Commit | Line | Data |
---|---|---|
7a8e76a3 SR |
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/spinlock.h> | |
8 | #include <linux/debugfs.h> | |
9 | #include <linux/uaccess.h> | |
10 | #include <linux/module.h> | |
11 | #include <linux/percpu.h> | |
12 | #include <linux/mutex.h> | |
13 | #include <linux/sched.h> /* used for sched_clock() (for now) */ | |
14 | #include <linux/init.h> | |
15 | #include <linux/hash.h> | |
16 | #include <linux/list.h> | |
17 | #include <linux/fs.h> | |
18 | ||
182e9f5f SR |
19 | #include "trace.h" |
20 | ||
033601a3 SR |
21 | /* |
22 | * A fast way to enable or disable all ring buffers is to | |
23 | * call tracing_on or tracing_off. Turning off the ring buffers | |
24 | * prevents all ring buffers from being recorded to. | |
25 | * Turning this switch on, makes it OK to write to the | |
26 | * ring buffer, if the ring buffer is enabled itself. | |
27 | * | |
28 | * There's three layers that must be on in order to write | |
29 | * to the ring buffer. | |
30 | * | |
31 | * 1) This global flag must be set. | |
32 | * 2) The ring buffer must be enabled for recording. | |
33 | * 3) The per cpu buffer must be enabled for recording. | |
34 | * | |
35 | * In case of an anomaly, this global flag has a bit set that | |
36 | * will permantly disable all ring buffers. | |
37 | */ | |
38 | ||
39 | /* | |
40 | * Global flag to disable all recording to ring buffers | |
41 | * This has two bits: ON, DISABLED | |
42 | * | |
43 | * ON DISABLED | |
44 | * ---- ---------- | |
45 | * 0 0 : ring buffers are off | |
46 | * 1 0 : ring buffers are on | |
47 | * X 1 : ring buffers are permanently disabled | |
48 | */ | |
49 | ||
50 | enum { | |
51 | RB_BUFFERS_ON_BIT = 0, | |
52 | RB_BUFFERS_DISABLED_BIT = 1, | |
53 | }; | |
54 | ||
55 | enum { | |
56 | RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT, | |
57 | RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT, | |
58 | }; | |
59 | ||
60 | static long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; | |
a3583244 SR |
61 | |
62 | /** | |
63 | * tracing_on - enable all tracing buffers | |
64 | * | |
65 | * This function enables all tracing buffers that may have been | |
66 | * disabled with tracing_off. | |
67 | */ | |
68 | void tracing_on(void) | |
69 | { | |
033601a3 | 70 | set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); |
a3583244 SR |
71 | } |
72 | ||
73 | /** | |
74 | * tracing_off - turn off all tracing buffers | |
75 | * | |
76 | * This function stops all tracing buffers from recording data. | |
77 | * It does not disable any overhead the tracers themselves may | |
78 | * be causing. This function simply causes all recording to | |
79 | * the ring buffers to fail. | |
80 | */ | |
81 | void tracing_off(void) | |
82 | { | |
033601a3 SR |
83 | clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); |
84 | } | |
85 | ||
86 | /** | |
87 | * tracing_off_permanent - permanently disable ring buffers | |
88 | * | |
89 | * This function, once called, will disable all ring buffers | |
90 | * permanenty. | |
91 | */ | |
92 | void tracing_off_permanent(void) | |
93 | { | |
94 | set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags); | |
a3583244 SR |
95 | } |
96 | ||
d06bbd66 IM |
97 | #include "trace.h" |
98 | ||
7a8e76a3 SR |
99 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
100 | #define DEBUG_SHIFT 0 | |
101 | ||
102 | /* FIXME!!! */ | |
103 | u64 ring_buffer_time_stamp(int cpu) | |
104 | { | |
47e74f2b SR |
105 | u64 time; |
106 | ||
107 | preempt_disable_notrace(); | |
7a8e76a3 | 108 | /* shift to debug/test normalization and TIME_EXTENTS */ |
47e74f2b SR |
109 | time = sched_clock() << DEBUG_SHIFT; |
110 | preempt_enable_notrace(); | |
111 | ||
112 | return time; | |
7a8e76a3 SR |
113 | } |
114 | ||
115 | void ring_buffer_normalize_time_stamp(int cpu, u64 *ts) | |
116 | { | |
117 | /* Just stupid testing the normalize function and deltas */ | |
118 | *ts >>= DEBUG_SHIFT; | |
119 | } | |
120 | ||
121 | #define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event)) | |
122 | #define RB_ALIGNMENT_SHIFT 2 | |
123 | #define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT) | |
124 | #define RB_MAX_SMALL_DATA 28 | |
125 | ||
126 | enum { | |
127 | RB_LEN_TIME_EXTEND = 8, | |
128 | RB_LEN_TIME_STAMP = 16, | |
129 | }; | |
130 | ||
131 | /* inline for ring buffer fast paths */ | |
132 | static inline unsigned | |
133 | rb_event_length(struct ring_buffer_event *event) | |
134 | { | |
135 | unsigned length; | |
136 | ||
137 | switch (event->type) { | |
138 | case RINGBUF_TYPE_PADDING: | |
139 | /* undefined */ | |
140 | return -1; | |
141 | ||
142 | case RINGBUF_TYPE_TIME_EXTEND: | |
143 | return RB_LEN_TIME_EXTEND; | |
144 | ||
145 | case RINGBUF_TYPE_TIME_STAMP: | |
146 | return RB_LEN_TIME_STAMP; | |
147 | ||
148 | case RINGBUF_TYPE_DATA: | |
149 | if (event->len) | |
150 | length = event->len << RB_ALIGNMENT_SHIFT; | |
151 | else | |
152 | length = event->array[0]; | |
153 | return length + RB_EVNT_HDR_SIZE; | |
154 | default: | |
155 | BUG(); | |
156 | } | |
157 | /* not hit */ | |
158 | return 0; | |
159 | } | |
160 | ||
161 | /** | |
162 | * ring_buffer_event_length - return the length of the event | |
163 | * @event: the event to get the length of | |
164 | */ | |
165 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) | |
166 | { | |
167 | return rb_event_length(event); | |
168 | } | |
169 | ||
170 | /* inline for ring buffer fast paths */ | |
171 | static inline void * | |
172 | rb_event_data(struct ring_buffer_event *event) | |
173 | { | |
174 | BUG_ON(event->type != RINGBUF_TYPE_DATA); | |
175 | /* If length is in len field, then array[0] has the data */ | |
176 | if (event->len) | |
177 | return (void *)&event->array[0]; | |
178 | /* Otherwise length is in array[0] and array[1] has the data */ | |
179 | return (void *)&event->array[1]; | |
180 | } | |
181 | ||
182 | /** | |
183 | * ring_buffer_event_data - return the data of the event | |
184 | * @event: the event to get the data from | |
185 | */ | |
186 | void *ring_buffer_event_data(struct ring_buffer_event *event) | |
187 | { | |
188 | return rb_event_data(event); | |
189 | } | |
190 | ||
191 | #define for_each_buffer_cpu(buffer, cpu) \ | |
192 | for_each_cpu_mask(cpu, buffer->cpumask) | |
193 | ||
194 | #define TS_SHIFT 27 | |
195 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) | |
196 | #define TS_DELTA_TEST (~TS_MASK) | |
197 | ||
198 | /* | |
199 | * This hack stolen from mm/slob.c. | |
200 | * We can store per page timing information in the page frame of the page. | |
201 | * Thanks to Peter Zijlstra for suggesting this idea. | |
202 | */ | |
203 | struct buffer_page { | |
e4c2ce82 | 204 | u64 time_stamp; /* page time stamp */ |
bf41a158 SR |
205 | local_t write; /* index for next write */ |
206 | local_t commit; /* write commited index */ | |
6f807acd | 207 | unsigned read; /* index for next read */ |
e4c2ce82 SR |
208 | struct list_head list; /* list of free pages */ |
209 | void *page; /* Actual data page */ | |
7a8e76a3 SR |
210 | }; |
211 | ||
ed56829c SR |
212 | /* |
213 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing | |
214 | * this issue out. | |
215 | */ | |
216 | static inline void free_buffer_page(struct buffer_page *bpage) | |
217 | { | |
e4c2ce82 | 218 | if (bpage->page) |
6ae2a076 | 219 | free_page((unsigned long)bpage->page); |
e4c2ce82 | 220 | kfree(bpage); |
ed56829c SR |
221 | } |
222 | ||
7a8e76a3 SR |
223 | /* |
224 | * We need to fit the time_stamp delta into 27 bits. | |
225 | */ | |
226 | static inline int test_time_stamp(u64 delta) | |
227 | { | |
228 | if (delta & TS_DELTA_TEST) | |
229 | return 1; | |
230 | return 0; | |
231 | } | |
232 | ||
233 | #define BUF_PAGE_SIZE PAGE_SIZE | |
234 | ||
235 | /* | |
236 | * head_page == tail_page && head == tail then buffer is empty. | |
237 | */ | |
238 | struct ring_buffer_per_cpu { | |
239 | int cpu; | |
240 | struct ring_buffer *buffer; | |
f83c9d0f | 241 | spinlock_t reader_lock; /* serialize readers */ |
3e03fb7f | 242 | raw_spinlock_t lock; |
7a8e76a3 SR |
243 | struct lock_class_key lock_key; |
244 | struct list_head pages; | |
6f807acd SR |
245 | struct buffer_page *head_page; /* read from head */ |
246 | struct buffer_page *tail_page; /* write to tail */ | |
bf41a158 | 247 | struct buffer_page *commit_page; /* commited pages */ |
d769041f | 248 | struct buffer_page *reader_page; |
7a8e76a3 SR |
249 | unsigned long overrun; |
250 | unsigned long entries; | |
251 | u64 write_stamp; | |
252 | u64 read_stamp; | |
253 | atomic_t record_disabled; | |
254 | }; | |
255 | ||
256 | struct ring_buffer { | |
257 | unsigned long size; | |
258 | unsigned pages; | |
259 | unsigned flags; | |
260 | int cpus; | |
261 | cpumask_t cpumask; | |
262 | atomic_t record_disabled; | |
263 | ||
264 | struct mutex mutex; | |
265 | ||
266 | struct ring_buffer_per_cpu **buffers; | |
267 | }; | |
268 | ||
269 | struct ring_buffer_iter { | |
270 | struct ring_buffer_per_cpu *cpu_buffer; | |
271 | unsigned long head; | |
272 | struct buffer_page *head_page; | |
273 | u64 read_stamp; | |
274 | }; | |
275 | ||
f536aafc | 276 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
bf41a158 | 277 | #define RB_WARN_ON(buffer, cond) \ |
3e89c7bb SR |
278 | ({ \ |
279 | int _____ret = unlikely(cond); \ | |
280 | if (_____ret) { \ | |
bf41a158 SR |
281 | atomic_inc(&buffer->record_disabled); \ |
282 | WARN_ON(1); \ | |
283 | } \ | |
3e89c7bb SR |
284 | _____ret; \ |
285 | }) | |
f536aafc | 286 | |
7a8e76a3 SR |
287 | /** |
288 | * check_pages - integrity check of buffer pages | |
289 | * @cpu_buffer: CPU buffer with pages to test | |
290 | * | |
291 | * As a safty measure we check to make sure the data pages have not | |
292 | * been corrupted. | |
293 | */ | |
294 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
295 | { | |
296 | struct list_head *head = &cpu_buffer->pages; | |
297 | struct buffer_page *page, *tmp; | |
298 | ||
3e89c7bb SR |
299 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
300 | return -1; | |
301 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) | |
