Messages in this thread | | | From | Herbert Xu <> | Subject | Re: [PATCH 6/24] make atomic_read() behave consistently on frv | Date | Mon, 13 Aug 2007 13:15:52 +0800 |
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Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > On Sat, Aug 11, 2007 at 08:54:46AM +0800, Herbert Xu wrote: >> Chris Snook <csnook@redhat.com> wrote: >> > >> > cpu_relax() contains a barrier, so it should do the right thing. For >> > non-smp architectures, I'm concerned about interacting with interrupt >> > handlers. Some drivers do use atomic_* operations. >> >> What problems with interrupt handlers? Access to int/long must >> be atomic or we're in big trouble anyway. > > Reordering due to compiler optimizations. CPU reordering does not > affect interactions with interrupt handlers on a given CPU, but > reordering due to compiler code-movement optimization does. Since > volatile can in some cases suppress code-movement optimizations, > it can affect interactions with interrupt handlers.
If such reordering matters, then you should use one of the *mb macros or barrier() rather than relying on possibly hidden volatile cast.
Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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