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

[Michael Mirwaldt]

On Tue, 29 Jun 2021 14:52:55 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_01_NoAlgorithm.java line 2:
> 
>> 1: /*
>> 2:  * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
> 
> Here and later: the year is 2021. :)

done

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_01_NoAlgorithm.java line 52:
> 
>> 50:  * If one actor after another enters the critical section,
>> 51:  * the first actor will read 0 for v and increment v to 1 for its result
>> 52:  * the second actor will read 1 for v and increment v to 2 for its result.
> 
> Yeah, I don't think this explanation is necessary. You can just say something like: "All samples for mutex algorithms use the non-atomic increment example from API_01_Sample."
> 
> And yes, it is true that we don't actually need this test, as we have API_01_Sample -- we can just go ahead and start testing the mutexes.

Removed Mutex_01_NoAlgorithm.java

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_02_PetersonAlgorithm.java line 62:
> 
>> 60:         flagForActor1 = true;
>> 61:         turn = 2;
>> 62:         while (flagForActor2 && turn == 2) ;
> 
> Suggestion:
> 
>         while (flagForActor2 && turn == 2); // wait

done

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_02_PetersonAlgorithm.java line 73:
> 
>> 71:         flagForActor2 = true;
>> 72:         turn = 1;
>> 73:         while (flagForActor1 && turn == 1) ;
> 
> Suggestion:
> 
>         while (flagForActor1 && turn == 1); // wait

done

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_04_AtomicBoolean.java line 32:
> 
>> 30: import org.openjdk.jcstress.annotations.State;
>> 31: import org.openjdk.jcstress.infra.results.II_Result;
>> 32: import org.openjdk.jcstress.infra.results.ZZ_Result;
> 
> Here and other places, `ZZ_Result` is not needed anymore?

imports of ZZ_Result removed

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_04_AtomicBoolean.java line 53:
> 
>> 51: @State
>> 52: public class Mutex_04_AtomicBoolean {
>> 53:     private final AtomicBoolean canEnterCriticalSection = new AtomicBoolean(true);
> 
> Invert and call it `taken`?

Done. Please notice this invertion also inverts the used boolean values: what was true before is now false and vice versa.

> jcstress-samples/src/main/java/org/openjdk/jcstress/samples/concurreny/mutex/Mutex_04_AtomicBoolean.java line 67:
> 
>> 65:     @Actor
>> 66:     public void actor2(II_Result r) {
>> 67:         while(!canEnterCriticalSection.compareAndSet(true, false)) ;
> 
> Suggestion:
> 
>         while (!canEnterCriticalSection.compareAndSet(true, false)); // spin

done

-------------

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