Fix a deadlock in GPIO monitor

libnymea-gpio/gpio.cpp

@@ -139,6 +139,7 @@ Gpio::Gpio(int gpio, QObject *parent) :
     m_direction(Gpio::DirectionInvalid),
     m_gpioDirectory(QDir(QString("/sys/class/gpio/gpio%1").arg(QString::number(gpio))))
 {
+    qRegisterMetaType<Gpio::Value>();
 
 }
 

libnymea-gpio/gpiomonitor.cpp

@@ -81,8 +81,8 @@ GpioMonitor::GpioMonitor(int gpio, QObject *parent) :
     m_gpioNumber(gpio)
 {
     // Inform about the thread status
-    connect(this, &GpioMonitor::started, this, &GpioMonitor::onThreadStarted, Qt::DirectConnection);
-    connect(this, &GpioMonitor::finished, this, &GpioMonitor::onThreadFinished, Qt::DirectConnection);
+    connect(this, &GpioMonitor::started, this, &GpioMonitor::onThreadStarted);
+    connect(this, &GpioMonitor::finished, this, &GpioMonitor::onThreadFinished);
 }
 
 /*! Destroys and unexports the Gpio. */
@@ -130,7 +130,6 @@ void GpioMonitor::setActiveLow(bool activeLow)
 /*! Returns the current value of the Gpio. */
 Gpio::Value GpioMonitor::value()
 {
-    QMutexLocker valueLocker(&m_valueMutex);
     return m_value;
 }
 
@@ -140,9 +139,8 @@ bool GpioMonitor::enabled() const
     return m_enabled;
 }
 
-void GpioMonitor::setValue(Gpio::Value value)
+void GpioMonitor::onValueChanged(Gpio::Value value)
 {
-    QMutexLocker valueLocker(&m_valueMutex);
     m_value = value;
 
     switch (m_value) {
@@ -241,11 +239,8 @@ void GpioMonitor::run()
 
             // Notify the main thread about the interrupt
             readStream >> valueString;
-            if (valueString == "0") {
-                setValue(Gpio::ValueLow);
-            } else {
-                setValue(Gpio::ValueHigh);
-            }
+            Gpio::Value value = valueString == "1" ? Gpio::ValueHigh : Gpio::ValueLow;
+            QMetaObject::invokeMethod(this, "onValueChanged", Qt::QueuedConnection, Q_ARG(Gpio::Value, value));
         }
     }
 
@@ -280,7 +275,6 @@ bool GpioMonitor::enable()
         return false;
     }
 
-    QMutexLocker locker(&m_stopMutex);
     m_stop = false;
 
     // Everything looks good, lets start the poll thread and inform about the result
@@ -294,6 +288,5 @@ void GpioMonitor::disable()
     qCDebug(dcGpio()) << "Disabling gpio monitor";
     // Stop the thread if not already disabled
     QMutexLocker locker(&m_stopMutex);
-    if (m_stop) return;
     m_stop = true;
 }

libnymea-gpio/gpiomonitor.h

@@ -62,14 +62,11 @@ private:
     bool m_activeLow = true;
     bool m_enabled = false;
 
-    // Thread stuff
-    QMutex m_valueMutex;
     Gpio::Value m_value = Gpio::ValueInvalid;
 
     QMutex m_stopMutex;
     bool m_stop = false;
 
-    void setValue(Gpio::Value value);
     void setEnabled(bool enabled);
 
 protected:
@@ -82,6 +79,7 @@ signals:
 private slots:
     void onThreadStarted();
     void onThreadFinished();
+    void onValueChanged(Gpio::Value value);
 
 public slots:
     bool enable();