Fix Bug 606 - New AWT threading implementation breaks .. ; Fix GLAutoDrawable multi-threading w/ proper pattern (hope so)

Considering code changes and remarks:
  3ed491213f8f7f05d7b9866b50d764370d8ff5f6
  1a91ec5c8b6fd9d9db7bc115569c369fe7b38e9b
  3334a924309a9361a448d69bc707d4cce416b430
  4f27bcecf7484dc041551f52a5c49e2884cb3867

It seems necessary to have

- recursive locking employed for all semantic actions which changes drawable & context (and the Window resource)

- to avoid deadlock, we have to ensure the locked code segment will not spawn
  off to another thread, or a thread holds the lock, spawns of an action requiring the lock. .. sure

- other read-only methods (flags, ..) shall at least utilize a safe local copy of a volatile field
  if further use to produce the result is necessary.

- flags like sendReshape require to be volatile to guarantee it's being processed

Patch impacts: AWT/SWT GLCanvas, GLAutoDrawableBase [and it's specializations]
and hopefully closes any loopholes of missing a cache hit, etc.

If you review this and find optimizations, i.e. removing a lock due to semantics etc,
don't hold back and discuss it, please.

6 files changed, 500 insertions, 328 deletions

diff --git a/src/jogl/classes/com/jogamp/opengl/swt/GLCanvas.java b/src/jogl/classes/com/jogamp/opengl/swt/GLCanvas.java
index 0d9d3ddf5..64ee1c1ad 100644
--- a/src/jogl/classes/com/jogamp/opengl/swt/GLCanvas.java
+++ b/src/jogl/classes/com/jogamp/opengl/swt/GLCanvas.java
@@ -63,25 +63,13 @@ import org.eclipse.swt.widgets.Shell;
 import com.jogamp.common.GlueGenVersion;
 import com.jogamp.common.os.Platform;
 import com.jogamp.common.util.VersionUtil;
+import com.jogamp.common.util.locks.LockFactory;
+import com.jogamp.common.util.locks.RecursiveLock;
 import com.jogamp.nativewindow.swt.SWTAccessor;
 import com.jogamp.opengl.JoglVersion;
 
 /**
  * Native SWT Canvas implementing GLAutoDrawable
- * <p>
- * FIXME: If this instance runs in multithreading mode, see {@link Threading#isSingleThreaded()} (impossible), 
- *        proper recursive locking is required for drawable/context @ destroy and display. 
- *        Recreation etc could pull those instances while animating!
- *        Simply locking before using drawable/context offthread
- *        would allow a deadlock situation!
- * </p>
- * <p>
- * NOTE: [MT-0] Methods utilizing [volatile] drawable/context are not synchronized.
-         In case any of the methods are called outside of a locked state
-         extra care should be added. Maybe we shall expose locking facilities to the user.
-         However, since the user shall stick to the GLEventListener model while utilizing
-         GLAutoDrawable implementations, she is safe due to the implicit locked state.
- * </p>
  */
 public class GLCanvas extends Canvas implements GLAutoDrawable {
 
@@ -97,8 +85,9 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
    //private static final boolean useSWTThread = ThreadingImpl.getMode() != ThreadingImpl.WORKER;
 
    /* GL Stuff */
+   private final RecursiveLock lock = LockFactory.createRecursiveLock();
    private final GLDrawableHelper helper = new GLDrawableHelper();
-   private volatile GLDrawable drawable; // volatile avoids locking all accessors. FIXME still need to sync destroy/display
+   private volatile GLDrawable drawable; // volatile: avoid locking for read-only access
    private GLContext context;
 
    /* Native window surface */
@@ -112,7 +101,7 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
    private final GLCapabilitiesImmutable glCapsRequested;
 
    /* Flag indicating whether an unprocessed reshape is pending. */
-   private volatile boolean sendReshape;
+   private volatile boolean sendReshape; // volatile: maybe written by WindowManager thread w/o locking
 
    /*
     * Invokes init(...) on all GLEventListeners. Assumes context is current when run.
@@ -141,10 +130,16 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
    };
 
    /* Action to make specified context current prior to running displayAction */
-   private final Runnable makeCurrentAndDisplayAction = new Runnable() {
+   private final Runnable makeCurrentAndDisplayOnEDTAction = new Runnable() {
       @Override
       public void run() {
-         helper.invokeGL(drawable, context, displayAction, initAction);
+        final RecursiveLock _lock = lock;
+        _lock.lock();
+        try {            
+            helper.invokeGL(drawable, context, displayAction, initAction);
+        } finally {
+            _lock.unlock();
+        }
       }
    };
 
@@ -157,10 +152,16 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
    };
 
    /* Swaps buffers, making the GLContext current first */
-   private final Runnable makeCurrentAndSwapBuffersAction = new Runnable() {
+   private final Runnable makeCurrentAndSwapBuffersOnEDTAction = new Runnable() {
       @Override
       public void run() {
-         helper.invokeGL(drawable, context, swapBuffersAction, initAction);
+         final RecursiveLock _lock = lock;
+         _lock.lock();
+         try {            
+           helper.invokeGL(drawable, context, swapBuffersAction, initAction);
+         } finally {
+             _lock.unlock();
+         }
       }
    };
 
@@ -181,16 +182,33 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
    private final Runnable disposeOnEDTGLAction = new Runnable() {
       @Override
       public void run() {
-         helper.disposeGL(GLCanvas.this, drawable, context, postDisposeGLAction);
-      }
-   };
-
-   private final Runnable disposeGraphicsDeviceAction = new Runnable() {
-      @Override
-      public void run() {
-         if (null != device) {
-            device.close();
-            device = null;
+         final RecursiveLock _lock = lock;
+         _lock.lock();
+         try {
+             if (null != drawable && null != context) {
+                boolean animatorPaused = false;
+                final GLAnimatorControl animator = getAnimator();
+                if (null != animator) {
+                   animatorPaused = animator.pause();
+                }
+        
+                if(context.isCreated()) {
+                    helper.disposeGL(GLCanvas.this, drawable, context, postDisposeGLAction);
+                }
+        
+                if (animatorPaused) {
+                   animator.resume();
+                }
+             }
+             // SWT is owner of the device handle, not us.
+             // Hence close() operation is a NOP. 
+             if (null != device) {
+                device.close();
+                device = null;
+             }
+             SWTAccessor.setRealized(GLCanvas.this, false); // unrealize ..
+         } finally {
+             _lock.unlock();
          }
       }
    };
@@ -229,7 +247,8 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
       clientArea = GLCanvas.this.getClientArea();
 
