-// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
//! Atomic types
//!
//! Atomic types provide primitive shared-memory communication between
//! types.
//!
//! This module defines atomic versions of a select number of primitive
-//! types, including `AtomicBool`, `AtomicIsize`, and `AtomicUsize`.
+//! types, including [`AtomicBool`], [`AtomicIsize`], [`AtomicUsize`],
+//! [`AtomicI8`], [`AtomicU16`], etc.
//! Atomic types present operations that, when used correctly, synchronize
//! updates between threads.
//!
-//! Each method takes an `Ordering` which represents the strength of
+//! [`AtomicBool`]: struct.AtomicBool.html
+//! [`AtomicIsize`]: struct.AtomicIsize.html
+//! [`AtomicUsize`]: struct.AtomicUsize.html
+//! [`AtomicI8`]: struct.AtomicI8.html
+//! [`AtomicU16`]: struct.AtomicU16.html
+//!
+//! Each method takes an [`Ordering`] which represents the strength of
//! the memory barrier for that operation. These orderings are the
-//! same as [LLVM atomic orderings][1].
+//! same as the [C++20 atomic orderings][1]. For more information see the [nomicon][2].
//!
-//! [1]: http://llvm.org/docs/LangRef.html#memory-model-for-concurrent-operations
+//! [`Ordering`]: enum.Ordering.html
//!
-//! Atomic variables are safe to share between threads (they implement `Sync`)
-//! but they do not themselves provide the mechanism for sharing. The most
-//! common way to share an atomic variable is to put it into an `Arc` (an
+//! [1]: https://en.cppreference.com/w/cpp/atomic/memory_order
+//! [2]: ../../../nomicon/atomics.html
+//!
+//! Atomic variables are safe to share between threads (they implement [`Sync`])
+//! but they do not themselves provide the mechanism for sharing and follow the
+//! [threading model](../../../std/thread/index.html#the-threading-model) of Rust.
+//! The most common way to share an atomic variable is to put it into an [`Arc`][arc] (an
//! atomically-reference-counted shared pointer).
//!
-//! Most atomic types may be stored in static variables, initialized using
-//! the provided static initializers like `INIT_ATOMIC_BOOL`. Atomic statics
+//! [`Sync`]: ../../marker/trait.Sync.html
+//! [arc]: ../../../std/sync/struct.Arc.html
+//!
+//! Atomic types may be stored in static variables, initialized using
+//! the constant initializers like [`AtomicBool::new`]. Atomic statics
//! are often used for lazy global initialization.
//!
+//! [`AtomicBool::new`]: struct.AtomicBool.html#method.new
+//!
+//! # Portability
+//!
+//! All atomic types in this module are guaranteed to be [lock-free] if they're
+//! available. This means they don't internally acquire a global mutex. Atomic
+//! types and operations are not guaranteed to be wait-free. This means that
+//! operations like `fetch_or` may be implemented with a compare-and-swap loop.
+//!
+//! Atomic operations may be implemented at the instruction layer with
+//! larger-size atomics. For example some platforms use 4-byte atomic
+//! instructions to implement `AtomicI8`. Note that this emulation should not
+//! have an impact on correctness of code, it's just something to be aware of.
+//!
+//! The atomic types in this module may not be available on all platforms. The
+//! atomic types here are all widely available, however, and can generally be
+//! relied upon existing. Some notable exceptions are:
+//!
+//! * PowerPC and MIPS platforms with 32-bit pointers do not have `AtomicU64` or
+//! `AtomicI64` types.
+//! * ARM platforms like `armv5te` that aren't for Linux do not have any atomics
+//! at all.
+//! * ARM targets with `thumbv6m` do not have atomic operations at all.
+//!
+//! Note that future platforms may be added that also do not have support for
+//! some atomic operations. Maximally portable code will want to be careful
+//! about which atomic types are used. `AtomicUsize` and `AtomicIsize` are
+//! generally the most portable, but even then they're not available everywhere.
+//! For reference, the `std` library requires pointer-sized atomics, although
+//! `core` does not.
+//!
+//! Currently you'll need to use `#[cfg(target_arch)]` primarily to
+//! conditionally compile in code with atomics. There is an unstable
+//! `#[cfg(target_has_atomic)]` as well which may be stabilized in the future.
+//!
+//! [lock-free]: https://en.wikipedia.org/wiki/Non-blocking_algorithm
//!
//! # Examples
//!
//! let spinlock = Arc::new(AtomicUsize::new(1));
//!
//! let spinlock_clone = spinlock.clone();
-//! thread::spawn(move|| {
+//! let thread = thread::spawn(move|| {
//! spinlock_clone.store(0, Ordering::SeqCst);
//! });
//!
//! // Wait for the other thread to release the lock
//! while spinlock.load(Ordering::SeqCst) != 0 {}
+//!
+//! if let Err(panic) = thread.join() {
+//! println!("Thread had an error: {:?}", panic);
+//! }
//! }
//! ```
//!
//! Keep a global count of live threads:
//!
//! ```
-//! use std::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
+//! use std::sync::atomic::{AtomicUsize, Ordering};
//!
-//! static GLOBAL_THREAD_COUNT: AtomicUsize = ATOMIC_USIZE_INIT;
+//! static GLOBAL_THREAD_COUNT: AtomicUsize = AtomicUsize::new(0);
//!
//! let old_thread_count = GLOBAL_THREAD_COUNT.fetch_add(1, Ordering::SeqCst);
//! println!("live threads: {}", old_thread_count + 1);
//! ```
+// ignore-tidy-undocumented-unsafe
+
#![stable(feature = "rust1", since = "1.0.0")]
+#![cfg_attr(not(target_has_atomic_load_store = "8"), allow(dead_code))]
+#![cfg_attr(not(target_has_atomic_load_store = "8"), allow(unused_imports))]
use self::Ordering::*;
-use marker::{Send, Sync};
+use crate::intrinsics;
+use crate::cell::UnsafeCell;
+use crate::fmt;
-use intrinsics;
-use cell::UnsafeCell;
+use crate::hint::spin_loop;
-use default::Default;
-use fmt;
+/// Signals the processor that it is inside a busy-wait spin-loop ("spin lock").
+///
+/// Upon receiving spin-loop signal the processor can optimize its behavior by, for example, saving
+/// power or switching hyper-threads.
+///
+/// This function is different from [`std::thread::yield_now`] which directly yields to the
+/// system's scheduler, whereas `spin_loop_hint` does not interact with the operating system.
+///
+/// Spin locks can be very efficient for short lock durations because they do not involve context
+/// switches or interaction with the operating system. For long lock durations they become wasteful
+/// however because they use CPU cycles for the entire lock duration, and using a
+/// [`std::sync::Mutex`] is likely the better approach. If actively spinning for a long time is
+/// required, e.g. because code polls a non-blocking API, calling [`std::thread::yield_now`]
+/// or [`std::thread::sleep`] may be the best option.
+///
+/// **Note**: Spin locks are based on the underlying assumption that another thread will release
+/// the lock 'soon'. In order for this to work, that other thread must run on a different CPU or
+/// core (at least potentially). Spin locks do not work efficiently on single CPU / core platforms.
+///
+/// **Note**: On platforms that do not support receiving spin-loop hints this function does not
+/// do anything at all.
+///
+/// [`std::thread::yield_now`]: ../../../std/thread/fn.yield_now.html
+/// [`std::thread::sleep`]: ../../../std/thread/fn.sleep.html
+/// [`std::sync::Mutex`]: ../../../std/sync/struct.Mutex.html
+#[inline]
+#[stable(feature = "spin_loop_hint", since = "1.24.0")]
+pub fn spin_loop_hint() {
+ spin_loop()
+}
/// A boolean type which can be safely shared between threads.
+///
+/// This type has the same in-memory representation as a [`bool`].
+///
+/// [`bool`]: ../../../std/primitive.bool.html
+#[cfg(target_has_atomic_load_store = "8")]
#[stable(feature = "rust1", since = "1.0.0")]
+#[repr(C, align(1))]
pub struct AtomicBool {
- v: UnsafeCell<usize>,
-}
-
-impl Default for AtomicBool {
- fn default() -> Self {
- Self::new(Default::default())
- }
+ v: UnsafeCell<u8>,
}
-unsafe impl Sync for AtomicBool {}
-
-/// A signed integer type which can be safely shared between threads.
+#[cfg(target_has_atomic_load_store = "8")]
#[stable(feature = "rust1", since = "1.0.0")]
-pub struct AtomicIsize {
- v: UnsafeCell<isize>,
-}
-
-impl Default for AtomicIsize {
+impl Default for AtomicBool {
+ /// Creates an `AtomicBool` initialized to `false`.
fn default() -> Self {
- Self::new(Default::default())
+ Self::new(false)
}
}
-unsafe impl Sync for AtomicIsize {}
-
-/// An unsigned integer type which can be safely shared between threads.
+// Send is implicitly implemented for AtomicBool.
+#[cfg(target_has_atomic_load_store = "8")]
#[stable(feature = "rust1", since = "1.0.0")]
-pub struct AtomicUsize {
- v: UnsafeCell<usize>,
-}
-
-impl Default for AtomicUsize {
- fn default() -> Self {
- Self::new(Default::default())
- }
-}
-
-unsafe impl Sync for AtomicUsize {}
+unsafe impl Sync for AtomicBool {}
/// A raw pointer type which can be safely shared between threads.
+///
+/// This type has the same in-memory representation as a `*mut T`.
+#[cfg(target_has_atomic_load_store = "ptr")]
#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(target_pointer_width = "16", repr(C, align(2)))]
+#[cfg_attr(target_pointer_width = "32", repr(C, align(4)))]
+#[cfg_attr(target_pointer_width = "64", repr(C, align(8)))]
pub struct AtomicPtr<T> {
p: UnsafeCell<*mut T>,
}
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[stable(feature = "rust1", since = "1.0.0")]
impl<T> Default for AtomicPtr<T> {
+ /// Creates a null `AtomicPtr<T>`.
fn default() -> AtomicPtr<T> {
- AtomicPtr::new(::ptr::null_mut())
+ AtomicPtr::new(crate::ptr::null_mut())
}
}
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T> Send for AtomicPtr<T> {}
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T> Sync for AtomicPtr<T> {}
/// 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.
+/// Memory orderings specify the way atomic operations synchronize memory.
+/// In its weakest [`Relaxed`][Ordering::Relaxed], only the memory directly touched by the
+/// operation is synchronized. On the other hand, a store-load pair of [`SeqCst`][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](https://en.cppreference.com/w/cpp/atomic/memory_order).
///
-/// Rust's memory orderings are [the same as
-/// LLVM's](http://llvm.org/docs/LangRef.html#memory-model-for-concurrent-operations).
+/// For more information see the [nomicon].
+///
+/// [nomicon]: ../../../nomicon/atomics.html
+/// [Ordering::Relaxed]: #variant.Relaxed
+/// [Ordering::SeqCst]: #variant.SeqCst
#[stable(feature = "rust1", since = "1.0.0")]
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
+#[non_exhaustive]
pub enum Ordering {
/// No ordering constraints, only atomic operations.
+ ///
+ /// Corresponds to [`memory_order_relaxed`] in C++20.
+ ///
+ /// [`memory_order_relaxed`]: https://en.cppreference.com/w/cpp/atomic/memory_order#Relaxed_ordering
#[stable(feature = "rust1", since = "1.0.0")]
Relaxed,
- /// When coupled with a store, all previous writes become visible
- /// to another thread that performs a load with `Acquire` ordering
- /// on the same value.
+ /// 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.
+ ///
+ /// [`Release`]: #variant.Release
+ /// [`Acquire`]: #variant.Acquire
+ /// [`Relaxed`]: #variant.Relaxed
+ /// [`memory_order_release`]: https://en.cppreference.com/w/cpp/atomic/memory_order#Release-Acquire_ordering
#[stable(feature = "rust1", since = "1.0.0")]
Release,
- /// When coupled with a load, all subsequent loads will see data
- /// written before a store with `Release` ordering on the same value
- /// in another thread.
