chore: checkpoint before Python removal

vendor/tokio/src/util/as_ref.rs

@@ -0,0 +1,38 @@
+use super::typeid;
+
+#[derive(Debug)]
+pub(crate) enum OwnedBuf {
+    Vec(Vec<u8>),
+    #[cfg(feature = "io-util")]
+    Bytes(bytes::Bytes),
+}
+
+impl AsRef<[u8]> for OwnedBuf {
+    fn as_ref(&self) -> &[u8] {
+        match self {
+            Self::Vec(vec) => vec,
+            #[cfg(feature = "io-util")]
+            Self::Bytes(bytes) => bytes,
+        }
+    }
+}
+
+pub(crate) fn upgrade<B: AsRef<[u8]>>(buf: B) -> OwnedBuf {
+    let buf = match unsafe { typeid::try_transmute::<B, Vec<u8>>(buf) } {
+        Ok(vec) => return OwnedBuf::Vec(vec),
+        Err(original_buf) => original_buf,
+    };
+
+    let buf = match unsafe { typeid::try_transmute::<B, String>(buf) } {
+        Ok(string) => return OwnedBuf::Vec(string.into_bytes()),
+        Err(original_buf) => original_buf,
+    };
+
+    #[cfg(feature = "io-util")]
+    let buf = match unsafe { typeid::try_transmute::<B, bytes::Bytes>(buf) } {
+        Ok(bytes) => return OwnedBuf::Bytes(bytes),
+        Err(original_buf) => original_buf,
+    };
+
+    OwnedBuf::Vec(buf.as_ref().to_owned())
+}

vendor/tokio/src/util/atomic_cell.rs

@@ -0,0 +1,51 @@
+use crate::loom::sync::atomic::AtomicPtr;
+
+use std::ptr;
+use std::sync::atomic::Ordering::AcqRel;
+
+pub(crate) struct AtomicCell<T> {
+    data: AtomicPtr<T>,
+}
+
+unsafe impl<T: Send> Send for AtomicCell<T> {}
+unsafe impl<T: Send> Sync for AtomicCell<T> {}
+
+impl<T> AtomicCell<T> {
+    pub(crate) fn new(data: Option<Box<T>>) -> AtomicCell<T> {
+        AtomicCell {
+            data: AtomicPtr::new(to_raw(data)),
+        }
+    }
+
+    pub(crate) fn swap(&self, val: Option<Box<T>>) -> Option<Box<T>> {
+        let old = self.data.swap(to_raw(val), AcqRel);
+        from_raw(old)
+    }
+
+    pub(crate) fn set(&self, val: Box<T>) {
+        let _ = self.swap(Some(val));
+    }
+
+    pub(crate) fn take(&self) -> Option<Box<T>> {
+        self.swap(None)
+    }
+}
+
+fn to_raw<T>(data: Option<Box<T>>) -> *mut T {
+    data.map_or(ptr::null_mut(), Box::into_raw)
+}
+
+fn from_raw<T>(val: *mut T) -> Option<Box<T>> {
+    if val.is_null() {
+        None
+    } else {
+        Some(unsafe { Box::from_raw(val) })
+    }
+}
+
+impl<T> Drop for AtomicCell<T> {
+    fn drop(&mut self) {
+        // Free any data still held by the cell
+        let _ = self.take();
+    }
+}

vendor/tokio/src/util/bit.rs

@@ -0,0 +1,64 @@
+use std::fmt;
+
+#[derive(Clone, Copy, PartialEq)]
+pub(crate) struct Pack {
+    mask: usize,
+    shift: u32,
+}
+
+impl Pack {
+    /// Value is packed in the `width` least-significant bits.
+    pub(crate) const fn least_significant(width: u32) -> Pack {
+        let mask = mask_for(width);
+
+        Pack { mask, shift: 0 }
+    }
+
+    /// Value is packed in the `width` more-significant bits.
+    pub(crate) const fn then(&self, width: u32) -> Pack {
+        let shift = usize::BITS - self.mask.leading_zeros();
+        let mask = mask_for(width) << shift;
+
+        Pack { mask, shift }
+    }
+
+    /// Width, in bits, dedicated to storing the value.
+    pub(crate) const fn width(&self) -> u32 {
+        usize::BITS - (self.mask >> self.shift).leading_zeros()
+    }
+
+    /// Max representable value.
+    pub(crate) const fn max_value(&self) -> usize {
+        (1 << self.width()) - 1
+    }
+
+    pub(crate) fn pack(&self, value: usize, base: usize) -> usize {
+        assert!(value <= self.max_value());
+        (base & !self.mask) | (value << self.shift)
+    }
+
+    pub(crate) fn unpack(&self, src: usize) -> usize {
+        unpack(src, self.mask, self.shift)
+    }
+}
+
+impl fmt::Debug for Pack {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            fmt,
+            "Pack {{ mask: {:b}, shift: {} }}",
+            self.mask, self.shift
+        )
+    }
+}
+
+/// Returns a `usize` with the right-most `n` bits set.
+pub(crate) const fn mask_for(n: u32) -> usize {
+    let shift = 1usize.wrapping_shl(n - 1);
+    shift | (shift - 1)
+}
+
+/// Unpacks a value using a mask & shift.
+pub(crate) const fn unpack(src: usize, mask: usize, shift: u32) -> usize {
+    (src & mask) >> shift
+}

vendor/tokio/src/util/blocking_check.rs

@@ -0,0 +1,29 @@
+#[cfg(unix)]
+use std::os::fd::AsFd;
+
+#[cfg(unix)]
+#[allow(unused_variables)]
+#[track_caller]
+pub(crate) fn check_socket_for_blocking<S: AsFd>(s: &S) -> crate::io::Result<()> {
+    #[cfg(not(tokio_allow_from_blocking_fd))]
+    {
+        let sock = socket2::SockRef::from(s);
+
+        debug_assert!(
+            sock.nonblocking()?,
+            "Registering a blocking socket with the tokio runtime is unsupported. \
+            If you wish to do anyways, please add `--cfg tokio_allow_from_blocking_fd` to your \
+            RUSTFLAGS. See github.com/tokio-rs/tokio/issues/7172 for details."
+        );
+    }
+
+    Ok(())
+}
+
+#[cfg(not(unix))]
+#[allow(unused_variables)]
+pub(crate) fn check_socket_for_blocking<S>(s: &S) -> crate::io::Result<()> {
+    // we cannot retrieve the nonblocking status on windows
+    // and i dont know how to support wasi yet
+    Ok(())
+}

vendor/tokio/src/util/cacheline.rs

@@ -0,0 +1,89 @@
+#![cfg_attr(not(feature = "sync"), allow(dead_code, unreachable_pub))]
+use std::ops::{Deref, DerefMut};
+
+/// Pads and aligns a value to the length of a cache line.
+#[derive(Clone, Copy, Default, Hash, PartialEq, Eq)]
+// Starting from Intel's Sandy Bridge, spatial prefetcher is now pulling pairs of 64-byte cache
+// lines at a time, so we have to align to 128 bytes rather than 64.
+//
+// Sources:
+// - https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-optimization-manual.pdf
+// - https://github.com/facebook/folly/blob/1b5288e6eea6df074758f877c849b6e73bbb9fbb/folly/lang/Align.h#L107
+//
+// ARM's big.LITTLE architecture has asymmetric cores and "big" cores have 128-byte cache line size.
+//
+// Sources:
+// - https://www.mono-project.com/news/2016/09/12/arm64-icache/
+//
+// powerpc64 has 128-byte cache line size.
+//
+// Sources:
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_ppc64x.go#L9
+#[cfg_attr(
+    any(
+        target_arch = "x86_64",
+        target_arch = "aarch64",
+        target_arch = "powerpc64",
+    ),
+    repr(align(128))
+)]
+// arm, mips and mips64 have 32-byte cache line size.
+//
+// Sources:
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_arm.go#L7
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips.go#L7
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mipsle.go#L7
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_mips64x.go#L9
+#[cfg_attr(
+    any(target_arch = "arm", target_arch = "mips", target_arch = "mips64",),
+    repr(align(32))
+)]
+// s390x has 256-byte cache line size.
+//
+// Sources:
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_s390x.go#L7
+#[cfg_attr(target_arch = "s390x", repr(align(256)))]
+// x86, riscv and wasm have 64-byte cache line size.
+//
+// Sources:
+// - https://github.com/golang/go/blob/dda2991c2ea0c5914714469c4defc2562a907230/src/internal/cpu/cpu_x86.go#L9
+// - https://github.com/golang/go/blob/3dd58676054223962cd915bb0934d1f9f489d4d2/src/internal/cpu/cpu_wasm.go#L7
+// - https://github.com/torvalds/linux/blob/3516bd729358a2a9b090c1905bd2a3fa926e24c6/arch/riscv/include/asm/cache.h#L10
+//
+// All others are assumed to have 64-byte cache line size.
+#[cfg_attr(
+    not(any(
+        target_arch = "x86_64",
+        target_arch = "aarch64",
+        target_arch = "powerpc64",
+        target_arch = "arm",
+        target_arch = "mips",
+        target_arch = "mips64",
+        target_arch = "s390x",
+    )),
+    repr(align(64))
+)]
+pub(crate) struct CachePadded<T> {
+    value: T,
+}
+
+impl<T> CachePadded<T> {
+    /// Pads and aligns a value to the length of a cache line.
+    pub(crate) fn new(value: T) -> CachePadded<T> {
+        CachePadded::<T> { value }
+    }
+}
+
+impl<T> Deref for CachePadded<T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &self.value
+    }
+}
+
+impl<T> DerefMut for CachePadded<T> {
+    fn deref_mut(&mut self) -> &mut T {
+        &mut self.value
+    }
+}

vendor/tokio/src/util/error.rs

@@ -0,0 +1,16 @@
+// Some combinations of features may not use these constants.
+#![cfg_attr(not(feature = "full"), allow(dead_code))]
+
+/// Error string explaining that the Tokio context hasn't been instantiated.
+pub(crate) const CONTEXT_MISSING_ERROR: &str =
+    "there is no reactor running, must be called from the context of a Tokio 1.x runtime";
+
+/// Error string explaining that the Tokio context is shutting down and cannot drive timers.
+pub(crate) const RUNTIME_SHUTTING_DOWN_ERROR: &str =
+    "A Tokio 1.x context was found, but it is being shutdown.";
+
+/// Error string explaining that the Tokio context is not available because the
+/// thread-local storing it has been destroyed. This usually only happens during
+/// destructors of other thread-locals.
+pub(crate) const THREAD_LOCAL_DESTROYED_ERROR: &str =
+    "The Tokio context thread-local variable has been destroyed.";

