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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 E3B7CC2D0DB for ; Sat, 25 Jan 2020 17:54:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B602420801 for ; Sat, 25 Jan 2020 17:54:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="mwKXJKhE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727278AbgAYRyt (ORCPT ); Sat, 25 Jan 2020 12:54:49 -0500 Received: from mail.skyhub.de ([5.9.137.197]:47910 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbgAYRys (ORCPT ); Sat, 25 Jan 2020 12:54:48 -0500 Received: from zn.tnic (p200300EC2F1CE9005D0519DC199D089A.dip0.t-ipconnect.de [IPv6:2003:ec:2f1c:e900:5d05:19dc:199d:89a]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 70B101EC0CD0; Sat, 25 Jan 2020 18:54:46 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1579974886; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=8/QEBnGZzWynfauzlDvurEb7IGLRdsmpQsi9B2RTlqQ=; b=mwKXJKhEBXerhu5Iv/tiq5hHqE/knLsBaUoBlRwrAeQgrNZaJbvSQOAcy5ZpjgPFzCXukX WUwfpn7Y3zY1Q5fFVCCTMSe4gFVcIcOnBIxjyRfQFk93bV2tZLPDdvmuibHSMMx9U/vfVQ bSDLFGCv3NGTGZru5u1dLSARpv2Co6w= Date: Sat, 25 Jan 2020 18:54:42 +0100 From: Borislav Petkov To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, x86 Subject: Re: [tip: core/rcu] rcu: Enable tick for nohz_full CPUs slow to provide expedited QS Message-ID: <20200125175442.GA4369@zn.tnic> References: <157994897654.396.5667707782512768142.tip-bot2@tip-bot2> <20200125131425.GB16136@zn.tnic> <20200125161050.GE2935@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200125161050.GE2935@paulmck-ThinkPad-P72> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 25, 2020 at 08:10:50AM -0800, Paul E. McKenney wrote: > How big? (Seriously, given that the fix may depend on the number of CPUs.) [ 7.660017] smp: Brought up 2 nodes, 256 CPUs > So the problem appears to be that some of the boot-time processing > is looping in the kernel, which is preventing the grace period from > completing. One could argue that such code should be fixed, but on the > other hand, boot time is a bit special. Later in -rcu's dev branch, > there are commits that forgive this boot-time misbehavior, but this is > a bit late in process to dump all of those commits into -tip. Aha. > The RT guys might need the warning, and it was them that I was thinking > of when adding it. But "boot time is a bit special". Or do they care about deadlines during boot too? > But let's see what works for mainline first. And > since your box was booting fine without the warning before, I bet that > it boots just fine with that warning removed. Yes, it does. > So could you please try out the (untested) patch below? Warning's gone. > If that works, I will re-introduce the warning with proper protection > for the merge window following this coming one. My big box is at your service if you need stuff tested later. Thx Paul. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette