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SubjectRe: [PATCH/RFC] mutex: Fix optimistic spinning vs. BKL
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On Wed, 2010-04-28 at 14:38 +1000, Benjamin Herrenschmidt wrote:
> Currently, we can hit a nasty case with optimistic spinning on mutexes:
>
> CPU A tries to take a mutex, while holding the BKL
>
> CPU B tried to take the BLK while holding the mutex
>
> This looks like a AB-BA scenario but in practice, is allowed and happens
> due to the auto-release-on-schedule nature of the BKL.

.../...

BTW. The patch is only compile-tested so far :-) It's going to be
hammered with the test case that triggered the original bug hopefully
tonight.

Cheers,
Ben.




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