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886d51a3 MD |
1 | #ifndef _LIB_RING_BUFFER_BACKEND_INTERNAL_H |
2 | #define _LIB_RING_BUFFER_BACKEND_INTERNAL_H | |
f3bc08c5 MD |
3 | |
4 | /* | |
886d51a3 | 5 | * lib/ringbuffer/backend_internal.h |
f3bc08c5 MD |
6 | * |
7 | * Ring buffer backend (internal helpers). | |
8 | * | |
886d51a3 MD |
9 | * Copyright (C) 2008-2012 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 | |
f3bc08c5 MD |
24 | */ |
25 | ||
26 | #include "../../wrapper/ringbuffer/config.h" | |
494a81f5 | 27 | #include "../../wrapper/ringbuffer/backend_types.h" |
f3bc08c5 MD |
28 | #include "../../wrapper/ringbuffer/frontend_types.h" |
29 | #include <linux/string.h> | |
4ea00e4f | 30 | #include <linux/uaccess.h> |
f3bc08c5 MD |
31 | |
32 | /* Ring buffer backend API presented to the frontend */ | |
33 | ||
34 | /* Ring buffer and channel backend create/free */ | |
35 | ||
36 | int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb, | |
37 | struct channel_backend *chan, int cpu); | |
38 | void channel_backend_unregister_notifiers(struct channel_backend *chanb); | |
39 | void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb); | |
40 | int channel_backend_init(struct channel_backend *chanb, | |
41 | const char *name, | |
42 | const struct lib_ring_buffer_config *config, | |
43 | void *priv, size_t subbuf_size, | |
44 | size_t num_subbuf); | |
45 | void channel_backend_free(struct channel_backend *chanb); | |
46 | ||
47 | void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb); | |
48 | void channel_backend_reset(struct channel_backend *chanb); | |
49 | ||
50 | int lib_ring_buffer_backend_init(void); | |
51 | void lib_ring_buffer_backend_exit(void); | |
52 | ||
53 | extern void _lib_ring_buffer_write(struct lib_ring_buffer_backend *bufb, | |
54 | size_t offset, const void *src, size_t len, | |
55 | ssize_t pagecpy); | |
4ea00e4f JD |
56 | extern void _lib_ring_buffer_memset(struct lib_ring_buffer_backend *bufb, |
57 | size_t offset, int c, size_t len, | |
58 | ssize_t pagecpy); | |
7b8ea3a5 | 59 | extern void _lib_ring_buffer_copy_from_user_inatomic(struct lib_ring_buffer_backend *bufb, |
4ea00e4f JD |
60 | size_t offset, const void *src, |
61 | size_t len, ssize_t pagecpy); | |
f3bc08c5 MD |
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 | ||
75 | #define HALF_ULONG_BITS (BITS_PER_LONG >> 1) | |
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 | |
101 | unsigned long subbuffer_id(const struct lib_ring_buffer_config *config, | |
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 | |
118 | int subbuffer_id_compare_offset(const struct lib_ring_buffer_config *config, | |
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 | |
125 | unsigned long subbuffer_id_get_index(const struct lib_ring_buffer_config *config, | |
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 | |
135 | unsigned long subbuffer_id_is_noref(const struct lib_ring_buffer_config *config, | |
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 | |
149 | void subbuffer_id_set_noref(const struct lib_ring_buffer_config *config, | |
150 | unsigned long *id) | |
151 | { | |
152 | if (config->mode == RING_BUFFER_OVERWRITE) | |
153 | *id |= SB_ID_NOREF_MASK; | |
154 | } | |
155 | ||
156 | static inline | |
157 | void subbuffer_id_set_noref_offset(const struct lib_ring_buffer_config *config, | |
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. */ | |
168 | ACCESS_ONCE(*id) = tmp; | |
169 | } | |
170 | } | |
171 | ||
172 | /* No volatile access, since already used locally */ | |
173 | static inline | |
174 | void subbuffer_id_clear_noref(const struct lib_ring_buffer_config *config, | |
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 | |
189 | int subbuffer_id_check_index(const struct lib_ring_buffer_config *config, | |
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 | |
199 | void subbuffer_count_record(const struct lib_ring_buffer_config *config, | |
200 | struct lib_ring_buffer_backend *bufb, | |
201 | unsigned long idx) | |
202 | { | |
203 | unsigned long sb_bindex; | |
204 | ||
205 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
206 | v_inc(config, &bufb->array[sb_bindex]->records_commit); | |
207 | } | |
208 | ||
209 | /* | |
210 | * Reader has exclusive subbuffer access for record consumption. No need to | |
211 | * perform the decrement atomically. | |
212 | */ | |
213 | static inline | |
214 | void subbuffer_consume_record(const struct lib_ring_buffer_config *config, | |
215 | struct lib_ring_buffer_backend *bufb) | |
216 | { | |
217 | unsigned long sb_bindex; | |
218 | ||
219 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
220 | CHAN_WARN_ON(bufb->chan, | |
221 | !v_read(config, &bufb->array[sb_bindex]->records_unread)); | |
222 | /* Non-atomic decrement protected by exclusive subbuffer access */ | |
223 | _v_dec(config, &bufb->array[sb_bindex]->records_unread); | |
224 | v_inc(config, &bufb->records_read); | |
225 | } | |
226 | ||
227 | static inline | |
228 | unsigned long subbuffer_get_records_count( | |
229 | const struct lib_ring_buffer_config *config, | |
230 | struct lib_ring_buffer_backend *bufb, | |
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 | return v_read(config, &bufb->array[sb_bindex]->records_commit); | |
237 | } | |
238 | ||
239 | /* | |
240 | * Must be executed at subbuffer delivery when the writer has _exclusive_ | |
241 | * subbuffer access. See ring_buffer_check_deliver() for details. | |
242 | * ring_buffer_get_records_count() must be called to get the records count | |
243 | * before this function, because it resets the records_commit count. | |
244 | */ | |
245 | static inline | |
246 | unsigned long subbuffer_count_records_overrun( | |
247 | const struct lib_ring_buffer_config *config, | |
248 | struct lib_ring_buffer_backend *bufb, | |
249 | unsigned long idx) | |
250 | { | |
251 | struct lib_ring_buffer_backend_pages *pages; | |
252 | unsigned long overruns, sb_bindex; | |
253 | ||
254 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
255 | pages = bufb->array[sb_bindex]; | |
256 | overruns = v_read(config, &pages->records_unread); | |
257 | v_set(config, &pages->records_unread, | |
258 | v_read(config, &pages->records_commit)); | |
259 | v_set(config, &pages->records_commit, 0); | |
260 | ||
261 | return overruns; | |
262 | } | |
263 | ||
264 | static inline | |
265 | void subbuffer_set_data_size(const struct lib_ring_buffer_config *config, | |
266 | struct lib_ring_buffer_backend *bufb, | |
267 | unsigned long idx, | |
268 | unsigned long data_size) | |
269 | { | |
270 | struct lib_ring_buffer_backend_pages *pages; | |
271 | unsigned long sb_bindex; | |
272 | ||
273 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
274 | pages = bufb->array[sb_bindex]; | |
275 | pages->data_size = data_size; | |
276 | } | |
277 | ||
278 | static inline | |
279 | unsigned long subbuffer_get_read_data_size( | |
280 | const struct lib_ring_buffer_config *config, | |
281 | struct lib_ring_buffer_backend *bufb) | |
282 | { | |
283 | struct lib_ring_buffer_backend_pages *pages; | |
284 | unsigned long sb_bindex; | |
285 | ||
286 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id); | |
287 | pages = bufb->array[sb_bindex]; | |
288 | return pages->data_size; | |
289 | } | |
290 | ||
291 | static inline | |
292 | unsigned long subbuffer_get_data_size( | |
293 | const struct lib_ring_buffer_config *config, | |
294 | struct lib_ring_buffer_backend *bufb, | |
295 | unsigned long idx) | |
296 | { | |
297 | struct lib_ring_buffer_backend_pages *pages; | |
298 | unsigned long sb_bindex; | |
299 | ||
300 | sb_bindex = subbuffer_id_get_index(config, bufb->buf_wsb[idx].id); | |
301 | pages = bufb->array[sb_bindex]; | |
302 | return pages->data_size; | |
303 | } | |
304 | ||
305 | /** | |
306 | * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by | |
307 | * writer. | |
308 | */ | |
309 | static inline | |
310 | void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config, | |
311 | struct lib_ring_buffer_backend *bufb, | |
312 | unsigned long idx) | |
313 | { | |
314 | unsigned long id, new_id; | |
315 | ||
316 | if (config->mode != RING_BUFFER_OVERWRITE) | |
317 | return; | |
318 | ||
319 | /* | |
320 | * Performing a volatile access to read the sb_pages, because we want to | |
321 | * read a coherent version of the pointer and the associated noref flag. | |
322 | */ | |
323 | id = ACCESS_ONCE(bufb->buf_wsb[idx].id); | |
324 | for (;;) { | |
325 | /* This check is called on the fast path for each record. */ | |
326 | if (likely(!subbuffer_id_is_noref(config, id))) { | |
327 | /* | |
328 | * Store after load dependency ordering the writes to | |
329 | * the subbuffer after load and test of the noref flag | |
330 | * matches the memory barrier implied by the cmpxchg() | |
331 | * in update_read_sb_index(). | |
332 | */ | |
333 | return; /* Already writing to this buffer */ | |
334 | } | |
335 | new_id = id; | |
336 | subbuffer_id_clear_noref(config, &new_id); | |
337 | new_id = cmpxchg(&bufb->buf_wsb[idx].id, id, new_id); | |
338 | if (likely(new_id == id)) | |
339 | break; | |
340 | id = new_id; | |
341 | } | |
342 | } | |
343 | ||
344 | /** | |
345 | * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset, | |
346 | * called by writer. | |
347 | */ | |
348 | static inline | |
349 | void lib_ring_buffer_set_noref_offset(const struct lib_ring_buffer_config *config, | |
350 | struct lib_ring_buffer_backend *bufb, | |
351 | unsigned long idx, unsigned long offset) | |
352 | { | |
353 | if (config->mode != RING_BUFFER_OVERWRITE) | |
354 | return; | |
355 | ||
356 | /* | |
357 | * Because ring_buffer_set_noref() is only called by a single thread | |
358 | * (the one which updated the cc_sb value), there are no concurrent | |
359 | * updates to take care of: other writers have not updated cc_sb, so | |
360 | * they cannot set the noref flag, and concurrent readers cannot modify | |
361 | * the pointer because the noref flag is not set yet. | |
362 | * The smp_wmb() in ring_buffer_commit() takes care of ordering writes | |
363 | * to the subbuffer before this set noref operation. | |
364 | * subbuffer_set_noref() uses a volatile store to deal with concurrent | |
365 | * readers of the noref flag. | |
366 | */ | |
367 | CHAN_WARN_ON(bufb->chan, | |
368 | subbuffer_id_is_noref(config, bufb->buf_wsb[idx].id)); | |
369 | /* | |
370 | * Memory barrier that ensures counter stores are ordered before set | |
371 | * noref and offset. | |
372 | */ | |
373 | smp_mb(); | |
374 | subbuffer_id_set_noref_offset(config, &bufb->buf_wsb[idx].id, offset); | |
375 | } | |
376 | ||
377 | /** | |
378 | * update_read_sb_index - Read-side subbuffer index update. | |
379 | */ | |
380 | static inline | |
381 | int update_read_sb_index(const struct lib_ring_buffer_config *config, | |
382 | struct lib_ring_buffer_backend *bufb, | |
383 | struct channel_backend *chanb, | |
384 | unsigned long consumed_idx, | |
385 | unsigned long consumed_count) | |
386 | { | |
387 | unsigned long old_id, new_id; | |
388 | ||
389 | if (config->mode == RING_BUFFER_OVERWRITE) { | |
390 | /* | |
391 | * Exchange the target writer subbuffer with our own unused | |
392 | * subbuffer. No need to use ACCESS_ONCE() here to read the | |
393 | * old_wpage, because the value read will be confirmed by the | |
394 | * following cmpxchg(). | |
395 | */ | |
396 | old_id = bufb->buf_wsb[consumed_idx].id; | |
397 | if (unlikely(!subbuffer_id_is_noref(config, old_id))) | |
398 | return -EAGAIN; | |
399 | /* | |
400 | * Make sure the offset count we are expecting matches the one | |
401 | * indicated by the writer. | |
402 | */ | |
403 | if (unlikely(!subbuffer_id_compare_offset(config, old_id, | |
404 | consumed_count))) | |
405 | return -EAGAIN; | |
406 | CHAN_WARN_ON(bufb->chan, | |
407 | !subbuffer_id_is_noref(config, bufb->buf_rsb.id)); | |
408 | subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id, | |
409 | consumed_count); | |
410 | new_id = cmpxchg(&bufb->buf_wsb[consumed_idx].id, old_id, | |
411 | bufb->buf_rsb.id); | |
412 | if (unlikely(old_id != new_id)) | |
413 | return -EAGAIN; | |
414 | bufb->buf_rsb.id = new_id; | |
415 | } else { | |
416 | /* No page exchange, use the writer page directly */ | |
417 | bufb->buf_rsb.id = bufb->buf_wsb[consumed_idx].id; | |
418 | } | |
419 | return 0; | |
420 | } | |
421 | ||
422 | /* | |
423 | * Use the architecture-specific memcpy implementation for constant-sized | |
424 | * inputs, but rely on an inline memcpy for length statically unknown. | |
425 | * The function call to memcpy is just way too expensive for a fast path. | |
426 | */ | |
427 | #define lib_ring_buffer_do_copy(config, dest, src, len) \ | |
428 | do { \ | |
429 | size_t __len = (len); \ | |
430 | if (__builtin_constant_p(len)) \ | |
431 | memcpy(dest, src, __len); \ | |
432 | else \ | |
433 | inline_memcpy(dest, src, __len); \ | |
434 | } while (0) | |
435 | ||
4ea00e4f | 436 | /* |
7b8ea3a5 | 437 | * We use __copy_from_user_inatomic to copy userspace data since we already |
4ea00e4f JD |
438 | * did the access_ok for the whole range. |
439 | */ | |
440 | static inline | |
7b8ea3a5 | 441 | unsigned long lib_ring_buffer_do_copy_from_user_inatomic(void *dest, |
4ea00e4f JD |
442 | const void __user *src, |
443 | unsigned long len) | |
444 | { | |
7b8ea3a5 | 445 | return __copy_from_user_inatomic(dest, src, len); |
4ea00e4f JD |
446 | } |
447 | ||
448 | /* | |
449 | * write len bytes to dest with c | |
450 | */ | |
451 | static inline | |
452 | void lib_ring_buffer_do_memset(char *dest, int c, | |
453 | unsigned long len) | |
454 | { | |
455 | unsigned long i; | |
456 | ||
457 | for (i = 0; i < len; i++) | |
458 | dest[i] = c; | |
459 | } | |
460 | ||
886d51a3 | 461 | #endif /* _LIB_RING_BUFFER_BACKEND_INTERNAL_H */ |