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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> |
7a8e76a3 | 14 | #include <linux/uaccess.h> |
a81bd80a | 15 | #include <linux/hardirq.h> |
6c43e554 | 16 | #include <linux/kthread.h> /* for self test */ |
7a8e76a3 SR |
17 | #include <linux/module.h> |
18 | #include <linux/percpu.h> | |
19 | #include <linux/mutex.h> | |
6c43e554 | 20 | #include <linux/delay.h> |
5a0e3ad6 | 21 | #include <linux/slab.h> |
7a8e76a3 SR |
22 | #include <linux/init.h> |
23 | #include <linux/hash.h> | |
24 | #include <linux/list.h> | |
554f786e | 25 | #include <linux/cpu.h> |
927e56db | 26 | #include <linux/oom.h> |
7a8e76a3 | 27 | |
79615760 | 28 | #include <asm/local.h> |
182e9f5f | 29 | |
83f40318 VN |
30 | static void update_pages_handler(struct work_struct *work); |
31 | ||
d1b182a8 SR |
32 | /* |
33 | * The ring buffer header is special. We must manually up keep it. | |
34 | */ | |
35 | int ring_buffer_print_entry_header(struct trace_seq *s) | |
36 | { | |
c0cd93aa SRRH |
37 | trace_seq_puts(s, "# compressed entry header\n"); |
38 | trace_seq_puts(s, "\ttype_len : 5 bits\n"); | |
39 | trace_seq_puts(s, "\ttime_delta : 27 bits\n"); | |
40 | trace_seq_puts(s, "\tarray : 32 bits\n"); | |
41 | trace_seq_putc(s, '\n'); | |
42 | trace_seq_printf(s, "\tpadding : type == %d\n", | |
43 | RINGBUF_TYPE_PADDING); | |
44 | trace_seq_printf(s, "\ttime_extend : type == %d\n", | |
45 | RINGBUF_TYPE_TIME_EXTEND); | |
dc4e2801 TZ |
46 | trace_seq_printf(s, "\ttime_stamp : type == %d\n", |
47 | RINGBUF_TYPE_TIME_STAMP); | |
c0cd93aa SRRH |
48 | trace_seq_printf(s, "\tdata max type_len == %d\n", |
49 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); | |
50 | ||
51 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
52 | } |
53 | ||
5cc98548 SR |
54 | /* |
55 | * The ring buffer is made up of a list of pages. A separate list of pages is | |
56 | * allocated for each CPU. A writer may only write to a buffer that is | |
57 | * associated with the CPU it is currently executing on. A reader may read | |
58 | * from any per cpu buffer. | |
59 | * | |
60 | * The reader is special. For each per cpu buffer, the reader has its own | |
61 | * reader page. When a reader has read the entire reader page, this reader | |
62 | * page is swapped with another page in the ring buffer. | |
63 | * | |
64 | * Now, as long as the writer is off the reader page, the reader can do what | |
65 | * ever it wants with that page. The writer will never write to that page | |
66 | * again (as long as it is out of the ring buffer). | |
67 | * | |
68 | * Here's some silly ASCII art. | |
69 | * | |
70 | * +------+ | |
71 | * |reader| RING BUFFER | |
72 | * |page | | |
73 | * +------+ +---+ +---+ +---+ | |
74 | * | |-->| |-->| | | |
75 | * +---+ +---+ +---+ | |
76 | * ^ | | |
77 | * | | | |
78 | * +---------------+ | |
79 | * | |
80 | * | |
81 | * +------+ | |
82 | * |reader| RING BUFFER | |
83 | * |page |------------------v | |
84 | * +------+ +---+ +---+ +---+ | |
85 | * | |-->| |-->| | | |
86 | * +---+ +---+ +---+ | |
87 | * ^ | | |
88 | * | | | |
89 | * +---------------+ | |
90 | * | |
91 | * | |
92 | * +------+ | |
93 | * |reader| RING BUFFER | |
94 | * |page |------------------v | |
95 | * +------+ +---+ +---+ +---+ | |
96 | * ^ | |-->| |-->| | | |
97 | * | +---+ +---+ +---+ | |
98 | * | | | |
99 | * | | | |
100 | * +------------------------------+ | |
101 | * | |
102 | * | |
103 | * +------+ | |
104 | * |buffer| RING BUFFER | |
105 | * |page |------------------v | |
106 | * +------+ +---+ +---+ +---+ | |
107 | * ^ | | | |-->| | | |
108 | * | New +---+ +---+ +---+ | |
109 | * | Reader------^ | | |
110 | * | page | | |
111 | * +------------------------------+ | |
112 | * | |
113 | * | |
114 | * After we make this swap, the reader can hand this page off to the splice | |
115 | * code and be done with it. It can even allocate a new page if it needs to | |
116 | * and swap that into the ring buffer. | |
117 | * | |
118 | * We will be using cmpxchg soon to make all this lockless. | |
119 | * | |
120 | */ | |
121 | ||
499e5470 SR |
122 | /* Used for individual buffers (after the counter) */ |
123 | #define RB_BUFFER_OFF (1 << 20) | |
a3583244 | 124 | |
499e5470 | 125 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
033601a3 | 126 | |
e3d6bf0a | 127 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
67d34724 | 128 | #define RB_ALIGNMENT 4U |
334d4169 | 129 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
c7b09308 | 130 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
334d4169 | 131 | |
649508f6 | 132 | #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS |
2271048d SR |
133 | # define RB_FORCE_8BYTE_ALIGNMENT 0 |
134 | # define RB_ARCH_ALIGNMENT RB_ALIGNMENT | |
135 | #else | |
136 | # define RB_FORCE_8BYTE_ALIGNMENT 1 | |
137 | # define RB_ARCH_ALIGNMENT 8U | |
138 | #endif | |
139 | ||
649508f6 JH |
140 | #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) |
141 | ||
334d4169 LJ |
142 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
143 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX | |
7a8e76a3 SR |
144 | |
145 | enum { | |
146 | RB_LEN_TIME_EXTEND = 8, | |
dc4e2801 | 147 | RB_LEN_TIME_STAMP = 8, |
7a8e76a3 SR |
148 | }; |
149 | ||
69d1b839 SR |
150 | #define skip_time_extend(event) \ |
151 | ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) | |
152 | ||
dc4e2801 TZ |
153 | #define extended_time(event) \ |
154 | (event->type_len >= RINGBUF_TYPE_TIME_EXTEND) | |
155 | ||
2d622719 TZ |
156 | static inline int rb_null_event(struct ring_buffer_event *event) |
157 | { | |
a1863c21 | 158 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
2d622719 TZ |
159 | } |
160 | ||
161 | static void rb_event_set_padding(struct ring_buffer_event *event) | |
162 | { | |
a1863c21 | 163 | /* padding has a NULL time_delta */ |
334d4169 | 164 | event->type_len = RINGBUF_TYPE_PADDING; |
2d622719 TZ |
165 | event->time_delta = 0; |
166 | } | |
167 | ||
34a148bf | 168 | static unsigned |
2d622719 | 169 | rb_event_data_length(struct ring_buffer_event *event) |
7a8e76a3 SR |
170 | { |
171 | unsigned length; | |
172 | ||
334d4169 LJ |
173 | if (event->type_len) |
174 | length = event->type_len * RB_ALIGNMENT; | |
2d622719 TZ |
175 | else |
176 | length = event->array[0]; | |
177 | return length + RB_EVNT_HDR_SIZE; | |
178 | } | |
179 | ||
69d1b839 SR |
180 | /* |
181 | * Return the length of the given event. Will return | |
182 | * the length of the time extend if the event is a | |
183 | * time extend. | |
184 | */ | |
185 | static inline unsigned | |
2d622719 TZ |
186 | rb_event_length(struct ring_buffer_event *event) |
187 | { | |
334d4169 | 188 | switch (event->type_len) { |
7a8e76a3 | 189 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
190 | if (rb_null_event(event)) |
191 | /* undefined */ | |
192 | return -1; | |
334d4169 | 193 | return event->array[0] + RB_EVNT_HDR_SIZE; |
7a8e76a3 SR |
194 | |
195 | case RINGBUF_TYPE_TIME_EXTEND: | |
196 | return RB_LEN_TIME_EXTEND; | |
197 | ||
198 | case RINGBUF_TYPE_TIME_STAMP: | |
199 | return RB_LEN_TIME_STAMP; | |
200 | ||
201 | case RINGBUF_TYPE_DATA: | |
2d622719 | 202 | return rb_event_data_length(event); |
7a8e76a3 SR |
203 | default: |
204 | BUG(); | |
205 | } | |
206 | /* not hit */ | |
207 | return 0; | |
208 | } | |
209 | ||
69d1b839 SR |
210 | /* |
211 | * Return total length of time extend and data, | |
212 | * or just the event length for all other events. | |
213 | */ | |
214 | static inline unsigned | |
215 | rb_event_ts_length(struct ring_buffer_event *event) | |
216 | { | |
217 | unsigned len = 0; | |
218 | ||
dc4e2801 | 219 | if (extended_time(event)) { |
69d1b839 SR |
220 | /* time extends include the data event after it */ |
221 | len = RB_LEN_TIME_EXTEND; | |
222 | event = skip_time_extend(event); | |
223 | } | |
224 | return len + rb_event_length(event); | |
225 | } | |
226 | ||
7a8e76a3 SR |
227 | /** |
228 | * ring_buffer_event_length - return the length of the event | |
229 | * @event: the event to get the length of | |
69d1b839 SR |
230 | * |
231 | * Returns the size of the data load of a data event. | |
232 | * If the event is something other than a data event, it | |
233 | * returns the size of the event itself. With the exception | |
234 | * of a TIME EXTEND, where it still returns the size of the | |
235 | * data load of the data event after it. | |
7a8e76a3 SR |
236 | */ |
237 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) | |
238 | { | |
69d1b839 SR |
239 | unsigned length; |
240 | ||
dc4e2801 | 241 | if (extended_time(event)) |
69d1b839 SR |
242 | event = skip_time_extend(event); |
243 | ||
244 | length = rb_event_length(event); | |
334d4169 | 245 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
465634ad RR |
246 | return length; |
247 | length -= RB_EVNT_HDR_SIZE; | |
248 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) | |
249 | length -= sizeof(event->array[0]); | |
250 | return length; | |
7a8e76a3 | 251 | } |
c4f50183 | 252 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
7a8e76a3 SR |
253 | |
254 | /* inline for ring buffer fast paths */ | |
929ddbf3 | 255 | static __always_inline void * |
7a8e76a3 SR |
256 | rb_event_data(struct ring_buffer_event *event) |
257 | { | |
dc4e2801 | 258 | if (extended_time(event)) |
69d1b839 | 259 | event = skip_time_extend(event); |
334d4169 | 260 | BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
7a8e76a3 | 261 | /* If length is in len field, then array[0] has the data */ |
334d4169 | 262 | if (event->type_len) |
7a8e76a3 SR |
263 | return (void *)&event->array[0]; |
264 | /* Otherwise length is in array[0] and array[1] has the data */ | |
265 | return (void *)&event->array[1]; | |
266 | } | |
267 | ||
268 | /** | |
269 | * ring_buffer_event_data - return the data of the event | |
270 | * @event: the event to get the data from | |
271 | */ | |
272 | void *ring_buffer_event_data(struct ring_buffer_event *event) | |
273 | { | |
274 | return rb_event_data(event); | |
275 | } | |
c4f50183 | 276 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
7a8e76a3 SR |
277 | |
278 | #define for_each_buffer_cpu(buffer, cpu) \ | |
9e01c1b7 | 279 | for_each_cpu(cpu, buffer->cpumask) |
7a8e76a3 SR |
280 | |
281 | #define TS_SHIFT 27 | |
282 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) | |
283 | #define TS_DELTA_TEST (~TS_MASK) | |
284 | ||
dc4e2801 TZ |
285 | /** |
286 | * ring_buffer_event_time_stamp - return the event's extended timestamp | |
287 | * @event: the event to get the timestamp of | |
288 | * | |
289 | * Returns the extended timestamp associated with a data event. | |
290 | * An extended time_stamp is a 64-bit timestamp represented | |
291 | * internally in a special way that makes the best use of space | |
292 | * contained within a ring buffer event. This function decodes | |
293 | * it and maps it to a straight u64 value. | |
294 | */ | |
295 | u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) | |
296 | { | |
297 | u64 ts; | |
298 | ||
299 | ts = event->array[0]; | |
300 | ts <<= TS_SHIFT; | |
301 | ts += event->time_delta; | |
302 | ||
303 | return ts; | |
304 | } | |
305 | ||
66a8cb95 SR |
306 | /* Flag when events were overwritten */ |
307 | #define RB_MISSED_EVENTS (1 << 31) | |
ff0ff84a SR |
308 | /* Missed count stored at end */ |
309 | #define RB_MISSED_STORED (1 << 30) | |
66a8cb95 | 310 | |
45d8b80c SRV |
311 | #define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED) |
312 | ||
abc9b56d | 313 | struct buffer_data_page { |
e4c2ce82 | 314 | u64 time_stamp; /* page time stamp */ |
c3706f00 | 315 | local_t commit; /* write committed index */ |
649508f6 | 316 | unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
abc9b56d SR |
317 | }; |
318 | ||
77ae365e SR |
319 | /* |
320 | * Note, the buffer_page list must be first. The buffer pages | |
321 | * are allocated in cache lines, which means that each buffer | |
322 | * page will be at the beginning of a cache line, and thus | |
323 | * the least significant bits will be zero. We use this to | |
324 | * add flags in the list struct pointers, to make the ring buffer | |
325 | * lockless. | |
326 | */ | |
abc9b56d | 327 | struct buffer_page { |
778c55d4 | 328 | struct list_head list; /* list of buffer pages */ |
abc9b56d | 329 | local_t write; /* index for next write */ |
6f807acd | 330 | unsigned read; /* index for next read */ |
778c55d4 | 331 | local_t entries; /* entries on this page */ |
ff0ff84a | 332 | unsigned long real_end; /* real end of data */ |
abc9b56d | 333 | struct buffer_data_page *page; /* Actual data page */ |
7a8e76a3 SR |
334 | }; |
335 | ||
77ae365e SR |
336 | /* |
337 | * The buffer page counters, write and entries, must be reset | |
338 | * atomically when crossing page boundaries. To synchronize this | |
339 | * update, two counters are inserted into the number. One is | |
340 | * the actual counter for the write position or count on the page. | |
341 | * | |
342 | * The other is a counter of updaters. Before an update happens | |
343 | * the update partition of the counter is incremented. This will | |
344 | * allow the updater to update the counter atomically. | |
345 | * | |
346 | * The counter is 20 bits, and the state data is 12. | |
347 | */ | |
348 | #define RB_WRITE_MASK 0xfffff | |
349 | #define RB_WRITE_INTCNT (1 << 20) | |
350 | ||
044fa782 | 351 | static void rb_init_page(struct buffer_data_page *bpage) |
abc9b56d | 352 | { |
044fa782 | 353 | local_set(&bpage->commit, 0); |
abc9b56d SR |
354 | } |
355 | ||
ed56829c SR |
356 | /* |
357 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing | |
358 | * this issue out. | |
359 | */ | |
34a148bf | 360 | static void free_buffer_page(struct buffer_page *bpage) |
ed56829c | 361 | { |
34a148bf | 362 | free_page((unsigned long)bpage->page); |
e4c2ce82 | 363 | kfree(bpage); |
ed56829c SR |
364 | } |
365 | ||
7a8e76a3 SR |
366 | /* |
367 | * We need to fit the time_stamp delta into 27 bits. | |
368 | */ | |
369 | static inline int test_time_stamp(u64 delta) | |
370 | { | |
371 | if (delta & TS_DELTA_TEST) | |
372 | return 1; | |
373 | return 0; | |
374 | } | |
375 | ||
474d32b6 | 376 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
7a8e76a3 | 377 | |
be957c44 SR |
378 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
379 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) | |
380 | ||
d1b182a8 SR |
381 | int ring_buffer_print_page_header(struct trace_seq *s) |
382 | { | |
383 | struct buffer_data_page field; | |
c0cd93aa SRRH |
384 | |
385 | trace_seq_printf(s, "\tfield: u64 timestamp;\t" | |
386 | "offset:0;\tsize:%u;\tsigned:%u;\n", | |
387 | (unsigned int)sizeof(field.time_stamp), | |
388 | (unsigned int)is_signed_type(u64)); | |
389 | ||
390 | trace_seq_printf(s, "\tfield: local_t commit;\t" | |
391 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
392 | (unsigned int)offsetof(typeof(field), commit), | |
393 | (unsigned int)sizeof(field.commit), | |
394 | (unsigned int)is_signed_type(long)); | |
395 | ||
396 | trace_seq_printf(s, "\tfield: int overwrite;\t" | |
397 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
398 | (unsigned int)offsetof(typeof(field), commit), | |
399 | 1, | |
400 | (unsigned int)is_signed_type(long)); | |
401 | ||
402 | trace_seq_printf(s, "\tfield: char data;\t" | |
403 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
404 | (unsigned int)offsetof(typeof(field), data), | |
405 | (unsigned int)BUF_PAGE_SIZE, | |
406 | (unsigned int)is_signed_type(char)); | |
407 | ||
408 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
409 | } |
410 | ||
15693458 SRRH |
411 | struct rb_irq_work { |
412 | struct irq_work work; | |
413 | wait_queue_head_t waiters; | |
1e0d6714 | 414 | wait_queue_head_t full_waiters; |
15693458 | 415 | bool waiters_pending; |
1e0d6714 SRRH |
416 | bool full_waiters_pending; |
417 | bool wakeup_full; | |
15693458 SRRH |
418 | }; |
419 | ||
fcc742ea SRRH |
420 | /* |
421 | * Structure to hold event state and handle nested events. | |
422 | */ | |
423 | struct rb_event_info { | |
424 | u64 ts; | |
425 | u64 delta; | |
426 | unsigned long length; | |
427 | struct buffer_page *tail_page; | |
428 | int add_timestamp; | |
429 | }; | |
430 | ||
a497adb4 SRRH |
431 | /* |
432 | * Used for which event context the event is in. | |
433 | * NMI = 0 | |
434 | * IRQ = 1 | |
435 | * SOFTIRQ = 2 | |
436 | * NORMAL = 3 | |
437 | * | |
438 | * See trace_recursive_lock() comment below for more details. | |
439 | */ | |
440 | enum { | |
441 | RB_CTX_NMI, | |
442 | RB_CTX_IRQ, | |
443 | RB_CTX_SOFTIRQ, | |
444 | RB_CTX_NORMAL, | |
445 | RB_CTX_MAX | |
446 | }; | |
447 | ||
7a8e76a3 SR |
448 | /* |
449 | * head_page == tail_page && head == tail then buffer is empty. | |
450 | */ | |
451 | struct ring_buffer_per_cpu { | |
452 | int cpu; | |
985023de | 453 | atomic_t record_disabled; |
7a8e76a3 | 454 | struct ring_buffer *buffer; |
5389f6fa | 455 | raw_spinlock_t reader_lock; /* serialize readers */ |
445c8951 | 456 | arch_spinlock_t lock; |
7a8e76a3 | 457 | struct lock_class_key lock_key; |
73a757e6 | 458 | struct buffer_data_page *free_page; |
9b94a8fb | 459 | unsigned long nr_pages; |
58a09ec6 | 460 | unsigned int current_context; |
3adc54fa | 461 | struct list_head *pages; |
6f807acd SR |
462 | struct buffer_page *head_page; /* read from head */ |
463 | struct buffer_page *tail_page; /* write to tail */ | |
c3706f00 | 464 | struct buffer_page *commit_page; /* committed pages */ |
d769041f | 465 | struct buffer_page *reader_page; |
66a8cb95 SR |
466 | unsigned long lost_events; |
467 | unsigned long last_overrun; | |
8e012066 | 468 | unsigned long nest; |
c64e148a | 469 | local_t entries_bytes; |
e4906eff | 470 | local_t entries; |
884bfe89 SP |
471 | local_t overrun; |
472 | local_t commit_overrun; | |
473 | local_t dropped_events; | |
fa743953 SR |
474 | local_t committing; |
475 | local_t commits; | |
2c2b0a78 SRV |
476 | local_t pages_touched; |
477 | local_t pages_read; | |
03329f99 | 478 | long last_pages_touch; |
2c2b0a78 | 479 | size_t shortest_full; |
77ae365e | 480 | unsigned long read; |
c64e148a | 481 | unsigned long read_bytes; |
7a8e76a3 SR |
482 | u64 write_stamp; |
483 | u64 read_stamp; | |
438ced17 | 484 | /* ring buffer pages to update, > 0 to add, < 0 to remove */ |
9b94a8fb | 485 | long nr_pages_to_update; |
438ced17 | 486 | struct list_head new_pages; /* new pages to add */ |
83f40318 | 487 | struct work_struct update_pages_work; |
05fdd70d | 488 | struct completion update_done; |
15693458 SRRH |
489 | |
490 | struct rb_irq_work irq_work; | |
7a8e76a3 SR |
491 | }; |
492 | ||
493 | struct ring_buffer { | |
7a8e76a3 SR |
494 | unsigned flags; |
495 | int cpus; | |
7a8e76a3 | 496 | atomic_t record_disabled; |
83f40318 | 497 | atomic_t resize_disabled; |
00f62f61 | 498 | cpumask_var_t cpumask; |
7a8e76a3 | 499 | |
1f8a6a10 PZ |
500 | struct lock_class_key *reader_lock_key; |
501 | ||
7a8e76a3 SR |
502 | struct mutex mutex; |
503 | ||
504 | struct ring_buffer_per_cpu **buffers; | |
554f786e | 505 | |
b32614c0 | 506 | struct hlist_node node; |
37886f6a | 507 | u64 (*clock)(void); |
15693458 SRRH |
508 | |
509 | struct rb_irq_work irq_work; | |
00b41452 | 510 | bool time_stamp_abs; |
7a8e76a3 SR |
511 | }; |
512 | ||
513 | struct ring_buffer_iter { | |
514 | struct ring_buffer_per_cpu *cpu_buffer; | |
515 | unsigned long head; | |
516 | struct buffer_page *head_page; | |
492a74f4 SR |
517 | struct buffer_page *cache_reader_page; |
518 | unsigned long cache_read; | |
7a8e76a3 SR |
519 | u64 read_stamp; |
520 | }; | |
521 | ||
2c2b0a78 SRV |
522 | /** |
523 | * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer | |
524 | * @buffer: The ring_buffer to get the number of pages from | |
525 | * @cpu: The cpu of the ring_buffer to get the number of pages from | |
526 | * | |
527 | * Returns the number of pages used by a per_cpu buffer of the ring buffer. | |
528 | */ | |
529 | size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu) | |
530 | { | |
531 | return buffer->buffers[cpu]->nr_pages; | |
532 | } | |
533 | ||
534 | /** | |
535 | * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer | |
536 | * @buffer: The ring_buffer to get the number of pages from | |
537 | * @cpu: The cpu of the ring_buffer to get the number of pages from | |
538 | * | |
539 | * Returns the number of pages that have content in the ring buffer. | |
540 | */ | |
541 | size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu) | |
542 | { | |
543 | size_t read; | |
544 | size_t cnt; | |
545 | ||
546 | read = local_read(&buffer->buffers[cpu]->pages_read); | |
547 | cnt = local_read(&buffer->buffers[cpu]->pages_touched); | |
548 | /* The reader can read an empty page, but not more than that */ | |
549 | if (cnt < read) { | |
550 | WARN_ON_ONCE(read > cnt + 1); | |
551 | return 0; | |
552 | } | |
553 | ||
554 | return cnt - read; | |
555 | } | |
556 | ||
15693458 SRRH |
557 | /* |
558 | * rb_wake_up_waiters - wake up tasks waiting for ring buffer input | |
559 | * | |
560 | * Schedules a delayed work to wake up any task that is blocked on the | |
561 | * ring buffer waiters queue. | |
562 | */ | |
563 | static void rb_wake_up_waiters(struct irq_work *work) | |
564 | { | |
565 | struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); | |
566 | ||
567 | wake_up_all(&rbwork->waiters); | |
1e0d6714 SRRH |
568 | if (rbwork->wakeup_full) { |
569 | rbwork->wakeup_full = false; | |
570 | wake_up_all(&rbwork->full_waiters); | |
571 | } | |
15693458 SRRH |
572 | } |
573 | ||
574 | /** | |
575 | * ring_buffer_wait - wait for input to the ring buffer | |
576 | * @buffer: buffer to wait on | |
577 | * @cpu: the cpu buffer to wait on | |
e30f53aa | 578 | * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS |
15693458 SRRH |
579 | * |
580 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
581 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
582 | * it will wait for data to be added to a specific cpu buffer. | |
583 | */ | |
2c2b0a78 | 584 | int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full) |
15693458 | 585 | { |
e30f53aa | 586 | struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer); |
15693458 SRRH |
587 | DEFINE_WAIT(wait); |
588 | struct rb_irq_work *work; | |
e30f53aa | 589 | int ret = 0; |
15693458 SRRH |
590 | |
591 | /* | |
592 | * Depending on what the caller is waiting for, either any | |
593 | * data in any cpu buffer, or a specific buffer, put the | |
594 | * caller on the appropriate wait queue. | |
595 | */ | |
1e0d6714 | 596 | if (cpu == RING_BUFFER_ALL_CPUS) { |
15693458 | 597 | work = &buffer->irq_work; |
1e0d6714 | 598 | /* Full only makes sense on per cpu reads */ |
2c2b0a78 | 599 | full = 0; |
1e0d6714 | 600 | } else { |
8b8b3683 SRRH |
601 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
602 | return -ENODEV; | |
15693458 SRRH |
603 | cpu_buffer = buffer->buffers[cpu]; |
604 | work = &cpu_buffer->irq_work; | |
605 | } | |
606 | ||
607 | ||
e30f53aa | 608 | while (true) { |
1e0d6714 SRRH |
609 | if (full) |
610 | prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); | |
611 | else | |
612 | prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); | |
e30f53aa RV |
613 | |
614 | /* | |
615 | * The events can happen in critical sections where | |
616 | * checking a work queue can cause deadlocks. | |
617 | * After adding a task to the queue, this flag is set | |
618 | * only to notify events to try to wake up the queue | |
619 | * using irq_work. | |
620 | * | |
621 | * We don't clear it even if the buffer is no longer | |
622 | * empty. The flag only causes the next event to run | |
623 | * irq_work to do the work queue wake up. The worse | |
624 | * that can happen if we race with !trace_empty() is that | |
625 | * an event will cause an irq_work to try to wake up | |
626 | * an empty queue. | |
627 | * | |
628 | * There's no reason to protect this flag either, as | |
629 | * the work queue and irq_work logic will do the necessary | |
630 | * synchronization for the wake ups. The only thing | |
631 | * that is necessary is that the wake up happens after | |
632 | * a task has been queued. It's OK for spurious wake ups. | |
633 | */ | |
1e0d6714 SRRH |
634 | if (full) |
635 | work->full_waiters_pending = true; | |
636 | else | |
637 | work->waiters_pending = true; | |
e30f53aa RV |
638 | |
639 | if (signal_pending(current)) { | |
640 | ret = -EINTR; | |
641 | break; | |
642 | } | |
643 | ||
644 | if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) | |
645 | break; | |
646 | ||
647 | if (cpu != RING_BUFFER_ALL_CPUS && | |
648 | !ring_buffer_empty_cpu(buffer, cpu)) { | |
649 | unsigned long flags; | |
650 | bool pagebusy; | |
2c2b0a78 SRV |
651 | size_t nr_pages; |
652 | size_t dirty; | |
e30f53aa RV |
653 | |
654 | if (!full) | |
655 | break; | |
656 | ||
657 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
658 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; | |
2c2b0a78 SRV |
659 | nr_pages = cpu_buffer->nr_pages; |
660 | dirty = ring_buffer_nr_dirty_pages(buffer, cpu); | |
661 | if (!cpu_buffer->shortest_full || | |
662 | cpu_buffer->shortest_full < full) | |
663 | cpu_buffer->shortest_full = full; | |
e30f53aa | 664 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
2c2b0a78 SRV |
665 | if (!pagebusy && |
666 | (!nr_pages || (dirty * 100) > full * nr_pages)) | |
e30f53aa RV |
667 | break; |
668 | } | |
15693458 | 669 | |
15693458 | 670 | schedule(); |
e30f53aa | 671 | } |
15693458 | 672 | |
1e0d6714 SRRH |
673 | if (full) |
674 | finish_wait(&work->full_waiters, &wait); | |
675 | else | |
676 | finish_wait(&work->waiters, &wait); | |
e30f53aa RV |
677 | |
678 | return ret; | |
15693458 SRRH |
679 | } |
680 | ||
681 | /** | |
682 | * ring_buffer_poll_wait - poll on buffer input | |
683 | * @buffer: buffer to wait on | |
684 | * @cpu: the cpu buffer to wait on | |
685 | * @filp: the file descriptor | |
686 | * @poll_table: The poll descriptor | |
687 | * | |
688 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
689 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
690 | * it will wait for data to be added to a specific cpu buffer. | |
691 | * | |
a9a08845 | 692 | * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, |
15693458 SRRH |
693 | * zero otherwise. |
694 | */ | |
ecf92700 | 695 | __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu, |
15693458 SRRH |
696 | struct file *filp, poll_table *poll_table) |
697 | { | |
698 | struct ring_buffer_per_cpu *cpu_buffer; | |
699 | struct rb_irq_work *work; | |
700 | ||
15693458 SRRH |
701 | if (cpu == RING_BUFFER_ALL_CPUS) |
702 | work = &buffer->irq_work; | |
703 | else { | |
6721cb60 SRRH |
704 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
705 | return -EINVAL; | |
706 | ||
15693458 SRRH |
707 | cpu_buffer = buffer->buffers[cpu]; |
708 | work = &cpu_buffer->irq_work; | |
709 | } | |
710 | ||
15693458 | 711 | poll_wait(filp, &work->waiters, poll_table); |
4ce97dbf JB |
712 | work->waiters_pending = true; |
713 | /* | |
714 | * There's a tight race between setting the waiters_pending and | |
715 | * checking if the ring buffer is empty. Once the waiters_pending bit | |
716 | * is set, the next event will wake the task up, but we can get stuck | |
717 | * if there's only a single event in. | |
718 | * | |
719 | * FIXME: Ideally, we need a memory barrier on the writer side as well, | |
720 | * but adding a memory barrier to all events will cause too much of a | |
721 | * performance hit in the fast path. We only need a memory barrier when | |
722 | * the buffer goes from empty to having content. But as this race is | |
723 | * extremely small, and it's not a problem if another event comes in, we | |
724 | * will fix it later. | |
725 | */ | |
726 | smp_mb(); | |
15693458 SRRH |
727 | |
728 | if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || | |
729 | (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) | |
a9a08845 | 730 | return EPOLLIN | EPOLLRDNORM; |
15693458 SRRH |
731 | return 0; |
732 | } | |
733 | ||
f536aafc | 734 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
077c5407 SR |
735 | #define RB_WARN_ON(b, cond) \ |
736 | ({ \ | |
737 | int _____ret = unlikely(cond); \ | |
738 | if (_____ret) { \ | |
739 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ | |
740 | struct ring_buffer_per_cpu *__b = \ | |
741 | (void *)b; \ | |
742 | atomic_inc(&__b->buffer->record_disabled); \ | |
743 | } else \ | |
744 | atomic_inc(&b->record_disabled); \ | |
745 | WARN_ON(1); \ | |
746 | } \ | |
747 | _____ret; \ | |
3e89c7bb | 748 | }) |
f536aafc | 749 | |
37886f6a SR |
750 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
751 | #define DEBUG_SHIFT 0 | |
752 | ||
6d3f1e12 | 753 | static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
88eb0125 SR |
754 | { |
755 | /* shift to debug/test normalization and TIME_EXTENTS */ | |
756 | return buffer->clock() << DEBUG_SHIFT; | |
757 | } | |
758 | ||
37886f6a SR |
759 | u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
760 | { | |
761 | u64 time; | |
762 | ||
763 | preempt_disable_notrace(); | |
6d3f1e12 | 764 | time = rb_time_stamp(buffer); |
37886f6a SR |
765 | preempt_enable_no_resched_notrace(); |
766 | ||
767 | return time; | |
768 | } | |
769 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); | |
770 | ||
771 | void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, | |
772 | int cpu, u64 *ts) | |
773 | { | |
774 | /* Just stupid testing the normalize function and deltas */ | |
775 | *ts >>= DEBUG_SHIFT; | |
776 | } | |
777 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); | |
778 | ||
77ae365e SR |
779 | /* |
780 | * Making the ring buffer lockless makes things tricky. | |
781 | * Although writes only happen on the CPU that they are on, | |
782 | * and they only need to worry about interrupts. Reads can | |
783 | * happen on any CPU. | |
784 | * | |
785 | * The reader page is always off the ring buffer, but when the | |
786 | * reader finishes with a page, it needs to swap its page with | |
787 | * a new one from the buffer. The reader needs to take from | |
788 | * the head (writes go to the tail). But if a writer is in overwrite | |
789 | * mode and wraps, it must push the head page forward. | |
790 | * | |
791 | * Here lies the problem. | |
792 | * | |
793 | * The reader must be careful to replace only the head page, and | |
794 | * not another one. As described at the top of the file in the | |
795 | * ASCII art, the reader sets its old page to point to the next | |
796 | * page after head. It then sets the page after head to point to | |
797 | * the old reader page. But if the writer moves the head page | |
798 | * during this operation, the reader could end up with the tail. | |
799 | * | |
800 | * We use cmpxchg to help prevent this race. We also do something | |
801 | * special with the page before head. We set the LSB to 1. | |
802 | * | |
803 | * When the writer must push the page forward, it will clear the | |
804 | * bit that points to the head page, move the head, and then set | |
805 | * the bit that points to the new head page. | |
806 | * | |
807 | * We also don't want an interrupt coming in and moving the head | |
808 | * page on another writer. Thus we use the second LSB to catch | |
809 | * that too. Thus: | |
810 | * | |
811 | * head->list->prev->next bit 1 bit 0 | |
812 | * ------- ------- | |
813 | * Normal page 0 0 | |
814 | * Points to head page 0 1 | |
815 | * New head page 1 0 | |
816 | * | |
817 | * Note we can not trust the prev pointer of the head page, because: | |
818 | * | |
819 | * +----+ +-----+ +-----+ | |
820 | * | |------>| T |---X--->| N | | |
821 | * | |<------| | | | | |
822 | * +----+ +-----+ +-----+ | |
823 | * ^ ^ | | |
824 | * | +-----+ | | | |
825 | * +----------| R |----------+ | | |
826 | * | |<-----------+ | |
827 | * +-----+ | |
828 | * | |
829 | * Key: ---X--> HEAD flag set in pointer | |
830 | * T Tail page | |
831 | * R Reader page | |
832 | * N Next page | |
833 | * | |
834 | * (see __rb_reserve_next() to see where this happens) | |
835 | * | |
836 | * What the above shows is that the reader just swapped out | |
837 | * the reader page with a page in the buffer, but before it | |
838 | * could make the new header point back to the new page added | |
839 | * it was preempted by a writer. The writer moved forward onto | |
840 | * the new page added by the reader and is about to move forward | |
841 | * again. | |
842 | * | |
843 | * You can see, it is legitimate for the previous pointer of | |
844 | * the head (or any page) not to point back to itself. But only | |
6167c205 | 845 | * temporarily. |
77ae365e SR |
846 | */ |
847 | ||
848 | #define RB_PAGE_NORMAL 0UL | |
849 | #define RB_PAGE_HEAD 1UL | |
850 | #define RB_PAGE_UPDATE 2UL | |
851 | ||
852 | ||
853 | #define RB_FLAG_MASK 3UL | |
854 | ||
855 | /* PAGE_MOVED is not part of the mask */ | |
856 | #define RB_PAGE_MOVED 4UL | |
857 | ||
858 | /* | |
859 | * rb_list_head - remove any bit | |
860 | */ | |
861 | static struct list_head *rb_list_head(struct list_head *list) | |
862 | { | |
863 | unsigned long val = (unsigned long)list; | |
864 | ||
865 | return (struct list_head *)(val & ~RB_FLAG_MASK); | |
866 | } | |
867 | ||
868 | /* | |
6d3f1e12 | 869 | * rb_is_head_page - test if the given page is the head page |
77ae365e SR |
870 | * |
871 | * Because the reader may move the head_page pointer, we can | |
872 | * not trust what the head page is (it may be pointing to | |
873 | * the reader page). But if the next page is a header page, | |
874 | * its flags will be non zero. | |
875 | */ | |
42b16b3f | 876 | static inline int |
77ae365e SR |
877 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
878 | struct buffer_page *page, struct list_head *list) | |
879 | { | |
880 | unsigned long val; | |
881 | ||
882 | val = (unsigned long)list->next; | |
883 | ||
884 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) | |
885 | return RB_PAGE_MOVED; | |
886 | ||
887 | return val & RB_FLAG_MASK; | |
888 | } | |
889 | ||
890 | /* | |
891 | * rb_is_reader_page | |
892 | * | |
893 | * The unique thing about the reader page, is that, if the | |
894 | * writer is ever on it, the previous pointer never points | |
895 | * back to the reader page. | |
896 | */ | |
06ca3209 | 897 | static bool rb_is_reader_page(struct buffer_page *page) |
77ae365e SR |
898 | { |
899 | struct list_head *list = page->list.prev; | |
900 | ||
901 | return rb_list_head(list->next) != &page->list; | |
902 | } | |
903 | ||
904 | /* | |
905 | * rb_set_list_to_head - set a list_head to be pointing to head. | |
906 | */ | |
907 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, | |
908 | struct list_head *list) | |
909 | { | |
910 | unsigned long *ptr; | |
911 | ||
912 | ptr = (unsigned long *)&list->next; | |
913 | *ptr |= RB_PAGE_HEAD; | |
914 | *ptr &= ~RB_PAGE_UPDATE; | |
915 | } | |
916 | ||
917 | /* | |
918 | * rb_head_page_activate - sets up head page | |
919 | */ | |
920 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) | |
921 | { | |
922 | struct buffer_page *head; | |
923 | ||
924 | head = cpu_buffer->head_page; | |
925 | if (!head) | |
926 | return; | |
927 | ||
928 | /* | |
929 | * Set the previous list pointer to have the HEAD flag. | |
930 | */ | |
931 | rb_set_list_to_head(cpu_buffer, head->list.prev); | |
932 | } | |
933 | ||
934 | static void rb_list_head_clear(struct list_head *list) | |
935 | { | |
936 | unsigned long *ptr = (unsigned long *)&list->next; | |
937 | ||
938 | *ptr &= ~RB_FLAG_MASK; | |
939 | } | |
940 | ||
941 | /* | |
6167c205 | 942 | * rb_head_page_deactivate - clears head page ptr (for free list) |
77ae365e SR |
943 | */ |
944 | static void | |
945 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) | |
946 | { | |
947 | struct list_head *hd; | |
948 | ||
949 | /* Go through the whole list and clear any pointers found. */ | |
950 | rb_list_head_clear(cpu_buffer->pages); | |
951 | ||
952 | list_for_each(hd, cpu_buffer->pages) | |
953 | rb_list_head_clear(hd); | |
954 | } | |
955 | ||
956 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, | |
957 | struct buffer_page *head, | |
958 | struct buffer_page *prev, | |
959 | int old_flag, int new_flag) | |
960 | { | |
961 | struct list_head *list; | |
962 | unsigned long val = (unsigned long)&head->list; | |
963 | unsigned long ret; | |
964 | ||
965 | list = &prev->list; | |
966 | ||
967 | val &= ~RB_FLAG_MASK; | |
968 | ||
08a40816 SR |
969 | ret = cmpxchg((unsigned long *)&list->next, |
970 | val | old_flag, val | new_flag); | |
77ae365e SR |
971 | |
972 | /* check if the reader took the page */ | |
973 | if ((ret & ~RB_FLAG_MASK) != val) | |
974 | return RB_PAGE_MOVED; | |
975 | ||
976 | return ret & RB_FLAG_MASK; | |
977 | } | |
978 | ||
979 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, | |
980 | struct buffer_page *head, | |
981 | struct buffer_page *prev, | |
982 | int old_flag) | |
983 | { | |
984 | return rb_head_page_set(cpu_buffer, head, prev, | |
985 | old_flag, RB_PAGE_UPDATE); | |
986 | } | |
987 | ||
988 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, | |
989 | struct buffer_page *head, | |
990 | struct buffer_page *prev, | |
991 | int old_flag) | |
992 | { | |
993 | return rb_head_page_set(cpu_buffer, head, prev, | |
994 | old_flag, RB_PAGE_HEAD); | |
995 | } | |
996 | ||
997 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, | |
998 | struct buffer_page *head, | |
999 | struct buffer_page *prev, | |
1000 | int old_flag) | |
1001 | { | |
1002 | return rb_head_page_set(cpu_buffer, head, prev, | |
1003 | old_flag, RB_PAGE_NORMAL); | |
1004 | } | |
1005 | ||
1006 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, | |
1007 | struct buffer_page **bpage) | |
1008 | { | |
1009 | struct list_head *p = rb_list_head((*bpage)->list.next); | |
1010 | ||
1011 | *bpage = list_entry(p, struct buffer_page, list); | |
1012 | } | |
1013 | ||
1014 | static struct buffer_page * | |
1015 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) | |
1016 | { | |
1017 | struct buffer_page *head; | |
1018 | struct buffer_page *page; | |
1019 | struct list_head *list; | |
1020 | int i; | |
1021 | ||
1022 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) | |
1023 | return NULL; | |
1024 | ||
1025 | /* sanity check */ | |
1026 | list = cpu_buffer->pages; | |
1027 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) | |
1028 | return NULL; | |
1029 | ||
1030 | page = head = cpu_buffer->head_page; | |
1031 | /* | |
1032 | * It is possible that the writer moves the header behind | |
1033 | * where we started, and we miss in one loop. | |
1034 | * A second loop should grab the header, but we'll do | |
1035 | * three loops just because I'm paranoid. | |
1036 | */ | |
1037 | for (i = 0; i < 3; i++) { | |
1038 | do { | |
1039 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { | |
1040 | cpu_buffer->head_page = page; | |
1041 | return page; | |
1042 | } | |
1043 | rb_inc_page(cpu_buffer, &page); | |
1044 | } while (page != head); | |
1045 | } | |
1046 | ||
1047 | RB_WARN_ON(cpu_buffer, 1); | |
1048 | ||
1049 | return NULL; | |
1050 | } | |
1051 | ||
1052 | static int rb_head_page_replace(struct buffer_page *old, | |
1053 | struct buffer_page *new) | |
1054 | { | |
1055 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; | |
1056 | unsigned long val; | |
1057 | unsigned long ret; | |
1058 | ||
1059 | val = *ptr & ~RB_FLAG_MASK; | |
1060 | val |= RB_PAGE_HEAD; | |
1061 | ||
08a40816 | 1062 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
77ae365e SR |
1063 | |
1064 | return ret == val; | |
1065 | } | |
1066 | ||
1067 | /* | |
1068 | * rb_tail_page_update - move the tail page forward | |
77ae365e | 1069 | */ |
70004986 | 1070 | static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, |
77ae365e SR |
1071 | struct buffer_page *tail_page, |
1072 | struct buffer_page *next_page) | |
1073 | { | |
77ae365e SR |
1074 | unsigned long old_entries; |
1075 | unsigned long old_write; | |
77ae365e SR |
1076 | |
1077 | /* | |
1078 | * The tail page now needs to be moved forward. | |
1079 | * | |
1080 | * We need to reset the tail page, but without messing | |
1081 | * with possible erasing of data brought in by interrupts | |
1082 | * that have moved the tail page and are currently on it. | |
1083 | * | |
1084 | * We add a counter to the write field to denote this. | |
1085 | */ | |
1086 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); | |
1087 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); | |
1088 | ||
2c2b0a78 | 1089 | local_inc(&cpu_buffer->pages_touched); |
77ae365e SR |
1090 | /* |
1091 | * Just make sure we have seen our old_write and synchronize | |
1092 | * with any interrupts that come in. | |
1093 | */ | |
1094 | barrier(); | |
1095 | ||
1096 | /* | |
1097 | * If the tail page is still the same as what we think | |
1098 | * it is, then it is up to us to update the tail | |
1099 | * pointer. | |
1100 | */ | |
8573636e | 1101 | if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { |
77ae365e SR |
1102 | /* Zero the write counter */ |
1103 | unsigned long val = old_write & ~RB_WRITE_MASK; | |
1104 | unsigned long eval = old_entries & ~RB_WRITE_MASK; | |
1105 | ||
1106 | /* | |
1107 | * This will only succeed if an interrupt did | |
1108 | * not come in and change it. In which case, we | |
1109 | * do not want to modify it. | |
da706d8b LJ |
1110 | * |
1111 | * We add (void) to let the compiler know that we do not care | |
1112 | * about the return value of these functions. We use the | |
1113 | * cmpxchg to only update if an interrupt did not already | |
1114 | * do it for us. If the cmpxchg fails, we don't care. | |
77ae365e | 1115 | */ |
da706d8b LJ |
1116 | (void)local_cmpxchg(&next_page->write, old_write, val); |
1117 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); | |
77ae365e SR |
1118 | |
1119 | /* | |
1120 | * No need to worry about races with clearing out the commit. | |
1121 | * it only can increment when a commit takes place. But that | |
1122 | * only happens in the outer most nested commit. | |
1123 | */ | |
1124 | local_set(&next_page->page->commit, 0); | |
1125 | ||
70004986 SRRH |
1126 | /* Again, either we update tail_page or an interrupt does */ |
1127 | (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page); | |
77ae365e | 1128 | } |
77ae365e SR |
1129 | } |
1130 | ||
1131 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, | |
1132 | struct buffer_page *bpage) | |
1133 | { | |
1134 | unsigned long val = (unsigned long)bpage; | |
1135 | ||
1136 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) | |
1137 | return 1; | |
1138 | ||
1139 | return 0; | |
1140 | } | |
1141 | ||
1142 | /** | |
1143 | * rb_check_list - make sure a pointer to a list has the last bits zero | |
1144 | */ | |
1145 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, | |
1146 | struct list_head *list) | |
1147 | { | |
1148 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) | |
1149 | return 1; | |
1150 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) | |
1151 | return 1; | |
1152 | return 0; | |
1153 | } | |
1154 | ||
7a8e76a3 | 1155 | /** |
d611851b | 1156 | * rb_check_pages - integrity check of buffer pages |
7a8e76a3 SR |
1157 | * @cpu_buffer: CPU buffer with pages to test |
1158 | * | |
c3706f00 | 1159 | * As a safety measure we check to make sure the data pages have not |
7a8e76a3 SR |
1160 | * been corrupted. |
1161 | */ | |
1162 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
1163 | { | |
3adc54fa | 1164 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1165 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1166 | |
308f7eeb SR |
1167 | /* Reset the head page if it exists */ |
1168 | if (cpu_buffer->head_page) | |
1169 | rb_set_head_page(cpu_buffer); | |
1170 | ||
77ae365e SR |
1171 | rb_head_page_deactivate(cpu_buffer); |
1172 | ||
3e89c7bb SR |
1173 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
1174 | return -1; | |
1175 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) | |
1176 | return -1; | |
7a8e76a3 | 1177 | |
77ae365e SR |
1178 | if (rb_check_list(cpu_buffer, head)) |
1179 | return -1; | |
1180 | ||
044fa782 | 1181 | list_for_each_entry_safe(bpage, tmp, head, list) { |
3e89c7bb | 1182 | if (RB_WARN_ON(cpu_buffer, |
044fa782 | 1183 | bpage->list.next->prev != &bpage->list)) |
3e89c7bb SR |
1184 | return -1; |
1185 | if (RB_WARN_ON(cpu_buffer, | |
044fa782 | 1186 | bpage->list.prev->next != &bpage->list)) |
3e89c7bb | 1187 | return -1; |
77ae365e SR |
1188 | if (rb_check_list(cpu_buffer, &bpage->list)) |
1189 | return -1; | |
7a8e76a3 SR |
1190 | } |
1191 | ||
77ae365e SR |
1192 | rb_head_page_activate(cpu_buffer); |
1193 | ||
7a8e76a3 SR |
1194 | return 0; |
1195 | } | |
1196 | ||
9b94a8fb | 1197 | static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) |
7a8e76a3 | 1198 | { |
044fa782 | 1199 | struct buffer_page *bpage, *tmp; |
927e56db SRV |
1200 | bool user_thread = current->mm != NULL; |
1201 | gfp_t mflags; | |
9b94a8fb | 1202 | long i; |
3adc54fa | 1203 | |
927e56db SRV |
1204 | /* |
1205 | * Check if the available memory is there first. | |
1206 | * Note, si_mem_available() only gives us a rough estimate of available | |
1207 | * memory. It may not be accurate. But we don't care, we just want | |
1208 | * to prevent doing any allocation when it is obvious that it is | |
1209 | * not going to succeed. | |
1210 | */ | |
2a872fa4 SRV |
1211 | i = si_mem_available(); |
1212 | if (i < nr_pages) | |
1213 | return -ENOMEM; | |
1214 | ||
927e56db SRV |
1215 | /* |
1216 | * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails | |
1217 | * gracefully without invoking oom-killer and the system is not | |
1218 | * destabilized. | |
1219 | */ | |
1220 | mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL; | |
1221 | ||
1222 | /* | |
1223 | * If a user thread allocates too much, and si_mem_available() | |
1224 | * reports there's enough memory, even though there is not. | |
1225 | * Make sure the OOM killer kills this thread. This can happen | |
1226 | * even with RETRY_MAYFAIL because another task may be doing | |
1227 | * an allocation after this task has taken all memory. | |
1228 | * This is the task the OOM killer needs to take out during this | |
1229 | * loop, even if it was triggered by an allocation somewhere else. | |
1230 | */ | |
1231 | if (user_thread) | |
1232 | set_current_oom_origin(); | |
7a8e76a3 | 1233 | for (i = 0; i < nr_pages; i++) { |
7ea59064 | 1234 | struct page *page; |
927e56db | 1235 | |
044fa782 | 1236 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
927e56db | 1237 | mflags, cpu_to_node(cpu)); |
044fa782 | 1238 | if (!bpage) |
e4c2ce82 | 1239 | goto free_pages; |
77ae365e | 1240 | |
438ced17 | 1241 | list_add(&bpage->list, pages); |
77ae365e | 1242 | |
927e56db | 1243 | page = alloc_pages_node(cpu_to_node(cpu), mflags, 0); |
7ea59064 | 1244 | if (!page) |
7a8e76a3 | 1245 | goto free_pages; |
7ea59064 | 1246 | bpage->page = page_address(page); |
044fa782 | 1247 | rb_init_page(bpage->page); |
927e56db SRV |
1248 | |
1249 | if (user_thread && fatal_signal_pending(current)) | |
1250 | goto free_pages; | |
7a8e76a3 | 1251 | } |
927e56db SRV |
1252 | if (user_thread) |
1253 | clear_current_oom_origin(); | |
7a8e76a3 | 1254 | |
438ced17 VN |
1255 | return 0; |
1256 | ||
1257 | free_pages: | |
1258 | list_for_each_entry_safe(bpage, tmp, pages, list) { | |
1259 | list_del_init(&bpage->list); | |
1260 | free_buffer_page(bpage); | |
1261 | } | |
927e56db SRV |
1262 | if (user_thread) |
1263 | clear_current_oom_origin(); | |
438ced17 VN |
1264 | |
1265 | return -ENOMEM; | |
1266 | } | |
1267 | ||
1268 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, | |
9b94a8fb | 1269 | unsigned long nr_pages) |
438ced17 VN |
1270 | { |
1271 | LIST_HEAD(pages); | |
1272 | ||
1273 | WARN_ON(!nr_pages); | |
1274 | ||
1275 | if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu)) | |
1276 | return -ENOMEM; | |
1277 | ||
3adc54fa SR |
1278 | /* |
1279 | * The ring buffer page list is a circular list that does not | |
1280 | * start and end with a list head. All page list items point to | |
1281 | * other pages. | |
1282 | */ | |
1283 | cpu_buffer->pages = pages.next; | |
1284 | list_del(&pages); | |
7a8e76a3 | 1285 | |
438ced17 VN |
1286 | cpu_buffer->nr_pages = nr_pages; |
1287 | ||
7a8e76a3 SR |
1288 | rb_check_pages(cpu_buffer); |
1289 | ||
1290 | return 0; | |
7a8e76a3 SR |
1291 | } |
1292 | ||
1293 | static struct ring_buffer_per_cpu * | |
9b94a8fb | 1294 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu) |
7a8e76a3 SR |
1295 | { |
1296 | struct ring_buffer_per_cpu *cpu_buffer; | |
044fa782 | 1297 | struct buffer_page *bpage; |
7ea59064 | 1298 | struct page *page; |
7a8e76a3 SR |
1299 | int ret; |
1300 | ||
1301 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), | |
1302 | GFP_KERNEL, cpu_to_node(cpu)); | |
1303 | if (!cpu_buffer) | |
1304 | return NULL; | |
1305 | ||
1306 | cpu_buffer->cpu = cpu; | |
1307 | cpu_buffer->buffer = buffer; | |
5389f6fa | 1308 | raw_spin_lock_init(&cpu_buffer->reader_lock); |
1f8a6a10 | 1309 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
edc35bd7 | 1310 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
83f40318 | 1311 | INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
05fdd70d | 1312 | init_completion(&cpu_buffer->update_done); |
15693458 | 1313 | init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1314 | init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
1e0d6714 | 1315 | init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
7a8e76a3 | 1316 | |
044fa782 | 1317 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
e4c2ce82 | 1318 | GFP_KERNEL, cpu_to_node(cpu)); |
044fa782 | 1319 | if (!bpage) |
e4c2ce82 SR |
1320 | goto fail_free_buffer; |
1321 | ||
77ae365e SR |
1322 | rb_check_bpage(cpu_buffer, bpage); |
1323 | ||
044fa782 | 1324 | cpu_buffer->reader_page = bpage; |
7ea59064 VN |
1325 | page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
1326 | if (!page) | |
e4c2ce82 | 1327 | goto fail_free_reader; |
7ea59064 | 1328 | bpage->page = page_address(page); |
044fa782 | 1329 | rb_init_page(bpage->page); |
e4c2ce82 | 1330 | |
d769041f | 1331 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
44b99462 | 1332 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
d769041f | 1333 | |
438ced17 | 1334 | ret = rb_allocate_pages(cpu_buffer, nr_pages); |
7a8e76a3 | 1335 | if (ret < 0) |
d769041f | 1336 | goto fail_free_reader; |
7a8e76a3 SR |
1337 | |
1338 | cpu_buffer->head_page | |
