[jdk22u] RFR: 8329528: G1 does not update TAMS correctly when dropping retained regions during Concurrent Start pause

[Thomas Schatzl]

Hi all,

  please review this backport for https://bugs.openjdk.org/browse/JDK-8329528; it applies cleanly apart from the hunk now in `inline void HeapRegion::note_start_of_marking()` - in jdk23 this method moved from there to concurrent marking code, although the change itself is the same.

This issue causes random crashes in G1. There is no workaround.

The change baked in jdk23 for a week or so, with no issues. Risk is little at this point as the patch is small and well understood, and there is a regression test.

Testing: gha, tier1-5

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Commit messages:
 - fix for jdk22

Changes: https://git.openjdk.org/jdk22u/pull/145/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk22u&pr=145&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329528
  Stats: 85 lines in 4 files changed: 77 ins; 5 del; 3 mod
  Patch: https://git.openjdk.org/jdk22u/pull/145.diff
  Fetch: git fetch https://git.openjdk.org/jdk22u.git pull/145/head:pull/145

PR: https://git.openjdk.org/jdk22u/pull/145