RFR: 8236815: Shenandoah: Fix weak roots in final Traversal GC phase

[Zhengyu Gu]

Looks good.

-Zhengyu

On 1/8/20 4:25 PM, Roman Kennke wrote:
> We're not fixing up all weak roots in final-traversal. But we have to,
> because weak roots are not scanned+evacuated at init-traversal, and may
> thus keep dangling pointers that would leak out to the next cycle. This
> can lead to heap corruption, crashes, etc.
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8236815
> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8236815/webrev.00/
> 
> Testing: several runs of hotspot_gc_shenandoah, which *sometimes*
> exposed the bug. I couldn't reproduce it. I suggest to give it more
> spins in CI.
> 
> Can I please get a review?
> 
> Thanks,
> Roman
>