RFR: 8317440: Lock rank checking fails when code root set is modified with the Servicelock held after JDK-8315503

[Coleen Phillimore]

On Thu, 5 Oct 2023 17:19:35 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change that fixes lock ranking after recent changes to the code root set, now using a CHT.
> 
> The issue came up because the lock rank of the CHT lock has been larger than the rank of the Servicethread_lock where it is possible that code roots can be added.
> 
> The suggested solution is to fix up the lock rankings to work; actually this PR contains two variants:
> 1) one that statically sets the lock ranks of the CHT lock (and the ThreadSMR_lock that can be used during CHT operation) to something smaller than Servicethread_lock.
> 2) one that allows setting of the CHT lock rank via parameter as well (the last commit changed the code to variant 1).
> 
> The other lock ranking changes to Metaspace_lock and ContinuationRelativize_lock are simply undos of the respective changes in [JDK-8315503](https://bugs.openjdk.org/browse/JDK-8315503). 
> 
> Testing: tier1-8 for variant 2), tier 1-7 for variant 1)
> 
> Thanks,
>   Thomas

Going with variant 2.

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PR Comment: https://git.openjdk.org/jdk/pull/16062#issuecomment-1894522950