1 /* $NetBSD: lock.h,v 1.7 2005/12/28 19:09:29 perry Exp $ */
2
3 /*-
4 * Copyright (c) 2000, 2001 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. All advertising materials mentioning features or use of this software
19 * must display the following acknowledgement:
20 * This product includes software developed by the NetBSD
21 * Foundation, Inc. and its contributors.
22 * 4. Neither the name of The NetBSD Foundation nor the names of its
23 * contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36 * POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 /*
40 * Machine-dependent spin lock operations.
41 *
42 * NOTE: The SWP insn used here is available only on ARM architecture
43 * version 3 and later (as well as 2a). What we are going to do is
44 * expect that the kernel will trap and emulate the insn. That will
45 * be slow, but give us the atomicity that we need.
46 */
47
48 #ifndef _ARM_LOCK_H_
49 #define _ARM_LOCK_H_
50
51 static __inline int
__swp(int __val,volatile int * __ptr)52 __swp(int __val, volatile int *__ptr)
53 {
54
55 __asm volatile("swp %0, %1, [%2]"
56 : "=r" (__val) : "r" (__val), "r" (__ptr) : "memory");
57 return __val;
58 }
59
60 static __inline void __attribute__((__unused__))
__cpu_simple_lock_init(__cpu_simple_lock_t * alp)61 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
62 {
63
64 *alp = __SIMPLELOCK_UNLOCKED;
65 }
66
67 static __inline void __attribute__((__unused__))
__cpu_simple_lock(__cpu_simple_lock_t * alp)68 __cpu_simple_lock(__cpu_simple_lock_t *alp)
69 {
70
71 while (__swp(__SIMPLELOCK_LOCKED, alp) != __SIMPLELOCK_UNLOCKED)
72 continue;
73 }
74
75 static __inline int __attribute__((__unused__))
__cpu_simple_lock_try(__cpu_simple_lock_t * alp)76 __cpu_simple_lock_try(__cpu_simple_lock_t *alp)
77 {
78
79 return (__swp(__SIMPLELOCK_LOCKED, alp) == __SIMPLELOCK_UNLOCKED);
80 }
81
82 static __inline void __attribute__((__unused__))
__cpu_simple_unlock(__cpu_simple_lock_t * alp)83 __cpu_simple_unlock(__cpu_simple_lock_t *alp)
84 {
85
86 *alp = __SIMPLELOCK_UNLOCKED;
87 }
88
89 #endif /* _ARM_LOCK_H_ */
90