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8ad4ce58 MD |
1 | #ifndef _URCU_WFCQUEUE_STATIC_H |
2 | #define _URCU_WFCQUEUE_STATIC_H | |
3 | ||
4 | /* | |
47215721 | 5 | * urcu/static/wfcqueue.h |
8ad4ce58 MD |
6 | * |
7 | * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue | |
8 | * | |
07c2a4fd MD |
9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfcqueue.h for |
10 | * linking dynamically with the userspace rcu library. | |
8ad4ce58 MD |
11 | * |
12 | * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
13 | * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.com> | |
14 | * | |
15 | * This library is free software; you can redistribute it and/or | |
16 | * modify it under the terms of the GNU Lesser General Public | |
17 | * License as published by the Free Software Foundation; either | |
18 | * version 2.1 of the License, or (at your option) any later version. | |
19 | * | |
20 | * This library is distributed in the hope that it will be useful, | |
21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
23 | * Lesser General Public License for more details. | |
24 | * | |
25 | * You should have received a copy of the GNU Lesser General Public | |
26 | * License along with this library; if not, write to the Free Software | |
27 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
28 | */ | |
29 | ||
30 | #include <pthread.h> | |
31 | #include <assert.h> | |
32 | #include <poll.h> | |
33 | #include <stdbool.h> | |
34 | #include <urcu/compiler.h> | |
35 | #include <urcu/uatomic.h> | |
36 | ||
37 | #ifdef __cplusplus | |
38 | extern "C" { | |
39 | #endif | |
40 | ||
41 | /* | |
42 | * Concurrent queue with wait-free enqueue/blocking dequeue. | |
43 | * | |
ebfd2673 MD |
44 | * This queue has been designed and implemented collaboratively by |
45 | * Mathieu Desnoyers and Lai Jiangshan. Inspired from | |
46 | * half-wait-free/half-blocking queue implementation done by Paul E. | |
47 | * McKenney. | |
8ad4ce58 | 48 | * |
f878b49e MD |
49 | * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API |
50 | * | |
51 | * Synchronization table: | |
52 | * | |
53 | * External synchronization techniques described in the API below is | |
54 | * required between pairs marked with "X". No external synchronization | |
55 | * required between pairs marked with "-". | |
56 | * | |
57 | * Legend: | |
58 | * [1] cds_wfcq_enqueue | |
59 | * [2] __cds_wfcq_splice (destination queue) | |
60 | * [3] __cds_wfcq_dequeue | |
61 | * [4] __cds_wfcq_splice (source queue) | |
62 | * [5] __cds_wfcq_first | |
63 | * [6] __cds_wfcq_next | |
64 | * | |
65 | * [1] [2] [3] [4] [5] [6] | |
66 | * [1] - - - - - - | |
67 | * [2] - - - - - - | |
68 | * [3] - - X X X X | |
69 | * [4] - - X - X X | |
70 | * [5] - - X X - - | |
71 | * [6] - - X X - - | |
8ad4ce58 | 72 | * |
8ad4ce58 MD |
73 | * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock(). |
74 | * | |
75 | * For convenience, cds_wfcq_dequeue_blocking() and | |
76 | * cds_wfcq_splice_blocking() hold the dequeue lock. | |
1fe734e1 MD |
77 | * |
78 | * Besides locking, mutual exclusion of dequeue, splice and iteration | |
79 | * can be ensured by performing all of those operations from a single | |
80 | * thread, without requiring any lock. | |
8ad4ce58 MD |
81 | */ |
82 | ||
83 | #define WFCQ_ADAPT_ATTEMPTS 10 /* Retry if being set */ | |
84 | #define WFCQ_WAIT 10 /* Wait 10 ms if being set */ | |
85 | ||
86 | /* | |
87 | * cds_wfcq_node_init: initialize wait-free queue node. | |
88 | */ | |
89 | static inline void _cds_wfcq_node_init(struct cds_wfcq_node *node) | |
90 | { | |
91 | node->next = NULL; | |
92 | } | |
93 | ||
94 | /* | |
95 | * cds_wfcq_init: initialize wait-free queue. | |
96 | */ | |
97 | static inline void _cds_wfcq_init(struct cds_wfcq_head *head, | |
98 | struct cds_wfcq_tail *tail) | |
99 | { | |
100 | int ret; | |
101 | ||
102 | /* Set queue head and tail */ | |
103 | _cds_wfcq_node_init(&head->node); | |
104 | tail->p = &head->node; | |
105 | ret = pthread_mutex_init(&head->lock, NULL); | |
106 | assert(!ret); | |
107 | } | |
108 | ||
109 | /* | |
110 | * cds_wfcq_empty: return whether wait-free queue is empty. | |
111 | * | |
112 | * No memory barrier is issued. No mutual exclusion is required. | |
6d5729f7 MD |
113 | * |
114 | * We perform the test on head->node.next to check if the queue is | |
115 | * possibly empty, but we confirm this by checking if the tail pointer | |
116 | * points to the head node because the tail pointer is the linearisation | |
117 | * point of the enqueuers. Just checking the head next pointer could | |
118 | * make a queue appear empty if an enqueuer is preempted for a long time | |
119 | * between xchg() and setting the previous node's next pointer. | |
8ad4ce58 MD |
120 | */ |
121 | static inline bool _cds_wfcq_empty(struct cds_wfcq_head *head, | |
122 | struct cds_wfcq_tail *tail) | |
123 | { | |
124 | /* | |
125 | * Queue is empty if no node is pointed by head->node.next nor | |
126 | * tail->p. Even though the tail->p check is sufficient to find | |
127 | * out of the queue is empty, we first check head->node.next as a | |
128 | * common case to ensure that dequeuers do not frequently access | |
129 | * enqueuer's tail->p cache line. | |
130 | */ | |
131 | return CMM_LOAD_SHARED(head->node.next) == NULL | |
132 | && CMM_LOAD_SHARED(tail->p) == &head->node; | |
133 | } | |
134 | ||
135 | static inline void _cds_wfcq_dequeue_lock(struct cds_wfcq_head *head, | |
136 | struct cds_wfcq_tail *tail) | |
137 | { | |
138 | int ret; | |
139 | ||
140 | ret = pthread_mutex_lock(&head->lock); | |
141 | assert(!ret); | |
142 | } | |
143 | ||
144 | static inline void _cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head, | |
145 | struct cds_wfcq_tail *tail) | |
146 | { | |
147 | int ret; | |
148 | ||
149 | ret = pthread_mutex_unlock(&head->lock); | |
150 | assert(!ret); | |
151 | } | |
152 | ||
23773356 | 153 | static inline bool ___cds_wfcq_append(struct cds_wfcq_head *head, |
8ad4ce58 MD |
154 | struct cds_wfcq_tail *tail, |
155 | struct cds_wfcq_node *new_head, | |
156 | struct cds_wfcq_node *new_tail) | |
157 | { | |
158 | struct cds_wfcq_node *old_tail; | |
159 | ||
160 | /* | |
161 | * Implicit memory barrier before uatomic_xchg() orders earlier | |
162 | * stores to data structure containing node and setting | |
163 | * node->next to NULL before publication. | |
164 | */ | |
165 | old_tail = uatomic_xchg(&tail->p, new_tail); | |
166 | ||
167 | /* | |
168 | * Implicit memory barrier after uatomic_xchg() orders store to | |
169 | * q->tail before store to old_tail->next. | |
