Commit | Line | Data |
---|---|---|
7a8e76a3 SR |
1 | /* |
2 | * Generic ring buffer | |
3 | * | |
4 | * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> | |
5 | */ | |
af658dca | 6 | #include <linux/trace_events.h> |
7a8e76a3 | 7 | #include <linux/ring_buffer.h> |
14131f2f | 8 | #include <linux/trace_clock.h> |
0b07436d | 9 | #include <linux/trace_seq.h> |
7a8e76a3 | 10 | #include <linux/spinlock.h> |
15693458 | 11 | #include <linux/irq_work.h> |
7a8e76a3 | 12 | #include <linux/uaccess.h> |
a81bd80a | 13 | #include <linux/hardirq.h> |
6c43e554 | 14 | #include <linux/kthread.h> /* for self test */ |
1744a21d | 15 | #include <linux/kmemcheck.h> |
7a8e76a3 SR |
16 | #include <linux/module.h> |
17 | #include <linux/percpu.h> | |
18 | #include <linux/mutex.h> | |
6c43e554 | 19 | #include <linux/delay.h> |
5a0e3ad6 | 20 | #include <linux/slab.h> |
7a8e76a3 SR |
21 | #include <linux/init.h> |
22 | #include <linux/hash.h> | |
23 | #include <linux/list.h> | |
554f786e | 24 | #include <linux/cpu.h> |
7a8e76a3 | 25 | |
79615760 | 26 | #include <asm/local.h> |
182e9f5f | 27 | |
83f40318 VN |
28 | static void update_pages_handler(struct work_struct *work); |
29 | ||
d1b182a8 SR |
30 | /* |
31 | * The ring buffer header is special. We must manually up keep it. | |
32 | */ | |
33 | int ring_buffer_print_entry_header(struct trace_seq *s) | |
34 | { | |
c0cd93aa SRRH |
35 | trace_seq_puts(s, "# compressed entry header\n"); |
36 | trace_seq_puts(s, "\ttype_len : 5 bits\n"); | |
37 | trace_seq_puts(s, "\ttime_delta : 27 bits\n"); | |
38 | trace_seq_puts(s, "\tarray : 32 bits\n"); | |
39 | trace_seq_putc(s, '\n'); | |
40 | trace_seq_printf(s, "\tpadding : type == %d\n", | |
41 | RINGBUF_TYPE_PADDING); | |
42 | trace_seq_printf(s, "\ttime_extend : type == %d\n", | |
43 | RINGBUF_TYPE_TIME_EXTEND); | |
44 | trace_seq_printf(s, "\tdata max type_len == %d\n", | |
45 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); | |
46 | ||
47 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
48 | } |
49 | ||
5cc98548 SR |
50 | /* |
51 | * The ring buffer is made up of a list of pages. A separate list of pages is | |
52 | * allocated for each CPU. A writer may only write to a buffer that is | |
53 | * associated with the CPU it is currently executing on. A reader may read | |
54 | * from any per cpu buffer. | |
55 | * | |
56 | * The reader is special. For each per cpu buffer, the reader has its own | |
57 | * reader page. When a reader has read the entire reader page, this reader | |
58 | * page is swapped with another page in the ring buffer. | |
59 | * | |
60 | * Now, as long as the writer is off the reader page, the reader can do what | |
61 | * ever it wants with that page. The writer will never write to that page | |
62 | * again (as long as it is out of the ring buffer). | |
63 | * | |
64 | * Here's some silly ASCII art. | |
65 | * | |
66 | * +------+ | |
67 | * |reader| RING BUFFER | |
68 | * |page | | |
69 | * +------+ +---+ +---+ +---+ | |
70 | * | |-->| |-->| | | |
71 | * +---+ +---+ +---+ | |
72 | * ^ | | |
73 | * | | | |
74 | * +---------------+ | |
75 | * | |
76 | * | |
77 | * +------+ | |
78 | * |reader| RING BUFFER | |
79 | * |page |------------------v | |
80 | * +------+ +---+ +---+ +---+ | |
81 | * | |-->| |-->| | | |
82 | * +---+ +---+ +---+ | |
83 | * ^ | | |
84 | * | | | |
85 | * +---------------+ | |
86 | * | |
87 | * | |
88 | * +------+ | |
89 | * |reader| RING BUFFER | |
90 | * |page |------------------v | |
91 | * +------+ +---+ +---+ +---+ | |
92 | * ^ | |-->| |-->| | | |
93 | * | +---+ +---+ +---+ | |
94 | * | | | |
95 | * | | | |
96 | * +------------------------------+ | |
97 | * | |
98 | * | |
99 | * +------+ | |
100 | * |buffer| RING BUFFER | |
101 | * |page |------------------v | |
102 | * +------+ +---+ +---+ +---+ | |
103 | * ^ | | | |-->| | | |
104 | * | New +---+ +---+ +---+ | |
105 | * | Reader------^ | | |
106 | * | page | | |
107 | * +------------------------------+ | |
108 | * | |
109 | * | |
110 | * After we make this swap, the reader can hand this page off to the splice | |
111 | * code and be done with it. It can even allocate a new page if it needs to | |
112 | * and swap that into the ring buffer. | |
113 | * | |
114 | * We will be using cmpxchg soon to make all this lockless. | |
115 | * | |
116 | */ | |
117 | ||
033601a3 SR |
118 | /* |
119 | * A fast way to enable or disable all ring buffers is to | |
120 | * call tracing_on or tracing_off. Turning off the ring buffers | |
121 | * prevents all ring buffers from being recorded to. | |
122 | * Turning this switch on, makes it OK to write to the | |
123 | * ring buffer, if the ring buffer is enabled itself. | |
124 | * | |
125 | * There's three layers that must be on in order to write | |
126 | * to the ring buffer. | |
127 | * | |
128 | * 1) This global flag must be set. | |
129 | * 2) The ring buffer must be enabled for recording. | |
130 | * 3) The per cpu buffer must be enabled for recording. | |
131 | * | |
132 | * In case of an anomaly, this global flag has a bit set that | |
133 | * will permantly disable all ring buffers. | |
134 | */ | |
135 | ||
136 | /* | |
137 | * Global flag to disable all recording to ring buffers | |
138 | * This has two bits: ON, DISABLED | |
139 | * | |
140 | * ON DISABLED | |
141 | * ---- ---------- | |
142 | * 0 0 : ring buffers are off | |
143 | * 1 0 : ring buffers are on | |
144 | * X 1 : ring buffers are permanently disabled | |
145 | */ | |
146 | ||
147 | enum { | |
148 | RB_BUFFERS_ON_BIT = 0, | |
149 | RB_BUFFERS_DISABLED_BIT = 1, | |
150 | }; | |
151 | ||
152 | enum { | |
153 | RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT, | |
154 | RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT, | |
155 | }; | |
156 | ||
5e39841c | 157 | static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; |
a3583244 | 158 | |
499e5470 SR |
159 | /* Used for individual buffers (after the counter) */ |
160 | #define RB_BUFFER_OFF (1 << 20) | |
a3583244 | 161 | |
499e5470 | 162 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
033601a3 SR |
163 | |
164 | /** | |
165 | * tracing_off_permanent - permanently disable ring buffers | |
166 | * | |
167 | * This function, once called, will disable all ring buffers | |
c3706f00 | 168 | * permanently. |
033601a3 SR |
169 | */ |
170 | void tracing_off_permanent(void) | |
171 | { | |
172 | set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags); | |
a3583244 SR |
173 | } |
174 | ||
e3d6bf0a | 175 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
67d34724 | 176 | #define RB_ALIGNMENT 4U |
334d4169 | 177 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
c7b09308 | 178 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
334d4169 | 179 | |
649508f6 | 180 | #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS |
2271048d SR |
181 | # define RB_FORCE_8BYTE_ALIGNMENT 0 |
182 | # define RB_ARCH_ALIGNMENT RB_ALIGNMENT | |
183 | #else | |
184 | # define RB_FORCE_8BYTE_ALIGNMENT 1 | |
185 | # define RB_ARCH_ALIGNMENT 8U | |
186 | #endif | |
187 | ||
649508f6 JH |
188 | #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) |
189 | ||
334d4169 LJ |
190 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
191 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX | |
7a8e76a3 SR |
192 | |
193 | enum { | |
194 | RB_LEN_TIME_EXTEND = 8, | |
195 | RB_LEN_TIME_STAMP = 16, | |
196 | }; | |
197 | ||
69d1b839 SR |
198 | #define skip_time_extend(event) \ |
199 | ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) | |
200 | ||
2d622719 TZ |
201 | static inline int rb_null_event(struct ring_buffer_event *event) |
202 | { | |
a1863c21 | 203 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
2d622719 TZ |
204 | } |
205 | ||
206 | static void rb_event_set_padding(struct ring_buffer_event *event) | |
207 | { | |
a1863c21 | 208 | /* padding has a NULL time_delta */ |
334d4169 | 209 | event->type_len = RINGBUF_TYPE_PADDING; |
2d622719 TZ |
210 | event->time_delta = 0; |
211 | } | |
212 | ||
34a148bf | 213 | static unsigned |
2d622719 | 214 | rb_event_data_length(struct ring_buffer_event *event) |
7a8e76a3 SR |
215 | { |
216 | unsigned length; | |
217 | ||
334d4169 LJ |
218 | if (event->type_len) |
219 | length = event->type_len * RB_ALIGNMENT; | |
2d622719 TZ |
220 | else |
221 | length = event->array[0]; | |
222 | return length + RB_EVNT_HDR_SIZE; | |
223 | } | |
224 | ||
69d1b839 SR |
225 | /* |
226 | * Return the length of the given event. Will return | |
227 | * the length of the time extend if the event is a | |
228 | * time extend. | |
229 | */ | |
230 | static inline unsigned | |
2d622719 TZ |
231 | rb_event_length(struct ring_buffer_event *event) |
232 | { | |
334d4169 | 233 | switch (event->type_len) { |
7a8e76a3 | 234 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
235 | if (rb_null_event(event)) |
236 | /* undefined */ | |
237 | return -1; | |
334d4169 | 238 | return event->array[0] + RB_EVNT_HDR_SIZE; |
7a8e76a3 SR |
239 | |
240 | case RINGBUF_TYPE_TIME_EXTEND: | |
241 | return RB_LEN_TIME_EXTEND; | |
242 | ||
243 | case RINGBUF_TYPE_TIME_STAMP: | |
244 | return RB_LEN_TIME_STAMP; | |
245 | ||
246 | case RINGBUF_TYPE_DATA: | |
2d622719 | 247 | return rb_event_data_length(event); |
7a8e76a3 SR |
248 | default: |
249 | BUG(); | |
250 | } | |
251 | /* not hit */ | |
252 | return 0; | |
253 | } | |
254 | ||
69d1b839 SR |
255 | /* |
256 | * Return total length of time extend and data, | |
257 | * or just the event length for all other events. | |
258 | */ | |
259 | static inline unsigned | |
260 | rb_event_ts_length(struct ring_buffer_event *event) | |
261 | { | |
262 | unsigned len = 0; | |
263 | ||
264 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { | |
265 | /* time extends include the data event after it */ | |
266 | len = RB_LEN_TIME_EXTEND; | |
267 | event = skip_time_extend(event); | |
268 | } | |
269 | return len + rb_event_length(event); | |
270 | } | |
271 | ||
7a8e76a3 SR |
272 | /** |
273 | * ring_buffer_event_length - return the length of the event | |
274 | * @event: the event to get the length of | |
69d1b839 SR |
275 | * |
276 | * Returns the size of the data load of a data event. | |
277 | * If the event is something other than a data event, it | |
278 | * returns the size of the event itself. With the exception | |
279 | * of a TIME EXTEND, where it still returns the size of the | |
280 | * data load of the data event after it. | |
7a8e76a3 SR |
281 | */ |
282 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) | |
283 | { | |
69d1b839 SR |
284 | unsigned length; |
285 | ||
286 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) | |
287 | event = skip_time_extend(event); | |
288 | ||
289 | length = rb_event_length(event); | |
334d4169 | 290 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
465634ad RR |
291 | return length; |
292 | length -= RB_EVNT_HDR_SIZE; | |
293 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) | |
294 | length -= sizeof(event->array[0]); | |
295 | return length; | |
7a8e76a3 | 296 | } |
c4f50183 | 297 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
7a8e76a3 SR |
298 | |
299 | /* inline for ring buffer fast paths */ | |
34a148bf | 300 | static void * |
7a8e76a3 SR |
301 | rb_event_data(struct ring_buffer_event *event) |
302 | { | |
69d1b839 SR |
303 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
304 | event = skip_time_extend(event); | |
334d4169 | 305 | BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
7a8e76a3 | 306 | /* If length is in len field, then array[0] has the data */ |
334d4169 | 307 | if (event->type_len) |
7a8e76a3 SR |
308 | return (void *)&event->array[0]; |
309 | /* Otherwise length is in array[0] and array[1] has the data */ | |
310 | return (void *)&event->array[1]; | |
311 | } | |
312 | ||
313 | /** | |
314 | * ring_buffer_event_data - return the data of the event | |
315 | * @event: the event to get the data from | |
316 | */ | |
317 | void *ring_buffer_event_data(struct ring_buffer_event *event) | |
318 | { | |
319 | return rb_event_data(event); | |
320 | } | |
c4f50183 | 321 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
7a8e76a3 SR |
322 | |
323 | #define for_each_buffer_cpu(buffer, cpu) \ | |
9e01c1b7 | 324 | for_each_cpu(cpu, buffer->cpumask) |
7a8e76a3 SR |
325 | |
326 | #define TS_SHIFT 27 | |
327 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) | |
328 | #define TS_DELTA_TEST (~TS_MASK) | |
329 | ||
66a8cb95 SR |
330 | /* Flag when events were overwritten */ |
331 | #define RB_MISSED_EVENTS (1 << 31) | |
ff0ff84a SR |
332 | /* Missed count stored at end */ |
333 | #define RB_MISSED_STORED (1 << 30) | |
66a8cb95 | 334 | |
abc9b56d | 335 | struct buffer_data_page { |
e4c2ce82 | 336 | u64 time_stamp; /* page time stamp */ |
c3706f00 | 337 | local_t commit; /* write committed index */ |
649508f6 | 338 | unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
abc9b56d SR |
339 | }; |
340 | ||
77ae365e SR |
341 | /* |
342 | * Note, the buffer_page list must be first. The buffer pages | |
343 | * are allocated in cache lines, which means that each buffer | |
344 | * page will be at the beginning of a cache line, and thus | |
345 | * the least significant bits will be zero. We use this to | |
346 | * add flags in the list struct pointers, to make the ring buffer | |
347 | * lockless. | |
348 | */ | |
abc9b56d | 349 | struct buffer_page { |
778c55d4 | 350 | struct list_head list; /* list of buffer pages */ |
abc9b56d | 351 | local_t write; /* index for next write */ |
6f807acd | 352 | unsigned read; /* index for next read */ |
778c55d4 | 353 | local_t entries; /* entries on this page */ |
ff0ff84a | 354 | unsigned long real_end; /* real end of data */ |
abc9b56d | 355 | struct buffer_data_page *page; /* Actual data page */ |
7a8e76a3 SR |
356 | }; |
357 | ||
77ae365e SR |
358 | /* |
359 | * The buffer page counters, write and entries, must be reset | |
360 | * atomically when crossing page boundaries. To synchronize this | |
361 | * update, two counters are inserted into the number. One is | |
362 | * the actual counter for the write position or count on the page. | |
363 | * | |
364 | * The other is a counter of updaters. Before an update happens | |
365 | * the update partition of the counter is incremented. This will | |
366 | * allow the updater to update the counter atomically. | |
367 | * | |
368 | * The counter is 20 bits, and the state data is 12. | |
369 | */ | |
370 | #define RB_WRITE_MASK 0xfffff | |
371 | #define RB_WRITE_INTCNT (1 << 20) | |
372 | ||
044fa782 | 373 | static void rb_init_page(struct buffer_data_page *bpage) |
abc9b56d | 374 | { |
044fa782 | 375 | local_set(&bpage->commit, 0); |
abc9b56d SR |
376 | } |
377 | ||
474d32b6 SR |
378 | /** |
379 | * ring_buffer_page_len - the size of data on the page. | |
380 | * @page: The page to read | |
381 | * | |
382 | * Returns the amount of data on the page, including buffer page header. | |
383 | */ | |
ef7a4a16 SR |
384 | size_t ring_buffer_page_len(void *page) |
385 | { | |
474d32b6 SR |
386 | return local_read(&((struct buffer_data_page *)page)->commit) |
387 | + BUF_PAGE_HDR_SIZE; | |
ef7a4a16 SR |
388 | } |
389 | ||
ed56829c SR |
390 | /* |
391 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing | |
392 | * this issue out. | |
393 | */ | |
34a148bf | 394 | static void free_buffer_page(struct buffer_page *bpage) |
ed56829c | 395 | { |
34a148bf | 396 | free_page((unsigned long)bpage->page); |
e4c2ce82 | 397 | kfree(bpage); |
ed56829c SR |
398 | } |
399 | ||
7a8e76a3 SR |
400 | /* |
401 | * We need to fit the time_stamp delta into 27 bits. | |
402 | */ | |
403 | static inline int test_time_stamp(u64 delta) | |
404 | { | |
405 | if (delta & TS_DELTA_TEST) | |
406 | return 1; | |
407 | return 0; | |
408 | } | |
409 | ||
474d32b6 | 410 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
7a8e76a3 | 411 | |
be957c44 SR |
412 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
413 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) | |
414 | ||
d1b182a8 SR |
415 | int ring_buffer_print_page_header(struct trace_seq *s) |
416 | { | |
417 | struct buffer_data_page field; | |
c0cd93aa SRRH |
418 | |
419 | trace_seq_printf(s, "\tfield: u64 timestamp;\t" | |
420 | "offset:0;\tsize:%u;\tsigned:%u;\n", | |
421 | (unsigned int)sizeof(field.time_stamp), | |
422 | (unsigned int)is_signed_type(u64)); | |
423 | ||
424 | trace_seq_printf(s, "\tfield: local_t commit;\t" | |
425 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
426 | (unsigned int)offsetof(typeof(field), commit), | |
427 | (unsigned int)sizeof(field.commit), | |
428 | (unsigned int)is_signed_type(long)); | |
429 | ||
430 | trace_seq_printf(s, "\tfield: int overwrite;\t" | |
431 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
432 | (unsigned int)offsetof(typeof(field), commit), | |
433 | 1, | |
434 | (unsigned int)is_signed_type(long)); | |
435 | ||
436 | trace_seq_printf(s, "\tfield: char data;\t" | |
437 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
438 | (unsigned int)offsetof(typeof(field), data), | |
439 | (unsigned int)BUF_PAGE_SIZE, | |
440 | (unsigned int)is_signed_type(char)); | |
441 | ||
442 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
443 | } |
444 | ||
15693458 SRRH |
445 | struct rb_irq_work { |
446 | struct irq_work work; | |
447 | wait_queue_head_t waiters; | |
1e0d6714 | 448 | wait_queue_head_t full_waiters; |
15693458 | 449 | bool waiters_pending; |
1e0d6714 SRRH |
450 | bool full_waiters_pending; |
451 | bool wakeup_full; | |
15693458 SRRH |
452 | }; |
453 | ||
7a8e76a3 SR |
454 | /* |
455 | * head_page == tail_page && head == tail then buffer is empty. | |
456 | */ | |
457 | struct ring_buffer_per_cpu { | |
458 | int cpu; | |
985023de | 459 | atomic_t record_disabled; |
7a8e76a3 | 460 | struct ring_buffer *buffer; |
5389f6fa | 461 | raw_spinlock_t reader_lock; /* serialize readers */ |
445c8951 | 462 | arch_spinlock_t lock; |
7a8e76a3 | 463 | struct lock_class_key lock_key; |
438ced17 | 464 | unsigned int nr_pages; |
58a09ec6 | 465 | unsigned int current_context; |
3adc54fa | 466 | struct list_head *pages; |
6f807acd SR |
467 | struct buffer_page *head_page; /* read from head */ |
468 | struct buffer_page *tail_page; /* write to tail */ | |
c3706f00 | 469 | struct buffer_page *commit_page; /* committed pages */ |
d769041f | 470 | struct buffer_page *reader_page; |
66a8cb95 SR |
471 | unsigned long lost_events; |
472 | unsigned long last_overrun; | |
c64e148a | 473 | local_t entries_bytes; |
e4906eff | 474 | local_t entries; |
884bfe89 SP |
475 | local_t overrun; |
476 | local_t commit_overrun; | |
477 | local_t dropped_events; | |
fa743953 SR |
478 | local_t committing; |
479 | local_t commits; | |
77ae365e | 480 | unsigned long read; |
c64e148a | 481 | unsigned long read_bytes; |
7a8e76a3 SR |
482 | u64 write_stamp; |
483 | u64 read_stamp; | |
438ced17 VN |
484 | /* ring buffer pages to update, > 0 to add, < 0 to remove */ |
485 | int nr_pages_to_update; | |
486 | struct list_head new_pages; /* new pages to add */ | |
83f40318 | 487 | struct work_struct update_pages_work; |
05fdd70d | 488 | struct completion update_done; |
15693458 SRRH |
489 | |
490 | struct rb_irq_work irq_work; | |
7a8e76a3 SR |
491 | }; |
492 | ||
493 | struct ring_buffer { | |
7a8e76a3 SR |
494 | unsigned flags; |
495 | int cpus; | |
7a8e76a3 | 496 | atomic_t record_disabled; |
83f40318 | 497 | atomic_t resize_disabled; |
00f62f61 | 498 | cpumask_var_t cpumask; |
7a8e76a3 | 499 | |
1f8a6a10 PZ |
500 | struct lock_class_key *reader_lock_key; |
501 | ||
7a8e76a3 SR |
502 | struct mutex mutex; |
503 | ||
504 | struct ring_buffer_per_cpu **buffers; | |
554f786e | 505 | |
59222efe | 506 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
507 | struct notifier_block cpu_notify; |
508 | #endif | |
37886f6a | 509 | u64 (*clock)(void); |
15693458 SRRH |
510 | |
511 | struct rb_irq_work irq_work; | |
7a8e76a3 SR |
512 | }; |
513 | ||
514 | struct ring_buffer_iter { | |
515 | struct ring_buffer_per_cpu *cpu_buffer; | |
516 | unsigned long head; | |
517 | struct buffer_page *head_page; | |
492a74f4 SR |
518 | struct buffer_page *cache_reader_page; |
519 | unsigned long cache_read; | |
7a8e76a3 SR |
520 | u64 read_stamp; |
521 | }; | |
522 | ||
15693458 SRRH |
523 | /* |
524 | * rb_wake_up_waiters - wake up tasks waiting for ring buffer input | |
525 | * | |
526 | * Schedules a delayed work to wake up any task that is blocked on the | |
527 | * ring buffer waiters queue. | |
528 | */ | |
529 | static void rb_wake_up_waiters(struct irq_work *work) | |
530 | { | |
531 | struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); | |
532 | ||
533 | wake_up_all(&rbwork->waiters); | |
1e0d6714 SRRH |
534 | if (rbwork->wakeup_full) { |
535 | rbwork->wakeup_full = false; | |
536 | wake_up_all(&rbwork->full_waiters); | |
537 | } | |
15693458 SRRH |
538 | } |
539 | ||
540 | /** | |
541 | * ring_buffer_wait - wait for input to the ring buffer | |
542 | * @buffer: buffer to wait on | |
543 | * @cpu: the cpu buffer to wait on | |
e30f53aa | 544 | * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS |
15693458 SRRH |
545 | * |
546 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
547 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
548 | * it will wait for data to be added to a specific cpu buffer. | |
549 | */ | |
e30f53aa | 550 | int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full) |
15693458 | 551 | { |
e30f53aa | 552 | struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer); |
15693458 SRRH |
553 | DEFINE_WAIT(wait); |
554 | struct rb_irq_work *work; | |
e30f53aa | 555 | int ret = 0; |
15693458 SRRH |
556 | |
557 | /* | |
558 | * Depending on what the caller is waiting for, either any | |
559 | * data in any cpu buffer, or a specific buffer, put the | |
560 | * caller on the appropriate wait queue. | |
561 | */ | |
1e0d6714 | 562 | if (cpu == RING_BUFFER_ALL_CPUS) { |
15693458 | 563 | work = &buffer->irq_work; |
1e0d6714 SRRH |
564 | /* Full only makes sense on per cpu reads */ |
565 | full = false; | |
566 | } else { | |
8b8b3683 SRRH |
567 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
568 | return -ENODEV; | |
15693458 SRRH |
569 | cpu_buffer = buffer->buffers[cpu]; |
570 | work = &cpu_buffer->irq_work; | |
571 | } | |
572 | ||
573 | ||
e30f53aa | 574 | while (true) { |
1e0d6714 SRRH |
575 | if (full) |
576 | prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); | |
577 | else | |
578 | prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); | |
e30f53aa RV |
579 | |
580 | /* | |
581 | * The events can happen in critical sections where | |
582 | * checking a work queue can cause deadlocks. | |
583 | * After adding a task to the queue, this flag is set | |
584 | * only to notify events to try to wake up the queue | |
585 | * using irq_work. | |
586 | * | |
587 | * We don't clear it even if the buffer is no longer | |
588 | * empty. The flag only causes the next event to run | |
589 | * irq_work to do the work queue wake up. The worse | |
590 | * that can happen if we race with !trace_empty() is that | |
591 | * an event will cause an irq_work to try to wake up | |
592 | * an empty queue. | |
593 | * | |
594 | * There's no reason to protect this flag either, as | |
595 | * the work queue and irq_work logic will do the necessary | |
596 | * synchronization for the wake ups. The only thing | |
597 | * that is necessary is that the wake up happens after | |
598 | * a task has been queued. It's OK for spurious wake ups. | |
599 | */ | |
1e0d6714 SRRH |
600 | if (full) |
601 | work->full_waiters_pending = true; | |
602 | else | |
603 | work->waiters_pending = true; | |
e30f53aa RV |
604 | |
605 | if (signal_pending(current)) { | |
606 | ret = -EINTR; | |
607 | break; | |
608 | } | |
609 | ||
610 | if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) | |
611 | break; | |
612 | ||
613 | if (cpu != RING_BUFFER_ALL_CPUS && | |
614 | !ring_buffer_empty_cpu(buffer, cpu)) { | |
615 | unsigned long flags; | |
616 | bool pagebusy; | |
617 | ||
618 | if (!full) | |
619 | break; | |
620 | ||
621 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
622 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; | |
623 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
624 | ||
625 | if (!pagebusy) | |
626 | break; | |
627 | } | |
15693458 | 628 | |
15693458 | 629 | schedule(); |
e30f53aa | 630 | } |
15693458 | 631 | |
1e0d6714 SRRH |
632 | if (full) |
633 | finish_wait(&work->full_waiters, &wait); | |
634 | else | |
635 | finish_wait(&work->waiters, &wait); | |
e30f53aa RV |
636 | |
637 | return ret; | |
15693458 SRRH |
638 | } |
639 | ||
640 | /** | |
641 | * ring_buffer_poll_wait - poll on buffer input | |
642 | * @buffer: buffer to wait on | |
643 | * @cpu: the cpu buffer to wait on | |
644 | * @filp: the file descriptor | |
645 | * @poll_table: The poll descriptor | |
646 | * | |
647 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
648 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
649 | * it will wait for data to be added to a specific cpu buffer. | |
650 | * | |
651 | * Returns POLLIN | POLLRDNORM if data exists in the buffers, | |
652 | * zero otherwise. | |
653 | */ | |
654 | int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu, | |
655 | struct file *filp, poll_table *poll_table) | |
656 | { | |
657 | struct ring_buffer_per_cpu *cpu_buffer; | |
658 | struct rb_irq_work *work; | |
659 | ||
15693458 SRRH |
660 | if (cpu == RING_BUFFER_ALL_CPUS) |
661 | work = &buffer->irq_work; | |
662 | else { | |
6721cb60 SRRH |
663 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
664 | return -EINVAL; | |
665 | ||
15693458 SRRH |
666 | cpu_buffer = buffer->buffers[cpu]; |
667 | work = &cpu_buffer->irq_work; | |
668 | } | |
669 | ||
15693458 | 670 | poll_wait(filp, &work->waiters, poll_table); |
4ce97dbf JB |
671 | work->waiters_pending = true; |
672 | /* | |
673 | * There's a tight race between setting the waiters_pending and | |
674 | * checking if the ring buffer is empty. Once the waiters_pending bit | |
675 | * is set, the next event will wake the task up, but we can get stuck | |
676 | * if there's only a single event in. | |
677 | * | |
678 | * FIXME: Ideally, we need a memory barrier on the writer side as well, | |
679 | * but adding a memory barrier to all events will cause too much of a | |
680 | * performance hit in the fast path. We only need a memory barrier when | |
681 | * the buffer goes from empty to having content. But as this race is | |
682 | * extremely small, and it's not a problem if another event comes in, we | |
683 | * will fix it later. | |
684 | */ | |
685 | smp_mb(); | |
15693458 SRRH |
686 | |
687 | if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || | |
688 | (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) | |
689 | return POLLIN | POLLRDNORM; | |
690 | return 0; | |
691 | } | |
692 | ||
f536aafc | 693 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
077c5407 SR |
694 | #define RB_WARN_ON(b, cond) \ |
695 | ({ \ | |
696 | int _____ret = unlikely(cond); \ | |
697 | if (_____ret) { \ | |
698 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ | |
699 | struct ring_buffer_per_cpu *__b = \ | |
700 | (void *)b; \ | |
701 | atomic_inc(&__b->buffer->record_disabled); \ | |
702 | } else \ | |
703 | atomic_inc(&b->record_disabled); \ | |
704 | WARN_ON(1); \ | |
705 | } \ | |
706 | _____ret; \ | |
3e89c7bb | 707 | }) |
f536aafc | 708 | |
37886f6a SR |
709 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
710 | #define DEBUG_SHIFT 0 | |
711 | ||
6d3f1e12 | 712 | static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
88eb0125 SR |
713 | { |
714 | /* shift to debug/test normalization and TIME_EXTENTS */ | |
715 | return buffer->clock() << DEBUG_SHIFT; | |
716 | } | |
717 | ||
37886f6a SR |
718 | u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
719 | { | |
720 | u64 time; | |
721 | ||
722 | preempt_disable_notrace(); | |
6d3f1e12 | 723 | time = rb_time_stamp(buffer); |
37886f6a SR |
724 | preempt_enable_no_resched_notrace(); |
725 | ||
726 | return time; | |
727 | } | |
728 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); | |
729 | ||
730 | void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, | |
731 | int cpu, u64 *ts) | |
732 | { | |
733 | /* Just stupid testing the normalize function and deltas */ | |
734 | *ts >>= DEBUG_SHIFT; | |
735 | } | |
736 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); | |
737 | ||
77ae365e SR |
738 | /* |
739 | * Making the ring buffer lockless makes things tricky. | |
740 | * Although writes only happen on the CPU that they are on, | |
741 | * and they only need to worry about interrupts. Reads can | |
742 | * happen on any CPU. | |
743 | * | |
744 | * The reader page is always off the ring buffer, but when the | |
745 | * reader finishes with a page, it needs to swap its page with | |
746 | * a new one from the buffer. The reader needs to take from | |
747 | * the head (writes go to the tail). But if a writer is in overwrite | |
748 | * mode and wraps, it must push the head page forward. | |
749 | * | |
750 | * Here lies the problem. | |
751 | * | |
752 | * The reader must be careful to replace only the head page, and | |
753 | * not another one. As described at the top of the file in the | |
754 | * ASCII art, the reader sets its old page to point to the next | |
755 | * page after head. It then sets the page after head to point to | |
756 | * the old reader page. But if the writer moves the head page | |
757 | * during this operation, the reader could end up with the tail. | |
758 | * | |
759 | * We use cmpxchg to help prevent this race. We also do something | |
760 | * special with the page before head. We set the LSB to 1. | |
761 | * | |
762 | * When the writer must push the page forward, it will clear the | |
763 | * bit that points to the head page, move the head, and then set | |
764 | * the bit that points to the new head page. | |
765 | * | |
766 | * We also don't want an interrupt coming in and moving the head | |
767 | * page on another writer. Thus we use the second LSB to catch | |
768 | * that too. Thus: | |
769 | * | |
770 | * head->list->prev->next bit 1 bit 0 | |
771 | * ------- ------- | |
772 | * Normal page 0 0 | |
773 | * Points to head page 0 1 | |
774 | * New head page 1 0 | |
775 | * | |
776 | * Note we can not trust the prev pointer of the head page, because: | |
777 | * | |
778 | * +----+ +-----+ +-----+ | |
779 | * | |------>| T |---X--->| N | | |
780 | * | |<------| | | | | |
781 | * +----+ +-----+ +-----+ | |
782 | * ^ ^ | | |
783 | * | +-----+ | | | |
784 | * +----------| R |----------+ | | |
785 | * | |<-----------+ | |
786 | * +-----+ | |
787 | * | |
788 | * Key: ---X--> HEAD flag set in pointer | |
789 | * T Tail page | |
790 | * R Reader page | |
791 | * N Next page | |
792 | * | |
793 | * (see __rb_reserve_next() to see where this happens) | |
794 | * | |
795 | * What the above shows is that the reader just swapped out | |
796 | * the reader page with a page in the buffer, but before it | |
797 | * could make the new header point back to the new page added | |
798 | * it was preempted by a writer. The writer moved forward onto | |
799 | * the new page added by the reader and is about to move forward | |
800 | * again. | |
801 | * | |
802 | * You can see, it is legitimate for the previous pointer of | |
803 | * the head (or any page) not to point back to itself. But only | |
804 | * temporarially. | |
805 | */ | |
806 | ||
807 | #define RB_PAGE_NORMAL 0UL | |
808 | #define RB_PAGE_HEAD 1UL | |
809 | #define RB_PAGE_UPDATE 2UL | |
810 | ||
811 | ||
812 | #define RB_FLAG_MASK 3UL | |
813 | ||
814 | /* PAGE_MOVED is not part of the mask */ | |
815 | #define RB_PAGE_MOVED 4UL | |
816 | ||
817 | /* | |
818 | * rb_list_head - remove any bit | |
819 | */ | |
820 | static struct list_head *rb_list_head(struct list_head *list) | |
821 | { | |
822 | unsigned long val = (unsigned long)list; | |
823 | ||
824 | return (struct list_head *)(val & ~RB_FLAG_MASK); | |
825 | } | |
826 | ||
827 | /* | |
6d3f1e12 | 828 | * rb_is_head_page - test if the given page is the head page |
77ae365e SR |
829 | * |
830 | * Because the reader may move the head_page pointer, we can | |
831 | * not trust what the head page is (it may be pointing to | |
832 | * the reader page). But if the next page is a header page, | |
833 | * its flags will be non zero. | |
834 | */ | |
42b16b3f | 835 | static inline int |
77ae365e SR |
836 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
837 | struct buffer_page *page, struct list_head *list) | |
838 | { | |
839 | unsigned long val; | |
840 | ||
841 | val = (unsigned long)list->next; | |
842 | ||
843 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) | |
844 | return RB_PAGE_MOVED; | |
845 | ||
846 | return val & RB_FLAG_MASK; | |
847 | } | |
848 | ||
849 | /* | |
850 | * rb_is_reader_page | |
851 | * | |
852 | * The unique thing about the reader page, is that, if the | |
853 | * writer is ever on it, the previous pointer never points | |
854 | * back to the reader page. | |
855 | */ | |
856 | static int rb_is_reader_page(struct buffer_page *page) | |
857 | { | |
858 | struct list_head *list = page->list.prev; | |
859 | ||
860 | return rb_list_head(list->next) != &page->list; | |
861 | } | |
862 | ||
863 | /* | |
864 | * rb_set_list_to_head - set a list_head to be pointing to head. | |
865 | */ | |
866 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, | |
867 | struct list_head *list) | |
868 | { | |
869 | unsigned long *ptr; | |
870 | ||
871 | ptr = (unsigned long *)&list->next; | |
872 | *ptr |= RB_PAGE_HEAD; | |
873 | *ptr &= ~RB_PAGE_UPDATE; | |
874 | } | |
875 | ||
876 | /* | |
877 | * rb_head_page_activate - sets up head page | |
878 | */ | |
879 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) | |
880 | { | |
881 | struct buffer_page *head; | |
882 | ||
883 | head = cpu_buffer->head_page; | |
884 | if (!head) | |
885 | return; | |
886 | ||
887 | /* | |
888 | * Set the previous list pointer to have the HEAD flag. | |
889 | */ | |
890 | rb_set_list_to_head(cpu_buffer, head->list.prev); | |
891 | } | |
892 | ||
893 | static void rb_list_head_clear(struct list_head *list) | |
894 | { | |
895 | unsigned long *ptr = (unsigned long *)&list->next; | |
896 | ||
897 | *ptr &= ~RB_FLAG_MASK; | |
898 | } | |
899 | ||
900 | /* | |
901 | * rb_head_page_dactivate - clears head page ptr (for free list) | |
902 | */ | |
903 | static void | |
904 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) | |
905 | { | |
906 | struct list_head *hd; | |
907 | ||
908 | /* Go through the whole list and clear any pointers found. */ | |
909 | rb_list_head_clear(cpu_buffer->pages); | |
910 | ||
911 | list_for_each(hd, cpu_buffer->pages) | |
912 | rb_list_head_clear(hd); | |
913 | } | |
914 | ||
915 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, | |
916 | struct buffer_page *head, | |
917 | struct buffer_page *prev, | |
918 | int old_flag, int new_flag) | |
919 | { | |
920 | struct list_head *list; | |
921 | unsigned long val = (unsigned long)&head->list; | |
922 | unsigned long ret; | |
923 | ||
924 | list = &prev->list; | |
925 | ||
926 | val &= ~RB_FLAG_MASK; | |
927 | ||
08a40816 SR |
928 | ret = cmpxchg((unsigned long *)&list->next, |
929 | val | old_flag, val | new_flag); | |
77ae365e SR |
930 | |
931 | /* check if the reader took the page */ | |
932 | if ((ret & ~RB_FLAG_MASK) != val) | |
933 | return RB_PAGE_MOVED; | |
934 | ||
935 | return ret & RB_FLAG_MASK; | |
936 | } | |
937 | ||
938 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, | |
939 | struct buffer_page *head, | |
940 | struct buffer_page *prev, | |
941 | int old_flag) | |
942 | { | |
943 | return rb_head_page_set(cpu_buffer, head, prev, | |
944 | old_flag, RB_PAGE_UPDATE); | |
945 | } | |
946 | ||
947 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, | |
948 | struct buffer_page *head, | |
949 | struct buffer_page *prev, | |
950 | int old_flag) | |
951 | { | |
952 | return rb_head_page_set(cpu_buffer, head, prev, | |
953 | old_flag, RB_PAGE_HEAD); | |
954 | } | |
955 | ||
956 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, | |
957 | struct buffer_page *head, | |
958 | struct buffer_page *prev, | |
959 | int old_flag) | |
960 | { | |
961 | return rb_head_page_set(cpu_buffer, head, prev, | |
962 | old_flag, RB_PAGE_NORMAL); | |
963 | } | |
964 | ||
965 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, | |
966 | struct buffer_page **bpage) | |
967 | { | |
968 | struct list_head *p = rb_list_head((*bpage)->list.next); | |
969 | ||
970 | *bpage = list_entry(p, struct buffer_page, list); | |
971 | } | |
972 | ||
973 | static struct buffer_page * | |
974 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) | |
975 | { | |
976 | struct buffer_page *head; | |
977 | struct buffer_page *page; | |
978 | struct list_head *list; | |
979 | int i; | |
980 | ||
981 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) | |
982 | return NULL; | |
983 | ||
984 | /* sanity check */ | |
985 | list = cpu_buffer->pages; | |
986 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) | |
987 | return NULL; | |
988 | ||
989 | page = head = cpu_buffer->head_page; | |
990 | /* | |
991 | * It is possible that the writer moves the header behind | |
992 | * where we started, and we miss in one loop. | |
993 | * A second loop should grab the header, but we'll do | |
994 | * three loops just because I'm paranoid. | |
995 | */ | |
996 | for (i = 0; i < 3; i++) { | |
997 | do { | |
998 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { | |
999 | cpu_buffer->head_page = page; | |
1000 | return page; | |
1001 | } | |
1002 | rb_inc_page(cpu_buffer, &page); | |
1003 | } while (page != head); | |
1004 | } | |
1005 | ||
1006 | RB_WARN_ON(cpu_buffer, 1); | |
1007 | ||
1008 | return NULL; | |
1009 | } | |
1010 | ||
1011 | static int rb_head_page_replace(struct buffer_page *old, | |
1012 | struct buffer_page *new) | |
1013 | { | |
1014 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; | |
1015 | unsigned long val; | |
1016 | unsigned long ret; | |
1017 | ||
1018 | val = *ptr & ~RB_FLAG_MASK; | |
1019 | val |= RB_PAGE_HEAD; | |
1020 | ||
08a40816 | 1021 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
77ae365e SR |
1022 | |
1023 | return ret == val; | |
1024 | } | |
1025 | ||
1026 | /* | |
1027 | * rb_tail_page_update - move the tail page forward | |
1028 | * | |
1029 | * Returns 1 if moved tail page, 0 if someone else did. | |
1030 | */ | |
1031 | static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, | |
1032 | struct buffer_page *tail_page, | |
1033 | struct buffer_page *next_page) | |
1034 | { | |
1035 | struct buffer_page *old_tail; | |
1036 | unsigned long old_entries; | |
1037 | unsigned long old_write; | |
1038 | int ret = 0; | |
1039 | ||
1040 | /* | |
1041 | * The tail page now needs to be moved forward. | |
1042 | * | |
1043 | * We need to reset the tail page, but without messing | |
1044 | * with possible erasing of data brought in by interrupts | |
1045 | * that have moved the tail page and are currently on it. | |
1046 | * | |
1047 | * We add a counter to the write field to denote this. | |
1048 | */ | |
1049 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); | |
1050 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); | |
1051 | ||
1052 | /* | |
1053 | * Just make sure we have seen our old_write and synchronize | |
1054 | * with any interrupts that come in. | |
1055 | */ | |
1056 | barrier(); | |
1057 | ||
1058 | /* | |
1059 | * If the tail page is still the same as what we think | |
1060 | * it is, then it is up to us to update the tail | |
1061 | * pointer. | |
1062 | */ | |
1063 | if (tail_page == cpu_buffer->tail_page) { | |
1064 | /* Zero the write counter */ | |
1065 | unsigned long val = old_write & ~RB_WRITE_MASK; | |
1066 | unsigned long eval = old_entries & ~RB_WRITE_MASK; | |
1067 | ||
1068 | /* | |
1069 | * This will only succeed if an interrupt did | |
1070 | * not come in and change it. In which case, we | |
1071 | * do not want to modify it. | |
da706d8b LJ |
1072 | * |
1073 | * We add (void) to let the compiler know that we do not care | |
1074 | * about the return value of these functions. We use the | |
1075 | * cmpxchg to only update if an interrupt did not already | |
1076 | * do it for us. If the cmpxchg fails, we don't care. | |
77ae365e | 1077 | */ |
da706d8b LJ |
1078 | (void)local_cmpxchg(&next_page->write, old_write, val); |
1079 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); | |
77ae365e SR |
1080 | |
1081 | /* | |
1082 | * No need to worry about races with clearing out the commit. | |
1083 | * it only can increment when a commit takes place. But that | |
1084 | * only happens in the outer most nested commit. | |
1085 | */ | |
1086 | local_set(&next_page->page->commit, 0); | |
1087 | ||
1088 | old_tail = cmpxchg(&cpu_buffer->tail_page, | |
1089 | tail_page, next_page); | |
1090 | ||
1091 | if (old_tail == tail_page) | |
1092 | ret = 1; | |
1093 | } | |
1094 | ||
1095 | return ret; | |
1096 | } | |
1097 | ||
1098 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, | |
1099 | struct buffer_page *bpage) | |
1100 | { | |
1101 | unsigned long val = (unsigned long)bpage; | |
1102 | ||
1103 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) | |
1104 | return 1; | |
1105 | ||
1106 | return 0; | |
1107 | } | |
1108 | ||
1109 | /** | |
1110 | * rb_check_list - make sure a pointer to a list has the last bits zero | |
1111 | */ | |
1112 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, | |
1113 | struct list_head *list) | |
1114 | { | |
1115 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) | |
1116 | return 1; | |
1117 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) | |
1118 | return 1; | |
1119 | return 0; | |
1120 | } | |
1121 | ||
7a8e76a3 | 1122 | /** |
d611851b | 1123 | * rb_check_pages - integrity check of buffer pages |
7a8e76a3 SR |
1124 | * @cpu_buffer: CPU buffer with pages to test |
1125 | * | |
c3706f00 | 1126 | * As a safety measure we check to make sure the data pages have not |
7a8e76a3 SR |
1127 | * been corrupted. |
1128 | */ | |
1129 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
1130 | { | |
3adc54fa | 1131 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1132 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1133 | |
308f7eeb SR |
1134 | /* Reset the head page if it exists */ |
1135 | if (cpu_buffer->head_page) | |
1136 | rb_set_head_page(cpu_buffer); | |
1137 | ||
77ae365e SR |
1138 | rb_head_page_deactivate(cpu_buffer); |
1139 | ||
3e89c7bb SR |
1140 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
1141 | return -1; | |
1142 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) | |
1143 | return -1; | |
7a8e76a3 | 1144 | |
77ae365e SR |
1145 | if (rb_check_list(cpu_buffer, head)) |
1146 | return -1; | |
1147 | ||
044fa782 | 1148 | list_for_each_entry_safe(bpage, tmp, head, list) { |
3e89c7bb | 1149 | if (RB_WARN_ON(cpu_buffer, |
044fa782 | 1150 | bpage->list.next->prev != &bpage->list)) |
3e89c7bb SR |
1151 | return -1; |
1152 | if (RB_WARN_ON(cpu_buffer, | |
044fa782 | 1153 | bpage->list.prev->next != &bpage->list)) |
3e89c7bb | 1154 | return -1; |
77ae365e SR |
1155 | if (rb_check_list(cpu_buffer, &bpage->list)) |
1156 | return -1; | |
7a8e76a3 SR |
1157 | } |
1158 | ||
77ae365e SR |
1159 | rb_head_page_activate(cpu_buffer); |
1160 | ||
7a8e76a3 SR |
1161 | return 0; |
1162 | } | |
1163 | ||
438ced17 | 1164 | static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu) |
7a8e76a3 | 1165 | { |
438ced17 | 1166 | int i; |
044fa782 | 1167 | struct buffer_page *bpage, *tmp; |
3adc54fa | 1168 | |
7a8e76a3 | 1169 | for (i = 0; i < nr_pages; i++) { |
7ea59064 | 1170 | struct page *page; |
d7ec4bfe VN |
1171 | /* |
1172 | * __GFP_NORETRY flag makes sure that the allocation fails | |
1173 | * gracefully without invoking oom-killer and the system is | |
1174 | * not destabilized. | |
1175 | */ | |
044fa782 | 1176 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
d7ec4bfe | 1177 | GFP_KERNEL | __GFP_NORETRY, |
438ced17 | 1178 | cpu_to_node(cpu)); |
044fa782 | 1179 | if (!bpage) |
e4c2ce82 | 1180 | goto free_pages; |
77ae365e | 1181 | |
438ced17 | 1182 | list_add(&bpage->list, pages); |
77ae365e | 1183 | |
438ced17 | 1184 | page = alloc_pages_node(cpu_to_node(cpu), |
d7ec4bfe | 1185 | GFP_KERNEL | __GFP_NORETRY, 0); |
7ea59064 | 1186 | if (!page) |
7a8e76a3 | 1187 | goto free_pages; |
7ea59064 | 1188 | bpage->page = page_address(page); |
044fa782 | 1189 | rb_init_page(bpage->page); |
7a8e76a3 SR |
1190 | } |
1191 | ||
438ced17 VN |
1192 | return 0; |
1193 | ||
1194 | free_pages: | |
1195 | list_for_each_entry_safe(bpage, tmp, pages, list) { | |
1196 | list_del_init(&bpage->list); | |
1197 | free_buffer_page(bpage); | |
1198 | } | |
1199 | ||
1200 | return -ENOMEM; | |
1201 | } | |
1202 | ||
1203 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, | |
1204 | unsigned nr_pages) | |
1205 | { | |
1206 | LIST_HEAD(pages); | |
1207 | ||
1208 | WARN_ON(!nr_pages); | |
1209 | ||
1210 | if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu)) | |
1211 | return -ENOMEM; | |
1212 | ||
3adc54fa SR |
1213 | /* |
1214 | * The ring buffer page list is a circular list that does not | |
1215 | * start and end with a list head. All page list items point to | |
1216 | * other pages. | |
1217 | */ | |
1218 | cpu_buffer->pages = pages.next; | |
1219 | list_del(&pages); | |
7a8e76a3 | 1220 | |
438ced17 VN |
1221 | cpu_buffer->nr_pages = nr_pages; |
1222 | ||
7a8e76a3 SR |
1223 | rb_check_pages(cpu_buffer); |
1224 | ||
1225 | return 0; | |
7a8e76a3 SR |
1226 | } |
1227 | ||
1228 | static struct ring_buffer_per_cpu * | |
438ced17 | 1229 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu) |
7a8e76a3 SR |
1230 | { |
1231 | struct ring_buffer_per_cpu *cpu_buffer; | |
044fa782 | 1232 | struct buffer_page *bpage; |
7ea59064 | 1233 | struct page *page; |
7a8e76a3 SR |
1234 | int ret; |
1235 | ||
1236 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), | |
1237 | GFP_KERNEL, cpu_to_node(cpu)); | |
1238 | if (!cpu_buffer) | |
1239 | return NULL; | |
1240 | ||
1241 | cpu_buffer->cpu = cpu; | |
1242 | cpu_buffer->buffer = buffer; | |
5389f6fa | 1243 | raw_spin_lock_init(&cpu_buffer->reader_lock); |
1f8a6a10 | 1244 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
edc35bd7 | 1245 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
83f40318 | 1246 | INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
05fdd70d | 1247 | init_completion(&cpu_buffer->update_done); |
15693458 | 1248 | init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1249 | init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
1e0d6714 | 1250 | init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
7a8e76a3 | 1251 | |
044fa782 | 1252 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
e4c2ce82 | 1253 | GFP_KERNEL, cpu_to_node(cpu)); |
044fa782 | 1254 | if (!bpage) |
e4c2ce82 SR |
1255 | goto fail_free_buffer; |
1256 | ||
77ae365e SR |
1257 | rb_check_bpage(cpu_buffer, bpage); |
1258 | ||
044fa782 | 1259 | cpu_buffer->reader_page = bpage; |
7ea59064 VN |
1260 | page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
1261 | if (!page) | |
e4c2ce82 | 1262 | goto fail_free_reader; |
7ea59064 | 1263 | bpage->page = page_address(page); |
044fa782 | 1264 | rb_init_page(bpage->page); |
e4c2ce82 | 1265 | |
d769041f | 1266 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
44b99462 | 1267 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
d769041f | 1268 | |
438ced17 | 1269 | ret = rb_allocate_pages(cpu_buffer, nr_pages); |
7a8e76a3 | 1270 | if (ret < 0) |
d769041f | 1271 | goto fail_free_reader; |
7a8e76a3 SR |
1272 | |
1273 | cpu_buffer->head_page | |
3adc54fa | 1274 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 1275 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
7a8e76a3 | 1276 | |
77ae365e SR |
