Line data Source code
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_recursion.h>
8 : #include <linux/trace_events.h>
9 : #include <linux/ring_buffer.h>
10 : #include <linux/trace_clock.h>
11 : #include <linux/sched/clock.h>
12 : #include <linux/trace_seq.h>
13 : #include <linux/spinlock.h>
14 : #include <linux/irq_work.h>
15 : #include <linux/security.h>
16 : #include <linux/uaccess.h>
17 : #include <linux/hardirq.h>
18 : #include <linux/kthread.h> /* for self test */
19 : #include <linux/module.h>
20 : #include <linux/percpu.h>
21 : #include <linux/mutex.h>
22 : #include <linux/delay.h>
23 : #include <linux/slab.h>
24 : #include <linux/init.h>
25 : #include <linux/hash.h>
26 : #include <linux/list.h>
27 : #include <linux/cpu.h>
28 : #include <linux/oom.h>
29 :
30 : #include <asm/local.h>
31 :
32 : static void update_pages_handler(struct work_struct *work);
33 :
34 : /*
35 : * The ring buffer header is special. We must manually up keep it.
36 : */
37 0 : int ring_buffer_print_entry_header(struct trace_seq *s)
38 : {
39 0 : trace_seq_puts(s, "# compressed entry header\n");
40 0 : trace_seq_puts(s, "\ttype_len : 5 bits\n");
41 0 : trace_seq_puts(s, "\ttime_delta : 27 bits\n");
42 0 : trace_seq_puts(s, "\tarray : 32 bits\n");
43 0 : trace_seq_putc(s, '\n');
44 0 : trace_seq_printf(s, "\tpadding : type == %d\n",
45 : RINGBUF_TYPE_PADDING);
46 0 : trace_seq_printf(s, "\ttime_extend : type == %d\n",
47 : RINGBUF_TYPE_TIME_EXTEND);
48 0 : trace_seq_printf(s, "\ttime_stamp : type == %d\n",
49 : RINGBUF_TYPE_TIME_STAMP);
50 0 : trace_seq_printf(s, "\tdata max type_len == %d\n",
51 : RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
52 :
53 0 : return !trace_seq_has_overflowed(s);
54 : }
55 :
56 : /*
57 : * The ring buffer is made up of a list of pages. A separate list of pages is
58 : * allocated for each CPU. A writer may only write to a buffer that is
59 : * associated with the CPU it is currently executing on. A reader may read
60 : * from any per cpu buffer.
61 : *
62 : * The reader is special. For each per cpu buffer, the reader has its own
63 : * reader page. When a reader has read the entire reader page, this reader
64 : * page is swapped with another page in the ring buffer.
65 : *
66 : * Now, as long as the writer is off the reader page, the reader can do what
67 : * ever it wants with that page. The writer will never write to that page
68 : * again (as long as it is out of the ring buffer).
69 : *
70 : * Here's some silly ASCII art.
71 : *
72 : * +------+
73 : * |reader| RING BUFFER
74 : * |page |
75 : * +------+ +---+ +---+ +---+
76 : * | |-->| |-->| |
77 : * +---+ +---+ +---+
78 : * ^ |
79 : * | |
80 : * +---------------+
81 : *
82 : *
83 : * +------+
84 : * |reader| RING BUFFER
85 : * |page |------------------v
86 : * +------+ +---+ +---+ +---+
87 : * | |-->| |-->| |
88 : * +---+ +---+ +---+
89 : * ^ |
90 : * | |
91 : * +---------------+
92 : *
93 : *
94 : * +------+
95 : * |reader| RING BUFFER
96 : * |page |------------------v
97 : * +------+ +---+ +---+ +---+
98 : * ^ | |-->| |-->| |
99 : * | +---+ +---+ +---+
100 : * | |
101 : * | |
102 : * +------------------------------+
103 : *
104 : *
105 : * +------+
106 : * |buffer| RING BUFFER
107 : * |page |------------------v
108 : * +------+ +---+ +---+ +---+
109 : * ^ | | | |-->| |
110 : * | New +---+ +---+ +---+
111 : * | Reader------^ |
112 : * | page |
113 : * +------------------------------+
114 : *
115 : *
116 : * After we make this swap, the reader can hand this page off to the splice
117 : * code and be done with it. It can even allocate a new page if it needs to
118 : * and swap that into the ring buffer.
119 : *
120 : * We will be using cmpxchg soon to make all this lockless.
121 : *
122 : */
123 :
124 : /* Used for individual buffers (after the counter) */
125 : #define RB_BUFFER_OFF (1 << 20)
126 :
127 : #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
128 :
129 : #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
130 : #define RB_ALIGNMENT 4U
131 : #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
132 : #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
133 :
134 : #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
135 : # define RB_FORCE_8BYTE_ALIGNMENT 0
136 : # define RB_ARCH_ALIGNMENT RB_ALIGNMENT
137 : #else
138 : # define RB_FORCE_8BYTE_ALIGNMENT 1
139 : # define RB_ARCH_ALIGNMENT 8U
140 : #endif
141 :
142 : #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
143 :
144 : /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
145 : #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
146 :
147 : enum {
148 : RB_LEN_TIME_EXTEND = 8,
149 : RB_LEN_TIME_STAMP = 8,
150 : };
151 :
152 : #define skip_time_extend(event) \
153 : ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
154 :
155 : #define extended_time(event) \
156 : (event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
157 :
158 0 : static inline int rb_null_event(struct ring_buffer_event *event)
159 : {
160 0 : return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
161 : }
162 :
163 0 : static void rb_event_set_padding(struct ring_buffer_event *event)
164 : {
165 : /* padding has a NULL time_delta */
166 0 : event->type_len = RINGBUF_TYPE_PADDING;
167 0 : event->time_delta = 0;
168 : }
169 :
170 : static unsigned
171 0 : rb_event_data_length(struct ring_buffer_event *event)
172 : {
173 0 : unsigned length;
174 :
175 0 : if (event->type_len)
176 0 : length = event->type_len * RB_ALIGNMENT;
177 : else
178 0 : length = event->array[0];
179 0 : return length + RB_EVNT_HDR_SIZE;
180 : }
181 :
182 : /*
183 : * Return the length of the given event. Will return
184 : * the length of the time extend if the event is a
185 : * time extend.
186 : */
187 : static inline unsigned
188 0 : rb_event_length(struct ring_buffer_event *event)
189 : {
190 0 : switch (event->type_len) {
191 : case RINGBUF_TYPE_PADDING:
192 0 : if (rb_null_event(event))
193 : /* undefined */
194 : return -1;
195 0 : return event->array[0] + RB_EVNT_HDR_SIZE;
196 :
197 : case RINGBUF_TYPE_TIME_EXTEND:
198 : return RB_LEN_TIME_EXTEND;
199 :
200 : case RINGBUF_TYPE_TIME_STAMP:
201 : return RB_LEN_TIME_STAMP;
202 :
203 : case RINGBUF_TYPE_DATA:
204 0 : return rb_event_data_length(event);
205 : default:
206 0 : WARN_ON_ONCE(1);
207 : }
208 : /* not hit */
209 0 : return 0;
210 : }
211 :
212 : /*
213 : * Return total length of time extend and data,
214 : * or just the event length for all other events.
215 : */
216 : static inline unsigned
217 0 : rb_event_ts_length(struct ring_buffer_event *event)
218 : {
219 0 : unsigned len = 0;
220 :
221 0 : if (extended_time(event)) {
222 : /* time extends include the data event after it */
223 0 : len = RB_LEN_TIME_EXTEND;
224 0 : event = skip_time_extend(event);
225 : }
226 0 : return len + rb_event_length(event);
227 : }
228 :
229 : /**
230 : * ring_buffer_event_length - return the length of the event
231 : * @event: the event to get the length of
232 : *
233 : * Returns the size of the data load of a data event.
234 : * If the event is something other than a data event, it
235 : * returns the size of the event itself. With the exception
236 : * of a TIME EXTEND, where it still returns the size of the
237 : * data load of the data event after it.
238 : */
239 0 : unsigned ring_buffer_event_length(struct ring_buffer_event *event)
240 : {
241 0 : unsigned length;
242 :
243 0 : if (extended_time(event))
244 0 : event = skip_time_extend(event);
245 :
246 0 : length = rb_event_length(event);
247 0 : if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
248 : return length;
249 0 : length -= RB_EVNT_HDR_SIZE;
250 0 : if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
251 0 : length -= sizeof(event->array[0]);
252 : return length;
253 : }
254 : EXPORT_SYMBOL_GPL(ring_buffer_event_length);
255 :
256 : /* inline for ring buffer fast paths */
257 : static __always_inline void *
258 0 : rb_event_data(struct ring_buffer_event *event)
259 : {
260 0 : if (extended_time(event))
261 0 : event = skip_time_extend(event);
262 0 : WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
263 : /* If length is in len field, then array[0] has the data */
264 0 : if (event->type_len)
265 0 : return (void *)&event->array[0];
266 : /* Otherwise length is in array[0] and array[1] has the data */
267 0 : return (void *)&event->array[1];
268 : }
269 :
270 : /**
271 : * ring_buffer_event_data - return the data of the event
272 : * @event: the event to get the data from
273 : */
274 0 : void *ring_buffer_event_data(struct ring_buffer_event *event)
275 : {
276 0 : return rb_event_data(event);
277 : }
278 : EXPORT_SYMBOL_GPL(ring_buffer_event_data);
279 :
280 : #define for_each_buffer_cpu(buffer, cpu) \
281 : for_each_cpu(cpu, buffer->cpumask)
282 :
283 : #define for_each_online_buffer_cpu(buffer, cpu) \
284 : for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
285 :
286 : #define TS_SHIFT 27
287 : #define TS_MASK ((1ULL << TS_SHIFT) - 1)
288 : #define TS_DELTA_TEST (~TS_MASK)
289 :
290 : /**
291 : * ring_buffer_event_time_stamp - return the event's extended timestamp
292 : * @event: the event to get the timestamp of
293 : *
294 : * Returns the extended timestamp associated with a data event.
295 : * An extended time_stamp is a 64-bit timestamp represented
296 : * internally in a special way that makes the best use of space
297 : * contained within a ring buffer event. This function decodes
298 : * it and maps it to a straight u64 value.
299 : */
300 0 : u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)
301 : {
302 0 : u64 ts;
303 :
304 0 : ts = event->array[0];
305 0 : ts <<= TS_SHIFT;
306 0 : ts += event->time_delta;
307 :
308 0 : return ts;
309 : }
310 :
311 : /* Flag when events were overwritten */
312 : #define RB_MISSED_EVENTS (1 << 31)
313 : /* Missed count stored at end */
314 : #define RB_MISSED_STORED (1 << 30)
315 :
316 : struct buffer_data_page {
317 : u64 time_stamp; /* page time stamp */
318 : local_t commit; /* write committed index */
319 : unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
320 : };
321 :
322 : /*
323 : * Note, the buffer_page list must be first. The buffer pages
324 : * are allocated in cache lines, which means that each buffer
325 : * page will be at the beginning of a cache line, and thus
326 : * the least significant bits will be zero. We use this to
327 : * add flags in the list struct pointers, to make the ring buffer
328 : * lockless.
329 : */
330 : struct buffer_page {
331 : struct list_head list; /* list of buffer pages */
332 : local_t write; /* index for next write */
333 : unsigned read; /* index for next read */
334 : local_t entries; /* entries on this page */
335 : unsigned long real_end; /* real end of data */
336 : struct buffer_data_page *page; /* Actual data page */
337 : };
338 :
339 : /*
340 : * The buffer page counters, write and entries, must be reset
341 : * atomically when crossing page boundaries. To synchronize this
342 : * update, two counters are inserted into the number. One is
343 : * the actual counter for the write position or count on the page.
344 : *
345 : * The other is a counter of updaters. Before an update happens
346 : * the update partition of the counter is incremented. This will
347 : * allow the updater to update the counter atomically.
348 : *
349 : * The counter is 20 bits, and the state data is 12.
350 : */
351 : #define RB_WRITE_MASK 0xfffff
352 : #define RB_WRITE_INTCNT (1 << 20)
353 :
354 24 : static void rb_init_page(struct buffer_data_page *bpage)
355 : {
356 48 : local_set(&bpage->commit, 0);
357 : }
358 :
359 : /*
360 : * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
361 : * this issue out.
362 : */
363 0 : static void free_buffer_page(struct buffer_page *bpage)
364 : {
365 0 : free_page((unsigned long)bpage->page);
366 0 : kfree(bpage);
367 0 : }
368 :
369 : /*
370 : * We need to fit the time_stamp delta into 27 bits.
371 : */
372 0 : static inline int test_time_stamp(u64 delta)
373 : {
374 0 : if (delta & TS_DELTA_TEST)
375 0 : return 1;
376 : return 0;
377 : }
378 :
379 : #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
380 :
381 : /* Max payload is BUF_PAGE_SIZE - header (8bytes) */
382 : #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
383 :
384 0 : int ring_buffer_print_page_header(struct trace_seq *s)
385 : {
386 0 : struct buffer_data_page field;
387 :
388 0 : trace_seq_printf(s, "\tfield: u64 timestamp;\t"
389 : "offset:0;\tsize:%u;\tsigned:%u;\n",
390 : (unsigned int)sizeof(field.time_stamp),
391 : (unsigned int)is_signed_type(u64));
392 :
393 0 : trace_seq_printf(s, "\tfield: local_t commit;\t"
394 : "offset:%u;\tsize:%u;\tsigned:%u;\n",
395 : (unsigned int)offsetof(typeof(field), commit),
396 : (unsigned int)sizeof(field.commit),
397 : (unsigned int)is_signed_type(long));
398 :
399 0 : trace_seq_printf(s, "\tfield: int overwrite;\t"
400 : "offset:%u;\tsize:%u;\tsigned:%u;\n",
401 : (unsigned int)offsetof(typeof(field), commit),
402 : 1,
403 : (unsigned int)is_signed_type(long));
404 :
405 0 : trace_seq_printf(s, "\tfield: char data;\t"
406 : "offset:%u;\tsize:%u;\tsigned:%u;\n",
407 : (unsigned int)offsetof(typeof(field), data),
408 : (unsigned int)BUF_PAGE_SIZE,
409 : (unsigned int)is_signed_type(char));
410 :
411 0 : return !trace_seq_has_overflowed(s);
412 : }
413 :
414 : struct rb_irq_work {
415 : struct irq_work work;
416 : wait_queue_head_t waiters;
417 : wait_queue_head_t full_waiters;
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_read;
521 : long last_pages_touch;
522 : size_t shortest_full;
523 : unsigned long read;
524 : unsigned long read_bytes;
525 : rb_time_t write_stamp;
526 : rb_time_t before_stamp;
527 : u64 read_stamp;
528 : /* ring buffer pages to update, > 0 to add, < 0 to remove */
529 : long nr_pages_to_update;
530 : struct list_head new_pages; /* new pages to add */
531 : struct work_struct update_pages_work;
532 : struct completion update_done;
533 :
534 : struct rb_irq_work irq_work;
535 : };
536 :
537 : struct trace_buffer {
538 : unsigned flags;
539 : int cpus;
540 : atomic_t record_disabled;
541 : cpumask_var_t cpumask;
542 :
543 : struct lock_class_key *reader_lock_key;
544 :
545 : struct mutex mutex;
546 :
547 : struct ring_buffer_per_cpu **buffers;
548 :
549 : struct hlist_node node;
550 : u64 (*clock)(void);
551 :
552 : struct rb_irq_work irq_work;
553 : bool time_stamp_abs;
554 : };
555 :
556 : struct ring_buffer_iter {
557 : struct ring_buffer_per_cpu *cpu_buffer;
558 : unsigned long head;
559 : unsigned long next_event;
560 : struct buffer_page *head_page;
561 : struct buffer_page *cache_reader_page;
562 : unsigned long cache_read;
563 : u64 read_stamp;
564 : u64 page_stamp;
565 : struct ring_buffer_event *event;
566 : int missed_events;
567 : };
568 :
569 : #ifdef RB_TIME_32
570 :
571 : /*
572 : * On 32 bit machines, local64_t is very expensive. As the ring
573 : * buffer doesn't need all the features of a true 64 bit atomic,
574 : * on 32 bit, it uses these functions (64 still uses local64_t).
575 : *
576 : * For the ring buffer, 64 bit required operations for the time is
577 : * the following:
578 : *
579 : * - Only need 59 bits (uses 60 to make it even).
580 : * - Reads may fail if it interrupted a modification of the time stamp.
581 : * It will succeed if it did not interrupt another write even if
582 : * the read itself is interrupted by a write.
583 : * It returns whether it was successful or not.
584 : *
585 : * - Writes always succeed and will overwrite other writes and writes
586 : * that were done by events interrupting the current write.
587 : *
588 : * - A write followed by a read of the same time stamp will always succeed,
589 : * but may not contain the same value.
590 : *
591 : * - A cmpxchg will fail if it interrupted another write or cmpxchg.
592 : * Other than that, it acts like a normal cmpxchg.
593 : *
594 : * The 60 bit time stamp is broken up by 30 bits in a top and bottom half
595 : * (bottom being the least significant 30 bits of the 60 bit time stamp).
596 : *
597 : * The two most significant bits of each half holds a 2 bit counter (0-3).
598 : * Each update will increment this counter by one.
599 : * When reading the top and bottom, if the two counter bits match then the
600 : * top and bottom together make a valid 60 bit number.
601 : */
602 : #define RB_TIME_SHIFT 30
603 : #define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1)
604 :
605 : static inline int rb_time_cnt(unsigned long val)
606 : {
607 : return (val >> RB_TIME_SHIFT) & 3;
608 : }
609 :
610 : static inline u64 rb_time_val(unsigned long top, unsigned long bottom)
611 : {
612 : u64 val;
613 :
614 : val = top & RB_TIME_VAL_MASK;
615 : val <<= RB_TIME_SHIFT;
616 : val |= bottom & RB_TIME_VAL_MASK;
617 :
618 : return val;
619 : }
620 :
621 : static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt)
622 : {
623 : unsigned long top, bottom;
624 : unsigned long c;
625 :
626 : /*
627 : * If the read is interrupted by a write, then the cnt will
628 : * be different. Loop until both top and bottom have been read
629 : * without interruption.
630 : */
631 : do {
632 : c = local_read(&t->cnt);
633 : top = local_read(&t->top);
634 : bottom = local_read(&t->bottom);
635 : } while (c != local_read(&t->cnt));
636 :
637 : *cnt = rb_time_cnt(top);
638 :
639 : /* If top and bottom counts don't match, this interrupted a write */
640 : if (*cnt != rb_time_cnt(bottom))
641 : return false;
642 :
643 : *ret = rb_time_val(top, bottom);
644 : return true;
645 : }
646 :
647 : static bool rb_time_read(rb_time_t *t, u64 *ret)
648 : {
649 : unsigned long cnt;
650 :
651 : return __rb_time_read(t, ret, &cnt);
652 : }
653 :
654 : static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt)
655 : {
656 : return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT);
657 : }
658 :
659 : static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom)
660 : {
661 : *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK);
662 : *bottom = (unsigned long)(val & RB_TIME_VAL_MASK);
663 : }
664 :
665 : static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt)
666 : {
667 : val = rb_time_val_cnt(val, cnt);
668 : local_set(t, val);
669 : }
670 :
671 : static void rb_time_set(rb_time_t *t, u64 val)
672 : {
673 : unsigned long cnt, top, bottom;
674 :
675 : rb_time_split(val, &top, &bottom);
676 :
677 : /* Writes always succeed with a valid number even if it gets interrupted. */
678 : do {
679 : cnt = local_inc_return(&t->cnt);
680 : rb_time_val_set(&t->top, top, cnt);
681 : rb_time_val_set(&t->bottom, bottom, cnt);
682 : } while (cnt != local_read(&t->cnt));
683 : }
684 :
685 : static inline bool
686 : rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set)
687 : {
688 : unsigned long ret;
689 :
690 : ret = local_cmpxchg(l, expect, set);
691 : return ret == expect;
692 : }
693 :
694 : static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
695 : {
696 : unsigned long cnt, top, bottom;
697 : unsigned long cnt2, top2, bottom2;
698 : u64 val;
699 :
700 : /* The cmpxchg always fails if it interrupted an update */
701 : if (!__rb_time_read(t, &val, &cnt2))
702 : return false;
703 :
704 : if (val != expect)
705 : return false;
706 :
707 : cnt = local_read(&t->cnt);
708 : if ((cnt & 3) != cnt2)
709 : return false;
710 :
711 : cnt2 = cnt + 1;
712 :
713 : rb_time_split(val, &top, &bottom);
714 : top = rb_time_val_cnt(top, cnt);
715 : bottom = rb_time_val_cnt(bottom, cnt);
716 :
717 : rb_time_split(set, &top2, &bottom2);
718 : top2 = rb_time_val_cnt(top2, cnt2);
719 : bottom2 = rb_time_val_cnt(bottom2, cnt2);
720 :
721 : if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2))
722 : return false;
723 : if (!rb_time_read_cmpxchg(&t->top, top, top2))
724 : return false;
725 : if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2))
726 : return false;
727 : return true;
728 : }
729 :
730 : #else /* 64 bits */
731 :
732 : /* local64_t always succeeds */
733 :
734 0 : static inline bool rb_time_read(rb_time_t *t, u64 *ret)
735 : {
736 0 : *ret = local64_read(&t->time);
737 0 : return true;
738 : }
739 0 : static void rb_time_set(rb_time_t *t, u64 val)
740 : {
741 0 : local64_set(&t->time, val);
742 0 : }
743 :
744 0 : static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
745 : {
746 0 : u64 val;
747 0 : val = local64_cmpxchg(&t->time, expect, set);
748 0 : return val == expect;
749 : }
750 : #endif
751 :
752 : /**
753 : * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
754 : * @buffer: The ring_buffer to get the number of pages from
755 : * @cpu: The cpu of the ring_buffer to get the number of pages from
756 : *
757 : * Returns the number of pages used by a per_cpu buffer of the ring buffer.
758 : */
759 0 : size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
760 : {
761 0 : return buffer->buffers[cpu]->nr_pages;
762 : }
763 :
764 : /**
765 : * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer
766 : * @buffer: The ring_buffer to get the number of pages from
767 : * @cpu: The cpu of the ring_buffer to get the number of pages from
768 : *
769 : * Returns the number of pages that have content in the ring buffer.
770 : */
771 0 : size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
772 : {
773 0 : size_t read;
774 0 : size_t cnt;
775 :
776 0 : read = local_read(&buffer->buffers[cpu]->pages_read);
777 0 : cnt = local_read(&buffer->buffers[cpu]->pages_touched);
778 : /* The reader can read an empty page, but not more than that */
779 0 : if (cnt < read) {
780 0 : WARN_ON_ONCE(read > cnt + 1);
781 : return 0;
782 : }
783 :
784 0 : return cnt - read;
785 : }
786 :
787 : /*
788 : * rb_wake_up_waiters - wake up tasks waiting for ring buffer input
789 : *
790 : * Schedules a delayed work to wake up any task that is blocked on the
791 : * ring buffer waiters queue.
792 : */
793 0 : static void rb_wake_up_waiters(struct irq_work *work)
794 : {
795 0 : struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
796 :
797 0 : wake_up_all(&rbwork->waiters);
798 0 : if (rbwork->wakeup_full) {
799 0 : rbwork->wakeup_full = false;
800 0 : wake_up_all(&rbwork->full_waiters);
801 : }
802 0 : }
803 :
804 : /**
805 : * ring_buffer_wait - wait for input to the ring buffer
806 : * @buffer: buffer to wait on
807 : * @cpu: the cpu buffer to wait on
808 : * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
809 : *
810 : * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
811 : * as data is added to any of the @buffer's cpu buffers. Otherwise
812 : * it will wait for data to be added to a specific cpu buffer.
813 : */
814 0 : int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full)
815 : {
816 0 : struct ring_buffer_per_cpu *cpu_buffer;
817 0 : DEFINE_WAIT(wait);
818 0 : struct rb_irq_work *work;
819 0 : int ret = 0;
820 :
821 : /*
822 : * Depending on what the caller is waiting for, either any
823 : * data in any cpu buffer, or a specific buffer, put the
824 : * caller on the appropriate wait queue.
825 : */
826 0 : if (cpu == RING_BUFFER_ALL_CPUS) {
827 0 : work = &buffer->irq_work;
828 : /* Full only makes sense on per cpu reads */
829 0 : full = 0;
830 : } else {
831 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
832 : return -ENODEV;
833 0 : cpu_buffer = buffer->buffers[cpu];
834 0 : work = &cpu_buffer->irq_work;
835 : }
836 :
837 :
838 0 : while (true) {
839 0 : if (full)
840 0 : prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE);
841 : else
842 0 : prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE);
843 :
844 : /*
845 : * The events can happen in critical sections where
846 : * checking a work queue can cause deadlocks.
847 : * After adding a task to the queue, this flag is set
848 : * only to notify events to try to wake up the queue
849 : * using irq_work.
850 : *
851 : * We don't clear it even if the buffer is no longer
852 : * empty. The flag only causes the next event to run
853 : * irq_work to do the work queue wake up. The worse
854 : * that can happen if we race with !trace_empty() is that
855 : * an event will cause an irq_work to try to wake up
856 : * an empty queue.
857 : *
858 : * There's no reason to protect this flag either, as
859 : * the work queue and irq_work logic will do the necessary
860 : * synchronization for the wake ups. The only thing
861 : * that is necessary is that the wake up happens after
862 : * a task has been queued. It's OK for spurious wake ups.
