1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
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
28#ifndef _SYS__RWLOCK_H_
29#define	_SYS__RWLOCK_H_
30
31#include <machine/param.h>
32
33/*
34 * Reader/writer lock.
35 *
36 * All reader/writer lock implementations must always have a member
37 * called rw_lock.  Other locking primitive structures are not allowed to
38 * use this name for their members.
39 * If this rule needs to change, the bits in the reader/writer lock
40 * implementation must be modified appropriately.
41 */
42struct rwlock {
43	struct lock_object	lock_object;
44	volatile uintptr_t	rw_lock;
45};
46
47/*
48 * Members of struct rwlock_padalign must mirror members of struct rwlock.
49 * rwlock_padalign rwlocks can use the rwlock(9) API transparently without
50 * modification.
51 * Pad-aligned rwlocks used within structures should generally be the
52 * first member of the struct.  Otherwise, the compiler can generate
53 * additional padding for the struct to keep a correct alignment for
54 * the rwlock.
55 */
56struct rwlock_padalign {
57	struct lock_object	lock_object;
58	volatile uintptr_t	rw_lock;
59} __aligned(CACHE_LINE_SIZE);
60
61#endif /* !_SYS__RWLOCK_H_ */
62