needs to
117 * and swap that into the ring buffer.
118 *
119 * We will be using cmpxchg soon to make all this lockless.
120 *
121 */
122
123 /* Used for individual buffers (after the counter) */
124 #define RB_BUFFER_OFF (1 << 20)
125
126 #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
127
128 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
129 #define RB_ALIGNMENT 4U
130 #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
131 #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
132
133 #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
134 # define RB_FORCE_8BYTE_ALIGNMENT 0
135 # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
136 #else
137 # define RB_FORCE_8BYTE_ALIGNMENT 1
138 # define RB_ARCH_ALIGNMENT 8U
139 #endif
140
141 #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
142
143 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
144 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
145
146 enum {
147 RB_LEN_TIME_EXTEND = 8,
148 RB_LEN_TIME_STAMP = 8,
149 };
150
151 #define skip_time_extend(event) \
152 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
153
154 #define extended_time(event) \
155 (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
156
rb_null_event(struct ring_buffer_event * event)157 static inline int rb_null_event(struct ring_buffer_event *event)
158 {
159 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
160 }
161
rb_event_set_padding(struct ring_buffer_event * event)162 static void rb_event_set_padding(struct ring_buffer_event *event)
163 {
164 /* padding has a NULL time_delta */
165 event->type_len = RINGBUF_TYPE_PADDING;
166 event->time_delta = 0;
167 }
168
169 static unsigned
rb_event_data_length(struct ring_buffer_event * event)170 rb_event_data_length(struct ring_buffer_event *event)
171 {
172 unsigned length;
173
174 if (event->type_len)
175 length = event->type_len * RB_ALIGNMENT;
176 else
177 length = event->array[0];
178 return length + RB_EVNT_HDR_SIZE;
179 }
180
181 /*
182 * Return the length of the given event. Will return
183 * the length of the time extend if the event is a
184 * time extend.
185 */
186 static inline unsigned
rb_event_length(struct ring_buffer_event * event)187 rb_event_length(struct ring_buffer_event *event)
188 {
189 switch (event->type_len) {
190 case RINGBUF_TYPE_PADDING:
191 if (rb_null_event(event))
192 /* undefined */
193 return -1;
194 return event->array[0] + RB_EVNT_HDR_SIZE;
195
196 case RINGBUF_TYPE_TIME_EXTEND:
197 return RB_LEN_TIME_EXTEND;
198
199 case RINGBUF_TYPE_TIME_STAMP:
200 return RB_LEN_TIME_STAMP;
201
202 case RINGBUF_TYPE_DATA:
203 return rb_event_data_length(event);
204 default:
205 WARN_ON_ONCE(1);
206 }
207 /* not hit */
208 return 0;
209 }
210
211 /*
212 * Return total length of time extend and data,
213 * or just the event length for all other events.
214 */
215 static inline unsigned
rb_event_ts_length(struct ring_buffer_event * event)216 rb_event_ts_length(struct ring_buffer_event *event)
217 {
218 unsigned len = 0;
219
220 if (extended_time(event)) {
221 /* time extends include the data event after it */
222 len = RB_LEN_TIME_EXTEND;
223 event = skip_time_extend(event);
224 }
225 return len + rb_event_length(event);
226 }
227
228 /**
229 * ring_buffer_event_length - return the length of the event
230 * @event: the event to get the length of
231 *
232 * Returns the size of the data load of a data event.
233 * If the event is something other than a data event, it
234 * returns the size of the event itself. With the exception
235 * of a TIME EXTEND, where it still returns the size of the
236 * data load of the data event after it.
237 */
ring_buffer_event_length(struct ring_buffer_event * event)238 unsigned ring_buffer_event_length(struct ring_buffer_event *event)
239 {
240 unsigned length;
241
242 if (extended_time(event))
243 event = skip_time_extend(event);
244
245 length = rb_event_length(event);
246 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
247 return length;
248 length -= RB_EVNT_HDR_SIZE;
249 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
250 length -= sizeof(event->array[0]);
251 return length;
252 }
253 EXPORT_SYMBOL_GPL(ring_buffer_event_length);
254
255 /* inline for ring buffer fast paths */
256 static __always_inline void *
rb_event_data(struct ring_buffer_event * event)257 rb_event_data(struct ring_buffer_event *event)
258 {
259 if (extended_time(event))
260 event = skip_time_extend(event);
261 WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
262 /* If length is in len field, then array[0] has the data */
263 if (event->type_len)
264 return (void *)&event->array[0];
265 /* Otherwise length is in array[0] and array[1] has the data */
266 return (void *)&event->array[1];
267 }
268
269 /**
270 * ring_buffer_event_data - return the data of the event
271 * @event: the event to get the data from
272 */
ring_buffer_event_data(struct ring_buffer_event * event)273 void *ring_buffer_event_data(struct ring_buffer_event *event)
274 {
275 return rb_event_data(event);
276 }
277 EXPORT_SYMBOL_GPL(ring_buffer_event_data);
278
279 #define for_each_buffer_cpu(buffer, cpu) \
280 for_each_cpu(cpu, buffer->cpumask)
281
282 #define for_each_online_buffer_cpu(buffer, cpu) \
283 for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
284
285 #define TS_SHIFT 27
286 #define TS_MASK ((1ULL << TS_SHIFT) - 1)
287 #define TS_DELTA_TEST (~TS_MASK)
288
289 /**
290 * ring_buffer_event_time_stamp - return the event's extended timestamp
291 * @event: the event to get the timestamp of
292 *
293 * Returns the extended timestamp associated with a data event.
294 * An extended time_stamp is a 64-bit timestamp represented
295 * internally in a special way that makes the best use of space
296 * contained within a ring buffer event. This function decodes
297 * it and maps it to a straight u64 value.
298 */
ring_buffer_event_time_stamp(struct ring_buffer_event * event)299 u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
300 {
301 u64 ts;
302
303 ts = event->array[0];
304 ts <<= TS_SHIFT;
305 ts += event->time_delta;
306
307 return ts;
308 }
309
310 /* Flag when events were overwritten */
311 #define RB_MISSED_EVENTS (1 << 31)
312 /* Missed count stored at end */
313 #define RB_MISSED_STORED (1 << 30)
314
315 struct buffer_data_page {
316 u64 time_stamp; /* page time stamp */
317 local_t commit; /* write committed index */
318 unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
319 };
320
321 /*
322 * Note, the buffer_page list must be first. The buffer pages
323 * are allocated in cache lines, which means that each buffer
324 * page will be at the beginning of a cache line, and thus
325 * the least significant bits will be zero. We use this to
326 * add flags in the list struct pointers, to make the ring buffer
327 * lockless.
328 */
329 struct buffer_page {
330 struct list_head list; /* list of buffer pages */
331 local_t write; /* index for next write */
332 unsigned read; /* index for next read */
333 local_t entries; /* entries on this page */
334 unsigned long real_end; /* real end of data */
335 struct buffer_data_page *page; /* Actual data page */
336 };
337
338 /*
339 * The buffer page counters, write and entries, must be reset
340 * atomically when crossing page boundaries. To synchronize this
341 * update, two counters are inserted into the number. One is
342 * the actual counter for the write position or count on the page.
343 *
344 * The other is a counter of updaters. Before an update happens
345 * the update partition of the counter is incremented. This will
346 * allow the updater to update the counter atomically.
347 *
348 * The counter is 20 bits, and the state data is 12.
349 */
350 #define RB_WRITE_MASK 0xfffff
351 #define RB_WRITE_INTCNT (1 << 20)
352
rb_init_page(struct buffer_data_page * bpage)353 static void rb_init_page(struct buffer_data_page *bpage)
354 {
355 local_set(&bpage->commit, 0);
356 }
357
358 /*
359 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
360 * this issue out.
361 */
free_buffer_page(struct buffer_page * bpage)362 static void free_buffer_page(struct buffer_page *bpage)
363 {
364 free_page((unsigned long)bpage->page);
365 kfree(bpage);
366 }
367
368 /*
369 * We need to fit the time_stamp delta into 27 bits.
370 */
test_time_stamp(u64 delta)371 static inline int test_time_stamp(u64 delta)
372 {
373 if (delta & TS_DELTA_TEST)
374 return 1;
375 return 0;
376 }
377
378 #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
379
380 /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
381 #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
382
ring_buffer_print_page_header(struct trace_seq * s)383 int ring_buffer_print_page_header(struct trace_seq *s)
384 {
385 struct buffer_data_page field;
386
387 trace_seq_printf(s, "\tfield: u64 timestamp;\t"
388 "offset:0;\tsize:%u;\tsigned:%u;\n",
389 (unsigned int)sizeof(field.time_stamp),
390 (unsigned int)is_signed_type(u64));
391
392 trace_seq_printf(s, "\tfield: local_t commit;\t"
393 "offset:%u;\tsize:%u;\tsigned:%u;\n",
394 (unsigned int)offsetof(typeof(field), commit),
395 (unsigned int)sizeof(field.commit),
396 (unsigned int)is_signed_type(long));
397
398 trace_seq_printf(s, "\tfield: int overwrite;\t"
399 "offset:%u;\tsize:%u;\tsigned:%u;\n",
400 (unsigned int)offsetof(typeof(field), commit),
401 1,
402 (unsigned int)is_signed_type(long));
403
404 trace_seq_printf(s, "\tfield: char data;\t"
405 "offset:%u;\tsize:%u;\tsigned:%u;\n",
406 (unsigned int)offsetof(typeof(field), data),
407 (unsigned int)BUF_PAGE_SIZE,
408 (unsigned int)is_signed_type(char));
409
410 return !trace_seq_has_overflowed(s);
411 }
412
413 struct rb_irq_work {
414 struct irq_work work;
415 wait_queue_head_t waiters;
416 wait_queue_head_t full_waiters;
417 long wait_index;
418 bool waiters_pending;
419 bool full_waiters_pending;
420 bool wakeup_full;
421 };
422
423 /*
424 * Structure to hold event state and handle nested events.
425 */
426 struct rb_event_info {
427 u64 ts;
428 u64 delta;
429 u64 before;
430 u64 after;
431 unsigned long length;
432 struct buffer_page *tail_page;
433 int add_timestamp;
434 };
435
436 /*
437 * Used for the add_timestamp
438 * NONE
439 * EXTEND - wants a time extend
440 * ABSOLUTE - the buffer requests all events to have absolute time stamps
441 * FORCE - force a full time stamp.
442 */
443 enum {
444 RB_ADD_STAMP_NONE = 0,
445 RB_ADD_STAMP_EXTEND = BIT(1),
446 RB_ADD_STAMP_ABSOLUTE = BIT(2),
447 RB_ADD_STAMP_FORCE = BIT(3)
448 };
449 /*
450 * Used for which event context the event is in.
451 * TRANSITION = 0
452 * NMI = 1
453 * IRQ = 2
454 * SOFTIRQ = 3
455 * NORMAL = 4
456 *
457 * See trace_recursive_lock() comment below for more details.
458 */
459 enum {
460 RB_CTX_TRANSITION,
461 RB_CTX_NMI,
462 RB_CTX_IRQ,
463 RB_CTX_SOFTIRQ,
464 RB_CTX_NORMAL,
465 RB_CTX_MAX
466 };
467
468 #if BITS_PER_LONG == 32
469 #define RB_TIME_32
470 #endif
471
472 /* To test on 64 bit machines */
473 //#define RB_TIME_32
474
475 #ifdef RB_TIME_32
476
477 struct rb_time_struct {
478 local_t cnt;
479 local_t top;
480 local_t bottom;
481 };
482 #else
483 #include <asm/local64.h>
484 struct rb_time_struct {
485 local64_t time;
486 };
487 #endif
488 typedef struct rb_time_struct rb_time_t;
489
490 /*
491 * head_page == tail_page && head == tail then buffer is empty.
492 */
493 struct ring_buffer_per_cpu {
494 int cpu;
495 atomic_t record_disabled;
496 atomic_t resize_disabled;
497 struct trace_buffer *buffer;
498 raw_spinlock_t reader_lock; /* serialize readers */
499 arch_spinlock_t lock;
500 struct lock_class_key lock_key;
501 struct buffer_data_page *free_page;
502 unsigned long nr_pages;
503 unsigned int current_context;
504 struct list_head *pages;
505 struct buffer_page *head_page; /* read from head */
506 struct buffer_page *tail_page; /* write to tail */
507 struct buffer_page *commit_page; /* committed pages */
508 struct buffer_page *reader_page;
509 unsigned long lost_events;
510 unsigned long last_overrun;
511 unsigned long nest;
512 local_t entries_bytes;
513 local_t entries;
514 local_t overrun;
515 local_t commit_overrun;
516 local_t dropped_events;
517 local_t committing;
518 local_t commits;
519 local_t pages_touched;
520 local_t pages_lost;
521 local_t pages_read;
522 long last_pages_touch;
523 size_t shortest_full;
524 unsigned long read;
525 unsigned long read_bytes;
526 rb_time_t write_stamp;
527 rb_time_t before_stamp;
528 u64 read_stamp;
529 /* ring buffer pages to update, > 0 to add, < 0 to remove */
530 long nr_pages_to_update;
531 struct list_head new_pages; /* new pages to add */
532 struct work_struct update_pages_work;
533 struct completion update_done;
534
535 struct rb_irq_work irq_work;
536 };
537
538 struct trace_buffer {
539 unsigned flags;
540 int cpus;
541 atomic_t record_disabled;
542 cpumask_var_t cpumask;
543
544 struct lock_class_key *reader_lock_key;
545
546 struct mutex mutex;
547
548 struct ring_buffer_per_cpu **buffers;
549
550 struct hlist_node node;
551 u64 (*clock)(void);
552
553 struct rb_irq_work irq_work;
554 bool time_stamp_abs;
555 };
556
557 struct ring_buffer_iter {
558 struct ring_buffer_per_cpu *cpu_buffer;
559 unsigned long head;
560 unsigned long next_event;
561 struct buffer_page *head_page;
562 struct buffer_page *cache_reader_page;
563 unsigned long cache_read;
564 u64 read_stamp;
565 u64 page_stamp;
566 struct ring_buffer_event *event;
567 int missed_events;
568 };
569
570 #ifdef RB_TIME_32
571
572 /*
573 * On 32 bit machines, local64_t is very expensive. As the ring
574 * buffer doesn't need all the features of a true 64 bit atomic,
575 * on 32 bit, it uses these functions (64 still uses local64_t).
576 *
577 * For the ring buffer, 64 bit required operations for the time is
578 * the following:
579 *
580 * - Only need 59 bits (uses 60 to make it even).
581 * - Reads may fail if it interrupted a modification of the time stamp.
582 * It will succeed if it did not interrupt another write even if
583 * the read itself is interrupted by a write.
584 * It returns whether it was successful or not.
585 *
586 * - Writes always succeed and will overwrite other writes and writes
587 * that were done by events interrupting the current write.
588 *
589 * - A write followed by a read of the same time stamp will always succeed,
590 * but may not contain the same value.
591 *
592 * - A cmpxchg will fail if it interrupted another write or cmpxchg.
593 * Other than that, it acts like a normal cmpxchg.
594 *
595 * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
596 * (bottom being the least significant 30 bits of the 60 bit time stamp).
597 *
598 * The two most significant bits of each half holds a 2 bit counter (0-3).
599 * Each update will increment this counter by one.
600 * When reading the top and bottom, if the two counter bits match then the
601 * top and bottom together make a valid 60 bit number.
602 */
603 #define RB_TIME_SHIFT 30
604 #define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
605
rb_time_cnt(unsigned long val)606 static inline int rb_time_cnt(unsigned long val)
607 {
608 return (val >> RB_TIME_SHIFT) & 3;
609 }
610
rb_time_val(unsigned long top,unsigned long bottom)611 static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
612 {
613 u64 val;
614
615 val = top & RB_TIME_VAL_MASK;
616 val <<= RB_TIME_SHIFT;
617 val |= bottom & RB_TIME_VAL_MASK;
618
619 return val;
620 }
621
__rb_time_read(rb_time_t * t,u64 * ret,unsigned long * cnt)622 static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
623 {
624 unsigned long top, bottom;
625 unsigned long c;
626
627 /*
628 * If the read is interrupted by a write, then the cnt will
629 * be different. Loop until both top and bottom have been read
630 * without interruption.
631 */
632 do {
633 c = local_read(&t->cnt);
634 top = local_read(&t->top);
635 bottom = local_read(&t->bottom);
636 } while (c != local_read(&t->cnt));
637
638 *cnt = rb_time_cnt(top);
639
640 /* If top and bottom counts don't match, this interrupted a write */
641 if (*cnt != rb_time_cnt(bottom))
642 return false;
643
644 *ret = rb_time_val(top, bottom);
645 return true;
646 }
647
rb_time_read(rb_time_t * t,u64 * ret)648 static bool rb_time_read(rb_time_t *t, u64 *ret)
649 {
650 unsigned long cnt;
651
652 return __rb_time_read(t, ret, &cnt);
653 }
654
rb_time_val_cnt(unsigned long val,unsigned long cnt)655 static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
656 {
657 return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
658 }
659
rb_time_split(u64 val,unsigned long * top,unsigned long * bottom)660 static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom)
661 {
662 *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
663 *bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
664 }
665
rb_time_val_set(local_t * t,unsigned long val,unsigned long cnt)666 static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
667 {
668 val = rb_time_val_cnt(val, cnt);
669 local_set(t, val);
670 }
671
rb_time_set(rb_time_t * t,u64 val)672 static void rb_time_set(rb_time_t *t, u64 val)
673 {
674 unsigned long cnt, top, bottom;
675
676 rb_time_split(val, &top, &bottom);
677
678 /* Writes always succeed with a valid number even if it gets interrupted. */
679 do {
680 cnt = local_inc_return(&t->cnt);
681 rb_time_val_set(&t->top, top, cnt);
682 rb_time_val_set(&t->bottom, bottom, cnt);
683 } while (cnt != local_read(&t->cnt));
684 }
685
686 static inline bool
rb_time_read_cmpxchg(local_t * l,unsigned long expect,unsigned long set)687 rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
688 {
689 unsigned long ret;
690
691 ret = local_cmpxchg(l, expect, set);
692 return ret == expect;
693 }
694
rb_time_cmpxchg(rb_time_t * t,u64 expect,u64 set)695 static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
696 {
697 unsigned long cnt, top, bottom;
698 unsigned long cnt2, top2, bottom2;
699 u64 val;
700
701 /* The cmpxchg always fails if it interrupted an update */
702 if (!__rb_time_read(t, &val, &cnt2))
703 return false;
704
705 if (val != expect)
706 return false;
707
708 cnt = local_read(&t->cnt);
709 if ((cnt & 3) != cnt2)
710 return false;
711
712 cnt2 = cnt + 1;
713
714 rb_time_split(val, &top, &bottom);
715 top = rb_time_val_cnt(top, cnt);
716 bottom = rb_time_val_cnt(bottom, cnt);
717
718 rb_time_split(set, &top2, &bottom2);
719 top2 = rb_time_val_cnt(top2, cnt2);
720 bottom2 = rb_time_val_cnt(bottom2, cnt2);
721
722 if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
723 return false;
724 if (!rb_time_read_cmpxchg(&t->top, top, top2))
725 return false;
726 if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
727 return false;
728 return true;
729 }
730
731 #else /* 64 bits */
732
733 /* local64_t always succeeds */
734
rb_time_read(rb_time_t * t,u64 * ret)735 static inline bool rb_time_read(rb_time_t *t, u64 *ret)
736 {
737 *ret = local64_read(&t->time);
738 return true;
739 }
rb_time_set(rb_time_t * t,u64 val)740 static void rb_time_set(rb_time_t *t, u64 val)
741 {
742 local64_set(&t->time, val);
743 }
744
rb_time_cmpxchg(rb_time_t * t,u64 expect,u64 set)745 static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
746 {
747 u64 val;
748 val = local64_cmpxchg(&t->time, expect, set);
749 return val == expect;
750 }
751 #endif
752
753 /**
754 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
755 * @buffer: The ring_buffer to get the number of pages from
756 * @cpu: The cpu of the ring_buffer to get the number of pages from
757 *
758 * Returns the number of pages used by a per_cpu buffer of the ring buffer.
759 */
ring_buffer_nr_pages(struct trace_buffer * buffer,int cpu)760 size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
761 {
762 return buffer->buffers[cpu]->nr_pages;
763 }
764
765 /**
766 * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
767 * @buffer: The ring_buffer to get the number of pages from
768 * @cpu: The cpu of the ring_buffer to get the number of pages from
769 *
770 * Returns the number of pages that have content in the ring buffer.
771 */
ring_buffer_nr_dirty_pages(struct trace_buffer * buffer,int cpu)772 size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
773 {
774 size_t read;
775 size_t lost;
776 size_t cnt;
777
778 read = local_read(&buffer->buffers[cpu]->pages_read);
779 lost = local_read(&buffer->buffers[cpu]->pages_lost);
780 cnt = local_read(&buffer->buffers[cpu]->pages_touched);
781
782 if (WARN_ON_ONCE(cnt < lost))
783 return 0;
784
785 cnt -= lost;
786
787 /* The reader can read an empty page, but not more than that */
788 if (cnt < read) {
789 WARN_ON_ONCE(read > cnt + 1);
790 return 0;
791 }
792
793 return cnt - read;
794 }
795
full_hit(struct trace_buffer * buffer,int cpu,int full)796 static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
797 {
798 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
799 size_t nr_pages;
800 size_t dirty;
801
802 nr_pages = cpu_buffer->nr_pages;
803 if (!nr_pages || !full)
804 return true;
805
806 dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
807
808 return (dirty * 100) > (full * nr_pages);
809 }
810
811 /*
812 * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
813 *
814 * Schedules a delayed work to wake up any task that is blocked on the
815 * ring buffer waiters queue.
816 */
rb_wake_up_waiters(struct irq_work * work)817 static void rb_wake_up_waiters(struct irq_work *work)
818 {
819 struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
820
821 wake_up_all(&rbwork->waiters);
822 if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
823 rbwork->wakeup_full = false;
824 rbwork->full_waiters_pending = false;
825 wake_up_all(&rbwork->full_waiters);
826 }
827 }
828
829 /**
830 * ring_buffer_wake_waiters - wake up any waiters on this ring buffer
831 * @buffer: The ring buffer to wake waiters on
832 *
833 * In the case of a file that represents a ring buffer is closing,
834 * it is prudent to wake up any waiters that are on this.
835 */
ring_buffer_wake_waiters(struct trace_buffer * buffer,int cpu)836 void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
837 {
838 struct ring_buffer_per_cpu *cpu_buffer;
839 struct rb_irq_work *rbwork;
840
841 if (cpu == RING_BUFFER_ALL_CPUS) {
842
843 /* Wake up individual ones too. One level recursion */
844 for_each_buffer_cpu(buffer, cpu)
845 ring_buffer_wake_waiters(buffer, cpu);
846
847 rbwork = &buffer->irq_work;
848 } else {
849 cpu_buffer = buffer->buffers[cpu];
850 rbwork = &cpu_buffer->irq_work;
851 }
852
853 rbwork->wait_index++;
854 /* make sure the waiters see the new index */
855 smp_wmb();
856
857 rb_wake_up_waiters(&rbwork->work);
858 }
859
860 /**
861 * ring_buffer_wait - wait for input to the ring buffer
862 * @buffer: buffer to wait on
863 * @cpu: the cpu buffer to wait on
864 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
865 *
866 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
867 * as data is added to any of the @buffer's cpu buffers. Otherwise
868 * it will wait for data to be added to a specific cpu buffer.
