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.
  42  * Blocking operations: cds_wfs_pop, cds_wfs_pop_all, iteration on stack
  43  *                      head returned by pop_all.
  44  *
  45  * Synchronization table:
  46  *
  47  * External synchronization techniques described in the API below is
  48  * required between pairs marked with "X". No external synchronization
  49  * required between pairs marked with "-".
  50  *
  51  *                      cds_wfs_push  __cds_wfs_pop  __cds_wfs_pop_all
  52  * cds_wfs_push               -              -                  -
  53  * __cds_wfs_pop              -              X                  X
  54  * __cds_wfs_pop_all          -              X                  -
  55  *
  56  * cds_wfs_pop and cds_wfs_pop_all use an internal mutex to provide
  57  * synchronization.
  58  */
  59
  60 /*
  61  * struct cds_wfs_node is returned by __cds_wfs_pop, and also used as
  62  * iterator on stack. It is not safe to dereference the node next
  63  * pointer when returned by __cds_wfs_pop_blocking.
  64  */
  65 struct cds_wfs_node {
  66         struct cds_wfs_node *next;
  67 };
  68
  69 /*
  70  * struct cds_wfs_head is returned by __cds_wfs_pop_all, and can be used
  71  * to begin iteration on the stack. "node" needs to be the first field of
  72  * cds_wfs_head, so the end-of-stack pointer value can be used for both
  73  * types.
  74  */
  75 struct cds_wfs_head {
  76         struct cds_wfs_node node;
  77 };
  78
  79 struct cds_wfs_stack {
  80         struct cds_wfs_head *head;
  81         pthread_mutex_t lock;
  82 };
  83
  84 #ifdef _LGPL_SOURCE
  85
  86 #include <urcu/static/wfstack.h>
  87
  88 #define cds_wfs_node_init               _cds_wfs_node_init
  89 #define cds_wfs_init                    _cds_wfs_init
  90 #define cds_wfs_empty                   _cds_wfs_empty
  91 #define cds_wfs_push                    _cds_wfs_push
  92
  93 /* Locking performed internally */
  94 #define cds_wfs_pop_blocking            _cds_wfs_pop_blocking
  95 #define cds_wfs_pop_all_blocking        _cds_wfs_pop_all_blocking
  96
  97 /*
  98  * For iteration on cds_wfs_head returned by __cds_wfs_pop_all or
  99  * cds_wfs_pop_all_blocking.
 100  */
 101 #define cds_wfs_first                   _cds_wfs_first
 102 #define cds_wfs_next_blocking           _cds_wfs_next_blocking
 103
 104 /* Pop locking with internal mutex */
 105 #define cds_wfs_pop_lock                _cds_wfs_pop_lock
 106 #define cds_wfs_pop_unlock              _cds_wfs_pop_unlock
 107
 108 /* Synchronization ensured by the caller. See synchronization table. */
 109 #define __cds_wfs_pop_blocking          ___cds_wfs_pop_blocking
 110 #define __cds_wfs_pop_all               ___cds_wfs_pop_all
 111
 112 #else /* !_LGPL_SOURCE */
 113
 114 /*
 115  * cds_wfs_node_init: initialize wait-free stack node.
 116  */
 117 extern void cds_wfs_node_init(struct cds_wfs_node *node);
 118
 119 /*
 120  * cds_wfs_init: initialize wait-free stack.
 121  */
 122 extern void cds_wfs_init(struct cds_wfs_stack *s);
 123
 124 /*
 125  * cds_wfs_empty: return whether wait-free stack is empty.
 126  *
 127  * No memory barrier is issued. No mutual exclusion is required.
 128  */
 129 extern bool cds_wfs_empty(struct cds_wfs_stack *s);
 130
 131 /*
 132  * cds_wfs_push: push a node into the stack.
 133  *
 134  * Issues a full memory barrier before push. No mutual exclusion is
 135  * required.
 136  *
 137  * Returns 0 if the stack was empty prior to adding the node.
 138  * Returns non-zero otherwise.
 139  */
 140 extern int cds_wfs_push(struct cds_wfs_stack *s, struct cds_wfs_node *node);
 141
 142 /*
 143  * cds_wfs_pop_blocking: pop a node from the stack.
 144  *
 145  * Calls __cds_wfs_pop_blocking with an internal pop mutex held.
 146  */
 147 extern struct cds_wfs_node *cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 148
 149 /*
 150  * cds_wfs_pop_all_blocking: pop all nodes from a stack.
 151  *
 152  * Calls __cds_wfs_pop_all with an internal pop mutex held.
 153  */
 154 extern struct cds_wfs_head *cds_wfs_pop_all_blocking(struct cds_wfs_stack *s);
 155
 156 /*
 157  * cds_wfs_first: get first node of a popped stack.
 158  *
 159  * Content written into the node before enqueue is guaranteed to be
 160  * consistent, but no other memory ordering is ensured.
