[Linux] Fix hanging terminal

[bugadani]

Some terrible timer+signal hackery but this seems to be the recommended way in case tcdrain blocks indefinitely.

I've also added a bit of a flush-throttling so that we're not completely swamped by timeouting blocking calls on every keypress if the user mashes the keyboard.

The reason for all this is that nothing moves the data out of the USB endpoing on the device, so it doesn't accept new data.

I don't feel qualified, prepared or well enough equipped to try this on macOS.

cc #681

[SergioGasquez]

Thanks! Just tried it and works perfectly! Ill try to understand whats going on on Monday

[sirhcel]

I don't feel qualified, prepared or well enough equipped to try this on macOS.

Kudos for this deep dive @bugadani! I'm sorry that did not manage to to look deeper into it so far, but I gave the fix from this PR a spin on macOS 15.6 on a M1 machine. I still end up in a locked state after about ten key strokes in the monitor.

[bugadani]

Thanks for trying! I think it's not too surprising that a 1:1 port doesn't work - it took me quite a bit of trial and error to figure out something working. Can you perhaps share your code? Maybe it's a good enough start to work on.

[sirhcel]

Can you perhaps share your code?

I just ran espflash as of e05601d on macOS as follows:

$ cargo run -- flash --monitor test.elf

There was no bespoke code involved.

[bugadani]

Ah all the workarounds here are gated for linux (macos has a different timer API), and the small throttling shouldn't really affect much if the second flush never returns :)

[SergioGasquez]

LGTM, thanks! Im trying to investigate and port this changes to MacOS!

Edit: Mind rebasing your changes to resolve the conflict?

[sirhcel]

Ah all the workarounds here are gated for linux (macos has a different timer API), and the small throttling shouldn't really affect much if the second flush never returns :)

I'm sorry for the noise! I misread the description that this PR also applies to macOS and did not notice the gating. Thank you for #947 @SergioGasquez!