linux-kernel - Re: [PATCH 11/14] ARM: brcmstb: delete unneeded test before of_node

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Date:	Thu, 14 Aug 2014 07:37:28 +0200 (CEST)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Brian Norris <computersforpeace@...il.com>
cc:	Marc Carino <marc.ceeeee@...il.com>,
	kernel-janitors@...r.kernel.org,
	Christian Daudt <bcm@...thebug.org>,
	Matt Porter <mporter@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	bcm-kernel-feedback-list@...adcom.com,
	linux-kernel@...r.kernel.org,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH 11/14] ARM: brcmstb: delete unneeded test before
 of_node_put



On Wed, 13 Aug 2014, Brian Norris wrote:

> Hi Julia,
> 
> On Fri, Aug 08, 2014 at 12:07:52PM +0200, Julia Lawall wrote:
> > From: Julia Lawall <Julia.Lawall@...6.fr>
> > 
> > Simplify the error path to avoid calling of_node_put when it is not needed.
> > 
> > The semantic patch that finds this problem is as follows:
> > (http://coccinelle.lip6.fr/)
> > 
> > // <smpl>
> > @@
> > expression e;
> > @@
> > 
> > -if (e)
> >    of_node_put(e);
> > // </smpl>
> > 
> > Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
> > 
> > ---
> >  arch/arm/mach-bcm/platsmp-brcmstb.c |   14 ++++++--------
> 
> This file is being dropped temporarily, for rework/resubmission at a
> later time:
> 
>   https://lkml.org/lkml/2014/8/13/617
> 
> But thanks for the patch. I'll take it into account in the future. A few
> comments below.
> 
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> > 
> > diff --git a/arch/arm/mach-bcm/platsmp-brcmstb.c b/arch/arm/mach-bcm/platsmp-brcmstb.c
> > index af780e9..c515ea1 100644
> > --- a/arch/arm/mach-bcm/platsmp-brcmstb.c
> > +++ b/arch/arm/mach-bcm/platsmp-brcmstb.c
> > @@ -227,7 +227,7 @@ static int __init setup_hifcpubiuctrl_regs(struct device_node *np)
> >  	if (!syscon_np) {
> >  		pr_err("can't find phandle %s\n", name);
> >  		rc = -EINVAL;
> > -		goto cleanup;
> > +		goto out;
> >  	}
> >  
> >  	cpubiuctrl_block = of_iomap(syscon_np, 0);
> > @@ -256,9 +256,8 @@ static int __init setup_hifcpubiuctrl_regs(struct device_node *np)
> >  	}
> >  
> >  cleanup:
> > -	if (syscon_np)
> > -		of_node_put(syscon_np);
> > -
> > +	of_node_put(syscon_np);
> > +out:
> 
> Is there a good reason for this new label? I thought part of the point
> of this semantic patch is that the previous line (of_node_put()) is a
> no-op for NULL arguments.

Personally, I prefer code to only be executed if it needs to be.  It is 
helpful from a program analysis point of view, and I think it helps 
someone trying to understand the code.

That is, when I am trying to understand some unknown code, I may look at 
the cleanup code and try to figure out why each piece of it is executed.  
If some of it is statically known to be irrelevant, it is confusing.

But I you think the other way around, and would rather have just one label 
that contains anything that might ever be useful, then I guess that is a 
reasonable point of view as well.

julia


> >  	return rc;
> >  }
> >  
> > @@ -274,7 +273,7 @@ static int __init setup_hifcont_regs(struct device_node *np)
> >  	if (!syscon_np) {
> >  		pr_err("can't find phandle %s\n", name);
> >  		rc = -EINVAL;
> > -		goto cleanup;
> > +		goto out;
> >  	}
> >  
> >  	hif_cont_block = of_iomap(syscon_np, 0);
> > @@ -288,9 +287,8 @@ static int __init setup_hifcont_regs(struct device_node *np)
> >  	hif_cont_reg = 0;
> >  
> >  cleanup:
> > -	if (syscon_np)
> > -		of_node_put(syscon_np);
> > -
> > +	of_node_put(syscon_np);
> > +out:
> 
> Ditto.
> 
> >  	return rc;
> >  }
> >  
> > 
> 
> Brian
> 
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