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 /*
  62  * struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
  63  * iterator on stack. It is not safe to dereference the node next
  64  * pointer when returned by __cds_wfs_pop_blocking.
  65  */
  66 struct cds_wfs_node {
  67         struct cds_wfs_node *next;
  68 };
  69
  70 /*
  71  * struct cds_wfs_head is returned by __cds_wfs_pop_all, and can be used
  72  * to begin iteration on the stack. "node" needs to be the first field of
  73  * cds_wfs_head, so the end-of-stack pointer value can be used for both
  74  * types.
  75  */
  76 struct cds_wfs_head {
  77         struct cds_wfs_node node;
  78 };
  79
  80 struct cds_wfs_stack {
  81         struct cds_wfs_head *head;
  82         pthread_mutex_t lock;
  83 };
  84
  85 #ifdef _LGPL_SOURCE
  86
  87 #include <urcu/static/wfstack.h>
  88
  89 #define cds_wfs_node_init               _cds_wfs_node_init
  90 #define cds_wfs_init                    _cds_wfs_init
  91 #define cds_wfs_empty                   _cds_wfs_empty
  92 #define cds_wfs_push                    _cds_wfs_push
  93
  94 /* Locking performed internally */
  95 #define cds_wfs_pop_blocking            _cds_wfs_pop_blocking
  96 #define cds_wfs_pop_all_blocking        _cds_wfs_pop_all_blocking
  97
  98 /*
  99  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
 100  * cds_wfs_pop_all_blocking.
 101  */
 102 #define cds_wfs_first                   _cds_wfs_first
 103 #define cds_wfs_next_blocking           _cds_wfs_next_blocking
 104
 105 /* Pop locking with internal mutex */
 106 #define cds_wfs_pop_lock                _cds_wfs_pop_lock
 107 #define cds_wfs_pop_unlock              _cds_wfs_pop_unlock
 108
 109 /* Synchronization ensured by the caller. See synchronization table. */
 110 #define __cds_wfs_pop_blocking          ___cds_wfs_pop_blocking
 111 #define __cds_wfs_pop_all               ___cds_wfs_pop_all
 112
 113 #else /* !_LGPL_SOURCE */
 114
 115 /*
 116  * cds_wfs_node_init: initialize wait-free stack node.
 117  */
 118 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 119
 120 /*
 121  * cds_wfs_init: initialize wait-free stack.
 122  */
 123 extern void cds_wfs_init(struct cds_wfs_stack *s);
 124
 125 /*
 126  * cds_wfs_empty: return whether wait-free stack is empty.
 127  *
 128  * No memory barrier is issued. No mutual exclusion is required.
 129  */
 130 extern bool cds_wfs_empty(struct cds_wfs_stack *s);
 131
 132 /*
 133  * cds_wfs_push: push a node into the stack.
 134  *
 135  * Issues a full memory barrier before push. No mutual exclusion is
 136  * required.
 137  *
 138  * Returns 0 if the stack was empty prior to adding the node.
 139  * Returns non-zero otherwise.
 140  */
 141 extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node);
 142
 143 /*
 144  * cds_wfs_pop_blocking: pop a node from the stack.
 145  *
 146  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 147  */
 148 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 149
 150 /*
 151  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 152  *
 153  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 154  */
 155 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 156
 157 /*
 158  * cds_wfs_first: get first node of a popped stack.
 159  *
 160  * Content written into the node before enqueue is guaranteed to be
 161  * consistent, but no other memory ordering is ensured.
 162  *
 163  * Used by for-like iteration macros in urcu/wfstack.h:
 164  * cds_wfs_for_each_blocking()
 165  * cds_wfs_for_each_blocking_safe()
 166  *
 167  * Returns NULL if popped stack is empty, top stack node otherwise.
 168  */
 169 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 170
 171 /*
 172  * cds_wfs_next_blocking: get next node of a popped stack.
 173  *
 174  * Content written into the node before enqueue is guaranteed to be
 175  * consistent, but no other memory ordering is ensured.
 176  *
 177  * Used by for-like iteration macros in urcu/wfstack.h:
 178  * cds_wfs_for_each_blocking()
 179  * cds_wfs_for_each_blocking_safe()
 180  *
 181  * Returns NULL if reached end of popped stack, non-NULL next stack
 182  * node otherwise.
 183  */
 184 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 185
 186 /*
 187  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 188  */
 189 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 190
 191 /*
 192  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 193  */
 194 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 195
 196 /*
 197  * __cds_wfs_pop_blocking: pop a node from the stack.
 198  *
 199  * Returns NULL if stack is empty.
 200  *
 201  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 202  * following techniques:
 203  *
 204  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 205  *    section. The caller must wait for a grace period to pass before
 206  *    freeing the returned node or modifying the cds_wfs_node structure.
 207  * 2) Using mutual exclusion (e.g. mutexes) to protect
 208  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 209  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 210  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 211  */
 212 extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 213
 214 /*
 215  * __cds_wfs_pop_all: pop all nodes from a stack.
 216  *
 217  * __cds_wfs_pop_all does not require any synchronization with other
 218  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 219  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 220  *
 221  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 222  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 223  *    must wait for a grace period to pass before freeing the returned
 224  *    node or modifying the cds_wfs_node structure. However, no RCU
 225  *    read-side critical section is needed around __cds_wfs_pop_all.
 226  * 2) Using mutual exclusion (e.g. mutexes) to protect
 227  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 228  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 229  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 230  */
 231 extern struct cds_wfs_head *__cds_wfs_pop_all(struct cds_wfs_stack *s);
 232
 233 #endif /* !_LGPL_SOURCE */
 234
 235 #ifdef __cplusplus
 236 }
 237 #endif
 238
 239 /*
 240  * cds_wfs_for_each_blocking: Iterate over all nodes returned by
 241  * __cds_wfs_pop_all().
 242  * @head: head of the queue (struct cds_wfs_head pointer).
 243  * @node: iterator (struct cds_wfs_node pointer).
 244  *
 245  * Content written into each node before enqueue is guaranteed to be
 246  * consistent, but no other memory ordering is ensured.
 247  */
 248 #define cds_wfs_for_each_blocking(head, node)                   \
 249         for (node = cds_wfs_first(head);                        \
 250                 node != NULL;                                   \
 251                 node = cds_wfs_next_blocking(node))
 252
 253 /*
 254  * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
 255  * __cds_wfs_pop_all(). Safe against deletion.
 256  * @head: head of the queue (struct cds_wfs_head pointer).
 257  * @node: iterator (struct cds_wfs_node pointer).
 258  * @n: struct cds_wfs_node pointer holding the next pointer (used
 259  *     internally).
 260  *
 261  * Content written into each node before enqueue is guaranteed to be
 262  * consistent, but no other memory ordering is ensured.
 263  */
 264 #define cds_wfs_for_each_blocking_safe(head, node, n)                      \
 265         for (node = cds_wfs_first(head),                                   \
 266                         n = (node ? cds_wfs_next_blocking(node) : NULL);   \
 267                 node != NULL;                                              \
 268                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 269
 270 #endif /* _URCU_WFSTACK_H */