light-locker crashed with signal 5

[walkerstreet]

I am running Lubuntu with gnome desktop manager not light dm. I think light-locker should not even be installed. I will try removing it.

ProblemType: Crash
DistroRelease: Ubuntu 18.04
Package: light-locker 1.8.0-1ubuntu1
Uname: Linux 4.14.15-041415-generic x86_64
ApportVersion: 2.20.8-0ubuntu6
Architecture: amd64
CrashCounter: 1
CurrentDesktop: LXDE
Date: Thu Jan 25 11:27:27 2018
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/light-locker
ProcCmdline: light-locker
ProcEnviron:
 LANGUAGE=en_AU:en
 PATH=(custom, user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
Signal: 5
SourcePackage: light-locker
StacktraceTop:
 ()
 g_type_create_instance () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 g_object_new_with_properties () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
 g_object_new () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
Title: light-locker crashed with signal 5
UpgradeStatus: Upgraded to bionic on 2018-01-23 (1 days ago)
UserGroups: adm bumblebee cdrom dip lpadmin plugdev sambashare sudo

[Apport retracing service (apport)]

StacktraceTop:
 query_seat_path (listener=0x55a578341070) at gs-listener-dbus.c:2220
 init_seat_path (listener=0x55a578341070) at gs-listener-dbus.c:2278
 gs_listener_init (listener=0x55a578341070) at gs-listener-dbus.c:2296
 g_type_create_instance (type=<optimized out>) at ../../../../gobject/gtype.c:1866
 g_object_new_internal (class=class@entry=0x55a57834d620, params=params@entry=0x0, n_params=n_params@entry=0) at ../../../../gobject/gobject.c:1797

[walkerstreet (dbonner)]

I couldn't apt-get remove light-locker because I would have to remove lubuntu-desktop. I ended up switching my window manager to lightdm.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Peter Bennett (pgbennett)]

I have automatic lock disabled in power manager, yet light-locker crashes with SIGTRAP (5) (Trace/breakpoint trap) when I resume from sleep. Why does it use the breakpoint signal? That should be reserved for the debugger to use. Why is it running when I have requested no locking of the session?

[Fawzi Masri (fm64)]

I see this error when i xrdp to my ubuntnu server 18.04 after i have installed lubuntu-desktop over it.

[Travisgevans (travisgevans)]

After installing the xfce4 packages in Ubuntu 20.04 and starting a xfce4 session from the default bootup login screen, I immediately get a similar crash notification. If I launch light-locker from a terminal, I get the following output:

$ light-locker

** (light-locker:26216): ERROR **: 19:33:17.519: Environment variable XDG_SESSION_PATH not set. Is LightDM running?
zsh: trace trap (core dumped) light-locker

[Travisgevans (travisgevans)]

It appears what's going on (in my observed case, at least) is that the xfce4 package depends on xfce4-session, which pulls in light-locker as a Recommends, which in turn pulls in lightdm as a dependency. And when Xfce searches for a screen locker to use, it seems to discover light-locker first and tries to use it, which fails if lightdm is not in use. light-locker then signals the SIGTRAP “crash” (from the light-locker source code, this appears to be an intentional as a means of signaling that an error occurred).

So, the workaround appears to be either to use lightdm as the display manager instead, or to manually configure Xfce to use a different screen locker, or to manually remove the light-locker package and install, for instance, xfce4-screensaver (which is not installed by default from the xfce4 or xfce4-goodies metapackages) so that Xfce finds and uses it instead. Then, upon restarting Xfce, screen locking appears to work properly.