Function register_restartable_kernel_timer 

pub fn register_restartable_kernel_timer(
    deadline: MonotonicDeadline,
    callback: RestartableKernelTimerCallback,
) -> Result<KernelTimerHandle, TaskError>

Registers a stable callback that may rearm the same timer identity.

The callback runs in the owner CPU’s ktimers/%u task and returns either [KernelTimerAction::Complete] or an absolute deadline for the same entry. Cancellation remains non-blocking; if it races with an executing callback, the callback may finish but cannot rearm the cancelled registration.