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     ((struct cds_wfcq_node *) -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 };
  71
  72 struct cds_wfcq_head {
  73         struct cds_wfcq_node node;
  74         pthread_mutex_t lock;
  75 };
  76
  77 /*
  78  * The transparent union allows calling functions that work on both
  79  * struct cds_wfcq_head and struct __cds_wfcq_head on any of those two
  80  * types.
  81  */
  82 typedef union {
  83         struct __cds_wfcq_head *_h;
  84         struct cds_wfcq_head *h;
  85 } __attribute__((__transparent_union__)) cds_wfcq_head_ptr_t;
  86
  87 struct cds_wfcq_tail {
  88         struct cds_wfcq_node *p;
  89 };
  90
  91 #ifdef _LGPL_SOURCE
  92
  93 #include <urcu/static/wfcqueue.h>
  94
  95 #define cds_wfcq_node_init              _cds_wfcq_node_init
  96 #define cds_wfcq_init                   _cds_wfcq_init
  97 #define cds_wfcq_empty                  _cds_wfcq_empty
  98 #define cds_wfcq_enqueue                _cds_wfcq_enqueue
  99
 100 /* Dequeue locking */
 101 #define cds_wfcq_dequeue_lock           _cds_wfcq_dequeue_lock
 102 #define cds_wfcq_dequeue_unlock         _cds_wfcq_dequeue_unlock
 103
 104 /* Locking performed within cds_wfcq calls. */
 105 #define cds_wfcq_dequeue_blocking       _cds_wfcq_dequeue_blocking
 106 #define cds_wfcq_dequeue_with_state_blocking    \
 107                                         _cds_wfcq_dequeue_with_state_blocking
 108 #define cds_wfcq_splice_blocking        _cds_wfcq_splice_blocking
 109 #define cds_wfcq_first_blocking         _cds_wfcq_first_blocking
 110 #define cds_wfcq_next_blocking          _cds_wfcq_next_blocking
 111
 112 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
 113 #define __cds_wfcq_dequeue_blocking     ___cds_wfcq_dequeue_blocking
 114 #define __cds_wfcq_dequeue_with_state_blocking  \
 115                                         ___cds_wfcq_dequeue_with_state_blocking
 116 #define __cds_wfcq_splice_blocking      ___cds_wfcq_splice_blocking
 117 #define __cds_wfcq_first_blocking       ___cds_wfcq_first_blocking
 118 #define __cds_wfcq_next_blocking        ___cds_wfcq_next_blocking
 119
 120 /*
 121  * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
 122  * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
 123  * need to block. splice returns nonzero if it needs to block.
 124  */
 125 #define __cds_wfcq_dequeue_nonblocking  ___cds_wfcq_dequeue_nonblocking
 126 #define __cds_wfcq_dequeue_with_state_nonblocking       \
 127                                 ___cds_wfcq_dequeue_with_state_nonblocking
 128 #define __cds_wfcq_splice_nonblocking   ___cds_wfcq_splice_nonblocking
 129 #define __cds_wfcq_first_nonblocking    ___cds_wfcq_first_nonblocking
 130 #define __cds_wfcq_next_nonblocking     ___cds_wfcq_next_nonblocking
 131
 132 #else /* !_LGPL_SOURCE */
 133
 134 /*
 135  * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
 136  *
 137  * Synchronization table:
 138  *
 139  * External synchronization techniques described in the API below is
 140  * required between pairs marked with "X". No external synchronization
 141  * required between pairs marked with "-".
 142  *
 143  * Legend:
 144  * [1] cds_wfcq_enqueue
 145  * [2] __cds_wfcq_splice (destination queue)
 146  * [3] __cds_wfcq_dequeue
 147  * [4] __cds_wfcq_splice (source queue)
 148  * [5] __cds_wfcq_first
 149  * [6] __cds_wfcq_next
 150  *
 151  *     [1] [2] [3] [4] [5] [6]
 152  * [1]  -   -   -   -   -   -
 153  * [2]  -   -   -   -   -   -
 154  * [3]  -   -   X   X   X   X
 155  * [4]  -   -   X   -   X   X
 156  * [5]  -   -   X   X   -   -
 157  * [6]  -   -   X   X   -   -
 158  *
 159  * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
 160  *
 161  * For convenience, cds_wfcq_dequeue_blocking() and
 162  * cds_wfcq_splice_blocking() hold the dequeue lock.
 163  *
 164  * Besides locking, mutual exclusion of dequeue, splice and iteration
 165  * can be ensured by performing all of those operations from a single
 166  * thread, without requiring any lock.
 167  */
 168
 169 /*
 170  * cds_wfcq_node_init: initialize wait-free queue node.
 171  */
 172 extern void cds_wfcq_node_init(struct cds_wfcq_node *node);
 173
 174 /*
 175  * cds_wfcq_init: initialize wait-free queue.
 176  */
 177 extern void cds_wfcq_init(struct cds_wfcq_head *head,
 178                 struct cds_wfcq_tail *tail);
 179
 180 /*
 181  * __cds_wfcq_init: initialize wait-free queue.
 182  */
 183 extern void __cds_wfcq_init(struct __cds_wfcq_head *head,
 184                 struct cds_wfcq_tail *tail);
 185
 186 /*
 187  * cds_wfcq_empty: return whether wait-free queue is empty.
 188  *
 189  * No memory barrier is issued. No mutual exclusion is required.
 190  */
 191 extern bool cds_wfcq_empty(cds_wfcq_head_ptr_t head,
 192                 struct cds_wfcq_tail *tail);
 193
 194 /*
 195  * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
 196  */
 197 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
 198                 struct cds_wfcq_tail *tail);
 199
 200 /*
 201  * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
 202  */
 203 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
 204                 struct cds_wfcq_tail *tail);
 205
 206 /*
 207  * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
 208  *
 209  * Issues a full memory barrier before enqueue. No mutual exclusion is
 210  * required.
 211  *
 212  * Returns false if the queue was empty prior to adding the node.
 213  * Returns true otherwise.
 214  */
 215 extern bool cds_wfcq_enqueue(cds_wfcq_head_ptr_t head,
 216                 struct cds_wfcq_tail *tail,
 217                 struct cds_wfcq_node *node);
 218
 219 /*
 220  * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 221  *
 222  * Content written into the node before enqueue is guaranteed to be
 223  * consistent, but no other memory ordering is ensured.
 224  * It is valid to reuse and free a dequeued node immediately.
 225  * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
 226  * ensured.
 227  */
 228 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
 229                 struct cds_wfcq_head *head,
 230                 struct cds_wfcq_tail *tail);
 231
 232 /*
 233  * cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 234  *
 235  * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the
 236  * last node of the queue into state (CDS_WFCQ_STATE_LAST).
 237  */
 238 extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking(
 239                 struct cds_wfcq_head *head,
 240                 struct cds_wfcq_tail *tail,
 241                 int *state);
 242
 243 /*
 244  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 245  *
 246  * Dequeue all nodes from src_q.
 247  * dest_q must be already initialized.
 248  * Content written into the node before enqueue is guaranteed to be
 249  * consistent, but no other memory ordering is ensured.
 250  * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
 251  * ensured.
 252  *
 253  * Returns enum cds_wfcq_ret which indicates the state of the src or
 254  * dest queue.
 255  */
 256 extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
 257                 struct cds_wfcq_head *dest_q_head,
 258                 struct cds_wfcq_tail *dest_q_tail,
 259                 struct cds_wfcq_head *src_q_head,
 260                 struct cds_wfcq_tail *src_q_tail);
 261
 262 /*
 263  * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 264  *
 265  * Content written into the node before enqueue is guaranteed to be
 266  * consistent, but no other memory ordering is ensured.
 267  * It is valid to reuse and free a dequeued node immediately.
 268  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 269  * caller.
 270  */
 271 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
 272                 cds_wfcq_head_ptr_t head,
 273                 struct cds_wfcq_tail *tail);
 274
 275 /*
 276  * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 277  *
 278  * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the
 279  * last node of the queue into state (CDS_WFCQ_STATE_LAST).
 280  */
 281 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking(
 282                 cds_wfcq_head_ptr_t head,
 283                 struct cds_wfcq_tail *tail,
 284                 int *state);
 285
 286 /*
 287  * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
 288  *
 289  * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
 290  * if it needs to block.
 291  */
 292 extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
 293                 cds_wfcq_head_ptr_t head,
 294                 struct cds_wfcq_tail *tail);
 295
 296 /*
 297  * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 298  *
 299  * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing
 300  * the last node of the queue into state (CDS_WFCQ_STATE_LAST).
 301  */
 302 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking(
 303                 cds_wfcq_head_ptr_t head,
 304                 struct cds_wfcq_tail *tail,
 305                 int *state);
 306
 307 /*
 308  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 309  *
 310  * Dequeue all nodes from src_q.
 311  * dest_q must be already initialized.
 312  * Mutual exclusion for src_q should be ensured by the caller as
 313  * specified in the "Synchronisation table".
 314  * Returns enum cds_wfcq_ret which indicates the state of the src or
 315  * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK.
 316  */
 317 extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
 318                 cds_wfcq_head_ptr_t dest_q_head,
 319                 struct cds_wfcq_tail *dest_q_tail,
 320                 cds_wfcq_head_ptr_t src_q_head,
 321                 struct cds_wfcq_tail *src_q_tail);
 322
 323 /*
 324  * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
 325  *
 326  * Same as __cds_wfcq_splice_blocking, but returns
 327  * CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
 328  */
 329 extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
 330                 cds_wfcq_head_ptr_t dest_q_head,
 331                 struct cds_wfcq_tail *dest_q_tail,
 332                 cds_wfcq_head_ptr_t src_q_head,
 333                 struct cds_wfcq_tail *src_q_tail);
 334
 335 /*
 336  * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
 337  *
 338  * Content written into the node before enqueue is guaranteed to be
 339  * consistent, but no other memory ordering is ensured.
 340  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 341  * caller.
 342  *
 343  * Used by for-like iteration macros:
 344  * __cds_wfcq_for_each_blocking()
 345  * __cds_wfcq_for_each_blocking_safe()
 346  *
 347  * Returns NULL if queue is empty, first node otherwise.
 348  */
 349 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 350                 cds_wfcq_head_ptr_t head,
 351                 struct cds_wfcq_tail *tail);
 352
 353 /*
 354  * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
 355  *
 356  * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 357  * it needs to block.
 358  */
 359 extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
 360                 cds_wfcq_head_ptr_t head,
 361                 struct cds_wfcq_tail *tail);
 362
 363 /*
 364  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 365  *
 366  * Content written into the node before enqueue is guaranteed to be
 367  * consistent, but no other memory ordering is ensured.
 368  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 369  * caller.
 370  *
 371  * Used by for-like iteration macros:
 372  * __cds_wfcq_for_each_blocking()
 373  * __cds_wfcq_for_each_blocking_safe()
 374  *
 375  * Returns NULL if reached end of queue, non-NULL next queue node
 376  * otherwise.
 377  */
 378 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 379                 cds_wfcq_head_ptr_t head,
 380                 struct cds_wfcq_tail *tail,
 381                 struct cds_wfcq_node *node);
 382
 383 /*
 384  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 385  *
 386  * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 387  * it needs to block.
 388  */
 389 extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
 390                 cds_wfcq_head_ptr_t head,
 391                 struct cds_wfcq_tail *tail,
 392                 struct cds_wfcq_node *node);
 393
 394 #endif /* !_LGPL_SOURCE */
 395
 396 /*
 397  * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
 398  * without dequeuing them.
 399  * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
 400  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 401  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 402  *
 403  * Content written into each node before enqueue is guaranteed to be
 404  * consistent, but no other memory ordering is ensured.
 405  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 406  * caller.
 407  */
 408 #define __cds_wfcq_for_each_blocking(head, tail, node)          \
 409         for (node = __cds_wfcq_first_blocking(head, tail);      \
 410                 node != NULL;                                   \
 411                 node = __cds_wfcq_next_blocking(head, tail, node))
 412
 413 /*
 414  * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
 415  * without dequeuing them. Safe against deletion.
 416  * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
 417  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 418  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 419  * @n: struct cds_wfcq_node pointer holding the next pointer (used
 420  *     internally).
 421  *
 422  * Content written into each node before enqueue is guaranteed to be
 423  * consistent, but no other memory ordering is ensured.
 424  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 425  * caller.
 426  */
 427 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n)                 \
 428         for (node = __cds_wfcq_first_blocking(head, tail),                     \
 429                         n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
 430                 node != NULL;                                                  \
 431                 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
 432
 433 #ifdef __cplusplus
 434 }
 435 #endif
 436
 437 #endif /* _URCU_WFCQUEUE_H */