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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 | * | |
c0c0989a | 6 | * Ring buffer backend (internal helpers). |
852c2936 MD |
7 | */ |
8 | ||
c0c0989a MJ |
9 | #ifndef _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H |
10 | #define _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H | |
11 | ||
b4051ad8 | 12 | #include <stddef.h> |
fb31eb73 | 13 | #include <stdint.h> |
14641deb MD |
14 | #include <unistd.h> |
15 | #include <urcu/compiler.h> | |
16 | ||
4318ae1b | 17 | #include <lttng/ringbuffer-config.h> |
4931a13e MD |
18 | #include "backend_types.h" |
19 | #include "frontend_types.h" | |
a6352fd4 | 20 | #include "shm.h" |
852c2936 MD |
21 | |
22 | /* Ring buffer backend API presented to the frontend */ | |
23 | ||
24 | /* Ring buffer and channel backend create/free */ | |
25 | ||
ddabe860 | 26 | __attribute__((visibility("hidden"))) |
4cfec15c | 27 | int lib_ring_buffer_backend_create(struct lttng_ust_lib_ring_buffer_backend *bufb, |
a6352fd4 | 28 | struct channel_backend *chan, int cpu, |
38fae1d3 | 29 | struct lttng_ust_shm_handle *handle, |
1d498196 | 30 | struct shm_object *shmobj); |
ddabe860 MJ |
31 | |
32 | __attribute__((visibility("hidden"))) | |
852c2936 | 33 | void channel_backend_unregister_notifiers(struct channel_backend *chanb); |
ddabe860 MJ |
34 | |
35 | __attribute__((visibility("hidden"))) | |
4cfec15c | 36 | void lib_ring_buffer_backend_free(struct lttng_ust_lib_ring_buffer_backend *bufb); |
ddabe860 MJ |
37 | |
38 | __attribute__((visibility("hidden"))) | |
852c2936 MD |
39 | int channel_backend_init(struct channel_backend *chanb, |
40 | const char *name, | |
4cfec15c | 41 | const struct lttng_ust_lib_ring_buffer_config *config, |
a3f61e7f | 42 | size_t subbuf_size, |
a9ff648c | 43 | size_t num_subbuf, struct lttng_ust_shm_handle *handle, |
5ea386c3 | 44 | const int *stream_fds); |
ddabe860 MJ |
45 | |
46 | __attribute__((visibility("hidden"))) | |
1d498196 | 47 | void channel_backend_free(struct channel_backend *chanb, |
38fae1d3 | 48 | struct lttng_ust_shm_handle *handle); |
852c2936 | 49 | |
ddabe860 | 50 | __attribute__((visibility("hidden"))) |
4cfec15c | 51 | void lib_ring_buffer_backend_reset(struct lttng_ust_lib_ring_buffer_backend *bufb, |
38fae1d3 | 52 | struct lttng_ust_shm_handle *handle); |
ddabe860 MJ |
53 | |
54 | __attribute__((visibility("hidden"))) | |
852c2936 MD |
55 | void channel_backend_reset(struct channel_backend *chanb); |
56 | ||
ddabe860 | 57 | __attribute__((visibility("hidden"))) |
852c2936 | 58 | int lib_ring_buffer_backend_init(void); |
ddabe860 MJ |
59 | |
60 | __attribute__((visibility("hidden"))) | |
852c2936 MD |
61 | void lib_ring_buffer_backend_exit(void); |
62 | ||
ddabe860 | 63 | __attribute__((visibility("hidden"))) |
4cfec15c | 64 | extern void _lib_ring_buffer_write(struct lttng_ust_lib_ring_buffer_backend *bufb, |
852c2936 MD |
65 | size_t offset, const void *src, size_t len, |
66 | ssize_t pagecpy); | |
67 | ||
68 | /* | |
69 | * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be | |
70 | * exchanged atomically. | |
71 | * | |
72 | * Top half word, except lowest bit, belongs to "offset", which is used to keep | |
73 | * to count the produced buffers. For overwrite mode, this provides the | |
74 | * consumer with the capacity to read subbuffers in order, handling the | |
75 | * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit | |
76 | * systems) concurrently with a single execution of get_subbuf (between offset | |
