From bada884342efc0d065d4dcb0f7a800a39a740a6e Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Wed, 23 Jan 2013 17:38:28 +0000
Subject: [PATCH] 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   |  5 +++++
 src/osgViewer/Renderer.cpp   | 14 ++++++++++++++
 src/osgViewer/ViewerBase.cpp |  1 +
 3 files changed, 20 insertions(+)

diff --git a/include/osgViewer/Renderer b/include/osgViewer/Renderer
index 46b75846e..c2b7c328c 100644
--- a/include/osgViewer/Renderer
+++ b/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();
 
diff --git a/src/osgViewer/Renderer.cpp b/src/osgViewer/Renderer.cpp
index ae36229d3..2de31babe 100644
--- a/src/osgViewer/Renderer.cpp
+++ b/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)
diff --git a/src/osgViewer/ViewerBase.cpp b/src/osgViewer/ViewerBase.cpp
index facf3b841..7a2029d92 100644
--- a/src/osgViewer/ViewerBase.cpp
+++ b/src/osgViewer/ViewerBase.cpp
@@ -336,6 +336,7 @@ void ViewerBase::startThreading()
         {
             renderer->setGraphicsThreadDoesCull(graphicsThreadsDoesCull);
             renderer->setDone(false);
+            renderer->reset();
             ++numViewerDoubleBufferedRenderingOperation;
         }
     }