unity-panel-service crashed with SIGABRT in __kernel_vsyscall()

StacktraceTop:
 g_type_check_instance_cast (type_instance=0xb6237d98, iface_type=138005672) at /build/buildd/glib2.0-2.29.10/./gobject/gtype.c:3985
 gail_widget_notify_gtk (obj=0x8332008, pspec=0x82ac260) at /build/buildd/gtk+3.0-3.1.8/./modules/other/gail/gailwidget.c:954
 g_cclosure_marshal_VOID__PARAM (closure=0x839e600, return_value=0x0, n_param_values=2, param_values=0x83a3028, invocation_hint=0xbfd38570, marshal_data=0x0) at /build/buildd/glib2.0-2.29.10/./gobject/gmarshal.c:539
 g_closure_invoke (closure=0x839e600, return_value=0x0, n_param_values=2, param_values=0x83a3028, invocation_hint=0xbfd38570) at /build/buildd/glib2.0-2.29.10/./gobject/gclosure.c:773
 signal_emit_unlocked_R (node=0x8286f18, detail=433, instance=0x8332008, emission_return=0x0, instance_and_params=0x83a3028) at /build/buildd/glib2.0-2.29.10/./gobject/gsignal.c:3256

Tried Oneiric Alpha 3 (20110803.1) and this is still happening.

---
Ubuntu Bug Squad volunteer triager
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It sounds weird to me that the service can crash that hard and systematically.
Are you using a11y specifically, and does turning that off change the situation. I know that may not be practical, but it could clarify whether the issue comes under special circumstance or not.

Otherwise, is there a test procedure that we could follow to try and make it crash here as well? With a particular set of actions?

Last, i'd be interested to know which machines it's crashing on, and which are not prone to exposing the issue. That may also be HW related, but at this point it's just an hypothesis.

Thanks in advance for your feedback.

Hi David,

Thanks for looking at this report!

We do automated testing on a bunch of laptops, which are all network-installed using a preseed file which contains this line in the late_command:

in-target sudo -u ubuntu gconftool-2 --set --type bool /desktop/gnome/interface/accessibility true

The reason for this was to enable testing using mago, which requires the accessibility framework to be enabled.

So we don't actually need a11y specifically, but that's how we came across this problem.

In principle, disabling it makes things work correctly; in practice, however, I've found that using gconftool-2 on Oneiric gives weird results. If, after installing with the aforementioned command in the preseed, I go into "Universal Access" it shows everything as "Off" but the problem still occurs. However, if I toggle (On, then Off) the screen reader, accessibility gets disabled correctly and the panel stops crashing.

Steps to reproduce:

1- Install from an Oneiric Alpha 3 image using the attached preseed file. I created a custom CD image replacing the /preseed/ubuntu.seed file with the one I'm attaching. Note that this preseed file minimally modifies the stock one, just adding the gconftool-2 command as mentioned above.
2- When prompted for the user's data, the username should be "ubuntu", as that's the user the preseed file modifies.
3- Once the install completes, and upon logging in, you'll notice elevated CPU usage from the constant dying/respawning of unity-panel-service.
4- from the Unity app lens, launch gnome-terminal to witness how it shrinks due to the panel respawning.

This happens on every system I've tested Oneiric in, about 30 laptops, various makes/models, but more importantly, the test case I just gave works even on a virtual machine (I'm using VirtualBox 4 on Natty), so it's definitely not hardware-related. The systems where it did not happen, were the ones that were installed manually, hence, the gconftool command wasn't used.

Finally, I should mention that what hinted that accessibility was somehow related, was bug 798094 which describes a similar issue.

Thanks again!

This is the preseed file to use, it should be in /preseeds/ of your Ubuntu install media. I built a custom ISO using instructions from here:

https://help.ubuntu.com/community/LiveCDCustomization

The custom ISO was the easiest way for me to try this on a virtual machine. If using for instance USB install media on bare metal, just dropping this file in the needed location and maybe regenerating the md5sums file could potentially be easier.

I can confirm this issue on Ubuntu Oneiric Ocelot daily bulid (20110814).

We have recently fixed an issue related to the a11y stack in the panel. See bug #817477. Can you re-test with unity-4.16.0 and report? Thanks

Hi David,

I can no longer reproduce this problem, on systems installed from an image dated 20110908 and using unity 4.12.0-0ubuntu2, and the problem is no longer present. I checked that the /desktop/gnome/interface/accessibility setting is "true", and I also tried manually turning on screen reading to try and trigger the error, but I can't make it fail anymore.

I also tried a dist-upgrade as of today, bringing Unity up to 4.14.2-0ubuntu1, and it's still working correctly.

Based on the fact that it wasn't the fix you mention that solved it, we'd have to mark this Invalid (unknown fix), but based on bug 817477 I'll mark fix released instead. Please change if you feel this is incorrect.

Thanks so much for your help with this problem!

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

A list of all reports related to this bug can be found here:
http://laptop.qa.ubuntu.com/qatracker/reports/bugs/810145