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gpio: sysfs: fix race between gpiod export and unexport 

Make sure to deregister the class device (and release the irq) while
holding the sysfs lock in gpio_unexport to prevent racing with
gpio_export.

Note that this requires the recently introduced per-gpio locking to
avoid a deadlock with the kernfs active protection when waiting for the
attribute operations to drain during deregistration.

Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Johan Hovold 2015-05-04 17:10:45 +02:00 committed by Linus Walleij
parent 6ffcb79714
commit 72eba6f66a
1 changed files with 26 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
drivers/gpio/gpiolib-sysfs.c
View File

@ -674,9 +674,8 @@ EXPORT_SYMBOL_GPL(gpiod_export_link);
*/
void gpiod_unexport(struct gpio_desc *desc)
{
struct gpiod_data *data;
int status = 0;
struct device *dev = NULL;
struct gpiod_data *data;
struct device *dev;
if (!desc) {
pr_warn("%s: invalid GPIO\n", __func__);
@ -685,33 +684,35 @@ void gpiod_unexport(struct gpio_desc *desc)
mutex_lock(&sysfs_lock);
if (test_bit(FLAG_EXPORT, &desc->flags)) {
if (!test_bit(FLAG_EXPORT, &desc->flags))
goto err_unlock;
dev = class_find_device(&gpio_class, NULL, desc, match_export);
if (dev) {
clear_bit(FLAG_SYSFS_DIR, &desc->flags);
clear_bit(FLAG_EXPORT, &desc->flags);
} else
status = -ENODEV;
}
dev = class_find_device(&gpio_class, NULL, desc, match_export);
if (!dev)
goto err_unlock;
data = dev_get_drvdata(dev);
clear_bit(FLAG_SYSFS_DIR, &desc->flags);
clear_bit(FLAG_EXPORT, &desc->flags);
device_unregister(dev);
/*
* Release irq after deregistration to prevent race with edge_store.
*/
if (desc->flags & GPIO_TRIGGER_MASK)
gpio_sysfs_free_irq(dev);
mutex_unlock(&sysfs_lock);
if (dev) {
data = dev_get_drvdata(dev);
device_unregister(dev);
/*
* Release irq after deregistration to prevent race with
* edge_store.
*/
if (desc->flags & GPIO_TRIGGER_MASK)
gpio_sysfs_free_irq(dev);
put_device(dev);
kfree(data);
}
put_device(dev);
kfree(data);
if (status)
gpiod_dbg(desc, "%s: status %d\n", __func__, status);
return;
err_unlock:
mutex_unlock(&sysfs_lock);
}
EXPORT_SYMBOL_GPL(gpiod_unexport);