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Date: Fri, 24 Aug 2007 10:15:47 -0700 (PDT) From: Christoph Lameter <clameter@....com> To: Denys Vlasenko <vda.linux@...glemail.com> cc: Paul Mackerras <paulus@...ba.org>, Satyam Sharma <satyam@...radead.org>, 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, Herbert Xu <herbert@...dor.apana.org.au>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures On Fri, 24 Aug 2007, Denys Vlasenko wrote: > On Thursday 16 August 2007 00:22, Paul Mackerras wrote: > > Satyam Sharma writes: > > In the kernel we use atomic variables in precisely those situations > > where a variable is potentially accessed concurrently by multiple > > CPUs, and where each CPU needs to see updates done by other CPUs in a > > timely fashion. That is what they are for. Therefore the compiler > > must not cache values of atomic variables in registers; each > > atomic_read must result in a load and each atomic_set must result in a > > store. Anything else will just lead to subtle bugs. > > Amen. A "timely" fashion? One cannot rely on something like that when coding. The visibility of updates is insured by barriers and not by some fuzzy notion of "timeliness". - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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