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lock.h revision 1.2 
      1 /*	$NetBSD: lock.h,v 1.2 2001/11/15 19:22:32 thorpej Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2000, 2001 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  * NOTE: The SWP insn used here is available only on ARM architecture
     43  * version 3 and later (as well as 2a).  What we are going to do is
     44  * expect that the kernel will trap and emulate the insn.  That will
     45  * be slow, but give us the atomicity that we need.
     46  */
     47 
     48 #ifndef _ARM_LOCK_H_
     49 #define	_ARM_LOCK_H_
     50 
     51 typedef	__volatile int		__cpu_simple_lock_t;
     52 
     53 #define	__SIMPLELOCK_LOCKED	1
     54 #define	__SIMPLELOCK_UNLOCKED	0
     55 
     56 static __inline void __attribute__((__unused__))
     57 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
     58 {
     59 
     60 	*alp = __SIMPLELOCK_UNLOCKED;
     61 }
     62 
     63 static __inline void __attribute__((__unused__))
     64 __cpu_simple_lock(__cpu_simple_lock_t *alp)
     65 {
     66 	int __val = __SIMPLELOCK_LOCKED;
     67 
     68 	do {
     69 		__asm __volatile("swp %0, %1, [%2]"
     70 			: "=r" (__val)
     71 			: "0" (__val), "r" (alp)
     72 			: "memory");
     73 	} while (__val != __SIMPLELOCK_UNLOCKED);
     74 }
     75 
     76 static __inline int __attribute__((__unused__))
     77 __cpu_simple_lock_try(__cpu_simple_lock_t *alp)
     78 {
     79 	int __val = __SIMPLELOCK_LOCKED;
     80 
     81 	__asm __volatile("swp %0, %1, [%2]"
     82 		: "=r" (__val)
     83 		: "0" (__val), "r" (alp)
     84 		: "memory");
     85 
     86 	return ((__val == __SIMPLELOCK_UNLOCKED) ? 1 : 0);
     87 }
     88 
     89 static __inline void __attribute__((__unused__))
     90 __cpu_simple_unlock(__cpu_simple_lock_t *alp)
     91 {
     92 
     93 	*alp = __SIMPLELOCK_UNLOCKED;
     94 }
     95 
     96 #endif /* _ARM_LOCK_H_ */
     97