Struct RcuArc 

pub struct RcuArc<T: Send + Sync + 'static> { /* private fields */ }

A version of crate::RcuOptionArc which does not require T: RcuDroppable in exchange for some extra atomic checking on reads.

RcuArc allows arbitrary types to be used with RCU by separating Droping the type, which may not be safe to do on the RCU advancer thread, and freeing the allocation for the type, which is safe to do, once an RCU grace period has elapsed.

We do the former by Droping the old Arc<T> synchronously on the calling thread when we do a replace. We do the latter by first placing a Weak<T> in the RCU callback queue to hold the memory alive (but with a potential strong count of zero) until an RCU grace period has elapsed.

Since the strong count of the memory may drop to zero even while a reader holds an RcuReadScope, readers must verify the memory is safe to read. Readers safely do this by using a Weak::upgrade, which serializes with a compare_exchange loop on the strong count.

Implementations

impl<T: Send + Sync + 'static> RcuArc<T>

pub fn new(data: impl Into<Option<Arc<T>>>) -> Self

Create a new RcuArc from an Option<Arc<T>>.

pub fn upgrade(&self) -> Option<Arc<T>>

Read the contents of the RcuArc.

Returns None if the wrapped Arc is None or is no longer valid.

pub fn update(&self, data: impl Into<Option<Arc<T>>>)

Write a new Option<Arc<T>> to the RcuArc.

The old Arc<T> (if any) is dropped on the caller’s thread, running T::drop() synchronously if it was the last strong reference.

pub fn is_some(&self) -> bool

Returns true if the RCU wrapper currently contains a value.

Unlike self.upgrade().is_some(), this neither takes a transient strong reference nor enters an RcuReadScope. A non-null pointer stored in the RcuArc always owns a strong count, and the pointer is never dereferenced, so observing a non-null pointer is sufficient. This guarantees that calling is_some() can never result in the caller running T::drop(), which matters when T::drop() may acquire locks.

pub fn is_none(&self) -> bool

Returns true if the RCU wrapper does not contain a value.

See Self::is_some for why this does not upgrade.

Trait Implementations

impl<T: Send + Sync + 'static> Clone for RcuArc<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug + Send + Sync + 'static> Debug for RcuArc<T>

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

Formats the value using the given formatter.

impl<T: Send + Sync + 'static> Default for RcuArc<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T: Send + Sync + 'static> Drop for RcuArc<T>

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl<T: Send + Sync + 'static> From<Arc<T>> for RcuArc<T>

fn from(data: Arc<T>) -> Self

Converts to this type from the input type.

impl<T: Send + Sync + 'static> From<Option<Arc<T>>> for RcuArc<T>

fn from(data: Option<Arc<T>>) -> Self

Converts to this type from the input type.

impl<T: RcuDroppable + Sync> RcuDroppable for RcuArc<T>