RFR: 7902982: jcstress: Add samples for some mutex algorithms [v10]

[mmirwaldt for openjdk]

On Tue, 29 Jun 2021 15:34:56 GMT, Vladimir Sitnikov <vsitnikov at openjdk.org> wrote:

>> mmirwaldt for openjdk has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - gave state annotation its own line
>>  - reorganized the imports
>>  - changed the outcomes of the mutex samples
>
> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_01_PetersonAlgorithm.java line 46:
> 
>> 44: @JCStressTest
>> 45: @Outcome(id = {"1, 2", "2, 1"}, expect = ACCEPTABLE, desc = "Sequential execution.")
>> 46: @Outcome(id = "1, 1", expect = ACCEPTABLE_INTERESTING, desc = "Both actors came up with the same value: lock failure.")@State
> 
> Is lock failure "acceptable"? I would say it should be forbidden.

Well, @shipilev proposed it. I cannot find his comment.

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_03_AtomicBoolean.java line 53:
> 
>> 51:     @Actor
>> 52:     public void actor1(II_Result r) {
>> 53:         while(taken.get() || !taken.compareAndSet(false, true)); // spin
> 
> Suggestion:
> 
>         while(!taken.compareAndSet(false, true)) {
>             // wait for entering into the critical section
>         }
> 
> 
> I think `taken.get()` is not needed here, and adding explicit braces makes it easier to understand that the braces for "critical section" are different ones.

Well, @shipilev proposed it. I cannot find his comment.

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