Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934469AbaFST3Y (ORCPT ); Thu, 19 Jun 2014 15:29:24 -0400 Received: from www.linutronix.de ([62.245.132.108]:55127 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934265AbaFST3V (ORCPT ); Thu, 19 Jun 2014 15:29:21 -0400 Date: Thu, 19 Jun 2014 21:29:08 +0200 (CEST) From: Thomas Gleixner To: "Paul E. McKenney" cc: Christoph Lameter , Sasha Levin , Pekka Enberg , Matt Mackall , Andrew Morton , Dave Jones , "linux-mm@kvack.org" , LKML Subject: Re: slub/debugobjects: lockup when freeing memory In-Reply-To: <20140619165247.GA4904@linux.vnet.ibm.com> Message-ID: References: <53A2F406.4010109@oracle.com> <20140619165247.GA4904@linux.vnet.ibm.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 19 Jun 2014, Paul E. McKenney wrote: > On Thu, Jun 19, 2014 at 10:03:04AM -0500, Christoph Lameter wrote: > > On Thu, 19 Jun 2014, Sasha Levin wrote: > > > > > [ 690.770137] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) > > > [ 690.770137] __slab_alloc (mm/slub.c:1732 mm/slub.c:2205 mm/slub.c:2369) > > > [ 690.770137] ? __lock_acquire (kernel/locking/lockdep.c:3189) > > > [ 690.770137] ? __debug_object_init (lib/debugobjects.c:100 lib/debugobjects.c:312) > > > [ 690.770137] kmem_cache_alloc (mm/slub.c:2442 mm/slub.c:2484 mm/slub.c:2489) > > > [ 690.770137] ? __debug_object_init (lib/debugobjects.c:100 lib/debugobjects.c:312) > > > [ 690.770137] ? debug_object_activate (lib/debugobjects.c:439) > > > [ 690.770137] __debug_object_init (lib/debugobjects.c:100 lib/debugobjects.c:312) > > > [ 690.770137] debug_object_init (lib/debugobjects.c:365) > > > [ 690.770137] rcuhead_fixup_activate (kernel/rcu/update.c:231) > > > [ 690.770137] debug_object_activate (lib/debugobjects.c:280 lib/debugobjects.c:439) > > > [ 690.770137] ? discard_slab (mm/slub.c:1486) > > > [ 690.770137] __call_rcu (kernel/rcu/rcu.h:76 (discriminator 2) kernel/rcu/tree.c:2585 (discriminator 2)) > > > > __call_rcu does a slab allocation? This means __call_rcu can no longer be > > used in slab allocators? What happened? > > My guess is that the root cause is a double call_rcu(), call_rcu_sched(), > call_rcu_bh(), or call_srcu(). > > Perhaps the DEBUG_OBJECTS code now allocates memory to report errors? > That would be unfortunate... Well, no. Look at the callchain: __call_rcu debug_object_activate rcuhead_fixup_activate debug_object_init kmem_cache_alloc So call rcu activates the object, but the object has no reference in the debug objects code so the fixup code is called which inits the object and allocates a reference .... Thanks, tglx -- 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/