linux-kernel - Re: softlockup: automatically detect hung TASK

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Message-Id: <20080206163111.54088622.akpm@linux-foundation.org>
Date:	Wed, 6 Feb 2008 16:31:11 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org
Subject: Re: softlockup: automatically detect hung TASK_UNINTERRUPTIBLE
 tasks

On Thu, 7 Feb 2008 01:04:25 +0100
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> > > Does that kernel have:
> > > 
> > > commit ed50d6cbc394cd0966469d3e249353c9dd1d38b9
> > > Author: Peter Zijlstra <a.p.zijlstra@...llo.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).  

btw, mainline (plus this patch, not that it changed anything) prints

<stopping disk stuff>
Disabling non-boot CPUs
CPU 1 is now offline

and that's it.   This machine has eight cpus.  Might be a hint?

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