linux-kernel - Re: [Patch -mm 0/3] RFC: module unloading vs. release function

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Date:	Mon, 16 Apr 2007 11:47:16 -0700
From:	Greg KH <greg@...ah.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Tejun Heo <htejun@...il.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [Patch -mm 0/3] RFC: module unloading vs. release function

On Mon, Apr 16, 2007 at 02:30:17PM -0400, Dmitry Torokhov wrote:
> On 4/16/07, Cornelia Huck <cornelia.huck@...ibm.com> wrote:
> >Hi,
> >
> >based on the discussion in "How should an exit routine wait for
> >release() callbacks?", I've cooked up some patches that make module
> >unload wait until the last reference for a kobject has been dropped.
> >This should plug the "release function in already deleted module" race;
> >however, if the last kobject_put() from the module containing the
> >release function is not in the module's exit function, there's still a
> >small window (not sure if and how to plug this).
> 
> Unfortunately all this "wait for refcount in module's exit" schemas
> lead to the following deadlock:
> 
>        rmmod my_module < /path/to/some/file/incrementing/my/refcount

No, it should just return "module in use" as the reference count it
grabbed before rmmod is called.

But either way, that's just foolish to try to prevent that from failing
:)

thanks,

greg k-h
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