linux-kernel - Re: [PATCH 00/35] media: Fix coccinelle warning/errors

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Message-ID: <CANiDSCs_qOXkhzuL+cFhpw0hvFMwU0TYyN2B5ZdAStb96TTKFA@mail.gmail.com>
Date: Wed, 17 Apr 2024 18:19:14 +0200
From: Ricardo Ribalda <ribalda@...omium.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Dan Carpenter <dan.carpenter@...aro.org>, 
	Martin Tuma <martin.tuma@...iteqautomotive.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, Hans Verkuil <hverkuil-cisco@...all.nl>, 
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	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Chen-Yu Tsai <wens@...e.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, Thierry Reding <thierry.reding@...il.com>, 
	Jonathan Hunter <jonathanh@...dia.com>, Sowjanya Komatineni <skomatineni@...dia.com>, 
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	Kieran Bingham <kieran.bingham+renesas@...asonboard.com>, 
	Niklas Söderlund <niklas.soderlund+renesas@...natech.se>, 
	Pavel Machek <pavel@....cz>, linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
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	linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org, 
	Oleg Drokin <green@...uxhacker.ru>
Subject: Re: [PATCH 00/35] media: Fix coccinelle warning/errors

Hi Laurent

On Wed, 17 Apr 2024 at 17:51, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> On Tue, Apr 16, 2024 at 11:47:17AM +0300, Dan Carpenter wrote:
> > In my opinion, it's better to just ignore old warnings.
>
> I agree. Whatever checkers we enable, whatever code we test, there will
> always be false positives. A CI system needs to be able to ignore those
> false positives and only warn about new issues.

We already have support for that:
https://gitlab.freedesktop.org/linux-media/media-ci/-/tree/main/testdata/static?ref_type=heads

But it would be great if those lists were as small as possible:

- If we have a lot of warnings, two error messages can be combined and
will scape the filters
eg:
print(AAAA);
print(BBBB);
> AABBBAAB

- The filters might hide new errors if they are too broad


Most of the patches in this series are simple and make a nicer code:
Eg the non return minmax() ,
Other patches show real integer overflows.

Now that the patches are ready, let's bite the bullet and try to
reduce our technical debt.


Regards!
>
> > When code is new the warnings are going to be mostly correct.  The
> > original author is there and knows what the code does.  Someone has
> > the hardware ready to test any changes.  High value, low burden.
> >
> > When the code is old only the false positives are left.  No one is
> > testing the code.  It's low value, high burden.
> >
> > Plus it puts static checker authors in a difficult place because now
> > people have to work around our mistakes.  It creates animosity.
> >
> > Now we have to hold ourselves to a much higher standard for false
> > positives.  It sounds like I'm complaining and lazy, right?  But Oleg
> > Drokin has told me previously that I spend too much time trying to
> > silence false positives instead of working on new code.  He's has a
> > point which is that actually we have limited amount of time and we have
> > to make choices about what's the most useful thing we can do.
> >
> > So what I do and what the zero day bot does is we look at warnings one
> > time and we re-review old warnings whenever a file is changed.
> >
> > Kernel developers are very good at addressing static checker warnings
> > and fixing the real issues...  People sometimes ask me to create a
> > database of warnings which I have reviewed but the answer is that
> > anything old can be ignored.  As I write this, I've had a thought that
> > instead of a database of false positives maybe we should record a
> > database of real bugs to ensure that the fixes for anything real is
> > applied.
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda