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e92f3e28 MD |
1 | #ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H |
2 | #define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H | |
852c2936 MD |
3 | |
4 | /* | |
e92f3e28 | 5 | * libringbuffer/frontend_internal.h |
852c2936 MD |
6 | * |
7 | * Ring Buffer Library Synchronization Header (internal helpers). | |
8 | * | |
e92f3e28 MD |
9 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
10 | * | |
11 | * This library is free software; you can redistribute it and/or | |
12 | * modify it under the terms of the GNU Lesser General Public | |
13 | * License as published by the Free Software Foundation; only | |
14 | * version 2.1 of the License. | |
15 | * | |
16 | * This library is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
19 | * Lesser General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU Lesser General Public | |
22 | * License along with this library; if not, write to the Free Software | |
23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
24 | * | |
25 | * | |
852c2936 MD |
26 | * Author: |
27 | * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
28 | * | |
29 | * See ring_buffer_frontend.c for more information on wait-free algorithms. | |
30 | * | |
31 | * Dual LGPL v2.1/GPL v2 license. | |
32 | */ | |
33 | ||
14641deb | 34 | #include <urcu/compiler.h> |
2c44f5b9 MD |
35 | #include <signal.h> |
36 | #include <pthread.h> | |
14641deb | 37 | |
4318ae1b | 38 | #include <lttng/ringbuffer-config.h> |
4931a13e MD |
39 | #include "backend_types.h" |
40 | #include "frontend_types.h" | |
a6352fd4 | 41 | #include "shm.h" |
852c2936 MD |
42 | |
43 | /* Buffer offset macros */ | |
44 | ||
45 | /* buf_trunc mask selects only the buffer number. */ | |
46 | static inline | |
47 | unsigned long buf_trunc(unsigned long offset, struct channel *chan) | |
48 | { | |
49 | return offset & ~(chan->backend.buf_size - 1); | |
50 | ||
51 | } | |
52 | ||
53 | /* Select the buffer number value (counter). */ | |
54 | static inline | |
55 | unsigned long buf_trunc_val(unsigned long offset, struct channel *chan) | |
56 | { | |
57 | return buf_trunc(offset, chan) >> chan->backend.buf_size_order; | |
58 | } | |
59 | ||
60 | /* buf_offset mask selects only the offset within the current buffer. */ | |
61 | static inline | |
62 | unsigned long buf_offset(unsigned long offset, struct channel *chan) | |
63 | { | |
64 | return offset & (chan->backend.buf_size - 1); | |
65 | } | |
66 | ||
67 | /* subbuf_offset mask selects the offset within the current subbuffer. */ | |
68 | static inline | |
69 | unsigned long subbuf_offset(unsigned long offset, struct channel *chan) | |
70 | { | |
71 | return offset & (chan->backend.subbuf_size - 1); | |
72 | } | |
73 | ||
74 | /* subbuf_trunc mask selects the subbuffer number. */ | |
75 | static inline | |
76 | unsigned long subbuf_trunc(unsigned long offset, struct channel *chan) | |
77 | { | |
78 | return offset & ~(chan->backend.subbuf_size - 1); | |
79 | } | |
80 | ||
81 | /* subbuf_align aligns the offset to the next subbuffer. */ | |
82 | static inline | |
83 | unsigned long subbuf_align(unsigned long offset, struct channel *chan) | |
84 | { | |
85 | return (offset + chan->backend.subbuf_size) | |
86 | & ~(chan->backend.subbuf_size - 1); | |
87 | } | |
88 | ||
89 | /* subbuf_index returns the index of the current subbuffer within the buffer. */ | |
90 | static inline | |
91 | unsigned long subbuf_index(unsigned long offset, struct channel *chan) | |
92 | { | |
93 | return buf_offset(offset, chan) >> chan->backend.subbuf_size_order; | |
94 | } | |
95 | ||
96 | /* | |
97 | * Last TSC comparison functions. Check if the current TSC overflows tsc_bits | |
98 | * bits from the last TSC read. When overflows are detected, the full 64-bit | |
99 | * timestamp counter should be written in the record header. Reads and writes | |
100 | * last_tsc atomically. | |
101 | */ | |
102 | ||
14641deb | 103 | #if (CAA_BITS_PER_LONG == 32) |
852c2936 | 104 | static inline |
4cfec15c | 105 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 106 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
107 | { |
108 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
109 | return; | |
110 | ||
111 | /* | |
112 | * Ensure the compiler performs this update in a single instruction. | |
113 | */ | |
114 | v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits)); | |
115 | } | |
116 | ||
117 | static inline | |
4cfec15c | 118 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 119 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
120 | { |
121 | unsigned long tsc_shifted; | |
122 | ||
123 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
124 | return 0; | |
125 | ||
126 | tsc_shifted = (unsigned long)(tsc >> config->tsc_bits); | |
b5a3dfa5 | 127 | if (caa_unlikely(tsc_shifted |
852c2936 MD |
128 | - (unsigned long)v_read(config, &buf->last_tsc))) |
129 | return 1; | |
130 | else | |
131 | return 0; | |
132 | } | |
133 | #else | |
134 | static inline | |
4cfec15c | 135 | void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 136 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
137 | { |
138 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
139 | return; | |
140 | ||
141 | v_set(config, &buf->last_tsc, (unsigned long)tsc); | |
142 | } | |
143 | ||
144 | static inline | |
4cfec15c | 145 | int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config, |
2fed87ae | 146 | struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc) |
852c2936 MD |
147 | { |
148 | if (config->tsc_bits == 0 || config->tsc_bits == 64) | |
149 | return 0; | |
150 | ||
b5a3dfa5 | 151 | if (caa_unlikely((tsc - v_read(config, &buf->last_tsc)) |
852c2936 MD |
152 | >> config->tsc_bits)) |
153 | return 1; | |
154 | else | |
155 | return 0; | |
156 | } | |
157 | #endif | |
158 | ||
159 | extern | |
4cfec15c | 160 | int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx); |
852c2936 MD |
161 | |
162 | extern | |
4cfec15c | 163 | void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf, |
1d498196 | 164 | enum switch_mode mode, |
38fae1d3 | 165 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
166 | |
167 | /* Buffer write helpers */ | |
168 | ||
169 | static inline | |
4cfec15c | 170 | void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf, |
852c2936 MD |
171 | struct channel *chan, |
172 | unsigned long offset) | |
173 | { | |
174 | unsigned long consumed_old, consumed_new; | |
175 | ||
176 | do { | |
14641deb | 177 | consumed_old = uatomic_read(&buf->consumed); |
852c2936 MD |
178 | /* |
179 | * If buffer is in overwrite mode, push the reader consumed | |
180 | * count if the write position has reached it and we are not | |
181 | * at the first iteration (don't push the reader farther than | |
182 | * the writer). This operation can be done concurrently by many | |
183 | * writers in the same buffer, the writer being at the farthest | |
184 | * write position sub-buffer index in the buffer being the one | |
185 | * which will win this loop. | |
186 | */ | |
b5a3dfa5 | 187 | if (caa_unlikely(subbuf_trunc(offset, chan) |
852c2936 MD |
188 | - subbuf_trunc(consumed_old, chan) |
189 | >= chan->backend.buf_size)) | |
190 | consumed_new = subbuf_align(consumed_old, chan); | |
191 | else | |
192 | return; | |
b5a3dfa5 | 193 | } while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old, |
852c2936 MD |
194 | consumed_new) != consumed_old)); |
195 | } | |
196 | ||
197 | static inline | |
4cfec15c MD |
198 | void lib_ring_buffer_vmcore_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config, |
199 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 | 200 | unsigned long commit_count, |
1d498196 | 201 | unsigned long idx, |
38fae1d3 | 202 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
203 | { |
204 | if (config->oops == RING_BUFFER_OOPS_CONSISTENCY) | |
4746ae29 | 205 | v_set(config, &shmp_index(handle, buf->commit_hot, idx)->seq, commit_count); |
852c2936 MD |
206 | } |
207 | ||
208 | static inline | |
4cfec15c MD |
209 | int lib_ring_buffer_poll_deliver(const struct lttng_ust_lib_ring_buffer_config *config, |
210 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 211 | struct channel *chan, |
38fae1d3 | 212 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
213 | { |
214 | unsigned long consumed_old, consumed_idx, commit_count, write_offset; | |
215 | ||
14641deb | 216 | consumed_old = uatomic_read(&buf->consumed); |
852c2936 | 217 | consumed_idx = subbuf_index(consumed_old, chan); |
4746ae29 | 218 | commit_count = v_read(config, &shmp_index(handle, buf->commit_cold, consumed_idx)->cc_sb); |
852c2936 MD |
219 | /* |
220 | * No memory barrier here, since we are only interested | |
221 | * in a statistically correct polling result. The next poll will | |
222 | * get the data is we are racing. The mb() that ensures correct | |
223 | * memory order is in get_subbuf. | |
224 | */ | |
225 | write_offset = v_read(config, &buf->offset); | |
226 | ||
227 | /* | |
228 | * Check that the subbuffer we are trying to consume has been | |
229 | * already fully committed. | |
230 | */ | |
231 | ||
232 | if (((commit_count - chan->backend.subbuf_size) | |
233 | & chan->commit_count_mask) | |
234 | - (buf_trunc(consumed_old, chan) | |
235 | >> chan->backend.num_subbuf_order) | |
236 | != 0) | |
237 | return 0; | |
238 | ||
239 | /* | |
240 | * Check that we are not about to read the same subbuffer in | |
241 | * which the writer head is. | |
242 | */ | |
243 | if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_old, chan) | |
244 | == 0) | |
245 | return 0; | |
246 | ||
247 | return 1; | |
248 | ||
249 | } | |
250 | ||
251 | static inline | |
4cfec15c MD |
252 | int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config, |
253 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 MD |
254 | struct channel *chan) |
255 | { | |
256 | return !!subbuf_offset(v_read(config, &buf->offset), chan); | |
257 | } | |
258 | ||
259 | static inline | |
4cfec15c MD |
260 | unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config, |
261 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 262 | unsigned long idx, |
38fae1d3 | 263 | struct lttng_ust_shm_handle *handle) |
852c2936 | 264 | { |
1d498196 | 265 | return subbuffer_get_data_size(config, &buf->backend, idx, handle); |
852c2936 MD |
266 | } |
267 | ||
268 | /* | |
269 | * Check if all space reservation in a buffer have been committed. This helps | |
270 | * knowing if an execution context is nested (for per-cpu buffers only). | |
271 | * This is a very specific ftrace use-case, so we keep this as "internal" API. | |
272 | */ | |
273 | static inline | |
4cfec15c MD |
274 | int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config, |
275 | struct lttng_ust_lib_ring_buffer *buf, | |
1d498196 | 276 | struct channel *chan, |
38fae1d3 | 277 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
278 | { |
279 | unsigned long offset, idx, commit_count; | |
280 | ||
281 | CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU); | |
282 | CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU); | |
283 | ||
284 | /* | |
285 | * Read offset and commit count in a loop so they are both read | |
286 | * atomically wrt interrupts. By deal with interrupt concurrency by | |
287 | * restarting both reads if the offset has been pushed. Note that given | |
288 | * we only have to deal with interrupt concurrency here, an interrupt | |
289 | * modifying the commit count will also modify "offset", so it is safe | |
290 | * to only check for offset modifications. | |
291 | */ | |
292 | do { | |
293 | offset = v_read(config, &buf->offset); | |
294 | idx = subbuf_index(offset, chan); | |
4746ae29 | 295 | commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->cc); |
852c2936 MD |
296 | } while (offset != v_read(config, &buf->offset)); |
297 | ||
298 | return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) | |
299 | - (commit_count & chan->commit_count_mask) == 0); | |
300 | } | |
301 | ||
302 | static inline | |
4cfec15c MD |
303 | void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config, |
304 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 MD |
305 | struct channel *chan, |
306 | unsigned long offset, | |
307 | unsigned long commit_count, | |
1d498196 | 308 | unsigned long idx, |
38fae1d3 | 309 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
310 | { |
311 | unsigned long old_commit_count = commit_count | |
312 | - chan->backend.subbuf_size; | |
2fed87ae | 313 | uint64_t tsc; |
852c2936 MD |
314 | |
315 | /* Check if all commits have been done */ | |
b5a3dfa5 | 316 | if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order) |
852c2936 MD |
317 | - (old_commit_count & chan->commit_count_mask) == 0)) { |
318 | /* | |
319 | * If we succeeded at updating cc_sb below, we are the subbuffer | |
320 | * writer delivering the subbuffer. Deals with concurrent | |
321 | * updates of the "cc" value without adding a add_return atomic | |
322 | * operation to the fast path. | |
323 | * | |
324 | * We are doing the delivery in two steps: | |
325 | * - First, we cmpxchg() cc_sb to the new value | |
326 | * old_commit_count + 1. This ensures that we are the only | |
327 | * subbuffer user successfully filling the subbuffer, but we | |
328 | * do _not_ set the cc_sb value to "commit_count" yet. | |
329 | * Therefore, other writers that would wrap around the ring | |
330 | * buffer and try to start writing to our subbuffer would | |
331 | * have to drop records, because it would appear as | |
332 | * non-filled. | |
333 | * We therefore have exclusive access to the subbuffer control | |
334 | * structures. This mutual exclusion with other writers is | |
335 | * crucially important to perform record overruns count in | |
336 | * flight recorder mode locklessly. | |
337 | * - When we are ready to release the subbuffer (either for | |
338 | * reading or for overrun by other writers), we simply set the | |
339 | * cc_sb value to "commit_count" and perform delivery. | |
340 | * | |
341 | * The subbuffer size is least 2 bytes (minimum size: 1 page). | |
342 | * This guarantees that old_commit_count + 1 != commit_count. | |
343 | */ | |
b5a3dfa5 | 344 | if (caa_likely(v_cmpxchg(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb, |
852c2936 MD |
345 | old_commit_count, old_commit_count + 1) |
346 | == old_commit_count)) { | |
347 | /* | |
348 | * Start of exclusive subbuffer access. We are | |
349 | * guaranteed to be the last writer in this subbuffer | |
350 | * and any other writer trying to access this subbuffer | |
351 | * in this state is required to drop records. | |
352 | */ | |
353 | tsc = config->cb.ring_buffer_clock_read(chan); | |
354 | v_add(config, | |
355 | subbuffer_get_records_count(config, | |
1d498196 MD |
356 | &buf->backend, |
357 | idx, handle), | |
852c2936 MD |
358 | &buf->records_count); |
359 | v_add(config, | |
360 | subbuffer_count_records_overrun(config, | |
361 | &buf->backend, | |
1d498196 | 362 | idx, handle), |
852c2936 MD |
363 | &buf->records_overrun); |
364 | config->cb.buffer_end(buf, tsc, idx, | |
365 | lib_ring_buffer_get_data_size(config, | |
366 | buf, | |
1d498196 MD |
367 | idx, |
368 | handle), | |
369 | handle); | |
852c2936 MD |
370 | |
371 | /* | |
372 | * Set noref flag and offset for this subbuffer id. | |
373 | * Contains a memory barrier that ensures counter stores | |
374 | * are ordered before set noref and offset. | |
375 | */ | |
376 | lib_ring_buffer_set_noref_offset(config, &buf->backend, idx, | |
1d498196 | 377 | buf_trunc_val(offset, chan), handle); |
852c2936 MD |
378 | |
379 | /* | |
380 | * Order set_noref and record counter updates before the | |
381 | * end of subbuffer exclusive access. Orders with | |
382 | * respect to writers coming into the subbuffer after | |
383 | * wrap around, and also order wrt concurrent readers. | |
384 | */ | |
14641deb | 385 | cmm_smp_mb(); |
852c2936 | 386 | /* End of exclusive subbuffer access */ |
4746ae29 | 387 | v_set(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb, |
852c2936 MD |
388 | commit_count); |
389 | lib_ring_buffer_vmcore_check_deliver(config, buf, | |
1d498196 | 390 | commit_count, idx, handle); |
852c2936 MD |
391 | |
392 | /* | |
393 | * RING_BUFFER_WAKEUP_BY_WRITER wakeup is not lock-free. | |
394 | */ | |
395 | if (config->wakeup == RING_BUFFER_WAKEUP_BY_WRITER | |
824f40b8 MD |
396 | && (uatomic_read(&buf->active_readers) |
397 | || uatomic_read(&buf->active_shadow_readers)) | |
1d498196 | 398 | && lib_ring_buffer_poll_deliver(config, buf, chan, handle)) { |
5d61a504 MD |
399 | int wakeup_fd = shm_get_wakeup_fd(handle, &buf->self._ref); |
400 | ||
401 | if (wakeup_fd >= 0) { | |
2c44f5b9 MD |
402 | sigset_t sigpipe_set, pending_set, old_set; |
403 | int ret, sigpipe_was_pending = 0; | |
404 | ||
5d61a504 MD |
405 | /* |
406 | * Wake-up the other end by | |
407 | * writing a null byte in the | |
408 | * pipe (non-blocking). | |
49deb559 MD |
409 | * Important note: Because |
410 | * writing into the pipe is | |
411 | * non-blocking (and therefore | |
412 | * we allow dropping wakeup | |
413 | * data, as long as there is | |
414 | * wakeup data present in the | |
415 | * pipe buffer to wake up the | |
416 | * consumer), the consumer | |
417 | * should perform the following | |
418 | * sequence for waiting: | |
419 | * 1) empty the pipe (reads). | |
420 | * 2) check if there is data in | |
421 | * the buffer. | |
422 | * 3) wait on the pipe (poll). | |
2c44f5b9 MD |
423 | * |
424 | * Discard the SIGPIPE from write(), not | |
425 | * disturbing any SIGPIPE that might be | |
426 | * already pending. If a bogus SIGPIPE | |
427 | * is sent to the entire process | |
428 | * concurrently by a malicious user, it | |
429 | * may be simply discarded. | |
430 | */ | |
431 | ret = sigemptyset(&pending_set); | |
432 | assert(!ret); | |
433 | /* | |
434 | * sigpending returns the mask | |
435 | * of signals that are _both_ | |
436 | * blocked for the thread _and_ | |
437 | * pending for either the thread | |
438 | * or the entire process. | |
5d61a504 | 439 | */ |
2c44f5b9 MD |
440 | ret = sigpending(&pending_set); |
441 | assert(!ret); | |
442 | sigpipe_was_pending = sigismember(&pending_set, SIGPIPE); | |
443 | /* | |
444 | * If sigpipe was pending, it | |
445 | * means it was already blocked, | |
446 | * so no need to block it. | |
447 | */ | |
448 | if (!sigpipe_was_pending) { | |
449 | ret = sigemptyset(&sigpipe_set); | |
450 | assert(!ret); | |
451 | ret = sigaddset(&sigpipe_set, SIGPIPE); | |
452 | assert(!ret); | |
453 | ret = pthread_sigmask(SIG_BLOCK, &sigpipe_set, &old_set); | |
454 | assert(!ret); | |
455 | } | |
5d61a504 MD |
456 | do { |
457 | ret = write(wakeup_fd, "", 1); | |
458 | } while (ret == -1L && errno == EINTR); | |
2c44f5b9 MD |
459 | if (ret == -1L && errno == EPIPE && !sigpipe_was_pending) { |
460 | struct timespec timeout = { 0, 0 }; | |
461 | do { | |
462 | ret = sigtimedwait(&sigpipe_set, NULL, | |
463 | &timeout); | |
464 | } while (ret == -1L && errno == EINTR); | |
465 | } | |
466 | if (!sigpipe_was_pending) { | |
467 | ret = pthread_sigmask(SIG_SETMASK, &old_set, NULL); | |
468 | assert(!ret); | |
469 | } | |
5d61a504 | 470 | } |
852c2936 | 471 | } |
852c2936 MD |
472 | } |
473 | } | |
474 | } | |
475 | ||
476 | /* | |
477 | * lib_ring_buffer_write_commit_counter | |
478 | * | |
479 | * For flight recording. must be called after commit. | |
480 | * This function increments the subbuffer's commit_seq counter each time the | |
481 | * commit count reaches back the reserve offset (modulo subbuffer size). It is | |
482 | * useful for crash dump. | |
483 | */ | |
484 | static inline | |
4cfec15c MD |
485 | void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config, |
486 | struct lttng_ust_lib_ring_buffer *buf, | |
852c2936 MD |
487 | struct channel *chan, |
488 | unsigned long idx, | |
489 | unsigned long buf_offset, | |
490 | unsigned long commit_count, | |
1d498196 | 491 | size_t slot_size, |
38fae1d3 | 492 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
493 | { |
494 | unsigned long offset, commit_seq_old; | |
495 | ||
496 | if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) | |
497 | return; | |
498 | ||
499 | offset = buf_offset + slot_size; | |
500 | ||
501 | /* | |
502 | * subbuf_offset includes commit_count_mask. We can simply | |
503 | * compare the offsets within the subbuffer without caring about | |
504 | * buffer full/empty mismatch because offset is never zero here | |
505 | * (subbuffer header and record headers have non-zero length). | |
506 | */ | |
b5a3dfa5 | 507 | if (caa_unlikely(subbuf_offset(offset - commit_count, chan))) |
852c2936 MD |
508 | return; |
509 | ||
4746ae29 | 510 | commit_seq_old = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->seq); |
852c2936 | 511 | while ((long) (commit_seq_old - commit_count) < 0) |
4746ae29 | 512 | commit_seq_old = v_cmpxchg(config, &shmp_index(handle, buf->commit_hot, idx)->seq, |
852c2936 MD |
513 | commit_seq_old, commit_count); |
514 | } | |
515 | ||
4cfec15c | 516 | extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf, |
a6352fd4 | 517 | struct channel_backend *chanb, int cpu, |
38fae1d3 | 518 | struct lttng_ust_shm_handle *handle, |
1d498196 | 519 | struct shm_object *shmobj); |
4cfec15c | 520 | extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf, |
38fae1d3 | 521 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
522 | |
523 | /* Keep track of trap nesting inside ring buffer code */ | |
14641deb | 524 | extern __thread unsigned int lib_ring_buffer_nesting; |
852c2936 | 525 | |
e92f3e28 | 526 | #endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */ |