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d3d3857f MJ |
1 | // SPDX-FileCopyrightText: 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // | |
3 | // SPDX-License-Identifier: LGPL-2.1-or-later | |
4 | ||
edac6b69 MD |
5 | #ifndef _URCU_STATIC_WFSTACK_H |
6 | #define _URCU_STATIC_WFSTACK_H | |
294d3396 MD |
7 | |
8 | /* | |
edac6b69 | 9 | * Userspace RCU library - Stack with with wait-free push, blocking traversal. |
294d3396 | 10 | * |
07c2a4fd MD |
11 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfstack.h for |
12 | * linking dynamically with the userspace rcu library. | |
294d3396 MD |
13 | */ |
14 | ||
15 | #include <pthread.h> | |
b57aee66 | 16 | #include <poll.h> |
edac6b69 | 17 | #include <stdbool.h> |
01477510 | 18 | #include <urcu/assert.h> |
294d3396 | 19 | #include <urcu/compiler.h> |
a2e7bf9c | 20 | #include <urcu/uatomic.h> |
294d3396 MD |
21 | |
22 | #ifdef __cplusplus | |
23 | extern "C" { | |
24 | #endif | |
25 | ||
28757437 | 26 | #define CDS_WFS_END ((struct cds_wfs_head *) 0x1UL) |
16aa9ee8 DG |
27 | #define CDS_WFS_ADAPT_ATTEMPTS 10 /* Retry if being set */ |
28 | #define CDS_WFS_WAIT 10 /* Wait 10 ms if being set */ | |
294d3396 | 29 | |
edac6b69 MD |
30 | /* |
31 | * Stack with wait-free push, blocking traversal. | |
32 | * | |
33 | * Stack implementing push, pop, pop_all operations, as well as iterator | |
34 | * on the stack head returned by pop_all. | |
35 | * | |
c97c6ce5 MD |
36 | * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty, |
37 | * cds_wfs_first. | |
38 | * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next, | |
39 | * iteration on stack head returned by pop_all. | |
edac6b69 MD |
40 | * |
41 | * Synchronization table: | |
42 | * | |
43 | * External synchronization techniques described in the API below is | |
44 | * required between pairs marked with "X". No external synchronization | |
45 | * required between pairs marked with "-". | |
46 | * | |
47 | * cds_wfs_push __cds_wfs_pop __cds_wfs_pop_all | |
48 | * cds_wfs_push - - - | |
49 | * __cds_wfs_pop - X X | |
50 | * __cds_wfs_pop_all - X - | |
51 | * | |
52 | * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide | |
53 | * synchronization. | |
54 | */ | |
55 | ||
56 | /* | |
57 | * cds_wfs_node_init: initialize wait-free stack node. | |
58 | */ | |
756a0322 | 59 | static inline |
16aa9ee8 | 60 | void _cds_wfs_node_init(struct cds_wfs_node *node) |
294d3396 MD |
61 | { |
62 | node->next = NULL; | |
63 | } | |
64 | ||
718eb63e | 65 | /* |
200d100e MD |
66 | * __cds_wfs_init: initialize wait-free stack. Don't pair with |
67 | * any destroy function. | |
718eb63e EW |
68 | */ |
69 | static inline void ___cds_wfs_init(struct __cds_wfs_stack *s) | |
70 | { | |
71 | s->head = CDS_WFS_END; | |
72 | } | |
73 | ||
edac6b69 | 74 | /* |
200d100e MD |
75 | * cds_wfs_init: initialize wait-free stack. Pair with |
76 | * cds_wfs_destroy(). | |
edac6b69 | 77 | */ |
756a0322 | 78 | static inline |
16aa9ee8 | 79 | void _cds_wfs_init(struct cds_wfs_stack *s) |
294d3396 MD |
80 | { |
81 | int ret; | |
82 | ||
edac6b69 | 83 | s->head = CDS_WFS_END; |
294d3396 | 84 | ret = pthread_mutex_init(&s->lock, NULL); |
01477510 | 85 | urcu_posix_assert(!ret); |
294d3396 MD |
86 | } |
87 | ||
200d100e MD |
88 | /* |
89 | * cds_wfs_destroy: destroy wait-free stack. Pair with | |
90 | * cds_wfs_init(). | |
91 | */ | |
92 | static inline | |
93 | void _cds_wfs_destroy(struct cds_wfs_stack *s) | |
