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/* $OpenBSD: lock.h,v 1.4 2010/04/21 03:03:25 deraadt Exp $ */
/* $NetBSD: lock.h,v 1.3 2002/10/07 23:19:49 bjh21 Exp $ */
/*-
* Copyright (c) 2000, 2001 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Machine-dependent spin lock operations.
*
* NOTE: The SWP insn used here is available only on ARM architecture
* version 3 and later (as well as 2a). What we are going to do is
* expect that the kernel will trap and emulate the insn. That will
* be slow, but give us the atomicity that we need.
*/
#ifndef _ARM_LOCK_H_
#define _ARM_LOCK_H_
#include <arm/atomic.h>
typedef __volatile int __cpu_simple_lock_t;
#define __SIMPLELOCK_LOCKED 1
#define __SIMPLELOCK_UNLOCKED 0
static __inline int
__swp(int __val, __volatile int *__ptr)
{
__asm __volatile("swp %0, %1, [%2]"
: "=r" (__val) : "r" (__val), "r" (__ptr) : "memory");
return __val;
}
static __inline void __attribute__((__unused__))
__cpu_simple_lock_init(__cpu_simple_lock_t *alp)
{
*alp = __SIMPLELOCK_UNLOCKED;
}
static __inline void __attribute__((__unused__))
__cpu_simple_lock(__cpu_simple_lock_t *alp)
{
while (__swp(__SIMPLELOCK_LOCKED, alp) != __SIMPLELOCK_UNLOCKED)
continue;
}
static __inline int __attribute__((__unused__))
__cpu_simple_lock_try(__cpu_simple_lock_t *alp)
{
return (__swp(__SIMPLELOCK_LOCKED, alp) == __SIMPLELOCK_UNLOCKED);
}
static __inline void __attribute__((__unused__))
__cpu_simple_unlock(__cpu_simple_lock_t *alp)
{
*alp = __SIMPLELOCK_UNLOCKED;
}
#endif /* _ARM_LOCK_H_ */
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