| 1 | #ifndef _URCU_WFCQUEUE_STATIC_H |
| 2 | #define _URCU_WFCQUEUE_STATIC_H |
| 3 | |
| 4 | /* |
| 5 | * urcu/static/wfcqueue.h |
| 6 | * |
| 7 | * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue |
| 8 | * |
| 9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu/wfcqueue.h for |
| 10 | * linking dynamically with the userspace rcu library. |
| 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 | * |
| 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. |
| 48 | * |
| 49 | * Mutual exclusion of __cds_wfcq_* API |
| 50 | * |
| 51 | * Unless otherwise stated, the caller must ensure mutual exclusion of |
| 52 | * queue update operations "dequeue" and "splice" (for source queue). |
| 53 | * Queue read operations "first" and "next", which are used by |
| 54 | * "for_each" iterations, need to be protected against concurrent |
| 55 | * "dequeue" and "splice" (for source queue) by the caller. |
| 56 | * "enqueue", "splice" (for destination queue), and "empty" are the only |
| 57 | * operations that can be used without any mutual exclusion. |
| 58 | * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock(). |
| 59 | * |
| 60 | * For convenience, cds_wfcq_dequeue_blocking() and |
| 61 | * cds_wfcq_splice_blocking() hold the dequeue lock. |
| 62 | * |
| 63 | * Besides locking, mutual exclusion of dequeue, splice and iteration |
| 64 | * can be ensured by performing all of those operations from a single |
| 65 | * thread, without requiring any lock. |
| 66 | */ |
| 67 | |
| 68 | #define WFCQ_ADAPT_ATTEMPTS 10 /* Retry if being set */ |
| 69 | #define WFCQ_WAIT 10 /* Wait 10 ms if being set */ |
| 70 | |
| 71 | /* |
| 72 | * cds_wfcq_node_init: initialize wait-free queue node. |
| 73 | */ |
| 74 | static inline void _cds_wfcq_node_init(struct cds_wfcq_node *node) |
| 75 | { |
| 76 | node->next = NULL; |
| 77 | } |
| 78 | |
| 79 | /* |
| 80 | * cds_wfcq_init: initialize wait-free queue. |
| 81 | */ |
| 82 | static inline void _cds_wfcq_init(struct cds_wfcq_head *head, |
| 83 | struct cds_wfcq_tail *tail) |
| 84 | { |
| 85 | int ret; |
| 86 | |
| 87 | /* Set queue head and tail */ |
| 88 | _cds_wfcq_node_init(&head->node); |
| 89 | tail->p = &head->node; |
| 90 | ret = pthread_mutex_init(&head->lock, NULL); |
| 91 | assert(!ret); |
| 92 | } |
| 93 | |
| 94 | /* |
| 95 | * cds_wfcq_empty: return whether wait-free queue is empty. |
| 96 | * |
| 97 | * No memory barrier is issued. No mutual exclusion is required. |
| 98 | */ |
| 99 | static inline bool _cds_wfcq_empty(struct cds_wfcq_head *head, |
| 100 | struct cds_wfcq_tail *tail) |
| 101 | { |
| 102 | /* |
| 103 | * Queue is empty if no node is pointed by head->node.next nor |
| 104 | * tail->p. Even though the tail->p check is sufficient to find |
| 105 | * out of the queue is empty, we first check head->node.next as a |
| 106 | * common case to ensure that dequeuers do not frequently access |
| 107 | * enqueuer's tail->p cache line. |
| 108 | */ |
| 109 | return CMM_LOAD_SHARED(head->node.next) == NULL |
| 110 | && CMM_LOAD_SHARED(tail->p) == &head->node; |
| 111 | } |
| 112 | |
| 113 | static inline void _cds_wfcq_dequeue_lock(struct cds_wfcq_head *head, |
| 114 | struct cds_wfcq_tail *tail) |
| 115 | { |
| 116 | int ret; |
| 117 | |
| 118 | ret = pthread_mutex_lock(&head->lock); |
| 119 | assert(!ret); |
| 120 | } |
| 121 | |
| 122 | static inline void _cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head, |
| 123 | struct cds_wfcq_tail *tail) |
| 124 | { |
| 125 | int ret; |
| 126 | |
| 127 | ret = pthread_mutex_unlock(&head->lock); |
| 128 | assert(!ret); |
| 129 | } |
| 130 | |
| 131 | static inline bool ___cds_wfcq_append(struct cds_wfcq_head *head, |
