RFR: 7902982: jcstress: Add samples for some mutex algorithms [v8]

[Aleksey Shipilev]

On Tue, 29 Jun 2021 15:00:48 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> mmirwaldt for openjdk has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   replaced approach with taken1 and taken2 by the approach of using non atomic int increments
>
> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_04_AtomicBoolean.java line 58:
> 
>> 56:     @Actor
>> 57:     public void actor1(II_Result r) {
>> 58:         while(!canEnterCriticalSection.compareAndSet(true, false)) ;
> 
> Suggestion:
> 
>         while (!canEnterCriticalSection.compareAndSet(true, false)); // spin

...and should probably take the [TTAS](https://en.wikipedia.org/wiki/Test_and_test-and-set) form:


   while (taken.get() || !taken.compareAndSet(false, true)); // spin

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PR: https://git.openjdk.java.net/jcstress/pull/85