dom0 hang

[Mukesh Rathor <mukesh.rathor@oracle.com>]

Here are the details on the dom0 hang:

xen: 3.4.0
dom0: 2.6.18-128

dom0.vcpu0: spinning in schedule() on spinlock: spin_lock_irq(&rq->lock);
dom0.vcpu1: eip == ret after __HYPERVISOR_event_channel_op hypercall

Just of of curiosity, I set breakpoint at the above ret in kdb, and it never 
got hit. So I wondered why vcpu1 is not getting scheculed, and noticed that 
xen.schedule always schedules vcpu0. Two cpus on the box, other one is mostly 
in idle.

anyways, I've turned lock debugging on in dom0 and reproducing it right now.

thanks,
Mukesh