1 /* 2 * Copyright (c) 2005 Jeffrey M. Hsu. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Jeffrey M. Hsu. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of The DragonFly Project nor the names of its 16 * contributors may be used to endorse or promote products derived 17 * from this software without specific, prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 22 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 23 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 24 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 25 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 26 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 27 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 28 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 29 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * $DragonFly: src/sys/sys/spinlock.h,v 1.1 2005/08/28 15:27:05 hsu Exp $ 33 */ 34 35 #ifndef _SPINLOCK_H_ 36 #define _SPINLOCK_H_ 37 38 #ifdef _KERNEL 39 #include <sys/thread2.h> 40 #include <machine/atomic.h> 41 #include <machine/cpufunc.h> 42 #endif 43 44 #ifdef SMP 45 46 struct spinlock { 47 volatile int lock; /* 0 = unlocked, 1 = locked */ 48 }; 49 50 static __inline boolean_t 51 spin_trylock(struct spinlock *mtx) 52 { 53 if (atomic_swap_int(&mtx->lock, 1) == 0) 54 return (TRUE); 55 return (FALSE); 56 } 57 58 extern void spin_lock_contested(struct spinlock *mtx); 59 60 static __inline void 61 spin_lock(struct spinlock *mtx) 62 { 63 if (atomic_swap_int(&mtx->lock, 1) != 0) 64 spin_lock_contested(mtx); /* slow path */ 65 } 66 67 static __inline void 68 spin_unlock(struct spinlock *mtx) 69 { 70 cpu_sfence(); 71 mtx->lock = 0; /* non-bus-locked lock release */ 72 } 73 74 static __inline boolean_t 75 spin_is_locked(struct spinlock *mtx) 76 { 77 return (mtx->lock); 78 } 79 80 static __inline void 81 spin_init(struct spinlock *mtx) 82 { 83 mtx->lock = 0; 84 } 85 86 #else /* SMP */ 87 88 /* 89 * Non-MP case optimized at compile-time. 90 */ 91 92 struct spinlock { 93 #ifndef __GNUC__ /* GCC allows 0-sized structures */ 94 volatile int lock; 95 #endif 96 }; 97 98 static __inline boolean_t 99 spin_trylock(struct spinlock *mtx) 100 { 101 return (TRUE); 102 } 103 104 static __inline boolean_t 105 spin_is_locked(struct spinlock *mtx) 106 { 107 return (FALSE); 108 } 109 110 static __inline void spin_lock(struct spinlock *mtx) { } 111 static __inline void spin_unlock(struct spinlock *mtx) { } 112 static __inline void spin_init(struct spinlock *mtx) { } 113 114 #endif /* SMP */ 115 116 static __inline void 117 spin_lock_crit(struct spinlock *mtx) 118 { 119 crit_enter(); 120 spin_lock(mtx); 121 } 122 123 static __inline void 124 spin_unlock_crit(struct spinlock *mtx) 125 { 126 spin_unlock(mtx); 127 crit_exit(); 128 } 129 130 #endif 131