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 | ||
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, |
4774817f | 43 | size_t offset, const void *src, size_t len); |
e20c0fec | 44 | extern void _lib_ring_buffer_memset(struct lttng_kernel_ring_buffer_backend *bufb, |
4774817f | 45 | size_t offset, int c, size_t len); |
e20c0fec | 46 | extern void _lib_ring_buffer_strcpy(struct lttng_kernel_ring_buffer_backend *bufb, |
e5f1eb9a | 47 | size_t offset, const char *src, size_t len, int pad); |
0d1080f4 MD |
48 | extern void _lib_ring_buffer_pstrcpy(struct lttng_kernel_ring_buffer_backend *bufb, |
49 | size_t offset, const char *src, size_t len, int pad); | |
e20c0fec | 50 | extern void _lib_ring_buffer_copy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
4774817f | 51 | size_t offset, const void __user *src, size_t len); |
e20c0fec | 52 | extern void _lib_ring_buffer_strcpy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
e5f1eb9a | 53 | size_t offset, const char __user *src, size_t len, int pad); |
0d1080f4 MD |
54 | extern void _lib_ring_buffer_pstrcpy_from_user_inatomic(struct lttng_kernel_ring_buffer_backend *bufb, |
55 | size_t offset, const char __user *src, size_t len, int pad); | |
f3bc08c5 MD |
56 | |
57 | /* | |
58 | * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be | |
59 | * exchanged atomically. | |
60 | * | |
61 | * Top half word, except lowest bit, belongs to "offset", which is used to keep | |
62 | * to count the produced buffers. For overwrite mode, this provides the | |
63 | * consumer with the capacity to read subbuffers in order, handling the | |
64 | * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit | |
65 | * systems) concurrently with a single execution of get_subbuf (between offset | |
66 | * sampling and subbuffer ID exchange). | |
67 | */ | |
68 | ||
69 | #define HALF_ULONG_BITS (BITS_PER_LONG >> 1) | |
70 | ||
71 | #define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1) | |
72 | #define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT) | |
73 | #define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1)) | |
74 | /* | |
75 | * Lowest bit of top word half belongs to noref. Used only for overwrite mode. | |
76 | */ | |
77 | #define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1) | |
78 | #define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT) | |
79 | #define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT | |
80 | /* | |
81 | * In overwrite mode: lowest half of word is used for index. | |
82 | * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit. | |
83 | * In producer-consumer mode: whole word used for index. | |
84 | */ | |
85 | #define SB_ID_INDEX_SHIFT 0 | |
86 | #define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT) | |
87 | #define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1) | |
88 | ||
89 | /* | |
90 | * Construct the subbuffer id from offset, index and noref. Use only the index | |
91 | * for producer-consumer mode (offset and noref are only used in overwrite | |
92 | * mode). | |
93 | */ | |
94 | static inline | |
e20c0fec | 95 | unsigned long subbuffer_id(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
96 | unsigned long offset, unsigned long noref, |
97 | unsigned long index) | |
98 | { | |
99 | if (config->mode == RING_BUFFER_OVERWRITE) | |
100 | return (offset << SB_ID_OFFSET_SHIFT) | |
101 | | (noref << SB_ID_NOREF_SHIFT) | |
102 | | index; | |
103 | else | |
104 | return index; | |
105 | } | |
106 | ||
107 | /* | |
108 | * Compare offset with the offset contained within id. Return 1 if the offset | |
109 | * bits are identical, else 0. | |
110 | */ | |
111 | static inline | |
e20c0fec | 112 | int subbuffer_id_compare_offset(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
113 | unsigned long id, unsigned long offset) |
114 | { | |
115 | return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT); | |
116 | } | |
117 | ||
118 | static inline | |
e20c0fec | 119 | unsigned long subbuffer_id_get_index(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
120 | unsigned long id) |
121 | { | |
122 | if (config->mode == RING_BUFFER_OVERWRITE) | |
123 | return id & SB_ID_INDEX_MASK; | |
124 | else | |
125 | return id; | |
126 | } | |
127 | ||
128 | static inline | |
e20c0fec | 129 | unsigned long subbuffer_id_is_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
130 | unsigned long id) |
131 | { | |
132 | if (config->mode == RING_BUFFER_OVERWRITE) | |
133 | return !!(id & SB_ID_NOREF_MASK); | |
134 | else | |
135 | return 1; | |
136 | } | |
137 | ||
138 | /* | |
139 | * Only used by reader on subbuffer ID it has exclusive access to. No volatile | |
140 | * needed. | |
141 | */ | |
142 | static inline | |
e20c0fec | 143 | void subbuffer_id_set_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
144 | unsigned long *id) |
145 | { | |
146 | if (config->mode == RING_BUFFER_OVERWRITE) | |
147 | *id |= SB_ID_NOREF_MASK; | |
148 | } | |
149 | ||
150 | static inline | |
e20c0fec | 151 | void subbuffer_id_set_noref_offset(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
152 | unsigned long *id, unsigned long offset) |
153 | { | |
154 | unsigned long tmp; | |
155 | ||
156 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
157 | tmp = *id; | |
158 | tmp &= ~SB_ID_OFFSET_MASK; | |
159 | tmp |= offset << SB_ID_OFFSET_SHIFT; | |
160 | tmp |= SB_ID_NOREF_MASK; | |
161 | /* Volatile store, read concurrently by readers. */ | |
a8f2d0c7 | 162 | WRITE_ONCE(*id, tmp); |
f3bc08c5 MD |
163 | } |
164 | } | |
165 | ||
166 | /* No volatile access, since already used locally */ | |
167 | static inline | |
e20c0fec | 168 | void subbuffer_id_clear_noref(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
169 | unsigned long *id) |
170 | { | |
171 | if (config->mode == RING_BUFFER_OVERWRITE) | |
172 | *id &= ~SB_ID_NOREF_MASK; | |
173 | } | |
174 | ||
175 | /* | |
176 | * For overwrite mode, cap the number of subbuffers per buffer to: | |
177 | * 2^16 on 32-bit architectures | |
178 | * 2^32 on 64-bit architectures | |
179 | * This is required to fit in the index part of the ID. Return 0 on success, | |
180 | * -EPERM on failure. | |
181 | */ | |
182 | static inline | |
e20c0fec | 183 | int subbuffer_id_check_index(const struct lttng_kernel_ring_buffer_config *config, |
f3bc08c5 MD |
184 | unsigned long num_subbuf) |
185 | { | |
186 | if (config->mode == RING_BUFFER_OVERWRITE) | |
187 | return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0; | |
188 | else | |
189 | return 0; | |
190 | } | |
191 | ||
85a07c33 | 192 | static inline |
e20c0fec | 193 | void lib_ring_buffer_backend_get_pages(const struct lttng_kernel_ring_buffer_config *config, |
8a57ec02 | 194 | struct lttng_kernel_ring_buffer_ctx *ctx, |
e20c0fec | 195 | struct lttng_kernel_ring_buffer_backend_pages **backend_pages) |
85a07c33 | 196 | { |
e20c0fec | 197 | struct lttng_kernel_ring_buffer_backend *bufb = &ctx->priv.buf->backend; |
b1199bd3 MD |
198 | struct channel_backend *chanb = &ctx->priv.chan->backend; |
199 | size_t sbidx, offset = ctx->priv.buf_offset; | |
85a07c33 | 200 | unsigned long sb_bindex, id; |
e20c0fec | 201 | struct lttng_kernel_ring_buffer_backend_pages *rpages; |
85a07c33 MD |
202 | |
203 | offset &= chanb->buf_size - 1; | |
204 | sbidx = offset >> chanb->subbuf_size_order; | |
205 | id = bufb->buf_wsb[sbidx].id; | |
206 | sb_bindex = subbuffer_id_get_index(config, id); | |
207 | rpages = bufb->array[sb_bindex]; | |
b1199bd3 | 208 | CHAN_WARN_ON(ctx->priv.chan, |
85a07c33 MD |
209 | config->mode == RING_BUFFER_OVERWRITE |
210 | && subbuffer_id_is_noref(config, id)); | |
211 | *backend_pages = rpages; | |
212 | } | |
213 | ||
214 | /* Get backend pages from cache. */ | |
215 | static inline | |
e20c0fec MD |
216 | struct lttng_kernel_ring_buffer_backend_pages * |
217 | lib_ring_buffer_get_backend_pages_from_ctx(const struct lttng_kernel_ring_buffer_config *config, | |
8a57ec02 | 218 | struct lttng_kernel_ring_buffer_ctx *ctx) |
85a07c33 | 219 | { |
b1199bd3 | 220 | return ctx->priv.backend_pages; |
85a07c33 MD |
221 | } |
222 | ||
25337cb5 MD |
223 | /* |
224 | * The ring buffer can count events recorded and overwritten per buffer, | |
225 | * but it is disabled by default due to its performance overhead. | |
226 | */ | |
227 | #ifdef LTTNG_RING_BUFFER_COUNT_EVENTS | |
f3bc08c5 | 228 | static inline |
e20c0fec MD |
229 | void subbuffer_count_record(const struct lttng_kernel_ring_buffer_config *config, |
230 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
231 | unsigned long idx) |
232 | { | |
233 | unsigned long sb_bindex; | |
234 | ||
235 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
236 | v_inc(config, &bufb->array[sb_bindex]->records_commit); | |
237 | } | |
238 | ||
239 | /* | |
240 | * Reader has exclusive subbuffer access for record consumption. No need to | |
241 | * perform the decrement atomically. | |
242 | */ | |
243 | static inline | |
e20c0fec MD |
244 | void subbuffer_consume_record(const struct lttng_kernel_ring_buffer_config *config, |
245 | struct lttng_kernel_ring_buffer_backend *bufb) | |
f3bc08c5 MD |
246 | { |
247 | unsigned long sb_bindex; | |
248 | ||
249 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
250 | CHAN_WARN_ON(bufb->chan, | |
251 | !v_read(config, &bufb->array[sb_bindex]->records_unread)); | |
252 | /* Non-atomic decrement protected by exclusive subbuffer access */ | |
253 | _v_dec(config, &bufb->array[sb_bindex]->records_unread); | |
254 | v_inc(config, &bufb->records_read); | |
255 | } | |
935150de MD |
256 | #else /* LTTNG_RING_BUFFER_COUNT_EVENTS */ |
257 | static inline | |
e20c0fec MD |
258 | void subbuffer_count_record(const struct lttng_kernel_ring_buffer_config *config, |
259 | struct lttng_kernel_ring_buffer_backend *bufb, | |
935150de MD |
260 | unsigned long idx) |
261 | { | |
262 | } | |
263 | static inline | |
e20c0fec MD |
264 | void subbuffer_consume_record(const struct lttng_kernel_ring_buffer_config *config, |
265 | struct lttng_kernel_ring_buffer_backend *bufb) | |
935150de MD |
266 | { |
267 | } | |
268 | #endif /* #else LTTNG_RING_BUFFER_COUNT_EVENTS */ | |
f3bc08c5 MD |
269 | |
270 | static inline | |
271 | unsigned long subbuffer_get_records_count( | |
e20c0fec MD |
272 | const struct lttng_kernel_ring_buffer_config *config, |
273 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
274 | unsigned long idx) |
275 | { | |
276 | unsigned long sb_bindex; | |
277 | ||
278 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
279 | return v_read(config, &bufb->array[sb_bindex]->records_commit); | |
280 | } | |
281 | ||
282 | /* | |
283 | * Must be executed at subbuffer delivery when the writer has _exclusive_ | |
c68be968 MD |
284 | * subbuffer access. See lib_ring_buffer_check_deliver() for details. |
285 | * lib_ring_buffer_get_records_count() must be called to get the records | |
286 | * count before this function, because it resets the records_commit | |
287 | * count. | |
f3bc08c5 MD |
288 | */ |
289 | static inline | |
290 | unsigned long subbuffer_count_records_overrun( | |
e20c0fec MD |
291 | const struct lttng_kernel_ring_buffer_config *config, |
292 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
293 | unsigned long idx) |
294 | { | |
e20c0fec | 295 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
296 | unsigned long overruns, sb_bindex; |
297 | ||
298 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
299 | pages = bufb->array[sb_bindex]; | |
300 | overruns = v_read(config, &pages->records_unread); | |
301 | v_set(config, &pages->records_unread, | |
302 | v_read(config, &pages->records_commit)); | |
303 | v_set(config, &pages->records_commit, 0); | |
304 | ||
305 | return overruns; | |
306 | } | |
307 | ||
308 | static inline | |
e20c0fec MD |
309 | void subbuffer_set_data_size(const struct lttng_kernel_ring_buffer_config *config, |
310 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
311 | unsigned long idx, |
312 | unsigned long data_size) | |
313 | { | |
e20c0fec | 314 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
315 | unsigned long sb_bindex; |
316 | ||
317 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
318 | pages = bufb->array[sb_bindex]; | |
319 | pages->data_size = data_size; | |
320 | } | |
321 | ||
322 | static inline | |
323 | unsigned long subbuffer_get_read_data_size( | |
e20c0fec MD |
324 | const struct lttng_kernel_ring_buffer_config *config, |
325 | struct lttng_kernel_ring_buffer_backend *bufb) | |
f3bc08c5 | 326 | { |
e20c0fec | 327 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
328 | unsigned long sb_bindex; |
329 | ||
330 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
331 | pages = bufb->array[sb_bindex]; | |
332 | return pages->data_size; | |
333 | } | |
334 | ||
335 | static inline | |
336 | unsigned long subbuffer_get_data_size( | |
e20c0fec MD |
337 | const struct lttng_kernel_ring_buffer_config *config, |
338 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
339 | unsigned long idx) |
340 | { | |
e20c0fec | 341 | struct lttng_kernel_ring_buffer_backend_pages *pages; |
f3bc08c5 MD |
342 | unsigned long sb_bindex; |
343 | ||
344 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
345 | pages = bufb->array[sb_bindex]; | |
346 | return pages->data_size; | |
347 | } | |
348 | ||
5b3cf4f9 | 349 | static inline |
e20c0fec MD |
350 | void subbuffer_inc_packet_count(const struct lttng_kernel_ring_buffer_config *config, |
351 | struct lttng_kernel_ring_buffer_backend *bufb, | |
5b3cf4f9 JD |
352 | unsigned long idx) |
353 | { | |
354 | bufb->buf_cnt[idx].seq_cnt++; | |
355 | } | |
356 | ||
f3bc08c5 MD |
357 | /** |
358 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by | |
359 | * writer. | |
360 | */ | |
361 | static inline | |
e20c0fec MD |
362 | void lib_ring_buffer_clear_noref(const struct lttng_kernel_ring_buffer_config *config, |
363 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
364 | unsigned long idx) |
365 | { | |
366 | unsigned long id, new_id; | |
367 | ||
368 | if (config->mode != RING_BUFFER_OVERWRITE) | |
369 | return; | |
370 | ||
371 | /* | |
372 | * Performing a volatile access to read the sb_pages, because we want to | |
373 | * read a coherent version of the pointer and the associated noref flag. | |
374 | */ | |
585e5dcc | 375 | id = LTTNG_READ_ONCE(bufb->buf_wsb[idx].id); |
f3bc08c5 MD |
376 | for (;;) { |
377 | /* This check is called on the fast path for each record. */ | |
378 | if (likely(!subbuffer_id_is_noref(config, id))) { | |
379 | /* | |
380 | * Store after load dependency ordering the writes to | |
381 | * the subbuffer after load and test of the noref flag | |
382 | * matches the memory barrier implied by the cmpxchg() | |
383 | * in update_read_sb_index(). | |
384 | */ | |
385 | return; /* Already writing to this buffer */ | |
386 | } | |
387 | new_id = id; | |
388 | subbuffer_id_clear_noref(config, &new_id); | |
389 | new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id); | |
390 | if (likely(new_id == id)) | |
391 | break; | |
392 | id = new_id; | |
393 | } | |
394 | } | |
395 | ||
396 | /** | |
397 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, | |
398 | * called by writer. | |
399 | */ | |
400 | static inline | |
e20c0fec MD |
401 | void lib_ring_buffer_set_noref_offset(const struct lttng_kernel_ring_buffer_config *config, |
402 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
403 | unsigned long idx, unsigned long offset) |
404 | { | |
405 | if (config->mode != RING_BUFFER_OVERWRITE) | |
406 | return; | |
407 | ||
408 | /* | |
409 | * Because ring_buffer_set_noref() is only called by a single thread | |
410 | * (the one which updated the cc_sb value), there are no concurrent | |
411 | * updates to take care of: other writers have not updated cc_sb, so | |
412 | * they cannot set the noref flag, and concurrent readers cannot modify | |
413 | * the pointer because the noref flag is not set yet. | |
414 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes | |
415 | * to the subbuffer before this set noref operation. | |
416 | * subbuffer_set_noref() uses a volatile store to deal with concurrent | |
417 | * readers of the noref flag. | |
418 | */ | |
419 | CHAN_WARN_ON(bufb->chan, | |
420 | subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id)); | |
421 | /* | |
422 | * Memory barrier that ensures counter stores are ordered before set | |
423 | * noref and offset. | |
424 | */ | |
425 | smp_mb(); | |
426 | subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset); | |
427 | } | |
428 | ||
429 | /** | |
430 | * update_read_sb_index - Read-side subbuffer index update. | |
431 | */ | |
432 | static inline | |
e20c0fec MD |
433 | int update_read_sb_index(const struct lttng_kernel_ring_buffer_config *config, |
434 | struct lttng_kernel_ring_buffer_backend *bufb, | |
f3bc08c5 MD |
435 | struct channel_backend *chanb, |
436 | unsigned long consumed_idx, | |
437 | unsigned long consumed_count) | |
438 | { | |
439 | unsigned long old_id, new_id; | |
440 | ||
441 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
442 | /* | |
443 | * Exchange the target writer subbuffer with our own unused | |
a8f2d0c7 | 444 | * subbuffer. No need to use READ_ONCE() here to read the |
f3bc08c5 MD |
445 | * old_wpage, because the value read will be confirmed by the |
446 | * following cmpxchg(). | |
447 | */ | |
448 | old_id = bufb->buf_wsb[consumed_idx].id; | |
449 | if (unlikely(!subbuffer_id_is_noref(config, old_id))) | |
450 | return -EAGAIN; | |
451 | /* | |
452 | * Make sure the offset count we are expecting matches the one | |
453 | * indicated by the writer. | |
454 | */ | |
455 | if (unlikely(!subbuffer_id_compare_offset(config, old_id, | |
456 | consumed_count))) | |
457 | return -EAGAIN; | |
458 | CHAN_WARN_ON(bufb->chan, | |
459 | !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
460 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, | |
461 | consumed_count); | |
462 | new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id, | |
463 | bufb->buf_rsb.id); | |
464 | if (unlikely(old_id != new_id)) | |
465 | return -EAGAIN; | |
466 | bufb->buf_rsb.id = new_id; | |
467 | } else { | |
468 | /* No page exchange, use the writer page directly */ | |
469 | bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id; | |
470 | } | |
471 | return 0; | |
472 | } | |
473 | ||
327177e6 | 474 | static inline __attribute__((always_inline)) |
04707312 | 475 | void lttng_inline_memcpy(void *dest, const void *src, |
327177e6 MD |
476 | unsigned long len) |
477 | { | |
478 | switch (len) { | |
479 | case 1: | |
480 | *(uint8_t *) dest = *(const uint8_t *) src; | |
481 | break; | |
482 | case 2: | |
483 | *(uint16_t *) dest = *(const uint16_t *) src; | |
484 | break; | |
485 | case 4: | |
486 | *(uint32_t *) dest = *(const uint32_t *) src; | |
487 | break; | |
488 | case 8: | |
489 | *(uint64_t *) dest = *(const uint64_t *) src; | |
490 | break; | |
491 | default: | |
492 | inline_memcpy(dest, src, len); | |
493 | } | |
494 | } | |
495 | ||
f3bc08c5 MD |
496 | /* |
497 | * Use the architecture-specific memcpy implementation for constant-sized | |
498 | * inputs, but rely on an inline memcpy for length statically unknown. | |
499 | * The function call to memcpy is just way too expensive for a fast path. | |
500 | */ | |
501 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ | |
502 | do { \ | |
503 | size_t __len = (len); \ | |
504 | if (__builtin_constant_p(len)) \ | |
505 | memcpy(dest, src, __len); \ | |
506 | else \ | |
327177e6 | 507 | lttng_inline_memcpy(dest, src, __len); \ |
f3bc08c5 MD |
508 | } while (0) |
509 | ||
4ea00e4f | 510 | /* |
7b8ea3a5 | 511 | * We use __copy_from_user_inatomic to copy userspace data since we already |
4ea00e4f | 512 | * did the access_ok for the whole range. |
d87a9f03 MD |
513 | * |
514 | * Return 0 if OK, nonzero on error. | |
4ea00e4f JD |
515 | */ |
516 | static inline | |
7b8ea3a5 | 517 | unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest, |
4ea00e4f JD |
518 | const void __user *src, |
519 | unsigned long len) | |
520 | { | |
7b8ea3a5 | 521 | return __copy_from_user_inatomic(dest, src, len); |
4ea00e4f JD |
522 | } |
523 | ||
524 | /* | |
525 | * write len bytes to dest with c | |
526 | */ | |
527 | static inline | |
528 | void lib_ring_buffer_do_memset(char *dest, int c, | |
529 | unsigned long len) | |
530 | { | |
531 | unsigned long i; | |
532 | ||
533 | for (i = 0; i < len; i++) | |
534 | dest[i] = c; | |
535 | } | |
536 | ||
886d51a3 | 537 | #endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */ |