In Linux kernel 2.6.39.4, the sched_fork() will call the corresponding task_fork(), which is not implemented by sched_rt class. While in sched_fair class, task_fork_() will make sure the child runs first if sysctl_sched_child_runs_first is set. What about sched_rt? Does it mean the sysctl_sched_child_runs_first has no effect on the real time processes?
if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
// make sure the child runs first
swap(curr->vruntime, se->vruntime);
resched_task(rq->curr);
}