From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f182.google.com (mail-pd0-f182.google.com [209.85.192.182]) by kanga.kvack.org (Postfix) with ESMTP id 0F0989003C7 for ; Mon, 20 Jul 2015 20:48:13 -0400 (EDT) Received: by pdrg1 with SMTP id g1so109597597pdr.2 for ; Mon, 20 Jul 2015 17:48:12 -0700 (PDT) Received: from e31.co.us.ibm.com (e31.co.us.ibm.com. [32.97.110.149]) by mx.google.com with ESMTPS id i5si39478650pat.30.2015.07.20.17.48.10 for (version=TLSv1 cipher=AES128-SHA bits=128/128); Mon, 20 Jul 2015 17:48:12 -0700 (PDT) Received: from /spool/local by e31.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 20 Jul 2015 18:48:08 -0600 Received: from b03cxnp08025.gho.boulder.ibm.com (b03cxnp08025.gho.boulder.ibm.com [9.17.130.17]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 36FFB1FF0042 for ; Mon, 20 Jul 2015 18:39:15 -0600 (MDT) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t6L0lGax56230028 for ; Mon, 20 Jul 2015 17:47:16 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t6L0m4rR031100 for ; Mon, 20 Jul 2015 18:48:04 -0600 Date: Mon, 20 Jul 2015 17:48:03 -0700 From: "Paul E. McKenney" Subject: Re: cpu_hotplug vs oom_notify_list: possible circular locking dependency detected Message-ID: <20150721004803.GO3717@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150712105634.GA11708@marcin-Inspiron-7720> <20150714232943.GW3717@linux.vnet.ibm.com> <20150715222612.GP3717@linux.vnet.ibm.com> <20150719095818.GA7200@marcin-Inspiron-7720> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20150719095818.GA7200@marcin-Inspiron-7720> Sender: owner-linux-mm@kvack.org List-ID: To: Marcin =?utf-8?Q?=C5=9Alusarz?= Cc: David Rientjes , Tejun Heo , LKML , linux-mm@kvack.org On Sun, Jul 19, 2015 at 11:58:18AM +0200, Marcin A?lusarz wrote: > On Thu, Jul 16, 2015 at 02:01:56PM -0700, David Rientjes wrote: > > On Wed, 15 Jul 2015, Paul E. McKenney wrote: > > > > > On Tue, Jul 14, 2015 at 04:48:24PM -0700, David Rientjes wrote: > > > > On Tue, 14 Jul 2015, Paul E. McKenney wrote: > > > > > > > > > commit a1992f2f3b8e174d740a8f764d0d51344bed2eed > > > > > Author: Paul E. McKenney > > > > > Date: Tue Jul 14 16:24:14 2015 -0700 > > > > > > > > > > rcu: Don't disable CPU hotplug during OOM notifiers > > > > > > > > > > RCU's rcu_oom_notify() disables CPU hotplug in order to stabilize the > > > > > list of online CPUs, which it traverses. However, this is completely > > > > > pointless because smp_call_function_single() will quietly fail if invoked > > > > > on an offline CPU. Because the count of requests is incremented in the > > > > > rcu_oom_notify_cpu() function that is remotely invoked, everything works > > > > > nicely even in the face of concurrent CPU-hotplug operations. > > > > > > > > > > Furthermore, in recent kernels, invoking get_online_cpus() from an OOM > > > > > notifier can result in deadlock. This commit therefore removes the > > > > > call to get_online_cpus() and put_online_cpus() from rcu_oom_notify(). > > > > > > > > > > Reported-by: Marcin A?lusarz > > > > > Reported-by: David Rientjes > > > > > Signed-off-by: Paul E. McKenney > > > > > > > > Acked-by: David Rientjes > > > > > > Thank you! > > > > > > Any news on whether or not it solves the problem? > > > > > > > Marcin, is your lockdep violation reproducible? If so, does this patch > > fix it? > > I finally found enough time today to test it. I can reproduce it without > the above patch and can't with. So: > Tested-by: Marcin A?lusarz Thank you, applied! Thanx, Paul -- 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