Commit | Line | Data |
---|---|---|
7a8e76a3 SR |
1 | /* |
2 | * Generic ring buffer | |
3 | * | |
4 | * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> | |
5 | */ | |
af658dca | 6 | #include <linux/trace_events.h> |
7a8e76a3 | 7 | #include <linux/ring_buffer.h> |
14131f2f | 8 | #include <linux/trace_clock.h> |
0b07436d | 9 | #include <linux/trace_seq.h> |
7a8e76a3 | 10 | #include <linux/spinlock.h> |
15693458 | 11 | #include <linux/irq_work.h> |
7a8e76a3 | 12 | #include <linux/uaccess.h> |
a81bd80a | 13 | #include <linux/hardirq.h> |
6c43e554 | 14 | #include <linux/kthread.h> /* for self test */ |
1744a21d | 15 | #include <linux/kmemcheck.h> |
7a8e76a3 SR |
16 | #include <linux/module.h> |
17 | #include <linux/percpu.h> | |
18 | #include <linux/mutex.h> | |
6c43e554 | 19 | #include <linux/delay.h> |
5a0e3ad6 | 20 | #include <linux/slab.h> |
7a8e76a3 SR |
21 | #include <linux/init.h> |
22 | #include <linux/hash.h> | |
23 | #include <linux/list.h> | |
554f786e | 24 | #include <linux/cpu.h> |
7a8e76a3 | 25 | |
79615760 | 26 | #include <asm/local.h> |
182e9f5f | 27 | |
83f40318 VN |
28 | static void update_pages_handler(struct work_struct *work); |
29 | ||
d1b182a8 SR |
30 | /* |
31 | * The ring buffer header is special. We must manually up keep it. | |
32 | */ | |
33 | int ring_buffer_print_entry_header(struct trace_seq *s) | |
34 | { | |
c0cd93aa SRRH |
35 | trace_seq_puts(s, "# compressed entry header\n"); |
36 | trace_seq_puts(s, "\ttype_len : 5 bits\n"); | |
37 | trace_seq_puts(s, "\ttime_delta : 27 bits\n"); | |
38 | trace_seq_puts(s, "\tarray : 32 bits\n"); | |
39 | trace_seq_putc(s, '\n'); | |
40 | trace_seq_printf(s, "\tpadding : type == %d\n", | |
41 | RINGBUF_TYPE_PADDING); | |
42 | trace_seq_printf(s, "\ttime_extend : type == %d\n", | |
43 | RINGBUF_TYPE_TIME_EXTEND); | |
44 | trace_seq_printf(s, "\tdata max type_len == %d\n", | |
45 | RINGBUF_TYPE_DATA_TYPE_LEN_MAX); | |
46 | ||
47 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
48 | } |
49 | ||
5cc98548 SR |
50 | /* |
51 | * The ring buffer is made up of a list of pages. A separate list of pages is | |
52 | * allocated for each CPU. A writer may only write to a buffer that is | |
53 | * associated with the CPU it is currently executing on. A reader may read | |
54 | * from any per cpu buffer. | |
55 | * | |
56 | * The reader is special. For each per cpu buffer, the reader has its own | |
57 | * reader page. When a reader has read the entire reader page, this reader | |
58 | * page is swapped with another page in the ring buffer. | |
59 | * | |
60 | * Now, as long as the writer is off the reader page, the reader can do what | |
61 | * ever it wants with that page. The writer will never write to that page | |
62 | * again (as long as it is out of the ring buffer). | |
63 | * | |
64 | * Here's some silly ASCII art. | |
65 | * | |
66 | * +------+ | |
67 | * |reader| RING BUFFER | |
68 | * |page | | |
69 | * +------+ +---+ +---+ +---+ | |
70 | * | |-->| |-->| | | |
71 | * +---+ +---+ +---+ | |
72 | * ^ | | |
73 | * | | | |
74 | * +---------------+ | |
75 | * | |
76 | * | |
77 | * +------+ | |
78 | * |reader| RING BUFFER | |
79 | * |page |------------------v | |
80 | * +------+ +---+ +---+ +---+ | |
81 | * | |-->| |-->| | | |
82 | * +---+ +---+ +---+ | |
83 | * ^ | | |
84 | * | | | |
85 | * +---------------+ | |
86 | * | |
87 | * | |
88 | * +------+ | |
89 | * |reader| RING BUFFER | |
90 | * |page |------------------v | |
91 | * +------+ +---+ +---+ +---+ | |
92 | * ^ | |-->| |-->| | | |
93 | * | +---+ +---+ +---+ | |
94 | * | | | |
95 | * | | | |
96 | * +------------------------------+ | |
97 | * | |
98 | * | |
99 | * +------+ | |
100 | * |buffer| RING BUFFER | |
101 | * |page |------------------v | |
102 | * +------+ +---+ +---+ +---+ | |
103 | * ^ | | | |-->| | | |
104 | * | New +---+ +---+ +---+ | |
105 | * | Reader------^ | | |
106 | * | page | | |
107 | * +------------------------------+ | |
108 | * | |
109 | * | |
110 | * After we make this swap, the reader can hand this page off to the splice | |
111 | * code and be done with it. It can even allocate a new page if it needs to | |
112 | * and swap that into the ring buffer. | |
113 | * | |
114 | * We will be using cmpxchg soon to make all this lockless. | |
115 | * | |
116 | */ | |
117 | ||
499e5470 SR |
118 | /* Used for individual buffers (after the counter) */ |
119 | #define RB_BUFFER_OFF (1 << 20) | |
a3583244 | 120 | |
499e5470 | 121 | #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
033601a3 | 122 | |
e3d6bf0a | 123 | #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
67d34724 | 124 | #define RB_ALIGNMENT 4U |
334d4169 | 125 | #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
c7b09308 | 126 | #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
334d4169 | 127 | |
649508f6 | 128 | #ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS |
2271048d SR |
129 | # define RB_FORCE_8BYTE_ALIGNMENT 0 |
130 | # define RB_ARCH_ALIGNMENT RB_ALIGNMENT | |
131 | #else | |
132 | # define RB_FORCE_8BYTE_ALIGNMENT 1 | |
133 | # define RB_ARCH_ALIGNMENT 8U | |
134 | #endif | |
135 | ||
649508f6 JH |
136 | #define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT) |
137 | ||
334d4169 LJ |
138 | /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
139 | #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX | |
7a8e76a3 SR |
140 | |
141 | enum { | |
142 | RB_LEN_TIME_EXTEND = 8, | |
143 | RB_LEN_TIME_STAMP = 16, | |
144 | }; | |
145 | ||
69d1b839 SR |
146 | #define skip_time_extend(event) \ |
147 | ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) | |
148 | ||
2d622719 TZ |
149 | static inline int rb_null_event(struct ring_buffer_event *event) |
150 | { | |
a1863c21 | 151 | return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
2d622719 TZ |
152 | } |
153 | ||
154 | static void rb_event_set_padding(struct ring_buffer_event *event) | |
155 | { | |
a1863c21 | 156 | /* padding has a NULL time_delta */ |
334d4169 | 157 | event->type_len = RINGBUF_TYPE_PADDING; |
2d622719 TZ |
158 | event->time_delta = 0; |
159 | } | |
160 | ||
34a148bf | 161 | static unsigned |
2d622719 | 162 | rb_event_data_length(struct ring_buffer_event *event) |
7a8e76a3 SR |
163 | { |
164 | unsigned length; | |
165 | ||
334d4169 LJ |
166 | if (event->type_len) |
167 | length = event->type_len * RB_ALIGNMENT; | |
2d622719 TZ |
168 | else |
169 | length = event->array[0]; | |
170 | return length + RB_EVNT_HDR_SIZE; | |
171 | } | |
172 | ||
69d1b839 SR |
173 | /* |
174 | * Return the length of the given event. Will return | |
175 | * the length of the time extend if the event is a | |
176 | * time extend. | |
177 | */ | |
178 | static inline unsigned | |
2d622719 TZ |
179 | rb_event_length(struct ring_buffer_event *event) |
180 | { | |
334d4169 | 181 | switch (event->type_len) { |
7a8e76a3 | 182 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
183 | if (rb_null_event(event)) |
184 | /* undefined */ | |
185 | return -1; | |
334d4169 | 186 | return event->array[0] + RB_EVNT_HDR_SIZE; |
7a8e76a3 SR |
187 | |
188 | case RINGBUF_TYPE_TIME_EXTEND: | |
189 | return RB_LEN_TIME_EXTEND; | |
190 | ||
191 | case RINGBUF_TYPE_TIME_STAMP: | |
192 | return RB_LEN_TIME_STAMP; | |
193 | ||
194 | case RINGBUF_TYPE_DATA: | |
2d622719 | 195 | return rb_event_data_length(event); |
7a8e76a3 SR |
196 | default: |
197 | BUG(); | |
198 | } | |
199 | /* not hit */ | |
200 | return 0; | |
201 | } | |
202 | ||
69d1b839 SR |
203 | /* |
204 | * Return total length of time extend and data, | |
205 | * or just the event length for all other events. | |
206 | */ | |
207 | static inline unsigned | |
208 | rb_event_ts_length(struct ring_buffer_event *event) | |
209 | { | |
210 | unsigned len = 0; | |
211 | ||
212 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { | |
213 | /* time extends include the data event after it */ | |
214 | len = RB_LEN_TIME_EXTEND; | |
215 | event = skip_time_extend(event); | |
216 | } | |
217 | return len + rb_event_length(event); | |
218 | } | |
219 | ||
7a8e76a3 SR |
220 | /** |
221 | * ring_buffer_event_length - return the length of the event | |
222 | * @event: the event to get the length of | |
69d1b839 SR |
223 | * |
224 | * Returns the size of the data load of a data event. | |
225 | * If the event is something other than a data event, it | |
226 | * returns the size of the event itself. With the exception | |
227 | * of a TIME EXTEND, where it still returns the size of the | |
228 | * data load of the data event after it. | |
7a8e76a3 SR |
229 | */ |
230 | unsigned ring_buffer_event_length(struct ring_buffer_event *event) | |
231 | { | |
69d1b839 SR |
232 | unsigned length; |
233 | ||
234 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) | |
235 | event = skip_time_extend(event); | |
236 | ||
237 | length = rb_event_length(event); | |
334d4169 | 238 | if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
465634ad RR |
239 | return length; |
240 | length -= RB_EVNT_HDR_SIZE; | |
241 | if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) | |
242 | length -= sizeof(event->array[0]); | |
243 | return length; | |
7a8e76a3 | 244 | } |
c4f50183 | 245 | EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
7a8e76a3 SR |
246 | |
247 | /* inline for ring buffer fast paths */ | |
34a148bf | 248 | static void * |
7a8e76a3 SR |
249 | rb_event_data(struct ring_buffer_event *event) |
250 | { | |
69d1b839 SR |
251 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
252 | event = skip_time_extend(event); | |
334d4169 | 253 | BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
7a8e76a3 | 254 | /* If length is in len field, then array[0] has the data */ |
334d4169 | 255 | if (event->type_len) |
7a8e76a3 SR |
256 | return (void *)&event->array[0]; |
257 | /* Otherwise length is in array[0] and array[1] has the data */ | |
258 | return (void *)&event->array[1]; | |
259 | } | |
260 | ||
261 | /** | |
262 | * ring_buffer_event_data - return the data of the event | |
263 | * @event: the event to get the data from | |
264 | */ | |
265 | void *ring_buffer_event_data(struct ring_buffer_event *event) | |
266 | { | |
267 | return rb_event_data(event); | |
268 | } | |
c4f50183 | 269 | EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
7a8e76a3 SR |
270 | |
271 | #define for_each_buffer_cpu(buffer, cpu) \ | |
9e01c1b7 | 272 | for_each_cpu(cpu, buffer->cpumask) |
7a8e76a3 SR |
273 | |
274 | #define TS_SHIFT 27 | |
275 | #define TS_MASK ((1ULL << TS_SHIFT) - 1) | |
276 | #define TS_DELTA_TEST (~TS_MASK) | |
277 | ||
66a8cb95 SR |
278 | /* Flag when events were overwritten */ |
279 | #define RB_MISSED_EVENTS (1 << 31) | |
ff0ff84a SR |
280 | /* Missed count stored at end */ |
281 | #define RB_MISSED_STORED (1 << 30) | |
66a8cb95 | 282 | |
abc9b56d | 283 | struct buffer_data_page { |
e4c2ce82 | 284 | u64 time_stamp; /* page time stamp */ |
c3706f00 | 285 | local_t commit; /* write committed index */ |
649508f6 | 286 | unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
abc9b56d SR |
287 | }; |
288 | ||
77ae365e SR |
289 | /* |
290 | * Note, the buffer_page list must be first. The buffer pages | |
291 | * are allocated in cache lines, which means that each buffer | |
292 | * page will be at the beginning of a cache line, and thus | |
293 | * the least significant bits will be zero. We use this to | |
294 | * add flags in the list struct pointers, to make the ring buffer | |
295 | * lockless. | |
296 | */ | |
abc9b56d | 297 | struct buffer_page { |
778c55d4 | 298 | struct list_head list; /* list of buffer pages */ |
abc9b56d | 299 | local_t write; /* index for next write */ |
6f807acd | 300 | unsigned read; /* index for next read */ |
778c55d4 | 301 | local_t entries; /* entries on this page */ |
ff0ff84a | 302 | unsigned long real_end; /* real end of data */ |
abc9b56d | 303 | struct buffer_data_page *page; /* Actual data page */ |
7a8e76a3 SR |
304 | }; |
305 | ||
77ae365e SR |
306 | /* |
307 | * The buffer page counters, write and entries, must be reset | |
308 | * atomically when crossing page boundaries. To synchronize this | |
309 | * update, two counters are inserted into the number. One is | |
310 | * the actual counter for the write position or count on the page. | |
311 | * | |
312 | * The other is a counter of updaters. Before an update happens | |
313 | * the update partition of the counter is incremented. This will | |
314 | * allow the updater to update the counter atomically. | |
315 | * | |
316 | * The counter is 20 bits, and the state data is 12. | |
317 | */ | |
318 | #define RB_WRITE_MASK 0xfffff | |
319 | #define RB_WRITE_INTCNT (1 << 20) | |
320 | ||
044fa782 | 321 | static void rb_init_page(struct buffer_data_page *bpage) |
abc9b56d | 322 | { |
044fa782 | 323 | local_set(&bpage->commit, 0); |
abc9b56d SR |
324 | } |
325 | ||
474d32b6 SR |
326 | /** |
327 | * ring_buffer_page_len - the size of data on the page. | |
328 | * @page: The page to read | |
329 | * | |
330 | * Returns the amount of data on the page, including buffer page header. | |
331 | */ | |
ef7a4a16 SR |
332 | size_t ring_buffer_page_len(void *page) |
333 | { | |
474d32b6 SR |
334 | return local_read(&((struct buffer_data_page *)page)->commit) |
335 | + BUF_PAGE_HDR_SIZE; | |
ef7a4a16 SR |
336 | } |
337 | ||
ed56829c SR |
338 | /* |
339 | * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing | |
340 | * this issue out. | |
341 | */ | |
34a148bf | 342 | static void free_buffer_page(struct buffer_page *bpage) |
ed56829c | 343 | { |
34a148bf | 344 | free_page((unsigned long)bpage->page); |
e4c2ce82 | 345 | kfree(bpage); |
ed56829c SR |
346 | } |
347 | ||
7a8e76a3 SR |
348 | /* |
349 | * We need to fit the time_stamp delta into 27 bits. | |
350 | */ | |
351 | static inline int test_time_stamp(u64 delta) | |
352 | { | |
353 | if (delta & TS_DELTA_TEST) | |
354 | return 1; | |
355 | return 0; | |
356 | } | |
357 | ||
474d32b6 | 358 | #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
7a8e76a3 | 359 | |
be957c44 SR |
360 | /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
361 | #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) | |
362 | ||
d1b182a8 SR |
363 | int ring_buffer_print_page_header(struct trace_seq *s) |
364 | { | |
365 | struct buffer_data_page field; | |
c0cd93aa SRRH |
366 | |
367 | trace_seq_printf(s, "\tfield: u64 timestamp;\t" | |
368 | "offset:0;\tsize:%u;\tsigned:%u;\n", | |
369 | (unsigned int)sizeof(field.time_stamp), | |
370 | (unsigned int)is_signed_type(u64)); | |
371 | ||
372 | trace_seq_printf(s, "\tfield: local_t commit;\t" | |
373 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
374 | (unsigned int)offsetof(typeof(field), commit), | |
375 | (unsigned int)sizeof(field.commit), | |
376 | (unsigned int)is_signed_type(long)); | |
377 | ||
378 | trace_seq_printf(s, "\tfield: int overwrite;\t" | |
379 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
380 | (unsigned int)offsetof(typeof(field), commit), | |
381 | 1, | |
382 | (unsigned int)is_signed_type(long)); | |
383 | ||
384 | trace_seq_printf(s, "\tfield: char data;\t" | |
385 | "offset:%u;\tsize:%u;\tsigned:%u;\n", | |
386 | (unsigned int)offsetof(typeof(field), data), | |
387 | (unsigned int)BUF_PAGE_SIZE, | |
388 | (unsigned int)is_signed_type(char)); | |
389 | ||
390 | return !trace_seq_has_overflowed(s); | |
d1b182a8 SR |
391 | } |
392 | ||
15693458 SRRH |
393 | struct rb_irq_work { |
394 | struct irq_work work; | |
395 | wait_queue_head_t waiters; | |
1e0d6714 | 396 | wait_queue_head_t full_waiters; |
15693458 | 397 | bool waiters_pending; |
1e0d6714 SRRH |
398 | bool full_waiters_pending; |
399 | bool wakeup_full; | |
15693458 SRRH |
400 | }; |
401 | ||
a497adb4 SRRH |
402 | /* |
403 | * Used for which event context the event is in. | |
404 | * NMI = 0 | |
405 | * IRQ = 1 | |
406 | * SOFTIRQ = 2 | |
407 | * NORMAL = 3 | |
408 | * | |
409 | * See trace_recursive_lock() comment below for more details. | |
410 | */ | |
411 | enum { | |
412 | RB_CTX_NMI, | |
413 | RB_CTX_IRQ, | |
414 | RB_CTX_SOFTIRQ, | |
415 | RB_CTX_NORMAL, | |
416 | RB_CTX_MAX | |
417 | }; | |
418 | ||
7a8e76a3 SR |
419 | /* |
420 | * head_page == tail_page && head == tail then buffer is empty. | |
421 | */ | |
422 | struct ring_buffer_per_cpu { | |
423 | int cpu; | |
985023de | 424 | atomic_t record_disabled; |
7a8e76a3 | 425 | struct ring_buffer *buffer; |
5389f6fa | 426 | raw_spinlock_t reader_lock; /* serialize readers */ |
445c8951 | 427 | arch_spinlock_t lock; |
7a8e76a3 | 428 | struct lock_class_key lock_key; |
438ced17 | 429 | unsigned int nr_pages; |
58a09ec6 | 430 | unsigned int current_context; |
3adc54fa | 431 | struct list_head *pages; |
6f807acd SR |
432 | struct buffer_page *head_page; /* read from head */ |
433 | struct buffer_page *tail_page; /* write to tail */ | |
c3706f00 | 434 | struct buffer_page *commit_page; /* committed pages */ |
d769041f | 435 | struct buffer_page *reader_page; |
66a8cb95 SR |
436 | unsigned long lost_events; |
437 | unsigned long last_overrun; | |
c64e148a | 438 | local_t entries_bytes; |
e4906eff | 439 | local_t entries; |
884bfe89 SP |
440 | local_t overrun; |
441 | local_t commit_overrun; | |
442 | local_t dropped_events; | |
fa743953 SR |
443 | local_t committing; |
444 | local_t commits; | |
77ae365e | 445 | unsigned long read; |
c64e148a | 446 | unsigned long read_bytes; |
7a8e76a3 SR |
447 | u64 write_stamp; |
448 | u64 read_stamp; | |
438ced17 VN |
449 | /* ring buffer pages to update, > 0 to add, < 0 to remove */ |
450 | int nr_pages_to_update; | |
451 | struct list_head new_pages; /* new pages to add */ | |
83f40318 | 452 | struct work_struct update_pages_work; |
05fdd70d | 453 | struct completion update_done; |
15693458 SRRH |
454 | |
455 | struct rb_irq_work irq_work; | |
7a8e76a3 SR |
456 | }; |
457 | ||
458 | struct ring_buffer { | |
7a8e76a3 SR |
459 | unsigned flags; |
460 | int cpus; | |
7a8e76a3 | 461 | atomic_t record_disabled; |
83f40318 | 462 | atomic_t resize_disabled; |
00f62f61 | 463 | cpumask_var_t cpumask; |
7a8e76a3 | 464 | |
1f8a6a10 PZ |
465 | struct lock_class_key *reader_lock_key; |
466 | ||
7a8e76a3 SR |
467 | struct mutex mutex; |
468 | ||
469 | struct ring_buffer_per_cpu **buffers; | |
554f786e | 470 | |
59222efe | 471 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
472 | struct notifier_block cpu_notify; |
473 | #endif | |
37886f6a | 474 | u64 (*clock)(void); |
15693458 SRRH |
475 | |
476 | struct rb_irq_work irq_work; | |
7a8e76a3 SR |
477 | }; |
478 | ||
479 | struct ring_buffer_iter { | |
480 | struct ring_buffer_per_cpu *cpu_buffer; | |
481 | unsigned long head; | |
482 | struct buffer_page *head_page; | |
492a74f4 SR |
483 | struct buffer_page *cache_reader_page; |
484 | unsigned long cache_read; | |
7a8e76a3 SR |
485 | u64 read_stamp; |
486 | }; | |
487 | ||
15693458 SRRH |
488 | /* |
489 | * rb_wake_up_waiters - wake up tasks waiting for ring buffer input | |
490 | * | |
491 | * Schedules a delayed work to wake up any task that is blocked on the | |
492 | * ring buffer waiters queue. | |
493 | */ | |
494 | static void rb_wake_up_waiters(struct irq_work *work) | |
495 | { | |
496 | struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); | |
497 | ||
498 | wake_up_all(&rbwork->waiters); | |
1e0d6714 SRRH |
499 | if (rbwork->wakeup_full) { |
500 | rbwork->wakeup_full = false; | |
501 | wake_up_all(&rbwork->full_waiters); | |
502 | } | |
15693458 SRRH |
503 | } |
504 | ||
505 | /** | |
506 | * ring_buffer_wait - wait for input to the ring buffer | |
507 | * @buffer: buffer to wait on | |
508 | * @cpu: the cpu buffer to wait on | |
e30f53aa | 509 | * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS |
15693458 SRRH |
510 | * |
511 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
512 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
513 | * it will wait for data to be added to a specific cpu buffer. | |
514 | */ | |
e30f53aa | 515 | int ring_buffer_wait(struct ring_buffer *buffer, int cpu, bool full) |
15693458 | 516 | { |
e30f53aa | 517 | struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer); |
15693458 SRRH |
518 | DEFINE_WAIT(wait); |
519 | struct rb_irq_work *work; | |
e30f53aa | 520 | int ret = 0; |
15693458 SRRH |
521 | |
522 | /* | |
523 | * Depending on what the caller is waiting for, either any | |
524 | * data in any cpu buffer, or a specific buffer, put the | |
525 | * caller on the appropriate wait queue. | |
526 | */ | |
1e0d6714 | 527 | if (cpu == RING_BUFFER_ALL_CPUS) { |
15693458 | 528 | work = &buffer->irq_work; |
1e0d6714 SRRH |
529 | /* Full only makes sense on per cpu reads */ |
530 | full = false; | |
531 | } else { | |
8b8b3683 SRRH |
532 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
533 | return -ENODEV; | |
15693458 SRRH |
534 | cpu_buffer = buffer->buffers[cpu]; |
535 | work = &cpu_buffer->irq_work; | |
536 | } | |
537 | ||
538 | ||
e30f53aa | 539 | while (true) { |
1e0d6714 SRRH |
540 | if (full) |
541 | prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); | |
542 | else | |
543 | prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); | |
e30f53aa RV |
544 | |
545 | /* | |
546 | * The events can happen in critical sections where | |
547 | * checking a work queue can cause deadlocks. | |
548 | * After adding a task to the queue, this flag is set | |
549 | * only to notify events to try to wake up the queue | |
550 | * using irq_work. | |
551 | * | |
552 | * We don't clear it even if the buffer is no longer | |
553 | * empty. The flag only causes the next event to run | |
554 | * irq_work to do the work queue wake up. The worse | |
555 | * that can happen if we race with !trace_empty() is that | |
556 | * an event will cause an irq_work to try to wake up | |
557 | * an empty queue. | |
558 | * | |
559 | * There's no reason to protect this flag either, as | |
560 | * the work queue and irq_work logic will do the necessary | |
561 | * synchronization for the wake ups. The only thing | |
562 | * that is necessary is that the wake up happens after | |
563 | * a task has been queued. It's OK for spurious wake ups. | |
564 | */ | |
1e0d6714 SRRH |
565 | if (full) |
566 | work->full_waiters_pending = true; | |
567 | else | |
568 | work->waiters_pending = true; | |
e30f53aa RV |
569 | |
570 | if (signal_pending(current)) { | |
571 | ret = -EINTR; | |
572 | break; | |
573 | } | |
574 | ||
575 | if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) | |
576 | break; | |
577 | ||
578 | if (cpu != RING_BUFFER_ALL_CPUS && | |
579 | !ring_buffer_empty_cpu(buffer, cpu)) { | |
580 | unsigned long flags; | |
581 | bool pagebusy; | |
582 | ||
583 | if (!full) | |
584 | break; | |
585 | ||
586 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); | |
587 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; | |
588 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); | |
589 | ||
590 | if (!pagebusy) | |
591 | break; | |
592 | } | |
15693458 | 593 | |
15693458 | 594 | schedule(); |
e30f53aa | 595 | } |
15693458 | 596 | |
1e0d6714 SRRH |
597 | if (full) |
598 | finish_wait(&work->full_waiters, &wait); | |
599 | else | |
600 | finish_wait(&work->waiters, &wait); | |
e30f53aa RV |
601 | |
602 | return ret; | |
15693458 SRRH |
603 | } |
604 | ||
605 | /** | |
606 | * ring_buffer_poll_wait - poll on buffer input | |
607 | * @buffer: buffer to wait on | |
608 | * @cpu: the cpu buffer to wait on | |
609 | * @filp: the file descriptor | |
610 | * @poll_table: The poll descriptor | |
611 | * | |
612 | * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon | |
613 | * as data is added to any of the @buffer's cpu buffers. Otherwise | |
614 | * it will wait for data to be added to a specific cpu buffer. | |
615 | * | |
616 | * Returns POLLIN | POLLRDNORM if data exists in the buffers, | |
617 | * zero otherwise. | |
618 | */ | |
619 | int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu, | |
620 | struct file *filp, poll_table *poll_table) | |
621 | { | |
622 | struct ring_buffer_per_cpu *cpu_buffer; | |
