Expose the "epoll_pwait2()" function

[ChrysoliteAzalea]

Hello everyone!

I propose exposing the epoll_pwait2() function. Epoll is a event polling/waiting feature in Linux. It is similar to poll(), but while poll() requires passing an event list on each call, epoll works by creating a file descriptor which can be filled with events on file descriptors and then be waited/polled multiple times. File descriptors and events can be added, modified and deleted during epoll fd lifetime, which is good for server applications -- they can watch the listening socket and register connection sockets for watching.

Polling and waiting happens by calling epoll_wait(), epoll_pwait() or epoll_pwait2(). The first system call implements only millisecond precision of wait timeout and does not provide a way to atomically alter the signal mask during wait. The second system call accepts a signal mask that will be the signal mask of the waiting thread until the system call returns. The third system call also allows setting the timeout with nanosecond precision. The libc crates exposes the first two but not the third one.

Related man-page

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[ChrysoliteAzalea]

It looks like all failures here a related to musl. I've tried to use epoll_pwait2() with the upstream version of libc crate by exposing epoll_pwait2() through the extern block in my program. It works fine when built with glibc, but fails to build with musl. It looks like musl doesn't provide a wrapper function for epoll_pwait2().

P.S. I've looked up musl source code, and I haven't found a wrapper function for epoll_pwait2(). So I think I'll have to mark this PR as draft.

[ChrysoliteAzalea]

Now all the checks are passing, the pull request is ready for review.

[tgross35]

Thanks! Can you squash please?

[ChrysoliteAzalea]

Thanks! Can you squash please?

OK, squashed.

[tgross35]

Thanks, looks like the CI failure was spurious so hopefully it passes this time.

[ChrysoliteAzalea]

Thank you!

[ChrysoliteAzalea]

@tgross35
I wonder, since it's not a breaking change, can it be included in libc-0.2?

[tgross35]

It has the stable-nominated label already

[ChrysoliteAzalea]

It has the stable-nominated label already

Oh, I see (I've looked at the labels now), thank you!