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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 885EEC31E5B for ; Mon, 17 Jun 2019 19:05:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F68A208CB for ; Mon, 17 Jun 2019 19:05:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560798358; bh=gwzKMKnkmpb67LuXLZlwngatPFxjDRv5Gfxfrd5eRt0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=P7ZWQNvxzjQeeEwF1MJUQoFn524cKxk13M619QOvmSTyamjNQxysJyq1AVmBgi/GY 3VNazLe4kB1M1LWpNu9qD75zs3dowBYeIoZ7+Yizpx2AwYNo+SbLnCMMoUtcowsFOL VPERtwf7AHpguhMnfaPBQe2mJ+/a+2/sMNibiAqs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728718AbfFQTF5 (ORCPT ); Mon, 17 Jun 2019 15:05:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:54732 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725497AbfFQTF4 (ORCPT ); Mon, 17 Jun 2019 15:05:56 -0400 Received: from localhost (lfbn-1-18355-218.w90-101.abo.wanadoo.fr [90.101.143.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id CE28D208C0; Mon, 17 Jun 2019 19:05:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560798356; bh=gwzKMKnkmpb67LuXLZlwngatPFxjDRv5Gfxfrd5eRt0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JN8AQdeqXwbZLY0TGP1Dn54Mw3jGKe3Db5jPGYTh1Ui3UoHhoNMeybWRQnEqir62z GZspIYxrYFO6ED600iqleEgHADxoH12TxLn+uksww4mdqXBj4er0ZCRIPW+gShMHBQ 8tPEGvva7imgFptxqpivsZJiaYS413/0gqWYXUtg= Date: Mon, 17 Jun 2019 21:05:53 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: Nicholas Piggin , linux-kernel@vger.kernel.org, Ingo Molnar Subject: Re: [PATCH] kernel/isolation: Asset that a housekeeping CPU comes up at boot time Message-ID: <20190617190552.GA10264@lerouge> References: <20190601113919.2678-1-npiggin@gmail.com> <1560151344.y4aukciain.astroid@bobo.none> <20190617155931.GK3436@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190617155931.GK3436@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 17, 2019 at 05:59:31PM +0200, Peter Zijlstra wrote: > 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. > Sorry I just came back from vacation. Any chance we can use a WARN() instead? I prefer to use panic() only when data is really threatened or such. Thanks.