Commit | Line | Data |
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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 | ||
a2a1b5ab | 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); | |
a2a1b5ab | 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, | |
a2a1b5ab | 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 | ||
a2a1b5ab | 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 | ||
a2a1b5ab | 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); |
a2a1b5ab | 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); |
a2a1b5ab | 48 | extern void _lib_ring_buffer_strcpy(struct lttng_kernel_ring_buffer_backend *bufb, |
bddf7ce3 | 49 | size_t offset, const char *src, size_t len, int pad); |
959132c9 MD |
50 | extern void _lib_ring_buffer_pstrcpy(struct lttng_kernel_ring_buffer_backend *bufb, |
51 | size_t offset, const char *src, size_t len, int pad); | |
a2a1b5ab | 52 | extern void _lib_ring_buffer_copy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
4ea00e4f | 53 | size_t offset, const void *src, |
bfe529f9 | 54 | size_t len, size_t pagecpy); |
a2a1b5ab | 55 | extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
bddf7ce3 | 56 | size_t offset, const char __user *src, size_t len, int pad); |
959132c9 MD |
57 | extern void _lib_ring_buffer_pstrcpy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
58 | size_t offset, const char __user *src, size_t len, int pad); | |
f3bc08c5 MD |
59 | |
60 | /* | |
61 | * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be | |
62 | * exchanged atomically. | |
63 | * | |
64 | * Top half word, except lowest bit, belongs to "offset", which is used to keep | |
65 | * to count the produced buffers. For overwrite mode, this provides the | |
66 | * consumer with the capacity to read subbuffers in order, handling the | |
67 | * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit | |
68 | * systems) concurrently with a single execution of get_subbuf (between offset | |
69 | * sampling and subbuffer ID exchange). | |
70 | */ | |
71 | ||
72 | #define HALF_ULONG_BITS (BITS_PER_LONG >> 1) | |
73 | ||
74 | #define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1) | |
75 | #define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT) | |
76 | #define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1)) | |
77 | /* | |
78 | * Lowest bit of top word half belongs to noref. Used only for overwrite mode. | |
79 | */ | |
80 | #define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1) | |
81 | #define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT) | |
82 | #define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT | |
83 | /* | |
84 | * In overwrite mode: lowest half of word is used for index. | |
85 | * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit. | |
86 | * In producer-consumer mode: whole word used for index. | |
87 | */ | |
88 | #define SB_ID_INDEX_SHIFT 0 | |
89 | #define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT) | |
90 | #define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1) | |
91 | ||
92 | /* | |
93 | * Construct the subbuffer id from offset, index and noref. Use only the index | |
94 | * for producer-consumer mode (offset and noref are only used in overwrite | |
95 | * mode). | |
96 | */ | |
97 | static inline | |
a2a1b5ab | 98 | unsigned long subbuffer_id(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
99 | unsigned long offset, unsigned long noref, |
100 | unsigned long index) | |
101 | { | |
102 | if (config->mode == RING_BUFFER_OVERWRITE) | |
103 | return (offset << SB_ID_OFFSET_SHIFT) | |
104 | | (noref << SB_ID_NOREF_SHIFT) | |
105 | | index; | |
106 | else | |
107 | return index; | |
108 | } | |
109 | ||
110 | /* | |
111 | * Compare offset with the offset contained within id. Return 1 if the offset | |
112 | * bits are identical, else 0. | |
113 | */ | |
114 | static inline | |
a2a1b5ab | 115 | int subbuffer_id_compare_offset(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
116 | unsigned long id, unsigned long offset) |
117 | { | |
118 | return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT); | |
119 | } | |
120 | ||
121 | static inline | |
a2a1b5ab | 122 | unsigned long subbuffer_id_get_index(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
123 | unsigned long id) |
124 | { | |
125 | if (config->mode == RING_BUFFER_OVERWRITE) | |
126 | return id & SB_ID_INDEX_MASK; | |
127 | else | |
128 | return id; | |
129 | } | |
130 | ||
131 | static inline | |
a2a1b5ab | 132 | unsigned long subbuffer_id_is_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
133 | unsigned long id) |
134 | { | |
135 | if (config->mode == RING_BUFFER_OVERWRITE) | |
136 | return !!(id & SB_ID_NOREF_MASK); | |
137 | else | |
138 | return 1; | |
139 | } | |
140 | ||
141 | /* | |
142 | * Only used by reader on subbuffer ID it has exclusive access to. No volatile | |
143 | * needed. | |
144 | */ | |
145 | static inline | |
a2a1b5ab | 146 | void subbuffer_id_set_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
147 | unsigned long *id) |
148 | { | |
149 | if (config->mode == RING_BUFFER_OVERWRITE) | |
150 | *id |= SB_ID_NOREF_MASK; | |
151 | } | |
152 | ||
153 | static inline | |
a2a1b5ab | 154 | void subbuffer_id_set_noref_offset(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
155 | unsigned long *id, unsigned long offset) |
156 | { | |
157 | unsigned long tmp; | |
158 | ||
159 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
160 | tmp = *id; | |
161 | tmp &= ~SB_ID_OFFSET_MASK; | |
162 | tmp |= offset << SB_ID_OFFSET_SHIFT; | |
163 | tmp |= SB_ID_NOREF_MASK; | |
164 | /* Volatile store, read concurrently by readers. */ | |
a8f2d0c7 | 165 | WRITE_ONCE(*id, tmp); |
f3bc08c5 MD |
166 | } |
167 | } | |
168 | ||
169 | /* No volatile access, since already used locally */ | |
170 | static inline | |
a2a1b5ab | 171 | void subbuffer_id_clear_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
172 | unsigned long *id) |
173 | { | |
174 | if (config->mode == RING_BUFFER_OVERWRITE) | |
175 | *id &= ~SB_ID_NOREF_MASK; | |
176 | } | |
177 | ||
178 | /* | |
179 | * For overwrite mode, cap the number of subbuffers per buffer to: | |
180 | * 2^16 on 32-bit architectures | |
181 | * 2^32 on 64-bit architectures | |
182 | * This is required to fit in the index part of the ID. Return 0 on success, | |
183 | * -EPERM on failure. | |
184 | */ | |
185 | static inline | |
a2a1b5ab | 186 | int subbuffer_id_check_index(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
187 | unsigned long num_subbuf) |
188 | { | |
189 | if (config->mode == RING_BUFFER_OVERWRITE) | |
190 | return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0; | |
191 | else | |
192 | return 0; | |
193 | } | |
194 | ||
85a07c33 | 195 | static inline |
a2a1b5ab | 196 | void lib_ring_buffer_backend_get_pages(const struct lttng_kernel_ring_buffer_config *config, |
e27e4381 | 197 | struct lttng_kernel_ring_buffer_ctx *ctx, |
a2a1b5ab | 198 | struct lttng_kernel_ring_buffer_backend_pages **backend_pages) |
85a07c33 | 199 | { |
a2a1b5ab | 200 | struct lttng_kernel_ring_buffer_backend *bufb = &ctx->priv.buf->backend; |
c7d9db61 MD |
201 | struct channel_backend *chanb = &ctx->priv.chan->backend; |
202 | size_t sbidx, offset = ctx->priv.buf_offset; | |
85a07c33 | 203 | unsigned long sb_bindex, id; |
a2a1b5ab | 204 | struct lttng_kernel_ring_buffer_backend_pages *rpages; |
85a07c33 MD |
205 | |
206 | offset &= chanb->buf_size - 1; | |
207 | sbidx = offset >> chanb->subbuf_size_order; | |
208 | id = bufb->buf_wsb[sbidx].id; | |
209 | sb_bindex = subbuffer_id_get_index(config, id); | |
210 | rpages = bufb->array[sb_bindex]; | |
c7d9db61 | 211 | CHAN_WARN_ON(ctx->priv.chan, |
85a07c33 MD |
212 | config->mode == RING_BUFFER_OVERWRITE |
213 | && subbuffer_id_is_noref(config, id)); | |
214 | *backend_pages = rpages; | |
215 | } | |
216 | ||
217 | /* Get backend pages from cache. */ | |
218 | static inline | |
a2a1b5ab MD |
219 | struct lttng_kernel_ring_buffer_backend_pages * |
220 | lib_ring_buffer_get_backend_pages_from_ctx(const struct lttng_kernel_ring_buffer_config *config, | |
e27e4381 | 221 | struct lttng_kernel_ring_buffer_ctx *ctx) |
85a07c33 | 222 | { |
c7d9db61 | 223 | return ctx->priv.backend_pages; |
85a07c33 MD |
224 | } |
225 | ||
25337cb5 MD |
226 | /* |
227 | * The ring buffer can count events recorded and overwritten per buffer, | |
228 | * but it is disabled by default due to its performance overhead. | |
229 | */ | |
230 | #ifdef LTTNG_RING_BUFFER_COUNT_EVENTS | |
f3bc08c5 | 231 | static inline |
a2a1b5ab MD |
232 | void subbuffer_count_record(const struct lttng_kernel_ring_buffer_config *config, |
233 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
234 | unsigned long idx) |
235 | { | |
236 | unsigned long sb_bindex; | |
237 | ||
238 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
239 | v_inc(config, &bufb->array[sb_bindex]->records_commit); | |
240 | } | |
241 | ||
242 | /* | |
243 | * Reader has exclusive subbuffer access for record consumption. No need to | |
244 | * perform the decrement atomically. | |
245 | */ | |
246 | static inline | |
a2a1b5ab MD |
247 | void subbuffer_consume_record(const struct lttng_kernel_ring_buffer_config *config, |
248 | struct lttng_kernel_ring_buffer_backend *bufb) | |
f3bc08c5 MD |
249 | { |
250 | unsigned long sb_bindex; | |
251 | ||
252 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
253 | CHAN_WARN_ON(bufb->chan, | |
254 | !v_read(config, &bufb->array[sb_bindex]->records_unread)); | |
255 | /* Non-atomic decrement protected by exclusive subbuffer access */ | |
256 | _v_dec(config, &bufb->array[sb_bindex]->records_unread); | |
257 | v_inc(config, &bufb->records_read); | |
258 | } | |
935150de MD |
259 | #else /* LTTNG_RING_BUFFER_COUNT_EVENTS */ |
260 | static inline | |
a2a1b5ab MD |
261 | void subbuffer_count_record(const struct lttng_kernel_ring_buffer_config *config, |
262 | struct lttng_kernel_ring_buffer_backend *bufb, | |
935150de MD |
263 | unsigned long idx) |
264 | { | |
265 | } | |
266 | static inline | |
a2a1b5ab MD |
267 | void subbuffer_consume_record(const struct lttng_kernel_ring_buffer_config *config, |
268 | struct lttng_kernel_ring_buffer_backend *bufb) | |
935150de MD |
269 | { |
270 | } | |
271 | #endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */ | |
f3bc08c5 MD |
272 | |
273 | static inline | |
274 | unsigned long subbuffer_get_records_count( | |
a2a1b5ab MD |
275 | const struct lttng_kernel_ring_buffer_config *config, |
276 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
277 | unsigned long idx) |
278 | { | |
279 | unsigned long sb_bindex; | |
280 | ||
281 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
282 | return v_read(config, &bufb->array[sb_bindex]->records_commit); | |
283 | } | |
284 | ||
285 | /* | |
286 | * Must be executed at subbuffer delivery when the writer has _exclusive_ | |
c68be968 MD |
287 | * subbuffer access. See lib_ring_buffer_check_deliver() for details. |
288 | * lib_ring_buffer_get_records_count() must be called to get the records | |
289 | * count before this function, because it resets the records_commit | |
290 | * count. | |
f3bc08c5 MD |
291 | */ |
292 | static inline | |
293 | unsigned long subbuffer_count_records_overrun( | |
a2a1b5ab MD |
294 | const struct lttng_kernel_ring_buffer_config *config, |
295 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
296 | unsigned long idx) |
297 | { | |
a2a1b5ab | 298 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
299 | unsigned long overruns, sb_bindex; |
300 | ||
301 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
302 | pages = bufb->array[sb_bindex]; | |
303 | overruns = v_read(config, &pages->records_unread); | |
304 | v_set(config, &pages->records_unread, | |
305 | v_read(config, &pages->records_commit)); | |
306 | v_set(config, &pages->records_commit, 0); | |
307 | ||
308 | return overruns; | |
309 | } | |
310 | ||
311 | static inline | |
a2a1b5ab MD |
312 | void subbuffer_set_data_size(const struct lttng_kernel_ring_buffer_config *config, |
313 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
314 | unsigned long idx, |
315 | unsigned long data_size) | |
316 | { | |
a2a1b5ab | 317 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
318 | unsigned long sb_bindex; |
319 | ||
320 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
321 | pages = bufb->array[sb_bindex]; | |
322 | pages->data_size = data_size; | |
323 | } | |
324 | ||
325 | static inline | |
326 | unsigned long subbuffer_get_read_data_size( | |
a2a1b5ab MD |
327 | const struct lttng_kernel_ring_buffer_config *config, |
328 | struct lttng_kernel_ring_buffer_backend *bufb) | |
f3bc08c5 | 329 | { |
a2a1b5ab | 330 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
331 | unsigned long sb_bindex; |
332 | ||
333 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
334 | pages = bufb->array[sb_bindex]; | |
335 | return pages->data_size; | |
336 | } | |
337 | ||
338 | static inline | |
339 | unsigned long subbuffer_get_data_size( | |
a2a1b5ab MD |
340 | const struct lttng_kernel_ring_buffer_config *config, |
341 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
342 | unsigned long idx) |
343 | { | |
a2a1b5ab | 344 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
345 | unsigned long sb_bindex; |
346 | ||
347 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
348 | pages = bufb->array[sb_bindex]; | |
349 | return pages->data_size; | |
350 | } | |
351 | ||
5b3cf4f9 | 352 | static inline |
a2a1b5ab MD |
353 | void subbuffer_inc_packet_count(const struct lttng_kernel_ring_buffer_config *config, |
354 | struct lttng_kernel_ring_buffer_backend *bufb, | |
5b3cf4f9 JD |
355 | unsigned long idx) |
356 | { | |
357 | bufb->buf_cnt[idx].seq_cnt++; | |
358 | } | |
359 | ||
f3bc08c5 MD |
360 | /** |
361 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by | |
362 | * writer. | |
363 | */ | |
364 | static inline | |
a2a1b5ab MD |
365 | void lib_ring_buffer_clear_noref(const struct lttng_kernel_ring_buffer_config *config, |
366 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
367 | unsigned long idx) |
368 | { | |
369 | unsigned long id, new_id; | |
370 | ||
371 | if (config->mode != RING_BUFFER_OVERWRITE) | |
372 | return; | |
373 | ||
374 | /* | |
375 | * Performing a volatile access to read the sb_pages, because we want to | |
376 | * read a coherent version of the pointer and the associated noref flag. | |
377 | */ | |
585e5dcc | 378 | id = LTTNG_READ_ONCE(bufb->buf_wsb[idx].id); |
f3bc08c5 MD |
379 | for (;;) { |
380 | /* This check is called on the fast path for each record. */ | |
381 | if (likely(!subbuffer_id_is_noref(config, id))) { | |
382 | /* | |
383 | * Store after load dependency ordering the writes to | |
384 | * the subbuffer after load and test of the noref flag | |
385 | * matches the memory barrier implied by the cmpxchg() | |
386 | * in update_read_sb_index(). | |
387 | */ | |
388 | return; /* Already writing to this buffer */ | |
389 | } | |
390 | new_id = id; | |
391 | subbuffer_id_clear_noref(config, &new_id); | |
392 | new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id); | |
393 | if (likely(new_id == id)) | |
394 | break; | |
395 | id = new_id; | |
396 | } | |
397 | } | |
398 | ||
399 | /** | |
400 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, | |
401 | * called by writer. | |
402 | */ | |
403 | static inline | |
a2a1b5ab MD |
404 | void lib_ring_buffer_set_noref_offset(const struct lttng_kernel_ring_buffer_config *config, |
405 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
406 | unsigned long idx, unsigned long offset) |
407 | { | |
408 | if (config->mode != RING_BUFFER_OVERWRITE) | |
409 | return; | |
410 | ||
411 | /* | |
412 | * Because ring_buffer_set_noref() is only called by a single thread | |
413 | * (the one which updated the cc_sb value), there are no concurrent | |
414 | * updates to take care of: other writers have not updated cc_sb, so | |
415 | * they cannot set the noref flag, and concurrent readers cannot modify | |
416 | * the pointer because the noref flag is not set yet. | |
417 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes | |
418 | * to the subbuffer before this set noref operation. | |
419 | * subbuffer_set_noref() uses a volatile store to deal with concurrent | |
420 | * readers of the noref flag. | |
421 | */ | |
422 | CHAN_WARN_ON(bufb->chan, | |
423 | subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id)); | |
424 | /* | |
425 | * Memory barrier that ensures counter stores are ordered before set | |
426 | * noref and offset. | |
427 | */ | |
428 | smp_mb(); | |
429 | subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset); | |
430 | } | |
431 | ||
432 | /** | |
433 | * update_read_sb_index - Read-side subbuffer index update. | |
434 | */ | |
435 | static inline | |
a2a1b5ab MD |
436 | int update_read_sb_index(const struct lttng_kernel_ring_buffer_config *config, |
437 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
438 | struct channel_backend *chanb, |
439 | unsigned long consumed_idx, | |
440 | unsigned long consumed_count) | |
441 | { | |
442 | unsigned long old_id, new_id; | |
443 | ||
444 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
445 | /* | |
446 | * Exchange the target writer subbuffer with our own unused | |
a8f2d0c7 | 447 | * subbuffer. No need to use READ_ONCE() here to read the |
f3bc08c5 MD |
448 | * old_wpage, because the value read will be confirmed by the |
449 | * following cmpxchg(). | |
450 | */ | |
451 | old_id = bufb->buf_wsb[consumed_idx].id; | |
452 | if (unlikely(!subbuffer_id_is_noref(config, old_id))) | |
453 | return -EAGAIN; | |
454 | /* | |
455 | * Make sure the offset count we are expecting matches the one | |
456 | * indicated by the writer. | |
457 | */ | |
458 | if (unlikely(!subbuffer_id_compare_offset(config, old_id, | |
459 | consumed_count))) | |
460 | return -EAGAIN; | |
461 | CHAN_WARN_ON(bufb->chan, | |
462 | !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
463 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, | |
464 | consumed_count); | |
465 | new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id, | |
466 | bufb->buf_rsb.id); | |
467 | if (unlikely(old_id != new_id)) | |
468 | return -EAGAIN; | |
469 | bufb->buf_rsb.id = new_id; | |
470 | } else { | |
471 | /* No page exchange, use the writer page directly */ | |
472 | bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id; | |
473 | } | |
474 | return 0; | |
475 | } | |
476 | ||
327177e6 | 477 | static inline __attribute__((always_inline)) |
04707312 | 478 | void lttng_inline_memcpy(void *dest, const void *src, |
327177e6 MD |
479 | unsigned long len) |
480 | { | |
481 | switch (len) { | |
482 | case 1: | |
483 | *(uint8_t *) dest = *(const uint8_t *) src; | |
484 | break; | |
485 | case 2: | |
486 | *(uint16_t *) dest = *(const uint16_t *) src; | |
487 | break; | |
488 | case 4: | |
489 | *(uint32_t *) dest = *(const uint32_t *) src; | |
490 | break; | |
491 | case 8: | |
492 | *(uint64_t *) dest = *(const uint64_t *) src; | |
493 | break; | |
494 | default: | |
495 | inline_memcpy(dest, src, len); | |
496 | } | |
497 | } | |
498 | ||
f3bc08c5 MD |
499 | /* |
500 | * Use the architecture-specific memcpy implementation for constant-sized | |
501 | * inputs, but rely on an inline memcpy for length statically unknown. | |
502 | * The function call to memcpy is just way too expensive for a fast path. | |
503 | */ | |
504 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ | |
505 | do { \ | |
506 | size_t __len = (len); \ | |
507 | if (__builtin_constant_p(len)) \ | |
508 | memcpy(dest, src, __len); \ | |
509 | else \ | |
327177e6 | 510 | lttng_inline_memcpy(dest, src, __len); \ |
f3bc08c5 MD |
511 | } while (0) |
512 | ||
4ea00e4f | 513 | /* |
7b8ea3a5 | 514 | * We use __copy_from_user_inatomic to copy userspace data since we already |
4ea00e4f | 515 | * did the access_ok for the whole range. |
d87a9f03 MD |
516 | * |
517 | * Return 0 if OK, nonzero on error. | |
4ea00e4f JD |
518 | */ |
519 | static inline | |
7b8ea3a5 | 520 | unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest, |
4ea00e4f JD |
521 | const void __user *src, |
522 | unsigned long len) | |
523 | { | |
7b8ea3a5 | 524 | return __copy_from_user_inatomic(dest, src, len); |
4ea00e4f JD |
525 | } |
526 | ||
527 | /* | |
528 | * write len bytes to dest with c | |
529 | */ | |
530 | static inline | |
531 | void lib_ring_buffer_do_memset(char *dest, int c, | |
532 | unsigned long len) | |
533 | { | |
534 | unsigned long i; | |
535 | ||
536 | for (i = 0; i < len; i++) | |
537 | dest[i] = c; | |
538 | } | |
539 | ||
886d51a3 | 540 | #endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */ |