acpi : acpi_bus_trim() stops removing devices when failing to remove the device

acpi_bus_trim() stops removing devices, when acpi_bus_remove() return error number. But acpi_bus_remove() cannot return error number correctly. acpi_bus_remove() only return -EINVAL, when dev argument is NULL. Thus even if device cannot be removed correctly, acpi_bus_trim() ignores and continues to remove devices. acpi_bus_hot_remove_device() uses acpi_bus_trim() for removing devices. Therefore acpi_bus_hot_remove_device() can send "_EJ0" to firmware, even if the device is running on the system. In this case, the system cannot work well.

Vasilis hit the bug at memory hotplug and reported it as follow:
https://lkml.org/lkml/2012/9/26/318

So acpi_bus_trim() should check whether device was removed or not correctly. The patch adds error check into some functions to remove the device.

Applying the patch, acpi_bus_trim() stops removing devices when failing to remove the device. But I think there is no impact with the exceptionof CPU and Memory hotplug path. Because other device also fails but the fail is an irregular case like device is NULL.

Signed-off-by Yasuaki Ishimatsu <[email protected]>

---
 drivers/acpi/scan.c    |   15 ++++++++++++---
 drivers/base/dd.c      |   22 +++++++++++++++++-----
 include/linux/device.h |    2 +-
 3 files changed, 30 insertions(+), 9 deletions(-)

Index: linux-3.6/drivers/acpi/scan.c
===================================================================

drivers/acpi/scan.c +1 -0

@@ -445,12 +445,17 @@ static int acpi_device_remove(struct dev
 {
 	struct acpi_device *acpi_dev = to_acpi_device(dev);
 	struct acpi_driver *acpi_drv = acpi_dev->driver;
+	int ret;

drivers/acpi/scan.c +7 -1

+				return ret;
+		}
 	}
 	acpi_dev->driver = NULL;
 	acpi_dev->driver_data = NULL;

@@ -1226,11 +1231,15 @@ static int acpi_device_set_context(struc
 
 static int acpi_bus_remove(struct acpi_device *dev, int rmdevice)
 {
+	int ret;
+
 	if (!dev)
 		return -EINVAL;
 
 	dev->removal_type = ACPI_BUS_REMOVAL_EJECT;
-	device_release_driver(&dev->dev);
+	ret = device_release_driver(&dev->dev);
+	if (ret)
+		return ret;
 
 	if (!rmdevice)
 		return 0;

Index: linux-3.6/drivers/base/dd.c
===================================================================

drivers/base/dd.c +17 -5

@@ -475,9 +475,10 @@ EXPORT_SYMBOL_GPL(driver_attach);
  * __device_release_driver() must be called with @dev lock held.
  * When called for a USB interface, @dev->parent lock must be held as well.
  */
-static void __device_release_driver(struct device *dev)
+static int __device_release_driver(struct device *dev)
 {
 	struct device_driver *drv;
+	int ret = 0;
 
 	drv = dev->driver;
 	if (drv) {

@@ -493,9 +494,11 @@ static void __device_release_driver(stru
 		pm_runtime_put_sync(dev);
 
 		if (dev->bus && dev->bus->remove)
-			dev->bus->remove(dev);
+			ret = dev->bus->remove(dev);
 		else if (drv->remove)
-			drv->remove(dev);
+			ret = drv->remove(dev);
+		if (ret)
+			goto rollback;
 		devres_release_all(dev);
 		dev->driver = NULL;
 		dev_set_drvdata(dev, NULL);

@@ -506,6 +509,12 @@ static void __device_release_driver(stru
 						     dev);
 
 	}
+
+	return ret;
+
+rollback:
+	driver_sysfs_add(dev);
+	return ret;
 }
 
 /**

@@ -515,16 +524,19 @@ static void __device_release_driver(stru
  * Manually detach device from driver.
  * When called for a USB interface, @dev->parent lock must be held.
  */
-void device_release_driver(struct device *dev)
+int device_release_driver(struct device *dev)
 {
+	int ret;
 	/*
 	 * If anyone calls device_release_driver() recursively from
 	 * within their ->remove callback for the same device, they
 	 * will deadlock right here.
 	 */
 	device_lock(dev);
-	__device_release_driver(dev);
+	ret = __device_release_driver(dev);
 	device_unlock(dev);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(device_release_driver);
 

