RFR: 8296492: Remove ObjectLocker in JVMTI get_subgroups call [v2]

[Alan Bateman]

On Tue, 8 Nov 2022 12:30:37 GMT, Coleen Phillimore <coleenp 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.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Handle non OOM exceptions and rename subgroupsAsArray.

I wonder if the intermediate resource array is needed now. With the change, subgroupsAsArray returns a Java array,  JvmtiEnvBase::get_subgroups creates a resource array with a handle to each of the thread group oops, then JvmtiEnvBase::new_jthreadArray creates a new local ref for each group.

src/java.base/share/classes/java/lang/ThreadGroup.java line 796:

> 794: 
> 795:     /**
> 796:      * Returns an snapshot of the subgroups as an array, used by JVMTI.

The update looks good, just a typo here where it should be "a snapshot".

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