Commit | Line | Data |
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bcea3f96 | 1 | // SPDX-License-Identifier: GPL-2.0 |
7a8e76a3 SR |
2 | /* |
3 | * Generic ring buffer | |
4 | * | |
5 | * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> | |
6 | */ | |
af658dca | 7 | #include <linux/trace_events.h> |
7a8e76a3 | 8 | #include <linux/ring_buffer.h> |
14131f2f | 9 | #include <linux/trace_clock.h> |
e6017571 | 10 | #include <linux/sched/clock.h> |
0b07436d | 11 | #include <linux/trace_seq.h> |
7a8e76a3 | 12 | #include <linux/spinlock.h> |
15693458 | 13 | #include <linux/irq_work.h> |
a356646a | 14 | #include <linux/security.h> |
7a8e76a3 | 15 | #include <linux/uaccess.h> |
a81bd80a | 16 | #include <linux/hardirq.h> |
6c43e554 | 17 | #include <linux/kthread.h> /* for self test */ |
7a8e76a3 SR |
18 | #include <linux/module.h> |
19 | #include <linux/percpu.h> | |
20 | #include <linux/mutex.h> | |
6c43e554 | 21 | #include <linux/delay.h> |
5a0e3ad6 | 22 | #include <linux/slab.h> |
7a8e76a3 SR |
23 | #include <linux/init.h> |
24 | #include <linux/hash.h> | |
25 | #include <linux/list.h> | |
554f786e | 26 | #include <linux/cpu.h> |
927e56db | 27 | #include <linux/oom.h> |
7a8e76a3 | 28 | |
79615760 | 29 | #include <asm/local.h> |
182e9f5f | 30 | |
83f40318 VN |
31 | static void update_pages_handler(struct work_struct *work); |
32 | ||
d1b182a8 SR |
33 | /* |
34 | * The ring buffer header is special. We must manually up keep it. | |
35 | */ | |
36 | int ring_buffer_print_entry_header(struct trace_seq *s) | |
37 | { | |
c0cd93aa SRRH |
38 | trace_seq_puts(s, "# compressed entry header\n"); |
39 | trace_seq_puts(s, "\ttype_len : 5 bits\n"); | |
40 | trace_seq_puts(s, "\ttime_delta : 27 bits\n"); | |
41 | trace_seq_puts(s, "\tarray : 32 bits\n"); | |
42 | trace_seq_putc(s, '\n'); | |
43 | trace_seq_printf(s, "\tpadding : type == %d\n", | |
44 | RINGBUF_TYPE_PADDING); | |
45 | trace_seq_printf(s, "\ttime_extend : type == %d\n", | |
46 | RINGBUF_TYPE_TIME_EXTEND); | |
dc4e2801 TZ |
47 | trace_seq_printf(s, "\ttime_stamp : type == %d\n", |
48 | RINGBUF_TYPE_TIME_STAMP); | |
c0cd93aa SRRH |
49 | trace_seq_printf(s, "\tdata max type_len == %d\n", |
50 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); | |
51 | ||
52 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
53 | } |
54 | ||
5cc98548 SR |
55 | /* |
56 | * The ring buffer is made up of a list of pages. A separate list of pages is | |
57 | * allocated for each CPU. A writer may only write to a buffer that is | |
58 | * associated with the CPU it is currently executing on. A reader may read | |
59 | * from any per cpu buffer. | |
60 | * | |
61 | * The reader is special. For each per cpu buffer, the reader has its own | |
62 | * reader page. When a reader has read the entire reader page, this reader | |
63 | * page is swapped with another page in the ring buffer. | |
64 | * | |
65 | * Now, as long as the writer is off the reader page, the reader can do what | |
66 | * ever it wants with that page. The writer will never write to that page | |
67 | * again (as long as it is out of the ring buffer). | |
68 | * | |
69 | * Here's some silly ASCII art. | |
70 | * | |
71 | * +------+ | |
72 | * |reader| RING BUFFER | |
73 | * |page | | |
74 | * +------+ +---+ +---+ +---+ | |
75 | * | |-->| |-->| | | |
76 | * +---+ +---+ +---+ | |
77 | * ^ | | |
78 | * | | | |
79 | * +---------------+ | |
80 | * | |
81 | * | |
82 | * +------+ | |
83 | * |reader| RING BUFFER | |
84 | * |page |------------------v | |
85 | * +------+ +---+ +---+ +---+ | |
86 | * | |-->| |-->| | | |
87 | * +---+ +---+ +---+ | |
88 | * ^ | | |
89 | * | | | |
90 | * +---------------+ | |
91 | * | |
92 | * | |
93 | * +------+ | |
94 | * |reader| RING BUFFER | |
95 | * |page |------------------v | |
96 | * +------+ +---+ +---+ +---+ | |
97 | * ^ | |-->| |-->| | | |
98 | * | +---+ +---+ +---+ | |
99 | * | | | |
100 | * | | | |
101 | * +------------------------------+ | |
102 | * | |
103 | * | |
104 | * +------+ | |
105 | * |buffer| RING BUFFER | |
106 | * |page |------------------v | |
107 | * +------+ +---+ +---+ +---+ | |
108 | * ^ | | | |-->| | | |
109 | * | New +---+ +---+ +---+ | |
110 | * | Reader------^ | | |
111 | * | page | | |
112 | * +------------------------------+ | |
113 | * | |
114 | * | |
115 | * After we make this swap, the reader can hand this page off to the splice | |
116 | * code and be done with it. It can even allocate a new page if it needs to | |
117 | * and swap that into the ring buffer. | |
118 | * | |
119 | * We will be using cmpxchg soon to make all this lockless. | |
120 | * | |
121 | */ | |
122 | ||
499e5470 SR |
123 | /* Used for individual buffers (after the counter) */ |
124 | #define RB_BUFFER_OFF (1 << 20) | |
a3583244 | 125 | |
499e5470 | 126 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
033601a3 | 127 | |
e3d6bf0a | 128 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
67d34724 | 129 | #define RB_ALIGNMENT 4U |
334d4169 | 130 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
c7b09308 | 131 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
86b3de60 | 132 | #define RB_ALIGN_DATA __aligned(RB_ALIGNMENT) |
649508f6 | 133 | |
334d4169 LJ |
134 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
135 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX | |
7a8e76a3 SR |
136 | |
137 | enum { | |
138 | RB_LEN_TIME_EXTEND = 8, | |
dc4e2801 | 139 | RB_LEN_TIME_STAMP = 8, |
7a8e76a3 SR |
140 | }; |
141 | ||
69d1b839 SR |
142 | #define skip_time_extend(event) \ |
143 | ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) | |
144 | ||
dc4e2801 TZ |
145 | #define extended_time(event) \ |
146 | (event->type_len >= RINGBUF_TYPE_TIME_EXTEND) | |
147 | ||
2d622719 TZ |
148 | static inline int rb_null_event(struct ring_buffer_event *event) |
149 | { | |
a1863c21 | 150 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
2d622719 TZ |
151 | } |
152 | ||
153 | static void rb_event_set_padding(struct ring_buffer_event *event) | |
154 | { | |
a1863c21 | 155 | /* padding has a NULL time_delta */ |
334d4169 | 156 | event->type_len = RINGBUF_TYPE_PADDING; |
2d622719 TZ |
157 | event->time_delta = 0; |
158 | } | |
159 | ||
34a148bf | 160 | static unsigned |
2d622719 | 161 | rb_event_data_length(struct ring_buffer_event *event) |
7a8e76a3 SR |
162 | { |
163 | unsigned length; | |
164 | ||
334d4169 LJ |
165 | if (event->type_len) |
166 | length = event->type_len * RB_ALIGNMENT; | |
2d622719 TZ |
167 | else |
168 | length = event->array[0]; | |
169 | return length + RB_EVNT_HDR_SIZE; | |
170 | } | |
171 | ||
69d1b839 SR |
172 | /* |
173 | * Return the length of the given event. Will return | |
174 | * the length of the time extend if the event is a | |
175 | * time extend. | |
176 | */ | |
177 | static inline unsigned | |
2d622719 TZ |
178 | rb_event_length(struct ring_buffer_event *event) |
179 | { | |
334d4169 | 180 | switch (event->type_len) { |
7a8e76a3 | 181 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
182 | if (rb_null_event(event)) |
183 | /* undefined */ | |
184 | return -1; | |
334d4169 | 185 | return event->array[0] + RB_EVNT_HDR_SIZE; |
7a8e76a3 SR |
186 | |
187 | case RINGBUF_TYPE_TIME_EXTEND: | |
188 | return RB_LEN_TIME_EXTEND; | |
189 | ||
190 | case RINGBUF_TYPE_TIME_STAMP: | |
191 | return RB_LEN_TIME_STAMP; | |
192 | ||
193 | case RINGBUF_TYPE_DATA: | |
2d622719 | 194 | return rb_event_data_length(event); |
7a8e76a3 | 195 | default: |
da4d401a | 196 | WARN_ON_ONCE(1); |
7a8e76a3 SR |
197 | } |
198 | /* not hit */ | |
199 | return 0; | |
200 | } | |
201 | ||
69d1b839 SR |
202 | /* |
203 | * Return total length of time extend and data, | |
204 | * or just the event length for all other events. | |
205 | */ | |
206 | static inline unsigned | |
207 | rb_event_ts_length(struct ring_buffer_event *event) | |
208 | { | |
209 | unsigned len = 0; | |
210 | ||
dc4e2801 | 211 | if (extended_time(event)) { |
69d1b839 SR |
212 | /* time extends include the data event after it */ |
213 | len = RB_LEN_TIME_EXTEND; | |
214 | event = skip_time_extend(event); | |
215 | } | |
216 | return len + rb_event_length(event); | |
217 | } | |
218 | ||
7a8e76a3 SR |
219 | /** |
220 | * ring_buffer_event_length - return the length of the event | |
221 | * @event: the event to get the length of | |
69d1b839 SR |
222 | * |
223 | * Returns the size of the data load of a data event. | |
224 | * If the event is something other than a data event, it | |
225 | * returns the size of the event itself. With the exception | |
226 | * of a TIME EXTEND, where it still returns the size of the | |
227 | * data load of the data event after it. | |
7a8e76a3 SR |
228 | */ |
229 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) | |
230 | { | |
69d1b839 SR |
231 | unsigned length; |
232 | ||
dc4e2801 | 233 | if (extended_time(event)) |
69d1b839 SR |
234 | event = skip_time_extend(event); |
235 | ||
236 | length = rb_event_length(event); | |
334d4169 | 237 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
465634ad RR |
238 | return length; |
239 | length -= RB_EVNT_HDR_SIZE; | |
240 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) | |
241 | length -= sizeof(event->array[0]); | |
242 | return length; | |
7a8e76a3 | 243 | } |
c4f50183 | 244 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
7a8e76a3 SR |
245 | |
246 | /* inline for ring buffer fast paths */ | |
929ddbf3 | 247 | static __always_inline void * |
7a8e76a3 SR |
248 | rb_event_data(struct ring_buffer_event *event) |
249 | { | |
dc4e2801 | 250 | if (extended_time(event)) |
69d1b839 | 251 | event = skip_time_extend(event); |
da4d401a | 252 | WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
7a8e76a3 | 253 | /* If length is in len field, then array[0] has the data */ |
334d4169 | 254 | if (event->type_len) |
7a8e76a3 SR |
255 | return (void *)&event->array[0]; |
256 | /* Otherwise length is in array[0] and array[1] has the data */ | |
257 | return (void *)&event->array[1]; | |
258 | } | |
259 | ||
260 | /** | |
261 | * ring_buffer_event_data - return the data of the event | |
262 | * @event: the event to get the data from | |
263 | */ | |
264 | void *ring_buffer_event_data(struct ring_buffer_event *event) | |
265 | { | |
266 | return rb_event_data(event); | |
267 | } | |
c4f50183 | 268 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
7a8e76a3 SR |
269 | |
270 | #define for_each_buffer_cpu(buffer, cpu) \ | |
9e01c1b7 | 271 | for_each_cpu(cpu, buffer->cpumask) |
7a8e76a3 | 272 | |
b23d7a5f NP |
273 | #define for_each_online_buffer_cpu(buffer, cpu) \ |
274 | for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask) | |
275 | ||
7a8e76a3 SR |
276 | #define TS_SHIFT 27 |
277 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) | |
278 | #define TS_DELTA_TEST (~TS_MASK) | |
279 | ||
dc4e2801 TZ |
280 | /** |
281 | * ring_buffer_event_time_stamp - return the event's extended timestamp | |
282 | * @event: the event to get the timestamp of | |
283 | * | |
284 | * Returns the extended timestamp associated with a data event. | |
285 | * An extended time_stamp is a 64-bit timestamp represented | |
286 | * internally in a special way that makes the best use of space | |
287 | * contained within a ring buffer event. This function decodes | |
288 | * it and maps it to a straight u64 value. | |
289 | */ | |
290 | u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) | |
291 | { | |
292 | u64 ts; | |
293 | ||
294 | ts = event->array[0]; | |
295 | ts <<= TS_SHIFT; | |
296 | ts += event->time_delta; | |
297 | ||
298 | return ts; | |
299 | } | |
300 | ||
66a8cb95 SR |
301 | /* Flag when events were overwritten */ |
302 | #define RB_MISSED_EVENTS (1 << 31) | |
ff0ff84a SR |
303 | /* Missed count stored at end */ |
304 | #define RB_MISSED_STORED (1 << 30) | |
66a8cb95 | 305 | |
abc9b56d | 306 | struct buffer_data_page { |
e4c2ce82 | 307 | u64 time_stamp; /* page time stamp */ |
c3706f00 | 308 | local_t commit; /* write committed index */ |
649508f6 | 309 | unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
abc9b56d SR |
310 | }; |
311 | ||
77ae365e SR |
312 | /* |
313 | * Note, the buffer_page list must be first. The buffer pages | |
314 | * are allocated in cache lines, which means that each buffer | |
315 | * page will be at the beginning of a cache line, and thus | |
316 | * the least significant bits will be zero. We use this to | |
317 | * add flags in the list struct pointers, to make the ring buffer | |
318 | * lockless. | |
319 | */ | |
abc9b56d | 320 | struct buffer_page { |
778c55d4 | 321 | struct list_head list; /* list of buffer pages */ |
abc9b56d | 322 | local_t write; /* index for next write */ |
6f807acd | 323 | unsigned read; /* index for next read */ |
778c55d4 | 324 | local_t entries; /* entries on this page */ |
ff0ff84a | 325 | unsigned long real_end; /* real end of data */ |
abc9b56d | 326 | struct buffer_data_page *page; /* Actual data page */ |
7a8e76a3 SR |
327 | }; |
328 | ||
77ae365e SR |
329 | /* |
330 | * The buffer page counters, write and entries, must be reset | |
331 | * atomically when crossing page boundaries. To synchronize this | |
332 | * update, two counters are inserted into the number. One is | |
333 | * the actual counter for the write position or count on the page. | |
334 | * | |
335 | * The other is a counter of updaters. Before an update happens | |
336 | * the update partition of the counter is incremented. This will | |
337 | * allow the updater to update the counter atomically. | |
338 | * | |
339 | * The counter is 20 bits, and the state data is 12. | |
340 | */ | |
341 | #define RB_WRITE_MASK 0xfffff | |
342 | #define RB_WRITE_INTCNT (1 << 20) | |
343 | ||
044fa782 | 344 | static void rb_init_page(struct buffer_data_page *bpage) |
abc9b56d | 345 | { |
044fa782 | 346 | local_set(&bpage->commit, 0); |
abc9b56d SR |
347 | } |
348 | ||
ed56829c SR |
349 | /* |
350 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing | |
351 | * this issue out. | |
352 | */ | |
34a148bf | 353 | static void free_buffer_page(struct buffer_page *bpage) |
ed56829c | 354 | { |
34a148bf | 355 | free_page((unsigned long)bpage->page); |
e4c2ce82 | 356 | kfree(bpage); |
ed56829c SR |
357 | } |
358 | ||
7a8e76a3 SR |
359 | /* |
360 | * We need to fit the time_stamp delta into 27 bits. | |
361 | */ | |
362 | static inline int test_time_stamp(u64 delta) | |
363 | { | |
364 | if (delta & TS_DELTA_TEST) | |
365 | return 1; | |
366 | return 0; | |
367 | } | |
368 | ||
474d32b6 | 369 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
7a8e76a3 | 370 | |
be957c44 SR |
371 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
372 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) | |
373 | ||
d1b182a8 SR |
374 | int ring_buffer_print_page_header(struct trace_seq *s) |
375 | { | |
376 | struct buffer_data_page field; | |
c0cd93aa SRRH |
377 | |
378 | trace_seq_printf(s, "\tfield: u64 timestamp;\t" | |
379 | "offset:0;\tsize:%u;\tsigned:%u;\n", | |
380 | (unsigned int)sizeof(field.time_stamp), | |
381 | (unsigned int)is_signed_type(u64)); | |
382 | ||
383 | trace_seq_printf(s, "\tfield: local_t commit;\t" | |
384 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
385 | (unsigned int)offsetof(typeof(field), commit), | |
386 | (unsigned int)sizeof(field.commit), | |
387 | (unsigned int)is_signed_type(long)); | |
388 | ||
389 | trace_seq_printf(s, "\tfield: int overwrite;\t" | |
390 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
391 | (unsigned int)offsetof(typeof(field), commit), | |
392 | 1, | |
393 | (unsigned int)is_signed_type(long)); | |
394 | ||
395 | trace_seq_printf(s, "\tfield: char data;\t" | |
396 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
397 | (unsigned int)offsetof(typeof(field), data), | |
398 | (unsigned int)BUF_PAGE_SIZE, | |
399 | (unsigned int)is_signed_type(char)); | |
400 | ||
401 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
402 | } |
403 | ||
15693458 SRRH |
404 | struct rb_irq_work { |
405 | struct irq_work work; | |
406 | wait_queue_head_t waiters; | |
1e0d6714 | 407 | wait_queue_head_t full_waiters; |
15693458 | 408 | bool waiters_pending; |
1e0d6714 SRRH |
409 | bool full_waiters_pending; |
410 | bool wakeup_full; | |
15693458 SRRH |
411 | }; |
412 | ||
fcc742ea SRRH |
413 | /* |
414 | * Structure to hold event state and handle nested events. | |
415 | */ | |
416 | struct rb_event_info { | |
417 | u64 ts; | |
418 | u64 delta; | |
58fbc3c6 SRV |
419 | u64 before; |
420 | u64 after; | |
fcc742ea SRRH |
421 | unsigned long length; |
422 | struct buffer_page *tail_page; | |
423 | int add_timestamp; | |
424 | }; | |
425 | ||
a389d86f SRV |
426 | /* |
427 | * Used for the add_timestamp | |
428 | * NONE | |
7c4b4a51 SRV |
429 | * EXTEND - wants a time extend |
430 | * ABSOLUTE - the buffer requests all events to have absolute time stamps | |
a389d86f SRV |
431 | * FORCE - force a full time stamp. |
432 | */ | |
433 | enum { | |
7c4b4a51 SRV |
434 | RB_ADD_STAMP_NONE = 0, |
435 | RB_ADD_STAMP_EXTEND = BIT(1), | |
436 | RB_ADD_STAMP_ABSOLUTE = BIT(2), | |
437 | RB_ADD_STAMP_FORCE = BIT(3) | |
a389d86f | 438 | }; |
a497adb4 SRRH |
439 | /* |
440 | * Used for which event context the event is in. | |
b02414c8 SRV |
441 | * TRANSITION = 0 |
442 | * NMI = 1 | |
443 | * IRQ = 2 | |
444 | * SOFTIRQ = 3 | |
445 | * NORMAL = 4 | |
a497adb4 SRRH |
446 | * |
447 | * See trace_recursive_lock() comment below for more details. | |
448 | */ | |
449 | enum { | |
b02414c8 | 450 | RB_CTX_TRANSITION, |
a497adb4 SRRH |
451 | RB_CTX_NMI, |
452 | RB_CTX_IRQ, | |
453 | RB_CTX_SOFTIRQ, | |
454 | RB_CTX_NORMAL, | |
455 | RB_CTX_MAX | |
456 | }; | |
457 | ||
10464b4a SRV |
458 | #if BITS_PER_LONG == 32 |
459 | #define RB_TIME_32 | |
460 | #endif | |
461 | ||
462 | /* To test on 64 bit machines */ | |
463 | //#define RB_TIME_32 | |
464 | ||
465 | #ifdef RB_TIME_32 | |
466 | ||
467 | struct rb_time_struct { | |
468 | local_t cnt; | |
469 | local_t top; | |
470 | local_t bottom; | |
471 | }; | |
472 | #else | |
473 | #include <asm/local64.h> | |
474 | struct rb_time_struct { | |
475 | local64_t time; | |
476 | }; | |
477 | #endif | |
478 | typedef struct rb_time_struct rb_time_t; | |
479 | ||
7a8e76a3 SR |
480 | /* |
481 | * head_page == tail_page && head == tail then buffer is empty. | |
482 | */ | |
483 | struct ring_buffer_per_cpu { | |
484 | int cpu; | |
985023de | 485 | atomic_t record_disabled; |
07b8b10e | 486 | atomic_t resize_disabled; |
13292494 | 487 | struct trace_buffer *buffer; |
5389f6fa | 488 | raw_spinlock_t reader_lock; /* serialize readers */ |
445c8951 | 489 | arch_spinlock_t lock; |
7a8e76a3 | 490 | struct lock_class_key lock_key; |
73a757e6 | 491 | struct buffer_data_page *free_page; |
9b94a8fb | 492 | unsigned long nr_pages; |
58a09ec6 | 493 | unsigned int current_context; |
3adc54fa | 494 | struct list_head *pages; |
6f807acd SR |
495 | struct buffer_page *head_page; /* read from head */ |
496 | struct buffer_page *tail_page; /* write to tail */ | |
c3706f00 | 497 | struct buffer_page *commit_page; /* committed pages */ |
d769041f | 498 | struct buffer_page *reader_page; |
66a8cb95 SR |
499 | unsigned long lost_events; |
500 | unsigned long last_overrun; | |
8e012066 | 501 | unsigned long nest; |
c64e148a | 502 | local_t entries_bytes; |
e4906eff | 503 | local_t entries; |
884bfe89 SP |
504 | local_t overrun; |
505 | local_t commit_overrun; | |
506 | local_t dropped_events; | |
fa743953 SR |
507 | local_t committing; |
508 | local_t commits; | |
2c2b0a78 SRV |
509 | local_t pages_touched; |
510 | local_t pages_read; | |
03329f99 | 511 | long last_pages_touch; |
2c2b0a78 | 512 | size_t shortest_full; |
77ae365e | 513 | unsigned long read; |
c64e148a | 514 | unsigned long read_bytes; |
10464b4a SRV |
515 | rb_time_t write_stamp; |
516 | rb_time_t before_stamp; | |
7a8e76a3 | 517 | u64 read_stamp; |
438ced17 | 518 | /* ring buffer pages to update, > 0 to add, < 0 to remove */ |
9b94a8fb | 519 | long nr_pages_to_update; |
438ced17 | 520 | struct list_head new_pages; /* new pages to add */ |
83f40318 | 521 | struct work_struct update_pages_work; |
05fdd70d | 522 | struct completion update_done; |
15693458 SRRH |
523 | |
524 | struct rb_irq_work irq_work; | |
7a8e76a3 SR |
525 | }; |
526 | ||
13292494 | 527 | struct trace_buffer { |
7a8e76a3 SR |
528 | unsigned flags; |
529 | int cpus; | |
7a8e76a3 | 530 | atomic_t record_disabled; |
00f62f61 | 531 | cpumask_var_t cpumask; |
7a8e76a3 | 532 | |
1f8a6a10 PZ |
533 | struct lock_class_key *reader_lock_key; |
534 | ||
7a8e76a3 SR |
535 | struct mutex mutex; |
536 | ||
537 | struct ring_buffer_per_cpu **buffers; | |
554f786e | 538 | |
b32614c0 | 539 | struct hlist_node node; |
37886f6a | 540 | u64 (*clock)(void); |
15693458 SRRH |
541 | |
542 | struct rb_irq_work irq_work; | |
00b41452 | 543 | bool time_stamp_abs; |
7a8e76a3 SR |
544 | }; |
545 | ||
546 | struct ring_buffer_iter { | |
547 | struct ring_buffer_per_cpu *cpu_buffer; | |
548 | unsigned long head; | |
785888c5 | 549 | unsigned long next_event; |
7a8e76a3 | 550 | struct buffer_page *head_page; |
492a74f4 SR |
551 | struct buffer_page *cache_reader_page; |
552 | unsigned long cache_read; | |
7a8e76a3 | 553 | u64 read_stamp; |
28e3fc56 | 554 | u64 page_stamp; |
785888c5 | 555 | struct ring_buffer_event *event; |
c9b7a4a7 | 556 | int missed_events; |
7a8e76a3 SR |
557 | }; |
558 | ||
10464b4a SRV |
559 | #ifdef RB_TIME_32 |
560 | ||
561 | /* | |
562 | * On 32 bit machines, local64_t is very expensive. As the ring | |
563 | * buffer doesn't need all the features of a true 64 bit atomic, | |
564 | * on 32 bit, it uses these functions (64 still uses local64_t). | |
565 | * | |
566 | * For the ring buffer, 64 bit required operations for the time is | |
567 | * the following: | |
568 | * | |
569 | * - Only need 59 bits (uses 60 to make it even). | |
570 | * - Reads may fail if it interrupted a modification of the time stamp. | |
571 | * It will succeed if it did not interrupt another write even if | |
572 | * the read itself is interrupted by a write. | |
573 | * It returns whether it was successful or not. | |
574 | * | |
575 | * - Writes always succeed and will overwrite other writes and writes | |
576 | * that were done by events interrupting the current write. | |
577 | * | |
578 | * - A write followed by a read of the same time stamp will always succeed, | |
579 | * but may not contain the same value. | |
580 | * | |
581 | * - A cmpxchg will fail if it interrupted another write or cmpxchg. | |
582 | * Other than that, it acts like a normal cmpxchg. | |
583 | * | |
584 | * The 60 bit time stamp is broken up by 30 bits in a top and bottom half | |
585 | * (bottom being the least significant 30 bits of the 60 bit time stamp). | |
586 | * | |
587 | * The two most significant bits of each half holds a 2 bit counter (0-3). | |
588 | * Each update will increment this counter by one. | |
589 | * When reading the top and bottom, if the two counter bits match then the | |
590 | * top and bottom together make a valid 60 bit number. | |
591 | */ | |
592 | #define RB_TIME_SHIFT 30 | |
593 | #define RB_TIME_VAL_MASK ((1 << RB_TIME_SHIFT) - 1) | |
594 | ||
595 | static inline int rb_time_cnt(unsigned long val) | |
596 | { | |
597 | return (val >> RB_TIME_SHIFT) & 3; | |
598 | } | |
599 | ||
600 | static inline u64 rb_time_val(unsigned long top, unsigned long bottom) | |
601 | { | |
602 | u64 val; | |
603 | ||
604 | val = top & RB_TIME_VAL_MASK; | |
605 | val <<= RB_TIME_SHIFT; | |
606 | val |= bottom & RB_TIME_VAL_MASK; | |
607 | ||
608 | return val; | |
609 | } | |
610 | ||
611 | static inline bool __rb_time_read(rb_time_t *t, u64 *ret, unsigned long *cnt) | |
612 | { | |
613 | unsigned long top, bottom; | |
614 | unsigned long c; | |
615 | ||
616 | /* | |
617 | * If the read is interrupted by a write, then the cnt will | |
618 | * be different. Loop until both top and bottom have been read | |
619 | * without interruption. | |
620 | */ | |
621 | do { | |
622 | c = local_read(&t->cnt); | |
623 | top = local_read(&t->top); | |
624 | bottom = local_read(&t->bottom); | |
625 | } while (c != local_read(&t->cnt)); | |
626 | ||
627 | *cnt = rb_time_cnt(top); | |
628 | ||
629 | /* If top and bottom counts don't match, this interrupted a write */ | |
630 | if (*cnt != rb_time_cnt(bottom)) | |
631 | return false; | |
632 | ||
633 | *ret = rb_time_val(top, bottom); | |
634 | return true; | |
635 | } | |
636 | ||
637 | static bool rb_time_read(rb_time_t *t, u64 *ret) | |
638 | { | |
639 | unsigned long cnt; | |
640 | ||
641 | return __rb_time_read(t, ret, &cnt); | |
642 | } | |
643 | ||
644 | static inline unsigned long rb_time_val_cnt(unsigned long val, unsigned long cnt) | |
645 | { | |
646 | return (val & RB_TIME_VAL_MASK) | ((cnt & 3) << RB_TIME_SHIFT); | |
647 | } | |
648 | ||
649 | static inline void rb_time_split(u64 val, unsigned long *top, unsigned long *bottom) | |
650 | { | |
651 | *top = (unsigned long)((val >> RB_TIME_SHIFT) & RB_TIME_VAL_MASK); | |
652 | *bottom = (unsigned long)(val & RB_TIME_VAL_MASK); | |
653 | } | |
654 | ||
655 | static inline void rb_time_val_set(local_t *t, unsigned long val, unsigned long cnt) | |
656 | { | |
657 | val = rb_time_val_cnt(val, cnt); | |
658 | local_set(t, val); | |
659 | } | |
660 | ||
661 | static void rb_time_set(rb_time_t *t, u64 val) | |
662 | { | |
663 | unsigned long cnt, top, bottom; | |
664 | ||
665 | rb_time_split(val, &top, &bottom); | |
666 | ||
667 | /* Writes always succeed with a valid number even if it gets interrupted. */ | |
668 | do { | |
669 | cnt = local_inc_return(&t->cnt); | |
670 | rb_time_val_set(&t->top, top, cnt); | |
671 | rb_time_val_set(&t->bottom, bottom, cnt); | |
672 | } while (cnt != local_read(&t->cnt)); | |
673 | } | |
674 | ||
675 | static inline bool | |
676 | rb_time_read_cmpxchg(local_t *l, unsigned long expect, unsigned long set) | |
677 | { | |
678 | unsigned long ret; | |
679 | ||
680 | ret = local_cmpxchg(l, expect, set); | |
681 | return ret == expect; | |
682 | } | |
683 | ||
684 | static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) | |
685 | { | |
686 | unsigned long cnt, top, bottom; | |
687 | unsigned long cnt2, top2, bottom2; | |
688 | u64 val; | |
689 | ||
690 | /* The cmpxchg always fails if it interrupted an update */ | |
691 | if (!__rb_time_read(t, &val, &cnt2)) | |
692 | return false; | |
693 | ||
694 | if (val != expect) | |
695 | return false; | |
696 | ||
697 | cnt = local_read(&t->cnt); | |
698 | if ((cnt & 3) != cnt2) | |
699 | return false; | |
700 | ||
701 | cnt2 = cnt + 1; | |
702 | ||
703 | rb_time_split(val, &top, &bottom); | |
704 | top = rb_time_val_cnt(top, cnt); | |
705 | bottom = rb_time_val_cnt(bottom, cnt); | |
706 | ||
707 | rb_time_split(set, &top2, &bottom2); | |
708 | top2 = rb_time_val_cnt(top2, cnt2); | |
709 | bottom2 = rb_time_val_cnt(bottom2, cnt2); | |
710 | ||
711 | if (!rb_time_read_cmpxchg(&t->cnt, cnt, cnt2)) | |
712 | return false; | |
713 | if (!rb_time_read_cmpxchg(&t->top, top, top2)) | |
714 | return false; | |
715 | if (!rb_time_read_cmpxchg(&t->bottom, bottom, bottom2)) | |
716 | return false; | |
717 | return true; | |
718 | } | |
719 | ||
720 | #else /* 64 bits */ | |
721 | ||
722 | /* local64_t always succeeds */ | |
723 | ||
724 | static inline bool rb_time_read(rb_time_t *t, u64 *ret) | |
725 | { | |
726 | *ret = local64_read(&t->time); | |
727 | return true; | |
728 | } | |
729 | static void rb_time_set(rb_time_t *t, u64 val) | |
730 | { | |
731 | local64_set(&t->time, val); | |
732 | } | |
733 | ||
734 | static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) | |
735 | { | |
736 | u64 val; | |
737 | val = local64_cmpxchg(&t->time, expect, set); | |
738 | return val == expect; | |
739 | } | |
740 | #endif | |
741 | ||
2c2b0a78 SRV |
742 | /** |
743 | * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer | |
744 | * @buffer: The ring_buffer to get the number of pages from | |
745 | * @cpu: The cpu of the ring_buffer to get the number of pages from | |
746 | * | |
747 | * Returns the number of pages used by a per_cpu buffer of the ring buffer. | |
748 | */ | |
13292494 | 749 | size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu) |
2c2b0a78 SRV |
750 | { |
