Commit | Line | Data |
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852c2936 | 1 | /* |
c0c0989a | 2 | * SPDX-License-Identifier: LGPL-2.1-only |
852c2936 | 3 | * |
e92f3e28 MD |
4 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
5 | * | |
852c2936 MD |
6 | * Ring buffer wait-free buffer synchronization. Producer-consumer and flight |
7 | * recorder (overwrite) modes. See thesis: | |
8 | * | |
9 | * Desnoyers, Mathieu (2009), "Low-Impact Operating System Tracing", Ph.D. | |
10 | * dissertation, Ecole Polytechnique de Montreal. | |
11 | * http://www.lttng.org/pub/thesis/desnoyers-dissertation-2009-12.pdf | |
12 | * | |
13 | * - Algorithm presentation in Chapter 5: | |
14 | * "Lockless Multi-Core High-Throughput Buffering". | |
15 | * - Algorithm formal verification in Section 8.6: | |
16 | * "Formal verification of LTTng" | |
17 | * | |
18 | * Author: | |
19 | * Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
20 | * | |
21 | * Inspired from LTT and RelayFS: | |
22 | * Karim Yaghmour <karim@opersys.com> | |
23 | * Tom Zanussi <zanussi@us.ibm.com> | |
24 | * Bob Wisniewski <bob@watson.ibm.com> | |
25 | * And from K42 : | |
26 | * Bob Wisniewski <bob@watson.ibm.com> | |
27 | * | |
28 | * Buffer reader semantic : | |
29 | * | |
30 | * - get_subbuf_size | |
31 | * while buffer is not finalized and empty | |
32 | * - get_subbuf | |
33 | * - if return value != 0, continue | |
34 | * - splice one subbuffer worth of data to a pipe | |
35 | * - splice the data from pipe to disk/network | |
36 | * - put_subbuf | |
852c2936 MD |
37 | */ |
38 | ||
3fbec7dc | 39 | #define _LGPL_SOURCE |
a6352fd4 | 40 | #include <sys/types.h> |
431d5cf0 MD |
41 | #include <sys/mman.h> |
42 | #include <sys/stat.h> | |
03d2d293 | 43 | #include <unistd.h> |
431d5cf0 | 44 | #include <fcntl.h> |
03d2d293 MD |
45 | #include <signal.h> |
46 | #include <time.h> | |
932b85fa | 47 | #include <stdbool.h> |
fb31eb73 | 48 | #include <stdint.h> |
14641deb | 49 | #include <urcu/compiler.h> |
a6352fd4 | 50 | #include <urcu/ref.h> |
8c90a710 | 51 | #include <urcu/tls-compat.h> |
327d9447 | 52 | #include <poll.h> |
9d315d6d | 53 | #include "common/macros.h" |
14641deb | 54 | |
eae3c729 | 55 | #include <lttng/ust-utils.h> |
0b4b8811 | 56 | #include <lttng/ust-ringbuffer-context.h> |
3d3a2bb8 | 57 | |
74cc1f59 | 58 | #include "common/smp.h" |
0466ac28 | 59 | #include "ringbuffer-config.h" |
2fed87ae | 60 | #include "vatomic.h" |
4931a13e MD |
61 | #include "backend.h" |
62 | #include "frontend.h" | |
a6352fd4 | 63 | #include "shm.h" |
6f97f9c2 | 64 | #include "rb-init.h" |
27b98e6c | 65 | #include "common/compat/errno.h" /* For ENODATA */ |
97572c04 | 66 | #include "common/populate.h" |
852c2936 | 67 | |
64493e4f MD |
68 | /* Print DBG() messages about events lost only every 1048576 hits */ |
69 | #define DBG_PRINT_NR_LOST (1UL << 20) | |
70 | ||
34a91bdb MD |
71 | #define LTTNG_UST_RB_SIG_FLUSH SIGRTMIN |
72 | #define LTTNG_UST_RB_SIG_READ SIGRTMIN + 1 | |
73 | #define LTTNG_UST_RB_SIG_TEARDOWN SIGRTMIN + 2 | |
03d2d293 | 74 | #define CLOCKID CLOCK_MONOTONIC |
dddba398 MD |
75 | #define LTTNG_UST_RING_BUFFER_GET_RETRY 10 |
76 | #define LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS 10 | |
6f97f9c2 | 77 | #define RETRY_DELAY_MS 100 /* 100 ms. */ |
03d2d293 | 78 | |
a9ff648c MD |
79 | /* |
80 | * Non-static to ensure the compiler does not optimize away the xor. | |
81 | */ | |
95fa2ba4 MJ |
82 | uint8_t lttng_crash_magic_xor[] |
83 | __attribute__((visibility("hidden"))); | |
a9ff648c MD |
84 | uint8_t lttng_crash_magic_xor[] = RB_CRASH_DUMP_ABI_MAGIC_XOR; |
85 | ||
2432c3c9 MD |
86 | /* |
87 | * Use POSIX SHM: shm_open(3) and shm_unlink(3). | |
88 | * close(2) to close the fd returned by shm_open. | |
89 | * shm_unlink releases the shared memory object name. | |
90 | * ftruncate(2) sets the size of the memory object. | |
91 | * mmap/munmap maps the shared memory obj to a virtual address in the | |
92 | * calling proceess (should be done both in libust and consumer). | |
93 | * See shm_overview(7) for details. | |
94 | * Pass file descriptor returned by shm_open(3) to ltt-sessiond through | |
95 | * a UNIX socket. | |
96 | * | |
97 | * Since we don't need to access the object using its name, we can | |
98 | * immediately shm_unlink(3) it, and only keep the handle with its file | |
99 | * descriptor. | |
100 | */ | |
101 | ||
852c2936 MD |
102 | /* |
103 | * Internal structure representing offsets to use at a sub-buffer switch. | |
104 | */ | |
105 | struct switch_offsets { | |
106 | unsigned long begin, end, old; | |
107 | size_t pre_header_padding, size; | |
1ad21f70 MD |
108 | unsigned int switch_new_start:1, switch_new_end:1, switch_old_start:1, |
109 | switch_old_end:1; | |
852c2936 MD |
110 | }; |
111 | ||
16adecf1 | 112 | DEFINE_URCU_TLS(unsigned int, lib_ring_buffer_nesting); |
852c2936 | 113 | |
cb7378b3 MD |
114 | /* |
115 | * wakeup_fd_mutex protects wakeup fd use by timer from concurrent | |
116 | * close. | |
117 | */ | |
118 | static pthread_mutex_t wakeup_fd_mutex = PTHREAD_MUTEX_INITIALIZER; | |
119 | ||
852c2936 | 120 | static |
b5457df5 MD |
121 | void lib_ring_buffer_print_errors(struct lttng_ust_ring_buffer_channel *chan, |
122 | struct lttng_ust_ring_buffer *buf, int cpu, | |
009769ca | 123 | struct lttng_ust_shm_handle *handle); |
852c2936 | 124 | |
03d2d293 MD |
125 | /* |
126 | * Handle timer teardown race wrt memory free of private data by | |
127 | * ring buffer signals are handled by a single thread, which permits | |
128 | * a synchronization point between handling of each signal. | |
64bf51a6 | 129 | * Protected by the lock within the structure. |
03d2d293 MD |
130 | */ |
131 | struct timer_signal_data { | |
132 | pthread_t tid; /* thread id managing signals */ | |
133 | int setup_done; | |
134 | int qs_done; | |
64bf51a6 | 135 | pthread_mutex_t lock; |
03d2d293 MD |
136 | }; |
137 | ||
64bf51a6 MD |
138 | static struct timer_signal_data timer_signal = { |
139 | .tid = 0, | |
140 | .setup_done = 0, | |
141 | .qs_done = 0, | |
142 | .lock = PTHREAD_MUTEX_INITIALIZER, | |
143 | }; | |
03d2d293 | 144 | |
b2c5f61a | 145 | static bool lttng_ust_allow_blocking; |
6f97f9c2 | 146 | |
b2c5f61a | 147 | void lttng_ust_ringbuffer_set_allow_blocking(void) |
6f97f9c2 | 148 | { |
b2c5f61a MD |
149 | lttng_ust_allow_blocking = true; |
150 | } | |
151 | ||
152 | /* Get blocking timeout, in ms */ | |
b5457df5 | 153 | static int lttng_ust_ringbuffer_get_timeout(struct lttng_ust_ring_buffer_channel *chan) |
b2c5f61a MD |
154 | { |
155 | if (!lttng_ust_allow_blocking) | |
156 | return 0; | |
157 | return chan->u.s.blocking_timeout_ms; | |
6f97f9c2 MD |
158 | } |
159 | ||
852c2936 MD |
160 | /** |
161 | * lib_ring_buffer_reset - Reset ring buffer to initial values. | |
162 | * @buf: Ring buffer. | |
163 | * | |
164 | * Effectively empty the ring buffer. Should be called when the buffer is not | |
165 | * used for writing. The ring buffer can be opened for reading, but the reader | |
166 | * should not be using the iterator concurrently with reset. The previous | |
167 | * current iterator record is reset. | |
168 | */ | |
b5457df5 | 169 | void lib_ring_buffer_reset(struct lttng_ust_ring_buffer *buf, |
38fae1d3 | 170 | struct lttng_ust_shm_handle *handle) |
852c2936 | 171 | { |
b5457df5 MD |
172 | struct lttng_ust_ring_buffer_channel *chan; |
173 | const struct lttng_ust_ring_buffer_config *config; | |
852c2936 MD |
174 | unsigned int i; |
175 | ||
34daae3e MD |
176 | chan = shmp(handle, buf->backend.chan); |
177 | if (!chan) | |
15500a1b | 178 | return; |
34daae3e | 179 | config = &chan->backend.config; |
852c2936 MD |
180 | /* |
181 | * Reset iterator first. It will put the subbuffer if it currently holds | |
182 | * it. | |
183 | */ | |
852c2936 MD |
184 | v_set(config, &buf->offset, 0); |
185 | for (i = 0; i < chan->backend.num_subbuf; i++) { | |
15500a1b MD |
186 | struct commit_counters_hot *cc_hot; |
187 | struct commit_counters_cold *cc_cold; | |
6c737d05 | 188 | uint64_t *ts_end; |
15500a1b MD |
189 | |
190 | cc_hot = shmp_index(handle, buf->commit_hot, i); | |
191 | if (!cc_hot) | |
192 | return; | |
193 | cc_cold = shmp_index(handle, buf->commit_cold, i); | |
194 | if (!cc_cold) | |
195 | return; | |
6c737d05 MD |
196 | ts_end = shmp_index(handle, buf->ts_end, i); |
197 | if (!ts_end) | |
198 | return; | |
15500a1b MD |
199 | v_set(config, &cc_hot->cc, 0); |
200 | v_set(config, &cc_hot->seq, 0); | |
201 | v_set(config, &cc_cold->cc_sb, 0); | |
6c737d05 | 202 | *ts_end = 0; |
852c2936 | 203 | } |
a6352fd4 MD |
204 | uatomic_set(&buf->consumed, 0); |
205 | uatomic_set(&buf->record_disabled, 0); | |
373ea80a | 206 | v_set(config, &buf->last_timestamp, 0); |
1d498196 | 207 | lib_ring_buffer_backend_reset(&buf->backend, handle); |
852c2936 MD |
208 | /* Don't reset number of active readers */ |
209 | v_set(config, &buf->records_lost_full, 0); | |
210 | v_set(config, &buf->records_lost_wrap, 0); | |
211 | v_set(config, &buf->records_lost_big, 0); | |
212 | v_set(config, &buf->records_count, 0); | |
213 | v_set(config, &buf->records_overrun, 0); | |
214 | buf->finalized = 0; | |
215 | } | |
852c2936 MD |
216 | |
217 | /** | |
218 | * channel_reset - Reset channel to initial values. | |
219 | * @chan: Channel. | |
220 | * | |
221 | * Effectively empty the channel. Should be called when the channel is not used | |
222 | * for writing. The channel can be opened for reading, but the reader should not | |
223 | * be using the iterator concurrently with reset. The previous current iterator | |
224 | * record is reset. | |
225 | */ | |
b5457df5 | 226 | void channel_reset(struct lttng_ust_ring_buffer_channel *chan) |
852c2936 MD |
227 | { |
228 | /* | |
229 | * Reset iterators first. Will put the subbuffer if held for reading. | |
230 | */ | |
a6352fd4 | 231 | uatomic_set(&chan->record_disabled, 0); |
852c2936 MD |
232 | /* Don't reset commit_count_mask, still valid */ |
233 | channel_backend_reset(&chan->backend); | |
234 | /* Don't reset switch/read timer interval */ | |
235 | /* Don't reset notifiers and notifier enable bits */ | |
236 | /* Don't reset reader reference count */ | |
237 | } | |
852c2936 | 238 | |
a9ff648c | 239 | static |
b5457df5 | 240 | void init_crash_abi(const struct lttng_ust_ring_buffer_config *config, |
a9ff648c | 241 | struct lttng_crash_abi *crash_abi, |
b5457df5 | 242 | struct lttng_ust_ring_buffer *buf, |
a9ff648c MD |
243 | struct channel_backend *chanb, |
244 | struct shm_object *shmobj, | |
245 | struct lttng_ust_shm_handle *handle) | |
246 | { | |
247 | int i; | |
248 | ||
249 | for (i = 0; i < RB_CRASH_DUMP_ABI_MAGIC_LEN; i++) | |
250 | crash_abi->magic[i] = lttng_crash_magic_xor[i] ^ 0xFF; | |
251 | crash_abi->mmap_length = shmobj->memory_map_size; | |
252 | crash_abi->endian = RB_CRASH_ENDIAN; | |
253 | crash_abi->major = RB_CRASH_DUMP_ABI_MAJOR; | |
254 | crash_abi->minor = RB_CRASH_DUMP_ABI_MINOR; | |
255 | crash_abi->word_size = sizeof(unsigned long); | |
256 | crash_abi->layout_type = LTTNG_CRASH_TYPE_UST; | |
257 | ||
258 | /* Offset of fields */ | |
259 | crash_abi->offset.prod_offset = | |
260 | (uint32_t) ((char *) &buf->offset - (char *) buf); | |
261 | crash_abi->offset.consumed_offset = | |
262 | (uint32_t) ((char *) &buf->consumed - (char *) buf); | |
263 | crash_abi->offset.commit_hot_array = | |
264 | (uint32_t) ((char *) shmp(handle, buf->commit_hot) - (char *) buf); | |
265 | crash_abi->offset.commit_hot_seq = | |
266 | offsetof(struct commit_counters_hot, seq); | |
267 | crash_abi->offset.buf_wsb_array = | |
268 | (uint32_t) ((char *) shmp(handle, buf->backend.buf_wsb) - (char *) buf); | |
269 | crash_abi->offset.buf_wsb_id = | |
b5457df5 | 270 | offsetof(struct lttng_ust_ring_buffer_backend_subbuffer, id); |
a9ff648c MD |
271 | crash_abi->offset.sb_array = |
272 | (uint32_t) ((char *) shmp(handle, buf->backend.array) - (char *) buf); | |
273 | crash_abi->offset.sb_array_shmp_offset = | |
b5457df5 | 274 | offsetof(struct lttng_ust_ring_buffer_backend_pages_shmp, |
a9ff648c MD |
275 | shmp._ref.offset); |
276 | crash_abi->offset.sb_backend_p_offset = | |
b5457df5 | 277 | offsetof(struct lttng_ust_ring_buffer_backend_pages, |
a9ff648c MD |
278 | p._ref.offset); |
279 | ||
280 | /* Field length */ | |
281 | crash_abi->length.prod_offset = sizeof(buf->offset); | |
282 | crash_abi->length.consumed_offset = sizeof(buf->consumed); | |
283 | crash_abi->length.commit_hot_seq = | |
284 | sizeof(((struct commit_counters_hot *) NULL)->seq); | |
285 | crash_abi->length.buf_wsb_id = | |
b5457df5 | 286 | sizeof(((struct lttng_ust_ring_buffer_backend_subbuffer *) NULL)->id); |
a9ff648c | 287 | crash_abi->length.sb_array_shmp_offset = |
b5457df5 | 288 | sizeof(((struct lttng_ust_ring_buffer_backend_pages_shmp *) NULL)->shmp._ref.offset); |
a9ff648c | 289 | crash_abi->length.sb_backend_p_offset = |
b5457df5 | 290 | sizeof(((struct lttng_ust_ring_buffer_backend_pages *) NULL)->p._ref.offset); |
a9ff648c MD |
291 | |
292 | /* Array stride */ | |
293 | crash_abi->stride.commit_hot_array = | |
294 | sizeof(struct commit_counters_hot); | |
295 | crash_abi->stride.buf_wsb_array = | |
b5457df5 | 296 | sizeof(struct lttng_ust_ring_buffer_backend_subbuffer); |
a9ff648c | 297 | crash_abi->stride.sb_array = |
b5457df5 | 298 | sizeof(struct lttng_ust_ring_buffer_backend_pages_shmp); |
a9ff648c MD |
299 | |
300 | /* Buffer constants */ | |
301 | crash_abi->buf_size = chanb->buf_size; | |
302 | crash_abi->subbuf_size = chanb->subbuf_size; | |
303 | crash_abi->num_subbuf = chanb->num_subbuf; | |
304 | crash_abi->mode = (uint32_t) chanb->config.mode; | |
305 | ||
306 | if (config->cb.content_size_field) { | |
307 | size_t offset, length; | |
308 | ||
309 | config->cb.content_size_field(config, &offset, &length); | |
310 | crash_abi->offset.content_size = offset; | |
311 | crash_abi->length.content_size = length; | |
312 | } else { | |
313 | crash_abi->offset.content_size = 0; | |
314 | crash_abi->length.content_size = 0; | |
315 | } | |
316 | if (config->cb.packet_size_field) { | |
317 | size_t offset, length; | |
318 | ||
