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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 CF69DC433F5 for ; Mon, 3 Sep 2018 07:25:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 76A2F2054F for ; Mon, 3 Sep 2018 07:25:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Za/gXSoZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 76A2F2054F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1727271AbeICLoO (ORCPT ); Mon, 3 Sep 2018 07:44:14 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51482 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725869AbeICLoO (ORCPT ); Mon, 3 Sep 2018 07:44:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=yBsUIgUoPik/3KlRQnmvHUuE/MeBnkctniuaPTCzbnI=; b=Za/gXSoZ3ZVUXNP7dfKHpEA+O svel1f2Nt5sVDsOmXMIyqIqsOxBNOjixuHveXZVy5bv5Mtl0jDUxDMSSqAv6ROipNIinYDGqF9fqP 5LgLWgOeJlZBmx6XCFb1o+NCZMYbl8GyBWYYJ3O+68+jMY6Ey85kNScISyR0JJbdl+auEJymnNzw9 VzqWkGOrSnwzGRyKEStG2hT4GYCfOQZNCWpWBkd6CvpdfzOnsTYHAGtfE5zuGQlfP+eT9C/DsXpjx dwG2aaMkH6DrAEmbdfVPywudeoEa65j9mXEn8uCtLp+8rQDdvXC5e7eHThxAHjmJUxRRoX1cF7szo HYEmsdc4A==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fwjEU-0003h7-3E; Mon, 03 Sep 2018 07:25:10 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 6DD8B205F864C; Mon, 3 Sep 2018 09:25:06 +0200 (CEST) Date: Mon, 3 Sep 2018 09:25:06 +0200 From: Peter Zijlstra To: Kevin Shanahan Cc: Siegfried Metz , linux-kernel@vger.kernel.org, tglx@linutronix.de, 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 Message-ID: <20180903072506.GS24124@hirez.programming.kicks-ass.net> References: <74c5abc8-7430-5bc9-2f8a-a2205608bee7@mailbox.org> <20180830130439.GM24082@hirez.programming.kicks-ass.net> <20180901022125.GO4941@tuon.disenchant.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180901022125.GO4941@tuon.disenchant.local> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 01, 2018 at 11:51:26AM +0930, Kevin Shanahan wrote: > On Thu, Aug 30, 2018 at 03:04:39PM +0200, Peter Zijlstra wrote: > > On Thu, Aug 30, 2018 at 12:55:30PM +0200, Siegfried Metz wrote: > > > Dear kernel developers, > > > > > > since mainline kernel 4.18 (up to the latest mainline kernel 4.18.5) > > > Intel Core 2 Duo processors are affected by boot stalling early in the > > > boot process. As it is so early there is no dmesg output (or any log). > > > > > > A few users in the Arch Linux community used git bisect and tracked the > > > issue down to this the bad commit: > > > 7197e77abcb65a71d0b21d67beb24f153a96055e clocksource: Remove kthread > > > > I just dug out my core2duo laptop (Lenovo T500) and build a tip/master > > kernel for it (x86_64 debian distro .config). > > > > Seems to boot just fine.. 3/3 so far. > > > > Any other clues? > > One additional data point, my affected system is a Dell Latitude E6400 > laptop which has a P8400 CPU: > > vendor_id : GenuineIntel > cpu family : 6 > model : 23 > model name : Intel(R) Core(TM)2 Duo CPU P8400 @ 2.26GHz > stepping : 6 > microcode : 0x610 > > Judging from what is being discussed in the Arch forums, it does seem > to related to the CPU having unstable TSC and transitioning to another > clock source. Yes; Core2 doesn't have stable TSC. > Workarounds that seem to be reliable are either booting > with clocksource= or with nosmp. nosmp is weird; because even on UP TSC should stop in C state. processor_idle (acpi_idle) should mark the TSC as unstable on Core2 when it loads (does so on my T500). > One person did point out that the commit that introduced the kthread > did so to remove a deadlock - is the circular locking dependency > mentioned in that commit still relevant? > > 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.