linux-kernel - Re: 2.6.27-rc6 xen soft lockup

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Message-ID: <48C81F12.9040208@goop.org>
Date:	Wed, 10 Sep 2008 12:25:06 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Rambaldi <rambaldi@...all.nl>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: 2.6.27-rc6 xen soft lockup

Rambaldi wrote:
> The machine has two Intel(R) Xeon(R) E5420's so that gives a total of
> 8 cpu's
> During the time of the lockup the cpu load, as measured with cacti,
> was about 4%
> with a increase to 15% at the time the BUG was triggered. So I would
> say mostly idle
> but not very idle.

So that's the cpu load within the domain?  How about the overall system
load?  What other domains are running?

>
> > Did anything fail or misbehave?
> No nothing failed or misbehaved (as far as I could tell)
>
> With dynticks I guess you mean: CONFIG_NO_HZ ; this option is not set.

(In general its a good idea to set it for virtual machines, to avoid
spuriously scheduling vcpus.)

> I have attached my .config. I have also attached the output of
> (date ; cat /proc/interrupts ; sleep 10 ; date ;  cat /proc/interrupts
> )> /tmp/interrupts
> to give an impression about the number of interrupts after 11:30 hours
> of uptime.

Well, there were 1001 interrupts on cpu 1 in that interval, which shows
that the timer interrupts are going at full rate on the idle cpu.

I'm a bit confused.  I'm not sure what would trigger a lockup at that
point, unless it really stopped taking interrupts for a while. 
Unfortunately the RIP and backtrace are not particularly helpful.  I'm
assuming the message is spurious, and indicates some other kind of
timekeeping bug.

> Any other info that you need?

Full dmesg output, for completeness.

    J
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