623 | struct rb_irq_work *work; | |
624 | ||
15693458 SRRH |
625 | if (cpu == RING_BUFFER_ALL_CPUS) |
626 | work = &buffer->irq_work; | |
627 | else { | |
6721cb60 SRRH |
628 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
629 | return -EINVAL; | |
630 | ||
15693458 SRRH |
631 | cpu_buffer = buffer->buffers[cpu]; |
632 | work = &cpu_buffer->irq_work; | |
633 | } | |
634 | ||
15693458 | 635 | poll_wait(filp, &work->waiters, poll_table); |
4ce97dbf JB |
636 | work->waiters_pending = true; |
637 | /* | |
638 | * There's a tight race between setting the waiters_pending and | |
639 | * checking if the ring buffer is empty. Once the waiters_pending bit | |
640 | * is set, the next event will wake the task up, but we can get stuck | |
641 | * if there's only a single event in. | |
642 | * | |
643 | * FIXME: Ideally, we need a memory barrier on the writer side as well, | |
644 | * but adding a memory barrier to all events will cause too much of a | |
645 | * performance hit in the fast path. We only need a memory barrier when | |
646 | * the buffer goes from empty to having content. But as this race is | |
647 | * extremely small, and it's not a problem if another event comes in, we | |
648 | * will fix it later. | |
649 | */ | |
650 | smp_mb(); | |
15693458 SRRH |
651 | |
652 | if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || | |
653 | (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) | |
654 | return POLLIN | POLLRDNORM; | |
655 | return 0; | |
656 | } | |
657 | ||
f536aafc | 658 | /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
077c5407 SR |
659 | #define RB_WARN_ON(b, cond) \ |
660 | ({ \ | |
661 | int _____ret = unlikely(cond); \ | |
662 | if (_____ret) { \ | |
663 | if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ | |
664 | struct ring_buffer_per_cpu *__b = \ | |
665 | (void *)b; \ | |
666 | atomic_inc(&__b->buffer->record_disabled); \ | |
667 | } else \ | |
668 | atomic_inc(&b->record_disabled); \ | |
669 | WARN_ON(1); \ | |
670 | } \ | |
671 | _____ret; \ | |
3e89c7bb | 672 | }) |
f536aafc | 673 | |
37886f6a SR |
674 | /* Up this if you want to test the TIME_EXTENTS and normalization */ |
675 | #define DEBUG_SHIFT 0 | |
676 | ||
6d3f1e12 | 677 | static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
88eb0125 SR |
678 | { |
679 | /* shift to debug/test normalization and TIME_EXTENTS */ | |
680 | return buffer->clock() << DEBUG_SHIFT; | |
681 | } | |
682 | ||
37886f6a SR |
683 | u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
684 | { | |
685 | u64 time; | |
686 | ||
687 | preempt_disable_notrace(); | |
6d3f1e12 | 688 | time = rb_time_stamp(buffer); |
37886f6a SR |
689 | preempt_enable_no_resched_notrace(); |
690 | ||
691 | return time; | |
692 | } | |
693 | EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); | |
694 | ||
695 | void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, | |
696 | int cpu, u64 *ts) | |
697 | { | |
698 | /* Just stupid testing the normalize function and deltas */ | |
699 | *ts >>= DEBUG_SHIFT; | |
700 | } | |
701 | EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); | |
702 | ||
77ae365e SR |
703 | /* |
704 | * Making the ring buffer lockless makes things tricky. | |
705 | * Although writes only happen on the CPU that they are on, | |
706 | * and they only need to worry about interrupts. Reads can | |
707 | * happen on any CPU. | |
708 | * | |
709 | * The reader page is always off the ring buffer, but when the | |
710 | * reader finishes with a page, it needs to swap its page with | |
711 | * a new one from the buffer. The reader needs to take from | |
712 | * the head (writes go to the tail). But if a writer is in overwrite | |
713 | * mode and wraps, it must push the head page forward. | |
714 | * | |
715 | * Here lies the problem. | |
716 | * | |
717 | * The reader must be careful to replace only the head page, and | |
718 | * not another one. As described at the top of the file in the | |
719 | * ASCII art, the reader sets its old page to point to the next | |
720 | * page after head. It then sets the page after head to point to | |
721 | * the old reader page. But if the writer moves the head page | |
722 | * during this operation, the reader could end up with the tail. | |
723 | * | |
724 | * We use cmpxchg to help prevent this race. We also do something | |
725 | * special with the page before head. We set the LSB to 1. | |
726 | * | |
727 | * When the writer must push the page forward, it will clear the | |
728 | * bit that points to the head page, move the head, and then set | |
729 | * the bit that points to the new head page. | |
730 | * | |
731 | * We also don't want an interrupt coming in and moving the head | |
732 | * page on another writer. Thus we use the second LSB to catch | |
733 | * that too. Thus: | |
734 | * | |
735 | * head->list->prev->next bit 1 bit 0 | |
736 | * ------- ------- | |
737 | * Normal page 0 0 | |
738 | * Points to head page 0 1 | |
739 | * New head page 1 0 | |
740 | * | |
741 | * Note we can not trust the prev pointer of the head page, because: | |
742 | * | |
743 | * +----+ +-----+ +-----+ | |
744 | * | |------>| T |---X--->| N | | |
745 | * | |<------| | | | | |
746 | * +----+ +-----+ +-----+ | |
747 | * ^ ^ | | |
748 | * | +-----+ | | | |
749 | * +----------| R |----------+ | | |
750 | * | |<-----------+ | |
751 | * +-----+ | |
752 | * | |
753 | * Key: ---X--> HEAD flag set in pointer | |
754 | * T Tail page | |
755 | * R Reader page | |
756 | * N Next page | |
757 | * | |
758 | * (see __rb_reserve_next() to see where this happens) | |
759 | * | |
760 | * What the above shows is that the reader just swapped out | |
761 | * the reader page with a page in the buffer, but before it | |
762 | * could make the new header point back to the new page added | |
763 | * it was preempted by a writer. The writer moved forward onto | |
764 | * the new page added by the reader and is about to move forward | |
765 | * again. | |
766 | * | |
767 | * You can see, it is legitimate for the previous pointer of | |
768 | * the head (or any page) not to point back to itself. But only | |
769 | * temporarially. | |
770 | */ | |
771 | ||
772 | #define RB_PAGE_NORMAL 0UL | |
773 | #define RB_PAGE_HEAD 1UL | |
774 | #define RB_PAGE_UPDATE 2UL | |
775 | ||
776 | ||
777 | #define RB_FLAG_MASK 3UL | |
778 | ||
779 | /* PAGE_MOVED is not part of the mask */ | |
780 | #define RB_PAGE_MOVED 4UL | |
781 | ||
782 | /* | |
783 | * rb_list_head - remove any bit | |
784 | */ | |
785 | static struct list_head *rb_list_head(struct list_head *list) | |
786 | { | |
787 | unsigned long val = (unsigned long)list; | |
788 | ||
789 | return (struct list_head *)(val & ~RB_FLAG_MASK); | |
790 | } | |
791 | ||
792 | /* | |
6d3f1e12 | 793 | * rb_is_head_page - test if the given page is the head page |
77ae365e SR |
794 | * |
795 | * Because the reader may move the head_page pointer, we can | |
796 | * not trust what the head page is (it may be pointing to | |
797 | * the reader page). But if the next page is a header page, | |
798 | * its flags will be non zero. | |
799 | */ | |
42b16b3f | 800 | static inline int |
77ae365e SR |
801 | rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
802 | struct buffer_page *page, struct list_head *list) | |
803 | { | |
804 | unsigned long val; | |
805 | ||
806 | val = (unsigned long)list->next; | |
807 | ||
808 | if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) | |
809 | return RB_PAGE_MOVED; | |
810 | ||
811 | return val & RB_FLAG_MASK; | |
812 | } | |
813 | ||
814 | /* | |
815 | * rb_is_reader_page | |
816 | * | |
817 | * The unique thing about the reader page, is that, if the | |
818 | * writer is ever on it, the previous pointer never points | |
819 | * back to the reader page. | |
820 | */ | |
821 | static int rb_is_reader_page(struct buffer_page *page) | |
822 | { | |
823 | struct list_head *list = page->list.prev; | |
824 | ||
825 | return rb_list_head(list->next) != &page->list; | |
826 | } | |
827 | ||
828 | /* | |
829 | * rb_set_list_to_head - set a list_head to be pointing to head. | |
830 | */ | |
831 | static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, | |
832 | struct list_head *list) | |
833 | { | |
834 | unsigned long *ptr; | |
835 | ||
836 | ptr = (unsigned long *)&list->next; | |
837 | *ptr |= RB_PAGE_HEAD; | |
838 | *ptr &= ~RB_PAGE_UPDATE; | |
839 | } | |
840 | ||
841 | /* | |
842 | * rb_head_page_activate - sets up head page | |
843 | */ | |
844 | static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) | |
845 | { | |
846 | struct buffer_page *head; | |
847 | ||
848 | head = cpu_buffer->head_page; | |
849 | if (!head) | |
850 | return; | |
851 | ||
852 | /* | |
853 | * Set the previous list pointer to have the HEAD flag. | |
854 | */ | |
855 | rb_set_list_to_head(cpu_buffer, head->list.prev); | |
856 | } | |
857 | ||
858 | static void rb_list_head_clear(struct list_head *list) | |
859 | { | |
860 | unsigned long *ptr = (unsigned long *)&list->next; | |
861 | ||
862 | *ptr &= ~RB_FLAG_MASK; | |
863 | } | |
864 | ||
865 | /* | |
866 | * rb_head_page_dactivate - clears head page ptr (for free list) | |
867 | */ | |
868 | static void | |
869 | rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) | |
870 | { | |
871 | struct list_head *hd; | |
872 | ||
873 | /* Go through the whole list and clear any pointers found. */ | |
874 | rb_list_head_clear(cpu_buffer->pages); | |
875 | ||
876 | list_for_each(hd, cpu_buffer->pages) | |
877 | rb_list_head_clear(hd); | |
878 | } | |
879 | ||
880 | static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, | |
881 | struct buffer_page *head, | |
882 | struct buffer_page *prev, | |
883 | int old_flag, int new_flag) | |
884 | { | |
885 | struct list_head *list; | |
886 | unsigned long val = (unsigned long)&head->list; | |
887 | unsigned long ret; | |
888 | ||
889 | list = &prev->list; | |
890 | ||
891 | val &= ~RB_FLAG_MASK; | |
892 | ||
08a40816 SR |
893 | ret = cmpxchg((unsigned long *)&list->next, |
894 | val | old_flag, val | new_flag); | |
77ae365e SR |
895 | |
896 | /* check if the reader took the page */ | |
897 | if ((ret & ~RB_FLAG_MASK) != val) | |
898 | return RB_PAGE_MOVED; | |
899 | ||
900 | return ret & RB_FLAG_MASK; | |
901 | } | |
902 | ||
903 | static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, | |
904 | struct buffer_page *head, | |
905 | struct buffer_page *prev, | |
906 | int old_flag) | |
907 | { | |
908 | return rb_head_page_set(cpu_buffer, head, prev, | |
909 | old_flag, RB_PAGE_UPDATE); | |
910 | } | |
911 | ||
912 | static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, | |
913 | struct buffer_page *head, | |
914 | struct buffer_page *prev, | |
915 | int old_flag) | |
916 | { | |
917 | return rb_head_page_set(cpu_buffer, head, prev, | |
918 | old_flag, RB_PAGE_HEAD); | |
919 | } | |
920 | ||
921 | static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, | |
922 | struct buffer_page *head, | |
923 | struct buffer_page *prev, | |
924 | int old_flag) | |
925 | { | |
926 | return rb_head_page_set(cpu_buffer, head, prev, | |
927 | old_flag, RB_PAGE_NORMAL); | |
928 | } | |
929 | ||
930 | static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, | |
931 | struct buffer_page **bpage) | |
932 | { | |
933 | struct list_head *p = rb_list_head((*bpage)->list.next); | |
934 | ||
935 | *bpage = list_entry(p, struct buffer_page, list); | |
936 | } | |
937 | ||
938 | static struct buffer_page * | |
939 | rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) | |
940 | { | |
941 | struct buffer_page *head; | |
942 | struct buffer_page *page; | |
943 | struct list_head *list; | |
944 | int i; | |
945 | ||
946 | if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) | |
947 | return NULL; | |
948 | ||
949 | /* sanity check */ | |
950 | list = cpu_buffer->pages; | |
951 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) | |
952 | return NULL; | |
953 | ||
954 | page = head = cpu_buffer->head_page; | |
955 | /* | |
956 | * It is possible that the writer moves the header behind | |
957 | * where we started, and we miss in one loop. | |
958 | * A second loop should grab the header, but we'll do | |
959 | * three loops just because I'm paranoid. | |
960 | */ | |
961 | for (i = 0; i < 3; i++) { | |
962 | do { | |
963 | if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { | |
964 | cpu_buffer->head_page = page; | |
965 | return page; | |
966 | } | |
967 | rb_inc_page(cpu_buffer, &page); | |
968 | } while (page != head); | |
969 | } | |
970 | ||
971 | RB_WARN_ON(cpu_buffer, 1); | |
972 | ||
973 | return NULL; | |
974 | } | |
975 | ||
976 | static int rb_head_page_replace(struct buffer_page *old, | |
977 | struct buffer_page *new) | |
978 | { | |
979 | unsigned long *ptr = (unsigned long *)&old->list.prev->next; | |
980 | unsigned long val; | |
981 | unsigned long ret; | |
982 | ||
983 | val = *ptr & ~RB_FLAG_MASK; | |
984 | val |= RB_PAGE_HEAD; | |
985 | ||
08a40816 | 986 | ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
77ae365e SR |
987 | |
988 | return ret == val; | |
989 | } | |
990 | ||
991 | /* | |
992 | * rb_tail_page_update - move the tail page forward | |
993 | * | |
994 | * Returns 1 if moved tail page, 0 if someone else did. | |
995 | */ | |
996 | static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, | |
997 | struct buffer_page *tail_page, | |
998 | struct buffer_page *next_page) | |
999 | { | |
1000 | struct buffer_page *old_tail; | |
1001 | unsigned long old_entries; | |
1002 | unsigned long old_write; | |
1003 | int ret = 0; | |
1004 | ||
1005 | /* | |
1006 | * The tail page now needs to be moved forward. | |
1007 | * | |
1008 | * We need to reset the tail page, but without messing | |
1009 | * with possible erasing of data brought in by interrupts | |
1010 | * that have moved the tail page and are currently on it. | |
1011 | * | |
1012 | * We add a counter to the write field to denote this. | |
1013 | */ | |
1014 | old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); | |
1015 | old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); | |
1016 | ||
1017 | /* | |
1018 | * Just make sure we have seen our old_write and synchronize | |
1019 | * with any interrupts that come in. | |
1020 | */ | |
1021 | barrier(); | |
1022 | ||
1023 | /* | |
1024 | * If the tail page is still the same as what we think | |
1025 | * it is, then it is up to us to update the tail | |
1026 | * pointer. | |
1027 | */ | |
1028 | if (tail_page == cpu_buffer->tail_page) { | |
1029 | /* Zero the write counter */ | |
1030 | unsigned long val = old_write & ~RB_WRITE_MASK; | |
1031 | unsigned long eval = old_entries & ~RB_WRITE_MASK; | |
1032 | ||
1033 | /* | |
1034 | * This will only succeed if an interrupt did | |
1035 | * not come in and change it. In which case, we | |
1036 | * do not want to modify it. | |
da706d8b LJ |
1037 | * |
1038 | * We add (void) to let the compiler know that we do not care | |
1039 | * about the return value of these functions. We use the | |
1040 | * cmpxchg to only update if an interrupt did not already | |
1041 | * do it for us. If the cmpxchg fails, we don't care. | |
77ae365e | 1042 | */ |
da706d8b LJ |
1043 | (void)local_cmpxchg(&next_page->write, old_write, val); |
1044 | (void)local_cmpxchg(&next_page->entries, old_entries, eval); | |
77ae365e SR |
1045 | |
1046 | /* | |
1047 | * No need to worry about races with clearing out the commit. | |
1048 | * it only can increment when a commit takes place. But that | |
1049 | * only happens in the outer most nested commit. | |
1050 | */ | |
1051 | local_set(&next_page->page->commit, 0); | |
1052 | ||
1053 | old_tail = cmpxchg(&cpu_buffer->tail_page, | |
1054 | tail_page, next_page); | |
1055 | ||
1056 | if (old_tail == tail_page) | |
1057 | ret = 1; | |
1058 | } | |
1059 | ||
1060 | return ret; | |
1061 | } | |
1062 | ||
1063 | static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, | |
1064 | struct buffer_page *bpage) | |
1065 | { | |
1066 | unsigned long val = (unsigned long)bpage; | |
1067 | ||
1068 | if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) | |
1069 | return 1; | |
1070 | ||
1071 | return 0; | |
1072 | } | |
1073 | ||
1074 | /** | |
1075 | * rb_check_list - make sure a pointer to a list has the last bits zero | |
1076 | */ | |
1077 | static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, | |
1078 | struct list_head *list) | |
1079 | { | |
1080 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) | |
1081 | return 1; | |
1082 | if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) | |
1083 | return 1; | |
1084 | return 0; | |
1085 | } | |
1086 | ||
7a8e76a3 | 1087 | /** |
d611851b | 1088 | * rb_check_pages - integrity check of buffer pages |
7a8e76a3 SR |
1089 | * @cpu_buffer: CPU buffer with pages to test |
1090 | * | |
c3706f00 | 1091 | * As a safety measure we check to make sure the data pages have not |
7a8e76a3 SR |
1092 | * been corrupted. |
1093 | */ | |
1094 | static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
1095 | { | |
3adc54fa | 1096 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1097 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1098 | |
308f7eeb SR |
1099 | /* Reset the head page if it exists */ |
1100 | if (cpu_buffer->head_page) | |
1101 | rb_set_head_page(cpu_buffer); | |
1102 | ||
77ae365e SR |
1103 | rb_head_page_deactivate(cpu_buffer); |
1104 | ||
3e89c7bb SR |
1105 | if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
1106 | return -1; | |
1107 | if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) | |
1108 | return -1; | |
7a8e76a3 | 1109 | |
77ae365e SR |
1110 | if (rb_check_list(cpu_buffer, head)) |
1111 | return -1; | |
1112 | ||
044fa782 | 1113 | list_for_each_entry_safe(bpage, tmp, head, list) { |
3e89c7bb | 1114 | if (RB_WARN_ON(cpu_buffer, |
044fa782 | 1115 | bpage->list.next->prev != &bpage->list)) |
3e89c7bb SR |
1116 | return -1; |
1117 | if (RB_WARN_ON(cpu_buffer, | |
044fa782 | 1118 | bpage->list.prev->next != &bpage->list)) |
3e89c7bb | 1119 | return -1; |
77ae365e SR |
1120 | if (rb_check_list(cpu_buffer, &bpage->list)) |
1121 | return -1; | |
7a8e76a3 SR |
1122 | } |
1123 | ||
77ae365e SR |
1124 | rb_head_page_activate(cpu_buffer); |
1125 | ||
7a8e76a3 SR |
1126 | return 0; |
1127 | } | |
1128 | ||
438ced17 | 1129 | static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu) |
7a8e76a3 | 1130 | { |
438ced17 | 1131 | int i; |
044fa782 | 1132 | struct buffer_page *bpage, *tmp; |
3adc54fa | 1133 | |
7a8e76a3 | 1134 | for (i = 0; i < nr_pages; i++) { |
7ea59064 | 1135 | struct page *page; |
d7ec4bfe VN |
1136 | /* |
1137 | * __GFP_NORETRY flag makes sure that the allocation fails | |
1138 | * gracefully without invoking oom-killer and the system is | |
1139 | * not destabilized. | |
1140 | */ | |
044fa782 | 1141 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
d7ec4bfe | 1142 | GFP_KERNEL | __GFP_NORETRY, |
438ced17 | 1143 | cpu_to_node(cpu)); |
044fa782 | 1144 | if (!bpage) |
e4c2ce82 | 1145 | goto free_pages; |
77ae365e | 1146 | |
438ced17 | 1147 | list_add(&bpage->list, pages); |
77ae365e | 1148 | |
438ced17 | 1149 | page = alloc_pages_node(cpu_to_node(cpu), |
d7ec4bfe | 1150 | GFP_KERNEL | __GFP_NORETRY, 0); |
7ea59064 | 1151 | if (!page) |
7a8e76a3 | 1152 | goto free_pages; |
7ea59064 | 1153 | bpage->page = page_address(page); |
044fa782 | 1154 | rb_init_page(bpage->page); |
7a8e76a3 SR |
1155 | } |
1156 | ||
438ced17 VN |
1157 | return 0; |
1158 | ||
1159 | free_pages: | |
1160 | list_for_each_entry_safe(bpage, tmp, pages, list) { | |
1161 | list_del_init(&bpage->list); | |
1162 | free_buffer_page(bpage); | |
1163 | } | |
1164 | ||
1165 | return -ENOMEM; | |
1166 | } | |
1167 | ||
1168 | static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, | |
1169 | unsigned nr_pages) | |
1170 | { | |
1171 | LIST_HEAD(pages); | |
1172 | ||
1173 | WARN_ON(!nr_pages); | |
1174 | ||
1175 | if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu)) | |
1176 | return -ENOMEM; | |
1177 | ||
3adc54fa SR |
1178 | /* |
1179 | * The ring buffer page list is a circular list that does not | |
1180 | * start and end with a list head. All page list items point to | |
1181 | * other pages. | |
1182 | */ | |
1183 | cpu_buffer->pages = pages.next; | |
1184 | list_del(&pages); | |
7a8e76a3 | 1185 | |
438ced17 VN |
1186 | cpu_buffer->nr_pages = nr_pages; |
1187 | ||
7a8e76a3 SR |
1188 | rb_check_pages(cpu_buffer); |
1189 | ||
1190 | return 0; | |
7a8e76a3 SR |
1191 | } |
1192 | ||
1193 | static struct ring_buffer_per_cpu * | |
438ced17 | 1194 | rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu) |
7a8e76a3 SR |
1195 | { |
1196 | struct ring_buffer_per_cpu *cpu_buffer; | |
044fa782 | 1197 | struct buffer_page *bpage; |
7ea59064 | 1198 | struct page *page; |
7a8e76a3 SR |
1199 | int ret; |
1200 | ||
1201 | cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), | |
1202 | GFP_KERNEL, cpu_to_node(cpu)); | |
1203 | if (!cpu_buffer) | |
1204 | return NULL; | |
1205 | ||
1206 | cpu_buffer->cpu = cpu; | |
1207 | cpu_buffer->buffer = buffer; | |
5389f6fa | 1208 | raw_spin_lock_init(&cpu_buffer->reader_lock); |
1f8a6a10 | 1209 | lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
edc35bd7 | 1210 | cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
83f40318 | 1211 | INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
05fdd70d | 1212 | init_completion(&cpu_buffer->update_done); |
15693458 | 1213 | init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1214 | init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
1e0d6714 | 1215 | init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
7a8e76a3 | 1216 | |
044fa782 | 1217 | bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
e4c2ce82 | 1218 | GFP_KERNEL, cpu_to_node(cpu)); |
044fa782 | 1219 | if (!bpage) |
e4c2ce82 SR |
1220 | goto fail_free_buffer; |
1221 | ||
77ae365e SR |
1222 | rb_check_bpage(cpu_buffer, bpage); |
1223 | ||
044fa782 | 1224 | cpu_buffer->reader_page = bpage; |
7ea59064 VN |
1225 | page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
1226 | if (!page) | |
e4c2ce82 | 1227 | goto fail_free_reader; |
7ea59064 | 1228 | bpage->page = page_address(page); |
044fa782 | 1229 | rb_init_page(bpage->page); |
e4c2ce82 | 1230 | |
d769041f | 1231 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
44b99462 | 1232 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
d769041f | 1233 | |
438ced17 | 1234 | ret = rb_allocate_pages(cpu_buffer, nr_pages); |
7a8e76a3 | 1235 | if (ret < 0) |
d769041f | 1236 | goto fail_free_reader; |
7a8e76a3 SR |
1237 | |
1238 | cpu_buffer->head_page | |
3adc54fa | 1239 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 1240 | cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
7a8e76a3 | 1241 | |
77ae365e SR |
1242 | rb_head_page_activate(cpu_buffer); |
1243 | ||
7a8e76a3 SR |
1244 | return cpu_buffer; |
1245 | ||
d769041f SR |
1246 | fail_free_reader: |
1247 | free_buffer_page(cpu_buffer->reader_page); | |
1248 | ||
7a8e76a3 SR |
1249 | fail_free_buffer: |
1250 | kfree(cpu_buffer); | |
1251 | return NULL; | |
1252 | } | |
1253 | ||
1254 | static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) | |
1255 | { | |
3adc54fa | 1256 | struct list_head *head = cpu_buffer->pages; |
044fa782 | 1257 | struct buffer_page *bpage, *tmp; |
7a8e76a3 | 1258 | |
d769041f SR |
1259 | free_buffer_page(cpu_buffer->reader_page); |
1260 | ||
77ae365e SR |
1261 | rb_head_page_deactivate(cpu_buffer); |
1262 | ||
3adc54fa SR |
1263 | if (head) { |
1264 | list_for_each_entry_safe(bpage, tmp, head, list) { | |
1265 | list_del_init(&bpage->list); | |
1266 | free_buffer_page(bpage); | |
1267 | } | |
1268 | bpage = list_entry(head, struct buffer_page, list); | |
044fa782 | 1269 | free_buffer_page(bpage); |
7a8e76a3 | 1270 | } |
3adc54fa | 1271 | |
7a8e76a3 SR |
1272 | kfree(cpu_buffer); |
1273 | } | |
1274 | ||
59222efe | 1275 | #ifdef CONFIG_HOTPLUG_CPU |
09c9e84d FW |
