xen 3.2 freezing under load

For a number of weeks now I’ve been fighting a Xen host (dom0) that’s been freezing up periodically. It’s been a complete freeze of the Linux kernel, dom0, all domU’s, everything. SysRq doesn’t work either.

Today I finally found a reliable way to reproduce it.

On this dom0 I have a USB sound adapter attached. Pulseaudio runs in the dom0 so I can have sound from various domU’s. I had this connected via a powered USB 2 hub. It seems that this combination is the problem. Removing just the hub and connecting the USB sound driver directly seems to improve things.

I did try to freeze the system generating USB load to another USB device (UPS) but it seemed stable. This could be because I can’t generate anywhere near the load to a UPS as to a sound adapter.

Anyway, I made a couple of other changes a couple weeks ago such that I no longer have to use the hub, so I’ve pulled it out of the chain entirely.

Now I’m hoping this was the only way to crash the system and that I now have it solved. Only time will tell.