RFR (sh/8): [backport] 8221435: Shenandoah should not mark through weak roots

[Zhengyu Gu]

Looks good to me.

Thanks,

-Zhengyu

On 11/26/19 4:31 PM, Roman Kennke wrote:
> This backports JDK-8221435 from sh/jdk11. The sh/jdk11 change is this one:
> 
> https://hg.openjdk.java.net/shenandoah/jdk11/rev/6e176ad4e069
> 
> The change is different in sh/jdk8 because there the weak roots are
> tangled up with strong roots in systemdictionary, and we cannot easily
> decouple them. The intention of the change is that weak roots only need
> to be processed when unloading classes, but has nothing to do with
> processing weak references (despite the name). The backport tries to
> follow that intention without doing the refactorings.
> 
> http://cr.openjdk.java.net/~rkennke/JDK-8221435-sh8/webrev.00/
> 
> Testing: hotspot_gc_shenandoah
> 
> Can I please get a review?
> 
> Thanks,
> Roman
>