Struct CompletionStatus 

pub struct CompletionStatus { /* private fields */ }

A read-only view of whether the completion queue has entries pending.

Obtained from CompletionQueue::status. Unlike the queue itself this borrows nothing, so it can be captured once at startup and consulted from anywhere afterwards. The check costs two loads, with no system call, no locking, and no access to the ring — which is what a thread-per-core runtime needs on its preemption check, where reaching the queue would cost more than the comparison does.

Staleness

The answer is stale as soon as it is returned: the kernel may post a completion immediately after the load. This is inherent — any check that does not enter the kernel is a snapshot — and it makes this suitable for hints such as “should I stop what I am doing and poll?”, where being one iteration late costs nothing. It is not a synchronization primitive, and CompletionQueue::is_empty carries exactly the same caveat.

Implementations

impl CompletionStatus

pub fn is_empty(&self) -> bool

Returns true if the kernel has posted no completions beyond those already consumed.

See the note on staleness in the type documentation.

Trait Implementations

impl Debug for CompletionStatus

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

Formats the value using the given formatter.