From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751936Ab3LORBZ (ORCPT ); Sun, 15 Dec 2013 12:01:25 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:35369 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751624Ab3LORBY (ORCPT ); Sun, 15 Dec 2013 12:01:24 -0500 Date: Sun, 15 Dec 2013 09:03:25 -0800 From: Greg Kroah-Hartman To: Levente Kurusa Cc: Bjorn Helgaas , LKML Subject: Re: [PATCH 0/4] treewide: add missing put_device calls Message-ID: <20131215170325.GA28799@kroah.com> References: <1386962557-8899-1-git-send-email-levex@linux.com> <20131214172419.GC22520@kroah.com> <52AD606F.50408@linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52AD606F.50408@linux.com> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 15, 2013 at 08:55:27AM +0100, Levente Kurusa wrote: > On 12/14/2013 06:24 PM, Greg Kroah-Hartman wrote: > > On Fri, Dec 13, 2013 at 01:42:05PM -0700, Bjorn Helgaas wrote: > >> [+cc Greg] > >> > >> On Fri, Dec 13, 2013 at 12:22 PM, Levente Kurusa wrote: > >>> Hi, > >>> > >>> This is just the beginning of patchset-set that aims to fix possible > >>> problems caused by not calling put_device() if device_register() fails. > >>> > >>> The root cause for the need to call put_device() is that the underlying > >>> kobject still has a reference count of 1. Thus, device.release() will not > >>> be called and the device will just sit there waiting for a put_device(). > >>> Adding the put_device() also removes the need for the call to kfree() as most > >>> release functions already call kfree() on the container of the device. > >>> > >>> While these have not been experienced, they are potential issues and thus > >>> they need to be fixed. Also, they are a few more files that have the same > >>> kind of issue, those will be fixed if these are accepted. > >> > >> Thanks for doing this. This is the sort of mistake that just gets > >> copied everywhere, so fixing the examples in the tree will help > >> prevent the problem from spreading more. > >> > >> I don't know if there's really value in having device_register() > >> return an error but rely on the caller to do the put_device(). Are > >> there cases where the caller still needs the struct device even if > >> device_register() fails? E.g., could we do something like this > >> instead (I know some callers would also require corresponding changes > >> to avoid double puts): > > There are cases where it is needed. There are quite a few files which > when device_register() fails, the driver print an error messages. That shouldn't be needed, and can be removed. > IIRC, there are also a few where the device is also unregistered from > the specific subsystem's core. Do you have a specific example of this? This should happen in the release function of the device already, not in some other code. thanks, greg k-h