ryu.topology.switches cannot be stopped when observing links

[badcodebuilder]

Problem

When running ryu.topology.switches and sending Ctrl+C, it will stuck. Command is here

ryu-manager ryu.topology.switches --observe-links
loading app ryu.topology.switches
loading app ryu.controller.ofp_handler
instantiating app ryu.topology.switches of Switches
instantiating app ryu.controller.ofp_handler of OFPHandler
^C

I analysis the code and find it stuck at

ryu/ryu/topology/switches.py

Line 950 in d6cda4f

self.lldp_event.wait(timeout=timeout)

timeout=None makes it wait forever.

My solution

Add event set at the end of link_loop

ryu/ryu/topology/switches.py

Line 979 in d6cda4f

self.link_event.wait(timeout=self.TIMEOUT_CHECK_PERIOD)

            ...
            self.link_event.wait(timeout=self.TIMEOUT_CHECK_PERIOD)
        if not self.lldp_event.is_set():
            self.lldp_event.set()

I do not know if my solution is correct when really being used, because I only test whether it can work or not, I do not connect it to Mininet.