77 | * sampling and subbuffer ID exchange). | |
78 | */ | |
79 | ||
14641deb | 80 | #define HALF_ULONG_BITS (CAA_BITS_PER_LONG >> 1) |
852c2936 MD |
81 | |
82 | #define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1) | |
83 | #define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT) | |
84 | #define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1)) | |
85 | /* | |
86 | * Lowest bit of top word half belongs to noref. Used only for overwrite mode. | |
87 | */ | |
88 | #define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1) | |
89 | #define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT) | |
90 | #define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT | |
91 | /* | |
92 | * In overwrite mode: lowest half of word is used for index. | |
93 | * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit. | |
94 | * In producer-consumer mode: whole word used for index. | |
95 | */ | |
96 | #define SB_ID_INDEX_SHIFT 0 | |
97 | #define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT) | |
98 | #define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1) | |
99 | ||
100 | /* | |
101 | * Construct the subbuffer id from offset, index and noref. Use only the index | |
102 | * for producer-consumer mode (offset and noref are only used in overwrite | |
103 | * mode). | |
104 | */ | |
105 | static inline | |
4cfec15c | 106 | unsigned long subbuffer_id(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
107 | unsigned long offset, unsigned long noref, |
108 | unsigned long index) | |
109 | { | |
110 | if (config->mode == RING_BUFFER_OVERWRITE) | |
111 | return (offset << SB_ID_OFFSET_SHIFT) | |
112 | | (noref << SB_ID_NOREF_SHIFT) | |
113 | | index; | |
114 | else | |
115 | return index; | |
116 | } | |
117 | ||
118 | /* | |
119 | * Compare offset with the offset contained within id. Return 1 if the offset | |
120 | * bits are identical, else 0. | |
121 | */ | |
122 | static inline | |
4cfec15c | 123 | int subbuffer_id_compare_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
124 | unsigned long id, unsigned long offset) |
125 | { | |
126 | return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT); | |
127 | } | |
128 | ||
129 | static inline | |
4cfec15c | 130 | unsigned long subbuffer_id_get_index(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
131 | unsigned long id) |
132 | { | |
133 | if (config->mode == RING_BUFFER_OVERWRITE) | |
134 | return id & SB_ID_INDEX_MASK; | |
135 | else | |
136 | return id; | |
137 | } | |
138 | ||
139 | static inline | |
4cfec15c | 140 | unsigned long subbuffer_id_is_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
141 | unsigned long id) |
142 | { | |
143 | if (config->mode == RING_BUFFER_OVERWRITE) | |
144 | return !!(id & SB_ID_NOREF_MASK); | |
145 | else | |
146 | return 1; | |
147 | } | |
148 | ||
149 | /* | |
150 | * Only used by reader on subbuffer ID it has exclusive access to. No volatile | |
151 | * needed. | |
152 | */ | |
153 | static inline | |
4cfec15c | 154 | void subbuffer_id_set_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
155 | unsigned long *id) |
156 | { | |
157 | if (config->mode == RING_BUFFER_OVERWRITE) | |
158 | *id |= SB_ID_NOREF_MASK; | |
159 | } | |
160 | ||
161 | static inline | |
4cfec15c | 162 | void subbuffer_id_set_noref_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
163 | unsigned long *id, unsigned long offset) |
164 | { | |
165 | unsigned long tmp; | |
166 | ||