170 | * | |
171 | * At this point, dequeuers see a NULL tail->p->next, which | |
172 | * indicates that the queue is being appended to. The following | |
173 | * store will append "node" to the queue from a dequeuer | |
174 | * perspective. | |
175 | */ | |
176 | CMM_STORE_SHARED(old_tail->next, new_head); | |
23773356 MD |
177 | /* |
178 | * Return false if queue was empty prior to adding the node, | |
179 | * else return true. | |
180 | */ | |
181 | return old_tail != &head->node; | |
8ad4ce58 MD |
182 | } |
183 | ||
184 | /* | |
185 | * cds_wfcq_enqueue: enqueue a node into a wait-free queue. | |
186 | * | |
187 | * Issues a full memory barrier before enqueue. No mutual exclusion is | |
188 | * required. | |
23773356 MD |
189 | * |
190 | * Returns false if the queue was empty prior to adding the node. | |
191 | * Returns true otherwise. | |
8ad4ce58 | 192 | */ |
23773356 | 193 | static inline bool _cds_wfcq_enqueue(struct cds_wfcq_head *head, |
8ad4ce58 MD |
194 | struct cds_wfcq_tail *tail, |
195 | struct cds_wfcq_node *new_tail) | |
196 | { | |
23773356 | 197 | return ___cds_wfcq_append(head, tail, new_tail, new_tail); |
8ad4ce58 MD |
198 | } |
199 | ||
f878b49e MD |
200 | /* |
201 | * ___cds_wfcq_busy_wait: adaptative busy-wait. | |
202 | * | |
203 | * Returns 1 if nonblocking and needs to block, 0 otherwise. | |
204 | */ | |
205 | static inline bool | |
206 | ___cds_wfcq_busy_wait(int *attempt, int blocking) | |
207 | { | |
208 | if (!blocking) | |
209 | return 1; | |
210 | if (++(*attempt) >= WFCQ_ADAPT_ATTEMPTS) { | |
211 | poll(NULL, 0, WFCQ_WAIT); /* Wait for 10ms */ | |
212 | *attempt = 0; | |
213 | } else { | |
214 | caa_cpu_relax(); | |
215 | } | |
216 | return 0; | |
217 | } | |
218 | ||
8ad4ce58 MD |
219 | /* |
220 | * Waiting for enqueuer to complete enqueue and return the next node. | |
221 | */ | |
222 | static inline struct cds_wfcq_node * | |
47215721 | 223 | ___cds_wfcq_node_sync_next(struct cds_wfcq_node *node, int blocking) |
8ad4ce58 MD |
224 | { |
225 | struct cds_wfcq_node *next; | |
226 | int attempt = 0; | |
227 | ||
228 | /* | |
229 | * Adaptative busy-looping waiting for enqueuer to complete enqueue. | |
230 | */ | |
231 | while ((next = CMM_LOAD_SHARED(node->next)) == NULL) { | |
f878b49e | 232 | if (___cds_wfcq_busy_wait(&attempt, blocking)) |
47215721 | 233 | return CDS_WFCQ_WOULDBLOCK; |
8ad4ce58 MD |
234 | } |
235 | ||
236 | return next; | |
237 | } | |
238 | ||
8ad4ce58 | 239 | static inline struct cds_wfcq_node * |
47215721 MD |
240 | ___cds_wfcq_first(struct cds_wfcq_head *head, |
241 | struct cds_wfcq_tail *tail, | |
242 | int blocking) | |
8ad4ce58 MD |
243 | { |
244 | struct cds_wfcq_node *node; | |
245 | ||
246 | if (_cds_wfcq_empty(head, tail)) | |
247 | return NULL; | |
47215721 | 248 | node = ___cds_wfcq_node_sync_next(&head->node, blocking); |
8ad4ce58 MD |
249 | /* Load head->node.next before loading node's content */ |
250 | cmm_smp_read_barrier_depends(); | |
251 | return node; | |
252 | } | |
253 | ||
254 | /* | |
47215721 | 255 | * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing. |
8ad4ce58 MD |
256 | * |
257 | * Content written into the node before enqueue is guaranteed to be | |
258 | * consistent, but no other memory ordering is ensured. | |
1fe734e1 MD |
259 | * Dequeue/splice/iteration mutual exclusion should be ensured by the |
260 | * caller. | |
f94061a3 MD |
261 | * |
262 | * Used by for-like iteration macros in urcu/wfqueue.h: | |
263 | * __cds_wfcq_for_each_blocking() | |
264 | * __cds_wfcq_for_each_blocking_safe() | |
131a29a6 MD |
265 | * |
266 | * Returns NULL if queue is empty, first node otherwise. | |
8ad4ce58 MD |
267 | */ |
268 | static inline struct cds_wfcq_node * | |
47215721 MD |
269 | ___cds_wfcq_first_blocking(struct cds_wfcq_head *head, |
270 | struct cds_wfcq_tail *tail) | |
271 | { | |
272 | return ___cds_wfcq_first(head, tail, 1); | |
273 | } | |
274 | ||
275 | ||
276 | /* | |
277 | * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing. | |
278 | * | |
279 | * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if | |
280 | * it needs to block. | |
281 | */ | |
282 | static inline struct cds_wfcq_node * | |
283 | ___cds_wfcq_first_nonblocking(struct cds_wfcq_head *head, | |
284 | struct cds_wfcq_tail *tail) | |
285 | { | |
286 | return ___cds_wfcq_first(head, tail, 0); | |
287 | } | |
288 | ||
289 | static inline struct cds_wfcq_node * | |
290 | ___cds_wfcq_next(struct cds_wfcq_head *head, | |
8ad4ce58 | 291 | struct cds_wfcq_tail *tail, |
47215721 MD |
292 | struct cds_wfcq_node *node, |
293 | int blocking) | |
8ad4ce58 MD |
294 | { |
295 | struct cds_wfcq_node *next; | |
296 | ||
297 | /* | |
298 | * Even though the following tail->p check is sufficient to find | |
299 | * out if we reached the end of the queue, we first check | |
300 | * node->next as a common case to ensure that iteration on nodes | |
301 | * do not frequently access enqueuer's tail->p cache line. | |
302 | */ | |
303 | if ((next = CMM_LOAD_SHARED(node->next)) == NULL) { | |
304 | /* Load node->next before tail->p */ | |
305 | cmm_smp_rmb(); | |
306 | if (CMM_LOAD_SHARED(tail->p) == node) | |
307 | return NULL; | |
47215721 | 308 | next = ___cds_wfcq_node_sync_next(node, blocking); |
8ad4ce58 MD |
309 | } |
310 | /* Load node->next before loading next's content */ | |
311 | cmm_smp_read_barrier_depends(); | |
312 | return next; | |
313 | } | |
314 | ||
315 | /* | |
47215721 | 316 | * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing. |
8ad4ce58 | 317 | * |
8ad4ce58 MD |
318 | * Content written into the node before enqueue is guaranteed to be |
319 | * consistent, but no other memory ordering is ensured. | |
1fe734e1 MD |
320 | * Dequeue/splice/iteration mutual exclusion should be ensured by the |
321 | * caller. | |
47215721 MD |
322 | * |
323 | * Used by for-like iteration macros in urcu/wfqueue.h: | |
324 | * __cds_wfcq_for_each_blocking() | |
325 | * __cds_wfcq_for_each_blocking_safe() | |
131a29a6 MD |
326 | * |
327 | * Returns NULL if reached end of queue, non-NULL next queue node | |
328 | * otherwise. | |
8ad4ce58 MD |
329 | */ |
330 | static inline struct cds_wfcq_node * | |
47215721 MD |
331 | ___cds_wfcq_next_blocking(struct cds_wfcq_head *head, |
332 | struct cds_wfcq_tail *tail, | |
333 | struct cds_wfcq_node *node) | |
334 | { | |
335 | return ___cds_wfcq_next(head, tail, node, 1); | |
336 | } | |
337 | ||
338 | /* | |
339 | * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing. | |
340 | * | |
341 | * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if | |
342 | * it needs to block. | |
