diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index 08cadca29c85..2002ab0f7c9b 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -2798,7 +2798,7 @@ static inline void maybe_queue_balance_callback(struct rq *rq)
 
 static int balance_one(struct rq *rq, struct task_struct *prev)
 {
-	struct scx_sched *sch = scx_root;
+	struct scx_sched *sch = scx_root_protected_live();
 	s32 cpu = cpu_of(rq);
 
 	lockdep_assert_rq_held(rq);
@@ -2954,7 +2954,7 @@ preempt_reason_from_class(const struct sched_class *class)
 
 static void switch_class(struct rq *rq, struct task_struct *next)
 {
-	struct scx_sched *sch = scx_root;
+	struct scx_sched *sch = scx_root_protected_live();
 	const struct sched_class *next_class = next->sched_class;
 
 	if (!(sch->ops.flags & SCX_OPS_HAS_CPU_PREEMPT))
@@ -3345,7 +3345,7 @@ static void set_cpus_allowed_scx(struct task_struct *p,
 
 static void handle_hotplug(struct rq *rq, bool online)
 {
-	struct scx_sched *sch = scx_root;
+	struct scx_sched *sch = scx_root_protected();
 	s32 cpu = cpu_of(rq);
 	s32 cpu_or_cid = cpu;
 
@@ -3809,7 +3809,7 @@ int scx_fork(struct task_struct *p, struct kernel_clone_args *kargs)
 #ifdef CONFIG_EXT_SUB_SCHED
 		struct scx_sched *sch = scx_cgroup_sched(kargs->cset->dfl_cgrp);
 #else
-		struct scx_sched *sch = scx_root;
+		struct scx_sched *sch = scx_root_protected_live();
 #endif
 		scx_set_task_state(p, SCX_TASK_INIT_BEGIN);
 		ret = __scx_init_task(sch, p, NULL, true);
@@ -5741,7 +5741,7 @@ void scx_disable_bypass_dsp(struct scx_sched *sch)
 static void unbypass_renotify_idle(struct rq *rq, struct scx_sched *pos,
 				   struct scx_sched_pcpu *pcpu)
 {
-	if (pos == scx_root) {
+	if (!pos->level) {
 		rq->scx.flags |= SCX_RQ_ROOT_IDLE_RENOTIFY;
 		return;
 	}
@@ -7109,7 +7109,7 @@ int scx_validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
 	 * enabled it.
 	 */
 	if ((ops->flags & SCX_OPS_TID_TO_TASK) && scx_parent(sch) &&
-	    !(scx_root->ops.flags & SCX_OPS_TID_TO_TASK)) {
+	    !(sch->ancestors[0]->ops.flags & SCX_OPS_TID_TO_TASK)) {
 		scx_error(sch, "SCX_OPS_TID_TO_TASK requires root scheduler to enable it");
 		return -EINVAL;
 	}
diff --git a/kernel/sched/ext/idle.c b/kernel/sched/ext/idle.c
index ae28f583f54c..3e9d6a44bf43 100644
--- a/kernel/sched/ext/idle.c
+++ b/kernel/sched/ext/idle.c
@@ -742,30 +742,29 @@ static void scx_idle_notify(struct rq *rq, bool idle, bool do_notify, bool root_
 {
 	s32 cpu = cpu_of(rq);
 	s32 cid = scx_cpu_arg(cpu);
+	struct scx_sched *root = scx_root_protected_live();
 	struct scx_sched *pos;
 
 	lockdep_assert_rq_held(rq);
 
 	/* with no sub-sched, only the root can be owed a notification */
 	if (!scx_has_subs()) {
-		struct scx_sched *sch = scx_root;
-
 		if ((do_notify || root_renotify) &&
-		    SCX_HAS_OP(sch, update_idle) && !scx_bypassing(sch, cpu))
-			SCX_CALL_OP(sch, update_idle, rq, cid, idle);
+		    SCX_HAS_OP(root, update_idle) && !scx_bypassing(root, cpu))
+			SCX_CALL_OP(root, update_idle, rq, cid, idle);
 		return;
 	}
 
-	pos = scx_next_descendant_pre(NULL, scx_root);
+	pos = scx_next_descendant_pre(NULL, root);
 	while (pos) {
 		bool forced = false;
 
 		if (unlikely(scx_missing_caps(pos, cpu, SCX_CAP_BASE))) {
-			pos = scx_skip_subtree_pre(pos, scx_root);
+			pos = scx_skip_subtree_pre(pos, root);
 			continue;
 		}
 
-		if (pos == scx_root) {
+		if (!pos->level) {
 			forced = root_renotify;
 		}
 #ifdef CONFIG_EXT_SUB_SCHED
@@ -777,7 +776,7 @@ static void scx_idle_notify(struct rq *rq, bool idle, bool do_notify, bool root_
 		if ((do_notify || forced) && SCX_HAS_OP(pos, update_idle) &&
 		    !scx_bypassing(pos, cpu))
 			SCX_CALL_OP(pos, update_idle, rq, cid, idle);
-		pos = scx_next_descendant_pre(pos, scx_root);
+		pos = scx_next_descendant_pre(pos, root);
 	}
 }
 
diff --git a/kernel/sched/ext/internal.h b/kernel/sched/ext/internal.h
index 886f1d132e6b..39dddcbb3b7d 100644
--- a/kernel/sched/ext/internal.h
+++ b/kernel/sched/ext/internal.h
@@ -2025,6 +2025,33 @@ extern struct scx_sched *scx_enabling_sub_sched;
 #define scx_error(sch, fmt, args...)						\
 	scx_exit((sch), SCX_EXIT_ERROR, 0, fmt, ##args)
 
+/**
+ * scx_root_protected_live - Root sched for paths that only run while live
+ *
+ * scx_root is published before the scheduler goes live and cleared only after
+ * it is fully drained, so a path that only executes while the scheduler is live
+ * can never race an update. Return the root sched with a plain load, never
+ * %NULL.
+ */
+static inline struct scx_sched *scx_root_protected_live(void)
+{
+	return rcu_dereference_protected(scx_root, true);
+}
+
+/**
+ * scx_root_protected - Root sched for contexts that exclude its updates
+ *
+ * Both scx_root updates run under the locks checked below, so holding one
+ * excludes them. Return the root sched with a plain load, %NULL if no scheduler
+ * is loaded.
+ */
+static inline struct scx_sched *scx_root_protected(void)
+{
+	return rcu_dereference_protected(scx_root,
+					 lockdep_is_cpus_held() ||
+					 lockdep_is_held(&scx_enable_mutex));
+}
+
 static inline struct scx_dispatch_q *scx_bypass_dsq(struct scx_sched *sch, s32 cpu)
 {
 	return &per_cpu_ptr(sch->pcpu, cpu)->bypass_dsq;
diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
index 2a8c979c7976..824fe35f00ee 100644
--- a/kernel/sched/ext/sub.c
+++ b/kernel/sched/ext/sub.c
@@ -477,7 +477,7 @@ static void queue_sync_ecaps(struct scx_sched *sch, s32 cid)
 	if (llist_on_list(&pcpu->ecaps_to_sync_node))
 		return;
 	if (llist_add(&pcpu->ecaps_to_sync_node, &cpu_rq(cpu)->scx.ecaps_to_sync))
-		scx_kick_cpu(scx_root, cpu, 0);
+		scx_kick_cpu(sch->ancestors[0], cpu, 0);
 }
 
 /* discard @rq's queued ecaps syncs */
@@ -638,7 +638,7 @@ void scx_unbypass_replay_ecaps(struct rq *rq, struct scx_sched *sch)
  */
 void scx_online_ecaps(struct rq *rq)
 {
-	struct scx_sched *pos;
+	struct scx_sched *root, *pos;
 	s32 cid, shard;
 
 	/*
@@ -652,14 +652,15 @@ void scx_online_ecaps(struct rq *rq)
 
 	guard(rq_lock_irqsave)(rq);
 
+	root = scx_root_protected();
 	cid = __scx_cpu_to_cid(cpu_of(rq));
 	shard = rcu_dereference_all(scx_cid_to_shard)[cid];
 
-	scx_for_each_descendant_pre(pos, scx_root) {
+	scx_for_each_descendant_pre(pos, root) {
 		struct scx_pshard *ps;
 
 		/* root holds every cap and never uses ecaps */
-		if (pos == scx_root)
+		if (!pos->level)
 			continue;
 
 		ps = pos->pshard[shard];
@@ -679,13 +680,15 @@ void scx_online_ecaps(struct rq *rq)
 void scx_offline_ecaps(struct rq *rq)
 {
 	s32 cpu = cpu_of(rq);
-	struct scx_sched *pos;
+	struct scx_sched *root, *pos;
 
 	guard(rq_lock_irqsave)(rq);
 
-	scx_for_each_descendant_pre(pos, scx_root) {
+	root = scx_root_protected();
+
+	scx_for_each_descendant_pre(pos, root) {
 		/* root holds every cap and never uses ecaps */
-		if (pos == scx_root)
+		if (!pos->level)
 			continue;
 
 		WRITE_ONCE(per_cpu_ptr(pos->pcpu, cpu)->ecaps, 0);