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_init                  ___cds_lfs_init
  85 #define cds_lfs_empty                   _cds_lfs_empty
  86 #define cds_lfs_push                    _cds_lfs_push
  87
  88 /* Locking performed internally */
  89 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
  90 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
  91
  92 /* Synchronize pop with internal mutex */
  93 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
  94 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
  95
  96 /* Synchronization ensured by the caller. See synchronization table. */
  97 #define __cds_lfs_pop                   ___cds_lfs_pop
  98 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
  99
 100 #else /* !_LGPL_SOURCE */
 101
 102 /*
 103  * cds_lfs_node_init: initialize lock-free stack node.
 104  */
 105 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 106
 107 /*
 108  * cds_lfs_init: initialize lock-free stack.
 109  */
 110 extern void cds_lfs_init(struct cds_lfs_stack *s);
 111
 112 /*
 113  * cds_lfs_empty: return whether lock-free stack is empty.
 114  *
 115  * No memory barrier is issued. No mutual exclusion is required.
 116  */
 117 extern bool cds_lfs_empty(struct cds_lfs_stack *s);
 118
 119 /*
 120  * cds_lfs_push: push a node into the stack.
 121  *
 122  * Does not require any synchronization with other push nor pop.
 123  *
 124  * Returns 0 if the stack was empty prior to adding the node.
 125  * Returns non-zero otherwise.
 126  */
 127 extern bool cds_lfs_push(struct cds_lfs_stack *s,
 128                         struct cds_lfs_node *node);
 129
 130 /*
 131  * cds_lfs_pop_blocking: pop a node from the stack.
 132  *
 133  * Calls __cds_lfs_pop with an internal pop mutex held.
 134  */
 135 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 136
 137 /*
 138  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 139  *
 140  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 141  */
 142 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 143
 144 /*
 145  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 146  */
 147 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 148
 149 /*
 150  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 151  */
 152 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 153
 154 /*
 155  * __cds_lfs_pop: pop a node from the stack.
 156  *
 157  * Returns NULL if stack is empty.
 158  *
 159  * __cds_lfs_pop needs to be synchronized using one of the following
 160  * techniques:
 161  *
 162  * 1) Calling __cds_lfs_pop under rcu read lock critical section. The
 163  *    caller must wait for a grace period to pass before freeing the
 164  *    returned node or modifying the cds_lfs_node structure.
 165  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 166  *    and __cds_lfs_pop_all callers.
 167  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 168  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 169  */
 170 extern struct cds_lfs_node *__cds_lfs_pop(struct cds_lfs_stack *s);
 171
 172 /*
 173  * __cds_lfs_pop_all: pop all nodes from a stack.
 174  *
 175  * __cds_lfs_pop_all does not require any synchronization with other
 176  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 177  * matching the technique used to synchronize __cds_lfs_pop:
 178  *
 179  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 180  *    both __cds_lfs_pop and cds_lfs_pop_all callers must wait for a
 181  *    grace period to pass before freeing the returned node or modifying
 182  *    the cds_lfs_node structure. However, no RCU read-side critical
 183  *    section is needed around __cds_lfs_pop_all.
 184  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 185  *    __cds_lfs_pop_all callers.
 186  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 187  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 188  */
 189 extern struct cds_lfs_head *__cds_lfs_pop_all(struct cds_lfs_stack *s);
 190
 191 #endif /* !_LGPL_SOURCE */
 192
 193 /*
 194  * cds_lfs_for_each: Iterate over all nodes returned by
 195  *                   __cds_lfs_pop_all.
 196  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 197  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 198  *
 199  * Content written into each node before push is guaranteed to be
 200  * consistent, but no other memory ordering is ensured.
 201  */
 202 #define cds_lfs_for_each(__head, __node)        \
 203         for (__node = &__head->node;            \
 204                 __node != NULL;                 \
 205                 __node = __node->next)
 206
 207 /*
 208  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 209  *                        __cds_lfs_pop_all, safe against node deletion.
 210  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 211  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 212  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 213  *       internally).
 214  *
 215  * Content written into each node before push is guaranteed to be
 216  * consistent, but no other memory ordering is ensured.
 217  */
 218 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 219         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 220                 __node != NULL;                                            \
 221                 __node = __n, __n = (__node ? __node->next : NULL))
 222
 223 #ifdef __cplusplus
 224 }
 225 #endif
 226
 227 #endif /* _URCU_LFSTACK_H */