The stack trace is the following:

Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: ------                        Green Thread                        ------
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/bin/neutron-linuxbridge-agent:8 in <module>
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `sys.exit(main())`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/cmd/eventlet/plugins/linuxbridge_neutron_agent.py:21 in main
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `agent_main.main()`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py:1055 in main
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `manager = LinuxBridgeManager(bridge_mappings, interface_mappings)`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py:93 in __init__
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `self.check_vxlan_support()`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py:745 in check_vxlan_sup
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `if self.vxlan_ucast_supported():`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py:706 in vxlan_ucast_sup
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `ip_lib.vxlan_in_use(seg_id)):`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/agent/linux/ip_lib.py:741 in vxlan_in_use
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `interfaces = get_devices_info(namespace)`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/neutron/agent/linux/ip_lib.py:1379 in get_devices_info
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `devices = privileged.get_link_devices(namespace, **kwargs)`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/oslo_privsep/priv_context.py:247 in _wrap
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `return self.channel.remote_call(name, args, kwargs)`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/oslo_privsep/daemon.py:214 in remote_call
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `result = self.send_recv((Message.CALL.value, name, args, kwargs))`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/oslo_privsep/comm.py:172 in send_recv
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `reply = future.result()`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/oslo_privsep/comm.py:109 in result
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `self.condvar.wait()`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /usr/lib/python3.6/threading.py:295 in wait
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `waiter.acquire()`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/eventlet/semaphore.py:115 in acquire
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `hubs.get_hub().switch()`
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]: /openstack/venvs/neutron-21.2.6/lib/python3.6/site-packages/eventlet/hubs/hub.py:298 in switch
Dec 01 07:19:38 tctrko1 neutron-linuxbridge-agent[18892]:     `return self.greenlet.switch()`

In this case it looks like `privileged.get_link_devices` is what needs to be optimized which was not covered by the fix.