Bug 464732 - plasmashell hangs at a futex related to QXcbConnection::xi2HandleDeviceChangedEvent
Summary: plasmashell hangs at a futex related to QXcbConnection::xi2HandleDeviceChange...
Status: RESOLVED DUPLICATE of bug 457847
Alias: None
Product: plasmashell
Classification: Plasma
Component: generic-performance (show other bugs)
Version: 5.25.5
Platform: Ubuntu Linux
: NOR normal
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2023-01-24 11:01 UTC by Pellaeon Lin
Modified: 2023-02-28 07:06 UTC (History)
1 user (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
backtrace (274.57 KB, image/jpeg)
2023-01-24 11:01 UTC, Pellaeon Lin
Details

Note You need to log in before you can comment on or make changes to this bug.
Description Pellaeon Lin 2023-01-24 11:01:28 UTC
Created attachment 155554 [details]
backtrace

SUMMARY
Plasmashell and applications freeze randomly, none of them respond to keyboard or mouse input. I use my computer everyday and this happens about twice a week. It only happens since my upgrade from Ubuntu 22.04 to 22.10.

I switched to tty and used `sudo strace -p` on the plasmashell process. It showed that plasmashell stucked at a futex call. I loaded the debug symbols and attached the process with gdb. It showed that plasmashell stuck at a xcb_wait_for_reply call inside QXcbConnection::xi2HandleDeviceChangedEvent.

However, I did not plug / unplug any device from the computer at the time of freeze. This freeze also happens when the computer (Thinkpad X13 Gen 2 AMD) is not connected to any external device (no bluetooth device either).

The backtrace is attached.

I understand this might be hard to debug, so please tell me things I can try and information to collect, and I will collect them when the next crash happens.

STEPS TO REPRODUCE
1. Use desktop normally


OBSERVED RESULT
Desktop freezes

EXPECTED RESULT
Desktop not freeze

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Ubuntu 22.10 (System installed via Ubuntu installer, then apt install kubuntu-desktop afterwards)
(available in About System)
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.98.0
Qt Version: 5.15.6

ADDITIONAL INFORMATION
Graphics platform: X11
Comment 1 Bug Janitor Service 2023-01-24 11:33:30 UTC
Thank you for the bug report!

Please note that Plasma 5.25.5 is not supported for much longer by KDE; supported versions are 5.24, and 5.26 or newer.

If at all possible please upgrade to a supported version and verify that the bug is still happening there.

If you're unsure how to do this, contact your distributor about it.
Comment 2 Pellaeon Lin 2023-02-14 02:39:34 UTC
The bug happened a few more times after my initial reporting, usually once around every 3 days. I'd like to add a few points of observations and questions:

When the last time freeze happened, I tried doing the following things:
1. Switch to tty2 using Ctrl+Alt+F2 and log in
2. Run `killall plasmashell`
3. Switch back to tty1 using Ctrl+Alt+F1
4. I observe that the screen does not change, displaying the same content as it was frozen. It does not respond to any keyboard input (except for Capslock). I can still move the mouse but clicking has no effect.
5. I observe that I can still toggle Caps Lock (the light will switch on/off).

I have the following questions:
1. According to this thread https://forum.manjaro.org/t/plasmashell-freezes/127677 , `killall plasmashell` should stop the shell and I can launch a new terminal and run `plasmashell --replace` to restart it. However as I mentioned in (4) above it stays frozen. Does this mean that this problem is not related to plasmashell?
2. According to https://wiki.ubuntu.com/X/Troubleshooting/Freeze , my symptons might indicate a X server issue?
Comment 3 Pellaeon Lin 2023-02-28 07:06:43 UTC
I saw a similar bug report https://bugs.kde.org/show_bug.cgi?id=457847 and tried its workaround downgrading Mesa. It seems to work. I haven't experienced any freezes for two weeks now. Closing this as duplicate.

*** This bug has been marked as a duplicate of bug 457847 ***