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e92f3e28 MD |
1 | #ifndef _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H |
2 | #define _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H | |
852c2936 MD |
3 | |
4 | /* | |
e92f3e28 | 5 | * libringbuffer/backend_internal.h |
852c2936 MD |
6 | * |
7 | * Ring buffer backend (internal helpers). | |
8 | * | |
e92f3e28 MD |
9 | * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
10 | * | |
11 | * This library is free software; you can redistribute it and/or | |
12 | * modify it under the terms of the GNU Lesser General Public | |
13 | * License as published by the Free Software Foundation; only | |
14 | * version 2.1 of the License. | |
15 | * | |
16 | * This library is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
19 | * Lesser General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU Lesser General Public | |
22 | * License along with this library; if not, write to the Free Software | |
23 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
852c2936 MD |
24 | */ |
25 | ||
14641deb MD |
26 | #include <unistd.h> |
27 | #include <urcu/compiler.h> | |
28 | ||
4318ae1b | 29 | #include <lttng/ringbuffer-config.h> |
4931a13e MD |
30 | #include "backend_types.h" |
31 | #include "frontend_types.h" | |
a6352fd4 | 32 | #include "shm.h" |
852c2936 MD |
33 | |
34 | /* Ring buffer backend API presented to the frontend */ | |
35 | ||
36 | /* Ring buffer and channel backend create/free */ | |
37 | ||
4cfec15c | 38 | int lib_ring_buffer_backend_create(struct lttng_ust_lib_ring_buffer_backend *bufb, |
a6352fd4 | 39 | struct channel_backend *chan, int cpu, |
38fae1d3 | 40 | struct lttng_ust_shm_handle *handle, |
1d498196 | 41 | struct shm_object *shmobj); |
852c2936 | 42 | void channel_backend_unregister_notifiers(struct channel_backend *chanb); |
4cfec15c | 43 | void lib_ring_buffer_backend_free(struct lttng_ust_lib_ring_buffer_backend *bufb); |
852c2936 MD |
44 | int channel_backend_init(struct channel_backend *chanb, |
45 | const char *name, | |
4cfec15c | 46 | const struct lttng_ust_lib_ring_buffer_config *config, |
a3f61e7f | 47 | size_t subbuf_size, |
38fae1d3 | 48 | size_t num_subbuf, struct lttng_ust_shm_handle *handle); |
1d498196 | 49 | void channel_backend_free(struct channel_backend *chanb, |
38fae1d3 | 50 | struct lttng_ust_shm_handle *handle); |
852c2936 | 51 | |
4cfec15c | 52 | void lib_ring_buffer_backend_reset(struct lttng_ust_lib_ring_buffer_backend *bufb, |
38fae1d3 | 53 | struct lttng_ust_shm_handle *handle); |
852c2936 MD |
54 | void channel_backend_reset(struct channel_backend *chanb); |
55 | ||
56 | int lib_ring_buffer_backend_init(void); | |
57 | void lib_ring_buffer_backend_exit(void); | |
58 | ||
4cfec15c | 59 | extern void _lib_ring_buffer_write(struct lttng_ust_lib_ring_buffer_backend *bufb, |
852c2936 MD |
60 | size_t offset, const void *src, size_t len, |
61 | ssize_t pagecpy); | |
62 | ||
63 | /* | |
64 | * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be | |
65 | * exchanged atomically. | |
66 | * | |
67 | * Top half word, except lowest bit, belongs to "offset", which is used to keep | |
68 | * to count the produced buffers. For overwrite mode, this provides the | |
69 | * consumer with the capacity to read subbuffers in order, handling the | |
70 | * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit | |
71 | * systems) concurrently with a single execution of get_subbuf (between offset | |
72 | * sampling and subbuffer ID exchange). | |
73 | */ | |
