Issue seen in VTS testbed, not in any other setups...

There is an assumption that the main thread is not processing packets, thus would not create connections and enqueue them. The conn cleaner in the main thread thus assumes there will never be entries on the thread0, and checks its list heads along with all the other threads.

If there is a packet queued, the cleaner tries to schedule an interrupt to thread0 but because there is no interrupt handler, it never succeeds. The loop in the cleaner thread is rather tight, thus this condition "hangs" the control plane.