Question regarding segfault (lxqt-panel/xpad)

Hi altogether,

I´m posting my question here in the hope that somebody may help me with a certain “problem”. :blush:
I already posted it on Lxqt-panel restarted (and xpad shut down) - Lubuntu Support - Lubuntu Discourse (the lubuntu-forum) but never received an answer.

I´m using Lubuntu 20.04 and until now it happened 3 times that lxqt-panel shut down and immediately after that restarted.
In each case xpad (“sticky note application for X”) also terminated its process.
So my guess is that the weird behaviour of lxqt-panel might have something to do with xpad… :question:

Anyhow, I looked at the logs (using lnav) each time and I think it´s best to post them here in case they may help:

│Feb 10 17:59:12 rosika-10159 kernel: [  217.370577] lxqt-panel[1293]: segfault at 8 ip 00007f4dce24dedc sp 00007ffe9049a730 error 4 in[7f4dce0af000+3c4000]                                                      
│Feb 10 17:59:12 rosika-10159 kernel: [  217.370591] Code: c0 4d 85 ed 74 08 4c 89 ef e8 60 d0 e6 ff 48 8b 7b 48 4c 89 6b 50 48 89 43 48 48 85 ff 74 0b f0 83 2f 01 75 05 e8 e4 d0 e6 ff <49> 8b 45 08 48 89 98 c8 02 00 00 48 89 6b 08 48│
│Feb 10 17:59:12 rosika-10159 kernel: [  217.948033] traps: xpad[1538] trap int3 ip:7f7ed35d90b5 sp:7ffc45f50e80 error:0 in[7f7ed359d000+84000]                                                                   │


│Mar 26 13:35:05 rosika-10159 kernel: [  307.450650] lxqt-panel[1391]: segfault at 8 ip 00007f2beb1a8edc sp 00007fff4c5c7f70 error 4 in[7f2beb00a000+3c4000]                                                      │
│Mar 26 13:35:05 rosika-10159 kernel: [  307.450663] Code: c0 4d 85 ed 74 08 4c 89 ef e8 60 d0 e6 ff 48 8b 7b 48 4c 89 6b 50 48 89 43 48 48 85 ff 74 0b f0 83 2f 01 75 05 e8 e4 d0 e6 ff <49> 8b 45 08 48 89 98 c8 02 00 00 48 89 6b 08 48│
│Mar 26 13:35:08 rosika-10159 kernel: [  311.231993] traps: xpad[1622] trap int3 ip:7fdcec67e295 sp:7ffe2f2b0230 error:0 in[7fdcec642000+84000]                                                                   │


│Mar 30 18:47:57 rosika-10159 kernel: [20829.104808] lxqt-panel[1406]: segfault at 8 ip 00007f774c1deedc sp 00007ffe85c0ee30 error 4 in[7f774c040000+3c4000]                                                      │
│Mar 30 18:47:57 rosika-10159 kernel: [20829.104821] Code: c0 4d 85 ed 74 08 4c 89 ef e8 60 d0 e6 ff 48 8b 7b 48 4c 89 6b 50 48 89 43 48 48 85 ff 74 0b f0 83 2f 01 75 05 e8 e4 d0 e6 ff <49> 8b 45 08 48 89 98 c8 02 00 00 48 89 6b 08 48│
│Mar 30 18:47:59 rosika-10159 kernel: [20830.676874] traps: xpad[1620] trap int3 ip:7f354d213295 sp:7fff44367990 error:0 in[7f354d1d7000+84000]                                                                  

Basically I´m at a loss as what to make of it. :thinking:
Any help is welcome.

Thanks a lot in advance.
Mana greetings.
Rosika :slightly_smiling_face:

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Did the problem start on the 10th day of February?

Did the problem occur the whole time until now?

Do you regularly apt update && apt upgrade your system?

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Hello Akito, :wave:

thanks so much for your reply.

Well, as far as the respective dates are concerned I just looked them up (as I tend to make notes of almost everything :blush:).

I performed a fresh/clean install of Lubuntu 20.04 on Jan 20 this year.

So indeed the first occurrence of the phenomenon was on Feb 10. After that Mar 26 and then yesterday when I was in the middle of shutting down the system (but hadn´t initiated the shutdown process yet).

So this lxqt-panel/xpad thing doesn´t happen on a regular basis. Rather seldom and unpredictably.

Yes, that I do. Almost on a daily basis. So my system is up-to-date.

