Bug: 174788900

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  1. 60859b4 Allow using spin from DnsResolver by Bernie Innocenti · 5 weeks ago master
  2. d5ebf60 Merge "Android.bp: add tests" by Treehugger Robot · 6 weeks ago
  3. 0b3587a Add Android.bp am: 9cd4e97acf by Jeff Vander Stoep · 6 weeks ago
  4. 0a191c6 spin crate v0.7.0 am: b00717e375 by Jeff Vander Stoep · 6 weeks ago
  5. a39d048 Android.bp: add tests by Jeff Vander Stoep · 6 weeks ago


Crates.io version docs.rs Build Status

Spin-based synchronization primitives.

This crate provides spin-based versions of the primitives in std::sync. Because synchronization is done through spinning, the primitives are suitable for use in no_std environments.

Before deciding to use spin, we recommend reading this superb blog post by @matklad that discusses the pros and cons of spinlocks. If you have access to std, it's likely that the primitives in std::sync will serve you better except in very specific circumstances.


  • Mutex, RwLock and Once equivalents
  • Support for no_std environments
  • lock_api compatibility
  • Upgradeable RwLock guards
  • Guards can be sent and shared between threads
  • Guard leaking
  • std feature to enable yield to the OS scheduler in busy loops
  • Mutex can become a ticket lock


Include the following under the [dependencies] section in your Cargo.toml file.

spin = "x.y"


When calling lock on a Mutex you will get a guard value that provides access to the data. When this guard is dropped, the lock will be unlocked.

extern crate spin;
use std::{sync::Arc, thread};

fn main() {
    let counter = Arc::new(spin::Mutex::new(0));

    let thread = thread::spawn({
        let counter = counter.clone();
        move || {
            for _ in 0..10 {
                *counter.lock() += 1;

    for _ in 0..10 {
        *counter.lock() += 1;


    assert_eq!(*counter.lock(), 20);

Feature flags

The crate comes with a few feature flags that you may wish to use.

  • lock_api enabled support for lock_api

  • ticket_mutex uses a ticket lock for the implementation of Mutex

  • std enables support for thread yielding instead of spinning


It is often desirable to have a lock shared between threads. Wrapping the lock in an std::sync::Arc is route through which this might be achieved.

Locks provide zero-overhead access to their data when accessed through a mutable reference by using their get_mut methods.

The behaviour of these lock is similar to their namesakes in std::sync. they differ on the following:

  • Locks will not be poisoned in case of failure.
  • Threads will not yield to the OS scheduler when encounter a lock that cannot be accessed. Instead, they will ‘spin’ in a busy loop until the lock becomes available.


spin is distributed under the MIT License, (See LICENSE).