Re: [PATCH] Driver core: fix refcounting bug

Andrew Morton
2007-01-09T04:24:07Z

On Mon, 8 Jan 2007 11:06:44 -0500 (EST)
Alan Stern <stern@rowland.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@rowland.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?

More importantly: does 2.6.20-rc4 need fixing?