include/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 {
  88         struct __cds_lfs_stack *_s;
  89         struct cds_lfs_stack *s;
  90 } __attribute__((__transparent_union__)) 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_destroy                 _cds_lfs_destroy
  99 #define __cds_lfs_init                  ___cds_lfs_init
 100 #define cds_lfs_empty                   _cds_lfs_empty
 101 #define cds_lfs_push                    _cds_lfs_push
 102
 103 /* Locking performed internally */
 104 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
 105 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
 106
 107 /* Synchronize pop with internal mutex */
 108 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
 109 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
 110
 111 /* Synchronization ensured by the caller. See synchronization table. */
 112 #define __cds_lfs_pop                   ___cds_lfs_pop
 113 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
 114
 115 #else /* !_LGPL_SOURCE */
 116
 117 /*
 118  * cds_lfs_node_init: initialize lock-free stack node.
 119  */
 120 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 121
 122 /*
 123  * cds_lfs_init: initialize lock-free stack (with locking). Pair with
 124  * cds_lfs_destroy().
 125  */
 126 extern void cds_lfs_init(struct cds_lfs_stack *s);
 127
 128 /*
 129  * cds_lfs_destroy: destroy lock-free stack (with lock). Pair with
 130  * cds_lfs_init().
 131  */
 132 extern void cds_lfs_destroy(struct cds_lfs_stack *s);
 133
 134 /*
 135  * __cds_lfs_init: initialize lock-free stack (without lock).
 136  * Don't pair with any destroy function.
 137  */
 138 extern void __cds_lfs_init(struct __cds_lfs_stack *s);
 139
 140 /*
 141  * cds_lfs_empty: return whether lock-free stack is empty.
 142  *
 143  * No memory barrier is issued. No mutual exclusion is required.
 144  */
 145 extern bool cds_lfs_empty(cds_lfs_stack_ptr_t s);
 146
 147 /*
 148  * cds_lfs_push: push a node into the stack.
 149  *
 150  * Does not require any synchronization with other push nor pop.
 151  *
 152  * Returns 0 if the stack was empty prior to adding the node.
 153  * Returns non-zero otherwise.
 154  */
 155 extern bool cds_lfs_push(cds_lfs_stack_ptr_t s,
 156                         struct cds_lfs_node *node);
 157
 158 /*
 159  * cds_lfs_pop_blocking: pop a node from the stack.
 160  *
 161  * Calls __cds_lfs_pop with an internal pop mutex held.
 162  */
 163 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 164
 165 /*
 166  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 167  *
 168  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 169  */
 170 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 171
 172 /*
 173  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 174  */
 175 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 176
 177 /*
 178  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 179  */
 180 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 181
 182 /*
 183  * __cds_lfs_pop: pop a node from the stack.
 184  *
 185  * Returns NULL if stack is empty.
 186  *
 187  * __cds_lfs_pop needs to be synchronized using one of the following
 188  * techniques:
 189  *
 190  * 1) Calling __cds_lfs_pop under rcu read lock critical section.
 191  *    Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 192  *    grace period to pass before freeing the returned node or pushing
 193  *    the node back into the stack. It is valid to overwrite the content
 194  *    of cds_lfs_node immediately after __cds_lfs_pop and
 195  *    __cds_lfs_pop_all.
 196  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 197  *    and __cds_lfs_pop_all callers.
 198  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 199  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 200  */
 201 extern struct cds_lfs_node *__cds_lfs_pop(cds_lfs_stack_ptr_t s);
 202
 203 /*
 204  * __cds_lfs_pop_all: pop all nodes from a stack.
 205  *
 206  * __cds_lfs_pop_all does not require any synchronization with other
 207  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 208  * matching the technique used to synchronize __cds_lfs_pop:
 209  *
 210  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 211  *    both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 212  *    grace period to pass before freeing the returned node or pushing
 213  *    the node back into the stack. It is valid to overwrite the content
 214  *    of cds_lfs_node immediately after __cds_lfs_pop and
 215  *    __cds_lfs_pop_all. No RCU read-side critical section is needed
 216  *    around __cds_lfs_pop_all.
 217  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 218  *    __cds_lfs_pop_all callers.
 219  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 220  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 221  */
 222 extern struct cds_lfs_head *__cds_lfs_pop_all(cds_lfs_stack_ptr_t s);
 223
 224 #endif /* !_LGPL_SOURCE */
 225
 226 /*
 227  * cds_lfs_for_each: Iterate over all nodes returned by
 228  *                   __cds_lfs_pop_all.
 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  *
 232  * Content written into each node before push is guaranteed to be
 233  * consistent, but no other memory ordering is ensured.
 234  */
 235 #define cds_lfs_for_each(__head, __node)        \
 236         for (__node = &__head->node;            \
 237                 __node != NULL;                 \
 238                 __node = __node->next)
 239
 240 /*
 241  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 242  *                        __cds_lfs_pop_all, safe against node deletion.
 243  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 244  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 245  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 246  *       internally).
 247  *
 248  * Content written into each node before push is guaranteed to be
 249  * consistent, but no other memory ordering is ensured.
 250  */
 251 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 252         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 253                 __node != NULL;                                            \
 254                 __node = __n, __n = (__node ? __node->next : NULL))
 255
 256 #ifdef __cplusplus
 257 }
 258 #endif
 259
 260 #endif /* _URCU_LFSTACK_H */