Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751081AbaAEDmS (ORCPT ); Sat, 4 Jan 2014 22:42:18 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:58016 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750806AbaAEDmR (ORCPT ); Sat, 4 Jan 2014 22:42:17 -0500 Date: Sat, 4 Jan 2014 19:42:28 -0800 From: Greg Kroah-Hartman To: Mikulas Patocka Cc: Jeff Mahoney , torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, tglx@linutronix.de, paulmck@linux.vnet.ibm.com, mingo@kernel.org Subject: Re: [PATCH] kobject: provide kobject_put_wait to fix module unload race Message-ID: <20140105034228.GC22595@kroah.com> References: <20140104181620.GA2087@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Content-Length: 1680 Lines: 42 On Sat, Jan 04, 2014 at 03:35:39PM -0500, Mikulas Patocka wrote: > > > On Sat, 4 Jan 2014, Greg Kroah-Hartman wrote: > > > On Sat, Jan 04, 2014 at 01:06:01PM -0500, Mikulas Patocka wrote: > > > Hi > > > > > > I noticed that Jeff Mahoney added a new structure kobj_completion, defined > > > in include/linux/kobj_completion.h to the kernel 3.13-rc1 in the patch > > > eee031649707db3c9920d9498f8d03819b74fc23. In the current upstream kernel, > > > this interface is still unused. > > > > There are pending btrfs patches to use this interface. > > > > > However, converting the drivers to use kobj_completion is not trivial > > > (note that all users of the original kobject interface are buggy - so all > > > of them need to be converted). > > > > Wait, what? How are "all users" buggy? Please explain this in detail. > > 1) some code takes a reference to a kobject > 2) the user unloads the device > 3) the device driver unload routine calls kobject_put (but there is still > reference, so the kobject is not destroyed) A driver should never be messing around with "raw" kobjects, they should be using a 'struct device' which is created/managed by the subsystem they belong to. See Dmitry's example of input and serio as ways to do this, also USB and PCI do this properly. Perhaps your sybsystem isn't doing this properly? What code do you have that creates raw kobjects and has this problem? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/