Pressing Num Lock in the lock screen causes disk thrashing & CPU starvation

[Louis Simard]

Scenario:

Using the GNOME Classic no-effects session (gnome-session-fallback / gnome-panel) in Ubuntu Precise.

Lock the screen (using Ctrl+Alt+L by default). Pressing Num Lock while the lock screen is up causes the 'dconf-service' process to continuously use up 1 full CPU core and a good portion of another. Meanwhile, the 'gnome-settings-daemon' process becomes frozen; unlocking the screen and then logging out brings up a dialog stating that the GNOME Settings Daemon is preventing the session from ending. Until the session is ended, one of these two processes writes to the disk continuously. This makes the entire computer very difficult to use.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: dconf-service 0.12.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic-pae 3.2.14
Uname: Linux 3.2.0-24-generic-pae i686
NonfreeKernelModules: fglrx
ApportVersion: 2.0.1-0ubuntu7
Architecture: i386
Date: Thu May 24 16:36:58 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
ProcEnviron:
 LANGUAGE=en_CA:en
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_CA.UTF-8
 SHELL=/bin/bash
SourcePackage: d-conf
UpgradeStatus: No upgrade log present (probably fresh install)

[Louis Simard (louis-simard-deactivatedaccount)]

Additional details: The Num Lock status light on the keyboard is flashed continuously while the daemon is thrashing the disk as a result of this bug, at a rate of over 50 flashes per second.

When my computer is not on the lock screen, I sometimes press Num Lock to dim the light because it is particularly bright on this keyboard, and it may flash once then return to its old status. This means that it probably fires twice in quick succession, both outside and inside the lock screen.

[Launchpad Janitor (janitor)]

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