Enum core::sync::atomic::Ordering

1.0.0 · source ·
#[non_exhaustive]
pub enum Ordering { Relaxed, Release, Acquire, AcqRel, SeqCst, }
Expand description

Atomic memory orderings

Memory orderings specify the way atomic operations synchronize memory. In its weakest Ordering::Relaxed, only the memory directly touched by the operation is synchronized. On the other hand, a store-load pair of Ordering::SeqCst operations synchronize other memory while additionally preserving a total order of such operations across all threads.

Rust’s memory orderings are the same as those of C++20.

For more information see the nomicon.

Variants (Non-exhaustive)§

This enum is marked as non-exhaustive
Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.
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Relaxed

No ordering constraints, only atomic operations.

Corresponds to memory_order_relaxed in C++20.

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Release

When coupled with a store, all previous operations become ordered before any load of this value with Acquire (or stronger) ordering. In particular, all previous writes become visible to all threads that perform an Acquire (or stronger) load of this value.

Notice that using this ordering for an operation that combines loads and stores leads to a Relaxed load operation!

This ordering is only applicable for operations that can perform a store.

Corresponds to memory_order_release in C++20.

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Acquire

When coupled with a load, if the loaded value was written by a store operation with Release (or stronger) ordering, then all subsequent operations become ordered after that store. In particular, all subsequent loads will see data written before the store.

Notice that using this ordering for an operation that combines loads and stores leads to a Relaxed store operation!

This ordering is only applicable for operations that can perform a load.

Corresponds to memory_order_acquire in C++20.

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AcqRel

Has the effects of both Acquire and Release together: For loads it uses Acquire ordering. For stores it uses the Release ordering.

Notice that in the case of compare_and_swap, it is possible that the operation ends up not performing any store and hence it has just Acquire ordering. However, AcqRel will never perform Relaxed accesses.

This ordering is only applicable for operations that combine both loads and stores.

Corresponds to memory_order_acq_rel in C++20.

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SeqCst

Like Acquire/Release/AcqRel (for load, store, and load-with-store operations, respectively) with the additional guarantee that all threads see all sequentially consistent operations in the same order.

Corresponds to memory_order_seq_cst in C++20.

Trait Implementations§

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impl Clone for Ordering

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fn clone(&self) -> Ordering

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Ordering

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl Hash for Ordering

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fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher. Read more
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fn hash_slice<H: Hasher>(data: &[Self], state: &mut H)where Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl PartialEq<Ordering> for Ordering

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fn eq(&self, other: &Ordering) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl Copy for Ordering

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impl Eq for Ordering

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impl StructuralEq for Ordering

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impl StructuralPartialEq for Ordering

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.