863 : */
864 0 : if (full)
865 0 : work->full_waiters_pending = true;
866 : else
867 0 : work->waiters_pending = true;
868 :
869 0 : if (signal_pending(current)) {
870 : ret = -EINTR;
871 : break;
872 : }
873 :
874 0 : if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer))
875 : break;
876 :
877 0 : if (cpu != RING_BUFFER_ALL_CPUS &&
878 0 : !ring_buffer_empty_cpu(buffer, cpu)) {
879 0 : unsigned long flags;
880 0 : bool pagebusy;
881 0 : size_t nr_pages;
882 0 : size_t dirty;
883 :
884 0 : if (!full)
885 : break;
886 :
887 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
888 0 : pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
889 0 : nr_pages = cpu_buffer->nr_pages;
890 0 : dirty = ring_buffer_nr_dirty_pages(buffer, cpu);
891 0 : if (!cpu_buffer->shortest_full ||
892 0 : cpu_buffer->shortest_full < full)
893 0 : cpu_buffer->shortest_full = full;
894 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
895 0 : if (!pagebusy &&
896 0 : (!nr_pages || (dirty * 100) > full * nr_pages))
897 : break;
898 : }
899 :
900 0 : schedule();
901 : }
902 :
903 0 : if (full)
904 0 : finish_wait(&work->full_waiters, &wait);
905 : else
906 0 : finish_wait(&work->waiters, &wait);
907 :
908 : return ret;
909 : }
910 :
911 : /**
912 : * ring_buffer_poll_wait - poll on buffer input
913 : * @buffer: buffer to wait on
914 : * @cpu: the cpu buffer to wait on
915 : * @filp: the file descriptor
916 : * @poll_table: The poll descriptor
917 : *
918 : * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
919 : * as data is added to any of the @buffer's cpu buffers. Otherwise
920 : * it will wait for data to be added to a specific cpu buffer.
921 : *
922 : * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
923 : * zero otherwise.
924 : */
925 0 : __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
926 : struct file *filp, poll_table *poll_table)
927 : {
928 0 : struct ring_buffer_per_cpu *cpu_buffer;
929 0 : struct rb_irq_work *work;
930 :
931 0 : if (cpu == RING_BUFFER_ALL_CPUS)
932 0 : work = &buffer->irq_work;
933 : else {
934 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
935 : return -EINVAL;
936 :
937 0 : cpu_buffer = buffer->buffers[cpu];
938 0 : work = &cpu_buffer->irq_work;
939 : }
940 :
941 0 : poll_wait(filp, &work->waiters, poll_table);
942 0 : work->waiters_pending = true;
943 : /*
944 : * There's a tight race between setting the waiters_pending and
945 : * checking if the ring buffer is empty. Once the waiters_pending bit
946 : * is set, the next event will wake the task up, but we can get stuck
947 : * if there's only a single event in.
948 : *
949 : * FIXME: Ideally, we need a memory barrier on the writer side as well,
950 : * but adding a memory barrier to all events will cause too much of a
951 : * performance hit in the fast path. We only need a memory barrier when
952 : * the buffer goes from empty to having content. But as this race is
953 : * extremely small, and it's not a problem if another event comes in, we
954 : * will fix it later.
955 : */
956 0 : smp_mb();
957 :
958 0 : if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
959 0 : (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
960 0 : return EPOLLIN | EPOLLRDNORM;
961 : return 0;
962 : }
963 :
964 : /* buffer may be either ring_buffer or ring_buffer_per_cpu */
965 : #define RB_WARN_ON(b, cond) \
966 : ({ \
967 : int _____ret = unlikely(cond); \
968 : if (_____ret) { \
969 : if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
970 : struct ring_buffer_per_cpu *__b = \
971 : (void *)b; \
972 : atomic_inc(&__b->buffer->record_disabled); \
973 : } else \
974 : atomic_inc(&b->record_disabled); \
975 : WARN_ON(1); \
976 : } \
977 : _____ret; \
978 : })
979 :
980 : /* Up this if you want to test the TIME_EXTENTS and normalization */
981 : #define DEBUG_SHIFT 0
982 :
983 0 : static inline u64 rb_time_stamp(struct trace_buffer *buffer)
984 : {
985 0 : u64 ts;
986 :
987 : /* Skip retpolines :-( */
988 0 : if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local))
989 : ts = trace_clock_local();
990 : else
991 0 : ts = buffer->clock();
992 :
993 : /* shift to debug/test normalization and TIME_EXTENTS */
994 0 : return ts << DEBUG_SHIFT;
995 : }
996 :
997 0 : u64 ring_buffer_time_stamp(struct trace_buffer *buffer, int cpu)
998 : {
999 0 : u64 time;
1000 :
1001 0 : preempt_disable_notrace();
1002 0 : time = rb_time_stamp(buffer);
1003 0 : preempt_enable_notrace();
1004 :
1005 0 : return time;
1006 : }
1007 : EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
1008 :
1009 0 : void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
1010 : int cpu, u64 *ts)
1011 : {
1012 : /* Just stupid testing the normalize function and deltas */
1013 0 : *ts >>= DEBUG_SHIFT;
1014 0 : }
1015 : EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
1016 :
1017 : /*
1018 : * Making the ring buffer lockless makes things tricky.
1019 : * Although writes only happen on the CPU that they are on,
1020 : * and they only need to worry about interrupts. Reads can
1021 : * happen on any CPU.
1022 : *
1023 : * The reader page is always off the ring buffer, but when the
1024 : * reader finishes with a page, it needs to swap its page with
1025 : * a new one from the buffer. The reader needs to take from
1026 : * the head (writes go to the tail). But if a writer is in overwrite
1027 : * mode and wraps, it must push the head page forward.
1028 : *
1029 : * Here lies the problem.
1030 : *
1031 : * The reader must be careful to replace only the head page, and
1032 : * not another one. As described at the top of the file in the
1033 : * ASCII art, the reader sets its old page to point to the next
1034 : * page after head. It then sets the page after head to point to
1035 : * the old reader page. But if the writer moves the head page
1036 : * during this operation, the reader could end up with the tail.
1037 : *
1038 : * We use cmpxchg to help prevent this race. We also do something
1039 : * special with the page before head. We set the LSB to 1.
1040 : *
1041 : * When the writer must push the page forward, it will clear the
1042 : * bit that points to the head page, move the head, and then set
1043 : * the bit that points to the new head page.
1044 : *
1045 : * We also don't want an interrupt coming in and moving the head
1046 : * page on another writer. Thus we use the second LSB to catch
1047 : * that too. Thus:
1048 : *
1049 : * head->list->prev->next bit 1 bit 0
1050 : * ------- -------
1051 : * Normal page 0 0
1052 : * Points to head page 0 1
1053 : * New head page 1 0
1054 : *
1055 : * Note we can not trust the prev pointer of the head page, because:
1056 : *
1057 : * +----+ +-----+ +-----+
1058 : * | |------>| T |---X--->| N |
1059 : * | |<------| | | |
1060 : * +----+ +-----+ +-----+
1061 : * ^ ^ |
1062 : * | +-----+ | |
1063 : * +----------| R |----------+ |
1064 : * | |<-----------+
1065 : * +-----+
1066 : *
1067 : * Key: ---X--> HEAD flag set in pointer
1068 : * T Tail page
1069 : * R Reader page
1070 : * N Next page
1071 : *
1072 : * (see __rb_reserve_next() to see where this happens)
1073 : *
1074 : * What the above shows is that the reader just swapped out
1075 : * the reader page with a page in the buffer, but before it
1076 : * could make the new header point back to the new page added
1077 : * it was preempted by a writer. The writer moved forward onto
1078 : * the new page added by the reader and is about to move forward
1079 : * again.
1080 : *
1081 : * You can see, it is legitimate for the previous pointer of
1082 : * the head (or any page) not to point back to itself. But only
1083 : * temporarily.
1084 : */
1085 :
1086 : #define RB_PAGE_NORMAL 0UL
1087 : #define RB_PAGE_HEAD 1UL
1088 : #define RB_PAGE_UPDATE 2UL
1089 :
1090 :
1091 : #define RB_FLAG_MASK 3UL
1092 :
1093 : /* PAGE_MOVED is not part of the mask */
1094 : #define RB_PAGE_MOVED 4UL
1095 :
1096 : /*
1097 : * rb_list_head - remove any bit
1098 : */
1099 32 : static struct list_head *rb_list_head(struct list_head *list)
1100 : {
1101 32 : unsigned long val = (unsigned long)list;
1102 :
1103 32 : return (struct list_head *)(val & ~RB_FLAG_MASK);
1104 : }
1105 :
1106 : /*
1107 : * rb_is_head_page - test if the given page is the head page
1108 : *
1109 : * Because the reader may move the head_page pointer, we can
1110 : * not trust what the head page is (it may be pointing to
1111 : * the reader page). But if the next page is a header page,
1112 : * its flags will be non zero.
1113 : */
1114 : static inline int
1115 0 : rb_is_head_page(struct buffer_page *page, struct list_head *list)
1116 : {
1117 0 : unsigned long val;
1118 :
1119 0 : val = (unsigned long)list->next;
1120 :
1121 0 : if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
1122 : return RB_PAGE_MOVED;
1123 :
1124 0 : return val & RB_FLAG_MASK;
1125 : }
1126 :
1127 : /*
1128 : * rb_is_reader_page
1129 : *
1130 : * The unique thing about the reader page, is that, if the
1131 : * writer is ever on it, the previous pointer never points
1132 : * back to the reader page.
1133 : */
1134 0 : static bool rb_is_reader_page(struct buffer_page *page)
1135 : {
1136 0 : struct list_head *list = page->list.prev;
1137 :
1138 0 : return rb_list_head(list->next) != &page->list;
1139 : }
1140 :
1141 : /*
1142 : * rb_set_list_to_head - set a list_head to be pointing to head.
1143 : */
1144 8 : static void rb_set_list_to_head(struct list_head *list)
1145 : {
1146 8 : unsigned long *ptr;
1147 :
1148 8 : ptr = (unsigned long *)&list->next;
1149 8 : *ptr |= RB_PAGE_HEAD;
1150 8 : *ptr &= ~RB_PAGE_UPDATE;
1151 8 : }
1152 :
1153 : /*
1154 : * rb_head_page_activate - sets up head page
1155 : */
1156 16 : static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
1157 : {
1158 16 : struct buffer_page *head;
1159 :
1160 16 : head = cpu_buffer->head_page;
1161 16 : if (!head)
1162 : return;
1163 :
1164 : /*
1165 : * Set the previous list pointer to have the HEAD flag.
1166 : */
1167 8 : rb_set_list_to_head(head->list.prev);
1168 : }
1169 :
1170 16 : static void rb_list_head_clear(struct list_head *list)
1171 : {
1172 16 : unsigned long *ptr = (unsigned long *)&list->next;
1173 :
1174 16 : *ptr &= ~RB_FLAG_MASK;
1175 : }
1176 :
1177 : /*
1178 : * rb_head_page_deactivate - clears head page ptr (for free list)
1179 : */
1180 : static void
1181 8 : rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
1182 : {
1183 8 : struct list_head *hd;
1184 :
1185 : /* Go through the whole list and clear any pointers found. */
1186 8 : rb_list_head_clear(cpu_buffer->pages);
1187 :
1188 16 : list_for_each(hd, cpu_buffer->pages)
1189 8 : rb_list_head_clear(hd);
1190 8 : }
1191 :
1192 0 : static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
1193 : struct buffer_page *head,
1194 : struct buffer_page *prev,
1195 : int old_flag, int new_flag)
1196 : {
1197 0 : struct list_head *list;
1198 0 : unsigned long val = (unsigned long)&head->list;
1199 0 : unsigned long ret;
1200 :
1201 0 : list = &prev->list;
1202 :
1203 0 : val &= ~RB_FLAG_MASK;
1204 :
1205 0 : ret = cmpxchg((unsigned long *)&list->next,
1206 : val | old_flag, val | new_flag);
1207 :
1208 : /* check if the reader took the page */
1209 0 : if ((ret & ~RB_FLAG_MASK) != val)
1210 : return RB_PAGE_MOVED;
1211 :
1212 0 : return ret & RB_FLAG_MASK;
1213 : }
1214 :
1215 0 : static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
1216 : struct buffer_page *head,
1217 : struct buffer_page *prev,
1218 : int old_flag)
1219 : {
1220 0 : return rb_head_page_set(cpu_buffer, head, prev,
1221 : old_flag, RB_PAGE_UPDATE);
1222 : }
1223 :
1224 0 : static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
1225 : struct buffer_page *head,
1226 : struct buffer_page *prev,
1227 : int old_flag)
1228 : {
1229 0 : return rb_head_page_set(cpu_buffer, head, prev,
1230 : old_flag, RB_PAGE_HEAD);
1231 : }
1232 :
1233 0 : static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
1234 : struct buffer_page *head,
1235 : struct buffer_page *prev,
1236 : int old_flag)
1237 : {
1238 0 : return rb_head_page_set(cpu_buffer, head, prev,
1239 : old_flag, RB_PAGE_NORMAL);
1240 : }
1241 :
1242 0 : static inline void rb_inc_page(struct buffer_page **bpage)
1243 : {
1244 0 : struct list_head *p = rb_list_head((*bpage)->list.next);
1245 :
1246 0 : *bpage = list_entry(p, struct buffer_page, list);
1247 0 : }
1248 :
1249 : static struct buffer_page *
1250 0 : rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
1251 : {
1252 0 : struct buffer_page *head;
1253 0 : struct buffer_page *page;
1254 0 : struct list_head *list;
1255 0 : int i;
1256 :
1257 0 : if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
1258 : return NULL;
1259 :
1260 : /* sanity check */
1261 0 : list = cpu_buffer->pages;
1262 0 : if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
1263 : return NULL;
1264 :
1265 0 : page = head = cpu_buffer->head_page;
1266 : /*
1267 : * It is possible that the writer moves the header behind
1268 : * where we started, and we miss in one loop.
1269 : * A second loop should grab the header, but we'll do
1270 : * three loops just because I'm paranoid.
1271 : */
1272 0 : for (i = 0; i < 3; i++) {
1273 0 : do {
1274 0 : if (rb_is_head_page(page, page->list.prev)) {
1275 0 : cpu_buffer->head_page = page;
1276 0 : return page;
1277 : }
1278 0 : rb_inc_page(&page);
1279 0 : } while (page != head);
1280 : }
1281 :
1282 0 : RB_WARN_ON(cpu_buffer, 1);
1283 :
1284 0 : return NULL;
1285 : }
1286 :
1287 0 : static int rb_head_page_replace(struct buffer_page *old,
1288 : struct buffer_page *new)
1289 : {
1290 0 : unsigned long *ptr = (unsigned long *)&old->list.prev->next;
1291 0 : unsigned long val;
1292 0 : unsigned long ret;
1293 :
1294 0 : val = *ptr & ~RB_FLAG_MASK;
1295 0 : val |= RB_PAGE_HEAD;
1296 :
1297 0 : ret = cmpxchg(ptr, val, (unsigned long)&new->list);
1298 :
1299 0 : return ret == val;
1300 : }
1301 :
1302 : /*
1303 : * rb_tail_page_update - move the tail page forward
1304 : */
1305 0 : static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
1306 : struct buffer_page *tail_page,
1307 : struct buffer_page *next_page)
1308 : {
1309 0 : unsigned long old_entries;
1310 0 : unsigned long old_write;
1311 :
1312 : /*
1313 : * The tail page now needs to be moved forward.
1314 : *
1315 : * We need to reset the tail page, but without messing
1316 : * with possible erasing of data brought in by interrupts
1317 : * that have moved the tail page and are currently on it.
1318 : *
1319 : * We add a counter to the write field to denote this.
1320 : */
1321 0 : old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
1322 0 : old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
1323 :
1324 0 : local_inc(&cpu_buffer->pages_touched);
1325 : /*
1326 : * Just make sure we have seen our old_write and synchronize
1327 : * with any interrupts that come in.
1328 : */
1329 0 : barrier();
1330 :
1331 : /*
1332 : * If the tail page is still the same as what we think
1333 : * it is, then it is up to us to update the tail
1334 : * pointer.
1335 : */
1336 0 : if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
1337 : /* Zero the write counter */
1338 0 : unsigned long val = old_write & ~RB_WRITE_MASK;
1339 0 : unsigned long eval = old_entries & ~RB_WRITE_MASK;
1340 :
1341 : /*
1342 : * This will only succeed if an interrupt did
1343 : * not come in and change it. In which case, we
1344 : * do not want to modify it.
1345 : *
1346 : * We add (void) to let the compiler know that we do not care
1347 : * about the return value of these functions. We use the
1348 : * cmpxchg to only update if an interrupt did not already
1349 : * do it for us. If the cmpxchg fails, we don't care.
1350 : */
1351 0 : (void)local_cmpxchg(&next_page->write, old_write, val);
1352 0 : (void)local_cmpxchg(&next_page->entries, old_entries, eval);
1353 :
1354 : /*
1355 : * No need to worry about races with clearing out the commit.
1356 : * it only can increment when a commit takes place. But that
1357 : * only happens in the outer most nested commit.
1358 : */
1359 0 : local_set(&next_page->page->commit, 0);
1360 :
1361 : /* Again, either we update tail_page or an interrupt does */
1362 0 : (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page);
1363 : }
1364 0 : }
1365 :
1366 24 : static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
1367 : struct buffer_page *bpage)
1368 : {
1369 24 : unsigned long val = (unsigned long)bpage;
1370 :
1371 24 : if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
1372 0 : return 1;
1373 :
1374 : return 0;
1375 : }
1376 :
1377 : /**
1378 : * rb_check_list - make sure a pointer to a list has the last bits zero
1379 : */
1380 16 : static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
1381 : struct list_head *list)
1382 : {
1383 16 : if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
1384 : return 1;
1385 16 : if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
1386 0 : return 1;
1387 : return 0;
1388 : }
1389 :
1390 : /**
1391 : * rb_check_pages - integrity check of buffer pages
1392 : * @cpu_buffer: CPU buffer with pages to test
1393 : *
1394 : * As a safety measure we check to make sure the data pages have not
1395 : * been corrupted.
1396 : */
1397 8 : static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
1398 : {
1399 8 : struct list_head *head = cpu_buffer->pages;
1400 8 : struct buffer_page *bpage, *tmp;
1401 :
1402 : /* Reset the head page if it exists */
1403 8 : if (cpu_buffer->head_page)
1404 0 : rb_set_head_page(cpu_buffer);
1405 :
1406 8 : rb_head_page_deactivate(cpu_buffer);
1407 :
1408 8 : if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
1409 : return -1;
1410 8 : if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
1411 : return -1;
1412 :
1413 8 : if (rb_check_list(cpu_buffer, head))
1414 : return -1;
1415 :
1416 16 : list_for_each_entry_safe(bpage, tmp, head, list) {
1417 8 : if (RB_WARN_ON(cpu_buffer,
1418 : bpage->list.next->prev != &bpage->list))
1419 : return -1;
1420 8 : if (RB_WARN_ON(cpu_buffer,
1421 : bpage->list.prev->next != &bpage->list))
1422 : return -1;
1423 8 : if (rb_check_list(cpu_buffer, &bpage->list))
1424 : return -1;
1425 : }
1426 :
1427 8 : rb_head_page_activate(cpu_buffer);
1428 :
1429 : return 0;
1430 : }
1431 :
1432 8 : static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1433 : long nr_pages, struct list_head *pages)
1434 : {
1435 8 : struct buffer_page *bpage, *tmp;
1436 8 : bool user_thread = current->mm != NULL;
1437 8 : gfp_t mflags;
1438 8 : long i;
1439 :
1440 : /*
1441 : * Check if the available memory is there first.
1442 : * Note, si_mem_available() only gives us a rough estimate of available
1443 : * memory. It may not be accurate. But we don't care, we just want
1444 : * to prevent doing any allocation when it is obvious that it is
1445 : * not going to succeed.
1446 : */
1447 8 : i = si_mem_available();
1448 8 : if (i < nr_pages)
1449 : return -ENOMEM;
1450 :
1451 : /*
1452 : * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
1453 : * gracefully without invoking oom-killer and the system is not
1454 : * destabilized.
1455 : */
1456 8 : mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
1457 :
1458 : /*
1459 : * If a user thread allocates too much, and si_mem_available()
1460 : * reports there's enough memory, even though there is not.
1461 : * Make sure the OOM killer kills this thread. This can happen
1462 : * even with RETRY_MAYFAIL because another task may be doing
1463 : * an allocation after this task has taken all memory.
1464 : * This is the task the OOM killer needs to take out during this
1465 : * loop, even if it was triggered by an allocation somewhere else.
1466 : */
1467 8 : if (user_thread)
1468 0 : set_current_oom_origin();
1469 24 : for (i = 0; i < nr_pages; i++) {
1470 16 : struct page *page;
1471 :
1472 16 : bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1473 : mflags, cpu_to_node(cpu_buffer->cpu));
1474 16 : if (!bpage)
1475 0 : goto free_pages;
1476 :
1477 16 : rb_check_bpage(cpu_buffer, bpage);
1478 :
1479 16 : list_add(&bpage->list, pages);
1480 :
1481 16 : page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu), mflags, 0);
1482 16 : if (!page)
1483 0 : goto free_pages;
1484 16 : bpage->page = page_address(page);
1485 16 : rb_init_page(bpage->page);
1486 :
1487 16 : if (user_thread && fatal_signal_pending(current))
1488 0 : goto free_pages;
1489 : }
1490 8 : if (user_thread)
1491 0 : clear_current_oom_origin();
1492 :
1493 : return 0;
1494 :
1495 0 : free_pages:
1496 0 : list_for_each_entry_safe(bpage, tmp, pages, list) {
1497 0 : list_del_init(&bpage->list);
1498 0 : free_buffer_page(bpage);
1499 : }
1500 0 : if (user_thread)
1501 0 : clear_current_oom_origin();
1502 :
1503 : return -ENOMEM;
1504 : }
1505 :
1506 8 : static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1507 : unsigned long nr_pages)
1508 : {
1509 8 : LIST_HEAD(pages);
1510 :
1511 8 : WARN_ON(!nr_pages);
1512 :
1513 8 : if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
1514 : return -ENOMEM;
1515 :
1516 : /*
1517 : * The ring buffer page list is a circular list that does not
1518 : * start and end with a list head. All page list items point to
1519 : * other pages.
1520 : */
1521 8 : cpu_buffer->pages = pages.next;
1522 8 : list_del(&pages);
1523 :
1524 8 : cpu_buffer->nr_pages = nr_pages;
1525 :
1526 8 : rb_check_pages(cpu_buffer);
1527 :
1528 8 : return 0;
1529 : }
1530 :
1531 : static struct ring_buffer_per_cpu *
1532 8 : rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
1533 : {
1534 8 : struct ring_buffer_per_cpu *cpu_buffer;
1535 8 : struct buffer_page *bpage;
1536 8 : struct page *page;
1537 8 : int ret;
1538 :
1539 8 : cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1540 : GFP_KERNEL, cpu_to_node(cpu));
1541 8 : if (!cpu_buffer)
1542 : return NULL;
1543 :
1544 8 : cpu_buffer->cpu = cpu;
1545 8 : cpu_buffer->buffer = buffer;
1546 8 : raw_spin_lock_init(&cpu_buffer->reader_lock);
1547 8 : lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
1548 8 : cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
1549 8 : INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
1550 8 : init_completion(&cpu_buffer->update_done);
1551 8 : init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
1552 8 : init_waitqueue_head(&cpu_buffer->irq_work.waiters);
1553 8 : init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
1554 :
1555 8 : bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
1556 : GFP_KERNEL, cpu_to_node(cpu));
1557 8 : if (!bpage)
1558 0 : goto fail_free_buffer;
1559 :
1560 8 : rb_check_bpage(cpu_buffer, bpage);
1561 :
1562 8 : cpu_buffer->reader_page = bpage;
1563 8 : page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1564 8 : if (!page)
1565 0 : goto fail_free_reader;
1566 8 : bpage->page = page_address(page);
1567 8 : rb_init_page(bpage->page);
1568 :
1569 8 : INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
1570 8 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
1571 :
1572 8 : ret = rb_allocate_pages(cpu_buffer, nr_pages);
1573 8 : if (ret < 0)
1574 0 : goto fail_free_reader;
1575 :
1576 8 : cpu_buffer->head_page
1577 8 : = list_entry(cpu_buffer->pages, struct buffer_page, list);
1578 8 : cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
1579 :
1580 8 : rb_head_page_activate(cpu_buffer);
1581 :
1582 : return cpu_buffer;
1583 :
1584 0 : fail_free_reader:
1585 0 : free_buffer_page(cpu_buffer->reader_page);
1586 :
1587 0 : fail_free_buffer:
1588 0 : kfree(cpu_buffer);
1589 0 : return NULL;
1590 : }
1591 :
1592 0 : static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1593 : {
1594 0 : struct list_head *head = cpu_buffer->pages;
1595 0 : struct buffer_page *bpage, *tmp;
1596 :
1597 0 : free_buffer_page(cpu_buffer->reader_page);
1598 :
1599 0 : rb_head_page_deactivate(cpu_buffer);
1600 :
1601 0 : if (head) {
1602 0 : list_for_each_entry_safe(bpage, tmp, head, list) {
1603 0 : list_del_init(&bpage->list);
1604 0 : free_buffer_page(bpage);
1605 : }
1606 0 : bpage = list_entry(head, struct buffer_page, list);
1607 0 : free_buffer_page(bpage);
1608 : }
1609 :
1610 0 : kfree(cpu_buffer);
1611 0 : }
1612 :
1613 : /**
1614 : * __ring_buffer_alloc - allocate a new ring_buffer
1615 : * @size: the size in bytes per cpu that is needed.
1616 : * @flags: attributes to set for the ring buffer.
1617 : * @key: ring buffer reader_lock_key.
1618 : *
1619 : * Currently the only flag that is available is the RB_FL_OVERWRITE
1620 : * flag. This flag means that the buffer will overwrite old data
1621 : * when the buffer wraps. If this flag is not set, the buffer will
1622 : * drop data when the tail hits the head.
1623 : */
1624 2 : struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1625 : struct lock_class_key *key)
1626 : {
1627 2 : struct trace_buffer *buffer;
1628 2 : long nr_pages;
1629 2 : int bsize;
1630 2 : int cpu;
1631 2 : int ret;
1632 :
1633 : /* keep it in its own cache line */
1634 2 : buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1635 : GFP_KERNEL);
1636 2 : if (!buffer)
1637 : return NULL;
1638 :
1639 2 : if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1640 : goto fail_free_buffer;
1641 :
1642 2 : nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1643 2 : buffer->flags = flags;
1644 2 : buffer->clock = trace_clock_local;
1645 2 : buffer->reader_lock_key = key;
1646 :
1647 2 : init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
1648 2 : init_waitqueue_head(&buffer->irq_work.waiters);
1649 :
1650 : /* need at least two pages */
1651 2 : if (nr_pages < 2)
1652 : nr_pages = 2;
1653 :
1654 2 : buffer->cpus = nr_cpu_ids;
1655 :
1656 2 : bsize = sizeof(void *) * nr_cpu_ids;
1657 2 : buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1658 : GFP_KERNEL);
1659 2 : if (!buffer->buffers)
1660 0 : goto fail_free_cpumask;
1661 :
1662 2 : cpu = raw_smp_processor_id();
1663 2 : cpumask_set_cpu(cpu, buffer->cpumask);
1664 2 : buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
1665 2 : if (!buffer->buffers[cpu])
1666 0 : goto fail_free_buffers;
1667 :
1668 2 : ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1669 2 : if (ret < 0)
1670 0 : goto fail_free_buffers;
1671 :
1672 2 : mutex_init(&buffer->mutex);
1673 :
1674 2 : return buffer;
1675 :
1676 : fail_free_buffers:
1677 0 : for_each_buffer_cpu(buffer, cpu) {
1678 0 : if (buffer->buffers[cpu])
1679 0 : rb_free_cpu_buffer(buffer->buffers[cpu]);
1680 : }
1681 0 : kfree(buffer->buffers);
1682 :
1683 0 : fail_free_cpumask:
1684 0 : free_cpumask_var(buffer->cpumask);
1685 :
1686 0 : fail_free_buffer:
1687 0 : kfree(buffer);
1688 0 : return NULL;
1689 : }
1690 : EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
1691 :
1692 : /**
1693 : * ring_buffer_free - free a ring buffer.
1694 : * @buffer: the buffer to free.
1695 : */
1696 : void
1697 0 : ring_buffer_free(struct trace_buffer *buffer)
1698 : {
1699 0 : int cpu;
1700 :
1701 0 : cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
1702 :
1703 0 : for_each_buffer_cpu(buffer, cpu)
1704 0 : rb_free_cpu_buffer(buffer->buffers[cpu]);
1705 :
1706 0 : kfree(buffer->buffers);
1707 0 : free_cpumask_var(buffer->cpumask);
1708 :
1709 0 : kfree(buffer);
1710 0 : }
1711 : EXPORT_SYMBOL_GPL(ring_buffer_free);
1712 :
1713 0 : void ring_buffer_set_clock(struct trace_buffer *buffer,
1714 : u64 (*clock)(void))
1715 : {
1716 0 : buffer->clock = clock;
1717 0 : }
1718 :
1719 0 : void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
1720 : {
1721 0 : buffer->time_stamp_abs = abs;
1722 0 : }
1723 :
1724 0 : bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
1725 : {
1726 0 : return buffer->time_stamp_abs;
1727 : }
1728 :
1729 : static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1730 :
1731 0 : static inline unsigned long rb_page_entries(struct buffer_page *bpage)
1732 : {
1733 0 : return local_read(&bpage->entries) & RB_WRITE_MASK;
1734 : }
1735 :
1736 0 : static inline unsigned long rb_page_write(struct buffer_page *bpage)
1737 : {
1738 0 : return local_read(&bpage->write) & RB_WRITE_MASK;
1739 : }
1740 :
1741 : static int
1742 0 : rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
1743 : {
1744 0 : struct list_head *tail_page, *to_remove, *next_page;
1745 0 : struct buffer_page *to_remove_page, *tmp_iter_page;
1746 0 : struct buffer_page *last_page, *first_page;
1747 0 : unsigned long nr_removed;
1748 0 : unsigned long head_bit;
1749 0 : int page_entries;
1750 :
1751 0 : head_bit = 0;
1752 :
1753 0 : raw_spin_lock_irq(&cpu_buffer->reader_lock);
1754 0 : atomic_inc(&cpu_buffer->record_disabled);
1755 : /*
1756 : * We don't race with the readers since we have acquired the reader
1757 : * lock. We also don't race with writers after disabling recording.
1758 : * This makes it easy to figure out the first and the last page to be
1759 : * removed from the list. We unlink all the pages in between including
1760 : * the first and last pages. This is done in a busy loop so that we
1761 : * lose the least number of traces.
1762 : * The pages are freed after we restart recording and unlock readers.
1763 : */
1764 0 : tail_page = &cpu_buffer->tail_page->list;
1765 :
1766 : /*
1767 : * tail page might be on reader page, we remove the next page
1768 : * from the ring buffer
1769 : */
1770 0 : if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1771 0 : tail_page = rb_list_head(tail_page->next);
1772 0 : to_remove = tail_page;
1773 :
1774 : /* start of pages to remove */
1775 0 : first_page = list_entry(rb_list_head(to_remove->next),
1776 : struct buffer_page, list);
1777 :
1778 0 : for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1779 0 : to_remove = rb_list_head(to_remove)->next;
1780 0 : head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
1781 : }
1782 :
1783 0 : next_page = rb_list_head(to_remove)->next;
1784 :
1785 : /*
1786 : * Now we remove all pages between tail_page and next_page.
1787 : * Make sure that we have head_bit value preserved for the
1788 : * next page
1789 : */
1790 0 : tail_page->next = (struct list_head *)((unsigned long)next_page |
1791 : head_bit);
1792 0 : next_page = rb_list_head(next_page);
1793 0 : next_page->prev = tail_page;
1794 :
1795 : /* make sure pages points to a valid page in the ring buffer */
1796 0 : cpu_buffer->pages = next_page;
1797 :
1798 : /* update head page */
1799 0 : if (head_bit)
1800 0 : cpu_buffer->head_page = list_entry(next_page,
1801 : struct buffer_page, list);
1802 :
1803 : /*
1804 : * change read pointer to make sure any read iterators reset
1805 : * themselves
1806 : */
1807 0 : cpu_buffer->read = 0;
1808 :
1809 : /* pages are removed, resume tracing and then free the pages */
1810 0 : atomic_dec(&cpu_buffer->record_disabled);
1811 0 : raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1812 :
1813 0 : RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1814 :
1815 : /* last buffer page to remove */
1816 0 : last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1817 : list);
1818 : tmp_iter_page = first_page;
1819 :
1820 0 : do {
1821 0 : cond_resched();
1822 :
1823 0 : to_remove_page = tmp_iter_page;
1824 0 : rb_inc_page(&tmp_iter_page);
1825 :
1826 : /* update the counters */
1827 0 : page_entries = rb_page_entries(to_remove_page);
1828 0 : if (page_entries) {
1829 : /*
1830 : * If something was added to this page, it was full
1831 : * since it is not the tail page. So we deduct the
1832 : * bytes consumed in ring buffer from here.
1833 : * Increment overrun to account for the lost events.
1834 : */
1835 0 : local_add(page_entries, &cpu_buffer->overrun);
1836 0 : local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1837 : }
1838 :
1839 : /*
1840 : * We have already removed references to this list item, just
1841 : * free up the buffer_page and its page
1842 : */
1843 0 : free_buffer_page(to_remove_page);
1844 0 : nr_removed--;
1845 :
1846 0 : } while (to_remove_page != last_page);
1847 :
1848 0 : RB_WARN_ON(cpu_buffer, nr_removed);
1849 :
1850 0 : return nr_removed == 0;
1851 : }
1852 :
1853 : static int
1854 0 : rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
1855 : {
1856 0 : struct list_head *pages = &cpu_buffer->new_pages;
1857 0 : int retries, success;
1858 :
1859 0 : raw_spin_lock_irq(&cpu_buffer->reader_lock);
1860 : /*
1861 : * We are holding the reader lock, so the reader page won't be swapped
1862 : * in the ring buffer. Now we are racing with the writer trying to
1863 : * move head page and the tail page.
1864 : * We are going to adapt the reader page update process where:
1865 : * 1. We first splice the start and end of list of new pages between
1866 : * the head page and its previous page.
1867 : * 2. We cmpxchg the prev_page->next to point from head page to the
1868 : * start of new pages list.
1869 : * 3. Finally, we update the head->prev to the end of new list.
1870 : *
1871 : * We will try this process 10 times, to make sure that we don't keep
1872 : * spinning.
1873 : */
1874 0 : retries = 10;
1875 0 : success = 0;
1876 0 : while (retries--) {
1877 0 : struct list_head *head_page, *prev_page, *r;
1878 0 : struct list_head *last_page, *first_page;
1879 0 : struct list_head *head_page_with_bit;
1880 :
1881 0 : head_page = &rb_set_head_page(cpu_buffer)->list;
1882 0 : if (!head_page)
1883 : break;
1884 0 : prev_page = head_page->prev;
1885 :
1886 0 : first_page = pages->next;
1887 0 : last_page = pages->prev;
1888 :
1889 0 : head_page_with_bit = (struct list_head *)
1890 0 : ((unsigned long)head_page | RB_PAGE_HEAD);
1891 :
1892 0 : last_page->next = head_page_with_bit;
1893 0 : first_page->prev = prev_page;
1894 :
1895 0 : r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1896 :
1897 0 : if (r == head_page_with_bit) {
1898 : /*
1899 : * yay, we replaced the page pointer to our new list,
1900 : * now, we just have to update to head page's prev
1901 : * pointer to point to end of list
1902 : */
1903 0 : head_page->prev = last_page;
1904 0 : success = 1;
1905 0 : break;
1906 : }
1907 : }
1908 :
1909 0 : if (success)
1910 0 : INIT_LIST_HEAD(pages);
1911 : /*
1912 : * If we weren't successful in adding in new pages, warn and stop
1913 : * tracing
1914 : */
1915 0 : RB_WARN_ON(cpu_buffer, !success);
1916 0 : raw_spin_unlock_irq(&cpu_buffer->reader_lock);
1917 :
1918 : /* free pages if they weren't inserted */
1919 0 : if (!success) {
1920 0 : struct buffer_page *bpage, *tmp;
1921 0 : list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1922 : list) {
1923 0 : list_del_init(&bpage->list);
1924 0 : free_buffer_page(bpage);
1925 : }
1926 : }
1927 0 : return success;
1928 : }
1929 :
1930 0 : static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
1931 : {
1932 0 : int success;
1933 :
1934 0 : if (cpu_buffer->nr_pages_to_update > 0)
1935 0 : success = rb_insert_pages(cpu_buffer);
1936 : else
1937 0 : success = rb_remove_pages(cpu_buffer,
1938 0 : -cpu_buffer->nr_pages_to_update);
1939 :
1940 0 : if (success)
1941 0 : cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
1942 0 : }
1943 :
1944 0 : static void update_pages_handler(struct work_struct *work)
1945 : {
1946 0 : struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1947 : struct ring_buffer_per_cpu, update_pages_work);
1948 0 : rb_update_pages(cpu_buffer);
1949 0 : complete(&cpu_buffer->update_done);
1950 0 : }
1951 :
1952 : /**
1953 : * ring_buffer_resize - resize the ring buffer
1954 : * @buffer: the buffer to resize.
1955 : * @size: the new size.
1956 : * @cpu_id: the cpu buffer to resize
1957 : *
1958 : * Minimum size is 2 * BUF_PAGE_SIZE.
1959 : *
1960 : * Returns 0 on success and < 0 on failure.
1961 : */
1962 0 : int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
1963 : int cpu_id)
1964 : {
1965 0 : struct ring_buffer_per_cpu *cpu_buffer;
1966 0 : unsigned long nr_pages;
1967 0 : int cpu, err;
1968 :
1969 : /*
1970 : * Always succeed at resizing a non-existent buffer:
1971 : */
1972 0 : if (!buffer)
1973 : return 0;
1974 :
1975 : /* Make sure the requested buffer exists */
1976 0 : if (cpu_id != RING_BUFFER_ALL_CPUS &&
1977 0 : !cpumask_test_cpu(cpu_id, buffer->cpumask))
1978 : return 0;
1979 :
1980 0 : nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1981 :
1982 : /* we need a minimum of two pages */
1983 0 : if (nr_pages < 2)
1984 0 : nr_pages = 2;
1985 :
1986 : /* prevent another thread from changing buffer sizes */
1987 0 : mutex_lock(&buffer->mutex);
1988 :
1989 :
1990 0 : if (cpu_id == RING_BUFFER_ALL_CPUS) {
1991 : /*
1992 : * Don't succeed if resizing is disabled, as a reader might be
1993 : * manipulating the ring buffer and is expecting a sane state while
1994 : * this is true.
1995 : */
1996 0 : for_each_buffer_cpu(buffer, cpu) {
1997 0 : cpu_buffer = buffer->buffers[cpu];
1998 0 : if (atomic_read(&cpu_buffer->resize_disabled)) {
1999 0 : err = -EBUSY;
2000 0 : goto out_err_unlock;
2001 : }
2002 : }
2003 :
2004 : /* calculate the pages to update */
2005 0 : for_each_buffer_cpu(buffer, cpu) {
2006 0 : cpu_buffer = buffer->buffers[cpu];
2007 :
2008 0 : cpu_buffer->nr_pages_to_update = nr_pages -
2009 0 : cpu_buffer->nr_pages;
2010 : /*
2011 : * nothing more to do for removing pages or no update
2012 : */
2013 0 : if (cpu_buffer->nr_pages_to_update <= 0)
2014 0 : continue;
2015 : /*
2016 : * to add pages, make sure all new pages can be
2017 : * allocated without receiving ENOMEM
2018 : */
2019 0 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
2020 0 : if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2021 : &cpu_buffer->new_pages)) {
2022 : /* not enough memory for new pages */
2023 0 : err = -ENOMEM;
2024 0 : goto out_err;
2025 : }
2026 : }
2027 :
2028 0 : get_online_cpus();
2029 : /*
2030 : * Fire off all the required work handlers
2031 : * We can't schedule on offline CPUs, but it's not necessary
2032 : * since we can change their buffer sizes without any race.
2033 : */
2034 0 : for_each_buffer_cpu(buffer, cpu) {
2035 0 : cpu_buffer = buffer->buffers[cpu];
2036 0 : if (!cpu_buffer->nr_pages_to_update)
2037 0 : continue;
2038 :
2039 : /* Can't run something on an offline CPU. */
2040 0 : if (!cpu_online(cpu)) {
2041 0 : rb_update_pages(cpu_buffer);
2042 0 : cpu_buffer->nr_pages_to_update = 0;
2043 : } else {
2044 0 : schedule_work_on(cpu,
2045 : &cpu_buffer->update_pages_work);
2046 : }
2047 : }
2048 :
2049 : /* wait for all the updates to complete */
2050 0 : for_each_buffer_cpu(buffer, cpu) {
2051 0 : cpu_buffer = buffer->buffers[cpu];
2052 0 : if (!cpu_buffer->nr_pages_to_update)
2053 0 : continue;
2054 :
2055 0 : if (cpu_online(cpu))
2056 0 : wait_for_completion(&cpu_buffer->update_done);
2057 0 : cpu_buffer->nr_pages_to_update = 0;
2058 : }
2059 :
2060 0 : put_online_cpus();
2061 : } else {
2062 0 : cpu_buffer = buffer->buffers[cpu_id];
2063 :
2064 0 : if (nr_pages == cpu_buffer->nr_pages)
2065 0 : goto out;
2066 :
2067 : /*
2068 : * Don't succeed if resizing is disabled, as a reader might be
2069 : * manipulating the ring buffer and is expecting a sane state while
2070 : * this is true.
2071 : */
2072 0 : if (atomic_read(&cpu_buffer->resize_disabled)) {
2073 0 : err = -EBUSY;
2074 0 : goto out_err_unlock;
2075 : }
2076 :
2077 0 : cpu_buffer->nr_pages_to_update = nr_pages -
2078 0 : cpu_buffer->nr_pages;
2079 :
2080 0 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
2081 0 : if (cpu_buffer->nr_pages_to_update > 0 &&
2082 0 : __rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
2083 : &cpu_buffer->new_pages)) {
2084 0 : err = -ENOMEM;
2085 0 : goto out_err;
2086 : }
2087 :
2088 0 : get_online_cpus();
2089 :
2090 : /* Can't run something on an offline CPU. */
2091 0 : if (!cpu_online(cpu_id))
2092 0 : rb_update_pages(cpu_buffer);
2093 : else {
2094 0 : schedule_work_on(cpu_id,
2095 : &cpu_buffer->update_pages_work);
2096 0 : wait_for_completion(&cpu_buffer->update_done);
2097 : }
2098 :
2099 0 : cpu_buffer->nr_pages_to_update = 0;
2100 0 : put_online_cpus();
2101 : }
2102 :
2103 0 : out:
2104 : /*
2105 : * The ring buffer resize can happen with the ring buffer
2106 : * enabled, so that the update disturbs the tracing as little
2107 : * as possible. But if the buffer is disabled, we do not need
2108 : * to worry about that, and we can take the time to verify
2109 : * that the buffer is not corrupt.
2110 : */
2111 0 : if (atomic_read(&buffer->record_disabled)) {
2112 0 : atomic_inc(&buffer->record_disabled);
2113 : /*
2114 : * Even though the buffer was disabled, we must make sure
2115 : * that it is truly disabled before calling rb_check_pages.
2116 : * There could have been a race between checking
2117 : * record_disable and incrementing it.
2118 : */
2119 0 : synchronize_rcu();
2120 0 : for_each_buffer_cpu(buffer, cpu) {
2121 0 : cpu_buffer = buffer->buffers[cpu];
2122 0 : rb_check_pages(cpu_buffer);
2123 : }
2124 0 : atomic_dec(&buffer->record_disabled);
2125 : }
2126 :
2127 0 : mutex_unlock(&buffer->mutex);
2128 0 : return 0;
2129 :
2130 : out_err:
2131 0 : for_each_buffer_cpu(buffer, cpu) {
2132 0 : struct buffer_page *bpage, *tmp;
2133 :
2134 0 : cpu_buffer = buffer->buffers[cpu];
2135 0 : cpu_buffer->nr_pages_to_update = 0;
2136 :
2137 0 : if (list_empty(&cpu_buffer->new_pages))
2138 0 : continue;
2139 :
2140 0 : list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
2141 : list) {
2142 0 : list_del_init(&bpage->list);
2143 0 : free_buffer_page(bpage);
2144 : }
2145 : }
2146 0 : out_err_unlock:
2147 0 : mutex_unlock(&buffer->mutex);
2148 0 : return err;
2149 : }
2150 : EXPORT_SYMBOL_GPL(ring_buffer_resize);
2151 :
2152 0 : void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
2153 : {
2154 0 : mutex_lock(&buffer->mutex);
2155 0 : if (val)
2156 0 : buffer->flags |= RB_FL_OVERWRITE;
2157 : else
2158 0 : buffer->flags &= ~RB_FL_OVERWRITE;
2159 0 : mutex_unlock(&buffer->mutex);
2160 0 : }
2161 : EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
2162 :
2163 0 : static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
2164 : {
2165 0 : return bpage->page->data + index;
2166 : }
2167 :
2168 : static __always_inline struct ring_buffer_event *
2169 0 : rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
2170 : {
2171 0 : return __rb_page_index(cpu_buffer->reader_page,
2172 0 : cpu_buffer->reader_page->read);
2173 : }
2174 :
2175 0 : static __always_inline unsigned rb_page_commit(struct buffer_page *bpage)
2176 : {
2177 0 : return local_read(&bpage->page->commit);
2178 : }
2179 :
2180 : static struct ring_buffer_event *
2181 0 : rb_iter_head_event(struct ring_buffer_iter *iter)
2182 : {
2183 0 : struct ring_buffer_event *event;
2184 0 : struct buffer_page *iter_head_page = iter->head_page;
2185 0 : unsigned long commit;
2186 0 : unsigned length;
2187 :
2188 0 : if (iter->head != iter->next_event)
2189 0 : return iter->event;
2190 :
2191 : /*
2192 : * When the writer goes across pages, it issues a cmpxchg which
2193 : * is a mb(), which will synchronize with the rmb here.
2194 : * (see rb_tail_page_update() and __rb_reserve_next())
2195 : */
2196 0 : commit = rb_page_commit(iter_head_page);
2197 0 : smp_rmb();
2198 0 : event = __rb_page_index(iter_head_page, iter->head);
2199 0 : length = rb_event_length(event);
2200 :
2201 : /*
2202 : * READ_ONCE() doesn't work on functions and we don't want the
2203 : * compiler doing any crazy optimizations with length.
2204 : */
2205 0 : barrier();
2206 :
2207 0 : if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE)
2208 : /* Writer corrupted the read? */
2209 0 : goto reset;
2210 :
2211 0 : memcpy(iter->event, event, length);
2212 : /*
2213 : * If the page stamp is still the same after this rmb() then the
2214 : * event was safely copied without the writer entering the page.
2215 : */
2216 0 : smp_rmb();
2217 :
2218 : /* Make sure the page didn't change since we read this */
2219 0 : if (iter->page_stamp != iter_head_page->page->time_stamp ||
2220 0 : commit > rb_page_commit(iter_head_page))
2221 0 : goto reset;
2222 :
2223 0 : iter->next_event = iter->head + length;
2224 0 : return iter->event;
2225 0 : reset:
2226 : /* Reset to the beginning */
2227 0 : iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2228 0 : iter->head = 0;
2229 0 : iter->next_event = 0;
2230 0 : iter->missed_events = 1;
2231 0 : return NULL;
2232 : }
2233 :
2234 : /* Size is determined by what has been committed */
2235 0 : static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
2236 : {
2237 0 : return rb_page_commit(bpage);
2238 : }
2239 :
2240 : static __always_inline unsigned
2241 0 : rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
2242 : {
2243 0 : return rb_page_commit(cpu_buffer->commit_page);
2244 : }
2245 :
2246 : static __always_inline unsigned
2247 0 : rb_event_index(struct ring_buffer_event *event)
2248 : {
2249 0 : unsigned long addr = (unsigned long)event;
2250 :
2251 0 : return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
2252 : }
2253 :
2254 0 : static void rb_inc_iter(struct ring_buffer_iter *iter)
2255 : {
2256 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
2257 :
2258 : /*
2259 : * The iterator could be on the reader page (it starts there).
2260 : * But the head could have moved, since the reader was
2261 : * found. Check for this case and assign the iterator
2262 : * to the head page instead of next.
2263 : */
2264 0 : if (iter->head_page == cpu_buffer->reader_page)
2265 0 : iter->head_page = rb_set_head_page(cpu_buffer);
2266 : else
2267 0 : rb_inc_page(&iter->head_page);
2268 :
2269 0 : iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
2270 0 : iter->head = 0;
2271 0 : iter->next_event = 0;
2272 0 : }
2273 :
2274 : /*
2275 : * rb_handle_head_page - writer hit the head page
2276 : *
2277 : * Returns: +1 to retry page
2278 : * 0 to continue
2279 : * -1 on error
2280 : */
2281 : static int
2282 0 : rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
2283 : struct buffer_page *tail_page,
2284 : struct buffer_page *next_page)
2285 : {
2286 0 : struct buffer_page *new_head;
2287 0 : int entries;
2288 0 : int type;
2289 0 : int ret;
2290 :
2291 0 : entries = rb_page_entries(next_page);
2292 :
2293 : /*
2294 : * The hard part is here. We need to move the head
2295 : * forward, and protect against both readers on
2296 : * other CPUs and writers coming in via interrupts.
2297 : */
2298 0 : type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
2299 : RB_PAGE_HEAD);
2300 :
2301 : /*
2302 : * type can be one of four:
2303 : * NORMAL - an interrupt already moved it for us
2304 : * HEAD - we are the first to get here.
2305 : * UPDATE - we are the interrupt interrupting
2306 : * a current move.
2307 : * MOVED - a reader on another CPU moved the next
2308 : * pointer to its reader page. Give up
2309 : * and try again.
2310 : */
2311 :
2312 0 : switch (type) {
2313 0 : case RB_PAGE_HEAD:
2314 : /*
2315 : * We changed the head to UPDATE, thus
2316 : * it is our responsibility to update
2317 : * the counters.
2318 : */
2319 0 : local_add(entries, &cpu_buffer->overrun);
2320 0 : local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
2321 :
2322 : /*
2323 : * The entries will be zeroed out when we move the
2324 : * tail page.
2325 : */
2326 :
2327 : /* still more to do */
2328 : break;
2329 :
2330 : case RB_PAGE_UPDATE:
2331 : /*
2332 : * This is an interrupt that interrupt the
2333 : * previous update. Still more to do.
2334 : */
2335 : break;
2336 : case RB_PAGE_NORMAL:
2337 : /*
2338 : * An interrupt came in before the update
2339 : * and processed this for us.
2340 : * Nothing left to do.
2341 : */
2342 : return 1;
2343 : case RB_PAGE_MOVED:
2344 : /*
2345 : * The reader is on another CPU and just did
2346 : * a swap with our next_page.
2347 : * Try again.
2348 : */
2349 : return 1;
2350 : default:
2351 0 : RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
2352 0 : return -1;
2353 : }
2354 :
2355 : /*
2356 : * Now that we are here, the old head pointer is
2357 : * set to UPDATE. This will keep the reader from
2358 : * swapping the head page with the reader page.
2359 : * The reader (on another CPU) will spin till
2360 : * we are finished.
2361 : *
2362 : * We just need to protect against interrupts
2363 : * doing the job. We will set the next pointer
2364 : * to HEAD. After that, we set the old pointer
2365 : * to NORMAL, but only if it was HEAD before.
2366 : * otherwise we are an interrupt, and only
2367 : * want the outer most commit to reset it.
2368 : */
2369 0 : new_head = next_page;
2370 0 : rb_inc_page(&new_head);
2371 :
2372 0 : ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
2373 : RB_PAGE_NORMAL);
2374 :
2375 : /*
2376 : * Valid returns are:
2377 : * HEAD - an interrupt came in and already set it.
2378 : * NORMAL - One of two things:
2379 : * 1) We really set it.
2380 : * 2) A bunch of interrupts came in and moved
2381 : * the page forward again.
2382 : */
2383 0 : switch (ret) {
2384 : case RB_PAGE_HEAD:
2385 : case RB_PAGE_NORMAL:
2386 : /* OK */
2387 0 : break;
2388 : default:
2389 0 : RB_WARN_ON(cpu_buffer, 1);
2390 0 : return -1;
2391 : }
2392 :
2393 : /*
2394 : * It is possible that an interrupt came in,
2395 : * set the head up, then more interrupts came in
2396 : * and moved it again. When we get back here,
2397 : * the page would have been set to NORMAL but we
2398 : * just set it back to HEAD.
2399 : *
2400 : * How do you detect this? Well, if that happened
2401 : * the tail page would have moved.
2402 : */
2403 0 : if (ret == RB_PAGE_NORMAL) {
2404 0 : struct buffer_page *buffer_tail_page;
2405 :
2406 0 : buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
2407 : /*
2408 : * If the tail had moved passed next, then we need
2409 : * to reset the pointer.
2410 : */
2411 0 : if (buffer_tail_page != tail_page &&
2412 0 : buffer_tail_page != next_page)
2413 0 : rb_head_page_set_normal(cpu_buffer, new_head,
2414 : next_page,
2415 : RB_PAGE_HEAD);
2416 : }
2417 :
2418 : /*
2419 : * If this was the outer most commit (the one that
2420 : * changed the original pointer from HEAD to UPDATE),
2421 : * then it is up to us to reset it to NORMAL.
2422 : */
2423 0 : if (type == RB_PAGE_HEAD) {
2424 0 : ret = rb_head_page_set_normal(cpu_buffer, next_page,
2425 : tail_page,
2426 : RB_PAGE_UPDATE);
2427 0 : if (RB_WARN_ON(cpu_buffer,
2428 : ret != RB_PAGE_UPDATE))
2429 0 : return -1;
2430 : }
2431 :
2432 : return 0;
2433 : }
2434 :
2435 : static inline void
2436 0 : rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2437 : unsigned long tail, struct rb_event_info *info)
2438 : {
2439 0 : struct buffer_page *tail_page = info->tail_page;
2440 0 : struct ring_buffer_event *event;
2441 0 : unsigned long length = info->length;
2442 :
2443 : /*
2444 : * Only the event that crossed the page boundary
2445 : * must fill the old tail_page with padding.
2446 : */
2447 0 : if (tail >= BUF_PAGE_SIZE) {
2448 : /*
2449 : * If the page was filled, then we still need
2450 : * to update the real_end. Reset it to zero
2451 : * and the reader will ignore it.
2452 : */
2453 0 : if (tail == BUF_PAGE_SIZE)
2454 0 : tail_page->real_end = 0;
2455 :
2456 0 : local_sub(length, &tail_page->write);
2457 0 : return;
2458 : }
2459 :
2460 0 : event = __rb_page_index(tail_page, tail);
2461 :
2462 : /* account for padding bytes */
2463 0 : local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2464 :
2465 : /*
2466 : * Save the original length to the meta data.
2467 : * This will be used by the reader to add lost event
2468 : * counter.
2469 : */
2470 0 : tail_page->real_end = tail;
2471 :
2472 : /*
2473 : * If this event is bigger than the minimum size, then
2474 : * we need to be careful that we don't subtract the
2475 : * write counter enough to allow another writer to slip
2476 : * in on this page.
2477 : * We put in a discarded commit instead, to make sure
2478 : * that this space is not used again.
2479 : *
2480 : * If we are less than the minimum size, we don't need to
2481 : * worry about it.
2482 : */
2483 0 : if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2484 : /* No room for any events */
2485 :
2486 : /* Mark the rest of the page with padding */
2487 0 : rb_event_set_padding(event);
2488 :
2489 : /* Set the write back to the previous setting */
2490 0 : local_sub(length, &tail_page->write);
2491 0 : return;
2492 : }
2493 :
2494 : /* Put in a discarded event */
2495 0 : event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2496 0 : event->type_len = RINGBUF_TYPE_PADDING;
2497 : /* time delta must be non zero */
2498 0 : event->time_delta = 1;
2499 :
2500 : /* Set write to end of buffer */
2501 0 : length = (tail + length) - BUF_PAGE_SIZE;
2502 0 : local_sub(length, &tail_page->write);
2503 : }
2504 :
2505 : static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
2506 :
2507 : /*
2508 : * This is the slow path, force gcc not to inline it.
2509 : */
2510 : static noinline struct ring_buffer_event *
2511 0 : rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2512 : unsigned long tail, struct rb_event_info *info)
2513 : {
2514 0 : struct buffer_page *tail_page = info->tail_page;
2515 0 : struct buffer_page *commit_page = cpu_buffer->commit_page;
2516 0 : struct trace_buffer *buffer = cpu_buffer->buffer;
2517 0 : struct buffer_page *next_page;
2518 0 : int ret;
2519 :
2520 0 : next_page = tail_page;
2521 :
2522 0 : rb_inc_page(&next_page);
2523 :
2524 : /*
2525 : * If for some reason, we had an interrupt storm that made
2526 : * it all the way around the buffer, bail, and warn
2527 : * about it.
2528 : */
2529 0 : if (unlikely(next_page == commit_page)) {
2530 0 : local_inc(&cpu_buffer->commit_overrun);
2531 0 : goto out_reset;
2532 : }
2533 :
2534 : /*
2535 : * This is where the fun begins!
2536 : *
2537 : * We are fighting against races between a reader that
2538 : * could be on another CPU trying to swap its reader
2539 : * page with the buffer head.
2540 : *
2541 : * We are also fighting against interrupts coming in and
2542 : * moving the head or tail on us as well.
2543 : *
2544 : * If the next page is the head page then we have filled
2545 : * the buffer, unless the commit page is still on the
2546 : * reader page.
2547 : */
2548 0 : if (rb_is_head_page(next_page, &tail_page->list)) {
2549 :
2550 : /*
2551 : * If the commit is not on the reader page, then
2552 : * move the header page.
2553 : */
2554 0 : if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2555 : /*
2556 : * If we are not in overwrite mode,
2557 : * this is easy, just stop here.
2558 : */
2559 0 : if (!(buffer->flags & RB_FL_OVERWRITE)) {
2560 0 : local_inc(&cpu_buffer->dropped_events);
2561 0 : goto out_reset;
2562 : }
2563 :
2564 0 : ret = rb_handle_head_page(cpu_buffer,
2565 : tail_page,
2566 : next_page);
2567 0 : if (ret < 0)
2568 0 : goto out_reset;
2569 0 : if (ret)
2570 0 : goto out_again;
2571 : } else {
2572 : /*
2573 : * We need to be careful here too. The
2574 : * commit page could still be on the reader
2575 : * page. We could have a small buffer, and
2576 : * have filled up the buffer with events
2577 : * from interrupts and such, and wrapped.
2578 : *
2579 : * Note, if the tail page is also on the
2580 : * reader_page, we let it move out.
2581 : */
2582 0 : if (unlikely((cpu_buffer->commit_page !=
2583 : cpu_buffer->tail_page) &&
2584 : (cpu_buffer->commit_page ==
2585 : cpu_buffer->reader_page))) {
2586 0 : local_inc(&cpu_buffer->commit_overrun);
2587 0 : goto out_reset;
2588 : }
2589 : }
2590 : }
2591 :
2592 0 : rb_tail_page_update(cpu_buffer, tail_page, next_page);
2593 :
2594 0 : out_again:
2595 :
2596 0 : rb_reset_tail(cpu_buffer, tail, info);
2597 :
2598 : /* Commit what we have for now. */
2599 0 : rb_end_commit(cpu_buffer);
2600 : /* rb_end_commit() decs committing */
2601 0 : local_inc(&cpu_buffer->committing);
2602 :
2603 : /* fail and let the caller try again */
2604 0 : return ERR_PTR(-EAGAIN);
2605 :
2606 0 : out_reset:
2607 : /* reset write */
2608 0 : rb_reset_tail(cpu_buffer, tail, info);
2609 :
2610 0 : return NULL;
2611 : }
2612 :
2613 : /* Slow path */
2614 : static struct ring_buffer_event *
2615 0 : rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
2616 : {
2617 0 : if (abs)
2618 0 : event->type_len = RINGBUF_TYPE_TIME_STAMP;
2619 : else
2620 0 : event->type_len = RINGBUF_TYPE_TIME_EXTEND;
2621 :
2622 : /* Not the first event on the page, or not delta? */
2623 0 : if (abs || rb_event_index(event)) {
2624 0 : event->time_delta = delta & TS_MASK;
2625 0 : event->array[0] = delta >> TS_SHIFT;
2626 : } else {
2627 : /* nope, just zero it */
2628 0 : event->time_delta = 0;
2629 0 : event->array[0] = 0;
2630 : }
2631 :
2632 0 : return skip_time_extend(event);
2633 : }
2634 :
2635 : #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2636 : static inline bool sched_clock_stable(void)
2637 : {
2638 : return true;
2639 : }
2640 : #endif
2641 :
2642 : static void
2643 0 : rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2644 : struct rb_event_info *info)
2645 : {
2646 0 : u64 write_stamp;
2647 :
2648 0 : WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
2649 : (unsigned long long)info->delta,
2650 : (unsigned long long)info->ts,
2651 : (unsigned long long)info->before,
2652 : (unsigned long long)info->after,
2653 : (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0),
2654 : sched_clock_stable() ? "" :
2655 : "If you just came from a suspend/resume,\n"
2656 : "please switch to the trace global clock:\n"
2657 : " echo global > /sys/kernel/debug/tracing/trace_clock\n"
2658 : "or add trace_clock=global to the kernel command line\n");
2659 0 : }
2660 :
2661 0 : static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
2662 : struct ring_buffer_event **event,
2663 : struct rb_event_info *info,
2664 : u64 *delta,
2665 : unsigned int *length)
2666 : {
2667 0 : bool abs = info->add_timestamp &
2668 : (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
2669 :
2670 0 : if (unlikely(info->delta > (1ULL << 59))) {
2671 : /* did the clock go backwards */
2672 0 : if (info->before == info->after && info->before > info->ts) {
2673 : /* not interrupted */
2674 0 : static int once;
2675 :
2676 : /*
2677 : * This is possible with a recalibrating of the TSC.
2678 : * Do not produce a call stack, but just report it.
2679 : */
2680 0 : if (!once) {
2681 0 : once++;
2682 0 : pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
2683 : info->before, info->ts);
2684 : }
2685 : } else
2686 0 : rb_check_timestamp(cpu_buffer, info);
2687 0 : if (!abs)
2688 0 : info->delta = 0;
2689 : }
2690 0 : *event = rb_add_time_stamp(*event, info->delta, abs);
2691 0 : *length -= RB_LEN_TIME_EXTEND;
2692 0 : *delta = 0;
2693 0 : }
2694 :
2695 : /**
2696 : * rb_update_event - update event type and data
2697 : * @cpu_buffer: The per cpu buffer of the @event
2698 : * @event: the event to update
2699 : * @info: The info to update the @event with (contains length and delta)
2700 : *
2701 : * Update the type and data fields of the @event. The length
2702 : * is the actual size that is written to the ring buffer,
2703 : * and with this, we can determine what to place into the
2704 : * data field.
2705 : */
2706 : static void
2707 0 : rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
2708 : struct ring_buffer_event *event,
2709 : struct rb_event_info *info)
2710 : {
2711 0 : unsigned length = info->length;
2712 0 : u64 delta = info->delta;
2713 :
2714 : /*
2715 : * If we need to add a timestamp, then we
2716 : * add it to the start of the reserved space.
2717 : */
2718 0 : if (unlikely(info->add_timestamp))
2719 0 : rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
2720 :
2721 0 : event->time_delta = delta;
2722 0 : length -= RB_EVNT_HDR_SIZE;
2723 0 : if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
2724 0 : event->type_len = 0;
2725 0 : event->array[0] = length;
2726 : } else
2727 0 : event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
2728 0 : }
2729 :
2730 0 : static unsigned rb_calculate_event_length(unsigned length)
2731 : {
2732 0 : struct ring_buffer_event event; /* Used only for sizeof array */
2733 :
2734 : /* zero length can cause confusions */
2735 0 : if (!length)
2736 : length++;
2737 :
2738 0 : if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
2739 0 : length += sizeof(event.array[0]);
2740 :
2741 0 : length += RB_EVNT_HDR_SIZE;
2742 0 : length = ALIGN(length, RB_ARCH_ALIGNMENT);
2743 :
2744 : /*
2745 : * In case the time delta is larger than the 27 bits for it
2746 : * in the header, we need to add a timestamp. If another
2747 : * event comes in when trying to discard this one to increase
2748 : * the length, then the timestamp will be added in the allocated
2749 : * space of this event. If length is bigger than the size needed
2750 : * for the TIME_EXTEND, then padding has to be used. The events
2751 : * length must be either RB_LEN_TIME_EXTEND, or greater than or equal
2752 : * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
2753 : * As length is a multiple of 4, we only need to worry if it
2754 : * is 12 (RB_LEN_TIME_EXTEND + 4).
2755 : */
2756 0 : if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
2757 0 : length += RB_ALIGNMENT;
2758 :
2759 0 : return length;
2760 : }
2761 :
2762 0 : static u64 rb_time_delta(struct ring_buffer_event *event)
2763 : {
2764 0 : switch (event->type_len) {
2765 : case RINGBUF_TYPE_PADDING:
2766 : return 0;
2767 :
2768 : case RINGBUF_TYPE_TIME_EXTEND:
2769 0 : return ring_buffer_event_time_stamp(event);
2770 :
2771 : case RINGBUF_TYPE_TIME_STAMP:
2772 : return 0;
2773 :
2774 0 : case RINGBUF_TYPE_DATA:
2775 0 : return event->time_delta;
2776 : default:
2777 : return 0;
2778 : }
2779 : }
2780 :
2781 : static inline int
2782 0 : rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2783 : struct ring_buffer_event *event)
2784 : {
2785 0 : unsigned long new_index, old_index;
2786 0 : struct buffer_page *bpage;
2787 0 : unsigned long index;
2788 0 : unsigned long addr;
2789 0 : u64 write_stamp;
2790 0 : u64 delta;
2791 :
2792 0 : new_index = rb_event_index(event);
2793 0 : old_index = new_index + rb_event_ts_length(event);
2794 0 : addr = (unsigned long)event;
2795 0 : addr &= PAGE_MASK;
2796 :
2797 0 : bpage = READ_ONCE(cpu_buffer->tail_page);
2798 :
2799 0 : delta = rb_time_delta(event);
2800 :
2801 0 : if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp))
2802 : return 0;
2803 :
2804 : /* Make sure the write stamp is read before testing the location */
2805 0 : barrier();
2806 :
2807 0 : if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
2808 0 : unsigned long write_mask =
2809 0 : local_read(&bpage->write) & ~RB_WRITE_MASK;
2810 0 : unsigned long event_length = rb_event_length(event);
2811 :
2812 : /* Something came in, can't discard */
2813 0 : if (!rb_time_cmpxchg(&cpu_buffer->write_stamp,
2814 : write_stamp, write_stamp - delta))
2815 : return 0;
2816 :
2817 : /*
2818 : * It's possible that the event time delta is zero
2819 : * (has the same time stamp as the previous event)
2820 : * in which case write_stamp and before_stamp could
2821 : * be the same. In such a case, force before_stamp
2822 : * to be different than write_stamp. It doesn't
2823 : * matter what it is, as long as its different.
2824 : */
2825 0 : if (!delta)
2826 0 : rb_time_set(&cpu_buffer->before_stamp, 0);
2827 :
2828 : /*
2829 : * If an event were to come in now, it would see that the
2830 : * write_stamp and the before_stamp are different, and assume
2831 : * that this event just added itself before updating
2832 : * the write stamp. The interrupting event will fix the
2833 : * write stamp for us, and use the before stamp as its delta.
2834 : */
2835 :
2836 : /*
2837 : * This is on the tail page. It is possible that
2838 : * a write could come in and move the tail page
2839 : * and write to the next page. That is fine
2840 : * because we just shorten what is on this page.
2841 : */
2842 0 : old_index += write_mask;
2843 0 : new_index += write_mask;
2844 0 : index = local_cmpxchg(&bpage->write, old_index, new_index);
2845 0 : if (index == old_index) {
2846 : /* update counters */
2847 0 : local_sub(event_length, &cpu_buffer->entries_bytes);
2848 0 : return 1;
2849 : }
2850 : }
2851 :
2852 : /* could not discard */
2853 : return 0;
2854 : }
2855 :
2856 0 : static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2857 : {
2858 0 : local_inc(&cpu_buffer->committing);
2859 0 : local_inc(&cpu_buffer->commits);
2860 : }
2861 :
2862 : static __always_inline void
2863 : rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
2864 : {
2865 0 : unsigned long max_count;
2866 :
2867 : /*
2868 : * We only race with interrupts and NMIs on this CPU.
2869 : * If we own the commit event, then we can commit
2870 : * all others that interrupted us, since the interruptions
2871 : * are in stack format (they finish before they come
2872 : * back to us). This allows us to do a simple loop to
2873 : * assign the commit to the tail.
2874 : */
2875 0 : again:
2876 0 : max_count = cpu_buffer->nr_pages * 100;
2877 :
2878 0 : while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
2879 0 : if (RB_WARN_ON(cpu_buffer, !(--max_count)))
2880 : return;
2881 0 : if (RB_WARN_ON(cpu_buffer,
2882 : rb_is_reader_page(cpu_buffer->tail_page)))
2883 : return;
2884 0 : local_set(&cpu_buffer->commit_page->page->commit,
2885 : rb_page_write(cpu_buffer->commit_page));
2886 0 : rb_inc_page(&cpu_buffer->commit_page);
2887 : /* add barrier to keep gcc from optimizing too much */
2888 0 : barrier();
2889 : }
2890 0 : while (rb_commit_index(cpu_buffer) !=
2891 0 : rb_page_write(cpu_buffer->commit_page)) {
2892 :
2893 0 : local_set(&cpu_buffer->commit_page->page->commit,
2894 : rb_page_write(cpu_buffer->commit_page));
2895 0 : RB_WARN_ON(cpu_buffer,
2896 : local_read(&cpu_buffer->commit_page->page->commit) &
2897 : ~RB_WRITE_MASK);
2898 0 : barrier();
2899 : }
2900 :
2901 : /* again, keep gcc from optimizing */
2902 0 : barrier();
2903 :
2904 : /*
2905 : * If an interrupt came in just after the first while loop
2906 : * and pushed the tail page forward, we will be left with
2907 : * a dangling commit that will never go forward.
2908 : */
2909 0 : if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
2910 0 : goto again;
2911 : }
2912 :
2913 0 : static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
2914 : {
2915 0 : unsigned long commits;
2916 :
2917 0 : if (RB_WARN_ON(cpu_buffer,
2918 : !local_read(&cpu_buffer->committing)))
2919 : return;
2920 :
2921 0 : again:
2922 0 : commits = local_read(&cpu_buffer->commits);
2923 : /* synchronize with interrupts */
2924 0 : barrier();
2925 0 : if (local_read(&cpu_buffer->committing) == 1)
2926 0 : rb_set_commit_to_write(cpu_buffer);
2927 :
2928 0 : local_dec(&cpu_buffer->committing);
2929 :
2930 : /* synchronize with interrupts */
2931 0 : barrier();
2932 :
2933 : /*
2934 : * Need to account for interrupts coming in between the
2935 : * updating of the commit page and the clearing of the
2936 : * committing counter.
2937 : */
2938 0 : if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2939 0 : !local_read(&cpu_buffer->committing)) {
2940 0 : local_inc(&cpu_buffer->committing);
2941 0 : goto again;
2942 : }
2943 : }
2944 :
2945 0 : static inline void rb_event_discard(struct ring_buffer_event *event)
2946 : {
2947 0 : if (extended_time(event))
2948 0 : event = skip_time_extend(event);
2949 :
2950 : /* array[0] holds the actual length for the discarded event */
2951 0 : event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2952 0 : event->type_len = RINGBUF_TYPE_PADDING;
2953 : /* time delta must be non zero */
2954 0 : if (!event->time_delta)
2955 0 : event->time_delta = 1;
2956 0 : }
2957 :
2958 0 : static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2959 : struct ring_buffer_event *event)
2960 : {
2961 0 : local_inc(&cpu_buffer->entries);
2962 0 : rb_end_commit(cpu_buffer);
2963 0 : }
2964 :
2965 : static __always_inline void
2966 0 : rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
2967 : {
2968 0 : size_t nr_pages;
2969 0 : size_t dirty;
2970 0 : size_t full;
2971 :
2972 0 : if (buffer->irq_work.waiters_pending) {
2973 0 : buffer->irq_work.waiters_pending = false;
2974 : /* irq_work_queue() supplies it's own memory barriers */
2975 0 : irq_work_queue(&buffer->irq_work.work);
2976 : }
2977 :
2978 0 : if (cpu_buffer->irq_work.waiters_pending) {
2979 0 : cpu_buffer->irq_work.waiters_pending = false;
2980 : /* irq_work_queue() supplies it's own memory barriers */
2981 0 : irq_work_queue(&cpu_buffer->irq_work.work);
2982 : }
2983 :
2984 0 : if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
2985 : return;
2986 :
2987 0 : if (cpu_buffer->reader_page == cpu_buffer->commit_page)
2988 : return;
2989 :
2990 0 : if (!cpu_buffer->irq_work.full_waiters_pending)
2991 : return;
2992 :
2993 0 : cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
2994 :
2995 0 : full = cpu_buffer->shortest_full;
2996 0 : nr_pages = cpu_buffer->nr_pages;
2997 0 : dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu);
2998 0 : if (full && nr_pages && (dirty * 100) <= full * nr_pages)
2999 : return;
3000 :
3001 0 : cpu_buffer->irq_work.wakeup_full = true;
3002 0 : cpu_buffer->irq_work.full_waiters_pending = false;
3003 : /* irq_work_queue() supplies it's own memory barriers */
3004 0 : irq_work_queue(&cpu_buffer->irq_work.work);
3005 : }
3006 :
3007 : #ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
3008 : # define do_ring_buffer_record_recursion() \
3009 : do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
3010 : #else
3011 : # define do_ring_buffer_record_recursion() do { } while (0)
3012 : #endif
3013 :
3014 : /*
3015 : * The lock and unlock are done within a preempt disable section.
3016 : * The current_context per_cpu variable can only be modified
3017 : * by the current task between lock and unlock. But it can
3018 : * be modified more than once via an interrupt. To pass this
3019 : * information from the lock to the unlock without having to
3020 : * access the 'in_interrupt()' functions again (which do show
3021 : * a bit of overhead in something as critical as function tracing,
3022 : * we use a bitmask trick.
3023 : *
3024 : * bit 1 = NMI context
3025 : * bit 2 = IRQ context
3026 : * bit 3 = SoftIRQ context
3027 : * bit 4 = normal context.
3028 : *
3029 : * This works because this is the order of contexts that can
3030 : * preempt other contexts. A SoftIRQ never preempts an IRQ
3031 : * context.
3032 : *
3033 : * When the context is determined, the corresponding bit is
3034 : * checked and set (if it was set, then a recursion of that context
3035 : * happened).
3036 : *
3037 : * On unlock, we need to clear this bit. To do so, just subtract
3038 : * 1 from the current_context and AND it to itself.
3039 : *
3040 : * (binary)
3041 : * 101 - 1 = 100
3042 : * 101 & 100 = 100 (clearing bit zero)
3043 : *
3044 : * 1010 - 1 = 1001
3045 : * 1010 & 1001 = 1000 (clearing bit 1)
3046 : *
3047 : * The least significant bit can be cleared this way, and it
3048 : * just so happens that it is the same bit corresponding to
3049 : * the current context.
3050 : *
3051 : * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
3052 : * is set when a recursion is detected at the current context, and if
3053 : * the TRANSITION bit is already set, it will fail the recursion.
3054 : * This is needed because there's a lag between the changing of
3055 : * interrupt context and updating the preempt count. In this case,
3056 : * a false positive will be found. To handle this, one extra recursion
3057 : * is allowed, and this is done by the TRANSITION bit. If the TRANSITION
3058 : * bit is already set, then it is considered a recursion and the function
3059 : * ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
3060 : *
3061 : * On the trace_recursive_unlock(), the TRANSITION bit will be the first
3062 : * to be cleared. Even if it wasn't the context that set it. That is,
3063 : * if an interrupt comes in while NORMAL bit is set and the ring buffer
3064 : * is called before preempt_count() is updated, since the check will
3065 : * be on the NORMAL bit, the TRANSITION bit will then be set. If an
3066 : * NMI then comes in, it will set the NMI bit, but when the NMI code
3067 : * does the trace_recursive_unlock() it will clear the TRANSTION bit
3068 : * and leave the NMI bit set. But this is fine, because the interrupt
3069 : * code that set the TRANSITION bit will then clear the NMI bit when it
3070 : * calls trace_recursive_unlock(). If another NMI comes in, it will
3071 : * set the TRANSITION bit and continue.
3072 : *
3073 : * Note: The TRANSITION bit only handles a single transition between context.
3074 : */
3075 :
3076 : static __always_inline int
3077 0 : trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
3078 : {
3079 0 : unsigned int val = cpu_buffer->current_context;
3080 0 : unsigned long pc = preempt_count();
3081 0 : int bit;
3082 :
3083 0 : if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
3084 : bit = RB_CTX_NORMAL;
3085 : else
3086 0 : bit = pc & NMI_MASK ? RB_CTX_NMI :
3087 0 : pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
3088 :
3089 0 : if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
3090 : /*
3091 : * It is possible that this was called by transitioning
3092 : * between interrupt context, and preempt_count() has not
3093 : * been updated yet. In this case, use the TRANSITION bit.
3094 : */
3095 0 : bit = RB_CTX_TRANSITION;
3096 0 : if (val & (1 << (bit + cpu_buffer->nest))) {
3097 : do_ring_buffer_record_recursion();
3098 : return 1;
3099 : }
3100 : }
3101 :
3102 0 : val |= (1 << (bit + cpu_buffer->nest));
3103 0 : cpu_buffer->current_context = val;
3104 :
3105 0 : return 0;
3106 : }
3107 :
3108 : static __always_inline void
3109 0 : trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
3110 : {
3111 0 : cpu_buffer->current_context &=
3112 0 : cpu_buffer->current_context - (1 << cpu_buffer->nest);
3113 0 : }
3114 :
3115 : /* The recursive locking above uses 5 bits */
3116 : #define NESTED_BITS 5
3117 :
3118 : /**
3119 : * ring_buffer_nest_start - Allow to trace while nested
3120 : * @buffer: The ring buffer to modify
3121 : *
3122 : * The ring buffer has a safety mechanism to prevent recursion.
3123 : * But there may be a case where a trace needs to be done while
3124 : * tracing something else. In this case, calling this function
3125 : * will allow this function to nest within a currently active
3126 : * ring_buffer_lock_reserve().
3127 : *
3128 : * Call this function before calling another ring_buffer_lock_reserve() and
3129 : * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
3130 : */
3131 0 : void ring_buffer_nest_start(struct trace_buffer *buffer)
3132 : {
3133 0 : struct ring_buffer_per_cpu *cpu_buffer;
3134 0 : int cpu;
3135 :
3136 : /* Enabled by ring_buffer_nest_end() */
3137 0 : preempt_disable_notrace();
3138 0 : cpu = raw_smp_processor_id();
3139 0 : cpu_buffer = buffer->buffers[cpu];
3140 : /* This is the shift value for the above recursive locking */
3141 0 : cpu_buffer->nest += NESTED_BITS;
3142 0 : }
3143 :
3144 : /**
3145 : * ring_buffer_nest_end - Allow to trace while nested
3146 : * @buffer: The ring buffer to modify
3147 : *
3148 : * Must be called after ring_buffer_nest_start() and after the
3149 : * ring_buffer_unlock_commit().
3150 : */
3151 0 : void ring_buffer_nest_end(struct trace_buffer *buffer)
3152 : {
3153 0 : struct ring_buffer_per_cpu *cpu_buffer;
3154 0 : int cpu;
3155 :
3156 : /* disabled by ring_buffer_nest_start() */
3157 0 : cpu = raw_smp_processor_id();
3158 0 : cpu_buffer = buffer->buffers[cpu];
3159 : /* This is the shift value for the above recursive locking */
3160 0 : cpu_buffer->nest -= NESTED_BITS;
3161 0 : preempt_enable_notrace();
3162 0 : }
3163 :
3164 : /**
3165 : * ring_buffer_unlock_commit - commit a reserved
3166 : * @buffer: The buffer to commit to
3167 : * @event: The event pointer to commit.
3168 : *
3169 : * This commits the data to the ring buffer, and releases any locks held.
3170 : *
3171 : * Must be paired with ring_buffer_lock_reserve.
3172 : */
3173 0 : int ring_buffer_unlock_commit(struct trace_buffer *buffer,
3174 : struct ring_buffer_event *event)
3175 : {
3176 0 : struct ring_buffer_per_cpu *cpu_buffer;
3177 0 : int cpu = raw_smp_processor_id();
3178 :
3179 0 : cpu_buffer = buffer->buffers[cpu];
3180 :
3181 0 : rb_commit(cpu_buffer, event);
3182 :
3183 0 : rb_wakeups(buffer, cpu_buffer);
3184 :
3185 0 : trace_recursive_unlock(cpu_buffer);
3186 :
3187 0 : preempt_enable_notrace();
3188 :
3189 0 : return 0;
3190 : }
3191 : EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
3192 :
3193 : /* Special value to validate all deltas on a page. */
3194 : #define CHECK_FULL_PAGE 1L
3195 :
3196 : #ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
3197 : static void dump_buffer_page(struct buffer_data_page *bpage,
3198 : struct rb_event_info *info,
3199 : unsigned long tail)
3200 : {
3201 : struct ring_buffer_event *event;
3202 : u64 ts, delta;
3203 : int e;
3204 :
3205 : ts = bpage->time_stamp;
3206 : pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
3207 :
3208 : for (e = 0; e < tail; e += rb_event_length(event)) {
3209 :
3210 : event = (struct ring_buffer_event *)(bpage->data + e);
3211 :
3212 : switch (event->type_len) {
3213 :
3214 : case RINGBUF_TYPE_TIME_EXTEND:
3215 : delta = ring_buffer_event_time_stamp(event);
3216 : ts += delta;
3217 : pr_warn(" [%lld] delta:%lld TIME EXTEND\n", ts, delta);
3218 : break;
3219 :
3220 : case RINGBUF_TYPE_TIME_STAMP:
3221 : delta = ring_buffer_event_time_stamp(event);
3222 : ts = delta;
3223 : pr_warn(" [%lld] absolute:%lld TIME STAMP\n", ts, delta);
3224 : break;
3225 :
3226 : case RINGBUF_TYPE_PADDING:
3227 : ts += event->time_delta;
3228 : pr_warn(" [%lld] delta:%d PADDING\n", ts, event->time_delta);
3229 : break;
3230 :
3231 : case RINGBUF_TYPE_DATA:
3232 : ts += event->time_delta;
3233 : pr_warn(" [%lld] delta:%d\n", ts, event->time_delta);
3234 : break;
3235 :
3236 : default:
3237 : break;
3238 : }
3239 : }
3240 : }
3241 :
3242 : static DEFINE_PER_CPU(atomic_t, checking);
3243 : static atomic_t ts_dump;
3244 :
3245 : /*
3246 : * Check if the current event time stamp matches the deltas on
3247 : * the buffer page.
3248 : */
3249 : static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3250 : struct rb_event_info *info,
3251 : unsigned long tail)
3252 : {
3253 : struct ring_buffer_event *event;
3254 : struct buffer_data_page *bpage;
3255 : u64 ts, delta;
3256 : bool full = false;
3257 : int e;
3258 :
3259 : bpage = info->tail_page->page;
3260 :
3261 : if (tail == CHECK_FULL_PAGE) {
3262 : full = true;
3263 : tail = local_read(&bpage->commit);
3264 : } else if (info->add_timestamp &
3265 : (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
3266 : /* Ignore events with absolute time stamps */
3267 : return;
3268 : }
3269 :
3270 : /*
3271 : * Do not check the first event (skip possible extends too).
3272 : * Also do not check if previous events have not been committed.
3273 : */
3274 : if (tail <= 8 || tail > local_read(&bpage->commit))
3275 : return;
3276 :
3277 : /*
3278 : * If this interrupted another event,
3279 : */
3280 : if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
3281 : goto out;
3282 :
3283 : ts = bpage->time_stamp;
3284 :
3285 : for (e = 0; e < tail; e += rb_event_length(event)) {
3286 :
3287 : event = (struct ring_buffer_event *)(bpage->data + e);
3288 :
3289 : switch (event->type_len) {
3290 :
3291 : case RINGBUF_TYPE_TIME_EXTEND:
3292 : delta = ring_buffer_event_time_stamp(event);
3293 : ts += delta;
3294 : break;
3295 :
3296 : case RINGBUF_TYPE_TIME_STAMP:
3297 : delta = ring_buffer_event_time_stamp(event);
3298 : ts = delta;
3299 : break;
3300 :
3301 : case RINGBUF_TYPE_PADDING:
3302 : if (event->time_delta == 1)
3303 : break;
3304 : /* fall through */
3305 : case RINGBUF_TYPE_DATA:
3306 : ts += event->time_delta;
3307 : break;
3308 :
3309 : default:
3310 : RB_WARN_ON(cpu_buffer, 1);
3311 : }
3312 : }
3313 : if ((full && ts > info->ts) ||
3314 : (!full && ts + info->delta != info->ts)) {
3315 : /* If another report is happening, ignore this one */
3316 : if (atomic_inc_return(&ts_dump) != 1) {
3317 : atomic_dec(&ts_dump);
3318 : goto out;
3319 : }
3320 : atomic_inc(&cpu_buffer->record_disabled);
3321 : /* There's some cases in boot up that this can happen */
3322 : WARN_ON_ONCE(system_state != SYSTEM_BOOTING);
3323 : pr_warn("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s\n",
3324 : cpu_buffer->cpu,
3325 : ts + info->delta, info->ts, info->delta,
3326 : info->before, info->after,
3327 : full ? " (full)" : "");
3328 : dump_buffer_page(bpage, info, tail);
3329 : atomic_dec(&ts_dump);
3330 : /* Do not re-enable checking */
3331 : return;
3332 : }
3333 : out:
3334 : atomic_dec(this_cpu_ptr(&checking));
3335 : }
3336 : #else
3337 0 : static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
3338 : struct rb_event_info *info,
3339 : unsigned long tail)
3340 : {
3341 0 : }
3342 : #endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
3343 :
3344 : static struct ring_buffer_event *
3345 0 : __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
3346 : struct rb_event_info *info)
3347 : {
3348 0 : struct ring_buffer_event *event;
3349 0 : struct buffer_page *tail_page;
3350 0 : unsigned long tail, write, w;
3351 0 : bool a_ok;
3352 0 : bool b_ok;
3353 :
3354 : /* Don't let the compiler play games with cpu_buffer->tail_page */
3355 0 : tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
3356 :
3357 0 : /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
3358 0 : barrier();
3359 0 : b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3360 0 : a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3361 0 : barrier();
3362 0 : info->ts = rb_time_stamp(cpu_buffer->buffer);
3363 :
3364 0 : if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
3365 0 : info->delta = info->ts;
3366 : } else {
3367 : /*
3368 : * If interrupting an event time update, we may need an
3369 : * absolute timestamp.
3370 : * Don't bother if this is the start of a new page (w == 0).
3371 : */
3372 0 : if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) {
3373 0 : info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
3374 0 : info->length += RB_LEN_TIME_EXTEND;
3375 : } else {
3376 0 : info->delta = info->ts - info->after;
3377 0 : if (unlikely(test_time_stamp(info->delta))) {
3378 0 : info->add_timestamp |= RB_ADD_STAMP_EXTEND;
3379 0 : info->length += RB_LEN_TIME_EXTEND;
3380 : }
3381 : }
3382 : }
3383 :
3384 0 : /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
3385 :
3386 0 : /*C*/ write = local_add_return(info->length, &tail_page->write);
3387 :
3388 : /* set write to only the index of the write */
3389 0 : write &= RB_WRITE_MASK;
3390 :
3391 0 : tail = write - info->length;
3392 :
3393 : /* See if we shot pass the end of this buffer page */
3394 0 : if (unlikely(write > BUF_PAGE_SIZE)) {
3395 : /* before and after may now different, fix it up*/
3396 0 : b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before);
3397 0 : a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3398 0 : if (a_ok && b_ok && info->before != info->after)
3399 0 : (void)rb_time_cmpxchg(&cpu_buffer->before_stamp,
3400 : info->before, info->after);
3401 0 : if (a_ok && b_ok)
3402 0 : check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
3403 0 : return rb_move_tail(cpu_buffer, tail, info);
3404 : }
3405 :
3406 0 : if (likely(tail == w)) {
3407 0 : u64 save_before;
3408 0 : bool s_ok;
3409 :
3410 : /* Nothing interrupted us between A and C */
3411 0 : /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
3412 0 : barrier();
3413 0 : /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before);
3414 0 : RB_WARN_ON(cpu_buffer, !s_ok);
3415 0 : if (likely(!(info->add_timestamp &
3416 : (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3417 : /* This did not interrupt any time update */
3418 0 : info->delta = info->ts - info->after;
3419 : else
3420 : /* Just use full timestamp for interrupting event */
3421 0 : info->delta = info->ts;
3422 0 : barrier();
3423 0 : check_buffer(cpu_buffer, info, tail);
3424 0 : if (unlikely(info->ts != save_before)) {
3425 : /* SLOW PATH - Interrupted between C and E */
3426 :
3427 0 : a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3428 0 : RB_WARN_ON(cpu_buffer, !a_ok);
3429 :
3430 : /* Write stamp must only go forward */
3431 0 : if (save_before > info->after) {
3432 : /*
3433 : * We do not care about the result, only that
3434 : * it gets updated atomically.
3435 : */
3436 0 : (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
3437 : info->after, save_before);
3438 : }
3439 : }
3440 : } else {
3441 0 : u64 ts;
3442 : /* SLOW PATH - Interrupted between A and C */
3443 0 : a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after);
3444 : /* Was interrupted before here, write_stamp must be valid */
3445 0 : RB_WARN_ON(cpu_buffer, !a_ok);
3446 0 : ts = rb_time_stamp(cpu_buffer->buffer);
3447 0 : barrier();
3448 0 : /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
3449 0 : info->after < ts &&
3450 0 : rb_time_cmpxchg(&cpu_buffer->write_stamp,
3451 : info->after, ts)) {
3452 : /* Nothing came after this event between C and E */
3453 0 : info->delta = ts - info->after;
3454 0 : info->ts = ts;
3455 : } else {
3456 : /*
3457 : * Interrupted between C and E:
3458 : * Lost the previous events time stamp. Just set the
3459 : * delta to zero, and this will be the same time as
3460 : * the event this event interrupted. And the events that
3461 : * came after this will still be correct (as they would
3462 : * have built their delta on the previous event.
3463 : */
3464 0 : info->delta = 0;
3465 : }
3466 0 : info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
3467 : }
3468 :
3469 : /*
3470 : * If this is the first commit on the page, then it has the same
3471 : * timestamp as the page itself.
3472 : */
3473 0 : if (unlikely(!tail && !(info->add_timestamp &
3474 : (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
3475 0 : info->delta = 0;
3476 :
3477 : /* We reserved something on the buffer */
3478 :
3479 0 : event = __rb_page_index(tail_page, tail);
3480 0 : rb_update_event(cpu_buffer, event, info);
3481 :
3482 0 : local_inc(&tail_page->entries);
3483 :
3484 : /*
3485 : * If this is the first commit on the page, then update
3486 : * its timestamp.
3487 : */
3488 0 : if (unlikely(!tail))
3489 0 : tail_page->page->time_stamp = info->ts;
3490 :
3491 : /* account for these added bytes */
3492 0 : local_add(info->length, &cpu_buffer->entries_bytes);
3493 :
3494 0 : return event;
3495 : }
3496 :
3497 : static __always_inline struct ring_buffer_event *
3498 0 : rb_reserve_next_event(struct trace_buffer *buffer,
3499 : struct ring_buffer_per_cpu *cpu_buffer,
3500 : unsigned long length)
3501 : {
3502 0 : struct ring_buffer_event *event;
3503 0 : struct rb_event_info info;
3504 0 : int nr_loops = 0;
3505 0 : int add_ts_default;
3506 :
3507 0 : rb_start_commit(cpu_buffer);
3508 : /* The commit page can not change after this */
3509 :
3510 : #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
3511 : /*
3512 : * Due to the ability to swap a cpu buffer from a buffer
3513 : * it is possible it was swapped before we committed.
3514 : * (committing stops a swap). We check for it here and
3515 : * if it happened, we have to fail the write.
3516 : */
3517 : barrier();
3518 : if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
3519 : local_dec(&cpu_buffer->committing);
3520 : local_dec(&cpu_buffer->commits);
3521 : return NULL;
3522 : }
3523 : #endif
3524 :
3525 0 : info.length = rb_calculate_event_length(length);
3526 :
3527 0 : if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
3528 0 : add_ts_default = RB_ADD_STAMP_ABSOLUTE;
3529 0 : info.length += RB_LEN_TIME_EXTEND;
3530 : } else {
3531 0 : add_ts_default = RB_ADD_STAMP_NONE;
3532 : }
3533 :
3534 0 : again:
3535 0 : info.add_timestamp = add_ts_default;
3536 0 : info.delta = 0;
3537 :
3538 : /*
3539 : * We allow for interrupts to reenter here and do a trace.
3540 : * If one does, it will cause this original code to loop
3541 : * back here. Even with heavy interrupts happening, this
3542 : * should only happen a few times in a row. If this happens
3543 : * 1000 times in a row, there must be either an interrupt
3544 : * storm or we have something buggy.
3545 : * Bail!
3546 : */
3547 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
3548 0 : goto out_fail;
3549 :
3550 0 : event = __rb_reserve_next(cpu_buffer, &info);
3551 :
3552 0 : if (unlikely(PTR_ERR(event) == -EAGAIN)) {
3553 0 : if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
3554 0 : info.length -= RB_LEN_TIME_EXTEND;
3555 0 : goto again;
3556 : }
3557 :
3558 0 : if (likely(event))
3559 : return event;
3560 0 : out_fail:
3561 0 : rb_end_commit(cpu_buffer);
3562 : return NULL;
3563 : }
3564 :
3565 : /**
3566 : * ring_buffer_lock_reserve - reserve a part of the buffer
3567 : * @buffer: the ring buffer to reserve from
3568 : * @length: the length of the data to reserve (excluding event header)
3569 : *
3570 : * Returns a reserved event on the ring buffer to copy directly to.
3571 : * The user of this interface will need to get the body to write into
3572 : * and can use the ring_buffer_event_data() interface.
3573 : *
3574 : * The length is the length of the data needed, not the event length
3575 : * which also includes the event header.
3576 : *
3577 : * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
3578 : * If NULL is returned, then nothing has been allocated or locked.
3579 : */
3580 : struct ring_buffer_event *
3581 0 : ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
3582 : {
3583 0 : struct ring_buffer_per_cpu *cpu_buffer;
3584 0 : struct ring_buffer_event *event;
3585 0 : int cpu;
3586 :
3587 : /* If we are tracing schedule, we don't want to recurse */
3588 0 : preempt_disable_notrace();
3589 :
3590 0 : if (unlikely(atomic_read(&buffer->record_disabled)))
3591 0 : goto out;
3592 :
3593 0 : cpu = raw_smp_processor_id();
3594 :
3595 0 : if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
3596 0 : goto out;
3597 :
3598 0 : cpu_buffer = buffer->buffers[cpu];
3599 :
3600 0 : if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
3601 0 : goto out;
3602 :
3603 0 : if (unlikely(length > BUF_MAX_DATA_SIZE))
3604 0 : goto out;
3605 :
3606 0 : if (unlikely(trace_recursive_lock(cpu_buffer)))
3607 0 : goto out;
3608 :
3609 0 : event = rb_reserve_next_event(buffer, cpu_buffer, length);
3610 0 : if (!event)
3611 0 : goto out_unlock;
3612 :
3613 : return event;
3614 :
3615 0 : out_unlock:
3616 0 : trace_recursive_unlock(cpu_buffer);
3617 0 : out:
3618 0 : preempt_enable_notrace();
3619 0 : return NULL;
3620 : }
3621 : EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
3622 :
3623 : /*
3624 : * Decrement the entries to the page that an event is on.
3625 : * The event does not even need to exist, only the pointer
3626 : * to the page it is on. This may only be called before the commit
3627 : * takes place.
3628 : */
3629 : static inline void
3630 0 : rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
3631 : struct ring_buffer_event *event)
3632 : {
3633 0 : unsigned long addr = (unsigned long)event;
3634 0 : struct buffer_page *bpage = cpu_buffer->commit_page;
3635 0 : struct buffer_page *start;
3636 :
3637 0 : addr &= PAGE_MASK;
3638 :
3639 : /* Do the likely case first */
3640 0 : if (likely(bpage->page == (void *)addr)) {
3641 0 : local_dec(&bpage->entries);
3642 0 : return;
3643 : }
3644 :
3645 : /*
3646 : * Because the commit page may be on the reader page we
3647 : * start with the next page and check the end loop there.
3648 : */
3649 0 : rb_inc_page(&bpage);
3650 0 : start = bpage;
3651 0 : do {
3652 0 : if (bpage->page == (void *)addr) {
3653 0 : local_dec(&bpage->entries);
3654 0 : return;
3655 : }
3656 0 : rb_inc_page(&bpage);
3657 0 : } while (bpage != start);
3658 :
3659 : /* commit not part of this buffer?? */
3660 0 : RB_WARN_ON(cpu_buffer, 1);
3661 : }
3662 :
3663 : /**
3664 : * ring_buffer_discard_commit - discard an event that has not been committed
3665 : * @buffer: the ring buffer
3666 : * @event: non committed event to discard
3667 : *
3668 : * Sometimes an event that is in the ring buffer needs to be ignored.
3669 : * This function lets the user discard an event in the ring buffer
3670 : * and then that event will not be read later.
3671 : *
3672 : * This function only works if it is called before the item has been
3673 : * committed. It will try to free the event from the ring buffer
3674 : * if another event has not been added behind it.
3675 : *
3676 : * If another event has been added behind it, it will set the event
3677 : * up as discarded, and perform the commit.
3678 : *
3679 : * If this function is called, do not call ring_buffer_unlock_commit on
3680 : * the event.
3681 : */
3682 0 : void ring_buffer_discard_commit(struct trace_buffer *buffer,
3683 : struct ring_buffer_event *event)
3684 : {
3685 0 : struct ring_buffer_per_cpu *cpu_buffer;
3686 0 : int cpu;
3687 :
3688 : /* The event is discarded regardless */
3689 0 : rb_event_discard(event);
3690 :
3691 0 : cpu = smp_processor_id();
3692 0 : cpu_buffer = buffer->buffers[cpu];
3693 :
3694 : /*
3695 : * This must only be called if the event has not been
3696 : * committed yet. Thus we can assume that preemption
3697 : * is still disabled.
3698 : */
3699 0 : RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
3700 :
3701 0 : rb_decrement_entry(cpu_buffer, event);
3702 0 : if (rb_try_to_discard(cpu_buffer, event))
3703 : goto out;
3704 :
3705 0 : out:
3706 0 : rb_end_commit(cpu_buffer);
3707 :
3708 0 : trace_recursive_unlock(cpu_buffer);
3709 :
3710 0 : preempt_enable_notrace();
3711 :
3712 0 : }
3713 : EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
3714 :
3715 : /**
3716 : * ring_buffer_write - write data to the buffer without reserving
3717 : * @buffer: The ring buffer to write to.
3718 : * @length: The length of the data being written (excluding the event header)
3719 : * @data: The data to write to the buffer.
3720 : *
3721 : * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
3722 : * one function. If you already have the data to write to the buffer, it
3723 : * may be easier to simply call this function.
3724 : *
3725 : * Note, like ring_buffer_lock_reserve, the length is the length of the data
3726 : * and not the length of the event which would hold the header.
3727 : */
3728 0 : int ring_buffer_write(struct trace_buffer *buffer,
3729 : unsigned long length,
3730 : void *data)
3731 : {
3732 0 : struct ring_buffer_per_cpu *cpu_buffer;
3733 0 : struct ring_buffer_event *event;
3734 0 : void *body;
3735 0 : int ret = -EBUSY;
3736 0 : int cpu;
3737 :
3738 0 : preempt_disable_notrace();
3739 :
3740 0 : if (atomic_read(&buffer->record_disabled))
3741 0 : goto out;
3742 :
3743 0 : cpu = raw_smp_processor_id();
3744 :
3745 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3746 0 : goto out;
3747 :
3748 0 : cpu_buffer = buffer->buffers[cpu];
3749 :
3750 0 : if (atomic_read(&cpu_buffer->record_disabled))
3751 0 : goto out;
3752 :
3753 0 : if (length > BUF_MAX_DATA_SIZE)
3754 0 : goto out;
3755 :
3756 0 : if (unlikely(trace_recursive_lock(cpu_buffer)))
3757 0 : goto out;
3758 :
3759 0 : event = rb_reserve_next_event(buffer, cpu_buffer, length);
3760 0 : if (!event)
3761 0 : goto out_unlock;
3762 :
3763 0 : body = rb_event_data(event);
3764 :
3765 0 : memcpy(body, data, length);
3766 :
3767 0 : rb_commit(cpu_buffer, event);
3768 :
3769 0 : rb_wakeups(buffer, cpu_buffer);
3770 :
3771 : ret = 0;
3772 :
3773 0 : out_unlock:
3774 0 : trace_recursive_unlock(cpu_buffer);
3775 :
3776 0 : out:
3777 0 : preempt_enable_notrace();
3778 :
3779 0 : return ret;
3780 : }
3781 : EXPORT_SYMBOL_GPL(ring_buffer_write);
3782 :
3783 0 : static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
3784 : {
3785 0 : struct buffer_page *reader = cpu_buffer->reader_page;
3786 0 : struct buffer_page *head = rb_set_head_page(cpu_buffer);
3787 0 : struct buffer_page *commit = cpu_buffer->commit_page;
3788 :
3789 : /* In case of error, head will be NULL */
3790 0 : if (unlikely(!head))
3791 : return true;
3792 :
3793 0 : return reader->read == rb_page_commit(reader) &&
3794 0 : (commit == reader ||
3795 0 : (commit == head &&
3796 0 : head->read == rb_page_commit(commit)));
3797 : }
3798 :
3799 : /**
3800 : * ring_buffer_record_disable - stop all writes into the buffer
3801 : * @buffer: The ring buffer to stop writes to.
3802 : *
3803 : * This prevents all writes to the buffer. Any attempt to write
3804 : * to the buffer after this will fail and return NULL.
3805 : *
3806 : * The caller should call synchronize_rcu() after this.
3807 : */
3808 0 : void ring_buffer_record_disable(struct trace_buffer *buffer)
3809 : {
3810 0 : atomic_inc(&buffer->record_disabled);
3811 0 : }
3812 : EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
3813 :
3814 : /**
3815 : * ring_buffer_record_enable - enable writes to the buffer
3816 : * @buffer: The ring buffer to enable writes
3817 : *
3818 : * Note, multiple disables will need the same number of enables
3819 : * to truly enable the writing (much like preempt_disable).
3820 : */
3821 0 : void ring_buffer_record_enable(struct trace_buffer *buffer)
3822 : {
3823 0 : atomic_dec(&buffer->record_disabled);
3824 0 : }
3825 : EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
3826 :
3827 : /**
3828 : * ring_buffer_record_off - stop all writes into the buffer
3829 : * @buffer: The ring buffer to stop writes to.
3830 : *
3831 : * This prevents all writes to the buffer. Any attempt to write
3832 : * to the buffer after this will fail and return NULL.
3833 : *
3834 : * This is different than ring_buffer_record_disable() as
3835 : * it works like an on/off switch, where as the disable() version
3836 : * must be paired with a enable().
3837 : */
3838 0 : void ring_buffer_record_off(struct trace_buffer *buffer)
3839 : {
3840 0 : unsigned int rd;
3841 0 : unsigned int new_rd;
3842 :
3843 0 : do {
3844 0 : rd = atomic_read(&buffer->record_disabled);
3845 0 : new_rd = rd | RB_BUFFER_OFF;
3846 0 : } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3847 0 : }
3848 : EXPORT_SYMBOL_GPL(ring_buffer_record_off);
3849 :
3850 : /**
3851 : * ring_buffer_record_on - restart writes into the buffer
3852 : * @buffer: The ring buffer to start writes to.
3853 : *
3854 : * This enables all writes to the buffer that was disabled by
3855 : * ring_buffer_record_off().
3856 : *
3857 : * This is different than ring_buffer_record_enable() as
3858 : * it works like an on/off switch, where as the enable() version
3859 : * must be paired with a disable().
3860 : */
3861 0 : void ring_buffer_record_on(struct trace_buffer *buffer)
3862 : {
3863 0 : unsigned int rd;
3864 0 : unsigned int new_rd;
3865 :
3866 0 : do {
3867 0 : rd = atomic_read(&buffer->record_disabled);
3868 0 : new_rd = rd & ~RB_BUFFER_OFF;
3869 0 : } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
3870 0 : }
3871 : EXPORT_SYMBOL_GPL(ring_buffer_record_on);
3872 :
3873 : /**
3874 : * ring_buffer_record_is_on - return true if the ring buffer can write
3875 : * @buffer: The ring buffer to see if write is enabled
3876 : *
3877 : * Returns true if the ring buffer is in a state that it accepts writes.
3878 : */
3879 0 : bool ring_buffer_record_is_on(struct trace_buffer *buffer)
3880 : {
3881 0 : return !atomic_read(&buffer->record_disabled);
3882 : }
3883 :
3884 : /**
3885 : * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
3886 : * @buffer: The ring buffer to see if write is set enabled
3887 : *
3888 : * Returns true if the ring buffer is set writable by ring_buffer_record_on().
3889 : * Note that this does NOT mean it is in a writable state.
3890 : *
3891 : * It may return true when the ring buffer has been disabled by
3892 : * ring_buffer_record_disable(), as that is a temporary disabling of
3893 : * the ring buffer.
3894 : */
3895 0 : bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
3896 : {
3897 0 : return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
3898 : }
3899 :
3900 : /**
3901 : * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
3902 : * @buffer: The ring buffer to stop writes to.
3903 : * @cpu: The CPU buffer to stop
3904 : *
3905 : * This prevents all writes to the buffer. Any attempt to write
3906 : * to the buffer after this will fail and return NULL.
3907 : *
3908 : * The caller should call synchronize_rcu() after this.
3909 : */
3910 0 : void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
3911 : {
3912 0 : struct ring_buffer_per_cpu *cpu_buffer;
3913 :
3914 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3915 : return;
3916 :
3917 0 : cpu_buffer = buffer->buffers[cpu];
3918 0 : atomic_inc(&cpu_buffer->record_disabled);
3919 : }
3920 : EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
3921 :
3922 : /**
3923 : * ring_buffer_record_enable_cpu - enable writes to the buffer
3924 : * @buffer: The ring buffer to enable writes
3925 : * @cpu: The CPU to enable.
3926 : *
3927 : * Note, multiple disables will need the same number of enables
3928 : * to truly enable the writing (much like preempt_disable).
3929 : */
3930 0 : void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
3931 : {
3932 0 : struct ring_buffer_per_cpu *cpu_buffer;
3933 :
3934 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3935 : return;
3936 :
3937 0 : cpu_buffer = buffer->buffers[cpu];
3938 0 : atomic_dec(&cpu_buffer->record_disabled);
3939 : }
3940 : EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
3941 :
3942 : /*
3943 : * The total entries in the ring buffer is the running counter
3944 : * of entries entered into the ring buffer, minus the sum of
3945 : * the entries read from the ring buffer and the number of
3946 : * entries that were overwritten.
3947 : */
3948 : static inline unsigned long
3949 0 : rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
3950 : {
3951 0 : return local_read(&cpu_buffer->entries) -
3952 0 : (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
3953 : }
3954 :
3955 : /**
3956 : * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
3957 : * @buffer: The ring buffer
3958 : * @cpu: The per CPU buffer to read from.
3959 : */
3960 0 : u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
3961 : {
3962 0 : unsigned long flags;
3963 0 : struct ring_buffer_per_cpu *cpu_buffer;
3964 0 : struct buffer_page *bpage;
3965 0 : u64 ret = 0;
3966 :
3967 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3968 : return 0;
3969 :
3970 0 : cpu_buffer = buffer->buffers[cpu];
3971 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
3972 : /*
3973 : * if the tail is on reader_page, oldest time stamp is on the reader
3974 : * page
3975 : */
3976 0 : if (cpu_buffer->tail_page == cpu_buffer->reader_page)
3977 : bpage = cpu_buffer->reader_page;
3978 : else
3979 0 : bpage = rb_set_head_page(cpu_buffer);
3980 0 : if (bpage)
3981 0 : ret = bpage->page->time_stamp;
3982 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
3983 :
3984 0 : return ret;
3985 : }
3986 : EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
3987 :
3988 : /**
3989 : * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
3990 : * @buffer: The ring buffer
3991 : * @cpu: The per CPU buffer to read from.
3992 : */
3993 0 : unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
3994 : {
3995 0 : struct ring_buffer_per_cpu *cpu_buffer;
3996 0 : unsigned long ret;
3997 :
3998 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
3999 : return 0;
4000 :
4001 0 : cpu_buffer = buffer->buffers[cpu];
4002 0 : ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
4003 :
4004 0 : return ret;
4005 : }
4006 : EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
4007 :
4008 : /**
4009 : * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
4010 : * @buffer: The ring buffer
4011 : * @cpu: The per CPU buffer to get the entries from.
4012 : */
4013 0 : unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
4014 : {
4015 0 : struct ring_buffer_per_cpu *cpu_buffer;
4016 :
4017 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4018 : return 0;
4019 :
4020 0 : cpu_buffer = buffer->buffers[cpu];
4021 :
4022 0 : return rb_num_of_entries(cpu_buffer);
4023 : }
4024 : EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
4025 :
4026 : /**
4027 : * ring_buffer_overrun_cpu - get the number of overruns caused by the ring
4028 : * buffer wrapping around (only if RB_FL_OVERWRITE is on).
4029 : * @buffer: The ring buffer
4030 : * @cpu: The per CPU buffer to get the number of overruns from
4031 : */
4032 0 : unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
4033 : {
4034 0 : struct ring_buffer_per_cpu *cpu_buffer;
4035 0 : unsigned long ret;
4036 :
4037 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4038 : return 0;
4039 :
4040 0 : cpu_buffer = buffer->buffers[cpu];
4041 0 : ret = local_read(&cpu_buffer->overrun);
4042 :
4043 0 : return ret;
4044 : }
4045 : EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
4046 :
4047 : /**
4048 : * ring_buffer_commit_overrun_cpu - get the number of overruns caused by
4049 : * commits failing due to the buffer wrapping around while there are uncommitted
4050 : * events, such as during an interrupt storm.
4051 : * @buffer: The ring buffer
4052 : * @cpu: The per CPU buffer to get the number of overruns from
4053 : */
4054 : unsigned long
4055 0 : ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
4056 : {
4057 0 : struct ring_buffer_per_cpu *cpu_buffer;
4058 0 : unsigned long ret;
4059 :
4060 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4061 : return 0;
4062 :
4063 0 : cpu_buffer = buffer->buffers[cpu];
4064 0 : ret = local_read(&cpu_buffer->commit_overrun);
4065 :
4066 0 : return ret;
4067 : }
4068 : EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
4069 :
4070 : /**
4071 : * ring_buffer_dropped_events_cpu - get the number of dropped events caused by
4072 : * the ring buffer filling up (only if RB_FL_OVERWRITE is off).
4073 : * @buffer: The ring buffer
4074 : * @cpu: The per CPU buffer to get the number of overruns from
4075 : */
4076 : unsigned long
4077 0 : ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
4078 : {
4079 0 : struct ring_buffer_per_cpu *cpu_buffer;
4080 0 : unsigned long ret;
4081 :
4082 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4083 : return 0;
4084 :
4085 0 : cpu_buffer = buffer->buffers[cpu];
4086 0 : ret = local_read(&cpu_buffer->dropped_events);
4087 :
4088 0 : return ret;
4089 : }
4090 : EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
4091 :
4092 : /**
4093 : * ring_buffer_read_events_cpu - get the number of events successfully read
4094 : * @buffer: The ring buffer
4095 : * @cpu: The per CPU buffer to get the number of events read
4096 : */
4097 : unsigned long
4098 0 : ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
4099 : {
4100 0 : struct ring_buffer_per_cpu *cpu_buffer;
4101 :
4102 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4103 : return 0;
4104 :
4105 0 : cpu_buffer = buffer->buffers[cpu];
4106 0 : return cpu_buffer->read;
4107 : }
4108 : EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
4109 :
4110 : /**
4111 : * ring_buffer_entries - get the number of entries in a buffer
4112 : * @buffer: The ring buffer
4113 : *
4114 : * Returns the total number of entries in the ring buffer
4115 : * (all CPU entries)
4116 : */
4117 0 : unsigned long ring_buffer_entries(struct trace_buffer *buffer)
4118 : {
4119 0 : struct ring_buffer_per_cpu *cpu_buffer;
4120 0 : unsigned long entries = 0;
4121 0 : int cpu;
4122 :
4123 : /* if you care about this being correct, lock the buffer */
4124 0 : for_each_buffer_cpu(buffer, cpu) {
4125 0 : cpu_buffer = buffer->buffers[cpu];
4126 0 : entries += rb_num_of_entries(cpu_buffer);
4127 : }
4128 :
4129 0 : return entries;
4130 : }
4131 : EXPORT_SYMBOL_GPL(ring_buffer_entries);
4132 :
4133 : /**
4134 : * ring_buffer_overruns - get the number of overruns in buffer
4135 : * @buffer: The ring buffer
4136 : *
4137 : * Returns the total number of overruns in the ring buffer
4138 : * (all CPU entries)
4139 : */
4140 0 : unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
4141 : {
4142 0 : struct ring_buffer_per_cpu *cpu_buffer;
4143 0 : unsigned long overruns = 0;
4144 0 : int cpu;
4145 :
4146 : /* if you care about this being correct, lock the buffer */
4147 0 : for_each_buffer_cpu(buffer, cpu) {
4148 0 : cpu_buffer = buffer->buffers[cpu];
4149 0 : overruns += local_read(&cpu_buffer->overrun);
4150 : }
4151 :
4152 0 : return overruns;
4153 : }
4154 : EXPORT_SYMBOL_GPL(ring_buffer_overruns);
4155 :
4156 0 : static void rb_iter_reset(struct ring_buffer_iter *iter)
4157 : {
4158 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4159 :
4160 : /* Iterator usage is expected to have record disabled */
4161 0 : iter->head_page = cpu_buffer->reader_page;
4162 0 : iter->head = cpu_buffer->reader_page->read;
4163 0 : iter->next_event = iter->head;
4164 :
4165 0 : iter->cache_reader_page = iter->head_page;
4166 0 : iter->cache_read = cpu_buffer->read;
4167 :
4168 0 : if (iter->head) {
4169 0 : iter->read_stamp = cpu_buffer->read_stamp;
4170 0 : iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
4171 : } else {
4172 0 : iter->read_stamp = iter->head_page->page->time_stamp;
4173 0 : iter->page_stamp = iter->read_stamp;
4174 : }
4175 0 : }
4176 :
4177 : /**
4178 : * ring_buffer_iter_reset - reset an iterator
4179 : * @iter: The iterator to reset
4180 : *
4181 : * Resets the iterator, so that it will start from the beginning
4182 : * again.
4183 : */
4184 0 : void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
4185 : {
4186 0 : struct ring_buffer_per_cpu *cpu_buffer;
4187 0 : unsigned long flags;
4188 :
4189 0 : if (!iter)
4190 : return;
4191 :
4192 0 : cpu_buffer = iter->cpu_buffer;
4193 :
4194 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4195 0 : rb_iter_reset(iter);
4196 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4197 : }
4198 : EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
4199 :
4200 : /**
4201 : * ring_buffer_iter_empty - check if an iterator has no more to read
4202 : * @iter: The iterator to check
4203 : */
4204 0 : int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
4205 : {
4206 0 : struct ring_buffer_per_cpu *cpu_buffer;
4207 0 : struct buffer_page *reader;
4208 0 : struct buffer_page *head_page;
4209 0 : struct buffer_page *commit_page;
4210 0 : struct buffer_page *curr_commit_page;
4211 0 : unsigned commit;
4212 0 : u64 curr_commit_ts;
4213 0 : u64 commit_ts;
4214 :
4215 0 : cpu_buffer = iter->cpu_buffer;
4216 0 : reader = cpu_buffer->reader_page;
4217 0 : head_page = cpu_buffer->head_page;
4218 0 : commit_page = cpu_buffer->commit_page;
4219 0 : commit_ts = commit_page->page->time_stamp;
4220 :
4221 : /*
4222 : * When the writer goes across pages, it issues a cmpxchg which
4223 : * is a mb(), which will synchronize with the rmb here.
4224 : * (see rb_tail_page_update())
4225 : */
4226 0 : smp_rmb();
4227 0 : commit = rb_page_commit(commit_page);
4228 : /* We want to make sure that the commit page doesn't change */
4229 0 : smp_rmb();
4230 :
4231 : /* Make sure commit page didn't change */
4232 0 : curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
4233 0 : curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
4234 :
4235 : /* If the commit page changed, then there's more data */
4236 0 : if (curr_commit_page != commit_page ||
4237 0 : curr_commit_ts != commit_ts)
4238 : return 0;
4239 :
4240 : /* Still racy, as it may return a false positive, but that's OK */
4241 0 : return ((iter->head_page == commit_page && iter->head >= commit) ||
4242 0 : (iter->head_page == reader && commit_page == head_page &&
4243 0 : head_page->read == commit &&
4244 0 : iter->head == rb_page_commit(cpu_buffer->reader_page)));
4245 : }
4246 : EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
4247 :
4248 : static void
4249 0 : rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
4250 : struct ring_buffer_event *event)
4251 : {
4252 0 : u64 delta;
4253 :
4254 0 : switch (event->type_len) {
4255 : case RINGBUF_TYPE_PADDING:
4256 : return;
4257 :
4258 : case RINGBUF_TYPE_TIME_EXTEND:
4259 0 : delta = ring_buffer_event_time_stamp(event);
4260 0 : cpu_buffer->read_stamp += delta;
4261 0 : return;
4262 :
4263 : case RINGBUF_TYPE_TIME_STAMP:
4264 0 : delta = ring_buffer_event_time_stamp(event);
4265 0 : cpu_buffer->read_stamp = delta;
4266 0 : return;
4267 :
4268 0 : case RINGBUF_TYPE_DATA:
4269 0 : cpu_buffer->read_stamp += event->time_delta;
4270 0 : return;
4271 :
4272 : default:
4273 0 : RB_WARN_ON(cpu_buffer, 1);
4274 : }
4275 0 : return;
4276 : }
4277 :
4278 : static void
4279 0 : rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
4280 : struct ring_buffer_event *event)
4281 : {
4282 0 : u64 delta;
4283 :
4284 0 : switch (event->type_len) {
4285 : case RINGBUF_TYPE_PADDING:
4286 : return;
4287 :
4288 : case RINGBUF_TYPE_TIME_EXTEND:
4289 0 : delta = ring_buffer_event_time_stamp(event);
4290 0 : iter->read_stamp += delta;
4291 0 : return;
4292 :
4293 : case RINGBUF_TYPE_TIME_STAMP:
4294 0 : delta = ring_buffer_event_time_stamp(event);
4295 0 : iter->read_stamp = delta;
4296 0 : return;
4297 :
4298 0 : case RINGBUF_TYPE_DATA:
4299 0 : iter->read_stamp += event->time_delta;
4300 0 : return;
4301 :
4302 : default:
4303 0 : RB_WARN_ON(iter->cpu_buffer, 1);
4304 : }
4305 0 : return;
4306 : }
4307 :
4308 : static struct buffer_page *
4309 0 : rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
4310 : {
4311 0 : struct buffer_page *reader = NULL;
4312 0 : unsigned long overwrite;
4313 0 : unsigned long flags;
4314 0 : int nr_loops = 0;
4315 0 : int ret;
4316 :
4317 0 : local_irq_save(flags);
4318 0 : arch_spin_lock(&cpu_buffer->lock);
4319 :
4320 0 : again:
4321 : /*
4322 : * This should normally only loop twice. But because the
4323 : * start of the reader inserts an empty page, it causes
4324 : * a case where we will loop three times. There should be no
4325 : * reason to loop four times (that I know of).
4326 : */
4327 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
4328 0 : reader = NULL;
4329 0 : goto out;
4330 : }
4331 :
4332 0 : reader = cpu_buffer->reader_page;
4333 :
4334 : /* If there's more to read, return this page */
4335 0 : if (cpu_buffer->reader_page->read < rb_page_size(reader))
4336 0 : goto out;
4337 :
4338 : /* Never should we have an index greater than the size */
4339 0 : if (RB_WARN_ON(cpu_buffer,
4340 : cpu_buffer->reader_page->read > rb_page_size(reader)))
4341 0 : goto out;
4342 :
4343 : /* check if we caught up to the tail */
4344 0 : reader = NULL;
4345 0 : if (cpu_buffer->commit_page == cpu_buffer->reader_page)
4346 0 : goto out;
4347 :
4348 : /* Don't bother swapping if the ring buffer is empty */
4349 0 : if (rb_num_of_entries(cpu_buffer) == 0)
4350 0 : goto out;
4351 :
4352 : /*
4353 : * Reset the reader page to size zero.
4354 : */
4355 0 : local_set(&cpu_buffer->reader_page->write, 0);
4356 0 : local_set(&cpu_buffer->reader_page->entries, 0);
4357 0 : local_set(&cpu_buffer->reader_page->page->commit, 0);
4358 0 : cpu_buffer->reader_page->real_end = 0;
4359 :
4360 0 : spin:
4361 : /*
4362 : * Splice the empty reader page into the list around the head.
4363 : */
4364 0 : reader = rb_set_head_page(cpu_buffer);
4365 0 : if (!reader)
4366 0 : goto out;
4367 0 : cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
4368 0 : cpu_buffer->reader_page->list.prev = reader->list.prev;
4369 :
4370 : /*
4371 : * cpu_buffer->pages just needs to point to the buffer, it
4372 : * has no specific buffer page to point to. Lets move it out
4373 : * of our way so we don't accidentally swap it.
4374 : */
4375 0 : cpu_buffer->pages = reader->list.prev;
4376 :
4377 : /* The reader page will be pointing to the new head */
4378 0 : rb_set_list_to_head(&cpu_buffer->reader_page->list);
4379 :
4380 : /*
4381 : * We want to make sure we read the overruns after we set up our
4382 : * pointers to the next object. The writer side does a
4383 : * cmpxchg to cross pages which acts as the mb on the writer
4384 : * side. Note, the reader will constantly fail the swap
4385 : * while the writer is updating the pointers, so this
4386 : * guarantees that the overwrite recorded here is the one we
4387 : * want to compare with the last_overrun.
4388 : */
4389 0 : smp_mb();
4390 0 : overwrite = local_read(&(cpu_buffer->overrun));
4391 :
4392 : /*
4393 : * Here's the tricky part.
4394 : *
4395 : * We need to move the pointer past the header page.
4396 : * But we can only do that if a writer is not currently
4397 : * moving it. The page before the header page has the
4398 : * flag bit '1' set if it is pointing to the page we want.
4399 : * but if the writer is in the process of moving it
4400 : * than it will be '2' or already moved '0'.
4401 : */
4402 :
4403 0 : ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
4404 :
4405 : /*
4406 : * If we did not convert it, then we must try again.
4407 : */
4408 0 : if (!ret)
4409 0 : goto spin;
4410 :
4411 : /*
4412 : * Yay! We succeeded in replacing the page.
4413 : *
4414 : * Now make the new head point back to the reader page.
4415 : */
4416 0 : rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
4417 0 : rb_inc_page(&cpu_buffer->head_page);
4418 :
4419 0 : local_inc(&cpu_buffer->pages_read);
4420 :
4421 : /* Finally update the reader page to the new head */
4422 0 : cpu_buffer->reader_page = reader;
4423 0 : cpu_buffer->reader_page->read = 0;
4424 :
4425 0 : if (overwrite != cpu_buffer->last_overrun) {
4426 0 : cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
4427 0 : cpu_buffer->last_overrun = overwrite;
4428 : }
4429 :
4430 0 : goto again;
4431 :
4432 0 : out:
4433 : /* Update the read_stamp on the first event */
4434 0 : if (reader && reader->read == 0)
4435 0 : cpu_buffer->read_stamp = reader->page->time_stamp;
4436 :
4437 0 : arch_spin_unlock(&cpu_buffer->lock);
4438 0 : local_irq_restore(flags);
4439 :
4440 0 : return reader;
4441 : }
4442 :
4443 0 : static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
4444 : {
4445 0 : struct ring_buffer_event *event;
4446 0 : struct buffer_page *reader;
4447 0 : unsigned length;
4448 :
4449 0 : reader = rb_get_reader_page(cpu_buffer);
4450 :
4451 : /* This function should not be called when buffer is empty */
4452 0 : if (RB_WARN_ON(cpu_buffer, !reader))
4453 : return;
4454 :
4455 0 : event = rb_reader_event(cpu_buffer);
4456 :
4457 0 : if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
4458 0 : cpu_buffer->read++;
4459 :
4460 0 : rb_update_read_stamp(cpu_buffer, event);
4461 :
4462 0 : length = rb_event_length(event);
4463 0 : cpu_buffer->reader_page->read += length;
4464 : }
4465 :
4466 0 : static void rb_advance_iter(struct ring_buffer_iter *iter)
4467 : {
4468 0 : struct ring_buffer_per_cpu *cpu_buffer;
4469 :
4470 0 : cpu_buffer = iter->cpu_buffer;
4471 :
4472 : /* If head == next_event then we need to jump to the next event */
4473 0 : if (iter->head == iter->next_event) {
4474 : /* If the event gets overwritten again, there's nothing to do */
4475 0 : if (rb_iter_head_event(iter) == NULL)
4476 : return;
4477 : }
4478 :
4479 0 : iter->head = iter->next_event;
4480 :
4481 : /*
4482 : * Check if we are at the end of the buffer.
4483 : */
4484 0 : if (iter->next_event >= rb_page_size(iter->head_page)) {
4485 : /* discarded commits can make the page empty */
4486 0 : if (iter->head_page == cpu_buffer->commit_page)
4487 : return;
4488 0 : rb_inc_iter(iter);
4489 0 : return;
4490 : }
4491 :
4492 0 : rb_update_iter_read_stamp(iter, iter->event);
4493 : }
4494 :
4495 0 : static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
4496 : {
4497 0 : return cpu_buffer->lost_events;
4498 : }
4499 :
4500 : static struct ring_buffer_event *
4501 0 : rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
4502 : unsigned long *lost_events)
4503 : {
4504 0 : struct ring_buffer_event *event;
4505 0 : struct buffer_page *reader;
4506 0 : int nr_loops = 0;
4507 :
4508 0 : if (ts)
4509 0 : *ts = 0;
4510 0 : again:
4511 : /*
4512 : * We repeat when a time extend is encountered.
