Date: Wed, 15 Aug 2007 10:18:41 +0200
From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Chris Snook <csnook@redhat.com>, satyam@infradead.org, clameter@sgi.com,
       linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
       torvalds@linux-foundation.org, netdev@vger.kernel.org,
       akpm@linux-foundation.org, ak@suse.de, davem@davemloft.net,
       schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au,
       wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org,
       rpjday@mindspring.com, jesper.juhl@gmail.com,
       segher@kernel.crashing.org
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all
	architectures
Message-ID: <20070815081841.GA16551@osiris.boeblingen.de.ibm.com>
References: <46C2350A.1010807@redhat.com> <E1ILCgh-00052A-00@gondolin.me.apana.org.au>
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On Wed, Aug 15, 2007 at 02:49:03PM +0800, Herbert Xu wrote:
> Chris Snook <csnook@redhat.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.

Btw.: we still have

include/asm-i386/mach-es7000/mach_wakecpu.h:  while (!atomic_read(deassert));
include/asm-i386/mach-default/mach_wakecpu.h: while (!atomic_read(deassert));

Looks like they need to be fixed as well.
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