Re: [PATCH 1/5] Add a global synchronization point for pvclock

[Peter Zijlstra]

On Fri, 2010-04-16 at 13:36 -0700, Jeremy Fitzhardinge wrote:
> > +     do {
> > +             last = last_value;
> >   
> Does this need a barrier() to prevent the compiler from re-reading
> last_value for the subsequent lines?  Otherwise "(ret < last)" and
> "return last" could execute with different values for "last".
> 
ACCESS_ONCE() is your friend.

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