P_TREE_GRPEXITED
p->p_pgrp, (p->p_treeflag & P_TREE_GRPEXITED) != 0,
(pp->p_treeflag & P_TREE_GRPEXITED) == 0)
(pp->p_treeflag & P_TREE_GRPEXITED) == 0)
if ((q->p_treeflag & P_TREE_GRPEXITED) != 0 ||
MPASS((p->p_treeflag & P_TREE_GRPEXITED) == 0);
p->p_treeflag |= P_TREE_GRPEXITED;