<AWT Dev> [8] Review request for 8005465: [macosx] Evaluate if checking for the -XstartOnFirstThread is still needed in awt.m

Anthony Petrov anthony.petrov at oracle.com
Fri Jan 11 03:57:32 PST 2013


On 1/10/2013 20:23, Petr Pchelko wrote:
> Sergey wrote:
>>> As far as I understand from the discussion SWT doesn't survive situation, when we open 2 window(SWT and AWT) and close SWT window first. Since in this case SWT stops appkit run loop. This fix works in this case and this means that we should apply the same patch to SWT.
>>> Petr, can you clarify this? Thanks
> 
> I have applied the patch and tried a little example with SWT Window and AWT Frame. The app still hangs in case the SWT Frame is closed first. The problem is that in SWT the common pattern is to put such code to the end of main:
> 
>  while (!shell.isDisposed()) {
>             if (!display.readAndDispatch()) display.sleep();
>  }
>  display.dispose();
> //end of main function
> 
> (It is so common that it is in the first helloworld example in the SWT documentation)
> 
> So, SWT does not care about the native events, it shuts down as soon as Shell gets disposed. The main thread finishes and AWT hangs. 
> 
> I don't think we could fix the issue in AWT, but there is a simple workaround to add a dispose listener to the shell which would spin the runloop until AWTAutoShutdown.isReadyToShutdown, so it could be fixed in SWT. 
> However, the case when AWT and SWT windows are opened simultaneously is so likely to produce deadlocks that I am not sure we want to support this case at all. JDK6 does not.

OK. So let me get it straight: it didn't work before with SWT, and for 
now it's not going to work even with my fix? But my fix itself does not 
worsen things up when running with SWT anyway, right? Is this all correct?


> As for the embedded case, the issue with shutdown is fixed on the SWT side, however, making the AWTAutoShutdown method public would allow to make the solution better. 

No, why? We don't want to export AWTAutoShutdown. Now that AWT will send 
keep alive pings after my fix, SWT, if they want to, could simply listen 
to these pings (using the run loop observers), and return false from the 
shell.isDisposed() at least for 1 second after the last keep-alive ping. 
This will enable both SWT and AWT to co-exist, prevent any hangs, and 
allow both of them to terminate w/o problems when both are finished.

But this is unrelated to the AWT side of things. This is a possible 
enhancement for the SWT itself.

--
best regards,
Anthony

> 
> With best regards. Petr. 
> 
> This fix actually does not help in the case when SWT 
> On Jan 10, 2013, at 6:24 PM, Petr Pchelko wrote:
> 
>> Yes. SWT did not survive in such a situation. A will try to apply the fix and test if it helps with the SWT.
>>
>> With best regards. Petr.
>>
>> On Jan 10, 2013, at 6:13 PM, Sergey Bylokhov wrote:
>>
>>> 10.01.2013 17:55, Anthony Petrov wrote:
>>>> Thanks Petr. I think we don't want to do the same in FX because we don't even want to call any AWT APIs from there in the first place. Instead, my current solution offers a way to terminate both toolkits graciously.
>>> As far as I understand from the discussion SWT doesn't survive situation, when we open 2 window(SWT and AWT) and close SWT window first. Since in this case SWT stops appkit run loop. This fix works in this case and this means that we should apply the same patch to SWT.
>>> Petr, can you clarify this? Thanks
>>>> Sergey, does this resolve your concern?
>>>>
>>>> -- 
>>>> best regards,
>>>> Anthony
>>>>
>>>> On 12/28/12 23:06, Petr Pchelko wrote:
>>>>> Hello.
>>>>>
>>>>> As I understood while implementing the EmbeddedFrame, when we embed AWT into SWT, SWT did not care if AWT is OK to terminate, SWT just called dispose() for a frame and terminated without looking at AWT. This resulted in issues when AWT was still terminating but the main SWT thread was already finished. When AWT was calling something to synchronously perform selectors on the main thread deadlocks occurred. So we had to add a dispose listener to the SWT container, which spinned the main runloop until AWT frame finished disposing.
>>>>>
>>>>> However, I may have misunderstood something.
>>>>>
>>>>> With best regards, Petr.
>>>>>
>>>>> 28.12.2012, в 20:58, Anthony Petrov<anthony.petrov at oracle.com>  написал(а):
>>>>>
>>>>>> On 12/28/2012 20:36, Sergey Bylokhov wrote:
>>>>>>>> http://cr.openjdk.java.net/~anthony/8-52-startOnFirstThreadCheck-8005465.0/ 
>>>>>>>> 2. Introducing an AWTKeepAlive thread activated in the embedded mode only. This thread will send an event to the native event queue every 500ms as long as there are active AWT objects present. This activity will notify the embedder toolkit that the Java application as a whole is still alive and needs not exit yet.
>>>>>>> Why it wasn't necessary for awt-swt bridge?
>>>>>> I don't know. Perhaps we should ask someone who's familiar with SWT? Steve? How does SWT determine that AWT is dead and therefore it's OK to terminate the native event loop and exit on the Mac?
>>>>>>
>>>>>> -- 
>>>>>> best regards,
>>>>>> Anthony
>>>
>>> -- 
>>> Best regards, Sergey.
>>>
> 



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