From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752789AbdHJOX6 (ORCPT ); Thu, 10 Aug 2017 10:23:58 -0400 Received: from mail-wm0-f68.google.com ([74.125.82.68]:36001 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752666AbdHJOXz (ORCPT ); Thu, 10 Aug 2017 10:23:55 -0400 Date: Thu, 10 Aug 2017 16:23:52 +0200 From: Ingo Molnar To: Vitaly Kuznetsov Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Subject: Re: [PATCH RESEND] x86/smpboot: Unbreak CPU0 hotplug Message-ID: <20170810142351.b7h6usaou66aoywm@gmail.com> References: <20170803105818.9934-1-vkuznets@redhat.com> <87fucztyww.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87fucztyww.fsf@vitty.brq.redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Vitaly Kuznetsov wrote: > Vitaly Kuznetsov writes: > > > A hang on CPU0 onlining after a preceding offlining is observed. Trace > > shows that CPU0 is stuck in check_tsc_sync_target() waiting for source > > CPU to run check_tsc_sync_source() but this never happens. Source CPU, > > in its turn, is stuck on synchronize_sched() which is called from > > native_cpu_up() -> do_boot_cpu() -> unregister_nmi_handler(). > > > > Fix the issue by moving unregister_nmi_handler() from do_boot_cpu() to > > native_cpu_up() after cpu onlining is done. Looks like a classic ABBA deadlock, due to the use of synchronize_sched() in unregister_nmi_handler(), right? > > > > Signed-off-by: Vitaly Kuznetsov > > --- > > It's been awile since my v1 submission, no comments so far. Resending. > > Sorry, but > > ping? > > I haven't received a single comment on this since the initial submission > on June, 26 - is it so bad? :-) So the fix looks good to me at first sight, but wanted to wait for Thomas to ack it - once he gets back from vacation. Thanks, Ingo