Index: linux-3.6/include/linux/device.h
===================================================================

include/linux/device.h +1 -1

@@ -834,7 +834,7 @@ static inline void *dev_get_platdata(con
  * for information on use.
  */
 extern int __must_check device_bind_driver(struct device *dev);
-extern void device_release_driver(struct device *dev);
+extern int device_release_driver(struct device *dev);
 extern int  __must_check device_attach(struct device *dev);
 extern int __must_check driver_attach(struct device_driver *drv);
 extern int __must_check device_reprobe(struct device *dev);

Quoted 37 lines · Yasuaki Ishimatsu

acpi_bus_trim() stops removing devices, when acpi_bus_remove() return error number. But acpi_bus_remove() cannot return error number correctly. acpi_bus_remove() only return -EINVAL, when dev argument is NULL. Thus even if device cannot be removed correctly, acpi_bus_trim() ignores and continues to remove devices. acpi_bus_hot_remove_device() uses acpi_bus_trim() for removing devices. Therefore acpi_bus_hot_remove_device() can send "_EJ0" to firmware, even if the device is running on the system. In this case, the system cannot work well.

Vasilis hit the bug at memory hotplug and reported it as follow:
https://lkml.org/lkml/2012/9/26/318

So acpi_bus_trim() should check whether device was removed or not correctly. The patch adds error check into some functions to remove the device.

Applying the patch, acpi_bus_trim() stops removing devices when failing to remove the device. But I think there is no impact with the exceptionof CPU and Memory hotplug path. Because other device also fails but the fail is an irregular case like device is NULL.

Signed-off-by Yasuaki Ishimatsu <[email protected]>

---
  drivers/acpi/scan.c    |   15 ++++++++++++---
  drivers/base/dd.c      |   22 +++++++++++++++++-----
  include/linux/device.h |    2 +-
  3 files changed, 30 insertions(+), 9 deletions(-)

Index: linux-3.6/drivers/acpi/scan.c
===================================================================

drivers/acpi/scan.c +1 -0

@@ -445,12 +445,17 @@ static int acpi_device_remove(struct dev
  {
  	struct acpi_device *acpi_dev = to_acpi_device(dev);
  	struct acpi_driver *acpi_drv = acpi_dev->driver;
+	int ret;

drivers/acpi/scan.c static int acpi_device_remove(struct dev · line 456

Quoted 10 lines

drivers/acpi/scan.c +4 -2

 
  	if (acpi_drv) {
  		if (acpi_drv->ops.notify)
  			acpi_device_remove_notify_handler(acpi_dev);
-		if (acpi_drv->ops.remove)
-			acpi_drv->ops.remove(acpi_dev, acpi_dev->removal_type);
+		if (acpi_drv->ops.remove) {
+			ret = acpi_drv->ops.remove(acpi_dev,
+						   acpi_dev->removal_type);
+			if (ret)

Hi Yasuaki,

Shouldn't the notify handler be reinstalled here if it was removed by the acpi_device_remove_notify_handler() above?

Thanks,
-Toshi

Quoted 101 lines

drivers/acpi/scan.c +7 -1

+				return ret;
+		}
  	}
  	acpi_dev->driver = NULL;
  	acpi_dev->driver_data = NULL;

@@ -1226,11 +1231,15 @@ static int acpi_device_set_context(struc
 
  static int acpi_bus_remove(struct acpi_device *dev, int rmdevice)
  {
+	int ret;
+
  	if (!dev)
  		return -EINVAL;
 
  	dev->removal_type = ACPI_BUS_REMOVAL_EJECT;
-	device_release_driver(&dev->dev);
+	ret = device_release_driver(&dev->dev);
+	if (ret)
+		return ret;
 
  	if (!rmdevice)
  		return 0;

Index: linux-3.6/drivers/base/dd.c
===================================================================

drivers/base/dd.c +17 -5

@@ -475,9 +475,10 @@ EXPORT_SYMBOL_GPL(driver_attach);
   * __device_release_driver() must be called with @dev lock held.
   * When called for a USB interface, @dev->parent lock must be held as well.
   */
-static void __device_release_driver(struct device *dev)
+static int __device_release_driver(struct device *dev)
  {
  	struct device_driver *drv;
+	int ret = 0;
 
  	drv = dev->driver;
  	if (drv) {

@@ -493,9 +494,11 @@ static void __device_release_driver(stru
  		pm_runtime_put_sync(dev);
 
  		if (dev->bus && dev->bus->remove)
-			dev->bus->remove(dev);
+			ret = dev->bus->remove(dev);
  		else if (drv->remove)
-			drv->remove(dev);
+			ret = drv->remove(dev);
+		if (ret)
+			goto rollback;
  		devres_release_all(dev);
  		dev->driver = NULL;
  		dev_set_drvdata(dev, NULL);

