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 <mingo@kernel.org>

1 files changed, 26 insertions, 30 deletions

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 44af55e6d5d0..c5565c3c515f 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1803,44 +1803,40 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
 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));
 
-        /*
-         * Update the migration status of the RQ if we have an RT task
-         * which is running AND changing its weight value.
-         */
-        if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
-                struct rq *rq = task_rq(p);
-
-                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);
+        if (!p->on_rq)
+                return;
 
-                        /*
-                         * Requeue if our weight is changing and still > 1
-                         */
-                        if (weight > 1)
-                                enqueue_pushable_task(rq, p);
+        weight = cpumask_weight(new_mask);
 
-                }
+        /*
+         * Only update if the process changes its state from whether it
+         * can migrate or not.
+         */
+        if ((p->rt.nr_cpus_allowed > 1) == (weight > 1))
+                return;
 
-                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--;
-                }
+        rq = task_rq(p);
 
-                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 */