RFR: 8373054: Shenandoah: Remove unnecessary BarrierSetNMethod::arm in shenandoahCodeRoots

[William Kemper]

On Wed, 3 Dec 2025 21:33:50 GMT, Ben Taylor <btaylor at openjdk.org> wrote:

> The call to arm is redundant, and can be replaced with an assert to ensure the precondition remains true.
> 
> The same set of tier1 tests pass before and after this change with a fastdebug and Shenandoah GC.

Let's change the misleading comment.

src/hotspot/share/gc/shenandoah/shenandoahCodeRoots.cpp line 147:

> 145:       ShenandoahReentrantLocker locker(nm_data->lock());
> 146: 
> 147:       // Heal oops and disarm

Suggestion:

      // Heal oops and leave the nmethod armed because code cache unloading needs to know about on-stack nmethods.

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Changes requested by wkemper (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28648#pullrequestreview-3537029053
PR Review Comment: https://git.openjdk.org/jdk/pull/28648#discussion_r2586693272