P_SUSPSINGLE
curp->p_flag & (P_SUSPSINGLE | P_SUSPSIG));
ISSET(q->p_flag, P_SUSPSIG | P_SUSPSINGLE) == 0) {
KASSERT(ISSET(p->p_flag, P_SUSPSIG | P_SUSPSINGLE) == 0);
if (atomic_load_int(&p->p_flag) & (P_SUSPSINGLE | P_SUSPSIG))
process_stop(pr, P_SUSPSINGLE, mode);
KASSERT((pr->ps_single->p_flag & P_SUSPSINGLE) == 0);
process_continue(pr, P_SUSPSINGLE);