PlasmaLoginManager Blank Screen only on first, cold boot

Help
1

Hello,

I’m running a new install of Fedora43 + KDE.

$ distro
	Name: Fedora Linux 43 (Forty Three)
	Version: 43
	Codename:
$ rpm -qa | grep plasma.*login
	plasma-login-manager-6.6.3-1.fc43.x86_64
	kcm-plasmalogin-6.6.3-1.fc43.x86_64
	kde-settings-plasmalogin-43.101-3.fc43.noarch
$ rpm -qa | grep qt6.*-gui
	qt6-qtbase-gui-6.10.2-2.fc43.x86_64
$ systemctl get-default
	graphical.target

On EVERY system cold boot, the system boots to a blank screen.
It is functional @ shell, accessible via ssh, etc.; just the graphical env has an issue.

Checking dmesg I see
…
plasma-login-greeter segfault at 8e ip 00007f072e553124 sp 00007fff88e5e858 error 4 in libQt6Gui.so.6.10.2[153124,7f072e400000+797000] likely on CPU 1 (core 1, socket 0)
…
every time.

An immediate warm-reboot solves the problem. The system boots to greeter screen, login works, and the Plasma Desktop is up.
No error in dmesg this second time around.

I can reboot all day long and it’s good.

If I shutdown, then cold boot. It happens again, same error.

I don’t know much at all about debugging KDE packages yet.

Just want to first check if this is a known problem with a fix? Bad config maybe?
Or a real bug?

Thanks,

Len

2

I’m running Arch and have the same problem on my desktop pc only (not my laptop).

$ pacman -Q | grep plasma.*login
plasma-login-manager 6.6.4-1
$ pacman -Q | grep qt6-base
qt6-base 6.11.0-2
$ sudo systemctl get-default
graphical.target

Stack trace:

Process 946 (plasma-login-gr) of user 955 dumped core.
                                             
                                             Stack trace of thread 946:
                                             #0  0x00007f40424178e4 _ZNK7QWindow6screenEv (libQt6Gui.so.6 + 0x2178e4)
                                             #1  0x000055f9dd87f32e n/a (/usr/lib/plasma-login-greeter + 0xe32e)
                                             #2  0x00007f4041bdc9c2 n/a (libQt6Core.so.6 + 0x1dc9c2)
                                             #3  0x00007f404242c182 _ZN22QWindowSystemInterface19handleScreenRemovedEP15QPlatformScreen (libQt6Gui.so.6 + 0x22c182)
                                             #4  0x00007f40419653cc _ZN15QtWaylandClient15QWaylandDisplay23handleScreenInitializedEPNS_14QWaylandScreenE (libQt6WaylandClient.so.6 + 0x753cc)
                                             #5  0x00007f40419922c6 _ZN15QtWaylandClient14QWaylandScreen15maybeInitializeEv (libQt6WaylandClient.so.6 + 0xa22c6)
                                             #6  0x00007f403ef40ac6 n/a (libffi.so.8 + 0x7ac6)
                                             #7  0x00007f403ef3d76b n/a (libffi.so.8 + 0x476b)
                                             #8  0x00007f403ef4006e ffi_call (libffi.so.8 + 0x706e)
                                             #9  0x00007f4043d5f48d n/a (libwayland-client.so.0 + 0x448d)
                                             #10 0x00007f4043d602e9 n/a (libwayland-client.so.0 + 0x52e9)
                                             #11 0x00007f4043d606f3 wl_display_dispatch_queue_pending (libwayland-client.so.0 + 0x56f3)
                                             #12 0x00007f404195ed76 _ZN15QtWaylandClient15QWaylandDisplay13flushRequestsEv (libQt6WaylandClient.so.6 + 0x6ed76)
                                             #13 0x00007f4041bd4614 _ZN7QObject5eventEP6QEvent (libQt6Core.so.6 + 0x1d4614)
                                             #14 0x00007f4041b76c98 _ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent (libQt6Core.so.6 + 0x176c98)
                                             #15 0x00007f4041b77070 _ZN23QCoreApplicationPrivate16sendPostedEventsEP7QObjectiP11QThreadData (libQt6Core.so.6 + 0x177070)
                                             #16 0x00007f4041e75d98 n/a (libQt6Core.so.6 + 0x475d98)
                                             #17 0x00007f403fb06f4d n/a (libglib-2.0.so.0 + 0x5ef4d)
                                             #18 0x00007f403fb08607 n/a (libglib-2.0.so.0 + 0x60607)
                                             #19 0x00007f403fb08815 g_main_context_iteration (libglib-2.0.so.0 + 0x60815)
                                             #20 0x00007f4041e72222 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt6Core.so.6 + 0x472222)
                                             #21 0x00007f4041b845d6 _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt6Core.so.6 + 0x1845d6)
                                             #22 0x00007f4041b7a311 _ZN16QCoreApplication4execEv (libQt6Core.so.6 + 0x17a311)
                                             #23 0x000055f9dd87cbbb n/a (/usr/lib/plasma-login-greeter + 0xbbbb)
                                             #24 0x00007f40414366c1 n/a (libc.so.6 + 0x276c1)
                                             #25 0x00007f40414367f9 __libc_start_main (libc.so.6 + 0x277f9)
                                             #26 0x000055f9dd87cee5 n/a (/usr/lib/plasma-login-greeter + 0xbee5)
                                             
