mirror of https://github.com/torvalds/linux.git
105 lines
3.6 KiB
Rust
105 lines
3.6 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Memory orderings.
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//!
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//! The semantics of these orderings follows the [`LKMM`] definitions and rules.
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//!
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//! - [`Acquire`] provides ordering between the load part of the annotated operation and all the
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//! following memory accesses, and if there is a store part, the store part has the [`Relaxed`]
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//! ordering.
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//! - [`Release`] provides ordering between all the preceding memory accesses and the store part of
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//! the annotated operation, and if there is a load part, the load part has the [`Relaxed`]
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//! ordering.
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//! - [`Full`] means "fully-ordered", that is:
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//! - It provides ordering between all the preceding memory accesses and the annotated operation.
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//! - It provides ordering between the annotated operation and all the following memory accesses.
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//! - It provides ordering between all the preceding memory accesses and all the following memory
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//! accesses.
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//! - All the orderings are the same strength as a full memory barrier (i.e. `smp_mb()`).
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//! - [`Relaxed`] provides no ordering except the dependency orderings. Dependency orderings are
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//! described in "DEPENDENCY RELATIONS" in [`LKMM`]'s [`explanation`].
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//!
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//! [`LKMM`]: srctree/tools/memory-model/
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//! [`explanation`]: srctree/tools/memory-model/Documentation/explanation.txt
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/// The annotation type for relaxed memory ordering, for the description of relaxed memory
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/// ordering, see [module-level documentation].
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///
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/// [module-level documentation]: crate::sync::atomic::ordering
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pub struct Relaxed;
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/// The annotation type for acquire memory ordering, for the description of acquire memory
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/// ordering, see [module-level documentation].
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///
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/// [module-level documentation]: crate::sync::atomic::ordering
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pub struct Acquire;
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/// The annotation type for release memory ordering, for the description of release memory
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/// ordering, see [module-level documentation].
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///
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/// [module-level documentation]: crate::sync::atomic::ordering
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pub struct Release;
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/// The annotation type for fully-ordered memory ordering, for the description fully-ordered memory
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/// ordering, see [module-level documentation].
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///
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/// [module-level documentation]: crate::sync::atomic::ordering
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pub struct Full;
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/// Describes the exact memory ordering.
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#[doc(hidden)]
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pub enum OrderingType {
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/// Relaxed ordering.
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Relaxed,
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/// Acquire ordering.
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Acquire,
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/// Release ordering.
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Release,
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/// Fully-ordered.
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Full,
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}
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mod internal {
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/// Sealed trait, can be only implemented inside atomic mod.
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pub trait Sealed {}
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impl Sealed for super::Relaxed {}
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impl Sealed for super::Acquire {}
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impl Sealed for super::Release {}
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impl Sealed for super::Full {}
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}
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/// The trait bound for annotating operations that support any ordering.
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pub trait Ordering: internal::Sealed {
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/// Describes the exact memory ordering.
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const TYPE: OrderingType;
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}
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impl Ordering for Relaxed {
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const TYPE: OrderingType = OrderingType::Relaxed;
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}
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impl Ordering for Acquire {
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const TYPE: OrderingType = OrderingType::Acquire;
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}
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impl Ordering for Release {
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const TYPE: OrderingType = OrderingType::Release;
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}
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impl Ordering for Full {
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const TYPE: OrderingType = OrderingType::Full;
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}
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/// The trait bound for operations that only support acquire or relaxed ordering.
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pub trait AcquireOrRelaxed: Ordering {}
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impl AcquireOrRelaxed for Acquire {}
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impl AcquireOrRelaxed for Relaxed {}
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/// The trait bound for operations that only support release or relaxed ordering.
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pub trait ReleaseOrRelaxed: Ordering {}
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impl ReleaseOrRelaxed for Release {}
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impl ReleaseOrRelaxed for Relaxed {}
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