 161  *
 162  * Used by for-like iteration macros in urcu/wfstack.h:
 163  * cds_wfs_for_each_blocking()
 164  * cds_wfs_for_each_blocking_safe()
 165  *
 166  * Returns NULL if popped stack is empty, top stack node otherwise.
 167  */
 168 extern struct cds_wfs_node *cds_wfs_first(struct cds_wfs_head *head);
 169
 170 /*
 171  * cds_wfs_next_blocking: get next node of a popped stack.
 172  *
 173  * Content written into the node before enqueue is guaranteed to be
 174  * consistent, but no other memory ordering is ensured.
 175  *
 176  * Used by for-like iteration macros in urcu/wfstack.h:
 177  * cds_wfs_for_each_blocking()
 178  * cds_wfs_for_each_blocking_safe()
 179  *
 180  * Returns NULL if reached end of popped stack, non-NULL next stack
 181  * node otherwise.
 182  */
 183 extern struct cds_wfs_node *cds_wfs_next_blocking(struct cds_wfs_node *node);
 184
 185 /*
 186  * cds_wfs_pop_lock: lock stack pop-protection mutex.
 187  */
 188 extern void cds_wfs_pop_lock(struct cds_wfs_stack *s);
 189
 190 /*
 191  * cds_wfs_pop_unlock: unlock stack pop-protection mutex.
 192  */
 193 extern void cds_wfs_pop_unlock(struct cds_wfs_stack *s);
 194
 195 /*
 196  * __cds_wfs_pop_blocking: pop a node from the stack.
 197  *
 198  * Returns NULL if stack is empty.
 199  *
 200  * __cds_wfs_pop_blocking needs to be synchronized using one of the
 201  * following techniques:
 202  *
 203  * 1) Calling __cds_wfs_pop_blocking under rcu read lock critical
 204  *    section. The caller must wait for a grace period to pass before
 205  *    freeing the returned node or modifying the cds_wfs_node structure.
 206  * 2) Using mutual exclusion (e.g. mutexes) to protect
 207  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 208  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 209  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 210  */
 211 extern struct cds_wfs_node *__cds_wfs_pop_blocking(struct cds_wfs_stack *s);
 212
 213 /*
 214  * __cds_wfs_pop_all: pop all nodes from a stack.
 215  *
 216  * __cds_wfs_pop_all does not require any synchronization with other
 217  * push, nor with other __cds_wfs_pop_all, but requires synchronization
 218  * matching the technique used to synchronize __cds_wfs_pop_blocking:
 219  *
 220  * 1) If __cds_wfs_pop_blocking is called under rcu read lock critical
 221  *    section, both __cds_wfs_pop_blocking and cds_wfs_pop_all callers
 222  *    must wait for a grace period to pass before freeing the returned
 223  *    node or modifying the cds_wfs_node structure. However, no RCU
 224  *    read-side critical section is needed around __cds_wfs_pop_all.
 225  * 2) Using mutual exclusion (e.g. mutexes) to protect
 226  *     __cds_wfs_pop_blocking and __cds_wfs_pop_all callers.
 227  * 3) Ensuring that only ONE thread can call __cds_wfs_pop_blocking()
 228  *    and __cds_wfs_pop_all(). (multi-provider/single-consumer scheme).
 229  */
 230 extern struct cds_wfs_head *__cds_wfs_pop_all(struct cds_wfs_stack *s);
 231
 232 #endif /* !_LGPL_SOURCE */
 233
 234 #ifdef __cplusplus
 235 }
 236 #endif
 237
 238 /*
 239  * cds_wfs_for_each_blocking: Iterate over all nodes returned by
 240  * __cds_wfs_pop_all().
 241  * @head: head of the queue (struct cds_wfs_head pointer).
 242  * @node: iterator (struct cds_wfs_node pointer).
 243  *
 244  * Content written into each node before enqueue is guaranteed to be
 245  * consistent, but no other memory ordering is ensured.
 246  */
 247 #define cds_wfs_for_each_blocking(head, node)                   \
 248         for (node = cds_wfs_first(head);                        \
 249                 node != NULL;                                   \
 250                 node = cds_wfs_next_blocking(node))
 251
 252 /*
 253  * cds_wfs_for_each_blocking_safe: Iterate over all nodes returned by
 254  * __cds_wfs_pop_all(). Safe against deletion.
 255  * @head: head of the queue (struct cds_wfs_head pointer).
 256  * @node: iterator (struct cds_wfs_node pointer).
 257  * @n: struct cds_wfs_node pointer holding the next pointer (used
 258  *     internally).
 259  *
 260  * Content written into each node before enqueue is guaranteed to be
 261  * consistent, but no other memory ordering is ensured.
 262  */
 263 #define cds_wfs_for_each_blocking_safe(head, node, n)                      \
 264         for (node = cds_wfs_first(head),                                   \
 265                         n = (node ? cds_wfs_next_blocking(node) : NULL);   \
 266                 node != NULL;                                              \
 267                 node = n, n = (node ? cds_wfs_next_blocking(node) : NULL))
 268
 269 #endif /* _URCU_WFSTACK_H */