RFR: 8279540: Shenandoah: Should only clear CLD::_claim_strong mark for strong CLD iterations

[Aleksey Shipilev]

On Thu, 6 Jan 2022 13:27:16 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> JDK-8273559 started to use CLD::_claim_other for heap iteration in supporting multi-threaded heap walk. For regular CLD, it still uses CLD::_claim_strong, but for those walks, it clears all claim bits, instead of just _claim_strong bit.
> 
> I don't think it is a fatal bug, it just means heap iteration may walk a CLD by multiple workers, which impacts performance.
> 
> Test:
> - [x] hotspot_gc_shenandoah

Looks reasonable.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6980