3adc54fa | 1339 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 1340 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
7a8e76a3 | 1341 | |
77ae365e SR |
1342 | rb_head_page_activate(cpu_buffer); |
1343 | ||
7a8e76a3 SR |
1344 | return cpu_buffer; |
1345 | ||
d769041f SR |
1346 | fail_free_reader: |
1347 | free_buffer_page(cpu_buffer->reader_page); | |
1348 | ||
7a8e76a3 SR |
1349 | fail_free_buffer: |
1350 | kfree(cpu_buffer); | |
1351 | return NULL; | |
1352 | } | |
1353 | ||
1354 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
1355 | { | |
3adc54fa | 1356 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1357 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1358 | |
d769041f SR |
1359 | free_buffer_page(cpu_buffer->reader_page); |
1360 | ||
77ae365e SR |
1361 | rb_head_page_deactivate(cpu_buffer); |
1362 | ||
3adc54fa SR |
1363 | if (head) { |
1364 | list_for_each_entry_safe(bpage, tmp, head, list) { | |
1365 | list_del_init(&bpage->list); | |
1366 | free_buffer_page(bpage); | |
1367 | } | |
1368 | bpage = list_entry(head, struct buffer_page, list); | |
044fa782 | 1369 | free_buffer_page(bpage); |
7a8e76a3 | 1370 | } |
3adc54fa | 1371 | |
7a8e76a3 SR |
1372 | kfree(cpu_buffer); |
1373 | } | |
1374 | ||
1375 | /** | |
d611851b | 1376 | * __ring_buffer_alloc - allocate a new ring_buffer |
68814b58 | 1377 | * @size: the size in bytes per cpu that is needed. |
7a8e76a3 SR |
1378 | * @flags: attributes to set for the ring buffer. |
1379 | * | |
1380 | * Currently the only flag that is available is the RB_FL_OVERWRITE | |
1381 | * flag. This flag means that the buffer will overwrite old data | |
1382 | * when the buffer wraps. If this flag is not set, the buffer will | |
1383 | * drop data when the tail hits the head. | |
1384 | */ | |
1f8a6a10 PZ |
1385 | struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1386 | struct lock_class_key *key) | |
7a8e76a3 SR |
1387 | { |
1388 | struct ring_buffer *buffer; | |
9b94a8fb | 1389 | long nr_pages; |
7a8e76a3 | 1390 | int bsize; |
9b94a8fb | 1391 | int cpu; |
b32614c0 | 1392 | int ret; |
7a8e76a3 SR |
1393 | |
1394 | /* keep it in its own cache line */ | |
1395 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), | |
1396 | GFP_KERNEL); | |
1397 | if (!buffer) | |
1398 | return NULL; | |
1399 | ||
b18cc3de | 1400 | if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
9e01c1b7 RR |
1401 | goto fail_free_buffer; |
1402 | ||
438ced17 | 1403 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
7a8e76a3 | 1404 | buffer->flags = flags; |
37886f6a | 1405 | buffer->clock = trace_clock_local; |
1f8a6a10 | 1406 | buffer->reader_lock_key = key; |
7a8e76a3 | 1407 | |
15693458 | 1408 | init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1409 | init_waitqueue_head(&buffer->irq_work.waiters); |
15693458 | 1410 | |
7a8e76a3 | 1411 | /* need at least two pages */ |
438ced17 VN |
1412 | if (nr_pages < 2) |
1413 | nr_pages = 2; | |
7a8e76a3 | 1414 | |
7a8e76a3 SR |
1415 | buffer->cpus = nr_cpu_ids; |
1416 | ||
1417 | bsize = sizeof(void *) * nr_cpu_ids; | |
1418 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), | |
1419 | GFP_KERNEL); | |
1420 | if (!buffer->buffers) | |
9e01c1b7 | 1421 | goto fail_free_cpumask; |
7a8e76a3 | 1422 | |
b32614c0 SAS |
1423 | cpu = raw_smp_processor_id(); |
1424 | cpumask_set_cpu(cpu, buffer->cpumask); | |
1425 | buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); | |
1426 | if (!buffer->buffers[cpu]) | |
1427 | goto fail_free_buffers; | |
7a8e76a3 | 1428 | |
b32614c0 SAS |
1429 | ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
1430 | if (ret < 0) | |
1431 | goto fail_free_buffers; | |
554f786e | 1432 | |
7a8e76a3 SR |
1433 | mutex_init(&buffer->mutex); |
1434 | ||
1435 | return buffer; | |
1436 | ||
1437 | fail_free_buffers: | |
1438 | for_each_buffer_cpu(buffer, cpu) { | |
1439 | if (buffer->buffers[cpu]) | |
1440 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1441 | } | |
1442 | kfree(buffer->buffers); | |
1443 | ||
9e01c1b7 RR |
1444 | fail_free_cpumask: |
1445 | free_cpumask_var(buffer->cpumask); | |
1446 | ||
7a8e76a3 SR |
1447 | fail_free_buffer: |
1448 | kfree(buffer); | |
1449 | return NULL; | |
1450 | } | |
1f8a6a10 | 1451 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
7a8e76a3 SR |
1452 | |
1453 | /** | |
1454 | * ring_buffer_free - free a ring buffer. | |
1455 | * @buffer: the buffer to free. | |
1456 | */ | |
1457 | void | |
1458 | ring_buffer_free(struct ring_buffer *buffer) | |
1459 | { | |
1460 | int cpu; | |
1461 | ||
b32614c0 | 1462 | cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
554f786e | 1463 | |
7a8e76a3 SR |
1464 | for_each_buffer_cpu(buffer, cpu) |
1465 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1466 | ||
bd3f0221 | 1467 | kfree(buffer->buffers); |
9e01c1b7 RR |
1468 | free_cpumask_var(buffer->cpumask); |
1469 | ||
7a8e76a3 SR |
1470 | kfree(buffer); |
1471 | } | |
c4f50183 | 1472 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
7a8e76a3 | 1473 | |
37886f6a SR |
1474 | void ring_buffer_set_clock(struct ring_buffer *buffer, |
1475 | u64 (*clock)(void)) | |
1476 | { | |
1477 | buffer->clock = clock; | |
1478 | } | |
1479 | ||
00b41452 TZ |
1480 | void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs) |
1481 | { | |
1482 | buffer->time_stamp_abs = abs; | |
1483 | } | |
1484 | ||
1485 | bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer) | |
1486 | { | |
1487 | return buffer->time_stamp_abs; | |
1488 | } | |
1489 | ||
7a8e76a3 SR |
1490 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1491 | ||
83f40318 VN |
1492 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1493 | { | |
1494 | return local_read(&bpage->entries) & RB_WRITE_MASK; | |
1495 | } | |
1496 | ||
1497 | static inline unsigned long rb_page_write(struct buffer_page *bpage) | |
1498 | { | |
1499 | return local_read(&bpage->write) & RB_WRITE_MASK; | |
1500 | } | |
1501 | ||
5040b4b7 | 1502 | static int |
9b94a8fb | 1503 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) |
7a8e76a3 | 1504 | { |
83f40318 VN |
1505 | struct list_head *tail_page, *to_remove, *next_page; |
1506 | struct buffer_page *to_remove_page, *tmp_iter_page; | |
1507 | struct buffer_page *last_page, *first_page; | |
9b94a8fb | 1508 | unsigned long nr_removed; |
83f40318 VN |
1509 | unsigned long head_bit; |
1510 | int page_entries; | |
1511 | ||
1512 | head_bit = 0; | |
7a8e76a3 | 1513 | |
5389f6fa | 1514 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1515 | atomic_inc(&cpu_buffer->record_disabled); |
1516 | /* | |
1517 | * We don't race with the readers since we have acquired the reader | |
1518 | * lock. We also don't race with writers after disabling recording. | |
1519 | * This makes it easy to figure out the first and the last page to be | |
1520 | * removed from the list. We unlink all the pages in between including | |
1521 | * the first and last pages. This is done in a busy loop so that we | |
1522 | * lose the least number of traces. | |
1523 | * The pages are freed after we restart recording and unlock readers. | |
1524 | */ | |
1525 | tail_page = &cpu_buffer->tail_page->list; | |
77ae365e | 1526 | |
83f40318 VN |
1527 | /* |
1528 | * tail page might be on reader page, we remove the next page | |
1529 | * from the ring buffer | |
1530 | */ | |
1531 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
1532 | tail_page = rb_list_head(tail_page->next); | |
1533 | to_remove = tail_page; | |
1534 | ||
1535 | /* start of pages to remove */ | |
1536 | first_page = list_entry(rb_list_head(to_remove->next), | |
1537 | struct buffer_page, list); | |
1538 | ||
1539 | for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { | |
1540 | to_remove = rb_list_head(to_remove)->next; | |
1541 | head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; | |
7a8e76a3 | 1542 | } |
7a8e76a3 | 1543 | |
83f40318 | 1544 | next_page = rb_list_head(to_remove)->next; |
7a8e76a3 | 1545 | |
83f40318 VN |
1546 | /* |
1547 | * Now we remove all pages between tail_page and next_page. | |
1548 | * Make sure that we have head_bit value preserved for the | |
1549 | * next page | |
1550 | */ | |
1551 | tail_page->next = (struct list_head *)((unsigned long)next_page | | |
1552 | head_bit); | |
1553 | next_page = rb_list_head(next_page); | |
1554 | next_page->prev = tail_page; | |
1555 | ||
1556 | /* make sure pages points to a valid page in the ring buffer */ | |
1557 | cpu_buffer->pages = next_page; | |
1558 | ||
1559 | /* update head page */ | |
1560 | if (head_bit) | |
1561 | cpu_buffer->head_page = list_entry(next_page, | |
1562 | struct buffer_page, list); | |
1563 | ||
1564 | /* | |
1565 | * change read pointer to make sure any read iterators reset | |
1566 | * themselves | |
1567 | */ | |
1568 | cpu_buffer->read = 0; | |
1569 | ||
1570 | /* pages are removed, resume tracing and then free the pages */ | |
1571 | atomic_dec(&cpu_buffer->record_disabled); | |
5389f6fa | 1572 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1573 | |
1574 | RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); | |
1575 | ||
1576 | /* last buffer page to remove */ | |
1577 | last_page = list_entry(rb_list_head(to_remove), struct buffer_page, | |
1578 | list); | |
1579 | tmp_iter_page = first_page; | |
1580 | ||
1581 | do { | |
83f36555 VN |
1582 | cond_resched(); |
1583 | ||
83f40318 VN |
1584 | to_remove_page = tmp_iter_page; |
1585 | rb_inc_page(cpu_buffer, &tmp_iter_page); | |
1586 | ||
1587 | /* update the counters */ | |
1588 | page_entries = rb_page_entries(to_remove_page); | |
1589 | if (page_entries) { | |
1590 | /* | |
1591 | * If something was added to this page, it was full | |
1592 | * since it is not the tail page. So we deduct the | |
1593 | * bytes consumed in ring buffer from here. | |
48fdc72f | 1594 | * Increment overrun to account for the lost events. |
83f40318 | 1595 | */ |
48fdc72f | 1596 | local_add(page_entries, &cpu_buffer->overrun); |
83f40318 VN |
1597 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
1598 | } | |
1599 | ||
1600 | /* | |
1601 | * We have already removed references to this list item, just | |
1602 | * free up the buffer_page and its page | |
1603 | */ | |
1604 | free_buffer_page(to_remove_page); | |
1605 | nr_removed--; | |
1606 | ||
1607 | } while (to_remove_page != last_page); | |
1608 | ||
1609 | RB_WARN_ON(cpu_buffer, nr_removed); | |
5040b4b7 VN |
1610 | |
1611 | return nr_removed == 0; | |
7a8e76a3 SR |
1612 | } |
1613 | ||
5040b4b7 VN |
1614 | static int |
1615 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 1616 | { |
5040b4b7 VN |
1617 | struct list_head *pages = &cpu_buffer->new_pages; |
1618 | int retries, success; | |
7a8e76a3 | 1619 | |
5389f6fa | 1620 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1621 | /* |
1622 | * We are holding the reader lock, so the reader page won't be swapped | |
1623 | * in the ring buffer. Now we are racing with the writer trying to | |
1624 | * move head page and the tail page. | |
1625 | * We are going to adapt the reader page update process where: | |
1626 | * 1. We first splice the start and end of list of new pages between | |
1627 | * the head page and its previous page. | |
1628 | * 2. We cmpxchg the prev_page->next to point from head page to the | |
1629 | * start of new pages list. | |
1630 | * 3. Finally, we update the head->prev to the end of new list. | |
1631 | * | |
1632 | * We will try this process 10 times, to make sure that we don't keep | |
1633 | * spinning. | |
1634 | */ | |
1635 | retries = 10; | |
1636 | success = 0; | |
1637 | while (retries--) { | |
1638 | struct list_head *head_page, *prev_page, *r; | |
1639 | struct list_head *last_page, *first_page; | |
1640 | struct list_head *head_page_with_bit; | |
77ae365e | 1641 | |
5040b4b7 | 1642 | head_page = &rb_set_head_page(cpu_buffer)->list; |
54f7be5b SR |
1643 | if (!head_page) |
1644 | break; | |
5040b4b7 VN |
1645 | prev_page = head_page->prev; |
1646 | ||
1647 | first_page = pages->next; | |
1648 | last_page = pages->prev; | |
1649 | ||
1650 | head_page_with_bit = (struct list_head *) | |
1651 | ((unsigned long)head_page | RB_PAGE_HEAD); | |
1652 | ||
1653 | last_page->next = head_page_with_bit; | |
1654 | first_page->prev = prev_page; | |
1655 | ||
1656 | r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); | |
1657 | ||
1658 | if (r == head_page_with_bit) { | |
1659 | /* | |
1660 | * yay, we replaced the page pointer to our new list, | |
1661 | * now, we just have to update to head page's prev | |
1662 | * pointer to point to end of list | |
1663 | */ | |
1664 | head_page->prev = last_page; | |
1665 | success = 1; | |
1666 | break; | |
1667 | } | |
7a8e76a3 | 1668 | } |
7a8e76a3 | 1669 | |
5040b4b7 VN |
1670 | if (success) |
1671 | INIT_LIST_HEAD(pages); | |
1672 | /* | |
1673 | * If we weren't successful in adding in new pages, warn and stop | |
1674 | * tracing | |
1675 | */ | |
1676 | RB_WARN_ON(cpu_buffer, !success); | |
5389f6fa | 1677 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1678 | |
1679 | /* free pages if they weren't inserted */ | |
1680 | if (!success) { | |
1681 | struct buffer_page *bpage, *tmp; | |
1682 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, | |
1683 | list) { | |
1684 | list_del_init(&bpage->list); | |
1685 | free_buffer_page(bpage); | |
1686 | } | |
1687 | } | |
1688 | return success; | |
7a8e76a3 SR |
1689 | } |
1690 | ||
83f40318 | 1691 | static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
438ced17 | 1692 | { |
5040b4b7 VN |
1693 | int success; |
1694 | ||
438ced17 | 1695 | if (cpu_buffer->nr_pages_to_update > 0) |
5040b4b7 | 1696 | success = rb_insert_pages(cpu_buffer); |
438ced17 | 1697 | else |
5040b4b7 VN |
1698 | success = rb_remove_pages(cpu_buffer, |
1699 | -cpu_buffer->nr_pages_to_update); | |
83f40318 | 1700 | |
5040b4b7 VN |
1701 | if (success) |
1702 | cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; | |
83f40318 VN |
1703 | } |
1704 | ||
1705 | static void update_pages_handler(struct work_struct *work) | |
1706 | { | |
1707 | struct ring_buffer_per_cpu *cpu_buffer = container_of(work, | |
1708 | struct ring_buffer_per_cpu, update_pages_work); | |
1709 | rb_update_pages(cpu_buffer); | |
05fdd70d | 1710 | complete(&cpu_buffer->update_done); |
438ced17 VN |
1711 | } |
1712 | ||
7a8e76a3 SR |
1713 | /** |
1714 | * ring_buffer_resize - resize the ring buffer | |
1715 | * @buffer: the buffer to resize. | |
1716 | * @size: the new size. | |
d611851b | 1717 | * @cpu_id: the cpu buffer to resize |
7a8e76a3 | 1718 | * |
7a8e76a3 SR |
1719 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1720 | * | |
83f40318 | 1721 | * Returns 0 on success and < 0 on failure. |
7a8e76a3 | 1722 | */ |
438ced17 VN |
1723 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, |
1724 | int cpu_id) | |
7a8e76a3 SR |
1725 | { |
1726 | struct ring_buffer_per_cpu *cpu_buffer; | |
9b94a8fb | 1727 | unsigned long nr_pages; |
83f40318 | 1728 | int cpu, err = 0; |
7a8e76a3 | 1729 | |
ee51a1de IM |
1730 | /* |
1731 | * Always succeed at resizing a non-existent buffer: | |
1732 | */ | |
1733 | if (!buffer) | |
1734 | return size; | |
1735 | ||
6a31e1f1 SR |
1736 | /* Make sure the requested buffer exists */ |
1737 | if (cpu_id != RING_BUFFER_ALL_CPUS && | |
1738 | !cpumask_test_cpu(cpu_id, buffer->cpumask)) | |
1739 | return size; | |
1740 | ||
59643d15 | 1741 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
7a8e76a3 SR |
1742 | |
1743 | /* we need a minimum of two pages */ | |
59643d15 SRRH |
1744 | if (nr_pages < 2) |
1745 | nr_pages = 2; | |
7a8e76a3 | 1746 | |
59643d15 | 1747 | size = nr_pages * BUF_PAGE_SIZE; |
18421015 | 1748 | |
83f40318 VN |
1749 | /* |
1750 | * Don't succeed if resizing is disabled, as a reader might be | |
1751 | * manipulating the ring buffer and is expecting a sane state while | |
1752 | * this is true. | |
1753 | */ | |
1754 | if (atomic_read(&buffer->resize_disabled)) | |
1755 | return -EBUSY; | |
18421015 | 1756 | |
83f40318 | 1757 | /* prevent another thread from changing buffer sizes */ |
7a8e76a3 | 1758 | mutex_lock(&buffer->mutex); |
7a8e76a3 | 1759 | |
438ced17 VN |
1760 | if (cpu_id == RING_BUFFER_ALL_CPUS) { |
1761 | /* calculate the pages to update */ | |
7a8e76a3 SR |
1762 | for_each_buffer_cpu(buffer, cpu) { |
1763 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 1764 | |
438ced17 VN |
1765 | cpu_buffer->nr_pages_to_update = nr_pages - |
1766 | cpu_buffer->nr_pages; | |
438ced17 VN |
1767 | /* |
1768 | * nothing more to do for removing pages or no update | |
1769 | */ | |
1770 | if (cpu_buffer->nr_pages_to_update <= 0) | |
1771 | continue; | |
d7ec4bfe | 1772 | /* |
438ced17 VN |
1773 | * to add pages, make sure all new pages can be |
1774 | * allocated without receiving ENOMEM | |
d7ec4bfe | 1775 | */ |
438ced17 VN |
1776 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
1777 | if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 | 1778 | &cpu_buffer->new_pages, cpu)) { |
438ced17 | 1779 | /* not enough memory for new pages */ |
83f40318 VN |
1780 | err = -ENOMEM; |
1781 | goto out_err; | |
1782 | } | |
1783 | } | |
1784 | ||
1785 | get_online_cpus(); | |
1786 | /* | |
1787 | * Fire off all the required work handlers | |
05fdd70d | 1788 | * We can't schedule on offline CPUs, but it's not necessary |
83f40318 VN |
1789 | * since we can change their buffer sizes without any race. |
1790 | */ | |
1791 | for_each_buffer_cpu(buffer, cpu) { | |
1792 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 1793 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
1794 | continue; |
1795 | ||
021c5b34 CM |
1796 | /* Can't run something on an offline CPU. */ |
1797 | if (!cpu_online(cpu)) { | |
f5eb5588 SRRH |
1798 | rb_update_pages(cpu_buffer); |
1799 | cpu_buffer->nr_pages_to_update = 0; | |
1800 | } else { | |
05fdd70d VN |
1801 | schedule_work_on(cpu, |
1802 | &cpu_buffer->update_pages_work); | |
f5eb5588 | 1803 | } |
7a8e76a3 | 1804 | } |
7a8e76a3 | 1805 | |
438ced17 VN |
1806 | /* wait for all the updates to complete */ |
1807 | for_each_buffer_cpu(buffer, cpu) { | |
1808 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 1809 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
1810 | continue; |
1811 | ||
05fdd70d VN |
1812 | if (cpu_online(cpu)) |
1813 | wait_for_completion(&cpu_buffer->update_done); | |
83f40318 | 1814 | cpu_buffer->nr_pages_to_update = 0; |
438ced17 | 1815 | } |
83f40318 VN |
1816 | |
1817 | put_online_cpus(); | |
438ced17 | 1818 | } else { |
6167c205 | 1819 | /* Make sure this CPU has been initialized */ |
8e49f418 VN |
1820 | if (!cpumask_test_cpu(cpu_id, buffer->cpumask)) |
1821 | goto out; | |
1822 | ||
438ced17 | 1823 | cpu_buffer = buffer->buffers[cpu_id]; |
83f40318 | 1824 | |
438ced17 VN |
1825 | if (nr_pages == cpu_buffer->nr_pages) |
1826 | goto out; | |
7a8e76a3 | 1827 | |
438ced17 VN |
1828 | cpu_buffer->nr_pages_to_update = nr_pages - |
1829 | cpu_buffer->nr_pages; | |
1830 | ||
1831 | INIT_LIST_HEAD(&cpu_buffer->new_pages); | |
1832 | if (cpu_buffer->nr_pages_to_update > 0 && | |
1833 | __rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 VN |
1834 | &cpu_buffer->new_pages, cpu_id)) { |
1835 | err = -ENOMEM; | |
1836 | goto out_err; | |
1837 | } | |
438ced17 | 1838 | |
83f40318 VN |
1839 | get_online_cpus(); |
1840 | ||
021c5b34 CM |
1841 | /* Can't run something on an offline CPU. */ |
1842 | if (!cpu_online(cpu_id)) | |
f5eb5588 SRRH |
1843 | rb_update_pages(cpu_buffer); |
1844 | else { | |
83f40318 VN |
1845 | schedule_work_on(cpu_id, |
1846 | &cpu_buffer->update_pages_work); | |
05fdd70d | 1847 | wait_for_completion(&cpu_buffer->update_done); |
f5eb5588 | 1848 | } |
83f40318 | 1849 | |
83f40318 | 1850 | cpu_buffer->nr_pages_to_update = 0; |
05fdd70d | 1851 | put_online_cpus(); |
438ced17 | 1852 | } |
7a8e76a3 SR |
1853 | |
1854 | out: | |
659f451f SR |
1855 | /* |
1856 | * The ring buffer resize can happen with the ring buffer | |
1857 | * enabled, so that the update disturbs the tracing as little | |
1858 | * as possible. But if the buffer is disabled, we do not need | |
1859 | * to worry about that, and we can take the time to verify | |
1860 | * that the buffer is not corrupt. | |
1861 | */ | |
1862 | if (atomic_read(&buffer->record_disabled)) { | |
1863 | atomic_inc(&buffer->record_disabled); | |
1864 | /* | |
1865 | * Even though the buffer was disabled, we must make sure | |
1866 | * that it is truly disabled before calling rb_check_pages. | |
1867 | * There could have been a race between checking | |
1868 | * record_disable and incrementing it. | |
1869 | */ | |
74401729 | 1870 | synchronize_rcu(); |
659f451f SR |
1871 | for_each_buffer_cpu(buffer, cpu) { |
1872 | cpu_buffer = buffer->buffers[cpu]; | |
1873 | rb_check_pages(cpu_buffer); | |
1874 | } | |
1875 | atomic_dec(&buffer->record_disabled); | |
1876 | } | |
1877 | ||
7a8e76a3 | 1878 | mutex_unlock(&buffer->mutex); |
7a8e76a3 SR |
1879 | return size; |
1880 | ||
83f40318 | 1881 | out_err: |
438ced17 VN |
1882 | for_each_buffer_cpu(buffer, cpu) { |
1883 | struct buffer_page *bpage, *tmp; | |
83f40318 | 1884 | |
438ced17 | 1885 | cpu_buffer = buffer->buffers[cpu]; |
438ced17 | 1886 | cpu_buffer->nr_pages_to_update = 0; |
83f40318 | 1887 | |
438ced17 VN |
1888 | if (list_empty(&cpu_buffer->new_pages)) |
1889 | continue; | |
83f40318 | 1890 | |
438ced17 VN |
1891 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
1892 | list) { | |
1893 | list_del_init(&bpage->list); | |
1894 | free_buffer_page(bpage); | |
1895 | } | |
7a8e76a3 | 1896 | } |
641d2f63 | 1897 | mutex_unlock(&buffer->mutex); |
83f40318 | 1898 | return err; |
7a8e76a3 | 1899 | } |
c4f50183 | 1900 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
7a8e76a3 | 1901 | |
750912fa DS |
1902 | void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) |
1903 | { | |
1904 | mutex_lock(&buffer->mutex); | |
1905 | if (val) | |
1906 | buffer->flags |= RB_FL_OVERWRITE; | |
1907 | else | |
1908 | buffer->flags &= ~RB_FL_OVERWRITE; | |
1909 | mutex_unlock(&buffer->mutex); | |
1910 | } | |
1911 | EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); | |
1912 | ||
2289d567 | 1913 | static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
7a8e76a3 | 1914 | { |
044fa782 | 1915 | return bpage->page->data + index; |
7a8e76a3 SR |
1916 | } |
1917 | ||
2289d567 | 1918 | static __always_inline struct ring_buffer_event * |
d769041f | 1919 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1920 | { |
6f807acd SR |
1921 | return __rb_page_index(cpu_buffer->reader_page, |
1922 | cpu_buffer->reader_page->read); | |
1923 | } | |
1924 | ||
2289d567 | 1925 | static __always_inline struct ring_buffer_event * |
7a8e76a3 SR |
1926 | rb_iter_head_event(struct ring_buffer_iter *iter) |
1927 | { | |
6f807acd | 1928 | return __rb_page_index(iter->head_page, iter->head); |
7a8e76a3 SR |
1929 | } |
1930 | ||
2289d567 | 1931 | static __always_inline unsigned rb_page_commit(struct buffer_page *bpage) |
bf41a158 | 1932 | { |
abc9b56d | 1933 | return local_read(&bpage->page->commit); |
bf41a158 SR |
1934 | } |
1935 | ||
25985edc | 1936 | /* Size is determined by what has been committed */ |
2289d567 | 1937 | static __always_inline unsigned rb_page_size(struct buffer_page *bpage) |
bf41a158 SR |
1938 | { |
1939 | return rb_page_commit(bpage); | |
1940 | } | |
1941 | ||
2289d567 | 1942 | static __always_inline unsigned |
bf41a158 SR |
1943 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) |
1944 | { | |
1945 | return rb_page_commit(cpu_buffer->commit_page); | |
1946 | } | |
1947 | ||
2289d567 | 1948 | static __always_inline unsigned |
bf41a158 SR |
1949 | rb_event_index(struct ring_buffer_event *event) |
1950 | { | |
1951 | unsigned long addr = (unsigned long)event; | |
1952 | ||
22f470f8 | 1953 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
bf41a158 SR |
1954 | } |
1955 | ||
34a148bf | 1956 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
d769041f SR |
1957 | { |
1958 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1959 | ||
1960 | /* | |
1961 | * The iterator could be on the reader page (it starts there). | |
1962 | * But the head could have moved, since the reader was | |
1963 | * found. Check for this case and assign the iterator | |
1964 | * to the head page instead of next. | |
1965 | */ | |
1966 | if (iter->head_page == cpu_buffer->reader_page) | |
77ae365e | 1967 | iter->head_page = rb_set_head_page(cpu_buffer); |
d769041f SR |
1968 | else |
1969 | rb_inc_page(cpu_buffer, &iter->head_page); | |
1970 | ||
abc9b56d | 1971 | iter->read_stamp = iter->head_page->page->time_stamp; |
7a8e76a3 SR |
1972 | iter->head = 0; |
1973 | } | |
1974 | ||
77ae365e SR |
1975 | /* |
1976 | * rb_handle_head_page - writer hit the head page | |
1977 | * | |
1978 | * Returns: +1 to retry page | |
1979 | * 0 to continue | |
1980 | * -1 on error | |
1981 | */ | |
1982 | static int | |
1983 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, | |
1984 | struct buffer_page *tail_page, | |
1985 | struct buffer_page *next_page) | |
1986 | { | |
1987 | struct buffer_page *new_head; | |
1988 | int entries; | |
1989 | int type; | |
1990 | int ret; | |
1991 | ||
1992 | entries = rb_page_entries(next_page); | |
1993 | ||
1994 | /* | |
1995 | * The hard part is here. We need to move the head | |
1996 | * forward, and protect against both readers on | |
1997 | * other CPUs and writers coming in via interrupts. | |
1998 | */ | |
1999 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, | |
2000 | RB_PAGE_HEAD); | |
2001 | ||
2002 | /* | |
2003 | * type can be one of four: | |
2004 | * NORMAL - an interrupt already moved it for us | |
2005 | * HEAD - we are the first to get here. | |
2006 | * UPDATE - we are the interrupt interrupting | |
2007 | * a current move. | |
2008 | * MOVED - a reader on another CPU moved the next | |
2009 | * pointer to its reader page. Give up | |
2010 | * and try again. | |
2011 | */ | |
2012 | ||
2013 | switch (type) { | |
2014 | case RB_PAGE_HEAD: | |
2015 | /* | |
2016 | * We changed the head to UPDATE, thus | |
2017 | * it is our responsibility to update | |
2018 | * the counters. | |
2019 | */ | |
2020 | local_add(entries, &cpu_buffer->overrun); | |
c64e148a | 2021 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
77ae365e SR |
2022 | |
2023 | /* | |
2024 | * The entries will be zeroed out when we move the | |
2025 | * tail page. | |
2026 | */ | |
2027 | ||
2028 | /* still more to do */ | |
2029 | break; | |
2030 | ||
2031 | case RB_PAGE_UPDATE: | |
2032 | /* | |
2033 | * This is an interrupt that interrupt the | |
2034 | * previous update. Still more to do. | |
2035 | */ | |
2036 | break; | |
2037 | case RB_PAGE_NORMAL: | |
2038 | /* | |
2039 | * An interrupt came in before the update | |
2040 | * and processed this for us. | |
2041 | * Nothing left to do. | |
2042 | */ | |
2043 | return 1; | |
2044 | case RB_PAGE_MOVED: | |
2045 | /* | |
2046 | * The reader is on another CPU and just did | |
2047 | * a swap with our next_page. | |
2048 | * Try again. | |
2049 | */ | |
2050 | return 1; | |
2051 | default: | |
2052 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ | |
2053 | return -1; | |
2054 | } | |
2055 | ||
2056 | /* | |
2057 | * Now that we are here, the old head pointer is | |
2058 | * set to UPDATE. This will keep the reader from | |
2059 | * swapping the head page with the reader page. | |
2060 | * The reader (on another CPU) will spin till | |
2061 | * we are finished. | |
2062 | * | |
2063 | * We just need to protect against interrupts | |
2064 | * doing the job. We will set the next pointer | |
2065 | * to HEAD. After that, we set the old pointer | |
2066 | * to NORMAL, but only if it was HEAD before. | |
2067 | * otherwise we are an interrupt, and only | |
2068 | * want the outer most commit to reset it. | |
2069 | */ | |
2070 | new_head = next_page; | |
2071 | rb_inc_page(cpu_buffer, &new_head); | |
2072 | ||
2073 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, | |
2074 | RB_PAGE_NORMAL); | |
2075 | ||
2076 | /* | |
2077 | * Valid returns are: | |
2078 | * HEAD - an interrupt came in and already set it. | |
2079 | * NORMAL - One of two things: | |
2080 | * 1) We really set it. | |
2081 | * 2) A bunch of interrupts came in and moved | |
2082 | * the page forward again. | |
2083 | */ | |
2084 | switch (ret) { | |
2085 | case RB_PAGE_HEAD: | |
2086 | case RB_PAGE_NORMAL: | |
2087 | /* OK */ | |
2088 | break; | |
2089 | default: | |
2090 | RB_WARN_ON(cpu_buffer, 1); | |
2091 | return -1; | |
2092 | } | |
2093 | ||
2094 | /* | |
2095 | * It is possible that an interrupt came in, | |
2096 | * set the head up, then more interrupts came in | |
2097 | * and moved it again. When we get back here, | |
2098 | * the page would have been set to NORMAL but we | |
2099 | * just set it back to HEAD. | |
2100 | * | |
2101 | * How do you detect this? Well, if that happened | |
2102 | * the tail page would have moved. | |
2103 | */ | |
2104 | if (ret == RB_PAGE_NORMAL) { | |
8573636e SRRH |
2105 | struct buffer_page *buffer_tail_page; |
2106 | ||
2107 | buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); | |
77ae365e SR |
2108 | /* |
2109 | * If the tail had moved passed next, then we need | |
2110 | * to reset the pointer. | |
2111 | */ | |
8573636e SRRH |
2112 | if (buffer_tail_page != tail_page && |
2113 | buffer_tail_page != next_page) | |
77ae365e SR |
2114 | rb_head_page_set_normal(cpu_buffer, new_head, |
2115 | next_page, | |
2116 | RB_PAGE_HEAD); | |
2117 | } | |
2118 | ||
2119 | /* | |
2120 | * If this was the outer most commit (the one that | |
2121 | * changed the original pointer from HEAD to UPDATE), | |
2122 | * then it is up to us to reset it to NORMAL. | |
2123 | */ | |
2124 | if (type == RB_PAGE_HEAD) { | |
2125 | ret = rb_head_page_set_normal(cpu_buffer, next_page, | |
2126 | tail_page, | |
2127 | RB_PAGE_UPDATE); | |
2128 | if (RB_WARN_ON(cpu_buffer, | |
2129 | ret != RB_PAGE_UPDATE)) | |
2130 | return -1; | |
2131 | } | |
2132 | ||
2133 | return 0; | |
2134 | } | |
2135 | ||
c7b09308 SR |
2136 | static inline void |
2137 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, | |
fcc742ea | 2138 | unsigned long tail, struct rb_event_info *info) |
c7b09308 | 2139 | { |
fcc742ea | 2140 | struct buffer_page *tail_page = info->tail_page; |
c7b09308 | 2141 | struct ring_buffer_event *event; |
fcc742ea | 2142 | unsigned long length = info->length; |
c7b09308 SR |
2143 | |
2144 | /* | |
2145 | * Only the event that crossed the page boundary | |
2146 | * must fill the old tail_page with padding. | |
2147 | */ | |
2148 | if (tail >= BUF_PAGE_SIZE) { | |
b3230c8b SR |
2149 | /* |
2150 | * If the page was filled, then we still need | |
2151 | * to update the real_end. Reset it to zero | |
2152 | * and the reader will ignore it. | |
2153 | */ | |
2154 | if (tail == BUF_PAGE_SIZE) | |
2155 | tail_page->real_end = 0; | |
2156 | ||
c7b09308 SR |
2157 | local_sub(length, &tail_page->write); |
2158 | return; | |
2159 | } | |
2160 | ||
2161 | event = __rb_page_index(tail_page, tail); | |
2162 | ||
c64e148a VN |
2163 | /* account for padding bytes */ |
2164 | local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); | |
2165 | ||
ff0ff84a SR |
2166 | /* |
2167 | * Save the original length to the meta data. | |
2168 | * This will be used by the reader to add lost event | |
2169 | * counter. | |
2170 | */ | |
2171 | tail_page->real_end = tail; | |
2172 | ||
c7b09308 SR |
2173 | /* |
2174 | * If this event is bigger than the minimum size, then | |
2175 | * we need to be careful that we don't subtract the | |
2176 | * write counter enough to allow another writer to slip | |
2177 | * in on this page. | |
2178 | * We put in a discarded commit instead, to make sure | |
2179 | * that this space is not used again. | |
2180 | * | |
2181 | * If we are less than the minimum size, we don't need to | |
2182 | * worry about it. | |
2183 | */ | |
2184 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { | |
2185 | /* No room for any events */ | |
2186 | ||
2187 | /* Mark the rest of the page with padding */ | |
2188 | rb_event_set_padding(event); | |
2189 | ||
2190 | /* Set the write back to the previous setting */ | |
2191 | local_sub(length, &tail_page->write); | |
2192 | return; | |
2193 | } | |
2194 | ||
2195 | /* Put in a discarded event */ | |
2196 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; | |
2197 | event->type_len = RINGBUF_TYPE_PADDING; | |
2198 | /* time delta must be non zero */ | |
2199 | event->time_delta = 1; | |
c7b09308 SR |
2200 | |
2201 | /* Set write to end of buffer */ | |
2202 | length = (tail + length) - BUF_PAGE_SIZE; | |
2203 | local_sub(length, &tail_page->write); | |
2204 | } | |
6634ff26 | 2205 | |
4239c38f SRRH |
2206 | static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer); |
2207 | ||
747e94ae SR |
2208 | /* |
2209 | * This is the slow path, force gcc not to inline it. | |
2210 | */ | |
2211 | static noinline struct ring_buffer_event * | |
6634ff26 | 2212 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
fcc742ea | 2213 | unsigned long tail, struct rb_event_info *info) |
7a8e76a3 | 2214 | { |
fcc742ea | 2215 | struct buffer_page *tail_page = info->tail_page; |
5a50e33c | 2216 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
7a8e76a3 | 2217 | struct ring_buffer *buffer = cpu_buffer->buffer; |
77ae365e SR |
2218 | struct buffer_page *next_page; |
2219 | int ret; | |
aa20ae84 SR |
2220 | |
2221 | next_page = tail_page; | |
2222 | ||
aa20ae84 SR |
2223 | rb_inc_page(cpu_buffer, &next_page); |
2224 | ||
aa20ae84 SR |
2225 | /* |
2226 | * If for some reason, we had an interrupt storm that made | |
2227 | * it all the way around the buffer, bail, and warn | |
2228 | * about it. | |
2229 | */ | |
2230 | if (unlikely(next_page == commit_page)) { | |
77ae365e | 2231 | local_inc(&cpu_buffer->commit_overrun); |
aa20ae84 SR |
2232 | goto out_reset; |
2233 | } | |
2234 | ||
77ae365e SR |
2235 | /* |
2236 | * This is where the fun begins! | |
2237 | * | |
2238 | * We are fighting against races between a reader that | |
2239 | * could be on another CPU trying to swap its reader | |
2240 | * page with the buffer head. | |
2241 | * | |
2242 | * We are also fighting against interrupts coming in and | |
2243 | * moving the head or tail on us as well. | |
2244 | * | |
2245 | * If the next page is the head page then we have filled | |
2246 | * the buffer, unless the commit page is still on the | |
2247 | * reader page. | |
2248 | */ | |
2249 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { | |
aa20ae84 | 2250 | |
77ae365e SR |
2251 | /* |
2252 | * If the commit is not on the reader page, then | |
2253 | * move the header page. | |
2254 | */ | |
2255 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { | |
2256 | /* | |
2257 | * If we are not in overwrite mode, | |
2258 | * this is easy, just stop here. | |
2259 | */ | |
884bfe89 SP |
2260 | if (!(buffer->flags & RB_FL_OVERWRITE)) { |
2261 | local_inc(&cpu_buffer->dropped_events); | |
77ae365e | 2262 | goto out_reset; |
884bfe89 | 2263 | } |
77ae365e SR |
2264 | |
2265 | ret = rb_handle_head_page(cpu_buffer, | |
2266 | tail_page, | |
2267 | next_page); | |
2268 | if (ret < 0) | |
2269 | goto out_reset; | |
2270 | if (ret) | |
2271 | goto out_again; | |
2272 | } else { | |
2273 | /* | |
2274 | * We need to be careful here too. The | |
2275 | * commit page could still be on the reader | |
2276 | * page. We could have a small buffer, and | |
2277 | * have filled up the buffer with events | |
2278 | * from interrupts and such, and wrapped. | |
2279 | * | |
2280 | * Note, if the tail page is also the on the | |
2281 | * reader_page, we let it move out. | |
2282 | */ | |
2283 | if (unlikely((cpu_buffer->commit_page != | |
2284 | cpu_buffer->tail_page) && | |
2285 | (cpu_buffer->commit_page == | |
2286 | cpu_buffer->reader_page))) { | |
2287 | local_inc(&cpu_buffer->commit_overrun); | |
2288 | goto out_reset; | |
2289 | } | |
aa20ae84 SR |
2290 | } |
2291 | } | |
2292 | ||
70004986 | 2293 | rb_tail_page_update(cpu_buffer, tail_page, next_page); |
aa20ae84 | 2294 | |
77ae365e | 2295 | out_again: |
aa20ae84 | 2296 | |
fcc742ea | 2297 | rb_reset_tail(cpu_buffer, tail, info); |
aa20ae84 | 2298 | |
4239c38f SRRH |
2299 | /* Commit what we have for now. */ |
2300 | rb_end_commit(cpu_buffer); | |
2301 | /* rb_end_commit() decs committing */ | |
2302 | local_inc(&cpu_buffer->committing); | |
2303 | ||
aa20ae84 SR |
2304 | /* fail and let the caller try again */ |
2305 | return ERR_PTR(-EAGAIN); | |
2306 | ||
45141d46 | 2307 | out_reset: |
6f3b3440 | 2308 | /* reset write */ |
fcc742ea | 2309 | rb_reset_tail(cpu_buffer, tail, info); |
6f3b3440 | 2310 | |
bf41a158 | 2311 | return NULL; |
7a8e76a3 SR |
2312 | } |
2313 | ||
d90fd774 SRRH |
2314 | /* Slow path, do not inline */ |
2315 | static noinline struct ring_buffer_event * | |
dc4e2801 | 2316 | rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs) |
9826b273 | 2317 | { |
dc4e2801 TZ |
2318 | if (abs) |
2319 | event->type_len = RINGBUF_TYPE_TIME_STAMP; | |
2320 | else | |
2321 | event->type_len = RINGBUF_TYPE_TIME_EXTEND; | |
9826b273 | 2322 | |
dc4e2801 TZ |
2323 | /* Not the first event on the page, or not delta? */ |
2324 | if (abs || rb_event_index(event)) { | |
d90fd774 SRRH |
2325 | event->time_delta = delta & TS_MASK; |
2326 | event->array[0] = delta >> TS_SHIFT; | |
2327 | } else { | |
2328 | /* nope, just zero it */ | |
2329 | event->time_delta = 0; | |
2330 | event->array[0] = 0; | |
2331 | } | |
a4543a2f | 2332 | |
d90fd774 SRRH |
2333 | return skip_time_extend(event); |
2334 | } | |
a4543a2f | 2335 | |
cdb2a0a9 | 2336 | static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
b7dc42fd SRRH |
2337 | struct ring_buffer_event *event); |
2338 | ||
d90fd774 SRRH |
2339 | /** |
2340 | * rb_update_event - update event type and data | |
2341 | * @event: the event to update | |
2342 | * @type: the type of event | |
2343 | * @length: the size of the event field in the ring buffer | |
2344 | * | |
2345 | * Update the type and data fields of the event. The length | |
2346 | * is the actual size that is written to the ring buffer, | |
2347 | * and with this, we can determine what to place into the | |
2348 | * data field. | |
2349 | */ | |
b7dc42fd | 2350 | static void |
d90fd774 SRRH |
2351 | rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
2352 | struct ring_buffer_event *event, | |
2353 | struct rb_event_info *info) | |
2354 | { | |
2355 | unsigned length = info->length; | |
2356 | u64 delta = info->delta; | |
a4543a2f | 2357 | |
b7dc42fd SRRH |
2358 | /* Only a commit updates the timestamp */ |
2359 | if (unlikely(!rb_event_is_commit(cpu_buffer, event))) | |
2360 | delta = 0; | |
2361 | ||
a4543a2f | 2362 | /* |
d90fd774 | 2363 | * If we need to add a timestamp, then we |
6167c205 | 2364 | * add it to the start of the reserved space. |
a4543a2f | 2365 | */ |
d90fd774 | 2366 | if (unlikely(info->add_timestamp)) { |
dc4e2801 TZ |
2367 | bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer); |
2368 | ||
2369 | event = rb_add_time_stamp(event, info->delta, abs); | |
d90fd774 SRRH |
2370 | length -= RB_LEN_TIME_EXTEND; |
2371 | delta = 0; | |
a4543a2f SRRH |
2372 | } |
2373 | ||
d90fd774 SRRH |
2374 | event->time_delta = delta; |
2375 | length -= RB_EVNT_HDR_SIZE; | |
2376 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { | |
2377 | event->type_len = 0; | |
2378 | event->array[0] = length; | |
2379 | } else | |
2380 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); | |
2381 | } | |
2382 | ||
2383 | static unsigned rb_calculate_event_length(unsigned length) | |
2384 | { | |
2385 | struct ring_buffer_event event; /* Used only for sizeof array */ | |
2386 | ||
2387 | /* zero length can cause confusions */ | |
2388 | if (!length) | |
2389 | length++; | |
2390 | ||
2391 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) | |
2392 | length += sizeof(event.array[0]); | |
2393 | ||
2394 | length += RB_EVNT_HDR_SIZE; | |
2395 | length = ALIGN(length, RB_ARCH_ALIGNMENT); | |
2396 | ||
2397 | /* | |
2398 | * In case the time delta is larger than the 27 bits for it | |
2399 | * in the header, we need to add a timestamp. If another | |
2400 | * event comes in when trying to discard this one to increase | |
2401 | * the length, then the timestamp will be added in the allocated | |
2402 | * space of this event. If length is bigger than the size needed | |
2403 | * for the TIME_EXTEND, then padding has to be used. The events | |
2404 | * length must be either RB_LEN_TIME_EXTEND, or greater than or equal | |
2405 | * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. | |
2406 | * As length is a multiple of 4, we only need to worry if it | |
2407 | * is 12 (RB_LEN_TIME_EXTEND + 4). | |
2408 | */ | |
2409 | if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) | |
2410 | length += RB_ALIGNMENT; | |
2411 | ||
2412 | return length; | |
2413 | } | |
2414 | ||
2415 | #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK | |
2416 | static inline bool sched_clock_stable(void) | |
2417 | { | |
2418 | return true; | |
2419 | } | |
2420 | #endif | |
2421 | ||
2422 | static inline int | |
2423 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, | |
2424 | struct ring_buffer_event *event) | |
2425 | { | |
2426 | unsigned long new_index, old_index; | |
2427 | struct buffer_page *bpage; | |
2428 | unsigned long index; | |
2429 | unsigned long addr; | |
2430 | ||
2431 | new_index = rb_event_index(event); | |
2432 | old_index = new_index + rb_event_ts_length(event); | |
2433 | addr = (unsigned long)event; | |
2434 | addr &= PAGE_MASK; | |
2435 | ||
8573636e | 2436 | bpage = READ_ONCE(cpu_buffer->tail_page); |
d90fd774 SRRH |
2437 | |
2438 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { | |
2439 | unsigned long write_mask = | |
2440 | local_read(&bpage->write) & ~RB_WRITE_MASK; | |
2441 | unsigned long event_length = rb_event_length(event); | |
2442 | /* | |
2443 | * This is on the tail page. It is possible that | |
2444 | * a write could come in and move the tail page | |
2445 | * and write to the next page. That is fine | |
2446 | * because we just shorten what is on this page. | |
2447 | */ | |
2448 | old_index += write_mask; | |
2449 | new_index += write_mask; | |
2450 | index = local_cmpxchg(&bpage->write, old_index, new_index); | |
2451 | if (index == old_index) { | |
2452 | /* update counters */ | |
2453 | local_sub(event_length, &cpu_buffer->entries_bytes); | |
2454 | return 1; | |
2455 | } | |
2456 | } | |
2457 | ||
2458 | /* could not discard */ | |
2459 | return 0; | |
2460 | } | |
2461 | ||
2462 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) | |
2463 | { | |
2464 | local_inc(&cpu_buffer->committing); | |
2465 | local_inc(&cpu_buffer->commits); | |
2466 | } | |
2467 | ||
38e11df1 | 2468 | static __always_inline void |
d90fd774 SRRH |
2469 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
2470 | { | |
2471 | unsigned long max_count; | |
2472 | ||
2473 | /* | |
2474 | * We only race with interrupts and NMIs on this CPU. | |
2475 | * If we own the commit event, then we can commit | |
2476 | * all others that interrupted us, since the interruptions | |
2477 | * are in stack format (they finish before they come | |
2478 | * back to us). This allows us to do a simple loop to | |
2479 | * assign the commit to the tail. | |
2480 | */ | |
2481 | again: | |
2482 | max_count = cpu_buffer->nr_pages * 100; | |
2483 | ||
8573636e | 2484 | while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { |
d90fd774 SRRH |
2485 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
2486 | return; | |
2487 | if (RB_WARN_ON(cpu_buffer, | |
2488 | rb_is_reader_page(cpu_buffer->tail_page))) | |
2489 | return; | |
2490 | local_set(&cpu_buffer->commit_page->page->commit, | |
2491 | rb_page_write(cpu_buffer->commit_page)); | |
2492 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); | |
70004986 SRRH |
2493 | /* Only update the write stamp if the page has an event */ |
2494 | if (rb_page_write(cpu_buffer->commit_page)) | |
2495 | cpu_buffer->write_stamp = | |
2496 | cpu_buffer->commit_page->page->time_stamp; | |
d90fd774 SRRH |
2497 | /* add barrier to keep gcc from optimizing too much */ |
2498 | barrier(); | |
2499 | } | |
2500 | while (rb_commit_index(cpu_buffer) != | |
2501 | rb_page_write(cpu_buffer->commit_page)) { | |
2502 | ||
2503 | local_set(&cpu_buffer->commit_page->page->commit, | |
2504 | rb_page_write(cpu_buffer->commit_page)); | |
2505 | RB_WARN_ON(cpu_buffer, | |
2506 | local_read(&cpu_buffer->commit_page->page->commit) & | |
2507 | ~RB_WRITE_MASK); | |
2508 | barrier(); | |
2509 | } | |
2510 | ||
2511 | /* again, keep gcc from optimizing */ | |
2512 | barrier(); | |
2513 | ||
2514 | /* | |
2515 | * If an interrupt came in just after the first while loop | |
2516 | * and pushed the tail page forward, we will be left with | |
2517 | * a dangling commit that will never go forward. | |
2518 | */ | |
8573636e | 2519 | if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) |
d90fd774 SRRH |
2520 | goto again; |
2521 | } | |
2522 | ||
38e11df1 | 2523 | static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
d90fd774 SRRH |
2524 | { |
2525 | unsigned long commits; | |
2526 | ||
2527 | if (RB_WARN_ON(cpu_buffer, | |
2528 | !local_read(&cpu_buffer->committing))) | |
2529 | return; | |
2530 | ||
2531 | again: | |
2532 | commits = local_read(&cpu_buffer->commits); | |
2533 | /* synchronize with interrupts */ | |
2534 | barrier(); | |
2535 | if (local_read(&cpu_buffer->committing) == 1) | |
2536 | rb_set_commit_to_write(cpu_buffer); | |
2537 | ||
2538 | local_dec(&cpu_buffer->committing); | |
2539 | ||
2540 | /* synchronize with interrupts */ | |
2541 | barrier(); | |
2542 | ||
2543 | /* | |
2544 | * Need to account for interrupts coming in between the | |
2545 | * updating of the commit page and the clearing of the | |
2546 | * committing counter. | |
2547 | */ | |
2548 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && | |
2549 | !local_read(&cpu_buffer->committing)) { | |
2550 | local_inc(&cpu_buffer->committing); | |
2551 | goto again; | |
2552 | } | |
2553 | } | |
2554 | ||
2555 | static inline void rb_event_discard(struct ring_buffer_event *event) | |
2556 | { | |
dc4e2801 | 2557 | if (extended_time(event)) |
d90fd774 SRRH |
2558 | event = skip_time_extend(event); |
2559 | ||
2560 | /* array[0] holds the actual length for the discarded event */ | |
2561 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; | |
2562 | event->type_len = RINGBUF_TYPE_PADDING; | |
2563 | /* time delta must be non zero */ | |
2564 | if (!event->time_delta) | |
2565 | event->time_delta = 1; | |
2566 | } | |
2567 | ||
babe3fce | 2568 | static __always_inline bool |
d90fd774 SRRH |
2569 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2570 | struct ring_buffer_event *event) | |
2571 | { | |
2572 | unsigned long addr = (unsigned long)event; | |
2573 | unsigned long index; | |
2574 | ||
2575 | index = rb_event_index(event); | |
2576 | addr &= PAGE_MASK; | |
2577 | ||
2578 | return cpu_buffer->commit_page->page == (void *)addr && | |
2579 | rb_commit_index(cpu_buffer) == index; | |
2580 | } | |
2581 | ||
babe3fce | 2582 | static __always_inline void |
d90fd774 SRRH |
2583 | rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
2584 | struct ring_buffer_event *event) | |
2585 | { | |
2586 | u64 delta; | |
2587 | ||
2588 | /* | |
2589 | * The event first in the commit queue updates the | |
2590 | * time stamp. | |
2591 | */ | |
2592 | if (rb_event_is_commit(cpu_buffer, event)) { | |
2593 | /* | |
2594 | * A commit event that is first on a page | |
2595 | * updates the write timestamp with the page stamp | |
2596 | */ | |
2597 | if (!rb_event_index(event)) | |
2598 | cpu_buffer->write_stamp = | |
2599 | cpu_buffer->commit_page->page->time_stamp; | |
2600 | else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { | |
dc4e2801 | 2601 | delta = ring_buffer_event_time_stamp(event); |
d90fd774 | 2602 | cpu_buffer->write_stamp += delta; |
dc4e2801 TZ |
2603 | } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) { |
2604 | delta = ring_buffer_event_time_stamp(event); | |
2605 | cpu_buffer->write_stamp = delta; | |
d90fd774 SRRH |
2606 | } else |
2607 | cpu_buffer->write_stamp += event->time_delta; | |
2608 | } | |
2609 | } | |
2610 | ||
2611 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, | |
2612 | struct ring_buffer_event *event) | |
2613 | { | |
2614 | local_inc(&cpu_buffer->entries); | |
2615 | rb_update_write_stamp(cpu_buffer, event); | |
2616 | rb_end_commit(cpu_buffer); | |
2617 | } | |
2618 | ||
2619 | static __always_inline void | |
2620 | rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) | |
2621 | { | |
03329f99 SRV |
2622 | size_t nr_pages; |
2623 | size_t dirty; | |
2624 | size_t full; | |
d90fd774 SRRH |
2625 | |
2626 | if (buffer->irq_work.waiters_pending) { | |
2627 | buffer->irq_work.waiters_pending = false; | |
2628 | /* irq_work_queue() supplies it's own memory barriers */ | |
2629 | irq_work_queue(&buffer->irq_work.work); | |
2630 | } | |
2631 | ||
2632 | if (cpu_buffer->irq_work.waiters_pending) { | |
2633 | cpu_buffer->irq_work.waiters_pending = false; | |
2634 | /* irq_work_queue() supplies it's own memory barriers */ | |
2635 | irq_work_queue(&cpu_buffer->irq_work.work); | |
2636 | } | |
2637 | ||
03329f99 SRV |
2638 | if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) |
2639 | return; | |
d90fd774 | 2640 | |
03329f99 SRV |
2641 | if (cpu_buffer->reader_page == cpu_buffer->commit_page) |
2642 | return; | |
2c2b0a78 | 2643 | |
03329f99 SRV |
2644 | if (!cpu_buffer->irq_work.full_waiters_pending) |
2645 | return; | |
2c2b0a78 | 2646 | |
03329f99 SRV |
2647 | cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched); |
2648 | ||
2649 | full = cpu_buffer->shortest_full; | |
2650 | nr_pages = cpu_buffer->nr_pages; | |
2651 | dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu); | |
2652 | if (full && nr_pages && (dirty * 100) <= full * nr_pages) | |
2653 | return; | |
2654 | ||
2655 | cpu_buffer->irq_work.wakeup_full = true; | |
2656 | cpu_buffer->irq_work.full_waiters_pending = false; | |
2657 | /* irq_work_queue() supplies it's own memory barriers */ | |
2658 | irq_work_queue(&cpu_buffer->irq_work.work); | |
d90fd774 SRRH |
2659 | } |
2660 | ||
2661 | /* | |
2662 | * The lock and unlock are done within a preempt disable section. | |
2663 | * The current_context per_cpu variable can only be modified | |
2664 | * by the current task between lock and unlock. But it can | |
a0e3a18f SRV |
2665 | * be modified more than once via an interrupt. To pass this |
2666 | * information from the lock to the unlock without having to | |