vendor/tokio/src/util/idle_notified_set.rs

@@ -0,0 +1,512 @@
+//! This module defines an `IdleNotifiedSet`, which is a collection of elements.
+//! Each element is intended to correspond to a task, and the collection will
+//! keep track of which tasks have had their waker notified, and which have not.
+//!
+//! Each entry in the set holds some user-specified value. The value's type is
+//! specified using the `T` parameter. It will usually be a `JoinHandle` or
+//! similar.
+
+use std::marker::PhantomPinned;
+use std::mem::ManuallyDrop;
+use std::ptr::NonNull;
+use std::task::{Context, Waker};
+
+use crate::loom::cell::UnsafeCell;
+use crate::loom::sync::{Arc, Mutex};
+use crate::util::linked_list::{self, Link};
+use crate::util::{waker_ref, Wake};
+
+type LinkedList<T> =
+    linked_list::LinkedList<ListEntry<T>, <ListEntry<T> as linked_list::Link>::Target>;
+
+/// This is the main handle to the collection.
+pub(crate) struct IdleNotifiedSet<T> {
+    lists: Arc<Lists<T>>,
+    length: usize,
+}
+
+/// A handle to an entry that is guaranteed to be stored in the idle or notified
+/// list of its `IdleNotifiedSet`. This value borrows the `IdleNotifiedSet`
+/// mutably to prevent the entry from being moved to the `Neither` list, which
+/// only the `IdleNotifiedSet` may do.
+///
+/// The main consequence of being stored in one of the lists is that the `value`
+/// field has not yet been consumed.
+///
+/// Note: This entry can be moved from the idle to the notified list while this
+/// object exists by waking its waker.
+pub(crate) struct EntryInOneOfTheLists<'a, T> {
+    entry: Arc<ListEntry<T>>,
+    set: &'a mut IdleNotifiedSet<T>,
+}
+
+type Lists<T> = Mutex<ListsInner<T>>;
+
+/// The linked lists hold strong references to the `ListEntry` items, and the
+/// `ListEntry` items also hold a strong reference back to the Lists object, but
+/// the destructor of the `IdleNotifiedSet` will clear the two lists, so once
+/// that object is destroyed, no ref-cycles will remain.
+struct ListsInner<T> {
+    notified: LinkedList<T>,
+    idle: LinkedList<T>,
+    /// Whenever an element in the `notified` list is woken, this waker will be
+    /// notified and consumed, if it exists.
+    waker: Option<Waker>,
+}
+
+/// Which of the two lists in the shared Lists object is this entry stored in?
+///
+/// If the value is `Idle`, then an entry's waker may move it to the notified
+/// list. Otherwise, only the `IdleNotifiedSet` may move it.
+///
+/// If the value is `Neither`, then it is still possible that the entry is in
+/// some third external list (this happens in `drain`).
+#[derive(Copy, Clone, Eq, PartialEq)]
+enum List {
+    Notified,
+    Idle,
+    Neither,
+}
+
+/// An entry in the list.
+///
+/// # Safety
+///
+/// The `my_list` field must only be accessed while holding the mutex in
+/// `parent`. It is an invariant that the value of `my_list` corresponds to
+/// which linked list in the `parent` holds this entry. Once this field takes
+/// the value `Neither`, then it may never be modified again.
+///
+/// If the value of `my_list` is `Notified` or `Idle`, then the `pointers` field
+/// must only be accessed while holding the mutex. If the value of `my_list` is
+/// `Neither`, then the `pointers` field may be accessed by the
+/// `IdleNotifiedSet` (this happens inside `drain`).
+///
+/// The `value` field is owned by the `IdleNotifiedSet` and may only be accessed
+/// by the `IdleNotifiedSet`. The operation that sets the value of `my_list` to
+/// `Neither` assumes ownership of the `value`, and it must either drop it or
+/// move it out from this entry to prevent it from getting leaked. (Since the
+/// two linked lists are emptied in the destructor of `IdleNotifiedSet`, the
+/// value should not be leaked.)
+struct ListEntry<T> {
+    /// The linked list pointers of the list this entry is in.
+    pointers: linked_list::Pointers<ListEntry<T>>,
+    /// Pointer to the shared `Lists` struct.
+    parent: Arc<Lists<T>>,
+    /// The value stored in this entry.
+    value: UnsafeCell<ManuallyDrop<T>>,
+    /// Used to remember which list this entry is in.
+    my_list: UnsafeCell<List>,
+    /// Required by the `linked_list::Pointers` field.
+    _pin: PhantomPinned,
+}
+
+generate_addr_of_methods! {
+    impl<T> ListEntry<T> {
+        unsafe fn addr_of_pointers(self: NonNull<Self>) -> NonNull<linked_list::Pointers<ListEntry<T>>> {
+            &self.pointers
+        }
+    }
+}
+
+// With mutable access to the `IdleNotifiedSet`, you can get mutable access to
+// the values.
+unsafe impl<T: Send> Send for IdleNotifiedSet<T> {}
+// With the current API we strictly speaking don't even need `T: Sync`, but we
+// require it anyway to support adding &self APIs that access the values in the
+// future.
+unsafe impl<T: Sync> Sync for IdleNotifiedSet<T> {}
+
+// These impls control when it is safe to create a Waker. Since the waker does
+// not allow access to the value in any way (including its destructor), it is
+// not necessary for `T` to be Send or Sync.
+unsafe impl<T> Send for ListEntry<T> {}
+unsafe impl<T> Sync for ListEntry<T> {}
+
+impl<T> IdleNotifiedSet<T> {
+    /// Create a new `IdleNotifiedSet`.
+    pub(crate) fn new() -> Self {
+        let lists = Mutex::new(ListsInner {
+            notified: LinkedList::new(),
+            idle: LinkedList::new(),
+            waker: None,
+        });
+
+        IdleNotifiedSet {
+            lists: Arc::new(lists),
+            length: 0,
+        }
+    }
+
+    pub(crate) fn len(&self) -> usize {
+        self.length
+    }
+
+    pub(crate) fn is_empty(&self) -> bool {
+        self.length == 0
+    }
+
+    /// Insert the given value into the `idle` list.
+    pub(crate) fn insert_idle(&mut self, value: T) -> EntryInOneOfTheLists<'_, T> {
+        self.length += 1;
+
+        let entry = Arc::new(ListEntry {
+            parent: self.lists.clone(),
+            value: UnsafeCell::new(ManuallyDrop::new(value)),
+            my_list: UnsafeCell::new(List::Idle),
+            pointers: linked_list::Pointers::new(),
+            _pin: PhantomPinned,
+        });
+
+        {
+            let mut lock = self.lists.lock();
+            lock.idle.push_front(entry.clone());
+        }
+
+        // Safety: We just put the entry in the idle list, so it is in one of the lists.
+        EntryInOneOfTheLists { entry, set: self }
+    }
+
+    /// Pop an entry from the notified list to poll it. The entry is moved to
+    /// the idle list atomically.
+    pub(crate) fn pop_notified(&mut self, waker: &Waker) -> Option<EntryInOneOfTheLists<'_, T>> {
+        // We don't decrement the length because this call moves the entry to
+        // the idle list rather than removing it.
+        if self.length == 0 {
+            // Fast path.
+            return None;
+        }
+
+        let mut lock = self.lists.lock();
+
+        let should_update_waker = match lock.waker.as_mut() {
+            Some(cur_waker) => !waker.will_wake(cur_waker),
+            None => true,
+        };
+        if should_update_waker {
+            lock.waker = Some(waker.clone());
+        }
+
+        // Pop the entry, returning None if empty.
+        let entry = lock.notified.pop_back()?;
+
+        lock.idle.push_front(entry.clone());
+
+        // Safety: We are holding the lock.
+        entry.my_list.with_mut(|ptr| unsafe {
+            *ptr = List::Idle;
+        });
+
+        drop(lock);
+
+        // Safety: We just put the entry in the idle list, so it is in one of the lists.
+        Some(EntryInOneOfTheLists { entry, set: self })
+    }
+
+    /// Tries to pop an entry from the notified list to poll it. The entry is moved to
+    /// the idle list atomically.
+    pub(crate) fn try_pop_notified(&mut self) -> Option<EntryInOneOfTheLists<'_, T>> {
+        // We don't decrement the length because this call moves the entry to
+        // the idle list rather than removing it.
+        if self.length == 0 {
+            // Fast path.
+            return None;
+        }
+
+        let mut lock = self.lists.lock();
+
+        // Pop the entry, returning None if empty.
+        let entry = lock.notified.pop_back()?;
+
+        lock.idle.push_front(entry.clone());
+
+        // Safety: We are holding the lock.
+        entry.my_list.with_mut(|ptr| unsafe {
+            *ptr = List::Idle;
+        });
+
+        drop(lock);
+
+        // Safety: We just put the entry in the idle list, so it is in one of the lists.
+        Some(EntryInOneOfTheLists { entry, set: self })
+    }
+
+    /// Call a function on every element in this list.
+    pub(crate) fn for_each<F: FnMut(&mut T)>(&mut self, mut func: F) {
+        fn get_ptrs<T>(list: &mut LinkedList<T>, ptrs: &mut Vec<*mut T>) {
+            let mut node = list.last();
+
+            while let Some(entry) = node {
+                ptrs.push(entry.value.with_mut(|ptr| {
+                    let ptr: *mut ManuallyDrop<T> = ptr;
+                    let ptr: *mut T = ptr.cast();
+                    ptr
+                }));
+
+                let prev = entry.pointers.get_prev();
+                node = prev.map(|prev| unsafe { &*prev.as_ptr() });
+            }
+        }
+
+        // Atomically get a raw pointer to the value of every entry.
+        //
+        // Since this only locks the mutex once, it is not possible for a value
+        // to get moved from the idle list to the notified list during the
+        // operation, which would otherwise result in some value being listed
+        // twice.
+        let mut ptrs = Vec::with_capacity(self.len());
+        {
+            let mut lock = self.lists.lock();
+
+            get_ptrs(&mut lock.idle, &mut ptrs);
+            get_ptrs(&mut lock.notified, &mut ptrs);
+        }
+        debug_assert_eq!(ptrs.len(), ptrs.capacity());
+
+        for ptr in ptrs {
+            // Safety: When we grabbed the pointers, the entries were in one of
+            // the two lists. This means that their value was valid at the time,
+            // and it must still be valid because we are the IdleNotifiedSet,
+            // and only we can remove an entry from the two lists. (It's
+            // possible that an entry is moved from one list to the other during
+            // this loop, but that is ok.)
+            func(unsafe { &mut *ptr });
+        }
+    }
+
+    /// Remove all entries in both lists, applying some function to each element.
+    ///
+    /// The closure is called on all elements even if it panics. Having it panic
+    /// twice is a double-panic, and will abort the application.
+    pub(crate) fn drain<F: FnMut(T)>(&mut self, func: F) {
+        if self.length == 0 {
+            // Fast path.
+            return;
+        }
+        self.length = 0;
+
+        // The LinkedList is not cleared on panic, so we use a bomb to clear it.
+        //
+        // This value has the invariant that any entry in its `all_entries` list
+        // has `my_list` set to `Neither` and that the value has not yet been
+        // dropped.
+        struct AllEntries<T, F: FnMut(T)> {
+            all_entries: LinkedList<T>,
+            func: F,
+        }
+
+        impl<T, F: FnMut(T)> AllEntries<T, F> {
+            fn pop_next(&mut self) -> bool {
+                if let Some(entry) = self.all_entries.pop_back() {
+                    // Safety: We just took this value from the list, so we can
+                    // destroy the value in the entry.
+                    entry
+                        .value
+                        .with_mut(|ptr| unsafe { (self.func)(ManuallyDrop::take(&mut *ptr)) });
+                    true
+                } else {
+                    false
+                }
+            }
+        }
+
+        impl<T, F: FnMut(T)> Drop for AllEntries<T, F> {
+            fn drop(&mut self) {
+                while self.pop_next() {}
+            }
+        }
+
+        let mut all_entries = AllEntries {
+            all_entries: LinkedList::new(),
+            func,
+        };
+
+        // Atomically move all entries to the new linked list in the AllEntries
+        // object.
+        {
+            let mut lock = self.lists.lock();
+            unsafe {
+                // Safety: We are holding the lock and `all_entries` is a new
+                // LinkedList.
+                move_to_new_list(&mut lock.idle, &mut all_entries.all_entries);
+                move_to_new_list(&mut lock.notified, &mut all_entries.all_entries);
+            }
+        }
+
+        // Keep destroying entries in the list until it is empty.
+        //
+        // If the closure panics, then the destructor of the `AllEntries` bomb
+        // ensures that we keep running the destructor on the remaining values.
+        // A second panic will abort the program.
+        while all_entries.pop_next() {}
+    }
+}
+
+/// # Safety
+///
+/// The mutex for the entries must be held, and the target list must be such
+/// that setting `my_list` to `Neither` is ok.
+unsafe fn move_to_new_list<T>(from: &mut LinkedList<T>, to: &mut LinkedList<T>) {
+    while let Some(entry) = from.pop_back() {
+        entry.my_list.with_mut(|ptr| {
+            // Safety: pointer is accessed while holding the mutex.
+            unsafe {
+                *ptr = List::Neither;
+            }
+        });
+        to.push_front(entry);
+    }
+}
+
+impl<'a, T> EntryInOneOfTheLists<'a, T> {
+    /// Remove this entry from the list it is in, returning the value associated
+    /// with the entry.
+    ///
+    /// This consumes the value, since it is no longer guaranteed to be in a
+    /// list.
+    pub(crate) fn remove(self) -> T {
+        self.set.length -= 1;
+
+        {
+            let mut lock = self.set.lists.lock();
+
+            // Safety: We are holding the lock so there is no race, and we will
+            // remove the entry afterwards to uphold invariants.
+            let old_my_list = self.entry.my_list.with_mut(|ptr| unsafe {
+                let old_my_list = *ptr;
+                *ptr = List::Neither;
+                old_my_list
+            });
+
+            let list = match old_my_list {
+                List::Idle => &mut lock.idle,
+                List::Notified => &mut lock.notified,
+                // An entry in one of the lists is in one of the lists.
+                List::Neither => unreachable!(),
+            };
+
+            unsafe {
+                // Safety: We just checked that the entry is in this particular
+                // list.
+                list.remove(ListEntry::as_raw(&self.entry)).unwrap();
+            }
+        }
+
+        // By setting `my_list` to `Neither`, we have taken ownership of the
+        // value. We return it to the caller.
+        //
+        // Safety: We have a mutable reference to the `IdleNotifiedSet` that
+        // owns this entry, so we can use its permission to access the value.
+        self.entry
+            .value
+            .with_mut(|ptr| unsafe { ManuallyDrop::take(&mut *ptr) })
+    }
+
+    /// Access the value in this entry together with a context for its waker.
+    pub(crate) fn with_value_and_context<F, U>(&mut self, func: F) -> U
+    where
+        F: FnOnce(&mut T, &mut Context<'_>) -> U,
+        T: 'static,
+    {
+        let waker = waker_ref(&self.entry);
+
+        let mut context = Context::from_waker(&waker);
+
+        // Safety: We have a mutable reference to the `IdleNotifiedSet` that
+        // owns this entry, so we can use its permission to access the value.
+        self.entry
+            .value
+            .with_mut(|ptr| unsafe { func(&mut *ptr, &mut context) })
+    }
+}
+
+impl<T> Drop for IdleNotifiedSet<T> {
+    fn drop(&mut self) {
+        // Clear both lists.
+        self.drain(drop);
+
+        #[cfg(debug_assertions)]
+        if !std::thread::panicking() {
+            let lock = self.lists.lock();
+            assert!(lock.idle.is_empty());
+            assert!(lock.notified.is_empty());
+        }
+    }
+}
+
+impl<T: 'static> Wake for ListEntry<T> {
+    fn wake_by_ref(me: &Arc<Self>) {
+        let mut lock = me.parent.lock();
+
+        // Safety: We are holding the lock and we will update the lists to
+        // maintain invariants.
+        let old_my_list = me.my_list.with_mut(|ptr| unsafe {
+            let old_my_list = *ptr;
+            if old_my_list == List::Idle {
+                *ptr = List::Notified;
+            }
+            old_my_list
+        });
+
+        if old_my_list == List::Idle {
+            // We move ourself to the notified list.
+            let me = unsafe {
+                // Safety: We just checked that we are in this particular list.
+                lock.idle.remove(ListEntry::as_raw(me)).unwrap()
+            };
+            lock.notified.push_front(me);
+
+            if let Some(waker) = lock.waker.take() {
+                drop(lock);
+                waker.wake();
+            }
+        }
+    }
+
+    fn wake(me: Arc<Self>) {
+        Self::wake_by_ref(&me);
+    }
+}
+
+/// # Safety
+///
+/// `ListEntry` is forced to be !Unpin.
+unsafe impl<T> linked_list::Link for ListEntry<T> {
+    type Handle = Arc<ListEntry<T>>;
+    type Target = ListEntry<T>;
+
+    fn as_raw(handle: &Self::Handle) -> NonNull<ListEntry<T>> {
+        let ptr: *const ListEntry<T> = Arc::as_ptr(handle);
+        // Safety: We can't get a null pointer from `Arc::as_ptr`.
+        unsafe { NonNull::new_unchecked(ptr as *mut ListEntry<T>) }
+    }
+
+    unsafe fn from_raw(ptr: NonNull<ListEntry<T>>) -> Arc<ListEntry<T>> {
+        unsafe { Arc::from_raw(ptr.as_ptr()) }
+    }
+
+    unsafe fn pointers(
+        target: NonNull<ListEntry<T>>,
+    ) -> NonNull<linked_list::Pointers<ListEntry<T>>> {
+        unsafe { ListEntry::addr_of_pointers(target) }
+    }
+}
+
+#[cfg(all(test, not(loom)))]
+mod tests {
+    use crate::runtime::Builder;
+    use crate::task::JoinSet;
+
+    // A test that runs under miri.
+    //
+    // https://github.com/tokio-rs/tokio/pull/5693
+    #[test]
+    fn join_set_test() {
+        let rt = Builder::new_current_thread().build().unwrap();
+
+        let mut set = JoinSet::new();
+        set.spawn_on(futures::future::ready(()), rt.handle());
+
+        rt.block_on(set.join_next()).unwrap().unwrap();
+    }
+}

vendor/tokio/src/util/linked_list.rs

@@ -0,0 +1,808 @@
+#![cfg_attr(not(feature = "full"), allow(dead_code))]
+// It doesn't make sense to enforce `unsafe_op_in_unsafe_fn` for this module because
+//
+// * The intrusive linked list naturally relies on unsafe operations.
+// * Excessive `unsafe {}` blocks hurt readability significantly.
+// TODO: replace with `#[expect(unsafe_op_in_unsafe_fn)]` after bumpping
+// the MSRV to 1.81.0.
+#![allow(unsafe_op_in_unsafe_fn)]
+
+//! An intrusive double linked list of data.
+//!
+//! The data structure supports tracking pinned nodes. Most of the data
+//! structure's APIs are `unsafe` as they require the caller to ensure the
+//! specified node is actually contained by the list.
+
+use core::cell::UnsafeCell;
+use core::fmt;
+use core::marker::{PhantomData, PhantomPinned};
+use core::mem::ManuallyDrop;
+use core::ptr::{self, NonNull};
+
+/// An intrusive linked list.
+///
+/// Currently, the list is not emptied on drop. It is the caller's
+/// responsibility to ensure the list is empty before dropping it.
+pub(crate) struct LinkedList<L, T> {
+    /// Linked list head
+    head: Option<NonNull<T>>,
+
+    /// Linked list tail
+    tail: Option<NonNull<T>>,
+
+    /// Node type marker.
+    _marker: PhantomData<*const L>,
+}
+
+unsafe impl<L: Link> Send for LinkedList<L, L::Target> where L::Target: Send {}
+unsafe impl<L: Link> Sync for LinkedList<L, L::Target> where L::Target: Sync {}
+
+/// Defines how a type is tracked within a linked list.
+///
+/// In order to support storing a single type within multiple lists, accessing
+/// the list pointers is decoupled from the entry type.
+///
+/// # Safety
+///
+/// Implementations must guarantee that `Target` types are pinned in memory. In
+/// other words, when a node is inserted, the value will not be moved as long as
+/// it is stored in the list.
+pub(crate) unsafe trait Link {
+    /// Handle to the list entry.
+    ///
+    /// This is usually a pointer-ish type.
+    type Handle;
+
+    /// Node type.
+    type Target;
+
+    /// Convert the handle to a raw pointer without consuming the handle.
+    #[allow(clippy::wrong_self_convention)]
+    fn as_raw(handle: &Self::Handle) -> NonNull<Self::Target>;
+
+    /// Convert the raw pointer to a handle
+    unsafe fn from_raw(ptr: NonNull<Self::Target>) -> Self::Handle;
+
+    /// Return the pointers for a node
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer should have the same tag in the stacked-borrows
+    /// stack as the argument. In particular, the method may not create an
+    /// intermediate reference in the process of creating the resulting raw
+    /// pointer.
+    ///
+    /// The `target` pointer must be valid.
+    unsafe fn pointers(target: NonNull<Self::Target>) -> NonNull<Pointers<Self::Target>>;
+}
+
+/// Previous / next pointers.
+pub(crate) struct Pointers<T> {
+    inner: UnsafeCell<PointersInner<T>>,
+}
+/// We do not want the compiler to put the `noalias` attribute on mutable
+/// references to this type, so the type has been made `!Unpin` with a
+/// `PhantomPinned` field.
+///
+/// Additionally, we never access the `prev` or `next` fields directly, as any
+/// such access would implicitly involve the creation of a reference to the
+/// field, which we want to avoid since the fields are not `!Unpin`, and would
+/// hence be given the `noalias` attribute if we were to do such an access. As
+/// an alternative to accessing the fields directly, the `Pointers` type
+/// provides getters and setters for the two fields, and those are implemented
+/// using `ptr`-specific methods which avoids the creation of intermediate
+/// references.
+///
+/// See this link for more information:
+/// <https://github.com/rust-lang/rust/pull/82834>
+struct PointersInner<T> {
+    /// The previous node in the list. null if there is no previous node.
+    prev: Option<NonNull<T>>,
+
+    /// The next node in the list. null if there is no previous node.
+    next: Option<NonNull<T>>,
+
+    /// This type is !Unpin due to the heuristic from:
+    /// <https://github.com/rust-lang/rust/pull/82834>
+    _pin: PhantomPinned,
+}
+
+unsafe impl<T: Send> Send for Pointers<T> {}
+unsafe impl<T: Sync> Sync for Pointers<T> {}
+
+// ===== impl LinkedList =====
+
+impl<L, T> LinkedList<L, T> {
+    /// Creates an empty linked list.
+    pub(crate) const fn new() -> LinkedList<L, T> {
+        LinkedList {
+            head: None,
+            tail: None,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<L: Link> LinkedList<L, L::Target> {
+    /// Adds an element first in the list.
+    pub(crate) fn push_front(&mut self, val: L::Handle) {
+        // The value should not be dropped, it is being inserted into the list
+        let val = ManuallyDrop::new(val);
+        let ptr = L::as_raw(&val);
+        assert_ne!(self.head, Some(ptr));
+        unsafe {
+            L::pointers(ptr).as_mut().set_next(self.head);
+            L::pointers(ptr).as_mut().set_prev(None);
+
+            if let Some(head) = self.head {
+                L::pointers(head).as_mut().set_prev(Some(ptr));
+            }
+
+            self.head = Some(ptr);
+
+            if self.tail.is_none() {
+                self.tail = Some(ptr);
+            }
+        }
+    }
+
+    /// Removes the first element from a list and returns it, or None if it is
+    /// empty.
+    pub(crate) fn pop_front(&mut self) -> Option<L::Handle> {
+        unsafe {
+            let head = self.head?;
+            self.head = L::pointers(head).as_ref().get_next();
+
+            if let Some(new_head) = L::pointers(head).as_ref().get_next() {
+                L::pointers(new_head).as_mut().set_prev(None);
+            } else {
+                self.tail = None;
+            }
+
+            L::pointers(head).as_mut().set_prev(None);
+            L::pointers(head).as_mut().set_next(None);
+
+            Some(L::from_raw(head))
+        }
+    }
+
+    /// Removes the last element from a list and returns it, or None if it is
+    /// empty.
+    pub(crate) fn pop_back(&mut self) -> Option<L::Handle> {
+        unsafe {
+            let last = self.tail?;
+            self.tail = L::pointers(last).as_ref().get_prev();
+
+            if let Some(prev) = L::pointers(last).as_ref().get_prev() {
+                L::pointers(prev).as_mut().set_next(None);
+            } else {
+                self.head = None;
+            }
+
+            L::pointers(last).as_mut().set_prev(None);
+            L::pointers(last).as_mut().set_next(None);
+
+            Some(L::from_raw(last))
+        }
+    }
+
+    /// Returns whether the linked list does not contain any node
+    pub(crate) fn is_empty(&self) -> bool {
+        if self.head.is_some() {
+            return false;
+        }
+
+        assert!(self.tail.is_none());
+        true
+    }
+
+    /// Removes the specified node from the list
+    ///
+    /// # Safety
+    ///
+    /// The caller **must** ensure that exactly one of the following is true:
+    /// - `node` is currently contained by `self`,
+    /// - `node` is not contained by any list,
+    /// - `node` is currently contained by some other `GuardedLinkedList` **and**
+    ///   the caller has an exclusive access to that list. This condition is
+    ///   used by the linked list in `sync::Notify`.
+    pub(crate) unsafe fn remove(&mut self, node: NonNull<L::Target>) -> Option<L::Handle> {
+        if let Some(prev) = L::pointers(node).as_ref().get_prev() {
+            debug_assert_eq!(L::pointers(prev).as_ref().get_next(), Some(node));
+            L::pointers(prev)
+                .as_mut()
+                .set_next(L::pointers(node).as_ref().get_next());
+        } else {
+            if self.head != Some(node) {
+                return None;
+            }
+
+            self.head = L::pointers(node).as_ref().get_next();
+        }
+
+        if let Some(next) = L::pointers(node).as_ref().get_next() {
+            debug_assert_eq!(L::pointers(next).as_ref().get_prev(), Some(node));
+            L::pointers(next)
+                .as_mut()
+                .set_prev(L::pointers(node).as_ref().get_prev());
+        } else {
+            // This might be the last item in the list
+            if self.tail != Some(node) {
+                return None;
+            }
+
+            self.tail = L::pointers(node).as_ref().get_prev();
+        }
+
+        L::pointers(node).as_mut().set_next(None);
+        L::pointers(node).as_mut().set_prev(None);
+
+        Some(L::from_raw(node))
+    }
+}
+
+impl<L: Link> fmt::Debug for LinkedList<L, L::Target> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("LinkedList")
+            .field("head", &self.head)
+            .field("tail", &self.tail)
+            .finish()
+    }
+}
+
+#[cfg(any(
+    feature = "fs",
+    feature = "rt",
+    all(unix, feature = "process"),
+    feature = "signal",
+    feature = "sync",
+))]
+impl<L: Link> LinkedList<L, L::Target> {
+    pub(crate) fn last(&self) -> Option<&L::Target> {
+        let tail = self.tail.as_ref()?;
+        unsafe { Some(&*tail.as_ptr()) }
+    }
+}
+
+impl<L: Link> Default for LinkedList<L, L::Target> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+// ===== impl DrainFilter =====
+
+cfg_io_driver_impl! {
+    pub(crate) struct DrainFilter<'a, T: Link, F> {
+        list: &'a mut LinkedList<T, T::Target>,
+        filter: F,
+        curr: Option<NonNull<T::Target>>,
+    }
+
+    impl<T: Link> LinkedList<T, T::Target> {
+        pub(crate) fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F>
+        where
+            F: FnMut(&T::Target) -> bool,
+        {
+            let curr = self.head;
+            DrainFilter {
+                curr,
+                filter,
+                list: self,
+            }
+        }
+    }
+
+    impl<'a, T, F> Iterator for DrainFilter<'a, T, F>
+    where
+        T: Link,
+        F: FnMut(&T::Target) -> bool,
+    {
+        type Item = T::Handle;
+
+        fn next(&mut self) -> Option<Self::Item> {
+            while let Some(curr) = self.curr {
+                // safety: the pointer references data contained by the list
+                self.curr = unsafe { T::pointers(curr).as_ref() }.get_next();
+
+                // safety: the value is still owned by the linked list.
+                if (self.filter)(unsafe { &mut *curr.as_ptr() }) {
+                    return unsafe { self.list.remove(curr) };
+                }
+            }
+
+            None
+        }
+    }
+}
+
+cfg_taskdump! {
+    impl<T: Link> LinkedList<T, T::Target> {
+        pub(crate) fn for_each<F>(&mut self, mut f: F)
+        where
+            F: FnMut(&T::Handle),
+        {
+            let mut next = self.head;
+
+            while let Some(curr) = next {
+                unsafe {
+                    let handle = ManuallyDrop::new(T::from_raw(curr));
+                    f(&handle);
+                    next = T::pointers(curr).as_ref().get_next();
+                }
+            }
+        }
+    }
+}
+
+// ===== impl GuardedLinkedList =====
+
+feature! {
+    #![any(
+        feature = "process",
+        feature = "sync",
+        feature = "rt",
+        feature = "signal",
+    )]
+
+    /// An intrusive linked list, but instead of keeping pointers to the head
+    /// and tail nodes, it uses a special guard node linked with those nodes.
+    /// It means that the list is circular and every pointer of a node from
+    /// the list is not `None`, including pointers from the guard node.
+    ///
+    /// If a list is empty, then both pointers of the guard node are pointing
+    /// at the guard node itself.
+    pub(crate) struct GuardedLinkedList<L, T> {
+        /// Pointer to the guard node.
+        guard: NonNull<T>,
+
+        /// Node type marker.
+        _marker: PhantomData<*const L>,
+    }
+
+    impl<L: Link> LinkedList<L, L::Target> {
+        /// Turns a linked list into the guarded version by linking the guard node
+        /// with the head and tail nodes. Like with other nodes, you should guarantee
+        /// that the guard node is pinned in memory.
+        pub(crate) fn into_guarded(self, guard_handle: L::Handle) -> GuardedLinkedList<L, L::Target> {
+            // `guard_handle` is a NonNull pointer, we don't have to care about dropping it.
+            let guard = L::as_raw(&guard_handle);
+
+            unsafe {
+                if let Some(head) = self.head {
+                    debug_assert!(L::pointers(head).as_ref().get_prev().is_none());
+                    L::pointers(head).as_mut().set_prev(Some(guard));
+                    L::pointers(guard).as_mut().set_next(Some(head));
+
+                    // The list is not empty, so the tail cannot be `None`.
+                    let tail = self.tail.unwrap();
