linux-kernel - Re: Incorrect uses of get_driver()/put

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Message-ID: <20120109181449.GF15083@core.coreip.homeip.net>
Date:	Mon, 9 Jan 2012 10:14:49 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Michael Büsch <m@...s.ch>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Joerg Roedel <joerg.roedel@....com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Incorrect uses of get_driver()/put_driver()

On Mon, Jan 09, 2012 at 07:03:21PM +0100, Michael Büsch wrote:
> On Mon, 9 Jan 2012 12:35:09 -0500 (EST)
> Alan Stern <stern@...land.harvard.edu> wrote:
> 
> > drivers/ssb/main.c:146:               get_driver(&drv->drv);
> > drivers/ssb/main.c:153:               put_driver(&drv->drv);
> > 
> > Michael, these are part of ssb_driver_get() and ssb_driver_put(), used
> > in ssb_devices_freeze() and ssb_devices_thaw().  They don't currently
> > do anything, but it looks as if they are meant to prevent the driver
> > from being unloaded.  Should they be replaced with try_module_get()?  
> > Or would it be good enough to call device_attach() in 
> > ssb_devices_thaw()?
> 
> Hm, It seems that this code is trying to pin the ssb_driver, so that
> it doesn't become invalid during the freeze period. So it most likely wants
> to protect against module unload and driver unbind here. Not sure
> if that actually works, though :/
> 

Not at all ;)

-- 
Dmitry
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