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  * In C, the transparent union allows calling functions that work on
  84  * both struct cds_lfs_stack and struct __cds_lfs_stack on any of those
  85  * two types.
  86  *
  87  * In C++, implement static inline wrappers using function overloading
  88  * to obtain an API similar to C.
  89  *
  90  * Avoid complaints from clang++ not knowing the transparent union
  91  * attribute.
  92  */
  93 #if defined(__clang__)
  94 #pragma clang diagnostic push
  95 #pragma clang diagnostic ignored "-Wignored-attributes"
  96 #endif
  97 typedef union {
  98         struct __cds_lfs_stack *_s;
  99         struct cds_lfs_stack *s;
 100 } __attribute__((__transparent_union__)) cds_lfs_stack_ptr_t;
 101 #if defined(__clang__)
 102 #pragma clang diagnostic pop
 103 #endif
 104
 105 #ifdef _LGPL_SOURCE
 106
 107 #include <urcu/static/lfstack.h>
 108
 109 #define cds_lfs_node_init               _cds_lfs_node_init
 110 #define cds_lfs_init                    _cds_lfs_init
 111 #define cds_lfs_destroy                 _cds_lfs_destroy
 112 #define __cds_lfs_init                  ___cds_lfs_init
 113 #define cds_lfs_empty                   _cds_lfs_empty
 114 #define cds_lfs_push                    _cds_lfs_push
 115
 116 /* Locking performed internally */
 117 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
 118 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
 119
 120 /* Synchronize pop with internal mutex */
 121 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
 122 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
 123
 124 /* Synchronization ensured by the caller. See synchronization table. */
 125 #define __cds_lfs_pop                   ___cds_lfs_pop
 126 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
 127
 128 #else /* !_LGPL_SOURCE */
 129
 130 /*
 131  * cds_lfs_node_init: initialize lock-free stack node.
 132  */
 133 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 134
 135 /*
 136  * cds_lfs_init: initialize lock-free stack (with locking). Pair with
 137  * cds_lfs_destroy().
 138  */
 139 extern void cds_lfs_init(struct cds_lfs_stack *s);
 140
 141 /*
 142  * cds_lfs_destroy: destroy lock-free stack (with lock). Pair with
 143  * cds_lfs_init().
 144  */
 145 extern void cds_lfs_destroy(struct cds_lfs_stack *s);
 146
 147 /*
 148  * __cds_lfs_init: initialize lock-free stack (without lock).
 149  * Don't pair with any destroy function.
 150  */
 151 extern void __cds_lfs_init(struct __cds_lfs_stack *s);
 152
 153 /*
 154  * cds_lfs_empty: return whether lock-free stack is empty.
 155  *
 156  * No memory barrier is issued. No mutual exclusion is required.
 157  */
 158 extern bool cds_lfs_empty(cds_lfs_stack_ptr_t s);
 159
 160 /*
 161  * cds_lfs_push: push a node into the stack.
 162  *
 163  * Does not require any synchronization with other push nor pop.
 164  *
 165  * Returns 0 if the stack was empty prior to adding the node.
 166  * Returns non-zero otherwise.
 167  */
 168 extern bool cds_lfs_push(cds_lfs_stack_ptr_t s,
 169                         struct cds_lfs_node *node);
 170
 171 /*
 172  * cds_lfs_pop_blocking: pop a node from the stack.
 173  *
 174  * Calls __cds_lfs_pop with an internal pop mutex held.
 175  */
 176 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 177
 178 /*
 179  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 180  *
 181  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 182  */
 183 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 184
 185 /*
 186  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 187  */
 188 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 189
 190 /*
 191  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 192  */
 193 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 194
 195 /*
 196  * __cds_lfs_pop: pop a node from the stack.
 197  *
 198  * Returns NULL if stack is empty.
 199  *
 200  * __cds_lfs_pop needs to be synchronized using one of the following
 201  * techniques:
 202  *
 203  * 1) Calling __cds_lfs_pop under rcu read lock critical section.
