io: make repeat and sink cooperative

tokio/src/io/util/empty.rs

@@ -1,3 +1,4 @@
+use crate::io::util::poll_proceed_and_make_progress;
 use crate::io::{AsyncBufRead, AsyncRead, AsyncWrite, ReadBuf};
 
 use std::fmt;
@@ -138,20 +139,6 @@ impl fmt::Debug for Empty {
     }
 }
 
-cfg_coop! {
-    fn poll_proceed_and_make_progress(cx: &mut Context<'_>) -> Poll<()> {
-        let coop = ready!(crate::runtime::coop::poll_proceed(cx));
-        coop.made_progress();
-        Poll::Ready(())
-    }
-}
-
-cfg_not_coop! {
-    fn poll_proceed_and_make_progress(_: &mut Context<'_>) -> Poll<()> {
-        Poll::Ready(())
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

tokio/src/io/util/mod.rs

@@ -85,6 +85,20 @@ cfg_io_util! {
     // used by `BufReader` and `BufWriter`
     // https://github.com/rust-lang/rust/blob/master/library/std/src/sys_common/io.rs#L1
     const DEFAULT_BUF_SIZE: usize = 8 * 1024;
+
+    cfg_coop! {
+        fn poll_proceed_and_make_progress(cx: &mut std::task::Context<'_>) -> std::task::Poll<()> {
+            let coop = ready!(crate::runtime::coop::poll_proceed(cx));
+            coop.made_progress();
+            std::task::Poll::Ready(())
+        }
+    }
+
+    cfg_not_coop! {
+        fn poll_proceed_and_make_progress(_: &mut std::task::Context<'_>) -> std::task::Poll<()> {
+            std::task::Poll::Ready(())
+        }
+    }
 }
 
 cfg_not_io_util! {

tokio/src/io/util/repeat.rs

@@ -1,3 +1,4 @@
+use crate::io::util::poll_proceed_and_make_progress;
 use crate::io::{AsyncRead, ReadBuf};
 
 use std::io;
@@ -50,9 +51,11 @@ impl AsyncRead for Repeat {
     #[inline]
     fn poll_read(
         self: Pin<&mut Self>,
-        _: &mut Context<'_>,
+        cx: &mut Context<'_>,
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
+        ready!(crate::trace::trace_leaf(cx));
+        ready!(poll_proceed_and_make_progress(cx));
         // TODO: could be faster, but should we unsafe it?
         while buf.remaining() != 0 {
             buf.put_slice(&[self.byte]);

tokio/src/io/util/sink.rs

@@ -1,3 +1,4 @@
+use crate::io::util::poll_proceed_and_make_progress;
 use crate::io::AsyncWrite;
 
 use std::fmt;
@@ -53,9 +54,11 @@ impl AsyncWrite for Sink {
     #[inline]
     fn poll_write(
         self: Pin<&mut Self>,
-        _: &mut Context<'_>,
+        cx: &mut Context<'_>,
         buf: &[u8],
     ) -> Poll<Result<usize, io::Error>> {
+        ready!(crate::trace::trace_leaf(cx));
+        ready!(poll_proceed_and_make_progress(cx));
         Poll::Ready(Ok(buf.len()))
     }
 

tokio/tests/io_repeat.rs

@@ -0,0 +1,18 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full"))]
+
+use tokio::io::AsyncReadExt;
+
+#[tokio::test]
+async fn repeat_is_cooperative() {
+    tokio::select! {
+        biased;
+        _ = async {
+            loop {
+                let mut buf = [0u8; 4096];
+                tokio::io::repeat(0b101).read_exact(&mut buf).await.unwrap();
+            }
+        } => {},
+        _ = tokio::task::yield_now() => {}
+    }
+}

tokio/tests/io_sink.rs

@@ -0,0 +1,18 @@
+#![warn(rust_2018_idioms)]
+#![cfg(all(feature = "full"))]
+
+use tokio::io::AsyncWriteExt;
+
+#[tokio::test]
+async fn sink_is_cooperative() {
+    tokio::select! {
+        biased;
+        _ = async {
+            loop {
+                let buf = vec![1, 2, 3];
+                tokio::io::sink().write_all(&buf).await.unwrap();
+            }
+        } => {},
+        _ = tokio::task::yield_now() => {}
+    }
+}