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lock.h revision 1.2 
      1 /*	$NetBSD: lock.h,v 1.2 2003/05/08 01:04:34 fvdl Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2000 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe.
      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 /*
     40  * Machine-dependent spin lock operations.
     41  */
     42 
     43 #ifndef _I386_LOCK_H_
     44 #define	_I386_LOCK_H_
     45 
     46 #if defined(_KERNEL_OPT)
     47 #include "opt_lockdebug.h"
     48 #endif
     49 
     50 #include <machine/cpufunc.h>
     51 
     52 typedef	__volatile int		__cpu_simple_lock_t;
     53 
     54 #define	__SIMPLELOCK_LOCKED	1
     55 #define	__SIMPLELOCK_UNLOCKED	0
     56 
     57 /*
     58  * compiler barrier: prevent reordering of instructions.
     59  * XXX something similar will move to <sys/cdefs.h>
     60  * or thereabouts.
     61  * This prevents the compiler from reordering code around
     62  * this "instruction", acting as a sequence point for code generation.
     63  */
     64 
     65 #define __lockbarrier() __asm __volatile("": : :"memory")
     66 
     67 #ifdef LOCKDEBUG
     68 
     69 extern void __cpu_simple_lock_init __P((__cpu_simple_lock_t *));
     70 extern void __cpu_simple_lock __P((__cpu_simple_lock_t *));
     71 extern int __cpu_simple_lock_try __P((__cpu_simple_lock_t *));
     72 extern void __cpu_simple_unlock __P((__cpu_simple_lock_t *));
     73 
     74 #else
     75 
     76 #include <machine/atomic.h>
     77 
     78 static __inline void __cpu_simple_lock_init __P((__cpu_simple_lock_t *))
     79 	__attribute__((__unused__));
     80 static __inline void __cpu_simple_lock __P((__cpu_simple_lock_t *))
     81 	__attribute__((__unused__));
     82 static __inline int __cpu_simple_lock_try __P((__cpu_simple_lock_t *))
     83 	__attribute__((__unused__));
     84 static __inline void __cpu_simple_unlock __P((__cpu_simple_lock_t *))
     85 	__attribute__((__unused__));
     86 
     87 static __inline void
     88 __cpu_simple_lock_init(__cpu_simple_lock_t *lockp)
     89 {
     90 
     91 	*lockp = __SIMPLELOCK_UNLOCKED;
     92 	__lockbarrier();
     93 }
     94 
     95 static __inline void
     96 __cpu_simple_lock(__cpu_simple_lock_t *lockp)
     97 {
     98 
     99 	while (x86_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
    100 	    != __SIMPLELOCK_UNLOCKED)
    101 		x86_pause();
    102 	__lockbarrier();
    103 }
    104 
    105 static __inline int
    106 __cpu_simple_lock_try(__cpu_simple_lock_t *lockp)
    107 {
    108 	int r = (x86_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
    109 	    == __SIMPLELOCK_UNLOCKED);
    110 
    111 	__lockbarrier();
    112 
    113 	return (r);
    114 }
    115 
    116 static __inline void
    117 __cpu_simple_unlock(__cpu_simple_lock_t *lockp)
    118 {
    119 
    120 	__lockbarrier();
    121 	*lockp = __SIMPLELOCK_UNLOCKED;
    122 }
    123 
    124 #endif /* !LOCKDEBUG */
    125 
    126 #endif /* _I386_LOCK_H_ */
    127