[PATCH] gpio: initialize descriptor SRCU structure before adding OF-based chips

[PATCH] gpio: initialize descriptor SRCU structure before adding OF-based chips

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

In certain situations we may end up taking the GPIO descriptor SRCU read
lock in of_gpiochip_add() before the SRCU struct is initialized. Move
the initialization before the call to of_gpiochip_add().

Fixes: be711caa87c5 ("gpio: add SRCU infrastructure to struct gpio_desc")
Fixes: 1f2bcb8c8ccd ("gpio: protect the descriptor label with SRCU")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202402122228.e607a080-lkp@intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 82811d9a4477..f5434e559382 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -991,10 +991,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	if (ret)
 		goto err_cleanup_gdev_srcu;
 
-	ret = of_gpiochip_add(gc);
-	if (ret)
-		goto err_free_gpiochip_mask;
-
 	for (i = 0; i < gc->ngpio; i++) {
 		struct gpio_desc *desc = &gdev->descs[i];
 
@@ -1002,7 +998,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 		if (ret) {
 			for (j = 0; j < i; j++)
 				cleanup_srcu_struct(&gdev->descs[j].srcu);
-			goto err_remove_of_chip;
+			goto err_free_gpiochip_mask;
 		}
 
 		if (gc->get_direction && gpiochip_line_is_valid(gc, i)) {
@@ -1014,10 +1010,14 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 		}
 	}
 
-	ret = gpiochip_add_pin_ranges(gc);
+	ret = of_gpiochip_add(gc);
 	if (ret)
 		goto err_cleanup_desc_srcu;
 
+	ret = gpiochip_add_pin_ranges(gc);
+	if (ret)
+		goto err_remove_of_chip;
+
 	acpi_gpiochip_add(gc);
 
 	machine_gpiochip_add(gc);
@@ -1055,12 +1055,12 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	gpiochip_irqchip_free_valid_mask(gc);
 err_remove_acpi_chip:
 	acpi_gpiochip_remove(gc);
-err_cleanup_desc_srcu:
-	for (i = 0; i < gdev->ngpio; i++)
-		cleanup_srcu_struct(&gdev->descs[i].srcu);
 err_remove_of_chip:
 	gpiochip_free_hogs(gc);
 	of_gpiochip_remove(gc);
+err_cleanup_desc_srcu:
+	for (i = 0; i < gdev->ngpio; i++)
+		cleanup_srcu_struct(&gdev->descs[i].srcu);
 err_free_gpiochip_mask:
 	gpiochip_remove_pin_ranges(gc);
 	gpiochip_free_valid_mask(gc);
-- 
2.40.1

Re: [PATCH] gpio: initialize descriptor SRCU structure before adding OF-based chips

[Andy Shevchenko]

On Mon, Feb 12, 2024 at 10:39:20PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> In certain situations we may end up taking the GPIO descriptor SRCU read
> lock in of_gpiochip_add() before the SRCU struct is initialized. Move
> the initialization before the call to of_gpiochip_add().

...

This is a bit unclear why you moved to that place and how it had been tested.

> @@ -991,10 +991,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>  	if (ret)
>  		goto err_cleanup_gdev_srcu;
>  
> -	ret = of_gpiochip_add(gc);
> -	if (ret)
> -		goto err_free_gpiochip_mask;
> -
>  	for (i = 0; i < gc->ngpio; i++) {
>  		struct gpio_desc *desc = &gdev->descs[i];
>  

>  		if (ret) {
>  			for (j = 0; j < i; j++)
>  				cleanup_srcu_struct(&gdev->descs[j].srcu);
> -			goto err_remove_of_chip;
> +			goto err_free_gpiochip_mask;
>  		}
>  
>  		if (gc->get_direction && gpiochip_line_is_valid(gc, i)) {

>  		}
>  	}
>  
> -	ret = gpiochip_add_pin_ranges(gc);
> +	ret = of_gpiochip_add(gc);
>  	if (ret)
>  		goto err_cleanup_desc_srcu;
>  
> +	ret = gpiochip_add_pin_ranges(gc);
> +	if (ret)
> +		goto err_remove_of_chip;
> +
>  	acpi_gpiochip_add(gc);

My logic tells me that if you need to call gpiochip_add_pin_ranges() before
calling of_gpiochip_add(). It won't collide right now, but allows to cleanup
further (with the gpio-ranges parser be generalized for fwnodes and be moved
to gpiolib.c from gpiolib-of.c).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] gpio: initialize descriptor SRCU structure before adding OF-based chips

[Bartosz Golaszewski]

On Tue, Feb 13, 2024 at 3:43 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Feb 12, 2024 at 10:39:20PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > In certain situations we may end up taking the GPIO descriptor SRCU read
> > lock in of_gpiochip_add() before the SRCU struct is initialized. Move
> > the initialization before the call to of_gpiochip_add().
>
> ...
>
> This is a bit unclear why you moved to that place and how it had been tested.
>

I didn't move it, I just added SRCU before it. It can be triggered by
a simple hog from DT. The link leads to a crash report.

> > @@ -991,10 +991,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
> >       if (ret)
> >               goto err_cleanup_gdev_srcu;
> >
> > -     ret = of_gpiochip_add(gc);
> > -     if (ret)
> > -             goto err_free_gpiochip_mask;
> > -
> >       for (i = 0; i < gc->ngpio; i++) {
> >               struct gpio_desc *desc = &gdev->descs[i];
> >
>
> >               if (ret) {
> >                       for (j = 0; j < i; j++)
> >                               cleanup_srcu_struct(&gdev->descs[j].srcu);
> > -                     goto err_remove_of_chip;
> > +                     goto err_free_gpiochip_mask;
> >               }
> >
> >               if (gc->get_direction && gpiochip_line_is_valid(gc, i)) {
>
> >               }
> >       }
> >
> > -     ret = gpiochip_add_pin_ranges(gc);
> > +     ret = of_gpiochip_add(gc);
> >       if (ret)
> >               goto err_cleanup_desc_srcu;
> >
> > +     ret = gpiochip_add_pin_ranges(gc);
> > +     if (ret)
> > +             goto err_remove_of_chip;
> > +
> >       acpi_gpiochip_add(gc);
>
> My logic tells me that if you need to call gpiochip_add_pin_ranges() before
> calling of_gpiochip_add(). It won't collide right now, but allows to cleanup
> further (with the gpio-ranges parser be generalized for fwnodes and be moved
> to gpiolib.c from gpiolib-of.c).
>

But it was already called before gpiochip_add_pin_ranges() so it's
material for another patch.

Bart

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

Re: [PATCH] gpio: initialize descriptor SRCU structure before adding OF-based chips

[Bartosz Golaszewski]

On Mon, Feb 12, 2024 at 10:39 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>
> In certain situations we may end up taking the GPIO descriptor SRCU read
> lock in of_gpiochip_add() before the SRCU struct is initialized. Move
> the initialization before the call to of_gpiochip_add().
>
> Fixes: be711caa87c5 ("gpio: add SRCU infrastructure to struct gpio_desc")
> Fixes: 1f2bcb8c8ccd ("gpio: protect the descriptor label with SRCU")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202402122228.e607a080-lkp@intel.com
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> ---

I'm queuing this quickly because next is currently broken for many platforms.

Bartosz