tokio/task/
unconstrained.rs

1use pin_project_lite::pin_project;
2use std::future::Future;
3use std::pin::Pin;
4use std::task::{Context, Poll};
5
6pin_project! {
7    /// Future for the [`unconstrained`](unconstrained) method.
8    #[cfg_attr(docsrs, doc(cfg(feature = "rt")))]
9    #[must_use = "Unconstrained does nothing unless polled"]
10    pub struct Unconstrained<F> {
11        #[pin]
12        inner: F,
13    }
14}
15
16impl<F> Future for Unconstrained<F>
17where
18    F: Future,
19{
20    type Output = <F as Future>::Output;
21
22    cfg_coop! {
23        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
24            let inner = self.project().inner;
25            crate::runtime::coop::with_unconstrained(|| inner.poll(cx))
26        }
27    }
28
29    cfg_not_coop! {
30        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
31            let inner = self.project().inner;
32            inner.poll(cx)
33        }
34    }
35}
36
37/// Turn off cooperative scheduling for a future. The future will never be forced to yield by
38/// Tokio. Using this exposes your service to starvation if the unconstrained future never yields
39/// otherwise.
40///
41/// See also the usage example in the [task module](index.html#unconstrained).
42#[cfg_attr(docsrs, doc(cfg(feature = "rt")))]
43pub fn unconstrained<F>(inner: F) -> Unconstrained<F> {
44    Unconstrained { inner }
45}
tokio/task/unconstrained.rs

tokio/task/
unconstrained.rs
