Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:
 "Misc fixes: a (rare) PSI crash fix, a CPU affinity related balancing
  fix, and a toning down of active migration attempts"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cfs: fix spurious active migration
  sched/fair: Fix find_idlest_group() to handle CPU affinity
  psi: Fix a division error in psi poll()
  sched/psi: Fix sampling error and rare div0 crashes with cgroups and high uptime

2 files changed, 15 insertions, 3 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 08a233e97a01..ba749f579714 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7328,7 +7328,14 @@ static int detach_tasks(struct lb_env *env)
 			    load < 16 && !env->sd->nr_balance_failed)
 				goto next;
 
-			if (load/2 > env->imbalance)
+			/*
+			 * Make sure that we don't migrate too much load.
+			 * Nevertheless, let relax the constraint if
+			 * scheduler fails to find a good waiting task to
+			 * migrate.
+			 */
+			if (load/2 > env->imbalance &&
+			    env->sd->nr_balance_failed <= env->sd->cache_nice_tries)
 				goto next;
 
 			env->imbalance -= load;
@@ -8417,6 +8424,10 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
 	if (!idlest)
 		return NULL;
 
+	/* The local group has been skipped because of CPU affinity */
+	if (!local)
+		return idlest;
+
 	/*
 	 * If the local group is idler than the selected idlest group
 	 * don't try and push the task.
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 517e3719027e..ce8f6748678a 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -185,7 +185,8 @@ static void group_init(struct psi_group *group)
 
 	for_each_possible_cpu(cpu)
 		seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq);
-	group->avg_next_update = sched_clock() + psi_period;
+	group->avg_last_update = sched_clock();
+	group->avg_next_update = group->avg_last_update + psi_period;
 	INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work);
 	mutex_init(&group->avgs_lock);
 	/* Init trigger-related members */
@@ -481,7 +482,7 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
 		u32 remaining;
 
 		remaining = win->size - elapsed;
-		growth += div_u64(win->prev_growth * remaining, win->size);
+		growth += div64_u64(win->prev_growth * remaining, win->size);
 	}
 
 	return growth;