2667 | * access the 'in_interrupt()' functions again (which do show | |
2668 | * a bit of overhead in something as critical as function tracing, | |
2669 | * we use a bitmask trick. | |
d90fd774 | 2670 | * |
a0e3a18f SRV |
2671 | * bit 0 = NMI context |
2672 | * bit 1 = IRQ context | |
2673 | * bit 2 = SoftIRQ context | |
2674 | * bit 3 = normal context. | |
d90fd774 | 2675 | * |
a0e3a18f SRV |
2676 | * This works because this is the order of contexts that can |
2677 | * preempt other contexts. A SoftIRQ never preempts an IRQ | |
2678 | * context. | |
2679 | * | |
2680 | * When the context is determined, the corresponding bit is | |
2681 | * checked and set (if it was set, then a recursion of that context | |
2682 | * happened). | |
2683 | * | |
2684 | * On unlock, we need to clear this bit. To do so, just subtract | |
2685 | * 1 from the current_context and AND it to itself. | |
2686 | * | |
2687 | * (binary) | |
2688 | * 101 - 1 = 100 | |
2689 | * 101 & 100 = 100 (clearing bit zero) | |
2690 | * | |
2691 | * 1010 - 1 = 1001 | |
2692 | * 1010 & 1001 = 1000 (clearing bit 1) | |
2693 | * | |
2694 | * The least significant bit can be cleared this way, and it | |
2695 | * just so happens that it is the same bit corresponding to | |
2696 | * the current context. | |
d90fd774 SRRH |
2697 | */ |
2698 | ||
2699 | static __always_inline int | |
2700 | trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) | |
2701 | { | |
a0e3a18f SRV |
2702 | unsigned int val = cpu_buffer->current_context; |
2703 | unsigned long pc = preempt_count(); | |
2704 | int bit; | |
2705 | ||
2706 | if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) | |
2707 | bit = RB_CTX_NORMAL; | |
2708 | else | |
2709 | bit = pc & NMI_MASK ? RB_CTX_NMI : | |
0164e0d7 | 2710 | pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ; |
a0e3a18f | 2711 | |
8e012066 | 2712 | if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) |
d90fd774 SRRH |
2713 | return 1; |
2714 | ||
8e012066 | 2715 | val |= (1 << (bit + cpu_buffer->nest)); |
a0e3a18f | 2716 | cpu_buffer->current_context = val; |
d90fd774 SRRH |
2717 | |
2718 | return 0; | |
2719 | } | |
2720 | ||
2721 | static __always_inline void | |
2722 | trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) | |
2723 | { | |
8e012066 SRV |
2724 | cpu_buffer->current_context &= |
2725 | cpu_buffer->current_context - (1 << cpu_buffer->nest); | |
2726 | } | |
2727 | ||
2728 | /* The recursive locking above uses 4 bits */ | |
2729 | #define NESTED_BITS 4 | |
2730 | ||
2731 | /** | |
2732 | * ring_buffer_nest_start - Allow to trace while nested | |
2733 | * @buffer: The ring buffer to modify | |
2734 | * | |
6167c205 | 2735 | * The ring buffer has a safety mechanism to prevent recursion. |
8e012066 SRV |
2736 | * But there may be a case where a trace needs to be done while |
2737 | * tracing something else. In this case, calling this function | |
2738 | * will allow this function to nest within a currently active | |
2739 | * ring_buffer_lock_reserve(). | |
2740 | * | |
2741 | * Call this function before calling another ring_buffer_lock_reserve() and | |
2742 | * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). | |
2743 | */ | |
2744 | void ring_buffer_nest_start(struct ring_buffer *buffer) | |
2745 | { | |
2746 | struct ring_buffer_per_cpu *cpu_buffer; | |
2747 | int cpu; | |
2748 | ||
2749 | /* Enabled by ring_buffer_nest_end() */ | |
2750 | preempt_disable_notrace(); | |
2751 | cpu = raw_smp_processor_id(); | |
2752 | cpu_buffer = buffer->buffers[cpu]; | |
6167c205 | 2753 | /* This is the shift value for the above recursive locking */ |
8e012066 SRV |
2754 | cpu_buffer->nest += NESTED_BITS; |
2755 | } | |
2756 | ||
2757 | /** | |
2758 | * ring_buffer_nest_end - Allow to trace while nested | |
2759 | * @buffer: The ring buffer to modify | |
2760 | * | |
2761 | * Must be called after ring_buffer_nest_start() and after the | |
2762 | * ring_buffer_unlock_commit(). | |
2763 | */ | |
2764 | void ring_buffer_nest_end(struct ring_buffer *buffer) | |
2765 | { | |
2766 | struct ring_buffer_per_cpu *cpu_buffer; | |
2767 | int cpu; | |
2768 | ||
2769 | /* disabled by ring_buffer_nest_start() */ | |
2770 | cpu = raw_smp_processor_id(); | |
2771 | cpu_buffer = buffer->buffers[cpu]; | |
6167c205 | 2772 | /* This is the shift value for the above recursive locking */ |
8e012066 SRV |
2773 | cpu_buffer->nest -= NESTED_BITS; |
2774 | preempt_enable_notrace(); | |
d90fd774 SRRH |
2775 | } |
2776 | ||
2777 | /** | |
2778 | * ring_buffer_unlock_commit - commit a reserved | |
2779 | * @buffer: The buffer to commit to | |
2780 | * @event: The event pointer to commit. | |
2781 | * | |
2782 | * This commits the data to the ring buffer, and releases any locks held. | |
2783 | * | |
2784 | * Must be paired with ring_buffer_lock_reserve. | |
2785 | */ | |
2786 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, | |
2787 | struct ring_buffer_event *event) | |
2788 | { | |
2789 | struct ring_buffer_per_cpu *cpu_buffer; | |
2790 | int cpu = raw_smp_processor_id(); | |
2791 | ||
2792 | cpu_buffer = buffer->buffers[cpu]; | |
2793 | ||
2794 | rb_commit(cpu_buffer, event); | |
2795 | ||
2796 | rb_wakeups(buffer, cpu_buffer); | |
2797 | ||
2798 | trace_recursive_unlock(cpu_buffer); | |
2799 | ||
2800 | preempt_enable_notrace(); | |
2801 | ||
2802 | return 0; | |
2803 | } | |
2804 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); | |
2805 | ||
2806 | static noinline void | |
2807 | rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer, | |
d90fd774 SRRH |
2808 | struct rb_event_info *info) |
2809 | { | |
d90fd774 SRRH |
2810 | WARN_ONCE(info->delta > (1ULL << 59), |
2811 | KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s", | |
2812 | (unsigned long long)info->delta, | |
2813 | (unsigned long long)info->ts, | |
2814 | (unsigned long long)cpu_buffer->write_stamp, | |
2815 | sched_clock_stable() ? "" : | |
2816 | "If you just came from a suspend/resume,\n" | |
2817 | "please switch to the trace global clock:\n" | |
913ea4d0 CW |
2818 | " echo global > /sys/kernel/debug/tracing/trace_clock\n" |
2819 | "or add trace_clock=global to the kernel command line\n"); | |
b7dc42fd | 2820 | info->add_timestamp = 1; |
9826b273 SRRH |
2821 | } |
2822 | ||
6634ff26 SR |
2823 | static struct ring_buffer_event * |
2824 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, | |
fcc742ea | 2825 | struct rb_event_info *info) |
6634ff26 | 2826 | { |
6634ff26 | 2827 | struct ring_buffer_event *event; |
fcc742ea | 2828 | struct buffer_page *tail_page; |
6634ff26 | 2829 | unsigned long tail, write; |
b7dc42fd SRRH |
2830 | |
2831 | /* | |
2832 | * If the time delta since the last event is too big to | |
2833 | * hold in the time field of the event, then we append a | |
2834 | * TIME EXTEND event ahead of the data event. | |
2835 | */ | |
2836 | if (unlikely(info->add_timestamp)) | |
2837 | info->length += RB_LEN_TIME_EXTEND; | |
69d1b839 | 2838 | |
8573636e SRRH |
2839 | /* Don't let the compiler play games with cpu_buffer->tail_page */ |
2840 | tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); | |
fcc742ea | 2841 | write = local_add_return(info->length, &tail_page->write); |
77ae365e SR |
2842 | |
2843 | /* set write to only the index of the write */ | |
2844 | write &= RB_WRITE_MASK; | |
fcc742ea | 2845 | tail = write - info->length; |
6634ff26 | 2846 | |
6634ff26 | 2847 | /* |
a4543a2f | 2848 | * If this is the first commit on the page, then it has the same |
b7dc42fd | 2849 | * timestamp as the page itself. |
6634ff26 | 2850 | */ |
dc4e2801 | 2851 | if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer)) |
a4543a2f SRRH |
2852 | info->delta = 0; |
2853 | ||
b7dc42fd SRRH |
2854 | /* See if we shot pass the end of this buffer page */ |
2855 | if (unlikely(write > BUF_PAGE_SIZE)) | |
2856 | return rb_move_tail(cpu_buffer, tail, info); | |
a4543a2f | 2857 | |
b7dc42fd SRRH |
2858 | /* We reserved something on the buffer */ |
2859 | ||
2860 | event = __rb_page_index(tail_page, tail); | |
a4543a2f SRRH |
2861 | rb_update_event(cpu_buffer, event, info); |
2862 | ||
2863 | local_inc(&tail_page->entries); | |
6634ff26 | 2864 | |
b7dc42fd SRRH |
2865 | /* |
2866 | * If this is the first commit on the page, then update | |
2867 | * its timestamp. | |
2868 | */ | |
2869 | if (!tail) | |
2870 | tail_page->page->time_stamp = info->ts; | |
2871 | ||
c64e148a | 2872 | /* account for these added bytes */ |
fcc742ea | 2873 | local_add(info->length, &cpu_buffer->entries_bytes); |
c64e148a | 2874 | |
6634ff26 SR |
2875 | return event; |
2876 | } | |
2877 | ||
fa7ffb39 | 2878 | static __always_inline struct ring_buffer_event * |
62f0b3eb SR |
2879 | rb_reserve_next_event(struct ring_buffer *buffer, |
2880 | struct ring_buffer_per_cpu *cpu_buffer, | |
1cd8d735 | 2881 | unsigned long length) |
7a8e76a3 SR |
2882 | { |
2883 | struct ring_buffer_event *event; | |
fcc742ea | 2884 | struct rb_event_info info; |
818e3dd3 | 2885 | int nr_loops = 0; |
b7dc42fd | 2886 | u64 diff; |
7a8e76a3 | 2887 | |
fa743953 SR |
2888 | rb_start_commit(cpu_buffer); |
2889 | ||
85bac32c | 2890 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
62f0b3eb SR |
2891 | /* |
2892 | * Due to the ability to swap a cpu buffer from a buffer | |
2893 | * it is possible it was swapped before we committed. | |
2894 | * (committing stops a swap). We check for it here and | |
2895 | * if it happened, we have to fail the write. | |
2896 | */ | |
2897 | barrier(); | |
6aa7de05 | 2898 | if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { |
62f0b3eb SR |
2899 | local_dec(&cpu_buffer->committing); |
2900 | local_dec(&cpu_buffer->commits); | |
2901 | return NULL; | |
2902 | } | |
85bac32c | 2903 | #endif |
b7dc42fd | 2904 | |
fcc742ea | 2905 | info.length = rb_calculate_event_length(length); |
a4543a2f | 2906 | again: |
b7dc42fd SRRH |
2907 | info.add_timestamp = 0; |
2908 | info.delta = 0; | |
2909 | ||
818e3dd3 SR |
2910 | /* |
2911 | * We allow for interrupts to reenter here and do a trace. | |
2912 | * If one does, it will cause this original code to loop | |
2913 | * back here. Even with heavy interrupts happening, this | |
2914 | * should only happen a few times in a row. If this happens | |
2915 | * 1000 times in a row, there must be either an interrupt | |
2916 | * storm or we have something buggy. | |
2917 | * Bail! | |
2918 | */ | |
3e89c7bb | 2919 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
fa743953 | 2920 | goto out_fail; |
818e3dd3 | 2921 | |
b7dc42fd SRRH |
2922 | info.ts = rb_time_stamp(cpu_buffer->buffer); |
2923 | diff = info.ts - cpu_buffer->write_stamp; | |
2924 | ||
2925 | /* make sure this diff is calculated here */ | |
2926 | barrier(); | |
2927 | ||
dc4e2801 TZ |
2928 | if (ring_buffer_time_stamp_abs(buffer)) { |
2929 | info.delta = info.ts; | |
2930 | rb_handle_timestamp(cpu_buffer, &info); | |
2931 | } else /* Did the write stamp get updated already? */ | |
2932 | if (likely(info.ts >= cpu_buffer->write_stamp)) { | |
b7dc42fd SRRH |
2933 | info.delta = diff; |
2934 | if (unlikely(test_time_stamp(info.delta))) | |
2935 | rb_handle_timestamp(cpu_buffer, &info); | |
2936 | } | |
2937 | ||
fcc742ea SRRH |
2938 | event = __rb_reserve_next(cpu_buffer, &info); |
2939 | ||
bd1b7cd3 SRRH |
2940 | if (unlikely(PTR_ERR(event) == -EAGAIN)) { |
2941 | if (info.add_timestamp) | |
2942 | info.length -= RB_LEN_TIME_EXTEND; | |
bf41a158 | 2943 | goto again; |
bd1b7cd3 | 2944 | } |
bf41a158 | 2945 | |
fa743953 SR |
2946 | if (!event) |
2947 | goto out_fail; | |
7a8e76a3 | 2948 | |
7a8e76a3 | 2949 | return event; |
fa743953 SR |
2950 | |
2951 | out_fail: | |
2952 | rb_end_commit(cpu_buffer); | |
2953 | return NULL; | |
7a8e76a3 SR |
2954 | } |
2955 | ||
2956 | /** | |
2957 | * ring_buffer_lock_reserve - reserve a part of the buffer | |
2958 | * @buffer: the ring buffer to reserve from | |
2959 | * @length: the length of the data to reserve (excluding event header) | |
7a8e76a3 | 2960 | * |
6167c205 | 2961 | * Returns a reserved event on the ring buffer to copy directly to. |
7a8e76a3 SR |
2962 | * The user of this interface will need to get the body to write into |
2963 | * and can use the ring_buffer_event_data() interface. | |
2964 | * | |
2965 | * The length is the length of the data needed, not the event length | |
2966 | * which also includes the event header. | |
2967 | * | |
2968 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. | |
2969 | * If NULL is returned, then nothing has been allocated or locked. | |
2970 | */ | |
2971 | struct ring_buffer_event * | |
0a987751 | 2972 | ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
7a8e76a3 SR |
2973 | { |
2974 | struct ring_buffer_per_cpu *cpu_buffer; | |
2975 | struct ring_buffer_event *event; | |
5168ae50 | 2976 | int cpu; |
7a8e76a3 | 2977 | |
bf41a158 | 2978 | /* If we are tracing schedule, we don't want to recurse */ |
5168ae50 | 2979 | preempt_disable_notrace(); |
bf41a158 | 2980 | |
3205f806 | 2981 | if (unlikely(atomic_read(&buffer->record_disabled))) |
58a09ec6 | 2982 | goto out; |
261842b7 | 2983 | |
7a8e76a3 SR |
2984 | cpu = raw_smp_processor_id(); |
2985 | ||
3205f806 | 2986 | if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
d769041f | 2987 | goto out; |
7a8e76a3 SR |
2988 | |
2989 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 2990 | |
3205f806 | 2991 | if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
d769041f | 2992 | goto out; |
7a8e76a3 | 2993 | |
3205f806 | 2994 | if (unlikely(length > BUF_MAX_DATA_SIZE)) |
bf41a158 | 2995 | goto out; |
7a8e76a3 | 2996 | |
58a09ec6 SRRH |
2997 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
2998 | goto out; | |
2999 | ||
62f0b3eb | 3000 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 3001 | if (!event) |
58a09ec6 | 3002 | goto out_unlock; |
7a8e76a3 SR |
3003 | |
3004 | return event; | |
3005 | ||
58a09ec6 SRRH |
3006 | out_unlock: |
3007 | trace_recursive_unlock(cpu_buffer); | |
d769041f | 3008 | out: |
5168ae50 | 3009 | preempt_enable_notrace(); |
7a8e76a3 SR |
3010 | return NULL; |
3011 | } | |
c4f50183 | 3012 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
7a8e76a3 | 3013 | |
a1863c21 SR |
3014 | /* |
3015 | * Decrement the entries to the page that an event is on. | |
3016 | * The event does not even need to exist, only the pointer | |
3017 | * to the page it is on. This may only be called before the commit | |
3018 | * takes place. | |
3019 | */ | |
3020 | static inline void | |
3021 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, | |
3022 | struct ring_buffer_event *event) | |
3023 | { | |
3024 | unsigned long addr = (unsigned long)event; | |
3025 | struct buffer_page *bpage = cpu_buffer->commit_page; | |
3026 | struct buffer_page *start; | |
3027 | ||
3028 | addr &= PAGE_MASK; | |
3029 | ||
3030 | /* Do the likely case first */ | |
3031 | if (likely(bpage->page == (void *)addr)) { | |
3032 | local_dec(&bpage->entries); | |
3033 | return; | |
3034 | } | |
3035 | ||
3036 | /* | |
3037 | * Because the commit page may be on the reader page we | |
3038 | * start with the next page and check the end loop there. | |
3039 | */ | |
3040 | rb_inc_page(cpu_buffer, &bpage); | |
3041 | start = bpage; | |
3042 | do { | |
3043 | if (bpage->page == (void *)addr) { | |
3044 | local_dec(&bpage->entries); | |
3045 | return; | |
3046 | } | |
3047 | rb_inc_page(cpu_buffer, &bpage); | |
3048 | } while (bpage != start); | |
3049 | ||
3050 | /* commit not part of this buffer?? */ | |
3051 | RB_WARN_ON(cpu_buffer, 1); | |
3052 | } | |
3053 | ||
fa1b47dd SR |
3054 | /** |
3055 | * ring_buffer_commit_discard - discard an event that has not been committed | |
3056 | * @buffer: the ring buffer | |
3057 | * @event: non committed event to discard | |
3058 | * | |
dc892f73 SR |
3059 | * Sometimes an event that is in the ring buffer needs to be ignored. |
3060 | * This function lets the user discard an event in the ring buffer | |
3061 | * and then that event will not be read later. | |
3062 | * | |
6167c205 | 3063 | * This function only works if it is called before the item has been |
dc892f73 | 3064 | * committed. It will try to free the event from the ring buffer |
fa1b47dd SR |
3065 | * if another event has not been added behind it. |
3066 | * | |
3067 | * If another event has been added behind it, it will set the event | |
3068 | * up as discarded, and perform the commit. | |
3069 | * | |
3070 | * If this function is called, do not call ring_buffer_unlock_commit on | |
3071 | * the event. | |
3072 | */ | |
3073 | void ring_buffer_discard_commit(struct ring_buffer *buffer, | |
3074 | struct ring_buffer_event *event) | |
3075 | { | |
3076 | struct ring_buffer_per_cpu *cpu_buffer; | |
fa1b47dd SR |
3077 | int cpu; |
3078 | ||
3079 | /* The event is discarded regardless */ | |
f3b9aae1 | 3080 | rb_event_discard(event); |
fa1b47dd | 3081 | |
fa743953 SR |
3082 | cpu = smp_processor_id(); |
3083 | cpu_buffer = buffer->buffers[cpu]; | |
3084 | ||
fa1b47dd SR |
3085 | /* |
3086 | * This must only be called if the event has not been | |
3087 | * committed yet. Thus we can assume that preemption | |
3088 | * is still disabled. | |
3089 | */ | |
fa743953 | 3090 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
fa1b47dd | 3091 | |
a1863c21 | 3092 | rb_decrement_entry(cpu_buffer, event); |
0f2541d2 | 3093 | if (rb_try_to_discard(cpu_buffer, event)) |
edd813bf | 3094 | goto out; |
fa1b47dd SR |
3095 | |
3096 | /* | |
3097 | * The commit is still visible by the reader, so we | |
a1863c21 | 3098 | * must still update the timestamp. |
fa1b47dd | 3099 | */ |
a1863c21 | 3100 | rb_update_write_stamp(cpu_buffer, event); |
fa1b47dd | 3101 | out: |
fa743953 | 3102 | rb_end_commit(cpu_buffer); |
fa1b47dd | 3103 | |
58a09ec6 | 3104 | trace_recursive_unlock(cpu_buffer); |
f3b9aae1 | 3105 | |
5168ae50 | 3106 | preempt_enable_notrace(); |
fa1b47dd SR |
3107 | |
3108 | } | |
3109 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); | |
3110 | ||
7a8e76a3 SR |
3111 | /** |
3112 | * ring_buffer_write - write data to the buffer without reserving | |
3113 | * @buffer: The ring buffer to write to. | |
3114 | * @length: The length of the data being written (excluding the event header) | |
3115 | * @data: The data to write to the buffer. | |
3116 | * | |
3117 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as | |
3118 | * one function. If you already have the data to write to the buffer, it | |
3119 | * may be easier to simply call this function. | |
3120 | * | |
3121 | * Note, like ring_buffer_lock_reserve, the length is the length of the data | |
3122 | * and not the length of the event which would hold the header. | |
3123 | */ | |
3124 | int ring_buffer_write(struct ring_buffer *buffer, | |
01e3e710 DS |
3125 | unsigned long length, |
3126 | void *data) | |
7a8e76a3 SR |
3127 | { |
3128 | struct ring_buffer_per_cpu *cpu_buffer; | |
3129 | struct ring_buffer_event *event; | |
7a8e76a3 SR |
3130 | void *body; |
3131 | int ret = -EBUSY; | |
5168ae50 | 3132 | int cpu; |
7a8e76a3 | 3133 | |
5168ae50 | 3134 | preempt_disable_notrace(); |
bf41a158 | 3135 | |
52fbe9cd LJ |
3136 | if (atomic_read(&buffer->record_disabled)) |
3137 | goto out; | |
3138 | ||
7a8e76a3 SR |
3139 | cpu = raw_smp_processor_id(); |
3140 | ||
9e01c1b7 | 3141 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
d769041f | 3142 | goto out; |
7a8e76a3 SR |
3143 | |
3144 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
3145 | |
3146 | if (atomic_read(&cpu_buffer->record_disabled)) | |
3147 | goto out; | |
3148 | ||
be957c44 SR |
3149 | if (length > BUF_MAX_DATA_SIZE) |
3150 | goto out; | |
3151 | ||
985e871b SRRH |
3152 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
3153 | goto out; | |
3154 | ||
62f0b3eb | 3155 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 3156 | if (!event) |
985e871b | 3157 | goto out_unlock; |
7a8e76a3 SR |
3158 | |
3159 | body = rb_event_data(event); | |
3160 | ||
3161 | memcpy(body, data, length); | |
3162 | ||
3163 | rb_commit(cpu_buffer, event); | |
3164 | ||
15693458 SRRH |
3165 | rb_wakeups(buffer, cpu_buffer); |
3166 | ||
7a8e76a3 | 3167 | ret = 0; |
985e871b SRRH |
3168 | |
3169 | out_unlock: | |
3170 | trace_recursive_unlock(cpu_buffer); | |
3171 | ||
7a8e76a3 | 3172 | out: |
5168ae50 | 3173 | preempt_enable_notrace(); |
7a8e76a3 SR |
3174 | |
3175 | return ret; | |
3176 | } | |
c4f50183 | 3177 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
7a8e76a3 | 3178 | |
da58834c | 3179 | static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
bf41a158 SR |
3180 | { |
3181 | struct buffer_page *reader = cpu_buffer->reader_page; | |
77ae365e | 3182 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
bf41a158 SR |
3183 | struct buffer_page *commit = cpu_buffer->commit_page; |
3184 | ||
77ae365e SR |
3185 | /* In case of error, head will be NULL */ |
3186 | if (unlikely(!head)) | |
da58834c | 3187 | return true; |
77ae365e | 3188 | |
bf41a158 SR |
3189 | return reader->read == rb_page_commit(reader) && |
3190 | (commit == reader || | |
3191 | (commit == head && | |
3192 | head->read == rb_page_commit(commit))); | |
3193 | } | |
3194 | ||
7a8e76a3 SR |
3195 | /** |
3196 | * ring_buffer_record_disable - stop all writes into the buffer | |
3197 | * @buffer: The ring buffer to stop writes to. | |
3198 | * | |
3199 | * This prevents all writes to the buffer. Any attempt to write | |
3200 | * to the buffer after this will fail and return NULL. | |
3201 | * | |
74401729 | 3202 | * The caller should call synchronize_rcu() after this. |
7a8e76a3 SR |
3203 | */ |
3204 | void ring_buffer_record_disable(struct ring_buffer *buffer) | |
3205 | { | |
3206 | atomic_inc(&buffer->record_disabled); | |
3207 | } | |
c4f50183 | 3208 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
7a8e76a3 SR |
3209 | |
3210 | /** | |
3211 | * ring_buffer_record_enable - enable writes to the buffer | |
3212 | * @buffer: The ring buffer to enable writes | |
3213 | * | |
3214 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3215 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
3216 | */ |
3217 | void ring_buffer_record_enable(struct ring_buffer *buffer) | |
3218 | { | |
3219 | atomic_dec(&buffer->record_disabled); | |
3220 | } | |
c4f50183 | 3221 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
7a8e76a3 | 3222 | |
499e5470 SR |
3223 | /** |
3224 | * ring_buffer_record_off - stop all writes into the buffer | |
3225 | * @buffer: The ring buffer to stop writes to. | |
3226 | * | |
3227 | * This prevents all writes to the buffer. Any attempt to write | |
3228 | * to the buffer after this will fail and return NULL. | |
3229 | * | |
3230 | * This is different than ring_buffer_record_disable() as | |
87abb3b1 | 3231 | * it works like an on/off switch, where as the disable() version |
499e5470 SR |
3232 | * must be paired with a enable(). |
3233 | */ | |
3234 | void ring_buffer_record_off(struct ring_buffer *buffer) | |
3235 | { | |
3236 | unsigned int rd; | |
3237 | unsigned int new_rd; | |
3238 | ||
3239 | do { | |
3240 | rd = atomic_read(&buffer->record_disabled); | |
3241 | new_rd = rd | RB_BUFFER_OFF; | |
3242 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3243 | } | |
3244 | EXPORT_SYMBOL_GPL(ring_buffer_record_off); | |
3245 | ||
3246 | /** | |
3247 | * ring_buffer_record_on - restart writes into the buffer | |
3248 | * @buffer: The ring buffer to start writes to. | |
3249 | * | |
3250 | * This enables all writes to the buffer that was disabled by | |
3251 | * ring_buffer_record_off(). | |
3252 | * | |
3253 | * This is different than ring_buffer_record_enable() as | |
87abb3b1 | 3254 | * it works like an on/off switch, where as the enable() version |
499e5470 SR |
3255 | * must be paired with a disable(). |
3256 | */ | |
3257 | void ring_buffer_record_on(struct ring_buffer *buffer) | |
3258 | { | |
3259 | unsigned int rd; | |
3260 | unsigned int new_rd; | |
3261 | ||
3262 | do { | |
3263 | rd = atomic_read(&buffer->record_disabled); | |
3264 | new_rd = rd & ~RB_BUFFER_OFF; | |
3265 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3266 | } | |
3267 | EXPORT_SYMBOL_GPL(ring_buffer_record_on); | |
3268 | ||
3269 | /** | |
3270 | * ring_buffer_record_is_on - return true if the ring buffer can write | |
3271 | * @buffer: The ring buffer to see if write is enabled | |
3272 | * | |
3273 | * Returns true if the ring buffer is in a state that it accepts writes. | |
3274 | */ | |
3ebea280 | 3275 | bool ring_buffer_record_is_on(struct ring_buffer *buffer) |
499e5470 SR |
3276 | { |
3277 | return !atomic_read(&buffer->record_disabled); | |
3278 | } | |
3279 | ||
73c8d894 MH |
3280 | /** |
3281 | * ring_buffer_record_is_set_on - return true if the ring buffer is set writable | |
3282 | * @buffer: The ring buffer to see if write is set enabled | |
3283 | * | |
3284 | * Returns true if the ring buffer is set writable by ring_buffer_record_on(). | |
3285 | * Note that this does NOT mean it is in a writable state. | |
3286 | * | |
3287 | * It may return true when the ring buffer has been disabled by | |
3288 | * ring_buffer_record_disable(), as that is a temporary disabling of | |
3289 | * the ring buffer. | |
3290 | */ | |
d7224c0e | 3291 | bool ring_buffer_record_is_set_on(struct ring_buffer *buffer) |
73c8d894 MH |
3292 | { |
3293 | return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); | |
3294 | } | |
3295 | ||
7a8e76a3 SR |
3296 | /** |
3297 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer | |
3298 | * @buffer: The ring buffer to stop writes to. | |
3299 | * @cpu: The CPU buffer to stop | |
3300 | * | |
3301 | * This prevents all writes to the buffer. Any attempt to write | |
3302 | * to the buffer after this will fail and return NULL. | |
3303 | * | |
74401729 | 3304 | * The caller should call synchronize_rcu() after this. |
7a8e76a3 SR |
3305 | */ |
3306 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) | |
3307 | { | |
3308 | struct ring_buffer_per_cpu *cpu_buffer; | |
3309 | ||
9e01c1b7 | 3310 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3311 | return; |
7a8e76a3 SR |
3312 | |
3313 | cpu_buffer = buffer->buffers[cpu]; | |
3314 | atomic_inc(&cpu_buffer->record_disabled); | |
3315 | } | |
c4f50183 | 3316 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
7a8e76a3 SR |
3317 | |
3318 | /** | |
3319 | * ring_buffer_record_enable_cpu - enable writes to the buffer | |
3320 | * @buffer: The ring buffer to enable writes | |
3321 | * @cpu: The CPU to enable. | |
3322 | * | |
3323 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3324 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
3325 | */ |
3326 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) | |
3327 | { | |
3328 | struct ring_buffer_per_cpu *cpu_buffer; | |
3329 | ||
9e01c1b7 | 3330 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3331 | return; |
7a8e76a3 SR |
3332 | |
3333 | cpu_buffer = buffer->buffers[cpu]; | |
3334 | atomic_dec(&cpu_buffer->record_disabled); | |
3335 | } | |
c4f50183 | 3336 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
7a8e76a3 | 3337 | |
f6195aa0 SR |
3338 | /* |
3339 | * The total entries in the ring buffer is the running counter | |
3340 | * of entries entered into the ring buffer, minus the sum of | |
3341 | * the entries read from the ring buffer and the number of | |
3342 | * entries that were overwritten. | |
3343 | */ | |
3344 | static inline unsigned long | |
3345 | rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) | |
3346 | { | |
3347 | return local_read(&cpu_buffer->entries) - | |
3348 | (local_read(&cpu_buffer->overrun) + cpu_buffer->read); | |
3349 | } | |
3350 | ||
c64e148a VN |
3351 | /** |
3352 | * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer | |
3353 | * @buffer: The ring buffer | |
3354 | * @cpu: The per CPU buffer to read from. | |
3355 | */ | |
50ecf2c3 | 3356 | u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) |
c64e148a VN |
3357 | { |
3358 | unsigned long flags; | |
3359 | struct ring_buffer_per_cpu *cpu_buffer; | |
3360 | struct buffer_page *bpage; | |
da830e58 | 3361 | u64 ret = 0; |
c64e148a VN |
3362 | |
3363 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3364 | return 0; | |
3365 | ||
3366 | cpu_buffer = buffer->buffers[cpu]; | |
7115e3fc | 3367 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3368 | /* |
3369 | * if the tail is on reader_page, oldest time stamp is on the reader | |
3370 | * page | |
3371 | */ | |
3372 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
3373 | bpage = cpu_buffer->reader_page; | |
3374 | else | |
3375 | bpage = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3376 | if (bpage) |
3377 | ret = bpage->page->time_stamp; | |
7115e3fc | 3378 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3379 | |
3380 | return ret; | |
3381 | } | |
3382 | EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); | |
3383 | ||
3384 | /** | |
3385 | * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer | |
3386 | * @buffer: The ring buffer | |
3387 | * @cpu: The per CPU buffer to read from. | |
3388 | */ | |
3389 | unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu) | |
3390 | { | |
3391 | struct ring_buffer_per_cpu *cpu_buffer; | |
3392 | unsigned long ret; | |
3393 | ||
3394 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3395 | return 0; | |
3396 | ||
3397 | cpu_buffer = buffer->buffers[cpu]; | |
3398 | ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; | |
3399 | ||
3400 | return ret; | |
3401 | } | |
3402 | EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); | |
3403 | ||
7a8e76a3 SR |
3404 | /** |
3405 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer | |
3406 | * @buffer: The ring buffer | |
3407 | * @cpu: The per CPU buffer to get the entries from. | |
3408 | */ | |
3409 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) | |
3410 | { | |
3411 | struct ring_buffer_per_cpu *cpu_buffer; | |
3412 | ||
9e01c1b7 | 3413 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3414 | return 0; |
7a8e76a3 SR |
3415 | |
3416 | cpu_buffer = buffer->buffers[cpu]; | |
554f786e | 3417 | |
f6195aa0 | 3418 | return rb_num_of_entries(cpu_buffer); |
7a8e76a3 | 3419 | } |
c4f50183 | 3420 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
7a8e76a3 SR |
3421 | |
3422 | /** | |
884bfe89 SP |
3423 | * ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
3424 | * buffer wrapping around (only if RB_FL_OVERWRITE is on). | |
7a8e76a3 SR |
3425 | * @buffer: The ring buffer |
3426 | * @cpu: The per CPU buffer to get the number of overruns from | |
3427 | */ | |
3428 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
3429 | { | |
3430 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 3431 | unsigned long ret; |
7a8e76a3 | 3432 | |
9e01c1b7 | 3433 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3434 | return 0; |
7a8e76a3 SR |
3435 | |
3436 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3437 | ret = local_read(&cpu_buffer->overrun); |
554f786e SR |
3438 | |
3439 | return ret; | |
7a8e76a3 | 3440 | } |
c4f50183 | 3441 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
7a8e76a3 | 3442 | |
f0d2c681 | 3443 | /** |
884bfe89 SP |
3444 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by |
3445 | * commits failing due to the buffer wrapping around while there are uncommitted | |
3446 | * events, such as during an interrupt storm. | |
f0d2c681 SR |
3447 | * @buffer: The ring buffer |
3448 | * @cpu: The per CPU buffer to get the number of overruns from | |
3449 | */ | |
3450 | unsigned long | |
3451 | ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
3452 | { | |
3453 | struct ring_buffer_per_cpu *cpu_buffer; | |
3454 | unsigned long ret; | |
3455 | ||
3456 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3457 | return 0; | |
3458 | ||
3459 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3460 | ret = local_read(&cpu_buffer->commit_overrun); |
f0d2c681 SR |
3461 | |
3462 | return ret; | |
3463 | } | |
3464 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); | |
3465 | ||
884bfe89 SP |
3466 | /** |
3467 | * ring_buffer_dropped_events_cpu - get the number of dropped events caused by | |
3468 | * the ring buffer filling up (only if RB_FL_OVERWRITE is off). | |
3469 | * @buffer: The ring buffer | |
3470 | * @cpu: The per CPU buffer to get the number of overruns from | |
3471 | */ | |
3472 | unsigned long | |
3473 | ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu) | |
3474 | { | |
3475 | struct ring_buffer_per_cpu *cpu_buffer; | |
3476 | unsigned long ret; | |
3477 | ||
3478 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3479 | return 0; | |
3480 | ||
3481 | cpu_buffer = buffer->buffers[cpu]; | |
3482 | ret = local_read(&cpu_buffer->dropped_events); | |
3483 | ||
3484 | return ret; | |
3485 | } | |
3486 | EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); | |
3487 | ||
ad964704 SRRH |
3488 | /** |
3489 | * ring_buffer_read_events_cpu - get the number of events successfully read | |
3490 | * @buffer: The ring buffer | |
3491 | * @cpu: The per CPU buffer to get the number of events read | |
3492 | */ | |
3493 | unsigned long | |
3494 | ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu) | |
3495 | { | |
3496 | struct ring_buffer_per_cpu *cpu_buffer; | |
3497 | ||
3498 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3499 | return 0; | |
3500 | ||
3501 | cpu_buffer = buffer->buffers[cpu]; | |
3502 | return cpu_buffer->read; | |
3503 | } | |
3504 | EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); | |
3505 | ||
7a8e76a3 SR |
3506 | /** |
3507 | * ring_buffer_entries - get the number of entries in a buffer | |
3508 | * @buffer: The ring buffer | |
3509 | * | |
3510 | * Returns the total number of entries in the ring buffer | |
3511 | * (all CPU entries) | |
3512 | */ | |
3513 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) | |
3514 | { | |
3515 | struct ring_buffer_per_cpu *cpu_buffer; | |
3516 | unsigned long entries = 0; | |
3517 | int cpu; | |
3518 | ||
3519 | /* if you care about this being correct, lock the buffer */ | |
3520 | for_each_buffer_cpu(buffer, cpu) { | |
3521 | cpu_buffer = buffer->buffers[cpu]; | |
f6195aa0 | 3522 | entries += rb_num_of_entries(cpu_buffer); |
7a8e76a3 SR |
3523 | } |
3524 | ||
3525 | return entries; | |
3526 | } | |
c4f50183 | 3527 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
7a8e76a3 SR |
3528 | |
3529 | /** | |
67b394f7 | 3530 | * ring_buffer_overruns - get the number of overruns in buffer |
7a8e76a3 SR |
3531 | * @buffer: The ring buffer |
3532 | * | |
3533 | * Returns the total number of overruns in the ring buffer | |
3534 | * (all CPU entries) | |
3535 | */ | |
3536 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) | |
3537 | { | |
3538 | struct ring_buffer_per_cpu *cpu_buffer; | |
3539 | unsigned long overruns = 0; | |
3540 | int cpu; | |
3541 | ||
3542 | /* if you care about this being correct, lock the buffer */ | |
3543 | for_each_buffer_cpu(buffer, cpu) { | |
3544 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3545 | overruns += local_read(&cpu_buffer->overrun); |
7a8e76a3 SR |
3546 | } |
3547 | ||
3548 | return overruns; | |
3549 | } | |
c4f50183 | 3550 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
7a8e76a3 | 3551 | |
642edba5 | 3552 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
7a8e76a3 SR |
3553 | { |
3554 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3555 | ||
d769041f | 3556 | /* Iterator usage is expected to have record disabled */ |
651e22f2 SRRH |
3557 | iter->head_page = cpu_buffer->reader_page; |
3558 | iter->head = cpu_buffer->reader_page->read; | |
3559 | ||
3560 | iter->cache_reader_page = iter->head_page; | |
24607f11 | 3561 | iter->cache_read = cpu_buffer->read; |
651e22f2 | 3562 | |
d769041f SR |
3563 | if (iter->head) |
3564 | iter->read_stamp = cpu_buffer->read_stamp; | |
3565 | else | |
abc9b56d | 3566 | iter->read_stamp = iter->head_page->page->time_stamp; |
642edba5 | 3567 | } |
f83c9d0f | 3568 | |
642edba5 SR |
3569 | /** |
3570 | * ring_buffer_iter_reset - reset an iterator | |
3571 | * @iter: The iterator to reset | |
3572 | * | |
3573 | * Resets the iterator, so that it will start from the beginning | |
3574 | * again. | |
3575 | */ | |
3576 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) | |
3577 | { | |
554f786e | 3578 | struct ring_buffer_per_cpu *cpu_buffer; |
642edba5 SR |
3579 | unsigned long flags; |
3580 | ||
554f786e SR |
3581 | if (!iter) |
3582 | return; | |
3583 | ||
3584 | cpu_buffer = iter->cpu_buffer; | |
3585 | ||
5389f6fa | 3586 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
642edba5 | 3587 | rb_iter_reset(iter); |
5389f6fa | 3588 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 3589 | } |
c4f50183 | 3590 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
7a8e76a3 SR |
3591 | |
3592 | /** | |
3593 | * ring_buffer_iter_empty - check if an iterator has no more to read | |
3594 | * @iter: The iterator to check | |
3595 | */ | |
3596 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) | |
3597 | { | |
3598 | struct ring_buffer_per_cpu *cpu_buffer; | |
78f7a45d SRV |
3599 | struct buffer_page *reader; |
3600 | struct buffer_page *head_page; | |
3601 | struct buffer_page *commit_page; | |
3602 | unsigned commit; | |
7a8e76a3 SR |
3603 | |
3604 | cpu_buffer = iter->cpu_buffer; | |
3605 | ||
78f7a45d SRV |
3606 | /* Remember, trace recording is off when iterator is in use */ |
3607 | reader = cpu_buffer->reader_page; | |
3608 | head_page = cpu_buffer->head_page; | |
3609 | commit_page = cpu_buffer->commit_page; | |
3610 | commit = rb_page_commit(commit_page); | |
3611 | ||
3612 | return ((iter->head_page == commit_page && iter->head == commit) || | |
3613 | (iter->head_page == reader && commit_page == head_page && | |
3614 | head_page->read == commit && | |
3615 | iter->head == rb_page_commit(cpu_buffer->reader_page))); | |
7a8e76a3 | 3616 | } |
c4f50183 | 3617 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
7a8e76a3 SR |
3618 | |
3619 | static void | |
3620 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
3621 | struct ring_buffer_event *event) | |
3622 | { | |
3623 | u64 delta; | |
3624 | ||
334d4169 | 3625 | switch (event->type_len) { |
7a8e76a3 SR |
3626 | case RINGBUF_TYPE_PADDING: |
3627 | return; | |
3628 | ||
3629 | case RINGBUF_TYPE_TIME_EXTEND: | |
dc4e2801 | 3630 | delta = ring_buffer_event_time_stamp(event); |
7a8e76a3 SR |
3631 | cpu_buffer->read_stamp += delta; |
3632 | return; | |
3633 | ||
3634 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
3635 | delta = ring_buffer_event_time_stamp(event); |
3636 | cpu_buffer->read_stamp = delta; | |
7a8e76a3 SR |
3637 | return; |
3638 | ||
3639 | case RINGBUF_TYPE_DATA: | |
3640 | cpu_buffer->read_stamp += event->time_delta; | |
3641 | return; | |
3642 | ||
3643 | default: | |
3644 | BUG(); | |
3645 | } | |
3646 | return; | |
3647 | } | |
3648 | ||
3649 | static void | |
3650 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, | |
3651 | struct ring_buffer_event *event) | |
3652 | { | |
3653 | u64 delta; | |
3654 | ||
334d4169 | 3655 | switch (event->type_len) { |
7a8e76a3 SR |
3656 | case RINGBUF_TYPE_PADDING: |
3657 | return; | |
3658 | ||
3659 | case RINGBUF_TYPE_TIME_EXTEND: | |
dc4e2801 | 3660 | delta = ring_buffer_event_time_stamp(event); |
7a8e76a3 SR |
3661 | iter->read_stamp += delta; |
3662 | return; | |
3663 | ||
3664 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
3665 | delta = ring_buffer_event_time_stamp(event); |
3666 | iter->read_stamp = delta; | |
7a8e76a3 SR |
3667 | return; |
3668 | ||
3669 | case RINGBUF_TYPE_DATA: | |
3670 | iter->read_stamp += event->time_delta; | |
3671 | return; | |
3672 | ||
3673 | default: | |
3674 | BUG(); | |
3675 | } | |
3676 | return; | |
3677 | } | |
3678 | ||
d769041f SR |
3679 | static struct buffer_page * |
3680 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 3681 | { |
d769041f | 3682 | struct buffer_page *reader = NULL; |
66a8cb95 | 3683 | unsigned long overwrite; |
d769041f | 3684 | unsigned long flags; |
818e3dd3 | 3685 | int nr_loops = 0; |
77ae365e | 3686 | int ret; |
d769041f | 3687 | |
3e03fb7f | 3688 | local_irq_save(flags); |
0199c4e6 | 3689 | arch_spin_lock(&cpu_buffer->lock); |
d769041f SR |
3690 | |
3691 | again: | |
818e3dd3 SR |
3692 | /* |
3693 | * This should normally only loop twice. But because the | |
3694 | * start of the reader inserts an empty page, it causes | |
3695 | * a case where we will loop three times. There should be no | |
3696 | * reason to loop four times (that I know of). | |
3697 | */ | |
3e89c7bb | 3698 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
818e3dd3 SR |
3699 | reader = NULL; |
3700 | goto out; | |
3701 | } | |
3702 | ||
d769041f SR |
3703 | reader = cpu_buffer->reader_page; |
3704 | ||
3705 | /* If there's more to read, return this page */ | |
bf41a158 | 3706 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
d769041f SR |
3707 | goto out; |
3708 | ||
3709 | /* Never should we have an index greater than the size */ | |
3e89c7bb SR |
3710 | if (RB_WARN_ON(cpu_buffer, |
3711 | cpu_buffer->reader_page->read > rb_page_size(reader))) | |
3712 | goto out; | |
d769041f SR |
3713 | |
3714 | /* check if we caught up to the tail */ | |
3715 | reader = NULL; | |
bf41a158 | 3716 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
d769041f | 3717 | goto out; |
7a8e76a3 | 3718 | |
a5fb8331 SR |
3719 | /* Don't bother swapping if the ring buffer is empty */ |
3720 | if (rb_num_of_entries(cpu_buffer) == 0) | |
3721 | goto out; | |
3722 | ||
7a8e76a3 | 3723 | /* |
d769041f | 3724 | * Reset the reader page to size zero. |
7a8e76a3 | 3725 | */ |
77ae365e SR |
3726 | local_set(&cpu_buffer->reader_page->write, 0); |
3727 | local_set(&cpu_buffer->reader_page->entries, 0); | |
3728 | local_set(&cpu_buffer->reader_page->page->commit, 0); | |
ff0ff84a | 3729 | cpu_buffer->reader_page->real_end = 0; |
7a8e76a3 | 3730 | |
77ae365e SR |
3731 | spin: |
3732 | /* | |
3733 | * Splice the empty reader page into the list around the head. | |
3734 | */ | |
3735 | reader = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3736 | if (!reader) |
3737 | goto out; | |
0e1ff5d7 | 3738 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
d769041f | 3739 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
bf41a158 | 3740 | |
3adc54fa SR |
3741 | /* |
3742 | * cpu_buffer->pages just needs to point to the buffer, it | |
3743 | * has no specific buffer page to point to. Lets move it out | |
25985edc | 3744 | * of our way so we don't accidentally swap it. |
3adc54fa SR |
3745 | */ |
3746 | cpu_buffer->pages = reader->list.prev; | |
3747 | ||
77ae365e SR |
3748 | /* The reader page will be pointing to the new head */ |
3749 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); | |
7a8e76a3 | 3750 | |
66a8cb95 SR |
3751 | /* |
3752 | * We want to make sure we read the overruns after we set up our | |
3753 | * pointers to the next object. The writer side does a | |
3754 | * cmpxchg to cross pages which acts as the mb on the writer | |
3755 | * side. Note, the reader will constantly fail the swap | |
3756 | * while the writer is updating the pointers, so this | |
3757 | * guarantees that the overwrite recorded here is the one we | |
3758 | * want to compare with the last_overrun. | |
3759 | */ | |
3760 | smp_mb(); | |
3761 | overwrite = local_read(&(cpu_buffer->overrun)); | |
3762 | ||
77ae365e SR |
3763 | /* |
3764 | * Here's the tricky part. | |
3765 | * | |
3766 | * We need to move the pointer past the header page. | |
3767 | * But we can only do that if a writer is not currently | |
3768 | * moving it. The page before the header page has the | |
3769 | * flag bit '1' set if it is pointing to the page we want. | |
3770 | * but if the writer is in the process of moving it | |
3771 | * than it will be '2' or already moved '0'. | |
3772 | */ | |
3773 | ||
3774 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); | |
7a8e76a3 SR |
3775 | |
3776 | /* | |
77ae365e | 3777 | * If we did not convert it, then we must try again. |
7a8e76a3 | 3778 | */ |
77ae365e SR |
3779 | if (!ret) |
3780 | goto spin; | |
7a8e76a3 | 3781 | |
77ae365e | 3782 | /* |
2c2b0a78 | 3783 | * Yay! We succeeded in replacing the page. |
77ae365e SR |
3784 | * |
3785 | * Now make the new head point back to the reader page. | |
3786 | */ | |
5ded3dc6 | 3787 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
77ae365e | 3788 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
d769041f | 3789 | |
2c2b0a78 SRV |
3790 | local_inc(&cpu_buffer->pages_read); |
3791 | ||
d769041f SR |
3792 | /* Finally update the reader page to the new head */ |
3793 | cpu_buffer->reader_page = reader; | |
b81f472a | 3794 | cpu_buffer->reader_page->read = 0; |
d769041f | 3795 | |
66a8cb95 SR |
3796 | if (overwrite != cpu_buffer->last_overrun) { |
3797 | cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; | |
3798 | cpu_buffer->last_overrun = overwrite; | |
3799 | } | |
3800 | ||
d769041f SR |
3801 | goto again; |
3802 | ||
3803 | out: | |
b81f472a SRRH |
3804 | /* Update the read_stamp on the first event */ |
3805 | if (reader && reader->read == 0) | |
3806 | cpu_buffer->read_stamp = reader->page->time_stamp; | |
3807 | ||
0199c4e6 | 3808 | arch_spin_unlock(&cpu_buffer->lock); |
3e03fb7f | 3809 | local_irq_restore(flags); |
d769041f SR |
3810 | |
3811 | return reader; | |
3812 | } | |
3813 | ||
3814 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) | |
3815 | { | |
3816 | struct ring_buffer_event *event; | |
3817 | struct buffer_page *reader; | |
3818 | unsigned length; | |
3819 | ||
3820 | reader = rb_get_reader_page(cpu_buffer); | |
7a8e76a3 | 3821 | |
d769041f | 3822 | /* This function should not be called when buffer is empty */ |
3e89c7bb SR |
3823 | if (RB_WARN_ON(cpu_buffer, !reader)) |
3824 | return; | |
7a8e76a3 | 3825 | |
d769041f SR |
3826 | event = rb_reader_event(cpu_buffer); |
3827 | ||
a1863c21 | 3828 | if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
e4906eff | 3829 | cpu_buffer->read++; |
d769041f SR |
3830 | |
3831 | rb_update_read_stamp(cpu_buffer, event); | |
3832 | ||
3833 | length = rb_event_length(event); | |
6f807acd | 3834 | cpu_buffer->reader_page->read += length; |
7a8e76a3 SR |
3835 | } |
3836 | ||
3837 | static void rb_advance_iter(struct ring_buffer_iter *iter) | |
3838 | { | |
7a8e76a3 SR |
3839 | struct ring_buffer_per_cpu *cpu_buffer; |
3840 | struct ring_buffer_event *event; | |
3841 | unsigned length; | |
3842 | ||
3843 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 SR |
3844 | |
3845 | /* | |
3846 | * Check if we are at the end of the buffer. | |
3847 | */ | |
bf41a158 | 3848 | if (iter->head >= rb_page_size(iter->head_page)) { |
ea05b57c SR |
3849 | /* discarded commits can make the page empty */ |
3850 | if (iter->head_page == cpu_buffer->commit_page) | |
3e89c7bb | 3851 | return; |
d769041f | 3852 | rb_inc_iter(iter); |
7a8e76a3 SR |
3853 | return; |
3854 | } | |
3855 | ||
3856 | event = rb_iter_head_event(iter); | |
3857 | ||
3858 | length = rb_event_length(event); | |
3859 | ||
3860 | /* | |
3861 | * This should not be called to advance the header if we are | |
3862 | * at the tail of the buffer. | |
3863 | */ | |
3e89c7bb | 3864 | if (RB_WARN_ON(cpu_buffer, |
f536aafc | 3865 | (iter->head_page == cpu_buffer->commit_page) && |
3e89c7bb SR |
3866 | (iter->head + length > rb_commit_index(cpu_buffer)))) |
3867 | return; | |
7a8e76a3 SR |
3868 | |
3869 | rb_update_iter_read_stamp(iter, event); | |
3870 | ||
3871 | iter->head += length; | |
3872 | ||
3873 | /* check for end of page padding */ | |
bf41a158 SR |
3874 | if ((iter->head >= rb_page_size(iter->head_page)) && |
3875 | (iter->head_page != cpu_buffer->commit_page)) | |
771e0384 | 3876 | rb_inc_iter(iter); |
7a8e76a3 SR |
3877 | } |
3878 | ||
66a8cb95 SR |
3879 | static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) |
3880 | { | |
3881 | return cpu_buffer->lost_events; | |
3882 | } | |
3883 | ||
f83c9d0f | 3884 | static struct ring_buffer_event * |
66a8cb95 SR |
3885 | rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, |
3886 | unsigned long *lost_events) | |
7a8e76a3 | 3887 | { |
7a8e76a3 | 3888 | struct ring_buffer_event *event; |
d769041f | 3889 | struct buffer_page *reader; |
818e3dd3 | 3890 | int nr_loops = 0; |
7a8e76a3 | 3891 | |
dc4e2801 TZ |
3892 | if (ts) |
3893 | *ts = 0; | |
7a8e76a3 | 3894 | again: |
818e3dd3 | 3895 | /* |
69d1b839 SR |
3896 | * We repeat when a time extend is encountered. |
3897 | * Since the time extend is always attached to a data event, | |
3898 | * we should never loop more than once. | |
3899 | * (We never hit the following condition more than twice). | |
818e3dd3 | 3900 | */ |
69d1b839 | 3901 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
818e3dd3 | 3902 | return NULL; |
818e3dd3 | 3903 | |
d769041f SR |
3904 | reader = rb_get_reader_page(cpu_buffer); |
3905 | if (!reader) | |
7a8e76a3 SR |
3906 | return NULL; |
3907 | ||
d769041f | 3908 | event = rb_reader_event(cpu_buffer); |
7a8e76a3 | 3909 | |
334d4169 | 3910 | switch (event->type_len) { |
7a8e76a3 | 3911 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3912 | if (rb_null_event(event)) |
3913 | RB_WARN_ON(cpu_buffer, 1); | |
3914 | /* | |
3915 | * Because the writer could be discarding every | |
3916 | * event it creates (which would probably be bad) | |
3917 | * if we were to go back to "again" then we may never | |
3918 | * catch up, and will trigger the warn on, or lock | |
3919 | * the box. Return the padding, and we will release | |
3920 | * the current locks, and try again. | |
3921 | */ | |
2d622719 | 3922 | return event; |
7a8e76a3 SR |
3923 | |
3924 | case RINGBUF_TYPE_TIME_EXTEND: | |
3925 | /* Internal data, OK to advance */ | |
d769041f | 3926 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3927 | goto again; |
3928 | ||
3929 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
3930 | if (ts) { |
3931 | *ts = ring_buffer_event_time_stamp(event); | |
3932 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, | |
3933 | cpu_buffer->cpu, ts); | |
3934 | } | |
3935 | /* Internal data, OK to advance */ | |
d769041f | 3936 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3937 | goto again; |
3938 | ||
3939 | case RINGBUF_TYPE_DATA: | |
dc4e2801 | 3940 | if (ts && !(*ts)) { |
7a8e76a3 | 3941 | *ts = cpu_buffer->read_stamp + event->time_delta; |
d8eeb2d3 | 3942 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
37886f6a | 3943 | cpu_buffer->cpu, ts); |
7a8e76a3 | 3944 | } |
66a8cb95 SR |
3945 | if (lost_events) |
3946 | *lost_events = rb_lost_events(cpu_buffer); | |
7a8e76a3 SR |
3947 | return event; |
3948 | ||
3949 | default: | |
3950 | BUG(); | |
