]>
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> | |
14131f2f | 7 | #include <linux/trace_clock.h> |
78d904b4 | 8 | #include <linux/ftrace_irq.h> |
7a8e76a3 SR |
9 | #include <linux/spinlock.h> |
10 | #include <linux/debugfs.h> | |
11 | #include <linux/uaccess.h> | |
a81bd80a | 12 | #include <linux/hardirq.h> |
1744a21d | 13 | #include <linux/kmemcheck.h> |
7a8e76a3 SR |
14 | #include <linux/module.h> |
15 | #include <linux/percpu.h> | |
16 | #include <linux/mutex.h> | |
7a8e76a3 SR |
17 | #include <linux/init.h> |
18 | #include <linux/hash.h> | |
19 | #include <linux/list.h> | |
554f786e | 20 | #include <linux/cpu.h> |
7a8e76a3 SR |
21 | #include <linux/fs.h> |
22 | ||
79615760 | 23 | #include <asm/local.h> |
182e9f5f SR |
24 | #include "trace.h" |
25 | ||
d1b182a8 SR |
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 | ||
334d4169 LJ |
33 | ret = trace_seq_printf(s, "# compressed entry header\n"); |
34 | ret = trace_seq_printf(s, "\ttype_len : 5 bits\n"); | |
d1b182a8 SR |
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); | |
334d4169 LJ |
42 | ret = trace_seq_printf(s, "\tdata max type_len == %d\n", |
43 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); | |
d1b182a8 SR |
44 | |
45 | return ret; | |
46 | } | |
47 | ||
5cc98548 SR |
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 | ||
033601a3 SR |
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 | ||
5e39841c | 155 | static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; |
a3583244 | 156 | |
474d32b6 SR |
157 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
158 | ||
a3583244 SR |
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 | { | |
033601a3 | 167 | set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); |
a3583244 | 168 | } |
c4f50183 | 169 | EXPORT_SYMBOL_GPL(tracing_on); |
a3583244 SR |
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 | { | |
033601a3 SR |
181 | clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); |
182 | } | |
c4f50183 | 183 | EXPORT_SYMBOL_GPL(tracing_off); |
033601a3 SR |
184 | |
185 | /** | |
186 | * tracing_off_permanent - permanently disable ring buffers | |
187 | * | |
188 | * This function, once called, will disable all ring buffers | |
c3706f00 | 189 | * permanently. |
033601a3 SR |
190 | */ |
191 | void tracing_off_permanent(void) | |
192 | { | |
193 | set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags); | |
a3583244 SR |
194 | } |
195 | ||
988ae9d6 SR |
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 | ||
e3d6bf0a | 205 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
67d34724 | 206 | #define RB_ALIGNMENT 4U |
334d4169 | 207 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
c7b09308 | 208 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
334d4169 | 209 | |
2271048d SR |
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 | ||
334d4169 LJ |
218 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
219 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX | |
7a8e76a3 SR |
220 | |
221 | enum { | |
222 | RB_LEN_TIME_EXTEND = 8, | |
223 | RB_LEN_TIME_STAMP = 16, | |
224 | }; | |
225 | ||
2d622719 TZ |
226 | static inline int rb_null_event(struct ring_buffer_event *event) |
227 | { | |
a1863c21 | 228 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
2d622719 TZ |
229 | } |
230 | ||
231 | static void rb_event_set_padding(struct ring_buffer_event *event) | |
232 | { | |
a1863c21 | 233 | /* padding has a NULL time_delta */ |
334d4169 | 234 | event->type_len = RINGBUF_TYPE_PADDING; |
2d622719 TZ |
235 | event->time_delta = 0; |
236 | } | |
237 | ||
34a148bf | 238 | static unsigned |
2d622719 | 239 | rb_event_data_length(struct ring_buffer_event *event) |
7a8e76a3 SR |
240 | { |
241 | unsigned length; | |
242 | ||
334d4169 LJ |
243 | if (event->type_len) |
244 | length = event->type_len * RB_ALIGNMENT; | |
2d622719 TZ |
245 | else |
246 | length = event->array[0]; | |
247 | return length + RB_EVNT_HDR_SIZE; | |
248 | } | |
249 | ||
250 | /* inline for ring buffer fast paths */ | |
251 | static unsigned | |
252 | rb_event_length(struct ring_buffer_event *event) | |
253 | { | |
334d4169 | 254 | switch (event->type_len) { |
7a8e76a3 | 255 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
256 | if (rb_null_event(event)) |
257 | /* undefined */ | |
258 | return -1; | |
334d4169 | 259 | return event->array[0] + RB_EVNT_HDR_SIZE; |
7a8e76a3 SR |
260 | |
261 | case RINGBUF_TYPE_TIME_EXTEND: | |
262 | return RB_LEN_TIME_EXTEND; | |
263 | ||
264 | case RINGBUF_TYPE_TIME_STAMP: | |
265 | return RB_LEN_TIME_STAMP; | |
266 | ||
267 | case RINGBUF_TYPE_DATA: | |
2d622719 | 268 | return rb_event_data_length(event); |
7a8e76a3 SR |
269 | default: |
270 | BUG(); | |
271 | } | |
272 | /* not hit */ | |
273 | return 0; | |
274 | } | |
275 | ||
276 | /** | |
277 | * ring_buffer_event_length - return the length of the event | |
278 | * @event: the event to get the length of | |
279 | */ | |
280 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) | |
281 | { | |
465634ad | 282 | unsigned length = rb_event_length(event); |
334d4169 | 283 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
465634ad RR |
284 | return length; |
285 | length -= RB_EVNT_HDR_SIZE; | |
286 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) | |
287 | length -= sizeof(event->array[0]); | |
288 | return length; | |
7a8e76a3 | 289 | } |
c4f50183 | 290 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
7a8e76a3 SR |
291 | |
292 | /* inline for ring buffer fast paths */ | |
34a148bf | 293 | static void * |
7a8e76a3 SR |
294 | rb_event_data(struct ring_buffer_event *event) |
295 | { | |
334d4169 | 296 | BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
7a8e76a3 | 297 | /* If length is in len field, then array[0] has the data */ |
334d4169 | 298 | if (event->type_len) |
7a8e76a3 SR |
299 | return (void *)&event->array[0]; |
300 | /* Otherwise length is in array[0] and array[1] has the data */ | |
301 | return (void *)&event->array[1]; | |
302 | } | |
303 | ||
304 | /** | |
305 | * ring_buffer_event_data - return the data of the event | |
306 | * @event: the event to get the data from | |
307 | */ | |
308 | void *ring_buffer_event_data(struct ring_buffer_event *event) | |
309 | { | |
310 | return rb_event_data(event); | |
311 | } | |
c4f50183 | 312 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
7a8e76a3 SR |
313 | |
314 | #define for_each_buffer_cpu(buffer, cpu) \ | |
9e01c1b7 | 315 | for_each_cpu(cpu, buffer->cpumask) |
7a8e76a3 SR |
316 | |
317 | #define TS_SHIFT 27 | |
318 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) | |
319 | #define TS_DELTA_TEST (~TS_MASK) | |
320 | ||
abc9b56d | 321 | struct buffer_data_page { |
e4c2ce82 | 322 | u64 time_stamp; /* page time stamp */ |
c3706f00 | 323 | local_t commit; /* write committed index */ |
abc9b56d SR |
324 | unsigned char data[]; /* data of buffer page */ |
325 | }; | |
326 | ||
77ae365e SR |
327 | /* |
328 | * Note, the buffer_page list must be first. The buffer pages | |
329 | * are allocated in cache lines, which means that each buffer | |
330 | * page will be at the beginning of a cache line, and thus | |
331 | * the least significant bits will be zero. We use this to | |
332 | * add flags in the list struct pointers, to make the ring buffer | |
333 | * lockless. | |
334 | */ | |
abc9b56d | 335 | struct buffer_page { |
778c55d4 | 336 | struct list_head list; /* list of buffer pages */ |
abc9b56d | 337 | local_t write; /* index for next write */ |
6f807acd | 338 | unsigned read; /* index for next read */ |
778c55d4 | 339 | local_t entries; /* entries on this page */ |
abc9b56d | 340 | struct buffer_data_page *page; /* Actual data page */ |
7a8e76a3 SR |
341 | }; |
342 | ||
77ae365e SR |
343 | /* |
344 | * The buffer page counters, write and entries, must be reset | |
345 | * atomically when crossing page boundaries. To synchronize this | |
346 | * update, two counters are inserted into the number. One is | |
347 | * the actual counter for the write position or count on the page. | |
348 | * | |
349 | * The other is a counter of updaters. Before an update happens | |
350 | * the update partition of the counter is incremented. This will | |
351 | * allow the updater to update the counter atomically. | |
352 | * | |
353 | * The counter is 20 bits, and the state data is 12. | |
354 | */ | |
355 | #define RB_WRITE_MASK 0xfffff | |
356 | #define RB_WRITE_INTCNT (1 << 20) | |
357 | ||
044fa782 | 358 | static void rb_init_page(struct buffer_data_page *bpage) |
abc9b56d | 359 | { |
044fa782 | 360 | local_set(&bpage->commit, 0); |
abc9b56d SR |
361 | } |
362 | ||
474d32b6 SR |
363 | /** |
364 | * ring_buffer_page_len - the size of data on the page. | |
365 | * @page: The page to read | |
366 | * | |
367 | * Returns the amount of data on the page, including buffer page header. | |
368 | */ | |
ef7a4a16 SR |
369 | size_t ring_buffer_page_len(void *page) |
370 | { | |
474d32b6 SR |
371 | return local_read(&((struct buffer_data_page *)page)->commit) |
372 | + BUF_PAGE_HDR_SIZE; | |
ef7a4a16 SR |
373 | } |
374 | ||
ed56829c SR |
375 | /* |
376 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing | |
377 | * this issue out. | |
378 | */ | |
34a148bf | 379 | static void free_buffer_page(struct buffer_page *bpage) |
ed56829c | 380 | { |
34a148bf | 381 | free_page((unsigned long)bpage->page); |
e4c2ce82 | 382 | kfree(bpage); |
ed56829c SR |
383 | } |
384 | ||
7a8e76a3 SR |
385 | /* |
386 | * We need to fit the time_stamp delta into 27 bits. | |
387 | */ | |
388 | static inline int test_time_stamp(u64 delta) | |
389 | { | |
390 | if (delta & TS_DELTA_TEST) | |
391 | return 1; | |
392 | return 0; | |
393 | } | |
394 | ||
474d32b6 | 395 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
7a8e76a3 | 396 | |
be957c44 SR |
397 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
398 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) | |
399 | ||
ea05b57c SR |
400 | /* Max number of timestamps that can fit on a page */ |
401 | #define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP) | |
402 | ||
d1b182a8 SR |
403 | int ring_buffer_print_page_header(struct trace_seq *s) |
404 | { | |
405 | struct buffer_data_page field; | |
406 | int ret; | |
407 | ||
408 | ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t" | |
26a50744 TZ |
409 | "offset:0;\tsize:%u;\tsigned:%u;\n", |
410 | (unsigned int)sizeof(field.time_stamp), | |
411 | (unsigned int)is_signed_type(u64)); | |
d1b182a8 SR |
412 | |
413 | ret = trace_seq_printf(s, "\tfield: local_t commit;\t" | |
26a50744 | 414 | "offset:%u;\tsize:%u;\tsigned:%u;\n", |
d1b182a8 | 415 | (unsigned int)offsetof(typeof(field), commit), |
26a50744 TZ |
416 | (unsigned int)sizeof(field.commit), |
417 | (unsigned int)is_signed_type(long)); | |
d1b182a8 SR |
418 | |
419 | ret = trace_seq_printf(s, "\tfield: char data;\t" | |
26a50744 | 420 | "offset:%u;\tsize:%u;\tsigned:%u;\n", |
d1b182a8 | 421 | (unsigned int)offsetof(typeof(field), data), |
26a50744 TZ |
422 | (unsigned int)BUF_PAGE_SIZE, |
423 | (unsigned int)is_signed_type(char)); | |
d1b182a8 SR |
424 | |
425 | return ret; | |
426 | } | |
427 | ||
7a8e76a3 SR |
428 | /* |
429 | * head_page == tail_page && head == tail then buffer is empty. | |
430 | */ | |
431 | struct ring_buffer_per_cpu { | |
432 | int cpu; | |
433 | struct ring_buffer *buffer; | |
77ae365e | 434 | spinlock_t reader_lock; /* serialize readers */ |
445c8951 | 435 | arch_spinlock_t lock; |
7a8e76a3 | 436 | struct lock_class_key lock_key; |
3adc54fa | 437 | struct list_head *pages; |
6f807acd SR |
438 | struct buffer_page *head_page; /* read from head */ |
439 | struct buffer_page *tail_page; /* write to tail */ | |
c3706f00 | 440 | struct buffer_page *commit_page; /* committed pages */ |
d769041f | 441 | struct buffer_page *reader_page; |
77ae365e SR |
442 | local_t commit_overrun; |
443 | local_t overrun; | |
e4906eff | 444 | local_t entries; |
fa743953 SR |
445 | local_t committing; |
446 | local_t commits; | |
77ae365e | 447 | unsigned long read; |
7a8e76a3 SR |
448 | u64 write_stamp; |
449 | u64 read_stamp; | |
450 | atomic_t record_disabled; | |
451 | }; | |
452 | ||
453 | struct ring_buffer { | |
7a8e76a3 SR |
454 | unsigned pages; |
455 | unsigned flags; | |
456 | int cpus; | |
7a8e76a3 | 457 | atomic_t record_disabled; |
00f62f61 | 458 | cpumask_var_t cpumask; |
7a8e76a3 | 459 | |
1f8a6a10 PZ |
460 | struct lock_class_key *reader_lock_key; |
461 | ||
7a8e76a3 SR |
462 | struct mutex mutex; |
463 | ||
464 | struct ring_buffer_per_cpu **buffers; | |
554f786e | 465 | |
59222efe | 466 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
467 | struct notifier_block cpu_notify; |
468 | #endif | |
37886f6a | 469 | u64 (*clock)(void); |
7a8e76a3 SR |
470 | }; |
471 | ||
472 | struct ring_buffer_iter { | |
473 | struct ring_buffer_per_cpu *cpu_buffer; | |
474 | unsigned long head; | |
475 | struct buffer_page *head_page; | |
492a74f4 SR |
476 | struct buffer_page *cache_reader_page; |
477 | unsigned long cache_read; | |
7a8e76a3 SR |
478 | u64 read_stamp; |
479 | }; | |
480 | ||
f536aafc | 481 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
077c5407 SR |
482 | #define RB_WARN_ON(b, cond) \ |
483 | ({ \ | |
484 | int _____ret = unlikely(cond); \ | |
485 | if (_____ret) { \ | |
486 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ | |
487 | struct ring_buffer_per_cpu *__b = \ | |
488 | (void *)b; \ | |
489 | atomic_inc(&__b->buffer->record_disabled); \ | |
490 | } else \ | |
491 | atomic_inc(&b->record_disabled); \ | |
492 | WARN_ON(1); \ | |
493 | } \ | |
494 | _____ret; \ | |
3e89c7bb | 495 | }) |
f536aafc | 496 | |
37886f6a SR |
497 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
498 | #define DEBUG_SHIFT 0 | |
499 | ||
6d3f1e12 | 500 | static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
88eb0125 SR |
501 | { |
502 | /* shift to debug/test normalization and TIME_EXTENTS */ | |
503 | return buffer->clock() << DEBUG_SHIFT; | |
504 | } | |
505 | ||
37886f6a SR |
506 | u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
507 | { | |
508 | u64 time; | |
509 | ||
510 | preempt_disable_notrace(); | |
6d3f1e12 | 511 | time = rb_time_stamp(buffer); |
37886f6a SR |
512 | preempt_enable_no_resched_notrace(); |
513 | ||
514 | return time; | |
515 | } | |
516 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); | |
517 | ||
518 | void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, | |
519 | int cpu, u64 *ts) | |
520 | { | |
521 | /* Just stupid testing the normalize function and deltas */ | |
522 | *ts >>= DEBUG_SHIFT; | |
523 | } | |
524 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); | |
525 | ||
77ae365e SR |
526 | /* |
527 | * Making the ring buffer lockless makes things tricky. | |
528 | * Although writes only happen on the CPU that they are on, | |
529 | * and they only need to worry about interrupts. Reads can | |
530 | * happen on any CPU. | |
531 | * | |
532 | * The reader page is always off the ring buffer, but when the | |
533 | * reader finishes with a page, it needs to swap its page with | |
534 | * a new one from the buffer. The reader needs to take from | |
535 | * the head (writes go to the tail). But if a writer is in overwrite | |
536 | * mode and wraps, it must push the head page forward. | |
537 | * | |
538 | * Here lies the problem. | |
539 | * | |
540 | * The reader must be careful to replace only the head page, and | |
541 | * not another one. As described at the top of the file in the | |
542 | * ASCII art, the reader sets its old page to point to the next | |
543 | * page after head. It then sets the page after head to point to | |
544 | * the old reader page. But if the writer moves the head page | |
545 | * during this operation, the reader could end up with the tail. | |
546 | * | |
547 | * We use cmpxchg to help prevent this race. We also do something | |
548 | * special with the page before head. We set the LSB to 1. | |
549 | * | |
550 | * When the writer must push the page forward, it will clear the | |
551 | * bit that points to the head page, move the head, and then set | |
552 | * the bit that points to the new head page. | |
553 | * | |
554 | * We also don't want an interrupt coming in and moving the head | |
555 | * page on another writer. Thus we use the second LSB to catch | |
556 | * that too. Thus: | |
557 | * | |
558 | * head->list->prev->next bit 1 bit 0 | |
559 | * ------- ------- | |
560 | * Normal page 0 0 | |
561 | * Points to head page 0 1 | |
562 | * New head page 1 0 | |
563 | * | |
564 | * Note we can not trust the prev pointer of the head page, because: | |
565 | * | |
566 | * +----+ +-----+ +-----+ | |
567 | * | |------>| T |---X--->| N | | |
568 | * | |<------| | | | | |
569 | * +----+ +-----+ +-----+ | |
570 | * ^ ^ | | |
571 | * | +-----+ | | | |
572 | * +----------| R |----------+ | | |
573 | * | |<-----------+ | |
574 | * +-----+ | |
575 | * | |
576 | * Key: ---X--> HEAD flag set in pointer | |
577 | * T Tail page | |
578 | * R Reader page | |
579 | * N Next page | |
580 | * | |
581 | * (see __rb_reserve_next() to see where this happens) | |
582 | * | |
583 | * What the above shows is that the reader just swapped out | |
584 | * the reader page with a page in the buffer, but before it | |
585 | * could make the new header point back to the new page added | |
586 | * it was preempted by a writer. The writer moved forward onto | |
587 | * the new page added by the reader and is about to move forward | |
588 | * again. | |
589 | * | |
590 | * You can see, it is legitimate for the previous pointer of | |
591 | * the head (or any page) not to point back to itself. But only | |
592 | * temporarially. | |
593 | */ | |
594 | ||
595 | #define RB_PAGE_NORMAL 0UL | |
596 | #define RB_PAGE_HEAD 1UL | |
597 | #define RB_PAGE_UPDATE 2UL | |
598 | ||
599 | ||
600 | #define RB_FLAG_MASK 3UL | |
601 | ||
602 | /* PAGE_MOVED is not part of the mask */ | |
603 | #define RB_PAGE_MOVED 4UL | |
604 | ||
605 | /* | |
606 | * rb_list_head - remove any bit | |
607 | */ | |
608 | static struct list_head *rb_list_head(struct list_head *list) | |
609 | { | |
610 | unsigned long val = (unsigned long)list; | |
611 | ||
612 | return (struct list_head *)(val & ~RB_FLAG_MASK); | |
613 | } | |
614 | ||
615 | /* | |
6d3f1e12 | 616 | * rb_is_head_page - test if the given page is the head page |
77ae365e SR |
617 | * |
618 | * Because the reader may move the head_page pointer, we can | |
619 | * not trust what the head page is (it may be pointing to | |
620 | * the reader page). But if the next page is a header page, | |
621 | * its flags will be non zero. | |
622 | */ | |
623 | static int inline | |
624 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, | |
625 | struct buffer_page *page, struct list_head *list) | |
626 | { | |
627 | unsigned long val; | |
628 | ||
629 | val = (unsigned long)list->next; | |
630 | ||
631 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) | |
632 | return RB_PAGE_MOVED; | |
633 | ||
634 | return val & RB_FLAG_MASK; | |
635 | } | |
636 | ||
637 | /* | |
638 | * rb_is_reader_page | |
639 | * | |
640 | * The unique thing about the reader page, is that, if the | |
641 | * writer is ever on it, the previous pointer never points | |
642 | * back to the reader page. | |
643 | */ | |
644 | static int rb_is_reader_page(struct buffer_page *page) | |
645 | { | |
646 | struct list_head *list = page->list.prev; | |
647 | ||
648 | return rb_list_head(list->next) != &page->list; | |
649 | } | |
650 | ||
651 | /* | |
652 | * rb_set_list_to_head - set a list_head to be pointing to head. | |
653 | */ | |
654 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, | |
655 | struct list_head *list) | |
656 | { | |
657 | unsigned long *ptr; | |
658 | ||
659 | ptr = (unsigned long *)&list->next; | |
660 | *ptr |= RB_PAGE_HEAD; | |
661 | *ptr &= ~RB_PAGE_UPDATE; | |
662 | } | |
663 | ||
664 | /* | |
665 | * rb_head_page_activate - sets up head page | |
666 | */ | |
667 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) | |
668 | { | |
669 | struct buffer_page *head; | |
670 | ||
671 | head = cpu_buffer->head_page; | |
672 | if (!head) | |
673 | return; | |
674 | ||
675 | /* | |
676 | * Set the previous list pointer to have the HEAD flag. | |
677 | */ | |
678 | rb_set_list_to_head(cpu_buffer, head->list.prev); | |
679 | } | |
680 | ||
681 | static void rb_list_head_clear(struct list_head *list) | |
682 | { | |
683 | unsigned long *ptr = (unsigned long *)&list->next; | |
684 | ||
685 | *ptr &= ~RB_FLAG_MASK; | |
686 | } | |
687 | ||
688 | /* | |
689 | * rb_head_page_dactivate - clears head page ptr (for free list) | |
690 | */ | |
691 | static void | |
692 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) | |
693 | { | |
694 | struct list_head *hd; | |
695 | ||
696 | /* Go through the whole list and clear any pointers found. */ | |
697 | rb_list_head_clear(cpu_buffer->pages); | |
698 | ||
699 | list_for_each(hd, cpu_buffer->pages) | |
700 | rb_list_head_clear(hd); | |
701 | } | |
702 | ||
703 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, | |
704 | struct buffer_page *head, | |
705 | struct buffer_page *prev, | |
706 | int old_flag, int new_flag) | |
707 | { | |
708 | struct list_head *list; | |
709 | unsigned long val = (unsigned long)&head->list; | |
710 | unsigned long ret; | |
711 | ||
712 | list = &prev->list; | |
713 | ||
714 | val &= ~RB_FLAG_MASK; | |
715 | ||
08a40816 SR |
716 | ret = cmpxchg((unsigned long *)&list->next, |
717 | val | old_flag, val | new_flag); | |
77ae365e SR |
718 | |
719 | /* check if the reader took the page */ | |
720 | if ((ret & ~RB_FLAG_MASK) != val) | |
721 | return RB_PAGE_MOVED; | |
722 | ||
723 | return ret & RB_FLAG_MASK; | |
724 | } | |
725 | ||
726 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, | |
727 | struct buffer_page *head, | |
728 | struct buffer_page *prev, | |
729 | int old_flag) | |
730 | { | |
731 | return rb_head_page_set(cpu_buffer, head, prev, | |
732 | old_flag, RB_PAGE_UPDATE); | |
733 | } | |
734 | ||
735 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, | |
736 | struct buffer_page *head, | |
737 | struct buffer_page *prev, | |
738 | int old_flag) | |
739 | { | |
740 | return rb_head_page_set(cpu_buffer, head, prev, | |
741 | old_flag, RB_PAGE_HEAD); | |
742 | } | |
743 | ||
744 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, | |
745 | struct buffer_page *head, | |
746 | struct buffer_page *prev, | |
747 | int old_flag) | |
748 | { | |
749 | return rb_head_page_set(cpu_buffer, head, prev, | |
750 | old_flag, RB_PAGE_NORMAL); | |
751 | } | |
752 | ||
753 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, | |
754 | struct buffer_page **bpage) | |
755 | { | |
756 | struct list_head *p = rb_list_head((*bpage)->list.next); | |
757 | ||
758 | *bpage = list_entry(p, struct buffer_page, list); | |
759 | } | |
760 | ||
761 | static struct buffer_page * | |
762 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) | |
763 | { | |
764 | struct buffer_page *head; | |
765 | struct buffer_page *page; | |
766 | struct list_head *list; | |
767 | int i; | |
768 | ||
769 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) | |
770 | return NULL; | |
771 | ||
772 | /* sanity check */ | |
773 | list = cpu_buffer->pages; | |
774 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) | |
775 | return NULL; | |
776 | ||
777 | page = head = cpu_buffer->head_page; | |
778 | /* | |
779 | * It is possible that the writer moves the header behind | |
780 | * where we started, and we miss in one loop. | |
781 | * A second loop should grab the header, but we'll do | |
782 | * three loops just because I'm paranoid. | |
783 | */ | |
784 | for (i = 0; i < 3; i++) { | |
785 | do { | |
786 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { | |
787 | cpu_buffer->head_page = page; | |
788 | return page; | |
789 | } | |
790 | rb_inc_page(cpu_buffer, &page); | |
791 | } while (page != head); | |
792 | } | |
793 | ||
794 | RB_WARN_ON(cpu_buffer, 1); | |
795 | ||
796 | return NULL; | |
797 | } | |
798 | ||
799 | static int rb_head_page_replace(struct buffer_page *old, | |
800 | struct buffer_page *new) | |
801 | { | |
802 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; | |
803 | unsigned long val; | |
804 | unsigned long ret; | |
805 | ||
806 | val = *ptr & ~RB_FLAG_MASK; | |
807 | val |= RB_PAGE_HEAD; | |
808 | ||
08a40816 | 809 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
77ae365e SR |
810 | |
811 | return ret == val; | |
812 | } | |
813 | ||
814 | /* | |
815 | * rb_tail_page_update - move the tail page forward | |
816 | * | |
817 | * Returns 1 if moved tail page, 0 if someone else did. | |
818 | */ | |
819 | static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, | |
820 | struct buffer_page *tail_page, | |
821 | struct buffer_page *next_page) | |
822 | { | |
823 | struct buffer_page *old_tail; | |
824 | unsigned long old_entries; | |
825 | unsigned long old_write; | |
826 | int ret = 0; | |
827 | ||
828 | /* | |
829 | * The tail page now needs to be moved forward. | |
830 | * | |
831 | * We need to reset the tail page, but without messing | |
832 | * with possible erasing of data brought in by interrupts | |
833 | * that have moved the tail page and are currently on it. | |
834 | * | |
835 | * We add a counter to the write field to denote this. | |
836 | */ | |
837 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); | |
838 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); | |
839 | ||
840 | /* | |
841 | * Just make sure we have seen our old_write and synchronize | |
842 | * with any interrupts that come in. | |
843 | */ | |
844 | barrier(); | |
845 | ||
846 | /* | |
847 | * If the tail page is still the same as what we think | |
848 | * it is, then it is up to us to update the tail | |
849 | * pointer. | |
850 | */ | |
851 | if (tail_page == cpu_buffer->tail_page) { | |
852 | /* Zero the write counter */ | |
853 | unsigned long val = old_write & ~RB_WRITE_MASK; | |
854 | unsigned long eval = old_entries & ~RB_WRITE_MASK; | |
855 | ||
856 | /* | |
857 | * This will only succeed if an interrupt did | |
858 | * not come in and change it. In which case, we | |
859 | * do not want to modify it. | |
da706d8b LJ |
860 | * |
861 | * We add (void) to let the compiler know that we do not care | |
862 | * about the return value of these functions. We use the | |
863 | * cmpxchg to only update if an interrupt did not already | |
864 | * do it for us. If the cmpxchg fails, we don't care. | |
77ae365e | 865 | */ |
da706d8b LJ |
866 | (void)local_cmpxchg(&next_page->write, old_write, val); |
867 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); | |
77ae365e SR |
868 | |
869 | /* | |
870 | * No need to worry about races with clearing out the commit. | |
871 | * it only can increment when a commit takes place. But that | |
872 | * only happens in the outer most nested commit. | |
873 | */ | |
874 | local_set(&next_page->page->commit, 0); | |
875 | ||
876 | old_tail = cmpxchg(&cpu_buffer->tail_page, | |
877 | tail_page, next_page); | |
878 | ||
879 | if (old_tail == tail_page) | |
880 | ret = 1; | |
881 | } | |
882 | ||
883 | return ret; | |
884 | } | |
885 | ||
886 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, | |
887 | struct buffer_page *bpage) | |
888 | { | |
889 | unsigned long val = (unsigned long)bpage; | |
890 | ||
891 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) | |
892 | return 1; | |
893 | ||
894 | return 0; | |
895 | } | |
896 | ||
897 | /** | |
898 | * rb_check_list - make sure a pointer to a list has the last bits zero | |
899 | */ | |
900 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, | |
901 | struct list_head *list) | |
902 | { | |
903 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) | |
904 | return 1; | |
905 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) | |
906 | return 1; | |
907 | return 0; | |
908 | } | |
909 | ||
7a8e76a3 SR |
910 | /** |
911 | * check_pages - integrity check of buffer pages | |
912 | * @cpu_buffer: CPU buffer with pages to test | |
913 | * | |
c3706f00 | 914 | * As a safety measure we check to make sure the data pages have not |
7a8e76a3 SR |
915 | * been corrupted. |
916 | */ | |
917 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
918 | { | |
3adc54fa | 919 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 920 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 921 | |
77ae365e SR |
922 | rb_head_page_deactivate(cpu_buffer); |
923 | ||
3e89c7bb SR |
924 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
925 | return -1; | |
926 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) | |
927 | return -1; | |
7a8e76a3 | 928 | |
77ae365e SR |
929 | if (rb_check_list(cpu_buffer, head)) |
930 | return -1; | |
931 | ||
044fa782 | 932 | list_for_each_entry_safe(bpage, tmp, head, list) { |
3e89c7bb | 933 | if (RB_WARN_ON(cpu_buffer, |
044fa782 | 934 | bpage->list.next->prev != &bpage->list)) |
3e89c7bb SR |
935 | return -1; |
936 | if (RB_WARN_ON(cpu_buffer, | |
044fa782 | 937 | bpage->list.prev->next != &bpage->list)) |
3e89c7bb | 938 | return -1; |
77ae365e SR |
939 | if (rb_check_list(cpu_buffer, &bpage->list)) |
940 | return -1; | |
7a8e76a3 SR |
941 | } |
942 | ||
77ae365e SR |
943 | rb_head_page_activate(cpu_buffer); |
944 | ||
7a8e76a3 SR |
945 | return 0; |
946 | } | |
947 | ||
7a8e76a3 SR |
948 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
949 | unsigned nr_pages) | |
950 | { | |
044fa782 | 951 | struct buffer_page *bpage, *tmp; |
7a8e76a3 SR |
952 | unsigned long addr; |
953 | LIST_HEAD(pages); | |
954 | unsigned i; | |
955 | ||
3adc54fa SR |
956 | WARN_ON(!nr_pages); |
957 | ||
7a8e76a3 | 958 | for (i = 0; i < nr_pages; i++) { |
044fa782 | 959 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
aa1e0e3b | 960 | GFP_KERNEL, cpu_to_node(cpu_buffer->cpu)); |
044fa782 | 961 | if (!bpage) |
e4c2ce82 | 962 | goto free_pages; |
77ae365e SR |
963 | |
964 | rb_check_bpage(cpu_buffer, bpage); | |
965 | ||
044fa782 | 966 | list_add(&bpage->list, &pages); |
e4c2ce82 | 967 | |
7a8e76a3 SR |
968 | addr = __get_free_page(GFP_KERNEL); |
969 | if (!addr) | |
970 | goto free_pages; | |
044fa782 SR |
971 | bpage->page = (void *)addr; |
972 | rb_init_page(bpage->page); | |
7a8e76a3 SR |
973 | } |
974 | ||
3adc54fa SR |
975 | /* |
976 | * The ring buffer page list is a circular list that does not | |
977 | * start and end with a list head. All page list items point to | |
978 | * other pages. | |
979 | */ | |
980 | cpu_buffer->pages = pages.next; | |
981 | list_del(&pages); | |
7a8e76a3 SR |
982 | |
983 | rb_check_pages(cpu_buffer); | |
984 | ||
985 | return 0; | |
986 | ||
987 | free_pages: | |
044fa782 SR |
988 | list_for_each_entry_safe(bpage, tmp, &pages, list) { |
989 | list_del_init(&bpage->list); | |
990 | free_buffer_page(bpage); | |
7a8e76a3 SR |
991 | } |
992 | return -ENOMEM; | |
993 | } | |
994 | ||
995 | static struct ring_buffer_per_cpu * | |
996 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) | |
997 | { | |
998 | struct ring_buffer_per_cpu *cpu_buffer; | |
044fa782 | 999 | struct buffer_page *bpage; |
d769041f | 1000 | unsigned long addr; |
7a8e76a3 SR |
1001 | int ret; |
1002 | ||
1003 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), | |
1004 | GFP_KERNEL, cpu_to_node(cpu)); | |
1005 | if (!cpu_buffer) | |
1006 | return NULL; | |
1007 | ||
1008 | cpu_buffer->cpu = cpu; | |
1009 | cpu_buffer->buffer = buffer; | |
f83c9d0f | 1010 | spin_lock_init(&cpu_buffer->reader_lock); |
1f8a6a10 | 1011 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
edc35bd7 | 1012 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
7a8e76a3 | 1013 | |
044fa782 | 1014 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
e4c2ce82 | 1015 | GFP_KERNEL, cpu_to_node(cpu)); |
044fa782 | 1016 | if (!bpage) |
e4c2ce82 SR |
1017 | goto fail_free_buffer; |
1018 | ||
77ae365e SR |
1019 | rb_check_bpage(cpu_buffer, bpage); |
1020 | ||
044fa782 | 1021 | cpu_buffer->reader_page = bpage; |
d769041f SR |
1022 | addr = __get_free_page(GFP_KERNEL); |
1023 | if (!addr) | |
e4c2ce82 | 1024 | goto fail_free_reader; |
044fa782 SR |
1025 | bpage->page = (void *)addr; |
1026 | rb_init_page(bpage->page); | |
e4c2ce82 | 1027 | |
d769041f | 1028 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
d769041f | 1029 | |
7a8e76a3 SR |
1030 | ret = rb_allocate_pages(cpu_buffer, buffer->pages); |
1031 | if (ret < 0) | |
d769041f | 1032 | goto fail_free_reader; |
7a8e76a3 SR |
1033 | |
1034 | cpu_buffer->head_page | |
3adc54fa | 1035 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 1036 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
7a8e76a3 | 1037 | |
77ae365e SR |
1038 | rb_head_page_activate(cpu_buffer); |
1039 | ||
7a8e76a3 SR |
1040 | return cpu_buffer; |
1041 | ||
d769041f SR |
1042 | fail_free_reader: |
1043 | free_buffer_page(cpu_buffer->reader_page); | |
1044 | ||
7a8e76a3 SR |
1045 | fail_free_buffer: |
1046 | kfree(cpu_buffer); | |
1047 | return NULL; | |
1048 | } | |
1049 | ||
1050 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
1051 | { | |
3adc54fa | 1052 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1053 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1054 | |
d769041f SR |
1055 | free_buffer_page(cpu_buffer->reader_page); |
1056 | ||
77ae365e SR |
1057 | rb_head_page_deactivate(cpu_buffer); |
1058 | ||
3adc54fa SR |
1059 | if (head) { |
1060 | list_for_each_entry_safe(bpage, tmp, head, list) { | |
1061 | list_del_init(&bpage->list); | |
1062 | free_buffer_page(bpage); | |
1063 | } | |
1064 | bpage = list_entry(head, struct buffer_page, list); | |
044fa782 | 1065 | free_buffer_page(bpage); |
7a8e76a3 | 1066 | } |
3adc54fa | 1067 | |
7a8e76a3 SR |
1068 | kfree(cpu_buffer); |
1069 | } | |
1070 | ||
59222efe | 1071 | #ifdef CONFIG_HOTPLUG_CPU |
09c9e84d FW |
1072 | static int rb_cpu_notify(struct notifier_block *self, |
1073 | unsigned long action, void *hcpu); | |
554f786e SR |
1074 | #endif |
1075 | ||
7a8e76a3 SR |
1076 | /** |
1077 | * ring_buffer_alloc - allocate a new ring_buffer | |
68814b58 | 1078 | * @size: the size in bytes per cpu that is needed. |
7a8e76a3 SR |
1079 | * @flags: attributes to set for the ring buffer. |
1080 | * | |
1081 | * Currently the only flag that is available is the RB_FL_OVERWRITE | |
1082 | * flag. This flag means that the buffer will overwrite old data | |
1083 | * when the buffer wraps. If this flag is not set, the buffer will | |
1084 | * drop data when the tail hits the head. | |
1085 | */ | |
1f8a6a10 PZ |
1086 | struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1087 | struct lock_class_key *key) | |
7a8e76a3 SR |
1088 | { |
1089 | struct ring_buffer *buffer; | |
1090 | int bsize; | |
1091 | int cpu; | |
1092 | ||
1093 | /* keep it in its own cache line */ | |
1094 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), | |
1095 | GFP_KERNEL); | |
1096 | if (!buffer) | |
1097 | return NULL; | |
1098 | ||
9e01c1b7 RR |
1099 | if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
