Synchronizing if_xennet_xenbus detach with event-handling

[Rohan Desai]

I'm getting a panic due to a race between the detach path
(xennet_xenbus_detach) and event handling (xennet_handler called from
triggered event channel). xennet_xenbus_detach frees up the tx ring and
xennet_handler tries to access it. I'm not sure what event the event
channel is being poked for (tx complete, rx ready, other). Does anybody
know how these two code-paths are supposed to be synchronized ?