Commit | Line | Data |
---|---|---|
b7cdc182 | 1 | /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only) |
9f36eaed | 2 | * |
24591303 | 3 | * ringbuffer/backend_internal.h |
f3bc08c5 MD |
4 | * |
5 | * Ring buffer backend (internal helpers). | |
6 | * | |
886d51a3 | 7 | * Copyright (C) 2008-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
f3bc08c5 MD |
8 | */ |
9 | ||
9f36eaed MJ |
10 | #ifndef _LIB_RING_BUFFER_BACKEND_INTERNAL_H |
11 | #define _LIB_RING_BUFFER_BACKEND_INTERNAL_H | |
12 | ||
a8f2d0c7 | 13 | #include <wrapper/compiler.h> |
24591303 MD |
14 | #include <wrapper/inline_memcpy.h> |
15 | #include <ringbuffer/config.h> | |
16 | #include <ringbuffer/backend_types.h> | |
17 | #include <ringbuffer/frontend_types.h> | |
f3bc08c5 | 18 | #include <linux/string.h> |
4ea00e4f | 19 | #include <linux/uaccess.h> |
f3bc08c5 MD |
20 | |
21 | /* Ring buffer backend API presented to the frontend */ | |
22 | ||
23 | /* Ring buffer and channel backend create/free */ | |
24 | ||
e20c0fec | 25 | int lib_ring_buffer_backend_create(struct lttng_kernel_ring_buffer_backend *bufb, |
f3bc08c5 MD |
26 | struct channel_backend *chan, int cpu); |
27 | void channel_backend_unregister_notifiers(struct channel_backend *chanb); | |
e20c0fec | 28 | void lib_ring_buffer_backend_free(struct lttng_kernel_ring_buffer_backend *bufb); |
f3bc08c5 MD |
29 | int channel_backend_init(struct channel_backend *chanb, |
30 | const char *name, | |
e20c0fec | 31 | const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
32 | void *priv, size_t subbuf_size, |
33 | size_t num_subbuf); | |
34 | void channel_backend_free(struct channel_backend *chanb); | |
35 | ||
e20c0fec | 36 | void lib_ring_buffer_backend_reset(struct lttng_kernel_ring_buffer_backend *bufb); |
f3bc08c5 MD |
37 | void channel_backend_reset(struct channel_backend *chanb); |
38 | ||
39 | int lib_ring_buffer_backend_init(void); | |
40 | void lib_ring_buffer_backend_exit(void); | |
41 | ||
e20c0fec | 42 | extern void _lib_ring_buffer_write(struct lttng_kernel_ring_buffer_backend *bufb, |
f3bc08c5 | 43 | size_t offset, const void *src, size_t len, |
bfe529f9 | 44 | size_t pagecpy); |
e20c0fec | 45 | extern void _lib_ring_buffer_memset(struct lttng_kernel_ring_buffer_backend *bufb, |
4ea00e4f | 46 | size_t offset, int c, size_t len, |
bfe529f9 | 47 | size_t pagecpy); |
e20c0fec | 48 | extern void _lib_ring_buffer_strcpy(struct lttng_kernel_ring_buffer_backend *bufb, |
16f78f3a MD |
49 | size_t offset, const char *src, size_t len, |
50 | size_t pagecpy, int pad); | |
0d1080f4 MD |
51 | extern void _lib_ring_buffer_pstrcpy(struct lttng_kernel_ring_buffer_backend *bufb, |
52 | size_t offset, const char *src, size_t len, int pad); | |
e20c0fec | 53 | extern void _lib_ring_buffer_copy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
4ea00e4f | 54 | size_t offset, const void *src, |
bfe529f9 | 55 | size_t len, size_t pagecpy); |
e20c0fec | 56 | extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
16f78f3a MD |
57 | size_t offset, const char __user *src, size_t len, |
58 | size_t pagecpy, int pad); | |
0d1080f4 MD |
59 | extern void _lib_ring_buffer_pstrcpy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
60 | size_t offset, const char __user *src, size_t len, int pad); | |
f3bc08c5 MD |
61 | |
62 | /* | |
63 | * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be | |
64 | * exchanged atomically. | |
65 | * | |
66 | * Top half word, except lowest bit, belongs to "offset", which is used to keep | |
67 | * to count the produced buffers. For overwrite mode, this provides the | |
68 | * consumer with the capacity to read subbuffers in order, handling the | |
69 | * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit | |
70 | * systems) concurrently with a single execution of get_subbuf (between offset | |
71 | * sampling and subbuffer ID exchange). | |
72 | */ | |
73 | ||
74 | #define HALF_ULONG_BITS (BITS_PER_LONG >> 1) | |
75 | ||
76 | #define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1) | |
77 | #define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT) | |
78 | #define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1)) | |
79 | /* | |
80 | * Lowest bit of top word half belongs to noref. Used only for overwrite mode. | |
81 | */ | |
82 | #define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1) | |
83 | #define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT) | |
84 | #define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT | |
85 | /* | |
86 | * In overwrite mode: lowest half of word is used for index. | |
87 | * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit. | |
88 | * In producer-consumer mode: whole word used for index. | |
89 | */ | |
90 | #define SB_ID_INDEX_SHIFT 0 | |
91 | #define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT) | |
92 | #define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1) | |
93 | ||
94 | /* | |
95 | * Construct the subbuffer id from offset, index and noref. Use only the index | |
96 | * for producer-consumer mode (offset and noref are only used in overwrite | |
97 | * mode). | |
98 | */ | |
99 | static inline | |
e20c0fec | 100 | unsigned long subbuffer_id(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
101 | unsigned long offset, unsigned long noref, |
102 | unsigned long index) | |
103 | { | |
104 | if (config->mode == RING_BUFFER_OVERWRITE) | |
105 | return (offset << SB_ID_OFFSET_SHIFT) | |
106 | | (noref << SB_ID_NOREF_SHIFT) | |
107 | | index; | |
108 | else | |
109 | return index; | |
110 | } | |
111 | ||
112 | /* | |
113 | * Compare offset with the offset contained within id. Return 1 if the offset | |
114 | * bits are identical, else 0. | |
115 | */ | |
116 | static inline | |
e20c0fec | 117 | int subbuffer_id_compare_offset(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
118 | unsigned long id, unsigned long offset) |
119 | { | |
120 | return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT); | |
121 | } | |
122 | ||
123 | static inline | |
e20c0fec | 124 | unsigned long subbuffer_id_get_index(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
125 | unsigned long id) |
126 | { | |
127 | if (config->mode == RING_BUFFER_OVERWRITE) | |
128 | return id & SB_ID_INDEX_MASK; | |
129 | else | |
130 | return id; | |
131 | } | |
132 | ||
133 | static inline | |
e20c0fec | 134 | unsigned long subbuffer_id_is_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
135 | unsigned long id) |
136 | { | |
137 | if (config->mode == RING_BUFFER_OVERWRITE) | |
138 | return !!(id & SB_ID_NOREF_MASK); | |
139 | else | |
140 | return 1; | |
141 | } | |
142 | ||
143 | /* | |
144 | * Only used by reader on subbuffer ID it has exclusive access to. No volatile | |
145 | * needed. | |
146 | */ | |
147 | static inline | |
e20c0fec | 148 | void subbuffer_id_set_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
149 | unsigned long *id) |
150 | { | |
151 | if (config->mode == RING_BUFFER_OVERWRITE) | |
152 | *id |= SB_ID_NOREF_MASK; | |
153 | } | |
154 | ||
155 | static inline | |
e20c0fec | 156 | void subbuffer_id_set_noref_offset(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
157 | unsigned long *id, unsigned long offset) |
158 | { | |
159 | unsigned long tmp; | |
160 | ||
161 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
162 | tmp = *id; | |
163 | tmp &= ~SB_ID_OFFSET_MASK; | |
164 | tmp |= offset << SB_ID_OFFSET_SHIFT; | |
165 | tmp |= SB_ID_NOREF_MASK; | |
166 | /* Volatile store, read concurrently by readers. */ | |
