Merge branch 'tip/sched/core' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into sched/core

Pull a scheduler optimization commit from Steven Rostedt.

Signed-off-by: Ingo Molnar <[e-mail]>

kernel/sched/rt.c

···
 static void set_cpus_allowed_rt(struct task_struct *p,
 				const struct cpumask *new_mask)
 {
-	int weight = cpumask_weight(new_mask);
+	struct rq *rq;
+	int weight;
 
 	BUG_ON(!rt_task(p));
 
+	if (!p->on_rq)
+		return;
+
+	weight = cpumask_weight(new_mask);
+
 	/*
-	 * Update the migration status of the RQ if we have an RT task
-	 * which is running AND changing its weight value.
+	 * Only update if the process changes its state from whether it
+	 * can migrate or not.
 	 */
-	if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
-		struct rq *rq = task_rq(p);
+	if ((p->rt.nr_cpus_allowed > 1) == (weight > 1))
+		return;
 
-		if (!task_current(rq, p)) {
-			/*
-			 * Make sure we dequeue this task from the pushable list
-			 * before going further.  It will either remain off of
-			 * the list because we are no longer pushable, or it
-			 * will be requeued.
-			 */
-			if (p->rt.nr_cpus_allowed > 1)
-				dequeue_pushable_task(rq, p);
+	rq = task_rq(p);
 
-			/*
-			 * Requeue if our weight is changing and still > 1
-			 */
-			if (weight > 1)
-				enqueue_pushable_task(rq, p);
-
-		}
-
-		if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
-			rq->rt.rt_nr_migratory++;
-		} else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
-			BUG_ON(!rq->rt.rt_nr_migratory);
-			rq->rt.rt_nr_migratory--;
-		}
-
-		update_rt_migration(&rq->rt);
+	/*
+	 * The process used to be able to migrate OR it can now migrate
+	 */
+	if (weight <= 1) {
+		if (!task_current(rq, p))
+			dequeue_pushable_task(rq, p);
+		BUG_ON(!rq->rt.rt_nr_migratory);
+		rq->rt.rt_nr_migratory--;
+	} else {
+		if (!task_current(rq, p))
+			enqueue_pushable_task(rq, p);
+		rq->rt.rt_nr_migratory++;
 	}
+
+	update_rt_migration(&rq->rt);
 }
 
 /* Assumes rq->lock is held */