This is a backport of PR #10151 as merged into master (7c12b1a).

What do these changes do?

If the keepalive handler is called too soon, it reschedules itself. The test used now <= close_time, which means that an exactly on-time notification is treated as "too soon", causing an automatic rescheduling. For real systems the time will eventually advance and break the loop, but with async-solipsism, time doesn't advance until there is some reason to sleep and the loop is infinite.

Are there changes in behavior for the user?

This will fix infinite loops when using async-solipsism.

Is it a substantial burden for the maintainers to support this?

No. This does not increase the amount of code at all.

Related issue number

Fixes #10149.

Checklist

• I think the code is well written
• Unit tests for the changes exist (I am assuming that the keepalive functionality has existing test coverage)
• Documentation reflects the changes (no documentation change needed)
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