Package: gnome-session-bin
Version: 48.0-1+deb13u1
Severity: important
During shutdown of a GNOME Wayland session, |gnome-session-ctl|can fail
to restart the persistent user D-Bus if a D-Bus-activated service
concurrently causes |xdg-desktop-portal.service|to be queued for startup.
This leaves the old user-bus/portal state behind and can delay
application startup after the following graphical login until
D-Bus/portal activation timeouts of 120 seconds expire.
I have a reproducible A/B test for the race.
The affected system is Debian 13 (trixie), GNOME 48, Wayland. I also
have persistent SSH sessions, so the systemd user manager and user D-Bus
remain alive across graphical logout.
In my case the trigger is a late D-Bus activation of Nextcloud by
Firefox. This is a separate known Nextcloud issue and is not the bug I
am reporting here; it merely provides a reliable way of triggering the
gnome-session race.
During logout, after the normal Nextcloud instance has already been
terminated, Firefox requests:
|com.nextcloudgmbh.Nextcloud|
D-Bus starts:
|/usr/bin/nextcloud --background|
The graphical session is already being torn down, so this newly started
Nextcloud process cannot connect to Wayland/X11. Before terminating,
however, it requests:
|org.freedesktop.portal.Desktop|
This queues |xdg-desktop-portal.service|for startup just as GNOME runs
|gnome-session-restart-dbus.service|.
The journal then shows:
|systemd: Starting xdg-desktop-portal.service - Portal service...
systemd: Starting gnome-session-restart-dbus.service - Restart DBus
after GNOME Session shutdown... systemd: Requested transaction
contradicts existing jobs: Transaction for dbus.service/stop is
destructive (xdg-desktop-portal.service has 'start' job queued, but
'stop' is included in transaction). gnome-session-ctl: Failed to restart
DBus service:
GDBus.Error:org.freedesktop.systemd1.TransactionIsDestructive:
Transaction for dbus.service/stop is destructive
(xdg-desktop-portal.service has 'start' job queued, but 'stop' is
included in transaction).|
At this point |graphical-session.target|is already inactive. The newly
started portal attempts to activate the GNOME portal backend, which
consequently fails its dependency.
The graphical logout itself completes. However, the intended restart of
the user D-Bus has failed.
After the next graphical login, portal activation becomes stuck. The
journal subsequently shows errors including:
|Error calling StartServiceByName for org.freedesktop.portal.Desktop:
Timeout was reached|
and:
|xdg-desktop-portal.service: start operation timed out. Terminating.|
Eventually D-Bus reports activation timeouts with:
|service_start_timeout=120000ms|
During this interval applications launched from the desktop appear not
to start. They eventually appear together after the timeout/race has
resolved.
I can prevent the triggering activation without otherwise changing the
session by installing this per-user D-Bus override:
|~/.local/share/dbus-1/services/com.nextcloudgmbh.Nextcloud.service|
containing:
|[D-BUS Service] Name=com.nextcloudgmbh.Nextcloud Exec=/bin/false|
This provides a reproducible A/B test.
With the override installed, Firefox makes exactly the same request for
|com.nextcloudgmbh.Nextcloud|during logout, but activation fails
immediately.
The journal then shows, in the same second:
|Activated service 'com.nextcloudgmbh.Nextcloud' failed: Process
com.nextcloudgmbh.Nextcloud exited with status 1 Starting
gnome-session-restart-dbus.service - Restart DBus after GNOME Session
shutdown... Started gnome-session-restart-dbus.service - Restart DBus
after GNOME Session shutdown. Stopping dbus.service - D-Bus User Message
Bus... Stopped dbus.service - D-Bus User Message Bus.|
The following login is immediate.
Nextcloud is then started normally by GNOME autostart. It requests
|org.freedesktop.portal.Desktop|, and the portal services start normally
within approximately one second.
I repeated this test, including deliberately waiting until a Nextcloud
desktop notification appeared before launching applications. Application
startup remained immediate. Thus the notifications are unrelated to the
delay.
The Nextcloud D-Bus activation problem has separately been reported as a
follow-up to Debian bug #1072382 and upstream in Nextcloud Desktop issue
#7653. It is not necessary for this gnome-session bug: any sufficiently
late D-Bus activation which queues a service depending on
|dbus.service|appears capable of producing the race.
The problem here is that |gnome-session-restart-dbus.service|is
specifically intended to restart the persistent user bus after
graphical-session shutdown, but a concurrently queued D-Bus activation
can make that restart fail with |TransactionIsDestructive|. The failure
then leaves state from the old graphical session in the persistent user
manager and affects the following login.
I believe gnome-session should ensure that the intended D-Bus restart
completes even when another D-Bus activation races with session
shutdown. At minimum, |TransactionIsDestructive|should not cause the
restart to be abandoned without recovery.
Relevant versions:
|gnome-session-bin 48.0-1+deb13u1 gnome-session-common 48.0-1+deb13u1
systemd 257.13-1~deb13u1 dbus-user-session 1.16.2-2 firefox-esr
140.16.0esr-1~deb13u1 nextcloud-desktop 3.16.7-1~deb13u1
xdg-desktop-portal 1.22.1+ds-1~bpo13+1 xdg-desktop-portal-gnome 48.0-2
fuse3 3.18.3-1~bpo13+1 libfuse3-4 3.18.3-1~bpo13+1|
|xdg-desktop-portal|1.22.1 and FUSE 3.18.3 are local backports built
from Debian testing source on Debian 13. I installed them while
investigating an earlier, separate |xdg-document-portal|shutdown problem.
The D-Bus restart race described above occurred after those newer
versions were already installed. In particular,
|xdg-document-portal|itself stopped and started promptly in the tests
described here.
The affected computer is older hardware (from 2018), but otherwise
performs normally. The observed delay is not general system slowness: it
corresponds to explicit 120-second service activation timeouts and
disappears completely in the A/B test above.
