Comment 5 for bug 831599

I bet it's this (a similar backtrace is in Soren's log):

2011-08-28 11:01:52,770 DEBUG nova.virt.xenapi.fake [-] Calling VM.start <bound
method FakeSessionForVMTests.VM_start of <nova.tests.xenapi.stubs.FakeSessionFor
VMTests object at 0x1077cb4c>> from (pid=9342) callit /opt/jenkins/workspace/uni
t-nova/upstream/nova/virt/xenapi/fake.py:431
2011-08-28 11:01:52,772 DEBUG nova.virt.xenapi.vmops [-] Starting instance 2 fro
m (pid=9342) _start /opt/jenkins/workspace/unit-nova/upstream/nova/virt/xenapi/v
mops.py:134
Traceback (most recent call last):
  File "/opt/jenkins/workspace/unit-nova/upstream/.nova-venv/lib/python2.6/site-
packages/eventlet/hubs/hub.py", line 336, in fire_timers
    timer()
2011-08-28 11:01:52,773 DEBUG nova.virt.xenapi.fake [-] Calling VM.start <bound
method FakeSessionForVMTests.VM_start of <nova.tests.xenapi.stubs.FakeSessionFor
VMTests object at 0x1077cb4c>> from (pid=9342) callit /opt/jenkins/workspace/uni
t-nova/upstream/nova/virt/xenapi/fake.py:431
  File "/opt/jenkins/workspace/unit-nova/upstream/.nova-venv/lib/python2.6/site-
packages/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
  File "/opt/jenkins/workspace/unit-nova/upstream/.nova-venv/lib/python2.6/site-
packages/eventlet/semaphore.py", line 95, in _do_acquire
    waiter.switch()
error: cannot switch to a different thread