linux-kernel - Re: [BUG,2.6.28,s390] Fails to boot in Hercules S/390 emulator

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Message-Id: <1236833245.7680.266.camel@localhost.localdomain>
Date:	Wed, 11 Mar 2009 21:47:25 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Frans Pop <elendil@...net.nl>
Cc:	linux-s390@...r.kernel.org, Roman Zippel <zippel@...ux-m68k.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BUG,2.6.28,s390] Fails to boot in Hercules S/390 emulator

On Wed, 2009-03-11 at 17:34 -0700, john stultz wrote:
> I'm still a little baffled, but I figure I can try to reproduce this
> myself. So I'm working setting up hercules environment here to see if I
> can't trigger it. Any help with config or links to your environment
> would be great.

Ok. I've got this up and reproduced with the hercules emulator. 

A couple of interesting  hints:
*  The issue seems to go away if we disable NO_HZ/dynticks in
the .config

*  nohz=off does not affect the issue.

*  The issue also seems to go away if HZ is anything except 250

*  Commenting out clocksource_adjust(), which does the clock steering,
seems to avoid the issue.

*  When the problem triggers we don't seem to transfer to the TOD clock,
and the jiffies clocksource seems to be in use.

* The jiffies clocksource mult value seems to be ever increasing, again
pointing to something wrong in the clock steering.

* Reverting both 6c9bacb41c10 and 5cd1c9c5cf30 against 2.6-git did not
seem to help the issue, as originally reported. I also reverted
49b5cf34727a as well just in case, and it didn't help either.

That's about all I can get for today. I'm out of town until Monday, so
I'll start digging back into it then.

thanks
-john

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