linux-kernel - Re: BUG in: Driver core: convert block from raw kobjects to core devices

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Date:	Fri, 19 Oct 2007 10:09:48 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Kay Sievers <kay.sievers@...y.org>
cc:	Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: BUG in: Driver core: convert block from raw kobjects to core
 devices

On Fri, 19 Oct 2007, Kay Sievers wrote:

> > This accounts for everything in del_gendisk except the final
> > put_device.  Evidently it doesn't belong there.  There's no matching 
> > get_device in add_disk or register_disk.
> 
> Hmm, do you have kobject debugging enabled? Do you ever see something
> like: "kobject sdb: cleaning up" when you remove the put_device()?

I didn't enable kobject debugging, but I did put a printk statement in
drivers/scsi/sd.c:scsi_disk_release(), which is the release routine for
the scsi_disk structure.  It does the final put_disk() call -- or at 
least, this is _supposed_ to be the final call.

With my patch, just before the call to put_disk the value of 
disk->dev.kobj.kref.refcount is 1.  Without my patch, the value is 
garbage (probably a slab poison value, but I printed it in decimal 
rather than hex so I can't be sure).

Don't you have a USB storage device?  It should be easy for you to test 
this on your own system.

Alan Stern

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