[crac] RFR: 8351695: [CRaC] Cannot restore immediately without default restore data

[Timofei Pushkin]

On Tue, 11 Mar 2025 20:23:30 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> The issue was not caught by the test suite because `crexec` always provides restore data even if none was set.
>
> Do I understand that this happens with `CRAC_CRIU_LEAVE_RUNNING`? If we are missing a test for that (I suppose rather using `-XX:CRaCEngineOpts=keep_running=true`, could you please add one?

@rvansa There is a test for keep running/leave running (`jdk/crack/LeaveRunning`). But since crexec always returns some restore data, even if it hasn't been set (in that case it returns zero), the issue doesn't appear. So, to get a test for this not a test should be added but the behavior of crexec should be changed (easy to implement, I just wasn't sure if it is needed).

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PR Comment: https://git.openjdk.org/crac/pull/210#issuecomment-2715637776