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SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
On Fri, Aug 17, 2007 at 03:09:57PM +1000, Paul Mackerras wrote:
> Herbert Xu writes:
>
> > Can you find an actual atomic_read code snippet there that is
> > broken without the volatile modifier?
>
> There are some in arch-specific code, for example line 1073 of
> arch/mips/kernel/smtc.c. On mips, cpu_relax() is just barrier(), so
> the empty loop body is ok provided that atomic_read actually does the
> load each time around the loop.

A barrier() is all you need to force the compiler to reread
the value.

The people advocating volatile in this thread are talking
about code that doesn't use barrier()/cpu_relax().

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/
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