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 enum cds_wfcq_ret {
  49         CDS_WFCQ_RET_WOULDBLOCK =       -1,
  50         CDS_WFCQ_RET_DEST_EMPTY =       0,
  51         CDS_WFCQ_RET_DEST_NON_EMPTY =   1,
  52         CDS_WFCQ_RET_SRC_EMPTY =        2,
  53 };
  54
  55 struct cds_wfcq_node {
  56         struct cds_wfcq_node *next;
  57 };
  58
  59 /*
  60  * Do not put head and tail on the same cache-line if concurrent
  61  * enqueue/dequeue are expected from many CPUs. This eliminates
  62  * false-sharing between enqueue and dequeue.
  63  */
  64 struct cds_wfcq_head {
  65         struct cds_wfcq_node node;
  66         pthread_mutex_t lock;
  67 };
  68
  69 struct cds_wfcq_tail {
  70         struct cds_wfcq_node *p;
  71 };
  72
  73 #ifdef _LGPL_SOURCE
  74
  75 #include <urcu/static/wfcqueue.h>
  76
  77 #define cds_wfcq_node_init              _cds_wfcq_node_init
  78 #define cds_wfcq_init                   _cds_wfcq_init
  79 #define cds_wfcq_empty                  _cds_wfcq_empty
  80 #define cds_wfcq_enqueue                _cds_wfcq_enqueue
  81
  82 /* Dequeue locking */
  83 #define cds_wfcq_dequeue_lock           _cds_wfcq_dequeue_lock
  84 #define cds_wfcq_dequeue_unlock         _cds_wfcq_dequeue_unlock
  85
  86 /* Locking performed within cds_wfcq calls. */
  87 #define cds_wfcq_dequeue_blocking       _cds_wfcq_dequeue_blocking
  88 #define cds_wfcq_splice_blocking        _cds_wfcq_splice_blocking
  89 #define cds_wfcq_first_blocking         _cds_wfcq_first_blocking
  90 #define cds_wfcq_next_blocking          _cds_wfcq_next_blocking
  91
  92 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
  93 #define __cds_wfcq_dequeue_blocking     ___cds_wfcq_dequeue_blocking
  94 #define __cds_wfcq_splice_blocking      ___cds_wfcq_splice_blocking
  95 #define __cds_wfcq_first_blocking       ___cds_wfcq_first_blocking
  96 #define __cds_wfcq_next_blocking        ___cds_wfcq_next_blocking
  97
  98 /*
  99  * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
 100  * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
 101  * need to block. splice returns nonzero if it needs to block.
 102  */
 103 #define __cds_wfcq_dequeue_nonblocking  ___cds_wfcq_dequeue_nonblocking
 104 #define __cds_wfcq_splice_nonblocking   ___cds_wfcq_splice_nonblocking
 105 #define __cds_wfcq_first_nonblocking    ___cds_wfcq_first_nonblocking
 106 #define __cds_wfcq_next_nonblocking     ___cds_wfcq_next_nonblocking
 107
 108 #else /* !_LGPL_SOURCE */
 109
 110 /*
 111  * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
 112  *
 113  * Synchronization table:
 114  *
 115  * External synchronization techniques described in the API below is
 116  * required between pairs marked with "X". No external synchronization
 117  * required between pairs marked with "-".
 118  *
 119  * Legend:
 120  * [1] cds_wfcq_enqueue
 121  * [2] __cds_wfcq_splice (destination queue)
 122  * [3] __cds_wfcq_dequeue
 123  * [4] __cds_wfcq_splice (source queue)
 124  * [5] __cds_wfcq_first
 125  * [6] __cds_wfcq_next
 126  *
 127  *     [1] [2] [3] [4] [5] [6]
 128  * [1]  -   -   -   -   -   -
 129  * [2]  -   -   -   -   -   -
 130  * [3]  -   -   X   X   X   X
 131  * [4]  -   -   X   -   X   X
 132  * [5]  -   -   X   X   -   -
 133  * [6]  -   -   X   X   -   -
 134  *
 135  * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
 136  *
 137  * For convenience, cds_wfcq_dequeue_blocking() and
 138  * cds_wfcq_splice_blocking() hold the dequeue lock.
 139  *
 140  * Besides locking, mutual exclusion of dequeue, splice and iteration
 141  * can be ensured by performing all of those operations from a single
 142  * thread, without requiring any lock.
 143  */
 144
 145 /*
 146  * cds_wfcq_node_init: initialize wait-free queue node.
 147  */
 148 extern void cds_wfcq_node_init(struct cds_wfcq_node *node);
 149
 150 /*
 151  * cds_wfcq_init: initialize wait-free queue.
 152  */
 153 extern void cds_wfcq_init(struct cds_wfcq_head *head,
 154                 struct cds_wfcq_tail *tail);
 155
 156 /*
 157  * cds_wfcq_empty: return whether wait-free queue is empty.
 158  *
 159  * No memory barrier is issued. No mutual exclusion is required.
 160  */
 161 extern bool cds_wfcq_empty(struct cds_wfcq_head *head,
 162                 struct cds_wfcq_tail *tail);
 163
 164 /*
 165  * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
 166  */
 167 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
 168                 struct cds_wfcq_tail *tail);
 169
 170 /*
 171  * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
 172  */
 173 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
 174                 struct cds_wfcq_tail *tail);
 175
 176 /*
 177  * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
 178  *
 179  * Issues a full memory barrier before enqueue. No mutual exclusion is
 180  * required.
 181  *
 182  * Returns false if the queue was empty prior to adding the node.
 183  * Returns true otherwise.
 184  */
 185 extern bool cds_wfcq_enqueue(struct cds_wfcq_head *head,
 186                 struct cds_wfcq_tail *tail,
 187                 struct cds_wfcq_node *node);
 188
 189 /*
 190  * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 191  *
 192  * Content written into the node before enqueue is guaranteed to be
 193  * consistent, but no other memory ordering is ensured.
 194  * It is valid to reuse and free a dequeued node immediately.
 195  * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
 196  * ensured.
 197  */
 198 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
 199                 struct cds_wfcq_head *head,
 200                 struct cds_wfcq_tail *tail);
 201
 202 /*
 203  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 204  *
 205  * Dequeue all nodes from src_q.
 206  * dest_q must be already initialized.
 207  * Content written into the node before enqueue is guaranteed to be
 208  * consistent, but no other memory ordering is ensured.
 209  * Mutual exlusion with cds_wfcq_dequeue_blocking and dequeue lock is
 210  * ensured.
 211  *
 212  * Returns enum cds_wfcq_ret which indicates the state of the src or
 213  * dest queue. Cannot block.
 214  */
 215 extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
 216                 struct cds_wfcq_head *dest_q_head,
 217                 struct cds_wfcq_tail *dest_q_tail,
 218                 struct cds_wfcq_head *src_q_head,
 219                 struct cds_wfcq_tail *src_q_tail);
 220
 221 /*
 222  * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 223  *
 224  * Content written into the node before enqueue is guaranteed to be
 225  * consistent, but no other memory ordering is ensured.
 226  * It is valid to reuse and free a dequeued node immediately.
 227  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 228  * caller.
 229  */
 230 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
 231                 struct cds_wfcq_head *head,
 232                 struct cds_wfcq_tail *tail);
 233
 234 /*
 235  * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
 236  *
 237  * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
 238  * if it needs to block.
 239  */
 240 extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
 241                 struct cds_wfcq_head *head,
 242                 struct cds_wfcq_tail *tail);
 243
 244 /*
 245  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 246  *
 247  * Dequeue all nodes from src_q.
 248  * dest_q must be already initialized.
 249  * Mutual exclusion for src_q should be ensured by the caller as
 250  * specified in the "Synchronisation table".
 251  * Returns enum cds_wfcq_ret which indicates the state of the src or
 252  * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK.
 253  */
 254 extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
 255                 struct cds_wfcq_head *dest_q_head,
 256                 struct cds_wfcq_tail *dest_q_tail,
 257                 struct cds_wfcq_head *src_q_head,
 258                 struct cds_wfcq_tail *src_q_tail);
 259
 260 /*
 261  * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
 262  *
 263  * Same as __cds_wfcq_splice_blocking, but returns
 264  * CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
 265  */
 266 extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
 267                 struct cds_wfcq_head *dest_q_head,
 268                 struct cds_wfcq_tail *dest_q_tail,
 269                 struct cds_wfcq_head *src_q_head,
 270                 struct cds_wfcq_tail *src_q_tail);
 271
 272 /*
 273  * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
 274  *
 275  * Content written into the node before enqueue is guaranteed to be
 276  * consistent, but no other memory ordering is ensured.
 277  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 278  * caller.
 279  *
 280  * Used by for-like iteration macros:
 281  * __cds_wfcq_for_each_blocking()
 282  * __cds_wfcq_for_each_blocking_safe()
 283  */
 284 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 285                 struct cds_wfcq_head *head,
 286                 struct cds_wfcq_tail *tail);
 287
 288 /*
 289  * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
 290  *
 291  * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 292  * it needs to block.
 293  */
 294 extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
 295                 struct cds_wfcq_head *head,
 296                 struct cds_wfcq_tail *tail);
 297
 298 /*
 299  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 300  *
 301  * Content written into the node before enqueue is guaranteed to be
 302  * consistent, but no other memory ordering is ensured.
 303  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 304  * caller.
 305  *
 306  * Used by for-like iteration macros:
 307  * __cds_wfcq_for_each_blocking()
 308  * __cds_wfcq_for_each_blocking_safe()
 309  */
 310 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 311                 struct cds_wfcq_head *head,
 312                 struct cds_wfcq_tail *tail,
 313                 struct cds_wfcq_node *node);
 314
 315 /*
 316  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 317  *
 318  * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 319  * it needs to block.
 320  */
 321 extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
 322                 struct cds_wfcq_head *head,
 323                 struct cds_wfcq_tail *tail,
 324                 struct cds_wfcq_node *node);
 325
 326 #endif /* !_LGPL_SOURCE */
 327
 328 /*
 329  * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
 330  * without dequeuing them.
 331  * @head: head of the queue (struct cds_wfcq_head pointer).
 332  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 333  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 334  *
 335  * Content written into each node before enqueue is guaranteed to be
 336  * consistent, but no other memory ordering is ensured.
 337  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 338  * caller.
 339  */
 340 #define __cds_wfcq_for_each_blocking(head, tail, node)          \
 341         for (node = __cds_wfcq_first_blocking(head, tail);      \
 342                 node != NULL;                                   \
 343                 node = __cds_wfcq_next_blocking(head, tail, node))
 344
 345 /*
 346  * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
 347  * without dequeuing them. Safe against deletion.
 348  * @head: head of the queue (struct cds_wfcq_head pointer).
 349  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 350  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 351  * @n: struct cds_wfcq_node pointer holding the next pointer (used
 352  *     internally).
 353  *
 354  * Content written into each node before enqueue is guaranteed to be
 355  * consistent, but no other memory ordering is ensured.
 356  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 357  * caller.
 358  */
 359 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n)                 \
 360         for (node = __cds_wfcq_first_blocking(head, tail),                     \
 361                         n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
 362                 node != NULL;                                                  \
 363                 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
 364
 365 #ifdef __cplusplus
 366 }
 367 #endif
 368
 369 #endif /* _URCU_WFCQUEUE_H */