struct tty_driver *tty_find_polling_driver(char *name, int *line)
{
	struct tty_driver *p, *res = NULL;
	int tty_line = 0;
	int len;
	char *str, *stp;

	for (str = name; *str; str++)
		if ((*str >= '0' && *str <= '9') || *str == ',')
			break;
	if (!*str)
		return NULL;

	len = str - name;
	tty_line = simple_strtoul(str, &str, 10);

	mutex_lock(&tty_mutex);
	/* Search through the tty devices to look for a match */
	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		if (strncmp(name, p->name, len) != 0)
			continue;
		stp = str;
		if (*stp == ',')
			stp++;
		if (*stp == '\0')
			stp = NULL;

		if (tty_line >= 0 && tty_line < p->num && p->ops &&
		    p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
			res = tty_driver_kref_get(p);
			*line = tty_line;
			break;
		}
	}
	mutex_unlock(&tty_mutex);

	return res;
}

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.