RFR: 8219197: ThreadGroup.enumerate() may return wrong value

[Daniel Fuchs]

Hi Pavel,

On 13/03/2019 16:35, Pavel Rappo wrote:
> Using a bunch of Semaphores here seems a bit surprising. One more CountDownLatch
> or CyclicBarrier *might* have been better. But I guess it's not of concern.

Agreed, but I won't change it. The reason is that I had a more
extensive version of the test with which I tested a prototype
fix for another related ThreadGroup issue - and the semaphore
as opposed to latches were useful for that ;-)
That other issue is still in my TODO list - but I might take more
time to get to it as its fix is a bit more controversial.

> For the diagnostic purposes I would add a newline between
> 
>    t4.join(); t3.join();
> 
> since they throw exceptions. Otherwise looks good. Thanks for doing this.

OK, will do.

Thanks for the feedback!

-- daniel