linux-kernel - RE: [PATCH v4] irqchip/renesas-rzg2l: Fix missing put

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Message-ID:
 <TY3PR01MB120897A4A7AEF860A13F87E72C2FD2@TY3PR01MB12089.jpnprd01.prod.outlook.com>
Date: Tue, 11 Feb 2025 15:49:31 +0000
From: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Markus Elfring
	<elfring@...rs.sourceforge.net>, Markus Elfring <Markus.Elfring@....de>, Marc
 Zyngier <maz@...nel.org>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Chris Paterson <Chris.Paterson2@...esas.com>,
	Biju Das <biju.das.jz@...renesas.com>, "linux-renesas-soc@...r.kernel.org"
	<linux-renesas-soc@...r.kernel.org>
Subject: RE: [PATCH v4] irqchip/renesas-rzg2l: Fix missing put_device

Hi Geert,

Thanks for your feedback!

> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: 11 February 2025 15:12
> Subject: Re: [PATCH v4] irqchip/renesas-rzg2l: Fix missing put_device
> 
> Hi Fabrizio,
> 
> On Fri, 11 Oct 2024 at 19:20, Fabrizio Castro
> <fabrizio.castro.jz@...esas.com> wrote:
> > rzg2l_irqc_common_init calls of_find_device_by_node, but the
> > corresponding put_device call is missing.
> > This also gets reported by make coccicheck.
> >
> > Make use of the cleanup interfaces from cleanup.h to call into
> > __free_put_device (which in turn calls into put_device) when
> > leaving function rzg2l_irqc_common_init and variable "dev" goes
> > out of scope.
> >
> > Mind that we don't want to "put" "dev" when rzg2l_irqc_common_init
> > completes successfully, therefore assign NULL to "dev" to prevent
> > __free_put_device from calling into put_device within the successful
> > path.
> >
> > "make coccicheck" will still complain about missing put_device calls,
> > but those are false positives now.
> >
> > Fixes: 3fed09559cd8 ("irqchip: Add RZ/G2L IA55 Interrupt Controller driver")
> > Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
> 
> Revisiting commit d038109ac1c6bf61 ("irqchip/renesas-rzg2l: Fix missing
> put_device")...
> 
> > --- a/drivers/irqchip/irq-renesas-rzg2l.c
> > +++ b/drivers/irqchip/irq-renesas-rzg2l.c
> > @@ -8,6 +8,7 @@
> >   */
> >
> >  #include <linux/bitfield.h>
> > +#include <linux/cleanup.h>
> >  #include <linux/clk.h>
> >  #include <linux/err.h>
> >  #include <linux/io.h>
> > @@ -530,12 +531,12 @@ static int rzg2l_irqc_parse_interrupts(struct rzg2l_irqc_priv *priv,
> >  static int rzg2l_irqc_common_init(struct device_node *node, struct device_node *parent,
> >                                   const struct irq_chip *irq_chip)
> >  {
> > +       struct platform_device *pdev = of_find_device_by_node(node);
> > +       struct device *dev __free(put_device) = pdev ? &pdev->dev : NULL;
> 
> Now there is a variable holding "&pdev->dev", all below references
> to the latter can be replaced by "dev"...

Right! I will shortly send a patch for this.

> 
> >         struct irq_domain *irq_domain, *parent_domain;
> > -       struct platform_device *pdev;
> >         struct reset_control *resetn;
> >         int ret;
> >
> > -       pdev = of_find_device_by_node(node);
> >         if (!pdev)
> >                 return -ENODEV;
> >
> > @@ -591,6 +592,17 @@ static int rzg2l_irqc_common_init(struct device_node *node, struct device_node
> *
> >
> >         register_syscore_ops(&rzg2l_irqc_syscore_ops);
> >
> > +       /*
> > +        * Prevent the cleanup function from invoking put_device by assigning
> > +        * NULL to dev.
> > +        *
> > +        * make coccicheck will complain about missing put_device calls, but
> > +        * those are false positives, as dev will be automatically "put" via
> > +        * __free_put_device on the failing path.
> > +        * On the successful path we don't actually want to "put" dev.
> > +        */
> > +       dev = NULL;
> > +
> >         return 0;
> 
> Can't the above be replaced by
> 
>     no_free_ptr(dev);
> 
> ? Or would Coccinelle still complain?

If I use no_free_ptr the compiler complains that its return value is not used:

In file included from ../drivers/irqchip/irq-renesas-rzg2l.c:11:
../drivers/irqchip/irq-renesas-rzg2l.c: In function ‘rzg2l_irqc_common_init’:
../include/linux/cleanup.h:215:15: warning: ignoring return value of ‘__must_check_fn’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  215 |  ((typeof(p)) __must_check_fn(__get_and_null(p, NULL)))
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/irqchip/irq-renesas-rzg2l.c:595:2: note: in expansion of macro ‘no_free_ptr’
  595 |  no_free_ptr(dev);
      |  ^~~~~~~~~~~


Cheers,
Fab

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds