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 enum cds_wfcq_state {
  56         CDS_WFCQ_STATE_LAST =           (1U << 0),
  57 };
  58
  59 struct cds_wfcq_node {
  60         struct cds_wfcq_node *next;
  61 };
  62
  63 /*
  64  * Do not put head and tail on the same cache-line if concurrent
  65  * enqueue/dequeue are expected from many CPUs. This eliminates
  66  * false-sharing between enqueue and dequeue.
  67  */
  68 struct cds_wfcq_head {
  69         struct cds_wfcq_node node;
  70         pthread_mutex_t lock;
  71 };
  72
  73 struct cds_wfcq_tail {
  74         struct cds_wfcq_node *p;
  75 };
  76
  77 #ifdef _LGPL_SOURCE
  78
  79 #include <urcu/static/wfcqueue.h>
  80
  81 #define cds_wfcq_node_init              _cds_wfcq_node_init
  82 #define cds_wfcq_init                   _cds_wfcq_init
  83 #define cds_wfcq_destroy                _cds_wfcq_destroy
  84 #define cds_wfcq_empty                  _cds_wfcq_empty
  85 #define cds_wfcq_enqueue                _cds_wfcq_enqueue
  86
  87 /* Dequeue locking */
  88 #define cds_wfcq_dequeue_lock           _cds_wfcq_dequeue_lock
  89 #define cds_wfcq_dequeue_unlock         _cds_wfcq_dequeue_unlock
  90
  91 /* Locking performed within cds_wfcq calls. */
  92 #define cds_wfcq_dequeue_blocking       _cds_wfcq_dequeue_blocking
  93 #define cds_wfcq_dequeue_with_state_blocking    \
  94                                         _cds_wfcq_dequeue_with_state_blocking
  95 #define cds_wfcq_splice_blocking        _cds_wfcq_splice_blocking
  96 #define cds_wfcq_first_blocking         _cds_wfcq_first_blocking
  97 #define cds_wfcq_next_blocking          _cds_wfcq_next_blocking
  98
  99 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
 100 #define __cds_wfcq_dequeue_blocking     ___cds_wfcq_dequeue_blocking
 101 #define __cds_wfcq_dequeue_with_state_blocking  \
 102                                         ___cds_wfcq_dequeue_with_state_blocking
 103 #define __cds_wfcq_splice_blocking      ___cds_wfcq_splice_blocking
 104 #define __cds_wfcq_first_blocking       ___cds_wfcq_first_blocking
 105 #define __cds_wfcq_next_blocking        ___cds_wfcq_next_blocking
 106
 107 /*
 108  * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
 109  * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
 110  * need to block. splice returns nonzero if it needs to block.
 111  */
 112 #define __cds_wfcq_dequeue_nonblocking  ___cds_wfcq_dequeue_nonblocking
 113 #define __cds_wfcq_dequeue_with_state_nonblocking       \
 114                                 ___cds_wfcq_dequeue_with_state_nonblocking
 115 #define __cds_wfcq_splice_nonblocking   ___cds_wfcq_splice_nonblocking
 116 #define __cds_wfcq_first_nonblocking    ___cds_wfcq_first_nonblocking
 117 #define __cds_wfcq_next_nonblocking     ___cds_wfcq_next_nonblocking
 118
 119 #else /* !_LGPL_SOURCE */
 120
 121 /*
 122  * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
 123  *
 124  * Synchronization table:
 125  *
 126  * External synchronization techniques described in the API below is
 127  * required between pairs marked with "X". No external synchronization
 128  * required between pairs marked with "-".
 129  *
 130  * Legend:
 131  * [1] cds_wfcq_enqueue
 132  * [2] __cds_wfcq_splice (destination queue)
 133  * [3] __cds_wfcq_dequeue
 134  * [4] __cds_wfcq_splice (source queue)
 135  * [5] __cds_wfcq_first
 136  * [6] __cds_wfcq_next
 137  *
 138  *     [1] [2] [3] [4] [5] [6]
 139  * [1]  -   -   -   -   -   -
 140  * [2]  -   -   -   -   -   -
 141  * [3]  -   -   X   X   X   X
 142  * [4]  -   -   X   -   X   X
 143  * [5]  -   -   X   X   -   -
 144  * [6]  -   -   X   X   -   -
 145  *
 146  * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
 147  *
 148  * For convenience, cds_wfcq_dequeue_blocking() and
 149  * cds_wfcq_splice_blocking() hold the dequeue lock.
 150  *
 151  * Besides locking, mutual exclusion of dequeue, splice and iteration
 152  * can be ensured by performing all of those operations from a single
 153  * thread, without requiring any lock.
 154  */
 155
 156 /*
 157  * cds_wfcq_node_init: initialize wait-free queue node.
 158  */
 159 extern void cds_wfcq_node_init(struct cds_wfcq_node *node);
 160
 161 /*
 162  * cds_wfcq_init: initialize wait-free queue. Pair with
 163  * cds_wfcq_destroy().
 164  */
 165 extern void cds_wfcq_init(struct cds_wfcq_head *head,
 166                 struct cds_wfcq_tail *tail);
 167
 168 /*
 169  * cds_wfcq_destroy: destroy wait-free queue. Pair with
 170  * cds_wfcq_init().
 171  */
 172 extern void cds_wfcq_destroy(struct cds_wfcq_head *head,
 173                 struct cds_wfcq_tail *tail);
 174
 175 /*
 176  * cds_wfcq_empty: return whether wait-free queue is empty.
 177  *
 178  * No memory barrier is issued. No mutual exclusion is required.
 179  */
 180 extern bool cds_wfcq_empty(struct cds_wfcq_head *head,
 181                 struct cds_wfcq_tail *tail);
 182
 183 /*
 184  * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
 185  */
 186 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
 187                 struct cds_wfcq_tail *tail);
 188
 189 /*
 190  * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
 191  */
 192 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
 193                 struct cds_wfcq_tail *tail);
 194
 195 /*
 196  * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
 197  *
 198  * Issues a full memory barrier before enqueue. No mutual exclusion is
 199  * required.
 200  *
 201  * Returns false if the queue was empty prior to adding the node.
 202  * Returns true otherwise.
 203  */
 204 extern bool cds_wfcq_enqueue(struct cds_wfcq_head *head,
 205                 struct cds_wfcq_tail *tail,
 206                 struct cds_wfcq_node *node);
 207
 208 /*
 209  * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 210  *
 211  * Content written into the node before enqueue is guaranteed to be
 212  * consistent, but no other memory ordering is ensured.
 213  * It is valid to reuse and free a dequeued node immediately.
 214  * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
 215  * ensured.
 216  */
 217 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
 218                 struct cds_wfcq_head *head,
 219                 struct cds_wfcq_tail *tail);
 220
 221 /*
 222  * cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 223  *
 224  * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the
 225  * last node of the queue into state (CDS_WFCQ_STATE_LAST).
 226  */
 227 extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking(
 228                 struct cds_wfcq_head *head,
 229                 struct cds_wfcq_tail *tail,
 230                 int *state);
 231
 232 /*
 233  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 234  *
 235  * Dequeue all nodes from src_q.
 236  * dest_q must be already initialized.
 237  * Content written into the node before enqueue is guaranteed to be
 238  * consistent, but no other memory ordering is ensured.
 239  * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
 240  * ensured.
 241  *
 242  * Returns enum cds_wfcq_ret which indicates the state of the src or
 243  * dest queue. Cannot block.
 244  */
 245 extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
 246                 struct cds_wfcq_head *dest_q_head,
 247                 struct cds_wfcq_tail *dest_q_tail,
 248                 struct cds_wfcq_head *src_q_head,
 249                 struct cds_wfcq_tail *src_q_tail);
 250
 251 /*
 252  * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 253  *
 254  * Content written into the node before enqueue is guaranteed to be
 255  * consistent, but no other memory ordering is ensured.
 256  * It is valid to reuse and free a dequeued node immediately.
 257  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 258  * caller.
 259  */
 260 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
 261                 struct cds_wfcq_head *head,
 262                 struct cds_wfcq_tail *tail);
 263
 264 /*
 265  * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 266  *
 267  * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the
 268  * last node of the queue into state (CDS_WFCQ_STATE_LAST).
 269  */
 270 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking(
 271                 struct cds_wfcq_head *head,
 272                 struct cds_wfcq_tail *tail,
 273                 int *state);
 274
 275 /*
 276  * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
 277  *
 278  * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
 279  * if it needs to block.
 280  */
 281 extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
 282                 struct cds_wfcq_head *head,
 283                 struct cds_wfcq_tail *tail);
 284
 285 /*
 286  * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 287  *
 288  * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing
 289  * the last node of the queue into state (CDS_WFCQ_STATE_LAST).
 290  */
 291 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking(
 292                 struct cds_wfcq_head *head,
 293                 struct cds_wfcq_tail *tail,
 294                 int *state);
 295
 296 /*
 297  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 298  *
 299  * Dequeue all nodes from src_q.
 300  * dest_q must be already initialized.
 301  * Mutual exclusion for src_q should be ensured by the caller as
 302  * specified in the "Synchronisation table".
 303  * Returns enum cds_wfcq_ret which indicates the state of the src or
 304  * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK.
 305  */
 306 extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
 307                 struct cds_wfcq_head *dest_q_head,
 308                 struct cds_wfcq_tail *dest_q_tail,
 309                 struct cds_wfcq_head *src_q_head,
 310                 struct cds_wfcq_tail *src_q_tail);
 311
 312 /*
 313  * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
 314  *
 315  * Same as __cds_wfcq_splice_blocking, but returns
 316  * CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
 317  */
 318 extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
 319                 struct cds_wfcq_head *dest_q_head,
 320                 struct cds_wfcq_tail *dest_q_tail,
 321                 struct cds_wfcq_head *src_q_head,
 322                 struct cds_wfcq_tail *src_q_tail);
 323
 324 /*
 325  * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
 326  *
 327  * Content written into the node before enqueue is guaranteed to be
 328  * consistent, but no other memory ordering is ensured.
 329  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 330  * caller.
 331  *
 332  * Used by for-like iteration macros:
 333  * __cds_wfcq_for_each_blocking()
 334  * __cds_wfcq_for_each_blocking_safe()
 335  *
 336  * Returns NULL if queue is empty, first node otherwise.
 337  */
 338 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 339                 struct cds_wfcq_head *head,
 340                 struct cds_wfcq_tail *tail);
 341
 342 /*
 343  * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
 344  *
 345  * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 346  * it needs to block.
 347  */
 348 extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
 349                 struct cds_wfcq_head *head,
 350                 struct cds_wfcq_tail *tail);
 351
 352 /*
 353  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 354  *
 355  * Content written into the node before enqueue is guaranteed to be
 356  * consistent, but no other memory ordering is ensured.
 357  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 358  * caller.
 359  *
 360  * Used by for-like iteration macros:
 361  * __cds_wfcq_for_each_blocking()
 362  * __cds_wfcq_for_each_blocking_safe()
 363  *
 364  * Returns NULL if reached end of queue, non-NULL next queue node
 365  * otherwise.
 366  */
 367 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 368                 struct cds_wfcq_head *head,
 369                 struct cds_wfcq_tail *tail,
 370                 struct cds_wfcq_node *node);
 371
 372 /*
 373  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 374  *
 375  * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 376  * it needs to block.
 377  */
 378 extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
 379                 struct cds_wfcq_head *head,
 380                 struct cds_wfcq_tail *tail,
 381                 struct cds_wfcq_node *node);
 382
 383 #endif /* !_LGPL_SOURCE */
 384
 385 /*
 386  * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
 387  * without dequeuing them.
 388  * @head: head of the queue (struct cds_wfcq_head pointer).
 389  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 390  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 391  *
 392  * Content written into each node before enqueue is guaranteed to be
 393  * consistent, but no other memory ordering is ensured.
 394  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 395  * caller.
 396  */
 397 #define __cds_wfcq_for_each_blocking(head, tail, node)          \
 398         for (node = __cds_wfcq_first_blocking(head, tail);      \
 399                 node != NULL;                                   \
 400                 node = __cds_wfcq_next_blocking(head, tail, node))
 401
 402 /*
 403  * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
 404  * without dequeuing them. Safe against deletion.
 405  * @head: head of the queue (struct cds_wfcq_head pointer).
 406  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 407  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 408  * @n: struct cds_wfcq_node pointer holding the next pointer (used
 409  *     internally).
 410  *
 411  * Content written into each node before enqueue is guaranteed to be
 412  * consistent, but no other memory ordering is ensured.
 413  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 414  * caller.
 415  */
 416 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n)                 \
 417         for (node = __cds_wfcq_first_blocking(head, tail),                     \
 418                         n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
 419                 node != NULL;                                                  \
 420                 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
 421
 422 #ifdef __cplusplus
 423 }
 424 #endif
 425
 426 #endif /* _URCU_WFCQUEUE_H */