1 /* $NetBSD: lock.h,v 1.10 2000/05/05 20:12:00 hannken 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 /* 47 * The value for __SIMPLELOCK_LOCKED is what ldstub() naturally stores 48 * `lock_data' given its address (and the fact that SPARC is big-endian). 49 */ 50 51 typedef __volatile int __cpu_simple_lock_t; 52 53 #define __SIMPLELOCK_LOCKED 0xff000000 54 #define __SIMPLELOCK_UNLOCKED 0 55 56 /* XXX So we can expose this to userland. */ 57 #ifdef __lint__ 58 #define __ldstub(__addr) (__addr) 59 #else /* !__lint__ */ 60 #define __ldstub(__addr) \ 61 ({ \ 62 int __v; \ 63 \ 64 __asm __volatile("ldstub [%1],%0" \ 65 : "=r" (__v) \ 66 : "r" (__addr) \ 67 : "memory"); \ 68 \ 69 __v; \ 70 }) 71 #endif /* __lint__ */ 72 73 static __inline void __cpu_simple_lock_init __P((__cpu_simple_lock_t *)) 74 __attribute__((__unused__)); 75 static __inline void __cpu_simple_lock __P((__cpu_simple_lock_t *)) 76 __attribute__((__unused__)); 77 static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *)) 78 __attribute__((__unused__)); 79 static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *)) 80 __attribute__((__unused__)); 81 82 static __inline void 83 __cpu_simple_lock_init(__cpu_simple_lock_t *alp) 84 { 85 86 *alp = __SIMPLELOCK_UNLOCKED; 87 } 88 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 } 105 106 static __inline int 107 __cpu_simple_lock_try(__cpu_simple_lock_t *alp) 108 { 109 110 return (__ldstub(alp) == __SIMPLELOCK_UNLOCKED); 111 } 112 113 static __inline void 114 __cpu_simple_unlock(__cpu_simple_lock_t *alp) 115 { 116 117 *alp = __SIMPLELOCK_UNLOCKED; 118 } 119 120 #endif /* _MACHINE_LOCK_H */ 121