Guard the flag used for deferred session configure.

src/base/bittorrent/session.cpp

@@ -911,6 +911,9 @@ void Session::adjustLimits()
 void Session::configure()
 {
     qDebug("Configuring session");
+    if (!m_deferredConfigureScheduled) return; // Obtaining the lock is expensive, let's check early
+    QWriteLocker locker(&m_lock);
+    if (!m_deferredConfigureScheduled) return; // something might have changed while we were getting the lock
 #if LIBTORRENT_VERSION_NUM < 10100
     libt::session_settings sessionSettings = m_nativeSession->settings();
     configure(sessionSettings);
@@ -2957,11 +2960,13 @@ void Session::initResumeFolder()
 
 void Session::configureDeferred()
 {
-    if (!m_deferredConfigureScheduled) {
+    if (m_deferredConfigureScheduled) return; // Obtaining the lock is expensive, let's check early
+    QWriteLocker locker(&m_lock);
+    if (m_deferredConfigureScheduled) return; // something might have changed while we were getting the lock
+
     QMetaObject::invokeMethod(this, "configure", Qt::QueuedConnection);
     m_deferredConfigureScheduled = true;
 }
-}
 
 // Enable IP Filtering
 void Session::enableIPFilter()

src/base/bittorrent/session.h

@@ -41,6 +41,7 @@
 #endif
 #include <QNetworkConfigurationManager>
 #include <QPointer>
+#include <QReadWriteLock>
 #include <QStringList>
 #include <QVector>
 #include <QWaitCondition>
@@ -604,6 +605,8 @@ namespace BitTorrent
 
         QNetworkConfigurationManager m_networkManager;
 
+        mutable QReadWriteLock m_lock;
+
         static Session *m_instance;
     };
 }