linux-kernel - Re: [PATCH 2/3] drivers:hv Convert VMBus and its descendants to PnP

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Date:	Wed, 18 Feb 2015 13:24:07 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Jake Oshins <jakeo@...rosoft.com>
Cc:	rafael.j.wysocki@...el.com, gregkh@...uxfoundation.org,
	kys@...rosoft.com, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
	vkuznets@...hat.com
Subject: Re: [PATCH 2/3] drivers:hv Convert VMBus and its descendants to PnP

On Tue, Feb 17, 2015 at 11:41:50AM -0800, Jake Oshins wrote:
>  
> +	ret = pnp_add_descendant(child_device_obj->pnp_dev);
>  	if (ret)
> +		goto register_exit;
> +
> +	added = TRUE;
> +
> +	ret = pnp_activate_dev(child_device_obj->pnp_dev);
> +
> +register_exit:
> +
> +	if (ret) {
> +		if (added)
> +			pnp_remove_descendant(child_device_obj->pnp_dev);
> +		free_pnp_descendant(child_device_obj->pnp_dev);
>  		pr_err("Unable to register child device\n");
> -	else
> +	} else
>  		pr_debug("child device %s registered\n",
> -			dev_name(&child_device_obj->device));
> +			 dev_name(&child_device_obj->pnp_dev->dev));
>  
>  	return ret;
>  }

This error handling is horribly ugly and has a bug.  Please, read my
essay on how to do error handling properly.

https://plus.google.com/106378716002406849458/posts/dnanfhQ4mHQ

1) Don't do "One Err" style error handling.
2) Don't twist the success path and the error paths together.
3) Don't use the "added" variable.
4) Don't initialize "ret" at the start of the function.
5) Don't forget to undo pnp_descendant_memory_option()

It should look something like:

	return 0;

err_remove_desc:
	pnp_remove_descendant(child_device_obj->pnp_dev);
err_remove_option:
	if (bytes)
		remove_whatever();
err_free_desc:
	free_pnp_descendant(child_device_obj->pnp_dev);

	return ret;

regards,
dan carpenter

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