Struct pinned_sync::RwLock

pub struct RwLock<T: ?Sized> { /* fields omitted */ }

A reader-writer lock

This type of lock allows a number of readers or at most one writer at any point in time. The write portion of this lock typically allows modification of the underlying data (exclusive access) and the read portion of this lock typically allows for read-only access (shared access).

In comparison, a [Mutex] does not distinguish between readers or writers that acquire the lock, therefore blocking any threads waiting for the lock to become available. An RwLock will allow any number of readers to acquire the lock as long as a writer is not holding the lock.

The priority policy of the lock is dependent on the underlying operating system’s implementation, and this type does not guarantee that any particular policy will be used.

The type parameter T represents the data that this lock protects. It is required that T satisfies Send to be shared across threads and Sync to allow concurrent access through readers. The RAII guards returned from the locking methods implement Deref (and DerefMut for the write methods) to allow access to the content of the lock.

Poisoning

An RwLock, like [Mutex], will become poisoned on a panic. Note, however, that an RwLock may only be poisoned if a panic occurs while it is locked exclusively (write mode). If a panic occurs in any reader, then the lock will not be poisoned.

Implementations

impl<T> RwLock<T>

pub const fn uninit(value: T) -> Self

Create a new, uninitialized read-write lock.

This is NOT equivalent to MaybeUninit::uninit().assume_init(), which will cause undefined behaviour if used to create a new read-write lock.

pub fn boxed(value: T) -> Pin<Box<Self>>

Create a new, initialized read-write lock.

The resulting read-write lock is wrapped and ready for use.

pub fn arc(value: T) -> Pin<Arc<Self>>

Create a new, initialized read-write lock.

The resulting read-write lock is wrapped and ready for use.

impl<T: ?Sized> RwLock<T>

pub fn init(self: Pin<&Self>)

Initialize a read-write lock, making it ready for use.

Panics

This function may panic if the read-write lock was already initialized.

pub fn read(self: Pin<&Self>) -> LockResult<RwLockReadGuard<'_, T>>

Locks this rwlock with shared read access, blocking the current thread until it can be acquired.

The calling thread will be blocked until there are no more writers which hold the lock. There may be other readers currently inside the lock when this method returns. This method does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.

Returns an RAII guard which will release this thread’s shared access once it is dropped.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. The failure will occur immediately after the lock has been acquired.

Panics

This function might panic when called if the lock is already held by the current thread.

This function may panic if the lock is not initialized.

pub fn try_read(self: Pin<&Self>) -> TryLockResult<RwLockReadGuard<'_, T>>

Attempts to acquire this rwlock with shared read access.

If the access could not be granted at this time, then Err is returned. Otherwise, an RAII guard is returned which will release the shared access when it is dropped.

This function does not block.

This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will only be returned if the lock would have otherwise been acquired.

Panics

This function may panic if the lock is not initialized.

pub fn write(self: Pin<&Self>) -> LockResult<RwLockWriteGuard<'_, T>>

Locks this rwlock with exclusive write access, blocking the current thread until it can be acquired.

This function will not return while other writers or other readers currently have access to the lock.

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

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will be returned when the lock is acquired.

Panics

This function might panic when called if the lock is already held by the current thread.

This function may panic if the lock is not initialized.

pub fn try_write(self: Pin<&Self>) -> TryLockResult<RwLockWriteGuard<'_, T>>

Attempts to lock this rwlock with exclusive write access.

If the lock could not be acquired at this time, then Err is returned. Otherwise, an RAII guard is returned which will release the lock when it is dropped.

This function does not block.

This function does not provide any guarantees with respect to the ordering of whether contentious readers or writers will acquire the lock first.

Errors

This function will return an error if the RwLock is poisoned. An RwLock is poisoned whenever a writer panics while holding an exclusive lock. An error will only be returned if the lock would have otherwise been acquired.

Panics

This function may panic if the lock is not initialized.

pub fn is_poisoned(self: Pin<&Self>) -> bool

Determines whether the read-write lock is poisoned.

If another thread is active, the read-write lock can still become poisoned at any time. You should not trust a false value for program correctness without additional synchronization.

pub fn into_inner(self) -> LockResult<T> where
    T: Sized, 

Consumes this read-write lock, returning the underlying data.

Errors

If another user of this read-write lock panicked while holding the read-write lock, then this call will return an error instead.

pub fn get_mut(&mut self) -> LockResult<&mut T>

Returns a mutable reference to the underlying data.

Since this call borrows the RwLock mutably, no actual locking needs to take place – the mutable borrow statically guarantees no locks exist.

Errors

If another user of this read-write lock panicked while holding the read-write lock, then this call will return an error instead.

Trait Implementations

impl<T: ?Sized + Send> Send for RwLock<T>

impl<T: ?Sized + Send + Sync> Sync for RwLock<T>