302 | return -1; | |
7a8e76a3 SR |
303 | |
304 | list_for_each_entry_safe(page, tmp, head, list) { | |
3e89c7bb SR |
305 | if (RB_WARN_ON(cpu_buffer, |
306 | page->list.next->prev != &page->list)) | |
307 | return -1; | |
308 | if (RB_WARN_ON(cpu_buffer, | |
309 | page->list.prev->next != &page->list)) | |
310 | return -1; | |
7a8e76a3 SR |
311 | } |
312 | ||
313 | return 0; | |
314 | } | |
315 | ||
7a8e76a3 SR |
316 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
317 | unsigned nr_pages) | |
318 | { | |
319 | struct list_head *head = &cpu_buffer->pages; | |
320 | struct buffer_page *page, *tmp; | |
321 | unsigned long addr; | |
322 | LIST_HEAD(pages); | |
323 | unsigned i; | |
324 | ||
325 | for (i = 0; i < nr_pages; i++) { | |
e4c2ce82 | 326 | page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()), |
aa1e0e3b | 327 | GFP_KERNEL, cpu_to_node(cpu_buffer->cpu)); |
e4c2ce82 SR |
328 | if (!page) |
329 | goto free_pages; | |
330 | list_add(&page->list, &pages); | |
331 | ||
7a8e76a3 SR |
332 | addr = __get_free_page(GFP_KERNEL); |
333 | if (!addr) | |
334 | goto free_pages; | |
e4c2ce82 | 335 | page->page = (void *)addr; |
7a8e76a3 SR |
336 | } |
337 | ||
338 | list_splice(&pages, head); | |
339 | ||
340 | rb_check_pages(cpu_buffer); | |
341 | ||
342 | return 0; | |
343 | ||
344 | free_pages: | |
345 | list_for_each_entry_safe(page, tmp, &pages, list) { | |
346 | list_del_init(&page->list); | |
ed56829c | 347 | free_buffer_page(page); |
7a8e76a3 SR |
348 | } |
349 | return -ENOMEM; | |
350 | } | |
351 | ||
352 | static struct ring_buffer_per_cpu * | |
353 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) | |
354 | { | |
355 | struct ring_buffer_per_cpu *cpu_buffer; | |
e4c2ce82 | 356 | struct buffer_page *page; |
d769041f | 357 | unsigned long addr; |
7a8e76a3 SR |
358 | int ret; |
359 | ||
360 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), | |
361 | GFP_KERNEL, cpu_to_node(cpu)); | |
362 | if (!cpu_buffer) | |
363 | return NULL; | |
364 | ||
365 | cpu_buffer->cpu = cpu; | |
366 | cpu_buffer->buffer = buffer; | |
f83c9d0f | 367 | spin_lock_init(&cpu_buffer->reader_lock); |
3e03fb7f | 368 | cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; |
7a8e76a3 SR |
369 | INIT_LIST_HEAD(&cpu_buffer->pages); |
370 | ||
e4c2ce82 SR |
371 | page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()), |
372 | GFP_KERNEL, cpu_to_node(cpu)); | |
373 | if (!page) | |
374 | goto fail_free_buffer; | |
375 | ||
376 | cpu_buffer->reader_page = page; | |
d769041f SR |
377 | addr = __get_free_page(GFP_KERNEL); |
378 | if (!addr) | |
e4c2ce82 SR |
379 | goto fail_free_reader; |
380 | page->page = (void *)addr; | |
381 | ||
d769041f | 382 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
d769041f | 383 | |
7a8e76a3 SR |
384 | ret = rb_allocate_pages(cpu_buffer, buffer->pages); |
385 | if (ret < 0) | |
d769041f | 386 | goto fail_free_reader; |
7a8e76a3 SR |
387 | |
388 | cpu_buffer->head_page | |
389 | = list_entry(cpu_buffer->pages.next, struct buffer_page, list); | |
bf41a158 | 390 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
7a8e76a3 SR |
391 | |
392 | return cpu_buffer; | |
393 | ||
d769041f SR |
394 | fail_free_reader: |
395 | free_buffer_page(cpu_buffer->reader_page); | |
396 | ||
7a8e76a3 SR |
397 | fail_free_buffer: |
398 | kfree(cpu_buffer); | |
399 | return NULL; | |
400 | } | |
401 | ||
402 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
403 | { | |
404 | struct list_head *head = &cpu_buffer->pages; | |
405 | struct buffer_page *page, *tmp; | |
406 | ||
d769041f SR |
407 | list_del_init(&cpu_buffer->reader_page->list); |
408 | free_buffer_page(cpu_buffer->reader_page); | |
409 | ||
7a8e76a3 SR |
410 | list_for_each_entry_safe(page, tmp, head, list) { |
411 | list_del_init(&page->list); | |
ed56829c | 412 | free_buffer_page(page); |
7a8e76a3 SR |
413 | } |
414 | kfree(cpu_buffer); | |
415 | } | |
416 | ||
a7b13743 SR |
417 | /* |
418 | * Causes compile errors if the struct buffer_page gets bigger | |
419 | * than the struct page. | |
420 | */ | |
421 | extern int ring_buffer_page_too_big(void); | |
422 | ||
7a8e76a3 SR |
423 | /** |
424 | * ring_buffer_alloc - allocate a new ring_buffer | |
425 | * @size: the size in bytes that is needed. | |
426 | * @flags: attributes to set for the ring buffer. | |
427 | * | |
428 | * Currently the only flag that is available is the RB_FL_OVERWRITE | |
429 | * flag. This flag means that the buffer will overwrite old data | |
430 | * when the buffer wraps. If this flag is not set, the buffer will | |
431 | * drop data when the tail hits the head. | |
432 | */ | |
433 | struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags) | |
434 | { | |
435 | struct ring_buffer *buffer; | |
436 | int bsize; | |
437 | int cpu; | |
438 | ||
a7b13743 SR |
439 | /* Paranoid! Optimizes out when all is well */ |
440 | if (sizeof(struct buffer_page) > sizeof(struct page)) | |
441 | ring_buffer_page_too_big(); | |
442 | ||
443 | ||
7a8e76a3 SR |
444 | /* keep it in its own cache line */ |
445 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), | |
446 | GFP_KERNEL); | |
447 | if (!buffer) | |
448 | return NULL; | |
449 | ||
450 | buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); | |
451 | buffer->flags = flags; | |
452 | ||
453 | /* need at least two pages */ | |
454 | if (buffer->pages == 1) | |
455 | buffer->pages++; | |
456 | ||
457 | buffer->cpumask = cpu_possible_map; | |
458 | buffer->cpus = nr_cpu_ids; | |
459 | ||
460 | bsize = sizeof(void *) * nr_cpu_ids; | |
461 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), | |
462 | GFP_KERNEL); | |
463 | if (!buffer->buffers) | |
464 | goto fail_free_buffer; | |
465 | ||
466 | for_each_buffer_cpu(buffer, cpu) { | |
467 | buffer->buffers[cpu] = | |
468 | rb_allocate_cpu_buffer(buffer, cpu); | |
469 | if (!buffer->buffers[cpu]) | |
470 | goto fail_free_buffers; | |
471 | } | |
472 | ||
473 | mutex_init(&buffer->mutex); | |
474 | ||
475 | return buffer; | |
476 | ||
477 | fail_free_buffers: | |
478 | for_each_buffer_cpu(buffer, cpu) { | |
479 | if (buffer->buffers[cpu]) | |
480 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
481 | } | |
482 | kfree(buffer->buffers); | |
483 | ||
484 | fail_free_buffer: | |
485 | kfree(buffer); | |
486 | return NULL; | |
487 | } | |
488 | ||
489 | /** | |
490 | * ring_buffer_free - free a ring buffer. | |
491 | * @buffer: the buffer to free. | |
492 | */ | |
493 | void | |
494 | ring_buffer_free(struct ring_buffer *buffer) | |
495 | { | |
496 | int cpu; | |
497 | ||
498 | for_each_buffer_cpu(buffer, cpu) | |
499 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
500 | ||
501 | kfree(buffer); | |
502 | } | |
503 | ||
504 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); | |
505 | ||
506 | static void | |
507 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) | |
508 | { | |
509 | struct buffer_page *page; | |
510 | struct list_head *p; | |
511 | unsigned i; | |
512 | ||
513 | atomic_inc(&cpu_buffer->record_disabled); | |
514 | synchronize_sched(); | |
515 | ||
516 | for (i = 0; i < nr_pages; i++) { | |
3e89c7bb SR |
517 | if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages))) |
518 | return; | |
7a8e76a3 SR |
519 | p = cpu_buffer->pages.next; |
520 | page = list_entry(p, struct buffer_page, list); | |
521 | list_del_init(&page->list); | |
ed56829c | 522 | free_buffer_page(page); |
7a8e76a3 | 523 | } |
3e89c7bb SR |
524 | if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages))) |
525 | return; | |
7a8e76a3 SR |
526 | |
527 | rb_reset_cpu(cpu_buffer); | |
528 | ||
529 | rb_check_pages(cpu_buffer); | |
530 | ||
531 | atomic_dec(&cpu_buffer->record_disabled); | |
532 | ||
533 | } | |
534 | ||
535 | static void | |
536 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, | |
537 | struct list_head *pages, unsigned nr_pages) | |
538 | { | |
539 | struct buffer_page *page; | |
540 | struct list_head *p; | |
541 | unsigned i; | |
542 | ||
543 | atomic_inc(&cpu_buffer->record_disabled); | |
544 | synchronize_sched(); | |
545 | ||
546 | for (i = 0; i < nr_pages; i++) { | |
3e89c7bb SR |
547 | if (RB_WARN_ON(cpu_buffer, list_empty(pages))) |
548 | return; | |
7a8e76a3 SR |
549 | p = pages->next; |
550 | page = list_entry(p, struct buffer_page, list); | |
551 | list_del_init(&page->list); | |
552 | list_add_tail(&page->list, &cpu_buffer->pages); | |
553 | } | |
554 | rb_reset_cpu(cpu_buffer); | |
555 | ||
556 | rb_check_pages(cpu_buffer); | |
557 | ||
558 | atomic_dec(&cpu_buffer->record_disabled); | |
559 | } | |
560 | ||
561 | /** | |
562 | * ring_buffer_resize - resize the ring buffer | |
563 | * @buffer: the buffer to resize. | |
564 | * @size: the new size. | |
565 | * | |
566 | * The tracer is responsible for making sure that the buffer is | |
567 | * not being used while changing the size. | |
568 | * Note: We may be able to change the above requirement by using | |
569 | * RCU synchronizations. | |
570 | * | |
571 | * Minimum size is 2 * BUF_PAGE_SIZE. | |
572 | * | |
573 | * Returns -1 on failure. | |
574 | */ | |
575 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) | |
576 | { | |
577 | struct ring_buffer_per_cpu *cpu_buffer; | |
578 | unsigned nr_pages, rm_pages, new_pages; | |
579 | struct buffer_page *page, *tmp; | |
580 | unsigned long buffer_size; | |
581 | unsigned long addr; | |
582 | LIST_HEAD(pages); | |
583 | int i, cpu; | |
584 | ||
ee51a1de IM |
585 | /* |
586 | * Always succeed at resizing a non-existent buffer: | |
587 | */ | |
588 | if (!buffer) | |
589 | return size; | |
590 | ||
7a8e76a3 SR |
591 | size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
592 | size *= BUF_PAGE_SIZE; | |
593 | buffer_size = buffer->pages * BUF_PAGE_SIZE; | |
594 | ||
595 | /* we need a minimum of two pages */ | |
596 | if (size < BUF_PAGE_SIZE * 2) | |
597 | size = BUF_PAGE_SIZE * 2; | |
598 | ||
599 | if (size == buffer_size) | |
600 | return size; | |
601 | ||
602 | mutex_lock(&buffer->mutex); | |
603 | ||
604 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); | |
605 | ||
