https://bugs.kde.org/show_bug.cgi?id=521892
Bug ID: 521892
Summary: KWin crash on start after upgrade to 6.7.0
Classification: Plasma
Product: kwin
Version First 6.7.0
Reported In:
Platform: Arch Linux
OS: Linux
Status: REPORTED
Severity: crash
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 193460
--> https://bugs.kde.org/attachment.cgi?id=193460&action=edit
gdb full backtrace of my crash
DESCRIPTION
Arch Linux Kernel 7.0.12-arch1-1, amdgpu Mesa 26.1.3-arch1.2, AMD Ryzen 7 PRO
7840U (780M Graphics)
After upgrading to plasma 6.7.0 and restarting, SDDM would allow login but
would enter crash loop before desktop loaded with several crash handlers
(couldn't interact) popping up on black background before sending me back to
SDDM login. Looking in logs it appeared to only mention a C++ stdlib optional
assertion before entering the crash. Switching to PLM caused PLM to crash (The
login screen would load for 1 second then switch to a black screen with cursor)
with same KWin error as was seen with SDDM.
Running `KWIN_COMPOSE=Q startplasma-wayland` allows complete startup of Plasma.
Attempts to run with `KWIN_DRM_USE_EGL_STREAMS=0` or `KWIN_DRM_NO_AMS=1` result
in same crashing behavior.
STEPS TO REPRODUCE
1. Migrate from Kwin 6.6.5-4 to 6.7.0-1 on an arch linux system with Linux
kernel 7.0.12-arch-1 and Mesa 26.1.3-arch1.2
2. Reboot system
3. If using PLM it will crash before user interaction. Using SDDM requires a
login attempt. Or use `startplasma-wayland` from TTY.
OBSERVED RESULT
Kwin_wayland will be the first process to error and issue a core dump and
`SIGABRT` before a cascade of other services will error with messages to the
effect of "Did the compositor die?" PLM will not try to recover. An actual
login attempt will result in kwin being restarted several times but following
the same pattern and crashing the same way each time.
EXPECTED RESULT
Kwin_wayland should not `SIGABRT` and should not crash.
SOFTWARE/OS VERSIONS
Operating System (available in the Info Center app, or by running `kinfo` in a
terminal window):
Gathered with pacman -Qs
KDE Plasma Version: plasma-meta 6.7-2
KDE Frameworks Version: kwallet 6.27.0-1 (kf6) [kwallet is not directly related
to issue but was just a convenient framework package on my system]
Qt Version: qt6-wayland 6.11.1 (qt6)
ADDITIONAL INFORMATION
My own analysis of the backtrace attached is that it appears the issue comes
from `KWin::isCandidate` in `/src/scene/workspacescene.cpp`. I took a copy of
the tagged 6.7.0 release from GitLab. And in my IDE I noticed how in the
function the variable `info` is of type `const optional<FormatInfo>` and in the
return call it checks `info->bitsPerPixel` which requires the optional to be de
referenced and would cause the assertion exception seen in the core dump. I do
not know what `info` is exactly or why it is not present in this case. But I
did see a commit from 4 days ago by Shaun Ren in master that creates an
explicit check for this case (a3a03fee). But that would force kwin to not see
it as a viable candidate and this being my only screen would not be a good
thing.
My main question is the higher level reason `info` is not present? Is it
something wrong in my configuration? A regression? Any help would be
appreciated.
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