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SubjectRe: [PATH -mm -v2] Fix a race condtion of oops_in_progress
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> > > As far as I know, barriers don't cause changes to be visible on other
> > > CPUs faster too. It just guarantees corresponding operations after will
> > > not get executed until that before have finished. And, I don't think we
> > > need make changes to be visible on other CPUs faster.
> >
> > You're correct that barrier() has no impact on other CPUs. wmb() and rmb() do.
> > If we don't need to make changes visible any faster, what's the point in using
> > atomic_set()? It's not any less racy. atomic_inc() and atomic_dec() would be
> > less racy, but you're not using those.
>
> In default bust_spinlocks() implementation in lib/bust_spinlocks.c,
> atomic_inc() and atomic_dec_and_test() is used. Which is used by x86
> too. In some other architecture, atomic_set() is used to replace
> "oops_in_progress = <xxx>". So this patch fixes architectures which use
> default bust_spinlocks(), other architectures can be fixed by
> corresponding architecture developers.

I think Chris is right.
So, I reccomend to read Documentation/memory-barriers.txt

Almost architecture gurantee atomic_inc cause barrier implicitly.
but not _all_ architecture.





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