1276 | static int rb_cpu_notify(struct notifier_block *self, |
1277 | unsigned long action, void *hcpu); | |
554f786e SR |
1278 | #endif |
1279 | ||
7a8e76a3 | 1280 | /** |
d611851b | 1281 | * __ring_buffer_alloc - allocate a new ring_buffer |
68814b58 | 1282 | * @size: the size in bytes per cpu that is needed. |
7a8e76a3 SR |
1283 | * @flags: attributes to set for the ring buffer. |
1284 | * | |
1285 | * Currently the only flag that is available is the RB_FL_OVERWRITE | |
1286 | * flag. This flag means that the buffer will overwrite old data | |
1287 | * when the buffer wraps. If this flag is not set, the buffer will | |
1288 | * drop data when the tail hits the head. | |
1289 | */ | |
1f8a6a10 PZ |
1290 | struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
1291 | struct lock_class_key *key) | |
7a8e76a3 SR |
1292 | { |
1293 | struct ring_buffer *buffer; | |
1294 | int bsize; | |
438ced17 | 1295 | int cpu, nr_pages; |
7a8e76a3 SR |
1296 | |
1297 | /* keep it in its own cache line */ | |
1298 | buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), | |
1299 | GFP_KERNEL); | |
1300 | if (!buffer) | |
1301 | return NULL; | |
1302 | ||
9e01c1b7 RR |
1303 | if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
1304 | goto fail_free_buffer; | |
1305 | ||
438ced17 | 1306 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
7a8e76a3 | 1307 | buffer->flags = flags; |
37886f6a | 1308 | buffer->clock = trace_clock_local; |
1f8a6a10 | 1309 | buffer->reader_lock_key = key; |
7a8e76a3 | 1310 | |
15693458 | 1311 | init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
f1dc6725 | 1312 | init_waitqueue_head(&buffer->irq_work.waiters); |
15693458 | 1313 | |
7a8e76a3 | 1314 | /* need at least two pages */ |
438ced17 VN |
1315 | if (nr_pages < 2) |
1316 | nr_pages = 2; | |
7a8e76a3 | 1317 | |
3bf832ce FW |
1318 | /* |
1319 | * In case of non-hotplug cpu, if the ring-buffer is allocated | |
1320 | * in early initcall, it will not be notified of secondary cpus. | |
1321 | * In that off case, we need to allocate for all possible cpus. | |
1322 | */ | |
1323 | #ifdef CONFIG_HOTPLUG_CPU | |
d39ad278 | 1324 | cpu_notifier_register_begin(); |
554f786e | 1325 | cpumask_copy(buffer->cpumask, cpu_online_mask); |
3bf832ce FW |
1326 | #else |
1327 | cpumask_copy(buffer->cpumask, cpu_possible_mask); | |
1328 | #endif | |
7a8e76a3 SR |
1329 | buffer->cpus = nr_cpu_ids; |
1330 | ||
1331 | bsize = sizeof(void *) * nr_cpu_ids; | |
1332 | buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), | |
1333 | GFP_KERNEL); | |
1334 | if (!buffer->buffers) | |
9e01c1b7 | 1335 | goto fail_free_cpumask; |
7a8e76a3 SR |
1336 | |
1337 | for_each_buffer_cpu(buffer, cpu) { | |
1338 | buffer->buffers[cpu] = | |
438ced17 | 1339 | rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
7a8e76a3 SR |
1340 | if (!buffer->buffers[cpu]) |
1341 | goto fail_free_buffers; | |
1342 | } | |
1343 | ||
59222efe | 1344 | #ifdef CONFIG_HOTPLUG_CPU |
554f786e SR |
1345 | buffer->cpu_notify.notifier_call = rb_cpu_notify; |
1346 | buffer->cpu_notify.priority = 0; | |
d39ad278 SB |
1347 | __register_cpu_notifier(&buffer->cpu_notify); |
1348 | cpu_notifier_register_done(); | |
554f786e SR |
1349 | #endif |
1350 | ||
7a8e76a3 SR |
1351 | mutex_init(&buffer->mutex); |
1352 | ||
1353 | return buffer; | |
1354 | ||
1355 | fail_free_buffers: | |
1356 | for_each_buffer_cpu(buffer, cpu) { | |
1357 | if (buffer->buffers[cpu]) | |
1358 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1359 | } | |
1360 | kfree(buffer->buffers); | |
1361 | ||
9e01c1b7 RR |
1362 | fail_free_cpumask: |
1363 | free_cpumask_var(buffer->cpumask); | |
d39ad278 SB |
1364 | #ifdef CONFIG_HOTPLUG_CPU |
1365 | cpu_notifier_register_done(); | |
1366 | #endif | |
9e01c1b7 | 1367 | |
7a8e76a3 SR |
1368 | fail_free_buffer: |
1369 | kfree(buffer); | |
1370 | return NULL; | |
1371 | } | |
1f8a6a10 | 1372 | EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
7a8e76a3 SR |
1373 | |
1374 | /** | |
1375 | * ring_buffer_free - free a ring buffer. | |
1376 | * @buffer: the buffer to free. | |
1377 | */ | |
1378 | void | |
1379 | ring_buffer_free(struct ring_buffer *buffer) | |
1380 | { | |
1381 | int cpu; | |
1382 | ||
59222efe | 1383 | #ifdef CONFIG_HOTPLUG_CPU |
d39ad278 SB |
1384 | cpu_notifier_register_begin(); |
1385 | __unregister_cpu_notifier(&buffer->cpu_notify); | |
554f786e SR |
1386 | #endif |
1387 | ||
7a8e76a3 SR |
1388 | for_each_buffer_cpu(buffer, cpu) |
1389 | rb_free_cpu_buffer(buffer->buffers[cpu]); | |
1390 | ||
d39ad278 SB |
1391 | #ifdef CONFIG_HOTPLUG_CPU |
1392 | cpu_notifier_register_done(); | |
1393 | #endif | |
554f786e | 1394 | |
bd3f0221 | 1395 | kfree(buffer->buffers); |
9e01c1b7 RR |
1396 | free_cpumask_var(buffer->cpumask); |
1397 | ||
7a8e76a3 SR |
1398 | kfree(buffer); |
1399 | } | |
c4f50183 | 1400 | EXPORT_SYMBOL_GPL(ring_buffer_free); |
7a8e76a3 | 1401 | |
37886f6a SR |
1402 | void ring_buffer_set_clock(struct ring_buffer *buffer, |
1403 | u64 (*clock)(void)) | |
1404 | { | |
1405 | buffer->clock = clock; | |
1406 | } | |
1407 | ||
7a8e76a3 SR |
1408 | static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
1409 | ||
83f40318 VN |
1410 | static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
1411 | { | |
1412 | return local_read(&bpage->entries) & RB_WRITE_MASK; | |
1413 | } | |
1414 | ||
1415 | static inline unsigned long rb_page_write(struct buffer_page *bpage) | |
1416 | { | |
1417 | return local_read(&bpage->write) & RB_WRITE_MASK; | |
1418 | } | |
1419 | ||
5040b4b7 | 1420 | static int |
83f40318 | 1421 | rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages) |
7a8e76a3 | 1422 | { |
83f40318 VN |
1423 | struct list_head *tail_page, *to_remove, *next_page; |
1424 | struct buffer_page *to_remove_page, *tmp_iter_page; | |
1425 | struct buffer_page *last_page, *first_page; | |
1426 | unsigned int nr_removed; | |
1427 | unsigned long head_bit; | |
1428 | int page_entries; | |
1429 | ||
1430 | head_bit = 0; | |
7a8e76a3 | 1431 | |
5389f6fa | 1432 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1433 | atomic_inc(&cpu_buffer->record_disabled); |
1434 | /* | |
1435 | * We don't race with the readers since we have acquired the reader | |
1436 | * lock. We also don't race with writers after disabling recording. | |
1437 | * This makes it easy to figure out the first and the last page to be | |
1438 | * removed from the list. We unlink all the pages in between including | |
1439 | * the first and last pages. This is done in a busy loop so that we | |
1440 | * lose the least number of traces. | |
1441 | * The pages are freed after we restart recording and unlock readers. | |
1442 | */ | |
1443 | tail_page = &cpu_buffer->tail_page->list; | |
77ae365e | 1444 | |
83f40318 VN |
1445 | /* |
1446 | * tail page might be on reader page, we remove the next page | |
1447 | * from the ring buffer | |
1448 | */ | |
1449 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
1450 | tail_page = rb_list_head(tail_page->next); | |
1451 | to_remove = tail_page; | |
1452 | ||
1453 | /* start of pages to remove */ | |
1454 | first_page = list_entry(rb_list_head(to_remove->next), | |
1455 | struct buffer_page, list); | |
1456 | ||
1457 | for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { | |
1458 | to_remove = rb_list_head(to_remove)->next; | |
1459 | head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; | |
7a8e76a3 | 1460 | } |
7a8e76a3 | 1461 | |
83f40318 | 1462 | next_page = rb_list_head(to_remove)->next; |
7a8e76a3 | 1463 | |
83f40318 VN |
1464 | /* |
1465 | * Now we remove all pages between tail_page and next_page. | |
1466 | * Make sure that we have head_bit value preserved for the | |
1467 | * next page | |
1468 | */ | |
1469 | tail_page->next = (struct list_head *)((unsigned long)next_page | | |
1470 | head_bit); | |
1471 | next_page = rb_list_head(next_page); | |
1472 | next_page->prev = tail_page; | |
1473 | ||
1474 | /* make sure pages points to a valid page in the ring buffer */ | |
1475 | cpu_buffer->pages = next_page; | |
1476 | ||
1477 | /* update head page */ | |
1478 | if (head_bit) | |
1479 | cpu_buffer->head_page = list_entry(next_page, | |
1480 | struct buffer_page, list); | |
1481 | ||
1482 | /* | |
1483 | * change read pointer to make sure any read iterators reset | |
1484 | * themselves | |
1485 | */ | |
1486 | cpu_buffer->read = 0; | |
1487 | ||
1488 | /* pages are removed, resume tracing and then free the pages */ | |
1489 | atomic_dec(&cpu_buffer->record_disabled); | |
5389f6fa | 1490 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
83f40318 VN |
1491 | |
1492 | RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); | |
1493 | ||
1494 | /* last buffer page to remove */ | |
1495 | last_page = list_entry(rb_list_head(to_remove), struct buffer_page, | |
1496 | list); | |
1497 | tmp_iter_page = first_page; | |
1498 | ||
1499 | do { | |
1500 | to_remove_page = tmp_iter_page; | |
1501 | rb_inc_page(cpu_buffer, &tmp_iter_page); | |
1502 | ||
1503 | /* update the counters */ | |
1504 | page_entries = rb_page_entries(to_remove_page); | |
1505 | if (page_entries) { | |
1506 | /* | |
1507 | * If something was added to this page, it was full | |
1508 | * since it is not the tail page. So we deduct the | |
1509 | * bytes consumed in ring buffer from here. | |
48fdc72f | 1510 | * Increment overrun to account for the lost events. |
83f40318 | 1511 | */ |
48fdc72f | 1512 | local_add(page_entries, &cpu_buffer->overrun); |
83f40318 VN |
1513 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
1514 | } | |
1515 | ||
1516 | /* | |
1517 | * We have already removed references to this list item, just | |
1518 | * free up the buffer_page and its page | |
1519 | */ | |
1520 | free_buffer_page(to_remove_page); | |
1521 | nr_removed--; | |
1522 | ||
1523 | } while (to_remove_page != last_page); | |
1524 | ||
1525 | RB_WARN_ON(cpu_buffer, nr_removed); | |
5040b4b7 VN |
1526 | |
1527 | return nr_removed == 0; | |
7a8e76a3 SR |
1528 | } |
1529 | ||
5040b4b7 VN |
1530 | static int |
1531 | rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 1532 | { |
5040b4b7 VN |
1533 | struct list_head *pages = &cpu_buffer->new_pages; |
1534 | int retries, success; | |
7a8e76a3 | 1535 | |
5389f6fa | 1536 | raw_spin_lock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1537 | /* |
1538 | * We are holding the reader lock, so the reader page won't be swapped | |
1539 | * in the ring buffer. Now we are racing with the writer trying to | |
1540 | * move head page and the tail page. | |
1541 | * We are going to adapt the reader page update process where: | |
1542 | * 1. We first splice the start and end of list of new pages between | |
1543 | * the head page and its previous page. | |
1544 | * 2. We cmpxchg the prev_page->next to point from head page to the | |
1545 | * start of new pages list. | |
1546 | * 3. Finally, we update the head->prev to the end of new list. | |
1547 | * | |
1548 | * We will try this process 10 times, to make sure that we don't keep | |
1549 | * spinning. | |
1550 | */ | |
1551 | retries = 10; | |
1552 | success = 0; | |
1553 | while (retries--) { | |
1554 | struct list_head *head_page, *prev_page, *r; | |
1555 | struct list_head *last_page, *first_page; | |
1556 | struct list_head *head_page_with_bit; | |
77ae365e | 1557 | |
5040b4b7 | 1558 | head_page = &rb_set_head_page(cpu_buffer)->list; |
54f7be5b SR |
1559 | if (!head_page) |
1560 | break; | |
5040b4b7 VN |
1561 | prev_page = head_page->prev; |
1562 | ||
1563 | first_page = pages->next; | |
1564 | last_page = pages->prev; | |
1565 | ||
1566 | head_page_with_bit = (struct list_head *) | |
1567 | ((unsigned long)head_page | RB_PAGE_HEAD); | |
1568 | ||
1569 | last_page->next = head_page_with_bit; | |
1570 | first_page->prev = prev_page; | |
1571 | ||
1572 | r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); | |
1573 | ||
1574 | if (r == head_page_with_bit) { | |
1575 | /* | |
1576 | * yay, we replaced the page pointer to our new list, | |
1577 | * now, we just have to update to head page's prev | |
1578 | * pointer to point to end of list | |
1579 | */ | |
1580 | head_page->prev = last_page; | |
1581 | success = 1; | |
1582 | break; | |
1583 | } | |
7a8e76a3 | 1584 | } |
7a8e76a3 | 1585 | |
5040b4b7 VN |
1586 | if (success) |
1587 | INIT_LIST_HEAD(pages); | |
1588 | /* | |
1589 | * If we weren't successful in adding in new pages, warn and stop | |
1590 | * tracing | |
1591 | */ | |
1592 | RB_WARN_ON(cpu_buffer, !success); | |
5389f6fa | 1593 | raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
5040b4b7 VN |
1594 | |
1595 | /* free pages if they weren't inserted */ | |
1596 | if (!success) { | |
1597 | struct buffer_page *bpage, *tmp; | |
1598 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, | |
1599 | list) { | |
1600 | list_del_init(&bpage->list); | |
1601 | free_buffer_page(bpage); | |
1602 | } | |
1603 | } | |
1604 | return success; | |
7a8e76a3 SR |
1605 | } |
1606 | ||
83f40318 | 1607 | static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
438ced17 | 1608 | { |
5040b4b7 VN |
1609 | int success; |
1610 | ||
438ced17 | 1611 | if (cpu_buffer->nr_pages_to_update > 0) |
5040b4b7 | 1612 | success = rb_insert_pages(cpu_buffer); |
438ced17 | 1613 | else |
5040b4b7 VN |
1614 | success = rb_remove_pages(cpu_buffer, |
1615 | -cpu_buffer->nr_pages_to_update); | |
83f40318 | 1616 | |
5040b4b7 VN |
1617 | if (success) |
1618 | cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; | |
83f40318 VN |
1619 | } |
1620 | ||
1621 | static void update_pages_handler(struct work_struct *work) | |
1622 | { | |
1623 | struct ring_buffer_per_cpu *cpu_buffer = container_of(work, | |
1624 | struct ring_buffer_per_cpu, update_pages_work); | |
1625 | rb_update_pages(cpu_buffer); | |
05fdd70d | 1626 | complete(&cpu_buffer->update_done); |
438ced17 VN |
1627 | } |
1628 | ||
7a8e76a3 SR |
1629 | /** |
1630 | * ring_buffer_resize - resize the ring buffer | |
1631 | * @buffer: the buffer to resize. | |
1632 | * @size: the new size. | |
d611851b | 1633 | * @cpu_id: the cpu buffer to resize |
7a8e76a3 | 1634 | * |
7a8e76a3 SR |
1635 | * Minimum size is 2 * BUF_PAGE_SIZE. |
1636 | * | |
83f40318 | 1637 | * Returns 0 on success and < 0 on failure. |
7a8e76a3 | 1638 | */ |
438ced17 VN |
1639 | int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, |
1640 | int cpu_id) | |
7a8e76a3 SR |
1641 | { |
1642 | struct ring_buffer_per_cpu *cpu_buffer; | |
438ced17 | 1643 | unsigned nr_pages; |
83f40318 | 1644 | int cpu, err = 0; |
7a8e76a3 | 1645 | |
ee51a1de IM |
1646 | /* |
1647 | * Always succeed at resizing a non-existent buffer: | |
1648 | */ | |
1649 | if (!buffer) | |
1650 | return size; | |
1651 | ||
6a31e1f1 SR |
1652 | /* Make sure the requested buffer exists */ |
1653 | if (cpu_id != RING_BUFFER_ALL_CPUS && | |
1654 | !cpumask_test_cpu(cpu_id, buffer->cpumask)) | |
1655 | return size; | |
1656 | ||
7a8e76a3 SR |
1657 | size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
1658 | size *= BUF_PAGE_SIZE; | |
7a8e76a3 SR |
1659 | |
1660 | /* we need a minimum of two pages */ | |
1661 | if (size < BUF_PAGE_SIZE * 2) | |
1662 | size = BUF_PAGE_SIZE * 2; | |
1663 | ||
83f40318 | 1664 | nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
18421015 | 1665 | |
83f40318 VN |
1666 | /* |
1667 | * Don't succeed if resizing is disabled, as a reader might be | |
1668 | * manipulating the ring buffer and is expecting a sane state while | |
1669 | * this is true. | |
1670 | */ | |
1671 | if (atomic_read(&buffer->resize_disabled)) | |
1672 | return -EBUSY; | |
18421015 | 1673 | |
83f40318 | 1674 | /* prevent another thread from changing buffer sizes */ |
7a8e76a3 | 1675 | mutex_lock(&buffer->mutex); |
7a8e76a3 | 1676 | |
438ced17 VN |
1677 | if (cpu_id == RING_BUFFER_ALL_CPUS) { |
1678 | /* calculate the pages to update */ | |
7a8e76a3 SR |
1679 | for_each_buffer_cpu(buffer, cpu) { |
1680 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 1681 | |
438ced17 VN |
1682 | cpu_buffer->nr_pages_to_update = nr_pages - |
1683 | cpu_buffer->nr_pages; | |
438ced17 VN |
1684 | /* |
1685 | * nothing more to do for removing pages or no update | |
1686 | */ | |
1687 | if (cpu_buffer->nr_pages_to_update <= 0) | |
1688 | continue; | |
d7ec4bfe | 1689 | /* |
438ced17 VN |
1690 | * to add pages, make sure all new pages can be |
1691 | * allocated without receiving ENOMEM | |
d7ec4bfe | 1692 | */ |
438ced17 VN |
1693 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
1694 | if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 | 1695 | &cpu_buffer->new_pages, cpu)) { |
438ced17 | 1696 | /* not enough memory for new pages */ |
83f40318 VN |
1697 | err = -ENOMEM; |
1698 | goto out_err; | |
1699 | } | |
1700 | } | |
1701 | ||
1702 | get_online_cpus(); | |
1703 | /* | |
1704 | * Fire off all the required work handlers | |
05fdd70d | 1705 | * We can't schedule on offline CPUs, but it's not necessary |
83f40318 VN |
1706 | * since we can change their buffer sizes without any race. |
1707 | */ | |
1708 | for_each_buffer_cpu(buffer, cpu) { | |
1709 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 1710 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
1711 | continue; |
1712 | ||
021c5b34 CM |
1713 | /* Can't run something on an offline CPU. */ |
1714 | if (!cpu_online(cpu)) { | |
f5eb5588 SRRH |
1715 | rb_update_pages(cpu_buffer); |
1716 | cpu_buffer->nr_pages_to_update = 0; | |
1717 | } else { | |
05fdd70d VN |
1718 | schedule_work_on(cpu, |
1719 | &cpu_buffer->update_pages_work); | |
f5eb5588 | 1720 | } |
7a8e76a3 | 1721 | } |
7a8e76a3 | 1722 | |
438ced17 VN |
1723 | /* wait for all the updates to complete */ |
1724 | for_each_buffer_cpu(buffer, cpu) { | |
1725 | cpu_buffer = buffer->buffers[cpu]; | |
05fdd70d | 1726 | if (!cpu_buffer->nr_pages_to_update) |
83f40318 VN |
1727 | continue; |
1728 | ||
05fdd70d VN |
1729 | if (cpu_online(cpu)) |
1730 | wait_for_completion(&cpu_buffer->update_done); | |
83f40318 | 1731 | cpu_buffer->nr_pages_to_update = 0; |
438ced17 | 1732 | } |
83f40318 VN |
1733 | |
1734 | put_online_cpus(); | |
438ced17 | 1735 | } else { |
8e49f418 VN |
1736 | /* Make sure this CPU has been intitialized */ |
1737 | if (!cpumask_test_cpu(cpu_id, buffer->cpumask)) | |
1738 | goto out; | |
1739 | ||
438ced17 | 1740 | cpu_buffer = buffer->buffers[cpu_id]; |
83f40318 | 1741 | |
438ced17 VN |
1742 | if (nr_pages == cpu_buffer->nr_pages) |
1743 | goto out; | |
7a8e76a3 | 1744 | |
438ced17 VN |
1745 | cpu_buffer->nr_pages_to_update = nr_pages - |
1746 | cpu_buffer->nr_pages; | |
1747 | ||
1748 | INIT_LIST_HEAD(&cpu_buffer->new_pages); | |
1749 | if (cpu_buffer->nr_pages_to_update > 0 && | |
1750 | __rb_allocate_pages(cpu_buffer->nr_pages_to_update, | |
83f40318 VN |
1751 | &cpu_buffer->new_pages, cpu_id)) { |
1752 | err = -ENOMEM; | |
1753 | goto out_err; | |
1754 | } | |
438ced17 | 1755 | |
83f40318 VN |
1756 | get_online_cpus(); |
1757 | ||
021c5b34 CM |
1758 | /* Can't run something on an offline CPU. */ |
1759 | if (!cpu_online(cpu_id)) | |
f5eb5588 SRRH |
1760 | rb_update_pages(cpu_buffer); |
1761 | else { | |
83f40318 VN |
1762 | schedule_work_on(cpu_id, |
1763 | &cpu_buffer->update_pages_work); | |
05fdd70d | 1764 | wait_for_completion(&cpu_buffer->update_done); |
f5eb5588 | 1765 | } |
83f40318 | 1766 | |
83f40318 | 1767 | cpu_buffer->nr_pages_to_update = 0; |
05fdd70d | 1768 | put_online_cpus(); |
438ced17 | 1769 | } |
7a8e76a3 SR |
1770 | |
1771 | out: | |
659f451f SR |
1772 | /* |
1773 | * The ring buffer resize can happen with the ring buffer | |
1774 | * enabled, so that the update disturbs the tracing as little | |
1775 | * as possible. But if the buffer is disabled, we do not need | |
1776 | * to worry about that, and we can take the time to verify | |
1777 | * that the buffer is not corrupt. | |
1778 | */ | |
1779 | if (atomic_read(&buffer->record_disabled)) { | |
1780 | atomic_inc(&buffer->record_disabled); | |
1781 | /* | |
1782 | * Even though the buffer was disabled, we must make sure | |
1783 | * that it is truly disabled before calling rb_check_pages. | |
1784 | * There could have been a race between checking | |
1785 | * record_disable and incrementing it. | |
1786 | */ | |
1787 | synchronize_sched(); | |
1788 | for_each_buffer_cpu(buffer, cpu) { | |
1789 | cpu_buffer = buffer->buffers[cpu]; | |
1790 | rb_check_pages(cpu_buffer); | |
1791 | } | |
1792 | atomic_dec(&buffer->record_disabled); | |
1793 | } | |
1794 | ||
7a8e76a3 | 1795 | mutex_unlock(&buffer->mutex); |
7a8e76a3 SR |
1796 | return size; |
1797 | ||
83f40318 | 1798 | out_err: |
438ced17 VN |
1799 | for_each_buffer_cpu(buffer, cpu) { |
1800 | struct buffer_page *bpage, *tmp; | |
83f40318 | 1801 | |
438ced17 | 1802 | cpu_buffer = buffer->buffers[cpu]; |
438ced17 | 1803 | cpu_buffer->nr_pages_to_update = 0; |
83f40318 | 1804 | |
438ced17 VN |
1805 | if (list_empty(&cpu_buffer->new_pages)) |
1806 | continue; | |
83f40318 | 1807 | |
438ced17 VN |
1808 | list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
1809 | list) { | |
1810 | list_del_init(&bpage->list); | |
1811 | free_buffer_page(bpage); | |
1812 | } | |
7a8e76a3 | 1813 | } |
641d2f63 | 1814 | mutex_unlock(&buffer->mutex); |
83f40318 | 1815 | return err; |
7a8e76a3 | 1816 | } |
c4f50183 | 1817 | EXPORT_SYMBOL_GPL(ring_buffer_resize); |
7a8e76a3 | 1818 | |
750912fa DS |
1819 | void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) |
1820 | { | |
1821 | mutex_lock(&buffer->mutex); | |
1822 | if (val) | |
1823 | buffer->flags |= RB_FL_OVERWRITE; | |
1824 | else | |
1825 | buffer->flags &= ~RB_FL_OVERWRITE; | |
1826 | mutex_unlock(&buffer->mutex); | |
1827 | } | |
1828 | EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); | |
1829 | ||
8789a9e7 | 1830 | static inline void * |
044fa782 | 1831 | __rb_data_page_index(struct buffer_data_page *bpage, unsigned index) |
8789a9e7 | 1832 | { |
044fa782 | 1833 | return bpage->data + index; |
8789a9e7 SR |
1834 | } |
1835 | ||
044fa782 | 1836 | static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
7a8e76a3 | 1837 | { |
044fa782 | 1838 | return bpage->page->data + index; |
7a8e76a3 SR |
1839 | } |
1840 | ||
1841 | static inline struct ring_buffer_event * | |
d769041f | 1842 | rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1843 | { |
6f807acd SR |
1844 | return __rb_page_index(cpu_buffer->reader_page, |
1845 | cpu_buffer->reader_page->read); | |
1846 | } | |
1847 | ||
7a8e76a3 SR |
1848 | static inline struct ring_buffer_event * |
1849 | rb_iter_head_event(struct ring_buffer_iter *iter) | |
1850 | { | |
6f807acd | 1851 | return __rb_page_index(iter->head_page, iter->head); |
7a8e76a3 SR |
1852 | } |
1853 | ||
bf41a158 SR |
1854 | static inline unsigned rb_page_commit(struct buffer_page *bpage) |
1855 | { | |
abc9b56d | 1856 | return local_read(&bpage->page->commit); |
bf41a158 SR |
1857 | } |
1858 | ||
25985edc | 1859 | /* Size is determined by what has been committed */ |
bf41a158 SR |
1860 | static inline unsigned rb_page_size(struct buffer_page *bpage) |
1861 | { | |
1862 | return rb_page_commit(bpage); | |
1863 | } | |
1864 | ||
1865 | static inline unsigned | |
1866 | rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) | |
1867 | { | |
1868 | return rb_page_commit(cpu_buffer->commit_page); | |
1869 | } | |
1870 | ||
bf41a158 SR |
1871 | static inline unsigned |
1872 | rb_event_index(struct ring_buffer_event *event) | |
1873 | { | |
1874 | unsigned long addr = (unsigned long)event; | |
1875 | ||
22f470f8 | 1876 | return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
bf41a158 SR |
1877 | } |
1878 | ||
0f0c85fc | 1879 | static inline int |
fa743953 SR |
1880 | rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
1881 | struct ring_buffer_event *event) | |
bf41a158 SR |
1882 | { |
1883 | unsigned long addr = (unsigned long)event; | |
1884 | unsigned long index; | |
1885 | ||
1886 | index = rb_event_index(event); | |
1887 | addr &= PAGE_MASK; | |
1888 | ||