a8f2d0c7 | 167 | WRITE_ONCE(*id, tmp); |
f3bc08c5 MD |
168 | } |
169 | } | |
170 | ||
171 | /* No volatile access, since already used locally */ | |
172 | static inline | |
e20c0fec | 173 | void subbuffer_id_clear_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
174 | unsigned long *id) |
175 | { | |
176 | if (config->mode == RING_BUFFER_OVERWRITE) | |
177 | *id &= ~SB_ID_NOREF_MASK; | |
178 | } | |
179 | ||
180 | /* | |
181 | * For overwrite mode, cap the number of subbuffers per buffer to: | |
182 | * 2^16 on 32-bit architectures | |
183 | * 2^32 on 64-bit architectures | |
184 | * This is required to fit in the index part of the ID. Return 0 on success, | |
185 | * -EPERM on failure. | |
186 | */ | |
187 | static inline | |
e20c0fec | 188 | int subbuffer_id_check_index(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
189 | unsigned long num_subbuf) |
190 | { | |
191 | if (config->mode == RING_BUFFER_OVERWRITE) | |
192 | return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0; | |
193 | else | |
194 | return 0; | |
195 | } | |
196 | ||
85a07c33 | 197 | static inline |
e20c0fec | 198 | void lib_ring_buffer_backend_get_pages(const struct lttng_kernel_ring_buffer_config *config, |
8a57ec02 | 199 | struct lttng_kernel_ring_buffer_ctx *ctx, |
e20c0fec | 200 | struct lttng_kernel_ring_buffer_backend_pages **backend_pages) |
85a07c33 | 201 | { |
e20c0fec | 202 | struct lttng_kernel_ring_buffer_backend *bufb = &ctx->priv.buf->backend; |
b1199bd3 MD |
203 | struct channel_backend *chanb = &ctx->priv.chan->backend; |
204 | size_t sbidx, offset = ctx->priv.buf_offset; | |
85a07c33 | 205 | unsigned long sb_bindex, id; |
e20c0fec | 206 | struct lttng_kernel_ring_buffer_backend_pages *rpages; |
85a07c33 MD |
207 | |
208 | offset &= chanb->buf_size - 1; | |
209 | sbidx = offset >> chanb->subbuf_size_order; | |
210 | id = bufb->buf_wsb[sbidx].id; | |
211 | sb_bindex = subbuffer_id_get_index(config, id); | |
212 | rpages = bufb->array[sb_bindex]; | |
b1199bd3 | 213 | CHAN_WARN_ON(ctx->priv.chan, |
85a07c33 MD |
214 | config->mode == RING_BUFFER_OVERWRITE |
215 | && subbuffer_id_is_noref(config, id)); | |
216 | *backend_pages = rpages; | |
217 | } | |
218 | ||
219 | /* Get backend pages from cache. */ | |
220 | static inline | |
e20c0fec MD |
221 | struct lttng_kernel_ring_buffer_backend_pages * |
222 | lib_ring_buffer_get_backend_pages_from_ctx(const struct lttng_kernel_ring_buffer_config *config, | |
8a57ec02 | 223 | struct lttng_kernel_ring_buffer_ctx *ctx) |
85a07c33 | 224 | { |
b1199bd3 | 225 | return ctx->priv.backend_pages; |
85a07c33 MD |
226 | } |
227 | ||
25337cb5 MD |
228 | /* |
229 | * The ring buffer can count events recorded and overwritten per buffer, | |
230 | * but it is disabled by default due to its performance overhead. | |
231 | */ | |
232 | #ifdef LTTNG_RING_BUFFER_COUNT_EVENTS | |
f3bc08c5 | 233 | static inline |
e20c0fec MD |
234 | void subbuffer_count_record(const struct lttng_kernel_ring_buffer_config *config, |
235 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
236 | unsigned long idx) |
237 | { | |
238 | unsigned long sb_bindex; | |
239 | ||
240 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
241 | v_inc(config, &bufb->array[sb_bindex]->records_commit); | |
242 | } | |
243 | ||
244 | /* | |
245 | * Reader has exclusive subbuffer access for record consumption. No need to | |
246 | * perform the decrement atomically. | |
247 | */ | |
248 | static inline | |
e20c0fec MD |
249 | void subbuffer_consume_record(const struct lttng_kernel_ring_buffer_config *config, |
250 | struct lttng_kernel_ring_buffer_backend *bufb) | |
f3bc08c5 MD |
251 | { |
252 | unsigned long sb_bindex; | |
253 | ||
254 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
255 | CHAN_WARN_ON(bufb->chan, | |
