RFR: 8319867: GenShen: Make old regions parseable at end of concurrent cycles

[William Kemper]

On Sat, 11 Nov 2023 00:11:32 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> assert(_state != BOOTSTRAP && _state != WAITING_FOR_BOOTSTRAP, "Illegal transition");
>
> I am thinking that the most parsimonious way of covering all bases is by associating a pre-condition with entering each state and a post-condition with exiting each state, and verifying those conditions in the transition validation methods. But may be that can be done as a separate PR if it makes sense.

Hmm - I thought that's what this code is doing. Or rather, it is asserting what conditions must hold to _be_ in this state (checking pre/post conditions simultaneously).

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/355#discussion_r1390064292