Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753230AbbGNXsa (ORCPT ); Tue, 14 Jul 2015 19:48:30 -0400 Received: from mail-ie0-f171.google.com ([209.85.223.171]:34057 "EHLO mail-ie0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753188AbbGNXs0 (ORCPT ); Tue, 14 Jul 2015 19:48:26 -0400 Date: Tue, 14 Jul 2015 16:48:24 -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: <20150714232943.GW3717@linux.vnet.ibm.com> Message-ID: References: <20150712105634.GA11708@marcin-Inspiron-7720> <20150714232943.GW3717@linux.vnet.ibm.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="397176738-422283606-1436917705=:16182" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1745 Lines: 37 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --397176738-422283606-1436917705=:16182 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT 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 --397176738-422283606-1436917705=:16182-- -- 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/