While working with some fix I have faced the following deadlock:

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2006-07-31 17:22:36
Full thread dump Java HotSpot(TM) Client VM (1.6.0-rc-b88 mixed mode):

"Image Fetcher 3" daemon prio=8 tid=0x0b13bc00 nid=0xcf4 in Object.wait() [0x0b84f000..0x0b84fb94]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x02a90148> (a java.util.Vector)
        at sun.awt.image.ImageFetcher.nextImage(ImageFetcher.java:114)
        - locked <0x02a90148> (a java.util.Vector)
        at sun.awt.image.ImageFetcher.fetchloop(ImageFetcher.java:167)
        at sun.awt.image.ImageFetcher.run(ImageFetcher.java:136)

"AWT-EventQueue-0" prio=6 tid=0x0b0fb000 nid=0xc14 runnable [0x0b6ef000..0x0b6efc14]
   java.lang.Thread.State: RUNNABLE
        at sun.awt.KeyboardFocusManagerPeerImpl.getNativeFocusedWindow(Native Method)
        at sun.awt.KeyboardFocusManagerPeerImpl.getCurrentFocusedWindow(KeyboardFocusManagerPeerImpl.java:27)
        at java.awt.KeyboardFocusManager.getNativeFocusedWindow(KeyboardFocusManager.java:566)
        at java.awt.KeyboardFocusManager.markClearGlobalFocusOwner(KeyboardFocusManager.java:2474)
        - locked <0x02ef7980> (a java.util.LinkedList)
        at java.awt.KeyboardFocusManager._clearGlobalFocusOwner(KeyboardFocusManager.java:551)
        at java.awt.KeyboardFocusManager.clearGlobalFocusOwner(KeyboardFocusManager.java:547)
        at java.awt.Component.doAutoTransfer(Component.java:7246)
        at java.awt.Component.autoTransferFocus(Component.java:7237)
        at java.awt.Component.autoTransferFocus(Component.java:7212)
        at java.awt.Component.hide(Component.java:1448)
        - locked <0x02efc9c8> (a java.awt.Component$AWTTreeLock)
        at javax.swing.JInternalFrame.hide(JInternalFrame.java:1744)
        at java.awt.Component.show(Component.java:1418)
        at java.awt.Component.setVisible(Component.java:1369)
        at javax.swing.JComponent.setVisible(JComponent.java:2585)
        at javax.swing.JInternalFrame.setClosed(JInternalFrame.java:809)
        at javax.swing.JOptionPane$5.propertyChange(JOptionPane.java:1523)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
        at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)
        at java.awt.Component.firePropertyChange(Component.java:7810)
        at javax.swing.JOptionPane.setValue(JOptionPane.java:1940)
        at javax.swing.plaf.basic.BasicOptionPaneUI$ButtonActionListener.actionPerformed(BasicOptionPaneUI.java:
1184)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:5999)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3240)
        at java.awt.Component.processEvent(Component.java:5764)
        at java.awt.Container.processEvent(Container.java:1984)
        at java.awt.Component.dispatchEventImpl(Component.java:4407)
        at java.awt.Container.dispatchEventImpl(Container.java:2042)
        at java.awt.Component.dispatchEvent(Component.java:4237)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4252)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3921)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3851)
        at java.awt.Container.dispatchEventImpl(Container.java:2028)
        at java.awt.Window.dispatchEventImpl(Window.java:2415)
        at java.awt.Component.dispatchEvent(Component.java:4237)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:600)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:164)
        at java.awt.Container$2.run(Container.java:2627)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:598)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

"AWT-Windows" daemon prio=6 tid=0x0b0b8000 nid=0xfb8 waiting for monitor entry [0x0b45f000..0x0b45fc94]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at java.awt.KeyboardFocusManager.shouldNativelyFocusHeavyweight(KeyboardFocusManager.java:2282)
        - waiting to lock <0x02ef7980> (a java.util.LinkedList)
        at sun.awt.windows.WToolkit.eventLoop(Native Method)
        at sun.awt.windows.WToolkit.run(WToolkit.java:290)
        at java.lang.Thread.run(Thread.java:619)

"AWT-Shutdown" prio=6 tid=0x0b0b7400 nid=0xf04 in Object.wait() [0x0b40f000..0x0b40fd14]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x02ef4db8> (a java.lang.Object)
        at java.lang.Object.wait(Object.java:485)
        at sun.awt.AWTAutoShutdown.run(AWTAutoShutdown.java:259)
        - locked <0x02ef4db8> (a java.lang.Object)
        at java.lang.Thread.run(Thread.java:619)

"Java2D Disposer" daemon prio=10 tid=0x0b0c4400 nid=0x6c8 in Object.wait() [0x0b3bf000..0x0b3bfd94]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x02ef4e50> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:116)
        - locked <0x02ef4e50> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:132)
        at sun.java2d.Disposer.run(Disposer.java:125)
        at java.lang.Thread.run(Thread.java:619)

"Low Memory Detector" daemon prio=6 tid=0x0aaa7000 nid=0xc04 runnable [0x00000000..0x00000000]
   java.lang.Thread.State: RUNNABLE

"CompilerThread0" daemon prio=10 tid=0x0aaa5400 nid=0xf60 waiting on condition [0x00000000..0x0ad2f71c]
   java.lang.Thread.State: RUNNABLE

"Attach Listener" daemon prio=10 tid=0x0aaa3400 nid=0x9a4 runnable [0x00000000..0x00000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=10 tid=0x0aaa2800 nid=0xf2c waiting on condition [0x00000000..0x00000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=8 tid=0x0aa93000 nid=0x9ac in Object.wait() [0x0ac3f000..0x0ac3fc94]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x02ef50a8> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:116)
        - locked <0x02ef50a8> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:132)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)

"Reference Handler" daemon prio=10 tid=0x0aa8ec00 nid=0xdb4 in Object.wait() [0x0abef000..0x0abefd14]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0x02ef5138> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:485)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:116)
        - locked <0x02ef5138> (a java.lang.ref.Reference$Lock)

"main" prio=6 tid=0x00296000 nid=0x720 runnable [0x003ff000..0x003ffe54]
   java.lang.Thread.State: RUNNABLE
        at sun.awt.windows.WComponentPeer._requestFocus(Native Method)
        at sun.awt.windows.WComponentPeer.requestFocus(WComponentPeer.java:551)
        at java.awt.Component.requestFocusHelper(Component.java:7109)
        at java.awt.Component.requestFocusHelper(Component.java:7070)
        at java.awt.Component.requestFocus(Component.java:6890)
        at javax.swing.JComponent.requestFocus(JComponent.java:1424)
        at javax.swing.JOptionPane.showInternalOptionDialog(JOptionPane.java:1300)
        at javax.swing.JOptionPane.showInternalMessageDialog(JOptionPane.java:1068)
        at javax.swing.JOptionPane.showInternalMessageDialog(JOptionPane.java:1042)
        at javax.swing.JOptionPane.showInternalMessageDialog(JOptionPane.java:1016)
        at OptionPaneTest.main(OptionPaneTest.java:36)

"VM Thread" prio=10 tid=0x0aa8bc00 nid=0x824 runnable

"VM Periodic Task Thread" prio=10 tid=0x0aaa8800 nid=0xf1c waiting on condition

JNI global references: 1369

Heap
 def new generation total 960K, used 292K [0x029b0000, 0x02ab0000, 0x02e90000)
  eden space 896K, 25% used [0x029b0000, 0x029e9370, 0x02a90000)
  from space 64K, 100% used [0x02a90000, 0x02aa0000, 0x02aa0000)
  to space 64K, 0% used [0x02aa0000, 0x02aa0000, 0x02ab0000)
 tenured generation total 4096K, used 527K [0x02e90000, 0x03290000, 0x069b0000)
   the space 4096K, 12% used [0x02e90000, 0x02f13de8, 0x02f13e00, 0x03290000)
 compacting perm gen total 12288K, used 7512K [0x069b0000, 0x075b0000, 0x0a9b0000)
   the space 12288K, 61% used [0x069b0000, 0x071063d0, 0x07106400, 0x075b0000)
No shared spaces configured.

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The test to reproduce the problem is attached, however it can be used to reproduce the bug only with the suggested fix for 6178755. That fix doesn't touch any of the focus issues (which are clearly seen in the stack trace above), but it makes the deadlock to happen more often.