Merge tag 'sched_urgent_for_v6.18_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fix from Borislav Petkov:

 - Make sure a CFS runqueue on a throttled hierarchy has its PELT clock
   throttled otherwise task movement and manipulation would lead to
   dangling cfs_rq references and an eventual crash

* tag 'sched_urgent_for_v6.18_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Start a cfs_rq on throttled hierarchy with PELT clock throttled

Author: torvalds

kernel/sched/fair.c

@@ -6437,6 +6437,16 @@ static void sync_throttle(struct task_group *tg, int cpu)
 
 	cfs_rq->throttle_count = pcfs_rq->throttle_count;
 	cfs_rq->throttled_clock_pelt = rq_clock_pelt(cpu_rq(cpu));
+
+	/*
+	 * It is not enough to sync the "pelt_clock_throttled" indicator
+	 * with the parent cfs_rq when the hierarchy is not queued.
+	 * Always join a throttled hierarchy with PELT clock throttled
+	 * and leaf it to the first enqueue, or distribution to
+	 * unthrottle the PELT clock.
+	 */
+	if (cfs_rq->throttle_count)
+		cfs_rq->pelt_clock_throttled = 1;
 }
 
 /* conditionally throttle active cfs_rq's from put_prev_entity() */
@@ -13187,6 +13197,8 @@ static void propagate_entity_cfs_rq(struct sched_entity *se)
 		if (!cfs_rq_pelt_clock_throttled(cfs_rq))
 			list_add_leaf_cfs_rq(cfs_rq);
 	}
+
+	assert_list_leaf_cfs_rq(rq_of(cfs_rq));
 }
 #else /* !CONFIG_FAIR_GROUP_SCHED: */
 static void propagate_entity_cfs_rq(struct sched_entity *se) { }