RFR: 8223312: Utilize handshakes instead of is_thread_fully_suspended [v2]

[Robbin Ehn]

On Wed, 21 Oct 2020 08:32:25 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>>> Thanks, I'm exploring what we need to execute the EB inside the handshake.
>> 
>> I want to experiment with object reallocation without referencing a frame. I think a should be possible to reallocate objects given only the corresponding compiled pc. If so, then a handshake/vm operation can fail with the request to reallocate objects at a pc. This can be done concurrently and then the handshake/vm operation can be restarted.
>
> I pushed the merge. (I manage to pick up bad state in first merge, so I did a second merge to get the fixes for that)
> Please have a look.
> 
> Still running test, but there were some interest in this change-set (it seem to fix an unrelated bug also) so I published it.

No issues in testing.

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PR: https://git.openjdk.java.net/jdk/pull/729