linux-kernel - [PATCH v2 1/4] gpio: take the SRCU read lock in gpiod

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Message-Id: <20240214084419.6194-2-brgl@bgdev.pl>
Date: Wed, 14 Feb 2024 09:44:16 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>,
	Kent Gibson <warthog618@...il.com>,
	Alex Elder <elder@...aro.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Mark Brown <broonie@...nel.org>,
	Dan Carpenter <dan.carpenter@...aro.org>
Cc: linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	kernel test robot <oliver.sang@...el.com>
Subject: [PATCH v2 1/4] gpio: take the SRCU read lock in gpiod_hog()

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.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@...el.com>
Closes: https://lore.kernel.org/oe-lkp/202402122234.d85cca9b-lkp@intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
---
 drivers/gpio/gpiolib.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f5434e559382..439d32d5aa38 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;
 	}
 
-- 
2.40.1