167 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
168 | tmp = *id; | |
169 | tmp &= ~SB_ID_OFFSET_MASK; | |
170 | tmp |= offset << SB_ID_OFFSET_SHIFT; | |
171 | tmp |= SB_ID_NOREF_MASK; | |
172 | /* Volatile store, read concurrently by readers. */ | |
14641deb | 173 | CMM_ACCESS_ONCE(*id) = tmp; |
852c2936 MD |
174 | } |
175 | } | |
176 | ||
177 | /* No volatile access, since already used locally */ | |
178 | static inline | |
4cfec15c | 179 | void subbuffer_id_clear_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
180 | unsigned long *id) |
181 | { | |
182 | if (config->mode == RING_BUFFER_OVERWRITE) | |
183 | *id &= ~SB_ID_NOREF_MASK; | |
184 | } | |
185 | ||
186 | /* | |
187 | * For overwrite mode, cap the number of subbuffers per buffer to: | |
188 | * 2^16 on 32-bit architectures | |
189 | * 2^32 on 64-bit architectures | |
190 | * This is required to fit in the index part of the ID. Return 0 on success, | |
191 | * -EPERM on failure. | |
192 | */ | |
193 | static inline | |
4cfec15c | 194 | int subbuffer_id_check_index(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
195 | unsigned long num_subbuf) |
196 | { | |
197 | if (config->mode == RING_BUFFER_OVERWRITE) | |
198 | return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0; | |
199 | else | |
200 | return 0; | |
201 | } | |
202 | ||
a3492932 MD |
203 | static inline |
204 | int lib_ring_buffer_backend_get_pages(const struct lttng_ust_lib_ring_buffer_config *config, | |
205 | struct lttng_ust_lib_ring_buffer_ctx *ctx, | |
206 | struct lttng_ust_lib_ring_buffer_backend_pages **backend_pages) | |
207 | { | |
208 | struct lttng_ust_lib_ring_buffer_backend *bufb = &ctx->buf->backend; | |
209 | struct channel_backend *chanb = &ctx->chan->backend; | |
210 | struct lttng_ust_shm_handle *handle = ctx->handle; | |
211 | size_t sbidx; | |
212 | size_t offset = ctx->buf_offset; | |
213 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; | |
214 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
215 | unsigned long sb_bindex, id; | |
216 | struct lttng_ust_lib_ring_buffer_backend_pages *_backend_pages; | |
217 | ||
218 | offset &= chanb->buf_size - 1; | |
219 | sbidx = offset >> chanb->subbuf_size_order; | |
220 | wsb = shmp_index(handle, bufb->buf_wsb, sbidx); | |
221 | if (caa_unlikely(!wsb)) | |
222 | return -1; | |
223 | id = wsb->id; | |
224 | sb_bindex = subbuffer_id_get_index(config, id); | |
225 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
226 | if (caa_unlikely(!rpages)) | |
227 | return -1; | |
228 | CHAN_WARN_ON(ctx->chan, | |
229 | config->mode == RING_BUFFER_OVERWRITE | |
230 | && subbuffer_id_is_noref(config, id)); | |
231 | _backend_pages = shmp(handle, rpages->shmp); | |
232 | if (caa_unlikely(!_backend_pages)) | |
233 | return -1; | |
234 | *backend_pages = _backend_pages; | |
235 | return 0; | |
236 | } | |
237 | ||
238 | /* Get backend pages from cache. */ | |
239 | static inline | |
240 | struct lttng_ust_lib_ring_buffer_backend_pages * | |
241 | lib_ring_buffer_get_backend_pages_from_ctx(const struct lttng_ust_lib_ring_buffer_config *config, | |
242 | struct lttng_ust_lib_ring_buffer_ctx *ctx) | |
243 | { | |
a3492932 MD |
244 | return ctx->backend_pages; |
245 | } | |
246 | ||
9c995331 MD |
247 | /* |
248 | * The ring buffer can count events recorded and overwritten per buffer, | |
249 | * but it is disabled by default due to its performance overhead. | |
250 | */ | |
251 | #ifdef LTTNG_RING_BUFFER_COUNT_EVENTS | |
852c2936 | 252 | static inline |