751 | return buffer->buffers[cpu]->nr_pages; | |
752 | } | |
753 | ||
754 | /** | |
755 | * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer | |
756 | * @buffer: The ring_buffer to get the number of pages from | |
757 | * @cpu: The cpu of the ring_buffer to get the number of pages from | |
758 | * | |
759 | * Returns the number of pages that have content in the ring buffer. | |
760 | */ | |
13292494 | 761 | size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu) |
2c2b0a78 SRV |
762 | { |
763 | size_t read; | |
764 | size_t cnt; | |
765 | ||
766 | read = local_read(&buffer->buffers[cpu]->pages_read); | |
767 | cnt = local_read(&buffer->buffers[cpu]->pages_touched); | |
768 | /* The reader can read an empty page, but not more than that */ | |
769 | if (cnt < read) { | |
770 | WARN_ON_ONCE(read > cnt + 1); | |
771 | return 0; | |
772 | } | |
773 | ||
774 | return cnt - read; | |
775 | } | |
776 | ||
15693458 SRRH |
777 | /* |
778 | * rb_wake_up_waiters - wake up tasks waiting for ring buffer input | |
779 | * | |
780 | * Schedules a delayed work to wake up any task that is blocked on the | |
781 | * ring buffer waiters queue. | |
782 | */ | |
783 | static void rb_wake_up_waiters(struct irq_work *work) | |
784 | { | |
785 | struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); | |
786 | ||
787 | wake_up_all(&rbwork->waiters); | |
1e0d6714 SRRH |
788 | if (rbwork->wakeup_full) { |
789 | rbwork->wakeup_full = false; | |
790 | wake_up_all(&rbwork->full_waiters); | |
791 | } | |
15693458 SRRH |
792 | } |
793 | ||
794 | /** | |
795 | * ring_buffer_wait - wait for input to the ring buffer | |
796 | * @buffer: buffer to wait on | |
797 | * @cpu: the cpu buffer to wait on | |
e1981f75 | 798 | * @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS |
15693458 SRRH |
799 | * |
800 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
801 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
802 | * it will wait for data to be added to a specific cpu buffer. | |
803 | */ | |
13292494 | 804 | int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full) |
15693458 | 805 | { |
3f649ab7 | 806 | struct ring_buffer_per_cpu *cpu_buffer; |
15693458 SRRH |
807 | DEFINE_WAIT(wait); |
808 | struct rb_irq_work *work; | |
e30f53aa | 809 | int ret = 0; |
15693458 SRRH |
810 | |
811 | /* | |
812 | * Depending on what the caller is waiting for, either any | |
813 | * data in any cpu buffer, or a specific buffer, put the | |
814 | * caller on the appropriate wait queue. | |
815 | */ | |
1e0d6714 | 816 | if (cpu == RING_BUFFER_ALL_CPUS) { |
15693458 | 817 | work = &buffer->irq_work; |
1e0d6714 | 818 | /* Full only makes sense on per cpu reads */ |
2c2b0a78 | 819 | full = 0; |
1e0d6714 | 820 | } else { |
8b8b3683 SRRH |
821 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
822 | return -ENODEV; | |
15693458 SRRH |
823 | cpu_buffer = buffer->buffers[cpu]; |
824 | work = &cpu_buffer->irq_work; | |
825 | } | |
826 | ||
827 | ||
e30f53aa | 828 | while (true) { |
1e0d6714 SRRH |
829 | if (full) |
830 | prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); | |
831 | else | |
832 | prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); | |
e30f53aa RV |
833 | |
834 | /* | |
835 | * The events can happen in critical sections where | |
836 | * checking a work queue can cause deadlocks. | |
837 | * After adding a task to the queue, this flag is set | |
838 | * only to notify events to try to wake up the queue | |
839 | * using irq_work. | |
840 | * | |
841 | * We don't clear it even if the buffer is no longer | |
842 | * empty. The flag only causes the next event to run | |
843 | * irq_work to do the work queue wake up. The worse | |
844 | * that can happen if we race with !trace_empty() is that | |
845 | * an event will cause an irq_work to try to wake up | |
846 | * an empty queue. | |
847 | * | |
848 | * There's no reason to protect this flag either, as | |
849 | * the work queue and irq_work logic will do the necessary | |
850 | * synchronization for the wake ups. The only thing | |
851 | * that is necessary is that the wake up happens after | |
852 | * a task has been queued. It's OK for spurious wake ups. | |
853 | */ | |
1e0d6714 SRRH |
854 | if (full) |
855 | work->full_waiters_pending = true; | |
856 | else | |
857 | work->waiters_pending = true; | |
e30f53aa RV |
858 | |
859 | if (signal_pending(current)) { | |
860 | ret = -EINTR; | |
861 | break; | |
862 | } | |
863 | ||
864 | if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) | |
865 | break; | |
866 | ||
867 | if (cpu != RING_BUFFER_ALL_CPUS && | |
868 | !ring_buffer_empty_cpu(buffer, cpu)) { | |
869 | unsigned long flags; | |
870 | bool pagebusy; | |
2c2b0a78 SRV |
871 | size_t nr_pages; |
872 | size_t dirty; | |
e30f53aa RV |
873 | |
874 | if (!full) | |
875 | break; | |
876 | ||
877 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
878 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; | |
2c2b0a78 SRV |
879 | nr_pages = cpu_buffer->nr_pages; |
880 | dirty = ring_buffer_nr_dirty_pages(buffer, cpu); | |
881 | if (!cpu_buffer->shortest_full || | |
882 | cpu_buffer->shortest_full < full) | |
883 | cpu_buffer->shortest_full = full; | |
e30f53aa | 884 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
2c2b0a78 SRV |
885 | if (!pagebusy && |
886 | (!nr_pages || (dirty * 100) > full * nr_pages)) | |
e30f53aa RV |
887 | break; |
888 | } | |
15693458 | 889 | |
15693458 | 890 | schedule(); |
e30f53aa | 891 | } |
15693458 | 892 | |
1e0d6714 SRRH |
893 | if (full) |
894 | finish_wait(&work->full_waiters, &wait); | |
895 | else | |
896 | finish_wait(&work->waiters, &wait); | |
e30f53aa RV |
897 | |
898 | return ret; | |
15693458 SRRH |
899 | } |
900 | ||
901 | /** | |
902 | * ring_buffer_poll_wait - poll on buffer input | |
903 | * @buffer: buffer to wait on | |
904 | * @cpu: the cpu buffer to wait on | |
905 | * @filp: the file descriptor | |
906 | * @poll_table: The poll descriptor | |
907 | * | |
908 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
909 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
910 | * it will wait for data to be added to a specific cpu buffer. | |
911 | * | |
a9a08845 | 912 | * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, |
15693458 SRRH |
913 | * zero otherwise. |
914 | */ | |
13292494 | 915 | __poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu, |
15693458 SRRH |
916 | struct file *filp, poll_table *poll_table) |
917 | { | |
918 | struct ring_buffer_per_cpu *cpu_buffer; | |
919 | struct rb_irq_work *work; | |
920 | ||
15693458 SRRH |
921 | if (cpu == RING_BUFFER_ALL_CPUS) |
922 | work = &buffer->irq_work; | |
923 | else { | |
6721cb60 SRRH |
924 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
925 | return -EINVAL; | |
926 | ||
15693458 SRRH |
927 | cpu_buffer = buffer->buffers[cpu]; |
928 | work = &cpu_buffer->irq_work; | |
929 | } | |
930 | ||
15693458 | 931 | poll_wait(filp, &work->waiters, poll_table); |
4ce97dbf JB |
932 | work->waiters_pending = true; |
933 | /* | |
934 | * There's a tight race between setting the waiters_pending and | |
935 | * checking if the ring buffer is empty. Once the waiters_pending bit | |
936 | * is set, the next event will wake the task up, but we can get stuck | |
937 | * if there's only a single event in. | |
938 | * | |
939 | * FIXME: Ideally, we need a memory barrier on the writer side as well, | |
940 | * but adding a memory barrier to all events will cause too much of a | |
941 | * performance hit in the fast path. We only need a memory barrier when | |
942 | * the buffer goes from empty to having content. But as this race is | |
943 | * extremely small, and it's not a problem if another event comes in, we | |
944 | * will fix it later. | |
945 | */ | |
946 | smp_mb(); | |
15693458 SRRH |
947 | |
948 | if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || | |
949 | (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) | |
a9a08845 | 950 | return EPOLLIN | EPOLLRDNORM; |
15693458 SRRH |
951 | return 0; |
952 | } | |
953 | ||
f536aafc | 954 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
077c5407 SR |
955 | #define RB_WARN_ON(b, cond) \ |
956 | ({ \ | |
957 | int _____ret = unlikely(cond); \ | |
958 | if (_____ret) { \ | |
959 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ | |
960 | struct ring_buffer_per_cpu *__b = \ | |
961 | (void *)b; \ | |
962 | atomic_inc(&__b->buffer->record_disabled); \ | |
963 | } else \ | |
964 | atomic_inc(&b->record_disabled); \ | |
965 | WARN_ON(1); \ | |
966 | } \ | |
967 | _____ret; \ | |
3e89c7bb | 968 | }) |
f536aafc | 969 | |
37886f6a SR |
970 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
971 | #define DEBUG_SHIFT 0 | |
972 | ||
13292494 | 973 | static inline u64 rb_time_stamp(struct trace_buffer *buffer) |
88eb0125 | 974 | { |
bbeba3e5 SRV |
975 | u64 ts; |
976 | ||
977 | /* Skip retpolines :-( */ | |
978 | if (IS_ENABLED(CONFIG_RETPOLINE) && likely(buffer->clock == trace_clock_local)) | |
979 | ts = trace_clock_local(); | |
980 | else | |
981 | ts = buffer->clock(); | |
982 | ||
88eb0125 | 983 | /* shift to debug/test normalization and TIME_EXTENTS */ |
bbeba3e5 | 984 | return ts << DEBUG_SHIFT; |
88eb0125 SR |
985 | } |
986 | ||
13292494 | 987 | u64 ring_buffer_time_stamp(struct trace_buffer *buffer, int cpu) |
37886f6a SR |
988 | { |
989 | u64 time; | |
990 | ||
991 | preempt_disable_notrace(); | |
6d3f1e12 | 992 | time = rb_time_stamp(buffer); |
d6097c9e | 993 | preempt_enable_notrace(); |
37886f6a SR |
994 | |
995 | return time; | |
996 | } | |
997 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); | |
998 | ||
13292494 | 999 | void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer, |
37886f6a SR |
1000 | int cpu, u64 *ts) |
1001 | { | |
1002 | /* Just stupid testing the normalize function and deltas */ | |
1003 | *ts >>= DEBUG_SHIFT; | |
1004 | } | |
1005 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); | |
1006 | ||
77ae365e SR |
1007 | /* |
1008 | * Making the ring buffer lockless makes things tricky. | |
1009 | * Although writes only happen on the CPU that they are on, | |
1010 | * and they only need to worry about interrupts. Reads can | |
1011 | * happen on any CPU. | |
1012 | * | |
1013 | * The reader page is always off the ring buffer, but when the | |
1014 | * reader finishes with a page, it needs to swap its page with | |
1015 | * a new one from the buffer. The reader needs to take from | |
1016 | * the head (writes go to the tail). But if a writer is in overwrite | |
1017 | * mode and wraps, it must push the head page forward. | |
1018 | * | |
1019 | * Here lies the problem. | |
1020 | * | |
1021 | * The reader must be careful to replace only the head page, and | |
1022 | * not another one. As described at the top of the file in the | |
1023 | * ASCII art, the reader sets its old page to point to the next | |
1024 | * page after head. It then sets the page after head to point to | |
1025 | * the old reader page. But if the writer moves the head page | |
1026 | * during this operation, the reader could end up with the tail. | |
1027 | * | |
1028 | * We use cmpxchg to help prevent this race. We also do something | |
1029 | * special with the page before head. We set the LSB to 1. | |
1030 | * | |
1031 | * When the writer must push the page forward, it will clear the | |
1032 | * bit that points to the head page, move the head, and then set | |
1033 | * the bit that points to the new head page. | |
1034 | * | |
1035 | * We also don't want an interrupt coming in and moving the head | |
1036 | * page on another writer. Thus we use the second LSB to catch | |
1037 | * that too. Thus: | |
1038 | * | |
1039 | * head->list->prev->next bit 1 bit 0 | |
1040 | * ------- ------- | |
1041 | * Normal page 0 0 | |
1042 | * Points to head page 0 1 | |
1043 | * New head page 1 0 | |
1044 | * | |
1045 | * Note we can not trust the prev pointer of the head page, because: | |
1046 | * | |
1047 | * +----+ +-----+ +-----+ | |
1048 | * | |------>| T |---X--->| N | | |
1049 | * | |<------| | | | | |
1050 | * +----+ +-----+ +-----+ | |
1051 | * ^ ^ | | |
1052 | * | +-----+ | | | |
1053 | * +----------| R |----------+ | | |
1054 | * | |<-----------+ | |
1055 | * +-----+ | |
1056 | * | |
1057 | * Key: ---X--> HEAD flag set in pointer | |
1058 | * T Tail page | |
1059 | * R Reader page | |
1060 | * N Next page | |
1061 | * | |
1062 | * (see __rb_reserve_next() to see where this happens) | |
1063 | * | |
1064 | * What the above shows is that the reader just swapped out | |
1065 | * the reader page with a page in the buffer, but before it | |
1066 | * could make the new header point back to the new page added | |
1067 | * it was preempted by a writer. The writer moved forward onto | |
1068 | * the new page added by the reader and is about to move forward | |
1069 | * again. | |
1070 | * | |
1071 | * You can see, it is legitimate for the previous pointer of | |
1072 | * the head (or any page) not to point back to itself. But only | |
6167c205 | 1073 | * temporarily. |
77ae365e SR |
1074 | */ |
1075 | ||
1076 | #define RB_PAGE_NORMAL 0UL | |
1077 | #define RB_PAGE_HEAD 1UL | |
1078 | #define RB_PAGE_UPDATE 2UL | |
1079 | ||
1080 | ||
1081 | #define RB_FLAG_MASK 3UL | |
1082 | ||
1083 | /* PAGE_MOVED is not part of the mask */ | |
1084 | #define RB_PAGE_MOVED 4UL | |
1085 | ||
1086 | /* | |
1087 | * rb_list_head - remove any bit | |
1088 | */ | |
1089 | static struct list_head *rb_list_head(struct list_head *list) | |
1090 | { | |
1091 | unsigned long val = (unsigned long)list; | |
1092 | ||
1093 | return (struct list_head *)(val & ~RB_FLAG_MASK); | |
1094 | } | |
1095 | ||
1096 | /* | |
6d3f1e12 | 1097 | * rb_is_head_page - test if the given page is the head page |
77ae365e SR |
1098 | * |
1099 | * Because the reader may move the head_page pointer, we can | |
1100 | * not trust what the head page is (it may be pointing to | |
1101 | * the reader page). But if the next page is a header page, | |
1102 | * its flags will be non zero. | |
1103 | */ | |
42b16b3f | 1104 | static inline int |
77ae365e SR |
1105 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
1106 | struct buffer_page *page, struct list_head *list) | |
1107 | { | |
1108 | unsigned long val; | |
1109 | ||
1110 | val = (unsigned long)list->next; | |
1111 | ||
1112 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) | |
1113 | return RB_PAGE_MOVED; | |
1114 | ||
1115 | return val & RB_FLAG_MASK; | |
1116 | } | |
1117 | ||
1118 | /* | |
1119 | * rb_is_reader_page | |
1120 | * | |
1121 | * The unique thing about the reader page, is that, if the | |
1122 | * writer is ever on it, the previous pointer never points | |
1123 | * back to the reader page. | |
1124 | */ | |
06ca3209 | 1125 | static bool rb_is_reader_page(struct buffer_page *page) |
77ae365e SR |
1126 | { |
1127 | struct list_head *list = page->list.prev; | |
1128 | ||
1129 | return rb_list_head(list->next) != &page->list; | |
1130 | } | |
1131 | ||
1132 | /* | |
1133 | * rb_set_list_to_head - set a list_head to be pointing to head. | |
1134 | */ | |
1135 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, | |
1136 | struct list_head *list) | |
1137 | { | |
1138 | unsigned long *ptr; | |
1139 | ||
1140 | ptr = (unsigned long *)&list->next; | |
1141 | *ptr |= RB_PAGE_HEAD; | |
1142 | *ptr &= ~RB_PAGE_UPDATE; | |
1143 | } | |
1144 | ||
1145 | /* | |
1146 | * rb_head_page_activate - sets up head page | |
1147 | */ | |
1148 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) | |
1149 | { | |
1150 | struct buffer_page *head; | |
1151 | ||
1152 | head = cpu_buffer->head_page; | |
1153 | if (!head) | |
1154 | return; | |
1155 | ||
1156 | /* | |
1157 | * Set the previous list pointer to have the HEAD flag. | |
1158 | */ | |
1159 | rb_set_list_to_head(cpu_buffer, head->list.prev); | |
1160 | } | |
1161 | ||
1162 | static void rb_list_head_clear(struct list_head *list) | |
1163 | { | |
1164 | unsigned long *ptr = (unsigned long *)&list->next; | |
1165 | ||
1166 | *ptr &= ~RB_FLAG_MASK; | |
1167 | } | |
1168 | ||
1169 | /* | |
6167c205 | 1170 | * rb_head_page_deactivate - clears head page ptr (for free list) |
77ae365e SR |
1171 | */ |
1172 | static void | |
1173 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) | |
1174 | { | |
1175 | struct list_head *hd; | |
1176 | ||
1177 | /* Go through the whole list and clear any pointers found. */ | |
1178 | rb_list_head_clear(cpu_buffer->pages); | |
1179 | ||
1180 | list_for_each(hd, cpu_buffer->pages) | |
1181 | rb_list_head_clear(hd); | |
1182 | } | |
1183 | ||
1184 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, | |
1185 | struct buffer_page *head, | |
1186 | struct buffer_page *prev, | |
1187 | int old_flag, int new_flag) | |
1188 | { | |
1189 | struct list_head *list; | |
1190 | unsigned long val = (unsigned long)&head->list; | |
1191 | unsigned long ret; | |
1192 | ||
1193 | list = &prev->list; | |
1194 | ||
1195 | val &= ~RB_FLAG_MASK; | |
1196 | ||
08a40816 SR |
1197 | ret = cmpxchg((unsigned long *)&list->next, |
1198 | val | old_flag, val | new_flag); | |
77ae365e SR |
1199 | |
1200 | /* check if the reader took the page */ | |
1201 | if ((ret & ~RB_FLAG_MASK) != val) | |
1202 | return RB_PAGE_MOVED; | |
1203 | ||
1204 | return ret & RB_FLAG_MASK; | |
1205 | } | |
1206 | ||
1207 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, | |
1208 | struct buffer_page *head, | |
1209 | struct buffer_page *prev, | |
1210 | int old_flag) | |
1211 | { | |
1212 | return rb_head_page_set(cpu_buffer, head, prev, | |
1213 | old_flag, RB_PAGE_UPDATE); | |
1214 | } | |
1215 | ||
1216 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, | |
1217 | struct buffer_page *head, | |
1218 | struct buffer_page *prev, | |
1219 | int old_flag) | |
1220 | { | |
1221 | return rb_head_page_set(cpu_buffer, head, prev, | |
1222 | old_flag, RB_PAGE_HEAD); | |
1223 | } | |
1224 | ||
1225 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, | |
1226 | struct buffer_page *head, | |
1227 | struct buffer_page *prev, | |
1228 | int old_flag) | |
1229 | { | |
1230 | return rb_head_page_set(cpu_buffer, head, prev, | |
1231 | old_flag, RB_PAGE_NORMAL); | |
1232 | } | |
1233 | ||
1234 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, | |
1235 | struct buffer_page **bpage) | |
1236 | { | |
1237 | struct list_head *p = rb_list_head((*bpage)->list.next); | |
1238 | ||
1239 | *bpage = list_entry(p, struct buffer_page, list); | |
1240 | } | |
1241 | ||
1242 | static struct buffer_page * | |
1243 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) | |
1244 | { | |
1245 | struct buffer_page *head; | |
1246 | struct buffer_page *page; | |
1247 | struct list_head *list; | |
1248 | int i; | |
1249 | ||
1250 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) | |
1251 | return NULL; | |
1252 | ||
1253 | /* sanity check */ | |
1254 | list = cpu_buffer->pages; | |
1255 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) | |
1256 | return NULL; | |
1257 | ||
1258 | page = head = cpu_buffer->head_page; | |
1259 | /* | |
1260 | * It is possible that the writer moves the header behind | |
1261 | * where we started, and we miss in one loop. | |
1262 | * A second loop should grab the header, but we'll do | |
1263 | * three loops just because I'm paranoid. | |
1264 | */ | |
1265 | for (i = 0; i < 3; i++) { | |
1266 | do { | |
1267 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { | |
1268 | cpu_buffer->head_page = page; | |
1269 | return page; | |
1270 | } | |
1271 | rb_inc_page(cpu_buffer, &page); | |
1272 | } while (page != head); | |
1273 | } | |
1274 | ||
1275 | RB_WARN_ON(cpu_buffer, 1); | |
1276 | ||
1277 | return NULL; | |
1278 | } | |
1279 | ||
1280 | static int rb_head_page_replace(struct buffer_page *old, | |
1281 | struct buffer_page *new) | |
1282 | { | |
1283 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; | |
1284 | unsigned long val; | |
1285 | unsigned long ret; | |
1286 | ||
1287 | val = *ptr & ~RB_FLAG_MASK; | |
1288 | val |= RB_PAGE_HEAD; | |
1289 | ||
08a40816 | 1290 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
77ae365e SR |
1291 | |
1292 | return ret == val; | |
1293 | } | |
1294 | ||
1295 | /* | |
1296 | * rb_tail_page_update - move the tail page forward | |
77ae365e | 1297 | */ |
70004986 | 1298 | static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, |
77ae365e SR |
1299 | struct buffer_page *tail_page, |
1300 | struct buffer_page *next_page) | |
1301 | { | |
77ae365e SR |
1302 | unsigned long old_entries; |
1303 | unsigned long old_write; | |
77ae365e SR |
1304 | |
1305 | /* | |
1306 | * The tail page now needs to be moved forward. | |
1307 | * | |
1308 | * We need to reset the tail page, but without messing | |
1309 | * with possible erasing of data brought in by interrupts | |
1310 | * that have moved the tail page and are currently on it. | |
1311 | * | |
1312 | * We add a counter to the write field to denote this. | |
1313 | */ | |
1314 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); | |
1315 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); | |
1316 | ||
2c2b0a78 | 1317 | local_inc(&cpu_buffer->pages_touched); |
77ae365e SR |
1318 | /* |
1319 | * Just make sure we have seen our old_write and synchronize | |
1320 | * with any interrupts that come in. | |
1321 | */ | |
1322 | barrier(); | |
1323 | ||
1324 | /* | |
1325 | * If the tail page is still the same as what we think | |
1326 | * it is, then it is up to us to update the tail | |
1327 | * pointer. | |
1328 | */ | |
8573636e | 1329 | if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { |
77ae365e SR |
1330 | /* Zero the write counter */ |
1331 | unsigned long val = old_write & ~RB_WRITE_MASK; | |
1332 | unsigned long eval = old_entries & ~RB_WRITE_MASK; | |
1333 | ||
1334 | /* | |
1335 | * This will only succeed if an interrupt did | |
1336 | * not come in and change it. In which case, we | |
1337 | * do not want to modify it. | |
da706d8b LJ |
1338 | * |
1339 | * We add (void) to let the compiler know that we do not care | |
1340 | * about the return value of these functions. We use the | |
1341 | * cmpxchg to only update if an interrupt did not already | |
1342 | * do it for us. If the cmpxchg fails, we don't care. | |
77ae365e | 1343 | */ |
da706d8b LJ |
1344 | (void)local_cmpxchg(&next_page->write, old_write, val); |
1345 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); | |
77ae365e SR |
1346 | |
1347 | /* | |
1348 | * No need to worry about races with clearing out the commit. | |
1349 | * it only can increment when a commit takes place. But that | |
1350 | * only happens in the outer most nested commit. | |
1351 | */ | |
1352 | local_set(&next_page->page->commit, 0); | |
1353 | ||
70004986 SRRH |
1354 | /* Again, either we update tail_page or an interrupt does */ |
1355 | (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page); | |
77ae365e | 1356 | } |
77ae365e SR |
1357 | } |
1358 | ||
1359 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, | |
1360 | struct buffer_page *bpage) | |
1361 | { | |
1362 | unsigned long val = (unsigned long)bpage; | |
1363 | ||
1364 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) | |
1365 | return 1; | |
1366 | ||
1367 | return 0; | |
1368 | } | |
1369 | ||
1370 | /** | |
1371 | * rb_check_list - make sure a pointer to a list has the last bits zero | |
1372 | */ | |
1373 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, | |
1374 | struct list_head *list) | |
1375 | { | |
1376 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) | |
1377 | return 1; | |
1378 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) | |
1379 | return 1; | |
1380 | return 0; | |
1381 | } | |
1382 | ||
7a8e76a3 | 1383 | /** |
d611851b | 1384 | * rb_check_pages - integrity check of buffer pages |
7a8e76a3 SR |
1385 | * @cpu_buffer: CPU buffer with pages to test |
1386 | * | |
c3706f00 | 1387 | * As a safety measure we check to make sure the data pages have not |
7a8e76a3 SR |
1388 | * been corrupted. |
1389 | */ | |
1390 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
1391 | { | |
3adc54fa | 1392 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1393 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1394 | |
308f7eeb SR |
1395 | /* Reset the head page if it exists */ |
1396 | if (cpu_buffer->head_page) | |
1397 | rb_set_head_page(cpu_buffer); | |
1398 | ||
77ae365e SR |
1399 | rb_head_page_deactivate(cpu_buffer); |
1400 | ||
3e89c7bb SR |
1401 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
1402 | return -1; | |
1403 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) | |
1404 | return -1; | |
7a8e76a3 | 1405 | |
77ae365e SR |
1406 | if (rb_check_list(cpu_buffer, head)) |
1407 | return -1; | |
1408 | ||
044fa782 | 1409 | list_for_each_entry_safe(bpage, tmp, head, list) { |
3e89c7bb | 1410 | if (RB_WARN_ON(cpu_buffer, |
044fa782 | 1411 | bpage->list.next->prev != &bpage->list)) |
3e89c7bb SR |
1412 | return -1; |
1413 | if (RB_WARN_ON(cpu_buffer, | |
044fa782 | 1414 | bpage->list.prev->next != &bpage->list)) |
3e89c7bb | 1415 | return -1; |
77ae365e SR |
1416 | if (rb_check_list(cpu_buffer, &bpage->list)) |
1417 | return -1; | |
7a8e76a3 SR |
1418 | } |
1419 | ||
77ae365e SR |
1420 | rb_head_page_activate(cpu_buffer); |
1421 | ||
7a8e76a3 SR |
1422 | return 0; |
1423 | } | |
1424 | ||
9b94a8fb | 1425 | static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) |
7a8e76a3 | 1426 | { |
044fa782 | 1427 | struct buffer_page *bpage, *tmp; |
927e56db SRV |
1428 | bool user_thread = current->mm != NULL; |
1429 | gfp_t mflags; | |
9b94a8fb | 1430 | long i; |
3adc54fa | 1431 | |
927e56db SRV |
1432 | /* |
1433 | * Check if the available memory is there first. | |
1434 | * Note, si_mem_available() only gives us a rough estimate of available | |
1435 | * memory. It may not be accurate. But we don't care, we just want | |
1436 | * to prevent doing any allocation when it is obvious that it is | |
1437 | * not going to succeed. | |
1438 | */ | |
2a872fa4 SRV |
1439 | i = si_mem_available(); |
1440 | if (i < nr_pages) | |
1441 | return -ENOMEM; | |
1442 | ||
927e56db SRV |
1443 | /* |
1444 | * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails | |
1445 | * gracefully without invoking oom-killer and the system is not | |
1446 | * destabilized. | |
1447 | */ | |
1448 | mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL; | |
1449 | ||
1450 | /* | |
1451 | * If a user thread allocates too much, and si_mem_available() | |
1452 | * reports there's enough memory, even though there is not. | |
1453 | * Make sure the OOM killer kills this thread. This can happen | |
1454 | * even with RETRY_MAYFAIL because another task may be doing | |
1455 | * an allocation after this task has taken all memory. | |
1456 | * This is the task the OOM killer needs to take out during this | |
1457 | * loop, even if it was triggered by an allocation somewhere else. | |
1458 | */ | |
1459 | if (user_thread) | |
1460 | set_current_oom_origin(); | |
7a8e76a3 | 1461 | for (i = 0; i < nr_pages; i++) { |
7ea59064 | 1462 | struct page *page; |
927e56db | 1463 | |
044fa782 | 1464 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
927e56db | 1465 | mflags, cpu_to_node(cpu)); |
044fa782 | 1466 | if (!bpage) |
e4c2ce82 | 1467 | goto free_pages; |
77ae365e | 1468 | |
438ced17 | 1469 | list_add(&bpage->list, pages); |
77ae365e | 1470 | |
927e56db | 1471 | page = alloc_pages_node(cpu_to_node(cpu), mflags, 0); |
7ea59064 | 1472 | if (!page) |
7a8e76a3 | 1473 | goto free_pages; |
7ea59064 | 1474 | bpage->page = page_address(page); |
044fa782 | 1475 | rb_init_page(bpage->page); |
927e56db SRV |
1476 | |
1477 | if (user_thread && fatal_signal_pending(current)) | |
1478 | goto free_pages; | |
7a8e76a3 | 1479 | } |
927e56db SRV |
1480 | if (user_thread) |
1481 | clear_current_oom_origin(); | |
7a8e76a3 | 1482 | |
438ced17 VN |
1483 | return 0; |
1484 | ||
1485 | free_pages: | |
1486 | list_for_each_entry_safe(bpage, tmp, pages, list) { | |
1487 | list_del_init(&bpage->list); | |
1488 | free_buffer_page(bpage); | |
1489 | } | |
927e56db SRV |
1490 | if (user_thread) |
1491 | clear_current_oom_origin(); | |
438ced17 VN |
1492 | |
1493 | return -ENOMEM; | |
1494 | } | |
1495 | ||
1496 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, | |
9b94a8fb | 1497 | unsigned long nr_pages) |
438ced17 VN |
1498 | { |
1499 | LIST_HEAD(pages); | |
1500 | ||
1501 | WARN_ON(!nr_pages); | |
1502 | ||
1503 | if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu)) | |
1504 | return -ENOMEM; | |
1505 | ||
3adc54fa SR |
1506 | /* |
1507 | * The ring buffer page list is a circular list that does not | |
1508 | * start and end with a list head. All page list items point to | |
1509 | * other pages. | |
1510 | */ | |
1511 | cpu_buffer->pages = pages.next; | |
1512 | list_del(&pages); | |
7a8e76a3 | 1513 | |
438ced17 VN |
1514 | cpu_buffer->nr_pages = nr_pages; |
1515 | ||
7a8e76a3 SR |
1516 | rb_check_pages(cpu_buffer); |
1517 | ||
1518 | return 0; | |
7a8e76a3 SR |
1519 | } |
1520 | ||
1521 | static struct ring_buffer_per_cpu * | |
13292494 | 1522 | rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu) |
7a8e76a3 SR |
1523 | { |
1524 | struct ring_buffer_per_cpu *cpu_buffer; | |
044fa782 | 1525 | struct buffer_page *bpage; |
7ea59064 | 1526 | struct page *page; |
7a8e76a3 SR |
1527 | int ret; |
1528 | ||
1529 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), | |
1530 | GFP_KERNEL, cpu_to_node(cpu)); | |
1531 | if (!cpu_buffer) | |
1532 | return NULL; | |
1533 | ||
1534 | cpu_buffer->cpu = cpu; | |
1535 | cpu_buffer->buffer = buffer; | |
5389f6fa | 1536 | raw_spin_lock_init(&cpu_buffer->reader_lock); |
1f8a6a10 | 1537 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
edc35bd7 | 1538 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
83f40318 | 1539 | INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
05fdd70d | 1540 | init_completion(&cpu_buffer->update_done); |
15693458 | 1541 | init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1542 | init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
1e0d6714 | 1543 | init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
7a8e76a3 | 1544 | |
044fa782 | 1545 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
e4c2ce82 | 1546 | GFP_KERNEL, cpu_to_node(cpu)); |
044fa782 | 1547 | if (!bpage) |
e4c2ce82 SR |
1548 | goto fail_free_buffer; |
1549 | ||
77ae365e SR |
1550 | rb_check_bpage(cpu_buffer, bpage); |
1551 | ||
044fa782 | 1552 | cpu_buffer->reader_page = bpage; |
7ea59064 VN |
1553 | page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
1554 | if (!page) | |
e4c2ce82 | 1555 | goto fail_free_reader; |
7ea59064 | 1556 | bpage->page = page_address(page); |
044fa782 | 1557 | rb_init_page(bpage->page); |
e4c2ce82 | 1558 | |
d769041f | 1559 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
44b99462 | 1560 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
d769041f | 1561 | |
438ced17 | 1562 | ret = rb_allocate_pages(cpu_buffer, nr_pages); |
7a8e76a3 | 1563 | if (ret < 0) |
d769041f | 1564 | goto fail_free_reader; |
7a8e76a3 SR |
1565 | |
1566 | cpu_buffer->head_page | |
3adc54fa | 1567 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 1568 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
7a8e76a3 | 1569 | |
77ae365e SR |
1570 | rb_head_page_activate(cpu_buffer); |
1571 | ||
7a8e76a3 SR |
1572 | return cpu_buffer; |
1573 | ||
d769041f SR |
1574 | fail_free_reader: |
1575 | free_buffer_page(cpu_buffer->reader_page); | |
1576 | ||
7a8e76a3 SR |
1577 | fail_free_buffer: |
1578 | kfree(cpu_buffer); | |
1579 | return NULL; | |
1580 | } | |
1581 | ||
1582 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
1583 | { | |
3adc54fa | 1584 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1585 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1586 | |
d769041f SR |
1587 | free_buffer_page(cpu_buffer->reader_page); |
1588 | ||
77ae365e SR |
1589 | rb_head_page_deactivate(cpu_buffer); |
1590 | ||
3adc54fa SR |
1591 | if (head) { |
1592 | list_for_each_entry_safe(bpage, tmp, head, list) { | |
1593 | list_del_init(&bpage->list); | |
1594 | free_buffer_page(bpage); | |
1595 | } | |
1596 | bpage = list_entry(head, struct buffer_page, list); | |
044fa782 | 1597 | free_buffer_page(bpage); |
7a8e76a3 | 1598 | } |
3adc54fa | 1599 | |
7a8e76a3 SR |
1600 | kfree(cpu_buffer); |
1601 | } | |
1602 | ||
1603 | /** | |
d611851b | 1604 | * __ring_buffer_alloc - allocate a new ring_buffer |
68814b58 | 1605 | * @size: the size in bytes per cpu that is needed. |
7a8e76a3 | 1606 | * @flags: attributes to set for the ring buffer. |
59e7cffe | 1607 | * @key: ring buffer reader_lock_key. |
7a8e76a3 SR |
1608 | * |
1609 | * Currently the only flag that is available is the RB_FL_OVERWRITE | |
1610 | * flag. This flag means that the buffer will overwrite old data | |
1611 | * when the buffer wraps. If this flag is not set, the buffer will | |
1612 | * drop data when the tail hits the head. | |
1613 | */ | |
13292494 | 1614 | struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1f8a6a10 | 1615 | struct lock_class_key *key) |
7a8e76a3 | 1616 | { |
13292494 | 1617 | struct trace_buffer *buffer; |
9b94a8fb | 1618 | long nr_pages; |
7a8e76a3 | 1619 | int bsize; |
9b94a8fb | 1620 | int cpu; |
b32614c0 | 1621 | int ret; |
7a8e76a3 SR |
1622 | |
1623 | /* keep it in its own cache line */ | |
1624 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), | |
1625 | GFP_KERNEL); | |
1626 | if (!buffer) | |
1627 | return NULL; | |
1628 | ||
b18cc3de | 1629 | if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
9e01c1b7 RR |
1630 | goto fail_free_buffer; |
1631 | ||
438ced17 | 1632 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
7a8e76a3 | 1633 | buffer->flags = flags; |
37886f6a | 1634 | buffer->clock = trace_clock_local; |
1f8a6a10 | 1635 | buffer->reader_lock_key = key; |
7a8e76a3 | 1636 | |
15693458 | 1637 | init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1638 | init_waitqueue_head(&buffer->irq_work.waiters); |
15693458 | 1639 | |
7a8e76a3 | 1640 | /* need at least two pages */ |
438ced17 VN |
1641 | if (nr_pages < 2) |
1642 | nr_pages = 2; | |
7a8e76a3 | 1643 | |
7a8e76a3 SR |
1644 | buffer->cpus = nr_cpu_ids; |
1645 | ||
1646 | bsize = sizeof(void *) * nr_cpu_ids; | |
1647 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), | |
1648 | GFP_KERNEL); | |
1649 | if (!buffer->buffers) | |
9e01c1b7 | 1650 | goto fail_free_cpumask; |
7a8e76a3 | 1651 | |
b32614c0 SAS |
1652 | cpu = raw_smp_processor_id(); |
1653 | cpumask_set_cpu(cpu, buffer->cpumask); | |
1654 | buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); | |
1655 | if (!buffer->buffers[cpu]) | |
1656 | goto fail_free_buffers; | |
7a8e76a3 | 1657 | |
b32614c0 SAS |
1658 | ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
1659 | if (ret < 0) | |
1660 | goto fail_free_buffers; | |
554f786e | 1661 | |
7a8e76a3 SR |
1662 | mutex_init(&buffer->mutex); |
1663 | ||
1664 | return buffer; | |
1665 | ||
1666 | fail_free_buffers: | |
1667 | for_each_buffer_cpu(buffer, cpu) { | |
1668 | if (buffer->buffers[cpu]) | |
1669 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1670 | } | |
1671 | kfree(buffer->buffers); | |
1672 | ||
9e01c1b7 RR |
1673 | fail_free_cpumask: |
1674 | free_cpumask_var(buffer->cpumask); | |
1675 | ||
7a8e76a3 SR |
1676 | fail_free_buffer: |
1677 | kfree(buffer); | |
1678 | return NULL; | |
1679 | } | |
1f8a6a10 | 1680 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
7a8e76a3 SR |
1681 | |
1682 | /** | |
1683 | * ring_buffer_free - free a ring buffer. | |
1684 | * @buffer: the buffer to free. | |
1685 | */ | |
1686 | void | |
13292494 | 1687 | ring_buffer_free(struct trace_buffer *buffer) |
7a8e76a3 SR |
1688 | { |
1689 | int cpu; | |
1690 | ||
b32614c0 | 1691 | cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
554f786e | 1692 | |
7a8e76a3 SR |
1693 | for_each_buffer_cpu(buffer, cpu) |
1694 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1695 | ||
bd3f0221 | 1696 | kfree(buffer->buffers); |
9e01c1b7 RR |
1697 | free_cpumask_var(buffer->cpumask); |
1698 | ||
7a8e76a3 SR |
1699 | kfree(buffer); |
1700 | } | |
c4f50183 | 1701 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
7a8e76a3 | 1702 | |
13292494 | 1703 | void ring_buffer_set_clock(struct trace_buffer *buffer, |
37886f6a SR |
1704 | u64 (*clock)(void)) |
1705 | { | |
1706 | buffer->clock = clock; | |
1707 | } | |
1708 | ||
13292494 | 1709 | void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs) |
00b41452 TZ |
1710 | { |
1711 | buffer->time_stamp_abs = abs; | |
1712 | } | |
1713 | ||
13292494 | 1714 | bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer) |
00b41452 TZ |
1715 | { |
1716 | return buffer->time_stamp_abs; | |
1717 | } | |
1718 | ||
7a8e76a3 SR |
1719 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1720 | ||
83f40318 VN |
1721 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1722 | { | |
1723 | return local_read(&bpage->entries) & RB_WRITE_MASK; | |
1724 | } | |
1725 | ||
1726 | static inline unsigned long rb_page_write(struct buffer_page *bpage) | |
1727 | { | |
1728 | return local_read(&bpage->write) & RB_WRITE_MASK; | |
1729 | } | |
1730 | ||
5040b4b7 | 1731 | static int |
9b94a8fb | 1732 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) |
7a8e76a3 | 1733 | { |
83f40318 VN |
1734 | struct list_head *tail_page, *to_remove, *next_page; |
1735 | struct buffer_page *to_remove_page, *tmp_iter_page; | |
1736 | struct buffer_page *last_page, *first_page; | |
9b94a8fb | 1737 | unsigned long nr_removed; |
83f40318 VN |
1738 | unsigned long head_bit; |
1739 | int page_entries; | |
1740 | ||
1741 | head_bit = 0; | |
7a8e76a3 | 1742 | |
5389f6fa | 1743 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1744 | atomic_inc(&cpu_buffer->record_disabled); |
1745 | /* | |
1746 | * We don't race with the readers since we have acquired the reader | |
1747 | * lock. We also don't race with writers after disabling recording. | |
1748 | * This makes it easy to figure out the first and the last page to be | |
1749 | * removed from the list. We unlink all the pages in between including | |
1750 | * the first and last pages. This is done in a busy loop so that we | |
1751 | * lose the least number of traces. | |
1752 | * The pages are freed after we restart recording and unlock readers. | |
1753 | */ | |
1754 | tail_page = &cpu_buffer->tail_page->list; | |
77ae365e | 1755 | |
83f40318 VN |
1756 | /* |
1757 | * tail page might be on reader page, we remove the next page | |
1758 | * from the ring buffer | |
1759 | */ | |
1760 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
1761 | tail_page = rb_list_head(tail_page->next); | |
1762 | to_remove = tail_page; | |
1763 | ||
1764 | /* start of pages to remove */ | |
1765 | first_page = list_entry(rb_list_head(to_remove->next), | |
1766 | struct buffer_page, list); | |
1767 | ||
1768 | for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { | |
1769 | to_remove = rb_list_head(to_remove)->next; | |
1770 | head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; | |
7a8e76a3 | 1771 | } |
7a8e76a3 | 1772 | |
83f40318 | 1773 | next_page = rb_list_head(to_remove)->next; |
7a8e76a3 | 1774 | |
83f40318 VN |
1775 | /* |
1776 | * Now we remove all pages between tail_page and next_page. | |
1777 | * Make sure that we have head_bit value preserved for the | |
1778 | * next page | |
1779 | */ | |
1780 | tail_page->next = (struct list_head *)((unsigned long)next_page | | |
1781 | head_bit); | |
1782 | next_page = rb_list_head(next_page); | |
1783 | next_page->prev = tail_page; | |
1784 | ||
1785 | /* make sure pages points to a valid page in the ring buffer */ | |
1786 | cpu_buffer->pages = next_page; | |
1787 | ||
1788 | /* update head page */ | |
1789 | if (head_bit) | |
1790 | cpu_buffer->head_page = list_entry(next_page, | |
1791 | struct buffer_page, list); | |
1792 | ||
1793 | /* | |
1794 | * change read pointer to make sure any read iterators reset | |
1795 | * themselves | |
1796 | */ | |
1797 | cpu_buffer->read = 0; | |
1798 | ||
1799 | /* pages are removed, resume tracing and then free the pages */ | |
1800 | atomic_dec(&cpu_buffer->record_disabled); | |
5389f6fa | 1801 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1802 | |
1803 | RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); | |
1804 | ||
1805 | /* last buffer page to remove */ | |
1806 | last_page = list_entry(rb_list_head(to_remove), struct buffer_page, | |
1807 | list); | |
1808 | tmp_iter_page = first_page; | |
1809 | ||
1810 | do { | |
83f36555 VN |
1811 | cond_resched(); |
1812 | ||
83f40318 VN |
1813 | to_remove_page = tmp_iter_page; |
1814 | rb_inc_page(cpu_buffer, &tmp_iter_page); | |
1815 | ||
1816 | /* update the counters */ | |
1817 | page_entries = rb_page_entries(to_remove_page); | |
1818 | if (page_entries) { | |
1819 | /* | |
1820 | * If something was added to this page, it was full | |
1821 | * since it is not the tail page. So we deduct the | |
1822 | * bytes consumed in ring buffer from here. | |
48fdc72f | 1823 | * Increment overrun to account for the lost events. |
83f40318 | 1824 | */ |
48fdc72f | 1825 | local_add(page_entries, &cpu_buffer->overrun); |
83f40318 VN |
1826 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
1827 | } | |
1828 | ||
1829 | /* | |
1830 | * We have already removed references to this list item, just | |
1831 | * free up the buffer_page and its page | |
1832 | */ | |
1833 | free_buffer_page(to_remove_page); | |
1834 | nr_removed--; | |
1835 | ||
1836 | } while (to_remove_page != last_page); | |
1837 | ||
1838 | RB_WARN_ON(cpu_buffer, nr_removed); | |
5040b4b7 VN |
1839 | |
1840 | return nr_removed == 0; | |
7a8e76a3 SR |
1841 | } |
1842 | ||
5040b4b7 VN |
1843 | static int |
1844 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 1845 | { |
5040b4b7 VN |
1846 | struct list_head *pages = &cpu_buffer->new_pages; |
1847 | int retries, success; | |
7a8e76a3 | 1848 | |
5389f6fa | 1849 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1850 | /* |
1851 | * We are holding the reader lock, so the reader page won't be swapped | |
1852 | * in the ring buffer. Now we are racing with the writer trying to | |
1853 | * move head page and the tail page. | |
1854 | * We are going to adapt the reader page update process where: | |
1855 | * 1. We first splice the start and end of list of new pages between | |
1856 | * the head page and its previous page. | |
1857 | * 2. We cmpxchg the prev_page->next to point from head page to the | |
1858 | * start of new pages list. | |
1859 | * 3. Finally, we update the head->prev to the end of new list. | |
1860 | * | |
1861 | * We will try this process 10 times, to make sure that we don't keep | |
1862 | * spinning. | |
1863 | */ | |
1864 | retries = 10; | |
1865 | success = 0; | |
1866 | while (retries--) { | |
1867 | struct list_head *head_page, *prev_page, *r; | |
1868 | struct list_head *last_page, *first_page; | |
1869 | struct list_head *head_page_with_bit; | |
77ae365e | 1870 | |
5040b4b7 | 1871 | head_page = &rb_set_head_page(cpu_buffer)->list; |
54f7be5b SR |
1872 | if (!head_page) |
1873 | break; | |
5040b4b7 VN |
1874 | prev_page = head_page->prev; |
1875 | ||
1876 | first_page = pages->next; | |
1877 | last_page = pages->prev; | |
1878 | ||
1879 | head_page_with_bit = (struct list_head *) | |
1880 | ((unsigned long)head_page | RB_PAGE_HEAD); | |
1881 | ||
1882 | last_page->next = head_page_with_bit; | |
1883 | first_page->prev = prev_page; | |
1884 | ||
1885 | r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); | |
1886 | ||
1887 | if (r == head_page_with_bit) { | |
1888 | /* | |
1889 | * yay, we replaced the page pointer to our new list, | |
1890 | * now, we just have to update to head page's prev | |
1891 | * pointer to point to end of list | |
1892 | */ | |
1893 | head_page->prev = last_page; | |
1894 | success = 1; | |
1895 | break; | |
1896 | } | |
7a8e76a3 | 1897 | } |
7a8e76a3 | 1898 | |
5040b4b7 VN |
1899 | if (success) |
1900 | INIT_LIST_HEAD(pages); | |
1901 | /* | |
1902 | * If we weren't successful in adding in new pages, warn and stop | |
1903 | * tracing | |
1904 | */ | |
1905 | RB_WARN_ON(cpu_buffer, !success); | |
5389f6fa | 1906 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1907 | |
1908 | /* free pages if they weren't inserted */ | |
1909 | if (!success) { | |
1910 | struct buffer_page *bpage, *tmp; | |
1911 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, | |
1912 | list) { | |
1913 | list_del_init(&bpage->list); | |
1914 | free_buffer_page(bpage); | |
1915 | } | |
1916 | } | |
1917 | return success; | |
7a8e76a3 SR |
1918 | } |
1919 | ||
83f40318 | 1920 | static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
438ced17 | 1921 | { |
5040b4b7 VN |
1922 | int success; |
1923 | ||
438ced17 | 1924 | if (cpu_buffer->nr_pages_to_update > 0) |
5040b4b7 | 1925 | success = rb_insert_pages(cpu_buffer); |
438ced17 | 1926 | else |
5040b4b7 VN |
1927 | success = rb_remove_pages(cpu_buffer, |
1928 | -cpu_buffer->nr_pages_to_update); | |
83f40318 | 1929 | |
5040b4b7 VN |
1930 | if (success) |
1931 | cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; | |
83f40318 VN |
1932 | } |
1933 | ||
1934 | static void update_pages_handler(struct work_struct *work) | |
1935 | { | |
1936 | struct ring_buffer_per_cpu *cpu_buffer = container_of(work, | |
1937 | struct ring_buffer_per_cpu, update_pages_work); | |
1938 | rb_update_pages(cpu_buffer); | |
05fdd70d | 1939 | complete(&cpu_buffer->update_done); |
438ced17 VN |
1940 | } |
1941 | ||
7a8e76a3 SR |
1942 | /** |
1943 | * ring_buffer_resize - resize the ring buffer | |
1944 | * @buffer: the buffer to resize. | |
1945 | * @size: the new size. | |
d611851b | 1946 | * @cpu_id: the cpu buffer to resize |
7a8e76a3 | 1947 | * |
7a8e76a3 SR |
1948 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1949 | * | |
83f40318 | 1950 | * Returns 0 on success and < 0 on failure. |
7a8e76a3 | 1951 | */ |
13292494 | 1952 | int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, |
438ced17 | 1953 | int cpu_id) |
7a8e76a3 SR |
1954 | { |
1955 | struct ring_buffer_per_cpu *cpu_buffer; | |
9b94a8fb | 1956 | unsigned long nr_pages; |
0a1754b2 | 1957 | int cpu, err; |
7a8e76a3 | 1958 | |
ee51a1de IM |
1959 | /* |
1960 | * Always succeed at resizing a non-existent buffer: | |
1961 | */ | |
1962 | if (!buffer) | |
0a1754b2 | 1963 | return 0; |
ee51a1de | 1964 | |
6a31e1f1 SR |
1965 | /* Make sure the requested buffer exists */ |
1966 | if (cpu_id != RING_BUFFER_ALL_CPUS && | |
1967 | !cpumask_test_cpu(cpu_id, buffer->cpumask)) | |
0a1754b2 | 1968 | return 0; |
6a31e1f1 | 1969 | |
59643d15 | 1970 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
7a8e76a3 SR |
1971 | |
1972 | /* we need a minimum of two pages */ | |
59643d15 SRRH |
1973 | if (nr_pages < 2) |
1974 | nr_pages = 2; | |
7a8e76a3 | 1975 | |
59643d15 | 1976 | size = nr_pages * BUF_PAGE_SIZE; |
18421015 | 1977 | |
83f40318 | 1978 | /* prevent another thread from changing buffer sizes */ |
7a8e76a3 | 1979 | mutex_lock(&buffer->mutex); |
7a8e76a3 | 1980 | |
07b8b10e | 1981 | |
438ced17 | 1982 | if (cpu_id == RING_BUFFER_ALL_CPUS) { |
07b8b10e SRV |
1983 | /* |
1984 | * Don't succeed if resizing is disabled, as a reader might be | |
1985 | * manipulating the ring buffer and is expecting a sane state while | |
1986 | * this is true. | |
1987 | */ | |
1988 | for_each_buffer_cpu(buffer, cpu) { | |
1989 | cpu_buffer = buffer->buffers[cpu]; | |
1990 | if (atomic_read(&cpu_buffer->resize_disabled)) { | |
1991 | err = -EBUSY; | |
1992 | goto out_err_unlock; | |
1993 | } | |
1994 | } | |
1995 | ||
438ced17 | 1996 | /* calculate the pages to update */ |
7a8e76a3 SR |
1997 | for_each_buffer_cpu(buffer, cpu) { |
1998 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 1999 | |
438ced17 VN |
2000 | cpu_buffer->nr_pages_to_update = nr_pages - |
2001 | cpu_buffer->nr_pages; | |
438ced17 VN |
2002 | /* |
2003 | * nothing more to do for removing pages or no update | |
2004 | */ | |
2005 | if (cpu_buffer->nr_pages_to_update <= 0) | |
2006 | continue; | |
d7ec4bfe | 2007 | /* |
438ced17 VN |
2008 | * to add pages, make sure all new pages can be |
2009 | * allocated without receiving ENOMEM | |
d7ec4bfe | 2010 | */ |
438ced17 VN |
2011 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
2012 | if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 | 2013 | &cpu_buffer->new_pages, cpu)) { |
438ced17 | 2014 | /* not enough memory for new pages */ |
83f40318 VN |
2015 | err = -ENOMEM; |
2016 | goto out_err; | |
2017 | } | |
2018 | } | |
2019 | ||
2020 | get_online_cpus(); | |
2021 | /* | |
2022 | * Fire off all the required work handlers | |
05fdd70d | 2023 | * We can't schedule on offline CPUs, but it's not necessary |
83f40318 VN |
2024 | * since we can change their buffer sizes without any race. |
2025 | */ | |
2026 | for_each_buffer_cpu(buffer, cpu) { | |
2027 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 2028 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
2029 | continue; |
2030 | ||
021c5b34 CM |
2031 | /* Can't run something on an offline CPU. */ |
2032 | if (!cpu_online(cpu)) { | |
f5eb5588 SRRH |
2033 | rb_update_pages(cpu_buffer); |
2034 | cpu_buffer->nr_pages_to_update = 0; | |
2035 | } else { | |
05fdd70d VN |
2036 | schedule_work_on(cpu, |
2037 | &cpu_buffer->update_pages_work); | |
f5eb5588 | 2038 | } |
7a8e76a3 | 2039 | } |
7a8e76a3 | 2040 | |
438ced17 VN |
2041 | /* wait for all the updates to complete */ |
2042 | for_each_buffer_cpu(buffer, cpu) { | |
2043 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 2044 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
2045 | continue; |
2046 | ||
05fdd70d VN |
2047 | if (cpu_online(cpu)) |
2048 | wait_for_completion(&cpu_buffer->update_done); | |
83f40318 | 2049 | cpu_buffer->nr_pages_to_update = 0; |
438ced17 | 2050 | } |
83f40318 VN |
2051 | |
2052 | put_online_cpus(); | |
438ced17 | 2053 | } else { |
6167c205 | 2054 | /* Make sure this CPU has been initialized */ |
8e49f418 VN |
2055 | if (!cpumask_test_cpu(cpu_id, buffer->cpumask)) |
2056 | goto out; | |
2057 | ||
438ced17 | 2058 | cpu_buffer = buffer->buffers[cpu_id]; |
83f40318 | 2059 | |
438ced17 VN |
2060 | if (nr_pages == cpu_buffer->nr_pages) |
2061 | goto out; | |
7a8e76a3 | 2062 | |
07b8b10e SRV |
2063 | /* |
2064 | * Don't succeed if resizing is disabled, as a reader might be | |
2065 | * manipulating the ring buffer and is expecting a sane state while | |
2066 | * this is true. | |
2067 | */ | |
2068 | if (atomic_read(&cpu_buffer->resize_disabled)) { | |
2069 | err = -EBUSY; | |
2070 | goto out_err_unlock; | |
2071 | } | |
2072 | ||
438ced17 VN |
2073 | cpu_buffer->nr_pages_to_update = nr_pages - |
2074 | cpu_buffer->nr_pages; | |
2075 | ||
2076 | INIT_LIST_HEAD(&cpu_buffer->new_pages); | |
2077 | if (cpu_buffer->nr_pages_to_update > 0 && | |
2078 | __rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 VN |
2079 | &cpu_buffer->new_pages, cpu_id)) { |
2080 | err = -ENOMEM; | |
2081 | goto out_err; | |
2082 | } | |
438ced17 | 2083 | |
83f40318 VN |
2084 | get_online_cpus(); |
2085 | ||
021c5b34 CM |
2086 | /* Can't run something on an offline CPU. */ |
2087 | if (!cpu_online(cpu_id)) | |
f5eb5588 SRRH |
2088 | rb_update_pages(cpu_buffer); |
2089 | else { | |
83f40318 VN |
2090 | schedule_work_on(cpu_id, |
2091 | &cpu_buffer->update_pages_work); | |
05fdd70d | 2092 | wait_for_completion(&cpu_buffer->update_done); |
f5eb5588 | 2093 | } |
83f40318 | 2094 | |
83f40318 | 2095 | cpu_buffer->nr_pages_to_update = 0; |
05fdd70d | 2096 | put_online_cpus(); |
438ced17 | 2097 | } |
7a8e76a3 SR |
2098 | |
2099 | out: | |
659f451f SR |
2100 | /* |
2101 | * The ring buffer resize can happen with the ring buffer | |
2102 | * enabled, so that the update disturbs the tracing as little | |
2103 | * as possible. But if the buffer is disabled, we do not need | |
2104 | * to worry about that, and we can take the time to verify | |
2105 | * that the buffer is not corrupt. | |
2106 | */ | |
2107 | if (atomic_read(&buffer->record_disabled)) { | |
2108 | atomic_inc(&buffer->record_disabled); | |
2109 | /* | |
2110 | * Even though the buffer was disabled, we must make sure | |
2111 | * that it is truly disabled before calling rb_check_pages. | |
2112 | * There could have been a race between checking | |
2113 | * record_disable and incrementing it. | |
2114 | */ | |
74401729 | 2115 | synchronize_rcu(); |
659f451f SR |
2116 | for_each_buffer_cpu(buffer, cpu) { |
2117 | cpu_buffer = buffer->buffers[cpu]; | |
2118 | rb_check_pages(cpu_buffer); | |
2119 | } | |
2120 | atomic_dec(&buffer->record_disabled); | |
2121 | } | |
2122 | ||
7a8e76a3 | 2123 | mutex_unlock(&buffer->mutex); |
0a1754b2 | 2124 | return 0; |
7a8e76a3 | 2125 | |
83f40318 | 2126 | out_err: |
438ced17 VN |
2127 | for_each_buffer_cpu(buffer, cpu) { |
2128 | struct buffer_page *bpage, *tmp; | |
83f40318 | 2129 | |
438ced17 | 2130 | cpu_buffer = buffer->buffers[cpu]; |
438ced17 | 2131 | cpu_buffer->nr_pages_to_update = 0; |
83f40318 | 2132 | |
438ced17 VN |
2133 | if (list_empty(&cpu_buffer->new_pages)) |
2134 | continue; | |
83f40318 | 2135 | |
438ced17 VN |
2136 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
2137 | list) { | |
2138 | list_del_init(&bpage->list); | |
2139 | free_buffer_page(bpage); | |
2140 | } | |
7a8e76a3 | 2141 | } |
07b8b10e | 2142 | out_err_unlock: |
641d2f63 | 2143 | mutex_unlock(&buffer->mutex); |
83f40318 | 2144 | return err; |
7a8e76a3 | 2145 | } |
c4f50183 | 2146 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
7a8e76a3 | 2147 | |
13292494 | 2148 | void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val) |
750912fa DS |
2149 | { |
2150 | mutex_lock(&buffer->mutex); | |
2151 | if (val) | |
2152 | buffer->flags |= RB_FL_OVERWRITE; | |
2153 | else | |
2154 | buffer->flags &= ~RB_FL_OVERWRITE; | |
2155 | mutex_unlock(&buffer->mutex); | |
2156 | } | |
2157 | EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); | |
2158 | ||
2289d567 | 2159 | static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
7a8e76a3 | 2160 | { |
044fa782 | 2161 | return bpage->page->data + index; |
7a8e76a3 SR |
2162 | } |
2163 | ||
2289d567 | 2164 | static __always_inline struct ring_buffer_event * |
d769041f | 2165 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 2166 | { |
6f807acd SR |
2167 | return __rb_page_index(cpu_buffer->reader_page, |
2168 | cpu_buffer->reader_page->read); | |
2169 | } | |
2170 | ||
785888c5 | 2171 | static __always_inline unsigned rb_page_commit(struct buffer_page *bpage) |
7a8e76a3 | 2172 | { |
785888c5 | 2173 | return local_read(&bpage->page->commit); |
7a8e76a3 SR |
2174 | } |
2175 | ||
785888c5 SRV |
2176 | static struct ring_buffer_event * |
2177 | rb_iter_head_event(struct ring_buffer_iter *iter) | |
bf41a158 | 2178 | { |
785888c5 SRV |
2179 | struct ring_buffer_event *event; |
2180 | struct buffer_page *iter_head_page = iter->head_page; | |
2181 | unsigned long commit; | |
2182 | unsigned length; | |
2183 | ||
153368ce SRV |
2184 | if (iter->head != iter->next_event) |
2185 | return iter->event; | |
2186 | ||
785888c5 SRV |
2187 | /* |
2188 | * When the writer goes across pages, it issues a cmpxchg which | |
2189 | * is a mb(), which will synchronize with the rmb here. | |
2190 | * (see rb_tail_page_update() and __rb_reserve_next()) | |
2191 | */ | |
2192 | commit = rb_page_commit(iter_head_page); | |
2193 | smp_rmb(); | |
2194 | event = __rb_page_index(iter_head_page, iter->head); | |
2195 | length = rb_event_length(event); | |
2196 | ||
2197 | /* | |
2198 | * READ_ONCE() doesn't work on functions and we don't want the | |
2199 | * compiler doing any crazy optimizations with length. | |
2200 | */ | |
2201 | barrier(); | |
2202 | ||
2203 | if ((iter->head + length) > commit || length > BUF_MAX_DATA_SIZE) | |
2204 | /* Writer corrupted the read? */ | |
2205 | goto reset; | |
2206 | ||
2207 | memcpy(iter->event, event, length); | |
2208 | /* | |
2209 | * If the page stamp is still the same after this rmb() then the | |
2210 | * event was safely copied without the writer entering the page. | |
2211 | */ | |
2212 | smp_rmb(); | |
2213 | ||
2214 | /* Make sure the page didn't change since we read this */ | |
2215 | if (iter->page_stamp != iter_head_page->page->time_stamp || | |
2216 | commit > rb_page_commit(iter_head_page)) | |
2217 | goto reset; | |
2218 | ||
2219 | iter->next_event = iter->head + length; | |
2220 | return iter->event; | |
2221 | reset: | |
2222 | /* Reset to the beginning */ | |
2223 | iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; | |
2224 | iter->head = 0; | |
2225 | iter->next_event = 0; | |
c9b7a4a7 | 2226 | iter->missed_events = 1; |
785888c5 | 2227 | return NULL; |
bf41a158 SR |
2228 | } |
2229 | ||
25985edc | 2230 | /* Size is determined by what has been committed */ |
2289d567 | 2231 | static __always_inline unsigned rb_page_size(struct buffer_page *bpage) |
bf41a158 SR |
2232 | { |
2233 | return rb_page_commit(bpage); | |
2234 | } | |
2235 | ||
2289d567 | 2236 | static __always_inline unsigned |
bf41a158 SR |
2237 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) |
2238 | { | |
2239 | return rb_page_commit(cpu_buffer->commit_page); | |
2240 | } | |
2241 | ||
2289d567 | 2242 | static __always_inline unsigned |
bf41a158 SR |
2243 | rb_event_index(struct ring_buffer_event *event) |
2244 | { | |
2245 | unsigned long addr = (unsigned long)event; | |
2246 | ||
22f470f8 | 2247 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
bf41a158 SR |
2248 | } |
2249 | ||
34a148bf | 2250 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
d769041f SR |
2251 | { |
2252 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
2253 | ||
2254 | /* | |
2255 | * The iterator could be on the reader page (it starts there). | |
2256 | * But the head could have moved, since the reader was | |
2257 | * found. Check for this case and assign the iterator | |
2258 | * to the head page instead of next. | |
2259 | */ | |
2260 | if (iter->head_page == cpu_buffer->reader_page) | |
77ae365e | 2261 | iter->head_page = rb_set_head_page(cpu_buffer); |
d769041f SR |
2262 | else |
2263 | rb_inc_page(cpu_buffer, &iter->head_page); | |
2264 | ||
28e3fc56 | 2265 | iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp; |
7a8e76a3 | 2266 | iter->head = 0; |
785888c5 | 2267 | iter->next_event = 0; |
7a8e76a3 SR |
2268 | } |
2269 | ||
77ae365e SR |
2270 | /* |
2271 | * rb_handle_head_page - writer hit the head page | |
2272 | * | |
2273 | * Returns: +1 to retry page | |
2274 | * 0 to continue | |
2275 | * -1 on error | |
2276 | */ | |
2277 | static int | |
2278 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, | |
2279 | struct buffer_page *tail_page, | |
2280 | struct buffer_page *next_page) | |
2281 | { | |
2282 | struct buffer_page *new_head; | |
2283 | int entries; | |
2284 | int type; | |
2285 | int ret; | |
2286 | ||
2287 | entries = rb_page_entries(next_page); | |
2288 | ||
2289 | /* | |
2290 | * The hard part is here. We need to move the head | |
2291 | * forward, and protect against both readers on | |
2292 | * other CPUs and writers coming in via interrupts. | |
2293 | */ | |
2294 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, | |
2295 | RB_PAGE_HEAD); | |
2296 | ||
2297 | /* | |
2298 | * type can be one of four: | |
2299 | * NORMAL - an interrupt already moved it for us | |
2300 | * HEAD - we are the first to get here. | |
2301 | * UPDATE - we are the interrupt interrupting | |
2302 | * a current move. | |
2303 | * MOVED - a reader on another CPU moved the next | |
2304 | * pointer to its reader page. Give up | |
2305 | * and try again. | |
2306 | */ | |
2307 | ||
2308 | switch (type) { | |
2309 | case RB_PAGE_HEAD: | |
2310 | /* | |
2311 | * We changed the head to UPDATE, thus | |
2312 | * it is our responsibility to update | |
2313 | * the counters. | |
2314 | */ | |
2315 | local_add(entries, &cpu_buffer->overrun); | |
c64e148a | 2316 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
77ae365e SR |
2317 | |
2318 | /* | |
2319 | * The entries will be zeroed out when we move the | |
2320 | * tail page. | |
2321 | */ | |
2322 | ||
2323 | /* still more to do */ | |
2324 | break; | |
2325 | ||
2326 | case RB_PAGE_UPDATE: | |
2327 | /* | |
2328 | * This is an interrupt that interrupt the | |
2329 | * previous update. Still more to do. | |
2330 | */ | |
2331 | break; | |
2332 | case RB_PAGE_NORMAL: | |
2333 | /* | |
2334 | * An interrupt came in before the update | |
2335 | * and processed this for us. | |
2336 | * Nothing left to do. | |
2337 | */ | |
2338 | return 1; | |
2339 | case RB_PAGE_MOVED: | |
2340 | /* | |
2341 | * The reader is on another CPU and just did | |
2342 | * a swap with our next_page. | |
2343 | * Try again. | |
2344 | */ | |
2345 | return 1; | |
2346 | default: | |
2347 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ | |
2348 | return -1; | |
2349 | } | |
2350 | ||
2351 | /* | |
2352 | * Now that we are here, the old head pointer is | |
2353 | * set to UPDATE. This will keep the reader from | |
2354 | * swapping the head page with the reader page. | |
2355 | * The reader (on another CPU) will spin till | |
2356 | * we are finished. | |
2357 | * | |
2358 | * We just need to protect against interrupts | |
2359 | * doing the job. We will set the next pointer | |
2360 | * to HEAD. After that, we set the old pointer | |
2361 | * to NORMAL, but only if it was HEAD before. | |
2362 | * otherwise we are an interrupt, and only | |
2363 | * want the outer most commit to reset it. | |
2364 | */ | |
2365 | new_head = next_page; | |
2366 | rb_inc_page(cpu_buffer, &new_head); | |
2367 | ||
2368 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, | |
2369 | RB_PAGE_NORMAL); | |
2370 | ||
2371 | /* | |
2372 | * Valid returns are: | |
2373 | * HEAD - an interrupt came in and already set it. | |
2374 | * NORMAL - One of two things: | |
2375 | * 1) We really set it. | |
2376 | * 2) A bunch of interrupts came in and moved | |
2377 | * the page forward again. | |
2378 | */ | |
2379 | switch (ret) { | |
2380 | case RB_PAGE_HEAD: | |
2381 | case RB_PAGE_NORMAL: | |
2382 | /* OK */ | |
2383 | break; | |
2384 | default: | |
2385 | RB_WARN_ON(cpu_buffer, 1); | |
2386 | return -1; | |
2387 | } | |
2388 | ||
2389 | /* | |
2390 | * It is possible that an interrupt came in, | |
2391 | * set the head up, then more interrupts came in | |
2392 | * and moved it again. When we get back here, | |
2393 | * the page would have been set to NORMAL but we | |
2394 | * just set it back to HEAD. | |
2395 | * | |
2396 | * How do you detect this? Well, if that happened | |
2397 | * the tail page would have moved. | |
2398 | */ | |
2399 | if (ret == RB_PAGE_NORMAL) { | |
8573636e SRRH |
2400 | struct buffer_page *buffer_tail_page; |
2401 | ||
2402 | buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); | |
77ae365e SR |
2403 | /* |
2404 | * If the tail had moved passed next, then we need | |
2405 | * to reset the pointer. | |
2406 | */ | |
8573636e SRRH |
2407 | if (buffer_tail_page != tail_page && |
2408 | buffer_tail_page != next_page) | |
77ae365e SR |
2409 | rb_head_page_set_normal(cpu_buffer, new_head, |
2410 | next_page, | |
2411 | RB_PAGE_HEAD); | |
2412 | } | |
2413 | ||
2414 | /* | |
2415 | * If this was the outer most commit (the one that | |
2416 | * changed the original pointer from HEAD to UPDATE), | |
2417 | * then it is up to us to reset it to NORMAL. | |
2418 | */ | |
2419 | if (type == RB_PAGE_HEAD) { | |
2420 | ret = rb_head_page_set_normal(cpu_buffer, next_page, | |
2421 | tail_page, | |
2422 | RB_PAGE_UPDATE); | |
2423 | if (RB_WARN_ON(cpu_buffer, | |
2424 | ret != RB_PAGE_UPDATE)) | |
2425 | return -1; | |
2426 | } | |
2427 | ||
2428 | return 0; | |
2429 | } | |
2430 | ||
c7b09308 SR |
2431 | static inline void |
2432 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, | |
fcc742ea | 2433 | unsigned long tail, struct rb_event_info *info) |
c7b09308 | 2434 | { |
fcc742ea | 2435 | struct buffer_page *tail_page = info->tail_page; |
c7b09308 | 2436 | struct ring_buffer_event *event; |
fcc742ea | 2437 | unsigned long length = info->length; |
c7b09308 SR |
2438 | |
2439 | /* | |
2440 | * Only the event that crossed the page boundary | |
2441 | * must fill the old tail_page with padding. | |
2442 | */ | |
2443 | if (tail >= BUF_PAGE_SIZE) { | |
b3230c8b SR |
2444 | /* |
2445 | * If the page was filled, then we still need | |
2446 | * to update the real_end. Reset it to zero | |
2447 | * and the reader will ignore it. | |
2448 | */ | |
2449 | if (tail == BUF_PAGE_SIZE) | |
2450 | tail_page->real_end = 0; | |
2451 | ||
c7b09308 SR |
2452 | local_sub(length, &tail_page->write); |
2453 | return; | |
2454 | } | |
2455 | ||
2456 | event = __rb_page_index(tail_page, tail); | |
2457 | ||
c64e148a VN |
2458 | /* account for padding bytes */ |
2459 | local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); | |
2460 | ||
ff0ff84a SR |
2461 | /* |
2462 | * Save the original length to the meta data. | |
2463 | * This will be used by the reader to add lost event | |
2464 | * counter. | |
2465 | */ | |
2466 | tail_page->real_end = tail; | |
2467 | ||
c7b09308 SR |
2468 | /* |
2469 | * If this event is bigger than the minimum size, then | |
2470 | * we need to be careful that we don't subtract the | |
2471 | * write counter enough to allow another writer to slip | |
2472 | * in on this page. | |
2473 | * We put in a discarded commit instead, to make sure | |
2474 | * that this space is not used again. | |
2475 | * | |
2476 | * If we are less than the minimum size, we don't need to | |
2477 | * worry about it. | |
2478 | */ | |
2479 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { | |
2480 | /* No room for any events */ | |
2481 | ||
2482 | /* Mark the rest of the page with padding */ | |
2483 | rb_event_set_padding(event); | |
2484 | ||
2485 | /* Set the write back to the previous setting */ | |
2486 | local_sub(length, &tail_page->write); | |
2487 | return; | |
2488 | } | |
2489 | ||
2490 | /* Put in a discarded event */ | |
2491 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; | |
2492 | event->type_len = RINGBUF_TYPE_PADDING; | |
2493 | /* time delta must be non zero */ | |
2494 | event->time_delta = 1; | |
c7b09308 SR |
2495 | |
2496 | /* Set write to end of buffer */ | |
2497 | length = (tail + length) - BUF_PAGE_SIZE; | |
2498 | local_sub(length, &tail_page->write); | |
2499 | } | |
6634ff26 | 2500 | |
4239c38f SRRH |
2501 | static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer); |
2502 | ||
747e94ae SR |
2503 | /* |
2504 | * This is the slow path, force gcc not to inline it. | |
2505 | */ | |
2506 | static noinline struct ring_buffer_event * | |
6634ff26 | 2507 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
fcc742ea | 2508 | unsigned long tail, struct rb_event_info *info) |
7a8e76a3 | 2509 | { |
fcc742ea | 2510 | struct buffer_page *tail_page = info->tail_page; |
5a50e33c | 2511 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
13292494 | 2512 | struct trace_buffer *buffer = cpu_buffer->buffer; |
77ae365e SR |
2513 | struct buffer_page *next_page; |
2514 | int ret; | |
aa20ae84 SR |
2515 | |
2516 | next_page = tail_page; | |
2517 | ||
aa20ae84 SR |
2518 | rb_inc_page(cpu_buffer, &next_page); |
2519 | ||
aa20ae84 SR |
2520 | /* |
2521 | * If for some reason, we had an interrupt storm that made | |
2522 | * it all the way around the buffer, bail, and warn | |
2523 | * about it. | |
2524 | */ | |
2525 | if (unlikely(next_page == commit_page)) { | |
77ae365e | 2526 | local_inc(&cpu_buffer->commit_overrun); |
aa20ae84 SR |
2527 | goto out_reset; |
2528 | } | |
2529 | ||
77ae365e SR |
2530 | /* |
2531 | * This is where the fun begins! | |
2532 | * | |
2533 | * We are fighting against races between a reader that | |
2534 | * could be on another CPU trying to swap its reader | |
2535 | * page with the buffer head. | |
2536 | * | |
2537 | * We are also fighting against interrupts coming in and | |
2538 | * moving the head or tail on us as well. | |
2539 | * | |
2540 | * If the next page is the head page then we have filled | |
2541 | * the buffer, unless the commit page is still on the | |
2542 | * reader page. | |
2543 | */ | |
2544 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { | |
aa20ae84 | 2545 | |
77ae365e SR |
2546 | /* |
2547 | * If the commit is not on the reader page, then | |
2548 | * move the header page. | |
2549 | */ | |
2550 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { | |
2551 | /* | |
2552 | * If we are not in overwrite mode, | |
2553 | * this is easy, just stop here. | |
2554 | */ | |
884bfe89 SP |
2555 | if (!(buffer->flags & RB_FL_OVERWRITE)) { |
2556 | local_inc(&cpu_buffer->dropped_events); | |
77ae365e | 2557 | goto out_reset; |
884bfe89 | 2558 | } |
77ae365e SR |
2559 | |
2560 | ret = rb_handle_head_page(cpu_buffer, | |
2561 | tail_page, | |
2562 | next_page); | |
2563 | if (ret < 0) | |
2564 | goto out_reset; | |
2565 | if (ret) | |
2566 | goto out_again; | |
2567 | } else { | |
2568 | /* | |
2569 | * We need to be careful here too. The | |
2570 | * commit page could still be on the reader | |
2571 | * page. We could have a small buffer, and | |
2572 | * have filled up the buffer with events | |
2573 | * from interrupts and such, and wrapped. | |
2574 | * | |
2575 | * Note, if the tail page is also the on the | |
2576 | * reader_page, we let it move out. | |
2577 | */ | |
2578 | if (unlikely((cpu_buffer->commit_page != | |
2579 | cpu_buffer->tail_page) && | |
2580 | (cpu_buffer->commit_page == | |
2581 | cpu_buffer->reader_page))) { | |
2582 | local_inc(&cpu_buffer->commit_overrun); | |
2583 | goto out_reset; | |
2584 | } | |
aa20ae84 SR |
2585 | } |
2586 | } | |
2587 | ||
70004986 | 2588 | rb_tail_page_update(cpu_buffer, tail_page, next_page); |
aa20ae84 | 2589 | |
77ae365e | 2590 | out_again: |
aa20ae84 | 2591 | |
fcc742ea | 2592 | rb_reset_tail(cpu_buffer, tail, info); |
aa20ae84 | 2593 | |
4239c38f SRRH |
2594 | /* Commit what we have for now. */ |
2595 | rb_end_commit(cpu_buffer); | |
2596 | /* rb_end_commit() decs committing */ | |
2597 | local_inc(&cpu_buffer->committing); | |
2598 | ||
aa20ae84 SR |
2599 | /* fail and let the caller try again */ |
2600 | return ERR_PTR(-EAGAIN); | |
2601 | ||
45141d46 | 2602 | out_reset: |
6f3b3440 | 2603 | /* reset write */ |
fcc742ea | 2604 | rb_reset_tail(cpu_buffer, tail, info); |
6f3b3440 | 2605 | |
bf41a158 | 2606 | return NULL; |
7a8e76a3 SR |
2607 | } |
2608 | ||
74e87937 SRV |
2609 | /* Slow path */ |
2610 | static struct ring_buffer_event * | |
dc4e2801 | 2611 | rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs) |
9826b273 | 2612 | { |
dc4e2801 TZ |
2613 | if (abs) |
2614 | event->type_len = RINGBUF_TYPE_TIME_STAMP; | |
2615 | else | |
2616 | event->type_len = RINGBUF_TYPE_TIME_EXTEND; | |
9826b273 | 2617 | |
dc4e2801 TZ |
2618 | /* Not the first event on the page, or not delta? */ |
2619 | if (abs || rb_event_index(event)) { | |
d90fd774 SRRH |
2620 | event->time_delta = delta & TS_MASK; |
2621 | event->array[0] = delta >> TS_SHIFT; | |
2622 | } else { | |
2623 | /* nope, just zero it */ | |
2624 | event->time_delta = 0; | |
2625 | event->array[0] = 0; | |
2626 | } | |
a4543a2f | 2627 | |
d90fd774 SRRH |
2628 | return skip_time_extend(event); |
2629 | } | |
a4543a2f | 2630 | |
cdb2a0a9 | 2631 | static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
b7dc42fd SRRH |
2632 | struct ring_buffer_event *event); |
2633 | ||
58fbc3c6 SRV |
2634 | #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK |
2635 | static inline bool sched_clock_stable(void) | |
2636 | { | |
2637 | return true; | |
2638 | } | |
2639 | #endif | |
2640 | ||
74e87937 | 2641 | static void |
58fbc3c6 SRV |
2642 | rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer, |
2643 | struct rb_event_info *info) | |
2644 | { | |
2645 | u64 write_stamp; | |
2646 | ||
29ce2451 | 2647 | WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s", |
58fbc3c6 SRV |
2648 | (unsigned long long)info->delta, |
2649 | (unsigned long long)info->ts, | |
2650 | (unsigned long long)info->before, | |
2651 | (unsigned long long)info->after, | |
2652 | (unsigned long long)(rb_time_read(&cpu_buffer->write_stamp, &write_stamp) ? write_stamp : 0), | |
2653 | sched_clock_stable() ? "" : | |
2654 | "If you just came from a suspend/resume,\n" | |
2655 | "please switch to the trace global clock:\n" | |
2656 | " echo global > /sys/kernel/debug/tracing/trace_clock\n" | |
2657 | "or add trace_clock=global to the kernel command line\n"); | |
2658 | } | |
2659 | ||
74e87937 SRV |
2660 | static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer, |
2661 | struct ring_buffer_event **event, | |
2662 | struct rb_event_info *info, | |
2663 | u64 *delta, | |
2664 | unsigned int *length) | |
2665 | { | |
2666 | bool abs = info->add_timestamp & | |
2667 | (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE); | |
2668 | ||
29ce2451 SRV |
2669 | if (unlikely(info->delta > (1ULL << 59))) { |
2670 | /* did the clock go backwards */ | |
2671 | if (info->before == info->after && info->before > info->ts) { | |
2672 | /* not interrupted */ | |
2673 | static int once; | |
2674 | ||
2675 | /* | |
2676 | * This is possible with a recalibrating of the TSC. | |
2677 | * Do not produce a call stack, but just report it. | |
2678 | */ | |
2679 | if (!once) { | |
2680 | once++; | |
2681 | pr_warn("Ring buffer clock went backwards: %llu -> %llu\n", | |
2682 | info->before, info->ts); | |
2683 | } | |
2684 | } else | |
2685 | rb_check_timestamp(cpu_buffer, info); | |
2686 | if (!abs) | |
2687 | info->delta = 0; | |
2688 | } | |
74e87937 SRV |
2689 | *event = rb_add_time_stamp(*event, info->delta, abs); |
2690 | *length -= RB_LEN_TIME_EXTEND; | |
2691 | *delta = 0; | |
2692 | } | |
2693 | ||
d90fd774 SRRH |
2694 | /** |
2695 | * rb_update_event - update event type and data | |
cfc585a4 | 2696 | * @cpu_buffer: The per cpu buffer of the @event |
d90fd774 | 2697 | * @event: the event to update |
cfc585a4 | 2698 | * @info: The info to update the @event with (contains length and delta) |
d90fd774 | 2699 | * |
cfc585a4 | 2700 | * Update the type and data fields of the @event. The length |
d90fd774 SRRH |
2701 | * is the actual size that is written to the ring buffer, |
2702 | * and with this, we can determine what to place into the | |
2703 | * data field. | |
2704 | */ | |
b7dc42fd | 2705 | static void |
d90fd774 SRRH |
2706 | rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
2707 | struct ring_buffer_event *event, | |
2708 | struct rb_event_info *info) | |
2709 | { | |
2710 | unsigned length = info->length; | |
2711 | u64 delta = info->delta; | |
a4543a2f SRRH |
2712 | |
2713 | /* | |
d90fd774 | 2714 | * If we need to add a timestamp, then we |
6167c205 | 2715 | * add it to the start of the reserved space. |
a4543a2f | 2716 | */ |
74e87937 SRV |
2717 | if (unlikely(info->add_timestamp)) |
2718 | rb_add_timestamp(cpu_buffer, &event, info, &delta, &length); | |
a4543a2f | 2719 | |
d90fd774 SRRH |
2720 | event->time_delta = delta; |
2721 | length -= RB_EVNT_HDR_SIZE; | |
86b3de60 | 2722 | if (length > RB_MAX_SMALL_DATA) { |
d90fd774 SRRH |
2723 | event->type_len = 0; |
2724 | event->array[0] = length; | |
2725 | } else | |
2726 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); | |
2727 | } | |
2728 | ||
2729 | static unsigned rb_calculate_event_length(unsigned length) | |
2730 | { | |
2731 | struct ring_buffer_event event; /* Used only for sizeof array */ | |
2732 | ||
2733 | /* zero length can cause confusions */ | |
2734 | if (!length) | |
2735 | length++; | |
2736 | ||
86b3de60 | 2737 | if (length > RB_MAX_SMALL_DATA) |
d90fd774 SRRH |
2738 | length += sizeof(event.array[0]); |
2739 | ||
2740 | length += RB_EVNT_HDR_SIZE; | |
86b3de60 | 2741 | length = ALIGN(length, RB_ALIGNMENT); |
d90fd774 SRRH |
2742 | |
2743 | /* | |
2744 | * In case the time delta is larger than the 27 bits for it | |
2745 | * in the header, we need to add a timestamp. If another | |
2746 | * event comes in when trying to discard this one to increase | |
2747 | * the length, then the timestamp will be added in the allocated | |
2748 | * space of this event. If length is bigger than the size needed | |
2749 | * for the TIME_EXTEND, then padding has to be used. The events | |
2750 | * length must be either RB_LEN_TIME_EXTEND, or greater than or equal | |
2751 | * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. | |
2752 | * As length is a multiple of 4, we only need to worry if it | |
2753 | * is 12 (RB_LEN_TIME_EXTEND + 4). | |
2754 | */ | |
2755 | if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) | |
2756 | length += RB_ALIGNMENT; | |
2757 | ||
2758 | return length; | |
2759 | } | |
2760 | ||
a389d86f SRV |
2761 | static __always_inline bool |
2762 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, | |
2763 | struct ring_buffer_event *event) | |
d90fd774 | 2764 | { |
a389d86f SRV |
2765 | unsigned long addr = (unsigned long)event; |
2766 | unsigned long index; | |
2767 | ||
2768 | index = rb_event_index(event); | |
2769 | addr &= PAGE_MASK; | |
2770 | ||
2771 | return cpu_buffer->commit_page->page == (void *)addr && | |
2772 | rb_commit_index(cpu_buffer) == index; | |
2773 | } | |
2774 | ||
2775 | static u64 rb_time_delta(struct ring_buffer_event *event) | |
2776 | { | |
2777 | switch (event->type_len) { | |
2778 | case RINGBUF_TYPE_PADDING: | |
2779 | return 0; | |
2780 | ||
2781 | case RINGBUF_TYPE_TIME_EXTEND: | |
2782 | return ring_buffer_event_time_stamp(event); | |
2783 | ||
2784 | case RINGBUF_TYPE_TIME_STAMP: | |
2785 | return 0; | |
2786 | ||
2787 | case RINGBUF_TYPE_DATA: | |
2788 | return event->time_delta; | |
2789 | default: | |
2790 | return 0; | |
2791 | } | |
d90fd774 | 2792 | } |
d90fd774 SRRH |
2793 | |
2794 | static inline int | |
2795 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, | |
2796 | struct ring_buffer_event *event) | |
2797 | { | |
2798 | unsigned long new_index, old_index; | |
2799 | struct buffer_page *bpage; | |
2800 | unsigned long index; | |
2801 | unsigned long addr; | |
a389d86f SRV |
2802 | u64 write_stamp; |
2803 | u64 delta; | |
d90fd774 SRRH |
2804 | |
2805 | new_index = rb_event_index(event); | |
2806 | old_index = new_index + rb_event_ts_length(event); | |
2807 | addr = (unsigned long)event; | |
2808 | addr &= PAGE_MASK; | |
2809 | ||
8573636e | 2810 | bpage = READ_ONCE(cpu_buffer->tail_page); |
d90fd774 | 2811 | |
a389d86f SRV |
2812 | delta = rb_time_delta(event); |
2813 | ||
10464b4a SRV |
2814 | if (!rb_time_read(&cpu_buffer->write_stamp, &write_stamp)) |
2815 | return 0; | |
a389d86f SRV |
2816 | |
2817 | /* Make sure the write stamp is read before testing the location */ | |
2818 | barrier(); | |
2819 | ||
d90fd774 SRRH |
2820 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { |
2821 | unsigned long write_mask = | |
2822 | local_read(&bpage->write) & ~RB_WRITE_MASK; | |
2823 | unsigned long event_length = rb_event_length(event); | |
a389d86f | 2824 | |
a389d86f | 2825 | /* Something came in, can't discard */ |
10464b4a SRV |
2826 | if (!rb_time_cmpxchg(&cpu_buffer->write_stamp, |
2827 | write_stamp, write_stamp - delta)) | |
a389d86f SRV |
2828 | return 0; |
2829 | ||
2830 | /* | |
2831 | * If an event were to come in now, it would see that the | |
2832 | * write_stamp and the before_stamp are different, and assume | |
2833 | * that this event just added itself before updating | |
2834 | * the write stamp. The interrupting event will fix the | |
2835 | * write stamp for us, and use the before stamp as its delta. | |
2836 | */ | |
2837 | ||
d90fd774 SRRH |
2838 | /* |
2839 | * This is on the tail page. It is possible that | |
2840 | * a write could come in and move the tail page | |
2841 | * and write to the next page. That is fine | |
2842 | * because we just shorten what is on this page. | |
2843 | */ | |
2844 | old_index += write_mask; | |
2845 | new_index += write_mask; | |
2846 | index = local_cmpxchg(&bpage->write, old_index, new_index); | |
2847 | if (index == old_index) { | |
2848 | /* update counters */ | |
2849 | local_sub(event_length, &cpu_buffer->entries_bytes); | |
2850 | return 1; | |
2851 | } | |
2852 | } | |
2853 | ||
2854 | /* could not discard */ | |
2855 | return 0; | |
2856 | } | |
2857 | ||
2858 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) | |
2859 | { | |
2860 | local_inc(&cpu_buffer->committing); | |
2861 | local_inc(&cpu_buffer->commits); | |
2862 | } | |
2863 | ||
38e11df1 | 2864 | static __always_inline void |
d90fd774 SRRH |
2865 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
2866 | { | |
2867 | unsigned long max_count; | |
2868 | ||
2869 | /* | |
2870 | * We only race with interrupts and NMIs on this CPU. | |
2871 | * If we own the commit event, then we can commit | |
2872 | * all others that interrupted us, since the interruptions | |
2873 | * are in stack format (they finish before they come | |
2874 | * back to us). This allows us to do a simple loop to | |
2875 | * assign the commit to the tail. | |
2876 | */ | |
2877 | again: | |
2878 | max_count = cpu_buffer->nr_pages * 100; | |
2879 | ||
8573636e | 2880 | while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { |
d90fd774 SRRH |
2881 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
2882 | return; | |
2883 | if (RB_WARN_ON(cpu_buffer, | |
2884 | rb_is_reader_page(cpu_buffer->tail_page))) | |
2885 | return; | |
2886 | local_set(&cpu_buffer->commit_page->page->commit, | |
2887 | rb_page_write(cpu_buffer->commit_page)); | |
2888 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); | |
d90fd774 SRRH |
2889 | /* add barrier to keep gcc from optimizing too much */ |
2890 | barrier(); | |
2891 | } | |
2892 | while (rb_commit_index(cpu_buffer) != | |
2893 | rb_page_write(cpu_buffer->commit_page)) { | |
2894 | ||
2895 | local_set(&cpu_buffer->commit_page->page->commit, | |
2896 | rb_page_write(cpu_buffer->commit_page)); | |
2897 | RB_WARN_ON(cpu_buffer, | |
2898 | local_read(&cpu_buffer->commit_page->page->commit) & | |
2899 | ~RB_WRITE_MASK); | |
2900 | barrier(); | |
2901 | } | |
2902 | ||
2903 | /* again, keep gcc from optimizing */ | |
2904 | barrier(); | |
2905 | ||
2906 | /* | |
2907 | * If an interrupt came in just after the first while loop | |
2908 | * and pushed the tail page forward, we will be left with | |
2909 | * a dangling commit that will never go forward. | |
2910 | */ | |
8573636e | 2911 | if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) |
d90fd774 SRRH |
2912 | goto again; |
2913 | } | |
2914 | ||
38e11df1 | 2915 | static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
d90fd774 SRRH |
2916 | { |
2917 | unsigned long commits; | |
2918 | ||
2919 | if (RB_WARN_ON(cpu_buffer, | |
2920 | !local_read(&cpu_buffer->committing))) | |
2921 | return; | |
2922 | ||
2923 | again: | |
2924 | commits = local_read(&cpu_buffer->commits); | |
2925 | /* synchronize with interrupts */ | |
2926 | barrier(); | |
2927 | if (local_read(&cpu_buffer->committing) == 1) | |
2928 | rb_set_commit_to_write(cpu_buffer); | |
2929 | ||
2930 | local_dec(&cpu_buffer->committing); | |
2931 | ||
2932 | /* synchronize with interrupts */ | |
2933 | barrier(); | |
2934 | ||
2935 | /* | |
2936 | * Need to account for interrupts coming in between the | |
2937 | * updating of the commit page and the clearing of the | |
2938 | * committing counter. | |
2939 | */ | |
2940 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && | |
2941 | !local_read(&cpu_buffer->committing)) { | |
2942 | local_inc(&cpu_buffer->committing); | |
2943 | goto again; | |
2944 | } | |
2945 | } | |
2946 | ||
2947 | static inline void rb_event_discard(struct ring_buffer_event *event) | |
2948 | { | |
dc4e2801 | 2949 | if (extended_time(event)) |
d90fd774 SRRH |
2950 | event = skip_time_extend(event); |
2951 | ||
2952 | /* array[0] holds the actual length for the discarded event */ | |
2953 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; | |
2954 | event->type_len = RINGBUF_TYPE_PADDING; | |
2955 | /* time delta must be non zero */ | |
2956 | if (!event->time_delta) | |
2957 | event->time_delta = 1; | |
2958 | } | |
2959 | ||
d90fd774 SRRH |
2960 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2961 | struct ring_buffer_event *event) | |
2962 | { | |
2963 | local_inc(&cpu_buffer->entries); | |
d90fd774 SRRH |
2964 | rb_end_commit(cpu_buffer); |
2965 | } | |
2966 | ||
2967 | static __always_inline void | |
13292494 | 2968 | rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) |
d90fd774 | 2969 | { |
03329f99 SRV |
2970 | size_t nr_pages; |
2971 | size_t dirty; | |
2972 | size_t full; | |
d90fd774 SRRH |
2973 | |
2974 | if (buffer->irq_work.waiters_pending) { | |
2975 | buffer->irq_work.waiters_pending = false; | |
2976 | /* irq_work_queue() supplies it's own memory barriers */ | |
2977 | irq_work_queue(&buffer->irq_work.work); | |
2978 | } | |
2979 | ||
2980 | if (cpu_buffer->irq_work.waiters_pending) { | |
2981 | cpu_buffer->irq_work.waiters_pending = false; | |
2982 | /* irq_work_queue() supplies it's own memory barriers */ | |
2983 | irq_work_queue(&cpu_buffer->irq_work.work); | |
2984 | } | |
2985 | ||
03329f99 SRV |
2986 | if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) |
2987 | return; | |
d90fd774 | 2988 | |
03329f99 SRV |
2989 | if (cpu_buffer->reader_page == cpu_buffer->commit_page) |
2990 | return; | |
2c2b0a78 | 2991 | |
03329f99 SRV |
2992 | if (!cpu_buffer->irq_work.full_waiters_pending) |
2993 | return; | |
2c2b0a78 | 2994 | |
03329f99 SRV |
2995 | cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched); |
2996 | ||
2997 | full = cpu_buffer->shortest_full; | |
2998 | nr_pages = cpu_buffer->nr_pages; | |
2999 | dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu); | |
3000 | if (full && nr_pages && (dirty * 100) <= full * nr_pages) | |
3001 | return; | |
3002 | ||
3003 | cpu_buffer->irq_work.wakeup_full = true; | |
3004 | cpu_buffer->irq_work.full_waiters_pending = false; | |
3005 | /* irq_work_queue() supplies it's own memory barriers */ | |
3006 | irq_work_queue(&cpu_buffer->irq_work.work); | |
d90fd774 SRRH |
3007 | } |
3008 | ||
3009 | /* | |
3010 | * The lock and unlock are done within a preempt disable section. | |
3011 | * The current_context per_cpu variable can only be modified | |
3012 | * by the current task between lock and unlock. But it can | |
a0e3a18f SRV |
3013 | * be modified more than once via an interrupt. To pass this |
3014 | * information from the lock to the unlock without having to | |
3015 | * access the 'in_interrupt()' functions again (which do show | |
3016 | * a bit of overhead in something as critical as function tracing, | |
3017 | * we use a bitmask trick. | |
d90fd774 | 3018 | * |
b02414c8 SRV |
3019 | * bit 1 = NMI context |
3020 | * bit 2 = IRQ context | |
3021 | * bit 3 = SoftIRQ context | |
3022 | * bit 4 = normal context. | |
d90fd774 | 3023 | * |
a0e3a18f SRV |
3024 | * This works because this is the order of contexts that can |
3025 | * preempt other contexts. A SoftIRQ never preempts an IRQ | |
3026 | * context. | |
3027 | * | |
3028 | * When the context is determined, the corresponding bit is | |
3029 | * checked and set (if it was set, then a recursion of that context | |
3030 | * happened). | |
3031 | * | |
3032 | * On unlock, we need to clear this bit. To do so, just subtract | |
3033 | * 1 from the current_context and AND it to itself. | |
3034 | * | |
3035 | * (binary) | |
3036 | * 101 - 1 = 100 | |
3037 | * 101 & 100 = 100 (clearing bit zero) | |
3038 | * | |
3039 | * 1010 - 1 = 1001 | |
3040 | * 1010 & 1001 = 1000 (clearing bit 1) | |
3041 | * | |
3042 | * The least significant bit can be cleared this way, and it | |
3043 | * just so happens that it is the same bit corresponding to | |
3044 | * the current context. | |
b02414c8 SRV |
3045 | * |
3046 | * Now the TRANSITION bit breaks the above slightly. The TRANSITION bit | |
3047 | * is set when a recursion is detected at the current context, and if | |
3048 | * the TRANSITION bit is already set, it will fail the recursion. | |
3049 | * This is needed because there's a lag between the changing of | |
3050 | * interrupt context and updating the preempt count. In this case, | |
3051 | * a false positive will be found. To handle this, one extra recursion | |
3052 | * is allowed, and this is done by the TRANSITION bit. If the TRANSITION | |
3053 | * bit is already set, then it is considered a recursion and the function | |
3054 | * ends. Otherwise, the TRANSITION bit is set, and that bit is returned. | |
3055 | * | |
3056 | * On the trace_recursive_unlock(), the TRANSITION bit will be the first | |
3057 | * to be cleared. Even if it wasn't the context that set it. That is, | |
3058 | * if an interrupt comes in while NORMAL bit is set and the ring buffer | |
3059 | * is called before preempt_count() is updated, since the check will | |
3060 | * be on the NORMAL bit, the TRANSITION bit will then be set. If an | |
3061 | * NMI then comes in, it will set the NMI bit, but when the NMI code | |
3062 | * does the trace_recursive_unlock() it will clear the TRANSTION bit | |
3063 | * and leave the NMI bit set. But this is fine, because the interrupt | |
3064 | * code that set the TRANSITION bit will then clear the NMI bit when it | |
3065 | * calls trace_recursive_unlock(). If another NMI comes in, it will | |
3066 | * set the TRANSITION bit and continue. | |
3067 | * | |
3068 | * Note: The TRANSITION bit only handles a single transition between context. | |
d90fd774 SRRH |
3069 | */ |
3070 | ||
3071 | static __always_inline int | |
3072 | trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) | |
3073 | { | |
a0e3a18f SRV |
3074 | unsigned int val = cpu_buffer->current_context; |
3075 | unsigned long pc = preempt_count(); | |
3076 | int bit; | |
3077 | ||
3078 | if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) | |
3079 | bit = RB_CTX_NORMAL; | |
3080 | else | |
3081 | bit = pc & NMI_MASK ? RB_CTX_NMI : | |
0164e0d7 | 3082 | pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ; |
a0e3a18f | 3083 | |
b02414c8 SRV |
3084 | if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) { |
3085 | /* | |
3086 | * It is possible that this was called by transitioning | |
3087 | * between interrupt context, and preempt_count() has not | |
3088 | * been updated yet. In this case, use the TRANSITION bit. | |
3089 | */ | |
3090 | bit = RB_CTX_TRANSITION; | |
3091 | if (val & (1 << (bit + cpu_buffer->nest))) | |
3092 | return 1; | |
3093 | } | |
d90fd774 | 3094 | |
8e012066 | 3095 | val |= (1 << (bit + cpu_buffer->nest)); |
a0e3a18f | 3096 | cpu_buffer->current_context = val; |
d90fd774 SRRH |
3097 | |
3098 | return 0; | |
3099 | } | |
3100 | ||
3101 | static __always_inline void | |
3102 | trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) | |
3103 | { | |
8e012066 SRV |
3104 | cpu_buffer->current_context &= |
3105 | cpu_buffer->current_context - (1 << cpu_buffer->nest); | |
3106 | } | |
3107 | ||
b02414c8 SRV |
3108 | /* The recursive locking above uses 5 bits */ |
3109 | #define NESTED_BITS 5 | |
8e012066 SRV |
3110 | |
3111 | /** | |
3112 | * ring_buffer_nest_start - Allow to trace while nested | |
3113 | * @buffer: The ring buffer to modify | |
3114 | * | |
6167c205 | 3115 | * The ring buffer has a safety mechanism to prevent recursion. |
8e012066 SRV |
3116 | * But there may be a case where a trace needs to be done while |
3117 | * tracing something else. In this case, calling this function | |
3118 | * will allow this function to nest within a currently active | |
3119 | * ring_buffer_lock_reserve(). | |
3120 | * | |
3121 | * Call this function before calling another ring_buffer_lock_reserve() and | |
3122 | * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). | |
3123 | */ | |
13292494 | 3124 | void ring_buffer_nest_start(struct trace_buffer *buffer) |
8e012066 SRV |
3125 | { |
3126 | struct ring_buffer_per_cpu *cpu_buffer; | |
3127 | int cpu; | |
3128 | ||
3129 | /* Enabled by ring_buffer_nest_end() */ | |
3130 | preempt_disable_notrace(); | |
3131 | cpu = raw_smp_processor_id(); | |
3132 | cpu_buffer = buffer->buffers[cpu]; | |
6167c205 | 3133 | /* This is the shift value for the above recursive locking */ |
8e012066 SRV |
3134 | cpu_buffer->nest += NESTED_BITS; |
3135 | } | |
3136 | ||
3137 | /** | |
3138 | * ring_buffer_nest_end - Allow to trace while nested | |
3139 | * @buffer: The ring buffer to modify | |
3140 | * | |
3141 | * Must be called after ring_buffer_nest_start() and after the | |
3142 | * ring_buffer_unlock_commit(). | |
3143 | */ | |
13292494 | 3144 | void ring_buffer_nest_end(struct trace_buffer *buffer) |
8e012066 SRV |
3145 | { |
3146 | struct ring_buffer_per_cpu *cpu_buffer; | |
3147 | int cpu; | |
3148 | ||
3149 | /* disabled by ring_buffer_nest_start() */ | |
3150 | cpu = raw_smp_processor_id(); | |
3151 | cpu_buffer = buffer->buffers[cpu]; | |
6167c205 | 3152 | /* This is the shift value for the above recursive locking */ |
8e012066 SRV |
3153 | cpu_buffer->nest -= NESTED_BITS; |
3154 | preempt_enable_notrace(); | |
d90fd774 SRRH |
3155 | } |
3156 | ||
3157 | /** | |
3158 | * ring_buffer_unlock_commit - commit a reserved | |
3159 | * @buffer: The buffer to commit to | |
3160 | * @event: The event pointer to commit. | |
3161 | * | |
3162 | * This commits the data to the ring buffer, and releases any locks held. | |
3163 | * | |
3164 | * Must be paired with ring_buffer_lock_reserve. | |
3165 | */ | |
13292494 | 3166 | int ring_buffer_unlock_commit(struct trace_buffer *buffer, |
d90fd774 SRRH |
3167 | struct ring_buffer_event *event) |
3168 | { | |
3169 | struct ring_buffer_per_cpu *cpu_buffer; | |
3170 | int cpu = raw_smp_processor_id(); | |
3171 | ||
3172 | cpu_buffer = buffer->buffers[cpu]; | |
3173 | ||
3174 | rb_commit(cpu_buffer, event); | |
3175 | ||
3176 | rb_wakeups(buffer, cpu_buffer); | |
3177 | ||
3178 | trace_recursive_unlock(cpu_buffer); | |
3179 | ||
3180 | preempt_enable_notrace(); | |
3181 | ||
3182 | return 0; | |
3183 | } | |
3184 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); | |
3185 | ||
6634ff26 SR |
3186 | static struct ring_buffer_event * |
3187 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, | |
fcc742ea | 3188 | struct rb_event_info *info) |
6634ff26 | 3189 | { |
6634ff26 | 3190 | struct ring_buffer_event *event; |
fcc742ea | 3191 | struct buffer_page *tail_page; |
a389d86f | 3192 | unsigned long tail, write, w; |
10464b4a SRV |
3193 | bool a_ok; |
3194 | bool b_ok; | |
69d1b839 | 3195 | |
8573636e SRRH |
3196 | /* Don't let the compiler play games with cpu_buffer->tail_page */ |
3197 | tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); | |
a389d86f SRV |
3198 | |
3199 | /*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK; | |
3200 | barrier(); | |
58fbc3c6 SRV |
3201 | b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before); |
3202 | a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); | |
a389d86f SRV |
3203 | barrier(); |
3204 | info->ts = rb_time_stamp(cpu_buffer->buffer); | |
3205 | ||
58fbc3c6 | 3206 | if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) { |
a389d86f | 3207 | info->delta = info->ts; |
a389d86f | 3208 | } else { |
58fbc3c6 SRV |
3209 | /* |
3210 | * If interrupting an event time update, we may need an | |
3211 | * absolute timestamp. | |
3212 | * Don't bother if this is the start of a new page (w == 0). | |
3213 | */ | |
3214 | if (unlikely(!a_ok || !b_ok || (info->before != info->after && w))) { | |
3215 | info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND; | |
3216 | info->length += RB_LEN_TIME_EXTEND; | |
3217 | } else { | |
3218 | info->delta = info->ts - info->after; | |
3219 | if (unlikely(test_time_stamp(info->delta))) { | |
3220 | info->add_timestamp |= RB_ADD_STAMP_EXTEND; | |
3221 | info->length += RB_LEN_TIME_EXTEND; | |
3222 | } | |
10464b4a | 3223 | } |
7c4b4a51 | 3224 | } |
b7dc42fd | 3225 | |
10464b4a | 3226 | /*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts); |
a389d86f SRV |
3227 | |
3228 | /*C*/ write = local_add_return(info->length, &tail_page->write); | |
77ae365e SR |
3229 | |
3230 | /* set write to only the index of the write */ | |
3231 | write &= RB_WRITE_MASK; | |
a389d86f | 3232 | |
fcc742ea | 3233 | tail = write - info->length; |
6634ff26 | 3234 | |
a389d86f SRV |
3235 | /* See if we shot pass the end of this buffer page */ |
3236 | if (unlikely(write > BUF_PAGE_SIZE)) { | |
3237 | if (tail != w) { | |
3238 | /* before and after may now different, fix it up*/ | |
58fbc3c6 SRV |
3239 | b_ok = rb_time_read(&cpu_buffer->before_stamp, &info->before); |
3240 | a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); | |
3241 | if (a_ok && b_ok && info->before != info->after) | |
3242 | (void)rb_time_cmpxchg(&cpu_buffer->before_stamp, | |
3243 | info->before, info->after); | |
a389d86f SRV |
3244 | } |
3245 | return rb_move_tail(cpu_buffer, tail, info); | |
3246 | } | |
3247 | ||
3248 | if (likely(tail == w)) { | |
3249 | u64 save_before; | |
10464b4a | 3250 | bool s_ok; |
a389d86f SRV |
3251 | |
3252 | /* Nothing interrupted us between A and C */ | |
10464b4a | 3253 | /*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts); |
a389d86f | 3254 | barrier(); |
10464b4a SRV |
3255 | /*E*/ s_ok = rb_time_read(&cpu_buffer->before_stamp, &save_before); |
3256 | RB_WARN_ON(cpu_buffer, !s_ok); | |
7c4b4a51 SRV |
3257 | if (likely(!(info->add_timestamp & |
3258 | (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) | |
a389d86f | 3259 | /* This did not interrupt any time update */ |
58fbc3c6 | 3260 | info->delta = info->ts - info->after; |
a389d86f SRV |
3261 | else |
3262 | /* Just use full timestamp for inerrupting event */ | |
3263 | info->delta = info->ts; | |
3264 | barrier(); | |
3265 | if (unlikely(info->ts != save_before)) { | |
3266 | /* SLOW PATH - Interrupted between C and E */ | |
3267 | ||
58fbc3c6 | 3268 | a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); |
10464b4a SRV |
3269 | RB_WARN_ON(cpu_buffer, !a_ok); |
3270 | ||
a389d86f | 3271 | /* Write stamp must only go forward */ |
58fbc3c6 | 3272 | if (save_before > info->after) { |
a389d86f SRV |
3273 | /* |
3274 | * We do not care about the result, only that | |
3275 | * it gets updated atomically. | |
3276 | */ | |
58fbc3c6 SRV |
3277 | (void)rb_time_cmpxchg(&cpu_buffer->write_stamp, |
3278 | info->after, save_before); | |
a389d86f SRV |
3279 | } |
3280 | } | |
3281 | } else { | |
3282 | u64 ts; | |
3283 | /* SLOW PATH - Interrupted between A and C */ | |
58fbc3c6 | 3284 | a_ok = rb_time_read(&cpu_buffer->write_stamp, &info->after); |
10464b4a SRV |
3285 | /* Was interrupted before here, write_stamp must be valid */ |
3286 | RB_WARN_ON(cpu_buffer, !a_ok); | |
a389d86f SRV |
3287 | ts = rb_time_stamp(cpu_buffer->buffer); |
3288 | barrier(); | |
3289 | /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) && | |
8785f51a AR |
3290 | info->after < ts && |
3291 | rb_time_cmpxchg(&cpu_buffer->write_stamp, | |
3292 | info->after, ts)) { | |
a389d86f | 3293 | /* Nothing came after this event between C and E */ |
58fbc3c6 | 3294 | info->delta = ts - info->after; |
a389d86f SRV |
3295 | info->ts = ts; |
3296 | } else { | |
3297 | /* | |
3298 | * Interrupted beween C and E: | |
3299 | * Lost the previous events time stamp. Just set the | |
3300 | * delta to zero, and this will be the same time as | |
3301 | * the event this event interrupted. And the events that | |
3302 | * came after this will still be correct (as they would | |
3303 | * have built their delta on the previous event. | |
3304 | */ | |
3305 | info->delta = 0; | |
3306 | } | |
7c4b4a51 | 3307 | info->add_timestamp &= ~RB_ADD_STAMP_FORCE; |
a389d86f SRV |
3308 | } |
3309 | ||
6634ff26 | 3310 | /* |
a4543a2f | 3311 | * If this is the first commit on the page, then it has the same |
b7dc42fd | 3312 | * timestamp as the page itself. |
6634ff26 | 3313 | */ |
7c4b4a51 SRV |
3314 | if (unlikely(!tail && !(info->add_timestamp & |
3315 | (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)))) | |
a4543a2f SRRH |
3316 | info->delta = 0; |
3317 | ||
b7dc42fd SRRH |
3318 | /* We reserved something on the buffer */ |
3319 | ||
3320 | event = __rb_page_index(tail_page, tail); | |
a4543a2f SRRH |
3321 | rb_update_event(cpu_buffer, event, info); |
3322 | ||
3323 | local_inc(&tail_page->entries); | |
6634ff26 | 3324 | |
b7dc42fd SRRH |
3325 | /* |
3326 | * If this is the first commit on the page, then update | |
3327 | * its timestamp. | |
3328 | */ | |
75b21c6d | 3329 | if (unlikely(!tail)) |
b7dc42fd SRRH |
3330 | tail_page->page->time_stamp = info->ts; |
3331 | ||
c64e148a | 3332 | /* account for these added bytes */ |
fcc742ea | 3333 | local_add(info->length, &cpu_buffer->entries_bytes); |
c64e148a | 3334 | |
6634ff26 SR |
3335 | return event; |
3336 | } | |
3337 | ||
fa7ffb39 | 3338 | static __always_inline struct ring_buffer_event * |
13292494 | 3339 | rb_reserve_next_event(struct trace_buffer *buffer, |
62f0b3eb | 3340 | struct ring_buffer_per_cpu *cpu_buffer, |
1cd8d735 | 3341 | unsigned long length) |
7a8e76a3 SR |
3342 | { |
3343 | struct ring_buffer_event *event; | |
fcc742ea | 3344 | struct rb_event_info info; |
818e3dd3 | 3345 | int nr_loops = 0; |
58fbc3c6 | 3346 | int add_ts_default; |
7a8e76a3 | 3347 | |
fa743953 | 3348 | rb_start_commit(cpu_buffer); |
a389d86f | 3349 | /* The commit page can not change after this */ |
fa743953 | 3350 | |
85bac32c | 3351 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
62f0b3eb SR |
3352 | /* |
3353 | * Due to the ability to swap a cpu buffer from a buffer | |
3354 | * it is possible it was swapped before we committed. | |
3355 | * (committing stops a swap). We check for it here and | |
3356 | * if it happened, we have to fail the write. | |
3357 | */ | |
3358 | barrier(); | |
6aa7de05 | 3359 | if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { |
62f0b3eb SR |
3360 | local_dec(&cpu_buffer->committing); |
3361 | local_dec(&cpu_buffer->commits); | |
3362 | return NULL; | |
3363 | } | |
85bac32c | 3364 | #endif |
b7dc42fd | 3365 | |
fcc742ea | 3366 | info.length = rb_calculate_event_length(length); |
58fbc3c6 SRV |
3367 | |
3368 | if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) { | |
3369 | add_ts_default = RB_ADD_STAMP_ABSOLUTE; | |
3370 | info.length += RB_LEN_TIME_EXTEND; | |
3371 | } else { | |
3372 | add_ts_default = RB_ADD_STAMP_NONE; | |
3373 | } | |
3374 | ||
a4543a2f | 3375 | again: |
58fbc3c6 | 3376 | info.add_timestamp = add_ts_default; |
b7dc42fd SRRH |
3377 | info.delta = 0; |
3378 | ||
818e3dd3 SR |
3379 | /* |
3380 | * We allow for interrupts to reenter here and do a trace. | |
3381 | * If one does, it will cause this original code to loop | |
3382 | * back here. Even with heavy interrupts happening, this | |
3383 | * should only happen a few times in a row. If this happens | |
3384 | * 1000 times in a row, there must be either an interrupt | |
3385 | * storm or we have something buggy. | |
3386 | * Bail! | |
3387 | */ | |
3e89c7bb | 3388 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
fa743953 | 3389 | goto out_fail; |
818e3dd3 | 3390 | |
fcc742ea SRRH |
3391 | event = __rb_reserve_next(cpu_buffer, &info); |
3392 | ||
bd1b7cd3 | 3393 | if (unlikely(PTR_ERR(event) == -EAGAIN)) { |
58fbc3c6 | 3394 | if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND)) |
bd1b7cd3 | 3395 | info.length -= RB_LEN_TIME_EXTEND; |
bf41a158 | 3396 | goto again; |
bd1b7cd3 | 3397 | } |
bf41a158 | 3398 | |
a389d86f SRV |
3399 | if (likely(event)) |
3400 | return event; | |
fa743953 SR |
3401 | out_fail: |
3402 | rb_end_commit(cpu_buffer); | |
3403 | return NULL; | |
7a8e76a3 SR |
3404 | } |
3405 | ||
3406 | /** | |
3407 | * ring_buffer_lock_reserve - reserve a part of the buffer | |
3408 | * @buffer: the ring buffer to reserve from | |
3409 | * @length: the length of the data to reserve (excluding event header) | |
7a8e76a3 | 3410 | * |
6167c205 | 3411 | * Returns a reserved event on the ring buffer to copy directly to. |
7a8e76a3 SR |
3412 | * The user of this interface will need to get the body to write into |
3413 | * and can use the ring_buffer_event_data() interface. | |
3414 | * | |
3415 | * The length is the length of the data needed, not the event length | |
3416 | * which also includes the event header. | |
3417 | * | |
3418 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. | |
3419 | * If NULL is returned, then nothing has been allocated or locked. | |
3420 | */ | |
3421 | struct ring_buffer_event * | |
13292494 | 3422 | ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length) |
7a8e76a3 SR |
3423 | { |
3424 | struct ring_buffer_per_cpu *cpu_buffer; | |
3425 | struct ring_buffer_event *event; | |
5168ae50 | 3426 | int cpu; |
7a8e76a3 | 3427 | |
bf41a158 | 3428 | /* If we are tracing schedule, we don't want to recurse */ |
5168ae50 | 3429 | preempt_disable_notrace(); |
bf41a158 | 3430 | |
3205f806 | 3431 | if (unlikely(atomic_read(&buffer->record_disabled))) |
58a09ec6 | 3432 | goto out; |
261842b7 | 3433 | |
7a8e76a3 SR |
3434 | cpu = raw_smp_processor_id(); |
3435 | ||
3205f806 | 3436 | if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
d769041f | 3437 | goto out; |
7a8e76a3 SR |
3438 | |
3439 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 3440 | |
3205f806 | 3441 | if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
d769041f | 3442 | goto out; |
7a8e76a3 | 3443 | |
3205f806 | 3444 | if (unlikely(length > BUF_MAX_DATA_SIZE)) |
bf41a158 | 3445 | goto out; |
7a8e76a3 | 3446 | |
58a09ec6 SRRH |
3447 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
3448 | goto out; | |
3449 | ||
62f0b3eb | 3450 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 3451 | if (!event) |
58a09ec6 | 3452 | goto out_unlock; |
7a8e76a3 SR |
3453 | |
3454 | return event; | |
3455 | ||
58a09ec6 SRRH |
3456 | out_unlock: |
3457 | trace_recursive_unlock(cpu_buffer); | |
d769041f | 3458 | out: |
5168ae50 | 3459 | preempt_enable_notrace(); |
7a8e76a3 SR |
3460 | return NULL; |
3461 | } | |
c4f50183 | 3462 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
7a8e76a3 | 3463 | |
a1863c21 SR |
3464 | /* |
3465 | * Decrement the entries to the page that an event is on. | |
3466 | * The event does not even need to exist, only the pointer | |
3467 | * to the page it is on. This may only be called before the commit | |
3468 | * takes place. | |
3469 | */ | |
3470 | static inline void | |
3471 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, | |
3472 | struct ring_buffer_event *event) | |
3473 | { | |
3474 | unsigned long addr = (unsigned long)event; | |
3475 | struct buffer_page *bpage = cpu_buffer->commit_page; | |
3476 | struct buffer_page *start; | |
3477 | ||
3478 | addr &= PAGE_MASK; | |
3479 | ||
3480 | /* Do the likely case first */ | |
3481 | if (likely(bpage->page == (void *)addr)) { | |
3482 | local_dec(&bpage->entries); | |
3483 | return; | |
3484 | } | |
3485 | ||
3486 | /* | |
3487 | * Because the commit page may be on the reader page we | |
3488 | * start with the next page and check the end loop there. | |
3489 | */ | |
3490 | rb_inc_page(cpu_buffer, &bpage); | |
3491 | start = bpage; | |
3492 | do { | |
3493 | if (bpage->page == (void *)addr) { | |
3494 | local_dec(&bpage->entries); | |
3495 | return; | |
3496 | } | |
3497 | rb_inc_page(cpu_buffer, &bpage); | |
3498 | } while (bpage != start); | |
3499 | ||
3500 | /* commit not part of this buffer?? */ | |
3501 | RB_WARN_ON(cpu_buffer, 1); | |
3502 | } | |
3503 | ||
fa1b47dd SR |
3504 | /** |
3505 | * ring_buffer_commit_discard - discard an event that has not been committed | |
3506 | * @buffer: the ring buffer | |
3507 | * @event: non committed event to discard | |
3508 | * | |
dc892f73 SR |
3509 | * Sometimes an event that is in the ring buffer needs to be ignored. |
3510 | * This function lets the user discard an event in the ring buffer | |
3511 | * and then that event will not be read later. | |
3512 | * | |
6167c205 | 3513 | * This function only works if it is called before the item has been |
dc892f73 | 3514 | * committed. It will try to free the event from the ring buffer |
fa1b47dd SR |
3515 | * if another event has not been added behind it. |
3516 | * | |
3517 | * If another event has been added behind it, it will set the event | |
3518 | * up as discarded, and perform the commit. | |
3519 | * | |
3520 | * If this function is called, do not call ring_buffer_unlock_commit on | |
3521 | * the event. | |
3522 | */ | |
13292494 | 3523 | void ring_buffer_discard_commit(struct trace_buffer *buffer, |
fa1b47dd SR |
3524 | struct ring_buffer_event *event) |
3525 | { | |
3526 | struct ring_buffer_per_cpu *cpu_buffer; | |
fa1b47dd SR |
3527 | int cpu; |
3528 | ||
3529 | /* The event is discarded regardless */ | |
f3b9aae1 | 3530 | rb_event_discard(event); |
fa1b47dd | 3531 | |
fa743953 SR |
3532 | cpu = smp_processor_id(); |
3533 | cpu_buffer = buffer->buffers[cpu]; | |
3534 | ||
fa1b47dd SR |
3535 | /* |
3536 | * This must only be called if the event has not been | |
3537 | * committed yet. Thus we can assume that preemption | |
3538 | * is still disabled. | |
3539 | */ | |
fa743953 | 3540 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
fa1b47dd | 3541 | |
a1863c21 | 3542 | rb_decrement_entry(cpu_buffer, event); |
0f2541d2 | 3543 | if (rb_try_to_discard(cpu_buffer, event)) |
edd813bf | 3544 | goto out; |
fa1b47dd | 3545 | |
fa1b47dd | 3546 | out: |
fa743953 | 3547 | rb_end_commit(cpu_buffer); |
fa1b47dd | 3548 | |
58a09ec6 | 3549 | trace_recursive_unlock(cpu_buffer); |
f3b9aae1 | 3550 | |
5168ae50 | 3551 | preempt_enable_notrace(); |
fa1b47dd SR |
3552 | |
3553 | } | |
3554 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); | |
3555 | ||
7a8e76a3 SR |
3556 | /** |
3557 | * ring_buffer_write - write data to the buffer without reserving | |
3558 | * @buffer: The ring buffer to write to. | |
3559 | * @length: The length of the data being written (excluding the event header) | |
3560 | * @data: The data to write to the buffer. | |
3561 | * | |
3562 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as | |
3563 | * one function. If you already have the data to write to the buffer, it | |
3564 | * may be easier to simply call this function. | |
3565 | * | |
3566 | * Note, like ring_buffer_lock_reserve, the length is the length of the data | |
3567 | * and not the length of the event which would hold the header. | |
3568 | */ | |
13292494 | 3569 | int ring_buffer_write(struct trace_buffer *buffer, |
01e3e710 DS |
3570 | unsigned long length, |
3571 | void *data) | |
7a8e76a3 SR |
3572 | { |
3573 | struct ring_buffer_per_cpu *cpu_buffer; | |
3574 | struct ring_buffer_event *event; | |
7a8e76a3 SR |
3575 | void *body; |
3576 | int ret = -EBUSY; | |
5168ae50 | 3577 | int cpu; |
7a8e76a3 | 3578 | |
5168ae50 | 3579 | preempt_disable_notrace(); |
bf41a158 | 3580 | |
52fbe9cd LJ |
3581 | if (atomic_read(&buffer->record_disabled)) |
3582 | goto out; | |
3583 | ||
7a8e76a3 SR |
3584 | cpu = raw_smp_processor_id(); |
3585 | ||
9e01c1b7 | 3586 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
d769041f | 3587 | goto out; |
7a8e76a3 SR |
3588 | |
3589 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
3590 | |
3591 | if (atomic_read(&cpu_buffer->record_disabled)) | |
3592 | goto out; | |
3593 | ||
be957c44 SR |
3594 | if (length > BUF_MAX_DATA_SIZE) |
3595 | goto out; | |
3596 | ||
985e871b SRRH |
3597 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
3598 | goto out; | |
3599 | ||
62f0b3eb | 3600 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 3601 | if (!event) |
985e871b | 3602 | goto out_unlock; |
7a8e76a3 SR |
3603 | |
3604 | body = rb_event_data(event); | |
3605 | ||
3606 | memcpy(body, data, length); | |
3607 | ||
3608 | rb_commit(cpu_buffer, event); | |
3609 | ||
15693458 SRRH |
3610 | rb_wakeups(buffer, cpu_buffer); |
3611 | ||
7a8e76a3 | 3612 | ret = 0; |
985e871b SRRH |
3613 | |
3614 | out_unlock: | |
3615 | trace_recursive_unlock(cpu_buffer); | |
3616 | ||
7a8e76a3 | 3617 | out: |
5168ae50 | 3618 | preempt_enable_notrace(); |
7a8e76a3 SR |
3619 | |
3620 | return ret; | |
3621 | } | |
c4f50183 | 3622 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
7a8e76a3 | 3623 | |
da58834c | 3624 | static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
bf41a158 SR |
3625 | { |
3626 | struct buffer_page *reader = cpu_buffer->reader_page; | |
77ae365e | 3627 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
bf41a158 SR |
3628 | struct buffer_page *commit = cpu_buffer->commit_page; |
3629 | ||
77ae365e SR |
3630 | /* In case of error, head will be NULL */ |
3631 | if (unlikely(!head)) | |
da58834c | 3632 | return true; |
77ae365e | 3633 | |
bf41a158 SR |
3634 | return reader->read == rb_page_commit(reader) && |
3635 | (commit == reader || | |
3636 | (commit == head && | |
3637 | head->read == rb_page_commit(commit))); | |
