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
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_queue_rcu
;
45 struct cds_lfq_node_rcu
{
46 struct cds_lfq_node_rcu
*next
;
48 struct cds_lfq_queue_rcu
*queue
;
49 struct rcu_head rcu_head
;
52 struct cds_lfq_queue_rcu
{
53 struct cds_lfq_node_rcu
*head
, *tail
;
54 struct cds_lfq_node_rcu init
; /* Dummy initialization node */
55 void (*release
)(struct urcu_ref
*ref
);
60 #include <urcu/static/rculfqueue.h>
62 #define cds_lfq_node_init_rcu _cds_lfq_node_init_rcu
63 #define cds_lfq_init_rcu _cds_lfq_init_rcu
64 #define cds_lfq_enqueue_rcu _cds_lfq_enqueue_rcu
65 #define cds_lfq_dequeue_rcu _cds_lfq_dequeue_rcu
67 #else /* !_LGPL_SOURCE */
69 extern void cds_lfq_node_init_rcu(struct cds_lfq_node_rcu
*node
);
70 extern void cds_lfq_init_rcu(struct cds_lfq_queue_rcu
*q
,
71 void (*release
)(struct urcu_ref
*ref
));
74 * Should be called under rcu read lock critical section.
76 extern void cds_lfq_enqueue_rcu(struct cds_lfq_queue_rcu
*q
,
77 struct cds_lfq_node_rcu
*node
);
80 * Should be called under rcu read lock critical section.
82 * The entry returned by dequeue must be taken care of by doing a
83 * sequence of urcu_ref_put which release handler should do a call_rcu.
85 * In other words, the entry lfq node returned by dequeue must not be
86 * modified/re-used/freed until the reference count reaches zero and a grace
87 * period has elapsed (after the refcount reached 0).
90 struct cds_lfq_node_rcu
*cds_lfq_dequeue_rcu(struct cds_lfq_queue_rcu
*q
);
92 #endif /* !_LGPL_SOURCE */
98 #endif /* _URCU_RCULFQUEUE_H */
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