1100 | goto fail_free_buffer; | |
1101 | ||
7a8e76a3 SR |
1102 | buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1103 | buffer->flags = flags; | |
37886f6a | 1104 | buffer->clock = trace_clock_local; |
1f8a6a10 | 1105 | buffer->reader_lock_key = key; |
7a8e76a3 SR |
1106 | |
1107 | /* need at least two pages */ | |
5f78abee SR |
1108 | if (buffer->pages < 2) |
1109 | buffer->pages = 2; | |
7a8e76a3 | 1110 | |
3bf832ce FW |
1111 | /* |
1112 | * In case of non-hotplug cpu, if the ring-buffer is allocated | |
1113 | * in early initcall, it will not be notified of secondary cpus. | |
1114 | * In that off case, we need to allocate for all possible cpus. | |
1115 | */ | |
1116 | #ifdef CONFIG_HOTPLUG_CPU | |
554f786e SR |
1117 | get_online_cpus(); |
1118 | cpumask_copy(buffer->cpumask, cpu_online_mask); | |
3bf832ce FW |
1119 | #else |
1120 | cpumask_copy(buffer->cpumask, cpu_possible_mask); | |
1121 | #endif | |
7a8e76a3 SR |
1122 | buffer->cpus = nr_cpu_ids; |
1123 | ||
1124 | bsize = sizeof(void *) * nr_cpu_ids; | |
1125 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), | |
1126 | GFP_KERNEL); | |
1127 | if (!buffer->buffers) | |
9e01c1b7 | 1128 | goto fail_free_cpumask; |
7a8e76a3 SR |
1129 | |
1130 | for_each_buffer_cpu(buffer, cpu) { | |
1131 | buffer->buffers[cpu] = | |
1132 | rb_allocate_cpu_buffer(buffer, cpu); | |
1133 | if (!buffer->buffers[cpu]) | |
1134 | goto fail_free_buffers; | |
1135 | } | |
1136 | ||
59222efe | 1137 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
1138 | buffer->cpu_notify.notifier_call = rb_cpu_notify; |
1139 | buffer->cpu_notify.priority = 0; | |
1140 | register_cpu_notifier(&buffer->cpu_notify); | |
1141 | #endif | |
1142 | ||
1143 | put_online_cpus(); | |
7a8e76a3 SR |
1144 | mutex_init(&buffer->mutex); |
1145 | ||
1146 | return buffer; | |
1147 | ||
1148 | fail_free_buffers: | |
1149 | for_each_buffer_cpu(buffer, cpu) { | |
1150 | if (buffer->buffers[cpu]) | |
1151 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1152 | } | |
1153 | kfree(buffer->buffers); | |
1154 | ||
9e01c1b7 RR |
1155 | fail_free_cpumask: |
1156 | free_cpumask_var(buffer->cpumask); | |
554f786e | 1157 | put_online_cpus(); |
9e01c1b7 | 1158 | |
7a8e76a3 SR |
1159 | fail_free_buffer: |
1160 | kfree(buffer); | |
1161 | return NULL; | |
1162 | } | |
1f8a6a10 | 1163 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
7a8e76a3 SR |
1164 | |
1165 | /** | |
1166 | * ring_buffer_free - free a ring buffer. | |
1167 | * @buffer: the buffer to free. | |
1168 | */ | |
1169 | void | |
1170 | ring_buffer_free(struct ring_buffer *buffer) | |
1171 | { | |
1172 | int cpu; | |
1173 | ||
554f786e SR |
1174 | get_online_cpus(); |
1175 | ||
59222efe | 1176 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
1177 | unregister_cpu_notifier(&buffer->cpu_notify); |
1178 | #endif | |
1179 | ||
7a8e76a3 SR |
1180 | for_each_buffer_cpu(buffer, cpu) |
1181 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1182 | ||
554f786e SR |
1183 | put_online_cpus(); |
1184 | ||
bd3f0221 | 1185 | kfree(buffer->buffers); |
9e01c1b7 RR |
1186 | free_cpumask_var(buffer->cpumask); |
1187 | ||
7a8e76a3 SR |
1188 | kfree(buffer); |
1189 | } | |
c4f50183 | 1190 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
7a8e76a3 | 1191 | |
37886f6a SR |
1192 | void ring_buffer_set_clock(struct ring_buffer *buffer, |
1193 | u64 (*clock)(void)) | |
1194 | { | |
1195 | buffer->clock = clock; | |
1196 | } | |
1197 | ||
7a8e76a3 SR |
1198 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1199 | ||
1200 | static void | |
1201 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) | |
1202 | { | |
044fa782 | 1203 | struct buffer_page *bpage; |
7a8e76a3 SR |
1204 | struct list_head *p; |
1205 | unsigned i; | |
1206 | ||
f7112949 | 1207 | spin_lock_irq(&cpu_buffer->reader_lock); |
77ae365e SR |
1208 | rb_head_page_deactivate(cpu_buffer); |
1209 | ||
7a8e76a3 | 1210 | for (i = 0; i < nr_pages; i++) { |
3adc54fa | 1211 | if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages))) |
292f60c0 | 1212 | goto out; |
3adc54fa | 1213 | p = cpu_buffer->pages->next; |
044fa782 SR |
1214 | bpage = list_entry(p, struct buffer_page, list); |
1215 | list_del_init(&bpage->list); | |
1216 | free_buffer_page(bpage); | |
7a8e76a3 | 1217 | } |
3adc54fa | 1218 | if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages))) |
292f60c0 | 1219 | goto out; |
7a8e76a3 SR |
1220 | |
1221 | rb_reset_cpu(cpu_buffer); | |
7a8e76a3 SR |
1222 | rb_check_pages(cpu_buffer); |
1223 | ||
292f60c0 | 1224 | out: |
dd7f5943 | 1225 | spin_unlock_irq(&cpu_buffer->reader_lock); |
7a8e76a3 SR |
1226 | } |
1227 | ||
1228 | static void | |
1229 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, | |
1230 | struct list_head *pages, unsigned nr_pages) | |
1231 | { | |
044fa782 | 1232 | struct buffer_page *bpage; |
7a8e76a3 SR |
1233 | struct list_head *p; |
1234 | unsigned i; | |
1235 | ||
77ae365e SR |
1236 | spin_lock_irq(&cpu_buffer->reader_lock); |
1237 | rb_head_page_deactivate(cpu_buffer); | |
1238 | ||
7a8e76a3 | 1239 | for (i = 0; i < nr_pages; i++) { |
3e89c7bb | 1240 | if (RB_WARN_ON(cpu_buffer, list_empty(pages))) |
292f60c0 | 1241 | goto out; |
7a8e76a3 | 1242 | p = pages->next; |
044fa782 SR |
1243 | bpage = list_entry(p, struct buffer_page, list); |
1244 | list_del_init(&bpage->list); | |
3adc54fa | 1245 | list_add_tail(&bpage->list, cpu_buffer->pages); |
7a8e76a3 SR |
1246 | } |
1247 | rb_reset_cpu(cpu_buffer); | |
7a8e76a3 SR |
1248 | rb_check_pages(cpu_buffer); |
1249 | ||
292f60c0 | 1250 | out: |
dd7f5943 | 1251 | spin_unlock_irq(&cpu_buffer->reader_lock); |
7a8e76a3 SR |
1252 | } |
1253 | ||
1254 | /** | |
1255 | * ring_buffer_resize - resize the ring buffer | |
1256 | * @buffer: the buffer to resize. | |
1257 | * @size: the new size. | |
1258 | * | |
7a8e76a3 SR |
1259 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1260 | * | |
1261 | * Returns -1 on failure. | |
1262 | */ | |
1263 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) | |
1264 | { | |
1265 | struct ring_buffer_per_cpu *cpu_buffer; | |
1266 | unsigned nr_pages, rm_pages, new_pages; | |
044fa782 | 1267 | struct buffer_page *bpage, *tmp; |
7a8e76a3 SR |
1268 | unsigned long buffer_size; |
1269 | unsigned long addr; | |
1270 | LIST_HEAD(pages); | |
1271 | int i, cpu; | |
1272 | ||
ee51a1de IM |
1273 | /* |
1274 | * Always succeed at resizing a non-existent buffer: | |
1275 | */ | |
1276 | if (!buffer) | |
1277 | return size; | |
1278 | ||
7a8e76a3 SR |
1279 | size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1280 | size *= BUF_PAGE_SIZE; | |
1281 | buffer_size = buffer->pages * BUF_PAGE_SIZE; | |
1282 | ||
1283 | /* we need a minimum of two pages */ | |
1284 | if (size < BUF_PAGE_SIZE * 2) | |
1285 | size = BUF_PAGE_SIZE * 2; | |
1286 | ||
1287 | if (size == buffer_size) | |
1288 | return size; | |
1289 | ||
18421015 SR |
1290 | atomic_inc(&buffer->record_disabled); |
1291 | ||
1292 | /* Make sure all writers are done with this buffer. */ | |
1293 | synchronize_sched(); | |
1294 | ||
7a8e76a3 | 1295 | mutex_lock(&buffer->mutex); |
554f786e | 1296 | get_online_cpus(); |
7a8e76a3 SR |
1297 | |
1298 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); | |
1299 | ||
1300 | if (size < buffer_size) { | |
1301 | ||
1302 | /* easy case, just free pages */ | |
554f786e SR |
1303 | if (RB_WARN_ON(buffer, nr_pages >= buffer->pages)) |
1304 | goto out_fail; | |
7a8e76a3 SR |
1305 | |
1306 | rm_pages = buffer->pages - nr_pages; | |
1307 | ||
1308 | for_each_buffer_cpu(buffer, cpu) { | |
1309 | cpu_buffer = buffer->buffers[cpu]; | |
1310 | rb_remove_pages(cpu_buffer, rm_pages); | |
1311 | } | |
1312 | goto out; | |
1313 | } | |
1314 | ||
1315 | /* | |
1316 | * This is a bit more difficult. We only want to add pages | |
1317 | * when we can allocate enough for all CPUs. We do this | |
1318 | * by allocating all the pages and storing them on a local | |
1319 | * link list. If we succeed in our allocation, then we | |
1320 | * add these pages to the cpu_buffers. Otherwise we just free | |
1321 | * them all and return -ENOMEM; | |
1322 | */ | |
554f786e SR |
1323 | if (RB_WARN_ON(buffer, nr_pages <= buffer->pages)) |
1324 | goto out_fail; | |
f536aafc | 1325 | |
7a8e76a3 SR |
1326 | new_pages = nr_pages - buffer->pages; |
1327 | ||
1328 | for_each_buffer_cpu(buffer, cpu) { | |
1329 | for (i = 0; i < new_pages; i++) { | |
044fa782 | 1330 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), |
e4c2ce82 SR |
1331 | cache_line_size()), |
1332 | GFP_KERNEL, cpu_to_node(cpu)); | |
044fa782 | 1333 | if (!bpage) |
e4c2ce82 | 1334 | goto free_pages; |
044fa782 | 1335 | list_add(&bpage->list, &pages); |
7a8e76a3 SR |
1336 | addr = __get_free_page(GFP_KERNEL); |
1337 | if (!addr) | |
1338 | goto free_pages; | |
044fa782 SR |
1339 | bpage->page = (void *)addr; |
1340 | rb_init_page(bpage->page); | |
7a8e76a3 SR |
1341 | } |
1342 | } | |
1343 | ||
1344 | for_each_buffer_cpu(buffer, cpu) { | |
1345 | cpu_buffer = buffer->buffers[cpu]; | |
1346 | rb_insert_pages(cpu_buffer, &pages, new_pages); | |
1347 | } | |
1348 | ||
554f786e SR |
1349 | if (RB_WARN_ON(buffer, !list_empty(&pages))) |
1350 | goto out_fail; | |
7a8e76a3 SR |
1351 | |
1352 | out: | |
1353 | buffer->pages = nr_pages; | |
554f786e | 1354 | put_online_cpus(); |
7a8e76a3 SR |
1355 | mutex_unlock(&buffer->mutex); |
1356 | ||
18421015 SR |
1357 | atomic_dec(&buffer->record_disabled); |
1358 | ||
7a8e76a3 SR |
1359 | return size; |
1360 | ||
1361 | free_pages: | |
044fa782 SR |
1362 | list_for_each_entry_safe(bpage, tmp, &pages, list) { |
1363 | list_del_init(&bpage->list); | |
1364 | free_buffer_page(bpage); | |
7a8e76a3 | 1365 | } |
554f786e | 1366 | put_online_cpus(); |
641d2f63 | 1367 | mutex_unlock(&buffer->mutex); |
18421015 | 1368 | atomic_dec(&buffer->record_disabled); |
7a8e76a3 | 1369 | return -ENOMEM; |
554f786e SR |
1370 | |
1371 | /* | |
1372 | * Something went totally wrong, and we are too paranoid | |
1373 | * to even clean up the mess. | |
1374 | */ | |
1375 | out_fail: | |
1376 | put_online_cpus(); | |
1377 | mutex_unlock(&buffer->mutex); | |
18421015 | 1378 | atomic_dec(&buffer->record_disabled); |
554f786e | 1379 | return -1; |
7a8e76a3 | 1380 | } |
c4f50183 | 1381 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
7a8e76a3 | 1382 | |
8789a9e7 | 1383 | static inline void * |
044fa782 | 1384 | __rb_data_page_index(struct buffer_data_page *bpage, unsigned index) |
8789a9e7 | 1385 | { |
044fa782 | 1386 | return bpage->data + index; |
8789a9e7 SR |
1387 | } |
1388 | ||
044fa782 | 1389 | static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
7a8e76a3 | 1390 | { |
044fa782 | 1391 | return bpage->page->data + index; |
7a8e76a3 SR |
1392 | } |
1393 | ||
1394 | static inline struct ring_buffer_event * | |
d769041f | 1395 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1396 | { |
6f807acd SR |
1397 | return __rb_page_index(cpu_buffer->reader_page, |
1398 | cpu_buffer->reader_page->read); | |
1399 | } | |
1400 | ||
7a8e76a3 SR |
1401 | static inline struct ring_buffer_event * |
1402 | rb_iter_head_event(struct ring_buffer_iter *iter) | |
1403 | { | |
6f807acd | 1404 | return __rb_page_index(iter->head_page, iter->head); |
7a8e76a3 SR |
1405 | } |
1406 | ||
77ae365e | 1407 | static inline unsigned long rb_page_write(struct buffer_page *bpage) |
bf41a158 | 1408 | { |
77ae365e | 1409 | return local_read(&bpage->write) & RB_WRITE_MASK; |
bf41a158 SR |
1410 | } |
1411 | ||
1412 | static inline unsigned rb_page_commit(struct buffer_page *bpage) | |
1413 | { | |
abc9b56d | 1414 | return local_read(&bpage->page->commit); |
bf41a158 SR |
1415 | } |
1416 | ||
77ae365e SR |
1417 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1418 | { | |
1419 | return local_read(&bpage->entries) & RB_WRITE_MASK; | |
1420 | } | |
1421 | ||
bf41a158 SR |
1422 | /* Size is determined by what has been commited */ |
1423 | static inline unsigned rb_page_size(struct buffer_page *bpage) | |
1424 | { | |
1425 | return rb_page_commit(bpage); | |
1426 | } | |
1427 | ||
1428 | static inline unsigned | |
1429 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) | |
1430 | { | |
1431 | return rb_page_commit(cpu_buffer->commit_page); | |
1432 | } | |
1433 | ||
bf41a158 SR |
1434 | static inline unsigned |
1435 | rb_event_index(struct ring_buffer_event *event) | |
1436 | { | |
1437 | unsigned long addr = (unsigned long)event; | |
1438 | ||
22f470f8 | 1439 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
bf41a158 SR |
1440 | } |
1441 | ||
0f0c85fc | 1442 | static inline int |
fa743953 SR |
1443 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
1444 | struct ring_buffer_event *event) | |
bf41a158 SR |
1445 | { |
1446 | unsigned long addr = (unsigned long)event; | |
1447 | unsigned long index; | |
1448 | ||
1449 | index = rb_event_index(event); | |
1450 | addr &= PAGE_MASK; | |
1451 | ||
1452 | return cpu_buffer->commit_page->page == (void *)addr && | |
1453 | rb_commit_index(cpu_buffer) == index; | |
1454 | } | |
1455 | ||
34a148bf | 1456 | static void |
bf41a158 | 1457 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1458 | { |
77ae365e SR |
1459 | unsigned long max_count; |
1460 | ||
bf41a158 SR |
1461 | /* |
1462 | * We only race with interrupts and NMIs on this CPU. | |
1463 | * If we own the commit event, then we can commit | |
1464 | * all others that interrupted us, since the interruptions | |
1465 | * are in stack format (they finish before they come | |
1466 | * back to us). This allows us to do a simple loop to | |
1467 | * assign the commit to the tail. | |
1468 | */ | |
a8ccf1d6 | 1469 | again: |
77ae365e SR |
1470 | max_count = cpu_buffer->buffer->pages * 100; |
1471 | ||
bf41a158 | 1472 | while (cpu_buffer->commit_page != cpu_buffer->tail_page) { |
77ae365e SR |
1473 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
1474 | return; | |
1475 | if (RB_WARN_ON(cpu_buffer, | |
1476 | rb_is_reader_page(cpu_buffer->tail_page))) | |
1477 | return; | |
1478 | local_set(&cpu_buffer->commit_page->page->commit, | |
1479 | rb_page_write(cpu_buffer->commit_page)); | |
bf41a158 | 1480 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); |
abc9b56d SR |
1481 | cpu_buffer->write_stamp = |
1482 | cpu_buffer->commit_page->page->time_stamp; | |
bf41a158 SR |
1483 | /* add barrier to keep gcc from optimizing too much */ |
1484 | barrier(); | |
1485 | } | |
1486 | while (rb_commit_index(cpu_buffer) != | |
1487 | rb_page_write(cpu_buffer->commit_page)) { | |
77ae365e SR |
1488 | |
1489 | local_set(&cpu_buffer->commit_page->page->commit, | |
1490 | rb_page_write(cpu_buffer->commit_page)); | |
1491 | RB_WARN_ON(cpu_buffer, | |
1492 | local_read(&cpu_buffer->commit_page->page->commit) & | |
1493 | ~RB_WRITE_MASK); | |
bf41a158 SR |
1494 | barrier(); |
1495 | } | |
a8ccf1d6 SR |
1496 | |
1497 | /* again, keep gcc from optimizing */ | |
1498 | barrier(); | |
1499 | ||
1500 | /* | |
1501 | * If an interrupt came in just after the first while loop | |
1502 | * and pushed the tail page forward, we will be left with | |
1503 | * a dangling commit that will never go forward. | |
1504 | */ | |
1505 | if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page)) | |
1506 | goto again; | |
7a8e76a3 SR |
1507 | } |
1508 | ||
d769041f | 1509 | static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1510 | { |
abc9b56d | 1511 | cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp; |
6f807acd | 1512 | cpu_buffer->reader_page->read = 0; |
d769041f SR |
1513 | } |
1514 | ||
34a148bf | 1515 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
d769041f SR |
1516 | { |
1517 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1518 | ||
1519 | /* | |
1520 | * The iterator could be on the reader page (it starts there). | |
1521 | * But the head could have moved, since the reader was | |
1522 | * found. Check for this case and assign the iterator | |
1523 | * to the head page instead of next. | |
1524 | */ | |
1525 | if (iter->head_page == cpu_buffer->reader_page) | |
77ae365e | 1526 | iter->head_page = rb_set_head_page(cpu_buffer); |
d769041f SR |
1527 | else |
1528 | rb_inc_page(cpu_buffer, &iter->head_page); | |
1529 | ||
abc9b56d | 1530 | iter->read_stamp = iter->head_page->page->time_stamp; |
7a8e76a3 SR |
1531 | iter->head = 0; |
1532 | } | |
1533 | ||
1534 | /** | |
1535 | * ring_buffer_update_event - update event type and data | |
1536 | * @event: the even to update | |
1537 | * @type: the type of event | |
1538 | * @length: the size of the event field in the ring buffer | |
1539 | * | |
1540 | * Update the type and data fields of the event. The length | |
1541 | * is the actual size that is written to the ring buffer, | |
1542 | * and with this, we can determine what to place into the | |
1543 | * data field. | |
1544 | */ | |
34a148bf | 1545 | static void |
7a8e76a3 SR |
1546 | rb_update_event(struct ring_buffer_event *event, |
1547 | unsigned type, unsigned length) | |
1548 | { | |
334d4169 | 1549 | event->type_len = type; |
7a8e76a3 SR |
1550 | |
1551 | switch (type) { | |
1552 | ||
1553 | case RINGBUF_TYPE_PADDING: | |
7a8e76a3 | 1554 | case RINGBUF_TYPE_TIME_EXTEND: |
7a8e76a3 | 1555 | case RINGBUF_TYPE_TIME_STAMP: |
7a8e76a3 SR |
1556 | break; |
1557 | ||
334d4169 | 1558 | case 0: |
7a8e76a3 | 1559 | length -= RB_EVNT_HDR_SIZE; |
2271048d | 1560 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
7a8e76a3 | 1561 | event->array[0] = length; |
334d4169 LJ |
1562 | else |