 204  *    Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 205  *    grace period to pass before freeing the returned node or pushing
 206  *    the node back into the stack. It is valid to overwrite the content
 207  *    of cds_lfs_node immediately after __cds_lfs_pop and
 208  *    __cds_lfs_pop_all.
 209  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 210  *    and __cds_lfs_pop_all callers.
 211  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 212  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 213  */
 214 extern struct cds_lfs_node *__cds_lfs_pop(cds_lfs_stack_ptr_t s);
 215
 216 /*
 217  * __cds_lfs_pop_all: pop all nodes from a stack.
 218  *
 219  * __cds_lfs_pop_all does not require any synchronization with other
 220  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 221  * matching the technique used to synchronize __cds_lfs_pop:
 222  *
 223  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 224  *    both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 225  *    grace period to pass before freeing the returned node or pushing
 226  *    the node back into the stack. It is valid to overwrite the content
 227  *    of cds_lfs_node immediately after __cds_lfs_pop and
 228  *    __cds_lfs_pop_all. No RCU read-side critical section is needed
 229  *    around __cds_lfs_pop_all.
 230  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 231  *    __cds_lfs_pop_all callers.
 232  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 233  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 234  */
 235 extern struct cds_lfs_head *__cds_lfs_pop_all(cds_lfs_stack_ptr_t s);
 236
 237 #endif /* !_LGPL_SOURCE */
 238
 239 /*
 240  * cds_lfs_for_each: Iterate over all nodes returned by
 241  *                   __cds_lfs_pop_all.
 242  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 243  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 244  *
 245  * Content written into each node before push is guaranteed to be
 246  * consistent, but no other memory ordering is ensured.
 247  */
 248 #define cds_lfs_for_each(__head, __node)        \
 249         for (__node = &__head->node;            \
 250                 __node != NULL;                 \
 251                 __node = __node->next)
 252
 253 /*
 254  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 255  *                        __cds_lfs_pop_all, safe against node deletion.
 256  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 257  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 258  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 259  *       internally).
 260  *
 261  * Content written into each node before push is guaranteed to be
 262  * consistent, but no other memory ordering is ensured.
 263  */
 264 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 265         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 266                 __node != NULL;                                            \
 267                 __node = __n, __n = (__node ? __node->next : NULL))
 268
 269 #ifdef __cplusplus
 270 }
 271
 272 /*
 273  * In C++, implement static inline wrappers using function overloading
 274  * to obtain an API similar to C.
 275  */
 276
 277 static inline cds_lfs_stack_ptr_t cds_lfs_stack_cast(struct __cds_lfs_stack *s)
 278 {
 279         cds_lfs_stack_ptr_t ret = {
 280                 ._s = s,
 281         };
 282         return ret;
 283 }
 284
 285 static inline cds_lfs_stack_ptr_t cds_lfs_stack_cast(struct cds_lfs_stack *s)
 286 {
 287         cds_lfs_stack_ptr_t ret = {
 288                 .s = s,
 289         };
 290         return ret;
 291 }
 292
 293 template<typename T> static inline bool cds_lfs_empty(T s)
 294 {
 295         return cds_lfs_empty(cds_lfs_stack_cast(s));
 296 }
 297
 298 template<typename T> static inline bool cds_lfs_push(T s,
 299                         struct cds_lfs_node *node)
 300 {
 301         return cds_lfs_push(cds_lfs_stack_cast(s), node);
 302 }
 303
 304 template<typename T> static inline struct cds_lfs_node *__cds_lfs_pop(T s)
 305 {
 306         return __cds_lfs_pop(cds_lfs_stack_cast(s));
 307 }
 308
 309 template<typename T> static inline struct cds_lfs_head *__cds_lfs_pop_all(T s)
 310 {
 311         return __cds_lfs_pop_all(cds_lfs_stack_cast(s));
 312 }
 313
 314 #endif  /* __cplusplus */
 315
 316 #endif /* _URCU_LFSTACK_H */