Struct lock_api::MutexGuard

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

Expand description

An RAII implementation of a “scoped lock” of a mutex. When this structure is dropped (falls out of scope), the lock will be unlocked.

The data protected by the mutex can be accessed through this guard via its Deref and DerefMut implementations.

Implementations

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impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> MutexGuard<'a, R, T>

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

Returns a reference to the original Mutex object.

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

Makes a new MappedMutexGuard for a component of the locked data.

This operation cannot fail as the MutexGuard passed in already locked the mutex.

This is an associated function that needs to be used as MutexGuard::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<MappedMutexGuard<'a, R, U>, Self> where
 F: FnOnce(&mut T) -> Option<&mut U>,

Attempts to make a new MappedMutexGuard for a component of the locked data. The original guard is returned if the closure returns None.

This operation cannot fail as the MutexGuard passed in already locked the mutex.

This is an associated function that needs to be used as MutexGuard::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) -> U where
F: FnOnce() -> U,

Temporarily unlocks the mutex to execute the given function.

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

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impl<'a, R: RawMutexFair + 'a, T: ?Sized + 'a> MutexGuard<'a, R, T>

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pub fn unlock_fair(s: Self)

Unlocks the mutex using a fair unlock protocol.

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

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

Temporarily unlocks the mutex to execute the given function.

The mutex is unlocked using a fair unlock protocol.

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

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pub fn bump(s: &mut Self)

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

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