From 4f79634bcd3283574e45429b23afbc942b0f6537 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Thu, 8 Feb 2007 22:36:16 +0000
Subject: [PATCH] =?UTF-8?q?From=20Andr=C3=A9=20Garneau,=20"Attached=20is?=
 =?UTF-8?q?=20a=20fix=20for=20the=20hang=20occuring=20on=20Win32=20when=20?=
 =?UTF-8?q?the=20thread=20model=20is=20changed.?=
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The issue was caused by the mutex in the ViewerDoubleBufferRenderingOperation being released even though they were not owned. This was causing the underlying critical section object lock count values becoming negative; the next time the lock was acquired it would block because of that."
---
 src/osgViewer/Viewer.cpp | 42 ++++++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 6 deletions(-)

diff --git a/src/osgViewer/Viewer.cpp b/src/osgViewer/Viewer.cpp
index 5eca20b25..d4773ac5b 100644
--- a/src/osgViewer/Viewer.cpp
+++ b/src/osgViewer/Viewer.cpp
@@ -228,6 +228,9 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
         _done(false),
         _databasePager(databasePager)
     {
+        _lockHeld[0]  = false;
+        _lockHeld[1]  = false;
+
         _sceneView[0] = sv0;
         _sceneView[0]->getCullVisitor()->setDatabaseRequestHandler(_databasePager.get());
 
@@ -239,7 +242,11 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
         
         // lock the mutex for the current cull SceneView to
         // prevent the draw traversal from reading from it before the cull traversal has been completed.
-        if (!_graphicsThreadDoesCull) _mutex[_currentCull].lock();
+        if (!_graphicsThreadDoesCull)
+        {
+             _mutex[_currentCull].lock();
+             _lockHeld[_currentCull] = true;
+        }
     
         // osg::notify(osg::NOTICE)<<"constructed"<<std::endl;
     }
@@ -258,13 +265,23 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
         if (_graphicsThreadDoesCull)
         {
             // need to disable any locks held by the cull
-            _mutex[0].unlock();
-            _mutex[1].unlock();
+            if (_lockHeld[0])
+            {
+                _lockHeld[0] = false;
+                _mutex[0].unlock();
+            }
+
+            if (_lockHeld[1])
+            {
+                _lockHeld[1] = false;
+                _mutex[1].unlock();
+            }
         }
         else
         {
             // need to set a lock for cull
             _mutex[_currentCull].lock();
+            _lockHeld[_currentCull] = true;
         }
     }
     
@@ -311,7 +328,8 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
         }
 
 
-        // relase the mutex associated with this cull traversal, let the draw commense.
+        // relase the mutex associated with this cull traversal, let the draw commence.
+        _lockHeld[_currentCull] = false;
         _mutex[_currentCull].unlock();
         
         // swap which SceneView we need to do cull traversal on next.
@@ -319,6 +337,7 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
         
         // aquire the lock for it for the new cull traversal
         _mutex[_currentCull].lock();
+        _lockHeld[_currentCull] = true;
     }
     
     void draw()
@@ -518,8 +537,18 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
     {
         osg::notify(osg::INFO)<<"ViewerDoubleBufferedRenderingOperation::release()"<<std::endl;
         _done = true;
-        _mutex[0].unlock();
-        _mutex[1].unlock();
+
+        if (_lockHeld[0])
+        {
+            _lockHeld[0] = false;
+            _mutex[0].unlock();
+        }
+
+        if (_lockHeld[1])
+        {
+            _lockHeld[1] = false;
+            _mutex[1].unlock();
+        }
     }
 
     bool                                    _graphicsThreadDoesCull;
@@ -528,6 +557,7 @@ struct ViewerDoubleBufferedRenderingOperation : public osg::Operation, public Vi
     unsigned int                            _currentDraw;
     
     OpenThreads::Mutex                      _mutex[2];
+    bool                                    _lockHeld[2];
     osg::observer_ptr<osgUtil::SceneView>   _sceneView[2];
     int                                     _frameNumber[2];
     osg::observer_ptr<osgDB::DatabasePager> _databasePager;