Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934563AbaFSUh2 (ORCPT ); Thu, 19 Jun 2014 16:37:28 -0400 Received: from www.linutronix.de ([62.245.132.108]:55392 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933503AbaFSUh0 (ORCPT ); Thu, 19 Jun 2014 16:37:26 -0400 Date: Thu, 19 Jun 2014 22:37:17 +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: <20140619202928.GG4904@linux.vnet.ibm.com> Message-ID: References: <53A2F406.4010109@oracle.com> <20140619165247.GA4904@linux.vnet.ibm.com> <20140619202928.GG4904@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 09:29:08PM +0200, Thomas Gleixner wrote: > > On Thu, 19 Jun 2014, Paul E. McKenney wrote: > > 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 .... > > OK, got it. And you are right, call_rcu() has done this for a very > long time, so not sure what changed. But it seems like the right > approach is to provide a debug-object-free call_rcu_alloc() for use > by the memory allocators. > > Seem reasonable? If so, please see the following patch. Not really, you're torpedoing the whole purpose of debugobjects :) So, why can't we just init the rcu head when the stuff is created? If that's impossible due to other memory allocator constraints, then instead of inventing a whole new API we can simply flag the relevent data in the memory allocator as we do with the debug objects mem cache itself (SLAB_DEBUG_OBJECTS). 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/