RFR: 8257831: Suspend with handshakes [v2]

[Robbin Ehn]

On Wed, 7 Apr 2021 12:57:01 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> src/hotspot/share/runtime/handshake.cpp line 677:
>> 
>>> 675:     } else {
>>> 676:       // Target is going to wake up and leave suspension.
>>> 677:       // Let's just stop the thread from doing that.
>> 
>> IIUC this would be the case where the target was hit with a suspend request but has not yet processed the actual suspension handshake op, then a resume comes in so suspended is no longer true, and then another suspend request is made (this one) which simply turns the suspended flag back on - is that right?
>> Overall I'm finding it very hard to see what the two suspend state flags actually signify. I'd like to see that written up somewhere.
>
> Sure

I pushed some changes with some more comments and renamed the flag.
I hope that help, if not, let me know.

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PR: https://git.openjdk.java.net/jdk/pull/3191