sched: fix: move the CPU check into ->task_new_fair()

noticed by Peter Zijlstra:

fix: move the CPU check into ->task_new_fair(), this way we
can call place_entity() and get child ->vruntime right at
initial wakeup time.

(without this there can be large latencies)
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>

kernel/sched.c

@@ -1660,17 +1660,14 @@ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
 {
 	unsigned long flags;
 	struct rq *rq;
-	int this_cpu;
 
 	rq = task_rq_lock(p, &flags);
 	BUG_ON(p->state != TASK_RUNNING);
-	this_cpu = smp_processor_id(); /* parent's CPU */
 	update_rq_clock(rq);
 
 	p->prio = effective_prio(p);
 
-	if (task_cpu(p) != this_cpu || !p->sched_class->task_new ||
-							!current->se.on_rq) {
+	if (!p->sched_class->task_new || !current->se.on_rq || !rq->cfs.curr) {
 		activate_task(rq, p, 0);
 	} else {
 		/*

kernel/sched_fair.c

@@ -1007,13 +1007,14 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
 {
 	struct cfs_rq *cfs_rq = task_cfs_rq(p);
 	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
+	int this_cpu = smp_processor_id();
 
 	sched_info_queued(p);
 
 	update_curr(cfs_rq);
 	place_entity(cfs_rq, se, 1);
 
-	if (sysctl_sched_child_runs_first &&
+	if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
 			curr->vruntime < se->vruntime) {
 		/*
 		 * Upon rescheduling, sched_class::put_prev_task() will place