linux-kernel - Re: [PATCH] make atomic_t volatile on all architectures

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Message-ID: <alpine.LFD.0.999.0708091055080.25146@woody.linux-foundation.org>
Date:	Thu, 9 Aug 2007 10:55:46 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chuck Ebbert <cebbert@...hat.com>
cc:	Chris Snook <csnook@...hat.com>, akpm@...ux-foundation.org,
	ak@...e.de, heiko.carstens@...ibm.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	schwidefsky@...ibm.com, wensong@...ux-vs.org, horms@...ge.net.au,
	wjiang@...ilience.com, cfriesen@...tel.com, zlynx@....org
Subject: Re: [PATCH] make atomic_t volatile on all architectures



On Thu, 9 Aug 2007, Chuck Ebbert wrote:
> 
> You can use this forget() macro to make the compiler reread a variable:
> 
> #define forget(var) asm volatile ("" : "=m"(var))

No. That will also make the compiler "forget" any previous writes to it, 
so it changes behaviour.

You'd have to use "+m".

		Linus
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