urcu/wfstack.h

   1 #ifndef _URCU_WFSTACK_H
   2 #define _URCU_WFSTACK_H
   3
   4 /*
   5  * urcu/wfstack.h
   6  *
   7  * Userspace RCU library - Stack with wait-free push, blocking traversal.
   8  *
   9  * Copyright 2010-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * This library is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU Lesser General Public
  13  * License as published by the Free Software Foundation; either
  14  * version 2.1 of the License, or (at your option) any later version.
  15  *
  16  * This library is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  * Lesser General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU Lesser General Public
  22  * License along with this library; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  24  */
  25
  26 #include <pthread.h>
  27 #include <assert.h>
  28 #include <stdbool.h>
  29 #include <urcu/compiler.h>
  30
  31 #ifdef __cplusplus
  32 extern "C" {
  33 #endif
  34
  35 /*
  36  * Stack with wait-free push, blocking traversal.
  37  *
  38  * Stack implementing push, pop, pop_all operations, as well as iterator
  39  * on the stack head returned by pop_all.
  40  *
  41  * Wait-free operations: cds_wfs_push, __cds_wfs_pop_all, cds_wfs_empty,
  42  *                       cds_wfs_first.
  43  * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, cds_wfs_next,
  44  *                      iteration on stack head returned by pop_all.
  45  *
  46  * Synchronization table:
  47  *
  48  * External synchronization techniques described in the API below is
  49  * required between pairs marked with "X". No external synchronization
  50  * required between pairs marked with "-".
  51  *
  52  *                      cds_wfs_push  __cds_wfs_pop  __cds_wfs_pop_all
  53  * cds_wfs_push               -              -                  -
  54  * __cds_wfs_pop              -              X                  X
  55  * __cds_wfs_pop_all          -              X                  -
  56  *
  57  * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
  58  * synchronization.
  59  */
  60
  61 #define CDS_WFS_WOULDBLOCK      ((void *) -1UL)
  62
  63 enum cds_wfs_state {
  64         CDS_WFS_STATE_LAST =            (1U << 0),
  65 };
  66
  67 /*
  68  * struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
  69  * iterator on stack. It is not safe to dereference the node next
  70  * pointer when returned by __cds_wfs_pop_blocking.
  71  */
  72 struct cds_wfs_node {
  73         struct cds_wfs_node *next;
  74 };
  75
  76 /*
  77  * struct cds_wfs_head is returned by __cds_wfs_pop_all, and can be used
  78  * to begin iteration on the stack. "node" needs to be the first field of
  79  * cds_wfs_head, so the end-of-stack pointer value can be used for both
  80  * types.
  81  */
  82 struct cds_wfs_head {
  83         struct cds_wfs_node node;
  84 };
  85
  86 struct cds_wfs_stack {
  87         struct cds_wfs_head *head;
  88         pthread_mutex_t lock;
  89 };
  90
  91 #ifdef _LGPL_SOURCE
  92
  93 #include <urcu/static/wfstack.h>
  94
  95 #define cds_wfs_node_init               _cds_wfs_node_init
  96 #define cds_wfs_init                    _cds_wfs_init
  97 #define cds_wfs_empty                   _cds_wfs_empty
  98 #define cds_wfs_push                    _cds_wfs_push
  99
 100 /* Locking performed internally */
 101 #define cds_wfs_pop_blocking            _cds_wfs_pop_blocking
 102 #define cds_wfs_pop_with_state_blocking _cds_wfs_pop_with_state_blocking
 103 #define cds_wfs_pop_all_blocking        _cds_wfs_pop_all_blocking
 104
 105 /*
 106  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
 107  * cds_wfs_pop_all_blocking.
 108  */
 109 #define cds_wfs_first                   _cds_wfs_first
 110 #define cds_wfs_next_blocking           _cds_wfs_next_blocking
 111 #define cds_wfs_next_nonblocking        _cds_wfs_next_nonblocking
 112
 113 /* Pop locking with internal mutex */
 114 #define cds_wfs_pop_lock                _cds_wfs_pop_lock
 115 #define cds_wfs_pop_unlock              _cds_wfs_pop_unlock
 116
 117 /* Synchronization ensured by the caller. See synchronization table. */
 118 #define __cds_wfs_pop_blocking          ___cds_wfs_pop_blocking
 119 #define __cds_wfs_pop_with_state_blocking       \
 120                                         ___cds_wfs_pop_with_state_blocking
 121 #define __cds_wfs_pop_nonblocking       ___cds_wfs_pop_nonblocking
 122 #define __cds_wfs_pop_with_state_nonblocking    \
 123                                         ___cds_wfs_pop_with_state_nonblocking
 124 #define __cds_wfs_pop_all               ___cds_wfs_pop_all
 125
 126 #else /* !_LGPL_SOURCE */
 127
 128 /*
 129  * cds_wfs_node_init: initialize wait-free stack node.
 130  */
 131 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 132
 133 /*
 134  * cds_wfs_init: initialize wait-free stack.
 135  */
 136 extern void cds_wfs_init(struct cds_wfs_stack *s);
 137
 138 /*
 139  * cds_wfs_empty: return whether wait-free stack is empty.
 140  *
 141  * No memory barrier is issued. No mutual exclusion is required.
 142  */
 143 extern bool cds_wfs_empty(struct cds_wfs_stack *s);
 144
 145 /*
 146  * cds_wfs_push: push a node into the stack.
 147  *
 148  * Issues a full memory barrier before push. No mutual exclusion is
 149  * required.
 150  *
 151  * Returns 0 if the stack was empty prior to adding the node.
 152  * Returns non-zero otherwise.
 153  */
 154 extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node);
 155
 156 /*
 157  * cds_wfs_pop_blocking: pop a node from the stack.
 158  *
 159  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 160  */
 161 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 162
 163 /*
 164  * cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 165  *
 166  * Same as cds_wfs_pop_blocking, but stores whether the stack was
 167  * empty into state (CDS_WFS_STATE_LAST).
 168  */
 169 extern struct cds_wfs_node *
 170         cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 171
 172 /*
 173  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 174  *
 175  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 176  */
 177 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 178
 179 /*
 180  * cds_wfs_first: get first node of a popped stack.
 181  *
 182  * Content written into the node before enqueue is guaranteed to be
 183  * consistent, but no other memory ordering is ensured.
 184  *
 185  * Used by for-like iteration macros in urcu/wfstack.h:
 186  * cds_wfs_for_each_blocking()
 187  * cds_wfs_for_each_blocking_safe()
 188  *
 189  * Returns NULL if popped stack is empty, top stack node otherwise.
 190  */
 191 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 192
 193 /*
 194  * cds_wfs_next_blocking: get next node of a popped stack.
 195  *
 196  * Content written into the node before enqueue is guaranteed to be
 197  * consistent, but no other memory ordering is ensured.
 198  *
 199  * Used by for-like iteration macros in urcu/wfstack.h:
 200  * cds_wfs_for_each_blocking()
 201  * cds_wfs_for_each_blocking_safe()
 202  *
 203  * Returns NULL if reached end of popped stack, non-NULL next stack
 204  * node otherwise.
 205  */
 206 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 207
 208 /*
 209  * cds_wfs_next_nonblocking: get next node of a popped stack.
 210  *
 211  * Same as cds_wfs_next_blocking, but returns CDS_WFS_WOULDBLOCK if it
 212  * needs to block.
 213  */
 214 extern struct cds_wfs_node *cds_wfs_next_nonblocking(struct cds_wfs_node *node);
 215
 216 /*
 217  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 218  */
 219 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 220
 221 /*
 222  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 223  */
 224 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 225
 226 /*
 227  * __cds_wfs_pop_blocking: pop a node from the stack.
 228  *
 229  * Returns NULL if stack is empty.
 230  *
 231  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 232  * following techniques:
 233  *
 234  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 235  *    section. The caller must wait for a grace period to pass before
 236  *    freeing the returned node or modifying the cds_wfs_node structure.
 237  * 2) Using mutual exclusion (e.g. mutexes) to protect
 238  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 239  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 240  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 241  */
 242 extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 243
 244 /*
 245  * __cds_wfs_pop_with_state_blocking: pop a node from the stack, with state.
 246  *
 247  * Same as __cds_wfs_pop_blocking, but stores whether the stack was
 248  * empty into state (CDS_WFS_STATE_LAST).
 249  */
 250 extern struct cds_wfs_node *
 251         __cds_wfs_pop_with_state_blocking(struct cds_wfs_stack *s, int *state);
 252
 253 /*
 254  * __cds_wfs_pop_nonblocking: pop a node from the stack.
 255  *
 256  * Same as __cds_wfs_pop_blocking, but returns CDS_WFS_WOULDBLOCK if
 257  * it needs to block.
 258  */
 259 extern struct cds_wfs_node *__cds_wfs_pop_nonblocking(struct cds_wfs_stack *s);
 260
 261 /*
 262  * __cds_wfs_pop_with_state_nonblocking: pop a node from the stack, with state.
 263  *
 264  * Same as __cds_wfs_pop_nonblocking, but stores whether the stack was
 265  * empty into state (CDS_WFS_STATE_LAST).
 266  */
 267 extern struct cds_wfs_node *
 268         __cds_wfs_pop_with_state_nonblocking(struct cds_wfs_stack *s,
 269                 int *state);
 270
 271 /*
 272  * __cds_wfs_pop_all: pop all nodes from a stack.
 273  *
 274  * __cds_wfs_pop_all does not require any synchronization with other
 275  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 276  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 277  *
 278  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 279  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 280  *    must wait for a grace period to pass before freeing the returned
 281  *    node or modifying the cds_wfs_node structure. However, no RCU
 282  *    read-side critical section is needed around __cds_wfs_pop_all.
 283  * 2) Using mutual exclusion (e.g. mutexes) to protect
 284  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 285  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 286  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 287  */
 288 extern struct cds_wfs_head *__cds_wfs_pop_all(struct cds_wfs_stack *s);
 289
 290 #endif /* !_LGPL_SOURCE */
 291
 292 #ifdef __cplusplus
 293 }
 294 #endif
 295
 296 /*
 297  * cds_wfs_for_each_blocking: Iterate over all nodes returned by
 298  * __cds_wfs_pop_all().
 299  * @head: head of the queue (struct cds_wfs_head pointer).
 300  * @node: iterator (struct cds_wfs_node pointer).
 301  *
 302  * Content written into each node before enqueue is guaranteed to be
 303  * consistent, but no other memory ordering is ensured.
 304  */
 305 #define cds_wfs_for_each_blocking(head, node)                   \
 306         for (node = cds_wfs_first(head);                        \
 307                 node != NULL;                                   \
 308                 node = cds_wfs_next_blocking(node))
 309
 310 /*
 311  * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
 312  * __cds_wfs_pop_all(). Safe against deletion.
 313  * @head: head of the queue (struct cds_wfs_head pointer).
 314  * @node: iterator (struct cds_wfs_node pointer).
 315  * @n: struct cds_wfs_node pointer holding the next pointer (used
 316  *     internally).
 317  *
 318  * Content written into each node before enqueue is guaranteed to be
 319  * consistent, but no other memory ordering is ensured.
 320  */
 321 #define cds_wfs_for_each_blocking_safe(head, node, n)                      \
 322         for (node = cds_wfs_first(head),                                   \
 323                         n = (node ? cds_wfs_next_blocking(node) : NULL);   \
 324                 node != NULL;                                              \
 325                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 326
 327 #endif /* _URCU_WFSTACK_H */