1 #ifndef _URCU_RCULFQUEUE_H
2 #define _URCU_RCULFQUEUE_H
7 * Userspace RCU library - Lock-Free RCU Queue
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
26 #include <urcu/urcu_ref.h>
34 * Lock-free RCU queue using reference counting. Enqueue and dequeue operations
35 * hold a RCU read lock to deal with cmpxchg ABA problem. This implementation
36 * keeps a dummy head node to ensure we can always update the queue locklessly.
37 * Given that this is a queue, the dummy head node must always advance as we
38 * dequeue entries. Therefore, we keep a reference count on each entry we are
39 * dequeueing, so they can be kept as dummy head node until the next dequeue, at
40 * which point their reference count will be decremented.
43 struct cds_lfq_node_rcu
{
44 struct cds_lfq_node_rcu
*next
;
48 struct cds_lfq_queue_rcu
{
49 struct cds_lfq_node_rcu
*head
, *tail
;
50 struct cds_lfq_node_rcu init
; /* Dummy initialization node */
55 #include <urcu/rculfqueue-static.h>
57 #define cds_lfq_node_init_rcu _cds_lfq_node_init_rcu
58 #define cds_lfq_init_rcu _cds_lfq_init_rcu
59 #define cds_lfq_enqueue_rcu _cds_lfq_enqueue_rcu
60 #define cds_lfq_dequeue_rcu _cds_lfq_dequeue_rcu
62 #else /* !_LGPL_SOURCE */
64 extern void cds_lfq_node_init_rcu(struct cds_lfq_node_rcu
*node
);
65 extern void cds_lfq_init_rcu(struct cds_lfq_queue_rcu
*q
);
66 extern void cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu
*q
, struct cds_lfq_node_rcu
*node
);
69 * The entry returned by dequeue must be taken care of by doing a urcu_ref_put,
70 * which calls the release primitive when the reference count drops to zero. A
71 * grace period must be waited after execution of the release callback before
72 * performing the actual memory reclamation or modifying the cds_lfq_node_rcu
74 * In other words, the entry lfq node returned by dequeue must not be
75 * modified/re-used/freed until the reference count reaches zero and a grace
76 * period has elapsed (after the refcount reached 0).
78 extern struct cds_lfq_node_rcu
*
79 cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu
*q
, void (*release
)(struct urcu_ref
*));
81 #endif /* !_LGPL_SOURCE */
87 #endif /* _URCU_RCULFQUEUE_H */
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