RFR (XS): 8202049: G1: ReferenceProcessor doesn't handle mark stack overflow

[Kim Barrett]

> On Jun 4, 2018, at 6:35 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8202049
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8202049/webrev
> Testing:
> running this patch for months in my usual testing routine for other
> patches without any error.
> 
> Thanks,
>  Thomas

I think this ought to use fatal(...) rather than log_error + ShouldNotReachHere.