Created attachment 147251 [details]
journal for a boot where the black screen problem happened with the xdg-desktop-portal-kde crashes.

SUMMARY

Logging out of Plasma 5.24.2 on Wayland in a Fedora 36 KDE Plasma installation sometimes showed a black screen with a blinking underscore _ at the top left of the screen. This black screen problem happened about 20-30% of the time when logging out. plasmashell and powerdevil aborted usually 5 times each on some such logouts with errors that the Wayland connection had broken. xdg-desktop-portal-kde aborted multiple times on other logouts with the same errors. Traces of plasmashell and xdg-desktop-portal-kde crashes are the following.

Core was generated by `/usr/bin/plasmashell --no-respawn'.
Program terminated with signal SIGABRT, Aborted.

#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, 
    no_tid=no_tid@entry=0) at pthread_kill.c:44
44            return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
(gdb) bt
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, 
    no_tid=no_tid@entry=0) at pthread_kill.c:44
#1  0x00007efe10755f43 in __pthread_kill_internal (signo=6, threadid=<optimized out>)
    at pthread_kill.c:78
#2  0x00007efe10705a36 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3  0x00007efe106ef82f in __GI_abort () at abort.c:79
#4  0x00007efe10bb4517 in qt_message_fatal (message=<synthetic pointer>..., context=...)
    at global/qlogging.cpp:1914
#5  QMessageLogger::fatal (this=this@entry=0x7ffdf43de820, msg=msg@entry=0x7efe115ea407 "%s")
    at global/qlogging.cpp:893
#6  0x00007efe111f60ef in init_platform (argv=<optimized out>, argc=<optimized out>, 
    platformThemeName=..., platformPluginPath=..., pluginNamesWithArguments=...)
    at kernel/qguiapplication.cpp:1254
#7  QGuiApplicationPrivate::createPlatformIntegration (this=0x55f08fd64ed0)
    at kernel/qguiapplication.cpp:1474
#8  0x00007efe111f65c8 in QGuiApplicationPrivate::createEventDispatcher (this=<optimized out>)
    at kernel/qguiapplication.cpp:1491
#9  0x00007efe10db2be1 in QCoreApplicationPrivate::init (this=this@entry=0x55f08fd64ed0)
    at kernel/qcoreapplication.cpp:835
#10 0x00007efe111f8973 in QGuiApplicationPrivate::init (this=this@entry=0x55f08fd64ed0)
    at kernel/qguiapplication.cpp:1520
#11 0x00007efe11a8672d in QApplicationPrivate::init (this=0x55f08fd64ed0)
    at kernel/qapplication.cpp:513
#12 0x000055f08fb330a0 in main (argc=<optimized out>, argv=0x7ffdf43ded88)
--Type <RET> for more, q to quit, c to continue without paging--c
    at /usr/src/debug/plasma-workspace-5.24.2-1.fc36.x86_64/shell/main.cpp:82

Core was generated by `/usr/libexec/xdg-desktop-portal-kde'.
Missing separate debuginfos, use: dnf debuginfo-install xdg-desktop-portal-kde-5.24.2-1.fc36.x86_64
--Type <RET> for more, q to quit, c to continue without paging--
Program terminated with signal SIGABRT, Aborted.
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, 
    no_tid=no_tid@entry=0) at pthread_kill.c:44
44            return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
(gdb) bt
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, 
    no_tid=no_tid@entry=0) at pthread_kill.c:44
#1  0x00007f028b20dea3 in __pthread_kill_internal (signo=6, threadid=<optimized out>)
    at pthread_kill.c:78
#2  0x00007f028b1bda16 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#3  0x00007f028b1a782f in __GI_abort () at abort.c:79
#4  0x00007f028b66c517 in qt_message_fatal (message=<synthetic pointer>..., context=...)
    at global/qlogging.cpp:1914
#5  QMessageLogger::fatal (this=this@entry=0x7ffd17e9bf70, msg=msg@entry=0x7f028c89a407 "%s")
    at global/qlogging.cpp:893
#6  0x00007f028c4a60ef in init_platform (argv=<optimized out>, argc=<optimized out>, 
    platformThemeName=..., platformPluginPath=..., pluginNamesWithArguments=...)
    at kernel/qguiapplication.cpp:1254
#7  QGuiApplicationPrivate::createPlatformIntegration (this=0x56223197cb20)
    at kernel/qguiapplication.cpp:1474
#8  0x00007f028c4a65c8 in QGuiApplicationPrivate::createEventDispatcher (this=<optimized out>)
    at kernel/qguiapplication.cpp:1491
#9  0x00007f028b86abe1 in QCoreApplicationPrivate::init (this=this@entry=0x56223197cb20)
    at kernel/qcoreapplication.cpp:835
#10 0x00007f028c4a8973 in QGuiApplicationPrivate::init (this=this@entry=0x56223197cb20)
    at kernel/qguiapplication.cpp:1520
#11 0x00007f028d09672d in QApplicationPrivate::init (this=0x56223197cb20)
    at kernel/qapplication.cpp:513
#12 0x00005622306fc423 in main ()

When I switched to another VT and logged in, loginctl showed that the first user session I logged out from was still active. The user session might not have been stopped properly maybe due to the crashes. Running sudo systemctl restart sddm made sddm appear again.

STEPS TO REPRODUCE
1. Boot a Fedora 36 KDE Plasma installation updated to 2022-3-2 with updates-testing enabled
2. Log into Plasma on Wayland from sddm on Wayland
3. Log out of Plasma
4. If the problem didn't happen, repeat 2-3 until it does

OBSERVED RESULT
Logging out of Plasma on Wayland sometimes resulted in a black screen and plasmashell, powerdevil, and xde-desktop-portal-kde aborts

EXPECTED RESULT
Plasma would log out to sddm normally

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 36
(available in About System)
KDE Plasma Version: 5.24.2
KDE Frameworks Version: 5.91.0
Qt Version: 5.15.2 + KDE Qt patches

ADDITIONAL INFORMATION
I'll attach the journal for a boot where the black screen problem happened with the xdg-desktop-portal-kde crashes.