RFR: 8336707: Contention of ForkJoinPool grows when stealing works [v3]

[Doug Lea]

> This addresses tendencies in previous update to increase fencing, scanning, and signalling that can increase contention, and slow down performance especially on ARM platforms. It also uses more ARM-friendly constructions to reduce overhead (leading to several changes that all of the same form),

Doug Lea 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 19 additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8336707
 - adjust type tests
 - Better disinguish need for exhaustive scans
 - Consistent constructions; remove no-longer needed checks; update internal docs
 - Reconcile constuctions
 - Fencing
 - experiment
 - Merge branch 'openjdk:master' into JDK-8336707
 - Reactivation
 - Recheck
 - ... and 9 more: https://git.openjdk.org/jdk/compare/4e057aad...0bf0bfa0

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21507/files
  - new: https://git.openjdk.org/jdk/pull/21507/files/0e3e9def..0bf0bfa0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21507&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21507&range=01-02

  Stats: 124555 lines in 967 files changed: 116531 ins; 4015 del; 4009 mod
  Patch: https://git.openjdk.org/jdk/pull/21507.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21507/head:pull/21507

PR: https://git.openjdk.org/jdk/pull/21507