RFR: 8365939: [Redo] G1: Move collection set related full gc reset code into abandon_collection_set() method

[Thomas Schatzl]

On Wed, 27 Aug 2025 17:06:22 GMT, Ivan Walulya <iwalulya at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this attempt on clearing the young regions cset group early in `abandon_collection_set()` during full gc.
>> 
>> The initial attempt failed because some verification code depended on the young gen remembered set being `Complete` and contain valid card entries.
>> 
>> This change fixes both:
>> 
>> - we need to clear the `young_regions_cset_group` with `uninstall_group_cardsets` being `true` to a) remove the cards and b) make it incomplete
>> - some verification expects that the young gen remset is always complete, which is not necessary during full gc.
>> 
>> Test: tier1-5, the failing test that caused the failures in JDK-8365780 passes always.
>> 
>> Thanks,
>>   Thomas
>
> Marked as reviewed by iwalulya (Reviewer).

Thanks @walulyai @albertnetymk for your reviews

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PR Comment: https://git.openjdk.org/jdk/pull/26948#issuecomment-3232659042