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

Masami Hiramatsu
2009-11-24T21:18:03Z

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 :-)