Re: Kernel panic on Xen virtualisation in Debian

[Andreas Ziegler <ml@andreas-ziegler.de>]

Hello,

one of the servers that crashes sometimes because of this issue is mine.
Jan is also using this server and therefore interested in a solution.

We are not sure whether it is a Xen or Kernel Issue, but on the Kernel
and Debian bugtrackers no one answered, so we figured it might be worth
a try asking on this list.

The kernel panics first happened in summer 2014, multiple times a week.
We tried various kernel versions back then - it suddenly stopped
although we didn't change anything after the latest crash back then.

After that, the server ran without problems running Kernel 3.15.7 on Xen
4.4.0 until November 2015.
After that, the server ran on Xen 4.4.4-pre and Debians 3.16 Kernel.
The crash happend again in May and after that, running Xen 4.4.4 and an
updated Debian 3.16 Kernel, it happened in June.

In May, Ingo Jürgensmann also started experiencing this problem and
blogged about it:
https://blog.windfluechter.net/content/blog/2016/03/23/1721-xen-randomly-crashing-server
https://blog.windfluechter.net/content/blog/2016/05/12/1723-xen-randomly-crashing-server-part-2

He is pretty sure, that the problem went away after disabling IPv6.
But: we can't say for sure, because on our server it sometimes happened
often in a short period of time, but then it didn't for months.
and: disabling IPv6 is no option for me at all.

@Wei
So far we didn't find a way to reproduce the kernel panic...


Andreas.


-------- Original-Nachricht --------
Betreff: Re: [Xen-devel] Kernel panic on Xen virtualisation in Debian
Von: Jan Prunk <janprunk@gmail.com>
An: Wei Liu <wei.liu2@citrix.com>
Datum: Fri, 8 Jul 2016 14:22:37 +0200

> Hello,
> 
> Please also send a CC: to 804079@bugs.debian.org
> <mailto:804079@bugs.debian.org> for future reference.
> The administrator of the server is Andreas Ziegler <mail@conemu.de
> <mailto:mail@conemu.de>>,
> maybe he will be able to log/reproduce the bug, I was only an initial
> reporter.
> 
> Kind regards,
> Jan
> 
> On Fri, Jul 8, 2016 at 1:14 PM, Wei Liu <wei.liu2@citrix.com
> <mailto:wei.liu2@citrix.com>> wrote:
> 
>     On Wed, Jul 06, 2016 at 03:14:15PM +0100, George Dunlap wrote:
>     > On Mon, Jul 4, 2016 at 7:06 PM, Jan Prunk <janprunk@gmail.com <mailto:janprunk@gmail.com>> wrote:
>     > > Hello !
>     > >
>     > > I am posting Xen virtualisation bug links to this e-mail address,
>     > > because I wasn't able to find the Xen specific bugtracker list.
>     > > This bug has been discovered in 2015 and so far it hasn't been
>     > > resolved through the Debian/Kernel bug lists. I submit the
>     > > links to bug reports for you.
>     > >
>     > > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=804079
>     >
>     > The serial log at the bottom looks like there was a crash in the ipv6
>     > handling as the result of a packet delivery, perhaps?  David / Wei, do
>     > you have any ideas?  Not sure who else has worked on the netback side
>     > of things.
>     >
> 
>     The original bug report showed that there was a exception in the middle
>     of memcpy instruction while the latest log showed that the exception
>     could potentially be somewhere else.  Both logs showed that the
>     exception took place when ipv6 was involved.
> 
>     If Jan can come up with a reliable repro I might be able to have a look.
> 
>     Wei.
> 
>     >  -George
> 

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