RFR: 8241123: Refactor vmTestbase stress framework to use j.u.c and make creation of threads more flexible

[Igor Ignatyev]

Hi Leonid,

I've started looking at your webrev, and so far have a couple questions:

> Test vmTestbase/nsk/jdi/ObjectReference/referringObjects/referringObjects003/referringObjects003a.java was updated to don't use Wicket. (The lock has a reference to thread which affects test.)
can't you use just a volatile boolean field?

> Wicket "finished" in class ThreadsRunner was changed to atomicInt/sleep to avoid OOME in j.u.c.l.Condition::await() which might happened in stress GC tests.
won't j.u.c.CountDownLatch be more appropriate and cleaner solution here?

I need more time to get grasp of Wicket and your changes in it; will come back to you after I understand them. 

-- Igor

> On Mar 18, 2020, at 12:37 PM, Leonid Mesnik <leonid.mesnik at oracle.com> wrote:
> 
> Hi
> 
> Could you please review following fix which slightly refactor vmTestbase stress test harness. This refactoring helps to add virtual threads testing support.
> 
> The Wicket uses plain sync/wait/notify mechanism which cause carrier thread starvation and should not be used in virtual threads. The ManagedThread is a subclass of Thread so it couldn't be virtual thread.
> 
> 
> Following fix changes Wicket to use locks/conditions to don't pin vthread to carrier thread while starting testing.
> 
> ManagedThread is fixed to keep execution thread as the thread variable and isolate it's creation.
> 
> Test vmTestbase/nsk/jdi/ObjectReference/referringObjects/referringObjects003/referringObjects003a.java was updated to don't use Wicket. (The lock has a reference to thread which affects test.)
> 
> Wicket "finished" in class ThreadsRunner was changed to atomicInt/sleep to avoid OOME in j.u.c.l.Condition::await() which might happened in stress GC tests.
> 
> webrev: http://cr.openjdk.java.net/~lmesnik/8241123/webrev.00/
> 
> bug: https://bugs.openjdk.java.net/browse/JDK-8241123
> 
> 
> Leonid
>