Race condition in /etc/xen/scripts/block

[Bastian de Groot <degroot@univention.de>]

Hello,

I am trying to figure out the behavior of the hook-script for block devices 
(/etc/xen/scripts/block).

Here is the problem:
I want to start a VM. It shall boot from a dm-device, which is setup by a  
script executed in the script /etc/xen/scripts/block. The dm-device doesn't  
exist when "xm start " is executed . 

When I place the setup script at the top of the block-script, everything  
works fine (http://pastebin.com/UYYbGupC). But when the script is placed in  
the phy case branch of the block-script, the VM won't start 
(http://pastebin.com/iPdJ65AH).

Whether the VM starts or not, also depends on the runtime of the setup script. 
When the script is executed fast, it is much more likely that the VM starts.

So, is there a way to setup a device in the hook-script?

My configuration: Xen 3.4 on a 2.6.32 Kernel

I would appreciate your help on that very much,
Bastian