Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756379AbaAFVb1 (ORCPT ); Mon, 6 Jan 2014 16:31:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43217 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755924AbaAFVbZ (ORCPT ); Mon, 6 Jan 2014 16:31:25 -0500 Date: Mon, 6 Jan 2014 16:31:11 -0500 From: Mike Snitzer To: Mikulas Patocka Cc: Greg Kroah-Hartman , Bart Van Assche , Jeff Mahoney , linux-kernel@vger.kernel.org, device-mapper development , tglx@linutronix.de, paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org, mingo@kernel.org Subject: Re: kobject: provide kobject_put_wait to fix module unload race Message-ID: <20140106213111.GA2536@redhat.com> References: <52C98BCC.9040900@acm.org> <20140105182640.GA2522@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 06 2014 at 1:55pm -0500, Mikulas Patocka wrote: > > > On Sun, 5 Jan 2014, Greg Kroah-Hartman wrote: > > > On Sun, Jan 05, 2014 at 05:43:56PM +0100, Bart Van Assche wrote: > > > On 01/04/14 19:06, Mikulas Patocka wrote: > > > > - if (t && !t->release) > > > > - pr_debug("kobject: '%s' (%p): does not have a release() " > > > > - "function, it is broken and must be fixed.\n", > > > > - kobject_name(kobj), kobj); > > > > - > > > > > > Has it been considered to issue a warning if no release function has > > > been defined and free_completion == NULL instead of removing the above > > > debug message entirely ? I think even with this patch applied it is > > > still wrong to invoke kobject_put() on an object without defining a > > > release function. > > > > This patch isn't going to be applied, and I've reverted the original > > commit, so there shouldn't be any issues anymore with this code. > > Why? This patch does the same thing as > eee031649707db3c9920d9498f8d03819b74fc23, but it's smaller. So why did you > accept eee031649707db3c9920d9498f8d03819b74fc23 and not this? > > The code to wait for kobject destruction using completion already exists > in cpufreq_sysfs_release, cpuidle_sysfs_release, > cpuidle_state_sysfs_release, cpuidle_driver_sysfs_release, > ext4_sb_release, ext4_feat_release, f2fs_sb_release (these are the only > kobject users that are correct w.r.t. module unloading), so if you accept > this patch, you can simplify them to use kobject_put_wait. Hi Mikulas, Please just submit a DM-only patch that follows the same racey pattern of firing a completion from the kobj_type .release method in dm_mod. I'll get it queued up for 3.14. If/when we gets reports of a crash due to dm_mod unload racing with kobject_put we can revisit this. Thanks, Mike -- 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/