if (tty_register_ldisc(N_PPP, NULL) != 0) 
if (tty_unregister_ldisc(N_PPP) != 0) 
static void __exit ppp_async_cleanup(void){	if (tty_register_ldisc(N_PPP, NULL) != 0)		printk(KERN_ERR "failed to unregister PPP line discipline\n");}
4520	/local/tlutelli/issta_data/temp/c/2005_temp/2005/4520/64ccd715d3cf498318b14b646ce5f97e7ab15bb5/ppp_async.c/buggy/drivers/net/ppp_async.c