RFR: 8273300: Check Mutex ranking during a safepoint [v6]

[Coleen Phillimore]

On Wed, 15 Sep 2021 16:32:22 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This change checks lock ranking during a safepoint.  For some reason, safepoint checking was excluded, probably from the days where Safepoint_lock and Threads_lock were used.
>> Because of checking during a safepoint, some locks had to get lower ranks.  The CR has the details of which locks these were.  The Service_lock complicates things because it's held during oops_do, which may take out other G1 locks.
>> This was built and tested with Shenandoah.  Thanks to @zhengyu123 for the changes in Shenandoah.
>> Tests run tier1-8.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove safepoint conditional from other assert. The locks should now be in decreasing order.

Thanks Patricio for the code review.  Thanks David for all the comments.

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PR: https://git.openjdk.java.net/jdk/pull/5467