RFR: 8351091: Shenandoah: global marking context completeness is not accurately maintained [v4]

[William Kemper]

On Fri, 7 Mar 2025 01:10:26 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> Thanks for the confirmation, I added assert as below since it gc_generation could be global :
>> 
>> 
>> assert(!_heap->gc_generation()->is_old(), "Sanity check");
>
> The assert may be fine, but the treatment of completeness of the marking context seems very brittle to me and apt to cause problems in the future. I would prefer a cleaner separation of these. May be we can sync up separately to discuss this along with @earthling-amzn .

Yes, regions may be promoted during a global cycle. Completing the mark for a global cycle also completes the mark for the young and old generations.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23886#discussion_r1985512202