74 | ||
14641deb | 75 | #define HALF_ULONG_BITS (CAA_BITS_PER_LONG >> 1) |
852c2936 MD |
76 | |
77 | #define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1) | |
78 | #define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT) | |
79 | #define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1)) | |
80 | /* | |
81 | * Lowest bit of top word half belongs to noref. Used only for overwrite mode. | |
82 | */ | |
83 | #define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1) | |
84 | #define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT) | |
85 | #define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT | |
86 | /* | |
87 | * In overwrite mode: lowest half of word is used for index. | |
88 | * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit. | |
89 | * In producer-consumer mode: whole word used for index. | |
90 | */ | |
91 | #define SB_ID_INDEX_SHIFT 0 | |
92 | #define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT) | |
93 | #define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1) | |
94 | ||
95 | /* | |
96 | * Construct the subbuffer id from offset, index and noref. Use only the index | |
97 | * for producer-consumer mode (offset and noref are only used in overwrite | |
98 | * mode). | |
99 | */ | |
100 | static inline | |
4cfec15c | 101 | unsigned long subbuffer_id(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
102 | unsigned long offset, unsigned long noref, |
103 | unsigned long index) | |
104 | { | |
105 | if (config->mode == RING_BUFFER_OVERWRITE) | |
106 | return (offset << SB_ID_OFFSET_SHIFT) | |
107 | | (noref << SB_ID_NOREF_SHIFT) | |
108 | | index; | |
109 | else | |
110 | return index; | |
111 | } | |
112 | ||
113 | /* | |
114 | * Compare offset with the offset contained within id. Return 1 if the offset | |
115 | * bits are identical, else 0. | |
116 | */ | |
117 | static inline | |
4cfec15c | 118 | int subbuffer_id_compare_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
119 | unsigned long id, unsigned long offset) |
120 | { | |
121 | return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT); | |
122 | } | |
123 | ||
124 | static inline | |
4cfec15c | 125 | unsigned long subbuffer_id_get_index(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
126 | unsigned long id) |
127 | { | |
128 | if (config->mode == RING_BUFFER_OVERWRITE) | |
129 | return id & SB_ID_INDEX_MASK; | |
130 | else | |
131 | return id; | |
132 | } | |
133 | ||
134 | static inline | |
4cfec15c | 135 | unsigned long subbuffer_id_is_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
136 | unsigned long id) |
137 | { | |
138 | if (config->mode == RING_BUFFER_OVERWRITE) | |
139 | return !!(id & SB_ID_NOREF_MASK); | |
140 | else | |
141 | return 1; | |
142 | } | |
143 | ||
144 | /* | |
145 | * Only used by reader on subbuffer ID it has exclusive access to. No volatile | |
146 | * needed. | |
147 | */ | |
148 | static inline | |
4cfec15c | 149 | void subbuffer_id_set_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
150 | unsigned long *id) |
151 | { | |
152 | if (config->mode == RING_BUFFER_OVERWRITE) | |
153 | *id |= SB_ID_NOREF_MASK; | |
154 | } | |
155 | ||
156 | static inline | |
4cfec15c | 157 | void subbuffer_id_set_noref_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
158 | unsigned long *id, unsigned long offset) |
159 | { | |
160 | unsigned long tmp; | |
161 | ||
162 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
163 | tmp = *id; | |
164 | tmp &= ~SB_ID_OFFSET_MASK; | |