-      /* Get the nativewindow-Graphics Device associated with this control (which is determined by the parent Composite) */
+      /* Get the nativewindow-Graphics Device associated with this control (which is determined by the parent Composite). 
+       * Note: SWT is owner of the native handle, hence no closing operation will be a NOP. */
       device = SWTAccessor.getDevice(this);
       /* Since we have no means of querying the screen index yet, assume 0. Good choice due to Xinerama alike settings anyways. */
       final int screenIdx = 0;
@@ -345,7 +364,7 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public void display() {
-      runInGLThread(makeCurrentAndDisplayAction);
+      runInGLThread(makeCurrentAndDisplayOnEDTAction);
    }
 
    @Override
@@ -370,7 +389,8 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public GL getGL() {
-      return (null == context) ? null : context.getGL();
+      final GLContext _context = context;
+      return (null == _context) ? null : _context.getGL();
    }
 
    @Override
@@ -400,27 +420,35 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public GLContext setContext(GLContext newCtx) {
-      final GLContext oldCtx = context;
-      final boolean newCtxCurrent = helper.switchContext(drawable, oldCtx, newCtx, additionalCtxCreationFlags);
-      context=(GLContextImpl)newCtx;
-      if(newCtxCurrent) {
-          context.makeCurrent();
+      final RecursiveLock _lock = lock;
+      _lock.lock();
+      try {            
+          final GLContext oldCtx = context;
+          final boolean newCtxCurrent = helper.switchContext(drawable, oldCtx, newCtx, additionalCtxCreationFlags);
+          context=(GLContextImpl)newCtx;
+          if(newCtxCurrent) {
+              context.makeCurrent();
+          }
+          return oldCtx;
+      } finally {
+          _lock.unlock();
       }
-      return oldCtx;
    }
 
    @Override
    public void setContextCreationFlags(final int arg0) {
       additionalCtxCreationFlags = arg0;
-      if(null != context) {
-        context.setContextCreationFlags(additionalCtxCreationFlags);
+      final GLContext _context = context;
+      if(null != _context) {
+        _context.setContextCreationFlags(additionalCtxCreationFlags);
       }
    }
 
    @Override
    public GL setGL(final GL arg0) {
-      if (null != context) {
-         context.setGL(arg0);
+       final GLContext _context = context;
+      if (null != _context) {
+         _context.setGL(arg0);
          return arg0;
       }
       return null;
@@ -428,12 +456,18 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public GLContext createContext(final GLContext shareWith) {
-     if(drawable != null) {
-         final GLContext _ctx = drawable.createContext(shareWith);
-         _ctx.setContextCreationFlags(additionalCtxCreationFlags);
-         return _ctx;
+     final RecursiveLock _lock = lock;
+     _lock.lock();
+     try {
+         if(drawable != null) {
+             final GLContext _ctx = drawable.createContext(shareWith);
+             _ctx.setContextCreationFlags(additionalCtxCreationFlags);
+             return _ctx;
+         }
+         return null;
+     } finally {
+         _lock.unlock();
      }
-     return null;
    }
 
    @Override
@@ -452,7 +486,8 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public GLDrawableFactory getFactory() {
-      return (drawable != null) ? drawable.getFactory() : null;
+      final GLDrawable _drawable = drawable;
+      return (_drawable != null) ? _drawable.getFactory() : null;
    }
 
    @Override
@@ -462,17 +497,20 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public long getHandle() {
-      return (drawable != null) ? drawable.getHandle() : 0;
+      final GLDrawable _drawable = drawable; 
+      return (_drawable != null) ? _drawable.getHandle() : 0;
    }
 
    @Override
    public NativeSurface getNativeSurface() {
-      return (drawable != null) ? drawable.getNativeSurface() : null;
+      final GLDrawable _drawable = drawable;
+      return (_drawable != null) ? _drawable.getNativeSurface() : null;
    }
 
    @Override
    public boolean isRealized() {
-      return (drawable != null) ? drawable.isRealized() : false;
+      final GLDrawable _drawable = drawable;
+      return (_drawable != null) ? _drawable.isRealized() : false;
    }
 
    @Override
@@ -482,41 +520,19 @@ public class GLCanvas extends Canvas implements GLAutoDrawable {
 
    @Override
    public void swapBuffers() throws GLException {
-      runInGLThread(makeCurrentAndSwapBuffersAction);
+      runInGLThread(makeCurrentAndSwapBuffersOnEDTAction);
    }
 
    // FIXME: API of update() method ?
    @Override
    public void update() {
-    // FIXME:     display();
+      // FIXME: display(); ?
    }
 
    @Override
    public void dispose() {
-     if (null != drawable && null != context) { // drawable is volatile!
-        boolean animatorPaused = false;
-        final GLAnimatorControl animator = getAnimator();
-        if (null != animator) {
-           // can't remove us from animator for recreational addNotify()
-           animatorPaused = animator.pause();
-        }
-
-        if(context.isCreated()) {
-            runInGLThread(disposeOnEDTGLAction);
-        }
-
-        if (animatorPaused) {
-           animator.resume();
-        }
-     }
-     final Display display = getDisplay();
-
-     if (display.getThread() == Thread.currentThread()) {
-        disposeGraphicsDeviceAction.run();
-     } else {
-        display.syncExec(disposeGraphicsDeviceAction);
-     }
-     super.dispose();
+      runInGLThread(disposeOnEDTGLAction);
+      super.dispose();
    }
 
    /**
diff --git a/src/jogl/classes/javax/media/opengl/GLAutoDrawableDelegate.java b/src/jogl/classes/javax/media/opengl/GLAutoDrawableDelegate.java
index 1f6166719..76959f3f4 100644
--- a/src/jogl/classes/javax/media/opengl/GLAutoDrawableDelegate.java
+++ b/src/jogl/classes/javax/media/opengl/GLAutoDrawableDelegate.java
@@ -67,18 +67,18 @@ public class GLAutoDrawableDelegate extends GLAutoDrawableBase {
     }
     
     //
-    // make protected methods accessible
+    // expose default methods
     //
     
-    public void defaultWindowRepaintOp() {
+    public final void windowRepaintOp() {
         super.defaultWindowRepaintOp();
     }
     
-    public void defaultWindowResizedOp() {
+    public final void windowResizedOp() {
         super.defaultWindowResizedOp();
     }
     
-    public void defaultWindowDestroyNotifyOp() {
+    public final void windowDestroyNotifyOp() {
         super.defaultWindowDestroyNotifyOp();
     }
     
