From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753502AbaBCW5d (ORCPT ); Mon, 3 Feb 2014 17:57:33 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:59433 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbaBCW5a (ORCPT ); Mon, 3 Feb 2014 17:57:30 -0500 Date: Mon, 3 Feb 2014 14:57:25 -0800 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com, peterz@infradead.org Subject: [PATCH] Fix lockdep false positive in add_full() Message-ID: <20140203225725.GA4069@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14020322-0928-0000-0000-0000063B268F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: linux-mm@kvack.org Cc: cl@linux-foundation.org Cc: penberg@kernel.org Cc: mpm@selenic.com diff --git a/mm/slub.c b/mm/slub.c index 7e3e0458bce4..6fff4d980b7c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1004,7 +1004,8 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x) static void add_full(struct kmem_cache *s, struct kmem_cache_node *n, struct page *page) { - lockdep_assert_held(&n->list_lock); + if (kmem_cache_debug(s)) + lockdep_assert_held(&n->list_lock); if (!(s->flags & SLAB_STORE_USER)) return;