diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index a67ba1b32d16..914983387e95 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -279,6 +279,7 @@ static inline void dl_rebuild_rd_accounting(void)
 
 static inline void rebuild_sched_domains(void)
 {
+	guard(cpus_read_lock)();
 	partition_sched_domains(1, NULL, NULL);
 }
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 001140132a7d..6d881e530f89 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4934,7 +4934,12 @@ static int tg_cpus(struct task_group *tg)
 			nr = cpuset_num_cpus(cgrp);
 	}
 
-	return nr;
+	/*
+	 * An empty cpuset would propagate a 0 shares_max into
+	 * __calc_smp_shares(), where clamp() yields hi when hi < lo and so
+	 * defeats the MIN_SHARES floor. Match tg_tasks(), which floors at 1.
+	 */
+	return max(nr, 1);
 }
 
 static inline int tg_tasks(struct task_group *tg)