[jdk19] RFR: 8290867: Race freeing remembered set segments [v2]

[Kim Barrett]

On Wed, 3 Aug 2022 07:58:29 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Testing showed an issue with VM shutdown: VM shutdown calls the the destructor for the (global) free list pool, which in turn frees all segments; however at that time the VM is not in a state where `GlobalCounter` works (threads are detached, no valid threads list) and crashes. The last commit provides a workaround for that issue, not doing the global synchronization when shutting down. That is safe because the process is single-threaded in the `VM_Exit` operation anyway. This is a workaround for this issue that needs to be cleaned up, but it's too late imho in the release to find a better solution for this issue.

For the record, we discussed this before Thomas pushed, and I agree with his assessment.  The workaround is simple and safe, and doing something more principled might not fit in the current release schedule.

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PR: https://git.openjdk.org/jdk19/pull/152