Struct tokio::sync::RwLockWriteGuard

pub struct RwLockWriteGuard<'a, T: ?Sized> { /* fields omitted */ }

This is supported on crate feature sync only.

RAII structure used to release the exclusive write access of a lock when dropped.

This structure is created by the write and method on RwLock.

Implementations

impl<'a, T: ?Sized> RwLockWriteGuard<'a, T>

pub fn downgrade(self) -> RwLockReadGuard<'a, T>

Atomically downgrades a write lock into a read lock without allowing any writers to take exclusive access of the lock in the meantime.

Note: This won't necessarily allow any additional readers to acquire locks, since RwLock is fair and it is possible that a writer is next in line.

Returns an RAII guard which will drop the read access of this rwlock when dropped.

Examples

let lock = Arc::new(RwLock::new(1));

let n = lock.write().await;
   
let cloned_lock = lock.clone();
let handle = tokio::spawn(async move {
    *cloned_lock.write().await = 2;
});

let n = n.downgrade();
assert_eq!(*n, 1, "downgrade is atomic");

drop(n);
handle.await.unwrap();
assert_eq!(*lock.read().await, 2, "second writer obtained write lock");

Trait Implementations

impl<'a, T: ?Sized> Debug for RwLockWriteGuard<'a, T> where
    T: Debug, 

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

Formats the value using the given formatter.

impl<T: ?Sized> Deref for RwLockWriteGuard<'_, T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T: ?Sized> DerefMut for RwLockWriteGuard<'_, T>

fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<'a, T: ?Sized> Display for RwLockWriteGuard<'a, T> where
    T: Display, 

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

Formats the value using the given formatter.

impl<'a, T: ?Sized> Drop for RwLockWriteGuard<'a, T>

fn drop(&mut self)

Executes the destructor for this type.

impl<T: ?Sized> Send for RwLockWriteGuard<'_, T> where
    T: Send + Sync, 

impl<T: ?Sized> Sync for RwLockWriteGuard<'_, T> where
    T: Send + Sync,