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

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Date:	Fri, 24 Sep 2010 16:54:35 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	David Miller <davem@...emloft.net>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH 03/11] jump label: Base patch for jump label

* Steven Rostedt (rostedt@...dmis.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
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