linux-kernel - Re: [PATCH 1/2] gpio: sim: dispose of irq mappings before destroying the irq

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Message-ID: <ZOSo+CVYuOxYCNPZ@smile.fi.intel.com>
Date:   Tue, 22 Aug 2023 15:24:24 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 1/2] gpio: sim: dispose of irq mappings before destroying
 the irq_sim domain

On Tue, Aug 22, 2023 at 02:16:44PM +0200, Bartosz Golaszewski wrote:
> On Tue, Aug 22, 2023 at 2:12 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Tue, Aug 22, 2023 at 09:51:21AM +0200, Bartosz Golaszewski wrote:

...

> > > +static void gpio_sim_dispose_mappings(void *data)
> > > +{
> > > +     struct gpio_sim_chip *chip = data;
> > > +     unsigned int i, irq;
> > > +
> > > +     for (i = 0; i < chip->gc.ngpio; i++) {
> > > +             irq = irq_find_mapping(chip->irq_sim, i);
> >
> > > +             if (irq)
> >
> > This duplicates check in the following call.
> >
> 
> Ah so it can be a direct call:
> 
>     irq_dispose_mapping(irq_find_mapping(chip->irq_sim, i));
> 
> ?

Hehe, seems yes and no. According to the code — yes, but code seems buggy,
and compiler may effectively drop the check (haven't checked this, though).

OTOH, the problem may appear if and only if we have no sparse IRQ configuration
which is probably rare.

That said, I will go without check, it's not your issue.
And I found other places in IRQ framework that misses that check.

> > > +                     irq_dispose_mapping(irq);
> > > +     }
> > > +}

-- 
With Best Regards,
Andy Shevchenko