Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATH -mm -v2] Fix a race condtion of oops_in_progress | Date | Mon, 10 Nov 2008 16:35:01 +0900 (JST) |
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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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