606 | if (size < buffer_size) { | |
607 | ||
608 | /* easy case, just free pages */ | |
3e89c7bb SR |
609 | if (RB_WARN_ON(buffer, nr_pages >= buffer->pages)) { |
610 | mutex_unlock(&buffer->mutex); | |
611 | return -1; | |
612 | } | |
7a8e76a3 SR |
613 | |
614 | rm_pages = buffer->pages - nr_pages; | |
615 | ||
616 | for_each_buffer_cpu(buffer, cpu) { | |
617 | cpu_buffer = buffer->buffers[cpu]; | |
618 | rb_remove_pages(cpu_buffer, rm_pages); | |
619 | } | |
620 | goto out; | |
621 | } | |
622 | ||
623 | /* | |
624 | * This is a bit more difficult. We only want to add pages | |
625 | * when we can allocate enough for all CPUs. We do this | |
626 | * by allocating all the pages and storing them on a local | |
627 | * link list. If we succeed in our allocation, then we | |
628 | * add these pages to the cpu_buffers. Otherwise we just free | |
629 | * them all and return -ENOMEM; | |
630 | */ | |
3e89c7bb SR |
631 | if (RB_WARN_ON(buffer, nr_pages <= buffer->pages)) { |
632 | mutex_unlock(&buffer->mutex); | |
633 | return -1; | |
634 | } | |
f536aafc | 635 | |
7a8e76a3 SR |
636 | new_pages = nr_pages - buffer->pages; |
637 | ||
638 | for_each_buffer_cpu(buffer, cpu) { | |
639 | for (i = 0; i < new_pages; i++) { | |
e4c2ce82 SR |
640 | page = kzalloc_node(ALIGN(sizeof(*page), |
641 | cache_line_size()), | |
642 | GFP_KERNEL, cpu_to_node(cpu)); | |
643 | if (!page) | |
644 | goto free_pages; | |
645 | list_add(&page->list, &pages); | |
7a8e76a3 SR |
646 | addr = __get_free_page(GFP_KERNEL); |
647 | if (!addr) | |
648 | goto free_pages; | |
e4c2ce82 | 649 | page->page = (void *)addr; |
7a8e76a3 SR |
650 | } |
651 | } | |
652 | ||
653 | for_each_buffer_cpu(buffer, cpu) { | |
654 | cpu_buffer = buffer->buffers[cpu]; | |
655 | rb_insert_pages(cpu_buffer, &pages, new_pages); | |
656 | } | |
657 | ||
3e89c7bb SR |
658 | if (RB_WARN_ON(buffer, !list_empty(&pages))) { |
659 | mutex_unlock(&buffer->mutex); | |
660 | return -1; | |
661 | } | |
7a8e76a3 SR |
662 | |
663 | out: | |
664 | buffer->pages = nr_pages; | |
665 | mutex_unlock(&buffer->mutex); | |
666 | ||
667 | return size; | |
668 | ||
669 | free_pages: | |
670 | list_for_each_entry_safe(page, tmp, &pages, list) { | |
671 | list_del_init(&page->list); | |
ed56829c | 672 | free_buffer_page(page); |
7a8e76a3 | 673 | } |
641d2f63 | 674 | mutex_unlock(&buffer->mutex); |
7a8e76a3 SR |
675 | return -ENOMEM; |
676 | } | |
677 | ||
7a8e76a3 SR |
678 | static inline int rb_null_event(struct ring_buffer_event *event) |
679 | { | |
680 | return event->type == RINGBUF_TYPE_PADDING; | |
681 | } | |
682 | ||
6f807acd | 683 | static inline void *__rb_page_index(struct buffer_page *page, unsigned index) |
7a8e76a3 | 684 | { |
e4c2ce82 | 685 | return page->page + index; |
7a8e76a3 SR |
686 | } |
687 | ||
688 | static inline struct ring_buffer_event * | |
d769041f | 689 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 690 | { |
6f807acd SR |
691 | return __rb_page_index(cpu_buffer->reader_page, |
692 | cpu_buffer->reader_page->read); | |
693 | } | |
694 | ||
695 | static inline struct ring_buffer_event * | |
696 | rb_head_event(struct ring_buffer_per_cpu *cpu_buffer) | |
697 | { | |
698 | return __rb_page_index(cpu_buffer->head_page, | |
699 | cpu_buffer->head_page->read); | |
7a8e76a3 SR |
700 | } |
701 | ||
702 | static inline struct ring_buffer_event * | |
703 | rb_iter_head_event(struct ring_buffer_iter *iter) | |
704 | { | |
6f807acd | 705 | return __rb_page_index(iter->head_page, iter->head); |
7a8e76a3 SR |
706 | } |
707 | ||
bf41a158 SR |
708 | static inline unsigned rb_page_write(struct buffer_page *bpage) |
709 | { | |
710 | return local_read(&bpage->write); | |
711 | } | |
712 | ||
713 | static inline unsigned rb_page_commit(struct buffer_page *bpage) | |
714 | { | |
715 | return local_read(&bpage->commit); | |
716 | } | |
717 | ||
718 | /* Size is determined by what has been commited */ | |
719 | static inline unsigned rb_page_size(struct buffer_page *bpage) | |
720 | { | |
721 | return rb_page_commit(bpage); | |
722 | } | |
723 | ||
724 | static inline unsigned | |
725 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) | |
726 | { | |
727 | return rb_page_commit(cpu_buffer->commit_page); | |
728 | } | |
729 | ||
730 | static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer) | |
731 | { | |
732 | return rb_page_commit(cpu_buffer->head_page); | |
733 | } | |
734 | ||
7a8e76a3 SR |
735 | /* |
736 | * When the tail hits the head and the buffer is in overwrite mode, | |
737 | * the head jumps to the next page and all content on the previous | |
738 | * page is discarded. But before doing so, we update the overrun | |
739 | * variable of the buffer. | |
740 | */ | |
741 | static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer) | |
742 | { | |
743 | struct ring_buffer_event *event; | |
744 | unsigned long head; | |
745 | ||
746 | for (head = 0; head < rb_head_size(cpu_buffer); | |
747 | head += rb_event_length(event)) { | |
748 | ||
6f807acd | 749 | event = __rb_page_index(cpu_buffer->head_page, head); |
3e89c7bb SR |
750 | if (RB_WARN_ON(cpu_buffer, rb_null_event(event))) |
751 | return; | |
7a8e76a3 SR |
752 | /* Only count data entries */ |
753 | if (event->type != RINGBUF_TYPE_DATA) | |
754 | continue; | |
755 | cpu_buffer->overrun++; | |
756 | cpu_buffer->entries--; | |
757 | } | |
758 | } | |
759 | ||
760 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, | |
761 | struct buffer_page **page) | |
762 | { | |
763 | struct list_head *p = (*page)->list.next; | |
764 | ||
765 | if (p == &cpu_buffer->pages) | |
766 | p = p->next; | |
767 | ||
768 | *page = list_entry(p, struct buffer_page, list); | |
769 | } | |
770 | ||
bf41a158 SR |
771 | static inline unsigned |
772 | rb_event_index(struct ring_buffer_event *event) | |
773 | { | |
774 | unsigned long addr = (unsigned long)event; | |
775 | ||
776 | return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE); | |
777 | } | |
778 | ||
779 | static inline int | |
780 | rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer, | |
781 | struct ring_buffer_event *event) | |
782 | { | |
783 | unsigned long addr = (unsigned long)event; | |
784 | unsigned long index; | |
785 | ||
786 | index = rb_event_index(event); | |
787 | addr &= PAGE_MASK; | |
788 | ||
789 | return cpu_buffer->commit_page->page == (void *)addr && | |
790 | rb_commit_index(cpu_buffer) == index; | |
791 | } | |
792 | ||
7a8e76a3 | 793 | static inline void |
bf41a158 SR |
794 | rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer, |
795 | struct ring_buffer_event *event) | |
7a8e76a3 | 796 | { |
bf41a158 SR |
797 | unsigned long addr = (unsigned long)event; |
798 | unsigned long index; | |
799 | ||
800 | index = rb_event_index(event); | |
801 | addr &= PAGE_MASK; | |
802 | ||
803 | while (cpu_buffer->commit_page->page != (void *)addr) { | |
3e89c7bb SR |
804 | if (RB_WARN_ON(cpu_buffer, |
805 | cpu_buffer->commit_page == cpu_buffer->tail_page)) | |
806 | return; | |
bf41a158 SR |
807 | cpu_buffer->commit_page->commit = |
808 | cpu_buffer->commit_page->write; | |
809 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); | |
810 | cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp; | |
811 | } | |
812 | ||
813 | /* Now set the commit to the event's index */ | |
814 | local_set(&cpu_buffer->commit_page->commit, index); | |
7a8e76a3 SR |
815 | } |
816 | ||
bf41a158 SR |
817 | static inline void |
818 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 819 | { |
bf41a158 SR |
820 | /* |
821 | * We only race with interrupts and NMIs on this CPU. | |
822 | * If we own the commit event, then we can commit | |
823 | * all others that interrupted us, since the interruptions | |
824 | * are in stack format (they finish before they come | |
825 | * back to us). This allows us to do a simple loop to | |
826 | * assign the commit to the tail. | |
827 | */ | |
828 | while (cpu_buffer->commit_page != cpu_buffer->tail_page) { | |
829 | cpu_buffer->commit_page->commit = | |
830 | cpu_buffer->commit_page->write; | |
831 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); | |
832 | cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp; | |
833 | /* add barrier to keep gcc from optimizing too much */ | |
834 | barrier(); | |
835 | } | |
836 | while (rb_commit_index(cpu_buffer) != | |
837 | rb_page_write(cpu_buffer->commit_page)) { | |
838 | cpu_buffer->commit_page->commit = | |
839 | cpu_buffer->commit_page->write; | |
840 | barrier(); | |
841 | } | |
7a8e76a3 SR |
842 | } |
843 | ||
d769041f | 844 | static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 845 | { |
d769041f | 846 | cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp; |
6f807acd | 847 | cpu_buffer->reader_page->read = 0; |
d769041f SR |
848 | } |
849 | ||
850 | static inline void rb_inc_iter(struct ring_buffer_iter *iter) | |
851 | { | |
852 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
853 | ||
854 | /* | |
855 | * The iterator could be on the reader page (it starts there). | |
856 | * But the head could have moved, since the reader was | |
857 | * found. Check for this case and assign the iterator | |
858 | * to the head page instead of next. | |
859 | */ | |
860 | if (iter->head_page == cpu_buffer->reader_page) | |
861 | iter->head_page = cpu_buffer->head_page; | |
862 | else | |
863 | rb_inc_page(cpu_buffer, &iter->head_page); | |
864 | ||
7a8e76a3 SR |
865 | iter->read_stamp = iter->head_page->time_stamp; |
866 | iter->head = 0; | |
867 | } | |
868 | ||
869 | /** | |
870 | * ring_buffer_update_event - update event type and data | |
871 | * @event: the even to update | |
872 | * @type: the type of event | |
873 | * @length: the size of the event field in the ring buffer | |
874 | * | |
875 | * Update the type and data fields of the event. The length | |
876 | * is the actual size that is written to the ring buffer, | |
877 | * and with this, we can determine what to place into the | |
878 | * data field. | |
879 | */ | |
880 | static inline void | |
881 | rb_update_event(struct ring_buffer_event *event, | |
882 | unsigned type, unsigned length) | |
883 | { | |
