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}
105