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Revamp synchronization with the audio engine (#6881)

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The revamp consists of one lock. When the audio thread needs to render audio or another thread wants to run a change, acquiring the lock grants mutual exclusion to do one of the two. The intention is that this will provide stronger guarantees that changes do not run concurrently with the audio thread, as well as having the synchronization mechanism itself be free of data races (verified with TSan).
This commit is contained in:
saker
2023-11-18 15:28:01 -05:00
committed by GitHub
parent 1e2167d005
commit 7268827624
2 changed files with 17 additions and 106 deletions
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94
src/core/AudioEngine.cpp
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@@ -67,6 +67,7 @@ namespace lmms
using LocklessListElement = LocklessList<PlayHandle*>::Element;
static thread_local bool s_renderingThread;
static thread_local bool s_runningChange;
@@ -83,19 +84,12 @@ AudioEngine::AudioEngine( bool renderOnly ) :
m_newPlayHandles( PlayHandle::MaxNumber ),
m_qualitySettings( qualitySettings::Mode::Draft ),
m_masterGain( 1.0f ),
m_isProcessing( false ),
m_audioDev( nullptr ),
m_oldAudioDev( nullptr ),
m_audioDevStartFailed( false ),
m_profiler(),
m_metronomeActive(false),
m_clearSignal( false ),
m_changesSignal( false ),
m_changes( 0 ),
#if (QT_VERSION < QT_VERSION_CHECK(5,14,0))
m_doChangesMutex( QMutex::Recursive ),
#endif
m_waitingForWrite( false )
m_clearSignal(false)
{
for( int i = 0; i < 2; ++i )
{
@@ -165,8 +159,6 @@ AudioEngine::AudioEngine( bool renderOnly ) :
AudioEngine::~AudioEngine()
{
runChangesInModel();
for( int w = 0; w < m_numWorkers; ++w )
{
m_workers[w]->quit();
@@ -232,8 +224,6 @@ void AudioEngine::startProcessing(bool needsFifo)
}
m_audioDev->startProcessing();
m_isProcessing = true;
}
@@ -241,8 +231,6 @@ void AudioEngine::startProcessing(bool needsFifo)
void AudioEngine::stopProcessing()
{
m_isProcessing = false;
if( m_fifoWriter != nullptr )
{
m_fifoWriter->finish();
@@ -447,8 +435,6 @@ void AudioEngine::renderStageMix()
emit nextAudioBuffer(m_outputBufferRead);
runChangesInModel();
// and trigger LFOs
EnvelopeAndLfoParameters::instances()->trigger();
Controller::triggerFrameCounter();
@@ -459,6 +445,8 @@ void AudioEngine::renderStageMix()
const surroundSampleFrame *AudioEngine::renderNextBuffer()
{
const auto lock = std::lock_guard{m_changeMutex};
m_profiler.startPeriod();
s_renderingThread = true;
@@ -811,57 +799,16 @@ void AudioEngine::removePlayHandlesOfTypes(Track * track, PlayHandle::Types type
void AudioEngine::requestChangeInModel()
{
if( s_renderingThread )
return;
m_changesMutex.lock();
m_changes++;
m_changesMutex.unlock();
m_doChangesMutex.lock();
m_waitChangesMutex.lock();
if (m_isProcessing && !m_waitingForWrite && !m_changesSignal)
{
m_changesSignal = true;
m_changesRequestCondition.wait( &m_waitChangesMutex );
}
m_waitChangesMutex.unlock();
if (s_renderingThread || s_runningChange) { return; }
m_changeMutex.lock();
s_runningChange = true;
}
void AudioEngine::doneChangeInModel()
{
if( s_renderingThread )
return;
m_changesMutex.lock();
bool moreChanges = --m_changes;
m_changesMutex.unlock();
if( !moreChanges )
{
m_changesSignal = false;
m_changesAudioEngineCondition.wakeOne();
}
m_doChangesMutex.unlock();
}
void AudioEngine::runChangesInModel()
{
if( m_changesSignal )
{
m_waitChangesMutex.lock();
// allow changes in the model from other threads ...
m_changesRequestCondition.wakeOne();
// ... and wait until they are done
m_changesAudioEngineCondition.wait( &m_waitChangesMutex );
m_waitChangesMutex.unlock();
}
if (s_renderingThread || !s_runningChange) { return; }
m_changeMutex.unlock();
s_runningChange = false;
}
bool AudioEngine::isAudioDevNameValid(QString name)
@@ -1297,29 +1244,12 @@ void AudioEngine::fifoWriter::run()
auto buffer = new surroundSampleFrame[frames];
const surroundSampleFrame * b = m_audioEngine->renderNextBuffer();
memcpy( buffer, b, frames * sizeof( surroundSampleFrame ) );
write( buffer );
m_fifo->write(buffer);
}
// Let audio backend stop processing
write( nullptr );
m_fifo->write(nullptr);
m_fifo->waitUntilRead();
}
void AudioEngine::fifoWriter::write( surroundSampleFrame * buffer )
{
m_audioEngine->m_waitChangesMutex.lock();
m_audioEngine->m_waitingForWrite = true;
m_audioEngine->m_waitChangesMutex.unlock();
m_audioEngine->runChangesInModel();
m_fifo->write( buffer );
m_audioEngine->m_doChangesMutex.lock();
m_audioEngine->m_waitingForWrite = false;
m_audioEngine->m_doChangesMutex.unlock();
}
} // namespace lmms