Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756500AbbGPVCK (ORCPT ); Thu, 16 Jul 2015 17:02:10 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:32891 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756219AbbGPVB7 (ORCPT ); Thu, 16 Jul 2015 17:01:59 -0400 Date: Thu, 16 Jul 2015 14:01:56 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: "Paul E. McKenney" cc: =?UTF-8?Q?Marcin_=C5=9Alusarz?= , Tejun Heo , LKML , linux-mm@kvack.org Subject: Re: cpu_hotplug vs oom_notify_list: possible circular locking dependency detected In-Reply-To: <20150715222612.GP3717@linux.vnet.ibm.com> Message-ID: References: <20150712105634.GA11708@marcin-Inspiron-7720> <20150714232943.GW3717@linux.vnet.ibm.com> <20150715222612.GP3717@linux.vnet.ibm.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="397176738-1189911053-1437080517=:14938" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2111 Lines: 48 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --397176738-1189911053-1437080517=:14938 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT 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 Ślusarz > > > 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? --397176738-1189911053-1437080517=:14938-- -- 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/