RFR: 8320331: G1 Full GC Heap verification relies on metadata not reset before verification [v2]

[Thomas Schatzl]

> Hi all,
> 
>   please review this fix to full gc to properly set `parsable_bottom` for the heap regions marked through so that "during" verification (`-XX:+VerifyDuringGC`) does not access metadata already unlinked but not yet completely purged.
> 
> The test case reproduces crashes fairly well without the patch; the new test case is run with debug VMs only purely to save testing time.
> 
> Testing: gha, test case
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  iwaluya review, comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16733/files
  - new: https://git.openjdk.org/jdk/pull/16733/files/15812e5c..cc23c2d8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16733&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16733&range=00-01

  Stats: 14 lines in 2 files changed: 9 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/16733.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16733/head:pull/16733

PR: https://git.openjdk.org/jdk/pull/16733