From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f54.google.com (mail-bk0-f54.google.com [209.85.214.54]) by kanga.kvack.org (Postfix) with ESMTP id D82A26B0031 for ; Wed, 27 Nov 2013 08:45:05 -0500 (EST) Received: by mail-bk0-f54.google.com with SMTP id v16so3279411bkz.27 for ; Wed, 27 Nov 2013 05:45:05 -0800 (PST) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id tv4si8641611bkb.228.2013.11.27.05.45.04 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Wed, 27 Nov 2013 05:45:05 -0800 (PST) Date: Wed, 27 Nov 2013 14:44:58 +0100 (CET) From: Thomas Gleixner Subject: Re: netfilter: active obj WARN when cleaning up In-Reply-To: <20131127134015.GA6011@n2100.arm.linux.org.uk> Message-ID: References: <522B25B5.6000808@oracle.com> <5294F27D.4000108@oracle.com> <20131126230709.GA10948@localhost> <20131127113939.GL16735@n2100.arm.linux.org.uk> <20131127133231.GO16735@n2100.arm.linux.org.uk> <20131127134015.GA6011@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Russell King - ARM Linux Cc: Pablo Neira Ayuso , Sasha Levin , Patrick McHardy , kadlec@blackhole.kfki.hu, "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, LKML , linux-mm@kvack.org, Andrew Morton , Christoph Lameter , Greg KH On Wed, 27 Nov 2013, Russell King - ARM Linux wrote: > On Wed, Nov 27, 2013 at 01:32:31PM +0000, Russell King - ARM Linux wrote: > > On Wed, Nov 27, 2013 at 02:29:41PM +0100, Thomas Gleixner wrote: > > > Though the kobject is the only thing which has a delayed work embedded > > > inside struct kmem_cache. And the debug object splat points at the > > > kmem_cache_free() of the struct kmem_cache itself. That's why I > > > assumed the wreckage around that place. And indeed: > > > > > > kmem_cache_destroy(s) > > > __kmem_cache_shutdown(s) > > > sysfs_slab_remove(s) > > > .... > > > kobject_put(&s->kobj) > > > kref_put(&kobj->kref, kobject_release); > > > kobject_release(kref) > > > #ifdef CONFIG_DEBUG_KOBJECT_RELEASE > > > schedule_delayed_work(&kobj->release) > > > #else > > > kobject_cleanup(kobj) > > > #endif > > > > > > So in the CONFIG_DEBUG_KOBJECT_RELEASE=y case, schedule_delayed_work() > > > _IS_ called which arms the timer. debugobjects catches the attempt to > > > free struct kmem_cache which contains the armed timer. > > > > You fail to show where the free is in the above path. > > Right, there's a kmem_cache_free(kmem_cache, s); by the slob code > after the above sequence, which is The Bug(tm). > > As I said, a kobject has its own lifetime. If you embed that into > another structure, that structure inherits the lifetime of the kobject, > which is from the point at which it's created to the point at which the > kobject's release function is called. > > So no, the code here is buggy. The kobject debugging has yet again > found a violation of the kobject lifetime rules. slub needs fixing. I leave that discussion to you, greg and the slub folks. /me prepares deck chair, drinks and popcorn -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org