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

Anthony Petrov anthony.petrov at oracle.com
Wed Jul 11 08:35:53 PDT 2012

Hi Oleg,

  1. I suggest to rename isPending to isFlushing, as it reflects the current state of the PostEventQueue more precisely.

  2. I suggest to use the try{}finally{} pattern to set/reset the new flag in the flush() method to ensure the flag is reset even if the while() loop throws an exception.

Otherwise the fix looks good.

-- best regards, Anthony

On 7/11/2012 7:24 PM, Oleg Pekhovskiy wrote:

Hi!

Please review the fix for CR: http://bugs.sun.com/bugdatabase/viewbug.do?bugid=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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