<AWT Dev> [8] Review request for 8019623: Lack of synchronization in AppContext.getAppContext()

[Artem Ananiev]

Hi, Leonid,

the fix looks fine.

I believe it is possible to create a regression test for this fix. The 
test should create several thread groups and call AC.getAC() there, then 
check that all the returned AC's are equal. Although it won't 100% fail 
before your fix, it should 100% pass after it. What do you think about it?

Thanks,

Artem

On 10/2/2013 6:22 PM, Leonid Romanov wrote:
> Hello,
> Please, review a fix for 8019623: Lack of synchronization in AppContext.getAppContext(). I don't think it makes sense to ensure that AppContext.getAppContext()/SunToolkit.createNewAppContext() is thread safe, because in practice we haven't had any problems with this combination. What we have had problems with is the getAppContext()/getAppContext() combination because of the double mainAppContext initialization.  Therefore, the fix takes care of this issue. While I could have simply made the whole AppContext.getAppContext() method synchronized, I wanted the most common path through it (returning cached AppContext) to remain lock-free, so I decided to place the lock around the most critical part, where initMainAppContext() gets called.
> As for a regression test, I couldn't find a way to detect double initMainAppContext initialization. We put newly created AppContexts into a thread-safe map, so whatever AppContext wins the race remains in the map, and the other is simply lost, without any convenient means to detect its existence.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8019623
> Webrev: http://cr.openjdk.java.net/~leonidr/8019623/webrev.00/
>
> Thanks,
> Leonid.
>