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lock.h revision 1.5 
      1 /*	$NetBSD: lock.h,v 1.5 1999/07/27 22:22:33 thorpej 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 #if defined(_KERNEL)
     47 
     48 #include <sparc/sparc/asm.h>
     49 
     50 /*
     51  * The value for SIMPLELOCK_LOCKED is what ldstub() naturally stores
     52  * `lock_data' given its address (and the fact that SPARC is big-endian).
     53  */
     54 #define	SIMPLELOCK_LOCKED	0xff000000
     55 #define	SIMPLELOCK_UNLOCKED	0
     56 
     57 static void	cpu_simple_lock_init __P((__volatile struct simplelock *));
     58 static void	cpu_simple_lock __P((__volatile struct simplelock *));
     59 static int	cpu_simple_lock_try __P((__volatile struct simplelock *));
     60 static void	cpu_simple_unlock __P((__volatile struct simplelock *));
     61 
     62 static __inline__ void
     63 cpu_simple_lock_init (alp)
     64 	__volatile struct simplelock *alp;
     65 {
     66 
     67 	alp->lock_data = SIMPLELOCK_UNLOCKED;
     68 }
     69 
     70 static __inline__ void
     71 cpu_simple_lock (alp)
     72 	__volatile struct simplelock *alp;
     73 {
     74 
     75 	/*
     76 	 * If someone else holds the lock use simple
     77 	 * reads until it is released, then retry the
     78 	 * atomic operation. This reduces memory bus contention
     79 	 * becaused the cache-coherency logic does not have to
     80 	 * broadcast invalidates on the lock while we spin on it.
     81 	 */
     82 	while (ldstub(&alp->lock_data) != SIMPLELOCK_UNLOCKED) {
     83 		while (alp->lock_data != SIMPLELOCK_UNLOCKED)
     84 			/*void*/;
     85 	}
     86 }
     87 
     88 static __inline__ int
     89 cpu_simple_lock_try (alp)
     90 	__volatile struct simplelock *alp;
     91 {
     92 
     93 	return (ldstub(&alp->lock_data) == SIMPLELOCK_UNLOCKED);
     94 }
     95 
     96 static __inline__ void
     97 cpu_simple_unlock (alp)
     98 	__volatile struct simplelock *alp;
     99 {
    100 
    101 	alp->lock_data = SIMPLELOCK_UNLOCKED;
    102 }
    103 
    104 #endif /* _KERNEL */
    105 
    106 #endif /* _MACHINE_LOCK_H */
    107