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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,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 19823C43331 for ; Tue, 31 Mar 2020 20:58:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E4EB6207FF for ; Tue, 31 Mar 2020 20:58:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BmnABhqZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731335AbgCaU6K (ORCPT ); Tue, 31 Mar 2020 16:58:10 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:21554 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731303AbgCaU6I (ORCPT ); Tue, 31 Mar 2020 16:58:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585688287; 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: in-reply-to:in-reply-to:references:references; bh=nMTuWgH43GvSmLl3/vGFHtIMAhCbcDhmbQIosf8L0DQ=; b=BmnABhqZkM8Ecipy/dwn2qDoMFhcCoyaQC+v7aYMSxD4GmaQeYfVq+U8Mzex1nAWRGfAGL 7XRl+W3xNQZfF8suFbv69LGMIGue8T4A7K3YC5L9PKaaRR5LCPmuAiix8c3gP1P8PMSJ+x FCVAP6wj4X+mJzvk+gg/Z4flm2TY1So= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-15-bjSavILoN6KuVEDGmG00Ww-1; Tue, 31 Mar 2020 16:58:05 -0400 X-MC-Unique: bjSavILoN6KuVEDGmG00Ww-1 Received: by mail-wr1-f72.google.com with SMTP id m15so13564491wrb.0 for ; Tue, 31 Mar 2020 13:58:05 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=nMTuWgH43GvSmLl3/vGFHtIMAhCbcDhmbQIosf8L0DQ=; b=FI7r4tEqDtwN9TtEYQ5jdf6nYLdvqx7PpHHX3GfcDouMk3GzYrww1vXW3jAjJcMdNy gt/u0yfw78NiwMWbGOqPSs8C6rnf1cuhVBnMpRjqk6XRurIACccz0wFUKiARmSBPCmce YHOjLyeQBi3Wbt3Uylzc7ANfToTG+1fcoD6f9cQbFOjjw2sTDSq4Xkq55059UI+qvCD1 vGVGFv9n0UnKwWB/v0RIQYCQzQxxY8+EyHw10dMblY0Z8qO5CwlqPB7Fj7yTs58rHSZZ 0lmnyH+9JUuugZMBbuXJ0OglbnL58JNaURMr16QKM0X9ul0qDz+HZdfozvLw3eqHI5wu qPGw== X-Gm-Message-State: ANhLgQ16BqR5a5qfZbGOVAOVhKXNl88Q/xFZQKGl0Wp9uDIReClPuh8A AsOZs+FSMh1B6gkgr+EJNTHkGbPR9BSGvUySTDYSulHhbo7lNR1n/w1T2SnuABk7cTtEwawcknp k9mPJqxhNuQZK2lyNQ9CX+dSm X-Received: by 2002:a05:6000:10c8:: with SMTP id b8mr20964628wrx.138.1585688284479; Tue, 31 Mar 2020 13:58:04 -0700 (PDT) X-Google-Smtp-Source: ADFU+vtjE8SVKcDqJXpBwY3z/nljFiImBJhiy66LJgYJ18HOdry7Gow9qqZRHMNtuEBqfbVTRq42RQ== X-Received: by 2002:a05:6000:10c8:: with SMTP id b8mr20964598wrx.138.1585688284037; Tue, 31 Mar 2020 13:58:04 -0700 (PDT) Received: from xz-x1 ([2607:9880:19c0:32::2]) by smtp.gmail.com with ESMTPSA id e5sm27609022wru.92.2020.03.31.13.58.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2020 13:58:03 -0700 (PDT) Date: Tue, 31 Mar 2020 16:57:59 -0400 From: Peter Xu To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Ming Lei , Ingo Molnar , Peter Zijlstra , Juri Lelli , Luiz Capitulino Subject: Re: [PATCH] sched/isolation: Allow "isolcpus=" to skip unknown sub-parameters Message-ID: <20200331205759.GA648829@xz-x1> References: <20200204161639.267026-1-peterx@redhat.com> <20200214194008.GA1193332@xz-x1> <877e0oud5i.fsf@nanos.tec.linutronix.de> <20200309151917.GB4206@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200309151917.GB4206@xz-x1> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 09, 2020 at 11:19:17AM -0400, Peter Xu wrote: > On Fri, Feb 14, 2020 at 09:28:25PM +0100, Thomas Gleixner wrote: > > Peter Xu writes: > > > > > On Tue, Feb 04, 2020 at 11:16:39AM -0500, Peter Xu wrote: > > >> The "isolcpus=" parameter allows sub-parameters to exist before the > > >> cpulist is specified, and if it sees unknown sub-parameters the whole > > >> parameter will be ignored. This design is incompatible with itself > > >> when we add more sub-parameters to "isolcpus=", because the old > > >> kernels will not recognize the new "isolcpus=" sub-parameters, then it > > >> will invalidate the whole parameter so the CPU isolation will not > > >> really take effect if we start to use the new sub-parameters while > > >> later we reboot into an old kernel. Instead we will see this when > > >> booting the old kernel: > > >> > > >> isolcpus: Error, unknown flag > > >> > > >> The better and compatible way is to allow "isolcpus=" to skip unknown > > >> sub-parameters, so that even if we add new sub-parameters to it the > > >> old kernel will still be able to behave as usual even if with the new > > >> sub-parameter is specified. > > >> > > >> Ideally this patch should be there when we introduce the first > > >> sub-parameter for "isolcpus=", so it's already a bit late. However > > >> late is better than nothing. > > > > > > Ping - Hi, Thomas, do you have any further comment on this patch? > > > > Fine with me. > > > > Reviewed-by: Thomas Gleixner > > Thanks Thomas! > > Does anyone like to pick this up, or does this patch needs more > review? Another gentle ping with the hope that this patch can be picked up. It's a very simple patch, but I really hope it can be in asap because the latter means the more kernel versions will be affected by this isolcpus incompatibility defect (and imo should consider stable too). Thanks. -- Peter Xu