danmcd provided a stress test for implicit IP tunneling creation and deletion which unveiled a deadlock on the sdev_node->sdev_contents rwlock (I'm still root-causing the deadlock).
I'm guessing the same deadlock will occur with implicit VLAN creation and deletion. Basically, the test runs ifconfig plumb and ifconfig unplumb for implicit devices (like ip.tun#, but would be bge200# for VLANs) in parallel thousands of times with different device names. I would suggest running such stress tests with UV to make sure we're aware of the devname pitfalls here. -Seb
