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

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Message-Id: <E1ILCgh-00052A-00@gondolin.me.apana.org.au>
Date:	Wed, 15 Aug 2007 14:49:03 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	csnook@...hat.com (Chris Snook)
Cc:	satyam@...radead.org, clameter@....com,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	torvalds@...ux-foundation.org, netdev@...r.kernel.org,
	akpm@...ux-foundation.org, ak@...e.de, heiko.carstens@...ibm.com,
	davem@...emloft.net, schwidefsky@...ibm.com, wensong@...ux-vs.org,
	horms@...ge.net.au, wjiang@...ilience.com, cfriesen@...tel.com,
	zlynx@....org, rpjday@...dspring.com, jesper.juhl@...il.com,
	segher@...nel.crashing.org
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

Chris Snook <csnook@...hat.com> wrote:
> 
> Because atomic operations are generally used for synchronization, which requires 
> volatile behavior.  Most such codepaths currently use an inefficient barrier(). 
>  Some forget to and we get bugs, because people assume that atomic_read() 
> actually reads something, and atomic_write() actually writes something.  Worse, 
> these are architecture-specific, even compiler version-specific bugs that are 
> often difficult to track down.

I'm yet to see a single example from the current tree where
this patch series is the correct solution.  So far the only
example has been a buggy piece of code which has since been
fixed with a cpu_relax.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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