static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
{
	struct detach_data *data = _data;

	if (d_mountpoint(dentry)) {
		__dget_dlock(dentry);
		data->mountpoint = dentry;
		return D_WALK_QUIT;
	}

	return select_collect(&data->select, dentry);
}

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.