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Date: Wed, 6 Feb 2008 16:47:47 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: mingo@elte.hu, a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org
Subject: Re: softlockup: automatically detect hung TASK_UNINTERRUPTIBLE
 tasks
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On Wed, 6 Feb 2008 16:31:11 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Thu, 7 Feb 2008 01:04:25 +0100
> Ingo Molnar <mingo@elte.hu> wrote:
> 
> > 
> > * Andrew Morton <akpm@linux-foundation.org> wrote:
> > 
> > > > Does that kernel have:
> > > > 
> > > > commit ed50d6cbc394cd0966469d3e249353c9dd1d38b9
> > > > Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
> > > > Date:   Sat Feb 2 00:23:08 2008 +0100
> > > > 
> > > >     debug: softlockup looping fix
> > > 
> > > yup.  It was fetched less than 24 hours ago.
> > 
> > does the patch below improve the situation?
> > 
> 
> Nope.
> 
> But I tested it on mainline, and mainline exhibits the never-powers-off
> symptom, whereas ed50d6cbc394cd0966469d3e249353c9dd1d38b9 demonstrates the
> powers-off-after-20-seconds symptom.  
> 
> So we _may_ be dealing with two bugs here, and your patch might have fixed
> the first, but that success is obscured by the second.  I guess I need to
> prepare a tree which has ed50d6cbc394cd0966469d3e249353c9dd1d38b9 at its
> tip.  (Wonders how to do that).  

OK, I did this (tested on a ed50d6cbc394cd0966469d3e249353c9dd1d38b9-tipped
tree) and again, the patch made no difference: the machine still pauses
20-odd seconds before (correctly) powering off.