1889 | return cpu_buffer->commit_page->page == (void *)addr && | |
1890 | rb_commit_index(cpu_buffer) == index; | |
1891 | } | |
1892 | ||
34a148bf | 1893 | static void |
bf41a158 | 1894 | rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1895 | { |
77ae365e SR |
1896 | unsigned long max_count; |
1897 | ||
bf41a158 SR |
1898 | /* |
1899 | * We only race with interrupts and NMIs on this CPU. | |
1900 | * If we own the commit event, then we can commit | |
1901 | * all others that interrupted us, since the interruptions | |
1902 | * are in stack format (they finish before they come | |
1903 | * back to us). This allows us to do a simple loop to | |
1904 | * assign the commit to the tail. | |
1905 | */ | |
a8ccf1d6 | 1906 | again: |
438ced17 | 1907 | max_count = cpu_buffer->nr_pages * 100; |
77ae365e | 1908 | |
bf41a158 | 1909 | while (cpu_buffer->commit_page != cpu_buffer->tail_page) { |
77ae365e SR |
1910 | if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
1911 | return; | |
1912 | if (RB_WARN_ON(cpu_buffer, | |
1913 | rb_is_reader_page(cpu_buffer->tail_page))) | |
1914 | return; | |
1915 | local_set(&cpu_buffer->commit_page->page->commit, | |
1916 | rb_page_write(cpu_buffer->commit_page)); | |
bf41a158 | 1917 | rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); |
abc9b56d SR |
1918 | cpu_buffer->write_stamp = |
1919 | cpu_buffer->commit_page->page->time_stamp; | |
bf41a158 SR |
1920 | /* add barrier to keep gcc from optimizing too much */ |
1921 | barrier(); | |
1922 | } | |
1923 | while (rb_commit_index(cpu_buffer) != | |
1924 | rb_page_write(cpu_buffer->commit_page)) { | |
77ae365e SR |
1925 | |
1926 | local_set(&cpu_buffer->commit_page->page->commit, | |
1927 | rb_page_write(cpu_buffer->commit_page)); | |
1928 | RB_WARN_ON(cpu_buffer, | |
1929 | local_read(&cpu_buffer->commit_page->page->commit) & | |
1930 | ~RB_WRITE_MASK); | |
bf41a158 SR |
1931 | barrier(); |
1932 | } | |
a8ccf1d6 SR |
1933 | |
1934 | /* again, keep gcc from optimizing */ | |
1935 | barrier(); | |
1936 | ||
1937 | /* | |
1938 | * If an interrupt came in just after the first while loop | |
1939 | * and pushed the tail page forward, we will be left with | |
1940 | * a dangling commit that will never go forward. | |
1941 | */ | |
1942 | if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page)) | |
1943 | goto again; | |
7a8e76a3 SR |
1944 | } |
1945 | ||
d769041f | 1946 | static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) |
7a8e76a3 | 1947 | { |
abc9b56d | 1948 | cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp; |
6f807acd | 1949 | cpu_buffer->reader_page->read = 0; |
d769041f SR |
1950 | } |
1951 | ||
34a148bf | 1952 | static void rb_inc_iter(struct ring_buffer_iter *iter) |
d769041f SR |
1953 | { |
1954 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
1955 | ||
1956 | /* | |
1957 | * The iterator could be on the reader page (it starts there). | |
1958 | * But the head could have moved, since the reader was | |
1959 | * found. Check for this case and assign the iterator | |
1960 | * to the head page instead of next. | |
1961 | */ | |
1962 | if (iter->head_page == cpu_buffer->reader_page) | |
77ae365e | 1963 | iter->head_page = rb_set_head_page(cpu_buffer); |
d769041f SR |
1964 | else |
1965 | rb_inc_page(cpu_buffer, &iter->head_page); | |
1966 | ||
abc9b56d | 1967 | iter->read_stamp = iter->head_page->page->time_stamp; |
7a8e76a3 SR |
1968 | iter->head = 0; |
1969 | } | |
1970 | ||
69d1b839 SR |
1971 | /* Slow path, do not inline */ |
1972 | static noinline struct ring_buffer_event * | |
1973 | rb_add_time_stamp(struct ring_buffer_event *event, u64 delta) | |
1974 | { | |
1975 | event->type_len = RINGBUF_TYPE_TIME_EXTEND; | |
1976 | ||
1977 | /* Not the first event on the page? */ | |
1978 | if (rb_event_index(event)) { | |
1979 | event->time_delta = delta & TS_MASK; | |
1980 | event->array[0] = delta >> TS_SHIFT; | |
1981 | } else { | |
1982 | /* nope, just zero it */ | |
1983 | event->time_delta = 0; | |
1984 | event->array[0] = 0; | |
1985 | } | |
1986 | ||
1987 | return skip_time_extend(event); | |
1988 | } | |
1989 | ||
7a8e76a3 | 1990 | /** |
01e3e710 | 1991 | * rb_update_event - update event type and data |
021de3d9 | 1992 | * @event: the event to update |
7a8e76a3 SR |
1993 | * @type: the type of event |
1994 | * @length: the size of the event field in the ring buffer | |
1995 | * | |
1996 | * Update the type and data fields of the event. The length | |
1997 | * is the actual size that is written to the ring buffer, | |
1998 | * and with this, we can determine what to place into the | |
1999 | * data field. | |
2000 | */ | |
34a148bf | 2001 | static void |
69d1b839 SR |
2002 | rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
2003 | struct ring_buffer_event *event, unsigned length, | |
2004 | int add_timestamp, u64 delta) | |
7a8e76a3 | 2005 | { |
69d1b839 SR |
2006 | /* Only a commit updates the timestamp */ |
2007 | if (unlikely(!rb_event_is_commit(cpu_buffer, event))) | |
2008 | delta = 0; | |
7a8e76a3 | 2009 | |
69d1b839 SR |
2010 | /* |
2011 | * If we need to add a timestamp, then we | |
2012 | * add it to the start of the resevered space. | |
2013 | */ | |
2014 | if (unlikely(add_timestamp)) { | |
2015 | event = rb_add_time_stamp(event, delta); | |
2016 | length -= RB_LEN_TIME_EXTEND; | |
2017 | delta = 0; | |
7a8e76a3 | 2018 | } |
69d1b839 SR |
2019 | |
2020 | event->time_delta = delta; | |
2021 | length -= RB_EVNT_HDR_SIZE; | |
2022 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) { | |
2023 | event->type_len = 0; | |
2024 | event->array[0] = length; | |
2025 | } else | |
2026 | event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); | |
7a8e76a3 SR |
2027 | } |
2028 | ||
77ae365e SR |
2029 | /* |
2030 | * rb_handle_head_page - writer hit the head page | |
2031 | * | |
2032 | * Returns: +1 to retry page | |
2033 | * 0 to continue | |
2034 | * -1 on error | |
2035 | */ | |
2036 | static int | |
2037 | rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, | |
2038 | struct buffer_page *tail_page, | |
2039 | struct buffer_page *next_page) | |
2040 | { | |
2041 | struct buffer_page *new_head; | |
2042 | int entries; | |
2043 | int type; | |
2044 | int ret; | |
2045 | ||
2046 | entries = rb_page_entries(next_page); | |
2047 | ||
2048 | /* | |
2049 | * The hard part is here. We need to move the head | |
2050 | * forward, and protect against both readers on | |
2051 | * other CPUs and writers coming in via interrupts. | |
2052 | */ | |
2053 | type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, | |
2054 | RB_PAGE_HEAD); | |
2055 | ||
2056 | /* | |
2057 | * type can be one of four: | |
2058 | * NORMAL - an interrupt already moved it for us | |
2059 | * HEAD - we are the first to get here. | |
2060 | * UPDATE - we are the interrupt interrupting | |
2061 | * a current move. | |
2062 | * MOVED - a reader on another CPU moved the next | |
2063 | * pointer to its reader page. Give up | |
2064 | * and try again. | |
2065 | */ | |
2066 | ||
2067 | switch (type) { | |
2068 | case RB_PAGE_HEAD: | |
2069 | /* | |
2070 | * We changed the head to UPDATE, thus | |
2071 | * it is our responsibility to update | |
2072 | * the counters. | |
2073 | */ | |
2074 | local_add(entries, &cpu_buffer->overrun); | |
c64e148a | 2075 | local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
77ae365e SR |
2076 | |
2077 | /* | |
2078 | * The entries will be zeroed out when we move the | |
2079 | * tail page. | |
2080 | */ | |
2081 | ||
2082 | /* still more to do */ | |
2083 | break; | |
2084 | ||
2085 | case RB_PAGE_UPDATE: | |
2086 | /* | |
2087 | * This is an interrupt that interrupt the | |
2088 | * previous update. Still more to do. | |
2089 | */ | |
2090 | break; | |
2091 | case RB_PAGE_NORMAL: | |
2092 | /* | |
2093 | * An interrupt came in before the update | |
2094 | * and processed this for us. | |
2095 | * Nothing left to do. | |
2096 | */ | |
2097 | return 1; | |
2098 | case RB_PAGE_MOVED: | |
2099 | /* | |
2100 | * The reader is on another CPU and just did | |
2101 | * a swap with our next_page. | |
2102 | * Try again. | |
2103 | */ | |
2104 | return 1; | |
2105 | default: | |
2106 | RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ | |
2107 | return -1; | |
2108 | } | |
2109 | ||
2110 | /* | |
2111 | * Now that we are here, the old head pointer is | |
2112 | * set to UPDATE. This will keep the reader from | |
2113 | * swapping the head page with the reader page. | |
2114 | * The reader (on another CPU) will spin till | |
2115 | * we are finished. | |
2116 | * | |
2117 | * We just need to protect against interrupts | |
2118 | * doing the job. We will set the next pointer | |
2119 | * to HEAD. After that, we set the old pointer | |
2120 | * to NORMAL, but only if it was HEAD before. | |
2121 | * otherwise we are an interrupt, and only | |
2122 | * want the outer most commit to reset it. | |
2123 | */ | |
2124 | new_head = next_page; | |
2125 | rb_inc_page(cpu_buffer, &new_head); | |
2126 | ||
2127 | ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, | |
2128 | RB_PAGE_NORMAL); | |
2129 | ||
2130 | /* | |
2131 | * Valid returns are: | |
2132 | * HEAD - an interrupt came in and already set it. | |
2133 | * NORMAL - One of two things: | |
2134 | * 1) We really set it. | |
2135 | * 2) A bunch of interrupts came in and moved | |
2136 | * the page forward again. | |
2137 | */ | |
2138 | switch (ret) { | |
2139 | case RB_PAGE_HEAD: | |
2140 | case RB_PAGE_NORMAL: | |
2141 | /* OK */ | |
2142 | break; | |
2143 | default: | |
2144 | RB_WARN_ON(cpu_buffer, 1); | |
2145 | return -1; | |
2146 | } | |
2147 | ||
2148 | /* | |
2149 | * It is possible that an interrupt came in, | |
2150 | * set the head up, then more interrupts came in | |
2151 | * and moved it again. When we get back here, | |
2152 | * the page would have been set to NORMAL but we | |
2153 | * just set it back to HEAD. | |
2154 | * | |
2155 | * How do you detect this? Well, if that happened | |
2156 | * the tail page would have moved. | |
2157 | */ | |
2158 | if (ret == RB_PAGE_NORMAL) { | |
2159 | /* | |
2160 | * If the tail had moved passed next, then we need | |
2161 | * to reset the pointer. | |
2162 | */ | |
2163 | if (cpu_buffer->tail_page != tail_page && | |
2164 | cpu_buffer->tail_page != next_page) | |
2165 | rb_head_page_set_normal(cpu_buffer, new_head, | |
2166 | next_page, | |
2167 | RB_PAGE_HEAD); | |
2168 | } | |
2169 | ||
2170 | /* | |
2171 | * If this was the outer most commit (the one that | |
2172 | * changed the original pointer from HEAD to UPDATE), | |
2173 | * then it is up to us to reset it to NORMAL. | |
2174 | */ | |
2175 | if (type == RB_PAGE_HEAD) { | |
2176 | ret = rb_head_page_set_normal(cpu_buffer, next_page, | |
2177 | tail_page, | |
2178 | RB_PAGE_UPDATE); | |
2179 | if (RB_WARN_ON(cpu_buffer, | |
2180 | ret != RB_PAGE_UPDATE)) | |
2181 | return -1; | |
2182 | } | |
2183 | ||
2184 | return 0; | |
2185 | } | |
2186 | ||
34a148bf | 2187 | static unsigned rb_calculate_event_length(unsigned length) |
7a8e76a3 SR |
2188 | { |
2189 | struct ring_buffer_event event; /* Used only for sizeof array */ | |
2190 | ||
2191 | /* zero length can cause confusions */ | |
2192 | if (!length) | |
a497adb4 | 2193 | length++; |
7a8e76a3 | 2194 | |
2271048d | 2195 | if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) |
7a8e76a3 SR |
2196 | length += sizeof(event.array[0]); |
2197 | ||
2198 | length += RB_EVNT_HDR_SIZE; | |
2271048d | 2199 | length = ALIGN(length, RB_ARCH_ALIGNMENT); |
7a8e76a3 SR |
2200 | |
2201 | return length; | |
2202 | } | |
2203 | ||
c7b09308 SR |
2204 | static inline void |
2205 | rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, | |
2206 | struct buffer_page *tail_page, | |
2207 | unsigned long tail, unsigned long length) | |
2208 | { | |
2209 | struct ring_buffer_event *event; | |
2210 | ||
2211 | /* | |
2212 | * Only the event that crossed the page boundary | |
2213 | * must fill the old tail_page with padding. | |
2214 | */ | |
2215 | if (tail >= BUF_PAGE_SIZE) { | |
b3230c8b SR |
2216 | /* |
2217 | * If the page was filled, then we still need | |
2218 | * to update the real_end. Reset it to zero | |
2219 | * and the reader will ignore it. | |
2220 | */ | |
2221 | if (tail == BUF_PAGE_SIZE) | |
2222 | tail_page->real_end = 0; | |
2223 | ||
c7b09308 SR |
2224 | local_sub(length, &tail_page->write); |
2225 | return; | |
2226 | } | |
2227 | ||
2228 | event = __rb_page_index(tail_page, tail); | |
b0b7065b | 2229 | kmemcheck_annotate_bitfield(event, bitfield); |
c7b09308 | 2230 | |
c64e148a VN |
2231 | /* account for padding bytes */ |
2232 | local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); | |
2233 | ||
ff0ff84a SR |
2234 | /* |
2235 | * Save the original length to the meta data. | |
2236 | * This will be used by the reader to add lost event | |
2237 | * counter. | |
2238 | */ | |
2239 | tail_page->real_end = tail; | |
2240 | ||
c7b09308 SR |
2241 | /* |
2242 | * If this event is bigger than the minimum size, then | |
2243 | * we need to be careful that we don't subtract the | |
2244 | * write counter enough to allow another writer to slip | |
2245 | * in on this page. | |
2246 | * We put in a discarded commit instead, to make sure | |
2247 | * that this space is not used again. | |
2248 | * | |
2249 | * If we are less than the minimum size, we don't need to | |
2250 | * worry about it. | |
2251 | */ | |
2252 | if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { | |
2253 | /* No room for any events */ | |
2254 | ||
2255 | /* Mark the rest of the page with padding */ | |
2256 | rb_event_set_padding(event); | |
2257 | ||
2258 | /* Set the write back to the previous setting */ | |
2259 | local_sub(length, &tail_page->write); | |
2260 | return; | |
2261 | } | |
2262 | ||
2263 | /* Put in a discarded event */ | |
2264 | event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; | |
2265 | event->type_len = RINGBUF_TYPE_PADDING; | |
2266 | /* time delta must be non zero */ | |
2267 | event->time_delta = 1; | |
c7b09308 SR |
2268 | |
2269 | /* Set write to end of buffer */ | |
2270 | length = (tail + length) - BUF_PAGE_SIZE; | |
2271 | local_sub(length, &tail_page->write); | |
2272 | } | |
6634ff26 | 2273 | |
747e94ae SR |
2274 | /* |
2275 | * This is the slow path, force gcc not to inline it. | |
2276 | */ | |
2277 | static noinline struct ring_buffer_event * | |
6634ff26 SR |
2278 | rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
2279 | unsigned long length, unsigned long tail, | |
e8bc43e8 | 2280 | struct buffer_page *tail_page, u64 ts) |
7a8e76a3 | 2281 | { |
5a50e33c | 2282 | struct buffer_page *commit_page = cpu_buffer->commit_page; |
7a8e76a3 | 2283 | struct ring_buffer *buffer = cpu_buffer->buffer; |
77ae365e SR |
2284 | struct buffer_page *next_page; |
2285 | int ret; | |
aa20ae84 SR |
2286 | |
2287 | next_page = tail_page; | |
2288 | ||
aa20ae84 SR |
2289 | rb_inc_page(cpu_buffer, &next_page); |
2290 | ||
aa20ae84 SR |
2291 | /* |
2292 | * If for some reason, we had an interrupt storm that made | |
2293 | * it all the way around the buffer, bail, and warn | |
2294 | * about it. | |
2295 | */ | |
2296 | if (unlikely(next_page == commit_page)) { | |
77ae365e | 2297 | local_inc(&cpu_buffer->commit_overrun); |
aa20ae84 SR |
2298 | goto out_reset; |
2299 | } | |
2300 | ||
77ae365e SR |
2301 | /* |
2302 | * This is where the fun begins! | |
2303 | * | |
2304 | * We are fighting against races between a reader that | |
2305 | * could be on another CPU trying to swap its reader | |
2306 | * page with the buffer head. | |
2307 | * | |
2308 | * We are also fighting against interrupts coming in and | |
2309 | * moving the head or tail on us as well. | |
2310 | * | |
2311 | * If the next page is the head page then we have filled | |
2312 | * the buffer, unless the commit page is still on the | |
2313 | * reader page. | |
2314 | */ | |
2315 | if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { | |
aa20ae84 | 2316 | |
77ae365e SR |
2317 | /* |
2318 | * If the commit is not on the reader page, then | |
2319 | * move the header page. | |
2320 | */ | |
2321 | if (!rb_is_reader_page(cpu_buffer->commit_page)) { | |
2322 | /* | |
2323 | * If we are not in overwrite mode, | |
2324 | * this is easy, just stop here. | |
2325 | */ | |
884bfe89 SP |
2326 | if (!(buffer->flags & RB_FL_OVERWRITE)) { |
2327 | local_inc(&cpu_buffer->dropped_events); | |
77ae365e | 2328 | goto out_reset; |
884bfe89 | 2329 | } |
77ae365e SR |
2330 | |
2331 | ret = rb_handle_head_page(cpu_buffer, | |
2332 | tail_page, | |
2333 | next_page); | |
2334 | if (ret < 0) | |
2335 | goto out_reset; | |
2336 | if (ret) | |
2337 | goto out_again; | |
2338 | } else { | |
2339 | /* | |
2340 | * We need to be careful here too. The | |
2341 | * commit page could still be on the reader | |
2342 | * page. We could have a small buffer, and | |
2343 | * have filled up the buffer with events | |
2344 | * from interrupts and such, and wrapped. | |
2345 | * | |
2346 | * Note, if the tail page is also the on the | |
2347 | * reader_page, we let it move out. | |
2348 | */ | |
2349 | if (unlikely((cpu_buffer->commit_page != | |
2350 | cpu_buffer->tail_page) && | |
2351 | (cpu_buffer->commit_page == | |
2352 | cpu_buffer->reader_page))) { | |
2353 | local_inc(&cpu_buffer->commit_overrun); | |
2354 | goto out_reset; | |
2355 | } | |
aa20ae84 SR |
2356 | } |
2357 | } | |
2358 | ||
77ae365e SR |
2359 | ret = rb_tail_page_update(cpu_buffer, tail_page, next_page); |
2360 | if (ret) { | |
2361 | /* | |
2362 | * Nested commits always have zero deltas, so | |
2363 | * just reread the time stamp | |
2364 | */ | |
e8bc43e8 SR |
2365 | ts = rb_time_stamp(buffer); |
2366 | next_page->page->time_stamp = ts; | |
aa20ae84 SR |
2367 | } |
2368 | ||
77ae365e | 2369 | out_again: |
aa20ae84 | 2370 | |
77ae365e | 2371 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
aa20ae84 SR |
2372 | |
2373 | /* fail and let the caller try again */ | |
2374 | return ERR_PTR(-EAGAIN); | |
2375 | ||
45141d46 | 2376 | out_reset: |
6f3b3440 | 2377 | /* reset write */ |
c7b09308 | 2378 | rb_reset_tail(cpu_buffer, tail_page, tail, length); |
6f3b3440 | 2379 | |
bf41a158 | 2380 | return NULL; |
7a8e76a3 SR |
2381 | } |
2382 | ||
6634ff26 SR |
2383 | static struct ring_buffer_event * |
2384 | __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, | |
69d1b839 SR |
2385 | unsigned long length, u64 ts, |
2386 | u64 delta, int add_timestamp) | |
6634ff26 | 2387 | { |
5a50e33c | 2388 | struct buffer_page *tail_page; |
6634ff26 SR |
2389 | struct ring_buffer_event *event; |
2390 | unsigned long tail, write; | |
2391 | ||
69d1b839 SR |
2392 | /* |
2393 | * If the time delta since the last event is too big to | |
2394 | * hold in the time field of the event, then we append a | |
2395 | * TIME EXTEND event ahead of the data event. | |
2396 | */ | |
2397 | if (unlikely(add_timestamp)) | |
2398 | length += RB_LEN_TIME_EXTEND; | |
2399 | ||
6634ff26 SR |
2400 | tail_page = cpu_buffer->tail_page; |
2401 | write = local_add_return(length, &tail_page->write); | |
77ae365e SR |
2402 | |
2403 | /* set write to only the index of the write */ | |
2404 | write &= RB_WRITE_MASK; | |
6634ff26 SR |
2405 | tail = write - length; |
2406 | ||
d651aa1d SRRH |
2407 | /* |
2408 | * If this is the first commit on the page, then it has the same | |
2409 | * timestamp as the page itself. | |
2410 | */ | |
2411 | if (!tail) | |
2412 | delta = 0; | |
2413 | ||
6634ff26 | 2414 | /* See if we shot pass the end of this buffer page */ |
747e94ae | 2415 | if (unlikely(write > BUF_PAGE_SIZE)) |
6634ff26 | 2416 | return rb_move_tail(cpu_buffer, length, tail, |
5a50e33c | 2417 | tail_page, ts); |
6634ff26 SR |
2418 | |
2419 | /* We reserved something on the buffer */ | |
2420 | ||
6634ff26 | 2421 | event = __rb_page_index(tail_page, tail); |
1744a21d | 2422 | kmemcheck_annotate_bitfield(event, bitfield); |
69d1b839 | 2423 | rb_update_event(cpu_buffer, event, length, add_timestamp, delta); |
6634ff26 | 2424 | |
69d1b839 | 2425 | local_inc(&tail_page->entries); |
6634ff26 SR |
2426 | |
2427 | /* | |
fa743953 SR |
2428 | * If this is the first commit on the page, then update |
2429 | * its timestamp. | |
6634ff26 | 2430 | */ |
fa743953 | 2431 | if (!tail) |
e8bc43e8 | 2432 | tail_page->page->time_stamp = ts; |
6634ff26 | 2433 | |
c64e148a VN |
2434 | /* account for these added bytes */ |
2435 | local_add(length, &cpu_buffer->entries_bytes); | |
2436 | ||
6634ff26 SR |
2437 | return event; |
2438 | } | |
2439 | ||
edd813bf SR |
2440 | static inline int |
2441 | rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, | |
2442 | struct ring_buffer_event *event) | |
2443 | { | |
2444 | unsigned long new_index, old_index; | |
2445 | struct buffer_page *bpage; | |
2446 | unsigned long index; | |
2447 | unsigned long addr; | |
2448 | ||
2449 | new_index = rb_event_index(event); | |
69d1b839 | 2450 | old_index = new_index + rb_event_ts_length(event); |
edd813bf SR |
2451 | addr = (unsigned long)event; |
2452 | addr &= PAGE_MASK; | |
2453 | ||
2454 | bpage = cpu_buffer->tail_page; | |
2455 | ||
2456 | if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { | |
77ae365e SR |
2457 | unsigned long write_mask = |
2458 | local_read(&bpage->write) & ~RB_WRITE_MASK; | |
c64e148a | 2459 | unsigned long event_length = rb_event_length(event); |
edd813bf SR |
2460 | /* |
2461 | * This is on the tail page. It is possible that | |
2462 | * a write could come in and move the tail page | |
2463 | * and write to the next page. That is fine | |
2464 | * because we just shorten what is on this page. | |
2465 | */ | |
77ae365e SR |
2466 | old_index += write_mask; |
2467 | new_index += write_mask; | |
edd813bf | 2468 | index = local_cmpxchg(&bpage->write, old_index, new_index); |
c64e148a VN |
2469 | if (index == old_index) { |
2470 | /* update counters */ | |
2471 | local_sub(event_length, &cpu_buffer->entries_bytes); | |
edd813bf | 2472 | return 1; |
c64e148a | 2473 | } |
edd813bf SR |
2474 | } |
2475 | ||
2476 | /* could not discard */ | |
2477 | return 0; | |
2478 | } | |
2479 | ||
fa743953 SR |
2480 | static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
2481 | { | |
2482 | local_inc(&cpu_buffer->committing); | |
2483 | local_inc(&cpu_buffer->commits); | |
2484 | } | |
2485 | ||
d9abde21 | 2486 | static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
fa743953 SR |
2487 | { |
2488 | unsigned long commits; | |
2489 | ||
2490 | if (RB_WARN_ON(cpu_buffer, | |
2491 | !local_read(&cpu_buffer->committing))) | |
2492 | return; | |
2493 | ||
2494 | again: | |
2495 | commits = local_read(&cpu_buffer->commits); | |
2496 | /* synchronize with interrupts */ | |
2497 | barrier(); | |
2498 | if (local_read(&cpu_buffer->committing) == 1) | |
2499 | rb_set_commit_to_write(cpu_buffer); | |
2500 | ||
2501 | local_dec(&cpu_buffer->committing); | |
2502 | ||
2503 | /* synchronize with interrupts */ | |
2504 | barrier(); | |
2505 | ||
2506 | /* | |
2507 | * Need to account for interrupts coming in between the | |
2508 | * updating of the commit page and the clearing of the | |
2509 | * committing counter. | |
2510 | */ | |
2511 | if (unlikely(local_read(&cpu_buffer->commits) != commits) && | |
2512 | !local_read(&cpu_buffer->committing)) { | |
2513 | local_inc(&cpu_buffer->committing); | |
2514 | goto again; | |
2515 | } | |
2516 | } | |
2517 | ||
7a8e76a3 | 2518 | static struct ring_buffer_event * |
62f0b3eb SR |
2519 | rb_reserve_next_event(struct ring_buffer *buffer, |
2520 | struct ring_buffer_per_cpu *cpu_buffer, | |
1cd8d735 | 2521 | unsigned long length) |
7a8e76a3 SR |
2522 | { |
2523 | struct ring_buffer_event *event; | |
69d1b839 | 2524 | u64 ts, delta; |
818e3dd3 | 2525 | int nr_loops = 0; |
69d1b839 | 2526 | int add_timestamp; |
140ff891 | 2527 | u64 diff; |
7a8e76a3 | 2528 | |
fa743953 SR |
2529 | rb_start_commit(cpu_buffer); |
2530 | ||
85bac32c | 2531 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
62f0b3eb SR |
