RFR: JDK-8305334: GenShen: reference processing needs a card-marking barrier

[William Kemper]

On Fri, 31 Mar 2023 02:31:06 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> A visual examination of the card-scanning code reveals that the card-mark in the portion of code you pointed out is redundant because the card-scanning code always dirties the card containing a cross-generational pointer, irrespective of whether it's a weak or strong pointer. I'll work on eliding that unnecessary check and mark in a separate PR as I want to add some assertions and check it carefully.
>> 
>> Thanks for drawing my attention to this code which I had just glossed over before.
>> 
>> The diffs in my original PR stay unchanged and I'll not try to do anything about sharing the code, since I expect that piece of card-marking code in `drop()` to go away in the PR I promised above, for which I'll open a ticket momentarily.
>
> I opened https://bugs.openjdk.org/browse/JDK-8305335 to follow up on that.

Okay, thanks for taking a closer look.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/238#discussion_r1154821675