From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3B122C43334 for ; Mon, 3 Sep 2018 07:38:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D336F20843 for ; Mon, 3 Sep 2018 07:38:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D336F20843 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726052AbeICL5a (ORCPT ); Mon, 3 Sep 2018 07:57:30 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:54474 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725869AbeICL5a (ORCPT ); Mon, 3 Sep 2018 07:57:30 -0400 Received: from p4fea45ac.dip0.t-ipconnect.de ([79.234.69.172] helo=[192.168.0.145]) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1fwjR9-0003UN-IT; Mon, 03 Sep 2018 09:38:15 +0200 Date: Mon, 3 Sep 2018 09:38:15 +0200 (CEST) From: Thomas Gleixner To: Peter Zijlstra cc: Kevin Shanahan , Siegfried Metz , linux-kernel@vger.kernel.org, rafael.j.wysocki@intel.com, len.brown@intel.com, rjw@rjwysocki.net, diego.viola@gmail.com, rui.zhang@intel.com, viktor_jaegerskuepper@freenet.de Subject: Re: REGRESSION: boot stalls on several old dual core Intel CPUs In-Reply-To: <20180903072506.GS24124@hirez.programming.kicks-ass.net> Message-ID: References: <74c5abc8-7430-5bc9-2f8a-a2205608bee7@mailbox.org> <20180830130439.GM24082@hirez.programming.kicks-ass.net> <20180901022125.GO4941@tuon.disenchant.local> <20180903072506.GS24124@hirez.programming.kicks-ass.net> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 3 Sep 2018, Peter Zijlstra wrote: > On Sat, Sep 01, 2018 at 11:51:26AM +0930, Kevin Shanahan wrote: > > commit 01548f4d3e8e94caf323a4f664eb347fd34a34ab > > Author: Martin Schwidefsky > > Date: Tue Aug 18 17:09:42 2009 +0200 > > > > clocksource: Avoid clocksource watchdog circular locking dependency > > > > stop_machine from a multithreaded workqueue is not allowed because > > of a circular locking dependency between cpu_down and the workqueue > > execution. Use a kernel thread to do the clocksource downgrade. > > I cannot find stop_machine usage there; either it went away or I need to > like wake up. timekeeping_notify() which is involved in switching clock source uses stomp machine. Thanks, tglx