2532 | /* |
2533 | * Due to the ability to swap a cpu buffer from a buffer | |
2534 | * it is possible it was swapped before we committed. | |
2535 | * (committing stops a swap). We check for it here and | |
2536 | * if it happened, we have to fail the write. | |
2537 | */ | |
2538 | barrier(); | |
2539 | if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) { | |
2540 | local_dec(&cpu_buffer->committing); | |
2541 | local_dec(&cpu_buffer->commits); | |
2542 | return NULL; | |
2543 | } | |
85bac32c | 2544 | #endif |
62f0b3eb | 2545 | |
be957c44 | 2546 | length = rb_calculate_event_length(length); |
bf41a158 | 2547 | again: |
69d1b839 SR |
2548 | add_timestamp = 0; |
2549 | delta = 0; | |
2550 | ||
818e3dd3 SR |
2551 | /* |
2552 | * We allow for interrupts to reenter here and do a trace. | |
2553 | * If one does, it will cause this original code to loop | |
2554 | * back here. Even with heavy interrupts happening, this | |
2555 | * should only happen a few times in a row. If this happens | |
2556 | * 1000 times in a row, there must be either an interrupt | |
2557 | * storm or we have something buggy. | |
2558 | * Bail! | |
2559 | */ | |
3e89c7bb | 2560 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
fa743953 | 2561 | goto out_fail; |
818e3dd3 | 2562 | |
6d3f1e12 | 2563 | ts = rb_time_stamp(cpu_buffer->buffer); |
140ff891 | 2564 | diff = ts - cpu_buffer->write_stamp; |
7a8e76a3 | 2565 | |
140ff891 SR |
2566 | /* make sure this diff is calculated here */ |
2567 | barrier(); | |
bf41a158 | 2568 | |
140ff891 SR |
2569 | /* Did the write stamp get updated already? */ |
2570 | if (likely(ts >= cpu_buffer->write_stamp)) { | |
168b6b1d SR |
2571 | delta = diff; |
2572 | if (unlikely(test_time_stamp(delta))) { | |
31274d72 JO |
2573 | int local_clock_stable = 1; |
2574 | #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK | |
35af99e6 | 2575 | local_clock_stable = sched_clock_stable(); |
31274d72 | 2576 | #endif |
69d1b839 | 2577 | WARN_ONCE(delta > (1ULL << 59), |
31274d72 | 2578 | KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s", |
69d1b839 SR |
2579 | (unsigned long long)delta, |
2580 | (unsigned long long)ts, | |
31274d72 JO |
2581 | (unsigned long long)cpu_buffer->write_stamp, |
2582 | local_clock_stable ? "" : | |
2583 | "If you just came from a suspend/resume,\n" | |
2584 | "please switch to the trace global clock:\n" | |
2585 | " echo global > /sys/kernel/debug/tracing/trace_clock\n"); | |
69d1b839 | 2586 | add_timestamp = 1; |
7a8e76a3 | 2587 | } |
168b6b1d | 2588 | } |
7a8e76a3 | 2589 | |
69d1b839 SR |
2590 | event = __rb_reserve_next(cpu_buffer, length, ts, |
2591 | delta, add_timestamp); | |
168b6b1d | 2592 | if (unlikely(PTR_ERR(event) == -EAGAIN)) |
bf41a158 SR |
2593 | goto again; |
2594 | ||
fa743953 SR |
2595 | if (!event) |
2596 | goto out_fail; | |
7a8e76a3 | 2597 | |
7a8e76a3 | 2598 | return event; |
fa743953 SR |
2599 | |
2600 | out_fail: | |
2601 | rb_end_commit(cpu_buffer); | |
2602 | return NULL; | |
7a8e76a3 SR |
2603 | } |
2604 | ||
567cd4da SR |
2605 | /* |
2606 | * The lock and unlock are done within a preempt disable section. | |
2607 | * The current_context per_cpu variable can only be modified | |
2608 | * by the current task between lock and unlock. But it can | |
2609 | * be modified more than once via an interrupt. To pass this | |
2610 | * information from the lock to the unlock without having to | |
2611 | * access the 'in_interrupt()' functions again (which do show | |
2612 | * a bit of overhead in something as critical as function tracing, | |
2613 | * we use a bitmask trick. | |
2614 | * | |
2615 | * bit 0 = NMI context | |
2616 | * bit 1 = IRQ context | |
2617 | * bit 2 = SoftIRQ context | |
2618 | * bit 3 = normal context. | |
2619 | * | |
2620 | * This works because this is the order of contexts that can | |
2621 | * preempt other contexts. A SoftIRQ never preempts an IRQ | |
2622 | * context. | |
2623 | * | |
2624 | * When the context is determined, the corresponding bit is | |
2625 | * checked and set (if it was set, then a recursion of that context | |
2626 | * happened). | |
2627 | * | |
2628 | * On unlock, we need to clear this bit. To do so, just subtract | |
2629 | * 1 from the current_context and AND it to itself. | |
2630 | * | |
2631 | * (binary) | |
2632 | * 101 - 1 = 100 | |
2633 | * 101 & 100 = 100 (clearing bit zero) | |
2634 | * | |
2635 | * 1010 - 1 = 1001 | |
2636 | * 1010 & 1001 = 1000 (clearing bit 1) | |
2637 | * | |
2638 | * The least significant bit can be cleared this way, and it | |
2639 | * just so happens that it is the same bit corresponding to | |
2640 | * the current context. | |
2641 | */ | |
261842b7 | 2642 | |
58a09ec6 SRRH |
2643 | static __always_inline int |
2644 | trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) | |
261842b7 | 2645 | { |
58a09ec6 | 2646 | unsigned int val = cpu_buffer->current_context; |
567cd4da | 2647 | int bit; |
d9abde21 | 2648 | |
567cd4da SR |
2649 | if (in_interrupt()) { |
2650 | if (in_nmi()) | |
a497adb4 | 2651 | bit = RB_CTX_NMI; |
567cd4da | 2652 | else if (in_irq()) |
a497adb4 | 2653 | bit = RB_CTX_IRQ; |
567cd4da | 2654 | else |
a497adb4 | 2655 | bit = RB_CTX_SOFTIRQ; |
567cd4da | 2656 | } else |
a497adb4 | 2657 | bit = RB_CTX_NORMAL; |
d9abde21 | 2658 | |
567cd4da SR |
2659 | if (unlikely(val & (1 << bit))) |
2660 | return 1; | |
d9abde21 | 2661 | |
567cd4da | 2662 | val |= (1 << bit); |
58a09ec6 | 2663 | cpu_buffer->current_context = val; |
d9abde21 | 2664 | |
567cd4da | 2665 | return 0; |
261842b7 SR |
2666 | } |
2667 | ||
58a09ec6 SRRH |
2668 | static __always_inline void |
2669 | trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) | |
261842b7 | 2670 | { |
58a09ec6 | 2671 | cpu_buffer->current_context &= cpu_buffer->current_context - 1; |
261842b7 SR |
2672 | } |
2673 | ||
7a8e76a3 SR |
2674 | /** |
2675 | * ring_buffer_lock_reserve - reserve a part of the buffer | |
2676 | * @buffer: the ring buffer to reserve from | |
2677 | * @length: the length of the data to reserve (excluding event header) | |
7a8e76a3 SR |
2678 | * |
2679 | * Returns a reseverd event on the ring buffer to copy directly to. | |
2680 | * The user of this interface will need to get the body to write into | |
2681 | * and can use the ring_buffer_event_data() interface. | |
2682 | * | |
2683 | * The length is the length of the data needed, not the event length | |
2684 | * which also includes the event header. | |
2685 | * | |
2686 | * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. | |
2687 | * If NULL is returned, then nothing has been allocated or locked. | |
2688 | */ | |
2689 | struct ring_buffer_event * | |
0a987751 | 2690 | ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
7a8e76a3 SR |
2691 | { |
2692 | struct ring_buffer_per_cpu *cpu_buffer; | |
2693 | struct ring_buffer_event *event; | |
5168ae50 | 2694 | int cpu; |
7a8e76a3 | 2695 | |
bf41a158 | 2696 | /* If we are tracing schedule, we don't want to recurse */ |
5168ae50 | 2697 | preempt_disable_notrace(); |
bf41a158 | 2698 | |
3205f806 | 2699 | if (unlikely(atomic_read(&buffer->record_disabled))) |
58a09ec6 | 2700 | goto out; |
261842b7 | 2701 | |
7a8e76a3 SR |
2702 | cpu = raw_smp_processor_id(); |
2703 | ||
3205f806 | 2704 | if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
d769041f | 2705 | goto out; |
7a8e76a3 SR |
2706 | |
2707 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 | 2708 | |
3205f806 | 2709 | if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
d769041f | 2710 | goto out; |
7a8e76a3 | 2711 | |
3205f806 | 2712 | if (unlikely(length > BUF_MAX_DATA_SIZE)) |
bf41a158 | 2713 | goto out; |
7a8e76a3 | 2714 | |
58a09ec6 SRRH |
2715 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
2716 | goto out; | |
2717 | ||
62f0b3eb | 2718 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 2719 | if (!event) |
58a09ec6 | 2720 | goto out_unlock; |
7a8e76a3 SR |
2721 | |
2722 | return event; | |
2723 | ||
58a09ec6 SRRH |
2724 | out_unlock: |
2725 | trace_recursive_unlock(cpu_buffer); | |
d769041f | 2726 | out: |
5168ae50 | 2727 | preempt_enable_notrace(); |
7a8e76a3 SR |
2728 | return NULL; |
2729 | } | |
c4f50183 | 2730 | EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
7a8e76a3 | 2731 | |
a1863c21 SR |
2732 | static void |
2733 | rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
7a8e76a3 SR |
2734 | struct ring_buffer_event *event) |
2735 | { | |
69d1b839 SR |
2736 | u64 delta; |
2737 | ||
fa743953 SR |
2738 | /* |
2739 | * The event first in the commit queue updates the | |
2740 | * time stamp. | |
2741 | */ | |
69d1b839 SR |
2742 | if (rb_event_is_commit(cpu_buffer, event)) { |
2743 | /* | |
2744 | * A commit event that is first on a page | |
2745 | * updates the write timestamp with the page stamp | |
2746 | */ | |
2747 | if (!rb_event_index(event)) | |
2748 | cpu_buffer->write_stamp = | |
2749 | cpu_buffer->commit_page->page->time_stamp; | |
2750 | else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { | |
2751 | delta = event->array[0]; | |
2752 | delta <<= TS_SHIFT; | |
2753 | delta += event->time_delta; | |
2754 | cpu_buffer->write_stamp += delta; | |
2755 | } else | |
2756 | cpu_buffer->write_stamp += event->time_delta; | |
2757 | } | |
a1863c21 | 2758 | } |
bf41a158 | 2759 | |
a1863c21 SR |
2760 | static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
2761 | struct ring_buffer_event *event) | |
2762 | { | |
2763 | local_inc(&cpu_buffer->entries); | |
2764 | rb_update_write_stamp(cpu_buffer, event); | |
fa743953 | 2765 | rb_end_commit(cpu_buffer); |
7a8e76a3 SR |
2766 | } |
2767 | ||
15693458 SRRH |
2768 | static __always_inline void |
2769 | rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) | |
2770 | { | |
1e0d6714 SRRH |
2771 | bool pagebusy; |
2772 | ||
15693458 SRRH |
2773 | if (buffer->irq_work.waiters_pending) { |
2774 | buffer->irq_work.waiters_pending = false; | |
2775 | /* irq_work_queue() supplies it's own memory barriers */ | |
2776 | irq_work_queue(&buffer->irq_work.work); | |
2777 | } | |
2778 | ||
2779 | if (cpu_buffer->irq_work.waiters_pending) { | |
2780 | cpu_buffer->irq_work.waiters_pending = false; | |
2781 | /* irq_work_queue() supplies it's own memory barriers */ | |
2782 | irq_work_queue(&cpu_buffer->irq_work.work); | |
2783 | } | |
1e0d6714 SRRH |
2784 | |
2785 | pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; | |
2786 | ||
2787 | if (!pagebusy && cpu_buffer->irq_work.full_waiters_pending) { | |
2788 | cpu_buffer->irq_work.wakeup_full = true; | |
2789 | cpu_buffer->irq_work.full_waiters_pending = false; | |
2790 | /* irq_work_queue() supplies it's own memory barriers */ | |
2791 | irq_work_queue(&cpu_buffer->irq_work.work); | |
2792 | } | |
15693458 SRRH |
2793 | } |
2794 | ||
7a8e76a3 SR |
2795 | /** |
2796 | * ring_buffer_unlock_commit - commit a reserved | |
2797 | * @buffer: The buffer to commit to | |
2798 | * @event: The event pointer to commit. | |
7a8e76a3 SR |
2799 | * |
2800 | * This commits the data to the ring buffer, and releases any locks held. | |
2801 | * | |
2802 | * Must be paired with ring_buffer_lock_reserve. | |
2803 | */ | |
2804 | int ring_buffer_unlock_commit(struct ring_buffer *buffer, | |
0a987751 | 2805 | struct ring_buffer_event *event) |
7a8e76a3 SR |
2806 | { |
2807 | struct ring_buffer_per_cpu *cpu_buffer; | |
2808 | int cpu = raw_smp_processor_id(); | |
2809 | ||
2810 | cpu_buffer = buffer->buffers[cpu]; | |
2811 | ||
7a8e76a3 SR |
2812 | rb_commit(cpu_buffer, event); |
2813 | ||
15693458 SRRH |
2814 | rb_wakeups(buffer, cpu_buffer); |
2815 | ||
58a09ec6 | 2816 | trace_recursive_unlock(cpu_buffer); |
261842b7 | 2817 | |
5168ae50 | 2818 | preempt_enable_notrace(); |
7a8e76a3 SR |
2819 | |
2820 | return 0; | |
2821 | } | |
c4f50183 | 2822 | EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
7a8e76a3 | 2823 | |
f3b9aae1 FW |
2824 | static inline void rb_event_discard(struct ring_buffer_event *event) |
2825 | { | |
69d1b839 SR |
2826 | if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) |
2827 | event = skip_time_extend(event); | |
2828 | ||
334d4169 LJ |
2829 | /* array[0] holds the actual length for the discarded event */ |
2830 | event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; | |
2831 | event->type_len = RINGBUF_TYPE_PADDING; | |
f3b9aae1 FW |
2832 | /* time delta must be non zero */ |
2833 | if (!event->time_delta) | |
2834 | event->time_delta = 1; | |
2835 | } | |
2836 | ||
a1863c21 SR |
2837 | /* |
2838 | * Decrement the entries to the page that an event is on. | |
2839 | * The event does not even need to exist, only the pointer | |
2840 | * to the page it is on. This may only be called before the commit | |
2841 | * takes place. | |
2842 | */ | |
2843 | static inline void | |
2844 | rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, | |
2845 | struct ring_buffer_event *event) | |
2846 | { | |
2847 | unsigned long addr = (unsigned long)event; | |
2848 | struct buffer_page *bpage = cpu_buffer->commit_page; | |
2849 | struct buffer_page *start; | |
2850 | ||
2851 | addr &= PAGE_MASK; | |
2852 | ||
2853 | /* Do the likely case first */ | |
2854 | if (likely(bpage->page == (void *)addr)) { | |
2855 | local_dec(&bpage->entries); | |
2856 | return; | |
2857 | } | |
2858 | ||
2859 | /* | |
2860 | * Because the commit page may be on the reader page we | |
2861 | * start with the next page and check the end loop there. | |
2862 | */ | |
2863 | rb_inc_page(cpu_buffer, &bpage); | |
2864 | start = bpage; | |
2865 | do { | |
2866 | if (bpage->page == (void *)addr) { | |
2867 | local_dec(&bpage->entries); | |
2868 | return; | |
2869 | } | |
2870 | rb_inc_page(cpu_buffer, &bpage); | |
2871 | } while (bpage != start); | |
2872 | ||
2873 | /* commit not part of this buffer?? */ | |
2874 | RB_WARN_ON(cpu_buffer, 1); | |
2875 | } | |
2876 | ||
fa1b47dd SR |
2877 | /** |
2878 | * ring_buffer_commit_discard - discard an event that has not been committed | |
2879 | * @buffer: the ring buffer | |
2880 | * @event: non committed event to discard | |
2881 | * | |
dc892f73 SR |
2882 | * Sometimes an event that is in the ring buffer needs to be ignored. |
2883 | * This function lets the user discard an event in the ring buffer | |
2884 | * and then that event will not be read later. | |
2885 | * | |
2886 | * This function only works if it is called before the the item has been | |
2887 | * committed. It will try to free the event from the ring buffer | |
fa1b47dd SR |
2888 | * if another event has not been added behind it. |
2889 | * | |
2890 | * If another event has been added behind it, it will set the event | |
2891 | * up as discarded, and perform the commit. | |
2892 | * | |
2893 | * If this function is called, do not call ring_buffer_unlock_commit on | |
2894 | * the event. | |
2895 | */ | |
2896 | void ring_buffer_discard_commit(struct ring_buffer *buffer, | |
2897 | struct ring_buffer_event *event) | |
2898 | { | |
2899 | struct ring_buffer_per_cpu *cpu_buffer; | |
fa1b47dd SR |
2900 | int cpu; |
2901 | ||
2902 | /* The event is discarded regardless */ | |
f3b9aae1 | 2903 | rb_event_discard(event); |
fa1b47dd | 2904 | |
fa743953 SR |
2905 | cpu = smp_processor_id(); |
2906 | cpu_buffer = buffer->buffers[cpu]; | |
2907 | ||
fa1b47dd SR |
2908 | /* |
2909 | * This must only be called if the event has not been | |
2910 | * committed yet. Thus we can assume that preemption | |
2911 | * is still disabled. | |
2912 | */ | |
fa743953 | 2913 | RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
fa1b47dd | 2914 | |
a1863c21 | 2915 | rb_decrement_entry(cpu_buffer, event); |
0f2541d2 | 2916 | if (rb_try_to_discard(cpu_buffer, event)) |
edd813bf | 2917 | goto out; |
fa1b47dd SR |
2918 | |
2919 | /* | |
2920 | * The commit is still visible by the reader, so we | |
a1863c21 | 2921 | * must still update the timestamp. |
fa1b47dd | 2922 | */ |
a1863c21 | 2923 | rb_update_write_stamp(cpu_buffer, event); |
fa1b47dd | 2924 | out: |
fa743953 | 2925 | rb_end_commit(cpu_buffer); |
fa1b47dd | 2926 | |
58a09ec6 | 2927 | trace_recursive_unlock(cpu_buffer); |
f3b9aae1 | 2928 | |
5168ae50 | 2929 | preempt_enable_notrace(); |
fa1b47dd SR |
2930 | |
2931 | } | |
2932 | EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); | |
2933 | ||
7a8e76a3 SR |
2934 | /** |
2935 | * ring_buffer_write - write data to the buffer without reserving | |
2936 | * @buffer: The ring buffer to write to. | |
2937 | * @length: The length of the data being written (excluding the event header) | |
2938 | * @data: The data to write to the buffer. | |
2939 | * | |
2940 | * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as | |
2941 | * one function. If you already have the data to write to the buffer, it | |
2942 | * may be easier to simply call this function. | |
2943 | * | |
2944 | * Note, like ring_buffer_lock_reserve, the length is the length of the data | |
2945 | * and not the length of the event which would hold the header. | |
2946 | */ | |
2947 | int ring_buffer_write(struct ring_buffer *buffer, | |
01e3e710 DS |
2948 | unsigned long length, |
2949 | void *data) | |
7a8e76a3 SR |
2950 | { |
2951 | struct ring_buffer_per_cpu *cpu_buffer; | |
2952 | struct ring_buffer_event *event; | |
7a8e76a3 SR |
2953 | void *body; |
2954 | int ret = -EBUSY; | |
5168ae50 | 2955 | int cpu; |
7a8e76a3 | 2956 | |
5168ae50 | 2957 | preempt_disable_notrace(); |
bf41a158 | 2958 | |
52fbe9cd LJ |
2959 | if (atomic_read(&buffer->record_disabled)) |
2960 | goto out; | |
2961 | ||
7a8e76a3 SR |
2962 | cpu = raw_smp_processor_id(); |
2963 | ||
9e01c1b7 | 2964 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
d769041f | 2965 | goto out; |
7a8e76a3 SR |
2966 | |
2967 | cpu_buffer = buffer->buffers[cpu]; | |
7a8e76a3 SR |
2968 | |
2969 | if (atomic_read(&cpu_buffer->record_disabled)) | |
2970 | goto out; | |
2971 | ||
be957c44 SR |
2972 | if (length > BUF_MAX_DATA_SIZE) |
2973 | goto out; | |
2974 | ||
985e871b SRRH |
2975 | if (unlikely(trace_recursive_lock(cpu_buffer))) |
2976 | goto out; | |
2977 | ||
62f0b3eb | 2978 | event = rb_reserve_next_event(buffer, cpu_buffer, length); |
7a8e76a3 | 2979 | if (!event) |
985e871b | 2980 | goto out_unlock; |
7a8e76a3 SR |
2981 | |
2982 | body = rb_event_data(event); | |
2983 | ||
2984 | memcpy(body, data, length); | |
2985 | ||
2986 | rb_commit(cpu_buffer, event); | |
2987 | ||
15693458 SRRH |
2988 | rb_wakeups(buffer, cpu_buffer); |
2989 | ||
7a8e76a3 | 2990 | ret = 0; |
985e871b SRRH |
2991 | |
2992 | out_unlock: | |
2993 | trace_recursive_unlock(cpu_buffer); | |
2994 | ||
7a8e76a3 | 2995 | out: |
5168ae50 | 2996 | preempt_enable_notrace(); |
7a8e76a3 SR |
2997 | |
2998 | return ret; | |
2999 | } | |
c4f50183 | 3000 | EXPORT_SYMBOL_GPL(ring_buffer_write); |
7a8e76a3 | 3001 | |
34a148bf | 3002 | static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
bf41a158 SR |
3003 | { |
3004 | struct buffer_page *reader = cpu_buffer->reader_page; | |
77ae365e | 3005 | struct buffer_page *head = rb_set_head_page(cpu_buffer); |
bf41a158 SR |
3006 | struct buffer_page *commit = cpu_buffer->commit_page; |
3007 | ||
77ae365e SR |
3008 | /* In case of error, head will be NULL */ |
3009 | if (unlikely(!head)) | |
3010 | return 1; | |
3011 | ||
bf41a158 SR |
3012 | return reader->read == rb_page_commit(reader) && |
3013 | (commit == reader || | |
3014 | (commit == head && | |
3015 | head->read == rb_page_commit(commit))); | |
3016 | } | |
3017 | ||
7a8e76a3 SR |
3018 | /** |
3019 | * ring_buffer_record_disable - stop all writes into the buffer | |
3020 | * @buffer: The ring buffer to stop writes to. | |
3021 | * | |
3022 | * This prevents all writes to the buffer. Any attempt to write | |
3023 | * to the buffer after this will fail and return NULL. | |
3024 | * | |
3025 | * The caller should call synchronize_sched() after this. | |
3026 | */ | |
3027 | void ring_buffer_record_disable(struct ring_buffer *buffer) | |
3028 | { | |
3029 | atomic_inc(&buffer->record_disabled); | |
3030 | } | |
c4f50183 | 3031 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
7a8e76a3 SR |
3032 | |
3033 | /** | |
3034 | * ring_buffer_record_enable - enable writes to the buffer | |
3035 | * @buffer: The ring buffer to enable writes | |
3036 | * | |
3037 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3038 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
3039 | */ |
3040 | void ring_buffer_record_enable(struct ring_buffer *buffer) | |
3041 | { | |
3042 | atomic_dec(&buffer->record_disabled); | |
3043 | } | |
c4f50183 | 3044 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
7a8e76a3 | 3045 | |
499e5470 SR |
3046 | /** |
3047 | * ring_buffer_record_off - stop all writes into the buffer | |
3048 | * @buffer: The ring buffer to stop writes to. | |
3049 | * | |
3050 | * This prevents all writes to the buffer. Any attempt to write | |
3051 | * to the buffer after this will fail and return NULL. | |
3052 | * | |
3053 | * This is different than ring_buffer_record_disable() as | |
87abb3b1 | 3054 | * it works like an on/off switch, where as the disable() version |
499e5470 SR |
3055 | * must be paired with a enable(). |
3056 | */ | |
3057 | void ring_buffer_record_off(struct ring_buffer *buffer) | |
3058 | { | |
3059 | unsigned int rd; | |
3060 | unsigned int new_rd; | |
3061 | ||
3062 | do { | |
3063 | rd = atomic_read(&buffer->record_disabled); | |
3064 | new_rd = rd | RB_BUFFER_OFF; | |
3065 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3066 | } | |
3067 | EXPORT_SYMBOL_GPL(ring_buffer_record_off); | |
3068 | ||
3069 | /** | |
3070 | * ring_buffer_record_on - restart writes into the buffer | |
3071 | * @buffer: The ring buffer to start writes to. | |
3072 | * | |
3073 | * This enables all writes to the buffer that was disabled by | |
3074 | * ring_buffer_record_off(). | |
3075 | * | |
3076 | * This is different than ring_buffer_record_enable() as | |
87abb3b1 | 3077 | * it works like an on/off switch, where as the enable() version |
499e5470 SR |
3078 | * must be paired with a disable(). |
3079 | */ | |
3080 | void ring_buffer_record_on(struct ring_buffer *buffer) | |
3081 | { | |
3082 | unsigned int rd; | |
3083 | unsigned int new_rd; | |
3084 | ||
3085 | do { | |
3086 | rd = atomic_read(&buffer->record_disabled); | |
3087 | new_rd = rd & ~RB_BUFFER_OFF; | |
3088 | } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); | |
3089 | } | |
3090 | EXPORT_SYMBOL_GPL(ring_buffer_record_on); | |
3091 | ||
3092 | /** | |
3093 | * ring_buffer_record_is_on - return true if the ring buffer can write | |
3094 | * @buffer: The ring buffer to see if write is enabled | |
3095 | * | |
3096 | * Returns true if the ring buffer is in a state that it accepts writes. | |
3097 | */ | |
3098 | int ring_buffer_record_is_on(struct ring_buffer *buffer) | |
3099 | { | |
3100 | return !atomic_read(&buffer->record_disabled); | |
3101 | } | |
3102 | ||
7a8e76a3 SR |
3103 | /** |
3104 | * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer | |
3105 | * @buffer: The ring buffer to stop writes to. | |
3106 | * @cpu: The CPU buffer to stop | |
3107 | * | |
3108 | * This prevents all writes to the buffer. Any attempt to write | |
3109 | * to the buffer after this will fail and return NULL. | |
3110 | * | |
3111 | * The caller should call synchronize_sched() after this. | |
3112 | */ | |
3113 | void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) | |
3114 | { | |
3115 | struct ring_buffer_per_cpu *cpu_buffer; | |
3116 | ||
9e01c1b7 | 3117 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3118 | return; |
7a8e76a3 SR |
3119 | |
3120 | cpu_buffer = buffer->buffers[cpu]; | |
3121 | atomic_inc(&cpu_buffer->record_disabled); | |
3122 | } | |
c4f50183 | 3123 | EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
7a8e76a3 SR |
3124 | |
3125 | /** | |
3126 | * ring_buffer_record_enable_cpu - enable writes to the buffer | |
3127 | * @buffer: The ring buffer to enable writes | |
3128 | * @cpu: The CPU to enable. | |
3129 | * | |
