1 files changed, 45 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/task/unconstrained.rs b/third_party/rust/tokio/src/task/unconstrained.rs
new file mode 100644
index 0000000000..31c732bfc9
--- /dev/null
+++ b/third_party/rust/tokio/src/task/unconstrained.rs
@@ -0,0 +1,45 @@
+use pin_project_lite::pin_project;
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+pin_project! {
+    /// Future for the [`unconstrained`](unconstrained) method.
+    #[cfg_attr(docsrs, doc(cfg(feature = "rt")))]
+    #[must_use = "Unconstrained does nothing unless polled"]
+    pub struct Unconstrained<F> {
+        #[pin]
+        inner: F,
+    }
+}
+
+impl<F> Future for Unconstrained<F>
+where
+    F: Future,
+{
+    type Output = <F as Future>::Output;
+
+    cfg_coop! {
+        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+            let inner = self.project().inner;
+            crate::coop::with_unconstrained(|| inner.poll(cx))
+        }
+    }
+
+    cfg_not_coop! {
+        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+            let inner = self.project().inner;
+            inner.poll(cx)
+        }
+    }
+}
+
+/// Turn off cooperative scheduling for a future. The future will never be forced to yield by
+/// Tokio. Using this exposes your service to starvation if the unconstrained future never yields
+/// otherwise.
+///
+/// See also the usage example in the [task module](index.html#unconstrained).
+#[cfg_attr(docsrs, doc(cfg(feature = "rt")))]
+pub fn unconstrained<F>(inner: F) -> Unconstrained<F> {
+    Unconstrained { inner }
+}