884 | event->type = type; | |
885 | ||
886 | switch (type) { | |
887 | ||
888 | case RINGBUF_TYPE_PADDING: | |
889 | break; | |
890 | ||
891 | case RINGBUF_TYPE_TIME_EXTEND: | |
892 | event->len = | |
893 | (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1)) | |
894 | >> RB_ALIGNMENT_SHIFT; | |
895 | break; | |
896 | ||
897 | case RINGBUF_TYPE_TIME_STAMP: | |
898 | event->len = | |
899 | (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1)) | |
900 | >> RB_ALIGNMENT_SHIFT; | |
901 | break; | |
902 | ||
903 | case RINGBUF_TYPE_DATA: | |
904 | length -= RB_EVNT_HDR_SIZE; | |
905 | if (length > RB_MAX_SMALL_DATA) { | |
906 | event->len = 0; | |
907 | event->array[0] = length; | |
908 | } else | |
909 | event->len = | |
910 | (length + (RB_ALIGNMENT-1)) | |
911 | >> RB_ALIGNMENT_SHIFT; | |
912 | break; | |
913 | default: | |
914 | BUG(); | |
915 | } | |
916 | } | |
917 | ||
918 | static inline unsigned rb_calculate_event_length(unsigned length) | |
919 | { | |
920 | struct ring_buffer_event event; /* Used only for sizeof array */ | |
921 | ||
922 | /* zero length can cause confusions */ | |
923 | if (!length) | |
924 | length = 1; | |
925 | ||
926 | if (length > RB_MAX_SMALL_DATA) | |
927 | length += sizeof(event.array[0]); | |
928 | ||
929 | length += RB_EVNT_HDR_SIZE; | |
930 | length = ALIGN(length, RB_ALIGNMENT); | |
931 | ||
932 | return length; | |
933 | } | |
934 | ||
935 | static struct ring_buffer_event * | |
936 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, | |
937 | unsigned type, unsigned long length, u64 *ts) | |
938 | { | |
d769041f | 939 | struct buffer_page *tail_page, *head_page, *reader_page; |
bf41a158 | 940 | unsigned long tail, write; |
7a8e76a3 SR |
941 | struct ring_buffer *buffer = cpu_buffer->buffer; |
942 | struct ring_buffer_event *event; | |
bf41a158 | 943 | unsigned long flags; |
7a8e76a3 SR |
944 | |
945 | tail_page = cpu_buffer->tail_page; | |
bf41a158 SR |
946 | write = local_add_return(length, &tail_page->write); |
947 | tail = write - length; | |
7a8e76a3 | 948 | |
bf41a158 SR |
949 | /* See if we shot pass the end of this buffer page */ |
950 | if (write > BUF_PAGE_SIZE) { | |
7a8e76a3 SR |
951 | struct buffer_page *next_page = tail_page; |
952 | ||
3e03fb7f SR |
953 | local_irq_save(flags); |
954 | __raw_spin_lock(&cpu_buffer->lock); | |
bf41a158 | 955 | |
7a8e76a3 SR |
956 | rb_inc_page(cpu_buffer, &next_page); |
957 | ||
d769041f SR |
958 | head_page = cpu_buffer->head_page; |
959 | reader_page = cpu_buffer->reader_page; | |
960 | ||
961 | /* we grabbed the lock before incrementing */ | |
3e89c7bb SR |
962 | if (RB_WARN_ON(cpu_buffer, next_page == reader_page)) |
963 | goto out_unlock; | |
bf41a158 SR |
964 | |
965 | /* | |
966 | * If for some reason, we had an interrupt storm that made | |
967 | * it all the way around the buffer, bail, and warn | |
968 | * about it. | |
969 | */ | |
970 | if (unlikely(next_page == cpu_buffer->commit_page)) { | |
971 | WARN_ON_ONCE(1); | |
972 | goto out_unlock; | |
973 | } | |
d769041f | 974 | |
7a8e76a3 | 975 | if (next_page == head_page) { |
d769041f | 976 | if (!(buffer->flags & RB_FL_OVERWRITE)) { |
bf41a158 SR |
977 | /* reset write */ |
978 | if (tail <= BUF_PAGE_SIZE) | |
979 | local_set(&tail_page->write, tail); | |
980 | goto out_unlock; | |
d769041f | 981 | } |
7a8e76a3 | 982 | |
bf41a158 SR |
983 | /* tail_page has not moved yet? */ |
984 | if (tail_page == cpu_buffer->tail_page) { | |
985 | /* count overflows */ | |
986 | rb_update_overflow(cpu_buffer); | |
987 | ||
988 | rb_inc_page(cpu_buffer, &head_page); | |
989 | cpu_buffer->head_page = head_page; | |
990 | cpu_buffer->head_page->read = 0; | |
991 | } | |
992 | } | |
7a8e76a3 | 993 | |
bf41a158 SR |
994 | /* |
995 | * If the tail page is still the same as what we think | |
996 | * it is, then it is up to us to update the tail | |
997 | * pointer. | |
998 | */ | |
999 | if (tail_page == cpu_buffer->tail_page) { | |
1000 | local_set(&next_page->write, 0); | |
1001 | local_set(&next_page->commit, 0); | |
1002 | cpu_buffer->tail_page = next_page; | |
1003 | ||
1004 | /* reread the time stamp */ | |
1005 | *ts = ring_buffer_time_stamp(cpu_buffer->cpu); | |
1006 | cpu_buffer->tail_page->time_stamp = *ts; | |
7a8e76a3 SR |
1007 | } |
1008 | ||
bf41a158 SR |
1009 | /* |
1010 | * The actual tail page has moved forward. | |
1011 | */ | |
1012 | if (tail < BUF_PAGE_SIZE) { | |
1013 | /* Mark the rest of the page with padding */ | |
6f807acd | 1014 | event = __rb_page_index(tail_page, tail); |
7a8e76a3 SR |
1015 | event->type = RINGBUF_TYPE_PADDING; |
1016 | } | |
1017 | ||
bf41a158 SR |
1018 | if (tail <= BUF_PAGE_SIZE) |
1019 | /* Set the write back to the previous setting */ | |
1020 | local_set(&tail_page->write, tail); | |
1021 | ||
1022 | /* | |
1023 | * If this was a commit entry that failed, | |
1024 | * increment that too | |
1025 | */ | |
1026 | if (tail_page == cpu_buffer->commit_page && | |
1027 | tail == rb_commit_index(cpu_buffer)) { | |
1028 | rb_set_commit_to_write(cpu_buffer); | |
1029 | } | |
1030 | ||
3e03fb7f SR |
1031 | __raw_spin_unlock(&cpu_buffer->lock); |
1032 | local_irq_restore(flags); | |
bf41a158 SR |
1033 | |
1034 | /* fail and let the caller try again */ | |
1035 | return ERR_PTR(-EAGAIN); | |
7a8e76a3 SR |
1036 | } |
1037 | ||
bf41a158 SR |
1038 | /* We reserved something on the buffer */ |
1039 | ||
3e89c7bb SR |
1040 | if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE)) |
1041 | return NULL; | |
7a8e76a3 | 1042 | |
6f807acd | 1043 | event = __rb_page_index(tail_page, tail); |
7a8e76a3 SR |
1044 | rb_update_event(event, type, length); |
1045 | ||
bf41a158 SR |
1046 | /* |
1047 | * If this is a commit and the tail is zero, then update | |
1048 | * this page's time stamp. | |
1049 | */ | |
1050 | if (!tail && rb_is_commit(cpu_buffer, event)) | |
1051 | cpu_buffer->commit_page->time_stamp = *ts; | |
1052 | ||
7a8e76a3 | 1053 | return event; |
bf41a158 SR |
1054 | |
1055 | out_unlock: | |
3e03fb7f SR |
1056 | __raw_spin_unlock(&cpu_buffer->lock); |
1057 | local_irq_restore(flags); | |
bf41a158 | 1058 | return NULL; |
7a8e76a3 SR |
1059 | } |
1060 | ||
1061 | static int | |
1062 | rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
1063 | u64 *ts, u64 *delta) | |
1064 | { | |
1065 | struct ring_buffer_event *event; | |
1066 | static int once; | |
bf41a158 | 1067 | int ret; |
7a8e76a3 SR |
1068 | |
1069 | if (unlikely(*delta > (1ULL << 59) && !once++)) { | |
1070 | printk(KERN_WARNING "Delta way too big! %llu" | |
1071 | " ts=%llu write stamp = %llu\n", | |
e2862c94 SR |
1072 | (unsigned long long)*delta, |
1073 | (unsigned long long)*ts, | |
1074 | (unsigned long long)cpu_buffer->write_stamp); | |
7a8e76a3 SR |
1075 | WARN_ON(1); |
1076 | } | |
1077 | ||
1078 | /* | |
1079 | * The delta is too big, we to add a | |
1080 | * new timestamp. | |
1081 | */ | |
1082 | event = __rb_reserve_next(cpu_buffer, | |
1083 | RINGBUF_TYPE_TIME_EXTEND, | |
1084 | RB_LEN_TIME_EXTEND, | |
1085 | ts); | |
1086 | if (!event) | |
bf41a158 | 1087 | return -EBUSY; |
7a8e76a3 | 1088 | |
bf41a158 SR |
1089 | if (PTR_ERR(event) == -EAGAIN) |
1090 | return -EAGAIN; | |
1091 | ||
1092 | /* Only a commited time event can update the write stamp */ | |
1093 | if (rb_is_commit(cpu_buffer, event)) { | |
1094 | /* | |
1095 | * If this is the first on the page, then we need to | |
1096 | * update the page itself, and just put in a zero. | |
1097 | */ | |
1098 | if (rb_event_index(event)) { | |
1099 | event->time_delta = *delta & TS_MASK; | |
1100 | event->array[0] = *delta >> TS_SHIFT; | |
1101 | } else { | |
1102 | cpu_buffer->commit_page->time_stamp = *ts; | |
1103 | event->time_delta = 0; | |
1104 | event->array[0] = 0; | |
1105 | } | |
7a8e76a3 | 1106 | cpu_buffer->write_stamp = *ts; |
bf41a158 SR |
1107 | /* let the caller know this was the commit */ |
1108 | ret = 1; | |
1109 | } else { | |
1110 | /* Darn, this is just wasted space */ | |
1111 | event->time_delta = 0; | |
1112 | event->array[0] = 0; | |
1113 | ret = 0; | |
7a8e76a3 SR |
1114 | } |
1115 | ||
bf41a158 SR |
1116 | *delta = 0; |
1117 | ||
1118 | return ret; | |
7a8e76a3 SR |
1119 | } |
1120 | ||
1121 | static struct ring_buffer_event * | |
1122 | rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, | |
1123 | unsigned type, unsigned long length) | |
1124 | { | |
1125 | struct ring_buffer_event *event; | |
1126 | u64 ts, delta; | |
bf41a158 | 1127 | int commit = 0; |
818e3dd3 | 1128 | int nr_loops = 0; |
7a8e76a3 | 1129 | |
bf41a158 | 1130 | again: |
818e3dd3 SR |
1131 | /* |
1132 | * We allow for interrupts to reenter here and do a trace. | |
1133 | * If one does, it will cause this original code to loop | |
1134 | * back here. Even with heavy interrupts happening, this | |
1135 | * should only happen a few times in a row. If this happens | |
1136 | * 1000 times in a row, there must be either an interrupt | |
1137 | * storm or we have something buggy. | |
1138 | * Bail! | |
1139 | */ | |
3e89c7bb | 1140 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
818e3dd3 | 1141 | return NULL; |
818e3dd3 | 1142 | |
7a8e76a3 SR |
1143 | ts = ring_buffer_time_stamp(cpu_buffer->cpu); |
1144 | ||
bf41a158 SR |
1145 | /* |
1146 | * Only the first commit can update the timestamp. | |
1147 | * Yes there is a race here. If an interrupt comes in | |
1148 | * just after the conditional and it traces too, then it | |
1149 | * will also check the deltas. More than one timestamp may | |
1150 | * also be made. But only the entry that did the actual | |
1151 | * commit will be something other than zero. | |
1152 | */ | |
1153 | if (cpu_buffer->tail_page == cpu_buffer->commit_page && | |
1154 | rb_page_write(cpu_buffer->tail_page) == | |
1155 | rb_commit_index(cpu_buffer)) { | |
1156 | ||
7a8e76a3 SR |
1157 | delta = ts - cpu_buffer->write_stamp; |
1158 | ||
bf41a158 SR |
1159 | /* make sure this delta is calculated here */ |
1160 | barrier(); | |
1161 | ||
1162 | /* Did the write stamp get updated already? */ | |
1163 | if (unlikely(ts < cpu_buffer->write_stamp)) | |
4143c5cb | 1164 | delta = 0; |
