From 1b6a04ca5504955c571d1c97504fb45ea0befee4 Mon Sep 17 00:00:00 2001
From: Valentin Popov <valentin@popov.link>
Date: Mon, 8 Jan 2024 01:21:28 +0400
Subject: Initial vendor packages
Signed-off-by: Valentin Popov <valentin@popov.link>
---
vendor/crossbeam-utils/src/atomic/atomic_cell.rs | 1182 ++++++++++++++++++++
vendor/crossbeam-utils/src/atomic/consume.rs | 111 ++
vendor/crossbeam-utils/src/atomic/mod.rs | 37 +
vendor/crossbeam-utils/src/atomic/seq_lock.rs | 112 ++
vendor/crossbeam-utils/src/atomic/seq_lock_wide.rs | 155 +++
5 files changed, 1597 insertions(+)
create mode 100644 vendor/crossbeam-utils/src/atomic/atomic_cell.rs
create mode 100644 vendor/crossbeam-utils/src/atomic/consume.rs
create mode 100644 vendor/crossbeam-utils/src/atomic/mod.rs
create mode 100644 vendor/crossbeam-utils/src/atomic/seq_lock.rs
create mode 100644 vendor/crossbeam-utils/src/atomic/seq_lock_wide.rs
(limited to 'vendor/crossbeam-utils/src/atomic')
diff --git a/vendor/crossbeam-utils/src/atomic/atomic_cell.rs b/vendor/crossbeam-utils/src/atomic/atomic_cell.rs
new file mode 100644
index 0000000..06ccf2e
--- /dev/null
+++ b/vendor/crossbeam-utils/src/atomic/atomic_cell.rs
@@ -0,0 +1,1182 @@
+// Necessary for implementing atomic methods for `AtomicUnit`
+#![allow(clippy::unit_arg)]
+
+use crate::primitive::sync::atomic::{self, Ordering};
+use crate::CachePadded;
+use core::cell::UnsafeCell;
+use core::cmp;
+use core::fmt;
+use core::mem::{self, ManuallyDrop, MaybeUninit};
+use core::panic::{RefUnwindSafe, UnwindSafe};
+use core::ptr;
+
+use super::seq_lock::SeqLock;
+
+/// A thread-safe mutable memory location.
+///
+/// This type is equivalent to [`Cell`], except it can also be shared among multiple threads.
+///
+/// Operations on `AtomicCell`s use atomic instructions whenever possible, and synchronize using
+/// global locks otherwise. You can call [`AtomicCell::<T>::is_lock_free()`] to check whether
+/// atomic instructions or locks will be used.
+///
+/// Atomic loads use the [`Acquire`] ordering and atomic stores use the [`Release`] ordering.
+///
+/// [`Cell`]: std::cell::Cell
+/// [`AtomicCell::<T>::is_lock_free()`]: AtomicCell::is_lock_free
+/// [`Acquire`]: std::sync::atomic::Ordering::Acquire
+/// [`Release`]: std::sync::atomic::Ordering::Release
+#[repr(transparent)]
+pub struct AtomicCell<T> {
+ /// The inner value.
+ ///
+ /// If this value can be transmuted into a primitive atomic type, it will be treated as such.
+ /// Otherwise, all potentially concurrent operations on this data will be protected by a global
+ /// lock.
+ ///
+ /// Using MaybeUninit to prevent code outside the cell from observing partially initialized state:
+ /// <https://github.com/crossbeam-rs/crossbeam/issues/833>
+ ///
+ /// Note:
+ /// - we'll never store uninitialized `T` due to our API only using initialized `T`.
+ /// - this `MaybeUninit` does *not* fix <https://github.com/crossbeam-rs/crossbeam/issues/315>.
+ value: UnsafeCell<MaybeUninit<T>>,
+}
+
+unsafe impl<T: Send> Send for AtomicCell<T> {}
+unsafe impl<T: Send> Sync for AtomicCell<T> {}
+
+impl<T> UnwindSafe for AtomicCell<T> {}
+impl<T> RefUnwindSafe for AtomicCell<T> {}
+
+impl<T> AtomicCell<T> {
+ /// Creates a new atomic cell initialized with `val`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(7);
+ /// ```
+ pub const fn new(val: T) -> AtomicCell<T> {
+ AtomicCell {
+ value: UnsafeCell::new(MaybeUninit::new(val)),
+ }
+ }
+
+ /// Consumes the atomic and returns the contained value.
+ ///
+ /// This is safe because passing `self` by value guarantees that no other threads are
+ /// concurrently accessing the atomic data.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(7);
+ /// let v = a.into_inner();
+ ///
+ /// assert_eq!(v, 7);
+ /// ```
+ pub fn into_inner(self) -> T {
+ let this = ManuallyDrop::new(self);
+ // SAFETY:
+ // - passing `self` by value guarantees that no other threads are concurrently
+ // accessing the atomic data
+ // - the raw pointer passed in is valid because we got it from an owned value.
+ // - `ManuallyDrop` prevents double dropping `T`
+ unsafe { this.as_ptr().read() }
+ }
+
+ /// Returns `true` if operations on values of this type are lock-free.
+ ///
+ /// If the compiler or the platform doesn't support the necessary atomic instructions,
+ /// `AtomicCell<T>` will use global locks for every potentially concurrent atomic operation.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// // This type is internally represented as `AtomicUsize` so we can just use atomic
+ /// // operations provided by it.
+ /// assert_eq!(AtomicCell::<usize>::is_lock_free(), true);
+ ///
+ /// // A wrapper struct around `isize`.
+ /// struct Foo {
+ /// bar: isize,
+ /// }
+ /// // `AtomicCell<Foo>` will be internally represented as `AtomicIsize`.
+ /// assert_eq!(AtomicCell::<Foo>::is_lock_free(), true);
+ ///
+ /// // Operations on zero-sized types are always lock-free.