256 | !v_read(config, &bufb->array[sb_bindex]->records_unread)); | |
257 | /* Non-atomic decrement protected by exclusive subbuffer access */ | |
258 | _v_dec(config, &bufb->array[sb_bindex]->records_unread); | |
259 | v_inc(config, &bufb->records_read); | |
260 | } | |
935150de MD |
261 | #else /* LTTNG_RING_BUFFER_COUNT_EVENTS */ |
262 | static inline | |
e20c0fec MD |
263 | void subbuffer_count_record(const struct lttng_kernel_ring_buffer_config *config, |
264 | struct lttng_kernel_ring_buffer_backend *bufb, | |
935150de MD |
265 | unsigned long idx) |
266 | { | |
267 | } | |
268 | static inline | |
e20c0fec MD |
269 | void subbuffer_consume_record(const struct lttng_kernel_ring_buffer_config *config, |
270 | struct lttng_kernel_ring_buffer_backend *bufb) | |
935150de MD |
271 | { |
272 | } | |
273 | #endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */ | |
f3bc08c5 MD |
274 | |
275 | static inline | |
276 | unsigned long subbuffer_get_records_count( | |
e20c0fec MD |
277 | const struct lttng_kernel_ring_buffer_config *config, |
278 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
279 | unsigned long idx) |
280 | { | |
281 | unsigned long sb_bindex; | |
282 | ||
283 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
284 | return v_read(config, &bufb->array[sb_bindex]->records_commit); | |
285 | } | |
286 | ||
287 | /* | |
288 | * Must be executed at subbuffer delivery when the writer has _exclusive_ | |
c68be968 MD |
289 | * subbuffer access. See lib_ring_buffer_check_deliver() for details. |
290 | * lib_ring_buffer_get_records_count() must be called to get the records | |
291 | * count before this function, because it resets the records_commit | |
292 | * count. | |
f3bc08c5 MD |
293 | */ |
294 | static inline | |
295 | unsigned long subbuffer_count_records_overrun( | |
e20c0fec MD |
296 | const struct lttng_kernel_ring_buffer_config *config, |
297 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
298 | unsigned long idx) |
299 | { | |
e20c0fec | 300 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
301 | unsigned long overruns, sb_bindex; |
302 | ||
303 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
304 | pages = bufb->array[sb_bindex]; | |
305 | overruns = v_read(config, &pages->records_unread); | |
306 | v_set(config, &pages->records_unread, | |
307 | v_read(config, &pages->records_commit)); | |
308 | v_set(config, &pages->records_commit, 0); | |
309 | ||
310 | return overruns; | |
311 | } | |
312 | ||
313 | static inline | |
e20c0fec MD |
314 | void subbuffer_set_data_size(const struct lttng_kernel_ring_buffer_config *config, |
315 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
316 | unsigned long idx, |
317 | unsigned long data_size) | |
318 | { | |
e20c0fec | 319 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
320 | unsigned long sb_bindex; |
321 | ||
322 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
323 | pages = bufb->array[sb_bindex]; | |
324 | pages->data_size = data_size; | |
325 | } | |
326 | ||
327 | static inline | |
328 | unsigned long subbuffer_get_read_data_size( | |
e20c0fec MD |
329 | const struct lttng_kernel_ring_buffer_config *config, |
330 | struct lttng_kernel_ring_buffer_backend *bufb) | |
f3bc08c5 | 331 | { |
e20c0fec | 332 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
333 | unsigned long sb_bindex; |
334 | ||
335 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
336 | pages = bufb->array[sb_bindex]; | |
337 | return pages->data_size; | |
338 | } | |
339 | ||
340 | static inline | |
341 | unsigned long subbuffer_get_data_size( | |
e20c0fec MD |
342 | const struct lttng_kernel_ring_buffer_config *config, |
343 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
344 | unsigned long idx) |
345 | { | |
e20c0fec | 346 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
347 | unsigned long sb_bindex; |
348 | ||
349 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
350 | pages = bufb->array[sb_bindex]; | |
351 | return pages->data_size; | |
352 | } | |
353 | ||
5b3cf4f9 | 354 | static inline |
e20c0fec MD |
355 | void subbuffer_inc_packet_count(const struct lttng_kernel_ring_buffer_config *config, |
356 | struct lttng_kernel_ring_buffer_backend *bufb, | |
5b3cf4f9 JD |
357 | unsigned long idx) |
358 | { | |
359 | bufb->buf_cnt[idx].seq_cnt++; | |
360 | } | |
361 | ||
f3bc08c5 MD |
362 | /** |
363 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by | |
364 | * writer. | |
365 | */ | |
366 | static inline | |
e20c0fec MD |
367 | void lib_ring_buffer_clear_noref(const struct lttng_kernel_ring_buffer_config *config, |
368 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
369 | unsigned long idx) |
370 | { | |
371 | unsigned long id, new_id; | |
372 | ||
373 | if (config->mode != RING_BUFFER_OVERWRITE) | |
374 | return; | |
375 | ||
376 | /* | |
377 | * Performing a volatile access to read the sb_pages, because we want to | |
378 | * read a coherent version of the pointer and the associated noref flag. | |
379 | */ | |
585e5dcc | 380 | id = LTTNG_READ_ONCE(bufb->buf_wsb[idx].id); |
f3bc08c5 MD |
381 | for (;;) { |
382 | /* This check is called on the fast path for each record. */ | |
383 | if (likely(!subbuffer_id_is_noref(config, id))) { | |
384 | /* | |
385 | * Store after load dependency ordering the writes to | |
386 | * the subbuffer after load and test of the noref flag | |
387 | * matches the memory barrier implied by the cmpxchg() | |
388 | * in update_read_sb_index(). | |
389 | */ | |
390 | return; /* Already writing to this buffer */ | |
391 | } | |
392 | new_id = id; | |
393 | subbuffer_id_clear_noref(config, &new_id); | |
394 | new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id); | |
395 | if (likely(new_id == id)) | |
396 | break; | |
397 | id = new_id; | |
398 | } | |
399 | } | |
400 | ||
401 | /** | |
402 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, | |
403 | * called by writer. | |
404 | */ | |
405 | static inline | |
e20c0fec MD |
406 | void lib_ring_buffer_set_noref_offset(const struct lttng_kernel_ring_buffer_config *config, |
407 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
408 | unsigned long idx, unsigned long offset) |
409 | { | |
410 | if (config->mode != RING_BUFFER_OVERWRITE) | |
411 | return; | |
412 | ||
413 | /* | |
414 | * Because ring_buffer_set_noref() is only called by a single thread | |
415 | * (the one which updated the cc_sb value), there are no concurrent | |
416 | * updates to take care of: other writers have not updated cc_sb, so | |
417 | * they cannot set the noref flag, and concurrent readers cannot modify | |
418 | * the pointer because the noref flag is not set yet. | |
419 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes | |
420 | * to the subbuffer before this set noref operation. | |
421 | * subbuffer_set_noref() uses a volatile store to deal with concurrent | |
422 | * readers of the noref flag. | |
423 | */ | |
424 | CHAN_WARN_ON(bufb->chan, | |
425 | subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id)); | |
426 | /* | |
427 | * Memory barrier that ensures counter stores are ordered before set | |
428 | * noref and offset. | |
429 | */ | |
430 | smp_mb(); | |
431 | subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset); | |
432 | } | |
433 | ||
434 | /** | |
435 | * update_read_sb_index - Read-side subbuffer index update. | |
436 | */ | |
437 | static inline | |
e20c0fec MD |
438 | int update_read_sb_index(const struct lttng_kernel_ring_buffer_config *config, |
439 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
440 | struct channel_backend *chanb, |
441 | unsigned long consumed_idx, | |
442 | unsigned long consumed_count) | |
443 | { | |
444 | unsigned long old_id, new_id; | |
445 | ||
446 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
447 | /* | |
448 | * Exchange the target writer subbuffer with our own unused | |
a8f2d0c7 | 449 | * subbuffer. No need to use READ_ONCE() here to read the |
f3bc08c5 MD |
450 | * old_wpage, because the value read will be confirmed by the |
451 | * following cmpxchg(). | |
452 | */ | |
453 | old_id = bufb->buf_wsb[consumed_idx].id; | |
454 | if (unlikely(!subbuffer_id_is_noref(config, old_id))) | |
455 | return -EAGAIN; | |
456 | /* | |
457 | * Make sure the offset count we are expecting matches the one | |
458 | * indicated by the writer. | |
459 | */ | |
460 | if (unlikely(!subbuffer_id_compare_offset(config, old_id, | |
461 | consumed_count))) | |
462 | return -EAGAIN; | |
463 | CHAN_WARN_ON(bufb->chan, | |
464 | !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
465 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, | |
466 | consumed_count); | |
467 | new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id, | |
468 | bufb->buf_rsb.id); | |
469 | if (unlikely(old_id != new_id)) | |
470 | return -EAGAIN; | |
471 | bufb->buf_rsb.id = new_id; | |
472 | } else { | |
473 | /* No page exchange, use the writer page directly */ | |
474 | bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id; | |
475 | } | |
476 | return 0; | |
477 | } | |
478 | ||
327177e6 | 479 | static inline __attribute__((always_inline)) |
04707312 | 480 | void lttng_inline_memcpy(void *dest, const void *src, |
327177e6 MD |
481 | unsigned long len) |
482 | { | |
483 | switch (len) { | |
484 | case 1: | |
485 | *(uint8_t *) dest = *(const uint8_t *) src; | |
486 | break; | |
487 | case 2: | |
488 | *(uint16_t *) dest = *(const uint16_t *) src; | |
489 | break; | |
490 | case 4: | |
491 | *(uint32_t *) dest = *(const uint32_t *) src; | |
492 | break; | |
493 | case 8: | |
494 | *(uint64_t *) dest = *(const uint64_t *) src; | |
495 | break; | |
496 | default: | |
497 | inline_memcpy(dest, src, len); | |
498 | } | |
499 | } | |
500 | ||
f3bc08c5 MD |
501 | /* |
502 | * Use the architecture-specific memcpy implementation for constant-sized | |
503 | * inputs, but rely on an inline memcpy for length statically unknown. | |
504 | * The function call to memcpy is just way too expensive for a fast path. | |
505 | */ | |
506 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ | |
507 | do { \ | |
508 | size_t __len = (len); \ | |
509 | if (__builtin_constant_p(len)) \ | |
510 | memcpy(dest, src, __len); \ | |
511 | else \ | |
327177e6 | 512 | lttng_inline_memcpy(dest, src, __len); \ |
f3bc08c5 MD |
513 | } while (0) |
514 | ||
4ea00e4f | 515 | /* |
7b8ea3a5 | 516 | * We use __copy_from_user_inatomic to copy userspace data since we already |
4ea00e4f | 517 | * did the access_ok for the whole range. |
d87a9f03 MD |
518 | * |
519 | * Return 0 if OK, nonzero on error. | |
4ea00e4f JD |
520 | */ |
521 | static inline | |
7b8ea3a5 | 522 | unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest, |
4ea00e4f JD |
523 | const void __user *src, |
524 | unsigned long len) | |
525 | { | |
7b8ea3a5 | 526 | return __copy_from_user_inatomic(dest, src, len); |
4ea00e4f JD |
527 | } |
528 | ||
529 | /* | |
530 | * write len bytes to dest with c | |
531 | */ | |
532 | static inline | |
533 | void lib_ring_buffer_do_memset(char *dest, int c, | |
534 | unsigned long len) | |
535 | { | |
536 | unsigned long i; | |
537 | ||
538 | for (i = 0; i < len; i++) | |
539 | dest[i] = c; | |
540 | } | |
541 | ||
886d51a3 | 542 | #endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */ |