From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 16CAB6B0035 for ; Mon, 3 Feb 2014 18:31:43 -0500 (EST) Received: by mail-pa0-f53.google.com with SMTP id lj1so7661753pab.26 for ; Mon, 03 Feb 2014 15:31:42 -0800 (PST) Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id s7si11078994pae.243.2014.02.03.15.31.41 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 03 Feb 2014 15:31:42 -0800 (PST) Received: by mail-pa0-f47.google.com with SMTP id kp14so7687705pab.34 for ; Mon, 03 Feb 2014 15:31:41 -0800 (PST) Date: Mon, 3 Feb 2014 15:31:40 -0800 (PST) From: David Rientjes Subject: Re: [PATCH] Fix lockdep false positive in add_full() In-Reply-To: <20140203225725.GA4069@linux.vnet.ibm.com> Message-ID: References: <20140203225725.GA4069@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com, peterz@infradead.org 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? -- 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