RFR: 8288327: Executable.hasRealParameterData should not be volatile [v2]

[liach]

On Fri, 17 Jun 2022 05:34:25 GMT, ExE Boss <duke at openjdk.org> wrote:

>> Сергей Цыпанов has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8288327: Add clarifying comments
>
> src/java.base/share/classes/java/lang/reflect/Executable.java line 453:
> 
>> 451: 
>> 452:     private transient boolean hasRealParameterData;
>> 453:     private transient volatile Parameter[] parameters;
> 
> These can probably be annotated with `@Stable` (see also [GH‑8742]):
> Suggestion:
> 
>     private transient @Stable boolean hasRealParameterData;
>     private transient @Stable volatile Parameter[] parameters;
> 
> 
> [GH‑8742]: https://urldefense.com/v3/__https://github.com/openjdk/jdk/pull/8742__;!!ACWV5N9M2RV99hQ!LCGH0C1JTymKJBYhuf9QGi40oZ5nPH-YmfYHk30effXmBBfOpYlC9ixsITWo_Uhfgyu4l0w3837mmshCk-bM$ 

Another approach would be to keep the parameter array and the boolean in a record, and mark the record field as stable, possibly like what's done in #6889. Keeping them in a record like:

record ParameterData(Parameter[] parameters, boolean real) {}

private transient @Stable ParameterData parameterData;

private ParameterData parameterData() {
    ParameterData data = parameterData;
    if (data != null)
        return data;
    // Create parameter data, cache and return
}

boolean hasRealParameterData() { return parameterData().real(); }
private Parameter[] privateGetParameters() { return parameterData().parameters(); }


This code should be more maintainable in the long run as well, with more straightforward concurrency and caching model.

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PR: https://git.openjdk.org/jdk/pull/9143