RFR: 8350898: Shenandoah: Eliminate final roots safepoint [v5]

[Roman Kennke]

On Thu, 13 Mar 2025 20:43:05 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This PR converts the final roots safepoint operation into a handshake. The safepoint operation still exists, but is only executed when `ShenandoahVerify` is enabled. In addition to this change, this PR also improves the logging for the concurrent preparation for update references from [PR 22688](https://github.com/openjdk/jdk/pull/22688).
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comment explaining use of _trashed_oops

It looks good to me. I only have a small nit, up to you if you want to change that or not.

Thank you!

src/hotspot/share/gc/shenandoah/shenandoahClosures.hpp line 59:

> 57: //
> 58: 
> 59: class ShenandoahFlushSATBHandshakeClosure : public HandshakeClosure {

Maybe place the closure somewhere in shenandoahConcurrentGC.cpp, where it is used? Or is there a need to expose it on shenandoahClosures.hpp?

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Marked as reviewed by rkennke (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23830#pullrequestreview-2695514909
PR Review Comment: https://git.openjdk.org/jdk/pull/23830#discussion_r2001568319