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 };
  76
  77 struct cds_lfs_stack {
  78         struct cds_lfs_head *head;
  79         pthread_mutex_t lock;
  80 };
  81
  82 /*
  83  * The transparent union allows calling functions that work on both
  84  * struct cds_lfs_stack and struct __cds_lfs_stack on any of those two
  85  * types.
  86  */
  87 typedef union __attribute__((__transparent_union__)) {
  88         struct __cds_lfs_stack *_s;
  89         struct cds_lfs_stack *s;
  90 } cds_lfs_stack_ptr_t;
  91
  92 #ifdef _LGPL_SOURCE
  93
  94 #include <urcu/static/lfstack.h>
  95
  96 #define cds_lfs_node_init               _cds_lfs_node_init
  97 #define cds_lfs_init                    _cds_lfs_init
  98 #define __cds_lfs_init                  ___cds_lfs_init
  99 #define cds_lfs_empty                   _cds_lfs_empty
 100 #define cds_lfs_push                    _cds_lfs_push
 101
 102 /* Locking performed internally */
 103 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
 104 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
 105
 106 /* Synchronize pop with internal mutex */
 107 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
 108 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
 109
 110 /* Synchronization ensured by the caller. See synchronization table. */
 111 #define __cds_lfs_pop                   ___cds_lfs_pop
 112 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
 113
 114 #else /* !_LGPL_SOURCE */
 115
 116 /*
 117  * cds_lfs_node_init: initialize lock-free stack node.
 118  */
 119 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 120
 121 /*
 122  * cds_lfs_init: initialize lock-free stack.
 123  */
 124 extern void cds_lfs_init(struct cds_lfs_stack *s);
 125
 126 /*
 127  * __cds_lfs_init: initialize lock-free stack.
 128  */
 129 extern void __cds_lfs_init(struct __cds_lfs_stack *s);
 130
 131 /*
 132  * cds_lfs_empty: return whether lock-free stack is empty.
 133  *
 134  * No memory barrier is issued. No mutual exclusion is required.
 135  */
 136 extern bool cds_lfs_empty(cds_lfs_stack_ptr_t s);
 137
 138 /*
 139  * cds_lfs_push: push a node into the stack.
 140  *
 141  * Does not require any synchronization with other push nor pop.
 142  *
 143  * Returns 0 if the stack was empty prior to adding the node.
 144  * Returns non-zero otherwise.
 145  */
 146 extern bool cds_lfs_push(cds_lfs_stack_ptr_t s,
 147                         struct cds_lfs_node *node);
 148
 149 /*
 150  * cds_lfs_pop_blocking: pop a node from the stack.
 151  *
 152  * Calls __cds_lfs_pop with an internal pop mutex held.
 153  */
 154 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 155
 156 /*
 157  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 158  *
 159  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 160  */
 161 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 162
 163 /*
 164  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 165  */
 166 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 167
 168 /*
 169  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 170  */
 171 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 172
 173 /*
 174  * __cds_lfs_pop: pop a node from the stack.
 175  *
 176  * Returns NULL if stack is empty.
 177  *
 178  * __cds_lfs_pop needs to be synchronized using one of the following
 179  * techniques:
 180  *
 181  * 1) Calling __cds_lfs_pop under rcu read lock critical section. The
 182  *    caller must wait for a grace period to pass before freeing the
 183  *    returned node or modifying the cds_lfs_node structure.
 184  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 185  *    and __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_node *__cds_lfs_pop(cds_lfs_stack_ptr_t s);
 190
 191 /*
 192  * __cds_lfs_pop_all: pop all nodes from a stack.
 193  *
 194  * __cds_lfs_pop_all does not require any synchronization with other
 195  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 196  * matching the technique used to synchronize __cds_lfs_pop:
 197  *
 198  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 199  *    both __cds_lfs_pop and cds_lfs_pop_all callers must wait for a
 200  *    grace period to pass before freeing the returned node or modifying
 201  *    the cds_lfs_node structure. However, no RCU read-side critical
 202  *    section is needed around __cds_lfs_pop_all.
 203  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 204  *    __cds_lfs_pop_all callers.
 205  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 206  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 207  */
 208 extern struct cds_lfs_head *__cds_lfs_pop_all(cds_lfs_stack_ptr_t s);
 209
 210 #endif /* !_LGPL_SOURCE */
 211
 212 /*
 213  * cds_lfs_for_each: Iterate over all nodes returned by
 214  *                   __cds_lfs_pop_all.
 215  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 216  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 217  *
 218  * Content written into each node before push is guaranteed to be
 219  * consistent, but no other memory ordering is ensured.
 220  */
 221 #define cds_lfs_for_each(__head, __node)        \
 222         for (__node = &__head->node;            \
 223                 __node != NULL;                 \
 224                 __node = __node->next)
 225
 226 /*
 227  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 228  *                        __cds_lfs_pop_all, safe against node deletion.
 229  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 230  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 231  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 232  *       internally).
 233  *
 234  * Content written into each node before push is guaranteed to be
 235  * consistent, but no other memory ordering is ensured.
 236  */
 237 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 238         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 239                 __node != NULL;                                            \
 240                 __node = __n, __n = (__node ? __node->next : NULL))
 241
 242 #ifdef __cplusplus
 243 }
 244 #endif
 245
 246 #endif /* _URCU_LFSTACK_H */