94 | { | |
95 | int ret = pthread_mutex_destroy(&s->lock); | |
01477510 | 96 | urcu_posix_assert(!ret); |
200d100e MD |
97 | } |
98 | ||
edac6b69 MD |
99 | static inline bool ___cds_wfs_end(void *node) |
100 | { | |
101 | return node == CDS_WFS_END; | |
102 | } | |
103 | ||
191098fc | 104 | /* |
edac6b69 MD |
105 | * cds_wfs_empty: return whether wait-free stack is empty. |
106 | * | |
107 | * No memory barrier is issued. No mutual exclusion is required. | |
108 | */ | |
718eb63e | 109 | static inline bool _cds_wfs_empty(cds_wfs_stack_ptr_t u_stack) |
edac6b69 | 110 | { |
718eb63e EW |
111 | struct __cds_wfs_stack *s = u_stack._s; |
112 | ||
edac6b69 MD |
113 | return ___cds_wfs_end(CMM_LOAD_SHARED(s->head)); |
114 | } | |
115 | ||
116 | /* | |
117 | * cds_wfs_push: push a node into the stack. | |
118 | * | |
119 | * Issues a full memory barrier before push. No mutual exclusion is | |
120 | * required. | |
121 | * | |
122 | * Returns 0 if the stack was empty prior to adding the node. | |
123 | * Returns non-zero otherwise. | |
191098fc | 124 | */ |
756a0322 | 125 | static inline |
718eb63e | 126 | int _cds_wfs_push(cds_wfs_stack_ptr_t u_stack, struct cds_wfs_node *node) |
294d3396 | 127 | { |
718eb63e | 128 | struct __cds_wfs_stack *s = u_stack._s; |
edac6b69 | 129 | struct cds_wfs_head *old_head, *new_head; |
294d3396 | 130 | |
01477510 | 131 | urcu_posix_assert(node->next == NULL); |
edac6b69 | 132 | new_head = caa_container_of(node, struct cds_wfs_head, node); |
294d3396 | 133 | /* |
edac6b69 MD |
134 | * uatomic_xchg() implicit memory barrier orders earlier stores |
135 | * to node (setting it to NULL) before publication. | |
294d3396 | 136 | */ |
edac6b69 | 137 | old_head = uatomic_xchg(&s->head, new_head); |
294d3396 | 138 | /* |
edac6b69 MD |
139 | * At this point, dequeuers see a NULL node->next, they should |
140 | * busy-wait until node->next is set to old_head. | |
294d3396 | 141 | */ |
edac6b69 MD |
142 | CMM_STORE_SHARED(node->next, &old_head->node); |
143 | return !___cds_wfs_end(old_head); | |
294d3396 MD |
144 | } |
145 | ||
146 | /* | |
edac6b69 | 147 | * Waiting for push to complete enqueue and return the next node. |
294d3396 | 148 | */ |
edac6b69 | 149 | static inline struct cds_wfs_node * |
af67624d | 150 | ___cds_wfs_node_sync_next(struct cds_wfs_node *node, int blocking) |
294d3396 | 151 | { |
edac6b69 | 152 | struct cds_wfs_node *next; |
294d3396 MD |
153 | int attempt = 0; |
154 | ||
294d3396 MD |
155 | /* |
156 | * Adaptative busy-looping waiting for push to complete. | |
157 | */ | |
edac6b69 | 158 | while ((next = CMM_LOAD_SHARED(node->next)) == NULL) { |
af67624d MD |
159 | if (!blocking) |
160 | return CDS_WFS_WOULDBLOCK; | |
16aa9ee8 | 161 | if (++attempt >= CDS_WFS_ADAPT_ATTEMPTS) { |
d8a93add | 162 | (void) poll(NULL, 0, CDS_WFS_WAIT); /* Wait for 10ms */ |
294d3396 | 163 | attempt = 0; |
edac6b69 | 164 | } else { |
06f22bdb | 165 | caa_cpu_relax(); |
edac6b69 | 166 | } |
294d3396 | 167 | } |
edac6b69 MD |
168 | |
169 | return next; | |
294d3396 MD |
170 | } |
171 | ||
af67624d MD |
172 | static inline |
173 | struct cds_wfs_node * | |
711ff0f9 | 174 | ___cds_wfs_pop(cds_wfs_stack_ptr_t u_stack, int *state, int blocking) |
af67624d MD |
175 | { |
176 | struct cds_wfs_head *head, *new_head; | |
177 | struct cds_wfs_node *next; | |
711ff0f9 | 178 | struct __cds_wfs_stack *s = u_stack._s; |
af67624d | 179 | |
c8975b94 MD |
180 | if (state) |
