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

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Commit 710abda580 ("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: 710abda580 ("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>
This commit is contained in:
Bartosz Golaszewski 2026-03-25 12:06:38 +01:00
parent c720fb57d5
commit 310a4a9cbb
1 changed files with 28 additions and 28 deletions
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56
drivers/gpio/gpiolib-shared.c
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@ -533,48 +533,48 @@ 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",