+                    debug_assert!(L::pointers(tail).as_ref().get_next().is_none());
+                    L::pointers(tail).as_mut().set_next(Some(guard));
+                    L::pointers(guard).as_mut().set_prev(Some(tail));
+                } else {
+                    // The list is empty.
+                    L::pointers(guard).as_mut().set_prev(Some(guard));
+                    L::pointers(guard).as_mut().set_next(Some(guard));
+                }
+            }
+
+            GuardedLinkedList { guard, _marker: PhantomData }
+        }
+    }
+
+    impl<L: Link> GuardedLinkedList<L, L::Target> {
+        fn tail(&self) -> Option<NonNull<L::Target>> {
+            let tail_ptr = unsafe {
+                L::pointers(self.guard).as_ref().get_prev().unwrap()
+            };
+
+            // Compare the tail pointer with the address of the guard node itself.
+            // If the guard points at itself, then there are no other nodes and
+            // the list is considered empty.
+            if tail_ptr != self.guard {
+                Some(tail_ptr)
+            } else {
+                None
+            }
+        }
+
+        /// Removes the last element from a list and returns it, or None if it is
+        /// empty.
+        pub(crate) fn pop_back(&mut self) -> Option<L::Handle> {
+            unsafe {
+                let last = self.tail()?;
+                let before_last = L::pointers(last).as_ref().get_prev().unwrap();
+
+                L::pointers(self.guard).as_mut().set_prev(Some(before_last));
+                L::pointers(before_last).as_mut().set_next(Some(self.guard));
+
+                L::pointers(last).as_mut().set_prev(None);
+                L::pointers(last).as_mut().set_next(None);
+
+                Some(L::from_raw(last))
+            }
+        }
+    }
+}
+
+// ===== impl Pointers =====
+
+impl<T> Pointers<T> {
+    /// Create a new set of empty pointers
+    pub(crate) fn new() -> Pointers<T> {
+        Pointers {
+            inner: UnsafeCell::new(PointersInner {
+                prev: None,
+                next: None,
+                _pin: PhantomPinned,
+            }),
+        }
+    }
+
+    pub(crate) fn get_prev(&self) -> Option<NonNull<T>> {
+        // SAFETY: Field is accessed immutably through a reference.
+        unsafe { ptr::addr_of!((*self.inner.get()).prev).read() }
+    }
+    pub(crate) fn get_next(&self) -> Option<NonNull<T>> {
+        // SAFETY: Field is accessed immutably through a reference.
+        unsafe { ptr::addr_of!((*self.inner.get()).next).read() }
+    }
+
+    fn set_prev(&mut self, value: Option<NonNull<T>>) {
+        // SAFETY: Field is accessed mutably through a mutable reference.
+        unsafe {
+            ptr::addr_of_mut!((*self.inner.get()).prev).write(value);
+        }
+    }
+    fn set_next(&mut self, value: Option<NonNull<T>>) {
+        // SAFETY: Field is accessed mutably through a mutable reference.
+        unsafe {
+            ptr::addr_of_mut!((*self.inner.get()).next).write(value);
+        }
+    }
+}
+
+impl<T> fmt::Debug for Pointers<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let prev = self.get_prev();
+        let next = self.get_next();
+        f.debug_struct("Pointers")
+            .field("prev", &prev)
+            .field("next", &next)
+            .finish()
+    }
+}
+
+#[cfg(any(test, fuzzing))]
+#[cfg(not(loom))]
+pub(crate) mod tests {
+    use super::*;
+
+    use std::pin::Pin;
+
+    #[derive(Debug)]
+    #[repr(C)]
+    struct Entry {
+        pointers: Pointers<Entry>,
+        val: i32,
+    }
+
+    unsafe impl<'a> Link for &'a Entry {
+        type Handle = Pin<&'a Entry>;
+        type Target = Entry;
+
+        fn as_raw(handle: &Pin<&'_ Entry>) -> NonNull<Entry> {
+            NonNull::from(handle.get_ref())
+        }
+
+        unsafe fn from_raw(ptr: NonNull<Entry>) -> Pin<&'a Entry> {
+            Pin::new_unchecked(&*ptr.as_ptr())
+        }
+
+        unsafe fn pointers(target: NonNull<Entry>) -> NonNull<Pointers<Entry>> {
+            target.cast()
+        }
+    }
+
+    fn entry(val: i32) -> Pin<Box<Entry>> {
+        Box::pin(Entry {
+            pointers: Pointers::new(),
+            val,
+        })
+    }
+
+    fn ptr(r: &Pin<Box<Entry>>) -> NonNull<Entry> {
+        r.as_ref().get_ref().into()
+    }
+
+    fn collect_list(list: &mut LinkedList<&'_ Entry, <&'_ Entry as Link>::Target>) -> Vec<i32> {
+        let mut ret = vec![];
+
+        while let Some(entry) = list.pop_back() {
+            ret.push(entry.val);
+        }
+
+        ret
+    }
+
+    fn push_all<'a>(
+        list: &mut LinkedList<&'a Entry, <&'_ Entry as Link>::Target>,
+        entries: &[Pin<&'a Entry>],
+    ) {
+        for entry in entries.iter() {
+            list.push_front(*entry);
+        }
+    }
+
+    #[cfg(test)]
+    macro_rules! assert_clean {
+        ($e:ident) => {{
+            assert!($e.pointers.get_next().is_none());
+            assert!($e.pointers.get_prev().is_none());
+        }};
+    }
+
+    #[cfg(test)]
+    macro_rules! assert_ptr_eq {
+        ($a:expr, $b:expr) => {{
+            // Deal with mapping a Pin<&mut T> -> Option<NonNull<T>>
+            assert_eq!(Some($a.as_ref().get_ref().into()), $b)
+        }};
+    }
+
+    #[test]
+    fn const_new() {
+        const _: LinkedList<&Entry, <&Entry as Link>::Target> = LinkedList::new();
+    }
+
+    #[test]
+    fn push_and_drain() {
+        let a = entry(5);
+        let b = entry(7);
+        let c = entry(31);
+
+        let mut list = LinkedList::new();
+        assert!(list.is_empty());
+
+        list.push_front(a.as_ref());
+        assert!(!list.is_empty());
+        list.push_front(b.as_ref());
+        list.push_front(c.as_ref());
+
+        let items: Vec<i32> = collect_list(&mut list);
+        assert_eq!([5, 7, 31].to_vec(), items);
+
+        assert!(list.is_empty());
+    }
+
+    #[test]
+    fn push_pop_push_pop() {
+        let a = entry(5);
+        let b = entry(7);
+
+        let mut list = LinkedList::<&Entry, <&Entry as Link>::Target>::new();
+
+        list.push_front(a.as_ref());
+
+        let entry = list.pop_back().unwrap();
+        assert_eq!(5, entry.val);
+        assert!(list.is_empty());
+
+        list.push_front(b.as_ref());
+
+        let entry = list.pop_back().unwrap();
+        assert_eq!(7, entry.val);
+
+        assert!(list.is_empty());
+        assert!(list.pop_back().is_none());
+    }
+
+    #[test]
+    fn remove_by_address() {
+        let a = entry(5);
+        let b = entry(7);
+        let c = entry(31);
+
+        unsafe {
+            // Remove first
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[c.as_ref(), b.as_ref(), a.as_ref()]);
+            assert!(list.remove(ptr(&a)).is_some());
+            assert_clean!(a);
+            // `a` should be no longer there and can't be removed twice
+            assert!(list.remove(ptr(&a)).is_none());
+            assert!(!list.is_empty());
+
+            assert!(list.remove(ptr(&b)).is_some());
+            assert_clean!(b);
+            // `b` should be no longer there and can't be removed twice
+            assert!(list.remove(ptr(&b)).is_none());
+            assert!(!list.is_empty());
+
+            assert!(list.remove(ptr(&c)).is_some());
+            assert_clean!(c);
+            // `b` should be no longer there and can't be removed twice
+            assert!(list.remove(ptr(&c)).is_none());
+            assert!(list.is_empty());
+        }
+
+        unsafe {
+            // Remove middle
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[c.as_ref(), b.as_ref(), a.as_ref()]);
+
+            assert!(list.remove(ptr(&a)).is_some());
+            assert_clean!(a);
+
+            assert_ptr_eq!(b, list.head);
+            assert_ptr_eq!(c, b.pointers.get_next());
+            assert_ptr_eq!(b, c.pointers.get_prev());
+
+            let items = collect_list(&mut list);
+            assert_eq!([31, 7].to_vec(), items);
+        }
+
+        unsafe {
+            // Remove middle
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[c.as_ref(), b.as_ref(), a.as_ref()]);
+
+            assert!(list.remove(ptr(&b)).is_some());
+            assert_clean!(b);
+
+            assert_ptr_eq!(c, a.pointers.get_next());
+            assert_ptr_eq!(a, c.pointers.get_prev());
+
+            let items = collect_list(&mut list);
+            assert_eq!([31, 5].to_vec(), items);
+        }
+
+        unsafe {
+            // Remove last
+            // Remove middle
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[c.as_ref(), b.as_ref(), a.as_ref()]);
+
+            assert!(list.remove(ptr(&c)).is_some());
+            assert_clean!(c);
+
+            assert!(b.pointers.get_next().is_none());
+            assert_ptr_eq!(b, list.tail);
+
+            let items = collect_list(&mut list);
+            assert_eq!([7, 5].to_vec(), items);
+        }
+
+        unsafe {
+            // Remove first of two
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[b.as_ref(), a.as_ref()]);
+
+            assert!(list.remove(ptr(&a)).is_some());
+
+            assert_clean!(a);
+
+            // a should be no longer there and can't be removed twice
+            assert!(list.remove(ptr(&a)).is_none());
+
+            assert_ptr_eq!(b, list.head);
+            assert_ptr_eq!(b, list.tail);
+
+            assert!(b.pointers.get_next().is_none());
+            assert!(b.pointers.get_prev().is_none());
+
+            let items = collect_list(&mut list);
+            assert_eq!([7].to_vec(), items);
+        }
+
+        unsafe {
+            // Remove last of two
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[b.as_ref(), a.as_ref()]);
+
+            assert!(list.remove(ptr(&b)).is_some());
+
+            assert_clean!(b);
+
+            assert_ptr_eq!(a, list.head);
+            assert_ptr_eq!(a, list.tail);
+
+            assert!(a.pointers.get_next().is_none());
+            assert!(a.pointers.get_prev().is_none());
+
+            let items = collect_list(&mut list);
+            assert_eq!([5].to_vec(), items);
+        }
+
+        unsafe {
+            // Remove last item
+            let mut list = LinkedList::new();
+
+            push_all(&mut list, &[a.as_ref()]);
+
+            assert!(list.remove(ptr(&a)).is_some());
+            assert_clean!(a);
+
+            assert!(list.head.is_none());
+            assert!(list.tail.is_none());
+            let items = collect_list(&mut list);
+            assert!(items.is_empty());
+        }
+
+        unsafe {
+            // Remove missing
+            let mut list = LinkedList::<&Entry, <&Entry as Link>::Target>::new();
+
+            list.push_front(b.as_ref());
+            list.push_front(a.as_ref());
+
+            assert!(list.remove(ptr(&c)).is_none());
+        }
+    }
+
+    /// This is a fuzz test. You run it by entering `cargo fuzz run fuzz_linked_list` in CLI in `/tokio/` module.
+    #[cfg(fuzzing)]
+    pub fn fuzz_linked_list(ops: &[u8]) {
+        enum Op {
+            Push,
+            Pop,
+            Remove(usize),
+        }
+        use std::collections::VecDeque;
+
+        let ops = ops
+            .iter()
+            .map(|i| match i % 3u8 {
+                0 => Op::Push,
+                1 => Op::Pop,
+                2 => Op::Remove((i / 3u8) as usize),
+                _ => unreachable!(),
+            })
+            .collect::<Vec<_>>();
+
+        let mut ll = LinkedList::<&Entry, <&Entry as Link>::Target>::new();
+        let mut reference = VecDeque::new();
+
+        let entries: Vec<_> = (0..ops.len()).map(|i| entry(i as i32)).collect();
+
+        for (i, op) in ops.iter().enumerate() {
+            match op {
+                Op::Push => {
+                    reference.push_front(i as i32);
+                    assert_eq!(entries[i].val, i as i32);
+
+                    ll.push_front(entries[i].as_ref());
+                }
+                Op::Pop => {
+                    if reference.is_empty() {
+                        assert!(ll.is_empty());
+                        continue;
+                    }
+
+                    let v = reference.pop_back();
+                    assert_eq!(v, ll.pop_back().map(|v| v.val));
+                }
+                Op::Remove(n) => {
+                    if reference.is_empty() {
+                        assert!(ll.is_empty());
+                        continue;
+                    }
+
+                    let idx = n % reference.len();
+                    let expect = reference.remove(idx).unwrap();
+
+                    unsafe {
+                        let entry = ll.remove(ptr(&entries[expect as usize])).unwrap();
+                        assert_eq!(expect, entry.val);
+                    }
+                }
+            }
+        }
+    }
+}

vendor/tokio/src/util/markers.rs

@@ -0,0 +1,9 @@
+/// Marker for types that are `Sync` but not `Send`
+#[allow(dead_code)]
+pub(crate) struct SyncNotSend(#[allow(dead_code)] *mut ());
+
+unsafe impl Sync for SyncNotSend {}
+
+cfg_rt! {
+    pub(crate) struct NotSendOrSync(#[allow(dead_code)] *mut ());
+}

vendor/tokio/src/util/memchr.rs

@@ -0,0 +1,102 @@
+//! Search for a byte in a byte array using libc.
+//!
+//! When nothing pulls in libc, then just use a trivial implementation. Note
+//! that we only depend on libc on unix.
+
+#[cfg(not(all(unix, feature = "libc")))]
+fn memchr_inner(needle: u8, haystack: &[u8]) -> Option<usize> {
+    haystack.iter().position(|val| needle == *val)
+}
+
+#[cfg(all(unix, feature = "libc"))]
+fn memchr_inner(needle: u8, haystack: &[u8]) -> Option<usize> {
+    let start = haystack.as_ptr();
+
+    // SAFETY: `start` is valid for `haystack.len()` bytes.
+    let ptr = (unsafe { libc::memchr(start.cast(), needle as _, haystack.len()) })
+        .cast::<u8>()
+        .cast_const();
+
+    if ptr.is_null() {
+        None
+    } else {
+        // SAFETY: `ptr` will always be in bounds, since libc guarantees that the ptr will either
+        //          be to an element inside the array or the ptr will be null
+        //          since the ptr is in bounds the offset must also always be non null
+        //          and there can't be more than isize::MAX elements inside an array
+        //          as rust guarantees that the maximum number of bytes a allocation
+        //          may occupy is isize::MAX
+        unsafe {
+            // TODO(MSRV 1.87): When bumping MSRV, switch to `ptr.byte_offset_from_unsigned(start)`.
+            Some(usize::try_from(ptr.offset_from(start)).unwrap_unchecked())
+        }
+    }
+}
+
+pub(crate) fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
+    let index = memchr_inner(needle, haystack)?;
+
+    // SAFETY: `memchr_inner` returns Some(index) and in that case index must point to an element in haystack
+    //         or `memchr_inner` None which is guarded by the `?` operator above
+    //         therefore the index must **always** point to an element in the array
+    //         and so this indexing operation is safe
+    // TODO(MSRV 1.81): When bumping MSRV, switch to `std::hint::assert_unchecked(haystack.get(..=index).is_some());`
+    unsafe {
+        if haystack.get(..=index).is_none() {
+            std::hint::unreachable_unchecked()
+        }
+    }
+
+    Some(index)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::memchr;
+
+    #[test]
+    fn memchr_test() {
+        let haystack = b"123abc456\0\xffabc\n";
+
+        assert_eq!(memchr(b'1', haystack), Some(0));
+        assert_eq!(memchr(b'2', haystack), Some(1));
+        assert_eq!(memchr(b'3', haystack), Some(2));
+        assert_eq!(memchr(b'4', haystack), Some(6));
+        assert_eq!(memchr(b'5', haystack), Some(7));
+        assert_eq!(memchr(b'6', haystack), Some(8));
+        assert_eq!(memchr(b'7', haystack), None);
+        assert_eq!(memchr(b'a', haystack), Some(3));
+        assert_eq!(memchr(b'b', haystack), Some(4));
+        assert_eq!(memchr(b'c', haystack), Some(5));
+        assert_eq!(memchr(b'd', haystack), None);
+        assert_eq!(memchr(b'A', haystack), None);
+        assert_eq!(memchr(0, haystack), Some(9));
+        assert_eq!(memchr(0xff, haystack), Some(10));
+        assert_eq!(memchr(0xfe, haystack), None);
+        assert_eq!(memchr(1, haystack), None);
+        assert_eq!(memchr(b'\n', haystack), Some(14));
+        assert_eq!(memchr(b'\r', haystack), None);
+    }
+
+    #[test]
+    fn memchr_all() {
+        let mut arr = Vec::new();
+        for b in 0..=255 {
+            arr.push(b);
+        }
+        for b in 0..=255 {
+            assert_eq!(memchr(b, &arr), Some(b as usize));
+        }
+        arr.reverse();
+        for b in 0..=255 {
+            assert_eq!(memchr(b, &arr), Some(255 - b as usize));
+        }
+    }
+
+    #[test]
+    fn memchr_empty() {
+        for b in 0..=255 {
+            assert_eq!(memchr(b, b""), None);
+        }
+    }
+}

vendor/tokio/src/util/metric_atomics.rs

@@ -0,0 +1,81 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+cfg_64bit_metrics! {
+    use std::sync::atomic::AtomicU64;
+}
+
+/// `AtomicU64` that is a no-op on platforms without 64-bit atomics
+///
+/// When used on platforms without 64-bit atomics, writes to this are no-ops.
+/// The `load` method is only defined when 64-bit atomics are available.
+#[derive(Debug, Default)]
+pub(crate) struct MetricAtomicU64 {
+    #[cfg(target_has_atomic = "64")]
+    value: AtomicU64,
+}
+
+// some of these are currently only used behind cfg_unstable
+#[allow(dead_code)]
+impl MetricAtomicU64 {
+    // Load is only defined when supported
+    cfg_64bit_metrics! {
+        pub(crate) fn load(&self, ordering: Ordering) -> u64 {
+            self.value.load(ordering)
+        }
+    }
+
+    cfg_64bit_metrics! {
+        pub(crate) fn store(&self, val: u64, ordering: Ordering) {
+            self.value.store(val, ordering)
+        }
+
+        pub(crate) fn new(value: u64) -> Self {
+            Self { value: AtomicU64::new(value) }
+        }
+
+        pub(crate) fn add(&self, value: u64, ordering: Ordering) {
+            self.value.fetch_add(value, ordering);
+        }
+    }
+
+    cfg_no_64bit_metrics! {
+        pub(crate) fn store(&self, _val: u64, _ordering: Ordering) { }
+        // on platforms without 64-bit atomics, fetch-add returns unit
+        pub(crate) fn add(&self, _value: u64, _ordering: Ordering) {  }
+        pub(crate) fn new(_value: u64) -> Self { Self { } }
+    }
+}
+
+#[cfg_attr(not(all(tokio_unstable, feature = "rt")), allow(dead_code))]
+/// `AtomicUsize` for use in metrics.
+///
+/// This exposes simplified APIs for use in metrics & uses `std::sync` instead of Loom to avoid polluting loom logs with metric information.
+#[derive(Debug, Default)]
+pub(crate) struct MetricAtomicUsize {
+    value: AtomicUsize,
+}
+
+#[cfg_attr(not(all(tokio_unstable, feature = "rt")), allow(dead_code))]
+impl MetricAtomicUsize {
+    pub(crate) fn new(value: usize) -> Self {
+        Self {
+            value: AtomicUsize::new(value),
+        }
+    }
+
+    pub(crate) fn load(&self, ordering: Ordering) -> usize {
+        self.value.load(ordering)
+    }
+
+    pub(crate) fn store(&self, val: usize, ordering: Ordering) {
+        self.value.store(val, ordering)
+    }
+
+    pub(crate) fn increment(&self) -> usize {
+        self.value.fetch_add(1, Ordering::Relaxed)
+    }
+
+    pub(crate) fn decrement(&self) -> usize {
+        self.value.fetch_sub(1, Ordering::Relaxed)
+    }
+}

vendor/tokio/src/util/mod.rs

@@ -0,0 +1,110 @@
+cfg_io_driver! {
+    pub(crate) mod bit;
+}
+
+#[cfg(feature = "fs")]
+pub(crate) mod as_ref;
+
+#[cfg(feature = "rt")]
+pub(crate) mod atomic_cell;
+
+#[cfg(feature = "net")]
+mod blocking_check;
+#[cfg(feature = "net")]
+#[allow(unused_imports)]
+pub(crate) use blocking_check::check_socket_for_blocking;
+
+pub(crate) mod metric_atomics;
+
+#[cfg(any(
+    // io driver uses `WakeList` directly
+    feature = "net",
+    feature = "process",
+    // `sync` enables `Notify` and `batch_semaphore`, which require `WakeList`.
+    feature = "sync",
+    // `fs` uses `batch_semaphore`, which requires `WakeList`.
+    feature = "fs",
+    // rt and signal use `Notify`, which requires `WakeList`.
+    feature = "rt",
+    feature = "signal",
+    // time driver uses `WakeList` in `Handle::process_at_time`.
+    feature = "time",
+))]
+mod wake_list;
+#[cfg(any(
+    feature = "net",
+    feature = "process",
+    feature = "sync",
+    feature = "fs",
+    feature = "rt",
+    feature = "signal",
+    feature = "time",
+))]
+pub(crate) use wake_list::WakeList;
+
+#[cfg(any(
+    feature = "fs",
+    feature = "net",
+    feature = "process",
+    feature = "rt",
+    feature = "sync",
+    feature = "signal",
+    feature = "time",
+    fuzzing,
+))]
+pub(crate) mod linked_list;
+
+cfg_rt! {
+    pub(crate) mod sharded_list;
+}
+
+#[cfg(any(feature = "rt", feature = "macros"))]
+pub(crate) mod rand;
+
+cfg_rt! {
+    mod idle_notified_set;
+    pub(crate) use idle_notified_set::IdleNotifiedSet;
+
+    pub(crate) use self::rand::RngSeedGenerator;
+
+    mod wake;
+    pub(crate) use wake::WakerRef;
+    pub(crate) use wake::{waker_ref, Wake};
+
+    mod sync_wrapper;
+    pub(crate) use sync_wrapper::SyncWrapper;
+
+    mod rc_cell;
+    pub(crate) use rc_cell::RcCell;
+}
+
+cfg_rt_multi_thread! {
+    mod try_lock;
+    pub(crate) use try_lock::TryLock;
+}
+
+pub(crate) mod trace;
+
+#[cfg(feature = "fs")]
+pub(crate) mod typeid;
+
+pub(crate) mod error;
+
+#[cfg(feature = "io-util")]
+pub(crate) mod memchr;
+
+pub(crate) mod markers;
+
+pub(crate) mod cacheline;
+
+cfg_io_driver_impl! {
+    pub(crate) mod ptr_expose;
+}
+
+use std::{ops::DerefMut, pin::Pin};
+
+/// Copy of [`std::pin::Pin::as_deref_mut`].
+// TODO: Remove this once we bump the MSRV to 1.84.
+pub(crate) fn pin_as_deref_mut<P: DerefMut>(ptr: Pin<&mut Pin<P>>) -> Pin<&mut P::Target> {
+    unsafe { ptr.get_unchecked_mut() }.as_mut()
+}

vendor/tokio/src/util/ptr_expose.rs

@@ -0,0 +1,74 @@
+//! Utility for helping miri understand our exposed pointers.
+//!
+//! During normal execution, this module is equivalent to pointer casts. However, when running
+//! under miri, pointer casts are replaced with lookups in a hash map. This makes Tokio compatible
+//! with strict provenance when running under miri (which comes with a performance cost).
+
+use std::marker::PhantomData;
+#[cfg(miri)]
+use {crate::loom::sync::Mutex, std::collections::BTreeMap};
+
+pub(crate) struct PtrExposeDomain<T> {
+    #[cfg(miri)]
+    map: Mutex<BTreeMap<usize, *const T>>,
+    _phantom: PhantomData<T>,
+}
+
+// SAFETY: Actually using the pointers is unsafe, so it's sound to transfer them across threads.
+unsafe impl<T> Sync for PtrExposeDomain<T> {}
+
+impl<T> PtrExposeDomain<T> {
+    pub(crate) const fn new() -> Self {
+        Self {
+            #[cfg(miri)]
+            map: Mutex::const_new(BTreeMap::new()),
+            _phantom: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn expose_provenance(&self, ptr: *const T) -> usize {
+        #[cfg(miri)]
+        {
+            let addr: usize = ptr.addr();
+            self.map.lock().insert(addr, ptr);
+            addr
+        }
+
+        #[cfg(not(miri))]
+        {
+            ptr as usize
+        }
+    }
+
+    #[inline]
+    #[allow(clippy::wrong_self_convention)] // mirrors std name
+    pub(crate) fn from_exposed_addr(&self, addr: usize) -> *const T {
+        #[cfg(miri)]
+        {
+            let maybe_ptr = self.map.lock().get(&addr).copied();
+
+            // SAFETY: Intentionally trigger a miri failure if the provenance we want is not
+            // exposed.
+            unsafe { maybe_ptr.unwrap_unchecked() }
+        }
+
+        #[cfg(not(miri))]
+        {
+            addr as *const T
+        }
+    }
+
+    #[inline]
+    pub(crate) fn unexpose_provenance(&self, _ptr: *const T) {
+        #[cfg(miri)]
+        {
+            let addr: usize = _ptr.addr();
+            let maybe_ptr = self.map.lock().remove(&addr);
+
+            // SAFETY: Intentionally trigger a miri failure if the provenance we want is not
+            // exposed.
+            unsafe { maybe_ptr.unwrap_unchecked() };
+        }
+    }
+}

vendor/tokio/src/util/rand.rs

@@ -0,0 +1,95 @@
+cfg_rt! {
+    mod rt;
+    pub(crate) use rt::RngSeedGenerator;
+
+    cfg_unstable! {
+        mod rt_unstable;
+    }
+}
+
+/// A seed for random number generation.
+///
+/// In order to make certain functions within a runtime deterministic, a seed
+/// can be specified at the time of creation.
+#[allow(unreachable_pub)]
+#[derive(Clone, Debug)]
+pub struct RngSeed {
+    s: u32,
+    r: u32,
+}
+
+/// Fast random number generate.
+///
+/// Implement `xorshift64+`: 2 32-bit `xorshift` sequences added together.
+/// Shift triplet `[17,7,16]` was calculated as indicated in Marsaglia's
+/// `Xorshift` paper: <https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf>
+/// This generator passes the SmallCrush suite, part of TestU01 framework:
+/// <http://simul.iro.umontreal.ca/testu01/tu01.html>
+#[derive(Clone, Copy, Debug)]
+pub(crate) struct FastRand {
+    one: u32,
+    two: u32,
+}
+
+impl RngSeed {
+    /// Creates a random seed using loom internally.
+    pub(crate) fn new() -> Self {
+        Self::from_u64(crate::loom::rand::seed())
+    }
+
+    fn from_u64(seed: u64) -> Self {
+        let one = (seed >> 32) as u32;
+        let mut two = seed as u32;
+
+        if two == 0 {
+            // This value cannot be zero
+            two = 1;
+        }
+
+        Self::from_pair(one, two)
+    }
+
+    fn from_pair(s: u32, r: u32) -> Self {
+        Self { s, r }
+    }
+}
+
+impl FastRand {
+    /// Initialize a new fast random number generator using the default source of entropy.
+    pub(crate) fn new() -> FastRand {
+        FastRand::from_seed(RngSeed::new())
+    }
+
+    /// Initializes a new, thread-local, fast random number generator.
+    pub(crate) fn from_seed(seed: RngSeed) -> FastRand {
+        FastRand {
+            one: seed.s,
+            two: seed.r,
+        }
+    }
+
+    #[cfg(any(
+        feature = "macros",
+        feature = "rt-multi-thread",
+        all(feature = "sync", feature = "rt")
+    ))]
+    pub(crate) fn fastrand_n(&mut self, n: u32) -> u32 {
+        // This is similar to fastrand() % n, but faster.
+        // See https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+        let mul = (self.fastrand() as u64).wrapping_mul(n as u64);
+        (mul >> 32) as u32
+    }
+
+    fn fastrand(&mut self) -> u32 {
+        let mut s1 = self.one;
+        let s0 = self.two;
+
+        s1 ^= s1 << 17;
+        s1 = s1 ^ s0 ^ s1 >> 7 ^ s0 >> 16;
+
+        self.one = s0;
+        self.two = s1;
+
+        s0.wrapping_add(s1)
+    }
+}

vendor/tokio/src/util/rand/rt.rs

@@ -0,0 +1,61 @@
+use super::{FastRand, RngSeed};
+
+use std::sync::Mutex;
+
+/// A deterministic generator for seeds (and other generators).
+///
+/// Given the same initial seed, the generator will output the same sequence of seeds.
+///
+/// Since the seed generator will be kept in a runtime handle, we need to wrap `FastRand`
+/// in a Mutex to make it thread safe. Different to the `FastRand` that we keep in a
+/// thread local store, the expectation is that seed generation will not need to happen
+/// very frequently, so the cost of the mutex should be minimal.
+#[derive(Debug)]
+pub(crate) struct RngSeedGenerator {
+    /// Internal state for the seed generator. We keep it in a Mutex so that we can safely
+    /// use it across multiple threads.
+    state: Mutex<FastRand>,
+}
+
+impl RngSeedGenerator {
+    /// Returns a new generator from the provided seed.
+    pub(crate) fn new(seed: RngSeed) -> Self {
+        Self {
+            state: Mutex::new(FastRand::from_seed(seed)),
+        }
+    }
+
+    /// Returns the next seed in the sequence.
+    pub(crate) fn next_seed(&self) -> RngSeed {
+        let mut rng = self
+            .state
+            .lock()
+            .expect("RNG seed generator is internally corrupt");
+
+        let s = rng.fastrand();
+        let r = rng.fastrand();
+
+        RngSeed::from_pair(s, r)
+    }
+
+    /// Directly creates a generator using the next seed.
+    pub(crate) fn next_generator(&self) -> Self {
+        RngSeedGenerator::new(self.next_seed())
+    }
+}
+
+impl FastRand {
+    /// Replaces the state of the random number generator with the provided seed, returning
+    /// the seed that represents the previous state of the random number generator.
+    ///
+    /// The random number generator will become equivalent to one created with
+    /// the same seed.
+    pub(crate) fn replace_seed(&mut self, seed: RngSeed) -> RngSeed {
+        let old_seed = RngSeed::from_pair(self.one, self.two);
+
+        self.one = seed.s;
+        self.two = seed.r;
+
+        old_seed
+    }
+}

vendor/tokio/src/util/rand/rt_unstable.rs

@@ -0,0 +1,20 @@
+use super::RngSeed;
+
+use std::collections::hash_map::DefaultHasher;
+use std::hash::Hasher;
+
+impl RngSeed {
+    /// Generates a seed from the provided byte slice.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use tokio::runtime::RngSeed;
+    /// let seed = RngSeed::from_bytes(b"make me a seed");
+    /// ```
+    pub fn from_bytes(bytes: &[u8]) -> Self {
+        let mut hasher = DefaultHasher::default();
+        hasher.write(bytes);
+        Self::from_u64(hasher.finish())
+    }
+}

vendor/tokio/src/util/rc_cell.rs

@@ -0,0 +1,57 @@
+use crate::loom::cell::UnsafeCell;
+
+use std::rc::Rc;
+
+/// This is exactly like `Cell<Option<Rc<T>>>`, except that it provides a `get`
+/// method even though `Rc` is not `Copy`.
+pub(crate) struct RcCell<T> {
+    inner: UnsafeCell<Option<Rc<T>>>,
+}
+
+impl<T> RcCell<T> {
+    #[cfg(not(all(loom, test)))]
+    pub(crate) const fn new() -> Self {
+        Self {
+            inner: UnsafeCell::new(None),
+        }
+    }
+
+    // The UnsafeCell in loom does not have a const `new` fn.
+    #[cfg(all(loom, test))]
+    pub(crate) fn new() -> Self {
+        Self {
+            inner: UnsafeCell::new(None),
+        }
+    }
+
+    /// Safety: This method may not be called recursively.
+    #[inline]
+    unsafe fn with_inner<F, R>(&self, f: F) -> R
+    where
+        F: FnOnce(&mut Option<Rc<T>>) -> R,
+    {
+        // safety: This type is not Sync, so concurrent calls of this method
+        // cannot happen. Furthermore, the caller guarantees that the method is
+        // not called recursively. Finally, this is the only place that can
+        // create mutable references to the inner Rc. This ensures that any
+        // mutable references created here are exclusive.
+        self.inner.with_mut(|ptr| f(unsafe { &mut *ptr }))
+    }
+
+    pub(crate) fn get(&self) -> Option<Rc<T>> {
+        // safety: The `Rc::clone` method will not call any unknown user-code,
+        // so it will not result in a recursive call to `with_inner`.
+        unsafe { self.with_inner(|rc| rc.clone()) }
+    }
+
+    pub(crate) fn replace(&self, val: Option<Rc<T>>) -> Option<Rc<T>> {
+        // safety: No destructors or other unknown user-code will run inside the
+        // `with_inner` call, so no recursive call to `with_inner` can happen.
+        unsafe { self.with_inner(|rc| std::mem::replace(rc, val)) }
+    }
+
+    pub(crate) fn set(&self, val: Option<Rc<T>>) {
+        let old = self.replace(val);
+        drop(old);
+    }
+}

