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diff --git a/third_party/rust/futures-util/src/future/join_all.rs b/third_party/rust/futures-util/src/future/join_all.rs
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+++ b/third_party/rust/futures-util/src/future/join_all.rs
@@ -0,0 +1,166 @@
+//! Definition of the `JoinAll` combinator, waiting for all of a list of futures
+//! to finish.
+
+use alloc::boxed::Box;
+use alloc::vec::Vec;
+use core::fmt;
+use core::future::Future;
+use core::iter::FromIterator;
+use core::mem;
+use core::pin::Pin;
+use core::task::{Context, Poll};
+
+use super::{assert_future, MaybeDone};
+
+#[cfg(not(futures_no_atomic_cas))]
+use crate::stream::{Collect, FuturesOrdered, StreamExt};
+
+pub(crate) fn iter_pin_mut<T>(slice: Pin<&mut [T]>) -> impl Iterator<Item = Pin<&mut T>> {
+    // Safety: `std` _could_ make this unsound if it were to decide Pin's
+    // invariants aren't required to transmit through slices. Otherwise this has
+    // the same safety as a normal field pin projection.
+    unsafe { slice.get_unchecked_mut() }.iter_mut().map(|t| unsafe { Pin::new_unchecked(t) })
+}
+
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+/// Future for the [`join_all`] function.
+pub struct JoinAll<F>
+where
+    F: Future,
+{
+    kind: JoinAllKind<F>,
+}
+
+#[cfg(not(futures_no_atomic_cas))]
+pub(crate) const SMALL: usize = 30;
+
+enum JoinAllKind<F>
+where
+    F: Future,
+{
+    Small {
+        elems: Pin<Box<[MaybeDone<F>]>>,
+    },
+    #[cfg(not(futures_no_atomic_cas))]
+    Big {
+        fut: Collect<FuturesOrdered<F>, Vec<F::Output>>,
+    },
+}
+
+impl<F> fmt::Debug for JoinAll<F>
+where
+    F: Future + fmt::Debug,
+    F::Output: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.kind {
+            JoinAllKind::Small { ref elems } => {
+                f.debug_struct("JoinAll").field("elems", elems).finish()
+            }
+            #[cfg(not(futures_no_atomic_cas))]
+            JoinAllKind::Big { ref fut, .. } => fmt::Debug::fmt(fut, f),
+        }
+    }
+}
+
+/// Creates a future which represents a collection of the outputs of the futures
+/// given.
+///
+/// The returned future will drive execution for all of its underlying futures,
+/// collecting the results into a destination `Vec<T>` in the same order as they
+/// were provided.
+///
+/// This function is only available when the `std` or `alloc` feature of this
+/// library is activated, and it is activated by default.
+///
+/// # See Also
+///
+/// `join_all` will switch to the more powerful [`FuturesOrdered`] for performance
+/// reasons if the number of futures is large. You may want to look into using it or
+/// it's counterpart [`FuturesUnordered`][crate::stream::FuturesUnordered] directly.
+///
+/// Some examples for additional functionality provided by these are:
+///
+///  * Adding new futures to the set even after it has been started.
+///
+///  * Only polling the specific futures that have been woken. In cases where
+///    you have a lot of futures this will result in much more efficient polling.
+///
+/// # Examples
+///
+/// ```
+/// # futures::executor::block_on(async {
+/// use futures::future::join_all;
+///
+/// async fn foo(i: u32) -> u32 { i }
+///
+/// let futures = vec![foo(1), foo(2), foo(3)];
+///
+/// assert_eq!(join_all(futures).await, [1, 2, 3]);
+/// # });
+/// ```
+pub fn join_all<I>(iter: I) -> JoinAll<I::Item>
+where
+    I: IntoIterator,
+    I::Item: Future,
+{
+    let iter = iter.into_iter();
+
+    #[cfg(futures_no_atomic_cas)]
+    {
+        let kind =
+            JoinAllKind::Small { elems: iter.map(MaybeDone::Future).collect::<Box<[_]>>().into() };
+
+        assert_future::<Vec<<I::Item as Future>::Output>, _>(JoinAll { kind })
+    }
+
+    #[cfg(not(futures_no_atomic_cas))]
+    {
+        let kind = match iter.size_hint().1 {
+            Some(max) if max <= SMALL => JoinAllKind::Small {
+                elems: iter.map(MaybeDone::Future).collect::<Box<[_]>>().into(),
+            },
+            _ => JoinAllKind::Big { fut: iter.collect::<FuturesOrdered<_>>().collect() },
+        };
+
+        assert_future::<Vec<<I::Item as Future>::Output>, _>(JoinAll { kind })
+    }
+}
+
+impl<F> Future for JoinAll<F>
+where
+    F: Future,
+{
+    type Output = Vec<F::Output>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        match &mut self.kind {
+            JoinAllKind::Small { elems } => {
+                let mut all_done = true;
+
+                for elem in iter_pin_mut(elems.as_mut()) {
+                    if elem.poll(cx).is_pending() {
+                        all_done = false;
+                    }
+                }
+
+                if all_done {
+                    let mut elems = mem::replace(elems, Box::pin([]));
+                    let result =
+                        iter_pin_mut(elems.as_mut()).map(|e| e.take_output().unwrap()).collect();
+                    Poll::Ready(result)
+                } else {
+                    Poll::Pending
+                }
+            }
+            #[cfg(not(futures_no_atomic_cas))]
+            JoinAllKind::Big { fut } => Pin::new(fut).poll(cx),
+        }
+    }
+}
+
+impl<F: Future> FromIterator<F> for JoinAll<F> {
+    fn from_iter<T: IntoIterator<Item = F>>(iter: T) -> Self {
+        join_all(iter)
+    }
+}