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[urcu.git] / urcu / rculfqueue.h
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1#ifndef _URCU_RCULFQUEUE_H
2#define _URCU_RCULFQUEUE_H
3
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4/*
5 * rculfqueue.h
6 *
7 * Userspace RCU library - Lock-Free RCU Queue
8 *
9 * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
10 *
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.
15 *
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.
20 *
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
24 */
25
26#include <urcu/urcu_ref.h>
27#include <assert.h>
28
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29#ifdef __cplusplus
30extern "C" {
31#endif
32
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33/*
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.
41 */
42
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43struct cds_lfq_node_rcu {
44 struct cds_lfq_node_rcu *next;
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45 struct urcu_ref ref;
46};
47
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48struct cds_lfq_queue_rcu {
49 struct cds_lfq_node_rcu *head, *tail;
50 struct cds_lfq_node_rcu init; /* Dummy initialization node */
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51};
52
3d02c34d 53#ifdef _LGPL_SOURCE
453629a9 54
3d02c34d 55#include <urcu/rculfqueue-static.h>
453629a9 56
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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
453629a9 61
3d02c34d 62#else /* !_LGPL_SOURCE */
453629a9 63
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64extern void cds_lfq_node_init_rcu(struct cds_lfq_node_rcu *node);
65extern void cds_lfq_init_rcu(struct cds_lfq_queue_rcu *q);
66extern void cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu *q, struct cds_lfq_node_rcu *node);
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67
68/*
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
c97740a3 71 * grace period must be waited after execution of the release callback before
16aa9ee8 72 * performing the actual memory reclamation or modifying the cds_lfq_node_rcu
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73 * structure.
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).
453629a9 77 */
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78extern struct cds_lfq_node_rcu *
79cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu *q, void (*release)(struct urcu_ref *));
453629a9 80
3d02c34d 81#endif /* !_LGPL_SOURCE */
c3f74cb2 82
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83#ifdef __cplusplus
84}
85#endif
86
c3f74cb2 87#endif /* _URCU_RCULFQUEUE_H */
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