Alt-tab causes Unity to crash

[piratemurray]

Description: Ubuntu 11.10
Release: 11.10
Unity: 4.28.0-0ubuntu1

60% of the time Unity crashes whilst using alt-tab. Found this in the log viewer:

kernel: [ 73.464371] compiz[1961]: segfault at 3e1cb7bf ip b47710e7 sp bfd04230 error 4 in libunityshell.so[b45ef000+20e000]
gnome-session[1885]: WARNING: Application 'compiz.desktop' killed by signal
gnome-session[1885]: WARNING: App 'compiz.desktop' respawning too quickly
gnome-session[1885]: CRITICAL: We failed, but the fail whale is dead. Sorry....

At that point Unity failed to restart, had to hard reset since all the panels / window decorations were dead. Previous version of Unity and alt-tab did not cause this behaviour.

Steps to reproduce:
1) Press alt-tab on a newly booted system

Expected results:
Alt-tab window switcher appears

Actual results:
Occasionally unity crashes. Sometime unrecoverably. Can not consistently reproduce this. Happens about 60% of the time.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: unity 4.28.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-15.25-generic-pae 3.0.13
Uname: Linux 3.0.0-15-generic-pae i686
.tmp.unity.support.test.0:

ApportVersion: 1.23-0ubuntu4
Architecture: i386
CompizPlugins: [core,bailer,detection,composite,opengl,compiztoolbox,decor,place,imgpng,vpswitch,unitymtgrabhandles,session,grid,regex,resize,gnomecompat,move,mousepoll,animation,wall,workarounds,wobbly,expo,fade,ezoom,scale,unityshell]
CompositorRunning: compiz
Date: Tue Jan 17 09:27:45 2012
DistUpgraded: Log time: 2011-11-30 17:35:00.209305
DistroCodename: oneiric
DistroVariant: ubuntu
GraphicsCard:
 Intel Corporation Core Processor Integrated Graphics Controller [8086:0046] (rev 02) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:215a]
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
Lsusb:
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
 Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
MachineType: LENOVO 2522CT3
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.0.0-15-generic-pae root=/dev/mapper/ubuntu-root ro quiet splash vt.handoff=7
SourcePackage: unity
UpgradeStatus: Upgraded to oneiric on 2011-11-30 (47 days ago)
dmi.bios.date: 10/25/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 6IET74WW (1.34 )
dmi.board.name: 2522CT3
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr6IET74WW(1.34):bd10/25/2010:svnLENOVO:pn2522CT3:pvrThinkPadT410:rvnLENOVO:rn2522CT3:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2522CT3
dmi.product.version: ThinkPad T410
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.6+bzr20110929-0ubuntu6
version.libdrm2: libdrm2 2.4.26-1ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 7.11-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 7.11-0ubuntu3
version.xserver-xorg: xserver-xorg 1:7.6+7ubuntu7
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.6.0-1ubuntu13
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.14.99~git20110811.g93fc084-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.15.901-1ubuntu2.1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:0.0.16+git20110411+8378443-1

[Omer Akram (om26er)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. However, your crash report is either missing or challenging to deal with as a ".crash" file. Please follow these instructions to have apport report a new bug about your crash that can be dealt with by the automatic retracer.

If you are running the Ubuntu Stable Release you might need to enable apport in /etc/default/apport and restart.

Now open your file manager, navigate to your /var/crash directory and open the crash report you wish to submit.
If this fails you will have to open a terminal and file your report with 'ubuntu-bug /var/crash/_my_crash_report.crash' where _my_crash_report.crash is the crash you would like to report. If you get an error that you aren't allowed to access this report you will have to file it with 'sudo ubuntu-bug /var/crash/_my_crash_report.crash'.

I'm closing this bug report since the process outlined above will automatically open a new bug report which can then dealt with more efficiently. Thanks in advance for your cooperation and understanding.

[Abe Gong (agong)]

Just to chime in here, this bug also affects me. It just started in the last few days. I'm assuming it's due to an update. Please help fix it -- this is killing my workflow!

[Geert Jan Alsem (gj-alsem)]

I think this is a duplicate of Bug #916879

[Duane (duanedan)]

I wrote what i did to solve that on https://bugs.launchpad.net/ubuntu/+source/unity/+bug/946965?comments=all

[gferrie (gferrie-u)]

This is a serious bug which still remains to be unsolved for me. I am too entrenched in using Alt-Tab to prevent myself from doing it and it has caused a lot of problems with losing work having to relog or reboot. Making this a priority would certainly help a lot of us.

thanks

[Daniel van Vugt (vanvugt)]

gferrie, are you using Ubuntu 12.04 or an older version?

If you're using 12.04 (Unity 5.10+) and the bug still remains then this bug should be un-duplicated. If you're using an older version of Ubuntu then please put your comments in bug 916879.

[robmietto (robmietto)]

Hi all!

I had this problem. Let me say what I did:

compiz >> ubuntu unity plugin >> General tab. By default it was here, in "Key to show the HUD", the <alt> key, I changed it (I put <Super><alt>) then I have alt-tab working ok right now.

When we use alt-tab, the first one key is commonly alt, so first of all that key tried to bring HUD. I dont know, maybe this is a clue.

I am using ubuntu 13.04.

Regards.