343 | */ | |
344 | static inline struct cds_wfcq_node * | |
345 | ___cds_wfcq_next_nonblocking(struct cds_wfcq_head *head, | |
346 | struct cds_wfcq_tail *tail, | |
347 | struct cds_wfcq_node *node) | |
348 | { | |
349 | return ___cds_wfcq_next(head, tail, node, 0); | |
350 | } | |
351 | ||
352 | static inline struct cds_wfcq_node * | |
353 | ___cds_wfcq_dequeue(struct cds_wfcq_head *head, | |
354 | struct cds_wfcq_tail *tail, | |
355 | int blocking) | |
8ad4ce58 MD |
356 | { |
357 | struct cds_wfcq_node *node, *next; | |
358 | ||
359 | if (_cds_wfcq_empty(head, tail)) | |
360 | return NULL; | |
361 | ||
47215721 | 362 | node = ___cds_wfcq_node_sync_next(&head->node, blocking); |
dfb65fd3 MD |
363 | if (!blocking && node == CDS_WFCQ_WOULDBLOCK) |
364 | return CDS_WFCQ_WOULDBLOCK; | |
8ad4ce58 MD |
365 | |
366 | if ((next = CMM_LOAD_SHARED(node->next)) == NULL) { | |
367 | /* | |
368 | * @node is probably the only node in the queue. | |
369 | * Try to move the tail to &q->head. | |
370 | * q->head.next is set to NULL here, and stays | |
371 | * NULL if the cmpxchg succeeds. Should the | |
372 | * cmpxchg fail due to a concurrent enqueue, the | |
373 | * q->head.next will be set to the next node. | |
374 | * The implicit memory barrier before | |
375 | * uatomic_cmpxchg() orders load node->next | |
376 | * before loading q->tail. | |
377 | * The implicit memory barrier before uatomic_cmpxchg | |
378 | * orders load q->head.next before loading node's | |
379 | * content. | |
380 | */ | |
381 | _cds_wfcq_node_init(&head->node); | |
382 | if (uatomic_cmpxchg(&tail->p, node, &head->node) == node) | |
383 | return node; | |
47215721 | 384 | next = ___cds_wfcq_node_sync_next(node, blocking); |
dfb65fd3 MD |
385 | /* |
386 | * In nonblocking mode, if we would need to block to | |
387 | * get node's next, set the head next node pointer | |
388 | * (currently NULL) back to its original value. | |
389 | */ | |
390 | if (!blocking && next == CDS_WFCQ_WOULDBLOCK) { | |
391 | head->node.next = node; | |
392 | return CDS_WFCQ_WOULDBLOCK; | |
393 | } | |
8ad4ce58 MD |
394 | } |
395 | ||
396 | /* | |
397 | * Move queue head forward. | |
398 | */ | |
399 | head->node.next = next; | |
400 | ||
401 | /* Load q->head.next before loading node's content */ | |
402 | cmm_smp_read_barrier_depends(); | |
403 | return node; | |
404 | } | |
405 | ||
406 | /* | |
47215721 | 407 | * __cds_wfcq_dequeue_blocking: dequeue a node from the queue. |
8ad4ce58 | 408 | * |
47215721 MD |
409 | * Content written into the node before enqueue is guaranteed to be |
410 | * consistent, but no other memory ordering is ensured. | |
411 | * It is valid to reuse and free a dequeued node immediately. | |
412 | * Dequeue/splice/iteration mutual exclusion should be ensured by the | |
413 | * caller. | |
8ad4ce58 | 414 | */ |
47215721 MD |
415 | static inline struct cds_wfcq_node * |
416 | ___cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head, | |
417 | struct cds_wfcq_tail *tail) | |
418 | { | |
419 | return ___cds_wfcq_dequeue(head, tail, 1); | |
420 | } | |
421 | ||
422 | /* | |
423 | * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue. | |
424 | * | |
425 | * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK | |
426 | * if it needs to block. | |
427 | */ | |
