io: driver internal cleanup (#3124)

* Removes duplicated code by moving it to `Registration`.
* impl `Deref` for `PollEvented` to avoid `get_ref()`.
* Avoid extra waker clones in I/O driver.
* Add `Interest` wrapper around `mio::Interest`.

tokio/src/io/async_fd.rs

@@ -1,5 +1,4 @@
-use crate::io::driver::{Direction, Handle, ReadyEvent};
+use crate::io::driver::{Handle, Interest, ReadyEvent, Registration};
-use crate::io::registration::Registration;
 
 use mio::unix::SourceFd;
 use std::io;
@@ -74,7 +73,7 @@ pub struct AsyncFdReadyGuard<'a, T: AsRawFd> {
     event: Option<ReadyEvent>,
 }
 
-const ALL_INTEREST: mio::Interest = mio::Interest::READABLE.add(mio::Interest::WRITABLE);
+const ALL_INTEREST: Interest = Interest::READABLE.add(Interest::WRITABLE);
 
 impl<T: AsRawFd> AsyncFd<T> {
     /// Creates an AsyncFd backed by (and taking ownership of) an object
@@ -145,7 +144,7 @@ impl<T: AsRawFd> AsyncFd<T> {
         &'a self,
         cx: &mut Context<'_>,
     ) -> Poll<io::Result<AsyncFdReadyGuard<'a, T>>> {
-        let event = ready!(self.registration.poll_readiness(cx, Direction::Read))?;
+        let event = ready!(self.registration.poll_read_ready(cx))?;
 
         Ok(AsyncFdReadyGuard {
             async_fd: self,
@@ -170,7 +169,7 @@ impl<T: AsRawFd> AsyncFd<T> {
         &'a self,
         cx: &mut Context<'_>,
     ) -> Poll<io::Result<AsyncFdReadyGuard<'a, T>>> {
-        let event = ready!(self.registration.poll_readiness(cx, Direction::Write))?;
+        let event = ready!(self.registration.poll_write_ready(cx))?;
 
         Ok(AsyncFdReadyGuard {
             async_fd: self,
@@ -179,7 +178,7 @@ impl<T: AsRawFd> AsyncFd<T> {
         .into()
     }
 
-    async fn readiness(&self, interest: mio::Interest) -> io::Result<AsyncFdReadyGuard<'_, T>> {
+    async fn readiness(&self, interest: Interest) -> io::Result<AsyncFdReadyGuard<'_, T>> {
         let event = self.registration.readiness(interest).await?;
 
         Ok(AsyncFdReadyGuard {
@@ -193,7 +192,7 @@ impl<T: AsRawFd> AsyncFd<T> {
     ///
     /// [`AsyncFdReadyGuard`]: struct@self::AsyncFdReadyGuard
     pub async fn readable(&self) -> io::Result<AsyncFdReadyGuard<'_, T>> {
-        self.readiness(mio::Interest::READABLE).await
+        self.readiness(Interest::READABLE).await
     }
 
     /// Waits for the file descriptor to become writable, returning a
@@ -201,7 +200,7 @@ impl<T: AsRawFd> AsyncFd<T> {
     ///
     /// [`AsyncFdReadyGuard`]: struct@self::AsyncFdReadyGuard
     pub async fn writable(&self) -> io::Result<AsyncFdReadyGuard<'_, T>> {
-        self.readiness(mio::Interest::WRITABLE).await
+        self.readiness(Interest::WRITABLE).await
     }
 }
 

tokio/src/io/driver/interest.rs

@@ -0,0 +1,58 @@
+use std::fmt;
+use std::ops;
+
+/// Readiness event interest
+///
+/// Specifies the readiness events the caller is interested in when awaiting on
+/// I/O resource readiness states.
+#[derive(Clone, Copy)]
+pub(crate) struct Interest(mio::Interest);
+
+impl Interest {
+    /// Interest in all readable events
+    pub(crate) const READABLE: Interest = Interest(mio::Interest::READABLE);
+
+    /// Interest in all writable events
+    pub(crate) const WRITABLE: Interest = Interest(mio::Interest::WRITABLE);
+
+    /// Returns true if the value includes readable interest.
+    pub(crate) const fn is_readable(self) -> bool {
+        self.0.is_readable()
+    }
+
+    /// Returns true if the value includes writable interest.
+    pub(crate) const fn is_writable(self) -> bool {
+        self.0.is_writable()
+    }
+
+    /// Add together two `Interst` values.
+    pub(crate) const fn add(self, other: Interest) -> Interest {
+        Interest(self.0.add(other.0))
+    }
+
+    pub(crate) const fn to_mio(self) -> mio::Interest {
+        self.0
+    }
+}
+
+impl ops::BitOr for Interest {
+    type Output = Self;
+
+    #[inline]
+    fn bitor(self, other: Self) -> Self {
+        self.add(other)
+    }
+}
+
+impl ops::BitOrAssign for Interest {
+    #[inline]
+    fn bitor_assign(&mut self, other: Self) {
+        self.0 = (*self | other).0;
+    }
+}
+
+impl fmt::Debug for Interest {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(fmt)
+    }
+}

tokio/src/io/driver/mod.rs

@@ -1,10 +1,16 @@
 #![cfg_attr(not(feature = "rt"), allow(dead_code))]
 
+mod interest;
+pub(crate) use interest::Interest;
+
 mod ready;
 use ready::Ready;
 
+mod registration;
+pub(crate) use registration::Registration;
+
 mod scheduled_io;
-pub(crate) use scheduled_io::ScheduledIo; // pub(crate) for tests
+use scheduled_io::ScheduledIo;
 
 use crate::park::{Park, Unpark};
 use crate::util::slab::{self, Slab};
@@ -68,7 +74,7 @@ pub(super) struct Inner {
 }
 
 #[derive(Debug, Eq, PartialEq, Clone, Copy)]
-pub(super) enum Direction {
+enum Direction {
     Read,
     Write,
 }
@@ -313,7 +319,7 @@ impl Inner {
     pub(super) fn add_source(
         &self,
         source: &mut impl mio::event::Source,
-        interest: mio::Interest,
+        interest: Interest,
     ) -> io::Result<slab::Ref<ScheduledIo>> {
         let (address, shared) = self.io_dispatch.allocate().ok_or_else(|| {
             io::Error::new(
@@ -325,7 +331,7 @@ impl Inner {
         let token = GENERATION.pack(shared.generation(), ADDRESS.pack(address.as_usize(), 0));
 
         self.registry
-            .register(source, mio::Token(token), interest)?;
+            .register(source, mio::Token(token), interest.to_mio())?;
 
         Ok(shared)
     }

tokio/src/io/driver/ready.rs

@@ -114,8 +114,10 @@ impl Ready {
 }
 
 cfg_io_readiness! {
+    use crate::io::Interest;
+
     impl Ready {
-        pub(crate) fn from_interest(interest: mio::Interest) -> Ready {
+        pub(crate) fn from_interest(interest: Interest) -> Ready {
             let mut ready = Ready::EMPTY;
 
             if interest.is_readable() {
@@ -131,11 +133,11 @@ cfg_io_readiness! {
             ready
         }
 
-        pub(crate) fn intersection(self, interest: mio::Interest) -> Ready {
+        pub(crate) fn intersection(self, interest: Interest) -> Ready {
             Ready(self.0 & Ready::from_interest(interest).0)
         }
 
-        pub(crate) fn satisfies(self, interest: mio::Interest) -> bool {
+        pub(crate) fn satisfies(self, interest: Interest) -> bool {
             self.0 & Ready::from_interest(interest).0 != 0
         }
     }

tokio/src/io/driver/registration.rs

@@ -1,4 +1,4 @@
-use crate::io::driver::{Direction, Handle, ReadyEvent, ScheduledIo};
+use crate::io::driver::{Direction, Handle, Interest, ReadyEvent, ScheduledIo};
 use crate::util::slab;
 
 use mio::event::Source;
@@ -53,11 +53,12 @@ unsafe impl Sync for Registration {}
 // ===== impl Registration =====
 
 impl Registration {
-    /// Registers the I/O resource with the default reactor, for a specific `mio::Interest`.
+    /// Registers the I/O resource with the default reactor, for a specific
-    /// `new_with_interest` should be used over `new` when you need control over the readiness state,
+    /// `Interest`. `new_with_interest` should be used over `new` when you need
-    /// such as when a file descriptor only allows reads. This does not add `hup` or `error` so if
+    /// control over the readiness state, such as when a file descriptor only
-    /// you are interested in those states, you will need to add them to the readiness state passed
+    /// allows reads. This does not add `hup` or `error` so if you are
-    /// to this function.
+    /// interested in those states, you will need to add them to the readiness
+    /// state passed to this function.
     ///
     /// # Return
     ///
@@ -65,7 +66,7 @@ impl Registration {
     /// - `Err` if an error was encountered during registration
     pub(crate) fn new_with_interest_and_handle(
         io: &mut impl Source,
-        interest: mio::Interest,
+        interest: Interest,
         handle: Handle,
     ) -> io::Result<Registration> {
         let shared = if let Some(inner) = handle.inner() {
@@ -96,7 +97,7 @@ impl Registration {
     /// no longer result in notifications getting sent for this registration.
     ///
     /// `Err` is returned if an error is encountered.
-    pub(super) fn deregister(&mut self, io: &mut impl Source) -> io::Result<()> {
+    pub(crate) fn deregister(&mut self, io: &mut impl Source) -> io::Result<()> {
         let inner = match self.handle.inner() {
             Some(inner) => inner,
             None => return Err(io::Error::new(io::ErrorKind::Other, "reactor gone")),
@@ -104,15 +105,47 @@ impl Registration {
         inner.deregister_source(io)
     }
 
