The scheduler

With the task structure just described
Where init and job and separate
Where we rely on an ELF section
... the scheduler is trivial


    while (1) {
        for (best = t = task_first; t < task_last; t++)
            if  (time_before(t->nextrun, best->nextrun)
                best = t;
        while (time_before(jiffies, best->nexrun)
            ;
        best->job(best->arg, best); /* maybe use retval */
        best->nextrun += best->period; /* BUG! */
    }

And we can expand on this over time
But please remember to keep it simple, or you loose