RFR: 7902982: jcstress: Add samples for some mutex algorithms [v3]

[Michael Mirwaldt]

On Tue, 29 Jun 2021 13:22:44 GMT, Vladimir Sitnikov <vsitnikov at openjdk.org> wrote:

>> mmirwaldt for openjdk has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   removed ids for forbidden outcomes
>
> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_02_PetersonAlgorithm.java line 56:
> 
>> 54:     private final AtomicBoolean flagForActor2 = new AtomicBoolean();
>> 55:     private final AtomicInteger turn = new AtomicInteger();
>> 56:     private volatile boolean taken1, taken2;
> 
> `flagForActor1`, `flagForActor2`, and `turn` should be volatiles, taken1 and taken2 should be regular fields.

Can you explain me why taken1 and taken2 must not be volatile?
I mean actor1 and actor2 run in different threads, don't they?
If so, actor1 won't see the current value of taken2 when actor2 changes taken2 or am I wrong?

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