869 */
ring_buffer_wait(struct trace_buffer * buffer,int cpu,int full)870 int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
871 {
872 struct ring_buffer_per_cpu *cpu_buffer;
873 DEFINE_WAIT(wait);
874 struct rb_irq_work *work;
875 long wait_index;
876 int ret = 0;
877
878 /*
879 * Depending on what the caller is waiting for, either any
880 * data in any cpu buffer, or a specific buffer, put the
881 * caller on the appropriate wait queue.
882 */
883 if (cpu == RING_BUFFER_ALL_CPUS) {
884 work = &buffer->irq_work;
885 /* Full only makes sense on per cpu reads */
886 full = 0;
887 } else {
888 if (!cpumask_test_cpu(cpu, buffer->cpumask))
889 return -ENODEV;
890 cpu_buffer = buffer->buffers[cpu];
891 work = &cpu_buffer->irq_work;
892 }
893
894 wait_index = READ_ONCE(work->wait_index);
895
896 while (true) {
897 if (full)
898 prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
899 else
900 prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
901
902 /*
903 * The events can happen in critical sections where
904 * checking a work queue can cause deadlocks.
905 * After adding a task to the queue, this flag is set
906 * only to notify events to try to wake up the queue
907 * using irq_work.
908 *
909 * We don't clear it even if the buffer is no longer
910 * empty. The flag only causes the next event to run
911 * irq_work to do the work queue wake up. The worse
912 * that can happen if we race with !trace_empty() is that
913 * an event will cause an irq_work to try to wake up
914 * an empty queue.
915 *
916 * There's no reason to protect this flag either, as
917 * the work queue and irq_work logic will do the necessary
918 * synchronization for the wake ups. The only thing
919 * that is necessary is that the wake up happens after
920 * a task has been queued. It's OK for spurious wake ups.
921 */
922 if (full)
923 work->full_waiters_pending = true;
924 else
925 work->waiters_pending = true;
926
927 if (signal_pending(current)) {
928 ret = -EINTR;
929 break;
930 }
931
932 if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
933 break;
934
935 if (cpu != RING_BUFFER_ALL_CPUS &&
936 !ring_buffer_empty_cpu(buffer, cpu)) {
937 unsigned long flags;
938 bool pagebusy;
939 bool done;
940
941 if (!full)
942 break;
943
944 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
945 pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
946 done = !pagebusy && full_hit(buffer, cpu, full);
947
948 if (!cpu_buffer->shortest_full ||
949 cpu_buffer->shortest_full > full)
950 cpu_buffer->shortest_full = full;
951 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
952 if (done)
953 break;
954 }
955
956 schedule();
957
958 /* Make sure to see the new wait index */
959 smp_rmb();
960 if (wait_index != work->wait_index)
961 break;
962 }
963
964 if (full)
965 finish_wait(&work->full_waiters, &wait);
966 else
967 finish_wait(&work->waiters, &wait);
968
969 return ret;
970 }
971
972 /**
973 * ring_buffer_poll_wait - poll on buffer input
974 * @buffer: buffer to wait on
975 * @cpu: the cpu buffer to wait on
976 * @filp: the file descriptor
977 * @poll_table: The poll descriptor
978 * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
979 *
980 * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
981 * as data is added to any of the @buffer's cpu buffers. Otherwise
982 * it will wait for data to be added to a specific cpu buffer.
983 *
984 * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
985 * zero otherwise.
986 */
ring_buffer_poll_wait(struct trace_buffer * buffer,int cpu,struct file * filp,poll_table * poll_table,int full)987 __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
988 struct file *filp, poll_table *poll_table, int full)
989 {
990 struct ring_buffer_per_cpu *cpu_buffer;
991 struct rb_irq_work *work;
992
993 if (cpu == RING_BUFFER_ALL_CPUS) {
994 work = &buffer->irq_work;
995 full = 0;
996 } else {
997 if (!cpumask_test_cpu(cpu, buffer->cpumask))
998 return -EINVAL;
999
1000 cpu_buffer = buffer->buffers[cpu];
1001 work = &cpu_buffer->irq_work;
1002 }
1003
1004 if (full) {
1005 poll_wait(filp, &work->full_waiters, poll_table);
1006 work->full_waiters_pending = true;
1007 } else {
1008 poll_wait(filp, &work->waiters, poll_table);
1009 work->waiters_pending = true;
1010 }
1011
1012 /*
1013 * There's a tight race between setting the waiters_pending and
1014 * checking if the ring buffer is empty. Once the waiters_pending bit
1015 * is set, the next event will wake the task up, but we can get stuck
1016 * if there's only a single event in.
1017 *
1018 * FIXME: Ideally, we need a memory barrier on the writer side as well,
1019 * but adding a memory barrier to all events will cause too much of a
1020 * performance hit in the fast path. We only need a memory barrier when
1021 * the buffer goes from empty to having content. But as this race is
1022 * extremely small, and it's not a problem if another event comes in, we
1023 * will fix it later.
1024 */
1025 smp_mb();
1026
1027 if (full)
1028 return full_hit(buffer, cpu, full) ? EPOLLIN | EPOLLRDNORM : 0;
1029
1030 if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
1031 (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
1032 return EPOLLIN | EPOLLRDNORM;
1033 return 0;
1034 }
1035
1036 /* buffer may be either ring_buffer or ring_buffer_per_cpu */
1037 #define RB_WARN_ON(b, cond) \
1038 ({ \
1039 int _____ret = unlikely(cond); \
1040 if (_____ret) { \
1041 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
1042 struct ring_buffer_per_cpu *__b = \
1043 (void *)b; \
1044 atomic_inc(&__b->buffer->record_disabled); \
1045 } else \
1046 atomic_inc(&b->record_disabled); \
1047 WARN_ON(1); \
1048 } \
1049 _____ret; \
1050 })
1051
1052 /* Up this if you want to test the TIME_EXTENTS and normalization */
1053 #define DEBUG_SHIFT 0
1054
rb_time_stamp(struct trace_buffer * buffer)1055 static inline u64 rb_time_stamp(struct trace_buffer *buffer)
1056 {
1057 u64 ts;
1058
1059 /* Skip retpolines :-( */
1060 if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
1061 ts = trace_clock_local();
1062 else
1063 ts = buffer->clock();
1064
1065 /* shift to debug/test normalization and TIME_EXTENTS */
1066 return ts << DEBUG_SHIFT;
1067 }
1068
ring_buffer_time_stamp(struct trace_buffer * buffer,int cpu)1069 u64 ring_buffer_time_stamp(struct trace_buffer *buffer, int cpu)
1070 {
1071 u64 time;
1072
1073 preempt_disable_notrace();
1074 time = rb_time_stamp(buffer);
1075 preempt_enable_notrace();
1076
1077 return time;
1078 }
1079 EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1080
ring_buffer_normalize_time_stamp(struct trace_buffer * buffer,int cpu,u64 * ts)1081 void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1082 int cpu, u64 *ts)
1083 {
1084 /* Just stupid testing the normalize function and deltas */
1085 *ts >>= DEBUG_SHIFT;
1086 }
1087 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1088
1089 /*
1090 * Making the ring buffer lockless makes things tricky.
1091 * Although writes only happen on the CPU that they are on,
1092 * and they only need to worry about interrupts. Reads can
1093 * happen on any CPU.
1094 *
1095 * The reader page is always off the ring buffer, but when the
1096 * reader finishes with a page, it needs to swap its page with
1097 * a new one from the buffer. The reader needs to take from
1098 * the head (writes go to the tail). But if a writer is in overwrite
1099 * mode and wraps, it must push the head page forward.
1100 *
1101 * Here lies the problem.
1102 *
1103 * The reader must be careful to replace only the head page, and
1104 * not another one. As described at the top of the file in the
1105 * ASCII art, the reader sets its old page to point to the next
1106 * page after head. It then sets the page after head to point to
1107 * the old reader page. But if the writer moves the head page
1108 * during this operation, the reader could end up with the tail.
1109 *
1110 * We use cmpxchg to help prevent this race. We also do something
1111 * special with the page before head. We set the LSB to 1.
1112 *
1113 * When the writer must push the page forward, it will clear the
1114 * bit that points to the head page, move the head, and then set
1115 * the bit that points to the new head page.
1116 *
1117 * We also don't want an interrupt coming in and moving the head
1118 * page on another writer. Thus we use the second LSB to catch
1119 * that too. Thus:
1120 *
1121 * head->list->prev->next bit 1 bit 0
1122 * ------- -------
1123 * Normal page 0 0
1124 * Points to head page 0 1
1125 * New head page 1 0
1126 *
1127 * Note we can not trust the prev pointer of the head page, because:
1128 *
1129 * +----+ +-----+ +-----+
1130 * | |------>| T |---X--->| N |
1131 * | |<------| | | |
1132 * +----+ +-----+ +-----+
1133 * ^ ^ |
1134 * | +-----+ | |
1135 * +----------| R |----------+ |
1136 * | |<-----------+
1137 * +-----+
1138 *
1139 * Key: ---X--> HEAD flag set in pointer
1140 * T Tail page
1141 * R Reader page
1142 * N Next page
1143 *
1144 * (see __rb_reserve_next() to see where this happens)
1145 *
1146 * What the above shows is that the reader just swapped out
1147 * the reader page with a page in the buffer, but before it
1148 * could make the new header point back to the new page added
1149 * it was preempted by a writer. The writer moved forward onto
1150 * the new page added by the reader and is about to move forward
1151 * again.
1152 *
1153 * You can see, it is legitimate for the previous pointer of
1154 * the head (or any page) not to point back to itself. But only
1155 * temporarily.
1156 */
1157
1158 #define RB_PAGE_NORMAL 0UL
1159 #define RB_PAGE_HEAD 1UL
1160 #define RB_PAGE_UPDATE 2UL
1161
1162
1163 #define RB_FLAG_MASK 3UL
1164
1165 /* PAGE_MOVED is not part of the mask */
1166 #define RB_PAGE_MOVED 4UL
1167
1168 /*
1169 * rb_list_head - remove any bit
1170 */
rb_list_head(struct list_head * list)1171 static struct list_head *rb_list_head(struct list_head *list)
1172 {
1173 unsigned long val = (unsigned long)list;
1174
1175 return (struct list_head *)(val & ~RB_FLAG_MASK);
1176 }
1177
1178 /*
1179 * rb_is_head_page - test if the given page is the head page
1180 *
1181 * Because the reader may move the head_page pointer, we can
1182 * not trust what the head page is (it may be pointing to
1183 * the reader page). But if the next page is a header page,
1184 * its flags will be non zero.
1185 */
1186 static inline int
rb_is_head_page(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * page,struct list_head * list)1187 rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1188 struct buffer_page *page, struct list_head *list)
1189 {
1190 unsigned long val;
1191
1192 val = (unsigned long)list->next;
1193
1194 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1195 return RB_PAGE_MOVED;
1196
1197 return val & RB_FLAG_MASK;
1198 }
1199
1200 /*
1201 * rb_is_reader_page
1202 *
1203 * The unique thing about the reader page, is that, if the
1204 * writer is ever on it, the previous pointer never points
1205 * back to the reader page.
1206 */
rb_is_reader_page(struct buffer_page * page)1207 static bool rb_is_reader_page(struct buffer_page *page)
1208 {
1209 struct list_head *list = page->list.prev;
1210
1211 return rb_list_head(list->next) != &page->list;
1212 }
1213
1214 /*
1215 * rb_set_list_to_head - set a list_head to be pointing to head.
1216 */
rb_set_list_to_head(struct ring_buffer_per_cpu * cpu_buffer,struct list_head * list)1217 static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
1218 struct list_head *list)
1219 {
1220 unsigned long *ptr;
1221
1222 ptr = (unsigned long *)&list->next;
1223 *ptr |= RB_PAGE_HEAD;
1224 *ptr &= ~RB_PAGE_UPDATE;
1225 }
1226
1227 /*
1228 * rb_head_page_activate - sets up head page
1229 */
rb_head_page_activate(struct ring_buffer_per_cpu * cpu_buffer)1230 static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1231 {
1232 struct buffer_page *head;
1233
1234 head = cpu_buffer->head_page;
1235 if (!head)
1236 return;
1237
1238 /*
1239 * Set the previous list pointer to have the HEAD flag.
1240 */
1241 rb_set_list_to_head(cpu_buffer, head->list.prev);
1242 }
1243
rb_list_head_clear(struct list_head * list)1244 static void rb_list_head_clear(struct list_head *list)
1245 {
1246 unsigned long *ptr = (unsigned long *)&list->next;
1247
1248 *ptr &= ~RB_FLAG_MASK;
1249 }
1250
1251 /*
1252 * rb_head_page_deactivate - clears head page ptr (for free list)
1253 */
1254 static void
rb_head_page_deactivate(struct ring_buffer_per_cpu * cpu_buffer)1255 rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1256 {
1257 struct list_head *hd;
1258
1259 /* Go through the whole list and clear any pointers found. */
1260 rb_list_head_clear(cpu_buffer->pages);
1261
1262 list_for_each(hd, cpu_buffer->pages)
1263 rb_list_head_clear(hd);
1264 }
1265
rb_head_page_set(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag,int new_flag)1266 static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1267 struct buffer_page *head,
1268 struct buffer_page *prev,
1269 int old_flag, int new_flag)
1270 {
1271 struct list_head *list;
1272 unsigned long val = (unsigned long)&head->list;
1273 unsigned long ret;
1274
1275 list = &prev->list;
1276
1277 val &= ~RB_FLAG_MASK;
1278
1279 ret = cmpxchg((unsigned long *)&list->next,
1280 val | old_flag, val | new_flag);
1281
1282 /* check if the reader took the page */
1283 if ((ret & ~RB_FLAG_MASK) != val)
1284 return RB_PAGE_MOVED;
1285
1286 return ret & RB_FLAG_MASK;
1287 }
1288
rb_head_page_set_update(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag)1289 static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1290 struct buffer_page *head,
1291 struct buffer_page *prev,
1292 int old_flag)
1293 {
1294 return rb_head_page_set(cpu_buffer, head, prev,
1295 old_flag, RB_PAGE_UPDATE);
1296 }
1297
rb_head_page_set_head(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag)1298 static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1299 struct buffer_page *head,
1300 struct buffer_page *prev,
1301 int old_flag)
1302 {
1303 return rb_head_page_set(cpu_buffer, head, prev,
1304 old_flag, RB_PAGE_HEAD);
1305 }
1306
rb_head_page_set_normal(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * head,struct buffer_page * prev,int old_flag)1307 static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1308 struct buffer_page *head,
1309 struct buffer_page *prev,
1310 int old_flag)
1311 {
1312 return rb_head_page_set(cpu_buffer, head, prev,
1313 old_flag, RB_PAGE_NORMAL);
1314 }
1315
rb_inc_page(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page ** bpage)1316 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
1317 struct buffer_page **bpage)
1318 {
1319 struct list_head *p = rb_list_head((*bpage)->list.next);
1320
1321 *bpage = list_entry(p, struct buffer_page, list);
1322 }
1323
1324 static struct buffer_page *
rb_set_head_page(struct ring_buffer_per_cpu * cpu_buffer)1325 rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1326 {
1327 struct buffer_page *head;
1328 struct buffer_page *page;
1329 struct list_head *list;
1330 int i;
1331
1332 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1333 return NULL;
1334
1335 /* sanity check */
1336 list = cpu_buffer->pages;
1337 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1338 return NULL;
1339
1340 page = head = cpu_buffer->head_page;
1341 /*
1342 * It is possible that the writer moves the header behind
1343 * where we started, and we miss in one loop.
1344 * A second loop should grab the header, but we'll do
1345 * three loops just because I'm paranoid.
1346 */
1347 for (i = 0; i < 3; i++) {
1348 do {
1349 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
1350 cpu_buffer->head_page = page;
1351 return page;
1352 }
1353 rb_inc_page(cpu_buffer, &page);
1354 } while (page != head);
1355 }
1356
1357 RB_WARN_ON(cpu_buffer, 1);
1358
1359 return NULL;
1360 }
1361
rb_head_page_replace(struct buffer_page * old,struct buffer_page * new)1362 static int rb_head_page_replace(struct buffer_page *old,
1363 struct buffer_page *new)
1364 {
1365 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1366 unsigned long val;
1367 unsigned long ret;
1368
1369 val = *ptr & ~RB_FLAG_MASK;
1370 val |= RB_PAGE_HEAD;
1371
1372 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1373
1374 return ret == val;
1375 }
1376
1377 /*
1378 * rb_tail_page_update - move the tail page forward
1379 */
rb_tail_page_update(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * tail_page,struct buffer_page * next_page)1380 static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1381 struct buffer_page *tail_page,
1382 struct buffer_page *next_page)
1383 {
1384 unsigned long old_entries;
1385 unsigned long old_write;
1386
1387 /*
1388 * The tail page now needs to be moved forward.
1389 *
1390 * We need to reset the tail page, but without messing
1391 * with possible erasing of data brought in by interrupts
1392 * that have moved the tail page and are currently on it.
1393 *
1394 * We add a counter to the write field to denote this.
1395 */
1396 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1397 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1398
1399 local_inc(&cpu_buffer->pages_touched);
1400 /*
1401 * Just make sure we have seen our old_write and synchronize
1402 * with any interrupts that come in.
1403 */
1404 barrier();
1405
1406 /*
1407 * If the tail page is still the same as what we think
1408 * it is, then it is up to us to update the tail
1409 * pointer.
1410 */
1411 if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1412 /* Zero the write counter */
1413 unsigned long val = old_write & ~RB_WRITE_MASK;
1414 unsigned long eval = old_entries & ~RB_WRITE_MASK;
1415
1416 /*
1417 * This will only succeed if an interrupt did
1418 * not come in and change it. In which case, we
1419 * do not want to modify it.
1420 *
1421 * We add (void) to let the compiler know that we do not care
1422 * about the return value of these functions. We use the
1423 * cmpxchg to only update if an interrupt did not already
1424 * do it for us. If the cmpxchg fails, we don't care.
1425 */
1426 (void)local_cmpxchg(&next_page->write, old_write, val);
1427 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1428
1429 /*
1430 * No need to worry about races with clearing out the commit.
1431 * it only can increment when a commit takes place. But that
1432 * only happens in the outer most nested commit.
1433 */
1434 local_set(&next_page->page->commit, 0);
1435
1436 /* Again, either we update tail_page or an interrupt does */
1437 (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1438 }
1439 }
1440
rb_check_bpage(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * bpage)1441 static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1442 struct buffer_page *bpage)
1443 {
1444 unsigned long val = (unsigned long)bpage;
1445
1446 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1447 return 1;
1448
1449 return 0;
1450 }
1451
1452 /**
1453 * rb_check_list - make sure a pointer to a list has the last bits zero
1454 */
rb_check_list(struct ring_buffer_per_cpu * cpu_buffer,struct list_head * list)1455 static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1456 struct list_head *list)
1457 {
1458 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1459 return 1;
1460 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1461 return 1;
1462 return 0;
1463 }
1464
1465 /**
1466 * rb_check_pages - integrity check of buffer pages
1467 * @cpu_buffer: CPU buffer with pages to test
1468 *
1469 * As a safety measure we check to make sure the data pages have not
1470 * been corrupted.
1471 */
rb_check_pages(struct ring_buffer_per_cpu * cpu_buffer)1472 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1473 {
1474 struct list_head *head = cpu_buffer->pages;
1475 struct buffer_page *bpage, *tmp;
1476
1477 /* Reset the head page if it exists */
1478 if (cpu_buffer->head_page)
1479 rb_set_head_page(cpu_buffer);
1480
1481 rb_head_page_deactivate(cpu_buffer);
1482
1483 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1484 return -1;
1485 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1486 return -1;
1487
1488 if (rb_check_list(cpu_buffer, head))
1489 return -1;
1490
1491 list_for_each_entry_safe(bpage, tmp, head, list) {
1492 if (RB_WARN_ON(cpu_buffer,
1493 bpage->list.next->prev != &bpage->list))
1494 return -1;
1495 if (RB_WARN_ON(cpu_buffer,
1496 bpage->list.prev->next != &bpage->list))
1497 return -1;
1498 if (rb_check_list(cpu_buffer, &bpage->list))
1499 return -1;
1500 }
1501
1502 rb_head_page_activate(cpu_buffer);
1503
1504 return 0;
1505 }
1506
__rb_allocate_pages(long nr_pages,struct list_head * pages,int cpu)1507 static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
1508 {
1509 struct buffer_page *bpage, *tmp;
1510 bool user_thread = current->mm != NULL;
1511 gfp_t mflags;
1512 long i;
1513
1514 /*
1515 * Check if the available memory is there first.
1516 * Note, si_mem_available() only gives us a rough estimate of available
1517 * memory. It may not be accurate. But we don't care, we just want
1518 * to prevent doing any allocation when it is obvious that it is
1519 * not going to succeed.
1520 */
1521 i = si_mem_available();
1522 if (i < nr_pages)
1523 return -ENOMEM;
1524
1525 /*
1526 * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1527 * gracefully without invoking oom-killer and the system is not
1528 * destabilized.
1529 */
1530 mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1531
1532 /*
1533 * If a user thread allocates too much, and si_mem_available()
1534 * reports there's enough memory, even though there is not.
1535 * Make sure the OOM killer kills this thread. This can happen
1536 * even with RETRY_MAYFAIL because another task may be doing
1537 * an allocation after this task has taken all memory.
1538 * This is the task the OOM killer needs to take out during this
1539 * loop, even if it was triggered by an allocation somewhere else.
1540 */
1541 if (user_thread)
1542 set_current_oom_origin();
1543 for (i = 0; i < nr_pages; i++) {
1544 struct page *page;
1545
1546 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1547 mflags, cpu_to_node(cpu));
1548 if (!bpage)
1549 goto free_pages;
1550
1551 list_add(&bpage->list, pages);
1552
1553 page = alloc_pages_node(cpu_to_node(cpu), mflags, 0);
1554 if (!page)
1555 goto free_pages;
1556 bpage->page = page_address(page);
1557 rb_init_page(bpage->page);
1558
1559 if (user_thread && fatal_signal_pending(current))
1560 goto free_pages;
1561 }
1562 if (user_thread)
1563 clear_current_oom_origin();
1564
1565 return 0;
1566
1567 free_pages:
1568 list_for_each_entry_safe(bpage, tmp, pages, list) {
1569 list_del_init(&bpage->list);
1570 free_buffer_page(bpage);
1571 }
1572 if (user_thread)
1573 clear_current_oom_origin();
1574
1575 return -ENOMEM;
1576 }
1577
rb_allocate_pages(struct ring_buffer_per_cpu * cpu_buffer,unsigned long nr_pages)1578 static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1579 unsigned long nr_pages)
1580 {
1581 LIST_HEAD(pages);
1582
1583 WARN_ON(!nr_pages);
1584
1585 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1586 return -ENOMEM;
1587
1588 /*
1589 * The ring buffer page list is a circular list that does not
1590 * start and end with a list head. All page list items point to
1591 * other pages.
