openvswitch 驱动卸载失败（Module openvswitch is in use）

现象：

[root@ostack1 ~]# modprobe -r openvswitch
modprobe: FATAL: Module openvswitch is in use.

解决：

[root@ostack1 ~]# ovs-dpctl show
system@ovs-system:
lookups: hit:116587 missed:10543 lost:0
flows: 0
masks: hit:177459 total:0 hit/pkt:1.40
port 0: ovs-system (internal)

[root@ostack1 ~]# ovs-dpctl del-dp ovs-system
[root@ostack1 ~]# modprobe -r openvswitch