include/urcu/lfstack.h

   1 // SPDX-FileCopyrightText: 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 //
   3 // SPDX-License-Identifier: LGPL-2.1-or-later
   4
   5 #ifndef _URCU_LFSTACK_H
   6 #define _URCU_LFSTACK_H
   7
   8 /*
   9  * Userspace RCU library - Lock-Free Stack
  10  */
  11
  12 #ifdef __cplusplus
  13 extern "C" {
  14 #endif
  15
  16 #include <stdbool.h>
  17 #include <pthread.h>
  18
  19 /*
  20  * Lock-free stack.
  21  *
  22  * Stack implementing push, pop, pop_all operations, as well as iterator
  23  * on the stack head returned by pop_all.
  24  *
  25  * Synchronization table:
  26  *
  27  * External synchronization techniques described in the API below is
  28  * required between pairs marked with "X". No external synchronization
  29  * required between pairs marked with "-".
  30  *
  31  *                      cds_lfs_push  __cds_lfs_pop  __cds_lfs_pop_all
  32  * cds_lfs_push               -              -                  -
  33  * __cds_lfs_pop              -              X                  X
  34  * __cds_lfs_pop_all          -              X                  -
  35  *
  36  * cds_lfs_pop_blocking and cds_lfs_pop_all_blocking use an internal
  37  * mutex to provide synchronization.
  38  */
  39
  40 /*
  41  * struct cds_lfs_node is returned by cds_lfs_pop, and also used as
  42  * iterator on stack. It is not safe to dereference the node next
  43  * pointer when returned by cds_lfs_pop.
  44  */
  45 struct cds_lfs_node {
  46         struct cds_lfs_node *next;
  47 };
  48
  49 /*
  50  * struct cds_lfs_head is returned by __cds_lfs_pop_all, and can be used
  51  * to begin iteration on the stack. "node" needs to be the first field
  52  * of cds_lfs_head, so the end-of-stack pointer value can be used for
  53  * both types.
  54  */
  55 struct cds_lfs_head {
  56         struct cds_lfs_node node;
  57 };
  58
  59 struct __cds_lfs_stack {
  60         struct cds_lfs_head *head;
  61 };
  62
  63 struct cds_lfs_stack {
  64         struct cds_lfs_head *head;
  65         pthread_mutex_t lock;
  66 };
  67
  68 /*
  69  * In C, the transparent union allows calling functions that work on
  70  * both struct cds_lfs_stack and struct __cds_lfs_stack on any of those
  71  * two types.
  72  *
  73  * In C++, implement static inline wrappers using function overloading
  74  * to obtain an API similar to C.
  75  *
  76  * Avoid complaints from clang++ not knowing the transparent union
  77  * attribute.
  78  */
  79 #if defined(__clang__)
  80 #pragma clang diagnostic push
  81 #pragma clang diagnostic ignored "-Wignored-attributes"
  82 #endif
  83 typedef union {
  84         struct __cds_lfs_stack *_s;
  85         struct cds_lfs_stack *s;
  86 } __attribute__((__transparent_union__)) cds_lfs_stack_ptr_t;
  87
  88 typedef union {
  89         const struct __cds_lfs_stack *_s;
  90         const struct cds_lfs_stack *s;
  91 } __attribute__((__transparent_union__)) cds_lfs_stack_const_ptr_t;
  92 #if defined(__clang__)
  93 #pragma clang diagnostic pop
  94 #endif
  95
  96 #ifdef _LGPL_SOURCE
  97
  98 #include <urcu/static/lfstack.h>
  99
 100 #define cds_lfs_node_init               _cds_lfs_node_init
 101 #define cds_lfs_init                    _cds_lfs_init
 102 #define cds_lfs_destroy                 _cds_lfs_destroy
 103 #define __cds_lfs_init                  ___cds_lfs_init
 104 #define cds_lfs_empty                   _cds_lfs_empty
 105 #define cds_lfs_push                    _cds_lfs_push
 106
 107 /* Locking performed internally */
 108 #define cds_lfs_pop_blocking            _cds_lfs_pop_blocking
 109 #define cds_lfs_pop_all_blocking        _cds_lfs_pop_all_blocking
 110
 111 /* Synchronize pop with internal mutex */
 112 #define cds_lfs_pop_lock                _cds_lfs_pop_lock
 113 #define cds_lfs_pop_unlock              _cds_lfs_pop_unlock
 114
 115 /* Synchronization ensured by the caller. See synchronization table. */
 116 #define __cds_lfs_pop                   ___cds_lfs_pop
 117 #define __cds_lfs_pop_all               ___cds_lfs_pop_all
 118
 119 #else /* !_LGPL_SOURCE */
 120
 121 /*
 122  * cds_lfs_node_init: initialize lock-free stack node.
 123  */
 124 extern void cds_lfs_node_init(struct cds_lfs_node *node);
 125
 126 /*
 127  * cds_lfs_init: initialize lock-free stack (with locking). Pair with
 128  * cds_lfs_destroy().
 129  */
 130 extern void cds_lfs_init(struct cds_lfs_stack *s);
 131
 132 /*
 133  * cds_lfs_destroy: destroy lock-free stack (with lock). Pair with
 134  * cds_lfs_init().
 135  */
 136 extern void cds_lfs_destroy(struct cds_lfs_stack *s);
 137
 138 /*
 139  * __cds_lfs_init: initialize lock-free stack (without lock).
 140  * Don't pair with any destroy function.
 141  */
 142 extern void __cds_lfs_init(struct __cds_lfs_stack *s);
 143
 144 /*
 145  * cds_lfs_empty: return whether lock-free stack is empty.
 146  *
 147  * No memory barrier is issued. No mutual exclusion is required.
 148  */
 149 extern bool cds_lfs_empty(cds_lfs_stack_const_ptr_t s);
 150
 151 /*
 152  * cds_lfs_push: push a node into the stack.
 153  *
 154  * Does not require any synchronization with other push nor pop.
 155  *
 156  * Returns 0 if the stack was empty prior to adding the node.
 157  * Returns non-zero otherwise.
 158  */
 159 extern bool cds_lfs_push(cds_lfs_stack_ptr_t s,
 160                         struct cds_lfs_node *node);
 161
 162 /*
 163  * cds_lfs_pop_blocking: pop a node from the stack.
 164  *
 165  * Calls __cds_lfs_pop with an internal pop mutex held.
 166  */
 167 extern struct cds_lfs_node *cds_lfs_pop_blocking(struct cds_lfs_stack *s);
 168
 169 /*
 170  * cds_lfs_pop_all_blocking: pop all nodes from a stack.
 171  *
 172  * Calls __cds_lfs_pop_all with an internal pop mutex held.
 173  */
 174 extern struct cds_lfs_head *cds_lfs_pop_all_blocking(struct cds_lfs_stack *s);
 175
 176 /*
 177  * cds_lfs_pop_lock: lock stack pop-protection mutex.
 178  */
 179 extern void cds_lfs_pop_lock(struct cds_lfs_stack *s);
 180
 181 /*
 182  * cds_lfs_pop_unlock: unlock stack pop-protection mutex.
 183  */
 184 extern void cds_lfs_pop_unlock(struct cds_lfs_stack *s);
 185
 186 /*
 187  * __cds_lfs_pop: pop a node from the stack.
 188  *
 189  * Returns NULL if stack is empty.
 190  *
 191  * __cds_lfs_pop needs to be synchronized using one of the following
 192  * techniques:
 193  *
 194  * 1) Calling __cds_lfs_pop under rcu read lock critical section.
 195  *    Both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 196  *    grace period to pass before freeing the returned node or pushing
 197  *    the node back into the stack. It is valid to overwrite the content
 198  *    of cds_lfs_node immediately after __cds_lfs_pop and
 199  *    __cds_lfs_pop_all.
 200  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop
 201  *    and __cds_lfs_pop_all callers.
 202  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 203  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 204  */
 205 extern struct cds_lfs_node *__cds_lfs_pop(cds_lfs_stack_ptr_t s);
 206
 207 /*
 208  * __cds_lfs_pop_all: pop all nodes from a stack.
 209  *
 210  * __cds_lfs_pop_all does not require any synchronization with other
 211  * push, nor with other __cds_lfs_pop_all, but requires synchronization
 212  * matching the technique used to synchronize __cds_lfs_pop:
 213  *
 214  * 1) If __cds_lfs_pop is called under rcu read lock critical section,
 215  *    both __cds_lfs_pop and __cds_lfs_pop_all callers must wait for a
 216  *    grace period to pass before freeing the returned node or pushing
 217  *    the node back into the stack. It is valid to overwrite the content
 218  *    of cds_lfs_node immediately after __cds_lfs_pop and
 219  *    __cds_lfs_pop_all. No RCU read-side critical section is needed
 220  *    around __cds_lfs_pop_all.
 221  * 2) Using mutual exclusion (e.g. mutexes) to protect __cds_lfs_pop and
 222  *    __cds_lfs_pop_all callers.
 223  * 3) Ensuring that only ONE thread can call __cds_lfs_pop() and
 224  *    __cds_lfs_pop_all(). (multi-provider/single-consumer scheme).
 225  */
 226 extern struct cds_lfs_head *__cds_lfs_pop_all(cds_lfs_stack_ptr_t s);
 227
 228 #endif /* !_LGPL_SOURCE */
 229
 230 /*
 231  * cds_lfs_for_each: Iterate over all nodes returned by
 232  *                   __cds_lfs_pop_all.
 233  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 234  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 235  *
 236  * Content written into each node before push is guaranteed to be
 237  * consistent, but no other memory ordering is ensured.
 238  */
 239 #define cds_lfs_for_each(__head, __node)        \
 240         for (__node = &__head->node;            \
 241                 __node != NULL;                 \
 242                 __node = __node->next)
 243
 244 /*
 245  * cds_lfs_for_each_safe: Iterate over all nodes returned by
 246  *                        __cds_lfs_pop_all, safe against node deletion.
 247  * @__head: node returned by __cds_lfs_pop_all (struct cds_lfs_head pointer).
 248  * @__node: node to use as iterator (struct cds_lfs_node pointer).
 249  * @__n: struct cds_lfs_node pointer holding the next pointer (used
 250  *       internally).
 251  *
 252  * Content written into each node before push is guaranteed to be
 253  * consistent, but no other memory ordering is ensured.
 254  */
 255 #define cds_lfs_for_each_safe(__head, __node, __n)                         \
 256         for (__node = &__head->node, __n = (__node ? __node->next : NULL); \
 257                 __node != NULL;                                            \
 258                 __node = __n, __n = (__node ? __node->next : NULL))
 259
 260 #ifdef __cplusplus
 261 }
 262
 263 /*
 264  * In C++, implement static inline wrappers using function overloading
 265  * to obtain an API similar to C.
 266  */
 267
 268 static inline cds_lfs_stack_ptr_t cds_lfs_stack_cast(struct __cds_lfs_stack *s)
 269 {
 270         cds_lfs_stack_ptr_t ret = {
 271                 ._s = s,
 272         };
 273         return ret;
 274 }
 275
 276 static inline cds_lfs_stack_ptr_t cds_lfs_stack_cast(struct cds_lfs_stack *s)
 277 {
 278         cds_lfs_stack_ptr_t ret = {
 279                 .s = s,
 280         };
 281         return ret;
 282 }
 283
 284 static inline cds_lfs_stack_const_ptr_t cds_lfs_stack_const_cast(const struct __cds_lfs_stack *s)
 285 {
 286         cds_lfs_stack_const_ptr_t ret = {
 287                 ._s = s,
 288         };
 289         return ret;
 290 }
 291
 292 static inline cds_lfs_stack_const_ptr_t cds_lfs_stack_const_cast(const struct cds_lfs_stack *s)
 293 {
 294         cds_lfs_stack_const_ptr_t ret = {
 295                 .s = s,
 296         };
 297         return ret;
 298 }
 299
 300 template<typename T> static inline bool cds_lfs_empty(T s)
 301 {
 302         return cds_lfs_empty(cds_lfs_stack_const_cast(s));
 303 }
 304
 305 template<typename T> static inline bool cds_lfs_push(T s,
 306                         struct cds_lfs_node *node)
 307 {
 308         return cds_lfs_push(cds_lfs_stack_cast(s), node);
 309 }
 310
 311 template<typename T> static inline struct cds_lfs_node *__cds_lfs_pop(T s)
 312 {
 313         return __cds_lfs_pop(cds_lfs_stack_cast(s));
 314 }
 315
 316 template<typename T> static inline struct cds_lfs_head *__cds_lfs_pop_all(T s)
 317 {
 318         return __cds_lfs_pop_all(cds_lfs_stack_cast(s));
 319 }
 320
 321 #endif  /* __cplusplus */
 322
 323 #endif /* _URCU_LFSTACK_H */