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/* $OpenBSD: lock.h,v 1.2 2004/06/13 21:49:16 niklas Exp $ */
/* $NetBSD: lock.h,v 1.1.2.2 2000/05/03 14:40:55 sommerfeld Exp $ */
/*-
* Copyright (c) 2000 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* 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.
*/
#ifndef _I386_LOCK_H_
#define _I386_LOCK_H_
typedef __volatile int __cpu_simple_lock_t;
#define __SIMPLELOCK_LOCKED 1
#define __SIMPLELOCK_UNLOCKED 0
/*
* compiler barrier: prevent reordering of instructions.
* XXX something similar will move to <sys/cdefs.h>
* or thereabouts.
* This prevents the compiler from reordering code around
* this "instruction", acting as a sequence point for code generation.
*/
#define __lockbarrier() __asm __volatile("": : :"memory")
#ifdef LOCKDEBUG
extern void __cpu_simple_lock_init(__cpu_simple_lock_t *);
extern void __cpu_simple_lock(__cpu_simple_lock_t *);
extern int __cpu_simple_lock_try(__cpu_simple_lock_t *);
extern void __cpu_simple_unlock(__cpu_simple_lock_t *);
#else
#include <machine/atomic.h>
static __inline void __cpu_simple_lock_init(__cpu_simple_lock_t *)
__attribute__((__unused__));
static __inline void __cpu_simple_lock(__cpu_simple_lock_t *)
__attribute__((__unused__));
static __inline int __cpu_simple_lock_try(__cpu_simple_lock_t *)
__attribute__((__unused__));
static __inline void __cpu_simple_unlock(__cpu_simple_lock_t *)
__attribute__((__unused__));
static __inline void
__cpu_simple_lock_init(__cpu_simple_lock_t *lockp)
{
*lockp = __SIMPLELOCK_UNLOCKED;
__lockbarrier();
}
static __inline void
__cpu_simple_lock(__cpu_simple_lock_t *lockp)
{
while (i386_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
== __SIMPLELOCK_LOCKED) {
continue; /* spin */
}
__lockbarrier();
}
static __inline int
__cpu_simple_lock_try(__cpu_simple_lock_t *lockp)
{
int r = (i386_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
== __SIMPLELOCK_UNLOCKED);
__lockbarrier();
return (r);
}
static __inline void
__cpu_simple_unlock(__cpu_simple_lock_t *lockp)
{
__lockbarrier();
*lockp = __SIMPLELOCK_UNLOCKED;
}
#endif /* !LOCKDEBUG */
#endif /* _I386_LOCK_H_ */
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