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io: support PRIORITY epoll events (#5566)
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Add support for epoll priority events. The commit adds `Interest::PRIORITY`, `ready`, and `ready_mut` functions to `AsyncFd`.

Closes #4885
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folkertdev authored Jun 6, 2023
1 parent 779b9c1 commit 7b24b22
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Showing 7 changed files with 595 additions and 25 deletions.
2 changes: 1 addition & 1 deletion tokio/Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ pin-project-lite = "0.2.0"

# Everything else is optional...
bytes = { version = "1.0.0", optional = true }
mio = { version = "0.8.4", optional = true, default-features = false }
mio = { version = "0.8.6", optional = true, default-features = false }
num_cpus = { version = "1.8.0", optional = true }
parking_lot = { version = "0.12.0", optional = true }

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436 changes: 416 additions & 20 deletions tokio/src/io/async_fd.rs

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26 changes: 26 additions & 0 deletions tokio/src/io/interest.rs
Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,11 @@ impl Interest {
/// Writable interest includes write-closed events.
pub const WRITABLE: Interest = Interest(mio::Interest::WRITABLE);

/// Returns a `Interest` set representing priority completion interests.
#[cfg(any(target_os = "linux", target_os = "android"))]
#[cfg_attr(docsrs, doc(cfg(any(target_os = "linux", target_os = "android"))))]
pub const PRIORITY: Interest = Interest(mio::Interest::PRIORITY);

/// Returns true if the value includes readable interest.
///
/// # Examples
Expand Down Expand Up @@ -78,6 +83,25 @@ impl Interest {
self.0.is_writable()
}

/// Returns true if the value includes priority interest.
///
/// # Examples
///
/// ```
/// use tokio::io::Interest;
///
/// assert!(!Interest::READABLE.is_priority());
/// assert!(Interest::PRIORITY.is_priority());
///
/// let both = Interest::READABLE | Interest::PRIORITY;
/// assert!(both.is_priority());
/// ```
#[cfg(any(target_os = "linux", target_os = "android"))]
#[cfg_attr(docsrs, doc(cfg(any(target_os = "linux", target_os = "android"))))]
pub const fn is_priority(self) -> bool {
self.0.is_priority()
}

/// Add together two `Interest` values.
///
/// This function works from a `const` context.
Expand All @@ -104,6 +128,8 @@ impl Interest {
match self {
Interest::READABLE => Ready::READABLE | Ready::READ_CLOSED,
Interest::WRITABLE => Ready::WRITABLE | Ready::WRITE_CLOSED,
#[cfg(any(target_os = "linux", target_os = "android"))]
Interest::PRIORITY => Ready::PRIORITY | Ready::READ_CLOSED,
_ => Ready::EMPTY,
}
}
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3 changes: 3 additions & 0 deletions tokio/src/io/poll_evented.rs
Original file line number Diff line number Diff line change
Expand Up @@ -73,6 +73,9 @@ cfg_io_driver! {
impl<E: Source> PollEvented<E> {
/// Creates a new `PollEvented` associated with the default reactor.
///
/// The returned `PollEvented` has readable and writable interests. For more control, use
/// [`Self::new_with_interest`].
///
/// # Panics
///
/// This function panics if thread-local runtime is not set.
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55 changes: 51 additions & 4 deletions tokio/src/io/ready.rs
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@ const READABLE: usize = 0b0_01;
const WRITABLE: usize = 0b0_10;
const READ_CLOSED: usize = 0b0_0100;
const WRITE_CLOSED: usize = 0b0_1000;
#[cfg(any(target_os = "linux", target_os = "android"))]
const PRIORITY: usize = 0b1_0000;

/// Describes the readiness state of an I/O resources.
///
Expand All @@ -31,7 +33,17 @@ impl Ready {
/// Returns a `Ready` representing write closed readiness.
pub const WRITE_CLOSED: Ready = Ready(WRITE_CLOSED);

/// Returns a `Ready` representing priority readiness.
#[cfg(any(target_os = "linux", target_os = "android"))]
#[cfg_attr(docsrs, doc(cfg(any(target_os = "linux", target_os = "android"))))]
pub const PRIORITY: Ready = Ready(PRIORITY);

/// Returns a `Ready` representing readiness for all operations.
#[cfg(any(target_os = "linux", target_os = "android"))]
pub const ALL: Ready = Ready(READABLE | WRITABLE | READ_CLOSED | WRITE_CLOSED | PRIORITY);

/// Returns a `Ready` representing readiness for all operations.
#[cfg(not(any(target_os = "linux", target_os = "android")))]
pub const ALL: Ready = Ready(READABLE | WRITABLE | READ_CLOSED | WRITE_CLOSED);

// Must remain crate-private to avoid adding a public dependency on Mio.
Expand Down Expand Up @@ -65,6 +77,13 @@ impl Ready {
ready |= Ready::WRITE_CLOSED;
}

#[cfg(any(target_os = "linux", target_os = "android"))]
{
if event.is_priority() {
ready |= Ready::PRIORITY;
}
}

ready
}

Expand Down Expand Up @@ -144,6 +163,23 @@ impl Ready {
self.contains(Ready::WRITE_CLOSED)
}