1277 | rb_head_page_activate(cpu_buffer); |
1278 | ||
7a8e76a3 SR |
1279 | return cpu_buffer; |
1280 | ||
d769041f SR |
1281 | fail_free_reader: |
1282 | free_buffer_page(cpu_buffer->reader_page); | |
1283 | ||
7a8e76a3 SR |
1284 | fail_free_buffer: |
1285 | kfree(cpu_buffer); | |
1286 | return NULL; | |
1287 | } | |
1288 | ||
1289 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
1290 | { | |
3adc54fa | 1291 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1292 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1293 | |
d769041f SR |
1294 | free_buffer_page(cpu_buffer->reader_page); |
1295 | ||
77ae365e SR |
1296 | rb_head_page_deactivate(cpu_buffer); |
1297 | ||
3adc54fa SR |
1298 | if (head) { |
1299 | list_for_each_entry_safe(bpage, tmp, head, list) { | |
1300 | list_del_init(&bpage->list); | |
1301 | free_buffer_page(bpage); | |
1302 | } | |
1303 | bpage = list_entry(head, struct buffer_page, list); | |
044fa782 | 1304 | free_buffer_page(bpage); |
7a8e76a3 | 1305 | } |
3adc54fa | 1306 | |
7a8e76a3 SR |
1307 | kfree(cpu_buffer); |
1308 | } | |
1309 | ||
59222efe | 1310 | #ifdef CONFIG_HOTPLUG_CPU |
09c9e84d FW |
1311 | static int rb_cpu_notify(struct notifier_block *self, |
1312 | unsigned long action, void *hcpu); | |
554f786e SR |
1313 | #endif |
1314 | ||
7a8e76a3 | 1315 | /** |
d611851b | 1316 | * __ring_buffer_alloc - allocate a new ring_buffer |
68814b58 | 1317 | * @size: the size in bytes per cpu that is needed. |
7a8e76a3 SR |
1318 | * @flags: attributes to set for the ring buffer. |
1319 | * | |
1320 | * Currently the only flag that is available is the RB_FL_OVERWRITE | |
1321 | * flag. This flag means that the buffer will overwrite old data | |
1322 | * when the buffer wraps. If this flag is not set, the buffer will | |
1323 | * drop data when the tail hits the head. | |
1324 | */ | |
1f8a6a10 PZ |
1325 | struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1326 | struct lock_class_key *key) | |
7a8e76a3 SR |
1327 | { |
1328 | struct ring_buffer *buffer; | |
1329 | int bsize; | |
438ced17 | 1330 | int cpu, nr_pages; |
7a8e76a3 SR |
1331 | |
1332 | /* keep it in its own cache line */ | |
1333 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), | |
1334 | GFP_KERNEL); | |
1335 | if (!buffer) | |
1336 | return NULL; | |
1337 | ||
9e01c1b7 RR |
1338 | if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
1339 | goto fail_free_buffer; | |
1340 | ||
438ced17 | 1341 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
7a8e76a3 | 1342 | buffer->flags = flags; |
37886f6a | 1343 | buffer->clock = trace_clock_local; |
1f8a6a10 | 1344 | buffer->reader_lock_key = key; |
7a8e76a3 | 1345 | |
15693458 | 1346 | init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1347 | init_waitqueue_head(&buffer->irq_work.waiters); |
15693458 | 1348 | |
7a8e76a3 | 1349 | /* need at least two pages */ |
438ced17 VN |
1350 | if (nr_pages < 2) |
1351 | nr_pages = 2; | |
7a8e76a3 | 1352 | |
3bf832ce FW |
1353 | /* |
1354 | * In case of non-hotplug cpu, if the ring-buffer is allocated | |
1355 | * in early initcall, it will not be notified of secondary cpus. | |
1356 | * In that off case, we need to allocate for all possible cpus. | |
1357 | */ | |
1358 | #ifdef CONFIG_HOTPLUG_CPU | |
d39ad278 | 1359 | cpu_notifier_register_begin(); |
554f786e | 1360 | cpumask_copy(buffer->cpumask, cpu_online_mask); |
3bf832ce FW |
1361 | #else |
1362 | cpumask_copy(buffer->cpumask, cpu_possible_mask); | |
1363 | #endif | |
7a8e76a3 SR |
1364 | buffer->cpus = nr_cpu_ids; |
1365 | ||
1366 | bsize = sizeof(void *) * nr_cpu_ids; | |
1367 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), | |
1368 | GFP_KERNEL); | |
1369 | if (!buffer->buffers) | |
9e01c1b7 | 1370 | goto fail_free_cpumask; |
7a8e76a3 SR |
1371 | |
1372 | for_each_buffer_cpu(buffer, cpu) { | |
1373 | buffer->buffers[cpu] = | |
438ced17 | 1374 | rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
7a8e76a3 SR |
1375 | if (!buffer->buffers[cpu]) |
1376 | goto fail_free_buffers; | |
1377 | } | |
1378 | ||
59222efe | 1379 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
1380 | buffer->cpu_notify.notifier_call = rb_cpu_notify; |
1381 | buffer->cpu_notify.priority = 0; | |
d39ad278 SB |
1382 | __register_cpu_notifier(&buffer->cpu_notify); |
1383 | cpu_notifier_register_done(); | |
554f786e SR |
1384 | #endif |
1385 | ||
7a8e76a3 SR |
1386 | mutex_init(&buffer->mutex); |
1387 | ||
1388 | return buffer; | |
1389 | ||
1390 | fail_free_buffers: | |
1391 | for_each_buffer_cpu(buffer, cpu) { | |
1392 | if (buffer->buffers[cpu]) | |
1393 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1394 | } | |
1395 | kfree(buffer->buffers); | |
1396 | ||
9e01c1b7 RR |
1397 | fail_free_cpumask: |
1398 | free_cpumask_var(buffer->cpumask); | |
d39ad278 SB |
1399 | #ifdef CONFIG_HOTPLUG_CPU |
1400 | cpu_notifier_register_done(); | |
1401 | #endif | |
9e01c1b7 | 1402 | |
7a8e76a3 SR |
1403 | fail_free_buffer: |
1404 | kfree(buffer); | |
1405 | return NULL; | |
1406 | } | |
1f8a6a10 | 1407 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
7a8e76a3 SR |
1408 | |
1409 | /** | |
1410 | * ring_buffer_free - free a ring buffer. | |
1411 | * @buffer: the buffer to free. | |
1412 | */ | |
1413 | void | |
1414 | ring_buffer_free(struct ring_buffer *buffer) | |
1415 | { | |
1416 | int cpu; | |
1417 | ||
59222efe | 1418 | #ifdef CONFIG_HOTPLUG_CPU |
d39ad278 SB |
1419 | cpu_notifier_register_begin(); |
1420 | __unregister_cpu_notifier(&buffer->cpu_notify); | |
554f786e SR |
1421 | #endif |
1422 | ||
7a8e76a3 SR |
1423 | for_each_buffer_cpu(buffer, cpu) |
1424 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1425 | ||
d39ad278 SB |
1426 | #ifdef CONFIG_HOTPLUG_CPU |
1427 | cpu_notifier_register_done(); | |
1428 | #endif | |
554f786e | 1429 | |
bd3f0221 | 1430 | kfree(buffer->buffers); |
9e01c1b7 RR |
1431 | free_cpumask_var(buffer->cpumask); |
1432 | ||
7a8e76a3 SR |
1433 | kfree(buffer); |
1434 | } | |
c4f50183 | 1435 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
7a8e76a3 | 1436 | |
37886f6a SR |
1437 | void ring_buffer_set_clock(struct ring_buffer *buffer, |
1438 | u64 (*clock)(void)) | |
1439 | { | |
1440 | buffer->clock = clock; | |
1441 | } | |
1442 | ||
7a8e76a3 SR |
1443 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1444 | ||
83f40318 VN |
1445 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1446 | { | |
1447 | return local_read(&bpage->entries) & RB_WRITE_MASK; | |
1448 | } | |
1449 | ||
1450 | static inline unsigned long rb_page_write(struct buffer_page *bpage) | |
1451 | { | |
1452 | return local_read(&bpage->write) & RB_WRITE_MASK; | |
1453 | } | |
1454 | ||
5040b4b7 | 1455 | static int |
83f40318 | 1456 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages) |
7a8e76a3 | 1457 | { |
83f40318 VN |
1458 | struct list_head *tail_page, *to_remove, *next_page; |
1459 | struct buffer_page *to_remove_page, *tmp_iter_page; | |
1460 | struct buffer_page *last_page, *first_page; | |
1461 | unsigned int nr_removed; | |
1462 | unsigned long head_bit; | |
1463 | int page_entries; | |
1464 | ||
1465 | head_bit = 0; | |
7a8e76a3 | 1466 | |
5389f6fa | 1467 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1468 | atomic_inc(&cpu_buffer->record_disabled); |
1469 | /* | |
1470 | * We don't race with the readers since we have acquired the reader | |
1471 | * lock. We also don't race with writers after disabling recording. | |
1472 | * This makes it easy to figure out the first and the last page to be | |
1473 | * removed from the list. We unlink all the pages in between including | |
1474 | * the first and last pages. This is done in a busy loop so that we | |
1475 | * lose the least number of traces. | |
1476 | * The pages are freed after we restart recording and unlock readers. | |
1477 | */ | |
1478 | tail_page = &cpu_buffer->tail_page->list; | |
77ae365e | 1479 | |
83f40318 VN |
1480 | /* |
1481 | * tail page might be on reader page, we remove the next page | |
1482 | * from the ring buffer | |
1483 | */ | |
1484 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
1485 | tail_page = rb_list_head(tail_page->next); | |
1486 | to_remove = tail_page; | |
1487 | ||
1488 | /* start of pages to remove */ | |
1489 | first_page = list_entry(rb_list_head(to_remove->next), | |
1490 | struct buffer_page, list); | |
1491 | ||
1492 | for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { | |
1493 | to_remove = rb_list_head(to_remove)->next; | |
1494 | head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; | |
7a8e76a3 | 1495 | } |
7a8e76a3 | 1496 | |
83f40318 | 1497 | next_page = rb_list_head(to_remove)->next; |
7a8e76a3 | 1498 | |
83f40318 VN |
1499 | /* |
1500 | * Now we remove all pages between tail_page and next_page. | |
1501 | * Make sure that we have head_bit value preserved for the | |
1502 | * next page | |
1503 | */ | |
1504 | tail_page->next = (struct list_head *)((unsigned long)next_page | | |
1505 | head_bit); | |
1506 | next_page = rb_list_head(next_page); | |
1507 | next_page->prev = tail_page; | |
1508 | ||
1509 | /* make sure pages points to a valid page in the ring buffer */ | |
1510 | cpu_buffer->pages = next_page; | |
1511 | ||
1512 | /* update head page */ | |
1513 | if (head_bit) | |
1514 | cpu_buffer->head_page = list_entry(next_page, | |
1515 | struct buffer_page, list); | |
1516 | ||
1517 | /* | |
1518 | * change read pointer to make sure any read iterators reset | |
1519 | * themselves | |
1520 | */ | |
1521 | cpu_buffer->read = 0; | |
1522 | ||
1523 | /* pages are removed, resume tracing and then free the pages */ | |
1524 | atomic_dec(&cpu_buffer->record_disabled); | |
5389f6fa | 1525 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1526 | |
1527 | RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); | |
1528 | ||
1529 | /* last buffer page to remove */ | |
1530 | last_page = list_entry(rb_list_head(to_remove), struct buffer_page, | |
1531 | list); | |
1532 | tmp_iter_page = first_page; | |
1533 | ||
1534 | do { | |
1535 | to_remove_page = tmp_iter_page; | |
1536 | rb_inc_page(cpu_buffer, &tmp_iter_page); | |
1537 | ||
1538 | /* update the counters */ | |
1539 | page_entries = rb_page_entries(to_remove_page); | |
1540 | if (page_entries) { | |
1541 | /* | |
1542 | * If something was added to this page, it was full | |
1543 | * since it is not the tail page. So we deduct the | |
1544 | * bytes consumed in ring buffer from here. | |
48fdc72f | 1545 | * Increment overrun to account for the lost events. |
83f40318 | 1546 | */ |
48fdc72f | 1547 | local_add(page_entries, &cpu_buffer->overrun); |
83f40318 VN |
1548 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
1549 | } | |
1550 | ||
1551 | /* | |
1552 | * We have already removed references to this list item, just | |
1553 | * free up the buffer_page and its page | |
1554 | */ | |
1555 | free_buffer_page(to_remove_page); | |
1556 | nr_removed--; | |
1557 | ||
1558 | } while (to_remove_page != last_page); | |
1559 | ||
1560 | RB_WARN_ON(cpu_buffer, nr_removed); | |
5040b4b7 VN |
1561 | |
1562 | return nr_removed == 0; | |
7a8e76a3 SR |
1563 | } |
1564 | ||
5040b4b7 VN |
1565 | static int |
1566 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 1567 | { |
5040b4b7 VN |
1568 | struct list_head *pages = &cpu_buffer->new_pages; |
1569 | int retries, success; | |
7a8e76a3 | 1570 | |
5389f6fa | 1571 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1572 | /* |
1573 | * We are holding the reader lock, so the reader page won't be swapped | |
1574 | * in the ring buffer. Now we are racing with the writer trying to | |
1575 | * move head page and the tail page. | |
1576 | * We are going to adapt the reader page update process where: | |
1577 | * 1. We first splice the start and end of list of new pages between | |
1578 | * the head page and its previous page. | |
1579 | * 2. We cmpxchg the prev_page->next to point from head page to the | |
1580 | * start of new pages list. | |
1581 | * 3. Finally, we update the head->prev to the end of new list. | |
1582 | * | |
1583 | * We will try this process 10 times, to make sure that we don't keep | |
1584 | * spinning. | |
1585 | */ | |
1586 | retries = 10; | |
1587 | success = 0; | |
1588 | while (retries--) { | |
1589 | struct list_head *head_page, *prev_page, *r; | |
1590 | struct list_head *last_page, *first_page; | |
1591 | struct list_head *head_page_with_bit; | |
77ae365e | 1592 | |
5040b4b7 | 1593 | head_page = &rb_set_head_page(cpu_buffer)->list; |
54f7be5b SR |
1594 | if (!head_page) |
1595 | break; | |
5040b4b7 VN |
1596 | prev_page = head_page->prev; |
1597 | ||
1598 | first_page = pages->next; | |
1599 | last_page = pages->prev; | |
1600 | ||
1601 | head_page_with_bit = (struct list_head *) | |
1602 | ((unsigned long)head_page | RB_PAGE_HEAD); | |
1603 | ||
1604 | last_page->next = head_page_with_bit; | |
1605 | first_page->prev = prev_page; | |
1606 | ||
1607 | r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); | |
1608 | ||
1609 | if (r == head_page_with_bit) { | |
1610 | /* | |
1611 | * yay, we replaced the page pointer to our new list, | |
1612 | * now, we just have to update to head page's prev | |
1613 | * pointer to point to end of list | |
1614 | */ | |
1615 | head_page->prev = last_page; | |
1616 | success = 1; | |
1617 | break; | |
1618 | } | |
7a8e76a3 | 1619 | } |
7a8e76a3 | 1620 | |
5040b4b7 VN |
1621 | if (success) |
1622 | INIT_LIST_HEAD(pages); | |
1623 | /* | |
1624 | * If we weren't successful in adding in new pages, warn and stop | |
1625 | * tracing | |
1626 | */ | |
1627 | RB_WARN_ON(cpu_buffer, !success); | |
5389f6fa | 1628 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1629 | |
1630 | /* free pages if they weren't inserted */ | |
1631 | if (!success) { | |
1632 | struct buffer_page *bpage, *tmp; | |
1633 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, | |
1634 | list) { | |
1635 | list_del_init(&bpage->list); | |
1636 | free_buffer_page(bpage); | |
1637 | } | |
1638 | } | |
1639 | return success; | |
7a8e76a3 SR |
1640 | } |
1641 | ||
83f40318 | 1642 | static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
438ced17 | 1643 | { |
5040b4b7 VN |
1644 | int success; |
1645 | ||
438ced17 | 1646 | if (cpu_buffer->nr_pages_to_update > 0) |
5040b4b7 | 1647 | success = rb_insert_pages(cpu_buffer); |
438ced17 | 1648 | else |
5040b4b7 VN |
1649 | success = rb_remove_pages(cpu_buffer, |
1650 | -cpu_buffer->nr_pages_to_update); | |
83f40318 | 1651 | |
5040b4b7 VN |
1652 | if (success) |
1653 | cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; | |
83f40318 VN |
1654 | } |
1655 | ||
1656 | static void update_pages_handler(struct work_struct *work) | |
1657 | { | |
1658 | struct ring_buffer_per_cpu *cpu_buffer = container_of(work, | |
1659 | struct ring_buffer_per_cpu, update_pages_work); | |
1660 | rb_update_pages(cpu_buffer); | |
05fdd70d | 1661 | complete(&cpu_buffer->update_done); |
438ced17 VN |
1662 | } |
1663 | ||
7a8e76a3 SR |
1664 | /** |
1665 | * ring_buffer_resize - resize the ring buffer | |
1666 | * @buffer: the buffer to resize. | |
1667 | * @size: the new size. | |
d611851b | 1668 | * @cpu_id: the cpu buffer to resize |
7a8e76a3 | 1669 | * |
7a8e76a3 SR |
1670 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1671 | * | |
83f40318 | 1672 | * Returns 0 on success and < 0 on failure. |
7a8e76a3 | 1673 | */ |
438ced17 VN |
1674 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, |
1675 | int cpu_id) | |
7a8e76a3 SR |
1676 | { |
1677 | struct ring_buffer_per_cpu *cpu_buffer; | |
438ced17 | 1678 | unsigned nr_pages; |
83f40318 | 1679 | int cpu, err = 0; |
7a8e76a3 | 1680 | |
ee51a1de IM |
1681 | /* |
1682 | * Always succeed at resizing a non-existent buffer: | |
1683 | */ | |
1684 | if (!buffer) | |
1685 | return size; | |
1686 | ||
6a31e1f1 SR |
1687 | /* Make sure the requested buffer exists */ |
1688 | if (cpu_id != RING_BUFFER_ALL_CPUS && | |
1689 | !cpumask_test_cpu(cpu_id, buffer->cpumask)) | |
1690 | return size; | |
1691 | ||
7a8e76a3 SR |
1692 | size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1693 | size *= BUF_PAGE_SIZE; | |
7a8e76a3 SR |
1694 | |
1695 | /* we need a minimum of two pages */ | |
1696 | if (size < BUF_PAGE_SIZE * 2) | |
1697 | size = BUF_PAGE_SIZE * 2; | |
1698 | ||
83f40318 | 1699 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
18421015 | 1700 | |
83f40318 VN |
1701 | /* |
1702 | * Don't succeed if resizing is disabled, as a reader might be | |
1703 | * manipulating the ring buffer and is expecting a sane state while | |
1704 | * this is true. | |
1705 | */ | |
1706 | if (atomic_read(&buffer->resize_disabled)) | |
1707 | return -EBUSY; | |
18421015 | 1708 | |
83f40318 | 1709 | /* prevent another thread from changing buffer sizes */ |
7a8e76a3 | 1710 | mutex_lock(&buffer->mutex); |
7a8e76a3 | 1711 | |
438ced17 VN |
1712 | if (cpu_id == RING_BUFFER_ALL_CPUS) { |
1713 | /* calculate the pages to update */ | |
7a8e76a3 SR |
1714 | for_each_buffer_cpu(buffer, cpu) { |
1715 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 1716 | |
438ced17 VN |
1717 | cpu_buffer->nr_pages_to_update = nr_pages - |
1718 | cpu_buffer->nr_pages; | |
438ced17 VN |
1719 | /* |
1720 | * nothing more to do for removing pages or no update | |
1721 | */ | |
1722 | if (cpu_buffer->nr_pages_to_update <= 0) | |
1723 | continue; | |
d7ec4bfe | 1724 | /* |
438ced17 VN |
1725 | * to add pages, make sure all new pages can be |
1726 | * allocated without receiving ENOMEM | |
d7ec4bfe | 1727 | */ |
438ced17 VN |
1728 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
1729 | if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 | 1730 | &cpu_buffer->new_pages, cpu)) { |
438ced17 | 1731 | /* not enough memory for new pages */ |
83f40318 VN |
1732 | err = -ENOMEM; |
1733 | goto out_err; | |
1734 | } | |
1735 | } | |
1736 | ||
1737 | get_online_cpus(); | |
1738 | /* | |
1739 | * Fire off all the required work handlers | |
05fdd70d | 1740 | * We can't schedule on offline CPUs, but it's not necessary |
83f40318 VN |
1741 | * since we can change their buffer sizes without any race. |
1742 | */ | |
1743 | for_each_buffer_cpu(buffer, cpu) { | |
1744 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 1745 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
1746 | continue; |
1747 | ||
021c5b34 CM |
1748 | /* Can't run something on an offline CPU. */ |
1749 | if (!cpu_online(cpu)) { | |
f5eb5588 SRRH |
1750 | rb_update_pages(cpu_buffer); |
1751 | cpu_buffer->nr_pages_to_update = 0; | |
1752 | } else { | |
05fdd70d VN |
1753 | schedule_work_on(cpu, |
1754 | &cpu_buffer->update_pages_work); | |
f5eb5588 | 1755 | } |
7a8e76a3 | 1756 | } |
7a8e76a3 | 1757 | |
438ced17 VN |
1758 | /* wait for all the updates to complete */ |
1759 | for_each_buffer_cpu(buffer, cpu) { | |
1760 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 1761 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
1762 | continue; |
1763 | ||
05fdd70d VN |
1764 | if (cpu_online(cpu)) |
1765 | wait_for_completion(&cpu_buffer->update_done); | |
83f40318 | 1766 | cpu_buffer->nr_pages_to_update = 0; |
438ced17 | 1767 | } |
83f40318 VN |
1768 | |
1769 | put_online_cpus(); | |
438ced17 | 1770 | } else { |
8e49f418 VN |
1771 | /* Make sure this CPU has been intitialized */ |
1772 | if (!cpumask_test_cpu(cpu_id, buffer->cpumask)) | |
1773 | goto out; | |
1774 | ||
438ced17 | 1775 | cpu_buffer = buffer->buffers[cpu_id]; |
83f40318 | 1776 | |
438ced17 VN |
1777 | if (nr_pages == cpu_buffer->nr_pages) |
1778 | goto out; | |
7a8e76a3 | 1779 | |
438ced17 VN |
1780 | cpu_buffer->nr_pages_to_update = nr_pages - |
1781 | cpu_buffer->nr_pages; | |
1782 | ||
1783 | INIT_LIST_HEAD(&cpu_buffer->new_pages); | |
1784 | if (cpu_buffer->nr_pages_to_update > 0 && | |
1785 | __rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 VN |
1786 | &cpu_buffer->new_pages, cpu_id)) { |
1787 | err = -ENOMEM; | |
1788 | goto out_err; | |
1789 | } | |
438ced17 | 1790 | |
83f40318 VN |
1791 | get_online_cpus(); |
1792 | ||
021c5b34 CM |
1793 | /* Can't run something on an offline CPU. */ |
1794 | if (!cpu_online(cpu_id)) | |
f5eb5588 SRRH |
1795 | rb_update_pages(cpu_buffer); |
1796 | else { | |
83f40318 VN |
1797 | schedule_work_on(cpu_id, |
1798 | &cpu_buffer->update_pages_work); | |
05fdd70d | 1799 | wait_for_completion(&cpu_buffer->update_done); |
f5eb5588 | 1800 | } |
83f40318 | 1801 | |
83f40318 | 1802 | cpu_buffer->nr_pages_to_update = 0; |
05fdd70d | 1803 | put_online_cpus(); |
438ced17 | 1804 | } |
7a8e76a3 SR |
1805 | |
1806 | out: | |
659f451f SR |
1807 | /* |
1808 | * The ring buffer resize can happen with the ring buffer | |
1809 | * enabled, so that the update disturbs the tracing as little | |
1810 | * as possible. But if the buffer is disabled, we do not need | |
1811 | * to worry about that, and we can take the time to verify | |
1812 | * that the buffer is not corrupt. | |
1813 | */ | |
1814 | if (atomic_read(&buffer->record_disabled)) { | |
1815 | atomic_inc(&buffer->record_disabled); | |
1816 | /* | |
1817 | * Even though the buffer was disabled, we must make sure | |
1818 | * that it is truly disabled before calling rb_check_pages. | |
1819 | * There could have been a race between checking | |
1820 | * record_disable and incrementing it. | |
1821 | */ | |
1822 | synchronize_sched(); | |
1823 | for_each_buffer_cpu(buffer, cpu) { | |
1824 | cpu_buffer = buffer->buffers[cpu]; | |
1825 | rb_check_pages(cpu_buffer); | |
1826 | } | |
1827 | atomic_dec(&buffer->record_disabled); | |
1828 | } | |
1829 | ||
7a8e76a3 | 1830 | mutex_unlock(&buffer->mutex); |
7a8e76a3 SR |
1831 | return size; |
1832 | ||
83f40318 | 1833 | out_err: |
438ced17 VN |
1834 | for_each_buffer_cpu(buffer, cpu) { |
1835 | struct buffer_page *bpage, *tmp; | |
83f40318 | 1836 | |
438ced17 | 1837 | cpu_buffer = buffer->buffers[cpu]; |
438ced17 | 1838 | cpu_buffer->nr_pages_to_update = 0; |
83f40318 | 1839 | |
438ced17 VN |
1840 | if (list_empty(&cpu_buffer->new_pages)) |
1841 | continue; | |
83f40318 | 1842 | |
438ced17 VN |
1843 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
1844 | list) { | |
1845 | list_del_init(&bpage->list); | |
1846 | free_buffer_page(bpage); | |
1847 | } | |
7a8e76a3 | 1848 | } |
641d2f63 | 1849 | mutex_unlock(&buffer->mutex); |
83f40318 | 1850 | return err; |
7a8e76a3 | 1851 | } |
c4f50183 | 1852 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
7a8e76a3 | 1853 | |
750912fa DS |
1854 | void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) |
1855 | { | |
1856 | mutex_lock(&buffer->mutex); | |
1857 | if (val) | |
1858 | buffer->flags |= RB_FL_OVERWRITE; | |
1859 | else | |
1860 | buffer->flags &= ~RB_FL_OVERWRITE; | |
1861 | mutex_unlock(&buffer->mutex); | |
1862 | } | |
1863 | EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); | |
1864 | ||
8789a9e7 | 1865 | static inline void * |
044fa782 | 1866 | __rb_data_page_index(struct buffer_data_page *bpage, unsigned index) |
8789a9e7 | 1867 | { |
044fa782 | 1868 | return bpage->data + index; |
8789a9e7 SR |
1869 | } |
1870 | ||
044fa782 | 1871 | static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
7a8e76a3 | 1872 | { |
044fa782 | 1873 | return bpage->page->data + index; |
7a8e76a3 SR |
1874 | } |
1875 | ||
1876 | static inline struct ring_buffer_event * | |
d769041f | 1877 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1878 | { |
6f807acd SR |
1879 | return __rb_page_index(cpu_buffer->reader_page, |
1880 | cpu_buffer->reader_page->read); | |
1881 | } | |
1882 | ||
7a8e76a3 SR |
1883 | static inline struct ring_buffer_event * |
1884 | rb_iter_head_event(struct ring_buffer_iter *iter) | |
1885 | { | |
6f807acd | 1886 | return __rb_page_index(iter->head_page, iter->head); |
7a8e76a3 SR |
1887 | } |
1888 | ||
bf41a158 SR |
1889 | static inline unsigned rb_page_commit(struct buffer_page *bpage) |
1890 | { | |
abc9b56d | 1891 | return local_read(&bpage->page->commit); |
bf41a158 SR |
1892 | } |
1893 | ||
25985edc | 1894 | /* Size is determined by what has been committed */ |
bf41a158 SR |
1895 | static inline unsigned rb_page_size(struct buffer_page *bpage) |
1896 | { | |
1897 | return rb_page_commit(bpage); | |
1898 | } | |
1899 | ||
1900 | static inline unsigned | |
1901 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) | |
1902 | { | |
1903 | return rb_page_commit(cpu_buffer->commit_page); | |
1904 | } | |
1905 | ||
bf41a158 SR |
1906 | static inline unsigned |
1907 | rb_event_index(struct ring_buffer_event *event) | |
1908 | { | |
1909 | unsigned long addr = (unsigned long)event; | |
1910 | ||
22f470f8 | 1911 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
bf41a158 SR |
1912 | } |
1913 | ||
0f0c85fc | 1914 | static inline int |
fa743953 SR |
1915 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
1916 | struct ring_buffer_event *event) | |
bf41a158 SR |
1917 | { |
1918 | unsigned long addr = (unsigned long)event; | |
1919 | unsigned long index; | |
1920 | ||
1921 | index = rb_event_index(event); | |
1922 | addr &= PAGE_MASK; | |
1923 | ||
1924 | return cpu_buffer->commit_page->page == (void *)addr && | |
1925 | rb_commit_index(cpu_buffer) == index; | |
1926 | } | |
1927 | ||
34a148bf | 1928 | static void |
bf41a158 | 1929 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1930 | { |
77ae365e SR |
1931 | unsigned long max_count; |
1932 | ||
bf41a158 SR |
1933 | /* |
1934 | * We only race with interrupts and NMIs on this CPU. | |
1935 | * If we own the commit event, then we can commit | |
1936 | * all others that interrupted us, since the interruptions | |
1937 | * are in stack format (they finish before they come | |
1938 | * back to us). This allows us to do a simple loop to | |
1939 | * assign the commit to the tail. | |
1940 | */ | |
a8ccf1d6 | 1941 | again: |
438ced17 | 1942 | max_count = cpu_buffer->nr_pages * 100; |
77ae365e | 1943 | |
bf41a158 | 1944 | while (cpu_buffer->commit_page != cpu_buffer->tail_page) { |
77ae365e SR |
1945 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
1946 | return; | |
1947 | if (RB_WARN_ON(cpu_buffer, | |
1948 | rb_is_reader_page(cpu_buffer->tail_page))) | |
1949 | return; | |
1950 | local_set(&cpu_buffer->commit_page->page->commit, | |
1951 | rb_page_write(cpu_buffer->commit_page)); | |
bf41a158 | 1952 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); |
abc9b56d SR |
1953 | cpu_buffer->write_stamp = |
1954 | cpu_buffer->commit_page->page->time_stamp; | |
bf41a158 SR |
1955 | /* add barrier to keep gcc from optimizing too much */ |
1956 | barrier(); | |
1957 | } | |
1958 | while (rb_commit_index(cpu_buffer) != | |
1959 | rb_page_write(cpu_buffer->commit_page)) { | |
77ae365e SR |
1960 | |
1961 | local_set(&cpu_buffer->commit_page->page->commit, | |
1962 | rb_page_write(cpu_buffer->commit_page)); | |
1963 | RB_WARN_ON(cpu_buffer, | |
1964 | local_read(&cpu_buffer->commit_page->page->commit) & | |
1965 | ~RB_WRITE_MASK); | |
bf41a158 SR |
1966 | barrier(); |
1967 | } | |
a8ccf1d6 SR |
1968 | |
1969 | /* again, keep gcc from optimizing */ | |
1970 | barrier(); | |
1971 | ||
1972 | /* | |
1973 | * If an interrupt came in just after the first while loop | |
1974 | * and pushed the tail page forward, we will be left with | |
1975 | * a dangling commit that will never go forward. | |
1976 | */ | |
1977 | if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page)) | |
1978 | goto again; | |
7a8e76a3 SR |
1979 | } |
1980 | ||
d769041f | 1981 | static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1982 | { |
abc9b56d | 1983 | cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp; |
6f807acd | 1984 | cpu_buffer->reader_page->read = 0; |
d769041f SR |
1985 | } |
1986 | ||
34a148bf | 1987 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
d769041f SR |
1988 | { |
1989 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1990 | ||
1991 | /* | |
1992 | * The iterator could be on the reader page (it starts there). | |
1993 | * But the head could have moved, since the reader was | |
1994 | * found. Check for this case and assign the iterator | |
1995 | * to the head page instead of next. | |
1996 | */ | |
1997 | if (iter->head_page == cpu_buffer->reader_page) | |
77ae365e | 1998 | iter->head_page = rb_set_head_page(cpu_buffer); |
d769041f SR |
1999 | else |
2000 | rb_inc_page(cpu_buffer, &iter->head_page); | |
2001 | ||
abc9b56d | 2002 | iter->read_stamp = iter->head_page->page->time_stamp; |
7a8e76a3 SR |
2003 | iter->head = 0; |
2004 | } | |
2005 | ||
69d1b839 SR |
2006 | /* Slow path, do not inline */ |
2007 | static noinline struct ring_buffer_event * | |
2008 | rb_add_time_stamp(struct ring_buffer_event *event, u64 delta) | |
2009 | { | |
2010 | event->type_len = RINGBUF_TYPE_TIME_EXTEND; | |
2011 | ||
2012 | /* Not the first event on the page? */ | |
2013 | if (rb_event_index(event)) { | |
2014 | event->time_delta = delta & TS_MASK; | |
2015 | event->array[0] = delta >> TS_SHIFT; | |
2016 | } else { | |
2017 | /* nope, just zero it */ | |
2018 | event->time_delta = 0; | |
2019 | event->array[0] = 0; | |
2020 | } | |
2021 | ||
2022 | return skip_time_extend(event); | |
2023 | } | |
2024 | ||
7a8e76a3 | 2025 | /** |
01e3e710 | 2026 | * rb_update_event - update event type and data |
021de3d9 | 2027 | * @event: the event to update |
7a8e76a3 SR |
2028 | * @type: the type of event |
2029 | * @length: the size of the event field in the ring buffer | |
2030 | * | |
2031 | * Update the type and data fields of the event. The length | |
2032 | * is the actual size that is written to the ring buffer, | |
2033 | * and with this, we can determine what to place into the | |
2034 | * data field. | |
2035 | */ | |
34a148bf | 2036 | static void |
69d1b839 SR |
2037 | rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
2038 | struct ring_buffer_event *event, unsigned length, | |
2039 | int add_timestamp, u64 delta) | |
7a8e76a3 | 2040 | { |
69d1b839 SR |
2041 | /* Only a commit updates the timestamp */ |
2042 | if (unlikely(!rb_event_is_commit(cpu_buffer, event))) | |
2043 | delta = 0; | |
7a8e76a3 | 2044 | |
69d1b839 SR |
2045 | /* |
2046 | * If we need to add a timestamp, then we | |
2047 | * add it to the start of the resevered space. | |
2048 | */ | |
2049 | if (unlikely(add_timestamp)) { | |
2050 | event = rb_add_time_stamp(event, delta); | |
2051 | length -= RB_LEN_TIME_EXTEND; | |
2052 | delta = 0; | |
7a8e76a3 | 2053 | } |
69d1b839 SR |
2054 | |
2055 | event->time_delta = delta; | |
2056 | length -= RB_EVNT_HDR_SIZE; | |
2057 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { | |
2058 | event->type_len = 0; | |
2059 | event->array[0] = length; | |
2060 | } else | |
2061 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); | |
7a8e76a3 SR |
2062 | } |
2063 | ||
77ae365e SR |
2064 | /* |
2065 | * rb_handle_head_page - writer hit the head page | |
2066 | * | |
2067 | * Returns: +1 to retry page | |
2068 | * 0 to continue | |
2069 | * -1 on error | |
2070 | */ | |
2071 | static int | |
2072 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, | |
2073 | struct buffer_page *tail_page, | |
2074 | struct buffer_page *next_page) | |
2075 | { | |
2076 | struct buffer_page *new_head; | |
2077 | int entries; | |
2078 | int type; | |
2079 | int ret; | |
2080 | ||
2081 | entries = rb_page_entries(next_page); | |
2082 | ||
2083 | /* | |
2084 | * The hard part is here. We need to move the head | |
2085 | * forward, and protect against both readers on | |
2086 | * other CPUs and writers coming in via interrupts. | |
2087 | */ | |
2088 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, | |
2089 | RB_PAGE_HEAD); | |
2090 | ||
2091 | /* | |
2092 | * type can be one of four: | |
2093 | * NORMAL - an interrupt already moved it for us | |
2094 | * HEAD - we are the first to get here. | |
2095 | * UPDATE - we are the interrupt interrupting | |
2096 | * a current move. | |
2097 | * MOVED - a reader on another CPU moved the next | |
2098 | * pointer to its reader page. Give up | |
2099 | * and try again. | |
2100 | */ | |
2101 | ||
2102 | switch (type) { | |
2103 | case RB_PAGE_HEAD: | |
2104 | /* | |
2105 | * We changed the head to UPDATE, thus | |
2106 | * it is our responsibility to update | |
2107 | * the counters. | |
2108 | */ | |
2109 | local_add(entries, &cpu_buffer->overrun); | |
c64e148a | 2110 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
77ae365e SR |
2111 | |
2112 | /* | |
2113 | * The entries will be zeroed out when we move the | |
2114 | * tail page. | |
2115 | */ | |
2116 | ||
2117 | /* still more to do */ | |
2118 | break; | |
2119 | ||
2120 | case RB_PAGE_UPDATE: | |
2121 | /* | |
2122 | * This is an interrupt that interrupt the | |
2123 | * previous update. Still more to do. | |
2124 | */ | |
2125 | break; | |
2126 | case RB_PAGE_NORMAL: | |
2127 | /* | |
2128 | * An interrupt came in before the update | |
2129 | * and processed this for us. | |
2130 | * Nothing left to do. | |
2131 | */ | |
2132 | return 1; | |
2133 | case RB_PAGE_MOVED: | |
2134 | /* | |
2135 | * The reader is on another CPU and just did | |
2136 | * a swap with our next_page. | |
2137 | * Try again. | |
2138 | */ | |
2139 | return 1; | |
2140 | default: | |
2141 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ | |
2142 | return -1; | |
2143 | } | |
2144 | ||
2145 | /* | |
2146 | * Now that we are here, the old head pointer is | |
2147 | * set to UPDATE. This will keep the reader from | |
2148 | * swapping the head page with the reader page. | |
2149 | * The reader (on another CPU) will spin till | |
2150 | * we are finished. | |
2151 | * | |
2152 | * We just need to protect against interrupts | |
2153 | * doing the job. We will set the next pointer | |
2154 | * to HEAD. After that, we set the old pointer | |
2155 | * to NORMAL, but only if it was HEAD before. | |
2156 | * otherwise we are an interrupt, and only | |
2157 | * want the outer most commit to reset it. | |
2158 | */ | |
2159 | new_head = next_page; | |
2160 | rb_inc_page(cpu_buffer, &new_head); | |
2161 | ||
2162 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, | |
2163 | RB_PAGE_NORMAL); | |
2164 | ||
2165 | /* | |
2166 | * Valid returns are: | |
2167 | * HEAD - an interrupt came in and already set it. | |
2168 | * NORMAL - One of two things: | |
2169 | * 1) We really set it. | |
2170 | * 2) A bunch of interrupts came in and moved | |
2171 | * the page forward again. | |
2172 | */ | |
2173 | switch (ret) { | |
2174 | case RB_PAGE_HEAD: | |
2175 | case RB_PAGE_NORMAL: | |
2176 | /* OK */ | |
2177 | break; | |
2178 | default: | |
2179 | RB_WARN_ON(cpu_buffer, 1); | |
2180 | return -1; | |
2181 | } | |
2182 | ||
2183 | /* | |
2184 | * It is possible that an interrupt came in, | |
2185 | * set the head up, then more interrupts came in | |
2186 | * and moved it again. When we get back here, | |
2187 | * the page would have been set to NORMAL but we | |
2188 | * just set it back to HEAD. | |
2189 | * | |
2190 | * How do you detect this? Well, if that happened | |
2191 | * the tail page would have moved. | |
2192 | */ | |
2193 | if (ret == RB_PAGE_NORMAL) { | |
2194 | /* | |
2195 | * If the tail had moved passed next, then we need | |
2196 | * to reset the pointer. | |
2197 | */ | |
2198 | if (cpu_buffer->tail_page != tail_page && | |
2199 | cpu_buffer->tail_page != next_page) | |
2200 | rb_head_page_set_normal(cpu_buffer, new_head, | |
2201 | next_page, | |
2202 | RB_PAGE_HEAD); | |
2203 | } | |
2204 | ||
2205 | /* | |
2206 | * If this was the outer most commit (the one that | |
2207 | * changed the original pointer from HEAD to UPDATE), | |
2208 | * then it is up to us to reset it to NORMAL. | |
2209 | */ | |
2210 | if (type == RB_PAGE_HEAD) { | |
2211 | ret = rb_head_page_set_normal(cpu_buffer, next_page, | |
2212 | tail_page, | |
2213 | RB_PAGE_UPDATE); | |
2214 | if (RB_WARN_ON(cpu_buffer, | |
2215 | ret != RB_PAGE_UPDATE)) | |
2216 | return -1; | |
2217 | } | |
2218 | ||
2219 | return 0; | |
2220 | } | |
2221 | ||
34a148bf | 2222 | static unsigned rb_calculate_event_length(unsigned length) |
7a8e76a3 SR |
2223 | { |
2224 | struct ring_buffer_event event; /* Used only for sizeof array */ | |
2225 | ||
2226 | /* zero length can cause confusions */ | |
2227 | if (!length) | |
2228 | length = 1; | |
2229 | ||
2271048d | 2230 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
7a8e76a3 SR |
2231 | length += sizeof(event.array[0]); |
2232 | ||
2233 | length += RB_EVNT_HDR_SIZE; | |
2271048d | 2234 | length = ALIGN(length, RB_ARCH_ALIGNMENT); |
7a8e76a3 SR |
2235 | |
2236 | return length; | |
2237 | } | |
2238 | ||
c7b09308 SR |
2239 | static inline void |
2240 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, | |
2241 | struct buffer_page *tail_page, | |
2242 | unsigned long tail, unsigned long length) | |
2243 | { | |
2244 | struct ring_buffer_event *event; | |
2245 | ||
2246 | /* | |
2247 | * Only the event that crossed the page boundary | |
2248 | * must fill the old tail_page with padding. | |
2249 | */ | |
2250 | if (tail >= BUF_PAGE_SIZE) { | |
b3230c8b SR |
2251 | /* |
2252 | * If the page was filled, then we still need | |
2253 | * to update the real_end. Reset it to zero | |
2254 | * and the reader will ignore it. | |
2255 | */ | |
2256 | if (tail == BUF_PAGE_SIZE) | |
2257 | tail_page->real_end = 0; | |
2258 | ||
c7b09308 SR |
2259 | local_sub(length, &tail_page->write); |
2260 | return; | |
2261 | } | |
2262 | ||
2263 | event = __rb_page_index(tail_page, tail); | |
b0b7065b | 2264 | kmemcheck_annotate_bitfield(event, bitfield); |
c7b09308 | 2265 | |
c64e148a VN |
2266 | /* account for padding bytes */ |
2267 | local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); | |
2268 | ||
ff0ff84a SR |
2269 | /* |
2270 | * Save the original length to the meta data. | |
2271 | * This will be used by the reader to add lost event | |
2272 | * counter. | |
2273 | */ | |
2274 | tail_page->real_end = tail; | |
2275 | ||
c7b09308 SR |
2276 | /* |
2277 | * If this event is bigger than the minimum size, then | |
2278 | * we need to be careful that we don't subtract the | |
2279 | * write counter enough to allow another writer to slip | |
2280 | * in on this page. | |
2281 | * We put in a discarded commit instead, to make sure | |
2282 | * that this space is not used again. | |
2283 | * | |
2284 | * If we are less than the minimum size, we don't need to | |
2285 | * worry about it. | |
2286 | */ | |
2287 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { | |
2288 | /* No room for any events */ | |
2289 | ||
2290 | /* Mark the rest of the page with padding */ | |
2291 | rb_event_set_padding(event); | |
2292 | ||
2293 | /* Set the write back to the previous setting */ | |
2294 | local_sub(length, &tail_page->write); | |
2295 | return; | |
2296 | } | |
2297 | ||
2298 | /* Put in a discarded event */ | |
2299 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; | |
2300 | event->type_len = RINGBUF_TYPE_PADDING; | |
2301 | /* time delta must be non zero */ | |
2302 | event->time_delta = 1; | |
c7b09308 SR |
2303 | |
2304 | /* Set write to end of buffer */ | |
2305 | length = (tail + length) - BUF_PAGE_SIZE; | |
2306 | local_sub(length, &tail_page->write); | |
2307 | } | |
6634ff26 | 2308 | |
747e94ae SR |
2309 | /* |
2310 | * This is the slow path, force gcc not to inline it. | |
2311 | */ | |
2312 | static noinline struct ring_buffer_event * | |
6634ff26 SR |
2313 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
2314 | unsigned long length, unsigned long tail, | |
e8bc43e8 | 2315 | struct buffer_page *tail_page, u64 ts) |
7a8e76a3 | 2316 | { |
5a50e33c | 2317 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
7a8e76a3 | 2318 | struct ring_buffer *buffer = cpu_buffer->buffer; |
77ae365e SR |
2319 | struct buffer_page *next_page; |
2320 | int ret; | |
aa20ae84 SR |
2321 | |
2322 | next_page = tail_page; | |
2323 | ||
aa20ae84 SR |
2324 | rb_inc_page(cpu_buffer, &next_page); |
2325 | ||
aa20ae84 SR |
2326 | /* |
2327 | * If for some reason, we had an interrupt storm that made | |
2328 | * it all the way around the buffer, bail, and warn | |
2329 | * about it. | |
2330 | */ | |
2331 | if (unlikely(next_page == commit_page)) { | |
77ae365e | 2332 | local_inc(&cpu_buffer->commit_overrun); |
aa20ae84 SR |
2333 | goto out_reset; |
2334 | } | |
2335 | ||
77ae365e SR |
2336 | /* |
2337 | * This is where the fun begins! | |
2338 | * | |
2339 | * We are fighting against races between a reader that | |
2340 | * could be on another CPU trying to swap its reader | |
2341 | * page with the buffer head. | |
2342 | * | |
2343 | * We are also fighting against interrupts coming in and | |
2344 | * moving the head or tail on us as well. | |
2345 | * | |
2346 | * If the next page is the head page then we have filled | |
2347 | * the buffer, unless the commit page is still on the | |
2348 | * reader page. | |
2349 | */ | |
2350 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { | |
aa20ae84 | 2351 | |
77ae365e SR |
2352 | /* |
2353 | * If the commit is not on the reader page, then | |
2354 | * move the header page. | |
2355 | */ | |
2356 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { | |
2357 | /* | |
2358 | * If we are not in overwrite mode, | |
2359 | * this is easy, just stop here. | |
2360 | */ | |
884bfe89 SP |
2361 | if (!(buffer->flags & RB_FL_OVERWRITE)) { |
2362 | local_inc(&cpu_buffer->dropped_events); | |
77ae365e | 2363 | goto out_reset; |
884bfe89 | 2364 | } |
77ae365e SR |
2365 | |
2366 | ret = rb_handle_head_page(cpu_buffer, | |
2367 | tail_page, | |
2368 | next_page); | |
2369 | if (ret < 0) | |
2370 | goto out_reset; | |
2371 | if (ret) | |
2372 | goto out_again; | |
2373 | } else { | |
2374 | /* | |
2375 | * We need to be careful here too. The | |
2376 | * commit page could still be on the reader | |
2377 | * page. We could have a small buffer, and | |
2378 | * have filled up the buffer with events | |
2379 | * from interrupts and such, and wrapped. | |
2380 | * | |
2381 | * Note, if the tail page is also the on the | |
2382 | * reader_page, we let it move out. | |
2383 | */ | |
2384 | if (unlikely((cpu_buffer->commit_page != | |
2385 | cpu_buffer->tail_page) && | |
2386 | (cpu_buffer->commit_page == | |
2387 | cpu_buffer->reader_page))) { | |
2388 | local_inc(&cpu_buffer->commit_overrun); | |
2389 | goto out_reset; | |
2390 | } | |
aa20ae84 SR |
2391 | } |
2392 | } | |
2393 | ||
77ae365e SR |
2394 | ret = rb_tail_page_update(cpu_buffer, tail_page, next_page); |
2395 | if (ret) { | |
2396 | /* | |
2397 | * Nested commits always have zero deltas, so | |
2398 | * just reread the time stamp | |
2399 | */ | |
e8bc43e8 SR |
2400 | ts = rb_time_stamp(buffer); |
2401 | next_page->page->time_stamp = ts; | |
aa20ae84 SR |
2402 | } |
2403 | ||
77ae365e | 2404 | out_again: |
aa20ae84 | 2405 | |
77ae365e | 2406 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
aa20ae84 SR |
2407 | |
2408 | /* fail and let the caller try again */ | |
2409 | return ERR_PTR(-EAGAIN); | |
2410 | ||
45141d46 | 2411 | out_reset: |
6f3b3440 | 2412 | /* reset write */ |
c7b09308 | 2413 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
6f3b3440 | 2414 | |
bf41a158 | 2415 | return NULL; |
7a8e76a3 SR |
2416 | } |
2417 | ||
6634ff26 SR |
2418 | static struct ring_buffer_event * |
2419 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, | |
69d1b839 SR |
2420 | unsigned long length, u64 ts, |
2421 | u64 delta, int add_timestamp) | |
6634ff26 | 2422 | { |
5a50e33c | 2423 | struct buffer_page *tail_page; |
6634ff26 SR |
2424 | struct ring_buffer_event *event; |
2425 | unsigned long tail, write; | |
2426 | ||
69d1b839 SR |
2427 | /* |
2428 | * If the time delta since the last event is too big to | |
2429 | * hold in the time field of the event, then we append a | |
2430 | * TIME EXTEND event ahead of the data event. | |
2431 | */ | |
2432 | if (unlikely(add_timestamp)) | |
2433 | length += RB_LEN_TIME_EXTEND; | |
2434 | ||
6634ff26 SR |
2435 | tail_page = cpu_buffer->tail_page; |
2436 | write = local_add_return(length, &tail_page->write); | |
77ae365e SR |
2437 | |
2438 | /* set write to only the index of the write */ | |
2439 | write &= RB_WRITE_MASK; | |
6634ff26 SR |
2440 | tail = write - length; |
2441 | ||
d651aa1d SRRH |
2442 | /* |
2443 | * If this is the first commit on the page, then it has the same | |
2444 | * timestamp as the page itself. | |
2445 | */ | |
2446 | if (!tail) | |
2447 | delta = 0; | |
2448 | ||
6634ff26 | 2449 | /* See if we shot pass the end of this buffer page */ |
747e94ae | 2450 | if (unlikely(write > BUF_PAGE_SIZE)) |
6634ff26 | 2451 | return rb_move_tail(cpu_buffer, length, tail, |
5a50e33c | 2452 | tail_page, ts); |
6634ff26 SR |
2453 | |
2454 | /* We reserved something on the buffer */ | |
2455 | ||
6634ff26 | 2456 | event = __rb_page_index(tail_page, tail); |
1744a21d | 2457 | kmemcheck_annotate_bitfield(event, bitfield); |
69d1b839 | 2458 | rb_update_event(cpu_buffer, event, length, add_timestamp, delta); |
6634ff26 | 2459 | |
69d1b839 | 2460 | local_inc(&tail_page->entries); |
6634ff26 SR |
2461 | |
2462 | /* | |
fa743953 SR |
2463 | * If this is the first commit on the page, then update |
2464 | * its timestamp. | |
6634ff26 | 2465 | */ |
fa743953 | 2466 | if (!tail) |
e8bc43e8 | 2467 | tail_page->page->time_stamp = ts; |
6634ff26 | 2468 | |
c64e148a VN |
2469 | /* account for these added bytes */ |
2470 | local_add(length, &cpu_buffer->entries_bytes); | |
2471 | ||
6634ff26 SR |
2472 | return event; |
2473 | } | |
2474 | ||
edd813bf SR |
2475 | static inline int |
2476 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, | |
2477 | struct ring_buffer_event *event) | |
2478 | { | |
2479 | unsigned long new_index, old_index; | |
2480 | struct buffer_page *bpage; | |
2481 | unsigned long index; | |
2482 | unsigned long addr; | |
2483 | ||
2484 | new_index = rb_event_index(event); | |
69d1b839 | 2485 | old_index = new_index + rb_event_ts_length(event); |
edd813bf SR |
2486 | addr = (unsigned long)event; |
2487 | addr &= PAGE_MASK; | |
2488 | ||
2489 | bpage = cpu_buffer->tail_page; | |
2490 | ||
2491 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { | |
77ae365e SR |
2492 | unsigned long write_mask = |
2493 | local_read(&bpage->write) & ~RB_WRITE_MASK; | |
c64e148a | 2494 | unsigned long event_length = rb_event_length(event); |
edd813bf SR |
2495 | /* |
2496 | * This is on the tail page. It is possible that | |
2497 | * a write could come in and move the tail page | |
2498 | * and write to the next page. That is fine | |
2499 | * because we just shorten what is on this page. | |
2500 | */ | |
77ae365e SR |
2501 | old_index += write_mask; |
2502 | new_index += write_mask; | |
edd813bf | 2503 | index = local_cmpxchg(&bpage->write, old_index, new_index); |
c64e148a VN |
2504 | if (index == old_index) { |
2505 | /* update counters */ | |
2506 | local_sub(event_length, &cpu_buffer->entries_bytes); | |
edd813bf | 2507 | return 1; |
c64e148a | 2508 | } |
edd813bf SR |
2509 | } |
2510 | ||
2511 | /* could not discard */ | |
2512 | return 0; | |
2513 | } | |
2514 | ||
fa743953 SR |
2515 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2516 | { | |
2517 | local_inc(&cpu_buffer->committing); | |
2518 | local_inc(&cpu_buffer->commits); | |
2519 | } | |
2520 | ||
d9abde21 | 2521 | static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
fa743953 SR |
2522 | { |
2523 | unsigned long commits; | |
2524 | ||
2525 | if (RB_WARN_ON(cpu_buffer, | |
2526 | !local_read(&cpu_buffer->committing))) | |
2527 | return; | |
2528 | ||
2529 | again: | |
2530 | commits = local_read(&cpu_buffer->commits); | |
2531 | /* synchronize with interrupts */ | |
2532 | barrier(); | |
2533 | if (local_read(&cpu_buffer->committing) == 1) | |
2534 | rb_set_commit_to_write(cpu_buffer); | |
2535 | ||
2536 | local_dec(&cpu_buffer->committing); | |
2537 | ||
2538 | /* synchronize with interrupts */ | |
2539 | barrier(); | |
2540 | ||
2541 | /* | |
2542 | * Need to account for interrupts coming in between the | |
2543 | * updating of the commit page and the clearing of the | |
2544 | * committing counter. | |