@@ -506,6 +509,12 @@ static void __device_release_driver(stru
  						     dev);
 
  	}
+
+	return ret;
+
+rollback:
+	driver_sysfs_add(dev);
+	return ret;
  }
 
  /**

@@ -515,16 +524,19 @@ static void __device_release_driver(stru
   * Manually detach device from driver.
   * When called for a USB interface, @dev->parent lock must be held.
   */
-void device_release_driver(struct device *dev)
+int device_release_driver(struct device *dev)
  {
+	int ret;
  	/*
  	 * If anyone calls device_release_driver() recursively from
  	 * within their ->remove callback for the same device, they
  	 * will deadlock right here.
  	 */
  	device_lock(dev);
-	__device_release_driver(dev);
+	ret = __device_release_driver(dev);
  	device_unlock(dev);
+
+	return ret;
  }
  EXPORT_SYMBOL_GPL(device_release_driver);
 

Index: linux-3.6/include/linux/device.h
===================================================================

include/linux/device.h +1 -1

@@ -834,7 +834,7 @@ static inline void *dev_get_platdata(con
   * for information on use.
   */
  extern int __must_check device_bind_driver(struct device *dev);
-extern void device_release_driver(struct device *dev);
+extern int device_release_driver(struct device *dev);
  extern int  __must_check device_attach(struct device *dev);
  extern int __must_check driver_attach(struct device_driver *drv);
  extern int __must_check device_reprobe(struct device *dev);

Quoted 3 lines

Quoted 3 lines

  	if (acpi_drv) {
  		if (acpi_drv->ops.notify)
  			acpi_device_remove_notify_handler(acpi_dev);

Quoted 9 lines

drivers/acpi/scan.c static int acpi_device_remove(struct dev · line 456

Quoted 6 lines

drivers/acpi/scan.c +4 -2

-		if (acpi_drv->ops.remove)
-			acpi_drv->ops.remove(acpi_dev, acpi_dev->removal_type);
+		if (acpi_drv->ops.remove) {
+			ret = acpi_drv->ops.remove(acpi_dev,
+						   acpi_dev->removal_type);
+			if (ret)

Hi Yasuaki,

Quoted 2 lines

Shouldn't the notify handler be reinstalled here if it was removed by the acpi_device_remove_notify_handler() above?

I do not reinstall the notify handler.
The function has not been removed on linux-3.6. And the patch is created on linux-3.6. So the function remains in the patch.

On Wed, 2012-10-10 at 10:07 +0900, Yasuaki Ishimatsu wrote:
:

Quoted 3 lines

Quoted 3 lines

Quoted 3 lines

   	if (acpi_drv) {
   		if (acpi_drv->ops.notify)
   			acpi_device_remove_notify_handler(acpi_dev);

THIS CALL

Quoted 9 lines

Quoted 9 lines

drivers/acpi/scan.c static int acpi_device_remove(struct dev · line 456

Quoted 6 lines

drivers/acpi/scan.c +4 -2

-		if (acpi_drv->ops.remove)
-			acpi_drv->ops.remove(acpi_dev, acpi_dev->removal_type);
+		if (acpi_drv->ops.remove) {
+			ret = acpi_drv->ops.remove(acpi_dev,
+						   acpi_dev->removal_type);
+			if (ret)

Hi Yasuaki,

Quoted 6 lines

Quoted 2 lines

Shouldn't the notify handler be reinstalled here if it was removed by the acpi_device_remove_notify_handler() above?

I do not reinstall the notify handler.
The function has not been removed on linux-3.6. And the patch is created on linux-3.6. So the function remains in the patch.

Umm... I am not sure what you meant. Let me clarify my comment. When acpi_drv->ops.remove() failed, I thought we would need to roll-back the procedure done by the acpi_device_remove_notify_handler() call, which I indicated as "THIS CALL" above. So, in this error path, don't we need something like below?

if (acpi_drv->ops.notify)
acpi_device_install_notify_handler(acpi_dev)

Thanks,
-Toshi