Lmms: Problems with export of project with Sample Track

Created on 11 Feb 2017 · 12Comments · Source: LMMS/lmms

As discussed in PR https://github.com/LMMS/lmms/pull/3341 there is some issues with exporting projects containing a Sample Track. I've only seen this when using SDL. ALSA works fine and other sound engines I haven't tried.

The renderer process will simply hang and never return to main(). If you do a --rendertracks export it will stop on the first Sample Track it tries tor render.

I'm not done bisecting this but it may have happened around these commits 8497d39eec78f3f23f0581898e18868025d5070e e55ec80c3d956dea8674afc0755bc87831c64ce6

bug core

Source

zonkmachine

All 12 comments

(gdb)   thread apply all bt full

Thread 2 (Thread 0x7fffdffc5700 (LWP 21314)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
No locals.
#1  0x00007ffff685a816 in wait (time=18446744073709551615, this=0xb84070) at thread/qwaitcondition_unix.cpp:86
        code = <optimized out>
#2  QWaitCondition::wait (this=<optimized out>, mutex=0x7fffdffc4e40, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:158
No locals.
#3  0x0000000000535596 in MixerWorkerThread::run (this=0xa01840) at /home/zonkmachine/builds/lmms/lmms/src/core/MixerWorkerThread.cpp:162
        m = {d = 0x7fffd80013d0}
#4  0x00007ffff685a32f in QThreadPrivate::start (arg=0xa01840) at thread/qthread_unix.cpp:349
        __clframe = {__cancel_routine = 0x7ffff6859300 <QThreadPrivate::finish(void*)>, __cancel_arg = 0xa01840, __do_it = 1, 
          __cancel_type = <optimized out>}
        thr = 0xa01840
        data = <optimized out>
        objectName = {static null = {<No data fields>}, static shared_null = {ref = {_q_value = 1743}, alloc = 0, size = 0, 
            data = 0x7ffff6cc293a <QString::shared_null+26>, clean = 0, simpletext = 0, righttoleft = 0, asciiCache = 0, capacity = 0, reserved = 0, 
            array = {0}}, static shared_empty = {ref = {_q_value = 2}, alloc = 0, size = 0, data = 0x7ffff6cc291a <QString::shared_empty+26>, clean = 0, 
            simpletext = 0, righttoleft = 0, asciiCache = 0, capacity = 0, reserved = 0, array = {0}}, d = 0x7ffff6cc2920 <QString::shared_null>, 
          static codecForCStrings = 0x0}
#5  0x00007ffff7bc4184 in start_thread (arg=0x7fffdffc5700) at pthread_create.c:312
        __res = <optimized out>
        pd = 0x7fffdffc5700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140736951244544, -2079227267844162622, 1, 0, 140736951245248, 140736951244544, 2079156870619577282, 
                2079245381250431938}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <optimized out>
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#6  0x00007ffff3f35ffd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
No locals.

Thread 1 (Thread 0x7ffff7fab7c0 (LWP 21310)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
No locals.
#1  0x00007ffff685a816 in wait (time=18446744073709551615, this=0xa01e60) at thread/qwaitcondition_unix.cpp:86
        code = <optimized out>
#2  QWaitCondition::wait (this=<optimized out>, mutex=0xb7bff8, time=18446744073709551615) at thread/qwaitcondition_unix.cpp:158
No locals.
#3  0x0000000000530ce0 in Mixer::requestChangeInModel (this=0xb7bec0) at /home/zonkmachine/builds/lmms/lmms/src/core/Mixer.cpp:773
No locals.
#4  0x0000000000530a58 in Mixer::removePlayHandlesOfTypes (this=0xb7bec0, _track=0x7fffeac2a420, types=4 '\004')
    at /home/zonkmachine/builds/lmms/lmms/src/core/Mixer.cpp:734
        it = {i = 0x1}
#5  0x000000000062f0e3 in SampleTCO::playbackPositionChanged (this=0x7fffeac2a820) at /home/zonkmachine/builds/lmms/lmms/src/tracks/SampleTrack.cpp:168
        st = 0x7ffff6962e09 <QMetaObject::cast(QObject*) const+25>
#6  0x00000000006402af in SampleTCO::qt_static_metacall (_o=0x7fffeac2a820, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0x7fffa4003270)
    at /home/zonkmachine/builds/lmms/lmms/build/src/moc_SampleTrack.cpp:65
        _t = 0x7fffeac2a820
#7  0x00007ffff6974c1e in QObject::event (this=0x7fffeac2a820, e=<optimized out>) at kernel/qobject.cpp:1194
---Type <return> to continue, or q <return> to quit---
        mce = <optimized out>
        currentSender = {sender = 0xb80160, signal = 9, ref = 1}
        previousSender = 0x0

zonkmachine on 24 Jul 2017

Reproduced with ALSA.

PhysSong on 26 Jul 2017

@PhysSong can you elaborate
How long was the sample?
Where in the project was it placed?
Was there other tracks in the project (upload project on lsp
Was it a cmd-line export, and how did it go if the export was internal from menu?
Ogg or wave or both?

musikBear on 26 Jul 2017

@musikBear I can reproduce it for various samples. I used gui, and the exported file has .wav extension.
However, It seems to be a bug of LMMS core. I think it is from thread synchronization.

PhysSong on 26 Jul 2017

I think 5606a04 may be related. @jasp00 may know what goes wrong.

PhysSong on 27 Jul 2017

I used gui, : a bug of LMMS core. I think it is from thread synchronization.

Then its a critical :/

musikBear on 27 Jul 2017

Revert 8497d39: still stops.
Revert e55ec80: still stops.
Revert 5606a04: haven't tested yet.

PhysSong on 29 Jul 2017

After the exporting ends, ProjectRenderer::run() calls Song::stopExport(), it calls Song::stop(), and it emits playbackStateChanged(), so SampleTCO::playbackPositionChanged() receives the signal.

requestChangeInModel() waits for runChangesInModel(), which is called by AudioDevice::getNextBuffer() while exporting, or Mixer::fifoWriter::run() otherwise.
So, runChangesInModel() is never called between the end of export and the calling of restoreAudioDevice() in ~ProjectRenderer().

However, ~ProjectRenderer() isn't called until finished() signal is emitted by renderer. To be emitted finished(), event handling must be finished, but SampleTCO::playbackPositionChanged() is still waiting. Now there's a deadlock!

PhysSong on 30 Jul 2017

Easy to fix?

zonkmachine on 30 Jul 2017

I'm testing a simple fix: postpone the emitting of playbackStateChanged(). It looks fine, but I need more testings.

PhysSong on 30 Jul 2017

👍1