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/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
