commit bbc2908 introduces a race condition that occurs during serialization/deserialization of the bus name matchers. an easy way to reproduce is run:

while sudo systemctl is-active polkit.service; do sudo systemctl daemon-reload; sleep 0.5; done &
while sudo systemctl is-active polkit.service; do sudo systemctl restart polkit.service; sleep 2; done &

and wait for polkit to get stuck in 'activating', since systemd missed the NameOwnerChange signal from polkit. eventually polkit is timed out and killed, even though it is running fine.

i'm not very familiar with dbus api, so i think NameHasOwner needs to be called after matching NameOwnerChange.

friendly ping @zonque :)