1.0.0[][src]Enum core::sync::atomic::Ordering

#[non_exhaustive]
pub enum Ordering {
    Relaxed,
    Release,
    Acquire,
    AcqRel,
    SeqCst,
}

Atomic memory orderings

Memory orderings specify the way atomic operations synchronize memory. In its weakest Relaxed, only the memory directly touched by the operation is synchronized. On the other hand, a store-load pair of 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)

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.
Relaxed

No ordering constraints, only atomic operations.

Corresponds to memory_order_relaxed in C++20.

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.

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.

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.

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

impl StructuralPartialEq for Ordering[src]

impl StructuralEq for Ordering[src]

impl Copy for Ordering[src]

impl PartialEq<Ordering> for Ordering[src]

impl Eq for Ordering[src]

impl Clone for Ordering[src]

impl Hash for Ordering[src]

impl Debug for Ordering[src]

Auto Trait Implementations

impl Send for Ordering

impl Sync for Ordering

impl Unpin for Ordering

Blanket Implementations

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T> From<T> for T[src]

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

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

The type returned in the event of a conversion error.

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = !

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]