[rfc] [icedtea-web] Fix EDT hanging on OpenJDK 11

[Mario Torre]

Hi Laurent,

Yes, I approve.

I think we need to rework the threading aspect though.

Jiri, could you please push the patch for Laurent?

Cheers,
Mario

On Mon, Oct 1, 2018 at 12:13 PM Laurent Bourgès
<bourges.laurent at gmail.com> wrote:
>
> Mario,
> Do you approve the latest webrev, as it is ?
> Let's move forward, after this patch integrated.
> Laurent
>
> Le lun. 1 oct. 2018 à 11:17, Jiri Vanek <jvanek at redhat.com> a écrit :
>>
>> ...
>> >
>> >      >     3. It seems that methods that use "observable" are synchronized.
>> >      >     However, the EDT will use "observable" and it's not synchronized. Is
>> >      >     this safe?
>> >      >
>> >      >
>> >      > Ok, fixed:
>> >      >                 synchronized(observable) {
>> >      >                     if (observable.hasChanged() ||
>> >      > (Boolean.TRUE.equals(force))) {
>> >      >                         observable.notifyObservers(force);
>> >      >                     }
>> >      >                 }
>> >
>> >     Right, but I don't think this addresses the issue, one is synchronized
>> >     on the observable, the other methods are on the JavaConsole, so we
>> >     should probably pick one.
>> >
>> >
>> > Sorry, I did not catch the problem.
>> > My fix is very minimal and this patch does not fix synchronization issues already present in ITW.
>> > I tested javaws with the console opened and did not notice any problem.
>> >
>> >
>> >     By going through the code though, it seems like we could just ensure
>> >     that updateModel() always run in the EDT and remove all other
>> >     synchronised keywords from the methods, the only user of this method
>> >     which can execute outside the EDT is addMessage, but otherwise all other
>> >     consumers are executing in the EDT.
>> >
>> >
>> > Could we postpone this point later as I did not want to rewrite too much the JavaConsole ?
>> > You propose to remove all 'synchronized' keywords in JavaConsole, I am pretty sure the
>>
>> I would strongly advice against removing the synchronizations. The logging bottleneck is lazily
>> initiated singleton, and there were many troubles without it. Maybe with plugin gone, the troubles
>> will decrease a lot, But i doubt.
>>
>> On contrary:
>>
>>  >on the observable, the other methods are on the JavaConsole, so we
>>  >     should probably pick one.
>>
>> Sounds like straightforward fix. Anyway, this is on your judgement.
>>
>> > synchronization overhead does not hurt here...
>> > If you could propose an alternative, I am OK to integrate it.
>>
>> Please, as another changeset (if any).
>>
>>
>>
>> Thanx!
>>    J.



-- 
Mario Torre
Associate Manager, Software Engineering
Red Hat GmbH <https://www.redhat.com>
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