| 132 | struct cds_wfcq_tail *tail, |
| 133 | struct cds_wfcq_node *new_head, |
| 134 | struct cds_wfcq_node *new_tail) |
| 135 | { |
| 136 | struct cds_wfcq_node *old_tail; |
| 137 | |
| 138 | /* |
| 139 | * Implicit memory barrier before uatomic_xchg() orders earlier |
| 140 | * stores to data structure containing node and setting |
| 141 | * node->next to NULL before publication. |
| 142 | */ |
| 143 | old_tail = uatomic_xchg(&tail->p, new_tail); |
| 144 | |
| 145 | /* |
| 146 | * Implicit memory barrier after uatomic_xchg() orders store to |
| 147 | * q->tail before store to old_tail->next. |
| 148 | * |
| 149 | * At this point, dequeuers see a NULL tail->p->next, which |
| 150 | * indicates that the queue is being appended to. The following |
| 151 | * store will append "node" to the queue from a dequeuer |
| 152 | * perspective. |
| 153 | */ |
| 154 | CMM_STORE_SHARED(old_tail->next, new_head); |
| 155 | /* |
| 156 | * Return false if queue was empty prior to adding the node, |
| 157 | * else return true. |
| 158 | */ |
| 159 | return old_tail != &head->node; |
| 160 | } |
| 161 | |
| 162 | /* |
| 163 | * cds_wfcq_enqueue: enqueue a node into a wait-free queue. |
| 164 | * |
| 165 | * Issues a full memory barrier before enqueue. No mutual exclusion is |
| 166 | * required. |
| 167 | * |
| 168 | * Returns false if the queue was empty prior to adding the node. |
| 169 | * Returns true otherwise. |
| 170 | */ |
| 171 | static inline bool _cds_wfcq_enqueue(struct cds_wfcq_head *head, |
| 172 | struct cds_wfcq_tail *tail, |
| 173 | struct cds_wfcq_node *new_tail) |
| 174 | { |
| 175 | return ___cds_wfcq_append(head, tail, new_tail, new_tail); |
| 176 | } |
| 177 | |
| 178 | /* |
| 179 | * Waiting for enqueuer to complete enqueue and return the next node. |
| 180 | */ |
| 181 | static inline struct cds_wfcq_node * |
| 182 | ___cds_wfcq_node_sync_next(struct cds_wfcq_node *node, int blocking) |
| 183 | { |
| 184 | struct cds_wfcq_node *next; |
| 185 | int attempt = 0; |
| 186 | |
| 187 | /* |
| 188 | * Adaptative busy-looping waiting for enqueuer to complete enqueue. |
| 189 | */ |
| 190 | while ((next = CMM_LOAD_SHARED(node->next)) == NULL) { |
| 191 | if (!blocking) |
| 192 | return CDS_WFCQ_WOULDBLOCK; |
| 193 | if (++attempt >= WFCQ_ADAPT_ATTEMPTS) { |
| 194 | poll(NULL, 0, WFCQ_WAIT); /* Wait for 10ms */ |
| 195 | attempt = 0; |
| 196 | } else { |
| 197 | caa_cpu_relax(); |
| 198 | } |
| 199 | } |
| 200 | |
| 201 | return next; |
| 202 | } |
| 203 | |
| 204 | static inline struct cds_wfcq_node * |
| 205 | ___cds_wfcq_first(struct cds_wfcq_head *head, |
| 206 | struct cds_wfcq_tail *tail, |
| 207 | int blocking) |
| 208 | { |
| 209 | struct cds_wfcq_node *node; |
| 210 | |
| 211 | if (_cds_wfcq_empty(head, tail)) |
| 212 | return NULL; |
| 213 | node = ___cds_wfcq_node_sync_next(&head->node, blocking); |
| 214 | /* Load head->node.next before loading node's content */ |
| 215 | cmm_smp_read_barrier_depends(); |
| 216 | return node; |
| 217 | } |
| 218 | |
| 219 | /* |
| 220 | * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing. |
| 221 | * |
| 222 | * Content written into the node before enqueue is guaranteed to be |
| 223 | * consistent, but no other memory ordering is ensured. |
| 224 | * Dequeue/splice/iteration mutual exclusion should be ensured by the |
| 225 | * caller. |
| 226 | * |
| 227 | * Used by for-like iteration macros in urcu/wfqueue.h: |
| 228 | * __cds_wfcq_for_each_blocking() |
| 229 | * __cds_wfcq_for_each_blocking_safe() |
| 230 | */ |
| 231 | static inline struct cds_wfcq_node * |
| 232 | ___cds_wfcq_first_blocking(struct cds_wfcq_head *head, |
