[jdk17] RFR: 8269635: Stress test SEGV while emitting OldObjectSample [v3]

[Markus Grönlund]

> Greetings,
> 
> please help review this change set to protect the unloaded thread id set from growing, and hence de-allocated, in the middle of inspection.
> 
> Testing: jdk_jfr
> 
> Thanks
> Markus

Markus Grönlund has updated the pull request incrementally with two additional commits since the last revision:

 - move
 - add missing changes

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/218/files
  - new: https://git.openjdk.java.net/jdk17/pull/218/files/6f575377..03bcca6f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=218&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=218&range=01-02

  Stats: 4 lines in 2 files changed: 3 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/218.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/218/head:pull/218

PR: https://git.openjdk.java.net/jdk17/pull/218