2545 | */ | |
2546 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && | |
2547 | !local_read(&cpu_buffer->committing)) { | |
2548 | local_inc(&cpu_buffer->committing); | |
2549 | goto again; | |
2550 | } | |
2551 | } | |
2552 | ||
7a8e76a3 | 2553 | static struct ring_buffer_event * |
62f0b3eb SR |
2554 | rb_reserve_next_event(struct ring_buffer *buffer, |
2555 | struct ring_buffer_per_cpu *cpu_buffer, | |
1cd8d735 | 2556 | unsigned long length) |
7a8e76a3 SR |
2557 | { |
2558 | struct ring_buffer_event *event; | |
69d1b839 | 2559 | u64 ts, delta; |
818e3dd3 | 2560 | int nr_loops = 0; |
69d1b839 | 2561 | int add_timestamp; |
140ff891 | 2562 | u64 diff; |
7a8e76a3 | 2563 | |
fa743953 SR |
2564 | rb_start_commit(cpu_buffer); |
2565 | ||
85bac32c | 2566 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
62f0b3eb SR |
2567 | /* |
2568 | * Due to the ability to swap a cpu buffer from a buffer | |
2569 | * it is possible it was swapped before we committed. | |
2570 | * (committing stops a swap). We check for it here and | |
2571 | * if it happened, we have to fail the write. | |
2572 | */ | |
2573 | barrier(); | |
2574 | if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) { | |
2575 | local_dec(&cpu_buffer->committing); | |
2576 | local_dec(&cpu_buffer->commits); | |
2577 | return NULL; | |
2578 | } | |
85bac32c | 2579 | #endif |
62f0b3eb | 2580 | |
be957c44 | 2581 | length = rb_calculate_event_length(length); |
bf41a158 | 2582 | again: |
69d1b839 SR |
2583 | add_timestamp = 0; |
2584 | delta = 0; | |
2585 | ||
818e3dd3 SR |
2586 | /* |
2587 | * We allow for interrupts to reenter here and do a trace. | |
2588 | * If one does, it will cause this original code to loop | |
2589 | * back here. Even with heavy interrupts happening, this | |
2590 | * should only happen a few times in a row. If this happens | |
2591 | * 1000 times in a row, there must be either an interrupt | |
2592 | * storm or we have something buggy. | |
2593 | * Bail! | |
2594 | */ | |
3e89c7bb | 2595 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
fa743953 | 2596 | goto out_fail; |
818e3dd3 | 2597 | |
6d3f1e12 | 2598 | ts = rb_time_stamp(cpu_buffer->buffer); |
140ff891 | 2599 | diff = ts - cpu_buffer->write_stamp; |
7a8e76a3 | 2600 | |
140ff891 SR |
2601 | /* make sure this diff is calculated here */ |
2602 | barrier(); | |
bf41a158 | 2603 | |
140ff891 SR |
2604 | /* Did the write stamp get updated already? */ |
2605 | if (likely(ts >= cpu_buffer->write_stamp)) { | |
168b6b1d SR |
2606 | delta = diff; |
2607 | if (unlikely(test_time_stamp(delta))) { | |
31274d72 JO |
2608 | int local_clock_stable = 1; |
2609 | #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK | |
35af99e6 | 2610 | local_clock_stable = sched_clock_stable(); |
31274d72 | 2611 | #endif |
69d1b839 | 2612 | WARN_ONCE(delta > (1ULL << 59), |
31274d72 | 2613 | KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s", |
69d1b839 SR |
2614 | (unsigned long long)delta, |
2615 | (unsigned long long)ts, | |
31274d72 JO |
2616 | (unsigned long long)cpu_buffer->write_stamp, |
2617 | local_clock_stable ? "" : | |
2618 | "If you just came from a suspend/resume,\n" | |
2619 | "please switch to the trace global clock:\n" | |
2620 | " echo global > /sys/kernel/debug/tracing/trace_clock\n"); | |
69d1b839 | 2621 | add_timestamp = 1; |
7a8e76a3 | 2622 | } |
168b6b1d | 2623 | } |
7a8e76a3 | 2624 | |
69d1b839 SR |
2625 | event = __rb_reserve_next(cpu_buffer, length, ts, |
2626 | delta, add_timestamp); | |
168b6b1d | 2627 | if (unlikely(PTR_ERR(event) == -EAGAIN)) |
bf41a158 SR |
2628 | goto again; |
2629 | ||
fa743953 SR |
2630 | if (!event) |
2631 | goto out_fail; | |
7a8e76a3 | 2632 | |
7a8e76a3 | 2633 | return event; |
fa743953 SR |
2634 | |
2635 | out_fail: | |
2636 | rb_end_commit(cpu_buffer); | |
2637 | return NULL; | |
7a8e76a3 SR |
2638 | } |
2639 | ||
567cd4da SR |
2640 | /* |
2641 | * The lock and unlock are done within a preempt disable section. | |
2642 | * The current_context per_cpu variable can only be modified | |
2643 | * by the current task between lock and unlock. But it can | |
2644 | * be modified more than once via an interrupt. To pass this | |
2645 | * information from the lock to the unlock without having to | |
2646 | * access the 'in_interrupt()' functions again (which do show | |
2647 | * a bit of overhead in something as critical as function tracing, | |
2648 | * we use a bitmask trick. | |
2649 | * | |
2650 | * bit 0 = NMI context | |
2651 | * bit 1 = IRQ context | |
2652 | * bit 2 = SoftIRQ context | |
2653 | * bit 3 = normal context. | |
2654 | * | |
2655 | * This works because this is the order of contexts that can | |
2656 | * preempt other contexts. A SoftIRQ never preempts an IRQ | |
2657 | * context. | |
2658 | * | |
2659 | * When the context is determined, the corresponding bit is | |
2660 | * checked and set (if it was set, then a recursion of that context | |
2661 | * happened). | |
2662 | * | |
2663 | * On unlock, we need to clear this bit. To do so, just subtract | |
2664 | * 1 from the current_context and AND it to itself. | |
2665 | * | |
2666 | * (binary) | |
2667 | * 101 - 1 = 100 | |
2668 | * 101 & 100 = 100 (clearing bit zero) | |
2669 | * | |
2670 | * 1010 - 1 = 1001 | |
2671 | * 1010 & 1001 = 1000 (clearing bit 1) | |
2672 | * | |
2673 | * The least significant bit can be cleared this way, and it | |
2674 | * just so happens that it is the same bit corresponding to | |
2675 | * the current context. | |
2676 | */ | |
261842b7 | 2677 | |
58a09ec6 SRRH |
2678 | static __always_inline int |
2679 | trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) | |
261842b7 | 2680 | { |
58a09ec6 | 2681 | unsigned int val = cpu_buffer->current_context; |
567cd4da | 2682 | int bit; |
d9abde21 | 2683 | |
567cd4da SR |
2684 | if (in_interrupt()) { |
2685 | if (in_nmi()) | |
2686 | bit = 0; | |
2687 | else if (in_irq()) | |
2688 | bit = 1; | |
2689 | else | |
2690 | bit = 2; | |
2691 | } else | |
2692 | bit = 3; | |
d9abde21 | 2693 | |
567cd4da SR |
2694 | if (unlikely(val & (1 << bit))) |
2695 | return 1; | |
d9abde21 | 2696 | |
567cd4da | 2697 | val |= (1 << bit); |
58a09ec6 | 2698 | cpu_buffer->current_context = val; |
d9abde21 | 2699 | |
567cd4da | 2700 | return 0; |
261842b7 SR |
2701 | } |
2702 | ||
58a09ec6 SRRH |
2703 | static __always_inline void |
2704 | trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) | |
261842b7 | 2705 | { |
58a09ec6 | 2706 | cpu_buffer->current_context &= cpu_buffer->current_context - 1; |
261842b7 SR |
2707 | } |
2708 | ||
7a8e76a3 SR |
2709 | /** |
2710 | * ring_buffer_lock_reserve - reserve a part of the buffer | |
2711 | * @buffer: the ring buffer to reserve from | |
2712 | * @length: the length of the data to reserve (excluding event header) | |
7a8e76a3 SR |
2713 | * |
2714 | * Returns a reseverd event on the ring buffer to copy directly to. | |
2715 | * The user of this interface will need to get the body to write into | |
2716 | * and can use the ring_buffer_event_data() interface. | |
2717 | * | |
2718 | * The length is the length of the data needed, not the event length | |
2719 | * which also includes the event header. | |
2720 | * | |
2721 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. | |
2722 | * If NULL is returned, then nothing has been allocated or locked. | |
2723 | */ | |
2724 | struct ring_buffer_event * | |
0a987751 | 2725 | ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
7a8e76a3 SR |
2726 | { |
2727 | struct ring_buffer_per_cpu *cpu_buffer; | |
2728 | struct ring_buffer_event *event; | |
5168ae50 | 2729 | int cpu; |
7a8e76a3 | 2730 | |
033601a3 | 2731 | if (ring_buffer_flags != RB_BUFFERS_ON) |
a3583244 SR |
2732 | return NULL; |
2733 | ||
bf41a158 | 2734 | /* If we are tracing schedule, we don't want to recurse */ |
5168ae50 | 2735 | preempt_disable_notrace(); |
bf41a158 | 2736 | |
3205f806 | 2737 | if (unlikely(atomic_read(&buffer->record_disabled))) |
58a09ec6 | 2738 | goto out; |
261842b7 | 2739 | |
7a8e76a3 SR |
2740 | cpu = raw_smp_processor_id(); |
2741 | ||
3205f806 | 2742 | if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
d769041f | 2743 | goto out; |
7a8e76a3 SR |
2744 | |
2745 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 2746 | |
3205f806 | 2747 | if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
d769041f | 2748 | goto out; |
7a8e76a3 | 2749 | |
3205f806 | 2750 | if (unlikely(length > BUF_MAX_DATA_SIZE)) |
bf41a158 | 2751 | goto out; |
7a8e76a3 | 2752 | |
58a09ec6 SRRH |
2753 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
2754 | goto out; | |
2755 | ||
62f0b3eb | 2756 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 2757 | if (!event) |
58a09ec6 | 2758 | goto out_unlock; |
7a8e76a3 SR |
2759 | |
2760 | return event; | |
2761 | ||
58a09ec6 SRRH |
2762 | out_unlock: |
2763 | trace_recursive_unlock(cpu_buffer); | |
d769041f | 2764 | out: |
5168ae50 | 2765 | preempt_enable_notrace(); |
7a8e76a3 SR |
2766 | return NULL; |
2767 | } | |
c4f50183 | 2768 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
7a8e76a3 | 2769 | |
a1863c21 SR |
2770 | static void |
2771 | rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
7a8e76a3 SR |
2772 | struct ring_buffer_event *event) |
2773 | { | |
69d1b839 SR |
2774 | u64 delta; |
2775 | ||
fa743953 SR |
2776 | /* |
2777 | * The event first in the commit queue updates the | |
2778 | * time stamp. | |
2779 | */ | |
69d1b839 SR |
2780 | if (rb_event_is_commit(cpu_buffer, event)) { |
2781 | /* | |
2782 | * A commit event that is first on a page | |
2783 | * updates the write timestamp with the page stamp | |
2784 | */ | |
2785 | if (!rb_event_index(event)) | |
2786 | cpu_buffer->write_stamp = | |
2787 | cpu_buffer->commit_page->page->time_stamp; | |
2788 | else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { | |
2789 | delta = event->array[0]; | |
2790 | delta <<= TS_SHIFT; | |
2791 | delta += event->time_delta; | |
2792 | cpu_buffer->write_stamp += delta; | |
2793 | } else | |
2794 | cpu_buffer->write_stamp += event->time_delta; | |
2795 | } | |
a1863c21 | 2796 | } |
bf41a158 | 2797 | |
a1863c21 SR |
2798 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2799 | struct ring_buffer_event *event) | |
2800 | { | |
2801 | local_inc(&cpu_buffer->entries); | |
2802 | rb_update_write_stamp(cpu_buffer, event); | |
fa743953 | 2803 | rb_end_commit(cpu_buffer); |
7a8e76a3 SR |
2804 | } |
2805 | ||
15693458 SRRH |
2806 | static __always_inline void |
2807 | rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) | |
2808 | { | |
1e0d6714 SRRH |
2809 | bool pagebusy; |
2810 | ||
15693458 SRRH |
2811 | if (buffer->irq_work.waiters_pending) { |
2812 | buffer->irq_work.waiters_pending = false; | |
2813 | /* irq_work_queue() supplies it's own memory barriers */ | |
2814 | irq_work_queue(&buffer->irq_work.work); | |
2815 | } | |
2816 | ||
2817 | if (cpu_buffer->irq_work.waiters_pending) { | |
2818 | cpu_buffer->irq_work.waiters_pending = false; | |
2819 | /* irq_work_queue() supplies it's own memory barriers */ | |
2820 | irq_work_queue(&cpu_buffer->irq_work.work); | |
2821 | } | |
1e0d6714 SRRH |
2822 | |
2823 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; | |
2824 | ||
2825 | if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) { | |
2826 | cpu_buffer->irq_work.wakeup_full = true; | |
2827 | cpu_buffer->irq_work.full_waiters_pending = false; | |
2828 | /* irq_work_queue() supplies it's own memory barriers */ | |
2829 | irq_work_queue(&cpu_buffer->irq_work.work); | |
2830 | } | |
15693458 SRRH |
2831 | } |
2832 | ||
7a8e76a3 SR |
2833 | /** |
2834 | * ring_buffer_unlock_commit - commit a reserved | |
2835 | * @buffer: The buffer to commit to | |
2836 | * @event: The event pointer to commit. | |
7a8e76a3 SR |
2837 | * |
2838 | * This commits the data to the ring buffer, and releases any locks held. | |
2839 | * | |
2840 | * Must be paired with ring_buffer_lock_reserve. | |
2841 | */ | |
2842 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, | |
0a987751 | 2843 | struct ring_buffer_event *event) |
7a8e76a3 SR |
2844 | { |
2845 | struct ring_buffer_per_cpu *cpu_buffer; | |
2846 | int cpu = raw_smp_processor_id(); | |
2847 | ||
2848 | cpu_buffer = buffer->buffers[cpu]; | |
2849 | ||
7a8e76a3 SR |
2850 | rb_commit(cpu_buffer, event); |
2851 | ||
15693458 SRRH |
2852 | rb_wakeups(buffer, cpu_buffer); |
2853 | ||
58a09ec6 | 2854 | trace_recursive_unlock(cpu_buffer); |
261842b7 | 2855 | |
5168ae50 | 2856 | preempt_enable_notrace(); |
7a8e76a3 SR |
2857 | |
2858 | return 0; | |
2859 | } | |
c4f50183 | 2860 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
7a8e76a3 | 2861 | |
f3b9aae1 FW |
2862 | static inline void rb_event_discard(struct ring_buffer_event *event) |
2863 | { | |
69d1b839 SR |
2864 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
2865 | event = skip_time_extend(event); | |
2866 | ||
334d4169 LJ |
2867 | /* array[0] holds the actual length for the discarded event */ |
2868 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; | |
2869 | event->type_len = RINGBUF_TYPE_PADDING; | |
f3b9aae1 FW |
2870 | /* time delta must be non zero */ |
2871 | if (!event->time_delta) | |
2872 | event->time_delta = 1; | |
2873 | } | |
2874 | ||
a1863c21 SR |
2875 | /* |
2876 | * Decrement the entries to the page that an event is on. | |
2877 | * The event does not even need to exist, only the pointer | |
2878 | * to the page it is on. This may only be called before the commit | |
2879 | * takes place. | |
2880 | */ | |
2881 | static inline void | |
2882 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, | |
2883 | struct ring_buffer_event *event) | |
2884 | { | |
2885 | unsigned long addr = (unsigned long)event; | |
2886 | struct buffer_page *bpage = cpu_buffer->commit_page; | |
2887 | struct buffer_page *start; | |
2888 | ||
2889 | addr &= PAGE_MASK; | |
2890 | ||
2891 | /* Do the likely case first */ | |
2892 | if (likely(bpage->page == (void *)addr)) { | |
2893 | local_dec(&bpage->entries); | |
2894 | return; | |
2895 | } | |
2896 | ||
2897 | /* | |
2898 | * Because the commit page may be on the reader page we | |
2899 | * start with the next page and check the end loop there. | |
2900 | */ | |
2901 | rb_inc_page(cpu_buffer, &bpage); | |
2902 | start = bpage; | |
2903 | do { | |
2904 | if (bpage->page == (void *)addr) { | |
2905 | local_dec(&bpage->entries); | |
2906 | return; | |
2907 | } | |
2908 | rb_inc_page(cpu_buffer, &bpage); | |
2909 | } while (bpage != start); | |
2910 | ||
2911 | /* commit not part of this buffer?? */ | |
2912 | RB_WARN_ON(cpu_buffer, 1); | |
2913 | } | |
2914 | ||
fa1b47dd SR |
2915 | /** |
2916 | * ring_buffer_commit_discard - discard an event that has not been committed | |
2917 | * @buffer: the ring buffer | |
2918 | * @event: non committed event to discard | |
2919 | * | |
dc892f73 SR |
2920 | * Sometimes an event that is in the ring buffer needs to be ignored. |
2921 | * This function lets the user discard an event in the ring buffer | |
2922 | * and then that event will not be read later. | |
2923 | * | |
2924 | * This function only works if it is called before the the item has been | |
2925 | * committed. It will try to free the event from the ring buffer | |
fa1b47dd SR |
2926 | * if another event has not been added behind it. |
2927 | * | |
2928 | * If another event has been added behind it, it will set the event | |
2929 | * up as discarded, and perform the commit. | |
2930 | * | |
2931 | * If this function is called, do not call ring_buffer_unlock_commit on | |
2932 | * the event. | |
2933 | */ | |
2934 | void ring_buffer_discard_commit(struct ring_buffer *buffer, | |
2935 | struct ring_buffer_event *event) | |
2936 | { | |
2937 | struct ring_buffer_per_cpu *cpu_buffer; | |
fa1b47dd SR |
2938 | int cpu; |
2939 | ||
2940 | /* The event is discarded regardless */ | |
f3b9aae1 | 2941 | rb_event_discard(event); |
fa1b47dd | 2942 | |
fa743953 SR |
2943 | cpu = smp_processor_id(); |
2944 | cpu_buffer = buffer->buffers[cpu]; | |
2945 | ||
fa1b47dd SR |
2946 | /* |
2947 | * This must only be called if the event has not been | |
2948 | * committed yet. Thus we can assume that preemption | |
2949 | * is still disabled. | |
2950 | */ | |
fa743953 | 2951 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
fa1b47dd | 2952 | |
a1863c21 | 2953 | rb_decrement_entry(cpu_buffer, event); |
0f2541d2 | 2954 | if (rb_try_to_discard(cpu_buffer, event)) |
edd813bf | 2955 | goto out; |
fa1b47dd SR |
2956 | |
2957 | /* | |
2958 | * The commit is still visible by the reader, so we | |
a1863c21 | 2959 | * must still update the timestamp. |
fa1b47dd | 2960 | */ |
a1863c21 | 2961 | rb_update_write_stamp(cpu_buffer, event); |
fa1b47dd | 2962 | out: |
fa743953 | 2963 | rb_end_commit(cpu_buffer); |
fa1b47dd | 2964 | |
58a09ec6 | 2965 | trace_recursive_unlock(cpu_buffer); |
f3b9aae1 | 2966 | |
5168ae50 | 2967 | preempt_enable_notrace(); |
fa1b47dd SR |
2968 | |
2969 | } | |
2970 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); | |
2971 | ||
7a8e76a3 SR |
2972 | /** |
2973 | * ring_buffer_write - write data to the buffer without reserving | |
2974 | * @buffer: The ring buffer to write to. | |
2975 | * @length: The length of the data being written (excluding the event header) | |
2976 | * @data: The data to write to the buffer. | |
2977 | * | |
2978 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as | |
2979 | * one function. If you already have the data to write to the buffer, it | |
2980 | * may be easier to simply call this function. | |
2981 | * | |
2982 | * Note, like ring_buffer_lock_reserve, the length is the length of the data | |
2983 | * and not the length of the event which would hold the header. | |
2984 | */ | |
2985 | int ring_buffer_write(struct ring_buffer *buffer, | |
01e3e710 DS |
2986 | unsigned long length, |
2987 | void *data) | |
7a8e76a3 SR |
2988 | { |
2989 | struct ring_buffer_per_cpu *cpu_buffer; | |
2990 | struct ring_buffer_event *event; | |
7a8e76a3 SR |
2991 | void *body; |
2992 | int ret = -EBUSY; | |
5168ae50 | 2993 | int cpu; |
7a8e76a3 | 2994 | |
033601a3 | 2995 | if (ring_buffer_flags != RB_BUFFERS_ON) |
a3583244 SR |
2996 | return -EBUSY; |
2997 | ||
5168ae50 | 2998 | preempt_disable_notrace(); |
bf41a158 | 2999 | |
52fbe9cd LJ |
3000 | if (atomic_read(&buffer->record_disabled)) |
3001 | goto out; | |
3002 | ||
7a8e76a3 SR |
3003 | cpu = raw_smp_processor_id(); |
3004 | ||
9e01c1b7 | 3005 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
d769041f | 3006 | goto out; |
7a8e76a3 SR |
3007 | |
3008 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
3009 | |
3010 | if (atomic_read(&cpu_buffer->record_disabled)) | |
3011 | goto out; | |
3012 | ||
be957c44 SR |
3013 | if (length > BUF_MAX_DATA_SIZE) |
3014 | goto out; | |
3015 | ||
985e871b SRRH |
3016 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
3017 | goto out; | |
3018 | ||
62f0b3eb | 3019 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 3020 | if (!event) |
985e871b | 3021 | goto out_unlock; |
7a8e76a3 SR |
3022 | |
3023 | body = rb_event_data(event); | |
3024 | ||
3025 | memcpy(body, data, length); | |
3026 | ||
3027 | rb_commit(cpu_buffer, event); | |
3028 | ||
15693458 SRRH |
3029 | rb_wakeups(buffer, cpu_buffer); |
3030 | ||
7a8e76a3 | 3031 | ret = 0; |
985e871b SRRH |
3032 | |
3033 | out_unlock: | |
3034 | trace_recursive_unlock(cpu_buffer); | |
3035 | ||
7a8e76a3 | 3036 | out: |
5168ae50 | 3037 | preempt_enable_notrace(); |
7a8e76a3 SR |
3038 | |
3039 | return ret; | |
3040 | } | |
c4f50183 | 3041 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
7a8e76a3 | 3042 | |
34a148bf | 3043 | static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
bf41a158 SR |
3044 | { |
3045 | struct buffer_page *reader = cpu_buffer->reader_page; | |
77ae365e | 3046 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
bf41a158 SR |
3047 | struct buffer_page *commit = cpu_buffer->commit_page; |
3048 | ||
77ae365e SR |
3049 | /* In case of error, head will be NULL */ |
3050 | if (unlikely(!head)) | |
3051 | return 1; | |
3052 | ||
bf41a158 SR |
3053 | return reader->read == rb_page_commit(reader) && |
3054 | (commit == reader || | |
3055 | (commit == head && | |
3056 | head->read == rb_page_commit(commit))); | |
3057 | } | |
3058 | ||
7a8e76a3 SR |
3059 | /** |
3060 | * ring_buffer_record_disable - stop all writes into the buffer | |
3061 | * @buffer: The ring buffer to stop writes to. | |
3062 | * | |
3063 | * This prevents all writes to the buffer. Any attempt to write | |
3064 | * to the buffer after this will fail and return NULL. | |
3065 | * | |
3066 | * The caller should call synchronize_sched() after this. | |
3067 | */ | |
3068 | void ring_buffer_record_disable(struct ring_buffer *buffer) | |
3069 | { | |
3070 | atomic_inc(&buffer->record_disabled); | |
3071 | } | |
c4f50183 | 3072 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
7a8e76a3 SR |
3073 | |
3074 | /** | |
3075 | * ring_buffer_record_enable - enable writes to the buffer | |
3076 | * @buffer: The ring buffer to enable writes | |
3077 | * | |
3078 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3079 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
3080 | */ |
3081 | void ring_buffer_record_enable(struct ring_buffer *buffer) | |
3082 | { | |
3083 | atomic_dec(&buffer->record_disabled); | |
3084 | } | |
c4f50183 | 3085 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
7a8e76a3 | 3086 | |
499e5470 SR |
3087 | /** |
3088 | * ring_buffer_record_off - stop all writes into the buffer | |
3089 | * @buffer: The ring buffer to stop writes to. | |
3090 | * | |
3091 | * This prevents all writes to the buffer. Any attempt to write | |
3092 | * to the buffer after this will fail and return NULL. | |
3093 | * | |
3094 | * This is different than ring_buffer_record_disable() as | |
87abb3b1 | 3095 | * it works like an on/off switch, where as the disable() version |
499e5470 SR |
3096 | * must be paired with a enable(). |
3097 | */ | |
3098 | void ring_buffer_record_off(struct ring_buffer *buffer) | |
3099 | { | |
3100 | unsigned int rd; | |
3101 | unsigned int new_rd; | |
3102 | ||
3103 | do { | |
3104 | rd = atomic_read(&buffer->record_disabled); | |
3105 | new_rd = rd | RB_BUFFER_OFF; | |
3106 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3107 | } | |
3108 | EXPORT_SYMBOL_GPL(ring_buffer_record_off); | |
3109 | ||
3110 | /** | |
3111 | * ring_buffer_record_on - restart writes into the buffer | |
3112 | * @buffer: The ring buffer to start writes to. | |
3113 | * | |
3114 | * This enables all writes to the buffer that was disabled by | |
3115 | * ring_buffer_record_off(). | |
3116 | * | |
3117 | * This is different than ring_buffer_record_enable() as | |
87abb3b1 | 3118 | * it works like an on/off switch, where as the enable() version |
499e5470 SR |
3119 | * must be paired with a disable(). |
3120 | */ | |
3121 | void ring_buffer_record_on(struct ring_buffer *buffer) | |
3122 | { | |
3123 | unsigned int rd; | |
3124 | unsigned int new_rd; | |
3125 | ||
3126 | do { | |
3127 | rd = atomic_read(&buffer->record_disabled); | |
3128 | new_rd = rd & ~RB_BUFFER_OFF; | |
3129 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3130 | } | |
3131 | EXPORT_SYMBOL_GPL(ring_buffer_record_on); | |
3132 | ||
3133 | /** | |
3134 | * ring_buffer_record_is_on - return true if the ring buffer can write | |
3135 | * @buffer: The ring buffer to see if write is enabled | |
3136 | * | |
3137 | * Returns true if the ring buffer is in a state that it accepts writes. | |
3138 | */ | |
3139 | int ring_buffer_record_is_on(struct ring_buffer *buffer) | |
3140 | { | |
3141 | return !atomic_read(&buffer->record_disabled); | |
3142 | } | |
3143 | ||
7a8e76a3 SR |
3144 | /** |
3145 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer | |
3146 | * @buffer: The ring buffer to stop writes to. | |
3147 | * @cpu: The CPU buffer to stop | |
3148 | * | |
3149 | * This prevents all writes to the buffer. Any attempt to write | |
3150 | * to the buffer after this will fail and return NULL. | |
3151 | * | |
3152 | * The caller should call synchronize_sched() after this. | |
3153 | */ | |
3154 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) | |
3155 | { | |
3156 | struct ring_buffer_per_cpu *cpu_buffer; | |
3157 | ||
9e01c1b7 | 3158 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3159 | return; |
7a8e76a3 SR |
3160 | |
3161 | cpu_buffer = buffer->buffers[cpu]; | |
3162 | atomic_inc(&cpu_buffer->record_disabled); | |
3163 | } | |
c4f50183 | 3164 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
7a8e76a3 SR |
3165 | |
3166 | /** | |
3167 | * ring_buffer_record_enable_cpu - enable writes to the buffer | |
3168 | * @buffer: The ring buffer to enable writes | |
3169 | * @cpu: The CPU to enable. | |
3170 | * | |
3171 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3172 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
3173 | */ |
3174 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) | |
3175 | { | |
3176 | struct ring_buffer_per_cpu *cpu_buffer; | |
3177 | ||
9e01c1b7 | 3178 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3179 | return; |
7a8e76a3 SR |
3180 | |
3181 | cpu_buffer = buffer->buffers[cpu]; | |
3182 | atomic_dec(&cpu_buffer->record_disabled); | |
3183 | } | |
c4f50183 | 3184 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
7a8e76a3 | 3185 | |
f6195aa0 SR |
3186 | /* |
3187 | * The total entries in the ring buffer is the running counter | |
3188 | * of entries entered into the ring buffer, minus the sum of | |
3189 | * the entries read from the ring buffer and the number of | |
3190 | * entries that were overwritten. | |
3191 | */ | |
3192 | static inline unsigned long | |
3193 | rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) | |
3194 | { | |
3195 | return local_read(&cpu_buffer->entries) - | |
3196 | (local_read(&cpu_buffer->overrun) + cpu_buffer->read); | |
3197 | } | |
3198 | ||
c64e148a VN |
3199 | /** |
3200 | * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer | |
3201 | * @buffer: The ring buffer | |
3202 | * @cpu: The per CPU buffer to read from. | |
3203 | */ | |
50ecf2c3 | 3204 | u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) |
c64e148a VN |
3205 | { |
3206 | unsigned long flags; | |
3207 | struct ring_buffer_per_cpu *cpu_buffer; | |
3208 | struct buffer_page *bpage; | |
da830e58 | 3209 | u64 ret = 0; |
c64e148a VN |
3210 | |
3211 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3212 | return 0; | |
3213 | ||
3214 | cpu_buffer = buffer->buffers[cpu]; | |
7115e3fc | 3215 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3216 | /* |
3217 | * if the tail is on reader_page, oldest time stamp is on the reader | |
3218 | * page | |
3219 | */ | |
3220 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
3221 | bpage = cpu_buffer->reader_page; | |
3222 | else | |
3223 | bpage = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3224 | if (bpage) |
3225 | ret = bpage->page->time_stamp; | |
7115e3fc | 3226 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3227 | |
3228 | return ret; | |
3229 | } | |
3230 | EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); | |
3231 | ||
3232 | /** | |
3233 | * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer | |
3234 | * @buffer: The ring buffer | |
3235 | * @cpu: The per CPU buffer to read from. | |
3236 | */ | |
3237 | unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu) | |
3238 | { | |
3239 | struct ring_buffer_per_cpu *cpu_buffer; | |
3240 | unsigned long ret; | |
3241 | ||
3242 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3243 | return 0; | |
3244 | ||
3245 | cpu_buffer = buffer->buffers[cpu]; | |
3246 | ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; | |
3247 | ||
3248 | return ret; | |
3249 | } | |
3250 | EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); | |
3251 | ||
7a8e76a3 SR |
3252 | /** |
3253 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer | |
3254 | * @buffer: The ring buffer | |
3255 | * @cpu: The per CPU buffer to get the entries from. | |
3256 | */ | |
3257 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) | |
3258 | { | |
3259 | struct ring_buffer_per_cpu *cpu_buffer; | |
3260 | ||
9e01c1b7 | 3261 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3262 | return 0; |
7a8e76a3 SR |
3263 | |
3264 | cpu_buffer = buffer->buffers[cpu]; | |
554f786e | 3265 | |
f6195aa0 | 3266 | return rb_num_of_entries(cpu_buffer); |
7a8e76a3 | 3267 | } |
c4f50183 | 3268 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
7a8e76a3 SR |
3269 | |
3270 | /** | |
884bfe89 SP |
3271 | * ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
3272 | * buffer wrapping around (only if RB_FL_OVERWRITE is on). | |
7a8e76a3 SR |
3273 | * @buffer: The ring buffer |
3274 | * @cpu: The per CPU buffer to get the number of overruns from | |
3275 | */ | |
3276 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
3277 | { | |
3278 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 3279 | unsigned long ret; |
7a8e76a3 | 3280 | |
9e01c1b7 | 3281 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3282 | return 0; |
7a8e76a3 SR |
3283 | |
3284 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3285 | ret = local_read(&cpu_buffer->overrun); |
554f786e SR |
3286 | |
3287 | return ret; | |
7a8e76a3 | 3288 | } |
c4f50183 | 3289 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
7a8e76a3 | 3290 | |
f0d2c681 | 3291 | /** |
884bfe89 SP |
3292 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by |
3293 | * commits failing due to the buffer wrapping around while there are uncommitted | |
3294 | * events, such as during an interrupt storm. | |
f0d2c681 SR |
3295 | * @buffer: The ring buffer |
3296 | * @cpu: The per CPU buffer to get the number of overruns from | |
3297 | */ | |
3298 | unsigned long | |
3299 | ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
3300 | { | |
3301 | struct ring_buffer_per_cpu *cpu_buffer; | |
3302 | unsigned long ret; | |
3303 | ||
3304 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3305 | return 0; | |
3306 | ||
3307 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3308 | ret = local_read(&cpu_buffer->commit_overrun); |
f0d2c681 SR |
3309 | |
3310 | return ret; | |
3311 | } | |
3312 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); | |
3313 | ||
884bfe89 SP |
3314 | /** |
3315 | * ring_buffer_dropped_events_cpu - get the number of dropped events caused by | |
3316 | * the ring buffer filling up (only if RB_FL_OVERWRITE is off). | |
3317 | * @buffer: The ring buffer | |
3318 | * @cpu: The per CPU buffer to get the number of overruns from | |
3319 | */ | |
3320 | unsigned long | |
3321 | ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu) | |
3322 | { | |
3323 | struct ring_buffer_per_cpu *cpu_buffer; | |
3324 | unsigned long ret; | |
3325 | ||
3326 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3327 | return 0; | |
3328 | ||
3329 | cpu_buffer = buffer->buffers[cpu]; | |
3330 | ret = local_read(&cpu_buffer->dropped_events); | |
3331 | ||
3332 | return ret; | |
3333 | } | |
3334 | EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); | |
3335 | ||
ad964704 SRRH |
3336 | /** |
3337 | * ring_buffer_read_events_cpu - get the number of events successfully read | |
3338 | * @buffer: The ring buffer | |
3339 | * @cpu: The per CPU buffer to get the number of events read | |
3340 | */ | |
3341 | unsigned long | |
3342 | ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu) | |
3343 | { | |
3344 | struct ring_buffer_per_cpu *cpu_buffer; | |
3345 | ||
3346 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3347 | return 0; | |
3348 | ||
3349 | cpu_buffer = buffer->buffers[cpu]; | |
3350 | return cpu_buffer->read; | |
3351 | } | |
3352 | EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); | |
3353 | ||
7a8e76a3 SR |
3354 | /** |
3355 | * ring_buffer_entries - get the number of entries in a buffer | |
3356 | * @buffer: The ring buffer | |
3357 | * | |
3358 | * Returns the total number of entries in the ring buffer | |
3359 | * (all CPU entries) | |
3360 | */ | |
3361 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) | |
3362 | { | |
3363 | struct ring_buffer_per_cpu *cpu_buffer; | |
3364 | unsigned long entries = 0; | |
3365 | int cpu; | |
3366 | ||
3367 | /* if you care about this being correct, lock the buffer */ | |
3368 | for_each_buffer_cpu(buffer, cpu) { | |
3369 | cpu_buffer = buffer->buffers[cpu]; | |
f6195aa0 | 3370 | entries += rb_num_of_entries(cpu_buffer); |
7a8e76a3 SR |
3371 | } |
3372 | ||
3373 | return entries; | |
3374 | } | |
c4f50183 | 3375 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
7a8e76a3 SR |
3376 | |
3377 | /** | |
67b394f7 | 3378 | * ring_buffer_overruns - get the number of overruns in buffer |
7a8e76a3 SR |
3379 | * @buffer: The ring buffer |
3380 | * | |
3381 | * Returns the total number of overruns in the ring buffer | |
3382 | * (all CPU entries) | |
3383 | */ | |
3384 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) | |
3385 | { | |
3386 | struct ring_buffer_per_cpu *cpu_buffer; | |
3387 | unsigned long overruns = 0; | |
3388 | int cpu; | |
3389 | ||
3390 | /* if you care about this being correct, lock the buffer */ | |
3391 | for_each_buffer_cpu(buffer, cpu) { | |
3392 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3393 | overruns += local_read(&cpu_buffer->overrun); |
7a8e76a3 SR |
3394 | } |
3395 | ||
3396 | return overruns; | |
3397 | } | |
c4f50183 | 3398 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
7a8e76a3 | 3399 | |
642edba5 | 3400 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
7a8e76a3 SR |
3401 | { |
3402 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3403 | ||
d769041f | 3404 | /* Iterator usage is expected to have record disabled */ |
651e22f2 SRRH |
3405 | iter->head_page = cpu_buffer->reader_page; |
3406 | iter->head = cpu_buffer->reader_page->read; | |
3407 | ||
3408 | iter->cache_reader_page = iter->head_page; | |
24607f11 | 3409 | iter->cache_read = cpu_buffer->read; |
651e22f2 | 3410 | |
d769041f SR |
3411 | if (iter->head) |
3412 | iter->read_stamp = cpu_buffer->read_stamp; | |
3413 | else | |
abc9b56d | 3414 | iter->read_stamp = iter->head_page->page->time_stamp; |
642edba5 | 3415 | } |
f83c9d0f | 3416 | |
642edba5 SR |
3417 | /** |
3418 | * ring_buffer_iter_reset - reset an iterator | |
3419 | * @iter: The iterator to reset | |
3420 | * | |
3421 | * Resets the iterator, so that it will start from the beginning | |
3422 | * again. | |
3423 | */ | |
3424 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) | |
3425 | { | |
554f786e | 3426 | struct ring_buffer_per_cpu *cpu_buffer; |
642edba5 SR |
3427 | unsigned long flags; |
3428 | ||
554f786e SR |
3429 | if (!iter) |
3430 | return; | |
3431 | ||
3432 | cpu_buffer = iter->cpu_buffer; | |
3433 | ||
5389f6fa | 3434 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
642edba5 | 3435 | rb_iter_reset(iter); |
5389f6fa | 3436 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 3437 | } |
c4f50183 | 3438 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
7a8e76a3 SR |
3439 | |
3440 | /** | |
3441 | * ring_buffer_iter_empty - check if an iterator has no more to read | |
3442 | * @iter: The iterator to check | |
3443 | */ | |
3444 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) | |
3445 | { | |
3446 | struct ring_buffer_per_cpu *cpu_buffer; | |
3447 | ||
3448 | cpu_buffer = iter->cpu_buffer; | |
3449 | ||
bf41a158 SR |
3450 | return iter->head_page == cpu_buffer->commit_page && |
3451 | iter->head == rb_commit_index(cpu_buffer); | |
7a8e76a3 | 3452 | } |
c4f50183 | 3453 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
7a8e76a3 SR |
3454 | |
3455 | static void | |
3456 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
3457 | struct ring_buffer_event *event) | |
3458 | { | |
3459 | u64 delta; | |
3460 | ||
334d4169 | 3461 | switch (event->type_len) { |
7a8e76a3 SR |
3462 | case RINGBUF_TYPE_PADDING: |
3463 | return; | |
3464 | ||
3465 | case RINGBUF_TYPE_TIME_EXTEND: | |
3466 | delta = event->array[0]; | |
3467 | delta <<= TS_SHIFT; | |
3468 | delta += event->time_delta; | |
3469 | cpu_buffer->read_stamp += delta; | |
3470 | return; | |
3471 | ||
3472 | case RINGBUF_TYPE_TIME_STAMP: | |
3473 | /* FIXME: not implemented */ | |
3474 | return; | |
3475 | ||
3476 | case RINGBUF_TYPE_DATA: | |
3477 | cpu_buffer->read_stamp += event->time_delta; | |
3478 | return; | |
3479 | ||
3480 | default: | |
3481 | BUG(); | |
3482 | } | |
3483 | return; | |
3484 | } | |
3485 | ||
3486 | static void | |
3487 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, | |
3488 | struct ring_buffer_event *event) | |
3489 | { | |
3490 | u64 delta; | |
3491 | ||
334d4169 | 3492 | switch (event->type_len) { |
7a8e76a3 SR |
3493 | case RINGBUF_TYPE_PADDING: |
3494 | return; | |
3495 | ||
3496 | case RINGBUF_TYPE_TIME_EXTEND: | |
3497 | delta = event->array[0]; | |
3498 | delta <<= TS_SHIFT; | |
3499 | delta += event->time_delta; | |
3500 | iter->read_stamp += delta; | |
3501 | return; | |
3502 | ||
3503 | case RINGBUF_TYPE_TIME_STAMP: | |
3504 | /* FIXME: not implemented */ | |
3505 | return; | |
3506 | ||
3507 | case RINGBUF_TYPE_DATA: | |
3508 | iter->read_stamp += event->time_delta; | |
3509 | return; | |
3510 | ||
3511 | default: | |
3512 | BUG(); | |
3513 | } | |
3514 | return; | |
3515 | } | |
3516 | ||
d769041f SR |
3517 | static struct buffer_page * |
3518 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 3519 | { |
d769041f | 3520 | struct buffer_page *reader = NULL; |
66a8cb95 | 3521 | unsigned long overwrite; |
d769041f | 3522 | unsigned long flags; |
818e3dd3 | 3523 | int nr_loops = 0; |
77ae365e | 3524 | int ret; |
d769041f | 3525 | |
3e03fb7f | 3526 | local_irq_save(flags); |
0199c4e6 | 3527 | arch_spin_lock(&cpu_buffer->lock); |
d769041f SR |
3528 | |
3529 | again: | |
818e3dd3 SR |
3530 | /* |
3531 | * This should normally only loop twice. But because the | |
3532 | * start of the reader inserts an empty page, it causes | |
3533 | * a case where we will loop three times. There should be no | |
3534 | * reason to loop four times (that I know of). | |
3535 | */ | |
3e89c7bb | 3536 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
818e3dd3 SR |
3537 | reader = NULL; |
3538 | goto out; | |
3539 | } | |
3540 | ||
d769041f SR |
3541 | reader = cpu_buffer->reader_page; |
3542 | ||
3543 | /* If there's more to read, return this page */ | |
bf41a158 | 3544 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
d769041f SR |
3545 | goto out; |
3546 | ||
3547 | /* Never should we have an index greater than the size */ | |
3e89c7bb SR |
3548 | if (RB_WARN_ON(cpu_buffer, |
3549 | cpu_buffer->reader_page->read > rb_page_size(reader))) | |
3550 | goto out; | |
d769041f SR |
3551 | |
3552 | /* check if we caught up to the tail */ | |
3553 | reader = NULL; | |
bf41a158 | 3554 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
d769041f | 3555 | goto out; |
7a8e76a3 | 3556 | |
a5fb8331 SR |
3557 | /* Don't bother swapping if the ring buffer is empty */ |
3558 | if (rb_num_of_entries(cpu_buffer) == 0) | |
3559 | goto out; | |
3560 | ||
7a8e76a3 | 3561 | /* |
d769041f | 3562 | * Reset the reader page to size zero. |
7a8e76a3 | 3563 | */ |
77ae365e SR |
3564 | local_set(&cpu_buffer->reader_page->write, 0); |
3565 | local_set(&cpu_buffer->reader_page->entries, 0); | |
3566 | local_set(&cpu_buffer->reader_page->page->commit, 0); | |
ff0ff84a | 3567 | cpu_buffer->reader_page->real_end = 0; |
7a8e76a3 | 3568 | |
77ae365e SR |
3569 | spin: |
3570 | /* | |
3571 | * Splice the empty reader page into the list around the head. | |
3572 | */ | |
3573 | reader = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3574 | if (!reader) |
3575 | goto out; | |
0e1ff5d7 | 3576 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
d769041f | 3577 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
bf41a158 | 3578 | |
3adc54fa SR |
3579 | /* |
3580 | * cpu_buffer->pages just needs to point to the buffer, it | |
3581 | * has no specific buffer page to point to. Lets move it out | |
25985edc | 3582 | * of our way so we don't accidentally swap it. |
3adc54fa SR |
3583 | */ |
3584 | cpu_buffer->pages = reader->list.prev; | |
3585 | ||
77ae365e SR |
3586 | /* The reader page will be pointing to the new head */ |
3587 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); | |
7a8e76a3 | 3588 | |
66a8cb95 SR |
3589 | /* |
3590 | * We want to make sure we read the overruns after we set up our | |
3591 | * pointers to the next object. The writer side does a | |
3592 | * cmpxchg to cross pages which acts as the mb on the writer | |
3593 | * side. Note, the reader will constantly fail the swap | |
3594 | * while the writer is updating the pointers, so this | |
3595 | * guarantees that the overwrite recorded here is the one we | |
3596 | * want to compare with the last_overrun. | |
3597 | */ | |
3598 | smp_mb(); | |
3599 | overwrite = local_read(&(cpu_buffer->overrun)); | |
3600 | ||
77ae365e SR |
3601 | /* |
3602 | * Here's the tricky part. | |
3603 | * | |
3604 | * We need to move the pointer past the header page. | |
3605 | * But we can only do that if a writer is not currently | |
3606 | * moving it. The page before the header page has the | |
3607 | * flag bit '1' set if it is pointing to the page we want. | |
3608 | * but if the writer is in the process of moving it | |
3609 | * than it will be '2' or already moved '0'. | |
3610 | */ | |
3611 | ||
3612 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); | |
7a8e76a3 SR |
3613 | |
3614 | /* | |
77ae365e | 3615 | * If we did not convert it, then we must try again. |
7a8e76a3 | 3616 | */ |
77ae365e SR |
3617 | if (!ret) |
3618 | goto spin; | |
7a8e76a3 | 3619 | |
77ae365e SR |
3620 | /* |
3621 | * Yeah! We succeeded in replacing the page. | |
3622 | * | |
3623 | * Now make the new head point back to the reader page. | |
3624 | */ | |
5ded3dc6 | 3625 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
77ae365e | 3626 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
d769041f SR |
3627 | |
3628 | /* Finally update the reader page to the new head */ | |
3629 | cpu_buffer->reader_page = reader; | |
3630 | rb_reset_reader_page(cpu_buffer); | |
3631 | ||
66a8cb95 SR |
3632 | if (overwrite != cpu_buffer->last_overrun) { |
3633 | cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; | |
3634 | cpu_buffer->last_overrun = overwrite; | |
3635 | } | |
3636 | ||
d769041f SR |
3637 | goto again; |
3638 | ||
3639 | out: | |
0199c4e6 | 3640 | arch_spin_unlock(&cpu_buffer->lock); |
3e03fb7f | 3641 | local_irq_restore(flags); |
d769041f SR |
3642 | |
3643 | return reader; | |
3644 | } | |
3645 | ||
3646 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) | |
3647 | { | |
3648 | struct ring_buffer_event *event; | |
3649 | struct buffer_page *reader; | |
3650 | unsigned length; | |
3651 | ||
3652 | reader = rb_get_reader_page(cpu_buffer); | |
7a8e76a3 | 3653 | |
d769041f | 3654 | /* This function should not be called when buffer is empty */ |
3e89c7bb SR |
3655 | if (RB_WARN_ON(cpu_buffer, !reader)) |
3656 | return; | |
7a8e76a3 | 3657 | |
d769041f SR |
3658 | event = rb_reader_event(cpu_buffer); |
3659 | ||
a1863c21 | 3660 | if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
e4906eff | 3661 | cpu_buffer->read++; |
d769041f SR |
3662 | |
3663 | rb_update_read_stamp(cpu_buffer, event); | |
3664 | ||
3665 | length = rb_event_length(event); | |
6f807acd | 3666 | cpu_buffer->reader_page->read += length; |
7a8e76a3 SR |
3667 | } |
3668 | ||
3669 | static void rb_advance_iter(struct ring_buffer_iter *iter) | |
3670 | { | |
7a8e76a3 SR |
3671 | struct ring_buffer_per_cpu *cpu_buffer; |
3672 | struct ring_buffer_event *event; | |
3673 | unsigned length; | |
3674 | ||
3675 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 SR |
3676 | |
3677 | /* | |
3678 | * Check if we are at the end of the buffer. | |
3679 | */ | |
bf41a158 | 3680 | if (iter->head >= rb_page_size(iter->head_page)) { |
ea05b57c SR |
3681 | /* discarded commits can make the page empty */ |
3682 | if (iter->head_page == cpu_buffer->commit_page) | |
3e89c7bb | 3683 | return; |
d769041f | 3684 | rb_inc_iter(iter); |
7a8e76a3 SR |
3685 | return; |
3686 | } | |
3687 | ||
3688 | event = rb_iter_head_event(iter); | |
3689 | ||
3690 | length = rb_event_length(event); | |
3691 | ||
3692 | /* | |
3693 | * This should not be called to advance the header if we are | |
3694 | * at the tail of the buffer. | |
3695 | */ | |
3e89c7bb | 3696 | if (RB_WARN_ON(cpu_buffer, |
f536aafc | 3697 | (iter->head_page == cpu_buffer->commit_page) && |
3e89c7bb SR |
3698 | (iter->head + length > rb_commit_index(cpu_buffer)))) |
3699 | return; | |
7a8e76a3 SR |
3700 | |
3701 | rb_update_iter_read_stamp(iter, event); | |
3702 | ||
3703 | iter->head += length; | |
3704 | ||
3705 | /* check for end of page padding */ | |
bf41a158 SR |
3706 | if ((iter->head >= rb_page_size(iter->head_page)) && |
3707 | (iter->head_page != cpu_buffer->commit_page)) | |
771e0384 | 3708 | rb_inc_iter(iter); |
7a8e76a3 SR |
3709 | } |
3710 | ||
66a8cb95 SR |
3711 | static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) |
3712 | { | |
3713 | return cpu_buffer->lost_events; | |
3714 | } | |
3715 | ||
f83c9d0f | 3716 | static struct ring_buffer_event * |
66a8cb95 SR |
3717 | rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, |
3718 | unsigned long *lost_events) | |
7a8e76a3 | 3719 | { |
7a8e76a3 | 3720 | struct ring_buffer_event *event; |
d769041f | 3721 | struct buffer_page *reader; |
818e3dd3 | 3722 | int nr_loops = 0; |
7a8e76a3 | 3723 | |
7a8e76a3 | 3724 | again: |
818e3dd3 | 3725 | /* |
69d1b839 SR |
3726 | * We repeat when a time extend is encountered. |
3727 | * Since the time extend is always attached to a data event, | |
3728 | * we should never loop more than once. | |
3729 | * (We never hit the following condition more than twice). | |
818e3dd3 | 3730 | */ |
69d1b839 | 3731 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
818e3dd3 | 3732 | return NULL; |
818e3dd3 | 3733 | |
d769041f SR |
3734 | reader = rb_get_reader_page(cpu_buffer); |
3735 | if (!reader) | |
7a8e76a3 SR |
3736 | return NULL; |
3737 | ||
d769041f | 3738 | event = rb_reader_event(cpu_buffer); |
7a8e76a3 | 3739 | |
334d4169 | 3740 | switch (event->type_len) { |
7a8e76a3 | 3741 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3742 | if (rb_null_event(event)) |
3743 | RB_WARN_ON(cpu_buffer, 1); | |
3744 | /* | |
3745 | * Because the writer could be discarding every | |
3746 | * event it creates (which would probably be bad) | |
3747 | * if we were to go back to "again" then we may never | |
3748 | * catch up, and will trigger the warn on, or lock | |
3749 | * the box. Return the padding, and we will release | |
3750 | * the current locks, and try again. | |
3751 | */ | |
2d622719 | 3752 | return event; |
7a8e76a3 SR |
3753 | |
3754 | case RINGBUF_TYPE_TIME_EXTEND: | |
3755 | /* Internal data, OK to advance */ | |
d769041f | 3756 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3757 | goto again; |
3758 | ||
3759 | case RINGBUF_TYPE_TIME_STAMP: | |
3760 | /* FIXME: not implemented */ | |
d769041f | 3761 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3762 | goto again; |
3763 | ||
3764 | case RINGBUF_TYPE_DATA: | |
3765 | if (ts) { | |
3766 | *ts = cpu_buffer->read_stamp + event->time_delta; | |
d8eeb2d3 | 3767 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
37886f6a | 3768 | cpu_buffer->cpu, ts); |
7a8e76a3 | 3769 | } |
66a8cb95 SR |
3770 | if (lost_events) |
3771 | *lost_events = rb_lost_events(cpu_buffer); | |
7a8e76a3 SR |
3772 | return event; |
3773 | ||
3774 | default: | |
3775 | BUG(); | |
3776 | } | |
3777 | ||
3778 | return NULL; | |
3779 | } | |
c4f50183 | 3780 | EXPORT_SYMBOL_GPL(ring_buffer_peek); |
7a8e76a3 | 3781 | |
f83c9d0f SR |
3782 | static struct ring_buffer_event * |
3783 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
7a8e76a3 SR |
3784 | { |
3785 | struct ring_buffer *buffer; | |