Thanks, Akito, and many greetings.
Rosika :slightly_smiling_face:

Perhaps you can check out if this is the issue you are experiencing. If it is, you can notify whoever is responsible of this not being fixed. If it is not precisely the same issue, you could open a new bug report, referencing this one.

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Thanks a lot for the link.
I looked at it and I´m not quite sure whether that´s exactly the same issue.
The title is:

lxqt-panel crashes (segmentation fault) on start after upgrade of Qt libraries to version 5.9.3.

In my case it´s not necessarily “on start” (of the system). And it´s not reproducible on demand.
But it´s certainly similar.

Curiously enough I don´t seem to have any of those libraries installed:

rosika@rosika-10159 ~ [1]> dglob lib64qt
rosika@rosika-10159 ~ [1]> dpkg -l | grep lib64qt
rosika@rosika-10159 ~ [0|1]> 

But opening up a new bug report is certainly a good idea. Thanks, Akito. :+1:

I´ll try that at Issues · lxqt/lxqt · GitHub .
If anything comes up I´ll keep you posted.

Thanks again and many greetings from Rosika :slightly_smiling_face:

If that wouldn’t be the correct place, they will probably tell you where to post the bug report, so I think you are good to go.

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O.K., thanks @Akito for this good piece of advice of yours.

I just posted the issue on question regarding segfault (lxqt-panel/xpad) · Issue #1966 · lxqt/lxqt · GitHub .

Thanks a lot for your help. :relieved:

Many greetings and stay safe.
Rosika :slightly_smiling_face:

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I just received a response from github:

0.14.1 is outdated.

That being said, a backtrace would be appreciated (consult your distro doc on how to find a meaningful backtrace).

Oh, that´s funny. :thinking:
I looked up the package and it seems to be the latest version already:

sudo apt update
apt-get -s install liblxqt0
HINWEIS: Dies ist nur eine Simulation!
         apt-get benötigt root-Privilegien für die reale Ausführung.
         Behalten Sie ebenfalls in Hinterkopf, dass die Sperren deaktiviert
         sind, verlassen Sie sich also bezüglich des reellen aktuellen
         Status der Sperre nicht darauf!
Paketlisten werden gelesen... Fertig
Abhängigkeitsbaum wird aufgebaut.       
Statusinformationen werden eingelesen.... Fertig
liblxqt0 ist schon die neueste Version (0.14.1-0ubuntu2). # already the latest version
liblxqt0 wurde als manuell installiert festgelegt. # manually installed

I don´t want to mess around with package-management. If Lubuntu says it´s the latest version I really don´t want to force anything newer on it. :expressionless:

Not sure about the backtrace suggestion though.

Many greetings.
Rosika :slightly_smiling_face:

There will always be a discrepancy between what the distribution “thinks” is the newest version and what the developer or publisher thinks is the newest version, which is also actually the newest version.

That is certainly not the most bleeding edge distribution, there there are probably a lot of “outdated” packages, that mostly work fine, but are “outdated” according to the software developers who created the software that ultimately ends up as packages in your distribution.

Now if he referred to lxqt itself when saying that

0.14.1 is outdated

then the newest version is, as I assume 0.16.0:

So, you would need to use a distribution that uses this version or you would need to manually upgrade, but this is not so recommended, because it may break other things.

However, the point is, nobody at Github will care about this issue, as long as it is not confirmed to be an issue on the newest version. They first have to know if it is still an issue in the newest version. Only then, it is an issue that should be taken into account.
That is because there is no reason to fix an older version, if there is already a newer version that has the issue fixed. The only time that might seem reasonable is when developers need to backport fixes to older major versions, like it is the case with OpenVPN 2 or it was the case with Python 2.7, however usually one should just use the newest stable version.

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Thank you @Akito for taking out so much the time of your day in order to provide such detailed information. It´s highly appreciated. :smiley: :+1:

Thanks to your link I see now there´s a newer version of lxqt.
It seems to be provided by “tsujan”, the very person who responded to my query at github.

O.K., I see.

Since I don´t want to change distributions (as my Lubuntu installation is relatively new and in general I´m very satisfied with it) and I don´t want to manually upgrade either (thanks for your referring to that point :wink:) I think it´s best to leave things as they are at the moment.

Despite all I seem to have learnt quite a few things.
Thanks for your explanation, Akito.

Many greetings.
Rosika :slightly_smiling_face:

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