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

Pull scheduler fixes from Ingo Molnar:
 "Two rq-clock warnings related fixes, plus a cgroups related crash fix"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cgroup: Move sched_online_group() back into css_online() to fix crash
  sched/fair: Update rq clock before changing a task's CPU affinity
  sched/core: Fix update_rq_clock() splat on hotplug (and suspend/resume)

kernel/sched/core.c

@@ -1090,6 +1090,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 	int ret = 0;
 
 	rq = task_rq_lock(p, &rf);
+	update_rq_clock(rq);
 
 	if (p->flags & PF_KTHREAD) {
 		/*
@@ -5560,7 +5561,7 @@ static void migrate_tasks(struct rq *dead_rq)
 {
 	struct rq *rq = dead_rq;
 	struct task_struct *next, *stop = rq->stop;
-	struct rq_flags rf, old_rf;
+	struct rq_flags rf;
 	int dest_cpu;
 
 	/*
@@ -5579,7 +5580,9 @@ static void migrate_tasks(struct rq *dead_rq)
 	 * class method both need to have an up-to-date
 	 * value of rq->clock[_task]
 	 */
+	rq_pin_lock(rq, &rf);
 	update_rq_clock(rq);
+	rq_unpin_lock(rq, &rf);
 
 	for (;;) {
 		/*
@@ -5592,7 +5595,7 @@ static void migrate_tasks(struct rq *dead_rq)
 		/*
 		 * pick_next_task() assumes pinned rq->lock:
 		 */
-		rq_pin_lock(rq, &rf);
+		rq_repin_lock(rq, &rf);
 		next = pick_next_task(rq, &fake_task, &rf);
 		BUG_ON(!next);
 		next->sched_class->put_prev_task(rq, next);
@@ -5621,13 +5624,6 @@ static void migrate_tasks(struct rq *dead_rq)
 			continue;
 		}
 
-		/*
-		 * __migrate_task() may return with a different
-		 * rq->lock held and a new cookie in 'rf', but we need
-		 * to preserve rf::clock_update_flags for 'dead_rq'.
-		 */
-		old_rf = rf;
-
 		/* Find suitable destination for @next, with force if needed. */
 		dest_cpu = select_fallback_rq(dead_rq->cpu, next);
 
@@ -5636,7 +5632,6 @@ static void migrate_tasks(struct rq *dead_rq)
 			raw_spin_unlock(&rq->lock);
 			rq = dead_rq;
 			raw_spin_lock(&rq->lock);
-			rf = old_rf;
 		}
 		raw_spin_unlock(&next->pi_lock);
 	}
@@ -6819,11 +6814,20 @@ cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 	if (IS_ERR(tg))
 		return ERR_PTR(-ENOMEM);
 
-	sched_online_group(tg, parent);
-
 	return &tg->css;
 }
 
+/* Expose task group only after completing cgroup initialization */
+static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
+{
+	struct task_group *tg = css_tg(css);
+	struct task_group *parent = css_tg(css->parent);
+
+	if (parent)
+		sched_online_group(tg, parent);
+	return 0;
+}
+
 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
 {
 	struct task_group *tg = css_tg(css);
@@ -7229,6 +7233,7 @@ static struct cftype cpu_files[] = {
 
 struct cgroup_subsys cpu_cgrp_subsys = {
 	.css_alloc	= cpu_cgroup_css_alloc,
+	.css_online	= cpu_cgroup_css_online,
 	.css_released	= cpu_cgroup_css_released,
 	.css_free	= cpu_cgroup_css_free,
 	.fork		= cpu_cgroup_fork,