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#![no_std]
28#![doc(test(
29 no_crate_inject,
30 attr(
31 deny(warnings, rust_2018_idioms),
32 allow(dead_code, unused_assignments, unused_variables)
33 )
34))]
35#![warn(
36 missing_docs,
37 missing_debug_implementations,
38 rust_2018_idioms,
39 unreachable_pub
40)]
41
42#[cfg(feature = "std")]
43extern crate std;
44
45#[cfg(crossbeam_loom)]
46#[allow(unused_imports)]
47mod primitive {
48 pub(crate) mod hint {
49 pub(crate) use loom::hint::spin_loop;
50 }
51 pub(crate) mod sync {
52 pub(crate) mod atomic {
53 pub(crate) use loom::sync::atomic::{
54 AtomicBool, AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16,
55 AtomicU32, AtomicU64, AtomicU8, AtomicUsize, Ordering,
56 };
57
58 // FIXME: loom does not support compiler_fence at the moment.
59 // https://github.com/tokio-rs/loom/issues/117
60 // we use fence as a stand-in for compiler_fence for the time being.
61 // this may miss some races since fence is stronger than compiler_fence,
62 // but it's the best we can do for the time being.
63 pub(crate) use loom::sync::atomic::fence as compiler_fence;
64 }
65 pub(crate) use loom::sync::{Arc, Condvar, Mutex};
66 }
67}
68#[cfg(not(crossbeam_loom))]
69#[allow(unused_imports)]
70mod primitive {
71 pub(crate) mod hint {
72 pub(crate) use core::hint::spin_loop;
73 }
74 pub(crate) mod sync {
75 pub(crate) mod atomic {
76 pub(crate) use core::sync::atomic::{compiler_fence, Ordering};
77 #[cfg(not(crossbeam_no_atomic))]
78 pub(crate) use core::sync::atomic::{
79 AtomicBool, AtomicI16, AtomicI8, AtomicIsize, AtomicU16, AtomicU8, AtomicUsize,
80 };
81 #[cfg(not(crossbeam_no_atomic))]
82 #[cfg(any(target_has_atomic = "32", not(target_pointer_width = "16")))]
83 pub(crate) use core::sync::atomic::{AtomicI32, AtomicU32};
84 #[cfg(not(crossbeam_no_atomic))]
85 #[cfg(any(
86 target_has_atomic = "64",
87 not(any(target_pointer_width = "16", target_pointer_width = "32")),
88 ))]
89 pub(crate) use core::sync::atomic::{AtomicI64, AtomicU64};
90 }
91
92 #[cfg(feature = "std")]
93 pub(crate) use std::sync::{Arc, Condvar, Mutex};
94 }
95}
96
97pub mod atomic;
98
99mod cache_padded;
100pub use crate::cache_padded::CachePadded;
101
102mod backoff;
103pub use crate::backoff::Backoff;
104
105#[cfg(feature = "std")]
106pub mod sync;
107
108#[cfg(feature = "std")]
109#[cfg(not(crossbeam_loom))]
110pub mod thread;
111