[11u] RFR 8244340: Handshake processing thread lacks yielding

[Reingruber, Richard]

Hi,
 
Original bug:
  https://bugs.openjdk.java.net/browse/JDK-8244340
  https://hg.openjdk.java.net/jdk/jdk/rev/67a435ce2dc2

Prerequisite downport:
  https://bugs.openjdk.java.net/browse/JDK-8214180
 
Original patch does not apply cleanly to 11u because it is based on handshakes
in jdk15 which is quite different from handshakes in 11u, e.g. jdk15 has direct
handshakes.

11u webrev:
  http://cr.openjdk.java.net/~rrich/webrevs/8244340_11u_Handshake_processing_thread_lacks_yielding/webrev.0/
 
Testing:

Tier1 with and without ZGC.

With ZGC I got a few failures. Most of them if not all were OOME because 11u ZGC
cannot handle small heaps. The same tests fail without the patch.

CI testing @sap.
 
Thanks, Richard.