1563 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); | |
7a8e76a3 SR |
1564 | break; |
1565 | default: | |
1566 | BUG(); | |
1567 | } | |
1568 | } | |
1569 | ||
77ae365e SR |
1570 | /* |
1571 | * rb_handle_head_page - writer hit the head page | |
1572 | * | |
1573 | * Returns: +1 to retry page | |
1574 | * 0 to continue | |
1575 | * -1 on error | |
1576 | */ | |
1577 | static int | |
1578 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, | |
1579 | struct buffer_page *tail_page, | |
1580 | struct buffer_page *next_page) | |
1581 | { | |
1582 | struct buffer_page *new_head; | |
1583 | int entries; | |
1584 | int type; | |
1585 | int ret; | |
1586 | ||
1587 | entries = rb_page_entries(next_page); | |
1588 | ||
1589 | /* | |
1590 | * The hard part is here. We need to move the head | |
1591 | * forward, and protect against both readers on | |
1592 | * other CPUs and writers coming in via interrupts. | |
1593 | */ | |
1594 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, | |
1595 | RB_PAGE_HEAD); | |
1596 | ||
1597 | /* | |
1598 | * type can be one of four: | |
1599 | * NORMAL - an interrupt already moved it for us | |
1600 | * HEAD - we are the first to get here. | |
1601 | * UPDATE - we are the interrupt interrupting | |
1602 | * a current move. | |
1603 | * MOVED - a reader on another CPU moved the next | |
1604 | * pointer to its reader page. Give up | |
1605 | * and try again. | |
1606 | */ | |
1607 | ||
1608 | switch (type) { | |
1609 | case RB_PAGE_HEAD: | |
1610 | /* | |
1611 | * We changed the head to UPDATE, thus | |
1612 | * it is our responsibility to update | |
1613 | * the counters. | |
1614 | */ | |
1615 | local_add(entries, &cpu_buffer->overrun); | |
1616 | ||
1617 | /* | |
1618 | * The entries will be zeroed out when we move the | |
1619 | * tail page. | |
1620 | */ | |
1621 | ||
1622 | /* still more to do */ | |
1623 | break; | |
1624 | ||
1625 | case RB_PAGE_UPDATE: | |
1626 | /* | |
1627 | * This is an interrupt that interrupt the | |
1628 | * previous update. Still more to do. | |
1629 | */ | |
1630 | break; | |
1631 | case RB_PAGE_NORMAL: | |
1632 | /* | |
1633 | * An interrupt came in before the update | |
1634 | * and processed this for us. | |
1635 | * Nothing left to do. | |
1636 | */ | |
1637 | return 1; | |
1638 | case RB_PAGE_MOVED: | |
1639 | /* | |
1640 | * The reader is on another CPU and just did | |
1641 | * a swap with our next_page. | |
1642 | * Try again. | |
1643 | */ | |
1644 | return 1; | |
1645 | default: | |
1646 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ | |
1647 | return -1; | |
1648 | } | |
1649 | ||
1650 | /* | |
1651 | * Now that we are here, the old head pointer is | |
1652 | * set to UPDATE. This will keep the reader from | |
1653 | * swapping the head page with the reader page. | |
1654 | * The reader (on another CPU) will spin till | |
1655 | * we are finished. | |
1656 | * | |
1657 | * We just need to protect against interrupts | |
1658 | * doing the job. We will set the next pointer | |
1659 | * to HEAD. After that, we set the old pointer | |
1660 | * to NORMAL, but only if it was HEAD before. | |
1661 | * otherwise we are an interrupt, and only | |
1662 | * want the outer most commit to reset it. | |
1663 | */ | |
1664 | new_head = next_page; | |
1665 | rb_inc_page(cpu_buffer, &new_head); | |
1666 | ||
1667 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, | |
1668 | RB_PAGE_NORMAL); | |
1669 | ||
1670 | /* | |
1671 | * Valid returns are: | |
1672 | * HEAD - an interrupt came in and already set it. | |
1673 | * NORMAL - One of two things: | |
1674 | * 1) We really set it. | |
1675 | * 2) A bunch of interrupts came in and moved | |
1676 | * the page forward again. | |
1677 | */ | |
1678 | switch (ret) { | |
1679 | case RB_PAGE_HEAD: | |
1680 | case RB_PAGE_NORMAL: | |
1681 | /* OK */ | |
1682 | break; | |
1683 | default: | |
1684 | RB_WARN_ON(cpu_buffer, 1); | |
1685 | return -1; | |
1686 | } | |
1687 | ||
1688 | /* | |
1689 | * It is possible that an interrupt came in, | |
1690 | * set the head up, then more interrupts came in | |
1691 | * and moved it again. When we get back here, | |
1692 | * the page would have been set to NORMAL but we | |
1693 | * just set it back to HEAD. | |
1694 | * | |
1695 | * How do you detect this? Well, if that happened | |
1696 | * the tail page would have moved. | |
1697 | */ | |
1698 | if (ret == RB_PAGE_NORMAL) { | |
1699 | /* | |
1700 | * If the tail had moved passed next, then we need | |
1701 | * to reset the pointer. | |
1702 | */ | |
1703 | if (cpu_buffer->tail_page != tail_page && | |
1704 | cpu_buffer->tail_page != next_page) | |
1705 | rb_head_page_set_normal(cpu_buffer, new_head, | |
1706 | next_page, | |
1707 | RB_PAGE_HEAD); | |
1708 | } | |
1709 | ||
1710 | /* | |
1711 | * If this was the outer most commit (the one that | |
1712 | * changed the original pointer from HEAD to UPDATE), | |
1713 | * then it is up to us to reset it to NORMAL. | |
1714 | */ | |
1715 | if (type == RB_PAGE_HEAD) { | |
1716 | ret = rb_head_page_set_normal(cpu_buffer, next_page, | |
1717 | tail_page, | |
1718 | RB_PAGE_UPDATE); | |
1719 | if (RB_WARN_ON(cpu_buffer, | |
1720 | ret != RB_PAGE_UPDATE)) | |
1721 | return -1; | |
1722 | } | |
1723 | ||
1724 | return 0; | |
1725 | } | |
1726 | ||
34a148bf | 1727 | static unsigned rb_calculate_event_length(unsigned length) |
7a8e76a3 SR |
1728 | { |
1729 | struct ring_buffer_event event; /* Used only for sizeof array */ | |
1730 | ||
1731 | /* zero length can cause confusions */ | |
1732 | if (!length) | |
1733 | length = 1; | |
1734 | ||
2271048d | 1735 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
7a8e76a3 SR |
1736 | length += sizeof(event.array[0]); |
1737 | ||
1738 | length += RB_EVNT_HDR_SIZE; | |
2271048d | 1739 | length = ALIGN(length, RB_ARCH_ALIGNMENT); |
7a8e76a3 SR |
1740 | |
1741 | return length; | |
1742 | } | |
1743 | ||
c7b09308 SR |
1744 | static inline void |
1745 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, | |
1746 | struct buffer_page *tail_page, | |
1747 | unsigned long tail, unsigned long length) | |
1748 | { | |
1749 | struct ring_buffer_event *event; | |
1750 | ||
1751 | /* | |
1752 | * Only the event that crossed the page boundary | |
1753 | * must fill the old tail_page with padding. | |
1754 | */ | |
1755 | if (tail >= BUF_PAGE_SIZE) { | |
1756 | local_sub(length, &tail_page->write); | |
1757 | return; | |
1758 | } | |
1759 | ||
1760 | event = __rb_page_index(tail_page, tail); | |
b0b7065b | 1761 | kmemcheck_annotate_bitfield(event, bitfield); |
c7b09308 SR |
1762 | |
1763 | /* | |
1764 | * If this event is bigger than the minimum size, then | |
1765 | * we need to be careful that we don't subtract the | |
1766 | * write counter enough to allow another writer to slip | |
1767 | * in on this page. | |
1768 | * We put in a discarded commit instead, to make sure | |
1769 | * that this space is not used again. | |
1770 | * | |
1771 | * If we are less than the minimum size, we don't need to | |
1772 | * worry about it. | |
1773 | */ | |
1774 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { | |
1775 | /* No room for any events */ | |
1776 | ||
1777 | /* Mark the rest of the page with padding */ | |
1778 | rb_event_set_padding(event); | |
1779 | ||
1780 | /* Set the write back to the previous setting */ | |
1781 | local_sub(length, &tail_page->write); | |
1782 | return; | |
1783 | } | |
1784 | ||
1785 | /* Put in a discarded event */ | |
1786 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; | |
1787 | event->type_len = RINGBUF_TYPE_PADDING; | |
1788 | /* time delta must be non zero */ | |
1789 | event->time_delta = 1; | |
c7b09308 SR |
1790 | |
1791 | /* Set write to end of buffer */ | |
1792 | length = (tail + length) - BUF_PAGE_SIZE; | |
1793 | local_sub(length, &tail_page->write); | |
1794 | } | |
6634ff26 | 1795 | |
7a8e76a3 | 1796 | static struct ring_buffer_event * |
6634ff26 SR |
1797 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
1798 | unsigned long length, unsigned long tail, | |
6634ff26 | 1799 | struct buffer_page *tail_page, u64 *ts) |
7a8e76a3 | 1800 | { |
5a50e33c | 1801 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
7a8e76a3 | 1802 | struct ring_buffer *buffer = cpu_buffer->buffer; |
77ae365e SR |
1803 | struct buffer_page *next_page; |
1804 | int ret; | |
aa20ae84 SR |
1805 | |
1806 | next_page = tail_page; | |
1807 | ||
aa20ae84 SR |
1808 | rb_inc_page(cpu_buffer, &next_page); |
1809 | ||
aa20ae84 SR |
1810 | /* |
1811 | * If for some reason, we had an interrupt storm that made | |
1812 | * it all the way around the buffer, bail, and warn | |
1813 | * about it. | |
1814 | */ | |
1815 | if (unlikely(next_page == commit_page)) { | |
77ae365e | 1816 | local_inc(&cpu_buffer->commit_overrun); |
aa20ae84 SR |
1817 | goto out_reset; |
1818 | } | |
1819 | ||
77ae365e SR |
1820 | /* |
1821 | * This is where the fun begins! | |
1822 | * | |
1823 | * We are fighting against races between a reader that | |
1824 | * could be on another CPU trying to swap its reader | |
1825 | * page with the buffer head. | |
1826 | * | |
1827 | * We are also fighting against interrupts coming in and | |
1828 | * moving the head or tail on us as well. | |
1829 | * | |
1830 | * If the next page is the head page then we have filled | |
1831 | * the buffer, unless the commit page is still on the | |
1832 | * reader page. | |
1833 | */ | |
1834 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { | |
aa20ae84 | 1835 | |
77ae365e SR |
1836 | /* |
1837 | * If the commit is not on the reader page, then | |
1838 | * move the header page. | |
1839 | */ | |
1840 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { | |
1841 | /* | |
1842 | * If we are not in overwrite mode, | |
1843 | * this is easy, just stop here. | |
1844 | */ | |
1845 | if (!(buffer->flags & RB_FL_OVERWRITE)) | |
1846 | goto out_reset; | |
1847 | ||
1848 | ret = rb_handle_head_page(cpu_buffer, | |
1849 | tail_page, | |
1850 | next_page); | |
1851 | if (ret < 0) | |
1852 | goto out_reset; | |
1853 | if (ret) | |
1854 | goto out_again; | |
1855 | } else { | |
1856 | /* | |
1857 | * We need to be careful here too. The | |
1858 | * commit page could still be on the reader | |
1859 | * page. We could have a small buffer, and | |
1860 | * have filled up the buffer with events | |
1861 | * from interrupts and such, and wrapped. | |
1862 | * | |
1863 | * Note, if the tail page is also the on the | |
1864 | * reader_page, we let it move out. | |
1865 | */ | |
1866 | if (unlikely((cpu_buffer->commit_page != | |
1867 | cpu_buffer->tail_page) && | |
1868 | (cpu_buffer->commit_page == | |
1869 | cpu_buffer->reader_page))) { | |
1870 | local_inc(&cpu_buffer->commit_overrun); | |
1871 | goto out_reset; | |
1872 | } | |
aa20ae84 SR |
1873 | } |
1874 | } | |
1875 | ||
77ae365e SR |
1876 | ret = rb_tail_page_update(cpu_buffer, tail_page, next_page); |
1877 | if (ret) { | |
1878 | /* | |
1879 | * Nested commits always have zero deltas, so | |
1880 | * just reread the time stamp | |
1881 | */ | |
6d3f1e12 | 1882 | *ts = rb_time_stamp(buffer); |
77ae365e | 1883 | next_page->page->time_stamp = *ts; |
aa20ae84 SR |
1884 | } |
1885 | ||
77ae365e | 1886 | out_again: |
aa20ae84 | 1887 | |
77ae365e | 1888 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
aa20ae84 SR |
1889 | |
1890 | /* fail and let the caller try again */ | |
1891 | return ERR_PTR(-EAGAIN); | |
1892 | ||
45141d46 | 1893 | out_reset: |
6f3b3440 | 1894 | /* reset write */ |
c7b09308 | 1895 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
6f3b3440 | 1896 | |
bf41a158 | 1897 | return NULL; |
7a8e76a3 SR |
1898 | } |
1899 | ||
6634ff26 SR |
1900 | static struct ring_buffer_event * |
1901 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, | |
1902 | unsigned type, unsigned long length, u64 *ts) | |
1903 | { | |
5a50e33c | 1904 | struct buffer_page *tail_page; |
6634ff26 SR |
1905 | struct ring_buffer_event *event; |
1906 | unsigned long tail, write; | |
1907 | ||
6634ff26 SR |
1908 | tail_page = cpu_buffer->tail_page; |
1909 | write = local_add_return(length, &tail_page->write); | |
77ae365e SR |
1910 | |
1911 | /* set write to only the index of the write */ | |
1912 | write &= RB_WRITE_MASK; | |
6634ff26 SR |
1913 | tail = write - length; |
1914 | ||
1915 | /* See if we shot pass the end of this buffer page */ | |
1916 | if (write > BUF_PAGE_SIZE) | |
1917 | return rb_move_tail(cpu_buffer, length, tail, | |
5a50e33c | 1918 | tail_page, ts); |
6634ff26 SR |
1919 | |
1920 | /* We reserved something on the buffer */ | |
1921 | ||
6634ff26 | 1922 | event = __rb_page_index(tail_page, tail); |
1744a21d | 1923 | kmemcheck_annotate_bitfield(event, bitfield); |
6634ff26 SR |
1924 | rb_update_event(event, type, length); |
1925 | ||
1926 | /* The passed in type is zero for DATA */ | |
1927 | if (likely(!type)) | |
1928 | local_inc(&tail_page->entries); | |
1929 | ||
1930 | /* | |
fa743953 SR |
1931 | * If this is the first commit on the page, then update |
1932 | * its timestamp. | |
6634ff26 | 1933 | */ |
fa743953 SR |
1934 | if (!tail) |
1935 | tail_page->page->time_stamp = *ts; | |
6634ff26 SR |
1936 | |
1937 | return event; | |
1938 | } | |
1939 | ||
edd813bf SR |
1940 | static inline int |
1941 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, | |
1942 | struct ring_buffer_event *event) | |
1943 | { | |
1944 | unsigned long new_index, old_index; | |
1945 | struct buffer_page *bpage; | |
1946 | unsigned long index; | |
1947 | unsigned long addr; | |
1948 | ||
1949 | new_index = rb_event_index(event); | |
1950 | old_index = new_index + rb_event_length(event); | |
1951 | addr = (unsigned long)event; | |
1952 | addr &= PAGE_MASK; | |
1953 | ||
1954 | bpage = cpu_buffer->tail_page; | |
1955 | ||
1956 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { | |
77ae365e SR |
1957 | unsigned long write_mask = |
1958 | local_read(&bpage->write) & ~RB_WRITE_MASK; | |
edd813bf SR |
1959 | /* |
1960 | * This is on the tail page. It is possible that | |
1961 | * a write could come in and move the tail page | |
1962 | * and write to the next page. That is fine | |
1963 | * because we just shorten what is on this page. | |
1964 | */ | |
77ae365e SR |
1965 | old_index += write_mask; |
1966 | new_index += write_mask; | |
edd813bf SR |
1967 | index = local_cmpxchg(&bpage->write, old_index, new_index); |
1968 | if (index == old_index) | |
1969 | return 1; | |
1970 | } | |
1971 | ||
1972 | /* could not discard */ | |
1973 | return 0; | |
1974 | } | |
1975 | ||
7a8e76a3 SR |
1976 | static int |
1977 | rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
1978 | u64 *ts, u64 *delta) | |
1979 | { | |
1980 | struct ring_buffer_event *event; | |
1981 | static int once; | |
bf41a158 | 1982 | int ret; |
7a8e76a3 SR |
1983 | |
1984 | if (unlikely(*delta > (1ULL << 59) && !once++)) { | |
1985 | printk(KERN_WARNING "Delta way too big! %llu" | |
1986 | " ts=%llu write stamp = %llu\n", | |
e2862c94 SR |
1987 | (unsigned long long)*delta, |
1988 | (unsigned long long)*ts, | |
1989 | (unsigned long long)cpu_buffer->write_stamp); | |
7a8e76a3 SR |
1990 | WARN_ON(1); |
1991 | } | |
1992 | ||
1993 | /* | |
1994 | * The delta is too big, we to add a | |
1995 | * new timestamp. | |
1996 | */ | |
1997 | event = __rb_reserve_next(cpu_buffer, | |
1998 | RINGBUF_TYPE_TIME_EXTEND, | |
1999 | RB_LEN_TIME_EXTEND, | |
2000 | ts); | |
2001 | if (!event) | |
bf41a158 | 2002 | return -EBUSY; |
7a8e76a3 | 2003 | |
bf41a158 SR |
2004 | if (PTR_ERR(event) == -EAGAIN) |
2005 | return -EAGAIN; | |
2006 | ||
2007 | /* Only a commited time event can update the write stamp */ | |
fa743953 | 2008 | if (rb_event_is_commit(cpu_buffer, event)) { |
bf41a158 | 2009 | /* |
fa743953 SR |
2010 | * If this is the first on the page, then it was |
2011 | * updated with the page itself. Try to discard it | |
2012 | * and if we can't just make it zero. | |
bf41a158 SR |
2013 | */ |
2014 | if (rb_event_index(event)) { | |
2015 | event->time_delta = *delta & TS_MASK; | |
2016 | event->array[0] = *delta >> TS_SHIFT; | |
2017 | } else { | |
ea05b57c SR |
2018 | /* try to discard, since we do not need this */ |
2019 | if (!rb_try_to_discard(cpu_buffer, event)) { | |
2020 | /* nope, just zero it */ | |
2021 | event->time_delta = 0; | |
2022 | event->array[0] = 0; | |
2023 | } | |
bf41a158 | 2024 | } |
7a8e76a3 | 2025 | cpu_buffer->write_stamp = *ts; |
bf41a158 SR |
2026 | /* let the caller know this was the commit */ |
2027 | ret = 1; | |
2028 | } else { | |
edd813bf SR |
2029 | /* Try to discard the event */ |
2030 | if (!rb_try_to_discard(cpu_buffer, event)) { | |
2031 | /* Darn, this is just wasted space */ | |
2032 | event->time_delta = 0; | |
2033 | event->array[0] = 0; | |
edd813bf | 2034 | } |
f57a8a19 | 2035 | ret = 0; |
7a8e76a3 SR |
2036 | } |
2037 | ||
bf41a158 SR |
2038 | *delta = 0; |
2039 | ||
2040 | return ret; | |
7a8e76a3 SR |
2041 | } |
2042 | ||
fa743953 SR |
2043 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2044 | { | |
2045 | local_inc(&cpu_buffer->committing); | |
2046 | local_inc(&cpu_buffer->commits); | |
2047 | } | |
2048 | ||
2049 | static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) | |
2050 | { | |
2051 | unsigned long commits; | |
2052 | ||
2053 | if (RB_WARN_ON(cpu_buffer, | |
2054 | !local_read(&cpu_buffer->committing))) | |
2055 | return; | |
2056 | ||
2057 | again: | |
2058 | commits = local_read(&cpu_buffer->commits); | |
2059 | /* synchronize with interrupts */ | |
2060 | barrier(); | |