3638 | } | |
3639 | ||
7a8e76a3 SR |
3640 | /** |
3641 | * ring_buffer_record_disable - stop all writes into the buffer | |
3642 | * @buffer: The ring buffer to stop writes to. | |
3643 | * | |
3644 | * This prevents all writes to the buffer. Any attempt to write | |
3645 | * to the buffer after this will fail and return NULL. | |
3646 | * | |
74401729 | 3647 | * The caller should call synchronize_rcu() after this. |
7a8e76a3 | 3648 | */ |
13292494 | 3649 | void ring_buffer_record_disable(struct trace_buffer *buffer) |
7a8e76a3 SR |
3650 | { |
3651 | atomic_inc(&buffer->record_disabled); | |
3652 | } | |
c4f50183 | 3653 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
7a8e76a3 SR |
3654 | |
3655 | /** | |
3656 | * ring_buffer_record_enable - enable writes to the buffer | |
3657 | * @buffer: The ring buffer to enable writes | |
3658 | * | |
3659 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3660 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 | 3661 | */ |
13292494 | 3662 | void ring_buffer_record_enable(struct trace_buffer *buffer) |
7a8e76a3 SR |
3663 | { |
3664 | atomic_dec(&buffer->record_disabled); | |
3665 | } | |
c4f50183 | 3666 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
7a8e76a3 | 3667 | |
499e5470 SR |
3668 | /** |
3669 | * ring_buffer_record_off - stop all writes into the buffer | |
3670 | * @buffer: The ring buffer to stop writes to. | |
3671 | * | |
3672 | * This prevents all writes to the buffer. Any attempt to write | |
3673 | * to the buffer after this will fail and return NULL. | |
3674 | * | |
3675 | * This is different than ring_buffer_record_disable() as | |
87abb3b1 | 3676 | * it works like an on/off switch, where as the disable() version |
499e5470 SR |
3677 | * must be paired with a enable(). |
3678 | */ | |
13292494 | 3679 | void ring_buffer_record_off(struct trace_buffer *buffer) |
499e5470 SR |
3680 | { |
3681 | unsigned int rd; | |
3682 | unsigned int new_rd; | |
3683 | ||
3684 | do { | |
3685 | rd = atomic_read(&buffer->record_disabled); | |
3686 | new_rd = rd | RB_BUFFER_OFF; | |
3687 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3688 | } | |
3689 | EXPORT_SYMBOL_GPL(ring_buffer_record_off); | |
3690 | ||
3691 | /** | |
3692 | * ring_buffer_record_on - restart writes into the buffer | |
3693 | * @buffer: The ring buffer to start writes to. | |
3694 | * | |
3695 | * This enables all writes to the buffer that was disabled by | |
3696 | * ring_buffer_record_off(). | |
3697 | * | |
3698 | * This is different than ring_buffer_record_enable() as | |
87abb3b1 | 3699 | * it works like an on/off switch, where as the enable() version |
499e5470 SR |
3700 | * must be paired with a disable(). |
3701 | */ | |
13292494 | 3702 | void ring_buffer_record_on(struct trace_buffer *buffer) |
499e5470 SR |
3703 | { |
3704 | unsigned int rd; | |
3705 | unsigned int new_rd; | |
3706 | ||
3707 | do { | |
3708 | rd = atomic_read(&buffer->record_disabled); | |
3709 | new_rd = rd & ~RB_BUFFER_OFF; | |
3710 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3711 | } | |
3712 | EXPORT_SYMBOL_GPL(ring_buffer_record_on); | |
3713 | ||
3714 | /** | |
3715 | * ring_buffer_record_is_on - return true if the ring buffer can write | |
3716 | * @buffer: The ring buffer to see if write is enabled | |
3717 | * | |
3718 | * Returns true if the ring buffer is in a state that it accepts writes. | |
3719 | */ | |
13292494 | 3720 | bool ring_buffer_record_is_on(struct trace_buffer *buffer) |
499e5470 SR |
3721 | { |
3722 | return !atomic_read(&buffer->record_disabled); | |
3723 | } | |
3724 | ||
73c8d894 MH |
3725 | /** |
3726 | * ring_buffer_record_is_set_on - return true if the ring buffer is set writable | |
3727 | * @buffer: The ring buffer to see if write is set enabled | |
3728 | * | |
3729 | * Returns true if the ring buffer is set writable by ring_buffer_record_on(). | |
3730 | * Note that this does NOT mean it is in a writable state. | |
3731 | * | |
3732 | * It may return true when the ring buffer has been disabled by | |
3733 | * ring_buffer_record_disable(), as that is a temporary disabling of | |
3734 | * the ring buffer. | |
3735 | */ | |
13292494 | 3736 | bool ring_buffer_record_is_set_on(struct trace_buffer *buffer) |
73c8d894 MH |
3737 | { |
3738 | return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); | |
3739 | } | |
3740 | ||
7a8e76a3 SR |
3741 | /** |
3742 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer | |
3743 | * @buffer: The ring buffer to stop writes to. | |
3744 | * @cpu: The CPU buffer to stop | |
3745 | * | |
3746 | * This prevents all writes to the buffer. Any attempt to write | |
3747 | * to the buffer after this will fail and return NULL. | |
3748 | * | |
74401729 | 3749 | * The caller should call synchronize_rcu() after this. |
7a8e76a3 | 3750 | */ |
13292494 | 3751 | void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu) |
7a8e76a3 SR |
3752 | { |
3753 | struct ring_buffer_per_cpu *cpu_buffer; | |
3754 | ||
9e01c1b7 | 3755 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3756 | return; |
7a8e76a3 SR |
3757 | |
3758 | cpu_buffer = buffer->buffers[cpu]; | |
3759 | atomic_inc(&cpu_buffer->record_disabled); | |
3760 | } | |
c4f50183 | 3761 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
7a8e76a3 SR |
3762 | |
3763 | /** | |
3764 | * ring_buffer_record_enable_cpu - enable writes to the buffer | |
3765 | * @buffer: The ring buffer to enable writes | |
3766 | * @cpu: The CPU to enable. | |
3767 | * | |
3768 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3769 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 | 3770 | */ |
13292494 | 3771 | void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu) |
7a8e76a3 SR |
3772 | { |
3773 | struct ring_buffer_per_cpu *cpu_buffer; | |
3774 | ||
9e01c1b7 | 3775 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3776 | return; |
7a8e76a3 SR |
3777 | |
3778 | cpu_buffer = buffer->buffers[cpu]; | |
3779 | atomic_dec(&cpu_buffer->record_disabled); | |
3780 | } | |
c4f50183 | 3781 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
7a8e76a3 | 3782 | |
f6195aa0 SR |
3783 | /* |
3784 | * The total entries in the ring buffer is the running counter | |
3785 | * of entries entered into the ring buffer, minus the sum of | |
3786 | * the entries read from the ring buffer and the number of | |
3787 | * entries that were overwritten. | |
3788 | */ | |
3789 | static inline unsigned long | |
3790 | rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) | |
3791 | { | |
3792 | return local_read(&cpu_buffer->entries) - | |
3793 | (local_read(&cpu_buffer->overrun) + cpu_buffer->read); | |
3794 | } | |
3795 | ||
c64e148a VN |
3796 | /** |
3797 | * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer | |
3798 | * @buffer: The ring buffer | |
3799 | * @cpu: The per CPU buffer to read from. | |
3800 | */ | |
13292494 | 3801 | u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu) |
c64e148a VN |
3802 | { |
3803 | unsigned long flags; | |
3804 | struct ring_buffer_per_cpu *cpu_buffer; | |
3805 | struct buffer_page *bpage; | |
da830e58 | 3806 | u64 ret = 0; |
c64e148a VN |
3807 | |
3808 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3809 | return 0; | |
3810 | ||
3811 | cpu_buffer = buffer->buffers[cpu]; | |
7115e3fc | 3812 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3813 | /* |
3814 | * if the tail is on reader_page, oldest time stamp is on the reader | |
3815 | * page | |
3816 | */ | |
3817 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
3818 | bpage = cpu_buffer->reader_page; | |
3819 | else | |
3820 | bpage = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3821 | if (bpage) |
3822 | ret = bpage->page->time_stamp; | |
7115e3fc | 3823 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3824 | |
3825 | return ret; | |
3826 | } | |
3827 | EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); | |
3828 | ||
3829 | /** | |
3830 | * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer | |
3831 | * @buffer: The ring buffer | |
3832 | * @cpu: The per CPU buffer to read from. | |
3833 | */ | |
13292494 | 3834 | unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu) |
c64e148a VN |
3835 | { |
3836 | struct ring_buffer_per_cpu *cpu_buffer; | |
3837 | unsigned long ret; | |
3838 | ||
3839 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3840 | return 0; | |
3841 | ||
3842 | cpu_buffer = buffer->buffers[cpu]; | |
3843 | ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; | |
3844 | ||
3845 | return ret; | |
3846 | } | |
3847 | EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); | |
3848 | ||
7a8e76a3 SR |
3849 | /** |
3850 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer | |
3851 | * @buffer: The ring buffer | |
3852 | * @cpu: The per CPU buffer to get the entries from. | |
3853 | */ | |
13292494 | 3854 | unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu) |
7a8e76a3 SR |
3855 | { |
3856 | struct ring_buffer_per_cpu *cpu_buffer; | |
3857 | ||
9e01c1b7 | 3858 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3859 | return 0; |
7a8e76a3 SR |
3860 | |
3861 | cpu_buffer = buffer->buffers[cpu]; | |
554f786e | 3862 | |
f6195aa0 | 3863 | return rb_num_of_entries(cpu_buffer); |
7a8e76a3 | 3864 | } |
c4f50183 | 3865 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
7a8e76a3 SR |
3866 | |
3867 | /** | |
884bfe89 SP |
3868 | * ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
3869 | * buffer wrapping around (only if RB_FL_OVERWRITE is on). | |
7a8e76a3 SR |
3870 | * @buffer: The ring buffer |
3871 | * @cpu: The per CPU buffer to get the number of overruns from | |
3872 | */ | |
13292494 | 3873 | unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu) |
7a8e76a3 SR |
3874 | { |
3875 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 3876 | unsigned long ret; |
7a8e76a3 | 3877 | |
9e01c1b7 | 3878 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3879 | return 0; |
7a8e76a3 SR |
3880 | |
3881 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3882 | ret = local_read(&cpu_buffer->overrun); |
554f786e SR |
3883 | |
3884 | return ret; | |
7a8e76a3 | 3885 | } |
c4f50183 | 3886 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
7a8e76a3 | 3887 | |
f0d2c681 | 3888 | /** |
884bfe89 SP |
3889 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by |
3890 | * commits failing due to the buffer wrapping around while there are uncommitted | |
3891 | * events, such as during an interrupt storm. | |
f0d2c681 SR |
3892 | * @buffer: The ring buffer |
3893 | * @cpu: The per CPU buffer to get the number of overruns from | |
3894 | */ | |
3895 | unsigned long | |
13292494 | 3896 | ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu) |
f0d2c681 SR |
3897 | { |
3898 | struct ring_buffer_per_cpu *cpu_buffer; | |
3899 | unsigned long ret; | |
3900 | ||
3901 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3902 | return 0; | |
3903 | ||
3904 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3905 | ret = local_read(&cpu_buffer->commit_overrun); |
f0d2c681 SR |
3906 | |
3907 | return ret; | |
3908 | } | |
3909 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); | |
3910 | ||
884bfe89 SP |
3911 | /** |
3912 | * ring_buffer_dropped_events_cpu - get the number of dropped events caused by | |
3913 | * the ring buffer filling up (only if RB_FL_OVERWRITE is off). | |
3914 | * @buffer: The ring buffer | |
3915 | * @cpu: The per CPU buffer to get the number of overruns from | |
3916 | */ | |
3917 | unsigned long | |
13292494 | 3918 | ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu) |
884bfe89 SP |
3919 | { |
3920 | struct ring_buffer_per_cpu *cpu_buffer; | |
3921 | unsigned long ret; | |
3922 | ||
3923 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3924 | return 0; | |
3925 | ||
3926 | cpu_buffer = buffer->buffers[cpu]; | |
3927 | ret = local_read(&cpu_buffer->dropped_events); | |
3928 | ||
3929 | return ret; | |
3930 | } | |
3931 | EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); | |
3932 | ||
ad964704 SRRH |
3933 | /** |
3934 | * ring_buffer_read_events_cpu - get the number of events successfully read | |
3935 | * @buffer: The ring buffer | |
3936 | * @cpu: The per CPU buffer to get the number of events read | |
3937 | */ | |
3938 | unsigned long | |
13292494 | 3939 | ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu) |
ad964704 SRRH |
3940 | { |
3941 | struct ring_buffer_per_cpu *cpu_buffer; | |
3942 | ||
3943 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3944 | return 0; | |
3945 | ||
3946 | cpu_buffer = buffer->buffers[cpu]; | |
3947 | return cpu_buffer->read; | |
3948 | } | |
3949 | EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); | |
3950 | ||
7a8e76a3 SR |
3951 | /** |
3952 | * ring_buffer_entries - get the number of entries in a buffer | |
3953 | * @buffer: The ring buffer | |
3954 | * | |
3955 | * Returns the total number of entries in the ring buffer | |
3956 | * (all CPU entries) | |
3957 | */ | |
13292494 | 3958 | unsigned long ring_buffer_entries(struct trace_buffer *buffer) |
7a8e76a3 SR |
3959 | { |
3960 | struct ring_buffer_per_cpu *cpu_buffer; | |
3961 | unsigned long entries = 0; | |
3962 | int cpu; | |
3963 | ||
3964 | /* if you care about this being correct, lock the buffer */ | |
3965 | for_each_buffer_cpu(buffer, cpu) { | |
3966 | cpu_buffer = buffer->buffers[cpu]; | |
f6195aa0 | 3967 | entries += rb_num_of_entries(cpu_buffer); |
7a8e76a3 SR |
3968 | } |
3969 | ||
3970 | return entries; | |
3971 | } | |
c4f50183 | 3972 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
7a8e76a3 SR |
3973 | |
3974 | /** | |
67b394f7 | 3975 | * ring_buffer_overruns - get the number of overruns in buffer |
7a8e76a3 SR |
3976 | * @buffer: The ring buffer |
3977 | * | |
3978 | * Returns the total number of overruns in the ring buffer | |
3979 | * (all CPU entries) | |
3980 | */ | |
13292494 | 3981 | unsigned long ring_buffer_overruns(struct trace_buffer *buffer) |
7a8e76a3 SR |
3982 | { |
3983 | struct ring_buffer_per_cpu *cpu_buffer; | |
3984 | unsigned long overruns = 0; | |
3985 | int cpu; | |
3986 | ||
3987 | /* if you care about this being correct, lock the buffer */ | |
3988 | for_each_buffer_cpu(buffer, cpu) { | |
3989 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3990 | overruns += local_read(&cpu_buffer->overrun); |
7a8e76a3 SR |
3991 | } |
3992 | ||
3993 | return overruns; | |
3994 | } | |
c4f50183 | 3995 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
7a8e76a3 | 3996 | |
642edba5 | 3997 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
7a8e76a3 SR |
3998 | { |
3999 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
4000 | ||
d769041f | 4001 | /* Iterator usage is expected to have record disabled */ |
651e22f2 SRRH |
4002 | iter->head_page = cpu_buffer->reader_page; |
4003 | iter->head = cpu_buffer->reader_page->read; | |
785888c5 | 4004 | iter->next_event = iter->head; |
651e22f2 SRRH |
4005 | |
4006 | iter->cache_reader_page = iter->head_page; | |
24607f11 | 4007 | iter->cache_read = cpu_buffer->read; |
651e22f2 | 4008 | |
28e3fc56 | 4009 | if (iter->head) { |
d769041f | 4010 | iter->read_stamp = cpu_buffer->read_stamp; |
28e3fc56 SRV |
4011 | iter->page_stamp = cpu_buffer->reader_page->page->time_stamp; |
4012 | } else { | |
abc9b56d | 4013 | iter->read_stamp = iter->head_page->page->time_stamp; |
28e3fc56 SRV |
4014 | iter->page_stamp = iter->read_stamp; |
4015 | } | |
642edba5 | 4016 | } |
f83c9d0f | 4017 | |
642edba5 SR |
4018 | /** |
4019 | * ring_buffer_iter_reset - reset an iterator | |
4020 | * @iter: The iterator to reset | |
4021 | * | |
4022 | * Resets the iterator, so that it will start from the beginning | |
4023 | * again. | |
4024 | */ | |
4025 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) | |
4026 | { | |
554f786e | 4027 | struct ring_buffer_per_cpu *cpu_buffer; |
642edba5 SR |
4028 | unsigned long flags; |
4029 | ||
554f786e SR |
4030 | if (!iter) |
4031 | return; | |
4032 | ||
4033 | cpu_buffer = iter->cpu_buffer; | |
4034 | ||
5389f6fa | 4035 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
642edba5 | 4036 | rb_iter_reset(iter); |
5389f6fa | 4037 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 4038 | } |
c4f50183 | 4039 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
7a8e76a3 SR |
4040 | |
4041 | /** | |
4042 | * ring_buffer_iter_empty - check if an iterator has no more to read | |
4043 | * @iter: The iterator to check | |
4044 | */ | |
4045 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) | |
4046 | { | |
4047 | struct ring_buffer_per_cpu *cpu_buffer; | |
78f7a45d SRV |
4048 | struct buffer_page *reader; |
4049 | struct buffer_page *head_page; | |
4050 | struct buffer_page *commit_page; | |
ead6ecfd | 4051 | struct buffer_page *curr_commit_page; |
78f7a45d | 4052 | unsigned commit; |
ead6ecfd SRV |
4053 | u64 curr_commit_ts; |
4054 | u64 commit_ts; | |
7a8e76a3 SR |
4055 | |
4056 | cpu_buffer = iter->cpu_buffer; | |
78f7a45d SRV |
4057 | reader = cpu_buffer->reader_page; |
4058 | head_page = cpu_buffer->head_page; | |
4059 | commit_page = cpu_buffer->commit_page; | |
ead6ecfd SRV |
4060 | commit_ts = commit_page->page->time_stamp; |
4061 | ||
4062 | /* | |
4063 | * When the writer goes across pages, it issues a cmpxchg which | |
4064 | * is a mb(), which will synchronize with the rmb here. | |
4065 | * (see rb_tail_page_update()) | |
4066 | */ | |
4067 | smp_rmb(); | |
78f7a45d | 4068 | commit = rb_page_commit(commit_page); |
ead6ecfd SRV |
4069 | /* We want to make sure that the commit page doesn't change */ |
4070 | smp_rmb(); | |
4071 | ||
4072 | /* Make sure commit page didn't change */ | |
4073 | curr_commit_page = READ_ONCE(cpu_buffer->commit_page); | |
4074 | curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp); | |
4075 | ||
4076 | /* If the commit page changed, then there's more data */ | |
4077 | if (curr_commit_page != commit_page || | |
4078 | curr_commit_ts != commit_ts) | |
4079 | return 0; | |
78f7a45d | 4080 | |
ead6ecfd | 4081 | /* Still racy, as it may return a false positive, but that's OK */ |
785888c5 | 4082 | return ((iter->head_page == commit_page && iter->head >= commit) || |
78f7a45d SRV |
4083 | (iter->head_page == reader && commit_page == head_page && |
4084 | head_page->read == commit && | |
4085 | iter->head == rb_page_commit(cpu_buffer->reader_page))); | |
7a8e76a3 | 4086 | } |
c4f50183 | 4087 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
7a8e76a3 SR |
4088 | |
4089 | static void | |
4090 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
4091 | struct ring_buffer_event *event) | |
4092 | { | |
4093 | u64 delta; | |
4094 | ||
334d4169 | 4095 | switch (event->type_len) { |
7a8e76a3 SR |
4096 | case RINGBUF_TYPE_PADDING: |
4097 | return; | |
4098 | ||
4099 | case RINGBUF_TYPE_TIME_EXTEND: | |
dc4e2801 | 4100 | delta = ring_buffer_event_time_stamp(event); |
7a8e76a3 SR |
4101 | cpu_buffer->read_stamp += delta; |
4102 | return; | |
4103 | ||
4104 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
4105 | delta = ring_buffer_event_time_stamp(event); |
4106 | cpu_buffer->read_stamp = delta; | |
7a8e76a3 SR |
4107 | return; |
4108 | ||
4109 | case RINGBUF_TYPE_DATA: | |
4110 | cpu_buffer->read_stamp += event->time_delta; | |
4111 | return; | |
4112 | ||
4113 | default: | |
da4d401a | 4114 | RB_WARN_ON(cpu_buffer, 1); |
7a8e76a3 SR |
4115 | } |
4116 | return; | |
4117 | } | |
4118 | ||
4119 | static void | |
4120 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, | |
4121 | struct ring_buffer_event *event) | |
4122 | { | |
4123 | u64 delta; | |
4124 | ||
334d4169 | 4125 | switch (event->type_len) { |
7a8e76a3 SR |
4126 | case RINGBUF_TYPE_PADDING: |
4127 | return; | |
4128 | ||
4129 | case RINGBUF_TYPE_TIME_EXTEND: | |
dc4e2801 | 4130 | delta = ring_buffer_event_time_stamp(event); |
7a8e76a3 SR |
4131 | iter->read_stamp += delta; |
4132 | return; | |
4133 | ||
4134 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
4135 | delta = ring_buffer_event_time_stamp(event); |
4136 | iter->read_stamp = delta; | |
7a8e76a3 SR |
4137 | return; |
4138 | ||
4139 | case RINGBUF_TYPE_DATA: | |
4140 | iter->read_stamp += event->time_delta; | |
4141 | return; | |
4142 | ||
4143 | default: | |
da4d401a | 4144 | RB_WARN_ON(iter->cpu_buffer, 1); |
7a8e76a3 SR |
4145 | } |
4146 | return; | |
4147 | } | |
4148 | ||
d769041f SR |
4149 | static struct buffer_page * |
4150 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 4151 | { |
d769041f | 4152 | struct buffer_page *reader = NULL; |
66a8cb95 | 4153 | unsigned long overwrite; |
d769041f | 4154 | unsigned long flags; |
818e3dd3 | 4155 | int nr_loops = 0; |
77ae365e | 4156 | int ret; |
d769041f | 4157 | |
3e03fb7f | 4158 | local_irq_save(flags); |
0199c4e6 | 4159 | arch_spin_lock(&cpu_buffer->lock); |
d769041f SR |
4160 | |
4161 | again: | |
818e3dd3 SR |
4162 | /* |
4163 | * This should normally only loop twice. But because the | |
4164 | * start of the reader inserts an empty page, it causes | |
4165 | * a case where we will loop three times. There should be no | |
4166 | * reason to loop four times (that I know of). | |
4167 | */ | |
3e89c7bb | 4168 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
818e3dd3 SR |
4169 | reader = NULL; |
4170 | goto out; | |
4171 | } | |
4172 | ||
d769041f SR |
4173 | reader = cpu_buffer->reader_page; |
4174 | ||
4175 | /* If there's more to read, return this page */ | |
bf41a158 | 4176 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
d769041f SR |
4177 | goto out; |
4178 | ||
4179 | /* Never should we have an index greater than the size */ | |
3e89c7bb SR |
4180 | if (RB_WARN_ON(cpu_buffer, |
4181 | cpu_buffer->reader_page->read > rb_page_size(reader))) | |
4182 | goto out; | |
d769041f SR |
4183 | |
4184 | /* check if we caught up to the tail */ | |
4185 | reader = NULL; | |
bf41a158 | 4186 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
d769041f | 4187 | goto out; |
7a8e76a3 | 4188 | |
a5fb8331 SR |
4189 | /* Don't bother swapping if the ring buffer is empty */ |
4190 | if (rb_num_of_entries(cpu_buffer) == 0) | |
4191 | goto out; | |
4192 | ||
7a8e76a3 | 4193 | /* |
d769041f | 4194 | * Reset the reader page to size zero. |
7a8e76a3 | 4195 | */ |
77ae365e SR |
4196 | local_set(&cpu_buffer->reader_page->write, 0); |
4197 | local_set(&cpu_buffer->reader_page->entries, 0); | |
4198 | local_set(&cpu_buffer->reader_page->page->commit, 0); | |
ff0ff84a | 4199 | cpu_buffer->reader_page->real_end = 0; |
7a8e76a3 | 4200 | |
77ae365e SR |
4201 | spin: |
4202 | /* | |
4203 | * Splice the empty reader page into the list around the head. | |
4204 | */ | |
4205 | reader = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
4206 | if (!reader) |
4207 | goto out; | |
0e1ff5d7 | 4208 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
d769041f | 4209 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
bf41a158 | 4210 | |
3adc54fa SR |
4211 | /* |
4212 | * cpu_buffer->pages just needs to point to the buffer, it | |
4213 | * has no specific buffer page to point to. Lets move it out | |
25985edc | 4214 | * of our way so we don't accidentally swap it. |
3adc54fa SR |
4215 | */ |
4216 | cpu_buffer->pages = reader->list.prev; | |
4217 | ||
77ae365e SR |
4218 | /* The reader page will be pointing to the new head */ |
4219 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); | |
7a8e76a3 | 4220 | |
66a8cb95 SR |
4221 | /* |
4222 | * We want to make sure we read the overruns after we set up our | |
4223 | * pointers to the next object. The writer side does a | |
4224 | * cmpxchg to cross pages which acts as the mb on the writer | |
4225 | * side. Note, the reader will constantly fail the swap | |
4226 | * while the writer is updating the pointers, so this | |
4227 | * guarantees that the overwrite recorded here is the one we | |
4228 | * want to compare with the last_overrun. | |
4229 | */ | |
4230 | smp_mb(); | |
4231 | overwrite = local_read(&(cpu_buffer->overrun)); | |
4232 | ||
77ae365e SR |
4233 | /* |
4234 | * Here's the tricky part. | |
4235 | * | |
4236 | * We need to move the pointer past the header page. | |
4237 | * But we can only do that if a writer is not currently | |
4238 | * moving it. The page before the header page has the | |
4239 | * flag bit '1' set if it is pointing to the page we want. | |
4240 | * but if the writer is in the process of moving it | |
4241 | * than it will be '2' or already moved '0'. | |
4242 | */ | |
4243 | ||
4244 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); | |
7a8e76a3 SR |
4245 | |
4246 | /* | |
77ae365e | 4247 | * If we did not convert it, then we must try again. |
7a8e76a3 | 4248 | */ |
77ae365e SR |
4249 | if (!ret) |
4250 | goto spin; | |
7a8e76a3 | 4251 | |
77ae365e | 4252 | /* |
2c2b0a78 | 4253 | * Yay! We succeeded in replacing the page. |
77ae365e SR |
4254 | * |
4255 | * Now make the new head point back to the reader page. | |
4256 | */ | |
5ded3dc6 | 4257 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
77ae365e | 4258 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
d769041f | 4259 | |
2c2b0a78 SRV |
4260 | local_inc(&cpu_buffer->pages_read); |
4261 | ||
d769041f SR |
4262 | /* Finally update the reader page to the new head */ |
4263 | cpu_buffer->reader_page = reader; | |
b81f472a | 4264 | cpu_buffer->reader_page->read = 0; |
d769041f | 4265 | |
66a8cb95 SR |
4266 | if (overwrite != cpu_buffer->last_overrun) { |
4267 | cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; | |
4268 | cpu_buffer->last_overrun = overwrite; | |
4269 | } | |
4270 | ||
d769041f SR |
4271 | goto again; |
4272 | ||
4273 | out: | |
b81f472a SRRH |
4274 | /* Update the read_stamp on the first event */ |
4275 | if (reader && reader->read == 0) | |
4276 | cpu_buffer->read_stamp = reader->page->time_stamp; | |
4277 | ||
0199c4e6 | 4278 | arch_spin_unlock(&cpu_buffer->lock); |
3e03fb7f | 4279 | local_irq_restore(flags); |
d769041f SR |
4280 | |
4281 | return reader; | |
4282 | } | |
4283 | ||
4284 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) | |
4285 | { | |
4286 | struct ring_buffer_event *event; | |
4287 | struct buffer_page *reader; | |
4288 | unsigned length; | |
4289 | ||
4290 | reader = rb_get_reader_page(cpu_buffer); | |
7a8e76a3 | 4291 | |
d769041f | 4292 | /* This function should not be called when buffer is empty */ |
3e89c7bb SR |
4293 | if (RB_WARN_ON(cpu_buffer, !reader)) |
4294 | return; | |
7a8e76a3 | 4295 | |
d769041f SR |
4296 | event = rb_reader_event(cpu_buffer); |
4297 | ||
a1863c21 | 4298 | if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
e4906eff | 4299 | cpu_buffer->read++; |
d769041f SR |
4300 | |
4301 | rb_update_read_stamp(cpu_buffer, event); | |
4302 | ||
4303 | length = rb_event_length(event); | |
6f807acd | 4304 | cpu_buffer->reader_page->read += length; |
7a8e76a3 SR |
4305 | } |
4306 | ||
4307 | static void rb_advance_iter(struct ring_buffer_iter *iter) | |
4308 | { | |
7a8e76a3 | 4309 | struct ring_buffer_per_cpu *cpu_buffer; |
7a8e76a3 SR |
4310 | |
4311 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 | 4312 | |
785888c5 SRV |
4313 | /* If head == next_event then we need to jump to the next event */ |
4314 | if (iter->head == iter->next_event) { | |
4315 | /* If the event gets overwritten again, there's nothing to do */ | |
4316 | if (rb_iter_head_event(iter) == NULL) | |
4317 | return; | |
4318 | } | |
4319 | ||
4320 | iter->head = iter->next_event; | |
4321 | ||
7a8e76a3 SR |
4322 | /* |
4323 | * Check if we are at the end of the buffer. | |
4324 | */ | |
785888c5 | 4325 | if (iter->next_event >= rb_page_size(iter->head_page)) { |
ea05b57c SR |
4326 | /* discarded commits can make the page empty */ |
4327 | if (iter->head_page == cpu_buffer->commit_page) | |
3e89c7bb | 4328 | return; |
d769041f | 4329 | rb_inc_iter(iter); |
7a8e76a3 SR |
4330 | return; |
4331 | } | |
4332 | ||
785888c5 | 4333 | rb_update_iter_read_stamp(iter, iter->event); |
7a8e76a3 SR |
4334 | } |
4335 | ||
66a8cb95 SR |
4336 | static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) |
4337 | { | |
4338 | return cpu_buffer->lost_events; | |
4339 | } | |
4340 | ||
f83c9d0f | 4341 | static struct ring_buffer_event * |
66a8cb95 SR |
4342 | rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, |
