unity-panel-service crashed with SIGSEGV in g_main_context_dispatch()

[James]

I updated this morning and since then I can reproduce this segfault in unity-panel-service on my setup.

How I reproduced this:

1) Tail /var/log/syslog
1) Launch Eclipse PDT
2) Click on any other "View"
3) Click back to "PHP Explorer" view
4) /var/log/syslog shows a segfault happened (e.g.: note this may not be the same segfault as what apport collected)

Apr 13 14:48:04 jamesxps kernel: [22777.886622] unity-panel-ser[16573]: segfault at 8a0c ip 0000000000406375 sp 00007fff77b3c290 error 4 in unity-panel-service[400000+f000]

I am not sure why switching to the "PHP Explorer" view in particular is causing this segfault, I don't know where a link might be.

My particulars:

$ lsb_release -rd
Description: Ubuntu precise (development branch)
Release: 12.04

$ apt-cache policy unity
unity:
  Installed: 5.8.0-0ubuntu2
  Candidate: 5.8.0-0ubuntu2
  Version table:
 *** 5.8.0-0ubuntu2 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Crash
DistroRelease: Ubuntu 12.04
Package: unity-services 5.8.0-0ubuntu2
ProcVersionSignature: Ubuntu 3.2.0-22.35-generic 3.2.14
Uname: Linux 3.2.0-22-generic x86_64
ApportVersion: 2.0.1-0ubuntu2
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
Date: Fri Apr 13 14:43:42 2012
ExecutablePath: /usr/lib/unity/unity-panel-service
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120301)
ProcCmdline: /usr/lib/unity/unity-panel-service
ProcEnviron:
 SHELL=/bin/bash
 PATH=(custom, user)
 LANGUAGE=en_GB:en
 LANG=en_GB.UTF-8
SegvAnalysis:
 Segfault happened at: 0x406375: cmp %rax,(%rdx)
 PC (0x00406375) ok
 source "%rax" ok
 destination "(%rdx)" (0x000087ea) not located in a known VMA region (needed writable region)!
SegvReason: writing NULL VMA
Signal: 11
SourcePackage: unity
StacktraceTop:
 ?? ()
 ?? () from /usr/lib/x86_64-linux-gnu/gtk-3.0/modules/libatk-bridge.so
 g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
 g_main_loop_run () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
Title: unity-panel-service crashed with SIGSEGV in g_main_context_dispatch()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo

[Apport retracing service (apport)]

StacktraceTop:
 ?? ()
 ?? ()
 ?? ()
 ?? ()
 ?? ()

[Apport retracing service (apport)]

Thank you for your report!

However, processing it in order to get sufficient information for the
developers failed (it does not generate a useful symbolic stack trace). This
might be caused by some outdated packages which were installed on your system
at the time of the report:

unity-services version 5.8.0-0ubuntu2 required, but 5.10.0-0ubuntu2 is available
outdated debug symbol package for unity-services: package version 5.10.0-0ubuntu2 dbgsym version 5.8.0-0ubuntu2

Please upgrade your system to the latest package versions. If you still
encounter the crash, please file a new report.

Thank you for your understanding, and sorry for the inconvenience!

[James (jamesasgrim)]

It doesn't seem I can upgrade any further?

$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  linux-generic linux-headers-generic linux-image-generic virtualbox virtualbox-dkms virtualbox-qt
0 upgraded, 0 newly installed, 0 to remove and 6 not upgraded.

$ unity --version
unity 5.8.0

[James (jamesasgrim)]

This still happens with teh latest Unity:

$ apt-cache policy unity
unity:
  Installed: 5.10.0-0ubuntu3
  Candidate: 5.10.0-0ubuntu3
  Version table:
 *** 5.10.0-0ubuntu3 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages
        100 /var/lib/dpkg/status

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please try to obtain a backtrace following the instructions at http://wiki.ubuntu.com/DebuggingProgramCrash and upload the backtrace (as an attachment) to the bug report. This will greatly help us in tracking down your problem.

[James (jamesasgrim)]

Hi Sebastien
I have attached strace and gdb output. I couldn't find a way of starting Valgrind for an existing pid, nor could I find a way of starting unity-panel-service manually (I'm assuming it errors because it's already running...).

Hope this helps!

[James (jamesasgrim)]

This still happens consistently. Is there a way to stop this bug expiring after X days, as it's still an issue. I've lost count of how many times this has happened today...