linux-kernel - Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

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Message-Id: <d4c6e3846c4171eb1e74d0874d7c3b60@kernel.crashing.org>
Date:	Thu, 16 Aug 2007 21:33:40 +0200
From:	Segher Boessenkool <segher@...nel.crashing.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	heiko.carstens@...ibm.com, horms@...ge.net.au,
	linux-kernel@...r.kernel.org, rpjday@...dspring.com, ak@...e.de,
	netdev@...r.kernel.org, cfriesen@...tel.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	jesper.juhl@...il.com, linux-arch@...r.kernel.org, zlynx@....org,
	satyam@...radead.org, clameter@....com, schwidefsky@...ibm.com,
	Chris Snook <csnook@...hat.com>,
	Herbert Xu <herbert.xu@...hat.com>, davem@...emloft.net,
	wensong@...ux-vs.org, wjiang@...ilience.com
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

>> The only thing volatile on an asm does is create a side effect
>> on the asm statement; in effect, it tells the compiler "do not
>> remove this asm even if you don't need any of its outputs".
>>
>> It's not disabling optimisation likely to result in bugs,
>> heisen- or otherwise; _not_ putting the volatile on an asm
>> that needs it simply _is_ a bug :-)
>
> Yep.  And the reason it is a bug is that it fails to disable
> the relevant compiler optimizations.  So I suspect that we might
> actually be saying the same thing here.

We're not saying the same thing, but we do agree :-)


Segher

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