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

[Michael Mirwaldt]

On Tue, 29 Jun 2021 14:31:30 GMT, Michael Mirwaldt <github.com+6693355+mmirwaldt at openjdk.org> wrote:

>> Maybe we should recast the whole thing into atomicity test. This would alleviate any questions about how `taken` fields are actually working. I.e.:
>> 
>> 
>> int v;
>> 
>> @Actor 
>> public void actor1(II_Result r) {
>>   { // critical section (broken)
>>     r.r1 = ++v;
>>   }
>> }
>> 
>> @Actor 
>> public void actor2(II_Result r) {
>>   { // critical section (broken)
>>      r.r2 = ++v;
>>   }
>> }
>> 
>> 
>> ...then check that `(1, 1)` case is not possible in case of properly working lock.
>
> That's an interesting idea. If I get you right, you use here the fact that incrementing v is not an atomic operation. I guess it works because if both actors enter the critical section at the same time, they will both read 0 for v and increment it to 1 for their results.

I will replace the taken1 and taken2 by this solution here.

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