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From:   Yejune Deng <yejune.deng@gmail.com>
Date:   Wed, 30 Dec 2020 10:16:14 +0800
Message-ID: <CABWKuGUar=8HYkkS-KGjN_TB4NAh6+cSspk8J=sB+sZ70VyscQ@mail.gmail.com>
Subject: Re: [PATCH] irqchip/gic: add WARN_ON() to facilitate backtracking
To:     Marc Zyngier <maz@kernel.org>
Cc:     tglx@linutronix.de,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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OK=EF=BC=8CI will adopt it and resubmit.

On Tue, Dec 29, 2020 at 5:27 PM Marc Zyngier <maz@kernel.org> wrote:
>
> Yejune,
>
> On 2020-12-29 07:15, Yejune Deng wrote:
> > There is two function gic_of_init() and gic_of_init_child() called
> > gic_of_setup(),so add WARN_ON() to facilitate backtracking.
> >
> > Signed-off-by: Yejune Deng <yejune.deng@gmail.com>
> > ---
> >  drivers/irqchip/irq-gic.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> > index b1d9c22..7c11705 100644
> > --- a/drivers/irqchip/irq-gic.c
> > +++ b/drivers/irqchip/irq-gic.c
> > @@ -1380,7 +1380,7 @@ static bool gic_check_eoimode(struct device_node
> > *node, void __iomem **base)
> >
> >  static int gic_of_setup(struct gic_chip_data *gic, struct device_node
> > *node)
> >  {
> > -     if (!gic || !node)
> > +     if (WARN_ON(!gic || !node))
> >               return -EINVAL;
> >
> >       gic->raw_dist_base =3D of_iomap(node, 0);
>
> I don't immediately see what you gain with this. If you end-up here
> with NULL pointers, that either because:
>
> - you have failed to allocate the GIC private data structure:
>    but as it turns out, these allocations either cannot fail (gic_data[]
>    is static), or the dynamic allocation in gic_of_init_child() is
> already
>    checked.
>
> - node is NULL: both paths already check for a NULL node, so that cannot
>    fail either.
>
> My conclusion is that these checks can never trigger, and we should be
> able to *remove* them altogether.
>
> Am I missing something?
>
>          M.
> --
> Jazz is not dead. It just smells funny...