From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751967AbcCLI3H (ORCPT ); Sat, 12 Mar 2016 03:29:07 -0500 Received: from www.linutronix.de ([62.245.132.108]:40560 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751167AbcCLI26 (ORCPT ); Sat, 12 Mar 2016 03:28:58 -0500 Date: Sat, 12 Mar 2016 09:27:28 +0100 (CET) From: Thomas Gleixner To: "Luck, Tony" cc: LKML , Harry Junior , x86@kernel.org, Peter Zijlstra , Joe Lawrence , Borislav Petkov Subject: Re: [PATCH] x86/irq: Cure live lock in irq_force_complete_move() In-Reply-To: <20160311223357.GA2544@intel.com> Message-ID: References: <20160311223357.GA2544@intel.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 Fri, 11 Mar 2016, Luck, Tony wrote: > With this patch applied my system survives me doing > several rounds of: > > # echo 0 | tee /sys/devices/system/cpu/cpu*/online > # echo 1 | tee /sys/devices/system/cpu/cpu*/online > > whereas without the patch the first of those went to > > [152455.129604] NMI watchdog: Watchdog detected hard LOCKUP on cpu 96 > [152455.136943] Kernel panic - not syncing: Hard LOCKUP > > I'm not sure we care to optimize the cpu offline path, but I'll note here > that taking all (but one) cpus offline took 52 seconds (for a hundred > and mumble logical cpus). Bringing them all back is just 4 seconds. Yes. I noticed that as well. No idea where we waste all that time. I've put that on the todo list of our ongoing hotplug refactoring work. Thanks, tglx