static void tty_vhangup_session(struct tty_struct *tty)
{
	tty_debug_hangup(tty, "session hangup\n");
	__tty_hangup(tty, 1);
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.