From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f51.google.com (mail-wg0-f51.google.com [74.125.82.51]) by kanga.kvack.org (Postfix) with ESMTP id 7A1E46B0031 for ; Thu, 19 Jun 2014 17:32:56 -0400 (EDT) Received: by mail-wg0-f51.google.com with SMTP id x12so2879488wgg.22 for ; Thu, 19 Jun 2014 14:32:55 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id a17si7297906wib.72.2014.06.19.14.32.54 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Thu, 19 Jun 2014 14:32:55 -0700 (PDT) Date: Thu, 19 Jun 2014 23:32:41 +0200 (CEST) From: Thomas Gleixner Subject: Re: slub/debugobjects: lockup when freeing memory In-Reply-To: <20140619205307.GL4904@linux.vnet.ibm.com> Message-ID: References: <53A2F406.4010109@oracle.com> <20140619165247.GA4904@linux.vnet.ibm.com> <20140619202928.GG4904@linux.vnet.ibm.com> <20140619205307.GL4904@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: Christoph Lameter , Sasha Levin , Pekka Enberg , Matt Mackall , Andrew Morton , Dave Jones , "linux-mm@kvack.org" , LKML On Thu, 19 Jun 2014, Paul E. McKenney wrote: > On Thu, Jun 19, 2014 at 10:37:17PM +0200, Thomas Gleixner wrote: > > 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? > > That would allow me to keep my code unchanged, so I am in favor. ;-) Almost unchanged. You need to provide a function to do so, i.e. make use of debug_init_rcu_head() Thanks, tglx -- 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