# SpinMutex in spin::mutex - Rust
A spin lock providing mutually exclusive access to data.
Keywords: rust, rustlang, rust-lang, SpinMutex

# Struct spin::mutex::SpinMutex

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    pub struct SpinMutex<T: ?Sized> { /* private fields */ }

Expand description

A spin lock providing mutually exclusive access to data.

## Example

    use spin;

    let lock = spin::mutex::SpinMutex::new(0);

    // Modify the data
    *lock.lock() = 2;

    // Read the data
    let answer = *lock.lock();
    assert_eq!(answer, 2);

## Thread safety example

    use spin;
    use std::sync::{Arc, Barrier};

    let thread_count = 1000;
    let spin_mutex = Arc::new(spin::mutex::SpinMutex::new(0));

    // We use a barrier to ensure the readout happens after all writing
    let barrier = Arc::new(Barrier::new(thread_count + 1));

    for _ in (0..thread_count) {
        let my_barrier = barrier.clone();
        let my_lock = spin_mutex.clone();
        std::thread::spawn(move || {
            let mut guard = my_lock.lock();
            *guard += 1;

            // Release the lock to prevent a deadlock
            drop(guard);
            my_barrier.wait();
        });
    }

    barrier.wait();

    let answer = { *spin_mutex.lock() };
    assert_eq!(answer, thread_count);

## Implementations

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### impl<T> SpinMutex<T>

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#### pub const fn new(user_data: T) -> SpinMutex<T>

Creates a new `SpinMutex` wrapping the supplied data.

##### Example

    use spin::mutex::SpinMutex;

    static MUTEX: SpinMutex<()> = SpinMutex::new(());

    fn demo() {
        let lock = MUTEX.lock();
        // do something with lock
        drop(lock);
    }

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#### pub fn into_inner(self) -> T

Consumes this `SpinMutex` and unwraps the underlying data.

##### Example

    let lock = spin::mutex::SpinMutex::new(42);
    assert_eq!(42, lock.into_inner());

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### impl<T: ?Sized> SpinMutex<T>

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#### pub fn is_locked(&self) -> bool

Returns `true` if the lock is currently held.

##### Safety

This function provides no synchronization guarantees and so its result should be considered ‘out of date’ the instant it is called. Do not use it for synchronization purposes. However, it may be useful as a heuristic.

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#### pub fn lock(&self) -> SpinMutexGuard<'_, T>

Locks the `SpinMutex` and returns a guard that permits access to the inner data.

The returned value may be dereferenced for data access and the lock will be dropped when the guard falls out of scope.

    let lock = spin::mutex::SpinMutex::new(0);
    {
        let mut data = lock.lock();
        // The lock is now locked and the data can be accessed
        *data += 1;
        // The lock is implicitly dropped at the end of the scope
    }

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#### pub unsafe fn force_unlock(&self)

Force unlock this `SpinMutex`.

##### Safety

This is extremely unsafe if the lock is not held by the current thread. However, this can be useful in some instances for exposing the lock to FFI that doesn’t know how to deal with RAII.

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#### pub fn try_lock(&self) -> Option<SpinMutexGuard<'_, T>>

Try to lock this `SpinMutex`, returning a lock guard if successful.

##### Example

    let lock = spin::mutex::SpinMutex::new(42);

    let maybe_guard = lock.try_lock();
    assert!(maybe_guard.is_some());

    // `maybe_guard` is still held, so the second call fails
    let maybe_guard2 = lock.try_lock();
    assert!(maybe_guard2.is_none());

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#### pub fn get_mut(&mut self) -> &mut T

Returns a mutable reference to the underlying data.

Since this call borrows the `SpinMutex` mutably, and a mutable reference is guaranteed to be exclusive in Rust, no actual locking needs to take place – the mutable borrow statically guarantees no locks exist. As such, this is a ‘zero-cost’ operation.

##### Example

    let mut lock = spin::mutex::SpinMutex::new(0);
    *lock.get_mut() = 10;
    assert_eq!(*lock.lock(), 10);

## Trait Implementations

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### impl<T: ?Sized + Debug> Debug for SpinMutex<T>

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

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### impl<T: ?Sized + Default> Default for SpinMutex<T>

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#### fn default() -> SpinMutex<T>

Returns the “default value” for a type. Read more

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### impl<T> From<T> for SpinMutex<T>

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#### fn from(data: T) -> Self

Converts to this type from the input type.

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### impl<T: ?Sized + Send> Send for SpinMutex<T>

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### impl<T: ?Sized + Send> Sync for SpinMutex<T>

## Auto Trait Implementations

### impl<T> !RefUnwindSafe for SpinMutex<T>

### impl<T: ?Sized> Unpin for SpinMutex<T> where
T: Unpin,

### impl<T: ?Sized> UnwindSafe for SpinMutex<T> where
T: UnwindSafe,

## Blanket Implementations

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### impl<T> Any for T where
T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more

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### impl<T> Borrow<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more

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### impl<T> BorrowMut<T> for T where
T: ?Sized,

const: unstable · source

#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more

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### impl<T> From<!> for T

const: unstable · source

#### fn from(t: !) -> T

Converts to this type from the input type.

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### impl<T> From<T> for T

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.

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### impl<T, U> TryInto<U> for T where
U: TryFrom<T>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.