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Date: Fri, 9 Aug 2002 01:04:40 +0200 (CEST)
From: Roman Zippel <zippel@linux-m68k.org>
X-X-Sender: roman@serv
To: Luca Barbieri <ldb@ldb.ods.org>
cc: Linux-Kernel ML <linux-kernel@vger.kernel.org>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] [2.5] asm-generic/atomic.h and changes to arm, parisc,
 mips, m68k, sh, cris to use it
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Hi,

On 9 Aug 2002, Luca Barbieri wrote:

> > The compiler can cache the value in a register
> It shouldn't since it is volatile and the machine has instructions with
> memory operands.

volatile is no guarantee for that:

volatile int x;

void f(int y)
{
        x += y;
}

becomes:

	move.l x,%d0
	add.l 8(%a6),%d0
	move.l %d0,x

I agree that volatile should avoid caching, but it does not guarantee an
atomic modify.

bye, Roman

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