bf41a158 | 1165 | |
7a8e76a3 | 1166 | if (test_time_stamp(delta)) { |
7a8e76a3 | 1167 | |
bf41a158 SR |
1168 | commit = rb_add_time_stamp(cpu_buffer, &ts, &delta); |
1169 | ||
1170 | if (commit == -EBUSY) | |
7a8e76a3 | 1171 | return NULL; |
bf41a158 SR |
1172 | |
1173 | if (commit == -EAGAIN) | |
1174 | goto again; | |
1175 | ||
1176 | RB_WARN_ON(cpu_buffer, commit < 0); | |
7a8e76a3 | 1177 | } |
bf41a158 SR |
1178 | } else |
1179 | /* Non commits have zero deltas */ | |
7a8e76a3 | 1180 | delta = 0; |
7a8e76a3 SR |
1181 | |
1182 | event = __rb_reserve_next(cpu_buffer, type, length, &ts); | |
bf41a158 SR |
1183 | if (PTR_ERR(event) == -EAGAIN) |
1184 | goto again; | |
1185 | ||
1186 | if (!event) { | |
1187 | if (unlikely(commit)) | |
1188 | /* | |
1189 | * Ouch! We needed a timestamp and it was commited. But | |
1190 | * we didn't get our event reserved. | |
1191 | */ | |
1192 | rb_set_commit_to_write(cpu_buffer); | |
7a8e76a3 | 1193 | return NULL; |
bf41a158 | 1194 | } |
7a8e76a3 | 1195 | |
bf41a158 SR |
1196 | /* |
1197 | * If the timestamp was commited, make the commit our entry | |
1198 | * now so that we will update it when needed. | |
1199 | */ | |
1200 | if (commit) | |
1201 | rb_set_commit_event(cpu_buffer, event); | |
1202 | else if (!rb_is_commit(cpu_buffer, event)) | |
7a8e76a3 SR |
1203 | delta = 0; |
1204 | ||
1205 | event->time_delta = delta; | |
1206 | ||
1207 | return event; | |
1208 | } | |
1209 | ||
bf41a158 SR |
1210 | static DEFINE_PER_CPU(int, rb_need_resched); |
1211 | ||
7a8e76a3 SR |
1212 | /** |
1213 | * ring_buffer_lock_reserve - reserve a part of the buffer | |
1214 | * @buffer: the ring buffer to reserve from | |
1215 | * @length: the length of the data to reserve (excluding event header) | |
1216 | * @flags: a pointer to save the interrupt flags | |
1217 | * | |
1218 | * Returns a reseverd event on the ring buffer to copy directly to. | |
1219 | * The user of this interface will need to get the body to write into | |
1220 | * and can use the ring_buffer_event_data() interface. | |
1221 | * | |
1222 | * The length is the length of the data needed, not the event length | |
1223 | * which also includes the event header. | |
1224 | * | |
1225 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. | |
1226 | * If NULL is returned, then nothing has been allocated or locked. | |
1227 | */ | |
1228 | struct ring_buffer_event * | |
1229 | ring_buffer_lock_reserve(struct ring_buffer *buffer, | |
1230 | unsigned long length, | |
1231 | unsigned long *flags) | |
1232 | { | |
1233 | struct ring_buffer_per_cpu *cpu_buffer; | |
1234 | struct ring_buffer_event *event; | |
bf41a158 | 1235 | int cpu, resched; |
7a8e76a3 | 1236 | |
033601a3 | 1237 | if (ring_buffer_flags != RB_BUFFERS_ON) |
a3583244 SR |
1238 | return NULL; |
1239 | ||
7a8e76a3 SR |
1240 | if (atomic_read(&buffer->record_disabled)) |
1241 | return NULL; | |
1242 | ||
bf41a158 | 1243 | /* If we are tracing schedule, we don't want to recurse */ |
182e9f5f | 1244 | resched = ftrace_preempt_disable(); |
bf41a158 | 1245 | |
7a8e76a3 SR |
1246 | cpu = raw_smp_processor_id(); |
1247 | ||
1248 | if (!cpu_isset(cpu, buffer->cpumask)) | |
d769041f | 1249 | goto out; |
7a8e76a3 SR |
1250 | |
1251 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
1252 | |
1253 | if (atomic_read(&cpu_buffer->record_disabled)) | |
d769041f | 1254 | goto out; |
7a8e76a3 SR |
1255 | |
1256 | length = rb_calculate_event_length(length); | |
1257 | if (length > BUF_PAGE_SIZE) | |
bf41a158 | 1258 | goto out; |
7a8e76a3 SR |
1259 | |
1260 | event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length); | |
1261 | if (!event) | |
d769041f | 1262 | goto out; |
7a8e76a3 | 1263 | |
bf41a158 SR |
1264 | /* |
1265 | * Need to store resched state on this cpu. | |
1266 | * Only the first needs to. | |
1267 | */ | |
1268 | ||
1269 | if (preempt_count() == 1) | |
1270 | per_cpu(rb_need_resched, cpu) = resched; | |
1271 | ||
7a8e76a3 SR |
1272 | return event; |
1273 | ||
d769041f | 1274 | out: |
182e9f5f | 1275 | ftrace_preempt_enable(resched); |
7a8e76a3 SR |
1276 | return NULL; |
1277 | } | |
1278 | ||
1279 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, | |
1280 | struct ring_buffer_event *event) | |
1281 | { | |
7a8e76a3 | 1282 | cpu_buffer->entries++; |
bf41a158 SR |
1283 | |
1284 | /* Only process further if we own the commit */ | |
1285 | if (!rb_is_commit(cpu_buffer, event)) | |
1286 | return; | |
1287 | ||
1288 | cpu_buffer->write_stamp += event->time_delta; | |
1289 | ||
1290 | rb_set_commit_to_write(cpu_buffer); | |
7a8e76a3 SR |
1291 | } |
1292 | ||
1293 | /** | |
1294 | * ring_buffer_unlock_commit - commit a reserved | |
1295 | * @buffer: The buffer to commit to | |
1296 | * @event: The event pointer to commit. | |
1297 | * @flags: the interrupt flags received from ring_buffer_lock_reserve. | |
1298 | * | |
1299 | * This commits the data to the ring buffer, and releases any locks held. | |
1300 | * | |
1301 | * Must be paired with ring_buffer_lock_reserve. | |
1302 | */ | |
1303 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, | |
1304 | struct ring_buffer_event *event, | |
1305 | unsigned long flags) | |
1306 | { | |
1307 | struct ring_buffer_per_cpu *cpu_buffer; | |
1308 | int cpu = raw_smp_processor_id(); | |
1309 | ||
1310 | cpu_buffer = buffer->buffers[cpu]; | |
1311 | ||
7a8e76a3 SR |
1312 | rb_commit(cpu_buffer, event); |
1313 | ||
bf41a158 SR |
1314 | /* |
1315 | * Only the last preempt count needs to restore preemption. | |
1316 | */ | |
182e9f5f SR |
1317 | if (preempt_count() == 1) |
1318 | ftrace_preempt_enable(per_cpu(rb_need_resched, cpu)); | |
1319 | else | |
bf41a158 | 1320 | preempt_enable_no_resched_notrace(); |
7a8e76a3 SR |
1321 | |
1322 | return 0; | |
1323 | } | |
1324 | ||
1325 | /** | |
1326 | * ring_buffer_write - write data to the buffer without reserving | |
1327 | * @buffer: The ring buffer to write to. | |
1328 | * @length: The length of the data being written (excluding the event header) | |
1329 | * @data: The data to write to the buffer. | |
1330 | * | |
1331 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as | |
1332 | * one function. If you already have the data to write to the buffer, it | |
1333 | * may be easier to simply call this function. | |
1334 | * | |
1335 | * Note, like ring_buffer_lock_reserve, the length is the length of the data | |
1336 | * and not the length of the event which would hold the header. | |
1337 | */ | |
1338 | int ring_buffer_write(struct ring_buffer *buffer, | |
1339 | unsigned long length, | |
1340 | void *data) | |
1341 | { | |
1342 | struct ring_buffer_per_cpu *cpu_buffer; | |
1343 | struct ring_buffer_event *event; | |
bf41a158 | 1344 | unsigned long event_length; |
7a8e76a3 SR |
1345 | void *body; |
1346 | int ret = -EBUSY; | |
bf41a158 | 1347 | int cpu, resched; |
7a8e76a3 | 1348 | |
033601a3 | 1349 | if (ring_buffer_flags != RB_BUFFERS_ON) |
a3583244 SR |
1350 | return -EBUSY; |
1351 | ||
7a8e76a3 SR |
1352 | if (atomic_read(&buffer->record_disabled)) |
1353 | return -EBUSY; | |
1354 | ||
182e9f5f | 1355 | resched = ftrace_preempt_disable(); |
bf41a158 | 1356 | |
7a8e76a3 SR |
1357 | cpu = raw_smp_processor_id(); |
1358 | ||
1359 | if (!cpu_isset(cpu, buffer->cpumask)) | |
d769041f | 1360 | goto out; |
7a8e76a3 SR |
1361 | |
1362 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
1363 | |
1364 | if (atomic_read(&cpu_buffer->record_disabled)) | |
1365 | goto out; | |
1366 | ||
1367 | event_length = rb_calculate_event_length(length); | |
1368 | event = rb_reserve_next_event(cpu_buffer, | |
1369 | RINGBUF_TYPE_DATA, event_length); | |
1370 | if (!event) | |
1371 | goto out; | |
1372 | ||
1373 | body = rb_event_data(event); | |
1374 | ||
1375 | memcpy(body, data, length); | |
1376 | ||
1377 | rb_commit(cpu_buffer, event); | |
1378 | ||
1379 | ret = 0; | |
1380 | out: | |
182e9f5f | 1381 | ftrace_preempt_enable(resched); |
7a8e76a3 SR |
1382 | |
1383 | return ret; | |
1384 | } | |
1385 | ||
bf41a158 SR |
1386 | static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
1387 | { | |
1388 | struct buffer_page *reader = cpu_buffer->reader_page; | |
1389 | struct buffer_page *head = cpu_buffer->head_page; | |
1390 | struct buffer_page *commit = cpu_buffer->commit_page; | |
1391 | ||
1392 | return reader->read == rb_page_commit(reader) && | |
1393 | (commit == reader || | |
1394 | (commit == head && | |
1395 | head->read == rb_page_commit(commit))); | |
1396 | } | |
1397 | ||
7a8e76a3 SR |
1398 | /** |
1399 | * ring_buffer_record_disable - stop all writes into the buffer | |
1400 | * @buffer: The ring buffer to stop writes to. | |
1401 | * | |
1402 | * This prevents all writes to the buffer. Any attempt to write | |
1403 | * to the buffer after this will fail and return NULL. | |
1404 | * | |
1405 | * The caller should call synchronize_sched() after this. | |
1406 | */ | |
1407 | void ring_buffer_record_disable(struct ring_buffer *buffer) | |
1408 | { | |
1409 | atomic_inc(&buffer->record_disabled); | |
1410 | } | |
1411 | ||
1412 | /** | |
1413 | * ring_buffer_record_enable - enable writes to the buffer | |
1414 | * @buffer: The ring buffer to enable writes | |
1415 | * | |
1416 | * Note, multiple disables will need the same number of enables | |
1417 | * to truely enable the writing (much like preempt_disable). | |
1418 | */ | |
1419 | void ring_buffer_record_enable(struct ring_buffer *buffer) | |
1420 | { | |
1421 | atomic_dec(&buffer->record_disabled); | |
1422 | } | |
1423 | ||
1424 | /** | |
1425 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer | |
1426 | * @buffer: The ring buffer to stop writes to. | |
1427 | * @cpu: The CPU buffer to stop | |
1428 | * | |
1429 | * This prevents all writes to the buffer. Any attempt to write | |
1430 | * to the buffer after this will fail and return NULL. | |
1431 | * | |
1432 | * The caller should call synchronize_sched() after this. | |
1433 | */ | |
1434 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) | |
1435 | { | |
1436 | struct ring_buffer_per_cpu *cpu_buffer; | |
1437 | ||
1438 | if (!cpu_isset(cpu, buffer->cpumask)) | |
