121 lines
3.9 KiB
C
121 lines
3.9 KiB
C
/* $NetBSD: lock.h,v 1.8 2000/05/05 20:12:01 hannken Exp $ */
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/*-
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* Copyright (c) 1998, 1999 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 Paul Kranenburg.
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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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#ifndef _MACHINE_LOCK_H
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#define _MACHINE_LOCK_H
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/*
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* Machine dependent spin lock operations.
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*/
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/*
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* The value for __SIMPLELOCK_LOCKED is what ldstub() naturally stores
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* `lock_data' given its address (and the fact that SPARC is big-endian).
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*/
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typedef __volatile int __cpu_simple_lock_t;
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#define __SIMPLELOCK_LOCKED 0xff000000
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#define __SIMPLELOCK_UNLOCKED 0
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/* XXX So we can expose this to userland. */
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#ifdef __lint__
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#define __ldstub(__addr) (__addr)
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#else /* !__lint__ */
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#define __ldstub(__addr) \
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({ \
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int __v; \
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\
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__asm __volatile("ldstub [%1],%0" \
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: "=r" (__v) \
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: "r" (__addr) \
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: "memory"); \
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\
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__v; \
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})
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#endif /* __lint__ */
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static __inline void __cpu_simple_lock_init __P((__cpu_simple_lock_t *))
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__attribute__((__unused__));
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static __inline void __cpu_simple_lock __P((__cpu_simple_lock_t *))
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__attribute__((__unused__));
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static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *))
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__attribute__((__unused__));
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static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *))
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__attribute__((__unused__));
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static __inline void
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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
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__cpu_simple_lock(__cpu_simple_lock_t *alp)
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{
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/*
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* If someone else holds the lock use simple reads until it
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* is released, then retry the atomic operation. This reduces
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* memory bus contention because the cache-coherency logic
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* does not have to broadcast invalidates on the lock while
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* we spin on it.
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*/
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while (__ldstub(alp) != __SIMPLELOCK_UNLOCKED) {
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while (*alp != __SIMPLELOCK_UNLOCKED)
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/* spin */ ;
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}
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}
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static __inline int
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__cpu_simple_lock_try(__cpu_simple_lock_t *alp)
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{
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return (__ldstub(alp) == __SIMPLELOCK_UNLOCKED);
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}
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static __inline void
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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 /* _MACHINE_LOCK_H */
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