RFR: 8298059: Linked stack watermarks don't support nesting [v3]

[Chris Plummer]

On Tue, 6 Dec 2022 13:23:29 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

>> The KeepStackGCProcessedMark facility used to ensure a thread (possibly remote) remains fully processed in its scope, has not yet had to support nesting. As it turns out, they can now nest after JDK-8294924. So this patch adds support for nesting. Tested ZGC specific tests tier 1-8, general testing 1-3 and manually tested the two tests that failed and got problem listed.
>
> Erik Österlund has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Change from mtInternal to mtThread

@fisk Please make sure this gets pushed to 20. If you don't get it pushed before the fork, you'll need update the PR to target the jdk20 fork, or push to 21 and then backport to 20. If you do the later, please first change the fixVersion of the CR from 20 to 21.

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PR: https://git.openjdk.org/jdk/pull/11530