| 233 | struct cds_wfcq_tail *tail) |
| 234 | { |
| 235 | return ___cds_wfcq_first(head, tail, 1); |
| 236 | } |
| 237 | |
| 238 | |
| 239 | /* |
| 240 | * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing. |
| 241 | * |
| 242 | * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if |
| 243 | * it needs to block. |
| 244 | */ |
| 245 | static inline struct cds_wfcq_node * |
| 246 | ___cds_wfcq_first_nonblocking(struct cds_wfcq_head *head, |
| 247 | struct cds_wfcq_tail *tail) |
| 248 | { |
| 249 | return ___cds_wfcq_first(head, tail, 0); |
| 250 | } |
| 251 | |
| 252 | static inline struct cds_wfcq_node * |
| 253 | ___cds_wfcq_next(struct cds_wfcq_head *head, |
| 254 | struct cds_wfcq_tail *tail, |
| 255 | struct cds_wfcq_node *node, |
| 256 | int blocking) |
| 257 | { |
| 258 | struct cds_wfcq_node *next; |
| 259 | |
| 260 | /* |
| 261 | * Even though the following tail->p check is sufficient to find |
| 262 | * out if we reached the end of the queue, we first check |
| 263 | * node->next as a common case to ensure that iteration on nodes |
| 264 | * do not frequently access enqueuer's tail->p cache line. |
| 265 | */ |
| 266 | if ((next = CMM_LOAD_SHARED(node->next)) == NULL) { |
| 267 | /* Load node->next before tail->p */ |
| 268 | cmm_smp_rmb(); |
| 269 | if (CMM_LOAD_SHARED(tail->p) == node) |
| 270 | return NULL; |
| 271 | next = ___cds_wfcq_node_sync_next(node, blocking); |
| 272 | } |
| 273 | /* Load node->next before loading next's content */ |
| 274 | cmm_smp_read_barrier_depends(); |
| 275 | return next; |
| 276 | } |
| 277 | |
| 278 | /* |
| 279 | * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing. |
| 280 | * |
| 281 | * Content written into the node before enqueue is guaranteed to be |
| 282 | * consistent, but no other memory ordering is ensured. |
| 283 | * Dequeue/splice/iteration mutual exclusion should be ensured by the |
| 284 | * caller. |
| 285 | * |
| 286 | * Used by for-like iteration macros in urcu/wfqueue.h: |
| 287 | * __cds_wfcq_for_each_blocking() |
| 288 | * __cds_wfcq_for_each_blocking_safe() |
| 289 | */ |
| 290 | static inline struct cds_wfcq_node * |
| 291 | ___cds_wfcq_next_blocking(struct cds_wfcq_head *head, |
| 292 | struct cds_wfcq_tail *tail, |
| 293 | struct cds_wfcq_node *node) |
| 294 | { |
| 295 | return ___cds_wfcq_next(head, tail, node, 1); |
| 296 | } |
| 297 | |
| 298 | /* |
| 299 | * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing. |
| 300 | * |
| 301 | * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if |
| 302 | * it needs to block. |
| 303 | */ |
| 304 | static inline struct cds_wfcq_node * |
| 305 | ___cds_wfcq_next_nonblocking(struct cds_wfcq_head *head, |
| 306 | struct cds_wfcq_tail *tail, |
| 307 | struct cds_wfcq_node *node) |
| 308 | { |
| 309 | return ___cds_wfcq_next(head, tail, node, 0); |
| 310 | } |
| 311 | |
| 312 | static inline struct cds_wfcq_node * |
| 313 | ___cds_wfcq_dequeue(struct cds_wfcq_head *head, |
| 314 | struct cds_wfcq_tail *tail, |
| 315 | int blocking) |
| 316 | { |
| 317 | struct cds_wfcq_node *node, *next; |
| 318 | |
| 319 | if (_cds_wfcq_empty(head, tail)) |
| 320 | return NULL; |
| 321 | |
| 322 | node = ___cds_wfcq_node_sync_next(&head->node, blocking); |
| 323 | if (!blocking && node == CDS_WFCQ_WOULDBLOCK) |
| 324 | return CDS_WFCQ_WOULDBLOCK; |
| 325 | |
| 326 | if ((next = CMM_LOAD_SHARED(node->next)) == NULL) { |
| 327 | /* |
| 328 | * @node is probably the only node in the queue. |
| 329 | * Try to move the tail to &q->head. |
| 330 | * q->head.next is set to NULL here, and stays |
| 331 | * NULL if the cmpxchg succeeds. Should the |
| 332 | * cmpxchg fail due to a concurrent enqueue, the |
| 333 | * q->head.next will be set to the next node. |
| 334 | * The implicit memory barrier before |
| 335 | * uatomic_cmpxchg() orders load node->next |
| 336 | * before loading q->tail. |
| 337 | * The implicit memory barrier before uatomic_cmpxchg |
| 338 | * orders load q->head.next before loading node's |
| 339 | * content. |
| 340 | */ |
| 341 | _cds_wfcq_node_init(&head->node); |
| 342 | if (uatomic_cmpxchg(&tail->p, node, &head->node) == node) |
| 343 | return node; |
| 344 | next = ___cds_wfcq_node_sync_next(node, blocking); |
| 345 | /* |
| 346 | * In nonblocking mode, if we would need to block to |
| 347 | * get node's next, set the head next node pointer |
| 348 | * (currently NULL) back to its original value. |
| 349 | */ |
| 350 | if (!blocking && next == CDS_WFCQ_WOULDBLOCK) { |
| 351 | head->node.next = node; |
| 352 | return CDS_WFCQ_WOULDBLOCK; |
| 353 | } |
| 354 | } |
| 355 | |
| 356 | /* |
| 357 | * Move queue head forward. |
| 358 | */ |
| 359 | head->node.next = next; |
| 360 | |
| 361 | /* Load q->head.next before loading node's content */ |
| 362 | cmm_smp_read_barrier_depends(); |
| 363 | return node; |
| 364 | } |
| 365 | |
| 366 | /* |
| 367 | * __cds_wfcq_dequeue_blocking: dequeue a node from the queue. |
| 368 | * |
| 369 | * Content written into the node before enqueue is guaranteed to be |
| 370 | * consistent, but no other memory ordering is ensured. |
| 371 | * It is valid to reuse and free a dequeued node immediately. |
| 372 | * Dequeue/splice/iteration mutual exclusion should be ensured by the |
| 373 | * caller. |
| 374 | */ |
| 375 | static inline struct cds_wfcq_node * |
| 376 | ___cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head, |
| 377 | struct cds_wfcq_tail *tail) |
| 378 | { |
| 379 | return ___cds_wfcq_dequeue(head, tail, 1); |
| 380 | } |
| 381 | |
| 382 | /* |
| 383 | * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue. |
| 384 | * |
| 385 | * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK |
| 386 | * if it needs to block. |
| 387 | */ |
| 388 | static inline struct cds_wfcq_node * |
| 389 | ___cds_wfcq_dequeue_nonblocking(struct cds_wfcq_head *head, |
| 390 | struct cds_wfcq_tail *tail) |
| 391 | { |
| 392 | return ___cds_wfcq_dequeue(head, tail, 0); |
| 393 | } |
| 394 | |
| 395 | static inline enum cds_wfcq_ret |
| 396 | ___cds_wfcq_splice( |
| 397 | struct cds_wfcq_head *dest_q_head, |
| 398 | struct cds_wfcq_tail *dest_q_tail, |
| 399 | struct cds_wfcq_head *src_q_head, |
| 400 | struct cds_wfcq_tail *src_q_tail, |
| 401 | int blocking) |
| 402 | { |
| 403 | struct cds_wfcq_node *head, *tail; |
| 404 | |
| 405 | if (_cds_wfcq_empty(src_q_head, src_q_tail)) |
| 406 | return CDS_WFCQ_RET_SRC_EMPTY; |
| 407 | |
| 408 | head = ___cds_wfcq_node_sync_next(&src_q_head->node, blocking); |
| 409 | if (head == CDS_WFCQ_WOULDBLOCK) |
| 410 | return CDS_WFCQ_RET_WOULDBLOCK; |
| 411 | _cds_wfcq_node_init(&src_q_head->node); |
| 412 | |
| 413 | /* |
| 414 | * Memory barrier implied before uatomic_xchg() orders store to |
| 415 | * src_q->head before store to src_q->tail. This is required by |
| 416 | * concurrent enqueue on src_q, which exchanges the tail before |
| 417 | * updating the previous tail's next pointer. |
| 418 | */ |
| 419 | tail = uatomic_xchg(&src_q_tail->p, &src_q_head->node); |
| 420 | |
| 421 | /* |
| 422 | * Append the spliced content of src_q into dest_q. Does not |
| 423 | * require mutual exclusion on dest_q (wait-free). |
| 424 | */ |
| 425 | if (___cds_wfcq_append(dest_q_head, dest_q_tail, head, tail)) |
| 426 | return CDS_WFCQ_RET_DEST_NON_EMPTY; |
| 427 | else |
| 428 | return CDS_WFCQ_RET_DEST_EMPTY; |
| 429 | } |
| 430 | |
| 431 | |
| 432 | /* |
| 433 | * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q. |
| 434 | * |
| 435 | * Dequeue all nodes from src_q. |
| 436 | * dest_q must be already initialized. |
| 437 | * Dequeue/splice/iteration mutual exclusion for src_q should be ensured |
| 438 | * by the caller. |
| 439 | * Returns enum cds_wfcq_ret which indicates the state of the src or |
| 440 | * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK. |
| 441 | */ |
| 442 | static inline enum cds_wfcq_ret |
| 443 | ___cds_wfcq_splice_blocking( |
| 444 | struct cds_wfcq_head *dest_q_head, |
| 445 | struct cds_wfcq_tail *dest_q_tail, |
| 446 | struct cds_wfcq_head *src_q_head, |
| 447 | struct cds_wfcq_tail *src_q_tail) |
| 448 | { |
| 449 | return ___cds_wfcq_splice(dest_q_head, dest_q_tail, |
| 450 | src_q_head, src_q_tail, 1); |
| 451 | } |
| 452 | |
| 453 | /* |
| 454 | * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q. |
| 455 | * |
| 456 | * Same as __cds_wfcq_splice_blocking, but returns |
| 457 | * CDS_WFCQ_RET_WOULDBLOCK if it needs to block. |
| 458 | */ |
| 459 | static inline enum cds_wfcq_ret |
| 460 | ___cds_wfcq_splice_nonblocking( |
| 461 | struct cds_wfcq_head *dest_q_head, |
| 462 | struct cds_wfcq_tail *dest_q_tail, |
| 463 | struct cds_wfcq_head *src_q_head, |
| 464 | struct cds_wfcq_tail *src_q_tail) |
| 465 | { |
| 466 | return ___cds_wfcq_splice(dest_q_head, dest_q_tail, |
| 467 | src_q_head, src_q_tail, 0); |
| 468 | } |
| 469 | |
| 470 | /* |
| 471 | * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue. |
| 472 | * |
| 473 | * Content written into the node before enqueue is guaranteed to be |
| 474 | * consistent, but no other memory ordering is ensured. |
| 475 | * Mutual exlusion with cds_wfcq_splice_blocking and dequeue lock is |
| 476 | * ensured. |
| 477 | * It is valid to reuse and free a dequeued node immediately. |
| 478 | */ |
| 479 | static inline struct cds_wfcq_node * |
| 480 | _cds_wfcq_dequeue_blocking(struct cds_wfcq_head *head, |
| 481 | struct cds_wfcq_tail *tail) |
| 482 | { |
| 483 | struct cds_wfcq_node *retval; |
| 484 | |
| 485 | _cds_wfcq_dequeue_lock(head, tail); |
| 486 | retval = ___cds_wfcq_dequeue_blocking(head, tail); |
| 487 | _cds_wfcq_dequeue_unlock(head, tail); |
| 488 | return retval; |
| 489 | } |
| 490 | |
| 491 | /* |
| 492 | * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q. |
| 493 | * |
| 494 | * Dequeue all nodes from src_q. |
| 495 | * dest_q must be already initialized. |
| 496 | * Content written into the node before enqueue is guaranteed to be |
| 497 | * consistent, but no other memory ordering is ensured. |
| 498 | * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is |
| 499 | * ensured. |
| 500 | * Returns enum cds_wfcq_ret which indicates the state of the src or |
| 501 | * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK. |
| 502 | */ |
| 503 | static inline enum cds_wfcq_ret |
| 504 | _cds_wfcq_splice_blocking( |
| 505 | struct cds_wfcq_head *dest_q_head, |
| 506 | struct cds_wfcq_tail *dest_q_tail, |
| 507 | struct cds_wfcq_head *src_q_head, |
| 508 | struct cds_wfcq_tail *src_q_tail) |
| 509 | { |
| 510 | enum cds_wfcq_ret ret; |
| 511 | |
| 512 | _cds_wfcq_dequeue_lock(src_q_head, src_q_tail); |
| 513 | ret = ___cds_wfcq_splice_blocking(dest_q_head, dest_q_tail, |
| 514 | src_q_head, src_q_tail); |
| 515 | _cds_wfcq_dequeue_unlock(src_q_head, src_q_tail); |
| 516 | return ret; |
| 517 | } |
| 518 | |
| 519 | #ifdef __cplusplus |
| 520 | } |
| 521 | #endif |
| 522 | |
| 523 | #endif /* _URCU_WFCQUEUE_STATIC_H */ |