[7u6] Review request for 7177040: Deadlock between PostEventQueue.noEvents, EventQueue.isDispatchThread and SwingUtilities.invokeLater (original) (raw)

Oleg Pekhovskiy oleg.pekhovskiy at oracle.com
Wed Jul 11 08:24:40 PDT 2012

Hi!

Please review the fix for CR: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7177040

Webrev: http://cr.openjdk.java.net/~bagiras/7u6/7177040.1

The idea of the fix is that there are two concurrent threads that try to get two synchronization objects EventQueue.pushPopLock and PostEventQueue itself. 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 PostEventQueue.flush().

Thanks, Oleg

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