Mouse pointer trapped and keyboard not working

[Daniel]

Every week since installing Xubuntu 16.04, it happens once that my computer is locked but I can't move my mouse pointer more than about 80 pixels and I can't type anything in the password dialog.

The only way out of this lock is killing light-locker using the text console (Ctrl+Alt+F2), logging in and then

me:~$ ps ax | grep lock
   56 ? S< 0:00 [kblockd]
 4124 tty2 S+ 0:00 grep --color=auto lock
 9237 ? Sl 0:02 light-locker
me:~$ kill 9237

Currently, I have no clue what's the reason for this. It seems that the pointer can move but is set back immediately to the original position whenever I try to move it.

I have a very usual dual-screen setup and when it locks, the password dialog normally is on the right screen while my left screen is the primary one. I don't know if this is relevant.

I normally start my computer on monday and then this problem occurs around wednesday.

me:~$ xrandr
Screen 0: minimum 320 x 200, current 3840 x 1200, maximum 16384 x 16384
DisplayPort-0 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200 59.95*+
DisplayPort-1 disconnected (normal left inverted right x axis y axis)
DVI-0 connected 1920x1200+1920+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200 59.95*+

For me, this problem is somehow security relevant because after applying the work-around I have no locking anymore until shutting down.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: light-locker 1.7.0-2ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
Uname: Linux 4.4.0-22-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: XFCE
Date: Wed Jun 8 09:28:13 2016
ExecutablePath: /usr/bin/light-locker
InstallationDate: Installed on 2016-02-17 (111 days ago)
InstallationMedia: Xubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
SourcePackage: light-locker
UpgradeStatus: Upgraded to xenial on 2016-04-25 (43 days ago)

[Caleb Jensen (irishman2020)]

I am also having this issue. I have a similar setup with a few more updates since the time the bug was reported.

[Theo Linkspfeifer (lastonestanding)]

Did you encounter this problem in Xubuntu 18.04 also?

I assume that the bug is not in the light-locker code, but somewhere in lightdm-gtk-greeter, xorg or even the display driver.

Therefore, please check the log files in /var/log/lightdm and Xorg named ones in /var/log.

[Theo Linkspfeifer (lastonestanding)]

Similar report: bug 1666256

[Daniel (hackie)]

No. So far I remember, it was gone with 16.10 or even earlier. But to be honest, I don't remember anymore.
But I can say it doesn't happen in recent versions, namely 18.04

[Theo Linkspfeifer (lastonestanding)]

Alright. I think we can close this report then.