-    pub(super) fn clear_readiness(&self, event: ReadyEvent) {
+    pub(crate) fn clear_readiness(&self, event: ReadyEvent) {
         self.shared.clear_readiness(event);
     }
 
+    // Uses the poll path, requiring the caller to ensure mutual exclusion for
+    // correctness. Only the last task to call this function is notified.
+    pub(crate) fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<ReadyEvent>> {
+        self.poll_ready(cx, Direction::Read)
+    }
+
+    // Uses the poll path, requiring the caller to ensure mutual exclusion for
+    // correctness. Only the last task to call this function is notified.
+    pub(crate) fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<ReadyEvent>> {
+        self.poll_ready(cx, Direction::Write)
+    }
+
+    // Uses the poll path, requiring the caller to ensure mutual exclusion for
+    // correctness. Only the last task to call this function is notified.
+    pub(crate) fn poll_read_io<R>(
+        &self,
+        cx: &mut Context<'_>,
+        f: impl FnMut() -> io::Result<R>,
+    ) -> Poll<io::Result<R>> {
+        self.poll_io(cx, Direction::Read, f)
+    }
+
+    // Uses the poll path, requiring the caller to ensure mutual exclusion for
+    // correctness. Only the last task to call this function is notified.
+    pub(crate) fn poll_write_io<R>(
+        &self,
+        cx: &mut Context<'_>,
+        f: impl FnMut() -> io::Result<R>,
+    ) -> Poll<io::Result<R>> {
+        self.poll_io(cx, Direction::Write, f)
+    }
+
     /// Polls for events on the I/O resource's `direction` readiness stream.
     ///
     /// If called with a task context, notify the task when a new event is
     /// received.
-    pub(super) fn poll_readiness(
+    fn poll_ready(
         &self,
         cx: &mut Context<'_>,
         direction: Direction,
@@ -128,6 +161,27 @@ impl Registration {
         coop.made_progress();
         Poll::Ready(Ok(ev))
     }
+
+    fn poll_io<R>(
+        &self,
+        cx: &mut Context<'_>,
+        direction: Direction,
+        mut f: impl FnMut() -> io::Result<R>,
+    ) -> Poll<io::Result<R>> {
+        loop {
+            let ev = ready!(self.poll_ready(cx, direction))?;
+
+            match f() {
+                Ok(ret) => {
+                    return Poll::Ready(Ok(ret));
+                }
+                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+                    self.clear_readiness(ev);
+                }
+                Err(e) => return Poll::Ready(Err(e)),
+            }
+        }
+    }
 }
 
 fn gone() -> io::Error {
@@ -136,7 +190,7 @@ fn gone() -> io::Error {
 
 cfg_io_readiness! {
     impl Registration {
-        pub(super) async fn readiness(&self, interest: mio::Interest) -> io::Result<ReadyEvent> {
+        pub(crate) async fn readiness(&self, interest: Interest) -> io::Result<ReadyEvent> {
             use std::future::Future;
             use std::pin::Pin;
 
@@ -151,5 +205,18 @@ cfg_io_readiness! {
                 Pin::new(&mut fut).poll(cx).map(Ok)
             }).await
         }
+
+        pub(crate) async fn async_io<R>(&self, interest: Interest, mut f: impl FnMut() -> io::Result<R>) -> io::Result<R> {
+            loop {
+                let event = self.readiness(interest).await?;
+
+                match f() {
+                    Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+                        self.clear_readiness(event);
+                    }
+                    x => return x,
+                }
+            }
+        }
     }
 }

tokio/src/io/driver/scheduled_io.rs

@@ -49,6 +49,8 @@ struct Waiters {
 }
 
 cfg_io_readiness! {
+    use crate::io::Interest;
+
     #[derive(Debug)]
     struct Waiter {
         pointers: linked_list::Pointers<Waiter>,
@@ -57,7 +59,7 @@ cfg_io_readiness! {
         waker: Option<Waker>,
 
         /// The interest this waiter is waiting on
-        interest: mio::Interest,
+        interest: Interest,
 
         is_ready: bool,
 
@@ -283,7 +285,7 @@ impl ScheduledIo {
     /// These are to support `AsyncRead` and `AsyncWrite` polling methods,
     /// which cannot use the `async fn` version. This uses reserved reader
     /// and writer slots.
-    pub(in crate::io) fn poll_readiness(
+    pub(super) fn poll_readiness(
         &self,
         cx: &mut Context<'_>,
         direction: Direction,
@@ -299,7 +301,19 @@ impl ScheduledIo {
                 Direction::Read => &mut waiters.reader,
                 Direction::Write => &mut waiters.writer,
             };
-            *slot = Some(cx.waker().clone());
+
+            // Avoid cloning the waker if one is already stored that matches the
+            // current task.
+            match slot {
+                Some(existing) => {
+                    if !existing.will_wake(cx.waker()) {
+                        *existing = cx.waker().clone();
+                    }
+                }
+                None => {
+                    *slot = Some(cx.waker().clone());
+                }
+            }
 
             // Try again, in case the readiness was changed while we were
             // taking the waiters lock
@@ -348,7 +362,7 @@ unsafe impl Sync for ScheduledIo {}
 cfg_io_readiness! {
     impl ScheduledIo {
         /// An async version of `poll_readiness` which uses a linked list of wakers
-        pub(crate) async fn readiness(&self, interest: mio::Interest) -> ReadyEvent {
+        pub(crate) async fn readiness(&self, interest: Interest) -> ReadyEvent {
             self.readiness_fut(interest).await
         }
 
@@ -356,7 +370,7 @@ cfg_io_readiness! {
         // we are borrowing the `UnsafeCell` possibly over await boundaries.
         //
         // Go figure.
-        fn readiness_fut(&self, interest: mio::Interest) -> Readiness<'_> {
+        fn readiness_fut(&self, interest: Interest) -> Readiness<'_> {
             Readiness {
                 scheduled_io: self,
                 state: State::Init,

tokio/src/io/mod.rs

@@ -206,8 +206,7 @@ pub use std::io::{Error, ErrorKind, Result, SeekFrom};
 
 cfg_io_driver! {
     pub(crate) mod driver;
-
+    pub(crate) use driver::Interest;
-    mod registration;
 
     mod poll_evented;
 

tokio/src/io/poll_evented.rs

@@ -1,13 +1,9 @@
-use crate::io::driver::{Direction, Handle, ReadyEvent};
+use crate::io::driver::{Handle, Interest, Registration};
-use crate::io::registration::Registration;
-use crate::io::{AsyncRead, AsyncWrite, ReadBuf};
 
 use mio::event::Source;
 use std::fmt;
-use std::io::{self, Read, Write};
+use std::io;
-use std::marker::Unpin;
+use std::ops::Deref;
-use std::pin::Pin;
-use std::task::{Context, Poll};
 
 cfg_io_driver! {
     /// Associates an I/O resource that implements the [`std::io::Read`] and/or
@@ -89,30 +85,32 @@ impl<E: Source> PollEvented<E> {
     /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
     #[cfg_attr(feature = "signal", allow(unused))]
     pub(crate) fn new(io: E) -> io::Result<Self> {
-        PollEvented::new_with_interest(io, mio::Interest::READABLE | mio::Interest::WRITABLE)
+        PollEvented::new_with_interest(io, Interest::READABLE | Interest::WRITABLE)
     }
 
