RFR (XS): 8204618: The parallel GC reference processing task executor enqueues a wrong number of tasks into the queue

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that fixes some issue with
parallel gc reference processing task executor putting too many (always
max number of threads) reference processing tasks into the work queue?

The effects are benign (at least we have not observed any bad effects
so far since enabling -XX:UseDynamicNumberOfGCThreads) in that
reference processing will be called multiple times by the same active
threads, basically doing nothing (because the corresponding ref proc
queues are empty after the first time they are processed).

CR:
https://bugs.openjdk.java.net/browse/JDK-8204618
Webrev:
http://cr.openjdk.java.net/~tschatzl/8204618/webrev/
Testing:
hs-tier1-4,jdk-tier1-3 with +/-ParallelRefProcEnabled

Thanks,
  Thomas