Re: Xen paravirt frontend block hang

[Jeremy Fitzhardinge <jeremy@goop.org>]

Christopher S. Aker wrote:
> Sorry for the noise if this isn't the appropriate venue for this.  I
> posted this last month to xen-devel:
>
> http://lists.xensource.com/archives/html/xen-devel/2007-11/msg00777.html
>
> I can reliably cause a paravirt_ops Xen guest to hang during intensive
> IO.  My current recipe is an untar/tar loop, without compression, of a
> kernel tree.  For example:
>
> wget http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.23.tar.bz2
> bzip2 -d linux-2.6.23.tar.bz2
>
> while true;
>   echo `date`
>   tar xf linux-2.6.23.tar
>   tar cf linux-2.6.23.tar linux-2.6.23
> done
>
> After a few loops, anything that touches the xvd device that hung will
> get stuck in D state.
>
> This happens on both a 2.6.16 and 2.6.18 dom0 (3.1.2 tools).  Paravirt
> guests I've tried that exhibit the problem: 2.6.23.8, 2.6.23.12, and
> 2.6.24-rc6.  It does *not* occur using the Xensource 2.6.18 domU tree
> from 3.1.2.  In all cases, the host continues to run fine, nothing out
> of the ordinary is logged on the dom0 side, xenstore reports the
> status of the devices is fine.
>
> Can anyone reproduce this problem, or let me know what else I can
> provide to help track this down? 

Hi,

I'll try to track this down asap.  Have you tried any other kernel
versions?  In other words, did it just start happening, or its always
done it?  Also, could you try 2.6.24-rc6, just to make sure it hasn't
already been fixed (which is possible if its something that happened in
a higher layer or something).


Thanks,
    J