Comment 0 for bug 1248799

when unshelve a vm, if this vm has been offloaded, the process would involve re-scheduling.
in nova/conductor/manager.py def unshelve_instance(self, context, instance):

elif instance.vm_state == vm_states.SHELVED_OFFLOADED:
            try:
                with compute_utils.EventReporter(context, self.db,
                        'get_image_info', instance.uuid):
                    image = self._get_image(context,
                            sys_meta['shelved_image_id'])
            except exception.ImageNotFound:
                with excutils.save_and_reraise_exception():
                    LOG.error(_('Unshelve attempted but vm_state not SHELVED '
                                'or SHELVED_OFFLOADED'), instance=instance)
                    instance.vm_state = vm_states.ERROR
                    instance.save()

            filter_properties = {}
            hosts = self._schedule_instances(context, image,
                                             filter_properties, instance) <<<<<this would cause exception,when it occurs, the instance wil
                                                                                                                      <<<<<stuck in task_state: unshelving forever
            host = hosts.pop(0)['host']
            self.compute_rpcapi.unshelve_instance(context, instance, host,
                    image)