From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Date: Tue, 22 Jan 2019 10:39:16 -0800
Subject: device core: Consolidate locking and unlocking of parent and device
Patch-Mainline: 5.1-rc1
References: bsc#1106383
Git-commit: ed88747c6c4a2fc2f961a36d4c50cb0868c30229

Try to consolidate all of the locking and unlocking of both the parent and
device when attaching or removing a driver from a given device.

To do that I first consolidated the lock pattern into two functions
__device_driver_lock and __device_driver_unlock. After doing that I then
created functions specific to attaching and detaching the driver while
acquiring these locks. By doing this I was able to reduce the number of
spots where we touch need_parent_lock from 12 down to 4.

This patch should produce no functional changes, it is meant to be a code
clean-up/consolidation only.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/base/base.h |  2 ++
 drivers/base/bus.c  | 23 +++----------
 drivers/base/dd.c   | 95 ++++++++++++++++++++++++++++++++++++++++++-----------
 3 files changed, 81 insertions(+), 39 deletions(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index e3e9c5dca982..d13cb25d94ea 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -134,6 +134,8 @@ extern int device_add_groups(struct device *dev,
 			     const struct attribute_group **groups);
 extern void device_remove_groups(struct device *dev,
 				 const struct attribute_group **groups);
+int device_driver_attach(struct device_driver *drv, struct device *dev);
+void device_driver_detach(struct device *dev);
 
 extern char *make_class_name(const char *name, struct kobject *kobj);
 
diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index a7ae9a0e8a78..d1770c96f944 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -189,11 +189,7 @@ static ssize_t unbind_store(struct device_driver *drv, const char *buf,
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
 	if (dev && dev->driver == drv) {
-		if (dev->parent)	/* Needed for USB */
-			device_lock(dev->parent);
-		device_release_driver(dev);
-		if (dev->parent)
-			device_unlock(dev->parent);
+		device_driver_detach(dev);
 		err = count;
 	}
 	put_device(dev);
@@ -216,13 +212,7 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
 
 	dev = bus_find_device_by_name(bus, NULL, buf);
 	if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
-		if (dev->parent)	/* Needed for USB */
-			device_lock(dev->parent);
-		device_lock(dev);
-		err = driver_probe_device(drv, dev);
-		device_unlock(dev);
-		if (dev->parent)
-			device_unlock(dev->parent);
+		err = device_driver_attach(drv, dev);
 
 		if (err > 0) {
 			/* success */
@@ -812,13 +802,8 @@ EXPORT_SYMBOL_GPL(bus_rescan_devices);
  */
 int device_reprobe(struct device *dev)
 {
-	if (dev->driver) {
-		if (dev->parent)        /* Needed for USB */
-			device_lock(dev->parent);
-		device_release_driver(dev);
-		if (dev->parent)
-			device_unlock(dev->parent);
-	}
+	if (dev->driver)
+		device_driver_detach(dev);
 	return bus_rescan_devices_helper(dev, NULL);
 }
 EXPORT_SYMBOL_GPL(device_reprobe);
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 7c66f1b3e3fc..56ed47aac0ea 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -729,6 +729,64 @@ void device_initial_probe(struct device *dev)
 	__device_attach(dev, true);
 }
 
+/*
+ * __device_driver_lock - acquire locks needed to manipulate dev->drv
+ * @dev: Device we will update driver info for
+ * @parent: Parent device. Needed if the bus requires parent lock
+ *
+ * This function will take the required locks for manipulating dev->drv.
+ * Normally this will just be the @dev lock, but when called for a USB
+ * interface, @parent lock will be held as well.
+ */
+static void __device_driver_lock(struct device *dev, struct device *parent)
+{
+	if (parent)
+		device_lock(parent);
+	device_lock(dev);
+}
+
+/*
+ * __device_driver_unlock - release locks needed to manipulate dev->drv
+ * @dev: Device we will update driver info for
+ * @parent: Parent device. Needed if the bus requires parent lock
+ *
+ * This function will release the required locks for manipulating dev->drv.
+ * Normally this will just be the the @dev lock, but when called for a
+ * USB interface, @parent lock will be released as well.
+ */
+static void __device_driver_unlock(struct device *dev, struct device *parent)
+{
+	device_unlock(dev);
+	if (parent)
+		device_unlock(parent);
+}
+
+/**
+ * device_driver_attach - attach a specific driver to a specific device
+ * @drv: Driver to attach
+ * @dev: Device to attach it to
+ *
+ * Manually attach driver to a device. Will acquire both @dev lock and
+ * @dev->parent lock if needed.
+ */
+int device_driver_attach(struct device_driver *drv, struct device *dev)
+{
+	int ret = 0;
+
+	__device_driver_lock(dev, dev->parent);
+
+	/*
+	 * If device has been removed or someone has already successfully
+	 * bound a driver before us just skip the driver probe call.
+	 */
+	if (!dev->p->dead && !dev->driver)
+		ret = driver_probe_device(drv, dev);
+
+	__device_driver_unlock(dev, dev->parent);
+
+	return ret;
+}
+
 static int __driver_attach(struct device *dev, void *data)
 {
 	struct device_driver *drv = data;
@@ -756,14 +814,7 @@ static int __driver_attach(struct device *dev, void *data)
 		return ret;
 	} /* ret > 0 means positive match */
 
-	if (dev->parent)	/* Needed for USB */
-		device_lock(dev->parent);
-	device_lock(dev);
-	if (!dev->p->dead && !dev->driver)
-		driver_probe_device(drv, dev);
-	device_unlock(dev);
-	if (dev->parent)
-		device_unlock(dev->parent);
+	device_driver_attach(drv, dev);
 
 	return 0;
 }
@@ -794,15 +845,11 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 	drv = dev->driver;
 	if (drv) {
 		while (device_links_busy(dev)) {
-			device_unlock(dev);
-			if (parent)
-				device_unlock(parent);
+			__device_driver_unlock(dev, parent);
 
 			device_links_unbind_consumers(dev);
-			if (parent)
-				device_lock(parent);
 
-			device_lock(dev);
+			__device_driver_lock(dev, parent);
 			/*
 			 * A concurrent invocation of the same function might
 			 * have released the driver successfully while this one
@@ -852,16 +899,12 @@ void device_release_driver_internal(struct device *dev,
 				    struct device_driver *drv,
 				    struct device *parent)
 {
-	if (parent)
-		device_lock(parent);
+	__device_driver_lock(dev, parent);
 
-	device_lock(dev);
 	if (!drv || drv == dev->driver)
 		__device_release_driver(dev, parent);
 
-	device_unlock(dev);
-	if (parent)
-		device_unlock(parent);
+	__device_driver_unlock(dev, parent);
 }
 
 /**
@@ -886,6 +929,18 @@ void device_release_driver(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(device_release_driver);
 
+/**
+ * device_driver_detach - detach driver from a specific device
+ * @dev: device to detach driver from
+ *
+ * Detach driver from device. Will acquire both @dev lock and @dev->parent
+ * lock if needed.
+ */
+void device_driver_detach(struct device *dev)
+{
+	device_release_driver_internal(dev, NULL, dev->parent);
+}
+
 /**
  * driver_detach - detach driver from all devices it controls.
  * @drv: driver.
-- 
2.16.4