[jdk17u-dev] RFR: 8317960: [17u] Excessive CPU usage on AbstractQueuedSynchronized.isEnqueued [v2]

[David Alvarez]

> This patch brings the AbstractQueuedSynchronizer related changes from [JDK-8277090](https://bugs.openjdk.org/browse/JDK-8277090) to fix a performance issue that can happen in JDK17 too.
> 
> The rest of JDK-8277090 are done mostly in preparation of virtual threads and are covered under CSR [JDK-8285450](https://bugs.openjdk.org/browse/JDK-8285450). There is no plan at the moment to backport the rest of the changes to 17.

David Alvarez has updated the pull request incrementally with one additional commit since the last revision:

  Empty commit to trigger tests

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Changes:
  - all: https://git.openjdk.org/jdk17u-dev/pull/1875/files
  - new: https://git.openjdk.org/jdk17u-dev/pull/1875/files/b5582294..2e589554

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1875&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1875&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1875.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1875/head:pull/1875

PR: https://git.openjdk.org/jdk17u-dev/pull/1875