diff mbox series

[1/3] gpio: take the SRCU read lock in gpiod_hog()

Message ID 20240213093108.13922-2-brgl@bgdev.pl
State New
Headers show
Series gpio: fix SRCU bugs | expand

Commit Message

Bartosz Golaszewski Feb. 13, 2024, 9:31 a.m. UTC 
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiod_hog() may be called without the gpio_device SRCU read lock taken
so we need to do it here as well. It's alright if someone else is
already holding the lock as SRCU read critical sections can be nested.

Fixes: d83cee3d2bb1 ("gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202402122234.d85cca9b-lkp@intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Comments

Linus Walleij Feb. 13, 2024, 9:29 p.m. UTC | #1 
On Tue, Feb 13, 2024 at 10:31 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>
> gpiod_hog() may be called without the gpio_device SRCU read lock taken
> so we need to do it here as well. It's alright if someone else is
> already holding the lock as SRCU read critical sections can be nested.
>
> Fixes: d83cee3d2bb1 ("gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
> Reported-by: kernel test robot <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202402122234.d85cca9b-lkp@intel.com
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Looking at the CLASS() stuff I see this is definitely the way to go
with the code now that we face massive scaling. Nice work.

Yours,
Linus Walleij
diff mbox series

Patch

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 82811d9a4477..c1391a9a0af6 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -4492,24 +4492,27 @@  EXPORT_SYMBOL_GPL(gpiod_get_index_optional);
 int gpiod_hog(struct gpio_desc *desc, const char *name,
 	      unsigned long lflags, enum gpiod_flags dflags)
 {
-	struct gpio_chip *gc;
+	struct gpio_device *gdev = desc->gdev;
 	struct gpio_desc *local_desc;
 	int hwnum;
 	int ret;
 
+	CLASS(gpio_chip_guard, guard)(desc);
+	if (!guard.gc)
+		return -ENODEV;
+
 	if (test_and_set_bit(FLAG_IS_HOGGED, &desc->flags))
 		return 0;
 
-	gc = gpiod_to_chip(desc);
 	hwnum = gpio_chip_hwgpio(desc);
 
-	local_desc = gpiochip_request_own_desc(gc, hwnum, name,
+	local_desc = gpiochip_request_own_desc(guard.gc, hwnum, name,
 					       lflags, dflags);
 	if (IS_ERR(local_desc)) {
 		clear_bit(FLAG_IS_HOGGED, &desc->flags);
 		ret = PTR_ERR(local_desc);
 		pr_err("requesting hog GPIO %s (chip %s, offset %d) failed, %d\n",
-		       name, gc->label, hwnum, ret);
+		       name, gdev->label, hwnum, ret);
 		return ret;
 	}