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 #include <urcu/compiler.h>
  33
  34 /*
  35  * Lock-free stack.
  36  *
  37  * Stack implementing push, pop, pop_all operations, as well as iterator
  38  * on the stack head returned by pop_all.
  39  *
  40  * Synchronization table:
  41  *
  42  * External synchronization techniques described in the API below is
  43  * required between pairs marked with "X". No external synchronization
  44  * required between pairs marked with "-".
  45  *
  46  *                      cds_lfs_push  __cds_lfs_pop  __cds_lfs_pop_all
  47  * cds_lfs_push               -              -                  -
  48  * __cds_lfs_pop              -              X                  X
  49  * __cds_lfs_pop_all          -              X                  -
  50  *
  51  * cds_lfs_pop_blocking and cds_lfs_pop_all_blocking use an internal
  52  * mutex to provide synchronization.
  53  */
  54
  55 /*
  56  * struct cds_lfs_node is returned by cds_lfs_pop, and also used as
  57  * iterator on stack. It is not safe to dereference the node next
  58  * pointer when returned by cds_lfs_pop.
  59  */
  60 struct cds_lfs_node {
  61         struct cds_lfs_node *next;
  62 };
  63
  64 /*
  65  * struct cds_lfs_head is returned by __cds_lfs_pop_all, and can be used
  66  * to begin iteration on the stack. "node" needs to be the first field
  67  * of cds_lfs_head, so the end-of-stack pointer value can be used for
  68  * both types.
  69  */
  70 struct cds_lfs_head {
  71         struct cds_lfs_node node;
  72 };
  73
  74 struct __cds_lfs_stack {
  75         struct cds_lfs_head *head;
  76 };
  77
  78 struct cds_lfs_stack {
  79         struct cds_lfs_head *head;
  80         pthread_mutex_t lock;
  81 };
  82
  83 /*
  84  * The transparent union allows calling functions that work on both
  85  * struct cds_lfs_stack and struct __cds_lfs_stack on any of those two
  86  * types.
  87  *
  88  * Avoid complaints from clang++ not knowing this attribute.
  89  */
  90 typedef union {
  91         struct __cds_lfs_stack *_s;
  92         struct cds_lfs_stack *s;
  93 } caa_c_transparent_union cds_lfs_stack_ptr_t;
  94
  95 #ifdef _LGPL_SOURCE
  96
  97 #include <urcu/static/lfstack.h>
  98
  99 #define cds_lfs_node_init               _cds_lfs_node_init
 100 #define cds_lfs_init                    _cds_lfs_init
 101 #define cds_lfs_destroy                 _cds_lfs_destroy
 102 #define __cds_lfs_init                  ___cds_lfs_init
 103 #define cds_lfs_empty                   _cds_lfs_empty
 104 #define cds_lfs_push                    _cds_lfs_push
 105
 106 /* Locking performed internally */
 107 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
 108 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
 109
 110 /* Synchronize pop with internal mutex */
 111 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
 112 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
 113
 114 /* Synchronization ensured by the caller. See synchronization table. */
 115 #define __cds_lfs_pop                   ___cds_lfs_pop
 116 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
 117
 118 #else /* !_LGPL_SOURCE */
 119
 120 /*
 121  * cds_lfs_node_init: initialize lock-free stack node.
 122  */
 123 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 124
 125 /*
 126  * cds_lfs_init: initialize lock-free stack (with locking). Pair with
 127  * cds_lfs_destroy().
 128  */
 129 extern void cds_lfs_init(struct cds_lfs_stack *s);
 130
 131 /*
 132  * cds_lfs_destroy: destroy lock-free stack (with lock). Pair with
 133  * cds_lfs_init().
 134  */
 135 extern void cds_lfs_destroy(struct cds_lfs_stack *s);
 136
 137 /*
 138  * __cds_lfs_init: initialize lock-free stack (without lock).
 139  * Don't pair with any destroy function.
