[PATCH 0/3] gpio: Failure path fixes

[PATCH 0/3] gpio: Failure path fixes

[Geert Uytterhoeven]

	Hi Linus, Bartosz,

After making a silly mistake in a pin control driver, pinctrl driver
initialization failed, causing an avalanche of GPIO driver failures, and
I was greeted by the following scary messages:

    OF: ERROR: Bad of_node_put() on /soc/gpio@e6050000
    ...
    WARNING: CPU: 0 PID: 1 at lib/refcount.c:156 kobject_get+0x38/0x4c
    ...
    WARNING: CPU: 0 PID: 1 at lib/refcount.c:190 refcount_sub_and_test_checked+0x3c/0xa8

The first two patches fix bugs in related error paths, after which the
messages are gone.
The third patch is a drive-by fix for function comment.

Thanks for your comments!

Geert Uytterhoeven (3):
  gpio: of: Fix of_gpiochip_add() error path
  gpio: Fix gpiochip_add_data_with_key() error path
  gpio: Remove obsolete comment about gpiochip_free_hogs() usage

 drivers/gpio/gpiolib-of.c |  8 +++++++-
 drivers/gpio/gpiolib.c    | 14 ++++++++------
 2 files changed, 15 insertions(+), 7 deletions(-)

-- 
2.17.1

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

[PATCH 1/3] gpio: of: Fix of_gpiochip_add() error path

[Geert Uytterhoeven]

If the call to of_gpiochip_scan_gpios() in of_gpiochip_add() fails, no
error handling is performed.  This lead to the need of callers to call
of_gpiochip_remove() on failure, which causes "BAD of_node_put() on ..."
if the failure happened before the call to of_node_get().

Fix this by adding proper error handling.

Note that calling gpiochip_remove_pin_ranges() multiple times causes no
harm: subsequent calls are a no-op.

Fixes: dfbd379ba9b7431e ("gpio: of: Return error if gpio hog configuration failed")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/gpio/gpiolib-of.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 8b9c3ab70f6eade4..257be7bac032a855 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -717,7 +717,13 @@ int of_gpiochip_add(struct gpio_chip *chip)
 
 	of_node_get(chip->of_node);
 
-	return of_gpiochip_scan_gpios(chip);
+	status = of_gpiochip_scan_gpios(chip);
+	if (status) {
+		of_node_put(chip->of_node);
+		gpiochip_remove_pin_ranges(chip);
+	}
+
+	return status;
 }
 
 void of_gpiochip_remove(struct gpio_chip *chip)
-- 
2.17.1

Re: [PATCH 1/3] gpio: of: Fix of_gpiochip_add() error path

[Mukesh Ojha]

On 3/28/2019 6:43 PM, Geert Uytterhoeven wrote:
> If the call to of_gpiochip_scan_gpios() in of_gpiochip_add() fails, no
> error handling is performed.  This lead to the need of callers to call
> of_gpiochip_remove() on failure, which causes "BAD of_node_put() on ..."
> if the failure happened before the call to of_node_get().
>
> Fix this by adding proper error handling.
>
> Note that calling gpiochip_remove_pin_ranges() multiple times causes no
> harm: subsequent calls are a no-op.
>
> Fixes: dfbd379ba9b7431e ("gpio: of: Return error if gpio hog configuration failed")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>


Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

-Mukesh

> ---
>   drivers/gpio/gpiolib-of.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> index 8b9c3ab70f6eade4..257be7bac032a855 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -717,7 +717,13 @@ int of_gpiochip_add(struct gpio_chip *chip)
>   
>   	of_node_get(chip->of_node);
>   
> -	return of_gpiochip_scan_gpios(chip);
> +	status = of_gpiochip_scan_gpios(chip);
> +	if (status) {
> +		of_node_put(chip->of_node);
> +		gpiochip_remove_pin_ranges(chip);
> +	}
> +
> +	return status;
>   }
>   
>   void of_gpiochip_remove(struct gpio_chip *chip)

Re: [PATCH 1/3] gpio: of: Fix of_gpiochip_add() error path

[Linus Walleij]

On Thu, Mar 28, 2019 at 2:13 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:

> If the call to of_gpiochip_scan_gpios() in of_gpiochip_add() fails, no
> error handling is performed.  This lead to the need of callers to call
> of_gpiochip_remove() on failure, which causes "BAD of_node_put() on ..."
> if the failure happened before the call to of_node_get().
>
> Fix this by adding proper error handling.
>
> Note that calling gpiochip_remove_pin_ranges() multiple times causes no
> harm: subsequent calls are a no-op.
>
> Fixes: dfbd379ba9b7431e ("gpio: of: Return error if gpio hog configuration failed")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Patch applied.

Yours,
Linus Walleij

[PATCH 2/3] gpio: Fix gpiochip_add_data_with_key() error path

[Geert Uytterhoeven]

The err_remove_chip block is too coarse, and may perform cleanup that
must not be done.  E.g. if of_gpiochip_add() fails, of_gpiochip_remove()
is still called, causing:

    OF: ERROR: Bad of_node_put() on /soc/gpio@e6050000
    CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 5.1.0-rc2-koelsch+ #407
    Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
    Workqueue: events deferred_probe_work_func
    [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
    [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
    [<c07c1224>] (dump_stack) from [<c07c5a80>] (kobject_put+0x94/0xbc)
    [<c07c5a80>] (kobject_put) from [<c0470420>] (gpiochip_add_data_with_key+0x8d8/0xa3c)
    [<c0470420>] (gpiochip_add_data_with_key) from [<c0473738>] (gpio_rcar_probe+0x1d4/0x314)
    [<c0473738>] (gpio_rcar_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)

and later, if a GPIO consumer tries to use a GPIO from a failed
controller:

    WARNING: CPU: 0 PID: 1 at lib/refcount.c:156 kobject_get+0x38/0x4c
    refcount_t: increment on 0; use-after-free.
    Modules linked in:
    CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-rc2-koelsch+ #407
    Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
    [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
    [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
    [<c07c1224>] (dump_stack) from [<c0221580>] (__warn+0xd0/0xec)
    [<c0221580>] (__warn) from [<c02215e0>] (warn_slowpath_fmt+0x44/0x6c)
    [<c02215e0>] (warn_slowpath_fmt) from [<c07c58fc>] (kobject_get+0x38/0x4c)
    [<c07c58fc>] (kobject_get) from [<c068b3ec>] (of_node_get+0x14/0x1c)
    [<c068b3ec>] (of_node_get) from [<c0686f24>] (of_find_node_by_phandle+0xc0/0xf0)
    [<c0686f24>] (of_find_node_by_phandle) from [<c0686fbc>] (of_phandle_iterator_next+0x68/0x154)
    [<c0686fbc>] (of_phandle_iterator_next) from [<c0687fe4>] (__of_parse_phandle_with_args+0x40/0xd0)
    [<c0687fe4>] (__of_parse_phandle_with_args) from [<c0688204>] (of_parse_phandle_with_args_map+0x100/0x3ac)
    [<c0688204>] (of_parse_phandle_with_args_map) from [<c0471240>] (of_get_named_gpiod_flags+0x38/0x380)
    [<c0471240>] (of_get_named_gpiod_flags) from [<c046f864>] (gpiod_get_from_of_node+0x24/0xd8)
    [<c046f864>] (gpiod_get_from_of_node) from [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child+0xa0/0x144)
    [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child) from [<c05f425c>] (gpio_keys_probe+0x418/0x7bc)
    [<c05f425c>] (gpio_keys_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)

Fix this by splitting the cleanup block, and adding a missing call to
gpiochip_irqchip_remove().

Fixes: 28355f81969962cf ("gpio: defer probe if pinctrl cannot be found")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
I'm not so sure about the need for the call to
gpiochip_irqchip_remove(), as add/remove are not really symmetrical.
Any comments?
---
 drivers/gpio/gpiolib.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 144af07335815998..ed4da07effe0ac40 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1379,7 +1379,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 
 	status = gpiochip_add_irqchip(chip, lock_key, request_key);
 	if (status)
-		goto err_remove_chip;
+		goto err_free_irqchip_mask;
 
 	status = of_gpiochip_add(chip);
 	if (status)
@@ -1387,7 +1387,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 
 	status = gpiochip_init_valid_mask(chip);
 	if (status)
-		goto err_remove_chip;
+		goto err_remove_of_chip;
 
 	for (i = 0; i < chip->ngpio; i++) {
 		struct gpio_desc *desc = &gdev->descs[i];
@@ -1415,14 +1415,18 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 	if (gpiolib_initialized) {
 		status = gpiochip_setup_dev(gdev);
 		if (status)
-			goto err_remove_chip;
+			goto err_remove_acpi_chip;
 	}
 	return 0;
 
-err_remove_chip:
+err_remove_acpi_chip:
 	acpi_gpiochip_remove(chip);
+err_remove_of_chip:
 	gpiochip_free_hogs(chip);
 	of_gpiochip_remove(chip);
+err_remove_chip:
+	gpiochip_irqchip_remove(chip);
+err_free_irqchip_mask:
 	gpiochip_free_valid_mask(chip);
 err_remove_irqchip_mask:
 	gpiochip_irqchip_free_valid_mask(chip);
-- 
2.17.1

Re: [PATCH 2/3] gpio: Fix gpiochip_add_data_with_key() error path

[Mukesh Ojha]

On 3/28/2019 6:43 PM, Geert Uytterhoeven wrote:
> The err_remove_chip block is too coarse, and may perform cleanup that
> must not be done.  E.g. if of_gpiochip_add() fails, of_gpiochip_remove()
> is still called, causing:
>
>      OF: ERROR: Bad of_node_put() on /soc/gpio@e6050000
>      CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 5.1.0-rc2-koelsch+ #407
>      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>      Workqueue: events deferred_probe_work_func
>      [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
>      [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
>      [<c07c1224>] (dump_stack) from [<c07c5a80>] (kobject_put+0x94/0xbc)
>      [<c07c5a80>] (kobject_put) from [<c0470420>] (gpiochip_add_data_with_key+0x8d8/0xa3c)
>      [<c0470420>] (gpiochip_add_data_with_key) from [<c0473738>] (gpio_rcar_probe+0x1d4/0x314)
>      [<c0473738>] (gpio_rcar_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
>
> and later, if a GPIO consumer tries to use a GPIO from a failed
> controller:
>
>      WARNING: CPU: 0 PID: 1 at lib/refcount.c:156 kobject_get+0x38/0x4c
>      refcount_t: increment on 0; use-after-free.
>      Modules linked in:
>      CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-rc2-koelsch+ #407
>      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>      [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
>      [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
>      [<c07c1224>] (dump_stack) from [<c0221580>] (__warn+0xd0/0xec)
>      [<c0221580>] (__warn) from [<c02215e0>] (warn_slowpath_fmt+0x44/0x6c)
>      [<c02215e0>] (warn_slowpath_fmt) from [<c07c58fc>] (kobject_get+0x38/0x4c)
>      [<c07c58fc>] (kobject_get) from [<c068b3ec>] (of_node_get+0x14/0x1c)
>      [<c068b3ec>] (of_node_get) from [<c0686f24>] (of_find_node_by_phandle+0xc0/0xf0)
>      [<c0686f24>] (of_find_node_by_phandle) from [<c0686fbc>] (of_phandle_iterator_next+0x68/0x154)
>      [<c0686fbc>] (of_phandle_iterator_next) from [<c0687fe4>] (__of_parse_phandle_with_args+0x40/0xd0)
>      [<c0687fe4>] (__of_parse_phandle_with_args) from [<c0688204>] (of_parse_phandle_with_args_map+0x100/0x3ac)
>      [<c0688204>] (of_parse_phandle_with_args_map) from [<c0471240>] (of_get_named_gpiod_flags+0x38/0x380)
>      [<c0471240>] (of_get_named_gpiod_flags) from [<c046f864>] (gpiod_get_from_of_node+0x24/0xd8)
>      [<c046f864>] (gpiod_get_from_of_node) from [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child+0xa0/0x144)
>      [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child) from [<c05f425c>] (gpio_keys_probe+0x418/0x7bc)
>      [<c05f425c>] (gpio_keys_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
>
> Fix this by splitting the cleanup block, and adding a missing call to
> gpiochip_irqchip_remove().
>
> Fixes: 28355f81969962cf ("gpio: defer probe if pinctrl cannot be found")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> I'm not so sure about the need for the call to
> gpiochip_irqchip_remove(), as add/remove are not really symmetrical.
> Any comments?
> ---
>   drivers/gpio/gpiolib.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 144af07335815998..ed4da07effe0ac40 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1379,7 +1379,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   
>   	status = gpiochip_add_irqchip(chip, lock_key, request_key);
>   	if (status)
> -		goto err_remove_chip;
> +		goto err_free_irqchip_mask;

Name is quite confusing
this should be

s/err_free_irqchip_mask/err_free_gpiochip_mask


>   
>   	status = of_gpiochip_add(chip);
>   	if (status)
> @@ -1387,7 +1387,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   
>   	status = gpiochip_init_valid_mask(chip);
>   	if (status)
> -		goto err_remove_chip;
> +		goto err_remove_of_chip;
>   
>   	for (i = 0; i < chip->ngpio; i++) {
>   		struct gpio_desc *desc = &gdev->descs[i];
> @@ -1415,14 +1415,18 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
>   	if (gpiolib_initialized) {
>   		status = gpiochip_setup_dev(gdev);
>   		if (status)
> -			goto err_remove_chip;
> +			goto err_remove_acpi_chip;
>   	}
>   	return 0;
>   
> -err_remove_chip:
> +err_remove_acpi_chip:
>   	acpi_gpiochip_remove(chip);
> +err_remove_of_chip:
>   	gpiochip_free_hogs(chip);
>   	of_gpiochip_remove(chip);
> +err_remove_chip:
> +	gpiochip_irqchip_remove(chip);
> +err_free_irqchip_mask:


same here.

After reviewing back and forth it looks good, apart from the naming.
Please fix.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

-Mukesh


>   	gpiochip_free_valid_mask(chip);
>   err_remove_irqchip_mask:
>   	gpiochip_irqchip_free_valid_mask(chip);

Re: [PATCH 2/3] gpio: Fix gpiochip_add_data_with_key() error path

[Geert Uytterhoeven]

Hi Mukesj,

On Thu, Mar 28, 2019 at 4:31 PM Mukesh Ojha <mojha@codeaurora.org> wrote:
> On 3/28/2019 6:43 PM, Geert Uytterhoeven wrote:
> > The err_remove_chip block is too coarse, and may perform cleanup that
> > must not be done.  E.g. if of_gpiochip_add() fails, of_gpiochip_remove()
> > is still called, causing:
> >
> >      OF: ERROR: Bad of_node_put() on /soc/gpio@e6050000
> >      CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 5.1.0-rc2-koelsch+ #407
> >      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> >      Workqueue: events deferred_probe_work_func
> >      [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
> >      [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
> >      [<c07c1224>] (dump_stack) from [<c07c5a80>] (kobject_put+0x94/0xbc)
> >      [<c07c5a80>] (kobject_put) from [<c0470420>] (gpiochip_add_data_with_key+0x8d8/0xa3c)
> >      [<c0470420>] (gpiochip_add_data_with_key) from [<c0473738>] (gpio_rcar_probe+0x1d4/0x314)
> >      [<c0473738>] (gpio_rcar_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
> >
> > and later, if a GPIO consumer tries to use a GPIO from a failed
> > controller:
> >
> >      WARNING: CPU: 0 PID: 1 at lib/refcount.c:156 kobject_get+0x38/0x4c
> >      refcount_t: increment on 0; use-after-free.
> >      Modules linked in:
> >      CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-rc2-koelsch+ #407
> >      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> >      [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
> >      [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
> >      [<c07c1224>] (dump_stack) from [<c0221580>] (__warn+0xd0/0xec)
> >      [<c0221580>] (__warn) from [<c02215e0>] (warn_slowpath_fmt+0x44/0x6c)
> >      [<c02215e0>] (warn_slowpath_fmt) from [<c07c58fc>] (kobject_get+0x38/0x4c)
> >      [<c07c58fc>] (kobject_get) from [<c068b3ec>] (of_node_get+0x14/0x1c)
> >      [<c068b3ec>] (of_node_get) from [<c0686f24>] (of_find_node_by_phandle+0xc0/0xf0)
> >      [<c0686f24>] (of_find_node_by_phandle) from [<c0686fbc>] (of_phandle_iterator_next+0x68/0x154)
> >      [<c0686fbc>] (of_phandle_iterator_next) from [<c0687fe4>] (__of_parse_phandle_with_args+0x40/0xd0)
> >      [<c0687fe4>] (__of_parse_phandle_with_args) from [<c0688204>] (of_parse_phandle_with_args_map+0x100/0x3ac)
> >      [<c0688204>] (of_parse_phandle_with_args_map) from [<c0471240>] (of_get_named_gpiod_flags+0x38/0x380)
> >      [<c0471240>] (of_get_named_gpiod_flags) from [<c046f864>] (gpiod_get_from_of_node+0x24/0xd8)
> >      [<c046f864>] (gpiod_get_from_of_node) from [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child+0xa0/0x144)
> >      [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child) from [<c05f425c>] (gpio_keys_probe+0x418/0x7bc)
> >      [<c05f425c>] (gpio_keys_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
> >
> > Fix this by splitting the cleanup block, and adding a missing call to
> > gpiochip_irqchip_remove().
> >
> > Fixes: 28355f81969962cf ("gpio: defer probe if pinctrl cannot be found")
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > I'm not so sure about the need for the call to
> > gpiochip_irqchip_remove(), as add/remove are not really symmetrical.
> > Any comments?
> > ---
> >   drivers/gpio/gpiolib.c | 12 ++++++++----
> >   1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index 144af07335815998..ed4da07effe0ac40 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -1379,7 +1379,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
> >
> >       status = gpiochip_add_irqchip(chip, lock_key, request_key);
> >       if (status)
> > -             goto err_remove_chip;
> > +             goto err_free_irqchip_mask;
>
> Name is quite confusing
> this should be
>
> s/err_free_irqchip_mask/err_free_gpiochip_mask