2061 | if (local_read(&cpu_buffer->committing) == 1) | |
2062 | rb_set_commit_to_write(cpu_buffer); | |
2063 | ||
2064 | local_dec(&cpu_buffer->committing); | |
2065 | ||
2066 | /* synchronize with interrupts */ | |
2067 | barrier(); | |
2068 | ||
2069 | /* | |
2070 | * Need to account for interrupts coming in between the | |
2071 | * updating of the commit page and the clearing of the | |
2072 | * committing counter. | |
2073 | */ | |
2074 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && | |
2075 | !local_read(&cpu_buffer->committing)) { | |
2076 | local_inc(&cpu_buffer->committing); | |
2077 | goto again; | |
2078 | } | |
2079 | } | |
2080 | ||
7a8e76a3 | 2081 | static struct ring_buffer_event * |
62f0b3eb SR |
2082 | rb_reserve_next_event(struct ring_buffer *buffer, |
2083 | struct ring_buffer_per_cpu *cpu_buffer, | |
1cd8d735 | 2084 | unsigned long length) |
7a8e76a3 SR |
2085 | { |
2086 | struct ring_buffer_event *event; | |
168b6b1d | 2087 | u64 ts, delta = 0; |
bf41a158 | 2088 | int commit = 0; |
818e3dd3 | 2089 | int nr_loops = 0; |
7a8e76a3 | 2090 | |
fa743953 SR |
2091 | rb_start_commit(cpu_buffer); |
2092 | ||
85bac32c | 2093 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
62f0b3eb SR |
2094 | /* |
2095 | * Due to the ability to swap a cpu buffer from a buffer | |
2096 | * it is possible it was swapped before we committed. | |
2097 | * (committing stops a swap). We check for it here and | |
2098 | * if it happened, we have to fail the write. | |
2099 | */ | |
2100 | barrier(); | |
2101 | if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) { | |
2102 | local_dec(&cpu_buffer->committing); | |
2103 | local_dec(&cpu_buffer->commits); | |
2104 | return NULL; | |
2105 | } | |
85bac32c | 2106 | #endif |
62f0b3eb | 2107 | |
be957c44 | 2108 | length = rb_calculate_event_length(length); |
bf41a158 | 2109 | again: |
818e3dd3 SR |
2110 | /* |
2111 | * We allow for interrupts to reenter here and do a trace. | |
2112 | * If one does, it will cause this original code to loop | |
2113 | * back here. Even with heavy interrupts happening, this | |
2114 | * should only happen a few times in a row. If this happens | |
2115 | * 1000 times in a row, there must be either an interrupt | |
2116 | * storm or we have something buggy. | |
2117 | * Bail! | |
2118 | */ | |
3e89c7bb | 2119 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
fa743953 | 2120 | goto out_fail; |
818e3dd3 | 2121 | |
6d3f1e12 | 2122 | ts = rb_time_stamp(cpu_buffer->buffer); |
7a8e76a3 | 2123 | |
bf41a158 SR |
2124 | /* |
2125 | * Only the first commit can update the timestamp. | |
2126 | * Yes there is a race here. If an interrupt comes in | |
2127 | * just after the conditional and it traces too, then it | |
2128 | * will also check the deltas. More than one timestamp may | |
2129 | * also be made. But only the entry that did the actual | |
2130 | * commit will be something other than zero. | |
2131 | */ | |
0f0c85fc SR |
2132 | if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page && |
2133 | rb_page_write(cpu_buffer->tail_page) == | |
2134 | rb_commit_index(cpu_buffer))) { | |
168b6b1d | 2135 | u64 diff; |
bf41a158 | 2136 | |
168b6b1d | 2137 | diff = ts - cpu_buffer->write_stamp; |
7a8e76a3 | 2138 | |
168b6b1d | 2139 | /* make sure this diff is calculated here */ |
bf41a158 SR |
2140 | barrier(); |
2141 | ||
2142 | /* Did the write stamp get updated already? */ | |
2143 | if (unlikely(ts < cpu_buffer->write_stamp)) | |
168b6b1d | 2144 | goto get_event; |
bf41a158 | 2145 | |
168b6b1d SR |
2146 | delta = diff; |
2147 | if (unlikely(test_time_stamp(delta))) { | |
7a8e76a3 | 2148 | |
bf41a158 | 2149 | commit = rb_add_time_stamp(cpu_buffer, &ts, &delta); |
bf41a158 | 2150 | if (commit == -EBUSY) |
fa743953 | 2151 | goto out_fail; |
bf41a158 SR |
2152 | |
2153 | if (commit == -EAGAIN) | |
2154 | goto again; | |
2155 | ||
2156 | RB_WARN_ON(cpu_buffer, commit < 0); | |
7a8e76a3 | 2157 | } |
168b6b1d | 2158 | } |
7a8e76a3 | 2159 | |
168b6b1d | 2160 | get_event: |
1cd8d735 | 2161 | event = __rb_reserve_next(cpu_buffer, 0, length, &ts); |
168b6b1d | 2162 | if (unlikely(PTR_ERR(event) == -EAGAIN)) |
bf41a158 SR |
2163 | goto again; |
2164 | ||
fa743953 SR |
2165 | if (!event) |
2166 | goto out_fail; | |
7a8e76a3 | 2167 | |
fa743953 | 2168 | if (!rb_event_is_commit(cpu_buffer, event)) |
7a8e76a3 SR |
2169 | delta = 0; |
2170 | ||
2171 | event->time_delta = delta; | |
2172 | ||
2173 | return event; | |
fa743953 SR |
2174 | |
2175 | out_fail: | |
2176 | rb_end_commit(cpu_buffer); | |
2177 | return NULL; | |
7a8e76a3 SR |
2178 | } |
2179 | ||
1155de47 PM |
2180 | #ifdef CONFIG_TRACING |
2181 | ||
aa18efb2 | 2182 | #define TRACE_RECURSIVE_DEPTH 16 |
261842b7 SR |
2183 | |
2184 | static int trace_recursive_lock(void) | |
2185 | { | |
aa18efb2 | 2186 | current->trace_recursion++; |
261842b7 | 2187 | |
aa18efb2 SR |
2188 | if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH)) |
2189 | return 0; | |
e057a5e5 | 2190 | |
aa18efb2 SR |
2191 | /* Disable all tracing before we do anything else */ |
2192 | tracing_off_permanent(); | |
261842b7 | 2193 | |
7d7d2b80 | 2194 | printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:" |
aa18efb2 SR |
2195 | "HC[%lu]:SC[%lu]:NMI[%lu]\n", |
2196 | current->trace_recursion, | |
2197 | hardirq_count() >> HARDIRQ_SHIFT, | |
2198 | softirq_count() >> SOFTIRQ_SHIFT, | |
2199 | in_nmi()); | |
261842b7 | 2200 | |
aa18efb2 SR |
2201 | WARN_ON_ONCE(1); |
2202 | return -1; | |
261842b7 SR |
2203 | } |
2204 | ||
2205 | static void trace_recursive_unlock(void) | |
2206 | { | |
aa18efb2 | 2207 | WARN_ON_ONCE(!current->trace_recursion); |
261842b7 | 2208 | |
aa18efb2 | 2209 | current->trace_recursion--; |
261842b7 SR |
2210 | } |
2211 | ||
1155de47 PM |
2212 | #else |
2213 | ||
2214 | #define trace_recursive_lock() (0) | |
2215 | #define trace_recursive_unlock() do { } while (0) | |
2216 | ||
2217 | #endif | |
2218 | ||
bf41a158 SR |
2219 | static DEFINE_PER_CPU(int, rb_need_resched); |
2220 | ||
7a8e76a3 SR |
2221 | /** |
2222 | * ring_buffer_lock_reserve - reserve a part of the buffer | |
2223 | * @buffer: the ring buffer to reserve from | |
2224 | * @length: the length of the data to reserve (excluding event header) | |
7a8e76a3 SR |
2225 | * |
2226 | * Returns a reseverd event on the ring buffer to copy directly to. | |
2227 | * The user of this interface will need to get the body to write into | |
2228 | * and can use the ring_buffer_event_data() interface. | |
2229 | * | |
2230 | * The length is the length of the data needed, not the event length | |
2231 | * which also includes the event header. | |
2232 | * | |
2233 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. | |
2234 | * If NULL is returned, then nothing has been allocated or locked. | |
2235 | */ | |
2236 | struct ring_buffer_event * | |
0a987751 | 2237 | ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
7a8e76a3 SR |
2238 | { |
2239 | struct ring_buffer_per_cpu *cpu_buffer; | |
2240 | struct ring_buffer_event *event; | |
bf41a158 | 2241 | int cpu, resched; |
7a8e76a3 | 2242 | |
033601a3 | 2243 | if (ring_buffer_flags != RB_BUFFERS_ON) |
a3583244 SR |
2244 | return NULL; |
2245 | ||
bf41a158 | 2246 | /* If we are tracing schedule, we don't want to recurse */ |
182e9f5f | 2247 | resched = ftrace_preempt_disable(); |
bf41a158 | 2248 | |
52fbe9cd LJ |
2249 | if (atomic_read(&buffer->record_disabled)) |
2250 | goto out_nocheck; | |
2251 | ||
261842b7 SR |
2252 | if (trace_recursive_lock()) |
2253 | goto out_nocheck; | |
2254 | ||
7a8e76a3 SR |
2255 | cpu = raw_smp_processor_id(); |
2256 | ||
9e01c1b7 | 2257 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
d769041f | 2258 | goto out; |
7a8e76a3 SR |
2259 | |
2260 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
2261 | |
2262 | if (atomic_read(&cpu_buffer->record_disabled)) | |
d769041f | 2263 | goto out; |
7a8e76a3 | 2264 | |
be957c44 | 2265 | if (length > BUF_MAX_DATA_SIZE) |
bf41a158 | 2266 | goto out; |
7a8e76a3 | 2267 | |
62f0b3eb | 2268 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 2269 | if (!event) |
d769041f | 2270 | goto out; |
7a8e76a3 | 2271 | |
bf41a158 SR |
2272 | /* |
2273 | * Need to store resched state on this cpu. | |
2274 | * Only the first needs to. | |
2275 | */ | |
2276 | ||
2277 | if (preempt_count() == 1) | |
2278 | per_cpu(rb_need_resched, cpu) = resched; | |
2279 | ||
7a8e76a3 SR |
2280 | return event; |
2281 | ||
d769041f | 2282 | out: |
261842b7 SR |
2283 | trace_recursive_unlock(); |
2284 | ||
2285 | out_nocheck: | |
182e9f5f | 2286 | ftrace_preempt_enable(resched); |
7a8e76a3 SR |
2287 | return NULL; |
2288 | } | |
c4f50183 | 2289 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
7a8e76a3 | 2290 | |
a1863c21 SR |
2291 | static void |
2292 | rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
7a8e76a3 SR |
2293 | struct ring_buffer_event *event) |
2294 | { | |
fa743953 SR |
2295 | /* |
2296 | * The event first in the commit queue updates the | |
2297 | * time stamp. | |
2298 | */ | |
2299 | if (rb_event_is_commit(cpu_buffer, event)) | |
2300 | cpu_buffer->write_stamp += event->time_delta; | |
a1863c21 | 2301 | } |
bf41a158 | 2302 | |
a1863c21 SR |
2303 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2304 | struct ring_buffer_event *event) | |
2305 | { | |
2306 | local_inc(&cpu_buffer->entries); | |
2307 | rb_update_write_stamp(cpu_buffer, event); | |
fa743953 | 2308 | rb_end_commit(cpu_buffer); |
7a8e76a3 SR |
2309 | } |
2310 | ||
2311 | /** | |
2312 | * ring_buffer_unlock_commit - commit a reserved | |
2313 | * @buffer: The buffer to commit to | |
2314 | * @event: The event pointer to commit. | |
7a8e76a3 SR |
2315 | * |
2316 | * This commits the data to the ring buffer, and releases any locks held. | |
2317 | * | |
2318 | * Must be paired with ring_buffer_lock_reserve. | |
2319 | */ | |
2320 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, | |
0a987751 | 2321 | struct ring_buffer_event *event) |
7a8e76a3 SR |
2322 | { |
2323 | struct ring_buffer_per_cpu *cpu_buffer; | |
2324 | int cpu = raw_smp_processor_id(); | |
2325 | ||
2326 | cpu_buffer = buffer->buffers[cpu]; | |
2327 | ||
7a8e76a3 SR |
2328 | rb_commit(cpu_buffer, event); |
2329 | ||
261842b7 SR |
2330 | trace_recursive_unlock(); |
2331 | ||
bf41a158 SR |
2332 | /* |
2333 | * Only the last preempt count needs to restore preemption. | |
2334 | */ | |
182e9f5f SR |
2335 | if (preempt_count() == 1) |
2336 | ftrace_preempt_enable(per_cpu(rb_need_resched, cpu)); | |
2337 | else | |
bf41a158 | 2338 | preempt_enable_no_resched_notrace(); |
7a8e76a3 SR |
2339 | |
2340 | return 0; | |
2341 | } | |
c4f50183 | 2342 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
7a8e76a3 | 2343 | |
f3b9aae1 FW |
2344 | static inline void rb_event_discard(struct ring_buffer_event *event) |
2345 | { | |
334d4169 LJ |
2346 | /* array[0] holds the actual length for the discarded event */ |
2347 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; | |
2348 | event->type_len = RINGBUF_TYPE_PADDING; | |
f3b9aae1 FW |
2349 | /* time delta must be non zero */ |
2350 | if (!event->time_delta) | |
2351 | event->time_delta = 1; | |
2352 | } | |
2353 | ||
a1863c21 SR |
2354 | /* |
2355 | * Decrement the entries to the page that an event is on. | |
2356 | * The event does not even need to exist, only the pointer | |
2357 | * to the page it is on. This may only be called before the commit | |
2358 | * takes place. | |
2359 | */ | |
2360 | static inline void | |
2361 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, | |
2362 | struct ring_buffer_event *event) | |
2363 | { | |
2364 | unsigned long addr = (unsigned long)event; | |
2365 | struct buffer_page *bpage = cpu_buffer->commit_page; | |
2366 | struct buffer_page *start; | |
2367 | ||
2368 | addr &= PAGE_MASK; | |
2369 | ||
2370 | /* Do the likely case first */ | |
2371 | if (likely(bpage->page == (void *)addr)) { | |
2372 | local_dec(&bpage->entries); | |
2373 | return; | |
2374 | } | |
2375 | ||
2376 | /* | |
2377 | * Because the commit page may be on the reader page we | |
2378 | * start with the next page and check the end loop there. | |
2379 | */ | |
2380 | rb_inc_page(cpu_buffer, &bpage); | |
2381 | start = bpage; | |
2382 | do { | |
2383 | if (bpage->page == (void *)addr) { | |
2384 | local_dec(&bpage->entries); | |
2385 | return; | |
2386 | } | |
2387 | rb_inc_page(cpu_buffer, &bpage); | |
2388 | } while (bpage != start); | |
2389 | ||
2390 | /* commit not part of this buffer?? */ | |
2391 | RB_WARN_ON(cpu_buffer, 1); | |
2392 | } | |
2393 | ||
fa1b47dd SR |
2394 | /** |
2395 | * ring_buffer_commit_discard - discard an event that has not been committed | |
2396 | * @buffer: the ring buffer | |
2397 | * @event: non committed event to discard | |
2398 | * | |
dc892f73 SR |
2399 | * Sometimes an event that is in the ring buffer needs to be ignored. |
2400 | * This function lets the user discard an event in the ring buffer | |
2401 | * and then that event will not be read later. | |
2402 | * | |
2403 | * This function only works if it is called before the the item has been | |
2404 | * committed. It will try to free the event from the ring buffer | |
fa1b47dd SR |
2405 | * if another event has not been added behind it. |
2406 | * | |
2407 | * If another event has been added behind it, it will set the event | |
2408 | * up as discarded, and perform the commit. | |
2409 | * | |
2410 | * If this function is called, do not call ring_buffer_unlock_commit on | |
2411 | * the event. | |
2412 | */ | |
2413 | void ring_buffer_discard_commit(struct ring_buffer *buffer, | |
2414 | struct ring_buffer_event *event) | |
2415 | { | |
2416 | struct ring_buffer_per_cpu *cpu_buffer; | |
fa1b47dd SR |
2417 | int cpu; |
2418 | ||
2419 | /* The event is discarded regardless */ | |
f3b9aae1 | 2420 | rb_event_discard(event); |
fa1b47dd | 2421 | |
fa743953 SR |
2422 | cpu = smp_processor_id(); |
2423 | cpu_buffer = buffer->buffers[cpu]; | |
2424 | ||
fa1b47dd SR |
2425 | /* |
2426 | * This must only be called if the event has not been | |
2427 | * committed yet. Thus we can assume that preemption | |
2428 | * is still disabled. | |
2429 | */ | |
fa743953 | 2430 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
fa1b47dd | 2431 | |
a1863c21 | 2432 | rb_decrement_entry(cpu_buffer, event); |
0f2541d2 | 2433 | if (rb_try_to_discard(cpu_buffer, event)) |
edd813bf | 2434 | goto out; |
fa1b47dd SR |
2435 | |
2436 | /* | |
2437 | * The commit is still visible by the reader, so we | |
a1863c21 | 2438 | * must still update the timestamp. |
fa1b47dd | 2439 | */ |
a1863c21 | 2440 | rb_update_write_stamp(cpu_buffer, event); |
fa1b47dd | 2441 | out: |
fa743953 | 2442 | rb_end_commit(cpu_buffer); |
fa1b47dd | 2443 | |
f3b9aae1 FW |
2444 | trace_recursive_unlock(); |
2445 | ||
fa1b47dd SR |
2446 | /* |
2447 | * Only the last preempt count needs to restore preemption. | |
2448 | */ | |
2449 | if (preempt_count() == 1) | |
2450 | ftrace_preempt_enable(per_cpu(rb_need_resched, cpu)); | |
2451 | else | |
2452 | preempt_enable_no_resched_notrace(); | |
2453 | ||
2454 | } | |
2455 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); | |
2456 | ||
7a8e76a3 SR |
2457 | /** |
2458 | * ring_buffer_write - write data to the buffer without reserving | |
2459 | * @buffer: The ring buffer to write to. | |
2460 | * @length: The length of the data being written (excluding the event header) | |
2461 | * @data: The data to write to the buffer. | |
2462 | * | |
2463 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as | |
2464 | * one function. If you already have the data to write to the buffer, it | |
2465 | * may be easier to simply call this function. | |
2466 | * | |
2467 | * Note, like ring_buffer_lock_reserve, the length is the length of the data | |
2468 | * and not the length of the event which would hold the header. | |
2469 | */ | |
2470 | int ring_buffer_write(struct ring_buffer *buffer, | |
2471 | unsigned long length, | |
2472 | void *data) | |
2473 | { | |
2474 | struct ring_buffer_per_cpu *cpu_buffer; | |
2475 | struct ring_buffer_event *event; | |
7a8e76a3 SR |
2476 | void *body; |
2477 | int ret = -EBUSY; | |
bf41a158 | 2478 | int cpu, resched; |
7a8e76a3 | 2479 | |
033601a3 | 2480 | if (ring_buffer_flags != RB_BUFFERS_ON) |
a3583244 SR |
2481 | return -EBUSY; |
2482 | ||
182e9f5f | 2483 | resched = ftrace_preempt_disable(); |
bf41a158 | 2484 | |
52fbe9cd LJ |
2485 | if (atomic_read(&buffer->record_disabled)) |
2486 | goto out; | |
2487 | ||
7a8e76a3 SR |
2488 | cpu = raw_smp_processor_id(); |
2489 | ||
9e01c1b7 | 2490 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
d769041f | 2491 | goto out; |
7a8e76a3 SR |
2492 | |
2493 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
2494 | |
2495 | if (atomic_read(&cpu_buffer->record_disabled)) | |
2496 | goto out; | |
2497 | ||
be957c44 SR |
2498 | if (length > BUF_MAX_DATA_SIZE) |
2499 | goto out; | |
2500 | ||
62f0b3eb | 2501 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 SR |
2502 | if (!event) |
2503 | goto out; | |
2504 | ||
2505 | body = rb_event_data(event); | |
2506 | ||
2507 | memcpy(body, data, length); | |
2508 | ||
2509 | rb_commit(cpu_buffer, event); | |
2510 | ||
2511 | ret = 0; | |
2512 | out: | |
182e9f5f | 2513 | ftrace_preempt_enable(resched); |
7a8e76a3 SR |
2514 | |
2515 | return ret; | |
2516 | } | |
c4f50183 | 2517 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
7a8e76a3 | 2518 | |
34a148bf | 2519 | static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
