dump-flows failed with timeout:

2019-02-20 14:55:23.957 10229 INFO neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent [req-63c61d58-2a38-47fa-ba4a-9b74fd38d9fa - - - - -] Cleaning stale br-int flows
2019-02-20 14:57:25.450 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.openflow.native.ofswitch [req-63c61d58-2a38-47fa-ba4a-9b74fd38d9fa - - - - -] ofctl request version=0x4,msg_type=0x12,msg_len=0x38,xid=0x548ae654,OFPFlowStatsRequest(cookie=0,cookie_mask=0,flags=0,match=OFPMatch(oxm_fields={}),out_group=4294967295,out_port=4294967295,table_id=255,type=1) timed out: Timeout: 120 seconds
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent [req-63c61d58-2a38-47fa-ba4a-9b74fd38d9fa - - - - -] Error while processing VIF ports: RuntimeError: ofctl request version=0x4,msg_type=0x12,msg_len=0x38,xid=0x548ae654,OFPFlowStatsRequest(cookie=0,cookie_mask=0,flags=0,match=OFPMatch(oxm_fields={}),out_group=4294967295,out_port=4294967295,table_id=255,type=1) timed out
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent Traceback (most recent call last):
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/drivers/openvswitch/agent/ovs_neutron_agent.py", line 2120, in rpc_loop
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent     self.cleanup_stale_flows()
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent   File "/usr/lib/python2.7/site-packages/osprofiler/profiler.py", line 158, in wrapper
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent     result = f(*args, **kwargs)
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/drivers/openvswitch/agent/ovs_neutron_agent.py", line 1872, in cleanup_stale_flows
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent     bridge.cleanup_flows()
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ofswitch.py", line 154, in cleanup_flows
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent     cookies = set([f.cookie for f in self.dump_flows()]) - \
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ofswitch.py", line 147, in dump_flows
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent     reply_multi=True)
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ofswitch.py", line 95, in _send_msg
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent     raise RuntimeError(m)
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent RuntimeError: ofctl request version=0x4,msg_type=0x12,msg_len=0x38,xid=0x548ae654,OFPFlowStatsRequest(cookie=0,cookie_mask=0,flags=0,match=OFPMatch(oxm_fields={}),out_group=4294967295,out_port=4294967295,table_id=255,type=1) timed out
2019-02-20 14:57:25.451 10229 ERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent