RFR: Filter out invalid pointers picked up by old gen SATB [v2]

[Kelvin Nilsen]

On Wed, 11 May 2022 22:05:21 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> In some cases, the SATB barrier used to support old generation marking may capture a reference to an object that is later evacuated. Old gen marking will crash when it tries to mark through the reference.
>
> William Kemper has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Purge SATB in final update refs, rather than SATB filter
>  - Revert "Filter out invalid pointers picked up by old gen SATB"
>    
>    This reverts commit e1fa77a65aa72d7cd22732bb95b73af950b589b1.

Marked as reviewed by kdnilsen (Committer).

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PR: https://git.openjdk.java.net/shenandoah/pull/140