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/* $OpenBSD: _atomic_lock.c,v 1.4 2003/05/19 18:31:49 miod Exp $ */
/*
* Atomic lock for vax
* Written by Miodrag Vallat <miod@openbsd.org> - placed in the public domain.
*/
#include "spinlock.h"
int
_atomic_lock(volatile _spinlock_lock_t *lock)
{
_spinlock_lock_t old;
/*
* The Branch on Bit Set and Set Interlocked instruction
* sets a given bit in a register or a memory location, as an
* atomic, interlocked operation.
* If the bit was set, execution continues at the branch
* location.
*
* For more details, please refer to the Vax Architecture
* Reference Manual, chapter 3 (Instructions), section
* ``Control instructions''.
*/
__asm__ (
"movl $1, %1\n" /* _SPINLOCK_LOCKED */
"bbssi $0, %0, 1f\n"
"movl $0, %1\n" /* _SPINLOCK_UNLOCKED */
"1: \n"
: "=m" (*lock), "=r" (old) : "0" (*lock)
);
return (old != _SPINLOCK_UNLOCKED);
}
int
_atomic_is_locked(volatile _spinlock_lock_t *lock)
{
return (*lock != _SPINLOCK_UNLOCKED);
}
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