linux-kernel - Re: [PATCH] firmware: arm_sdei: fix wrong of_node

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Date:   Mon, 03 Dec 2018 13:25:55 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     James Morse <james.morse@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firmware: arm_sdei: fix wrong of_node_put() in init
 function

Hi James, thanks for the review! 

On Fri, 2018-11-30 at 18:31 +0000, James Morse wrote:
> Hi Nicolas,
> 
> On 26/11/2018 12:15, Nicolas Saenz Julienne wrote:
> > After finding a "firmware" dt node arm_sdei tries to match it's
> > compatible string with it. To do so it's calling
> > of_find_matching_node()
> > which already takes care of decreasing the refcount on the
> > "firmware"
> > node. We are then incorrectly decreasing the refcount on that node
> > again.
> > 
> > This patch removes the unwarranted call to of_node_put().
> > 
> > Fixes: ad6eb31ef903 ("firmware: arm_sdei: Add driver for Software
> > Delegated Exceptions")
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> 
> Thanks!, I agree this is unwarranted.
> Is there a tool that picks these up? I remember sparse giving me a
> headache, but
> I don't remember this one... I probably cargo-culted it from
> somewhere else.

We stumbled upon this one on a test system. TBH I don't really know
much about these tools so I can't tell. That said, I sent 4 more fixes
on this bug (one more in drivers/firmware) so there definitively was
some cargo-culting happening.

Regards,
Nicolas

> 
> Acked-by: James Morse <james.morse@....com>
> 
> 
> Thanks,
> 
> James
> 
> 
> > ---
> >  drivers/firmware/arm_sdei.c | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/drivers/firmware/arm_sdei.c
> > b/drivers/firmware/arm_sdei.c
> > index 1ea71640fdc2..dffb47c6b480 100644
> > --- a/drivers/firmware/arm_sdei.c
> > +++ b/drivers/firmware/arm_sdei.c
> > @@ -1017,7 +1017,6 @@ static bool __init sdei_present_dt(void)
> >  		return false;
> >  
> >  	np = of_find_matching_node(fw_np, sdei_of_match);
> > -	of_node_put(fw_np);
> >  	if (!np)
> >  		return false;
> >  
> > 


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