Fix occasional audio interface deadlock (#4450)

include/AudioJack.h

@@ -37,7 +37,6 @@
 #include <QtCore/QVector>
 #include <QtCore/QList>
 #include <QtCore/QMap>
-#include <QMutexLocker>
 
 #include "AudioDevice.h"
 #include "AudioDeviceSetupWidget.h"
@@ -108,7 +107,6 @@ private:
 
 	bool m_active;
 	bool m_stopped;
-	QMutex m_processingMutex;
 
 	MidiJack *m_midiClient;
 	QVector<jack_port_t *> m_outputPorts;

include/AudioPortAudio.h

@@ -145,7 +145,6 @@ private:
 	int m_outBufSize;
 
 	bool m_stopped;
-	QSemaphore m_stopSemaphore;
 
 } ;
 

include/AudioSoundIo.h

@@ -109,6 +109,8 @@ private:
 	fpp_t m_outBufFramesTotal;
 	fpp_t m_outBufFrameIndex;
 
+	bool m_stopped;
+
 	int m_disconnectErr;
 	void onBackendDisconnect(int err);
 

include/fifo_buffer.h

@@ -66,6 +66,12 @@ public:
 		return( element );
 	}
 
+	void waitUntilRead()
+	{
+		m_writer_sem.acquire( m_size );
+		m_writer_sem.release( m_size );
+	}
+
 	bool available()
 	{
 		return( m_reader_sem.available() );

src/core/Mixer.cpp

@@ -640,7 +640,7 @@ void Mixer::storeAudioDevice()
 
 void Mixer::restoreAudioDevice()
 {
-	if( m_oldAudioDev != NULL )
+	if( m_oldAudioDev && m_audioDev != m_oldAudioDev )
 	{
 		stopProcessing();
 		delete m_audioDev;
@@ -648,9 +648,9 @@ void Mixer::restoreAudioDevice()
 		m_audioDev = m_oldAudioDev;
 		emit sampleRateChanged();
 
-		m_oldAudioDev = NULL;
 		startProcessing();
 	}
+	m_oldAudioDev = NULL;
 }
 
 
@@ -1127,7 +1127,9 @@ void Mixer::fifoWriter::run()
 		write( buffer );
 	}
 
+	// Let audio backend stop processing
 	write( NULL );
+	m_fifo->waitUntilRead();
 }
 
 

src/core/audio/AudioJack.cpp

@@ -201,7 +201,6 @@ bool AudioJack::initJackClient()
 
 void AudioJack::startProcessing()
 {
-	QMutexLocker m( &m_processingMutex );
 	m_stopped = false;
 
 	if( m_active || m_client == NULL )
@@ -254,7 +253,6 @@ void AudioJack::startProcessing()
 
 void AudioJack::stopProcessing()
 {
-	QMutexLocker m( &m_processingMutex );
 	m_stopped = true;
 }
 
@@ -342,7 +340,6 @@ void AudioJack::renamePort( AudioPort * _port )
 
 int AudioJack::processCallback( jack_nframes_t _nframes, void * _udata )
 {
-	QMutexLocker m( &m_processingMutex );
 
 	// do midi processing first so that midi input can
 	// add to the following sound processing
@@ -406,6 +403,7 @@ int AudioJack::processCallback( jack_nframes_t _nframes, void * _udata )
 			m_framesDoneInCurBuf = 0;
 			if( !m_framesToDoInCurBuf )
 			{
+				m_stopped = true;
 				break;
 			}
 		}

src/core/audio/AudioPortAudio.cpp

@@ -57,8 +57,7 @@ AudioPortAudio::AudioPortAudio( bool & _success_ful, Mixer * _mixer ) :
 	m_paStream( NULL ),
 	m_wasPAInitError( false ),
 	m_outBuf( new surroundSampleFrame[mixer()->framesPerPeriod()] ),
-	m_outBufPos( 0 ),
-	m_stopSemaphore( 1 )
+	m_outBufPos( 0 )
 {
 	_success_ful = false;
 
@@ -167,8 +166,6 @@ AudioPortAudio::AudioPortAudio( bool & _success_ful, Mixer * _mixer ) :
 	printf( "Input device: '%s' backend: '%s'\n", Pa_GetDeviceInfo( inDevIdx )->name, Pa_GetHostApiInfo( Pa_GetDeviceInfo( inDevIdx )->hostApi )->name );
 	printf( "Output device: '%s' backend: '%s'\n", Pa_GetDeviceInfo( outDevIdx )->name, Pa_GetHostApiInfo( Pa_GetDeviceInfo( outDevIdx )->hostApi )->name );
 
-	m_stopSemaphore.acquire();
-
 	// TODO: debug Mixer::pushInputFrames()
 	//m_supportsCapture = true;
 
@@ -181,7 +178,6 @@ AudioPortAudio::AudioPortAudio( bool & _success_ful, Mixer * _mixer ) :
 AudioPortAudio::~AudioPortAudio()
 {
 	stopProcessing();
-	m_stopSemaphore.release();
 
 	if( !m_wasPAInitError )
 	{
@@ -212,8 +208,7 @@ void AudioPortAudio::stopProcessing()
 {
 	if( m_paStream && Pa_IsStreamActive( m_paStream ) )
 	{
-		m_stopSemaphore.acquire();
-		
+		m_stopped = true;
 		PaError err = Pa_StopStream( m_paStream );
 	
 		if( err != paNoError )
@@ -283,7 +278,6 @@ int AudioPortAudio::process_callback(
 			if( !frames )
 			{
 				m_stopped = true;
-				m_stopSemaphore.release();
 				memset( _outputBuffer, 0, _framesPerBuffer *
 					channels() * sizeof(float) );
 				return paComplete;

src/core/audio/AudioPulseAudio.cpp

@@ -103,6 +103,7 @@ void AudioPulseAudio::startProcessing()
 
 void AudioPulseAudio::stopProcessing()
 {
+	m_quit = true;
 	stopProcessingThread( this );
 }
 

src/core/audio/AudioSdl.cpp

@@ -168,6 +168,7 @@ void AudioSdl::sdlAudioCallback( Uint8 * _buf, int _len )
 			const fpp_t frames = getNextBuffer( m_outBuf );
 			if( !frames )
 			{
+				m_stopped = true;
 				memset( _buf, 0, _len );
 				return;
 			}

src/core/audio/AudioSoundIo.cpp

@@ -49,6 +49,7 @@ AudioSoundIo::AudioSoundIo( bool & outSuccessful, Mixer * _mixer ) :
 	m_disconnectErr = 0;
 	m_outBufFrameIndex = 0;
 	m_outBufFramesTotal = 0;
+	m_stopped = true;
 
 	m_soundio = soundio_create();
 	if (!m_soundio)
@@ -210,15 +211,18 @@ void AudioSoundIo::startProcessing()
 
 	m_outBuf = new surroundSampleFrame[m_outBufSize];
 
+	m_stopped = false;
 	int err;
 	if ((err = soundio_outstream_start(m_outstream)))
 	{
+		m_stopped = true;
 		fprintf(stderr, "soundio unable to start stream: %s\n", soundio_strerror(err));
 	}
 }
 
 void AudioSoundIo::stopProcessing()
 {
+	m_stopped = true;
 	if (m_outstream)
 	{
 		soundio_outstream_destroy(m_outstream);
@@ -244,6 +248,7 @@ void AudioSoundIo::underflowCallback()
 
 void AudioSoundIo::writeCallback(int frameCountMin, int frameCountMax)
 {
+	if (m_stopped) {return;}
 	const struct SoundIoChannelLayout *layout = &m_outstream->layout;
 	SoundIoChannelArea *areas;
 	int bytesPerSample = m_outstream->bytes_per_sample;
@@ -265,11 +270,27 @@ void AudioSoundIo::writeCallback(int frameCountMin, int frameCountMax)
 		if (!frameCount)
 			break;
 
+		
+		if (m_stopped)
+		{
+			for (int channel = 0; channel < layout->channel_count; ++channel)
+			{
+				memset(areas[channel].ptr, 0, bytesPerSample * frameCount);
+				areas[channel].ptr += areas[channel].step * frameCount;
+			}
+			continue;
+		}
+
 		for (int frame = 0; frame < frameCount; frame += 1)
 		{
 			if (m_outBufFrameIndex >= m_outBufFramesTotal)
 			{
 				m_outBufFramesTotal = getNextBuffer(m_outBuf);
+				if (m_outBufFramesTotal == 0)
+				{
+					m_stopped = true;
+					break;
+				}
 				m_outBufFrameIndex = 0;
 			}