The file net/tipc/port.c takes a lock using the function tipc_port_lock and
then releases the lock sometimes using tipc_port_unlock and sometimes using
spin_unlock_bh(p_ptr->publ.lock). tipc_port_unlock simply does the
spin_unlock_bh, but it seems cleaner to use it everywhere.
The problem was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/)