kobject - expose backend helpers to registration interface.

The interface should now be more sane and protect against races better. 

kobject_register() was split into two helpers: kobject_init() and kobject_add().
It calls both consecutively, though both are also exposed for use by users
that want to use the objects w/o adding them to the object hierarchy. 

kobject_unregister() was made simply a wrapper for kobject_del() and 
kobject_put(), which are both also exposed. The guts of kobject_put() was
moved into kobject_cleanup(), which it calls when the reference count hits
0. (This was done for clarity).

The infrastructure now takes a lot in kobject_get() and kobject_put() when
checking and modifying the objects' reference counts. This was an obvious
one that hsould have been fixed long ago. 

kobject_add() increments the refcount of the object, which is decremented
when kobject_del() is called. This guarantees that the object's memory
cannot be freed if it has been added to the hierarchy, and kobject_del() 
has not been called on it. 

kobject_init() is now the function that increments the refcount on the 
object's subsystem, which is decremented only after its release() method
has been called for the object in kobject_cleanup(). 

The documentation has been updated to reflect these changes. 

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index 40de16d0a227..7b3157a78f7e 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -24,6 +24,10 @@ struct kobject {
 };
 
 extern void kobject_init(struct kobject *);
+extern void kobject_cleanup(struct kobject *);
+
+extern int kobject_add(struct kobject *);
+extern void kobject_del(struct kobject *);
 
 extern int kobject_register(struct kobject *);
 extern void kobject_unregister(struct kobject *);