static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
						     struct cgroup_subsys *ss)
{
	struct cgroup_subsys_state *css;

	rcu_read_lock();
	css = cgroup_css(cgrp, ss);
	if (css && !css_tryget_online(css))
		css = NULL;
	rcu_read_unlock();

	return css;
}
static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
						     struct cgroup_subsys *ss)
{
	struct cgroup_subsys_state *css;

	rcu_read_lock();
	css = cgroup_css(cgrp, ss);
	if (css && !css_tryget_online(css))
		css = NULL;
	rcu_read_unlock();

	return css;
}