The 'Before' dependency between NM-dispatcher and NM causes a deadlock
when stopping the NM service. When terminating, NM wants to D-Bus
activate NM-dispatcher to synchronously handle pre-down events; but
NM-dispatcher start is ordered after NM shutdown due to the following
behavior described in systemd.unit(5) man page:
Given two units with any ordering dependency between them, if one
unit is shut down and the other is started up, the shutdown is
ordered before the start-up. It doesn't matter if the ordering
dependency is After= or Before=, in this case. It also doesn't
matter which of the two is shut down, as long as one is shut down
and the other is started up; the shutdown is ordered before the
start-up in all cases.
So, NM is waiting NM-dispatcher to start and NM-dispatcher is queued
by systemd, waiting that NM is stopped. The result is a 90 seconds
delay, after which systemd kills NM and continues.
The dependency was added so that during shutdown NM-dispatcher would
be stopped after NM. I don't think it worked as expected because
NM-dispatcher is not supposed to be active most of the times, and so
it doesn't need a dependency that delays its stop after NM.
This reverts commit acc335aad4.
(cherry picked from commit 105abf27c1)
(cherry picked from commit 08e8afcf17)
During shutdown, systemd should first stop NetworkManager and then
the dispatcher service. Note that dispatcher service is D-Bus activated,
so the two services don't Want/Require each other. But the ordering
still matters.
You're supposed to be able to use dispatcher scripts to spawn
long-running processes, but currently systemd will kill them when
nm-dispatcher exits. Fix that.
https://bugzilla.gnome.org/show_bug.cgi?id=725492
Lennart sez:
"Oh, I wasn't aware it is short-lived only. In that case, drop the
multi-user.target bit, and just make it create the dbus alias.
[Install]
Alias=dbus-org.freedesktop.nm-dispatcher.service
And yeah, adding Also=NetworkManager-dispatcher.service to
NetworkManager.service certainly would be a good idea."
