Commit 310a4a9c authored Mar 25, 2026 by Bartosz Golaszewski

gpio: shared: shorten the critical section in gpiochip_setup_shared()

Commit 710abda5 ("gpio: shared: call gpio_chip::of_xlate() if set")
introduced a critical section around the adjustmenet of entry->offset.
However this may cause a deadlock if we create the auxiliary shared
proxy devices with this lock taken. We only need to protect
entry->offset while it's read/written so shorten the critical section
and release the lock before creating the proxy device as the field in
question is no longer accessed at this point.

Fixes: 710abda5 ("gpio: shared: call gpio_chip::of_xlate() if set")
Reported-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260325-gpio-shared-deadlock-v1-1-e4e7a5319e95@oss.qualcomm.com

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

parent c720fb57

drivers/gpio/gpiolib-shared.c

+28 −28

Original line number	Diff line number	Diff line
		@@ -533,14 +533,13 @@ int gpiochip_setup_shared(struct gpio_chip *gc)
		* exposing shared pins. Find them and create the proxy devices.
		*/
		list_for_each_entry(entry, &gpio_shared_list, list) {
		guard(mutex)(&entry->lock);

		if (!device_match_fwnode(&gdev->dev, entry->fwnode))
		continue;

		if (list_count_nodes(&entry->refs) <= 1)
		continue;

		scoped_guard(mutex, &entry->lock) {
		#if IS_ENABLED(CONFIG_OF)
		if (is_of_node(entry->fwnode) && gc->of_xlate) {
		/*
		@@ -575,6 +574,7 @@ int gpiochip_setup_shared(struct gpio_chip *gc)

		pr_debug("GPIO %u owned by %s is shared by multiple consumers\n",
		entry->offset, gpio_device_get_label(gdev));
		}

		list_for_each_entry(ref, &entry->refs, list) {
		pr_debug("Setting up a shared GPIO entry for %s (con_id: '%s')\n",