crossbeam_utils/
lib.rs

1//! Miscellaneous tools for concurrent programming.
2//!
3//! ## Atomics
4//!
5//! * [`AtomicCell`], a thread-safe mutable memory location.
6//! * [`AtomicConsume`], for reading from primitive atomic types with "consume" ordering.
7//!
8//! ## Thread synchronization
9//!
10//! * [`Parker`], a thread parking primitive.
11//! * [`ShardedLock`], a sharded reader-writer lock with fast concurrent reads.
12//! * [`WaitGroup`], for synchronizing the beginning or end of some computation.
13//!
14//! ## Utilities
15//!
16//! * [`Backoff`], for exponential backoff in spin loops.
17//! * [`CachePadded`], for padding and aligning a value to the length of a cache line.
18//! * [`scope`], for spawning threads that borrow local variables from the stack.
19//!
20//! [`AtomicCell`]: atomic::AtomicCell
21//! [`AtomicConsume`]: atomic::AtomicConsume
22//! [`Parker`]: sync::Parker
23//! [`ShardedLock`]: sync::ShardedLock
24//! [`WaitGroup`]: sync::WaitGroup
25//! [`scope`]: thread::scope
26
27#![doc(test(
28    no_crate_inject,
29    attr(
30        deny(warnings, rust_2018_idioms),
31        allow(dead_code, unused_assignments, unused_variables)
32    )
33))]
34#![warn(
35    missing_docs,
36    missing_debug_implementations,
37    rust_2018_idioms,
38    unreachable_pub
39)]
40#![cfg_attr(not(feature = "std"), no_std)]
41
42#[cfg(crossbeam_loom)]
43#[allow(unused_imports)]
44mod primitive {
45    pub(crate) mod sync {
46        pub(crate) mod atomic {
47            pub(crate) use loom::sync::atomic::spin_loop_hint;
48            pub(crate) use loom::sync::atomic::{
49                AtomicBool, AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16,
50                AtomicU32, AtomicU64, AtomicU8, AtomicUsize,
51            };
52
53            // FIXME: loom does not support compiler_fence at the moment.
54            // https://github.com/tokio-rs/loom/issues/117
55            // we use fence as a stand-in for compiler_fence for the time being.
56            // this may miss some races since fence is stronger than compiler_fence,
57            // but it's the best we can do for the time being.
58            pub(crate) use loom::sync::atomic::fence as compiler_fence;
59        }
60        pub(crate) use loom::sync::{Arc, Condvar, Mutex};
61    }
62}
63#[cfg(not(crossbeam_loom))]
64#[allow(unused_imports)]
65mod primitive {
66    pub(crate) mod sync {
67        pub(crate) mod atomic {
68            pub(crate) use core::sync::atomic::compiler_fence;
69            // TODO(taiki-e): once we bump the minimum required Rust version to 1.49+,
70            // use [`core::hint::spin_loop`] instead.
71            #[allow(deprecated)]
72            pub(crate) use core::sync::atomic::spin_loop_hint;
73            #[cfg(not(crossbeam_no_atomic))]
74            pub(crate) use core::sync::atomic::{
75                AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32,
76                AtomicU8, AtomicUsize,
77            };
78            #[cfg(not(crossbeam_no_atomic_64))]
79            pub(crate) use core::sync::atomic::{AtomicI64, AtomicU64};
80        }
81
82        #[cfg(feature = "std")]
83        pub(crate) use std::sync::{Arc, Condvar, Mutex};
84    }
85}
86
87pub mod atomic;
88
89mod cache_padded;
90pub use crate::cache_padded::CachePadded;
91
92mod backoff;
93pub use crate::backoff::Backoff;
94
95use cfg_if::cfg_if;
96
97cfg_if! {
98    if #[cfg(feature = "std")] {
99        pub mod sync;
100
101        #[cfg(not(crossbeam_loom))]
102        pub mod thread;
103    }
104}
crossbeam_utils/lib.rs

crossbeam_utils/
lib.rs
