Add wrapper for timerfd_create, timerfd_settime, and timerfd_gettime to `os` module

[m-tmatma]

Feature or enhancement

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

Proposal:

eventfd is implemented at #20930 (#85173).
But timerfd is not implemented yet.

timerfd_create, timerfd_settime, and timerfd_gettime are Linux syscalls that create and operate on a timer that delivers timer expiration notifications via a file descriptor.

See https://man7.org/linux/man-pages/man2/timerfd_create.2.html

I propse to add those wrapper functions to os module.

Linked PRs

• gh-108277: Add wrapper for timerfd_create, timerfd_settime, and timerfd_gettime to os module #108382
• gh-108277: Fix test_os TimerfdTests #110515
• gh-108277: test_os tolerates 1 ms diff for timerfd #110661
• gh-108277: Make test_os tolerate 10 ms diff for timerfd on Android emulators #117223
• gh-108277: Make test_os tolerate 10 ms diff for timerfd #117231

[serhiy-storchaka]

Should not we first add POSIX conforming timer_create(), timer_settime(), timer_gettime(), timer_getoverrun()?

Also, I'm not sure if we should add these low-level platform-specific functions in the os module, or if it's better to add platform-independent functions that hide the platform-specific implementation under the hood in the time module.

What do you think about it, @vstinner?

[vstinner]

IMO it's a good thin to expose the API in the os, thin wrapper to the C functions. Then anyone is free to write their own high-level API on top of it.

Who is going to use these APIs? For which use case?

Should not we first add POSIX conforming timer_create(), timer_settime(), timer_gettime(), timer_getoverrun()?

Which platforms support these APIs?

timerfd_create, timerfd_settime, and timerfd_gettime

Only Linux support these APIs according to the doc.