Herbert Xu writes:
> 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().
Did you look at it? Here it is:
/* Someone else is initializing in parallel - let 'em finish */
while (atomic_read(&idle_hook_initialized) < 1000)
;
Paul.
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