/* $NetBSD: lock.h,v 1.14 2003/12/26 06:00:58 mrg Exp $ */ /*- * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Paul Kranenburg. * * 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. */ #ifndef _MACHINE_LOCK_H #define _MACHINE_LOCK_H /* * Machine dependent spin lock operations. */ /* XXX So we can expose this to userland. */ #ifdef __lint__ #define __ldstub(__addr) (__addr) #else /* !__lint__ */ static __inline__ int __ldstub(__cpu_simple_lock_t *addr); static __inline__ int __ldstub(__cpu_simple_lock_t *addr) { int v; __asm __volatile("ldstub [%1],%0" : "=r" (v) : "r" (addr) : "memory"); return v; } #endif /* __lint__ */ static __inline void __cpu_simple_lock_init __P((__cpu_simple_lock_t *)) __attribute__((__unused__)); static __inline void __cpu_simple_lock __P((__cpu_simple_lock_t *)) __attribute__((__unused__)); static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *)) __attribute__((__unused__)); static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *)) __attribute__((__unused__)); #if __SIMPLELOCK_UNLOCKED != 0 #error __SIMPLELOCK_UNLOCKED must be 0 for this implementation #endif static __inline void __cpu_simple_lock_init(__cpu_simple_lock_t *alp) { *alp = __SIMPLELOCK_UNLOCKED; } static __inline void __cpu_simple_lock(__cpu_simple_lock_t *alp) { /* * If someone else holds the lock use simple reads until it * is released, then retry the atomic operation. This reduces * memory bus contention because the cache-coherency logic * does not have to broadcast invalidates on the lock while * we spin on it. */ while (__ldstub(alp) != __SIMPLELOCK_UNLOCKED) { while (*alp != __SIMPLELOCK_UNLOCKED) /* spin */ ; } } static __inline int __cpu_simple_lock_try(__cpu_simple_lock_t *alp) { return (__ldstub(alp) == __SIMPLELOCK_UNLOCKED); } static __inline void __cpu_simple_unlock(__cpu_simple_lock_t *alp) { /* * Insert compiler barrier to prevent instruction re-ordering * around the lock release. */ __insn_barrier(); *alp = __SIMPLELOCK_UNLOCKED; } #endif /* _MACHINE_LOCK_H */