RFR: 8212827: GlobalCounter should support nested critical sections

[Erik Österlund]

Hi Kim,

Looks good.

Thanks,
/Erik

On 2018-10-23 19:07, Kim Barrett wrote:
> Please review this change to GlobalCounter to support nested critical
> sections.
>
> While in the area, cleaned up a few things:
> - Improved comments for GlobalCounter API.
> - Cleaned up write_synchronize global counter increment.
> - Removed a useless acquire barrier in critical_section_begin.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8212827
>
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8212827/open.00/
>
> Testing:
> mach5 tier1-5
> New gtest directly testing nested critical sections.
>
>