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