If both top and bottom panels are set to "top" then post upgrade to lucid gnome-panel hangs

[Daniel Thomas]

Binary package hint: gnome-panel

When I upgraded from karmic to lucid today I found that on login gnome panel hung (100% CPU and unresponsive) (I was expecting it to login successfully and show me my shiny new lucid desktop).

Based on the fact that it was flickering a bit I thought this might be because I have both my 'top' and 'bottom' panels at the top (as this was more reliable when switching between having 1 and two screens laid out vertically) I used vim to edit the '/apps/panel/toplevels/bottom_panel_screen0/orientation' key to 'bottom' rather than 'top' (using a shell I sued to from another user account). This mean that I could login again.

Hopefully this bug will be fairly easy to find and fix as the cause is well defined and ubuntu-bug should hopefully provide any other needed information.

Thank you.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: gnome-panel 1:2.30.0-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.32-22.35-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-22-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Fri Jun 4 22:25:17 2010
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANG=en_GB.utf8
 LANGUAGE=en_GB:en
SourcePackage: gnome-panel

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please answer these questions:

 * Is this reproducible?
 * If so, what specific steps should we take to recreate this bug?
 * Could you get a stacktrace of the hang?

 This will help us to find and resolve the problem.

[Daniel Thomas (drt24)]

Yes this bug is reproducible (before trying to reproduce this bug yourself you will want to know how to fix the system after trying it: see the workaround in the original bug report).
 * Right click on the bottom panel.
 * Properties -> Orientation -> Top
 * Logout and log back in again.
 * Gnome panel is now hung
 * Use Ctrl+Alt+F1 and follow workaround then kill Xorg to get back to the login prompt and log back in again
 * You now have a working system again.

I have attached a backtrace I wasn't able to get a backtrace of the start of the hang as I don't know how attach gdb to gnome-panel before it starts as it starts automatically on login but I attached it after it started running.
I had to modify the instructions slightly and use step 10000 rather than continue as continue resulted in a hang and Ctrl+C did not abort the program.

[Sebastien Bacher (seb128)]

thank you for the details, did that issue start recently?

[Daniel Thomas (drt24)]

This bug started in Lucid. It was not in Karmic. I can't be more specific than that as I first experienced it on the first time I booted lucid which is the day this bug report was originally filed.

[DavidW (d-david-w)]

I have also had this bug at upgrading from 9.10 to 10.04, amd64.
Since I made an image before upgrade, I just reversed it.
Processes ate up all my PC's resources until swap was full. See attached screenshot.
This took place at 1st July via internet upgrade (GUI).

I will retry upgrade when the bug is fixed.
I definitely want two panels at the top. This bug reads like this is not possible anymore.

[DavidW (d-david-w)]

I upgraded again from 9.10 to 10.4.1 yesterday, since I coudn't see the bug on my notebook a week before.
But it is still there!
I changed orientation to the bottom on the shell in ~/.gconf/apps/panel/toplevels/panel_0/%gconf.xml and could log in again. After putting it back to the top, login was broken again. After adding a new panel to the top and moving the applets to it, then removing the old panel, alle works ok and I can login again with two panels at the top.
Unfortunately I have only be able to reproduce this bug once on a seperate demo account: I switched bottom panel to the top. All worked great. Next I switched to human skin and no desktop effects. Then I was not able to login at the demo account! As said, unfortunately I have only been able to reproduce this once, yesterday.
If anyone is seriously interested in debugging this issue, I can send him my "buggy" .gconf directory from a backup of mine.

[Daniel Thomas (drt24)]

I just encountered this bug again today. Somewhat tedious. Still affecting lucid 10.4.4. Happens if top and bottom panels are both set to the top and then logout and log in again.