RFR: Cleanups, TODOs, asserts (part 1) [v2]

[Y. Srinivas Ramakrishna]

On Thu, 6 Apr 2023 17:11:40 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   New assert fires, but instead of fixing it, remove useless live_memory completely
>
> src/hotspot/share/gc/shenandoah/shenandoahConcurrentGC.cpp line 125:
> 
>> 123:     // Concurrent remembered set scanning
>> 124:     entry_scan_remembered_set();
>> 125:     // TODO: When RS scanning yields, we will need a check_cancellation_and_abort() degeneration point here.
> 
> We need to be really careful when transitioning to a degenerated cycle after RS scan is complete. Logically, the RS scan is part of the concurrent root scan, but it didn't get implemented with that pattern.

@earthling-amzn : should this go into the `entry_mark_roots()` below then? Clearly, it seems that we can't really have a degeneration point after remembered set scanning from how I understood your comment, so the documentation comment above (to which Aleksey merely added the `TODO:` prefix) is incorrect and should be either removed entirely or corrected suitably?

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/245#discussion_r1162099412