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 <hidave.darkstar@gmail.com>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 19 insertions, 17 deletions

diff --git a/drivers/base/base.h b/drivers/base/base.h
index c035dc23266a..31dc0cd84afa 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -44,7 +44,7 @@ struct driver_private {
  * @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.
  *
@@ -57,7 +57,7 @@ struct class_private {
         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)   \
diff --git a/drivers/base/class.c b/drivers/base/class.c
index 89000566690c..839d27cecb36 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -18,6 +18,7 @@
 #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)
@@ -147,7 +148,7 @@ int __class_register(struct class *cls, struct lock_class_key *key)
         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);
@@ -281,7 +282,7 @@ char *make_class_name(const char *name, struct kobject *kobj)
  * 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.
  */
@@ -293,7 +294,7 @@ int class_for_each_device(struct class *class, struct device *start,
 
         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)
@@ -306,7 +307,7 @@ int class_for_each_device(struct class *class, struct device *start,
                 if (error)
                         break;
         }
-        up(&class->p->class_sem);
+        mutex_unlock(&class->p->class_mutex);
 
         return error;
 }
@@ -329,7 +330,7 @@ EXPORT_SYMBOL_GPL(class_for_each_device);
  *
  * 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.
  */
@@ -343,7 +344,7 @@ struct device *class_find_device(struct class *class, struct device *start,
         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)
@@ -357,7 +358,7 @@ struct device *class_find_device(struct class *class, struct device *start,
                 } else
                         put_device(dev);
         }
-        up(&class->p->class_sem);
+        mutex_unlock(&class->p->class_mutex);
 
         return found ? dev : NULL;
 }
@@ -375,13 +376,13 @@ int class_interface_register(struct class_interface *class_intf)
         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;
 }
@@ -394,13 +395,13 @@ void class_interface_unregister(struct class_interface *class_intf)
         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);
 }
diff --git a/drivers/base/core.c b/drivers/base/core.c
index b90ae6f7be86..c05b1159023e 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -21,6 +21,7 @@
 #include <linux/genhd.h>
 #include <linux/kallsyms.h>
 #include <linux/semaphore.h>
+#include <linux/mutex.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -907,7 +908,7 @@ int device_add(struct device *dev)
                 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);
 
@@ -916,7 +917,7 @@ int device_add(struct device *dev)
                                     &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);
@@ -1017,7 +1018,7 @@ void device_del(struct 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)
@@ -1025,7 +1026,7 @@ void device_del(struct device *dev)
                                 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);