Thanks, makes perfect sense.

> After reviewing back and forth it looks good, apart from the naming.
> Please fix.

Done (locally).

> Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

Thanks!

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

Re: [PATCH 2/3] gpio: Fix gpiochip_add_data_with_key() error path

[Linus Walleij]

On Thu, Mar 28, 2019 at 2:13 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:

> The err_remove_chip block is too coarse, and may perform cleanup that
> must not be done.  E.g. if of_gpiochip_add() fails, of_gpiochip_remove()
> is still called, causing:
>
>     OF: ERROR: Bad of_node_put() on /soc/gpio@e6050000
>     CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 5.1.0-rc2-koelsch+ #407
>     Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>     Workqueue: events deferred_probe_work_func
>     [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
>     [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
>     [<c07c1224>] (dump_stack) from [<c07c5a80>] (kobject_put+0x94/0xbc)
>     [<c07c5a80>] (kobject_put) from [<c0470420>] (gpiochip_add_data_with_key+0x8d8/0xa3c)
>     [<c0470420>] (gpiochip_add_data_with_key) from [<c0473738>] (gpio_rcar_probe+0x1d4/0x314)
>     [<c0473738>] (gpio_rcar_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
>
> and later, if a GPIO consumer tries to use a GPIO from a failed
> controller:
>
>     WARNING: CPU: 0 PID: 1 at lib/refcount.c:156 kobject_get+0x38/0x4c
>     refcount_t: increment on 0; use-after-free.
>     Modules linked in:
>     CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-rc2-koelsch+ #407
>     Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>     [<c020ec74>] (unwind_backtrace) from [<c020ae58>] (show_stack+0x10/0x14)
>     [<c020ae58>] (show_stack) from [<c07c1224>] (dump_stack+0x7c/0x9c)
>     [<c07c1224>] (dump_stack) from [<c0221580>] (__warn+0xd0/0xec)
>     [<c0221580>] (__warn) from [<c02215e0>] (warn_slowpath_fmt+0x44/0x6c)
>     [<c02215e0>] (warn_slowpath_fmt) from [<c07c58fc>] (kobject_get+0x38/0x4c)
>     [<c07c58fc>] (kobject_get) from [<c068b3ec>] (of_node_get+0x14/0x1c)
>     [<c068b3ec>] (of_node_get) from [<c0686f24>] (of_find_node_by_phandle+0xc0/0xf0)
>     [<c0686f24>] (of_find_node_by_phandle) from [<c0686fbc>] (of_phandle_iterator_next+0x68/0x154)
>     [<c0686fbc>] (of_phandle_iterator_next) from [<c0687fe4>] (__of_parse_phandle_with_args+0x40/0xd0)
>     [<c0687fe4>] (__of_parse_phandle_with_args) from [<c0688204>] (of_parse_phandle_with_args_map+0x100/0x3ac)
>     [<c0688204>] (of_parse_phandle_with_args_map) from [<c0471240>] (of_get_named_gpiod_flags+0x38/0x380)
>     [<c0471240>] (of_get_named_gpiod_flags) from [<c046f864>] (gpiod_get_from_of_node+0x24/0xd8)
>     [<c046f864>] (gpiod_get_from_of_node) from [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child+0xa0/0x144)
>     [<c0470aa4>] (devm_fwnode_get_index_gpiod_from_child) from [<c05f425c>] (gpio_keys_probe+0x418/0x7bc)
>     [<c05f425c>] (gpio_keys_probe) from [<c052fca8>] (platform_drv_probe+0x48/0x94)
>
> Fix this by splitting the cleanup block, and adding a missing call to
> gpiochip_irqchip_remove().
>
> Fixes: 28355f81969962cf ("gpio: defer probe if pinctrl cannot be found")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> I'm not so sure about the need for the call to
> gpiochip_irqchip_remove(), as add/remove are not really symmetrical.
> Any comments?