-    /// Creates a new `PollEvented` associated with the default reactor, for specific `mio::Interest`
+    /// Creates a new `PollEvented` associated with the default reactor, for
-    /// state. `new_with_interest` should be used over `new` when you need control over the readiness
+    /// specific `Interest` state. `new_with_interest` should be used over `new`
-    /// state, such as when a file descriptor only allows reads. This does not add `hup` or `error`
+    /// when you need control over the readiness state, such as when a file
-    /// so if you are interested in those states, you will need to add them to the readiness state
+    /// descriptor only allows reads. This does not add `hup` or `error` so if
-    /// passed to this function.
+    /// you are interested in those states, you will need to add them to the
+    /// readiness state passed to this function.
     ///
     /// # Panics
     ///
     /// This function panics if thread-local runtime is not set.
     ///
-    /// The runtime is usually set implicitly when this function is called
+    /// The runtime is usually set implicitly when this function is called from
-    /// from a future driven by a tokio runtime, otherwise runtime can be set
+    /// a future driven by a tokio runtime, otherwise runtime can be set
-    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter) function.
+    /// explicitly with [`Runtime::enter`](crate::runtime::Runtime::enter)
+    /// function.
     #[cfg_attr(feature = "signal", allow(unused))]
-    pub(crate) fn new_with_interest(io: E, interest: mio::Interest) -> io::Result<Self> {
+    pub(crate) fn new_with_interest(io: E, interest: Interest) -> io::Result<Self> {
         Self::new_with_interest_and_handle(io, interest, Handle::current())
     }
 
     pub(crate) fn new_with_interest_and_handle(
         mut io: E,
-        interest: mio::Interest,
+        interest: Interest,
         handle: Handle,
     ) -> io::Result<Self> {
         let registration = Registration::new_with_interest_and_handle(&mut io, interest, handle)?;
@@ -122,177 +120,57 @@ impl<E: Source> PollEvented<E> {
         })
     }
 
-    /// Returns a shared reference to the underlying I/O object this readiness
+    /// Returns a reference to the registration
-    /// stream is wrapping.
+    pub(crate) fn registration(&self) -> &Registration {
-    #[cfg(any(feature = "net", feature = "process", feature = "signal"))]
+        &self.registration
-    pub(crate) fn get_ref(&self) -> &E {
-        self.io.as_ref().unwrap()
-    }
-
-    /// Returns a mutable reference to the underlying I/O object this readiness
-    /// stream is wrapping.
-    pub(crate) fn get_mut(&mut self) -> &mut E {
-        self.io.as_mut().unwrap()
-    }
-
-    pub(crate) fn clear_readiness(&self, event: ReadyEvent) {
-        self.registration.clear_readiness(event);
-    }
-
-    /// Checks the I/O resource's read readiness state.
-    ///
-    /// The mask argument allows specifying what readiness to notify on. This
-    /// can be any value, including platform specific readiness, **except**
-    /// `writable`. HUP is always implicitly included on platforms that support
-    /// it.
-    ///
-    /// If the resource is not ready for a read then `Poll::Pending` is returned
-    /// and the current task is notified once a new event is received.
-    ///
-    /// The I/O resource will remain in a read-ready state until readiness is
-    /// cleared by calling [`clear_read_ready`].
-    ///
-    /// [`clear_read_ready`]: method@Self::clear_read_ready
-    ///
-    /// # Panics
-    ///
-    /// This function panics if:
-    ///
-    /// * `ready` includes writable.
-    /// * called from outside of a task context.
-    ///
-    /// # Warning
-    ///
-    /// This method may not be called concurrently. It takes `&self` to allow
-    /// calling it concurrently with `poll_write_ready`.
-    pub(crate) fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<ReadyEvent>> {
-        self.registration.poll_readiness(cx, Direction::Read)
-    }
-
-    /// Checks the I/O resource's write readiness state.
-    ///
-    /// This always checks for writable readiness and also checks for HUP
-    /// readiness on platforms that support it.
-    ///
-    /// If the resource is not ready for a write then `Poll::Pending` is
-    /// returned and the current task is notified once a new event is received.
-    ///
-    /// The I/O resource will remain in a write-ready state until readiness is
-    /// cleared by calling [`clear_write_ready`].
-    ///
-    /// [`clear_write_ready`]: method@Self::clear_write_ready
-    ///
-    /// # Panics
-    ///
-    /// This function panics if:
-    ///
-    /// * `ready` contains bits besides `writable` and `hup`.
-    /// * called from outside of a task context.
-    ///
-    /// # Warning
-    ///
-    /// This method may not be called concurrently. It takes `&self` to allow
-    /// calling it concurrently with `poll_read_ready`.
-    pub(crate) fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<io::Result<ReadyEvent>> {
-        self.registration.poll_readiness(cx, Direction::Write)
     }
 }
 
-cfg_io_readiness! {
+feature! {
+    #![any(feature = "net", feature = "process")]
+
+    use crate::io::ReadBuf;
+    use std::task::{Context, Poll};
+
     impl<E: Source> PollEvented<E> {
-        pub(crate) async fn readiness(&self, interest: mio::Interest) -> io::Result<ReadyEvent> {
+        // Safety: The caller must ensure that `E` can read into uninitialized memory
-            self.registration.readiness(interest).await
+        pub(crate) unsafe fn poll_read<'a>(
-        }
+            &'a self,
-
+            cx: &mut Context<'_>,
-        pub(crate) async fn async_io<F, R>(&self, interest: mio::Interest, mut op: F) -> io::Result<R>
+            buf: &mut ReadBuf<'_>,
+        ) -> Poll<io::Result<()>>
         where
-            F: FnMut(&E) -> io::Result<R>,
+            &'a E: io::Read + 'a,
         {
-            loop {
+            use std::io::Read;
-                let event = self.readiness(interest).await?;
 
-                match op(self.get_ref()) {
+            let n = ready!(self.registration.poll_read_io(cx, || {
-                    Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+                let b = &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8]);
-                        self.clear_readiness(event);
+                self.io.as_ref().unwrap().read(b)
-                    }
+            }))?;
-                    x => return x,
+
-                }
+            // Safety: We trust `TcpStream::read` to have filled up `n` bytes in the
-            }
+            // buffer.
+            buf.assume_init(n);
+            buf.advance(n);
+            Poll::Ready(Ok(()))
+        }
+
+        pub(crate) fn poll_write<'a>(&'a self, cx: &mut Context<'_>, buf: &[u8]) -> Poll<io::Result<usize>>
+        where
+            &'a E: io::Write + 'a,
+        {
+            use std::io::Write;
+            self.registration.poll_write_io(cx, || self.io.as_ref().unwrap().write(buf))
         }
     }
 }
 
-// ===== Read / Write impls =====
+impl<E: Source> Deref for PollEvented<E> {
+    type Target = E;
 
-impl<E: Source + Read + Unpin> AsyncRead for PollEvented<E> {
+    fn deref(&self) -> &E {
-    fn poll_read(
+        self.io.as_ref().unwrap()
-        mut self: Pin<&mut Self>,
-        cx: &mut Context<'_>,
-        buf: &mut ReadBuf<'_>,
-    ) -> Poll<io::Result<()>> {
-        loop {
-            let ev = ready!(self.poll_read_ready(cx))?;
-
-            // We can't assume the `Read` won't look at the read buffer,
-            // so we have to force initialization here.
-            let r = (*self).get_mut().read(buf.initialize_unfilled());
-
-            if is_wouldblock(&r) {
-                self.clear_readiness(ev);
-                continue;
-            }
-
-            return Poll::Ready(r.map(|n| {
-                buf.advance(n);
-            }));
-        }
-    }
-}
-
-impl<E: Source + Write + Unpin> AsyncWrite for PollEvented<E> {
-    fn poll_write(
-        mut self: Pin<&mut Self>,
-        cx: &mut Context<'_>,
-        buf: &[u8],
-    ) -> Poll<io::Result<usize>> {
-        loop {
-            let ev = ready!(self.poll_write_ready(cx))?;
-
-            let r = (*self).get_mut().write(buf);
-
-            if is_wouldblock(&r) {
-                self.clear_readiness(ev);
-                continue;
-            }
-
-            return Poll::Ready(r);
-        }
-    }
-
-    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-        loop {
-            let ev = ready!(self.poll_write_ready(cx))?;
-
-            let r = (*self).get_mut().flush();
-
-            if is_wouldblock(&r) {
-                self.clear_readiness(ev);
-                continue;
-            }
-
-            return Poll::Ready(r);
-        }
-    }
-
-    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-        Poll::Ready(Ok(()))
-    }
-}
-
-fn is_wouldblock<T>(r: &io::Result<T>) -> bool {
-    match *r {
-        Ok(_) => false,
-        Err(ref e) => e.kind() == io::ErrorKind::WouldBlock,
     }
 }
 

tokio/src/macros/cfg.rs

@@ -1,5 +1,18 @@
 #![allow(unused_macros)]
 
