xref: /illumos-gate/usr/src/boot/sys/sys/_rwlock.h (revision 199767f8)
1 /*-
2  * Copyright (c) 2006 John Baldwin <jhb@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, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24  * SUCH DAMAGE.
25  *
26  * $FreeBSD$
27  */
28 
29 #ifndef _SYS__RWLOCK_H_
30 #define	_SYS__RWLOCK_H_
31 
32 #include <machine/param.h>
33 
34 /*
35  * Reader/writer lock.
36  *
37  * All reader/writer lock implementations must always have a member
38  * called rw_lock.  Other locking primitive structures are not allowed to
39  * use this name for their members.
40  * If this rule needs to change, the bits in the reader/writer lock
41  * implementation must be modified appropriately.
42  */
43 struct rwlock {
44 	struct lock_object	lock_object;
45 	volatile uintptr_t	rw_lock;
46 };
47 
48 /*
49  * Members of struct rwlock_padalign must mirror members of struct rwlock.
50  * rwlock_padalign rwlocks can use the rwlock(9) API transparently without
51  * modification.
52  * Pad-aligned rwlocks used within structures should generally be the
53  * first member of the struct.  Otherwise, the compiler can generate
54  * additional padding for the struct to keep a correct alignment for
55  * the rwlock.
56  */
57 struct rwlock_padalign {
58 	struct lock_object	lock_object;
59 	volatile uintptr_t	rw_lock;
60 } __aligned(CACHE_LINE_SIZE);
61 
62 #endif /* !_SYS__RWLOCK_H_ */
63