static int tty_cdev_add(struct tty_driver *driver, dev_t dev,
		unsigned int index, unsigned int count)
{
	int err;

	/* init here, since reused cdevs cause crashes */
	driver->cdevs[index] = cdev_alloc();
	if (!driver->cdevs[index])
		return -ENOMEM;
	driver->cdevs[index]->ops = &tty_fops;
	driver->cdevs[index]->owner = driver->owner;
	err = cdev_add(driver->cdevs[index], dev, count);
	if (err)
		kobject_put(&driver->cdevs[index]->kobj);
	return err;
}

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.