thread_single
if (thread_single(p, SINGLE_BOUNDARY) != 0)
thread_single(p, SINGLE_EXIT);
if (!thread_single(p, SINGLE_EXIT))
if (thread_single(p1, SINGLE_BOUNDARY)) {
if (thread_single(p1, SINGLE_BOUNDARY)) {
r = thread_single(p, SINGLE_ALLPROC);
if (sig_do_core(sig) && thread_single(p, SINGLE_NO_EXIT) == 0) {
int thread_single(struct proc *p, int how);