RFR: 8312174: missing JVMTI events from vthreads parked during JVMTI attach [v2]

[Serguei Spitsyn]

On Fri, 8 Sep 2023 03:08:33 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> test/hotspot/jtreg/serviceability/jvmti/vthread/VThreadEventTest/VThreadEventTest.java line 136:
>> 
>>> 134:             ready1.await();
>>> 135:             mready.decr();
>>> 136:             VirtualMachine vm = VirtualMachine.attach(String.valueOf(ProcessHandle.current().pid()));
>> 
>> I think sleep is needed here so threads which should be unmounted have time to unmount before attach.
>
> Would it makes sense also to check that thread state is TIMED_WAITING. It should be set  TIMED_WAITING unmounted threads https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/lang/Thread.State.html#TIMED_WAITING

It is strange that the the tested vthreads in sleep(timeout) have sate WAITING, not TIMED_WAITING.
It can be a bug in the implementation.
I've decided to add a short sleep. Checking states looks a little bit over complicated.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15467#discussion_r1320422072