static int kvm_ioctl_create_device(struct kvm *kvm,
				   struct kvm_create_device *cd)
{
	struct kvm_device_ops *ops = NULL;
	struct kvm_device *dev;
	bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
	int ret;

	if (cd->type >= ARRAY_SIZE(kvm_device_ops_table))
		return -ENODEV;

	ops = kvm_device_ops_table[cd->type];
	if (ops == NULL)
		return -ENODEV;

	if (test)
		return 0;

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev)
		return -ENOMEM;

	dev->ops = ops;
	dev->kvm = kvm;

	mutex_lock(&kvm->lock);
	ret = ops->create(dev, cd->type);
	if (ret < 0) {
		mutex_unlock(&kvm->lock);
		kfree(dev);
		return ret;
	}
	list_add(&dev->vm_node, &kvm->devices);
	mutex_unlock(&kvm->lock);

	if (ops->init)
		ops->init(dev);

	ret = anon_inode_getfd(ops->name, &kvm_device_fops, dev, O_RDWR | O_CLOEXEC);
	if (ret < 0) {
		mutex_lock(&kvm->lock);
		list_del(&dev->vm_node);
		mutex_unlock(&kvm->lock);
		ops->destroy(dev);
		return ret;
	}

	kvm_get_kvm(kvm);
	cd->fd = ret;
	return 0;
}
The program contains a code sequence that can run concurrently with other code, and the code sequence 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 that is operating concurrently.