Fix NEWT EDTUtil Deadlock on EDTUtil.start()

DisplayImpl.runOnEDTIfAvail(..) issues EDTUtil.start()
while holding it's object-lock - if the EDT is not running,
then invokes the given task.

EDTUtil.start() impl. holds it's own edt-lock
while starting, then releases it's edt-lock while issuing a null-task.

If another thread injects a blocking task right in-between
which also acquires the display's object-lock it deadlocks.

Simply remove issuing the null-task, so EDTUtil.start()
can return immediatly (releasing edt-lock)
and allowing DisplayImpl.runOnEDTIfAvail(..)
also to release it's object-lock.

The other threads task then can be executed,
where the 'starting task' would come second - which is OK,
even though a rare occasion.

Above situation was triggered via AWT/NEWT reparenting w/ forced recreation
via TestParenting01dAWT.

+++

The null-task at EDTUtil.start() was remaining code to ensure
that the EDT completed starting, which is redundant.

4 files changed, 15 insertions, 19 deletions

diff --git a/src/newt/classes/com/jogamp/newt/util/EDTUtil.java b/src/newt/classes/com/jogamp/newt/util/EDTUtil.java
index 582dc3e1f..58aa67105 100644
--- a/src/newt/classes/com/jogamp/newt/util/EDTUtil.java
+++ b/src/newt/classes/com/jogamp/newt/util/EDTUtil.java
@@ -71,13 +71,13 @@ public interface EDTUtil {
      * and the caller should wait {@link #waitUntilStopped() until it's stopped}.
      * </p>
      *
-     * @return true if EDT has been successfully restarted, otherwise false
      * @throws IllegalStateException if EDT is running and not subject to be stopped, i.e. {@link #isRunning()} returns true
+     * @throws RuntimeException if EDT could not be started
      *
      * @see #invokeStop(boolean, java.lang.Runnable)
      * @see #waitUntilStopped()
      */
-    public boolean start() throws IllegalStateException;
+    public void start() throws IllegalStateException;
 
     /**
      * Returns true if the current thread is the event dispatch thread (EDT).
diff --git a/src/newt/classes/jogamp/newt/DefaultEDTUtil.java b/src/newt/classes/jogamp/newt/DefaultEDTUtil.java
index d481ce8f9..7afa8d746 100644
--- a/src/newt/classes/jogamp/newt/DefaultEDTUtil.java
+++ b/src/newt/classes/jogamp/newt/DefaultEDTUtil.java
@@ -82,7 +82,7 @@ public class DefaultEDTUtil implements EDTUtil {
     }
 
     @Override
-    public final boolean start() throws IllegalStateException {
+    public final void start() throws IllegalStateException {
         synchronized(edtLock) {
             if( edt.isRunning() ) {
                 throw new IllegalStateException("EDT still running and not subject to stop. Curr "+Thread.currentThread().getName()+", EDT "+edt.getName()+", isRunning "+edt.isRunning+", shouldStop "+edt.shouldStop);
@@ -103,7 +103,9 @@ public class DefaultEDTUtil implements EDTUtil {
             }
             startImpl();
         }
-        return invoke(true, nullTask);
+        if( !edt.isRunning() ) {
+            throw new RuntimeException("EDT could not be started: "+edt);
+        }
     }
 
     private final void startImpl() {
diff --git a/src/newt/classes/jogamp/newt/driver/awt/AWTEDTUtil.java b/src/newt/classes/jogamp/newt/driver/awt/AWTEDTUtil.java
index 4a7193306..407d3abf9 100644
--- a/src/newt/classes/jogamp/newt/driver/awt/AWTEDTUtil.java
+++ b/src/newt/classes/jogamp/newt/driver/awt/AWTEDTUtil.java
@@ -68,7 +68,7 @@ public class AWTEDTUtil implements EDTUtil {
     }
 
     @Override
-    public final boolean start() throws IllegalStateException {
+    public final void start() throws IllegalStateException {
         synchronized(edtLock) {
             if( nedt.isRunning() ) {
                 throw new IllegalStateException("EDT still running and not subject to stop. Curr "+Thread.currentThread().getName()+", NEDT "+nedt.getName()+", isRunning "+nedt.isRunning+", shouldStop "+nedt.shouldStop+", on AWT-EDT "+EventQueue.isDispatchThread());
@@ -82,7 +82,9 @@ public class AWTEDTUtil implements EDTUtil {
             }
             startImpl();
         }
-        return invoke(true, nullTask);
+        if( !nedt.isRunning() ) {
+            throw new RuntimeException("EDT could not be started: "+nedt);
+        }
     }
 
     private final void startImpl() {
@@ -128,11 +130,6 @@ public class AWTEDTUtil implements EDTUtil {
         return invokeImpl(wait, task, false);
     }
 
-    private static Runnable nullTask = new Runnable() {
-        @Override
-        public void run() { }
-    };
-
     private final boolean invokeImpl(boolean wait, Runnable task, boolean stop) {
         Throwable throwable = null;
         RunnableTask rTask = null;
diff --git a/src/newt/classes/jogamp/newt/swt/SWTEDTUtil.java b/src/newt/classes/jogamp/newt/swt/SWTEDTUtil.java
index db89690f4..91c18f023 100644
--- a/src/newt/classes/jogamp/newt/swt/SWTEDTUtil.java
+++ b/src/newt/classes/jogamp/newt/swt/SWTEDTUtil.java
@@ -78,7 +78,7 @@ public class SWTEDTUtil implements EDTUtil {
     }
 
     @Override
-    public final boolean start() throws IllegalStateException {
+    public final void start() throws IllegalStateException {
         final boolean swtDisposed = swtDisplay.isDisposed();
         synchronized(edtLock) {
             if( nedt.isRunning() ) {
@@ -99,9 +99,11 @@ public class SWTEDTUtil implements EDTUtil {
             }
         }
         if( !swtDisposed ) {
-            return invoke(true, nullTask);
+            if( !nedt.isRunning() ) {
+                throw new RuntimeException("EDT could not be started: "+nedt);
+            }
         } else {
-            return false;
+            // FIXME: Throw exception ?
         }
     }
 
@@ -149,11 +151,6 @@ public class SWTEDTUtil implements EDTUtil {
         return invokeImpl(wait, task, false);
     }
 
-    private static Runnable nullTask = new Runnable() {
-        @Override
-        public void run() { }
-    };
-
     private final boolean invokeImpl(boolean wait, Runnable task, boolean stop) {
         Throwable throwable = null;
         RunnableTask rTask = null;