181 | *state = 0; | |
af67624d MD |
182 | for (;;) { |
183 | head = CMM_LOAD_SHARED(s->head); | |
c8975b94 | 184 | if (___cds_wfs_end(head)) { |
af67624d | 185 | return NULL; |
c8975b94 | 186 | } |
af67624d | 187 | next = ___cds_wfs_node_sync_next(&head->node, blocking); |
c8975b94 | 188 | if (!blocking && next == CDS_WFS_WOULDBLOCK) { |
af67624d | 189 | return CDS_WFS_WOULDBLOCK; |
c8975b94 | 190 | } |
af67624d | 191 | new_head = caa_container_of(next, struct cds_wfs_head, node); |
c8975b94 MD |
192 | if (uatomic_cmpxchg(&s->head, head, new_head) == head) { |
193 | if (state && ___cds_wfs_end(new_head)) | |
194 | *state |= CDS_WFS_STATE_LAST; | |
af67624d | 195 | return &head->node; |
c8975b94 MD |
196 | } |
197 | if (!blocking) { | |
af67624d | 198 | return CDS_WFS_WOULDBLOCK; |
c8975b94 | 199 | } |
af67624d MD |
200 | /* busy-loop if head changed under us */ |
201 | } | |
202 | } | |
203 | ||
edac6b69 | 204 | /* |
c8975b94 | 205 | * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state. |
edac6b69 MD |
206 | * |
207 | * Returns NULL if stack is empty. | |
208 | * | |
209 | * __cds_wfs_pop_blocking needs to be synchronized using one of the | |
210 | * following techniques: | |
211 | * | |
212 | * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical | |
213 | * section. The caller must wait for a grace period to pass before | |
214 | * freeing the returned node or modifying the cds_wfs_node structure. | |
215 | * 2) Using mutual exclusion (e.g. mutexes) to protect | |
216 | * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers. | |
217 | * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking() | |
218 | * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme). | |
c8975b94 MD |
219 | * |
220 | * "state" saves state flags atomically sampled with pop operation. | |
edac6b69 | 221 | */ |
c8975b94 MD |
222 | static inline |
223 | struct cds_wfs_node * | |
711ff0f9 | 224 | ___cds_wfs_pop_with_state_blocking(cds_wfs_stack_ptr_t u_stack, int *state) |
c8975b94 | 225 | { |
711ff0f9 | 226 | return ___cds_wfs_pop(u_stack, state, 1); |
c8975b94 MD |
227 | } |
228 | ||
756a0322 | 229 | static inline |
16aa9ee8 | 230 | struct cds_wfs_node * |
711ff0f9 | 231 | ___cds_wfs_pop_blocking(cds_wfs_stack_ptr_t u_stack) |
edac6b69 | 232 | { |
711ff0f9 | 233 | return ___cds_wfs_pop_with_state_blocking(u_stack, NULL); |
c8975b94 MD |
234 | } |
235 | ||
236 | /* | |
237 | * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack. | |
238 | * | |
239 | * Same as __cds_wfs_pop_with_state_blocking, but returns | |
240 | * CDS_WFS_WOULDBLOCK if it needs to block. | |
241 | * | |
242 | * "state" saves state flags atomically sampled with pop operation. | |
243 | */ | |
244 | static inline | |
245 | struct cds_wfs_node * | |
711ff0f9 | 246 | ___cds_wfs_pop_with_state_nonblocking(cds_wfs_stack_ptr_t u_stack, int *state) |
c8975b94 | 247 | { |
711ff0f9 | 248 | return ___cds_wfs_pop(u_stack, state, 0); |
af67624d | 249 | } |
edac6b69 | 250 | |
af67624d MD |
251 | /* |
252 | * __cds_wfs_pop_nonblocking: pop a node from the stack. | |
253 | * | |
254 | * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if | |
255 | * it needs to block. | |
256 | */ | |
257 | static inline | |
258 | struct cds_wfs_node * | |
711ff0f9 | 259 | ___cds_wfs_pop_nonblocking(cds_wfs_stack_ptr_t u_stack) |
af67624d | 260 | { |
711ff0f9 | 261 | return ___cds_wfs_pop_with_state_nonblocking(u_stack, NULL); |
edac6b69 MD |
