Fix CTRL_CLOSE, CTRL_LOGOFF and CTRL_SHUTDOWN on windows

[Finomnis]

Fixes #7039.

Motivation

According to https://learn.microsoft.com/en-us/windows/console/handlerroutine#remarks, the windows signals CTRL_CLOSE, CTRL_LOGOFF and CTRL_SHUTDOWN immediately kill the process upon being handled.

The intention is that the handler of those signals performs cleanup tasks, and once completed, it returns and the process is killed.

This behavior is sadly not really compatible with an async system that is based on signals.

Solution

There are multiple possible ways to solve this; the easiest one being to simply never return from the handler thread. This works because Rust calls ExitProcess after its main (to my knowledge). I tested it on a project of mine, and it seems to work indeed.

[dsherret]

Thanks for doing this. I tested this with CTRL_CLOSE and it works for me. FWIW, this is the same solution that libuv does: https://github.com/libuv/libuv/blob/23632e9104b6506d5bee0d85b807c2351617d226/src/win/signal.c#L130

[Finomnis]

@dsherret Actually, it doesn't. It only sleeps if someone handles the event, we should do that as well.

[Finomnis]

@dsherret would you mind testing the PR again now?

[dsherret]

Yup, still works.

[Finomnis]

@Darksonn Ready for another review

[Darksonn]

Why do we handle all three this way when libuv only does it for one of them?

[Finomnis]

Why do we handle all three this way when libuv only does it for one of them?

Why does libuv only handle one?
They say something about services, do we have a separate windows service interface?

[Finomnis]

@Darksonn Either way, the other two signals are completely pointless for Tokio if we don't handle them like this, according to the windows api docs. They also result in an immediate kill after returning from the handler.