Use QAudioStateMachine for state handling in PulseAudio source

The PulseAudio source used internal variables for state and error
updates, which are liable to data races if accessed from different
threads without protection.

This patch updates this to use QAudioStateMachine that enables
atomic state transitions to prevent possible data races.

Pick-to: 6.5
Change-Id: Ia24399184765a9852e665224ee9678c99f1c92e0
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
(cherry picked from commit c56b9ab3e08f72fb2ac9db0d5342d3df44198143)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit c5182bbe46a479795e818ebb940c116f7224031d)

2 files changed, 34 insertions, 80 deletions

diff --git a/src/multimedia/pulseaudio/qpulseaudiosource.cpp b/src/multimedia/pulseaudio/qpulseaudiosource.cpp
index 3c0640c06..e523fd21e 100644
--- a/src/multimedia/pulseaudio/qpulseaudiosource.cpp
+++ b/src/multimedia/pulseaudio/qpulseaudiosource.cpp
@@ -94,8 +94,6 @@ QPulseAudioSource::QPulseAudioSource(const QByteArray &device, QObject *parent)
     : QPlatformAudioSource(parent)
     , m_totalTimeValue(0)
     , m_audioSource(nullptr)
-    , m_errorState(QAudio::NoError)
-    , m_deviceState(QAudio::StoppedState)
     , m_volume(qreal(1.0f))
     , m_pullMode(true)
     , m_opened(false)
@@ -105,45 +103,31 @@ QPulseAudioSource::QPulseAudioSource(const QByteArray &device, QObject *parent)
     , m_periodTime(SourcePeriodTimeMs)
     , m_stream(nullptr)
     , m_device(device)
+    , m_stateMachine(*this)
 {
 }
 
 QPulseAudioSource::~QPulseAudioSource()
 {
-    close();
-}
-
-void QPulseAudioSource::setError(QAudio::Error error)
-{
-    if (m_errorState == error)
-        return;
-
-    m_errorState = error;
-    emit errorChanged(error);
+    qDebug() << Q_FUNC_INFO;
+    // TODO: Investigate draining the stream
+    if (auto notifier = m_stateMachine.stop())
+        close();
 }
 
 QAudio::Error QPulseAudioSource::error() const
 {
-    return m_errorState;
-}
-
-void QPulseAudioSource::setState(QAudio::State state)
-{
-    if (m_deviceState == state)
-        return;
-
-    m_deviceState = state;
-    emit stateChanged(state);
+    return m_stateMachine.error();
 }
 
 QAudio::State QPulseAudioSource::state() const
 {
-    return m_deviceState;
+    return m_stateMachine.state();
 }
 
 void QPulseAudioSource::setFormat(const QAudioFormat &format)
 {
-    if (m_deviceState == QAudio::StoppedState)
+    if (!m_stateMachine.isActiveOrIdle())
         m_format = format;
 }
 
@@ -154,8 +138,7 @@ QAudioFormat QPulseAudioSource::format() const
 
 void QPulseAudioSource::start(QIODevice *device)
 {
-    setState(QAudio::StoppedState);
-    setError(QAudio::NoError);
+    m_stateMachine.stopOrUpdateError();
 
     if (!m_pullMode && m_audioSource) {
         delete m_audioSource;
@@ -170,13 +153,12 @@ void QPulseAudioSource::start(QIODevice *device)
     m_pullMode = true;
     m_audioSource = device;
 
-    setState(QAudio::ActiveState);
+    m_stateMachine.start();
 }
 
 QIODevice *QPulseAudioSource::start()
 {
-    setState(QAudio::StoppedState);
-    setError(QAudio::NoError);
+    m_stateMachine.stopOrUpdateError();
 
     if (!m_pullMode && m_audioSource) {
         delete m_audioSource;
@@ -192,20 +174,15 @@ QIODevice *QPulseAudioSource::start()
     m_audioSource = new PulseInputPrivate(this);
     m_audioSource->open(QIODevice::ReadOnly | QIODevice::Unbuffered);
 
-    setState(QAudio::IdleState);
+    m_stateMachine.start(false);
 
     return m_audioSource;
 }
 
 void QPulseAudioSource::stop()
 {
-    if (m_deviceState == QAudio::StoppedState)
-        return;
-
-    close();
-
-    setError(QAudio::NoError);
-    setState(QAudio::StoppedState);
+    if (auto notifier = m_stateMachine.stop())
+        close();
 }
 
 bool QPulseAudioSource::open()
@@ -216,8 +193,7 @@ bool QPulseAudioSource::open()
     QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
 
     if (!pulseEngine->context() || pa_context_get_state(pulseEngine->context()) != PA_CONTEXT_READY) {
-        setError(QAudio::FatalError);
-        setState(QAudio::StoppedState);
+        m_stateMachine.stopOrUpdateError(QAudio::FatalError);
         return false;
     }
 
@@ -226,8 +202,7 @@ bool QPulseAudioSource::open()
     Q_ASSERT(spec.channels == channel_map.channels);
 
     if (!pa_sample_spec_valid(&spec)) {
-        setError(QAudio::OpenError);
-        setState(QAudio::StoppedState);
+        m_stateMachine.stopOrUpdateError(QAudio::OpenError);
         return false;
     }
 
@@ -279,8 +254,7 @@ bool QPulseAudioSource::open()
         pa_stream_unref(m_stream);
         m_stream = nullptr;
         pulseEngine->unlock();
-        setError(QAudio::OpenError);
-        setState(QAudio::StoppedState);
+        m_stateMachine.stopOrUpdateError(QAudio::OpenError);
         return false;
     }
 
@@ -345,12 +319,7 @@ void QPulseAudioSource::close()
 
 int QPulseAudioSource::checkBytesReady()
 {
-    if (m_deviceState != QAudio::ActiveState && m_deviceState != QAudio::IdleState) {
-        m_bytesAvailable = 0;
-    } else {
-        m_bytesAvailable = pa_stream_readable_size(m_stream);
-    }
-
+    m_bytesAvailable = m_stateMachine.isActiveOrIdle() ? pa_stream_readable_size(m_stream) : 0;
     return m_bytesAvailable;
 }
 
@@ -364,11 +333,7 @@ qint64 QPulseAudioSource::read(char *data, qint64 len)
     Q_ASSERT(data != nullptr || len == 0);
 
     m_bytesAvailable = checkBytesReady();
-
-    setError(QAudio::NoError);
-    if (state() == QAudio::IdleState)
-        setState(QAudio::ActiveState);
-
+    m_stateMachine.updateActiveOrIdle(true, QAudio::NoError);
     int readBytes = 0;
 
     if (!m_pullMode && !m_tempBuffer.isEmpty()) {
@@ -415,10 +380,7 @@ qint64 QPulseAudioSource::read(char *data, qint64 len)
 
             if (actualLength < qint64(readLength)) {
                 pulseEngine->unlock();
-
-                setError(QAudio::UnderrunError);
-                setState(QAudio::IdleState);
-
+                m_stateMachine.updateActiveOrIdle(false, QAudio::UnderrunError);
                 return actualLength;
             }
         } else {
@@ -469,20 +431,18 @@ void QPulseAudioSource::applyVolume(const void *src, void *dest, int len)
 
 void QPulseAudioSource::resume()
 {
-    if (m_deviceState == QAudio::SuspendedState || m_deviceState == QAudio::IdleState) {
-        QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
-
+    if (auto notifier = m_stateMachine.resume()) {
         {
+            QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
+
             std::lock_guard lock(*pulseEngine);
+
             PAOperationUPtr operation(
                     pa_stream_cork(m_stream, 0, inputStreamSuccessCallback, nullptr));
             pulseEngine->wait(operation.get());
         }
 
         m_timer.start(m_periodTime, this);
-
-        setState(QAudio::ActiveState);
-        setError(QAudio::NoError);
     }
 }
 
@@ -524,10 +484,7 @@ qint64 QPulseAudioSource::processedUSecs() const
 
 void QPulseAudioSource::suspend()
 {
-    if (m_deviceState == QAudio::ActiveState) {
-        setError(QAudio::NoError);
-        setState(QAudio::SuspendedState);
-
+    if (auto notifier = m_stateMachine.suspend()) {
         m_timer.stop();
 
         QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
@@ -549,7 +506,7 @@ void QPulseAudioSource::timerEvent(QTimerEvent *event)
 
 void QPulseAudioSource::userFeed()
 {
-    if (m_deviceState == QAudio::StoppedState || m_deviceState == QAudio::SuspendedState)
+    if (!m_stateMachine.isActiveOrIdle())
         return;
 #ifdef DEBUG_PULSE
 //    QTime now(QTime::currentTime());
@@ -572,8 +529,9 @@ bool QPulseAudioSource::deviceReady()
     }
     m_bytesAvailable = checkBytesReady();
 
-    if (m_deviceState != QAudio::ActiveState)
-        return true;
+    // TODO: This doesn't look correct, check how this should work
+//    if (m_deviceState != QAudio::ActiveState)
+//        return true;
 
     return true;
 }
@@ -586,10 +544,8 @@ void QPulseAudioSource::reset()
 
 void QPulseAudioSource::onPulseContextFailed()
 {
-    close();
-
-    setError(QAudio::FatalError);
-    setState(QAudio::StoppedState);
+    if (auto notifier = m_stateMachine.stopOrUpdateError(QAudio::FatalError))
+        close();
 }
 
 PulseInputPrivate::PulseInputPrivate(QPulseAudioSource *audio)
diff --git a/src/multimedia/pulseaudio/qpulseaudiosource_p.h b/src/multimedia/pulseaudio/qpulseaudiosource_p.h
index 5326e3889..3bf836dda 100644
--- a/src/multimedia/pulseaudio/qpulseaudiosource_p.h
+++ b/src/multimedia/pulseaudio/qpulseaudiosource_p.h
@@ -25,6 +25,7 @@
 #include "qaudio.h"
 #include "qaudiodevice.h"
 #include <private/qaudiosystem_p.h>
+#include <private/qaudiostatemachine_p.h>
 
 #include <pulse/pulseaudio.h>
 
@@ -63,8 +64,6 @@ public:
     qint64 m_totalTimeValue;
     QIODevice *m_audioSource;
     QAudioFormat m_format;
-    QAudio::Error m_errorState;
-    QAudio::State m_deviceState;
     qreal m_volume;
 
 protected:
@@ -76,9 +75,6 @@ private slots:
     void onPulseContextFailed();
 
 private:
-    void setState(QAudio::State state);
-    void setError(QAudio::Error error);
-
     void applyVolume(const void *src, void *dest, int len);
 
     int checkBytesReady();
@@ -98,6 +94,8 @@ private:
     QByteArray m_device;
     QByteArray m_tempBuffer;
     pa_sample_spec m_spec;
+
+    QAudioStateMachine m_stateMachine;
 };
 
 class PulseInputPrivate : public QIODevice