Struct lock_api::RwLockReadGuard

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pub struct RwLockReadGuard<'a, R: RawRwLock, T: ?Sized> { /* private fields */ }

Expand description

RAII structure used to release the shared read access of a lock when dropped.

Implementations

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impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T>

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pub fn rwlock(s: &Self) -> &'a RwLock<R, T>

Returns a reference to the original reader-writer lock object.

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pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedRwLockReadGuard<'a, R, U>where
F: FnOnce(&T) -> &U,

Make a new MappedRwLockReadGuard for a component of the locked data.

This operation cannot fail as the RwLockReadGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockReadGuard::map(...). A method would interfere with methods of the same name on the contents of the locked data.

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pub fn try_map<U: ?Sized, F>(
 s: Self,
 f: F
) -> Result<MappedRwLockReadGuard<'a, R, U>, Self>where
 F: FnOnce(&T) -> Option<&U>,

Attempts to make a new MappedRwLockReadGuard for a component of the locked data. Returns the original guard if the closure returns None.

This operation cannot fail as the RwLockReadGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockReadGuard::try_map(...). A method would interfere with methods of the same name on the contents of the locked data.

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pub fn unlocked<F, U>(s: &mut Self, f: F) -> Uwhere
F: FnOnce() -> U,

Temporarily unlocks the RwLock to execute the given function.

The RwLock is unlocked a fair unlock protocol.

This is safe because &mut guarantees that there exist no other references to the data protected by the RwLock.

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impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T>

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pub fn unlock_fair(s: Self)

Unlocks the RwLock using a fair unlock protocol.

By default, RwLock is unfair and allow the current thread to re-lock the RwLock before another has the chance to acquire the lock, even if that thread has been blocked on the RwLock for a long time. This is the default because it allows much higher throughput as it avoids forcing a context switch on every RwLock unlock. This can result in one thread acquiring a RwLock many more times than other threads.

However in some cases it can be beneficial to ensure fairness by forcing the lock to pass on to a waiting thread if there is one. This is done by using this method instead of dropping the RwLockReadGuard normally.

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pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> Uwhere
F: FnOnce() -> U,

Temporarily unlocks the RwLock to execute the given function.

The RwLock is unlocked a fair unlock protocol.

This is safe because &mut guarantees that there exist no other references to the data protected by the RwLock.

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pub fn bump(s: &mut Self)

Temporarily yields the RwLock to a waiting thread if there is one.

This method is functionally equivalent to calling unlock_fair followed by read, however it can be much more efficient in the case where there are no waiting threads.