DomU kernel panic under Xen with R1Soft CDP agent

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I ran into a weird problem on a freshly installed server today where one of the DomU virtual machines kept locking up with a kernel panic message:

BUG: soft lockup – CPU#1 stuck for 10s!

All of the other Xen DomU virtual machines running on the box were fine, so I was pretty sure it wasn’t a hardware bug. The only possible solutions that I could come up with were

  1. My somewhat aggressive stripping down of the Dom0 host
  2. Zimbra (as the Java process was always the one referenced as being stuck
  3. The kernel module for the R1Soft CDP backup agent that I had installed a few hours ago.

I’ve run Zimbra on a CentOS 5 Xen VM before (although not 5.4 admittedly), so didn’t think that would be the problem (anyway, user land software should never be able to cause a kernel panic – in theory at least ;-))
Again, the other Xen DomU virtual machines were fine, so hopefully the configuration on the Xen Dom0 host machine itself shouldn’t be causing the problem.

Just to be safe, I updated the kernel-xen package from the default 2.6.18-164.el5 to the latest 2.6.18-164.15.1 which was only released a few days ago and doesn’t appear to be on all of the mirrors yet!
With this done and the virtual machine restarted I had to run r1soft-cki to load an updated kernel module for the R1Soft CDP backup agent and the virtual machine has been stable for several hours now. Fingers crossed it stays that way!


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