Wait-free stack: rcu-less implementation

[urcu.git] / urcu / rcuwfstack.h

diff --git a/urcu/rcuwfstack.h b/urcu/rcuwfstack.h
deleted file mode 100644 (file)
index 71ecce8..0000000
--- a/urcu/rcuwfstack.h
+++ /dev/null
@@ -1,133 +0,0 @@
-#ifndef _URCU_RCUWFSTACK_H
-#define _URCU_RCUWFSTACK_H
-
-/*
- * rcuwfstack.h
- *
- * Userspace RCU library - RCU Stack with Wait-Free push, Blocking pop.
- *
- * 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
- */
-
-#include <assert.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
-#error "Dynamic loader LGPL wrappers not implemented yet"
-#endif
-
-#define RCU_WF_STACK_END               ((void *)0x1UL)
-#define RCU_WFS_ADAPT_ATTEMPTS         10      /* Retry if being set */
-#define RCU_WFS_WAIT                   10      /* Wait 10 ms if being set */
-
-extern int rcu_wfs_futex;
-
-struct rcu_wfs_node {
-       struct rcu_wfs_node *next;
-};
-
-struct rcu_wfs_stack {
-       struct rcu_wfs_node *head;
-};
-
-void rcu_wfs_node_init(struct rcu_wfs_node *node)
-{
-       node->next = NULL;
-}
-
-void rcu_wfs_init(struct rcu_wfs_stack *s)
-{
-       s->head = RCU_WF_STACK_END;
-}
-
-void rcu_wfs_push(struct rcu_wfs_stack *s, struct rcu_wfs_node *node)
-{
-       struct rcu_wfs_node *old_head;
-
-       assert(node->next == NULL);
-       /*
-        * uatomic_xchg() implicit memory barrier orders earlier stores to node
-        * (setting it to NULL) before publication.
-        */
-       old_head = uatomic_xchg(&s->head, node);
-       /*
-        * At this point, dequeuers see a NULL node->next, they should busy-wait
-        * until node->next is set to old_head.
-        */
-       STORE_SHARED(node->next, old_head);
-}
-
-/*
- * The caller must wait for a grace period before:
- * - freeing the returned node.
- * - modifying the ->next pointer of the returned node. (be careful with unions)
- * - passing the returned node back to push() on the same stack they got it
- *   from.
- *
- * Returns NULL if stack is empty.
- *
- * cmpxchg is protected from ABA races by holding a RCU read lock between
- * s->head read and cmpxchg modifying s->head and requiring that dequeuers wait
- * for a grace period before freeing the returned node.
- */
-struct rcu_wfs_node *
-rcu_wfs_pop_blocking(struct rcu_wfs_stack *s)
-{
-       int attempt = 0;
-
-       for (;;) {
-               struct rcu_wfs_node *head;
-
-               rcu_read_lock();
-               head = rcu_dereference(s->head);
-               if (head != RCU_WF_STACK_END) {
-                       struct rcu_wfs_node *next = rcu_dereference(head->next);
-
-                       /* Retry while head is being set by push(). */
-                       if (!next) {
-                               rcu_read_unlock();
-                               if (++attempt >= RCU_WFS_ADAPT_ATTEMPTS) {
-                                       /* Sleep for 10ms */
-                                       poll(NULL, 0, RCU_WFS_WAIT);
-                                       attempt = 0;
-                               }
-                               continue;
-                       }
-                       if (uatomic_cmpxchg(&s->head, head, next) == head) {
-                               rcu_read_unlock();
-                               return head;
-                       } else {
-                               /* Concurrent modification. Retry. */
-                               rcu_read_unlock();
-                               continue;
-                       }
-               } else {
-                       /* Empty stack */
-                       rcu_read_unlock();
-                       return NULL;
-               }
-       }
-}
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* _URCU_RCUWFSTACK_H */