Implement epoll shim #3712
Implement epoll shim #3712
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Co-authored-by: Oli Scherer <[email protected]>
Co-authored-by: Oli Scherer <[email protected]>
Co-authored-by: Oli Scherer <[email protected]>
| fn test_pointer() { | ||
| // Create an epoll instance. | ||
| let epfd = unsafe { libc::epoll_create1(0) }; | ||
| assert_ne!(epfd, -1); | ||
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| // Create a socketpair instance. | ||
| let mut fds = [-1, -1]; | ||
| let res = unsafe { libc::socketpair(libc::AF_UNIX, libc::SOCK_STREAM, 0, fds.as_mut_ptr()) }; | ||
| assert_eq!(res, 0); | ||
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| // Register fd[1] with EPOLLIN|EPOLLOUT|EPOLLET | ||
| // EPOLLET is negative number for i32 so casting is needed to do proper bitwise OR for u32. | ||
| let epollet = libc::EPOLLET as u32; | ||
| let flags = u32::try_from(libc::EPOLLIN | libc::EPOLLOUT | libc::EPOLLRDHUP).unwrap() | epollet; | ||
| let data = MaybeUninit::<u64>::uninit().as_ptr(); | ||
| let mut ev = libc::epoll_event { events: u32::try_from(flags).unwrap(), u64: data as u64 }; | ||
| let res = unsafe { libc::epoll_ctl(epfd, libc::EPOLL_CTL_ADD, fds[1], &mut ev) }; | ||
| assert_ne!(res, -1); | ||
| } |
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The cast causes an integer address to be produced. I think this means it can't be turned back into an actual pointer, but that's ok since we don't have a use case for it yet.
I think libc's epoll_event type is wrong and should be using a union for the data field. I guess for now anyone using this could be using https://doc.rust-lang.org/std/ptr/fn.with_exposed_provenance.html to get back a pointer on some platforms.
We'll need to evaluate whether tokio needs to store pointers here, but we can delay that to later imo
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Without knowing the context here -- if epoll has to store something that is "either an integer or a pointer", then Scalar would be the type to use, I think?
EDIT: Ah, postponing also works, as long as there is a comment in the code somewhere clarifying this.
| let epollet = libc::EPOLLET as u32; | ||
| let flags = u32::try_from(libc::EPOLLIN | libc::EPOLLOUT | libc::EPOLLRDHUP).unwrap() | epollet; | ||
| let data = MaybeUninit::<u64>::uninit().as_ptr(); | ||
| let mut ev = libc::epoll_event { events: u32::try_from(flags).unwrap(), u64: data as u64 }; |
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| let mut ev = libc::epoll_event { events: u32::try_from(flags).unwrap(), u64: data as u64 }; | |
| let mut ev = libc::epoll_event { events: u32::try_from(flags).unwrap(), u64: data.expose_provenance() as u64 }; |
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expose_provenance is on nightly so error will be thrown when it is used. Is there any way to get around this?
Error:
error[E0658]: use of unstable library feature 'exposed_provenance'
--> ./tests/pass-dep/libc/libc-epoll.rs:292:19
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292 | u64: data.expose_provenance() as u64,
| ^^^^^^^^^^^^^^^^^
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= note: see issue #95228 <https://github.com/rust-lang/rust/issues/95228> for more information
= help: add `#![feature(exposed_provenance)]` to the crate attributes to enable
= note: this compiler was built on 2024-07-06; consider upgrading it if it is out of date
error: aborting due to 1 previous errorThere was a problem hiding this comment.
you can add the feature gate
…tion is inserted to two different epoll instance
This PR implements non-blocking
epollfor #3448 . The design for this PR is documented in https://hackmd.io/@tiif/SJatftrH0 .