+ /// assert_eq!(AtomicCell::<()>::is_lock_free(), true);
+ ///
+ /// // Very large types cannot be represented as any of the standard atomic types, so atomic
+ /// // operations on them will have to use global locks for synchronization.
+ /// assert_eq!(AtomicCell::<[u8; 1000]>::is_lock_free(), false);
+ /// ```
+ pub const fn is_lock_free() -> bool {
+ atomic_is_lock_free::<T>()
+ }
+
+ /// Stores `val` into the atomic cell.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(7);
+ ///
+ /// assert_eq!(a.load(), 7);
+ /// a.store(8);
+ /// assert_eq!(a.load(), 8);
+ /// ```
+ pub fn store(&self, val: T) {
+ if mem::needs_drop::<T>() {
+ drop(self.swap(val));
+ } else {
+ unsafe {
+ atomic_store(self.as_ptr(), val);
+ }
+ }
+ }
+
+ /// Stores `val` into the atomic cell and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(7);
+ ///
+ /// assert_eq!(a.load(), 7);
+ /// assert_eq!(a.swap(8), 7);
+ /// assert_eq!(a.load(), 8);
+ /// ```
+ pub fn swap(&self, val: T) -> T {
+ unsafe { atomic_swap(self.as_ptr(), val) }
+ }
+
+ /// Returns a raw pointer to the underlying data in this atomic cell.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(5);
+ ///
+ /// let ptr = a.as_ptr();
+ /// ```
+ #[inline]
+ pub fn as_ptr(&self) -> *mut T {
+ self.value.get().cast::<T>()
+ }
+}
+
+impl<T: Default> AtomicCell<T> {
+ /// Takes the value of the atomic cell, leaving `Default::default()` in its place.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(5);
+ /// let five = a.take();
+ ///
+ /// assert_eq!(five, 5);
+ /// assert_eq!(a.into_inner(), 0);
+ /// ```
+ pub fn take(&self) -> T {
+ self.swap(Default::default())
+ }
+}
+
+impl<T: Copy> AtomicCell<T> {
+ /// Loads a value from the atomic cell.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(7);
+ ///
+ /// assert_eq!(a.load(), 7);
+ /// ```
+ pub fn load(&self) -> T {
+ unsafe { atomic_load(self.as_ptr()) }
+ }
+}
+
+impl<T: Copy + Eq> AtomicCell<T> {
+ /// If the current value equals `current`, stores `new` into the atomic cell.
+ ///
+ /// The return value is always the previous value. If it is equal to `current`, then the value
+ /// was updated.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # #![allow(deprecated)]
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(1);
+ ///
+ /// assert_eq!(a.compare_and_swap(2, 3), 1);
+ /// assert_eq!(a.load(), 1);
+ ///
+ /// assert_eq!(a.compare_and_swap(1, 2), 1);
+ /// assert_eq!(a.load(), 2);
+ /// ```
+ // TODO: remove in the next major version.
+ #[deprecated(note = "Use `compare_exchange` instead")]
+ pub fn compare_and_swap(&self, current: T, new: T) -> T {
+ match self.compare_exchange(current, new) {
+ Ok(v) => v,
+ Err(v) => v,
+ }
+ }
+
+ /// If the current value equals `current`, stores `new` into the atomic cell.
+ ///
+ /// The return value is a result indicating whether the new value was written and containing
+ /// the previous value. On success this value is guaranteed to be equal to `current`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(1);
+ ///
+ /// assert_eq!(a.compare_exchange(2, 3), Err(1));
+ /// assert_eq!(a.load(), 1);
+ ///
+ /// assert_eq!(a.compare_exchange(1, 2), Ok(1));
+ /// assert_eq!(a.load(), 2);
+ /// ```
+ pub fn compare_exchange(&self, current: T, new: T) -> Result<T, T> {
+ unsafe { atomic_compare_exchange_weak(self.as_ptr(), current, new) }
+ }
+
+ /// Fetches the value, and applies a function to it that returns an optional
+ /// new value. Returns a `Result` of `Ok(previous_value)` if the function returned `Some(_)`, else
+ /// `Err(previous_value)`.
+ ///
+ /// Note: This may call the function multiple times if the value has been changed from other threads in
+ /// the meantime, as long as the function returns `Some(_)`, but the function will have been applied
+ /// only once to the stored value.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(7);
+ /// assert_eq!(a.fetch_update(|_| None), Err(7));
+ /// assert_eq!(a.fetch_update(|a| Some(a + 1)), Ok(7));
+ /// assert_eq!(a.fetch_update(|a| Some(a + 1)), Ok(8));
+ /// assert_eq!(a.load(), 9);
+ /// ```
+ #[inline]
+ pub fn fetch_update<F>(&self, mut f: F) -> Result<T, T>
+ where
+ F: FnMut(T) -> Option<T>,
+ {
+ let mut prev = self.load();
+ while let Some(next) = f(prev) {
+ match self.compare_exchange(prev, next) {
+ x @ Ok(_) => return x,
+ Err(next_prev) => prev = next_prev,
+ }
+ }
+ Err(prev)
+ }
+}
+
+// `MaybeUninit` prevents `T` from being dropped, so we need to implement `Drop`
+// for `AtomicCell` to avoid leaks of non-`Copy` types.
+impl<T> Drop for AtomicCell<T> {
+ fn drop(&mut self) {
+ if mem::needs_drop::<T>() {
+ // SAFETY:
+ // - the mutable reference guarantees that no other threads are concurrently accessing the atomic data
+ // - the raw pointer passed in is valid because we got it from a reference
+ // - `MaybeUninit` prevents double dropping `T`
+ unsafe {
+ self.as_ptr().drop_in_place();
+ }
+ }
+ }
+}
+
+macro_rules! atomic {
+ // If values of type `$t` can be transmuted into values of the primitive atomic type `$atomic`,
+ // declares variable `$a` of type `$atomic` and executes `$atomic_op`, breaking out of the loop.
