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

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Message-ID: <Pine.LNX.4.64.0708161149120.17049@schroedinger.engr.sgi.com>
Date:	Thu, 16 Aug 2007 11:50:01 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Paul Mackerras <paulus@...ba.org>
cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Satyam Sharma <satyam@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	Chris Snook <csnook@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-arch@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	netdev@...r.kernel.org, Andrew Morton <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

On Thu, 16 Aug 2007, Paul Mackerras wrote:

> Herbert Xu writes:
> 
> > It doesn't matter.  The memory pressure flag is an *advisory*
> > flag.  If we get it wrong the worst that'll happen is that we'd
> > waste some time doing work that'll be thrown away.
> 
> Ah, so it's the "racy but I don't care because it's only an
> optimization" case.  That's fine.  Somehow I find it hard to believe
> that all the racy uses of atomic_read in the kernel are like that,
> though. :)

My use of atomic_read in SLUB is like that. Volatile does not magically 
sync up reads somehow.

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