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 #ifndef __cplusplus
  78 /*
  79  * The transparent union allows calling functions that work on both
  80  * struct cds_wfcq_head and struct __cds_wfcq_head on any of those two
  81  * types.
  82  */
  83 typedef union {
  84         struct __cds_wfcq_head *_h;
  85         struct cds_wfcq_head *h;
  86 } __attribute__((__transparent_union__)) cds_wfcq_head_ptr_t;
  87
  88 /*
  89  * This static inline is only present for compatibility with C++. It is
  90  * effect-less in C.
  91  */
  92 static inline struct __cds_wfcq_head *__cds_wfcq_head_cast(struct __cds_wfcq_head *head)
  93 {
  94         return head;
  95 }
  96
  97 /*
  98  * This static inline is only present for compatibility with C++. It is
  99  * effect-less in C.
 100  */
 101 static inline struct cds_wfcq_head *cds_wfcq_head_cast(struct cds_wfcq_head *head)
 102 {
 103         return head;
 104 }
 105 #else /* #ifndef __cplusplus */
 106
 107 /* C++ ignores transparent union. */
 108 typedef union {
 109         struct __cds_wfcq_head *_h;
 110         struct cds_wfcq_head *h;
 111 } cds_wfcq_head_ptr_t;
 112
 113 /* C++ ignores transparent union. Requires an explicit conversion. */
 114 static inline cds_wfcq_head_ptr_t __cds_wfcq_head_cast(struct __cds_wfcq_head *head)
 115 {
 116         cds_wfcq_head_ptr_t ret = { ._h = head };
 117         return ret;
 118 }
 119 /* C++ ignores transparent union. Requires an explicit conversion. */
 120 static inline cds_wfcq_head_ptr_t cds_wfcq_head_cast(struct cds_wfcq_head *head)
 121 {
 122         cds_wfcq_head_ptr_t ret = { .h = head };
 123         return ret;
 124 }
 125 #endif /* #else #ifndef __cplusplus */
 126
 127 struct cds_wfcq_tail {
 128         struct cds_wfcq_node *p;
 129 };
 130
 131 #ifdef _LGPL_SOURCE
 132
 133 #include <urcu/static/wfcqueue.h>
 134
 135 #define cds_wfcq_node_init              _cds_wfcq_node_init
 136 #define cds_wfcq_init                   _cds_wfcq_init
 137 #define __cds_wfcq_init                 ___cds_wfcq_init
 138 #define cds_wfcq_empty                  _cds_wfcq_empty
 139 #define cds_wfcq_enqueue                _cds_wfcq_enqueue
 140
 141 /* Dequeue locking */
 142 #define cds_wfcq_dequeue_lock           _cds_wfcq_dequeue_lock
 143 #define cds_wfcq_dequeue_unlock         _cds_wfcq_dequeue_unlock
 144
 145 /* Locking performed within cds_wfcq calls. */
 146 #define cds_wfcq_dequeue_blocking       _cds_wfcq_dequeue_blocking
 147 #define cds_wfcq_dequeue_with_state_blocking    \
 148                                         _cds_wfcq_dequeue_with_state_blocking
 149 #define cds_wfcq_splice_blocking        _cds_wfcq_splice_blocking
 150 #define cds_wfcq_first_blocking         _cds_wfcq_first_blocking
 151 #define cds_wfcq_next_blocking          _cds_wfcq_next_blocking
 152
 153 /* Locking ensured by caller by holding cds_wfcq_dequeue_lock() */
 154 #define __cds_wfcq_dequeue_blocking     ___cds_wfcq_dequeue_blocking
 155 #define __cds_wfcq_dequeue_with_state_blocking  \
 156                                         ___cds_wfcq_dequeue_with_state_blocking
 157 #define __cds_wfcq_splice_blocking      ___cds_wfcq_splice_blocking
 158 #define __cds_wfcq_first_blocking       ___cds_wfcq_first_blocking
 159 #define __cds_wfcq_next_blocking        ___cds_wfcq_next_blocking
 160
 161 /*
 162  * Locking ensured by caller by holding cds_wfcq_dequeue_lock().
 163  * Non-blocking: deque, first, next return CDS_WFCQ_WOULDBLOCK if they
 164  * need to block. splice returns nonzero if it needs to block.
