// Adding at the head of the list is better if we are in the middle of walking the list.
clist_add_head(&m->signal_list, &ms->n);
if (m->sig_pipe_recv < 0)
// Adding at the head of the list is better if we are in the middle of walking the list.
clist_add_head(&m->signal_list, &ms->n);
if (m->sig_pipe_recv < 0)