Fix unresponsive GUI on quit if a polling operation is in progress

app/backend/computermanager.cpp

@@ -7,6 +7,7 @@
 
 #include <QThread>
 #include <QThreadPool>
+#include <QCoreApplication>
 
 #define SER_HOSTS "hosts"
 
@@ -161,6 +162,13 @@ ComputerManager::ComputerManager(QObject *parent)
         m_KnownHosts[computer->uuid] = computer;
     }
     settings.endArray();
+
+    // To quit in a timely manner, we must block additional requests
+    // after we receive the aboutToQuit() signal. This is neccessary
+    // because NvHTTP uses aboutToQuit() to abort requests in progres
+    // while quitting, however this is a one time signal - additional
+    // requests would not be aborted and block termination.
+    connect(QCoreApplication::instance(), SIGNAL(aboutToQuit()), this, SLOT(handleAboutToQuit()));
 }
 
 ComputerManager::~ComputerManager()
@@ -343,6 +351,17 @@ void ComputerManager::deleteHost(NvComputer* computer)
     QThreadPool::globalInstance()->start(new DeferredHostDeletionTask(this, computer));
 }
 
+void ComputerManager::handleAboutToQuit()
+{
+    QWriteLocker lock(&m_Lock);
+
+    // Interrupt polling threads immediately, so they
+    // avoid making additional requests while quitting
+    for (ComputerPollingEntry* entry : m_PollEntries) {
+        entry->interrupt();
+    }
+}
+
 class PendingPairingTask : public QObject, public QRunnable
 {
     Q_OBJECT

app/backend/computermanager.h

@@ -161,6 +161,8 @@ signals:
     void quitAppCompleted(QVariant error);
 
 private slots:
+    void handleAboutToQuit();
+
     void handleComputerStateChanged(NvComputer* computer);
 
     void handleMdnsServiceResolved(MdnsPendingComputer* computer, const QHostAddress& address);