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To: linux-kernel@vger.kernel.org
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: Atomic operations
Date: 3 Jun 2002 12:49:36 -0700
Organization: Transmeta Corporation, Santa Clara CA
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In-Reply-To: <EE83E551E08D1D43AD52D50B9F5110927E7A10@ntserver2> <3CFBB7DB.831BE453@didntduck.org>
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Copyright: Copyright 2002 H. Peter Anvin - All Rights Reserved
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Followup to:  <3CFBB7DB.831BE453@didntduck.org>
By author:    Brian Gerst <bgerst@didntduck.org>
In newsgroup: linux.dev.kernel
> 
> int atomic_xadd(int i, atomic_t *v)
> {
> 	int ret;
> 	__asm__(LOCK "xaddl %1,%0"
> 		: "=m" (v->counter), "=r" (ret)
> 		: "0" (v->counter), "1" (i));
> 	return ret;
> }
> 
> This one only works on 486+, but there are practically no real 386 SMP
> systems.
> 

<slaps forehead>

Boy do I feel dumb now.

The only nitpick is that it's probably better coded as:

int atomic_xadd(int i, atomic_t *v)
{
	asm volatile(LOCK "xaddl %1,%0"
		: "+m" (v->counter), "+r" (i));
	return i;
}
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt	<amsp@zytor.com>
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