@@ -90,6 +90,9 @@ public class GLAutoDrawableDelegate extends GLAutoDrawableBase {
     private final Object upstreamWidget;
     
     @Override
+    protected final RecursiveLock getLock() { return lock; }
+    
+    @Override
     public final Object getUpstreamWidget() {
         return upstreamWidget;
     }
@@ -97,39 +100,21 @@ public class GLAutoDrawableDelegate extends GLAutoDrawableBase {
     /**
      * {@inheritDoc}
      * <p>
-     * This implementation calls {@link #defaultDestroyOp()}.
+     * This implementation calls {@link #defaultDestroy()}.
      * </p>
      * <p>
      * User still needs to destroy the upstream window, which details are hidden from this aspect.
+     * This can be performed by overriding {@link #destroyImplInLock()}. 
      * </p>
      */
     @Override
-    public void destroy() {
-        lock.lock();
-        try {
-            defaultDestroyOp();
-        } finally {
-            lock.unlock();
-        }
+    public final void destroy() {
+        defaultDestroy();
     }
 
     @Override
     public void display() {
-        if( sendDestroy ) {
-            sendDestroy=false;
-            destroy();
-            return;
-        }
-        
-        lock.lock(); // sync: context/drawable could been recreated/destroyed while animating
-        try {
-            if( null != drawable && drawable.isRealized() && null != context ) {
-                // surface is locked/unlocked implicit by context's makeCurrent/release
-                helper.invokeGL(drawable, context, defaultDisplayAction, defaultInitAction);
-            }
-        } finally {
-            lock.unlock();
-        }
+        defaultDisplay();
     }
     
     //
@@ -145,4 +130,9 @@ public class GLAutoDrawableDelegate extends GLAutoDrawableBase {
     public final void setRealized(boolean realized) {
     }
 
+    @Override
+    public final void swapBuffers() throws GLException {
+         defaultSwapBuffers();
+    }
+        
 }
diff --git a/src/jogl/classes/javax/media/opengl/awt/GLCanvas.java b/src/jogl/classes/javax/media/opengl/awt/GLCanvas.java
index c2e36ef9b..694a081b8 100644
--- a/src/jogl/classes/javax/media/opengl/awt/GLCanvas.java
+++ b/src/jogl/classes/javax/media/opengl/awt/GLCanvas.java
@@ -84,6 +84,8 @@ import javax.media.opengl.Threading;
 
 import com.jogamp.common.GlueGenVersion;
 import com.jogamp.common.util.VersionUtil;
+import com.jogamp.common.util.locks.LockFactory;
+import com.jogamp.common.util.locks.RecursiveLock;
 import com.jogamp.nativewindow.awt.AWTGraphicsConfiguration;
 import com.jogamp.nativewindow.awt.AWTGraphicsDevice;
 import com.jogamp.nativewindow.awt.AWTGraphicsScreen;
@@ -132,20 +134,6 @@ import jogamp.opengl.GLDrawableHelper;
  * <ul>
  *   <li><pre>sun.awt.noerasebackground=true</pre></li>
  * </ul>
- * <p>
- * FIXME: If this instance runs in multithreading mode, see {@link Threading#isSingleThreaded()} (default: single-thread), 
- *        proper recursive locking is required for drawable/context @ destroy and display. 
- *        Recreation etc could pull those instances while animating!
- *        Simply locking before using drawable/context offthread
- *        would allow a deadlock situation!
- * </p>
- * <p>
- * NOTE: [MT-0] Methods utilizing [volatile] drawable/context are not synchronized.
-         In case any of the methods are called outside of a locked state
-         extra care should be added. Maybe we shall expose locking facilities to the user.
-         However, since the user shall stick to the GLEventListener model while utilizing
-         GLAutoDrawable implementations, she is safe due to the implicit locked state.
- * </p>
  */
 
 @SuppressWarnings("serial")
@@ -153,11 +141,12 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   private static final boolean DEBUG = Debug.debug("GLCanvas");
 
+  private final RecursiveLock lock = LockFactory.createRecursiveLock();
   private final GLDrawableHelper helper = new GLDrawableHelper();
   private AWTGraphicsConfiguration awtConfig;
-  private volatile GLDrawable drawable;   // volatile avoids locking all accessors. FIXME still need to sync destroy/display
+  private volatile GLDrawable drawable; // volatile: avoid locking for read-only access
   private GLContextImpl context;
-  private boolean sendReshape = false;
+  private volatile boolean sendReshape = false; // volatile: maybe written by EDT w/o locking
 
   // copy of the cstr args, mainly for recreation
   private GLCapabilitiesImmutable capsReqUser;
@@ -278,8 +267,9 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   @Override
   public final boolean isOffscreenLayerSurfaceEnabled() {
-      if(null != drawable) {
-          return ((JAWTWindow)drawable.getNativeSurface()).isOffscreenLayerSurfaceEnabled();
+      final GLDrawable _drawable = drawable;
+      if(null != _drawable) {
+          return ((JAWTWindow)_drawable.getNativeSurface()).isOffscreenLayerSurfaceEnabled();
       }
       return false;
   }
@@ -398,12 +388,18 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   @Override
   public GLContext createContext(final GLContext shareWith) {
-    if(drawable != null) {
-      final GLContext _ctx = drawable.createContext(shareWith);
-      _ctx.setContextCreationFlags(additionalCtxCreationFlags);
-      return _ctx;
+    final RecursiveLock _lock = lock;
+    _lock.lock();
+    try {
+        if(drawable != null) {
+          final GLContext _ctx = drawable.createContext(shareWith);
+          _ctx.setContextCreationFlags(additionalCtxCreationFlags);
+          return _ctx;
+        }
+        return null;
+    } finally {
+        _lock.unlock();
     }
-    return null;
   }
     
   @Override
@@ -412,7 +408,8 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   @Override
   public boolean isRealized() {
-      return (null != drawable) ? drawable.isRealized() : false;
+      final GLDrawable _drawable = drawable;
+      return ( null != _drawable ) ? _drawable.isRealized() : false;
   }
 
