[Linux] Sleep until a specified real time

[4e554c4c]

See this issue for all context.

Tokio provides sleep_until which sleeps until a given instant of a monotonic clock. However, it does not provide any interfaces for sleeping until an absolute instant of a realtime clock (using posix timer terminology).
This means that it is possible to wait for a certain amount of thread time to complete, but not wait until a certain wall time has passed. These can be drastically different, considering that many devices spend most of their time suspended—where wall time elapses but CPU time does not.

This is possible in unix using a combination of CLOCK_REALTIME and TIMER_SETABSTIME, see this stackoverflow answer for more information. Is there any way to wait on an event like this using tokio? or without resorting to raw libc/librt calls?

[Darksonn]

You can do this using the TimerFd struct in the tokio-timerfd crate.

[4e554c4c]

yep, after poking around a bit there doesn't seem to be a place for this in the tokio library, its timer wheel is not designed for wall clock timers.
I'd prefer a solution that didn't only work on linux, so I might make a posix compliant crate that does this.

[Darksonn]

Please let me know about it if you make such a crate.

[4e554c4c]

https://git.sr.ht/~pounce/tokio-walltime