3786 | struct ring_buffer_per_cpu *cpu_buffer; | |
3787 | struct ring_buffer_event *event; | |
818e3dd3 | 3788 | int nr_loops = 0; |
7a8e76a3 | 3789 | |
7a8e76a3 SR |
3790 | cpu_buffer = iter->cpu_buffer; |
3791 | buffer = cpu_buffer->buffer; | |
3792 | ||
492a74f4 SR |
3793 | /* |
3794 | * Check if someone performed a consuming read to | |
3795 | * the buffer. A consuming read invalidates the iterator | |
3796 | * and we need to reset the iterator in this case. | |
3797 | */ | |
3798 | if (unlikely(iter->cache_read != cpu_buffer->read || | |
3799 | iter->cache_reader_page != cpu_buffer->reader_page)) | |
3800 | rb_iter_reset(iter); | |
3801 | ||
7a8e76a3 | 3802 | again: |
3c05d748 SR |
3803 | if (ring_buffer_iter_empty(iter)) |
3804 | return NULL; | |
3805 | ||
818e3dd3 | 3806 | /* |
021de3d9 SRRH |
3807 | * We repeat when a time extend is encountered or we hit |
3808 | * the end of the page. Since the time extend is always attached | |
3809 | * to a data event, we should never loop more than three times. | |
3810 | * Once for going to next page, once on time extend, and | |
3811 | * finally once to get the event. | |
3812 | * (We never hit the following condition more than thrice). | |
818e3dd3 | 3813 | */ |
021de3d9 | 3814 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) |
818e3dd3 | 3815 | return NULL; |
818e3dd3 | 3816 | |
7a8e76a3 SR |
3817 | if (rb_per_cpu_empty(cpu_buffer)) |
3818 | return NULL; | |
3819 | ||
10e83fd0 | 3820 | if (iter->head >= rb_page_size(iter->head_page)) { |
3c05d748 SR |
3821 | rb_inc_iter(iter); |
3822 | goto again; | |
3823 | } | |
3824 | ||
7a8e76a3 SR |
3825 | event = rb_iter_head_event(iter); |
3826 | ||
334d4169 | 3827 | switch (event->type_len) { |
7a8e76a3 | 3828 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3829 | if (rb_null_event(event)) { |
3830 | rb_inc_iter(iter); | |
3831 | goto again; | |
3832 | } | |
3833 | rb_advance_iter(iter); | |
3834 | return event; | |
7a8e76a3 SR |
3835 | |
3836 | case RINGBUF_TYPE_TIME_EXTEND: | |
3837 | /* Internal data, OK to advance */ | |
3838 | rb_advance_iter(iter); | |
3839 | goto again; | |
3840 | ||
3841 | case RINGBUF_TYPE_TIME_STAMP: | |
3842 | /* FIXME: not implemented */ | |
3843 | rb_advance_iter(iter); | |
3844 | goto again; | |
3845 | ||
3846 | case RINGBUF_TYPE_DATA: | |
3847 | if (ts) { | |
3848 | *ts = iter->read_stamp + event->time_delta; | |
37886f6a SR |
3849 | ring_buffer_normalize_time_stamp(buffer, |
3850 | cpu_buffer->cpu, ts); | |
7a8e76a3 SR |
3851 | } |
3852 | return event; | |
3853 | ||
3854 | default: | |
3855 | BUG(); | |
3856 | } | |
3857 | ||
3858 | return NULL; | |
3859 | } | |
c4f50183 | 3860 | EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
7a8e76a3 | 3861 | |
8d707e8e SR |
3862 | static inline int rb_ok_to_lock(void) |
3863 | { | |
3864 | /* | |
3865 | * If an NMI die dumps out the content of the ring buffer | |
3866 | * do not grab locks. We also permanently disable the ring | |
3867 | * buffer too. A one time deal is all you get from reading | |
3868 | * the ring buffer from an NMI. | |
3869 | */ | |
464e85eb | 3870 | if (likely(!in_nmi())) |
8d707e8e SR |
3871 | return 1; |
3872 | ||
3873 | tracing_off_permanent(); | |
3874 | return 0; | |
3875 | } | |
3876 | ||
f83c9d0f SR |
3877 | /** |
3878 | * ring_buffer_peek - peek at the next event to be read | |
3879 | * @buffer: The ring buffer to read | |
3880 | * @cpu: The cpu to peak at | |
3881 | * @ts: The timestamp counter of this event. | |
66a8cb95 | 3882 | * @lost_events: a variable to store if events were lost (may be NULL) |
f83c9d0f SR |
3883 | * |
3884 | * This will return the event that will be read next, but does | |
3885 | * not consume the data. | |
3886 | */ | |
3887 | struct ring_buffer_event * | |
66a8cb95 SR |
3888 | ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts, |
3889 | unsigned long *lost_events) | |
f83c9d0f SR |
3890 | { |
3891 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
8aabee57 | 3892 | struct ring_buffer_event *event; |
f83c9d0f | 3893 | unsigned long flags; |
8d707e8e | 3894 | int dolock; |
f83c9d0f | 3895 | |
554f786e | 3896 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3897 | return NULL; |
554f786e | 3898 | |
8d707e8e | 3899 | dolock = rb_ok_to_lock(); |
2d622719 | 3900 | again: |
8d707e8e SR |
3901 | local_irq_save(flags); |
3902 | if (dolock) | |
5389f6fa | 3903 | raw_spin_lock(&cpu_buffer->reader_lock); |
66a8cb95 | 3904 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
469535a5 RR |
3905 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3906 | rb_advance_reader(cpu_buffer); | |
8d707e8e | 3907 | if (dolock) |
5389f6fa | 3908 | raw_spin_unlock(&cpu_buffer->reader_lock); |
8d707e8e | 3909 | local_irq_restore(flags); |
f83c9d0f | 3910 | |
1b959e18 | 3911 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3912 | goto again; |
2d622719 | 3913 | |
f83c9d0f SR |
3914 | return event; |
3915 | } | |
3916 | ||
3917 | /** | |
3918 | * ring_buffer_iter_peek - peek at the next event to be read | |
3919 | * @iter: The ring buffer iterator | |
3920 | * @ts: The timestamp counter of this event. | |
3921 | * | |
3922 | * This will return the event that will be read next, but does | |
3923 | * not increment the iterator. | |
3924 | */ | |
3925 | struct ring_buffer_event * | |
3926 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
3927 | { | |
3928 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3929 | struct ring_buffer_event *event; | |
3930 | unsigned long flags; | |
3931 | ||
2d622719 | 3932 | again: |
5389f6fa | 3933 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 3934 | event = rb_iter_peek(iter, ts); |
5389f6fa | 3935 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 3936 | |
1b959e18 | 3937 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3938 | goto again; |
2d622719 | 3939 | |
f83c9d0f SR |
3940 | return event; |
3941 | } | |
3942 | ||
7a8e76a3 SR |
3943 | /** |
3944 | * ring_buffer_consume - return an event and consume it | |
3945 | * @buffer: The ring buffer to get the next event from | |
66a8cb95 SR |
3946 | * @cpu: the cpu to read the buffer from |
3947 | * @ts: a variable to store the timestamp (may be NULL) | |
3948 | * @lost_events: a variable to store if events were lost (may be NULL) | |
7a8e76a3 SR |
3949 | * |
3950 | * Returns the next event in the ring buffer, and that event is consumed. | |
3951 | * Meaning, that sequential reads will keep returning a different event, | |
3952 | * and eventually empty the ring buffer if the producer is slower. | |
3953 | */ | |
3954 | struct ring_buffer_event * | |
66a8cb95 SR |
3955 | ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, |
3956 | unsigned long *lost_events) | |
7a8e76a3 | 3957 | { |
554f786e SR |
3958 | struct ring_buffer_per_cpu *cpu_buffer; |
3959 | struct ring_buffer_event *event = NULL; | |
f83c9d0f | 3960 | unsigned long flags; |
8d707e8e SR |
3961 | int dolock; |
3962 | ||
3963 | dolock = rb_ok_to_lock(); | |
7a8e76a3 | 3964 | |
2d622719 | 3965 | again: |
554f786e SR |
3966 | /* might be called in atomic */ |
3967 | preempt_disable(); | |
3968 | ||
9e01c1b7 | 3969 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e | 3970 | goto out; |
7a8e76a3 | 3971 | |
554f786e | 3972 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e SR |
3973 | local_irq_save(flags); |
3974 | if (dolock) | |
5389f6fa | 3975 | raw_spin_lock(&cpu_buffer->reader_lock); |
f83c9d0f | 3976 | |
66a8cb95 SR |
3977 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
3978 | if (event) { | |
3979 | cpu_buffer->lost_events = 0; | |
469535a5 | 3980 | rb_advance_reader(cpu_buffer); |
66a8cb95 | 3981 | } |
7a8e76a3 | 3982 | |
8d707e8e | 3983 | if (dolock) |
5389f6fa | 3984 | raw_spin_unlock(&cpu_buffer->reader_lock); |
8d707e8e | 3985 | local_irq_restore(flags); |
f83c9d0f | 3986 | |
554f786e SR |
3987 | out: |
3988 | preempt_enable(); | |
3989 | ||
1b959e18 | 3990 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3991 | goto again; |
2d622719 | 3992 | |
7a8e76a3 SR |
3993 | return event; |
3994 | } | |
c4f50183 | 3995 | EXPORT_SYMBOL_GPL(ring_buffer_consume); |
7a8e76a3 SR |
3996 | |
3997 | /** | |
72c9ddfd | 3998 | * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer |
7a8e76a3 SR |
3999 | * @buffer: The ring buffer to read from |
4000 | * @cpu: The cpu buffer to iterate over | |
4001 | * | |
72c9ddfd DM |
4002 | * This performs the initial preparations necessary to iterate |
4003 | * through the buffer. Memory is allocated, buffer recording | |
4004 | * is disabled, and the iterator pointer is returned to the caller. | |
7a8e76a3 | 4005 | * |
72c9ddfd DM |
4006 | * Disabling buffer recordng prevents the reading from being |
4007 | * corrupted. This is not a consuming read, so a producer is not | |
4008 | * expected. | |
4009 | * | |
4010 | * After a sequence of ring_buffer_read_prepare calls, the user is | |
d611851b | 4011 | * expected to make at least one call to ring_buffer_read_prepare_sync. |
72c9ddfd DM |
4012 | * Afterwards, ring_buffer_read_start is invoked to get things going |
4013 | * for real. | |
4014 | * | |
d611851b | 4015 | * This overall must be paired with ring_buffer_read_finish. |
7a8e76a3 SR |
4016 | */ |
4017 | struct ring_buffer_iter * | |
72c9ddfd | 4018 | ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu) |
7a8e76a3 SR |
4019 | { |
4020 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 4021 | struct ring_buffer_iter *iter; |
7a8e76a3 | 4022 | |
9e01c1b7 | 4023 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4024 | return NULL; |
7a8e76a3 SR |
4025 | |
4026 | iter = kmalloc(sizeof(*iter), GFP_KERNEL); | |
4027 | if (!iter) | |
8aabee57 | 4028 | return NULL; |
7a8e76a3 SR |
4029 | |
4030 | cpu_buffer = buffer->buffers[cpu]; | |
4031 | ||
4032 | iter->cpu_buffer = cpu_buffer; | |
4033 | ||
83f40318 | 4034 | atomic_inc(&buffer->resize_disabled); |
7a8e76a3 | 4035 | atomic_inc(&cpu_buffer->record_disabled); |
72c9ddfd DM |
4036 | |
4037 | return iter; | |
4038 | } | |
4039 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); | |
4040 | ||
4041 | /** | |
4042 | * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls | |
4043 | * | |
4044 | * All previously invoked ring_buffer_read_prepare calls to prepare | |
4045 | * iterators will be synchronized. Afterwards, read_buffer_read_start | |
4046 | * calls on those iterators are allowed. | |
4047 | */ | |
4048 | void | |
4049 | ring_buffer_read_prepare_sync(void) | |
4050 | { | |
7a8e76a3 | 4051 | synchronize_sched(); |
72c9ddfd DM |
4052 | } |
4053 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); | |
4054 | ||
4055 | /** | |
4056 | * ring_buffer_read_start - start a non consuming read of the buffer | |
4057 | * @iter: The iterator returned by ring_buffer_read_prepare | |
4058 | * | |
4059 | * This finalizes the startup of an iteration through the buffer. | |
4060 | * The iterator comes from a call to ring_buffer_read_prepare and | |
4061 | * an intervening ring_buffer_read_prepare_sync must have been | |
4062 | * performed. | |
4063 | * | |
d611851b | 4064 | * Must be paired with ring_buffer_read_finish. |
72c9ddfd DM |
4065 | */ |
4066 | void | |
4067 | ring_buffer_read_start(struct ring_buffer_iter *iter) | |
4068 | { | |
4069 | struct ring_buffer_per_cpu *cpu_buffer; | |
4070 | unsigned long flags; | |
4071 | ||
4072 | if (!iter) | |
4073 | return; | |
4074 | ||
4075 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 | 4076 | |
5389f6fa | 4077 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
0199c4e6 | 4078 | arch_spin_lock(&cpu_buffer->lock); |
642edba5 | 4079 | rb_iter_reset(iter); |
0199c4e6 | 4080 | arch_spin_unlock(&cpu_buffer->lock); |
5389f6fa | 4081 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 4082 | } |
c4f50183 | 4083 | EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
7a8e76a3 SR |
4084 | |
4085 | /** | |
d611851b | 4086 | * ring_buffer_read_finish - finish reading the iterator of the buffer |
7a8e76a3 SR |
4087 | * @iter: The iterator retrieved by ring_buffer_start |
4088 | * | |
4089 | * This re-enables the recording to the buffer, and frees the | |
4090 | * iterator. | |
4091 | */ | |
4092 | void | |
4093 | ring_buffer_read_finish(struct ring_buffer_iter *iter) | |
4094 | { | |
4095 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
9366c1ba | 4096 | unsigned long flags; |
7a8e76a3 | 4097 | |
659f451f SR |
4098 | /* |
4099 | * Ring buffer is disabled from recording, here's a good place | |
9366c1ba SR |
4100 | * to check the integrity of the ring buffer. |
4101 | * Must prevent readers from trying to read, as the check | |
4102 | * clears the HEAD page and readers require it. | |
659f451f | 4103 | */ |
9366c1ba | 4104 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
659f451f | 4105 | rb_check_pages(cpu_buffer); |
9366c1ba | 4106 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
659f451f | 4107 | |
7a8e76a3 | 4108 | atomic_dec(&cpu_buffer->record_disabled); |
83f40318 | 4109 | atomic_dec(&cpu_buffer->buffer->resize_disabled); |
7a8e76a3 SR |
4110 | kfree(iter); |
4111 | } | |
c4f50183 | 4112 | EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
7a8e76a3 SR |
4113 | |
4114 | /** | |
4115 | * ring_buffer_read - read the next item in the ring buffer by the iterator | |
4116 | * @iter: The ring buffer iterator | |
4117 | * @ts: The time stamp of the event read. | |
4118 | * | |
4119 | * This reads the next event in the ring buffer and increments the iterator. | |
4120 | */ | |
4121 | struct ring_buffer_event * | |
4122 | ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) | |
4123 | { | |
4124 | struct ring_buffer_event *event; | |
f83c9d0f SR |
4125 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
4126 | unsigned long flags; | |
7a8e76a3 | 4127 | |
5389f6fa | 4128 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
7e9391cf | 4129 | again: |
f83c9d0f | 4130 | event = rb_iter_peek(iter, ts); |
7a8e76a3 | 4131 | if (!event) |
f83c9d0f | 4132 | goto out; |
7a8e76a3 | 4133 | |
7e9391cf SR |
4134 | if (event->type_len == RINGBUF_TYPE_PADDING) |
4135 | goto again; | |
4136 | ||
7a8e76a3 | 4137 | rb_advance_iter(iter); |
f83c9d0f | 4138 | out: |
5389f6fa | 4139 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 SR |
4140 | |
4141 | return event; | |
4142 | } | |
c4f50183 | 4143 | EXPORT_SYMBOL_GPL(ring_buffer_read); |
7a8e76a3 SR |
4144 | |
4145 | /** | |
4146 | * ring_buffer_size - return the size of the ring buffer (in bytes) | |
4147 | * @buffer: The ring buffer. | |
4148 | */ | |
438ced17 | 4149 | unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu) |
7a8e76a3 | 4150 | { |
438ced17 VN |
4151 | /* |
4152 | * Earlier, this method returned | |
4153 | * BUF_PAGE_SIZE * buffer->nr_pages | |
4154 | * Since the nr_pages field is now removed, we have converted this to | |
4155 | * return the per cpu buffer value. | |
4156 | */ | |
4157 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
4158 | return 0; | |
4159 | ||
4160 | return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages; | |
7a8e76a3 | 4161 | } |
c4f50183 | 4162 | EXPORT_SYMBOL_GPL(ring_buffer_size); |
7a8e76a3 SR |
4163 | |
4164 | static void | |
4165 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) | |
4166 | { | |
77ae365e SR |
4167 | rb_head_page_deactivate(cpu_buffer); |
4168 | ||
7a8e76a3 | 4169 | cpu_buffer->head_page |
3adc54fa | 4170 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 4171 | local_set(&cpu_buffer->head_page->write, 0); |
778c55d4 | 4172 | local_set(&cpu_buffer->head_page->entries, 0); |
abc9b56d | 4173 | local_set(&cpu_buffer->head_page->page->commit, 0); |
d769041f | 4174 | |
6f807acd | 4175 | cpu_buffer->head_page->read = 0; |
bf41a158 SR |
4176 | |
4177 | cpu_buffer->tail_page = cpu_buffer->head_page; | |
4178 | cpu_buffer->commit_page = cpu_buffer->head_page; | |
4179 | ||
4180 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); | |
5040b4b7 | 4181 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
bf41a158 | 4182 | local_set(&cpu_buffer->reader_page->write, 0); |
778c55d4 | 4183 | local_set(&cpu_buffer->reader_page->entries, 0); |
abc9b56d | 4184 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
6f807acd | 4185 | cpu_buffer->reader_page->read = 0; |
7a8e76a3 | 4186 | |
c64e148a | 4187 | local_set(&cpu_buffer->entries_bytes, 0); |
77ae365e | 4188 | local_set(&cpu_buffer->overrun, 0); |
884bfe89 SP |
4189 | local_set(&cpu_buffer->commit_overrun, 0); |
4190 | local_set(&cpu_buffer->dropped_events, 0); | |
e4906eff | 4191 | local_set(&cpu_buffer->entries, 0); |
fa743953 SR |
4192 | local_set(&cpu_buffer->committing, 0); |
4193 | local_set(&cpu_buffer->commits, 0); | |
77ae365e | 4194 | cpu_buffer->read = 0; |
c64e148a | 4195 | cpu_buffer->read_bytes = 0; |
69507c06 SR |
4196 | |
4197 | cpu_buffer->write_stamp = 0; | |
4198 | cpu_buffer->read_stamp = 0; | |
77ae365e | 4199 | |
66a8cb95 SR |
4200 | cpu_buffer->lost_events = 0; |
4201 | cpu_buffer->last_overrun = 0; | |
4202 | ||
77ae365e | 4203 | rb_head_page_activate(cpu_buffer); |
7a8e76a3 SR |
4204 | } |
4205 | ||
4206 | /** | |
4207 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
4208 | * @buffer: The ring buffer to reset a per cpu buffer of | |
4209 | * @cpu: The CPU buffer to be reset | |
4210 | */ | |
4211 | void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) | |
4212 | { | |
4213 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
4214 | unsigned long flags; | |
4215 | ||
9e01c1b7 | 4216 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4217 | return; |
7a8e76a3 | 4218 | |
83f40318 | 4219 | atomic_inc(&buffer->resize_disabled); |
41ede23e SR |
4220 | atomic_inc(&cpu_buffer->record_disabled); |
4221 | ||
83f40318 VN |
4222 | /* Make sure all commits have finished */ |
4223 | synchronize_sched(); | |
4224 | ||
5389f6fa | 4225 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4226 | |
41b6a95d SR |
4227 | if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) |
4228 | goto out; | |
4229 | ||
0199c4e6 | 4230 | arch_spin_lock(&cpu_buffer->lock); |
7a8e76a3 SR |
4231 | |
4232 | rb_reset_cpu(cpu_buffer); | |
4233 | ||
0199c4e6 | 4234 | arch_spin_unlock(&cpu_buffer->lock); |
f83c9d0f | 4235 | |
41b6a95d | 4236 | out: |
5389f6fa | 4237 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
41ede23e SR |
4238 | |
4239 | atomic_dec(&cpu_buffer->record_disabled); | |
83f40318 | 4240 | atomic_dec(&buffer->resize_disabled); |
7a8e76a3 | 4241 | } |
c4f50183 | 4242 | EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); |
7a8e76a3 SR |
4243 | |
4244 | /** | |
4245 | * ring_buffer_reset - reset a ring buffer | |
4246 | * @buffer: The ring buffer to reset all cpu buffers | |
4247 | */ | |
4248 | void ring_buffer_reset(struct ring_buffer *buffer) | |
4249 | { | |
7a8e76a3 SR |
4250 | int cpu; |
4251 | ||
7a8e76a3 | 4252 | for_each_buffer_cpu(buffer, cpu) |
d769041f | 4253 | ring_buffer_reset_cpu(buffer, cpu); |
7a8e76a3 | 4254 | } |
c4f50183 | 4255 | EXPORT_SYMBOL_GPL(ring_buffer_reset); |
7a8e76a3 SR |
4256 | |
4257 | /** | |
4258 | * rind_buffer_empty - is the ring buffer empty? | |
4259 | * @buffer: The ring buffer to test | |
4260 | */ | |
4261 | int ring_buffer_empty(struct ring_buffer *buffer) | |
4262 | { | |
4263 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4264 | unsigned long flags; |
8d707e8e | 4265 | int dolock; |
7a8e76a3 | 4266 | int cpu; |
d4788207 | 4267 | int ret; |
7a8e76a3 | 4268 | |
8d707e8e | 4269 | dolock = rb_ok_to_lock(); |
7a8e76a3 SR |
4270 | |
4271 | /* yes this is racy, but if you don't like the race, lock the buffer */ | |
4272 | for_each_buffer_cpu(buffer, cpu) { | |
4273 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e SR |
4274 | local_irq_save(flags); |
4275 | if (dolock) | |
5389f6fa | 4276 | raw_spin_lock(&cpu_buffer->reader_lock); |
d4788207 | 4277 | ret = rb_per_cpu_empty(cpu_buffer); |
8d707e8e | 4278 | if (dolock) |
5389f6fa | 4279 | raw_spin_unlock(&cpu_buffer->reader_lock); |
8d707e8e SR |
4280 | local_irq_restore(flags); |
4281 | ||
d4788207 | 4282 | if (!ret) |
7a8e76a3 SR |
4283 | return 0; |
4284 | } | |
554f786e | 4285 | |
7a8e76a3 SR |
4286 | return 1; |
4287 | } | |
c4f50183 | 4288 | EXPORT_SYMBOL_GPL(ring_buffer_empty); |
7a8e76a3 SR |
4289 | |
4290 | /** | |
4291 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? | |
4292 | * @buffer: The ring buffer | |
4293 | * @cpu: The CPU buffer to test | |
4294 | */ | |
4295 | int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) | |
4296 | { | |
4297 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4298 | unsigned long flags; |
8d707e8e | 4299 | int dolock; |
8aabee57 | 4300 | int ret; |
7a8e76a3 | 4301 | |
9e01c1b7 | 4302 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4303 | return 1; |
7a8e76a3 | 4304 | |
8d707e8e SR |
4305 | dolock = rb_ok_to_lock(); |
4306 | ||
7a8e76a3 | 4307 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e SR |
4308 | local_irq_save(flags); |
4309 | if (dolock) | |
5389f6fa | 4310 | raw_spin_lock(&cpu_buffer->reader_lock); |
554f786e | 4311 | ret = rb_per_cpu_empty(cpu_buffer); |
8d707e8e | 4312 | if (dolock) |
5389f6fa | 4313 | raw_spin_unlock(&cpu_buffer->reader_lock); |
8d707e8e | 4314 | local_irq_restore(flags); |
554f786e SR |
4315 | |
4316 | return ret; | |
7a8e76a3 | 4317 | } |
c4f50183 | 4318 | EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
7a8e76a3 | 4319 | |
85bac32c | 4320 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
7a8e76a3 SR |
4321 | /** |
4322 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers | |
4323 | * @buffer_a: One buffer to swap with | |
4324 | * @buffer_b: The other buffer to swap with | |
4325 | * | |
4326 | * This function is useful for tracers that want to take a "snapshot" | |
4327 | * of a CPU buffer and has another back up buffer lying around. | |
4328 | * it is expected that the tracer handles the cpu buffer not being | |
4329 | * used at the moment. | |
4330 | */ | |
4331 | int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, | |
4332 | struct ring_buffer *buffer_b, int cpu) | |
4333 | { | |
4334 | struct ring_buffer_per_cpu *cpu_buffer_a; | |
4335 | struct ring_buffer_per_cpu *cpu_buffer_b; | |
554f786e SR |
4336 | int ret = -EINVAL; |
4337 | ||
9e01c1b7 RR |
4338 | if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
4339 | !cpumask_test_cpu(cpu, buffer_b->cpumask)) | |
554f786e | 4340 | goto out; |
7a8e76a3 | 4341 | |
438ced17 VN |
4342 | cpu_buffer_a = buffer_a->buffers[cpu]; |
4343 | cpu_buffer_b = buffer_b->buffers[cpu]; | |
4344 | ||
7a8e76a3 | 4345 | /* At least make sure the two buffers are somewhat the same */ |
438ced17 | 4346 | if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) |
554f786e SR |
4347 | goto out; |
4348 | ||
4349 | ret = -EAGAIN; | |
7a8e76a3 | 4350 | |
97b17efe | 4351 | if (ring_buffer_flags != RB_BUFFERS_ON) |
554f786e | 4352 | goto out; |
97b17efe SR |
4353 | |
4354 | if (atomic_read(&buffer_a->record_disabled)) | |
554f786e | 4355 | goto out; |
97b17efe SR |
4356 | |
4357 | if (atomic_read(&buffer_b->record_disabled)) | |
554f786e | 4358 | goto out; |
97b17efe | 4359 | |
97b17efe | 4360 | if (atomic_read(&cpu_buffer_a->record_disabled)) |
554f786e | 4361 | goto out; |
97b17efe SR |
4362 | |
4363 | if (atomic_read(&cpu_buffer_b->record_disabled)) | |
554f786e | 4364 | goto out; |
97b17efe | 4365 | |
7a8e76a3 SR |
4366 | /* |
4367 | * We can't do a synchronize_sched here because this | |
4368 | * function can be called in atomic context. | |
4369 | * Normally this will be called from the same CPU as cpu. | |
4370 | * If not it's up to the caller to protect this. | |
4371 | */ | |
4372 | atomic_inc(&cpu_buffer_a->record_disabled); | |
4373 | atomic_inc(&cpu_buffer_b->record_disabled); | |
4374 | ||
98277991 SR |
4375 | ret = -EBUSY; |
4376 | if (local_read(&cpu_buffer_a->committing)) | |
4377 | goto out_dec; | |
4378 | if (local_read(&cpu_buffer_b->committing)) | |
4379 | goto out_dec; | |
4380 | ||
7a8e76a3 SR |
4381 | buffer_a->buffers[cpu] = cpu_buffer_b; |
