Struct RwLockUpgradableGuard

pub struct RwLockUpgradableGuard<'a, T: 'a + ?Sized, R = Spin> { /* private fields */ }

A guard that provides immutable data access but can be upgraded to RwLockWriteGuard.

No writers or other upgradeable guards can exist while this is in scope. New reader creation is prevented (to alleviate writer starvation) but there may be existing readers when the lock is acquired.

When the guard falls out of scope it will release the lock.

Implementations

impl<'rwlock, T: ?Sized, R: RelaxStrategy> RwLockUpgradableGuard<'rwlock, T, R>

pub fn upgrade(self) -> RwLockWriteGuard<'rwlock, T, R>

Upgrades an upgradeable lock guard to a writable lock guard.

let mylock = spin::RwLock::new(0);

let upgradeable = mylock.upgradeable_read(); // Readable, but not yet writable
let writable = upgradeable.upgrade();

impl<'rwlock, T: ?Sized, R> RwLockUpgradableGuard<'rwlock, T, R>

pub fn try_upgrade(self) -> Result<RwLockWriteGuard<'rwlock, T, R>, Self>

Tries to upgrade an upgradeable lock guard to a writable lock guard.

let mylock = spin::RwLock::new(0);
let upgradeable = mylock.upgradeable_read(); // Readable, but not yet writable

match upgradeable.try_upgrade() {
    Ok(writable) => /* upgrade successful - use writable lock guard */ (),
    Err(upgradeable) => /* upgrade unsuccessful */ (),
};

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

Downgrades the upgradeable lock guard to a readable, shared lock guard. Cannot fail and is guaranteed not to spin.

let mylock = spin::RwLock::new(1);

let upgradeable = mylock.upgradeable_read();
assert!(mylock.try_read().is_none());
assert_eq!(*upgradeable, 1);

let readable = upgradeable.downgrade(); // This is guaranteed not to spin
assert!(mylock.try_read().is_some());
assert_eq!(*readable, 1);

pub fn leak(this: Self) -> &'rwlock T

Leak the lock guard, yielding a reference to the underlying data.

Note that this function will permanently lock the original lock.

let mylock = spin::RwLock::new(0);

let data: &i32 = spin::RwLockUpgradableGuard::leak(mylock.upgradeable_read());

assert_eq!(*data, 0);

Trait Implementations

impl<'rwlock, T: ?Sized + Debug, R> Debug for RwLockUpgradableGuard<'rwlock, T, R>

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

Formats the value using the given formatter.

impl<'rwlock, T: ?Sized, R> Deref for RwLockUpgradableGuard<'rwlock, T, R>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<'rwlock, T: ?Sized + Display, R> Display for RwLockUpgradableGuard<'rwlock, T, R>

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

Formats the value using the given formatter.

impl<'rwlock, T: ?Sized, R> Drop for RwLockUpgradableGuard<'rwlock, T, R>

fn drop(&mut self)

Executes the destructor for this type.

impl<T: ?Sized + Send + Sync, R> Send for RwLockUpgradableGuard<'_, T, R>

impl<T: ?Sized + Send + Sync, R> Sync for RwLockUpgradableGuard<'_, T, R>