[systemd-devel] Cycle between logind and NetworkManager in case of remote user database

[Dan Williams]

On Mon, 2014-12-15 at 20:40 +0300, Andrei Borzenkov wrote:
> В Mon, 15 Dec 2014 11:34:17 -0600
> Dan Williams <dcbw at redhat.com> пишет:
> 
> > 
> > On Mon, 2014-12-15 at 16:11 +0100, Lennart Poettering wrote:
> > > On Sat, 13.12.14 10:09, Andrei Borzenkov (arvidjaar at gmail.com) wrote:
> > > 
> > > > NetworkManager sets logind inhibitor lock to monitor for suspend
> > > > events. So it implicitly requires logind to be present when NM
> > > > starts.
> > 
> > NM doesn't actually require that, it just wants to know about the
> > signals that logind sends and have a chance to respond to them.  If
> > logind isn't running, NM shouldn't really care.  But perhaps expectation
> > is not matching reality in the code.
> > 
> > > Any idea what it needs the inhibitor for?
> > 
> > To be aware of suspend/resume events of course.  NM may want to
> > disconnect the network cleanly before suspending, and on resume may need
> > to clean up network connections and restart certain operations.
> > 
> > > > logind is ordered after nss-user-lookup.target. If we have remote
> > user
> > > > database, it means that logind depends on network to be up and
> > running.
> > > > 
> > > > If network is provided by NetworkManager we have a loop.
> > > > 
> > > > Due to the fact that NetworkManager service itself does not declare
> > > > dependency on logind, it can be pretty hard to recognize.
> > > > 
> > > > Any idea how it can be solved nicely? I can only think of delaying
> > > > inhibitor logic in NM until logind is started. Not sure what side
> > > > effects it may have.
> > > 
> > > Yeah, I figure if they want to be able to run in early parts of boot
> > > they should watch logind's bus name and create their inhibitor only
> > > after it appears.
> > 
> > Does logind get D-Bus autolaunched?
> 
> Yes.
> 
> >                                    NM is just creating a bus proxy for
> > the logind DBus service, and then attempting to call a D-Bus method on
> > logind to take an inhibitor.  It doesn't actually care that much about
> > the result, but NM doesn't pass G_DBUS_CALL_FLAGS_NO_AUTO_START to
> > prohibit logind from launching.
> > 
> > Perhaps NM is requesting logind to start through D-Bus autolaunch, but
> > since the network isn't up yet logind then fails itself?
> > 
> 
> systemd tries to launch logind service which now waits for services it
> is ordered After and eventually times out.

NM patch filed for review by NM dev team:

https://bugzilla.gnome.org/show_bug.cgi?id=741572

Also, I don't think logind should fail if there is no network; no reason
for it to crash and burn just because everything isn't quite ready when
it starts.  I presume it's got capability to deal with sporadic network
outages, and that's not really different than waiting for networking to
show up soon after it starts.  But not my department...

Dan