RFR: 8288497: add support for JavaThread::is_gc_barrier_detached()

[Patricio Chilano Mateo]

On Wed, 15 Jun 2022 15:44:21 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

> A trivial fix to add support for JavaThread::is_gc_barrier_detached() which allows
> us to add checks to detect failures like:
> 
>     JDK-8288139 JavaThread touches oop after GC barrier is detached
>     https://bugs.openjdk.org/browse/JDK-8288139
> 
> This fix along with the fix for JDK-8288139 has been tested in Mach5 Tier[1-8].
> There are no related failures in Mach5 Tier[1-7]; Mach5 Tier8 is still running.

I think I would just use the _thread_terminated state rather than introducing a new _thread_gc_barrier_detached state just to detect failures. So the only extra things covered by _thread_gc_barrier_detached and not by _thread_terminated would be ThreadService::remove_thread() which just updates some counters, and ThreadsSMRSupport::remove_thread() which we overlooked before but now by inspection I don't see any other place where we touch oops there.

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PR: https://git.openjdk.org/jdk19/pull/20