rcu_sr_is_wait_head
WARN_ON_ONCE(!rcu_sr_is_wait_head(done));
if (!rcu_sr_is_wait_head(rcu)) {
WARN_ON_ONCE(!rcu_sr_is_wait_head(wait_tail));
if (rcu_sr_is_wait_head(rcu))
rcu_sr_is_wait_head(wait_tail->next) &&
if (!first || rcu_sr_is_wait_head(first))