urcu/lfstack.h

   1 #ifndef _URCU_LFSTACK_H
   2 #define _URCU_LFSTACK_H
   3
   4 /*
   5  * lfstack.h
   6  *
   7  * Userspace RCU library - Lock-Free Stack
   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 #ifdef __cplusplus
  27 extern "C" {
  28 #endif
  29
  30 #include <stdbool.h>
  31 #include <pthread.h>
  32
  33 /*
  34  * Lock-free stack.
  35  *
  36  * Stack implementing push, pop, pop_all operations, as well as iterator
  37  * on the stack head returned by pop_all.
  38  *
  39  * Synchronization table:
  40  *
  41  * External synchronization techniques described in the API below is
  42  * required between pairs marked with "X". No external synchronization
  43  * required between pairs marked with "-".
  44  *
  45  *                      cds_lfs_push  __cds_lfs_pop  __cds_lfs_pop_all
  46  * cds_lfs_push               -              -                  -
  47  * __cds_lfs_pop              -              X                  X
  48  * __cds_lfs_pop_all          -              X                  -
  49  *
  50  * cds_lfs_pop_blocking and cds_lfs_pop_all_blocking use an internal
  51  * mutex to provide synchronization.
  52  */
  53
  54 /*
  55  * struct cds_lfs_node is returned by cds_lfs_pop, and also used as
  56  * iterator on stack. It is not safe to dereference the node next
  57  * pointer when returned by cds_lfs_pop.
  58  */
  59 struct cds_lfs_node {
  60         struct cds_lfs_node *next;
  61 };
  62
  63 /*
  64  * struct cds_lfs_head is returned by __cds_lfs_pop_all, and can be used
  65  * to begin iteration on the stack. "node" needs to be the first field
  66  * of cds_lfs_head, so the end-of-stack pointer value can be used for
  67  * both types.
  68  */
  69 struct cds_lfs_head {
  70         struct cds_lfs_node node;
  71 };
  72
  73 struct cds_lfs_stack {
  74         struct cds_lfs_head *head;
  75         pthread_mutex_t lock;
  76 };
  77
  78 #ifdef _LGPL_SOURCE
  79
  80 #include <urcu/static/lfstack.h>
  81
  82 #define cds_lfs_node_init               _cds_lfs_node_init
  83 #define cds_lfs_init                    _cds_lfs_init
  84 #define cds_lfs_empty                   _cds_lfs_empty
  85 #define cds_lfs_push                    _cds_lfs_push
  86
  87 /* Locking performed internally */
  88 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
  89 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
  90
  91 /* Synchronize pop with internal mutex */
  92 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
  93 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
  94
  95 /* Synchronization ensured by the caller. See synchronization table. */
  96 #define __cds_lfs_pop                   ___cds_lfs_pop
  97 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
  98
  99 #else /* !_LGPL_SOURCE */
 100
 101 /*
 102  * cds_lfs_node_init: initialize lock-free stack node.
 103  */
 104 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 105
 106 /*
 107  * cds_lfs_init: initialize lock-free stack.
 108  */
 109 extern void cds_lfs_init(struct cds_lfs_stack *s);
 110
 111 /*
 112  * cds_lfs_empty: return whether lock-free stack is empty.
 113  *
 114  * No memory barrier is issued. No mutual exclusion is required.
 115  */
 116 extern bool cds_lfs_empty(struct cds_lfs_stack *s);
 117
 118 /*
 119  * cds_lfs_push: push a node into the stack.
 120  *
 121  * Does not require any synchronization with other push nor pop.
 122  *
 123  * Returns 0 if the stack was empty prior to adding the node.
 124  * Returns non-zero otherwise.
 125  */
 126 extern bool cds_lfs_push(struct cds_lfs_stack *s,
 127                         struct cds_lfs_node *node);
 128
 129 /*
 130  * cds_lfs_pop_blocking: pop a node from the stack.
 131  *
 132  * Calls __cds_lfs_pop with an internal pop mutex held.
 133  */
 134 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 135
 136 /*
 137  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 138  *
 139  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 140  */
 141 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 142
 143 /*
 144  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 145  */
 146 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 147
 148 /*
 149  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 150  */
 151 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 152
 153 /*
 154  * __cds_lfs_pop: pop a node from the stack.
 155  *
 156  * Returns NULL if stack is empty.
 157  *
 158  * __cds_lfs_pop needs to be synchronized using one of the following
 159  * techniques:
 160  *
 161  * 1) Calling __cds_lfs_pop under rcu read lock critical section. The
 162  *    caller must wait for a grace period to pass before freeing the
 163  *    returned node or modifying the cds_lfs_node structure.
 164  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 165  *    and __cds_lfs_pop_all callers.
 166  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 167  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 168  */
 169 extern struct cds_lfs_node *__cds_lfs_pop(struct cds_lfs_stack *s);
 170
 171 /*
 172  * __cds_lfs_pop_all: pop all nodes from a stack.
 173  *
 174  * __cds_lfs_pop_all does not require any synchronization with other
 175  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 176  * matching the technique used to synchronize __cds_lfs_pop:
 177  *
 178  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 179  *    both __cds_lfs_pop and cds_lfs_pop_all callers must wait for a
 180  *    grace period to pass before freeing the returned node or modifying
 181  *    the cds_lfs_node structure. However, no RCU read-side critical
 182  *    section is needed around __cds_lfs_pop_all.
 183  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 184  *    __cds_lfs_pop_all callers.
 185  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 186  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 187  */
 188 extern struct cds_lfs_head *__cds_lfs_pop_all(struct cds_lfs_stack *s);
 189
 190 #endif /* !_LGPL_SOURCE */
 191
 192 /*
 193  * cds_lfs_for_each: Iterate over all nodes returned by
 194  *                   __cds_lfs_pop_all.
 195  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 196  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 197  *
 198  * Content written into each node before push is guaranteed to be
 199  * consistent, but no other memory ordering is ensured.
 200  */
 201 #define cds_lfs_for_each(__head, __node)        \
 202         for (__node = &__head->node;            \
 203                 __node != NULL;                 \
 204                 __node = __node->next)
 205
 206 /*
 207  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 208  *                        __cds_lfs_pop_all, safe against node deletion.
 209  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 210  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 211  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 212  *       internally).
 213  *
 214  * Content written into each node before push is guaranteed to be
 215  * consistent, but no other memory ordering is ensured.
 216  */
 217 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 218         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 219                 __node != NULL;                                            \
 220                 __node = __n, __n = (__node ? __node->next : NULL))
 221
 222 #ifdef __cplusplus
 223 }
 224 #endif
 225
 226 #endif /* _URCU_LFSTACK_H */