RFR: 8307816: Add missing STS to ZGC

Wed May 10 13:51:23 UTC 2023

Testing in project Lilliput has revealed that ZGC is lacking one STS. Without it, ZGC could reach to already-deflated monitor when trying to fetch a displaced header, in order to get to an object's Klass* (e.g. to get its size).

Testing:
 - [x] hotspot_gc

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Commit messages:
 - 8307816: Add missing STS to ZGC

Changes: https://git.openjdk.org/jdk/pull/13904/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13904&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307816
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13904.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13904/head:pull/13904

PR: https://git.openjdk.org/jdk/pull/13904