linux-kernel - Re: [PATCH v2] pinctrl: ocelot: Fix interrupt controller

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Message-ID: <20220907194754.nw4jpghsjzuz2jcu@soft-dev3-1.localhost>
Date:   Wed, 7 Sep 2022 21:47:54 +0200
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH v2] pinctrl: ocelot: Fix interrupt controller

The 09/07/2022 11:36, Andy Shevchenko wrote:
> > +        * handler.
> > +        */
> > +       if (active && !ack) {
> > +               struct ocelot_irq_work *work;
> > +
> > +               work = kmalloc(sizeof(*work), GFP_ATOMIC);
> > +               if (!work)
> > +                       return;
> > +
> > +               work->irq_desc = desc;
> > +               INIT_WORK(&work->irq_work, ocelot_irq_work);
> > +               queue_work(system_wq, &work->irq_work);
> > +       }
> 
> Here I see potential issues with the object lifetime. 1) The memory is
> allocated here and what does guarantee its freeing? 2) What does
> guarantee that work will be not scheduled if the driver or its parts
> are gone?

You are right, if the driver is removed once the work is queued, then
that object will not be freed or even worst get NULL pointers.

A solution to this would be not to use system_wq but allocate own workqueue
and once the driver is removed, make sure to destroy it.
In this way we make sure that all the work is done.

> 
> --
> With Best Regards,
> Andy Shevchenko

-- 
/Horatiu