Fix Bug 527: Creating a context w/ shared context, while the latter is in use (threading)

Bug 527 describes the situation where wglShareLists() fails (throws exception)
while the shared context is in use by another thread (some Animator).

It was reported by Jerome Jouvie.

The exception happens not everytime, but at least around 20% on manual tests
I have performed on the Windows platform.

The context in question are all JOGL's GL2, which natively where bound to an OpenGL 3.0 profile.
The WGL_ARB_create_context spec says http://www.opengl.org/registry/specs/ARB/wgl_create_context.txt:
+++
    Future versions of OpenGL may only support being added to a share
    group at context creation time. Specifying such a version of a
    context as either the <hglrc1> or <hglrc2> arguments to
    wglShareLists will fail. wglShareLists will return FALSE, and
    GetLastError will return ERROR_INCOMPATIBLE_DEVICE_CONTEXTS_ARB.
+++
Hence the 1st patch was to remove 'wglShareLists()' usage in case
we use the new WGL_ARB_create_context context creation method.
Even though this is a desired change, and works in general, it didn't fix the issue.

It seems that the shared context, which is passed @ new context creation,
cannot be used while it is in use itself in another thread.

This conclusion leads to the actual fix, ie. locking the shared context
while creating the new context which shares it.
Manual tests using this patch could not reproduce this issue (40 attempts).

Test: TestSharedContextListNEWT2

1 files changed, 12 insertions, 2 deletions

diff --git a/src/jogl/classes/jogamp/opengl/GLContextImpl.java b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
index fd34d8ac4..9611a1651 100644
--- a/src/jogl/classes/jogamp/opengl/GLContextImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLContextImpl.java
@@ -458,7 +458,17 @@ public abstract class GLContextImpl extends GLContext {
           if (!isCreated()) {
             GLProfile.initProfiles(
                     getGLDrawable().getNativeSurface().getGraphicsConfiguration().getScreen().getDevice());
-            newCreated = createImpl(); // may throws exception if fails!
+            final GLContextImpl shareWith = (GLContextImpl) GLContextShareSet.getShareContext(this);
+            if (null != shareWith) {
+                shareWith.getDrawableImpl().lockSurface();
+            }
+            try {
+                newCreated = createImpl(shareWith); // may throws exception if fails!
+            } finally {
+                if (null != shareWith) {
+                    shareWith.getDrawableImpl().unlockSurface();
+                }                
+            }
             if (DEBUG) {
                 if(newCreated) {
                     System.err.println(getThreadName() + ": !!! Create GL context OK: " + toHexString(contextHandle) + " for " + getClass().getName());
@@ -485,7 +495,7 @@ public abstract class GLContextImpl extends GLContext {
     }
   }
   protected abstract void makeCurrentImpl(boolean newCreatedContext) throws GLException;
-  protected abstract boolean createImpl() throws GLException ;
+  protected abstract boolean createImpl(GLContextImpl sharedWith) throws GLException ;
 
   /** 
    * Platform dependent but harmonized implementation of the <code>ARB_create_context</code>