From: "Ludovic Courtès" <ludo@gnu.org>
To: Liliana Marie Prikler <liliana.prikler@gmail.com>
Cc: 55444@debbugs.gnu.org
Subject: bug#55444: elogind startup race between shepherd and dbus-daemon
Date: Wed, 25 May 2022 14:26:13 +0200 [thread overview]
Message-ID: <87zgj5hk7u.fsf@gnu.org> (raw)
In-Reply-To: <5a8b5f20da2676e03c696e33c029895292ed397e.camel@gmail.com> (Liliana Marie Prikler's message of "Tue, 24 May 2022 21:25:57 +0200")
Hi,
Liliana Marie Prikler <liliana.prikler@gmail.com> skribis:
> Am Montag, dem 16.05.2022 um 10:26 +0200 schrieb Ludovic Courtès:
>> [...]
>> So it would seem that the solution to this is to prevent dbus-daemon
>> from starting elogind. We can do that by changing
>> org.freedesktop.login1.service so that it has “Exec=true” instead of
>> “Exec=elogind --daemon”.
>>
>> “Exec=true” is a bit crude because it doesn’t guarantee that elogind
>> is really started; if that isn’t good enough, we could instead wait
>> for the PID file or something (as of Shepherd 0.9.0, invoking ‘herd
>> start elogind’ potentially leads shepherd to start a second instance
>> if the first one is still being started, so we can’t really do that).
> Why does shepherd race with itself here? That sounds like a very evil
> bug. Rather than waiting for a log file, I'd suggest writing an ad-hoc
> Guile script that communicates with shepherd and blocks until shepherd
> signals that elogind has been started, but this script too would have
> to work around shepherd racing against itself.
Right. Currently services have two states: stopped, and started.
Fixing that needs non-trivial changes to how shepherd handles state.
We’ll have to do that (the way I see it, we’ll move state out of
<service> and have a fiber explicitly handle state, including
distinguishing between “stopped” and “starting”), but I think/hope we
can fix this bug without first addressing this issue.
>> Depending on what we end up with, we might also revisit whether
>> xorg-server needs to explicitly depend on elogind.
> At least in the case of GDM I think it does heavily depend on elogind.
> For the future, I think we also should take over dbus-daemon's
> autostart in the same way systemd already has.
Agreed, though that one is trickier: we’d need an implementation of the
D-Bus protocol. There’s guile-ac-d-bus but it’s probably under-tested.
Thanks,
Ludo’.
next prev parent reply other threads:[~2022-05-25 12:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-16 8:26 bug#55444: elogind startup race between shepherd and dbus-daemon Ludovic Courtès
2022-05-24 2:27 ` Maxim Cournoyer
2022-05-25 12:45 ` Ludovic Courtès
2022-05-24 19:25 ` Liliana Marie Prikler
2022-05-25 12:26 ` Ludovic Courtès [this message]
2022-05-27 13:54 ` Ludovic Courtès
2022-05-27 20:54 ` Ludovic Courtès
2022-05-28 8:13 ` Josselin Poiret via Bug reports for GNU Guix
2022-05-28 21:26 ` Ludovic Courtès
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