<AWT Dev> [7u6] Review request for 7177040: Deadlock between PostEventQueue.noEvents, EventQueue.isDispatchThread and SwingUtilities.invokeLater

[Oleg Pekhovskiy]

Thank you, Anthony!

Oleg.

7/11/2012 8:15 PM, Anthony Petrov wrote:
> Thanks for addressing the issues. The fix looks fine now.
>
> -- 
> best regards,
> Anthony
>
> On 7/11/2012 8:08 PM, Oleg Pekhovskiy wrote:
>> Thank you for the review, Anthony,
>>
>> please review the next version of fix:
>> http://cr.openjdk.java.net/~bagiras/7u6/7177040.2
>>
>> I followed your suggestions there.
>> I also added 'volatile' for isFlushing because it could be accessed 
>> from different threads.
>>
>> Thanks,
>> Oleg
>>
>> 7/11/2012 7:35 PM, Anthony Petrov wrote:
>>> 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
>>