1592 */
1593 cpu_buffer->pages = pages.next;
1594 list_del(&pages);
1595
1596 cpu_buffer->nr_pages = nr_pages;
1597
1598 rb_check_pages(cpu_buffer);
1599
1600 return 0;
1601 }
1602
1603 static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct trace_buffer * buffer,long nr_pages,int cpu)1604 rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1605 {
1606 struct ring_buffer_per_cpu *cpu_buffer;
1607 struct buffer_page *bpage;
1608 struct page *page;
1609 int ret;
1610
1611 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1612 GFP_KERNEL, cpu_to_node(cpu));
1613 if (!cpu_buffer)
1614 return NULL;
1615
1616 cpu_buffer->cpu = cpu;
1617 cpu_buffer->buffer = buffer;
1618 raw_spin_lock_init(&cpu_buffer->reader_lock);
1619 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1620 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1621 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1622 init_completion(&cpu_buffer->update_done);
1623 init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1624 init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1625 init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1626
1627 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1628 GFP_KERNEL, cpu_to_node(cpu));
1629 if (!bpage)
1630 goto fail_free_buffer;
1631
1632 rb_check_bpage(cpu_buffer, bpage);
1633
1634 cpu_buffer->reader_page = bpage;
1635 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1636 if (!page)
1637 goto fail_free_reader;
1638 bpage->page = page_address(page);
1639 rb_init_page(bpage->page);
1640
1641 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1642 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1643
1644 ret = rb_allocate_pages(cpu_buffer, nr_pages);
1645 if (ret < 0)
1646 goto fail_free_reader;
1647
1648 cpu_buffer->head_page
1649 = list_entry(cpu_buffer->pages, struct buffer_page, list);
1650 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1651
1652 rb_head_page_activate(cpu_buffer);
1653
1654 return cpu_buffer;
1655
1656 fail_free_reader:
1657 free_buffer_page(cpu_buffer->reader_page);
1658
1659 fail_free_buffer:
1660 kfree(cpu_buffer);
1661 return NULL;
1662 }
1663
rb_free_cpu_buffer(struct ring_buffer_per_cpu * cpu_buffer)1664 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1665 {
1666 struct list_head *head = cpu_buffer->pages;
1667 struct buffer_page *bpage, *tmp;
1668
1669 free_buffer_page(cpu_buffer->reader_page);
1670
1671 if (head) {
1672 rb_head_page_deactivate(cpu_buffer);
1673
1674 list_for_each_entry_safe(bpage, tmp, head, list) {
1675 list_del_init(&bpage->list);
1676 free_buffer_page(bpage);
1677 }
1678 bpage = list_entry(head, struct buffer_page, list);
1679 free_buffer_page(bpage);
1680 }
1681
1682 kfree(cpu_buffer);
1683 }
1684
1685 /**
1686 * __ring_buffer_alloc - allocate a new ring_buffer
1687 * @size: the size in bytes per cpu that is needed.
1688 * @flags: attributes to set for the ring buffer.
1689 * @key: ring buffer reader_lock_key.
1690 *
1691 * Currently the only flag that is available is the RB_FL_OVERWRITE
1692 * flag. This flag means that the buffer will overwrite old data
1693 * when the buffer wraps. If this flag is not set, the buffer will
1694 * drop data when the tail hits the head.
1695 */
__ring_buffer_alloc(unsigned long size,unsigned flags,struct lock_class_key * key)1696 struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1697 struct lock_class_key *key)
1698 {
1699 struct trace_buffer *buffer;
1700 long nr_pages;
1701 int bsize;
1702 int cpu;
1703 int ret;
1704
1705 /* keep it in its own cache line */
1706 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1707 GFP_KERNEL);
1708 if (!buffer)
1709 return NULL;
1710
1711 if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1712 goto fail_free_buffer;
1713
1714 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1715 buffer->flags = flags;
1716 buffer->clock = trace_clock_local;
1717 buffer->reader_lock_key = key;
1718
1719 init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1720 init_waitqueue_head(&buffer->irq_work.waiters);
1721
1722 /* need at least two pages */
1723 if (nr_pages < 2)
1724 nr_pages = 2;
1725
1726 buffer->cpus = nr_cpu_ids;
1727
1728 bsize = sizeof(void *) * nr_cpu_ids;
1729 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1730 GFP_KERNEL);
1731 if (!buffer->buffers)
1732 goto fail_free_cpumask;
1733
1734 cpu = raw_smp_processor_id();
1735 cpumask_set_cpu(cpu, buffer->cpumask);
1736 buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1737 if (!buffer->buffers[cpu])
1738 goto fail_free_buffers;
1739
1740 ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1741 if (ret < 0)
1742 goto fail_free_buffers;
1743
1744 mutex_init(&buffer->mutex);
1745
1746 return buffer;
1747
1748 fail_free_buffers:
1749 for_each_buffer_cpu(buffer, cpu) {
1750 if (buffer->buffers[cpu])
1751 rb_free_cpu_buffer(buffer->buffers[cpu]);
1752 }
1753 kfree(buffer->buffers);
1754
1755 fail_free_cpumask:
1756 free_cpumask_var(buffer->cpumask);
1757
1758 fail_free_buffer:
1759 kfree(buffer);
1760 return NULL;
1761 }
1762 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1763
1764 /**
1765 * ring_buffer_free - free a ring buffer.
1766 * @buffer: the buffer to free.
1767 */
1768 void
ring_buffer_free(struct trace_buffer * buffer)1769 ring_buffer_free(struct trace_buffer *buffer)
1770 {
1771 int cpu;
1772
1773 cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1774
1775 for_each_buffer_cpu(buffer, cpu)
1776 rb_free_cpu_buffer(buffer->buffers[cpu]);
1777
1778 kfree(buffer->buffers);
1779 free_cpumask_var(buffer->cpumask);
1780
1781 kfree(buffer);
1782 }
1783 EXPORT_SYMBOL_GPL(ring_buffer_free);
1784
ring_buffer_set_clock(struct trace_buffer * buffer,u64 (* clock)(void))1785 void ring_buffer_set_clock(struct trace_buffer *buffer,
1786 u64 (*clock)(void))
1787 {
1788 buffer->clock = clock;
1789 }
1790
ring_buffer_set_time_stamp_abs(struct trace_buffer * buffer,bool abs)1791 void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1792 {
1793 buffer->time_stamp_abs = abs;
1794 }
1795
ring_buffer_time_stamp_abs(struct trace_buffer * buffer)1796 bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1797 {
1798 return buffer->time_stamp_abs;
1799 }
1800
1801 static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1802
rb_page_entries(struct buffer_page * bpage)1803 static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1804 {
1805 return local_read(&bpage->entries) & RB_WRITE_MASK;
1806 }
1807
rb_page_write(struct buffer_page * bpage)1808 static inline unsigned long rb_page_write(struct buffer_page *bpage)
1809 {
1810 return local_read(&bpage->write) & RB_WRITE_MASK;
1811 }
1812
1813 static int
rb_remove_pages(struct ring_buffer_per_cpu * cpu_buffer,unsigned long nr_pages)1814 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1815 {
1816 struct list_head *tail_page, *to_remove, *next_page;
1817 struct buffer_page *to_remove_page, *tmp_iter_page;
1818 struct buffer_page *last_page, *first_page;
1819 unsigned long nr_removed;
1820 unsigned long head_bit;
1821 int page_entries;
1822
1823 head_bit = 0;
1824
1825 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1826 atomic_inc(&cpu_buffer->record_disabled);
1827 /*
1828 * We don't race with the readers since we have acquired the reader
1829 * lock. We also don't race with writers after disabling recording.
1830 * This makes it easy to figure out the first and the last page to be
1831 * removed from the list. We unlink all the pages in between including
1832 * the first and last pages. This is done in a busy loop so that we
1833 * lose the least number of traces.
1834 * The pages are freed after we restart recording and unlock readers.
1835 */
1836 tail_page = &cpu_buffer->tail_page->list;
1837
1838 /*
1839 * tail page might be on reader page, we remove the next page
1840 * from the ring buffer
1841 */
1842 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1843 tail_page = rb_list_head(tail_page->next);
1844 to_remove = tail_page;
1845
1846 /* start of pages to remove */
1847 first_page = list_entry(rb_list_head(to_remove->next),
1848 struct buffer_page, list);
1849
1850 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1851 to_remove = rb_list_head(to_remove)->next;
1852 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1853 }
1854
1855 next_page = rb_list_head(to_remove)->next;
1856
1857 /*
1858 * Now we remove all pages between tail_page and next_page.
1859 * Make sure that we have head_bit value preserved for the
1860 * next page
1861 */
1862 tail_page->next = (struct list_head *)((unsigned long)next_page |
1863 head_bit);
1864 next_page = rb_list_head(next_page);
1865 next_page->prev = tail_page;
1866
1867 /* make sure pages points to a valid page in the ring buffer */
1868 cpu_buffer->pages = next_page;
1869
1870 /* update head page */
1871 if (head_bit)
1872 cpu_buffer->head_page = list_entry(next_page,
1873 struct buffer_page, list);
1874
1875 /*
1876 * change read pointer to make sure any read iterators reset
1877 * themselves
1878 */
1879 cpu_buffer->read = 0;
1880
1881 /* pages are removed, resume tracing and then free the pages */
1882 atomic_dec(&cpu_buffer->record_disabled);
1883 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1884
1885 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1886
1887 /* last buffer page to remove */
1888 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1889 list);
1890 tmp_iter_page = first_page;
1891
1892 do {
1893 cond_resched();
1894
1895 to_remove_page = tmp_iter_page;
1896 rb_inc_page(cpu_buffer, &tmp_iter_page);
1897
1898 /* update the counters */
1899 page_entries = rb_page_entries(to_remove_page);
1900 if (page_entries) {
1901 /*
1902 * If something was added to this page, it was full
1903 * since it is not the tail page. So we deduct the
1904 * bytes consumed in ring buffer from here.
1905 * Increment overrun to account for the lost events.
1906 */
1907 local_add(page_entries, &cpu_buffer->overrun);
1908 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1909 local_inc(&cpu_buffer->pages_lost);
1910 }
1911
1912 /*
1913 * We have already removed references to this list item, just
1914 * free up the buffer_page and its page
1915 */
1916 free_buffer_page(to_remove_page);
1917 nr_removed--;
1918
1919 } while (to_remove_page != last_page);
1920
1921 RB_WARN_ON(cpu_buffer, nr_removed);
1922
1923 return nr_removed == 0;
1924 }
1925
1926 static int
rb_insert_pages(struct ring_buffer_per_cpu * cpu_buffer)1927 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1928 {
1929 struct list_head *pages = &cpu_buffer->new_pages;
1930 int retries, success;
1931
1932 raw_spin_lock_irq(&cpu_buffer->reader_lock);
1933 /*
1934 * We are holding the reader lock, so the reader page won't be swapped
1935 * in the ring buffer. Now we are racing with the writer trying to
1936 * move head page and the tail page.
1937 * We are going to adapt the reader page update process where:
1938 * 1. We first splice the start and end of list of new pages between
1939 * the head page and its previous page.
1940 * 2. We cmpxchg the prev_page->next to point from head page to the
1941 * start of new pages list.
1942 * 3. Finally, we update the head->prev to the end of new list.
1943 *
1944 * We will try this process 10 times, to make sure that we don't keep
1945 * spinning.
1946 */
1947 retries = 10;
1948 success = 0;
1949 while (retries--) {
1950 struct list_head *head_page, *prev_page, *r;
1951 struct list_head *last_page, *first_page;
1952 struct list_head *head_page_with_bit;
1953
1954 head_page = &rb_set_head_page(cpu_buffer)->list;
1955 if (!head_page)
1956 break;
1957 prev_page = head_page->prev;
1958
1959 first_page = pages->next;
1960 last_page = pages->prev;
1961
1962 head_page_with_bit = (struct list_head *)
1963 ((unsigned long)head_page | RB_PAGE_HEAD);
1964
1965 last_page->next = head_page_with_bit;
1966 first_page->prev = prev_page;
1967
1968 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1969
1970 if (r == head_page_with_bit) {
1971 /*
1972 * yay, we replaced the page pointer to our new list,
1973 * now, we just have to update to head page's prev
1974 * pointer to point to end of list
1975 */
1976 head_page->prev = last_page;
1977 success = 1;
1978 break;
1979 }
1980 }
1981
1982 if (success)
1983 INIT_LIST_HEAD(pages);
1984 /*
1985 * If we weren't successful in adding in new pages, warn and stop
1986 * tracing
1987 */
1988 RB_WARN_ON(cpu_buffer, !success);
1989 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1990
1991 /* free pages if they weren't inserted */
1992 if (!success) {
1993 struct buffer_page *bpage, *tmp;
1994 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1995 list) {
1996 list_del_init(&bpage->list);
1997 free_buffer_page(bpage);
1998 }
1999 }
2000 return success;
2001 }
2002
rb_update_pages(struct ring_buffer_per_cpu * cpu_buffer)2003 static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
2004 {
2005 int success;
2006
2007 if (cpu_buffer->nr_pages_to_update > 0)
2008 success = rb_insert_pages(cpu_buffer);
2009 else
2010 success = rb_remove_pages(cpu_buffer,
2011 -cpu_buffer->nr_pages_to_update);
2012
2013 if (success)
2014 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
2015 }
2016
update_pages_handler(struct work_struct * work)2017 static void update_pages_handler(struct work_struct *work)
2018 {
2019 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
2020 struct ring_buffer_per_cpu, update_pages_work);
2021 rb_update_pages(cpu_buffer);
2022 complete(&cpu_buffer->update_done);
2023 }
2024
2025 /**
2026 * ring_buffer_resize - resize the ring buffer
2027 * @buffer: the buffer to resize.
2028 * @size: the new size.
2029 * @cpu_id: the cpu buffer to resize
2030 *
2031 * Minimum size is 2 * BUF_PAGE_SIZE.
2032 *
2033 * Returns 0 on success and < 0 on failure.
2034 */
ring_buffer_resize(struct trace_buffer * buffer,unsigned long size,int cpu_id)2035 int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
2036 int cpu_id)
2037 {
2038 struct ring_buffer_per_cpu *cpu_buffer;
2039 unsigned long nr_pages;
2040 int cpu, err;
2041
2042 /*
2043 * Always succeed at resizing a non-existent buffer:
2044 */
2045 if (!buffer)
2046 return 0;
2047
2048 /* Make sure the requested buffer exists */
2049 if (cpu_id != RING_BUFFER_ALL_CPUS &&
2050 !cpumask_test_cpu(cpu_id, buffer->cpumask))
2051 return 0;
2052
2053 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
2054
2055 /* we need a minimum of two pages */
2056 if (nr_pages < 2)
2057 nr_pages = 2;
2058
2059 size = nr_pages * BUF_PAGE_SIZE;
2060
2061 /* prevent another thread from changing buffer sizes */
2062 mutex_lock(&buffer->mutex);
2063
2064
2065 if (cpu_id == RING_BUFFER_ALL_CPUS) {
2066 /*
2067 * Don't succeed if resizing is disabled, as a reader might be
2068 * manipulating the ring buffer and is expecting a sane state while
2069 * this is true.
2070 */
2071 for_each_buffer_cpu(buffer, cpu) {
2072 cpu_buffer = buffer->buffers[cpu];
2073 if (atomic_read(&cpu_buffer->resize_disabled)) {
2074 err = -EBUSY;
2075 goto out_err_unlock;
2076 }
2077 }
2078
2079 /* calculate the pages to update */
2080 for_each_buffer_cpu(buffer, cpu) {
2081 cpu_buffer = buffer->buffers[cpu];
2082
2083 cpu_buffer->nr_pages_to_update = nr_pages -
2084 cpu_buffer->nr_pages;
2085 /*
2086 * nothing more to do for removing pages or no update
2087 */
2088 if (cpu_buffer->nr_pages_to_update <= 0)
2089 continue;
2090 /*
2091 * to add pages, make sure all new pages can be
2092 * allocated without receiving ENOMEM
2093 */
2094 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2095 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
2096 &cpu_buffer->new_pages, cpu)) {
2097 /* not enough memory for new pages */
2098 err = -ENOMEM;
2099 goto out_err;
2100 }
2101 }
2102
2103 get_online_cpus();
2104 /*
2105 * Fire off all the required work handlers
2106 * We can't schedule on offline CPUs, but it's not necessary
2107 * since we can change their buffer sizes without any race.
2108 */
2109 for_each_buffer_cpu(buffer, cpu) {
2110 cpu_buffer = buffer->buffers[cpu];
2111 if (!cpu_buffer->nr_pages_to_update)
2112 continue;
2113
2114 /* Can't run something on an offline CPU. */
2115 if (!cpu_online(cpu)) {
2116 rb_update_pages(cpu_buffer);
2117 cpu_buffer->nr_pages_to_update = 0;
2118 } else {
2119 schedule_work_on(cpu,
2120 &cpu_buffer->update_pages_work);
2121 }
2122 }
2123
2124 /* wait for all the updates to complete */
2125 for_each_buffer_cpu(buffer, cpu) {
2126 cpu_buffer = buffer->buffers[cpu];
2127 if (!cpu_buffer->nr_pages_to_update)
2128 continue;
2129
2130 if (cpu_online(cpu))
2131 wait_for_completion(&cpu_buffer->update_done);
2132 cpu_buffer->nr_pages_to_update = 0;
2133 }
2134
2135 put_online_cpus();
2136 } else {
2137 /* Make sure this CPU has been initialized */
2138 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
2139 goto out;
2140
2141 cpu_buffer = buffer->buffers[cpu_id];
2142
2143 if (nr_pages == cpu_buffer->nr_pages)
2144 goto out;
2145
2146 /*
2147 * Don't succeed if resizing is disabled, as a reader might be
2148 * manipulating the ring buffer and is expecting a sane state while
2149 * this is true.
2150 */
2151 if (atomic_read(&cpu_buffer->resize_disabled)) {
2152 err = -EBUSY;
2153 goto out_err_unlock;
2154 }
2155
2156 cpu_buffer->nr_pages_to_update = nr_pages -
2157 cpu_buffer->nr_pages;
2158
2159 INIT_LIST_HEAD(&cpu_buffer->new_pages);
2160 if (cpu_buffer->nr_pages_to_update > 0 &&
2161 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
2162 &cpu_buffer->new_pages, cpu_id)) {
2163 err = -ENOMEM;
2164 goto out_err;
2165 }
2166
2167 get_online_cpus();
2168
2169 /* Can't run something on an offline CPU. */
2170 if (!cpu_online(cpu_id))
2171 rb_update_pages(cpu_buffer);
2172 else {
2173 schedule_work_on(cpu_id,
2174 &cpu_buffer->update_pages_work);
2175 wait_for_completion(&cpu_buffer->update_done);
2176 }
2177
2178 cpu_buffer->nr_pages_to_update = 0;
2179 put_online_cpus();
2180 }
2181
2182 out:
2183 /*
2184 * The ring buffer resize can happen with the ring buffer
2185 * enabled, so that the update disturbs the tracing as little
2186 * as possible. But if the buffer is disabled, we do not need
2187 * to worry about that, and we can take the time to verify
2188 * that the buffer is not corrupt.
2189 */
2190 if (atomic_read(&buffer->record_disabled)) {
2191 atomic_inc(&buffer->record_disabled);
2192 /*
2193 * Even though the buffer was disabled, we must make sure
2194 * that it is truly disabled before calling rb_check_pages.
2195 * There could have been a race between checking
2196 * record_disable and incrementing it.
2197 */
2198 synchronize_rcu();
2199 for_each_buffer_cpu(buffer, cpu) {
2200 cpu_buffer = buffer->buffers[cpu];
2201 rb_check_pages(cpu_buffer);
2202 }
2203 atomic_dec(&buffer->record_disabled);
2204 }
2205
2206 mutex_unlock(&buffer->mutex);
2207 return 0;
2208
2209 out_err:
2210 for_each_buffer_cpu(buffer, cpu) {
2211 struct buffer_page *bpage, *tmp;
2212
2213 cpu_buffer = buffer->buffers[cpu];
2214 cpu_buffer->nr_pages_to_update = 0;
2215
2216 if (list_empty(&cpu_buffer->new_pages))
2217 continue;
2218
2219 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2220 list) {
2221 list_del_init(&bpage->list);
2222 free_buffer_page(bpage);
2223 }
2224 }
2225 out_err_unlock:
2226 mutex_unlock(&buffer->mutex);
2227 return err;
2228 }
2229 EXPORT_SYMBOL_GPL(ring_buffer_resize);
2230
ring_buffer_change_overwrite(struct trace_buffer * buffer,int val)2231 void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2232 {
2233 mutex_lock(&buffer->mutex);
2234 if (val)
2235 buffer->flags |= RB_FL_OVERWRITE;
2236 else
2237 buffer->flags &= ~RB_FL_OVERWRITE;
2238 mutex_unlock(&buffer->mutex);
2239 }
2240 EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2241
__rb_page_index(struct buffer_page * bpage,unsigned index)2242 static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2243 {
2244 return bpage->page->data + index;
2245 }
2246
2247 static __always_inline struct ring_buffer_event *
rb_reader_event(struct ring_buffer_per_cpu * cpu_buffer)2248 rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2249 {
2250 return __rb_page_index(cpu_buffer->reader_page,
2251 cpu_buffer->reader_page->read);
2252 }
2253
rb_page_commit(struct buffer_page * bpage)2254 static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
2255 {
2256 return local_read(&bpage->page->commit);
2257 }
2258
2259 static struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter * iter)2260 rb_iter_head_event(struct ring_buffer_iter *iter)
2261 {
2262 struct ring_buffer_event *event;
2263 struct buffer_page *iter_head_page = iter->head_page;
2264 unsigned long commit;
2265 unsigned length;
2266
2267 if (iter->head != iter->next_event)
2268 return iter->event;
2269
2270 /*
2271 * When the writer goes across pages, it issues a cmpxchg which
2272 * is a mb(), which will synchronize with the rmb here.
2273 * (see rb_tail_page_update() and __rb_reserve_next())
2274 */
2275 commit = rb_page_commit(iter_head_page);
2276 smp_rmb();
2277 event = __rb_page_index(iter_head_page, iter->head);
2278 length = rb_event_length(event);
2279
2280 /*
2281 * READ_ONCE() doesn't work on functions and we don't want the
2282 * compiler doing any crazy optimizations with length.
2283 */
2284 barrier();
2285
2286 if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
2287 /* Writer corrupted the read? */
2288 goto reset;
2289
2290 memcpy(iter->event, event, length);
2291 /*
2292 * If the page stamp is still the same after this rmb() then the
2293 * event was safely copied without the writer entering the page.
2294 */
2295 smp_rmb();
2296
2297 /* Make sure the page didn't change since we read this */
2298 if (iter->page_stamp != iter_head_page->page->time_stamp ||
2299 commit > rb_page_commit(iter_head_page))
2300 goto reset;
2301
2302 iter->next_event = iter->head + length;
2303 return iter->event;
2304 reset:
2305 /* Reset to the beginning */
2306 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2307 iter->head = 0;
2308 iter->next_event = 0;
2309 iter->missed_events = 1;
2310 return NULL;
2311 }
2312
2313 /* Size is determined by what has been committed */
rb_page_size(struct buffer_page * bpage)2314 static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2315 {
2316 return rb_page_commit(bpage);
2317 }
2318
2319 static __always_inline unsigned
rb_commit_index(struct ring_buffer_per_cpu * cpu_buffer)2320 rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2321 {
2322 return rb_page_commit(cpu_buffer->commit_page);
2323 }
2324
2325 static __always_inline unsigned
rb_event_index(struct ring_buffer_event * event)2326 rb_event_index(struct ring_buffer_event *event)
2327 {
2328 unsigned long addr = (unsigned long)event;
2329
2330 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
2331 }
2332
rb_inc_iter(struct ring_buffer_iter * iter)2333 static void rb_inc_iter(struct ring_buffer_iter *iter)
2334 {
2335 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2336
2337 /*
2338 * The iterator could be on the reader page (it starts there).
