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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,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 10CC2C282DD for ; Mon, 10 Jun 2019 07:26:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6A56207E0 for ; Mon, 10 Jun 2019 07:26:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Dqc1l/3r" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387981AbfFJH04 (ORCPT ); Mon, 10 Jun 2019 03:26:56 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:37201 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387541AbfFJH04 (ORCPT ); Mon, 10 Jun 2019 03:26:56 -0400 Received: by mail-pg1-f193.google.com with SMTP id 20so4557362pgr.4 for ; Mon, 10 Jun 2019 00:26:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:subject:to:cc:references:in-reply-to:mime-version :user-agent:message-id:content-transfer-encoding; bh=daFxAMryc0skAl9XtVIwXmNQD/X9Q30Ey2kxgBive84=; b=Dqc1l/3r07Dlb2xjooJOtEAGLplKK23A8/eyDg4VAEqZgsP+01f5Cr4w+9z9eEe7qt 2biIKGF3iAf24r5XEXkdEaygP/wEARYoEvHp1P7ukQ9LZV64gt6iO28UpjH+Rg4EBjs1 xAyItWOi/v9DQVk1xalnJ8wUicxrdx4bERuxtP3fAlHpDa51qugN3CZdFcDWuNbD7xMG dljZtJU8cwvVz07FDENnJKauePx/fKCw80YBYFzteThhIVwyD9hM38iI2H0vYMEBFDeO zVvpY4SPpR+zuPcp6XeCQKnecgzVEG/YcoUDJebTRDYUu9QvbFg75MBf4xaew/A/bXFc MtwA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:subject:to:cc:references:in-reply-to :mime-version:user-agent:message-id:content-transfer-encoding; bh=daFxAMryc0skAl9XtVIwXmNQD/X9Q30Ey2kxgBive84=; b=AZFIGZSw7DgS9H9+6jupGGEbVvUeN6zM4FciFBQHCzA8tHpWW/KIq0MFxPJTYotwki fkFPOArNys9SpG4dVtG7GAGVDreY479XRJiwjuxuOKSUyvpo42TOc5qtnh9WctSlehma ef9iZJ9BZF5Y/5821F2k6lEG5Tf6wfgq/1YwPYukv52rAUOC7ReoTl/KxLJXLlZiNlRa 6PleSc7yUkYDGh7BEAQ+VYrRYUiboL05+iqEbDKlDdtxUBAZkvjsT3Pqntc+uI+5xfo6 mbMfmh2hGp4MbAZqMztKhLuyCw8TjBXrEVtlqeZS+amu1sSp1ZlBlUOJWDo7MjpIdfi6 wjZg== X-Gm-Message-State: APjAAAUjaJTGpv/weyLtI+zHHQV8JejnsVYtnl2hubIsbP3hfh2Bpkwo x3s8bGQvKLk3/DVCKHkgLVKUizoh X-Google-Smtp-Source: APXvYqzKarQ+sze16KTV8Mm4YgzPTsOOLpx7rbSHrAC0nBsm5iePvKRCIcZuLzUi7v85R8KxXuaQLQ== X-Received: by 2002:a65:4b88:: with SMTP id t8mr14950808pgq.374.1560151615468; Mon, 10 Jun 2019 00:26:55 -0700 (PDT) Received: from localhost (60-241-56-246.tpgi.com.au. [60.241.56.246]) by smtp.gmail.com with ESMTPSA id a12sm11252494pgq.0.2019.06.10.00.26.54 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 10 Jun 2019 00:26:54 -0700 (PDT) Date: Mon, 10 Jun 2019 17:24:32 +1000 From: Nicholas Piggin Subject: Re: [PATCH] kernel/isolation: Asset that a housekeeping CPU comes up at boot time To: linux-kernel@vger.kernel.org Cc: Frederic Weisbecker , Ingo Molnar , Peter Zijlstra References: <20190601113919.2678-1-npiggin@gmail.com> In-Reply-To: <20190601113919.2678-1-npiggin@gmail.com> MIME-Version: 1.0 User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) Message-Id: <1560151344.y4aukciain.astroid@bobo.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nicholas Piggin's on June 1, 2019 9:39 pm: > With the change to allow the boot CPU0 to be isolated, it is possible > to specify command line options that result in no housekeeping CPU > online at boot. >=20 > An 8 CPU system booted with "nohz_full=3D0-6 maxcpus=3D4", for example. >=20 > It is not easily possible at housekeeping init time to know all the > various SMP options that will result in an invalid configuration, so > this patch adds a sanity check after SMP init, to ensure that a > housekeeping CPU has been onlined. >=20 > The panic is undesirable, but it's better than the alternative of an > obscure non deterministic failure. The panic will reliably happen > when advanced parameters are used incorrectly. Ping on this one? This should resolve Frederic's remaining objection to the series (at least until he solves it more generally). As the series has already been merged, should we get this upstream before release? Thanks, Nick =