rangelock.h revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2009 Konstantin Belousov <kib@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice unmodified, this list of conditions, and the following
12 *    disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * $FreeBSD: stable/11/sys/sys/rangelock.h 330897 2018-03-14 03:19:51Z eadler $
29 */
30
31#ifndef	_SYS_RANGELOCK_H
32#define	_SYS_RANGELOCK_H
33
34#include <sys/queue.h>
35
36#define	RL_LOCK_READ		0x0001
37#define	RL_LOCK_WRITE		0x0002
38#define	RL_LOCK_TYPE_MASK	0x0003
39#define	RL_LOCK_GRANTED		0x0004
40
41struct rl_q_entry;
42
43/*
44 * The structure representing the range lock.  Caller may request
45 * read or write access to the range of bytes. Access is granted if
46 * all existing lock owners are compatible with the request. Two lock
47 * owners are compatible if their ranges do not overlap, or both
48 * owners are for read.
49 *
50 * Access to the structure itself is synchronized with the externally
51 * supplied mutex.
52 *
53 * rl_waiters is the queue containing in order (a) granted write lock
54 * requests, (b) granted read lock requests, and (c) in order of arrival,
55 * lock requests which cannot be granted yet.
56 *
57 * rl_currdep is the first lock request that cannot be granted now due
58 * to the preceding requests conflicting with it (i.e., it points to
59 * position (c) in the list above).
60 */
61struct rangelock {
62	TAILQ_HEAD(, rl_q_entry) rl_waiters;
63	struct rl_q_entry	*rl_currdep;
64};
65
66#ifdef _KERNEL
67
68struct mtx;
69
70void	 rangelock_init(struct rangelock *lock);
71void	 rangelock_destroy(struct rangelock *lock);
72void	 rangelock_unlock(struct rangelock *lock, void *cookie,
73	    struct mtx *ilk);
74void	*rangelock_unlock_range(struct rangelock *lock, void *cookie,
75	    off_t start, off_t end, struct mtx *ilk);
76void	*rangelock_rlock(struct rangelock *lock, off_t start, off_t end,
77	    struct mtx *ilk);
78void	*rangelock_wlock(struct rangelock *lock, off_t start, off_t end,
79	    struct mtx *ilk);
80void	 rlqentry_free(struct rl_q_entry *rlqe);
81
82#endif	/* _KERNEL */
83
84#endif	/* _SYS_RANGELOCK_H */
85