2339 * But the head could have moved, since the reader was
2340 * found. Check for this case and assign the iterator
2341 * to the head page instead of next.
2342 */
2343 if (iter->head_page == cpu_buffer->reader_page)
2344 iter->head_page = rb_set_head_page(cpu_buffer);
2345 else
2346 rb_inc_page(cpu_buffer, &iter->head_page);
2347
2348 iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2349 iter->head = 0;
2350 iter->next_event = 0;
2351 }
2352
2353 /*
2354 * rb_handle_head_page - writer hit the head page
2355 *
2356 * Returns: +1 to retry page
2357 * 0 to continue
2358 * -1 on error
2359 */
2360 static int
rb_handle_head_page(struct ring_buffer_per_cpu * cpu_buffer,struct buffer_page * tail_page,struct buffer_page * next_page)2361 rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2362 struct buffer_page *tail_page,
2363 struct buffer_page *next_page)
2364 {
2365 struct buffer_page *new_head;
2366 int entries;
2367 int type;
2368 int ret;
2369
2370 entries = rb_page_entries(next_page);
2371
2372 /*
2373 * The hard part is here. We need to move the head
2374 * forward, and protect against both readers on
2375 * other CPUs and writers coming in via interrupts.
2376 */
2377 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2378 RB_PAGE_HEAD);
2379
2380 /*
2381 * type can be one of four:
2382 * NORMAL - an interrupt already moved it for us
2383 * HEAD - we are the first to get here.
2384 * UPDATE - we are the interrupt interrupting
2385 * a current move.
2386 * MOVED - a reader on another CPU moved the next
2387 * pointer to its reader page. Give up
2388 * and try again.
2389 */
2390
2391 switch (type) {
2392 case RB_PAGE_HEAD:
2393 /*
2394 * We changed the head to UPDATE, thus
2395 * it is our responsibility to update
2396 * the counters.
2397 */
2398 local_add(entries, &cpu_buffer->overrun);
2399 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2400 local_inc(&cpu_buffer->pages_lost);
2401
2402 /*
2403 * The entries will be zeroed out when we move the
2404 * tail page.
2405 */
2406
2407 /* still more to do */
2408 break;
2409
2410 case RB_PAGE_UPDATE:
2411 /*
2412 * This is an interrupt that interrupt the
2413 * previous update. Still more to do.
2414 */
2415 break;
2416 case RB_PAGE_NORMAL:
2417 /*
2418 * An interrupt came in before the update
2419 * and processed this for us.
2420 * Nothing left to do.
2421 */
2422 return 1;
2423 case RB_PAGE_MOVED:
2424 /*
2425 * The reader is on another CPU and just did
2426 * a swap with our next_page.
2427 * Try again.
2428 */
2429 return 1;
2430 default:
2431 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2432 return -1;
2433 }
2434
2435 /*
2436 * Now that we are here, the old head pointer is
2437 * set to UPDATE. This will keep the reader from
2438 * swapping the head page with the reader page.
2439 * The reader (on another CPU) will spin till
2440 * we are finished.
2441 *
2442 * We just need to protect against interrupts
2443 * doing the job. We will set the next pointer
2444 * to HEAD. After that, we set the old pointer
2445 * to NORMAL, but only if it was HEAD before.
2446 * otherwise we are an interrupt, and only
2447 * want the outer most commit to reset it.
2448 */
2449 new_head = next_page;
2450 rb_inc_page(cpu_buffer, &new_head);
2451
2452 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2453 RB_PAGE_NORMAL);
2454
2455 /*
2456 * Valid returns are:
2457 * HEAD - an interrupt came in and already set it.
2458 * NORMAL - One of two things:
2459 * 1) We really set it.
2460 * 2) A bunch of interrupts came in and moved
2461 * the page forward again.
2462 */
2463 switch (ret) {
2464 case RB_PAGE_HEAD:
2465 case RB_PAGE_NORMAL:
2466 /* OK */
2467 break;
2468 default:
2469 RB_WARN_ON(cpu_buffer, 1);
2470 return -1;
2471 }
2472
2473 /*
2474 * It is possible that an interrupt came in,
2475 * set the head up, then more interrupts came in
2476 * and moved it again. When we get back here,
2477 * the page would have been set to NORMAL but we
2478 * just set it back to HEAD.
2479 *
2480 * How do you detect this? Well, if that happened
2481 * the tail page would have moved.
2482 */
2483 if (ret == RB_PAGE_NORMAL) {
2484 struct buffer_page *buffer_tail_page;
2485
2486 buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2487 /*
2488 * If the tail had moved passed next, then we need
2489 * to reset the pointer.
2490 */
2491 if (buffer_tail_page != tail_page &&
2492 buffer_tail_page != next_page)
2493 rb_head_page_set_normal(cpu_buffer, new_head,
2494 next_page,
2495 RB_PAGE_HEAD);
2496 }
2497
2498 /*
2499 * If this was the outer most commit (the one that
2500 * changed the original pointer from HEAD to UPDATE),
2501 * then it is up to us to reset it to NORMAL.
2502 */
2503 if (type == RB_PAGE_HEAD) {
2504 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2505 tail_page,
2506 RB_PAGE_UPDATE);
2507 if (RB_WARN_ON(cpu_buffer,
2508 ret != RB_PAGE_UPDATE))
2509 return -1;
2510 }
2511
2512 return 0;
2513 }
2514
2515 static inline void
rb_reset_tail(struct ring_buffer_per_cpu * cpu_buffer,unsigned long tail,struct rb_event_info * info)2516 rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2517 unsigned long tail, struct rb_event_info *info)
2518 {
2519 struct buffer_page *tail_page = info->tail_page;
2520 struct ring_buffer_event *event;
2521 unsigned long length = info->length;
2522
2523 /*
2524 * Only the event that crossed the page boundary
2525 * must fill the old tail_page with padding.
2526 */
2527 if (tail >= BUF_PAGE_SIZE) {
2528 /*
2529 * If the page was filled, then we still need
2530 * to update the real_end. Reset it to zero
2531 * and the reader will ignore it.
2532 */
2533 if (tail == BUF_PAGE_SIZE)
2534 tail_page->real_end = 0;
2535
2536 local_sub(length, &tail_page->write);
2537 return;
2538 }
2539
2540 event = __rb_page_index(tail_page, tail);
2541
2542 /* account for padding bytes */
2543 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2544
2545 /*
2546 * Save the original length to the meta data.
2547 * This will be used by the reader to add lost event
2548 * counter.
2549 */
2550 tail_page->real_end = tail;
2551
2552 /*
2553 * If this event is bigger than the minimum size, then
2554 * we need to be careful that we don't subtract the
2555 * write counter enough to allow another writer to slip
2556 * in on this page.
2557 * We put in a discarded commit instead, to make sure
2558 * that this space is not used again.
2559 *
2560 * If we are less than the minimum size, we don't need to
2561 * worry about it.
2562 */
2563 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2564 /* No room for any events */
2565
2566 /* Mark the rest of the page with padding */
2567 rb_event_set_padding(event);
2568
2569 /* Make sure the padding is visible before the write update */
2570 smp_wmb();
2571
2572 /* Set the write back to the previous setting */
2573 local_sub(length, &tail_page->write);
2574 return;
2575 }
2576
2577 /* Put in a discarded event */
2578 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2579 event->type_len = RINGBUF_TYPE_PADDING;
2580 /* time delta must be non zero */
2581 event->time_delta = 1;
2582
2583 /* Make sure the padding is visible before the tail_page->write update */
2584 smp_wmb();
2585
2586 /* Set write to end of buffer */
2587 length = (tail + length) - BUF_PAGE_SIZE;
2588 local_sub(length, &tail_page->write);
2589 }
2590
2591 static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2592
2593 /*
2594 * This is the slow path, force gcc not to inline it.
2595 */
2596 static noinline struct ring_buffer_event *
rb_move_tail(struct ring_buffer_per_cpu * cpu_buffer,unsigned long tail,struct rb_event_info * info)2597 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2598 unsigned long tail, struct rb_event_info *info)
2599 {
2600 struct buffer_page *tail_page = info->tail_page;
2601 struct buffer_page *commit_page = cpu_buffer->commit_page;
2602 struct trace_buffer *buffer = cpu_buffer->buffer;
2603 struct buffer_page *next_page;
2604 int ret;
2605
2606 next_page = tail_page;
2607
2608 rb_inc_page(cpu_buffer, &next_page);
2609
2610 /*
2611 * If for some reason, we had an interrupt storm that made
2612 * it all the way around the buffer, bail, and warn
2613 * about it.
2614 */
2615 if (unlikely(next_page == commit_page)) {
2616 local_inc(&cpu_buffer->commit_overrun);
2617 goto out_reset;
2618 }
2619
2620 /*
2621 * This is where the fun begins!
2622 *
2623 * We are fighting against races between a reader that
2624 * could be on another CPU trying to swap its reader
2625 * page with the buffer head.
2626 *
2627 * We are also fighting against interrupts coming in and
2628 * moving the head or tail on us as well.
2629 *
2630 * If the next page is the head page then we have filled
2631 * the buffer, unless the commit page is still on the
2632 * reader page.
2633 */
2634 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
2635
2636 /*
2637 * If the commit is not on the reader page, then
2638 * move the header page.
2639 */
2640 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2641 /*
2642 * If we are not in overwrite mode,
2643 * this is easy, just stop here.
2644 */
2645 if (!(buffer->flags & RB_FL_OVERWRITE)) {
2646 local_inc(&cpu_buffer->dropped_events);
2647 goto out_reset;
2648 }
2649
2650 ret = rb_handle_head_page(cpu_buffer,
2651 tail_page,
2652 next_page);
2653 if (ret < 0)
2654 goto out_reset;
2655 if (ret)
2656 goto out_again;
2657 } else {
2658 /*
2659 * We need to be careful here too. The
2660 * commit page could still be on the reader
2661 * page. We could have a small buffer, and
2662 * have filled up the buffer with events
2663 * from interrupts and such, and wrapped.
2664 *
2665 * Note, if the tail page is also the on the
2666 * reader_page, we let it move out.
2667 */
2668 if (unlikely((cpu_buffer->commit_page !=
2669 cpu_buffer->tail_page) &&
2670 (cpu_buffer->commit_page ==
2671 cpu_buffer->reader_page))) {
2672 local_inc(&cpu_buffer->commit_overrun);
2673 goto out_reset;
2674 }
2675 }
2676 }
2677
2678 rb_tail_page_update(cpu_buffer, tail_page, next_page);
2679
2680 out_again:
2681
2682 rb_reset_tail(cpu_buffer, tail, info);
2683
2684 /* Commit what we have for now. */
2685 rb_end_commit(cpu_buffer);
2686 /* rb_end_commit() decs committing */
2687 local_inc(&cpu_buffer->committing);
2688
2689 /* fail and let the caller try again */
2690 return ERR_PTR(-EAGAIN);
2691
2692 out_reset:
2693 /* reset write */
2694 rb_reset_tail(cpu_buffer, tail, info);
2695
2696 return NULL;
2697 }
2698
2699 /* Slow path */
2700 static struct ring_buffer_event *
rb_add_time_stamp(struct ring_buffer_event * event,u64 delta,bool abs)2701 rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2702 {
2703 if (abs)
2704 event->type_len = RINGBUF_TYPE_TIME_STAMP;
2705 else
2706 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2707
2708 /* Not the first event on the page, or not delta? */
2709 if (abs || rb_event_index(event)) {
2710 event->time_delta = delta & TS_MASK;
2711 event->array[0] = delta >> TS_SHIFT;
2712 } else {
2713 /* nope, just zero it */
2714 event->time_delta = 0;
2715 event->array[0] = 0;
2716 }
2717
2718 return skip_time_extend(event);
2719 }
2720
2721 static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2722 struct ring_buffer_event *event);
2723
2724 #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
sched_clock_stable(void)2725 static inline bool sched_clock_stable(void)
2726 {
2727 return true;
2728 }
2729 #endif
2730
2731 static void
rb_check_timestamp(struct ring_buffer_per_cpu * cpu_buffer,struct rb_event_info * info)2732 rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2733 struct rb_event_info *info)
2734 {
2735 u64 write_stamp;
2736
2737 WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2738 (unsigned long long)info->delta,
2739 (unsigned long long)info->ts,
2740 (unsigned long long)info->before,
2741 (unsigned long long)info->after,
2742 (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
2743 sched_clock_stable() ? "" :
2744 "If you just came from a suspend/resume,\n"
2745 "please switch to the trace global clock:\n"
2746 " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2747 "or add trace_clock=global to the kernel command line\n");
2748 }
2749
rb_add_timestamp(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event ** event,struct rb_event_info * info,u64 * delta,unsigned int * length)2750 static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2751 struct ring_buffer_event **event,
2752 struct rb_event_info *info,
2753 u64 *delta,
2754 unsigned int *length)
2755 {
2756 bool abs = info->add_timestamp &
2757 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2758
2759 if (unlikely(info->delta > (1ULL << 59))) {
2760 /* did the clock go backwards */
2761 if (info->before == info->after && info->before > info->ts) {
2762 /* not interrupted */
2763 static int once;
2764
2765 /*
2766 * This is possible with a recalibrating of the TSC.
2767 * Do not produce a call stack, but just report it.
2768 */
2769 if (!once) {
2770 once++;
2771 pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2772 info->before, info->ts);
2773 }
2774 } else
2775 rb_check_timestamp(cpu_buffer, info);
2776 if (!abs)
2777 info->delta = 0;
2778 }
2779 *event = rb_add_time_stamp(*event, info->delta, abs);
2780 *length -= RB_LEN_TIME_EXTEND;
2781 *delta = 0;
2782 }
2783
2784 /**
2785 * rb_update_event - update event type and data
2786 * @cpu_buffer: The per cpu buffer of the @event
2787 * @event: the event to update
2788 * @info: The info to update the @event with (contains length and delta)
2789 *
2790 * Update the type and data fields of the @event. The length
2791 * is the actual size that is written to the ring buffer,
2792 * and with this, we can determine what to place into the
2793 * data field.
2794 */
2795 static void
rb_update_event(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event,struct rb_event_info * info)2796 rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2797 struct ring_buffer_event *event,
2798 struct rb_event_info *info)
2799 {
2800 unsigned length = info->length;
2801 u64 delta = info->delta;
2802
2803 /*
2804 * If we need to add a timestamp, then we
2805 * add it to the start of the reserved space.
2806 */
2807 if (unlikely(info->add_timestamp))
2808 rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2809
2810 event->time_delta = delta;
2811 length -= RB_EVNT_HDR_SIZE;
2812 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2813 event->type_len = 0;
2814 event->array[0] = length;
2815 } else
2816 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2817 }
2818
rb_calculate_event_length(unsigned length)2819 static unsigned rb_calculate_event_length(unsigned length)
2820 {
2821 struct ring_buffer_event event; /* Used only for sizeof array */
2822
2823 /* zero length can cause confusions */
2824 if (!length)
2825 length++;
2826
2827 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2828 length += sizeof(event.array[0]);
2829
2830 length += RB_EVNT_HDR_SIZE;
2831 length = ALIGN(length, RB_ARCH_ALIGNMENT);
2832
2833 /*
2834 * In case the time delta is larger than the 27 bits for it
2835 * in the header, we need to add a timestamp. If another
2836 * event comes in when trying to discard this one to increase
2837 * the length, then the timestamp will be added in the allocated
2838 * space of this event. If length is bigger than the size needed
2839 * for the TIME_EXTEND, then padding has to be used. The events
2840 * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2841 * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2842 * As length is a multiple of 4, we only need to worry if it
2843 * is 12 (RB_LEN_TIME_EXTEND + 4).
2844 */
2845 if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2846 length += RB_ALIGNMENT;
2847
2848 return length;
2849 }
2850
2851 static __always_inline bool
rb_event_is_commit(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)2852 rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
2853 struct ring_buffer_event *event)
2854 {
2855 unsigned long addr = (unsigned long)event;
2856 unsigned long index;
2857
2858 index = rb_event_index(event);
2859 addr &= PAGE_MASK;
2860
2861 return cpu_buffer->commit_page->page == (void *)addr &&
2862 rb_commit_index(cpu_buffer) == index;
2863 }
2864
rb_time_delta(struct ring_buffer_event * event)2865 static u64 rb_time_delta(struct ring_buffer_event *event)
2866 {
2867 switch (event->type_len) {
2868 case RINGBUF_TYPE_PADDING:
2869 return 0;
2870
2871 case RINGBUF_TYPE_TIME_EXTEND:
2872 return ring_buffer_event_time_stamp(event);
2873
2874 case RINGBUF_TYPE_TIME_STAMP:
2875 return 0;
2876
2877 case RINGBUF_TYPE_DATA:
2878 return event->time_delta;
2879 default:
2880 return 0;
2881 }
2882 }
2883
2884 static inline int
rb_try_to_discard(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)2885 rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2886 struct ring_buffer_event *event)
2887 {
2888 unsigned long new_index, old_index;
2889 struct buffer_page *bpage;
2890 unsigned long index;
2891 unsigned long addr;
2892 u64 write_stamp;
2893 u64 delta;
2894
2895 new_index = rb_event_index(event);
2896 old_index = new_index + rb_event_ts_length(event);
2897 addr = (unsigned long)event;
2898 addr &= PAGE_MASK;
2899
2900 bpage = READ_ONCE(cpu_buffer->tail_page);
2901
2902 delta = rb_time_delta(event);
2903
2904 if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
2905 return 0;
2906
2907 /* Make sure the write stamp is read before testing the location */
2908 barrier();
2909
2910 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2911 unsigned long write_mask =
2912 local_read(&bpage->write) & ~RB_WRITE_MASK;
2913 unsigned long event_length = rb_event_length(event);
2914
2915 /* Something came in, can't discard */
2916 if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
2917 write_stamp, write_stamp - delta))
2918 return 0;
2919
2920 /*
2921 * It's possible that the event time delta is zero
2922 * (has the same time stamp as the previous event)
2923 * in which case write_stamp and before_stamp could
2924 * be the same. In such a case, force before_stamp
2925 * to be different than write_stamp. It doesn't
2926 * matter what it is, as long as its different.
2927 */
2928 if (!delta)
2929 rb_time_set(&cpu_buffer->before_stamp, 0);
2930
2931 /*
2932 * If an event were to come in now, it would see that the
2933 * write_stamp and the before_stamp are different, and assume
2934 * that this event just added itself before updating
2935 * the write stamp. The interrupting event will fix the
2936 * write stamp for us, and use the before stamp as its delta.
2937 */
2938
2939 /*
2940 * This is on the tail page. It is possible that
2941 * a write could come in and move the tail page
2942 * and write to the next page. That is fine
2943 * because we just shorten what is on this page.
2944 */
2945 old_index += write_mask;
2946 new_index += write_mask;
2947 index = local_cmpxchg(&bpage->write, old_index, new_index);
2948 if (index == old_index) {
2949 /* update counters */
2950 local_sub(event_length, &cpu_buffer->entries_bytes);
2951 return 1;
2952 }
2953 }
2954
2955 /* could not discard */
2956 return 0;
2957 }
2958
rb_start_commit(struct ring_buffer_per_cpu * cpu_buffer)2959 static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2960 {
2961 local_inc(&cpu_buffer->committing);
2962 local_inc(&cpu_buffer->commits);
2963 }
2964
2965 static __always_inline void
rb_set_commit_to_write(struct ring_buffer_per_cpu * cpu_buffer)2966 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2967 {
2968 unsigned long max_count;
2969
2970 /*
2971 * We only race with interrupts and NMIs on this CPU.
2972 * If we own the commit event, then we can commit
2973 * all others that interrupted us, since the interruptions
2974 * are in stack format (they finish before they come
2975 * back to us). This allows us to do a simple loop to
2976 * assign the commit to the tail.
2977 */
2978 again:
2979 max_count = cpu_buffer->nr_pages * 100;
2980
2981 while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2982 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2983 return;
2984 if (RB_WARN_ON(cpu_buffer,
2985 rb_is_reader_page(cpu_buffer->tail_page)))
2986 return;
2987 local_set(&cpu_buffer->commit_page->page->commit,
2988 rb_page_write(cpu_buffer->commit_page));
2989 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
2990 /* add barrier to keep gcc from optimizing too much */
2991 barrier();
2992 }
2993 while (rb_commit_index(cpu_buffer) !=
2994 rb_page_write(cpu_buffer->commit_page)) {
2995
2996 local_set(&cpu_buffer->commit_page->page->commit,
2997 rb_page_write(cpu_buffer->commit_page));
2998 RB_WARN_ON(cpu_buffer,
2999 local_read(&cpu_buffer->commit_page->page->commit) &
3000 ~RB_WRITE_MASK);
3001 barrier();
3002 }
3003
3004 /* again, keep gcc from optimizing */
3005 barrier();
3006
3007 /*
3008 * If an interrupt came in just after the first while loop
3009 * and pushed the tail page forward, we will be left with
3010 * a dangling commit that will never go forward.
3011 */
3012 if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
3013 goto again;
3014 }
3015
rb_end_commit(struct ring_buffer_per_cpu * cpu_buffer)3016 static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
3017 {
3018 unsigned long commits;
3019
3020 if (RB_WARN_ON(cpu_buffer,
3021 !local_read(&cpu_buffer->committing)))
3022 return;
3023
3024 again:
3025 commits = local_read(&cpu_buffer->commits);
3026 /* synchronize with interrupts */
3027 barrier();
3028 if (local_read(&cpu_buffer->committing) == 1)
3029 rb_set_commit_to_write(cpu_buffer);
3030
3031 local_dec(&cpu_buffer->committing);
3032
3033 /* synchronize with interrupts */
3034 barrier();
3035
3036 /*
3037 * Need to account for interrupts coming in between the
3038 * updating of the commit page and the clearing of the
3039 * committing counter.