vendor/tokio/src/util/sharded_list.rs

@@ -0,0 +1,164 @@
+use std::ptr::NonNull;
+use std::sync::atomic::Ordering;
+
+use crate::loom::sync::{Mutex, MutexGuard};
+use crate::util::metric_atomics::{MetricAtomicU64, MetricAtomicUsize};
+
+use super::linked_list::{Link, LinkedList};
+
+/// An intrusive linked list supporting highly concurrent updates.
+///
+/// It currently relies on `LinkedList`, so it is the caller's
+/// responsibility to ensure the list is empty before dropping it.
+///
+/// Note: Due to its inner sharded design, the order of nodes cannot be guaranteed.
+pub(crate) struct ShardedList<L, T> {
+    lists: Box<[Mutex<LinkedList<L, T>>]>,
+    added: MetricAtomicU64,
+    count: MetricAtomicUsize,
+    shard_mask: usize,
+}
+
+/// Determines which linked list an item should be stored in.
+///
+/// # Safety
+///
+/// Implementations must guarantee that the id of an item does not change from
+/// call to call.
+pub(crate) unsafe trait ShardedListItem: Link {
+    /// # Safety
+    ///
+    /// The provided pointer must point at a valid list item.
+    unsafe fn get_shard_id(target: NonNull<Self::Target>) -> usize;
+}
+
+impl<L, T> ShardedList<L, T> {
+    /// Creates a new and empty sharded linked list with the specified size.
+    pub(crate) fn new(sharded_size: usize) -> Self {
+        assert!(sharded_size.is_power_of_two());
+
+        let shard_mask = sharded_size - 1;
+        let mut lists = Vec::with_capacity(sharded_size);
+        for _ in 0..sharded_size {
+            lists.push(Mutex::new(LinkedList::<L, T>::new()))
+        }
+        Self {
+            lists: lists.into_boxed_slice(),
+            added: MetricAtomicU64::new(0),
+            count: MetricAtomicUsize::new(0),
+            shard_mask,
+        }
+    }
+}
+
+/// Used to get the lock of shard.
+pub(crate) struct ShardGuard<'a, L, T> {
+    lock: MutexGuard<'a, LinkedList<L, T>>,
+    added: &'a MetricAtomicU64,
+    count: &'a MetricAtomicUsize,
+    id: usize,
+}
+
+impl<L: ShardedListItem> ShardedList<L, L::Target> {
+    /// Removes the last element from a list specified by `shard_id` and returns it, or None if it is
+    /// empty.
+    pub(crate) fn pop_back(&self, shard_id: usize) -> Option<L::Handle> {
+        let mut lock = self.shard_inner(shard_id);
+        let node = lock.pop_back();
+        if node.is_some() {
+            self.count.decrement();
+        }
+        node
+    }
+
+    /// Removes the specified node from the list.
+    ///
+    /// # Safety
+    ///
+    /// The caller **must** ensure that exactly one of the following is true:
+    /// - `node` is currently contained by `self`,
+    /// - `node` is not contained by any list,
+    /// - `node` is currently contained by some other `GuardedLinkedList`.
+    pub(crate) unsafe fn remove(&self, node: NonNull<L::Target>) -> Option<L::Handle> {
+        let id = unsafe { L::get_shard_id(node) };
+        let mut lock = self.shard_inner(id);
+        // SAFETY: Since the shard id cannot change, it's not possible for this node
+        // to be in any other list of the same sharded list.
+        let node = unsafe { lock.remove(node) };
+        if node.is_some() {
+            self.count.decrement();
+        }
+        node
+    }
+
+    /// Gets the lock of `ShardedList`, makes us have the write permission.
+    pub(crate) fn lock_shard(&self, val: &L::Handle) -> ShardGuard<'_, L, L::Target> {
+        let id = unsafe { L::get_shard_id(L::as_raw(val)) };
+        ShardGuard {
+            lock: self.shard_inner(id),
+            added: &self.added,
+            count: &self.count,
+            id,
+        }
+    }
+
+    /// Gets the count of elements in this list.
+    pub(crate) fn len(&self) -> usize {
+        self.count.load(Ordering::Relaxed)
+    }
+
+    cfg_unstable_metrics! {
+        cfg_64bit_metrics! {
+            /// Gets the total number of elements added to this list.
+            pub(crate) fn added(&self) -> u64 {
+                self.added.load(Ordering::Relaxed)
+            }
+        }
+    }
+
+    /// Returns whether the linked list does not contain any node.
+    pub(crate) fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Gets the shard size of this `SharedList`.
+    ///
+    /// Used to help us to decide the parameter `shard_id` of the `pop_back` method.
+    pub(crate) fn shard_size(&self) -> usize {
+        self.shard_mask + 1
+    }
+
+    #[inline]
+    fn shard_inner(&self, id: usize) -> MutexGuard<'_, LinkedList<L, <L as Link>::Target>> {
+        // Safety: This modulo operation ensures that the index is not out of bounds.
+        unsafe { self.lists.get_unchecked(id & self.shard_mask).lock() }
+    }
+}
+
+impl<'a, L: ShardedListItem> ShardGuard<'a, L, L::Target> {
+    /// Push a value to this shard.
+    pub(crate) fn push(mut self, val: L::Handle) {
+        let id = unsafe { L::get_shard_id(L::as_raw(&val)) };
+        assert_eq!(id, self.id);
+        self.lock.push_front(val);
+        self.added.add(1, Ordering::Relaxed);
+        self.count.increment();
+    }
+}
+
+cfg_taskdump! {
+    impl<L: ShardedListItem> ShardedList<L, L::Target> {
+        pub(crate) fn for_each<F>(&self, mut f: F)
+        where
+            F: FnMut(&L::Handle),
+        {
+            let mut guards = Vec::with_capacity(self.lists.len());
+            for list in self.lists.iter() {
+                guards.push(list.lock());
+            }
+            for g in &mut guards {
+                g.for_each(&mut f);
+            }
+        }
+    }
+}

vendor/tokio/src/util/sync_wrapper.rs

@@ -0,0 +1,37 @@
+//! This module contains a type that can make `Send + !Sync` types `Sync` by
+//! disallowing all immutable access to the value.
+//!
+//! A similar primitive is provided in the `sync_wrapper` crate.
+
+use std::any::Any;
+
+pub(crate) struct SyncWrapper<T> {
+    value: T,
+}
+
+// safety: The SyncWrapper being send allows you to send the inner value across
+// thread boundaries.
+unsafe impl<T: Send> Send for SyncWrapper<T> {}
+
+// safety: An immutable reference to a SyncWrapper is useless, so moving such an
+// immutable reference across threads is safe.
+unsafe impl<T> Sync for SyncWrapper<T> {}
+
+impl<T> SyncWrapper<T> {
+    pub(crate) fn new(value: T) -> Self {
+        Self { value }
+    }
+
+    pub(crate) fn into_inner(self) -> T {
+        self.value
+    }
+}
+
+impl SyncWrapper<Box<dyn Any + Send>> {
+    /// Attempt to downcast using `Any::downcast_ref()` to a type that is known to be `Sync`.
+    pub(crate) fn downcast_ref_sync<T: Any + Sync>(&self) -> Option<&T> {
+        // SAFETY: if the downcast fails, the inner value is not touched,
+        // so no thread-safety violation can occur.
+        self.value.downcast_ref()
+    }
+}

vendor/tokio/src/util/trace.rs

@@ -0,0 +1,191 @@
+cfg_rt! {
+    use std::marker::PhantomData;
+
+    #[derive(Copy, Clone)]
+    pub(crate) struct SpawnMeta<'a> {
+        /// The name of the task
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        pub(crate) name: Option<&'a str>,
+        /// The original size of the future or function being spawned
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        pub(crate) original_size: usize,
+        /// The source code location where the task was spawned.
+        ///
+        /// This is wrapped in a type that may be empty when `tokio_unstable` is
+        /// not enabled.
+        pub(crate) spawned_at: crate::runtime::task::SpawnLocation,
+        _pd: PhantomData<&'a ()>,
+    }
+
+    impl<'a> SpawnMeta<'a> {
+        /// Create new spawn meta with a name and original size (before possible auto-boxing)
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        #[track_caller]
+        pub(crate) fn new(name: Option<&'a str>, original_size: usize) -> Self {
+            Self {
+                name,
+                original_size,
+                spawned_at: crate::runtime::task::SpawnLocation::capture(),
+                _pd: PhantomData,
+            }
+        }
+
+        /// Create a new unnamed spawn meta with the original size (before possible auto-boxing)
+        #[track_caller]
+        pub(crate) fn new_unnamed(original_size: usize) -> Self {
+            #[cfg(not(all(tokio_unstable, feature = "tracing")))]
+            let _original_size = original_size;
+
+            Self {
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                name: None,
+                #[cfg(all(tokio_unstable, feature = "tracing"))]
+                original_size,
+                spawned_at: crate::runtime::task::SpawnLocation::capture(),
+                _pd: PhantomData,
+            }
+        }
+    }
+
+    cfg_trace! {
+        use core::{
+            pin::Pin,
+            task::{Context, Poll},
+        };
+        use pin_project_lite::pin_project;
+        use std::mem;
+        use std::future::Future;
+        use tracing::instrument::Instrument;
+        pub(crate) use tracing::instrument::Instrumented;
+
+        #[inline]
+        pub(crate) fn task<F>(task: F, kind: &'static str, meta: SpawnMeta<'_>, id: u64) -> Instrumented<F> {
+            fn get_span(kind: &'static str, spawn_meta: SpawnMeta<'_>, id: u64, task_size: usize) -> tracing::Span {
+                let original_size = if spawn_meta.original_size != task_size {
+                    Some(spawn_meta.original_size)
+                } else {
+                    None
+                };
+                tracing::trace_span!(
+                    target: "tokio::task",
+                    parent: None,
+                    "runtime.spawn",
+                    %kind,
+                    task.name = %spawn_meta.name.unwrap_or_default(),
+                    task.id = id,
+                    original_size.bytes = original_size,
+                    size.bytes = task_size,
+                    loc.file = spawn_meta.spawned_at.0.file(),
+                    loc.line = spawn_meta.spawned_at.0.line(),
+                    loc.col = spawn_meta.spawned_at.0.column(),
+                )
+            }
+            use tracing::instrument::Instrument;
+            let span = get_span(kind, meta, id, mem::size_of::<F>());
+            task.instrument(span)
+        }
+
+        #[inline]
+        pub(crate) fn blocking_task<Fn, Fut>(task: Fut, spawn_meta: SpawnMeta<'_>, id: u64) -> Instrumented<Fut> {
+            let fn_size = mem::size_of::<Fn>();
+            let original_size = if spawn_meta.original_size != fn_size {
+                Some(spawn_meta.original_size)
+            } else {
+                None
+            };
+
+            let span = tracing::trace_span!(
+                target: "tokio::task::blocking",
+                "runtime.spawn",
+                kind = %"blocking",
+                task.name = %spawn_meta.name.unwrap_or_default(),
+                task.id = id,
+                "fn" = %std::any::type_name::<Fn>(),
+                original_size.bytes = original_size,
+                size.bytes = fn_size,
+                loc.file = spawn_meta.spawned_at.0.file(),
+                loc.line = spawn_meta.spawned_at.0.line(),
+                loc.col = spawn_meta.spawned_at.0.column(),
+            );
+            task.instrument(span)
+
+        }
+
+        pub(crate) fn async_op<P,F>(inner: P, resource_span: tracing::Span, source: &str, poll_op_name: &'static str, inherits_child_attrs: bool) -> InstrumentedAsyncOp<F>
+        where P: FnOnce() -> F {
+            resource_span.in_scope(|| {
+                let async_op_span = tracing::trace_span!("runtime.resource.async_op", source = source, inherits_child_attrs = inherits_child_attrs);
+                let enter = async_op_span.enter();
+                let async_op_poll_span = tracing::trace_span!("runtime.resource.async_op.poll");
+                let inner = inner();
+                drop(enter);
+                let tracing_ctx = AsyncOpTracingCtx {
+                    async_op_span,
+                    async_op_poll_span,
+                    resource_span: resource_span.clone(),
+                };
+                InstrumentedAsyncOp {
+                    inner,
+                    tracing_ctx,
+                    poll_op_name,
+                }
+            })
+        }
+
+        #[derive(Debug, Clone)]
+        pub(crate) struct AsyncOpTracingCtx {
+            pub(crate) async_op_span: tracing::Span,
+            pub(crate) async_op_poll_span: tracing::Span,
+            pub(crate) resource_span: tracing::Span,
+        }
+
+
+        pin_project! {
+            #[derive(Debug, Clone)]
+            pub(crate) struct InstrumentedAsyncOp<F> {
+                #[pin]
+                pub(crate) inner: F,
+                pub(crate) tracing_ctx: AsyncOpTracingCtx,
+                pub(crate) poll_op_name: &'static str
+            }
+        }
+
+        impl<F: Future> Future for InstrumentedAsyncOp<F> {
+            type Output = F::Output;
+
+            fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+                let this = self.project();
+                let poll_op_name = &*this.poll_op_name;
+                let _res_enter = this.tracing_ctx.resource_span.enter();
+                let _async_op_enter = this.tracing_ctx.async_op_span.enter();
+                let _async_op_poll_enter = this.tracing_ctx.async_op_poll_span.enter();
+                trace_poll_op!(poll_op_name, this.inner.poll(cx))
+            }
+        }
+    }
+
+    cfg_not_trace! {
+        #[inline]
+        pub(crate) fn task<F>(task: F, _kind: &'static str, _meta: SpawnMeta<'_>, _id: u64) -> F {
+            // nop
+            task
+        }
+
+        #[inline]
+        pub(crate) fn blocking_task<Fn, Fut>(task: Fut, _spawn_meta: SpawnMeta<'_>, _id: u64) -> Fut {
+            let _ = PhantomData::<&Fn>;
+            // nop
+            task
+        }
+    }
+}
+
+cfg_time! {
+    #[track_caller]
+    pub(crate) fn caller_location() -> Option<&'static std::panic::Location<'static>> {
+        #[cfg(all(tokio_unstable, feature = "tracing"))]
+        return Some(std::panic::Location::caller());
+        #[cfg(not(all(tokio_unstable, feature = "tracing")))]
+        None
+    }
+}

vendor/tokio/src/util/try_lock.rs

@@ -0,0 +1,80 @@
+use crate::loom::sync::atomic::AtomicBool;
+
+use std::cell::UnsafeCell;
+use std::marker::PhantomData;
+use std::ops::{Deref, DerefMut};
+use std::sync::atomic::Ordering::SeqCst;
+
+pub(crate) struct TryLock<T> {
+    locked: AtomicBool,
+    data: UnsafeCell<T>,
+}
+
+pub(crate) struct LockGuard<'a, T> {
+    lock: &'a TryLock<T>,
+    _p: PhantomData<std::rc::Rc<()>>,
+}
+
+unsafe impl<T: Send> Send for TryLock<T> {}
+unsafe impl<T: Send> Sync for TryLock<T> {}
+
+unsafe impl<T: Sync> Sync for LockGuard<'_, T> {}
+
+macro_rules! new {
+    ($data:ident) => {
+        TryLock {
+            locked: AtomicBool::new(false),
+            data: UnsafeCell::new($data),
+        }
+    };
+}
+
+impl<T> TryLock<T> {
+    #[cfg(not(loom))]
+    /// Create a new `TryLock`
+    pub(crate) const fn new(data: T) -> TryLock<T> {
+        new!(data)
+    }
+
+    #[cfg(loom)]
+    /// Create a new `TryLock`
+    pub(crate) fn new(data: T) -> TryLock<T> {
+        new!(data)
+    }
+
+    /// Attempt to acquire lock
+    pub(crate) fn try_lock(&self) -> Option<LockGuard<'_, T>> {
+        if self
+            .locked
+            .compare_exchange(false, true, SeqCst, SeqCst)
+            .is_err()
+        {
+            return None;
+        }
+
+        Some(LockGuard {
+            lock: self,
+            _p: PhantomData,
+        })
+    }
+}
+
+impl<T> Deref for LockGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.lock.data.get() }
+    }
+}
+
+impl<T> DerefMut for LockGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.lock.data.get() }
+    }
+}
+
+impl<T> Drop for LockGuard<'_, T> {
+    fn drop(&mut self) {
+        self.lock.locked.store(false, SeqCst);
+    }
+}

vendor/tokio/src/util/typeid.rs

@@ -0,0 +1,45 @@
+use std::{
+    any::TypeId,
+    marker::PhantomData,
+    mem::{self, ManuallyDrop},
+};
+
+// SAFETY: this function does not compare lifetimes. Values returned as `Ok`
+// may have their lifetimes extended.
+pub(super) unsafe fn try_transmute<Src, Target: 'static>(x: Src) -> Result<Target, Src> {
+    if nonstatic_typeid::<Src>() == TypeId::of::<Target>() {
+        let x = ManuallyDrop::new(x);
+        // SAFETY: we have checked that the types are the same.
+        Ok(unsafe { mem::transmute_copy::<Src, Target>(&x) })
+    } else {
+        Err(x)
+    }
+}
+
+// https://github.com/dtolnay/typeid/blob/b06a3c08a0eaccc7df6091ade1ae4e3fb53609d5/src/lib.rs#L197-L222
+#[inline(always)]
+fn nonstatic_typeid<T>() -> TypeId
+where
+    T: ?Sized,
+{
+    trait NonStaticAny {
+        fn get_type_id(&self) -> TypeId
+        where
+            Self: 'static;
+    }
+
+    impl<T: ?Sized> NonStaticAny for PhantomData<T> {
+        #[inline(always)]
+        fn get_type_id(&self) -> TypeId
+        where
+            Self: 'static,
+        {
+            TypeId::of::<T>()
+        }
+    }
+
+    let phantom_data = PhantomData::<T>;
+    NonStaticAny::get_type_id(unsafe {
+        mem::transmute::<&dyn NonStaticAny, &(dyn NonStaticAny + 'static)>(&phantom_data)
+    })
+}

vendor/tokio/src/util/wake.rs

@@ -0,0 +1,78 @@
+use crate::loom::sync::Arc;
+
+use std::marker::PhantomData;
+use std::mem::ManuallyDrop;
+use std::ops::Deref;
+use std::task::{RawWaker, RawWakerVTable, Waker};
+
+/// Simplified waking interface based on Arcs.
+pub(crate) trait Wake: Send + Sync + Sized + 'static {
+    /// Wake by value.
+    fn wake(arc_self: Arc<Self>);
+
+    /// Wake by reference.
+    fn wake_by_ref(arc_self: &Arc<Self>);
+}
+
+/// A `Waker` that is only valid for a given lifetime.
+#[derive(Debug)]
+pub(crate) struct WakerRef<'a> {
+    waker: ManuallyDrop<Waker>,
+    _p: PhantomData<&'a ()>,
+}
+
+impl Deref for WakerRef<'_> {
+    type Target = Waker;
+
+    fn deref(&self) -> &Waker {
+        &self.waker
+    }
+}
+
+/// Creates a reference to a `Waker` from a reference to `Arc<impl Wake>`.
+pub(crate) fn waker_ref<W: Wake>(wake: &Arc<W>) -> WakerRef<'_> {
+    let ptr = Arc::as_ptr(wake).cast::<()>();
+
+    let waker = unsafe { Waker::from_raw(RawWaker::new(ptr, waker_vtable::<W>())) };
+
+    WakerRef {
+        waker: ManuallyDrop::new(waker),
+        _p: PhantomData,
+    }
+}
+
+fn waker_vtable<W: Wake>() -> &'static RawWakerVTable {
+    &RawWakerVTable::new(
+        clone_arc_raw::<W>,
+        wake_arc_raw::<W>,
+        wake_by_ref_arc_raw::<W>,
+        drop_arc_raw::<W>,
+    )
+}
+
+unsafe fn clone_arc_raw<T: Wake>(data: *const ()) -> RawWaker {
+    // Safety: `data` was created from an `Arc::as_ptr` in function `waker_ref`.
+    unsafe {
+        Arc::<T>::increment_strong_count(data as *const T);
+    }
+    RawWaker::new(data, waker_vtable::<T>())
+}
+
+unsafe fn wake_arc_raw<T: Wake>(data: *const ()) {
+    // Safety: `data` was created from an `Arc::as_ptr` in function `waker_ref`.
+    let arc: Arc<T> = unsafe { Arc::from_raw(data as *const T) };
+    Wake::wake(arc);
+}
+
+// used by `waker_ref`
+unsafe fn wake_by_ref_arc_raw<T: Wake>(data: *const ()) {
+    // Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
+    // Safety: `data` was created from an `Arc::as_ptr` in function `waker_ref`.
+    let arc = ManuallyDrop::new(unsafe { Arc::<T>::from_raw(data.cast()) });
+    Wake::wake_by_ref(&arc);
+}
+
+unsafe fn drop_arc_raw<T: Wake>(data: *const ()) {
+    // Safety: `data` was created from an `Arc::as_ptr` in function `waker_ref`.
+    drop(unsafe { Arc::<T>::from_raw(data.cast()) });
+}

vendor/tokio/src/util/wake_list.rs

@@ -0,0 +1,83 @@
+use core::mem::MaybeUninit;
+use core::ptr;
+use std::task::Waker;
+
+const NUM_WAKERS: usize = 32;
+
+/// A list of wakers to be woken.
+///
+/// # Invariants
+///
+/// The first `curr` elements of `inner` are initialized.
+pub(crate) struct WakeList {
+    inner: [MaybeUninit<Waker>; NUM_WAKERS],
+    curr: usize,
+}
+
+impl WakeList {
+    pub(crate) fn new() -> Self {
+        const UNINIT_WAKER: MaybeUninit<Waker> = MaybeUninit::uninit();
+
+        Self {
+            inner: [UNINIT_WAKER; NUM_WAKERS],
+            curr: 0,
+        }
+    }
+
+    #[inline]
+    pub(crate) fn can_push(&self) -> bool {
+        self.curr < NUM_WAKERS
+    }
+
+    pub(crate) fn push(&mut self, val: Waker) {
+        debug_assert!(self.can_push());
+
+        self.inner[self.curr] = MaybeUninit::new(val);
+        self.curr += 1;
+    }
+
+    pub(crate) fn wake_all(&mut self) {
+        struct DropGuard {
+            start: *mut Waker,
+            end: *mut Waker,
+        }
+
+        impl Drop for DropGuard {
+            fn drop(&mut self) {
+                // SAFETY: Both pointers are part of the same object, with `start <= end`.
+                let len = unsafe { self.end.offset_from(self.start) } as usize;
+                let slice = ptr::slice_from_raw_parts_mut(self.start, len);
+                // SAFETY: All elements in `start..len` are initialized, so we can drop them.
+                unsafe { ptr::drop_in_place(slice) };
+            }
+        }
+
+        debug_assert!(self.curr <= NUM_WAKERS);
+
+        let mut guard = {
+            let start = self.inner.as_mut_ptr().cast::<Waker>();
+            // SAFETY: The resulting pointer is in bounds or one after the length of the same object.
+            let end = unsafe { start.add(self.curr) };
+            // Transfer ownership of the wakers in `inner` to `DropGuard`.
+            self.curr = 0;
+            DropGuard { start, end }
+        };
+        while !ptr::eq(guard.start, guard.end) {
+            // SAFETY: `start` is always initialized if `start != end`.
+            let waker = unsafe { ptr::read(guard.start) };
+            // SAFETY: The resulting pointer is in bounds or one after the length of the same object.
+            guard.start = unsafe { guard.start.add(1) };
+            // If this panics, then `guard` will clean up the remaining wakers.
+            waker.wake();
+        }
+    }
+}
+
+impl Drop for WakeList {
+    fn drop(&mut self) {
+        let slice =
+            ptr::slice_from_raw_parts_mut(self.inner.as_mut_ptr().cast::<Waker>(), self.curr);
+        // SAFETY: The first `curr` elements are initialized, so we can drop them.
+        unsafe { ptr::drop_in_place(slice) };
+    }
+}