 140  */
 141 extern void __cds_lfs_init(struct __cds_lfs_stack *s);
 142
 143 /*
 144  * cds_lfs_empty: return whether lock-free stack is empty.
 145  *
 146  * No memory barrier is issued. No mutual exclusion is required.
 147  */
 148 extern bool cds_lfs_empty(cds_lfs_stack_ptr_t s);
 149
 150 /*
 151  * cds_lfs_push: push a node into the stack.
 152  *
 153  * Does not require any synchronization with other push nor pop.
 154  *
 155  * Returns 0 if the stack was empty prior to adding the node.
 156  * Returns non-zero otherwise.
 157  */
 158 extern bool cds_lfs_push(cds_lfs_stack_ptr_t s,
 159                         struct cds_lfs_node *node);
 160
 161 /*
 162  * cds_lfs_pop_blocking: pop a node from the stack.
 163  *
 164  * Calls __cds_lfs_pop with an internal pop mutex held.
 165  */
 166 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 167
 168 /*
 169  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 170  *
 171  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 172  */
 173 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 174
 175 /*
 176  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 177  */
 178 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 179
 180 /*
 181  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 182  */
 183 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 184
 185 /*
 186  * __cds_lfs_pop: pop a node from the stack.
 187  *
 188  * Returns NULL if stack is empty.
 189  *
 190  * __cds_lfs_pop needs to be synchronized using one of the following
 191  * techniques:
 192  *
 193  * 1) Calling __cds_lfs_pop under rcu read lock critical section.
 194  *    Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 195  *    grace period to pass before freeing the returned node or pushing
 196  *    the node back into the stack. It is valid to overwrite the content
 197  *    of cds_lfs_node immediately after __cds_lfs_pop and
 198  *    __cds_lfs_pop_all.
 199  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 200  *    and __cds_lfs_pop_all callers.
 201  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 202  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 203  */
 204 extern struct cds_lfs_node *__cds_lfs_pop(cds_lfs_stack_ptr_t s);
 205
 206 /*
 207  * __cds_lfs_pop_all: pop all nodes from a stack.
 208  *
 209  * __cds_lfs_pop_all does not require any synchronization with other
 210  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 211  * matching the technique used to synchronize __cds_lfs_pop:
 212  *
 213  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 214  *    both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 215  *    grace period to pass before freeing the returned node or pushing
 216  *    the node back into the stack. It is valid to overwrite the content
 217  *    of cds_lfs_node immediately after __cds_lfs_pop and
 218  *    __cds_lfs_pop_all. No RCU read-side critical section is needed
 219  *    around __cds_lfs_pop_all.
 220  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 221  *    __cds_lfs_pop_all callers.
 222  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 223  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 224  */
 225 extern struct cds_lfs_head *__cds_lfs_pop_all(cds_lfs_stack_ptr_t s);
 226
 227 #endif /* !_LGPL_SOURCE */
 228
 229 /*
 230  * cds_lfs_for_each: Iterate over all nodes returned by
 231  *                   __cds_lfs_pop_all.
 232  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 233  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 234  *
 235  * Content written into each node before push is guaranteed to be
 236  * consistent, but no other memory ordering is ensured.
 237  */
 238 #define cds_lfs_for_each(__head, __node)        \
 239         for (__node = &__head->node;            \
 240                 __node != NULL;                 \
 241                 __node = __node->next)
 242
 243 /*
 244  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 245  *                        __cds_lfs_pop_all, safe against node deletion.
 246  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 247  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 248  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 249  *       internally).
 250  *
 251  * Content written into each node before push is guaranteed to be
 252  * consistent, but no other memory ordering is ensured.
 253  */
 254 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 255         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 256                 __node != NULL;                                            \
 257                 __node = __n, __n = (__node ? __node->next : NULL))
 258
 259 #ifdef __cplusplus
 260 }
 261 #endif
 262
 263 #endif /* _URCU_LFSTACK_H */