From: Eric Blake <ebl...@redhat.com> CI shows our async handle fails to build on FreeBSD and MacOS (where epoll() is not available as a syscall, and therefore not available as a Rust crate). We can instead accomplish the same level-probing effects by doing a zero-timeout poll with mio (which defers under the hood to epoll on Linux, and kqueue on BSD).
Fixes: 223a9965 ("rust: async: Create an async friendly handle type") CC: Tage Johansson <tage.j.li...@posteo.net> Signed-off-by: Eric Blake <ebl...@redhat.com> --- rust/Cargo.toml | 3 ++- rust/src/async_handle.rs | 40 +++++++++++++++++++++++----------------- 2 files changed, 25 insertions(+), 18 deletions(-) diff --git a/rust/Cargo.toml b/rust/Cargo.toml index 0879b34..678848a 100644 --- a/rust/Cargo.toml +++ b/rust/Cargo.toml @@ -49,9 +49,10 @@ thiserror = "1.0.40" log = { version = "0.4.19", optional = true } libc = "0.2.147" tokio = { optional = true, version = "1.29.1", default-features = false, features = ["rt", "sync", "net"] } -epoll = "4.3.3" +mio = { optional = true, version = "0.8.0" } [features] +tokio = ["dep:tokio", "dep:mio"] default = ["log", "tokio"] [dev-dependencies] diff --git a/rust/src/async_handle.rs b/rust/src/async_handle.rs index 6793ce9..8f3e8df 100644 --- a/rust/src/async_handle.rs +++ b/rust/src/async_handle.rs @@ -35,9 +35,11 @@ use crate::sys; use crate::Handle; use crate::{Error, FatalErrorKind, Result}; use crate::{AIO_DIRECTION_BOTH, AIO_DIRECTION_READ, AIO_DIRECTION_WRITE}; -use epoll::Events; +use mio::unix::SourceFd; +use mio::{Events, Interest as MioInterest, Poll, Token}; use std::sync::Arc; use std::sync::Mutex; +use std::time::Duration; use tokio::io::{unix::AsyncFd, Interest, Ready as IoReady}; use tokio::sync::Notify; use tokio::task; @@ -176,13 +178,8 @@ async fn polling_task(handle_data: &HandleData) -> Result<(), FatalErrorKind> { } = handle_data; let fd = handle.aio_get_fd().map_err(Error::to_fatal)?; let tokio_fd = AsyncFd::new(fd)?; - let epfd = epoll::create(false)?; - epoll::ctl( - epfd, - epoll::ControlOptions::EPOLL_CTL_ADD, - fd, - epoll::Event::new(Events::EPOLLIN | Events::EPOLLOUT, 42), - )?; + let mut events = Events::with_capacity(1); + let mut poll = Poll::new()?; // The following loop does approximately the following things: // @@ -248,19 +245,28 @@ async fn polling_task(handle_data: &HandleData) -> Result<(), FatalErrorKind> { } drop(pending_cmds_lock); - // Use epoll to check the current read/write availability on the fd. + // Use mio poll to check the current read/write availability on the fd. // This is needed because Tokio supports only edge-triggered // notifications but Libnbd requires level-triggered notifications. - let mut revent = epoll::Event { data: 0, events: 0 }; // Setting timeout to 0 means that it will return immediately. - epoll::wait(epfd, 0, std::slice::from_mut(&mut revent))?; - let revents = Events::from_bits(revent.events).unwrap(); - if !revents.contains(Events::EPOLLIN) { - ready_guard.clear_ready_matching(IoReady::READABLE); - } - if !revents.contains(Events::EPOLLOUT) { - ready_guard.clear_ready_matching(IoReady::WRITABLE); + // mio states that it is OS-dependent on whether a single event + // can be both readable and writable, but we survive just fine + // if we only see one direction even when both are available. + poll.registry().register( + &mut SourceFd(&fd), + Token(0), + MioInterest::READABLE | MioInterest::WRITABLE, + )?; + poll.poll(&mut events, Some(Duration::ZERO))?; + for event in &events { + if !event.is_readable() { + ready_guard.clear_ready_matching(IoReady::READABLE); + } + if !event.is_writable() { + ready_guard.clear_ready_matching(IoReady::WRITABLE); + } } ready_guard.retain_ready(); + poll.registry().deregister(&mut SourceFd(&fd))?; } } base-commit: 9afb980d05d6144129c899285e44779757a380e8 prerequisite-patch-id: 8d1779610795021ed5a3d0973ddf9ef854cd6a24 prerequisite-patch-id: 1f0f333311f11ac9b1ff0be08f5aa0a9904ba4de prerequisite-patch-id: dc4af7343c57a4f99dc82918c07470030e542747 prerequisite-patch-id: 8e8f7a043c80d6c24e883967f5bd952a64db1228 prerequisite-patch-id: ba7b3482e2e16f76b5f285daeeda30b31a841912 prerequisite-patch-id: 219a9595e550a8caf43d466dcb2b044114e1b7bf prerequisite-patch-id: 3de46c9673221bff1d897970aa983b3f8e6cab74 prerequisite-patch-id: 4235d5e174fce05b9a947b3b838bebf968f0fa6a prerequisite-patch-id: 07773355d5718e0593c4030a8f035fc11fea3715 prerequisite-patch-id: f023deea8b706706e3c2980403064d90a254af3c prerequisite-patch-id: dd415a31fa127d90bcc7d993a2659e39d7d4cae8 prerequisite-patch-id: 618cc5f574207f36818ef803f2e586314c2458f5 prerequisite-patch-id: 8639c6cc4fec58f4761771c5d8a9476d538c6251 prerequisite-patch-id: 9bc660aed54a6266b014993ff0f388a26ac2982a prerequisite-patch-id: a334eeb471214d13ea2f47604b0a5b6d86b869b6 -- 2.42.0 _______________________________________________ Libguestfs mailing list Libguestfs@redhat.com https://listman.redhat.com/mailman/listinfo/libguestfs