linux-kernel - Re: GPU-DRM-TILCDC: Less function calls in tilcdc_convert_slave

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Date:   Thu, 22 Sep 2016 23:22:48 +0300
From:   Jyri Sarha <jsarha@...com>
To:     SF Markus Elfring <elfring@...rs.sourceforge.net>
CC:     <dri-devel@...ts.freedesktop.org>, David Airlie <airlied@...ux.ie>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        <kernel-janitors@...r.kernel.org>,
        Julia Lawall <julia.lawall@...6.fr>
Subject: Re: GPU-DRM-TILCDC: Less function calls in
 tilcdc_convert_slave_node() after error detection

On 09/22/16 21:38, SF Markus Elfring wrote:
>>> The of_node_put() function was called in some cases
>>> by the tilcdc_convert_slave_node() function during error handling
>>> even if the passed variable contained a null pointer.
>>>
>>> * Adjust jump targets according to the Linux coding style convention.
>>>
>>> * Split a condition check for resource detection failures so that
>>>   each pointer from these function calls will be checked immediately.
>>>
>>>   See also background information:
>>>   Topic "CWE-754: Improper check for unusual or exceptional conditions"
>>>   Link: https://cwe.mitre.org/data/definitions/754.html
>>>
>>
>> I don't really agree with this patch.
> 
> This kind of feedback can be fine at first glance.
> 
> 
>> There is no harm in calling of_node_put() with NULL as an argument
> 
> The cost of additional function calls will be eventually not noticed
> just because they belong to an exception handling implementation so far.
> 
> 
>> and because of that there is no point in making the function more complex
> 
> There is inherent software complexity involved.
> 

I think the "if (node)" in the of_node_put() is there on purpose,
because it potentially saves the caller one extra if()-statement and
keeps the caller code simpler.

> 
>> and harder to maintain.
> 
> How do you think about to discuss this aspect a bit more?
> 

Keeping the goto labels in right order needs precision and can lead to
subtle errors. Sometimes there is no way to avoid that, but here there is.

Best regards,
Jyri