[PATCH 6.19 140/311] gpio: shared: shorten the critical section in gpiochip_setup_shared()

Greg Kroah-Hartman
2026-04-08T18:57:13Z

From: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

[ Upstream commit 310a4a9cbb17037668ea440f6a3964d00705b400 ]

Commit 710abda58055 ("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: 710abda58055 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpio/gpiolib-shared.c | 56 +++++++++++++++++------------------
1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c
index 9c31736d29b77..692f568ffe7a4 100644
--- a/drivers/gpio/gpiolib-shared.c
+++ b/drivers/gpio/gpiolib-shared.c
@@ -538,48 +538,48 @@ 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) {
- /*
- * This is the earliest that we can tranlate the
- * devicetree offset to the chip offset.
- */
- struct of_phandle_args gpiospec = { };
+ if (is_of_node(entry->fwnode) && gc->of_xlate) {
+ /*
+ * This is the earliest that we can tranlate the
+ * devicetree offset to the chip offset.
+ */
+ struct of_phandle_args gpiospec = { };

- gpiospec.np = to_of_node(entry->fwnode);
- gpiospec.args_count = 2;
- gpiospec.args[0] = entry->offset;
+ gpiospec.np = to_of_node(entry->fwnode);
+ gpiospec.args_count = 2;
+ gpiospec.args[0] = entry->offset;

- ret = gc->of_xlate(gc, &gpiospec, NULL);
- if (ret < 0)
- return ret;
+ ret = gc->of_xlate(gc, &gpiospec, NULL);
+ if (ret < 0)
+ return ret;

- entry->offset = ret;
- }
+ entry->offset = ret;
+ }
#endif /* CONFIG_OF */

- desc = &gdev->descs[entry->offset];
+ desc = &gdev->descs[entry->offset];

- __set_bit(GPIOD_FLAG_SHARED, &desc->flags);
- /*
- * Shared GPIOs are not requested via the normal path. Make
- * them inaccessible to anyone even before we register the
- * chip.
- */
- ret = gpiod_request_commit(desc, "shared");
- if (ret)
- return ret;
+ __set_bit(GPIOD_FLAG_SHARED, &desc->flags);
+ /*
+ * Shared GPIOs are not requested via the normal path. Make
+ * them inaccessible to anyone even before we register the
+ * chip.
+ */
+ ret = gpiod_request_commit(desc, "shared");
+ if (ret)
+ return ret;

- pr_debug("GPIO %u owned by %s is shared by multiple consumers\n",
- entry->offset, gpio_device_get_label(gdev));
+ 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",
--
2.53.0