| | 1 | #ifndef _URCU_RCULFQUEUE_H |
| | 2 | #define _URCU_RCULFQUEUE_H |
| | 3 | |
| | 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 | |
| | 29 | #ifdef __cplusplus |
| | 30 | extern "C" { |
| | 31 | #endif |
| | 32 | |
| | 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 | |
| | 43 | struct rcu_lfq_node { |
| | 44 | struct rcu_lfq_node *next; |
| | 45 | struct urcu_ref ref; |
| | 46 | }; |
| | 47 | |
| | 48 | struct rcu_lfq_queue { |
| | 49 | struct rcu_lfq_node *head, *tail; |
| | 50 | struct rcu_lfq_node init; /* Dummy initialization node */ |
| | 51 | }; |
| | 52 | |
| | 53 | #ifdef _LGPL_SOURCE |
| | 54 | |
| | 55 | #include <urcu/rculfqueue-static.h> |
| | 56 | |
| | 57 | #define rcu_lfq_node_init _rcu_lfq_node_init |
| | 58 | #define rcu_lfq_init _rcu_lfq_init |
| | 59 | #define rcu_lfq_enqueue _rcu_lfq_enqueue |
| | 60 | #define rcu_lfq_dequeue _rcu_lfq_dequeue |
| | 61 | |
| | 62 | #else /* !_LGPL_SOURCE */ |
| | 63 | |
| | 64 | extern void rcu_lfq_node_init(struct rcu_lfq_node *node); |
| | 65 | extern void rcu_lfq_init(struct rcu_lfq_queue *q); |
| | 66 | extern void rcu_lfq_enqueue(struct rcu_lfq_queue *q, struct rcu_lfq_node *node); |
| | 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 |
| | 71 | * grace period must be waited after execution of the release callback before |
| | 72 | * performing the actual memory reclamation or modifying the rcu_lfq_node |
| | 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). |
| | 77 | */ |
| | 78 | extern struct rcu_lfq_node * |
| | 79 | rcu_lfq_dequeue(struct rcu_lfq_queue *q, void (*release)(struct urcu_ref *)); |
| | 80 | |
| | 81 | #endif /* !_LGPL_SOURCE */ |
| | 82 | |
| | 83 | #ifdef __cplusplus |
| | 84 | } |
| | 85 | #endif |
| | 86 | |
| | 87 | #endif /* _URCU_RCULFQUEUE_H */ |
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