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Date: Wed, 15 Aug 2007 20:18:53 -0600
From: "Chris Friesen" <cfriesen@nortel.com>
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Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all
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To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Satyam Sharma <satyam@infradead.org>, Christoph Lameter <clameter@sgi.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Paul Mackerras <paulus@samba.org>, Stefan Richter <stefanr@s5r6.in-berlin.de>, Chris Snook <csnook@redhat.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-arch@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>, netdev@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, ak@suse.de, heiko.carstens@de.ibm.com, davem@davemloft.net, schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au, wjiang@resilience.com, zlynx@acm.org, rpjday@mindspring.com, jesper.juhl@gmail.com, segher@kernel.crashing.org
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Herbert Xu wrote:

> But I have to say that I still don't know of a single place
> where one would actually use the volatile variant.

Given that many of the existing users do currently have "volatile", are 
you comfortable simply removing that behaviour from them?  Are you sure 
that you will not introduce any issues?

Forcing a re-read is only a performance penalty.  Removing it can cause 
behavioural changes.

I would be more comfortable making the default match the majority of the 
current implementations (ie: volatile semantics).  Then, if someone 
cares about performance they can explicitly validate the call path and 
convert it over to the non-volatile version.

Correctness before speed...

Chris