/// Returns `true` if the value includes priority `readiness`.
///
/// # Examples
///
/// ```
/// use tokio::io::Ready;
///
/// assert!(!Ready::EMPTY.is_priority());
/// assert!(!Ready::WRITABLE.is_priority());
/// assert!(Ready::PRIORITY.is_priority());
/// ```
#[cfg(any(target_os = "linux", target_os = "android"))]
#[cfg_attr(docsrs, doc(cfg(any(target_os = "linux", target_os = "android"))))]
pub fn is_priority(self) -> bool {
self.contains(Ready::PRIORITY)
}

/// Returns true if `self` is a superset of `other`.
///
/// `other` may represent more than one readiness operations, in which case
Expand Down Expand Up @@ -191,6 +227,12 @@ cfg_io_readiness! {
ready |= Ready::WRITE_CLOSED;
}

#[cfg(any(target_os = "linux", target_os = "android"))]
if interest.is_priority() {
ready |= Ready::PRIORITY;
ready |= Ready::READ_CLOSED;
}

ready
}

Expand Down Expand Up @@ -240,11 +282,16 @@ impl ops::Sub<Ready> for Ready {

impl fmt::Debug for Ready {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt.debug_struct("Ready")
.field("is_readable", &self.is_readable())
let mut fmt = fmt.debug_struct("Ready");

fmt.field("is_readable", &self.is_readable())
.field("is_writable", &self.is_writable())
.field("is_read_closed", &self.is_read_closed())
.field("is_write_closed", &self.is_write_closed())
.finish()
.field("is_write_closed", &self.is_write_closed());

#[cfg(any(target_os = "linux", target_os = "android"))]
fmt.field("is_priority", &self.is_priority());

fmt.finish()
}
}
12 changes: 12 additions & 0 deletions tokio/src/runtime/io/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,18 @@ pub(crate) struct ReadyEvent {
is_shutdown: bool,
}

cfg_net_unix!(
impl ReadyEvent {
pub(crate) fn with_ready(&self, ready: Ready) -> Self {
Self {
ready,
tick: self.tick,
is_shutdown: self.is_shutdown,
}
}
}
);

struct IoDispatcher {
allocator: slab::Allocator<ScheduledIo>,
is_shutdown: bool,
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86 changes: 86 additions & 0 deletions tokio/tests/io_async_fd.rs
Original file line number Diff line number Diff line change
Expand Up @@ -599,3 +599,89 @@ fn driver_shutdown_wakes_poll_race() {
assert_err!(futures::executor::block_on(poll_writable(&afd_a)));
}
}

#[tokio::test]
#[cfg(any(target_os = "linux", target_os = "android"))]
async fn priority_event_on_oob_data() {
use std::net::SocketAddr;

use tokio::io::Interest;

let addr: SocketAddr = "127.0.0.1:0".parse().unwrap();

let listener = std::net::TcpListener::bind(addr).unwrap();
let addr = listener.local_addr().unwrap();

let client = std::net::TcpStream::connect(addr).unwrap();
let client = AsyncFd::with_interest(client, Interest::PRIORITY).unwrap();

let (stream, _) = listener.accept().unwrap();

// Sending out of band data should trigger priority event.
send_oob_data(&stream, b"hello").unwrap();

let _ = client.ready(Interest::PRIORITY).await.unwrap();
}

#[cfg(any(target_os = "linux", target_os = "android"))]
fn send_oob_data<S: AsRawFd>(stream: &S, data: &[u8]) -> io::Result<usize> {
unsafe {
let res = libc::send(
stream.as_raw_fd(),
data.as_ptr().cast(),
data.len(),
libc::MSG_OOB,
);
if res == -1 {
Err(io::Error::last_os_error())
} else {
Ok(res as usize)
}
}
}

#[tokio::test]
async fn clear_ready_matching_clears_ready() {
use tokio::io::{Interest, Ready};

let (a, mut b) = socketpair();

let afd_a = AsyncFd::new(a).unwrap();
b.write_all(b"0").unwrap();

let mut guard = afd_a
.ready(Interest::READABLE | Interest::WRITABLE)
.await
.unwrap();

assert_eq!(guard.ready(), Ready::READABLE | Ready::WRITABLE);

guard.clear_ready_matching(Ready::READABLE);
assert_eq!(guard.ready(), Ready::WRITABLE);

guard.clear_ready_matching(Ready::WRITABLE);
assert_eq!(guard.ready(), Ready::EMPTY);
}

#[tokio::test]
async fn clear_ready_matching_clears_ready_mut() {
use tokio::io::{Interest, Ready};

let (a, mut b) = socketpair();

let mut afd_a = AsyncFd::new(a).unwrap();
b.write_all(b"0").unwrap();

let mut guard = afd_a
.ready_mut(Interest::READABLE | Interest::WRITABLE)
.await
.unwrap();

assert_eq!(guard.ready(), Ready::READABLE | Ready::WRITABLE);

guard.clear_ready_matching(Ready::READABLE);
assert_eq!(guard.ready(), Ready::WRITABLE);

guard.clear_ready_matching(Ready::WRITABLE);
assert_eq!(guard.ready(), Ready::EMPTY);
}

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