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 hint {
46 pub(crate) use loom::hint::spin_loop;
47 }
48 pub(crate) mod sync {
49 pub(crate) mod atomic {
50 pub(crate) use loom::sync::atomic::{
51 AtomicBool, AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16,
52 AtomicU32, AtomicU64, AtomicU8, AtomicUsize, Ordering,
53 };
54
55 // FIXME: loom does not support compiler_fence at the moment.
56 // https://github.com/tokio-rs/loom/issues/117
57 // we use fence as a stand-in for compiler_fence for the time being.
58 // this may miss some races since fence is stronger than compiler_fence,
59 // but it's the best we can do for the time being.
60 pub(crate) use loom::sync::atomic::fence as compiler_fence;
61 }
62 pub(crate) use loom::sync::{Arc, Condvar, Mutex};
63 }
64}
65#[cfg(not(crossbeam_loom))]
66#[allow(unused_imports)]
67mod primitive {
68 pub(crate) mod hint {
69 pub(crate) use core::hint::spin_loop;
70 }
71 pub(crate) mod sync {
72 pub(crate) mod atomic {
73 pub(crate) use core::sync::atomic::{compiler_fence, Ordering};
74 #[cfg(not(crossbeam_no_atomic))]
75 pub(crate) use core::sync::atomic::{
76 AtomicBool, AtomicI16, AtomicI8, AtomicIsize, AtomicU16, AtomicU8, AtomicUsize,
77 };
78 #[cfg(not(crossbeam_no_atomic))]
79 #[cfg(any(target_has_atomic = "32", not(target_pointer_width = "16")))]
80 pub(crate) use core::sync::atomic::{AtomicI32, AtomicU32};
81 #[cfg(not(crossbeam_no_atomic))]
82 #[cfg(any(
83 target_has_atomic = "64",
84 not(any(target_pointer_width = "16", target_pointer_width = "32")),
85 ))]
86 pub(crate) use core::sync::atomic::{AtomicI64, AtomicU64};
87 }
88
89 #[cfg(feature = "std")]
90 pub(crate) use std::sync::{Arc, Condvar, Mutex};
91 }
92}
93
94pub mod atomic;
95
96mod cache_padded;
97pub use crate::cache_padded::CachePadded;
98
99mod backoff;
100pub use crate::backoff::Backoff;
101
102#[cfg(feature = "std")]
103pub mod sync;
104
105#[cfg(feature = "std")]
106#[cfg(not(crossbeam_loom))]
107pub mod thread;
108