Add lock-free RCU queue and stack

[urcu.git] / urcu / rculfstack.h

diff --git a/urcu/rculfstack.h b/urcu/rculfstack.h
new file mode 100644 (file)
index 0000000..f43c9d8
--- /dev/null
+++ b/urcu/rculfstack.h
@@ -0,0 +1,88 @@
+/*
+ * rculfstack.h
+ *
+ * Userspace RCU library - Lock-Free RCU Stack
+ *
+ * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
+#error "Dynamic loader LGPL wrappers not implemented yet"
+#endif
+
+struct rcu_lfs_node {
+       struct rcu_lfs_node *next;
+};
+
+struct rcu_lfs_stack {
+       struct rcu_lfs_node *head;
+};
+
+void rcu_lfs_node_init(struct rcu_lfs_node *node)
+{
+}
+
+void rcu_lfs_init(struct rcu_lfs_stack *s)
+{
+       s->head = NULL;
+}
+
+void rcu_lfs_push(struct rcu_lfs_stack *s, struct rcu_lfs_node *node)
+{
+       rcu_read_lock();
+       for (;;) {
+               struct rcu_lfs_node *head = rcu_dereference(s->head);
+
+               node->next = head;
+               /*
+                * uatomic_cmpxchg() implicit memory barrier orders earlier
+                * stores to node before publication.
+                */
+               if (uatomic_cmpxchg(&s->head, head, node) == head) {
+                       rcu_read_unlock();
+                       return;
+               } else {
+                       /* Failure to prepend. Retry. */
+                       continue;
+               }
+       }
+}
+
+struct rcu_lfs_node *
+rcu_lfs_pop(struct rcu_lfs_stack *s)
+{
+       rcu_read_lock();
+       for (;;) {
+               struct rcu_lfs_node *head = rcu_dereference(s->head);
+
+               if (head) {
+                       struct rcu_lfs_node *next = rcu_dereference(head->next);
+
+                       if (uatomic_cmpxchg(&s->head, head, next) == head) {
+                               rcu_read_unlock();
+                               return head;
+                       } else {
+                               /* Concurrent modification. Retry. */
+                               continue;
+                       }
+               } else {
+                       /* Empty stack */
+                       rcu_read_unlock();
+                       return NULL;
+               }
+       }
+}