class: change internal semaphore to a mutex

Now that the lockdep infrastructure in the class core is in place, we
should be able to properly change the internal class semaphore to be a
mutex.

David wrote the original patch, and Greg fixed it up to apply properly
due to all of the recent changes in this area.

From: Dave Young <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Kay Sievers <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: James Bottomley <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/base.h

···
  * @class_devices - list of devices associated with this class
  * @class_interfaces - list of class_interfaces associated with this class
  * @class_dirs - "glue" directory for virtual devices associated with this class
- * @class_sem - semaphore to protect the children, devices, and interfaces lists.
+ * @class_mutex - mutex to protect the children, devices, and interfaces lists.
  * @class - pointer back to the struct class that this structure is associated
  * with.
  *
···
 	struct list_head class_devices;
 	struct list_head class_interfaces;
 	struct kset class_dirs;
-	struct semaphore class_sem;
+	struct mutex class_mutex;
 	struct class *class;
 };
 #define to_class(obj)	\

drivers/base/class.c

···
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/genhd.h>
+#include <linux/mutex.h>
 #include "base.h"
 
 #define to_class_attr(_attr) container_of(_attr, struct class_attribute, attr)
···
 	INIT_LIST_HEAD(&cp->class_devices);
 	INIT_LIST_HEAD(&cp->class_interfaces);
 	kset_init(&cp->class_dirs);
-	init_MUTEX(&cp->class_sem);
+	__mutex_init(&cp->class_mutex, "struct class mutex", key);
 	error = kobject_set_name(&cp->class_subsys.kobj, "%s", cls->name);
 	if (error) {
 		kfree(cp);
···
  * We check the return of @fn each time. If it returns anything
  * other than 0, we break out and return that value.
  *
- * Note, we hold class->class_sem in this function, so it can not be
+ * Note, we hold class->class_mutex in this function, so it can not be
  * re-acquired in @fn, otherwise it will self-deadlocking. For
  * example, calls to add or remove class members would be verboten.
  */
···
 
 	if (!class)
 		return -EINVAL;
-	down(&class->p->class_sem);
+	mutex_lock(&class->p->class_mutex);
 	list_for_each_entry(dev, &class->p->class_devices, node) {
 		if (start) {
 			if (start == dev)
···
 		if (error)
 			break;
 	}
-	up(&class->p->class_sem);
+	mutex_unlock(&class->p->class_mutex);
 
 	return error;
 }
···
  *
  * Note, you will need to drop the reference with put_device() after use.
  *
- * We hold class->class_sem in this function, so it can not be
+ * We hold class->class_mutex in this function, so it can not be
  * re-acquired in @match, otherwise it will self-deadlocking. For
  * example, calls to add or remove class members would be verboten.
  */
···
 	if (!class)
 		return NULL;
 
-	down(&class->p->class_sem);
+	mutex_lock(&class->p->class_mutex);
 	list_for_each_entry(dev, &class->p->class_devices, node) {
 		if (start) {
 			if (start == dev)
···
 		} else
 			put_device(dev);
 	}
-	up(&class->p->class_sem);
+	mutex_unlock(&class->p->class_mutex);
 
 	return found ? dev : NULL;
 }
···
 	if (!parent)
 		return -EINVAL;
 
-	down(&parent->p->class_sem);
+	mutex_lock(&parent->p->class_mutex);
 	list_add_tail(&class_intf->node, &parent->p->class_interfaces);
 	if (class_intf->add_dev) {
 		list_for_each_entry(dev, &parent->p->class_devices, node)
 			class_intf->add_dev(dev, class_intf);
 	}
-	up(&parent->p->class_sem);
+	mutex_unlock(&parent->p->class_mutex);
 
 	return 0;
 }
···
 	if (!parent)
 		return;
 
-	down(&parent->p->class_sem);
+	mutex_lock(&parent->p->class_mutex);
 	list_del_init(&class_intf->node);
 	if (class_intf->remove_dev) {
 		list_for_each_entry(dev, &parent->p->class_devices, node)
 			class_intf->remove_dev(dev, class_intf);
 	}
-	up(&parent->p->class_sem);
+	mutex_unlock(&parent->p->class_mutex);
 
 	class_put(parent);
 }

drivers/base/core.c

···
 #include <linux/genhd.h>
 #include <linux/kallsyms.h>
 #include <linux/semaphore.h>
+#include <linux/mutex.h>
 
 #include "base.h"
 #include "power/power.h"
···
 		klist_add_tail(&dev->knode_parent, &parent->klist_children);
 
 	if (dev->class) {
-		down(&dev->class->p->class_sem);
+		mutex_lock(&dev->class->p->class_mutex);
 		/* tie the class to the device */
 		list_add_tail(&dev->node, &dev->class->p->class_devices);
 
···
 				    &dev->class->p->class_interfaces, node)
 			if (class_intf->add_dev)
 				class_intf->add_dev(dev, class_intf);
-		up(&dev->class->p->class_sem);
+		mutex_unlock(&dev->class->p->class_mutex);
 	}
  Done:
 	put_device(dev);
···
 	if (dev->class) {
 		device_remove_class_symlinks(dev);
 
-		down(&dev->class->p->class_sem);
+		mutex_lock(&dev->class->p->class_mutex);
 		/* notify any interfaces that the device is now gone */
 		list_for_each_entry(class_intf,
 				    &dev->class->p->class_interfaces, node)
···
 				class_intf->remove_dev(dev, class_intf);
 		/* remove the device from the class list */
 		list_del_init(&dev->node);
-		up(&dev->class->p->class_sem);
+		mutex_unlock(&dev->class->p->class_mutex);
 	}
 	device_remove_file(dev, &uevent_attr);
 	device_remove_attrs(dev);