linux-kernel - Re: [Patch -mm 3/3] RFC: Introduce kobject->owner for refcounting.

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Date:	Tue, 17 Apr 2007 12:53:10 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Greg KH <greg@...ah.com>, Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Tejun Heo <htejun@...il.com>
Subject: Re: [Patch -mm 3/3] RFC: Introduce kobject->owner for refcounting.

On Mon, 2007-04-16 at 15:53 -0400, Alan Stern wrote:
> The fundamental rule is that whenever you hand out a pointer to a routine
> living in a module, the receiver has to increment the module's refcount.  
> But the driver core violates this rule all over the place.

Hi Alan,

	Your rule is overly simplistic, unfortunately.  You have two choices:
take a reference count, *or* ensure that the reference will go away when
the module's cleanup routine is called.  Network drivers are a classic
example of the latter.

	Note that you cannot do both: if the cleanup routine calls something
which drops a reference count, it implies that the cleanup routine needs
to be called with non-zero reference count, and it won't be (ignoring
--force).

I hope that clarifies?
Rusty.

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