Struct Semaphore 

pub struct Semaphore { /* private fields */ }

A tiny counting semaphore for bounding how many callers run a section of code concurrently. Used to cap concurrent qlmanage subprocess launches: QuickLook’s thumbnail-generation agent is a shared per-user service that doesn’t parallelize well, so letting many callers (e.g. a UI rendering hundreds of HEIC thumbnails at once) spawn qlmanage unbounded causes the agent, and the source drive’s I/O, to queue up and occasionally exceed even a generous per-call timeout.

Implementations

impl Semaphore

pub fn new(max: usize) -> Self

pub fn acquire(&self) -> SemaphorePermit<'_>

Blocks until fewer than max permits are held, then takes one. Released automatically when the returned guard drops.