                                             Stack trace of thread 988:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a23e4 n/a (libc.so.6 + 0x933e4)
                                             #3  0x00007f404151c2f6 ppoll (libc.so.6 + 0x10d2f6)
                                             #4  0x00007f403fb08734 n/a (libglib-2.0.so.0 + 0x60734)
                                             #5  0x00007f403fb08815 g_main_context_iteration (libglib-2.0.so.0 + 0x60815)
                                             #6  0x00007f4041e72222 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt6Core.so.6 + 0x472222)
                                             #7  0x00007f4041b845d6 _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt6Core.so.6 + 0x1845d6)
                                             #8  0x00007f4041c9efa2 _ZN7QThread4execEv (libQt6Core.so.6 + 0x29efa2)
                                             #9  0x00007f4042c2d50e n/a (libQt6DBus.so.6 + 0x3750e)
                                             #10 0x00007f4041d4d483 n/a (libQt6Core.so.6 + 0x34d483)
                                             #11 0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #12 0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 992:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f4041d50e80 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt6Core.so.6 + 0x350e80)
                                             #5  0x00007f404195eec9 n/a (libQt6WaylandClient.so.6 + 0x6eec9)
                                             #6  0x00007f4041d4d483 n/a (libQt6Core.so.6 + 0x34d483)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1010:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1011:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1004:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
Process 946 (plasma-login-gr) of user 955 dumped core.
                                             
                                             Stack trace of thread 946:
                                             #0  0x00007f40424178e4 _ZNK7QWindow6screenEv (libQt6Gui.so.6 + 0x2178e4)
                                             #1  0x000055f9dd87f32e n/a (/usr/lib/plasma-login-greeter + 0xe32e)
                                             #2  0x00007f4041bdc9c2 n/a (libQt6Core.so.6 + 0x1dc9c2)
                                             #3  0x00007f404242c182 _ZN22QWindowSystemInterface19handleScreenRemovedEP15QPlatformScreen (libQt6Gui.so.6 + 0x22c182)
                                             #4  0x00007f40419653cc _ZN15QtWaylandClient15QWaylandDisplay23handleScreenInitializedEPNS_14QWaylandScreenE (libQt6WaylandClient.so.6 + 0x753cc)
                                             #5  0x00007f40419922c6 _ZN15QtWaylandClient14QWaylandScreen15maybeInitializeEv (libQt6WaylandClient.so.6 + 0xa22c6)
                                             #6  0x00007f403ef40ac6 n/a (libffi.so.8 + 0x7ac6)
                                             #7  0x00007f403ef3d76b n/a (libffi.so.8 + 0x476b)
                                             #8  0x00007f403ef4006e ffi_call (libffi.so.8 + 0x706e)
                                             #9  0x00007f4043d5f48d n/a (libwayland-client.so.0 + 0x448d)
                                             #10 0x00007f4043d602e9 n/a (libwayland-client.so.0 + 0x52e9)
                                             #11 0x00007f4043d606f3 wl_display_dispatch_queue_pending (libwayland-client.so.0 + 0x56f3)
                                             #12 0x00007f404195ed76 _ZN15QtWaylandClient15QWaylandDisplay13flushRequestsEv (libQt6WaylandClient.so.6 + 0x6ed76)
                                             #13 0x00007f4041bd4614 _ZN7QObject5eventEP6QEvent (libQt6Core.so.6 + 0x1d4614)
                                             #14 0x00007f4041b76c98 _ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent (libQt6Core.so.6 + 0x176c98)
                                             #15 0x00007f4041b77070 _ZN23QCoreApplicationPrivate16sendPostedEventsEP7QObjectiP11QThreadData (libQt6Core.so.6 + 0x177070)
                                             #16 0x00007f4041e75d98 n/a (libQt6Core.so.6 + 0x475d98)
                                             #17 0x00007f403fb06f4d n/a (libglib-2.0.so.0 + 0x5ef4d)
                                             #18 0x00007f403fb08607 n/a (libglib-2.0.so.0 + 0x60607)
                                             #19 0x00007f403fb08815 g_main_context_iteration (libglib-2.0.so.0 + 0x60815)
                                             #20 0x00007f4041e72222 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt6Core.so.6 + 0x472222)
                                             #21 0x00007f4041b845d6 _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt6Core.so.6 + 0x1845d6)
                                             #22 0x00007f4041b7a311 _ZN16QCoreApplication4execEv (libQt6Core.so.6 + 0x17a311)
                                             #23 0x000055f9dd87cbbb n/a (/usr/lib/plasma-login-greeter + 0xbbbb)
                                             #24 0x00007f40414366c1 n/a (libc.so.6 + 0x276c1)
                                             #25 0x00007f40414367f9 __libc_start_main (libc.so.6 + 0x277f9)
                                             #26 0x000055f9dd87cee5 n/a (/usr/lib/plasma-login-greeter + 0xbee5)
                                             
