Re: [PATCH 03/11] jump label: Base patch for jump label

[Mathieu Desnoyers <compudj@krystal.dyndns.org>]

* Steven Rostedt (rostedt@goodmis.org) wrote:
> On Thu, 2010-09-23 at 14:40 -0400, Jason Baron wrote:
> 
> > I agree that we this synchronization for the module __init section.
> > 
> > However, I believe we are ok for module removal case. free_module() is
> > called *after* blocking_notifier_call_chain() call. The
> > blocking_notifier_call_chain() is going to call back into the jump label
> > code, grab the jump_label_mutex and remove the reference to the module that
> > is about to freed. Thus, the jump label code can no longer reference it.
> > 
> > So I think the following patch is all that is required here (lightly
> > tested).
> > 
> > Steve, I'll re-post as a separate patch, if we agree on this fix.
> 
> Ug, I'm struggling to get ready for my Tokyo trip. I'll try to look at
> it on the flight. But I still need to write my presentation :-)
> 
> I may have a response back till Monday or Tuesday.

As a note for when you review this patch, I have a strong preference for
adding a "pre-init-free notifier callback" rather than taking the rcu
read lock + adding a synchronize_rcu() in module.c. This will make our
life much easier when we end up doing modifications down in text_poke.

Thanks,

Mathieu

> 
> -- Steve
> 
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com