diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 77d9566d3aa68cfa9af9285530becd959765525c..2a7802ec480cc5d0ea03d1b4666d321f196eeb56 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -373,10 +373,10 @@ void clocksource_verify_percpu(struct clocksource *cs)
 	cpumask_clear(&cpus_ahead);
 	cpumask_clear(&cpus_behind);
 	cpus_read_lock();
-	preempt_disable();
+	migrate_disable();
 	clocksource_verify_choose_cpus();
 	if (cpumask_empty(&cpus_chosen)) {
-		preempt_enable();
+		migrate_enable();
 		cpus_read_unlock();
 		pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
 		return;
@@ -384,6 +384,7 @@ void clocksource_verify_percpu(struct clocksource *cs)
 	testcpu = smp_processor_id();
 	pr_info("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n",
 		cs->name, testcpu, cpumask_pr_args(&cpus_chosen));
+	preempt_disable();
 	for_each_cpu(cpu, &cpus_chosen) {
 		if (cpu == testcpu)
 			continue;
@@ -403,6 +404,7 @@ void clocksource_verify_percpu(struct clocksource *cs)
 			cs_nsec_min = cs_nsec;
 	}
 	preempt_enable();
+	migrate_enable();
 	cpus_read_unlock();
 	if (!cpumask_empty(&cpus_ahead))
 		pr_warn("        CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
diff --git a/kernel/time/timer_migration.c b/kernel/time/timer_migration.c
index 9cb9b6584ea18e2dd1c159e1ec490dd060c882a0..2f6330831f08458e853dc10e2e79351d45084e71 100644
--- a/kernel/time/timer_migration.c
+++ b/kernel/time/timer_migration.c
@@ -1675,6 +1675,9 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 
 	} while (i < tmigr_hierarchy_levels);
 
+	/* Assert single root */
+	WARN_ON_ONCE(!err && !group->parent && !list_is_singular(&tmigr_level_list[top]));
+
 	while (i > 0) {
 		group = stack[--i];
 
@@ -1716,7 +1719,12 @@ static int tmigr_setup_groups(unsigned int cpu, unsigned int node)
 		WARN_ON_ONCE(top == 0);
 
 		lvllist = &tmigr_level_list[top];
-		if (group->num_children == 1 && list_is_singular(lvllist)) {
+
+		/*
+		 * Newly created root level should have accounted the upcoming
+		 * CPU's child group and pre-accounted the old root.
+		 */
+		if (group->num_children == 2 && list_is_singular(lvllist)) {
 			/*
 			 * The target CPU must never do the prepare work, except
 			 * on early boot when the boot CPU is the target. Otherwise