3040 */
3041 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
3042 !local_read(&cpu_buffer->committing)) {
3043 local_inc(&cpu_buffer->committing);
3044 goto again;
3045 }
3046 }
3047
rb_event_discard(struct ring_buffer_event * event)3048 static inline void rb_event_discard(struct ring_buffer_event *event)
3049 {
3050 if (extended_time(event))
3051 event = skip_time_extend(event);
3052
3053 /* array[0] holds the actual length for the discarded event */
3054 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
3055 event->type_len = RINGBUF_TYPE_PADDING;
3056 /* time delta must be non zero */
3057 if (!event->time_delta)
3058 event->time_delta = 1;
3059 }
3060
rb_commit(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)3061 static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
3062 struct ring_buffer_event *event)
3063 {
3064 local_inc(&cpu_buffer->entries);
3065 rb_end_commit(cpu_buffer);
3066 }
3067
3068 static __always_inline void
rb_wakeups(struct trace_buffer * buffer,struct ring_buffer_per_cpu * cpu_buffer)3069 rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
3070 {
3071 if (buffer->irq_work.waiters_pending) {
3072 buffer->irq_work.waiters_pending = false;
3073 /* irq_work_queue() supplies it's own memory barriers */
3074 irq_work_queue(&buffer->irq_work.work);
3075 }
3076
3077 if (cpu_buffer->irq_work.waiters_pending) {
3078 cpu_buffer->irq_work.waiters_pending = false;
3079 /* irq_work_queue() supplies it's own memory barriers */
3080 irq_work_queue(&cpu_buffer->irq_work.work);
3081 }
3082
3083 if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
3084 return;
3085
3086 if (cpu_buffer->reader_page == cpu_buffer->commit_page)
3087 return;
3088
3089 if (!cpu_buffer->irq_work.full_waiters_pending)
3090 return;
3091
3092 cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
3093
3094 if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
3095 return;
3096
3097 cpu_buffer->irq_work.wakeup_full = true;
3098 cpu_buffer->irq_work.full_waiters_pending = false;
3099 /* irq_work_queue() supplies it's own memory barriers */
3100 irq_work_queue(&cpu_buffer->irq_work.work);
3101 }
3102
3103 /*
3104 * The lock and unlock are done within a preempt disable section.
3105 * The current_context per_cpu variable can only be modified
3106 * by the current task between lock and unlock. But it can
3107 * be modified more than once via an interrupt. To pass this
3108 * information from the lock to the unlock without having to
3109 * access the 'in_interrupt()' functions again (which do show
3110 * a bit of overhead in something as critical as function tracing,
3111 * we use a bitmask trick.
3112 *
3113 * bit 1 = NMI context
3114 * bit 2 = IRQ context
3115 * bit 3 = SoftIRQ context
3116 * bit 4 = normal context.
3117 *
3118 * This works because this is the order of contexts that can
3119 * preempt other contexts. A SoftIRQ never preempts an IRQ
3120 * context.
3121 *
3122 * When the context is determined, the corresponding bit is
3123 * checked and set (if it was set, then a recursion of that context
3124 * happened).
3125 *
3126 * On unlock, we need to clear this bit. To do so, just subtract
3127 * 1 from the current_context and AND it to itself.
3128 *
3129 * (binary)
3130 * 101 - 1 = 100
3131 * 101 & 100 = 100 (clearing bit zero)
3132 *
3133 * 1010 - 1 = 1001
3134 * 1010 & 1001 = 1000 (clearing bit 1)
3135 *
3136 * The least significant bit can be cleared this way, and it
3137 * just so happens that it is the same bit corresponding to
3138 * the current context.
3139 *
3140 * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3141 * is set when a recursion is detected at the current context, and if
3142 * the TRANSITION bit is already set, it will fail the recursion.
3143 * This is needed because there's a lag between the changing of
3144 * interrupt context and updating the preempt count. In this case,
3145 * a false positive will be found. To handle this, one extra recursion
3146 * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3147 * bit is already set, then it is considered a recursion and the function
3148 * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3149 *
3150 * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3151 * to be cleared. Even if it wasn't the context that set it. That is,
3152 * if an interrupt comes in while NORMAL bit is set and the ring buffer
3153 * is called before preempt_count() is updated, since the check will
3154 * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3155 * NMI then comes in, it will set the NMI bit, but when the NMI code
3156 * does the trace_recursive_unlock() it will clear the TRANSTION bit
3157 * and leave the NMI bit set. But this is fine, because the interrupt
3158 * code that set the TRANSITION bit will then clear the NMI bit when it
3159 * calls trace_recursive_unlock(). If another NMI comes in, it will
3160 * set the TRANSITION bit and continue.
3161 *
3162 * Note: The TRANSITION bit only handles a single transition between context.
3163 */
3164
3165 static __always_inline int
trace_recursive_lock(struct ring_buffer_per_cpu * cpu_buffer)3166 trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3167 {
3168 unsigned int val = cpu_buffer->current_context;
3169 unsigned long pc = preempt_count();
3170 int bit;
3171
3172 if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
3173 bit = RB_CTX_NORMAL;
3174 else
3175 bit = pc & NMI_MASK ? RB_CTX_NMI :
3176 pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
3177
3178 if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3179 /*
3180 * It is possible that this was called by transitioning
3181 * between interrupt context, and preempt_count() has not
3182 * been updated yet. In this case, use the TRANSITION bit.
3183 */
3184 bit = RB_CTX_TRANSITION;
3185 if (val & (1 << (bit + cpu_buffer->nest)))
3186 return 1;
3187 }
3188
3189 val |= (1 << (bit + cpu_buffer->nest));
3190 cpu_buffer->current_context = val;
3191
3192 return 0;
3193 }
3194
3195 static __always_inline void
trace_recursive_unlock(struct ring_buffer_per_cpu * cpu_buffer)3196 trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3197 {
3198 cpu_buffer->current_context &=
3199 cpu_buffer->current_context - (1 << cpu_buffer->nest);
3200 }
3201
3202 /* The recursive locking above uses 5 bits */
3203 #define NESTED_BITS 5
3204
3205 /**
3206 * ring_buffer_nest_start - Allow to trace while nested
3207 * @buffer: The ring buffer to modify
3208 *
3209 * The ring buffer has a safety mechanism to prevent recursion.
3210 * But there may be a case where a trace needs to be done while
3211 * tracing something else. In this case, calling this function
3212 * will allow this function to nest within a currently active
3213 * ring_buffer_lock_reserve().
3214 *
3215 * Call this function before calling another ring_buffer_lock_reserve() and
3216 * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3217 */
ring_buffer_nest_start(struct trace_buffer * buffer)3218 void ring_buffer_nest_start(struct trace_buffer *buffer)
3219 {
3220 struct ring_buffer_per_cpu *cpu_buffer;
3221 int cpu;
3222
3223 /* Enabled by ring_buffer_nest_end() */
3224 preempt_disable_notrace();
3225 cpu = raw_smp_processor_id();
3226 cpu_buffer = buffer->buffers[cpu];
3227 /* This is the shift value for the above recursive locking */
3228 cpu_buffer->nest += NESTED_BITS;
3229 }
3230
3231 /**
3232 * ring_buffer_nest_end - Allow to trace while nested
3233 * @buffer: The ring buffer to modify
3234 *
3235 * Must be called after ring_buffer_nest_start() and after the
3236 * ring_buffer_unlock_commit().
3237 */
ring_buffer_nest_end(struct trace_buffer * buffer)3238 void ring_buffer_nest_end(struct trace_buffer *buffer)
3239 {
3240 struct ring_buffer_per_cpu *cpu_buffer;
3241 int cpu;
3242
3243 /* disabled by ring_buffer_nest_start() */
3244 cpu = raw_smp_processor_id();
3245 cpu_buffer = buffer->buffers[cpu];
3246 /* This is the shift value for the above recursive locking */
3247 cpu_buffer->nest -= NESTED_BITS;
3248 preempt_enable_notrace();
3249 }
3250
3251 /**
3252 * ring_buffer_unlock_commit - commit a reserved
3253 * @buffer: The buffer to commit to
3254 * @event: The event pointer to commit.
3255 *
3256 * This commits the data to the ring buffer, and releases any locks held.
3257 *
3258 * Must be paired with ring_buffer_lock_reserve.
3259 */
ring_buffer_unlock_commit(struct trace_buffer * buffer,struct ring_buffer_event * event)3260 int ring_buffer_unlock_commit(struct trace_buffer *buffer,
3261 struct ring_buffer_event *event)
3262 {
3263 struct ring_buffer_per_cpu *cpu_buffer;
3264 int cpu = raw_smp_processor_id();
3265
3266 cpu_buffer = buffer->buffers[cpu];
3267
3268 rb_commit(cpu_buffer, event);
3269
3270 rb_wakeups(buffer, cpu_buffer);
3271
3272 trace_recursive_unlock(cpu_buffer);
3273
3274 preempt_enable_notrace();
3275
3276 return 0;
3277 }
3278 EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3279
3280 static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu * cpu_buffer,struct rb_event_info * info)3281 __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3282 struct rb_event_info *info)
3283 {
3284 struct ring_buffer_event *event;
3285 struct buffer_page *tail_page;
3286 unsigned long tail, write, w;
3287 bool a_ok;
3288 bool b_ok;
3289
3290 /* Don't let the compiler play games with cpu_buffer->tail_page */
3291 tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3292
3293 /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3294 barrier();
3295 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3296 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3297 barrier();
3298 info->ts = rb_time_stamp(cpu_buffer->buffer);
3299
3300 if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3301 info->delta = info->ts;
3302 } else {
3303 /*
3304 * If interrupting an event time update, we may need an
3305 * absolute timestamp.
3306 * Don't bother if this is the start of a new page (w == 0).
3307 */
3308 if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
3309 info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3310 info->length += RB_LEN_TIME_EXTEND;
3311 } else {
3312 info->delta = info->ts - info->after;
3313 if (unlikely(test_time_stamp(info->delta))) {
3314 info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3315 info->length += RB_LEN_TIME_EXTEND;
3316 }
3317 }
3318 }
3319
3320 /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3321
3322 /*C*/ write = local_add_return(info->length, &tail_page->write);
3323
3324 /* set write to only the index of the write */
3325 write &= RB_WRITE_MASK;
3326
3327 tail = write - info->length;
3328
3329 /* See if we shot pass the end of this buffer page */
3330 if (unlikely(write > BUF_PAGE_SIZE)) {
3331 /* before and after may now different, fix it up*/
3332 b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3333 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3334 if (a_ok && b_ok && info->before != info->after)
3335 (void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
3336 info->before, info->after);
3337 return rb_move_tail(cpu_buffer, tail, info);
3338 }
3339
3340 if (likely(tail == w)) {
3341 u64 save_before;
3342 bool s_ok;
3343
3344 /* Nothing interrupted us between A and C */
3345 /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3346 barrier();
3347 /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
3348 RB_WARN_ON(cpu_buffer, !s_ok);
3349 if (likely(!(info->add_timestamp &
3350 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3351 /* This did not interrupt any time update */
3352 info->delta = info->ts - info->after;
3353 else
3354 /* Just use full timestamp for inerrupting event */
3355 info->delta = info->ts;
3356 barrier();
3357 if (unlikely(info->ts != save_before)) {
3358 /* SLOW PATH - Interrupted between C and E */
3359
3360 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3361 RB_WARN_ON(cpu_buffer, !a_ok);
3362
3363 /* Write stamp must only go forward */
3364 if (save_before > info->after) {
3365 /*
3366 * We do not care about the result, only that
3367 * it gets updated atomically.
3368 */
3369 (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
3370 info->after, save_before);
3371 }
3372 }
3373 } else {
3374 u64 ts;
3375 /* SLOW PATH - Interrupted between A and C */
3376 a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3377 /* Was interrupted before here, write_stamp must be valid */
3378 RB_WARN_ON(cpu_buffer, !a_ok);
3379 ts = rb_time_stamp(cpu_buffer->buffer);
3380 barrier();
3381 /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3382 info->after < ts &&
3383 rb_time_cmpxchg(&cpu_buffer->write_stamp,
3384 info->after, ts)) {
3385 /* Nothing came after this event between C and E */
3386 info->delta = ts - info->after;
3387 info->ts = ts;
3388 } else {
3389 /*
3390 * Interrupted beween C and E:
3391 * Lost the previous events time stamp. Just set the
3392 * delta to zero, and this will be the same time as
3393 * the event this event interrupted. And the events that
3394 * came after this will still be correct (as they would
3395 * have built their delta on the previous event.
3396 */
3397 info->delta = 0;
3398 }
3399 info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3400 }
3401
3402 /*
3403 * If this is the first commit on the page, then it has the same
3404 * timestamp as the page itself.
3405 */
3406 if (unlikely(!tail && !(info->add_timestamp &
3407 (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3408 info->delta = 0;
3409
3410 /* We reserved something on the buffer */
3411
3412 event = __rb_page_index(tail_page, tail);
3413 rb_update_event(cpu_buffer, event, info);
3414
3415 local_inc(&tail_page->entries);
3416
3417 /*
3418 * If this is the first commit on the page, then update
3419 * its timestamp.
3420 */
3421 if (unlikely(!tail))
3422 tail_page->page->time_stamp = info->ts;
3423
3424 /* account for these added bytes */
3425 local_add(info->length, &cpu_buffer->entries_bytes);
3426
3427 return event;
3428 }
3429
3430 static __always_inline struct ring_buffer_event *
rb_reserve_next_event(struct trace_buffer * buffer,struct ring_buffer_per_cpu * cpu_buffer,unsigned long length)3431 rb_reserve_next_event(struct trace_buffer *buffer,
3432 struct ring_buffer_per_cpu *cpu_buffer,
3433 unsigned long length)
3434 {
3435 struct ring_buffer_event *event;
3436 struct rb_event_info info;
3437 int nr_loops = 0;
3438 int add_ts_default;
3439
3440 rb_start_commit(cpu_buffer);
3441 /* The commit page can not change after this */
3442
3443 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3444 /*
3445 * Due to the ability to swap a cpu buffer from a buffer
3446 * it is possible it was swapped before we committed.
3447 * (committing stops a swap). We check for it here and
3448 * if it happened, we have to fail the write.
3449 */
3450 barrier();
3451 if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3452 local_dec(&cpu_buffer->committing);
3453 local_dec(&cpu_buffer->commits);
3454 return NULL;
3455 }
3456 #endif
3457
3458 info.length = rb_calculate_event_length(length);
3459
3460 if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3461 add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3462 info.length += RB_LEN_TIME_EXTEND;
3463 } else {
3464 add_ts_default = RB_ADD_STAMP_NONE;
3465 }
3466
3467 again:
3468 info.add_timestamp = add_ts_default;
3469 info.delta = 0;
3470
3471 /*
3472 * We allow for interrupts to reenter here and do a trace.
3473 * If one does, it will cause this original code to loop
3474 * back here. Even with heavy interrupts happening, this
3475 * should only happen a few times in a row. If this happens
3476 * 1000 times in a row, there must be either an interrupt
3477 * storm or we have something buggy.
3478 * Bail!
3479 */
3480 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3481 goto out_fail;
3482
3483 event = __rb_reserve_next(cpu_buffer, &info);
3484
3485 if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3486 if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3487 info.length -= RB_LEN_TIME_EXTEND;
3488 goto again;
3489 }
3490
3491 if (likely(event))
3492 return event;
3493 out_fail:
3494 rb_end_commit(cpu_buffer);
3495 return NULL;
3496 }
3497
3498 /**
3499 * ring_buffer_lock_reserve - reserve a part of the buffer
3500 * @buffer: the ring buffer to reserve from
3501 * @length: the length of the data to reserve (excluding event header)
3502 *
3503 * Returns a reserved event on the ring buffer to copy directly to.
3504 * The user of this interface will need to get the body to write into
3505 * and can use the ring_buffer_event_data() interface.
3506 *
3507 * The length is the length of the data needed, not the event length
3508 * which also includes the event header.
3509 *
3510 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3511 * If NULL is returned, then nothing has been allocated or locked.
3512 */
3513 struct ring_buffer_event *
ring_buffer_lock_reserve(struct trace_buffer * buffer,unsigned long length)3514 ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3515 {
3516 struct ring_buffer_per_cpu *cpu_buffer;
3517 struct ring_buffer_event *event;
3518 int cpu;
3519
3520 /* If we are tracing schedule, we don't want to recurse */
3521 preempt_disable_notrace();
3522
3523 if (unlikely(atomic_read(&buffer->record_disabled)))
3524 goto out;
3525
3526 cpu = raw_smp_processor_id();
3527
3528 if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3529 goto out;
3530
3531 cpu_buffer = buffer->buffers[cpu];
3532
3533 if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3534 goto out;
3535
3536 if (unlikely(length > BUF_MAX_DATA_SIZE))
3537 goto out;
3538
3539 if (unlikely(trace_recursive_lock(cpu_buffer)))
3540 goto out;
3541
3542 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3543 if (!event)
3544 goto out_unlock;
3545
3546 return event;
3547
3548 out_unlock:
3549 trace_recursive_unlock(cpu_buffer);
3550 out:
3551 preempt_enable_notrace();
3552 return NULL;
3553 }
3554 EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3555
3556 /*
3557 * Decrement the entries to the page that an event is on.
3558 * The event does not even need to exist, only the pointer
3559 * to the page it is on. This may only be called before the commit
3560 * takes place.
3561 */
3562 static inline void
rb_decrement_entry(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)3563 rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3564 struct ring_buffer_event *event)
3565 {
3566 unsigned long addr = (unsigned long)event;
3567 struct buffer_page *bpage = cpu_buffer->commit_page;
3568 struct buffer_page *start;
3569
3570 addr &= PAGE_MASK;
3571
3572 /* Do the likely case first */
3573 if (likely(bpage->page == (void *)addr)) {
3574 local_dec(&bpage->entries);
3575 return;
3576 }
3577
3578 /*
3579 * Because the commit page may be on the reader page we
3580 * start with the next page and check the end loop there.
3581 */
3582 rb_inc_page(cpu_buffer, &bpage);
3583 start = bpage;
3584 do {
3585 if (bpage->page == (void *)addr) {
3586 local_dec(&bpage->entries);
3587 return;
3588 }
3589 rb_inc_page(cpu_buffer, &bpage);
3590 } while (bpage != start);
3591
3592 /* commit not part of this buffer?? */
3593 RB_WARN_ON(cpu_buffer, 1);
3594 }
3595
3596 /**
3597 * ring_buffer_commit_discard - discard an event that has not been committed
3598 * @buffer: the ring buffer
3599 * @event: non committed event to discard
3600 *
3601 * Sometimes an event that is in the ring buffer needs to be ignored.
3602 * This function lets the user discard an event in the ring buffer
3603 * and then that event will not be read later.
3604 *
3605 * This function only works if it is called before the item has been
3606 * committed. It will try to free the event from the ring buffer
3607 * if another event has not been added behind it.
3608 *
3609 * If another event has been added behind it, it will set the event
3610 * up as discarded, and perform the commit.
3611 *
3612 * If this function is called, do not call ring_buffer_unlock_commit on
3613 * the event.
3614 */
ring_buffer_discard_commit(struct trace_buffer * buffer,struct ring_buffer_event * event)3615 void ring_buffer_discard_commit(struct trace_buffer *buffer,
3616 struct ring_buffer_event *event)
3617 {
3618 struct ring_buffer_per_cpu *cpu_buffer;
3619 int cpu;
3620
3621 /* The event is discarded regardless */
3622 rb_event_discard(event);
3623
3624 cpu = smp_processor_id();
3625 cpu_buffer = buffer->buffers[cpu];
3626
3627 /*
3628 * This must only be called if the event has not been
3629 * committed yet. Thus we can assume that preemption
3630 * is still disabled.
3631 */
3632 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3633
3634 rb_decrement_entry(cpu_buffer, event);
3635 if (rb_try_to_discard(cpu_buffer, event))
3636 goto out;
3637
3638 out:
3639 rb_end_commit(cpu_buffer);
3640
3641 trace_recursive_unlock(cpu_buffer);
3642
3643 preempt_enable_notrace();
3644
3645 }
3646 EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3647
3648 /**
3649 * ring_buffer_write - write data to the buffer without reserving
3650 * @buffer: The ring buffer to write to.
3651 * @length: The length of the data being written (excluding the event header)
3652 * @data: The data to write to the buffer.
3653 *
3654 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3655 * one function. If you already have the data to write to the buffer, it
3656 * may be easier to simply call this function.
3657 *
3658 * Note, like ring_buffer_lock_reserve, the length is the length of the data
3659 * and not the length of the event which would hold the header.
3660 */
ring_buffer_write(struct trace_buffer * buffer,unsigned long length,void * data)3661 int ring_buffer_write(struct trace_buffer *buffer,
3662 unsigned long length,
3663 void *data)
3664 {
3665 struct ring_buffer_per_cpu *cpu_buffer;
3666 struct ring_buffer_event *event;
3667 void *body;
3668 int ret = -EBUSY;
3669 int cpu;
3670
3671 preempt_disable_notrace();
3672
3673 if (atomic_read(&buffer->record_disabled))
3674 goto out;
3675
3676 cpu = raw_smp_processor_id();
3677
3678 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3679 goto out;
3680
3681 cpu_buffer = buffer->buffers[cpu];
3682
3683 if (atomic_read(&cpu_buffer->record_disabled))
3684 goto out;
3685
3686 if (length > BUF_MAX_DATA_SIZE)
3687 goto out;
3688
3689 if (unlikely(trace_recursive_lock(cpu_buffer)))
3690 goto out;
3691
3692 event = rb_reserve_next_event(buffer, cpu_buffer, length);
3693 if (!event)
3694 goto out_unlock;
3695
3696 body = rb_event_data(event);
3697
3698 memcpy(body, data, length);
3699
3700 rb_commit(cpu_buffer, event);
3701
3702 rb_wakeups(buffer, cpu_buffer);
3703
3704 ret = 0;
3705
3706 out_unlock:
3707 trace_recursive_unlock(cpu_buffer);
3708
3709 out:
3710 preempt_enable_notrace();
3711
3712 return ret;
3713 }
3714 EXPORT_SYMBOL_GPL(ring_buffer_write);
3715
rb_per_cpu_empty(struct ring_buffer_per_cpu * cpu_buffer)3716 static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3717 {
3718 struct buffer_page *reader = cpu_buffer->reader_page;
3719 struct buffer_page *head = rb_set_head_page(cpu_buffer);
3720 struct buffer_page *commit = cpu_buffer->commit_page;
3721
3722 /* In case of error, head will be NULL */
3723 if (unlikely(!head))
3724 return true;
3725
3726 /* Reader should exhaust content in reader page */
3727 if (reader->read != rb_page_commit(reader))
3728 return false;
3729
3730 /*
3731 * If writers are committing on the reader page, knowing all
3732 * committed content has been read, the ring buffer is empty.
3733 */
3734 if (commit == reader)
3735 return true;
3736
3737 /*
3738 * If writers are committing on a page other than reader page
3739 * and head page, there should always be content to read.
3740 */
3741 if (commit != head)
3742 return false;
3743
3744 /*
3745 * Writers are committing on the head page, we just need
3746 * to care about there're committed data, and the reader will
3747 * swap reader page with head page when it is to read data.
3748 */
3749 return rb_page_commit(commit) == 0;
3750 }
3751
3752 /**
3753 * ring_buffer_record_disable - stop all writes into the buffer
3754 * @buffer: The ring buffer to stop writes to.
3755 *
3756 * This prevents all writes to the buffer. Any attempt to write
3757 * to the buffer after this will fail and return NULL.
3758 *
3759 * The caller should call synchronize_rcu() after this.
3760 */
ring_buffer_record_disable(struct trace_buffer * buffer)3761 void ring_buffer_record_disable(struct trace_buffer *buffer)
3762 {
3763 atomic_inc(&buffer->record_disabled);
3764 }
3765 EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3766
3767 /**
3768 * ring_buffer_record_enable - enable writes to the buffer
3769 * @buffer: The ring buffer to enable writes
3770 *
3771 * Note, multiple disables will need the same number of enables
3772 * to truly enable the writing (much like preempt_disable).
3773 */
ring_buffer_record_enable(struct trace_buffer * buffer)3774 void ring_buffer_record_enable(struct trace_buffer *buffer)
3775 {
3776 atomic_dec(&buffer->record_disabled);
3777 }
3778 EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3779
3780 /**
3781 * ring_buffer_record_off - stop all writes into the buffer
3782 * @buffer: The ring buffer to stop writes to.
3783 *
3784 * This prevents all writes to the buffer. Any attempt to write
3785 * to the buffer after this will fail and return NULL.
3786 *
3787 * This is different than ring_buffer_record_disable() as
3788 * it works like an on/off switch, where as the disable() version
3789 * must be paired with a enable().
3790 */
ring_buffer_record_off(struct trace_buffer * buffer)3791 void ring_buffer_record_off(struct trace_buffer *buffer)
3792 {
3793 unsigned int rd;
3794 unsigned int new_rd;
3795
3796 do {
3797 rd = atomic_read(&buffer->record_disabled);
3798 new_rd = rd | RB_BUFFER_OFF;
3799 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3800 }
3801 EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3802
3803 /**
3804 * ring_buffer_record_on - restart writes into the buffer
3805 * @buffer: The ring buffer to start writes to.
3806 *
3807 * This enables all writes to the buffer that was disabled by
3808 * ring_buffer_record_off().
3809 *
3810 * This is different than ring_buffer_record_enable() as
3811 * it works like an on/off switch, where as the enable() version
3812 * must be paired with a disable().
3813 */
ring_buffer_record_on(struct trace_buffer * buffer)3814 void ring_buffer_record_on(struct trace_buffer *buffer)
3815 {
3816 unsigned int rd;
3817 unsigned int new_rd;
3818
3819 do {
3820 rd = atomic_read(&buffer->record_disabled);
3821 new_rd = rd & ~RB_BUFFER_OFF;
3822 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3823 }
3824 EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3825
3826 /**
3827 * ring_buffer_record_is_on - return true if the ring buffer can write
3828 * @buffer: The ring buffer to see if write is enabled
3829 *
3830 * Returns true if the ring buffer is in a state that it accepts writes.
3831 */
ring_buffer_record_is_on(struct trace_buffer * buffer)3832 bool ring_buffer_record_is_on(struct trace_buffer *buffer)
3833 {
3834 return !atomic_read(&buffer->record_disabled);
3835 }
3836
3837 /**
3838 * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3839 * @buffer: The ring buffer to see if write is set enabled
3840 *
3841 * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3842 * Note that this does NOT mean it is in a writable state.
3843 *
3844 * It may return true when the ring buffer has been disabled by
3845 * ring_buffer_record_disable(), as that is a temporary disabling of
3846 * the ring buffer.
3847 */
ring_buffer_record_is_set_on(struct trace_buffer * buffer)3848 bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
3849 {
3850 return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
3851 }
3852
3853 /**
3854 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3855 * @buffer: The ring buffer to stop writes to.
3856 * @cpu: The CPU buffer to stop
3857 *
3858 * This prevents all writes to the buffer. Any attempt to write
3859 * to the buffer after this will fail and return NULL.
3860 *
3861 * The caller should call synchronize_rcu() after this.
3862 */
ring_buffer_record_disable_cpu(struct trace_buffer * buffer,int cpu)3863 void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
3864 {
3865 struct ring_buffer_per_cpu *cpu_buffer;
3866
3867 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3868 return;
3869
3870 cpu_buffer = buffer->buffers[cpu];
3871 atomic_inc(&cpu_buffer->record_disabled);
3872 }
3873 EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3874
3875 /**
3876 * ring_buffer_record_enable_cpu - enable writes to the buffer
3877 * @buffer: The ring buffer to enable writes
3878 * @cpu: The CPU to enable.
3879 *
3880 * Note, multiple disables will need the same number of enables
3881 * to truly enable the writing (much like preempt_disable).
3882 */
ring_buffer_record_enable_cpu(struct trace_buffer * buffer,int cpu)3883 void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
3884 {
3885 struct ring_buffer_per_cpu *cpu_buffer;
3886
3887 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3888 return;
3889
3890 cpu_buffer = buffer->buffers[cpu];
3891 atomic_dec(&cpu_buffer->record_disabled);
3892 }
3893 EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3894
3895 /*
3896 * The total entries in the ring buffer is the running counter
3897 * of entries entered into the ring buffer, minus the sum of
3898 * the entries read from the ring buffer and the number of
3899 * entries that were overwritten.
3900 */
3901 static inline unsigned long
rb_num_of_entries(struct ring_buffer_per_cpu * cpu_buffer)3902 rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3903 {
3904 return local_read(&cpu_buffer->entries) -
3905 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3906 }
3907
3908 /**
3909 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3910 * @buffer: The ring buffer
3911 * @cpu: The per CPU buffer to read from.
3912 */
ring_buffer_oldest_event_ts(struct trace_buffer * buffer,int cpu)3913 u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
3914 {
3915 unsigned long flags;
3916 struct ring_buffer_per_cpu *cpu_buffer;
3917 struct buffer_page *bpage;
3918 u64 ret = 0;
3919
3920 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3921 return 0;
3922
3923 cpu_buffer = buffer->buffers[cpu];
3924 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3925 /*
3926 * if the tail is on reader_page, oldest time stamp is on the reader
3927 * page
3928 */
3929 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3930 bpage = cpu_buffer->reader_page;
3931 else
3932 bpage = rb_set_head_page(cpu_buffer);
3933 if (bpage)
3934 ret = bpage->page->time_stamp;
3935 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3936
3937 return ret;
3938 }
3939 EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3940
3941 /**
3942 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3943 * @buffer: The ring buffer
3944 * @cpu: The per CPU buffer to read from.
3945 */
ring_buffer_bytes_cpu(struct trace_buffer * buffer,int cpu)3946 unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
3947 {
3948 struct ring_buffer_per_cpu *cpu_buffer;
3949 unsigned long ret;
3950
3951 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3952 return 0;
3953
3954 cpu_buffer = buffer->buffers[cpu];
3955 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
3956
3957 return ret;
3958 }
3959 EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
3960
3961 /**
3962 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
3963 * @buffer: The ring buffer
3964 * @cpu: The per CPU buffer to get the entries from.
3965 */
ring_buffer_entries_cpu(struct trace_buffer * buffer,int cpu)3966 unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
3967 {
3968 struct ring_buffer_per_cpu *cpu_buffer;
3969
3970 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3971 return 0;
3972
3973 cpu_buffer = buffer->buffers[cpu];
3974
3975 return rb_num_of_entries(cpu_buffer);
3976 }
3977 EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
3978
3979 /**
3980 * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
3981 * buffer wrapping around (only if RB_FL_OVERWRITE is on).
3982 * @buffer: The ring buffer
3983 * @cpu: The per CPU buffer to get the number of overruns from
3984 */
ring_buffer_overrun_cpu(struct trace_buffer * buffer,int cpu)3985 unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
3986 {
3987 struct ring_buffer_per_cpu *cpu_buffer;
3988 unsigned long ret;
3989
3990 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3991 return 0;
3992
3993 cpu_buffer = buffer->buffers[cpu];
3994 ret = local_read(&cpu_buffer->overrun);
3995
3996 return ret;
3997 }
3998 EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
3999
4000 /**
4001 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4002 * commits failing due to the buffer wrapping around while there are uncommitted
4003 * events, such as during an interrupt storm.
4004 * @buffer: The ring buffer
4005 * @cpu: The per CPU buffer to get the number of overruns from
4006 */
4007 unsigned long
ring_buffer_commit_overrun_cpu(struct trace_buffer * buffer,int cpu)4008 ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4009 {
4010 struct ring_buffer_per_cpu *cpu_buffer;
4011 unsigned long ret;
4012
4013 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4014 return 0;
4015
4016 cpu_buffer = buffer->buffers[cpu];
4017 ret = local_read(&cpu_buffer->commit_overrun);
4018
4019 return ret;
4020 }
4021 EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4022
4023 /**
4024 * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4025 * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4026 * @buffer: The ring buffer
4027 * @cpu: The per CPU buffer to get the number of overruns from
4028 */
4029 unsigned long
ring_buffer_dropped_events_cpu(struct trace_buffer * buffer,int cpu)4030 ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4031 {
4032 struct ring_buffer_per_cpu *cpu_buffer;
4033 unsigned long ret;
4034
4035 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4036 return 0;
4037
4038 cpu_buffer = buffer->buffers[cpu];
4039 ret = local_read(&cpu_buffer->dropped_events);
4040
4041 return ret;
4042 }
4043 EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4044
4045 /**
4046 * ring_buffer_read_events_cpu - get the number of events successfully read
4047 * @buffer: The ring buffer
4048 * @cpu: The per CPU buffer to get the number of events read
4049 */
4050 unsigned long
ring_buffer_read_events_cpu(struct trace_buffer * buffer,int cpu)4051 ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4052 {
4053 struct ring_buffer_per_cpu *cpu_buffer;
4054
4055 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4056 return 0;
4057
4058 cpu_buffer = buffer->buffers[cpu];
4059 return cpu_buffer->read;
4060 }
4061 EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4062
4063 /**
4064 * ring_buffer_entries - get the number of entries in a buffer
4065 * @buffer: The ring buffer
4066 *
4067 * Returns the total number of entries in the ring buffer
4068 * (all CPU entries)
4069 */
ring_buffer_entries(struct trace_buffer * buffer)4070 unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4071 {
4072 struct ring_buffer_per_cpu *cpu_buffer;
4073 unsigned long entries = 0;
4074 int cpu;
4075
4076 /* if you care about this being correct, lock the buffer */
4077 for_each_buffer_cpu(buffer, cpu) {
4078 cpu_buffer = buffer->buffers[cpu];
4079 entries += rb_num_of_entries(cpu_buffer);
4080 }
4081
4082 return entries;
4083 }
4084 EXPORT_SYMBOL_GPL(ring_buffer_entries);
4085
4086 /**
4087 * ring_buffer_overruns - get the number of overruns in buffer
4088 * @buffer: The ring buffer
4089 *
4090 * Returns the total number of overruns in the ring buffer
4091 * (all CPU entries)
4092 */
ring_buffer_overruns(struct trace_buffer * buffer)4093 unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4094 {
4095 struct ring_buffer_per_cpu *cpu_buffer;
4096 unsigned long overruns = 0;
4097 int cpu;
4098
4099 /* if you care about this being correct, lock the buffer */
4100 for_each_buffer_cpu(buffer, cpu) {
4101 cpu_buffer = buffer->buffers[cpu];
4102 overruns += local_read(&cpu_buffer->overrun);
4103 }
4104
4105 return overruns;
4106 }
4107 EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4108
rb_iter_reset(struct ring_buffer_iter * iter)4109 static void rb_iter_reset(struct ring_buffer_iter *iter)
4110 {
4111 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4112
4113 /* Iterator usage is expected to have record disabled */
4114 iter->head_page = cpu_buffer->reader_page;
4115 iter->head = cpu_buffer->reader_page->read;
4116 iter->next_event = iter->head;
4117
4118 iter->cache_reader_page = iter->head_page;
4119 iter->cache_read = cpu_buffer->read;
4120
4121 if (iter->head) {
4122 iter->read_stamp = cpu_buffer->read_stamp;
4123 iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4124 } else {
4125 iter->read_stamp = iter->head_page->page->time_stamp;
4126 iter->page_stamp = iter->read_stamp;
4127 }
4128 }
4129
4130 /**
4131 * ring_buffer_iter_reset - reset an iterator
4132 * @iter: The iterator to reset
4133 *
4134 * Resets the iterator, so that it will start from the beginning
4135 * again.
4136 */
ring_buffer_iter_reset(struct ring_buffer_iter * iter)4137 void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4138 {
4139 struct ring_buffer_per_cpu *cpu_buffer;
4140 unsigned long flags;
4141
4142 if (!iter)
4143 return;
4144
4145 cpu_buffer = iter->cpu_buffer;
4146
4147 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4148 rb_iter_reset(iter);
4149 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4150 }
4151 EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4152
4153 /**
4154 * ring_buffer_iter_empty - check if an iterator has no more to read
4155 * @iter: The iterator to check
4156 */
ring_buffer_iter_empty(struct ring_buffer_iter * iter)4157 int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4158 {
4159 struct ring_buffer_per_cpu *cpu_buffer;
4160 struct buffer_page *reader;
4161 struct buffer_page *head_page;
4162 struct buffer_page *commit_page;
4163 struct buffer_page *curr_commit_page;
4164 unsigned commit;
4165 u64 curr_commit_ts;
4166 u64 commit_ts;
4167
4168 cpu_buffer = iter->cpu_buffer;
4169 reader = cpu_buffer->reader_page;
4170 head_page = cpu_buffer->head_page;
4171 commit_page = cpu_buffer->commit_page;
4172 commit_ts = commit_page->page->time_stamp;
4173
4174 /*
4175 * When the writer goes across pages, it issues a cmpxchg which
4176 * is a mb(), which will synchronize with the rmb here.
4177 * (see rb_tail_page_update())
4178 */
4179 smp_rmb();
4180 commit = rb_page_commit(commit_page);
4181 /* We want to make sure that the commit page doesn't change */
4182 smp_rmb();
4183
4184 /* Make sure commit page didn't change */
4185 curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4186 curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4187
4188 /* If the commit page changed, then there's more data */
4189 if (curr_commit_page != commit_page ||
4190 curr_commit_ts != commit_ts)
4191 return 0;
4192
4193 /* Still racy, as it may return a false positive, but that's OK */
4194 return ((iter->head_page == commit_page && iter->head >= commit) ||
4195 (iter->head_page == reader && commit_page == head_page &&
4196 head_page->read == commit &&
4197 iter->head == rb_page_commit(cpu_buffer->reader_page)));
4198 }
4199 EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4200
4201 static void
rb_update_read_stamp(struct ring_buffer_per_cpu * cpu_buffer,struct ring_buffer_event * event)4202 rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4203 struct ring_buffer_event *event)
4204 {
4205 u64 delta;
4206
4207 switch (event->type_len) {
4208 case RINGBUF_TYPE_PADDING:
4209 return;
4210
4211 case RINGBUF_TYPE_TIME_EXTEND:
4212 delta = ring_buffer_event_time_stamp(event);
4213 cpu_buffer->read_stamp += delta;
4214 return;
4215
4216 case RINGBUF_TYPE_TIME_STAMP:
4217 delta = ring_buffer_event_time_stamp(event);
4218 cpu_buffer->read_stamp = delta;
4219 return;
4220
4221 case RINGBUF_TYPE_DATA:
4222 cpu_buffer->read_stamp += event->time_delta;
4223 return;
4224
4225 default:
4226 RB_WARN_ON(cpu_buffer, 1);
4227 }
4228 return;
4229 }
4230
4231 static void
rb_update_iter_read_stamp(struct ring_buffer_iter * iter,struct ring_buffer_event * event)4232 rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4233 struct ring_buffer_event *event)
4234 {
4235 u64 delta;
4236
4237 switch (event->type_len) {
4238 case RINGBUF_TYPE_PADDING:
4239 return;
4240
4241 case RINGBUF_TYPE_TIME_EXTEND:
4242 delta = ring_buffer_event_time_stamp(event);
4243 iter->read_stamp += delta;
4244 return;
4245
4246 case RINGBUF_TYPE_TIME_STAMP:
4247 delta = ring_buffer_event_time_stamp(event);
4248 iter->read_stamp = delta;
4249 return;
4250
4251 case RINGBUF_TYPE_DATA:
4252 iter->read_stamp += event->time_delta;
4253 return;
4254
4255 default:
4256 RB_WARN_ON(iter->cpu_buffer, 1);
4257 }
4258 return;
4259 }
4260
4261 static struct buffer_page *
rb_get_reader_page(struct ring_buffer_per_cpu * cpu_buffer)4262 rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4263 {
4264 struct buffer_page *reader = NULL;
4265 unsigned long overwrite;
4266 unsigned long flags;
4267 int nr_loops = 0;
4268 int ret;
4269
4270 local_irq_save(flags);
4271 arch_spin_lock(&cpu_buffer->lock);
4272
4273 again:
4274 /*
4275 * This should normally only loop twice. But because the
4276 * start of the reader inserts an empty page, it causes
4277 * a case where we will loop three times. There should be no
4278 * reason to loop four times (that I know of).
4279 */
4280 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4281 reader = NULL;
4282 goto out;
4283 }
4284
4285 reader = cpu_buffer->reader_page;
4286
4287 /* If there's more to read, return this page */
4288 if (cpu_buffer->reader_page->read < rb_page_size(reader))
4289 goto out;
4290
4291 /* Never should we have an index greater than the size */
4292 if (RB_WARN_ON(cpu_buffer,
4293 cpu_buffer->reader_page->read > rb_page_size(reader)))
4294 goto out;
4295
4296 /* check if we caught up to the tail */
4297 reader = NULL;
4298 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4299 goto out;
4300
4301 /* Don't bother swapping if the ring buffer is empty */
4302 if (rb_num_of_entries(cpu_buffer) == 0)
4303 goto out;
4304
4305 /*
4306 * Reset the reader page to size zero.
4307 */
4308 local_set(&cpu_buffer->reader_page->write, 0);
4309 local_set(&cpu_buffer->reader_page->entries, 0);
4310 local_set(&cpu_buffer->reader_page->page->commit, 0);
4311 cpu_buffer->reader_page->real_end = 0;
4312
4313 spin:
4314 /*
4315 * Splice the empty reader page into the list around the head.
4316 */
4317 reader = rb_set_head_page(cpu_buffer);
4318 if (!reader)
4319 goto out;
4320 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4321 cpu_buffer->reader_page->list.prev = reader->list.prev;
4322
4323 /*
4324 * cpu_buffer->pages just needs to point to the buffer, it
4325 * has no specific buffer page to point to. Lets move it out
4326 * of our way so we don't accidentally swap it.
4327 */
4328 cpu_buffer->pages = reader->list.prev;
4329
4330 /* The reader page will be pointing to the new head */
4331 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
4332
4333 /*
4334 * We want to make sure we read the overruns after we set up our
4335 * pointers to the next object. The writer side does a
4336 * cmpxchg to cross pages which acts as the mb on the writer
4337 * side. Note, the reader will constantly fail the swap
4338 * while the writer is updating the pointers, so this
4339 * guarantees that the overwrite recorded here is the one we
4340 * want to compare with the last_overrun.
4341 */
4342 smp_mb();
4343 overwrite = local_read(&(cpu_buffer->overrun));
4344
4345 /*
4346 * Here's the tricky part.
4347 *
4348 * We need to move the pointer past the header page.
4349 * But we can only do that if a writer is not currently
4350 * moving it. The page before the header page has the
4351 * flag bit '1' set if it is pointing to the page we want.
4352 * but if the writer is in the process of moving it
4353 * than it will be '2' or already moved '0'.
4354 */
4355
4356 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4357
4358 /*
4359 * If we did not convert it, then we must try again.
4360 */
4361 if (!ret)
4362 goto spin;
4363
4364 /*
4365 * Yay! We succeeded in replacing the page.
4366 *
4367 * Now make the new head point back to the reader page.
4368 */
4369 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4370 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
4371
4372 local_inc(&cpu_buffer->pages_read);
4373
4374 /* Finally update the reader page to the new head */
4375 cpu_buffer->reader_page = reader;
4376 cpu_buffer->reader_page->read = 0;
4377
4378 if (overwrite != cpu_buffer->last_overrun) {
4379 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4380 cpu_buffer->last_overrun = overwrite;
4381 }
4382
4383 goto again;
4384
4385 out:
4386 /* Update the read_stamp on the first event */
4387 if (reader && reader->read == 0)
4388 cpu_buffer->read_stamp = reader->page->time_stamp;
4389
4390 arch_spin_unlock(&cpu_buffer->lock);
4391 local_irq_restore(flags);
4392
4393 /*
4394 * The writer has preempt disable, wait for it. But not forever
4395 * Although, 1 second is pretty much "forever"
4396 */
4397 #define USECS_WAIT 1000000
4398 for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
4399 /* If the write is past the end of page, a writer is still updating it */
4400 if (likely(!reader || rb_page_write(reader) <= BUF_PAGE_SIZE))
4401 break;
4402
4403 udelay(1);
4404
4405 /* Get the latest version of the reader write value */
4406 smp_rmb();
4407 }
4408
4409 /* The writer is not moving forward? Something is wrong */
4410 if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
4411 reader = NULL;
4412
4413 /*
4414 * Make sure we see any padding after the write update
4415 * (see rb_reset_tail())
4416 */
4417 smp_rmb();
4418
4419
4420 return reader;
4421 }
4422
rb_advance_reader(struct ring_buffer_per_cpu * cpu_buffer)4423 static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4424 {
4425 struct ring_buffer_event *event;
4426 struct buffer_page *reader;
4427 unsigned length;
4428
4429 reader = rb_get_reader_page(cpu_buffer);
4430
4431 /* This function should not be called when buffer is empty */
4432 if (RB_WARN_ON(cpu_buffer, !reader))
4433 return;
4434
4435 event = rb_reader_event(cpu_buffer);
4436
4437 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4438 cpu_buffer->read++;
4439
4440 rb_update_read_stamp(cpu_buffer, event);
4441
4442 length = rb_event_length(event);
4443 cpu_buffer->reader_page->read += length;
4444 }
4445
rb_advance_iter(struct ring_buffer_iter * iter)4446 static void rb_advance_iter(struct ring_buffer_iter *iter)
4447 {
4448 struct ring_buffer_per_cpu *cpu_buffer;
4449
4450 cpu_buffer = iter->cpu_buffer;
4451
4452 /* If head == next_event then we need to jump to the next event */
4453 if (iter->head == iter->next_event) {
4454 /* If the event gets overwritten again, there's nothing to do */
4455 if (rb_iter_head_event(iter) == NULL)
4456 return;
4457 }
4458
4459 iter->head = iter->next_event;
4460
4461 /*
4462 * Check if we are at the end of the buffer.
4463 */
4464 if (iter->next_event >= rb_page_size(iter->head_page)) {
4465 /* discarded commits can make the page empty */
4466 if (iter->head_page == cpu_buffer->commit_page)
4467 return;
4468 rb_inc_iter(iter);
4469 return;
4470 }
4471
4472 rb_update_iter_read_stamp(iter, iter->event);
4473 }
4474
rb_lost_events(struct ring_buffer_per_cpu * cpu_buffer)4475 static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4476 {
4477 return cpu_buffer->lost_events;
4478 }
4479
4480 static struct ring_buffer_event *
rb_buffer_peek(struct ring_buffer_per_cpu * cpu_buffer,u64 * ts,unsigned long * lost_events)4481 rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4482 unsigned long *lost_events)
4483 {
4484 struct ring_buffer_event *event;
4485 struct buffer_page *reader;
4486 int nr_loops = 0;
4487
4488 if (ts)
4489 *ts = 0;
4490 again:
4491 /*
4492 * We repeat when a time extend is encountered.
4493 * Since the time extend is always attached to a data event,
4494 * we should never loop more than once.
4495 * (We never hit the following condition more than twice).
4496 */
4497 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4498 return NULL;
4499
4500 reader = rb_get_reader_page(cpu_buffer);
4501 if (!reader)
4502 return NULL;
4503
4504 event = rb_reader_event(cpu_buffer);
4505
4506 switch (event->type_len) {
4507 case RINGBUF_TYPE_PADDING:
4508 if (rb_null_event(event))
4509 RB_WARN_ON(cpu_buffer, 1);
4510 /*
4511 * Because the writer could be discarding every
4512 * event it creates (which would probably be bad)
4513 * if we were to go back to "again" then we may never
4514 * catch up, and will trigger the warn on, or lock
4515 * the box. Return the padding, and we will release
4516 * the current locks, and try again.
4517 */
4518 return event;
4519
4520 case RINGBUF_TYPE_TIME_EXTEND:
4521 /* Internal data, OK to advance */
4522 rb_advance_reader(cpu_buffer);
4523 goto again;
4524
4525 case RINGBUF_TYPE_TIME_STAMP:
4526 if (ts) {
4527 *ts = ring_buffer_event_time_stamp(event);
4528 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4529 cpu_buffer->cpu, ts);
4530 }
4531 /* Internal data, OK to advance */
4532 rb_advance_reader(cpu_buffer);
4533 goto again;
4534
4535 case RINGBUF_TYPE_DATA:
4536 if (ts && !(*ts)) {
4537 *ts = cpu_buffer->read_stamp + event->time_delta;
4538 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4539 cpu_buffer->cpu, ts);
4540 }
4541 if (lost_events)
4542 *lost_events = rb_lost_events(cpu_buffer);
4543 return event;
4544
4545 default:
4546 RB_WARN_ON(cpu_buffer, 1);
4547 }
4548
4549 return NULL;
4550 }
4551 EXPORT_SYMBOL_GPL(ring_buffer_peek);
4552
4553 static struct ring_buffer_event *
rb_iter_peek(struct ring_buffer_iter * iter,u64 * ts)4554 rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4555 {
4556 struct trace_buffer *buffer;
4557 struct ring_buffer_per_cpu *cpu_buffer;
4558 struct ring_buffer_event *event;
4559 int nr_loops = 0;
4560
4561 if (ts)
4562 *ts = 0;
4563
4564 cpu_buffer = iter->cpu_buffer;
4565 buffer = cpu_buffer->buffer;
4566
4567 /*
4568 * Check if someone performed a consuming read to
4569 * the buffer. A consuming read invalidates the iterator
4570 * and we need to reset the iterator in this case.
4571 */
4572 if (unlikely(iter->cache_read != cpu_buffer->read ||
4573 iter->cache_reader_page != cpu_buffer->reader_page))
4574 rb_iter_reset(iter);
4575
4576 again:
4577 if (ring_buffer_iter_empty(iter))
4578 return NULL;
4579
4580 /*
4581 * As the writer can mess with what the iterator is trying
4582 * to read, just give up if we fail to get an event after
4583 * three tries. The iterator is not as reliable when reading
4584 * the ring buffer with an active write as the consumer is.
4585 * Do not warn if the three failures is reached.
4586 */
4587 if (++nr_loops > 3)
4588 return NULL;
4589
4590 if (rb_per_cpu_empty(cpu_buffer))
4591 return NULL;
4592
4593 if (iter->head >= rb_page_size(iter->head_page)) {
4594 rb_inc_iter(iter);
4595 goto again;
4596 }
4597
4598 event = rb_iter_head_event(iter);
4599 if (!event)
4600 goto again;
4601
4602 switch (event->type_len) {
4603 case RINGBUF_TYPE_PADDING:
4604 if (rb_null_event(event)) {
4605 rb_inc_iter(iter);
4606 goto again;
4607 }
4608 rb_advance_iter(iter);
4609 return event;
4610
4611 case RINGBUF_TYPE_TIME_EXTEND:
4612 /* Internal data, OK to advance */
4613 rb_advance_iter(iter);
4614 goto again;
4615
4616 case RINGBUF_TYPE_TIME_STAMP:
4617 if (ts) {
4618 *ts = ring_buffer_event_time_stamp(event);
4619 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4620 cpu_buffer->cpu, ts);
4621 }
4622 /* Internal data, OK to advance */
4623 rb_advance_iter(iter);
4624 goto again;
4625
4626 case RINGBUF_TYPE_DATA:
4627 if (ts && !(*ts)) {
4628 *ts = iter->read_stamp + event->time_delta;
4629 ring_buffer_normalize_time_stamp(buffer,
4630 cpu_buffer->cpu, ts);
4631 }
4632 return event;
4633
4634 default:
4635 RB_WARN_ON(cpu_buffer, 1);
4636 }
4637
4638 return NULL;
4639 }
4640 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4641
rb_reader_lock(struct ring_buffer_per_cpu * cpu_buffer)4642 static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4643 {
4644 if (likely(!in_nmi())) {
4645 raw_spin_lock(&cpu_buffer->reader_lock);
4646 return true;
4647 }
4648
4649 /*
4650 * If an NMI die dumps out the content of the ring buffer
4651 * trylock must be used to prevent a deadlock if the NMI
4652 * preempted a task that holds the ring buffer locks. If
4653 * we get the lock then all is fine, if not, then continue
4654 * to do the read, but this can corrupt the ring buffer,
4655 * so it must be permanently disabled from future writes.
4656 * Reading from NMI is a oneshot deal.
4657 */
4658 if (raw_spin_trylock(&cpu_buffer->reader_lock))
4659 return true;
4660
4661 /* Continue without locking, but disable the ring buffer */
4662 atomic_inc(&cpu_buffer->record_disabled);
4663 return false;
4664 }
4665
4666 static inline void
rb_reader_unlock(struct ring_buffer_per_cpu * cpu_buffer,bool locked)4667 rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4668 {
4669 if (likely(locked))
4670 raw_spin_unlock(&cpu_buffer->reader_lock);
4671 return;
4672 }
4673
4674 /**
4675 * ring_buffer_peek - peek at the next event to be read
4676 * @buffer: The ring buffer to read
4677 * @cpu: The cpu to peak at
4678 * @ts: The timestamp counter of this event.
4679 * @lost_events: a variable to store if events were lost (may be NULL)
4680 *
4681 * This will return the event that will be read next, but does
4682 * not consume the data.
4683 */
4684 struct ring_buffer_event *
ring_buffer_peek(struct trace_buffer * buffer,int cpu,u64 * ts,unsigned long * lost_events)4685 ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4686 unsigned long *lost_events)
4687 {
4688 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4689 struct ring_buffer_event *event;
4690 unsigned long flags;
4691 bool dolock;
4692
4693 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4694 return NULL;
4695
4696 again:
4697 local_irq_save(flags);
4698 dolock = rb_reader_lock(cpu_buffer);
4699 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4700 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4701 rb_advance_reader(cpu_buffer);
4702 rb_reader_unlock(cpu_buffer, dolock);
4703 local_irq_restore(flags);
4704
4705 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4706 goto again;
4707
4708 return event;
4709 }
4710
4711 /** ring_buffer_iter_dropped - report if there are dropped events
4712 * @iter: The ring buffer iterator
4713 *
4714 * Returns true if there was dropped events since the last peek.
4715 */
ring_buffer_iter_dropped(struct ring_buffer_iter * iter)4716 bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4717 {
4718 bool ret = iter->missed_events != 0;
4719
4720 iter->missed_events = 0;
4721 return ret;
4722 }
4723 EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4724
4725 /**
4726 * ring_buffer_iter_peek - peek at the next event to be read
4727 * @iter: The ring buffer iterator
4728 * @ts: The timestamp counter of this event.
4729 *
4730 * This will return the event that will be read next, but does
4731 * not increment the iterator.
4732 */
4733 struct ring_buffer_event *
ring_buffer_iter_peek(struct ring_buffer_iter * iter,u64 * ts)4734 ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4735 {
4736 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4737 struct ring_buffer_event *event;
4738 unsigned long flags;
4739
4740 again:
4741 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4742 event = rb_iter_peek(iter, ts);
4743 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4744
4745 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4746 goto again;
4747
4748 return event;
4749 }
4750
4751 /**
4752 * ring_buffer_consume - return an event and consume it
4753 * @buffer: The ring buffer to get the next event from
4754 * @cpu: the cpu to read the buffer from
4755 * @ts: a variable to store the timestamp (may be NULL)
4756 * @lost_events: a variable to store if events were lost (may be NULL)
4757 *
4758 * Returns the next event in the ring buffer, and that event is consumed.
4759 * Meaning, that sequential reads will keep returning a different event,
4760 * and eventually empty the ring buffer if the producer is slower.
4761 */
4762 struct ring_buffer_event *
ring_buffer_consume(struct trace_buffer * buffer,int cpu,u64 * ts,unsigned long * lost_events)4763 ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4764 unsigned long *lost_events)
4765 {
4766 struct ring_buffer_per_cpu *cpu_buffer;
4767 struct ring_buffer_event *event = NULL;
4768 unsigned long flags;
4769 bool dolock;
4770
4771 again:
4772 /* might be called in atomic */
4773 preempt_disable();
4774
4775 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4776 goto out;
4777
4778 cpu_buffer = buffer->buffers[cpu];
4779 local_irq_save(flags);
4780 dolock = rb_reader_lock(cpu_buffer);
4781
4782 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4783 if (event) {
4784 cpu_buffer->lost_events = 0;
4785 rb_advance_reader(cpu_buffer);
4786 }
4787
4788 rb_reader_unlock(cpu_buffer, dolock);
4789 local_irq_restore(flags);
4790
4791 out:
4792 preempt_enable();
4793
4794 if (event && event->type_len == RINGBUF_TYPE_PADDING)
4795 goto again;
4796
4797 return event;
4798 }
4799 EXPORT_SYMBOL_GPL(ring_buffer_consume);
4800
4801 /**
4802 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4803 * @buffer: The ring buffer to read from
4804 * @cpu: The cpu buffer to iterate over
4805 * @flags: gfp flags to use for memory allocation
4806 *
4807 * This performs the initial preparations necessary to iterate
4808 * through the buffer. Memory is allocated, buffer recording
4809 * is disabled, and the iterator pointer is returned to the caller.
4810 *
4811 * Disabling buffer recording prevents the reading from being
4812 * corrupted. This is not a consuming read, so a producer is not
4813 * expected.
4814 *
4815 * After a sequence of ring_buffer_read_prepare calls, the user is
4816 * expected to make at least one call to ring_buffer_read_prepare_sync.
4817 * Afterwards, ring_buffer_read_start is invoked to get things going
4818 * for real.
4819 *
4820 * This overall must be paired with ring_buffer_read_finish.
4821 */
4822 struct ring_buffer_iter *
ring_buffer_read_prepare(struct trace_buffer * buffer,int cpu,gfp_t flags)4823 ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
4824 {
4825 struct ring_buffer_per_cpu *cpu_buffer;
4826 struct ring_buffer_iter *iter;
4827
4828 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4829 return NULL;
4830
4831 iter = kzalloc(sizeof(*iter), flags);
4832 if (!iter)
4833 return NULL;
4834
4835 iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
4836 if (!iter->event) {
4837 kfree(iter);
4838 return NULL;
4839 }
4840
4841 cpu_buffer = buffer->buffers[cpu];
4842
4843 iter->cpu_buffer = cpu_buffer;
4844
4845 atomic_inc(&cpu_buffer->resize_disabled);
4846
4847 return iter;
4848 }
4849 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4850
4851 /**
4852 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4853 *
4854 * All previously invoked ring_buffer_read_prepare calls to prepare
4855 * iterators will be synchronized. Afterwards, read_buffer_read_start
4856 * calls on those iterators are allowed.
4857 */
4858 void
ring_buffer_read_prepare_sync(void)4859 ring_buffer_read_prepare_sync(void)
4860 {
4861 synchronize_rcu();
4862 }
4863 EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4864
4865 /**
4866 * ring_buffer_read_start - start a non consuming read of the buffer
4867 * @iter: The iterator returned by ring_buffer_read_prepare
4868 *
4869 * This finalizes the startup of an iteration through the buffer.
4870 * The iterator comes from a call to ring_buffer_read_prepare and
4871 * an intervening ring_buffer_read_prepare_sync must have been
4872 * performed.
4873 *
4874 * Must be paired with ring_buffer_read_finish.
4875 */
4876 void
ring_buffer_read_start(struct ring_buffer_iter * iter)4877 ring_buffer_read_start(struct ring_buffer_iter *iter)
4878 {
4879 struct ring_buffer_per_cpu *cpu_buffer;
4880 unsigned long flags;
4881
4882 if (!iter)
4883 return;
4884
4885 cpu_buffer = iter->cpu_buffer;
4886
4887 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4888 arch_spin_lock(&cpu_buffer->lock);
4889 rb_iter_reset(iter);
4890 arch_spin_unlock(&cpu_buffer->lock);
4891 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4892 }
4893 EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4894
4895 /**
4896 * ring_buffer_read_finish - finish reading the iterator of the buffer
4897 * @iter: The iterator retrieved by ring_buffer_start
4898 *
4899 * This re-enables the recording to the buffer, and frees the
4900 * iterator.
4901 */
4902 void
ring_buffer_read_finish(struct ring_buffer_iter * iter)4903 ring_buffer_read_finish(struct ring_buffer_iter *iter)
4904 {
4905 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4906 unsigned long flags;
4907
4908 /*
4909 * Ring buffer is disabled from recording, here's a good place
4910 * to check the integrity of the ring buffer.
4911 * Must prevent readers from trying to read, as the check
4912 * clears the HEAD page and readers require it.
4913 */
4914 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4915 rb_check_pages(cpu_buffer);
4916 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4917
4918 atomic_dec(&cpu_buffer->resize_disabled);
4919 kfree(iter->event);
4920 kfree(iter);
4921 }
4922 EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4923
4924 /**
4925 * ring_buffer_iter_advance - advance the iterator to the next location
4926 * @iter: The ring buffer iterator
4927 *
4928 * Move the location of the iterator such that the next read will
4929 * be the next location of the iterator.
4930 */
ring_buffer_iter_advance(struct ring_buffer_iter * iter)4931 void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
4932 {
4933 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4934 unsigned long flags;
4935
4936 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4937
4938 rb_advance_iter(iter);
4939
4940 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4941 }
4942 EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
4943
4944 /**
4945 * ring_buffer_size - return the size of the ring buffer (in bytes)
4946 * @buffer: The ring buffer.
4947 * @cpu: The CPU to get ring buffer size from.
4948 */
ring_buffer_size(struct trace_buffer * buffer,int cpu)4949 unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
4950 {
4951 /*
4952 * Earlier, this method returned
4953 * BUF_PAGE_SIZE * buffer->nr_pages
4954 * Since the nr_pages field is now removed, we have converted this to
4955 * return the per cpu buffer value.
4956 */
4957 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4958 return 0;
4959
4960 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4961 }
4962 EXPORT_SYMBOL_GPL(ring_buffer_size);
4963
4964 static void
rb_reset_cpu(struct ring_buffer_per_cpu * cpu_buffer)4965 rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4966 {
4967 rb_head_page_deactivate(cpu_buffer);
4968
4969 cpu_buffer->head_page
4970 = list_entry(cpu_buffer->pages, struct buffer_page, list);
4971 local_set(&cpu_buffer->head_page->write, 0);
4972 local_set(&cpu_buffer->head_page->entries, 0);
4973 local_set(&cpu_buffer->head_page->page->commit, 0);
4974
4975 cpu_buffer->head_page->read = 0;
4976
4977 cpu_buffer->tail_page = cpu_buffer->head_page;
4978 cpu_buffer->commit_page = cpu_buffer->head_page;
4979
4980 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
4981 INIT_LIST_HEAD(&cpu_buffer->new_pages);
4982 local_set(&cpu_buffer->reader_page->write, 0);
4983 local_set(&cpu_buffer->reader_page->entries, 0);
4984 local_set(&cpu_buffer->reader_page->page->commit, 0);
4985 cpu_buffer->reader_page->read = 0;
4986
4987 local_set(&cpu_buffer->entries_bytes, 0);
4988 local_set(&cpu_buffer->overrun, 0);
4989 local_set(&cpu_buffer->commit_overrun, 0);
4990 local_set(&cpu_buffer->dropped_events, 0);
4991 local_set(&cpu_buffer->entries, 0);
4992 local_set(&cpu_buffer->committing, 0);
4993 local_set(&cpu_buffer->commits, 0);
4994 local_set(&cpu_buffer->pages_touched, 0);
4995 local_set(&cpu_buffer->pages_lost, 0);
4996 local_set(&cpu_buffer->pages_read, 0);
4997 cpu_buffer->last_pages_touch = 0;
4998 cpu_buffer->shortest_full = 0;
4999 cpu_buffer->read = 0;
5000 cpu_buffer->read_bytes = 0;
5001
5002 rb_time_set(&cpu_buffer->write_stamp, 0);
5003 rb_time_set(&cpu_buffer->before_stamp, 0);
5004
5005 cpu_buffer->lost_events = 0;
5006 cpu_buffer->last_overrun = 0;
5007
5008 rb_head_page_activate(cpu_buffer);
5009 }
5010
5011 /* Must have disabled the cpu buffer then done a synchronize_rcu */
reset_disabled_cpu_buffer(struct ring_buffer_per_cpu * cpu_buffer)5012 static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5013 {
5014 unsigned long flags;
5015
5016 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5017
5018 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5019 goto out;
5020
5021 arch_spin_lock(&cpu_buffer->lock);
5022
5023 rb_reset_cpu(cpu_buffer);
5024
5025 arch_spin_unlock(&cpu_buffer->lock);
5026
5027 out:
5028 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5029 }
5030
5031 /**
5032 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5033 * @buffer: The ring buffer to reset a per cpu buffer of
5034 * @cpu: The CPU buffer to be reset
5035 */
ring_buffer_reset_cpu(struct trace_buffer * buffer,int cpu)5036 void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5037 {
5038 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5039
5040 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5041 return;
5042
5043 /* prevent another thread from changing buffer sizes */
5044 mutex_lock(&buffer->mutex);
5045
5046 atomic_inc(&cpu_buffer->resize_disabled);
5047 atomic_inc(&cpu_buffer->record_disabled);
5048
5049 /* Make sure all commits have finished */
5050 synchronize_rcu();
5051
5052 reset_disabled_cpu_buffer(cpu_buffer);
5053
5054 atomic_dec(&cpu_buffer->record_disabled);
5055 atomic_dec(&cpu_buffer->resize_disabled);
5056
5057 mutex_unlock(&buffer->mutex);
5058 }
5059 EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5060
5061 /**
5062 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5063 * @buffer: The ring buffer to reset a per cpu buffer of
5064 * @cpu: The CPU buffer to be reset
5065 */
ring_buffer_reset_online_cpus(struct trace_buffer * buffer)5066 void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5067 {
5068 struct ring_buffer_per_cpu *cpu_buffer;
5069 int cpu;
5070
5071 /* prevent another thread from changing buffer sizes */
5072 mutex_lock(&buffer->mutex);
5073
5074 for_each_online_buffer_cpu(buffer, cpu) {
5075 cpu_buffer = buffer->buffers[cpu];
5076
5077 atomic_inc(&cpu_buffer->resize_disabled);
5078 atomic_inc(&cpu_buffer->record_disabled);
5079 }
5080
5081 /* Make sure all commits have finished */
5082 synchronize_rcu();
5083
5084 for_each_online_buffer_cpu(buffer, cpu) {
5085 cpu_buffer = buffer->buffers[cpu];
5086
5087 reset_disabled_cpu_buffer(cpu_buffer);
5088
5089 atomic_dec(&cpu_buffer->record_disabled);
5090 atomic_dec(&cpu_buffer->resize_disabled);
5091 }
5092
5093 mutex_unlock(&buffer->mutex);
5094 }
5095
5096 /**
5097 * ring_buffer_reset - reset a ring buffer
5098 * @buffer: The ring buffer to reset all cpu buffers
5099 */
ring_buffer_reset(struct trace_buffer * buffer)5100 void ring_buffer_reset(struct trace_buffer *buffer)
5101 {
5102 struct ring_buffer_per_cpu *cpu_buffer;
5103 int cpu;
5104
5105 /* prevent another thread from changing buffer sizes */
5106 mutex_lock(&buffer->mutex);
5107
5108 for_each_buffer_cpu(buffer, cpu) {
5109 cpu_buffer = buffer->buffers[cpu];
5110
5111 atomic_inc(&cpu_buffer->resize_disabled);
5112 atomic_inc(&cpu_buffer->record_disabled);
5113 }
5114
5115 /* Make sure all commits have finished */
5116 synchronize_rcu();
5117
5118 for_each_buffer_cpu(buffer, cpu) {
5119 cpu_buffer = buffer->buffers[cpu];
5120
5121 reset_disabled_cpu_buffer(cpu_buffer);
5122
5123 atomic_dec(&cpu_buffer->record_disabled);
5124 atomic_dec(&cpu_buffer->resize_disabled);
5125 }
5126
5127 mutex_unlock(&buffer->mutex);
5128 }
5129 EXPORT_SYMBOL_GPL(ring_buffer_reset);
5130
5131 /**
5132 * rind_buffer_empty - is the ring buffer empty?
5133 * @buffer: The ring buffer to test
5134 */
ring_buffer_empty(struct trace_buffer * buffer)5135 bool ring_buffer_empty(struct trace_buffer *buffer)
5136 {
5137 struct ring_buffer_per_cpu *cpu_buffer;
5138 unsigned long flags;
5139 bool dolock;
5140 int cpu;
5141 int ret;
5142
5143 /* yes this is racy, but if you don't like the race, lock the buffer */
5144 for_each_buffer_cpu(buffer, cpu) {
5145 cpu_buffer = buffer->buffers[cpu];
5146 local_irq_save(flags);
5147 dolock = rb_reader_lock(cpu_buffer);
5148 ret = rb_per_cpu_empty(cpu_buffer);
5149 rb_reader_unlock(cpu_buffer, dolock);
5150 local_irq_restore(flags);
5151
5152 if (!ret)
5153 return false;
5154 }
5155
5156 return true;
5157 }
5158 EXPORT_SYMBOL_GPL(ring_buffer_empty);
5159
5160 /**
5161 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5162 * @buffer: The ring buffer
5163 * @cpu: The CPU buffer to test
5164 */
ring_buffer_empty_cpu(struct trace_buffer * buffer,int cpu)5165 bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5166 {
5167 struct ring_buffer_per_cpu *cpu_buffer;
5168 unsigned long flags;
5169 bool dolock;
5170 int ret;
5171
5172 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5173 return true;
5174
5175 cpu_buffer = buffer->buffers[cpu];
5176 local_irq_save(flags);
5177 dolock = rb_reader_lock(cpu_buffer);
5178 ret = rb_per_cpu_empty(cpu_buffer);
5179 rb_reader_unlock(cpu_buffer, dolock);
5180 local_irq_restore(flags);
5181
5182 return ret;
5183 }
5184 EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5185
5186 #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5187 /**
5188 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5189 * @buffer_a: One buffer to swap with
5190 * @buffer_b: The other buffer to swap with
5191 * @cpu: the CPU of the buffers to swap
5192 *
5193 * This function is useful for tracers that want to take a "snapshot"
5194 * of a CPU buffer and has another back up buffer lying around.
5195 * it is expected that the tracer handles the cpu buffer not being
5196 * used at the moment.
5197 */
ring_buffer_swap_cpu(struct trace_buffer * buffer_a,struct trace_buffer * buffer_b,int cpu)5198 int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5199 struct trace_buffer *buffer_b, int cpu)
5200 {
5201 struct ring_buffer_per_cpu *cpu_buffer_a;
5202 struct ring_buffer_per_cpu *cpu_buffer_b;
5203 int ret = -EINVAL;
5204
5205 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5206 !cpumask_test_cpu(cpu, buffer_b->cpumask))
5207 goto out;
5208
5209 cpu_buffer_a = buffer_a->buffers[cpu];
5210 cpu_buffer_b = buffer_b->buffers[cpu];
5211
5212 /* At least make sure the two buffers are somewhat the same */
5213 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5214 goto out;
5215
5216 ret = -EAGAIN;
5217
5218 if (atomic_read(&buffer_a->record_disabled))
5219 goto out;
5220
5221 if (atomic_read(&buffer_b->record_disabled))
5222 goto out;
5223
5224 if (atomic_read(&cpu_buffer_a->record_disabled))
5225 goto out;
5226
5227 if (atomic_read(&cpu_buffer_b->record_disabled))
5228 goto out;
5229
5230 /*
5231 * We can't do a synchronize_rcu here because this
5232 * function can be called in atomic context.
5233 * Normally this will be called from the same CPU as cpu.
5234 * If not it's up to the caller to protect this.
5235 */
5236 atomic_inc(&cpu_buffer_a->record_disabled);
5237 atomic_inc(&cpu_buffer_b->record_disabled);
5238
5239 ret = -EBUSY;
5240 if (local_read(&cpu_buffer_a->committing))
5241 goto out_dec;
5242 if (local_read(&cpu_buffer_b->committing))
5243 goto out_dec;
5244
5245 buffer_a->buffers[cpu] = cpu_buffer_b;
5246 buffer_b->buffers[cpu] = cpu_buffer_a;
5247
5248 cpu_buffer_b->buffer = buffer_a;
5249 cpu_buffer_a->buffer = buffer_b;
5250
5251 ret = 0;
5252
5253 out_dec:
5254 atomic_dec(&cpu_buffer_a->record_disabled);
5255 atomic_dec(&cpu_buffer_b->record_disabled);
5256 out:
5257 return ret;
5258 }
5259 EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5260 #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5261
5262 /**
5263 * ring_buffer_alloc_read_page - allocate a page to read from buffer
5264 * @buffer: the buffer to allocate for.
5265 * @cpu: the cpu buffer to allocate.
5266 *
5267 * This function is used in conjunction with ring_buffer_read_page.
5268 * When reading a full page from the ring buffer, these functions
5269 * can be used to speed up the process. The calling function should
5270 * allocate a few pages first with this function. Then when it
5271 * needs to get pages from the ring buffer, it passes the result
5272 * of this function into ring_buffer_read_page, which will swap
5273 * the page that was allocated, with the read page of the buffer.
5274 *
5275 * Returns:
5276 * The page allocated, or ERR_PTR
5277 */
ring_buffer_alloc_read_page(struct trace_buffer * buffer,int cpu)5278 void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5279 {
5280 struct ring_buffer_per_cpu *cpu_buffer;
5281 struct buffer_data_page *bpage = NULL;
5282 unsigned long flags;
5283 struct page *page;
5284
5285 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5286 return ERR_PTR(-ENODEV);
5287
5288 cpu_buffer = buffer->buffers[cpu];
5289 local_irq_save(flags);
5290 arch_spin_lock(&cpu_buffer->lock);
5291
5292 if (cpu_buffer->free_page) {
5293 bpage = cpu_buffer->free_page;
5294 cpu_buffer->free_page = NULL;
5295 }
5296
5297 arch_spin_unlock(&cpu_buffer->lock);
5298 local_irq_restore(flags);
5299
5300 if (bpage)
5301 goto out;
5302
5303 page = alloc_pages_node(cpu_to_node(cpu),
5304 GFP_KERNEL | __GFP_NORETRY, 0);
5305 if (!page)
5306 return ERR_PTR(-ENOMEM);
5307
5308 bpage = page_address(page);
5309
5310 out:
5311 rb_init_page(bpage);
5312
5313 return bpage;
5314 }
5315 EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5316
5317 /**
5318 * ring_buffer_free_read_page - free an allocated read page
5319 * @buffer: the buffer the page was allocate for
5320 * @cpu: the cpu buffer the page came from
5321 * @data: the page to free
5322 *
5323 * Free a page allocated from ring_buffer_alloc_read_page.
5324 */
ring_buffer_free_read_page(struct trace_buffer * buffer,int cpu,void * data)5325 void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
5326 {
5327 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5328 struct buffer_data_page *bpage = data;
5329 struct page *page = virt_to_page(bpage);
5330 unsigned long flags;
5331
5332 /* If the page is still in use someplace else, we can't reuse it */
5333 if (page_ref_count(page) > 1)
5334 goto out;
5335
5336 local_irq_save(flags);
5337 arch_spin_lock(&cpu_buffer->lock);
5338
5339 if (!cpu_buffer->free_page) {
5340 cpu_buffer->free_page = bpage;
5341 bpage = NULL;
5342 }
5343
5344 arch_spin_unlock(&cpu_buffer->lock);
5345 local_irq_restore(flags);
5346
5347 out:
5348 free_page((unsigned long)bpage);
5349 }
5350 EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5351
5352 /**
5353 * ring_buffer_read_page - extract a page from the ring buffer
5354 * @buffer: buffer to extract from
5355 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5356 * @len: amount to extract
5357 * @cpu: the cpu of the buffer to extract
5358 * @full: should the extraction only happen when the page is full.
5359 *
5360 * This function will pull out a page from the ring buffer and consume it.
5361 * @data_page must be the address of the variable that was returned
5362 * from ring_buffer_alloc_read_page. This is because the page might be used
5363 * to swap with a page in the ring buffer.
5364 *
5365 * for example:
5366 * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5367 * if (IS_ERR(rpage))
5368 * return PTR_ERR(rpage);
5369 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5370 * if (ret >= 0)
5371 * process_page(rpage, ret);
5372 *
5373 * When @full is set, the function will not return true unless
5374 * the writer is off the reader page.
5375 *
5376 * Note: it is up to the calling functions to handle sleeps and wakeups.
5377 * The ring buffer can be used anywhere in the kernel and can not
5378 * blindly call wake_up. The layer that uses the ring buffer must be
5379 * responsible for that.
5380 *
5381 * Returns:
5382 * >=0 if data has been transferred, returns the offset of consumed data.
5383 * <0 if no data has been transferred.
5384 */
ring_buffer_read_page(struct trace_buffer * buffer,void ** data_page,size_t len,int cpu,int full)5385 int ring_buffer_read_page(struct trace_buffer *buffer,
5386 void **data_page, size_t len, int cpu, int full)
5387 {
5388 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5389 struct ring_buffer_event *event;
5390 struct buffer_data_page *bpage;
5391 struct buffer_page *reader;
5392 unsigned long missed_events;
5393 unsigned long flags;
5394 unsigned int commit;
5395 unsigned int read;
5396 u64 save_timestamp;
5397 int ret = -1;
5398
5399 if (!cpumask_test_cpu(cpu, buffer->cpumask))
5400 goto out;
5401
5402 /*
5403 * If len is not big enough to hold the page header, then
5404 * we can not copy anything.
5405 */
5406 if (len <= BUF_PAGE_HDR_SIZE)
5407 goto out;
5408
5409 len -= BUF_PAGE_HDR_SIZE;
5410
5411 if (!data_page)
5412 goto out;
5413
5414 bpage = *data_page;
5415 if (!bpage)
5416 goto out;
5417
5418 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5419
5420 reader = rb_get_reader_page(cpu_buffer);
5421 if (!reader)
5422 goto out_unlock;
5423
5424 event = rb_reader_event(cpu_buffer);
5425
5426 read = reader->read;
5427 commit = rb_page_commit(reader);
5428
5429 /* Check if any events were dropped */
5430 missed_events = cpu_buffer->lost_events;
5431
5432 /*
5433 * If this page has been partially read or
5434 * if len is not big enough to read the rest of the page or
5435 * a writer is still on the page, then
5436 * we must copy the data from the page to the buffer.
5437 * Otherwise, we can simply swap the page with the one passed in.
5438 */
5439 if (read || (len < (commit - read)) ||
5440 cpu_buffer->reader_page == cpu_buffer->commit_page) {
5441 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5442 unsigned int rpos = read;
5443 unsigned int pos = 0;
5444 unsigned int size;
5445
5446 /*
5447 * If a full page is expected, this can still be returned
5448 * if there's been a previous partial read and the
5449 * rest of the page can be read and the commit page is off
5450 * the reader page.
5451 */
5452 if (full &&
5453 (!read || (len < (commit - read)) ||
5454 cpu_buffer->reader_page == cpu_buffer->commit_page))
5455 goto out_unlock;
5456
5457 if (len > (commit - read))
5458 len = (commit - read);
5459
5460 /* Always keep the time extend and data together */
5461 size = rb_event_ts_length(event);
5462
5463 if (len < size)
5464 goto out_unlock;
5465
5466 /* save the current timestamp, since the user will need it */
5467 save_timestamp = cpu_buffer->read_stamp;
5468
5469 /* Need to copy one event at a time */
5470 do {
5471 /* We need the size of one event, because
5472 * rb_advance_reader only advances by one event,
5473 * whereas rb_event_ts_length may include the size of
5474 * one or two events.
5475 * We have already ensured there's enough space if this
5476 * is a time extend. */
5477 size = rb_event_length(event);
5478 memcpy(bpage->data + pos, rpage->data + rpos, size);
5479
5480 len -= size;
5481
5482 rb_advance_reader(cpu_buffer);
5483 rpos = reader->read;
5484 pos += size;
5485
5486 if (rpos >= commit)
5487 break;
5488
5489 event = rb_reader_event(cpu_buffer);
5490 /* Always keep the time extend and data together */
5491 size = rb_event_ts_length(event);
5492 } while (len >= size);
5493
5494 /* update bpage */
5495 local_set(&bpage->commit, pos);
5496 bpage->time_stamp = save_timestamp;
5497
5498 /* we copied everything to the beginning */
5499 read = 0;
5500 } else {
5501 /* update the entry counter */
5502 cpu_buffer->read += rb_page_entries(reader);
5503 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
5504
5505 /* swap the pages */
5506 rb_init_page(bpage);
5507 bpage = reader->page;
5508 reader->page = *data_page;
5509 local_set(&reader->write, 0);
5510 local_set(&reader->entries, 0);
5511 reader->read = 0;
5512 *data_page = bpage;
5513
5514 /*
5515 * Use the real_end for the data size,
5516 * This gives us a chance to store the lost events
5517 * on the page.
5518 */
5519 if (reader->real_end)
5520 local_set(&bpage->commit, reader->real_end);
5521 }
5522 ret = read;
5523
5524 cpu_buffer->lost_events = 0;
5525
5526 commit = local_read(&bpage->commit);
5527 /*
5528 * Set a flag in the commit field if we lost events
5529 */
5530 if (missed_events) {
5531 /* If there is room at the end of the page to save the
5532 * missed events, then record it there.
5533 */
5534 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
5535 memcpy(&bpage->data[commit], &missed_events,
5536 sizeof(missed_events));
5537 local_add(RB_MISSED_STORED, &bpage->commit);
5538 commit += sizeof(missed_events);
5539 }
5540 local_add(RB_MISSED_EVENTS, &bpage->commit);
5541 }
5542
5543 /*
5544 * This page may be off to user land. Zero it out here.
5545 */
5546 if (commit < BUF_PAGE_SIZE)
5547 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
5548
5549 out_unlock:
5550 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5551
5552 out:
5553 return ret;
5554 }
5555 EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5556
5557 /*
5558 * We only allocate new buffers, never free them if the CPU goes down.
5559 * If we were to free the buffer, then the user would lose any trace that was in
5560 * the buffer.
5561 */
trace_rb_cpu_prepare(unsigned int cpu,struct hlist_node * node)5562 int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
5563 {
5564 struct trace_buffer *buffer;
5565 long nr_pages_same;
5566 int cpu_i;
5567 unsigned long nr_pages;
5568
5569 buffer = container_of(node, struct trace_buffer, node);
5570 if (cpumask_test_cpu(cpu, buffer->cpumask))
5571 return 0;
5572
5573 nr_pages = 0;
5574 nr_pages_same = 1;
5575 /* check if all cpu sizes are same */
5576 for_each_buffer_cpu(buffer, cpu_i) {
5577 /* fill in the size from first enabled cpu */
5578 if (nr_pages == 0)
5579 nr_pages = buffer->buffers[cpu_i]->nr_pages;
5580 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
5581 nr_pages_same = 0;
5582 break;
5583 }
5584 }
5585 /* allocate minimum pages, user can later expand it */
5586 if (!nr_pages_same)
5587 nr_pages = 2;
5588 buffer->buffers[cpu] =
5589 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
5590 if (!buffer->buffers[cpu]) {
5591 WARN(1, "failed to allocate ring buffer on CPU %u\n",
5592 cpu);
5593 return -ENOMEM;
5594 }
5595 smp_wmb();
5596 cpumask_set_cpu(cpu, buffer->cpumask);
5597 return 0;
5598 }
5599
5600 #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5601 /*
5602 * This is a basic integrity check of the ring buffer.
5603 * Late in the boot cycle this test will run when configured in.
5604 * It will kick off a thread per CPU that will go into a loop
5605 * writing to the per cpu ring buffer various sizes of data.
5606 * Some of the data will be large items, some small.
5607 *
5608 * Another thread is created that goes into a spin, sending out
5609 * IPIs to the other CPUs to also write into the ring buffer.
5610 * this is to test the nesting ability of the buffer.
5611 *
5612 * Basic stats are recorded and reported. If something in the
5613 * ring buffer should happen that's not expected, a big warning
5614 * is displayed and all ring buffers are disabled.
5615 */
5616 static struct task_struct *rb_threads[NR_CPUS] __initdata;
5617
5618 struct rb_test_data {
5619 struct trace_buffer *buffer;
5620 unsigned long events;
5621 unsigned long bytes_written;
5622 unsigned long bytes_alloc;
5623 unsigned long bytes_dropped;
5624 unsigned long events_nested;
5625 unsigned long bytes_written_nested;
5626 unsigned long bytes_alloc_nested;
5627 unsigned long bytes_dropped_nested;
5628 int min_size_nested;
5629 int max_size_nested;
5630 int max_size;
5631 int min_size;
5632 int cpu;
5633 int cnt;
5634 };
5635
5636 static struct rb_test_data rb_data[NR_CPUS] __initdata;
5637
5638 /* 1 meg per cpu */
5639 #define RB_TEST_BUFFER_SIZE 1048576
5640
5641 static char rb_string[] __initdata =
5642 "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5643 "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5644 "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5645
5646 static bool rb_test_started __initdata;
5647
5648 struct rb_item {
5649 int size;
5650 char str[];
5651 };
5652
rb_write_something(struct rb_test_data * data,bool nested)5653 static __init int rb_write_something(struct rb_test_data *data, bool nested)
5654 {
5655 struct ring_buffer_event *event;
5656 struct rb_item *item;
5657 bool started;
5658 int event_len;
5659 int size;
5660 int len;
5661 int cnt;
5662
5663 /* Have nested writes different that what is written */
5664 cnt = data->cnt + (nested ? 27 : 0);
5665
5666 /* Multiply cnt by ~e, to make some unique increment */
5667 size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
5668
5669 len = size + sizeof(struct rb_item);
5670
5671 started = rb_test_started;
5672 /* read rb_test_started before checking buffer enabled */
5673 smp_rmb();
5674
5675 event = ring_buffer_lock_reserve(data->buffer, len);
5676 if (!event) {
5677 /* Ignore dropped events before test starts. */
5678 if (started) {
5679 if (nested)
5680 data->bytes_dropped += len;
5681 else
5682 data->bytes_dropped_nested += len;
5683 }
5684 return len;
5685 }
5686
5687 event_len = ring_buffer_event_length(event);
5688
5689 if (RB_WARN_ON(data->buffer, event_len < len))
5690 goto out;
5691
5692 item = ring_buffer_event_data(event);
5693 item->size = size;
5694 memcpy(item->str, rb_string, size);
5695
5696 if (nested) {
5697 data->bytes_alloc_nested += event_len;
5698 data->bytes_written_nested += len;
5699 data->events_nested++;
5700 if (!data->min_size_nested || len < data->min_size_nested)
5701 data->min_size_nested = len;
5702 if (len > data->max_size_nested)
5703 data->max_size_nested = len;
5704 } else {
5705 data->bytes_alloc += event_len;
5706 data->bytes_written += len;
5707 data->events++;
5708 if (!data->min_size || len < data->min_size)
5709 data->max_size = len;
5710 if (len > data->max_size)
5711 data->max_size = len;
5712 }
5713
5714 out:
5715 ring_buffer_unlock_commit(data->buffer, event);
5716
5717 return 0;
5718 }
5719
rb_test(void * arg)5720 static __init int rb_test(void *arg)
5721 {
5722 struct rb_test_data *data = arg;
5723
5724 while (!kthread_should_stop()) {
5725 rb_write_something(data, false);
5726 data->cnt++;
5727
5728 set_current_state(TASK_INTERRUPTIBLE);
5729 /* Now sleep between a min of 100-300us and a max of 1ms */
5730 usleep_range(((data->cnt % 3) + 1) * 100, 1000);
5731 }
5732
5733 return 0;
5734 }
5735
rb_ipi(void * ignore)5736 static __init void rb_ipi(void *ignore)
5737 {
5738 struct rb_test_data *data;
5739 int cpu = smp_processor_id();
5740
5741 data = &rb_data[cpu];
5742 rb_write_something(data, true);
5743 }
5744
rb_hammer_test(void * arg)5745 static __init int rb_hammer_test(void *arg)
5746 {
5747 while (!kthread_should_stop()) {
5748
5749 /* Send an IPI to all cpus to write data! */
5750 smp_call_function(rb_ipi, NULL, 1);
5751 /* No sleep, but for non preempt, let others run */
5752 schedule();
5753 }
5754
5755 return 0;
5756 }
5757
test_ringbuffer(void)5758 static __init int test_ringbuffer(void)
5759 {
5760 struct task_struct *rb_hammer;
5761 struct trace_buffer *buffer;
5762 int cpu;
5763 int ret = 0;
5764
5765 if (security_locked_down(LOCKDOWN_TRACEFS)) {
5766 pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
5767 return 0;
5768 }
5769
5770 pr_info("Running ring buffer tests...\n");
5771
5772 buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5773 if (WARN_ON(!buffer))
5774 return 0;
5775
5776 /* Disable buffer so that threads can't write to it yet */
5777 ring_buffer_record_off(buffer);
5778
5779 for_each_online_cpu(cpu) {
5780 rb_data[cpu].buffer = buffer;
5781 rb_data[cpu].cpu = cpu;
5782 rb_data[cpu].cnt = cpu;
5783 rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5784 "rbtester/%d", cpu);
5785 if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5786 pr_cont("FAILED\n");
5787 ret = PTR_ERR(rb_threads[cpu]);
5788 goto out_free;
5789 }
5790
5791 kthread_bind(rb_threads[cpu], cpu);
5792 wake_up_process(rb_threads[cpu]);
5793 }
5794
5795 /* Now create the rb hammer! */
5796 rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5797 if (WARN_ON(IS_ERR(rb_hammer))) {
5798 pr_cont("FAILED\n");
5799 ret = PTR_ERR(rb_hammer);
5800 goto out_free;
5801 }
5802
5803 ring_buffer_record_on(buffer);
5804 /*
5805 * Show buffer is enabled before setting rb_test_started.
5806 * Yes there's a small race window where events could be
5807 * dropped and the thread wont catch it. But when a ring
5808 * buffer gets enabled, there will always be some kind of
5809 * delay before other CPUs see it. Thus, we don't care about
5810 * those dropped events. We care about events dropped after
5811 * the threads see that the buffer is active.
5812 */
5813 smp_wmb();
5814 rb_test_started = true;
5815
5816 set_current_state(TASK_INTERRUPTIBLE);
5817 /* Just run for 10 seconds */;
5818 schedule_timeout(10 * HZ);
5819
5820 kthread_stop(rb_hammer);
5821
5822 out_free:
5823 for_each_online_cpu(cpu) {
5824 if (!rb_threads[cpu])
5825 break;
5826 kthread_stop(rb_threads[cpu]);
5827 }
5828 if (ret) {
5829 ring_buffer_free(buffer);
5830 return ret;
5831 }
5832
5833 /* Report! */
5834 pr_info("finished\n");
5835 for_each_online_cpu(cpu) {
5836 struct ring_buffer_event *event;
5837 struct rb_test_data *data = &rb_data[cpu];
5838 struct rb_item *item;
5839 unsigned long total_events;
5840 unsigned long total_dropped;
5841 unsigned long total_written;
5842 unsigned long total_alloc;
5843 unsigned long total_read = 0;
5844 unsigned long total_size = 0;
5845 unsigned long total_len = 0;
5846 unsigned long total_lost = 0;
5847 unsigned long lost;
5848 int big_event_size;
5849 int small_event_size;
5850
5851 ret = -1;
5852
5853 total_events = data->events + data->events_nested;
5854 total_written = data->bytes_written + data->bytes_written_nested;
5855 total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5856 total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5857
5858 big_event_size = data->max_size + data->max_size_nested;
5859 small_event_size = data->min_size + data->min_size_nested;
5860
5861 pr_info("CPU %d:\n", cpu);
5862 pr_info(" events: %ld\n", total_events);
5863 pr_info(" dropped bytes: %ld\n", total_dropped);
5864 pr_info(" alloced bytes: %ld\n", total_alloc);
5865 pr_info(" written bytes: %ld\n", total_written);
5866 pr_info(" biggest event: %d\n", big_event_size);
5867 pr_info(" smallest event: %d\n", small_event_size);
5868
5869 if (RB_WARN_ON(buffer, total_dropped))
5870 break;
5871
5872 ret = 0;
5873
5874 while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5875 total_lost += lost;
5876 item = ring_buffer_event_data(event);
5877 total_len += ring_buffer_event_length(event);
5878 total_size += item->size + sizeof(struct rb_item);
5879 if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5880 pr_info("FAILED!\n");
5881 pr_info("buffer had: %.*s\n", item->size, item->str);
5882 pr_info("expected: %.*s\n", item->size, rb_string);
5883 RB_WARN_ON(buffer, 1);
5884 ret = -1;
5885 break;
5886 }
5887 total_read++;
5888 }
5889 if (ret)
5890 break;
5891
5892 ret = -1;
5893
5894 pr_info(" read events: %ld\n", total_read);
5895 pr_info(" lost events: %ld\n", total_lost);
5896 pr_info(" total events: %ld\n", total_lost + total_read);
5897 pr_info(" recorded len bytes: %ld\n", total_len);
5898 pr_info(" recorded size bytes: %ld\n", total_size);
5899 if (total_lost)
5900 pr_info(" With dropped events, record len and size may not match\n"
5901 " alloced and written from above\n");
5902 if (!total_lost) {
5903 if (RB_WARN_ON(buffer, total_len != total_alloc ||
5904 total_size != total_written))
5905 break;
5906 }
5907 if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5908 break;
5909
5910 ret = 0;
5911 }
5912 if (!ret)
5913 pr_info("Ring buffer PASSED!\n");
5914
5915 ring_buffer_free(buffer);
5916 return 0;
5917 }
5918
5919 late_initcall(test_ringbuffer);
5920 #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
5921