RFR: 8221102: Allow GC threads to participate in threads claiming protocol

[Roman Kennke]

Hi Kim,

>>>> Also, the resetting logic warrants a test, it is so rare, it will otherwise not get executed, but if it fails, it would be catastrophic.
>>> I was hoping the resetting code was simple enough to not require a
>>> test.  I will see if I can come up with a sensible gtest.
>>
>> I guess the 'design' of the claiming protocol is just making almost everything not-obvious. I think for this reason alone I shall go ahead and work on limiting/eliminating its usage outside of thread.cpp anyway.
> 
> Another function similar to possibly_parallel_threads_do that operated
> on all threads seems like it would be a good thing to have.  Possibly
> stealing the existing name and renaming the old operation.  I'd like
> the defer that to a followup RFE rather than as part of this bug fix.

Yes, let's do that.


>> If it's too hard to come up with a gtest, then go ahead with your proposed change.
> 
> It turned out not to be *too* difficult to add a gtest.  New webrevs:
> 
> full: http://cr.openjdk.java.net/~kbarrett/8221102/open.01/
> incr: http://cr.openjdk.java.net/~kbarrett/8221102/open.01.inc/

Great! Patch looks good to me!

Thanks,
Roman