Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965831AbaFSWE4 (ORCPT ); Thu, 19 Jun 2014 18:04:56 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:48203 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965319AbaFSWEz (ORCPT ); Thu, 19 Jun 2014 18:04:55 -0400 Date: Thu, 19 Jun 2014 15:04:49 -0700 From: "Paul E. McKenney" To: Thomas Gleixner 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 Message-ID: <20140619220449.GT4904@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com 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 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14061922-1344-0000-0000-0000024F7A12 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 19, 2014 at 11:32:41PM +0200, Thomas Gleixner wrote: > > > 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() You mean like this? Thanx, Paul ------------------------------------------------------------------------ rcu: Export debug_init_rcu_head() and and debug_init_rcu_head() Currently, call_rcu() relies on implicit allocation and initialization for the debug-objects handling of RCU callbacks. If you hammer the kernel hard enough with Sasha's modified version of trinity, you can end up with the sl*b allocators recursing into themselves via this implicit call_rcu() allocation. This commit therefore exports the debug_init_rcu_head() and debug_rcu_head_free() functions, which permits the allocators to allocated and pre-initialize the debug-objects information, so that there no longer any need for call_rcu() to do that initialization, which in turn prevents the recursion into the memory allocators. Reported-by: Sasha Levin Suggested-by: Thomas Gleixner Signed-off-by: Paul E. McKenney diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 063a6bf1a2b6..34ae5c376e35 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -358,9 +358,19 @@ void wait_rcu_gp(call_rcu_func_t crf); * initialization. */ #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD +void debug_init_rcu_head(struct rcu_head *head); +void debug_rcu_head_free(struct rcu_head *head); void init_rcu_head_on_stack(struct rcu_head *head); void destroy_rcu_head_on_stack(struct rcu_head *head); #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +static inline void debug_init_rcu_head(struct rcu_head *head) +{ +} + +static inline void debug_rcu_head_free(struct rcu_head *head) +{ +} + static inline void init_rcu_head_on_stack(struct rcu_head *head) { } diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index a2aeb4df0f60..a41c81a26506 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -200,12 +200,12 @@ void wait_rcu_gp(call_rcu_func_t crf) EXPORT_SYMBOL_GPL(wait_rcu_gp); #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD -static inline void debug_init_rcu_head(struct rcu_head *head) +void debug_init_rcu_head(struct rcu_head *head) { debug_object_init(head, &rcuhead_debug_descr); } -static inline void debug_rcu_head_free(struct rcu_head *head) +void debug_rcu_head_free(struct rcu_head *head) { debug_object_free(head, &rcuhead_debug_descr); } -- 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/