71ecce8cce1c492f9ec48ccd90fb4c07ee1e5287
1 #ifndef _URCU_RCUWFSTACK_H
2 #define _URCU_RCUWFSTACK_H
7 * Userspace RCU library - RCU Stack with Wait-Free push, Blocking pop.
9 * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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.
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.
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
32 #if (!defined(_GNU_SOURCE) && !defined(_LGPL_SOURCE))
33 #error "Dynamic loader LGPL wrappers not implemented yet"
36 #define RCU_WF_STACK_END ((void *)0x1UL)
37 #define RCU_WFS_ADAPT_ATTEMPTS 10 /* Retry if being set */
38 #define RCU_WFS_WAIT 10 /* Wait 10 ms if being set */
40 extern int rcu_wfs_futex
;
43 struct rcu_wfs_node
*next
;
46 struct rcu_wfs_stack
{
47 struct rcu_wfs_node
*head
;
50 void rcu_wfs_node_init(struct rcu_wfs_node
*node
)
55 void rcu_wfs_init(struct rcu_wfs_stack
*s
)
57 s
->head
= RCU_WF_STACK_END
;
60 void rcu_wfs_push(struct rcu_wfs_stack
*s
, struct rcu_wfs_node
*node
)
62 struct rcu_wfs_node
*old_head
;
64 assert(node
->next
== NULL
);
66 * uatomic_xchg() implicit memory barrier orders earlier stores to node
67 * (setting it to NULL) before publication.
69 old_head
= uatomic_xchg(&s
->head
, node
);
71 * At this point, dequeuers see a NULL node->next, they should busy-wait
72 * until node->next is set to old_head.
74 STORE_SHARED(node
->next
, old_head
);
78 * The caller must wait for a grace period before:
79 * - freeing the returned node.
80 * - modifying the ->next pointer of the returned node. (be careful with unions)
81 * - passing the returned node back to push() on the same stack they got it
84 * Returns NULL if stack is empty.
86 * cmpxchg is protected from ABA races by holding a RCU read lock between
87 * s->head read and cmpxchg modifying s->head and requiring that dequeuers wait
88 * for a grace period before freeing the returned node.
91 rcu_wfs_pop_blocking(struct rcu_wfs_stack
*s
)
96 struct rcu_wfs_node
*head
;
99 head
= rcu_dereference(s
->head
);
100 if (head
!= RCU_WF_STACK_END
) {
101 struct rcu_wfs_node
*next
= rcu_dereference(head
->next
);
103 /* Retry while head is being set by push(). */
106 if (++attempt
>= RCU_WFS_ADAPT_ATTEMPTS
) {
108 poll(NULL
, 0, RCU_WFS_WAIT
);
113 if (uatomic_cmpxchg(&s
->head
, head
, next
) == head
) {
117 /* Concurrent modification. Retry. */
133 #endif /* _URCU_RCUWFSTACK_H */
This page took 0.031445 seconds and 4 git commands to generate.