Re: [PATCH -tip v5 03/10] kprobes: Introduce kprobes jumpoptimization

From: Frederic Weisbecker
Date: Tue Nov 24 2009 - 14:45:40 EST


On Tue, Nov 24, 2009 at 10:34:08AM -0500, Masami Hiramatsu wrote:
> > And this comment doesn't tell us much what this brings us.
> > The changelog tells it stands to avoid a text_mutex deadlock.
> > I'm not sure why we would deadlock without it.
>
> As Mathieu and I discussed on LKML (http://lkml.org/lkml/2009/11/21/187)
> text_mutex will be locked on the way of cpu-hotplug.
> Since kprobes locks text_mutex too and stop_machine() refers online_cpus,
> it will cause a dead-lock. So, I decided to use get_online_cpus() to
> locking hotplug while optimizing/unoptimizng.


Ah ok :)
Could you add a comment in the code that explains it?

Thanks.

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