urcu/rculfstack-static.h

   1 #ifndef _URCU_RCULFSTACK_STATIC_H
   2 #define _URCU_RCULFSTACK_STATIC_H
   3
   4 /*
   5  * rculfstack-static.h
   6  *
   7  * Userspace RCU library - Lock-Free RCU Stack
   8  *
   9  * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  *
  11  * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See rculfstack.h for linking
  12  * dynamically with the userspace rcu library.
  13  *
  14  * This library is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU Lesser General Public
  16  * License as published by the Free Software Foundation; either
  17  * version 2.1 of the License, or (at your option) any later version.
  18  *
  19  * This library is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22  * Lesser General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Lesser General Public
  25  * License along with this library; if not, write to the Free Software
  26  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  27  */
  28
  29 #include <urcu/uatomic_arch.h>
  30 /* A urcu implementation header should be already included. */
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 void _cds_lfs_node_init_rcu(struct cds_lfs_node_rcu *node)
  37 {
  38 }
  39
  40 void _cds_lfs_init_rcu(struct cds_lfs_stack_rcu *s)
  41 {
  42         s->head = NULL;
  43 }
  44
  45 void _cds_lfs_push_rcu(struct cds_lfs_stack_rcu *s, struct cds_lfs_node_rcu *node)
  46 {
  47         struct cds_lfs_node_rcu *head = NULL;
  48
  49         for (;;) {
  50                 struct cds_lfs_node_rcu *old_head = head;
  51
  52                 node->next = head;
  53                 /*
  54                  * uatomic_cmpxchg() implicit memory barrier orders earlier
  55                  * stores to node before publication.
  56                  */
  57                 head = uatomic_cmpxchg(&s->head, old_head, node);
  58                 if (old_head == head)
  59                         break;
  60         }
  61 }
  62
  63 /*
  64  * Should be called under rcu read-side lock.
  65  *
  66  * The caller must wait for a grace period to pass before freeing the returned
  67  * node or modifying the cds_lfs_node_rcu structure.
  68  * Returns NULL if stack is empty.
  69  */
  70 struct cds_lfs_node_rcu *
  71 _cds_lfs_pop_rcu(struct cds_lfs_stack_rcu *s)
  72 {
  73         for (;;) {
  74                 struct cds_lfs_node_rcu *head;
  75
  76                 head = rcu_dereference(s->head);
  77                 if (head) {
  78                         struct cds_lfs_node_rcu *next = rcu_dereference(head->next);
  79
  80                         if (uatomic_cmpxchg(&s->head, head, next) == head) {
  81                                 return head;
  82                         } else {
  83                                 /* Concurrent modification. Retry. */
  84                                 continue;
  85                         }
  86                 } else {
  87                         /* Empty stack */
  88                         return NULL;
  89                 }
  90         }
  91 }
  92
  93 #ifdef __cplusplus
  94 }
  95 #endif
  96
  97 #endif /* _URCU_RCULFSTACK_STATIC_H */