On Wed, 2007-03-07 at 06:39 +0100, Mike Galbraith wrote:
> On Tue, 2007-03-06 at 13:04 -0800, Greg KH wrote:
> > On Tue, Mar 06, 2007 at 06:43:22AM +0100, Mike Galbraith wrote:
> > > On Mon, 2007-03-05 at 16:25 -0800, Greg KH wrote:
> > > 
> > > > Mike, I've reverted this patch, and I don't see any references leaking.
> > > > And, as your patch released the reference on the driver, and the
> > > > module_add_driver() call would not grab a reference to the driver, only
> > > > the module kobject, I don't see what you were trying to fix with this
> > > > patch.
> > > > 
> > > > Do you have a test case that this fixes?
> > > 
> > > What it fixed for me was the hard hang reported below.
> > > 
> > > http://lkml.org/lkml/2007/2/16/96
> > 
> > What specific module are you trying to unload that causes the hang?  I
> > think it might just be a problem with that module, and not with all
> > others.
> 
> It's ipmi_si that's hanging, waits for completion that never comes.
> 
> > So, I'm going to revert your patch and work to try to find the real
> > cause of this problem.
> 
> Yeah, my stab at it seems busted.  I'll take another poke at it to see
> if I can find out why (post 725522b5453dd680412f2b6463a988e4fd148757)
> I'm left with a reference.

Ok, stab #2.

My reference count woes stem from module_remove_driver() not removing
the link created in module_add_driver().  With the below, my box boots
fine.  Since I obviously know spit about driver layer glue, I'll just
call this one a diagnostic, and head for the hills :)

--- linux-2.6.20-rc3/kernel/module.c.org        2007-03-10 15:16:47.000000000 
+0100
+++ linux-2.6.20-rc3/kernel/module.c    2007-03-10 15:43:09.000000000 +0100
@@ -2411,14 +2411,28 @@ void module_remove_driver(struct device_
                return;
 
        sysfs_remove_link(&drv->kobj, "module");
-       if (drv->owner && drv->owner->mkobj.drivers_dir) {
-               driver_name = make_driver_name(drv);
-               if (driver_name) {
-                       sysfs_remove_link(drv->owner->mkobj.drivers_dir,
+       driver_name = make_driver_name(drv);
+       if (!driver_name)
+               return;
+       if (drv->owner && drv->owner->mkobj.drivers_dir)
+               sysfs_remove_link(drv->owner->mkobj.drivers_dir,
                                          driver_name);
-                       kfree(driver_name);
-               }
+       else if (drv->mod_name) {
+               struct module_kobject *mk;
+               struct kobject *mkobj;
+
+               /* Lookup built-in module entry in /sys/modules */
+               mkobj = kset_find_obj(&module_subsys.kset, drv->mod_name);
+               if (!mkobj)
+                       goto out_free;
+               mk = container_of(mkobj, struct module_kobject, kobj);
+               module_create_drivers_dir(mk);
+               sysfs_remove_link(mk->drivers_dir, driver_name);
+               /* Release reference taken via lookup */
+               kobject_put(mkobj);
        }
+out_free:
+       kfree(driver_name);
 }
 EXPORT_SYMBOL(module_remove_driver);
 #endif


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