 165  */
 166 #define __cds_wfcq_dequeue_nonblocking  ___cds_wfcq_dequeue_nonblocking
 167 #define __cds_wfcq_dequeue_with_state_nonblocking       \
 168                                 ___cds_wfcq_dequeue_with_state_nonblocking
 169 #define __cds_wfcq_splice_nonblocking   ___cds_wfcq_splice_nonblocking
 170 #define __cds_wfcq_first_nonblocking    ___cds_wfcq_first_nonblocking
 171 #define __cds_wfcq_next_nonblocking     ___cds_wfcq_next_nonblocking
 172
 173 #else /* !_LGPL_SOURCE */
 174
 175 /*
 176  * Mutual exclusion of cds_wfcq_* / __cds_wfcq_* API
 177  *
 178  * Synchronization table:
 179  *
 180  * External synchronization techniques described in the API below is
 181  * required between pairs marked with "X". No external synchronization
 182  * required between pairs marked with "-".
 183  *
 184  * Legend:
 185  * [1] cds_wfcq_enqueue
 186  * [2] __cds_wfcq_splice (destination queue)
 187  * [3] __cds_wfcq_dequeue
 188  * [4] __cds_wfcq_splice (source queue)
 189  * [5] __cds_wfcq_first
 190  * [6] __cds_wfcq_next
 191  *
 192  *     [1] [2] [3] [4] [5] [6]
 193  * [1]  -   -   -   -   -   -
 194  * [2]  -   -   -   -   -   -
 195  * [3]  -   -   X   X   X   X
 196  * [4]  -   -   X   -   X   X
 197  * [5]  -   -   X   X   -   -
 198  * [6]  -   -   X   X   -   -
 199  *
 200  * Mutual exclusion can be ensured by holding cds_wfcq_dequeue_lock().
 201  *
 202  * For convenience, cds_wfcq_dequeue_blocking() and
 203  * cds_wfcq_splice_blocking() hold the dequeue lock.
 204  *
 205  * Besides locking, mutual exclusion of dequeue, splice and iteration
 206  * can be ensured by performing all of those operations from a single
 207  * thread, without requiring any lock.
 208  */
 209
 210 /*
 211  * cds_wfcq_node_init: initialize wait-free queue node.
 212  */
 213 extern void cds_wfcq_node_init(struct cds_wfcq_node *node);
 214
 215 /*
 216  * cds_wfcq_init: initialize wait-free queue.
 217  */
 218 extern void cds_wfcq_init(struct cds_wfcq_head *head,
 219                 struct cds_wfcq_tail *tail);
 220
 221 /*
 222  * __cds_wfcq_init: initialize wait-free queue.
 223  */
 224 extern void __cds_wfcq_init(struct __cds_wfcq_head *head,
 225                 struct cds_wfcq_tail *tail);
 226
 227 /*
 228  * cds_wfcq_empty: return whether wait-free queue is empty.
 229  *
 230  * No memory barrier is issued. No mutual exclusion is required.
 231  */
 232 extern bool cds_wfcq_empty(cds_wfcq_head_ptr_t head,
 233                 struct cds_wfcq_tail *tail);
 234
 235 /*
 236  * cds_wfcq_dequeue_lock: take the dequeue mutual exclusion lock.
 237  */
 238 extern void cds_wfcq_dequeue_lock(struct cds_wfcq_head *head,
 239                 struct cds_wfcq_tail *tail);
 240
 241 /*
 242  * cds_wfcq_dequeue_unlock: release the dequeue mutual exclusion lock.
 243  */
 244 extern void cds_wfcq_dequeue_unlock(struct cds_wfcq_head *head,
 245                 struct cds_wfcq_tail *tail);
 246
 247 /*
 248  * cds_wfcq_enqueue: enqueue a node into a wait-free queue.
 249  *
 250  * Issues a full memory barrier before enqueue. No mutual exclusion is
 251  * required.
 252  *
 253  * Returns false if the queue was empty prior to adding the node.
 254  * Returns true otherwise.
 255  */
 256 extern bool cds_wfcq_enqueue(cds_wfcq_head_ptr_t head,
 257                 struct cds_wfcq_tail *tail,
 258                 struct cds_wfcq_node *node);
 259
 260 /*
 261  * cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 262  *
 263  * Content written into the node before enqueue is guaranteed to be
 264  * consistent, but no other memory ordering is ensured.
 265  * It is valid to reuse and free a dequeued node immediately.
 266  * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
 267  * ensured.
 268  */
 269 extern struct cds_wfcq_node *cds_wfcq_dequeue_blocking(
 270                 struct cds_wfcq_head *head,
 271                 struct cds_wfcq_tail *tail);
 272
 273 /*
 274  * cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 275  *
 276  * Same as cds_wfcq_dequeue_blocking, but saves whether dequeueing the
 277  * last node of the queue into state (CDS_WFCQ_STATE_LAST).
 278  */
 279 extern struct cds_wfcq_node *cds_wfcq_dequeue_with_state_blocking(
 280                 struct cds_wfcq_head *head,
 281                 struct cds_wfcq_tail *tail,
 282                 int *state);
 283
 284 /*
 285  * cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 286  *
 287  * Dequeue all nodes from src_q.
 288  * dest_q must be already initialized.
 289  * Content written into the node before enqueue is guaranteed to be
 290  * consistent, but no other memory ordering is ensured.
 291  * Mutual exclusion with cds_wfcq_dequeue_blocking and dequeue lock is
 292  * ensured.
 293  *
 294  * Returns enum cds_wfcq_ret which indicates the state of the src or
 295  * dest queue.
 296  */
 297 extern enum cds_wfcq_ret cds_wfcq_splice_blocking(
 298                 struct cds_wfcq_head *dest_q_head,
 299                 struct cds_wfcq_tail *dest_q_tail,
 300                 struct cds_wfcq_head *src_q_head,
 301                 struct cds_wfcq_tail *src_q_tail);
 302
 303 /*
 304  * __cds_wfcq_dequeue_blocking: dequeue a node from a wait-free queue.
 305  *
 306  * Content written into the node before enqueue is guaranteed to be
 307  * consistent, but no other memory ordering is ensured.
 308  * It is valid to reuse and free a dequeued node immediately.
 309  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 310  * caller.
 311  */
 312 extern struct cds_wfcq_node *__cds_wfcq_dequeue_blocking(
 313                 cds_wfcq_head_ptr_t head,
 314                 struct cds_wfcq_tail *tail);
 315
 316 /*
 317  * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 318  *
 319  * Same as __cds_wfcq_dequeue_blocking, but saves whether dequeueing the
 320  * last node of the queue into state (CDS_WFCQ_STATE_LAST).
 321  */
 322 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_blocking(
 323                 cds_wfcq_head_ptr_t head,
 324                 struct cds_wfcq_tail *tail,
 325                 int *state);
 326
 327 /*
 328  * __cds_wfcq_dequeue_nonblocking: dequeue a node from a wait-free queue.
 329  *
 330  * Same as __cds_wfcq_dequeue_blocking, but returns CDS_WFCQ_WOULDBLOCK
 331  * if it needs to block.
 332  */
 333 extern struct cds_wfcq_node *__cds_wfcq_dequeue_nonblocking(
 334                 cds_wfcq_head_ptr_t head,
 335                 struct cds_wfcq_tail *tail);
 336
 337 /*
 338  * __cds_wfcq_dequeue_with_state_blocking: dequeue with state.
 339  *
 340  * Same as __cds_wfcq_dequeue_nonblocking, but saves whether dequeueing
 341  * the last node of the queue into state (CDS_WFCQ_STATE_LAST).
 342  */
 343 extern struct cds_wfcq_node *__cds_wfcq_dequeue_with_state_nonblocking(
 344                 cds_wfcq_head_ptr_t head,
 345                 struct cds_wfcq_tail *tail,
 346                 int *state);
 347
 348 /*
 349  * __cds_wfcq_splice_blocking: enqueue all src_q nodes at the end of dest_q.
 350  *
 351  * Dequeue all nodes from src_q.
 352  * dest_q must be already initialized.
 353  * Mutual exclusion for src_q should be ensured by the caller as
 354  * specified in the "Synchronisation table".
 355  * Returns enum cds_wfcq_ret which indicates the state of the src or
 356  * dest queue. Never returns CDS_WFCQ_RET_WOULDBLOCK.
 357  */
 358 extern enum cds_wfcq_ret __cds_wfcq_splice_blocking(
 359                 cds_wfcq_head_ptr_t dest_q_head,
 360                 struct cds_wfcq_tail *dest_q_tail,
 361                 cds_wfcq_head_ptr_t src_q_head,
 362                 struct cds_wfcq_tail *src_q_tail);
 363
 364 /*
 365  * __cds_wfcq_splice_nonblocking: enqueue all src_q nodes at the end of dest_q.
 366  *
 367  * Same as __cds_wfcq_splice_blocking, but returns
 368  * CDS_WFCQ_RET_WOULDBLOCK if it needs to block.
 369  */
 370 extern enum cds_wfcq_ret __cds_wfcq_splice_nonblocking(
 371                 cds_wfcq_head_ptr_t dest_q_head,
 372                 struct cds_wfcq_tail *dest_q_tail,
 373                 cds_wfcq_head_ptr_t src_q_head,
 374                 struct cds_wfcq_tail *src_q_tail);
 375
 376 /*
 377  * __cds_wfcq_first_blocking: get first node of a queue, without dequeuing.
 378  *
 379  * Content written into the node before enqueue is guaranteed to be
 380  * consistent, but no other memory ordering is ensured.
 381  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 382  * caller.
 383  *
 384  * Used by for-like iteration macros:
 385  * __cds_wfcq_for_each_blocking()
 386  * __cds_wfcq_for_each_blocking_safe()
 387  *
 388  * Returns NULL if queue is empty, first node otherwise.
 389  */
 390 extern struct cds_wfcq_node *__cds_wfcq_first_blocking(
 391                 cds_wfcq_head_ptr_t head,
 392                 struct cds_wfcq_tail *tail);
 393
 394 /*
 395  * __cds_wfcq_first_nonblocking: get first node of a queue, without dequeuing.
 396  *
 397  * Same as __cds_wfcq_first_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 398  * it needs to block.
 399  */
 400 extern struct cds_wfcq_node *__cds_wfcq_first_nonblocking(
 401                 cds_wfcq_head_ptr_t head,
 402                 struct cds_wfcq_tail *tail);
 403
 404 /*
 405  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 406  *
 407  * Content written into the node before enqueue is guaranteed to be
 408  * consistent, but no other memory ordering is ensured.
 409  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 410  * caller.
 411  *
 412  * Used by for-like iteration macros:
 413  * __cds_wfcq_for_each_blocking()
 414  * __cds_wfcq_for_each_blocking_safe()
 415  *
 416  * Returns NULL if reached end of queue, non-NULL next queue node
 417  * otherwise.
 418  */
 419 extern struct cds_wfcq_node *__cds_wfcq_next_blocking(
 420                 cds_wfcq_head_ptr_t head,
 421                 struct cds_wfcq_tail *tail,
 422                 struct cds_wfcq_node *node);
 423
 424 /*
 425  * __cds_wfcq_next_blocking: get next node of a queue, without dequeuing.
 426  *
 427  * Same as __cds_wfcq_next_blocking, but returns CDS_WFCQ_WOULDBLOCK if
 428  * it needs to block.
 429  */
 430 extern struct cds_wfcq_node *__cds_wfcq_next_nonblocking(
 431                 cds_wfcq_head_ptr_t head,
 432                 struct cds_wfcq_tail *tail,
 433                 struct cds_wfcq_node *node);
 434
 435 #endif /* !_LGPL_SOURCE */
 436
 437 /*
 438  * __cds_wfcq_for_each_blocking: Iterate over all nodes in a queue,
 439  * without dequeuing them.
 440  * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
 441  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 442  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 443  *
 444  * Content written into each node before enqueue is guaranteed to be
 445  * consistent, but no other memory ordering is ensured.
 446  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 447  * caller.
 448  */
 449 #define __cds_wfcq_for_each_blocking(head, tail, node)          \
 450         for (node = __cds_wfcq_first_blocking(head, tail);      \
 451                 node != NULL;                                   \
 452                 node = __cds_wfcq_next_blocking(head, tail, node))
 453
 454 /*
 455  * __cds_wfcq_for_each_blocking_safe: Iterate over all nodes in a queue,
 456  * without dequeuing them. Safe against deletion.
 457  * @head: head of the queue (struct cds_wfcq_head or __cds_wfcq_head pointer).
 458  * @tail: tail of the queue (struct cds_wfcq_tail pointer).
 459  * @node: iterator on the queue (struct cds_wfcq_node pointer).
 460  * @n: struct cds_wfcq_node pointer holding the next pointer (used
 461  *     internally).
 462  *
 463  * Content written into each node before enqueue is guaranteed to be
 464  * consistent, but no other memory ordering is ensured.
 465  * Dequeue/splice/iteration mutual exclusion should be ensured by the
 466  * caller.
 467  */
 468 #define __cds_wfcq_for_each_blocking_safe(head, tail, node, n)                 \
 469         for (node = __cds_wfcq_first_blocking(head, tail),                     \
 470                         n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL); \
 471                 node != NULL;                                                  \
 472                 node = n, n = (node ? __cds_wfcq_next_blocking(head, tail, node) : NULL))
 473
 474 #ifdef __cplusplus
 475 }
 476 #endif
 477
 478 #endif /* _URCU_WFCQUEUE_H */