_thr_send_sig
_thr_send_sig(pthread, SIGCANCEL);
_thr_send_sig(pthread, sig);
_thr_send_sig(pthread, sig);
int _thr_send_sig(struct pthread *, int sig) __hidden;
_thr_send_sig(curthread, SIGCANCEL);
_thr_send_sig(thread, SIGCANCEL);