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cleanup: spelling fixes in comments
[lttng-ust.git] / src / common / ringbuffer / backend_internal.h
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1/*
2 * SPDX-License-Identifier: LGPL-2.1-only
3 *
4 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
5 *
6 * Ring buffer backend (internal helpers).
7 */
8
9#ifndef _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H
10#define _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H
11
12#include <stddef.h>
13#include <stdint.h>
14#include <unistd.h>
15#include <urcu/compiler.h>
16
17#include <lttng/ust-ringbuffer-context.h>
18#include "ringbuffer-config.h"
19#include "backend_types.h"
20#include "frontend_types.h"
21#include "shm.h"
22
23/* Ring buffer backend API presented to the frontend */
24
25/* Ring buffer and channel backend create/free */
26
27int lib_ring_buffer_backend_create(struct lttng_ust_ring_buffer_backend *bufb,
28 struct channel_backend *chan,
29 int cpu,
30 struct lttng_ust_shm_handle *handle,
31 struct shm_object *shmobj)
32 __attribute__((visibility("hidden")));
33
34void channel_backend_unregister_notifiers(struct channel_backend *chanb)
35 __attribute__((visibility("hidden")));
36
37void lib_ring_buffer_backend_free(struct lttng_ust_ring_buffer_backend *bufb)
38 __attribute__((visibility("hidden")));
39
40int channel_backend_init(struct channel_backend *chanb,
41 const char *name,
42 const struct lttng_ust_ring_buffer_config *config,
43 size_t subbuf_size,
44 size_t num_subbuf, struct lttng_ust_shm_handle *handle,
45 const int *stream_fds)
46 __attribute__((visibility("hidden")));
47
48void channel_backend_free(struct channel_backend *chanb,
49 struct lttng_ust_shm_handle *handle)
50 __attribute__((visibility("hidden")));
51
52void lib_ring_buffer_backend_reset(struct lttng_ust_ring_buffer_backend *bufb,
53 struct lttng_ust_shm_handle *handle)
54 __attribute__((visibility("hidden")));
55
56void channel_backend_reset(struct channel_backend *chanb)
57 __attribute__((visibility("hidden")));
58
59int lib_ring_buffer_backend_init(void)
60 __attribute__((visibility("hidden")));
61
62void lib_ring_buffer_backend_exit(void)
63 __attribute__((visibility("hidden")));
64
65extern void _lib_ring_buffer_write(struct lttng_ust_ring_buffer_backend *bufb,
66 size_t offset, const void *src, size_t len,
67 ssize_t pagecpy)
68 __attribute__((visibility("hidden")));
69
70/*
71 * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be
72 * exchanged atomically.
73 *
74 * Top half word, except lowest bit, belongs to "offset", which is used to keep
75 * to count the produced buffers. For overwrite mode, this provides the
76 * consumer with the capacity to read subbuffers in order, handling the
77 * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit
78 * systems) concurrently with a single execution of get_subbuf (between offset
79 * sampling and subbuffer ID exchange).
80 */
81
82#define HALF_ULONG_BITS (CAA_BITS_PER_LONG >> 1)
83
84#define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1)
85#define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT)
86#define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1))
87/*
88 * Lowest bit of top word half belongs to noref. Used only for overwrite mode.
89 */
90#define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1)
91#define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT)
92#define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT
93/*
94 * In overwrite mode: lowest half of word is used for index.
95 * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit.
96 * In producer-consumer mode: whole word used for index.
97 */
98#define SB_ID_INDEX_SHIFT 0
99#define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT)
100#define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1)
101
102/*
103 * Construct the subbuffer id from offset, index and noref. Use only the index
104 * for producer-consumer mode (offset and noref are only used in overwrite
105 * mode).
106 */
107static inline
108unsigned long subbuffer_id(const struct lttng_ust_ring_buffer_config *config,
109 unsigned long offset, unsigned long noref,
110 unsigned long index)
111{
112 if (config->mode == RING_BUFFER_OVERWRITE)
113 return (offset << SB_ID_OFFSET_SHIFT)
114 | (noref << SB_ID_NOREF_SHIFT)
115 | index;
116 else
117 return index;
118}
119
120/*
121 * Compare offset with the offset contained within id. Return 1 if the offset
122 * bits are identical, else 0.
