1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Generic ring buffer |
4 | * |
5 | * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> |
6 | */ |
7 | #include <linux/trace_events.h> |
8 | #include <linux/ring_buffer.h> |
9 | #include <linux/trace_clock.h> |
10 | #include <linux/sched/clock.h> |
11 | #include <linux/trace_seq.h> |
12 | #include <linux/spinlock.h> |
13 | #include <linux/irq_work.h> |
14 | #include <linux/uaccess.h> |
15 | #include <linux/hardirq.h> |
16 | #include <linux/kthread.h> /* for self test */ |
17 | #include <linux/module.h> |
18 | #include <linux/percpu.h> |
19 | #include <linux/mutex.h> |
20 | #include <linux/delay.h> |
21 | #include <linux/slab.h> |
22 | #include <linux/init.h> |
23 | #include <linux/hash.h> |
24 | #include <linux/list.h> |
25 | #include <linux/cpu.h> |
26 | #include <linux/oom.h> |
27 | |
28 | #include <asm/local.h> |
29 | |
30 | static void update_pages_handler(struct work_struct *work); |
31 | |
32 | /* |
33 | * The ring buffer header is special. We must manually up keep it. |
34 | */ |
35 | int (struct trace_seq *s) |
36 | { |
37 | trace_seq_puts(s, "# compressed entry header\n" ); |
38 | trace_seq_puts(s, "\ttype_len : 5 bits\n" ); |
39 | trace_seq_puts(s, "\ttime_delta : 27 bits\n" ); |
40 | trace_seq_puts(s, "\tarray : 32 bits\n" ); |
41 | trace_seq_putc(s, '\n'); |
42 | trace_seq_printf(s, "\tpadding : type == %d\n" , |
43 | RINGBUF_TYPE_PADDING); |
44 | trace_seq_printf(s, "\ttime_extend : type == %d\n" , |
45 | RINGBUF_TYPE_TIME_EXTEND); |
46 | trace_seq_printf(s, "\ttime_stamp : type == %d\n" , |
47 | RINGBUF_TYPE_TIME_STAMP); |
48 | trace_seq_printf(s, "\tdata max type_len == %d\n" , |
49 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
50 | |
51 | return !trace_seq_has_overflowed(s); |
52 | } |
53 | |
54 | /* |
55 | * The ring buffer is made up of a list of pages. A separate list of pages is |
56 | * allocated for each CPU. A writer may only write to a buffer that is |
57 | * associated with the CPU it is currently executing on. A reader may read |
58 | * from any per cpu buffer. |
59 | * |
60 | * The reader is special. For each per cpu buffer, the reader has its own |
61 | * reader page. When a reader has read the entire reader page, this reader |
62 | * page is swapped with another page in the ring buffer. |
63 | * |
64 | * Now, as long as the writer is off the reader page, the reader can do what |
65 | * ever it wants with that page. The writer will never write to that page |
66 | * again (as long as it is out of the ring buffer). |
67 | * |
68 | * Here's some silly ASCII art. |
69 | * |
70 | * +------+ |
71 | * |reader| RING BUFFER |
72 | * |page | |
73 | * +------+ +---+ +---+ +---+ |
74 | * | |-->| |-->| | |
75 | * +---+ +---+ +---+ |
76 | * ^ | |
77 | * | | |
78 | * +---------------+ |
79 | * |
80 | * |
81 | * +------+ |
82 | * |reader| RING BUFFER |
83 | * |page |------------------v |
84 | * +------+ +---+ +---+ +---+ |
85 | * | |-->| |-->| | |
86 | * +---+ +---+ +---+ |
87 | * ^ | |
88 | * | | |
89 | * +---------------+ |
90 | * |
91 | * |
92 | * +------+ |
93 | * |reader| RING BUFFER |
94 | * |page |------------------v |
95 | * +------+ +---+ +---+ +---+ |
96 | * ^ | |-->| |-->| | |
97 | * | +---+ +---+ +---+ |
98 | * | | |
99 | * | | |
100 | * +------------------------------+ |
101 | * |
102 | * |
103 | * +------+ |
104 | * |buffer| RING BUFFER |
105 | * |page |------------------v |
106 | * +------+ +---+ +---+ +---+ |
107 | * ^ | | | |-->| | |
108 | * | New +---+ +---+ +---+ |
109 | * | Reader------^ | |
110 | * | page | |
111 | * +------------------------------+ |
112 | * |
113 | * |
114 | * After we make this swap, the reader can hand this page off to the splice |
115 | * code and be done with it. It can even allocate a new page if it needs to |
116 | * and swap that into the ring buffer. |
117 | * |
118 | * We will be using cmpxchg soon to make all this lockless. |
119 | * |
120 | */ |
121 | |
122 | /* Used for individual buffers (after the counter) */ |
123 | #define RB_BUFFER_OFF (1 << 20) |
124 | |
125 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
126 | |
127 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
128 | #define RB_ALIGNMENT 4U |
129 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
130 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
131 | |
132 | #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS |
133 | # define RB_FORCE_8BYTE_ALIGNMENT 0 |
134 | # define RB_ARCH_ALIGNMENT RB_ALIGNMENT |
135 | #else |
136 | # define RB_FORCE_8BYTE_ALIGNMENT 1 |
137 | # define RB_ARCH_ALIGNMENT 8U |
138 | #endif |
139 | |
140 | #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) |
141 | |
142 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
143 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX |
144 | |
145 | enum { |
146 | RB_LEN_TIME_EXTEND = 8, |
147 | RB_LEN_TIME_STAMP = 8, |
148 | }; |
149 | |
150 | #define skip_time_extend(event) \ |
151 | ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) |
152 | |
153 | #define extended_time(event) \ |
154 | (event->type_len >= RINGBUF_TYPE_TIME_EXTEND) |
155 | |
156 | static inline int rb_null_event(struct ring_buffer_event *event) |
157 | { |
158 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
159 | } |
160 | |
161 | static void rb_event_set_padding(struct ring_buffer_event *event) |
162 | { |
163 | /* padding has a NULL time_delta */ |
164 | event->type_len = RINGBUF_TYPE_PADDING; |
165 | event->time_delta = 0; |
166 | } |
167 | |
168 | static unsigned |
169 | rb_event_data_length(struct ring_buffer_event *event) |
170 | { |
171 | unsigned length; |
172 | |
173 | if (event->type_len) |
174 | length = event->type_len * RB_ALIGNMENT; |
175 | else |
176 | length = event->array[0]; |
177 | return length + RB_EVNT_HDR_SIZE; |
178 | } |
179 | |
180 | /* |
181 | * Return the length of the given event. Will return |
182 | * the length of the time extend if the event is a |
183 | * time extend. |
184 | */ |
185 | static inline unsigned |
186 | rb_event_length(struct ring_buffer_event *event) |
187 | { |
188 | switch (event->type_len) { |
189 | case RINGBUF_TYPE_PADDING: |
190 | if (rb_null_event(event)) |
191 | /* undefined */ |
192 | return -1; |
193 | return event->array[0] + RB_EVNT_HDR_SIZE; |
194 | |
195 | case RINGBUF_TYPE_TIME_EXTEND: |
196 | return RB_LEN_TIME_EXTEND; |
197 | |
198 | case RINGBUF_TYPE_TIME_STAMP: |
199 | return RB_LEN_TIME_STAMP; |
200 | |
201 | case RINGBUF_TYPE_DATA: |
202 | return rb_event_data_length(event); |
203 | default: |
204 | BUG(); |
205 | } |
206 | /* not hit */ |
207 | return 0; |
208 | } |
209 | |
210 | /* |
211 | * Return total length of time extend and data, |
212 | * or just the event length for all other events. |
213 | */ |
214 | static inline unsigned |
215 | rb_event_ts_length(struct ring_buffer_event *event) |
216 | { |
217 | unsigned len = 0; |
218 | |
219 | if (extended_time(event)) { |
220 | /* time extends include the data event after it */ |
221 | len = RB_LEN_TIME_EXTEND; |
222 | event = skip_time_extend(event); |
223 | } |
224 | return len + rb_event_length(event); |
225 | } |
226 | |
227 | /** |
228 | * ring_buffer_event_length - return the length of the event |
229 | * @event: the event to get the length of |
230 | * |
231 | * Returns the size of the data load of a data event. |
232 | * If the event is something other than a data event, it |
233 | * returns the size of the event itself. With the exception |
234 | * of a TIME EXTEND, where it still returns the size of the |
235 | * data load of the data event after it. |
236 | */ |
237 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) |
238 | { |
239 | unsigned length; |
240 | |
241 | if (extended_time(event)) |
242 | event = skip_time_extend(event); |
243 | |
244 | length = rb_event_length(event); |
245 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
246 | return length; |
247 | length -= RB_EVNT_HDR_SIZE; |
248 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) |
249 | length -= sizeof(event->array[0]); |
250 | return length; |
251 | } |
252 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
253 | |
254 | /* inline for ring buffer fast paths */ |
255 | static __always_inline void * |
256 | rb_event_data(struct ring_buffer_event *event) |
257 | { |
258 | if (extended_time(event)) |
259 | event = skip_time_extend(event); |
260 | BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
261 | /* If length is in len field, then array[0] has the data */ |
262 | if (event->type_len) |
263 | return (void *)&event->array[0]; |
264 | /* Otherwise length is in array[0] and array[1] has the data */ |
265 | return (void *)&event->array[1]; |
266 | } |
267 | |
268 | /** |
269 | * ring_buffer_event_data - return the data of the event |
270 | * @event: the event to get the data from |
271 | */ |
272 | void *ring_buffer_event_data(struct ring_buffer_event *event) |
273 | { |
274 | return rb_event_data(event); |
275 | } |
276 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
277 | |
278 | #define for_each_buffer_cpu(buffer, cpu) \ |
279 | for_each_cpu(cpu, buffer->cpumask) |
280 | |
281 | #define TS_SHIFT 27 |
282 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) |
283 | #define TS_DELTA_TEST (~TS_MASK) |
284 | |
285 | /** |
286 | * ring_buffer_event_time_stamp - return the event's extended timestamp |
287 | * @event: the event to get the timestamp of |
288 | * |
289 | * Returns the extended timestamp associated with a data event. |
290 | * An extended time_stamp is a 64-bit timestamp represented |
291 | * internally in a special way that makes the best use of space |
292 | * contained within a ring buffer event. This function decodes |
293 | * it and maps it to a straight u64 value. |
294 | */ |
295 | u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) |
296 | { |
297 | u64 ts; |
298 | |
299 | ts = event->array[0]; |
300 | ts <<= TS_SHIFT; |
301 | ts += event->time_delta; |
302 | |
303 | return ts; |
304 | } |
305 | |
306 | /* Flag when events were overwritten */ |
307 | #define RB_MISSED_EVENTS (1 << 31) |
308 | /* Missed count stored at end */ |
309 | #define RB_MISSED_STORED (1 << 30) |
310 | |
311 | #define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED) |
312 | |
313 | struct buffer_data_page { |
314 | u64 time_stamp; /* page time stamp */ |
315 | local_t commit; /* write committed index */ |
316 | unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
317 | }; |
318 | |
319 | /* |
320 | * Note, the buffer_page list must be first. The buffer pages |
321 | * are allocated in cache lines, which means that each buffer |
322 | * page will be at the beginning of a cache line, and thus |
323 | * the least significant bits will be zero. We use this to |
324 | * add flags in the list struct pointers, to make the ring buffer |
325 | * lockless. |
326 | */ |
327 | struct buffer_page { |
328 | struct list_head list; /* list of buffer pages */ |
329 | local_t write; /* index for next write */ |
330 | unsigned read; /* index for next read */ |
331 | local_t entries; /* entries on this page */ |
332 | unsigned long real_end; /* real end of data */ |
333 | struct buffer_data_page *page; /* Actual data page */ |
334 | }; |
335 | |
336 | /* |
337 | * The buffer page counters, write and entries, must be reset |
338 | * atomically when crossing page boundaries. To synchronize this |
339 | * update, two counters are inserted into the number. One is |
340 | * the actual counter for the write position or count on the page. |
341 | * |
342 | * The other is a counter of updaters. Before an update happens |
343 | * the update partition of the counter is incremented. This will |
344 | * allow the updater to update the counter atomically. |
345 | * |
346 | * The counter is 20 bits, and the state data is 12. |
347 | */ |
348 | #define RB_WRITE_MASK 0xfffff |
349 | #define RB_WRITE_INTCNT (1 << 20) |
350 | |
351 | static void rb_init_page(struct buffer_data_page *bpage) |
352 | { |
353 | local_set(&bpage->commit, 0); |
354 | } |
355 | |
356 | /* |
357 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing |
358 | * this issue out. |
359 | */ |
360 | static void free_buffer_page(struct buffer_page *bpage) |
361 | { |
362 | free_page((unsigned long)bpage->page); |
363 | kfree(bpage); |
364 | } |
365 | |
366 | /* |
367 | * We need to fit the time_stamp delta into 27 bits. |
368 | */ |
369 | static inline int test_time_stamp(u64 delta) |
370 | { |
371 | if (delta & TS_DELTA_TEST) |
372 | return 1; |
373 | return 0; |
374 | } |
375 | |
376 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
377 | |
378 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
379 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) |
380 | |
381 | int (struct trace_seq *s) |
382 | { |
383 | struct buffer_data_page field; |
384 | |
385 | trace_seq_printf(s, "\tfield: u64 timestamp;\t" |
386 | "offset:0;\tsize:%u;\tsigned:%u;\n" , |
387 | (unsigned int)sizeof(field.time_stamp), |
388 | (unsigned int)is_signed_type(u64)); |
389 | |
390 | trace_seq_printf(s, "\tfield: local_t commit;\t" |
391 | "offset:%u;\tsize:%u;\tsigned:%u;\n" , |
392 | (unsigned int)offsetof(typeof(field), commit), |
393 | (unsigned int)sizeof(field.commit), |
394 | (unsigned int)is_signed_type(long)); |
395 | |
396 | trace_seq_printf(s, "\tfield: int overwrite;\t" |
397 | "offset:%u;\tsize:%u;\tsigned:%u;\n" , |
398 | (unsigned int)offsetof(typeof(field), commit), |
399 | 1, |
400 | (unsigned int)is_signed_type(long)); |
401 | |
402 | trace_seq_printf(s, "\tfield: char data;\t" |
403 | "offset:%u;\tsize:%u;\tsigned:%u;\n" , |
404 | (unsigned int)offsetof(typeof(field), data), |
405 | (unsigned int)BUF_PAGE_SIZE, |
406 | (unsigned int)is_signed_type(char)); |
407 | |
408 | return !trace_seq_has_overflowed(s); |
409 | } |
410 | |
411 | struct rb_irq_work { |
412 | struct irq_work work; |
413 | wait_queue_head_t waiters; |
414 | wait_queue_head_t full_waiters; |
415 | bool waiters_pending; |
416 | bool full_waiters_pending; |
417 | bool wakeup_full; |
418 | }; |
419 | |
420 | /* |
421 | * Structure to hold event state and handle nested events. |
422 | */ |
423 | struct rb_event_info { |
424 | u64 ts; |
425 | u64 delta; |
426 | unsigned long length; |
427 | struct buffer_page *tail_page; |
428 | int add_timestamp; |
429 | }; |
430 | |
431 | /* |
432 | * Used for which event context the event is in. |
433 | * NMI = 0 |
434 | * IRQ = 1 |
435 | * SOFTIRQ = 2 |
436 | * NORMAL = 3 |
437 | * |
438 | * See trace_recursive_lock() comment below for more details. |
439 | */ |
440 | enum { |
441 | RB_CTX_NMI, |
442 | RB_CTX_IRQ, |
443 | RB_CTX_SOFTIRQ, |
444 | RB_CTX_NORMAL, |
445 | RB_CTX_MAX |
446 | }; |
447 | |
448 | /* |
449 | * head_page == tail_page && head == tail then buffer is empty. |
450 | */ |
451 | struct ring_buffer_per_cpu { |
452 | int cpu; |
453 | atomic_t record_disabled; |
454 | struct ring_buffer *buffer; |
455 | raw_spinlock_t reader_lock; /* serialize readers */ |
456 | arch_spinlock_t lock; |
457 | struct lock_class_key lock_key; |
458 | struct buffer_data_page *free_page; |
459 | unsigned long nr_pages; |
460 | unsigned int current_context; |
461 | struct list_head *pages; |
462 | struct buffer_page *head_page; /* read from head */ |
463 | struct buffer_page *tail_page; /* write to tail */ |
464 | struct buffer_page *commit_page; /* committed pages */ |
465 | struct buffer_page *reader_page; |
466 | unsigned long lost_events; |
467 | unsigned long last_overrun; |
468 | unsigned long nest; |
469 | local_t entries_bytes; |
470 | local_t entries; |
471 | local_t overrun; |
472 | local_t commit_overrun; |
473 | local_t dropped_events; |
474 | local_t committing; |
475 | local_t commits; |
476 | local_t pages_touched; |
477 | local_t pages_read; |
478 | long last_pages_touch; |
479 | size_t shortest_full; |
480 | unsigned long read; |
481 | unsigned long read_bytes; |
482 | u64 write_stamp; |
483 | u64 read_stamp; |
484 | /* ring buffer pages to update, > 0 to add, < 0 to remove */ |
485 | long nr_pages_to_update; |
486 | struct list_head new_pages; /* new pages to add */ |
487 | struct work_struct update_pages_work; |
488 | struct completion update_done; |
489 | |
490 | struct rb_irq_work irq_work; |
491 | }; |
492 | |
493 | struct ring_buffer { |
494 | unsigned flags; |
495 | int cpus; |
496 | atomic_t record_disabled; |
497 | atomic_t resize_disabled; |
498 | cpumask_var_t cpumask; |
499 | |
500 | struct lock_class_key *reader_lock_key; |
501 | |
502 | struct mutex mutex; |
503 | |
504 | struct ring_buffer_per_cpu **buffers; |
505 | |
506 | struct hlist_node node; |
507 | u64 (*clock)(void); |
508 | |
509 | struct rb_irq_work irq_work; |
510 | bool time_stamp_abs; |
511 | }; |
512 | |
513 | struct ring_buffer_iter { |
514 | struct ring_buffer_per_cpu *cpu_buffer; |
515 | unsigned long head; |
516 | struct buffer_page *head_page; |
517 | struct buffer_page *cache_reader_page; |
518 | unsigned long cache_read; |
519 | u64 read_stamp; |
520 | }; |
521 | |
522 | /** |
523 | * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer |
524 | * @buffer: The ring_buffer to get the number of pages from |
525 | * @cpu: The cpu of the ring_buffer to get the number of pages from |
526 | * |
527 | * Returns the number of pages used by a per_cpu buffer of the ring buffer. |
528 | */ |
529 | size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu) |
530 | { |
531 | return buffer->buffers[cpu]->nr_pages; |
532 | } |
533 | |
534 | /** |
535 | * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer |
536 | * @buffer: The ring_buffer to get the number of pages from |
537 | * @cpu: The cpu of the ring_buffer to get the number of pages from |
538 | * |
539 | * Returns the number of pages that have content in the ring buffer. |
540 | */ |
541 | size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu) |
542 | { |
543 | size_t read; |
544 | size_t cnt; |
545 | |
546 | read = local_read(&buffer->buffers[cpu]->pages_read); |
547 | cnt = local_read(&buffer->buffers[cpu]->pages_touched); |
548 | /* The reader can read an empty page, but not more than that */ |
549 | if (cnt < read) { |
550 | WARN_ON_ONCE(read > cnt + 1); |
551 | return 0; |
552 | } |
553 | |
554 | return cnt - read; |
555 | } |
556 | |
557 | /* |
558 | * rb_wake_up_waiters - wake up tasks waiting for ring buffer input |
559 | * |
560 | * Schedules a delayed work to wake up any task that is blocked on the |
561 | * ring buffer waiters queue. |
562 | */ |
563 | static void rb_wake_up_waiters(struct irq_work *work) |
564 | { |
565 | struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); |
566 | |
567 | wake_up_all(&rbwork->waiters); |
568 | if (rbwork->wakeup_full) { |
569 | rbwork->wakeup_full = false; |
570 | wake_up_all(&rbwork->full_waiters); |
571 | } |
572 | } |
573 | |
574 | /** |
575 | * ring_buffer_wait - wait for input to the ring buffer |
576 | * @buffer: buffer to wait on |
577 | * @cpu: the cpu buffer to wait on |
578 | * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS |
579 | * |
580 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon |
581 | * as data is added to any of the @buffer's cpu buffers. Otherwise |
582 | * it will wait for data to be added to a specific cpu buffer. |
583 | */ |
584 | int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full) |
585 | { |
586 | struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer); |
587 | DEFINE_WAIT(wait); |
588 | struct rb_irq_work *work; |
589 | int ret = 0; |
590 | |
591 | /* |
592 | * Depending on what the caller is waiting for, either any |
593 | * data in any cpu buffer, or a specific buffer, put the |
594 | * caller on the appropriate wait queue. |
595 | */ |
596 | if (cpu == RING_BUFFER_ALL_CPUS) { |
597 | work = &buffer->irq_work; |
598 | /* Full only makes sense on per cpu reads */ |
599 | full = 0; |
600 | } else { |
601 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
602 | return -ENODEV; |
603 | cpu_buffer = buffer->buffers[cpu]; |
604 | work = &cpu_buffer->irq_work; |
605 | } |
606 | |
607 | |
608 | while (true) { |
609 | if (full) |
610 | prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); |
611 | else |
612 | prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); |
613 | |
614 | /* |
615 | * The events can happen in critical sections where |
616 | * checking a work queue can cause deadlocks. |
617 | * After adding a task to the queue, this flag is set |
618 | * only to notify events to try to wake up the queue |
619 | * using irq_work. |
620 | * |
621 | * We don't clear it even if the buffer is no longer |
622 | * empty. The flag only causes the next event to run |
623 | * irq_work to do the work queue wake up. The worse |
624 | * that can happen if we race with !trace_empty() is that |
625 | * an event will cause an irq_work to try to wake up |
626 | * an empty queue. |
627 | * |
628 | * There's no reason to protect this flag either, as |
629 | * the work queue and irq_work logic will do the necessary |
630 | * synchronization for the wake ups. The only thing |
631 | * that is necessary is that the wake up happens after |
632 | * a task has been queued. It's OK for spurious wake ups. |
633 | */ |
634 | if (full) |
635 | work->full_waiters_pending = true; |
636 | else |
637 | work->waiters_pending = true; |
638 | |
639 | if (signal_pending(current)) { |
640 | ret = -EINTR; |
641 | break; |
642 | } |
643 | |
644 | if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) |
645 | break; |
646 | |
647 | if (cpu != RING_BUFFER_ALL_CPUS && |
648 | !ring_buffer_empty_cpu(buffer, cpu)) { |
649 | unsigned long flags; |
650 | bool pagebusy; |
651 | size_t nr_pages; |
652 | size_t dirty; |
653 | |
654 | if (!full) |
655 | break; |
656 | |
657 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
658 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; |
659 | nr_pages = cpu_buffer->nr_pages; |
660 | dirty = ring_buffer_nr_dirty_pages(buffer, cpu); |
661 | if (!cpu_buffer->shortest_full || |
662 | cpu_buffer->shortest_full < full) |
663 | cpu_buffer->shortest_full = full; |
664 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
665 | if (!pagebusy && |
666 | (!nr_pages || (dirty * 100) > full * nr_pages)) |
667 | break; |
668 | } |
669 | |
670 | schedule(); |
671 | } |
672 | |
673 | if (full) |
674 | finish_wait(&work->full_waiters, &wait); |
675 | else |
676 | finish_wait(&work->waiters, &wait); |
677 | |
678 | return ret; |
679 | } |
680 | |
681 | /** |
682 | * ring_buffer_poll_wait - poll on buffer input |
683 | * @buffer: buffer to wait on |
684 | * @cpu: the cpu buffer to wait on |
685 | * @filp: the file descriptor |
686 | * @poll_table: The poll descriptor |
687 | * |
688 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon |
689 | * as data is added to any of the @buffer's cpu buffers. Otherwise |
690 | * it will wait for data to be added to a specific cpu buffer. |
691 | * |
692 | * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, |
693 | * zero otherwise. |
694 | */ |
695 | __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu, |
696 | struct file *filp, poll_table *poll_table) |
697 | { |
698 | struct ring_buffer_per_cpu *cpu_buffer; |
699 | struct rb_irq_work *work; |
700 | |
701 | if (cpu == RING_BUFFER_ALL_CPUS) |
702 | work = &buffer->irq_work; |
703 | else { |
704 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
705 | return -EINVAL; |
706 | |
707 | cpu_buffer = buffer->buffers[cpu]; |
708 | work = &cpu_buffer->irq_work; |
709 | } |
710 | |
711 | poll_wait(filp, &work->waiters, poll_table); |
712 | work->waiters_pending = true; |
713 | /* |
714 | * There's a tight race between setting the waiters_pending and |
715 | * checking if the ring buffer is empty. Once the waiters_pending bit |
716 | * is set, the next event will wake the task up, but we can get stuck |
717 | * if there's only a single event in. |
718 | * |
719 | * FIXME: Ideally, we need a memory barrier on the writer side as well, |
720 | * but adding a memory barrier to all events will cause too much of a |
721 | * performance hit in the fast path. We only need a memory barrier when |
722 | * the buffer goes from empty to having content. But as this race is |
723 | * extremely small, and it's not a problem if another event comes in, we |
724 | * will fix it later. |
725 | */ |
726 | smp_mb(); |
727 | |
728 | if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || |
729 | (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) |
730 | return EPOLLIN | EPOLLRDNORM; |
731 | return 0; |
732 | } |
733 | |
734 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
735 | #define RB_WARN_ON(b, cond) \ |
736 | ({ \ |
737 | int _____ret = unlikely(cond); \ |
738 | if (_____ret) { \ |
739 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ |
740 | struct ring_buffer_per_cpu *__b = \ |
741 | (void *)b; \ |
742 | atomic_inc(&__b->buffer->record_disabled); \ |
743 | } else \ |
744 | atomic_inc(&b->record_disabled); \ |
745 | WARN_ON(1); \ |
746 | } \ |
747 | _____ret; \ |
748 | }) |
749 | |
750 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
751 | #define DEBUG_SHIFT 0 |
752 | |
753 | static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
754 | { |
755 | /* shift to debug/test normalization and TIME_EXTENTS */ |
756 | return buffer->clock() << DEBUG_SHIFT; |
757 | } |
758 | |
759 | u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
760 | { |
761 | u64 time; |
762 | |
763 | preempt_disable_notrace(); |
764 | time = rb_time_stamp(buffer); |
765 | preempt_enable_no_resched_notrace(); |
766 | |
767 | return time; |
768 | } |
769 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); |
770 | |
771 | void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, |
772 | int cpu, u64 *ts) |
773 | { |
774 | /* Just stupid testing the normalize function and deltas */ |
775 | *ts >>= DEBUG_SHIFT; |
776 | } |
777 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); |
778 | |
779 | /* |
780 | * Making the ring buffer lockless makes things tricky. |
781 | * Although writes only happen on the CPU that they are on, |
782 | * and they only need to worry about interrupts. Reads can |
783 | * happen on any CPU. |
784 | * |
785 | * The reader page is always off the ring buffer, but when the |
786 | * reader finishes with a page, it needs to swap its page with |
787 | * a new one from the buffer. The reader needs to take from |
788 | * the head (writes go to the tail). But if a writer is in overwrite |
789 | * mode and wraps, it must push the head page forward. |
790 | * |
791 | * Here lies the problem. |
792 | * |
793 | * The reader must be careful to replace only the head page, and |
794 | * not another one. As described at the top of the file in the |
795 | * ASCII art, the reader sets its old page to point to the next |
796 | * page after head. It then sets the page after head to point to |
797 | * the old reader page. But if the writer moves the head page |
798 | * during this operation, the reader could end up with the tail. |
799 | * |
800 | * We use cmpxchg to help prevent this race. We also do something |
801 | * special with the page before head. We set the LSB to 1. |
802 | * |
803 | * When the writer must push the page forward, it will clear the |
804 | * bit that points to the head page, move the head, and then set |
805 | * the bit that points to the new head page. |
806 | * |
807 | * We also don't want an interrupt coming in and moving the head |
808 | * page on another writer. Thus we use the second LSB to catch |
809 | * that too. Thus: |
810 | * |
811 | * head->list->prev->next bit 1 bit 0 |
812 | * ------- ------- |
813 | * Normal page 0 0 |
814 | * Points to head page 0 1 |
815 | * New head page 1 0 |
816 | * |
817 | * Note we can not trust the prev pointer of the head page, because: |
818 | * |
819 | * +----+ +-----+ +-----+ |
820 | * | |------>| T |---X--->| N | |
821 | * | |<------| | | | |
822 | * +----+ +-----+ +-----+ |
823 | * ^ ^ | |
824 | * | +-----+ | | |
825 | * +----------| R |----------+ | |
826 | * | |<-----------+ |
827 | * +-----+ |
828 | * |
829 | * Key: ---X--> HEAD flag set in pointer |
830 | * T Tail page |
831 | * R Reader page |
832 | * N Next page |
833 | * |
834 | * (see __rb_reserve_next() to see where this happens) |
835 | * |
836 | * What the above shows is that the reader just swapped out |
837 | * the reader page with a page in the buffer, but before it |
838 | * could make the new header point back to the new page added |
839 | * it was preempted by a writer. The writer moved forward onto |
840 | * the new page added by the reader and is about to move forward |
841 | * again. |
842 | * |
843 | * You can see, it is legitimate for the previous pointer of |
844 | * the head (or any page) not to point back to itself. But only |
845 | * temporarily. |
846 | */ |
847 | |
848 | #define RB_PAGE_NORMAL 0UL |
849 | #define RB_PAGE_HEAD 1UL |
850 | #define RB_PAGE_UPDATE 2UL |
851 | |
852 | |
853 | #define RB_FLAG_MASK 3UL |
854 | |
855 | /* PAGE_MOVED is not part of the mask */ |
856 | #define RB_PAGE_MOVED 4UL |
857 | |
858 | /* |
859 | * rb_list_head - remove any bit |
860 | */ |
861 | static struct list_head *rb_list_head(struct list_head *list) |
862 | { |
863 | unsigned long val = (unsigned long)list; |
864 | |
865 | return (struct list_head *)(val & ~RB_FLAG_MASK); |
866 | } |
867 | |
868 | /* |
869 | * rb_is_head_page - test if the given page is the head page |
870 | * |
871 | * Because the reader may move the head_page pointer, we can |
872 | * not trust what the head page is (it may be pointing to |
873 | * the reader page). But if the next page is a header page, |
874 | * its flags will be non zero. |
875 | */ |
876 | static inline int |
877 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
878 | struct buffer_page *page, struct list_head *list) |
879 | { |
880 | unsigned long val; |
881 | |
882 | val = (unsigned long)list->next; |
883 | |
884 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) |
885 | return RB_PAGE_MOVED; |
886 | |
887 | return val & RB_FLAG_MASK; |
888 | } |
889 | |
890 | /* |
891 | * rb_is_reader_page |
892 | * |
893 | * The unique thing about the reader page, is that, if the |
894 | * writer is ever on it, the previous pointer never points |
895 | * back to the reader page. |
896 | */ |
897 | static bool rb_is_reader_page(struct buffer_page *page) |
898 | { |
899 | struct list_head *list = page->list.prev; |
900 | |
901 | return rb_list_head(list->next) != &page->list; |
902 | } |
903 | |
904 | /* |
905 | * rb_set_list_to_head - set a list_head to be pointing to head. |
906 | */ |
907 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, |
908 | struct list_head *list) |
909 | { |
910 | unsigned long *ptr; |
911 | |
912 | ptr = (unsigned long *)&list->next; |
913 | *ptr |= RB_PAGE_HEAD; |
914 | *ptr &= ~RB_PAGE_UPDATE; |
915 | } |
916 | |
917 | /* |
918 | * rb_head_page_activate - sets up head page |
919 | */ |
920 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) |
921 | { |
922 | struct buffer_page *head; |
923 | |
924 | head = cpu_buffer->head_page; |
925 | if (!head) |
926 | return; |
927 | |
928 | /* |
929 | * Set the previous list pointer to have the HEAD flag. |
930 | */ |
931 | rb_set_list_to_head(cpu_buffer, head->list.prev); |
932 | } |
933 | |
934 | static void rb_list_head_clear(struct list_head *list) |
935 | { |
936 | unsigned long *ptr = (unsigned long *)&list->next; |
937 | |
938 | *ptr &= ~RB_FLAG_MASK; |
939 | } |
940 | |
941 | /* |
942 | * rb_head_page_deactivate - clears head page ptr (for free list) |
943 | */ |
944 | static void |
945 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) |
946 | { |
947 | struct list_head *hd; |
948 | |
949 | /* Go through the whole list and clear any pointers found. */ |
950 | rb_list_head_clear(cpu_buffer->pages); |
951 | |
952 | list_for_each(hd, cpu_buffer->pages) |
953 | rb_list_head_clear(hd); |
954 | } |
955 | |
956 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, |
957 | struct buffer_page *head, |
958 | struct buffer_page *prev, |
959 | int old_flag, int new_flag) |
960 | { |
961 | struct list_head *list; |
962 | unsigned long val = (unsigned long)&head->list; |
963 | unsigned long ret; |
964 | |
965 | list = &prev->list; |
966 | |
967 | val &= ~RB_FLAG_MASK; |
968 | |
969 | ret = cmpxchg((unsigned long *)&list->next, |
970 | val | old_flag, val | new_flag); |
971 | |
972 | /* check if the reader took the page */ |
973 | if ((ret & ~RB_FLAG_MASK) != val) |
974 | return RB_PAGE_MOVED; |
975 | |
976 | return ret & RB_FLAG_MASK; |
977 | } |
978 | |
979 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, |
980 | struct buffer_page *head, |
981 | struct buffer_page *prev, |
982 | int old_flag) |
983 | { |
984 | return rb_head_page_set(cpu_buffer, head, prev, |
985 | old_flag, RB_PAGE_UPDATE); |
986 | } |
987 | |
988 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, |
989 | struct buffer_page *head, |
990 | struct buffer_page *prev, |
991 | int old_flag) |
992 | { |
993 | return rb_head_page_set(cpu_buffer, head, prev, |
994 | old_flag, RB_PAGE_HEAD); |
995 | } |
996 | |
997 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, |
998 | struct buffer_page *head, |
999 | struct buffer_page *prev, |
1000 | int old_flag) |
1001 | { |
1002 | return rb_head_page_set(cpu_buffer, head, prev, |
1003 | old_flag, RB_PAGE_NORMAL); |
1004 | } |
1005 | |
1006 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, |
1007 | struct buffer_page **bpage) |
1008 | { |
1009 | struct list_head *p = rb_list_head((*bpage)->list.next); |
1010 | |
1011 | *bpage = list_entry(p, struct buffer_page, list); |
1012 | } |
1013 | |
1014 | static struct buffer_page * |
1015 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) |
1016 | { |
1017 | struct buffer_page *head; |
1018 | struct buffer_page *page; |
1019 | struct list_head *list; |
1020 | int i; |
1021 | |
1022 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) |
1023 | return NULL; |
1024 | |
1025 | /* sanity check */ |
1026 | list = cpu_buffer->pages; |
1027 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) |
1028 | return NULL; |
1029 | |
1030 | page = head = cpu_buffer->head_page; |
1031 | /* |
1032 | * It is possible that the writer moves the header behind |
1033 | * where we started, and we miss in one loop. |
1034 | * A second loop should grab the header, but we'll do |
1035 | * three loops just because I'm paranoid. |
1036 | */ |
1037 | for (i = 0; i < 3; i++) { |
1038 | do { |
1039 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { |
1040 | cpu_buffer->head_page = page; |
1041 | return page; |
1042 | } |
1043 | rb_inc_page(cpu_buffer, &page); |
1044 | } while (page != head); |
1045 | } |
1046 | |
1047 | RB_WARN_ON(cpu_buffer, 1); |
1048 | |
1049 | return NULL; |
1050 | } |
1051 | |
1052 | static int rb_head_page_replace(struct buffer_page *old, |
1053 | struct buffer_page *new) |
1054 | { |
1055 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; |
1056 | unsigned long val; |
1057 | unsigned long ret; |
1058 | |
1059 | val = *ptr & ~RB_FLAG_MASK; |
1060 | val |= RB_PAGE_HEAD; |
1061 | |
1062 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
1063 | |
1064 | return ret == val; |
1065 | } |
1066 | |
1067 | /* |
1068 | * rb_tail_page_update - move the tail page forward |
1069 | */ |
1070 | static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, |
1071 | struct buffer_page *tail_page, |
1072 | struct buffer_page *next_page) |
1073 | { |
1074 | unsigned long old_entries; |
1075 | unsigned long old_write; |
1076 | |
1077 | /* |
1078 | * The tail page now needs to be moved forward. |
1079 | * |
1080 | * We need to reset the tail page, but without messing |
1081 | * with possible erasing of data brought in by interrupts |
1082 | * that have moved the tail page and are currently on it. |
1083 | * |
1084 | * We add a counter to the write field to denote this. |
1085 | */ |
1086 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); |
1087 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); |
1088 | |
1089 | local_inc(&cpu_buffer->pages_touched); |
1090 | /* |
1091 | * Just make sure we have seen our old_write and synchronize |
1092 | * with any interrupts that come in. |
1093 | */ |
1094 | barrier(); |
1095 | |
1096 | /* |
1097 | * If the tail page is still the same as what we think |
1098 | * it is, then it is up to us to update the tail |
1099 | * pointer. |
1100 | */ |
1101 | if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { |
1102 | /* Zero the write counter */ |
1103 | unsigned long val = old_write & ~RB_WRITE_MASK; |
1104 | unsigned long eval = old_entries & ~RB_WRITE_MASK; |
1105 | |
1106 | /* |
1107 | * This will only succeed if an interrupt did |
1108 | * not come in and change it. In which case, we |
1109 | * do not want to modify it. |
1110 | * |
1111 | * We add (void) to let the compiler know that we do not care |
1112 | * about the return value of these functions. We use the |
1113 | * cmpxchg to only update if an interrupt did not already |
1114 | * do it for us. If the cmpxchg fails, we don't care. |
1115 | */ |
1116 | (void)local_cmpxchg(&next_page->write, old_write, val); |
1117 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); |
1118 | |
1119 | /* |
1120 | * No need to worry about races with clearing out the commit. |
1121 | * it only can increment when a commit takes place. But that |
1122 | * only happens in the outer most nested commit. |
1123 | */ |
1124 | local_set(&next_page->page->commit, 0); |
1125 | |
1126 | /* Again, either we update tail_page or an interrupt does */ |
1127 | (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page); |
1128 | } |
1129 | } |
1130 | |
1131 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, |
1132 | struct buffer_page *bpage) |
1133 | { |
1134 | unsigned long val = (unsigned long)bpage; |
1135 | |
1136 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) |
1137 | return 1; |
1138 | |
1139 | return 0; |
1140 | } |
1141 | |
1142 | /** |
1143 | * rb_check_list - make sure a pointer to a list has the last bits zero |
1144 | */ |
1145 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, |
1146 | struct list_head *list) |
1147 | { |
1148 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) |
1149 | return 1; |
1150 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) |
1151 | return 1; |
1152 | return 0; |
1153 | } |
1154 | |
1155 | /** |
1156 | * rb_check_pages - integrity check of buffer pages |
1157 | * @cpu_buffer: CPU buffer with pages to test |
1158 | * |
1159 | * As a safety measure we check to make sure the data pages have not |
1160 | * been corrupted. |
1161 | */ |
1162 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) |
1163 | { |
1164 | struct list_head *head = cpu_buffer->pages; |
1165 | struct buffer_page *bpage, *tmp; |
1166 | |
1167 | /* Reset the head page if it exists */ |
1168 | if (cpu_buffer->head_page) |
1169 | rb_set_head_page(cpu_buffer); |
1170 | |
1171 | rb_head_page_deactivate(cpu_buffer); |
1172 | |
1173 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
1174 | return -1; |
1175 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) |
1176 | return -1; |
1177 | |
1178 | if (rb_check_list(cpu_buffer, head)) |
1179 | return -1; |
1180 | |
1181 | list_for_each_entry_safe(bpage, tmp, head, list) { |
1182 | if (RB_WARN_ON(cpu_buffer, |
1183 | bpage->list.next->prev != &bpage->list)) |
1184 | return -1; |
1185 | if (RB_WARN_ON(cpu_buffer, |
1186 | bpage->list.prev->next != &bpage->list)) |
1187 | return -1; |
1188 | if (rb_check_list(cpu_buffer, &bpage->list)) |
1189 | return -1; |
1190 | } |
1191 | |
1192 | rb_head_page_activate(cpu_buffer); |
1193 | |
1194 | return 0; |
1195 | } |
1196 | |
1197 | static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) |
1198 | { |
1199 | struct buffer_page *bpage, *tmp; |
1200 | bool user_thread = current->mm != NULL; |
1201 | gfp_t mflags; |
1202 | long i; |
1203 | |
1204 | /* |
1205 | * Check if the available memory is there first. |
1206 | * Note, si_mem_available() only gives us a rough estimate of available |
1207 | * memory. It may not be accurate. But we don't care, we just want |
1208 | * to prevent doing any allocation when it is obvious that it is |
1209 | * not going to succeed. |
1210 | */ |
1211 | i = si_mem_available(); |
1212 | if (i < nr_pages) |
1213 | return -ENOMEM; |
1214 | |
1215 | /* |
1216 | * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails |
1217 | * gracefully without invoking oom-killer and the system is not |
1218 | * destabilized. |
1219 | */ |
1220 | mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL; |
1221 | |
1222 | /* |
1223 | * If a user thread allocates too much, and si_mem_available() |
1224 | * reports there's enough memory, even though there is not. |
1225 | * Make sure the OOM killer kills this thread. This can happen |
1226 | * even with RETRY_MAYFAIL because another task may be doing |
1227 | * an allocation after this task has taken all memory. |
1228 | * This is the task the OOM killer needs to take out during this |
1229 | * loop, even if it was triggered by an allocation somewhere else. |
1230 | */ |
1231 | if (user_thread) |
1232 | set_current_oom_origin(); |
1233 | for (i = 0; i < nr_pages; i++) { |
1234 | struct page *page; |
1235 | |
1236 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
1237 | mflags, cpu_to_node(cpu)); |
1238 | if (!bpage) |
1239 | goto free_pages; |
1240 | |
1241 | list_add(&bpage->list, pages); |
1242 | |
1243 | page = alloc_pages_node(cpu_to_node(cpu), mflags, 0); |
1244 | if (!page) |
1245 | goto free_pages; |
1246 | bpage->page = page_address(page); |
1247 | rb_init_page(bpage->page); |
1248 | |
1249 | if (user_thread && fatal_signal_pending(current)) |
1250 | goto free_pages; |
1251 | } |
1252 | if (user_thread) |
1253 | clear_current_oom_origin(); |
1254 | |
1255 | return 0; |
1256 | |
1257 | free_pages: |
1258 | list_for_each_entry_safe(bpage, tmp, pages, list) { |
1259 | list_del_init(&bpage->list); |
1260 | free_buffer_page(bpage); |
1261 | } |
1262 | if (user_thread) |
1263 | clear_current_oom_origin(); |
1264 | |
1265 | return -ENOMEM; |
1266 | } |
1267 | |
1268 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
1269 | unsigned long nr_pages) |
1270 | { |
1271 | LIST_HEAD(pages); |
1272 | |
1273 | WARN_ON(!nr_pages); |
1274 | |
1275 | if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu)) |
1276 | return -ENOMEM; |
1277 | |
1278 | /* |
1279 | * The ring buffer page list is a circular list that does not |
1280 | * start and end with a list head. All page list items point to |
1281 | * other pages. |
1282 | */ |
1283 | cpu_buffer->pages = pages.next; |
1284 | list_del(&pages); |
1285 | |
1286 | cpu_buffer->nr_pages = nr_pages; |
1287 | |
1288 | rb_check_pages(cpu_buffer); |
1289 | |
1290 | return 0; |
1291 | } |
1292 | |
1293 | static struct ring_buffer_per_cpu * |
1294 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu) |
1295 | { |
1296 | struct ring_buffer_per_cpu *cpu_buffer; |
1297 | struct buffer_page *bpage; |
1298 | struct page *page; |
1299 | int ret; |
1300 | |
1301 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), |
1302 | GFP_KERNEL, cpu_to_node(cpu)); |
1303 | if (!cpu_buffer) |
1304 | return NULL; |
1305 | |
1306 | cpu_buffer->cpu = cpu; |
1307 | cpu_buffer->buffer = buffer; |
1308 | raw_spin_lock_init(&cpu_buffer->reader_lock); |
1309 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
1310 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
1311 | INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
1312 | init_completion(&cpu_buffer->update_done); |
1313 | init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
1314 | init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
1315 | init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
1316 | |
1317 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
1318 | GFP_KERNEL, cpu_to_node(cpu)); |
1319 | if (!bpage) |
1320 | goto fail_free_buffer; |
1321 | |
1322 | rb_check_bpage(cpu_buffer, bpage); |
1323 | |
1324 | cpu_buffer->reader_page = bpage; |
1325 | page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
1326 | if (!page) |
1327 | goto fail_free_reader; |
1328 | bpage->page = page_address(page); |
1329 | rb_init_page(bpage->page); |
1330 | |
1331 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
1332 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
1333 | |
1334 | ret = rb_allocate_pages(cpu_buffer, nr_pages); |
1335 | if (ret < 0) |
1336 | goto fail_free_reader; |
1337 | |
1338 | cpu_buffer->head_page |
1339 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
1340 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
1341 | |
1342 | rb_head_page_activate(cpu_buffer); |
1343 | |
1344 | return cpu_buffer; |
1345 | |
1346 | fail_free_reader: |
1347 | free_buffer_page(cpu_buffer->reader_page); |
1348 | |
1349 | fail_free_buffer: |
1350 | kfree(cpu_buffer); |
1351 | return NULL; |
1352 | } |
1353 | |
1354 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) |
1355 | { |
1356 | struct list_head *head = cpu_buffer->pages; |
1357 | struct buffer_page *bpage, *tmp; |
1358 | |
1359 | free_buffer_page(cpu_buffer->reader_page); |
1360 | |
1361 | rb_head_page_deactivate(cpu_buffer); |
1362 | |
1363 | if (head) { |
1364 | list_for_each_entry_safe(bpage, tmp, head, list) { |
1365 | list_del_init(&bpage->list); |
1366 | free_buffer_page(bpage); |
1367 | } |
1368 | bpage = list_entry(head, struct buffer_page, list); |
1369 | free_buffer_page(bpage); |
1370 | } |
1371 | |
1372 | kfree(cpu_buffer); |
1373 | } |
1374 | |
1375 | /** |
1376 | * __ring_buffer_alloc - allocate a new ring_buffer |
1377 | * @size: the size in bytes per cpu that is needed. |
1378 | * @flags: attributes to set for the ring buffer. |
1379 | * |
1380 | * Currently the only flag that is available is the RB_FL_OVERWRITE |
1381 | * flag. This flag means that the buffer will overwrite old data |
1382 | * when the buffer wraps. If this flag is not set, the buffer will |
1383 | * drop data when the tail hits the head. |
1384 | */ |
1385 | struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1386 | struct lock_class_key *key) |
1387 | { |
1388 | struct ring_buffer *buffer; |
1389 | long nr_pages; |
1390 | int bsize; |
1391 | int cpu; |
1392 | int ret; |
1393 | |
1394 | /* keep it in its own cache line */ |
1395 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), |
1396 | GFP_KERNEL); |
1397 | if (!buffer) |
1398 | return NULL; |
1399 | |
1400 | if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
1401 | goto fail_free_buffer; |
1402 | |
1403 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1404 | buffer->flags = flags; |
1405 | buffer->clock = trace_clock_local; |
1406 | buffer->reader_lock_key = key; |
1407 | |
1408 | init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
1409 | init_waitqueue_head(&buffer->irq_work.waiters); |
1410 | |
1411 | /* need at least two pages */ |
1412 | if (nr_pages < 2) |
1413 | nr_pages = 2; |
1414 | |
1415 | buffer->cpus = nr_cpu_ids; |
1416 | |
1417 | bsize = sizeof(void *) * nr_cpu_ids; |
1418 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), |
1419 | GFP_KERNEL); |
1420 | if (!buffer->buffers) |
1421 | goto fail_free_cpumask; |
1422 | |
1423 | cpu = raw_smp_processor_id(); |
1424 | cpumask_set_cpu(cpu, buffer->cpumask); |
1425 | buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
1426 | if (!buffer->buffers[cpu]) |
1427 | goto fail_free_buffers; |
1428 | |
1429 | ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
1430 | if (ret < 0) |
1431 | goto fail_free_buffers; |
1432 | |
1433 | mutex_init(&buffer->mutex); |
1434 | |
1435 | return buffer; |
1436 | |
1437 | fail_free_buffers: |
1438 | for_each_buffer_cpu(buffer, cpu) { |
1439 | if (buffer->buffers[cpu]) |
1440 | rb_free_cpu_buffer(buffer->buffers[cpu]); |
1441 | } |
1442 | kfree(buffer->buffers); |
1443 | |
1444 | fail_free_cpumask: |
1445 | free_cpumask_var(buffer->cpumask); |
1446 | |
1447 | fail_free_buffer: |
1448 | kfree(buffer); |
1449 | return NULL; |
1450 | } |
1451 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
1452 | |
1453 | /** |
1454 | * ring_buffer_free - free a ring buffer. |
1455 | * @buffer: the buffer to free. |
1456 | */ |
1457 | void |
1458 | ring_buffer_free(struct ring_buffer *buffer) |
1459 | { |
1460 | int cpu; |
1461 | |
1462 | cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
1463 | |
1464 | for_each_buffer_cpu(buffer, cpu) |
1465 | rb_free_cpu_buffer(buffer->buffers[cpu]); |
1466 | |
1467 | kfree(buffer->buffers); |
1468 | free_cpumask_var(buffer->cpumask); |
1469 | |
1470 | kfree(buffer); |
1471 | } |
1472 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
1473 | |
1474 | void ring_buffer_set_clock(struct ring_buffer *buffer, |
1475 | u64 (*clock)(void)) |
1476 | { |
1477 | buffer->clock = clock; |
1478 | } |
1479 | |
1480 | void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs) |
1481 | { |
1482 | buffer->time_stamp_abs = abs; |
1483 | } |
1484 | |
1485 | bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer) |
1486 | { |
1487 | return buffer->time_stamp_abs; |
1488 | } |
1489 | |
1490 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1491 | |
1492 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1493 | { |
1494 | return local_read(&bpage->entries) & RB_WRITE_MASK; |
1495 | } |
1496 | |
1497 | static inline unsigned long rb_page_write(struct buffer_page *bpage) |
1498 | { |
1499 | return local_read(&bpage->write) & RB_WRITE_MASK; |
1500 | } |
1501 | |
1502 | static int |
1503 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) |
1504 | { |
1505 | struct list_head *tail_page, *to_remove, *next_page; |
1506 | struct buffer_page *to_remove_page, *tmp_iter_page; |
1507 | struct buffer_page *last_page, *first_page; |
1508 | unsigned long nr_removed; |
1509 | unsigned long head_bit; |
1510 | int page_entries; |
1511 | |
1512 | head_bit = 0; |
1513 | |
1514 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
1515 | atomic_inc(&cpu_buffer->record_disabled); |
1516 | /* |
1517 | * We don't race with the readers since we have acquired the reader |
1518 | * lock. We also don't race with writers after disabling recording. |
1519 | * This makes it easy to figure out the first and the last page to be |
1520 | * removed from the list. We unlink all the pages in between including |
1521 | * the first and last pages. This is done in a busy loop so that we |
1522 | * lose the least number of traces. |
1523 | * The pages are freed after we restart recording and unlock readers. |
1524 | */ |
1525 | tail_page = &cpu_buffer->tail_page->list; |
1526 | |
1527 | /* |
1528 | * tail page might be on reader page, we remove the next page |
1529 | * from the ring buffer |
1530 | */ |
1531 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) |
1532 | tail_page = rb_list_head(tail_page->next); |
1533 | to_remove = tail_page; |
1534 | |
1535 | /* start of pages to remove */ |
1536 | first_page = list_entry(rb_list_head(to_remove->next), |
1537 | struct buffer_page, list); |
1538 | |
1539 | for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { |
1540 | to_remove = rb_list_head(to_remove)->next; |
1541 | head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; |
1542 | } |
1543 | |
1544 | next_page = rb_list_head(to_remove)->next; |
1545 | |
1546 | /* |
1547 | * Now we remove all pages between tail_page and next_page. |
1548 | * Make sure that we have head_bit value preserved for the |
1549 | * next page |
1550 | */ |
1551 | tail_page->next = (struct list_head *)((unsigned long)next_page | |
1552 | head_bit); |
1553 | next_page = rb_list_head(next_page); |
1554 | next_page->prev = tail_page; |
1555 | |
1556 | /* make sure pages points to a valid page in the ring buffer */ |
1557 | cpu_buffer->pages = next_page; |
1558 | |
1559 | /* update head page */ |
1560 | if (head_bit) |
1561 | cpu_buffer->head_page = list_entry(next_page, |
1562 | struct buffer_page, list); |
1563 | |
1564 | /* |
1565 | * change read pointer to make sure any read iterators reset |
1566 | * themselves |
1567 | */ |
1568 | cpu_buffer->read = 0; |
1569 | |
1570 | /* pages are removed, resume tracing and then free the pages */ |
1571 | atomic_dec(&cpu_buffer->record_disabled); |
1572 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
1573 | |
1574 | RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); |
1575 | |
1576 | /* last buffer page to remove */ |
1577 | last_page = list_entry(rb_list_head(to_remove), struct buffer_page, |
1578 | list); |
1579 | tmp_iter_page = first_page; |
1580 | |
1581 | do { |
1582 | cond_resched(); |
1583 | |
1584 | to_remove_page = tmp_iter_page; |
1585 | rb_inc_page(cpu_buffer, &tmp_iter_page); |
1586 | |
1587 | /* update the counters */ |
1588 | page_entries = rb_page_entries(to_remove_page); |
1589 | if (page_entries) { |
1590 | /* |
1591 | * If something was added to this page, it was full |
1592 | * since it is not the tail page. So we deduct the |
1593 | * bytes consumed in ring buffer from here. |
1594 | * Increment overrun to account for the lost events. |
1595 | */ |
1596 | local_add(page_entries, &cpu_buffer->overrun); |
1597 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
1598 | } |
1599 | |
1600 | /* |
1601 | * We have already removed references to this list item, just |
1602 | * free up the buffer_page and its page |
1603 | */ |
1604 | free_buffer_page(to_remove_page); |
1605 | nr_removed--; |
1606 | |
1607 | } while (to_remove_page != last_page); |
1608 | |
1609 | RB_WARN_ON(cpu_buffer, nr_removed); |
1610 | |
1611 | return nr_removed == 0; |
1612 | } |
1613 | |
1614 | static int |
1615 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) |
1616 | { |
1617 | struct list_head *pages = &cpu_buffer->new_pages; |
1618 | int retries, success; |
1619 | |
1620 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
1621 | /* |
1622 | * We are holding the reader lock, so the reader page won't be swapped |
1623 | * in the ring buffer. Now we are racing with the writer trying to |
1624 | * move head page and the tail page. |
1625 | * We are going to adapt the reader page update process where: |
1626 | * 1. We first splice the start and end of list of new pages between |
1627 | * the head page and its previous page. |
1628 | * 2. We cmpxchg the prev_page->next to point from head page to the |
1629 | * start of new pages list. |
1630 | * 3. Finally, we update the head->prev to the end of new list. |
1631 | * |
1632 | * We will try this process 10 times, to make sure that we don't keep |
1633 | * spinning. |
1634 | */ |
1635 | retries = 10; |
1636 | success = 0; |
1637 | while (retries--) { |
1638 | struct list_head *head_page, *prev_page, *r; |
1639 | struct list_head *last_page, *first_page; |
1640 | struct list_head *head_page_with_bit; |
1641 | |
1642 | head_page = &rb_set_head_page(cpu_buffer)->list; |
1643 | if (!head_page) |
1644 | break; |
1645 | prev_page = head_page->prev; |
1646 | |
1647 | first_page = pages->next; |
1648 | last_page = pages->prev; |
1649 | |
1650 | head_page_with_bit = (struct list_head *) |
1651 | ((unsigned long)head_page | RB_PAGE_HEAD); |
1652 | |
1653 | last_page->next = head_page_with_bit; |
1654 | first_page->prev = prev_page; |
1655 | |
1656 | r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); |
1657 | |
1658 | if (r == head_page_with_bit) { |
1659 | /* |
1660 | * yay, we replaced the page pointer to our new list, |
1661 | * now, we just have to update to head page's prev |
1662 | * pointer to point to end of list |
1663 | */ |
1664 | head_page->prev = last_page; |
1665 | success = 1; |
1666 | break; |
1667 | } |
1668 | } |
1669 | |
1670 | if (success) |
1671 | INIT_LIST_HEAD(pages); |
1672 | /* |
1673 | * If we weren't successful in adding in new pages, warn and stop |
1674 | * tracing |
1675 | */ |
1676 | RB_WARN_ON(cpu_buffer, !success); |
1677 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
1678 | |
1679 | /* free pages if they weren't inserted */ |
1680 | if (!success) { |
1681 | struct buffer_page *bpage, *tmp; |
1682 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
1683 | list) { |
1684 | list_del_init(&bpage->list); |
1685 | free_buffer_page(bpage); |
1686 | } |
1687 | } |
1688 | return success; |
1689 | } |
1690 | |
1691 | static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
1692 | { |
1693 | int success; |
1694 | |
1695 | if (cpu_buffer->nr_pages_to_update > 0) |
1696 | success = rb_insert_pages(cpu_buffer); |
1697 | else |
1698 | success = rb_remove_pages(cpu_buffer, |
1699 | -cpu_buffer->nr_pages_to_update); |
1700 | |
1701 | if (success) |
1702 | cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; |
1703 | } |
1704 | |
1705 | static void update_pages_handler(struct work_struct *work) |
1706 | { |
1707 | struct ring_buffer_per_cpu *cpu_buffer = container_of(work, |
1708 | struct ring_buffer_per_cpu, update_pages_work); |
1709 | rb_update_pages(cpu_buffer); |
1710 | complete(&cpu_buffer->update_done); |
1711 | } |
1712 | |
1713 | /** |
1714 | * ring_buffer_resize - resize the ring buffer |
1715 | * @buffer: the buffer to resize. |
1716 | * @size: the new size. |
1717 | * @cpu_id: the cpu buffer to resize |
1718 | * |
1719 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1720 | * |
1721 | * Returns 0 on success and < 0 on failure. |
1722 | */ |
1723 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, |
1724 | int cpu_id) |
1725 | { |
1726 | struct ring_buffer_per_cpu *cpu_buffer; |
1727 | unsigned long nr_pages; |
1728 | int cpu, err = 0; |
1729 | |
1730 | /* |
1731 | * Always succeed at resizing a non-existent buffer: |
1732 | */ |
1733 | if (!buffer) |
1734 | return size; |
1735 | |
1736 | /* Make sure the requested buffer exists */ |
1737 | if (cpu_id != RING_BUFFER_ALL_CPUS && |
1738 | !cpumask_test_cpu(cpu_id, buffer->cpumask)) |
1739 | return size; |
1740 | |
1741 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1742 | |
1743 | /* we need a minimum of two pages */ |
1744 | if (nr_pages < 2) |
1745 | nr_pages = 2; |
1746 | |
1747 | size = nr_pages * BUF_PAGE_SIZE; |
1748 | |
1749 | /* |
1750 | * Don't succeed if resizing is disabled, as a reader might be |
1751 | * manipulating the ring buffer and is expecting a sane state while |
1752 | * this is true. |
1753 | */ |
1754 | if (atomic_read(&buffer->resize_disabled)) |
1755 | return -EBUSY; |
1756 | |
1757 | /* prevent another thread from changing buffer sizes */ |
1758 | mutex_lock(&buffer->mutex); |
1759 | |
1760 | if (cpu_id == RING_BUFFER_ALL_CPUS) { |
1761 | /* calculate the pages to update */ |
1762 | for_each_buffer_cpu(buffer, cpu) { |
1763 | cpu_buffer = buffer->buffers[cpu]; |
1764 | |
1765 | cpu_buffer->nr_pages_to_update = nr_pages - |
1766 | cpu_buffer->nr_pages; |
1767 | /* |
1768 | * nothing more to do for removing pages or no update |
1769 | */ |
1770 | if (cpu_buffer->nr_pages_to_update <= 0) |
1771 | continue; |
1772 | /* |
1773 | * to add pages, make sure all new pages can be |
1774 | * allocated without receiving ENOMEM |
1775 | */ |
1776 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
1777 | if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update, |
1778 | &cpu_buffer->new_pages, cpu)) { |
1779 | /* not enough memory for new pages */ |
1780 | err = -ENOMEM; |
1781 | goto out_err; |
1782 | } |
1783 | } |
1784 | |
1785 | get_online_cpus(); |
1786 | /* |
1787 | * Fire off all the required work handlers |
1788 | * We can't schedule on offline CPUs, but it's not necessary |
1789 | * since we can change their buffer sizes without any race. |
1790 | */ |
1791 | for_each_buffer_cpu(buffer, cpu) { |
1792 | cpu_buffer = buffer->buffers[cpu]; |
1793 | if (!cpu_buffer->nr_pages_to_update) |
1794 | continue; |
1795 | |
1796 | /* Can't run something on an offline CPU. */ |
1797 | if (!cpu_online(cpu)) { |
1798 | rb_update_pages(cpu_buffer); |
1799 | cpu_buffer->nr_pages_to_update = 0; |
1800 | } else { |
1801 | schedule_work_on(cpu, |
1802 | &cpu_buffer->update_pages_work); |
1803 | } |
1804 | } |
1805 | |
1806 | /* wait for all the updates to complete */ |
1807 | for_each_buffer_cpu(buffer, cpu) { |
1808 | cpu_buffer = buffer->buffers[cpu]; |
1809 | if (!cpu_buffer->nr_pages_to_update) |
1810 | continue; |
1811 | |
1812 | if (cpu_online(cpu)) |
1813 | wait_for_completion(&cpu_buffer->update_done); |
1814 | cpu_buffer->nr_pages_to_update = 0; |
1815 | } |
1816 | |
1817 | put_online_cpus(); |
1818 | } else { |
1819 | /* Make sure this CPU has been initialized */ |
1820 | if (!cpumask_test_cpu(cpu_id, buffer->cpumask)) |
1821 | goto out; |
1822 | |
1823 | cpu_buffer = buffer->buffers[cpu_id]; |
1824 | |
1825 | if (nr_pages == cpu_buffer->nr_pages) |
1826 | goto out; |
1827 | |
1828 | cpu_buffer->nr_pages_to_update = nr_pages - |
1829 | cpu_buffer->nr_pages; |
1830 | |
1831 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
1832 | if (cpu_buffer->nr_pages_to_update > 0 && |
1833 | __rb_allocate_pages(cpu_buffer->nr_pages_to_update, |
1834 | &cpu_buffer->new_pages, cpu_id)) { |
1835 | err = -ENOMEM; |
1836 | goto out_err; |
1837 | } |
1838 | |
1839 | get_online_cpus(); |
1840 | |
1841 | /* Can't run something on an offline CPU. */ |
1842 | if (!cpu_online(cpu_id)) |
1843 | rb_update_pages(cpu_buffer); |
1844 | else { |
1845 | schedule_work_on(cpu_id, |
1846 | &cpu_buffer->update_pages_work); |
1847 | wait_for_completion(&cpu_buffer->update_done); |
1848 | } |
1849 | |
1850 | cpu_buffer->nr_pages_to_update = 0; |
1851 | put_online_cpus(); |
1852 | } |
1853 | |
1854 | out: |
1855 | /* |
1856 | * The ring buffer resize can happen with the ring buffer |
1857 | * enabled, so that the update disturbs the tracing as little |
1858 | * as possible. But if the buffer is disabled, we do not need |
1859 | * to worry about that, and we can take the time to verify |
1860 | * that the buffer is not corrupt. |
1861 | */ |
1862 | if (atomic_read(&buffer->record_disabled)) { |
1863 | atomic_inc(&buffer->record_disabled); |
1864 | /* |
1865 | * Even though the buffer was disabled, we must make sure |
1866 | * that it is truly disabled before calling rb_check_pages. |
1867 | * There could have been a race between checking |
1868 | * record_disable and incrementing it. |
1869 | */ |
1870 | synchronize_rcu(); |
1871 | for_each_buffer_cpu(buffer, cpu) { |
1872 | cpu_buffer = buffer->buffers[cpu]; |
1873 | rb_check_pages(cpu_buffer); |
1874 | } |
1875 | atomic_dec(&buffer->record_disabled); |
1876 | } |
1877 | |
1878 | mutex_unlock(&buffer->mutex); |
1879 | return size; |
1880 | |
1881 | out_err: |
1882 | for_each_buffer_cpu(buffer, cpu) { |
1883 | struct buffer_page *bpage, *tmp; |
1884 | |
1885 | cpu_buffer = buffer->buffers[cpu]; |
1886 | cpu_buffer->nr_pages_to_update = 0; |
1887 | |
1888 | if (list_empty(&cpu_buffer->new_pages)) |
1889 | continue; |
1890 | |
1891 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
1892 | list) { |
1893 | list_del_init(&bpage->list); |
1894 | free_buffer_page(bpage); |
1895 | } |
1896 | } |
1897 | mutex_unlock(&buffer->mutex); |
1898 | return err; |
1899 | } |
1900 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
1901 | |
1902 | void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) |
1903 | { |
1904 | mutex_lock(&buffer->mutex); |
1905 | if (val) |
1906 | buffer->flags |= RB_FL_OVERWRITE; |
1907 | else |
1908 | buffer->flags &= ~RB_FL_OVERWRITE; |
1909 | mutex_unlock(&buffer->mutex); |
1910 | } |
1911 | EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); |
1912 | |
1913 | static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
1914 | { |
1915 | return bpage->page->data + index; |
1916 | } |
1917 | |
1918 | static __always_inline struct ring_buffer_event * |
1919 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
1920 | { |
1921 | return __rb_page_index(cpu_buffer->reader_page, |
1922 | cpu_buffer->reader_page->read); |
1923 | } |
1924 | |
1925 | static __always_inline struct ring_buffer_event * |
1926 | rb_iter_head_event(struct ring_buffer_iter *iter) |
1927 | { |
1928 | return __rb_page_index(iter->head_page, iter->head); |
1929 | } |
1930 | |
1931 | static __always_inline unsigned rb_page_commit(struct buffer_page *bpage) |
1932 | { |
1933 | return local_read(&bpage->page->commit); |
1934 | } |
1935 | |
1936 | /* Size is determined by what has been committed */ |
1937 | static __always_inline unsigned rb_page_size(struct buffer_page *bpage) |
1938 | { |
1939 | return rb_page_commit(bpage); |
1940 | } |
1941 | |
1942 | static __always_inline unsigned |
1943 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) |
1944 | { |
1945 | return rb_page_commit(cpu_buffer->commit_page); |
1946 | } |
1947 | |
1948 | static __always_inline unsigned |
1949 | rb_event_index(struct ring_buffer_event *event) |
1950 | { |
1951 | unsigned long addr = (unsigned long)event; |
1952 | |
1953 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
1954 | } |
1955 | |
1956 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
1957 | { |
1958 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
1959 | |
1960 | /* |
1961 | * The iterator could be on the reader page (it starts there). |
1962 | * But the head could have moved, since the reader was |
1963 | * found. Check for this case and assign the iterator |
1964 | * to the head page instead of next. |
1965 | */ |
1966 | if (iter->head_page == cpu_buffer->reader_page) |
1967 | iter->head_page = rb_set_head_page(cpu_buffer); |
1968 | else |
1969 | rb_inc_page(cpu_buffer, &iter->head_page); |
1970 | |
1971 | iter->read_stamp = iter->head_page->page->time_stamp; |
1972 | iter->head = 0; |
1973 | } |
1974 | |
1975 | /* |
1976 | * rb_handle_head_page - writer hit the head page |
1977 | * |
1978 | * Returns: +1 to retry page |
1979 | * 0 to continue |
1980 | * -1 on error |
1981 | */ |
1982 | static int |
1983 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
1984 | struct buffer_page *tail_page, |
1985 | struct buffer_page *next_page) |
1986 | { |
1987 | struct buffer_page *new_head; |
1988 | int entries; |
1989 | int type; |
1990 | int ret; |
1991 | |
1992 | entries = rb_page_entries(next_page); |
1993 | |
1994 | /* |
1995 | * The hard part is here. We need to move the head |
1996 | * forward, and protect against both readers on |
1997 | * other CPUs and writers coming in via interrupts. |
1998 | */ |
1999 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, |
2000 | RB_PAGE_HEAD); |
2001 | |
2002 | /* |
2003 | * type can be one of four: |
2004 | * NORMAL - an interrupt already moved it for us |
2005 | * HEAD - we are the first to get here. |
2006 | * UPDATE - we are the interrupt interrupting |
2007 | * a current move. |
2008 | * MOVED - a reader on another CPU moved the next |
2009 | * pointer to its reader page. Give up |
2010 | * and try again. |
2011 | */ |
2012 | |
2013 | switch (type) { |
2014 | case RB_PAGE_HEAD: |
2015 | /* |
2016 | * We changed the head to UPDATE, thus |
2017 | * it is our responsibility to update |
2018 | * the counters. |
2019 | */ |
2020 | local_add(entries, &cpu_buffer->overrun); |
2021 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
2022 | |
2023 | /* |
2024 | * The entries will be zeroed out when we move the |
2025 | * tail page. |
2026 | */ |
2027 | |
2028 | /* still more to do */ |
2029 | break; |
2030 | |
2031 | case RB_PAGE_UPDATE: |
2032 | /* |
2033 | * This is an interrupt that interrupt the |
2034 | * previous update. Still more to do. |
2035 | */ |
2036 | break; |
2037 | case RB_PAGE_NORMAL: |
2038 | /* |
2039 | * An interrupt came in before the update |
2040 | * and processed this for us. |
2041 | * Nothing left to do. |
2042 | */ |
2043 | return 1; |
2044 | case RB_PAGE_MOVED: |
2045 | /* |
2046 | * The reader is on another CPU and just did |
2047 | * a swap with our next_page. |
2048 | * Try again. |
2049 | */ |
2050 | return 1; |
2051 | default: |
2052 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ |
2053 | return -1; |
2054 | } |
2055 | |
2056 | /* |
2057 | * Now that we are here, the old head pointer is |
2058 | * set to UPDATE. This will keep the reader from |
2059 | * swapping the head page with the reader page. |
2060 | * The reader (on another CPU) will spin till |
2061 | * we are finished. |
2062 | * |
2063 | * We just need to protect against interrupts |
2064 | * doing the job. We will set the next pointer |
2065 | * to HEAD. After that, we set the old pointer |
2066 | * to NORMAL, but only if it was HEAD before. |
2067 | * otherwise we are an interrupt, and only |
2068 | * want the outer most commit to reset it. |
2069 | */ |
2070 | new_head = next_page; |
2071 | rb_inc_page(cpu_buffer, &new_head); |
2072 | |
2073 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, |
2074 | RB_PAGE_NORMAL); |
2075 | |
2076 | /* |
2077 | * Valid returns are: |
2078 | * HEAD - an interrupt came in and already set it. |
2079 | * NORMAL - One of two things: |
2080 | * 1) We really set it. |
2081 | * 2) A bunch of interrupts came in and moved |
2082 | * the page forward again. |
2083 | */ |
2084 | switch (ret) { |
2085 | case RB_PAGE_HEAD: |
2086 | case RB_PAGE_NORMAL: |
2087 | /* OK */ |
2088 | break; |
2089 | default: |
2090 | RB_WARN_ON(cpu_buffer, 1); |
2091 | return -1; |
2092 | } |
2093 | |
2094 | /* |
2095 | * It is possible that an interrupt came in, |
2096 | * set the head up, then more interrupts came in |
2097 | * and moved it again. When we get back here, |
2098 | * the page would have been set to NORMAL but we |
2099 | * just set it back to HEAD. |
2100 | * |
2101 | * How do you detect this? Well, if that happened |
2102 | * the tail page would have moved. |
2103 | */ |
2104 | if (ret == RB_PAGE_NORMAL) { |
2105 | struct buffer_page *buffer_tail_page; |
2106 | |
2107 | buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); |
2108 | /* |
2109 | * If the tail had moved passed next, then we need |
2110 | * to reset the pointer. |
2111 | */ |
2112 | if (buffer_tail_page != tail_page && |
2113 | buffer_tail_page != next_page) |
2114 | rb_head_page_set_normal(cpu_buffer, new_head, |
2115 | next_page, |
2116 | RB_PAGE_HEAD); |
2117 | } |
2118 | |
2119 | /* |
2120 | * If this was the outer most commit (the one that |
2121 | * changed the original pointer from HEAD to UPDATE), |
2122 | * then it is up to us to reset it to NORMAL. |
2123 | */ |
2124 | if (type == RB_PAGE_HEAD) { |
2125 | ret = rb_head_page_set_normal(cpu_buffer, next_page, |
2126 | tail_page, |
2127 | RB_PAGE_UPDATE); |
2128 | if (RB_WARN_ON(cpu_buffer, |
2129 | ret != RB_PAGE_UPDATE)) |
2130 | return -1; |
2131 | } |
2132 | |
2133 | return 0; |
2134 | } |
2135 | |
2136 | static inline void |
2137 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, |
2138 | unsigned long tail, struct rb_event_info *info) |
2139 | { |
2140 | struct buffer_page *tail_page = info->tail_page; |
2141 | struct ring_buffer_event *event; |
2142 | unsigned long length = info->length; |
2143 | |
2144 | /* |
2145 | * Only the event that crossed the page boundary |
2146 | * must fill the old tail_page with padding. |
2147 | */ |
2148 | if (tail >= BUF_PAGE_SIZE) { |
2149 | /* |
2150 | * If the page was filled, then we still need |
2151 | * to update the real_end. Reset it to zero |
2152 | * and the reader will ignore it. |
2153 | */ |
2154 | if (tail == BUF_PAGE_SIZE) |
2155 | tail_page->real_end = 0; |
2156 | |
2157 | local_sub(length, &tail_page->write); |
2158 | return; |
2159 | } |
2160 | |
2161 | event = __rb_page_index(tail_page, tail); |
2162 | |
2163 | /* account for padding bytes */ |
2164 | local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); |
2165 | |
2166 | /* |
2167 | * Save the original length to the meta data. |
2168 | * This will be used by the reader to add lost event |
2169 | * counter. |
2170 | */ |
2171 | tail_page->real_end = tail; |
2172 | |
2173 | /* |
2174 | * If this event is bigger than the minimum size, then |
2175 | * we need to be careful that we don't subtract the |
2176 | * write counter enough to allow another writer to slip |
2177 | * in on this page. |
2178 | * We put in a discarded commit instead, to make sure |
2179 | * that this space is not used again. |
2180 | * |
2181 | * If we are less than the minimum size, we don't need to |
2182 | * worry about it. |
2183 | */ |
2184 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { |
2185 | /* No room for any events */ |
2186 | |
2187 | /* Mark the rest of the page with padding */ |
2188 | rb_event_set_padding(event); |
2189 | |
2190 | /* Set the write back to the previous setting */ |
2191 | local_sub(length, &tail_page->write); |
2192 | return; |
2193 | } |
2194 | |
2195 | /* Put in a discarded event */ |
2196 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; |
2197 | event->type_len = RINGBUF_TYPE_PADDING; |
2198 | /* time delta must be non zero */ |
2199 | event->time_delta = 1; |
2200 | |
2201 | /* Set write to end of buffer */ |
2202 | length = (tail + length) - BUF_PAGE_SIZE; |
2203 | local_sub(length, &tail_page->write); |
2204 | } |
2205 | |
2206 | static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer); |
2207 | |
2208 | /* |
2209 | * This is the slow path, force gcc not to inline it. |
2210 | */ |
2211 | static noinline struct ring_buffer_event * |
2212 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
2213 | unsigned long tail, struct rb_event_info *info) |
2214 | { |
2215 | struct buffer_page *tail_page = info->tail_page; |
2216 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
2217 | struct ring_buffer *buffer = cpu_buffer->buffer; |
2218 | struct buffer_page *next_page; |
2219 | int ret; |
2220 | |
2221 | next_page = tail_page; |
2222 | |
2223 | rb_inc_page(cpu_buffer, &next_page); |
2224 | |
2225 | /* |
2226 | * If for some reason, we had an interrupt storm that made |
2227 | * it all the way around the buffer, bail, and warn |
2228 | * about it. |
2229 | */ |
2230 | if (unlikely(next_page == commit_page)) { |
2231 | local_inc(&cpu_buffer->commit_overrun); |
2232 | goto out_reset; |
2233 | } |
2234 | |
2235 | /* |
2236 | * This is where the fun begins! |
2237 | * |
2238 | * We are fighting against races between a reader that |
2239 | * could be on another CPU trying to swap its reader |
2240 | * page with the buffer head. |
2241 | * |
2242 | * We are also fighting against interrupts coming in and |
2243 | * moving the head or tail on us as well. |
2244 | * |
2245 | * If the next page is the head page then we have filled |
2246 | * the buffer, unless the commit page is still on the |
2247 | * reader page. |
2248 | */ |
2249 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { |
2250 | |
2251 | /* |
2252 | * If the commit is not on the reader page, then |
2253 | * move the header page. |
2254 | */ |
2255 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { |
2256 | /* |
2257 | * If we are not in overwrite mode, |
2258 | * this is easy, just stop here. |
2259 | */ |
2260 | if (!(buffer->flags & RB_FL_OVERWRITE)) { |
2261 | local_inc(&cpu_buffer->dropped_events); |
2262 | goto out_reset; |
2263 | } |
2264 | |
2265 | ret = rb_handle_head_page(cpu_buffer, |
2266 | tail_page, |
2267 | next_page); |
2268 | if (ret < 0) |
2269 | goto out_reset; |
2270 | if (ret) |
2271 | goto out_again; |
2272 | } else { |
2273 | /* |
2274 | * We need to be careful here too. The |
2275 | * commit page could still be on the reader |
2276 | * page. We could have a small buffer, and |
2277 | * have filled up the buffer with events |
2278 | * from interrupts and such, and wrapped. |
2279 | * |
2280 | * Note, if the tail page is also the on the |
2281 | * reader_page, we let it move out. |
2282 | */ |
2283 | if (unlikely((cpu_buffer->commit_page != |
2284 | cpu_buffer->tail_page) && |
2285 | (cpu_buffer->commit_page == |
2286 | cpu_buffer->reader_page))) { |
2287 | local_inc(&cpu_buffer->commit_overrun); |
2288 | goto out_reset; |
2289 | } |
2290 | } |
2291 | } |
2292 | |
2293 | rb_tail_page_update(cpu_buffer, tail_page, next_page); |
2294 | |
2295 | out_again: |
2296 | |
2297 | rb_reset_tail(cpu_buffer, tail, info); |
2298 | |
2299 | /* Commit what we have for now. */ |
2300 | rb_end_commit(cpu_buffer); |
2301 | /* rb_end_commit() decs committing */ |
2302 | local_inc(&cpu_buffer->committing); |
2303 | |
2304 | /* fail and let the caller try again */ |
2305 | return ERR_PTR(-EAGAIN); |
2306 | |
2307 | out_reset: |
2308 | /* reset write */ |
2309 | rb_reset_tail(cpu_buffer, tail, info); |
2310 | |
2311 | return NULL; |
2312 | } |
2313 | |
2314 | /* Slow path, do not inline */ |
2315 | static noinline struct ring_buffer_event * |
2316 | rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs) |
2317 | { |
2318 | if (abs) |
2319 | event->type_len = RINGBUF_TYPE_TIME_STAMP; |
2320 | else |
2321 | event->type_len = RINGBUF_TYPE_TIME_EXTEND; |
2322 | |
2323 | /* Not the first event on the page, or not delta? */ |
2324 | if (abs || rb_event_index(event)) { |
2325 | event->time_delta = delta & TS_MASK; |
2326 | event->array[0] = delta >> TS_SHIFT; |
2327 | } else { |
2328 | /* nope, just zero it */ |
2329 | event->time_delta = 0; |
2330 | event->array[0] = 0; |
2331 | } |
2332 | |
2333 | return skip_time_extend(event); |
2334 | } |
2335 | |
2336 | static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2337 | struct ring_buffer_event *event); |
2338 | |
2339 | /** |
2340 | * rb_update_event - update event type and data |
2341 | * @event: the event to update |
2342 | * @type: the type of event |
2343 | * @length: the size of the event field in the ring buffer |
2344 | * |
2345 | * Update the type and data fields of the event. The length |
2346 | * is the actual size that is written to the ring buffer, |
2347 | * and with this, we can determine what to place into the |
2348 | * data field. |
2349 | */ |
2350 | static void |
2351 | rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
2352 | struct ring_buffer_event *event, |
2353 | struct rb_event_info *info) |
2354 | { |
2355 | unsigned length = info->length; |
2356 | u64 delta = info->delta; |
2357 | |
2358 | /* Only a commit updates the timestamp */ |
2359 | if (unlikely(!rb_event_is_commit(cpu_buffer, event))) |
2360 | delta = 0; |
2361 | |
2362 | /* |
2363 | * If we need to add a timestamp, then we |
2364 | * add it to the start of the reserved space. |
2365 | */ |
2366 | if (unlikely(info->add_timestamp)) { |
2367 | bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer); |
2368 | |
2369 | event = rb_add_time_stamp(event, info->delta, abs); |
2370 | length -= RB_LEN_TIME_EXTEND; |
2371 | delta = 0; |
2372 | } |
2373 | |
2374 | event->time_delta = delta; |
2375 | length -= RB_EVNT_HDR_SIZE; |
2376 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { |
2377 | event->type_len = 0; |
2378 | event->array[0] = length; |
2379 | } else |
2380 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); |
2381 | } |
2382 | |
2383 | static unsigned rb_calculate_event_length(unsigned length) |
2384 | { |
2385 | struct ring_buffer_event event; /* Used only for sizeof array */ |
2386 | |
2387 | /* zero length can cause confusions */ |
2388 | if (!length) |
2389 | length++; |
2390 | |
2391 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
2392 | length += sizeof(event.array[0]); |
2393 | |
2394 | length += RB_EVNT_HDR_SIZE; |
2395 | length = ALIGN(length, RB_ARCH_ALIGNMENT); |
2396 | |
2397 | /* |
2398 | * In case the time delta is larger than the 27 bits for it |
2399 | * in the header, we need to add a timestamp. If another |
2400 | * event comes in when trying to discard this one to increase |
2401 | * the length, then the timestamp will be added in the allocated |
2402 | * space of this event. If length is bigger than the size needed |
2403 | * for the TIME_EXTEND, then padding has to be used. The events |
2404 | * length must be either RB_LEN_TIME_EXTEND, or greater than or equal |
2405 | * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. |
2406 | * As length is a multiple of 4, we only need to worry if it |
2407 | * is 12 (RB_LEN_TIME_EXTEND + 4). |
2408 | */ |
2409 | if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) |
2410 | length += RB_ALIGNMENT; |
2411 | |
2412 | return length; |
2413 | } |
2414 | |
2415 | #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK |
2416 | static inline bool sched_clock_stable(void) |
2417 | { |
2418 | return true; |
2419 | } |
2420 | #endif |
2421 | |
2422 | static inline int |
2423 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, |
2424 | struct ring_buffer_event *event) |
2425 | { |
2426 | unsigned long new_index, old_index; |
2427 | struct buffer_page *bpage; |
2428 | unsigned long index; |
2429 | unsigned long addr; |
2430 | |
2431 | new_index = rb_event_index(event); |
2432 | old_index = new_index + rb_event_ts_length(event); |
2433 | addr = (unsigned long)event; |
2434 | addr &= PAGE_MASK; |
2435 | |
2436 | bpage = READ_ONCE(cpu_buffer->tail_page); |
2437 | |
2438 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { |
2439 | unsigned long write_mask = |
2440 | local_read(&bpage->write) & ~RB_WRITE_MASK; |
2441 | unsigned long event_length = rb_event_length(event); |
2442 | /* |
2443 | * This is on the tail page. It is possible that |
2444 | * a write could come in and move the tail page |
2445 | * and write to the next page. That is fine |
2446 | * because we just shorten what is on this page. |
2447 | */ |
2448 | old_index += write_mask; |
2449 | new_index += write_mask; |
2450 | index = local_cmpxchg(&bpage->write, old_index, new_index); |
2451 | if (index == old_index) { |
2452 | /* update counters */ |
2453 | local_sub(event_length, &cpu_buffer->entries_bytes); |
2454 | return 1; |
2455 | } |
2456 | } |
2457 | |
2458 | /* could not discard */ |
2459 | return 0; |
2460 | } |
2461 | |
2462 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2463 | { |
2464 | local_inc(&cpu_buffer->committing); |
2465 | local_inc(&cpu_buffer->commits); |
2466 | } |
2467 | |
2468 | static __always_inline void |
2469 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
2470 | { |
2471 | unsigned long max_count; |
2472 | |
2473 | /* |
2474 | * We only race with interrupts and NMIs on this CPU. |
2475 | * If we own the commit event, then we can commit |
2476 | * all others that interrupted us, since the interruptions |
2477 | * are in stack format (they finish before they come |
2478 | * back to us). This allows us to do a simple loop to |
2479 | * assign the commit to the tail. |
2480 | */ |
2481 | again: |
2482 | max_count = cpu_buffer->nr_pages * 100; |
2483 | |
2484 | while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { |
2485 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
2486 | return; |
2487 | if (RB_WARN_ON(cpu_buffer, |
2488 | rb_is_reader_page(cpu_buffer->tail_page))) |
2489 | return; |
2490 | local_set(&cpu_buffer->commit_page->page->commit, |
2491 | rb_page_write(cpu_buffer->commit_page)); |
2492 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); |
2493 | /* Only update the write stamp if the page has an event */ |
2494 | if (rb_page_write(cpu_buffer->commit_page)) |
2495 | cpu_buffer->write_stamp = |
2496 | cpu_buffer->commit_page->page->time_stamp; |
2497 | /* add barrier to keep gcc from optimizing too much */ |
2498 | barrier(); |
2499 | } |
2500 | while (rb_commit_index(cpu_buffer) != |
2501 | rb_page_write(cpu_buffer->commit_page)) { |
2502 | |
2503 | local_set(&cpu_buffer->commit_page->page->commit, |
2504 | rb_page_write(cpu_buffer->commit_page)); |
2505 | RB_WARN_ON(cpu_buffer, |
2506 | local_read(&cpu_buffer->commit_page->page->commit) & |
2507 | ~RB_WRITE_MASK); |
2508 | barrier(); |
2509 | } |
2510 | |
2511 | /* again, keep gcc from optimizing */ |
2512 | barrier(); |
2513 | |
2514 | /* |
2515 | * If an interrupt came in just after the first while loop |
2516 | * and pushed the tail page forward, we will be left with |
2517 | * a dangling commit that will never go forward. |
2518 | */ |
2519 | if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) |
2520 | goto again; |
2521 | } |
2522 | |
2523 | static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2524 | { |
2525 | unsigned long commits; |
2526 | |
2527 | if (RB_WARN_ON(cpu_buffer, |
2528 | !local_read(&cpu_buffer->committing))) |
2529 | return; |
2530 | |
2531 | again: |
2532 | commits = local_read(&cpu_buffer->commits); |
2533 | /* synchronize with interrupts */ |
2534 | barrier(); |
2535 | if (local_read(&cpu_buffer->committing) == 1) |
2536 | rb_set_commit_to_write(cpu_buffer); |
2537 | |
2538 | local_dec(&cpu_buffer->committing); |
2539 | |
2540 | /* synchronize with interrupts */ |
2541 | barrier(); |
2542 | |
2543 | /* |
2544 | * Need to account for interrupts coming in between the |
2545 | * updating of the commit page and the clearing of the |
2546 | * committing counter. |
2547 | */ |
2548 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && |
2549 | !local_read(&cpu_buffer->committing)) { |
2550 | local_inc(&cpu_buffer->committing); |
2551 | goto again; |
2552 | } |
2553 | } |
2554 | |
2555 | static inline void rb_event_discard(struct ring_buffer_event *event) |
2556 | { |
2557 | if (extended_time(event)) |
2558 | event = skip_time_extend(event); |
2559 | |
2560 | /* array[0] holds the actual length for the discarded event */ |
2561 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; |
2562 | event->type_len = RINGBUF_TYPE_PADDING; |
2563 | /* time delta must be non zero */ |
2564 | if (!event->time_delta) |
2565 | event->time_delta = 1; |
2566 | } |
2567 | |
2568 | static __always_inline bool |
2569 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2570 | struct ring_buffer_event *event) |
2571 | { |
2572 | unsigned long addr = (unsigned long)event; |
2573 | unsigned long index; |
2574 | |
2575 | index = rb_event_index(event); |
2576 | addr &= PAGE_MASK; |
2577 | |
2578 | return cpu_buffer->commit_page->page == (void *)addr && |
2579 | rb_commit_index(cpu_buffer) == index; |
2580 | } |
2581 | |
2582 | static __always_inline void |
2583 | rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
2584 | struct ring_buffer_event *event) |
2585 | { |
2586 | u64 delta; |
2587 | |
2588 | /* |
2589 | * The event first in the commit queue updates the |
2590 | * time stamp. |
2591 | */ |
2592 | if (rb_event_is_commit(cpu_buffer, event)) { |
2593 | /* |
2594 | * A commit event that is first on a page |
2595 | * updates the write timestamp with the page stamp |
2596 | */ |
2597 | if (!rb_event_index(event)) |
2598 | cpu_buffer->write_stamp = |
2599 | cpu_buffer->commit_page->page->time_stamp; |
2600 | else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { |
2601 | delta = ring_buffer_event_time_stamp(event); |
2602 | cpu_buffer->write_stamp += delta; |
2603 | } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) { |
2604 | delta = ring_buffer_event_time_stamp(event); |
2605 | cpu_buffer->write_stamp = delta; |
2606 | } else |
2607 | cpu_buffer->write_stamp += event->time_delta; |
2608 | } |
2609 | } |
2610 | |
2611 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2612 | struct ring_buffer_event *event) |
2613 | { |
2614 | local_inc(&cpu_buffer->entries); |
2615 | rb_update_write_stamp(cpu_buffer, event); |
2616 | rb_end_commit(cpu_buffer); |
2617 | } |
2618 | |
2619 | static __always_inline void |
2620 | rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) |
2621 | { |
2622 | size_t nr_pages; |
2623 | size_t dirty; |
2624 | size_t full; |
2625 | |
2626 | if (buffer->irq_work.waiters_pending) { |
2627 | buffer->irq_work.waiters_pending = false; |
2628 | /* irq_work_queue() supplies it's own memory barriers */ |
2629 | irq_work_queue(&buffer->irq_work.work); |
2630 | } |
2631 | |
2632 | if (cpu_buffer->irq_work.waiters_pending) { |
2633 | cpu_buffer->irq_work.waiters_pending = false; |
2634 | /* irq_work_queue() supplies it's own memory barriers */ |
2635 | irq_work_queue(&cpu_buffer->irq_work.work); |
2636 | } |
2637 | |
2638 | if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) |
2639 | return; |
2640 | |
2641 | if (cpu_buffer->reader_page == cpu_buffer->commit_page) |
2642 | return; |
2643 | |
2644 | if (!cpu_buffer->irq_work.full_waiters_pending) |
2645 | return; |
2646 | |
2647 | cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched); |
2648 | |
2649 | full = cpu_buffer->shortest_full; |
2650 | nr_pages = cpu_buffer->nr_pages; |
2651 | dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu); |
2652 | if (full && nr_pages && (dirty * 100) <= full * nr_pages) |
2653 | return; |
2654 | |
2655 | cpu_buffer->irq_work.wakeup_full = true; |
2656 | cpu_buffer->irq_work.full_waiters_pending = false; |
2657 | /* irq_work_queue() supplies it's own memory barriers */ |
2658 | irq_work_queue(&cpu_buffer->irq_work.work); |
2659 | } |
2660 | |
2661 | /* |
2662 | * The lock and unlock are done within a preempt disable section. |
2663 | * The current_context per_cpu variable can only be modified |
2664 | * by the current task between lock and unlock. But it can |
2665 | * be modified more than once via an interrupt. To pass this |
2666 | * information from the lock to the unlock without having to |
2667 | * access the 'in_interrupt()' functions again (which do show |
2668 | * a bit of overhead in something as critical as function tracing, |
2669 | * we use a bitmask trick. |
2670 | * |
2671 | * bit 0 = NMI context |
2672 | * bit 1 = IRQ context |
2673 | * bit 2 = SoftIRQ context |
2674 | * bit 3 = normal context. |
2675 | * |
2676 | * This works because this is the order of contexts that can |
2677 | * preempt other contexts. A SoftIRQ never preempts an IRQ |
2678 | * context. |
2679 | * |
2680 | * When the context is determined, the corresponding bit is |
2681 | * checked and set (if it was set, then a recursion of that context |
2682 | * happened). |
2683 | * |
2684 | * On unlock, we need to clear this bit. To do so, just subtract |
2685 | * 1 from the current_context and AND it to itself. |
2686 | * |
2687 | * (binary) |
2688 | * 101 - 1 = 100 |
2689 | * 101 & 100 = 100 (clearing bit zero) |
2690 | * |
2691 | * 1010 - 1 = 1001 |
2692 | * 1010 & 1001 = 1000 (clearing bit 1) |
2693 | * |
2694 | * The least significant bit can be cleared this way, and it |
2695 | * just so happens that it is the same bit corresponding to |
2696 | * the current context. |
2697 | */ |
2698 | |
2699 | static __always_inline int |
2700 | trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) |
2701 | { |
2702 | unsigned int val = cpu_buffer->current_context; |
2703 | unsigned long pc = preempt_count(); |
2704 | int bit; |
2705 | |
2706 | if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) |
2707 | bit = RB_CTX_NORMAL; |
2708 | else |
2709 | bit = pc & NMI_MASK ? RB_CTX_NMI : |
2710 | pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ; |
2711 | |
2712 | if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) |
2713 | return 1; |
2714 | |
2715 | val |= (1 << (bit + cpu_buffer->nest)); |
2716 | cpu_buffer->current_context = val; |
2717 | |
2718 | return 0; |
2719 | } |
2720 | |
2721 | static __always_inline void |
2722 | trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) |
2723 | { |
2724 | cpu_buffer->current_context &= |
2725 | cpu_buffer->current_context - (1 << cpu_buffer->nest); |
2726 | } |
2727 | |
2728 | /* The recursive locking above uses 4 bits */ |
2729 | #define NESTED_BITS 4 |
2730 | |
2731 | /** |
2732 | * ring_buffer_nest_start - Allow to trace while nested |
2733 | * @buffer: The ring buffer to modify |
2734 | * |
2735 | * The ring buffer has a safety mechanism to prevent recursion. |
2736 | * But there may be a case where a trace needs to be done while |
2737 | * tracing something else. In this case, calling this function |
2738 | * will allow this function to nest within a currently active |
2739 | * ring_buffer_lock_reserve(). |
2740 | * |
2741 | * Call this function before calling another ring_buffer_lock_reserve() and |
2742 | * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). |
2743 | */ |
2744 | void ring_buffer_nest_start(struct ring_buffer *buffer) |
2745 | { |
2746 | struct ring_buffer_per_cpu *cpu_buffer; |
2747 | int cpu; |
2748 | |
2749 | /* Enabled by ring_buffer_nest_end() */ |
2750 | preempt_disable_notrace(); |
2751 | cpu = raw_smp_processor_id(); |
2752 | cpu_buffer = buffer->buffers[cpu]; |
2753 | /* This is the shift value for the above recursive locking */ |
2754 | cpu_buffer->nest += NESTED_BITS; |
2755 | } |
2756 | |
2757 | /** |
2758 | * ring_buffer_nest_end - Allow to trace while nested |
2759 | * @buffer: The ring buffer to modify |
2760 | * |
2761 | * Must be called after ring_buffer_nest_start() and after the |
2762 | * ring_buffer_unlock_commit(). |
2763 | */ |
2764 | void ring_buffer_nest_end(struct ring_buffer *buffer) |
2765 | { |
2766 | struct ring_buffer_per_cpu *cpu_buffer; |
2767 | int cpu; |
2768 | |
2769 | /* disabled by ring_buffer_nest_start() */ |
2770 | cpu = raw_smp_processor_id(); |
2771 | cpu_buffer = buffer->buffers[cpu]; |
2772 | /* This is the shift value for the above recursive locking */ |
2773 | cpu_buffer->nest -= NESTED_BITS; |
2774 | preempt_enable_notrace(); |
2775 | } |
2776 | |
2777 | /** |
2778 | * ring_buffer_unlock_commit - commit a reserved |
2779 | * @buffer: The buffer to commit to |
2780 | * @event: The event pointer to commit. |
2781 | * |
2782 | * This commits the data to the ring buffer, and releases any locks held. |
2783 | * |
2784 | * Must be paired with ring_buffer_lock_reserve. |
2785 | */ |
2786 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, |
2787 | struct ring_buffer_event *event) |
2788 | { |
2789 | struct ring_buffer_per_cpu *cpu_buffer; |
2790 | int cpu = raw_smp_processor_id(); |
2791 | |
2792 | cpu_buffer = buffer->buffers[cpu]; |
2793 | |
2794 | rb_commit(cpu_buffer, event); |
2795 | |
2796 | rb_wakeups(buffer, cpu_buffer); |
2797 | |
2798 | trace_recursive_unlock(cpu_buffer); |
2799 | |
2800 | preempt_enable_notrace(); |
2801 | |
2802 | return 0; |
2803 | } |
2804 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
2805 | |
2806 | static noinline void |
2807 | rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer, |
2808 | struct rb_event_info *info) |
2809 | { |
2810 | WARN_ONCE(info->delta > (1ULL << 59), |
2811 | KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s" , |
2812 | (unsigned long long)info->delta, |
2813 | (unsigned long long)info->ts, |
2814 | (unsigned long long)cpu_buffer->write_stamp, |
2815 | sched_clock_stable() ? "" : |
2816 | "If you just came from a suspend/resume,\n" |
2817 | "please switch to the trace global clock:\n" |
2818 | " echo global > /sys/kernel/debug/tracing/trace_clock\n" |
2819 | "or add trace_clock=global to the kernel command line\n" ); |
2820 | info->add_timestamp = 1; |
2821 | } |
2822 | |
2823 | static struct ring_buffer_event * |
2824 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, |
2825 | struct rb_event_info *info) |
2826 | { |
2827 | struct ring_buffer_event *event; |
2828 | struct buffer_page *tail_page; |
2829 | unsigned long tail, write; |
2830 | |
2831 | /* |
2832 | * If the time delta since the last event is too big to |
2833 | * hold in the time field of the event, then we append a |
2834 | * TIME EXTEND event ahead of the data event. |
2835 | */ |
2836 | if (unlikely(info->add_timestamp)) |
2837 | info->length += RB_LEN_TIME_EXTEND; |
2838 | |
2839 | /* Don't let the compiler play games with cpu_buffer->tail_page */ |
2840 | tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); |
2841 | write = local_add_return(info->length, &tail_page->write); |
2842 | |
2843 | /* set write to only the index of the write */ |
2844 | write &= RB_WRITE_MASK; |
2845 | tail = write - info->length; |
2846 | |
2847 | /* |
2848 | * If this is the first commit on the page, then it has the same |
2849 | * timestamp as the page itself. |
2850 | */ |
2851 | if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer)) |
2852 | info->delta = 0; |
2853 | |
2854 | /* See if we shot pass the end of this buffer page */ |
2855 | if (unlikely(write > BUF_PAGE_SIZE)) |
2856 | return rb_move_tail(cpu_buffer, tail, info); |
2857 | |
2858 | /* We reserved something on the buffer */ |
2859 | |
2860 | event = __rb_page_index(tail_page, tail); |
2861 | rb_update_event(cpu_buffer, event, info); |
2862 | |
2863 | local_inc(&tail_page->entries); |
2864 | |
2865 | /* |
2866 | * If this is the first commit on the page, then update |
2867 | * its timestamp. |
2868 | */ |
2869 | if (!tail) |
2870 | tail_page->page->time_stamp = info->ts; |
2871 | |
2872 | /* account for these added bytes */ |
2873 | local_add(info->length, &cpu_buffer->entries_bytes); |
2874 | |
2875 | return event; |
2876 | } |
2877 | |
2878 | static __always_inline struct ring_buffer_event * |
2879 | rb_reserve_next_event(struct ring_buffer *buffer, |
2880 | struct ring_buffer_per_cpu *cpu_buffer, |
2881 | unsigned long length) |
2882 | { |
2883 | struct ring_buffer_event *event; |
2884 | struct rb_event_info info; |
2885 | int nr_loops = 0; |
2886 | u64 diff; |
2887 | |
2888 | rb_start_commit(cpu_buffer); |
2889 | |
2890 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
2891 | /* |
2892 | * Due to the ability to swap a cpu buffer from a buffer |
2893 | * it is possible it was swapped before we committed. |
2894 | * (committing stops a swap). We check for it here and |
2895 | * if it happened, we have to fail the write. |
2896 | */ |
2897 | barrier(); |
2898 | if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { |
2899 | local_dec(&cpu_buffer->committing); |
2900 | local_dec(&cpu_buffer->commits); |
2901 | return NULL; |
2902 | } |
2903 | #endif |
2904 | |
2905 | info.length = rb_calculate_event_length(length); |
2906 | again: |
2907 | info.add_timestamp = 0; |
2908 | info.delta = 0; |
2909 | |
2910 | /* |
2911 | * We allow for interrupts to reenter here and do a trace. |
2912 | * If one does, it will cause this original code to loop |
2913 | * back here. Even with heavy interrupts happening, this |
2914 | * should only happen a few times in a row. If this happens |
2915 | * 1000 times in a row, there must be either an interrupt |
2916 | * storm or we have something buggy. |
2917 | * Bail! |
2918 | */ |
2919 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
2920 | goto out_fail; |
2921 | |
2922 | info.ts = rb_time_stamp(cpu_buffer->buffer); |
2923 | diff = info.ts - cpu_buffer->write_stamp; |
2924 | |
2925 | /* make sure this diff is calculated here */ |
2926 | barrier(); |
2927 | |
2928 | if (ring_buffer_time_stamp_abs(buffer)) { |
2929 | info.delta = info.ts; |
2930 | rb_handle_timestamp(cpu_buffer, &info); |
2931 | } else /* Did the write stamp get updated already? */ |
2932 | if (likely(info.ts >= cpu_buffer->write_stamp)) { |
2933 | info.delta = diff; |
2934 | if (unlikely(test_time_stamp(info.delta))) |
2935 | rb_handle_timestamp(cpu_buffer, &info); |
2936 | } |
2937 | |
2938 | event = __rb_reserve_next(cpu_buffer, &info); |
2939 | |
2940 | if (unlikely(PTR_ERR(event) == -EAGAIN)) { |
2941 | if (info.add_timestamp) |
2942 | info.length -= RB_LEN_TIME_EXTEND; |
2943 | goto again; |
2944 | } |
2945 | |
2946 | if (!event) |
2947 | goto out_fail; |
2948 | |
2949 | return event; |
2950 | |
2951 | out_fail: |
2952 | rb_end_commit(cpu_buffer); |
2953 | return NULL; |
2954 | } |
2955 | |
2956 | /** |
2957 | * ring_buffer_lock_reserve - reserve a part of the buffer |
2958 | * @buffer: the ring buffer to reserve from |
2959 | * @length: the length of the data to reserve (excluding event header) |
2960 | * |
2961 | * Returns a reserved event on the ring buffer to copy directly to. |
2962 | * The user of this interface will need to get the body to write into |
2963 | * and can use the ring_buffer_event_data() interface. |
2964 | * |
2965 | * The length is the length of the data needed, not the event length |
2966 | * which also includes the event header. |
2967 | * |
2968 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. |
2969 | * If NULL is returned, then nothing has been allocated or locked. |
2970 | */ |
2971 | struct ring_buffer_event * |
2972 | ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
2973 | { |
2974 | struct ring_buffer_per_cpu *cpu_buffer; |
2975 | struct ring_buffer_event *event; |
2976 | int cpu; |
2977 | |
2978 | /* If we are tracing schedule, we don't want to recurse */ |
2979 | preempt_disable_notrace(); |
2980 | |
2981 | if (unlikely(atomic_read(&buffer->record_disabled))) |
2982 | goto out; |
2983 | |
2984 | cpu = raw_smp_processor_id(); |
2985 | |
2986 | if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
2987 | goto out; |
2988 | |
2989 | cpu_buffer = buffer->buffers[cpu]; |
2990 | |
2991 | if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
2992 | goto out; |
2993 | |
2994 | if (unlikely(length > BUF_MAX_DATA_SIZE)) |
2995 | goto out; |
2996 | |
2997 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
2998 | goto out; |
2999 | |
3000 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
3001 | if (!event) |
3002 | goto out_unlock; |
3003 | |
3004 | return event; |
3005 | |
3006 | out_unlock: |
3007 | trace_recursive_unlock(cpu_buffer); |
3008 | out: |
3009 | preempt_enable_notrace(); |
3010 | return NULL; |
3011 | } |
3012 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
3013 | |
3014 | /* |
3015 | * Decrement the entries to the page that an event is on. |
3016 | * The event does not even need to exist, only the pointer |
3017 | * to the page it is on. This may only be called before the commit |
3018 | * takes place. |
3019 | */ |
3020 | static inline void |
3021 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, |
3022 | struct ring_buffer_event *event) |
3023 | { |
3024 | unsigned long addr = (unsigned long)event; |
3025 | struct buffer_page *bpage = cpu_buffer->commit_page; |
3026 | struct buffer_page *start; |
3027 | |
3028 | addr &= PAGE_MASK; |
3029 | |
3030 | /* Do the likely case first */ |
3031 | if (likely(bpage->page == (void *)addr)) { |
3032 | local_dec(&bpage->entries); |
3033 | return; |
3034 | } |
3035 | |
3036 | /* |
3037 | * Because the commit page may be on the reader page we |
3038 | * start with the next page and check the end loop there. |
3039 | */ |
3040 | rb_inc_page(cpu_buffer, &bpage); |
3041 | start = bpage; |
3042 | do { |
3043 | if (bpage->page == (void *)addr) { |
3044 | local_dec(&bpage->entries); |
3045 | return; |
3046 | } |
3047 | rb_inc_page(cpu_buffer, &bpage); |
3048 | } while (bpage != start); |
3049 | |
3050 | /* commit not part of this buffer?? */ |
3051 | RB_WARN_ON(cpu_buffer, 1); |
3052 | } |
3053 | |
3054 | /** |
3055 | * ring_buffer_commit_discard - discard an event that has not been committed |
3056 | * @buffer: the ring buffer |
3057 | * @event: non committed event to discard |
3058 | * |
3059 | * Sometimes an event that is in the ring buffer needs to be ignored. |
3060 | * This function lets the user discard an event in the ring buffer |
3061 | * and then that event will not be read later. |
3062 | * |
3063 | * This function only works if it is called before the item has been |
3064 | * committed. It will try to free the event from the ring buffer |
3065 | * if another event has not been added behind it. |
3066 | * |
3067 | * If another event has been added behind it, it will set the event |
3068 | * up as discarded, and perform the commit. |
3069 | * |
3070 | * If this function is called, do not call ring_buffer_unlock_commit on |
3071 | * the event. |
3072 | */ |
3073 | void ring_buffer_discard_commit(struct ring_buffer *buffer, |
3074 | struct ring_buffer_event *event) |
3075 | { |
3076 | struct ring_buffer_per_cpu *cpu_buffer; |
3077 | int cpu; |
3078 | |
3079 | /* The event is discarded regardless */ |
3080 | rb_event_discard(event); |
3081 | |
3082 | cpu = smp_processor_id(); |
3083 | cpu_buffer = buffer->buffers[cpu]; |
3084 | |
3085 | /* |
3086 | * This must only be called if the event has not been |
3087 | * committed yet. Thus we can assume that preemption |
3088 | * is still disabled. |
3089 | */ |
3090 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
3091 | |
3092 | rb_decrement_entry(cpu_buffer, event); |
3093 | if (rb_try_to_discard(cpu_buffer, event)) |
3094 | goto out; |
3095 | |
3096 | /* |
3097 | * The commit is still visible by the reader, so we |
3098 | * must still update the timestamp. |
3099 | */ |
3100 | rb_update_write_stamp(cpu_buffer, event); |
3101 | out: |
3102 | rb_end_commit(cpu_buffer); |
3103 | |
3104 | trace_recursive_unlock(cpu_buffer); |
3105 | |
3106 | preempt_enable_notrace(); |
3107 | |
3108 | } |
3109 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); |
3110 | |
3111 | /** |
3112 | * ring_buffer_write - write data to the buffer without reserving |
3113 | * @buffer: The ring buffer to write to. |
3114 | * @length: The length of the data being written (excluding the event header) |
3115 | * @data: The data to write to the buffer. |
3116 | * |
3117 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as |
3118 | * one function. If you already have the data to write to the buffer, it |
3119 | * may be easier to simply call this function. |
3120 | * |
3121 | * Note, like ring_buffer_lock_reserve, the length is the length of the data |
3122 | * and not the length of the event which would hold the header. |
3123 | */ |
3124 | int ring_buffer_write(struct ring_buffer *buffer, |
3125 | unsigned long length, |
3126 | void *data) |
3127 | { |
3128 | struct ring_buffer_per_cpu *cpu_buffer; |
3129 | struct ring_buffer_event *event; |
3130 | void *body; |
3131 | int ret = -EBUSY; |
3132 | int cpu; |
3133 | |
3134 | preempt_disable_notrace(); |
3135 | |
3136 | if (atomic_read(&buffer->record_disabled)) |
3137 | goto out; |
3138 | |
3139 | cpu = raw_smp_processor_id(); |
3140 | |
3141 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3142 | goto out; |
3143 | |
3144 | cpu_buffer = buffer->buffers[cpu]; |
3145 | |
3146 | if (atomic_read(&cpu_buffer->record_disabled)) |
3147 | goto out; |
3148 | |
3149 | if (length > BUF_MAX_DATA_SIZE) |
3150 | goto out; |
3151 | |
3152 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
3153 | goto out; |
3154 | |
3155 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
3156 | if (!event) |
3157 | goto out_unlock; |
3158 | |
3159 | body = rb_event_data(event); |
3160 | |
3161 | memcpy(body, data, length); |
3162 | |
3163 | rb_commit(cpu_buffer, event); |
3164 | |
3165 | rb_wakeups(buffer, cpu_buffer); |
3166 | |
3167 | ret = 0; |
3168 | |
3169 | out_unlock: |
3170 | trace_recursive_unlock(cpu_buffer); |
3171 | |
3172 | out: |
3173 | preempt_enable_notrace(); |
3174 | |
3175 | return ret; |
3176 | } |
3177 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
3178 | |
3179 | static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
3180 | { |
3181 | struct buffer_page *reader = cpu_buffer->reader_page; |
3182 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
3183 | struct buffer_page *commit = cpu_buffer->commit_page; |
3184 | |
3185 | /* In case of error, head will be NULL */ |
3186 | if (unlikely(!head)) |
3187 | return true; |
3188 | |
3189 | return reader->read == rb_page_commit(reader) && |
3190 | (commit == reader || |
3191 | (commit == head && |
3192 | head->read == rb_page_commit(commit))); |
3193 | } |
3194 | |
3195 | /** |
3196 | * ring_buffer_record_disable - stop all writes into the buffer |
3197 | * @buffer: The ring buffer to stop writes to. |
3198 | * |
3199 | * This prevents all writes to the buffer. Any attempt to write |
3200 | * to the buffer after this will fail and return NULL. |
3201 | * |
3202 | * The caller should call synchronize_rcu() after this. |
3203 | */ |
3204 | void ring_buffer_record_disable(struct ring_buffer *buffer) |
3205 | { |
3206 | atomic_inc(&buffer->record_disabled); |
3207 | } |
3208 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
3209 | |
3210 | /** |
3211 | * ring_buffer_record_enable - enable writes to the buffer |
3212 | * @buffer: The ring buffer to enable writes |
3213 | * |
3214 | * Note, multiple disables will need the same number of enables |
3215 | * to truly enable the writing (much like preempt_disable). |
3216 | */ |
3217 | void ring_buffer_record_enable(struct ring_buffer *buffer) |
3218 | { |
3219 | atomic_dec(&buffer->record_disabled); |
3220 | } |
3221 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
3222 | |
3223 | /** |
3224 | * ring_buffer_record_off - stop all writes into the buffer |
3225 | * @buffer: The ring buffer to stop writes to. |
3226 | * |
3227 | * This prevents all writes to the buffer. Any attempt to write |
3228 | * to the buffer after this will fail and return NULL. |
3229 | * |
3230 | * This is different than ring_buffer_record_disable() as |
3231 | * it works like an on/off switch, where as the disable() version |
3232 | * must be paired with a enable(). |
3233 | */ |
3234 | void ring_buffer_record_off(struct ring_buffer *buffer) |
3235 | { |
3236 | unsigned int rd; |
3237 | unsigned int new_rd; |
3238 | |
3239 | do { |
3240 | rd = atomic_read(&buffer->record_disabled); |
3241 | new_rd = rd | RB_BUFFER_OFF; |
3242 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); |
3243 | } |
3244 | EXPORT_SYMBOL_GPL(ring_buffer_record_off); |
3245 | |
3246 | /** |
3247 | * ring_buffer_record_on - restart writes into the buffer |
3248 | * @buffer: The ring buffer to start writes to. |
3249 | * |
3250 | * This enables all writes to the buffer that was disabled by |
3251 | * ring_buffer_record_off(). |
3252 | * |
3253 | * This is different than ring_buffer_record_enable() as |
3254 | * it works like an on/off switch, where as the enable() version |
3255 | * must be paired with a disable(). |
3256 | */ |
3257 | void ring_buffer_record_on(struct ring_buffer *buffer) |
3258 | { |
3259 | unsigned int rd; |
3260 | unsigned int new_rd; |
3261 | |
3262 | do { |
3263 | rd = atomic_read(&buffer->record_disabled); |
3264 | new_rd = rd & ~RB_BUFFER_OFF; |
3265 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); |
3266 | } |
3267 | EXPORT_SYMBOL_GPL(ring_buffer_record_on); |
3268 | |
3269 | /** |
3270 | * ring_buffer_record_is_on - return true if the ring buffer can write |
3271 | * @buffer: The ring buffer to see if write is enabled |
3272 | * |
3273 | * Returns true if the ring buffer is in a state that it accepts writes. |
3274 | */ |
3275 | bool ring_buffer_record_is_on(struct ring_buffer *buffer) |
3276 | { |
3277 | return !atomic_read(&buffer->record_disabled); |
3278 | } |
3279 | |
3280 | /** |
3281 | * ring_buffer_record_is_set_on - return true if the ring buffer is set writable |
3282 | * @buffer: The ring buffer to see if write is set enabled |
3283 | * |
3284 | * Returns true if the ring buffer is set writable by ring_buffer_record_on(). |
3285 | * Note that this does NOT mean it is in a writable state. |
3286 | * |
3287 | * It may return true when the ring buffer has been disabled by |
3288 | * ring_buffer_record_disable(), as that is a temporary disabling of |
3289 | * the ring buffer. |
3290 | */ |
3291 | bool ring_buffer_record_is_set_on(struct ring_buffer *buffer) |
3292 | { |
3293 | return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); |
3294 | } |
3295 | |
3296 | /** |
3297 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer |
3298 | * @buffer: The ring buffer to stop writes to. |
3299 | * @cpu: The CPU buffer to stop |
3300 | * |
3301 | * This prevents all writes to the buffer. Any attempt to write |
3302 | * to the buffer after this will fail and return NULL. |
3303 | * |
3304 | * The caller should call synchronize_rcu() after this. |
3305 | */ |
3306 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) |
3307 | { |
3308 | struct ring_buffer_per_cpu *cpu_buffer; |
3309 | |
3310 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3311 | return; |
3312 | |
3313 | cpu_buffer = buffer->buffers[cpu]; |
3314 | atomic_inc(&cpu_buffer->record_disabled); |
3315 | } |
3316 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
3317 | |
3318 | /** |
3319 | * ring_buffer_record_enable_cpu - enable writes to the buffer |
3320 | * @buffer: The ring buffer to enable writes |
3321 | * @cpu: The CPU to enable. |
3322 | * |
3323 | * Note, multiple disables will need the same number of enables |
3324 | * to truly enable the writing (much like preempt_disable). |
3325 | */ |
3326 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) |
3327 | { |
3328 | struct ring_buffer_per_cpu *cpu_buffer; |
3329 | |
3330 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3331 | return; |
3332 | |
3333 | cpu_buffer = buffer->buffers[cpu]; |
3334 | atomic_dec(&cpu_buffer->record_disabled); |
3335 | } |
3336 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
3337 | |
3338 | /* |
3339 | * The total entries in the ring buffer is the running counter |
3340 | * of entries entered into the ring buffer, minus the sum of |
3341 | * the entries read from the ring buffer and the number of |
3342 | * entries that were overwritten. |
3343 | */ |
3344 | static inline unsigned long |
3345 | rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) |
3346 | { |
3347 | return local_read(&cpu_buffer->entries) - |
3348 | (local_read(&cpu_buffer->overrun) + cpu_buffer->read); |
3349 | } |
3350 | |
3351 | /** |
3352 | * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer |
3353 | * @buffer: The ring buffer |
3354 | * @cpu: The per CPU buffer to read from. |
3355 | */ |
3356 | u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) |
3357 | { |
3358 | unsigned long flags; |
3359 | struct ring_buffer_per_cpu *cpu_buffer; |
3360 | struct buffer_page *bpage; |
3361 | u64 ret = 0; |
3362 | |
3363 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3364 | return 0; |
3365 | |
3366 | cpu_buffer = buffer->buffers[cpu]; |
3367 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3368 | /* |
3369 | * if the tail is on reader_page, oldest time stamp is on the reader |
3370 | * page |
3371 | */ |
3372 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) |
3373 | bpage = cpu_buffer->reader_page; |
3374 | else |
3375 | bpage = rb_set_head_page(cpu_buffer); |
3376 | if (bpage) |
3377 | ret = bpage->page->time_stamp; |
3378 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3379 | |
3380 | return ret; |
3381 | } |
3382 | EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); |
3383 | |
3384 | /** |
3385 | * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer |
3386 | * @buffer: The ring buffer |
3387 | * @cpu: The per CPU buffer to read from. |
3388 | */ |
3389 | unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu) |
3390 | { |
3391 | struct ring_buffer_per_cpu *cpu_buffer; |
3392 | unsigned long ret; |
3393 | |
3394 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3395 | return 0; |
3396 | |
3397 | cpu_buffer = buffer->buffers[cpu]; |
3398 | ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; |
3399 | |
3400 | return ret; |
3401 | } |
3402 | EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); |
3403 | |
3404 | /** |
3405 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer |
3406 | * @buffer: The ring buffer |
3407 | * @cpu: The per CPU buffer to get the entries from. |
3408 | */ |
3409 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) |
3410 | { |
3411 | struct ring_buffer_per_cpu *cpu_buffer; |
3412 | |
3413 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3414 | return 0; |
3415 | |
3416 | cpu_buffer = buffer->buffers[cpu]; |
3417 | |
3418 | return rb_num_of_entries(cpu_buffer); |
3419 | } |
3420 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
3421 | |
3422 | /** |
3423 | * ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
3424 | * buffer wrapping around (only if RB_FL_OVERWRITE is on). |
3425 | * @buffer: The ring buffer |
3426 | * @cpu: The per CPU buffer to get the number of overruns from |
3427 | */ |
3428 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) |
3429 | { |
3430 | struct ring_buffer_per_cpu *cpu_buffer; |
3431 | unsigned long ret; |
3432 | |
3433 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3434 | return 0; |
3435 | |
3436 | cpu_buffer = buffer->buffers[cpu]; |
3437 | ret = local_read(&cpu_buffer->overrun); |
3438 | |
3439 | return ret; |
3440 | } |
3441 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
3442 | |
3443 | /** |
3444 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by |
3445 | * commits failing due to the buffer wrapping around while there are uncommitted |
3446 | * events, such as during an interrupt storm. |
3447 | * @buffer: The ring buffer |
3448 | * @cpu: The per CPU buffer to get the number of overruns from |
3449 | */ |
3450 | unsigned long |
3451 | ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) |
3452 | { |
3453 | struct ring_buffer_per_cpu *cpu_buffer; |
3454 | unsigned long ret; |
3455 | |
3456 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3457 | return 0; |
3458 | |
3459 | cpu_buffer = buffer->buffers[cpu]; |
3460 | ret = local_read(&cpu_buffer->commit_overrun); |
3461 | |
3462 | return ret; |
3463 | } |
3464 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); |
3465 | |
3466 | /** |
3467 | * ring_buffer_dropped_events_cpu - get the number of dropped events caused by |
3468 | * the ring buffer filling up (only if RB_FL_OVERWRITE is off). |
3469 | * @buffer: The ring buffer |
3470 | * @cpu: The per CPU buffer to get the number of overruns from |
3471 | */ |
3472 | unsigned long |
3473 | ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu) |
3474 | { |
3475 | struct ring_buffer_per_cpu *cpu_buffer; |
3476 | unsigned long ret; |
3477 | |
3478 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3479 | return 0; |
3480 | |
3481 | cpu_buffer = buffer->buffers[cpu]; |
3482 | ret = local_read(&cpu_buffer->dropped_events); |
3483 | |
3484 | return ret; |
3485 | } |
3486 | EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); |
3487 | |
3488 | /** |
3489 | * ring_buffer_read_events_cpu - get the number of events successfully read |
3490 | * @buffer: The ring buffer |
3491 | * @cpu: The per CPU buffer to get the number of events read |
3492 | */ |
3493 | unsigned long |
3494 | ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu) |
3495 | { |
3496 | struct ring_buffer_per_cpu *cpu_buffer; |
3497 | |
3498 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3499 | return 0; |
3500 | |
3501 | cpu_buffer = buffer->buffers[cpu]; |
3502 | return cpu_buffer->read; |
3503 | } |
3504 | EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); |
3505 | |
3506 | /** |
3507 | * ring_buffer_entries - get the number of entries in a buffer |
3508 | * @buffer: The ring buffer |
3509 | * |
3510 | * Returns the total number of entries in the ring buffer |
3511 | * (all CPU entries) |
3512 | */ |
3513 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) |
3514 | { |
3515 | struct ring_buffer_per_cpu *cpu_buffer; |
3516 | unsigned long entries = 0; |
3517 | int cpu; |
3518 | |
3519 | /* if you care about this being correct, lock the buffer */ |
3520 | for_each_buffer_cpu(buffer, cpu) { |
3521 | cpu_buffer = buffer->buffers[cpu]; |
3522 | entries += rb_num_of_entries(cpu_buffer); |
3523 | } |
3524 | |
3525 | return entries; |
3526 | } |
3527 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
3528 | |
3529 | /** |
3530 | * ring_buffer_overruns - get the number of overruns in buffer |
3531 | * @buffer: The ring buffer |
3532 | * |
3533 | * Returns the total number of overruns in the ring buffer |
3534 | * (all CPU entries) |
3535 | */ |
3536 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) |
3537 | { |
3538 | struct ring_buffer_per_cpu *cpu_buffer; |
3539 | unsigned long overruns = 0; |
3540 | int cpu; |
3541 | |
3542 | /* if you care about this being correct, lock the buffer */ |
3543 | for_each_buffer_cpu(buffer, cpu) { |
3544 | cpu_buffer = buffer->buffers[cpu]; |
3545 | overruns += local_read(&cpu_buffer->overrun); |
3546 | } |
3547 | |
3548 | return overruns; |
3549 | } |
3550 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
3551 | |
3552 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
3553 | { |
3554 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
3555 | |
3556 | /* Iterator usage is expected to have record disabled */ |
3557 | iter->head_page = cpu_buffer->reader_page; |
3558 | iter->head = cpu_buffer->reader_page->read; |
3559 | |
3560 | iter->cache_reader_page = iter->head_page; |
3561 | iter->cache_read = cpu_buffer->read; |
3562 | |
3563 | if (iter->head) |
3564 | iter->read_stamp = cpu_buffer->read_stamp; |
3565 | else |
3566 | iter->read_stamp = iter->head_page->page->time_stamp; |
3567 | } |
3568 | |
3569 | /** |
3570 | * ring_buffer_iter_reset - reset an iterator |
3571 | * @iter: The iterator to reset |
3572 | * |
3573 | * Resets the iterator, so that it will start from the beginning |
3574 | * again. |
3575 | */ |
3576 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) |
3577 | { |
3578 | struct ring_buffer_per_cpu *cpu_buffer; |
3579 | unsigned long flags; |
3580 | |
3581 | if (!iter) |
3582 | return; |
3583 | |
3584 | cpu_buffer = iter->cpu_buffer; |
3585 | |
3586 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3587 | rb_iter_reset(iter); |
3588 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3589 | } |
3590 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
3591 | |
3592 | /** |
3593 | * ring_buffer_iter_empty - check if an iterator has no more to read |
3594 | * @iter: The iterator to check |
3595 | */ |
3596 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) |
3597 | { |
3598 | struct ring_buffer_per_cpu *cpu_buffer; |
3599 | struct buffer_page *reader; |
3600 | struct buffer_page *head_page; |
3601 | struct buffer_page *commit_page; |
3602 | unsigned commit; |
3603 | |
3604 | cpu_buffer = iter->cpu_buffer; |
3605 | |
3606 | /* Remember, trace recording is off when iterator is in use */ |
3607 | reader = cpu_buffer->reader_page; |
3608 | head_page = cpu_buffer->head_page; |
3609 | commit_page = cpu_buffer->commit_page; |
3610 | commit = rb_page_commit(commit_page); |
3611 | |
3612 | return ((iter->head_page == commit_page && iter->head == commit) || |
3613 | (iter->head_page == reader && commit_page == head_page && |
3614 | head_page->read == commit && |
3615 | iter->head == rb_page_commit(cpu_buffer->reader_page))); |
3616 | } |
3617 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
3618 | |
3619 | static void |
3620 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
3621 | struct ring_buffer_event *event) |
3622 | { |
3623 | u64 delta; |
3624 | |
3625 | switch (event->type_len) { |
3626 | case RINGBUF_TYPE_PADDING: |
3627 | return; |
3628 | |
3629 | case RINGBUF_TYPE_TIME_EXTEND: |
3630 | delta = ring_buffer_event_time_stamp(event); |
3631 | cpu_buffer->read_stamp += delta; |
3632 | return; |
3633 | |
3634 | case RINGBUF_TYPE_TIME_STAMP: |
3635 | delta = ring_buffer_event_time_stamp(event); |
3636 | cpu_buffer->read_stamp = delta; |
3637 | return; |
3638 | |
3639 | case RINGBUF_TYPE_DATA: |
3640 | cpu_buffer->read_stamp += event->time_delta; |
3641 | return; |
3642 | |
3643 | default: |
3644 | BUG(); |
3645 | } |
3646 | return; |
3647 | } |
3648 | |
3649 | static void |
3650 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, |
3651 | struct ring_buffer_event *event) |
3652 | { |
3653 | u64 delta; |
3654 | |
3655 | switch (event->type_len) { |
3656 | case RINGBUF_TYPE_PADDING: |
3657 | return; |
3658 | |
3659 | case RINGBUF_TYPE_TIME_EXTEND: |
3660 | delta = ring_buffer_event_time_stamp(event); |
3661 | iter->read_stamp += delta; |
3662 | return; |
3663 | |
3664 | case RINGBUF_TYPE_TIME_STAMP: |
3665 | delta = ring_buffer_event_time_stamp(event); |
3666 | iter->read_stamp = delta; |
3667 | return; |
3668 | |
3669 | case RINGBUF_TYPE_DATA: |
3670 | iter->read_stamp += event->time_delta; |
3671 | return; |
3672 | |
3673 | default: |
3674 | BUG(); |
3675 | } |
3676 | return; |
3677 | } |
3678 | |
3679 | static struct buffer_page * |
3680 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
3681 | { |
3682 | struct buffer_page *reader = NULL; |
3683 | unsigned long overwrite; |
3684 | unsigned long flags; |
3685 | int nr_loops = 0; |
3686 | int ret; |
3687 | |
3688 | local_irq_save(flags); |
3689 | arch_spin_lock(&cpu_buffer->lock); |
3690 | |
3691 | again: |
3692 | /* |
3693 | * This should normally only loop twice. But because the |
3694 | * start of the reader inserts an empty page, it causes |
3695 | * a case where we will loop three times. There should be no |
3696 | * reason to loop four times (that I know of). |
3697 | */ |
3698 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
3699 | reader = NULL; |
3700 | goto out; |
3701 | } |
3702 | |
3703 | reader = cpu_buffer->reader_page; |
3704 | |
3705 | /* If there's more to read, return this page */ |
3706 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
3707 | goto out; |
3708 | |
3709 | /* Never should we have an index greater than the size */ |
3710 | if (RB_WARN_ON(cpu_buffer, |
3711 | cpu_buffer->reader_page->read > rb_page_size(reader))) |
3712 | goto out; |
3713 | |
3714 | /* check if we caught up to the tail */ |
3715 | reader = NULL; |
3716 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
3717 | goto out; |
3718 | |
3719 | /* Don't bother swapping if the ring buffer is empty */ |
3720 | if (rb_num_of_entries(cpu_buffer) == 0) |
3721 | goto out; |
3722 | |
3723 | /* |
3724 | * Reset the reader page to size zero. |
3725 | */ |
3726 | local_set(&cpu_buffer->reader_page->write, 0); |
3727 | local_set(&cpu_buffer->reader_page->entries, 0); |
3728 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
3729 | cpu_buffer->reader_page->real_end = 0; |
3730 | |
3731 | spin: |
3732 | /* |
3733 | * Splice the empty reader page into the list around the head. |
3734 | */ |
3735 | reader = rb_set_head_page(cpu_buffer); |
3736 | if (!reader) |
3737 | goto out; |
3738 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
3739 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
3740 | |
3741 | /* |
3742 | * cpu_buffer->pages just needs to point to the buffer, it |
3743 | * has no specific buffer page to point to. Lets move it out |
3744 | * of our way so we don't accidentally swap it. |
3745 | */ |
3746 | cpu_buffer->pages = reader->list.prev; |
3747 | |
3748 | /* The reader page will be pointing to the new head */ |
3749 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); |
3750 | |
3751 | /* |
3752 | * We want to make sure we read the overruns after we set up our |
3753 | * pointers to the next object. The writer side does a |
3754 | * cmpxchg to cross pages which acts as the mb on the writer |
3755 | * side. Note, the reader will constantly fail the swap |
3756 | * while the writer is updating the pointers, so this |
3757 | * guarantees that the overwrite recorded here is the one we |
3758 | * want to compare with the last_overrun. |
3759 | */ |
3760 | smp_mb(); |
3761 | overwrite = local_read(&(cpu_buffer->overrun)); |
3762 | |
3763 | /* |
3764 | * Here's the tricky part. |
3765 | * |
3766 | * We need to move the pointer past the header page. |
3767 | * But we can only do that if a writer is not currently |
3768 | * moving it. The page before the header page has the |
3769 | * flag bit '1' set if it is pointing to the page we want. |
3770 | * but if the writer is in the process of moving it |
3771 | * than it will be '2' or already moved '0'. |
3772 | */ |
3773 | |
3774 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); |
3775 | |
3776 | /* |
3777 | * If we did not convert it, then we must try again. |
3778 | */ |
3779 | if (!ret) |
3780 | goto spin; |
3781 | |
3782 | /* |
3783 | * Yay! We succeeded in replacing the page. |
3784 | * |
3785 | * Now make the new head point back to the reader page. |
3786 | */ |
3787 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
3788 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
3789 | |
3790 | local_inc(&cpu_buffer->pages_read); |
3791 | |
3792 | /* Finally update the reader page to the new head */ |
3793 | cpu_buffer->reader_page = reader; |
3794 | cpu_buffer->reader_page->read = 0; |
3795 | |
3796 | if (overwrite != cpu_buffer->last_overrun) { |
3797 | cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; |
3798 | cpu_buffer->last_overrun = overwrite; |
3799 | } |
3800 | |
3801 | goto again; |
3802 | |
3803 | out: |
3804 | /* Update the read_stamp on the first event */ |
3805 | if (reader && reader->read == 0) |
3806 | cpu_buffer->read_stamp = reader->page->time_stamp; |
3807 | |
3808 | arch_spin_unlock(&cpu_buffer->lock); |
3809 | local_irq_restore(flags); |
3810 | |
3811 | return reader; |
3812 | } |
3813 | |
3814 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) |
3815 | { |
3816 | struct ring_buffer_event *event; |
3817 | struct buffer_page *reader; |
3818 | unsigned length; |
3819 | |
3820 | reader = rb_get_reader_page(cpu_buffer); |
3821 | |
3822 | /* This function should not be called when buffer is empty */ |
3823 | if ( |
---|