<AWT Dev> [7u6] Review request for 7177040: Deadlock between PostEventQueue.noEvents, EventQueue.isDispatchThread and SwingUtilities.invokeLater
oleg.pekhovskiy at oracle.com
Wed Jul 11 08:24:40 PDT 2012
Please review the fix for CR:
The idea of the fix is that there are two concurrent threads that try to
get two synchronization objects EventQueue.pushPopLock and
For NetBeans these threads are (EDT & WarmUp) or (EDT & TimerQueue).
Problem happens when EDT is interrupted and goes to
EventQueue.detachDispatchThread() where EventQueue.pushPopLock is owned and
EDT is waiting to own PostEventQueue when calling
SunToolkit.isPostEventQueueEmpty() -> PostEventQueue.noEvents().
At the same time another thread calls EventQueue.postEvent() that calls
EventQueue.flushPendingEvents() -> PostEventQueue.flush() where
PostEventQueue is owned
and another thread is waiting to own EventQueue.pushPopLock when calling
EventQueue.postEvent() -> EventQueue.postEventPrivate().
To avoid potential deadlock I moved synchronization out of postEvent()'s
cycle in PostEventQueue.flush(),
but to be clear about the existence of Events that are not posted to
EventQueue yet I added PostEventQueue.isPending flag that is true until
the end of the cycle.
There are only two classes that utilize PostEventQueue.flush() method:
SunToolkit.flushPendingEvents() and SunToolkitSubclass.flushPendingEvents().
They are both synchronized by static SunToolkit.flushLock. That
eliminates the situation when we have overlapped calls of
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