linux-kernel - Re: [alsa-devel] [PATCH] ALSA: ac97c: Fix an error handling path in 'atmel_ac97c

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Date:   Thu, 31 Aug 2017 12:19:51 +0200
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Julia Lawall <julia.lawall@...6.fr>, alsa-devel@...a-project.org,
        garsilva@...eddedor.com, arvind.yadav.cs@...il.com,
        bhumirks@...il.com, broonie@...nel.org,
        andriy.shevchenko@...ux.intel.com, nicolas.ferre@...rochip.com,
        perex@...ex.cz, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [alsa-devel] [PATCH] ALSA: ac97c: Fix an error handling path in
 'atmel_ac97c_probe()'

On 31/08/2017 at 12:13:00 +0200, Takashi Iwai wrote:
> On Thu, 31 Aug 2017 11:56:16 +0200,
> Alexandre Belloni wrote:
> > 
> > On 31/08/2017 at 10:23:19 +0200, Julia Lawall wrote:
> > > 
> > > 
> > > On Thu, 31 Aug 2017, Alexandre Belloni wrote:
> > > 
> > > > On 31/08/2017 at 06:40:42 +0200, Christophe JAILLET wrote:
> > > > > If 'clk_prepare_enable()' fails, we must release some resources before
> > > > > returning. Add a new label in the existing error handling path and 'goto'
> > > > > there.
> > > > >
> > > > > Fixes: 260ea95cc027 ("ASoC: atmel: ac97c: Handle return value of clk_prepare_enable.")
> > > > > Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > > >
> > > > And here is the fallout of the stupid, brainless "fixing" of issues
> > > > reported by static analysis tools.
> > > >
> > > > This clk_prepare_enable will never fail. If it was going to fail, the
> > > > platform would never boot to a point were it is able to execute that
> > > > code. It is really annoying to have so much churn for absolutely 0
> > > > benefit.
> > > 
> > > Would it be more productive to put the code back like it was before, ie no
> > > return value and no check, and add a comment to the definition of
> > > clk_prepare_enable indicating that there are many case where the call
> > > cannot fail?  Grepping through the code suggests that it is about 50-50 on
> > > checking the return value or not doing so, which might suggest that
> > > checking the value is often not required.
> > > 
> > 
> > I'd say that it is often useless to test the value. I don't have any
> > problem with the test as it doesn't add much (at least it doesn't print
> > an error message). So it may stays here. What I'm really unhappy about
> > is people sending hundreds of similar, autogenerated patches to
> > maintainers without actually putting any thought into them. That put all
> > the burden on the maintainers to weed out the incorrect patches.
> 
> I share your concerns, e.g. the burden of maintenance is a problem.
> 
> But in this case, the original code looks really buggy.  If the test
> doesn't make sense, don't test it but give a proper comment from the
> beginning.  Instead, the current code does check the return value yet
> with the incorrect error path.
> 
> The proposed "fix" won't change any actual behavior in practice, which
> is useless, yes.  (And this is good -- at least it's safe to apply :)
> OTOH, the semantics is a different question, and the patch corrects
> it, which isn't so stupid, IMO.
> 

Agreed, I'm complaining about the original patch adding the test, not
the current patch that fixes it.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com