From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752931AbaBCXxK (ORCPT ); Mon, 3 Feb 2014 18:53:10 -0500 Received: from e38.co.us.ibm.com ([32.97.110.159]:48095 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751322AbaBCXxI (ORCPT ); Mon, 3 Feb 2014 18:53:08 -0500 Date: Mon, 3 Feb 2014 15:53:02 -0800 From: "Paul E. McKenney" To: David Rientjes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com, peterz@infradead.org Subject: Re: [PATCH] Fix lockdep false positive in add_full() Message-ID: <20140203235302.GK4333@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140203225725.GA4069@linux.vnet.ibm.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) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14020323-1344-0000-0000-0000056A3E12 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 03, 2014 at 03:31:40PM -0800, David Rientjes wrote: > On Mon, 3 Feb 2014, Paul E. McKenney wrote: > > > Hello! > > > > The add_full() function currently has a lockdep_assert_held() requiring > > that the kmem_cache_node structure's ->list_lock be held. However, > > this lock is not acquired by add_full()'s caller deactivate_slab() > > in the full-node case unless debugging is enabled. Because full nodes > > are accessed only by debugging code, this state of affairs results in > > lockdep false-positive splats like the following: > > > > [ 43.942868] WARNING: CPU: 0 PID: 698 at /home/paulmck/public_git/linux-rcu/mm/slub.c:1007 deactivate_slab+0x509/0x720() > > [ 43.943016] Modules linked in: > > [ 43.943016] CPU: 0 PID: 698 Comm: torture_onoff Not tainted 3.14.0-rc1+ #1 > > [ 43.943016] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 > > [ 43.943016] 00000000000003ef ffff88001e3f5ba8 ffffffff818952ec 0000000000000046 > > [ 43.943016] 0000000000000000 ffff88001e3f5be8 ffffffff81049517 ffffea0000784e00 > > [ 43.943016] 0000000000000000 ffffea00007a9000 0000000000000002 0000000000000000 > > [ 43.943016] Call Trace: > > [ 43.943016] [] dump_stack+0x46/0x58 > > [ 43.943016] [] warn_slowpath_common+0x87/0xb0 > > [ 43.943016] [] warn_slowpath_null+0x15/0x20 > > [ 43.943016] [] deactivate_slab+0x509/0x720 > > [ 43.943016] [] ? slab_cpuup_callback+0x3b/0x100 > > [ 43.943016] [] ? slab_cpuup_callback+0xd2/0x100 > > [ 43.943016] [] slab_cpuup_callback+0xa4/0x100 > > [ 43.943016] [] notifier_call_chain+0x54/0x110 > > [ 43.943016] [] __raw_notifier_call_chain+0x9/0x10 > > [ 43.943016] [] __cpu_notify+0x1b/0x30 > > [ 43.943016] [] cpu_notify_nofail+0x10/0x20 > > [ 43.943016] [] _cpu_down+0x10d/0x2e0 > > [ 43.943016] [] cpu_down+0x30/0x50 > > [ 43.943016] [] torture_onoff+0xd3/0x3c0 > > [ 43.943016] [] ? torture_onoff_stats+0x90/0x90 > > [ 43.943016] [] kthread+0xdf/0x100 > > [ 43.943016] [] ? _raw_spin_unlock_irq+0x2b/0x40 > > [ 43.943016] [] ? flush_kthread_worker+0x130/0x130 > > [ 43.943016] [] ret_from_fork+0x7c/0xb0 > > [ 43.943016] [] ? flush_kthread_worker+0x130/0x130 > > > > This commit therefore does the lockdep check only if debuggging is > > enabled, thus avoiding the false positives. > > > > Signed-off-by: Paul E. McKenney > > This was discussed in http://marc.info/?t=139145791300002, what do you > think about the patch in that thread instead? Looks fine to me! I also tried it out and it avoided the splats, as noted in my mail in the other thread, so please feel free to add my Tested-by. Thanx, Paul