Re: [PATCH 6/24] make atomic_read() behave consistently on frv

Paul E. McKenney
2007-08-11T04:30:11Z

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.

Thanx, Paul