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

[Leonid Mesnik]

On 3/18/20 12:48 PM, Igor Ignatyev wrote:
> 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?
I can, but I don't see any benefits to use volatile fields instead of 
atomics. I prefer to use Atomic* anywhere because of it's clearer 
semantics. Using of explicit get/set and other similar accessors.
>
>> 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?

Unfortunately no. The CountDownLatch would be a nice solution but it is 
possible to get OOME in gc/lock (might be other) tests. I replaced 
Wicked by the same reason. Updating the AtomicInteger doesn't allocate 
any memory and don't cause OOME.

Leonid

>
> 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
>>