4cfec15c | 253 | void subbuffer_count_record(const struct lttng_ust_lib_ring_buffer_config *config, |
15500a1b | 254 | const struct lttng_ust_lib_ring_buffer_ctx *ctx, |
4cfec15c | 255 | struct lttng_ust_lib_ring_buffer_backend *bufb, |
38fae1d3 | 256 | unsigned long idx, struct lttng_ust_shm_handle *handle) |
852c2936 | 257 | { |
15500a1b | 258 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; |
852c2936 | 259 | |
15500a1b MD |
260 | backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx); |
261 | if (caa_unlikely(!backend_pages)) { | |
262 | if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages)) | |
263 | return; | |
264 | } | |
265 | v_inc(config, &backend_pages->records_commit); | |
852c2936 | 266 | } |
9c995331 MD |
267 | #else /* LTTNG_RING_BUFFER_COUNT_EVENTS */ |
268 | static inline | |
269 | void subbuffer_count_record(const struct lttng_ust_lib_ring_buffer_config *config, | |
15500a1b | 270 | const struct lttng_ust_lib_ring_buffer_ctx *ctx, |
9c995331 MD |
271 | struct lttng_ust_lib_ring_buffer_backend *bufb, |
272 | unsigned long idx, struct lttng_ust_shm_handle *handle) | |
273 | { | |
274 | } | |
275 | #endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */ | |
852c2936 MD |
276 | |
277 | /* | |
278 | * Reader has exclusive subbuffer access for record consumption. No need to | |
279 | * perform the decrement atomically. | |
280 | */ | |
281 | static inline | |
4cfec15c MD |
282 | void subbuffer_consume_record(const struct lttng_ust_lib_ring_buffer_config *config, |
283 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
38fae1d3 | 284 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
285 | { |
286 | unsigned long sb_bindex; | |
15500a1b MD |
287 | struct channel *chan; |
288 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages_shmp; | |
289 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
852c2936 MD |
290 | |
291 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
15500a1b MD |
292 | chan = shmp(handle, bufb->chan); |
293 | if (!chan) | |
294 | return; | |
295 | pages_shmp = shmp_index(handle, bufb->array, sb_bindex); | |
296 | if (!pages_shmp) | |
297 | return; | |
298 | backend_pages = shmp(handle, pages_shmp->shmp); | |
299 | if (!backend_pages) | |
300 | return; | |
301 | CHAN_WARN_ON(chan, !v_read(config, &backend_pages->records_unread)); | |
852c2936 | 302 | /* Non-atomic decrement protected by exclusive subbuffer access */ |
15500a1b | 303 | _v_dec(config, &backend_pages->records_unread); |
852c2936 MD |
304 | v_inc(config, &bufb->records_read); |
305 | } | |
306 | ||
307 | static inline | |
308 | unsigned long subbuffer_get_records_count( | |
4cfec15c MD |
309 | const struct lttng_ust_lib_ring_buffer_config *config, |
310 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 311 | unsigned long idx, |
38fae1d3 | 312 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
313 | { |
314 | unsigned long sb_bindex; | |
15500a1b MD |
315 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
316 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
317 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
852c2936 | 318 | |
15500a1b MD |
319 | wsb = shmp_index(handle, bufb->buf_wsb, idx); |
320 | if (!wsb) | |
321 | return 0; | |
322 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
323 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
324 | if (!rpages) | |
325 | return 0; | |
326 | backend_pages = shmp(handle, rpages->shmp); | |
327 | if (!backend_pages) | |
328 | return 0; | |
329 | return v_read(config, &backend_pages->records_commit); | |
852c2936 MD |
330 | } |
331 | ||
332 | /* | |
333 | * Must be executed at subbuffer delivery when the writer has _exclusive_ | |
3d1aec25 MD |
334 | * subbuffer access. See lib_ring_buffer_check_deliver() for details. |
335 | * lib_ring_buffer_get_records_count() must be called to get the records | |
336 | * count before this function, because it resets the records_commit | |
337 | * count. | |
852c2936 MD |
338 | */ |
339 | static inline | |
340 | unsigned long subbuffer_count_records_overrun( | |
4cfec15c MD |
341 | const struct lttng_ust_lib_ring_buffer_config *config, |
342 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 343 | unsigned long idx, |
38fae1d3 | 344 | struct lttng_ust_shm_handle *handle) |
852c2936 | 345 | { |
852c2936 | 346 | unsigned long overruns, sb_bindex; |
15500a1b MD |
347 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
348 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
349 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
852c2936 | 350 | |
15500a1b MD |
351 | wsb = shmp_index(handle, bufb->buf_wsb, idx); |
352 | if (!wsb) | |
353 | return 0; | |
354 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
355 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
356 | if (!rpages) | |
357 | return 0; | |
358 | backend_pages = shmp(handle, rpages->shmp); | |
359 | if (!backend_pages) | |
360 | return 0; | |
361 | overruns = v_read(config, &backend_pages->records_unread); | |
362 | v_set(config, &backend_pages->records_unread, | |
363 | v_read(config, &backend_pages->records_commit)); | |
364 | v_set(config, &backend_pages->records_commit, 0); | |
852c2936 MD |
365 | |
366 | return overruns; | |
367 | } | |
368 | ||
369 | static inline | |
4cfec15c MD |
370 | void subbuffer_set_data_size(const struct lttng_ust_lib_ring_buffer_config *config, |
371 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
852c2936 | 372 | unsigned long idx, |
1d498196 | 373 | unsigned long data_size, |
38fae1d3 | 374 | struct lttng_ust_shm_handle *handle) |
852c2936 | 375 | { |
852c2936 | 376 | unsigned long sb_bindex; |
15500a1b MD |
377 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
378 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
379 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
852c2936 | 380 | |
15500a1b MD |
381 | wsb = shmp_index(handle, bufb->buf_wsb, idx); |
382 | if (!wsb) | |
383 | return; | |
384 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
385 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
386 | if (!rpages) | |
387 | return; | |
388 | backend_pages = shmp(handle, rpages->shmp); | |
389 | if (!backend_pages) | |
390 | return; | |
391 | backend_pages->data_size = data_size; | |
852c2936 MD |
392 | } |
393 | ||
394 | static inline | |
395 | unsigned long subbuffer_get_read_data_size( | |
4cfec15c MD |
396 | const struct lttng_ust_lib_ring_buffer_config *config, |
397 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
38fae1d3 | 398 | struct lttng_ust_shm_handle *handle) |
852c2936 | 399 | { |
852c2936 | 400 | unsigned long sb_bindex; |
15500a1b MD |
401 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages_shmp; |
402 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
852c2936 MD |
403 | |
404 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
15500a1b MD |
405 | pages_shmp = shmp_index(handle, bufb->array, sb_bindex); |
406 | if (!pages_shmp) | |
407 | return 0; | |
408 | backend_pages = shmp(handle, pages_shmp->shmp); | |
409 | if (!backend_pages) | |
410 | return 0; | |
411 | return backend_pages->data_size; | |
852c2936 MD |
412 | } |
413 | ||
414 | static inline | |
415 | unsigned long subbuffer_get_data_size( | |
4cfec15c MD |
416 | const struct lttng_ust_lib_ring_buffer_config *config, |
417 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 418 | unsigned long idx, |
38fae1d3 | 419 | struct lttng_ust_shm_handle *handle) |
852c2936 | 420 | { |
852c2936 | 421 | unsigned long sb_bindex; |
15500a1b MD |
422 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
423 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages; | |
424 | struct lttng_ust_lib_ring_buffer_backend_pages *backend_pages; | |
852c2936 | 425 | |
15500a1b MD |
426 | wsb = shmp_index(handle, bufb->buf_wsb, idx); |
427 | if (!wsb) | |
428 | return 0; | |
429 | sb_bindex = subbuffer_id_get_index(config, wsb->id); | |
430 | rpages = shmp_index(handle, bufb->array, sb_bindex); | |
431 | if (!rpages) | |
432 | return 0; | |
433 | backend_pages = shmp(handle, rpages->shmp); | |
434 | if (!backend_pages) | |
435 | return 0; | |
436 | return backend_pages->data_size; | |
852c2936 MD |
437 | } |
438 | ||
1ff31389 JD |
439 | static inline |
440 | void subbuffer_inc_packet_count(const struct lttng_ust_lib_ring_buffer_config *config, | |
441 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
442 | unsigned long idx, struct lttng_ust_shm_handle *handle) | |
443 | { | |
15500a1b MD |
444 | struct lttng_ust_lib_ring_buffer_backend_counts *counts; |
445 | ||
446 | counts = shmp_index(handle, bufb->buf_cnt, idx); | |
447 | if (!counts) | |
448 | return; | |
449 | counts->seq_cnt++; | |
1ff31389 JD |
450 | } |
451 | ||
852c2936 MD |
452 | /** |
453 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by | |
454 | * writer. | |
455 | */ | |
456 | static inline | |
4cfec15c MD |
457 | void lib_ring_buffer_clear_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
458 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 459 | unsigned long idx, |
38fae1d3 | 460 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
461 | { |
462 | unsigned long id, new_id; | |
15500a1b | 463 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
852c2936 MD |
464 | |
465 | if (config->mode != RING_BUFFER_OVERWRITE) | |
466 | return; | |
467 | ||
468 | /* | |
469 | * Performing a volatile access to read the sb_pages, because we want to | |
470 | * read a coherent version of the pointer and the associated noref flag. | |
471 | */ | |
15500a1b MD |
472 | wsb = shmp_index(handle, bufb->buf_wsb, idx); |
473 | if (!wsb) | |
474 | return; | |
475 | id = CMM_ACCESS_ONCE(wsb->id); | |
852c2936 MD |
476 | for (;;) { |
477 | /* This check is called on the fast path for each record. */ | |
b5a3dfa5 | 478 | if (caa_likely(!subbuffer_id_is_noref(config, id))) { |
852c2936 MD |
479 | /* |
480 | * Store after load dependency ordering the writes to | |
481 | * the subbuffer after load and test of the noref flag | |
482 | * matches the memory barrier implied by the cmpxchg() | |
483 | * in update_read_sb_index(). | |
484 | */ | |
485 | return; /* Already writing to this buffer */ | |
486 | } | |
487 | new_id = id; | |
488 | subbuffer_id_clear_noref(config, &new_id); | |
15500a1b | 489 | new_id = uatomic_cmpxchg(&wsb->id, id, new_id); |
b5a3dfa5 | 490 | if (caa_likely(new_id == id)) |
852c2936 MD |
491 | break; |
492 | id = new_id; | |
493 | } | |
494 | } | |
495 | ||
496 | /** | |
497 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, | |
498 | * called by writer. | |
499 | */ | |
500 | static inline | |
4cfec15c MD |
501 | void lib_ring_buffer_set_noref_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
502 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 503 | unsigned long idx, unsigned long offset, |
38fae1d3 | 504 | struct lttng_ust_shm_handle *handle) |
852c2936 | 505 | { |
15500a1b MD |
506 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
507 | struct channel *chan; | |
508 | ||
852c2936 MD |
509 | if (config->mode != RING_BUFFER_OVERWRITE) |
510 | return; | |
511 | ||
15500a1b MD |
512 | wsb = shmp_index(handle, bufb->buf_wsb, idx); |
513 | if (!wsb) | |
514 | return; | |
852c2936 MD |
515 | /* |
516 | * Because ring_buffer_set_noref() is only called by a single thread | |
517 | * (the one which updated the cc_sb value), there are no concurrent | |
518 | * updates to take care of: other writers have not updated cc_sb, so | |
519 | * they cannot set the noref flag, and concurrent readers cannot modify | |
520 | * the pointer because the noref flag is not set yet. | |
521 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes | |
522 | * to the subbuffer before this set noref operation. | |
523 | * subbuffer_set_noref() uses a volatile store to deal with concurrent | |
524 | * readers of the noref flag. | |
525 | */ | |
15500a1b MD |
526 | chan = shmp(handle, bufb->chan); |
527 | if (!chan) | |
528 | return; | |
529 | CHAN_WARN_ON(chan, subbuffer_id_is_noref(config, wsb->id)); | |
852c2936 MD |
530 | /* |
531 | * Memory barrier that ensures counter stores are ordered before set | |
532 | * noref and offset. | |
533 | */ | |
14641deb | 534 | cmm_smp_mb(); |
15500a1b | 535 | subbuffer_id_set_noref_offset(config, &wsb->id, offset); |
852c2936 MD |
536 | } |
537 | ||
538 | /** | |
539 | * update_read_sb_index - Read-side subbuffer index update. | |
540 | */ | |
541 | static inline | |
4cfec15c MD |
542 | int update_read_sb_index(const struct lttng_ust_lib_ring_buffer_config *config, |
543 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
852c2936 MD |
544 | struct channel_backend *chanb, |
545 | unsigned long consumed_idx, | |
1d498196 | 546 | unsigned long consumed_count, |
38fae1d3 | 547 | struct lttng_ust_shm_handle *handle) |
852c2936 | 548 | { |
15500a1b | 549 | struct lttng_ust_lib_ring_buffer_backend_subbuffer *wsb; |
852c2936 MD |
550 | unsigned long old_id, new_id; |
551 | ||
15500a1b MD |
552 | wsb = shmp_index(handle, bufb->buf_wsb, consumed_idx); |
553 | if (caa_unlikely(!wsb)) | |
554 | return -EPERM; | |
555 | ||
852c2936 | 556 | if (config->mode == RING_BUFFER_OVERWRITE) { |
15500a1b MD |
557 | struct channel *chan; |
558 | ||
852c2936 MD |
559 | /* |
560 | * Exchange the target writer subbuffer with our own unused | |
14641deb | 561 | * subbuffer. No need to use CMM_ACCESS_ONCE() here to read the |
852c2936 MD |
562 | * old_wpage, because the value read will be confirmed by the |
563 | * following cmpxchg(). | |
564 | */ | |
15500a1b | 565 | old_id = wsb->id; |
b5a3dfa5 | 566 | if (caa_unlikely(!subbuffer_id_is_noref(config, old_id))) |
852c2936 MD |
567 | return -EAGAIN; |
568 | /* | |
569 | * Make sure the offset count we are expecting matches the one | |
570 | * indicated by the writer. | |
571 | */ | |
b5a3dfa5 | 572 | if (caa_unlikely(!subbuffer_id_compare_offset(config, old_id, |
852c2936 MD |
573 | consumed_count))) |
574 | return -EAGAIN; | |
15500a1b MD |
575 | chan = shmp(handle, bufb->chan); |
576 | if (caa_unlikely(!chan)) | |
577 | return -EPERM; | |
578 | CHAN_WARN_ON(chan, !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
852c2936 MD |
579 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, |
580 | consumed_count); | |
15500a1b | 581 | new_id = uatomic_cmpxchg(&wsb->id, old_id, bufb->buf_rsb.id); |
b5a3dfa5 | 582 | if (caa_unlikely(old_id != new_id)) |
852c2936 MD |
583 | return -EAGAIN; |
584 | bufb->buf_rsb.id = new_id; | |
585 | } else { | |
586 | /* No page exchange, use the writer page directly */ | |
15500a1b | 587 | bufb->buf_rsb.id = wsb->id; |
852c2936 MD |
588 | } |
589 | return 0; | |
590 | } | |
591 | ||
0d4aa2df MD |
592 | #ifndef inline_memcpy |
593 | #define inline_memcpy(dest, src, n) memcpy(dest, src, n) | |
594 | #endif | |
595 | ||
51b8f2fa MD |
596 | static inline __attribute__((always_inline)) |
597 | void lttng_inline_memcpy(void *dest, const void *src, | |
598 | unsigned long len) | |
599 | { | |
600 | switch (len) { | |
601 | case 1: | |
602 | *(uint8_t *) dest = *(const uint8_t *) src; | |
603 | break; | |
604 | case 2: | |
605 | *(uint16_t *) dest = *(const uint16_t *) src; | |
606 | break; | |
607 | case 4: | |
608 | *(uint32_t *) dest = *(const uint32_t *) src; | |
609 | break; | |
610 | case 8: | |
611 | *(uint64_t *) dest = *(const uint64_t *) src; | |
612 | break; | |
613 | default: | |
614 | inline_memcpy(dest, src, len); | |
615 | } | |
616 | } | |
617 | ||
852c2936 MD |
618 | /* |
619 | * Use the architecture-specific memcpy implementation for constant-sized | |
620 | * inputs, but rely on an inline memcpy for length statically unknown. | |
621 | * The function call to memcpy is just way too expensive for a fast path. | |
622 | */ | |
623 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ | |
624 | do { \ | |
625 | size_t __len = (len); \ | |
626 | if (__builtin_constant_p(len)) \ | |
627 | memcpy(dest, src, __len); \ | |
628 | else \ | |
51b8f2fa | 629 | lttng_inline_memcpy(dest, src, __len); \ |
852c2936 MD |
630 | } while (0) |
631 | ||
a44c74d9 MD |
632 | /* |
633 | * write len bytes to dest with c | |
634 | */ | |
635 | static inline | |
636 | void lib_ring_buffer_do_memset(char *dest, int c, unsigned long len) | |
637 | { | |
638 | unsigned long i; | |
639 | ||
640 | for (i = 0; i < len; i++) | |
641 | dest[i] = c; | |
642 | } | |
643 | ||
b728d87e MD |
644 | /* arch-agnostic implementation */ |
645 | ||
bfd26582 | 646 | static inline int lttng_ust_fls(unsigned int x) |
b728d87e MD |
647 | { |
648 | int r = 32; | |
649 | ||
650 | if (!x) | |
651 | return 0; | |
652 | if (!(x & 0xFFFF0000U)) { | |
653 | x <<= 16; | |
654 | r -= 16; | |
655 | } | |
656 | if (!(x & 0xFF000000U)) { | |
657 | x <<= 8; | |
658 | r -= 8; | |
659 | } | |
660 | if (!(x & 0xF0000000U)) { | |
661 | x <<= 4; | |
662 | r -= 4; | |
663 | } | |
664 | if (!(x & 0xC0000000U)) { | |
665 | x <<= 2; | |
666 | r -= 2; | |
667 | } | |
668 | if (!(x & 0x80000000U)) { | |
e2bd33a5 | 669 | /* No need to bit shift on last operation */ |
b728d87e MD |
670 | r -= 1; |
671 | } | |
672 | return r; | |
673 | } | |
674 | ||
675 | static inline int get_count_order(unsigned int count) | |
676 | { | |
677 | int order; | |
678 | ||
bfd26582 | 679 | order = lttng_ust_fls(count) - 1; |
b728d87e MD |
680 | if (count & (count - 1)) |
681 | order++; | |
682 | return order; | |
683 | } | |
684 | ||
e92f3e28 | 685 | #endif /* _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H */ |