diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 166a45019f66..505d86b16642 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2535,7 +2535,8 @@ static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
 	if (cs != &top_cpuset)
 		guarantee_online_cpus(task, cpus_attach);
 	else
-		cpumask_copy(cpus_attach, task_cpu_possible_mask(task));
+		cpumask_andnot(cpus_attach, task_cpu_possible_mask(task),
+			       cs->subparts_cpus);
 	/*
 	 * can_attach beforehand should guarantee that this doesn't
 	 * fail.  TODO: have a better way to handle failure here