std::sync::atomic::Ordering - Rust
Description: API documentation for the Rust `Ordering` enum in crate `std`.
Keywords: rust, rustlang, rust-lang, Ordering

# 1.0.0[−][src]Enum std::sync::atomic::Ordering

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

Atomic memory orderings

Memory orderings limit the ways that both the compiler and CPU may reorder instructions around atomic operations. At its most restrictive, "sequentially consistent" atomics allow neither reads nor writes to be moved either before or after the atomic operation; on the other end "relaxed" atomics allow all reorderings.

Rust's memory orderings are the same as LLVM's.

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 LLVM's `Monotonic` ordering.

`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 LLVM's `Release` ordering.

`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 LLVM's `Acquire` ordering.

`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 LLVM's `AcquireRelease` ordering.

`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 LLVM's `SequentiallyConsistent` ordering.

## Trait Implementations

###

`impl Copy for Ordering`

[src]

###

`impl Clone for Ordering`

[src]

####

`fn clone(&self) -> Ordering`

[src]

Returns a copy of the value. Read more

####

`fn clone_from(&mut self, source: &Self)`

[src]

Performs copy-assignment from `source`. Read more

###

`impl Debug for Ordering`

[src]

####

`fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

[src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

###

`impl Send for Ordering`

###

`impl Sync for Ordering`

## Blanket Implementations

###

`impl<T> From for T`

[src]

####

`fn from(t: T) -> T`

[src]

Performs the conversion.

###

`impl<T, U> TryFrom for T where T: From<U>,`

[src]

#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

`fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`

[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

`impl<T, U> TryInto for T where U: TryFrom<T>,`

[src]

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

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

`fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`

[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

`impl<T, U> Into for T where U: From<T>,`

[src]

####

`fn into(self) -> U`

[src]

Performs the conversion.

###

`impl<T> Borrow for T where T: ?Sized,`

[src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

`fn borrow(&self) -> &T`

[src]

Immutably borrows from an owned value. Read more

###

`impl<T> BorrowMut for T where T: ?Sized,`

[src]

####
ⓘImportant traits for &'_ mut I

### Important traits for &'_ mut I

`impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<'a, R: Read + ?Sized> Read for &'a mut Rimpl<'a, W: Write + ?Sized> Write for &'a mut W`

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

[src]

Mutably borrows from an owned value. Read more

###

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

[src]

####

`fn get_type_id(&self) -> TypeId`

[src]

🔬 This is a nightly-only experimental API. (`get_type_id` #27745)

this method will likely be replaced by an associated static

Gets the `TypeId` of `self`. Read more

###

`impl<T> ToOwned for T where T: Clone,`

[src]

#### `type Owned = T`

####

`fn to_owned(&self) -> T`

[src]

Creates owned data from borrowed data, usually by cloning. Read more

####

`fn clone_into(&self, target: &mut T)`

[src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

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