RFR Backport: 8166862: CMS needs klass_or_null_acquire

[Yangfei (Felix)]

Hi,

As mentioned in [1], JDK-8160369 have not been backported to JDK8u. This is necessary for RMO architectures like aarch64.

JDK- 8166862 is a subtask of JDK-8160369.
Original bug: https://bugs.openjdk.java.net/browse/JDK-8166862 
Original patch: http://hg.openjdk.java.net/jdk9/jdk9/hotspot/raw-rev/820e8a4db30d 

The original patch for JDK- 8166862 does not apply cleanly to jdk8u-dev due to path and code refactoring work in jdk9+.

Webrev for 8u:
    http://cr.openjdk.java.net/~fyang/8166862-8u/webrev.00/

Performed full jtreg test with release build both on aarch64-linux and x86_64-linux platforms.

OK to backport?

Note: JDK- 8166862 directly depends on JDK-8166583. I have send another mail at [2] backporting JDK-8166583.

Thanks,
Felix

[1] https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2020-July/030313.html
[2] https://mail.openjdk.java.net/pipermail/jdk8u-dev/2020-November/012930.html