[jdk21u] RFR: 8312182: THPs cause huge RSS due to thread start timing issue

[Thomas Stuefe]

Fixes a serious issue that may cause huge RSS bloat and thread startup performance degradation. Applies cleanly.

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Commit messages:
 - Merge branch 'openjdk:master' into tstuefe-backport-84b325b8
 - Backport 84b325b844c08809448a9c073a11443d9e3c3f8e

Changes: https://git.openjdk.org/jdk21u/pull/103/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=103&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312182
  Stats: 301 lines in 3 files changed: 294 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk21u/pull/103.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/103/head:pull/103

PR: https://git.openjdk.org/jdk21u/pull/103