319 | config->cb.packet_size_field(config, &offset, &length); | |
320 | crash_abi->offset.packet_size = offset; | |
321 | crash_abi->length.packet_size = length; | |
322 | } else { | |
323 | crash_abi->offset.packet_size = 0; | |
324 | crash_abi->length.packet_size = 0; | |
325 | } | |
326 | } | |
327 | ||
852c2936 MD |
328 | /* |
329 | * Must be called under cpu hotplug protection. | |
330 | */ | |
b5457df5 | 331 | int lib_ring_buffer_create(struct lttng_ust_ring_buffer *buf, |
a6352fd4 | 332 | struct channel_backend *chanb, int cpu, |
38fae1d3 | 333 | struct lttng_ust_shm_handle *handle, |
1d498196 | 334 | struct shm_object *shmobj) |
852c2936 | 335 | { |
b5457df5 MD |
336 | const struct lttng_ust_ring_buffer_config *config = &chanb->config; |
337 | struct lttng_ust_ring_buffer_channel *chan = caa_container_of(chanb, | |
338 | struct lttng_ust_ring_buffer_channel, backend); | |
339 | struct lttng_ust_ring_buffer_backend_subbuffer *wsb; | |
340 | struct lttng_ust_ring_buffer_channel *shmp_chan; | |
15500a1b | 341 | struct commit_counters_hot *cc_hot; |
f0fde1c3 | 342 | void *priv = channel_get_private_config(chan); |
852c2936 | 343 | size_t subbuf_header_size; |
373ea80a | 344 | uint64_t timestamp; |
852c2936 MD |
345 | int ret; |
346 | ||
347 | /* Test for cpu hotplug */ | |
348 | if (buf->backend.allocated) | |
349 | return 0; | |
350 | ||
1d498196 MD |
351 | align_shm(shmobj, __alignof__(struct commit_counters_hot)); |
352 | set_shmp(buf->commit_hot, | |
353 | zalloc_shm(shmobj, | |
354 | sizeof(struct commit_counters_hot) * chan->backend.num_subbuf)); | |
355 | if (!shmp(handle, buf->commit_hot)) { | |
a9ff648c | 356 | return -ENOMEM; |
852c2936 MD |
357 | } |
358 | ||
1d498196 MD |
359 | align_shm(shmobj, __alignof__(struct commit_counters_cold)); |
360 | set_shmp(buf->commit_cold, | |
361 | zalloc_shm(shmobj, | |
362 | sizeof(struct commit_counters_cold) * chan->backend.num_subbuf)); | |
363 | if (!shmp(handle, buf->commit_cold)) { | |
852c2936 MD |
364 | ret = -ENOMEM; |
365 | goto free_commit; | |
366 | } | |
367 | ||
6c737d05 MD |
368 | align_shm(shmobj, __alignof__(uint64_t)); |
369 | set_shmp(buf->ts_end, | |
370 | zalloc_shm(shmobj, | |
371 | sizeof(uint64_t) * chan->backend.num_subbuf)); | |
372 | if (!shmp(handle, buf->ts_end)) { | |
373 | ret = -ENOMEM; | |
374 | goto free_commit_cold; | |
375 | } | |
376 | ||
377 | ||
a9ff648c MD |
378 | ret = lib_ring_buffer_backend_create(&buf->backend, &chan->backend, |
379 | cpu, handle, shmobj); | |
380 | if (ret) { | |
381 | goto free_init; | |
382 | } | |
383 | ||
852c2936 MD |
384 | /* |
385 | * Write the subbuffer header for first subbuffer so we know the total | |
386 | * duration of data gathering. | |
387 | */ | |
388 | subbuf_header_size = config->cb.subbuffer_header_size(); | |
389 | v_set(config, &buf->offset, subbuf_header_size); | |
15500a1b MD |
390 | wsb = shmp_index(handle, buf->backend.buf_wsb, 0); |
391 | if (!wsb) { | |
392 | ret = -EPERM; | |
393 | goto free_chanbuf; | |
394 | } | |
395 | subbuffer_id_clear_noref(config, &wsb->id); | |
396 | shmp_chan = shmp(handle, buf->backend.chan); | |
397 | if (!shmp_chan) { | |
398 | ret = -EPERM; | |
399 | goto free_chanbuf; | |
400 | } | |
373ea80a MD |
401 | timestamp = config->cb.ring_buffer_clock_read(shmp_chan); |
402 | config->cb.buffer_begin(buf, timestamp, 0, handle); | |
15500a1b MD |
403 | cc_hot = shmp_index(handle, buf->commit_hot, 0); |
404 | if (!cc_hot) { | |
405 | ret = -EPERM; | |
406 | goto free_chanbuf; | |
407 | } | |
408 | v_add(config, subbuf_header_size, &cc_hot->cc); | |
409 | v_add(config, subbuf_header_size, &cc_hot->seq); | |
852c2936 MD |
410 | |
411 | if (config->cb.buffer_create) { | |
1d498196 | 412 | ret = config->cb.buffer_create(buf, priv, cpu, chanb->name, handle); |
852c2936 | 413 | if (ret) |
a9ff648c | 414 | goto free_chanbuf; |
852c2936 | 415 | } |
a9ff648c MD |
416 | |
417 | init_crash_abi(config, &buf->crash_abi, buf, chanb, shmobj, handle); | |
418 | ||
852c2936 | 419 | buf->backend.allocated = 1; |
852c2936 MD |
420 | return 0; |
421 | ||
422 | /* Error handling */ | |
423 | free_init: | |
6c737d05 MD |
424 | /* ts_end will be freed by shm teardown */ |
425 | free_commit_cold: | |
a6352fd4 | 426 | /* commit_cold will be freed by shm teardown */ |
852c2936 | 427 | free_commit: |
a6352fd4 | 428 | /* commit_hot will be freed by shm teardown */ |
852c2936 | 429 | free_chanbuf: |
852c2936 MD |
430 | return ret; |
431 | } | |
432 | ||
03d2d293 | 433 | static |
2208d8b5 MJ |
434 | void lib_ring_buffer_channel_switch_timer(int sig __attribute__((unused)), |
435 | siginfo_t *si, void *uc __attribute__((unused))) | |
852c2936 | 436 | { |
b5457df5 | 437 | const struct lttng_ust_ring_buffer_config *config; |
03d2d293 | 438 | struct lttng_ust_shm_handle *handle; |
b5457df5 | 439 | struct lttng_ust_ring_buffer_channel *chan; |
03d2d293 MD |
440 | int cpu; |
441 | ||
442 | assert(CMM_LOAD_SHARED(timer_signal.tid) == pthread_self()); | |
443 | ||
444 | chan = si->si_value.sival_ptr; | |
445 | handle = chan->handle; | |
446 | config = &chan->backend.config; | |
852c2936 | 447 | |
34a91bdb | 448 | DBG("Switch timer for channel %p\n", chan); |
03d2d293 | 449 | |
4dcd7e80 MD |
450 | /* |
451 | * Only flush buffers periodically if readers are active. | |
452 | */ | |
cb7378b3 | 453 | pthread_mutex_lock(&wakeup_fd_mutex); |
03d2d293 MD |
454 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { |
455 | for_each_possible_cpu(cpu) { | |
b5457df5 | 456 | struct lttng_ust_ring_buffer *buf = |
03d2d293 | 457 | shmp(handle, chan->backend.buf[cpu].shmp); |
34daae3e MD |
458 | |
459 | if (!buf) | |
15500a1b | 460 | goto end; |
4dcd7e80 MD |
461 | if (uatomic_read(&buf->active_readers)) |
462 | lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE, | |
463 | chan->handle); | |
03d2d293 MD |
464 | } |
465 | } else { | |
b5457df5 | 466 | struct lttng_ust_ring_buffer *buf = |
03d2d293 MD |
467 | shmp(handle, chan->backend.buf[0].shmp); |
468 | ||
34daae3e | 469 | if (!buf) |
15500a1b | 470 | goto end; |
34a91bdb MD |
471 | if (uatomic_read(&buf->active_readers)) |
472 | lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE, | |
473 | chan->handle); | |
474 | } | |
15500a1b | 475 | end: |
34a91bdb MD |
476 | pthread_mutex_unlock(&wakeup_fd_mutex); |
477 | return; | |
478 | } | |
479 | ||
b07cd987 | 480 | static |
b5457df5 MD |
481 | int lib_ring_buffer_poll_deliver(const struct lttng_ust_ring_buffer_config *config, |
482 | struct lttng_ust_ring_buffer *buf, | |
483 | struct lttng_ust_ring_buffer_channel *chan, | |
b07cd987 MD |
484 | struct lttng_ust_shm_handle *handle) |
485 | { | |
486 | unsigned long consumed_old, consumed_idx, commit_count, write_offset; | |
15500a1b | 487 | struct commit_counters_cold *cc_cold; |
b07cd987 MD |
488 | |
489 | consumed_old = uatomic_read(&buf->consumed); | |
490 | consumed_idx = subbuf_index(consumed_old, chan); | |
15500a1b MD |
491 | cc_cold = shmp_index(handle, buf->commit_cold, consumed_idx); |
492 | if (!cc_cold) | |
493 | return 0; | |
494 | commit_count = v_read(config, &cc_cold->cc_sb); | |
b07cd987 MD |
495 | /* |
496 | * No memory barrier here, since we are only interested | |
497 | * in a statistically correct polling result. The next poll will | |
498 | * get the data is we are racing. The mb() that ensures correct | |
499 | * memory order is in get_subbuf. | |
500 | */ | |
501 | write_offset = v_read(config, &buf->offset); | |
502 | ||
503 | /* | |
504 | * Check that the subbuffer we are trying to consume has been | |
505 | * already fully committed. | |
506 | */ | |
507 | ||
508 | if (((commit_count - chan->backend.subbuf_size) | |
509 | & chan->commit_count_mask) | |
510 | - (buf_trunc(consumed_old, chan) | |
511 | >> chan->backend.num_subbuf_order) | |
512 | != 0) | |
513 | return 0; | |
514 | ||
515 | /* | |
516 | * Check that we are not about to read the same subbuffer in | |
517 | * which the writer head is. | |
518 | */ | |
519 | if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_old, chan) | |
520 | == 0) | |
521 | return 0; | |
522 | ||
523 | return 1; | |
524 | } | |
525 | ||
526 | static | |
b5457df5 | 527 | void lib_ring_buffer_wakeup(struct lttng_ust_ring_buffer *buf, |
b07cd987 MD |
528 | struct lttng_ust_shm_handle *handle) |
529 | { | |
530 | int wakeup_fd = shm_get_wakeup_fd(handle, &buf->self._ref); | |
531 | sigset_t sigpipe_set, pending_set, old_set; | |
532 | int ret, sigpipe_was_pending = 0; | |
533 | ||
534 | if (wakeup_fd < 0) | |
535 | return; | |
536 | ||
537 | /* | |
538 | * Wake-up the other end by writing a null byte in the pipe | |
539 | * (non-blocking). Important note: Because writing into the | |
540 | * pipe is non-blocking (and therefore we allow dropping wakeup | |
541 | * data, as long as there is wakeup data present in the pipe | |
542 | * buffer to wake up the consumer), the consumer should perform | |
543 | * the following sequence for waiting: | |
544 | * 1) empty the pipe (reads). | |
545 | * 2) check if there is data in the buffer. | |
546 | * 3) wait on the pipe (poll). | |
547 | * | |
548 | * Discard the SIGPIPE from write(), not disturbing any SIGPIPE | |
549 | * that might be already pending. If a bogus SIGPIPE is sent to | |
550 | * the entire process concurrently by a malicious user, it may | |
551 | * be simply discarded. | |
552 | */ | |
553 | ret = sigemptyset(&pending_set); | |
554 | assert(!ret); | |
555 | /* | |
556 | * sigpending returns the mask of signals that are _both_ | |
557 | * blocked for the thread _and_ pending for either the thread or | |
558 | * the entire process. | |
559 | */ | |
560 | ret = sigpending(&pending_set); | |
561 | assert(!ret); | |
562 | sigpipe_was_pending = sigismember(&pending_set, SIGPIPE); | |
563 | /* | |
564 | * If sigpipe was pending, it means it was already blocked, so | |
565 | * no need to block it. | |
566 | */ | |
567 | if (!sigpipe_was_pending) { | |
568 | ret = sigemptyset(&sigpipe_set); | |
569 | assert(!ret); | |
570 | ret = sigaddset(&sigpipe_set, SIGPIPE); | |
571 | assert(!ret); | |
572 | ret = pthread_sigmask(SIG_BLOCK, &sigpipe_set, &old_set); | |
573 | assert(!ret); | |
574 | } | |
575 | do { | |
576 | ret = write(wakeup_fd, "", 1); | |
577 | } while (ret == -1L && errno == EINTR); | |
578 | if (ret == -1L && errno == EPIPE && !sigpipe_was_pending) { | |
579 | struct timespec timeout = { 0, 0 }; | |
580 | do { | |
581 | ret = sigtimedwait(&sigpipe_set, NULL, | |
582 | &timeout); | |
583 | } while (ret == -1L && errno == EINTR); | |
584 | } | |
585 | if (!sigpipe_was_pending) { | |
586 | ret = pthread_sigmask(SIG_SETMASK, &old_set, NULL); | |
587 | assert(!ret); | |
588 | } | |
589 | } | |
590 | ||
34a91bdb | 591 | static |
b5457df5 | 592 | void lib_ring_buffer_channel_do_read(struct lttng_ust_ring_buffer_channel *chan) |
34a91bdb | 593 | { |
b5457df5 | 594 | const struct lttng_ust_ring_buffer_config *config; |
34a91bdb MD |
595 | struct lttng_ust_shm_handle *handle; |
596 | int cpu; | |
597 | ||
598 | handle = chan->handle; | |
599 | config = &chan->backend.config; | |
600 | ||
601 | /* | |
602 | * Only flush buffers periodically if readers are active. | |
603 | */ | |
604 | pthread_mutex_lock(&wakeup_fd_mutex); | |
605 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
606 | for_each_possible_cpu(cpu) { | |
b5457df5 | 607 | struct lttng_ust_ring_buffer *buf = |
34a91bdb MD |
608 | shmp(handle, chan->backend.buf[cpu].shmp); |
609 | ||
34daae3e | 610 | if (!buf) |
15500a1b | 611 | goto end; |
34a91bdb MD |
612 | if (uatomic_read(&buf->active_readers) |
613 | && lib_ring_buffer_poll_deliver(config, buf, | |
614 | chan, handle)) { | |
615 | lib_ring_buffer_wakeup(buf, handle); | |
616 | } | |
617 | } | |
618 | } else { | |
b5457df5 | 619 | struct lttng_ust_ring_buffer *buf = |
34a91bdb MD |
620 | shmp(handle, chan->backend.buf[0].shmp); |
621 | ||
34daae3e | 622 | if (!buf) |
15500a1b | 623 | goto end; |
34a91bdb MD |
624 | if (uatomic_read(&buf->active_readers) |
625 | && lib_ring_buffer_poll_deliver(config, buf, | |
626 | chan, handle)) { | |
627 | lib_ring_buffer_wakeup(buf, handle); | |
628 | } | |
03d2d293 | 629 | } |
15500a1b | 630 | end: |
cb7378b3 | 631 | pthread_mutex_unlock(&wakeup_fd_mutex); |
34a91bdb MD |
632 | } |
633 | ||
634 | static | |
2208d8b5 MJ |
635 | void lib_ring_buffer_channel_read_timer(int sig __attribute__((unused)), |
636 | siginfo_t *si, void *uc __attribute__((unused))) | |
34a91bdb | 637 | { |
b5457df5 | 638 | struct lttng_ust_ring_buffer_channel *chan; |
34a91bdb MD |
639 | |
640 | assert(CMM_LOAD_SHARED(timer_signal.tid) == pthread_self()); | |
641 | chan = si->si_value.sival_ptr; | |
642 | DBG("Read timer for channel %p\n", chan); | |
643 | lib_ring_buffer_channel_do_read(chan); | |
03d2d293 MD |
644 | return; |
645 | } | |
646 | ||
647 | static | |
648 | void rb_setmask(sigset_t *mask) | |
649 | { | |
650 | int ret; | |
651 | ||
652 | ret = sigemptyset(mask); | |
653 | if (ret) { | |
654 | PERROR("sigemptyset"); | |
655 | } | |
34a91bdb MD |
656 | ret = sigaddset(mask, LTTNG_UST_RB_SIG_FLUSH); |
657 | if (ret) { | |
658 | PERROR("sigaddset"); | |
659 | } | |
660 | ret = sigaddset(mask, LTTNG_UST_RB_SIG_READ); | |
03d2d293 MD |
661 | if (ret) { |
662 | PERROR("sigaddset"); | |
663 | } | |
664 | ret = sigaddset(mask, LTTNG_UST_RB_SIG_TEARDOWN); | |
665 | if (ret) { | |
666 | PERROR("sigaddset"); | |
667 | } | |
668 | } | |
669 | ||
670 | static | |
2208d8b5 | 671 | void *sig_thread(void *arg __attribute__((unused))) |
03d2d293 MD |
672 | { |
673 | sigset_t mask; | |
674 | siginfo_t info; | |
675 | int signr; | |
676 | ||
677 | /* Only self thread will receive signal mask. */ | |
678 | rb_setmask(&mask); | |
679 | CMM_STORE_SHARED(timer_signal.tid, pthread_self()); | |
680 | ||
681 | for (;;) { | |
682 | signr = sigwaitinfo(&mask, &info); | |
683 | if (signr == -1) { | |
34a91bdb MD |
684 | if (errno != EINTR) |
685 | PERROR("sigwaitinfo"); | |
03d2d293 MD |
686 | continue; |
687 | } | |
34a91bdb | 688 | if (signr == LTTNG_UST_RB_SIG_FLUSH) { |
03d2d293 MD |
689 | lib_ring_buffer_channel_switch_timer(info.si_signo, |
690 | &info, NULL); | |
34a91bdb MD |
691 | } else if (signr == LTTNG_UST_RB_SIG_READ) { |
692 | lib_ring_buffer_channel_read_timer(info.si_signo, | |
693 | &info, NULL); | |
03d2d293 MD |
694 | } else if (signr == LTTNG_UST_RB_SIG_TEARDOWN) { |
695 | cmm_smp_mb(); | |
696 | CMM_STORE_SHARED(timer_signal.qs_done, 1); | |
697 | cmm_smp_mb(); | |
698 | } else { | |
699 | ERR("Unexptected signal %d\n", info.si_signo); | |
700 | } | |
701 | } | |
702 | return NULL; | |
703 | } | |
704 | ||
705 | /* | |
03d2d293 MD |
706 | * Ensure only a single thread listens on the timer signal. |
707 | */ | |
708 | static | |
709 | void lib_ring_buffer_setup_timer_thread(void) | |
710 | { | |
711 | pthread_t thread; | |
712 | int ret; | |
713 | ||
64bf51a6 | 714 | pthread_mutex_lock(&timer_signal.lock); |
03d2d293 | 715 | if (timer_signal.setup_done) |
64bf51a6 | 716 | goto end; |
03d2d293 MD |
717 | |
718 | ret = pthread_create(&thread, NULL, &sig_thread, NULL); | |
719 | if (ret) { | |
720 | errno = ret; | |
721 | PERROR("pthread_create"); | |
722 | } | |
723 | ret = pthread_detach(thread); | |
724 | if (ret) { | |
725 | errno = ret; | |
726 | PERROR("pthread_detach"); | |
727 | } | |
728 | timer_signal.setup_done = 1; | |
64bf51a6 MD |
729 | end: |
730 | pthread_mutex_unlock(&timer_signal.lock); | |
852c2936 MD |
731 | } |
732 | ||
03d2d293 | 733 | /* |
64bf51a6 | 734 | * Wait for signal-handling thread quiescent state. |
03d2d293 | 735 | */ |
64bf51a6 MD |
736 | static |
737 | void lib_ring_buffer_wait_signal_thread_qs(unsigned int signr) | |
738 | { | |
739 | sigset_t pending_set; | |
740 | int ret; | |
741 | ||
742 | /* | |
743 | * We need to be the only thread interacting with the thread | |
744 | * that manages signals for teardown synchronization. | |
745 | */ | |
746 | pthread_mutex_lock(&timer_signal.lock); | |
747 | ||
748 | /* | |
749 | * Ensure we don't have any signal queued for this channel. | |
750 | */ | |
751 | for (;;) { | |
752 | ret = sigemptyset(&pending_set); | |
753 | if (ret == -1) { | |
754 | PERROR("sigemptyset"); | |
755 | } | |
756 | ret = sigpending(&pending_set); | |
757 | if (ret == -1) { | |
758 | PERROR("sigpending"); | |
759 | } | |
760 | if (!sigismember(&pending_set, signr)) | |
761 | break; | |
762 | caa_cpu_relax(); | |
763 | } | |
764 | ||
765 | /* | |
766 | * From this point, no new signal handler will be fired that | |
767 | * would try to access "chan". However, we still need to wait | |
768 | * for any currently executing handler to complete. | |
769 | */ | |
770 | cmm_smp_mb(); | |
771 | CMM_STORE_SHARED(timer_signal.qs_done, 0); | |
772 | cmm_smp_mb(); | |
773 | ||
774 | /* | |
775 | * Kill with LTTNG_UST_RB_SIG_TEARDOWN, so signal management | |
776 | * thread wakes up. | |
777 | */ | |
778 | kill(getpid(), LTTNG_UST_RB_SIG_TEARDOWN); | |
779 | ||
780 | while (!CMM_LOAD_SHARED(timer_signal.qs_done)) | |
781 | caa_cpu_relax(); | |
782 | cmm_smp_mb(); | |
783 | ||
784 | pthread_mutex_unlock(&timer_signal.lock); | |
785 | } | |
786 | ||
03d2d293 | 787 | static |
b5457df5 | 788 | void lib_ring_buffer_channel_switch_timer_start(struct lttng_ust_ring_buffer_channel *chan) |
852c2936 | 789 | { |
03d2d293 MD |
790 | struct sigevent sev; |
791 | struct itimerspec its; | |
792 | int ret; | |
852c2936 | 793 | |
03d2d293 | 794 | if (!chan->switch_timer_interval || chan->switch_timer_enabled) |
852c2936 MD |
795 | return; |
796 | ||
03d2d293 MD |
797 | chan->switch_timer_enabled = 1; |
798 | ||
799 | lib_ring_buffer_setup_timer_thread(); | |
800 | ||
ba702529 | 801 | memset(&sev, 0, sizeof(sev)); |
03d2d293 | 802 | sev.sigev_notify = SIGEV_SIGNAL; |
34a91bdb | 803 | sev.sigev_signo = LTTNG_UST_RB_SIG_FLUSH; |
03d2d293 MD |
804 | sev.sigev_value.sival_ptr = chan; |
805 | ret = timer_create(CLOCKID, &sev, &chan->switch_timer); | |
806 | if (ret == -1) { | |
807 | PERROR("timer_create"); | |
808 | } | |
809 | ||
810 | its.it_value.tv_sec = chan->switch_timer_interval / 1000000; | |
f8921d33 | 811 | its.it_value.tv_nsec = (chan->switch_timer_interval % 1000000) * 1000; |
03d2d293 MD |
812 | its.it_interval.tv_sec = its.it_value.tv_sec; |
813 | its.it_interval.tv_nsec = its.it_value.tv_nsec; | |
814 | ||
815 | ret = timer_settime(chan->switch_timer, 0, &its, NULL); | |
816 | if (ret == -1) { | |
817 | PERROR("timer_settime"); | |
818 | } | |
819 | } | |
820 | ||
03d2d293 | 821 | static |
b5457df5 | 822 | void lib_ring_buffer_channel_switch_timer_stop(struct lttng_ust_ring_buffer_channel *chan) |
03d2d293 | 823 | { |
34a91bdb | 824 | int ret; |
03d2d293 MD |
825 | |
826 | if (!chan->switch_timer_interval || !chan->switch_timer_enabled) | |
827 | return; | |
828 | ||
829 | ret = timer_delete(chan->switch_timer); | |
830 | if (ret == -1) { | |
831 | PERROR("timer_delete"); | |
832 | } | |
833 | ||
64bf51a6 | 834 | lib_ring_buffer_wait_signal_thread_qs(LTTNG_UST_RB_SIG_FLUSH); |
03d2d293 MD |
835 | |
836 | chan->switch_timer = 0; | |
837 | chan->switch_timer_enabled = 0; | |
852c2936 MD |
838 | } |
839 | ||
34a91bdb | 840 | static |
b5457df5 | 841 | void lib_ring_buffer_channel_read_timer_start(struct lttng_ust_ring_buffer_channel *chan) |
852c2936 | 842 | { |
b5457df5 | 843 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
34a91bdb MD |
844 | struct sigevent sev; |
845 | struct itimerspec its; | |
846 | int ret; | |
852c2936 | 847 | |
34a91bdb MD |
848 | if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER |
849 | || !chan->read_timer_interval || chan->read_timer_enabled) | |
850 | return; | |
852c2936 | 851 | |
34a91bdb | 852 | chan->read_timer_enabled = 1; |
852c2936 | 853 | |
34a91bdb | 854 | lib_ring_buffer_setup_timer_thread(); |
852c2936 | 855 | |
34a91bdb MD |
856 | sev.sigev_notify = SIGEV_SIGNAL; |
857 | sev.sigev_signo = LTTNG_UST_RB_SIG_READ; | |
858 | sev.sigev_value.sival_ptr = chan; | |
859 | ret = timer_create(CLOCKID, &sev, &chan->read_timer); | |
860 | if (ret == -1) { | |
861 | PERROR("timer_create"); | |
862 | } | |
852c2936 | 863 | |
34a91bdb | 864 | its.it_value.tv_sec = chan->read_timer_interval / 1000000; |
f8921d33 | 865 | its.it_value.tv_nsec = (chan->read_timer_interval % 1000000) * 1000; |
34a91bdb MD |
866 | its.it_interval.tv_sec = its.it_value.tv_sec; |
867 | its.it_interval.tv_nsec = its.it_value.tv_nsec; | |
852c2936 | 868 | |
34a91bdb MD |
869 | ret = timer_settime(chan->read_timer, 0, &its, NULL); |
870 | if (ret == -1) { | |
871 | PERROR("timer_settime"); | |
872 | } | |
852c2936 MD |
873 | } |
874 | ||
34a91bdb | 875 | static |
b5457df5 | 876 | void lib_ring_buffer_channel_read_timer_stop(struct lttng_ust_ring_buffer_channel *chan) |
852c2936 | 877 | { |
b5457df5 | 878 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
34a91bdb | 879 | int ret; |
852c2936 MD |
880 | |
881 | if (config->wakeup != RING_BUFFER_WAKEUP_BY_TIMER | |
34a91bdb | 882 | || !chan->read_timer_interval || !chan->read_timer_enabled) |
852c2936 MD |
883 | return; |
884 | ||
34a91bdb MD |
885 | ret = timer_delete(chan->read_timer); |
886 | if (ret == -1) { | |
887 | PERROR("timer_delete"); | |
888 | } | |
889 | ||
852c2936 MD |
890 | /* |
891 | * do one more check to catch data that has been written in the last | |
892 | * timer period. | |
893 | */ | |
34a91bdb MD |
894 | lib_ring_buffer_channel_do_read(chan); |
895 | ||
64bf51a6 | 896 | lib_ring_buffer_wait_signal_thread_qs(LTTNG_UST_RB_SIG_READ); |
34a91bdb MD |
897 | |
898 | chan->read_timer = 0; | |
899 | chan->read_timer_enabled = 0; | |
852c2936 MD |
900 | } |
901 | ||
b5457df5 | 902 | static void channel_unregister_notifiers(struct lttng_ust_ring_buffer_channel *chan, |
2208d8b5 | 903 | struct lttng_ust_shm_handle *handle __attribute__((unused))) |
852c2936 | 904 | { |
03d2d293 | 905 | lib_ring_buffer_channel_switch_timer_stop(chan); |
34a91bdb | 906 | lib_ring_buffer_channel_read_timer_stop(chan); |
852c2936 MD |
907 | } |
908 | ||
b5457df5 | 909 | static void channel_print_errors(struct lttng_ust_ring_buffer_channel *chan, |
009769ca MD |
910 | struct lttng_ust_shm_handle *handle) |
911 | { | |
b5457df5 | 912 | const struct lttng_ust_ring_buffer_config *config = |
009769ca MD |
913 | &chan->backend.config; |
914 | int cpu; | |
915 | ||
916 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) { | |
917 | for_each_possible_cpu(cpu) { | |
b5457df5 | 918 | struct lttng_ust_ring_buffer *buf = |
009769ca | 919 | shmp(handle, chan->backend.buf[cpu].shmp); |
15500a1b MD |
920 | if (buf) |
921 | lib_ring_buffer_print_errors(chan, buf, cpu, handle); | |
009769ca MD |
922 | } |
923 | } else { | |
b5457df5 | 924 | struct lttng_ust_ring_buffer *buf = |
009769ca MD |
925 | shmp(handle, chan->backend.buf[0].shmp); |
926 | ||
15500a1b MD |
927 | if (buf) |
928 | lib_ring_buffer_print_errors(chan, buf, -1, handle); | |
009769ca MD |
929 | } |
930 | } | |
931 | ||
b5457df5 | 932 | static void channel_free(struct lttng_ust_ring_buffer_channel *chan, |
6548fca4 MD |
933 | struct lttng_ust_shm_handle *handle, |
934 | int consumer) | |
852c2936 | 935 | { |
74d81a6c | 936 | channel_backend_free(&chan->backend, handle); |
431d5cf0 | 937 | /* chan is freed by shm teardown */ |
6548fca4 | 938 | shm_object_table_destroy(handle->table, consumer); |
1d498196 | 939 | free(handle); |
852c2936 MD |
940 | } |
941 | ||
942 | /** | |
943 | * channel_create - Create channel. | |
944 | * @config: ring buffer instance configuration | |
945 | * @name: name of the channel | |
f0fde1c3 MD |
946 | * @priv_data_align: alignment, in bytes, of the private data area. (config) |
947 | * @priv_data_size: length, in bytes, of the private data area. (config) | |
948 | * @priv_data_init: initialization data for private data. (config) | |
949 | * @priv: local private data (memory owner by caller) | |
852c2936 MD |
950 | * @buf_addr: pointer the the beginning of the preallocated buffer contiguous |
951 | * address mapping. It is used only by RING_BUFFER_STATIC | |
952 | * configuration. It can be set to NULL for other backends. | |
953 | * @subbuf_size: subbuffer size | |
954 | * @num_subbuf: number of subbuffers | |
955 | * @switch_timer_interval: Time interval (in us) to fill sub-buffers with | |
956 | * padding to let readers get those sub-buffers. | |
957 | * Used for live streaming. | |
958 | * @read_timer_interval: Time interval (in us) to wake up pending readers. | |
5ea386c3 MD |
959 | * @stream_fds: array of stream file descriptors. |
960 | * @nr_stream_fds: number of file descriptors in array. | |
852c2936 MD |
961 | * |
962 | * Holds cpu hotplug. | |
963 | * Returns NULL on failure. | |
964 | */ | |
b5457df5 | 965 | struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_ring_buffer_config *config, |
a3f61e7f | 966 | const char *name, |
a3f61e7f MD |
967 | size_t priv_data_align, |
968 | size_t priv_data_size, | |
d028eddb | 969 | void *priv_data_init, |
f0fde1c3 | 970 | void *priv, |
2208d8b5 | 971 | void *buf_addr __attribute__((unused)), size_t subbuf_size, |
852c2936 | 972 | size_t num_subbuf, unsigned int switch_timer_interval, |
a9ff648c | 973 | unsigned int read_timer_interval, |
b2c5f61a MD |
974 | const int *stream_fds, int nr_stream_fds, |
975 | int64_t blocking_timeout) | |
852c2936 | 976 | { |
24622edc | 977 | int ret; |
a3f61e7f | 978 | size_t shmsize, chansize; |
b5457df5 | 979 | struct lttng_ust_ring_buffer_channel *chan; |
38fae1d3 | 980 | struct lttng_ust_shm_handle *handle; |
1d498196 | 981 | struct shm_object *shmobj; |
74d81a6c | 982 | unsigned int nr_streams; |
b2c5f61a | 983 | int64_t blocking_timeout_ms; |
97572c04 | 984 | bool populate = lttng_ust_map_populate_is_enabled(); |
74d81a6c MD |
985 | |
986 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
a616fb4e | 987 | nr_streams = get_possible_cpus_array_len(); |
74d81a6c MD |
988 | else |
989 | nr_streams = 1; | |
852c2936 | 990 | |
5ea386c3 MD |
991 | if (nr_stream_fds != nr_streams) |
992 | return NULL; | |
993 | ||
b2c5f61a MD |
994 | if (blocking_timeout < -1) { |
995 | return NULL; | |
996 | } | |
997 | /* usec to msec */ | |
998 | if (blocking_timeout == -1) { | |
999 | blocking_timeout_ms = -1; | |
1000 | } else { | |
1001 | blocking_timeout_ms = blocking_timeout / 1000; | |
1002 | if (blocking_timeout_ms != (int32_t) blocking_timeout_ms) { | |
1003 | return NULL; | |
1004 | } | |
1005 | } | |
1006 | ||
852c2936 MD |
1007 | if (lib_ring_buffer_check_config(config, switch_timer_interval, |
1008 | read_timer_interval)) | |
1009 | return NULL; | |
1010 | ||
97572c04 | 1011 | handle = zmalloc_populate(sizeof(struct lttng_ust_shm_handle), populate); |
431d5cf0 MD |
1012 | if (!handle) |
1013 | return NULL; | |
1014 | ||
1d498196 | 1015 | /* Allocate table for channel + per-cpu buffers */ |
97572c04 | 1016 | handle->table = shm_object_table_create(1 + get_possible_cpus_array_len(), populate); |
1d498196 MD |
1017 | if (!handle->table) |
1018 | goto error_table_alloc; | |
852c2936 | 1019 | |
1d498196 | 1020 | /* Calculate the shm allocation layout */ |
b5457df5 MD |
1021 | shmsize = sizeof(struct lttng_ust_ring_buffer_channel); |
1022 | shmsize += lttng_ust_offset_align(shmsize, __alignof__(struct lttng_ust_ring_buffer_shmp)); | |
1023 | shmsize += sizeof(struct lttng_ust_ring_buffer_shmp) * nr_streams; | |
a3f61e7f | 1024 | chansize = shmsize; |
74d81a6c | 1025 | if (priv_data_align) |
b72687b8 | 1026 | shmsize += lttng_ust_offset_align(shmsize, priv_data_align); |
a3f61e7f | 1027 | shmsize += priv_data_size; |
a6352fd4 | 1028 | |
74d81a6c | 1029 | /* Allocate normal memory for channel (not shared) */ |
a9ff648c | 1030 | shmobj = shm_object_table_alloc(handle->table, shmsize, SHM_OBJECT_MEM, |
97572c04 | 1031 | -1, -1, populate); |
b5a14697 MD |
1032 | if (!shmobj) |
1033 | goto error_append; | |
b5457df5 | 1034 | /* struct lttng_ust_ring_buffer_channel is at object 0, offset 0 (hardcoded) */ |
a3f61e7f | 1035 | set_shmp(handle->chan, zalloc_shm(shmobj, chansize)); |
57773204 MD |
1036 | assert(handle->chan._ref.index == 0); |
1037 | assert(handle->chan._ref.offset == 0); | |
1d498196 | 1038 | chan = shmp(handle, handle->chan); |
a6352fd4 | 1039 | if (!chan) |
1d498196 | 1040 | goto error_append; |
74d81a6c | 1041 | chan->nr_streams = nr_streams; |
a6352fd4 | 1042 | |
a3f61e7f MD |
1043 | /* space for private data */ |
1044 | if (priv_data_size) { | |
f0fde1c3 MD |
1045 | void *priv_config; |
1046 | ||
a3f61e7f MD |
1047 | DECLARE_SHMP(void, priv_data_alloc); |
1048 | ||
1049 | align_shm(shmobj, priv_data_align); | |
1050 | chan->priv_data_offset = shmobj->allocated_len; | |
1051 | set_shmp(priv_data_alloc, zalloc_shm(shmobj, priv_data_size)); | |
1052 | if (!shmp(handle, priv_data_alloc)) | |
1053 | goto error_append; | |
f0fde1c3 MD |
1054 | priv_config = channel_get_private_config(chan); |
1055 | memcpy(priv_config, priv_data_init, priv_data_size); | |
a3f61e7f MD |
1056 | } else { |
1057 | chan->priv_data_offset = -1; | |
a3f61e7f MD |
1058 | } |
1059 | ||
b2c5f61a MD |
1060 | chan->u.s.blocking_timeout_ms = (int32_t) blocking_timeout_ms; |
1061 | ||
f0fde1c3 MD |
1062 | channel_set_private(chan, priv); |
1063 | ||
a3f61e7f | 1064 | ret = channel_backend_init(&chan->backend, name, config, |
a9ff648c | 1065 | subbuf_size, num_subbuf, handle, |
5ea386c3 | 1066 | stream_fds); |
852c2936 | 1067 | if (ret) |
1d498196 | 1068 | goto error_backend_init; |
852c2936 | 1069 | |
03d2d293 | 1070 | chan->handle = handle; |
852c2936 | 1071 | chan->commit_count_mask = (~0UL >> chan->backend.num_subbuf_order); |
852c2936 | 1072 | |
34a91bdb MD |
1073 | chan->switch_timer_interval = switch_timer_interval; |
1074 | chan->read_timer_interval = read_timer_interval; | |
03d2d293 | 1075 | lib_ring_buffer_channel_switch_timer_start(chan); |
34a91bdb | 1076 | lib_ring_buffer_channel_read_timer_start(chan); |
852c2936 | 1077 | |
431d5cf0 | 1078 | return handle; |
852c2936 | 1079 | |
1d498196 MD |
1080 | error_backend_init: |
1081 | error_append: | |
6548fca4 | 1082 | shm_object_table_destroy(handle->table, 1); |
1d498196 | 1083 | error_table_alloc: |
431d5cf0 | 1084 | free(handle); |
852c2936 MD |
1085 | return NULL; |
1086 | } | |
852c2936 | 1087 | |
74d81a6c | 1088 | struct lttng_ust_shm_handle *channel_handle_create(void *data, |
ff0f5728 MD |
1089 | uint64_t memory_map_size, |
1090 | int wakeup_fd) | |
193183fb | 1091 | { |
38fae1d3 | 1092 | struct lttng_ust_shm_handle *handle; |
193183fb | 1093 | struct shm_object *object; |
97572c04 | 1094 | bool populate = lttng_ust_map_populate_is_enabled(); |
193183fb | 1095 | |
97572c04 | 1096 | handle = zmalloc_populate(sizeof(struct lttng_ust_shm_handle), populate); |
193183fb MD |
1097 | if (!handle) |
1098 | return NULL; | |
1099 | ||
1100 | /* Allocate table for channel + per-cpu buffers */ | |
97572c04 | 1101 | handle->table = shm_object_table_create(1 + get_possible_cpus_array_len(), populate); |
193183fb MD |
1102 | if (!handle->table) |
1103 | goto error_table_alloc; | |
1104 | /* Add channel object */ | |
74d81a6c | 1105 | object = shm_object_table_append_mem(handle->table, data, |
ff0f5728 | 1106 | memory_map_size, wakeup_fd); |
193183fb MD |
1107 | if (!object) |
1108 | goto error_table_object; | |
b5457df5 | 1109 | /* struct lttng_ust_ring_buffer_channel is at object 0, offset 0 (hardcoded) */ |
57773204 MD |
1110 | handle->chan._ref.index = 0; |
1111 | handle->chan._ref.offset = 0; | |
193183fb MD |
1112 | return handle; |
1113 | ||
1114 | error_table_object: | |
6548fca4 | 1115 | shm_object_table_destroy(handle->table, 0); |
193183fb MD |
1116 | error_table_alloc: |
1117 | free(handle); | |
1118 | return NULL; | |
1119 | } | |
1120 | ||
38fae1d3 | 1121 | int channel_handle_add_stream(struct lttng_ust_shm_handle *handle, |
74d81a6c MD |
1122 | int shm_fd, int wakeup_fd, uint32_t stream_nr, |
1123 | uint64_t memory_map_size) | |
193183fb MD |
1124 | { |
1125 | struct shm_object *object; | |
1126 | ||
1127 | /* Add stream object */ | |
74d81a6c MD |
1128 | object = shm_object_table_append_shm(handle->table, |
1129 | shm_fd, wakeup_fd, stream_nr, | |
97572c04 | 1130 | memory_map_size, lttng_ust_map_populate_cpu_is_enabled(stream_nr)); |
193183fb | 1131 | if (!object) |
74d81a6c | 1132 | return -EINVAL; |
193183fb MD |
1133 | return 0; |
1134 | } | |
1135 | ||
74d81a6c MD |
1136 | unsigned int channel_handle_get_nr_streams(struct lttng_ust_shm_handle *handle) |
1137 | { | |
1138 | assert(handle->table); | |
1139 | return handle->table->allocated_len - 1; | |
1140 | } | |
1141 | ||
852c2936 | 1142 | static |
b5457df5 | 1143 | void channel_release(struct lttng_ust_ring_buffer_channel *chan, struct lttng_ust_shm_handle *handle, |
6548fca4 | 1144 | int consumer) |
852c2936 | 1145 | { |
6548fca4 | 1146 | channel_free(chan, handle, consumer); |
852c2936 MD |
1147 | } |
1148 | ||
1149 | /** | |
1150 | * channel_destroy - Finalize, wait for q.s. and destroy channel. | |
1151 | * @chan: channel to destroy | |
1152 | * | |
1153 | * Holds cpu hotplug. | |
431d5cf0 MD |
1154 | * Call "destroy" callback, finalize channels, decrement the channel |
1155 | * reference count. Note that when readers have completed data | |
1156 | * consumption of finalized channels, get_subbuf() will return -ENODATA. | |
a60af3a5 | 1157 | * They should release their handle at that point. |
852c2936 | 1158 | */ |
b5457df5 | 1159 | void channel_destroy(struct lttng_ust_ring_buffer_channel *chan, struct lttng_ust_shm_handle *handle, |
74d81a6c | 1160 | int consumer) |
852c2936 | 1161 | { |
74d81a6c MD |
1162 | if (consumer) { |
1163 | /* | |
1164 | * Note: the consumer takes care of finalizing and | |
1165 | * switching the buffers. | |
1166 | */ | |
1167 | channel_unregister_notifiers(chan, handle); | |
3d0ef9f6 MD |
1168 | /* |
1169 | * The consumer prints errors. | |
1170 | */ | |
1171 | channel_print_errors(chan, handle); | |
824f40b8 MD |
1172 | } |
1173 | ||
431d5cf0 MD |
1174 | /* |
1175 | * sessiond/consumer are keeping a reference on the shm file | |
1176 | * descriptor directly. No need to refcount. | |
1177 | */ | |
6548fca4 | 1178 | channel_release(chan, handle, consumer); |
a3f61e7f | 1179 | return; |
852c2936 | 1180 | } |
852c2936 | 1181 | |
b5457df5 MD |
1182 | struct lttng_ust_ring_buffer *channel_get_ring_buffer( |
1183 | const struct lttng_ust_ring_buffer_config *config, | |
1184 | struct lttng_ust_ring_buffer_channel *chan, int cpu, | |
38fae1d3 | 1185 | struct lttng_ust_shm_handle *handle, |
74d81a6c MD |
1186 | int *shm_fd, int *wait_fd, |
1187 | int *wakeup_fd, | |
63b3205f MD |
1188 | uint64_t *memory_map_size, |
1189 | void **memory_map_addr) | |
852c2936 | 1190 | { |
381c0f1e MD |
1191 | struct shm_ref *ref; |
1192 | ||
1193 | if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) { | |
74d81a6c | 1194 | cpu = 0; |
381c0f1e | 1195 | } else { |
a616fb4e | 1196 | if (cpu >= get_possible_cpus_array_len()) |
e095d803 | 1197 | return NULL; |
381c0f1e | 1198 | } |
74d81a6c MD |
1199 | ref = &chan->backend.buf[cpu].shmp._ref; |
1200 | *shm_fd = shm_get_shm_fd(handle, ref); | |
1201 | *wait_fd = shm_get_wait_fd(handle, ref); | |
1202 | *wakeup_fd = shm_get_wakeup_fd(handle, ref); | |
1203 | if (shm_get_shm_size(handle, ref, memory_map_size)) | |
1204 | return NULL; | |
63b3205f | 1205 | *memory_map_addr = handle->table->objects[ref->index].memory_map; |
74d81a6c | 1206 | return shmp(handle, chan->backend.buf[cpu].shmp); |
852c2936 | 1207 | } |
852c2936 | 1208 | |
2208d8b5 | 1209 | int ring_buffer_channel_close_wait_fd( |
b5457df5 MD |
1210 | const struct lttng_ust_ring_buffer_config *config __attribute__((unused)), |
1211 | struct lttng_ust_ring_buffer_channel *chan __attribute__((unused)), | |
2208d8b5 | 1212 | struct lttng_ust_shm_handle *handle) |
ff0f5728 MD |
1213 | { |
1214 | struct shm_ref *ref; | |
1215 | ||
1216 | ref = &handle->chan._ref; | |
1217 | return shm_close_wait_fd(handle, ref); | |
1218 | } | |
1219 | ||
2208d8b5 | 1220 | int ring_buffer_channel_close_wakeup_fd( |
b5457df5 MD |
1221 | const struct lttng_ust_ring_buffer_config *config __attribute__((unused)), |
1222 | struct lttng_ust_ring_buffer_channel *chan __attribute__((unused)), | |
2208d8b5 | 1223 | struct lttng_ust_shm_handle *handle) |
ff0f5728 MD |
1224 | { |
1225 | struct shm_ref *ref; | |
1226 | ||
1227 | ref = &handle->chan._ref; | |
1228 | return shm_close_wakeup_fd(handle, ref); | |
1229 | } | |
1230 | ||
b5457df5 MD |
1231 | int ring_buffer_stream_close_wait_fd(const struct lttng_ust_ring_buffer_config *config, |
1232 | struct lttng_ust_ring_buffer_channel *chan, | |
74d81a6c MD |
1233 | struct lttng_ust_shm_handle *handle, |
1234 | int cpu) | |
852c2936 | 1235 | { |
74d81a6c MD |
1236 | struct shm_ref *ref; |
1237 | ||
1238 | if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) { | |
1239 | cpu = 0; | |
1240 | } else { | |
a616fb4e | 1241 | if (cpu >= get_possible_cpus_array_len()) |
74d81a6c | 1242 | return -EINVAL; |
824f40b8 | 1243 | } |
74d81a6c MD |
1244 | ref = &chan->backend.buf[cpu].shmp._ref; |
1245 | return shm_close_wait_fd(handle, ref); | |
1246 | } | |
1247 | ||
b5457df5 MD |
1248 | int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_ring_buffer_config *config, |
1249 | struct lttng_ust_ring_buffer_channel *chan, | |
74d81a6c MD |
1250 | struct lttng_ust_shm_handle *handle, |
1251 | int cpu) | |
1252 | { | |
1253 | struct shm_ref *ref; | |
cb7378b3 | 1254 | int ret; |
74d81a6c MD |
1255 | |
1256 | if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) { | |
1257 | cpu = 0; | |
1258 | } else { | |
a616fb4e | 1259 | if (cpu >= get_possible_cpus_array_len()) |
74d81a6c MD |
1260 | return -EINVAL; |
1261 | } | |
1262 | ref = &chan->backend.buf[cpu].shmp._ref; | |
cb7378b3 MD |
1263 | pthread_mutex_lock(&wakeup_fd_mutex); |
1264 | ret = shm_close_wakeup_fd(handle, ref); | |
1265 | pthread_mutex_unlock(&wakeup_fd_mutex); | |
1266 | return ret; | |
74d81a6c MD |
1267 | } |
1268 | ||
b5457df5 | 1269 | int lib_ring_buffer_open_read(struct lttng_ust_ring_buffer *buf, |
2208d8b5 | 1270 | struct lttng_ust_shm_handle *handle __attribute__((unused))) |
74d81a6c | 1271 | { |
a6352fd4 | 1272 | if (uatomic_cmpxchg(&buf->active_readers, 0, 1) != 0) |
852c2936 | 1273 | return -EBUSY; |
a6352fd4 | 1274 | cmm_smp_mb(); |
852c2936 MD |
1275 | return 0; |
1276 | } | |
852c2936 | 1277 | |
b5457df5 | 1278 | void lib_ring_buffer_release_read(struct lttng_ust_ring_buffer *buf, |
74d81a6c | 1279 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1280 | { |
b5457df5 | 1281 | struct lttng_ust_ring_buffer_channel *chan = shmp(handle, buf->backend.chan); |
852c2936 | 1282 | |
15500a1b MD |
1283 | if (!chan) |
1284 | return; | |
a6352fd4 MD |
1285 | CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1); |
1286 | cmm_smp_mb(); | |
1287 | uatomic_dec(&buf->active_readers); | |
852c2936 MD |
1288 | } |
1289 | ||
1290 | /** | |
1291 | * lib_ring_buffer_snapshot - save subbuffer position snapshot (for read) | |
1292 | * @buf: ring buffer | |
1293 | * @consumed: consumed count indicating the position where to read | |
1294 | * @produced: produced count, indicates position when to stop reading | |
1295 | * | |
1296 | * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no | |
1297 | * data to read at consumed position, or 0 if the get operation succeeds. | |
852c2936 MD |
1298 | */ |
1299 | ||
b5457df5 | 1300 | int lib_ring_buffer_snapshot(struct lttng_ust_ring_buffer *buf, |
1d498196 | 1301 | unsigned long *consumed, unsigned long *produced, |
38fae1d3 | 1302 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1303 | { |
b5457df5 MD |
1304 | struct lttng_ust_ring_buffer_channel *chan; |
1305 | const struct lttng_ust_ring_buffer_config *config; | |
852c2936 MD |
1306 | unsigned long consumed_cur, write_offset; |
1307 | int finalized; | |
1308 | ||
15500a1b MD |
1309 | chan = shmp(handle, buf->backend.chan); |
1310 | if (!chan) | |
1311 | return -EPERM; | |
1312 | config = &chan->backend.config; | |
14641deb | 1313 | finalized = CMM_ACCESS_ONCE(buf->finalized); |
852c2936 MD |
1314 | /* |
1315 | * Read finalized before counters. | |
1316 | */ | |
a6352fd4 MD |
1317 | cmm_smp_rmb(); |
1318 | consumed_cur = uatomic_read(&buf->consumed); | |
852c2936 MD |
1319 | /* |
1320 | * No need to issue a memory barrier between consumed count read and | |
1321 | * write offset read, because consumed count can only change | |
1322 | * concurrently in overwrite mode, and we keep a sequence counter | |
1323 | * identifier derived from the write offset to check we are getting | |
1324 | * the same sub-buffer we are expecting (the sub-buffers are atomically | |
1325 | * "tagged" upon writes, tags are checked upon read). | |
1326 | */ | |
1327 | write_offset = v_read(config, &buf->offset); | |
1328 | ||
1329 | /* | |
1330 | * Check that we are not about to read the same subbuffer in | |
1331 | * which the writer head is. | |
1332 | */ | |
1333 | if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_cur, chan) | |
1334 | == 0) | |
1335 | goto nodata; | |
1336 | ||
1337 | *consumed = consumed_cur; | |
1338 | *produced = subbuf_trunc(write_offset, chan); | |
1339 | ||
1340 | return 0; | |
1341 | ||
1342 | nodata: | |
1343 | /* | |
1344 | * The memory barriers __wait_event()/wake_up_interruptible() take care | |
1345 | * of "raw_spin_is_locked" memory ordering. | |
1346 | */ | |
1347 | if (finalized) | |
1348 | return -ENODATA; | |
852c2936 MD |
1349 | else |
1350 | return -EAGAIN; | |
1351 | } | |
852c2936 | 1352 | |
f45930b7 JG |
1353 | /** |
1354 | * Performs the same function as lib_ring_buffer_snapshot(), but the positions | |
1355 | * are saved regardless of whether the consumed and produced positions are | |
1356 | * in the same subbuffer. | |
1357 | * @buf: ring buffer | |
1358 | * @consumed: consumed byte count indicating the last position read | |
1359 | * @produced: produced byte count indicating the last position written | |
1360 | * | |
1361 | * This function is meant to provide information on the exact producer and | |
1362 | * consumer positions without regard for the "snapshot" feature. | |
1363 | */ | |
1364 | int lib_ring_buffer_snapshot_sample_positions( | |
b5457df5 | 1365 | struct lttng_ust_ring_buffer *buf, |
f45930b7 JG |
1366 | unsigned long *consumed, unsigned long *produced, |
1367 | struct lttng_ust_shm_handle *handle) | |
1368 | { | |
b5457df5 MD |
1369 | struct lttng_ust_ring_buffer_channel *chan; |
1370 | const struct lttng_ust_ring_buffer_config *config; | |
f45930b7 JG |
1371 | |
1372 | chan = shmp(handle, buf->backend.chan); | |
1373 | if (!chan) | |
1374 | return -EPERM; | |
1375 | config = &chan->backend.config; | |
1376 | cmm_smp_rmb(); | |
1377 | *consumed = uatomic_read(&buf->consumed); | |
1378 | /* | |
1379 | * No need to issue a memory barrier between consumed count read and | |
1380 | * write offset read, because consumed count can only change | |
1381 | * concurrently in overwrite mode, and we keep a sequence counter | |
1382 | * identifier derived from the write offset to check we are getting | |
1383 | * the same sub-buffer we are expecting (the sub-buffers are atomically | |
1384 | * "tagged" upon writes, tags are checked upon read). | |
1385 | */ | |
1386 | *produced = v_read(config, &buf->offset); | |
1387 | return 0; | |
1388 | } | |
1389 | ||
852c2936 | 1390 | /** |
d1a996f5 | 1391 | * lib_ring_buffer_move_consumer - move consumed counter forward |
852c2936 MD |
1392 | * @buf: ring buffer |
1393 | * @consumed_new: new consumed count value | |
1394 | */ | |
b5457df5 | 1395 | void lib_ring_buffer_move_consumer(struct lttng_ust_ring_buffer *buf, |
1d498196 | 1396 | unsigned long consumed_new, |
38fae1d3 | 1397 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1398 | { |
b5457df5 MD |
1399 | struct lttng_ust_ring_buffer_backend *bufb = &buf->backend; |
1400 | struct lttng_ust_ring_buffer_channel *chan; | |
852c2936 MD |
1401 | unsigned long consumed; |
1402 | ||
15500a1b MD |
1403 | chan = shmp(handle, bufb->chan); |
1404 | if (!chan) | |
1405 | return; | |
74d81a6c | 1406 | CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1); |
852c2936 MD |
1407 | |
1408 | /* | |
1409 | * Only push the consumed value forward. | |
1410 | * If the consumed cmpxchg fails, this is because we have been pushed by | |
1411 | * the writer in flight recorder mode. | |
1412 | */ | |
a6352fd4 | 1413 | consumed = uatomic_read(&buf->consumed); |
852c2936 | 1414 | while ((long) consumed - (long) consumed_new < 0) |
a6352fd4 MD |
1415 | consumed = uatomic_cmpxchg(&buf->consumed, consumed, |
1416 | consumed_new); | |
852c2936 | 1417 | } |
852c2936 MD |
1418 | |
1419 | /** | |
1420 | * lib_ring_buffer_get_subbuf - get exclusive access to subbuffer for reading | |
1421 | * @buf: ring buffer | |
1422 | * @consumed: consumed count indicating the position where to read | |
1423 | * | |
1424 | * Returns -ENODATA if buffer is finalized, -EAGAIN if there is currently no | |
1425 | * data to read at consumed position, or 0 if the get operation succeeds. | |
852c2936 | 1426 | */ |
b5457df5 | 1427 | int lib_ring_buffer_get_subbuf(struct lttng_ust_ring_buffer *buf, |
1d498196 | 1428 | unsigned long consumed, |
38fae1d3 | 1429 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1430 | { |
b5457df5 MD |
1431 | struct lttng_ust_ring_buffer_channel *chan; |
1432 | const struct lttng_ust_ring_buffer_config *config; | |
852c2936 | 1433 | unsigned long consumed_cur, consumed_idx, commit_count, write_offset; |
dddba398 | 1434 | int ret, finalized, nr_retry = LTTNG_UST_RING_BUFFER_GET_RETRY; |
15500a1b | 1435 | struct commit_counters_cold *cc_cold; |
852c2936 | 1436 | |
15500a1b MD |
1437 | chan = shmp(handle, buf->backend.chan); |
1438 | if (!chan) | |
1439 | return -EPERM; | |
1440 | config = &chan->backend.config; | |
852c2936 | 1441 | retry: |
14641deb | 1442 | finalized = CMM_ACCESS_ONCE(buf->finalized); |
852c2936 MD |
1443 | /* |
1444 | * Read finalized before counters. | |
1445 | */ | |
a6352fd4 MD |
1446 | cmm_smp_rmb(); |
1447 | consumed_cur = uatomic_read(&buf->consumed); | |
852c2936 | 1448 | consumed_idx = subbuf_index(consumed, chan); |
15500a1b MD |
1449 | cc_cold = shmp_index(handle, buf->commit_cold, consumed_idx); |
1450 | if (!cc_cold) | |
1451 | return -EPERM; | |
1452 | commit_count = v_read(config, &cc_cold->cc_sb); | |
852c2936 MD |
1453 | /* |
1454 | * Make sure we read the commit count before reading the buffer | |
1455 | * data and the write offset. Correct consumed offset ordering | |
1456 | * wrt commit count is insured by the use of cmpxchg to update | |
1457 | * the consumed offset. | |
852c2936 | 1458 | */ |
a6352fd4 MD |
1459 | /* |
1460 | * Local rmb to match the remote wmb to read the commit count | |
1461 | * before the buffer data and the write offset. | |
1462 | */ | |
1463 | cmm_smp_rmb(); | |
852c2936 MD |
1464 | |
1465 | write_offset = v_read(config, &buf->offset); | |
1466 | ||
1467 | /* | |
1468 | * Check that the buffer we are getting is after or at consumed_cur | |
1469 | * position. | |
1470 | */ | |
1471 | if ((long) subbuf_trunc(consumed, chan) | |
1472 | - (long) subbuf_trunc(consumed_cur, chan) < 0) | |
1473 | goto nodata; | |
1474 | ||
1475 | /* | |
1476 | * Check that the subbuffer we are trying to consume has been | |
dddba398 MD |
1477 | * already fully committed. There are a few causes that can make |
1478 | * this unavailability situation occur: | |
1479 | * | |
1480 | * Temporary (short-term) situation: | |
1481 | * - Application is running on a different CPU, between reserve | |
1482 | * and commit ring buffer operations, | |
1483 | * - Application is preempted between reserve and commit ring | |
1484 | * buffer operations, | |
1485 | * | |
1486 | * Long-term situation: | |
1487 | * - Application is stopped (SIGSTOP) between reserve and commit | |
1488 | * ring buffer operations. Could eventually be resumed by | |
1489 | * SIGCONT. | |
1490 | * - Application is killed (SIGTERM, SIGINT, SIGKILL) between | |
1491 | * reserve and commit ring buffer operation. | |
1492 | * | |
1493 | * From a consumer perspective, handling short-term | |
1494 | * unavailability situations is performed by retrying a few | |
1495 | * times after a delay. Handling long-term unavailability | |
1496 | * situations is handled by failing to get the sub-buffer. | |
1497 | * | |
1498 | * In all of those situations, if the application is taking a | |
1499 | * long time to perform its commit after ring buffer space | |
1500 | * reservation, we can end up in a situation where the producer | |
1501 | * will fill the ring buffer and try to write into the same | |
1502 | * sub-buffer again (which has a missing commit). This is | |
1503 | * handled by the producer in the sub-buffer switch handling | |
1504 | * code of the reserve routine by detecting unbalanced | |
1505 | * reserve/commit counters and discarding all further events | |
1506 | * until the situation is resolved in those situations. Two | |
1507 | * scenarios can occur: | |
1508 | * | |
1509 | * 1) The application causing the reserve/commit counters to be | |
1510 | * unbalanced has been terminated. In this situation, all | |
1511 | * further events will be discarded in the buffers, and no | |
1512 | * further buffer data will be readable by the consumer | |
1513 | * daemon. Tearing down the UST tracing session and starting | |
1514 | * anew is a work-around for those situations. Note that this | |
1515 | * only affects per-UID tracing. In per-PID tracing, the | |
1516 | * application vanishes with the termination, and therefore | |
1517 | * no more data needs to be written to the buffers. | |
1518 | * 2) The application causing the unbalance has been delayed for | |
1519 | * a long time, but will eventually try to increment the | |
1520 | * commit counter after eventually writing to the sub-buffer. | |
1521 | * This situation can cause events to be discarded until the | |
1522 | * application resumes its operations. | |
852c2936 MD |
1523 | */ |
1524 | if (((commit_count - chan->backend.subbuf_size) | |
1525 | & chan->commit_count_mask) | |
0bade047 | 1526 | - (buf_trunc(consumed, chan) |
852c2936 | 1527 | >> chan->backend.num_subbuf_order) |
dddba398 MD |
1528 | != 0) { |
1529 | if (nr_retry-- > 0) { | |
1530 | if (nr_retry <= (LTTNG_UST_RING_BUFFER_GET_RETRY >> 1)) | |
1531 | (void) poll(NULL, 0, LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS); | |
1532 | goto retry; | |
1533 | } else { | |
1534 | goto nodata; | |
1535 | } | |
1536 | } | |
852c2936 MD |
1537 | |
1538 | /* | |
1539 | * Check that we are not about to read the same subbuffer in | |
1540 | * which the writer head is. | |
1541 | */ | |
0bade047 | 1542 | if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed, chan) |
852c2936 MD |
1543 | == 0) |
1544 | goto nodata; | |
1545 | ||
1546 | /* | |
1547 | * Failure to get the subbuffer causes a busy-loop retry without going | |
1548 | * to a wait queue. These are caused by short-lived race windows where | |
1549 | * the writer is getting access to a subbuffer we were trying to get | |
1550 | * access to. Also checks that the "consumed" buffer count we are | |
1551 | * looking for matches the one contained in the subbuffer id. | |
dddba398 MD |
1552 | * |
1553 | * The short-lived race window described here can be affected by | |
1554 | * application signals and preemption, thus requiring to bound | |
1555 | * the loop to a maximum number of retry. | |
852c2936 MD |
1556 | */ |
1557 | ret = update_read_sb_index(config, &buf->backend, &chan->backend, | |
1d498196 MD |
1558 | consumed_idx, buf_trunc_val(consumed, chan), |
1559 | handle); | |
dddba398 MD |
1560 | if (ret) { |
1561 | if (nr_retry-- > 0) { | |
1562 | if (nr_retry <= (LTTNG_UST_RING_BUFFER_GET_RETRY >> 1)) | |
1563 | (void) poll(NULL, 0, LTTNG_UST_RING_BUFFER_RETRY_DELAY_MS); | |
1564 | goto retry; | |
1565 | } else { | |
1566 | goto nodata; | |
1567 | } | |
1568 | } | |
852c2936 MD |
1569 | subbuffer_id_clear_noref(config, &buf->backend.buf_rsb.id); |
1570 | ||
1571 | buf->get_subbuf_consumed = consumed; | |
1572 | buf->get_subbuf = 1; | |
1573 | ||
1574 | return 0; | |
1575 | ||
1576 | nodata: | |
1577 | /* | |
1578 | * The memory barriers __wait_event()/wake_up_interruptible() take care | |
1579 | * of "raw_spin_is_locked" memory ordering. | |
1580 | */ | |
1581 | if (finalized) | |
1582 | return -ENODATA; | |
852c2936 MD |
1583 | else |
1584 | return -EAGAIN; | |
1585 | } | |
852c2936 MD |
1586 | |
1587 | /** | |
1588 | * lib_ring_buffer_put_subbuf - release exclusive subbuffer access | |
1589 | * @buf: ring buffer | |
1590 | */ | |
b5457df5 | 1591 | void lib_ring_buffer_put_subbuf(struct lttng_ust_ring_buffer *buf, |
38fae1d3 | 1592 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1593 | { |
b5457df5 MD |
1594 | struct lttng_ust_ring_buffer_backend *bufb = &buf->backend; |
1595 | struct lttng_ust_ring_buffer_channel *chan; | |
1596 | const struct lttng_ust_ring_buffer_config *config; | |
15500a1b | 1597 | unsigned long sb_bindex, consumed_idx, consumed; |
b5457df5 MD |
1598 | struct lttng_ust_ring_buffer_backend_pages_shmp *rpages; |
1599 | struct lttng_ust_ring_buffer_backend_pages *backend_pages; | |
852c2936 | 1600 | |
15500a1b MD |
1601 | chan = shmp(handle, bufb->chan); |
1602 | if (!chan) | |
1603 | return; | |
1604 | config = &chan->backend.config; | |
74d81a6c | 1605 | CHAN_WARN_ON(chan, uatomic_read(&buf->active_readers) != 1); |
852c2936 MD |
1606 | |
1607 | if (!buf->get_subbuf) { | |
1608 | /* | |
1609 | * Reader puts a subbuffer it did not get. | |
1610 | */ | |
1611 | CHAN_WARN_ON(chan, 1); | |
1612 | return; | |
1613 | } | |
1614 | consumed = buf->get_subbuf_consumed; | |
1615 | buf->get_subbuf = 0; | |
1616 | ||
1617 | /* | |
1618 | * Clear the records_unread counter. (overruns counter) | |
1619 | * Can still be non-zero if a file reader simply grabbed the data | |
1620 | * without using iterators. | |
1621 | * Can be below zero if an iterator is used on a snapshot more than | |
1622 | * once. | |
1623 | */ | |
15500a1b MD |
1624 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); |
1625 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
1626 | if (!rpages) | |
1627 | return; | |
1628 | backend_pages = shmp(handle, rpages->shmp); | |
1629 | if (!backend_pages) | |
1630 | return; | |
1631 | v_add(config, v_read(config, &backend_pages->records_unread), | |
1632 | &bufb->records_read); | |
1633 | v_set(config, &backend_pages->records_unread, 0); | |
852c2936 MD |
1634 | CHAN_WARN_ON(chan, config->mode == RING_BUFFER_OVERWRITE |
1635 | && subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
1636 | subbuffer_id_set_noref(config, &bufb->buf_rsb.id); | |
1637 | ||
1638 | /* | |
1639 | * Exchange the reader subbuffer with the one we put in its place in the | |
1640 | * writer subbuffer table. Expect the original consumed count. If | |
1641 | * update_read_sb_index fails, this is because the writer updated the | |
1642 | * subbuffer concurrently. We should therefore keep the subbuffer we | |
1643 | * currently have: it has become invalid to try reading this sub-buffer | |
1644 | * consumed count value anyway. | |
1645 | */ | |
1646 | consumed_idx = subbuf_index(consumed, chan); | |
1647 | update_read_sb_index(config, &buf->backend, &chan->backend, | |
1d498196 MD |
1648 | consumed_idx, buf_trunc_val(consumed, chan), |
1649 | handle); | |
852c2936 MD |
1650 | /* |
1651 | * update_read_sb_index return value ignored. Don't exchange sub-buffer | |
1652 | * if the writer concurrently updated it. | |
1653 | */ | |
1654 | } | |
852c2936 MD |
1655 | |
1656 | /* | |
1657 | * cons_offset is an iterator on all subbuffer offsets between the reader | |
1658 | * position and the writer position. (inclusive) | |
1659 | */ | |
1660 | static | |
b5457df5 MD |
1661 | void lib_ring_buffer_print_subbuffer_errors(struct lttng_ust_ring_buffer *buf, |
1662 | struct lttng_ust_ring_buffer_channel *chan, | |
852c2936 | 1663 | unsigned long cons_offset, |
1d498196 | 1664 | int cpu, |
38fae1d3 | 1665 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1666 | { |
b5457df5 | 1667 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
852c2936 | 1668 | unsigned long cons_idx, commit_count, commit_count_sb; |
15500a1b MD |
1669 | struct commit_counters_hot *cc_hot; |
1670 | struct commit_counters_cold *cc_cold; | |
852c2936 MD |
1671 | |
1672 | cons_idx = subbuf_index(cons_offset, chan); | |
15500a1b MD |
1673 | cc_hot = shmp_index(handle, buf->commit_hot, cons_idx); |
1674 | if (!cc_hot) | |
1675 | return; | |
1676 | cc_cold = shmp_index(handle, buf->commit_cold, cons_idx); | |
1677 | if (!cc_cold) | |
1678 | return; | |
1679 | commit_count = v_read(config, &cc_hot->cc); | |
1680 | commit_count_sb = v_read(config, &cc_cold->cc_sb); | |
852c2936 MD |
1681 | |
1682 | if (subbuf_offset(commit_count, chan) != 0) | |
4d3c9523 | 1683 | DBG("ring buffer %s, cpu %d: " |
852c2936 MD |
1684 | "commit count in subbuffer %lu,\n" |
1685 | "expecting multiples of %lu bytes\n" | |
1686 | " [ %lu bytes committed, %lu bytes reader-visible ]\n", | |
1687 | chan->backend.name, cpu, cons_idx, | |
1688 | chan->backend.subbuf_size, | |
1689 | commit_count, commit_count_sb); | |
1690 | ||
4d3c9523 | 1691 | DBG("ring buffer: %s, cpu %d: %lu bytes committed\n", |
852c2936 MD |
1692 | chan->backend.name, cpu, commit_count); |
1693 | } | |
1694 | ||
1695 | static | |
b5457df5 MD |
1696 | void lib_ring_buffer_print_buffer_errors(struct lttng_ust_ring_buffer *buf, |
1697 | struct lttng_ust_ring_buffer_channel *chan, | |
f0fde1c3 | 1698 | int cpu, struct lttng_ust_shm_handle *handle) |
852c2936 | 1699 | { |
b5457df5 | 1700 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
852c2936 MD |
1701 | unsigned long write_offset, cons_offset; |
1702 | ||
852c2936 MD |
1703 | /* |
1704 | * No need to order commit_count, write_offset and cons_offset reads | |
1705 | * because we execute at teardown when no more writer nor reader | |
1706 | * references are left. | |
1707 | */ | |
1708 | write_offset = v_read(config, &buf->offset); | |
a6352fd4 | 1709 | cons_offset = uatomic_read(&buf->consumed); |
852c2936 | 1710 | if (write_offset != cons_offset) |
4d3c9523 | 1711 | DBG("ring buffer %s, cpu %d: " |
852c2936 MD |
1712 | "non-consumed data\n" |
1713 | " [ %lu bytes written, %lu bytes read ]\n", | |
1714 | chan->backend.name, cpu, write_offset, cons_offset); | |
1715 | ||
a6352fd4 | 1716 | for (cons_offset = uatomic_read(&buf->consumed); |
852c2936 MD |
1717 | (long) (subbuf_trunc((unsigned long) v_read(config, &buf->offset), |
1718 | chan) | |
1719 | - cons_offset) > 0; | |
1720 | cons_offset = subbuf_align(cons_offset, chan)) | |
1721 | lib_ring_buffer_print_subbuffer_errors(buf, chan, cons_offset, | |
1d498196 | 1722 | cpu, handle); |
852c2936 MD |
1723 | } |
1724 | ||
1725 | static | |
b5457df5 MD |
1726 | void lib_ring_buffer_print_errors(struct lttng_ust_ring_buffer_channel *chan, |
1727 | struct lttng_ust_ring_buffer *buf, int cpu, | |
009769ca | 1728 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1729 | { |
b5457df5 | 1730 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
852c2936 | 1731 | |
a1360615 MD |
1732 | if (!strcmp(chan->backend.name, "relay-metadata-mmap")) { |
1733 | DBG("ring buffer %s: %lu records written, " | |
1734 | "%lu records overrun\n", | |
1735 | chan->backend.name, | |
1736 | v_read(config, &buf->records_count), | |
1737 | v_read(config, &buf->records_overrun)); | |
1738 | } else { | |
1739 | DBG("ring buffer %s, cpu %d: %lu records written, " | |
1740 | "%lu records overrun\n", | |
1741 | chan->backend.name, cpu, | |
1742 | v_read(config, &buf->records_count), | |
1743 | v_read(config, &buf->records_overrun)); | |
1744 | ||
1745 | if (v_read(config, &buf->records_lost_full) | |
1746 | || v_read(config, &buf->records_lost_wrap) | |
1747 | || v_read(config, &buf->records_lost_big)) | |
1748 | DBG("ring buffer %s, cpu %d: records were lost. Caused by:\n" | |
1749 | " [ %lu buffer full, %lu nest buffer wrap-around, " | |
1750 | "%lu event too big ]\n", | |
1751 | chan->backend.name, cpu, | |
1752 | v_read(config, &buf->records_lost_full), | |
1753 | v_read(config, &buf->records_lost_wrap), | |
1754 | v_read(config, &buf->records_lost_big)); | |
1755 | } | |
f0fde1c3 | 1756 | lib_ring_buffer_print_buffer_errors(buf, chan, cpu, handle); |
852c2936 MD |
1757 | } |
1758 | ||
1759 | /* | |
1760 | * lib_ring_buffer_switch_old_start: Populate old subbuffer header. | |
1761 | * | |
48f22436 MD |
1762 | * Only executed by SWITCH_FLUSH, which can be issued while tracing is |
1763 | * active or at buffer finalization (destroy). | |
852c2936 MD |
1764 | */ |
1765 | static | |
b5457df5 MD |
1766 | void lib_ring_buffer_switch_old_start(struct lttng_ust_ring_buffer *buf, |
1767 | struct lttng_ust_ring_buffer_channel *chan, | |
852c2936 | 1768 | struct switch_offsets *offsets, |
f27b0770 | 1769 | const struct lttng_ust_ring_buffer_ctx *ctx, |
38fae1d3 | 1770 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1771 | { |
b5457df5 | 1772 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
852c2936 MD |
1773 | unsigned long oldidx = subbuf_index(offsets->old, chan); |
1774 | unsigned long commit_count; | |
3d3c3833 | 1775 | struct commit_counters_hot *cc_hot; |
852c2936 | 1776 | |
373ea80a | 1777 | config->cb.buffer_begin(buf, ctx->priv->timestamp, oldidx, handle); |
852c2936 MD |
1778 | |
1779 | /* | |
1780 | * Order all writes to buffer before the commit count update that will | |
1781 | * determine that the subbuffer is full. | |
1782 | */ | |
a6352fd4 | 1783 | cmm_smp_wmb(); |
3d3c3833 | 1784 | cc_hot = shmp_index(handle, buf->commit_hot, oldidx); |
15500a1b MD |
1785 | if (!cc_hot) |
1786 | return; | |
852c2936 | 1787 | v_add(config, config->cb.subbuffer_header_size(), |
3d3c3833 MD |
1788 | &cc_hot->cc); |
1789 | commit_count = v_read(config, &cc_hot->cc); | |
852c2936 MD |
1790 | /* Check if the written buffer has to be delivered */ |
1791 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->old, | |
f27b0770 | 1792 | commit_count, oldidx, handle, ctx); |
d2fe4771 | 1793 | lib_ring_buffer_write_commit_counter(config, buf, chan, |
80249235 | 1794 | offsets->old + config->cb.subbuffer_header_size(), |
3d3c3833 | 1795 | commit_count, handle, cc_hot); |
852c2936 MD |
1796 | } |
1797 | ||
1798 | /* | |
1799 | * lib_ring_buffer_switch_old_end: switch old subbuffer | |
1800 | * | |
1801 | * Note : offset_old should never be 0 here. It is ok, because we never perform | |
1802 | * buffer switch on an empty subbuffer in SWITCH_ACTIVE mode. The caller | |
1803 | * increments the offset_old value when doing a SWITCH_FLUSH on an empty | |
1804 | * subbuffer. | |
1805 | */ | |
1806 | static | |
b5457df5 MD |
1807 | void lib_ring_buffer_switch_old_end(struct lttng_ust_ring_buffer *buf, |
1808 | struct lttng_ust_ring_buffer_channel *chan, | |
852c2936 | 1809 | struct switch_offsets *offsets, |
f27b0770 | 1810 | const struct lttng_ust_ring_buffer_ctx *ctx, |
38fae1d3 | 1811 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1812 | { |
b5457df5 | 1813 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
852c2936 MD |
1814 | unsigned long oldidx = subbuf_index(offsets->old - 1, chan); |
1815 | unsigned long commit_count, padding_size, data_size; | |
3d3c3833 | 1816 | struct commit_counters_hot *cc_hot; |
6c737d05 | 1817 | uint64_t *ts_end; |
852c2936 MD |
1818 | |
1819 | data_size = subbuf_offset(offsets->old - 1, chan) + 1; | |
1820 | padding_size = chan->backend.subbuf_size - data_size; | |
1d498196 MD |
1821 | subbuffer_set_data_size(config, &buf->backend, oldidx, data_size, |
1822 | handle); | |
852c2936 | 1823 | |
6c737d05 MD |
1824 | ts_end = shmp_index(handle, buf->ts_end, oldidx); |
1825 | if (!ts_end) | |
1826 | return; | |
852c2936 | 1827 | /* |
6c737d05 MD |
1828 | * This is the last space reservation in that sub-buffer before |
1829 | * it gets delivered. This provides exclusive access to write to | |
1830 | * this sub-buffer's ts_end. There are also no concurrent | |
1831 | * readers of that ts_end because delivery of that sub-buffer is | |
1832 | * postponed until the commit counter is incremented for the | |
1833 | * current space reservation. | |
1834 | */ | |
373ea80a | 1835 | *ts_end = ctx->priv->timestamp; |
6c737d05 MD |
1836 | |
1837 | /* | |
1838 | * Order all writes to buffer and store to ts_end before the commit | |
1839 | * count update that will determine that the subbuffer is full. | |
852c2936 | 1840 | */ |
a6352fd4 | 1841 | cmm_smp_wmb(); |
3d3c3833 | 1842 | cc_hot = shmp_index(handle, buf->commit_hot, oldidx); |
15500a1b MD |
1843 | if (!cc_hot) |
1844 | return; | |
3d3c3833 MD |
1845 | v_add(config, padding_size, &cc_hot->cc); |
1846 | commit_count = v_read(config, &cc_hot->cc); | |
852c2936 | 1847 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->old - 1, |
f27b0770 | 1848 | commit_count, oldidx, handle, ctx); |
d2fe4771 MD |
1849 | lib_ring_buffer_write_commit_counter(config, buf, chan, |
1850 | offsets->old + padding_size, commit_count, handle, | |
3d3c3833 | 1851 | cc_hot); |
852c2936 MD |
1852 | } |
1853 | ||
1854 | /* | |
1855 | * lib_ring_buffer_switch_new_start: Populate new subbuffer. | |
1856 | * | |
1857 | * This code can be executed unordered : writers may already have written to the | |
1858 | * sub-buffer before this code gets executed, caution. The commit makes sure | |
1859 | * that this code is executed before the deliver of this sub-buffer. | |
1860 | */ | |
1861 | static | |
b5457df5 MD |
1862 | void lib_ring_buffer_switch_new_start(struct lttng_ust_ring_buffer *buf, |
1863 | struct lttng_ust_ring_buffer_channel *chan, | |
852c2936 | 1864 | struct switch_offsets *offsets, |
f27b0770 | 1865 | const struct lttng_ust_ring_buffer_ctx *ctx, |
38fae1d3 | 1866 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1867 | { |
b5457df5 | 1868 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
852c2936 MD |
1869 | unsigned long beginidx = subbuf_index(offsets->begin, chan); |
1870 | unsigned long commit_count; | |
3d3c3833 | 1871 | struct commit_counters_hot *cc_hot; |
852c2936 | 1872 | |
373ea80a | 1873 | config->cb.buffer_begin(buf, ctx->priv->timestamp, beginidx, handle); |
852c2936 MD |
1874 | |
1875 | /* | |
1876 | * Order all writes to buffer before the commit count update that will | |
1877 | * determine that the subbuffer is full. | |
1878 | */ | |
a6352fd4 | 1879 | cmm_smp_wmb(); |
3d3c3833 | 1880 | cc_hot = shmp_index(handle, buf->commit_hot, beginidx); |
15500a1b MD |
1881 | if (!cc_hot) |
1882 | return; | |
1883 | v_add(config, config->cb.subbuffer_header_size(), &cc_hot->cc); | |
3d3c3833 | 1884 | commit_count = v_read(config, &cc_hot->cc); |
852c2936 MD |
1885 | /* Check if the written buffer has to be delivered */ |
1886 | lib_ring_buffer_check_deliver(config, buf, chan, offsets->begin, | |
f27b0770 | 1887 | commit_count, beginidx, handle, ctx); |
d2fe4771 | 1888 | lib_ring_buffer_write_commit_counter(config, buf, chan, |
80249235 | 1889 | offsets->begin + config->cb.subbuffer_header_size(), |
3d3c3833 | 1890 | commit_count, handle, cc_hot); |
852c2936 MD |
1891 | } |
1892 | ||
1ad21f70 MD |
1893 | /* |
1894 | * lib_ring_buffer_switch_new_end: finish switching current subbuffer | |
1895 | * | |
3962118d MD |
1896 | * Calls subbuffer_set_data_size() to set the data size of the current |
1897 | * sub-buffer. We do not need to perform check_deliver nor commit here, | |
1898 | * since this task will be done by the "commit" of the event for which | |
1899 | * we are currently doing the space reservation. | |
1ad21f70 MD |
1900 | */ |
1901 | static | |
b5457df5 MD |
1902 | void lib_ring_buffer_switch_new_end(struct lttng_ust_ring_buffer *buf, |
1903 | struct lttng_ust_ring_buffer_channel *chan, | |
1ad21f70 | 1904 | struct switch_offsets *offsets, |
f27b0770 | 1905 | const struct lttng_ust_ring_buffer_ctx *ctx, |
1ad21f70 MD |
1906 | struct lttng_ust_shm_handle *handle) |
1907 | { | |
b5457df5 | 1908 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
3962118d | 1909 | unsigned long endidx, data_size; |
6c737d05 | 1910 | uint64_t *ts_end; |
1ad21f70 | 1911 | |
3962118d | 1912 | endidx = subbuf_index(offsets->end - 1, chan); |
1ad21f70 | 1913 | data_size = subbuf_offset(offsets->end - 1, chan) + 1; |
1ad21f70 MD |
1914 | subbuffer_set_data_size(config, &buf->backend, endidx, data_size, |
1915 | handle); | |
6c737d05 MD |
1916 | ts_end = shmp_index(handle, buf->ts_end, endidx); |
1917 | if (!ts_end) | |
1918 | return; | |
1919 | /* | |
1920 | * This is the last space reservation in that sub-buffer before | |
1921 | * it gets delivered. This provides exclusive access to write to | |
1922 | * this sub-buffer's ts_end. There are also no concurrent | |
1923 | * readers of that ts_end because delivery of that sub-buffer is | |
1924 | * postponed until the commit counter is incremented for the | |
1925 | * current space reservation. | |
1926 | */ | |
373ea80a | 1927 | *ts_end = ctx->priv->timestamp; |
1ad21f70 MD |
1928 | } |
1929 | ||
852c2936 MD |
1930 | /* |
1931 | * Returns : | |
1932 | * 0 if ok | |
1933 | * !0 if execution must be aborted. | |
1934 | */ | |
1935 | static | |
1936 | int lib_ring_buffer_try_switch_slow(enum switch_mode mode, | |
b5457df5 MD |
1937 | struct lttng_ust_ring_buffer *buf, |
1938 | struct lttng_ust_ring_buffer_channel *chan, | |
852c2936 | 1939 | struct switch_offsets *offsets, |
f27b0770 | 1940 | struct lttng_ust_ring_buffer_ctx *ctx, |
2dac206d | 1941 | struct lttng_ust_shm_handle *handle) |
852c2936 | 1942 | { |
b5457df5 | 1943 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
2dac206d | 1944 | unsigned long off, reserve_commit_diff; |
852c2936 MD |
1945 | |
1946 | offsets->begin = v_read(config, &buf->offset); | |
1947 | offsets->old = offsets->begin; | |
1948 | offsets->switch_old_start = 0; | |
1949 | off = subbuf_offset(offsets->begin, chan); | |
1950 | ||
373ea80a | 1951 | ctx->priv->timestamp = config->cb.ring_buffer_clock_read(chan); |
852c2936 MD |
1952 | |
1953 | /* | |
1954 | * Ensure we flush the header of an empty subbuffer when doing the | |
1955 | * finalize (SWITCH_FLUSH). This ensures that we end up knowing the | |
1956 | * total data gathering duration even if there were no records saved | |
1957 | * after the last buffer switch. | |
1958 | * In SWITCH_ACTIVE mode, switch the buffer when it contains events. | |
1959 | * SWITCH_ACTIVE only flushes the current subbuffer, dealing with end of | |
1960 | * subbuffer header as appropriate. | |
1961 | * The next record that reserves space will be responsible for | |
1962 | * populating the following subbuffer header. We choose not to populate | |
1963 | * the next subbuffer header here because we want to be able to use | |
a6352fd4 MD |
1964 | * SWITCH_ACTIVE for periodical buffer flush, which must |
1965 | * guarantee that all the buffer content (records and header | |
1966 | * timestamps) are visible to the reader. This is required for | |
1967 | * quiescence guarantees for the fusion merge. | |
852c2936 | 1968 | */ |
2dac206d MD |
1969 | if (mode != SWITCH_FLUSH && !off) |
1970 | return -1; /* we do not have to switch : buffer is empty */ | |
1971 | ||
1972 | if (caa_unlikely(off == 0)) { | |
1973 | unsigned long sb_index, commit_count; | |
15500a1b | 1974 | struct commit_counters_cold *cc_cold; |
2dac206d MD |
1975 | |
1976 | /* | |
48f22436 MD |
1977 | * We are performing a SWITCH_FLUSH. There may be concurrent |
1978 | * writes into the buffer if e.g. invoked while performing a | |
1979 | * snapshot on an active trace. | |
2dac206d | 1980 | * |
48f22436 MD |
1981 | * If the client does not save any header information |
1982 | * (sub-buffer header size == 0), don't switch empty subbuffer | |
1983 | * on finalize, because it is invalid to deliver a completely | |
1984 | * empty subbuffer. | |
2dac206d MD |
1985 | */ |
1986 | if (!config->cb.subbuffer_header_size()) | |
1987 | return -1; | |
1988 | ||
1989 | /* Test new buffer integrity */ | |
1990 | sb_index = subbuf_index(offsets->begin, chan); | |
15500a1b MD |
1991 | cc_cold = shmp_index(handle, buf->commit_cold, sb_index); |
1992 | if (!cc_cold) | |
1993 | return -1; | |
1994 | commit_count = v_read(config, &cc_cold->cc_sb); | |
2dac206d MD |
1995 | reserve_commit_diff = |
1996 | (buf_trunc(offsets->begin, chan) | |
1997 | >> chan->backend.num_subbuf_order) | |
1998 | - (commit_count & chan->commit_count_mask); | |
1999 | if (caa_likely(reserve_commit_diff == 0)) { | |
2000 | /* Next subbuffer not being written to. */ | |
2001 | if (caa_unlikely(config->mode != RING_BUFFER_OVERWRITE && | |
2002 | subbuf_trunc(offsets->begin, chan) | |
2003 | - subbuf_trunc((unsigned long) | |
2004 | uatomic_read(&buf->consumed), chan) | |
2005 | >= chan->backend.buf_size)) { | |
2006 | /* | |
2007 | * We do not overwrite non consumed buffers | |
2008 | * and we are full : don't switch. | |
2009 | */ | |
852c2936 | 2010 | return -1; |
2dac206d MD |
2011 | } else { |
2012 | /* | |
2013 | * Next subbuffer not being written to, and we | |
2014 | * are either in overwrite mode or the buffer is | |
2015 | * not full. It's safe to write in this new | |
2016 | * subbuffer. | |
2017 | */ | |
2018 | } | |
2019 | } else { | |
852c2936 | 2020 | /* |
2dac206d MD |
2021 | * Next subbuffer reserve offset does not match the |
2022 | * commit offset. Don't perform switch in | |
2023 | * producer-consumer and overwrite mode. Caused by | |
2024 | * either a writer OOPS or too many nested writes over a | |
2025 | * reserve/commit pair. | |
852c2936 | 2026 | */ |
2dac206d | 2027 | return -1; |
852c2936 | 2028 | } |
2dac206d MD |
2029 | |
2030 | /* | |
2031 | * Need to write the subbuffer start header on finalize. | |
2032 | */ | |
2033 | offsets->switch_old_start = 1; | |
2034 | } | |
2035 | offsets->begin = subbuf_align(offsets->begin, chan); | |
852c2936 MD |
2036 | /* Note: old points to the next subbuf at offset 0 */ |
2037 | offsets->end = offsets->begin; | |
f27b0770 MD |
2038 | /* |
2039 | * Populate the records lost counters prior to performing a | |
2040 | * sub-buffer switch. | |
2041 | */ | |
2042 | ctx->priv->records_lost_full = v_read(config, &buf->records_lost_full); | |
2043 | ctx->priv->records_lost_wrap = v_read(config, &buf->records_lost_wrap); | |
2044 | ctx->priv->records_lost_big = v_read(config, &buf->records_lost_big); | |
852c2936 MD |
2045 | return 0; |
2046 | } | |
2047 | ||
2048 | /* | |
2049 | * Force a sub-buffer switch. This operation is completely reentrant : can be | |
2050 | * called while tracing is active with absolutely no lock held. | |
2051 | * | |
ef1a13e0 MD |
2052 | * For RING_BUFFER_SYNC_PER_CPU ring buffers, as a v_cmpxchg is used for |
2053 | * some atomic operations, this function must be called from the CPU | |
2054 | * which owns the buffer for a ACTIVE flush. However, for | |
2055 | * RING_BUFFER_SYNC_GLOBAL ring buffers, this function can be called | |
2056 | * from any CPU. | |
852c2936 | 2057 | */ |
b5457df5 | 2058 | void lib_ring_buffer_switch_slow(struct lttng_ust_ring_buffer *buf, enum switch_mode mode, |
38fae1d3 | 2059 | struct lttng_ust_shm_handle *handle) |
852c2936 | 2060 | { |
b5457df5 MD |
2061 | struct lttng_ust_ring_buffer_channel *chan; |
2062 | const struct lttng_ust_ring_buffer_config *config; | |
f27b0770 MD |
2063 | struct lttng_ust_ring_buffer_ctx_private ctx_priv; |
2064 | struct lttng_ust_ring_buffer_ctx ctx; | |
852c2936 MD |
2065 | struct switch_offsets offsets; |
2066 | unsigned long oldidx; | |
852c2936 | 2067 | |
f27b0770 | 2068 | ctx.priv = &ctx_priv; |
15500a1b MD |
2069 | chan = shmp(handle, buf->backend.chan); |
2070 | if (!chan) | |
2071 | return; | |
2072 | config = &chan->backend.config; | |
2073 | ||
852c2936 MD |
2074 | offsets.size = 0; |
2075 | ||
2076 | /* | |
2077 | * Perform retryable operations. | |
2078 | */ | |
2079 | do { | |
2080 | if (lib_ring_buffer_try_switch_slow(mode, buf, chan, &offsets, | |
f27b0770 | 2081 | &ctx, handle)) |
852c2936 MD |
2082 | return; /* Switch not needed */ |
2083 | } while (v_cmpxchg(config, &buf->offset, offsets.old, offsets.end) | |
2084 | != offsets.old); | |
2085 | ||
2086 | /* | |
373ea80a MD |
2087 | * Atomically update last_timestamp. This update races against concurrent |
2088 | * atomic updates, but the race will always cause supplementary full | |
2089 | * timestamp records, never the opposite (missing a full timestamp | |
2090 | * record when it would be needed). | |
852c2936 | 2091 | */ |
373ea80a | 2092 | save_last_timestamp(config, buf, ctx.priv->timestamp); |
852c2936 MD |
2093 | |
2094 | /* | |
2095 | * Push the reader if necessary | |
2096 | */ | |
2097 | lib_ring_buffer_reserve_push_reader(buf, chan, offsets.old); | |
2098 | ||
2099 | oldidx = subbuf_index(offsets.old, chan); | |
1d498196 | 2100 | lib_ring_buffer_clear_noref(config, &buf->backend, oldidx, handle); |
852c2936 MD |
2101 | |
2102 | /* | |
2103 | * May need to populate header start on SWITCH_FLUSH. | |
2104 | */ | |
2105 | if (offsets.switch_old_start) { | |
f27b0770 | 2106 | lib_ring_buffer_switch_old_start(buf, chan, &offsets, &ctx, handle); |
852c2936 MD |
2107 | offsets.old += config->cb.subbuffer_header_size(); |
2108 | } | |
2109 | ||
2110 | /* | |
2111 | * Switch old subbuffer. | |
2112 | */ | |
f27b0770 | 2113 | lib_ring_buffer_switch_old_end(buf, chan, &offsets, &ctx, handle); |
852c2936 | 2114 | } |
852c2936 | 2115 | |
6f97f9c2 MD |
2116 | static |
2117 | bool handle_blocking_retry(int *timeout_left_ms) | |
2118 | { | |
2119 | int timeout = *timeout_left_ms, delay; | |
2120 | ||
2121 | if (caa_likely(!timeout)) | |
2122 | return false; /* Do not retry, discard event. */ | |
2123 | if (timeout < 0) /* Wait forever. */ | |
2124 | delay = RETRY_DELAY_MS; | |
2125 | else | |
2126 | delay = min_t(int, timeout, RETRY_DELAY_MS); | |
2127 | (void) poll(NULL, 0, delay); | |
2128 | if (timeout > 0) | |
2129 | *timeout_left_ms -= delay; | |
2130 | return true; /* Retry. */ | |
2131 | } | |
2132 | ||
852c2936 MD |
2133 | /* |
2134 | * Returns : | |
2135 | * 0 if ok | |
2136 | * -ENOSPC if event size is too large for packet. | |
2137 | * -ENOBUFS if there is currently not enough space in buffer for the event. | |
2138 | * -EIO if data cannot be written into the buffer for any other reason. | |
2139 | */ | |
2140 | static | |
b5457df5 MD |
2141 | int lib_ring_buffer_try_reserve_slow(struct lttng_ust_ring_buffer *buf, |
2142 | struct lttng_ust_ring_buffer_channel *chan, | |
852c2936 | 2143 | struct switch_offsets *offsets, |
b5457df5 | 2144 | struct lttng_ust_ring_buffer_ctx *ctx, |
e56bb47c | 2145 | void *client_ctx) |
852c2936 | 2146 | { |
b5457df5 MD |
2147 | struct lttng_ust_ring_buffer_ctx_private *ctx_private = ctx->priv; |
2148 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; | |
8936b6c0 | 2149 | struct lttng_ust_shm_handle *handle = chan->handle; |
e185cf4b | 2150 | unsigned long reserve_commit_diff, offset_cmp; |
b2c5f61a | 2151 | int timeout_left_ms = lttng_ust_ringbuffer_get_timeout(chan); |
852c2936 | 2152 | |
e185cf4b MD |
2153 | retry: |
2154 | offsets->begin = offset_cmp = v_read(config, &buf->offset); | |
852c2936 MD |
2155 | offsets->old = offsets->begin; |
2156 | offsets->switch_new_start = 0; | |
1ad21f70 | 2157 | offsets->switch_new_end = 0; |
852c2936 MD |
2158 | offsets->switch_old_end = 0; |
2159 | offsets->pre_header_padding = 0; | |
2160 | ||
373ea80a MD |
2161 | ctx_private->timestamp = config->cb.ring_buffer_clock_read(chan); |
2162 | if ((int64_t) ctx_private->timestamp == -EIO) | |
852c2936 MD |
2163 | return -EIO; |
2164 | ||
373ea80a MD |
2165 | if (last_timestamp_overflow(config, buf, ctx_private->timestamp)) |
2166 | ctx_private->rflags |= RING_BUFFER_RFLAG_FULL_TIMESTAMP; | |
852c2936 | 2167 | |
8936b6c0 | 2168 | if (caa_unlikely(subbuf_offset(offsets->begin, chan) == 0)) { |
852c2936 MD |
2169 | offsets->switch_new_start = 1; /* For offsets->begin */ |
2170 | } else { | |
2171 | offsets->size = config->cb.record_header_size(config, chan, | |
2172 | offsets->begin, | |
2173 | &offsets->pre_header_padding, | |
e56bb47c | 2174 | ctx, client_ctx); |
852c2936 | 2175 | offsets->size += |
b5457df5 | 2176 | lttng_ust_ring_buffer_align(offsets->begin + offsets->size, |
8936b6c0 | 2177 | ctx->largest_align) |
852c2936 | 2178 | + ctx->data_size; |
b5a3dfa5 | 2179 | if (caa_unlikely(subbuf_offset(offsets->begin, chan) + |
852c2936 MD |
2180 | offsets->size > chan->backend.subbuf_size)) { |
2181 | offsets->switch_old_end = 1; /* For offsets->old */ | |
2182 | offsets->switch_new_start = 1; /* For offsets->begin */ | |
2183 | } | |
2184 | } | |
b5a3dfa5 | 2185 | if (caa_unlikely(offsets->switch_new_start)) { |
e185cf4b | 2186 | unsigned long sb_index, commit_count; |
15500a1b | 2187 | struct commit_counters_cold *cc_cold; |
852c2936 MD |
2188 | |
2189 | /* | |
2190 | * We are typically not filling the previous buffer completely. | |
2191 | */ | |
b5a3dfa5 | 2192 | if (caa_likely(offsets->switch_old_end)) |
852c2936 MD |
2193 | offsets->begin = subbuf_align(offsets->begin, chan); |
2194 | offsets->begin = offsets->begin | |
2195 | + config->cb.subbuffer_header_size(); | |
2196 | /* Test new buffer integrity */ | |
2197 | sb_index = subbuf_index(offsets->begin, chan); | |
e185cf4b MD |
2198 | /* |
2199 | * Read buf->offset before buf->commit_cold[sb_index].cc_sb. | |
2200 | * lib_ring_buffer_check_deliver() has the matching | |
2201 | * memory barriers required around commit_cold cc_sb | |
2202 | * updates to ensure reserve and commit counter updates | |
2203 | * are not seen reordered when updated by another CPU. | |
2204 | */ | |
2205 | cmm_smp_rmb(); | |
15500a1b MD |
2206 | cc_cold = shmp_index(handle, buf->commit_cold, sb_index); |
2207 | if (!cc_cold) | |
2208 | return -1; | |
2209 | commit_count = v_read(config, &cc_cold->cc_sb); | |
e185cf4b MD |
2210 | /* Read buf->commit_cold[sb_index].cc_sb before buf->offset. */ |
2211 | cmm_smp_rmb(); | |
2212 | if (caa_unlikely(offset_cmp != v_read(config, &buf->offset))) { | |
2213 | /* | |
2214 | * The reserve counter have been concurrently updated | |
2215 | * while we read the commit counter. This means the | |
2216 | * commit counter we read might not match buf->offset | |
2217 | * due to concurrent update. We therefore need to retry. | |
2218 | */ | |
2219 | goto retry; | |
2220 | } | |
852c2936 MD |
2221 | reserve_commit_diff = |
2222 | (buf_trunc(offsets->begin, chan) | |
2223 | >> chan->backend.num_subbuf_order) | |
e185cf4b | 2224 | - (commit_count & chan->commit_count_mask); |
b5a3dfa5 | 2225 | if (caa_likely(reserve_commit_diff == 0)) { |
852c2936 | 2226 | /* Next subbuffer not being written to. */ |
b5a3dfa5 | 2227 | if (caa_unlikely(config->mode != RING_BUFFER_OVERWRITE && |
852c2936 MD |
2228 | subbuf_trunc(offsets->begin, chan) |
2229 | - subbuf_trunc((unsigned long) | |
a6352fd4 | 2230 | uatomic_read(&buf->consumed), chan) |
852c2936 | 2231 | >= chan->backend.buf_size)) { |
64493e4f MD |
2232 | unsigned long nr_lost; |
2233 | ||
6f97f9c2 MD |
2234 | if (handle_blocking_retry(&timeout_left_ms)) |
2235 | goto retry; | |
2236 | ||
852c2936 MD |
2237 | /* |
2238 | * We do not overwrite non consumed buffers | |
2239 | * and we are full : record is lost. | |
2240 | */ | |
64493e4f | 2241 | nr_lost = v_read(config, &buf->records_lost_full); |
852c2936 | 2242 | v_inc(config, &buf->records_lost_full); |
64493e4f MD |
2243 | if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) { |
2244 | DBG("%lu or more records lost in (%s:%d) (buffer full)\n", | |
2245 | nr_lost + 1, chan->backend.name, | |
2246 | buf->backend.cpu); | |
2247 | } | |
852c2936 MD |
2248 | return -ENOBUFS; |
2249 | } else { | |
2250 | /* | |
2251 | * Next subbuffer not being written to, and we | |
2252 | * are either in overwrite mode or the buffer is | |
2253 | * not full. It's safe to write in this new | |
2254 | * subbuffer. | |
2255 | */ | |
2256 | } | |
2257 | } else { | |
64493e4f MD |
2258 | unsigned long nr_lost; |
2259 | ||
852c2936 MD |
2260 | /* |
2261 | * Next subbuffer reserve offset does not match the | |
e185cf4b MD |
2262 | * commit offset, and this did not involve update to the |
2263 | * reserve counter. Drop record in producer-consumer and | |
852c2936 MD |
2264 | * overwrite mode. Caused by either a writer OOPS or too |
2265 | * many nested writes over a reserve/commit pair. | |
2266 | */ | |
64493e4f | 2267 | nr_lost = v_read(config, &buf->records_lost_wrap); |
852c2936 | 2268 | v_inc(config, &buf->records_lost_wrap); |
64493e4f MD |
2269 | if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) { |
2270 | DBG("%lu or more records lost in (%s:%d) (wrap-around)\n", | |
2271 | nr_lost + 1, chan->backend.name, | |
2272 | buf->backend.cpu); | |
2273 | } | |
852c2936 MD |
2274 | return -EIO; |
2275 | } | |
2276 | offsets->size = | |
2277 | config->cb.record_header_size(config, chan, | |
2278 | offsets->begin, | |
2279 | &offsets->pre_header_padding, | |
e56bb47c | 2280 | ctx, client_ctx); |
852c2936 | 2281 | offsets->size += |
b5457df5 | 2282 | lttng_ust_ring_buffer_align(offsets->begin + offsets->size, |
852c2936 MD |
2283 | ctx->largest_align) |
2284 | + ctx->data_size; | |
b5a3dfa5 | 2285 | if (caa_unlikely(subbuf_offset(offsets->begin, chan) |
852c2936 | 2286 | + offsets->size > chan->backend.subbuf_size)) { |
64493e4f MD |
2287 | unsigned long nr_lost; |
2288 | ||
852c2936 MD |
2289 | /* |
2290 | * Record too big for subbuffers, report error, don't | |
2291 | * complete the sub-buffer switch. | |
2292 | */ | |
64493e4f | 2293 | nr_lost = v_read(config, &buf->records_lost_big); |
852c2936 | 2294 | v_inc(config, &buf->records_lost_big); |
64493e4f MD |
2295 | if ((nr_lost & (DBG_PRINT_NR_LOST - 1)) == 0) { |
2296 | DBG("%lu or more records lost in (%s:%d) record size " | |
2297 | " of %zu bytes is too large for buffer\n", | |
2298 | nr_lost + 1, chan->backend.name, | |
2299 | buf->backend.cpu, offsets->size); | |
2300 | } | |
852c2936 MD |
2301 | return -ENOSPC; |
2302 | } else { | |
2303 | /* | |
2304 | * We just made a successful buffer switch and the | |
2305 | * record fits in the new subbuffer. Let's write. | |
2306 | */ | |
2307 | } | |
2308 | } else { | |
2309 | /* | |
2310 | * Record fits in the current buffer and we are not on a switch | |
2311 | * boundary. It's safe to write. | |
2312 | */ | |
2313 | } | |
2314 | offsets->end = offsets->begin + offsets->size; | |
1ad21f70 MD |
2315 | |
2316 | if (caa_unlikely(subbuf_offset(offsets->end, chan) == 0)) { | |
2317 | /* | |
2318 | * The offset_end will fall at the very beginning of the next | |
2319 | * subbuffer. | |
2320 | */ | |
2321 | offsets->switch_new_end = 1; /* For offsets->begin */ | |
2322 | } | |
f27b0770 MD |
2323 | /* |
2324 | * Populate the records lost counters when the space reservation | |
2325 | * may cause a sub-buffer switch. | |
2326 | */ | |
2327 | if (offsets->switch_new_end || offsets->switch_old_end) { | |
2328 | ctx_private->records_lost_full = v_read(config, &buf->records_lost_full); | |
2329 | ctx_private->records_lost_wrap = v_read(config, &buf->records_lost_wrap); | |
2330 | ctx_private->records_lost_big = v_read(config, &buf->records_lost_big); | |
2331 | } | |
852c2936 MD |
2332 | return 0; |
2333 | } | |
2334 | ||
2335 | /** | |
2336 | * lib_ring_buffer_reserve_slow - Atomic slot reservation in a buffer. | |
2337 | * @ctx: ring buffer context. | |
2338 | * | |
2339 | * Return : -NOBUFS if not enough space, -ENOSPC if event size too large, | |
2340 | * -EIO for other errors, else returns 0. | |
2341 | * It will take care of sub-buffer switching. | |
2342 | */ | |
b5457df5 | 2343 | int lib_ring_buffer_reserve_slow(struct lttng_ust_ring_buffer_ctx *ctx, |
e56bb47c | 2344 | void *client_ctx) |
852c2936 | 2345 | { |
b5457df5 MD |
2346 | struct lttng_ust_ring_buffer_ctx_private *ctx_private = ctx->priv; |
2347 | struct lttng_ust_ring_buffer_channel *chan = ctx_private->chan; | |
8936b6c0 | 2348 | struct lttng_ust_shm_handle *handle = chan->handle; |
b5457df5 MD |
2349 | const struct lttng_ust_ring_buffer_config *config = &chan->backend.config; |
2350 | struct lttng_ust_ring_buffer *buf; | |
852c2936 MD |
2351 | struct switch_offsets offsets; |
2352 | int ret; | |
2353 | ||
2354 | if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) | |
8936b6c0 | 2355 | buf = shmp(handle, chan->backend.buf[ctx_private->reserve_cpu].shmp); |
852c2936 | 2356 | else |
1d498196 | 2357 | buf = shmp(handle, chan->backend.buf[0].shmp); |
15500a1b MD |
2358 | if (!buf) |
2359 | return -EIO; | |
8936b6c0 | 2360 | ctx_private->buf = buf; |
852c2936 MD |
2361 | |
2362 | offsets.size = 0; | |
2363 | ||
2364 | do { | |
2365 | ret = lib_ring_buffer_try_reserve_slow(buf, chan, &offsets, | |
e56bb47c | 2366 | ctx, client_ctx); |
b5a3dfa5 | 2367 | if (caa_unlikely(ret)) |
852c2936 | 2368 | return ret; |
b5a3dfa5 | 2369 | } while (caa_unlikely(v_cmpxchg(config, &buf->offset, offsets.old, |
852c2936 MD |
2370 | offsets.end) |
2371 | != offsets.old)); | |
2372 | ||
2373 | /* | |
373ea80a MD |
2374 | * Atomically update last_timestamp. This update races against concurrent |
2375 | * atomic updates, but the race will always cause supplementary full | |
2376 | * timestamp records, never the opposite (missing a full timestamp | |
2377 | * record when it would be needed). | |
852c2936 | 2378 | */ |
373ea80a | 2379 | save_last_timestamp(config, buf, ctx_private->timestamp); |
852c2936 MD |
2380 | |
2381 | /* | |
2382 | * Push the reader if necessary | |
2383 | */ | |
2384 | lib_ring_buffer_reserve_push_reader(buf, chan, offsets.end - 1); | |
2385 | ||
2386 | /* | |
2387 | * Clear noref flag for this subbuffer. | |
2388 | */ | |
2389 | lib_ring_buffer_clear_noref(config, &buf->backend, | |
1d498196 MD |
2390 | subbuf_index(offsets.end - 1, chan), |
2391 | handle); | |
852c2936 MD |
2392 | |
2393 | /* | |
2394 | * Switch old subbuffer if needed. | |
2395 | */ | |
b5a3dfa5 | 2396 | if (caa_unlikely(offsets.switch_old_end)) { |
852c2936 | 2397 | lib_ring_buffer_clear_noref(config, &buf->backend, |
1d498196 MD |
2398 | subbuf_index(offsets.old - 1, chan), |
2399 | handle); | |
f27b0770 | 2400 | lib_ring_buffer_switch_old_end(buf, chan, &offsets, ctx, handle); |
852c2936 MD |
2401 | } |
2402 | ||
2403 | /* | |
2404 | * Populate new subbuffer. | |
2405 | */ | |
b5a3dfa5 | 2406 | if (caa_unlikely(offsets.switch_new_start)) |
f27b0770 | 2407 | lib_ring_buffer_switch_new_start(buf, chan, &offsets, ctx, handle); |
852c2936 | 2408 | |
1ad21f70 | 2409 | if (caa_unlikely(offsets.switch_new_end)) |
f27b0770 | 2410 | lib_ring_buffer_switch_new_end(buf, chan, &offsets, ctx, handle); |
1ad21f70 | 2411 | |
8936b6c0 MD |
2412 | ctx_private->slot_size = offsets.size; |
2413 | ctx_private->pre_offset = offsets.begin; | |
2414 | ctx_private->buf_offset = offsets.begin + offsets.pre_header_padding; | |
852c2936 MD |
2415 | return 0; |
2416 | } | |
f645cfa7 | 2417 | |
b07cd987 | 2418 | static |
b5457df5 MD |
2419 | void lib_ring_buffer_vmcore_check_deliver(const struct lttng_ust_ring_buffer_config *config, |
2420 | struct lttng_ust_ring_buffer *buf, | |
b07cd987 MD |
2421 | unsigned long commit_count, |
2422 | unsigned long idx, | |
2423 | struct lttng_ust_shm_handle *handle) | |
2424 | { | |
15500a1b MD |
2425 | struct commit_counters_hot *cc_hot; |
2426 | ||
2427 | if (config->oops != RING_BUFFER_OOPS_CONSISTENCY) | |
2428 | return; | |
2429 | cc_hot = shmp_index(handle, buf->commit_hot, idx); | |
2430 | if (!cc_hot) | |
2431 | return; | |
2432 | v_set(config, &cc_hot->seq, commit_count); | |
b07cd987 MD |
2433 | } |
2434 | ||
9c995331 MD |
2435 | /* |
2436 | * The ring buffer can count events recorded and overwritten per buffer, | |
2437 | * but it is disabled by default due to its performance overhead. | |
2438 | */ | |
2439 | #ifdef LTTNG_RING_BUFFER_COUNT_EVENTS | |
2440 | static | |
b5457df5 MD |
2441 | void deliver_count_events(const struct lttng_ust_ring_buffer_config *config, |
2442 | struct lttng_ust_ring_buffer *buf, | |
9c995331 MD |
2443 | unsigned long idx, |
2444 | struct lttng_ust_shm_handle *handle) | |
2445 | { | |
2446 | v_add(config, subbuffer_get_records_count(config, | |
2447 | &buf->backend, idx, handle), | |
2448 | &buf->records_count); | |
2449 | v_add(config, subbuffer_count_records_overrun(config, | |
2450 | &buf->backend, idx, handle), | |
2451 | &buf->records_overrun); | |
2452 | } | |
2453 | #else /* LTTNG_RING_BUFFER_COUNT_EVENTS */ | |
2454 | static | |
2208d8b5 | 2455 | void deliver_count_events( |
b5457df5 MD |
2456 | const struct lttng_ust_ring_buffer_config *config __attribute__((unused)), |
2457 | struct lttng_ust_ring_buffer *buf __attribute__((unused)), | |
2208d8b5 MJ |
2458 | unsigned long idx __attribute__((unused)), |
2459 | struct lttng_ust_shm_handle *handle __attribute__((unused))) | |
9c995331 MD |
2460 | { |
2461 | } | |
2462 | #endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */ | |
2463 | ||
b5457df5 MD |
2464 | void lib_ring_buffer_check_deliver_slow(const struct lttng_ust_ring_buffer_config *config, |
2465 | struct lttng_ust_ring_buffer *buf, | |
2466 | struct lttng_ust_ring_buffer_channel *chan, | |
b07cd987 MD |
2467 | unsigned long offset, |
2468 | unsigned long commit_count, | |
2469 | unsigned long idx, | |
2470 | struct lttng_ust_shm_handle *handle, | |
f27b0770 | 2471 | const struct lttng_ust_ring_buffer_ctx *ctx) |
b07cd987 MD |
2472 | { |
2473 | unsigned long old_commit_count = commit_count | |
2474 | - chan->backend.subbuf_size; | |
15500a1b | 2475 | struct commit_counters_cold *cc_cold; |
b07cd987 MD |
2476 | |
2477 | /* | |
2478 | * If we succeeded at updating cc_sb below, we are the subbuffer | |
2479 | * writer delivering the subbuffer. Deals with concurrent | |
2480 | * updates of the "cc" value without adding a add_return atomic | |
2481 | * operation to the fast path. | |
2482 | * | |
2483 | * We are doing the delivery in two steps: | |
2484 | * - First, we cmpxchg() cc_sb to the new value | |
2485 | * old_commit_count + 1. This ensures that we are the only | |
2486 | * subbuffer user successfully filling the subbuffer, but we | |
2487 | * do _not_ set the cc_sb value to "commit_count" yet. | |
2488 | * Therefore, other writers that would wrap around the ring | |
2489 | * buffer and try to start writing to our subbuffer would | |
2490 | * have to drop records, because it would appear as | |
2491 | * non-filled. | |
2492 | * We therefore have exclusive access to the subbuffer control | |
2493 | * structures. This mutual exclusion with other writers is | |
2494 | * crucially important to perform record overruns count in | |
2495 | * flight recorder mode locklessly. | |
2496 | * - When we are ready to release the subbuffer (either for | |
2497 | * reading or for overrun by other writers), we simply set the | |
2498 | * cc_sb value to "commit_count" and perform delivery. | |
2499 | * | |
2500 | * The subbuffer size is least 2 bytes (minimum size: 1 page). | |
2501 | * This guarantees that old_commit_count + 1 != commit_count. | |
2502 | */ | |
2503 | ||
2504 | /* | |
2505 | * Order prior updates to reserve count prior to the | |
2506 | * commit_cold cc_sb update. | |
2507 | */ | |
2508 | cmm_smp_wmb(); | |
15500a1b MD |
2509 | cc_cold = shmp_index(handle, buf->commit_cold, idx); |
2510 | if (!cc_cold) | |
2511 | return; | |
2512 | if (caa_likely(v_cmpxchg(config, &cc_cold->cc_sb, | |
b07cd987 MD |
2513 | old_commit_count, old_commit_count + 1) |
2514 | == old_commit_count)) { | |
6c737d05 MD |
2515 | uint64_t *ts_end; |
2516 | ||
b07cd987 MD |
2517 | /* |
2518 | * Start of exclusive subbuffer access. We are | |
2519 | * guaranteed to be the last writer in this subbuffer | |
2520 | * and any other writer trying to access this subbuffer | |
2521 | * in this state is required to drop records. | |
6c737d05 MD |
2522 | * |
2523 | * We can read the ts_end for the current sub-buffer | |
2524 | * which has been saved by the very last space | |
2525 | * reservation for the current sub-buffer. | |
2526 | * | |
2527 | * Order increment of commit counter before reading ts_end. | |
b07cd987 | 2528 | */ |
6c737d05 MD |
2529 | cmm_smp_mb(); |
2530 | ts_end = shmp_index(handle, buf->ts_end, idx); | |
2531 | if (!ts_end) | |
2532 | return; | |
9c995331 | 2533 | deliver_count_events(config, buf, idx, handle); |
6c737d05 | 2534 | config->cb.buffer_end(buf, *ts_end, idx, |
b07cd987 MD |
2535 | lib_ring_buffer_get_data_size(config, |
2536 | buf, | |
2537 | idx, | |
2538 | handle), | |
f27b0770 | 2539 | handle, ctx); |
b07cd987 MD |
2540 | |
2541 | /* | |
2542 | * Increment the packet counter while we have exclusive | |
2543 | * access. | |
2544 | */ | |
2545 | subbuffer_inc_packet_count(config, &buf->backend, idx, handle); | |
2546 | ||
2547 | /* | |
2548 | * Set noref flag and offset for this subbuffer id. | |
2549 | * Contains a memory barrier that ensures counter stores | |
2550 | * are ordered before set noref and offset. | |
2551 | */ | |
2552 | lib_ring_buffer_set_noref_offset(config, &buf->backend, idx, | |
2553 | buf_trunc_val(offset, chan), handle); | |
2554 | ||
2555 | /* | |
2556 | * Order set_noref and record counter updates before the | |
2557 | * end of subbuffer exclusive access. Orders with | |
2558 | * respect to writers coming into the subbuffer after | |
2559 | * wrap around, and also order wrt concurrent readers. | |
2560 | */ | |
2561 | cmm_smp_mb(); | |
2562 | /* End of exclusive subbuffer access */ | |
15500a1b | 2563 | v_set(config, &cc_cold->cc_sb, commit_count); |
b07cd987 MD |
2564 | /* |
2565 | * Order later updates to reserve count after | |
2566 | * the commit cold cc_sb update. | |
2567 | */ | |
2568 | cmm_smp_wmb(); | |
2569 | lib_ring_buffer_vmcore_check_deliver(config, buf, | |
2570 | commit_count, idx, handle); | |
2571 | ||
2572 | /* | |
2573 | * RING_BUFFER_WAKEUP_BY_WRITER wakeup is not lock-free. | |
2574 | */ | |
2575 | if (config->wakeup == RING_BUFFER_WAKEUP_BY_WRITER | |
2576 | && uatomic_read(&buf->active_readers) | |
2577 | && lib_ring_buffer_poll_deliver(config, buf, chan, handle)) { | |
2578 | lib_ring_buffer_wakeup(buf, handle); | |
2579 | } | |
2580 | } | |
2581 | } | |
2582 | ||
f645cfa7 | 2583 | /* |
a9fd951a | 2584 | * Force a read (imply TLS allocation for dlopen) of TLS variables. |
f645cfa7 | 2585 | */ |
a9fd951a | 2586 | void lttng_ringbuffer_alloc_tls(void) |
f645cfa7 | 2587 | { |
742ac92a | 2588 | __asm__ __volatile__ ("" : : "m" (URCU_TLS(lib_ring_buffer_nesting))); |
f645cfa7 | 2589 | } |
03d2d293 MD |
2590 | |
2591 | void lib_ringbuffer_signal_init(void) | |
2592 | { | |
2593 | sigset_t mask; | |
2594 | int ret; | |
2595 | ||
2596 | /* | |
2597 | * Block signal for entire process, so only our thread processes | |
2598 | * it. | |
2599 | */ | |
2600 | rb_setmask(&mask); | |
2601 | ret = pthread_sigmask(SIG_BLOCK, &mask, NULL); | |
2602 | if (ret) { | |
2603 | errno = ret; | |
2604 | PERROR("pthread_sigmask"); | |
2605 | } | |
2606 | } |