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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 D8F5DC433DB for ; Thu, 7 Jan 2021 07:08:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C2E8230FC for ; Thu, 7 Jan 2021 07:08:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726779AbhAGHII (ORCPT ); Thu, 7 Jan 2021 02:08:08 -0500 Received: from mail.skyhub.de ([5.9.137.197]:59320 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725862AbhAGHIH (ORCPT ); Thu, 7 Jan 2021 02:08:07 -0500 Received: from zn.tnic (p200300ec2f0e340040aa7c2c4e2416a1.dip0.t-ipconnect.de [IPv6:2003:ec:2f0e:3400:40aa:7c2c:4e24:16a1]) (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 4AC701EC0249; Thu, 7 Jan 2021 08:07:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1610003246; 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=KGFgHoScXK7gB6fZQoDz8zCs6uUeA+Ptsmqs8FOCUSM=; b=XAlB6YxFl3hMIWbrMLDgTPBh+P8vAOdOBCQL6FPsxbviydKlnstDQ5ZuT8GD1/I/QrP5sy E39IkG2lhmx+5hqJV+g6UktV6JJ0RzYwfKHFDX+iEI+NtJtOZK9HIuh0m30bitnm02r8+5 d36WzkMrMLJWGohHXGwwSeEs7r1Ve4g= Date: Thu, 7 Jan 2021 08:07:24 +0100 From: Borislav Petkov To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, x86@kernel.org, linux-edac@vger.kernel.org, tony.luck@intel.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, kernel-team@fb.com Subject: Re: [PATCH RFC x86/mce] Make mce_timed_out() identify holdout CPUs Message-ID: <20210107070724.GC14697@zn.tnic> References: <20210106174102.GA23874@paulmck-ThinkPad-P72> <20210106183244.GA24607@zn.tnic> <20210106191353.GA2743@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210106191353.GA2743@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 06, 2021 at 11:13:53AM -0800, Paul E. McKenney wrote: > Not yet, it isn't! Well, except in -rcu. ;-) Of course it is - saying "This commit" in this commit's commit message is very much a tautology. :-) > You are suggesting dropping mce_missing_cpus and just doing this? > > if (!cpumask_andnot(&mce_present_cpus, cpu_online_mask, &mce_present_cpus)) Yes. And pls don't call it "holdout CPUs" and change the order so that it is more user-friendly (yap, you don't need __func__ either): [ 78.946153] mce: Not all CPUs (24-47,120-143) entered the broadcast exception handler. [ 78.946153] Kernel panic - not syncing: Timeout: MCA synchronization. or so. And that's fine if it appears twice as long as it is the same info - the MCA code is one complex mess so you can probably guess why I'd like to have new stuff added to it be as simplistic as possible. > I was worried (perhaps unnecessarily) about the possibility of CPUs > checking in during the printout operation, which would set rather than > clear the bit. But perhaps the possible false positives that Tony points > out make this race not worth worrying about. > > Thoughts? Yah, apparently, it is not going to be a precise report as you wanted it to be but at least it'll tell you which *sockets* you can rule out, if not cores. :-) -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette