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1 | /* |
2 | * Generic ring buffer |
3 | * |
4 | * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> |
5 | */ |
6 | #include <linux/ring_buffer.h> |
7 | #include <linux/trace_clock.h> |
8 | #include <linux/spinlock.h> |
9 | #include <linux/debugfs.h> |
10 | #include <linux/uaccess.h> |
11 | #include <linux/hardirq.h> |
12 | #include <linux/kmemcheck.h> |
13 | #include <linux/module.h> |
14 | #include <linux/percpu.h> |
15 | #include <linux/mutex.h> |
16 | #include <linux/slab.h> |
17 | #include <linux/init.h> |
18 | #include <linux/hash.h> |
19 | #include <linux/list.h> |
20 | #include <linux/cpu.h> |
21 | #include <linux/fs.h> |
22 | |
23 | #include <asm/local.h> |
24 | #include "trace.h" |
25 | |
26 | /* |
27 | * The ring buffer header is special. We must manually up keep it. |
28 | */ |
29 | int ring_buffer_print_entry_header(struct trace_seq *s) |
30 | { |
31 | int ret; |
32 | |
33 | ret = trace_seq_printf(s, "# compressed entry header\n"); |
34 | ret = trace_seq_printf(s, "\ttype_len : 5 bits\n"); |
35 | ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n"); |
36 | ret = trace_seq_printf(s, "\tarray : 32 bits\n"); |
37 | ret = trace_seq_printf(s, "\n"); |
38 | ret = trace_seq_printf(s, "\tpadding : type == %d\n", |
39 | RINGBUF_TYPE_PADDING); |
40 | ret = trace_seq_printf(s, "\ttime_extend : type == %d\n", |
41 | RINGBUF_TYPE_TIME_EXTEND); |
42 | ret = trace_seq_printf(s, "\tdata max type_len == %d\n", |
43 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
44 | |
45 | return ret; |
46 | } |
47 | |
48 | /* |
49 | * The ring buffer is made up of a list of pages. A separate list of pages is |
50 | * allocated for each CPU. A writer may only write to a buffer that is |
51 | * associated with the CPU it is currently executing on. A reader may read |
52 | * from any per cpu buffer. |
53 | * |
54 | * The reader is special. For each per cpu buffer, the reader has its own |
55 | * reader page. When a reader has read the entire reader page, this reader |
56 | * page is swapped with another page in the ring buffer. |
57 | * |
58 | * Now, as long as the writer is off the reader page, the reader can do what |
59 | * ever it wants with that page. The writer will never write to that page |
60 | * again (as long as it is out of the ring buffer). |
61 | * |
62 | * Here's some silly ASCII art. |
63 | * |
64 | * +------+ |
65 | * |reader| RING BUFFER |
66 | * |page | |
67 | * +------+ +---+ +---+ +---+ |
68 | * | |-->| |-->| | |
69 | * +---+ +---+ +---+ |
70 | * ^ | |
71 | * | | |
72 | * +---------------+ |
73 | * |
74 | * |
75 | * +------+ |
76 | * |reader| RING BUFFER |
77 | * |page |------------------v |
78 | * +------+ +---+ +---+ +---+ |
79 | * | |-->| |-->| | |
80 | * +---+ +---+ +---+ |
81 | * ^ | |
82 | * | | |
83 | * +---------------+ |
84 | * |
85 | * |
86 | * +------+ |
87 | * |reader| RING BUFFER |
88 | * |page |------------------v |
89 | * +------+ +---+ +---+ +---+ |
90 | * ^ | |-->| |-->| | |
91 | * | +---+ +---+ +---+ |
92 | * | | |
93 | * | | |
94 | * +------------------------------+ |
95 | * |
96 | * |
97 | * +------+ |
98 | * |buffer| RING BUFFER |
99 | * |page |------------------v |
100 | * +------+ +---+ +---+ +---+ |
101 | * ^ | | | |-->| | |
102 | * | New +---+ +---+ +---+ |
103 | * | Reader------^ | |
104 | * | page | |
105 | * +------------------------------+ |
106 | * |
107 | * |
108 | * After we make this swap, the reader can hand this page off to the splice |
109 | * code and be done with it. It can even allocate a new page if it needs to |
110 | * and swap that into the ring buffer. |
111 | * |
112 | * We will be using cmpxchg soon to make all this lockless. |
113 | * |
114 | */ |
115 | |
116 | /* |
117 | * A fast way to enable or disable all ring buffers is to |
118 | * call tracing_on or tracing_off. Turning off the ring buffers |
119 | * prevents all ring buffers from being recorded to. |
120 | * Turning this switch on, makes it OK to write to the |
121 | * ring buffer, if the ring buffer is enabled itself. |
122 | * |
123 | * There's three layers that must be on in order to write |
124 | * to the ring buffer. |
125 | * |
126 | * 1) This global flag must be set. |
127 | * 2) The ring buffer must be enabled for recording. |
128 | * 3) The per cpu buffer must be enabled for recording. |
129 | * |
130 | * In case of an anomaly, this global flag has a bit set that |
131 | * will permantly disable all ring buffers. |
132 | */ |
133 | |
134 | /* |
135 | * Global flag to disable all recording to ring buffers |
136 | * This has two bits: ON, DISABLED |
137 | * |
138 | * ON DISABLED |
139 | * ---- ---------- |
140 | * 0 0 : ring buffers are off |
141 | * 1 0 : ring buffers are on |
142 | * X 1 : ring buffers are permanently disabled |
143 | */ |
144 | |
145 | enum { |
146 | RB_BUFFERS_ON_BIT = 0, |
147 | RB_BUFFERS_DISABLED_BIT = 1, |
148 | }; |
149 | |
150 | enum { |
151 | RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT, |
152 | RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT, |
153 | }; |
154 | |
155 | static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; |
156 | |
157 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
158 | |
159 | /** |
160 | * tracing_on - enable all tracing buffers |
161 | * |
162 | * This function enables all tracing buffers that may have been |
163 | * disabled with tracing_off. |
164 | */ |
165 | void tracing_on(void) |
166 | { |
167 | set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); |
168 | } |
169 | EXPORT_SYMBOL_GPL(tracing_on); |
170 | |
171 | /** |
172 | * tracing_off - turn off all tracing buffers |
173 | * |
174 | * This function stops all tracing buffers from recording data. |
175 | * It does not disable any overhead the tracers themselves may |
176 | * be causing. This function simply causes all recording to |
177 | * the ring buffers to fail. |
178 | */ |
179 | void tracing_off(void) |
180 | { |
181 | clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); |
182 | } |
183 | EXPORT_SYMBOL_GPL(tracing_off); |
184 | |
185 | /** |
186 | * tracing_off_permanent - permanently disable ring buffers |
187 | * |
188 | * This function, once called, will disable all ring buffers |
189 | * permanently. |
190 | */ |
191 | void tracing_off_permanent(void) |
192 | { |
193 | set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags); |
194 | } |
195 | |
196 | /** |
197 | * tracing_is_on - show state of ring buffers enabled |
198 | */ |
199 | int tracing_is_on(void) |
200 | { |
201 | return ring_buffer_flags == RB_BUFFERS_ON; |
202 | } |
203 | EXPORT_SYMBOL_GPL(tracing_is_on); |
204 | |
205 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
206 | #define RB_ALIGNMENT 4U |
207 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
208 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
209 | |
210 | #if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) |
211 | # define RB_FORCE_8BYTE_ALIGNMENT 0 |
212 | # define RB_ARCH_ALIGNMENT RB_ALIGNMENT |
213 | #else |
214 | # define RB_FORCE_8BYTE_ALIGNMENT 1 |
215 | # define RB_ARCH_ALIGNMENT 8U |
216 | #endif |
217 | |
218 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
219 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX |
220 | |
221 | enum { |
222 | RB_LEN_TIME_EXTEND = 8, |
223 | RB_LEN_TIME_STAMP = 16, |
224 | }; |
225 | |
226 | #define skip_time_extend(event) \ |
227 | ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) |
228 | |
229 | static inline int rb_null_event(struct ring_buffer_event *event) |
230 | { |
231 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
232 | } |
233 | |
234 | static void rb_event_set_padding(struct ring_buffer_event *event) |
235 | { |
236 | /* padding has a NULL time_delta */ |
237 | event->type_len = RINGBUF_TYPE_PADDING; |
238 | event->time_delta = 0; |
239 | } |
240 | |
241 | static unsigned |
242 | rb_event_data_length(struct ring_buffer_event *event) |
243 | { |
244 | unsigned length; |
245 | |
246 | if (event->type_len) |
247 | length = event->type_len * RB_ALIGNMENT; |
248 | else |
249 | length = event->array[0]; |
250 | return length + RB_EVNT_HDR_SIZE; |
251 | } |
252 | |
253 | /* |
254 | * Return the length of the given event. Will return |
255 | * the length of the time extend if the event is a |
256 | * time extend. |
257 | */ |
258 | static inline unsigned |
259 | rb_event_length(struct ring_buffer_event *event) |
260 | { |
261 | switch (event->type_len) { |
262 | case RINGBUF_TYPE_PADDING: |
263 | if (rb_null_event(event)) |
264 | /* undefined */ |
265 | return -1; |
266 | return event->array[0] + RB_EVNT_HDR_SIZE; |
267 | |
268 | case RINGBUF_TYPE_TIME_EXTEND: |
269 | return RB_LEN_TIME_EXTEND; |
270 | |
271 | case RINGBUF_TYPE_TIME_STAMP: |
272 | return RB_LEN_TIME_STAMP; |
273 | |
274 | case RINGBUF_TYPE_DATA: |
275 | return rb_event_data_length(event); |
276 | default: |
277 | BUG(); |
278 | } |
279 | /* not hit */ |
280 | return 0; |
281 | } |
282 | |
283 | /* |
284 | * Return total length of time extend and data, |
285 | * or just the event length for all other events. |
286 | */ |
287 | static inline unsigned |
288 | rb_event_ts_length(struct ring_buffer_event *event) |
289 | { |
290 | unsigned len = 0; |
291 | |
292 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { |
293 | /* time extends include the data event after it */ |
294 | len = RB_LEN_TIME_EXTEND; |
295 | event = skip_time_extend(event); |
296 | } |
297 | return len + rb_event_length(event); |
298 | } |
299 | |
300 | /** |
301 | * ring_buffer_event_length - return the length of the event |
302 | * @event: the event to get the length of |
303 | * |
304 | * Returns the size of the data load of a data event. |
305 | * If the event is something other than a data event, it |
306 | * returns the size of the event itself. With the exception |
307 | * of a TIME EXTEND, where it still returns the size of the |
308 | * data load of the data event after it. |
309 | */ |
310 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) |
311 | { |
312 | unsigned length; |
313 | |
314 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
315 | event = skip_time_extend(event); |
316 | |
317 | length = rb_event_length(event); |
318 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
319 | return length; |
320 | length -= RB_EVNT_HDR_SIZE; |
321 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) |
322 | length -= sizeof(event->array[0]); |
323 | return length; |
324 | } |
325 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
326 | |
327 | /* inline for ring buffer fast paths */ |
328 | static void * |
329 | rb_event_data(struct ring_buffer_event *event) |
330 | { |
331 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
332 | event = skip_time_extend(event); |
333 | BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
334 | /* If length is in len field, then array[0] has the data */ |
335 | if (event->type_len) |
336 | return (void *)&event->array[0]; |
337 | /* Otherwise length is in array[0] and array[1] has the data */ |
338 | return (void *)&event->array[1]; |
339 | } |
340 | |
341 | /** |
342 | * ring_buffer_event_data - return the data of the event |
343 | * @event: the event to get the data from |
344 | */ |
345 | void *ring_buffer_event_data(struct ring_buffer_event *event) |
346 | { |
347 | return rb_event_data(event); |
348 | } |
349 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
350 | |
351 | #define for_each_buffer_cpu(buffer, cpu) \ |
352 | for_each_cpu(cpu, buffer->cpumask) |
353 | |
354 | #define TS_SHIFT 27 |
355 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) |
356 | #define TS_DELTA_TEST (~TS_MASK) |
357 | |
358 | /* Flag when events were overwritten */ |
359 | #define RB_MISSED_EVENTS (1 << 31) |
360 | /* Missed count stored at end */ |
361 | #define RB_MISSED_STORED (1 << 30) |
362 | |
363 | struct buffer_data_page { |
364 | u64 time_stamp; /* page time stamp */ |
365 | local_t commit; /* write committed index */ |
366 | unsigned char data[]; /* data of buffer page */ |
367 | }; |
368 | |
369 | /* |
370 | * Note, the buffer_page list must be first. The buffer pages |
371 | * are allocated in cache lines, which means that each buffer |
372 | * page will be at the beginning of a cache line, and thus |
373 | * the least significant bits will be zero. We use this to |
374 | * add flags in the list struct pointers, to make the ring buffer |
375 | * lockless. |
376 | */ |
377 | struct buffer_page { |
378 | struct list_head list; /* list of buffer pages */ |
379 | local_t write; /* index for next write */ |
380 | unsigned read; /* index for next read */ |
381 | local_t entries; /* entries on this page */ |
382 | unsigned long real_end; /* real end of data */ |
383 | struct buffer_data_page *page; /* Actual data page */ |
384 | }; |
385 | |
386 | /* |
387 | * The buffer page counters, write and entries, must be reset |
388 | * atomically when crossing page boundaries. To synchronize this |
389 | * update, two counters are inserted into the number. One is |
390 | * the actual counter for the write position or count on the page. |
391 | * |
392 | * The other is a counter of updaters. Before an update happens |
393 | * the update partition of the counter is incremented. This will |
394 | * allow the updater to update the counter atomically. |
395 | * |
396 | * The counter is 20 bits, and the state data is 12. |
397 | */ |
398 | #define RB_WRITE_MASK 0xfffff |
399 | #define RB_WRITE_INTCNT (1 << 20) |
400 | |
401 | static void rb_init_page(struct buffer_data_page *bpage) |
402 | { |
403 | local_set(&bpage->commit, 0); |
404 | } |
405 | |
406 | /** |
407 | * ring_buffer_page_len - the size of data on the page. |
408 | * @page: The page to read |
409 | * |
410 | * Returns the amount of data on the page, including buffer page header. |
411 | */ |
412 | size_t ring_buffer_page_len(void *page) |
413 | { |
414 | return local_read(&((struct buffer_data_page *)page)->commit) |
415 | + BUF_PAGE_HDR_SIZE; |
416 | } |
417 | |
418 | /* |
419 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing |
420 | * this issue out. |
421 | */ |
422 | static void free_buffer_page(struct buffer_page *bpage) |
423 | { |
424 | free_page((unsigned long)bpage->page); |
425 | kfree(bpage); |
426 | } |
427 | |
428 | /* |
429 | * We need to fit the time_stamp delta into 27 bits. |
430 | */ |
431 | static inline int test_time_stamp(u64 delta) |
432 | { |
433 | if (delta & TS_DELTA_TEST) |
434 | return 1; |
435 | return 0; |
436 | } |
437 | |
438 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
439 | |
440 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
441 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) |
442 | |
443 | int ring_buffer_print_page_header(struct trace_seq *s) |
444 | { |
445 | struct buffer_data_page field; |
446 | int ret; |
447 | |
448 | ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t" |
449 | "offset:0;\tsize:%u;\tsigned:%u;\n", |
450 | (unsigned int)sizeof(field.time_stamp), |
451 | (unsigned int)is_signed_type(u64)); |
452 | |
453 | ret = trace_seq_printf(s, "\tfield: local_t commit;\t" |
454 | "offset:%u;\tsize:%u;\tsigned:%u;\n", |
455 | (unsigned int)offsetof(typeof(field), commit), |
456 | (unsigned int)sizeof(field.commit), |
457 | (unsigned int)is_signed_type(long)); |
458 | |
459 | ret = trace_seq_printf(s, "\tfield: int overwrite;\t" |
460 | "offset:%u;\tsize:%u;\tsigned:%u;\n", |
461 | (unsigned int)offsetof(typeof(field), commit), |
462 | 1, |
463 | (unsigned int)is_signed_type(long)); |
464 | |
465 | ret = trace_seq_printf(s, "\tfield: char data;\t" |
466 | "offset:%u;\tsize:%u;\tsigned:%u;\n", |
467 | (unsigned int)offsetof(typeof(field), data), |
468 | (unsigned int)BUF_PAGE_SIZE, |
469 | (unsigned int)is_signed_type(char)); |
470 | |
471 | return ret; |
472 | } |
473 | |
474 | /* |
475 | * head_page == tail_page && head == tail then buffer is empty. |
476 | */ |
477 | struct ring_buffer_per_cpu { |
478 | int cpu; |
479 | atomic_t record_disabled; |
480 | struct ring_buffer *buffer; |
481 | spinlock_t reader_lock; /* serialize readers */ |
482 | arch_spinlock_t lock; |
483 | struct lock_class_key lock_key; |
484 | struct list_head *pages; |
485 | struct buffer_page *head_page; /* read from head */ |
486 | struct buffer_page *tail_page; /* write to tail */ |
487 | struct buffer_page *commit_page; /* committed pages */ |
488 | struct buffer_page *reader_page; |
489 | unsigned long lost_events; |
490 | unsigned long last_overrun; |
491 | local_t commit_overrun; |
492 | local_t overrun; |
493 | local_t entries; |
494 | local_t committing; |
495 | local_t commits; |
496 | unsigned long read; |
497 | u64 write_stamp; |
498 | u64 read_stamp; |
499 | }; |
500 | |
501 | struct ring_buffer { |
502 | unsigned pages; |
503 | unsigned flags; |
504 | int cpus; |
505 | atomic_t record_disabled; |
506 | cpumask_var_t cpumask; |
507 | |
508 | struct lock_class_key *reader_lock_key; |
509 | |
510 | struct mutex mutex; |
511 | |
512 | struct ring_buffer_per_cpu **buffers; |
513 | |
514 | #ifdef CONFIG_HOTPLUG_CPU |
515 | struct notifier_block cpu_notify; |
516 | #endif |
517 | u64 (*clock)(void); |
518 | }; |
519 | |
520 | struct ring_buffer_iter { |
521 | struct ring_buffer_per_cpu *cpu_buffer; |
522 | unsigned long head; |
523 | struct buffer_page *head_page; |
524 | struct buffer_page *cache_reader_page; |
525 | unsigned long cache_read; |
526 | u64 read_stamp; |
527 | }; |
528 | |
529 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
530 | #define RB_WARN_ON(b, cond) \ |
531 | ({ \ |
532 | int _____ret = unlikely(cond); \ |
533 | if (_____ret) { \ |
534 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ |
535 | struct ring_buffer_per_cpu *__b = \ |
536 | (void *)b; \ |
537 | atomic_inc(&__b->buffer->record_disabled); \ |
538 | } else \ |
539 | atomic_inc(&b->record_disabled); \ |
540 | WARN_ON(1); \ |
541 | } \ |
542 | _____ret; \ |
543 | }) |
544 | |
545 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
546 | #define DEBUG_SHIFT 0 |
547 | |
548 | static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
549 | { |
550 | /* shift to debug/test normalization and TIME_EXTENTS */ |
551 | return buffer->clock() << DEBUG_SHIFT; |
552 | } |
553 | |
554 | u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
555 | { |
556 | u64 time; |
557 | |
558 | preempt_disable_notrace(); |
559 | time = rb_time_stamp(buffer); |
560 | preempt_enable_no_resched_notrace(); |
561 | |
562 | return time; |
563 | } |
564 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); |
565 | |
566 | void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, |
567 | int cpu, u64 *ts) |
568 | { |
569 | /* Just stupid testing the normalize function and deltas */ |
570 | *ts >>= DEBUG_SHIFT; |
571 | } |
572 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); |
573 | |
574 | /* |
575 | * Making the ring buffer lockless makes things tricky. |
576 | * Although writes only happen on the CPU that they are on, |
577 | * and they only need to worry about interrupts. Reads can |
578 | * happen on any CPU. |
579 | * |
580 | * The reader page is always off the ring buffer, but when the |
581 | * reader finishes with a page, it needs to swap its page with |
582 | * a new one from the buffer. The reader needs to take from |
583 | * the head (writes go to the tail). But if a writer is in overwrite |
584 | * mode and wraps, it must push the head page forward. |
585 | * |
586 | * Here lies the problem. |
587 | * |
588 | * The reader must be careful to replace only the head page, and |
589 | * not another one. As described at the top of the file in the |
590 | * ASCII art, the reader sets its old page to point to the next |
591 | * page after head. It then sets the page after head to point to |
592 | * the old reader page. But if the writer moves the head page |
593 | * during this operation, the reader could end up with the tail. |
594 | * |
595 | * We use cmpxchg to help prevent this race. We also do something |
596 | * special with the page before head. We set the LSB to 1. |
597 | * |
598 | * When the writer must push the page forward, it will clear the |
599 | * bit that points to the head page, move the head, and then set |
600 | * the bit that points to the new head page. |
601 | * |
602 | * We also don't want an interrupt coming in and moving the head |
603 | * page on another writer. Thus we use the second LSB to catch |
604 | * that too. Thus: |
605 | * |
606 | * head->list->prev->next bit 1 bit 0 |
607 | * ------- ------- |
608 | * Normal page 0 0 |
609 | * Points to head page 0 1 |
610 | * New head page 1 0 |
611 | * |
612 | * Note we can not trust the prev pointer of the head page, because: |
613 | * |
614 | * +----+ +-----+ +-----+ |
615 | * | |------>| T |---X--->| N | |
616 | * | |<------| | | | |
617 | * +----+ +-----+ +-----+ |
618 | * ^ ^ | |
619 | * | +-----+ | | |
620 | * +----------| R |----------+ | |
621 | * | |<-----------+ |
622 | * +-----+ |
623 | * |
624 | * Key: ---X--> HEAD flag set in pointer |
625 | * T Tail page |
626 | * R Reader page |
627 | * N Next page |
628 | * |
629 | * (see __rb_reserve_next() to see where this happens) |
630 | * |
631 | * What the above shows is that the reader just swapped out |
632 | * the reader page with a page in the buffer, but before it |
633 | * could make the new header point back to the new page added |
634 | * it was preempted by a writer. The writer moved forward onto |
635 | * the new page added by the reader and is about to move forward |
636 | * again. |
637 | * |
638 | * You can see, it is legitimate for the previous pointer of |
639 | * the head (or any page) not to point back to itself. But only |
640 | * temporarially. |
641 | */ |
642 | |
643 | #define RB_PAGE_NORMAL 0UL |
644 | #define RB_PAGE_HEAD 1UL |
645 | #define RB_PAGE_UPDATE 2UL |
646 | |
647 | |
648 | #define RB_FLAG_MASK 3UL |
649 | |
650 | /* PAGE_MOVED is not part of the mask */ |
651 | #define RB_PAGE_MOVED 4UL |
652 | |
653 | /* |
654 | * rb_list_head - remove any bit |
655 | */ |
656 | static struct list_head *rb_list_head(struct list_head *list) |
657 | { |
658 | unsigned long val = (unsigned long)list; |
659 | |
660 | return (struct list_head *)(val & ~RB_FLAG_MASK); |
661 | } |
662 | |
663 | /* |
664 | * rb_is_head_page - test if the given page is the head page |
665 | * |
666 | * Because the reader may move the head_page pointer, we can |
667 | * not trust what the head page is (it may be pointing to |
668 | * the reader page). But if the next page is a header page, |
669 | * its flags will be non zero. |
670 | */ |
671 | static inline int |
672 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
673 | struct buffer_page *page, struct list_head *list) |
674 | { |
675 | unsigned long val; |
676 | |
677 | val = (unsigned long)list->next; |
678 | |
679 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) |
680 | return RB_PAGE_MOVED; |
681 | |
682 | return val & RB_FLAG_MASK; |
683 | } |
684 | |
685 | /* |
686 | * rb_is_reader_page |
687 | * |
688 | * The unique thing about the reader page, is that, if the |
689 | * writer is ever on it, the previous pointer never points |
690 | * back to the reader page. |
691 | */ |
692 | static int rb_is_reader_page(struct buffer_page *page) |
693 | { |
694 | struct list_head *list = page->list.prev; |
695 | |
696 | return rb_list_head(list->next) != &page->list; |
697 | } |
698 | |
699 | /* |
700 | * rb_set_list_to_head - set a list_head to be pointing to head. |
701 | */ |
702 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, |
703 | struct list_head *list) |
704 | { |
705 | unsigned long *ptr; |
706 | |
707 | ptr = (unsigned long *)&list->next; |
708 | *ptr |= RB_PAGE_HEAD; |
709 | *ptr &= ~RB_PAGE_UPDATE; |
710 | } |
711 | |
712 | /* |
713 | * rb_head_page_activate - sets up head page |
714 | */ |
715 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) |
716 | { |
717 | struct buffer_page *head; |
718 | |
719 | head = cpu_buffer->head_page; |
720 | if (!head) |
721 | return; |
722 | |
723 | /* |
724 | * Set the previous list pointer to have the HEAD flag. |
725 | */ |
726 | rb_set_list_to_head(cpu_buffer, head->list.prev); |
727 | } |
728 | |
729 | static void rb_list_head_clear(struct list_head *list) |
730 | { |
731 | unsigned long *ptr = (unsigned long *)&list->next; |
732 | |
733 | *ptr &= ~RB_FLAG_MASK; |
734 | } |
735 | |
736 | /* |
737 | * rb_head_page_dactivate - clears head page ptr (for free list) |
738 | */ |
739 | static void |
740 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) |
741 | { |
742 | struct list_head *hd; |
743 | |
744 | /* Go through the whole list and clear any pointers found. */ |
745 | rb_list_head_clear(cpu_buffer->pages); |
746 | |
747 | list_for_each(hd, cpu_buffer->pages) |
748 | rb_list_head_clear(hd); |
749 | } |
750 | |
751 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, |
752 | struct buffer_page *head, |
753 | struct buffer_page *prev, |
754 | int old_flag, int new_flag) |
755 | { |
756 | struct list_head *list; |
757 | unsigned long val = (unsigned long)&head->list; |
758 | unsigned long ret; |
759 | |
760 | list = &prev->list; |
761 | |
762 | val &= ~RB_FLAG_MASK; |
763 | |
764 | ret = cmpxchg((unsigned long *)&list->next, |
765 | val | old_flag, val | new_flag); |
766 | |
767 | /* check if the reader took the page */ |
768 | if ((ret & ~RB_FLAG_MASK) != val) |
769 | return RB_PAGE_MOVED; |
770 | |
771 | return ret & RB_FLAG_MASK; |
772 | } |
773 | |
774 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, |
775 | struct buffer_page *head, |
776 | struct buffer_page *prev, |
777 | int old_flag) |
778 | { |
779 | return rb_head_page_set(cpu_buffer, head, prev, |
780 | old_flag, RB_PAGE_UPDATE); |
781 | } |
782 | |
783 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, |
784 | struct buffer_page *head, |
785 | struct buffer_page *prev, |
786 | int old_flag) |
787 | { |
788 | return rb_head_page_set(cpu_buffer, head, prev, |
789 | old_flag, RB_PAGE_HEAD); |
790 | } |
791 | |
792 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, |
793 | struct buffer_page *head, |
794 | struct buffer_page *prev, |
795 | int old_flag) |
796 | { |
797 | return rb_head_page_set(cpu_buffer, head, prev, |
798 | old_flag, RB_PAGE_NORMAL); |
799 | } |
800 | |
801 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, |
802 | struct buffer_page **bpage) |
803 | { |
804 | struct list_head *p = rb_list_head((*bpage)->list.next); |
805 | |
806 | *bpage = list_entry(p, struct buffer_page, list); |
807 | } |
808 | |
809 | static struct buffer_page * |
810 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) |
811 | { |
812 | struct buffer_page *head; |
813 | struct buffer_page *page; |
814 | struct list_head *list; |
815 | int i; |
816 | |
817 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) |
818 | return NULL; |
819 | |
820 | /* sanity check */ |
821 | list = cpu_buffer->pages; |
822 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) |
823 | return NULL; |
824 | |
825 | page = head = cpu_buffer->head_page; |
826 | /* |
827 | * It is possible that the writer moves the header behind |
828 | * where we started, and we miss in one loop. |
829 | * A second loop should grab the header, but we'll do |
830 | * three loops just because I'm paranoid. |
831 | */ |
832 | for (i = 0; i < 3; i++) { |
833 | do { |
834 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { |
835 | cpu_buffer->head_page = page; |
836 | return page; |
837 | } |
838 | rb_inc_page(cpu_buffer, &page); |
839 | } while (page != head); |
840 | } |
841 | |
842 | RB_WARN_ON(cpu_buffer, 1); |
843 | |
844 | return NULL; |
845 | } |
846 | |
847 | static int rb_head_page_replace(struct buffer_page *old, |
848 | struct buffer_page *new) |
849 | { |
850 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; |
851 | unsigned long val; |
852 | unsigned long ret; |
853 | |
854 | val = *ptr & ~RB_FLAG_MASK; |
855 | val |= RB_PAGE_HEAD; |
856 | |
857 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
858 | |
859 | return ret == val; |
860 | } |
861 | |
862 | /* |
863 | * rb_tail_page_update - move the tail page forward |
864 | * |
865 | * Returns 1 if moved tail page, 0 if someone else did. |
866 | */ |
867 | static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, |
868 | struct buffer_page *tail_page, |
869 | struct buffer_page *next_page) |
870 | { |
871 | struct buffer_page *old_tail; |
872 | unsigned long old_entries; |
873 | unsigned long old_write; |
874 | int ret = 0; |
875 | |
876 | /* |
877 | * The tail page now needs to be moved forward. |
878 | * |
879 | * We need to reset the tail page, but without messing |
880 | * with possible erasing of data brought in by interrupts |
881 | * that have moved the tail page and are currently on it. |
882 | * |
883 | * We add a counter to the write field to denote this. |
884 | */ |
885 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); |
886 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); |
887 | |
888 | /* |
889 | * Just make sure we have seen our old_write and synchronize |
890 | * with any interrupts that come in. |
891 | */ |
892 | barrier(); |
893 | |
894 | /* |
895 | * If the tail page is still the same as what we think |
896 | * it is, then it is up to us to update the tail |
897 | * pointer. |
898 | */ |
899 | if (tail_page == cpu_buffer->tail_page) { |
900 | /* Zero the write counter */ |
901 | unsigned long val = old_write & ~RB_WRITE_MASK; |
902 | unsigned long eval = old_entries & ~RB_WRITE_MASK; |
903 | |
904 | /* |
905 | * This will only succeed if an interrupt did |
906 | * not come in and change it. In which case, we |
907 | * do not want to modify it. |
908 | * |
909 | * We add (void) to let the compiler know that we do not care |
910 | * about the return value of these functions. We use the |
911 | * cmpxchg to only update if an interrupt did not already |
912 | * do it for us. If the cmpxchg fails, we don't care. |
913 | */ |
914 | (void)local_cmpxchg(&next_page->write, old_write, val); |
915 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); |
916 | |
917 | /* |
918 | * No need to worry about races with clearing out the commit. |
919 | * it only can increment when a commit takes place. But that |
920 | * only happens in the outer most nested commit. |
921 | */ |
922 | local_set(&next_page->page->commit, 0); |
923 | |
924 | old_tail = cmpxchg(&cpu_buffer->tail_page, |
925 | tail_page, next_page); |
926 | |
927 | if (old_tail == tail_page) |
928 | ret = 1; |
929 | } |
930 | |
931 | return ret; |
932 | } |
933 | |
934 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, |
935 | struct buffer_page *bpage) |
936 | { |
937 | unsigned long val = (unsigned long)bpage; |
938 | |
939 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) |
940 | return 1; |
941 | |
942 | return 0; |
943 | } |
944 | |
945 | /** |
946 | * rb_check_list - make sure a pointer to a list has the last bits zero |
947 | */ |
948 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, |
949 | struct list_head *list) |
950 | { |
951 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) |
952 | return 1; |
953 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) |
954 | return 1; |
955 | return 0; |
956 | } |
957 | |
958 | /** |
959 | * check_pages - integrity check of buffer pages |
960 | * @cpu_buffer: CPU buffer with pages to test |
961 | * |
962 | * As a safety measure we check to make sure the data pages have not |
963 | * been corrupted. |
964 | */ |
965 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) |
966 | { |
967 | struct list_head *head = cpu_buffer->pages; |
968 | struct buffer_page *bpage, *tmp; |
969 | |
970 | rb_head_page_deactivate(cpu_buffer); |
971 | |
972 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
973 | return -1; |
974 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) |
975 | return -1; |
976 | |
977 | if (rb_check_list(cpu_buffer, head)) |
978 | return -1; |
979 | |
980 | list_for_each_entry_safe(bpage, tmp, head, list) { |
981 | if (RB_WARN_ON(cpu_buffer, |
982 | bpage->list.next->prev != &bpage->list)) |
983 | return -1; |
984 | if (RB_WARN_ON(cpu_buffer, |
985 | bpage->list.prev->next != &bpage->list)) |
986 | return -1; |
987 | if (rb_check_list(cpu_buffer, &bpage->list)) |
988 | return -1; |
989 | } |
990 | |
991 | rb_head_page_activate(cpu_buffer); |
992 | |
993 | return 0; |
994 | } |
995 | |
996 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
997 | unsigned nr_pages) |
998 | { |
999 | struct buffer_page *bpage, *tmp; |
1000 | unsigned long addr; |
1001 | LIST_HEAD(pages); |
1002 | unsigned i; |
1003 | |
1004 | WARN_ON(!nr_pages); |
1005 | |
1006 | for (i = 0; i < nr_pages; i++) { |
1007 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
1008 | GFP_KERNEL, cpu_to_node(cpu_buffer->cpu)); |
1009 | if (!bpage) |
1010 | goto free_pages; |
1011 | |
1012 | rb_check_bpage(cpu_buffer, bpage); |
1013 | |
1014 | list_add(&bpage->list, &pages); |
1015 | |
1016 | addr = __get_free_page(GFP_KERNEL); |
1017 | if (!addr) |
1018 | goto free_pages; |
1019 | bpage->page = (void *)addr; |
1020 | rb_init_page(bpage->page); |
1021 | } |
1022 | |
1023 | /* |
1024 | * The ring buffer page list is a circular list that does not |
1025 | * start and end with a list head. All page list items point to |
1026 | * other pages. |
1027 | */ |
1028 | cpu_buffer->pages = pages.next; |
1029 | list_del(&pages); |
1030 | |
1031 | rb_check_pages(cpu_buffer); |
1032 | |
1033 | return 0; |
1034 | |
1035 | free_pages: |
1036 | list_for_each_entry_safe(bpage, tmp, &pages, list) { |
1037 | list_del_init(&bpage->list); |
1038 | free_buffer_page(bpage); |
1039 | } |
1040 | return -ENOMEM; |
1041 | } |
1042 | |
1043 | static struct ring_buffer_per_cpu * |
1044 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) |
1045 | { |
1046 | struct ring_buffer_per_cpu *cpu_buffer; |
1047 | struct buffer_page *bpage; |
1048 | unsigned long addr; |
1049 | int ret; |
1050 | |
1051 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), |
1052 | GFP_KERNEL, cpu_to_node(cpu)); |
1053 | if (!cpu_buffer) |
1054 | return NULL; |
1055 | |
1056 | cpu_buffer->cpu = cpu; |
1057 | cpu_buffer->buffer = buffer; |
1058 | spin_lock_init(&cpu_buffer->reader_lock); |
1059 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
1060 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
1061 | |
1062 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
1063 | GFP_KERNEL, cpu_to_node(cpu)); |
1064 | if (!bpage) |
1065 | goto fail_free_buffer; |
1066 | |
1067 | rb_check_bpage(cpu_buffer, bpage); |
1068 | |
1069 | cpu_buffer->reader_page = bpage; |
1070 | addr = __get_free_page(GFP_KERNEL); |
1071 | if (!addr) |
1072 | goto fail_free_reader; |
1073 | bpage->page = (void *)addr; |
1074 | rb_init_page(bpage->page); |
1075 | |
1076 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
1077 | |
1078 | ret = rb_allocate_pages(cpu_buffer, buffer->pages); |
1079 | if (ret < 0) |
1080 | goto fail_free_reader; |
1081 | |
1082 | cpu_buffer->head_page |
1083 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
1084 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
1085 | |
1086 | rb_head_page_activate(cpu_buffer); |
1087 | |
1088 | return cpu_buffer; |
1089 | |
1090 | fail_free_reader: |
1091 | free_buffer_page(cpu_buffer->reader_page); |
1092 | |
1093 | fail_free_buffer: |
1094 | kfree(cpu_buffer); |
1095 | return NULL; |
1096 | } |
1097 | |
1098 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) |
1099 | { |
1100 | struct list_head *head = cpu_buffer->pages; |
1101 | struct buffer_page *bpage, *tmp; |
1102 | |
1103 | free_buffer_page(cpu_buffer->reader_page); |
1104 | |
1105 | rb_head_page_deactivate(cpu_buffer); |
1106 | |
1107 | if (head) { |
1108 | list_for_each_entry_safe(bpage, tmp, head, list) { |
1109 | list_del_init(&bpage->list); |
1110 | free_buffer_page(bpage); |
1111 | } |
1112 | bpage = list_entry(head, struct buffer_page, list); |
1113 | free_buffer_page(bpage); |
1114 | } |
1115 | |
1116 | kfree(cpu_buffer); |
1117 | } |
1118 | |
1119 | #ifdef CONFIG_HOTPLUG_CPU |
1120 | static int rb_cpu_notify(struct notifier_block *self, |
1121 | unsigned long action, void *hcpu); |
1122 | #endif |
1123 | |
1124 | /** |
1125 | * ring_buffer_alloc - allocate a new ring_buffer |
1126 | * @size: the size in bytes per cpu that is needed. |
1127 | * @flags: attributes to set for the ring buffer. |
1128 | * |
1129 | * Currently the only flag that is available is the RB_FL_OVERWRITE |
1130 | * flag. This flag means that the buffer will overwrite old data |
1131 | * when the buffer wraps. If this flag is not set, the buffer will |
1132 | * drop data when the tail hits the head. |
1133 | */ |
1134 | struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1135 | struct lock_class_key *key) |
1136 | { |
1137 | struct ring_buffer *buffer; |
1138 | int bsize; |
1139 | int cpu; |
1140 | |
1141 | /* keep it in its own cache line */ |
1142 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), |
1143 | GFP_KERNEL); |
1144 | if (!buffer) |
1145 | return NULL; |
1146 | |
1147 | if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
1148 | goto fail_free_buffer; |
1149 | |
1150 | buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1151 | buffer->flags = flags; |
1152 | buffer->clock = trace_clock_local; |
1153 | buffer->reader_lock_key = key; |
1154 | |
1155 | /* need at least two pages */ |
1156 | if (buffer->pages < 2) |
1157 | buffer->pages = 2; |
1158 | |
1159 | /* |
1160 | * In case of non-hotplug cpu, if the ring-buffer is allocated |
1161 | * in early initcall, it will not be notified of secondary cpus. |
1162 | * In that off case, we need to allocate for all possible cpus. |
1163 | */ |
1164 | #ifdef CONFIG_HOTPLUG_CPU |
1165 | get_online_cpus(); |
1166 | cpumask_copy(buffer->cpumask, cpu_online_mask); |
1167 | #else |
1168 | cpumask_copy(buffer->cpumask, cpu_possible_mask); |
1169 | #endif |
1170 | buffer->cpus = nr_cpu_ids; |
1171 | |
1172 | bsize = sizeof(void *) * nr_cpu_ids; |
1173 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), |
1174 | GFP_KERNEL); |
1175 | if (!buffer->buffers) |
1176 | goto fail_free_cpumask; |
1177 | |
1178 | for_each_buffer_cpu(buffer, cpu) { |
1179 | buffer->buffers[cpu] = |
1180 | rb_allocate_cpu_buffer(buffer, cpu); |
1181 | if (!buffer->buffers[cpu]) |
1182 | goto fail_free_buffers; |
1183 | } |
1184 | |
1185 | #ifdef CONFIG_HOTPLUG_CPU |
1186 | buffer->cpu_notify.notifier_call = rb_cpu_notify; |
1187 | buffer->cpu_notify.priority = 0; |
1188 | register_cpu_notifier(&buffer->cpu_notify); |
1189 | #endif |
1190 | |
1191 | put_online_cpus(); |
1192 | mutex_init(&buffer->mutex); |
1193 | |
1194 | return buffer; |
1195 | |
1196 | fail_free_buffers: |
1197 | for_each_buffer_cpu(buffer, cpu) { |
1198 | if (buffer->buffers[cpu]) |
1199 | rb_free_cpu_buffer(buffer->buffers[cpu]); |
1200 | } |
1201 | kfree(buffer->buffers); |
1202 | |
1203 | fail_free_cpumask: |
1204 | free_cpumask_var(buffer->cpumask); |
1205 | put_online_cpus(); |
1206 | |
1207 | fail_free_buffer: |
1208 | kfree(buffer); |
1209 | return NULL; |
1210 | } |
1211 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
1212 | |
1213 | /** |
1214 | * ring_buffer_free - free a ring buffer. |
1215 | * @buffer: the buffer to free. |
1216 | */ |
1217 | void |
1218 | ring_buffer_free(struct ring_buffer *buffer) |
1219 | { |
1220 | int cpu; |
1221 | |
1222 | get_online_cpus(); |
1223 | |
1224 | #ifdef CONFIG_HOTPLUG_CPU |
1225 | unregister_cpu_notifier(&buffer->cpu_notify); |
1226 | #endif |
1227 | |
1228 | for_each_buffer_cpu(buffer, cpu) |
1229 | rb_free_cpu_buffer(buffer->buffers[cpu]); |
1230 | |
1231 | put_online_cpus(); |
1232 | |
1233 | kfree(buffer->buffers); |
1234 | free_cpumask_var(buffer->cpumask); |
1235 | |
1236 | kfree(buffer); |
1237 | } |
1238 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
1239 | |
1240 | void ring_buffer_set_clock(struct ring_buffer *buffer, |
1241 | u64 (*clock)(void)) |
1242 | { |
1243 | buffer->clock = clock; |
1244 | } |
1245 | |
1246 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1247 | |
1248 | static void |
1249 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) |
1250 | { |
1251 | struct buffer_page *bpage; |
1252 | struct list_head *p; |
1253 | unsigned i; |
1254 | |
1255 | spin_lock_irq(&cpu_buffer->reader_lock); |
1256 | rb_head_page_deactivate(cpu_buffer); |
1257 | |
1258 | for (i = 0; i < nr_pages; i++) { |
1259 | if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages))) |
1260 | goto out; |
1261 | p = cpu_buffer->pages->next; |
1262 | bpage = list_entry(p, struct buffer_page, list); |
1263 | list_del_init(&bpage->list); |
1264 | free_buffer_page(bpage); |
1265 | } |
1266 | if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages))) |
1267 | goto out; |
1268 | |
1269 | rb_reset_cpu(cpu_buffer); |
1270 | rb_check_pages(cpu_buffer); |
1271 | |
1272 | out: |
1273 | spin_unlock_irq(&cpu_buffer->reader_lock); |
1274 | } |
1275 | |
1276 | static void |
1277 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, |
1278 | struct list_head *pages, unsigned nr_pages) |
1279 | { |
1280 | struct buffer_page *bpage; |
1281 | struct list_head *p; |
1282 | unsigned i; |
1283 | |
1284 | spin_lock_irq(&cpu_buffer->reader_lock); |
1285 | rb_head_page_deactivate(cpu_buffer); |
1286 | |
1287 | for (i = 0; i < nr_pages; i++) { |
1288 | if (RB_WARN_ON(cpu_buffer, list_empty(pages))) |
1289 | goto out; |
1290 | p = pages->next; |
1291 | bpage = list_entry(p, struct buffer_page, list); |
1292 | list_del_init(&bpage->list); |
1293 | list_add_tail(&bpage->list, cpu_buffer->pages); |
1294 | } |
1295 | rb_reset_cpu(cpu_buffer); |
1296 | rb_check_pages(cpu_buffer); |
1297 | |
1298 | out: |
1299 | spin_unlock_irq(&cpu_buffer->reader_lock); |
1300 | } |
1301 | |
1302 | /** |
1303 | * ring_buffer_resize - resize the ring buffer |
1304 | * @buffer: the buffer to resize. |
1305 | * @size: the new size. |
1306 | * |
1307 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1308 | * |
1309 | * Returns -1 on failure. |
1310 | */ |
1311 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) |
1312 | { |
1313 | struct ring_buffer_per_cpu *cpu_buffer; |
1314 | unsigned nr_pages, rm_pages, new_pages; |
1315 | struct buffer_page *bpage, *tmp; |
1316 | unsigned long buffer_size; |
1317 | unsigned long addr; |
1318 | LIST_HEAD(pages); |
1319 | int i, cpu; |
1320 | |
1321 | /* |
1322 | * Always succeed at resizing a non-existent buffer: |
1323 | */ |
1324 | if (!buffer) |
1325 | return size; |
1326 | |
1327 | size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1328 | size *= BUF_PAGE_SIZE; |
1329 | buffer_size = buffer->pages * BUF_PAGE_SIZE; |
1330 | |
1331 | /* we need a minimum of two pages */ |
1332 | if (size < BUF_PAGE_SIZE * 2) |
1333 | size = BUF_PAGE_SIZE * 2; |
1334 | |
1335 | if (size == buffer_size) |
1336 | return size; |
1337 | |
1338 | atomic_inc(&buffer->record_disabled); |
1339 | |
1340 | /* Make sure all writers are done with this buffer. */ |
1341 | synchronize_sched(); |
1342 | |
1343 | mutex_lock(&buffer->mutex); |
1344 | get_online_cpus(); |
1345 | |
1346 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1347 | |
1348 | if (size < buffer_size) { |
1349 | |
1350 | /* easy case, just free pages */ |
1351 | if (RB_WARN_ON(buffer, nr_pages >= buffer->pages)) |
1352 | goto out_fail; |
1353 | |
1354 | rm_pages = buffer->pages - nr_pages; |
1355 | |
1356 | for_each_buffer_cpu(buffer, cpu) { |
1357 | cpu_buffer = buffer->buffers[cpu]; |
1358 | rb_remove_pages(cpu_buffer, rm_pages); |
1359 | } |
1360 | goto out; |
1361 | } |
1362 | |
1363 | /* |
1364 | * This is a bit more difficult. We only want to add pages |
1365 | * when we can allocate enough for all CPUs. We do this |
1366 | * by allocating all the pages and storing them on a local |
1367 | * link list. If we succeed in our allocation, then we |
1368 | * add these pages to the cpu_buffers. Otherwise we just free |
1369 | * them all and return -ENOMEM; |
1370 | */ |
1371 | if (RB_WARN_ON(buffer, nr_pages <= buffer->pages)) |
1372 | goto out_fail; |
1373 | |
1374 | new_pages = nr_pages - buffer->pages; |
1375 | |
1376 | for_each_buffer_cpu(buffer, cpu) { |
1377 | for (i = 0; i < new_pages; i++) { |
1378 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), |
1379 | cache_line_size()), |
1380 | GFP_KERNEL, cpu_to_node(cpu)); |
1381 | if (!bpage) |
1382 | goto free_pages; |
1383 | list_add(&bpage->list, &pages); |
1384 | addr = __get_free_page(GFP_KERNEL); |
1385 | if (!addr) |
1386 | goto free_pages; |
1387 | bpage->page = (void *)addr; |
1388 | rb_init_page(bpage->page); |
1389 | } |
1390 | } |
1391 | |
1392 | for_each_buffer_cpu(buffer, cpu) { |
1393 | cpu_buffer = buffer->buffers[cpu]; |
1394 | rb_insert_pages(cpu_buffer, &pages, new_pages); |
1395 | } |
1396 | |
1397 | if (RB_WARN_ON(buffer, !list_empty(&pages))) |
1398 | goto out_fail; |
1399 | |
1400 | out: |
1401 | buffer->pages = nr_pages; |
1402 | put_online_cpus(); |
1403 | mutex_unlock(&buffer->mutex); |
1404 | |
1405 | atomic_dec(&buffer->record_disabled); |
1406 | |
1407 | return size; |
1408 | |
1409 | free_pages: |
1410 | list_for_each_entry_safe(bpage, tmp, &pages, list) { |
1411 | list_del_init(&bpage->list); |
1412 | free_buffer_page(bpage); |
1413 | } |
1414 | put_online_cpus(); |
1415 | mutex_unlock(&buffer->mutex); |
1416 | atomic_dec(&buffer->record_disabled); |
1417 | return -ENOMEM; |
1418 | |
1419 | /* |
1420 | * Something went totally wrong, and we are too paranoid |
1421 | * to even clean up the mess. |
1422 | */ |
1423 | out_fail: |
1424 | put_online_cpus(); |
1425 | mutex_unlock(&buffer->mutex); |
1426 | atomic_dec(&buffer->record_disabled); |
1427 | return -1; |
1428 | } |
1429 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
1430 | |
1431 | void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) |
1432 | { |
1433 | mutex_lock(&buffer->mutex); |
1434 | if (val) |
1435 | buffer->flags |= RB_FL_OVERWRITE; |
1436 | else |
1437 | buffer->flags &= ~RB_FL_OVERWRITE; |
1438 | mutex_unlock(&buffer->mutex); |
1439 | } |
1440 | EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); |
1441 | |
1442 | static inline void * |
1443 | __rb_data_page_index(struct buffer_data_page *bpage, unsigned index) |
1444 | { |
1445 | return bpage->data + index; |
1446 | } |
1447 | |
1448 | static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
1449 | { |
1450 | return bpage->page->data + index; |
1451 | } |
1452 | |
1453 | static inline struct ring_buffer_event * |
1454 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
1455 | { |
1456 | return __rb_page_index(cpu_buffer->reader_page, |
1457 | cpu_buffer->reader_page->read); |
1458 | } |
1459 | |
1460 | static inline struct ring_buffer_event * |
1461 | rb_iter_head_event(struct ring_buffer_iter *iter) |
1462 | { |
1463 | return __rb_page_index(iter->head_page, iter->head); |
1464 | } |
1465 | |
1466 | static inline unsigned long rb_page_write(struct buffer_page *bpage) |
1467 | { |
1468 | return local_read(&bpage->write) & RB_WRITE_MASK; |
1469 | } |
1470 | |
1471 | static inline unsigned rb_page_commit(struct buffer_page *bpage) |
1472 | { |
1473 | return local_read(&bpage->page->commit); |
1474 | } |
1475 | |
1476 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1477 | { |
1478 | return local_read(&bpage->entries) & RB_WRITE_MASK; |
1479 | } |
1480 | |
1481 | /* Size is determined by what has been committed */ |
1482 | static inline unsigned rb_page_size(struct buffer_page *bpage) |
1483 | { |
1484 | return rb_page_commit(bpage); |
1485 | } |
1486 | |
1487 | static inline unsigned |
1488 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) |
1489 | { |
1490 | return rb_page_commit(cpu_buffer->commit_page); |
1491 | } |
1492 | |
1493 | static inline unsigned |
1494 | rb_event_index(struct ring_buffer_event *event) |
1495 | { |
1496 | unsigned long addr = (unsigned long)event; |
1497 | |
1498 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
1499 | } |
1500 | |
1501 | static inline int |
1502 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
1503 | struct ring_buffer_event *event) |
1504 | { |
1505 | unsigned long addr = (unsigned long)event; |
1506 | unsigned long index; |
1507 | |
1508 | index = rb_event_index(event); |
1509 | addr &= PAGE_MASK; |
1510 | |
1511 | return cpu_buffer->commit_page->page == (void *)addr && |
1512 | rb_commit_index(cpu_buffer) == index; |
1513 | } |
1514 | |
1515 | static void |
1516 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
1517 | { |
1518 | unsigned long max_count; |
1519 | |
1520 | /* |
1521 | * We only race with interrupts and NMIs on this CPU. |
1522 | * If we own the commit event, then we can commit |
1523 | * all others that interrupted us, since the interruptions |
1524 | * are in stack format (they finish before they come |
1525 | * back to us). This allows us to do a simple loop to |
1526 | * assign the commit to the tail. |
1527 | */ |
1528 | again: |
1529 | max_count = cpu_buffer->buffer->pages * 100; |
1530 | |
1531 | while (cpu_buffer->commit_page != cpu_buffer->tail_page) { |
1532 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
1533 | return; |
1534 | if (RB_WARN_ON(cpu_buffer, |
1535 | rb_is_reader_page(cpu_buffer->tail_page))) |
1536 | return; |
1537 | local_set(&cpu_buffer->commit_page->page->commit, |
1538 | rb_page_write(cpu_buffer->commit_page)); |
1539 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); |
1540 | cpu_buffer->write_stamp = |
1541 | cpu_buffer->commit_page->page->time_stamp; |
1542 | /* add barrier to keep gcc from optimizing too much */ |
1543 | barrier(); |
1544 | } |
1545 | while (rb_commit_index(cpu_buffer) != |
1546 | rb_page_write(cpu_buffer->commit_page)) { |
1547 | |
1548 | local_set(&cpu_buffer->commit_page->page->commit, |
1549 | rb_page_write(cpu_buffer->commit_page)); |
1550 | RB_WARN_ON(cpu_buffer, |
1551 | local_read(&cpu_buffer->commit_page->page->commit) & |
1552 | ~RB_WRITE_MASK); |
1553 | barrier(); |
1554 | } |
1555 | |
1556 | /* again, keep gcc from optimizing */ |
1557 | barrier(); |
1558 | |
1559 | /* |
1560 | * If an interrupt came in just after the first while loop |
1561 | * and pushed the tail page forward, we will be left with |
1562 | * a dangling commit that will never go forward. |
1563 | */ |
1564 | if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page)) |
1565 | goto again; |
1566 | } |
1567 | |
1568 | static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
1569 | { |
1570 | cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp; |
1571 | cpu_buffer->reader_page->read = 0; |
1572 | } |
1573 | |
1574 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
1575 | { |
1576 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
1577 | |
1578 | /* |
1579 | * The iterator could be on the reader page (it starts there). |
1580 | * But the head could have moved, since the reader was |
1581 | * found. Check for this case and assign the iterator |
1582 | * to the head page instead of next. |
1583 | */ |
1584 | if (iter->head_page == cpu_buffer->reader_page) |
1585 | iter->head_page = rb_set_head_page(cpu_buffer); |
1586 | else |
1587 | rb_inc_page(cpu_buffer, &iter->head_page); |
1588 | |
1589 | iter->read_stamp = iter->head_page->page->time_stamp; |
1590 | iter->head = 0; |
1591 | } |
1592 | |
1593 | /* Slow path, do not inline */ |
1594 | static noinline struct ring_buffer_event * |
1595 | rb_add_time_stamp(struct ring_buffer_event *event, u64 delta) |
1596 | { |
1597 | event->type_len = RINGBUF_TYPE_TIME_EXTEND; |
1598 | |
1599 | /* Not the first event on the page? */ |
1600 | if (rb_event_index(event)) { |
1601 | event->time_delta = delta & TS_MASK; |
1602 | event->array[0] = delta >> TS_SHIFT; |
1603 | } else { |
1604 | /* nope, just zero it */ |
1605 | event->time_delta = 0; |
1606 | event->array[0] = 0; |
1607 | } |
1608 | |
1609 | return skip_time_extend(event); |
1610 | } |
1611 | |
1612 | /** |
1613 | * ring_buffer_update_event - update event type and data |
1614 | * @event: the even to update |
1615 | * @type: the type of event |
1616 | * @length: the size of the event field in the ring buffer |
1617 | * |
1618 | * Update the type and data fields of the event. The length |
1619 | * is the actual size that is written to the ring buffer, |
1620 | * and with this, we can determine what to place into the |
1621 | * data field. |
1622 | */ |
1623 | static void |
1624 | rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
1625 | struct ring_buffer_event *event, unsigned length, |
1626 | int add_timestamp, u64 delta) |
1627 | { |
1628 | /* Only a commit updates the timestamp */ |
1629 | if (unlikely(!rb_event_is_commit(cpu_buffer, event))) |
1630 | delta = 0; |
1631 | |
1632 | /* |
1633 | * If we need to add a timestamp, then we |
1634 | * add it to the start of the resevered space. |
1635 | */ |
1636 | if (unlikely(add_timestamp)) { |
1637 | event = rb_add_time_stamp(event, delta); |
1638 | length -= RB_LEN_TIME_EXTEND; |
1639 | delta = 0; |
1640 | } |
1641 | |
1642 | event->time_delta = delta; |
1643 | length -= RB_EVNT_HDR_SIZE; |
1644 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { |
1645 | event->type_len = 0; |
1646 | event->array[0] = length; |
1647 | } else |
1648 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); |
1649 | } |
1650 | |
1651 | /* |
1652 | * rb_handle_head_page - writer hit the head page |
1653 | * |
1654 | * Returns: +1 to retry page |
1655 | * 0 to continue |
1656 | * -1 on error |
1657 | */ |
1658 | static int |
1659 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
1660 | struct buffer_page *tail_page, |
1661 | struct buffer_page *next_page) |
1662 | { |
1663 | struct buffer_page *new_head; |
1664 | int entries; |
1665 | int type; |
1666 | int ret; |
1667 | |
1668 | entries = rb_page_entries(next_page); |
1669 | |
1670 | /* |
1671 | * The hard part is here. We need to move the head |
1672 | * forward, and protect against both readers on |
1673 | * other CPUs and writers coming in via interrupts. |
1674 | */ |
1675 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, |
1676 | RB_PAGE_HEAD); |
1677 | |
1678 | /* |
1679 | * type can be one of four: |
1680 | * NORMAL - an interrupt already moved it for us |
1681 | * HEAD - we are the first to get here. |
1682 | * UPDATE - we are the interrupt interrupting |
1683 | * a current move. |
1684 | * MOVED - a reader on another CPU moved the next |
1685 | * pointer to its reader page. Give up |
1686 | * and try again. |
1687 | */ |
1688 | |
1689 | switch (type) { |
1690 | case RB_PAGE_HEAD: |
1691 | /* |
1692 | * We changed the head to UPDATE, thus |
1693 | * it is our responsibility to update |
1694 | * the counters. |
1695 | */ |
1696 | local_add(entries, &cpu_buffer->overrun); |
1697 | |
1698 | /* |
1699 | * The entries will be zeroed out when we move the |
1700 | * tail page. |
1701 | */ |
1702 | |
1703 | /* still more to do */ |
1704 | break; |
1705 | |
1706 | case RB_PAGE_UPDATE: |
1707 | /* |
1708 | * This is an interrupt that interrupt the |
1709 | * previous update. Still more to do. |
1710 | */ |
1711 | break; |
1712 | case RB_PAGE_NORMAL: |
1713 | /* |
1714 | * An interrupt came in before the update |
1715 | * and processed this for us. |
1716 | * Nothing left to do. |
1717 | */ |
1718 | return 1; |
1719 | case RB_PAGE_MOVED: |
1720 | /* |
1721 | * The reader is on another CPU and just did |
1722 | * a swap with our next_page. |
1723 | * Try again. |
1724 | */ |
1725 | return 1; |
1726 | default: |
1727 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ |
1728 | return -1; |
1729 | } |
1730 | |
1731 | /* |
1732 | * Now that we are here, the old head pointer is |
1733 | * set to UPDATE. This will keep the reader from |
1734 | * swapping the head page with the reader page. |
1735 | * The reader (on another CPU) will spin till |
1736 | * we are finished. |
1737 | * |
1738 | * We just need to protect against interrupts |
1739 | * doing the job. We will set the next pointer |
1740 | * to HEAD. After that, we set the old pointer |
1741 | * to NORMAL, but only if it was HEAD before. |
1742 | * otherwise we are an interrupt, and only |
1743 | * want the outer most commit to reset it. |
1744 | */ |
1745 | new_head = next_page; |
1746 | rb_inc_page(cpu_buffer, &new_head); |
1747 | |
1748 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, |
1749 | RB_PAGE_NORMAL); |
1750 | |
1751 | /* |
1752 | * Valid returns are: |
1753 | * HEAD - an interrupt came in and already set it. |
1754 | * NORMAL - One of two things: |
1755 | * 1) We really set it. |
1756 | * 2) A bunch of interrupts came in and moved |
1757 | * the page forward again. |
1758 | */ |
1759 | switch (ret) { |
1760 | case RB_PAGE_HEAD: |
1761 | case RB_PAGE_NORMAL: |
1762 | /* OK */ |
1763 | break; |
1764 | default: |
1765 | RB_WARN_ON(cpu_buffer, 1); |
1766 | return -1; |
1767 | } |
1768 | |
1769 | /* |
1770 | * It is possible that an interrupt came in, |
1771 | * set the head up, then more interrupts came in |
1772 | * and moved it again. When we get back here, |
1773 | * the page would have been set to NORMAL but we |
1774 | * just set it back to HEAD. |
1775 | * |
1776 | * How do you detect this? Well, if that happened |
1777 | * the tail page would have moved. |
1778 | */ |
1779 | if (ret == RB_PAGE_NORMAL) { |
1780 | /* |
1781 | * If the tail had moved passed next, then we need |
1782 | * to reset the pointer. |
1783 | */ |
1784 | if (cpu_buffer->tail_page != tail_page && |
1785 | cpu_buffer->tail_page != next_page) |
1786 | rb_head_page_set_normal(cpu_buffer, new_head, |
1787 | next_page, |
1788 | RB_PAGE_HEAD); |
1789 | } |
1790 | |
1791 | /* |
1792 | * If this was the outer most commit (the one that |
1793 | * changed the original pointer from HEAD to UPDATE), |
1794 | * then it is up to us to reset it to NORMAL. |
1795 | */ |
1796 | if (type == RB_PAGE_HEAD) { |
1797 | ret = rb_head_page_set_normal(cpu_buffer, next_page, |
1798 | tail_page, |
1799 | RB_PAGE_UPDATE); |
1800 | if (RB_WARN_ON(cpu_buffer, |
1801 | ret != RB_PAGE_UPDATE)) |
1802 | return -1; |
1803 | } |
1804 | |
1805 | return 0; |
1806 | } |
1807 | |
1808 | static unsigned rb_calculate_event_length(unsigned length) |
1809 | { |
1810 | struct ring_buffer_event event; /* Used only for sizeof array */ |
1811 | |
1812 | /* zero length can cause confusions */ |
1813 | if (!length) |
1814 | length = 1; |
1815 | |
1816 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
1817 | length += sizeof(event.array[0]); |
1818 | |
1819 | length += RB_EVNT_HDR_SIZE; |
1820 | length = ALIGN(length, RB_ARCH_ALIGNMENT); |
1821 | |
1822 | return length; |
1823 | } |
1824 | |
1825 | static inline void |
1826 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, |
1827 | struct buffer_page *tail_page, |
1828 | unsigned long tail, unsigned long length) |
1829 | { |
1830 | struct ring_buffer_event *event; |
1831 | |
1832 | /* |
1833 | * Only the event that crossed the page boundary |
1834 | * must fill the old tail_page with padding. |
1835 | */ |
1836 | if (tail >= BUF_PAGE_SIZE) { |
1837 | /* |
1838 | * If the page was filled, then we still need |
1839 | * to update the real_end. Reset it to zero |
1840 | * and the reader will ignore it. |
1841 | */ |
1842 | if (tail == BUF_PAGE_SIZE) |
1843 | tail_page->real_end = 0; |
1844 | |
1845 | local_sub(length, &tail_page->write); |
1846 | return; |
1847 | } |
1848 | |
1849 | event = __rb_page_index(tail_page, tail); |
1850 | kmemcheck_annotate_bitfield(event, bitfield); |
1851 | |
1852 | /* |
1853 | * Save the original length to the meta data. |
1854 | * This will be used by the reader to add lost event |
1855 | * counter. |
1856 | */ |
1857 | tail_page->real_end = tail; |
1858 | |
1859 | /* |
1860 | * If this event is bigger than the minimum size, then |
1861 | * we need to be careful that we don't subtract the |
1862 | * write counter enough to allow another writer to slip |
1863 | * in on this page. |
1864 | * We put in a discarded commit instead, to make sure |
1865 | * that this space is not used again. |
1866 | * |
1867 | * If we are less than the minimum size, we don't need to |
1868 | * worry about it. |
1869 | */ |
1870 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { |
1871 | /* No room for any events */ |
1872 | |
1873 | /* Mark the rest of the page with padding */ |
1874 | rb_event_set_padding(event); |
1875 | |
1876 | /* Set the write back to the previous setting */ |
1877 | local_sub(length, &tail_page->write); |
1878 | return; |
1879 | } |
1880 | |
1881 | /* Put in a discarded event */ |
1882 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; |
1883 | event->type_len = RINGBUF_TYPE_PADDING; |
1884 | /* time delta must be non zero */ |
1885 | event->time_delta = 1; |
1886 | |
1887 | /* Set write to end of buffer */ |
1888 | length = (tail + length) - BUF_PAGE_SIZE; |
1889 | local_sub(length, &tail_page->write); |
1890 | } |
1891 | |
1892 | /* |
1893 | * This is the slow path, force gcc not to inline it. |
1894 | */ |
1895 | static noinline struct ring_buffer_event * |
1896 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
1897 | unsigned long length, unsigned long tail, |
1898 | struct buffer_page *tail_page, u64 ts) |
1899 | { |
1900 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
1901 | struct ring_buffer *buffer = cpu_buffer->buffer; |
1902 | struct buffer_page *next_page; |
1903 | int ret; |
1904 | |
1905 | next_page = tail_page; |
1906 | |
1907 | rb_inc_page(cpu_buffer, &next_page); |
1908 | |
1909 | /* |
1910 | * If for some reason, we had an interrupt storm that made |
1911 | * it all the way around the buffer, bail, and warn |
1912 | * about it. |
1913 | */ |
1914 | if (unlikely(next_page == commit_page)) { |
1915 | local_inc(&cpu_buffer->commit_overrun); |
1916 | goto out_reset; |
1917 | } |
1918 | |
1919 | /* |
1920 | * This is where the fun begins! |
1921 | * |
1922 | * We are fighting against races between a reader that |
1923 | * could be on another CPU trying to swap its reader |
1924 | * page with the buffer head. |
1925 | * |
1926 | * We are also fighting against interrupts coming in and |
1927 | * moving the head or tail on us as well. |
1928 | * |
1929 | * If the next page is the head page then we have filled |
1930 | * the buffer, unless the commit page is still on the |
1931 | * reader page. |
1932 | */ |
1933 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { |
1934 | |
1935 | /* |
1936 | * If the commit is not on the reader page, then |
1937 | * move the header page. |
1938 | */ |
1939 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { |
1940 | /* |
1941 | * If we are not in overwrite mode, |
1942 | * this is easy, just stop here. |
1943 | */ |
1944 | if (!(buffer->flags & RB_FL_OVERWRITE)) |
1945 | goto out_reset; |
1946 | |
1947 | ret = rb_handle_head_page(cpu_buffer, |
1948 | tail_page, |
1949 | next_page); |
1950 | if (ret < 0) |
1951 | goto out_reset; |
1952 | if (ret) |
1953 | goto out_again; |
1954 | } else { |
1955 | /* |
1956 | * We need to be careful here too. The |
1957 | * commit page could still be on the reader |
1958 | * page. We could have a small buffer, and |
1959 | * have filled up the buffer with events |
1960 | * from interrupts and such, and wrapped. |
1961 | * |
1962 | * Note, if the tail page is also the on the |
1963 | * reader_page, we let it move out. |
1964 | */ |
1965 | if (unlikely((cpu_buffer->commit_page != |
1966 | cpu_buffer->tail_page) && |
1967 | (cpu_buffer->commit_page == |
1968 | cpu_buffer->reader_page))) { |
1969 | local_inc(&cpu_buffer->commit_overrun); |
1970 | goto out_reset; |
1971 | } |
1972 | } |
1973 | } |
1974 | |
1975 | ret = rb_tail_page_update(cpu_buffer, tail_page, next_page); |
1976 | if (ret) { |
1977 | /* |
1978 | * Nested commits always have zero deltas, so |
1979 | * just reread the time stamp |
1980 | */ |
1981 | ts = rb_time_stamp(buffer); |
1982 | next_page->page->time_stamp = ts; |
1983 | } |
1984 | |
1985 | out_again: |
1986 | |
1987 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
1988 | |
1989 | /* fail and let the caller try again */ |
1990 | return ERR_PTR(-EAGAIN); |
1991 | |
1992 | out_reset: |
1993 | /* reset write */ |
1994 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
1995 | |
1996 | return NULL; |
1997 | } |
1998 | |
1999 | static struct ring_buffer_event * |
2000 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, |
2001 | unsigned long length, u64 ts, |
2002 | u64 delta, int add_timestamp) |
2003 | { |
2004 | struct buffer_page *tail_page; |
2005 | struct ring_buffer_event *event; |
2006 | unsigned long tail, write; |
2007 | |
2008 | /* |
2009 | * If the time delta since the last event is too big to |
2010 | * hold in the time field of the event, then we append a |
2011 | * TIME EXTEND event ahead of the data event. |
2012 | */ |
2013 | if (unlikely(add_timestamp)) |
2014 | length += RB_LEN_TIME_EXTEND; |
2015 | |
2016 | tail_page = cpu_buffer->tail_page; |
2017 | write = local_add_return(length, &tail_page->write); |
2018 | |
2019 | /* set write to only the index of the write */ |
2020 | write &= RB_WRITE_MASK; |
2021 | tail = write - length; |
2022 | |
2023 | /* See if we shot pass the end of this buffer page */ |
2024 | if (unlikely(write > BUF_PAGE_SIZE)) |
2025 | return rb_move_tail(cpu_buffer, length, tail, |
2026 | tail_page, ts); |
2027 | |
2028 | /* We reserved something on the buffer */ |
2029 | |
2030 | event = __rb_page_index(tail_page, tail); |
2031 | kmemcheck_annotate_bitfield(event, bitfield); |
2032 | rb_update_event(cpu_buffer, event, length, add_timestamp, delta); |
2033 | |
2034 | local_inc(&tail_page->entries); |
2035 | |
2036 | /* |
2037 | * If this is the first commit on the page, then update |
2038 | * its timestamp. |
2039 | */ |
2040 | if (!tail) |
2041 | tail_page->page->time_stamp = ts; |
2042 | |
2043 | return event; |
2044 | } |
2045 | |
2046 | static inline int |
2047 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, |
2048 | struct ring_buffer_event *event) |
2049 | { |
2050 | unsigned long new_index, old_index; |
2051 | struct buffer_page *bpage; |
2052 | unsigned long index; |
2053 | unsigned long addr; |
2054 | |
2055 | new_index = rb_event_index(event); |
2056 | old_index = new_index + rb_event_ts_length(event); |
2057 | addr = (unsigned long)event; |
2058 | addr &= PAGE_MASK; |
2059 | |
2060 | bpage = cpu_buffer->tail_page; |
2061 | |
2062 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { |
2063 | unsigned long write_mask = |
2064 | local_read(&bpage->write) & ~RB_WRITE_MASK; |
2065 | /* |
2066 | * This is on the tail page. It is possible that |
2067 | * a write could come in and move the tail page |
2068 | * and write to the next page. That is fine |
2069 | * because we just shorten what is on this page. |
2070 | */ |
2071 | old_index += write_mask; |
2072 | new_index += write_mask; |
2073 | index = local_cmpxchg(&bpage->write, old_index, new_index); |
2074 | if (index == old_index) |
2075 | return 1; |
2076 | } |
2077 | |
2078 | /* could not discard */ |
2079 | return 0; |
2080 | } |
2081 | |
2082 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2083 | { |
2084 | local_inc(&cpu_buffer->committing); |
2085 | local_inc(&cpu_buffer->commits); |
2086 | } |
2087 | |
2088 | static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2089 | { |
2090 | unsigned long commits; |
2091 | |
2092 | if (RB_WARN_ON(cpu_buffer, |
2093 | !local_read(&cpu_buffer->committing))) |
2094 | return; |
2095 | |
2096 | again: |
2097 | commits = local_read(&cpu_buffer->commits); |
2098 | /* synchronize with interrupts */ |
2099 | barrier(); |
2100 | if (local_read(&cpu_buffer->committing) == 1) |
2101 | rb_set_commit_to_write(cpu_buffer); |
2102 | |
2103 | local_dec(&cpu_buffer->committing); |
2104 | |
2105 | /* synchronize with interrupts */ |
2106 | barrier(); |
2107 | |
2108 | /* |
2109 | * Need to account for interrupts coming in between the |
2110 | * updating of the commit page and the clearing of the |
2111 | * committing counter. |
2112 | */ |
2113 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && |
2114 | !local_read(&cpu_buffer->committing)) { |
2115 | local_inc(&cpu_buffer->committing); |
2116 | goto again; |
2117 | } |
2118 | } |
2119 | |
2120 | static struct ring_buffer_event * |
2121 | rb_reserve_next_event(struct ring_buffer *buffer, |
2122 | struct ring_buffer_per_cpu *cpu_buffer, |
2123 | unsigned long length) |
2124 | { |
2125 | struct ring_buffer_event *event; |
2126 | u64 ts, delta; |
2127 | int nr_loops = 0; |
2128 | int add_timestamp; |
2129 | u64 diff; |
2130 | |
2131 | rb_start_commit(cpu_buffer); |
2132 | |
2133 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
2134 | /* |
2135 | * Due to the ability to swap a cpu buffer from a buffer |
2136 | * it is possible it was swapped before we committed. |
2137 | * (committing stops a swap). We check for it here and |
2138 | * if it happened, we have to fail the write. |
2139 | */ |
2140 | barrier(); |
2141 | if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) { |
2142 | local_dec(&cpu_buffer->committing); |
2143 | local_dec(&cpu_buffer->commits); |
2144 | return NULL; |
2145 | } |
2146 | #endif |
2147 | |
2148 | length = rb_calculate_event_length(length); |
2149 | again: |
2150 | add_timestamp = 0; |
2151 | delta = 0; |
2152 | |
2153 | /* |
2154 | * We allow for interrupts to reenter here and do a trace. |
2155 | * If one does, it will cause this original code to loop |
2156 | * back here. Even with heavy interrupts happening, this |
2157 | * should only happen a few times in a row. If this happens |
2158 | * 1000 times in a row, there must be either an interrupt |
2159 | * storm or we have something buggy. |
2160 | * Bail! |
2161 | */ |
2162 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
2163 | goto out_fail; |
2164 | |
2165 | ts = rb_time_stamp(cpu_buffer->buffer); |
2166 | diff = ts - cpu_buffer->write_stamp; |
2167 | |
2168 | /* make sure this diff is calculated here */ |
2169 | barrier(); |
2170 | |
2171 | /* Did the write stamp get updated already? */ |
2172 | if (likely(ts >= cpu_buffer->write_stamp)) { |
2173 | delta = diff; |
2174 | if (unlikely(test_time_stamp(delta))) { |
2175 | int local_clock_stable = 1; |
2176 | #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK |
2177 | local_clock_stable = sched_clock_stable; |
2178 | #endif |
2179 | WARN_ONCE(delta > (1ULL << 59), |
2180 | KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s", |
2181 | (unsigned long long)delta, |
2182 | (unsigned long long)ts, |
2183 | (unsigned long long)cpu_buffer->write_stamp, |
2184 | local_clock_stable ? "" : |
2185 | "If you just came from a suspend/resume,\n" |
2186 | "please switch to the trace global clock:\n" |
2187 | " echo global > /sys/kernel/debug/tracing/trace_clock\n"); |
2188 | add_timestamp = 1; |
2189 | } |
2190 | } |
2191 | |
2192 | event = __rb_reserve_next(cpu_buffer, length, ts, |
2193 | delta, add_timestamp); |
2194 | if (unlikely(PTR_ERR(event) == -EAGAIN)) |
2195 | goto again; |
2196 | |
2197 | if (!event) |
2198 | goto out_fail; |
2199 | |
2200 | return event; |
2201 | |
2202 | out_fail: |
2203 | rb_end_commit(cpu_buffer); |
2204 | return NULL; |
2205 | } |
2206 | |
2207 | #ifdef CONFIG_TRACING |
2208 | |
2209 | #define TRACE_RECURSIVE_DEPTH 16 |
2210 | |
2211 | /* Keep this code out of the fast path cache */ |
2212 | static noinline void trace_recursive_fail(void) |
2213 | { |
2214 | /* Disable all tracing before we do anything else */ |
2215 | tracing_off_permanent(); |
2216 | |
2217 | printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:" |
2218 | "HC[%lu]:SC[%lu]:NMI[%lu]\n", |
2219 | trace_recursion_buffer(), |
2220 | hardirq_count() >> HARDIRQ_SHIFT, |
2221 | softirq_count() >> SOFTIRQ_SHIFT, |
2222 | in_nmi()); |
2223 | |
2224 | WARN_ON_ONCE(1); |
2225 | } |
2226 | |
2227 | static inline int trace_recursive_lock(void) |
2228 | { |
2229 | trace_recursion_inc(); |
2230 | |
2231 | if (likely(trace_recursion_buffer() < TRACE_RECURSIVE_DEPTH)) |
2232 | return 0; |
2233 | |
2234 | trace_recursive_fail(); |
2235 | |
2236 | return -1; |
2237 | } |
2238 | |
2239 | static inline void trace_recursive_unlock(void) |
2240 | { |
2241 | WARN_ON_ONCE(!trace_recursion_buffer()); |
2242 | |
2243 | trace_recursion_dec(); |
2244 | } |
2245 | |
2246 | #else |
2247 | |
2248 | #define trace_recursive_lock() (0) |
2249 | #define trace_recursive_unlock() do { } while (0) |
2250 | |
2251 | #endif |
2252 | |
2253 | /** |
2254 | * ring_buffer_lock_reserve - reserve a part of the buffer |
2255 | * @buffer: the ring buffer to reserve from |
2256 | * @length: the length of the data to reserve (excluding event header) |
2257 | * |
2258 | * Returns a reseverd event on the ring buffer to copy directly to. |
2259 | * The user of this interface will need to get the body to write into |
2260 | * and can use the ring_buffer_event_data() interface. |
2261 | * |
2262 | * The length is the length of the data needed, not the event length |
2263 | * which also includes the event header. |
2264 | * |
2265 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. |
2266 | * If NULL is returned, then nothing has been allocated or locked. |
2267 | */ |
2268 | struct ring_buffer_event * |
2269 | ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
2270 | { |
2271 | struct ring_buffer_per_cpu *cpu_buffer; |
2272 | struct ring_buffer_event *event; |
2273 | int cpu; |
2274 | |
2275 | if (ring_buffer_flags != RB_BUFFERS_ON) |
2276 | return NULL; |
2277 | |
2278 | /* If we are tracing schedule, we don't want to recurse */ |
2279 | preempt_disable_notrace(); |
2280 | |
2281 | if (atomic_read(&buffer->record_disabled)) |
2282 | goto out_nocheck; |
2283 | |
2284 | if (trace_recursive_lock()) |
2285 | goto out_nocheck; |
2286 | |
2287 | cpu = raw_smp_processor_id(); |
2288 | |
2289 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2290 | goto out; |
2291 | |
2292 | cpu_buffer = buffer->buffers[cpu]; |
2293 | |
2294 | if (atomic_read(&cpu_buffer->record_disabled)) |
2295 | goto out; |
2296 | |
2297 | if (length > BUF_MAX_DATA_SIZE) |
2298 | goto out; |
2299 | |
2300 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
2301 | if (!event) |
2302 | goto out; |
2303 | |
2304 | return event; |
2305 | |
2306 | out: |
2307 | trace_recursive_unlock(); |
2308 | |
2309 | out_nocheck: |
2310 | preempt_enable_notrace(); |
2311 | return NULL; |
2312 | } |
2313 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
2314 | |
2315 | static void |
2316 | rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
2317 | struct ring_buffer_event *event) |
2318 | { |
2319 | u64 delta; |
2320 | |
2321 | /* |
2322 | * The event first in the commit queue updates the |
2323 | * time stamp. |
2324 | */ |
2325 | if (rb_event_is_commit(cpu_buffer, event)) { |
2326 | /* |
2327 | * A commit event that is first on a page |
2328 | * updates the write timestamp with the page stamp |
2329 | */ |
2330 | if (!rb_event_index(event)) |
2331 | cpu_buffer->write_stamp = |
2332 | cpu_buffer->commit_page->page->time_stamp; |
2333 | else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { |
2334 | delta = event->array[0]; |
2335 | delta <<= TS_SHIFT; |
2336 | delta += event->time_delta; |
2337 | cpu_buffer->write_stamp += delta; |
2338 | } else |
2339 | cpu_buffer->write_stamp += event->time_delta; |
2340 | } |
2341 | } |
2342 | |
2343 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2344 | struct ring_buffer_event *event) |
2345 | { |
2346 | local_inc(&cpu_buffer->entries); |
2347 | rb_update_write_stamp(cpu_buffer, event); |
2348 | rb_end_commit(cpu_buffer); |
2349 | } |
2350 | |
2351 | /** |
2352 | * ring_buffer_unlock_commit - commit a reserved |
2353 | * @buffer: The buffer to commit to |
2354 | * @event: The event pointer to commit. |
2355 | * |
2356 | * This commits the data to the ring buffer, and releases any locks held. |
2357 | * |
2358 | * Must be paired with ring_buffer_lock_reserve. |
2359 | */ |
2360 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, |
2361 | struct ring_buffer_event *event) |
2362 | { |
2363 | struct ring_buffer_per_cpu *cpu_buffer; |
2364 | int cpu = raw_smp_processor_id(); |
2365 | |
2366 | cpu_buffer = buffer->buffers[cpu]; |
2367 | |
2368 | rb_commit(cpu_buffer, event); |
2369 | |
2370 | trace_recursive_unlock(); |
2371 | |
2372 | preempt_enable_notrace(); |
2373 | |
2374 | return 0; |
2375 | } |
2376 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
2377 | |
2378 | static inline void rb_event_discard(struct ring_buffer_event *event) |
2379 | { |
2380 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
2381 | event = skip_time_extend(event); |
2382 | |
2383 | /* array[0] holds the actual length for the discarded event */ |
2384 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; |
2385 | event->type_len = RINGBUF_TYPE_PADDING; |
2386 | /* time delta must be non zero */ |
2387 | if (!event->time_delta) |
2388 | event->time_delta = 1; |
2389 | } |
2390 | |
2391 | /* |
2392 | * Decrement the entries to the page that an event is on. |
2393 | * The event does not even need to exist, only the pointer |
2394 | * to the page it is on. This may only be called before the commit |
2395 | * takes place. |
2396 | */ |
2397 | static inline void |
2398 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, |
2399 | struct ring_buffer_event *event) |
2400 | { |
2401 | unsigned long addr = (unsigned long)event; |
2402 | struct buffer_page *bpage = cpu_buffer->commit_page; |
2403 | struct buffer_page *start; |
2404 | |
2405 | addr &= PAGE_MASK; |
2406 | |
2407 | /* Do the likely case first */ |
2408 | if (likely(bpage->page == (void *)addr)) { |
2409 | local_dec(&bpage->entries); |
2410 | return; |
2411 | } |
2412 | |
2413 | /* |
2414 | * Because the commit page may be on the reader page we |
2415 | * start with the next page and check the end loop there. |
2416 | */ |
2417 | rb_inc_page(cpu_buffer, &bpage); |
2418 | start = bpage; |
2419 | do { |
2420 | if (bpage->page == (void *)addr) { |
2421 | local_dec(&bpage->entries); |
2422 | return; |
2423 | } |
2424 | rb_inc_page(cpu_buffer, &bpage); |
2425 | } while (bpage != start); |
2426 | |
2427 | /* commit not part of this buffer?? */ |
2428 | RB_WARN_ON(cpu_buffer, 1); |
2429 | } |
2430 | |
2431 | /** |
2432 | * ring_buffer_commit_discard - discard an event that has not been committed |
2433 | * @buffer: the ring buffer |
2434 | * @event: non committed event to discard |
2435 | * |
2436 | * Sometimes an event that is in the ring buffer needs to be ignored. |
2437 | * This function lets the user discard an event in the ring buffer |
2438 | * and then that event will not be read later. |
2439 | * |
2440 | * This function only works if it is called before the the item has been |
2441 | * committed. It will try to free the event from the ring buffer |
2442 | * if another event has not been added behind it. |
2443 | * |
2444 | * If another event has been added behind it, it will set the event |
2445 | * up as discarded, and perform the commit. |
2446 | * |
2447 | * If this function is called, do not call ring_buffer_unlock_commit on |
2448 | * the event. |
2449 | */ |
2450 | void ring_buffer_discard_commit(struct ring_buffer *buffer, |
2451 | struct ring_buffer_event *event) |
2452 | { |
2453 | struct ring_buffer_per_cpu *cpu_buffer; |
2454 | int cpu; |
2455 | |
2456 | /* The event is discarded regardless */ |
2457 | rb_event_discard(event); |
2458 | |
2459 | cpu = smp_processor_id(); |
2460 | cpu_buffer = buffer->buffers[cpu]; |
2461 | |
2462 | /* |
2463 | * This must only be called if the event has not been |
2464 | * committed yet. Thus we can assume that preemption |
2465 | * is still disabled. |
2466 | */ |
2467 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
2468 | |
2469 | rb_decrement_entry(cpu_buffer, event); |
2470 | if (rb_try_to_discard(cpu_buffer, event)) |
2471 | goto out; |
2472 | |
2473 | /* |
2474 | * The commit is still visible by the reader, so we |
2475 | * must still update the timestamp. |
2476 | */ |
2477 | rb_update_write_stamp(cpu_buffer, event); |
2478 | out: |
2479 | rb_end_commit(cpu_buffer); |
2480 | |
2481 | trace_recursive_unlock(); |
2482 | |
2483 | preempt_enable_notrace(); |
2484 | |
2485 | } |
2486 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); |
2487 | |
2488 | /** |
2489 | * ring_buffer_write - write data to the buffer without reserving |
2490 | * @buffer: The ring buffer to write to. |
2491 | * @length: The length of the data being written (excluding the event header) |
2492 | * @data: The data to write to the buffer. |
2493 | * |
2494 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as |
2495 | * one function. If you already have the data to write to the buffer, it |
2496 | * may be easier to simply call this function. |
2497 | * |
2498 | * Note, like ring_buffer_lock_reserve, the length is the length of the data |
2499 | * and not the length of the event which would hold the header. |
2500 | */ |
2501 | int ring_buffer_write(struct ring_buffer *buffer, |
2502 | unsigned long length, |
2503 | void *data) |
2504 | { |
2505 | struct ring_buffer_per_cpu *cpu_buffer; |
2506 | struct ring_buffer_event *event; |
2507 | void *body; |
2508 | int ret = -EBUSY; |
2509 | int cpu; |
2510 | |
2511 | if (ring_buffer_flags != RB_BUFFERS_ON) |
2512 | return -EBUSY; |
2513 | |
2514 | preempt_disable_notrace(); |
2515 | |
2516 | if (atomic_read(&buffer->record_disabled)) |
2517 | goto out; |
2518 | |
2519 | cpu = raw_smp_processor_id(); |
2520 | |
2521 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2522 | goto out; |
2523 | |
2524 | cpu_buffer = buffer->buffers[cpu]; |
2525 | |
2526 | if (atomic_read(&cpu_buffer->record_disabled)) |
2527 | goto out; |
2528 | |
2529 | if (length > BUF_MAX_DATA_SIZE) |
2530 | goto out; |
2531 | |
2532 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
2533 | if (!event) |
2534 | goto out; |
2535 | |
2536 | body = rb_event_data(event); |
2537 | |
2538 | memcpy(body, data, length); |
2539 | |
2540 | rb_commit(cpu_buffer, event); |
2541 | |
2542 | ret = 0; |
2543 | out: |
2544 | preempt_enable_notrace(); |
2545 | |
2546 | return ret; |
2547 | } |
2548 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
2549 | |
2550 | static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
2551 | { |
2552 | struct buffer_page *reader = cpu_buffer->reader_page; |
2553 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
2554 | struct buffer_page *commit = cpu_buffer->commit_page; |
2555 | |
2556 | /* In case of error, head will be NULL */ |
2557 | if (unlikely(!head)) |
2558 | return 1; |
2559 | |
2560 | return reader->read == rb_page_commit(reader) && |
2561 | (commit == reader || |
2562 | (commit == head && |
2563 | head->read == rb_page_commit(commit))); |
2564 | } |
2565 | |
2566 | /** |
2567 | * ring_buffer_record_disable - stop all writes into the buffer |
2568 | * @buffer: The ring buffer to stop writes to. |
2569 | * |
2570 | * This prevents all writes to the buffer. Any attempt to write |
2571 | * to the buffer after this will fail and return NULL. |
2572 | * |
2573 | * The caller should call synchronize_sched() after this. |
2574 | */ |
2575 | void ring_buffer_record_disable(struct ring_buffer *buffer) |
2576 | { |
2577 | atomic_inc(&buffer->record_disabled); |
2578 | } |
2579 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
2580 | |
2581 | /** |
2582 | * ring_buffer_record_enable - enable writes to the buffer |
2583 | * @buffer: The ring buffer to enable writes |
2584 | * |
2585 | * Note, multiple disables will need the same number of enables |
2586 | * to truly enable the writing (much like preempt_disable). |
2587 | */ |
2588 | void ring_buffer_record_enable(struct ring_buffer *buffer) |
2589 | { |
2590 | atomic_dec(&buffer->record_disabled); |
2591 | } |
2592 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
2593 | |
2594 | /** |
2595 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer |
2596 | * @buffer: The ring buffer to stop writes to. |
2597 | * @cpu: The CPU buffer to stop |
2598 | * |
2599 | * This prevents all writes to the buffer. Any attempt to write |
2600 | * to the buffer after this will fail and return NULL. |
2601 | * |
2602 | * The caller should call synchronize_sched() after this. |
2603 | */ |
2604 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) |
2605 | { |
2606 | struct ring_buffer_per_cpu *cpu_buffer; |
2607 | |
2608 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2609 | return; |
2610 | |
2611 | cpu_buffer = buffer->buffers[cpu]; |
2612 | atomic_inc(&cpu_buffer->record_disabled); |
2613 | } |
2614 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
2615 | |
2616 | /** |
2617 | * ring_buffer_record_enable_cpu - enable writes to the buffer |
2618 | * @buffer: The ring buffer to enable writes |
2619 | * @cpu: The CPU to enable. |
2620 | * |
2621 | * Note, multiple disables will need the same number of enables |
2622 | * to truly enable the writing (much like preempt_disable). |
2623 | */ |
2624 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) |
2625 | { |
2626 | struct ring_buffer_per_cpu *cpu_buffer; |
2627 | |
2628 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2629 | return; |
2630 | |
2631 | cpu_buffer = buffer->buffers[cpu]; |
2632 | atomic_dec(&cpu_buffer->record_disabled); |
2633 | } |
2634 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
2635 | |
2636 | /* |
2637 | * The total entries in the ring buffer is the running counter |
2638 | * of entries entered into the ring buffer, minus the sum of |
2639 | * the entries read from the ring buffer and the number of |
2640 | * entries that were overwritten. |
2641 | */ |
2642 | static inline unsigned long |
2643 | rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) |
2644 | { |
2645 | return local_read(&cpu_buffer->entries) - |
2646 | (local_read(&cpu_buffer->overrun) + cpu_buffer->read); |
2647 | } |
2648 | |
2649 | /** |
2650 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer |
2651 | * @buffer: The ring buffer |
2652 | * @cpu: The per CPU buffer to get the entries from. |
2653 | */ |
2654 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) |
2655 | { |
2656 | struct ring_buffer_per_cpu *cpu_buffer; |
2657 | |
2658 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2659 | return 0; |
2660 | |
2661 | cpu_buffer = buffer->buffers[cpu]; |
2662 | |
2663 | return rb_num_of_entries(cpu_buffer); |
2664 | } |
2665 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
2666 | |
2667 | /** |
2668 | * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer |
2669 | * @buffer: The ring buffer |
2670 | * @cpu: The per CPU buffer to get the number of overruns from |
2671 | */ |
2672 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) |
2673 | { |
2674 | struct ring_buffer_per_cpu *cpu_buffer; |
2675 | unsigned long ret; |
2676 | |
2677 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2678 | return 0; |
2679 | |
2680 | cpu_buffer = buffer->buffers[cpu]; |
2681 | ret = local_read(&cpu_buffer->overrun); |
2682 | |
2683 | return ret; |
2684 | } |
2685 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
2686 | |
2687 | /** |
2688 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits |
2689 | * @buffer: The ring buffer |
2690 | * @cpu: The per CPU buffer to get the number of overruns from |
2691 | */ |
2692 | unsigned long |
2693 | ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) |
2694 | { |
2695 | struct ring_buffer_per_cpu *cpu_buffer; |
2696 | unsigned long ret; |
2697 | |
2698 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
2699 | return 0; |
2700 | |
2701 | cpu_buffer = buffer->buffers[cpu]; |
2702 | ret = local_read(&cpu_buffer->commit_overrun); |
2703 | |
2704 | return ret; |
2705 | } |
2706 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); |
2707 | |
2708 | /** |
2709 | * ring_buffer_entries - get the number of entries in a buffer |
2710 | * @buffer: The ring buffer |
2711 | * |
2712 | * Returns the total number of entries in the ring buffer |
2713 | * (all CPU entries) |
2714 | */ |
2715 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) |
2716 | { |
2717 | struct ring_buffer_per_cpu *cpu_buffer; |
2718 | unsigned long entries = 0; |
2719 | int cpu; |
2720 | |
2721 | /* if you care about this being correct, lock the buffer */ |
2722 | for_each_buffer_cpu(buffer, cpu) { |
2723 | cpu_buffer = buffer->buffers[cpu]; |
2724 | entries += rb_num_of_entries(cpu_buffer); |
2725 | } |
2726 | |
2727 | return entries; |
2728 | } |
2729 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
2730 | |
2731 | /** |
2732 | * ring_buffer_overruns - get the number of overruns in buffer |
2733 | * @buffer: The ring buffer |
2734 | * |
2735 | * Returns the total number of overruns in the ring buffer |
2736 | * (all CPU entries) |
2737 | */ |
2738 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) |
2739 | { |
2740 | struct ring_buffer_per_cpu *cpu_buffer; |
2741 | unsigned long overruns = 0; |
2742 | int cpu; |
2743 | |
2744 | /* if you care about this being correct, lock the buffer */ |
2745 | for_each_buffer_cpu(buffer, cpu) { |
2746 | cpu_buffer = buffer->buffers[cpu]; |
2747 | overruns += local_read(&cpu_buffer->overrun); |
2748 | } |
2749 | |
2750 | return overruns; |
2751 | } |
2752 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
2753 | |
2754 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
2755 | { |
2756 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
2757 | |
2758 | /* Iterator usage is expected to have record disabled */ |
2759 | if (list_empty(&cpu_buffer->reader_page->list)) { |
2760 | iter->head_page = rb_set_head_page(cpu_buffer); |
2761 | if (unlikely(!iter->head_page)) |
2762 | return; |
2763 | iter->head = iter->head_page->read; |
2764 | } else { |
2765 | iter->head_page = cpu_buffer->reader_page; |
2766 | iter->head = cpu_buffer->reader_page->read; |
2767 | } |
2768 | if (iter->head) |
2769 | iter->read_stamp = cpu_buffer->read_stamp; |
2770 | else |
2771 | iter->read_stamp = iter->head_page->page->time_stamp; |
2772 | iter->cache_reader_page = cpu_buffer->reader_page; |
2773 | iter->cache_read = cpu_buffer->read; |
2774 | } |
2775 | |
2776 | /** |
2777 | * ring_buffer_iter_reset - reset an iterator |
2778 | * @iter: The iterator to reset |
2779 | * |
2780 | * Resets the iterator, so that it will start from the beginning |
2781 | * again. |
2782 | */ |
2783 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) |
2784 | { |
2785 | struct ring_buffer_per_cpu *cpu_buffer; |
2786 | unsigned long flags; |
2787 | |
2788 | if (!iter) |
2789 | return; |
2790 | |
2791 | cpu_buffer = iter->cpu_buffer; |
2792 | |
2793 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
2794 | rb_iter_reset(iter); |
2795 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
2796 | } |
2797 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
2798 | |
2799 | /** |
2800 | * ring_buffer_iter_empty - check if an iterator has no more to read |
2801 | * @iter: The iterator to check |
2802 | */ |
2803 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) |
2804 | { |
2805 | struct ring_buffer_per_cpu *cpu_buffer; |
2806 | |
2807 | cpu_buffer = iter->cpu_buffer; |
2808 | |
2809 | return iter->head_page == cpu_buffer->commit_page && |
2810 | iter->head == rb_commit_index(cpu_buffer); |
2811 | } |
2812 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
2813 | |
2814 | static void |
2815 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
2816 | struct ring_buffer_event *event) |
2817 | { |
2818 | u64 delta; |
2819 | |
2820 | switch (event->type_len) { |
2821 | case RINGBUF_TYPE_PADDING: |
2822 | return; |
2823 | |
2824 | case RINGBUF_TYPE_TIME_EXTEND: |
2825 | delta = event->array[0]; |
2826 | delta <<= TS_SHIFT; |
2827 | delta += event->time_delta; |
2828 | cpu_buffer->read_stamp += delta; |
2829 | return; |
2830 | |
2831 | case RINGBUF_TYPE_TIME_STAMP: |
2832 | /* FIXME: not implemented */ |
2833 | return; |
2834 | |
2835 | case RINGBUF_TYPE_DATA: |
2836 | cpu_buffer->read_stamp += event->time_delta; |
2837 | return; |
2838 | |
2839 | default: |
2840 | BUG(); |
2841 | } |
2842 | return; |
2843 | } |
2844 | |
2845 | static void |
2846 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, |
2847 | struct ring_buffer_event *event) |
2848 | { |
2849 | u64 delta; |
2850 | |
2851 | switch (event->type_len) { |
2852 | case RINGBUF_TYPE_PADDING: |
2853 | return; |
2854 | |
2855 | case RINGBUF_TYPE_TIME_EXTEND: |
2856 | delta = event->array[0]; |
2857 | delta <<= TS_SHIFT; |
2858 | delta += event->time_delta; |
2859 | iter->read_stamp += delta; |
2860 | return; |
2861 | |
2862 | case RINGBUF_TYPE_TIME_STAMP: |
2863 | /* FIXME: not implemented */ |
2864 | return; |
2865 | |
2866 | case RINGBUF_TYPE_DATA: |
2867 | iter->read_stamp += event->time_delta; |
2868 | return; |
2869 | |
2870 | default: |
2871 | BUG(); |
2872 | } |
2873 | return; |
2874 | } |
2875 | |
2876 | static struct buffer_page * |
2877 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
2878 | { |
2879 | struct buffer_page *reader = NULL; |
2880 | unsigned long overwrite; |
2881 | unsigned long flags; |
2882 | int nr_loops = 0; |
2883 | int ret; |
2884 | |
2885 | local_irq_save(flags); |
2886 | arch_spin_lock(&cpu_buffer->lock); |
2887 | |
2888 | again: |
2889 | /* |
2890 | * This should normally only loop twice. But because the |
2891 | * start of the reader inserts an empty page, it causes |
2892 | * a case where we will loop three times. There should be no |
2893 | * reason to loop four times (that I know of). |
2894 | */ |
2895 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
2896 | reader = NULL; |
2897 | goto out; |
2898 | } |
2899 | |
2900 | reader = cpu_buffer->reader_page; |
2901 | |
2902 | /* If there's more to read, return this page */ |
2903 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
2904 | goto out; |
2905 | |
2906 | /* Never should we have an index greater than the size */ |
2907 | if (RB_WARN_ON(cpu_buffer, |
2908 | cpu_buffer->reader_page->read > rb_page_size(reader))) |
2909 | goto out; |
2910 | |
2911 | /* check if we caught up to the tail */ |
2912 | reader = NULL; |
2913 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
2914 | goto out; |
2915 | |
2916 | /* |
2917 | * Reset the reader page to size zero. |
2918 | */ |
2919 | local_set(&cpu_buffer->reader_page->write, 0); |
2920 | local_set(&cpu_buffer->reader_page->entries, 0); |
2921 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
2922 | cpu_buffer->reader_page->real_end = 0; |
2923 | |
2924 | spin: |
2925 | /* |
2926 | * Splice the empty reader page into the list around the head. |
2927 | */ |
2928 | reader = rb_set_head_page(cpu_buffer); |
2929 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
2930 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
2931 | |
2932 | /* |
2933 | * cpu_buffer->pages just needs to point to the buffer, it |
2934 | * has no specific buffer page to point to. Lets move it out |
2935 | * of our way so we don't accidentally swap it. |
2936 | */ |
2937 | cpu_buffer->pages = reader->list.prev; |
2938 | |
2939 | /* The reader page will be pointing to the new head */ |
2940 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); |
2941 | |
2942 | /* |
2943 | * We want to make sure we read the overruns after we set up our |
2944 | * pointers to the next object. The writer side does a |
2945 | * cmpxchg to cross pages which acts as the mb on the writer |
2946 | * side. Note, the reader will constantly fail the swap |
2947 | * while the writer is updating the pointers, so this |
2948 | * guarantees that the overwrite recorded here is the one we |
2949 | * want to compare with the last_overrun. |
2950 | */ |
2951 | smp_mb(); |
2952 | overwrite = local_read(&(cpu_buffer->overrun)); |
2953 | |
2954 | /* |
2955 | * Here's the tricky part. |
2956 | * |
2957 | * We need to move the pointer past the header page. |
2958 | * But we can only do that if a writer is not currently |
2959 | * moving it. The page before the header page has the |
2960 | * flag bit '1' set if it is pointing to the page we want. |
2961 | * but if the writer is in the process of moving it |
2962 | * than it will be '2' or already moved '0'. |
2963 | */ |
2964 | |
2965 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); |
2966 | |
2967 | /* |
2968 | * If we did not convert it, then we must try again. |
2969 | */ |
2970 | if (!ret) |
2971 | goto spin; |
2972 | |
2973 | /* |
2974 | * Yeah! We succeeded in replacing the page. |
2975 | * |
2976 | * Now make the new head point back to the reader page. |
2977 | */ |
2978 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
2979 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
2980 | |
2981 | /* Finally update the reader page to the new head */ |
2982 | cpu_buffer->reader_page = reader; |
2983 | rb_reset_reader_page(cpu_buffer); |
2984 | |
2985 | if (overwrite != cpu_buffer->last_overrun) { |
2986 | cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; |
2987 | cpu_buffer->last_overrun = overwrite; |
2988 | } |
2989 | |
2990 | goto again; |
2991 | |
2992 | out: |
2993 | arch_spin_unlock(&cpu_buffer->lock); |
2994 | local_irq_restore(flags); |
2995 | |
2996 | return reader; |
2997 | } |
2998 | |
2999 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) |
3000 | { |
3001 | struct ring_buffer_event *event; |
3002 | struct buffer_page *reader; |
3003 | unsigned length; |
3004 | |
3005 | reader = rb_get_reader_page(cpu_buffer); |
3006 | |
3007 | /* This function should not be called when buffer is empty */ |
3008 | if (RB_WARN_ON(cpu_buffer, !reader)) |
3009 | return; |
3010 | |
3011 | event = rb_reader_event(cpu_buffer); |
3012 | |
3013 | if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
3014 | cpu_buffer->read++; |
3015 | |
3016 | rb_update_read_stamp(cpu_buffer, event); |
3017 | |
3018 | length = rb_event_length(event); |
3019 | cpu_buffer->reader_page->read += length; |
3020 | } |
3021 | |
3022 | static void rb_advance_iter(struct ring_buffer_iter *iter) |
3023 | { |
3024 | struct ring_buffer_per_cpu *cpu_buffer; |
3025 | struct ring_buffer_event *event; |
3026 | unsigned length; |
3027 | |
3028 | cpu_buffer = iter->cpu_buffer; |
3029 | |
3030 | /* |
3031 | * Check if we are at the end of the buffer. |
3032 | */ |
3033 | if (iter->head >= rb_page_size(iter->head_page)) { |
3034 | /* discarded commits can make the page empty */ |
3035 | if (iter->head_page == cpu_buffer->commit_page) |
3036 | return; |
3037 | rb_inc_iter(iter); |
3038 | return; |
3039 | } |
3040 | |
3041 | event = rb_iter_head_event(iter); |
3042 | |
3043 | length = rb_event_length(event); |
3044 | |
3045 | /* |
3046 | * This should not be called to advance the header if we are |
3047 | * at the tail of the buffer. |
3048 | */ |
3049 | if (RB_WARN_ON(cpu_buffer, |
3050 | (iter->head_page == cpu_buffer->commit_page) && |
3051 | (iter->head + length > rb_commit_index(cpu_buffer)))) |
3052 | return; |
3053 | |
3054 | rb_update_iter_read_stamp(iter, event); |
3055 | |
3056 | iter->head += length; |
3057 | |
3058 | /* check for end of page padding */ |
3059 | if ((iter->head >= rb_page_size(iter->head_page)) && |
3060 | (iter->head_page != cpu_buffer->commit_page)) |
3061 | rb_advance_iter(iter); |
3062 | } |
3063 | |
3064 | static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) |
3065 | { |
3066 | return cpu_buffer->lost_events; |
3067 | } |
3068 | |
3069 | static struct ring_buffer_event * |
3070 | rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, |
3071 | unsigned long *lost_events) |
3072 | { |
3073 | struct ring_buffer_event *event; |
3074 | struct buffer_page *reader; |
3075 | int nr_loops = 0; |
3076 | |
3077 | again: |
3078 | /* |
3079 | * We repeat when a time extend is encountered. |
3080 | * Since the time extend is always attached to a data event, |
3081 | * we should never loop more than once. |
3082 | * (We never hit the following condition more than twice). |
3083 | */ |
3084 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
3085 | return NULL; |
3086 | |
3087 | reader = rb_get_reader_page(cpu_buffer); |
3088 | if (!reader) |
3089 | return NULL; |
3090 | |
3091 | event = rb_reader_event(cpu_buffer); |
3092 | |
3093 | switch (event->type_len) { |
3094 | case RINGBUF_TYPE_PADDING: |
3095 | if (rb_null_event(event)) |
3096 | RB_WARN_ON(cpu_buffer, 1); |
3097 | /* |
3098 | * Because the writer could be discarding every |
3099 | * event it creates (which would probably be bad) |
3100 | * if we were to go back to "again" then we may never |
3101 | * catch up, and will trigger the warn on, or lock |
3102 | * the box. Return the padding, and we will release |
3103 | * the current locks, and try again. |
3104 | */ |
3105 | return event; |
3106 | |
3107 | case RINGBUF_TYPE_TIME_EXTEND: |
3108 | /* Internal data, OK to advance */ |
3109 | rb_advance_reader(cpu_buffer); |
3110 | goto again; |
3111 | |
3112 | case RINGBUF_TYPE_TIME_STAMP: |
3113 | /* FIXME: not implemented */ |
3114 | rb_advance_reader(cpu_buffer); |
3115 | goto again; |
3116 | |
3117 | case RINGBUF_TYPE_DATA: |
3118 | if (ts) { |
3119 | *ts = cpu_buffer->read_stamp + event->time_delta; |
3120 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
3121 | cpu_buffer->cpu, ts); |
3122 | } |
3123 | if (lost_events) |
3124 | *lost_events = rb_lost_events(cpu_buffer); |
3125 | return event; |
3126 | |
3127 | default: |
3128 | BUG(); |
3129 | } |
3130 | |
3131 | return NULL; |
3132 | } |
3133 | EXPORT_SYMBOL_GPL(ring_buffer_peek); |
3134 | |
3135 | static struct ring_buffer_event * |
3136 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) |
3137 | { |
3138 | struct ring_buffer *buffer; |
3139 | struct ring_buffer_per_cpu *cpu_buffer; |
3140 | struct ring_buffer_event *event; |
3141 | int nr_loops = 0; |
3142 | |
3143 | cpu_buffer = iter->cpu_buffer; |
3144 | buffer = cpu_buffer->buffer; |
3145 | |
3146 | /* |
3147 | * Check if someone performed a consuming read to |
3148 | * the buffer. A consuming read invalidates the iterator |
3149 | * and we need to reset the iterator in this case. |
3150 | */ |
3151 | if (unlikely(iter->cache_read != cpu_buffer->read || |
3152 | iter->cache_reader_page != cpu_buffer->reader_page)) |
3153 | rb_iter_reset(iter); |
3154 | |
3155 | again: |
3156 | if (ring_buffer_iter_empty(iter)) |
3157 | return NULL; |
3158 | |
3159 | /* |
3160 | * We repeat when a time extend is encountered. |
3161 | * Since the time extend is always attached to a data event, |
3162 | * we should never loop more than once. |
3163 | * (We never hit the following condition more than twice). |
3164 | */ |
3165 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
3166 | return NULL; |
3167 | |
3168 | if (rb_per_cpu_empty(cpu_buffer)) |
3169 | return NULL; |
3170 | |
3171 | if (iter->head >= local_read(&iter->head_page->page->commit)) { |
3172 | rb_inc_iter(iter); |
3173 | goto again; |
3174 | } |
3175 | |
3176 | event = rb_iter_head_event(iter); |
3177 | |
3178 | switch (event->type_len) { |
3179 | case RINGBUF_TYPE_PADDING: |
3180 | if (rb_null_event(event)) { |
3181 | rb_inc_iter(iter); |
3182 | goto again; |
3183 | } |
3184 | rb_advance_iter(iter); |
3185 | return event; |
3186 | |
3187 | case RINGBUF_TYPE_TIME_EXTEND: |
3188 | /* Internal data, OK to advance */ |
3189 | rb_advance_iter(iter); |
3190 | goto again; |
3191 | |
3192 | case RINGBUF_TYPE_TIME_STAMP: |
3193 | /* FIXME: not implemented */ |
3194 | rb_advance_iter(iter); |
3195 | goto again; |
3196 | |
3197 | case RINGBUF_TYPE_DATA: |
3198 | if (ts) { |
3199 | *ts = iter->read_stamp + event->time_delta; |
3200 | ring_buffer_normalize_time_stamp(buffer, |
3201 | cpu_buffer->cpu, ts); |
3202 | } |
3203 | return event; |
3204 | |
3205 | default: |
3206 | BUG(); |
3207 | } |
3208 | |
3209 | return NULL; |
3210 | } |
3211 | EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
3212 | |
3213 | static inline int rb_ok_to_lock(void) |
3214 | { |
3215 | /* |
3216 | * If an NMI die dumps out the content of the ring buffer |
3217 | * do not grab locks. We also permanently disable the ring |
3218 | * buffer too. A one time deal is all you get from reading |
3219 | * the ring buffer from an NMI. |
3220 | */ |
3221 | if (likely(!in_nmi())) |
3222 | return 1; |
3223 | |
3224 | tracing_off_permanent(); |
3225 | return 0; |
3226 | } |
3227 | |
3228 | /** |
3229 | * ring_buffer_peek - peek at the next event to be read |
3230 | * @buffer: The ring buffer to read |
3231 | * @cpu: The cpu to peak at |
3232 | * @ts: The timestamp counter of this event. |
3233 | * @lost_events: a variable to store if events were lost (may be NULL) |
3234 | * |
3235 | * This will return the event that will be read next, but does |
3236 | * not consume the data. |
3237 | */ |
3238 | struct ring_buffer_event * |
3239 | ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts, |
3240 | unsigned long *lost_events) |
3241 | { |
3242 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
3243 | struct ring_buffer_event *event; |
3244 | unsigned long flags; |
3245 | int dolock; |
3246 | |
3247 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3248 | return NULL; |
3249 | |
3250 | dolock = rb_ok_to_lock(); |
3251 | again: |
3252 | local_irq_save(flags); |
3253 | if (dolock) |
3254 | spin_lock(&cpu_buffer->reader_lock); |
3255 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
3256 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3257 | rb_advance_reader(cpu_buffer); |
3258 | if (dolock) |
3259 | spin_unlock(&cpu_buffer->reader_lock); |
3260 | local_irq_restore(flags); |
3261 | |
3262 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3263 | goto again; |
3264 | |
3265 | return event; |
3266 | } |
3267 | |
3268 | /** |
3269 | * ring_buffer_iter_peek - peek at the next event to be read |
3270 | * @iter: The ring buffer iterator |
3271 | * @ts: The timestamp counter of this event. |
3272 | * |
3273 | * This will return the event that will be read next, but does |
3274 | * not increment the iterator. |
3275 | */ |
3276 | struct ring_buffer_event * |
3277 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) |
3278 | { |
3279 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
3280 | struct ring_buffer_event *event; |
3281 | unsigned long flags; |
3282 | |
3283 | again: |
3284 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3285 | event = rb_iter_peek(iter, ts); |
3286 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3287 | |
3288 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3289 | goto again; |
3290 | |
3291 | return event; |
3292 | } |
3293 | |
3294 | /** |
3295 | * ring_buffer_consume - return an event and consume it |
3296 | * @buffer: The ring buffer to get the next event from |
3297 | * @cpu: the cpu to read the buffer from |
3298 | * @ts: a variable to store the timestamp (may be NULL) |
3299 | * @lost_events: a variable to store if events were lost (may be NULL) |
3300 | * |
3301 | * Returns the next event in the ring buffer, and that event is consumed. |
3302 | * Meaning, that sequential reads will keep returning a different event, |
3303 | * and eventually empty the ring buffer if the producer is slower. |
3304 | */ |
3305 | struct ring_buffer_event * |
3306 | ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, |
3307 | unsigned long *lost_events) |
3308 | { |
3309 | struct ring_buffer_per_cpu *cpu_buffer; |
3310 | struct ring_buffer_event *event = NULL; |
3311 | unsigned long flags; |
3312 | int dolock; |
3313 | |
3314 | dolock = rb_ok_to_lock(); |
3315 | |
3316 | again: |
3317 | /* might be called in atomic */ |
3318 | preempt_disable(); |
3319 | |
3320 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3321 | goto out; |
3322 | |
3323 | cpu_buffer = buffer->buffers[cpu]; |
3324 | local_irq_save(flags); |
3325 | if (dolock) |
3326 | spin_lock(&cpu_buffer->reader_lock); |
3327 | |
3328 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
3329 | if (event) { |
3330 | cpu_buffer->lost_events = 0; |
3331 | rb_advance_reader(cpu_buffer); |
3332 | } |
3333 | |
3334 | if (dolock) |
3335 | spin_unlock(&cpu_buffer->reader_lock); |
3336 | local_irq_restore(flags); |
3337 | |
3338 | out: |
3339 | preempt_enable(); |
3340 | |
3341 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3342 | goto again; |
3343 | |
3344 | return event; |
3345 | } |
3346 | EXPORT_SYMBOL_GPL(ring_buffer_consume); |
3347 | |
3348 | /** |
3349 | * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer |
3350 | * @buffer: The ring buffer to read from |
3351 | * @cpu: The cpu buffer to iterate over |
3352 | * |
3353 | * This performs the initial preparations necessary to iterate |
3354 | * through the buffer. Memory is allocated, buffer recording |
3355 | * is disabled, and the iterator pointer is returned to the caller. |
3356 | * |
3357 | * Disabling buffer recordng prevents the reading from being |
3358 | * corrupted. This is not a consuming read, so a producer is not |
3359 | * expected. |
3360 | * |
3361 | * After a sequence of ring_buffer_read_prepare calls, the user is |
3362 | * expected to make at least one call to ring_buffer_prepare_sync. |
3363 | * Afterwards, ring_buffer_read_start is invoked to get things going |
3364 | * for real. |
3365 | * |
3366 | * This overall must be paired with ring_buffer_finish. |
3367 | */ |
3368 | struct ring_buffer_iter * |
3369 | ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu) |
3370 | { |
3371 | struct ring_buffer_per_cpu *cpu_buffer; |
3372 | struct ring_buffer_iter *iter; |
3373 | |
3374 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3375 | return NULL; |
3376 | |
3377 | iter = kmalloc(sizeof(*iter), GFP_KERNEL); |
3378 | if (!iter) |
3379 | return NULL; |
3380 | |
3381 | cpu_buffer = buffer->buffers[cpu]; |
3382 | |
3383 | iter->cpu_buffer = cpu_buffer; |
3384 | |
3385 | atomic_inc(&cpu_buffer->record_disabled); |
3386 | |
3387 | return iter; |
3388 | } |
3389 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); |
3390 | |
3391 | /** |
3392 | * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls |
3393 | * |
3394 | * All previously invoked ring_buffer_read_prepare calls to prepare |
3395 | * iterators will be synchronized. Afterwards, read_buffer_read_start |
3396 | * calls on those iterators are allowed. |
3397 | */ |
3398 | void |
3399 | ring_buffer_read_prepare_sync(void) |
3400 | { |
3401 | synchronize_sched(); |
3402 | } |
3403 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); |
3404 | |
3405 | /** |
3406 | * ring_buffer_read_start - start a non consuming read of the buffer |
3407 | * @iter: The iterator returned by ring_buffer_read_prepare |
3408 | * |
3409 | * This finalizes the startup of an iteration through the buffer. |
3410 | * The iterator comes from a call to ring_buffer_read_prepare and |
3411 | * an intervening ring_buffer_read_prepare_sync must have been |
3412 | * performed. |
3413 | * |
3414 | * Must be paired with ring_buffer_finish. |
3415 | */ |
3416 | void |
3417 | ring_buffer_read_start(struct ring_buffer_iter *iter) |
3418 | { |
3419 | struct ring_buffer_per_cpu *cpu_buffer; |
3420 | unsigned long flags; |
3421 | |
3422 | if (!iter) |
3423 | return; |
3424 | |
3425 | cpu_buffer = iter->cpu_buffer; |
3426 | |
3427 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3428 | arch_spin_lock(&cpu_buffer->lock); |
3429 | rb_iter_reset(iter); |
3430 | arch_spin_unlock(&cpu_buffer->lock); |
3431 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3432 | } |
3433 | EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
3434 | |
3435 | /** |
3436 | * ring_buffer_finish - finish reading the iterator of the buffer |
3437 | * @iter: The iterator retrieved by ring_buffer_start |
3438 | * |
3439 | * This re-enables the recording to the buffer, and frees the |
3440 | * iterator. |
3441 | */ |
3442 | void |
3443 | ring_buffer_read_finish(struct ring_buffer_iter *iter) |
3444 | { |
3445 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
3446 | |
3447 | atomic_dec(&cpu_buffer->record_disabled); |
3448 | kfree(iter); |
3449 | } |
3450 | EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
3451 | |
3452 | /** |
3453 | * ring_buffer_read - read the next item in the ring buffer by the iterator |
3454 | * @iter: The ring buffer iterator |
3455 | * @ts: The time stamp of the event read. |
3456 | * |
3457 | * This reads the next event in the ring buffer and increments the iterator. |
3458 | */ |
3459 | struct ring_buffer_event * |
3460 | ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) |
3461 | { |
3462 | struct ring_buffer_event *event; |
3463 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
3464 | unsigned long flags; |
3465 | |
3466 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3467 | again: |
3468 | event = rb_iter_peek(iter, ts); |
3469 | if (!event) |
3470 | goto out; |
3471 | |
3472 | if (event->type_len == RINGBUF_TYPE_PADDING) |
3473 | goto again; |
3474 | |
3475 | rb_advance_iter(iter); |
3476 | out: |
3477 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3478 | |
3479 | return event; |
3480 | } |
3481 | EXPORT_SYMBOL_GPL(ring_buffer_read); |
3482 | |
3483 | /** |
3484 | * ring_buffer_size - return the size of the ring buffer (in bytes) |
3485 | * @buffer: The ring buffer. |
3486 | */ |
3487 | unsigned long ring_buffer_size(struct ring_buffer *buffer) |
3488 | { |
3489 | return BUF_PAGE_SIZE * buffer->pages; |
3490 | } |
3491 | EXPORT_SYMBOL_GPL(ring_buffer_size); |
3492 | |
3493 | static void |
3494 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) |
3495 | { |
3496 | rb_head_page_deactivate(cpu_buffer); |
3497 | |
3498 | cpu_buffer->head_page |
3499 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
3500 | local_set(&cpu_buffer->head_page->write, 0); |
3501 | local_set(&cpu_buffer->head_page->entries, 0); |
3502 | local_set(&cpu_buffer->head_page->page->commit, 0); |
3503 | |
3504 | cpu_buffer->head_page->read = 0; |
3505 | |
3506 | cpu_buffer->tail_page = cpu_buffer->head_page; |
3507 | cpu_buffer->commit_page = cpu_buffer->head_page; |
3508 | |
3509 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
3510 | local_set(&cpu_buffer->reader_page->write, 0); |
3511 | local_set(&cpu_buffer->reader_page->entries, 0); |
3512 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
3513 | cpu_buffer->reader_page->read = 0; |
3514 | |
3515 | local_set(&cpu_buffer->commit_overrun, 0); |
3516 | local_set(&cpu_buffer->overrun, 0); |
3517 | local_set(&cpu_buffer->entries, 0); |
3518 | local_set(&cpu_buffer->committing, 0); |
3519 | local_set(&cpu_buffer->commits, 0); |
3520 | cpu_buffer->read = 0; |
3521 | |
3522 | cpu_buffer->write_stamp = 0; |
3523 | cpu_buffer->read_stamp = 0; |
3524 | |
3525 | cpu_buffer->lost_events = 0; |
3526 | cpu_buffer->last_overrun = 0; |
3527 | |
3528 | rb_head_page_activate(cpu_buffer); |
3529 | } |
3530 | |
3531 | /** |
3532 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer |
3533 | * @buffer: The ring buffer to reset a per cpu buffer of |
3534 | * @cpu: The CPU buffer to be reset |
3535 | */ |
3536 | void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) |
3537 | { |
3538 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
3539 | unsigned long flags; |
3540 | |
3541 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3542 | return; |
3543 | |
3544 | atomic_inc(&cpu_buffer->record_disabled); |
3545 | |
3546 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3547 | |
3548 | if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) |
3549 | goto out; |
3550 | |
3551 | arch_spin_lock(&cpu_buffer->lock); |
3552 | |
3553 | rb_reset_cpu(cpu_buffer); |
3554 | |
3555 | arch_spin_unlock(&cpu_buffer->lock); |
3556 | |
3557 | out: |
3558 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3559 | |
3560 | atomic_dec(&cpu_buffer->record_disabled); |
3561 | } |
3562 | EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); |
3563 | |
3564 | /** |
3565 | * ring_buffer_reset - reset a ring buffer |
3566 | * @buffer: The ring buffer to reset all cpu buffers |
3567 | */ |
3568 | void ring_buffer_reset(struct ring_buffer *buffer) |
3569 | { |
3570 | int cpu; |
3571 | |
3572 | for_each_buffer_cpu(buffer, cpu) |
3573 | ring_buffer_reset_cpu(buffer, cpu); |
3574 | } |
3575 | EXPORT_SYMBOL_GPL(ring_buffer_reset); |
3576 | |
3577 | /** |
3578 | * rind_buffer_empty - is the ring buffer empty? |
3579 | * @buffer: The ring buffer to test |
3580 | */ |
3581 | int ring_buffer_empty(struct ring_buffer *buffer) |
3582 | { |
3583 | struct ring_buffer_per_cpu *cpu_buffer; |
3584 | unsigned long flags; |
3585 | int dolock; |
3586 | int cpu; |
3587 | int ret; |
3588 | |
3589 | dolock = rb_ok_to_lock(); |
3590 | |
3591 | /* yes this is racy, but if you don't like the race, lock the buffer */ |
3592 | for_each_buffer_cpu(buffer, cpu) { |
3593 | cpu_buffer = buffer->buffers[cpu]; |
3594 | local_irq_save(flags); |
3595 | if (dolock) |
3596 | spin_lock(&cpu_buffer->reader_lock); |
3597 | ret = rb_per_cpu_empty(cpu_buffer); |
3598 | if (dolock) |
3599 | spin_unlock(&cpu_buffer->reader_lock); |
3600 | local_irq_restore(flags); |
3601 | |
3602 | if (!ret) |
3603 | return 0; |
3604 | } |
3605 | |
3606 | return 1; |
3607 | } |
3608 | EXPORT_SYMBOL_GPL(ring_buffer_empty); |
3609 | |
3610 | /** |
3611 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? |
3612 | * @buffer: The ring buffer |
3613 | * @cpu: The CPU buffer to test |
3614 | */ |
3615 | int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) |
3616 | { |
3617 | struct ring_buffer_per_cpu *cpu_buffer; |
3618 | unsigned long flags; |
3619 | int dolock; |
3620 | int ret; |
3621 | |
3622 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3623 | return 1; |
3624 | |
3625 | dolock = rb_ok_to_lock(); |
3626 | |
3627 | cpu_buffer = buffer->buffers[cpu]; |
3628 | local_irq_save(flags); |
3629 | if (dolock) |
3630 | spin_lock(&cpu_buffer->reader_lock); |
3631 | ret = rb_per_cpu_empty(cpu_buffer); |
3632 | if (dolock) |
3633 | spin_unlock(&cpu_buffer->reader_lock); |
3634 | local_irq_restore(flags); |
3635 | |
3636 | return ret; |
3637 | } |
3638 | EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
3639 | |
3640 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
3641 | /** |
3642 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers |
3643 | * @buffer_a: One buffer to swap with |
3644 | * @buffer_b: The other buffer to swap with |
3645 | * |
3646 | * This function is useful for tracers that want to take a "snapshot" |
3647 | * of a CPU buffer and has another back up buffer lying around. |
3648 | * it is expected that the tracer handles the cpu buffer not being |
3649 | * used at the moment. |
3650 | */ |
3651 | int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, |
3652 | struct ring_buffer *buffer_b, int cpu) |
3653 | { |
3654 | struct ring_buffer_per_cpu *cpu_buffer_a; |
3655 | struct ring_buffer_per_cpu *cpu_buffer_b; |
3656 | int ret = -EINVAL; |
3657 | |
3658 | if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
3659 | !cpumask_test_cpu(cpu, buffer_b->cpumask)) |
3660 | goto out; |
3661 | |
3662 | /* At least make sure the two buffers are somewhat the same */ |
3663 | if (buffer_a->pages != buffer_b->pages) |
3664 | goto out; |
3665 | |
3666 | ret = -EAGAIN; |
3667 | |
3668 | if (ring_buffer_flags != RB_BUFFERS_ON) |
3669 | goto out; |
3670 | |
3671 | if (atomic_read(&buffer_a->record_disabled)) |
3672 | goto out; |
3673 | |
3674 | if (atomic_read(&buffer_b->record_disabled)) |
3675 | goto out; |
3676 | |
3677 | cpu_buffer_a = buffer_a->buffers[cpu]; |
3678 | cpu_buffer_b = buffer_b->buffers[cpu]; |
3679 | |
3680 | if (atomic_read(&cpu_buffer_a->record_disabled)) |
3681 | goto out; |
3682 | |
3683 | if (atomic_read(&cpu_buffer_b->record_disabled)) |
3684 | goto out; |
3685 | |
3686 | /* |
3687 | * We can't do a synchronize_sched here because this |
3688 | * function can be called in atomic context. |
3689 | * Normally this will be called from the same CPU as cpu. |
3690 | * If not it's up to the caller to protect this. |
3691 | */ |
3692 | atomic_inc(&cpu_buffer_a->record_disabled); |
3693 | atomic_inc(&cpu_buffer_b->record_disabled); |
3694 | |
3695 | ret = -EBUSY; |
3696 | if (local_read(&cpu_buffer_a->committing)) |
3697 | goto out_dec; |
3698 | if (local_read(&cpu_buffer_b->committing)) |
3699 | goto out_dec; |
3700 | |
3701 | buffer_a->buffers[cpu] = cpu_buffer_b; |
3702 | buffer_b->buffers[cpu] = cpu_buffer_a; |
3703 | |
3704 | cpu_buffer_b->buffer = buffer_a; |
3705 | cpu_buffer_a->buffer = buffer_b; |
3706 | |
3707 | ret = 0; |
3708 | |
3709 | out_dec: |
3710 | atomic_dec(&cpu_buffer_a->record_disabled); |
3711 | atomic_dec(&cpu_buffer_b->record_disabled); |
3712 | out: |
3713 | return ret; |
3714 | } |
3715 | EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
3716 | #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
3717 | |
3718 | /** |
3719 | * ring_buffer_alloc_read_page - allocate a page to read from buffer |
3720 | * @buffer: the buffer to allocate for. |
3721 | * |
3722 | * This function is used in conjunction with ring_buffer_read_page. |
3723 | * When reading a full page from the ring buffer, these functions |
3724 | * can be used to speed up the process. The calling function should |
3725 | * allocate a few pages first with this function. Then when it |
3726 | * needs to get pages from the ring buffer, it passes the result |
3727 | * of this function into ring_buffer_read_page, which will swap |
3728 | * the page that was allocated, with the read page of the buffer. |
3729 | * |
3730 | * Returns: |
3731 | * The page allocated, or NULL on error. |
3732 | */ |
3733 | void *ring_buffer_alloc_read_page(struct ring_buffer *buffer) |
3734 | { |
3735 | struct buffer_data_page *bpage; |
3736 | unsigned long addr; |
3737 | |
3738 | addr = __get_free_page(GFP_KERNEL); |
3739 | if (!addr) |
3740 | return NULL; |
3741 | |
3742 | bpage = (void *)addr; |
3743 | |
3744 | rb_init_page(bpage); |
3745 | |
3746 | return bpage; |
3747 | } |
3748 | EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
3749 | |
3750 | /** |
3751 | * ring_buffer_free_read_page - free an allocated read page |
3752 | * @buffer: the buffer the page was allocate for |
3753 | * @data: the page to free |
3754 | * |
3755 | * Free a page allocated from ring_buffer_alloc_read_page. |
3756 | */ |
3757 | void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) |
3758 | { |
3759 | free_page((unsigned long)data); |
3760 | } |
3761 | EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
3762 | |
3763 | /** |
3764 | * ring_buffer_read_page - extract a page from the ring buffer |
3765 | * @buffer: buffer to extract from |
3766 | * @data_page: the page to use allocated from ring_buffer_alloc_read_page |
3767 | * @len: amount to extract |
3768 | * @cpu: the cpu of the buffer to extract |
3769 | * @full: should the extraction only happen when the page is full. |
3770 | * |
3771 | * This function will pull out a page from the ring buffer and consume it. |
3772 | * @data_page must be the address of the variable that was returned |
3773 | * from ring_buffer_alloc_read_page. This is because the page might be used |
3774 | * to swap with a page in the ring buffer. |
3775 | * |
3776 | * for example: |
3777 | * rpage = ring_buffer_alloc_read_page(buffer); |
3778 | * if (!rpage) |
3779 | * return error; |
3780 | * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
3781 | * if (ret >= 0) |
3782 | * process_page(rpage, ret); |
3783 | * |
3784 | * When @full is set, the function will not return true unless |
3785 | * the writer is off the reader page. |
3786 | * |
3787 | * Note: it is up to the calling functions to handle sleeps and wakeups. |
3788 | * The ring buffer can be used anywhere in the kernel and can not |
3789 | * blindly call wake_up. The layer that uses the ring buffer must be |
3790 | * responsible for that. |
3791 | * |
3792 | * Returns: |
3793 | * >=0 if data has been transferred, returns the offset of consumed data. |
3794 | * <0 if no data has been transferred. |
3795 | */ |
3796 | int ring_buffer_read_page(struct ring_buffer *buffer, |
3797 | void **data_page, size_t len, int cpu, int full) |
3798 | { |
3799 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
3800 | struct ring_buffer_event *event; |
3801 | struct buffer_data_page *bpage; |
3802 | struct buffer_page *reader; |
3803 | unsigned long missed_events; |
3804 | unsigned long flags; |
3805 | unsigned int commit; |
3806 | unsigned int read; |
3807 | u64 save_timestamp; |
3808 | int ret = -1; |
3809 | |
3810 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3811 | goto out; |
3812 | |
3813 | /* |
3814 | * If len is not big enough to hold the page header, then |
3815 | * we can not copy anything. |
3816 | */ |
3817 | if (len <= BUF_PAGE_HDR_SIZE) |
3818 | goto out; |
3819 | |
3820 | len -= BUF_PAGE_HDR_SIZE; |
3821 | |
3822 | if (!data_page) |
3823 | goto out; |
3824 | |
3825 | bpage = *data_page; |
3826 | if (!bpage) |
3827 | goto out; |
3828 | |
3829 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3830 | |
3831 | reader = rb_get_reader_page(cpu_buffer); |
3832 | if (!reader) |
3833 | goto out_unlock; |
3834 | |
3835 | event = rb_reader_event(cpu_buffer); |
3836 | |
3837 | read = reader->read; |
3838 | commit = rb_page_commit(reader); |
3839 | |
3840 | /* Check if any events were dropped */ |
3841 | missed_events = cpu_buffer->lost_events; |
3842 | |
3843 | /* |
3844 | * If this page has been partially read or |
3845 | * if len is not big enough to read the rest of the page or |
3846 | * a writer is still on the page, then |
3847 | * we must copy the data from the page to the buffer. |
3848 | * Otherwise, we can simply swap the page with the one passed in. |
3849 | */ |
3850 | if (read || (len < (commit - read)) || |
3851 | cpu_buffer->reader_page == cpu_buffer->commit_page) { |
3852 | struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
3853 | unsigned int rpos = read; |
3854 | unsigned int pos = 0; |
3855 | unsigned int size; |
3856 | |
3857 | if (full) |
3858 | goto out_unlock; |
3859 | |
3860 | if (len > (commit - read)) |
3861 | len = (commit - read); |
3862 | |
3863 | /* Always keep the time extend and data together */ |
3864 | size = rb_event_ts_length(event); |
3865 | |
3866 | if (len < size) |
3867 | goto out_unlock; |
3868 | |
3869 | /* save the current timestamp, since the user will need it */ |
3870 | save_timestamp = cpu_buffer->read_stamp; |
3871 | |
3872 | /* Need to copy one event at a time */ |
3873 | do { |
3874 | /* We need the size of one event, because |
3875 | * rb_advance_reader only advances by one event, |
3876 | * whereas rb_event_ts_length may include the size of |
3877 | * one or two events. |
3878 | * We have already ensured there's enough space if this |
3879 | * is a time extend. */ |
3880 | size = rb_event_length(event); |
3881 | memcpy(bpage->data + pos, rpage->data + rpos, size); |
3882 | |
3883 | len -= size; |
3884 | |
3885 | rb_advance_reader(cpu_buffer); |
3886 | rpos = reader->read; |
3887 | pos += size; |
3888 | |
3889 | if (rpos >= commit) |
3890 | break; |
3891 | |
3892 | event = rb_reader_event(cpu_buffer); |
3893 | /* Always keep the time extend and data together */ |
3894 | size = rb_event_ts_length(event); |
3895 | } while (len >= size); |
3896 | |
3897 | /* update bpage */ |
3898 | local_set(&bpage->commit, pos); |
3899 | bpage->time_stamp = save_timestamp; |
3900 | |
3901 | /* we copied everything to the beginning */ |
3902 | read = 0; |
3903 | } else { |
3904 | /* update the entry counter */ |
3905 | cpu_buffer->read += rb_page_entries(reader); |
3906 | |
3907 | /* swap the pages */ |
3908 | rb_init_page(bpage); |
3909 | bpage = reader->page; |
3910 | reader->page = *data_page; |
3911 | local_set(&reader->write, 0); |
3912 | local_set(&reader->entries, 0); |
3913 | reader->read = 0; |
3914 | *data_page = bpage; |
3915 | |
3916 | /* |
3917 | * Use the real_end for the data size, |
3918 | * This gives us a chance to store the lost events |
3919 | * on the page. |
3920 | */ |
3921 | if (reader->real_end) |
3922 | local_set(&bpage->commit, reader->real_end); |
3923 | } |
3924 | ret = read; |
3925 | |
3926 | cpu_buffer->lost_events = 0; |
3927 | |
3928 | commit = local_read(&bpage->commit); |
3929 | /* |
3930 | * Set a flag in the commit field if we lost events |
3931 | */ |
3932 | if (missed_events) { |
3933 | /* If there is room at the end of the page to save the |
3934 | * missed events, then record it there. |
3935 | */ |
3936 | if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { |
3937 | memcpy(&bpage->data[commit], &missed_events, |
3938 | sizeof(missed_events)); |
3939 | local_add(RB_MISSED_STORED, &bpage->commit); |
3940 | commit += sizeof(missed_events); |
3941 | } |
3942 | local_add(RB_MISSED_EVENTS, &bpage->commit); |
3943 | } |
3944 | |
3945 | /* |
3946 | * This page may be off to user land. Zero it out here. |
3947 | */ |
3948 | if (commit < BUF_PAGE_SIZE) |
3949 | memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit); |
3950 | |
3951 | out_unlock: |
3952 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3953 | |
3954 | out: |
3955 | return ret; |
3956 | } |
3957 | EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
3958 | |
3959 | #ifdef CONFIG_TRACING |
3960 | static ssize_t |
3961 | rb_simple_read(struct file *filp, char __user *ubuf, |
3962 | size_t cnt, loff_t *ppos) |
3963 | { |
3964 | unsigned long *p = filp->private_data; |
3965 | char buf[64]; |
3966 | int r; |
3967 | |
3968 | if (test_bit(RB_BUFFERS_DISABLED_BIT, p)) |
3969 | r = sprintf(buf, "permanently disabled\n"); |
3970 | else |
3971 | r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p)); |
3972 | |
3973 | return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); |
3974 | } |
3975 | |
3976 | static ssize_t |
3977 | rb_simple_write(struct file *filp, const char __user *ubuf, |
3978 | size_t cnt, loff_t *ppos) |
3979 | { |
3980 | unsigned long *p = filp->private_data; |
3981 | char buf[64]; |
3982 | unsigned long val; |
3983 | int ret; |
3984 | |
3985 | if (cnt >= sizeof(buf)) |
3986 | return -EINVAL; |
3987 | |
3988 | if (copy_from_user(&buf, ubuf, cnt)) |
3989 | return -EFAULT; |
3990 | |
3991 | buf[cnt] = 0; |
3992 | |
3993 | ret = strict_strtoul(buf, 10, &val); |
3994 | if (ret < 0) |
3995 | return ret; |
3996 | |
3997 | if (val) |
3998 | set_bit(RB_BUFFERS_ON_BIT, p); |
3999 | else |
4000 | clear_bit(RB_BUFFERS_ON_BIT, p); |
4001 | |
4002 | (*ppos)++; |
4003 | |
4004 | return cnt; |
4005 | } |
4006 | |
4007 | static const struct file_operations rb_simple_fops = { |
4008 | .open = tracing_open_generic, |
4009 | .read = rb_simple_read, |
4010 | .write = rb_simple_write, |
4011 | .llseek = default_llseek, |
4012 | }; |
4013 | |
4014 | |
4015 | static __init int rb_init_debugfs(void) |
4016 | { |
4017 | struct dentry *d_tracer; |
4018 | |
4019 | d_tracer = tracing_init_dentry(); |
4020 | |
4021 | trace_create_file("tracing_on", 0644, d_tracer, |
4022 | &ring_buffer_flags, &rb_simple_fops); |
4023 | |
4024 | return 0; |
4025 | } |
4026 | |
4027 | fs_initcall(rb_init_debugfs); |
4028 | #endif |
4029 | |
4030 | #ifdef CONFIG_HOTPLUG_CPU |
4031 | static int rb_cpu_notify(struct notifier_block *self, |
4032 | unsigned long action, void *hcpu) |
4033 | { |
4034 | struct ring_buffer *buffer = |
4035 | container_of(self, struct ring_buffer, cpu_notify); |
4036 | long cpu = (long)hcpu; |
4037 | |
4038 | switch (action) { |
4039 | case CPU_UP_PREPARE: |
4040 | case CPU_UP_PREPARE_FROZEN: |
4041 | if (cpumask_test_cpu(cpu, buffer->cpumask)) |
4042 | return NOTIFY_OK; |
4043 | |
4044 | buffer->buffers[cpu] = |
4045 | rb_allocate_cpu_buffer(buffer, cpu); |
4046 | if (!buffer->buffers[cpu]) { |
4047 | WARN(1, "failed to allocate ring buffer on CPU %ld\n", |
4048 | cpu); |
4049 | return NOTIFY_OK; |
4050 | } |
4051 | smp_wmb(); |
4052 | cpumask_set_cpu(cpu, buffer->cpumask); |
4053 | break; |
4054 | case CPU_DOWN_PREPARE: |
4055 | case CPU_DOWN_PREPARE_FROZEN: |
4056 | /* |
4057 | * Do nothing. |
4058 | * If we were to free the buffer, then the user would |
4059 | * lose any trace that was in the buffer. |
4060 | */ |
4061 | break; |
4062 | default: |
4063 | break; |
4064 | } |
4065 | return NOTIFY_OK; |
4066 | } |
4067 | #endif |
4068 |
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