RFR: JDK-8222227: Shenandoah: Fix Traversal GC weak roots handling in final-traversal pause

[Zhengyu Gu]

Looks good.

-Zhengyu


On 4/9/19 4:30 PM, Roman Kennke wrote:
> We currently clean weak roots only when weak-references are processed in
> Traversal GC. This is wrong, because it should be independent whether or
> not it's doing reference-processing.
> Also, (weak) roots need to be updated and cleaned before classes get
> unloaded (currently), because this is how class-unloaded detects
> unreachable classes.
> With all this, we no longer need to run class-unloading and
> reference-processing every cycle, which covered up those bugs.
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8222227
> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8222227/webrev.02/
> 
> Testing: hotspot_gc_shenandoah
> 
> Roman
>