Disabling superfluous "Laptop" display output hangs reboot somewhere(?)

Bug #1229450 reported by Richard Elkins on 2013-09-23
Affects Status Importance Assigned to Milestone
lightdm (Ubuntu)

Bug Description

I made a guess at the applicable package; apologies if I guessed wrong. I could have guessed grub-common as well.

Just installed Xubuntu Saucy Beta-2 today alongside of another OS (Linux Mint 15 Mate).
Mini-ITX motherboard home-build: Intel D2550MUD2 (Intel Atom 2550 GMA3650 i.e. Cedartrail).
The motherboard BIOS has not been updated since I purchased the motherboard.
In general, I have no complaints about quality and speed of Xubuntu Saucy components that were automatically selected:
   * Kernel graphics module: gma500_gfx.
   * Xorg video driver: Modesetting.

One oddity that I do not understand: in the Settings Manager > Hardware > Display application, it shows me two displays:
   * Acer Technologies 22" (correct)
   * "Laptop" (This is fictitious. How could have it been "detected"???)

By default, both displays have "Use this output" checked i.e. enabled. When "Laptop" is enabled, it overlays part of the actual Acer display.

In the default situation, when I request a reboot function from the Panel-0 Session Menu reboot item, click on the Panel-0 reboot Action Button, or enter `sudo reboot` from a terminal window, rebooting proceeds consistently as expected.

However, the "Laptop" display is a nuisance in these circumstances as it is not useful as it blocks part of the Acer display. I thought this would be an easy fix: Uncheck "Use this output" for the "Laptop" display and accept the changes. However, when I subsequently request a reboot from one of the actions described above, the shutdown aspect of the reboot process seems to hang up somewhere because the motherboard BIOS never restarts.

To summarize,
   * "Laptop" enabled: Reboot always proceeds.
   * "Laptop" disabled: Reboot always hangs.

The attached extra debug information will be automatically collected in the "Laptop" disabled case.

I would appreciate it if someone with a more mainstream motherboard than mine and only one physical monitor would do the following and report back:
1. After installation, how many displays are presented?
2. If there are two, please try what I did above.

Thank you.

If it turns out that this is just another Intel "feature" in Cedar Trail (one of the abandoned Intel motherboard product), I'll have to resigning myself to cursing a lot [(-:], installing Windoze 7 on this rig, and selling it on eBay! )-:

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: xfce4-taskmanager 1.0.0-3
ProcVersionSignature: Ubuntu 3.11.0-8.15-generic 3.11.1
Uname: Linux 3.11.0-8-generic x86_64
ApportVersion: 2.12.4-0ubuntu1
Architecture: amd64
Date: Mon Sep 23 16:39:26 2013
InstallationDate: Installed on 2013-09-23 (0 days ago)
InstallationMedia: Xubuntu 13.10 "Saucy Salamander" - Beta amd64 (20130923.1)
MarkForUpload: True
SourcePackage: xfce4-taskmanager
UpgradeStatus: No upgrade log present (probably fresh install)

Richard Elkins (texadactyl) wrote :
Ubuntu QA Website (ubuntuqa) wrote :

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:

tags: added: iso-testing
Richard Elkins (texadactyl) wrote :

Similar behavior when a Shutdown without reboot is requested:
   * "Laptop" enabled: Shutdown always proceeds to motherboard power-off.
   * "Laptop" disabled: Shutdown never gets to motherboard power-off (hangs somewhere).

Richard Elkins (texadactyl) wrote :

I'd really like to break in during a hung reboot or shutdown. Unfortunately, Xubuntu (xorg? lightdm?) is masking out the ability to Ctrl-Alt-F1. Did I overlook something?

I attached /var/log/lightdm/lightdm/lightdm.log.old after a successful reboot (laptop_enabled.log) and a failed reboot (laptop_disabled.log) inside a zip file.

Lightdm exits cleanly when the Laptop display is enabled.
[+144.02s] DEBUG: DisplayServer x-0: X server stopped
[+144.02s] DEBUG: Releasing VT 7
[+144.02s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
[+144.02s] DEBUG: Seat: Display server stopped
[+144.93s] DEBUG: Session pid=959: Exited with return value 0
[+144.93s] DEBUG: Seat: Session stopped
[+144.93s] DEBUG: Seat: Stopped
[+144.93s] DEBUG: Display manager stopped
[+144.93s] DEBUG: Stopping daemon
[+144.93s] DEBUG: Exiting with return value 0

However, Lightdm does not show any evidence of exiting when the Laptop display is disabled. The end of the log:
[+256.40s] DEBUG: Stopping display manager
[+256.40s] DEBUG: Seat: Stopping
[+256.40s] DEBUG: Seat: Stopping display server
[+256.40s] DEBUG: Sending signal 15 to process 970
[+256.40s] DEBUG: Seat: Stopping session
[+256.40s] DEBUG: Session pid=979: Sending SIGTERM
[+257.08s] DEBUG: Session pid=979: Exited with return value 0
[+257.08s] DEBUG: Seat: Session stopped
[+261.41s] DEBUG: Sending signal 9 to process 970

Richard Elkins (texadactyl) wrote :

It seems to me that choosing "lightdm" is more accurate for a starting point based on the lightdm log.

affects: xfce4-taskmanager (Ubuntu) → lightdm (Ubuntu)
Richard Elkins (texadactyl) wrote :

Effective work-around:
* Keep the fictitious "Laptop" monitor.
* On the desktop, right click and select Desktop Settings
* Pick a background
* Select "Stretch this background across all monitors."

For me, I achieved the effect that I wanted without actuallydisabling the 2nd monitor (Laptop).

Richard Elkins (texadactyl) wrote :

Still an anomaly in 14.04 (Trusty).

Richard Elkins (texadactyl) wrote :

No longer can I detect a phantom 2nd "Laptop" monitor in 14.04 or 13.10. Testing with 2 motherboards that are documented on my launchpad home page (~texadactyl).

Richard Elkins (texadactyl) wrote :

One year after I reported it fixed, it was still maked "undecided" and "new". I just marked it "fix released" because it appears so and has not reappeared.

Changed in lightdm (Ubuntu):
status: New → Fix Released
To post a comment you must log in.
This report contains Public information  Edit
Everyone can see this information.

Other bug subscribers