<AWT Dev> <Awt Dev> [9] Review Request for 8132664: closed/javax/swing/DataTransfer/DefaultNoDrop/DefaultNoDrop.java locks on Windows

Semyon Sadetsky semyon.sadetsky at oracle.com
Thu Sep 3 14:43:24 UTC 2015

On 8/5/2015 2:33 PM, Sergey Bylokhov wrote:
> On 05.08.15 14:20, Semyon Sadetsky wrote:
>> On 8/5/2015 1:39 PM, Sergey Bylokhov wrote:
>>> On 05.08.15 13:18, Semyon Sadetsky wrote:
>>>> On 8/5/2015 12:27 PM, Sergey Bylokhov wrote:
>>>>> On 04.08.15 14:54, Semyon Sadetsky wrote:
>>>>>> On 8/3/2015 6:05 PM, Sergey Bylokhov wrote:
>>>>>>> Hi, Semyon
>>>>>>> Did you try to change dwMilliseconds from INFINITE to the 
>>>>>>> timeout(10 seconds by default?) which is passed to the method? 
>>>>>>> It does not help? Because even when dnd is not used we should 
>>>>>>> not wait event for infinite time.
>>>>>> It would not help to fix the issue because 10 seconds is too big 
>>>>>> interval. But for consistency it is not bad to have a time limit.
>>>>>> http://cr.openjdk.java.net/~ssadetsky/8132664/webrev.01/
>>>>> Note that syncNativeQueue is intended to wait until the native 
>>>>> event queue is flushed or until timeout will expire. So even if 
>>>>> timeout is expired we collect the native events during this period 
>>>>> of time.Can you double check that the event counter is incremented 
>>>>> during dnd? I do not know how we block the toolkit thread, 
>>>>> probably we create some nested loops which ignore our event posted 
>>>>> from syncNativeQueue, can we change that?
>>>> Yes, this is an internal secondary loop which waits for mouse 
>>>> release event.
>>> Can we change the condition and process the sync event in this loop?
>> Why? Will receive all events on the toolkit thread when doDragDrop 
>> returns.
> When how we get dragenter/exit events?

On the platform side they are not events but callbacks which are 
converted into events on the java side and added to the queue. So they 
will be detected by isEQEmpty() and waitForIdle() will be repeated.

>>>> Event counter is not changed during toolkit thread blocking of 
>>>> cause. Not sure that we can change that. But since toolkit queue is 
>>>> blocked we can assume that we are synced.
>>>>> The timeout value is maintained on the shared level and actually 
>>>>> this test will fail with timeout on osx as well JDK-7185258. The 
>>>>> test will fail even if the time out will be changed to ±100ms, 
>>>>> because it call realsync on each pixel move, ±200 times. This 
>>>>> problem can be fixed in different ways like tweak of timeouts and 
>>>>> numbers of iterations, or changing the test to call w4idle only 
>>>>> after the latest move(actually I think this method can be moved to 
>>>>> the robot class).
>>>>> So I still think that the right fix for a deadlock, which is 
>>>>> subject of this bug, is simply change the syncNativeQueue and 
>>>>> waits using a timeout if it is positive, and waits forever if 
>>>>> timeout is negative (the same bug on osx JDK-8080504).
>>>> I'm not sure that waiting brings any value. What do you propose to 
>>>> return if it timed out? The event counter will not be changed 
>>>> regardless of waiting.
>>> But it should be changed, because we get native events from the 
>>> system during dnd and in each such callback we should update this 
>>> counter. If callbacks were not called=>counter was not updated then 
>>> sync assume that currently we do not process events. If callbacks 
>>> were called then sync assume that we have events in the native queue 
>>> and should try to sync again on the next iteration.
>> No. Events are not processed while toolkit is blocked in 
>> doDragDrop(). The application state is frozen on that period. That is 
>> Windows approach.
>>>> With such waiting the test will fail because of either jtreg timeout
>>> Default timeout is 120 seconds for everything, the test try to sync 
>>> the queue 200 of times after each move, so yes it can fail with 
>>> timeout even if spend in nativesync 200 ms, the possible solutions 
>>> were in my previous email.
>>>> either InfiniteLoop exception.
>>> This exception will be disabled by default lately in jdk9 timeframe, 
>>> right now it helps to find some related issues.
>>>>>>> On 03.08.15 17:26, Semyon Sadetsky wrote:
>>>>>>>> Hello,
>>>>>>>> Please review fix for JDK9:
>>>>>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8132664
>>>>>>>> webrev: http://cr.openjdk.java.net/~ssadetsky/8132664/webrev.00/
>>>>>>>> DoDragDrop() is blocking, so upon drag operation is triggered 
>>>>>>>> the toolkit thread is blocked and the WM_AWT_WAIT cannot be 
>>>>>>>> processed which in its turn blocks the AWT robot.
>>>>>>>> The solution is to escape AWT robot waiting in 
>>>>>>>> syncNativeQueue() if drag operation is in progress.
>>>>>>>> --Semyon

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