   @Override
@@ -427,50 +424,13 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   @Override
   public void display() {
-    if( !validateGLDrawable() ) {
-        if(DEBUG) {
-            System.err.println(getThreadName()+": Info: GLCanvas display - skipped GL render, drawable not valid yet");
-        }
-        return; // not yet available ..
-    }
     Threading.invoke(true, displayOnEDTAction, getTreeLock());
-
     awtWindowClosingProtocol.addClosingListenerOneShot();
   }
 
   private void dispose(boolean regenerate) {
-    final GLAnimatorControl animator =  getAnimator();
-    if(DEBUG) {
-        System.err.println(getThreadName()+": Info: dispose("+regenerate+") - START, hasContext " +
-                (null!=context) + ", hasDrawable " + (null!=drawable)+", "+animator);
-        Thread.dumpStack();
-    }
-
-    if(null!=drawable && null!=context) { // drawable is volatile!
-        boolean animatorPaused = false;
-        if(null!=animator) {
-            // can't remove us from animator for recreational addNotify()
-            animatorPaused = animator.pause();
-        }
-
-        disposeRegenerate=regenerate;
-
-        if(context.isCreated()) {
-            Threading.invoke(true, disposeOnEDTAction, getTreeLock());
-        }
-
-        if(animatorPaused) {
-            animator.resume();
-        }
-    }
-
-    if(!regenerate) {
-        disposeAbstractGraphicsDevice();
-    }
-
-    if(DEBUG) {
-        System.err.println(getThreadName()+": dispose("+regenerate+") - END, "+animator);
-    }
+    disposeRegenerate=regenerate;
+    Threading.invoke(true, disposeOnEDTAction, getTreeLock());
   }
 
   /**
@@ -530,43 +490,49 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
     @SuppressWarnings("deprecation")
     @Override
   public void addNotify() {
-    if(DEBUG) {
-        System.err.println(getThreadName()+": Info: addNotify - start, bounds: "+this.getBounds());
-        Thread.dumpStack();
-    }
-
-    /**
-     * 'super.addNotify()' determines the GraphicsConfiguration,
-     * while calling this class's overriden 'getGraphicsConfiguration()' method
-     * after which it creates the native peer.
-     * Hence we have to set the 'awtConfig' before since it's GraphicsConfiguration
-     * is being used in getGraphicsConfiguration().
-     * This code order also allows recreation, ie re-adding the GLCanvas.
-     */
-    awtConfig = chooseGraphicsConfiguration(capsReqUser, capsReqUser, chooser, device);
-    if(null==awtConfig) {
-        throw new GLException("Error: NULL AWTGraphicsConfiguration");
-    }
-
-    // before native peer is valid: X11
-    disableBackgroundErase();
-
-    // issues getGraphicsConfiguration() and creates the native peer
-    super.addNotify();
-
-    // after native peer is valid: Windows
-    disableBackgroundErase();
-
-    if (!Beans.isDesignTime()) {
-        createDrawableAndContext();
-    }
-
-    // init drawable by paint/display makes the init sequence more equal
-    // for all launch flavors (applet/javaws/..)
-    // validateGLDrawable();
-
-    if(DEBUG) {
-        System.err.println(getThreadName()+": Info: addNotify - end: peer: "+getPeer());
+    final RecursiveLock _lock = lock;
+    _lock.lock();
+    try {    
+        if(DEBUG) {
+            System.err.println(getThreadName()+": Info: addNotify - start, bounds: "+this.getBounds());
+            Thread.dumpStack();
+        }
+    
+        /**
+         * 'super.addNotify()' determines the GraphicsConfiguration,
+         * while calling this class's overriden 'getGraphicsConfiguration()' method
+         * after which it creates the native peer.
+         * Hence we have to set the 'awtConfig' before since it's GraphicsConfiguration
+         * is being used in getGraphicsConfiguration().
+         * This code order also allows recreation, ie re-adding the GLCanvas.
+         */
+        awtConfig = chooseGraphicsConfiguration(capsReqUser, capsReqUser, chooser, device);
+        if(null==awtConfig) {
+            throw new GLException("Error: NULL AWTGraphicsConfiguration");
+        }
+    
+        // before native peer is valid: X11
+        disableBackgroundErase();
+    
+        // issues getGraphicsConfiguration() and creates the native peer
+        super.addNotify();
+    
+        // after native peer is valid: Windows
+        disableBackgroundErase();
+    
+        if (!Beans.isDesignTime()) {
+            createDrawableAndContext();
+        }
+    
+        // init drawable by paint/display makes the init sequence more equal
+        // for all launch flavors (applet/javaws/..)
+        // validateGLDrawable();
+    
+        if(DEBUG) {
+            System.err.println(getThreadName()+": Info: addNotify - end: peer: "+getPeer());
+        }
+    } finally {
+        _lock.unlock();
     }
   }
 
@@ -585,23 +551,24 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
   }
 
   private boolean validateGLDrawable() {
-    boolean realized = false;
-    if (!Beans.isDesignTime()) {
-        if ( null != drawable ) { // OK: drawable is volatile
-            realized = drawable.isRealized();
-            if ( !realized && 0 < drawable.getWidth() * drawable.getHeight() ) {
-                // make sure drawable realization happens on AWT EDT, due to AWTTree lock
-                AWTEDTExecutor.singleton.invoke(true, setRealizedOnEDTAction);
-                realized = true;
-                sendReshape=true; // ensure a reshape is being send ..
-                if(DEBUG) {
-                    System.err.println(getThreadName()+": Realized Drawable: "+drawable.toString());
-                    Thread.dumpStack();
-                }
+    final GLDrawable _drawable = drawable;
+    if ( null != _drawable ) {
+        if( _drawable.isRealized() ) {
+            return true;
+        }
+        if (!Beans.isDesignTime() &&
+             0 < _drawable.getWidth() * _drawable.getHeight() ) {
+            // make sure drawable realization happens on AWT EDT, due to AWTTree lock
+            AWTEDTExecutor.singleton.invoke(true, setRealizedOnEDTAction);
+            sendReshape=true; // ensure a reshape is being send ..
+            if(DEBUG) {
+                System.err.println(getThreadName()+": Realized Drawable: "+_drawable.toString());
+                Thread.dumpStack();
             }
+            return true;
         }
     }
-    return realized;
+    return false;
   }
   private Runnable setRealizedOnEDTAction = new Runnable() {
       @Override
@@ -633,9 +600,6 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
       try {
         dispose(false);
       } finally {
-        context=null;
-        drawable=null;
-        awtConfig=null;
         super.removeNotify();
       }
     }
@@ -655,7 +619,8 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
     @Override
   public void reshape(int x, int y, int width, int height) {
     super.reshape(x, y, width, height);
-    if(null != drawable && drawable.isRealized() && !drawable.getChosenGLCapabilities().isOnscreen()) {
+    final GLDrawable _drawable = drawable;
+    if(null != _drawable && _drawable.isRealized() && !_drawable.getChosenGLCapabilities().isOnscreen()) {
         dispose(true);
     } else {
         sendReshape = true;
@@ -710,13 +675,19 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   @Override
   public GLContext setContext(GLContext newCtx) {
-      final GLContext oldCtx = context;
-      final boolean newCtxCurrent = helper.switchContext(drawable, oldCtx, newCtx, additionalCtxCreationFlags);
-      context=(GLContextImpl)newCtx;
-      if(newCtxCurrent) {
-          context.makeCurrent();
+      final RecursiveLock _lock = lock;
+      _lock.lock();
+      try {
+          final GLContext oldCtx = context;
+          final boolean newCtxCurrent = helper.switchContext(drawable, oldCtx, newCtx, additionalCtxCreationFlags);
+          context=(GLContextImpl)newCtx;
+          if(newCtxCurrent) {
+              context.makeCurrent();
+          }
+          return oldCtx;
+      } finally {
+          _lock.unlock();
       }
-      return oldCtx;
   }
 
   @Override
@@ -729,15 +700,15 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
     if (Beans.isDesignTime()) {
       return null;
     }
-    GLContext ctx = getContext();
-    return (ctx == null) ? null : ctx.getGL();
+    final GLContext _context = context;
+    return (_context == null) ? null : _context.getGL();
   }
 
   @Override
   public GL setGL(GL gl) {
-    GLContext ctx = getContext();
-    if (ctx != null) {
-      ctx.setGL(gl);
+    final GLContext _context = context;
+    if (_context != null) {
+      _context.setGL(gl);
       return gl;
     }
     return null;
@@ -762,8 +733,9 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
   @Override
   public void setContextCreationFlags(int flags) {
     additionalCtxCreationFlags = flags;
-    if(null != context) {
-      context.setContextCreationFlags(additionalCtxCreationFlags);
+    final GLContext _context = context;
+    if(null != _context) {
+      _context.setContextCreationFlags(additionalCtxCreationFlags);
     }
   }
 
@@ -796,26 +768,30 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
 
   @Override
   public NativeSurface getNativeSurface() {
-    return (null != drawable) ? drawable.getNativeSurface() : null;
+    final GLDrawable _drawable = drawable;
+    return (null != _drawable) ? _drawable.getNativeSurface() : null;
   }
 
   @Override
   public long getHandle() {
-    return (null != drawable) ? drawable.getHandle() : 0;
+    final GLDrawable _drawable = drawable;
+    return (null != _drawable) ? _drawable.getHandle() : 0;
   }
 
   @Override
   public GLDrawableFactory getFactory() {
-    return (null != drawable) ? drawable.getFactory() : null;
+    final GLDrawable _drawable = drawable;
+    return (null != _drawable) ? _drawable.getFactory() : null;
   }
 
   @Override
   public String toString() {
-    final int dw = (null!=drawable) ? drawable.getWidth() : -1;
-    final int dh = (null!=drawable) ? drawable.getHeight() : -1;
+    final GLDrawable _drawable = drawable;
+    final int dw = (null!=_drawable) ? _drawable.getWidth() : -1;
+    final int dh = (null!=_drawable) ? _drawable.getHeight() : -1;
 
     return "AWT-GLCanvas[Realized "+isRealized()+
-                          ",\n\t"+((null!=drawable)?drawable.getClass().getName():"null-drawable")+
+                          ",\n\t"+((null!=_drawable)?_drawable.getClass().getName():"null-drawable")+
                           ",\n\tFactory   "+getFactory()+
                           ",\n\thandle    0x"+Long.toHexString(getHandle())+
                           ",\n\tDrawable size "+dw+"x"+dh+
@@ -829,7 +805,7 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
   //
 
   private boolean disposeRegenerate;
-  private final Runnable postDisposeAction = new Runnable() {
+  private final Runnable postDisposeOnEDTAction = new Runnable() {
     @Override
     public void run() {
       context=null;
@@ -859,7 +835,47 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
   private final Runnable disposeOnEDTAction = new Runnable() {
     @Override
     public void run() {
-      helper.disposeGL(GLCanvas.this, drawable, context, postDisposeAction);
+        final RecursiveLock _lock = lock;
+        _lock.lock();
+        try {            
+            final GLAnimatorControl animator =  getAnimator();
+
+            if(DEBUG) {
+                System.err.println(getThreadName()+": Info: dispose("+disposeRegenerate+") - START, hasContext " +
+                        (null!=context) + ", hasDrawable " + (null!=drawable)+", "+animator);
+                Thread.dumpStack();
+            }
+        
+            if(null!=drawable && null!=context) {
+                boolean animatorPaused = false;
+                if(null!=animator) {
+                    // can't remove us from animator for recreational addNotify()
+                    animatorPaused = animator.pause();
+                }
+        
+                if(context.isCreated()) {
+                    helper.disposeGL(GLCanvas.this, drawable, context, postDisposeOnEDTAction);
+                }
+        
+                if(animatorPaused) {
+                    animator.resume();
+                }
+            }
+        
+            if(!disposeRegenerate) {
+                if(null != awtConfig) {
+                    disposeAbstractGraphicsDevice();
+                }
+                awtConfig=null;
+            }
+        
+            if(DEBUG) {
+                System.err.println(getThreadName()+": dispose("+disposeRegenerate+") - END, "+animator);
+            }
+            
+        } finally {
+            _lock.unlock();
+        }
     }
   };
 
@@ -879,7 +895,6 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
           if(DEBUG) {
             System.err.println(getThreadName()+": GLCanvas.dispose(false): closed GraphicsDevice: "+adeviceMsg+", result: "+closed);
           }
-          awtConfig=null;
       }
     }
   };
@@ -890,7 +905,7 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
    *
    * @see #chooseGraphicsConfiguration(javax.media.opengl.GLCapabilitiesImmutable, javax.media.opengl.GLCapabilitiesImmutable, javax.media.opengl.GLCapabilitiesChooser, java.awt.GraphicsDevice)
    */
-  void disposeAbstractGraphicsDevice()  {
+  private void disposeAbstractGraphicsDevice()  {
     if( EventQueue.isDispatchThread() || Thread.holdsLock(getTreeLock()) ) {
         disposeAbstractGraphicsDeviceAction.run();
     } else {
@@ -941,14 +956,30 @@ public class GLCanvas extends Canvas implements AWTGLAutoDrawable, WindowClosing
   private final Runnable displayOnEDTAction = new Runnable() {
     @Override
     public void run() {
-        helper.invokeGL(drawable, context, displayAction, initAction);
+        final RecursiveLock _lock = lock;
+        _lock.lock();
+        try {            
+            if( validateGLDrawable() ) {
+                helper.invokeGL(drawable, context, displayAction, initAction);
+            } else if(DEBUG) {
+                System.err.println(getThreadName()+": Info: GLCanvas display - skipped GL render, drawable not valid yet");
+            }
+        } finally {
+            _lock.unlock();
+        }
     }
   };
 
