1 files changed, 86 insertions, 64 deletions

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6bf5332136e5..6853ecd98bcb 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/bitops.h>
+#include <linux/cleanup.h>
 #include <linux/device.h>
 #include <linux/idr.h>
 #include <linux/init.h>
@@ -13,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
+#include <linux/srcu.h>
 #include <linux/sysfs.h>
 #include <linux/types.h>
 
@@ -170,6 +172,10 @@ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 	unsigned long irq_flags;
 	int ret;
 
+	CLASS(gpio_chip_guard, guard)(desc);
+	if (!guard.gc)
+		return -ENODEV;
+
 	data->irq = gpiod_to_irq(desc);
 	if (data->irq < 0)
 		return -EIO;
@@ -194,7 +200,7 @@ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 	 *        Remove this redundant call (along with the corresponding
 	 *        unlock) when those drivers have been fixed.
 	 */
-	ret = gpiochip_lock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
+	ret = gpiochip_lock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
 	if (ret < 0)
 		goto err_put_kn;
 
@@ -208,7 +214,7 @@ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 	return 0;
 
 err_unlock:
-	gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
+	gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
 err_put_kn:
 	sysfs_put(data->value_kn);
 
@@ -224,9 +230,13 @@ static void gpio_sysfs_free_irq(struct device *dev)
 	struct gpiod_data *data = dev_get_drvdata(dev);
 	struct gpio_desc *desc = data->desc;
 
+	CLASS(gpio_chip_guard, guard)(desc);
+	if (!guard.gc)
+		return;
+
 	data->irq_flags = 0;
 	free_irq(data->irq, data);
-	gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
+	gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
 	sysfs_put(data->value_kn);
 }
 
@@ -400,27 +410,27 @@ static const struct attribute_group *gpio_groups[] = {
 static ssize_t base_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
-	const struct gpio_chip *chip = dev_get_drvdata(dev);
+	const struct gpio_device *gdev = dev_get_drvdata(dev);
 
-	return sysfs_emit(buf, "%d\n", chip->base);
+	return sysfs_emit(buf, "%d\n", gdev->base);
 }
 static DEVICE_ATTR_RO(base);
 
 static ssize_t label_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
-	const struct gpio_chip *chip = dev_get_drvdata(dev);
+	const struct gpio_device *gdev = dev_get_drvdata(dev);
 
-	return sysfs_emit(buf, "%s\n", chip->label ?: "");
+	return sysfs_emit(buf, "%s\n", gdev->label);
 }
 static DEVICE_ATTR_RO(label);
 
 static ssize_t ngpio_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
-	const struct gpio_chip *chip = dev_get_drvdata(dev);
+	const struct gpio_device *gdev = dev_get_drvdata(dev);
 
-	return sysfs_emit(buf, "%u\n", chip->ngpio);
+	return sysfs_emit(buf, "%u\n", gdev->ngpio);
 }
 static DEVICE_ATTR_RO(ngpio);
 
@@ -443,13 +453,12 @@ static ssize_t export_store(const struct class *class,
 				const char *buf, size_t len)
 {
 	struct gpio_desc *desc;
-	struct gpio_chip *gc;
 	int status, offset;
 	long gpio;
 
 	status = kstrtol(buf, 0, &gpio);
-	if (status < 0)
-		goto done;
+	if (status)
+		return status;
 
 	desc = gpio_to_desc(gpio);
 	/* reject invalid GPIOs */
@@ -457,9 +466,13 @@ static ssize_t export_store(const struct class *class,
 		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
 		return -EINVAL;
 	}
-	gc = desc->gdev->chip;
+
+	CLASS(gpio_chip_guard, guard)(desc);
+	if (!guard.gc)
+		return -ENODEV;
+
 	offset = gpio_chip_hwgpio(desc);
-	if (!gpiochip_line_is_valid(gc, offset)) {
+	if (!gpiochip_line_is_valid(guard.gc, offset)) {
 		pr_warn("%s: GPIO %ld masked\n", __func__, gpio);
 		return -EINVAL;
 	}
@@ -562,8 +575,6 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 	const char *ioname = NULL;
 	struct gpio_device *gdev;
 	struct gpiod_data *data;
-	struct gpio_chip *chip;
-	unsigned long flags;
 	struct device *dev;
 	int status, offset;
 
@@ -578,29 +589,28 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 		return -EINVAL;
 	}
 
+	CLASS(gpio_chip_guard, guard)(desc);
+	if (!guard.gc)
+		return -ENODEV;
+
+	if (test_and_set_bit(FLAG_EXPORT, &desc->flags))
+		return -EPERM;
+
 	gdev = desc->gdev;
-	chip = gdev->chip;
 
 	mutex_lock(&sysfs_lock);
 
 	/* check if chip is being removed */
-	if (!chip || !gdev->mockdev) {
+	if (!gdev->mockdev) {
 		status = -ENODEV;
 		goto err_unlock;
 	}
 
-	spin_lock_irqsave(&gpio_lock, flags);
-	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
-	     test_bit(FLAG_EXPORT, &desc->flags)) {
-		spin_unlock_irqrestore(&gpio_lock, flags);
-		gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n",
-				__func__,
-				test_bit(FLAG_REQUESTED, &desc->flags),
-				test_bit(FLAG_EXPORT, &desc->flags));
+	if (!test_bit(FLAG_REQUESTED, &desc->flags)) {
+		gpiod_dbg(desc, "%s: unavailable (not requested)\n", __func__);
 		status = -EPERM;
 		goto err_unlock;
 	}
-	spin_unlock_irqrestore(&gpio_lock, flags);
 
 	data = kzalloc(sizeof(*data), GFP_KERNEL);
 	if (!data) {
@@ -610,14 +620,14 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 
 	data->desc = desc;
 	mutex_init(&data->mutex);
-	if (chip->direction_input && chip->direction_output)
+	if (guard.gc->direction_input && guard.gc->direction_output)
 		data->direction_can_change = direction_may_change;
 	else
 		data->direction_can_change = false;
 
 	offset = gpio_chip_hwgpio(desc);
-	if (chip->names && chip->names[offset])
-		ioname = chip->names[offset];
+	if (guard.gc->names && guard.gc->names[offset])
+		ioname = guard.gc->names[offset];
 
 	dev = device_create_with_groups(&gpio_class, &gdev->dev,
 					MKDEV(0, 0), data, gpio_groups,
@@ -628,7 +638,6 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 		goto err_free_data;
 	}
 
-	set_bit(FLAG_EXPORT, &desc->flags);
 	mutex_unlock(&sysfs_lock);
 	return 0;
 
@@ -636,6 +645,7 @@ err_free_data:
 	kfree(data);
 err_unlock:
 	mutex_unlock(&sysfs_lock);
+	clear_bit(FLAG_EXPORT, &desc->flags);
 	gpiod_dbg(desc, "%s: status %d\n", __func__, status);
 	return status;
 }
@@ -732,7 +742,7 @@ EXPORT_SYMBOL_GPL(gpiod_unexport);
 
 int gpiochip_sysfs_register(struct gpio_device *gdev)
 {
-	struct gpio_chip *chip = gdev->chip;
+	struct gpio_chip *chip;
 	struct device *parent;
 	struct device *dev;
 
@@ -745,6 +755,12 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 	if (!class_is_registered(&gpio_class))
 		return 0;
 
+	guard(srcu)(&gdev->srcu);
+
+	chip = srcu_dereference(gdev->chip, &gdev->srcu);
+	if (!chip)
+		return -ENODEV;
+
 	/*
 	 * For sysfs backward compatibility we need to preserve this
 	 * preferred parenting to the gpio_chip parent field, if set.
@@ -755,7 +771,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 		parent = &gdev->dev;
 
 	/* use chip->base for the ID; it's already known to be unique */
-	dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), chip,
+	dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), gdev,
 					gpiochip_groups, GPIOCHIP_NAME "%d",
 					chip->base);
 	if (IS_ERR(dev))
@@ -771,17 +787,23 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 {
 	struct gpio_desc *desc;
-	struct gpio_chip *chip = gdev->chip;
+	struct gpio_chip *chip;
 
-	if (!gdev->mockdev)
-		return;
+	scoped_guard(mutex, &sysfs_lock) {
+		if (!gdev->mockdev)
+			return;
 
-	device_unregister(gdev->mockdev);
+		device_unregister(gdev->mockdev);
 
-	/* prevent further gpiod exports */
-	mutex_lock(&sysfs_lock);
-	gdev->mockdev = NULL;
-	mutex_unlock(&sysfs_lock);
+		/* prevent further gpiod exports */
+		gdev->mockdev = NULL;
+	}
+
+	guard(srcu)(&gdev->srcu);
+
+	chip = srcu_dereference(gdev->chip, &gdev->srcu);
+	if (!chip)
+		return;
 
 	/* unregister gpiod class devices owned by sysfs */
 	for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS) {
@@ -790,11 +812,29 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 	}
 }
 
+/*
+ * We're not really looking for a device - we just want to iterate over the
+ * list and call this callback for each GPIO device. This is why this function
+ * always returns 0.
+ */
+static int gpiofind_sysfs_register(struct gpio_chip *gc, const void *data)
+{
+	struct gpio_device *gdev = gc->gpiodev;
+	int ret;
+
+	if (gdev->mockdev)
+		return 0;
+
+	ret = gpiochip_sysfs_register(gdev);
+	if (ret)
+		chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
+
+	return 0;
+}
+
 static int __init gpiolib_sysfs_init(void)
 {
-	int		status;
-	unsigned long	flags;
-	struct gpio_device *gdev;
+	int status;
 
 	status = class_register(&gpio_class);
 	if (status < 0)
@@ -806,26 +846,8 @@ static int __init gpiolib_sysfs_init(void)
 	 * We run before arch_initcall() so chip->dev nodes can have
 	 * registered, and so arch_initcall() can always gpiod_export().
 	 */
-	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(gdev, &gpio_devices, list) {
-		if (gdev->mockdev)
-			continue;
-
-		/*
-		 * TODO we yield gpio_lock here because
-		 * gpiochip_sysfs_register() acquires a mutex. This is unsafe
-		 * and needs to be fixed.
-		 *
-		 * Also it would be nice to use gpio_device_find() here so we
-		 * can keep gpio_chips local to gpiolib.c, but the yield of
-		 * gpio_lock prevents us from doing this.
-		 */
-		spin_unlock_irqrestore(&gpio_lock, flags);
-		status = gpiochip_sysfs_register(gdev);
-		spin_lock_irqsave(&gpio_lock, flags);
-	}
-	spin_unlock_irqrestore(&gpio_lock, flags);
+	(void)gpio_device_find(NULL, gpiofind_sysfs_register);
 
-	return status;
+	return 0;
 }
 postcore_initcall(gpiolib_sysfs_init);