From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752261AbaCFNcR (ORCPT ); Thu, 6 Mar 2014 08:32:17 -0500 Received: from mail-ee0-f52.google.com ([74.125.83.52]:45327 "EHLO mail-ee0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbaCFNcP (ORCPT ); Thu, 6 Mar 2014 08:32:15 -0500 Date: Thu, 6 Mar 2014 14:32:11 +0100 From: Ingo Molnar To: Igor Mammedov 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: <20140306133211.GA2220@gmail.com> References: <1394030723-15084-1-git-send-email-imammedo@redhat.com> <20140306070832.GA1277@gmail.com> <20140306101009.34ba6c3c@nial.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140306101009.34ba6c3c@nial.usersys.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Igor Mammedov wrote: > 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. Okay, cool - please update the patch description with that and resubmit. Thanks, Ingo