1 /* $NetBSD: lock.h,v 1.19 2005/12/11 12:19:05 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Paul Kranenburg. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #ifndef _MACHINE_LOCK_H 40 #define _MACHINE_LOCK_H 41 42 /* 43 * Machine dependent spin lock operations. 44 */ 45 46 #if __SIMPLELOCK_UNLOCKED != 0 47 #error __SIMPLELOCK_UNLOCKED must be 0 for this implementation 48 #endif 49 50 /* XXX So we can expose this to userland. */ 51 #ifdef __lint__ 52 #define __ldstub(__addr) (__addr) 53 #else /* !__lint__ */ 54 static __inline__ int __ldstub(__cpu_simple_lock_t *addr); 55 static __inline__ int __ldstub(__cpu_simple_lock_t *addr) 56 { 57 int v; 58 59 __asm __volatile("ldstub [%1],%0" 60 : "=&r" (v) 61 : "r" (addr) 62 : "memory"); 63 64 return v; 65 } 66 #endif /* __lint__ */ 67 68 static __inline void __cpu_simple_lock_init __P((__cpu_simple_lock_t *)) 69 __attribute__((__unused__)); 70 static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *)) 71 __attribute__((__unused__)); 72 static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *)) 73 __attribute__((__unused__)); 74 #ifndef __CPU_SIMPLE_LOCK_NOINLINE 75 static __inline void __cpu_simple_lock __P((__cpu_simple_lock_t *)) 76 __attribute__((__unused__)); 77 #else 78 extern void __cpu_simple_lock __P((__cpu_simple_lock_t *)); 79 #endif 80 81 static __inline void 82 __cpu_simple_lock_init(__cpu_simple_lock_t *alp) 83 { 84 85 *alp = __SIMPLELOCK_UNLOCKED; 86 } 87 88 #ifndef __CPU_SIMPLE_LOCK_NOINLINE 89 static __inline void 90 __cpu_simple_lock(__cpu_simple_lock_t *alp) 91 { 92 93 /* 94 * If someone else holds the lock use simple reads until it 95 * is released, then retry the atomic operation. This reduces 96 * memory bus contention because the cache-coherency logic 97 * does not have to broadcast invalidates on the lock while 98 * we spin on it. 99 */ 100 while (__ldstub(alp) != __SIMPLELOCK_UNLOCKED) { 101 while (*alp != __SIMPLELOCK_UNLOCKED) 102 /* spin */ ; 103 } 104 } 105 #endif /* __CPU_SIMPLE_LOCK_NOINLINE */ 106 107 static __inline int 108 __cpu_simple_lock_try(__cpu_simple_lock_t *alp) 109 { 110 111 return (__ldstub(alp) == __SIMPLELOCK_UNLOCKED); 112 } 113 114 static __inline void 115 __cpu_simple_unlock(__cpu_simple_lock_t *alp) 116 { 117 118 /* 119 * Insert compiler barrier to prevent instruction re-ordering 120 * around the lock release. 121 */ 122 __insn_barrier(); 123 *alp = __SIMPLELOCK_UNLOCKED; 124 } 125 126 #endif /* _MACHINE_LOCK_H */ 127