RFR: 8337511: Implement JEP 404: Generational Shenandoah (Experimental) [v8]

[Y. Srinivas Ramakrishna]

On Thu, 21 Nov 2024 13:34:51 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> William Kemper has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 524 commits:
>> 
>>  - Merge remote-tracking branch 'shenandoah/master' into great-genshen-pr-redux
>>  - 8344670: GenShen: Use concurrent worker session for concurrent mark phase
>>    
>>    Reviewed-by: kdnilsen
>>  - 8344640: GenShen: Reuse existing card mark barrier function when dropping references
>>    
>>    Reviewed-by: shade, ysr
>>  - 8344592: GenShen: Remove unnecessary comments and changes
>>    
>>    Reviewed-by: kdnilsen
>>  - 8344263: GenShen: Reduce extraneous log messages at INFO level
>>    
>>    Reviewed-by: ysr, shade
>>  - 8344638: GenShen: Verifier should not touch claim token
>>    
>>    Reviewed-by: shade
>>  - Merge
>>  - 8344320: GenShen: Possible null pointer usage in shGenerationalHeap
>>    
>>    Reviewed-by: wkemper, ysr
>>  - 8344321: GenShen: Fix various sonar scan warnings
>>    
>>    Reviewed-by: kdnilsen, shade
>>  - 8344264: GenShen: Improve comments and method names
>>    
>>    Reviewed-by: shade
>>  - ... and 514 more: https://git.openjdk.org/jdk/compare/95a00f8a...7ab16403
>
> src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp line 1972:
> 
>> 1970:   // Check that if concurrent weak root is set then active_gen isn't null
>> 1971:   assert(!is_concurrent_weak_root_in_progress() || active_generation() != nullptr, "Error");
>> 1972:   shenandoah_assert_generations_reconciled();
> 
> Why all of this is checked here? I would have thought `gc_state` machinery should only check things related to gc-state.

Likely debugging detritus that I unintentionally left behind. Feel free to delete.
I think the `shenandoah_assert_generations_reconciled()` is already checked in a most spots where it's needed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21273#discussion_r1852820087