[jdk17u-dev] RFR: 8306929: Avoid CleanClassLoaderDataMetaspaces safepoints when previous versions are shared [v2]

[Oli Gillespie]

> Hi all,
> 
> This pull request contains a backport of commit [408cec51](https://github.com/openjdk/jdk/commit/408cec516bb5fd82fb6dcddeee934ac0c5ecffaf) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.
> 
> The commit being backported was authored by Stefan Johansson on 4 May 2023 and was reviewed by Coleen Phillimore and Serguei Spitsyn.
> 
> It's clean except for the surrounding context changing between NULL and nullptr which was trivial to resolve. It comes with its own test, but I also confirmed that it fixes the reproducer shared on the issue.
> 
> Thanks!

Oli Gillespie has updated the pull request incrementally with one additional commit since the last revision:

  Backport 29233e0a001adde71a3fa5d56292ccfba8409ea5

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

Changes:
  - all: https://git.openjdk.org/jdk17u-dev/pull/2776/files
  - new: https://git.openjdk.org/jdk17u-dev/pull/2776/files/350f7696..9409b2f3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2776&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2776&range=00-01

  Stats: 10 lines in 1 file changed: 1 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2776.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2776/head:pull/2776

PR: https://git.openjdk.org/jdk17u-dev/pull/2776