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.

[Darksonn]

Overall LGTM, just some comments on tests.

[Darksonn]

cc @ipetkov please review

[ipetkov]

I don't have the means to test this myself, but since others have commented this works for them I'll trust that its helping!

[Astlaan]

I can test it tomorrow if needed

[Finomnis]

I can test it tomorrow if needed

Yes, please.

[Astlaan]

Maybe I'm just too tired right now, but shouldn't this work?:
https://github.com/Astlaan/test-tokio-ctrl-close/blob/main/src/main.rs

[dsherret]

What's the actual behaviour? (I'm AFK atm. My guess is it creates a single file and exits, which is fine I think?)

[Finomnis]

Maybe I'm just too tired right now, but shouldn't this work?: https://github.com/Astlaan/test-tokio-ctrl-close/blob/main/src/main.rs

Yes, it should create 4-5 files and then be killed.

I'm not sure why, but in my own tests it seemed to work in cmd, but not in powershell.

[Finomnis]

@Astlaan is it the same behavior I described here? #7039 (comment)

[Finomnis]

@dsherret You said it works, right? I'd merge anyway if @Astlaan does not respond

[dsherret]

Yes, it works for me.

By the way, that example correctly creates 4-5 files on both cmd and powershell from windows terminal and windows console host. Also, I see now that 4-5 files is the expected behaviour because there's a 5000ms timeout before windows kills the process.

[Astlaan]

Yes, it works for me.

By the way, that example correctly creates 4-5 files on both cmd and powershell from windows terminal and windows console host. Also, I see now that 4-5 files is the expected behaviour because there's a 5000ms timeout before windows kills the process.

Are you using my code? Because for me I see no files being created at all.

[dsherret]

Yup. What terminal are you using?

[Astlaan]

Yup. What terminal are you using?

I tried with both cmd and powershell.
I opened them in the repo, then ran "cargo run", click the close button in the powershell, but no files were created.

[dsherret]

Try cargo build and launch the executable directly. I think maybe cargo run is preventing it from receiving the signal. I’m not at my computer right now, but I ran the executable directly.

Also, is cmd and powershell being launched with windows console host? Does it work for you in windows terminal with cmd and powershell? I think windows console host/windows terminal is what sends the event.

[Astlaan]

Try cargo build and launch the executable directly. I think maybe cargo run is preventing it from receiving the signal. I’m not at my computer right now, but I ran the executable directly.

This was the issue indeed. It runs fine if I run it directly.

[Finomnis]

In that case, ready for merging, @Darksonn.

[Darksonn]

Thank you.