Function prepare_cpu_offline 

pub fn prepare_cpu_offline(__arg0: RuntimeCpuId) -> RuntimeStatus

Stops one owner CPU’s runtime facilities before final offline publication.

The scheduler has already closed remote admission and proved the CPU quiescent, but still reports it online while this hook runs. The implementation must stop every CPU-local wake source, including its physical clockevent, before returning success. Failure must leave the runtime retryable. The hook must not allocate, block, invoke callbacks, or re-enter ax-task.