sched: Remove unnecessary RCU exclusion

commit fb58bac5 upstream

As Nick pointed out, and realized by myself when doing:
   sched: Fix balance vs hotplug race
the patch:
   sched: for_each_domain() vs RCU

is wrong, sched_domains are freed after synchronize_sched(), which
means disabling preemption is enough.
Reported-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

kernel/sched_fair.c

@@ -1410,7 +1410,6 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
 		new_cpu = prev_cpu;
 	}
 
-	rcu_read_lock();
 	for_each_domain(cpu, tmp) {
 		if (!(tmp->flags & SD_LOAD_BALANCE))
 			continue;
@@ -1500,10 +1499,8 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
 		}
 	}
 
-	if (affine_sd && wake_affine(affine_sd, p, sync)) {
-		new_cpu = cpu;
-		goto out;
-	}
+	if (affine_sd && wake_affine(affine_sd, p, sync))
+		return cpu;
 
 	while (sd) {
 		int load_idx = sd->forkexec_idx;
@@ -1544,8 +1541,6 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
 		/* while loop will break here if sd == NULL */
 	}
 
-out:
-	rcu_read_unlock();
 	return new_cpu;
 }
 #endif /* CONFIG_SMP */