Even more race precautions

* It did not break yet, but I could not sleep without this commit.

src/libtomahawk/Source.cpp

@@ -477,6 +477,11 @@ Source::playlistInterface()
     return m_playlistInterface;
 }
 
+QSharedPointer<QMutex> Source::acquireLock()
+{
+    return QSharedPointer<QMutexLocker>( new QMutexLocker( &m_mutex ) );
+}
+
 
 void
 Source::onPlaybackStarted( const Tomahawk::track_ptr& track, unsigned int duration )

src/libtomahawk/Source.h

@@ -102,6 +102,8 @@ public:
 
     Tomahawk::playlistinterface_ptr playlistInterface();
 
+    QSharedPointer<QMutex> acquireLock();
+
 signals:
     void syncedWithDatabase();
     void synced();
@@ -175,6 +177,7 @@ private:
     QString m_lastCmdGuid;
     mutable QMutex m_cmdMutex;
     QMutex m_setControlConnectionMutex;
+    QMutex m_mutex;
 
     Tomahawk::playlistinterface_ptr m_playlistInterface;
 };

src/libtomahawk/network/ControlConnection.cpp

@@ -100,6 +100,7 @@ ControlConnection::setup()
 
     // setup source and remote collection for this peer
     m_source = SourceList::instance()->get( id(), friendlyName, true );
+    QSharedPointer<QMutexLocker> locker = m_source->acquireLock();
     if ( m_source->setControlConnection( this ) )
     {
         // We are the new ControlConnection for this source
@@ -128,6 +129,10 @@ ControlConnection::setup()
 // source was synced to DB, set it up properly:
 void
 ControlConnection::registerSource()
+{
+    QSharedPointer<QMutexLocker> locker = m_source->acquireLock();
+    // Only continue if we are still the ControlConnection associated with this source.
+    if ( m_source->controlConnection() == this )
     {
         qDebug() << Q_FUNC_INFO << m_source->id();
         Source* source = (Source*) sender();
@@ -137,6 +142,7 @@ ControlConnection::registerSource()
         m_registered = true;
         setupDbSyncConnection();
     }
+}
 
 
 void