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

[David Holmes]

On Wed, 15 Jun 2022 15:50:18 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.
>
> src/hotspot/share/runtime/thread.inline.hpp line 264:
> 
>> 262: inline bool JavaThread::is_exiting() const {
>> 263:   // Use load-acquire so that setting of _terminated by
>> 264:   // JavaThread::set_terminated() is seen more quickly.
> 
> This comment should have been updated when the code in
> JavaThread::exit() was refactored into JavaThread::set_terminated().
> I'm doing it as part of this fix for clarity.

It is a bogus comment - acquire semantics has nothing to do with seeing things more quickly.

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