linux-kernel - Re: 2.6.33: ftrace triggers soft lockup

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Date:	Thu, 4 Mar 2010 05:06:41 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: 2.6.33: ftrace triggers soft lockup

On Wed, Mar 03, 2010 at 10:18:26PM -0500, Steven Rostedt wrote:
> On Thu, 2010-03-04 at 11:01 +0800, Américo Wang wrote:
> 
> > >
> > > So it is stuck in stop machine. I wonder where exactly. I see some do_exit
> > > at the top but I wonder how much they are reliable.
> > 
> > Well, I think 'kstop' is just random, sometimes I got 'watchdog' or some other
> > process.
> > 
> > >
> > > Anyway, as Steve said, we really need a full config to reproduce it.
> > >
> > 
> > Done in another reply.
> 
> Thanks!
> 
> Frederic, I notice that lockdep is on, did anything change that might
> slow down the code in lockdep, or is the function graph tracer doing
> more locking?


No,
there doesn't seem to be intrusive changes in lockdep between .32 and .33
And the function graph tracer is still fully lockless (and hopefully
it will be forever).

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