4343 | unsigned long *lost_events) | |
7a8e76a3 | 4344 | { |
7a8e76a3 | 4345 | struct ring_buffer_event *event; |
d769041f | 4346 | struct buffer_page *reader; |
818e3dd3 | 4347 | int nr_loops = 0; |
7a8e76a3 | 4348 | |
dc4e2801 TZ |
4349 | if (ts) |
4350 | *ts = 0; | |
7a8e76a3 | 4351 | again: |
818e3dd3 | 4352 | /* |
69d1b839 SR |
4353 | * We repeat when a time extend is encountered. |
4354 | * Since the time extend is always attached to a data event, | |
4355 | * we should never loop more than once. | |
4356 | * (We never hit the following condition more than twice). | |
818e3dd3 | 4357 | */ |
69d1b839 | 4358 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
818e3dd3 | 4359 | return NULL; |
818e3dd3 | 4360 | |
d769041f SR |
4361 | reader = rb_get_reader_page(cpu_buffer); |
4362 | if (!reader) | |
7a8e76a3 SR |
4363 | return NULL; |
4364 | ||
d769041f | 4365 | event = rb_reader_event(cpu_buffer); |
7a8e76a3 | 4366 | |
334d4169 | 4367 | switch (event->type_len) { |
7a8e76a3 | 4368 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
4369 | if (rb_null_event(event)) |
4370 | RB_WARN_ON(cpu_buffer, 1); | |
4371 | /* | |
4372 | * Because the writer could be discarding every | |
4373 | * event it creates (which would probably be bad) | |
4374 | * if we were to go back to "again" then we may never | |
4375 | * catch up, and will trigger the warn on, or lock | |
4376 | * the box. Return the padding, and we will release | |
4377 | * the current locks, and try again. | |
4378 | */ | |
2d622719 | 4379 | return event; |
7a8e76a3 SR |
4380 | |
4381 | case RINGBUF_TYPE_TIME_EXTEND: | |
4382 | /* Internal data, OK to advance */ | |
d769041f | 4383 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
4384 | goto again; |
4385 | ||
4386 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
4387 | if (ts) { |
4388 | *ts = ring_buffer_event_time_stamp(event); | |
4389 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, | |
4390 | cpu_buffer->cpu, ts); | |
4391 | } | |
4392 | /* Internal data, OK to advance */ | |
d769041f | 4393 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
4394 | goto again; |
4395 | ||
4396 | case RINGBUF_TYPE_DATA: | |
dc4e2801 | 4397 | if (ts && !(*ts)) { |
7a8e76a3 | 4398 | *ts = cpu_buffer->read_stamp + event->time_delta; |
d8eeb2d3 | 4399 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
37886f6a | 4400 | cpu_buffer->cpu, ts); |
7a8e76a3 | 4401 | } |
66a8cb95 SR |
4402 | if (lost_events) |
4403 | *lost_events = rb_lost_events(cpu_buffer); | |
7a8e76a3 SR |
4404 | return event; |
4405 | ||
4406 | default: | |
da4d401a | 4407 | RB_WARN_ON(cpu_buffer, 1); |
7a8e76a3 SR |
4408 | } |
4409 | ||
4410 | return NULL; | |
4411 | } | |
c4f50183 | 4412 | EXPORT_SYMBOL_GPL(ring_buffer_peek); |
7a8e76a3 | 4413 | |
f83c9d0f SR |
4414 | static struct ring_buffer_event * |
4415 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
7a8e76a3 | 4416 | { |
13292494 | 4417 | struct trace_buffer *buffer; |
7a8e76a3 SR |
4418 | struct ring_buffer_per_cpu *cpu_buffer; |
4419 | struct ring_buffer_event *event; | |
818e3dd3 | 4420 | int nr_loops = 0; |
7a8e76a3 | 4421 | |
dc4e2801 TZ |
4422 | if (ts) |
4423 | *ts = 0; | |
4424 | ||
7a8e76a3 SR |
4425 | cpu_buffer = iter->cpu_buffer; |
4426 | buffer = cpu_buffer->buffer; | |
4427 | ||
492a74f4 SR |
4428 | /* |
4429 | * Check if someone performed a consuming read to | |
4430 | * the buffer. A consuming read invalidates the iterator | |
4431 | * and we need to reset the iterator in this case. | |
4432 | */ | |
4433 | if (unlikely(iter->cache_read != cpu_buffer->read || | |
4434 | iter->cache_reader_page != cpu_buffer->reader_page)) | |
4435 | rb_iter_reset(iter); | |
4436 | ||
7a8e76a3 | 4437 | again: |
3c05d748 SR |
4438 | if (ring_buffer_iter_empty(iter)) |
4439 | return NULL; | |
4440 | ||
818e3dd3 | 4441 | /* |
3d2353de SRV |
4442 | * As the writer can mess with what the iterator is trying |
4443 | * to read, just give up if we fail to get an event after | |
4444 | * three tries. The iterator is not as reliable when reading | |
4445 | * the ring buffer with an active write as the consumer is. | |
4446 | * Do not warn if the three failures is reached. | |
818e3dd3 | 4447 | */ |
3d2353de | 4448 | if (++nr_loops > 3) |
818e3dd3 | 4449 | return NULL; |
818e3dd3 | 4450 | |
7a8e76a3 SR |
4451 | if (rb_per_cpu_empty(cpu_buffer)) |
4452 | return NULL; | |
4453 | ||
10e83fd0 | 4454 | if (iter->head >= rb_page_size(iter->head_page)) { |
3c05d748 SR |
4455 | rb_inc_iter(iter); |
4456 | goto again; | |
4457 | } | |
4458 | ||
7a8e76a3 | 4459 | event = rb_iter_head_event(iter); |
3d2353de | 4460 | if (!event) |
785888c5 | 4461 | goto again; |
7a8e76a3 | 4462 | |
334d4169 | 4463 | switch (event->type_len) { |
7a8e76a3 | 4464 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
4465 | if (rb_null_event(event)) { |
4466 | rb_inc_iter(iter); | |
4467 | goto again; | |
4468 | } | |
4469 | rb_advance_iter(iter); | |
4470 | return event; | |
7a8e76a3 SR |
4471 | |
4472 | case RINGBUF_TYPE_TIME_EXTEND: | |
4473 | /* Internal data, OK to advance */ | |
4474 | rb_advance_iter(iter); | |
4475 | goto again; | |
4476 | ||
4477 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
4478 | if (ts) { |
4479 | *ts = ring_buffer_event_time_stamp(event); | |
4480 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, | |
4481 | cpu_buffer->cpu, ts); | |
4482 | } | |
4483 | /* Internal data, OK to advance */ | |
7a8e76a3 SR |
4484 | rb_advance_iter(iter); |
4485 | goto again; | |
4486 | ||
4487 | case RINGBUF_TYPE_DATA: | |
dc4e2801 | 4488 | if (ts && !(*ts)) { |
7a8e76a3 | 4489 | *ts = iter->read_stamp + event->time_delta; |
37886f6a SR |
4490 | ring_buffer_normalize_time_stamp(buffer, |
4491 | cpu_buffer->cpu, ts); | |
7a8e76a3 SR |
4492 | } |
4493 | return event; | |
4494 | ||
4495 | default: | |
da4d401a | 4496 | RB_WARN_ON(cpu_buffer, 1); |
7a8e76a3 SR |
4497 | } |
4498 | ||
4499 | return NULL; | |
4500 | } | |
c4f50183 | 4501 | EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
7a8e76a3 | 4502 | |
289a5a25 | 4503 | static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) |
8d707e8e | 4504 | { |
289a5a25 SRRH |
4505 | if (likely(!in_nmi())) { |
4506 | raw_spin_lock(&cpu_buffer->reader_lock); | |
4507 | return true; | |
4508 | } | |
4509 | ||
8d707e8e SR |
4510 | /* |
4511 | * If an NMI die dumps out the content of the ring buffer | |
289a5a25 SRRH |
4512 | * trylock must be used to prevent a deadlock if the NMI |
4513 | * preempted a task that holds the ring buffer locks. If | |
4514 | * we get the lock then all is fine, if not, then continue | |
4515 | * to do the read, but this can corrupt the ring buffer, | |
4516 | * so it must be permanently disabled from future writes. | |
4517 | * Reading from NMI is a oneshot deal. | |
8d707e8e | 4518 | */ |
289a5a25 SRRH |
4519 | if (raw_spin_trylock(&cpu_buffer->reader_lock)) |
4520 | return true; | |
8d707e8e | 4521 | |
289a5a25 SRRH |
4522 | /* Continue without locking, but disable the ring buffer */ |
4523 | atomic_inc(&cpu_buffer->record_disabled); | |
4524 | return false; | |
4525 | } | |
4526 | ||
4527 | static inline void | |
4528 | rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked) | |
4529 | { | |
4530 | if (likely(locked)) | |
4531 | raw_spin_unlock(&cpu_buffer->reader_lock); | |
4532 | return; | |
8d707e8e SR |
4533 | } |
4534 | ||
f83c9d0f SR |
4535 | /** |
4536 | * ring_buffer_peek - peek at the next event to be read | |
4537 | * @buffer: The ring buffer to read | |
4538 | * @cpu: The cpu to peak at | |
4539 | * @ts: The timestamp counter of this event. | |
66a8cb95 | 4540 | * @lost_events: a variable to store if events were lost (may be NULL) |
f83c9d0f SR |
4541 | * |
4542 | * This will return the event that will be read next, but does | |
4543 | * not consume the data. | |
4544 | */ | |
4545 | struct ring_buffer_event * | |
13292494 | 4546 | ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts, |
66a8cb95 | 4547 | unsigned long *lost_events) |
f83c9d0f SR |
4548 | { |
4549 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
8aabee57 | 4550 | struct ring_buffer_event *event; |
f83c9d0f | 4551 | unsigned long flags; |
289a5a25 | 4552 | bool dolock; |
f83c9d0f | 4553 | |
554f786e | 4554 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4555 | return NULL; |
554f786e | 4556 | |
2d622719 | 4557 | again: |
8d707e8e | 4558 | local_irq_save(flags); |
289a5a25 | 4559 | dolock = rb_reader_lock(cpu_buffer); |
66a8cb95 | 4560 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
469535a5 RR |
4561 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
4562 | rb_advance_reader(cpu_buffer); | |
289a5a25 | 4563 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 4564 | local_irq_restore(flags); |
f83c9d0f | 4565 | |
1b959e18 | 4566 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 4567 | goto again; |
2d622719 | 4568 | |
f83c9d0f SR |
4569 | return event; |
4570 | } | |
4571 | ||
c9b7a4a7 SRV |
4572 | /** ring_buffer_iter_dropped - report if there are dropped events |
4573 | * @iter: The ring buffer iterator | |
4574 | * | |
4575 | * Returns true if there was dropped events since the last peek. | |
4576 | */ | |
4577 | bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter) | |
4578 | { | |
4579 | bool ret = iter->missed_events != 0; | |
4580 | ||
4581 | iter->missed_events = 0; | |
4582 | return ret; | |
4583 | } | |
4584 | EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped); | |
4585 | ||
f83c9d0f SR |
4586 | /** |
4587 | * ring_buffer_iter_peek - peek at the next event to be read | |
4588 | * @iter: The ring buffer iterator | |
4589 | * @ts: The timestamp counter of this event. | |
4590 | * | |
4591 | * This will return the event that will be read next, but does | |
4592 | * not increment the iterator. | |
4593 | */ | |
4594 | struct ring_buffer_event * | |
4595 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
4596 | { | |
4597 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
4598 | struct ring_buffer_event *event; | |
4599 | unsigned long flags; | |
4600 | ||
2d622719 | 4601 | again: |
5389f6fa | 4602 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4603 | event = rb_iter_peek(iter, ts); |
5389f6fa | 4604 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4605 | |
1b959e18 | 4606 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 4607 | goto again; |
2d622719 | 4608 | |
f83c9d0f SR |
4609 | return event; |
4610 | } | |
4611 | ||
7a8e76a3 SR |
4612 | /** |
4613 | * ring_buffer_consume - return an event and consume it | |
4614 | * @buffer: The ring buffer to get the next event from | |
66a8cb95 SR |
4615 | * @cpu: the cpu to read the buffer from |
4616 | * @ts: a variable to store the timestamp (may be NULL) | |
4617 | * @lost_events: a variable to store if events were lost (may be NULL) | |
7a8e76a3 SR |
4618 | * |
4619 | * Returns the next event in the ring buffer, and that event is consumed. | |
4620 | * Meaning, that sequential reads will keep returning a different event, | |
4621 | * and eventually empty the ring buffer if the producer is slower. | |
4622 | */ | |
4623 | struct ring_buffer_event * | |
13292494 | 4624 | ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts, |
66a8cb95 | 4625 | unsigned long *lost_events) |
7a8e76a3 | 4626 | { |
554f786e SR |
4627 | struct ring_buffer_per_cpu *cpu_buffer; |
4628 | struct ring_buffer_event *event = NULL; | |
f83c9d0f | 4629 | unsigned long flags; |
289a5a25 | 4630 | bool dolock; |
7a8e76a3 | 4631 | |
2d622719 | 4632 | again: |
554f786e SR |
4633 | /* might be called in atomic */ |
4634 | preempt_disable(); | |
4635 | ||
9e01c1b7 | 4636 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e | 4637 | goto out; |
7a8e76a3 | 4638 | |
554f786e | 4639 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e | 4640 | local_irq_save(flags); |
289a5a25 | 4641 | dolock = rb_reader_lock(cpu_buffer); |
f83c9d0f | 4642 | |
66a8cb95 SR |
4643 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
4644 | if (event) { | |
4645 | cpu_buffer->lost_events = 0; | |
469535a5 | 4646 | rb_advance_reader(cpu_buffer); |
66a8cb95 | 4647 | } |
7a8e76a3 | 4648 | |
289a5a25 | 4649 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 4650 | local_irq_restore(flags); |
f83c9d0f | 4651 | |
554f786e SR |
4652 | out: |
4653 | preempt_enable(); | |
4654 | ||
1b959e18 | 4655 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 4656 | goto again; |
2d622719 | 4657 | |
7a8e76a3 SR |
4658 | return event; |
4659 | } | |
c4f50183 | 4660 | EXPORT_SYMBOL_GPL(ring_buffer_consume); |
7a8e76a3 SR |
4661 | |
4662 | /** | |
72c9ddfd | 4663 | * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer |
7a8e76a3 SR |
4664 | * @buffer: The ring buffer to read from |
4665 | * @cpu: The cpu buffer to iterate over | |
31b265b3 | 4666 | * @flags: gfp flags to use for memory allocation |
7a8e76a3 | 4667 | * |
72c9ddfd DM |
4668 | * This performs the initial preparations necessary to iterate |
4669 | * through the buffer. Memory is allocated, buffer recording | |
4670 | * is disabled, and the iterator pointer is returned to the caller. | |
7a8e76a3 | 4671 | * |
6167c205 | 4672 | * Disabling buffer recording prevents the reading from being |
72c9ddfd DM |
4673 | * corrupted. This is not a consuming read, so a producer is not |
4674 | * expected. | |
4675 | * | |
4676 | * After a sequence of ring_buffer_read_prepare calls, the user is | |
d611851b | 4677 | * expected to make at least one call to ring_buffer_read_prepare_sync. |
72c9ddfd DM |
4678 | * Afterwards, ring_buffer_read_start is invoked to get things going |
4679 | * for real. | |
4680 | * | |
d611851b | 4681 | * This overall must be paired with ring_buffer_read_finish. |
7a8e76a3 SR |
4682 | */ |
4683 | struct ring_buffer_iter * | |
13292494 | 4684 | ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags) |
7a8e76a3 SR |
4685 | { |
4686 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 4687 | struct ring_buffer_iter *iter; |
7a8e76a3 | 4688 | |
9e01c1b7 | 4689 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4690 | return NULL; |
7a8e76a3 | 4691 | |
785888c5 | 4692 | iter = kzalloc(sizeof(*iter), flags); |
7a8e76a3 | 4693 | if (!iter) |
8aabee57 | 4694 | return NULL; |
7a8e76a3 | 4695 | |
785888c5 SRV |
4696 | iter->event = kmalloc(BUF_MAX_DATA_SIZE, flags); |
4697 | if (!iter->event) { | |
4698 | kfree(iter); | |
4699 | return NULL; | |
4700 | } | |
4701 | ||
7a8e76a3 SR |
4702 | cpu_buffer = buffer->buffers[cpu]; |
4703 | ||
4704 | iter->cpu_buffer = cpu_buffer; | |
4705 | ||
07b8b10e | 4706 | atomic_inc(&cpu_buffer->resize_disabled); |
72c9ddfd DM |
4707 | |
4708 | return iter; | |
4709 | } | |
4710 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); | |
4711 | ||
4712 | /** | |
4713 | * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls | |
4714 | * | |
4715 | * All previously invoked ring_buffer_read_prepare calls to prepare | |
4716 | * iterators will be synchronized. Afterwards, read_buffer_read_start | |
4717 | * calls on those iterators are allowed. | |
4718 | */ | |
4719 | void | |
4720 | ring_buffer_read_prepare_sync(void) | |
4721 | { | |
74401729 | 4722 | synchronize_rcu(); |
72c9ddfd DM |
4723 | } |
4724 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); | |
4725 | ||
4726 | /** | |
4727 | * ring_buffer_read_start - start a non consuming read of the buffer | |
4728 | * @iter: The iterator returned by ring_buffer_read_prepare | |
4729 | * | |
4730 | * This finalizes the startup of an iteration through the buffer. | |
4731 | * The iterator comes from a call to ring_buffer_read_prepare and | |
4732 | * an intervening ring_buffer_read_prepare_sync must have been | |
4733 | * performed. | |
4734 | * | |
d611851b | 4735 | * Must be paired with ring_buffer_read_finish. |
72c9ddfd DM |
4736 | */ |
4737 | void | |
4738 | ring_buffer_read_start(struct ring_buffer_iter *iter) | |
4739 | { | |
4740 | struct ring_buffer_per_cpu *cpu_buffer; | |
4741 | unsigned long flags; | |
4742 | ||
4743 | if (!iter) | |
4744 | return; | |
4745 | ||
4746 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 | 4747 | |
5389f6fa | 4748 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
0199c4e6 | 4749 | arch_spin_lock(&cpu_buffer->lock); |
642edba5 | 4750 | rb_iter_reset(iter); |
0199c4e6 | 4751 | arch_spin_unlock(&cpu_buffer->lock); |
5389f6fa | 4752 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 4753 | } |
c4f50183 | 4754 | EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
7a8e76a3 SR |
4755 | |
4756 | /** | |
d611851b | 4757 | * ring_buffer_read_finish - finish reading the iterator of the buffer |
7a8e76a3 SR |
4758 | * @iter: The iterator retrieved by ring_buffer_start |
4759 | * | |
4760 | * This re-enables the recording to the buffer, and frees the | |
4761 | * iterator. | |
4762 | */ | |
4763 | void | |
4764 | ring_buffer_read_finish(struct ring_buffer_iter *iter) | |
4765 | { | |
4766 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
9366c1ba | 4767 | unsigned long flags; |
7a8e76a3 | 4768 | |
659f451f SR |
4769 | /* |
4770 | * Ring buffer is disabled from recording, here's a good place | |
9366c1ba SR |
4771 | * to check the integrity of the ring buffer. |
4772 | * Must prevent readers from trying to read, as the check | |
4773 | * clears the HEAD page and readers require it. | |
659f451f | 4774 | */ |
9366c1ba | 4775 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
659f451f | 4776 | rb_check_pages(cpu_buffer); |
9366c1ba | 4777 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
659f451f | 4778 | |
07b8b10e | 4779 | atomic_dec(&cpu_buffer->resize_disabled); |
785888c5 | 4780 | kfree(iter->event); |
7a8e76a3 SR |
4781 | kfree(iter); |
4782 | } | |
c4f50183 | 4783 | EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
7a8e76a3 SR |
4784 | |
4785 | /** | |
bc1a72af | 4786 | * ring_buffer_iter_advance - advance the iterator to the next location |
7a8e76a3 | 4787 | * @iter: The ring buffer iterator |
7a8e76a3 | 4788 | * |
bc1a72af SRV |
4789 | * Move the location of the iterator such that the next read will |
4790 | * be the next location of the iterator. | |
7a8e76a3 | 4791 | */ |
bc1a72af | 4792 | void ring_buffer_iter_advance(struct ring_buffer_iter *iter) |
7a8e76a3 | 4793 | { |
f83c9d0f SR |
4794 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
4795 | unsigned long flags; | |
7a8e76a3 | 4796 | |
5389f6fa | 4797 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
7e9391cf | 4798 | |
7a8e76a3 SR |
4799 | rb_advance_iter(iter); |
4800 | ||
bc1a72af | 4801 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 4802 | } |
bc1a72af | 4803 | EXPORT_SYMBOL_GPL(ring_buffer_iter_advance); |
7a8e76a3 SR |
4804 | |
4805 | /** | |
4806 | * ring_buffer_size - return the size of the ring buffer (in bytes) | |
4807 | * @buffer: The ring buffer. | |
59e7cffe | 4808 | * @cpu: The CPU to get ring buffer size from. |
7a8e76a3 | 4809 | */ |
13292494 | 4810 | unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu) |
7a8e76a3 | 4811 | { |
438ced17 VN |
4812 | /* |
4813 | * Earlier, this method returned | |
4814 | * BUF_PAGE_SIZE * buffer->nr_pages | |
4815 | * Since the nr_pages field is now removed, we have converted this to | |
4816 | * return the per cpu buffer value. | |
4817 | */ | |
4818 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
4819 | return 0; | |
4820 | ||
4821 | return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages; | |
7a8e76a3 | 4822 | } |
c4f50183 | 4823 | EXPORT_SYMBOL_GPL(ring_buffer_size); |
7a8e76a3 SR |
4824 | |
4825 | static void | |
4826 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) | |
4827 | { | |
77ae365e SR |
4828 | rb_head_page_deactivate(cpu_buffer); |
4829 | ||
7a8e76a3 | 4830 | cpu_buffer->head_page |
3adc54fa | 4831 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 4832 | local_set(&cpu_buffer->head_page->write, 0); |
778c55d4 | 4833 | local_set(&cpu_buffer->head_page->entries, 0); |
abc9b56d | 4834 | local_set(&cpu_buffer->head_page->page->commit, 0); |
d769041f | 4835 | |
6f807acd | 4836 | cpu_buffer->head_page->read = 0; |
bf41a158 SR |
4837 | |
4838 | cpu_buffer->tail_page = cpu_buffer->head_page; | |
4839 | cpu_buffer->commit_page = cpu_buffer->head_page; | |
4840 | ||
4841 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); | |
5040b4b7 | 4842 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
bf41a158 | 4843 | local_set(&cpu_buffer->reader_page->write, 0); |
778c55d4 | 4844 | local_set(&cpu_buffer->reader_page->entries, 0); |
abc9b56d | 4845 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
6f807acd | 4846 | cpu_buffer->reader_page->read = 0; |
7a8e76a3 | 4847 | |
c64e148a | 4848 | local_set(&cpu_buffer->entries_bytes, 0); |
77ae365e | 4849 | local_set(&cpu_buffer->overrun, 0); |
884bfe89 SP |
4850 | local_set(&cpu_buffer->commit_overrun, 0); |
4851 | local_set(&cpu_buffer->dropped_events, 0); | |
e4906eff | 4852 | local_set(&cpu_buffer->entries, 0); |
fa743953 SR |
4853 | local_set(&cpu_buffer->committing, 0); |
4854 | local_set(&cpu_buffer->commits, 0); | |
2c2b0a78 SRV |
4855 | local_set(&cpu_buffer->pages_touched, 0); |
4856 | local_set(&cpu_buffer->pages_read, 0); | |
03329f99 | 4857 | cpu_buffer->last_pages_touch = 0; |
2c2b0a78 | 4858 | cpu_buffer->shortest_full = 0; |
77ae365e | 4859 | cpu_buffer->read = 0; |
c64e148a | 4860 | cpu_buffer->read_bytes = 0; |
69507c06 | 4861 | |
10464b4a SRV |
4862 | rb_time_set(&cpu_buffer->write_stamp, 0); |
4863 | rb_time_set(&cpu_buffer->before_stamp, 0); | |
77ae365e | 4864 | |
66a8cb95 SR |
4865 | cpu_buffer->lost_events = 0; |
4866 | cpu_buffer->last_overrun = 0; | |
4867 | ||
77ae365e | 4868 | rb_head_page_activate(cpu_buffer); |
7a8e76a3 SR |
4869 | } |
4870 | ||
b23d7a5f NP |
4871 | /* Must have disabled the cpu buffer then done a synchronize_rcu */ |
4872 | static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
4873 | { | |
4874 | unsigned long flags; | |
4875 | ||
4876 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
4877 | ||
4878 | if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) | |
4879 | goto out; | |
4880 | ||
4881 | arch_spin_lock(&cpu_buffer->lock); | |
4882 | ||
4883 | rb_reset_cpu(cpu_buffer); | |
4884 | ||
4885 | arch_spin_unlock(&cpu_buffer->lock); | |
4886 | ||
4887 | out: | |
4888 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
4889 | } | |
4890 | ||
7a8e76a3 SR |
4891 | /** |
4892 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
4893 | * @buffer: The ring buffer to reset a per cpu buffer of | |
4894 | * @cpu: The CPU buffer to be reset | |
4895 | */ | |
13292494 | 4896 | void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu) |
7a8e76a3 SR |
4897 | { |
4898 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 4899 | |
9e01c1b7 | 4900 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4901 | return; |
7a8e76a3 | 4902 | |
bbeb9746 GK |
4903 | /* prevent another thread from changing buffer sizes */ |
4904 | mutex_lock(&buffer->mutex); | |
4905 | ||
07b8b10e | 4906 | atomic_inc(&cpu_buffer->resize_disabled); |
41ede23e SR |
4907 | atomic_inc(&cpu_buffer->record_disabled); |
4908 | ||
83f40318 | 4909 | /* Make sure all commits have finished */ |
74401729 | 4910 | synchronize_rcu(); |
83f40318 | 4911 | |
b23d7a5f | 4912 | reset_disabled_cpu_buffer(cpu_buffer); |
f83c9d0f | 4913 | |
b23d7a5f NP |
4914 | atomic_dec(&cpu_buffer->record_disabled); |
4915 | atomic_dec(&cpu_buffer->resize_disabled); | |
bbeb9746 GK |
4916 | |
4917 | mutex_unlock(&buffer->mutex); | |
b23d7a5f NP |
4918 | } |
4919 | EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); | |
41b6a95d | 4920 | |
b23d7a5f NP |
4921 | /** |
4922 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
4923 | * @buffer: The ring buffer to reset a per cpu buffer of | |
4924 | * @cpu: The CPU buffer to be reset | |
4925 | */ | |
4926 | void ring_buffer_reset_online_cpus(struct trace_buffer *buffer) | |
4927 | { | |
4928 | struct ring_buffer_per_cpu *cpu_buffer; | |
4929 | int cpu; | |
7a8e76a3 | 4930 | |
bbeb9746 GK |
4931 | /* prevent another thread from changing buffer sizes */ |
4932 | mutex_lock(&buffer->mutex); | |
4933 | ||
b23d7a5f NP |
4934 | for_each_online_buffer_cpu(buffer, cpu) { |
4935 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 4936 | |
b23d7a5f NP |
4937 | atomic_inc(&cpu_buffer->resize_disabled); |
4938 | atomic_inc(&cpu_buffer->record_disabled); | |
4939 | } | |
f83c9d0f | 4940 | |
b23d7a5f NP |
4941 | /* Make sure all commits have finished */ |
4942 | synchronize_rcu(); | |
41ede23e | 4943 | |
b23d7a5f NP |
4944 | for_each_online_buffer_cpu(buffer, cpu) { |
4945 | cpu_buffer = buffer->buffers[cpu]; | |
4946 | ||
4947 | reset_disabled_cpu_buffer(cpu_buffer); | |
4948 | ||
4949 | atomic_dec(&cpu_buffer->record_disabled); | |
4950 | atomic_dec(&cpu_buffer->resize_disabled); | |
4951 | } | |
bbeb9746 GK |
4952 | |
4953 | mutex_unlock(&buffer->mutex); | |
7a8e76a3 SR |
4954 | } |
4955 | ||
4956 | /** | |
4957 | * ring_buffer_reset - reset a ring buffer | |
4958 | * @buffer: The ring buffer to reset all cpu buffers | |
4959 | */ | |
13292494 | 4960 | void ring_buffer_reset(struct trace_buffer *buffer) |
7a8e76a3 | 4961 | { |
b23d7a5f | 4962 | struct ring_buffer_per_cpu *cpu_buffer; |
7a8e76a3 SR |
4963 | int cpu; |
4964 | ||
b23d7a5f NP |
4965 | for_each_buffer_cpu(buffer, cpu) { |
4966 | cpu_buffer = buffer->buffers[cpu]; | |
4967 | ||
4968 | atomic_inc(&cpu_buffer->resize_disabled); | |
4969 | atomic_inc(&cpu_buffer->record_disabled); | |
4970 | } | |
4971 | ||
4972 | /* Make sure all commits have finished */ | |
4973 | synchronize_rcu(); | |
4974 | ||
4975 | for_each_buffer_cpu(buffer, cpu) { | |
4976 | cpu_buffer = buffer->buffers[cpu]; | |
4977 | ||
4978 | reset_disabled_cpu_buffer(cpu_buffer); | |
4979 | ||
4980 | atomic_dec(&cpu_buffer->record_disabled); | |
4981 | atomic_dec(&cpu_buffer->resize_disabled); | |
4982 | } | |
7a8e76a3 | 4983 | } |
c4f50183 | 4984 | EXPORT_SYMBOL_GPL(ring_buffer_reset); |
7a8e76a3 SR |
4985 | |
4986 | /** | |
4987 | * rind_buffer_empty - is the ring buffer empty? | |
4988 | * @buffer: The ring buffer to test | |
4989 | */ | |
13292494 | 4990 | bool ring_buffer_empty(struct trace_buffer *buffer) |
7a8e76a3 SR |
4991 | { |
4992 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4993 | unsigned long flags; |
289a5a25 | 4994 | bool dolock; |
7a8e76a3 | 4995 | int cpu; |
d4788207 | 4996 | int ret; |
7a8e76a3 SR |
4997 | |
4998 | /* yes this is racy, but if you don't like the race, lock the buffer */ | |
4999 | for_each_buffer_cpu(buffer, cpu) { | |
5000 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e | 5001 | local_irq_save(flags); |
289a5a25 | 5002 | dolock = rb_reader_lock(cpu_buffer); |
d4788207 | 5003 | ret = rb_per_cpu_empty(cpu_buffer); |
289a5a25 | 5004 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e SR |
5005 | local_irq_restore(flags); |
5006 | ||
d4788207 | 5007 | if (!ret) |
3d4e204d | 5008 | return false; |
7a8e76a3 | 5009 | } |
554f786e | 5010 | |
3d4e204d | 5011 | return true; |
7a8e76a3 | 5012 | } |
c4f50183 | 5013 | EXPORT_SYMBOL_GPL(ring_buffer_empty); |
7a8e76a3 SR |
5014 | |
5015 | /** | |
5016 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? | |
5017 | * @buffer: The ring buffer | |
5018 | * @cpu: The CPU buffer to test | |
5019 | */ | |
13292494 | 5020 | bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu) |
7a8e76a3 SR |
5021 | { |
5022 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 5023 | unsigned long flags; |
289a5a25 | 5024 | bool dolock; |
8aabee57 | 5025 | int ret; |
7a8e76a3 | 5026 | |
9e01c1b7 | 5027 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3d4e204d | 5028 | return true; |
7a8e76a3 SR |
5029 | |
5030 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e | 5031 | local_irq_save(flags); |
289a5a25 | 5032 | dolock = rb_reader_lock(cpu_buffer); |
554f786e | 5033 | ret = rb_per_cpu_empty(cpu_buffer); |
289a5a25 | 5034 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 5035 | local_irq_restore(flags); |
554f786e SR |
5036 | |
5037 | return ret; | |
7a8e76a3 | 5038 | } |
c4f50183 | 5039 | EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
7a8e76a3 | 5040 | |
85bac32c | 5041 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
