StdLib/Include/Arm/machine/lock.h

   1 /*      $NetBSD: lock.h,v 1.7 2005/12/28 19:09:29 perry 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 static __inline int
  52 __swp(int __val, volatile int *__ptr)
  53 {
  54
  55         __asm volatile("swp %0, %1, [%2]"
  56             : "=r" (__val) : "r" (__val), "r" (__ptr) : "memory");
  57         return __val;
  58 }
  59
  60 static __inline void __attribute__((__unused__))
  61 __cpu_simple_lock_init(__cpu_simple_lock_t *alp)
  62 {
  63
  64         *alp = __SIMPLELOCK_UNLOCKED;
  65 }
  66
  67 static __inline void __attribute__((__unused__))
  68 __cpu_simple_lock(__cpu_simple_lock_t *alp)
  69 {
  70
  71         while (__swp(__SIMPLELOCK_LOCKED, alp) != __SIMPLELOCK_UNLOCKED)
  72                 continue;
  73 }
  74
  75 static __inline int __attribute__((__unused__))
  76 __cpu_simple_lock_try(__cpu_simple_lock_t *alp)
  77 {
  78
  79         return (__swp(__SIMPLELOCK_LOCKED, alp) == __SIMPLELOCK_UNLOCKED);
  80 }
  81
  82 static __inline void __attribute__((__unused__))
  83 __cpu_simple_unlock(__cpu_simple_lock_t *alp)
  84 {
  85
  86         *alp = __SIMPLELOCK_UNLOCKED;
  87 }
  88
  89 #endif /* _ARM_LOCK_H_ */