4382 | buffer_b->buffers[cpu] = cpu_buffer_a; | |
4383 | ||
4384 | cpu_buffer_b->buffer = buffer_a; | |
4385 | cpu_buffer_a->buffer = buffer_b; | |
4386 | ||
98277991 SR |
4387 | ret = 0; |
4388 | ||
4389 | out_dec: | |
7a8e76a3 SR |
4390 | atomic_dec(&cpu_buffer_a->record_disabled); |
4391 | atomic_dec(&cpu_buffer_b->record_disabled); | |
554f786e | 4392 | out: |
554f786e | 4393 | return ret; |
7a8e76a3 | 4394 | } |
c4f50183 | 4395 | EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
85bac32c | 4396 | #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
7a8e76a3 | 4397 | |
8789a9e7 SR |
4398 | /** |
4399 | * ring_buffer_alloc_read_page - allocate a page to read from buffer | |
4400 | * @buffer: the buffer to allocate for. | |
d611851b | 4401 | * @cpu: the cpu buffer to allocate. |
8789a9e7 SR |
4402 | * |
4403 | * This function is used in conjunction with ring_buffer_read_page. | |
4404 | * When reading a full page from the ring buffer, these functions | |
4405 | * can be used to speed up the process. The calling function should | |
4406 | * allocate a few pages first with this function. Then when it | |
4407 | * needs to get pages from the ring buffer, it passes the result | |
4408 | * of this function into ring_buffer_read_page, which will swap | |
4409 | * the page that was allocated, with the read page of the buffer. | |
4410 | * | |
4411 | * Returns: | |
4412 | * The page allocated, or NULL on error. | |
4413 | */ | |
7ea59064 | 4414 | void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu) |
8789a9e7 | 4415 | { |
044fa782 | 4416 | struct buffer_data_page *bpage; |
7ea59064 | 4417 | struct page *page; |
8789a9e7 | 4418 | |
d7ec4bfe VN |
4419 | page = alloc_pages_node(cpu_to_node(cpu), |
4420 | GFP_KERNEL | __GFP_NORETRY, 0); | |
7ea59064 | 4421 | if (!page) |
8789a9e7 SR |
4422 | return NULL; |
4423 | ||
7ea59064 | 4424 | bpage = page_address(page); |
8789a9e7 | 4425 | |
ef7a4a16 SR |
4426 | rb_init_page(bpage); |
4427 | ||
044fa782 | 4428 | return bpage; |
8789a9e7 | 4429 | } |
d6ce96da | 4430 | EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
8789a9e7 SR |
4431 | |
4432 | /** | |
4433 | * ring_buffer_free_read_page - free an allocated read page | |
4434 | * @buffer: the buffer the page was allocate for | |
4435 | * @data: the page to free | |
4436 | * | |
4437 | * Free a page allocated from ring_buffer_alloc_read_page. | |
4438 | */ | |
4439 | void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) | |
4440 | { | |
4441 | free_page((unsigned long)data); | |
4442 | } | |
d6ce96da | 4443 | EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
8789a9e7 SR |
4444 | |
4445 | /** | |
4446 | * ring_buffer_read_page - extract a page from the ring buffer | |
4447 | * @buffer: buffer to extract from | |
4448 | * @data_page: the page to use allocated from ring_buffer_alloc_read_page | |
ef7a4a16 | 4449 | * @len: amount to extract |
8789a9e7 SR |
4450 | * @cpu: the cpu of the buffer to extract |
4451 | * @full: should the extraction only happen when the page is full. | |
4452 | * | |
4453 | * This function will pull out a page from the ring buffer and consume it. | |
4454 | * @data_page must be the address of the variable that was returned | |
4455 | * from ring_buffer_alloc_read_page. This is because the page might be used | |
4456 | * to swap with a page in the ring buffer. | |
4457 | * | |
4458 | * for example: | |
d611851b | 4459 | * rpage = ring_buffer_alloc_read_page(buffer, cpu); |
8789a9e7 SR |
4460 | * if (!rpage) |
4461 | * return error; | |
ef7a4a16 | 4462 | * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
667d2412 LJ |
4463 | * if (ret >= 0) |
4464 | * process_page(rpage, ret); | |
8789a9e7 SR |
4465 | * |
4466 | * When @full is set, the function will not return true unless | |
4467 | * the writer is off the reader page. | |
4468 | * | |
4469 | * Note: it is up to the calling functions to handle sleeps and wakeups. | |
4470 | * The ring buffer can be used anywhere in the kernel and can not | |
4471 | * blindly call wake_up. The layer that uses the ring buffer must be | |
4472 | * responsible for that. | |
4473 | * | |
4474 | * Returns: | |
667d2412 LJ |
4475 | * >=0 if data has been transferred, returns the offset of consumed data. |
4476 | * <0 if no data has been transferred. | |
8789a9e7 SR |
4477 | */ |
4478 | int ring_buffer_read_page(struct ring_buffer *buffer, | |
ef7a4a16 | 4479 | void **data_page, size_t len, int cpu, int full) |
8789a9e7 SR |
4480 | { |
4481 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
4482 | struct ring_buffer_event *event; | |
044fa782 | 4483 | struct buffer_data_page *bpage; |
ef7a4a16 | 4484 | struct buffer_page *reader; |
ff0ff84a | 4485 | unsigned long missed_events; |
8789a9e7 | 4486 | unsigned long flags; |
ef7a4a16 | 4487 | unsigned int commit; |
667d2412 | 4488 | unsigned int read; |
4f3640f8 | 4489 | u64 save_timestamp; |
667d2412 | 4490 | int ret = -1; |
8789a9e7 | 4491 | |
554f786e SR |
4492 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
4493 | goto out; | |
4494 | ||
474d32b6 SR |
4495 | /* |
4496 | * If len is not big enough to hold the page header, then | |
4497 | * we can not copy anything. | |
4498 | */ | |
4499 | if (len <= BUF_PAGE_HDR_SIZE) | |
554f786e | 4500 | goto out; |
474d32b6 SR |
4501 | |
4502 | len -= BUF_PAGE_HDR_SIZE; | |
4503 | ||
8789a9e7 | 4504 | if (!data_page) |
554f786e | 4505 | goto out; |
8789a9e7 | 4506 | |
044fa782 SR |
4507 | bpage = *data_page; |
4508 | if (!bpage) | |
554f786e | 4509 | goto out; |
8789a9e7 | 4510 | |
5389f6fa | 4511 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 4512 | |
ef7a4a16 SR |
4513 | reader = rb_get_reader_page(cpu_buffer); |
4514 | if (!reader) | |
554f786e | 4515 | goto out_unlock; |
8789a9e7 | 4516 | |
ef7a4a16 SR |
4517 | event = rb_reader_event(cpu_buffer); |
4518 | ||
4519 | read = reader->read; | |
4520 | commit = rb_page_commit(reader); | |
667d2412 | 4521 | |
66a8cb95 | 4522 | /* Check if any events were dropped */ |
ff0ff84a | 4523 | missed_events = cpu_buffer->lost_events; |
66a8cb95 | 4524 | |
8789a9e7 | 4525 | /* |
474d32b6 SR |
4526 | * If this page has been partially read or |
4527 | * if len is not big enough to read the rest of the page or | |
4528 | * a writer is still on the page, then | |
4529 | * we must copy the data from the page to the buffer. | |
4530 | * Otherwise, we can simply swap the page with the one passed in. | |
8789a9e7 | 4531 | */ |
474d32b6 | 4532 | if (read || (len < (commit - read)) || |
ef7a4a16 | 4533 | cpu_buffer->reader_page == cpu_buffer->commit_page) { |
667d2412 | 4534 | struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
474d32b6 SR |
4535 | unsigned int rpos = read; |
4536 | unsigned int pos = 0; | |
ef7a4a16 | 4537 | unsigned int size; |
8789a9e7 SR |
4538 | |
4539 | if (full) | |
554f786e | 4540 | goto out_unlock; |
8789a9e7 | 4541 | |
ef7a4a16 SR |
4542 | if (len > (commit - read)) |
4543 | len = (commit - read); | |
4544 | ||
69d1b839 SR |
4545 | /* Always keep the time extend and data together */ |
4546 | size = rb_event_ts_length(event); | |
ef7a4a16 SR |
4547 | |
4548 | if (len < size) | |
554f786e | 4549 | goto out_unlock; |
ef7a4a16 | 4550 | |
4f3640f8 SR |
4551 | /* save the current timestamp, since the user will need it */ |
4552 | save_timestamp = cpu_buffer->read_stamp; | |
4553 | ||
ef7a4a16 SR |
4554 | /* Need to copy one event at a time */ |
4555 | do { | |
e1e35927 DS |
4556 | /* We need the size of one event, because |
4557 | * rb_advance_reader only advances by one event, | |
4558 | * whereas rb_event_ts_length may include the size of | |
4559 | * one or two events. | |
4560 | * We have already ensured there's enough space if this | |
4561 | * is a time extend. */ | |
4562 | size = rb_event_length(event); | |
474d32b6 | 4563 | memcpy(bpage->data + pos, rpage->data + rpos, size); |
ef7a4a16 SR |
4564 | |
4565 | len -= size; | |
4566 | ||
4567 | rb_advance_reader(cpu_buffer); | |
474d32b6 SR |
4568 | rpos = reader->read; |
4569 | pos += size; | |
ef7a4a16 | 4570 | |
18fab912 HY |
4571 | if (rpos >= commit) |
4572 | break; | |
4573 | ||
ef7a4a16 | 4574 | event = rb_reader_event(cpu_buffer); |
69d1b839 SR |
4575 | /* Always keep the time extend and data together */ |
4576 | size = rb_event_ts_length(event); | |
e1e35927 | 4577 | } while (len >= size); |
667d2412 LJ |
4578 | |
4579 | /* update bpage */ | |
ef7a4a16 | 4580 | local_set(&bpage->commit, pos); |
4f3640f8 | 4581 | bpage->time_stamp = save_timestamp; |
ef7a4a16 | 4582 | |
474d32b6 SR |
4583 | /* we copied everything to the beginning */ |
4584 | read = 0; | |
8789a9e7 | 4585 | } else { |
afbab76a | 4586 | /* update the entry counter */ |
77ae365e | 4587 | cpu_buffer->read += rb_page_entries(reader); |
c64e148a | 4588 | cpu_buffer->read_bytes += BUF_PAGE_SIZE; |
afbab76a | 4589 | |
8789a9e7 | 4590 | /* swap the pages */ |
044fa782 | 4591 | rb_init_page(bpage); |
ef7a4a16 SR |
4592 | bpage = reader->page; |
4593 | reader->page = *data_page; | |
4594 | local_set(&reader->write, 0); | |
778c55d4 | 4595 | local_set(&reader->entries, 0); |
ef7a4a16 | 4596 | reader->read = 0; |
044fa782 | 4597 | *data_page = bpage; |
ff0ff84a SR |
4598 | |
4599 | /* | |
4600 | * Use the real_end for the data size, | |
4601 | * This gives us a chance to store the lost events | |
4602 | * on the page. | |
4603 | */ | |
4604 | if (reader->real_end) | |
4605 | local_set(&bpage->commit, reader->real_end); | |
8789a9e7 | 4606 | } |
667d2412 | 4607 | ret = read; |
8789a9e7 | 4608 | |
66a8cb95 | 4609 | cpu_buffer->lost_events = 0; |
2711ca23 SR |
4610 | |
4611 | commit = local_read(&bpage->commit); | |
66a8cb95 SR |
4612 | /* |
4613 | * Set a flag in the commit field if we lost events | |
4614 | */ | |
ff0ff84a | 4615 | if (missed_events) { |
ff0ff84a SR |
4616 | /* If there is room at the end of the page to save the |
4617 | * missed events, then record it there. | |
4618 | */ | |
4619 | if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { | |
4620 | memcpy(&bpage->data[commit], &missed_events, | |
4621 | sizeof(missed_events)); | |
4622 | local_add(RB_MISSED_STORED, &bpage->commit); | |
2711ca23 | 4623 | commit += sizeof(missed_events); |
ff0ff84a | 4624 | } |
66a8cb95 | 4625 | local_add(RB_MISSED_EVENTS, &bpage->commit); |
ff0ff84a | 4626 | } |
66a8cb95 | 4627 | |
2711ca23 SR |
4628 | /* |
4629 | * This page may be off to user land. Zero it out here. | |
4630 | */ | |
4631 | if (commit < BUF_PAGE_SIZE) | |
4632 | memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit); | |
4633 | ||
554f786e | 4634 | out_unlock: |
5389f6fa | 4635 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 4636 | |
554f786e | 4637 | out: |
8789a9e7 SR |
4638 | return ret; |
4639 | } | |
d6ce96da | 4640 | EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
8789a9e7 | 4641 | |
59222efe | 4642 | #ifdef CONFIG_HOTPLUG_CPU |
09c9e84d FW |
4643 | static int rb_cpu_notify(struct notifier_block *self, |
4644 | unsigned long action, void *hcpu) | |
554f786e SR |
4645 | { |
4646 | struct ring_buffer *buffer = | |
4647 | container_of(self, struct ring_buffer, cpu_notify); | |
4648 | long cpu = (long)hcpu; | |
438ced17 VN |
4649 | int cpu_i, nr_pages_same; |
4650 | unsigned int nr_pages; | |
554f786e SR |
4651 | |
4652 | switch (action) { | |
4653 | case CPU_UP_PREPARE: | |
4654 | case CPU_UP_PREPARE_FROZEN: | |
3f237a79 | 4655 | if (cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e SR |
4656 | return NOTIFY_OK; |
4657 | ||
438ced17 VN |
4658 | nr_pages = 0; |
4659 | nr_pages_same = 1; | |
4660 | /* check if all cpu sizes are same */ | |
4661 | for_each_buffer_cpu(buffer, cpu_i) { | |
4662 | /* fill in the size from first enabled cpu */ | |
4663 | if (nr_pages == 0) | |
4664 | nr_pages = buffer->buffers[cpu_i]->nr_pages; | |
4665 | if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { | |
4666 | nr_pages_same = 0; | |
4667 | break; | |
4668 | } | |
4669 | } | |
4670 | /* allocate minimum pages, user can later expand it */ | |
4671 | if (!nr_pages_same) | |
4672 | nr_pages = 2; | |
554f786e | 4673 | buffer->buffers[cpu] = |
438ced17 | 4674 | rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
554f786e SR |
4675 | if (!buffer->buffers[cpu]) { |
4676 | WARN(1, "failed to allocate ring buffer on CPU %ld\n", | |
4677 | cpu); | |
4678 | return NOTIFY_OK; | |
4679 | } | |
4680 | smp_wmb(); | |
3f237a79 | 4681 | cpumask_set_cpu(cpu, buffer->cpumask); |
554f786e SR |
4682 | break; |
4683 | case CPU_DOWN_PREPARE: | |
4684 | case CPU_DOWN_PREPARE_FROZEN: | |
4685 | /* | |
4686 | * Do nothing. | |
4687 | * If we were to free the buffer, then the user would | |
4688 | * lose any trace that was in the buffer. | |
4689 | */ | |
4690 | break; | |
4691 | default: | |
4692 | break; | |
4693 | } | |
4694 | return NOTIFY_OK; | |
4695 | } | |
4696 | #endif | |
6c43e554 SRRH |
4697 | |
4698 | #ifdef CONFIG_RING_BUFFER_STARTUP_TEST | |
4699 | /* | |
4700 | * This is a basic integrity check of the ring buffer. | |
4701 | * Late in the boot cycle this test will run when configured in. | |
4702 | * It will kick off a thread per CPU that will go into a loop | |
4703 | * writing to the per cpu ring buffer various sizes of data. | |
4704 | * Some of the data will be large items, some small. | |
4705 | * | |
4706 | * Another thread is created that goes into a spin, sending out | |
4707 | * IPIs to the other CPUs to also write into the ring buffer. | |
4708 | * this is to test the nesting ability of the buffer. | |
4709 | * | |
4710 | * Basic stats are recorded and reported. If something in the | |
4711 | * ring buffer should happen that's not expected, a big warning | |
4712 | * is displayed and all ring buffers are disabled. | |
4713 | */ | |
4714 | static struct task_struct *rb_threads[NR_CPUS] __initdata; | |
4715 | ||
4716 | struct rb_test_data { | |
4717 | struct ring_buffer *buffer; | |
4718 | unsigned long events; | |
4719 | unsigned long bytes_written; | |
4720 | unsigned long bytes_alloc; | |
4721 | unsigned long bytes_dropped; | |
4722 | unsigned long events_nested; | |
4723 | unsigned long bytes_written_nested; | |
4724 | unsigned long bytes_alloc_nested; | |
4725 | unsigned long bytes_dropped_nested; | |
4726 | int min_size_nested; | |
4727 | int max_size_nested; | |
4728 | int max_size; | |
4729 | int min_size; | |
4730 | int cpu; | |
4731 | int cnt; | |
4732 | }; | |
4733 | ||
4734 | static struct rb_test_data rb_data[NR_CPUS] __initdata; | |
4735 | ||
4736 | /* 1 meg per cpu */ | |
4737 | #define RB_TEST_BUFFER_SIZE 1048576 | |
4738 | ||
4739 | static char rb_string[] __initdata = | |
4740 | "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" | |
4741 | "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" | |
4742 | "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv"; | |
4743 | ||
4744 | static bool rb_test_started __initdata; | |
4745 | ||
4746 | struct rb_item { | |
4747 | int size; | |
4748 | char str[]; | |
4749 | }; | |
4750 | ||
4751 | static __init int rb_write_something(struct rb_test_data *data, bool nested) | |
4752 | { | |
4753 | struct ring_buffer_event *event; | |
4754 | struct rb_item *item; | |
4755 | bool started; | |
4756 | int event_len; | |
4757 | int size; | |
4758 | int len; | |
4759 | int cnt; | |
4760 | ||
4761 | /* Have nested writes different that what is written */ | |
4762 | cnt = data->cnt + (nested ? 27 : 0); | |
4763 | ||
4764 | /* Multiply cnt by ~e, to make some unique increment */ | |
4765 | size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1); | |
4766 | ||
4767 | len = size + sizeof(struct rb_item); | |
4768 | ||
4769 | started = rb_test_started; | |
4770 | /* read rb_test_started before checking buffer enabled */ | |
4771 | smp_rmb(); | |
4772 | ||
4773 | event = ring_buffer_lock_reserve(data->buffer, len); | |
4774 | if (!event) { | |
4775 | /* Ignore dropped events before test starts. */ | |
4776 | if (started) { | |
4777 | if (nested) | |
4778 | data->bytes_dropped += len; | |
4779 | else | |
4780 | data->bytes_dropped_nested += len; | |
4781 | } | |
4782 | return len; | |
4783 | } | |
4784 | ||
4785 | event_len = ring_buffer_event_length(event); | |
4786 | ||
4787 | if (RB_WARN_ON(data->buffer, event_len < len)) | |
4788 | goto out; | |
4789 | ||
4790 | item = ring_buffer_event_data(event); | |
4791 | item->size = size; | |
4792 | memcpy(item->str, rb_string, size); | |
4793 | ||
4794 | if (nested) { | |
4795 | data->bytes_alloc_nested += event_len; | |
4796 | data->bytes_written_nested += len; | |
4797 | data->events_nested++; | |
4798 | if (!data->min_size_nested || len < data->min_size_nested) | |
4799 | data->min_size_nested = len; | |
4800 | if (len > data->max_size_nested) | |
4801 | data->max_size_nested = len; | |
4802 | } else { | |
4803 | data->bytes_alloc += event_len; | |
4804 | data->bytes_written += len; | |
4805 | data->events++; | |
4806 | if (!data->min_size || len < data->min_size) | |
4807 | data->max_size = len; | |
4808 | if (len > data->max_size) | |
4809 | data->max_size = len; | |
4810 | } | |
4811 | ||
4812 | out: | |
4813 | ring_buffer_unlock_commit(data->buffer, event); | |
4814 | ||
4815 | return 0; | |
4816 | } | |
4817 | ||
4818 | static __init int rb_test(void *arg) | |
4819 | { | |
4820 | struct rb_test_data *data = arg; | |
4821 | ||
4822 | while (!kthread_should_stop()) { | |
4823 | rb_write_something(data, false); | |
4824 | data->cnt++; | |
4825 | ||
4826 | set_current_state(TASK_INTERRUPTIBLE); | |
4827 | /* Now sleep between a min of 100-300us and a max of 1ms */ | |
4828 | usleep_range(((data->cnt % 3) + 1) * 100, 1000); | |
4829 | } | |
4830 | ||
4831 | return 0; | |
4832 | } | |
4833 | ||
4834 | static __init void rb_ipi(void *ignore) | |
4835 | { | |
4836 | struct rb_test_data *data; | |
4837 | int cpu = smp_processor_id(); | |
4838 | ||
4839 | data = &rb_data[cpu]; | |
4840 | rb_write_something(data, true); | |
4841 | } | |
4842 | ||
4843 | static __init int rb_hammer_test(void *arg) | |
4844 | { | |
4845 | while (!kthread_should_stop()) { | |
4846 | ||
4847 | /* Send an IPI to all cpus to write data! */ | |
4848 | smp_call_function(rb_ipi, NULL, 1); | |
4849 | /* No sleep, but for non preempt, let others run */ | |
4850 | schedule(); | |
4851 | } | |
4852 | ||
4853 | return 0; | |
4854 | } | |
4855 | ||
4856 | static __init int test_ringbuffer(void) | |
4857 | { | |
4858 | struct task_struct *rb_hammer; | |
4859 | struct ring_buffer *buffer; | |
4860 | int cpu; | |
4861 | int ret = 0; | |
4862 | ||
4863 | pr_info("Running ring buffer tests...\n"); | |
4864 | ||
4865 | buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); | |
4866 | if (WARN_ON(!buffer)) | |
4867 | return 0; | |
4868 | ||
4869 | /* Disable buffer so that threads can't write to it yet */ | |
4870 | ring_buffer_record_off(buffer); | |
4871 | ||
4872 | for_each_online_cpu(cpu) { | |
4873 | rb_data[cpu].buffer = buffer; | |
4874 | rb_data[cpu].cpu = cpu; | |
4875 | rb_data[cpu].cnt = cpu; | |
4876 | rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu], | |
4877 | "rbtester/%d", cpu); | |
4878 | if (WARN_ON(!rb_threads[cpu])) { | |
4879 | pr_cont("FAILED\n"); | |
4880 | ret = -1; | |
4881 | goto out_free; | |
4882 | } | |
4883 | ||
4884 | kthread_bind(rb_threads[cpu], cpu); | |
4885 | wake_up_process(rb_threads[cpu]); | |
4886 | } | |
4887 | ||
4888 | /* Now create the rb hammer! */ | |
4889 | rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); | |
4890 | if (WARN_ON(!rb_hammer)) { | |
4891 | pr_cont("FAILED\n"); | |
4892 | ret = -1; | |
4893 | goto out_free; | |
4894 | } | |
4895 | ||
4896 | ring_buffer_record_on(buffer); | |
4897 | /* | |
4898 | * Show buffer is enabled before setting rb_test_started. | |
4899 | * Yes there's a small race window where events could be | |
4900 | * dropped and the thread wont catch it. But when a ring | |
4901 | * buffer gets enabled, there will always be some kind of | |
4902 | * delay before other CPUs see it. Thus, we don't care about | |
4903 | * those dropped events. We care about events dropped after | |
4904 | * the threads see that the buffer is active. | |
4905 | */ | |
4906 | smp_wmb(); | |
4907 | rb_test_started = true; | |
4908 | ||
4909 | set_current_state(TASK_INTERRUPTIBLE); | |
4910 | /* Just run for 10 seconds */; | |
4911 | schedule_timeout(10 * HZ); | |
4912 | ||
4913 | kthread_stop(rb_hammer); | |
4914 | ||
4915 | out_free: | |
4916 | for_each_online_cpu(cpu) { | |
4917 | if (!rb_threads[cpu]) | |
4918 | break; | |
4919 | kthread_stop(rb_threads[cpu]); | |
4920 | } | |
4921 | if (ret) { | |
4922 | ring_buffer_free(buffer); | |
4923 | return ret; | |
4924 | } | |
4925 | ||
4926 | /* Report! */ | |
4927 | pr_info("finished\n"); | |
4928 | for_each_online_cpu(cpu) { | |
4929 | struct ring_buffer_event *event; | |
4930 | struct rb_test_data *data = &rb_data[cpu]; | |
4931 | struct rb_item *item; | |
4932 | unsigned long total_events; | |
4933 | unsigned long total_dropped; | |
4934 | unsigned long total_written; | |
4935 | unsigned long total_alloc; | |
4936 | unsigned long total_read = 0; | |
4937 | unsigned long total_size = 0; | |
4938 | unsigned long total_len = 0; | |
4939 | unsigned long total_lost = 0; | |
4940 | unsigned long lost; | |
4941 | int big_event_size; | |
4942 | int small_event_size; | |
4943 | ||
4944 | ret = -1; | |
4945 | ||
4946 | total_events = data->events + data->events_nested; | |
4947 | total_written = data->bytes_written + data->bytes_written_nested; | |
4948 | total_alloc = data->bytes_alloc + data->bytes_alloc_nested; | |
4949 | total_dropped = data->bytes_dropped + data->bytes_dropped_nested; | |
4950 | ||
4951 | big_event_size = data->max_size + data->max_size_nested; | |
4952 | small_event_size = data->min_size + data->min_size_nested; | |
4953 | ||
4954 | pr_info("CPU %d:\n", cpu); | |
4955 | pr_info(" events: %ld\n", total_events); | |
4956 | pr_info(" dropped bytes: %ld\n", total_dropped); | |
4957 | pr_info(" alloced bytes: %ld\n", total_alloc); | |
4958 | pr_info(" written bytes: %ld\n", total_written); | |
4959 | pr_info(" biggest event: %d\n", big_event_size); | |
4960 | pr_info(" smallest event: %d\n", small_event_size); | |
4961 | ||
4962 | if (RB_WARN_ON(buffer, total_dropped)) | |
4963 | break; | |
4964 | ||
4965 | ret = 0; | |
4966 | ||
4967 | while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { | |
4968 | total_lost += lost; | |
4969 | item = ring_buffer_event_data(event); | |
4970 | total_len += ring_buffer_event_length(event); | |
4971 | total_size += item->size + sizeof(struct rb_item); | |
4972 | if (memcmp(&item->str[0], rb_string, item->size) != 0) { | |
4973 | pr_info("FAILED!\n"); | |
4974 | pr_info("buffer had: %.*s\n", item->size, item->str); | |
4975 | pr_info("expected: %.*s\n", item->size, rb_string); | |
4976 | RB_WARN_ON(buffer, 1); | |
4977 | ret = -1; | |
4978 | break; | |
4979 | } | |
4980 | total_read++; | |
4981 | } | |
4982 | if (ret) | |
4983 | break; | |
4984 | ||
4985 | ret = -1; | |
4986 | ||
4987 | pr_info(" read events: %ld\n", total_read); | |
4988 | pr_info(" lost events: %ld\n", total_lost); | |
4989 | pr_info(" total events: %ld\n", total_lost + total_read); | |
4990 | pr_info(" recorded len bytes: %ld\n", total_len); | |
4991 | pr_info(" recorded size bytes: %ld\n", total_size); | |
4992 | if (total_lost) | |
4993 | pr_info(" With dropped events, record len and size may not match\n" | |
4994 | " alloced and written from above\n"); | |
4995 | if (!total_lost) { | |
4996 | if (RB_WARN_ON(buffer, total_len != total_alloc || | |
4997 | total_size != total_written)) | |
4998 | break; | |
4999 | } | |
5000 | if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) | |
5001 | break; | |
5002 | ||
5003 | ret = 0; | |
5004 | } | |
5005 | if (!ret) | |
5006 | pr_info("Ring buffer PASSED!\n"); | |
5007 | ||
5008 | ring_buffer_free(buffer); | |
5009 | return 0; | |
5010 | } | |
5011 | ||
5012 | late_initcall(test_ringbuffer); | |
5013 | #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */ |