RFR: 8348347: Cleanup JavaThread subclass support in SA [v2]

[Kevin Walls]

On Thu, 6 Feb 2025 22:44:48 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Cleanup SA JavaThread support. Details in first comment:
>> 
>> Testing:
>> - Tier1
>> - Tier2 svc
>> - Tier3
>> - Tier5 svc
>> - Local testing of debuggee using graal java compiler threads. Verified that the compiler threads shows up in jstack output if the property is set.
>
> Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update comments

Looks good.

I think we need a HiddenJavaThread class,  and "visibility" cannot just be a boolean field in JavaThread, because virtualConstructor.addMapping wants a mapping to a class that will already know whether it's hidden.

In calling it HiddenJavaThread we might be labelling threads "JavaThread" when they don't run Java, but those I looked at are derived from JavaThread in native hotspot so it must be the right name.

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Marked as reviewed by kevinw (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23456#pullrequestreview-2606714536