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/* $OpenBSD: _atomic_lock.c,v 1.7 2016/04/09 06:03:48 jsg Exp $ */
/*
* Copyright (c) 2004 Dale Rahn. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Atomic lock for arm
*/
#include <sys/types.h>
#include <machine/spinlock.h>
int
_atomic_lock(volatile _atomic_lock_t *lock)
{
_atomic_lock_t old;
#ifdef ARM_V7PLUS_LOCKS
uint32_t scratch = 0;
old = 0;
__asm__("1: ldrex %0, [%1] \n"
" strex %2, %3, [%1] \n"
" cmp %2, #0 \n"
" bne 1b \n"
" dmb sy \n"
: "+r" (old), "+r" (lock), "+r" (scratch)
: "r" (_ATOMIC_LOCK_LOCKED));
#else
__asm__("swp %0, %2, [%1]"
: "=r" (old), "=r" (lock)
: "r" (_ATOMIC_LOCK_LOCKED), "1" (lock) );
#endif
return (old != _ATOMIC_LOCK_UNLOCKED);
}
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