spin-sync is a module providing synchronization primitives using spinlock. (Wikipedia Spinlock)

The main features are as follows.

• Declaring public structs Mutex and RwLock, whose interfaces are resembles those of std::sync.
• Ensuring safety as much as std::sync.
• Unfortunately, rust nightly version is required so far.

How to use

1. Add the following line in dependencies section in your Cargo.toml.

   Cargo.toml spin-sync = "0.0.1"

2. Make sure to install rust nightly toolchain.

   shell rustup toolchain install nightly

3. Build, test and run your project.

   shell cargo +nightly build cargo +nightly test cargo +nightly run

Why nightly toolchain is required?

To implement negative trait !Sync.

It is necessary to enable the rust compiler to find a kind of bug. (std::sync do the same thing, too.) Rust compiler requests the feature option_builtin_traits and the nightly toolchain to do it except for the std library.

Examples

Mutex

Mutex::lock() acquires the exclusive lock and returns an RAII guard object. The lock will be released when the guard is dropped (falls out of scope.)

The data protected by the mutex can be accessed through this guard via its Defer and DeferMut implementations.

``` extern crate spin_sync;

use spin_sync::Mutex; use std::sync::Arc; use std::thread;

/// Create a variable protected by a Mutex, increment it in worker threads, /// and check the variable was updated rightly. fn main() { const WORKERNUM: usize = 10; let mut handles = Vec::withcapacity(WORKER_NUM);

// Decrare a variable protected by Mutex.
// It is wrapped in std::Arc to share this mutex itself among threads.
let mutex = Arc::new(Mutex::new(0));

// Create worker threads to inclement the value by 1.
for _ in 0..WORKER_NUM {
    let mutex = mutex.clone();

    let handle = thread::spawn(move || {
        let mut num = mutex.lock().unwrap();
        *num += 1;
    });

    handles.push(handle);
}

// Wait for the all worker threads are finished.
for handle in handles {
    handle.join().unwrap();
}

// Make sure the value is incremented by the worker count.
let num = mutex.lock().unwrap();
assert_eq!(WORKER_NUM, *num);

} ```

RwLock

RwLock resembles Mutex except for it distinguishes readers and writers.

RwLock::write() behaves like Mutex::lock(). It acquires the exclusive write lock and returns an RAII guard object. The lock will be released when the guard is dropped (falls out of scope.) This guard allows read/write access (exclusive access) to the underlying data via its Defer and DeferMut implementations.

RwLock::read() behaves like RwLock::write() except for it acquires a shared read lock (i.e. this method allows any number of readers to hold a shared read lock at the same time as long as no writer is not holding the exclusive write lock.) This guard allows read-only access (shared access) to the underlying data via its Defer implementation.

``` extern crate spin_sync;

use spin_sync::RwLock; use std::sync::Arc; use std::thread;

/// Create a variable protected by a RwLock, increment it by 2 in worker threads, /// and check the variable was updated rightly. fn main() { const WORKERNUM: usize = 10; let mut handles = Vec::withcapacity(WORKER_NUM);

// Decrare a variable protected by RwLock.
// It is wrapped in std::Arc to share this instance itself among threads.
let rwlock = Arc::new(RwLock::new(0));

// Create worker threads to inclement the value by 2.
for _ in 0..WORKER_NUM {
    let c_rwlock = rwlock.clone();

    let handle = thread::spawn(move || {
        let mut num = c_rwlock.write().unwrap();
        *num += 2;
    });

    handles.push(handle);
}

// Make sure the value is always multipile of 2 even if some worker threads
// are working (it is incremented by 2.)
//
// Enclosing the lock with `{}` to drop it before waiting for the worker
// threads; otherwise, deadlocks could be occurred.
{
    let num = rwlock.read().unwrap();
    assert_eq!(0, *num % 2);
}

// Wait for the all worker threads are finished.
for handle in handles {
    handle.join().unwrap();
}

// Make sure the value is incremented by 2 times the worker count.
let num = rwlock.read().unwrap();
assert_eq!(2 * WORKER_NUM, *num);

} ```