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

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Message-Id: <20070108202359.1e7a6670.akpm@osdl.org>
Date:	Mon, 8 Jan 2007 20:23:59 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Greg KH <greg@...ah.com>, Kay Sievers <kay.sievers@...ell.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Driver core: fix refcounting bug

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?

More importantly: does 2.6.20-rc4 need fixing?
-
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