Re: remove cpu hotplug bustification in cpufreq.

From: Arjan van de Ven
Date: Sun Jul 23 2006 - 04:30:25 EST


> > Well, I just got Ashok's trial patches which turns the thing into a rwsem
> > as I outlined earlier.
> Mark my words ;)
> > I'll try them out. If they don't work, we should just delete the lock and
> > go totally back to square 1.
> rwsem conversion has the potential to merely hide the problem. Ingo, does
> lockdep detect recursive down_read()?

lockdep detects and warns about those.

I think we're about equally skeptical about this; I'm extremely hesitant
about any place in the kernel that uses rwsems for anything other than a
performance tweak. I've ended up with a mental model of rwsems that
basically comes down to "you need to be able to replace it with a mutex
without breaking correctness". Now of course that model is somewhat of
an oversimplification, but not by that much...

Arjan van de Ven
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