                                             Stack trace of thread 988:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a23e4 n/a (libc.so.6 + 0x933e4)
                                             #3  0x00007f404151c2f6 ppoll (libc.so.6 + 0x10d2f6)
                                             #4  0x00007f403fb08734 n/a (libglib-2.0.so.0 + 0x60734)
                                             #5  0x00007f403fb08815 g_main_context_iteration (libglib-2.0.so.0 + 0x60815)
                                             #6  0x00007f4041e72222 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt6Core.so.6 + 0x472222)
                                             #7  0x00007f4041b845d6 _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt6Core.so.6 + 0x1845d6)
                                             #8  0x00007f4041c9efa2 _ZN7QThread4execEv (libQt6Core.so.6 + 0x29efa2)
                                             #9  0x00007f4042c2d50e n/a (libQt6DBus.so.6 + 0x3750e)
                                             #10 0x00007f4041d4d483 n/a (libQt6Core.so.6 + 0x34d483)
                                             #11 0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #12 0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 992:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f4041d50e80 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt6Core.so.6 + 0x350e80)
                                             #5  0x00007f404195eec9 n/a (libQt6WaylandClient.so.6 + 0x6eec9)
                                             #6  0x00007f4041d4d483 n/a (libQt6Core.so.6 + 0x34d483)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1010:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1011:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1004:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1012:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 993:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a23e4 n/a (libc.so.6 + 0x933e4)
                                             #3  0x00007f404151bdae __poll (libc.so.6 + 0x10cdae)
                                             #4  0x00007f404195ef30 n/a (libQt6WaylandClient.so.6 + 0x6ef30)
                                             #5  0x00007f4041d4d483 n/a (libQt6Core.so.6 + 0x34d483)
                                             #6  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #7  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1018:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1017:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1114:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1204:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a23e4 n/a (libc.so.6 + 0x933e4)
                                             #3  0x00007f404151c2f6 ppoll (libc.so.6 + 0x10d2f6)
                                             #4  0x00007f403fb08734 n/a (libglib-2.0.so.0 + 0x60734)
                                             #5  0x00007f403fb08815 g_main_context_iteration (libglib-2.0.so.0 + 0x60815)
                                             #6  0x00007f4041e72222 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt6Core.so.6 + 0x472222)
                                             #7  0x00007f4041b845d6 _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt6Core.so.6 + 0x1845d6)
                                             #8  0x00007f4041c9efa2 _ZN7QThread4execEv (libQt6Core.so.6 + 0x29efa2)
                                             #9  0x00007f4041d4d483 n/a (libQt6Core.so.6 + 0x34d483)
                                             #10 0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #11 0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             
                                             Stack trace of thread 1016:
                                             #0  0x00007f40414adf32 n/a (libc.so.6 + 0x9ef32)
                                             #1  0x00007f40414a239c n/a (libc.so.6 + 0x9339c)
                                             #2  0x00007f40414a268c n/a (libc.so.6 + 0x9368c)
                                             #3  0x00007f40414a4e5e pthread_cond_wait (libc.so.6 + 0x95e5e)
                                             #4  0x00007f40291eca1e n/a (libgallium-26.0.4-arch1.1.so + 0x5eca1e)
                                             #5  0x00007f40291a1dbd n/a (libgallium-26.0.4-arch1.1.so + 0x5a1dbd)
                                             #6  0x00007f40291ec95d n/a (libgallium-26.0.4-arch1.1.so + 0x5ec95d)
                                             #7  0x00007f40414a597a n/a (libc.so.6 + 0x9697a)
                                             #8  0x00007f40415292bc n/a (libc.so.6 + 0x11a2bc)
                                             ELF object binary architecture: AMD x86-64
3

