5a9767e3de
in its own little inline function, and this allows us to get rid of all the automatic variables elsewhere. This subtly changes the semantics of __cpu_simple_lock() such that the loop ends up one instruction longer, but I'm not sure that's a particularly bad thing.
95 lines
3.2 KiB
C
95 lines
3.2 KiB
C
/* $NetBSD: lock.h,v 1.3 2002/10/07 23:19:49 bjh21 Exp $ */
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/*-
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* Copyright (c) 2000, 2001 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Machine-dependent spin lock operations.
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*
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* NOTE: The SWP insn used here is available only on ARM architecture
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* version 3 and later (as well as 2a). What we are going to do is
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* expect that the kernel will trap and emulate the insn. That will
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* be slow, but give us the atomicity that we need.
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*/
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#ifndef _ARM_LOCK_H_
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#define _ARM_LOCK_H_
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typedef __volatile int __cpu_simple_lock_t;
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#define __SIMPLELOCK_LOCKED 1
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#define __SIMPLELOCK_UNLOCKED 0
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static __inline int
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__swp(int __val, __volatile int *__ptr)
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{
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__asm __volatile("swp %0, %1, [%2]"
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: "=r" (__val) : "r" (__val), "r" (__ptr) : "memory");
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return __val;
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}
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static __inline void __attribute__((__unused__))
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__cpu_simple_lock_init(__cpu_simple_lock_t *alp)
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{
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*alp = __SIMPLELOCK_UNLOCKED;
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}
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static __inline void __attribute__((__unused__))
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__cpu_simple_lock(__cpu_simple_lock_t *alp)
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{
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while (__swp(__SIMPLELOCK_LOCKED, alp) != __SIMPLELOCK_UNLOCKED)
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continue;
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}
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static __inline int __attribute__((__unused__))
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__cpu_simple_lock_try(__cpu_simple_lock_t *alp)
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{
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return (__swp(__SIMPLELOCK_LOCKED, alp) == __SIMPLELOCK_UNLOCKED);
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}
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static __inline void __attribute__((__unused__))
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__cpu_simple_unlock(__cpu_simple_lock_t *alp)
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{
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*alp = __SIMPLELOCK_UNLOCKED;
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}
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#endif /* _ARM_LOCK_H_ */
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