[PATCH] kset: make ksets have a spinlock, and use that to lock their lists

Do this instead of using the rwsem of a subsys.
Smaller, faster, and I'm trying to get rid of the rwsem in the subsys.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/kobject.h

@@ -20,6 +20,7 @@
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/sysfs.h>
+#include <linux/spinlock.h>
 #include <linux/rwsem.h>
 #include <linux/kref.h>
 #include <linux/kobject_uevent.h>
@@ -102,6 +103,7 @@ struct kset {
 	struct subsystem	* subsys;
 	struct kobj_type	* ktype;
 	struct list_head	list;
+	spinlock_t		list_lock;
 	struct kobject		kobj;
 	struct kset_hotplug_ops	* hotplug_ops;
 };

lib/kobject.c

@@ -140,9 +140,9 @@ void kobject_init(struct kobject * kobj)
 static void unlink(struct kobject * kobj)
 {
 	if (kobj->kset) {
-		down_write(&kobj->kset->subsys->rwsem);
+		spin_lock(&kobj->kset->list_lock);
 		list_del_init(&kobj->entry);
-		up_write(&kobj->kset->subsys->rwsem);
+		spin_unlock(&kobj->kset->list_lock);
 	}
 	kobject_put(kobj);
 }
@@ -168,13 +168,13 @@ int kobject_add(struct kobject * kobj)
 		 kobj->kset ? kobj->kset->kobj.name : "<NULL>" );
 
 	if (kobj->kset) {
-		down_write(&kobj->kset->subsys->rwsem);
+		spin_lock(&kobj->kset->list_lock);
 
 		if (!parent)
 			parent = kobject_get(&kobj->kset->kobj);
 
 		list_add_tail(&kobj->entry,&kobj->kset->list);
-		up_write(&kobj->kset->subsys->rwsem);
+		spin_unlock(&kobj->kset->list_lock);
 	}
 	kobj->parent = parent;
 
@@ -380,6 +380,7 @@ void kset_init(struct kset * k)
 {
 	kobject_init(&k->kobj);
 	INIT_LIST_HEAD(&k->list);
+	spin_lock_init(&k->list_lock);
 }
 
 
@@ -444,7 +445,7 @@ struct kobject * kset_find_obj(struct kset * kset, const char * name)
 	struct list_head * entry;
 	struct kobject * ret = NULL;
 
-	down_read(&kset->subsys->rwsem);
+	spin_lock(&kset->list_lock);
 	list_for_each(entry,&kset->list) {
 		struct kobject * k = to_kobj(entry);
 		if (kobject_name(k) && !strcmp(kobject_name(k),name)) {
@@ -452,7 +453,7 @@ struct kobject * kset_find_obj(struct kset * kset, const char * name)
 			break;
 		}
 	}
-	up_read(&kset->subsys->rwsem);
+	spin_unlock(&kset->list_lock);
 	return ret;
 }