RFR: 8257831: Suspend with handshakes [v2]

[Robbin Ehn]

On Wed, 31 Mar 2021 08:01:27 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> I think this relates to why the PEM was moved from the loop-scope to the sync op case only. That said it isn't clear why we need the HM or PEM.
>
> I guess it should be "... must not execute ~PreserveExceptionMark ..."
> ~PreserveExceptionMark calls _thread->pending_exception() which is an oop and that would be illegal as the vm could be at a safepoint when the async handshake returns.

I don't think we need HM or PEM.
PEM was added if the handshake would execute code that did throw an exception.

Yes, exactly we don't want to be touching "_thread->pending_exception()" during a safepoint.

Updating comment.

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