linux-kernel - Re: [PATCH] Driver core: fix refcounting bug

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Date:	Mon, 8 Jan 2007 23:13:21 -0800
From:	Greg KH <greg@...ah.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Kay Sievers <kay.sievers@...ell.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Driver core: fix refcounting bug

On Mon, Jan 08, 2007 at 08:23:59PM -0800, Andrew Morton wrote:
> On Mon, 8 Jan 2007 11:06:44 -0500 (EST)
> Alan Stern <stern@...land.harvard.edu> wrote:
> 
> > This patch (as832) fixes a newly-introduced bug in the driver core.
> > When a kobject is assigned to a kset, it must acquire a reference to
> > the kset.
> > 
> > Signed-off-by: Alan Stern <stern@...land.harvard.edu>
> > 
> > ---
> > 
> > The bug was introduced in Kay's "unify /sys/class and /sys/bus at 
> > /sys/subsystem" patch.
> > 
> > I left the assignment of class_dev->kobj.parent as it was, although it is 
> > not needed.  The following call to kobject_add() will end up doing the 
> > same thing.
> > 
> > Alan Stern
> > 
> > P.S.: Tracking down refcounting bugs is a real pain!  I spent an entire 
> > afternoon on this one...  :-(
> > 
> > 
> > Index: usb-2.6/drivers/base/class.c
> > ===================================================================
> > --- usb-2.6.orig/drivers/base/class.c
> > +++ usb-2.6/drivers/base/class.c
> > @@ -648,7 +648,7 @@ int class_device_add(struct class_device
> >  		class_dev->kobj.parent = &parent_class_dev->kobj;
> >  	else {
> >  		/* assign parent kset for uevent hook */
> > -		class_dev->kobj.kset = &parent_class->devices_dir;
> > +		class_dev->kobj.kset = kset_get(&parent_class->devices_dir);
> >  		/* the device directory in /sys/subsystem/<name>/devices */
> >  		class_dev->kobj.parent = &parent_class->devices_dir.kobj;
> >  	}
> 
> OK, I give up.  What kernel is this against?

I think this is against my private tree, with the "driver-class" patches
that are not in -mm (for good reason at this point in time.)  Right
Alan?

thanks,

greg k-h
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