LP_PREEMPTING
if ((l->l_pflag & LP_PREEMPTING) != 0) {
l->l_pflag |= LP_PREEMPTING;
l->l_pflag |= LP_PREEMPTING;
if ((l->l_pflag & LP_PREEMPTING) != 0) {
l->l_pflag &= ~LP_PREEMPTING;
l->l_pflag &= ~LP_PREEMPTING;