From Pjotr Svetachov, "when you restart threading

with startThreading/stopThreading the _drawQueue and _availableQueue
are not reset properly. This can lead to a deadlock when threading is
started again. So before threading is started again the queues must be
reset. This deadlock is also reported earlier by someone else in here:
http://forum.openscenegraph.org/viewtopic.php?p=43415#43415"

include/osgViewer/Renderer

@@ -69,6 +69,8 @@ class OSGVIEWER_EXPORT Renderer : public osg::GraphicsOperation
 
         virtual void release();
 
+        virtual void reset();
+
         /** Force update of state associated with cameras. */
         void setCameraRequiresSetUp(bool flag);
         bool getCameraRequiresSetUp() const;
@@ -101,6 +103,9 @@ class OSGVIEWER_EXPORT Renderer : public osg::GraphicsOperation
             /** Release any thread waiting on the queue, even if the queue is empty. */
             void release();
 
+            /** Reset to fefault state (_isReleased = false)*/
+            void reset();
+
             /** Take a SceneView from the queue. Can return 0 if release() is called when the queue is empty. */
             osgUtil::SceneView* takeFront();
 

src/osgViewer/Renderer.cpp

@@ -304,6 +304,13 @@ void Renderer::ThreadSafeQueue::release()
     _cond.broadcast();
 }
 
+void Renderer::ThreadSafeQueue::reset()
+{
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+    _queue.clear();
+    _isReleased = false;
+}
+
 osgUtil::SceneView* Renderer::ThreadSafeQueue::takeFront()
 {
     OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
@@ -902,6 +909,13 @@ void Renderer::release()
     _drawQueue.release();
 }
 
+void Renderer::reset(){
+    _availableQueue.reset();
+    _availableQueue.add(_sceneView[0].get());
+    _availableQueue.add(_sceneView[1].get());
+    _drawQueue.reset();
+}
+
 void Renderer::setCameraRequiresSetUp(bool flag)
 {
     for (int i = 0; i < 2; ++i)

src/osgViewer/ViewerBase.cpp

@@ -336,6 +336,7 @@ void ViewerBase::startThreading()
         {
             renderer->setGraphicsThreadDoesCull(graphicsThreadsDoesCull);
             renderer->setDone(false);
+            renderer->reset();
             ++numViewerDoubleBufferedRenderingOperation;
         }
     }