7a8e76a3 SR |
5042 | /** |
5043 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers | |
5044 | * @buffer_a: One buffer to swap with | |
5045 | * @buffer_b: The other buffer to swap with | |
59e7cffe | 5046 | * @cpu: the CPU of the buffers to swap |
7a8e76a3 SR |
5047 | * |
5048 | * This function is useful for tracers that want to take a "snapshot" | |
5049 | * of a CPU buffer and has another back up buffer lying around. | |
5050 | * it is expected that the tracer handles the cpu buffer not being | |
5051 | * used at the moment. | |
5052 | */ | |
13292494 SRV |
5053 | int ring_buffer_swap_cpu(struct trace_buffer *buffer_a, |
5054 | struct trace_buffer *buffer_b, int cpu) | |
7a8e76a3 SR |
5055 | { |
5056 | struct ring_buffer_per_cpu *cpu_buffer_a; | |
5057 | struct ring_buffer_per_cpu *cpu_buffer_b; | |
554f786e SR |
5058 | int ret = -EINVAL; |
5059 | ||
9e01c1b7 RR |
5060 | if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
5061 | !cpumask_test_cpu(cpu, buffer_b->cpumask)) | |
554f786e | 5062 | goto out; |
7a8e76a3 | 5063 | |
438ced17 VN |
5064 | cpu_buffer_a = buffer_a->buffers[cpu]; |
5065 | cpu_buffer_b = buffer_b->buffers[cpu]; | |
5066 | ||
7a8e76a3 | 5067 | /* At least make sure the two buffers are somewhat the same */ |
438ced17 | 5068 | if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) |
554f786e SR |
5069 | goto out; |
5070 | ||
5071 | ret = -EAGAIN; | |
7a8e76a3 | 5072 | |
97b17efe | 5073 | if (atomic_read(&buffer_a->record_disabled)) |
554f786e | 5074 | goto out; |
97b17efe SR |
5075 | |
5076 | if (atomic_read(&buffer_b->record_disabled)) | |
554f786e | 5077 | goto out; |
97b17efe | 5078 | |
97b17efe | 5079 | if (atomic_read(&cpu_buffer_a->record_disabled)) |
554f786e | 5080 | goto out; |
97b17efe SR |
5081 | |
5082 | if (atomic_read(&cpu_buffer_b->record_disabled)) | |
554f786e | 5083 | goto out; |
97b17efe | 5084 | |
7a8e76a3 | 5085 | /* |
74401729 | 5086 | * We can't do a synchronize_rcu here because this |
7a8e76a3 SR |
5087 | * function can be called in atomic context. |
5088 | * Normally this will be called from the same CPU as cpu. | |
5089 | * If not it's up to the caller to protect this. | |
5090 | */ | |
5091 | atomic_inc(&cpu_buffer_a->record_disabled); | |
5092 | atomic_inc(&cpu_buffer_b->record_disabled); | |
5093 | ||
98277991 SR |
5094 | ret = -EBUSY; |
5095 | if (local_read(&cpu_buffer_a->committing)) | |
5096 | goto out_dec; | |
5097 | if (local_read(&cpu_buffer_b->committing)) | |
5098 | goto out_dec; | |
5099 | ||
7a8e76a3 SR |
5100 | buffer_a->buffers[cpu] = cpu_buffer_b; |
5101 | buffer_b->buffers[cpu] = cpu_buffer_a; | |
5102 | ||
5103 | cpu_buffer_b->buffer = buffer_a; | |
5104 | cpu_buffer_a->buffer = buffer_b; | |
5105 | ||
98277991 SR |
5106 | ret = 0; |
5107 | ||
5108 | out_dec: | |
7a8e76a3 SR |
5109 | atomic_dec(&cpu_buffer_a->record_disabled); |
5110 | atomic_dec(&cpu_buffer_b->record_disabled); | |
554f786e | 5111 | out: |
554f786e | 5112 | return ret; |
7a8e76a3 | 5113 | } |
c4f50183 | 5114 | EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
85bac32c | 5115 | #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
7a8e76a3 | 5116 | |
8789a9e7 SR |
5117 | /** |
5118 | * ring_buffer_alloc_read_page - allocate a page to read from buffer | |
5119 | * @buffer: the buffer to allocate for. | |
d611851b | 5120 | * @cpu: the cpu buffer to allocate. |
8789a9e7 SR |
5121 | * |
5122 | * This function is used in conjunction with ring_buffer_read_page. | |
5123 | * When reading a full page from the ring buffer, these functions | |
5124 | * can be used to speed up the process. The calling function should | |
5125 | * allocate a few pages first with this function. Then when it | |
5126 | * needs to get pages from the ring buffer, it passes the result | |
5127 | * of this function into ring_buffer_read_page, which will swap | |
5128 | * the page that was allocated, with the read page of the buffer. | |
5129 | * | |
5130 | * Returns: | |
a7e52ad7 | 5131 | * The page allocated, or ERR_PTR |
8789a9e7 | 5132 | */ |
13292494 | 5133 | void *ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu) |
8789a9e7 | 5134 | { |
a7e52ad7 | 5135 | struct ring_buffer_per_cpu *cpu_buffer; |
73a757e6 SRV |
5136 | struct buffer_data_page *bpage = NULL; |
5137 | unsigned long flags; | |
7ea59064 | 5138 | struct page *page; |
8789a9e7 | 5139 | |
a7e52ad7 SRV |
5140 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
5141 | return ERR_PTR(-ENODEV); | |
5142 | ||
5143 | cpu_buffer = buffer->buffers[cpu]; | |
73a757e6 SRV |
5144 | local_irq_save(flags); |
5145 | arch_spin_lock(&cpu_buffer->lock); | |
5146 | ||
5147 | if (cpu_buffer->free_page) { | |
5148 | bpage = cpu_buffer->free_page; | |
5149 | cpu_buffer->free_page = NULL; | |
5150 | } | |
5151 | ||
5152 | arch_spin_unlock(&cpu_buffer->lock); | |
5153 | local_irq_restore(flags); | |
5154 | ||
5155 | if (bpage) | |
5156 | goto out; | |
5157 | ||
d7ec4bfe VN |
5158 | page = alloc_pages_node(cpu_to_node(cpu), |
5159 | GFP_KERNEL | __GFP_NORETRY, 0); | |
7ea59064 | 5160 | if (!page) |
a7e52ad7 | 5161 | return ERR_PTR(-ENOMEM); |
8789a9e7 | 5162 | |
7ea59064 | 5163 | bpage = page_address(page); |
8789a9e7 | 5164 | |
73a757e6 | 5165 | out: |
ef7a4a16 SR |
5166 | rb_init_page(bpage); |
5167 | ||
044fa782 | 5168 | return bpage; |
8789a9e7 | 5169 | } |
d6ce96da | 5170 | EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
8789a9e7 SR |
5171 | |
5172 | /** | |
5173 | * ring_buffer_free_read_page - free an allocated read page | |
5174 | * @buffer: the buffer the page was allocate for | |
73a757e6 | 5175 | * @cpu: the cpu buffer the page came from |
8789a9e7 SR |
5176 | * @data: the page to free |
5177 | * | |
5178 | * Free a page allocated from ring_buffer_alloc_read_page. | |
5179 | */ | |
13292494 | 5180 | void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data) |
8789a9e7 | 5181 | { |
73a757e6 SRV |
5182 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
5183 | struct buffer_data_page *bpage = data; | |
ae415fa4 | 5184 | struct page *page = virt_to_page(bpage); |
73a757e6 SRV |
5185 | unsigned long flags; |
5186 | ||
ae415fa4 SRV |
5187 | /* If the page is still in use someplace else, we can't reuse it */ |
5188 | if (page_ref_count(page) > 1) | |
5189 | goto out; | |
5190 | ||
73a757e6 SRV |
5191 | local_irq_save(flags); |
5192 | arch_spin_lock(&cpu_buffer->lock); | |
5193 | ||
5194 | if (!cpu_buffer->free_page) { | |
5195 | cpu_buffer->free_page = bpage; | |
5196 | bpage = NULL; | |
5197 | } | |
5198 | ||
5199 | arch_spin_unlock(&cpu_buffer->lock); | |
5200 | local_irq_restore(flags); | |
5201 | ||
ae415fa4 | 5202 | out: |
73a757e6 | 5203 | free_page((unsigned long)bpage); |
8789a9e7 | 5204 | } |
d6ce96da | 5205 | EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
8789a9e7 SR |
5206 | |
5207 | /** | |
5208 | * ring_buffer_read_page - extract a page from the ring buffer | |
5209 | * @buffer: buffer to extract from | |
5210 | * @data_page: the page to use allocated from ring_buffer_alloc_read_page | |
ef7a4a16 | 5211 | * @len: amount to extract |
8789a9e7 SR |
5212 | * @cpu: the cpu of the buffer to extract |
5213 | * @full: should the extraction only happen when the page is full. | |
5214 | * | |
5215 | * This function will pull out a page from the ring buffer and consume it. | |
5216 | * @data_page must be the address of the variable that was returned | |
5217 | * from ring_buffer_alloc_read_page. This is because the page might be used | |
5218 | * to swap with a page in the ring buffer. | |
5219 | * | |
5220 | * for example: | |
d611851b | 5221 | * rpage = ring_buffer_alloc_read_page(buffer, cpu); |
a7e52ad7 SRV |
5222 | * if (IS_ERR(rpage)) |
5223 | * return PTR_ERR(rpage); | |
ef7a4a16 | 5224 | * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
667d2412 LJ |
5225 | * if (ret >= 0) |
5226 | * process_page(rpage, ret); | |
8789a9e7 SR |
5227 | * |
5228 | * When @full is set, the function will not return true unless | |
5229 | * the writer is off the reader page. | |
5230 | * | |
5231 | * Note: it is up to the calling functions to handle sleeps and wakeups. | |
5232 | * The ring buffer can be used anywhere in the kernel and can not | |
5233 | * blindly call wake_up. The layer that uses the ring buffer must be | |
5234 | * responsible for that. | |
5235 | * | |
5236 | * Returns: | |
667d2412 LJ |
5237 | * >=0 if data has been transferred, returns the offset of consumed data. |
5238 | * <0 if no data has been transferred. | |
8789a9e7 | 5239 | */ |
13292494 | 5240 | int ring_buffer_read_page(struct trace_buffer *buffer, |
ef7a4a16 | 5241 | void **data_page, size_t len, int cpu, int full) |
8789a9e7 SR |
5242 | { |
5243 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
5244 | struct ring_buffer_event *event; | |
044fa782 | 5245 | struct buffer_data_page *bpage; |
ef7a4a16 | 5246 | struct buffer_page *reader; |
ff0ff84a | 5247 | unsigned long missed_events; |
8789a9e7 | 5248 | unsigned long flags; |
ef7a4a16 | 5249 | unsigned int commit; |
667d2412 | 5250 | unsigned int read; |
4f3640f8 | 5251 | u64 save_timestamp; |
667d2412 | 5252 | int ret = -1; |
8789a9e7 | 5253 | |
554f786e SR |
5254 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
5255 | goto out; | |
5256 | ||
474d32b6 SR |
5257 | /* |
5258 | * If len is not big enough to hold the page header, then | |
5259 | * we can not copy anything. | |
5260 | */ | |
5261 | if (len <= BUF_PAGE_HDR_SIZE) | |
554f786e | 5262 | goto out; |
474d32b6 SR |
5263 | |
5264 | len -= BUF_PAGE_HDR_SIZE; | |
5265 | ||
8789a9e7 | 5266 | if (!data_page) |
554f786e | 5267 | goto out; |
8789a9e7 | 5268 | |
044fa782 SR |
5269 | bpage = *data_page; |
5270 | if (!bpage) | |
554f786e | 5271 | goto out; |
8789a9e7 | 5272 | |
5389f6fa | 5273 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 5274 | |
ef7a4a16 SR |
5275 | reader = rb_get_reader_page(cpu_buffer); |
5276 | if (!reader) | |
554f786e | 5277 | goto out_unlock; |
8789a9e7 | 5278 | |
ef7a4a16 SR |
5279 | event = rb_reader_event(cpu_buffer); |
5280 | ||
5281 | read = reader->read; | |
5282 | commit = rb_page_commit(reader); | |
667d2412 | 5283 | |
66a8cb95 | 5284 | /* Check if any events were dropped */ |
ff0ff84a | 5285 | missed_events = cpu_buffer->lost_events; |
66a8cb95 | 5286 | |
8789a9e7 | 5287 | /* |
474d32b6 SR |
5288 | * If this page has been partially read or |
5289 | * if len is not big enough to read the rest of the page or | |
5290 | * a writer is still on the page, then | |
5291 | * we must copy the data from the page to the buffer. | |
5292 | * Otherwise, we can simply swap the page with the one passed in. | |
8789a9e7 | 5293 | */ |
474d32b6 | 5294 | if (read || (len < (commit - read)) || |
ef7a4a16 | 5295 | cpu_buffer->reader_page == cpu_buffer->commit_page) { |
667d2412 | 5296 | struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
474d32b6 SR |
5297 | unsigned int rpos = read; |
5298 | unsigned int pos = 0; | |
ef7a4a16 | 5299 | unsigned int size; |
8789a9e7 SR |
5300 | |
5301 | if (full) | |
554f786e | 5302 | goto out_unlock; |
8789a9e7 | 5303 | |
ef7a4a16 SR |
5304 | if (len > (commit - read)) |
5305 | len = (commit - read); | |
5306 | ||
69d1b839 SR |
5307 | /* Always keep the time extend and data together */ |
5308 | size = rb_event_ts_length(event); | |
ef7a4a16 SR |
5309 | |
5310 | if (len < size) | |
554f786e | 5311 | goto out_unlock; |
ef7a4a16 | 5312 | |
4f3640f8 SR |
5313 | /* save the current timestamp, since the user will need it */ |
5314 | save_timestamp = cpu_buffer->read_stamp; | |
5315 | ||
ef7a4a16 SR |
5316 | /* Need to copy one event at a time */ |
5317 | do { | |
e1e35927 DS |
5318 | /* We need the size of one event, because |
5319 | * rb_advance_reader only advances by one event, | |
5320 | * whereas rb_event_ts_length may include the size of | |
5321 | * one or two events. | |
5322 | * We have already ensured there's enough space if this | |
5323 | * is a time extend. */ | |
5324 | size = rb_event_length(event); | |
474d32b6 | 5325 | memcpy(bpage->data + pos, rpage->data + rpos, size); |
ef7a4a16 SR |
5326 | |
5327 | len -= size; | |
5328 | ||
5329 | rb_advance_reader(cpu_buffer); | |
474d32b6 SR |
5330 | rpos = reader->read; |
5331 | pos += size; | |
ef7a4a16 | 5332 | |
18fab912 HY |
5333 | if (rpos >= commit) |
5334 | break; | |
5335 | ||
ef7a4a16 | 5336 | event = rb_reader_event(cpu_buffer); |
69d1b839 SR |
5337 | /* Always keep the time extend and data together */ |
5338 | size = rb_event_ts_length(event); | |
e1e35927 | 5339 | } while (len >= size); |
667d2412 LJ |
5340 | |
5341 | /* update bpage */ | |
ef7a4a16 | 5342 | local_set(&bpage->commit, pos); |
4f3640f8 | 5343 | bpage->time_stamp = save_timestamp; |
ef7a4a16 | 5344 | |
474d32b6 SR |
5345 | /* we copied everything to the beginning */ |
5346 | read = 0; | |
8789a9e7 | 5347 | } else { |
afbab76a | 5348 | /* update the entry counter */ |
77ae365e | 5349 | cpu_buffer->read += rb_page_entries(reader); |
c64e148a | 5350 | cpu_buffer->read_bytes += BUF_PAGE_SIZE; |
afbab76a | 5351 | |
8789a9e7 | 5352 | /* swap the pages */ |
044fa782 | 5353 | rb_init_page(bpage); |
ef7a4a16 SR |
5354 | bpage = reader->page; |
5355 | reader->page = *data_page; | |
5356 | local_set(&reader->write, 0); | |
778c55d4 | 5357 | local_set(&reader->entries, 0); |
ef7a4a16 | 5358 | reader->read = 0; |
044fa782 | 5359 | *data_page = bpage; |
ff0ff84a SR |
5360 | |
5361 | /* | |
5362 | * Use the real_end for the data size, | |
5363 | * This gives us a chance to store the lost events | |
5364 | * on the page. | |
5365 | */ | |
5366 | if (reader->real_end) | |
5367 | local_set(&bpage->commit, reader->real_end); | |
8789a9e7 | 5368 | } |
667d2412 | 5369 | ret = read; |
8789a9e7 | 5370 | |
66a8cb95 | 5371 | cpu_buffer->lost_events = 0; |
2711ca23 SR |
5372 | |
5373 | commit = local_read(&bpage->commit); | |
66a8cb95 SR |
5374 | /* |
5375 | * Set a flag in the commit field if we lost events | |
5376 | */ | |
ff0ff84a | 5377 | if (missed_events) { |
ff0ff84a SR |
5378 | /* If there is room at the end of the page to save the |
5379 | * missed events, then record it there. | |
5380 | */ | |
5381 | if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { | |
5382 | memcpy(&bpage->data[commit], &missed_events, | |
5383 | sizeof(missed_events)); | |
5384 | local_add(RB_MISSED_STORED, &bpage->commit); | |
2711ca23 | 5385 | commit += sizeof(missed_events); |
ff0ff84a | 5386 | } |
66a8cb95 | 5387 | local_add(RB_MISSED_EVENTS, &bpage->commit); |
ff0ff84a | 5388 | } |
66a8cb95 | 5389 | |
2711ca23 SR |
5390 | /* |
5391 | * This page may be off to user land. Zero it out here. | |
5392 | */ | |
5393 | if (commit < BUF_PAGE_SIZE) | |
5394 | memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit); | |
5395 | ||
554f786e | 5396 | out_unlock: |
5389f6fa | 5397 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 5398 | |
554f786e | 5399 | out: |
8789a9e7 SR |
5400 | return ret; |
5401 | } | |
d6ce96da | 5402 | EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
8789a9e7 | 5403 | |
b32614c0 SAS |
5404 | /* |
5405 | * We only allocate new buffers, never free them if the CPU goes down. | |
5406 | * If we were to free the buffer, then the user would lose any trace that was in | |
5407 | * the buffer. | |
5408 | */ | |
5409 | int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node) | |
554f786e | 5410 | { |
13292494 | 5411 | struct trace_buffer *buffer; |
9b94a8fb SRRH |
5412 | long nr_pages_same; |
5413 | int cpu_i; | |
5414 | unsigned long nr_pages; | |
554f786e | 5415 | |
13292494 | 5416 | buffer = container_of(node, struct trace_buffer, node); |
b32614c0 SAS |
5417 | if (cpumask_test_cpu(cpu, buffer->cpumask)) |
5418 | return 0; | |
5419 | ||
5420 | nr_pages = 0; | |
5421 | nr_pages_same = 1; | |
5422 | /* check if all cpu sizes are same */ | |
5423 | for_each_buffer_cpu(buffer, cpu_i) { | |
5424 | /* fill in the size from first enabled cpu */ | |
5425 | if (nr_pages == 0) | |
5426 | nr_pages = buffer->buffers[cpu_i]->nr_pages; | |
5427 | if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { | |
5428 | nr_pages_same = 0; | |
5429 | break; | |
554f786e | 5430 | } |
554f786e | 5431 | } |
b32614c0 SAS |
5432 | /* allocate minimum pages, user can later expand it */ |
5433 | if (!nr_pages_same) | |
5434 | nr_pages = 2; | |
5435 | buffer->buffers[cpu] = | |
5436 | rb_allocate_cpu_buffer(buffer, nr_pages, cpu); | |
5437 | if (!buffer->buffers[cpu]) { | |
5438 | WARN(1, "failed to allocate ring buffer on CPU %u\n", | |
5439 | cpu); | |
5440 | return -ENOMEM; | |
5441 | } | |
5442 | smp_wmb(); | |
5443 | cpumask_set_cpu(cpu, buffer->cpumask); | |
5444 | return 0; | |
554f786e | 5445 | } |
6c43e554 SRRH |
5446 | |
5447 | #ifdef CONFIG_RING_BUFFER_STARTUP_TEST | |
5448 | /* | |
5449 | * This is a basic integrity check of the ring buffer. | |
5450 | * Late in the boot cycle this test will run when configured in. | |
5451 | * It will kick off a thread per CPU that will go into a loop | |
5452 | * writing to the per cpu ring buffer various sizes of data. | |
5453 | * Some of the data will be large items, some small. | |
5454 | * | |
5455 | * Another thread is created that goes into a spin, sending out | |
5456 | * IPIs to the other CPUs to also write into the ring buffer. | |
5457 | * this is to test the nesting ability of the buffer. | |
5458 | * | |
5459 | * Basic stats are recorded and reported. If something in the | |
5460 | * ring buffer should happen that's not expected, a big warning | |
5461 | * is displayed and all ring buffers are disabled. | |
5462 | */ | |
5463 | static struct task_struct *rb_threads[NR_CPUS] __initdata; | |
5464 | ||
5465 | struct rb_test_data { | |
13292494 | 5466 | struct trace_buffer *buffer; |
6c43e554 SRRH |
5467 | unsigned long events; |
5468 | unsigned long bytes_written; | |
5469 | unsigned long bytes_alloc; | |
5470 | unsigned long bytes_dropped; | |
5471 | unsigned long events_nested; | |
5472 | unsigned long bytes_written_nested; | |
5473 | unsigned long bytes_alloc_nested; | |
5474 | unsigned long bytes_dropped_nested; | |
5475 | int min_size_nested; | |
5476 | int max_size_nested; | |
5477 | int max_size; | |
5478 | int min_size; | |
5479 | int cpu; | |
5480 | int cnt; | |
5481 | }; | |
5482 | ||
5483 | static struct rb_test_data rb_data[NR_CPUS] __initdata; | |
5484 | ||
5485 | /* 1 meg per cpu */ | |
5486 | #define RB_TEST_BUFFER_SIZE 1048576 | |
5487 | ||
5488 | static char rb_string[] __initdata = | |
5489 | "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" | |
5490 | "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" | |
5491 | "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv"; | |
5492 | ||
5493 | static bool rb_test_started __initdata; | |
5494 | ||
5495 | struct rb_item { | |
5496 | int size; | |
5497 | char str[]; | |
5498 | }; | |
5499 | ||
5500 | static __init int rb_write_something(struct rb_test_data *data, bool nested) | |
5501 | { | |
5502 | struct ring_buffer_event *event; | |
5503 | struct rb_item *item; | |
5504 | bool started; | |
5505 | int event_len; | |
5506 | int size; | |
5507 | int len; | |
5508 | int cnt; | |
5509 | ||
5510 | /* Have nested writes different that what is written */ | |
5511 | cnt = data->cnt + (nested ? 27 : 0); | |
5512 | ||
5513 | /* Multiply cnt by ~e, to make some unique increment */ | |
40ed29b3 | 5514 | size = (cnt * 68 / 25) % (sizeof(rb_string) - 1); |
6c43e554 SRRH |
5515 | |
5516 | len = size + sizeof(struct rb_item); | |
5517 | ||
5518 | started = rb_test_started; | |
5519 | /* read rb_test_started before checking buffer enabled */ | |
5520 | smp_rmb(); | |
5521 | ||
5522 | event = ring_buffer_lock_reserve(data->buffer, len); | |
5523 | if (!event) { | |
5524 | /* Ignore dropped events before test starts. */ | |
5525 | if (started) { | |
5526 | if (nested) | |
5527 | data->bytes_dropped += len; | |
5528 | else | |
5529 | data->bytes_dropped_nested += len; | |
5530 | } | |
5531 | return len; | |
5532 | } | |
5533 | ||
5534 | event_len = ring_buffer_event_length(event); | |
5535 | ||
5536 | if (RB_WARN_ON(data->buffer, event_len < len)) | |
5537 | goto out; | |
5538 | ||
5539 | item = ring_buffer_event_data(event); | |
5540 | item->size = size; | |
5541 | memcpy(item->str, rb_string, size); | |
5542 | ||
5543 | if (nested) { | |
5544 | data->bytes_alloc_nested += event_len; | |
5545 | data->bytes_written_nested += len; | |
5546 | data->events_nested++; | |
5547 | if (!data->min_size_nested || len < data->min_size_nested) | |
5548 | data->min_size_nested = len; | |
5549 | if (len > data->max_size_nested) | |
5550 | data->max_size_nested = len; | |
5551 | } else { | |
5552 | data->bytes_alloc += event_len; | |
5553 | data->bytes_written += len; | |
5554 | data->events++; | |
5555 | if (!data->min_size || len < data->min_size) | |
5556 | data->max_size = len; | |
5557 | if (len > data->max_size) | |
5558 | data->max_size = len; | |
5559 | } | |
5560 | ||
5561 | out: | |
5562 | ring_buffer_unlock_commit(data->buffer, event); | |
5563 | ||
5564 | return 0; | |
5565 | } | |
5566 | ||
5567 | static __init int rb_test(void *arg) | |
5568 | { | |
5569 | struct rb_test_data *data = arg; | |
5570 | ||
5571 | while (!kthread_should_stop()) { | |
5572 | rb_write_something(data, false); | |
5573 | data->cnt++; | |
5574 | ||
5575 | set_current_state(TASK_INTERRUPTIBLE); | |
5576 | /* Now sleep between a min of 100-300us and a max of 1ms */ | |
5577 | usleep_range(((data->cnt % 3) + 1) * 100, 1000); | |
5578 | } | |
5579 | ||
5580 | return 0; | |
5581 | } | |
5582 | ||
5583 | static __init void rb_ipi(void *ignore) | |
5584 | { | |
5585 | struct rb_test_data *data; | |
5586 | int cpu = smp_processor_id(); | |
5587 | ||
5588 | data = &rb_data[cpu]; | |
5589 | rb_write_something(data, true); | |
5590 | } | |
5591 | ||
5592 | static __init int rb_hammer_test(void *arg) | |
5593 | { | |
5594 | while (!kthread_should_stop()) { | |
5595 | ||
5596 | /* Send an IPI to all cpus to write data! */ | |
5597 | smp_call_function(rb_ipi, NULL, 1); | |
5598 | /* No sleep, but for non preempt, let others run */ | |
5599 | schedule(); | |
5600 | } | |
5601 | ||
5602 | return 0; | |
5603 | } | |
5604 | ||
5605 | static __init int test_ringbuffer(void) | |
5606 | { | |
5607 | struct task_struct *rb_hammer; | |
13292494 | 5608 | struct trace_buffer *buffer; |
6c43e554 SRRH |
5609 | int cpu; |
5610 | int ret = 0; | |
5611 | ||
a356646a | 5612 | if (security_locked_down(LOCKDOWN_TRACEFS)) { |
ee195452 | 5613 | pr_warn("Lockdown is enabled, skipping ring buffer tests\n"); |
a356646a SRV |
5614 | return 0; |
5615 | } | |
5616 | ||
6c43e554 SRRH |
5617 | pr_info("Running ring buffer tests...\n"); |
5618 | ||
5619 | buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); | |
5620 | if (WARN_ON(!buffer)) | |
5621 | return 0; | |
5622 | ||
5623 | /* Disable buffer so that threads can't write to it yet */ | |
5624 | ring_buffer_record_off(buffer); | |
5625 | ||
5626 | for_each_online_cpu(cpu) { | |
5627 | rb_data[cpu].buffer = buffer; | |
5628 | rb_data[cpu].cpu = cpu; | |
5629 | rb_data[cpu].cnt = cpu; | |
5630 | rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu], | |
5631 | "rbtester/%d", cpu); | |
62277de7 | 5632 | if (WARN_ON(IS_ERR(rb_threads[cpu]))) { |
6c43e554 | 5633 | pr_cont("FAILED\n"); |
62277de7 | 5634 | ret = PTR_ERR(rb_threads[cpu]); |
6c43e554 SRRH |
5635 | goto out_free; |
5636 | } | |
5637 | ||
5638 | kthread_bind(rb_threads[cpu], cpu); | |
5639 | wake_up_process(rb_threads[cpu]); | |
5640 | } | |
5641 | ||
5642 | /* Now create the rb hammer! */ | |
5643 | rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); | |
62277de7 | 5644 | if (WARN_ON(IS_ERR(rb_hammer))) { |
6c43e554 | 5645 | pr_cont("FAILED\n"); |
62277de7 | 5646 | ret = PTR_ERR(rb_hammer); |
6c43e554 SRRH |
5647 | goto out_free; |
5648 | } | |
5649 | ||
5650 | ring_buffer_record_on(buffer); | |
5651 | /* | |
5652 | * Show buffer is enabled before setting rb_test_started. | |
5653 | * Yes there's a small race window where events could be | |
5654 | * dropped and the thread wont catch it. But when a ring | |
5655 | * buffer gets enabled, there will always be some kind of | |
5656 | * delay before other CPUs see it. Thus, we don't care about | |
5657 | * those dropped events. We care about events dropped after | |
5658 | * the threads see that the buffer is active. | |
5659 | */ | |
5660 | smp_wmb(); | |
5661 | rb_test_started = true; | |
5662 | ||
5663 | set_current_state(TASK_INTERRUPTIBLE); | |
5664 | /* Just run for 10 seconds */; | |
5665 | schedule_timeout(10 * HZ); | |
5666 | ||
5667 | kthread_stop(rb_hammer); | |
5668 | ||
5669 | out_free: | |
5670 | for_each_online_cpu(cpu) { | |
5671 | if (!rb_threads[cpu]) | |
5672 | break; | |
5673 | kthread_stop(rb_threads[cpu]); | |
5674 | } | |
5675 | if (ret) { | |
5676 | ring_buffer_free(buffer); | |
5677 | return ret; | |
5678 | } | |
5679 | ||
5680 | /* Report! */ | |
5681 | pr_info("finished\n"); | |
5682 | for_each_online_cpu(cpu) { | |
5683 | struct ring_buffer_event *event; | |
5684 | struct rb_test_data *data = &rb_data[cpu]; | |
5685 | struct rb_item *item; | |
5686 | unsigned long total_events; | |
5687 | unsigned long total_dropped; | |
5688 | unsigned long total_written; | |
5689 | unsigned long total_alloc; | |
5690 | unsigned long total_read = 0; | |
5691 | unsigned long total_size = 0; | |
5692 | unsigned long total_len = 0; | |
5693 | unsigned long total_lost = 0; | |
5694 | unsigned long lost; | |
5695 | int big_event_size; | |
5696 | int small_event_size; | |
5697 | ||
5698 | ret = -1; | |
5699 | ||
5700 | total_events = data->events + data->events_nested; | |
5701 | total_written = data->bytes_written + data->bytes_written_nested; | |
5702 | total_alloc = data->bytes_alloc + data->bytes_alloc_nested; | |
5703 | total_dropped = data->bytes_dropped + data->bytes_dropped_nested; | |
5704 | ||
5705 | big_event_size = data->max_size + data->max_size_nested; | |
5706 | small_event_size = data->min_size + data->min_size_nested; | |
5707 | ||
5708 | pr_info("CPU %d:\n", cpu); | |
5709 | pr_info(" events: %ld\n", total_events); | |
5710 | pr_info(" dropped bytes: %ld\n", total_dropped); | |
5711 | pr_info(" alloced bytes: %ld\n", total_alloc); | |
5712 | pr_info(" written bytes: %ld\n", total_written); | |
5713 | pr_info(" biggest event: %d\n", big_event_size); | |
5714 | pr_info(" smallest event: %d\n", small_event_size); | |
5715 | ||
5716 | if (RB_WARN_ON(buffer, total_dropped)) | |
5717 | break; | |
5718 | ||
5719 | ret = 0; | |
5720 | ||
5721 | while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { | |
5722 | total_lost += lost; | |
5723 | item = ring_buffer_event_data(event); | |
5724 | total_len += ring_buffer_event_length(event); | |
5725 | total_size += item->size + sizeof(struct rb_item); | |
5726 | if (memcmp(&item->str[0], rb_string, item->size) != 0) { | |
5727 | pr_info("FAILED!\n"); | |
5728 | pr_info("buffer had: %.*s\n", item->size, item->str); | |
5729 | pr_info("expected: %.*s\n", item->size, rb_string); | |
5730 | RB_WARN_ON(buffer, 1); | |
5731 | ret = -1; | |
5732 | break; | |
5733 | } | |
5734 | total_read++; | |
5735 | } | |
5736 | if (ret) | |
5737 | break; | |
5738 | ||
5739 | ret = -1; | |
5740 | ||
5741 | pr_info(" read events: %ld\n", total_read); | |
5742 | pr_info(" lost events: %ld\n", total_lost); | |
5743 | pr_info(" total events: %ld\n", total_lost + total_read); | |
5744 | pr_info(" recorded len bytes: %ld\n", total_len); | |
5745 | pr_info(" recorded size bytes: %ld\n", total_size); | |
5746 | if (total_lost) | |
5747 | pr_info(" With dropped events, record len and size may not match\n" | |
5748 | " alloced and written from above\n"); | |
5749 | if (!total_lost) { | |
5750 | if (RB_WARN_ON(buffer, total_len != total_alloc || | |
5751 | total_size != total_written)) | |
5752 | break; | |
5753 | } | |
5754 | if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) | |
5755 | break; | |
5756 | ||
5757 | ret = 0; | |
5758 | } | |
5759 | if (!ret) | |
5760 | pr_info("Ring buffer PASSED!\n"); | |
5761 | ||
5762 | ring_buffer_free(buffer); | |
5763 | return 0; | |
5764 | } | |
5765 | ||
5766 | late_initcall(test_ringbuffer); | |
5767 | #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */ |