atomics

Basic utils for concurrent programming.

Installation

[dependencies]
atomics = "0.1"

Types

Backoff

Basic exponential backoff implementaiton.

• If its generic param is 0, it will always execute thread::yield_now().
• If its generic params is positive, it will execute a number of hint::spin_loop() before it starts to thread::yield_now().
• If its generic param is negative, it will just execute hint::spin_loop() without ever yielding.

atomic_t::AtomicT{Usize,64,32,16,8}

Wrapps the type in atomic. Type size must match the size of the atomic. Type must be Copy and have no uninit bytes.

new constructior is unsafe, since you need to guarantee that the type contains no uninit bytes.

With bytemuck feature, there is a safe constructor: new_no_uninit.

atomic_t_mut::AtomicT{Usize,64,32,16,8}

Alsmost the same as atomic_t::*, but uses atomic_maybe_uninit crate to support types that have uninit bytes.

This makes new constructor safe.

Downside is that atomic_maybe_uninit crate uses inline assembly to support this, which means you cannot use miri to test programs that use it.

SpinMutex

• Default type SpinMutex used Backoff<6>.
• You can use SpinSeqLockEx with a custom backoff param.

SpinRwLock

• Default type SpinRwLock used Backoff<6>.
• You can use SpinRwLockEx with a custom backoff param.

SpinSeqLock

Reference implementation: Amanieu/seqlock

• Default type SpinSeqLock used Backoff<6>.
• You can use SpinSeqLockEx with a custom backoff param.

Sequence locks support "optimistic reading" that can load() Copy types without writing to shared memory.

Downside is that "optimistic reading" is technically UB under Rust/C++ memory model. It is a well known "hole" in the model, but people have been using it in both Rust/C/C++ without issues (citation needed!).

Actual LLVM memory model allows for this use case, which might be part of the reason reason why things dont blow up.

Use it with caution!

NOTE: Since miri will recognize it as UB, optimistic reads are disabled for miri.

Features

• std - Enables thread::yield_now() for Backoff, otherwise it will awalys use just hint::spin_loop().
• serde - Enables Serialize and Deserialize for SpinSeqLock. TODO: support serde for other types!
• bytemuck - Enables safe constructor for atomic_t::* types.