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Date: Mon, 10 Mar 2003 17:15:32 -0800
From: Greg KH <greg@kroah.com>
To: Roman Zippel <zippel@linux-m68k.org>
Cc: Oliver Neukum <oliver@neukum.name>,
       Linux Kernel List <linux-kernel@vger.kernel.org>,
       Patrick Mochel <mochel@osdl.org>,
       Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
       Jeff Garzik <jgarzik@pobox.com>, Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: PCI driver module unload race?
Message-ID: <20030311011532.GH13145@kroah.com>
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On Tue, Mar 11, 2003 at 02:04:20AM +0100, Roman Zippel wrote:
> On Mon, 10 Mar 2003, Greg KH wrote:
> 
> > > It seems that the semaphore in bus_add_device() makes this unnecessary.
> > 
> > Hm, yes.  I think you are correct.
> > 
> > So this patch is not needed, and the struct module * can be ripped out
> > of struct usb_driver too :)
> 
> I think it's not easy. I haven't studied the code completely yet, but e.g. 
> when you attach a device to a driver you also have to get a reference to 
> the driver.

You get a link to the driver, but you can't increment the module count
of the driver at that time, as we have to be able to remove a module
somehow :)

> I think there are more interesting races, e.g. when you create a sysfs 
> symlink, that symlink might also have references to a module.

Yeah, I still think there are some nasty issues with regards to being in
a sysfs directory, with a open file handle, and the module is removed.
But I haven't checked stuff like that in a while.

CONFIG_MODULE_UNLOAD, just say no.

thanks,

greg k-h
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