4513 : * Since the time extend is always attached to a data event,
4514 : * we should never loop more than once.
4515 : * (We never hit the following condition more than twice).
4516 : */
4517 0 : if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
4518 : return NULL;
4519 :
4520 0 : reader = rb_get_reader_page(cpu_buffer);
4521 0 : if (!reader)
4522 : return NULL;
4523 :
4524 0 : event = rb_reader_event(cpu_buffer);
4525 :
4526 0 : switch (event->type_len) {
4527 : case RINGBUF_TYPE_PADDING:
4528 0 : if (rb_null_event(event))
4529 0 : RB_WARN_ON(cpu_buffer, 1);
4530 : /*
4531 : * Because the writer could be discarding every
4532 : * event it creates (which would probably be bad)
4533 : * if we were to go back to "again" then we may never
4534 : * catch up, and will trigger the warn on, or lock
4535 : * the box. Return the padding, and we will release
4536 : * the current locks, and try again.
4537 : */
4538 : return event;
4539 :
4540 0 : case RINGBUF_TYPE_TIME_EXTEND:
4541 : /* Internal data, OK to advance */
4542 0 : rb_advance_reader(cpu_buffer);
4543 0 : goto again;
4544 :
4545 0 : case RINGBUF_TYPE_TIME_STAMP:
4546 0 : if (ts) {
4547 0 : *ts = ring_buffer_event_time_stamp(event);
4548 0 : ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4549 : cpu_buffer->cpu, ts);
4550 : }
4551 : /* Internal data, OK to advance */
4552 0 : rb_advance_reader(cpu_buffer);
4553 0 : goto again;
4554 :
4555 0 : case RINGBUF_TYPE_DATA:
4556 0 : if (ts && !(*ts)) {
4557 0 : *ts = cpu_buffer->read_stamp + event->time_delta;
4558 0 : ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4559 : cpu_buffer->cpu, ts);
4560 : }
4561 0 : if (lost_events)
4562 0 : *lost_events = rb_lost_events(cpu_buffer);
4563 : return event;
4564 :
4565 : default:
4566 0 : RB_WARN_ON(cpu_buffer, 1);
4567 : }
4568 :
4569 0 : return NULL;
4570 : }
4571 : EXPORT_SYMBOL_GPL(ring_buffer_peek);
4572 :
4573 : static struct ring_buffer_event *
4574 0 : rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4575 : {
4576 0 : struct trace_buffer *buffer;
4577 0 : struct ring_buffer_per_cpu *cpu_buffer;
4578 0 : struct ring_buffer_event *event;
4579 0 : int nr_loops = 0;
4580 :
4581 0 : if (ts)
4582 0 : *ts = 0;
4583 :
4584 0 : cpu_buffer = iter->cpu_buffer;
4585 0 : buffer = cpu_buffer->buffer;
4586 :
4587 : /*
4588 : * Check if someone performed a consuming read to
4589 : * the buffer. A consuming read invalidates the iterator
4590 : * and we need to reset the iterator in this case.
4591 : */
4592 0 : if (unlikely(iter->cache_read != cpu_buffer->read ||
4593 : iter->cache_reader_page != cpu_buffer->reader_page))
4594 0 : rb_iter_reset(iter);
4595 :
4596 0 : again:
4597 0 : if (ring_buffer_iter_empty(iter))
4598 : return NULL;
4599 :
4600 : /*
4601 : * As the writer can mess with what the iterator is trying
4602 : * to read, just give up if we fail to get an event after
4603 : * three tries. The iterator is not as reliable when reading
4604 : * the ring buffer with an active write as the consumer is.
4605 : * Do not warn if the three failures is reached.
4606 : */
4607 0 : if (++nr_loops > 3)
4608 : return NULL;
4609 :
4610 0 : if (rb_per_cpu_empty(cpu_buffer))
4611 : return NULL;
4612 :
4613 0 : if (iter->head >= rb_page_size(iter->head_page)) {
4614 0 : rb_inc_iter(iter);
4615 0 : goto again;
4616 : }
4617 :
4618 0 : event = rb_iter_head_event(iter);
4619 0 : if (!event)
4620 0 : goto again;
4621 :
4622 0 : switch (event->type_len) {
4623 : case RINGBUF_TYPE_PADDING:
4624 0 : if (rb_null_event(event)) {
4625 0 : rb_inc_iter(iter);
4626 0 : goto again;
4627 : }
4628 0 : rb_advance_iter(iter);
4629 0 : return event;
4630 :
4631 0 : case RINGBUF_TYPE_TIME_EXTEND:
4632 : /* Internal data, OK to advance */
4633 0 : rb_advance_iter(iter);
4634 0 : goto again;
4635 :
4636 0 : case RINGBUF_TYPE_TIME_STAMP:
4637 0 : if (ts) {
4638 0 : *ts = ring_buffer_event_time_stamp(event);
4639 0 : ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
4640 : cpu_buffer->cpu, ts);
4641 : }
4642 : /* Internal data, OK to advance */
4643 0 : rb_advance_iter(iter);
4644 0 : goto again;
4645 :
4646 0 : case RINGBUF_TYPE_DATA:
4647 0 : if (ts && !(*ts)) {
4648 0 : *ts = iter->read_stamp + event->time_delta;
4649 0 : ring_buffer_normalize_time_stamp(buffer,
4650 : cpu_buffer->cpu, ts);
4651 : }
4652 : return event;
4653 :
4654 : default:
4655 0 : RB_WARN_ON(cpu_buffer, 1);
4656 : }
4657 :
4658 0 : return NULL;
4659 : }
4660 : EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
4661 :
4662 0 : static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
4663 : {
4664 0 : if (likely(!in_nmi())) {
4665 0 : raw_spin_lock(&cpu_buffer->reader_lock);
4666 0 : return true;
4667 : }
4668 :
4669 : /*
4670 : * If an NMI die dumps out the content of the ring buffer
4671 : * trylock must be used to prevent a deadlock if the NMI
4672 : * preempted a task that holds the ring buffer locks. If
4673 : * we get the lock then all is fine, if not, then continue
4674 : * to do the read, but this can corrupt the ring buffer,
4675 : * so it must be permanently disabled from future writes.
4676 : * Reading from NMI is a oneshot deal.
4677 : */
4678 0 : if (raw_spin_trylock(&cpu_buffer->reader_lock))
4679 : return true;
4680 :
4681 : /* Continue without locking, but disable the ring buffer */
4682 0 : atomic_inc(&cpu_buffer->record_disabled);
4683 0 : return false;
4684 : }
4685 :
4686 : static inline void
4687 0 : rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
4688 : {
4689 0 : if (likely(locked))
4690 0 : raw_spin_unlock(&cpu_buffer->reader_lock);
4691 0 : return;
4692 : }
4693 :
4694 : /**
4695 : * ring_buffer_peek - peek at the next event to be read
4696 : * @buffer: The ring buffer to read
4697 : * @cpu: The cpu to peak at
4698 : * @ts: The timestamp counter of this event.
4699 : * @lost_events: a variable to store if events were lost (may be NULL)
4700 : *
4701 : * This will return the event that will be read next, but does
4702 : * not consume the data.
4703 : */
4704 : struct ring_buffer_event *
4705 0 : ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
4706 : unsigned long *lost_events)
4707 : {
4708 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4709 0 : struct ring_buffer_event *event;
4710 0 : unsigned long flags;
4711 0 : bool dolock;
4712 :
4713 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4714 : return NULL;
4715 :
4716 0 : again:
4717 0 : local_irq_save(flags);
4718 0 : dolock = rb_reader_lock(cpu_buffer);
4719 0 : event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4720 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4721 0 : rb_advance_reader(cpu_buffer);
4722 0 : rb_reader_unlock(cpu_buffer, dolock);
4723 0 : local_irq_restore(flags);
4724 :
4725 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4726 0 : goto again;
4727 :
4728 : return event;
4729 : }
4730 :
4731 : /** ring_buffer_iter_dropped - report if there are dropped events
4732 : * @iter: The ring buffer iterator
4733 : *
4734 : * Returns true if there was dropped events since the last peek.
4735 : */
4736 0 : bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
4737 : {
4738 0 : bool ret = iter->missed_events != 0;
4739 :
4740 0 : iter->missed_events = 0;
4741 0 : return ret;
4742 : }
4743 : EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
4744 :
4745 : /**
4746 : * ring_buffer_iter_peek - peek at the next event to be read
4747 : * @iter: The ring buffer iterator
4748 : * @ts: The timestamp counter of this event.
4749 : *
4750 : * This will return the event that will be read next, but does
4751 : * not increment the iterator.
4752 : */
4753 : struct ring_buffer_event *
4754 0 : ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
4755 : {
4756 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4757 0 : struct ring_buffer_event *event;
4758 0 : unsigned long flags;
4759 :
4760 0 : again:
4761 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4762 0 : event = rb_iter_peek(iter, ts);
4763 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4764 :
4765 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4766 0 : goto again;
4767 :
4768 0 : return event;
4769 : }
4770 :
4771 : /**
4772 : * ring_buffer_consume - return an event and consume it
4773 : * @buffer: The ring buffer to get the next event from
4774 : * @cpu: the cpu to read the buffer from
4775 : * @ts: a variable to store the timestamp (may be NULL)
4776 : * @lost_events: a variable to store if events were lost (may be NULL)
4777 : *
4778 : * Returns the next event in the ring buffer, and that event is consumed.
4779 : * Meaning, that sequential reads will keep returning a different event,
4780 : * and eventually empty the ring buffer if the producer is slower.
4781 : */
4782 : struct ring_buffer_event *
4783 0 : ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
4784 : unsigned long *lost_events)
4785 : {
4786 0 : struct ring_buffer_per_cpu *cpu_buffer;
4787 0 : struct ring_buffer_event *event = NULL;
4788 0 : unsigned long flags;
4789 0 : bool dolock;
4790 :
4791 0 : again:
4792 : /* might be called in atomic */
4793 0 : preempt_disable();
4794 :
4795 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4796 0 : goto out;
4797 :
4798 0 : cpu_buffer = buffer->buffers[cpu];
4799 0 : local_irq_save(flags);
4800 0 : dolock = rb_reader_lock(cpu_buffer);
4801 :
4802 0 : event = rb_buffer_peek(cpu_buffer, ts, lost_events);
4803 0 : if (event) {
4804 0 : cpu_buffer->lost_events = 0;
4805 0 : rb_advance_reader(cpu_buffer);
4806 : }
4807 :
4808 0 : rb_reader_unlock(cpu_buffer, dolock);
4809 0 : local_irq_restore(flags);
4810 :
4811 0 : out:
4812 0 : preempt_enable();
4813 :
4814 0 : if (event && event->type_len == RINGBUF_TYPE_PADDING)
4815 0 : goto again;
4816 :
4817 0 : return event;
4818 : }
4819 : EXPORT_SYMBOL_GPL(ring_buffer_consume);
4820 :
4821 : /**
4822 : * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
4823 : * @buffer: The ring buffer to read from
4824 : * @cpu: The cpu buffer to iterate over
4825 : * @flags: gfp flags to use for memory allocation
4826 : *
4827 : * This performs the initial preparations necessary to iterate
4828 : * through the buffer. Memory is allocated, buffer recording
4829 : * is disabled, and the iterator pointer is returned to the caller.
4830 : *
4831 : * Disabling buffer recording prevents the reading from being
4832 : * corrupted. This is not a consuming read, so a producer is not
4833 : * expected.
4834 : *
4835 : * After a sequence of ring_buffer_read_prepare calls, the user is
4836 : * expected to make at least one call to ring_buffer_read_prepare_sync.
4837 : * Afterwards, ring_buffer_read_start is invoked to get things going
4838 : * for real.
4839 : *
4840 : * This overall must be paired with ring_buffer_read_finish.
4841 : */
4842 : struct ring_buffer_iter *
4843 0 : ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
4844 : {
4845 0 : struct ring_buffer_per_cpu *cpu_buffer;
4846 0 : struct ring_buffer_iter *iter;
4847 :
4848 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4849 : return NULL;
4850 :
4851 0 : iter = kzalloc(sizeof(*iter), flags);
4852 0 : if (!iter)
4853 : return NULL;
4854 :
4855 0 : iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags);
4856 0 : if (!iter->event) {
4857 0 : kfree(iter);
4858 0 : return NULL;
4859 : }
4860 :
4861 0 : cpu_buffer = buffer->buffers[cpu];
4862 :
4863 0 : iter->cpu_buffer = cpu_buffer;
4864 :
4865 0 : atomic_inc(&cpu_buffer->resize_disabled);
4866 :
4867 0 : return iter;
4868 : }
4869 : EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
4870 :
4871 : /**
4872 : * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
4873 : *
4874 : * All previously invoked ring_buffer_read_prepare calls to prepare
4875 : * iterators will be synchronized. Afterwards, read_buffer_read_start
4876 : * calls on those iterators are allowed.
4877 : */
4878 : void
4879 0 : ring_buffer_read_prepare_sync(void)
4880 : {
4881 0 : synchronize_rcu();
4882 0 : }
4883 : EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
4884 :
4885 : /**
4886 : * ring_buffer_read_start - start a non consuming read of the buffer
4887 : * @iter: The iterator returned by ring_buffer_read_prepare
4888 : *
4889 : * This finalizes the startup of an iteration through the buffer.
4890 : * The iterator comes from a call to ring_buffer_read_prepare and
4891 : * an intervening ring_buffer_read_prepare_sync must have been
4892 : * performed.
4893 : *
4894 : * Must be paired with ring_buffer_read_finish.
4895 : */
4896 : void
4897 0 : ring_buffer_read_start(struct ring_buffer_iter *iter)
4898 : {
4899 0 : struct ring_buffer_per_cpu *cpu_buffer;
4900 0 : unsigned long flags;
4901 :
4902 0 : if (!iter)
4903 : return;
4904 :
4905 0 : cpu_buffer = iter->cpu_buffer;
4906 :
4907 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4908 0 : arch_spin_lock(&cpu_buffer->lock);
4909 0 : rb_iter_reset(iter);
4910 0 : arch_spin_unlock(&cpu_buffer->lock);
4911 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4912 : }
4913 : EXPORT_SYMBOL_GPL(ring_buffer_read_start);
4914 :
4915 : /**
4916 : * ring_buffer_read_finish - finish reading the iterator of the buffer
4917 : * @iter: The iterator retrieved by ring_buffer_start
4918 : *
4919 : * This re-enables the recording to the buffer, and frees the
4920 : * iterator.
4921 : */
4922 : void
4923 0 : ring_buffer_read_finish(struct ring_buffer_iter *iter)
4924 : {
4925 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4926 0 : unsigned long flags;
4927 :
4928 : /*
4929 : * Ring buffer is disabled from recording, here's a good place
4930 : * to check the integrity of the ring buffer.
4931 : * Must prevent readers from trying to read, as the check
4932 : * clears the HEAD page and readers require it.
4933 : */
4934 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4935 0 : rb_check_pages(cpu_buffer);
4936 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4937 :
4938 0 : atomic_dec(&cpu_buffer->resize_disabled);
4939 0 : kfree(iter->event);
4940 0 : kfree(iter);
4941 0 : }
4942 : EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
4943 :
4944 : /**
4945 : * ring_buffer_iter_advance - advance the iterator to the next location
4946 : * @iter: The ring buffer iterator
4947 : *
4948 : * Move the location of the iterator such that the next read will
4949 : * be the next location of the iterator.
4950 : */
4951 0 : void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
4952 : {
4953 0 : struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
4954 0 : unsigned long flags;
4955 :
4956 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
4957 :
4958 0 : rb_advance_iter(iter);
4959 :
4960 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
4961 0 : }
4962 : EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
4963 :
4964 : /**
4965 : * ring_buffer_size - return the size of the ring buffer (in bytes)
4966 : * @buffer: The ring buffer.
4967 : * @cpu: The CPU to get ring buffer size from.
4968 : */
4969 1 : unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
4970 : {
4971 : /*
4972 : * Earlier, this method returned
4973 : * BUF_PAGE_SIZE * buffer->nr_pages
4974 : * Since the nr_pages field is now removed, we have converted this to
4975 : * return the per cpu buffer value.
4976 : */
4977 1 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
4978 : return 0;
4979 :
4980 1 : return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
4981 : }
4982 : EXPORT_SYMBOL_GPL(ring_buffer_size);
4983 :
4984 : static void
4985 0 : rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
4986 : {
4987 0 : rb_head_page_deactivate(cpu_buffer);
4988 :
4989 0 : cpu_buffer->head_page
4990 0 : = list_entry(cpu_buffer->pages, struct buffer_page, list);
4991 0 : local_set(&cpu_buffer->head_page->write, 0);
4992 0 : local_set(&cpu_buffer->head_page->entries, 0);
4993 0 : local_set(&cpu_buffer->head_page->page->commit, 0);
4994 :
4995 0 : cpu_buffer->head_page->read = 0;
4996 :
4997 0 : cpu_buffer->tail_page = cpu_buffer->head_page;
4998 0 : cpu_buffer->commit_page = cpu_buffer->head_page;
4999 :
5000 0 : INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
5001 0 : INIT_LIST_HEAD(&cpu_buffer->new_pages);
5002 0 : local_set(&cpu_buffer->reader_page->write, 0);
5003 0 : local_set(&cpu_buffer->reader_page->entries, 0);
5004 0 : local_set(&cpu_buffer->reader_page->page->commit, 0);
5005 0 : cpu_buffer->reader_page->read = 0;
5006 :
5007 0 : local_set(&cpu_buffer->entries_bytes, 0);
5008 0 : local_set(&cpu_buffer->overrun, 0);
5009 0 : local_set(&cpu_buffer->commit_overrun, 0);
5010 0 : local_set(&cpu_buffer->dropped_events, 0);
5011 0 : local_set(&cpu_buffer->entries, 0);
5012 0 : local_set(&cpu_buffer->committing, 0);
5013 0 : local_set(&cpu_buffer->commits, 0);
5014 0 : local_set(&cpu_buffer->pages_touched, 0);
5015 0 : local_set(&cpu_buffer->pages_read, 0);
5016 0 : cpu_buffer->last_pages_touch = 0;
5017 0 : cpu_buffer->shortest_full = 0;
5018 0 : cpu_buffer->read = 0;
5019 0 : cpu_buffer->read_bytes = 0;
5020 :
5021 0 : rb_time_set(&cpu_buffer->write_stamp, 0);
5022 0 : rb_time_set(&cpu_buffer->before_stamp, 0);
5023 :
5024 0 : cpu_buffer->lost_events = 0;
5025 0 : cpu_buffer->last_overrun = 0;
5026 :
5027 0 : rb_head_page_activate(cpu_buffer);
5028 0 : }
5029 :
5030 : /* Must have disabled the cpu buffer then done a synchronize_rcu */
5031 0 : static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
5032 : {
5033 0 : unsigned long flags;
5034 :
5035 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5036 :
5037 0 : if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
5038 0 : goto out;
5039 :
5040 0 : arch_spin_lock(&cpu_buffer->lock);
5041 :
5042 0 : rb_reset_cpu(cpu_buffer);
5043 :
5044 0 : arch_spin_unlock(&cpu_buffer->lock);
5045 :
5046 0 : out:
5047 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5048 0 : }
5049 :
5050 : /**
5051 : * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5052 : * @buffer: The ring buffer to reset a per cpu buffer of
5053 : * @cpu: The CPU buffer to be reset
5054 : */
5055 0 : void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
5056 : {
5057 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5058 :
5059 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
5060 : return;
5061 :
5062 : /* prevent another thread from changing buffer sizes */
5063 0 : mutex_lock(&buffer->mutex);
5064 :
5065 0 : atomic_inc(&cpu_buffer->resize_disabled);
5066 0 : atomic_inc(&cpu_buffer->record_disabled);
5067 :
5068 : /* Make sure all commits have finished */
5069 0 : synchronize_rcu();
5070 :
5071 0 : reset_disabled_cpu_buffer(cpu_buffer);
5072 :
5073 0 : atomic_dec(&cpu_buffer->record_disabled);
5074 0 : atomic_dec(&cpu_buffer->resize_disabled);
5075 :
5076 0 : mutex_unlock(&buffer->mutex);
5077 : }
5078 : EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
5079 :
5080 : /**
5081 : * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
5082 : * @buffer: The ring buffer to reset a per cpu buffer of
5083 : * @cpu: The CPU buffer to be reset
5084 : */
5085 0 : void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
5086 : {
5087 0 : struct ring_buffer_per_cpu *cpu_buffer;
5088 0 : int cpu;
5089 :
5090 : /* prevent another thread from changing buffer sizes */
5091 0 : mutex_lock(&buffer->mutex);
5092 :
5093 0 : for_each_online_buffer_cpu(buffer, cpu) {
5094 0 : cpu_buffer = buffer->buffers[cpu];
5095 :
5096 0 : atomic_inc(&cpu_buffer->resize_disabled);
5097 0 : atomic_inc(&cpu_buffer->record_disabled);
5098 : }
5099 :
5100 : /* Make sure all commits have finished */
5101 0 : synchronize_rcu();
5102 :
5103 0 : for_each_online_buffer_cpu(buffer, cpu) {
5104 0 : cpu_buffer = buffer->buffers[cpu];
5105 :
5106 0 : reset_disabled_cpu_buffer(cpu_buffer);
5107 :
5108 0 : atomic_dec(&cpu_buffer->record_disabled);
5109 0 : atomic_dec(&cpu_buffer->resize_disabled);
5110 : }
5111 :
5112 0 : mutex_unlock(&buffer->mutex);
5113 0 : }
5114 :
5115 : /**
5116 : * ring_buffer_reset - reset a ring buffer
5117 : * @buffer: The ring buffer to reset all cpu buffers
5118 : */
5119 0 : void ring_buffer_reset(struct trace_buffer *buffer)
5120 : {
5121 0 : struct ring_buffer_per_cpu *cpu_buffer;
5122 0 : int cpu;
5123 :
5124 0 : for_each_buffer_cpu(buffer, cpu) {
5125 0 : cpu_buffer = buffer->buffers[cpu];
5126 :
5127 0 : atomic_inc(&cpu_buffer->resize_disabled);
5128 0 : atomic_inc(&cpu_buffer->record_disabled);
5129 : }
5130 :
5131 : /* Make sure all commits have finished */
5132 0 : synchronize_rcu();
5133 :
5134 0 : for_each_buffer_cpu(buffer, cpu) {
5135 0 : cpu_buffer = buffer->buffers[cpu];
5136 :
5137 0 : reset_disabled_cpu_buffer(cpu_buffer);
5138 :
5139 0 : atomic_dec(&cpu_buffer->record_disabled);
5140 0 : atomic_dec(&cpu_buffer->resize_disabled);
5141 : }
5142 0 : }
5143 : EXPORT_SYMBOL_GPL(ring_buffer_reset);
5144 :
5145 : /**
5146 : * rind_buffer_empty - is the ring buffer empty?
5147 : * @buffer: The ring buffer to test
5148 : */
5149 0 : bool ring_buffer_empty(struct trace_buffer *buffer)
5150 : {
5151 0 : struct ring_buffer_per_cpu *cpu_buffer;
5152 0 : unsigned long flags;
5153 0 : bool dolock;
5154 0 : int cpu;
5155 0 : int ret;
5156 :
5157 : /* yes this is racy, but if you don't like the race, lock the buffer */
5158 0 : for_each_buffer_cpu(buffer, cpu) {
5159 0 : cpu_buffer = buffer->buffers[cpu];
5160 0 : local_irq_save(flags);
5161 0 : dolock = rb_reader_lock(cpu_buffer);
5162 0 : ret = rb_per_cpu_empty(cpu_buffer);
5163 0 : rb_reader_unlock(cpu_buffer, dolock);
5164 0 : local_irq_restore(flags);
5165 :
5166 0 : if (!ret)
5167 : return false;
5168 : }
5169 :
5170 : return true;
5171 : }
5172 : EXPORT_SYMBOL_GPL(ring_buffer_empty);
5173 :
5174 : /**
5175 : * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
5176 : * @buffer: The ring buffer
5177 : * @cpu: The CPU buffer to test
5178 : */
5179 0 : bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
5180 : {
5181 0 : struct ring_buffer_per_cpu *cpu_buffer;
5182 0 : unsigned long flags;
5183 0 : bool dolock;
5184 0 : int ret;
5185 :
5186 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
5187 : return true;
5188 :
5189 0 : cpu_buffer = buffer->buffers[cpu];
5190 0 : local_irq_save(flags);
5191 0 : dolock = rb_reader_lock(cpu_buffer);
5192 0 : ret = rb_per_cpu_empty(cpu_buffer);
5193 0 : rb_reader_unlock(cpu_buffer, dolock);
5194 0 : local_irq_restore(flags);
5195 :
5196 : return ret;
5197 : }
5198 : EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
5199 :
5200 : #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
5201 : /**
5202 : * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
5203 : * @buffer_a: One buffer to swap with
5204 : * @buffer_b: The other buffer to swap with
5205 : * @cpu: the CPU of the buffers to swap
5206 : *
5207 : * This function is useful for tracers that want to take a "snapshot"
5208 : * of a CPU buffer and has another back up buffer lying around.
5209 : * it is expected that the tracer handles the cpu buffer not being
5210 : * used at the moment.
