netdev - Re: [BUG] netconsole broken by scheduler updates

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Message-ID: <alpine.DEB.2.02.1105261217240.5114@localhost6.localdomain6>
Date:	Thu, 26 May 2011 12:35:19 +0200 (CEST)
From:	Laurent Riffard <laurent.riffard@...e.fr>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc:	Laurent Riffard <laurent.riffard@...e.fr>, netdev@...r.kernel.org
Subject: Re: [BUG] netconsole broken by scheduler updates



On Thu, 26 May 2011, Peter Zijlstra wrote:
> On Thu, 2011-05-26 at 11:21 +0200, Laurent Riffard wrote:
>> Hi,
>>
>> Recently, netconsole was broken by some scheduler updates. Kernel hangs
>> on boot near the network card initialization. I noticed that it does
>> hang just where a "inconsistent lock state" message normally appears.
>>
>> I did a bisection : e4a52bcb9a18142d79e231b6733cabdbf2e67c1f is the
>> first bad commit.
>> commit e4a52bcb9a18142d79e231b6733cabdbf2e67c1f
>> Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> Date:   Tue Apr 5 17:23:54 2011 +0200
>>
>>     sched: Remove rq->lock from the first half of ttwu()
>>
>>
>> Before this commit, kernel was booting succesfully despite the
>> "inconsistent lock state" message. After this commit, the kernel does
>> hang on boot, I have to push the reset button.
>
> Do you have CONFIG_HARDLOCKUP_DETECTOR=y, and do you get an NMI splat
> after some 10 seconds? It would be interesting to see where its stuck.

CONFIG_HARDLOCKUP_DETECTOR is not set for now. I'll give it a try.

> Also, are you very _very_ sure that lockdep message is a false positive?

I can't answer this question. I just know that before commit e4a52bcb9, 
the kernel was able to boot with netconsole despite this message.

Maybe some netconsole developper knows.
~~
laurent
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