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SubjectRe: RFC: mutex: hung tasks on SMP platforms with asm-generic/mutex-xchg.h
Hi Peter,

On Mon, Aug 13, 2012 at 09:15:04AM +0100, Peter Zijlstra wrote:
> On Thu, 2012-08-09 at 12:57 -0400, Nicolas Pitre wrote:
> >
> > In other words, I think this should look like this:
> >
> > diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
> > index 580a6d35c7..44a66c99c8 100644
> > --- a/include/asm-generic/mutex-xchg.h
> > +++ b/include/asm-generic/mutex-xchg.h
> > @@ -25,8 +25,11 @@
> > static inline void
> > __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
> > {
> > - if (unlikely(atomic_xchg(count, 0) != 1))
> > - fail_fn(count);
> > + if (unlikely(atomic_xchg(count, 0) != 1)) {
> > + /* Mark lock contention explicitly */
> > + if (likely(atomic_xchg(count, -1) != 1))
> > + fail_fn(count);
> > + }
> > }
>
> OK, I like this.. Thanks guys! Will will you send a final and complete
> patch?

I sent one out on Friday but somehow managed to drop you from CC -- sorry
about that:

http://thread.gmane.org/gmane.linux.kernel/1341305

Cheers,

Will


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