RFR: 8081474: SwingWorker calls 'done' before the 'doInBackground' is finished [v3]

[Alexey Ivanov]

On Mon, 30 Jan 2023 08:34:59 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

>> src/java.desktop/share/classes/javax/swing/SwingWorker.java line 762:
>> 
>>> 760:                     } catch (InterruptedException e) {}
>>> 761:                 } while (state != StateValue.DONE);
>>> 762:             }
>> 
>> In the previous iteration, using `sleep` for waiting was *the concern*, you're still using `sleep`.
>> 
>> This is not going to work because it makes `cancel` wait until `DONE` state is reached, which is not what one would expect, especially taking into account that `cancel` is likely called from EDT to cancel the background operation and blocking EDT is not acceptable.
>
> I removed sleep from EDT case and not blocking EDT and guess sleep is now being done for non-EDT case...
> If it is to be called from EDT then it should go to "if" block and not to "else" which is what I based my fix on..
> 
> Anyway, I appreciate your fix and will see to it..

Yet having `sleep` is an indication of busy wait. You could've used `CountDownLatch` in conjunction with `setState` to avoid `sleep` at all.

> I removed sleep from EDT case and not blocking EDT and guess sleep is now being done for non-EDT case...

Ah, right. But then if `cancel` is called on EDT, `done` is invoked before `doInBackground` completes, isn't it?

If `cancel` is called from another thread, the main thread as in the test, it doesn't return until `doInBackground` completes. With your test case and fix, `cancel` blocks for 5 seconds.

Either way, the behaviour does not look right.

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PR: https://git.openjdk.org/jdk/pull/11940