From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755984AbcCCHd1 (ORCPT ); Thu, 3 Mar 2016 02:33:27 -0500 Received: from www.linutronix.de ([62.245.132.108]:56148 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751412AbcCCHdZ (ORCPT ); Thu, 3 Mar 2016 02:33:25 -0500 Date: Thu, 3 Mar 2016 08:31:35 +0100 (CET) From: Thomas Gleixner To: "Paul E. McKenney" cc: rafael.j.wysocki@intel.com, peterz@infradead.org, riel@redhat.com, arjan@linux.intel.com, rusty@rustcorp.com.au, tj@kernel.org, srivatsa@mit.edu, torvalds@linux-foundation.org, bigeasy@linutronix.de, pjt@google.com, akpm@linux-foundation.org, hpa@zytor.com, oleg@redhat.com, mingo@kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, linux-tip-commits@vger.kernel.org Subject: Re: [tip:smp/hotplug] rcu: Make CPU_DYING_IDLE an explicit call In-Reply-To: <20160302201127.GA23440@linux.vnet.ibm.com> Message-ID: References: <20160226182341.870167933@linutronix.de> <20160302201127.GA23440@linux.vnet.ibm.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2 Mar 2016, Paul E. McKenney wrote: > > --- a/kernel/cpu.c > > +++ b/kernel/cpu.c > > @@ -762,6 +762,7 @@ void cpuhp_report_idle_dead(void) > > BUG_ON(st->state != CPUHP_AP_OFFLINE); > > st->state = CPUHP_AP_IDLE_DEAD; > > complete(&st->done); > > Not to be repetitive or anything, but if we delay here, it can break > RCU on a number of architectures. Either the CPU can be killed holding > one of RCU's locks or RCU can wrongly see the CPU as still being alive. > Either can prevent future RCU grace periods from ever completing, thus > OOMing the system. Thanks for the reminder. I wanted to fix that, but then forgot again. Fix is on the way. Thanks, tglx