+ (@check, $t:ty, $atomic:ty, $a:ident, $atomic_op:expr) => {
+ if can_transmute::<$t, $atomic>() {
+ let $a: &$atomic;
+ break $atomic_op;
+ }
+ };
+
+ // If values of type `$t` can be transmuted into values of a primitive atomic type, declares
+ // variable `$a` of that type and executes `$atomic_op`. Otherwise, just executes
+ // `$fallback_op`.
+ ($t:ty, $a:ident, $atomic_op:expr, $fallback_op:expr) => {
+ loop {
+ atomic!(@check, $t, AtomicUnit, $a, $atomic_op);
+
+ atomic!(@check, $t, atomic::AtomicU8, $a, $atomic_op);
+ atomic!(@check, $t, atomic::AtomicU16, $a, $atomic_op);
+ atomic!(@check, $t, atomic::AtomicU32, $a, $atomic_op);
+ #[cfg(target_has_atomic = "64")]
+ atomic!(@check, $t, atomic::AtomicU64, $a, $atomic_op);
+ // TODO: AtomicU128 is unstable
+ // atomic!(@check, $t, atomic::AtomicU128, $a, $atomic_op);
+
+ break $fallback_op;
+ }
+ };
+}
+
+macro_rules! impl_arithmetic {
+ ($t:ty, fallback, $example:tt) => {
+ impl AtomicCell<$t> {
+ /// Increments the current value by `val` and returns the previous value.
+ ///
+ /// The addition wraps on overflow.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_add(3), 7);
+ /// assert_eq!(a.load(), 10);
+ /// ```
+ #[inline]
+ pub fn fetch_add(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = value.wrapping_add(val);
+ old
+ }
+
+ /// Decrements the current value by `val` and returns the previous value.
+ ///
+ /// The subtraction wraps on overflow.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_sub(3), 7);
+ /// assert_eq!(a.load(), 4);
+ /// ```
+ #[inline]
+ pub fn fetch_sub(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = value.wrapping_sub(val);
+ old
+ }
+
+ /// Applies bitwise "and" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_and(3), 7);
+ /// assert_eq!(a.load(), 3);
+ /// ```
+ #[inline]
+ pub fn fetch_and(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value &= val;
+ old
+ }
+
+ /// Applies bitwise "nand" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_nand(3), 7);
+ /// assert_eq!(a.load(), !(7 & 3));
+ /// ```
+ #[inline]
+ pub fn fetch_nand(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = !(old & val);
+ old
+ }
+
+ /// Applies bitwise "or" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_or(16), 7);
+ /// assert_eq!(a.load(), 23);
+ /// ```
+ #[inline]
+ pub fn fetch_or(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value |= val;
+ old
+ }
+
+ /// Applies bitwise "xor" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_xor(2), 7);
+ /// assert_eq!(a.load(), 5);
+ /// ```
+ #[inline]
+ pub fn fetch_xor(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value ^= val;
+ old
+ }
+
+ /// Compares and sets the maximum of the current value and `val`,
+ /// and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_max(2), 7);
+ /// assert_eq!(a.load(), 7);
+ /// ```
+ #[inline]
+ pub fn fetch_max(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = cmp::max(old, val);
+ old
+ }
+
+ /// Compares and sets the minimum of the current value and `val`,
+ /// and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_min(2), 7);
+ /// assert_eq!(a.load(), 2);
+ /// ```
+ #[inline]
+ pub fn fetch_min(&self, val: $t) -> $t {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = cmp::min(old, val);
+ old
+ }
+ }
+ };
+ ($t:ty, $atomic:ident, $example:tt) => {
+ impl AtomicCell<$t> {
+ /// Increments the current value by `val` and returns the previous value.
+ ///
+ /// The addition wraps on overflow.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_add(3), 7);
+ /// assert_eq!(a.load(), 10);
+ /// ```
+ #[inline]
+ pub fn fetch_add(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_add(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = value.wrapping_add(val);
+ old
+ }
+ }
+ }
+
+ /// Decrements the current value by `val` and returns the previous value.
+ ///
+ /// The subtraction wraps on overflow.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_sub(3), 7);
+ /// assert_eq!(a.load(), 4);
+ /// ```
+ #[inline]
+ pub fn fetch_sub(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_sub(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = value.wrapping_sub(val);
+ old
+ }
+ }
+ }
+
+ /// Applies bitwise "and" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_and(3), 7);
+ /// assert_eq!(a.load(), 3);
+ /// ```
+ #[inline]
+ pub fn fetch_and(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_and(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value &= val;
+ old
+ }
+ }
+ }
+
+ /// Applies bitwise "nand" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_nand(3), 7);
+ /// assert_eq!(a.load(), !(7 & 3));
+ /// ```
+ #[inline]
+ pub fn fetch_nand(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_nand(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = !(old & val);
+ old
+ }
+ }
+ }
+
+ /// Applies bitwise "or" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_or(16), 7);
+ /// assert_eq!(a.load(), 23);
+ /// ```
+ #[inline]
+ pub fn fetch_or(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_or(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value |= val;
+ old
+ }
+ }
+ }
+
+ /// Applies bitwise "xor" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_xor(2), 7);
+ /// assert_eq!(a.load(), 5);
+ /// ```
+ #[inline]
+ pub fn fetch_xor(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_xor(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value ^= val;
+ old
+ }
+ }
+ }
+
+ /// Compares and sets the maximum of the current value and `val`,
+ /// and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_max(9), 7);
+ /// assert_eq!(a.load(), 9);
+ /// ```
+ #[inline]
+ pub fn fetch_max(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_max(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = cmp::max(old, val);
+ old
+ }
+ }
+ }
+
+ /// Compares and sets the minimum of the current value and `val`,
+ /// and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ #[doc = $example]
+ ///
+ /// assert_eq!(a.fetch_min(2), 7);
+ /// assert_eq!(a.load(), 2);
+ /// ```
+ #[inline]
+ pub fn fetch_min(&self, val: $t) -> $t {
+ atomic! {
+ $t, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::$atomic) };
+ a.fetch_min(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = cmp::min(old, val);
+ old
+ }
+ }
+ }
+ }
+ };
+}
+
+impl_arithmetic!(u8, AtomicU8, "let a = AtomicCell::new(7u8);");
+impl_arithmetic!(i8, AtomicI8, "let a = AtomicCell::new(7i8);");
+impl_arithmetic!(u16, AtomicU16, "let a = AtomicCell::new(7u16);");
+impl_arithmetic!(i16, AtomicI16, "let a = AtomicCell::new(7i16);");
+
+impl_arithmetic!(u32, AtomicU32, "let a = AtomicCell::new(7u32);");
+impl_arithmetic!(i32, AtomicI32, "let a = AtomicCell::new(7i32);");
+
+#[cfg(target_has_atomic = "64")]
+impl_arithmetic!(u64, AtomicU64, "let a = AtomicCell::new(7u64);");
+#[cfg(target_has_atomic = "64")]
+impl_arithmetic!(i64, AtomicI64, "let a = AtomicCell::new(7i64);");
+#[cfg(not(target_has_atomic = "64"))]
+impl_arithmetic!(u64, fallback, "let a = AtomicCell::new(7u64);");
+#[cfg(not(target_has_atomic = "64"))]
+impl_arithmetic!(i64, fallback, "let a = AtomicCell::new(7i64);");
+
+// TODO: AtomicU128 is unstable
+// impl_arithmetic!(u128, AtomicU128, "let a = AtomicCell::new(7u128);");
+// impl_arithmetic!(i128, AtomicI128, "let a = AtomicCell::new(7i128);");
+impl_arithmetic!(u128, fallback, "let a = AtomicCell::new(7u128);");
+impl_arithmetic!(i128, fallback, "let a = AtomicCell::new(7i128);");
+
+impl_arithmetic!(usize, AtomicUsize, "let a = AtomicCell::new(7usize);");
+impl_arithmetic!(isize, AtomicIsize, "let a = AtomicCell::new(7isize);");
+
+impl AtomicCell<bool> {
+ /// Applies logical "and" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(true);
+ ///
+ /// assert_eq!(a.fetch_and(true), true);
+ /// assert_eq!(a.load(), true);
+ ///
+ /// assert_eq!(a.fetch_and(false), true);
+ /// assert_eq!(a.load(), false);
+ /// ```
+ #[inline]
+ pub fn fetch_and(&self, val: bool) -> bool {
+ atomic! {
+ bool, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::AtomicBool) };
+ a.fetch_and(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value &= val;
+ old
+ }
+ }
+ }
+
+ /// Applies logical "nand" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(true);
+ ///
+ /// assert_eq!(a.fetch_nand(false), true);
+ /// assert_eq!(a.load(), true);
+ ///
+ /// assert_eq!(a.fetch_nand(true), true);
+ /// assert_eq!(a.load(), false);
+ ///
+ /// assert_eq!(a.fetch_nand(false), false);
+ /// assert_eq!(a.load(), true);
+ /// ```
+ #[inline]
+ pub fn fetch_nand(&self, val: bool) -> bool {
+ atomic! {
+ bool, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::AtomicBool) };
+ a.fetch_nand(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value = !(old & val);
+ old
+ }
+ }
+ }
+
+ /// Applies logical "or" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(false);
+ ///
+ /// assert_eq!(a.fetch_or(false), false);
+ /// assert_eq!(a.load(), false);
+ ///
+ /// assert_eq!(a.fetch_or(true), false);
+ /// assert_eq!(a.load(), true);
+ /// ```
+ #[inline]
+ pub fn fetch_or(&self, val: bool) -> bool {
+ atomic! {
+ bool, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::AtomicBool) };
+ a.fetch_or(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value |= val;
+ old
+ }
+ }
+ }
+
+ /// Applies logical "xor" to the current value and returns the previous value.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use crossbeam_utils::atomic::AtomicCell;
+ ///
+ /// let a = AtomicCell::new(true);
+ ///
+ /// assert_eq!(a.fetch_xor(false), true);
+ /// assert_eq!(a.load(), true);
+ ///
+ /// assert_eq!(a.fetch_xor(true), true);
+ /// assert_eq!(a.load(), false);
+ /// ```
+ #[inline]
+ pub fn fetch_xor(&self, val: bool) -> bool {
+ atomic! {
+ bool, _a,
+ {
+ let a = unsafe { &*(self.as_ptr() as *const atomic::AtomicBool) };
+ a.fetch_xor(val, Ordering::AcqRel)
+ },
+ {
+ let _guard = lock(self.as_ptr() as usize).write();
+ let value = unsafe { &mut *(self.as_ptr()) };
+ let old = *value;
+ *value ^= val;
+ old
+ }
+ }
+ }
+}
+
+impl<T: Default> Default for AtomicCell<T> {
+ fn default() -> AtomicCell<T> {
+ AtomicCell::new(T::default())
+ }
+}
+
+impl<T> From<T> for AtomicCell<T> {
+ #[inline]
+ fn from(val: T) -> AtomicCell<T> {
+ AtomicCell::new(val)
+ }
+}
+
+impl<T: Copy + fmt::Debug> fmt::Debug for AtomicCell<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.debug_struct("AtomicCell")
+ .field("value", &self.load())
+ .finish()
+ }
+}
+
+/// Returns `true` if values of type `A` can be transmuted into values of type `B`.
+const fn can_transmute<A, B>() -> bool {
+ // Sizes must be equal, but alignment of `A` must be greater or equal than that of `B`.
+ (mem::size_of::<A>() == mem::size_of::<B>()) & (mem::align_of::<A>() >= mem::align_of::<B>())
+}
+
+/// Returns a reference to the global lock associated with the `AtomicCell` at address `addr`.
+///
+/// This function is used to protect atomic data which doesn't fit into any of the primitive atomic
+/// types in `std::sync::atomic`. Operations on such atomics must therefore use a global lock.
+///
+/// However, there is not only one global lock but an array of many locks, and one of them is
+/// picked based on the given address. Having many locks reduces contention and improves
+/// scalability.
+#[inline]
+#[must_use]
+fn lock(addr: usize) -> &'static SeqLock {
+ // The number of locks is a prime number because we want to make sure `addr % LEN` gets
+ // dispersed across all locks.
+ //
+ // Note that addresses are always aligned to some power of 2, depending on type `T` in
+ // `AtomicCell<T>`. If `LEN` was an even number, then `addr % LEN` would be an even number,
+ // too, which means only half of the locks would get utilized!
+ //
+ // It is also possible for addresses to accidentally get aligned to a number that is not a
+ // power of 2. Consider this example:
+ //
+ // ```
+ // #[repr(C)]
+ // struct Foo {
+ // a: AtomicCell<u8>,
+ // b: u8,
+ // c: u8,
+ // }
+ // ```
+ //
+ // Now, if we have a slice of type `&[Foo]`, it is possible that field `a` in all items gets
+ // stored at addresses that are multiples of 3. It'd be too bad if `LEN` was divisible by 3.
+ // In order to protect from such cases, we simply choose a large prime number for `LEN`.
+ const LEN: usize = 67;
+ #[allow(clippy::declare_interior_mutable_const)]
+ const L: CachePadded<SeqLock> = CachePadded::new(SeqLock::new());
+ static LOCKS: [CachePadded<SeqLock>; LEN] = [L; LEN];
+
+ // If the modulus is a constant number, the compiler will use crazy math to transform this into
+ // a sequence of cheap arithmetic operations rather than using the slow modulo instruction.
+ &LOCKS[addr % LEN]
+}
+
+/// An atomic `()`.
+///
+/// All operations are noops.
+struct AtomicUnit;
+
+impl AtomicUnit {
+ #[inline]
+ fn load(&self, _order: Ordering) {}
+
+ #[inline]
+ fn store(&self, _val: (), _order: Ordering) {}
+
+ #[inline]
+ fn swap(&self, _val: (), _order: Ordering) {}
+
+ #[inline]
+ fn compare_exchange_weak(
+ &self,
+ _current: (),
+ _new: (),
+ _success: Ordering,
+ _failure: Ordering,
+ ) -> Result<(), ()> {
+ Ok(())
+ }
+}
+
+/// Returns `true` if operations on `AtomicCell<T>` are lock-free.
+const fn atomic_is_lock_free<T>() -> bool {
+ atomic! { T, _a, true, false }
+}
+
+/// Atomically reads data from `src`.
+///
+/// This operation uses the `Acquire` ordering. If possible, an atomic instructions is used, and a
+/// global lock otherwise.
+unsafe fn atomic_load<T>(src: *mut T) -> T
+where
+ T: Copy,
+{
+ atomic! {
+ T, a,
+ {
+ a = &*(src as *const _ as *const _);
+ mem::transmute_copy(&a.load(Ordering::Acquire))
+ },
+ {
+ let lock = lock(src as usize);
+
+ // Try doing an optimistic read first.
+ if let Some(stamp) = lock.optimistic_read() {
+ // We need a volatile read here because other threads might concurrently modify the
+ // value. In theory, data races are *always* UB, even if we use volatile reads and
+ // discard the data when a data race is detected. The proper solution would be to
+ // do atomic reads and atomic writes, but we can't atomically read and write all
+ // kinds of data since `AtomicU8` is not available on stable Rust yet.
+ // Load as `MaybeUninit` because we may load a value that is not valid as `T`.
+ let val = ptr::read_volatile(src.cast::<MaybeUninit<T>>());
+
+ if lock.validate_read(stamp) {
+ return val.assume_init();
+ }
+ }
+
+ // Grab a regular write lock so that writers don't starve this load.
+ let guard = lock.write();
+ let val = ptr::read(src);
+ // The value hasn't been changed. Drop the guard without incrementing the stamp.
+ guard.abort();
+ val
+ }
+ }
+}
+
+/// Atomically writes `val` to `dst`.
+///
+/// This operation uses the `Release` ordering. If possible, an atomic instructions is used, and a
+/// global lock otherwise.
+unsafe fn atomic_store<T>(dst: *mut T, val: T) {
+ atomic! {
+ T, a,
+ {
+ a = &*(dst as *const _ as *const _);
+ a.store(mem::transmute_copy(&val), Ordering::Release);
+ mem::forget(val);
+ },
+ {
+ let _guard = lock(dst as usize).write();
+ ptr::write(dst, val);
+ }
+ }
+}
+
+/// Atomically swaps data at `dst` with `val`.
+///
+/// This operation uses the `AcqRel` ordering. If possible, an atomic instructions is used, and a
+/// global lock otherwise.
+unsafe fn atomic_swap<T>(dst: *mut T, val: T) -> T {
+ atomic! {
+ T, a,
+ {
+ a = &*(dst as *const _ as *const _);
+ let res = mem::transmute_copy(&a.swap(mem::transmute_copy(&val), Ordering::AcqRel));
+ mem::forget(val);
+ res
+ },
+ {
+ let _guard = lock(dst as usize).write();
+ ptr::replace(dst, val)
+ }
+ }
+}
+
+/// Atomically compares data at `dst` to `current` and, if equal byte-for-byte, exchanges data at
+/// `dst` with `new`.
+///
+/// Returns the old value on success, or the current value at `dst` on failure.
+///
+/// This operation uses the `AcqRel` ordering. If possible, an atomic instructions is used, and a
+/// global lock otherwise.
+#[allow(clippy::let_unit_value)]
+unsafe fn atomic_compare_exchange_weak<T>(dst: *mut T, mut current: T, new: T) -> Result<T, T>
+where
+ T: Copy + Eq,
+{
+ atomic! {
+ T, a,
+ {
+ a = &*(dst as *const _ as *const _);
+ let mut current_raw = mem::transmute_copy(¤t);
+ let new_raw = mem::transmute_copy(&new);
+
+ loop {
+ match a.compare_exchange_weak(
+ current_raw,
+ new_raw,
+ Ordering::AcqRel,
+ Ordering::Acquire,
+ ) {
+ Ok(_) => break Ok(current),
+ Err(previous_raw) => {
+ let previous = mem::transmute_copy(&previous_raw);
+
+ if !T::eq(&previous, ¤t) {
+ break Err(previous);
+ }
+
+ // The compare-exchange operation has failed and didn't store `new`. The
+ // failure is either spurious, or `previous` was semantically equal to
+ // `current` but not byte-equal. Let's retry with `previous` as the new
+ // `current`.
+ current = previous;
+ current_raw = previous_raw;
+ }
+ }
+ }
+ },
+ {
+ let guard = lock(dst as usize).write();
+
+ if T::eq(&*dst, ¤t) {
+ Ok(ptr::replace(dst, new))
+ } else {
+ let val = ptr::read(dst);
+ // The value hasn't been changed. Drop the guard without incrementing the stamp.
+ guard.abort();
+ Err(val)
+ }
+ }
+ }
+}
diff --git a/vendor/crossbeam-utils/src/atomic/consume.rs b/vendor/crossbeam-utils/src/atomic/consume.rs
new file mode 100644
index 0000000..ff8e316
--- /dev/null
+++ b/vendor/crossbeam-utils/src/atomic/consume.rs
@@ -0,0 +1,111 @@
+#[cfg(not(crossbeam_no_atomic))]
+use core::sync::atomic::Ordering;
+
+/// Trait which allows reading from primitive atomic types with "consume" ordering.
+pub trait AtomicConsume {
+ /// Type returned by `load_consume`.
+ type Val;
+
+ /// Loads a value from the atomic using a "consume" memory ordering.
+ ///
+ /// This is similar to the "acquire" ordering, except that an ordering is
+ /// only guaranteed with operations that "depend on" the result of the load.
+ /// However consume loads are usually much faster than acquire loads on
+ /// architectures with a weak memory model since they don't require memory
+ /// fence instructions.
+ ///
+ /// The exact definition of "depend on" is a bit vague, but it works as you
+ /// would expect in practice since a lot of software, especially the Linux
+ /// kernel, rely on this behavior.
+ ///
+ /// This is currently only implemented on ARM and AArch64, where a fence
+ /// can be avoided. On other architectures this will fall back to a simple
+ /// `load(Ordering::Acquire)`.
+ fn load_consume(&self) -> Self::Val;
+}
+
+#[cfg(not(crossbeam_no_atomic))]
+// Miri and Loom don't support "consume" ordering and ThreadSanitizer doesn't treat
+// load(Relaxed) + compiler_fence(Acquire) as "consume" load.
+// LLVM generates machine code equivalent to fence(Acquire) in compiler_fence(Acquire)
+// on PowerPC, MIPS, etc. (https://godbolt.org/z/hffvjvW7h), so for now the fence
+// can be actually avoided here only on ARM and AArch64. See also
+// https://github.com/rust-lang/rust/issues/62256.
+#[cfg(all(
+ any(target_arch = "arm", target_arch = "aarch64"),
+ not(any(miri, crossbeam_loom, crossbeam_sanitize_thread)),
+))]
+macro_rules! impl_consume {
+ () => {
+ #[inline]
+ fn load_consume(&self) -> Self::Val {
+ use crate::primitive::sync::atomic::compiler_fence;
+ let result = self.load(Ordering::Relaxed);
+ compiler_fence(Ordering::Acquire);
+ result
+ }
+ };
+}
+
+#[cfg(not(crossbeam_no_atomic))]
+#[cfg(not(all(
+ any(target_arch = "arm", target_arch = "aarch64"),
+ not(any(miri, crossbeam_loom, crossbeam_sanitize_thread)),
+)))]
+macro_rules! impl_consume {
+ () => {
+ #[inline]
+ fn load_consume(&self) -> Self::Val {
+ self.load(Ordering::Acquire)
+ }
+ };
+}
+
+macro_rules! impl_atomic {
+ ($atomic:ident, $val:ty) => {
+ #[cfg(not(crossbeam_no_atomic))]
+ impl AtomicConsume for core::sync::atomic::$atomic {
+ type Val = $val;
+ impl_consume!();
+ }
+ #[cfg(crossbeam_loom)]
+ impl AtomicConsume for loom::sync::atomic::$atomic {
+ type Val = $val;
+ impl_consume!();
+ }
+ };
+}
+
+impl_atomic!(AtomicBool, bool);
+impl_atomic!(AtomicUsize, usize);
+impl_atomic!(AtomicIsize, isize);
+impl_atomic!(AtomicU8, u8);
+impl_atomic!(AtomicI8, i8);
+impl_atomic!(AtomicU16, u16);
+impl_atomic!(AtomicI16, i16);
+#[cfg(any(target_has_atomic = "32", not(target_pointer_width = "16")))]
+impl_atomic!(AtomicU32, u32);
+#[cfg(any(target_has_atomic = "32", not(target_pointer_width = "16")))]
+impl_atomic!(AtomicI32, i32);
+#[cfg(any(
+ target_has_atomic = "64",
+ not(any(target_pointer_width = "16", target_pointer_width = "32")),
+))]
+impl_atomic!(AtomicU64, u64);
+#[cfg(any(
+ target_has_atomic = "64",
+ not(any(target_pointer_width = "16", target_pointer_width = "32")),
+))]
+impl_atomic!(AtomicI64, i64);
+
+#[cfg(not(crossbeam_no_atomic))]
+impl<T> AtomicConsume for core::sync::atomic::AtomicPtr<T> {
+ type Val = *mut T;
+ impl_consume!();
+}
+
+#[cfg(crossbeam_loom)]
+impl<T> AtomicConsume for loom::sync::atomic::AtomicPtr<T> {
+ type Val = *mut T;
+ impl_consume!();
+}
diff --git a/vendor/crossbeam-utils/src/atomic/mod.rs b/vendor/crossbeam-utils/src/atomic/mod.rs
new file mode 100644
index 0000000..4332cc3
--- /dev/null
+++ b/vendor/crossbeam-utils/src/atomic/mod.rs
@@ -0,0 +1,37 @@
+//! Atomic types.
+//!
+//! * [`AtomicCell`], a thread-safe mutable memory location.
+//! * [`AtomicConsume`], for reading from primitive atomic types with "consume" ordering.
+
+#[cfg(target_has_atomic = "ptr")]
+#[cfg(not(crossbeam_loom))]
+cfg_if::cfg_if! {
+ // Use "wide" sequence lock if the pointer width <= 32 for preventing its counter against wrap
+ // around.
+ //
+ // We are ignoring too wide architectures (pointer width >= 256), since such a system will not
+ // appear in a conceivable future.
+ //
+ // In narrow architectures (pointer width <= 16), the counter is still <= 32-bit and may be
+ // vulnerable to wrap around. But it's mostly okay, since in such a primitive hardware, the
+ // counter will not be increased that fast.
+ if #[cfg(any(target_pointer_width = "64", target_pointer_width = "128"))] {
+ mod seq_lock;
+ } else {
+ #[path = "seq_lock_wide.rs"]
+ mod seq_lock;
+ }
+}
+
+#[cfg(target_has_atomic = "ptr")]
+// We cannot provide AtomicCell under cfg(crossbeam_loom) because loom's atomic
+// types have a different in-memory representation than the underlying type.
+// TODO: The latest loom supports fences, so fallback using seqlock may be available.
+#[cfg(not(crossbeam_loom))]
+mod atomic_cell;
+mod consume;
+
+#[cfg(target_has_atomic = "ptr")]
+#[cfg(not(crossbeam_loom))]
+pub use self::atomic_cell::AtomicCell;
+pub use self::consume::AtomicConsume;
diff --git a/vendor/crossbeam-utils/src/atomic/seq_lock.rs b/vendor/crossbeam-utils/src/atomic/seq_lock.rs
new file mode 100644
index 0000000..ff8defd
--- /dev/null
+++ b/vendor/crossbeam-utils/src/atomic/seq_lock.rs
@@ -0,0 +1,112 @@
+use core::mem;
+use core::sync::atomic::{self, AtomicUsize, Ordering};
+
+use crate::Backoff;
+
+/// A simple stamped lock.
+pub(crate) struct SeqLock {
+ /// The current state of the lock.
+ ///
+ /// All bits except the least significant one hold the current stamp. When locked, the state
+ /// equals 1 and doesn't contain a valid stamp.
+ state: AtomicUsize,
+}
+
+impl SeqLock {
+ pub(crate) const fn new() -> Self {
+ Self {
+ state: AtomicUsize::new(0),
+ }
+ }
+
+ /// If not locked, returns the current stamp.
+ ///
+ /// This method should be called before optimistic reads.
+ #[inline]
+ pub(crate) fn optimistic_read(&self) -> Option<usize> {
+ let state = self.state.load(Ordering::Acquire);
+ if state == 1 {
+ None
+ } else {
+ Some(state)
+ }
+ }
+
+ /// Returns `true` if the current stamp is equal to `stamp`.
+ ///
+ /// This method should be called after optimistic reads to check whether they are valid. The
+ /// argument `stamp` should correspond to the one returned by method `optimistic_read`.
+ #[inline]
+ pub(crate) fn validate_read(&self, stamp: usize) -> bool {
+ atomic::fence(Ordering::Acquire);
+ self.state.load(Ordering::Relaxed) == stamp
+ }
+
+ /// Grabs the lock for writing.
+ #[inline]
+ pub(crate) fn write(&'static self) -> SeqLockWriteGuard {
+ let backoff = Backoff::new();
+ loop {
+ let previous = self.state.swap(1, Ordering::Acquire);
+
+ if previous != 1 {
+ atomic::fence(Ordering::Release);
+
+ return SeqLockWriteGuard {
+ lock: self,
+ state: previous,
+ };
+ }
+
+ backoff.snooze();
+ }
+ }
+}
+
+/// An RAII guard that releases the lock and increments the stamp when dropped.
+pub(crate) struct SeqLockWriteGuard {
+ /// The parent lock.
+ lock: &'static SeqLock,
+
+ /// The stamp before locking.
+ state: usize,
+}
+
+impl SeqLockWriteGuard {
+ /// Releases the lock without incrementing the stamp.
+ #[inline]
+ pub(crate) fn abort(self) {
+ self.lock.state.store(self.state, Ordering::Release);
+
+ // We specifically don't want to call drop(), since that's
+ // what increments the stamp.
+ mem::forget(self);
+ }
+}
+
+impl Drop for SeqLockWriteGuard {
+ #[inline]
+ fn drop(&mut self) {
+ // Release the lock and increment the stamp.
+ self.lock
+ .state
+ .store(self.state.wrapping_add(2), Ordering::Release);
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::SeqLock;
+
+ #[test]
+ fn test_abort() {
+ static LK: SeqLock = SeqLock::new();
+ let before = LK.optimistic_read().unwrap();
+ {
+ let guard = LK.write();
+ guard.abort();
+ }
+ let after = LK.optimistic_read().unwrap();
+ assert_eq!(before, after, "aborted write does not update the stamp");
+ }
+}
diff --git a/vendor/crossbeam-utils/src/atomic/seq_lock_wide.rs b/vendor/crossbeam-utils/src/atomic/seq_lock_wide.rs
new file mode 100644
index 0000000..ef5d94a
--- /dev/null
+++ b/vendor/crossbeam-utils/src/atomic/seq_lock_wide.rs
@@ -0,0 +1,155 @@
+use core::mem;
+use core::sync::atomic::{self, AtomicUsize, Ordering};
+
+use crate::Backoff;
+
+/// A simple stamped lock.
+///
+/// The state is represented as two `AtomicUsize`: `state_hi` for high bits and `state_lo` for low
+/// bits.
+pub(crate) struct SeqLock {
+ /// The high bits of the current state of the lock.
+ state_hi: AtomicUsize,
+
+ /// The low bits of the current state of the lock.
+ ///
+ /// All bits except the least significant one hold the current stamp. When locked, the state_lo
+ /// equals 1 and doesn't contain a valid stamp.
+ state_lo: AtomicUsize,
+}
+
+impl SeqLock {
+ pub(crate) const fn new() -> Self {
+ Self {
+ state_hi: AtomicUsize::new(0),
+ state_lo: AtomicUsize::new(0),
+ }
+ }
+
+ /// If not locked, returns the current stamp.
+ ///
+ /// This method should be called before optimistic reads.
+ #[inline]
+ pub(crate) fn optimistic_read(&self) -> Option<(usize, usize)> {
+ // The acquire loads from `state_hi` and `state_lo` synchronize with the release stores in
+ // `SeqLockWriteGuard::drop`.
+ //
+ // As a consequence, we can make sure that (1) all writes within the era of `state_hi - 1`
+ // happens before now; and therefore, (2) if `state_lo` is even, all writes within the
+ // critical section of (`state_hi`, `state_lo`) happens before now.
+ let state_hi = self.state_hi.load(Ordering::Acquire);
+ let state_lo = self.state_lo.load(Ordering::Acquire);
+ if state_lo == 1 {
+ None
+ } else {
+ Some((state_hi, state_lo))
+ }
+ }
+
+ /// Returns `true` if the current stamp is equal to `stamp`.
+ ///
+ /// This method should be called after optimistic reads to check whether they are valid. The
+ /// argument `stamp` should correspond to the one returned by method `optimistic_read`.
+ #[inline]
+ pub(crate) fn validate_read(&self, stamp: (usize, usize)) -> bool {
+ // Thanks to the fence, if we're noticing any modification to the data at the critical
+ // section of `(a, b)`, then the critical section's write of 1 to state_lo should be
+ // visible.
+ atomic::fence(Ordering::Acquire);
+
+ // So if `state_lo` coincides with `stamp.1`, then either (1) we're noticing no modification
+ // to the data after the critical section of `(stamp.0, stamp.1)`, or (2) `state_lo` wrapped
+ // around.
+ //
+ // If (2) is the case, the acquire ordering ensures we see the new value of `state_hi`.
+ let state_lo = self.state_lo.load(Ordering::Acquire);
+
+ // If (2) is the case and `state_hi` coincides with `stamp.0`, then `state_hi` also wrapped
+ // around, which we give up to correctly validate the read.
+ let state_hi = self.state_hi.load(Ordering::Relaxed);
+
+ // Except for the case that both `state_hi` and `state_lo` wrapped around, the following
+ // condition implies that we're noticing no modification to the data after the critical
+ // section of `(stamp.0, stamp.1)`.
+ (state_hi, state_lo) == stamp
+ }
+
+ /// Grabs the lock for writing.
+ #[inline]
+ pub(crate) fn write(&'static self) -> SeqLockWriteGuard {
+ let backoff = Backoff::new();
+ loop {
+ let previous = self.state_lo.swap(1, Ordering::Acquire);
+
+ if previous != 1 {
+ // To synchronize with the acquire fence in `validate_read` via any modification to
+ // the data at the critical section of `(state_hi, previous)`.
+ atomic::fence(Ordering::Release);
+
+ return SeqLockWriteGuard {
+ lock: self,
+ state_lo: previous,
+ };
+ }
+
+ backoff.snooze();
+ }
+ }
+}
+
+/// An RAII guard that releases the lock and increments the stamp when dropped.
+pub(crate) struct SeqLockWriteGuard {
+ /// The parent lock.
+ lock: &'static SeqLock,
+
+ /// The stamp before locking.
+ state_lo: usize,
+}
+
+impl SeqLockWriteGuard {
+ /// Releases the lock without incrementing the stamp.
+ #[inline]
+ pub(crate) fn abort(self) {
+ self.lock.state_lo.store(self.state_lo, Ordering::Release);
+ mem::forget(self);
+ }
+}
+
+impl Drop for SeqLockWriteGuard {
+ #[inline]
+ fn drop(&mut self) {
+ let state_lo = self.state_lo.wrapping_add(2);
+
+ // Increase the high bits if the low bits wrap around.
+ //
+ // Release ordering for synchronizing with `optimistic_read`.
+ if state_lo == 0 {
+ let state_hi = self.lock.state_hi.load(Ordering::Relaxed);
+ self.lock
+ .state_hi
+ .store(state_hi.wrapping_add(1), Ordering::Release);
+ }
+
+ // Release the lock and increment the stamp.
+ //
+ // Release ordering for synchronizing with `optimistic_read`.
+ self.lock.state_lo.store(state_lo, Ordering::Release);
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::SeqLock;
+
+ #[test]
+ fn test_abort() {
+ static LK: SeqLock = SeqLock::new();
+ let before = LK.optimistic_read().unwrap();
+ {
+ let guard = LK.write();
+ guard.abort();
+ }
+ let after = LK.optimistic_read().unwrap();
+ assert_eq!(before, after, "aborted write does not update the stamp");
+ }
+}
--
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