3130 | * Note, multiple disables will need the same number of enables | |
c41b20e7 | 3131 | * to truly enable the writing (much like preempt_disable). |
7a8e76a3 SR |
3132 | */ |
3133 | void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) | |
3134 | { | |
3135 | struct ring_buffer_per_cpu *cpu_buffer; | |
3136 | ||
9e01c1b7 | 3137 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3138 | return; |
7a8e76a3 SR |
3139 | |
3140 | cpu_buffer = buffer->buffers[cpu]; | |
3141 | atomic_dec(&cpu_buffer->record_disabled); | |
3142 | } | |
c4f50183 | 3143 | EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
7a8e76a3 | 3144 | |
f6195aa0 SR |
3145 | /* |
3146 | * The total entries in the ring buffer is the running counter | |
3147 | * of entries entered into the ring buffer, minus the sum of | |
3148 | * the entries read from the ring buffer and the number of | |
3149 | * entries that were overwritten. | |
3150 | */ | |
3151 | static inline unsigned long | |
3152 | rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) | |
3153 | { | |
3154 | return local_read(&cpu_buffer->entries) - | |
3155 | (local_read(&cpu_buffer->overrun) + cpu_buffer->read); | |
3156 | } | |
3157 | ||
c64e148a VN |
3158 | /** |
3159 | * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer | |
3160 | * @buffer: The ring buffer | |
3161 | * @cpu: The per CPU buffer to read from. | |
3162 | */ | |
50ecf2c3 | 3163 | u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) |
c64e148a VN |
3164 | { |
3165 | unsigned long flags; | |
3166 | struct ring_buffer_per_cpu *cpu_buffer; | |
3167 | struct buffer_page *bpage; | |
da830e58 | 3168 | u64 ret = 0; |
c64e148a VN |
3169 | |
3170 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3171 | return 0; | |
3172 | ||
3173 | cpu_buffer = buffer->buffers[cpu]; | |
7115e3fc | 3174 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3175 | /* |
3176 | * if the tail is on reader_page, oldest time stamp is on the reader | |
3177 | * page | |
3178 | */ | |
3179 | if (cpu_buffer->tail_page == cpu_buffer->reader_page) | |
3180 | bpage = cpu_buffer->reader_page; | |
3181 | else | |
3182 | bpage = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3183 | if (bpage) |
3184 | ret = bpage->page->time_stamp; | |
7115e3fc | 3185 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
c64e148a VN |
3186 | |
3187 | return ret; | |
3188 | } | |
3189 | EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); | |
3190 | ||
3191 | /** | |
3192 | * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer | |
3193 | * @buffer: The ring buffer | |
3194 | * @cpu: The per CPU buffer to read from. | |
3195 | */ | |
3196 | unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu) | |
3197 | { | |
3198 | struct ring_buffer_per_cpu *cpu_buffer; | |
3199 | unsigned long ret; | |
3200 | ||
3201 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3202 | return 0; | |
3203 | ||
3204 | cpu_buffer = buffer->buffers[cpu]; | |
3205 | ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; | |
3206 | ||
3207 | return ret; | |
3208 | } | |
3209 | EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); | |
3210 | ||
7a8e76a3 SR |
3211 | /** |
3212 | * ring_buffer_entries_cpu - get the number of entries in a cpu buffer | |
3213 | * @buffer: The ring buffer | |
3214 | * @cpu: The per CPU buffer to get the entries from. | |
3215 | */ | |
3216 | unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) | |
3217 | { | |
3218 | struct ring_buffer_per_cpu *cpu_buffer; | |
3219 | ||
9e01c1b7 | 3220 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3221 | return 0; |
7a8e76a3 SR |
3222 | |
3223 | cpu_buffer = buffer->buffers[cpu]; | |
554f786e | 3224 | |
f6195aa0 | 3225 | return rb_num_of_entries(cpu_buffer); |
7a8e76a3 | 3226 | } |
c4f50183 | 3227 | EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
7a8e76a3 SR |
3228 | |
3229 | /** | |
884bfe89 SP |
3230 | * ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
3231 | * buffer wrapping around (only if RB_FL_OVERWRITE is on). | |
7a8e76a3 SR |
3232 | * @buffer: The ring buffer |
3233 | * @cpu: The per CPU buffer to get the number of overruns from | |
3234 | */ | |
3235 | unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
3236 | { | |
3237 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 3238 | unsigned long ret; |
7a8e76a3 | 3239 | |
9e01c1b7 | 3240 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3241 | return 0; |
7a8e76a3 SR |
3242 | |
3243 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3244 | ret = local_read(&cpu_buffer->overrun); |
554f786e SR |
3245 | |
3246 | return ret; | |
7a8e76a3 | 3247 | } |
c4f50183 | 3248 | EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); |
7a8e76a3 | 3249 | |
f0d2c681 | 3250 | /** |
884bfe89 SP |
3251 | * ring_buffer_commit_overrun_cpu - get the number of overruns caused by |
3252 | * commits failing due to the buffer wrapping around while there are uncommitted | |
3253 | * events, such as during an interrupt storm. | |
f0d2c681 SR |
3254 | * @buffer: The ring buffer |
3255 | * @cpu: The per CPU buffer to get the number of overruns from | |
3256 | */ | |
3257 | unsigned long | |
3258 | ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu) | |
3259 | { | |
3260 | struct ring_buffer_per_cpu *cpu_buffer; | |
3261 | unsigned long ret; | |
3262 | ||
3263 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3264 | return 0; | |
3265 | ||
3266 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3267 | ret = local_read(&cpu_buffer->commit_overrun); |
f0d2c681 SR |
3268 | |
3269 | return ret; | |
3270 | } | |
3271 | EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu); | |
3272 | ||
884bfe89 SP |
3273 | /** |
3274 | * ring_buffer_dropped_events_cpu - get the number of dropped events caused by | |
3275 | * the ring buffer filling up (only if RB_FL_OVERWRITE is off). | |
3276 | * @buffer: The ring buffer | |
3277 | * @cpu: The per CPU buffer to get the number of overruns from | |
3278 | */ | |
3279 | unsigned long | |
3280 | ring_buffer_dropped_events_cpu(struct ring_buffer *buffer, int cpu) | |
3281 | { | |
3282 | struct ring_buffer_per_cpu *cpu_buffer; | |
3283 | unsigned long ret; | |
3284 | ||
3285 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3286 | return 0; | |
3287 | ||
3288 | cpu_buffer = buffer->buffers[cpu]; | |
3289 | ret = local_read(&cpu_buffer->dropped_events); | |
3290 | ||
3291 | return ret; | |
3292 | } | |
3293 | EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu); | |
3294 | ||
ad964704 SRRH |
3295 | /** |
3296 | * ring_buffer_read_events_cpu - get the number of events successfully read | |
3297 | * @buffer: The ring buffer | |
3298 | * @cpu: The per CPU buffer to get the number of events read | |
3299 | */ | |
3300 | unsigned long | |
3301 | ring_buffer_read_events_cpu(struct ring_buffer *buffer, int cpu) | |
3302 | { | |
3303 | struct ring_buffer_per_cpu *cpu_buffer; | |
3304 | ||
3305 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
3306 | return 0; | |
3307 | ||
3308 | cpu_buffer = buffer->buffers[cpu]; | |
3309 | return cpu_buffer->read; | |
3310 | } | |
3311 | EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu); | |
3312 | ||
7a8e76a3 SR |
3313 | /** |
3314 | * ring_buffer_entries - get the number of entries in a buffer | |
3315 | * @buffer: The ring buffer | |
3316 | * | |
3317 | * Returns the total number of entries in the ring buffer | |
3318 | * (all CPU entries) | |
3319 | */ | |
3320 | unsigned long ring_buffer_entries(struct ring_buffer *buffer) | |
3321 | { | |
3322 | struct ring_buffer_per_cpu *cpu_buffer; | |
3323 | unsigned long entries = 0; | |
3324 | int cpu; | |
3325 | ||
3326 | /* if you care about this being correct, lock the buffer */ | |
3327 | for_each_buffer_cpu(buffer, cpu) { | |
3328 | cpu_buffer = buffer->buffers[cpu]; | |
f6195aa0 | 3329 | entries += rb_num_of_entries(cpu_buffer); |
7a8e76a3 SR |
3330 | } |
3331 | ||
3332 | return entries; | |
3333 | } | |
c4f50183 | 3334 | EXPORT_SYMBOL_GPL(ring_buffer_entries); |
7a8e76a3 SR |
3335 | |
3336 | /** | |
67b394f7 | 3337 | * ring_buffer_overruns - get the number of overruns in buffer |
7a8e76a3 SR |
3338 | * @buffer: The ring buffer |
3339 | * | |
3340 | * Returns the total number of overruns in the ring buffer | |
3341 | * (all CPU entries) | |
3342 | */ | |
3343 | unsigned long ring_buffer_overruns(struct ring_buffer *buffer) | |
3344 | { | |
3345 | struct ring_buffer_per_cpu *cpu_buffer; | |
3346 | unsigned long overruns = 0; | |
3347 | int cpu; | |
3348 | ||
3349 | /* if you care about this being correct, lock the buffer */ | |
3350 | for_each_buffer_cpu(buffer, cpu) { | |
3351 | cpu_buffer = buffer->buffers[cpu]; | |
77ae365e | 3352 | overruns += local_read(&cpu_buffer->overrun); |
7a8e76a3 SR |
3353 | } |
3354 | ||
3355 | return overruns; | |
3356 | } | |
c4f50183 | 3357 | EXPORT_SYMBOL_GPL(ring_buffer_overruns); |
7a8e76a3 | 3358 | |
642edba5 | 3359 | static void rb_iter_reset(struct ring_buffer_iter *iter) |
7a8e76a3 SR |
3360 | { |
3361 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3362 | ||
d769041f | 3363 | /* Iterator usage is expected to have record disabled */ |
651e22f2 SRRH |
3364 | iter->head_page = cpu_buffer->reader_page; |
3365 | iter->head = cpu_buffer->reader_page->read; | |
3366 | ||
3367 | iter->cache_reader_page = iter->head_page; | |
24607f11 | 3368 | iter->cache_read = cpu_buffer->read; |
651e22f2 | 3369 | |
d769041f SR |
3370 | if (iter->head) |
3371 | iter->read_stamp = cpu_buffer->read_stamp; | |
3372 | else | |
abc9b56d | 3373 | iter->read_stamp = iter->head_page->page->time_stamp; |
642edba5 | 3374 | } |
f83c9d0f | 3375 | |
642edba5 SR |
3376 | /** |
3377 | * ring_buffer_iter_reset - reset an iterator | |
3378 | * @iter: The iterator to reset | |
3379 | * | |
3380 | * Resets the iterator, so that it will start from the beginning | |
3381 | * again. | |
3382 | */ | |
3383 | void ring_buffer_iter_reset(struct ring_buffer_iter *iter) | |
3384 | { | |
554f786e | 3385 | struct ring_buffer_per_cpu *cpu_buffer; |
642edba5 SR |
3386 | unsigned long flags; |
3387 | ||
554f786e SR |
3388 | if (!iter) |
3389 | return; | |
3390 | ||
3391 | cpu_buffer = iter->cpu_buffer; | |
3392 | ||
5389f6fa | 3393 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
642edba5 | 3394 | rb_iter_reset(iter); |
5389f6fa | 3395 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 3396 | } |
c4f50183 | 3397 | EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); |
7a8e76a3 SR |
3398 | |
3399 | /** | |
3400 | * ring_buffer_iter_empty - check if an iterator has no more to read | |
3401 | * @iter: The iterator to check | |
3402 | */ | |
3403 | int ring_buffer_iter_empty(struct ring_buffer_iter *iter) | |
3404 | { | |
3405 | struct ring_buffer_per_cpu *cpu_buffer; | |
3406 | ||
3407 | cpu_buffer = iter->cpu_buffer; | |
3408 | ||
bf41a158 SR |
3409 | return iter->head_page == cpu_buffer->commit_page && |
3410 | iter->head == rb_commit_index(cpu_buffer); | |
7a8e76a3 | 3411 | } |
c4f50183 | 3412 | EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |
7a8e76a3 SR |
3413 | |
3414 | static void | |
3415 | rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, | |
3416 | struct ring_buffer_event *event) | |
3417 | { | |
3418 | u64 delta; | |
3419 | ||
334d4169 | 3420 | switch (event->type_len) { |
7a8e76a3 SR |
3421 | case RINGBUF_TYPE_PADDING: |
3422 | return; | |
3423 | ||
3424 | case RINGBUF_TYPE_TIME_EXTEND: | |
3425 | delta = event->array[0]; | |
3426 | delta <<= TS_SHIFT; | |
3427 | delta += event->time_delta; | |
3428 | cpu_buffer->read_stamp += delta; | |
3429 | return; | |
3430 | ||
3431 | case RINGBUF_TYPE_TIME_STAMP: | |
3432 | /* FIXME: not implemented */ | |
3433 | return; | |
3434 | ||
3435 | case RINGBUF_TYPE_DATA: | |
3436 | cpu_buffer->read_stamp += event->time_delta; | |
3437 | return; | |
3438 | ||
3439 | default: | |
3440 | BUG(); | |
3441 | } | |
3442 | return; | |
3443 | } | |
3444 | ||
3445 | static void | |
3446 | rb_update_iter_read_stamp(struct ring_buffer_iter *iter, | |
3447 | struct ring_buffer_event *event) | |
3448 | { | |
3449 | u64 delta; | |
3450 | ||
334d4169 | 3451 | switch (event->type_len) { |
7a8e76a3 SR |
3452 | case RINGBUF_TYPE_PADDING: |
3453 | return; | |
3454 | ||
3455 | case RINGBUF_TYPE_TIME_EXTEND: | |
3456 | delta = event->array[0]; | |
3457 | delta <<= TS_SHIFT; | |
3458 | delta += event->time_delta; | |
3459 | iter->read_stamp += delta; | |
3460 | return; | |
3461 | ||
3462 | case RINGBUF_TYPE_TIME_STAMP: | |
3463 | /* FIXME: not implemented */ | |
3464 | return; | |
3465 | ||
3466 | case RINGBUF_TYPE_DATA: | |
3467 | iter->read_stamp += event->time_delta; | |
3468 | return; | |
3469 | ||
3470 | default: | |
3471 | BUG(); | |
3472 | } | |
3473 | return; | |
3474 | } | |
3475 | ||
d769041f SR |
3476 | static struct buffer_page * |
3477 | rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) | |
7a8e76a3 | 3478 | { |
d769041f | 3479 | struct buffer_page *reader = NULL; |
66a8cb95 | 3480 | unsigned long overwrite; |
d769041f | 3481 | unsigned long flags; |
818e3dd3 | 3482 | int nr_loops = 0; |
77ae365e | 3483 | int ret; |
d769041f | 3484 | |
3e03fb7f | 3485 | local_irq_save(flags); |
0199c4e6 | 3486 | arch_spin_lock(&cpu_buffer->lock); |
d769041f SR |
3487 | |
3488 | again: | |
818e3dd3 SR |
3489 | /* |
3490 | * This should normally only loop twice. But because the | |
3491 | * start of the reader inserts an empty page, it causes | |
3492 | * a case where we will loop three times. There should be no | |
3493 | * reason to loop four times (that I know of). | |
3494 | */ | |
3e89c7bb | 3495 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { |
818e3dd3 SR |
3496 | reader = NULL; |
3497 | goto out; | |
3498 | } | |
3499 | ||
d769041f SR |
3500 | reader = cpu_buffer->reader_page; |
3501 | ||
3502 | /* If there's more to read, return this page */ | |
bf41a158 | 3503 | if (cpu_buffer->reader_page->read < rb_page_size(reader)) |
d769041f SR |
3504 | goto out; |
3505 | ||
3506 | /* Never should we have an index greater than the size */ | |
3e89c7bb SR |
3507 | if (RB_WARN_ON(cpu_buffer, |
3508 | cpu_buffer->reader_page->read > rb_page_size(reader))) | |
3509 | goto out; | |
d769041f SR |
3510 | |
3511 | /* check if we caught up to the tail */ | |
3512 | reader = NULL; | |
bf41a158 | 3513 | if (cpu_buffer->commit_page == cpu_buffer->reader_page) |
d769041f | 3514 | goto out; |
7a8e76a3 | 3515 | |
a5fb8331 SR |
3516 | /* Don't bother swapping if the ring buffer is empty */ |
3517 | if (rb_num_of_entries(cpu_buffer) == 0) | |
3518 | goto out; | |
3519 | ||
7a8e76a3 | 3520 | /* |
d769041f | 3521 | * Reset the reader page to size zero. |
7a8e76a3 | 3522 | */ |
77ae365e SR |
3523 | local_set(&cpu_buffer->reader_page->write, 0); |
3524 | local_set(&cpu_buffer->reader_page->entries, 0); | |
3525 | local_set(&cpu_buffer->reader_page->page->commit, 0); | |
ff0ff84a | 3526 | cpu_buffer->reader_page->real_end = 0; |
7a8e76a3 | 3527 | |
77ae365e SR |
3528 | spin: |
3529 | /* | |
3530 | * Splice the empty reader page into the list around the head. | |
3531 | */ | |
3532 | reader = rb_set_head_page(cpu_buffer); | |
54f7be5b SR |
3533 | if (!reader) |
3534 | goto out; | |
0e1ff5d7 | 3535 | cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); |
d769041f | 3536 | cpu_buffer->reader_page->list.prev = reader->list.prev; |
bf41a158 | 3537 | |
3adc54fa SR |
3538 | /* |
3539 | * cpu_buffer->pages just needs to point to the buffer, it | |
3540 | * has no specific buffer page to point to. Lets move it out | |
25985edc | 3541 | * of our way so we don't accidentally swap it. |
3adc54fa SR |
3542 | */ |
3543 | cpu_buffer->pages = reader->list.prev; | |
3544 | ||
77ae365e SR |
3545 | /* The reader page will be pointing to the new head */ |
3546 | rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list); | |
7a8e76a3 | 3547 | |
66a8cb95 SR |
3548 | /* |
3549 | * We want to make sure we read the overruns after we set up our | |
3550 | * pointers to the next object. The writer side does a | |
3551 | * cmpxchg to cross pages which acts as the mb on the writer | |
3552 | * side. Note, the reader will constantly fail the swap | |
3553 | * while the writer is updating the pointers, so this | |
3554 | * guarantees that the overwrite recorded here is the one we | |
3555 | * want to compare with the last_overrun. | |
3556 | */ | |
3557 | smp_mb(); | |
3558 | overwrite = local_read(&(cpu_buffer->overrun)); | |
3559 | ||
77ae365e SR |
3560 | /* |
3561 | * Here's the tricky part. | |
3562 | * | |
3563 | * We need to move the pointer past the header page. | |
3564 | * But we can only do that if a writer is not currently | |
3565 | * moving it. The page before the header page has the | |
3566 | * flag bit '1' set if it is pointing to the page we want. | |
3567 | * but if the writer is in the process of moving it | |
3568 | * than it will be '2' or already moved '0'. | |
3569 | */ | |
3570 | ||
3571 | ret = rb_head_page_replace(reader, cpu_buffer->reader_page); | |
7a8e76a3 SR |
3572 | |
3573 | /* | |
77ae365e | 3574 | * If we did not convert it, then we must try again. |
7a8e76a3 | 3575 | */ |
77ae365e SR |
3576 | if (!ret) |
3577 | goto spin; | |
7a8e76a3 | 3578 | |
77ae365e SR |
3579 | /* |
3580 | * Yeah! We succeeded in replacing the page. | |
3581 | * | |
3582 | * Now make the new head point back to the reader page. | |
3583 | */ | |
5ded3dc6 | 3584 | rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list; |
77ae365e | 3585 | rb_inc_page(cpu_buffer, &cpu_buffer->head_page); |
d769041f SR |
3586 | |
3587 | /* Finally update the reader page to the new head */ | |
3588 | cpu_buffer->reader_page = reader; | |
3589 | rb_reset_reader_page(cpu_buffer); | |
3590 | ||
66a8cb95 SR |
3591 | if (overwrite != cpu_buffer->last_overrun) { |
3592 | cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun; | |
3593 | cpu_buffer->last_overrun = overwrite; | |
3594 | } | |
3595 | ||
d769041f SR |
3596 | goto again; |
3597 | ||
3598 | out: | |
0199c4e6 | 3599 | arch_spin_unlock(&cpu_buffer->lock); |
3e03fb7f | 3600 | local_irq_restore(flags); |
d769041f SR |
3601 | |
3602 | return reader; | |
3603 | } | |
3604 | ||
3605 | static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) | |
3606 | { | |
3607 | struct ring_buffer_event *event; | |
3608 | struct buffer_page *reader; | |
3609 | unsigned length; | |
3610 | ||
3611 | reader = rb_get_reader_page(cpu_buffer); | |
7a8e76a3 | 3612 | |
d769041f | 3613 | /* This function should not be called when buffer is empty */ |
3e89c7bb SR |
3614 | if (RB_WARN_ON(cpu_buffer, !reader)) |
3615 | return; | |
7a8e76a3 | 3616 | |
d769041f SR |
3617 | event = rb_reader_event(cpu_buffer); |
3618 | ||
a1863c21 | 3619 | if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
e4906eff | 3620 | cpu_buffer->read++; |
d769041f SR |
3621 | |
3622 | rb_update_read_stamp(cpu_buffer, event); | |
3623 | ||
3624 | length = rb_event_length(event); | |
6f807acd | 3625 | cpu_buffer->reader_page->read += length; |
7a8e76a3 SR |
3626 | } |
3627 | ||
3628 | static void rb_advance_iter(struct ring_buffer_iter *iter) | |
3629 | { | |
7a8e76a3 SR |
3630 | struct ring_buffer_per_cpu *cpu_buffer; |
3631 | struct ring_buffer_event *event; | |
3632 | unsigned length; | |
3633 | ||
3634 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 SR |
3635 | |
3636 | /* | |
3637 | * Check if we are at the end of the buffer. | |
3638 | */ | |
bf41a158 | 3639 | if (iter->head >= rb_page_size(iter->head_page)) { |
ea05b57c SR |
3640 | /* discarded commits can make the page empty */ |
3641 | if (iter->head_page == cpu_buffer->commit_page) | |
3e89c7bb | 3642 | return; |
d769041f | 3643 | rb_inc_iter(iter); |
7a8e76a3 SR |
3644 | return; |
3645 | } | |
3646 | ||
3647 | event = rb_iter_head_event(iter); | |
3648 | ||
3649 | length = rb_event_length(event); | |
3650 | ||
3651 | /* | |
3652 | * This should not be called to advance the header if we are | |
3653 | * at the tail of the buffer. | |
3654 | */ | |
3e89c7bb | 3655 | if (RB_WARN_ON(cpu_buffer, |
f536aafc | 3656 | (iter->head_page == cpu_buffer->commit_page) && |
3e89c7bb SR |
3657 | (iter->head + length > rb_commit_index(cpu_buffer)))) |
3658 | return; | |
7a8e76a3 SR |
3659 | |
3660 | rb_update_iter_read_stamp(iter, event); | |
3661 | ||
3662 | iter->head += length; | |
3663 | ||
3664 | /* check for end of page padding */ | |
bf41a158 SR |
3665 | if ((iter->head >= rb_page_size(iter->head_page)) && |
3666 | (iter->head_page != cpu_buffer->commit_page)) | |
771e0384 | 3667 | rb_inc_iter(iter); |
7a8e76a3 SR |
3668 | } |
3669 | ||
66a8cb95 SR |
3670 | static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) |
3671 | { | |
3672 | return cpu_buffer->lost_events; | |
3673 | } | |
3674 | ||
f83c9d0f | 3675 | static struct ring_buffer_event * |
66a8cb95 SR |
3676 | rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, |
3677 | unsigned long *lost_events) | |
7a8e76a3 | 3678 | { |
7a8e76a3 | 3679 | struct ring_buffer_event *event; |
d769041f | 3680 | struct buffer_page *reader; |
818e3dd3 | 3681 | int nr_loops = 0; |
7a8e76a3 | 3682 | |
7a8e76a3 | 3683 | again: |
818e3dd3 | 3684 | /* |
69d1b839 SR |
3685 | * We repeat when a time extend is encountered. |
3686 | * Since the time extend is always attached to a data event, | |
3687 | * we should never loop more than once. | |
3688 | * (We never hit the following condition more than twice). | |
818e3dd3 | 3689 | */ |
69d1b839 | 3690 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2)) |
818e3dd3 | 3691 | return NULL; |
818e3dd3 | 3692 | |
d769041f SR |
3693 | reader = rb_get_reader_page(cpu_buffer); |
3694 | if (!reader) | |
7a8e76a3 SR |
3695 | return NULL; |
3696 | ||
d769041f | 3697 | event = rb_reader_event(cpu_buffer); |
7a8e76a3 | 3698 | |
334d4169 | 3699 | switch (event->type_len) { |
7a8e76a3 | 3700 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3701 | if (rb_null_event(event)) |
3702 | RB_WARN_ON(cpu_buffer, 1); | |
3703 | /* | |
3704 | * Because the writer could be discarding every | |
3705 | * event it creates (which would probably be bad) | |
3706 | * if we were to go back to "again" then we may never | |
3707 | * catch up, and will trigger the warn on, or lock | |
3708 | * the box. Return the padding, and we will release | |
3709 | * the current locks, and try again. | |
3710 | */ | |
2d622719 | 3711 | return event; |
7a8e76a3 SR |
3712 | |
3713 | case RINGBUF_TYPE_TIME_EXTEND: | |
3714 | /* Internal data, OK to advance */ | |
d769041f | 3715 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3716 | goto again; |
3717 | ||
3718 | case RINGBUF_TYPE_TIME_STAMP: | |
3719 | /* FIXME: not implemented */ | |
d769041f | 3720 | rb_advance_reader(cpu_buffer); |
7a8e76a3 SR |
3721 | goto again; |
3722 | ||
3723 | case RINGBUF_TYPE_DATA: | |
3724 | if (ts) { | |
3725 | *ts = cpu_buffer->read_stamp + event->time_delta; | |
d8eeb2d3 | 3726 | ring_buffer_normalize_time_stamp(cpu_buffer->buffer, |
37886f6a | 3727 | cpu_buffer->cpu, ts); |
7a8e76a3 | 3728 | } |
66a8cb95 SR |
3729 | if (lost_events) |
3730 | *lost_events = rb_lost_events(cpu_buffer); | |
7a8e76a3 SR |
3731 | return event; |
3732 | ||
3733 | default: | |
3734 | BUG(); | |
3735 | } | |
3736 | ||
3737 | return NULL; | |
3738 | } | |
c4f50183 | 3739 | EXPORT_SYMBOL_GPL(ring_buffer_peek); |
7a8e76a3 | 3740 | |
f83c9d0f SR |
3741 | static struct ring_buffer_event * |
3742 | rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
7a8e76a3 SR |
3743 | { |
3744 | struct ring_buffer *buffer; | |
3745 | struct ring_buffer_per_cpu *cpu_buffer; | |
3746 | struct ring_buffer_event *event; | |
818e3dd3 | 3747 | int nr_loops = 0; |
7a8e76a3 | 3748 | |
7a8e76a3 SR |
3749 | cpu_buffer = iter->cpu_buffer; |
3750 | buffer = cpu_buffer->buffer; | |
3751 | ||
492a74f4 SR |
3752 | /* |
3753 | * Check if someone performed a consuming read to | |
3754 | * the buffer. A consuming read invalidates the iterator | |
3755 | * and we need to reset the iterator in this case. | |
