segfault in DSP::Delay::get

[Stephane Bernaud]

while trying to reproduce segfault described in #1810381, i was able to find a way to produce another segfault that i could easily reproduce :
 - load a song
 - play it
 - really quickly activate/deactivate effect bank 1 AND, in the same time, activate/deactivate (really quickly too) reverb (effect bank 1 / slot 3)
 - after few seconds a segfault is signaled

I have a core generated for this segfault.
Here is a backtrace :

Core was generated by `./bin/mixxx'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 DSP::Delay::get (this=0x562c2018a848) at lib/reverb/dsp/Delay.h:75
75 sample_t x = data [read];

Thread 1 (Thread 0x7f355dffb700 (LWP 3594)):
#0 0x0000562bfe35513f in DSP::Delay::get() (this=0x562c2018a848) at lib/reverb/dsp/Delay.h:75
#1 0x0000562bfe35513f in Lattice::process(float, double) (d=0, x=<optimized out>, this=0x562c2018a848)
    at lib/reverb/Reverb.h:65
#2 0x0000562bfe35513f in PlateStub::process(float, float, float*, float*) (this=this@entry=0x562c2018a82
0, x=<optimized out>, decay=decay@entry=0.444999993, _xl=_xl@entry=0x7f35a5418020, _xr=0x7f35a5418020,
    _xr@entry=0x7f35a5418024) at lib/reverb/Reverb.cc:249
#3 0x0000562bfe355be7 in MixxxPlateX2::processBuffer(float const*, float*, unsigned int, float, float, f
loat, float, float) (this=this@entry=0x562c2018a820, in=in@entry=0x7f35a537b020, out=out@entry=0x7f35a541
8020, frames=<optimized out>, bandwidthParam=<optimized out>, decayParam=<optimized out>, dampingParam=0,
 currentSend=currentSend@entry=0.111572266, previousSend=<optimized out>) at lib/reverb/Reverb.cc:458
#4 0x0000562bfe554e65 in ReverbEffect::processChannel(ChannelHandle const&, ReverbGroupState*, float const*, float*, mixxx::EngineParameters const&, EffectEnableState, GroupFeatureState const&) (this=<optimized out>, handle=..., pState=0x562c2018a810, pInput=0x7f35a537b020, pOutput=0x7f35a5418020, bufferParameters=..., enableState=EffectEnableState::Disabling, groupFeatures=...)
    at src/effects/builtin/reverbeffect.cpp:117
#5 0x0000562bfe55982e in EffectProcessorImpl<ReverbGroupState>::process(ChannelHandle const&, ChannelHandle const&, float const*, float*, mixxx::EngineParameters const&, EffectEnableState, GroupFeatureState const&) (this=0x7f35a516e010, inputHandle=..., outputHandle=..., pInput=0x7f35a537b020, pOutput=0x7f35a5418020, bufferParameters=..., enableState=EffectEnableState::Disabling, groupFeatures=...)
    at src/effects/effectprocessor.h:157
#6 0x0000562bfe64b0e2 in EngineEffect::process(ChannelHandle const&, ChannelHandle const&, float const*, float*, unsigned int, unsigned int, EffectEnableState, GroupFeatureState const&) (this=this@entry=0x7f35a51f1010, inputHandle=..., outputHandle=..., pInput=pInput@entry=0x7f35a537b020, pOutput=pOutput@entry=0x7f35a5418020, numSamples=numSamples@entry=2048, sampleRate=44100, chainEnableState=<optimized out>, groupFeatures=...) at src/engine/effects/engineeffect.cpp:197
#7 0x0000562bfe64e926 in EngineEffectChain::process(ChannelHandle const&, ChannelHandle const&, float*, float*, unsigned int, unsigned int, GroupFeatureState const&) (this=this@entry=0x7f35a54b5010, inputHandle=..., outputHandle=..., pIn=pIn@entry=0x7f3668066020, pOut=pOut@entry=0x7f35d6b16020, numSamples=numSamples@entry=2048, sampleRate=<optimized out>, groupFeatures=...)
    at src/engine/effects/engineeffectchain.cpp:277
#8 0x0000562bfe652ffd in EngineEffectRack::process(ChannelHandle const&, ChannelHandle const&, float*, float*, unsigned int, unsigned int, GroupFeatureState const&) (this=this@entry=0x562bffa17050, inputHandle=..., outputHandle=..., pIn=pIn@entry=0x7f3668066020, pOut=pOut@entry=0x7f3660713020, numSamples=2048, sampleRate=44100, groupFeatures=...) at src/engine/effects/engineeffectrack.cpp:79
#9 0x0000562bfe65473f in EngineEffectsManager::processInner(SignalProcessingStage, ChannelHandle const&, ChannelHandle const&, float*, float*, unsigned int, unsigned int, GroupFeatureState const&, float, float) (this=this@entry=0x562bff85b9f0, stage=stage@entry=SignalProcessingStage::Postfader, inputHandle=..., outputHandle=..., pIn=<optimized out>, pOut=pOut@entry=0x7f366037a020, numSamples=<optimized out>, sampleRate=<optimized out>, groupFeatures=..., oldGain=oldGain@entry=0, newGain=<optimized out>)
    at src/engine/effects/engineeffectsmanager.cpp:222
#10 0x0000562bfe6551a5 in EngineEffectsManager::processPostFaderAndMix(ChannelHandle const&, ChannelHandle const&, float*, float*, unsigned int, unsigned int, GroupFeatureState const&, float, float) (this=this@entry=0x562bff85b9f0, inputHandle=..., outputHandle=..., pIn=<optimized out>, pOut=pOut@entry=0x7f366037a020, numSamples=numSamples@entry=2048, sampleRate=44100, groupFeatures=..., oldGain=oldGain@entry=0, newGain=<optimized out>) at src/engine/effects/engineeffectsmanager.cpp:164
#11 0x0000562bfe5e78a5 in ChannelMixer::applyEffectsAndMixChannels(EngineMaster::GainCalculator const&, QVarLengthArray<EngineMaster::ChannelInfo*, 64>*, QVarLengthArray<EngineMaster::GainCache, 64>*, float*, ChannelHandle const&, unsigned int, unsigned int, EngineEffectsManager*) (gainCalculator=..., activeChannels=activeChannels@entry=0x562bff8b99b8, channelGainCache=channelGainCache@entry=0x562bff8b8d58, pOutput=0x7f366037a020, outputHandle=..., iBufferSize=2048, iSampleRate=44100, pEngineEffectsManager=0x562bff85b9f0) at src/engine/channelmixer_autogen.cpp:48
#12 0x0000562bfe679f6c in EngineMaster::process(int) (this=0x562bff8b88f0, iBufferSize=iBufferSize@entry=2048) at src/engine/enginemaster.cpp:422

(gdb) p read
$1 = 0
(gdb) p data
$2 = (sample_t *) 0x0

Operating system :
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.1 LTS
Release: 18.04
Codename: bionic

CPU architecture : Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz
$ uname -a
Linux oleg 4.15.0-43-generic #46-Ubuntu SMP Thu Dec 6 14:45:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Your video
$ sudo lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 620 (rev 02)

sound hardware
traktor kontrol S4 mk2 one

mixxx version : 2.2

git log --max-count=1
commit 56b2c05d16a7ddf893b356e4bd4562e7ceccd627 (HEAD -> 2.2, origin/2.2)
Merge: 98c1be601 0e13a3d38
Author: RJ Skerry-Ryan <email address hidden>
Date: Tue Jan 1 08:05:42 2019 -0800

    Merge pull request #1970 from sblaisot/2.2-2019

[Be (be.ing)]

Does this happen with other effects or only Reverb?

[Stephane Bernaud (uraoul)]

for now, i can only reproduce with reverb.

Activating cue button (the one that sends the track to headphone) while reverb effect is on can triggers this segfault too.

[Daniel Schürmann (daschuer)]

I cannot reproduce this with Mixxx 2.2.1 on ubuntu Xenial.

The backtrace looks as if the delay[] is accessed before setup or after destroying.
I have just checked but the delay object is always used from the same thread, so I cannot explain how this can happen.

Can you still produce it with lasted Mixxx Version 2.2.1?

[Daniel Schürmann (daschuer)]

I have removed the milestone to let it expire.

[Launchpad Janitor (janitor)]

[Expired for Mixxx because there has been no activity for 60 days.]

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/9563