3951 | } | |
3952 | ||
3953 | return NULL; | |
3954 | } | |
c4f50183 | 3955 | EXPORT_SYMBOL_GPL(ring_buffer_peek); |
7a8e76a3 | 3956 | |
f83c9d0f SR |
3957 | static struct ring_buffer_event * |
3958 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
7a8e76a3 SR |
3959 | { |
3960 | struct ring_buffer *buffer; | |
3961 | struct ring_buffer_per_cpu *cpu_buffer; | |
3962 | struct ring_buffer_event *event; | |
818e3dd3 | 3963 | int nr_loops = 0; |
7a8e76a3 | 3964 | |
dc4e2801 TZ |
3965 | if (ts) |
3966 | *ts = 0; | |
3967 | ||
7a8e76a3 SR |
3968 | cpu_buffer = iter->cpu_buffer; |
3969 | buffer = cpu_buffer->buffer; | |
3970 | ||
492a74f4 SR |
3971 | /* |
3972 | * Check if someone performed a consuming read to | |
3973 | * the buffer. A consuming read invalidates the iterator | |
3974 | * and we need to reset the iterator in this case. | |
3975 | */ | |
3976 | if (unlikely(iter->cache_read != cpu_buffer->read || | |
3977 | iter->cache_reader_page != cpu_buffer->reader_page)) | |
3978 | rb_iter_reset(iter); | |
3979 | ||
7a8e76a3 | 3980 | again: |
3c05d748 SR |
3981 | if (ring_buffer_iter_empty(iter)) |
3982 | return NULL; | |
3983 | ||
818e3dd3 | 3984 | /* |
021de3d9 SRRH |
3985 | * We repeat when a time extend is encountered or we hit |
3986 | * the end of the page. Since the time extend is always attached | |
3987 | * to a data event, we should never loop more than three times. | |
3988 | * Once for going to next page, once on time extend, and | |
3989 | * finally once to get the event. | |
3990 | * (We never hit the following condition more than thrice). | |
818e3dd3 | 3991 | */ |
021de3d9 | 3992 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) |
818e3dd3 | 3993 | return NULL; |
818e3dd3 | 3994 | |
7a8e76a3 SR |
3995 | if (rb_per_cpu_empty(cpu_buffer)) |
3996 | return NULL; | |
3997 | ||
10e83fd0 | 3998 | if (iter->head >= rb_page_size(iter->head_page)) { |
3c05d748 SR |
3999 | rb_inc_iter(iter); |
4000 | goto again; | |
4001 | } | |
4002 | ||
7a8e76a3 SR |
4003 | event = rb_iter_head_event(iter); |
4004 | ||
334d4169 | 4005 | switch (event->type_len) { |
7a8e76a3 | 4006 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
4007 | if (rb_null_event(event)) { |
4008 | rb_inc_iter(iter); | |
4009 | goto again; | |
4010 | } | |
4011 | rb_advance_iter(iter); | |
4012 | return event; | |
7a8e76a3 SR |
4013 | |
4014 | case RINGBUF_TYPE_TIME_EXTEND: | |
4015 | /* Internal data, OK to advance */ | |
4016 | rb_advance_iter(iter); | |
4017 | goto again; | |
4018 | ||
4019 | case RINGBUF_TYPE_TIME_STAMP: | |
dc4e2801 TZ |
4020 | if (ts) { |
4021 | *ts = ring_buffer_event_time_stamp(event); | |
4022 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, | |
4023 | cpu_buffer->cpu, ts); | |
4024 | } | |
4025 | /* Internal data, OK to advance */ | |
7a8e76a3 SR |
4026 | rb_advance_iter(iter); |
4027 | goto again; | |
4028 | ||
4029 | case RINGBUF_TYPE_DATA: | |
dc4e2801 | 4030 | if (ts && !(*ts)) { |
7a8e76a3 | 4031 | *ts = iter->read_stamp + event->time_delta; |
37886f6a SR |
4032 | ring_buffer_normalize_time_stamp(buffer, |
4033 | cpu_buffer->cpu, ts); | |
7a8e76a3 SR |
4034 | } |
4035 | return event; | |
4036 | ||
4037 | default: | |
4038 | BUG(); | |
4039 | } | |
4040 | ||
4041 | return NULL; | |
4042 | } | |
c4f50183 | 4043 | EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
7a8e76a3 | 4044 | |
289a5a25 | 4045 | static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) |
8d707e8e | 4046 | { |
289a5a25 SRRH |
4047 | if (likely(!in_nmi())) { |
4048 | raw_spin_lock(&cpu_buffer->reader_lock); | |
4049 | return true; | |
4050 | } | |
4051 | ||
8d707e8e SR |
4052 | /* |
4053 | * If an NMI die dumps out the content of the ring buffer | |
289a5a25 SRRH |
4054 | * trylock must be used to prevent a deadlock if the NMI |
4055 | * preempted a task that holds the ring buffer locks. If | |
4056 | * we get the lock then all is fine, if not, then continue | |
4057 | * to do the read, but this can corrupt the ring buffer, | |
4058 | * so it must be permanently disabled from future writes. | |
4059 | * Reading from NMI is a oneshot deal. | |
8d707e8e | 4060 | */ |
289a5a25 SRRH |
4061 | if (raw_spin_trylock(&cpu_buffer->reader_lock)) |
4062 | return true; | |
8d707e8e | 4063 | |
289a5a25 SRRH |
4064 | /* Continue without locking, but disable the ring buffer */ |
4065 | atomic_inc(&cpu_buffer->record_disabled); | |
4066 | return false; | |
4067 | } | |
4068 | ||
4069 | static inline void | |
4070 | rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked) | |
4071 | { | |
4072 | if (likely(locked)) | |
4073 | raw_spin_unlock(&cpu_buffer->reader_lock); | |
4074 | return; | |
8d707e8e SR |
4075 | } |
4076 | ||
f83c9d0f SR |
4077 | /** |
4078 | * ring_buffer_peek - peek at the next event to be read | |
4079 | * @buffer: The ring buffer to read | |
4080 | * @cpu: The cpu to peak at | |
4081 | * @ts: The timestamp counter of this event. | |
66a8cb95 | 4082 | * @lost_events: a variable to store if events were lost (may be NULL) |
f83c9d0f SR |
4083 | * |
4084 | * This will return the event that will be read next, but does | |
4085 | * not consume the data. | |
4086 | */ | |
4087 | struct ring_buffer_event * | |
66a8cb95 SR |
4088 | ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts, |
4089 | unsigned long *lost_events) | |
f83c9d0f SR |
4090 | { |
4091 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
8aabee57 | 4092 | struct ring_buffer_event *event; |
f83c9d0f | 4093 | unsigned long flags; |
289a5a25 | 4094 | bool dolock; |
f83c9d0f | 4095 | |
554f786e | 4096 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4097 | return NULL; |
554f786e | 4098 | |
2d622719 | 4099 | again: |
8d707e8e | 4100 | local_irq_save(flags); |
289a5a25 | 4101 | dolock = rb_reader_lock(cpu_buffer); |
66a8cb95 | 4102 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
469535a5 RR |
4103 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
4104 | rb_advance_reader(cpu_buffer); | |
289a5a25 | 4105 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 4106 | local_irq_restore(flags); |
f83c9d0f | 4107 | |
1b959e18 | 4108 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 4109 | goto again; |
2d622719 | 4110 | |
f83c9d0f SR |
4111 | return event; |
4112 | } | |
4113 | ||
4114 | /** | |
4115 | * ring_buffer_iter_peek - peek at the next event to be read | |
4116 | * @iter: The ring buffer iterator | |
4117 | * @ts: The timestamp counter of this event. | |
4118 | * | |
4119 | * This will return the event that will be read next, but does | |
4120 | * not increment the iterator. | |
4121 | */ | |
4122 | struct ring_buffer_event * | |
4123 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
4124 | { | |
4125 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
4126 | struct ring_buffer_event *event; | |
4127 | unsigned long flags; | |
4128 | ||
2d622719 | 4129 | again: |
5389f6fa | 4130 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4131 | event = rb_iter_peek(iter, ts); |
5389f6fa | 4132 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4133 | |
1b959e18 | 4134 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 4135 | goto again; |
2d622719 | 4136 | |
f83c9d0f SR |
4137 | return event; |
4138 | } | |
4139 | ||
7a8e76a3 SR |
4140 | /** |
4141 | * ring_buffer_consume - return an event and consume it | |
4142 | * @buffer: The ring buffer to get the next event from | |
66a8cb95 SR |
4143 | * @cpu: the cpu to read the buffer from |
4144 | * @ts: a variable to store the timestamp (may be NULL) | |
4145 | * @lost_events: a variable to store if events were lost (may be NULL) | |
7a8e76a3 SR |
4146 | * |
4147 | * Returns the next event in the ring buffer, and that event is consumed. | |
4148 | * Meaning, that sequential reads will keep returning a different event, | |
4149 | * and eventually empty the ring buffer if the producer is slower. | |
4150 | */ | |
4151 | struct ring_buffer_event * | |
66a8cb95 SR |
4152 | ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, |
4153 | unsigned long *lost_events) | |
7a8e76a3 | 4154 | { |
554f786e SR |
4155 | struct ring_buffer_per_cpu *cpu_buffer; |
4156 | struct ring_buffer_event *event = NULL; | |
f83c9d0f | 4157 | unsigned long flags; |
289a5a25 | 4158 | bool dolock; |
7a8e76a3 | 4159 | |
2d622719 | 4160 | again: |
554f786e SR |
4161 | /* might be called in atomic */ |
4162 | preempt_disable(); | |
4163 | ||
9e01c1b7 | 4164 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e | 4165 | goto out; |
7a8e76a3 | 4166 | |
554f786e | 4167 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e | 4168 | local_irq_save(flags); |
289a5a25 | 4169 | dolock = rb_reader_lock(cpu_buffer); |
f83c9d0f | 4170 | |
66a8cb95 SR |
4171 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
4172 | if (event) { | |
4173 | cpu_buffer->lost_events = 0; | |
469535a5 | 4174 | rb_advance_reader(cpu_buffer); |
66a8cb95 | 4175 | } |
7a8e76a3 | 4176 | |
289a5a25 | 4177 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 4178 | local_irq_restore(flags); |
f83c9d0f | 4179 | |
554f786e SR |
4180 | out: |
4181 | preempt_enable(); | |
4182 | ||
1b959e18 | 4183 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 4184 | goto again; |
2d622719 | 4185 | |
7a8e76a3 SR |
4186 | return event; |
4187 | } | |
c4f50183 | 4188 | EXPORT_SYMBOL_GPL(ring_buffer_consume); |
7a8e76a3 SR |
4189 | |
4190 | /** | |
72c9ddfd | 4191 | * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer |
7a8e76a3 SR |
4192 | * @buffer: The ring buffer to read from |
4193 | * @cpu: The cpu buffer to iterate over | |
31b265b3 | 4194 | * @flags: gfp flags to use for memory allocation |
7a8e76a3 | 4195 | * |
72c9ddfd DM |
4196 | * This performs the initial preparations necessary to iterate |
4197 | * through the buffer. Memory is allocated, buffer recording | |
4198 | * is disabled, and the iterator pointer is returned to the caller. | |
7a8e76a3 | 4199 | * |
6167c205 | 4200 | * Disabling buffer recording prevents the reading from being |
72c9ddfd DM |
4201 | * corrupted. This is not a consuming read, so a producer is not |
4202 | * expected. | |
4203 | * | |
4204 | * After a sequence of ring_buffer_read_prepare calls, the user is | |
d611851b | 4205 | * expected to make at least one call to ring_buffer_read_prepare_sync. |
72c9ddfd DM |
4206 | * Afterwards, ring_buffer_read_start is invoked to get things going |
4207 | * for real. | |
4208 | * | |
d611851b | 4209 | * This overall must be paired with ring_buffer_read_finish. |
7a8e76a3 SR |
4210 | */ |
4211 | struct ring_buffer_iter * | |
31b265b3 | 4212 | ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu, gfp_t flags) |
7a8e76a3 SR |
4213 | { |
4214 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 4215 | struct ring_buffer_iter *iter; |
7a8e76a3 | 4216 | |
9e01c1b7 | 4217 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4218 | return NULL; |
7a8e76a3 | 4219 | |
31b265b3 | 4220 | iter = kmalloc(sizeof(*iter), flags); |
7a8e76a3 | 4221 | if (!iter) |
8aabee57 | 4222 | return NULL; |
7a8e76a3 SR |
4223 | |
4224 | cpu_buffer = buffer->buffers[cpu]; | |
4225 | ||
4226 | iter->cpu_buffer = cpu_buffer; | |
4227 | ||
83f40318 | 4228 | atomic_inc(&buffer->resize_disabled); |
7a8e76a3 | 4229 | atomic_inc(&cpu_buffer->record_disabled); |
72c9ddfd DM |
4230 | |
4231 | return iter; | |
4232 | } | |
4233 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); | |
4234 | ||
4235 | /** | |
4236 | * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls | |
4237 | * | |
4238 | * All previously invoked ring_buffer_read_prepare calls to prepare | |
4239 | * iterators will be synchronized. Afterwards, read_buffer_read_start | |
4240 | * calls on those iterators are allowed. | |
4241 | */ | |
4242 | void | |
4243 | ring_buffer_read_prepare_sync(void) | |
4244 | { | |
74401729 | 4245 | synchronize_rcu(); |
72c9ddfd DM |
4246 | } |
4247 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); | |
4248 | ||
4249 | /** | |
4250 | * ring_buffer_read_start - start a non consuming read of the buffer | |
4251 | * @iter: The iterator returned by ring_buffer_read_prepare | |
4252 | * | |
4253 | * This finalizes the startup of an iteration through the buffer. | |
4254 | * The iterator comes from a call to ring_buffer_read_prepare and | |
4255 | * an intervening ring_buffer_read_prepare_sync must have been | |
4256 | * performed. | |
4257 | * | |
d611851b | 4258 | * Must be paired with ring_buffer_read_finish. |
72c9ddfd DM |
4259 | */ |
4260 | void | |
4261 | ring_buffer_read_start(struct ring_buffer_iter *iter) | |
4262 | { | |
4263 | struct ring_buffer_per_cpu *cpu_buffer; | |
4264 | unsigned long flags; | |
4265 | ||
4266 | if (!iter) | |
4267 | return; | |
4268 | ||
4269 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 | 4270 | |
5389f6fa | 4271 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
0199c4e6 | 4272 | arch_spin_lock(&cpu_buffer->lock); |
642edba5 | 4273 | rb_iter_reset(iter); |
0199c4e6 | 4274 | arch_spin_unlock(&cpu_buffer->lock); |
5389f6fa | 4275 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 4276 | } |
c4f50183 | 4277 | EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
7a8e76a3 SR |
4278 | |
4279 | /** | |
d611851b | 4280 | * ring_buffer_read_finish - finish reading the iterator of the buffer |
7a8e76a3 SR |
4281 | * @iter: The iterator retrieved by ring_buffer_start |
4282 | * | |
4283 | * This re-enables the recording to the buffer, and frees the | |
4284 | * iterator. | |
4285 | */ | |
4286 | void | |
4287 | ring_buffer_read_finish(struct ring_buffer_iter *iter) | |
4288 | { | |
4289 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
9366c1ba | 4290 | unsigned long flags; |
7a8e76a3 | 4291 | |
659f451f SR |
4292 | /* |
4293 | * Ring buffer is disabled from recording, here's a good place | |
9366c1ba SR |
4294 | * to check the integrity of the ring buffer. |
4295 | * Must prevent readers from trying to read, as the check | |
4296 | * clears the HEAD page and readers require it. | |
659f451f | 4297 | */ |
9366c1ba | 4298 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
659f451f | 4299 | rb_check_pages(cpu_buffer); |
9366c1ba | 4300 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
659f451f | 4301 | |
7a8e76a3 | 4302 | atomic_dec(&cpu_buffer->record_disabled); |
83f40318 | 4303 | atomic_dec(&cpu_buffer->buffer->resize_disabled); |
7a8e76a3 SR |
4304 | kfree(iter); |
4305 | } | |
c4f50183 | 4306 | EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
7a8e76a3 SR |
4307 | |
4308 | /** | |
4309 | * ring_buffer_read - read the next item in the ring buffer by the iterator | |
4310 | * @iter: The ring buffer iterator | |
4311 | * @ts: The time stamp of the event read. | |
4312 | * | |
4313 | * This reads the next event in the ring buffer and increments the iterator. | |
4314 | */ | |
4315 | struct ring_buffer_event * | |
4316 | ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) | |
4317 | { | |
4318 | struct ring_buffer_event *event; | |
f83c9d0f SR |
4319 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
4320 | unsigned long flags; | |
7a8e76a3 | 4321 | |
5389f6fa | 4322 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
7e9391cf | 4323 | again: |
f83c9d0f | 4324 | event = rb_iter_peek(iter, ts); |
7a8e76a3 | 4325 | if (!event) |
f83c9d0f | 4326 | goto out; |
7a8e76a3 | 4327 | |
7e9391cf SR |
4328 | if (event->type_len == RINGBUF_TYPE_PADDING) |
4329 | goto again; | |
4330 | ||
7a8e76a3 | 4331 | rb_advance_iter(iter); |
f83c9d0f | 4332 | out: |
5389f6fa | 4333 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 SR |
4334 | |
4335 | return event; | |
4336 | } | |
c4f50183 | 4337 | EXPORT_SYMBOL_GPL(ring_buffer_read); |
7a8e76a3 SR |
4338 | |
4339 | /** | |
4340 | * ring_buffer_size - return the size of the ring buffer (in bytes) | |
4341 | * @buffer: The ring buffer. | |
4342 | */ | |
438ced17 | 4343 | unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu) |
7a8e76a3 | 4344 | { |
438ced17 VN |
4345 | /* |
4346 | * Earlier, this method returned | |
4347 | * BUF_PAGE_SIZE * buffer->nr_pages | |
4348 | * Since the nr_pages field is now removed, we have converted this to | |
4349 | * return the per cpu buffer value. | |
4350 | */ | |
4351 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
4352 | return 0; | |
4353 | ||
4354 | return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages; | |
7a8e76a3 | 4355 | } |
c4f50183 | 4356 | EXPORT_SYMBOL_GPL(ring_buffer_size); |
7a8e76a3 SR |
4357 | |
4358 | static void | |
4359 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) | |
4360 | { | |
77ae365e SR |
4361 | rb_head_page_deactivate(cpu_buffer); |
4362 | ||
7a8e76a3 | 4363 | cpu_buffer->head_page |
3adc54fa | 4364 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 4365 | local_set(&cpu_buffer->head_page->write, 0); |
778c55d4 | 4366 | local_set(&cpu_buffer->head_page->entries, 0); |
abc9b56d | 4367 | local_set(&cpu_buffer->head_page->page->commit, 0); |
d769041f | 4368 | |
6f807acd | 4369 | cpu_buffer->head_page->read = 0; |
bf41a158 SR |
4370 | |
4371 | cpu_buffer->tail_page = cpu_buffer->head_page; | |
4372 | cpu_buffer->commit_page = cpu_buffer->head_page; | |
4373 | ||
4374 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); | |
5040b4b7 | 4375 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
bf41a158 | 4376 | local_set(&cpu_buffer->reader_page->write, 0); |
778c55d4 | 4377 | local_set(&cpu_buffer->reader_page->entries, 0); |
abc9b56d | 4378 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
6f807acd | 4379 | cpu_buffer->reader_page->read = 0; |
7a8e76a3 | 4380 | |
c64e148a | 4381 | local_set(&cpu_buffer->entries_bytes, 0); |
77ae365e | 4382 | local_set(&cpu_buffer->overrun, 0); |
884bfe89 SP |
4383 | local_set(&cpu_buffer->commit_overrun, 0); |
4384 | local_set(&cpu_buffer->dropped_events, 0); | |
e4906eff | 4385 | local_set(&cpu_buffer->entries, 0); |
fa743953 SR |
4386 | local_set(&cpu_buffer->committing, 0); |
4387 | local_set(&cpu_buffer->commits, 0); | |
2c2b0a78 SRV |
4388 | local_set(&cpu_buffer->pages_touched, 0); |
4389 | local_set(&cpu_buffer->pages_read, 0); | |
03329f99 | 4390 | cpu_buffer->last_pages_touch = 0; |
2c2b0a78 | 4391 | cpu_buffer->shortest_full = 0; |
77ae365e | 4392 | cpu_buffer->read = 0; |
c64e148a | 4393 | cpu_buffer->read_bytes = 0; |
69507c06 SR |
4394 | |
4395 | cpu_buffer->write_stamp = 0; | |
4396 | cpu_buffer->read_stamp = 0; | |
77ae365e | 4397 | |
66a8cb95 SR |
4398 | cpu_buffer->lost_events = 0; |
4399 | cpu_buffer->last_overrun = 0; | |
4400 | ||
77ae365e | 4401 | rb_head_page_activate(cpu_buffer); |
7a8e76a3 SR |
4402 | } |
4403 | ||
4404 | /** | |
4405 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
4406 | * @buffer: The ring buffer to reset a per cpu buffer of | |
4407 | * @cpu: The CPU buffer to be reset | |
4408 | */ | |
4409 | void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) | |
4410 | { | |
4411 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
4412 | unsigned long flags; | |
4413 | ||
9e01c1b7 | 4414 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4415 | return; |
7a8e76a3 | 4416 | |
83f40318 | 4417 | atomic_inc(&buffer->resize_disabled); |
41ede23e SR |
4418 | atomic_inc(&cpu_buffer->record_disabled); |
4419 | ||
83f40318 | 4420 | /* Make sure all commits have finished */ |
74401729 | 4421 | synchronize_rcu(); |
83f40318 | 4422 | |
5389f6fa | 4423 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4424 | |
41b6a95d SR |
4425 | if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) |
4426 | goto out; | |
4427 | ||
0199c4e6 | 4428 | arch_spin_lock(&cpu_buffer->lock); |
7a8e76a3 SR |
4429 | |
4430 | rb_reset_cpu(cpu_buffer); | |
4431 | ||
0199c4e6 | 4432 | arch_spin_unlock(&cpu_buffer->lock); |
f83c9d0f | 4433 | |
41b6a95d | 4434 | out: |
5389f6fa | 4435 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
41ede23e SR |
4436 | |
4437 | atomic_dec(&cpu_buffer->record_disabled); | |
83f40318 | 4438 | atomic_dec(&buffer->resize_disabled); |
7a8e76a3 | 4439 | } |
c4f50183 | 4440 | EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); |
7a8e76a3 SR |
4441 | |
4442 | /** | |
4443 | * ring_buffer_reset - reset a ring buffer | |
4444 | * @buffer: The ring buffer to reset all cpu buffers | |
4445 | */ | |
4446 | void ring_buffer_reset(struct ring_buffer *buffer) | |
4447 | { | |
7a8e76a3 SR |
4448 | int cpu; |
4449 | ||
7a8e76a3 | 4450 | for_each_buffer_cpu(buffer, cpu) |
d769041f | 4451 | ring_buffer_reset_cpu(buffer, cpu); |
7a8e76a3 | 4452 | } |
c4f50183 | 4453 | EXPORT_SYMBOL_GPL(ring_buffer_reset); |
7a8e76a3 SR |
4454 | |
4455 | /** | |
4456 | * rind_buffer_empty - is the ring buffer empty? | |
4457 | * @buffer: The ring buffer to test | |
4458 | */ | |
3d4e204d | 4459 | bool ring_buffer_empty(struct ring_buffer *buffer) |
7a8e76a3 SR |
4460 | { |
4461 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4462 | unsigned long flags; |
289a5a25 | 4463 | bool dolock; |
7a8e76a3 | 4464 | int cpu; |
d4788207 | 4465 | int ret; |
7a8e76a3 SR |
4466 | |
4467 | /* yes this is racy, but if you don't like the race, lock the buffer */ | |
4468 | for_each_buffer_cpu(buffer, cpu) { | |
4469 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e | 4470 | local_irq_save(flags); |
289a5a25 | 4471 | dolock = rb_reader_lock(cpu_buffer); |
d4788207 | 4472 | ret = rb_per_cpu_empty(cpu_buffer); |
289a5a25 | 4473 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e SR |
4474 | local_irq_restore(flags); |
4475 | ||
d4788207 | 4476 | if (!ret) |
3d4e204d | 4477 | return false; |
7a8e76a3 | 4478 | } |
554f786e | 4479 | |
3d4e204d | 4480 | return true; |
7a8e76a3 | 4481 | } |
c4f50183 | 4482 | EXPORT_SYMBOL_GPL(ring_buffer_empty); |
7a8e76a3 SR |
4483 | |
4484 | /** | |
4485 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? | |
4486 | * @buffer: The ring buffer | |
4487 | * @cpu: The CPU buffer to test | |
4488 | */ | |
3d4e204d | 4489 | bool ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) |
7a8e76a3 SR |
4490 | { |
4491 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4492 | unsigned long flags; |
289a5a25 | 4493 | bool dolock; |
8aabee57 | 4494 | int ret; |
7a8e76a3 | 4495 | |
9e01c1b7 | 4496 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
3d4e204d | 4497 | return true; |
7a8e76a3 SR |
4498 | |
4499 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e | 4500 | local_irq_save(flags); |
289a5a25 | 4501 | dolock = rb_reader_lock(cpu_buffer); |
554f786e | 4502 | ret = rb_per_cpu_empty(cpu_buffer); |
289a5a25 | 4503 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 4504 | local_irq_restore(flags); |
554f786e SR |
4505 | |
4506 | return ret; | |
7a8e76a3 | 4507 | } |
c4f50183 | 4508 | EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
7a8e76a3 | 4509 | |
85bac32c | 4510 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
7a8e76a3 SR |
4511 | /** |
4512 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers | |
4513 | * @buffer_a: One buffer to swap with | |
4514 | * @buffer_b: The other buffer to swap with | |
4515 | * | |
4516 | * This function is useful for tracers that want to take a "snapshot" | |
4517 | * of a CPU buffer and has another back up buffer lying around. | |
4518 | * it is expected that the tracer handles the cpu buffer not being | |
4519 | * used at the moment. | |
4520 | */ | |
4521 | int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, | |
4522 | struct ring_buffer *buffer_b, int cpu) | |
4523 | { | |
4524 | struct ring_buffer_per_cpu *cpu_buffer_a; | |
4525 | struct ring_buffer_per_cpu *cpu_buffer_b; | |
554f786e SR |
4526 | int ret = -EINVAL; |
4527 | ||
9e01c1b7 RR |
4528 | if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
4529 | !cpumask_test_cpu(cpu, buffer_b->cpumask)) | |
554f786e | 4530 | goto out; |
7a8e76a3 | 4531 | |
438ced17 VN |
4532 | cpu_buffer_a = buffer_a->buffers[cpu]; |
4533 | cpu_buffer_b = buffer_b->buffers[cpu]; | |
4534 | ||
7a8e76a3 | 4535 | /* At least make sure the two buffers are somewhat the same */ |
438ced17 | 4536 | if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) |
554f786e SR |
4537 | goto out; |
4538 | ||
4539 | ret = -EAGAIN; | |
7a8e76a3 | 4540 | |
97b17efe | 4541 | if (atomic_read(&buffer_a->record_disabled)) |
554f786e | 4542 | goto out; |
97b17efe SR |
4543 | |
4544 | if (atomic_read(&buffer_b->record_disabled)) | |
554f786e | 4545 | goto out; |
97b17efe | 4546 | |
97b17efe | 4547 | if (atomic_read(&cpu_buffer_a->record_disabled)) |
554f786e | 4548 | goto out; |
97b17efe SR |
4549 | |
4550 | if (atomic_read(&cpu_buffer_b->record_disabled)) | |
554f786e | 4551 | goto out; |
97b17efe | 4552 | |
7a8e76a3 | 4553 | /* |
74401729 | 4554 | * We can't do a synchronize_rcu here because this |
7a8e76a3 SR |
4555 | * function can be called in atomic context. |
4556 | * Normally this will be called from the same CPU as cpu. | |
4557 | * If not it's up to the caller to protect this. | |
4558 | */ | |
4559 | atomic_inc(&cpu_buffer_a->record_disabled); | |
4560 | atomic_inc(&cpu_buffer_b->record_disabled); | |
4561 | ||
98277991 SR |
4562 | ret = -EBUSY; |
4563 | if (local_read(&cpu_buffer_a->committing)) | |
4564 | goto out_dec; | |
4565 | if (local_read(&cpu_buffer_b->committing)) | |
4566 | goto out_dec; | |
4567 | ||
7a8e76a3 SR |
4568 | buffer_a->buffers[cpu] = cpu_buffer_b; |
4569 | buffer_b->buffers[cpu] = cpu_buffer_a; | |
4570 | ||
4571 | cpu_buffer_b->buffer = buffer_a; | |
4572 | cpu_buffer_a->buffer = buffer_b; | |
4573 | ||
98277991 SR |
4574 | ret = 0; |
4575 | ||
4576 | out_dec: | |
7a8e76a3 SR |
4577 | atomic_dec(&cpu_buffer_a->record_disabled); |
4578 | atomic_dec(&cpu_buffer_b->record_disabled); | |
554f786e | 4579 | out: |
554f786e | 4580 | return ret; |
7a8e76a3 | 4581 | } |
c4f50183 | 4582 | EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
85bac32c | 4583 | #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
7a8e76a3 | 4584 | |
8789a9e7 SR |
4585 | /** |
4586 | * ring_buffer_alloc_read_page - allocate a page to read from buffer | |
4587 | * @buffer: the buffer to allocate for. | |
d611851b | 4588 | * @cpu: the cpu buffer to allocate. |
8789a9e7 SR |
4589 | * |
4590 | * This function is used in conjunction with ring_buffer_read_page. | |
4591 | * When reading a full page from the ring buffer, these functions | |
4592 | * can be used to speed up the process. The calling function should | |
4593 | * allocate a few pages first with this function. Then when it | |
4594 | * needs to get pages from the ring buffer, it passes the result | |
4595 | * of this function into ring_buffer_read_page, which will swap | |
4596 | * the page that was allocated, with the read page of the buffer. | |
4597 | * | |
4598 | * Returns: | |
a7e52ad7 | 4599 | * The page allocated, or ERR_PTR |
8789a9e7 | 4600 | */ |
7ea59064 | 4601 | void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu) |
8789a9e7 | 4602 | { |
a7e52ad7 | 4603 | struct ring_buffer_per_cpu *cpu_buffer; |
73a757e6 SRV |
4604 | struct buffer_data_page *bpage = NULL; |
4605 | unsigned long flags; | |
7ea59064 | 4606 | struct page *page; |
8789a9e7 | 4607 | |
a7e52ad7 SRV |
4608 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
4609 | return ERR_PTR(-ENODEV); | |
4610 | ||
4611 | cpu_buffer = buffer->buffers[cpu]; | |
73a757e6 SRV |
4612 | local_irq_save(flags); |
4613 | arch_spin_lock(&cpu_buffer->lock); | |
4614 | ||
4615 | if (cpu_buffer->free_page) { | |
4616 | bpage = cpu_buffer->free_page; | |
4617 | cpu_buffer->free_page = NULL; | |
4618 | } | |
4619 | ||
4620 | arch_spin_unlock(&cpu_buffer->lock); | |
4621 | local_irq_restore(flags); | |
4622 | ||
4623 | if (bpage) | |
4624 | goto out; | |
4625 | ||
d7ec4bfe VN |
4626 | page = alloc_pages_node(cpu_to_node(cpu), |
4627 | GFP_KERNEL | __GFP_NORETRY, 0); | |
7ea59064 | 4628 | if (!page) |
a7e52ad7 | 4629 | return ERR_PTR(-ENOMEM); |
8789a9e7 | 4630 | |
7ea59064 | 4631 | bpage = page_address(page); |
8789a9e7 | 4632 | |
73a757e6 | 4633 | out: |
ef7a4a16 SR |
4634 | rb_init_page(bpage); |
4635 | ||
044fa782 | 4636 | return bpage; |
8789a9e7 | 4637 | } |
d6ce96da | 4638 | EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
8789a9e7 SR |
4639 | |
4640 | /** | |
4641 | * ring_buffer_free_read_page - free an allocated read page | |
4642 | * @buffer: the buffer the page was allocate for | |
73a757e6 | 4643 | * @cpu: the cpu buffer the page came from |
8789a9e7 SR |
4644 | * @data: the page to free |
4645 | * | |
4646 | * Free a page allocated from ring_buffer_alloc_read_page. | |
4647 | */ | |
73a757e6 | 4648 | void ring_buffer_free_read_page(struct ring_buffer *buffer, int cpu, void *data) |
8789a9e7 | 4649 | { |
73a757e6 SRV |
4650 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; |
4651 | struct buffer_data_page *bpage = data; | |
ae415fa4 | 4652 | struct page *page = virt_to_page(bpage); |
73a757e6 SRV |
4653 | unsigned long flags; |
4654 | ||
ae415fa4 SRV |
4655 | /* If the page is still in use someplace else, we can't reuse it */ |
4656 | if (page_ref_count(page) > 1) | |
4657 | goto out; | |
4658 | ||
73a757e6 SRV |
4659 | local_irq_save(flags); |
4660 | arch_spin_lock(&cpu_buffer->lock); | |
4661 | ||
4662 | if (!cpu_buffer->free_page) { | |
4663 | cpu_buffer->free_page = bpage; | |
4664 | bpage = NULL; | |
4665 | } | |
4666 | ||
4667 | arch_spin_unlock(&cpu_buffer->lock); | |
4668 | local_irq_restore(flags); | |
4669 | ||
ae415fa4 | 4670 | out: |
73a757e6 | 4671 | free_page((unsigned long)bpage); |
8789a9e7 | 4672 | } |
d6ce96da | 4673 | EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
8789a9e7 SR |
4674 | |
4675 | /** | |
4676 | * ring_buffer_read_page - extract a page from the ring buffer | |
4677 | * @buffer: buffer to extract from | |
4678 | * @data_page: the page to use allocated from ring_buffer_alloc_read_page | |
ef7a4a16 | 4679 | * @len: amount to extract |
8789a9e7 SR |
4680 | * @cpu: the cpu of the buffer to extract |
4681 | * @full: should the extraction only happen when the page is full. | |
4682 | * | |
4683 | * This function will pull out a page from the ring buffer and consume it. | |
4684 | * @data_page must be the address of the variable that was returned | |
4685 | * from ring_buffer_alloc_read_page. This is because the page might be used | |
4686 | * to swap with a page in the ring buffer. | |
4687 | * | |
4688 | * for example: | |
d611851b | 4689 | * rpage = ring_buffer_alloc_read_page(buffer, cpu); |
a7e52ad7 SRV |
4690 | * if (IS_ERR(rpage)) |
4691 | * return PTR_ERR(rpage); | |
ef7a4a16 | 4692 | * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
667d2412 LJ |
4693 | * if (ret >= 0) |
4694 | * process_page(rpage, ret); | |
8789a9e7 SR |
4695 | * |
4696 | * When @full is set, the function will not return true unless | |
4697 | * the writer is off the reader page. | |
4698 | * | |
4699 | * Note: it is up to the calling functions to handle sleeps and wakeups. | |
4700 | * The ring buffer can be used anywhere in the kernel and can not | |
4701 | * blindly call wake_up. The layer that uses the ring buffer must be | |
4702 | * responsible for that. | |
4703 | * | |
4704 | * Returns: | |
667d2412 LJ |
4705 | * >=0 if data has been transferred, returns the offset of consumed data. |
4706 | * <0 if no data has been transferred. | |
8789a9e7 SR |
4707 | */ |
4708 | int ring_buffer_read_page(struct ring_buffer *buffer, | |
ef7a4a16 | 4709 | void **data_page, size_t len, int cpu, int full) |
8789a9e7 SR |
4710 | { |
4711 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
4712 | struct ring_buffer_event *event; | |
044fa782 | 4713 | struct buffer_data_page *bpage; |
ef7a4a16 | 4714 | struct buffer_page *reader; |
ff0ff84a | 4715 | unsigned long missed_events; |
8789a9e7 | 4716 | unsigned long flags; |
ef7a4a16 | 4717 | unsigned int commit; |
667d2412 | 4718 | unsigned int read; |
4f3640f8 | 4719 | u64 save_timestamp; |
667d2412 | 4720 | int ret = -1; |
8789a9e7 | 4721 | |
554f786e SR |
4722 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
4723 | goto out; | |
4724 | ||
474d32b6 SR |
4725 | /* |
4726 | * If len is not big enough to hold the page header, then | |
4727 | * we can not copy anything. | |
4728 | */ | |
4729 | if (len <= BUF_PAGE_HDR_SIZE) | |
554f786e | 4730 | goto out; |
474d32b6 SR |
4731 | |
4732 | len -= BUF_PAGE_HDR_SIZE; | |
4733 | ||
8789a9e7 | 4734 | if (!data_page) |
554f786e | 4735 | goto out; |
8789a9e7 | 4736 | |
044fa782 SR |
4737 | bpage = *data_page; |
4738 | if (!bpage) | |
554f786e | 4739 | goto out; |
8789a9e7 | 4740 | |
5389f6fa | 4741 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 4742 | |
ef7a4a16 SR |
4743 | reader = rb_get_reader_page(cpu_buffer); |
4744 | if (!reader) | |
554f786e | 4745 | goto out_unlock; |
8789a9e7 | 4746 | |
ef7a4a16 SR |
4747 | event = rb_reader_event(cpu_buffer); |
4748 | ||
4749 | read = reader->read; | |
4750 | commit = rb_page_commit(reader); | |
667d2412 | 4751 | |
66a8cb95 | 4752 | /* Check if any events were dropped */ |
ff0ff84a | 4753 | missed_events = cpu_buffer->lost_events; |
66a8cb95 | 4754 | |
8789a9e7 | 4755 | /* |
474d32b6 SR |
4756 | * If this page has been partially read or |
4757 | * if len is not big enough to read the rest of the page or | |
4758 | * a writer is still on the page, then | |
4759 | * we must copy the data from the page to the buffer. | |
4760 | * Otherwise, we can simply swap the page with the one passed in. | |
8789a9e7 | 4761 | */ |
474d32b6 | 4762 | if (read || (len < (commit - read)) || |
ef7a4a16 | 4763 | cpu_buffer->reader_page == cpu_buffer->commit_page) { |
667d2412 | 4764 | struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
474d32b6 SR |
4765 | unsigned int rpos = read; |
4766 | unsigned int pos = 0; | |
ef7a4a16 | 4767 | unsigned int size; |
8789a9e7 SR |
4768 | |
4769 | if (full) | |
554f786e | 4770 | goto out_unlock; |
8789a9e7 | 4771 | |
ef7a4a16 SR |
4772 | if (len > (commit - read)) |
4773 | len = (commit - read); | |
4774 | ||
69d1b839 SR |
4775 | /* Always keep the time extend and data together */ |
4776 | size = rb_event_ts_length(event); | |
ef7a4a16 SR |
4777 | |
4778 | if (len < size) | |
554f786e | 4779 | goto out_unlock; |
ef7a4a16 | 4780 | |
4f3640f8 SR |
4781 | /* save the current timestamp, since the user will need it */ |
4782 | save_timestamp = cpu_buffer->read_stamp; | |
4783 | ||
ef7a4a16 SR |
4784 | /* Need to copy one event at a time */ |
4785 | do { | |
e1e35927 DS |
4786 | /* We need the size of one event, because |
4787 | * rb_advance_reader only advances by one event, | |
4788 | * whereas rb_event_ts_length may include the size of | |
4789 | * one or two events. | |
4790 | * We have already ensured there's enough space if this | |
4791 | * is a time extend. */ | |
4792 | size = rb_event_length(event); | |
474d32b6 | 4793 | memcpy(bpage->data + pos, rpage->data + rpos, size); |
ef7a4a16 SR |
4794 | |
4795 | len -= size; | |
4796 | ||
4797 | rb_advance_reader(cpu_buffer); | |
474d32b6 SR |
4798 | rpos = reader->read; |
4799 | pos += size; | |
ef7a4a16 | 4800 | |
18fab912 HY |
4801 | if (rpos >= commit) |
4802 | break; | |
4803 | ||
ef7a4a16 | 4804 | event = rb_reader_event(cpu_buffer); |
69d1b839 SR |
4805 | /* Always keep the time extend and data together */ |
4806 | size = rb_event_ts_length(event); | |
e1e35927 | 4807 | } while (len >= size); |
667d2412 LJ |
4808 | |
4809 | /* update bpage */ | |
ef7a4a16 | 4810 | local_set(&bpage->commit, pos); |
4f3640f8 | 4811 | bpage->time_stamp = save_timestamp; |
ef7a4a16 | 4812 | |
474d32b6 SR |
4813 | /* we copied everything to the beginning */ |
4814 | read = 0; | |
8789a9e7 | 4815 | } else { |
afbab76a | 4816 | /* update the entry counter */ |
77ae365e | 4817 | cpu_buffer->read += rb_page_entries(reader); |
c64e148a | 4818 | cpu_buffer->read_bytes += BUF_PAGE_SIZE; |
afbab76a | 4819 | |
8789a9e7 | 4820 | /* swap the pages */ |
044fa782 | 4821 | rb_init_page(bpage); |
ef7a4a16 SR |
4822 | bpage = reader->page; |
4823 | reader->page = *data_page; | |
4824 | local_set(&reader->write, 0); | |
778c55d4 | 4825 | local_set(&reader->entries, 0); |
ef7a4a16 | 4826 | reader->read = 0; |
044fa782 | 4827 | *data_page = bpage; |
ff0ff84a SR |
4828 | |
4829 | /* | |
4830 | * Use the real_end for the data size, | |
4831 | * This gives us a chance to store the lost events | |
4832 | * on the page. | |
4833 | */ | |
4834 | if (reader->real_end) | |
4835 | local_set(&bpage->commit, reader->real_end); | |
8789a9e7 | 4836 | } |
667d2412 | 4837 | ret = read; |
8789a9e7 | 4838 | |
66a8cb95 | 4839 | cpu_buffer->lost_events = 0; |
2711ca23 SR |
4840 | |
4841 | commit = local_read(&bpage->commit); | |
66a8cb95 SR |
4842 | /* |
4843 | * Set a flag in the commit field if we lost events | |
4844 | */ | |
ff0ff84a | 4845 | if (missed_events) { |
ff0ff84a SR |
4846 | /* If there is room at the end of the page to save the |
4847 | * missed events, then record it there. | |
4848 | */ | |
4849 | if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { | |
4850 | memcpy(&bpage->data[commit], &missed_events, | |
4851 | sizeof(missed_events)); | |
4852 | local_add(RB_MISSED_STORED, &bpage->commit); | |
2711ca23 | 4853 | commit += sizeof(missed_events); |
ff0ff84a | 4854 | } |
66a8cb95 | 4855 | local_add(RB_MISSED_EVENTS, &bpage->commit); |
ff0ff84a | 4856 | } |
66a8cb95 | 4857 | |
2711ca23 SR |
4858 | /* |
4859 | * This page may be off to user land. Zero it out here. | |
4860 | */ | |
4861 | if (commit < BUF_PAGE_SIZE) | |
4862 | memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit); | |
4863 | ||
554f786e | 4864 | out_unlock: |
5389f6fa | 4865 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 4866 | |
554f786e | 4867 | out: |
8789a9e7 SR |
4868 | return ret; |
4869 | } | |
d6ce96da | 4870 | EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
8789a9e7 | 4871 | |
b32614c0 SAS |
4872 | /* |
4873 | * We only allocate new buffers, never free them if the CPU goes down. | |
4874 | * If we were to free the buffer, then the user would lose any trace that was in | |
4875 | * the buffer. | |
4876 | */ | |
4877 | int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node) | |
554f786e | 4878 | { |
b32614c0 | 4879 | struct ring_buffer *buffer; |
9b94a8fb SRRH |
4880 | long nr_pages_same; |
4881 | int cpu_i; | |
4882 | unsigned long nr_pages; | |
554f786e | 4883 | |
b32614c0 SAS |
4884 | buffer = container_of(node, struct ring_buffer, node); |
4885 | if (cpumask_test_cpu(cpu, buffer->cpumask)) | |
4886 | return 0; | |
4887 | ||
4888 | nr_pages = 0; | |
4889 | nr_pages_same = 1; | |
4890 | /* check if all cpu sizes are same */ | |
4891 | for_each_buffer_cpu(buffer, cpu_i) { | |
4892 | /* fill in the size from first enabled cpu */ | |
4893 | if (nr_pages == 0) | |
4894 | nr_pages = buffer->buffers[cpu_i]->nr_pages; | |
4895 | if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { | |
4896 | nr_pages_same = 0; | |
4897 | break; | |
554f786e | 4898 | } |
554f786e | 4899 | } |
b32614c0 SAS |
4900 | /* allocate minimum pages, user can later expand it */ |
4901 | if (!nr_pages_same) | |
4902 | nr_pages = 2; | |
4903 | buffer->buffers[cpu] = | |
4904 | rb_allocate_cpu_buffer(buffer, nr_pages, cpu); | |
4905 | if (!buffer->buffers[cpu]) { | |
4906 | WARN(1, "failed to allocate ring buffer on CPU %u\n", | |
4907 | cpu); | |
4908 | return -ENOMEM; | |
4909 | } | |
4910 | smp_wmb(); | |
4911 | cpumask_set_cpu(cpu, buffer->cpumask); | |
4912 | return 0; | |
554f786e | 4913 | } |
6c43e554 SRRH |
4914 | |
4915 | #ifdef CONFIG_RING_BUFFER_STARTUP_TEST | |
4916 | /* | |
4917 | * This is a basic integrity check of the ring buffer. | |
4918 | * Late in the boot cycle this test will run when configured in. | |
4919 | * It will kick off a thread per CPU that will go into a loop | |
4920 | * writing to the per cpu ring buffer various sizes of data. | |
4921 | * Some of the data will be large items, some small. | |
4922 | * | |
4923 | * Another thread is created that goes into a spin, sending out | |
4924 | * IPIs to the other CPUs to also write into the ring buffer. | |
4925 | * this is to test the nesting ability of the buffer. | |
4926 | * | |
4927 | * Basic stats are recorded and reported. If something in the | |
4928 | * ring buffer should happen that's not expected, a big warning | |
4929 | * is displayed and all ring buffers are disabled. | |
4930 | */ | |
4931 | static struct task_struct *rb_threads[NR_CPUS] __initdata; | |
4932 | ||
4933 | struct rb_test_data { | |
4934 | struct ring_buffer *buffer; | |
4935 | unsigned long events; | |
4936 | unsigned long bytes_written; | |
4937 | unsigned long bytes_alloc; | |
4938 | unsigned long bytes_dropped; | |
4939 | unsigned long events_nested; | |
4940 | unsigned long bytes_written_nested; | |
4941 | unsigned long bytes_alloc_nested; | |
4942 | unsigned long bytes_dropped_nested; | |
4943 | int min_size_nested; | |
4944 | int max_size_nested; | |
4945 | int max_size; | |
4946 | int min_size; | |
4947 | int cpu; | |
4948 | int cnt; | |
4949 | }; | |
4950 | ||
4951 | static struct rb_test_data rb_data[NR_CPUS] __initdata; | |
4952 | ||
4953 | /* 1 meg per cpu */ | |
4954 | #define RB_TEST_BUFFER_SIZE 1048576 | |
4955 | ||
4956 | static char rb_string[] __initdata = | |
4957 | "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" | |
4958 | "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" | |
4959 | "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv"; | |
4960 | ||
4961 | static bool rb_test_started __initdata; | |
4962 | ||
4963 | struct rb_item { | |
4964 | int size; | |
4965 | char str[]; | |
4966 | }; | |
4967 | ||
4968 | static __init int rb_write_something(struct rb_test_data *data, bool nested) | |
4969 | { | |
4970 | struct ring_buffer_event *event; | |
4971 | struct rb_item *item; | |
4972 | bool started; | |
4973 | int event_len; | |
4974 | int size; | |
4975 | int len; | |
4976 | int cnt; | |
4977 | ||
4978 | /* Have nested writes different that what is written */ | |
4979 | cnt = data->cnt + (nested ? 27 : 0); | |
4980 | ||
4981 | /* Multiply cnt by ~e, to make some unique increment */ | |
4982 | size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1); | |
4983 | ||
4984 | len = size + sizeof(struct rb_item); | |
4985 | ||
4986 | started = rb_test_started; | |
4987 | /* read rb_test_started before checking buffer enabled */ | |
4988 | smp_rmb(); | |
4989 | ||
4990 | event = ring_buffer_lock_reserve(data->buffer, len); | |
4991 | if (!event) { | |
4992 | /* Ignore dropped events before test starts. */ | |
4993 | if (started) { | |
4994 | if (nested) | |
4995 | data->bytes_dropped += len; | |
4996 | else | |
4997 | data->bytes_dropped_nested += len; | |
4998 | } | |
4999 | return len; | |
5000 | } | |
5001 | ||
5002 | event_len = ring_buffer_event_length(event); | |
5003 | ||
5004 | if (RB_WARN_ON(data->buffer, event_len < len)) | |
5005 | goto out; | |
5006 | ||
5007 | item = ring_buffer_event_data(event); | |
5008 | item->size = size; | |
5009 | memcpy(item->str, rb_string, size); | |
5010 | ||
5011 | if (nested) { | |
5012 | data->bytes_alloc_nested += event_len; | |
5013 | data->bytes_written_nested += len; | |
5014 | data->events_nested++; | |
5015 | if (!data->min_size_nested || len < data->min_size_nested) | |
5016 | data->min_size_nested = len; | |
5017 | if (len > data->max_size_nested) | |
5018 | data->max_size_nested = len; | |
5019 | } else { | |
5020 | data->bytes_alloc += event_len; | |
5021 | data->bytes_written += len; | |
5022 | data->events++; | |
5023 | if (!data->min_size || len < data->min_size) | |
5024 | data->max_size = len; | |
5025 | if (len > data->max_size) | |
5026 | data->max_size = len; | |
5027 | } | |
5028 | ||
5029 | out: | |
5030 | ring_buffer_unlock_commit(data->buffer, event); | |
5031 | ||
5032 | return 0; | |
5033 | } | |
5034 | ||
5035 | static __init int rb_test(void *arg) | |
5036 | { | |
5037 | struct rb_test_data *data = arg; | |
5038 | ||
5039 | while (!kthread_should_stop()) { | |
5040 | rb_write_something(data, false); | |
5041 | data->cnt++; | |
5042 | ||
5043 | set_current_state(TASK_INTERRUPTIBLE); | |
5044 | /* Now sleep between a min of 100-300us and a max of 1ms */ | |
5045 | usleep_range(((data->cnt % 3) + 1) * 100, 1000); | |
5046 | } | |
5047 | ||
5048 | return 0; | |
5049 | } | |
5050 | ||
5051 | static __init void rb_ipi(void *ignore) | |
5052 | { | |
5053 | struct rb_test_data *data; | |
5054 | int cpu = smp_processor_id(); | |
5055 | ||
5056 | data = &rb_data[cpu]; | |
5057 | rb_write_something(data, true); | |
5058 | } | |
5059 | ||
5060 | static __init int rb_hammer_test(void *arg) | |
5061 | { | |
5062 | while (!kthread_should_stop()) { | |
5063 | ||
5064 | /* Send an IPI to all cpus to write data! */ | |
5065 | smp_call_function(rb_ipi, NULL, 1); | |
5066 | /* No sleep, but for non preempt, let others run */ | |
5067 | schedule(); | |
5068 | } | |
5069 | ||
5070 | return 0; | |
5071 | } | |
5072 | ||
5073 | static __init int test_ringbuffer(void) | |
5074 | { | |
5075 | struct task_struct *rb_hammer; | |
5076 | struct ring_buffer *buffer; | |
5077 | int cpu; | |
5078 | int ret = 0; | |
5079 | ||
5080 | pr_info("Running ring buffer tests...\n"); | |
5081 | ||
5082 | buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); | |
5083 | if (WARN_ON(!buffer)) | |
5084 | return 0; | |
5085 | ||
5086 | /* Disable buffer so that threads can't write to it yet */ | |
5087 | ring_buffer_record_off(buffer); | |
5088 | ||
5089 | for_each_online_cpu(cpu) { | |
5090 | rb_data[cpu].buffer = buffer; | |
5091 | rb_data[cpu].cpu = cpu; | |
5092 | rb_data[cpu].cnt = cpu; | |
5093 | rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu], | |
5094 | "rbtester/%d", cpu); | |
62277de7 | 5095 | if (WARN_ON(IS_ERR(rb_threads[cpu]))) { |
6c43e554 | 5096 | pr_cont("FAILED\n"); |
62277de7 | 5097 | ret = PTR_ERR(rb_threads[cpu]); |
6c43e554 SRRH |
5098 | goto out_free; |
5099 | } | |
5100 | ||
5101 | kthread_bind(rb_threads[cpu], cpu); | |
5102 | wake_up_process(rb_threads[cpu]); | |
5103 | } | |
5104 | ||
5105 | /* Now create the rb hammer! */ | |
5106 | rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); | |
62277de7 | 5107 | if (WARN_ON(IS_ERR(rb_hammer))) { |
6c43e554 | 5108 | pr_cont("FAILED\n"); |
62277de7 | 5109 | ret = PTR_ERR(rb_hammer); |
6c43e554 SRRH |
5110 | goto out_free; |
5111 | } | |
5112 | ||
5113 | ring_buffer_record_on(buffer); | |
5114 | /* | |
5115 | * Show buffer is enabled before setting rb_test_started. | |
5116 | * Yes there's a small race window where events could be | |
5117 | * dropped and the thread wont catch it. But when a ring | |
5118 | * buffer gets enabled, there will always be some kind of | |
5119 | * delay before other CPUs see it. Thus, we don't care about | |
5120 | * those dropped events. We care about events dropped after | |
5121 | * the threads see that the buffer is active. | |
5122 | */ | |
5123 | smp_wmb(); | |
5124 | rb_test_started = true; | |
5125 | ||
5126 | set_current_state(TASK_INTERRUPTIBLE); | |
5127 | /* Just run for 10 seconds */; | |
5128 | schedule_timeout(10 * HZ); | |
5129 | ||
5130 | kthread_stop(rb_hammer); | |
5131 | ||
5132 | out_free: | |
5133 | for_each_online_cpu(cpu) { | |
5134 | if (!rb_threads[cpu]) | |
5135 | break; | |
5136 | kthread_stop(rb_threads[cpu]); | |
5137 | } | |
5138 | if (ret) { | |
5139 | ring_buffer_free(buffer); | |
5140 | return ret; | |
5141 | } | |
5142 | ||
5143 | /* Report! */ | |
5144 | pr_info("finished\n"); | |
5145 | for_each_online_cpu(cpu) { | |
5146 | struct ring_buffer_event *event; | |
5147 | struct rb_test_data *data = &rb_data[cpu]; | |
5148 | struct rb_item *item; | |
5149 | unsigned long total_events; | |
5150 | unsigned long total_dropped; | |
5151 | unsigned long total_written; | |
5152 | unsigned long total_alloc; | |
5153 | unsigned long total_read = 0; | |
5154 | unsigned long total_size = 0; | |
5155 | unsigned long total_len = 0; | |
5156 | unsigned long total_lost = 0; | |
5157 | unsigned long lost; | |
5158 | int big_event_size; | |
5159 | int small_event_size; | |
5160 | ||
5161 | ret = -1; | |
5162 | ||
5163 | total_events = data->events + data->events_nested; | |
5164 | total_written = data->bytes_written + data->bytes_written_nested; | |
5165 | total_alloc = data->bytes_alloc + data->bytes_alloc_nested; | |
5166 | total_dropped = data->bytes_dropped + data->bytes_dropped_nested; | |
5167 | ||
5168 | big_event_size = data->max_size + data->max_size_nested; | |
5169 | small_event_size = data->min_size + data->min_size_nested; | |
5170 | ||
5171 | pr_info("CPU %d:\n", cpu); | |
5172 | pr_info(" events: %ld\n", total_events); | |
5173 | pr_info(" dropped bytes: %ld\n", total_dropped); | |
5174 | pr_info(" alloced bytes: %ld\n", total_alloc); | |
5175 | pr_info(" written bytes: %ld\n", total_written); | |
5176 | pr_info(" biggest event: %d\n", big_event_size); | |
5177 | pr_info(" smallest event: %d\n", small_event_size); | |
5178 | ||
5179 | if (RB_WARN_ON(buffer, total_dropped)) | |
5180 | break; | |
5181 | ||
5182 | ret = 0; | |
5183 | ||
5184 | while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { | |
5185 | total_lost += lost; | |
5186 | item = ring_buffer_event_data(event); | |
5187 | total_len += ring_buffer_event_length(event); | |
5188 | total_size += item->size + sizeof(struct rb_item); | |
5189 | if (memcmp(&item->str[0], rb_string, item->size) != 0) { | |
5190 | pr_info("FAILED!\n"); | |
5191 | pr_info("buffer had: %.*s\n", item->size, item->str); | |
5192 | pr_info("expected: %.*s\n", item->size, rb_string); | |
5193 | RB_WARN_ON(buffer, 1); | |
5194 | ret = -1; | |
5195 | break; | |
5196 | } | |
5197 | total_read++; | |
5198 | } | |
5199 | if (ret) | |
5200 | break; | |
5201 | ||
5202 | ret = -1; | |
5203 | ||
5204 | pr_info(" read events: %ld\n", total_read); | |
5205 | pr_info(" lost events: %ld\n", total_lost); | |
5206 | pr_info(" total events: %ld\n", total_lost + total_read); | |
5207 | pr_info(" recorded len bytes: %ld\n", total_len); | |
5208 | pr_info(" recorded size bytes: %ld\n", total_size); | |
5209 | if (total_lost) | |
5210 | pr_info(" With dropped events, record len and size may not match\n" | |
5211 | " alloced and written from above\n"); | |
5212 | if (!total_lost) { | |
5213 | if (RB_WARN_ON(buffer, total_len != total_alloc || | |
5214 | total_size != total_written)) | |
5215 | break; | |
5216 | } | |
5217 | if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) | |
5218 | break; | |
5219 | ||
5220 | ret = 0; | |
5221 | } | |
5222 | if (!ret) | |
5223 | pr_info("Ring buffer PASSED!\n"); | |
5224 | ||
5225 | ring_buffer_free(buffer); | |
5226 | return 0; | |
5227 | } | |
5228 | ||
5229 | late_initcall(test_ringbuffer); | |
5230 | #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */ |