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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, 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 04BB6C31E5C for ; Mon, 17 Jun 2019 15:59:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF43C208C4 for ; Mon, 17 Jun 2019 15:59:47 +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="LiH0vbSF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728540AbfFQP7q (ORCPT ); Mon, 17 Jun 2019 11:59:46 -0400 Received: from merlin.infradead.org ([205.233.59.134]:35148 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726047AbfFQP7q (ORCPT ); Mon, 17 Jun 2019 11:59:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=38YySIuBWDGCH+kJBVm7kEsuVhxcLDts6v3f1Sg1uSE=; b=LiH0vbSFLGaZrExrZ6z3On83x DSETELwD4Fl/808GzekFxZWg7zoheZNzHN/qy0w/8462gyXQ85IaXnKAfJn5iiHdUpyA+a/BwXnwf wJaAGhRIQmD9v3zU6qbQyWrpNuAXZzwD9qX6PztjHO6y79mKvSb/nJdKfSlLi0fQTvq+buSVgkgfU 9gG+NhMn58Lk/oDwI0Aprm2NKkZ39JfycL9ZkhBRK8Xz7yo/QHOF/NoTfkxpkQPVQH/TsgJCtYDGU RYDYOchSP7VNLklSlvbtqMZ2oOcC1I6+WtQh8YPjzuSWZrEdV4Fk/YpzoKitPvoJ9qReZY5YNf0YZ U9Ah/YdJw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hcu2g-0000hZ-Bk; Mon, 17 Jun 2019 15:59:38 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 92229201F4619; Mon, 17 Jun 2019 17:59:31 +0200 (CEST) Date: Mon, 17 Jun 2019 17:59:31 +0200 From: Peter Zijlstra To: Nicholas Piggin Cc: linux-kernel@vger.kernel.org, Frederic Weisbecker , Ingo Molnar Subject: Re: [PATCH] kernel/isolation: Asset that a housekeeping CPU comes up at boot time Message-ID: <20190617155931.GK3436@hirez.programming.kicks-ass.net> References: <20190601113919.2678-1-npiggin@gmail.com> <1560151344.y4aukciain.astroid@bobo.none> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1560151344.y4aukciain.astroid@bobo.none> 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 Mon, Jun 10, 2019 at 05:24:32PM +1000, Nicholas Piggin wrote: > 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. > > > > An 8 CPU system booted with "nohz_full=0-6 maxcpus=4", for example. > > > > 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. > > > > 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? I was hoping for feedback from Frederic, lacking that, I've queued it now.