+ /// 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.
+ ///
+ /// [`Acquire`]: #variant.Acquire
+ /// [`Release`]: #variant.Release
+ /// [`Relaxed`]: #variant.Relaxed
+ /// [`memory_order_acquire`]: https://en.cppreference.com/w/cpp/atomic/memory_order#Release-Acquire_ordering
#[stable(feature = "rust1", since = "1.0.0")]
Acquire,
- /// When coupled with a load, uses `Acquire` ordering, and with a store
- /// `Release` ordering.
+ /// 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.
+ ///
+ /// [`memory_order_acq_rel`]: https://en.cppreference.com/w/cpp/atomic/memory_order#Release-Acquire_ordering
+ /// [`Acquire`]: #variant.Acquire
+ /// [`Release`]: #variant.Release
+ /// [`Relaxed`]: #variant.Relaxed
#[stable(feature = "rust1", since = "1.0.0")]
AcqRel,
- /// Like `AcqRel` with the additional guarantee that all threads see all
+ /// 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.
+ ///
+ /// [`memory_order_seq_cst`]: https://en.cppreference.com/w/cpp/atomic/memory_order#Sequentially-consistent_ordering
+ /// [`Acquire`]: #variant.Acquire
+ /// [`Release`]: #variant.Release
+ /// [`AcqRel`]: #variant.AcqRel
#[stable(feature = "rust1", since = "1.0.0")]
SeqCst,
}
-/// An `AtomicBool` initialized to `false`.
+/// An [`AtomicBool`] initialized to `false`.
+///
+/// [`AtomicBool`]: struct.AtomicBool.html
+#[cfg(target_has_atomic_load_store = "8")]
#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_deprecated(
+ since = "1.34.0",
+ reason = "the `new` function is now preferred",
+ suggestion = "AtomicBool::new(false)",
+)]
pub const ATOMIC_BOOL_INIT: AtomicBool = AtomicBool::new(false);
-/// An `AtomicIsize` initialized to `0`.
-#[stable(feature = "rust1", since = "1.0.0")]
-pub const ATOMIC_ISIZE_INIT: AtomicIsize = AtomicIsize::new(0);
-/// An `AtomicUsize` initialized to `0`.
-#[stable(feature = "rust1", since = "1.0.0")]
-pub const ATOMIC_USIZE_INIT: AtomicUsize = AtomicUsize::new(0);
-
-// NB: Needs to be -1 (0b11111111...) to make fetch_nand work correctly
-const UINT_TRUE: usize = !0;
+#[cfg(target_has_atomic_load_store = "8")]
impl AtomicBool {
/// Creates a new `AtomicBool`.
///
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_atomic_new", since = "1.32.0"))]
pub const fn new(v: bool) -> AtomicBool {
- AtomicBool { v: UnsafeCell::new(-(v as isize) as usize) }
+ AtomicBool { v: UnsafeCell::new(v as u8) }
+ }
+
+ /// Returns a mutable reference to the underlying [`bool`].
+ ///
+ /// This is safe because the mutable reference guarantees that no other threads are
+ /// concurrently accessing the atomic data.
+ ///
+ /// [`bool`]: ../../../std/primitive.bool.html
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::atomic::{AtomicBool, Ordering};
+ ///
+ /// let mut some_bool = AtomicBool::new(true);
+ /// assert_eq!(*some_bool.get_mut(), true);
+ /// *some_bool.get_mut() = false;
+ /// assert_eq!(some_bool.load(Ordering::SeqCst), false);
+ /// ```
+ #[inline]
+ #[stable(feature = "atomic_access", since = "1.15.0")]
+ pub fn get_mut(&mut self) -> &mut bool {
+ unsafe { &mut *(self.v.get() as *mut bool) }
+ }
+
+ /// 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 std::sync::atomic::AtomicBool;
+ ///
+ /// let some_bool = AtomicBool::new(true);
+ /// assert_eq!(some_bool.into_inner(), true);
+ /// ```
+ #[inline]
+ #[stable(feature = "atomic_access", since = "1.15.0")]
+ pub fn into_inner(self) -> bool {
+ self.v.into_inner() != 0
}
/// Loads a value from the bool.
///
- /// `load` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// `load` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. Possible values are [`SeqCst`], [`Acquire`] and [`Relaxed`].
///
/// # Panics
///
- /// Panics if `order` is `Release` or `AcqRel`.
+ /// Panics if `order` is [`Release`] or [`AcqRel`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
///
/// # Examples
///
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn load(&self, order: Ordering) -> bool {
- unsafe { atomic_load(self.v.get(), order) > 0 }
+ unsafe { atomic_load(self.v.get(), order) != 0 }
}
/// Stores a value into the bool.
///
- /// `store` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// `store` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. Possible values are [`SeqCst`], [`Release`] and [`Relaxed`].
+ ///
+ /// # Panics
+ ///
+ /// Panics if `order` is [`Acquire`] or [`AcqRel`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
///
/// # Examples
///
/// some_bool.store(false, Ordering::Relaxed);
/// assert_eq!(some_bool.load(Ordering::Relaxed), false);
/// ```
- ///
- /// # Panics
- ///
- /// Panics if `order` is `Acquire` or `AcqRel`.
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn store(&self, val: bool, order: Ordering) {
- let val = if val { UINT_TRUE } else { 0 };
-
- unsafe { atomic_store(self.v.get(), val, order); }
+ unsafe {
+ atomic_store(self.v.get(), val as u8, order);
+ }
}
- /// Stores a value into the bool, returning the old value.
+ /// Stores a value into the bool, returning the previous value.
///
- /// `swap` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// `swap` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. All ordering modes are possible. Note that using
+ /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
+ /// using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
///
/// # Examples
///
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg(target_has_atomic = "8")]
pub fn swap(&self, val: bool, order: Ordering) -> bool {
- let val = if val { UINT_TRUE } else { 0 };
-
- unsafe { atomic_swap(self.v.get(), val, order) > 0 }
+ unsafe { atomic_swap(self.v.get(), val as u8, order) != 0 }
}
- /// Stores a value into the `bool` if the current value is the same as the `current` value.
+ /// Stores a value into the [`bool`] if the current value is the same as the `current` value.
///
/// The return value is always the previous value. If it is equal to `current`, then the value
/// was updated.
///
- /// `compare_and_swap` also takes an `Ordering` argument which describes the memory ordering of
- /// this operation.
+ /// `compare_and_swap` also takes an [`Ordering`] argument which describes the memory
+ /// ordering of this operation. Notice that even when using [`AcqRel`], the operation
+ /// might fail and hence just perform an `Acquire` load, but not have `Release` semantics.
+ /// Using [`Acquire`] makes the store part of this operation [`Relaxed`] if it
+ /// happens, and using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+ /// [`bool`]: ../../../std/primitive.bool.html
///
/// # Examples
///
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg(target_has_atomic = "8")]
pub fn compare_and_swap(&self, current: bool, new: bool, order: Ordering) -> bool {
- let current = if current { UINT_TRUE } else { 0 };
- let new = if new { UINT_TRUE } else { 0 };
+ match self.compare_exchange(current, new, order, strongest_failure_ordering(order)) {
+ Ok(x) => x,
+ Err(x) => x,
+ }
+ }
+
+ /// Stores a value into the [`bool`] if the current value is the same as the `current` value.
+ ///
+ /// 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`.
+ ///
+ /// `compare_exchange` takes two [`Ordering`] arguments to describe the memory
+ /// ordering of this operation. The first describes the required ordering if the
+ /// operation succeeds while the second describes the required ordering when the
+ /// operation fails. Using [`Acquire`] as success ordering makes the store part
+ /// of this operation [`Relaxed`], and using [`Release`] makes the successful load
+ /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+ /// and must be equivalent to or weaker than the success ordering.
+ ///
+ ///
+ /// [`bool`]: ../../../std/primitive.bool.html
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::atomic::{AtomicBool, Ordering};
+ ///
+ /// let some_bool = AtomicBool::new(true);
+ ///
+ /// assert_eq!(some_bool.compare_exchange(true,
+ /// false,
+ /// Ordering::Acquire,
+ /// Ordering::Relaxed),
+ /// Ok(true));
+ /// assert_eq!(some_bool.load(Ordering::Relaxed), false);
+ ///
+ /// assert_eq!(some_bool.compare_exchange(true, true,
+ /// Ordering::SeqCst,
+ /// Ordering::Acquire),
+ /// Err(false));
+ /// assert_eq!(some_bool.load(Ordering::Relaxed), false);
+ /// ```
+ #[inline]
+ #[stable(feature = "extended_compare_and_swap", since = "1.10.0")]
+ #[cfg(target_has_atomic = "8")]
+ pub fn compare_exchange(&self,
+ current: bool,
+ new: bool,
+ success: Ordering,
+ failure: Ordering)
+ -> Result<bool, bool> {
+ match unsafe {
+ atomic_compare_exchange(self.v.get(), current as u8, new as u8, success, failure)
+ } {
+ Ok(x) => Ok(x != 0),
+ Err(x) => Err(x != 0),
+ }
+ }
- unsafe { atomic_compare_and_swap(self.v.get(), current, new, order) > 0 }
+ /// Stores a value into the [`bool`] if the current value is the same as the `current` value.
+ ///
+ /// Unlike [`compare_exchange`], this function is allowed to spuriously fail even when the
+ /// comparison succeeds, which can result in more efficient code on some platforms. The
+ /// return value is a result indicating whether the new value was written and containing the
+ /// previous value.
+ ///
+ /// `compare_exchange_weak` takes two [`Ordering`] arguments to describe the memory
+ /// ordering of this operation. The first describes the required ordering if the
+ /// operation succeeds while the second describes the required ordering when the
+ /// operation fails. Using [`Acquire`] as success ordering makes the store part
+ /// of this operation [`Relaxed`], and using [`Release`] makes the successful load
+ /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+ /// and must be equivalent to or weaker than the success ordering.
+ ///
+ /// [`bool`]: ../../../std/primitive.bool.html
+ /// [`compare_exchange`]: #method.compare_exchange
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::sync::atomic::{AtomicBool, Ordering};
+ ///
+ /// let val = AtomicBool::new(false);
+ ///
+ /// let new = true;
+ /// let mut old = val.load(Ordering::Relaxed);
+ /// loop {
+ /// match val.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
+ /// Ok(_) => break,
+ /// Err(x) => old = x,
+ /// }
+ /// }
+ /// ```
+ #[inline]
+ #[stable(feature = "extended_compare_and_swap", since = "1.10.0")]
+ #[cfg(target_has_atomic = "8")]
+ pub fn compare_exchange_weak(&self,
+ current: bool,
+ new: bool,
+ success: Ordering,
+ failure: Ordering)
+ -> Result<bool, bool> {
+ match unsafe {
+ atomic_compare_exchange_weak(self.v.get(), current as u8, new as u8, success, failure)
+ } {
+ Ok(x) => Ok(x != 0),
+ Err(x) => Err(x != 0),
+ }
}
/// Logical "and" with a boolean value.
///
/// Returns the previous value.
///
+ /// `fetch_and` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. All ordering modes are possible. Note that using
+ /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
+ /// using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ ///
/// # Examples
///
/// ```
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg(target_has_atomic = "8")]
pub fn fetch_and(&self, val: bool, order: Ordering) -> bool {
- let val = if val { UINT_TRUE } else { 0 };
-
- unsafe { atomic_and(self.v.get(), val, order) > 0 }
+ unsafe { atomic_and(self.v.get(), val as u8, order) != 0 }
}
/// Logical "nand" with a boolean value.
///
/// Returns the previous value.
///
+ /// `fetch_nand` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. All ordering modes are possible. Note that using
+ /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
+ /// using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ ///
/// # Examples
///
/// ```
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg(target_has_atomic = "8")]
pub fn fetch_nand(&self, val: bool, order: Ordering) -> bool {
- let val = if val { UINT_TRUE } else { 0 };
-
- unsafe { atomic_nand(self.v.get(), val, order) > 0 }
+ // We can't use atomic_nand here because it can result in a bool with
+ // an invalid value. This happens because the atomic operation is done
+ // with an 8-bit integer internally, which would set the upper 7 bits.
+ // So we just use fetch_xor or swap instead.
+ if val {
+ // !(x & true) == !x
+ // We must invert the bool.
+ self.fetch_xor(true, order)
+ } else {
+ // !(x & false) == true
+ // We must set the bool to true.
+ self.swap(true, order)
+ }
}
/// Logical "or" with a boolean value.
///
/// Returns the previous value.
///
+ /// `fetch_or` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. All ordering modes are possible. Note that using
+ /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
+ /// using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ ///
/// # Examples
///
/// ```
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg(target_has_atomic = "8")]
pub fn fetch_or(&self, val: bool, order: Ordering) -> bool {
- let val = if val { UINT_TRUE } else { 0 };
-
- unsafe { atomic_or(self.v.get(), val, order) > 0 }
+ unsafe { atomic_or(self.v.get(), val as u8, order) != 0 }
}
/// Logical "xor" with a boolean value.
///
/// Returns the previous value.
///
+ /// `fetch_xor` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. All ordering modes are possible. Note that using
+ /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
+ /// using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ ///
/// # Examples
///
/// ```
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+ #[cfg(target_has_atomic = "8")]
pub fn fetch_xor(&self, val: bool, order: Ordering) -> bool {
- let val = if val { UINT_TRUE } else { 0 };
-
- unsafe { atomic_xor(self.v.get(), val, order) > 0 }
+ unsafe { atomic_xor(self.v.get(), val as u8, order) != 0 }
}
-}
-#[stable(feature = "rust1", since = "1.0.0")]
-impl AtomicIsize {
- /// Creates a new `AtomicIsize`.
+ /// Returns a mutable pointer to the underlying [`bool`].
///
- /// # Examples
+ /// Doing non-atomic reads and writes on the resulting integer can be a data race.
+ /// This method is mostly useful for FFI, where the function signature may use
+ /// `*mut bool` instead of `&AtomicBool`.
///
- /// ```
- /// use std::sync::atomic::AtomicIsize;
+ /// Returning an `*mut` pointer from a shared reference to this atomic is safe because the
+ /// atomic types work with interior mutability. All modifications of an atomic change the value
+ /// through a shared reference, and can do so safely as long as they use atomic operations. Any
+ /// use of the returned raw pointer requires an `unsafe` block and still has to uphold the same
+ /// restriction: operations on it must be atomic.
///
- /// let atomic_forty_two = AtomicIsize::new(42);
+ /// [`bool`]: ../../../std/primitive.bool.html
+ ///
+ /// # Examples
+ ///
+ /// ```ignore (extern-declaration)
+ /// # fn main() {
+ /// use std::sync::atomic::AtomicBool;
+ /// extern {
+ /// fn my_atomic_op(arg: *mut bool);
+ /// }
+ ///
+ /// let mut atomic = AtomicBool::new(true);
+ /// unsafe {
+ /// my_atomic_op(atomic.as_mut_ptr());
+ /// }
+ /// # }
/// ```
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub const fn new(v: isize) -> AtomicIsize {
- AtomicIsize {v: UnsafeCell::new(v)}
+ #[unstable(feature = "atomic_mut_ptr",
+ reason = "recently added",
+ issue = "66893")]
+ pub fn as_mut_ptr(&self) -> *mut bool {
+ self.v.get() as *mut bool
}
+}
- /// Loads a value from the isize.
- ///
- /// `load` takes an `Ordering` argument which describes the memory ordering of this operation.
- ///
- /// # Panics
- ///
- /// Panics if `order` is `Release` or `AcqRel`.
+#[cfg(target_has_atomic_load_store = "ptr")]
+impl<T> AtomicPtr<T> {
+ /// Creates a new `AtomicPtr`.
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
- ///
- /// let some_isize = AtomicIsize::new(5);
+ /// use std::sync::atomic::AtomicPtr;
///
- /// assert_eq!(some_isize.load(Ordering::Relaxed), 5);
+ /// let ptr = &mut 5;
+ /// let atomic_ptr = AtomicPtr::new(ptr);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
- pub fn load(&self, order: Ordering) -> isize {
- unsafe { atomic_load(self.v.get(), order) }
+ #[cfg_attr(not(bootstrap), rustc_const_stable(feature = "const_atomic_new", since = "1.32.0"))]
+ pub const fn new(p: *mut T) -> AtomicPtr<T> {
+ AtomicPtr { p: UnsafeCell::new(p) }
}
- /// Stores a value into the isize.
+ /// Returns a mutable reference to the underlying pointer.
///
- /// `store` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// This is safe because the mutable reference guarantees that no other threads are
+ /// concurrently accessing the atomic data.
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
- ///
- /// let some_isize = AtomicIsize::new(5);
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
///
- /// some_isize.store(10, Ordering::Relaxed);
- /// assert_eq!(some_isize.load(Ordering::Relaxed), 10);
+ /// let mut atomic_ptr = AtomicPtr::new(&mut 10);
+ /// *atomic_ptr.get_mut() = &mut 5;
+ /// assert_eq!(unsafe { *atomic_ptr.load(Ordering::SeqCst) }, 5);
/// ```
- ///
- /// # Panics
- ///
- /// Panics if `order` is `Acquire` or `AcqRel`.
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn store(&self, val: isize, order: Ordering) {
- unsafe { atomic_store(self.v.get(), val, order); }
+ #[stable(feature = "atomic_access", since = "1.15.0")]
+ pub fn get_mut(&mut self) -> &mut *mut T {
+ unsafe { &mut *self.p.get() }
}
- /// Stores a value into the isize, returning the old value.
+ /// Consumes the atomic and returns the contained value.
///
- /// `swap` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// This is safe because passing `self` by value guarantees that no other threads are
+ /// concurrently accessing the atomic data.
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
- ///
- /// let some_isize = AtomicIsize::new(5);
+ /// use std::sync::atomic::AtomicPtr;
///
- /// assert_eq!(some_isize.swap(10, Ordering::Relaxed), 5);
+ /// let atomic_ptr = AtomicPtr::new(&mut 5);
+ /// assert_eq!(unsafe { *atomic_ptr.into_inner() }, 5);
/// ```
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn swap(&self, val: isize, order: Ordering) -> isize {
- unsafe { atomic_swap(self.v.get(), val, order) }
+ #[stable(feature = "atomic_access", since = "1.15.0")]
+ pub fn into_inner(self) -> *mut T {
+ self.p.into_inner()
}
- /// Stores a value into the `isize` if the current value is the same as the `current` value.
+ /// Loads a value from the pointer.
///
- /// The return value is always the previous value. If it is equal to `current`, then the value
- /// was updated.
+ /// `load` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. Possible values are [`SeqCst`], [`Acquire`] and [`Relaxed`].
+ ///
+ /// # Panics
///
- /// `compare_and_swap` also takes an `Ordering` argument which describes the memory ordering of
- /// this operation.
+ /// Panics if `order` is [`Release`] or [`AcqRel`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
- ///
- /// let some_isize = AtomicIsize::new(5);
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
///
- /// assert_eq!(some_isize.compare_and_swap(5, 10, Ordering::Relaxed), 5);
- /// assert_eq!(some_isize.load(Ordering::Relaxed), 10);
+ /// let ptr = &mut 5;
+ /// let some_ptr = AtomicPtr::new(ptr);
///
- /// assert_eq!(some_isize.compare_and_swap(6, 12, Ordering::Relaxed), 10);
- /// assert_eq!(some_isize.load(Ordering::Relaxed), 10);
+ /// let value = some_ptr.load(Ordering::Relaxed);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
- pub fn compare_and_swap(&self, current: isize, new: isize, order: Ordering) -> isize {
- unsafe { atomic_compare_and_swap(self.v.get(), current, new, order) }
+ pub fn load(&self, order: Ordering) -> *mut T {
+ unsafe { atomic_load(self.p.get() as *mut usize, order) as *mut T }
}
- /// Add an isize to the current value, returning the previous value.
+ /// Stores a value into the pointer.
///
- /// # Examples
+ /// `store` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. Possible values are [`SeqCst`], [`Release`] and [`Relaxed`].
///
- /// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
+ /// # Panics
///
- /// let foo = AtomicIsize::new(0);
- /// assert_eq!(foo.fetch_add(10, Ordering::SeqCst), 0);
- /// assert_eq!(foo.load(Ordering::SeqCst), 10);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_add(&self, val: isize, order: Ordering) -> isize {
- unsafe { atomic_add(self.v.get(), val, order) }
- }
-
- /// Subtract an isize from the current value, returning the previous value.
+ /// Panics if `order` is [`Acquire`] or [`AcqRel`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
+ ///
+ /// let ptr = &mut 5;
+ /// let some_ptr = AtomicPtr::new(ptr);
+ ///
+ /// let other_ptr = &mut 10;
///
- /// let foo = AtomicIsize::new(0);
- /// assert_eq!(foo.fetch_sub(10, Ordering::SeqCst), 0);
- /// assert_eq!(foo.load(Ordering::SeqCst), -10);
+ /// some_ptr.store(other_ptr, Ordering::Relaxed);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_sub(&self, val: isize, order: Ordering) -> isize {
- unsafe { atomic_sub(self.v.get(), val, order) }
+ pub fn store(&self, ptr: *mut T, order: Ordering) {
+ unsafe {
+ atomic_store(self.p.get() as *mut usize, ptr as usize, order);
+ }
}
- /// Bitwise and with the current isize, returning the previous value.
+ /// Stores a value into the pointer, returning the previous value.
+ ///
+ /// `swap` takes an [`Ordering`] argument which describes the memory ordering
+ /// of this operation. All ordering modes are possible. Note that using
+ /// [`Acquire`] makes the store part of this operation [`Relaxed`], and
+ /// using [`Release`] makes the load part [`Relaxed`].
+ ///
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
///
- /// let foo = AtomicIsize::new(0b101101);
- /// assert_eq!(foo.fetch_and(0b110011, Ordering::SeqCst), 0b101101);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0b100001);
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_and(&self, val: isize, order: Ordering) -> isize {
- unsafe { atomic_and(self.v.get(), val, order) }
- }
-
- /// Bitwise or with the current isize, returning the previous value.
+ /// let ptr = &mut 5;
+ /// let some_ptr = AtomicPtr::new(ptr);
///
- /// # Examples
+ /// let other_ptr = &mut 10;
///
+ /// let value = some_ptr.swap(other_ptr, Ordering::Relaxed);
/// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
- ///
- /// let foo = AtomicIsize::new(0b101101);
- /// assert_eq!(foo.fetch_or(0b110011, Ordering::SeqCst), 0b101101);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0b111111);
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_or(&self, val: isize, order: Ordering) -> isize {
- unsafe { atomic_or(self.v.get(), val, order) }
+ #[cfg(target_has_atomic = "ptr")]
+ pub fn swap(&self, ptr: *mut T, order: Ordering) -> *mut T {
+ unsafe { atomic_swap(self.p.get() as *mut usize, ptr as usize, order) as *mut T }
}
- /// Bitwise xor with the current isize, returning the previous value.
+ /// Stores a value into the pointer if the current value is the same as the `current` value.
///
- /// # Examples
+ /// The return value is always the previous value. If it is equal to `current`, then the value
+ /// was updated.
///
- /// ```
- /// use std::sync::atomic::{AtomicIsize, Ordering};
+ /// `compare_and_swap` also takes an [`Ordering`] argument which describes the memory
+ /// ordering of this operation. Notice that even when using [`AcqRel`], the operation
+ /// might fail and hence just perform an `Acquire` load, but not have `Release` semantics.
+ /// Using [`Acquire`] makes the store part of this operation [`Relaxed`] if it
+ /// happens, and using [`Release`] makes the load part [`Relaxed`].
///
- /// let foo = AtomicIsize::new(0b101101);
- /// assert_eq!(foo.fetch_xor(0b110011, Ordering::SeqCst), 0b101101);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0b011110);
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_xor(&self, val: isize, order: Ordering) -> isize {
- unsafe { atomic_xor(self.v.get(), val, order) }
- }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl AtomicUsize {
- /// Creates a new `AtomicUsize`.
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::AtomicUsize;
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
+ ///
+ /// let ptr = &mut 5;
+ /// let some_ptr = AtomicPtr::new(ptr);
+ ///
+ /// let other_ptr = &mut 10;
///
- /// let atomic_forty_two = AtomicUsize::new(42);
+ /// let value = some_ptr.compare_and_swap(ptr, other_ptr, Ordering::Relaxed);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
- pub const fn new(v: usize) -> AtomicUsize {
- AtomicUsize { v: UnsafeCell::new(v) }
+ #[cfg(target_has_atomic = "ptr")]
+ pub fn compare_and_swap(&self, current: *mut T, new: *mut T, order: Ordering) -> *mut T {
+ match self.compare_exchange(current, new, order, strongest_failure_ordering(order)) {
+ Ok(x) => x,
+ Err(x) => x,
+ }
}
- /// Loads a value from the usize.
+ /// Stores a value into the pointer if the current value is the same as the `current` value.
///
- /// `load` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// 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`.
///
- /// # Panics
+ /// `compare_exchange` takes two [`Ordering`] arguments to describe the memory
+ /// ordering of this operation. The first describes the required ordering if the
+ /// operation succeeds while the second describes the required ordering when the
+ /// operation fails. Using [`Acquire`] as success ordering makes the store part
+ /// of this operation [`Relaxed`], and using [`Release`] makes the successful load
+ /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+ /// and must be equivalent to or weaker than the success ordering.
///
- /// Panics if `order` is `Release` or `AcqRel`.
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
///
- /// let some_usize = AtomicUsize::new(5);
+ /// let ptr = &mut 5;
+ /// let some_ptr = AtomicPtr::new(ptr);
+ ///
+ /// let other_ptr = &mut 10;
///
- /// assert_eq!(some_usize.load(Ordering::Relaxed), 5);
+ /// let value = some_ptr.compare_exchange(ptr, other_ptr,
+ /// Ordering::SeqCst, Ordering::Relaxed);
/// ```
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn load(&self, order: Ordering) -> usize {
- unsafe { atomic_load(self.v.get(), order) }
+ #[stable(feature = "extended_compare_and_swap", since = "1.10.0")]
+ #[cfg(target_has_atomic = "ptr")]
+ pub fn compare_exchange(&self,
+ current: *mut T,
+ new: *mut T,
+ success: Ordering,
+ failure: Ordering)
+ -> Result<*mut T, *mut T> {
+ unsafe {
+ let res = atomic_compare_exchange(self.p.get() as *mut usize,
+ current as usize,
+ new as usize,
+ success,
+ failure);
+ match res {
+ Ok(x) => Ok(x as *mut T),
+ Err(x) => Err(x as *mut T),
+ }
+ }
}
- /// Stores a value into the usize.
+ /// Stores a value into the pointer if the current value is the same as the `current` value.
///
- /// `store` takes an `Ordering` argument which describes the memory ordering of this operation.
+ /// Unlike [`compare_exchange`], this function is allowed to spuriously fail even when the
+ /// comparison succeeds, which can result in more efficient code on some platforms. The
+ /// return value is a result indicating whether the new value was written and containing the
+ /// previous value.
+ ///
+ /// `compare_exchange_weak` takes two [`Ordering`] arguments to describe the memory
+ /// ordering of this operation. The first describes the required ordering if the
+ /// operation succeeds while the second describes the required ordering when the
+ /// operation fails. Using [`Acquire`] as success ordering makes the store part
+ /// of this operation [`Relaxed`], and using [`Release`] makes the successful load
+ /// [`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+ /// and must be equivalent to or weaker than the success ordering.
+ ///
+ /// [`compare_exchange`]: #method.compare_exchange
+ /// [`Ordering`]: enum.Ordering.html
+ /// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+ /// [`Release`]: enum.Ordering.html#variant.Release
+ /// [`Acquire`]: enum.Ordering.html#variant.Acquire
+ /// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
+ /// use std::sync::atomic::{AtomicPtr, Ordering};
///
- /// let some_usize = AtomicUsize::new(5);
+ /// let some_ptr = AtomicPtr::new(&mut 5);
///
- /// some_usize.store(10, Ordering::Relaxed);
- /// assert_eq!(some_usize.load(Ordering::Relaxed), 10);
+ /// let new = &mut 10;
+ /// let mut old = some_ptr.load(Ordering::Relaxed);
+ /// loop {
+ /// match some_ptr.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
+ /// Ok(_) => break,
+ /// Err(x) => old = x,
+ /// }
+ /// }
/// ```
- ///
- /// # Panics
- ///
- /// Panics if `order` is `Acquire` or `AcqRel`.
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn store(&self, val: usize, order: Ordering) {
- unsafe { atomic_store(self.v.get(), val, order); }
+ #[stable(feature = "extended_compare_and_swap", since = "1.10.0")]
+ #[cfg(target_has_atomic = "ptr")]
+ pub fn compare_exchange_weak(&self,
+ current: *mut T,
+ new: *mut T,
+ success: Ordering,
+ failure: Ordering)
+ -> Result<*mut T, *mut T> {
+ unsafe {
+ let res = atomic_compare_exchange_weak(self.p.get() as *mut usize,
+ current as usize,
+ new as usize,
+ success,
+ failure);
+ match res {
+ Ok(x) => Ok(x as *mut T),
+ Err(x) => Err(x as *mut T),
+ }
+ }
}
+}
- /// Stores a value into the usize, returning the old value.
- ///
- /// `swap` takes an `Ordering` argument which describes the memory ordering of this operation.
+#[cfg(target_has_atomic_load_store = "8")]
+#[stable(feature = "atomic_bool_from", since = "1.24.0")]
+impl From<bool> for AtomicBool {
+ /// Converts a `bool` into an `AtomicBool`.
///
/// # Examples
///
/// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let some_usize= AtomicUsize::new(5);
- ///
- /// assert_eq!(some_usize.swap(10, Ordering::Relaxed), 5);
- /// assert_eq!(some_usize.load(Ordering::Relaxed), 10);
+ /// use std::sync::atomic::AtomicBool;
+ /// let atomic_bool = AtomicBool::from(true);
+ /// assert_eq!(format!("{:?}", atomic_bool), "true")
/// ```
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn swap(&self, val: usize, order: Ordering) -> usize {
- unsafe { atomic_swap(self.v.get(), val, order) }
- }
+ fn from(b: bool) -> Self { Self::new(b) }
+}
- /// Stores a value into the `usize` if the current value is the same as the `current` value.
- ///
- /// The return value is always the previous value. If it is equal to `current`, then the value
- /// was updated.
- ///
- /// `compare_and_swap` also takes an `Ordering` argument which describes the memory ordering of
- /// this operation.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let some_usize = AtomicUsize::new(5);
- ///
- /// assert_eq!(some_usize.compare_and_swap(5, 10, Ordering::Relaxed), 5);
- /// assert_eq!(some_usize.load(Ordering::Relaxed), 10);
- ///
- /// assert_eq!(some_usize.compare_and_swap(6, 12, Ordering::Relaxed), 10);
- /// assert_eq!(some_usize.load(Ordering::Relaxed), 10);
- /// ```
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[stable(feature = "atomic_from", since = "1.23.0")]
+impl<T> From<*mut T> for AtomicPtr<T> {
#[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn compare_and_swap(&self, current: usize, new: usize, order: Ordering) -> usize {
- unsafe { atomic_compare_and_swap(self.v.get(), current, new, order) }
- }
+ fn from(p: *mut T) -> Self { Self::new(p) }
+}
- /// Add to the current usize, returning the previous value.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let foo = AtomicUsize::new(0);
- /// assert_eq!(foo.fetch_add(10, Ordering::SeqCst), 0);
- /// assert_eq!(foo.load(Ordering::SeqCst), 10);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_add(&self, val: usize, order: Ordering) -> usize {
- unsafe { atomic_add(self.v.get(), val, order) }
- }
+#[cfg(target_has_atomic_load_store = "8")]
+macro_rules! atomic_int {
+ ($cfg_cas:meta,
+ $stable:meta,
+ $stable_cxchg:meta,
+ $stable_debug:meta,
+ $stable_access:meta,
+ $stable_from:meta,
+ $stable_nand:meta,
+ $const_stable:meta,
+ $stable_init_const:meta,
+ $s_int_type:expr, $int_ref:expr,
+ $extra_feature:expr,
+ $min_fn:ident, $max_fn:ident,
+ $align:expr,
+ $atomic_new:expr,
+ $int_type:ident $atomic_type:ident $atomic_init:ident) => {
+ /// An integer type which can be safely shared between threads.
+ ///
+ /// This type has the same in-memory representation as the underlying
+ /// integer type, [`
+ #[doc = $s_int_type]
+ /// `](
+ #[doc = $int_ref]
+ /// ). For more about the differences between atomic types and
+ /// non-atomic types as well as information about the portability of
+ /// this type, please see the [module-level documentation].
+ ///
+ /// [module-level documentation]: index.html
+ #[$stable]
+ #[repr(C, align($align))]
+ pub struct $atomic_type {
+ v: UnsafeCell<$int_type>,
+ }
- /// Subtract from the current usize, returning the previous value.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let foo = AtomicUsize::new(10);
- /// assert_eq!(foo.fetch_sub(10, Ordering::SeqCst), 10);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_sub(&self, val: usize, order: Ordering) -> usize {
- unsafe { atomic_sub(self.v.get(), val, order) }
- }
+ /// An atomic integer initialized to `0`.
+ #[$stable_init_const]
+ #[rustc_deprecated(
+ since = "1.34.0",
+ reason = "the `new` function is now preferred",
+ suggestion = $atomic_new,
+ )]
+ pub const $atomic_init: $atomic_type = $atomic_type::new(0);
+
+ #[$stable]
+ impl Default for $atomic_type {
+ fn default() -> Self {
+ Self::new(Default::default())
+ }
+ }
- /// Bitwise and with the current usize, returning the previous value.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let foo = AtomicUsize::new(0b101101);
- /// assert_eq!(foo.fetch_and(0b110011, Ordering::SeqCst), 0b101101);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0b100001);
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_and(&self, val: usize, order: Ordering) -> usize {
- unsafe { atomic_and(self.v.get(), val, order) }
- }
+ #[$stable_from]
+ impl From<$int_type> for $atomic_type {
+ doc_comment! {
+ concat!(
+"Converts an `", stringify!($int_type), "` into an `", stringify!($atomic_type), "`."),
+ #[inline]
+ fn from(v: $int_type) -> Self { Self::new(v) }
+ }
+ }
- /// Bitwise or with the current usize, returning the previous value.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let foo = AtomicUsize::new(0b101101);
- /// assert_eq!(foo.fetch_or(0b110011, Ordering::SeqCst), 0b101101);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0b111111);
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_or(&self, val: usize, order: Ordering) -> usize {
- unsafe { atomic_or(self.v.get(), val, order) }
- }
+ #[$stable_debug]
+ impl fmt::Debug for $atomic_type {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&self.load(Ordering::SeqCst), f)
+ }
+ }
- /// Bitwise xor with the current usize, returning the previous value.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicUsize, Ordering};
- ///
- /// let foo = AtomicUsize::new(0b101101);
- /// assert_eq!(foo.fetch_xor(0b110011, Ordering::SeqCst), 0b101101);
- /// assert_eq!(foo.load(Ordering::SeqCst), 0b011110);
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn fetch_xor(&self, val: usize, order: Ordering) -> usize {
- unsafe { atomic_xor(self.v.get(), val, order) }
+ // Send is implicitly implemented.
+ #[$stable]
+ unsafe impl Sync for $atomic_type {}
+
+ impl $atomic_type {
+ doc_comment! {
+ concat!("Creates a new atomic integer.
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::", stringify!($atomic_type), ";
+
+let atomic_forty_two = ", stringify!($atomic_type), "::new(42);
+```"),
+ #[inline]
+ #[$stable]
+ #[cfg_attr(not(bootstrap), $const_stable)]
+ pub const fn new(v: $int_type) -> Self {
+ Self {v: UnsafeCell::new(v)}
+ }
+ }
+
+ doc_comment! {
+ concat!("Returns a mutable reference to the underlying integer.
+
+This is safe because the mutable reference guarantees that no other threads are
+concurrently accessing the atomic data.
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let mut some_var = ", stringify!($atomic_type), "::new(10);
+assert_eq!(*some_var.get_mut(), 10);
+*some_var.get_mut() = 5;
+assert_eq!(some_var.load(Ordering::SeqCst), 5);
+```"),
+ #[inline]
+ #[$stable_access]
+ pub fn get_mut(&mut self) -> &mut $int_type {
+ unsafe { &mut *self.v.get() }
+ }
+ }
+
+ doc_comment! {
+ concat!("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
+
+```
+", $extra_feature, "use std::sync::atomic::", stringify!($atomic_type), ";
+
+let some_var = ", stringify!($atomic_type), "::new(5);
+assert_eq!(some_var.into_inner(), 5);
+```"),
+ #[inline]
+ #[$stable_access]
+ pub fn into_inner(self) -> $int_type {
+ self.v.into_inner()
+ }
+ }
+
+ doc_comment! {
+ concat!("Loads a value from the atomic integer.
+
+`load` takes an [`Ordering`] argument which describes the memory ordering of this operation.
+Possible values are [`SeqCst`], [`Acquire`] and [`Relaxed`].
+
+# Panics
+
+Panics if `order` is [`Release`] or [`AcqRel`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+[`AcqRel`]: enum.Ordering.html#variant.AcqRel
+[`SeqCst`]: enum.Ordering.html#variant.SeqCst
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let some_var = ", stringify!($atomic_type), "::new(5);
+
+assert_eq!(some_var.load(Ordering::Relaxed), 5);
+```"),
+ #[inline]
+ #[$stable]
+ pub fn load(&self, order: Ordering) -> $int_type {
+ unsafe { atomic_load(self.v.get(), order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Stores a value into the atomic integer.
+
+`store` takes an [`Ordering`] argument which describes the memory ordering of this operation.
+ Possible values are [`SeqCst`], [`Release`] and [`Relaxed`].
+
+# Panics
+
+Panics if `order` is [`Acquire`] or [`AcqRel`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+[`AcqRel`]: enum.Ordering.html#variant.AcqRel
+[`SeqCst`]: enum.Ordering.html#variant.SeqCst
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let some_var = ", stringify!($atomic_type), "::new(5);
+
+some_var.store(10, Ordering::Relaxed);
+assert_eq!(some_var.load(Ordering::Relaxed), 10);
+```"),
+ #[inline]
+ #[$stable]
+ pub fn store(&self, val: $int_type, order: Ordering) {
+ unsafe { atomic_store(self.v.get(), val, order); }
+ }
+ }
+
+ doc_comment! {
+ concat!("Stores a value into the atomic integer, returning the previous value.
+
+`swap` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let some_var = ", stringify!($atomic_type), "::new(5);
+
+assert_eq!(some_var.swap(10, Ordering::Relaxed), 5);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn swap(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_swap(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Stores a value into the atomic integer if the current value is the same as
+the `current` value.
+
+The return value is always the previous value. If it is equal to `current`, then the
+value was updated.
+
+`compare_and_swap` also takes an [`Ordering`] argument which describes the memory
+ordering of this operation. Notice that even when using [`AcqRel`], the operation
+might fail and hence just perform an `Acquire` load, but not have `Release` semantics.
+Using [`Acquire`] makes the store part of this operation [`Relaxed`] if it
+happens, and using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+[`AcqRel`]: enum.Ordering.html#variant.AcqRel
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let some_var = ", stringify!($atomic_type), "::new(5);
+
+assert_eq!(some_var.compare_and_swap(5, 10, Ordering::Relaxed), 5);
+assert_eq!(some_var.load(Ordering::Relaxed), 10);
+
+assert_eq!(some_var.compare_and_swap(6, 12, Ordering::Relaxed), 10);
+assert_eq!(some_var.load(Ordering::Relaxed), 10);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn compare_and_swap(&self,
+ current: $int_type,
+ new: $int_type,
+ order: Ordering) -> $int_type {
+ match self.compare_exchange(current,
+ new,
+ order,
+ strongest_failure_ordering(order)) {
+ Ok(x) => x,
+ Err(x) => x,
+ }
+ }
+ }
+
+ doc_comment! {
+ concat!("Stores a value into the atomic integer if the current value is the same as
+the `current` value.
+
+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`.
+
+`compare_exchange` takes two [`Ordering`] arguments to describe the memory
+ordering of this operation. The first describes the required ordering if the
+operation succeeds while the second describes the required ordering when the
+operation fails. Using [`Acquire`] as success ordering makes the store part
+of this operation [`Relaxed`], and using [`Release`] makes the successful load
+[`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+and must be equivalent to or weaker than the success ordering.
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+[`SeqCst`]: enum.Ordering.html#variant.SeqCst
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let some_var = ", stringify!($atomic_type), "::new(5);
+
+assert_eq!(some_var.compare_exchange(5, 10,
+ Ordering::Acquire,
+ Ordering::Relaxed),
+ Ok(5));
+assert_eq!(some_var.load(Ordering::Relaxed), 10);
+
+assert_eq!(some_var.compare_exchange(6, 12,
+ Ordering::SeqCst,
+ Ordering::Acquire),
+ Err(10));
+assert_eq!(some_var.load(Ordering::Relaxed), 10);
+```"),
+ #[inline]
+ #[$stable_cxchg]
+ #[$cfg_cas]
+ pub fn compare_exchange(&self,
+ current: $int_type,
+ new: $int_type,
+ success: Ordering,
+ failure: Ordering) -> Result<$int_type, $int_type> {
+ unsafe { atomic_compare_exchange(self.v.get(), current, new, success, failure) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Stores a value into the atomic integer if the current value is the same as
+the `current` value.
+
+Unlike [`compare_exchange`], this function is allowed to spuriously fail even
+when the comparison succeeds, which can result in more efficient code on some
+platforms. The return value is a result indicating whether the new value was
+written and containing the previous value.
+
+`compare_exchange_weak` takes two [`Ordering`] arguments to describe the memory
+ordering of this operation. The first describes the required ordering if the
+operation succeeds while the second describes the required ordering when the
+operation fails. Using [`Acquire`] as success ordering makes the store part
+of this operation [`Relaxed`], and using [`Release`] makes the successful load
+[`Relaxed`]. The failure ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+and must be equivalent to or weaker than the success ordering.
+
+[`compare_exchange`]: #method.compare_exchange
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+[`SeqCst`]: enum.Ordering.html#variant.SeqCst
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let val = ", stringify!($atomic_type), "::new(4);
+
+let mut old = val.load(Ordering::Relaxed);
+loop {
+ let new = old * 2;
+ match val.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
+ Ok(_) => break,
+ Err(x) => old = x,
}
}
+```"),
+ #[inline]
+ #[$stable_cxchg]
+ #[$cfg_cas]
+ pub fn compare_exchange_weak(&self,
+ current: $int_type,
+ new: $int_type,
+ success: Ordering,
+ failure: Ordering) -> Result<$int_type, $int_type> {
+ unsafe {
+ atomic_compare_exchange_weak(self.v.get(), current, new, success, failure)
+ }
+ }
+ }
-impl<T> AtomicPtr<T> {
- /// Creates a new `AtomicPtr`.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::AtomicPtr;
- ///
- /// let ptr = &mut 5;
- /// let atomic_ptr = AtomicPtr::new(ptr);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub const fn new(p: *mut T) -> AtomicPtr<T> {
- AtomicPtr { p: UnsafeCell::new(p) }
- }
+ doc_comment! {
+ concat!("Adds to the current value, returning the previous value.
- /// Loads a value from the pointer.
- ///
- /// `load` takes an `Ordering` argument which describes the memory ordering of this operation.
- ///
- /// # Panics
- ///
- /// Panics if `order` is `Release` or `AcqRel`.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicPtr, Ordering};
- ///
- /// let ptr = &mut 5;
- /// let some_ptr = AtomicPtr::new(ptr);
- ///
- /// let value = some_ptr.load(Ordering::Relaxed);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn load(&self, order: Ordering) -> *mut T {
- unsafe {
- atomic_load(self.p.get() as *mut usize, order) as *mut T
- }
- }
+This operation wraps around on overflow.
- /// Stores a value into the pointer.
- ///
- /// `store` takes an `Ordering` argument which describes the memory ordering of this operation.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicPtr, Ordering};
- ///
- /// let ptr = &mut 5;
- /// let some_ptr = AtomicPtr::new(ptr);
- ///
- /// let other_ptr = &mut 10;
- ///
- /// some_ptr.store(other_ptr, Ordering::Relaxed);
- /// ```
- ///
- /// # Panics
- ///
- /// Panics if `order` is `Acquire` or `AcqRel`.
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn store(&self, ptr: *mut T, order: Ordering) {
- unsafe { atomic_store(self.p.get() as *mut usize, ptr as usize, order); }
- }
+`fetch_add` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
- /// Stores a value into the pointer, returning the old value.
- ///
- /// `swap` takes an `Ordering` argument which describes the memory ordering of this operation.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicPtr, Ordering};
- ///
- /// let ptr = &mut 5;
- /// let some_ptr = AtomicPtr::new(ptr);
- ///
- /// let other_ptr = &mut 10;
- ///
- /// let value = some_ptr.swap(other_ptr, Ordering::Relaxed);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn swap(&self, ptr: *mut T, order: Ordering) -> *mut T {
- unsafe { atomic_swap(self.p.get() as *mut usize, ptr as usize, order) as *mut T }
- }
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
- /// Stores a value into the pointer if the current value is the same as the `current` value.
- ///
- /// The return value is always the previous value. If it is equal to `current`, then the value
- /// was updated.
- ///
- /// `compare_and_swap` also takes an `Ordering` argument which describes the memory ordering of
- /// this operation.
- ///
- /// # Examples
- ///
- /// ```
- /// use std::sync::atomic::{AtomicPtr, Ordering};
- ///
- /// let ptr = &mut 5;
- /// let some_ptr = AtomicPtr::new(ptr);
- ///
- /// let other_ptr = &mut 10;
- /// let another_ptr = &mut 10;
- ///
- /// let value = some_ptr.compare_and_swap(other_ptr, another_ptr, Ordering::Relaxed);
- /// ```
- #[inline]
- #[stable(feature = "rust1", since = "1.0.0")]
- pub fn compare_and_swap(&self, current: *mut T, new: *mut T, order: Ordering) -> *mut T {
- unsafe {
- atomic_compare_and_swap(self.p.get() as *mut usize, current as usize,
- new as usize, order) as *mut T
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(0);
+assert_eq!(foo.fetch_add(10, Ordering::SeqCst), 0);
+assert_eq!(foo.load(Ordering::SeqCst), 10);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn fetch_add(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_add(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Subtracts from the current value, returning the previous value.
+
+This operation wraps around on overflow.
+
+`fetch_sub` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(20);
+assert_eq!(foo.fetch_sub(10, Ordering::SeqCst), 20);
+assert_eq!(foo.load(Ordering::SeqCst), 10);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn fetch_sub(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_sub(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Bitwise \"and\" with the current value.
+
+Performs a bitwise \"and\" operation on the current value and the argument `val`, and
+sets the new value to the result.
+
+Returns the previous value.
+
+`fetch_and` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(0b101101);
+assert_eq!(foo.fetch_and(0b110011, Ordering::SeqCst), 0b101101);
+assert_eq!(foo.load(Ordering::SeqCst), 0b100001);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn fetch_and(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_and(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Bitwise \"nand\" with the current value.
+
+Performs a bitwise \"nand\" operation on the current value and the argument `val`, and
+sets the new value to the result.
+
+Returns the previous value.
+
+`fetch_nand` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+", $extra_feature, "
+use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(0x13);
+assert_eq!(foo.fetch_nand(0x31, Ordering::SeqCst), 0x13);
+assert_eq!(foo.load(Ordering::SeqCst), !(0x13 & 0x31));
+```"),
+ #[inline]
+ #[$stable_nand]
+ #[$cfg_cas]
+ pub fn fetch_nand(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_nand(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Bitwise \"or\" with the current value.
+
+Performs a bitwise \"or\" operation on the current value and the argument `val`, and
+sets the new value to the result.
+
+Returns the previous value.
+
+`fetch_or` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(0b101101);
+assert_eq!(foo.fetch_or(0b110011, Ordering::SeqCst), 0b101101);
+assert_eq!(foo.load(Ordering::SeqCst), 0b111111);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn fetch_or(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_or(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Bitwise \"xor\" with the current value.
+
+Performs a bitwise \"xor\" operation on the current value and the argument `val`, and
+sets the new value to the result.
+
+Returns the previous value.
+
+`fetch_xor` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(0b101101);
+assert_eq!(foo.fetch_xor(0b110011, Ordering::SeqCst), 0b101101);
+assert_eq!(foo.load(Ordering::SeqCst), 0b011110);
+```"),
+ #[inline]
+ #[$stable]
+ #[$cfg_cas]
+ pub fn fetch_xor(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { atomic_xor(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("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
+but once to the stored value.
+
+`fetch_update` takes two [`Ordering`] arguments to describe the memory
+ordering of this operation. The first describes the required ordering for loads
+and failed updates while the second describes the required ordering when the
+operation finally succeeds. Beware that this is different from the two
+modes in [`compare_exchange`]!
+
+Using [`Acquire`] as success ordering makes the store part
+of this operation [`Relaxed`], and using [`Release`] makes the final successful load
+[`Relaxed`]. The (failed) load ordering can only be [`SeqCst`], [`Acquire`] or [`Relaxed`]
+and must be equivalent to or weaker than the success ordering.
+
+[`bool`]: ../../../std/primitive.bool.html
+[`compare_exchange`]: #method.compare_exchange
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+[`SeqCst`]: enum.Ordering.html#variant.SeqCst
+
+# Examples
+
+```rust
+#![feature(no_more_cas)]
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let x = ", stringify!($atomic_type), "::new(7);
+assert_eq!(x.fetch_update(|_| None, Ordering::SeqCst, Ordering::SeqCst), Err(7));
+assert_eq!(x.fetch_update(|x| Some(x + 1), Ordering::SeqCst, Ordering::SeqCst), Ok(7));
+assert_eq!(x.fetch_update(|x| Some(x + 1), Ordering::SeqCst, Ordering::SeqCst), Ok(8));
+assert_eq!(x.load(Ordering::SeqCst), 9);
+```"),
+ #[inline]
+ #[unstable(feature = "no_more_cas",
+ reason = "no more CAS loops in user code",
+ issue = "48655")]
+ #[$cfg_cas]
+ pub fn fetch_update<F>(&self,
+ mut f: F,
+ fetch_order: Ordering,
+ set_order: Ordering) -> Result<$int_type, $int_type>
+ where F: FnMut($int_type) -> Option<$int_type> {
+ let mut prev = self.load(fetch_order);
+ while let Some(next) = f(prev) {
+ match self.compare_exchange_weak(prev, next, set_order, fetch_order) {
+ x @ Ok(_) => return x,
+ Err(next_prev) => prev = next_prev
+ }
+ }
+ Err(prev)
+ }
+ }
+
+ doc_comment! {
+ concat!("Maximum with the current value.
+
+Finds the maximum of the current value and the argument `val`, and
+sets the new value to the result.
+
+Returns the previous value.
+
+`fetch_max` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+#![feature(atomic_min_max)]
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(23);
+assert_eq!(foo.fetch_max(42, Ordering::SeqCst), 23);
+assert_eq!(foo.load(Ordering::SeqCst), 42);
+```
+
+If you want to obtain the maximum value in one step, you can use the following:
+
+```
+#![feature(atomic_min_max)]
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(23);
+let bar = 42;
+let max_foo = foo.fetch_max(bar, Ordering::SeqCst).max(bar);
+assert!(max_foo == 42);
+```"),
+ #[inline]
+ #[unstable(feature = "atomic_min_max",
+ reason = "easier and faster min/max than writing manual CAS loop",
+ issue = "48655")]
+ #[$cfg_cas]
+ pub fn fetch_max(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { $max_fn(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Minimum with the current value.
+
+Finds the minimum of the current value and the argument `val`, and
+sets the new value to the result.
+
+Returns the previous value.
+
+`fetch_min` takes an [`Ordering`] argument which describes the memory ordering
+of this operation. All ordering modes are possible. Note that using
+[`Acquire`] makes the store part of this operation [`Relaxed`], and
+using [`Release`] makes the load part [`Relaxed`].
+
+[`Ordering`]: enum.Ordering.html
+[`Relaxed`]: enum.Ordering.html#variant.Relaxed
+[`Release`]: enum.Ordering.html#variant.Release
+[`Acquire`]: enum.Ordering.html#variant.Acquire
+
+# Examples
+
+```
+#![feature(atomic_min_max)]
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(23);
+assert_eq!(foo.fetch_min(42, Ordering::Relaxed), 23);
+assert_eq!(foo.load(Ordering::Relaxed), 23);
+assert_eq!(foo.fetch_min(22, Ordering::Relaxed), 23);
+assert_eq!(foo.load(Ordering::Relaxed), 22);
+```
+
+If you want to obtain the minimum value in one step, you can use the following:
+
+```
+#![feature(atomic_min_max)]
+", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
+
+let foo = ", stringify!($atomic_type), "::new(23);
+let bar = 12;
+let min_foo = foo.fetch_min(bar, Ordering::SeqCst).min(bar);
+assert_eq!(min_foo, 12);
+```"),
+ #[inline]
+ #[unstable(feature = "atomic_min_max",
+ reason = "easier and faster min/max than writing manual CAS loop",
+ issue = "48655")]
+ #[$cfg_cas]
+ pub fn fetch_min(&self, val: $int_type, order: Ordering) -> $int_type {
+ unsafe { $min_fn(self.v.get(), val, order) }
+ }
+ }
+
+ doc_comment! {
+ concat!("Returns a mutable pointer to the underlying integer.
+
+Doing non-atomic reads and writes on the resulting integer can be a data race.
+This method is mostly useful for FFI, where the function signature may use
+`*mut ", stringify!($int_type), "` instead of `&", stringify!($atomic_type), "`.
+
+Returning an `*mut` pointer from a shared reference to this atomic is safe because the
+atomic types work with interior mutability. All modifications of an atomic change the value
+through a shared reference, and can do so safely as long as they use atomic operations. Any
+use of the returned raw pointer requires an `unsafe` block and still has to uphold the same
+restriction: operations on it must be atomic.
+
+# Examples
+
+```ignore (extern-declaration)
+# fn main() {
+", $extra_feature, "use std::sync::atomic::", stringify!($atomic_type), ";
+
+extern {
+ fn my_atomic_op(arg: *mut ", stringify!($int_type), ");
+}
+
+let mut atomic = ", stringify!($atomic_type), "::new(1);
+unsafe {
+ my_atomic_op(atomic.as_mut_ptr());
+}
+# }
+```"),
+ #[inline]
+ #[unstable(feature = "atomic_mut_ptr",
+ reason = "recently added",
+ issue = "66893")]
+ pub fn as_mut_ptr(&self) -> *mut $int_type {
+ self.v.get()
+ }
+ }
}
}
}
+#[cfg(target_has_atomic_load_store = "8")]
+atomic_int! {
+ cfg(target_has_atomic = "8"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "i8", "../../../std/primitive.i8.html",
+ "",
+ atomic_min, atomic_max,
+ 1,
+ "AtomicI8::new(0)",
+ i8 AtomicI8 ATOMIC_I8_INIT
+}
+#[cfg(target_has_atomic_load_store = "8")]
+atomic_int! {
+ cfg(target_has_atomic = "8"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "u8", "../../../std/primitive.u8.html",
+ "",
+ atomic_umin, atomic_umax,
+ 1,
+ "AtomicU8::new(0)",
+ u8 AtomicU8 ATOMIC_U8_INIT
+}
+#[cfg(target_has_atomic_load_store = "16")]
+atomic_int! {
+ cfg(target_has_atomic = "16"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "i16", "../../../std/primitive.i16.html",
+ "",
+ atomic_min, atomic_max,
+ 2,
+ "AtomicI16::new(0)",
+ i16 AtomicI16 ATOMIC_I16_INIT
+}
+#[cfg(target_has_atomic_load_store = "16")]
+atomic_int! {
+ cfg(target_has_atomic = "16"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "u16", "../../../std/primitive.u16.html",
+ "",
+ atomic_umin, atomic_umax,
+ 2,
+ "AtomicU16::new(0)",
+ u16 AtomicU16 ATOMIC_U16_INIT
+}
+#[cfg(target_has_atomic_load_store = "32")]
+atomic_int! {
+ cfg(target_has_atomic = "32"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "i32", "../../../std/primitive.i32.html",
+ "",
+ atomic_min, atomic_max,
+ 4,
+ "AtomicI32::new(0)",
+ i32 AtomicI32 ATOMIC_I32_INIT
+}
+#[cfg(target_has_atomic_load_store = "32")]
+atomic_int! {
+ cfg(target_has_atomic = "32"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "u32", "../../../std/primitive.u32.html",
+ "",
+ atomic_umin, atomic_umax,
+ 4,
+ "AtomicU32::new(0)",
+ u32 AtomicU32 ATOMIC_U32_INIT
+}
+#[cfg(target_has_atomic_load_store = "64")]
+atomic_int! {
+ cfg(target_has_atomic = "64"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "i64", "../../../std/primitive.i64.html",
+ "",
+ atomic_min, atomic_max,
+ 8,
+ "AtomicI64::new(0)",
+ i64 AtomicI64 ATOMIC_I64_INIT
+}
+#[cfg(target_has_atomic_load_store = "64")]
+atomic_int! {
+ cfg(target_has_atomic = "64"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ stable(feature = "integer_atomics_stable", since = "1.34.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "u64", "../../../std/primitive.u64.html",
+ "",
+ atomic_umin, atomic_umax,
+ 8,
+ "AtomicU64::new(0)",
+ u64 AtomicU64 ATOMIC_U64_INIT
+}
+#[cfg(target_has_atomic_load_store = "128")]
+atomic_int! {
+ cfg(target_has_atomic = "128"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "i128", "../../../std/primitive.i128.html",
+ "#![feature(integer_atomics)]\n\n",
+ atomic_min, atomic_max,
+ 16,
+ "AtomicI128::new(0)",
+ i128 AtomicI128 ATOMIC_I128_INIT
+}
+#[cfg(target_has_atomic_load_store = "128")]
+atomic_int! {
+ cfg(target_has_atomic = "128"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ unstable(feature = "integer_atomics", issue = "32976"),
+ "u128", "../../../std/primitive.u128.html",
+ "#![feature(integer_atomics)]\n\n",
+ atomic_umin, atomic_umax,
+ 16,
+ "AtomicU128::new(0)",
+ u128 AtomicU128 ATOMIC_U128_INIT
+}
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[cfg(target_pointer_width = "16")]
+macro_rules! ptr_width {
+ () => { 2 }
+}
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[cfg(target_pointer_width = "32")]
+macro_rules! ptr_width {
+ () => { 4 }
+}
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[cfg(target_pointer_width = "64")]
+macro_rules! ptr_width {
+ () => { 8 }
+}
+#[cfg(target_has_atomic_load_store = "ptr")]
+atomic_int!{
+ cfg(target_has_atomic = "ptr"),
+ stable(feature = "rust1", since = "1.0.0"),
+ stable(feature = "extended_compare_and_swap", since = "1.10.0"),
+ stable(feature = "atomic_debug", since = "1.3.0"),
+ stable(feature = "atomic_access", since = "1.15.0"),
+ stable(feature = "atomic_from", since = "1.23.0"),
+ stable(feature = "atomic_nand", since = "1.27.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ stable(feature = "rust1", since = "1.0.0"),
+ "isize", "../../../std/primitive.isize.html",
+ "",
+ atomic_min, atomic_max,
+ ptr_width!(),
+ "AtomicIsize::new(0)",
+ isize AtomicIsize ATOMIC_ISIZE_INIT
+}
+#[cfg(target_has_atomic_load_store = "ptr")]
+atomic_int!{
+ cfg(target_has_atomic = "ptr"),
+ stable(feature = "rust1", since = "1.0.0"),
+ stable(feature = "extended_compare_and_swap", since = "1.10.0"),
+ stable(feature = "atomic_debug", since = "1.3.0"),
+ stable(feature = "atomic_access", since = "1.15.0"),
+ stable(feature = "atomic_from", since = "1.23.0"),
+ stable(feature = "atomic_nand", since = "1.27.0"),
+ rustc_const_stable(feature = "const_integer_atomics", since = "1.34.0"),
+ stable(feature = "rust1", since = "1.0.0"),
+ "usize", "../../../std/primitive.usize.html",
+ "",
+ atomic_umin, atomic_umax,
+ ptr_width!(),
+ "AtomicUsize::new(0)",
+ usize AtomicUsize ATOMIC_USIZE_INIT
+}
+
+#[inline]
+#[cfg(target_has_atomic = "8")]
+fn strongest_failure_ordering(order: Ordering) -> Ordering {
+ match order {
+ Release => Relaxed,
+ Relaxed => Relaxed,
+ SeqCst => SeqCst,
+ Acquire => Acquire,
+ AcqRel => Acquire,
+ }
+}
+
#[inline]
-unsafe fn atomic_store<T>(dst: *mut T, val: T, order:Ordering) {
+unsafe fn atomic_store<T>(dst: *mut T, val: T, order: Ordering) {
match order {
Release => intrinsics::atomic_store_rel(dst, val),
Relaxed => intrinsics::atomic_store_relaxed(dst, val),
- SeqCst => intrinsics::atomic_store(dst, val),
+ SeqCst => intrinsics::atomic_store(dst, val),
Acquire => panic!("there is no such thing as an acquire store"),
- AcqRel => panic!("there is no such thing as an acquire/release store"),
+ AcqRel => panic!("there is no such thing as an acquire/release store"),
}
}
#[inline]
-unsafe fn atomic_load<T>(dst: *const T, order:Ordering) -> T {
+unsafe fn atomic_load<T>(dst: *const T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_load_acq(dst),
Relaxed => intrinsics::atomic_load_relaxed(dst),
- SeqCst => intrinsics::atomic_load(dst),
+ SeqCst => intrinsics::atomic_load(dst),
Release => panic!("there is no such thing as a release load"),
- AcqRel => panic!("there is no such thing as an acquire/release load"),
+ AcqRel => panic!("there is no such thing as an acquire/release load"),
}
}
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_swap<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_xchg_acq(dst, val),
Release => intrinsics::atomic_xchg_rel(dst, val),
- AcqRel => intrinsics::atomic_xchg_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_xchg_acqrel(dst, val),
Relaxed => intrinsics::atomic_xchg_relaxed(dst, val),
- SeqCst => intrinsics::atomic_xchg(dst, val)
+ SeqCst => intrinsics::atomic_xchg(dst, val),
}
}
-/// Returns the old value (like __sync_fetch_and_add).
+/// Returns the previous value (like __sync_fetch_and_add).
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_add<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_xadd_acq(dst, val),
Release => intrinsics::atomic_xadd_rel(dst, val),
- AcqRel => intrinsics::atomic_xadd_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_xadd_acqrel(dst, val),
Relaxed => intrinsics::atomic_xadd_relaxed(dst, val),
- SeqCst => intrinsics::atomic_xadd(dst, val)
+ SeqCst => intrinsics::atomic_xadd(dst, val),
}
}
-/// Returns the old value (like __sync_fetch_and_sub).
+/// Returns the previous value (like __sync_fetch_and_sub).
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_sub<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_xsub_acq(dst, val),
Release => intrinsics::atomic_xsub_rel(dst, val),
- AcqRel => intrinsics::atomic_xsub_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_xsub_acqrel(dst, val),
Relaxed => intrinsics::atomic_xsub_relaxed(dst, val),
- SeqCst => intrinsics::atomic_xsub(dst, val)
+ SeqCst => intrinsics::atomic_xsub(dst, val),
}
}
#[inline]
-unsafe fn atomic_compare_and_swap<T>(dst: *mut T, old:T, new:T, order: Ordering) -> T {
- match order {
- Acquire => intrinsics::atomic_cxchg_acq(dst, old, new),
- Release => intrinsics::atomic_cxchg_rel(dst, old, new),
- AcqRel => intrinsics::atomic_cxchg_acqrel(dst, old, new),
- Relaxed => intrinsics::atomic_cxchg_relaxed(dst, old, new),
- SeqCst => intrinsics::atomic_cxchg(dst, old, new),
- }
+#[cfg(target_has_atomic = "8")]
+unsafe fn atomic_compare_exchange<T>(dst: *mut T,
+ old: T,
+ new: T,
+ success: Ordering,
+ failure: Ordering)
+ -> Result<T, T> {
+ let (val, ok) = match (success, failure) {
+ (Acquire, Acquire) => intrinsics::atomic_cxchg_acq(dst, old, new),
+ (Release, Relaxed) => intrinsics::atomic_cxchg_rel(dst, old, new),
+ (AcqRel, Acquire) => intrinsics::atomic_cxchg_acqrel(dst, old, new),
+ (Relaxed, Relaxed) => intrinsics::atomic_cxchg_relaxed(dst, old, new),
+ (SeqCst, SeqCst) => intrinsics::atomic_cxchg(dst, old, new),
+ (Acquire, Relaxed) => intrinsics::atomic_cxchg_acq_failrelaxed(dst, old, new),
+ (AcqRel, Relaxed) => intrinsics::atomic_cxchg_acqrel_failrelaxed(dst, old, new),
+ (SeqCst, Relaxed) => intrinsics::atomic_cxchg_failrelaxed(dst, old, new),
+ (SeqCst, Acquire) => intrinsics::atomic_cxchg_failacq(dst, old, new),
+ (_, AcqRel) => panic!("there is no such thing as an acquire/release failure ordering"),
+ (_, Release) => panic!("there is no such thing as a release failure ordering"),
+ _ => panic!("a failure ordering can't be stronger than a success ordering"),
+ };
+ if ok { Ok(val) } else { Err(val) }
+}
+
+#[inline]
+#[cfg(target_has_atomic = "8")]
+unsafe fn atomic_compare_exchange_weak<T>(dst: *mut T,
+ old: T,
+ new: T,
+ success: Ordering,
+ failure: Ordering)
+ -> Result<T, T> {
+ let (val, ok) = match (success, failure) {
+ (Acquire, Acquire) => intrinsics::atomic_cxchgweak_acq(dst, old, new),
+ (Release, Relaxed) => intrinsics::atomic_cxchgweak_rel(dst, old, new),
+ (AcqRel, Acquire) => intrinsics::atomic_cxchgweak_acqrel(dst, old, new),
+ (Relaxed, Relaxed) => intrinsics::atomic_cxchgweak_relaxed(dst, old, new),
+ (SeqCst, SeqCst) => intrinsics::atomic_cxchgweak(dst, old, new),
+ (Acquire, Relaxed) => intrinsics::atomic_cxchgweak_acq_failrelaxed(dst, old, new),
+ (AcqRel, Relaxed) => intrinsics::atomic_cxchgweak_acqrel_failrelaxed(dst, old, new),
+ (SeqCst, Relaxed) => intrinsics::atomic_cxchgweak_failrelaxed(dst, old, new),
+ (SeqCst, Acquire) => intrinsics::atomic_cxchgweak_failacq(dst, old, new),
+ (_, AcqRel) => panic!("there is no such thing as an acquire/release failure ordering"),
+ (_, Release) => panic!("there is no such thing as a release failure ordering"),
+ _ => panic!("a failure ordering can't be stronger than a success ordering"),
+ };
+ if ok { Ok(val) } else { Err(val) }
}
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_and<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_and_acq(dst, val),
Release => intrinsics::atomic_and_rel(dst, val),
- AcqRel => intrinsics::atomic_and_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_and_acqrel(dst, val),
Relaxed => intrinsics::atomic_and_relaxed(dst, val),
- SeqCst => intrinsics::atomic_and(dst, val)
+ SeqCst => intrinsics::atomic_and(dst, val),
}
}
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_nand<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_nand_acq(dst, val),
Release => intrinsics::atomic_nand_rel(dst, val),
- AcqRel => intrinsics::atomic_nand_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_nand_acqrel(dst, val),
Relaxed => intrinsics::atomic_nand_relaxed(dst, val),
- SeqCst => intrinsics::atomic_nand(dst, val)
+ SeqCst => intrinsics::atomic_nand(dst, val),
}
}
-
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_or<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_or_acq(dst, val),
Release => intrinsics::atomic_or_rel(dst, val),
- AcqRel => intrinsics::atomic_or_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_or_acqrel(dst, val),
Relaxed => intrinsics::atomic_or_relaxed(dst, val),
- SeqCst => intrinsics::atomic_or(dst, val)
+ SeqCst => intrinsics::atomic_or(dst, val),
}
}
-
#[inline]
+#[cfg(target_has_atomic = "8")]
unsafe fn atomic_xor<T>(dst: *mut T, val: T, order: Ordering) -> T {
match order {
Acquire => intrinsics::atomic_xor_acq(dst, val),
Release => intrinsics::atomic_xor_rel(dst, val),
- AcqRel => intrinsics::atomic_xor_acqrel(dst, val),
+ AcqRel => intrinsics::atomic_xor_acqrel(dst, val),
Relaxed => intrinsics::atomic_xor_relaxed(dst, val),
- SeqCst => intrinsics::atomic_xor(dst, val)
+ SeqCst => intrinsics::atomic_xor(dst, val),
+ }
+}
+
+/// returns the max value (signed comparison)
+#[inline]
+#[cfg(target_has_atomic = "8")]
+unsafe fn atomic_max<T>(dst: *mut T, val: T, order: Ordering) -> T {
+ match order {
+ Acquire => intrinsics::atomic_max_acq(dst, val),
+ Release => intrinsics::atomic_max_rel(dst, val),
+ AcqRel => intrinsics::atomic_max_acqrel(dst, val),
+ Relaxed => intrinsics::atomic_max_relaxed(dst, val),
+ SeqCst => intrinsics::atomic_max(dst, val),
}
}
+/// returns the min value (signed comparison)
+#[inline]
+#[cfg(target_has_atomic = "8")]
+unsafe fn atomic_min<T>(dst: *mut T, val: T, order: Ordering) -> T {
+ match order {
+ Acquire => intrinsics::atomic_min_acq(dst, val),
+ Release => intrinsics::atomic_min_rel(dst, val),
+ AcqRel => intrinsics::atomic_min_acqrel(dst, val),
+ Relaxed => intrinsics::atomic_min_relaxed(dst, val),
+ SeqCst => intrinsics::atomic_min(dst, val),
+ }
+}
+
+/// returns the max value (signed comparison)
+#[inline]
+#[cfg(target_has_atomic = "8")]
+unsafe fn atomic_umax<T>(dst: *mut T, val: T, order: Ordering) -> T {
+ match order {
+ Acquire => intrinsics::atomic_umax_acq(dst, val),
+ Release => intrinsics::atomic_umax_rel(dst, val),
+ AcqRel => intrinsics::atomic_umax_acqrel(dst, val),
+ Relaxed => intrinsics::atomic_umax_relaxed(dst, val),
+ SeqCst => intrinsics::atomic_umax(dst, val),
+ }
+}
+
+/// returns the min value (signed comparison)
+#[inline]
+#[cfg(target_has_atomic = "8")]
+unsafe fn atomic_umin<T>(dst: *mut T, val: T, order: Ordering) -> T {
+ match order {
+ Acquire => intrinsics::atomic_umin_acq(dst, val),
+ Release => intrinsics::atomic_umin_rel(dst, val),
+ AcqRel => intrinsics::atomic_umin_acqrel(dst, val),
+ Relaxed => intrinsics::atomic_umin_relaxed(dst, val),
+ SeqCst => intrinsics::atomic_umin(dst, val),
+ }
+}
/// An atomic fence.
///
-/// A fence 'A' which has `Release` ordering semantics, synchronizes with a
-/// fence 'B' with (at least) `Acquire` semantics, if and only if there exists
-/// atomic operations X and Y, both operating on some atomic object 'M' such
+/// Depending on the specified order, a fence prevents the compiler and CPU from
+/// reordering certain types of memory operations around it.
+/// That creates synchronizes-with relationships between it and atomic operations
+/// or fences in other threads.
+///
+/// A fence 'A' which has (at least) [`Release`] ordering semantics, synchronizes
+/// with a fence 'B' with (at least) [`Acquire`] semantics, if and only if there
+/// exist operations X and Y, both operating on some atomic object 'M' such
/// that A is sequenced before X, Y is synchronized before B and Y observes
/// the change to M. This provides a happens-before dependence between A and B.
///
-/// Atomic operations with `Release` or `Acquire` semantics can also synchronize
+/// ```text
+/// Thread 1 Thread 2
+///
+/// fence(Release); A --------------
+/// x.store(3, Relaxed); X --------- |
+/// | |
+/// | |
+/// -------------> Y if x.load(Relaxed) == 3 {
+/// |-------> B fence(Acquire);
+/// ...
+/// }
+/// ```
+///
+/// Atomic operations with [`Release`] or [`Acquire`] semantics can also synchronize
/// with a fence.
///
-/// A fence which has `SeqCst` ordering, in addition to having both `Acquire`
-/// and `Release` semantics, participates in the global program order of the
-/// other `SeqCst` operations and/or fences.
+/// A fence which has [`SeqCst`] ordering, in addition to having both [`Acquire`]
+/// and [`Release`] semantics, participates in the global program order of the
+/// other [`SeqCst`] operations and/or fences.
///
-/// Accepts `Acquire`, `Release`, `AcqRel` and `SeqCst` orderings.
+/// Accepts [`Acquire`], [`Release`], [`AcqRel`] and [`SeqCst`] orderings.
///
/// # Panics
///
-/// Panics if `order` is `Relaxed`.
+/// Panics if `order` is [`Relaxed`].
+///
+/// # Examples
+///
+/// ```
+/// use std::sync::atomic::AtomicBool;
+/// use std::sync::atomic::fence;
+/// use std::sync::atomic::Ordering;
+///
+/// // A mutual exclusion primitive based on spinlock.
+/// pub struct Mutex {
+/// flag: AtomicBool,
+/// }
+///
+/// impl Mutex {
+/// pub fn new() -> Mutex {
+/// Mutex {
+/// flag: AtomicBool::new(false),
+/// }
+/// }
+///
+/// pub fn lock(&self) {
+/// while !self.flag.compare_and_swap(false, true, Ordering::Relaxed) {}
+/// // This fence synchronizes-with store in `unlock`.
+/// fence(Ordering::Acquire);
+/// }
+///
+/// pub fn unlock(&self) {
+/// self.flag.store(false, Ordering::Release);
+/// }
+/// }
+/// ```
+///
+/// [`Ordering`]: enum.Ordering.html
+/// [`Acquire`]: enum.Ordering.html#variant.Acquire
+/// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
+/// [`Release`]: enum.Ordering.html#variant.Release
+/// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+/// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(target_arch = "wasm32", allow(unused_variables))]
pub fn fence(order: Ordering) {
+ // On wasm32 it looks like fences aren't implemented in LLVM yet in that
+ // they will cause LLVM to abort. The wasm instruction set doesn't have
+ // fences right now. There's discussion online about the best way for tools
+ // to conventionally implement fences at
+ // https://github.com/WebAssembly/tool-conventions/issues/59. We should
+ // follow that discussion and implement a solution when one comes about!
+ #[cfg(not(target_arch = "wasm32"))]
unsafe {
match order {
Acquire => intrinsics::atomic_fence_acq(),
Release => intrinsics::atomic_fence_rel(),
- AcqRel => intrinsics::atomic_fence_acqrel(),
- SeqCst => intrinsics::atomic_fence(),
- Relaxed => panic!("there is no such thing as a relaxed fence")
+ AcqRel => intrinsics::atomic_fence_acqrel(),
+ SeqCst => intrinsics::atomic_fence(),
+ Relaxed => panic!("there is no such thing as a relaxed fence"),
}
}
}
-macro_rules! impl_Debug {
- ($($t:ident)*) => ($(
- #[stable(feature = "atomic_debug", since = "1.3.0")]
- impl fmt::Debug for $t {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- f.debug_tuple(stringify!($t)).field(&self.load(Ordering::SeqCst)).finish()
- }
+
+/// A compiler memory fence.
+///
+/// `compiler_fence` does not emit any machine code, but restricts the kinds
+/// of memory re-ordering the compiler is allowed to do. Specifically, depending on
+/// the given [`Ordering`] semantics, the compiler may be disallowed from moving reads
+/// or writes from before or after the call to the other side of the call to
+/// `compiler_fence`. Note that it does **not** prevent the *hardware*
+/// from doing such re-ordering. This is not a problem in a single-threaded,
+/// execution context, but when other threads may modify memory at the same
+/// time, stronger synchronization primitives such as [`fence`] are required.
+///
+/// The re-ordering prevented by the different ordering semantics are:
+///
+/// - with [`SeqCst`], no re-ordering of reads and writes across this point is allowed.
+/// - with [`Release`], preceding reads and writes cannot be moved past subsequent writes.
+/// - with [`Acquire`], subsequent reads and writes cannot be moved ahead of preceding reads.
+/// - with [`AcqRel`], both of the above rules are enforced.
+///
+/// `compiler_fence` is generally only useful for preventing a thread from
+/// racing *with itself*. That is, if a given thread is executing one piece
+/// of code, and is then interrupted, and starts executing code elsewhere
+/// (while still in the same thread, and conceptually still on the same
+/// core). In traditional programs, this can only occur when a signal
+/// handler is registered. In more low-level code, such situations can also
+/// arise when handling interrupts, when implementing green threads with
+/// pre-emption, etc. Curious readers are encouraged to read the Linux kernel's
+/// discussion of [memory barriers].
+///
+/// # Panics
+///
+/// Panics if `order` is [`Relaxed`].
+///
+/// # Examples
+///
+/// Without `compiler_fence`, the `assert_eq!` in following code
+/// is *not* guaranteed to succeed, despite everything happening in a single thread.
+/// To see why, remember that the compiler is free to swap the stores to
+/// `IMPORTANT_VARIABLE` and `IS_READ` since they are both
+/// `Ordering::Relaxed`. If it does, and the signal handler is invoked right
+/// after `IS_READY` is updated, then the signal handler will see
+/// `IS_READY=1`, but `IMPORTANT_VARIABLE=0`.
+/// Using a `compiler_fence` remedies this situation.
+///
+/// ```
+/// use std::sync::atomic::{AtomicBool, AtomicUsize};
+/// use std::sync::atomic::Ordering;
+/// use std::sync::atomic::compiler_fence;
+///
+/// static IMPORTANT_VARIABLE: AtomicUsize = AtomicUsize::new(0);
+/// static IS_READY: AtomicBool = AtomicBool::new(false);
+///
+/// fn main() {
+/// IMPORTANT_VARIABLE.store(42, Ordering::Relaxed);
+/// // prevent earlier writes from being moved beyond this point
+/// compiler_fence(Ordering::Release);
+/// IS_READY.store(true, Ordering::Relaxed);
+/// }
+///
+/// fn signal_handler() {
+/// if IS_READY.load(Ordering::Relaxed) {
+/// assert_eq!(IMPORTANT_VARIABLE.load(Ordering::Relaxed), 42);
+/// }
+/// }
+/// ```
+///
+/// [`fence`]: fn.fence.html
+/// [`Ordering`]: enum.Ordering.html
+/// [`Acquire`]: enum.Ordering.html#variant.Acquire
+/// [`SeqCst`]: enum.Ordering.html#variant.SeqCst
+/// [`Release`]: enum.Ordering.html#variant.Release
+/// [`AcqRel`]: enum.Ordering.html#variant.AcqRel
+/// [`Relaxed`]: enum.Ordering.html#variant.Relaxed
+/// [memory barriers]: https://www.kernel.org/doc/Documentation/memory-barriers.txt
+#[inline]
+#[stable(feature = "compiler_fences", since = "1.21.0")]
+pub fn compiler_fence(order: Ordering) {
+ unsafe {
+ match order {
+ Acquire => intrinsics::atomic_singlethreadfence_acq(),
+ Release => intrinsics::atomic_singlethreadfence_rel(),
+ AcqRel => intrinsics::atomic_singlethreadfence_acqrel(),
+ SeqCst => intrinsics::atomic_singlethreadfence(),
+ Relaxed => panic!("there is no such thing as a relaxed compiler fence"),
}
- )*);
+ }
}
-impl_Debug!{ AtomicUsize AtomicIsize AtomicBool }
+#[cfg(target_has_atomic_load_store = "8")]
+#[stable(feature = "atomic_debug", since = "1.3.0")]
+impl fmt::Debug for AtomicBool {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&self.load(Ordering::SeqCst), f)
+ }
+}
+
+#[cfg(target_has_atomic_load_store = "ptr")]
#[stable(feature = "atomic_debug", since = "1.3.0")]
impl<T> fmt::Debug for AtomicPtr<T> {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- f.debug_tuple("AtomicPtr").field(&self.load(Ordering::SeqCst)).finish()
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&self.load(Ordering::SeqCst), f)
+ }
+}
+
+#[cfg(target_has_atomic_load_store = "ptr")]
+#[stable(feature = "atomic_pointer", since = "1.24.0")]
+impl<T> fmt::Pointer for AtomicPtr<T> {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Pointer::fmt(&self.load(Ordering::SeqCst), f)
}
}
projects / rustc.git / blobdiff