428 | static inline struct cds_wfcq_node * | |
429 | ___cds_wfcq_dequeue_nonblocking(struct cds_wfcq_head *head, | |
430 | struct cds_wfcq_tail *tail) | |
431 | { | |
432 | return ___cds_wfcq_dequeue(head, tail, 0); | |
433 | } | |
434 | ||
f878b49e MD |
435 | /* |
436 | * __cds_wfcq_splice: enqueue all src_q nodes at the end of dest_q. | |
437 | * | |
438 | * Dequeue all nodes from src_q. | |
439 | * dest_q must be already initialized. | |
440 | * Mutual exclusion for src_q should be ensured by the caller as | |
441 | * specified in the "Synchronisation table". | |
442 | * Returns enum cds_wfcq_ret which indicates the state of the src or | |
443 | * dest queue. | |
444 | */ | |
23773356 | 445 | static inline enum cds_wfcq_ret |
47215721 | 446 | ___cds_wfcq_splice( |
8ad4ce58 MD |
447 | struct cds_wfcq_head *dest_q_head, |
448 | struct cds_wfcq_tail *dest_q_tail, | |
449 | struct cds_wfcq_head *src_q_head, | |
47215721 MD |
450 | struct cds_wfcq_tail *src_q_tail, |
451 | int blocking) | |
8ad4ce58 MD |
452 | { |
453 | struct cds_wfcq_node *head, *tail; | |
f878b49e | 454 | int attempt = 0; |
8ad4ce58 | 455 | |
f878b49e MD |
456 | /* |
457 | * Initial emptiness check to speed up cases where queue is | |
458 | * empty: only require loads to check if queue is empty. | |
459 | */ | |
8ad4ce58 | 460 | if (_cds_wfcq_empty(src_q_head, src_q_tail)) |
23773356 | 461 | return CDS_WFCQ_RET_SRC_EMPTY; |
8ad4ce58 | 462 | |
f878b49e MD |
463 | for (;;) { |
464 | /* | |
465 | * Open-coded _cds_wfcq_empty() by testing result of | |
466 | * uatomic_xchg, as well as tail pointer vs head node | |
467 | * address. | |
468 | */ | |
469 | head = uatomic_xchg(&src_q_head->node.next, NULL); | |
470 | if (head) | |
471 | break; /* non-empty */ | |
472 | if (CMM_LOAD_SHARED(src_q_tail->p) == &src_q_head->node) | |
473 | return CDS_WFCQ_RET_SRC_EMPTY; | |
474 | if (___cds_wfcq_busy_wait(&attempt, blocking)) | |
475 | return CDS_WFCQ_RET_WOULDBLOCK; | |
476 | } | |
8ad4ce58 MD |
477 | |
478 | /* | |
479 | * Memory barrier implied before uatomic_xchg() orders store to | |
480 | * src_q->head before store to src_q->tail. This is required by | |
481 | * concurrent enqueue on src_q, which exchanges the tail before | |
482 | * updating the previous tail's next pointer. | |
483 | */ | |
484 | tail = uatomic_xchg(&src_q_tail->p, &src_q_head->node); | |
485 | ||
486 | /* | |
487 | * Append the spliced content of src_q into dest_q. Does not | |
488 | * require mutual exclusion on dest_q (wait-free). | |
489 | */ | |
23773356 MD |
490 | if (___cds_wfcq_append(dest_q_head, dest_q_tail, head, tail)) |
491 | return CDS_WFCQ_RET_DEST_NON_EMPTY; | |
492 | else | |
493 | return CDS_WFCQ_RET_DEST_EMPTY; | |
47215721 MD |
494 | } |
495 | ||
47215721 MD |
496 | /* |
497 | * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q. | |
498 | * | |
499 | * Dequeue all nodes from src_q. | |
500 | * dest_q must be already initialized. | |
f878b49e MD |
501 | * Mutual exclusion for src_q should be ensured by the caller as |
502 | * specified in the "Synchronisation table". | |
23773356 MD |
503 | * Returns enum cds_wfcq_ret which indicates the state of the src or |
504 | * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK. | |
47215721 | 505 | */ |
23773356 | 506 | static inline enum cds_wfcq_ret |
47215721 MD |
507 | ___cds_wfcq_splice_blocking( |
508 | struct cds_wfcq_head *dest_q_head, | |
509 | struct cds_wfcq_tail *dest_q_tail, | |
510 | struct cds_wfcq_head *src_q_head, | |
511 | struct cds_wfcq_tail *src_q_tail) | |
512 | { | |
23773356 | 513 | return ___cds_wfcq_splice(dest_q_head, dest_q_tail, |
47215721 MD |
514 | src_q_head, src_q_tail, 1); |
515 | } | |
516 | ||
517 | /* | |
518 | * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q. | |
519 | * | |
23773356 MD |
520 | * Same as __cds_wfcq_splice_blocking, but returns |
521 | * CDS_WFCQ_RET_WOULDBLOCK if it needs to block. | |
47215721 | 522 | */ |
23773356 | 523 | static inline enum cds_wfcq_ret |
47215721 MD |
524 | ___cds_wfcq_splice_nonblocking( |
525 | struct cds_wfcq_head *dest_q_head, | |
526 | struct cds_wfcq_tail *dest_q_tail, | |
527 | struct cds_wfcq_head *src_q_head, | |
528 | struct cds_wfcq_tail *src_q_tail) | |
529 | { | |
530 | return ___cds_wfcq_splice(dest_q_head, dest_q_tail, | |
531 | src_q_head, src_q_tail, 0); | |
8ad4ce58 MD |
532 | } |
533 | ||
534 | /* | |
535 | * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue. | |
536 | * | |
537 | * Content written into the node before enqueue is guaranteed to be | |
538 | * consistent, but no other memory ordering is ensured. | |
ffa11a18 | 539 | * Mutual exclusion with cds_wfcq_splice_blocking and dequeue lock is |
8ad4ce58 MD |
540 | * ensured. |
541 | * It is valid to reuse and free a dequeued node immediately. | |
542 | */ | |
543 | static inline struct cds_wfcq_node * | |
544 | _cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head, | |
545 | struct cds_wfcq_tail *tail) | |
546 | { | |
547 | struct cds_wfcq_node *retval; | |
548 | ||
549 | _cds_wfcq_dequeue_lock(head, tail); | |
550 | retval = ___cds_wfcq_dequeue_blocking(head, tail); | |
551 | _cds_wfcq_dequeue_unlock(head, tail); | |
552 | return retval; | |
553 | } | |
554 | ||
555 | /* | |
556 | * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q. | |
557 | * | |
558 | * Dequeue all nodes from src_q. | |
559 | * dest_q must be already initialized. | |
560 | * Content written into the node before enqueue is guaranteed to be | |
561 | * consistent, but no other memory ordering is ensured. | |
ffa11a18 | 562 | * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is |
8ad4ce58 | 563 | * ensured. |
23773356 MD |
564 | * Returns enum cds_wfcq_ret which indicates the state of the src or |
565 | * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK. | |
8ad4ce58 | 566 | */ |
23773356 | 567 | static inline enum cds_wfcq_ret |
8ad4ce58 MD |
568 | _cds_wfcq_splice_blocking( |
569 | struct cds_wfcq_head *dest_q_head, | |
570 | struct cds_wfcq_tail *dest_q_tail, | |
571 | struct cds_wfcq_head *src_q_head, | |
572 | struct cds_wfcq_tail *src_q_tail) | |
573 | { | |
23773356 MD |
574 | enum cds_wfcq_ret ret; |
575 | ||
8ad4ce58 | 576 | _cds_wfcq_dequeue_lock(src_q_head, src_q_tail); |
23773356 | 577 | ret = ___cds_wfcq_splice_blocking(dest_q_head, dest_q_tail, |
8ad4ce58 MD |
578 | src_q_head, src_q_tail); |
579 | _cds_wfcq_dequeue_unlock(src_q_head, src_q_tail); | |
23773356 | 580 | return ret; |
8ad4ce58 MD |
581 | } |
582 | ||
583 | #ifdef __cplusplus | |
584 | } | |
585 | #endif | |
586 | ||
587 | #endif /* _URCU_WFCQUEUE_STATIC_H */ |