linux-kernel - Re: [Bugfix] unregister_trace_probe needs to be called under mutex

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Date:	Tue, 6 Jul 2010 10:38:57 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [Bugfix] unregister_trace_probe needs to be called under mutex

Ingo, 

Any particular reason to not pick this patch?

Steven Rostedt and Masami Hiramatsu agree that this patch needs to be
pushed in.

--
Thanks and Regards
Srikar

> Srikar Dronamraju wrote:
> > Comment in unregister_trace_probe() says probe_lock will be held
> > when it gets called. However there is a case where it might called
> > without the probe_lock being held. Also since we are traversing the
> > probe_list and deleting an element from the probe_list, probe_lock
> > should be held.
> > 
> > This was first pointed in uprobes traceevent review by Frederic
> > Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)
> > 
> > This patch is needed for both 2.6.35-rc3 and 2.6.35-rc3-tip
> > 
> > Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> 
> Ah, right! That's definately needed.
> 
> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> 
> Thank you!
> 
> 
> > ---
> > 
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 4f11a56..67670cd 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -269,14 +269,17 @@ static int create_trace_probe(int argc, char **argv)
> >  			pr_info("Delete command needs an event name.\n");
> >  			return -EINVAL;
> >  		}
> > +		mutex_lock(&probe_lock);
> >  		tp = find_probe_event(event, group);
> >  		if (!tp) {
> > +			mutex_unlock(&probe_lock);
> >  			pr_info("Event %s/%s doesn't exist.\n", group, event);
> >  			return -ENOENT;
> >  		}
> >  		/* delete an event */
> >  		unregister_trace_probe(tp);
> >  		free_trace_probe(tp);
> > +		mutex_unlock(&probe_lock);
> >  		return 0;
> >  	}
> >  
> 
--
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