Intel ixbge hardware error causes hung task and kernel panic

Issue

• Intel ixbge hardware error causes hung task and kernel panic
• Upon a TX timeout or other error causing the netdev watchdog or driver to reset the NIC, the ixgbe driver service routine ixgbe_service_task() takes the rtnl_lock() and then calls unregister_netdev() which tries to take the lock again, causing a deadlock situation.