From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753384Ab3LOHzg (ORCPT ); Sun, 15 Dec 2013 02:55:36 -0500 Received: from mail-ea0-f175.google.com ([209.85.215.175]:56446 "EHLO mail-ea0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751106Ab3LOHzd (ORCPT ); Sun, 15 Dec 2013 02:55:33 -0500 Message-ID: <52AD606F.50408@linux.com> Date: Sun, 15 Dec 2013 08:55:27 +0100 From: Levente Kurusa Reply-To: Levente Kurusa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Greg Kroah-Hartman , Bjorn Helgaas CC: LKML Subject: Re: [PATCH 0/4] treewide: add missing put_device calls References: <1386962557-8899-1-git-send-email-levex@linux.com> <20131214172419.GC22520@kroah.com> In-Reply-To: <20131214172419.GC22520@kroah.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. IIRC, there are also a few where the device is also unregistered from the specific subsystem's core. -- Regards, Levente Kurusa