RFR: 8296492: Remove ObjectLocker in JVMTI get_subgroups call

[Coleen Phillimore]

On Tue, 8 Nov 2022 10:05:34 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> The JVM code took a ThreadGroup lock before poking into ThreadGroup fields.  Call a method in the ThreadGroup to call the synchronized method instead.
>> Tested with tier 1-4.
>
> src/java.base/share/classes/java/lang/ThreadGroup.java line 802:
> 
>> 800:         int length = groups.size();
>> 801:         return groups.toArray(new ThreadGroup[length]);
>> 802:     }
> 
> Would you mind changing the comment to "Returns a snapshot of the subgroups as an array, used by JVMTI.", only to be consistent with the other methods that return subgroups as they all document it as a "snapshot". Also I think I would rename this to subgroupsAsArray as there isn't a "subgroups array".
> 
> If you want, `return groups.toArray(new ThreadGroup[0]);` will do the sizing for you.
> 
> Minor nit, you've additional blank lines after this method, I assume you only meant to add one.

Thank you for looking at this - that's a much better name and comment and thanks for the Java hints (I copied that from somewhere else).

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

PR: https://git.openjdk.org/jdk/pull/11033