1439 | return; | |
1440 | ||
1441 | cpu_buffer = buffer->buffers[cpu]; | |
1442 | atomic_inc(&cpu_buffer->record_disabled); | |
1443 | } | |
1444 | ||
1445 | /** | |
1446 | * ring_buffer_record_enable_cpu - enable writes to the buffer | |
1447 | * @buffer: The ring buffer to enable writes | |
1448 | * @cpu: The CPU to enable. | |
1449 | * | |
1450 | * Note, multiple disables will need the same number of enables | |
1451 | * to truely enable the writing (much like preempt_disable). | |
1452 | */ | |
1453 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) | |
1454 | { | |
1455 | struct ring_buffer_per_cpu *cpu_buffer; | |
1456 | ||
1457 | if (!cpu_isset(cpu, buffer->cpumask)) | |
1458 | return; | |
1459 | ||
1460 | cpu_buffer = buffer->buffers[cpu]; | |
1461 | atomic_dec(&cpu_buffer->record_disabled); | |
1462 | } | |
1463 | ||
1464 | /** | |
1465 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer | |
1466 | * @buffer: The ring buffer | |
1467 | * @cpu: The per CPU buffer to get the entries from. | |
1468 | */ | |
1469 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) | |
1470 | { | |
1471 | struct ring_buffer_per_cpu *cpu_buffer; | |
1472 | ||
1473 | if (!cpu_isset(cpu, buffer->cpumask)) | |
1474 | return 0; | |
1475 | ||
1476 | cpu_buffer = buffer->buffers[cpu]; | |
1477 | return cpu_buffer->entries; | |
1478 | } | |
1479 | ||
1480 | /** | |
1481 | * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer | |
1482 | * @buffer: The ring buffer | |
1483 | * @cpu: The per CPU buffer to get the number of overruns from | |
1484 | */ | |
1485 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
1486 | { | |
1487 | struct ring_buffer_per_cpu *cpu_buffer; | |
1488 | ||
1489 | if (!cpu_isset(cpu, buffer->cpumask)) | |
1490 | return 0; | |
1491 | ||
1492 | cpu_buffer = buffer->buffers[cpu]; | |
1493 | return cpu_buffer->overrun; | |
1494 | } | |
1495 | ||
1496 | /** | |
1497 | * ring_buffer_entries - get the number of entries in a buffer | |
1498 | * @buffer: The ring buffer | |
1499 | * | |
1500 | * Returns the total number of entries in the ring buffer | |
1501 | * (all CPU entries) | |
1502 | */ | |
1503 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) | |
1504 | { | |
1505 | struct ring_buffer_per_cpu *cpu_buffer; | |
1506 | unsigned long entries = 0; | |
1507 | int cpu; | |
1508 | ||
1509 | /* if you care about this being correct, lock the buffer */ | |
1510 | for_each_buffer_cpu(buffer, cpu) { | |
1511 | cpu_buffer = buffer->buffers[cpu]; | |
1512 | entries += cpu_buffer->entries; | |
1513 | } | |
1514 | ||
1515 | return entries; | |
1516 | } | |
1517 | ||
1518 | /** | |
1519 | * ring_buffer_overrun_cpu - get the number of overruns in buffer | |
1520 | * @buffer: The ring buffer | |
1521 | * | |
1522 | * Returns the total number of overruns in the ring buffer | |
1523 | * (all CPU entries) | |
1524 | */ | |
1525 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) | |
1526 | { | |
1527 | struct ring_buffer_per_cpu *cpu_buffer; | |
1528 | unsigned long overruns = 0; | |
1529 | int cpu; | |
1530 | ||
1531 | /* if you care about this being correct, lock the buffer */ | |
1532 | for_each_buffer_cpu(buffer, cpu) { | |
1533 | cpu_buffer = buffer->buffers[cpu]; | |
1534 | overruns += cpu_buffer->overrun; | |
1535 | } | |
1536 | ||
1537 | return overruns; | |
1538 | } | |
1539 | ||
642edba5 | 1540 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
7a8e76a3 SR |
1541 | { |
1542 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1543 | ||
d769041f SR |
1544 | /* Iterator usage is expected to have record disabled */ |
1545 | if (list_empty(&cpu_buffer->reader_page->list)) { | |
1546 | iter->head_page = cpu_buffer->head_page; | |
6f807acd | 1547 | iter->head = cpu_buffer->head_page->read; |
d769041f SR |
1548 | } else { |
1549 | iter->head_page = cpu_buffer->reader_page; | |
6f807acd | 1550 | iter->head = cpu_buffer->reader_page->read; |
d769041f SR |
1551 | } |
1552 | if (iter->head) | |
1553 | iter->read_stamp = cpu_buffer->read_stamp; | |
1554 | else | |
1555 | iter->read_stamp = iter->head_page->time_stamp; | |
642edba5 | 1556 | } |
f83c9d0f | 1557 | |
642edba5 SR |
1558 | /** |
1559 | * ring_buffer_iter_reset - reset an iterator | |
1560 | * @iter: The iterator to reset | |
1561 | * | |
1562 | * Resets the iterator, so that it will start from the beginning | |
1563 | * again. | |
1564 | */ | |
1565 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) | |
1566 | { | |
1567 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1568 | unsigned long flags; | |
1569 | ||
1570 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
1571 | rb_iter_reset(iter); | |
f83c9d0f | 1572 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 SR |
1573 | } |
1574 | ||
1575 | /** | |
1576 | * ring_buffer_iter_empty - check if an iterator has no more to read | |
1577 | * @iter: The iterator to check | |
1578 | */ | |
1579 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) | |
1580 | { | |
1581 | struct ring_buffer_per_cpu *cpu_buffer; | |
1582 | ||
1583 | cpu_buffer = iter->cpu_buffer; | |
1584 | ||
bf41a158 SR |
1585 | return iter->head_page == cpu_buffer->commit_page && |
1586 | iter->head == rb_commit_index(cpu_buffer); | |
7a8e76a3 SR |
1587 | } |
1588 | ||
1589 | static void | |
1590 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
1591 | struct ring_buffer_event *event) | |
1592 | { | |
1593 | u64 delta; | |
1594 | ||
1595 | switch (event->type) { | |
1596 | case RINGBUF_TYPE_PADDING: | |
1597 | return; | |
1598 | ||
1599 | case RINGBUF_TYPE_TIME_EXTEND: | |
1600 | delta = event->array[0]; | |
1601 | delta <<= TS_SHIFT; | |
1602 | delta += event->time_delta; | |
1603 | cpu_buffer->read_stamp += delta; | |
1604 | return; | |
1605 | ||
1606 | case RINGBUF_TYPE_TIME_STAMP: | |
1607 | /* FIXME: not implemented */ | |
1608 | return; | |
1609 | ||
1610 | case RINGBUF_TYPE_DATA: | |
1611 | cpu_buffer->read_stamp += event->time_delta; | |
1612 | return; | |
1613 | ||
1614 | default: | |
1615 | BUG(); | |
1616 | } | |
1617 | return; | |
1618 | } | |
1619 | ||
1620 | static void | |
1621 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, | |
1622 | struct ring_buffer_event *event) | |
1623 | { | |
1624 | u64 delta; | |
1625 | ||
1626 | switch (event->type) { | |
1627 | case RINGBUF_TYPE_PADDING: | |
1628 | return; | |
1629 | ||
1630 | case RINGBUF_TYPE_TIME_EXTEND: | |
1631 | delta = event->array[0]; | |
1632 | delta <<= TS_SHIFT; | |
1633 | delta += event->time_delta; | |
1634 | iter->read_stamp += delta; | |
1635 | return; | |
1636 | ||
1637 | case RINGBUF_TYPE_TIME_STAMP: | |
1638 | /* FIXME: not implemented */ | |
1639 | return; | |
1640 | ||
1641 | case RINGBUF_TYPE_DATA: | |
1642 | iter->read_stamp += event->time_delta; | |
1643 | return; | |
1644 | ||
1645 | default: | |
1646 | BUG(); | |
1647 | } | |
1648 | return; | |
1649 | } | |
1650 | ||
d769041f SR |
1651 | static struct buffer_page * |
1652 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 1653 | { |
d769041f SR |
1654 | struct buffer_page *reader = NULL; |
1655 | unsigned long flags; | |
818e3dd3 | 1656 | int nr_loops = 0; |
d769041f | 1657 | |
3e03fb7f SR |
1658 | local_irq_save(flags); |
1659 | __raw_spin_lock(&cpu_buffer->lock); | |
d769041f SR |
1660 | |
1661 | again: | |
818e3dd3 SR |
1662 | /* |
1663 | * This should normally only loop twice. But because the | |
1664 | * start of the reader inserts an empty page, it causes | |
1665 | * a case where we will loop three times. There should be no | |
1666 | * reason to loop four times (that I know of). | |
1667 | */ | |
3e89c7bb | 1668 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
818e3dd3 SR |
1669 | reader = NULL; |
1670 | goto out; | |
1671 | } | |
1672 | ||
d769041f SR |
1673 | reader = cpu_buffer->reader_page; |
1674 | ||
1675 | /* If there's more to read, return this page */ | |
bf41a158 | 1676 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
d769041f SR |
1677 | goto out; |
1678 | ||
1679 | /* Never should we have an index greater than the size */ | |
3e89c7bb SR |
1680 | if (RB_WARN_ON(cpu_buffer, |
1681 | cpu_buffer->reader_page->read > rb_page_size(reader))) | |
1682 | goto out; | |
d769041f SR |
1683 | |
1684 | /* check if we caught up to the tail */ | |
1685 | reader = NULL; | |
bf41a158 | 1686 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
d769041f | 1687 | goto out; |
7a8e76a3 SR |
1688 | |
1689 | /* | |
d769041f SR |
1690 | * Splice the empty reader page into the list around the head. |
1691 | * Reset the reader page to size zero. | |
7a8e76a3 | 1692 | */ |
7a8e76a3 | 1693 | |
d769041f SR |
1694 | reader = cpu_buffer->head_page; |
1695 | cpu_buffer->reader_page->list.next = reader->list.next; | |
1696 | cpu_buffer->reader_page->list.prev = reader->list.prev; | |
bf41a158 SR |
1697 | |
1698 | local_set(&cpu_buffer->reader_page->write, 0); | |
1699 | local_set(&cpu_buffer->reader_page->commit, 0); | |
7a8e76a3 | 1700 | |
d769041f SR |
1701 | /* Make the reader page now replace the head */ |
1702 | reader->list.prev->next = &cpu_buffer->reader_page->list; | |
1703 | reader->list.next->prev = &cpu_buffer->reader_page->list; | |
7a8e76a3 SR |
1704 | |
1705 | /* | |
d769041f SR |
1706 | * If the tail is on the reader, then we must set the head |
1707 | * to the inserted page, otherwise we set it one before. | |
7a8e76a3 | 1708 | */ |
d769041f | 1709 | cpu_buffer->head_page = cpu_buffer->reader_page; |
7a8e76a3 | 1710 | |
bf41a158 | 1711 | if (cpu_buffer->commit_page != reader) |
d769041f SR |
1712 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
1713 | ||
1714 | /* Finally update the reader page to the new head */ | |
1715 | cpu_buffer->reader_page = reader; | |
1716 | rb_reset_reader_page(cpu_buffer); | |
1717 | ||
1718 | goto again; | |
1719 | ||
1720 | out: | |
3e03fb7f SR |
1721 | __raw_spin_unlock(&cpu_buffer->lock); |
1722 | local_irq_restore(flags); | |
d769041f SR |
1723 | |
1724 | return reader; | |
1725 | } | |
1726 | ||
1727 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) | |
1728 | { | |
1729 | struct ring_buffer_event *event; | |
1730 | struct buffer_page *reader; | |
1731 | unsigned length; | |
1732 | ||
1733 | reader = rb_get_reader_page(cpu_buffer); | |
7a8e76a3 | 1734 | |
d769041f | 1735 | /* This function should not be called when buffer is empty */ |
3e89c7bb SR |
1736 | if (RB_WARN_ON(cpu_buffer, !reader)) |
1737 | return; | |
7a8e76a3 | 1738 | |
d769041f SR |
1739 | event = rb_reader_event(cpu_buffer); |
1740 | ||
1741 | if (event->type == RINGBUF_TYPE_DATA) | |
1742 | cpu_buffer->entries--; | |
1743 | ||
1744 | rb_update_read_stamp(cpu_buffer, event); | |
1745 | ||
1746 | length = rb_event_length(event); | |
6f807acd | 1747 | cpu_buffer->reader_page->read += length; |
7a8e76a3 SR |
1748 | } |
1749 | ||
1750 | static void rb_advance_iter(struct ring_buffer_iter *iter) | |
1751 | { | |
1752 | struct ring_buffer *buffer; | |
1753 | struct ring_buffer_per_cpu *cpu_buffer; | |
1754 | struct ring_buffer_event *event; | |
1755 | unsigned length; | |
1756 | ||
1757 | cpu_buffer = iter->cpu_buffer; | |
1758 | buffer = cpu_buffer->buffer; | |
1759 | ||
1760 | /* | |
1761 | * Check if we are at the end of the buffer. | |
1762 | */ | |
bf41a158 | 1763 | if (iter->head >= rb_page_size(iter->head_page)) { |
3e89c7bb SR |
1764 | if (RB_WARN_ON(buffer, |
1765 | iter->head_page == cpu_buffer->commit_page)) | |
1766 | return; | |
d769041f | 1767 | rb_inc_iter(iter); |
7a8e76a3 SR |
1768 | return; |
1769 | } | |
1770 | ||
1771 | event = rb_iter_head_event(iter); | |
1772 | ||
1773 | length = rb_event_length(event); | |
1774 | ||
1775 | /* | |
1776 | * This should not be called to advance the header if we are | |
1777 | * at the tail of the buffer. | |
1778 | */ | |
3e89c7bb | 1779 | if (RB_WARN_ON(cpu_buffer, |
f536aafc | 1780 | (iter->head_page == cpu_buffer->commit_page) && |
3e89c7bb SR |
1781 | (iter->head + length > rb_commit_index(cpu_buffer)))) |
1782 | return; | |
7a8e76a3 SR |
1783 | |
1784 | rb_update_iter_read_stamp(iter, event); | |
1785 | ||
1786 | iter->head += length; | |
1787 | ||
1788 | /* check for end of page padding */ | |
bf41a158 SR |
1789 | if ((iter->head >= rb_page_size(iter->head_page)) && |
1790 | (iter->head_page != cpu_buffer->commit_page)) | |
7a8e76a3 SR |
1791 | rb_advance_iter(iter); |
1792 | } | |
1793 | ||
f83c9d0f SR |
1794 | static struct ring_buffer_event * |
1795 | rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) | |
7a8e76a3 SR |
1796 | { |
1797 | struct ring_buffer_per_cpu *cpu_buffer; | |
1798 | struct ring_buffer_event *event; | |
d769041f | 1799 | struct buffer_page *reader; |
818e3dd3 | 1800 | int nr_loops = 0; |
7a8e76a3 SR |
1801 | |
1802 | if (!cpu_isset(cpu, buffer->cpumask)) | |
1803 | return NULL; | |
1804 | ||
1805 | cpu_buffer = buffer->buffers[cpu]; | |
1806 | ||
1807 | again: | |
818e3dd3 SR |
1808 | /* |
1809 | * We repeat when a timestamp is encountered. It is possible | |
1810 | * to get multiple timestamps from an interrupt entering just | |
1811 | * as one timestamp is about to be written. The max times | |
1812 | * that this can happen is the number of nested interrupts we | |
1813 | * can have. Nesting 10 deep of interrupts is clearly | |
1814 | * an anomaly. | |
1815 | */ | |
3e89c7bb | 1816 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10)) |
818e3dd3 | 1817 | return NULL; |
818e3dd3 | 1818 | |
d769041f SR |
1819 | reader = rb_get_reader_page(cpu_buffer); |
1820 | if (!reader) | |
7a8e76a3 SR |
1821 | return NULL; |
1822 | ||
d769041f | 1823 | event = rb_reader_event(cpu_buffer); |
7a8e76a3 SR |
1824 | |
1825 | switch (event->type) { | |
1826 | case RINGBUF_TYPE_PADDING: | |
bf41a158 | 1827 | RB_WARN_ON(cpu_buffer, 1); |
d769041f SR |
1828 | rb_advance_reader(cpu_buffer); |
1829 | return NULL; | |
7a8e76a3 SR |
1830 | |
1831 | case RINGBUF_TYPE_TIME_EXTEND: | |
1832 | /* Internal data, OK to advance */ | |
d769041f | 1833 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
1834 | goto again; |
1835 | ||
1836 | case RINGBUF_TYPE_TIME_STAMP: | |
1837 | /* FIXME: not implemented */ | |
d769041f | 1838 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
1839 | goto again; |
1840 | ||
1841 | case RINGBUF_TYPE_DATA: | |
1842 | if (ts) { | |
1843 | *ts = cpu_buffer->read_stamp + event->time_delta; | |
1844 | ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts); | |
1845 | } | |
1846 | return event; | |
1847 | ||
1848 | default: | |
1849 | BUG(); | |
1850 | } | |
1851 | ||
1852 | return NULL; | |
1853 | } | |
1854 | ||
f83c9d0f SR |
1855 | static struct ring_buffer_event * |
1856 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
7a8e76a3 SR |
1857 | { |
1858 | struct ring_buffer *buffer; | |
1859 | struct ring_buffer_per_cpu *cpu_buffer; | |
1860 | struct ring_buffer_event *event; | |
818e3dd3 | 1861 | int nr_loops = 0; |
7a8e76a3 SR |
1862 | |
1863 | if (ring_buffer_iter_empty(iter)) | |
1864 | return NULL; | |
1865 | ||
1866 | cpu_buffer = iter->cpu_buffer; | |
1867 | buffer = cpu_buffer->buffer; | |
1868 | ||
1869 | again: | |
818e3dd3 SR |
1870 | /* |
1871 | * We repeat when a timestamp is encountered. It is possible | |
1872 | * to get multiple timestamps from an interrupt entering just | |
1873 | * as one timestamp is about to be written. The max times | |
1874 | * that this can happen is the number of nested interrupts we | |
1875 | * can have. Nesting 10 deep of interrupts is clearly | |
1876 | * an anomaly. | |
1877 | */ | |
3e89c7bb | 1878 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10)) |
818e3dd3 | 1879 | return NULL; |
818e3dd3 | 1880 | |
7a8e76a3 SR |
1881 | if (rb_per_cpu_empty(cpu_buffer)) |
1882 | return NULL; | |
1883 | ||
1884 | event = rb_iter_head_event(iter); | |
1885 | ||
1886 | switch (event->type) { | |
1887 | case RINGBUF_TYPE_PADDING: | |
d769041f | 1888 | rb_inc_iter(iter); |
7a8e76a3 SR |
1889 | goto again; |
1890 | ||
1891 | case RINGBUF_TYPE_TIME_EXTEND: | |
1892 | /* Internal data, OK to advance */ | |
1893 | rb_advance_iter(iter); | |
1894 | goto again; | |
1895 | ||
1896 | case RINGBUF_TYPE_TIME_STAMP: | |
1897 | /* FIXME: not implemented */ | |
1898 | rb_advance_iter(iter); | |
1899 | goto again; | |
1900 | ||
1901 | case RINGBUF_TYPE_DATA: | |
1902 | if (ts) { | |
1903 | *ts = iter->read_stamp + event->time_delta; | |
1904 | ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts); | |
1905 | } | |
1906 | return event; | |
1907 | ||
1908 | default: | |
1909 | BUG(); | |
1910 | } | |
1911 | ||
1912 | return NULL; | |
1913 | } | |
1914 | ||
f83c9d0f SR |
1915 | /** |
1916 | * ring_buffer_peek - peek at the next event to be read | |
1917 | * @buffer: The ring buffer to read | |
1918 | * @cpu: The cpu to peak at | |
1919 | * @ts: The timestamp counter of this event. | |
1920 | * | |
1921 | * This will return the event that will be read next, but does | |
1922 | * not consume the data. | |
1923 | */ | |
1924 | struct ring_buffer_event * | |
1925 | ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) | |
1926 | { | |
1927 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
1928 | struct ring_buffer_event *event; | |
1929 | unsigned long flags; | |
1930 | ||
1931 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
1932 | event = rb_buffer_peek(buffer, cpu, ts); | |
1933 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
1934 | ||
1935 | return event; | |
1936 | } | |
1937 | ||
1938 | /** | |
1939 | * ring_buffer_iter_peek - peek at the next event to be read | |
1940 | * @iter: The ring buffer iterator | |
1941 | * @ts: The timestamp counter of this event. | |
1942 | * | |
1943 | * This will return the event that will be read next, but does | |
1944 | * not increment the iterator. | |
1945 | */ | |
1946 | struct ring_buffer_event * | |
1947 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
1948 | { | |
1949 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1950 | struct ring_buffer_event *event; | |
1951 | unsigned long flags; | |
1952 | ||
1953 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
1954 | event = rb_iter_peek(iter, ts); | |
1955 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
1956 | ||
1957 | return event; | |
1958 | } | |
1959 | ||
7a8e76a3 SR |
1960 | /** |
1961 | * ring_buffer_consume - return an event and consume it | |
1962 | * @buffer: The ring buffer to get the next event from | |
1963 | * | |
1964 | * Returns the next event in the ring buffer, and that event is consumed. | |
1965 | * Meaning, that sequential reads will keep returning a different event, | |
1966 | * and eventually empty the ring buffer if the producer is slower. | |
1967 | */ | |
1968 | struct ring_buffer_event * | |
1969 | ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) | |
1970 | { | |
f83c9d0f | 1971 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
7a8e76a3 | 1972 | struct ring_buffer_event *event; |
f83c9d0f | 1973 | unsigned long flags; |
7a8e76a3 SR |
1974 | |
1975 | if (!cpu_isset(cpu, buffer->cpumask)) | |
1976 | return NULL; | |
1977 | ||
f83c9d0f SR |
1978 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
1979 | ||
1980 | event = rb_buffer_peek(buffer, cpu, ts); | |
7a8e76a3 | 1981 | if (!event) |
f83c9d0f | 1982 | goto out; |
7a8e76a3 | 1983 | |
d769041f | 1984 | rb_advance_reader(cpu_buffer); |
7a8e76a3 | 1985 | |
f83c9d0f SR |
1986 | out: |
1987 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
1988 | ||
7a8e76a3 SR |
1989 | return event; |
1990 | } | |
1991 | ||
1992 | /** | |
1993 | * ring_buffer_read_start - start a non consuming read of the buffer | |
1994 | * @buffer: The ring buffer to read from | |
1995 | * @cpu: The cpu buffer to iterate over | |
1996 | * | |
1997 | * This starts up an iteration through the buffer. It also disables | |
1998 | * the recording to the buffer until the reading is finished. | |
1999 | * This prevents the reading from being corrupted. This is not | |
2000 | * a consuming read, so a producer is not expected. | |
2001 | * | |
2002 | * Must be paired with ring_buffer_finish. | |
2003 | */ | |
2004 | struct ring_buffer_iter * | |
2005 | ring_buffer_read_start(struct ring_buffer *buffer, int cpu) | |
2006 | { | |
