RFR: 8223312: Utilize handshakes instead of is_thread_fully_suspended [v3]

[Robbin Ehn]

On Thu, 22 Oct 2020 08:50:54 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> Depth 1 means top frame and its caller. In UpdateForPopTopFrameClosure::doit() line 1606(?) the 2 top frames are deoptimized. Reallocating objects while a frame pop request is processed does not work if reallocation fails therefore we use an EscapeBarrier to eagerly reallocate objects beforehand.
>
> @fisk for PopFrame the top frame needs to be deoptimized (if compiled) to be able to actually remove it when the thread is resumed. Its caller needs to be deoptimized to be able restart the call. For ForceEarlyReturn it is not necessary to restart. The target can return to a compiled caller and continue executing compiled code. So the caller frame is not deoptimized.
> 
> @robehn nothing is messed up. Thanks again for doing it.

Great!

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