RFR: 8377713: Shenandoah: Convert ShenandoahReferenceProcessor to use Atomic<T> [v2]

[William Kemper]

On Thu, 26 Feb 2026 22:07:20 GMT, Ben Taylor <btaylor at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoahReferenceProcessor.cpp line 579:
>> 
>>> 577: void ShenandoahReferenceProcessor::enqueue_references_locked() {
>>> 578:   // Prepend internal pending list to external pending list
>>> 579:   shenandoah_assert_not_in_cset_except(&_pending_list, _pending_list.load_relaxed(), ShenandoahHeap::heap()->cancelled_gc() || !ShenandoahLoadRefBarrier);
>> 
>> Not sure about this one. The first argument to `shenandoah_assert_not_in_cset_except` is a `void *`, so it will take just about anything. The argument is meant to be the "interior location" (i.e., address of the field holding the pointer given in the second argument). With this change, we are passing the address of the `Atomic` wrapper class, but I think we should be passing the address of the _value_ it is holding. So maybe `&_pending_list.load_relaxed()`?
>
> The problem with this is `T load_relaxed() const {` will end up giving you the address of a temporary copy of the value when used this way. There's no way to get a direct reference/pointer to the value, as doing so would violate the Atomic encapsulation. So the address of the Atomic itself seemed the most appropriate thing to provide

Okay, it looks like when this assert fires it will just say the `interior_loc` is outside the heap.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29767#discussion_r2861538661