5211 : */
5212 : int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
5213 : struct trace_buffer *buffer_b, int cpu)
5214 : {
5215 : struct ring_buffer_per_cpu *cpu_buffer_a;
5216 : struct ring_buffer_per_cpu *cpu_buffer_b;
5217 : int ret = -EINVAL;
5218 :
5219 : if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
5220 : !cpumask_test_cpu(cpu, buffer_b->cpumask))
5221 : goto out;
5222 :
5223 : cpu_buffer_a = buffer_a->buffers[cpu];
5224 : cpu_buffer_b = buffer_b->buffers[cpu];
5225 :
5226 : /* At least make sure the two buffers are somewhat the same */
5227 : if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
5228 : goto out;
5229 :
5230 : ret = -EAGAIN;
5231 :
5232 : if (atomic_read(&buffer_a->record_disabled))
5233 : goto out;
5234 :
5235 : if (atomic_read(&buffer_b->record_disabled))
5236 : goto out;
5237 :
5238 : if (atomic_read(&cpu_buffer_a->record_disabled))
5239 : goto out;
5240 :
5241 : if (atomic_read(&cpu_buffer_b->record_disabled))
5242 : goto out;
5243 :
5244 : /*
5245 : * We can't do a synchronize_rcu here because this
5246 : * function can be called in atomic context.
5247 : * Normally this will be called from the same CPU as cpu.
5248 : * If not it's up to the caller to protect this.
5249 : */
5250 : atomic_inc(&cpu_buffer_a->record_disabled);
5251 : atomic_inc(&cpu_buffer_b->record_disabled);
5252 :
5253 : ret = -EBUSY;
5254 : if (local_read(&cpu_buffer_a->committing))
5255 : goto out_dec;
5256 : if (local_read(&cpu_buffer_b->committing))
5257 : goto out_dec;
5258 :
5259 : buffer_a->buffers[cpu] = cpu_buffer_b;
5260 : buffer_b->buffers[cpu] = cpu_buffer_a;
5261 :
5262 : cpu_buffer_b->buffer = buffer_a;
5263 : cpu_buffer_a->buffer = buffer_b;
5264 :
5265 : ret = 0;
5266 :
5267 : out_dec:
5268 : atomic_dec(&cpu_buffer_a->record_disabled);
5269 : atomic_dec(&cpu_buffer_b->record_disabled);
5270 : out:
5271 : return ret;
5272 : }
5273 : EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
5274 : #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
5275 :
5276 : /**
5277 : * ring_buffer_alloc_read_page - allocate a page to read from buffer
5278 : * @buffer: the buffer to allocate for.
5279 : * @cpu: the cpu buffer to allocate.
5280 : *
5281 : * This function is used in conjunction with ring_buffer_read_page.
5282 : * When reading a full page from the ring buffer, these functions
5283 : * can be used to speed up the process. The calling function should
5284 : * allocate a few pages first with this function. Then when it
5285 : * needs to get pages from the ring buffer, it passes the result
5286 : * of this function into ring_buffer_read_page, which will swap
5287 : * the page that was allocated, with the read page of the buffer.
5288 : *
5289 : * Returns:
5290 : * The page allocated, or ERR_PTR
5291 : */
5292 0 : void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
5293 : {
5294 0 : struct ring_buffer_per_cpu *cpu_buffer;
5295 0 : struct buffer_data_page *bpage = NULL;
5296 0 : unsigned long flags;
5297 0 : struct page *page;
5298 :
5299 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
5300 0 : return ERR_PTR(-ENODEV);
5301 :
5302 0 : cpu_buffer = buffer->buffers[cpu];
5303 0 : local_irq_save(flags);
5304 0 : arch_spin_lock(&cpu_buffer->lock);
5305 :
5306 0 : if (cpu_buffer->free_page) {
5307 0 : bpage = cpu_buffer->free_page;
5308 0 : cpu_buffer->free_page = NULL;
5309 : }
5310 :
5311 0 : arch_spin_unlock(&cpu_buffer->lock);
5312 0 : local_irq_restore(flags);
5313 :
5314 0 : if (bpage)
5315 0 : goto out;
5316 :
5317 0 : page = alloc_pages_node(cpu_to_node(cpu),
5318 : GFP_KERNEL | __GFP_NORETRY, 0);
5319 0 : if (!page)
5320 0 : return ERR_PTR(-ENOMEM);
5321 :
5322 0 : bpage = page_address(page);
5323 :
5324 0 : out:
5325 0 : rb_init_page(bpage);
5326 :
5327 0 : return bpage;
5328 : }
5329 : EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
5330 :
5331 : /**
5332 : * ring_buffer_free_read_page - free an allocated read page
5333 : * @buffer: the buffer the page was allocate for
5334 : * @cpu: the cpu buffer the page came from
5335 : * @data: the page to free
5336 : *
5337 : * Free a page allocated from ring_buffer_alloc_read_page.
5338 : */
5339 0 : void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data)
5340 : {
5341 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5342 0 : struct buffer_data_page *bpage = data;
5343 0 : struct page *page = virt_to_page(bpage);
5344 0 : unsigned long flags;
5345 :
5346 : /* If the page is still in use someplace else, we can't reuse it */
5347 0 : if (page_ref_count(page) > 1)
5348 0 : goto out;
5349 :
5350 0 : local_irq_save(flags);
5351 0 : arch_spin_lock(&cpu_buffer->lock);
5352 :
5353 0 : if (!cpu_buffer->free_page) {
5354 0 : cpu_buffer->free_page = bpage;
5355 0 : bpage = NULL;
5356 : }
5357 :
5358 0 : arch_spin_unlock(&cpu_buffer->lock);
5359 0 : local_irq_restore(flags);
5360 :
5361 0 : out:
5362 0 : free_page((unsigned long)bpage);
5363 0 : }
5364 : EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
5365 :
5366 : /**
5367 : * ring_buffer_read_page - extract a page from the ring buffer
5368 : * @buffer: buffer to extract from
5369 : * @data_page: the page to use allocated from ring_buffer_alloc_read_page
5370 : * @len: amount to extract
5371 : * @cpu: the cpu of the buffer to extract
5372 : * @full: should the extraction only happen when the page is full.
5373 : *
5374 : * This function will pull out a page from the ring buffer and consume it.
5375 : * @data_page must be the address of the variable that was returned
5376 : * from ring_buffer_alloc_read_page. This is because the page might be used
5377 : * to swap with a page in the ring buffer.
5378 : *
5379 : * for example:
5380 : * rpage = ring_buffer_alloc_read_page(buffer, cpu);
5381 : * if (IS_ERR(rpage))
5382 : * return PTR_ERR(rpage);
5383 : * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
5384 : * if (ret >= 0)
5385 : * process_page(rpage, ret);
5386 : *
5387 : * When @full is set, the function will not return true unless
5388 : * the writer is off the reader page.
5389 : *
5390 : * Note: it is up to the calling functions to handle sleeps and wakeups.
5391 : * The ring buffer can be used anywhere in the kernel and can not
5392 : * blindly call wake_up. The layer that uses the ring buffer must be
5393 : * responsible for that.
5394 : *
5395 : * Returns:
5396 : * >=0 if data has been transferred, returns the offset of consumed data.
5397 : * <0 if no data has been transferred.
5398 : */
5399 0 : int ring_buffer_read_page(struct trace_buffer *buffer,
5400 : void **data_page, size_t len, int cpu, int full)
5401 : {
5402 0 : struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
5403 0 : struct ring_buffer_event *event;
5404 0 : struct buffer_data_page *bpage;
5405 0 : struct buffer_page *reader;
5406 0 : unsigned long missed_events;
5407 0 : unsigned long flags;
5408 0 : unsigned int commit;
5409 0 : unsigned int read;
5410 0 : u64 save_timestamp;
5411 0 : int ret = -1;
5412 :
5413 0 : if (!cpumask_test_cpu(cpu, buffer->cpumask))
5414 0 : goto out;
5415 :
5416 : /*
5417 : * If len is not big enough to hold the page header, then
5418 : * we can not copy anything.
5419 : */
5420 0 : if (len <= BUF_PAGE_HDR_SIZE)
5421 0 : goto out;
5422 :
5423 0 : len -= BUF_PAGE_HDR_SIZE;
5424 :
5425 0 : if (!data_page)
5426 0 : goto out;
5427 :
5428 0 : bpage = *data_page;
5429 0 : if (!bpage)
5430 0 : goto out;
5431 :
5432 0 : raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
5433 :
5434 0 : reader = rb_get_reader_page(cpu_buffer);
5435 0 : if (!reader)
5436 0 : goto out_unlock;
5437 :
5438 0 : event = rb_reader_event(cpu_buffer);
5439 :
5440 0 : read = reader->read;
5441 0 : commit = rb_page_commit(reader);
5442 :
5443 : /* Check if any events were dropped */
5444 0 : missed_events = cpu_buffer->lost_events;
5445 :
5446 : /*
5447 : * If this page has been partially read or
5448 : * if len is not big enough to read the rest of the page or
5449 : * a writer is still on the page, then
5450 : * we must copy the data from the page to the buffer.
5451 : * Otherwise, we can simply swap the page with the one passed in.
5452 : */
5453 0 : if (read || (len < (commit - read)) ||
5454 0 : cpu_buffer->reader_page == cpu_buffer->commit_page) {
5455 0 : struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
5456 0 : unsigned int rpos = read;
5457 0 : unsigned int pos = 0;
5458 0 : unsigned int size;
5459 :
5460 0 : if (full)
5461 0 : goto out_unlock;
5462 :
5463 0 : if (len > (commit - read))
5464 : len = (commit - read);
5465 :
5466 : /* Always keep the time extend and data together */
5467 0 : size = rb_event_ts_length(event);
5468 :
5469 0 : if (len < size)
5470 0 : goto out_unlock;
5471 :
5472 : /* save the current timestamp, since the user will need it */
5473 0 : save_timestamp = cpu_buffer->read_stamp;
5474 :
5475 : /* Need to copy one event at a time */
5476 0 : do {
5477 : /* We need the size of one event, because
5478 : * rb_advance_reader only advances by one event,
5479 : * whereas rb_event_ts_length may include the size of
5480 : * one or two events.
5481 : * We have already ensured there's enough space if this
5482 : * is a time extend. */
5483 0 : size = rb_event_length(event);
5484 0 : memcpy(bpage->data + pos, rpage->data + rpos, size);
5485 :
5486 0 : len -= size;
5487 :
5488 0 : rb_advance_reader(cpu_buffer);
5489 0 : rpos = reader->read;
5490 0 : pos += size;
5491 :
5492 0 : if (rpos >= commit)
5493 : break;
5494 :
5495 0 : event = rb_reader_event(cpu_buffer);
5496 : /* Always keep the time extend and data together */
5497 0 : size = rb_event_ts_length(event);
5498 0 : } while (len >= size);
5499 :
5500 : /* update bpage */
5501 0 : local_set(&bpage->commit, pos);
5502 0 : bpage->time_stamp = save_timestamp;
5503 :
5504 : /* we copied everything to the beginning */
5505 0 : read = 0;
5506 : } else {
5507 : /* update the entry counter */
5508 0 : cpu_buffer->read += rb_page_entries(reader);
5509 0 : cpu_buffer->read_bytes += BUF_PAGE_SIZE;
5510 :
5511 : /* swap the pages */
5512 0 : rb_init_page(bpage);
5513 0 : bpage = reader->page;
5514 0 : reader->page = *data_page;
5515 0 : local_set(&reader->write, 0);
5516 0 : local_set(&reader->entries, 0);
5517 0 : reader->read = 0;
5518 0 : *data_page = bpage;
5519 :
5520 : /*
5521 : * Use the real_end for the data size,
5522 : * This gives us a chance to store the lost events
5523 : * on the page.
5524 : */
5525 0 : if (reader->real_end)
5526 0 : local_set(&bpage->commit, reader->real_end);
5527 : }
5528 0 : ret = read;
5529 :
5530 0 : cpu_buffer->lost_events = 0;
5531 :
5532 0 : commit = local_read(&bpage->commit);
5533 : /*
5534 : * Set a flag in the commit field if we lost events
5535 : */
5536 0 : if (missed_events) {
5537 : /* If there is room at the end of the page to save the
5538 : * missed events, then record it there.
5539 : */
5540 0 : if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
5541 0 : memcpy(&bpage->data[commit], &missed_events,
5542 : sizeof(missed_events));
5543 0 : local_add(RB_MISSED_STORED, &bpage->commit);
5544 0 : commit += sizeof(missed_events);
5545 : }
5546 0 : local_add(RB_MISSED_EVENTS, &bpage->commit);
5547 : }
5548 :
5549 : /*
5550 : * This page may be off to user land. Zero it out here.
5551 : */
5552 0 : if (commit < BUF_PAGE_SIZE)
5553 0 : memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
5554 :
5555 0 : out_unlock:
5556 0 : raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
5557 :
5558 0 : out:
5559 0 : return ret;
5560 : }
5561 : EXPORT_SYMBOL_GPL(ring_buffer_read_page);
5562 :
5563 : /*
5564 : * We only allocate new buffers, never free them if the CPU goes down.
5565 : * If we were to free the buffer, then the user would lose any trace that was in
5566 : * the buffer.
5567 : */
5568 8 : int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
5569 : {
5570 8 : struct trace_buffer *buffer;
5571 8 : long nr_pages_same;
5572 8 : int cpu_i;
5573 8 : unsigned long nr_pages;
5574 :
5575 8 : buffer = container_of(node, struct trace_buffer, node);
5576 8 : if (cpumask_test_cpu(cpu, buffer->cpumask))
5577 : return 0;
5578 :
5579 : nr_pages = 0;
5580 18 : nr_pages_same = 1;
5581 : /* check if all cpu sizes are same */
5582 18 : for_each_buffer_cpu(buffer, cpu_i) {
5583 : /* fill in the size from first enabled cpu */
5584 12 : if (nr_pages == 0)
5585 6 : nr_pages = buffer->buffers[cpu_i]->nr_pages;
5586 12 : if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
5587 : nr_pages_same = 0;
5588 : break;
5589 : }
5590 : }
5591 : /* allocate minimum pages, user can later expand it */
5592 6 : if (!nr_pages_same)
5593 0 : nr_pages = 2;
5594 12 : buffer->buffers[cpu] =
5595 6 : rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
5596 6 : if (!buffer->buffers[cpu]) {
5597 0 : WARN(1, "failed to allocate ring buffer on CPU %u\n",
5598 : cpu);
5599 0 : return -ENOMEM;
5600 : }
5601 6 : smp_wmb();
5602 6 : cpumask_set_cpu(cpu, buffer->cpumask);
5603 6 : return 0;
5604 : }
5605 :
5606 : #ifdef CONFIG_RING_BUFFER_STARTUP_TEST
5607 : /*
5608 : * This is a basic integrity check of the ring buffer.
5609 : * Late in the boot cycle this test will run when configured in.
5610 : * It will kick off a thread per CPU that will go into a loop
5611 : * writing to the per cpu ring buffer various sizes of data.
5612 : * Some of the data will be large items, some small.
5613 : *
5614 : * Another thread is created that goes into a spin, sending out
5615 : * IPIs to the other CPUs to also write into the ring buffer.
5616 : * this is to test the nesting ability of the buffer.
5617 : *
5618 : * Basic stats are recorded and reported. If something in the
5619 : * ring buffer should happen that's not expected, a big warning
5620 : * is displayed and all ring buffers are disabled.
5621 : */
5622 : static struct task_struct *rb_threads[NR_CPUS] __initdata;
5623 :
5624 : struct rb_test_data {
5625 : struct trace_buffer *buffer;
5626 : unsigned long events;
5627 : unsigned long bytes_written;
5628 : unsigned long bytes_alloc;
5629 : unsigned long bytes_dropped;
5630 : unsigned long events_nested;
5631 : unsigned long bytes_written_nested;
5632 : unsigned long bytes_alloc_nested;
5633 : unsigned long bytes_dropped_nested;
5634 : int min_size_nested;
5635 : int max_size_nested;
5636 : int max_size;
5637 : int min_size;
5638 : int cpu;
5639 : int cnt;
5640 : };
5641 :
5642 : static struct rb_test_data rb_data[NR_CPUS] __initdata;
5643 :
5644 : /* 1 meg per cpu */
5645 : #define RB_TEST_BUFFER_SIZE 1048576
5646 :
5647 : static char rb_string[] __initdata =
5648 : "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
5649 : "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
5650 : "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
5651 :
5652 : static bool rb_test_started __initdata;
5653 :
5654 : struct rb_item {
5655 : int size;
5656 : char str[];
5657 : };
5658 :
5659 : static __init int rb_write_something(struct rb_test_data *data, bool nested)
5660 : {
5661 : struct ring_buffer_event *event;
5662 : struct rb_item *item;
5663 : bool started;
5664 : int event_len;
5665 : int size;
5666 : int len;
5667 : int cnt;
5668 :
5669 : /* Have nested writes different that what is written */
5670 : cnt = data->cnt + (nested ? 27 : 0);
5671 :
5672 : /* Multiply cnt by ~e, to make some unique increment */
5673 : size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
5674 :
5675 : len = size + sizeof(struct rb_item);
5676 :
5677 : started = rb_test_started;
5678 : /* read rb_test_started before checking buffer enabled */
5679 : smp_rmb();
5680 :
5681 : event = ring_buffer_lock_reserve(data->buffer, len);
5682 : if (!event) {
5683 : /* Ignore dropped events before test starts. */
5684 : if (started) {
5685 : if (nested)
5686 : data->bytes_dropped += len;
5687 : else
5688 : data->bytes_dropped_nested += len;
5689 : }
5690 : return len;
5691 : }
5692 :
5693 : event_len = ring_buffer_event_length(event);
5694 :
5695 : if (RB_WARN_ON(data->buffer, event_len < len))
5696 : goto out;
5697 :
5698 : item = ring_buffer_event_data(event);
5699 : item->size = size;
5700 : memcpy(item->str, rb_string, size);
5701 :
5702 : if (nested) {
5703 : data->bytes_alloc_nested += event_len;
5704 : data->bytes_written_nested += len;
5705 : data->events_nested++;
5706 : if (!data->min_size_nested || len < data->min_size_nested)
5707 : data->min_size_nested = len;
5708 : if (len > data->max_size_nested)
5709 : data->max_size_nested = len;
5710 : } else {
5711 : data->bytes_alloc += event_len;
5712 : data->bytes_written += len;
5713 : data->events++;
5714 : if (!data->min_size || len < data->min_size)
5715 : data->max_size = len;
5716 : if (len > data->max_size)
5717 : data->max_size = len;
5718 : }
5719 :
5720 : out:
5721 : ring_buffer_unlock_commit(data->buffer, event);
5722 :
5723 : return 0;
5724 : }
5725 :
5726 : static __init int rb_test(void *arg)
5727 : {
5728 : struct rb_test_data *data = arg;
5729 :
5730 : while (!kthread_should_stop()) {
5731 : rb_write_something(data, false);
5732 : data->cnt++;
5733 :
5734 : set_current_state(TASK_INTERRUPTIBLE);
5735 : /* Now sleep between a min of 100-300us and a max of 1ms */
5736 : usleep_range(((data->cnt % 3) + 1) * 100, 1000);
5737 : }
5738 :
5739 : return 0;
5740 : }
5741 :
5742 : static __init void rb_ipi(void *ignore)
5743 : {
5744 : struct rb_test_data *data;
5745 : int cpu = smp_processor_id();
5746 :
5747 : data = &rb_data[cpu];
5748 : rb_write_something(data, true);
5749 : }
5750 :
5751 : static __init int rb_hammer_test(void *arg)
5752 : {
5753 : while (!kthread_should_stop()) {
5754 :
5755 : /* Send an IPI to all cpus to write data! */
5756 : smp_call_function(rb_ipi, NULL, 1);
5757 : /* No sleep, but for non preempt, let others run */
5758 : schedule();
5759 : }
5760 :
5761 : return 0;
5762 : }
5763 :
5764 : static __init int test_ringbuffer(void)
5765 : {
5766 : struct task_struct *rb_hammer;
5767 : struct trace_buffer *buffer;
5768 : int cpu;
5769 : int ret = 0;
5770 :
5771 : if (security_locked_down(LOCKDOWN_TRACEFS)) {
5772 : pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
5773 : return 0;
5774 : }
5775 :
5776 : pr_info("Running ring buffer tests...\n");
5777 :
5778 : buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
5779 : if (WARN_ON(!buffer))
5780 : return 0;
5781 :
5782 : /* Disable buffer so that threads can't write to it yet */
5783 : ring_buffer_record_off(buffer);
5784 :
5785 : for_each_online_cpu(cpu) {
5786 : rb_data[cpu].buffer = buffer;
5787 : rb_data[cpu].cpu = cpu;
5788 : rb_data[cpu].cnt = cpu;
5789 : rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu],
5790 : "rbtester/%d", cpu);
5791 : if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
5792 : pr_cont("FAILED\n");
5793 : ret = PTR_ERR(rb_threads[cpu]);
5794 : goto out_free;
5795 : }
5796 :
5797 : kthread_bind(rb_threads[cpu], cpu);
5798 : wake_up_process(rb_threads[cpu]);
5799 : }
5800 :
5801 : /* Now create the rb hammer! */
5802 : rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
5803 : if (WARN_ON(IS_ERR(rb_hammer))) {
5804 : pr_cont("FAILED\n");
5805 : ret = PTR_ERR(rb_hammer);
5806 : goto out_free;
5807 : }
5808 :
5809 : ring_buffer_record_on(buffer);
5810 : /*
5811 : * Show buffer is enabled before setting rb_test_started.
5812 : * Yes there's a small race window where events could be
5813 : * dropped and the thread wont catch it. But when a ring
5814 : * buffer gets enabled, there will always be some kind of
5815 : * delay before other CPUs see it. Thus, we don't care about
5816 : * those dropped events. We care about events dropped after
5817 : * the threads see that the buffer is active.
5818 : */
5819 : smp_wmb();
5820 : rb_test_started = true;
5821 :
5822 : set_current_state(TASK_INTERRUPTIBLE);
5823 : /* Just run for 10 seconds */;
5824 : schedule_timeout(10 * HZ);
5825 :
5826 : kthread_stop(rb_hammer);
5827 :
5828 : out_free:
5829 : for_each_online_cpu(cpu) {
5830 : if (!rb_threads[cpu])
5831 : break;
5832 : kthread_stop(rb_threads[cpu]);
5833 : }
5834 : if (ret) {
5835 : ring_buffer_free(buffer);
5836 : return ret;
5837 : }
5838 :
5839 : /* Report! */
5840 : pr_info("finished\n");
5841 : for_each_online_cpu(cpu) {
5842 : struct ring_buffer_event *event;
5843 : struct rb_test_data *data = &rb_data[cpu];
5844 : struct rb_item *item;
5845 : unsigned long total_events;
5846 : unsigned long total_dropped;
5847 : unsigned long total_written;
5848 : unsigned long total_alloc;
5849 : unsigned long total_read = 0;
5850 : unsigned long total_size = 0;
5851 : unsigned long total_len = 0;
5852 : unsigned long total_lost = 0;
5853 : unsigned long lost;
5854 : int big_event_size;
5855 : int small_event_size;
5856 :
5857 : ret = -1;
5858 :
5859 : total_events = data->events + data->events_nested;
5860 : total_written = data->bytes_written + data->bytes_written_nested;
5861 : total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
5862 : total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
5863 :
5864 : big_event_size = data->max_size + data->max_size_nested;
5865 : small_event_size = data->min_size + data->min_size_nested;
5866 :
5867 : pr_info("CPU %d:\n", cpu);
5868 : pr_info(" events: %ld\n", total_events);
5869 : pr_info(" dropped bytes: %ld\n", total_dropped);
5870 : pr_info(" alloced bytes: %ld\n", total_alloc);
5871 : pr_info(" written bytes: %ld\n", total_written);
5872 : pr_info(" biggest event: %d\n", big_event_size);
5873 : pr_info(" smallest event: %d\n", small_event_size);
5874 :
5875 : if (RB_WARN_ON(buffer, total_dropped))
5876 : break;
5877 :
5878 : ret = 0;
5879 :
5880 : while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
5881 : total_lost += lost;
5882 : item = ring_buffer_event_data(event);
5883 : total_len += ring_buffer_event_length(event);
5884 : total_size += item->size + sizeof(struct rb_item);
5885 : if (memcmp(&item->str[0], rb_string, item->size) != 0) {
5886 : pr_info("FAILED!\n");
5887 : pr_info("buffer had: %.*s\n", item->size, item->str);
5888 : pr_info("expected: %.*s\n", item->size, rb_string);
5889 : RB_WARN_ON(buffer, 1);
5890 : ret = -1;
5891 : break;
5892 : }
5893 : total_read++;
5894 : }
5895 : if (ret)
5896 : break;
5897 :
5898 : ret = -1;
5899 :
5900 : pr_info(" read events: %ld\n", total_read);
5901 : pr_info(" lost events: %ld\n", total_lost);
5902 : pr_info(" total events: %ld\n", total_lost + total_read);
5903 : pr_info(" recorded len bytes: %ld\n", total_len);
5904 : pr_info(" recorded size bytes: %ld\n", total_size);
5905 : if (total_lost)
5906 : pr_info(" With dropped events, record len and size may not match\n"
5907 : " alloced and written from above\n");
5908 : if (!total_lost) {
5909 : if (RB_WARN_ON(buffer, total_len != total_alloc ||
5910 : total_size != total_written))
5911 : break;
5912 : }
5913 : if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
5914 : break;
5915 :
5916 : ret = 0;
5917 : }
5918 : if (!ret)
5919 : pr_info("Ring buffer PASSED!\n");
5920 :
5921 : ring_buffer_free(buffer);
5922 : return 0;
5923 : }
5924 :
5925 : late_initcall(test_ringbuffer);
5926 : #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
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