1/*-
2 * Copyright (c) 2009 Konstantin Belousov <kib@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 *
26 * $FreeBSD$
27 */
28
29#ifndef	_SYS_RANGELOCK_H
30#define	_SYS_RANGELOCK_H
31
32#include <sys/queue.h>
33
34#define	RL_LOCK_READ		0x0001
35#define	RL_LOCK_WRITE		0x0002
36#define	RL_LOCK_TYPE_MASK	0x0003
37#define	RL_LOCK_GRANTED		0x0004
38
39struct rl_q_entry;
40
41/*
42 * The structure representing the range lock.  Caller may request
43 * read or write access to the range of bytes. Access is granted if
44 * all existing lock owners are compatible with the request. Two lock
45 * owners are compatible if their ranges do not overlap, or both
46 * owners are for read.
47 *
48 * Access to the structure itself is synchronized with the externally
49 * supplied mutex.
50 *
51 * rl_waiters is the queue containing in order (a) granted write lock
52 * requests, (b) granted read lock requests, and (c) in order of arrival,
53 * lock requests which cannot be granted yet.
54 *
55 * rl_currdep is the first lock request that cannot be granted now due
56 * to the preceding requests conflicting with it (i.e., it points to
57 * position (c) in the list above).
58 */
59struct rangelock {
60	TAILQ_HEAD(, rl_q_entry) rl_waiters;
61	struct rl_q_entry	*rl_currdep;
62};
63
64#ifdef _KERNEL
65
66struct mtx;
67
68void	 rangelock_init(struct rangelock *lock);
69void	 rangelock_destroy(struct rangelock *lock);
70void	 rangelock_unlock(struct rangelock *lock, void *cookie,
71	    struct mtx *ilk);
72void	*rangelock_unlock_range(struct rangelock *lock, void *cookie,
73	    off_t start, off_t end, struct mtx *ilk);
74void	*rangelock_rlock(struct rangelock *lock, off_t start, off_t end,
75	    struct mtx *ilk);
76void	*rangelock_wlock(struct rangelock *lock, off_t start, off_t end,
77	    struct mtx *ilk);
78void	 rlqentry_free(struct rl_q_entry *rlqe);
79
80#endif	/* _KERNEL */
81
82#endif	/* _SYS_RANGELOCK_H */
83