   private final Runnable swapBuffersOnEDTAction = new Runnable() {
     @Override
     public void run() {
-        helper.invokeGL(drawable, context, swapBuffersAction, initAction);
+        final RecursiveLock _lock = lock;
+        _lock.lock();
+        try {            
+            helper.invokeGL(drawable, context, swapBuffersAction, initAction);
+        } finally {
+            _lock.unlock();
+        }
     }
   };
 
diff --git a/src/jogl/classes/jogamp/opengl/GLAutoDrawableBase.java b/src/jogl/classes/jogamp/opengl/GLAutoDrawableBase.java
index 5c6d7446a..fe6d0fd76 100644
--- a/src/jogl/classes/jogamp/opengl/GLAutoDrawableBase.java
+++ b/src/jogl/classes/jogamp/opengl/GLAutoDrawableBase.java
@@ -46,6 +46,7 @@ import javax.media.opengl.GLException;
 import javax.media.opengl.GLProfile;
 import javax.media.opengl.GLRunnable;
 
+import com.jogamp.common.util.locks.RecursiveLock;
 import com.jogamp.opengl.util.Animator;
 
 
@@ -63,11 +64,11 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
     protected final GLDrawableHelper helper = new GLDrawableHelper();
     protected final FPSCounterImpl fpsCounter = new FPSCounterImpl();
     
-    protected GLDrawableImpl drawable;
+    protected volatile GLDrawableImpl drawable; // volatile: avoid locking for read-only access
     protected GLContextImpl context;
     protected int additionalCtxCreationFlags = 0;
-    protected boolean sendReshape = false;
-    protected boolean sendDestroy = false;
+    protected volatile boolean sendReshape = false; // volatile: maybe written by WindowManager thread w/o locking
+    protected volatile boolean sendDestroy = false; // volatile: maybe written by WindowManager thread w/o locking
 
     public GLAutoDrawableBase(GLDrawableImpl drawable, GLContextImpl context) {
         this.drawable = drawable;
@@ -75,31 +76,47 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
         resetFPSCounter();        
     }
    
+    protected abstract RecursiveLock getLock();
+    
     /** Returns the delegated GLDrawable */
     public final GLDrawable getDelegatedDrawable() { return drawable; }
     
     /** Default implementation to handle repaint events from the windowing system */
-    protected void defaultWindowRepaintOp() {
-        if( null != drawable && drawable.isRealized() ) {
-            if( !drawable.getNativeSurface().isSurfaceLockedByOtherThread() && !helper.isAnimatorAnimating() ) {
+    protected final void defaultWindowRepaintOp() {
+        final GLDrawable _drawable = drawable;
+        if( null != _drawable && _drawable.isRealized() ) {
+            if( !_drawable.getNativeSurface().isSurfaceLockedByOtherThread() && !helper.isAnimatorAnimating() ) {
                 display();
             }
-        }        
+        }
     }
     
     /** Default implementation to handle resize events from the windowing system */
-    protected void defaultWindowResizedOp() {
-        if( null!=drawable ) {
+    protected final void defaultWindowResizedOp() {
+        final GLDrawable _drawable = drawable;
+        if( null!=_drawable ) {
             if(DEBUG) {
                 System.err.println("GLAutoDrawableBase.sizeChanged: ("+Thread.currentThread().getName()+"): "+getWidth()+"x"+getHeight()+" - surfaceHandle 0x"+Long.toHexString(getNativeSurface().getSurfaceHandle()));
             }
-            sendReshape = true;
-            defaultWindowRepaintOp();
+            sendReshape = true; // async if display() doesn't get called below, but avoiding deadlock
+            if( _drawable.isRealized() ) {
+                if( !_drawable.getNativeSurface().isSurfaceLockedByOtherThread() && !helper.isAnimatorAnimating() ) {
+                    display();
+                }
+            }        
         }
     }
 
-    /** Default implementation to handle destroy notifications from the windowing system */
-    protected void defaultWindowDestroyNotifyOp() {
+    /** 
+     * Default implementation to handle destroy notifications from the windowing system.
+     * 
+     * <p>
+     * If the {@link NativeSurface} does not implement {@link WindowClosingProtocol} 
+     * or {@link WindowClosingMode#DISPOSE_ON_CLOSE} is enabled (default),
+     * {@link #defaultDestroy()} is being called.
+     * </p> 
+     */
+    protected final void defaultWindowDestroyNotifyOp() {
         final NativeSurface ns = getNativeSurface();
         final boolean shallClose;
         if(ns instanceof WindowClosingProtocol) {
@@ -108,27 +125,66 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
             shallClose = true;
         }        
         if( shallClose ) {
-            // Is an animator thread perform rendering?
-            if (helper.isExternalAnimatorRunning()) {
-                // Pause animations before initiating safe destroy.
-                final GLAnimatorControl ctrl = helper.getAnimator();
-                final boolean isPaused = ctrl.pause();
-                destroy();
-                if(isPaused) {
-                    ctrl.resume();
-                }
-            } else if (null != ns && ns.isSurfaceLockedByOtherThread()) {
-                // surface is locked by another thread
-                // Flag that destroy should be performed on the next
-                // attempt to display.
-                sendDestroy = true;
-            } else {
-                // Without an external thread animating or locking the
-                // surface, we are safe.
-                destroy ();
-            }
+            destroyAvoidAwareOfLocking();
         }                
     }
+
+    /**
+     * Calls {@link #destroy()} 
+     * directly if the following requirements are met:
+     * <ul>
+     *   <li>An {@link GLAnimatorControl} is bound (see {@link #getAnimator()}) and running on another thread. 
+     *       Here we pause the animation while issuing the destruction.</li>
+     *   <li>Surface is not locked by another thread (considered anonymous).</li>
+     * </ul>
+     * <p>
+     * Otherwise destroy is being flagged to be called within the next 
+     * call of display().
+     * </p>
+     * <p>
+     * This method is being used to avoid deadlock if
+     * destruction is desired by <i>other</i> threads, e.g. the window manager.
+     * </p>
+     * @see #defaultWindowDestroyNotifyOp()
+     * @see #defaultDisplay()
+     */
+    protected final void destroyAvoidAwareOfLocking() {
+        final NativeSurface ns = getNativeSurface();
+        
+        final GLAnimatorControl ctrl = helper.getAnimator();
+        
+        // Is an animator thread perform rendering?
+        if ( helper.isAnimatorRunningOnOtherThread() ) {
+            // Pause animations before initiating safe destroy.
+            final boolean isPaused = ctrl.pause();
+            destroy();
+            if(isPaused) {
+                ctrl.resume();
+            }
+        } else if (null != ns && ns.isSurfaceLockedByOtherThread()) {
+            // surface is locked by another thread
+            // Flag that destroy should be performed on the next
+            // attempt to display.
+            sendDestroy = true; // async, but avoiding deadlock
+        } else {
+            // Without an external thread animating or locking the
+            // surface, we are safe.
+            destroy();
+        }
+    }
+    
+    /**
+     * Calls {@link #destroyImplInLock()} while claiming the lock. 
+     */
+    protected final void defaultDestroy() {
+        final RecursiveLock lock = getLock();
+        lock.lock();
+        try {
+            destroyImplInLock();
+        } finally {
+            lock.unlock();
+        }
+    }
     
     /**
      * Default implementation to destroys the drawable and context of this GLAutoDrawable:
@@ -137,24 +193,42 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
      *   <li>destroys the GLContext, if valid</li>
      *   <li>destroys the GLDrawable, if valid</li>
      * </ul>
+     * <p>Method assumes the lock is being hold.</p>
+     * <p>Override it to extend it to destroy your resources, i.e. the actual window.
+     * In such case call <code>super.destroyImplInLock</code> first.</p>
      */
-    protected void defaultDestroyOp() {
-        if( null != drawable && drawable.isRealized() ) {
-            if( null != context && context.isCreated() ) {
+    protected void destroyImplInLock() {
+        final GLContext _context = context;
+        final GLDrawable _drawable = drawable;
+        if( null != _drawable && _drawable.isRealized() ) {
+            if( null != _context && _context.isCreated() ) {
                 // Catch dispose GLExceptions by GLEventListener, just 'print' them
                 // so we can continue with the destruction.
                 try {
-                    helper.disposeGL(this, drawable, context, null);
+                    helper.disposeGL(this, _drawable, _context, null);
                 } catch (GLException gle) {
                     gle.printStackTrace();
                 }
             }
-            drawable.setRealized(false);
+            _drawable.setRealized(false);
         }
         context = null;
         drawable = null;        
     }
     
+    public final void defaultSwapBuffers() throws GLException {
+        final RecursiveLock _lock = getLock();
+        _lock.lock();
+        try {            
+            if(drawable!=null && context != null) {
+                drawable.swapBuffers();
+                helper.invokeGL(drawable, context, defaultSwapAction, defaultInitAction);
+            }
+        } finally {
+            _lock.unlock();
+        }
+    }
+
     //
     // GLAutoDrawable
     //
@@ -179,6 +253,30 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
             fpsCounter.tickFPS();
         } };
 
+    protected final void defaultDisplay() {
+        if( sendDestroy ) {
+            sendDestroy=false;
+            destroy();
+            return;
+        }
+        final RecursiveLock _lock = getLock();        
+        _lock.lock();
+        try {
+            if( null != context ) {
+                // surface is locked/unlocked implicit by context's makeCurrent/release
+                helper.invokeGL(drawable, context, defaultDisplayAction, defaultInitAction);
+            }
+        } finally {
+            _lock.unlock();
+        }
+    }
+        
+    protected final Runnable defaultSwapAction = new Runnable() {
+        @Override
+        public final void run() {
+            drawable.swapBuffers();
+        } } ;
+        
     @Override
     public final GLContext getContext() {
         return context;
@@ -186,27 +284,35 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
 
     @Override
     public final GLContext setContext(GLContext newCtx) {
-        final GLContext oldCtx = context;
-        final boolean newCtxCurrent = helper.switchContext(drawable, oldCtx, newCtx, additionalCtxCreationFlags);
-        context=(GLContextImpl)newCtx;
-        if(newCtxCurrent) {
-            context.makeCurrent();
+        final RecursiveLock lock = getLock();
+        lock.lock();
+        try {
+            final GLContext oldCtx = context;
+            final boolean newCtxCurrent = helper.switchContext(drawable, oldCtx, newCtx, additionalCtxCreationFlags);
+            context=(GLContextImpl)newCtx;
+            if(newCtxCurrent) {
+                context.makeCurrent();
+            }
+            return oldCtx;
+        } finally {
+            lock.unlock();
         }
-        return oldCtx;
     }
 
     @Override
     public final GL getGL() {
-        if (context == null) {
+        final GLContext _context = context;
+        if (_context == null) {
             return null;
         }
-        return context.getGL();
+        return _context.getGL();
     }
 
     @Override
     public final GL setGL(GL gl) {
-        if (context != null) {
-            context.setGL(gl);
+        final GLContext _context = context;
+        if (_context != null) {
+            _context.setGL(gl);
             return gl;
         }
         return null;
@@ -261,8 +367,9 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
     @Override
     public final void setContextCreationFlags(int flags) {
         additionalCtxCreationFlags = flags;        
-        if(null != context) {
-            context.setContextCreationFlags(additionalCtxCreationFlags);
+        final GLContext _context = context;
+        if(null != _context) {
+            _context.setContextCreationFlags(additionalCtxCreationFlags);
         }
     }
 
@@ -331,27 +438,36 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
         
     @Override
     public final GLContext createContext(final GLContext shareWith) {
-        if(drawable != null) {
-            final GLContext _ctx = drawable.createContext(shareWith);
-            _ctx.setContextCreationFlags(additionalCtxCreationFlags);
-            return _ctx;
+        final RecursiveLock lock = getLock();
+        lock.lock();
+        try {
+            if(drawable != null) {
+                final GLContext _ctx = drawable.createContext(shareWith);
+                _ctx.setContextCreationFlags(additionalCtxCreationFlags);
+                return _ctx;
+            }
+            return null;
+        } finally {
+            lock.unlock();
         }
-        return null;
     }
 
     @Override
     public final boolean isRealized() {
-        return null != drawable ? drawable.isRealized() : false;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.isRealized() : false;
     }
 
     @Override
     public int getWidth() {
-        return null != drawable ? drawable.getWidth() : 0;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.getWidth() : 0;
     }
 