+macro_rules! feature {
+    (
+        #![$meta:meta]
+        $($item:item)*
+    ) => {
+        $(
+            #[cfg($meta)]
+            #[cfg_attr(docsrs, doc(cfg($meta)))]
+            $item
+        )*
+    }
+}
+
 /// Enables enter::block_on
 macro_rules! cfg_block_on {
     ($($item:item)*) => {

tokio/src/net/tcp/listener.rs

@@ -1,4 +1,4 @@
-use crate::io::PollEvented;
+use crate::io::{Interest, PollEvented};
 use crate::net::tcp::TcpStream;
 use crate::net::{to_socket_addrs, ToSocketAddrs};
 
@@ -164,7 +164,8 @@ impl TcpListener {
     pub async fn accept(&self) -> io::Result<(TcpStream, SocketAddr)> {
         let (mio, addr) = self
             .io
-            .async_io(mio::Interest::READABLE, |sock| sock.accept())
+            .registration()
+            .async_io(Interest::READABLE, || self.io.accept())
             .await?;
 
         let stream = TcpStream::new(mio)?;
@@ -181,15 +182,15 @@ impl TcpListener {
     /// single task. Failing to do this could result in tasks hanging.
     pub fn poll_accept(&self, cx: &mut Context<'_>) -> Poll<io::Result<(TcpStream, SocketAddr)>> {
         loop {
-            let ev = ready!(self.io.poll_read_ready(cx))?;
+            let ev = ready!(self.io.registration().poll_read_ready(cx))?;
 
-            match self.io.get_ref().accept() {
+            match self.io.accept() {
                 Ok((io, addr)) => {
                     let io = TcpStream::new(io)?;
                     return Poll::Ready(Ok((io, addr)));
                 }
                 Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
+                    self.io.registration().clear_readiness(ev);
                 }
                 Err(e) => return Poll::Ready(Err(e)),
             }
@@ -266,7 +267,7 @@ impl TcpListener {
     /// }
     /// ```
     pub fn local_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().local_addr()
+        self.io.local_addr()
     }
 
     /// Gets the value of the `IP_TTL` option for this socket.
@@ -293,7 +294,7 @@ impl TcpListener {
     /// }
     /// ```
     pub fn ttl(&self) -> io::Result<u32> {
-        self.io.get_ref().ttl()
+        self.io.ttl()
     }
 
     /// Sets the value for the `IP_TTL` option on this socket.
@@ -318,7 +319,7 @@ impl TcpListener {
     /// }
     /// ```
     pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
-        self.io.get_ref().set_ttl(ttl)
+        self.io.set_ttl(ttl)
     }
 }
 
@@ -346,7 +347,7 @@ impl TryFrom<net::TcpListener> for TcpListener {
 
 impl fmt::Debug for TcpListener {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.io.get_ref().fmt(f)
+        self.io.fmt(f)
     }
 }
 
@@ -357,7 +358,7 @@ mod sys {
 
     impl AsRawFd for TcpListener {
         fn as_raw_fd(&self) -> RawFd {
-            self.io.get_ref().as_raw_fd()
+            self.io.as_raw_fd()
         }
     }
 }
@@ -369,7 +370,7 @@ mod sys {
 
     impl AsRawSocket for TcpListener {
         fn as_raw_socket(&self) -> RawSocket {
-            self.io.get_ref().as_raw_socket()
+            self.io.as_raw_socket()
         }
     }
 }

tokio/src/net/tcp/stream.rs

@@ -1,12 +1,12 @@
 use crate::future::poll_fn;
-use crate::io::{AsyncRead, AsyncWrite, PollEvented, ReadBuf};
+use crate::io::{AsyncRead, AsyncWrite, Interest, PollEvented, ReadBuf};
 use crate::net::tcp::split::{split, ReadHalf, WriteHalf};
 use crate::net::tcp::split_owned::{split_owned, OwnedReadHalf, OwnedWriteHalf};
 use crate::net::{to_socket_addrs, ToSocketAddrs};
 
 use std::convert::TryFrom;
 use std::fmt;
-use std::io::{self, Read, Write};
+use std::io;
 use std::net::{Shutdown, SocketAddr};
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -129,9 +129,9 @@ impl TcpStream {
         // actually hit an error or not.
         //
         // If all that succeeded then we ship everything on up.
-        poll_fn(|cx| stream.io.poll_write_ready(cx)).await?;
+        poll_fn(|cx| stream.io.registration().poll_write_ready(cx)).await?;
 
-        if let Some(e) = stream.io.get_ref().take_error()? {
+        if let Some(e) = stream.io.take_error()? {
             return Err(e);
         }
 
@@ -193,7 +193,7 @@ impl TcpStream {
     /// # }
     /// ```
     pub fn local_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().local_addr()
+        self.io.local_addr()
     }
 
     /// Returns the remote address that this stream is connected to.
@@ -211,7 +211,7 @@ impl TcpStream {
     /// # }
     /// ```
     pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().peer_addr()
+        self.io.peer_addr()
     }
 
     /// Attempts to receive data on the socket, without removing that data from
@@ -252,12 +252,12 @@ impl TcpStream {
     /// ```
     pub fn poll_peek(&self, cx: &mut Context<'_>, buf: &mut [u8]) -> Poll<io::Result<usize>> {
         loop {
-            let ev = ready!(self.io.poll_read_ready(cx))?;
+            let ev = ready!(self.io.registration().poll_read_ready(cx))?;
 
-            match self.io.get_ref().peek(buf) {
+            match self.io.peek(buf) {
                 Ok(ret) => return Poll::Ready(Ok(ret)),
                 Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
+                    self.io.registration().clear_readiness(ev);
                 }
                 Err(e) => return Poll::Ready(Err(e)),
             }
@@ -303,7 +303,8 @@ impl TcpStream {
     /// [`AsyncReadExt`]: trait@crate::io::AsyncReadExt
     pub async fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
         self.io
-            .async_io(mio::Interest::READABLE, |io| io.peek(buf))
+            .registration()
+            .async_io(Interest::READABLE, || self.io.peek(buf))
             .await
     }
 
@@ -332,7 +333,7 @@ impl TcpStream {
     /// }
     /// ```
     pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
-        self.io.get_ref().shutdown(how)
+        self.io.shutdown(how)
     }
 
     /// Gets the value of the `TCP_NODELAY` option on this socket.
@@ -354,7 +355,7 @@ impl TcpStream {
     /// # }
     /// ```
     pub fn nodelay(&self) -> io::Result<bool> {
-        self.io.get_ref().nodelay()
+        self.io.nodelay()
     }
 
     /// Sets the value of the `TCP_NODELAY` option on this socket.
@@ -378,7 +379,7 @@ impl TcpStream {
     /// # }
     /// ```
     pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
-        self.io.get_ref().set_nodelay(nodelay)
+        self.io.set_nodelay(nodelay)
     }
 
     /// Gets the value of the `IP_TTL` option for this socket.
@@ -400,7 +401,7 @@ impl TcpStream {
     /// # }
     /// ```
     pub fn ttl(&self) -> io::Result<u32> {
-        self.io.get_ref().ttl()
+        self.io.ttl()
     }
 
     /// Sets the value for the `IP_TTL` option on this socket.
@@ -421,7 +422,7 @@ impl TcpStream {
     /// # }
     /// ```
     pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
-        self.io.get_ref().set_ttl(ttl)
+        self.io.set_ttl(ttl)
     }
 
     // These lifetime markers also appear in the generated documentation, and make
@@ -469,29 +470,8 @@ impl TcpStream {
         cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
-        loop {
+        // Safety: `TcpStream::read` correctly handles reads into uninitialized memory
-            let ev = ready!(self.io.poll_read_ready(cx))?;
+        unsafe { self.io.poll_read(cx, buf) }
-
-            // Safety: `TcpStream::read` will not peek at the maybe uinitialized bytes.
-            let b = unsafe {
-                &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8])
-            };
-            match self.io.get_ref().read(b) {
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                Ok(n) => {
-                    // Safety: We trust `TcpStream::read` to have filled up `n` bytes
-                    // in the buffer.
-                    unsafe {
-                        buf.assume_init(n);
-                    }
-                    buf.advance(n);
-                    return Poll::Ready(Ok(()));
-                }
-                Err(e) => return Poll::Ready(Err(e)),
-            }
-        }
     }
 
     pub(super) fn poll_write_priv(
@@ -499,16 +479,7 @@ impl TcpStream {
         cx: &mut Context<'_>,
         buf: &[u8],
     ) -> Poll<io::Result<usize>> {
-        loop {
+        self.io.poll_write(cx, buf)
-            let ev = ready!(self.io.poll_write_ready(cx))?;
-
-            match self.io.get_ref().write(buf) {
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                x => return Poll::Ready(x),
-            }
-        }
     }
 }
 
@@ -559,7 +530,7 @@ impl AsyncWrite for TcpStream {
 
 impl fmt::Debug for TcpStream {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.io.get_ref().fmt(f)
+        self.io.fmt(f)
     }
 }
 
@@ -570,7 +541,7 @@ mod sys {
 
     impl AsRawFd for TcpStream {
         fn as_raw_fd(&self) -> RawFd {
-            self.io.get_ref().as_raw_fd()
+            self.io.as_raw_fd()
         }
     }
 }
@@ -582,7 +553,7 @@ mod sys {
 
     impl AsRawSocket for TcpStream {
         fn as_raw_socket(&self) -> RawSocket {
-            self.io.get_ref().as_raw_socket()
+            self.io.as_raw_socket()
         }
     }
 }

tokio/src/net/udp/socket.rs

@@ -1,4 +1,4 @@
-use crate::io::{PollEvented, ReadBuf};
+use crate::io::{Interest, PollEvented, ReadBuf};
 use crate::net::{to_socket_addrs, ToSocketAddrs};
 
 use std::convert::TryFrom;
@@ -216,7 +216,7 @@ impl UdpSocket {
     /// # }
     /// ```
     pub fn local_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().local_addr()
+        self.io.local_addr()
     }
 
     /// Connects the UDP socket setting the default destination for send() and
@@ -248,7 +248,7 @@ impl UdpSocket {
         let mut last_err = None;
 
         for addr in addrs {
-            match self.io.get_ref().connect(addr) {
+            match self.io.connect(addr) {
                 Ok(_) => return Ok(()),
                 Err(e) => last_err = Some(e),
             }
@@ -271,7 +271,8 @@ impl UdpSocket {
     /// [`connect`]: method@Self::connect
     pub async fn send(&self, buf: &[u8]) -> io::Result<usize> {
         self.io
-            .async_io(mio::Interest::WRITABLE, |sock| sock.send(buf))
+            .registration()
+            .async_io(Interest::WRITABLE, || self.io.send(buf))
             .await
     }
 
@@ -299,16 +300,9 @@ impl UdpSocket {
     ///
     /// [`connect`]: method@Self::connect
     pub fn poll_send(&self, cx: &mut Context<'_>, buf: &[u8]) -> Poll<io::Result<usize>> {
-        loop {
+        self.io
-            let ev = ready!(self.io.poll_write_ready(cx))?;
+            .registration()
-
+            .poll_write_io(cx, || self.io.send(buf))
-            match self.io.get_ref().send(buf) {
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                x => return Poll::Ready(x),
-            }
-        }
     }
 
     /// Try to send data on the socket to the remote address to which it is
@@ -322,7 +316,7 @@ impl UdpSocket {
     ///
     /// [`ErrorKind::WouldBlock`]: std::io::ErrorKind::WouldBlock
     pub fn try_send(&self, buf: &[u8]) -> io::Result<usize> {
-        self.io.get_ref().send(buf)
+        self.io.send(buf)
     }
 
     /// Returns a future that receives a single datagram message on the socket from
@@ -339,7 +333,8 @@ impl UdpSocket {
     /// [`connect`]: method@Self::connect
     pub async fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
         self.io
-            .async_io(mio::Interest::READABLE, |sock| sock.recv(buf))
+            .registration()
+            .async_io(Interest::READABLE, || self.io.recv(buf))
             .await
     }
 
@@ -367,29 +362,21 @@ impl UdpSocket {
     ///
     /// [`connect`]: method@Self::connect
     pub fn poll_recv(&self, cx: &mut Context<'_>, buf: &mut ReadBuf<'_>) -> Poll<io::Result<()>> {
-        loop {
+        let n = ready!(self.io.registration().poll_read_io(cx, || {
-            let ev = ready!(self.io.poll_read_ready(cx))?;
-
             // Safety: will not read the maybe uinitialized bytes.
             let b = unsafe {
                 &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8])
             };
-            match self.io.get_ref().recv(b) {
+
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+            self.io.recv(b)
-                    self.io.clear_readiness(ev);
+        }))?;
-                }
+
-                Err(e) => return Poll::Ready(Err(e)),
+        // Safety: We trust `recv` to have filled up `n` bytes in the buffer.
-                Ok(n) => {
+        unsafe {
-                    // Safety: We trust `recv` to have filled up `n` bytes
+            buf.assume_init(n);
-                    // in the buffer.
-                    unsafe {
-                        buf.assume_init(n);
-                    }
-                    buf.advance(n);
-                    return Poll::Ready(Ok(()));
-                }
-            }
         }
+        buf.advance(n);
+        Poll::Ready(Ok(()))
     }
 
     /// Returns a future that sends data on the socket to the given address.
@@ -448,16 +435,9 @@ impl UdpSocket {
         buf: &[u8],
         target: &SocketAddr,
     ) -> Poll<io::Result<usize>> {
-        loop {
+        self.io
-            let ev = ready!(self.io.poll_write_ready(cx))?;
+            .registration()
-
+            .poll_write_io(cx, || self.io.send_to(buf, *target))
-            match self.io.get_ref().send_to(buf, *target) {
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                x => return Poll::Ready(x),
-            }
-        }
     }
 
     /// Try to send data on the socket to the given address, but if the send is blocked
@@ -489,12 +469,13 @@ impl UdpSocket {
     ///
     /// [`ErrorKind::WouldBlock`]: std::io::ErrorKind::WouldBlock
     pub fn try_send_to(&self, buf: &[u8], target: SocketAddr) -> io::Result<usize> {
-        self.io.get_ref().send_to(buf, target)
+        self.io.send_to(buf, target)
     }
 
     async fn send_to_addr(&self, buf: &[u8], target: SocketAddr) -> io::Result<usize> {
         self.io
-            .async_io(mio::Interest::WRITABLE, |sock| sock.send_to(buf, target))
+            .registration()
+            .async_io(Interest::WRITABLE, || self.io.send_to(buf, target))
             .await
     }
 
@@ -522,7 +503,8 @@ impl UdpSocket {
     /// ```
     pub async fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
         self.io
-            .async_io(mio::Interest::READABLE, |sock| sock.recv_from(buf))
+            .registration()
+            .async_io(Interest::READABLE, || self.io.recv_from(buf))
             .await
     }
 
@@ -548,29 +530,21 @@ impl UdpSocket {
         cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<SocketAddr>> {
-        loop {
+        let (n, addr) = ready!(self.io.registration().poll_read_io(cx, || {
-            let ev = ready!(self.io.poll_read_ready(cx))?;
-
             // Safety: will not read the maybe uinitialized bytes.
             let b = unsafe {
                 &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8])
             };
-            match self.io.get_ref().recv_from(b) {
+
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+            self.io.recv_from(b)
-                    self.io.clear_readiness(ev);
+        }))?;
-                }
+
-                Err(e) => return Poll::Ready(Err(e)),
+        // Safety: We trust `recv` to have filled up `n` bytes in the buffer.
-                Ok((n, addr)) => {
+        unsafe {
-                    // Safety: We trust `recv` to have filled up `n` bytes
+            buf.assume_init(n);
-                    // in the buffer.
-                    unsafe {
-                        buf.assume_init(n);
-                    }
-                    buf.advance(n);
-                    return Poll::Ready(Ok(addr));
-                }
-            }
         }
+        buf.advance(n);
+        Poll::Ready(Ok(addr))
     }
 
     /// Receives data from the socket, without removing it from the input queue.
@@ -602,7 +576,8 @@ impl UdpSocket {
     /// ```
     pub async fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
         self.io
-            .async_io(mio::Interest::READABLE, |sock| sock.peek_from(buf))
+            .registration()
+            .async_io(Interest::READABLE, || self.io.peek_from(buf))
             .await
     }
 
@@ -637,29 +612,21 @@ impl UdpSocket {
         cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<SocketAddr>> {
-        loop {
+        let (n, addr) = ready!(self.io.registration().poll_read_io(cx, || {
-            let ev = ready!(self.io.poll_read_ready(cx))?;
-
             // Safety: will not read the maybe uinitialized bytes.
             let b = unsafe {
                 &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8])
             };
-            match self.io.get_ref().peek_from(b) {
+
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
+            self.io.peek_from(b)
-                    self.io.clear_readiness(ev);
+        }))?;
-                }
+
-                Err(e) => return Poll::Ready(Err(e)),
+        // Safety: We trust `recv` to have filled up `n` bytes in the buffer.
-                Ok((n, addr)) => {
+        unsafe {
-                    // Safety: We trust `recv` to have filled up `n` bytes
+            buf.assume_init(n);
-                    // in the buffer.
-                    unsafe {
-                        buf.assume_init(n);
-                    }
-                    buf.advance(n);
-                    return Poll::Ready(Ok(addr));
-                }
-            }
         }
+        buf.advance(n);
+        Poll::Ready(Ok(addr))
     }
 
     /// Gets the value of the `SO_BROADCAST` option for this socket.
@@ -668,7 +635,7 @@ impl UdpSocket {
     ///
     /// [`set_broadcast`]: method@Self::set_broadcast
     pub fn broadcast(&self) -> io::Result<bool> {
-        self.io.get_ref().broadcast()
+        self.io.broadcast()
     }
 
     /// Sets the value of the `SO_BROADCAST` option for this socket.
@@ -676,7 +643,7 @@ impl UdpSocket {
     /// When enabled, this socket is allowed to send packets to a broadcast
     /// address.
     pub fn set_broadcast(&self, on: bool) -> io::Result<()> {
-        self.io.get_ref().set_broadcast(on)
+        self.io.set_broadcast(on)
     }
 
     /// Gets the value of the `IP_MULTICAST_LOOP` option for this socket.
@@ -685,7 +652,7 @@ impl UdpSocket {
     ///
     /// [`set_multicast_loop_v4`]: method@Self::set_multicast_loop_v4
     pub fn multicast_loop_v4(&self) -> io::Result<bool> {
-        self.io.get_ref().multicast_loop_v4()
+        self.io.multicast_loop_v4()
     }
 
     /// Sets the value of the `IP_MULTICAST_LOOP` option for this socket.
@@ -696,7 +663,7 @@ impl UdpSocket {
     ///
     /// This may not have any affect on IPv6 sockets.
     pub fn set_multicast_loop_v4(&self, on: bool) -> io::Result<()> {
-        self.io.get_ref().set_multicast_loop_v4(on)
+        self.io.set_multicast_loop_v4(on)
     }
 
     /// Gets the value of the `IP_MULTICAST_TTL` option for this socket.
@@ -705,7 +672,7 @@ impl UdpSocket {
     ///
     /// [`set_multicast_ttl_v4`]: method@Self::set_multicast_ttl_v4
     pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
-        self.io.get_ref().multicast_ttl_v4()
+        self.io.multicast_ttl_v4()
     }
 
     /// Sets the value of the `IP_MULTICAST_TTL` option for this socket.
@@ -718,7 +685,7 @@ impl UdpSocket {
     ///
     /// This may not have any affect on IPv6 sockets.
     pub fn set_multicast_ttl_v4(&self, ttl: u32) -> io::Result<()> {
-        self.io.get_ref().set_multicast_ttl_v4(ttl)
+        self.io.set_multicast_ttl_v4(ttl)
     }
 
     /// Gets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
@@ -727,7 +694,7 @@ impl UdpSocket {
     ///
     /// [`set_multicast_loop_v6`]: method@Self::set_multicast_loop_v6
     pub fn multicast_loop_v6(&self) -> io::Result<bool> {
-        self.io.get_ref().multicast_loop_v6()
+        self.io.multicast_loop_v6()
     }
 
     /// Sets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
@@ -738,7 +705,7 @@ impl UdpSocket {
     ///
     /// This may not have any affect on IPv4 sockets.
     pub fn set_multicast_loop_v6(&self, on: bool) -> io::Result<()> {
-        self.io.get_ref().set_multicast_loop_v6(on)
+        self.io.set_multicast_loop_v6(on)
     }
 
     /// Gets the value of the `IP_TTL` option for this socket.
@@ -761,7 +728,7 @@ impl UdpSocket {
     /// # }
     /// ```
     pub fn ttl(&self) -> io::Result<u32> {
-        self.io.get_ref().ttl()
+        self.io.ttl()
     }
 
     /// Sets the value for the `IP_TTL` option on this socket.
@@ -783,7 +750,7 @@ impl UdpSocket {
     /// # }
     /// ```
     pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
-        self.io.get_ref().set_ttl(ttl)
+        self.io.set_ttl(ttl)
     }
 
     /// Executes an operation of the `IP_ADD_MEMBERSHIP` type.
@@ -794,7 +761,7 @@ impl UdpSocket {
     /// multicast group. If it's equal to `INADDR_ANY` then an appropriate
     /// interface is chosen by the system.
     pub fn join_multicast_v4(&self, multiaddr: Ipv4Addr, interface: Ipv4Addr) -> io::Result<()> {
-        self.io.get_ref().join_multicast_v4(&multiaddr, &interface)
+        self.io.join_multicast_v4(&multiaddr, &interface)
     }
 
     /// Executes an operation of the `IPV6_ADD_MEMBERSHIP` type.
@@ -803,7 +770,7 @@ impl UdpSocket {
     /// The address must be a valid multicast address, and `interface` is the
     /// index of the interface to join/leave (or 0 to indicate any interface).
     pub fn join_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
-        self.io.get_ref().join_multicast_v6(multiaddr, interface)
+        self.io.join_multicast_v6(multiaddr, interface)
     }
 
     /// Executes an operation of the `IP_DROP_MEMBERSHIP` type.
@@ -812,7 +779,7 @@ impl UdpSocket {
     ///
     /// [`join_multicast_v4`]: method@Self::join_multicast_v4
     pub fn leave_multicast_v4(&self, multiaddr: Ipv4Addr, interface: Ipv4Addr) -> io::Result<()> {
-        self.io.get_ref().leave_multicast_v4(&multiaddr, &interface)
+        self.io.leave_multicast_v4(&multiaddr, &interface)
     }
 
     /// Executes an operation of the `IPV6_DROP_MEMBERSHIP` type.
@@ -821,7 +788,7 @@ impl UdpSocket {
     ///
     /// [`join_multicast_v6`]: method@Self::join_multicast_v6
     pub fn leave_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
-        self.io.get_ref().leave_multicast_v6(multiaddr, interface)
+        self.io.leave_multicast_v6(multiaddr, interface)
     }
 
     /// Returns the value of the `SO_ERROR` option.
@@ -844,7 +811,7 @@ impl UdpSocket {
     /// # }
     /// ```
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-        self.io.get_ref().take_error()
+        self.io.take_error()
     }
 }
 
@@ -862,7 +829,7 @@ impl TryFrom<std::net::UdpSocket> for UdpSocket {
 
 impl fmt::Debug for UdpSocket {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.io.get_ref().fmt(f)
+        self.io.fmt(f)
     }
 }
 
@@ -873,7 +840,7 @@ mod sys {
 
     impl AsRawFd for UdpSocket {
         fn as_raw_fd(&self) -> RawFd {
-            self.io.get_ref().as_raw_fd()
+            self.io.as_raw_fd()
         }
     }
 }
@@ -885,7 +852,7 @@ mod sys {
 
     impl AsRawSocket for UdpSocket {
         fn as_raw_socket(&self) -> RawSocket {
-            self.io.get_ref().as_raw_socket()
+            self.io.as_raw_socket()
         }
     }
 }

tokio/src/net/unix/datagram/socket.rs

@@ -1,4 +1,4 @@
-use crate::io::PollEvented;
+use crate::io::{Interest, PollEvented};
 use crate::net::unix::SocketAddr;
 
 use std::convert::TryFrom;
@@ -270,7 +270,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn connect<P: AsRef<Path>>(&self, path: P) -> io::Result<()> {
-        self.io.get_ref().connect(path)
+        self.io.connect(path)
     }
 
     /// Sends data on the socket to the socket's peer.
@@ -301,7 +301,8 @@ impl UnixDatagram {
     /// ```
     pub async fn send(&self, buf: &[u8]) -> io::Result<usize> {
         self.io
-            .async_io(mio::Interest::WRITABLE, |sock| sock.send(buf))
+            .registration()
+            .async_io(Interest::WRITABLE, || self.io.send(buf))
             .await
     }
 
@@ -330,7 +331,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn try_send(&self, buf: &[u8]) -> io::Result<usize> {
-        self.io.get_ref().send(buf)
+        self.io.send(buf)
     }
 
     /// Try to send a datagram to the peer without waiting.
@@ -369,7 +370,7 @@ impl UnixDatagram {
     where
         P: AsRef<Path>,
     {
-        self.io.get_ref().send_to(buf, target)
+        self.io.send_to(buf, target)
     }
 
     /// Receives data from the socket.
@@ -400,7 +401,8 @@ impl UnixDatagram {
     /// ```
     pub async fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
         self.io
-            .async_io(mio::Interest::READABLE, |sock| sock.recv(buf))
+            .registration()
+            .async_io(Interest::READABLE, || self.io.recv(buf))
             .await
     }
 
@@ -429,7 +431,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn try_recv(&self, buf: &mut [u8]) -> io::Result<usize> {
-        self.io.get_ref().recv(buf)
+        self.io.recv(buf)
     }
 
     /// Sends data on the socket to the specified address.
@@ -470,9 +472,8 @@ impl UnixDatagram {
         P: AsRef<Path>,
     {
         self.io
-            .async_io(mio::Interest::WRITABLE, |sock| {
+            .registration()
-                sock.send_to(buf, target.as_ref())
+            .async_io(Interest::WRITABLE, || self.io.send_to(buf, target.as_ref()))
-            })
             .await
     }
 
@@ -512,7 +513,8 @@ impl UnixDatagram {
     pub async fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
         let (n, addr) = self
             .io
-            .async_io(mio::Interest::READABLE, |sock| sock.recv_from(buf))
+            .registration()
+            .async_io(Interest::READABLE, || self.io.recv_from(buf))
             .await?;
 
         Ok((n, SocketAddr(addr)))
@@ -551,7 +553,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn try_recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
-        let (n, addr) = self.io.get_ref().recv_from(buf)?;
+        let (n, addr) = self.io.recv_from(buf)?;
         Ok((n, SocketAddr(addr)))
     }
 
@@ -596,7 +598,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn local_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().local_addr().map(SocketAddr)
+        self.io.local_addr().map(SocketAddr)
     }
 
     /// Returns the address of this socket's peer.
@@ -645,7 +647,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().peer_addr().map(SocketAddr)
+        self.io.peer_addr().map(SocketAddr)
     }
 
     /// Returns the value of the `SO_ERROR` option.
@@ -668,7 +670,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-        self.io.get_ref().take_error()
+        self.io.take_error()
     }
 
     /// Shuts down the read, write, or both halves of this connection.
@@ -704,7 +706,7 @@ impl UnixDatagram {
     /// # }
     /// ```
     pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
-        self.io.get_ref().shutdown(how)
+        self.io.shutdown(how)
     }
 }
 
@@ -722,12 +724,12 @@ impl TryFrom<std::os::unix::net::UnixDatagram> for UnixDatagram {
 
 impl fmt::Debug for UnixDatagram {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.io.get_ref().fmt(f)
+        self.io.fmt(f)
     }
 }
 
 impl AsRawFd for UnixDatagram {
     fn as_raw_fd(&self) -> RawFd {
-        self.io.get_ref().as_raw_fd()
+        self.io.as_raw_fd()
     }
 }

tokio/src/net/unix/listener.rs

@@ -1,4 +1,4 @@
-use crate::io::PollEvented;
+use crate::io::{Interest, PollEvented};
 use crate::net::unix::{SocketAddr, UnixStream};
 
 use std::convert::TryFrom;
@@ -90,19 +90,20 @@ impl UnixListener {
 
     /// Returns the local socket address of this listener.
     pub fn local_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().local_addr().map(SocketAddr)
+        self.io.local_addr().map(SocketAddr)
     }
 
     /// Returns the value of the `SO_ERROR` option.
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-        self.io.get_ref().take_error()
+        self.io.take_error()
     }
 
     /// Accepts a new incoming connection to this listener.
     pub async fn accept(&self) -> io::Result<(UnixStream, SocketAddr)> {
         let (mio, addr) = self
             .io
-            .async_io(mio::Interest::READABLE, |sock| sock.accept())
+            .registration()
+            .async_io(Interest::READABLE, || self.io.accept())
             .await?;
 
         let addr = SocketAddr(addr);
@@ -119,21 +120,10 @@ impl UnixListener {
     /// The caller is responsible to ensure that `poll_accept` is called from a
     /// single task. Failing to do this could result in tasks hanging.
     pub fn poll_accept(&self, cx: &mut Context<'_>) -> Poll<io::Result<(UnixStream, SocketAddr)>> {
-        loop {
+        let (sock, addr) = ready!(self.io.registration().poll_read_io(cx, || self.io.accept()))?;
-            let ev = ready!(self.io.poll_read_ready(cx))?;
+        let addr = SocketAddr(addr);
-
+        let sock = UnixStream::new(sock)?;
-            match self.io.get_ref().accept() {
+        Poll::Ready(Ok((sock, addr)))
-                Ok((sock, addr)) => {
-                    let addr = SocketAddr(addr);
-                    let sock = UnixStream::new(sock)?;
-                    return Poll::Ready(Ok((sock, addr)));
-                }
-                Err(ref err) if err.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                Err(err) => return Err(err).into(),
-            }
-        }
     }
 }
 
@@ -161,12 +151,12 @@ impl TryFrom<std::os::unix::net::UnixListener> for UnixListener {
 
 impl fmt::Debug for UnixListener {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.io.get_ref().fmt(f)
+        self.io.fmt(f)
     }
 }
 
 impl AsRawFd for UnixListener {
     fn as_raw_fd(&self) -> RawFd {
-        self.io.get_ref().as_raw_fd()
+        self.io.as_raw_fd()
     }
 }

tokio/src/net/unix/stream.rs

@@ -7,7 +7,7 @@ use crate::net::unix::SocketAddr;
 
 use std::convert::TryFrom;
 use std::fmt;
-use std::io::{self, Read, Write};
+use std::io;
 use std::net::Shutdown;
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::os::unix::net;
@@ -39,7 +39,7 @@ impl UnixStream {
         let stream = mio::net::UnixStream::connect(path)?;
         let stream = UnixStream::new(stream)?;
 
-        poll_fn(|cx| stream.io.poll_write_ready(cx)).await?;
+        poll_fn(|cx| stream.io.registration().poll_write_ready(cx)).await?;
         Ok(stream)
     }
 
@@ -84,12 +84,12 @@ impl UnixStream {
 
     /// Returns the socket address of the local half of this connection.
     pub fn local_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().local_addr().map(SocketAddr)
+        self.io.local_addr().map(SocketAddr)
     }
 
     /// Returns the socket address of the remote half of this connection.
     pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-        self.io.get_ref().peer_addr().map(SocketAddr)
+        self.io.peer_addr().map(SocketAddr)
     }
 
     /// Returns effective credentials of the process which called `connect` or `pair`.
@@ -99,7 +99,7 @@ impl UnixStream {
 
     /// Returns the value of the `SO_ERROR` option.
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-        self.io.get_ref().take_error()
+        self.io.take_error()
     }
 
     /// Shuts down the read, write, or both halves of this connection.
@@ -108,7 +108,7 @@ impl UnixStream {
     /// specified portions to immediately return with an appropriate value
     /// (see the documentation of `Shutdown`).
     pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
-        self.io.get_ref().shutdown(how)
+        self.io.shutdown(how)
     }
 
     // These lifetime markers also appear in the generated documentation, and make
@@ -199,29 +199,8 @@ impl UnixStream {
         cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
-        loop {
+        // Safety: `UdpStream::read` correctly handles reads into uninitialized memory
-            let ev = ready!(self.io.poll_read_ready(cx))?;
+        unsafe { self.io.poll_read(cx, buf) }
-
-            // Safety: `UnixStream::read` will not peek at the maybe uinitialized bytes.
-            let b = unsafe {
-                &mut *(buf.unfilled_mut() as *mut [std::mem::MaybeUninit<u8>] as *mut [u8])
-            };
-            match self.io.get_ref().read(b) {
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                Ok(n) => {
-                    // Safety: We trust `UnixStream::read` to have filled up `n` bytes
-                    // in the buffer.
-                    unsafe {
-                        buf.assume_init(n);
-                    }
-                    buf.advance(n);
-                    return Poll::Ready(Ok(()));
-                }
-                Err(e) => return Poll::Ready(Err(e)),
-            }
-        }
     }
 
     pub(crate) fn poll_write_priv(
@@ -229,27 +208,18 @@ impl UnixStream {
         cx: &mut Context<'_>,
         buf: &[u8],
     ) -> Poll<io::Result<usize>> {
-        loop {
+        self.io.poll_write(cx, buf)
-            let ev = ready!(self.io.poll_write_ready(cx))?;
-
-            match self.io.get_ref().write(buf) {
-                Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
-                    self.io.clear_readiness(ev);
-                }
-                x => return Poll::Ready(x),
-            }
-        }
     }
 }
 
 impl fmt::Debug for UnixStream {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.io.get_ref().fmt(f)
+        self.io.fmt(f)
     }
 }
 
 impl AsRawFd for UnixStream {
     fn as_raw_fd(&self) -> RawFd {
-        self.io.get_ref().as_raw_fd()
+        self.io.as_raw_fd()
     }
 }

tokio/src/process/mod.rs

@@ -1038,39 +1038,41 @@ pub struct ChildStderr {
 
 impl AsyncWrite for ChildStdin {
     fn poll_write(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         cx: &mut Context<'_>,
         buf: &[u8],
     ) -> Poll<io::Result<usize>> {
-        Pin::new(&mut self.inner).poll_write(cx, buf)
+        self.inner.poll_write(cx, buf)
     }
 
-    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-        Pin::new(&mut self.inner).poll_flush(cx)
+        Poll::Ready(Ok(()))
     }
 
-    fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-        Pin::new(&mut self.inner).poll_shutdown(cx)
+        Poll::Ready(Ok(()))
     }
 }
 
 impl AsyncRead for ChildStdout {
     fn poll_read(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
-        Pin::new(&mut self.inner).poll_read(cx, buf)
+        // Safety: pipes support reading into uninitialized memory
+        unsafe { self.inner.poll_read(cx, buf) }
     }
 }
 
 impl AsyncRead for ChildStderr {
     fn poll_read(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
-        Pin::new(&mut self.inner).poll_read(cx, buf)
+        // Safety: pipes support reading into uninitialized memory
+        unsafe { self.inner.poll_read(cx, buf) }
     }
 }
 
@@ -1082,19 +1084,19 @@ mod sys {
 
     impl AsRawFd for ChildStdin {
         fn as_raw_fd(&self) -> RawFd {
-            self.inner.get_ref().as_raw_fd()
+            self.inner.as_raw_fd()
         }
     }
 
     impl AsRawFd for ChildStdout {
         fn as_raw_fd(&self) -> RawFd {
-            self.inner.get_ref().as_raw_fd()
+            self.inner.as_raw_fd()
         }
     }
 
     impl AsRawFd for ChildStderr {
         fn as_raw_fd(&self) -> RawFd {
-            self.inner.get_ref().as_raw_fd()
+            self.inner.as_raw_fd()
         }
     }
 }
@@ -1107,19 +1109,19 @@ mod sys {
 
     impl AsRawHandle for ChildStdin {
         fn as_raw_handle(&self) -> RawHandle {
-            self.inner.get_ref().as_raw_handle()
+            self.inner.as_raw_handle()
         }
     }
 
     impl AsRawHandle for ChildStdout {
         fn as_raw_handle(&self) -> RawHandle {
-            self.inner.get_ref().as_raw_handle()
+            self.inner.as_raw_handle()
         }
     }
 
     impl AsRawHandle for ChildStderr {
         fn as_raw_handle(&self) -> RawHandle {
-            self.inner.get_ref().as_raw_handle()
+            self.inner.as_raw_handle()
         }
     }
 }

tokio/src/process/unix/mod.rs

@@ -37,9 +37,10 @@ use crate::signal::unix::{signal, Signal, SignalKind};
 use mio::event::Source;
 use mio::unix::SourceFd;
 use std::fmt;
+use std::fs::File;
 use std::future::Future;
 use std::io;
-use std::os::unix::io::{AsRawFd, RawFd};
+use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
 use std::pin::Pin;
 use std::process::{Child as StdChild, ExitStatus};
 use std::task::Context;
@@ -141,45 +142,35 @@ impl Future for Child {
 }
 
 #[derive(Debug)]
-pub(crate) struct Fd<T> {
+pub(crate) struct Pipe {
-    inner: T,
+    // Actually a pipe and not a File. However, we are reusing `File` to get
+    // close on drop. This is a similar trick as `mio`.
+    fd: File,
 }
 
-impl<T> io::Read for Fd<T>
+impl<'a> io::Read for &'a Pipe {
-where
-    T: io::Read,
-{
     fn read(&mut self, bytes: &mut [u8]) -> io::Result<usize> {
-        self.inner.read(bytes)
+        (&self.fd).read(bytes)
     }
 }
 
-impl<T> io::Write for Fd<T>
+impl<'a> io::Write for &'a Pipe {
-where
-    T: io::Write,
-{
     fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
-        self.inner.write(bytes)
+        (&self.fd).write(bytes)
     }
 
     fn flush(&mut self) -> io::Result<()> {
-        self.inner.flush()
+        (&self.fd).flush()
     }
 }
 
-impl<T> AsRawFd for Fd<T>
+impl AsRawFd for Pipe {
-where
-    T: AsRawFd,
-{
     fn as_raw_fd(&self) -> RawFd {
-        self.inner.as_raw_fd()
+        self.fd.as_raw_fd()
     }
 }
 
-impl<T> Source for Fd<T>
+impl Source for Pipe {
-where
-    T: AsRawFd,
-{
     fn register(
         &mut self,
         registry: &mio::Registry,
@@ -203,13 +194,13 @@ where
     }
 }
 
-pub(crate) type ChildStdin = PollEvented<Fd<std::process::ChildStdin>>;
+pub(crate) type ChildStdin = PollEvented<Pipe>;
-pub(crate) type ChildStdout = PollEvented<Fd<std::process::ChildStdout>>;
+pub(crate) type ChildStdout = PollEvented<Pipe>;
-pub(crate) type ChildStderr = PollEvented<Fd<std::process::ChildStderr>>;
+pub(crate) type ChildStderr = PollEvented<Pipe>;
 
-fn stdio<T>(option: Option<T>) -> io::Result<Option<PollEvented<Fd<T>>>>
+fn stdio<T>(option: Option<T>) -> io::Result<Option<PollEvented<Pipe>>>
 where
-    T: AsRawFd,
+    T: IntoRawFd,
 {
     let io = match option {
         Some(io) => io,
@@ -217,8 +208,8 @@ where
     };
 
     // Set the fd to nonblocking before we pass it to the event loop
-    unsafe {
+    let fd = unsafe {
-        let fd = io.as_raw_fd();
+        let fd = io.into_raw_fd();
         let r = libc::fcntl(fd, libc::F_GETFL);
         if r == -1 {
             return Err(io::Error::last_os_error());
@@ -227,6 +218,9 @@ where
         if r == -1 {
             return Err(io::Error::last_os_error());
         }
-    }
+
-    Ok(Some(PollEvented::new(Fd { inner: io })?))
+        File::from_raw_fd(fd)
+    };
+
+    Ok(Some(PollEvented::new(Pipe { fd })?))
 }

tokio/src/signal/unix/driver.rs

@@ -3,7 +3,7 @@
 //! Signal driver
 
 use crate::io::driver::Driver as IoDriver;
-use crate::io::PollEvented;
+use crate::io::{Interest, PollEvented};
 use crate::park::Park;
 use crate::signal::registry::globals;
 
@@ -76,7 +76,7 @@ impl Driver {
         let receiver = UnixStream::from_std(original.try_clone()?);
         let receiver = PollEvented::new_with_interest_and_handle(
             receiver,
-            mio::Interest::READABLE | mio::Interest::WRITABLE,
+            Interest::READABLE | Interest::WRITABLE,
             park.handle(),
         )?;
 
@@ -103,7 +103,7 @@ impl Driver {
         let waker = unsafe { Waker::from_raw(RawWaker::new(ptr::null(), &NOOP_WAKER_VTABLE)) };
         let mut cx = Context::from_waker(&waker);
 
-        let ev = match self.receiver.poll_read_ready(&mut cx) {
+        let ev = match self.receiver.registration().poll_read_ready(&mut cx) {
             Poll::Ready(Ok(ev)) => ev,
             Poll::Ready(Err(e)) => panic!("reactor gone: {}", e),
             Poll::Pending => return, // No wake has arrived, bail
@@ -113,7 +113,7 @@ impl Driver {
         // if another signal has come in.
         let mut buf = [0; 128];
         loop {
-            match self.receiver.get_ref().read(&mut buf) {
+            match (&*self.receiver).read(&mut buf) {
                 Ok(0) => panic!("EOF on self-pipe"),
                 Ok(_) => continue, // Keep reading
                 Err(e) if e.kind() == io::ErrorKind::WouldBlock => break,
@@ -121,7 +121,7 @@ impl Driver {
             }
         }
 
-        self.receiver.clear_readiness(ev);
+        self.receiver.registration().clear_readiness(ev);
 
         // Broadcast any signals which were received
         globals().broadcast();