Struct METADATA_MUTEX

struct METADATA_MUTEX {
    __private_field: (),
}

Fields

__private_field: ()

Methods from Deref<Target = Mutex<()>>

pub async fn lock(&self) -> MutexGuard<'_, T>

Locks this mutex, causing the current task to yield until the lock has been acquired. When the lock has been acquired, function returns a [MutexGuard].

If the mutex is available to be acquired immediately, then this call will typically not yield to the runtime. However, this is not guaranteed under all circumstances.

Cancel safety

This method uses a queue to fairly distribute locks in the order they were requested. Cancelling a call to lock makes you lose your place in the queue.

Examples

use tokio::sync::Mutex;

#[tokio::main]
async fn main() {
    let mutex = Mutex::new(1);

    let mut n = mutex.lock().await;
    *n = 2;
}

pub fn blocking_lock(&self) -> MutexGuard<'_, T>

Blockingly locks this Mutex. When the lock has been acquired, function returns a [MutexGuard].

This method is intended for use cases where you need to use this mutex in asynchronous code as well as in synchronous code.

Panics

This function panics if called within an asynchronous execution context.

• If you find yourself in an asynchronous execution context and needing to call some (synchronous) function which performs one of these blocking_ operations, then consider wrapping that call inside [spawn_blocking()][crate::runtime::Handle::spawn_blocking] (or [block_in_place()][crate::task::block_in_place]).

Examples

use std::sync::Arc;
use tokio::sync::Mutex;

#[tokio::main]
async fn main() {
    let mutex =  Arc::new(Mutex::new(1));
    let lock = mutex.lock().await;

    let mutex1 = Arc::clone(&mutex);
    let blocking_task = tokio::task::spawn_blocking(move || {
        // This shall block until the `lock` is released.
        let mut n = mutex1.blocking_lock();
        *n = 2;
    });

    assert_eq!(*lock, 1);
    // Release the lock.
    drop(lock);

    // Await the completion of the blocking task.
    blocking_task.await.unwrap();

    // Assert uncontended.
    let n = mutex.try_lock().unwrap();
    assert_eq!(*n, 2);
}

pub fn blocking_lock_owned(self: Arc<Mutex<T>>) -> OwnedMutexGuard<T>

Blockingly locks this Mutex. When the lock has been acquired, function returns an [OwnedMutexGuard].

This method is identical to [Mutex::blocking_lock], except that the returned guard references the Mutex with an Arc rather than by borrowing it. Therefore, the Mutex must be wrapped in an Arc to call this method, and the guard will live for the 'static lifetime, as it keeps the Mutex alive by holding an Arc.

Panics

This function panics if called within an asynchronous execution context.

• If you find yourself in an asynchronous execution context and needing to call some (synchronous) function which performs one of these blocking_ operations, then consider wrapping that call inside [spawn_blocking()][crate::runtime::Handle::spawn_blocking] (or [block_in_place()][crate::task::block_in_place]).

Examples

use std::sync::Arc;
use tokio::sync::Mutex;

#[tokio::main]
async fn main() {
    let mutex =  Arc::new(Mutex::new(1));
    let lock = mutex.lock().await;

    let mutex1 = Arc::clone(&mutex);
    let blocking_task = tokio::task::spawn_blocking(move || {
        // This shall block until the `lock` is released.
        let mut n = mutex1.blocking_lock_owned();
        *n = 2;
    });

    assert_eq!(*lock, 1);
    // Release the lock.
    drop(lock);

    // Await the completion of the blocking task.
    blocking_task.await.unwrap();

    // Assert uncontended.
    let n = mutex.try_lock().unwrap();
    assert_eq!(*n, 2);
}

pub async fn lock_owned(self: Arc<Mutex<T>>) -> OwnedMutexGuard<T>

Locks this mutex, causing the current task to yield until the lock has been acquired. When the lock has been acquired, this returns an [OwnedMutexGuard].

If the mutex is available to be acquired immediately, then this call will typically not yield to the runtime. However, this is not guaranteed under all circumstances.

This method is identical to [Mutex::lock], except that the returned guard references the Mutex with an Arc rather than by borrowing it. Therefore, the Mutex must be wrapped in an Arc to call this method, and the guard will live for the 'static lifetime, as it keeps the Mutex alive by holding an Arc.

Cancel safety

This method uses a queue to fairly distribute locks in the order they were requested. Cancelling a call to lock_owned makes you lose your place in the queue.

Examples

use tokio::sync::Mutex;
use std::sync::Arc;

#[tokio::main]
async fn main() {
    let mutex = Arc::new(Mutex::new(1));

    let mut n = mutex.clone().lock_owned().await;
    *n = 2;
}

pub fn try_lock(&self) -> Result<MutexGuard<'_, T>, TryLockError>

Attempts to acquire the lock, and returns TryLockError if the lock is currently held somewhere else.

Examples

use tokio::sync::Mutex;

let mutex = Mutex::new(1);

let n = mutex.try_lock()?;
assert_eq!(*n, 1);

pub fn try_lock_owned( self: Arc<Mutex<T>>, ) -> Result<OwnedMutexGuard<T>, TryLockError>

Attempts to acquire the lock, and returns TryLockError if the lock is currently held somewhere else.

This method is identical to [Mutex::try_lock], except that the returned guard references the Mutex with an Arc rather than by borrowing it. Therefore, the Mutex must be wrapped in an Arc to call this method, and the guard will live for the 'static lifetime, as it keeps the Mutex alive by holding an Arc.

Examples

use tokio::sync::Mutex;
use std::sync::Arc;

let mutex = Arc::new(Mutex::new(1));

let n = mutex.clone().try_lock_owned()?;
assert_eq!(*n, 1);

Trait Implementations

impl Deref for METADATA_MUTEX

type Target = Mutex<()>

The resulting type after dereferencing.

fn deref(&self) -> &Mutex<()>

Dereferences the value.

impl LazyStatic for METADATA_MUTEX