bf41a158 SR |
2520 | { |
2521 | struct buffer_page *reader = cpu_buffer->reader_page; | |
77ae365e | 2522 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
bf41a158 SR |
2523 | struct buffer_page *commit = cpu_buffer->commit_page; |
2524 | ||
77ae365e SR |
2525 | /* In case of error, head will be NULL */ |
2526 | if (unlikely(!head)) | |
2527 | return 1; | |
2528 | ||
bf41a158 SR |
2529 | return reader->read == rb_page_commit(reader) && |
2530 | (commit == reader || | |
2531 | (commit == head && | |
2532 | head->read == rb_page_commit(commit))); | |
2533 | } | |
2534 | ||
7a8e76a3 SR |
2535 | /** |
2536 | * ring_buffer_record_disable - stop all writes into the buffer | |
2537 | * @buffer: The ring buffer to stop writes to. | |
2538 | * | |
2539 | * This prevents all writes to the buffer. Any attempt to write | |
2540 | * to the buffer after this will fail and return NULL. | |
2541 | * | |
2542 | * The caller should call synchronize_sched() after this. | |
2543 | */ | |
2544 | void ring_buffer_record_disable(struct ring_buffer *buffer) | |
2545 | { | |
2546 | atomic_inc(&buffer->record_disabled); | |
2547 | } | |
c4f50183 | 2548 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
7a8e76a3 SR |
2549 | |
2550 | /** | |
2551 | * ring_buffer_record_enable - enable writes to the buffer | |
2552 | * @buffer: The ring buffer to enable writes | |
2553 | * | |
2554 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 2555 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
2556 | */ |
2557 | void ring_buffer_record_enable(struct ring_buffer *buffer) | |
2558 | { | |
2559 | atomic_dec(&buffer->record_disabled); | |
2560 | } | |
c4f50183 | 2561 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
7a8e76a3 SR |
2562 | |
2563 | /** | |
2564 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer | |
2565 | * @buffer: The ring buffer to stop writes to. | |
2566 | * @cpu: The CPU buffer to stop | |
2567 | * | |
2568 | * This prevents all writes to the buffer. Any attempt to write | |
2569 | * to the buffer after this will fail and return NULL. | |
2570 | * | |
2571 | * The caller should call synchronize_sched() after this. | |
2572 | */ | |
2573 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) | |
2574 | { | |
2575 | struct ring_buffer_per_cpu *cpu_buffer; | |
2576 | ||
9e01c1b7 | 2577 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 2578 | return; |
7a8e76a3 SR |
2579 | |
2580 | cpu_buffer = buffer->buffers[cpu]; | |
2581 | atomic_inc(&cpu_buffer->record_disabled); | |
2582 | } | |
c4f50183 | 2583 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
7a8e76a3 SR |
2584 | |
2585 | /** | |
2586 | * ring_buffer_record_enable_cpu - enable writes to the buffer | |
2587 | * @buffer: The ring buffer to enable writes | |
2588 | * @cpu: The CPU to enable. | |
2589 | * | |
2590 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 2591 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
2592 | */ |
2593 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) | |
2594 | { | |
2595 | struct ring_buffer_per_cpu *cpu_buffer; | |
2596 | ||
9e01c1b7 | 2597 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 2598 | return; |
7a8e76a3 SR |
2599 | |
2600 | cpu_buffer = buffer->buffers[cpu]; | |
2601 | atomic_dec(&cpu_buffer->record_disabled); | |
2602 | } | |
c4f50183 | 2603 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
7a8e76a3 SR |
2604 | |
2605 | /** | |
2606 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer | |
2607 | * @buffer: The ring buffer | |
2608 | * @cpu: The per CPU buffer to get the entries from. | |
2609 | */ | |
2610 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) | |
2611 | { | |
2612 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 2613 | unsigned long ret; |
7a8e76a3 | 2614 | |
9e01c1b7 | 2615 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 2616 | return 0; |
7a8e76a3 SR |
2617 | |
2618 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 2619 | ret = (local_read(&cpu_buffer->entries) - local_read(&cpu_buffer->overrun)) |
e4906eff | 2620 | - cpu_buffer->read; |
554f786e SR |
2621 | |
2622 | return ret; | |
7a8e76a3 | 2623 | } |
c4f50183 | 2624 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
7a8e76a3 SR |
2625 | |
2626 | /** | |
2627 | * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer | |
2628 | * @buffer: The ring buffer | |
2629 | * @cpu: The per CPU buffer to get the number of overruns from | |
2630 | */ | |
2631 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
2632 | { | |
2633 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 2634 | unsigned long ret; |
7a8e76a3 | 2635 | |
9e01c1b7 | 2636 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 2637 | return 0; |
7a8e76a3 SR |
2638 | |
2639 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 2640 | ret = local_read(&cpu_buffer->overrun); |
554f786e SR |
2641 | |
2642 | return ret; | |
7a8e76a3 | 2643 | } |
c4f50183 | 2644 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
7a8e76a3 | 2645 | |
f0d2c681 SR |
2646 | /** |
2647 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits | |
2648 | * @buffer: The ring buffer | |
2649 | * @cpu: The per CPU buffer to get the number of overruns from | |
2650 | */ | |
2651 | unsigned long | |
2652 | ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
2653 | { | |
2654 | struct ring_buffer_per_cpu *cpu_buffer; | |
2655 | unsigned long ret; | |
2656 | ||
2657 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
2658 | return 0; | |
2659 | ||
2660 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 2661 | ret = local_read(&cpu_buffer->commit_overrun); |
f0d2c681 SR |
2662 | |
2663 | return ret; | |
2664 | } | |
2665 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); | |
2666 | ||
7a8e76a3 SR |
2667 | /** |
2668 | * ring_buffer_entries - get the number of entries in a buffer | |
2669 | * @buffer: The ring buffer | |
2670 | * | |
2671 | * Returns the total number of entries in the ring buffer | |
2672 | * (all CPU entries) | |
2673 | */ | |
2674 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) | |
2675 | { | |
2676 | struct ring_buffer_per_cpu *cpu_buffer; | |
2677 | unsigned long entries = 0; | |
2678 | int cpu; | |
2679 | ||
2680 | /* if you care about this being correct, lock the buffer */ | |
2681 | for_each_buffer_cpu(buffer, cpu) { | |
2682 | cpu_buffer = buffer->buffers[cpu]; | |
e4906eff | 2683 | entries += (local_read(&cpu_buffer->entries) - |
77ae365e | 2684 | local_read(&cpu_buffer->overrun)) - cpu_buffer->read; |
7a8e76a3 SR |
2685 | } |
2686 | ||
2687 | return entries; | |
2688 | } | |
c4f50183 | 2689 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
7a8e76a3 SR |
2690 | |
2691 | /** | |
67b394f7 | 2692 | * ring_buffer_overruns - get the number of overruns in buffer |
7a8e76a3 SR |
2693 | * @buffer: The ring buffer |
2694 | * | |
2695 | * Returns the total number of overruns in the ring buffer | |
2696 | * (all CPU entries) | |
2697 | */ | |
2698 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) | |
2699 | { | |
2700 | struct ring_buffer_per_cpu *cpu_buffer; | |
2701 | unsigned long overruns = 0; | |
2702 | int cpu; | |
2703 | ||
2704 | /* if you care about this being correct, lock the buffer */ | |
2705 | for_each_buffer_cpu(buffer, cpu) { | |
2706 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 2707 | overruns += local_read(&cpu_buffer->overrun); |
7a8e76a3 SR |
2708 | } |
2709 | ||
2710 | return overruns; | |
2711 | } | |
c4f50183 | 2712 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
7a8e76a3 | 2713 | |
642edba5 | 2714 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
7a8e76a3 SR |
2715 | { |
2716 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
2717 | ||
d769041f SR |
2718 | /* Iterator usage is expected to have record disabled */ |
2719 | if (list_empty(&cpu_buffer->reader_page->list)) { | |
77ae365e SR |
2720 | iter->head_page = rb_set_head_page(cpu_buffer); |
2721 | if (unlikely(!iter->head_page)) | |
2722 | return; | |
2723 | iter->head = iter->head_page->read; | |
d769041f SR |
2724 | } else { |
2725 | iter->head_page = cpu_buffer->reader_page; | |
6f807acd | 2726 | iter->head = cpu_buffer->reader_page->read; |
d769041f SR |
2727 | } |
2728 | if (iter->head) | |
2729 | iter->read_stamp = cpu_buffer->read_stamp; | |
2730 | else | |
abc9b56d | 2731 | iter->read_stamp = iter->head_page->page->time_stamp; |
492a74f4 SR |
2732 | iter->cache_reader_page = cpu_buffer->reader_page; |
2733 | iter->cache_read = cpu_buffer->read; | |
642edba5 | 2734 | } |
f83c9d0f | 2735 | |
642edba5 SR |
2736 | /** |
2737 | * ring_buffer_iter_reset - reset an iterator | |
2738 | * @iter: The iterator to reset | |
2739 | * | |
2740 | * Resets the iterator, so that it will start from the beginning | |
2741 | * again. | |
2742 | */ | |
2743 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) | |
2744 | { | |
554f786e | 2745 | struct ring_buffer_per_cpu *cpu_buffer; |
642edba5 SR |
2746 | unsigned long flags; |
2747 | ||
554f786e SR |
2748 | if (!iter) |
2749 | return; | |
2750 | ||
2751 | cpu_buffer = iter->cpu_buffer; | |
2752 | ||
642edba5 SR |
2753 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
2754 | rb_iter_reset(iter); | |
f83c9d0f | 2755 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 2756 | } |
c4f50183 | 2757 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
7a8e76a3 SR |
2758 | |
2759 | /** | |
2760 | * ring_buffer_iter_empty - check if an iterator has no more to read | |
2761 | * @iter: The iterator to check | |
2762 | */ | |
2763 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) | |
2764 | { | |
2765 | struct ring_buffer_per_cpu *cpu_buffer; | |
2766 | ||
2767 | cpu_buffer = iter->cpu_buffer; | |
2768 | ||
bf41a158 SR |
2769 | return iter->head_page == cpu_buffer->commit_page && |
2770 | iter->head == rb_commit_index(cpu_buffer); | |
7a8e76a3 | 2771 | } |
c4f50183 | 2772 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
7a8e76a3 SR |
2773 | |
2774 | static void | |
2775 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
2776 | struct ring_buffer_event *event) | |
2777 | { | |
2778 | u64 delta; | |
2779 | ||
334d4169 | 2780 | switch (event->type_len) { |
7a8e76a3 SR |
2781 | case RINGBUF_TYPE_PADDING: |
2782 | return; | |
2783 | ||
2784 | case RINGBUF_TYPE_TIME_EXTEND: | |
2785 | delta = event->array[0]; | |
2786 | delta <<= TS_SHIFT; | |
2787 | delta += event->time_delta; | |
2788 | cpu_buffer->read_stamp += delta; | |
2789 | return; | |
2790 | ||
2791 | case RINGBUF_TYPE_TIME_STAMP: | |
2792 | /* FIXME: not implemented */ | |
2793 | return; | |
2794 | ||
2795 | case RINGBUF_TYPE_DATA: | |
2796 | cpu_buffer->read_stamp += event->time_delta; | |
2797 | return; | |
2798 | ||
2799 | default: | |
2800 | BUG(); | |
2801 | } | |
2802 | return; | |
2803 | } | |
2804 | ||
2805 | static void | |
2806 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, | |
2807 | struct ring_buffer_event *event) | |
2808 | { | |
2809 | u64 delta; | |
2810 | ||
334d4169 | 2811 | switch (event->type_len) { |
7a8e76a3 SR |
2812 | case RINGBUF_TYPE_PADDING: |
2813 | return; | |
2814 | ||
2815 | case RINGBUF_TYPE_TIME_EXTEND: | |
2816 | delta = event->array[0]; | |
2817 | delta <<= TS_SHIFT; | |
2818 | delta += event->time_delta; | |
2819 | iter->read_stamp += delta; | |
2820 | return; | |
2821 | ||
2822 | case RINGBUF_TYPE_TIME_STAMP: | |
2823 | /* FIXME: not implemented */ | |
2824 | return; | |
2825 | ||
2826 | case RINGBUF_TYPE_DATA: | |
2827 | iter->read_stamp += event->time_delta; | |
2828 | return; | |
2829 | ||
2830 | default: | |
2831 | BUG(); | |
2832 | } | |
2833 | return; | |
2834 | } | |
2835 | ||
d769041f SR |
2836 | static struct buffer_page * |
2837 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 2838 | { |
d769041f SR |
2839 | struct buffer_page *reader = NULL; |
2840 | unsigned long flags; | |
818e3dd3 | 2841 | int nr_loops = 0; |
77ae365e | 2842 | int ret; |
d769041f | 2843 | |
3e03fb7f | 2844 | local_irq_save(flags); |
0199c4e6 | 2845 | arch_spin_lock(&cpu_buffer->lock); |
d769041f SR |
2846 | |
2847 | again: | |
818e3dd3 SR |
2848 | /* |
2849 | * This should normally only loop twice. But because the | |
2850 | * start of the reader inserts an empty page, it causes | |
2851 | * a case where we will loop three times. There should be no | |
2852 | * reason to loop four times (that I know of). | |
2853 | */ | |
3e89c7bb | 2854 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
818e3dd3 SR |
2855 | reader = NULL; |
2856 | goto out; | |
2857 | } | |
2858 | ||
d769041f SR |
2859 | reader = cpu_buffer->reader_page; |
2860 | ||
2861 | /* If there's more to read, return this page */ | |
bf41a158 | 2862 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
d769041f SR |
2863 | goto out; |
2864 | ||
2865 | /* Never should we have an index greater than the size */ | |
3e89c7bb SR |
2866 | if (RB_WARN_ON(cpu_buffer, |
2867 | cpu_buffer->reader_page->read > rb_page_size(reader))) | |
2868 | goto out; | |
d769041f SR |
2869 | |
2870 | /* check if we caught up to the tail */ | |
2871 | reader = NULL; | |
bf41a158 | 2872 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
d769041f | 2873 | goto out; |
7a8e76a3 SR |
2874 | |
2875 | /* | |
d769041f | 2876 | * Reset the reader page to size zero. |
7a8e76a3 | 2877 | */ |
77ae365e SR |
2878 | local_set(&cpu_buffer->reader_page->write, 0); |
2879 | local_set(&cpu_buffer->reader_page->entries, 0); | |
2880 | local_set(&cpu_buffer->reader_page->page->commit, 0); | |
7a8e76a3 | 2881 | |
77ae365e SR |
2882 | spin: |
2883 | /* | |
2884 | * Splice the empty reader page into the list around the head. | |
2885 | */ | |
2886 | reader = rb_set_head_page(cpu_buffer); | |
0e1ff5d7 | 2887 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
d769041f | 2888 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
bf41a158 | 2889 | |
3adc54fa SR |
2890 | /* |
2891 | * cpu_buffer->pages just needs to point to the buffer, it | |
2892 | * has no specific buffer page to point to. Lets move it out | |
2893 | * of our way so we don't accidently swap it. | |
2894 | */ | |
2895 | cpu_buffer->pages = reader->list.prev; | |
2896 | ||
77ae365e SR |
2897 | /* The reader page will be pointing to the new head */ |
2898 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); | |
7a8e76a3 | 2899 | |
77ae365e SR |
2900 | /* |
2901 | * Here's the tricky part. | |
2902 | * | |
2903 | * We need to move the pointer past the header page. | |
2904 | * But we can only do that if a writer is not currently | |
2905 | * moving it. The page before the header page has the | |
2906 | * flag bit '1' set if it is pointing to the page we want. | |
2907 | * but if the writer is in the process of moving it | |
2908 | * than it will be '2' or already moved '0'. | |
2909 | */ | |
2910 | ||
2911 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); | |
7a8e76a3 SR |
2912 | |
2913 | /* | |
77ae365e | 2914 | * If we did not convert it, then we must try again. |
7a8e76a3 | 2915 | */ |
77ae365e SR |
2916 | if (!ret) |
2917 | goto spin; | |
7a8e76a3 | 2918 | |
77ae365e SR |
2919 | /* |
2920 | * Yeah! We succeeded in replacing the page. | |
2921 | * | |
2922 | * Now make the new head point back to the reader page. | |
2923 | */ | |
5ded3dc6 | 2924 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
77ae365e | 2925 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
d769041f SR |
2926 | |
2927 | /* Finally update the reader page to the new head */ | |
2928 | cpu_buffer->reader_page = reader; | |
2929 | rb_reset_reader_page(cpu_buffer); | |
2930 | ||
2931 | goto again; | |
2932 | ||
2933 | out: | |
0199c4e6 | 2934 | arch_spin_unlock(&cpu_buffer->lock); |
3e03fb7f | 2935 | local_irq_restore(flags); |
d769041f SR |
2936 | |
2937 | return reader; | |
2938 | } | |
2939 | ||
2940 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) | |
2941 | { | |
2942 | struct ring_buffer_event *event; | |
2943 | struct buffer_page *reader; | |
2944 | unsigned length; | |
2945 | ||
2946 | reader = rb_get_reader_page(cpu_buffer); | |
7a8e76a3 | 2947 | |
d769041f | 2948 | /* This function should not be called when buffer is empty */ |
3e89c7bb SR |
2949 | if (RB_WARN_ON(cpu_buffer, !reader)) |
2950 | return; | |
7a8e76a3 | 2951 | |
d769041f SR |
2952 | event = rb_reader_event(cpu_buffer); |
2953 | ||
a1863c21 | 2954 | if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
e4906eff | 2955 | cpu_buffer->read++; |
d769041f SR |
2956 | |
2957 | rb_update_read_stamp(cpu_buffer, event); | |
2958 | ||
2959 | length = rb_event_length(event); | |
6f807acd | 2960 | cpu_buffer->reader_page->read += length; |
7a8e76a3 SR |
2961 | } |
2962 | ||
2963 | static void rb_advance_iter(struct ring_buffer_iter *iter) | |
2964 | { | |
2965 | struct ring_buffer *buffer; | |
2966 | struct ring_buffer_per_cpu *cpu_buffer; | |
2967 | struct ring_buffer_event *event; | |
2968 | unsigned length; | |
2969 | ||
2970 | cpu_buffer = iter->cpu_buffer; | |
2971 | buffer = cpu_buffer->buffer; | |
2972 | ||
2973 | /* | |
2974 | * Check if we are at the end of the buffer. | |
2975 | */ | |
bf41a158 | 2976 | if (iter->head >= rb_page_size(iter->head_page)) { |
ea05b57c SR |
2977 | /* discarded commits can make the page empty */ |
2978 | if (iter->head_page == cpu_buffer->commit_page) | |
3e89c7bb | 2979 | return; |
d769041f | 2980 | rb_inc_iter(iter); |
7a8e76a3 SR |
2981 | return; |
2982 | } | |
2983 | ||
2984 | event = rb_iter_head_event(iter); | |
2985 | ||
2986 | length = rb_event_length(event); | |
2987 | ||
2988 | /* | |
2989 | * This should not be called to advance the header if we are | |
2990 | * at the tail of the buffer. | |
2991 | */ | |
3e89c7bb | 2992 | if (RB_WARN_ON(cpu_buffer, |
f536aafc | 2993 | (iter->head_page == cpu_buffer->commit_page) && |
3e89c7bb SR |
2994 | (iter->head + length > rb_commit_index(cpu_buffer)))) |
2995 | return; | |
7a8e76a3 SR |
2996 | |
2997 | rb_update_iter_read_stamp(iter, event); | |
2998 | ||
2999 | iter->head += length; | |
3000 | ||
3001 | /* check for end of page padding */ | |
bf41a158 SR |
3002 | if ((iter->head >= rb_page_size(iter->head_page)) && |
3003 | (iter->head_page != cpu_buffer->commit_page)) | |
7a8e76a3 SR |
3004 | rb_advance_iter(iter); |
3005 | } | |
3006 | ||
f83c9d0f | 3007 | static struct ring_buffer_event * |
d8eeb2d3 | 3008 | rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts) |
7a8e76a3 | 3009 | { |
7a8e76a3 | 3010 | struct ring_buffer_event *event; |
d769041f | 3011 | struct buffer_page *reader; |
818e3dd3 | 3012 | int nr_loops = 0; |
7a8e76a3 | 3013 | |
7a8e76a3 | 3014 | again: |
818e3dd3 SR |
3015 | /* |
3016 | * We repeat when a timestamp is encountered. It is possible | |
3017 | * to get multiple timestamps from an interrupt entering just | |
ea05b57c SR |
3018 | * as one timestamp is about to be written, or from discarded |
3019 | * commits. The most that we can have is the number on a single page. | |
818e3dd3 | 3020 | */ |
ea05b57c | 3021 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE)) |
818e3dd3 | 3022 | return NULL; |
818e3dd3 | 3023 | |
d769041f SR |
3024 | reader = rb_get_reader_page(cpu_buffer); |
3025 | if (!reader) | |
7a8e76a3 SR |
3026 | return NULL; |
3027 | ||
d769041f | 3028 | event = rb_reader_event(cpu_buffer); |
7a8e76a3 | 3029 | |
334d4169 | 3030 | switch (event->type_len) { |
7a8e76a3 | 3031 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3032 | if (rb_null_event(event)) |
3033 | RB_WARN_ON(cpu_buffer, 1); | |
3034 | /* | |
3035 | * Because the writer could be discarding every | |
3036 | * event it creates (which would probably be bad) | |
3037 | * if we were to go back to "again" then we may never | |
3038 | * catch up, and will trigger the warn on, or lock | |
3039 | * the box. Return the padding, and we will release | |
3040 | * the current locks, and try again. | |
3041 | */ | |
2d622719 | 3042 | return event; |
7a8e76a3 SR |
3043 | |
3044 | case RINGBUF_TYPE_TIME_EXTEND: | |
3045 | /* Internal data, OK to advance */ | |
d769041f | 3046 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3047 | goto again; |
3048 | ||
3049 | case RINGBUF_TYPE_TIME_STAMP: | |
3050 | /* FIXME: not implemented */ | |
d769041f | 3051 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3052 | goto again; |
3053 | ||
3054 | case RINGBUF_TYPE_DATA: | |
3055 | if (ts) { | |
3056 | *ts = cpu_buffer->read_stamp + event->time_delta; | |
d8eeb2d3 | 3057 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
37886f6a | 3058 | cpu_buffer->cpu, ts); |
7a8e76a3 SR |
3059 | } |
3060 | return event; | |
3061 | ||
3062 | default: | |
3063 | BUG(); | |
3064 | } | |
3065 | ||
3066 | return NULL; | |
3067 | } | |
c4f50183 | 3068 | EXPORT_SYMBOL_GPL(ring_buffer_peek); |
7a8e76a3 | 3069 | |
f83c9d0f SR |
3070 | static struct ring_buffer_event * |
3071 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
7a8e76a3 SR |
3072 | { |
3073 | struct ring_buffer *buffer; | |
3074 | struct ring_buffer_per_cpu *cpu_buffer; | |
3075 | struct ring_buffer_event *event; | |
818e3dd3 | 3076 | int nr_loops = 0; |
7a8e76a3 | 3077 | |
7a8e76a3 SR |
3078 | cpu_buffer = iter->cpu_buffer; |
3079 | buffer = cpu_buffer->buffer; | |
3080 | ||
492a74f4 SR |
3081 | /* |
3082 | * Check if someone performed a consuming read to | |
3083 | * the buffer. A consuming read invalidates the iterator | |
3084 | * and we need to reset the iterator in this case. | |
3085 | */ | |
3086 | if (unlikely(iter->cache_read != cpu_buffer->read || | |
3087 | iter->cache_reader_page != cpu_buffer->reader_page)) | |
3088 | rb_iter_reset(iter); | |
3089 | ||
7a8e76a3 | 3090 | again: |
3c05d748 SR |
3091 | if (ring_buffer_iter_empty(iter)) |
3092 | return NULL; | |
3093 | ||
818e3dd3 | 3094 | /* |
ea05b57c SR |
3095 | * We repeat when a timestamp is encountered. |
3096 | * We can get multiple timestamps by nested interrupts or also | |
3097 | * if filtering is on (discarding commits). Since discarding | |
3098 | * commits can be frequent we can get a lot of timestamps. | |
3099 | * But we limit them by not adding timestamps if they begin | |
3100 | * at the start of a page. | |
818e3dd3 | 3101 | */ |
ea05b57c | 3102 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE)) |
818e3dd3 | 3103 | return NULL; |
818e3dd3 | 3104 | |
7a8e76a3 SR |
3105 | if (rb_per_cpu_empty(cpu_buffer)) |
3106 | return NULL; | |
3107 | ||
3c05d748 SR |
3108 | if (iter->head >= local_read(&iter->head_page->page->commit)) { |
3109 | rb_inc_iter(iter); | |
3110 | goto again; | |
3111 | } | |
3112 | ||
7a8e76a3 SR |
3113 | event = rb_iter_head_event(iter); |
3114 | ||
334d4169 | 3115 | switch (event->type_len) { |
7a8e76a3 | 3116 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3117 | if (rb_null_event(event)) { |
3118 | rb_inc_iter(iter); | |
3119 | goto again; | |
3120 | } | |
3121 | rb_advance_iter(iter); | |
3122 | return event; | |
7a8e76a3 SR |
3123 | |
3124 | case RINGBUF_TYPE_TIME_EXTEND: | |
3125 | /* Internal data, OK to advance */ | |
3126 | rb_advance_iter(iter); | |
3127 | goto again; | |
3128 | ||
3129 | case RINGBUF_TYPE_TIME_STAMP: | |
3130 | /* FIXME: not implemented */ | |
3131 | rb_advance_iter(iter); | |
3132 | goto again; | |
3133 | ||
3134 | case RINGBUF_TYPE_DATA: | |
3135 | if (ts) { | |
3136 | *ts = iter->read_stamp + event->time_delta; | |
37886f6a SR |
3137 | ring_buffer_normalize_time_stamp(buffer, |
3138 | cpu_buffer->cpu, ts); | |
7a8e76a3 SR |
3139 | } |
3140 | return event; | |
3141 | ||
3142 | default: | |
3143 | BUG(); | |
3144 | } | |
3145 | ||
3146 | return NULL; | |
3147 | } | |
c4f50183 | 3148 | EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
7a8e76a3 | 3149 | |
8d707e8e SR |
3150 | static inline int rb_ok_to_lock(void) |
3151 | { | |
3152 | /* | |
3153 | * If an NMI die dumps out the content of the ring buffer | |
3154 | * do not grab locks. We also permanently disable the ring | |
3155 | * buffer too. A one time deal is all you get from reading | |
3156 | * the ring buffer from an NMI. | |
3157 | */ | |
464e85eb | 3158 | if (likely(!in_nmi())) |
8d707e8e SR |
3159 | return 1; |
3160 | ||
3161 | tracing_off_permanent(); | |
3162 | return 0; | |
3163 | } | |
3164 | ||
f83c9d0f SR |
3165 | /** |
3166 | * ring_buffer_peek - peek at the next event to be read | |
3167 | * @buffer: The ring buffer to read | |
3168 | * @cpu: The cpu to peak at | |
3169 | * @ts: The timestamp counter of this event. | |
3170 | * | |
3171 | * This will return the event that will be read next, but does | |
3172 | * not consume the data. | |
3173 | */ | |
3174 | struct ring_buffer_event * | |
3175 | ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) | |
3176 | { | |
3177 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
8aabee57 | 3178 | struct ring_buffer_event *event; |
f83c9d0f | 3179 | unsigned long flags; |
8d707e8e | 3180 | int dolock; |
f83c9d0f | 3181 | |
554f786e | 3182 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3183 | return NULL; |
554f786e | 3184 | |
8d707e8e | 3185 | dolock = rb_ok_to_lock(); |
2d622719 | 3186 | again: |
8d707e8e SR |
3187 | local_irq_save(flags); |
3188 | if (dolock) | |
3189 | spin_lock(&cpu_buffer->reader_lock); | |
d8eeb2d3 | 3190 | event = rb_buffer_peek(cpu_buffer, ts); |
469535a5 RR |
3191 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3192 | rb_advance_reader(cpu_buffer); | |
8d707e8e SR |
3193 | if (dolock) |
3194 | spin_unlock(&cpu_buffer->reader_lock); | |
3195 | local_irq_restore(flags); | |
f83c9d0f | 3196 | |
1b959e18 | 3197 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3198 | goto again; |
2d622719 | 3199 | |
f83c9d0f SR |
3200 | return event; |
3201 | } | |
3202 | ||
3203 | /** | |
3204 | * ring_buffer_iter_peek - peek at the next event to be read | |
3205 | * @iter: The ring buffer iterator | |
3206 | * @ts: The timestamp counter of this event. | |
3207 | * | |
3208 | * This will return the event that will be read next, but does | |
3209 | * not increment the iterator. | |
3210 | */ | |
3211 | struct ring_buffer_event * | |
3212 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
3213 | { | |
3214 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3215 | struct ring_buffer_event *event; | |
3216 | unsigned long flags; | |
3217 | ||
2d622719 | 3218 | again: |
f83c9d0f SR |
3219 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3220 | event = rb_iter_peek(iter, ts); | |
3221 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
3222 | ||
1b959e18 | 3223 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3224 | goto again; |
2d622719 | 3225 | |
f83c9d0f SR |
3226 | return event; |
3227 | } | |
3228 | ||
7a8e76a3 SR |
3229 | /** |
3230 | * ring_buffer_consume - return an event and consume it | |
3231 | * @buffer: The ring buffer to get the next event from | |
3232 | * | |
3233 | * Returns the next event in the ring buffer, and that event is consumed. | |
3234 | * Meaning, that sequential reads will keep returning a different event, | |
3235 | * and eventually empty the ring buffer if the producer is slower. | |
3236 | */ | |
3237 | struct ring_buffer_event * | |
3238 | ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) | |
3239 | { | |
554f786e SR |
3240 | struct ring_buffer_per_cpu *cpu_buffer; |
3241 | struct ring_buffer_event *event = NULL; | |
f83c9d0f | 3242 | unsigned long flags; |
8d707e8e SR |
3243 | int dolock; |
3244 | ||
3245 | dolock = rb_ok_to_lock(); | |
7a8e76a3 | 3246 | |
2d622719 | 3247 | again: |
554f786e SR |
3248 | /* might be called in atomic */ |
3249 | preempt_disable(); | |
3250 | ||
9e01c1b7 | 3251 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e | 3252 | goto out; |
7a8e76a3 | 3253 | |
554f786e | 3254 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e SR |
3255 | local_irq_save(flags); |
3256 | if (dolock) | |
3257 | spin_lock(&cpu_buffer->reader_lock); | |
f83c9d0f | 3258 | |
d8eeb2d3 | 3259 | event = rb_buffer_peek(cpu_buffer, ts); |
469535a5 RR |
3260 | if (event) |
3261 | rb_advance_reader(cpu_buffer); | |
7a8e76a3 | 3262 | |
8d707e8e SR |
3263 | if (dolock) |
3264 | spin_unlock(&cpu_buffer->reader_lock); | |
3265 | local_irq_restore(flags); | |
f83c9d0f | 3266 | |
554f786e SR |
3267 | out: |
3268 | preempt_enable(); | |
3269 | ||
1b959e18 | 3270 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3271 | goto again; |
2d622719 | 3272 | |
7a8e76a3 SR |
3273 | return event; |
3274 | } | |
c4f50183 | 3275 | EXPORT_SYMBOL_GPL(ring_buffer_consume); |
7a8e76a3 SR |
3276 | |
3277 | /** | |
3278 | * ring_buffer_read_start - start a non consuming read of the buffer | |
3279 | * @buffer: The ring buffer to read from | |
3280 | * @cpu: The cpu buffer to iterate over | |
3281 | * | |
3282 | * This starts up an iteration through the buffer. It also disables | |
3283 | * the recording to the buffer until the reading is finished. | |
3284 | * This prevents the reading from being corrupted. This is not | |
3285 | * a consuming read, so a producer is not expected. | |
3286 | * | |
3287 | * Must be paired with ring_buffer_finish. | |
3288 | */ | |
3289 | struct ring_buffer_iter * | |
3290 | ring_buffer_read_start(struct ring_buffer *buffer, int cpu) | |
3291 | { | |
3292 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 3293 | struct ring_buffer_iter *iter; |
d769041f | 3294 | unsigned long flags; |
7a8e76a3 | 3295 | |
9e01c1b7 | 3296 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3297 | return NULL; |
7a8e76a3 SR |
3298 | |
3299 | iter = kmalloc(sizeof(*iter), GFP_KERNEL); | |
3300 | if (!iter) | |
8aabee57 | 3301 | return NULL; |
7a8e76a3 SR |
3302 | |
3303 | cpu_buffer = buffer->buffers[cpu]; | |
3304 | ||
3305 | iter->cpu_buffer = cpu_buffer; | |
3306 | ||
3307 | atomic_inc(&cpu_buffer->record_disabled); | |
3308 | synchronize_sched(); | |
3309 | ||
f83c9d0f | 3310 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
0199c4e6 | 3311 | arch_spin_lock(&cpu_buffer->lock); |
642edba5 | 3312 | rb_iter_reset(iter); |
0199c4e6 | 3313 | arch_spin_unlock(&cpu_buffer->lock); |
f83c9d0f | 3314 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 SR |
3315 | |
3316 | return iter; | |
3317 | } | |
c4f50183 | 3318 | EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
7a8e76a3 SR |
3319 | |
3320 | /** | |
3321 | * ring_buffer_finish - finish reading the iterator of the buffer | |
3322 | * @iter: The iterator retrieved by ring_buffer_start | |
3323 | * | |
3324 | * This re-enables the recording to the buffer, and frees the | |
3325 | * iterator. | |
3326 | */ | |
3327 | void | |
3328 | ring_buffer_read_finish(struct ring_buffer_iter *iter) | |
3329 | { | |
3330 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3331 | ||
3332 | atomic_dec(&cpu_buffer->record_disabled); | |
3333 | kfree(iter); | |
3334 | } | |
c4f50183 | 3335 | EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
7a8e76a3 SR |
3336 | |
3337 | /** | |
3338 | * ring_buffer_read - read the next item in the ring buffer by the iterator | |
3339 | * @iter: The ring buffer iterator | |
3340 | * @ts: The time stamp of the event read. | |
3341 | * | |
3342 | * This reads the next event in the ring buffer and increments the iterator. | |
3343 | */ | |
3344 | struct ring_buffer_event * | |
3345 | ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) | |
3346 | { | |
3347 | struct ring_buffer_event *event; | |
f83c9d0f SR |
3348 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
3349 | unsigned long flags; | |
7a8e76a3 | 3350 | |
f83c9d0f | 3351 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
7e9391cf | 3352 | again: |
f83c9d0f | 3353 | event = rb_iter_peek(iter, ts); |
7a8e76a3 | 3354 | if (!event) |
f83c9d0f | 3355 | goto out; |
7a8e76a3 | 3356 | |
7e9391cf SR |
3357 | if (event->type_len == RINGBUF_TYPE_PADDING) |
3358 | goto again; | |
3359 | ||
7a8e76a3 | 3360 | rb_advance_iter(iter); |
f83c9d0f SR |
3361 | out: |
3362 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
7a8e76a3 SR |
3363 | |
3364 | return event; | |
3365 | } | |
c4f50183 | 3366 | EXPORT_SYMBOL_GPL(ring_buffer_read); |
7a8e76a3 SR |
3367 | |
3368 | /** | |
3369 | * ring_buffer_size - return the size of the ring buffer (in bytes) | |
3370 | * @buffer: The ring buffer. | |
3371 | */ | |
3372 | unsigned long ring_buffer_size(struct ring_buffer *buffer) | |
3373 | { | |
3374 | return BUF_PAGE_SIZE * buffer->pages; | |
3375 | } | |
c4f50183 | 3376 | EXPORT_SYMBOL_GPL(ring_buffer_size); |
7a8e76a3 SR |
3377 | |
3378 | static void | |
3379 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) | |
3380 | { | |
77ae365e SR |
3381 | rb_head_page_deactivate(cpu_buffer); |
3382 | ||
7a8e76a3 | 3383 | cpu_buffer->head_page |
3adc54fa | 3384 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 3385 | local_set(&cpu_buffer->head_page->write, 0); |
778c55d4 | 3386 | local_set(&cpu_buffer->head_page->entries, 0); |
abc9b56d | 3387 | local_set(&cpu_buffer->head_page->page->commit, 0); |
d769041f | 3388 | |
6f807acd | 3389 | cpu_buffer->head_page->read = 0; |
bf41a158 SR |
3390 | |
3391 | cpu_buffer->tail_page = cpu_buffer->head_page; | |
3392 | cpu_buffer->commit_page = cpu_buffer->head_page; | |
3393 | ||
3394 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); | |
3395 | local_set(&cpu_buffer->reader_page->write, 0); | |
778c55d4 | 3396 | local_set(&cpu_buffer->reader_page->entries, 0); |
abc9b56d | 3397 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
6f807acd | 3398 | cpu_buffer->reader_page->read = 0; |
7a8e76a3 | 3399 | |
77ae365e SR |
3400 | local_set(&cpu_buffer->commit_overrun, 0); |
3401 | local_set(&cpu_buffer->overrun, 0); | |
e4906eff | 3402 | local_set(&cpu_buffer->entries, 0); |
fa743953 SR |
3403 | local_set(&cpu_buffer->committing, 0); |
3404 | local_set(&cpu_buffer->commits, 0); | |
77ae365e | 3405 | cpu_buffer->read = 0; |
69507c06 SR |
3406 | |
3407 | cpu_buffer->write_stamp = 0; | |
3408 | cpu_buffer->read_stamp = 0; | |
77ae365e SR |
3409 | |
3410 | rb_head_page_activate(cpu_buffer); | |
7a8e76a3 SR |
3411 | } |
3412 | ||
3413 | /** | |
3414 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
3415 | * @buffer: The ring buffer to reset a per cpu buffer of | |
3416 | * @cpu: The CPU buffer to be reset | |
3417 | */ | |
3418 | void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) | |
3419 | { | |
3420 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
3421 | unsigned long flags; | |
3422 | ||
9e01c1b7 | 3423 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3424 | return; |
7a8e76a3 | 3425 | |
41ede23e SR |
3426 | atomic_inc(&cpu_buffer->record_disabled); |
3427 | ||
f83c9d0f SR |
3428 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
3429 | ||
41b6a95d SR |
3430 | if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) |
3431 | goto out; | |
3432 | ||
0199c4e6 | 3433 | arch_spin_lock(&cpu_buffer->lock); |
7a8e76a3 SR |
3434 | |
3435 | rb_reset_cpu(cpu_buffer); | |
3436 | ||
0199c4e6 | 3437 | arch_spin_unlock(&cpu_buffer->lock); |
f83c9d0f | 3438 | |
41b6a95d | 3439 | out: |
f83c9d0f | 3440 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
41ede23e SR |
3441 | |
