From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Linus Walleij <linus.walleij@linaro.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: Re: [PATCH] gpiolib: don't call sleeping functions with a spinlock taken
Date: Fri, 20 Mar 2020 11:58:53 +0100 [thread overview]
Message-ID: <CAMuHMdXWrK3QjGmAPC0aPtQ_62buiQLopyRKB-qro6HBK5bDyg@mail.gmail.com> (raw)
In-Reply-To: <20200320093125.23092-1-brgl@bgdev.pl>
Hi Bartosz,
On Fri, Mar 20, 2020 at 10:31 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
> as it takes a mutex internally. Let's move the call before taking the
> spinlock and store the return value.
>
> This isn't perfect - there's a moment between calling
> pinctrl_gpio_can_use_line() and taking the spinlock where the situation
> can change but it isn't a regression either: previously this part wasn't
> protected at all and it only affects the information user-space is
> seeing.
>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Fixes: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Thanks for your patch!
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1154,8 +1154,19 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
> struct gpioline_info *info)
> {
> struct gpio_chip *chip = desc->gdev->chip;
> + bool ok_for_pinctrl;
> unsigned long flags;
>
> + /*
> + * This function takes a mutex so we must check this before taking
> + * the spinlock.
> + *
> + * FIXME: find a non-racy way to retrieve this information. Maybe a
> + * lock common to both frameworks?
> + */
> + ok_for_pinctrl = pinctrl_gpio_can_use_line(
> + chip->base + info->line_offset);
Note that this is now called unconditionally, while before it was only called
if all previous steps in the ||-pipeline failed.
> +
> spin_lock_irqsave(&gpio_lock, flags);
>
> if (desc->name) {
> @@ -1182,7 +1193,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
> test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
> test_bit(FLAG_EXPORT, &desc->flags) ||
> test_bit(FLAG_SYSFS, &desc->flags) ||
> - !pinctrl_gpio_can_use_line(chip->base + info->line_offset))
> + !ok_for_pinctrl)
> info->flags |= GPIOLINE_FLAG_KERNEL;
> if (test_bit(FLAG_IS_OUT, &desc->flags))
> info->flags |= GPIOLINE_FLAG_IS_OUT;
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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
next prev parent reply other threads:[~2020-03-20 10:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 9:31 [PATCH] gpiolib: don't call sleeping functions with a spinlock taken Bartosz Golaszewski
2020-03-20 10:58 ` Geert Uytterhoeven [this message]
2020-03-20 16:55 ` Bartosz Golaszewski
2020-04-14 12:00 ` Linus Walleij
2020-04-14 12:26 ` Bartosz Golaszewski
2020-04-16 11:19 ` Linus Walleij
2020-04-28 15:53 ` Andy Shevchenko
2020-04-29 6:40 ` Bartosz Golaszewski
2020-04-29 12:37 ` Andy Shevchenko
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