3756 | */ | |
3757 | if (unlikely(iter->cache_read != cpu_buffer->read || | |
3758 | iter->cache_reader_page != cpu_buffer->reader_page)) | |
3759 | rb_iter_reset(iter); | |
3760 | ||
7a8e76a3 | 3761 | again: |
3c05d748 SR |
3762 | if (ring_buffer_iter_empty(iter)) |
3763 | return NULL; | |
3764 | ||
818e3dd3 | 3765 | /* |
021de3d9 SRRH |
3766 | * We repeat when a time extend is encountered or we hit |
3767 | * the end of the page. Since the time extend is always attached | |
3768 | * to a data event, we should never loop more than three times. | |
3769 | * Once for going to next page, once on time extend, and | |
3770 | * finally once to get the event. | |
3771 | * (We never hit the following condition more than thrice). | |
818e3dd3 | 3772 | */ |
021de3d9 | 3773 | if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) |
818e3dd3 | 3774 | return NULL; |
818e3dd3 | 3775 | |
7a8e76a3 SR |
3776 | if (rb_per_cpu_empty(cpu_buffer)) |
3777 | return NULL; | |
3778 | ||
10e83fd0 | 3779 | if (iter->head >= rb_page_size(iter->head_page)) { |
3c05d748 SR |
3780 | rb_inc_iter(iter); |
3781 | goto again; | |
3782 | } | |
3783 | ||
7a8e76a3 SR |
3784 | event = rb_iter_head_event(iter); |
3785 | ||
334d4169 | 3786 | switch (event->type_len) { |
7a8e76a3 | 3787 | case RINGBUF_TYPE_PADDING: |
2d622719 TZ |
3788 | if (rb_null_event(event)) { |
3789 | rb_inc_iter(iter); | |
3790 | goto again; | |
3791 | } | |
3792 | rb_advance_iter(iter); | |
3793 | return event; | |
7a8e76a3 SR |
3794 | |
3795 | case RINGBUF_TYPE_TIME_EXTEND: | |
3796 | /* Internal data, OK to advance */ | |
3797 | rb_advance_iter(iter); | |
3798 | goto again; | |
3799 | ||
3800 | case RINGBUF_TYPE_TIME_STAMP: | |
3801 | /* FIXME: not implemented */ | |
3802 | rb_advance_iter(iter); | |
3803 | goto again; | |
3804 | ||
3805 | case RINGBUF_TYPE_DATA: | |
3806 | if (ts) { | |
3807 | *ts = iter->read_stamp + event->time_delta; | |
37886f6a SR |
3808 | ring_buffer_normalize_time_stamp(buffer, |
3809 | cpu_buffer->cpu, ts); | |
7a8e76a3 SR |
3810 | } |
3811 | return event; | |
3812 | ||
3813 | default: | |
3814 | BUG(); | |
3815 | } | |
3816 | ||
3817 | return NULL; | |
3818 | } | |
c4f50183 | 3819 | EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); |
7a8e76a3 | 3820 | |
289a5a25 | 3821 | static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) |
8d707e8e | 3822 | { |
289a5a25 SRRH |
3823 | if (likely(!in_nmi())) { |
3824 | raw_spin_lock(&cpu_buffer->reader_lock); | |
3825 | return true; | |
3826 | } | |
3827 | ||
8d707e8e SR |
3828 | /* |
3829 | * If an NMI die dumps out the content of the ring buffer | |
289a5a25 SRRH |
3830 | * trylock must be used to prevent a deadlock if the NMI |
3831 | * preempted a task that holds the ring buffer locks. If | |
3832 | * we get the lock then all is fine, if not, then continue | |
3833 | * to do the read, but this can corrupt the ring buffer, | |
3834 | * so it must be permanently disabled from future writes. | |
3835 | * Reading from NMI is a oneshot deal. | |
8d707e8e | 3836 | */ |
289a5a25 SRRH |
3837 | if (raw_spin_trylock(&cpu_buffer->reader_lock)) |
3838 | return true; | |
8d707e8e | 3839 | |
289a5a25 SRRH |
3840 | /* Continue without locking, but disable the ring buffer */ |
3841 | atomic_inc(&cpu_buffer->record_disabled); | |
3842 | return false; | |
3843 | } | |
3844 | ||
3845 | static inline void | |
3846 | rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked) | |
3847 | { | |
3848 | if (likely(locked)) | |
3849 | raw_spin_unlock(&cpu_buffer->reader_lock); | |
3850 | return; | |
8d707e8e SR |
3851 | } |
3852 | ||
f83c9d0f SR |
3853 | /** |
3854 | * ring_buffer_peek - peek at the next event to be read | |
3855 | * @buffer: The ring buffer to read | |
3856 | * @cpu: The cpu to peak at | |
3857 | * @ts: The timestamp counter of this event. | |
66a8cb95 | 3858 | * @lost_events: a variable to store if events were lost (may be NULL) |
f83c9d0f SR |
3859 | * |
3860 | * This will return the event that will be read next, but does | |
3861 | * not consume the data. | |
3862 | */ | |
3863 | struct ring_buffer_event * | |
66a8cb95 SR |
3864 | ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts, |
3865 | unsigned long *lost_events) | |
f83c9d0f SR |
3866 | { |
3867 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
8aabee57 | 3868 | struct ring_buffer_event *event; |
f83c9d0f | 3869 | unsigned long flags; |
289a5a25 | 3870 | bool dolock; |
f83c9d0f | 3871 | |
554f786e | 3872 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3873 | return NULL; |
554f786e | 3874 | |
2d622719 | 3875 | again: |
8d707e8e | 3876 | local_irq_save(flags); |
289a5a25 | 3877 | dolock = rb_reader_lock(cpu_buffer); |
66a8cb95 | 3878 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
469535a5 RR |
3879 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
3880 | rb_advance_reader(cpu_buffer); | |
289a5a25 | 3881 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 3882 | local_irq_restore(flags); |
f83c9d0f | 3883 | |
1b959e18 | 3884 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3885 | goto again; |
2d622719 | 3886 | |
f83c9d0f SR |
3887 | return event; |
3888 | } | |
3889 | ||
3890 | /** | |
3891 | * ring_buffer_iter_peek - peek at the next event to be read | |
3892 | * @iter: The ring buffer iterator | |
3893 | * @ts: The timestamp counter of this event. | |
3894 | * | |
3895 | * This will return the event that will be read next, but does | |
3896 | * not increment the iterator. | |
3897 | */ | |
3898 | struct ring_buffer_event * | |
3899 | ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) | |
3900 | { | |
3901 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
3902 | struct ring_buffer_event *event; | |
3903 | unsigned long flags; | |
3904 | ||
2d622719 | 3905 | again: |
5389f6fa | 3906 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 3907 | event = rb_iter_peek(iter, ts); |
5389f6fa | 3908 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 3909 | |
1b959e18 | 3910 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3911 | goto again; |
2d622719 | 3912 | |
f83c9d0f SR |
3913 | return event; |
3914 | } | |
3915 | ||
7a8e76a3 SR |
3916 | /** |
3917 | * ring_buffer_consume - return an event and consume it | |
3918 | * @buffer: The ring buffer to get the next event from | |
66a8cb95 SR |
3919 | * @cpu: the cpu to read the buffer from |
3920 | * @ts: a variable to store the timestamp (may be NULL) | |
3921 | * @lost_events: a variable to store if events were lost (may be NULL) | |
7a8e76a3 SR |
3922 | * |
3923 | * Returns the next event in the ring buffer, and that event is consumed. | |
3924 | * Meaning, that sequential reads will keep returning a different event, | |
3925 | * and eventually empty the ring buffer if the producer is slower. | |
3926 | */ | |
3927 | struct ring_buffer_event * | |
66a8cb95 SR |
3928 | ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, |
3929 | unsigned long *lost_events) | |
7a8e76a3 | 3930 | { |
554f786e SR |
3931 | struct ring_buffer_per_cpu *cpu_buffer; |
3932 | struct ring_buffer_event *event = NULL; | |
f83c9d0f | 3933 | unsigned long flags; |
289a5a25 | 3934 | bool dolock; |
7a8e76a3 | 3935 | |
2d622719 | 3936 | again: |
554f786e SR |
3937 | /* might be called in atomic */ |
3938 | preempt_disable(); | |
3939 | ||
9e01c1b7 | 3940 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e | 3941 | goto out; |
7a8e76a3 | 3942 | |
554f786e | 3943 | cpu_buffer = buffer->buffers[cpu]; |
8d707e8e | 3944 | local_irq_save(flags); |
289a5a25 | 3945 | dolock = rb_reader_lock(cpu_buffer); |
f83c9d0f | 3946 | |
66a8cb95 SR |
3947 | event = rb_buffer_peek(cpu_buffer, ts, lost_events); |
3948 | if (event) { | |
3949 | cpu_buffer->lost_events = 0; | |
469535a5 | 3950 | rb_advance_reader(cpu_buffer); |
66a8cb95 | 3951 | } |
7a8e76a3 | 3952 | |
289a5a25 | 3953 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 3954 | local_irq_restore(flags); |
f83c9d0f | 3955 | |
554f786e SR |
3956 | out: |
3957 | preempt_enable(); | |
3958 | ||
1b959e18 | 3959 | if (event && event->type_len == RINGBUF_TYPE_PADDING) |
2d622719 | 3960 | goto again; |
2d622719 | 3961 | |
7a8e76a3 SR |
3962 | return event; |
3963 | } | |
c4f50183 | 3964 | EXPORT_SYMBOL_GPL(ring_buffer_consume); |
7a8e76a3 SR |
3965 | |
3966 | /** | |
72c9ddfd | 3967 | * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer |
7a8e76a3 SR |
3968 | * @buffer: The ring buffer to read from |
3969 | * @cpu: The cpu buffer to iterate over | |
3970 | * | |
72c9ddfd DM |
3971 | * This performs the initial preparations necessary to iterate |
3972 | * through the buffer. Memory is allocated, buffer recording | |
3973 | * is disabled, and the iterator pointer is returned to the caller. | |
7a8e76a3 | 3974 | * |
72c9ddfd DM |
3975 | * Disabling buffer recordng prevents the reading from being |
3976 | * corrupted. This is not a consuming read, so a producer is not | |
3977 | * expected. | |
3978 | * | |
3979 | * After a sequence of ring_buffer_read_prepare calls, the user is | |
d611851b | 3980 | * expected to make at least one call to ring_buffer_read_prepare_sync. |
72c9ddfd DM |
3981 | * Afterwards, ring_buffer_read_start is invoked to get things going |
3982 | * for real. | |
3983 | * | |
d611851b | 3984 | * This overall must be paired with ring_buffer_read_finish. |
7a8e76a3 SR |
3985 | */ |
3986 | struct ring_buffer_iter * | |
72c9ddfd | 3987 | ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu) |
7a8e76a3 SR |
3988 | { |
3989 | struct ring_buffer_per_cpu *cpu_buffer; | |
8aabee57 | 3990 | struct ring_buffer_iter *iter; |
7a8e76a3 | 3991 | |
9e01c1b7 | 3992 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 3993 | return NULL; |
7a8e76a3 SR |
3994 | |
3995 | iter = kmalloc(sizeof(*iter), GFP_KERNEL); | |
3996 | if (!iter) | |
8aabee57 | 3997 | return NULL; |
7a8e76a3 SR |
3998 | |
3999 | cpu_buffer = buffer->buffers[cpu]; | |
4000 | ||
4001 | iter->cpu_buffer = cpu_buffer; | |
4002 | ||
83f40318 | 4003 | atomic_inc(&buffer->resize_disabled); |
7a8e76a3 | 4004 | atomic_inc(&cpu_buffer->record_disabled); |
72c9ddfd DM |
4005 | |
4006 | return iter; | |
4007 | } | |
4008 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare); | |
4009 | ||
4010 | /** | |
4011 | * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls | |
4012 | * | |
4013 | * All previously invoked ring_buffer_read_prepare calls to prepare | |
4014 | * iterators will be synchronized. Afterwards, read_buffer_read_start | |
4015 | * calls on those iterators are allowed. | |
4016 | */ | |
4017 | void | |
4018 | ring_buffer_read_prepare_sync(void) | |
4019 | { | |
7a8e76a3 | 4020 | synchronize_sched(); |
72c9ddfd DM |
4021 | } |
4022 | EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync); | |
4023 | ||
4024 | /** | |
4025 | * ring_buffer_read_start - start a non consuming read of the buffer | |
4026 | * @iter: The iterator returned by ring_buffer_read_prepare | |
4027 | * | |
4028 | * This finalizes the startup of an iteration through the buffer. | |
4029 | * The iterator comes from a call to ring_buffer_read_prepare and | |
4030 | * an intervening ring_buffer_read_prepare_sync must have been | |
4031 | * performed. | |
4032 | * | |
d611851b | 4033 | * Must be paired with ring_buffer_read_finish. |
72c9ddfd DM |
4034 | */ |
4035 | void | |
4036 | ring_buffer_read_start(struct ring_buffer_iter *iter) | |
4037 | { | |
4038 | struct ring_buffer_per_cpu *cpu_buffer; | |
4039 | unsigned long flags; | |
4040 | ||
4041 | if (!iter) | |
4042 | return; | |
4043 | ||
4044 | cpu_buffer = iter->cpu_buffer; | |
7a8e76a3 | 4045 | |
5389f6fa | 4046 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
0199c4e6 | 4047 | arch_spin_lock(&cpu_buffer->lock); |
642edba5 | 4048 | rb_iter_reset(iter); |
0199c4e6 | 4049 | arch_spin_unlock(&cpu_buffer->lock); |
5389f6fa | 4050 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 | 4051 | } |
c4f50183 | 4052 | EXPORT_SYMBOL_GPL(ring_buffer_read_start); |
7a8e76a3 SR |
4053 | |
4054 | /** | |
d611851b | 4055 | * ring_buffer_read_finish - finish reading the iterator of the buffer |
7a8e76a3 SR |
4056 | * @iter: The iterator retrieved by ring_buffer_start |
4057 | * | |
4058 | * This re-enables the recording to the buffer, and frees the | |
4059 | * iterator. | |
4060 | */ | |
4061 | void | |
4062 | ring_buffer_read_finish(struct ring_buffer_iter *iter) | |
4063 | { | |
4064 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; | |
9366c1ba | 4065 | unsigned long flags; |
7a8e76a3 | 4066 | |
659f451f SR |
4067 | /* |
4068 | * Ring buffer is disabled from recording, here's a good place | |
9366c1ba SR |
4069 | * to check the integrity of the ring buffer. |
4070 | * Must prevent readers from trying to read, as the check | |
4071 | * clears the HEAD page and readers require it. | |
659f451f | 4072 | */ |
9366c1ba | 4073 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
659f451f | 4074 | rb_check_pages(cpu_buffer); |
9366c1ba | 4075 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
659f451f | 4076 | |
7a8e76a3 | 4077 | atomic_dec(&cpu_buffer->record_disabled); |
83f40318 | 4078 | atomic_dec(&cpu_buffer->buffer->resize_disabled); |
7a8e76a3 SR |
4079 | kfree(iter); |
4080 | } | |
c4f50183 | 4081 | EXPORT_SYMBOL_GPL(ring_buffer_read_finish); |
7a8e76a3 SR |
4082 | |
4083 | /** | |
4084 | * ring_buffer_read - read the next item in the ring buffer by the iterator | |
4085 | * @iter: The ring buffer iterator | |
4086 | * @ts: The time stamp of the event read. | |
4087 | * | |
4088 | * This reads the next event in the ring buffer and increments the iterator. | |
4089 | */ | |
4090 | struct ring_buffer_event * | |
4091 | ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) | |
4092 | { | |
4093 | struct ring_buffer_event *event; | |
f83c9d0f SR |
4094 | struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
4095 | unsigned long flags; | |
7a8e76a3 | 4096 | |
5389f6fa | 4097 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
7e9391cf | 4098 | again: |
f83c9d0f | 4099 | event = rb_iter_peek(iter, ts); |
7a8e76a3 | 4100 | if (!event) |
f83c9d0f | 4101 | goto out; |
7a8e76a3 | 4102 | |
7e9391cf SR |
4103 | if (event->type_len == RINGBUF_TYPE_PADDING) |
4104 | goto again; | |
4105 | ||
7a8e76a3 | 4106 | rb_advance_iter(iter); |
f83c9d0f | 4107 | out: |
5389f6fa | 4108 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
7a8e76a3 SR |
4109 | |
4110 | return event; | |
4111 | } | |
c4f50183 | 4112 | EXPORT_SYMBOL_GPL(ring_buffer_read); |
7a8e76a3 SR |
4113 | |
4114 | /** | |
4115 | * ring_buffer_size - return the size of the ring buffer (in bytes) | |
4116 | * @buffer: The ring buffer. | |
4117 | */ | |
438ced17 | 4118 | unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu) |
7a8e76a3 | 4119 | { |
438ced17 VN |
4120 | /* |
4121 | * Earlier, this method returned | |
4122 | * BUF_PAGE_SIZE * buffer->nr_pages | |
4123 | * Since the nr_pages field is now removed, we have converted this to | |
4124 | * return the per cpu buffer value. | |
4125 | */ | |
4126 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) | |
4127 | return 0; | |
4128 | ||
4129 | return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages; | |
7a8e76a3 | 4130 | } |
c4f50183 | 4131 | EXPORT_SYMBOL_GPL(ring_buffer_size); |
7a8e76a3 SR |
4132 | |
4133 | static void | |
4134 | rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) | |
4135 | { | |
77ae365e SR |
4136 | rb_head_page_deactivate(cpu_buffer); |
4137 | ||
7a8e76a3 | 4138 | cpu_buffer->head_page |
3adc54fa | 4139 | = list_entry(cpu_buffer->pages, struct buffer_page, list); |
bf41a158 | 4140 | local_set(&cpu_buffer->head_page->write, 0); |
778c55d4 | 4141 | local_set(&cpu_buffer->head_page->entries, 0); |
abc9b56d | 4142 | local_set(&cpu_buffer->head_page->page->commit, 0); |
d769041f | 4143 | |
6f807acd | 4144 | cpu_buffer->head_page->read = 0; |
bf41a158 SR |
4145 | |
4146 | cpu_buffer->tail_page = cpu_buffer->head_page; | |
4147 | cpu_buffer->commit_page = cpu_buffer->head_page; | |
4148 | ||
4149 | INIT_LIST_HEAD(&cpu_buffer->reader_page->list); | |
5040b4b7 | 4150 | INIT_LIST_HEAD(&cpu_buffer->new_pages); |
bf41a158 | 4151 | local_set(&cpu_buffer->reader_page->write, 0); |
778c55d4 | 4152 | local_set(&cpu_buffer->reader_page->entries, 0); |
abc9b56d | 4153 | local_set(&cpu_buffer->reader_page->page->commit, 0); |
6f807acd | 4154 | cpu_buffer->reader_page->read = 0; |
7a8e76a3 | 4155 | |
c64e148a | 4156 | local_set(&cpu_buffer->entries_bytes, 0); |
77ae365e | 4157 | local_set(&cpu_buffer->overrun, 0); |
884bfe89 SP |
4158 | local_set(&cpu_buffer->commit_overrun, 0); |
4159 | local_set(&cpu_buffer->dropped_events, 0); | |
e4906eff | 4160 | local_set(&cpu_buffer->entries, 0); |
fa743953 SR |
4161 | local_set(&cpu_buffer->committing, 0); |
4162 | local_set(&cpu_buffer->commits, 0); | |
77ae365e | 4163 | cpu_buffer->read = 0; |
c64e148a | 4164 | cpu_buffer->read_bytes = 0; |
69507c06 SR |
4165 | |
4166 | cpu_buffer->write_stamp = 0; | |
4167 | cpu_buffer->read_stamp = 0; | |
77ae365e | 4168 | |
66a8cb95 SR |
4169 | cpu_buffer->lost_events = 0; |
4170 | cpu_buffer->last_overrun = 0; | |
4171 | ||
77ae365e | 4172 | rb_head_page_activate(cpu_buffer); |
7a8e76a3 SR |
4173 | } |
4174 | ||
4175 | /** | |
4176 | * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer | |
4177 | * @buffer: The ring buffer to reset a per cpu buffer of | |
4178 | * @cpu: The CPU buffer to be reset | |
4179 | */ | |
4180 | void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) | |
4181 | { | |
4182 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
4183 | unsigned long flags; | |
4184 | ||
9e01c1b7 | 4185 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4186 | return; |
7a8e76a3 | 4187 | |
83f40318 | 4188 | atomic_inc(&buffer->resize_disabled); |
41ede23e SR |
4189 | atomic_inc(&cpu_buffer->record_disabled); |
4190 | ||
83f40318 VN |
4191 | /* Make sure all commits have finished */ |
4192 | synchronize_sched(); | |
4193 | ||
5389f6fa | 4194 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
f83c9d0f | 4195 | |
41b6a95d SR |
4196 | if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing))) |
4197 | goto out; | |
4198 | ||
0199c4e6 | 4199 | arch_spin_lock(&cpu_buffer->lock); |
7a8e76a3 SR |
4200 | |
4201 | rb_reset_cpu(cpu_buffer); | |
4202 | ||
0199c4e6 | 4203 | arch_spin_unlock(&cpu_buffer->lock); |
f83c9d0f | 4204 | |
41b6a95d | 4205 | out: |
5389f6fa | 4206 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
41ede23e SR |
4207 | |
4208 | atomic_dec(&cpu_buffer->record_disabled); | |
83f40318 | 4209 | atomic_dec(&buffer->resize_disabled); |
7a8e76a3 | 4210 | } |
c4f50183 | 4211 | EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); |
7a8e76a3 SR |
4212 | |
4213 | /** | |
4214 | * ring_buffer_reset - reset a ring buffer | |
4215 | * @buffer: The ring buffer to reset all cpu buffers | |
4216 | */ | |
4217 | void ring_buffer_reset(struct ring_buffer *buffer) | |
4218 | { | |
7a8e76a3 SR |
4219 | int cpu; |
4220 | ||
7a8e76a3 | 4221 | for_each_buffer_cpu(buffer, cpu) |
d769041f | 4222 | ring_buffer_reset_cpu(buffer, cpu); |
7a8e76a3 | 4223 | } |
c4f50183 | 4224 | EXPORT_SYMBOL_GPL(ring_buffer_reset); |
7a8e76a3 SR |
4225 | |
4226 | /** | |
4227 | * rind_buffer_empty - is the ring buffer empty? | |
4228 | * @buffer: The ring buffer to test | |
4229 | */ | |
4230 | int ring_buffer_empty(struct ring_buffer *buffer) | |
4231 | { | |
4232 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4233 | unsigned long flags; |
289a5a25 | 4234 | bool dolock; |
7a8e76a3 | 4235 | int cpu; |
d4788207 | 4236 | int ret; |
7a8e76a3 SR |
4237 | |
4238 | /* yes this is racy, but if you don't like the race, lock the buffer */ | |
4239 | for_each_buffer_cpu(buffer, cpu) { | |
4240 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e | 4241 | local_irq_save(flags); |
289a5a25 | 4242 | dolock = rb_reader_lock(cpu_buffer); |
d4788207 | 4243 | ret = rb_per_cpu_empty(cpu_buffer); |
289a5a25 | 4244 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e SR |
4245 | local_irq_restore(flags); |
4246 | ||
d4788207 | 4247 | if (!ret) |
7a8e76a3 SR |
4248 | return 0; |
4249 | } | |
554f786e | 4250 | |
7a8e76a3 SR |
4251 | return 1; |
4252 | } | |
c4f50183 | 4253 | EXPORT_SYMBOL_GPL(ring_buffer_empty); |
7a8e76a3 SR |
4254 | |
4255 | /** | |
4256 | * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? | |
4257 | * @buffer: The ring buffer | |
4258 | * @cpu: The CPU buffer to test | |
4259 | */ | |
4260 | int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) | |
4261 | { | |
4262 | struct ring_buffer_per_cpu *cpu_buffer; | |
d4788207 | 4263 | unsigned long flags; |
289a5a25 | 4264 | bool dolock; |
8aabee57 | 4265 | int ret; |
7a8e76a3 | 4266 | |
9e01c1b7 | 4267 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
8aabee57 | 4268 | return 1; |
7a8e76a3 SR |
4269 | |
4270 | cpu_buffer = buffer->buffers[cpu]; | |
8d707e8e | 4271 | local_irq_save(flags); |
289a5a25 | 4272 | dolock = rb_reader_lock(cpu_buffer); |
554f786e | 4273 | ret = rb_per_cpu_empty(cpu_buffer); |
289a5a25 | 4274 | rb_reader_unlock(cpu_buffer, dolock); |
8d707e8e | 4275 | local_irq_restore(flags); |
554f786e SR |
4276 | |
4277 | return ret; | |
7a8e76a3 | 4278 | } |
c4f50183 | 4279 | EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); |
7a8e76a3 | 4280 | |
85bac32c | 4281 | #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
7a8e76a3 SR |
4282 | /** |
4283 | * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers | |
4284 | * @buffer_a: One buffer to swap with | |
4285 | * @buffer_b: The other buffer to swap with | |
4286 | * | |
4287 | * This function is useful for tracers that want to take a "snapshot" | |
4288 | * of a CPU buffer and has another back up buffer lying around. | |
4289 | * it is expected that the tracer handles the cpu buffer not being | |
4290 | * used at the moment. | |
4291 | */ | |
4292 | int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, | |
4293 | struct ring_buffer *buffer_b, int cpu) | |
4294 | { | |
4295 | struct ring_buffer_per_cpu *cpu_buffer_a; | |
4296 | struct ring_buffer_per_cpu *cpu_buffer_b; | |
554f786e SR |
4297 | int ret = -EINVAL; |
4298 | ||
9e01c1b7 RR |
4299 | if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || |
4300 | !cpumask_test_cpu(cpu, buffer_b->cpumask)) | |
554f786e | 4301 | goto out; |
7a8e76a3 | 4302 | |
438ced17 VN |
4303 | cpu_buffer_a = buffer_a->buffers[cpu]; |
4304 | cpu_buffer_b = buffer_b->buffers[cpu]; | |
4305 | ||
7a8e76a3 | 4306 | /* At least make sure the two buffers are somewhat the same */ |
438ced17 | 4307 | if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages) |
554f786e SR |
4308 | goto out; |
4309 | ||
4310 | ret = -EAGAIN; | |
7a8e76a3 | 4311 | |
97b17efe | 4312 | if (atomic_read(&buffer_a->record_disabled)) |
554f786e | 4313 | goto out; |
97b17efe SR |
4314 | |
4315 | if (atomic_read(&buffer_b->record_disabled)) | |
554f786e | 4316 | goto out; |
97b17efe | 4317 | |
97b17efe | 4318 | if (atomic_read(&cpu_buffer_a->record_disabled)) |
554f786e | 4319 | goto out; |
97b17efe SR |
4320 | |
4321 | if (atomic_read(&cpu_buffer_b->record_disabled)) | |
554f786e | 4322 | goto out; |
97b17efe | 4323 | |
7a8e76a3 SR |
4324 | /* |
4325 | * We can't do a synchronize_sched here because this | |
4326 | * function can be called in atomic context. | |
4327 | * Normally this will be called from the same CPU as cpu. | |
4328 | * If not it's up to the caller to protect this. | |
4329 | */ | |
4330 | atomic_inc(&cpu_buffer_a->record_disabled); | |
4331 | atomic_inc(&cpu_buffer_b->record_disabled); | |
4332 | ||
98277991 SR |
4333 | ret = -EBUSY; |
4334 | if (local_read(&cpu_buffer_a->committing)) | |
4335 | goto out_dec; | |
4336 | if (local_read(&cpu_buffer_b->committing)) | |
4337 | goto out_dec; | |
4338 | ||
7a8e76a3 SR |
4339 | buffer_a->buffers[cpu] = cpu_buffer_b; |
4340 | buffer_b->buffers[cpu] = cpu_buffer_a; | |
4341 | ||
4342 | cpu_buffer_b->buffer = buffer_a; | |
4343 | cpu_buffer_a->buffer = buffer_b; | |
4344 | ||
98277991 SR |
4345 | ret = 0; |
4346 | ||
4347 | out_dec: | |
7a8e76a3 SR |
4348 | atomic_dec(&cpu_buffer_a->record_disabled); |
4349 | atomic_dec(&cpu_buffer_b->record_disabled); | |
554f786e | 4350 | out: |
554f786e | 4351 | return ret; |
7a8e76a3 | 4352 | } |
c4f50183 | 4353 | EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); |
85bac32c | 4354 | #endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */ |
7a8e76a3 | 4355 | |
8789a9e7 SR |
4356 | /** |
4357 | * ring_buffer_alloc_read_page - allocate a page to read from buffer | |
4358 | * @buffer: the buffer to allocate for. | |
d611851b | 4359 | * @cpu: the cpu buffer to allocate. |
8789a9e7 SR |
4360 | * |
4361 | * This function is used in conjunction with ring_buffer_read_page. | |
4362 | * When reading a full page from the ring buffer, these functions | |
4363 | * can be used to speed up the process. The calling function should | |
4364 | * allocate a few pages first with this function. Then when it | |
4365 | * needs to get pages from the ring buffer, it passes the result | |
4366 | * of this function into ring_buffer_read_page, which will swap | |
4367 | * the page that was allocated, with the read page of the buffer. | |
4368 | * | |
4369 | * Returns: | |
4370 | * The page allocated, or NULL on error. | |
4371 | */ | |
7ea59064 | 4372 | void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu) |
8789a9e7 | 4373 | { |
044fa782 | 4374 | struct buffer_data_page *bpage; |
7ea59064 | 4375 | struct page *page; |
8789a9e7 | 4376 | |
d7ec4bfe VN |
4377 | page = alloc_pages_node(cpu_to_node(cpu), |
4378 | GFP_KERNEL | __GFP_NORETRY, 0); | |
7ea59064 | 4379 | if (!page) |
8789a9e7 SR |
4380 | return NULL; |
4381 | ||
7ea59064 | 4382 | bpage = page_address(page); |
8789a9e7 | 4383 | |
ef7a4a16 SR |
4384 | rb_init_page(bpage); |
4385 | ||
044fa782 | 4386 | return bpage; |
8789a9e7 | 4387 | } |
d6ce96da | 4388 | EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); |
8789a9e7 SR |
4389 | |
4390 | /** | |
4391 | * ring_buffer_free_read_page - free an allocated read page | |
4392 | * @buffer: the buffer the page was allocate for | |
4393 | * @data: the page to free | |
4394 | * | |
4395 | * Free a page allocated from ring_buffer_alloc_read_page. | |
4396 | */ | |
4397 | void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) | |
4398 | { | |
4399 | free_page((unsigned long)data); | |
4400 | } | |
d6ce96da | 4401 | EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); |
8789a9e7 SR |
4402 | |
4403 | /** | |
4404 | * ring_buffer_read_page - extract a page from the ring buffer | |
4405 | * @buffer: buffer to extract from | |
4406 | * @data_page: the page to use allocated from ring_buffer_alloc_read_page | |
ef7a4a16 | 4407 | * @len: amount to extract |
8789a9e7 SR |
4408 | * @cpu: the cpu of the buffer to extract |
4409 | * @full: should the extraction only happen when the page is full. | |
4410 | * | |
4411 | * This function will pull out a page from the ring buffer and consume it. | |
4412 | * @data_page must be the address of the variable that was returned | |
4413 | * from ring_buffer_alloc_read_page. This is because the page might be used | |
4414 | * to swap with a page in the ring buffer. | |
4415 | * | |
4416 | * for example: | |
d611851b | 4417 | * rpage = ring_buffer_alloc_read_page(buffer, cpu); |
8789a9e7 SR |
4418 | * if (!rpage) |
4419 | * return error; | |
ef7a4a16 | 4420 | * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); |
667d2412 LJ |
4421 | * if (ret >= 0) |
4422 | * process_page(rpage, ret); | |
8789a9e7 SR |
4423 | * |
4424 | * When @full is set, the function will not return true unless | |
4425 | * the writer is off the reader page. | |
4426 | * | |
4427 | * Note: it is up to the calling functions to handle sleeps and wakeups. | |
4428 | * The ring buffer can be used anywhere in the kernel and can not | |
4429 | * blindly call wake_up. The layer that uses the ring buffer must be | |
4430 | * responsible for that. | |
4431 | * | |
4432 | * Returns: | |
667d2412 LJ |
4433 | * >=0 if data has been transferred, returns the offset of consumed data. |
4434 | * <0 if no data has been transferred. | |
8789a9e7 SR |
4435 | */ |
4436 | int ring_buffer_read_page(struct ring_buffer *buffer, | |
ef7a4a16 | 4437 | void **data_page, size_t len, int cpu, int full) |
8789a9e7 SR |
4438 | { |
4439 | struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; | |
4440 | struct ring_buffer_event *event; | |
044fa782 | 4441 | struct buffer_data_page *bpage; |
ef7a4a16 | 4442 | struct buffer_page *reader; |
ff0ff84a | 4443 | unsigned long missed_events; |
8789a9e7 | 4444 | unsigned long flags; |
ef7a4a16 | 4445 | unsigned int commit; |
667d2412 | 4446 | unsigned int read; |
4f3640f8 | 4447 | u64 save_timestamp; |
667d2412 | 4448 | int ret = -1; |
8789a9e7 | 4449 | |
554f786e SR |
4450 | if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
4451 | goto out; | |
4452 | ||
474d32b6 SR |
4453 | /* |
4454 | * If len is not big enough to hold the page header, then | |
4455 | * we can not copy anything. | |
4456 | */ | |
4457 | if (len <= BUF_PAGE_HDR_SIZE) | |
554f786e | 4458 | goto out; |
474d32b6 SR |
4459 | |
4460 | len -= BUF_PAGE_HDR_SIZE; | |
4461 | ||
8789a9e7 | 4462 | if (!data_page) |
554f786e | 4463 | goto out; |
8789a9e7 | 4464 | |
044fa782 SR |
4465 | bpage = *data_page; |
4466 | if (!bpage) | |
554f786e | 4467 | goto out; |
8789a9e7 | 4468 | |
5389f6fa | 4469 | raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 4470 | |
ef7a4a16 SR |
4471 | reader = rb_get_reader_page(cpu_buffer); |
4472 | if (!reader) | |
554f786e | 4473 | goto out_unlock; |
8789a9e7 | 4474 | |
ef7a4a16 SR |
4475 | event = rb_reader_event(cpu_buffer); |
4476 | ||
4477 | read = reader->read; | |
4478 | commit = rb_page_commit(reader); | |
667d2412 | 4479 | |
66a8cb95 | 4480 | /* Check if any events were dropped */ |
ff0ff84a | 4481 | missed_events = cpu_buffer->lost_events; |
66a8cb95 | 4482 | |
8789a9e7 | 4483 | /* |
474d32b6 SR |
4484 | * If this page has been partially read or |
4485 | * if len is not big enough to read the rest of the page or | |
4486 | * a writer is still on the page, then | |
4487 | * we must copy the data from the page to the buffer. | |
4488 | * Otherwise, we can simply swap the page with the one passed in. | |
8789a9e7 | 4489 | */ |
474d32b6 | 4490 | if (read || (len < (commit - read)) || |
ef7a4a16 | 4491 | cpu_buffer->reader_page == cpu_buffer->commit_page) { |
667d2412 | 4492 | struct buffer_data_page *rpage = cpu_buffer->reader_page->page; |
474d32b6 SR |
4493 | unsigned int rpos = read; |
4494 | unsigned int pos = 0; | |
ef7a4a16 | 4495 | unsigned int size; |
8789a9e7 SR |
4496 | |
4497 | if (full) | |
554f786e | 4498 | goto out_unlock; |
8789a9e7 | 4499 | |
ef7a4a16 SR |
4500 | if (len > (commit - read)) |
4501 | len = (commit - read); | |
4502 | ||
69d1b839 SR |
4503 | /* Always keep the time extend and data together */ |
4504 | size = rb_event_ts_length(event); | |
ef7a4a16 SR |
4505 | |
4506 | if (len < size) | |
554f786e | 4507 | goto out_unlock; |
ef7a4a16 | 4508 | |
4f3640f8 SR |
4509 | /* save the current timestamp, since the user will need it */ |
4510 | save_timestamp = cpu_buffer->read_stamp; | |
4511 | ||
ef7a4a16 SR |
4512 | /* Need to copy one event at a time */ |
4513 | do { | |
e1e35927 DS |
4514 | /* We need the size of one event, because |
4515 | * rb_advance_reader only advances by one event, | |
4516 | * whereas rb_event_ts_length may include the size of | |
4517 | * one or two events. | |
4518 | * We have already ensured there's enough space if this | |
4519 | * is a time extend. */ | |
4520 | size = rb_event_length(event); | |
474d32b6 | 4521 | memcpy(bpage->data + pos, rpage->data + rpos, size); |
ef7a4a16 SR |
4522 | |
4523 | len -= size; | |
4524 | ||
4525 | rb_advance_reader(cpu_buffer); | |
474d32b6 SR |
4526 | rpos = reader->read; |
4527 | pos += size; | |
ef7a4a16 | 4528 | |
18fab912 HY |
4529 | if (rpos >= commit) |
4530 | break; | |
4531 | ||
ef7a4a16 | 4532 | event = rb_reader_event(cpu_buffer); |
69d1b839 SR |
4533 | /* Always keep the time extend and data together */ |
4534 | size = rb_event_ts_length(event); | |
e1e35927 | 4535 | } while (len >= size); |
667d2412 LJ |
4536 | |
4537 | /* update bpage */ | |
ef7a4a16 | 4538 | local_set(&bpage->commit, pos); |
4f3640f8 | 4539 | bpage->time_stamp = save_timestamp; |
ef7a4a16 | 4540 | |
474d32b6 SR |
4541 | /* we copied everything to the beginning */ |
4542 | read = 0; | |
8789a9e7 | 4543 | } else { |
afbab76a | 4544 | /* update the entry counter */ |
77ae365e | 4545 | cpu_buffer->read += rb_page_entries(reader); |
c64e148a | 4546 | cpu_buffer->read_bytes += BUF_PAGE_SIZE; |
afbab76a | 4547 | |
8789a9e7 | 4548 | /* swap the pages */ |
044fa782 | 4549 | rb_init_page(bpage); |
ef7a4a16 SR |
4550 | bpage = reader->page; |
4551 | reader->page = *data_page; | |
4552 | local_set(&reader->write, 0); | |
778c55d4 | 4553 | local_set(&reader->entries, 0); |
ef7a4a16 | 4554 | reader->read = 0; |
044fa782 | 4555 | *data_page = bpage; |
ff0ff84a SR |
4556 | |
4557 | /* | |
4558 | * Use the real_end for the data size, | |
4559 | * This gives us a chance to store the lost events | |
4560 | * on the page. | |
4561 | */ | |
4562 | if (reader->real_end) | |
4563 | local_set(&bpage->commit, reader->real_end); | |
8789a9e7 | 4564 | } |
667d2412 | 4565 | ret = read; |
8789a9e7 | 4566 | |
66a8cb95 | 4567 | cpu_buffer->lost_events = 0; |
2711ca23 SR |
4568 | |
4569 | commit = local_read(&bpage->commit); | |
66a8cb95 SR |
4570 | /* |
4571 | * Set a flag in the commit field if we lost events | |
4572 | */ | |
ff0ff84a | 4573 | if (missed_events) { |
ff0ff84a SR |
4574 | /* If there is room at the end of the page to save the |
4575 | * missed events, then record it there. | |
4576 | */ | |
4577 | if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) { | |
4578 | memcpy(&bpage->data[commit], &missed_events, | |
4579 | sizeof(missed_events)); | |
4580 | local_add(RB_MISSED_STORED, &bpage->commit); | |
2711ca23 | 4581 | commit += sizeof(missed_events); |
ff0ff84a | 4582 | } |
66a8cb95 | 4583 | local_add(RB_MISSED_EVENTS, &bpage->commit); |
ff0ff84a | 4584 | } |
66a8cb95 | 4585 | |
2711ca23 SR |
4586 | /* |
4587 | * This page may be off to user land. Zero it out here. | |
4588 | */ | |
4589 | if (commit < BUF_PAGE_SIZE) | |
4590 | memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit); | |
4591 | ||
554f786e | 4592 | out_unlock: |
5389f6fa | 4593 | raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
8789a9e7 | 4594 | |
554f786e | 4595 | out: |
8789a9e7 SR |
4596 | return ret; |
4597 | } | |
d6ce96da | 4598 | EXPORT_SYMBOL_GPL(ring_buffer_read_page); |
8789a9e7 | 4599 | |
59222efe | 4600 | #ifdef CONFIG_HOTPLUG_CPU |
09c9e84d FW |
4601 | static int rb_cpu_notify(struct notifier_block *self, |
4602 | unsigned long action, void *hcpu) | |
554f786e SR |
4603 | { |
4604 | struct ring_buffer *buffer = | |
4605 | container_of(self, struct ring_buffer, cpu_notify); | |
4606 | long cpu = (long)hcpu; | |
438ced17 VN |
4607 | int cpu_i, nr_pages_same; |
4608 | unsigned int nr_pages; | |
554f786e SR |
4609 | |
4610 | switch (action) { | |
4611 | case CPU_UP_PREPARE: | |
4612 | case CPU_UP_PREPARE_FROZEN: | |
3f237a79 | 4613 | if (cpumask_test_cpu(cpu, buffer->cpumask)) |
554f786e SR |
4614 | return NOTIFY_OK; |
4615 | ||
438ced17 VN |
4616 | nr_pages = 0; |
4617 | nr_pages_same = 1; | |
4618 | /* check if all cpu sizes are same */ | |
4619 | for_each_buffer_cpu(buffer, cpu_i) { | |
4620 | /* fill in the size from first enabled cpu */ | |
4621 | if (nr_pages == 0) | |
4622 | nr_pages = buffer->buffers[cpu_i]->nr_pages; | |
4623 | if (nr_pages != buffer->buffers[cpu_i]->nr_pages) { | |
4624 | nr_pages_same = 0; | |
4625 | break; | |
4626 | } | |
4627 | } | |
4628 | /* allocate minimum pages, user can later expand it */ | |
4629 | if (!nr_pages_same) | |
4630 | nr_pages = 2; | |
554f786e | 4631 | buffer->buffers[cpu] = |
438ced17 | 4632 | rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
554f786e SR |
4633 | if (!buffer->buffers[cpu]) { |
4634 | WARN(1, "failed to allocate ring buffer on CPU %ld\n", | |
4635 | cpu); | |
4636 | return NOTIFY_OK; | |
4637 | } | |
4638 | smp_wmb(); | |
3f237a79 | 4639 | cpumask_set_cpu(cpu, buffer->cpumask); |
554f786e SR |
4640 | break; |
4641 | case CPU_DOWN_PREPARE: | |
4642 | case CPU_DOWN_PREPARE_FROZEN: | |
4643 | /* | |
4644 | * Do nothing. | |
4645 | * If we were to free the buffer, then the user would | |
4646 | * lose any trace that was in the buffer. | |
4647 | */ | |
4648 | break; | |
4649 | default: | |
4650 | break; | |
4651 | } | |
4652 | return NOTIFY_OK; | |
4653 | } | |
4654 | #endif | |
6c43e554 SRRH |
4655 | |
4656 | #ifdef CONFIG_RING_BUFFER_STARTUP_TEST | |
4657 | /* | |
4658 | * This is a basic integrity check of the ring buffer. | |
4659 | * Late in the boot cycle this test will run when configured in. | |
4660 | * It will kick off a thread per CPU that will go into a loop | |
4661 | * writing to the per cpu ring buffer various sizes of data. | |
4662 | * Some of the data will be large items, some small. | |
4663 | * | |
4664 | * Another thread is created that goes into a spin, sending out | |
4665 | * IPIs to the other CPUs to also write into the ring buffer. | |
4666 | * this is to test the nesting ability of the buffer. | |
4667 | * | |
4668 | * Basic stats are recorded and reported. If something in the | |
4669 | * ring buffer should happen that's not expected, a big warning | |
4670 | * is displayed and all ring buffers are disabled. | |
4671 | */ | |
4672 | static struct task_struct *rb_threads[NR_CPUS] __initdata; | |
4673 | ||
4674 | struct rb_test_data { | |
4675 | struct ring_buffer *buffer; | |
4676 | unsigned long events; | |
4677 | unsigned long bytes_written; | |
4678 | unsigned long bytes_alloc; | |
4679 | unsigned long bytes_dropped; | |
4680 | unsigned long events_nested; | |
4681 | unsigned long bytes_written_nested; | |
4682 | unsigned long bytes_alloc_nested; | |
4683 | unsigned long bytes_dropped_nested; | |
4684 | int min_size_nested; | |
4685 | int max_size_nested; | |
4686 | int max_size; | |
4687 | int min_size; | |
4688 | int cpu; | |
4689 | int cnt; | |
4690 | }; | |
4691 | ||
4692 | static struct rb_test_data rb_data[NR_CPUS] __initdata; | |
4693 | ||
4694 | /* 1 meg per cpu */ | |
4695 | #define RB_TEST_BUFFER_SIZE 1048576 | |
4696 | ||
4697 | static char rb_string[] __initdata = | |
4698 | "abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\" | |
4699 | "?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890" | |
4700 | "!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv"; | |
4701 | ||
4702 | static bool rb_test_started __initdata; | |
4703 | ||
4704 | struct rb_item { | |
4705 | int size; | |
4706 | char str[]; | |
4707 | }; | |
4708 | ||
4709 | static __init int rb_write_something(struct rb_test_data *data, bool nested) | |
4710 | { | |
4711 | struct ring_buffer_event *event; | |
4712 | struct rb_item *item; | |
4713 | bool started; | |
4714 | int event_len; | |
4715 | int size; | |
4716 | int len; | |
4717 | int cnt; | |
4718 | ||
4719 | /* Have nested writes different that what is written */ | |
4720 | cnt = data->cnt + (nested ? 27 : 0); | |
4721 | ||
4722 | /* Multiply cnt by ~e, to make some unique increment */ | |
4723 | size = (data->cnt * 68 / 25) % (sizeof(rb_string) - 1); | |
4724 | ||
4725 | len = size + sizeof(struct rb_item); | |
4726 | ||
4727 | started = rb_test_started; | |
4728 | /* read rb_test_started before checking buffer enabled */ | |
4729 | smp_rmb(); | |
4730 | ||
4731 | event = ring_buffer_lock_reserve(data->buffer, len); | |
4732 | if (!event) { | |
4733 | /* Ignore dropped events before test starts. */ | |
4734 | if (started) { | |
4735 | if (nested) | |
4736 | data->bytes_dropped += len; | |
4737 | else | |
4738 | data->bytes_dropped_nested += len; | |
4739 | } | |
4740 | return len; | |
4741 | } | |
4742 | ||
4743 | event_len = ring_buffer_event_length(event); | |
4744 | ||
4745 | if (RB_WARN_ON(data->buffer, event_len < len)) | |
4746 | goto out; | |
4747 | ||
4748 | item = ring_buffer_event_data(event); | |
4749 | item->size = size; | |
4750 | memcpy(item->str, rb_string, size); | |
4751 | ||
4752 | if (nested) { | |
4753 | data->bytes_alloc_nested += event_len; | |
4754 | data->bytes_written_nested += len; | |
4755 | data->events_nested++; | |
4756 | if (!data->min_size_nested || len < data->min_size_nested) | |
4757 | data->min_size_nested = len; | |
4758 | if (len > data->max_size_nested) | |
4759 | data->max_size_nested = len; | |
4760 | } else { | |
4761 | data->bytes_alloc += event_len; | |
4762 | data->bytes_written += len; | |
4763 | data->events++; | |
4764 | if (!data->min_size || len < data->min_size) | |
4765 | data->max_size = len; | |
4766 | if (len > data->max_size) | |
4767 | data->max_size = len; | |
4768 | } | |
4769 | ||
4770 | out: | |
4771 | ring_buffer_unlock_commit(data->buffer, event); | |
4772 | ||
4773 | return 0; | |
4774 | } | |
4775 | ||
4776 | static __init int rb_test(void *arg) | |
4777 | { | |
4778 | struct rb_test_data *data = arg; | |
4779 | ||
4780 | while (!kthread_should_stop()) { | |
4781 | rb_write_something(data, false); | |
4782 | data->cnt++; | |
4783 | ||
4784 | set_current_state(TASK_INTERRUPTIBLE); | |
4785 | /* Now sleep between a min of 100-300us and a max of 1ms */ | |
4786 | usleep_range(((data->cnt % 3) + 1) * 100, 1000); | |
4787 | } | |
4788 | ||
4789 | return 0; | |
4790 | } | |
4791 | ||
4792 | static __init void rb_ipi(void *ignore) | |
4793 | { | |
4794 | struct rb_test_data *data; | |
4795 | int cpu = smp_processor_id(); | |
4796 | ||
4797 | data = &rb_data[cpu]; | |
4798 | rb_write_something(data, true); | |
4799 | } | |
4800 | ||
4801 | static __init int rb_hammer_test(void *arg) | |
4802 | { | |
4803 | while (!kthread_should_stop()) { | |
4804 | ||
4805 | /* Send an IPI to all cpus to write data! */ | |
4806 | smp_call_function(rb_ipi, NULL, 1); | |
4807 | /* No sleep, but for non preempt, let others run */ | |
4808 | schedule(); | |
4809 | } | |
4810 | ||
4811 | return 0; | |
4812 | } | |
4813 | ||
4814 | static __init int test_ringbuffer(void) | |
4815 | { | |
4816 | struct task_struct *rb_hammer; | |
4817 | struct ring_buffer *buffer; | |
4818 | int cpu; | |
4819 | int ret = 0; | |
4820 | ||
4821 | pr_info("Running ring buffer tests...\n"); | |
4822 | ||
4823 | buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE); | |
4824 | if (WARN_ON(!buffer)) | |
4825 | return 0; | |
4826 | ||
4827 | /* Disable buffer so that threads can't write to it yet */ | |
4828 | ring_buffer_record_off(buffer); | |
4829 | ||
4830 | for_each_online_cpu(cpu) { | |
4831 | rb_data[cpu].buffer = buffer; | |
4832 | rb_data[cpu].cpu = cpu; | |
4833 | rb_data[cpu].cnt = cpu; | |
4834 | rb_threads[cpu] = kthread_create(rb_test, &rb_data[cpu], | |
4835 | "rbtester/%d", cpu); | |
4836 | if (WARN_ON(!rb_threads[cpu])) { | |
4837 | pr_cont("FAILED\n"); | |
4838 | ret = -1; | |
4839 | goto out_free; | |
4840 | } | |
4841 | ||
4842 | kthread_bind(rb_threads[cpu], cpu); | |
4843 | wake_up_process(rb_threads[cpu]); | |
4844 | } | |
4845 | ||
4846 | /* Now create the rb hammer! */ | |
4847 | rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer"); | |
4848 | if (WARN_ON(!rb_hammer)) { | |
4849 | pr_cont("FAILED\n"); | |
4850 | ret = -1; | |
4851 | goto out_free; | |
4852 | } | |
4853 | ||
4854 | ring_buffer_record_on(buffer); | |
4855 | /* | |
4856 | * Show buffer is enabled before setting rb_test_started. | |
4857 | * Yes there's a small race window where events could be | |
4858 | * dropped and the thread wont catch it. But when a ring | |
4859 | * buffer gets enabled, there will always be some kind of | |
4860 | * delay before other CPUs see it. Thus, we don't care about | |
4861 | * those dropped events. We care about events dropped after | |
4862 | * the threads see that the buffer is active. | |
4863 | */ | |
4864 | smp_wmb(); | |
4865 | rb_test_started = true; | |
4866 | ||
4867 | set_current_state(TASK_INTERRUPTIBLE); | |
4868 | /* Just run for 10 seconds */; | |
4869 | schedule_timeout(10 * HZ); | |
4870 | ||
4871 | kthread_stop(rb_hammer); | |
4872 | ||
4873 | out_free: | |
4874 | for_each_online_cpu(cpu) { | |
4875 | if (!rb_threads[cpu]) | |
4876 | break; | |
4877 | kthread_stop(rb_threads[cpu]); | |
4878 | } | |
4879 | if (ret) { | |
4880 | ring_buffer_free(buffer); | |
4881 | return ret; | |
4882 | } | |
4883 | ||
4884 | /* Report! */ | |
4885 | pr_info("finished\n"); | |
4886 | for_each_online_cpu(cpu) { | |
4887 | struct ring_buffer_event *event; | |
4888 | struct rb_test_data *data = &rb_data[cpu]; | |
4889 | struct rb_item *item; | |
4890 | unsigned long total_events; | |
4891 | unsigned long total_dropped; | |
4892 | unsigned long total_written; | |
4893 | unsigned long total_alloc; | |
4894 | unsigned long total_read = 0; | |
4895 | unsigned long total_size = 0; | |
4896 | unsigned long total_len = 0; | |
4897 | unsigned long total_lost = 0; | |
4898 | unsigned long lost; | |
4899 | int big_event_size; | |
4900 | int small_event_size; | |
4901 | ||
4902 | ret = -1; | |
4903 | ||
4904 | total_events = data->events + data->events_nested; | |
4905 | total_written = data->bytes_written + data->bytes_written_nested; | |
4906 | total_alloc = data->bytes_alloc + data->bytes_alloc_nested; | |
4907 | total_dropped = data->bytes_dropped + data->bytes_dropped_nested; | |
4908 | ||
4909 | big_event_size = data->max_size + data->max_size_nested; | |
4910 | small_event_size = data->min_size + data->min_size_nested; | |
4911 | ||
4912 | pr_info("CPU %d:\n", cpu); | |
4913 | pr_info(" events: %ld\n", total_events); | |
4914 | pr_info(" dropped bytes: %ld\n", total_dropped); | |
4915 | pr_info(" alloced bytes: %ld\n", total_alloc); | |
4916 | pr_info(" written bytes: %ld\n", total_written); | |
4917 | pr_info(" biggest event: %d\n", big_event_size); | |
4918 | pr_info(" smallest event: %d\n", small_event_size); | |
4919 | ||
4920 | if (RB_WARN_ON(buffer, total_dropped)) | |
4921 | break; | |
4922 | ||
4923 | ret = 0; | |
4924 | ||
4925 | while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) { | |
4926 | total_lost += lost; | |
4927 | item = ring_buffer_event_data(event); | |
4928 | total_len += ring_buffer_event_length(event); | |
4929 | total_size += item->size + sizeof(struct rb_item); | |
4930 | if (memcmp(&item->str[0], rb_string, item->size) != 0) { | |
4931 | pr_info("FAILED!\n"); | |
4932 | pr_info("buffer had: %.*s\n", item->size, item->str); | |
4933 | pr_info("expected: %.*s\n", item->size, rb_string); | |
4934 | RB_WARN_ON(buffer, 1); | |
4935 | ret = -1; | |
4936 | break; | |
4937 | } | |
4938 | total_read++; | |
4939 | } | |
4940 | if (ret) | |
4941 | break; | |
4942 | ||
4943 | ret = -1; | |
4944 | ||
4945 | pr_info(" read events: %ld\n", total_read); | |
4946 | pr_info(" lost events: %ld\n", total_lost); | |
4947 | pr_info(" total events: %ld\n", total_lost + total_read); | |
4948 | pr_info(" recorded len bytes: %ld\n", total_len); | |
4949 | pr_info(" recorded size bytes: %ld\n", total_size); | |
4950 | if (total_lost) | |
4951 | pr_info(" With dropped events, record len and size may not match\n" | |
4952 | " alloced and written from above\n"); | |
4953 | if (!total_lost) { | |
4954 | if (RB_WARN_ON(buffer, total_len != total_alloc || | |
4955 | total_size != total_written)) | |
4956 | break; | |
4957 | } | |
4958 | if (RB_WARN_ON(buffer, total_lost + total_read != total_events)) | |
4959 | break; | |
4960 | ||
4961 | ret = 0; | |
4962 | } | |
4963 | if (!ret) | |
4964 | pr_info("Ring buffer PASSED!\n"); | |
4965 | ||
4966 | ring_buffer_free(buffer); | |
4967 | return 0; | |
4968 | } | |
4969 | ||
4970 | late_initcall(test_ringbuffer); | |
4971 | #endif /* CONFIG_RING_BUFFER_STARTUP_TEST */ |