262 | } |
263 | ||
264 | /* | |
265 | * __cds_wfs_pop_all: pop all nodes from a stack. | |
266 | * | |
267 | * __cds_wfs_pop_all does not require any synchronization with other | |
268 | * push, nor with other __cds_wfs_pop_all, but requires synchronization | |
269 | * matching the technique used to synchronize __cds_wfs_pop_blocking: | |
270 | * | |
271 | * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical | |
272 | * section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers | |
273 | * must wait for a grace period to pass before freeing the returned | |
274 | * node or modifying the cds_wfs_node structure. However, no RCU | |
275 | * read-side critical section is needed around __cds_wfs_pop_all. | |
276 | * 2) Using mutual exclusion (e.g. mutexes) to protect | |
277 | * __cds_wfs_pop_blocking and __cds_wfs_pop_all callers. | |
278 | * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking() | |
279 | * and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme). | |
280 | */ | |
281 | static inline | |
282 | struct cds_wfs_head * | |
718eb63e | 283 | ___cds_wfs_pop_all(cds_wfs_stack_ptr_t u_stack) |
edac6b69 | 284 | { |
718eb63e | 285 | struct __cds_wfs_stack *s = u_stack._s; |
edac6b69 MD |
286 | struct cds_wfs_head *head; |
287 | ||
288 | /* | |
289 | * Implicit memory barrier after uatomic_xchg() matches implicit | |
290 | * memory barrier before uatomic_xchg() in cds_wfs_push. It | |
291 | * ensures that all nodes of the returned list are consistent. | |
292 | * There is no need to issue memory barriers when iterating on | |
293 | * the returned list, because the full memory barrier issued | |
294 | * prior to each uatomic_cmpxchg, which each write to head, are | |
295 | * taking care to order writes to each node prior to the full | |
296 | * memory barrier after this uatomic_xchg(). | |
297 | */ | |
298 | head = uatomic_xchg(&s->head, CDS_WFS_END); | |
299 | if (___cds_wfs_end(head)) | |
300 | return NULL; | |
301 | return head; | |
302 | } | |
303 | ||
304 | /* | |
305 | * cds_wfs_pop_lock: lock stack pop-protection mutex. | |
306 | */ | |
307 | static inline void _cds_wfs_pop_lock(struct cds_wfs_stack *s) | |
294d3396 | 308 | { |
294d3396 MD |
309 | int ret; |
310 | ||
311 | ret = pthread_mutex_lock(&s->lock); | |
01477510 | 312 | urcu_posix_assert(!ret); |
edac6b69 MD |
313 | } |
314 | ||
315 | /* | |
316 | * cds_wfs_pop_unlock: unlock stack pop-protection mutex. | |
317 | */ | |
318 | static inline void _cds_wfs_pop_unlock(struct cds_wfs_stack *s) | |
319 | { | |
320 | int ret; | |
321 | ||
294d3396 | 322 | ret = pthread_mutex_unlock(&s->lock); |
01477510 | 323 | urcu_posix_assert(!ret); |
edac6b69 MD |
324 | } |
325 | ||
326 | /* | |
c8975b94 | 327 | * Call __cds_wfs_pop_with_state_blocking with an internal pop mutex held. |
edac6b69 MD |
328 | */ |
329 | static inline | |
330 | struct cds_wfs_node * | |
c8975b94 | 331 | _cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state) |
edac6b69 MD |
332 | { |
333 | struct cds_wfs_node *retnode; | |
28757437 | 334 | cds_wfs_stack_ptr_t stack; |
edac6b69 MD |
335 | |
336 | _cds_wfs_pop_lock(s); | |
28757437 SM |
337 | stack.s = s; |
338 | retnode = ___cds_wfs_pop_with_state_blocking(stack, state); | |
edac6b69 | 339 | _cds_wfs_pop_unlock(s); |
294d3396 MD |
340 | return retnode; |
341 | } | |
342 | ||
c8975b94 MD |
343 | /* |
344 | * Call _cds_wfs_pop_with_state_blocking without saving any state. | |
345 | */ | |
346 | static inline | |
347 | struct cds_wfs_node * | |
348 | _cds_wfs_pop_blocking(struct cds_wfs_stack *s) | |
349 | { | |
350 | return _cds_wfs_pop_with_state_blocking(s, NULL); | |
351 | } | |
352 | ||
edac6b69 MD |
353 | /* |
354 | * Call __cds_wfs_pop_all with an internal pop mutex held. | |
355 | */ | |
356 | static inline | |
357 | struct cds_wfs_head * | |
358 | _cds_wfs_pop_all_blocking(struct cds_wfs_stack *s) | |
359 | { | |
360 | struct cds_wfs_head *rethead; | |
28757437 | 361 | cds_wfs_stack_ptr_t stack; |
edac6b69 MD |
362 | |
363 | _cds_wfs_pop_lock(s); | |
28757437 SM |
364 | stack.s = s; |
365 | rethead = ___cds_wfs_pop_all(stack); | |
edac6b69 MD |
366 | _cds_wfs_pop_unlock(s); |
367 | return rethead; | |
368 | } | |
369 | ||
370 | /* | |
c7ba06ba | 371 | * cds_wfs_first: get first node of a popped stack. |
edac6b69 MD |
372 | * |
373 | * Content written into the node before enqueue is guaranteed to be | |
374 | * consistent, but no other memory ordering is ensured. | |
375 | * | |
376 | * Used by for-like iteration macros in urcu/wfstack.h: | |
377 | * cds_wfs_for_each_blocking() | |
378 | * cds_wfs_for_each_blocking_safe() | |
8af2956c MD |
379 | * |
380 | * Returns NULL if popped stack is empty, top stack node otherwise. | |
edac6b69 MD |
381 | */ |
382 | static inline struct cds_wfs_node * | |
c7ba06ba | 383 | _cds_wfs_first(struct cds_wfs_head *head) |
edac6b69 MD |
384 | { |
385 | if (___cds_wfs_end(head)) | |
386 | return NULL; | |
387 | return &head->node; | |
388 | } | |
389 | ||
af67624d MD |
390 | static inline struct cds_wfs_node * |
391 | ___cds_wfs_next(struct cds_wfs_node *node, int blocking) | |
392 | { | |
393 | struct cds_wfs_node *next; | |
394 | ||
395 | next = ___cds_wfs_node_sync_next(node, blocking); | |
396 | /* | |
397 | * CDS_WFS_WOULDBLOCK != CSD_WFS_END, so we can check for end | |
398 | * even if ___cds_wfs_node_sync_next returns CDS_WFS_WOULDBLOCK, | |
399 | * and still return CDS_WFS_WOULDBLOCK. | |
400 | */ | |
401 | if (___cds_wfs_end(next)) | |
402 | return NULL; | |
403 | return next; | |
404 | } | |
405 | ||
edac6b69 MD |
406 | /* |
407 | * cds_wfs_next_blocking: get next node of a popped stack. | |
408 | * | |
409 | * Content written into the node before enqueue is guaranteed to be | |
410 | * consistent, but no other memory ordering is ensured. | |
411 | * | |
412 | * Used by for-like iteration macros in urcu/wfstack.h: | |
413 | * cds_wfs_for_each_blocking() | |
414 | * cds_wfs_for_each_blocking_safe() | |
8af2956c MD |
415 | * |
416 | * Returns NULL if reached end of popped stack, non-NULL next stack | |
417 | * node otherwise. | |
edac6b69 MD |
418 | */ |
419 | static inline struct cds_wfs_node * | |
420 | _cds_wfs_next_blocking(struct cds_wfs_node *node) | |
421 | { | |
af67624d MD |
422 | return ___cds_wfs_next(node, 1); |
423 | } | |
edac6b69 | 424 | |
af67624d MD |
425 | |
426 | /* | |
427 | * cds_wfs_next_nonblocking: get next node of a popped stack. | |
428 | * | |
429 | * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it | |
430 | * needs to block. | |
431 | */ | |
432 | static inline struct cds_wfs_node * | |
433 | _cds_wfs_next_nonblocking(struct cds_wfs_node *node) | |
434 | { | |
435 | return ___cds_wfs_next(node, 0); | |
edac6b69 MD |
436 | } |
437 | ||
294d3396 MD |
438 | #ifdef __cplusplus |
439 | } | |
440 | #endif | |
441 | ||
edac6b69 | 442 | #endif /* _URCU_STATIC_WFSTACK_H */ |