[15] RFR 8236878: Use atomic instruction to update StringDedupTable's entries and entries_removed counters

[Roman Kennke]

OK.

Thanks,
Roman


> 
> Please review this small change that uses atomic operations to update
> StringDedupTable's entries and entries_removed counter.
> 
> This is *not* a correctness fix or performance enhancement, but for
> Shenandoah GC to move StringDedupTable cleanup task into concurrent
> phase, while holding StringDedupTable_lock.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8236878
> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8236878/webrev.00/index.html
> 
> Test:
>   hotspot_gc (fastdebug and release) on x86_64 Linux
>   Submit test in progress.
> 
> Thanks,
> 
> -Zhengyu
>