RFR: 8291714: Implement a Multi-Reader Single-Writer mutex for Hotspot [v2]

[David Holmes]

On Fri, 19 Aug 2022 15:34:45 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 updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review comments

src/hotspot/share/utilities/readWriteLock.hpp line 26:

> 24: 
> 25: #ifndef SHARE_RUNTIME_MRSWMUTEX_HPP
> 26: #define SHARE_RUNTIME_MRSWMUTEX_HPP

The include guards need updating to reflect the file renaming. (thanks for that)

src/hotspot/share/utilities/readWriteLock.hpp line 45:

> 43: private:
> 44:   NONCOPYABLE(ReadWriteLock);
> 45:   class NoTransition : public StackObj {

This is dead code now.

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