RFR: 8351091: Shenandoah: global marking context completeness is not accurately maintained [v8]

[Xiaolong Peng]

On Fri, 4 Apr 2025 18:18:30 GMT, Xiaolong Peng <xpeng at openjdk.org> wrote:

>> With the JEP 404: Generational Shenandoah implementation, there are generation specific marking completeness flags introduced, and the global marking context completeness flag is not updated at all after initialization, hence the global marking context completeness is not accurate anymore. This may cause expected behavior: [ShenandoahHeap::complete_marking_context()](https://github.com/openjdk/jdk/pull/23886/files#diff-d5ddf298c36b1c91bf33f9bff7bedcc063074edd68c298817f1fdf39d2ed970fL642) should throw assert error if the global marking context completeness flag is false, but now it always return the marking context even it marking is not complete, this may hide bugs where we expect the global/generational marking to be completed.
>> 
>> This change PR fix the bug in global marking context completeness flag, and update all the places using `ShenandoahHeap::complete_marking_context()` to use proper API.
>> 
>> ### Test
>> - [x] hotspot_gc_shenandoah
>> - [x] Tier 1
>> - [x]  Tier 2
>
> Xiaolong Peng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Address PR comments

thanks all for the reviews and suggestions!

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PR Comment: https://git.openjdk.org/jdk/pull/23886#issuecomment-2787875051