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Date: Fri, 10 Aug 2007 08:02:13 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Andi Kleen <ak@...e.de> Cc: Herbert Xu <herbert@...dor.apana.org.au>, csnook@...hat.com, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, torvalds@...ux-foundation.org, netdev@...r.kernel.org, akpm@...ux-foundation.org, 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 Subject: Re: [PATCH 1/24] make atomic_read() behave consistently on alpha On Fri, Aug 10, 2007 at 11:08:20AM +0200, Andi Kleen wrote: > On Friday 10 August 2007 10:21:46 Herbert Xu wrote: > > Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote: > > > > > > The compiler is within its rights to read a 32-bit quantity 16 bits at > > > at time, even on a 32-bit machine. I would be glad to help pummel any > > > compiler writer that pulls such a dirty trick, but the C standard really > > > does permit this. > > > > Code all over the kernel assumes that 32-bit reads/writes > > are atomic so while such a compiler might be legal it certainly > > can't compile Linux. > > Yes, the kernel requirements are much stricter than ISO-C. And besides > it is a heavy user of C extensions anyways. On the other hand some of the > C99 extensions are not allowed. And then there is sparse, which enforces > a language which sometimes is quite far from standard C. You could say it is > written in Linux-C, not ISO C. Understood. My question is "why do we want the semantics of atomic_read() and atomic_set() to differ?" Thanx, Paul - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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