RFR: 8279294: NonblockingQueue::try_pop may improperly indicate queue is empty [v2]

[Kim Barrett]

> Please review this improvement to NonblockingQueue::try_pop.  The old code
> returned an indication that the queue was empty in some cases where that
> wasn't true.  In particular, contending try_pop operations could result in
> some incorrectly indicating empty.  The change fixes that and improves the
> interaction between contending try_pops.
> 
> Testing:
> mach5 tier1-3
> 
> Lots of testing of this change in conjunction with others as part of
> investigating and fixing JDK-8273383.

Kim Barrett has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into fix-try-pop2
 - fix

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7149/files
  - new: https://git.openjdk.java.net/jdk/pull/7149/files/562729a1..fc29432d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7149&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7149&range=00-01

  Stats: 7328 lines in 498 files changed: 4297 ins; 1612 del; 1419 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7149.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7149/head:pull/7149

PR: https://git.openjdk.java.net/jdk/pull/7149