TestAWTPanels crashes with LWJGL v3 on Linux

[stephengold]

With "jme3-lwjgl3" in JME v3.4.0-beta4, TestAWTPanels hangs. No output is generated, and no window appears.

Debugger suggests a deadlock, with the "jME Main" thread parked in line 103:

            panelsAreReady.await();

[stephengold]

This issue dates back at least to JME v3.2.4-stable.

[stephengold]

When I tested #1690 I accidentally used LWJGL v2 instead of LWJGL v3.

I just re-tested TestAWTPanels on Linux with LWJGL v3.3.0 and latest "master". I got the following crash:

> Task :jme3-examples:run
[ALSOFT] (EE) Failed to set real-time priority for thread: Operation not permitted (1)
[ALSOFT] (EE) Failed to set real-time priority for thread: Operation not permitted (1)
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007f59932effc4, pid=9041, tid=0x00007f5965790700
#
# JRE version: OpenJDK Runtime Environment (8.0_212-b04) (build 1.8.0_212-b04)
# Java VM: OpenJDK 64-Bit Server VM (25.212-b04 mixed mode linux-amd64 compressed oops)
# Problematic frame:
# C  [libpthread.so.0+0xbfc4]  pthread_mutex_lock+0x4
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/sgold/Git/jmonkeyengine/jme3-examples/hs_err_pid9041.log
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.java.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#

> Task :jme3-examples:run FAILED

Here's the stack trace from hs_err_pid9041.log:

Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C  [libpthread.so.0+0xbfc4]  pthread_mutex_lock+0x4
C  0x0000000000000000

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
j  sun.awt.X11.XlibWrapper.XGetDefault(JLjava/lang/String;Ljava/lang/String;)Ljava/lang/String;+0
j  sun.awt.X11.XToolkit.initializeMultiClickTime()V+12
j  sun.awt.X11.XToolkit.getMultiClickTime()I+6
j  sun.awt.X11.XToolkit.initializeDesktopProperties()V+82
j  java.awt.Toolkit.getDesktopProperty(Ljava/lang/String;)Ljava/lang/Object;+32
j  sun.swing.SwingUtilities2$AATextInfo.getAATextInfo(Z)Lsun/swing/SwingUtilities2$AATextInfo;+11
j  javax.swing.plaf.metal.MetalLookAndFeel.initComponentDefaults(Ljavax/swing/UIDefaults;)V+12062
j  javax.swing.plaf.basic.BasicLookAndFeel.getDefaults()Ljavax/swing/UIDefaults;+25
j  javax.swing.plaf.metal.MetalLookAndFeel.getDefaults()Ljavax/swing/UIDefaults;+9
j  javax.swing.UIManager.setLookAndFeel(Ljavax/swing/LookAndFeel;)V+79
j  javax.swing.UIManager.setLookAndFeel(Ljava/lang/String;)V+16
j  javax.swing.UIManager.initializeDefaultLAF(Ljava/util/Properties;)V+55
j  javax.swing.UIManager.initialize()V+9
j  javax.swing.UIManager.maybeInitialize()V+22
j  javax.swing.UIManager.getUI(Ljavax/swing/JComponent;)Ljavax/swing/plaf/ComponentUI;+0
j  javax.swing.JPanel.updateUI()V+2
j  javax.swing.JPanel.<init>(Ljava/awt/LayoutManager;Z)V+24
j  javax.swing.JPanel.<init>(Z)V+9
j  javax.swing.JPanel.<init>()V+2
j  javax.swing.JRootPane.createGlassPane()Ljava/awt/Component;+4
j  javax.swing.JRootPane.<init>()V+11
j  javax.swing.JFrame.createRootPane()Ljavax/swing/JRootPane;+4
j  javax.swing.JFrame.frameInit()V+16
j  javax.swing.JFrame.<init>(Ljava/lang/String;)V+21
j  jme3test.awt.TestAwtPanels.createWindowForPanel(Lcom/jme3/system/awt/AwtPanel;I)V+23
j  jme3test.awt.TestAwtPanels.access$400(Lcom/jme3/system/awt/AwtPanel;I)V+2
j  jme3test.awt.TestAwtPanels$2.run()V+94
j  java.awt.event.InvocationEvent.dispatch()V+47
j  java.awt.EventQueue.dispatchEventImpl(Ljava/awt/AWTEvent;Ljava/lang/Object;)V+21
j  java.awt.EventQueue.access$500(Ljava/awt/EventQueue;Ljava/awt/AWTEvent;Ljava/lang/Object;)V+3
j  java.awt.EventQueue$3.run()Ljava/lang/Void;+32
j  java.awt.EventQueue$3.run()Ljava/lang/Object;+1
v  ~StubRoutines::call_stub
j  java.security.AccessController.doPrivileged(Ljava/security/PrivilegedAction;Ljava/security/AccessControlContext;)Ljava/lang/Object;+0
j  java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Ljava/security/PrivilegedAction;Ljava/security/AccessControlContext;Ljava/security/AccessControlContext;)Ljava/lang/Object;+18
j  java.awt.EventQueue.dispatchEvent(Ljava/awt/AWTEvent;)V+46
j  java.awt.EventDispatchThread.pumpOneEventForFilters(I)V+140
j  java.awt.EventDispatchThread.pumpEventsForFilter(ILjava/awt/Conditional;Ljava/awt/EventFilter;)V+35
j  java.awt.EventDispatchThread.pumpEventsForHierarchy(ILjava/awt/Conditional;Ljava/awt/Component;)V+11
j  java.awt.EventDispatchThread.pumpEvents(ILjava/awt/Conditional;)V+4
j  java.awt.EventDispatchThread.pumpEvents(Ljava/awt/Conditional;)V+3
j  java.awt.EventDispatchThread.run()V+9
v  ~StubRoutines::call_stub