165 | tmp |= offset << SB_ID_OFFSET_SHIFT; | |
166 | tmp |= SB_ID_NOREF_MASK; | |
167 | /* Volatile store, read concurrently by readers. */ | |
14641deb | 168 | CMM_ACCESS_ONCE(*id) = tmp; |
852c2936 MD |
169 | } |
170 | } | |
171 | ||
172 | /* No volatile access, since already used locally */ | |
173 | static inline | |
4cfec15c | 174 | void subbuffer_id_clear_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
175 | unsigned long *id) |
176 | { | |
177 | if (config->mode == RING_BUFFER_OVERWRITE) | |
178 | *id &= ~SB_ID_NOREF_MASK; | |
179 | } | |
180 | ||
181 | /* | |
182 | * For overwrite mode, cap the number of subbuffers per buffer to: | |
183 | * 2^16 on 32-bit architectures | |
184 | * 2^32 on 64-bit architectures | |
185 | * This is required to fit in the index part of the ID. Return 0 on success, | |
186 | * -EPERM on failure. | |
187 | */ | |
188 | static inline | |
4cfec15c | 189 | int subbuffer_id_check_index(const struct lttng_ust_lib_ring_buffer_config *config, |
852c2936 MD |
190 | unsigned long num_subbuf) |
191 | { | |
192 | if (config->mode == RING_BUFFER_OVERWRITE) | |
193 | return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0; | |
194 | else | |
195 | return 0; | |
196 | } | |
197 | ||
198 | static inline | |
4cfec15c MD |
199 | void subbuffer_count_record(const struct lttng_ust_lib_ring_buffer_config *config, |
200 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
38fae1d3 | 201 | unsigned long idx, struct lttng_ust_shm_handle *handle) |
852c2936 MD |
202 | { |
203 | unsigned long sb_bindex; | |
204 | ||
4746ae29 MD |
205 | sb_bindex = subbuffer_id_get_index(config, shmp_index(handle, bufb->buf_wsb, idx)->id); |
206 | v_inc(config, &shmp(handle, shmp_index(handle, bufb->array, sb_bindex)->shmp)->records_commit); | |
852c2936 MD |
207 | } |
208 | ||
209 | /* | |
210 | * Reader has exclusive subbuffer access for record consumption. No need to | |
211 | * perform the decrement atomically. | |
212 | */ | |
213 | static inline | |
4cfec15c MD |
214 | void subbuffer_consume_record(const struct lttng_ust_lib_ring_buffer_config *config, |
215 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
38fae1d3 | 216 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
217 | { |
218 | unsigned long sb_bindex; | |
219 | ||
220 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
1d498196 | 221 | CHAN_WARN_ON(shmp(handle, bufb->chan), |
4746ae29 | 222 | !v_read(config, &shmp(handle, shmp_index(handle, bufb->array, sb_bindex)->shmp)->records_unread)); |
852c2936 | 223 | /* Non-atomic decrement protected by exclusive subbuffer access */ |
4746ae29 | 224 | _v_dec(config, &shmp(handle, shmp_index(handle, bufb->array, sb_bindex)->shmp)->records_unread); |
852c2936 MD |
225 | v_inc(config, &bufb->records_read); |
226 | } | |
227 | ||
228 | static inline | |
229 | unsigned long subbuffer_get_records_count( | |
4cfec15c MD |
230 | const struct lttng_ust_lib_ring_buffer_config *config, |
231 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 232 | unsigned long idx, |
38fae1d3 | 233 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
234 | { |
235 | unsigned long sb_bindex; | |
236 | ||
4746ae29 MD |
237 | sb_bindex = subbuffer_id_get_index(config, shmp_index(handle, bufb->buf_wsb, idx)->id); |
238 | return v_read(config, &shmp(handle, shmp_index(handle, bufb->array, sb_bindex)->shmp)->records_commit); | |
852c2936 MD |
239 | } |
240 | ||
241 | /* | |
242 | * Must be executed at subbuffer delivery when the writer has _exclusive_ | |
243 | * subbuffer access. See ring_buffer_check_deliver() for details. | |
244 | * ring_buffer_get_records_count() must be called to get the records count | |
245 | * before this function, because it resets the records_commit count. | |
246 | */ | |
247 | static inline | |
248 | unsigned long subbuffer_count_records_overrun( | |
4cfec15c MD |
249 | const struct lttng_ust_lib_ring_buffer_config *config, |
250 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 251 | unsigned long idx, |
38fae1d3 | 252 | struct lttng_ust_shm_handle *handle) |
852c2936 | 253 | { |
4cfec15c | 254 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages; |
852c2936 MD |
255 | unsigned long overruns, sb_bindex; |
256 | ||
4746ae29 MD |
257 | sb_bindex = subbuffer_id_get_index(config, shmp_index(handle, bufb->buf_wsb, idx)->id); |
258 | pages = shmp_index(handle, bufb->array, sb_bindex); | |
1d498196 MD |
259 | overruns = v_read(config, &shmp(handle, pages->shmp)->records_unread); |
260 | v_set(config, &shmp(handle, pages->shmp)->records_unread, | |
261 | v_read(config, &shmp(handle, pages->shmp)->records_commit)); | |
262 | v_set(config, &shmp(handle, pages->shmp)->records_commit, 0); | |
852c2936 MD |
263 | |
264 | return overruns; | |
265 | } | |
266 | ||
267 | static inline | |
4cfec15c MD |
268 | void subbuffer_set_data_size(const struct lttng_ust_lib_ring_buffer_config *config, |
269 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
852c2936 | 270 | unsigned long idx, |
1d498196 | 271 | unsigned long data_size, |
38fae1d3 | 272 | struct lttng_ust_shm_handle *handle) |
852c2936 | 273 | { |
4cfec15c | 274 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages; |
852c2936 MD |
275 | unsigned long sb_bindex; |
276 | ||
4746ae29 MD |
277 | sb_bindex = subbuffer_id_get_index(config, shmp_index(handle, bufb->buf_wsb, idx)->id); |
278 | pages = shmp_index(handle, bufb->array, sb_bindex); | |
1d498196 | 279 | shmp(handle, pages->shmp)->data_size = data_size; |
852c2936 MD |
280 | } |
281 | ||
282 | static inline | |
283 | unsigned long subbuffer_get_read_data_size( | |
4cfec15c MD |
284 | const struct lttng_ust_lib_ring_buffer_config *config, |
285 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
38fae1d3 | 286 | struct lttng_ust_shm_handle *handle) |
852c2936 | 287 | { |
4cfec15c | 288 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages; |
852c2936 MD |
289 | unsigned long sb_bindex; |
290 | ||
291 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
4746ae29 | 292 | pages = shmp_index(handle, bufb->array, sb_bindex); |
1d498196 | 293 | return shmp(handle, pages->shmp)->data_size; |
852c2936 MD |
294 | } |
295 | ||
296 | static inline | |
297 | unsigned long subbuffer_get_data_size( | |
4cfec15c MD |
298 | const struct lttng_ust_lib_ring_buffer_config *config, |
299 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 300 | unsigned long idx, |
38fae1d3 | 301 | struct lttng_ust_shm_handle *handle) |
852c2936 | 302 | { |
4cfec15c | 303 | struct lttng_ust_lib_ring_buffer_backend_pages_shmp *pages; |
852c2936 MD |
304 | unsigned long sb_bindex; |
305 | ||
4746ae29 MD |
306 | sb_bindex = subbuffer_id_get_index(config, shmp_index(handle, bufb->buf_wsb, idx)->id); |
307 | pages = shmp_index(handle, bufb->array, sb_bindex); | |
1d498196 | 308 | return shmp(handle, pages->shmp)->data_size; |
852c2936 MD |
309 | } |
310 | ||
311 | /** | |
312 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by | |
313 | * writer. | |
314 | */ | |
315 | static inline | |
4cfec15c MD |
316 | void lib_ring_buffer_clear_noref(const struct lttng_ust_lib_ring_buffer_config *config, |
317 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 318 | unsigned long idx, |
38fae1d3 | 319 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
320 | { |
321 | unsigned long id, new_id; | |
322 | ||
323 | if (config->mode != RING_BUFFER_OVERWRITE) | |
324 | return; | |
325 | ||
326 | /* | |
327 | * Performing a volatile access to read the sb_pages, because we want to | |
328 | * read a coherent version of the pointer and the associated noref flag. | |
329 | */ | |
4746ae29 | 330 | id = CMM_ACCESS_ONCE(shmp_index(handle, bufb->buf_wsb, idx)->id); |
852c2936 MD |
331 | for (;;) { |
332 | /* This check is called on the fast path for each record. */ | |
b5a3dfa5 | 333 | if (caa_likely(!subbuffer_id_is_noref(config, id))) { |
852c2936 MD |
334 | /* |
335 | * Store after load dependency ordering the writes to | |
336 | * the subbuffer after load and test of the noref flag | |
337 | * matches the memory barrier implied by the cmpxchg() | |
338 | * in update_read_sb_index(). | |
339 | */ | |
340 | return; /* Already writing to this buffer */ | |
341 | } | |
342 | new_id = id; | |
343 | subbuffer_id_clear_noref(config, &new_id); | |
4746ae29 | 344 | new_id = uatomic_cmpxchg(&shmp_index(handle, bufb->buf_wsb, idx)->id, id, new_id); |
b5a3dfa5 | 345 | if (caa_likely(new_id == id)) |
852c2936 MD |
346 | break; |
347 | id = new_id; | |
348 | } | |
349 | } | |
350 | ||
351 | /** | |
352 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, | |
353 | * called by writer. | |
354 | */ | |
355 | static inline | |
4cfec15c MD |
356 | void lib_ring_buffer_set_noref_offset(const struct lttng_ust_lib_ring_buffer_config *config, |
357 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
1d498196 | 358 | unsigned long idx, unsigned long offset, |
38fae1d3 | 359 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
360 | { |
361 | if (config->mode != RING_BUFFER_OVERWRITE) | |
362 | return; | |
363 | ||
364 | /* | |
365 | * Because ring_buffer_set_noref() is only called by a single thread | |
366 | * (the one which updated the cc_sb value), there are no concurrent | |
367 | * updates to take care of: other writers have not updated cc_sb, so | |
368 | * they cannot set the noref flag, and concurrent readers cannot modify | |
369 | * the pointer because the noref flag is not set yet. | |
370 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes | |
371 | * to the subbuffer before this set noref operation. | |
372 | * subbuffer_set_noref() uses a volatile store to deal with concurrent | |
373 | * readers of the noref flag. | |
374 | */ | |
1d498196 | 375 | CHAN_WARN_ON(shmp(handle, bufb->chan), |
4746ae29 | 376 | subbuffer_id_is_noref(config, shmp_index(handle, bufb->buf_wsb, idx)->id)); |
852c2936 MD |
377 | /* |
378 | * Memory barrier that ensures counter stores are ordered before set | |
379 | * noref and offset. | |
380 | */ | |
14641deb | 381 | cmm_smp_mb(); |
4746ae29 | 382 | subbuffer_id_set_noref_offset(config, &shmp_index(handle, bufb->buf_wsb, idx)->id, offset); |
852c2936 MD |
383 | } |
384 | ||
385 | /** | |
386 | * update_read_sb_index - Read-side subbuffer index update. | |
387 | */ | |
388 | static inline | |
4cfec15c MD |
389 | int update_read_sb_index(const struct lttng_ust_lib_ring_buffer_config *config, |
390 | struct lttng_ust_lib_ring_buffer_backend *bufb, | |
852c2936 MD |
391 | struct channel_backend *chanb, |
392 | unsigned long consumed_idx, | |
1d498196 | 393 | unsigned long consumed_count, |
38fae1d3 | 394 | struct lttng_ust_shm_handle *handle) |
852c2936 MD |
395 | { |
396 | unsigned long old_id, new_id; | |
397 | ||
398 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
399 | /* | |
400 | * Exchange the target writer subbuffer with our own unused | |
14641deb | 401 | * subbuffer. No need to use CMM_ACCESS_ONCE() here to read the |
852c2936 MD |
402 | * old_wpage, because the value read will be confirmed by the |
403 | * following cmpxchg(). | |
404 | */ | |
4746ae29 | 405 | old_id = shmp_index(handle, bufb->buf_wsb, consumed_idx)->id; |
b5a3dfa5 | 406 | if (caa_unlikely(!subbuffer_id_is_noref(config, old_id))) |
852c2936 MD |
407 | return -EAGAIN; |
408 | /* | |
409 | * Make sure the offset count we are expecting matches the one | |
410 | * indicated by the writer. | |
411 | */ | |
b5a3dfa5 | 412 | if (caa_unlikely(!subbuffer_id_compare_offset(config, old_id, |
852c2936 MD |
413 | consumed_count))) |
414 | return -EAGAIN; | |
1d498196 | 415 | CHAN_WARN_ON(shmp(handle, bufb->chan), |
852c2936 MD |
416 | !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); |
417 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, | |
418 | consumed_count); | |
4746ae29 | 419 | new_id = uatomic_cmpxchg(&shmp_index(handle, bufb->buf_wsb, consumed_idx)->id, old_id, |
852c2936 | 420 | bufb->buf_rsb.id); |
b5a3dfa5 | 421 | if (caa_unlikely(old_id != new_id)) |
852c2936 MD |
422 | return -EAGAIN; |
423 | bufb->buf_rsb.id = new_id; | |
424 | } else { | |
425 | /* No page exchange, use the writer page directly */ | |
4746ae29 | 426 | bufb->buf_rsb.id = shmp_index(handle, bufb->buf_wsb, consumed_idx)->id; |
852c2936 MD |
427 | } |
428 | return 0; | |
429 | } | |
430 | ||
0d4aa2df MD |
431 | #ifndef inline_memcpy |
432 | #define inline_memcpy(dest, src, n) memcpy(dest, src, n) | |
433 | #endif | |
434 | ||
852c2936 MD |
435 | /* |
436 | * Use the architecture-specific memcpy implementation for constant-sized | |
437 | * inputs, but rely on an inline memcpy for length statically unknown. | |
438 | * The function call to memcpy is just way too expensive for a fast path. | |
439 | */ | |
440 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ | |
441 | do { \ | |
442 | size_t __len = (len); \ | |
443 | if (__builtin_constant_p(len)) \ | |
444 | memcpy(dest, src, __len); \ | |
445 | else \ | |
446 | inline_memcpy(dest, src, __len); \ | |
447 | } while (0) | |
448 | ||
b728d87e MD |
449 | /* arch-agnostic implementation */ |
450 | ||
bfd26582 | 451 | static inline int lttng_ust_fls(unsigned int x) |
b728d87e MD |
452 | { |
453 | int r = 32; | |
454 | ||
455 | if (!x) | |
456 | return 0; | |
457 | if (!(x & 0xFFFF0000U)) { | |
458 | x <<= 16; | |
459 | r -= 16; | |
460 | } | |
461 | if (!(x & 0xFF000000U)) { | |
462 | x <<= 8; | |
463 | r -= 8; | |
464 | } | |
465 | if (!(x & 0xF0000000U)) { | |
466 | x <<= 4; | |
467 | r -= 4; | |
468 | } | |
469 | if (!(x & 0xC0000000U)) { | |
470 | x <<= 2; | |
471 | r -= 2; | |
472 | } | |
473 | if (!(x & 0x80000000U)) { | |
474 | x <<= 1; | |
475 | r -= 1; | |
476 | } | |
477 | return r; | |
478 | } | |
479 | ||
480 | static inline int get_count_order(unsigned int count) | |
481 | { | |
482 | int order; | |
483 | ||
bfd26582 | 484 | order = lttng_ust_fls(count) - 1; |
b728d87e MD |
485 | if (count & (count - 1)) |
486 | order++; | |
487 | return order; | |
488 | } | |
489 | ||
e92f3e28 | 490 | #endif /* _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H */ |