     @Override
     public int getHeight() {
-        return null != drawable ? drawable.getHeight() : 0;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.getHeight() : 0;
     }
 
     /**
@@ -374,29 +490,26 @@ public abstract class GLAutoDrawableBase implements GLAutoDrawable, FPSCounter {
     }
 
     @Override
-    public final void swapBuffers() throws GLException {
-        if(drawable!=null && context != null) {
-            drawable.swapBuffers();
-        }
-    }
-
-    @Override
     public final GLCapabilitiesImmutable getChosenGLCapabilities() {
-        return null != drawable ? drawable.getChosenGLCapabilities() : null;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.getChosenGLCapabilities() : null;
     }
 
     @Override
     public final GLProfile getGLProfile() {
-        return null != drawable ? drawable.getGLProfile() : null;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.getGLProfile() : null;
     }
 
     @Override
     public final NativeSurface getNativeSurface() {
-        return null != drawable ? drawable.getNativeSurface() : null;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.getNativeSurface() : null;
     }
 
     @Override
     public final long getHandle() {
-        return null != drawable ? drawable.getHandle() : 0;
+        final GLDrawable _drawable = drawable;
+        return null != _drawable ? _drawable.getHandle() : 0;
     }
 }
diff --git a/src/jogl/classes/jogamp/opengl/GLDrawableHelper.java b/src/jogl/classes/jogamp/opengl/GLDrawableHelper.java
index 0c01aa676..090c5fe69 100644
--- a/src/jogl/classes/jogamp/opengl/GLDrawableHelper.java
+++ b/src/jogl/classes/jogamp/opengl/GLDrawableHelper.java
@@ -189,8 +189,9 @@ public class GLDrawableHelper {
    */
   public final void dispose(GLAutoDrawable drawable) {
     synchronized(listenersLock) {
-        for (int i=0; i < listeners.size(); i++) {
-          listeners.get(i).dispose(drawable);
+        final ArrayList<GLEventListener> _listeners = listeners;
+        for (int i=0; i < _listeners.size(); i++) {
+          _listeners.get(i).dispose(drawable);
         }
     }
   }
@@ -209,8 +210,9 @@ public class GLDrawableHelper {
   /** The default init action to be called once after ctx is being created @ 1st makeCurrent(). */
   public final void init(GLAutoDrawable drawable) {
     synchronized(listenersLock) {
-        for (int i=0; i < listeners.size(); i++) {
-          final GLEventListener listener = listeners.get(i) ;
+        final ArrayList<GLEventListener> _listeners = listeners;
+        for (int i=0; i < _listeners.size(); i++) {
+          final GLEventListener listener = _listeners.get(i) ;
 
           // If make current ctx, invoked by invokGL(..), results in a new ctx, init gets called.
           // This may happen not just for initial setup, but for ctx recreation due to resource change (drawable/window),
@@ -232,8 +234,9 @@ public class GLDrawableHelper {
   }
   private final void displayImpl(GLAutoDrawable drawable) {
       synchronized(listenersLock) {
-          for (int i=0; i < listeners.size(); i++) {
-            final GLEventListener listener = listeners.get(i) ;
+          final ArrayList<GLEventListener> _listeners = listeners;
+          for (int i=0; i < _listeners.size(); i++) {
+            final GLEventListener listener = _listeners.get(i) ;
             // GLEventListener may need to be init, 
             // in case this one is added after the realization of the GLAutoDrawable
             init( listener, drawable, true /* sendReshape */) ; 
@@ -324,7 +327,7 @@ public class GLDrawableHelper {
     }
   }
 
-  public final boolean isExternalAnimatorRunning() {
+  public final boolean isAnimatorRunningOnOtherThread() {
     return ( null != animatorCtrl ) ? animatorCtrl.isStarted() && animatorCtrl.getThread() != Thread.currentThread() : false ;
   }
 
diff --git a/src/jogl/classes/jogamp/opengl/GLPbufferImpl.java b/src/jogl/classes/jogamp/opengl/GLPbufferImpl.java
index bbc28e283..6b64120fe 100644
--- a/src/jogl/classes/jogamp/opengl/GLPbufferImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLPbufferImpl.java
@@ -42,10 +42,14 @@ package jogamp.opengl;
 
 import javax.media.opengl.GLCapabilitiesImmutable;
 import javax.media.opengl.GLContext;
+import javax.media.opengl.GLDrawable;
 import javax.media.opengl.GLDrawableFactory;
 import javax.media.opengl.GLException;
 import javax.media.opengl.GLPbuffer;
 
+import com.jogamp.common.util.locks.LockFactory;
+import com.jogamp.common.util.locks.RecursiveLock;
+
 /** Platform-independent class exposing pbuffer functionality to
     applications. This class is not exposed in the public API as it
     would probably add no value; however it implements the GLDrawable
@@ -101,7 +105,7 @@ public class GLPbufferImpl extends GLAutoDrawableBase implements GLPbuffer {
   //
   // GLDrawable delegation
   // 
-  
+    
   @Override
   public final void setRealized(boolean realized) {
   }
@@ -109,6 +113,10 @@ public class GLPbufferImpl extends GLAutoDrawableBase implements GLPbuffer {
   //
   // GLAutoDrawable completion
   //
+  private final RecursiveLock lock = LockFactory.createRecursiveLock();  // instance wide lock
+  
+  @Override
+  protected final RecursiveLock getLock() { return lock; }
   
   @Override
   public final Object getUpstreamWidget() {
@@ -117,7 +125,7 @@ public class GLPbufferImpl extends GLAutoDrawableBase implements GLPbuffer {
   
   @Override
   public void destroy() {
-    defaultDestroyOp();
+    defaultDestroy();
   }
 
   @Override
@@ -126,12 +134,23 @@ public class GLPbufferImpl extends GLAutoDrawableBase implements GLPbuffer {
   }
 
   @Override
-  public void display() {
-    if( null != drawable && drawable.isRealized() && null != context ) {
-      helper.invokeGL(drawable, context, defaultDisplayAction, initAction);
+  public final void display() {
+    final RecursiveLock _lock = lock;        
+    _lock.lock(); // sync: context/drawable could been recreated/destroyed while animating
+    try {
+        if( null != context ) {
+          helper.invokeGL(drawable, context, defaultDisplayAction, initAction);
+        }
+    } finally {
+        _lock.unlock();
     }
   }
 
+  @Override
+  public final void swapBuffers() throws GLException {
+      defaultSwapBuffers();
+  }
+  
   //----------------------------------------------------------------------
   // Internals only below this point
   //