RFR: 8357650: ThreadSnapshot to take snapshot of thread for thread dumps [v4]

[Alan Bateman]

On Thu, 29 May 2025 08:26:07 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> Something isn't right here. Are you sure walk_cont is correctly for the mounted virtual thread case? There are several tests failing now.
>
> Let's check the logic before and now:
>  - before:
>    `walk_cont = _java_thread != nullptr && !is_virtual && _thread->vthread_continuation() != nullptr`
>  - now:
>    `walk_cont = _java_thread != nullptr && _thread->vthread_continuation() != nullptr`
>  
>  Alan's concern is that the check for  `!is_virtual` is missed now.
>  I'm not sure yet if it created a problem but the logic is a bit different.

If renamed to bool vthread_carrier then it will be clearer to see that the logic isn't right. It should only be true when !is_virtual and there is a mounted virtual thread.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25425#discussion_r2113518924