[jdk21u-dev] RFR: 8345750: Shenandoah: Test TestJcmdHeapDump.java#aggressive intermittent assert(gc_cause() == GCCause::_no_gc) failed: Over-writing cause

[William Kemper]

This was not a clean backport, the conflicts were trivial to resolve. This addresses a fairly critical issue where in a mistimed heap dump may cause heap corruption or vm crashes for Shenandoah GC.

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Commit messages:
 - Backport 6a29a8110ec38b4adc8163ba8651cbc935353f1d

Changes: https://git.openjdk.org/jdk21u-dev/pull/1350/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1350&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345750
  Stats: 20 lines in 4 files changed: 13 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1350.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1350/head:pull/1350

PR: https://git.openjdk.org/jdk21u-dev/pull/1350