123 */
124static inline
125int subbuffer_id_compare_offset(
126 const struct lttng_ust_ring_buffer_config *config __attribute__((unused)),
127 unsigned long id, unsigned long offset)
128{
129 return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT);
130}
131
132static inline
133unsigned long subbuffer_id_get_index(const struct lttng_ust_ring_buffer_config *config,
134 unsigned long id)
135{
136 if (config->mode == RING_BUFFER_OVERWRITE)
137 return id & SB_ID_INDEX_MASK;
138 else
139 return id;
140}
141
142static inline
143unsigned long subbuffer_id_is_noref(const struct lttng_ust_ring_buffer_config *config,
144 unsigned long id)
145{
146 if (config->mode == RING_BUFFER_OVERWRITE)
147 return !!(id & SB_ID_NOREF_MASK);
148 else
149 return 1;
150}
151
152/*
153 * Only used by reader on subbuffer ID it has exclusive access to. No volatile
154 * needed.
155 */
156static inline
157void subbuffer_id_set_noref(const struct lttng_ust_ring_buffer_config *config,
158 unsigned long *id)
159{
160 if (config->mode == RING_BUFFER_OVERWRITE)
161 *id |= SB_ID_NOREF_MASK;
162}
163
164static inline
165void subbuffer_id_set_noref_offset(const struct lttng_ust_ring_buffer_config *config,
166 unsigned long *id, unsigned long offset)
167{
168 unsigned long tmp;
169
170 if (config->mode == RING_BUFFER_OVERWRITE) {
171 tmp = *id;
172 tmp &= ~SB_ID_OFFSET_MASK;
173 tmp |= offset << SB_ID_OFFSET_SHIFT;
174 tmp |= SB_ID_NOREF_MASK;
175 /* Volatile store, read concurrently by readers. */
176 CMM_ACCESS_ONCE(*id) = tmp;
177 }
178}
179
180/* No volatile access, since already used locally */
181static inline
182void subbuffer_id_clear_noref(const struct lttng_ust_ring_buffer_config *config,
183 unsigned long *id)
184{
185 if (config->mode == RING_BUFFER_OVERWRITE)
186 *id &= ~SB_ID_NOREF_MASK;
187}
188
189/*
190 * For overwrite mode, cap the number of subbuffers per buffer to:
191 * 2^16 on 32-bit architectures
192 * 2^32 on 64-bit architectures
193 * This is required to fit in the index part of the ID. Return 0 on success,
194 * -EPERM on failure.
195 */
196static inline
197int subbuffer_id_check_index(const struct lttng_ust_ring_buffer_config *config,
198 unsigned long num_subbuf)
199{
200 if (config->mode == RING_BUFFER_OVERWRITE)
201 return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0;
202 else
203 return 0;
204}
205
206static inline
207int lib_ring_buffer_backend_get_pages(const struct lttng_ust_ring_buffer_config *config,
208 struct lttng_ust_ring_buffer_ctx *ctx,
209 struct lttng_ust_ring_buffer_backend_pages **backend_pages)
210{
211 struct lttng_ust_ring_buffer_ctx_private *ctx_private = ctx->priv;
212 struct lttng_ust_ring_buffer_backend *bufb = &ctx_private->buf->backend;
213 struct channel_backend *chanb = &ctx_private->chan->backend;
214 struct lttng_ust_shm_handle *handle = ctx_private->chan->handle;
215 size_t sbidx;
216 size_t offset = ctx_private->buf_offset;
217 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
218 struct lttng_ust_ring_buffer_backend_pages_shmp *rpages;
219 unsigned long sb_bindex, id;
220 struct lttng_ust_ring_buffer_backend_pages *_backend_pages;
221
222 offset &= chanb->buf_size - 1;
223 sbidx = offset >> chanb->subbuf_size_order;
224 wsb = shmp_index(handle, bufb->buf_wsb, sbidx);
225 if (caa_unlikely(!wsb))
226 return -1;
227 id = wsb->id;
228 sb_bindex = subbuffer_id_get_index(config, id);
229 rpages = shmp_index(handle, bufb->array, sb_bindex);
230 if (caa_unlikely(!rpages))
231 return -1;
232 CHAN_WARN_ON(ctx_private->chan,
233 config->mode == RING_BUFFER_OVERWRITE
234 && subbuffer_id_is_noref(config, id));
235 _backend_pages = shmp(handle, rpages->shmp);
236 if (caa_unlikely(!_backend_pages))
237 return -1;
238 *backend_pages = _backend_pages;
239 return 0;
240}
241
242/* Get backend pages from cache. */
243static inline
244struct lttng_ust_ring_buffer_backend_pages *
245 lib_ring_buffer_get_backend_pages_from_ctx(
246 const struct lttng_ust_ring_buffer_config *config __attribute__((unused)),
247 struct lttng_ust_ring_buffer_ctx *ctx)
248{
249 return ctx->priv->backend_pages;
250}
251
252/*
253 * The ring buffer can count events recorded and overwritten per buffer,
254 * but it is disabled by default due to its performance overhead.
255 */
256#ifdef LTTNG_RING_BUFFER_COUNT_EVENTS
257static inline
258void subbuffer_count_record(const struct lttng_ust_ring_buffer_config *config,
259 const struct lttng_ust_ring_buffer_ctx *ctx,
260 struct lttng_ust_ring_buffer_backend *bufb,
261 unsigned long idx, struct lttng_ust_shm_handle *handle)
262{
263 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
264
265 backend_pages = lib_ring_buffer_get_backend_pages_from_ctx(config, ctx);
266 if (caa_unlikely(!backend_pages)) {
267 if (lib_ring_buffer_backend_get_pages(config, ctx, &backend_pages))
268 return;
269 }
270 v_inc(config, &backend_pages->records_commit);
271}
272#else /* LTTNG_RING_BUFFER_COUNT_EVENTS */
273static inline
274void subbuffer_count_record(const struct lttng_ust_ring_buffer_config *config __attribute__((unused)),
275 const struct lttng_ust_ring_buffer_ctx *ctx __attribute__((unused)),
276 struct lttng_ust_ring_buffer_backend *bufb __attribute__((unused)),
277 unsigned long idx __attribute__((unused)),
278 struct lttng_ust_shm_handle *handle __attribute__((unused)))
279{
280}
281#endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */
282
283/*
284 * Reader has exclusive subbuffer access for record consumption. No need to
285 * perform the decrement atomically.
286 */
287static inline
288void subbuffer_consume_record(const struct lttng_ust_ring_buffer_config *config,
289 struct lttng_ust_ring_buffer_backend *bufb,
290 struct lttng_ust_shm_handle *handle)
291{
292 unsigned long sb_bindex;
293 struct lttng_ust_ring_buffer_channel *chan;
294 struct lttng_ust_ring_buffer_backend_pages_shmp *pages_shmp;
295 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
296
297 sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
298 chan = shmp(handle, bufb->chan);
299 if (!chan)
300 return;
301 pages_shmp = shmp_index(handle, bufb->array, sb_bindex);
302 if (!pages_shmp)
303 return;
304 backend_pages = shmp(handle, pages_shmp->shmp);
305 if (!backend_pages)
306 return;
307 CHAN_WARN_ON(chan, !v_read(config, &backend_pages->records_unread));
308 /* Non-atomic decrement protected by exclusive subbuffer access */
309 _v_dec(config, &backend_pages->records_unread);
310 v_inc(config, &bufb->records_read);
311}
312
313static inline
314unsigned long subbuffer_get_records_count(
315 const struct lttng_ust_ring_buffer_config *config,
316 struct lttng_ust_ring_buffer_backend *bufb,
317 unsigned long idx,
318 struct lttng_ust_shm_handle *handle)
319{
320 unsigned long sb_bindex;
321 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
322 struct lttng_ust_ring_buffer_backend_pages_shmp *rpages;
323 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
324
325 wsb = shmp_index(handle, bufb->buf_wsb, idx);
326 if (!wsb)
327 return 0;
328 sb_bindex = subbuffer_id_get_index(config, wsb->id);
329 rpages = shmp_index(handle, bufb->array, sb_bindex);
330 if (!rpages)
331 return 0;
332 backend_pages = shmp(handle, rpages->shmp);
333 if (!backend_pages)
334 return 0;
335 return v_read(config, &backend_pages->records_commit);
336}
337
338/*
339 * Must be executed at subbuffer delivery when the writer has _exclusive_
340 * subbuffer access. See lib_ring_buffer_check_deliver() for details.
341 * lib_ring_buffer_get_records_count() must be called to get the records
342 * count before this function, because it resets the records_commit
343 * count.
344 */
345static inline
346unsigned long subbuffer_count_records_overrun(
347 const struct lttng_ust_ring_buffer_config *config,
348 struct lttng_ust_ring_buffer_backend *bufb,
349 unsigned long idx,
350 struct lttng_ust_shm_handle *handle)
351{
352 unsigned long overruns, sb_bindex;
353 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
354 struct lttng_ust_ring_buffer_backend_pages_shmp *rpages;
355 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
356
357 wsb = shmp_index(handle, bufb->buf_wsb, idx);
358 if (!wsb)
359 return 0;
360 sb_bindex = subbuffer_id_get_index(config, wsb->id);
361 rpages = shmp_index(handle, bufb->array, sb_bindex);
362 if (!rpages)
363 return 0;
364 backend_pages = shmp(handle, rpages->shmp);
365 if (!backend_pages)
366 return 0;
367 overruns = v_read(config, &backend_pages->records_unread);
368 v_set(config, &backend_pages->records_unread,
369 v_read(config, &backend_pages->records_commit));
370 v_set(config, &backend_pages->records_commit, 0);
371
372 return overruns;
373}
374
375static inline
376void subbuffer_set_data_size(const struct lttng_ust_ring_buffer_config *config,
377 struct lttng_ust_ring_buffer_backend *bufb,
378 unsigned long idx,
379 unsigned long data_size,
380 struct lttng_ust_shm_handle *handle)
381{
382 unsigned long sb_bindex;
383 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
384 struct lttng_ust_ring_buffer_backend_pages_shmp *rpages;
385 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
386
387 wsb = shmp_index(handle, bufb->buf_wsb, idx);
388 if (!wsb)
389 return;
390 sb_bindex = subbuffer_id_get_index(config, wsb->id);
391 rpages = shmp_index(handle, bufb->array, sb_bindex);
392 if (!rpages)
393 return;
394 backend_pages = shmp(handle, rpages->shmp);
395 if (!backend_pages)
396 return;
397 backend_pages->data_size = data_size;
398}
399
400static inline
401unsigned long subbuffer_get_read_data_size(
402 const struct lttng_ust_ring_buffer_config *config,
403 struct lttng_ust_ring_buffer_backend *bufb,
404 struct lttng_ust_shm_handle *handle)
405{
406 unsigned long sb_bindex;
407 struct lttng_ust_ring_buffer_backend_pages_shmp *pages_shmp;
408 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
409
410 sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
411 pages_shmp = shmp_index(handle, bufb->array, sb_bindex);
412 if (!pages_shmp)
413 return 0;
414 backend_pages = shmp(handle, pages_shmp->shmp);
415 if (!backend_pages)
416 return 0;
417 return backend_pages->data_size;
418}
419
420static inline
421unsigned long subbuffer_get_data_size(
422 const struct lttng_ust_ring_buffer_config *config,
423 struct lttng_ust_ring_buffer_backend *bufb,
424 unsigned long idx,
425 struct lttng_ust_shm_handle *handle)
426{
427 unsigned long sb_bindex;
428 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
429 struct lttng_ust_ring_buffer_backend_pages_shmp *rpages;
430 struct lttng_ust_ring_buffer_backend_pages *backend_pages;
431
432 wsb = shmp_index(handle, bufb->buf_wsb, idx);
433 if (!wsb)
434 return 0;
435 sb_bindex = subbuffer_id_get_index(config, wsb->id);
436 rpages = shmp_index(handle, bufb->array, sb_bindex);
437 if (!rpages)
438 return 0;
439 backend_pages = shmp(handle, rpages->shmp);
440 if (!backend_pages)
441 return 0;
442 return backend_pages->data_size;
443}
444
445static inline
446void subbuffer_inc_packet_count(
447 const struct lttng_ust_ring_buffer_config *config __attribute__((unused)),
448 struct lttng_ust_ring_buffer_backend *bufb,
449 unsigned long idx, struct lttng_ust_shm_handle *handle)
450{
451 struct lttng_ust_ring_buffer_backend_counts *counts;
452
453 counts = shmp_index(handle, bufb->buf_cnt, idx);
454 if (!counts)
455 return;
456 counts->seq_cnt++;
457}
458
459/**
460 * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by
461 * writer.
462 */
463static inline
464void lib_ring_buffer_clear_noref(const struct lttng_ust_ring_buffer_config *config,
465 struct lttng_ust_ring_buffer_backend *bufb,
466 unsigned long idx,
467 struct lttng_ust_shm_handle *handle)
468{
469 unsigned long id, new_id;
470 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
471
472 if (config->mode != RING_BUFFER_OVERWRITE)
473 return;
474
475 /*
476 * Performing a volatile access to read the sb_pages, because we want to
477 * read a coherent version of the pointer and the associated noref flag.
478 */
479 wsb = shmp_index(handle, bufb->buf_wsb, idx);
480 if (!wsb)
481 return;
482 id = CMM_ACCESS_ONCE(wsb->id);
483 for (;;) {
484 /* This check is called on the fast path for each record. */
485 if (caa_likely(!subbuffer_id_is_noref(config, id))) {
486 /*
487 * Store after load dependency ordering the writes to
488 * the subbuffer after load and test of the noref flag
489 * matches the memory barrier implied by the cmpxchg()
490 * in update_read_sb_index().
491 */
492 return; /* Already writing to this buffer */
493 }
494 new_id = id;
495 subbuffer_id_clear_noref(config, &new_id);
496 new_id = uatomic_cmpxchg(&wsb->id, id, new_id);
497 if (caa_likely(new_id == id))
498 break;
499 id = new_id;
500 }
501}
502
503/**
504 * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset,
505 * called by writer.
506 */
507static inline
508void lib_ring_buffer_set_noref_offset(const struct lttng_ust_ring_buffer_config *config,
509 struct lttng_ust_ring_buffer_backend *bufb,
510 unsigned long idx, unsigned long offset,
511 struct lttng_ust_shm_handle *handle)
512{
513 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
514 struct lttng_ust_ring_buffer_channel *chan;
515
516 if (config->mode != RING_BUFFER_OVERWRITE)
517 return;
518
519 wsb = shmp_index(handle, bufb->buf_wsb, idx);
520 if (!wsb)
521 return;
522 /*
523 * Because ring_buffer_set_noref() is only called by a single thread
524 * (the one which updated the cc_sb value), there are no concurrent
525 * updates to take care of: other writers have not updated cc_sb, so
526 * they cannot set the noref flag, and concurrent readers cannot modify
527 * the pointer because the noref flag is not set yet.
528 * The smp_wmb() in ring_buffer_commit() takes care of ordering writes
529 * to the subbuffer before this set noref operation.
530 * subbuffer_set_noref() uses a volatile store to deal with concurrent
531 * readers of the noref flag.
532 */
533 chan = shmp(handle, bufb->chan);
534 if (!chan)
535 return;
536 CHAN_WARN_ON(chan, subbuffer_id_is_noref(config, wsb->id));
537 /*
538 * Memory barrier that ensures counter stores are ordered before set
539 * noref and offset.
540 */
541 cmm_smp_mb();
542 subbuffer_id_set_noref_offset(config, &wsb->id, offset);
543}
544
545/**
546 * update_read_sb_index - Read-side subbuffer index update.
547 */
548static inline
549int update_read_sb_index(const struct lttng_ust_ring_buffer_config *config,
550 struct lttng_ust_ring_buffer_backend *bufb,
551 struct channel_backend *chanb __attribute__((unused)),
552 unsigned long consumed_idx,
553 unsigned long consumed_count,
554 struct lttng_ust_shm_handle *handle)
555{
556 struct lttng_ust_ring_buffer_backend_subbuffer *wsb;
557 unsigned long old_id, new_id;
558
559 wsb = shmp_index(handle, bufb->buf_wsb, consumed_idx);
560 if (caa_unlikely(!wsb))
561 return -EPERM;
562
563 if (config->mode == RING_BUFFER_OVERWRITE) {
564 struct lttng_ust_ring_buffer_channel *chan;
565
566 /*
567 * Exchange the target writer subbuffer with our own unused
568 * subbuffer. No need to use CMM_ACCESS_ONCE() here to read the
569 * old_wpage, because the value read will be confirmed by the
570 * following cmpxchg().
571 */
572 old_id = wsb->id;
573 if (caa_unlikely(!subbuffer_id_is_noref(config, old_id)))
574 return -EAGAIN;
575 /*
576 * Make sure the offset count we are expecting matches the one
577 * indicated by the writer.
578 */
579 if (caa_unlikely(!subbuffer_id_compare_offset(config, old_id,
580 consumed_count)))
581 return -EAGAIN;
582 chan = shmp(handle, bufb->chan);
583 if (caa_unlikely(!chan))
584 return -EPERM;
585 CHAN_WARN_ON(chan, !subbuffer_id_is_noref(config, bufb->buf_rsb.id));
586 subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id,
587 consumed_count);
588 new_id = uatomic_cmpxchg(&wsb->id, old_id, bufb->buf_rsb.id);
589 if (caa_unlikely(old_id != new_id))
590 return -EAGAIN;
591 bufb->buf_rsb.id = new_id;
592 } else {
593 /* No page exchange, use the writer page directly */
594 bufb->buf_rsb.id = wsb->id;
595 }
596 return 0;
597}
598
599#ifndef inline_memcpy
600#define inline_memcpy(dest, src, n) memcpy(dest, src, n)
601#endif
602
603static inline
604void lttng_inline_memcpy(void *dest, const void *src,
605 unsigned long len)
606 __attribute__((always_inline));
607static inline
608void lttng_inline_memcpy(void *dest, const void *src,
609 unsigned long len)
610{
611 switch (len) {
612 case 1:
613 *(uint8_t *) dest = *(const uint8_t *) src;
614 break;
615 case 2:
616 *(uint16_t *) dest = *(const uint16_t *) src;
617 break;
618 case 4:
619 *(uint32_t *) dest = *(const uint32_t *) src;
620 break;
621 case 8:
622 *(uint64_t *) dest = *(const uint64_t *) src;
623 break;
624 default:
625 inline_memcpy(dest, src, len);
626 }
627}
628
629/*
630 * Use the architecture-specific memcpy implementation for constant-sized
631 * inputs, but rely on an inline memcpy for length statically unknown.
632 * The function call to memcpy is just way too expensive for a fast path.
633 */
634#define lib_ring_buffer_do_copy(config, dest, src, len) \
635do { \
636 size_t __len = (len); \
637 if (__builtin_constant_p(len)) \
638 memcpy(dest, src, __len); \
639 else \
640 lttng_inline_memcpy(dest, src, __len); \
641} while (0)
642
643/*
644 * write len bytes to dest with c
645 */
646static inline
647void lib_ring_buffer_do_memset(char *dest, char c, unsigned long len)
648{
649 unsigned long i;
650
651 for (i = 0; i < len; i++)
652 dest[i] = c;
653}
654
655/* arch-agnostic implementation */
656
657static inline int lttng_ust_fls(unsigned int x)
658{
659 int r = 32;
660
661 if (!x)
662 return 0;
663 if (!(x & 0xFFFF0000U)) {
664 x <<= 16;
665 r -= 16;
666 }
667 if (!(x & 0xFF000000U)) {
668 x <<= 8;
669 r -= 8;
670 }
671 if (!(x & 0xF0000000U)) {
672 x <<= 4;
673 r -= 4;
674 }
675 if (!(x & 0xC0000000U)) {
676 x <<= 2;
677 r -= 2;
678 }
679 if (!(x & 0x80000000U)) {
680 /* No need to bit shift on last operation */
681 r -= 1;
682 }
683 return r;
684}
685
686static inline int get_count_order(unsigned int count)
687{
688 int order;
689
690 order = lttng_ust_fls(count) - 1;
691 if (count & (count - 1))
692 order++;
693 return order;
694}
695
696#endif /* _LTTNG_RING_BUFFER_BACKEND_INTERNAL_H */
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