freebsd-dev/lib/libc_r/arch/amd64/_atomic_lock.S

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/*
* Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
* copyright Douglas Santry 1996
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the above copyright is retained
* in the source form.
*
* THIS SOFTWARE IS PROVIDED BY Douglas Santry AND CONTRIBUTORS ``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 Douglas Santry OR CONTRIBUTORS 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.
*
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* $FreeBSD$
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*
*/
#if defined(LIBC_RCS) && !defined(lint)
.text
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.asciz "$FreeBSD$"
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#endif /* LIBC_RCS and not lint */
#include "DEFS.h"
/*
* Atomicly lock a location with an identifier provided the location
* is not currently locked.
*
* long _atomic_lock(long *);
* eax will contain the return value (zero if lock obtained).
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*/
ENTRY(_atomic_lock)
movl 4(%esp), %ecx
movl $1, %eax
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xchg %eax, (%ecx)
ret