From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752520AbaCFKVo (ORCPT ); Thu, 6 Mar 2014 05:21:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3393 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752362AbaCFKV2 (ORCPT ); Thu, 6 Mar 2014 05:21:28 -0500 Date: Thu, 6 Mar 2014 10:10:09 +0100 From: Igor Mammedov To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, drjones@redhat.com, toshi.kani@hp.com, prarit@redhat.com, kirill.shutemov@linux.intel.com, JBeulich@suse.com, peterz@infradead.org, paul.gortmaker@windriver.com, seiji.aguchi@hds.com, bp@suse.de, hpa@zytor.com, mingo@redhat.com, x86@kernel.org, tglx@linutronix.de, riel@redhat.com Subject: Re: [PATCH] abort secondary CPU bring-up gracefully if do_boot_cpu timed out on cpu_callin_mask Message-ID: <20140306101009.34ba6c3c@nial.usersys.redhat.com> In-Reply-To: <20140306070832.GA1277@gmail.com> References: <1394030723-15084-1-git-send-email-imammedo@redhat.com> <20140306070832.GA1277@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 6 Mar 2014 08:08:32 +0100 Ingo Molnar wrote: > > * Igor Mammedov wrote: > > > Master CPU may timeout before cpu_callin_mask is set and cancel > > booting CPU, but being onlined CPU still continues to boot, sets > > cpu_active_mask (CPU_STARTING notifiers) and spins in > > check_tsc_sync_target() for master cpu to arrive. Following attempt > > to online another cpu hangs in stop_machine, initiated from here: > > The changelog needs to prominently contain a description of the > practical relevance of this patch: has the hang triggered on any > system and under what circumstances, and did the patch resolve the > hang, etc.? Hang is observed on virtual machines during CPU hotplug, especially in big guests with many CPUs. (It happens more often if host is over-committed). Similar patch is carried in RHEL6 since 2012 and it fixes issue there, when applied to upstream kernel it also fixes issue. > > Thanks, > > Ingo Thanks, Igor.