diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index e0a558c4d3580..85f6a112344b2 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3129,6 +3129,15 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
 	return ret ?: nbytes;
 }
 
+/**
+ * cgroup_enable_threaded - make @cgrp threaded
+ * @cgrp: the target cgroup
+ *
+ * Called when "threaded" is written to the cgroup.type interface file and
+ * tries to make @cgrp threaded and join the parent's resource domain.
+ * This function is never called on the root cgroup as cgroup.type doesn't
+ * exist on it.
+ */
 static int cgroup_enable_threaded(struct cgroup *cgrp)
 {
 	struct cgroup *parent = cgroup_parent(cgrp);