RFR: 8210065: ZGC: Remove mode for treating weaks as strong

[Kim Barrett]

> On Aug 28, 2018, at 8:39 AM, Erik Österlund <erik.osterlund at oracle.com> wrote:
> 
> Hi,
> 
> In ZGC, the root processor has a mode for supporting treating weaks as strong. This makes no sense to use for a user as it only introduces memory leaks. We have supported it anyway because it was a neat debugging tool while implementing concurrent reference processing. But now it seems like it is time for this option to retire, as it makes the root scanning code unnecessarily complicated and bug prone.
> 
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8210065/webrev.00/
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8210065
> 
> Thanks,
> /Erik

Looks good.