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


Frederic Weisbecker wrote:
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?

Sure, of course :-)



-- Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com


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