linux-kernel - Re: [PATCH] of/irq: add missing of_node

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Date:   Wed, 1 Mar 2023 08:56:40 +0100
From:   Clément Léger <clement.leger@...tlin.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Jean Jacques Hiblot <jjhiblot@...phandler.com>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] of/irq: add missing of_node_put() for interrupt parent
 node

Le Tue, 28 Feb 2023 17:14:18 -0600,
Rob Herring <robh+dt@...nel.org> a écrit :

> +Saravana, Jean
> 
> On Tue, Jan 17, 2023 at 8:47 AM Clément Léger <clement.leger@...tlin.com> wrote:
> >
> > After calling of_irq_parse_one(), the node provided in the of_phandle_args
> > has a refcount increment by one. Add missing of_node_put in of_irq_get()
> > to decrement the refcount once used.
> >
> > Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> > ---
> >
> > While debugging a refcount problem with OF_DYNAMIC enabled (which is
> > actually the only case were node refcount are really used), I noticed that
> > platform_get_irq() was actually incrementing the refcount of an interrupt
> > controller node. Digging into that function shows that it calls
> > of_irq_get() which calls of_irq_parse_one() and finally of_irq_parse_raw().
> > Since it seems sane that the node returned in the of_phandle_args has a
> > refcount incremented, I thought it is better to put the of_node_put() in
> > the user even though it was hard to find any user doing so.  
> 
> While investigating [1], I stumbled back on this. Was the failing case
> you had using interrupts-extended? It looks to me like that path has a
> get, but the 'interrupts' path does not. If so, this change is wrong.

In my case, it was with a classic "interrupts" property. I can take
another look at the internal code to be sure this fix is correct.

Clément

> 
> Rob
> 
> [1] https://lore.kernel.org/all/20230228174019.4004581-1-jjhiblot@traphandler.com/
> 
> 
> >
> >  drivers/of/irq.c | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> > index e9bf5236ed89..174900072c18 100644
> > --- a/drivers/of/irq.c
> > +++ b/drivers/of/irq.c
> > @@ -438,10 +438,16 @@ int of_irq_get(struct device_node *dev, int index)
> >                 return rc;
> >
> >         domain = irq_find_host(oirq.np);
> > -       if (!domain)
> > -               return -EPROBE_DEFER;
> > +       if (!domain) {
> > +               rc = -EPROBE_DEFER;
> > +               goto out;
> > +       }
> >
> > -       return irq_create_of_mapping(&oirq);
> > +       rc = irq_create_of_mapping(&oirq);
> > +out:
> > +       of_node_put(oirq.np);
> > +
> > +       return rc;
> >  }
> >  EXPORT_SYMBOL_GPL(of_irq_get);
> >
> > --
> > 2.39.0
> >  



-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com