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:

quoted

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 [off-list ref]
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