3442 | atomic_dec(&cpu_buffer->record_disabled); | |
7a8e76a3 | 3443 | } |
c4f50183 | 3444 | EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); |
7a8e76a3 SR |
3445 | |
3446 | /** | |
3447 | * ring_buffer_reset - reset a ring buffer | |
3448 | * @buffer: The ring buffer to reset all cpu buffers | |
3449 | */ | |
3450 | void ring_buffer_reset(struct ring_buffer *buffer) | |
3451 | { | |
7a8e76a3 SR |
3452 | int cpu; |
3453 | ||
7a8e76a3 | 3454 | for_each_buffer_cpu(buffer, cpu) |
d769041f | 3455 | ring_buffer_reset_cpu(buffer, cpu); |
7a8e76a3 | 3456 | } |
c4f50183 | 3457 | EXPORT_SYMBOL_GPL(ring_buffer_reset); |
7a8e76a3 SR |
3458 | |
3459 | /** | |
3460 | * rind_buffer_empty - is the ring buffer empty? | |
3461 | * @buffer: The ring buffer to test | |
3462 | */ | |
3463 | int ring_buffer_empty(struct ring_buffer *buffer) | |
3464 | { | |
3465 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 3466 | unsigned long flags; |
8d707e8e | 3467 | int dolock; |
7a8e76a3 | 3468 | int cpu; |
d4788207 | 3469 | int ret; |
7a8e76a3 | 3470 | |
8d707e8e | 3471 | dolock = rb_ok_to_lock(); |
7a8e76a3 SR |
3472 | |
3473 | /* yes this is racy, but if you don't like the race, lock the buffer */ | |
3474 | for_each_buffer_cpu(buffer, cpu) { | |
3475 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e SR |
3476 | local_irq_save(flags); |
3477 | if (dolock) | |
3478 | spin_lock(&cpu_buffer->reader_lock); | |
d4788207 | 3479 | ret = rb_per_cpu_empty(cpu_buffer); |
8d707e8e SR |
3480 | if (dolock) |
3481 | spin_unlock(&cpu_buffer->reader_lock); | |
3482 | local_irq_restore(flags); | |
3483 | ||
d4788207 | 3484 | if (!ret) |
7a8e76a3 SR |
3485 | return 0; |
3486 | } | |
554f786e | 3487 | |
7a8e76a3 SR |
3488 | return 1; |
3489 | } | |
c4f50183 | 3490 | EXPORT_SYMBOL_GPL(ring_buffer_empty); |
7a8e76a3 SR |
3491 | |
3492 | /** | |
3493 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? | |
3494 | * @buffer: The ring buffer | |
3495 | * @cpu: The CPU buffer to test | |
3496 | */ | |
3497 | int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) | |
3498 | { | |
3499 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 3500 | unsigned long flags; |
8d707e8e | 3501 | int dolock; |
8aabee57 | 3502 | int ret; |
7a8e76a3 | 3503 | |
9e01c1b7 | 3504 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3505 | return 1; |
7a8e76a3 | 3506 | |
8d707e8e SR |
3507 | dolock = rb_ok_to_lock(); |
3508 | ||
7a8e76a3 | 3509 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e SR |
3510 | local_irq_save(flags); |
3511 | if (dolock) | |
3512 | spin_lock(&cpu_buffer->reader_lock); | |
554f786e | 3513 | ret = rb_per_cpu_empty(cpu_buffer); |
8d707e8e SR |
3514 | if (dolock) |
3515 | spin_unlock(&cpu_buffer->reader_lock); | |
3516 | local_irq_restore(flags); | |
554f786e SR |
3517 | |
3518 | return ret; | |
7a8e76a3 | 3519 | } |
c4f50183 | 3520 | EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
7a8e76a3 | 3521 | |
85bac32c | 3522 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
7a8e76a3 SR |
3523 | /** |
3524 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers | |
3525 | * @buffer_a: One buffer to swap with | |
3526 | * @buffer_b: The other buffer to swap with | |
3527 | * | |
3528 | * This function is useful for tracers that want to take a "snapshot" | |
3529 | * of a CPU buffer and has another back up buffer lying around. | |
3530 | * it is expected that the tracer handles the cpu buffer not being | |
3531 | * used at the moment. | |
3532 | */ | |
3533 | int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, | |
3534 | struct ring_buffer *buffer_b, int cpu) | |
3535 | { | |
3536 | struct ring_buffer_per_cpu *cpu_buffer_a; | |
3537 | struct ring_buffer_per_cpu *cpu_buffer_b; | |
554f786e SR |
3538 | int ret = -EINVAL; |
3539 | ||
9e01c1b7 RR |
3540 | if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
3541 | !cpumask_test_cpu(cpu, buffer_b->cpumask)) | |
554f786e | 3542 | goto out; |
7a8e76a3 SR |
3543 | |
3544 | /* At least make sure the two buffers are somewhat the same */ | |
6d102bc6 | 3545 | if (buffer_a->pages != buffer_b->pages) |
554f786e SR |
3546 | goto out; |
3547 | ||
3548 | ret = -EAGAIN; | |
7a8e76a3 | 3549 | |
97b17efe | 3550 | if (ring_buffer_flags != RB_BUFFERS_ON) |
554f786e | 3551 | goto out; |
97b17efe SR |
3552 | |
3553 | if (atomic_read(&buffer_a->record_disabled)) | |
554f786e | 3554 | goto out; |
97b17efe SR |
3555 | |
3556 | if (atomic_read(&buffer_b->record_disabled)) | |
554f786e | 3557 | goto out; |
97b17efe | 3558 | |
7a8e76a3 SR |
3559 | cpu_buffer_a = buffer_a->buffers[cpu]; |
3560 | cpu_buffer_b = buffer_b->buffers[cpu]; | |
3561 | ||
97b17efe | 3562 | if (atomic_read(&cpu_buffer_a->record_disabled)) |
554f786e | 3563 | goto out; |
97b17efe SR |
3564 | |
3565 | if (atomic_read(&cpu_buffer_b->record_disabled)) | |
554f786e | 3566 | goto out; |
97b17efe | 3567 | |
7a8e76a3 SR |
3568 | /* |
3569 | * We can't do a synchronize_sched here because this | |
3570 | * function can be called in atomic context. | |
3571 | * Normally this will be called from the same CPU as cpu. | |
3572 | * If not it's up to the caller to protect this. | |
3573 | */ | |
3574 | atomic_inc(&cpu_buffer_a->record_disabled); | |
3575 | atomic_inc(&cpu_buffer_b->record_disabled); | |
3576 | ||
98277991 SR |
3577 | ret = -EBUSY; |
3578 | if (local_read(&cpu_buffer_a->committing)) | |
3579 | goto out_dec; | |
3580 | if (local_read(&cpu_buffer_b->committing)) | |
3581 | goto out_dec; | |
3582 | ||
7a8e76a3 SR |
3583 | buffer_a->buffers[cpu] = cpu_buffer_b; |
3584 | buffer_b->buffers[cpu] = cpu_buffer_a; | |
3585 | ||
3586 | cpu_buffer_b->buffer = buffer_a; | |
3587 | cpu_buffer_a->buffer = buffer_b; | |
3588 | ||
98277991 SR |
3589 | ret = 0; |
3590 | ||
3591 | out_dec: | |
7a8e76a3 SR |
3592 | atomic_dec(&cpu_buffer_a->record_disabled); |
3593 | atomic_dec(&cpu_buffer_b->record_disabled); | |
554f786e | 3594 | out: |
554f786e | 3595 | return ret; |
7a8e76a3 | 3596 | } |
c4f50183 | 3597 | EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
85bac32c | 3598 | #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
7a8e76a3 | 3599 | |
8789a9e7 SR |
3600 | /** |
3601 | * ring_buffer_alloc_read_page - allocate a page to read from buffer | |
3602 | * @buffer: the buffer to allocate for. | |
3603 | * | |
3604 | * This function is used in conjunction with ring_buffer_read_page. | |
3605 | * When reading a full page from the ring buffer, these functions | |
3606 | * can be used to speed up the process. The calling function should | |
3607 | * allocate a few pages first with this function. Then when it | |
3608 | * needs to get pages from the ring buffer, it passes the result | |
3609 | * of this function into ring_buffer_read_page, which will swap | |
3610 | * the page that was allocated, with the read page of the buffer. | |
3611 | * | |
3612 | * Returns: | |
3613 | * The page allocated, or NULL on error. | |
3614 | */ | |
3615 | void *ring_buffer_alloc_read_page(struct ring_buffer *buffer) | |
3616 | { | |
044fa782 | 3617 | struct buffer_data_page *bpage; |
ef7a4a16 | 3618 | unsigned long addr; |
8789a9e7 SR |
3619 | |
3620 | addr = __get_free_page(GFP_KERNEL); | |
3621 | if (!addr) | |
3622 | return NULL; | |
3623 | ||
044fa782 | 3624 | bpage = (void *)addr; |
8789a9e7 | 3625 | |
ef7a4a16 SR |
3626 | rb_init_page(bpage); |
3627 | ||
044fa782 | 3628 | return bpage; |
8789a9e7 | 3629 | } |
d6ce96da | 3630 | EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
8789a9e7 SR |
3631 | |
3632 | /** | |
3633 | * ring_buffer_free_read_page - free an allocated read page | |
3634 | * @buffer: the buffer the page was allocate for | |
3635 | * @data: the page to free | |
3636 | * | |
3637 | * Free a page allocated from ring_buffer_alloc_read_page. | |
3638 | */ | |
3639 | void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) | |
3640 | { | |
3641 | free_page((unsigned long)data); | |
3642 | } | |
d6ce96da | 3643 | EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
8789a9e7 SR |
3644 | |
3645 | /** | |
3646 | * ring_buffer_read_page - extract a page from the ring buffer | |
3647 | * @buffer: buffer to extract from | |
3648 | * @data_page: the page to use allocated from ring_buffer_alloc_read_page | |
ef7a4a16 | 3649 | * @len: amount to extract |
8789a9e7 SR |
3650 | * @cpu: the cpu of the buffer to extract |
3651 | * @full: should the extraction only happen when the page is full. | |
3652 | * | |
3653 | * This function will pull out a page from the ring buffer and consume it. | |
3654 | * @data_page must be the address of the variable that was returned | |
3655 | * from ring_buffer_alloc_read_page. This is because the page might be used | |
3656 | * to swap with a page in the ring buffer. | |
3657 | * | |
3658 | * for example: | |
b85fa01e | 3659 | * rpage = ring_buffer_alloc_read_page(buffer); |
8789a9e7 SR |
3660 | * if (!rpage) |
3661 | * return error; | |
ef7a4a16 | 3662 | * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
667d2412 LJ |
3663 | * if (ret >= 0) |
3664 | * process_page(rpage, ret); | |
8789a9e7 SR |
3665 | * |
3666 | * When @full is set, the function will not return true unless | |
3667 | * the writer is off the reader page. | |
3668 | * | |
3669 | * Note: it is up to the calling functions to handle sleeps and wakeups. | |
3670 | * The ring buffer can be used anywhere in the kernel and can not | |
3671 | * blindly call wake_up. The layer that uses the ring buffer must be | |
3672 | * responsible for that. | |
3673 | * | |
3674 | * Returns: | |
667d2412 LJ |
3675 | * >=0 if data has been transferred, returns the offset of consumed data. |
3676 | * <0 if no data has been transferred. | |
8789a9e7 SR |
3677 | */ |
3678 | int ring_buffer_read_page(struct ring_buffer *buffer, | |
ef7a4a16 | 3679 | void **data_page, size_t len, int cpu, int full) |
8789a9e7 SR |
3680 | { |
3681 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
3682 | struct ring_buffer_event *event; | |
044fa782 | 3683 | struct buffer_data_page *bpage; |
ef7a4a16 | 3684 | struct buffer_page *reader; |
8789a9e7 | 3685 | unsigned long flags; |
ef7a4a16 | 3686 | unsigned int commit; |
667d2412 | 3687 | unsigned int read; |
4f3640f8 | 3688 | u64 save_timestamp; |
667d2412 | 3689 | int ret = -1; |
8789a9e7 | 3690 | |
554f786e SR |
3691 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3692 | goto out; | |
3693 | ||
474d32b6 SR |
3694 | /* |
3695 | * If len is not big enough to hold the page header, then | |
3696 | * we can not copy anything. | |
3697 | */ | |
3698 | if (len <= BUF_PAGE_HDR_SIZE) | |
554f786e | 3699 | goto out; |
474d32b6 SR |
3700 | |
3701 | len -= BUF_PAGE_HDR_SIZE; | |
3702 | ||
8789a9e7 | 3703 | if (!data_page) |
554f786e | 3704 | goto out; |
8789a9e7 | 3705 | |
044fa782 SR |
3706 | bpage = *data_page; |
3707 | if (!bpage) | |
554f786e | 3708 | goto out; |
8789a9e7 SR |
3709 | |
3710 | spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
3711 | ||
ef7a4a16 SR |
3712 | reader = rb_get_reader_page(cpu_buffer); |
3713 | if (!reader) | |
554f786e | 3714 | goto out_unlock; |
8789a9e7 | 3715 | |
ef7a4a16 SR |
3716 | event = rb_reader_event(cpu_buffer); |
3717 | ||
3718 | read = reader->read; | |
3719 | commit = rb_page_commit(reader); | |
667d2412 | 3720 | |
8789a9e7 | 3721 | /* |
474d32b6 SR |
3722 | * If this page has been partially read or |
3723 | * if len is not big enough to read the rest of the page or | |
3724 | * a writer is still on the page, then | |
3725 | * we must copy the data from the page to the buffer. | |
3726 | * Otherwise, we can simply swap the page with the one passed in. | |
8789a9e7 | 3727 | */ |
474d32b6 | 3728 | if (read || (len < (commit - read)) || |
ef7a4a16 | 3729 | cpu_buffer->reader_page == cpu_buffer->commit_page) { |
667d2412 | 3730 | struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
474d32b6 SR |
3731 | unsigned int rpos = read; |
3732 | unsigned int pos = 0; | |
ef7a4a16 | 3733 | unsigned int size; |
8789a9e7 SR |
3734 | |
3735 | if (full) | |
554f786e | 3736 | goto out_unlock; |
8789a9e7 | 3737 | |
ef7a4a16 SR |
3738 | if (len > (commit - read)) |
3739 | len = (commit - read); | |
3740 | ||
3741 | size = rb_event_length(event); | |
3742 | ||
3743 | if (len < size) | |
554f786e | 3744 | goto out_unlock; |
ef7a4a16 | 3745 | |
4f3640f8 SR |
3746 | /* save the current timestamp, since the user will need it */ |
3747 | save_timestamp = cpu_buffer->read_stamp; | |
3748 | ||
ef7a4a16 SR |
3749 | /* Need to copy one event at a time */ |
3750 | do { | |
474d32b6 | 3751 | memcpy(bpage->data + pos, rpage->data + rpos, size); |
ef7a4a16 SR |
3752 | |
3753 | len -= size; | |
3754 | ||
3755 | rb_advance_reader(cpu_buffer); | |
474d32b6 SR |
3756 | rpos = reader->read; |
3757 | pos += size; | |
ef7a4a16 SR |
3758 | |
3759 | event = rb_reader_event(cpu_buffer); | |
3760 | size = rb_event_length(event); | |
3761 | } while (len > size); | |
667d2412 LJ |
3762 | |
3763 | /* update bpage */ | |
ef7a4a16 | 3764 | local_set(&bpage->commit, pos); |
4f3640f8 | 3765 | bpage->time_stamp = save_timestamp; |
ef7a4a16 | 3766 | |
474d32b6 SR |
3767 | /* we copied everything to the beginning */ |
3768 | read = 0; | |
8789a9e7 | 3769 | } else { |
afbab76a | 3770 | /* update the entry counter */ |
77ae365e | 3771 | cpu_buffer->read += rb_page_entries(reader); |
afbab76a | 3772 | |
8789a9e7 | 3773 | /* swap the pages */ |
044fa782 | 3774 | rb_init_page(bpage); |
ef7a4a16 SR |
3775 | bpage = reader->page; |
3776 | reader->page = *data_page; | |
3777 | local_set(&reader->write, 0); | |
778c55d4 | 3778 | local_set(&reader->entries, 0); |
ef7a4a16 | 3779 | reader->read = 0; |
044fa782 | 3780 | *data_page = bpage; |
8789a9e7 | 3781 | } |
667d2412 | 3782 | ret = read; |
8789a9e7 | 3783 | |
554f786e | 3784 | out_unlock: |
8789a9e7 SR |
3785 | spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
3786 | ||
554f786e | 3787 | out: |
8789a9e7 SR |
3788 | return ret; |
3789 | } | |
d6ce96da | 3790 | EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
8789a9e7 | 3791 | |
1155de47 | 3792 | #ifdef CONFIG_TRACING |
a3583244 SR |
3793 | static ssize_t |
3794 | rb_simple_read(struct file *filp, char __user *ubuf, | |
3795 | size_t cnt, loff_t *ppos) | |
3796 | { | |
5e39841c | 3797 | unsigned long *p = filp->private_data; |
a3583244 SR |
3798 | char buf[64]; |
3799 | int r; | |
3800 | ||
033601a3 SR |
3801 | if (test_bit(RB_BUFFERS_DISABLED_BIT, p)) |
3802 | r = sprintf(buf, "permanently disabled\n"); | |
3803 | else | |
3804 | r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p)); | |
a3583244 SR |
3805 | |
3806 | return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); | |
3807 | } | |
3808 | ||
3809 | static ssize_t | |
3810 | rb_simple_write(struct file *filp, const char __user *ubuf, | |
3811 | size_t cnt, loff_t *ppos) | |
3812 | { | |
5e39841c | 3813 | unsigned long *p = filp->private_data; |
a3583244 | 3814 | char buf[64]; |
5e39841c | 3815 | unsigned long val; |
a3583244 SR |
3816 | int ret; |
3817 | ||
3818 | if (cnt >= sizeof(buf)) | |
3819 | return -EINVAL; | |
3820 | ||
3821 | if (copy_from_user(&buf, ubuf, cnt)) | |
3822 | return -EFAULT; | |
3823 | ||
3824 | buf[cnt] = 0; | |
3825 | ||
3826 | ret = strict_strtoul(buf, 10, &val); | |
3827 | if (ret < 0) | |
3828 | return ret; | |
3829 | ||
033601a3 SR |
3830 | if (val) |
3831 | set_bit(RB_BUFFERS_ON_BIT, p); | |
3832 | else | |
3833 | clear_bit(RB_BUFFERS_ON_BIT, p); | |
a3583244 SR |
3834 | |
3835 | (*ppos)++; | |
3836 | ||
3837 | return cnt; | |
3838 | } | |
3839 | ||
5e2336a0 | 3840 | static const struct file_operations rb_simple_fops = { |
a3583244 SR |
3841 | .open = tracing_open_generic, |
3842 | .read = rb_simple_read, | |
3843 | .write = rb_simple_write, | |
3844 | }; | |
3845 | ||
3846 | ||
3847 | static __init int rb_init_debugfs(void) | |
3848 | { | |
3849 | struct dentry *d_tracer; | |
a3583244 SR |
3850 | |
3851 | d_tracer = tracing_init_dentry(); | |
3852 | ||
5452af66 FW |
3853 | trace_create_file("tracing_on", 0644, d_tracer, |
3854 | &ring_buffer_flags, &rb_simple_fops); | |
a3583244 SR |
3855 | |
3856 | return 0; | |
3857 | } | |
3858 | ||
3859 | fs_initcall(rb_init_debugfs); | |
1155de47 | 3860 | #endif |
554f786e | 3861 | |
59222efe | 3862 | #ifdef CONFIG_HOTPLUG_CPU |
09c9e84d FW |
3863 | static int rb_cpu_notify(struct notifier_block *self, |
3864 | unsigned long action, void *hcpu) | |
554f786e SR |
3865 | { |
3866 | struct ring_buffer *buffer = | |
3867 | container_of(self, struct ring_buffer, cpu_notify); | |
3868 | long cpu = (long)hcpu; | |
3869 | ||
3870 | switch (action) { | |
3871 | case CPU_UP_PREPARE: | |
3872 | case CPU_UP_PREPARE_FROZEN: | |
3f237a79 | 3873 | if (cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e SR |
3874 | return NOTIFY_OK; |
3875 | ||
3876 | buffer->buffers[cpu] = | |
3877 | rb_allocate_cpu_buffer(buffer, cpu); | |
3878 | if (!buffer->buffers[cpu]) { | |
3879 | WARN(1, "failed to allocate ring buffer on CPU %ld\n", | |
3880 | cpu); | |
3881 | return NOTIFY_OK; | |
3882 | } | |
3883 | smp_wmb(); | |
3f237a79 | 3884 | cpumask_set_cpu(cpu, buffer->cpumask); |
554f786e SR |
3885 | break; |
3886 | case CPU_DOWN_PREPARE: | |
3887 | case CPU_DOWN_PREPARE_FROZEN: | |
3888 | /* | |
3889 | * Do nothing. | |
3890 | * If we were to free the buffer, then the user would | |
3891 | * lose any trace that was in the buffer. | |
3892 | */ | |
3893 | break; | |
3894 | default: | |
3895 | break; | |
3896 | } | |
3897 | return NOTIFY_OK; | |
3898 | } | |
3899 | #endif |