<Swing Dev> [9] Review Request for 8030702: Deadlock between subclass of AbstractDocument and UndoManager

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:
bug: https://bugs.openjdk.java.net/browse/JDK-8030702
webrev: http://cr.openjdk.java.net/~ssadetsky/8030702/webrev.00/

The deadlock happens if undo/redo is called on the document while its 
content is being updated from another thread.
The proposed solution is to reorder mutex acquisitions in the undo 
manager assigned to an AbstractDocument. Document's lock is obtained in 
its undo manager with a minimal change of the current API. A stress test 
scenario is added to reproduce the issue.

--Semyon