Qt assertion failure sending events to TIO from wrong thread

[RJ Skerry-Ryan]

Reported on the forums, reproducible:

Debug [AnalyserQueue 1]: Beat Calculation complete
Fatal [AnalyserQueue 1]: ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to objects owned by a different thread. Current thread 110dc79d0. Receiver '' (of type 'TrackInfoObject') was created in thread 105500080", file kernel/qcoreapplication.cpp, line 539

This is caused when we delete a track's BeatGrid/BeatMap from the analyzer thread.

Oddly, setParent_helper should only be called in ~QObject when the object's parent is non-NULL and both BeatMap and BeatGrid have NULL parents.

#7 0x0000000101476fc7 in QCoreApplicationPrivate::checkReceiverThread (this=0x105566cf0, receiver=0x1bca41780) at kernel/qcoreapplication.cpp:531
#8 0x0000000101a37398 in QApplication::notify (this=0x7fff5fbff078, receiver=0x1bca41780, e=0x13656a588) at qapplication.cpp:3841
#9 0x0000000100672039 in MixxxApplication::notify (this=0x7fff5fbff078, target=0x1bca41780, event=0x13656a588) at src/mixxxapplication.cpp:138
#10 0x00000001014791d4 in QCoreApplication::notifyInternal (this=0x7fff5fbff078, receiver=0x1bca41780, event=0x13656a588) at kernel/qcoreapplication.cpp:953
#11 0x000000010147d4f4 in QCoreApplication::sendEvent (receiver=0x1bca41780, event=0x13656a588) at qcoreapplication.h:231
#12 0x000000010149a06b in QObjectPrivate::setParent_helper (this=0x1bca41e90, o=0x0) at kernel/qobject.cpp:1933
#13 0x0000000101499cdd in QObject::~QObject (this=0x1bca41d10) at kernel/qobject.cpp:931
#14 0x0000000100745308 in BeatMap::~BeatMap (this=0x1bca41d10) at src/track/beatmap.cpp:88
#15 0x00000001007453d5 in BeatMap::~BeatMap (this=0x1bca41d10) at src/track/beatmap.cpp:87
#16 0x0000000100745428 in BeatMap::~BeatMap (this=0x1bca41d10) at src/track/beatmap.cpp:87
#17 0x000000010073fed6 in BeatFactory::deleteBeats (pBeats=0x1bca41d20) at src/track/beatfactory.cpp:138
#18 0x000000010074236a in QtSharedPointer::executeDeleter<Beats, void (*)(Beats*)> (t=0x1bca41d20, d=0x10073fe30 <BeatFactory::deleteBeats(Beats*)>) at qsharedpointer_impl.h:118
#19 0x00000001007422e9 in QtSharedPointer::ExternalRefCountWithCustomDeleter<Beats, void (*)(Beats*)>::deleter (self=0x1bca423f0) at qsharedpointer_impl.h:249
#20 0x00000001004753db in QtSharedPointer::ExternalRefCountWithDestroyFn::destroy (this=0x1bca423f0) at qsharedpointer_impl.h:219
#21 0x000000010009c40a in QtSharedPointer::ExternalRefCount<Beats>::deref (d=0x1bca423f0, value=0x1bca41d20) at qsharedpointer_impl.h:341
#22 0x000000010009c3af in QtSharedPointer::ExternalRefCount<Beats>::deref (this=0x13656aa60) at qsharedpointer_impl.h:336
#23 0x000000010009c385 in QtSharedPointer::ExternalRefCount<Beats>::~ExternalRefCount (this=0x13656aa60) at qsharedpointer_impl.h:401
#24 0x000000010009c365 in QSharedPointer<Beats>::~QSharedPointer (this=0x13656aa60) at qsharedpointer_impl.h:466
#25 0x000000010009b025 in QSharedPointer<Beats>::~QSharedPointer (this=0x13656aa60) at qsharedpointer_impl.h:466
#26 0x000000010009ab42 in AnalyserBeats::finalise (this=0x110dc8700, tio=<value temporarily unavailable, due to optimizations>) at src/analyserbeats.cpp:259

[RJ Skerry-Ryan (rryan)]

The event that is sent to the TIO is a QEvent::ChildRemoved event. I forgot that we parent the BeatGrid/BeatMap to the TIO here:
https://github.com/mixxxdj/mixxx/blob/master/src/track/beatfactory.cpp#L18

[RJ Skerry-Ryan (rryan)]

Hopefully fixed in
https://github.com/mixxxdj/mixxx/commit/80ab6ac5215d3d0c1f039655bf5a9d0fe8009fc2

[Michael S. (arbeit-u)]

I am nosey :-). But i must wait with testing until buildserver will start to work.

[Michael S. (arbeit-u)]

Test with W7/64 build 5124 over more as one hour:
Analysed over 170 flac in back. Playing with 2 decks. Pre hear songs and interupt loading song in free deck. YES it runs !

Grafik waveform has some hickups. Everytime while load file or scrolling in songlist. Not so critical because music is still playing correct. I remember (?) something read about this in other bugreport before.

Thanks ... looks gooooooood

[RJ Skerry-Ryan (rryan)]

Thank you for testing, Michael!

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7790