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lock.h revision 1.2 
      1 /*	$NetBSD: lock.h,v 1.2 1998/10/05 19:58:19 pk Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 1998 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 defined(_KERNEL)
     47 
     48 #include <sparc/sparc/asm.h>
     49 
     50 static void	simple_lock_init __P((__volatile struct simplelock *));
     51 static void	simple_lock __P((__volatile struct simplelock *));
     52 static int	simple_lock_try __P((__volatile struct simplelock *));
     53 static void	simple_unlock __P((__volatile struct simplelock *));
     54 
     55 static __inline__ void
     56 simple_lock_init (alp)
     57 	__volatile struct simplelock *alp;
     58 {
     59 
     60 	alp->lock_data = 0;
     61 }
     62 
     63 static __inline__ void
     64 simple_lock (alp)
     65 	__volatile struct simplelock *alp;
     66 {
     67 
     68 	/*
     69 	 * If someone else holds the lock use simple
     70 	 * reads until it is released, then retry the
     71 	 * atomic operation. This reduces memory bus contention
     72 	 * becaused the cache-coherency logic does not have to
     73 	 * broadcast invalidates on the lock while we spin on it.
     74 	 */
     75 	while (ldstub(&alp->lock_data) != 0) {
     76 		while (alp->lock_data != 0)
     77 			/*void*/;
     78 	}
     79 }
     80 
     81 static __inline__ int
     82 simple_lock_try (alp)
     83 	__volatile struct simplelock *alp;
     84 {
     85 
     86 	return (ldstub(&alp->lock_data) == 0);
     87 }
     88 
     89 static __inline__ void
     90 simple_unlock (alp)
     91 	__volatile struct simplelock *alp;
     92 {
     93 
     94 	alp->lock_data = 0;
     95 }
     96 #endif /* _KERNEL */
     97 
     98 #endif /* _MACHINE_LOCK_H */
     99