linux-kernel - [PATCH] gpiolib: read descriptor flags once in gpiolib_dbg

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Message-ID: <20250215100847.30136-1-brgl@bgdev.pl>
Date: Sat, 15 Feb 2025 11:08:47 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH] gpiolib: read descriptor flags once in gpiolib_dbg_show()

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

For consistency with most other code that can access requested
descriptors: read the flags once atomically and then test individual
bits from the helper variable. This avoids any potential discrepancies
should flags change during the debug print.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/gpiolib.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f4e14a7dbc87..7dd054f8141e 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -5003,6 +5003,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
 	unsigned int gpio = gdev->base;
 	struct gpio_desc *desc;
 	struct gpio_chip *gc;
+	unsigned long flags;
 	int value;
 
 	guard(srcu)(&gdev->srcu);
@@ -5015,12 +5016,13 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
 
 	for_each_gpio_desc(gc, desc) {
 		guard(srcu)(&desc->gdev->desc_srcu);
-		is_irq = test_bit(FLAG_USED_AS_IRQ, &desc->flags);
-		if (is_irq || test_bit(FLAG_REQUESTED, &desc->flags)) {
+		flags = READ_ONCE(desc->flags);
+		is_irq = test_bit(FLAG_USED_AS_IRQ, &flags);
+		if (is_irq || test_bit(FLAG_REQUESTED, &flags)) {
 			gpiod_get_direction(desc);
-			is_out = test_bit(FLAG_IS_OUT, &desc->flags);
+			is_out = test_bit(FLAG_IS_OUT, &flags);
 			value = gpio_chip_get_value(gc, desc);
-			active_low = test_bit(FLAG_ACTIVE_LOW, &desc->flags);
+			active_low = test_bit(FLAG_ACTIVE_LOW, &flags);
 			seq_printf(s, " gpio-%-3u (%-20.20s|%-20.20s) %s %s %s%s\n",
 				   gpio, desc->name ?: "", gpiod_get_label(desc),
 				   is_out ? "out" : "in ",
-- 
2.45.2