From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from out3-smtp.messagingengine.com ([66.111.4.27]:60652 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754694Ab2AYAHB (ORCPT ); Tue, 24 Jan 2012 19:07:01 -0500 Received: from compute4.internal (compute4.nyi.mail.srv.osa [10.202.2.44]) by gateway1.nyi.mail.srv.osa (Postfix) with ESMTP id DD87320FC2 for ; Tue, 24 Jan 2012 19:06:59 -0500 (EST) Date: Tue, 24 Jan 2012 16:06:34 -0800 From: Greg KH To: Alan Stern Cc: Dmitry Torokhov , Kyungmin Park , Andy Walls , Martin Schwidefsky , Jiri Kosina , Jesse Barnes , Dominik Brodowski , Sebastian Ott , "David S. Miller" , Konrad Rzeszutek Wilk , Michael Buesch , Joerg Roedel , linux-input@vger.kernel.org, linux-media@vger.kernel.org, netdev@vger.kernel.org, linux-pcmcia@lists.infradead.org, linux-s390@vger.kernel.org, USB list , xen-devel@lists.xensource.com, Kernel development list Subject: Re: [PATCH 0/5] Get rid of get_driver() and put_driver() Message-ID: <20120125000634.GA1178@kroah.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-media-owner@vger.kernel.org List-ID: On Tue, Jan 24, 2012 at 01:33:37PM -0500, Alan Stern wrote: > Greg: > > This patch series removes the get_driver() and put_driver() routines > from the kernel. > > Those routines don't do anything useful. Their comments say that they > increment and decrement the driver's reference count, just like > get_device()/put_device() and a lot of other utility routines. But a > struct driver is _not_ like a struct device! It resembles a piece of > code more than a piece of data -- it acts as an encapsulation of a > driver. Incrementing its refcount doesn't have much meaning because a > driver's lifetime isn't determined by the structure's refcount; it's > determined by when the driver's module gets unloaded. > > What really matters for a driver is whether or not it is registered. > Drivers expect, for example, that none of their methods will be called > after driver_unregister() returns. It doesn't matter if some other > thread still holds a reference to the driver structure; that reference > mustn't be used for accessing the driver code after unregistration. > get_driver() does not do any checking for this. > > People may have been misled by the kerneldoc into thinking that the > references obtained by get_driver() do somehow pin the driver structure > in memory. This simply isn't true; all it pins is the associated > private structure. Code that needs to pin a driver must do it some > other way (probably by calling try_module_get()). > > In short, these routines don't do anything useful and they can actively > mislead people. Removing them won't introduce any bugs that aren't > already present. There is no reason to keep them. Very nice work, all now applied, thanks for doing this. greg k-h