From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Date: Fri, 31 Mar 2006 02:45:11 +0000
Subject: RE: Synchronizing Bit operations V2
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To: 'Christoph Lameter' <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>, Zoltan Menyhart <Zoltan.Menyhart@bull.net>, "Boehm, Hans" <hans.boehm@hp.com>, "Grundler, Grant G" <grant.grundler@hp.com>, akpm@osdl.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org

Christoph Lameter wrote on Thursday, March 30, 2006 6:38 PM
> > > Neither one is correct because there will always be one combination of 
> > > clear_bit with these macros that does not generate the required memory 
> > > barrier.
> > 
> > Can you give an example?  Which combination?
> 
> For Option(1)
> 
> smp_mb__before_clear_bit()
> clear_bit(...)(

Sorry, you totally lost me.  It could me I'm extremely slow today.  For
option (1), on ia64, clear_bit has release semantic already.  The comb
of __before_clear_bit + clear_bit provides the required ordering.  Did
I miss something?  By the way, we are talking about detail implementation
on one specific architecture.  Not some generic concept that clear_bit
has no ordering stuff in there.

- Ken