RFR: 7902989: jcstress: Add samples for high-level race conditions [v5]

[Michael Mirwaldt]

On Thu, 1 Jul 2021 14:20:05 GMT, Vladimir Sitnikov <vsitnikov at openjdk.org> wrote:

>> Why should they be forbidden?
>> I think they are undesirable but allowed because the lack of the appropiate synchronisation causes these result within read-modify-write-sequences.
>
>>Why should they be forbidden?
> 
>> 17.4.4. Synchronization Order: https://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.4.4
>> A write to a volatile variable v (§8.3.1.4) synchronizes-with all subsequent reads of v by any thread (where "subsequent" is defined according to the synchronization order).

I think the synchronization with volatile is just too weak. It keeps the order of the statements, yes, that's right,
However, it doesn't force orders with the desired result without the effect of the read-modify-write sequence. 
We can remove volatile if you like.

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PR: https://git.openjdk.java.net/jcstress/pull/88