1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following 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 AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 * $FreeBSD$
28 */
29
30#ifndef _SYS__RWLOCK_H_
31#define	_SYS__RWLOCK_H_
32
33#include <machine/param.h>
34
35/*
36 * Reader/writer lock.
37 *
38 * All reader/writer lock implementations must always have a member
39 * called rw_lock.  Other locking primitive structures are not allowed to
40 * use this name for their members.
41 * If this rule needs to change, the bits in the reader/writer lock
42 * implementation must be modified appropriately.
43 */
44struct rwlock {
45	struct lock_object	lock_object;
46	volatile uintptr_t	rw_lock;
47};
48
49/*
50 * Members of struct rwlock_padalign must mirror members of struct rwlock.
51 * rwlock_padalign rwlocks can use the rwlock(9) API transparently without
52 * modification.
53 * Pad-aligned rwlocks used within structures should generally be the
54 * first member of the struct.  Otherwise, the compiler can generate
55 * additional padding for the struct to keep a correct alignment for
56 * the rwlock.
57 */
58struct rwlock_padalign {
59	struct lock_object	lock_object;
60	volatile uintptr_t	rw_lock;
61} __aligned(CACHE_LINE_SIZE);
62
63#endif /* !_SYS__RWLOCK_H_ */
64