RFR: 8291714: Implement a Multi-Reader Single-Writer mutex for Hotspot [v3]

[Johan Sjölén]

On Wed, 24 Aug 2022 14:23:49 GMT, Johan Sjölén <duke at openjdk.org> wrote:

>> May I please have a review for this PR which implements a `MRWMutex` class for Hotspot?
>> 
>> This PR does 3 things:
>> 
>> * Adds a port of ZGC's MRSW mutex (see [0]) to Hotspot
>> * Adds some new utilities for writing multi-threaded tests.
>> * Adds some tests for MRSW Mutex using these new utilities
>> 
>> The ticket has some comments which might be worth checking out: https://bugs.openjdk.org/browse/JDK-8291714
>> 
>> [0] Original source code here: https://github.com/openjdk/zgc/blob/zgc_generational/src/hotspot/share/gc/z/zJNICritical.cpp
>
> Johan Sjölén has refreshed the contents of this pull request, and previous commits have been removed. Incremental views are not available.

As no current review comments were alive I rebased onto master and force pushed. This reduces the PR a bit, as parts of it (additions to `threadHelper.inline.hpp`) was merged in another PR and as such could be removed.

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PR: https://git.openjdk.org/jdk/pull/9838