unity panel service error:0 - panel buttons unresponsive after button click

Asked by Jefferson Ferreira-Ferreira on 2018-01-17

Since more or less a month ago I experienced OS crashes when clicking any panel button (calendar, volume, battery, etc). Only the mouse pointer still moves, but the system becomes totally unresponsive. I checked my syslog and the message before the power off was:

Jan 16 14:13:07 jeco-pc kernel: [18048.538695] unity-panel-ser[1871]: segfault at 1ac32 ip 0000000000406ea9 sp 00007ffeedafe0a0 error 4 in unity-panel-service[400000+12000].

I thought it was a similar issue as reported in https://askubuntu.com/questions/992571/gui-unity-crashing-in-16-04-lts-after-updates-2018-01-04-compiz-segfaults. So I followed instructions and installed libgl1-mesa-dri from xenial-proposed. After that, clicks on panel buttons do not freeze the entire OS anymore. Instead, only the unity panel stops working. Even the time shown in the panel clock stops progressing. I checked my syslog and now the message related to this is:

Jan 17 09:38:12 jeco-pc kernel: [ 2911.154812] traps: unity-panel-ser[1994] general protection ip:406ea9 sp:7ffc881ee780 error:0 in unity-panel-service[400000+12000].

I'm wondering whether it is indeed a bug.

infos:
Ubuntu 16.04.3 LTS
Processor Intel Core i7-4500U CPU @ 1.8GHz x 4
Graphics Intel Haswell Mobile
OS type 64-bit

if you install a non-compoziting session like LXDE, is it OK?

I'm finishing my Ph.D. and not sure if it is safe now to change from Ubuntu to LUbuntu or perform any operation that could potentially put my work at risk. There is another way to diagnose this issue?

Its not Lubuntu. You are just installing LXDE to test.

Sorry if my question sounds too "newbie", but if the issue is related to unity panel service is not obvious that LXDE panel service will not present such error (after all it is an entirely different desktop environment) ?

Once we establish this, you can report a bug. You can also log into the LXDE session to get a usable system while the issue is resolved

I installed LXDE using "sudo apt-get install lubuntu-desktop". By default, I log in Ubuntu. All the system looks exactly like before. So the only thing that changed was the greeter (login screen). The By the way, I would like to restore the unity greeter. But in fact, the strange behavior I reported stopped. After a day of tests, now the panel and the panel buttons are perfectly responsive and functional.

I don't have plans to use LXDE. So, there is no logical reason to maintain LXDE on my machine (although LXDE has fixed unity panel service problems). If someone could point me a fix to unity panel service error, I would be grateful.

You just needed to install lxde as I said. You don't need the full session like that. If you log in to the LXDE session is it OK? You have duplicated a lot of functionality on your system.

yeah, it's ok now, working like a charm both sessions (Ubuntu and LXDE) - apparently just because I installed LXDE. To undo the installation I made am I supposed to hit "sudo apt-get remove lubuntu-desktop" ? Since my unity is working fine now, I'm planning to uinstall LXDE when the problem is fixed.

Is it really a unity bug?

That's just a meta-package. Removing it does not remove the contents. If you:

sudo apt-get --purge remove lxde openbox

Then it'll remove most of what you installed. Again, all you needed to install was lxde, not lubuntu-desktop

Thank you very much for your attention. You are helping me a lot. In fact, I'm a basic user, so I followed an instruction found on the internet. Anyway, this is a secondary question: how to totally remove what I installed. My main concern is that unity works properly without another desktop environment.

I'm wondering if the unity panel service failure was triggered by some software update made through sudo apt-get upgrade.

After some days of Lubuntu-LXDE installation, the problem came back. At least 5 times a day, clicks on panel buttons completely freezes the system. Should this question become a bug?

Please, if someone could help me, I will be grateful. I'm stuck on this error for months. There is some additional information I can provide?

Manfred Hampl (m-hampl) said : #14

What output do you get for the commands (to be executed in a terminal window)

uname -a
lsb_release -crid
sudo apt-get update
sudo apt-get dist-upgrade
apt-cache policy libegl1-mesa

Thanks Manfred.
Here are the outputs:

https://pastebin.ubuntu.com/26488967/

Manfred Hampl (m-hampl) said : #16

The output shows that you have already the current version of the mesa packages installed which are supposed to help for
Bug #1735594

Do you still see messages like
Jan 16 14:13:07 jeco-pc kernel: [18048.538695] unity-panel-ser[1871]: segfault at 1ac32 ip 0000000000406ea9 sp 00007ffeedafe0a0 error 4 in unity-panel-service[400000+12000]
in your system logs?

Remark: some of the settings related to repository sources are not fully correct, this leads to warnings during apt-get update

The last one was yesterday:
Jan 29 20:41:46 jeco-pc kernel: [ 4669.810054] unity-panel-ser[2162]: segfault at 10597 ip 0000000000406ea9 sp 00007fffe9301560 error 4 in unity-panel-service[400000+12000]

Since this morning (Jan/30) the problem doesn't happen. Earlier, a click on a panel button (or even in any app menu bar localized on the panel) meant a certain system crash. By now it is working, what looks unusual.

Anyway, It is not the first time the system stabilizes. After the mesa package update, the panel worked for a few days after the system crashing behavior come back. I'm going to monitor it for a few days.

Do you think apt-get dist-upgrade maybe could be fixed the problem? I always thought apt-get dist-upgrade was a command to upgrade the Ubuntu distro version (install 17.10 over 16.04, for example). But I was probably wrong.

PS.: I fixed repository warinigs.

Manfred Hampl (m-hampl) said : #18

"apt-get dist-upgrade" does not perform a release-upgrade (e.g. from 16.10 to 17.04), but it just install all available package updates for the release that you are running.
The difference between "apt-get update" and "apt-get dist-upgrade" is the following:

Let's assume that there is a package a version 1 which needs package b1 as dependency. Now there is a new version 2 of package 1 that has a new and different dependency, on package b2. There can be conflicts that do not allow the packages b1 and b2 being installed at the same time.
The upgrade of package a from version 1 to version 2 now requires that package b1 is uninstalled and b2 is installed.
"apt-get upgrade" will never uninstall packages and hence will leave package a at version 1.
only "apt-get dist-upgrade" will do these changes.

Initiating a release upgrade is done with a different command (sudo do-release-upgrade).

I suggest that you continue to keep an eye on your system, whether these crashes re-appear.

Today, the problem came back. I clicked on the calendar on the panel and the entire system crashed.

Jan 31 15:56:19 jeco-pc kernel: [ 3005.862110] unity-panel-ser[2200]: segfault at 61 ip 0000000000406ea0 sp 00007ffce922d1c0 error 4 in unity-panel-service[400000+12000]

I carefully inspected the system log and haven't found any clue besides the above message. What can I do?

Manfred Hampl (m-hampl) said : #20

Your case seems not to be caused by one of the two bugs with mesa and compiz, because the updates that are supposed to solve these problems have not helped on your system.

I suggest that you create a bug report. The command
ubuntu-bug unity
should collect the necessary information and start the reporting process.

That's great! Hope this help to solve the problem. I could reinstall all the system, but after 2 year and so many installations needed for my work purposes, it would be painful.

Thanks for your help @m-hampl!!