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Date: Thu, 19 Feb 2009 09:17:28 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       "Luis Claudio R. Goncalves" <lclaudio@uudg.org>
Subject: Re: [PATCH 0/6] [git pull] updates for tip/tracing/ftrace
Message-ID: <20090219081728.GA15452@elte.hu>
References: <20090217182048.233060814@goodmis.org> <20090218000952.GD12714@elte.hu> <20090218084041.GA27540@elte.hu> <20090218163524.GA5858@nowhere>
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* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> > the function-graph-tracer started locking up since the last 
> > batch of changes:
> > 
> >  Testing tracer sysprof: .. no entries found ..FAILED!
> >  initcall 0xffffffff812e91d1 returned -1 after 101562 usecs
> >  initcall 0xffffffff812e91d1 returned with error code -1 
> >  calling  0xffffffff812e91e3 @ 1
> >  Testing tracer function: PASSED
> >  Testing dynamic ftrace: 
> >  [hard lockup]
> 
> I've successfully reproduced it with your config.
> Note that I didn't built the function graph tracer.
> 
> I also tried to set ftrace=nop as a parameter to avoid the selftests and then
> enabled the function tracer after the boot. And then I had no problem.
> 
> Looks like it happens during dynamic ftrace initialization.
> Perhaps a problem with the recent mutex conversion and kstopmachine, which
> could result in a hardlockup in case of a deadlock.
> 
> But lockdep didn't say anything.
> I'm reverting some of the last patches and will see.

Frederic, Steve, any progress on this bug? It's blocking all new 
tracing patches.

	Ingo