2007 | struct ring_buffer_per_cpu *cpu_buffer; | |
2008 | struct ring_buffer_iter *iter; | |
d769041f | 2009 | unsigned long flags; |
7a8e76a3 SR |
2010 | |
2011 | if (!cpu_isset(cpu, buffer->cpumask)) | |
2012 | return NULL; | |
2013 | ||
2014 | iter = kmalloc(sizeof(*iter), GFP_KERNEL); | |
2015 | if (!iter) | |
2016 | return NULL; | |
2017 | ||
2018 | cpu_buffer = buffer->buffers[cpu]; | |
2019 | ||
2020 | iter->cpu_buffer = cpu_buffer; | |
2021 | ||
2022 | atomic_inc(&cpu_buffer->record_disabled); | |
2023 | synchronize_sched(); | |
2024 | ||
f83c9d0f | 2025 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3e03fb7f | 2026 | __raw_spin_lock(&cpu_buffer->lock); |
642edba5 | 2027 | rb_iter_reset(iter); |
3e03fb7f | 2028 | __raw_spin_unlock(&cpu_buffer->lock); |
f83c9d0f | 2029 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 SR |
2030 | |
2031 | return iter; | |
2032 | } | |
2033 | ||
2034 | /** | |
2035 | * ring_buffer_finish - finish reading the iterator of the buffer | |
2036 | * @iter: The iterator retrieved by ring_buffer_start | |
2037 | * | |
2038 | * This re-enables the recording to the buffer, and frees the | |
2039 | * iterator. | |
2040 | */ | |
2041 | void | |
2042 | ring_buffer_read_finish(struct ring_buffer_iter *iter) | |
2043 | { | |
2044 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
2045 | ||
2046 | atomic_dec(&cpu_buffer->record_disabled); | |
2047 | kfree(iter); | |
2048 | } | |
2049 | ||
2050 | /** | |
2051 | * ring_buffer_read - read the next item in the ring buffer by the iterator | |
2052 | * @iter: The ring buffer iterator | |
2053 | * @ts: The time stamp of the event read. | |
2054 | * | |
2055 | * This reads the next event in the ring buffer and increments the iterator. | |
2056 | */ | |
2057 | struct ring_buffer_event * | |
2058 | ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) | |
2059 | { | |
2060 | struct ring_buffer_event *event; | |
f83c9d0f SR |
2061 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
2062 | unsigned long flags; | |
7a8e76a3 | 2063 | |
f83c9d0f SR |
2064 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
2065 | event = rb_iter_peek(iter, ts); | |
7a8e76a3 | 2066 | if (!event) |
f83c9d0f | 2067 | goto out; |
7a8e76a3 SR |
2068 | |
2069 | rb_advance_iter(iter); | |
f83c9d0f SR |
2070 | out: |
2071 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
7a8e76a3 SR |
2072 | |
2073 | return event; | |
2074 | } | |
2075 | ||
2076 | /** | |
2077 | * ring_buffer_size - return the size of the ring buffer (in bytes) | |
2078 | * @buffer: The ring buffer. | |
2079 | */ | |
2080 | unsigned long ring_buffer_size(struct ring_buffer *buffer) | |
2081 | { | |
2082 | return BUF_PAGE_SIZE * buffer->pages; | |
2083 | } | |
2084 | ||
2085 | static void | |
2086 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) | |
2087 | { | |
2088 | cpu_buffer->head_page | |
2089 | = list_entry(cpu_buffer->pages.next, struct buffer_page, list); | |
bf41a158 SR |
2090 | local_set(&cpu_buffer->head_page->write, 0); |
2091 | local_set(&cpu_buffer->head_page->commit, 0); | |
d769041f | 2092 | |
6f807acd | 2093 | cpu_buffer->head_page->read = 0; |
bf41a158 SR |
2094 | |
2095 | cpu_buffer->tail_page = cpu_buffer->head_page; | |
2096 | cpu_buffer->commit_page = cpu_buffer->head_page; | |
2097 | ||
2098 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); | |
2099 | local_set(&cpu_buffer->reader_page->write, 0); | |
2100 | local_set(&cpu_buffer->reader_page->commit, 0); | |
6f807acd | 2101 | cpu_buffer->reader_page->read = 0; |
7a8e76a3 | 2102 | |
7a8e76a3 SR |
2103 | cpu_buffer->overrun = 0; |
2104 | cpu_buffer->entries = 0; | |
2105 | } | |
2106 | ||
2107 | /** | |
2108 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
2109 | * @buffer: The ring buffer to reset a per cpu buffer of | |
2110 | * @cpu: The CPU buffer to be reset | |
2111 | */ | |
2112 | void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) | |
2113 | { | |
2114 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
2115 | unsigned long flags; | |
2116 | ||
2117 | if (!cpu_isset(cpu, buffer->cpumask)) | |
2118 | return; | |
2119 | ||
f83c9d0f SR |
2120 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
2121 | ||
3e03fb7f | 2122 | __raw_spin_lock(&cpu_buffer->lock); |
7a8e76a3 SR |
2123 | |
2124 | rb_reset_cpu(cpu_buffer); | |
2125 | ||
3e03fb7f | 2126 | __raw_spin_unlock(&cpu_buffer->lock); |
f83c9d0f SR |
2127 | |
2128 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
7a8e76a3 SR |
2129 | } |
2130 | ||
2131 | /** | |
2132 | * ring_buffer_reset - reset a ring buffer | |
2133 | * @buffer: The ring buffer to reset all cpu buffers | |
2134 | */ | |
2135 | void ring_buffer_reset(struct ring_buffer *buffer) | |
2136 | { | |
7a8e76a3 SR |
2137 | int cpu; |
2138 | ||
7a8e76a3 | 2139 | for_each_buffer_cpu(buffer, cpu) |
d769041f | 2140 | ring_buffer_reset_cpu(buffer, cpu); |
7a8e76a3 SR |
2141 | } |
2142 | ||
2143 | /** | |
2144 | * rind_buffer_empty - is the ring buffer empty? | |
2145 | * @buffer: The ring buffer to test | |
2146 | */ | |
2147 | int ring_buffer_empty(struct ring_buffer *buffer) | |
2148 | { | |
2149 | struct ring_buffer_per_cpu *cpu_buffer; | |
2150 | int cpu; | |
2151 | ||
2152 | /* yes this is racy, but if you don't like the race, lock the buffer */ | |
2153 | for_each_buffer_cpu(buffer, cpu) { | |
2154 | cpu_buffer = buffer->buffers[cpu]; | |
2155 | if (!rb_per_cpu_empty(cpu_buffer)) | |
2156 | return 0; | |
2157 | } | |
2158 | return 1; | |
2159 | } | |
2160 | ||
2161 | /** | |
2162 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? | |
2163 | * @buffer: The ring buffer | |
2164 | * @cpu: The CPU buffer to test | |
2165 | */ | |
2166 | int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) | |
2167 | { | |
2168 | struct ring_buffer_per_cpu *cpu_buffer; | |
2169 | ||
2170 | if (!cpu_isset(cpu, buffer->cpumask)) | |
2171 | return 1; | |
2172 | ||
2173 | cpu_buffer = buffer->buffers[cpu]; | |
2174 | return rb_per_cpu_empty(cpu_buffer); | |
2175 | } | |
2176 | ||
2177 | /** | |
2178 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers | |
2179 | * @buffer_a: One buffer to swap with | |
2180 | * @buffer_b: The other buffer to swap with | |
2181 | * | |
2182 | * This function is useful for tracers that want to take a "snapshot" | |
2183 | * of a CPU buffer and has another back up buffer lying around. | |
2184 | * it is expected that the tracer handles the cpu buffer not being | |
2185 | * used at the moment. | |
2186 | */ | |
2187 | int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, | |
2188 | struct ring_buffer *buffer_b, int cpu) | |
2189 | { | |
2190 | struct ring_buffer_per_cpu *cpu_buffer_a; | |
2191 | struct ring_buffer_per_cpu *cpu_buffer_b; | |
2192 | ||
2193 | if (!cpu_isset(cpu, buffer_a->cpumask) || | |
2194 | !cpu_isset(cpu, buffer_b->cpumask)) | |
2195 | return -EINVAL; | |
2196 | ||
2197 | /* At least make sure the two buffers are somewhat the same */ | |
2198 | if (buffer_a->size != buffer_b->size || | |
2199 | buffer_a->pages != buffer_b->pages) | |
2200 | return -EINVAL; | |
2201 | ||
2202 | cpu_buffer_a = buffer_a->buffers[cpu]; | |
2203 | cpu_buffer_b = buffer_b->buffers[cpu]; | |
2204 | ||
2205 | /* | |
2206 | * We can't do a synchronize_sched here because this | |
2207 | * function can be called in atomic context. | |
2208 | * Normally this will be called from the same CPU as cpu. | |
2209 | * If not it's up to the caller to protect this. | |
2210 | */ | |
2211 | atomic_inc(&cpu_buffer_a->record_disabled); | |
2212 | atomic_inc(&cpu_buffer_b->record_disabled); | |
2213 | ||
2214 | buffer_a->buffers[cpu] = cpu_buffer_b; | |
2215 | buffer_b->buffers[cpu] = cpu_buffer_a; | |
2216 | ||
2217 | cpu_buffer_b->buffer = buffer_a; | |
2218 | cpu_buffer_a->buffer = buffer_b; | |
2219 | ||
2220 | atomic_dec(&cpu_buffer_a->record_disabled); | |
2221 | atomic_dec(&cpu_buffer_b->record_disabled); | |
2222 | ||
2223 | return 0; | |
2224 | } | |
2225 | ||
a3583244 SR |
2226 | static ssize_t |
2227 | rb_simple_read(struct file *filp, char __user *ubuf, | |
2228 | size_t cnt, loff_t *ppos) | |
2229 | { | |
033601a3 | 2230 | long *p = filp->private_data; |
a3583244 SR |
2231 | char buf[64]; |
2232 | int r; | |
2233 | ||
033601a3 SR |
2234 | if (test_bit(RB_BUFFERS_DISABLED_BIT, p)) |
2235 | r = sprintf(buf, "permanently disabled\n"); | |
2236 | else | |
2237 | r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p)); | |
a3583244 SR |
2238 | |
2239 | return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); | |
2240 | } | |
2241 | ||
2242 | static ssize_t | |
2243 | rb_simple_write(struct file *filp, const char __user *ubuf, | |
2244 | size_t cnt, loff_t *ppos) | |
2245 | { | |
033601a3 | 2246 | long *p = filp->private_data; |
a3583244 SR |
2247 | char buf[64]; |
2248 | long val; | |
2249 | int ret; | |
2250 | ||
2251 | if (cnt >= sizeof(buf)) | |
2252 | return -EINVAL; | |
2253 | ||
2254 | if (copy_from_user(&buf, ubuf, cnt)) | |
2255 | return -EFAULT; | |
2256 | ||
2257 | buf[cnt] = 0; | |
2258 | ||
2259 | ret = strict_strtoul(buf, 10, &val); | |
2260 | if (ret < 0) | |
2261 | return ret; | |
2262 | ||
033601a3 SR |
2263 | if (val) |
2264 | set_bit(RB_BUFFERS_ON_BIT, p); | |
2265 | else | |
2266 | clear_bit(RB_BUFFERS_ON_BIT, p); | |
a3583244 SR |
2267 | |
2268 | (*ppos)++; | |
2269 | ||
2270 | return cnt; | |
2271 | } | |
2272 | ||
2273 | static struct file_operations rb_simple_fops = { | |
2274 | .open = tracing_open_generic, | |
2275 | .read = rb_simple_read, | |
2276 | .write = rb_simple_write, | |
2277 | }; | |
2278 | ||
2279 | ||
2280 | static __init int rb_init_debugfs(void) | |
2281 | { | |
2282 | struct dentry *d_tracer; | |
2283 | struct dentry *entry; | |
2284 | ||
2285 | d_tracer = tracing_init_dentry(); | |
2286 | ||
2287 | entry = debugfs_create_file("tracing_on", 0644, d_tracer, | |
033601a3 | 2288 | &ring_buffer_flags, &rb_simple_fops); |
a3583244 SR |
2289 | if (!entry) |
2290 | pr_warning("Could not create debugfs 'tracing_on' entry\n"); | |
2291 | ||
2292 | return 0; | |
2293 | } | |
2294 | ||
2295 | fs_initcall(rb_init_debugfs); |