urcu/wfcqueue.h

   1 #ifndef _URCU_WFCQUEUE_H
   2 #define _URCU_WFCQUEUE_H
   3
   4 /*
   5  * urcu/wfcqueue.h
   6  *
   7  * Userspace RCU library - Concurrent Queue with Wait-Free Enqueue/Blocking Dequeue
   8  *
   9  * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  * Copyright 2011-2012 - Lai Jiangshan <laijs@cn.fujitsu.com>
  11  *
  12  * This library is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU Lesser General Public
  14  * License as published by the Free Software Foundation; either
  15  * version 2.1 of the License, or (at your option) any later version.
  16  *
  17  * This library is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * Lesser General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Lesser General Public
  23  * License along with this library; if not, write to the Free Software
  24  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  25  */
  26
  27 #include <pthread.h>
  28 #include <assert.h>
  29 #include <stdbool.h>
  30 #include <urcu/compiler.h>
  31 #include <urcu/arch.h>
  32
  33 #ifdef __cplusplus
  34 extern "C" {
  35 #endif
  36
  37 /*
  38  * Concurrent queue with wait-free enqueue/blocking dequeue.
  39  *
  40  * This queue has been designed and implemented collaboratively by
  41  * Mathieu Desnoyers and Lai Jiangshan. Inspired from
  42  * half-wait-free/half-blocking queue implementation done by Paul E.
  43  * McKenney.
  44  */
  45
  46 #define CDS_WFCQ_WOULDBLOCK     ((void *) -1UL)
  47
  48 struct cds_wfcq_node {
  49         struct cds_wfcq_node *next;
  50 };
  51
  52 /*
  53  * Do not put head and tail on the same cache-line if concurrent
  54  * enqueue/dequeue are expected from many CPUs. This eliminates
  55  * false-sharing between enqueue and dequeue.
  56  */
  57 struct cds_wfcq_head {
  58         struct cds_wfcq_node node;
  59         pthread_mutex_t lock;
  60 };
  61
  62 struct cds_wfcq_tail {
  63         struct cds_wfcq_node *p;
  64 };
  65
  66 #ifdef _LGPL_SOURCE
  67
  68 #include <urcu/static/wfcqueue.h>
  69
  70 #define cds_wfcq_node_init              _cds_wfcq_node_init
  71 #define cds_wfcq_init                   _cds_wfcq_init
  72 #define cds_wfcq_empty                  _cds_wfcq_empty
  73 #define cds_wfcq_enqueue                _cds_wfcq_enqueue
  74
  75 /* Dequeue locking */
  76 #define cds_wfcq_dequeue_lock           _cds_wfcq_dequeue_lock
  77 #define cds_wfcq_dequeue_unlock         _cds_wfcq_dequeue_unlock
  78
  79 /* Locking performed within cds_wfcq calls. */
  80 #define cds_wfcq_dequeue_blocking       _cds_wfcq_dequeue_blocking
  81 #define cds_wfcq_splice_blocking        _cds_wfcq_splice_blocking
  82 #define cds_wfcq_first_blocking         _cds_wfcq_first_blocking
  83 #define cds_wfcq_next_blocking          _cds_wfcq_next_blocking
  84
  85 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
  86 #define __cds_wfcq_dequeue_blocking     ___cds_wfcq_dequeue_blocking
  87 #define __cds_wfcq_splice_blocking      ___cds_wfcq_splice_blocking
  88 #define __cds_wfcq_first_blocking       ___cds_wfcq_first_blocking
  89 #define __cds_wfcq_next_blocking        ___cds_wfcq_next_blocking
  90
  91 /*
  92  * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
  93  * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
  94  * need to block. splice returns nonzero if it needs to block.
  95  */
  96 #define __cds_wfcq_dequeue_nonblocking  ___cds_wfcq_dequeue_nonblocking
  97 #define __cds_wfcq_splice_nonblocking   ___cds_wfcq_splice_nonblocking
  98 #define __cds_wfcq_first_nonblocking    ___cds_wfcq_first_nonblocking
  99 #define __cds_wfcq_next_nonblocking     ___cds_wfcq_next_nonblocking
 100
 101 #else /* !_LGPL_SOURCE */
 102
 103 /*
 104  * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
 105  *
 106  * Unless otherwise stated, the caller must ensure mutual exclusion of
 107  * queue update operations "dequeue" and "splice" (for source queue).
 108  * Queue read operations "first" and "next", which are used by
 109  * "for_each" iterations, need to be protected against concurrent
 110  * "dequeue" and "splice" (for source queue) by the caller.
 111  * "enqueue", "splice" (for destination queue), and "empty" are the only
 112  * operations that can be used without any mutual exclusion.
 113  * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
 114  *
 115  * For convenience, cds_wfcq_dequeue_blocking() and
 116  * cds_wfcq_splice_blocking() hold the dequeue lock.
 117  *
 118  * Besides locking, mutual exclusion of dequeue, splice and iteration
 119  * can be ensured by performing all of those operations from a single
 120  * thread, without requiring any lock.
 121  */
 122
 123 /*
 124  * cds_wfcq_node_init: initialize wait-free queue node.
 125  */
 126 extern void cds_wfcq_node_init(struct cds_wfcq_node *node);
 127
 128 /*
 129  * cds_wfcq_init: initialize wait-free queue.
 130  */
 131 extern void cds_wfcq_init(struct cds_wfcq_head *head,
 132                 struct cds_wfcq_tail *tail);
 133
 134 /*
 135  * cds_wfcq_empty: return whether wait-free queue is empty.
 136  *
 137  * No memory barrier is issued. No mutual exclusion is required.
 138  */
 139 extern bool cds_wfcq_empty(struct cds_wfcq_head *head,
 140                 struct cds_wfcq_tail *tail);
 141
 142 /*
 143  * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
 144  */
 145 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
 146                 struct cds_wfcq_tail *tail);
 147
 148 /*
 149  * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
 150  */
 151 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
 152                 struct cds_wfcq_tail *tail);
 153
 154 /*
 155  * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
 156  *
 157  * Issues a full memory barrier before enqueue. No mutual exclusion is
 158  * required.
 159  */
 160 extern void cds_wfcq_enqueue(struct cds_wfcq_head *head,
 161                 struct cds_wfcq_tail *tail,
 162                 struct cds_wfcq_node *node);
 163
 164 /*
 165  * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 166  *
 167  * Content written into the node before enqueue is guaranteed to be
 168  * consistent, but no other memory ordering is ensured.
 169  * It is valid to reuse and free a dequeued node immediately.
 170  * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
 171  * ensured.
 172  */
 173 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
 174                 struct cds_wfcq_head *head,
 175                 struct cds_wfcq_tail *tail);
 176
 177 /*
 178  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 179  *
 180  * Dequeue all nodes from src_q.
 181  * dest_q must be already initialized.
 182  * Content written into the node before enqueue is guaranteed to be
 183  * consistent, but no other memory ordering is ensured.
 184  * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
 185  * ensured.
 186  */
 187 extern void cds_wfcq_splice_blocking(
 188                 struct cds_wfcq_head *dest_q_head,
 189                 struct cds_wfcq_tail *dest_q_tail,
 190                 struct cds_wfcq_head *src_q_head,
 191                 struct cds_wfcq_tail *src_q_tail);
 192
 193 /*
 194  * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 195  *
 196  * Content written into the node before enqueue is guaranteed to be
 197  * consistent, but no other memory ordering is ensured.
 198  * It is valid to reuse and free a dequeued node immediately.
 199  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 200  * caller.
 201  */
 202 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
 203                 struct cds_wfcq_head *head,
 204                 struct cds_wfcq_tail *tail);
 205
 206 /*
 207  * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
 208  *
 209  * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
 210  * if it needs to block.
 211  */
 212 extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
 213                 struct cds_wfcq_head *head,
 214                 struct cds_wfcq_tail *tail);
 215
 216 /*
 217  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 218  *
 219  * Dequeue all nodes from src_q.
 220  * dest_q must be already initialized.
 221  * Content written into the node before enqueue is guaranteed to be
 222  * consistent, but no other memory ordering is ensured.
 223  * Dequeue/splice/iteration mutual exclusion for src_q should be ensured
 224  * by the caller.
 225  */
 226 extern void __cds_wfcq_splice_blocking(
 227                 struct cds_wfcq_head *dest_q_head,
 228                 struct cds_wfcq_tail *dest_q_tail,
 229                 struct cds_wfcq_head *src_q_head,
 230                 struct cds_wfcq_tail *src_q_tail);
 231
 232 /*
 233  * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
 234  *
 235  * Same as __cds_wfcq_splice_blocking, but returns nonzero if it needs to
 236  * block.
 237  */
 238 extern int __cds_wfcq_splice_nonblocking(
 239                 struct cds_wfcq_head *dest_q_head,
 240                 struct cds_wfcq_tail *dest_q_tail,
 241                 struct cds_wfcq_head *src_q_head,
 242                 struct cds_wfcq_tail *src_q_tail);
 243
 244 /*
 245  * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
 246  *
 247  * Content written into the node before enqueue is guaranteed to be
 248  * consistent, but no other memory ordering is ensured.
 249  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 250  * caller.
 251  *
 252  * Used by for-like iteration macros:
 253  * __cds_wfcq_for_each_blocking()
 254  * __cds_wfcq_for_each_blocking_safe()
 255  */
 256 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 257                 struct cds_wfcq_head *head,
 258                 struct cds_wfcq_tail *tail);
 259
 260 /*
 261  * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
 262  *
 263  * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 264  * it needs to block.
 265  */
 266 extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
 267                 struct cds_wfcq_head *head,
 268                 struct cds_wfcq_tail *tail);
 269
 270 /*
 271  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 272  *
 273  * Content written into the node before enqueue is guaranteed to be
 274  * consistent, but no other memory ordering is ensured.
 275  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 276  * caller.
 277  *
 278  * Used by for-like iteration macros:
 279  * __cds_wfcq_for_each_blocking()
 280  * __cds_wfcq_for_each_blocking_safe()
 281  */
 282 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 283                 struct cds_wfcq_head *head,
 284                 struct cds_wfcq_tail *tail,
 285                 struct cds_wfcq_node *node);
 286
 287 /*
 288  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 289  *
 290  * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 291  * it needs to block.
 292  */
 293 extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
 294                 struct cds_wfcq_head *head,
 295                 struct cds_wfcq_tail *tail,
 296                 struct cds_wfcq_node *node);
 297
 298 #endif /* !_LGPL_SOURCE */
 299
 300 /*
 301  * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
 302  * without dequeuing them.
 303  * @head: head of the queue (struct cds_wfcq_head pointer).
 304  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 305  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 306  *
 307  * Content written into each node before enqueue is guaranteed to be
 308  * consistent, but no other memory ordering is ensured.
 309  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 310  * caller.
 311  */
 312 #define __cds_wfcq_for_each_blocking(head, tail, node)          \
 313         for (node = __cds_wfcq_first_blocking(head, tail);      \
 314                 node != NULL;                                   \
 315                 node = __cds_wfcq_next_blocking(head, tail, node))
 316
 317 /*
 318  * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
 319  * without dequeuing them. Safe against deletion.
 320  * @head: head of the queue (struct cds_wfcq_head pointer).
 321  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 322  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 323  * @n: struct cds_wfcq_node pointer holding the next pointer (used
 324  *     internally).
 325  *
 326  * Content written into each node before enqueue is guaranteed to be
 327  * consistent, but no other memory ordering is ensured.
 328  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 329  * caller.
 330  */
 331 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n)                 \
 332         for (node = __cds_wfcq_first_blocking(head, tail),                     \
 333                         n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
 334                 node != NULL;                                                  \
 335                 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
 336
 337 #ifdef __cplusplus
 338 }
 339 #endif
 340
 341 #endif /* _URCU_WFCQUEUE_H */