diff --git a/tokio/src/io/util/empty.rs b/tokio/src/io/util/empty.rs index f964d18e6..77db60e40 100644 --- a/tokio/src/io/util/empty.rs +++ b/tokio/src/io/util/empty.rs @@ -50,16 +50,18 @@ impl AsyncRead for Empty { #[inline] fn poll_read( self: Pin<&mut Self>, - _: &mut Context<'_>, + cx: &mut Context<'_>, _: &mut ReadBuf<'_>, ) -> Poll> { + ready!(poll_proceed_and_make_progress(cx)); Poll::Ready(Ok(())) } } impl AsyncBufRead for Empty { #[inline] - fn poll_fill_buf(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll> { + fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll> { + ready!(poll_proceed_and_make_progress(cx)); Poll::Ready(Ok(&[])) } @@ -73,6 +75,20 @@ impl fmt::Debug for Empty { } } +cfg_coop! { + fn poll_proceed_and_make_progress(cx: &mut Context<'_>) -> Poll<()> { + let coop = ready!(crate::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::*; diff --git a/tokio/tests/io_util_empty.rs b/tokio/tests/io_util_empty.rs new file mode 100644 index 000000000..e49cd17fc --- /dev/null +++ b/tokio/tests/io_util_empty.rs @@ -0,0 +1,32 @@ +#![cfg(feature = "full")] +use tokio::io::{AsyncBufReadExt, AsyncReadExt}; + +#[tokio::test] +async fn empty_read_is_cooperative() { + tokio::select! { + biased; + + _ = async { + loop { + let mut buf = [0u8; 4096]; + let _ = tokio::io::empty().read(&mut buf).await; + } + } => {}, + _ = tokio::task::yield_now() => {} + } +} + +#[tokio::test] +async fn empty_buf_reads_are_cooperative() { + tokio::select! { + biased; + + _ = async { + loop { + let mut buf = String::new(); + let _ = tokio::io::empty().read_line(&mut buf).await; + } + } => {}, + _ = tokio::task::yield_now() => {} + } +}