static struct dentry *start_creating(const char *name, struct dentry *parent)
{
	struct dentry *dentry;
	int error;

	pr_debug("debugfs: creating file '%s'\n",name);

	if (IS_ERR(parent))
		return parent;

	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
			      &debugfs_mount_count);
	if (error)
		return ERR_PTR(error);

	/* If the parent is not specified, we create it in the root.
	 * We need the root dentry to do this, which is in the super
	 * block. A pointer to that is in the struct vfsmount that we
	 * have around.
	 */
	if (!parent)
		parent = debugfs_mount->mnt_root;

	inode_lock(d_inode(parent));
	dentry = lookup_one_len(name, parent, strlen(name));
	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
		dput(dentry);
		dentry = ERR_PTR(-EEXIST);
	}

	if (IS_ERR(dentry)) {
		inode_unlock(d_inode(parent));
		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
	}

	return 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.