Struct State 

struct State {
    heap: BinaryHeap<Reverse<Slot>>,
    seq: u64,
    stopping: bool,
    wakes: u64,
    last_sweep: Instant,
}

Everything the release thread and its registrars share under one lock.

Fields

heap: BinaryHeap<Reverse<Slot>>

A min-heap of armed deadlines.

seq: u64

Monotonic registration counter, the tie-break in Slot’s Ord.

stopping: bool

Set by ReleaseTimer’s Drop; the thread returns on its next wake.

wakes: u64

Loop iterations. Always compiled — it is one u64 increment under a lock the thread already holds — and read only by debug_wakes. The += counts as a read, so dead_code does not fire on it in a non-test build.

last_sweep: Instant

When the heap was last rebuilt to drop abandoned slots.