I was able to get a core dump.
Here’s a gdb report:

TITLE
plasma-login-greeter: SIGSEGV in QWindow::screen() via dangling QWindowPrivate
pointer when Wayland compositor replaces pending screen output during startup

COMPONENT
plasma-login-manager

VERSION
6.6.4-1.fc43

SEVERITY
Critical – process terminates on every cold boot




ENVIRONMENT

OS:         Fedora 43, x86_64 (kernel 6.19.11-200.fc43.x86_64)
Package:    plasma-login-manager-6.6.4-1.fc43.x86_64
Binary:     /usr/libexec/plasma-login-greeter
Build ID:   ec6b236da37d731156d601f1f4d19fae54a14ffb
Qt:         6.10.3 (libQt6Gui.so.6, libQt6WaylandClient.so.6)
Session:    Wayland
Display:    Single monitor
User:       plasmalogin (UID 967, GID 967)
Unit:       user@967.service → user unit plasma-login.service




OBSERVABLE BEHAVIOR

On every cold boot, plasma-login-greeter terminates with SIGSEGV approximately
140 seconds into the boot sequence. The greeter does not display. The crash
is visible in dmesg:

[140.093515] plasma-login-gr[2275]: segfault at 8e ip 00007ff359d532e4
sp 00007fff0cb6e7a8 error 4 in
libQt6Gui.so.6.10.3[1532e4,7ff359c00000+795000]
likely on CPU 1 (core 1, socket 0)

fault address: 0x8e (error 4 = user-mode read from unmapped address)
faulting IP:   libQt6Gui.so.6 + 0x1532e4 = QWindow::screen()




CRASH DETAILS

Signal:       SIGSEGV
Fault addr:   0x8e (0xe == 14 == likely vtable offset dereference on
freed/null object, classic use-after-free fingerprint)
Crash site:   QWindow::screen() – qwindow.cpp:2261

Source at crash point (qt6-qtbase-6.10.3):

// qwindow.cpp:2261
QScreen *QWindow::screen() const
{
Q_D(const QWindow);
return d->parentWindow ? d->parentWindow->screen()   // ← CRASH
: d->topLevelScreen.data();
}

d = 0xe

The d_func() macro expands to reinterpret_cast<const QWindowPrivate*>(d_ptr.d).
A value of 0xe for d_ptr.d means the QWindow object’s d-pointer is corrupt or
freed. Dereferencing 0xe + offset of parentWindow (0x80 in QWindowPrivate)
yields 0x8e, which matches the fault address exactly.




FULL BACKTRACE – THREAD 1 (crashing thread, LWP 2275)

#0  QWindow::screen (this=)
at qwindow.cpp:2261
d = 0xe                              ← QWindowPrivate* is freed/corrupt

#1  LoginGreeter::createWindowForScreen(QScreen*)::{lambda(QScreen*)#1}
::operator()(QScreen*) const
at src/frontend/greeter/main.cpp:56
window = 0x55b1c5a67200              ← captured QQuickWindow* (destroyed)
screenRemoved = 0x7ff2f46dab80       ← the removed QScreen*

#2-#6  Qt slot dispatch machinery
(QtPrivate::FunctorCall, QCallableObject::impl, QSlotObjectBase::call)

#7  QtPrivate::QSlotObjectBase::call
at qobjectdefs_impl.h:461
this = 0x55b1c59fe540

#8  doActivate
at qobject.cpp:4273
sender    = 0x7fff0cb6f300
receiver  = 0x7fff0cb6f340
signal_index (screenRemoved) = 10

#9  QMetaObject::activate
at qobject.cpp:4333

#10 QGuiApplication::screenRemoved
at moc_qguiapplication.cpp:313
_t1 = 0x7ff2f46dab80               ← the QScreen being removed

#11 QWindowSystemInterface::handleScreenRemoved
at qcoreapplication.h:97
platformScreen = 0x7ff2f45ec660
screen         = 0x7ff2f46dab80
newPrimaryScreen = 0x55b1c5993680

#12 QtWaylandClient::QWaylandDisplay::handleScreenInitialized
at qwaylanddisplay.cpp:617
(note: screen initialization triggering screen removal – see analysis)

#13 QtWaylandClient::QWaylandScreen::maybeInitialize
at qwaylandscreen.cpp:82

#14-#22  Wayland dispatch chain:
ffi_call_unix64 / ffi_call_int / ffi_call
wl_closure_invoke (libwayland-client.so.0)
dispatch_event / wl_display_dispatch_queue_pending
QtWaylandClient::EventThread::readAndDispatchEvents
QObject::event / QCoreApplication::notifyInternal2
QCoreApplicationPrivate::sendPostedEvents
postEventSourceDispatch / GLib main context dispatch

#23 main
at src/frontend/greeter/main.cpp:136




ROOT CAUSE ANALYSIS

WAYLAND OUTPUT NEGOTIATION DURING STARTUP

The Wayland protocol requires multiple round-trips before a wl_output
(screen) is considered fully initialized. Qt’s Wayland platform plugin
tracks this with a “pending screens” list and a set of required events
(e.g., wl_output.geometry, wl_output.mode, wl_output.done).

QWaylandScreen::maybeInitialize() (qwaylandscreen.cpp:73-82) checks
whether all required events have been received. Once they have,
QWaylandDisplay::handleScreenInitialized() is called.

In handleScreenInitialized() (qwaylanddisplay.cpp:617), Qt may determine
that the newly initialized output duplicates or replaces an existing
screen (e.g., a placeholder created before geometry was known). In that
case it calls QWindowSystemInterface::handleScreenRemoved() to remove the
superseded screen before promoting the new one.

This sequence fires the QGuiApplication::screenRemoved signal during the
compositor’s initial output negotiation phase – even on single-monitor
systems. It is not a multi-monitor scenario; it is a normal part of
single-monitor Wayland startup on this hardware/compositor combination.

THE GREETER’S screenRemoved HANDLER

In main.cpp, createWindowForScreen() creates a QQuickWindow per screen
and connects a lambda to QGuiApplication::screenRemoved:

// main.cpp:56 (reconstructed from backtrace symbols)
connect(app, &QGuiApplication::screenRemoved, greeter,
[window](QScreen *screenRemoved) {
if (window->screen() == screenRemoved) {   // ← CRASH
// presumably: close or move the window
}
});

The lambda captures window (a raw QQuickWindow*) by value. When
screenRemoved fires for the placeholder screen during output negotiation,
Qt may have already destroyed the QQuickWindow associated with that
placeholder (QWindowSystemInterface::handleScreenRemoved triggers
QWindow destruction for windows on the removed screen). By the time the
lambda executes, window is a dangling pointer. Calling window->screen()
dereferences d_ptr.d = 0xe and crashes.

WHY d = 0xe

QObject stores its private data at d_ptr.d. When a QObject subclass is
destroyed, the d-pointer is not explicitly zeroed. If the allocation is
reclaimed and partially reused before the dangling pointer is accessed,
d_ptr.d will contain whatever the allocator wrote there – in this case
0xe, producing a fault at 0xe + offsetof(QWindowPrivate, parentWindow)
= 0x8e, which matches the kernel’s reported fault address exactly.




SUGGESTED FIX

Use QPointer to safely detect window destruction before
dereferencing:

// main.cpp – createWindowForScreen()
QPointer safeWindow = window;

connect(app, &QGuiApplication::screenRemoved, greeter,
[safeWindow](QScreen *screenRemoved) {
if (!safeWindow)           // window was already destroyed
return;
if (safeWindow->screen() == screenRemoved) {
// handle screen removal
}
});

QPointer is automatically zeroed when the pointed-to QObject is destroyed,
making the null check safe without requiring manual lifecycle management.

Additionally, the connection should be disconnected or the lambda should
become a no-op once the greeter has finished initializing, to avoid acting
on screen topology changes that arrive after startup is complete.




WORKAROUND

None currently known that does not involve modifying the binary or compositor
configuration. The crash occurs on every cold boot; warm reboots may or may
not reproduce depending on compositor state at startup.




REPRODUCTION

Cold boot on affected hardware (confirmed single-monitor Wayland system)

Observe greeter fail to display

Confirm via: journalctl -b | grep plasma-login-greeter
dmesg | grep plasma-login-gr
coredumpctl list

Approximate time to crash from boot: 140 seconds (varies by hardware).




CORE DUMP

Captured via systemd-coredump.
coredumpctl info 2275

Storage: /var/lib/systemd/coredump/
core.plasma-login-gr.967..2275..zst
Size:    8.4M (compressed)
4