RFR: 8318053: GenShen: Control thread may ignore requests to start concurrent GC

[William Kemper]

On Thu, 12 Oct 2023 23:49:41 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> If a request to interrupt an old cycle is accepted, but there is an allocation failure before the requested cycle begins, then the control thread may become stuck in a state where it believes it should ignore further concurrent cycle requests.
>
> Thanks for figuring this out.

I updated the ticket with the command we used to reproduce it. I've seen the issue on the first run and @kdnilsen has seen it usually before the 10th run. If I can get 50 runs without the issue, I'll consider it fixed. 

Also, the additional logging showed the `_preeption_requested` flag was stuck on, when it shouldn't have been.

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PR Comment: https://git.openjdk.org/shenandoah/pull/339#issuecomment-1760557556