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lock.h revision 1.7 
      1 /*	$NetBSD: lock.h,v 1.7 2004/10/31 10:39:34 yamt 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 /*
     53  * compiler barrier: prevent reordering of instructions.
     54  * XXX something similar will move to <sys/cdefs.h>
     55  * or thereabouts.
     56  * This prevents the compiler from reordering code around
     57  * this "instruction", acting as a sequence point for code generation.
     58  */
     59 
     60 #define __lockbarrier() __asm __volatile("": : :"memory")
     61 
     62 #ifdef LOCKDEBUG
     63 
     64 extern void __cpu_simple_lock_init(__cpu_simple_lock_t *);
     65 extern void __cpu_simple_lock(__cpu_simple_lock_t *);
     66 extern int __cpu_simple_lock_try(__cpu_simple_lock_t *);
     67 extern void __cpu_simple_unlock(__cpu_simple_lock_t *);
     68 
     69 #else
     70 
     71 #include <machine/atomic.h>
     72 
     73 static __inline void __cpu_simple_lock_init(__cpu_simple_lock_t *)
     74 	__attribute__((__unused__));
     75 static __inline void __cpu_simple_lock(__cpu_simple_lock_t *)
     76 	__attribute__((__unused__));
     77 static __inline int __cpu_simple_lock_try(__cpu_simple_lock_t *)
     78 	__attribute__((__unused__));
     79 static __inline void __cpu_simple_unlock(__cpu_simple_lock_t *)
     80 	__attribute__((__unused__));
     81 
     82 static __inline void
     83 __cpu_simple_lock_init(__cpu_simple_lock_t *lockp)
     84 {
     85 
     86 	*lockp = __SIMPLELOCK_UNLOCKED;
     87 	__insn_barrier();
     88 }
     89 
     90 static __inline void
     91 __cpu_simple_lock(__cpu_simple_lock_t *lockp)
     92 {
     93 
     94 	while (x86_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
     95 	    != __SIMPLELOCK_UNLOCKED) {
     96 		do {
     97 			x86_pause();
     98 		} while (*lockp == __SIMPLELOCK_LOCKED);
     99 	}
    100 	__insn_barrier();
    101 }
    102 
    103 static __inline int
    104 __cpu_simple_lock_try(__cpu_simple_lock_t *lockp)
    105 {
    106 	int r = (x86_atomic_testset_i(lockp, __SIMPLELOCK_LOCKED)
    107 	    == __SIMPLELOCK_UNLOCKED);
    108 
    109 	__insn_barrier();
    110 
    111 	return (r);
    112 }
    113 
    114 static __inline void
    115 __cpu_simple_unlock(__cpu_simple_lock_t *lockp)
    116 {
    117 
    118 	__insn_barrier();
    119 	*lockp = __SIMPLELOCK_UNLOCKED;
    120 }
    121 
    122 #endif /* !LOCKDEBUG */
    123 
    124 #ifdef _KERNEL
    125 #define	SPINLOCK_SPIN_HOOK	x86_pause()
    126 #endif
    127 
    128 #endif /* _I386_LOCK_H_ */
    129