SUMMARY STEPS TO REPRODUCE 1. create an audio alarm with any sound of your choice 2. check "set volume" and make it any value except 0% 3. click "Try" OBSERVED RESULT KAlarm crashes EXPECTED RESULT Kalarm does not crash, and the sound plays. SOFTWARE/OS VERSIONS Linux/KDE Plasma: Fedora 42 KDE Plasma Version: 6.4.4 KDE Frameworks Version: 6.17.0 Qt Version: 6.9.1 ADDITIONAL INFORMATION There was no special configuration done on KAlarm. It crashes 100% of the time. This was not happening on Fedora 39. Backtrace (first time trying to gen and submit one, let me know if it's wrong or missing information) : #0 0x00007ffff4a83404 in pthread_mutex_lock@@GLIBC_2.2.5 () at /lib64/libc.so.6 #1 0x00007fffee94c9e5 in do_lock.isra () at /lib64/libpipewire-0.3.so.0 #2 0x00007fffee94d1d5 in pw_thread_loop_lock () at /lib64/libpipewire-0.3.so.0 #3 0x00007fffc0380e16 in vlc_pw_stream_set_volume () at /usr/lib64/vlc/plugins/audio_output/libaout_pipewire_plugin.so #4 0x00007fffc0380f60 in VolumeSet () at /usr/lib64/vlc/plugins/audio_output/libaout_pipewire_plugin.so #5 0x00007fffc31497a6 in aout_OutputUnlock () at /lib64/libvlccore.so.9 #6 0x00007fffc314fe08 in aout_VolumeSet () at /lib64/libvlccore.so.9 #7 0x00007fffc31e5fdb in libvlc_audio_set_volume () at /lib64/libvlc.so.5 #8 0x00007fffcedfe3d5 in AudioPlayerVlc::play (this=0x7fff90001ad0) at /usr/src/debug/kalarm-25.08.0-1.fc42.x86_64/src/audioplugin/audioplayer_vlc.cpp:123 #9 0x000055555564dab8 in AudioPlayerThread::checkAudioPlay (this=0x555556b12fa0) at /usr/src/debug/kalarm-25.08.0-1.fc42.x86_64/src/messagedisplayhelper.cpp:1105 #10 0x000055555564dfad in AudioPlayerThread::execute (this=0x555556b12fa0) at /usr/src/debug/kalarm-25.08.0-1.fc42.x86_64/src/messagedisplayhelper.cpp:1051 #11 0x00007ffff51658b7 in void doActivate<false>(QObject*, int, void**) () at /lib64/libQt6Core.so.6 #12 0x00007ffff5225f63 in QThread::started(QThread::QPrivateSignal) () at /lib64/libQt6Core.so.6 #13 0x00007ffff52c5b88 in QThreadPrivate::start(void*) () at /lib64/libQt6Core.so.6 #14 0x00007ffff4a7ff54 in start_thread () at /lib64/libc.so.6 #15 0x00007ffff4b0332c in __clone3 () at /lib64/libc.so.6
KAlarm in Fedora 39 was version 3.6, from KDE Gear 23.08. It used Phonon to play sounds. Because of the number of bugs reported for KAlarm relating to audio output (probably due to Phonon not being thread safe - see Bug 481334), it now uses VLC or MPV to play sounds. This could explain why you see the crash now, but not on Fedora 39. Provided that the distro has built KAlarm with both VLC and MPV options, the user can select which to use, although distros may only provide one of these options. If your version of KAlarm provides an MPV option (see Settings -> Configure KAlarm), you could try selecting MPV instead of VLC. The crash trace suggests that it's a bug in either VLC or libpipewire which has caused the crash, possibly related to your audio hardware. On my development system, using VLC version 3.0.20 and libpipewire 0.3, I don't get a crash when I set the volume, so I can't investigate it. It looks like Fedora 42 uses VLC version 3.0.21, so I can't test using an identical VLC version.
This crash is very similar to Bug 497742, which was on Fedora 41.