I need to think about this.

Also Mukesh had some comments on naming.

I will try to read through the code closer for v2 and
figure out if it is what we want to do. But I think we need it.

Yours,
Linus Walleij

[PATCH 3/3] gpio: Remove obsolete comment about gpiochip_free_hogs() usage

[Geert Uytterhoeven]

gpiochip_free_hogs() was always called from gpiochip_remove(), not
of_gpiochip_remove().  It is now also called from the failure patch in
gpiochip_add_data_with_key().

Fixes: f625d4601759f1cf ("gpio: add GPIO hogging mechanism")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/gpio/gpiolib.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index ed4da07effe0ac40..ec326bd84b1f1c50 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -4449,8 +4449,6 @@ int gpiod_hog(struct gpio_desc *desc, const char *name,
 /**
  * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
  * @chip:	gpio chip to act on
- *
- * This is only used by of_gpiochip_remove to free hogged gpios
  */
 static void gpiochip_free_hogs(struct gpio_chip *chip)
 {
-- 
2.17.1

Re: [PATCH 3/3] gpio: Remove obsolete comment about gpiochip_free_hogs() usage

[Mukesh Ojha]

On 3/28/2019 6:43 PM, Geert Uytterhoeven wrote:
> gpiochip_free_hogs() was always called from gpiochip_remove(), not
> of_gpiochip_remove().  It is now also called from the failure patch in
> gpiochip_add_data_with_key().
>
> Fixes: f625d4601759f1cf ("gpio: add GPIO hogging mechanism")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>


Looks good to be removed.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

-Mukesh

> ---
>   drivers/gpio/gpiolib.c | 2 --
>   1 file changed, 2 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index ed4da07effe0ac40..ec326bd84b1f1c50 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -4449,8 +4449,6 @@ int gpiod_hog(struct gpio_desc *desc, const char *name,
>   /**
>    * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
>    * @chip:	gpio chip to act on
> - *
> - * This is only used by of_gpiochip_remove to free hogged gpios
>    */
>   static void gpiochip_free_hogs(struct gpio_chip *chip)
>   {

Re: [PATCH 3/3] gpio: Remove obsolete comment about gpiochip_free_hogs() usage

[Linus Walleij]

On Thu, Mar 28, 2019 at 2:13 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:

> gpiochip_free_hogs() was always called from gpiochip_remove(), not
> of_gpiochip_remove().  It is now also called from the failure patch in
> gpiochip_add_data_with_key().
>
> Fixes: f625d4601759f1cf ("gpio: add GPIO hogging mechanism")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Patch applied for v5.2.

Yours,
Linus Walleij