From 32b7e0418b55d2fb6e45bff9a32103e532a9dab5 Mon Sep 17 00:00:00 2001
From: Fastigium <fastigiummusic@gmail.com>
Date: Mon, 14 Mar 2016 13:37:00 +0100
Subject: [PATCH] Fix two crashes when deleting FX channels

Lock the mixer before performing a channel delete to prevent any race
conditions causing a crash. Also, update the audioport FX channel when
an InstrumentTrack's FX channel is changed to prevent the audioport
mixing to a nonexistent channel.
---
 include/FxMixer.h              |  1 -
 include/InstrumentTrack.h      |  1 +
 src/core/FxMixer.cpp           | 13 +++++--------
 src/tracks/InstrumentTrack.cpp | 11 +++++++++--
 4 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/include/FxMixer.h b/include/FxMixer.h
index ac5c72530..a00df914a 100644
--- a/include/FxMixer.h
+++ b/include/FxMixer.h
@@ -56,7 +56,6 @@ class FxChannel : public ThreadableJob
 		BoolModel m_soloModel;
 		FloatModel m_volumeModel;
 		QString m_name;
-		QMutex m_lock;
 		int m_channelIndex; // what channel index are we
 		bool m_queued; // are we queued up for rendering yet?
 		bool m_muted; // are we muted? updated per period so we don't have to call m_muteModel.value() twice
diff --git a/include/InstrumentTrack.h b/include/InstrumentTrack.h
index 4067d2d37..f24097c9d 100644
--- a/include/InstrumentTrack.h
+++ b/include/InstrumentTrack.h
@@ -227,6 +227,7 @@ protected slots:
 	void updateBaseNote();
 	void updatePitch();
 	void updatePitchRange();
+	void updateEffectChannel();
 
 
 private:
diff --git a/src/core/FxMixer.cpp b/src/core/FxMixer.cpp
index be4378bd8..6ed83d45b 100644
--- a/src/core/FxMixer.cpp
+++ b/src/core/FxMixer.cpp
@@ -68,7 +68,6 @@ FxChannel::FxChannel( int idx, Model * _parent ) :
 	m_soloModel( false, _parent ),
 	m_volumeModel( 1.0, 0.0, 2.0, 0.001, _parent ),
 	m_name(),
-	m_lock(),
 	m_channelIndex( idx ),
 	m_queued( false ),
 	m_dependenciesMet( 0 )
@@ -284,7 +283,8 @@ void FxMixer::toggledSolo()
 
 void FxMixer::deleteChannel( int index )
 {
-	m_fxChannels[index]->m_lock.lock();
+	// lock the mixer so channel deletion is performed between mixer rounds
+	Engine::mixer()->lock();
 
 	FxChannel * ch = m_fxChannels[index];
 
@@ -344,6 +344,8 @@ void FxMixer::deleteChannel( int index )
 			r->updateName();
 		}
 	}
+
+	Engine::mixer()->unlock();
 }
 
 
@@ -543,15 +545,10 @@ FloatModel * FxMixer::channelSendModel( fx_ch_t fromChannel, fx_ch_t toChannel )
 
 void FxMixer::mixToChannel( const sampleFrame * _buf, fx_ch_t _ch )
 {
-	// The first check is for the case where the last fxchannel was deleted but
-	// there was a race condition where it had to be processed.
-	if( _ch < m_fxChannels.size() &&
-			m_fxChannels[_ch]->m_muteModel.value() == false )
+	if( m_fxChannels[_ch]->m_muteModel.value() == false )
 	{
-		m_fxChannels[_ch]->m_lock.lock();
 		MixHelpers::add( m_fxChannels[_ch]->m_buffer, _buf, Engine::mixer()->framesPerPeriod() );
 		m_fxChannels[_ch]->m_hasInput = true;
-		m_fxChannels[_ch]->m_lock.unlock();
 	}
 }
 
diff --git a/src/tracks/InstrumentTrack.cpp b/src/tracks/InstrumentTrack.cpp
index d1eb5bc1e..b98c9a1d5 100644
--- a/src/tracks/InstrumentTrack.cpp
+++ b/src/tracks/InstrumentTrack.cpp
@@ -139,6 +139,7 @@ InstrumentTrack::InstrumentTrack( TrackContainer* tc ) :
 	connect( &m_baseNoteModel, SIGNAL( dataChanged() ), this, SLOT( updateBaseNote() ) );
 	connect( &m_pitchModel, SIGNAL( dataChanged() ), this, SLOT( updatePitch() ) );
 	connect( &m_pitchRangeModel, SIGNAL( dataChanged() ), this, SLOT( updatePitchRange() ) );
+	connect( &m_effectChannelModel, SIGNAL( dataChanged() ), this, SLOT( updateEffectChannel() ) );
 }
 
 
@@ -220,8 +221,6 @@ void InstrumentTrack::processAudioBuffer( sampleFrame* buf, const fpp_t frames,
 			}
 		}
 	}
-
-	m_audioPort.setNextFxChannel( m_effectChannelModel.value() );
 }
 
 
@@ -558,6 +557,14 @@ void InstrumentTrack::updatePitchRange()
 
 
 
+void InstrumentTrack::updateEffectChannel()
+{
+	m_audioPort.setNextFxChannel( m_effectChannelModel.value() );
+}
+
+
+
+
 int InstrumentTrack::masterKey( int _midi_key ) const
 {