[PATCH 2/2] gpio: shared: fix lockdep false positive by removing unneeded lock

[Bartosz Golaszewski]

By the time gpio_device_teardown_shared() is called, the parent device
is gone from the global list of GPIO devices and all outstanding SRCU
read-side critical sections have completed. That means that no
concurrent gpio_find_and_request() can call
gpio_shared_add_proxy_lookup() for this device at this time. There's
also no risk of the parent device being re-bound to the driver before
the unbinding completes (including the child devices).

Lockdep produces a false-positive report about a possible circular
dependency as it doesn't know the ordering guarantee. Not taking the
ref->lock in gpio_device_teardown_shared() silences it and is safe to do.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: ea513dd3c066 ("gpio: shared: make locking more fine-grained")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
 drivers/gpio/gpiolib-shared.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c
index 087b64c06c9f42b698abe5741e63102538beb488..de72776fb154f1f2ec97a3e186dc96366f3cee8b 100644
--- a/drivers/gpio/gpiolib-shared.c
+++ b/drivers/gpio/gpiolib-shared.c
@@ -605,8 +605,6 @@ void gpio_device_teardown_shared(struct gpio_device *gdev)
 			gpiod_free_commit(&gdev->descs[entry->offset]);
 
 		list_for_each_entry(ref, &entry->refs, list) {
-			guard(mutex)(&ref->lock);
-
 			if (ref->lookup) {
 				gpiod_remove_lookup_table(ref->lookup);
 				kfree(ref->lookup->table[0].key);

-- 
2.47.3