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=-17.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 77792C433DB for ; Wed, 27 Jan 2021 03:43:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C5D220643 for ; Wed, 27 Jan 2021 03:43:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236835AbhA0DnL (ORCPT ); Tue, 26 Jan 2021 22:43:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:51274 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728291AbhAZWSh (ORCPT ); Tue, 26 Jan 2021 17:18:37 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 03B8F2065D; Tue, 26 Jan 2021 22:17:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611699476; bh=avnb89epXY17wmd58T7YmnHAkYv1wezl3UZyJ0MdJCI=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=EDU6iWaNswXQd25X5iZE9xQy4uqCObI8/PiaEuU/UyNkT3fx0g5zvEE5IgTExDedX Y/JTemd+0nYC4XLtHhIKm/oPVkbS7dKeV5gBSj9j4gs1f/EffabVn895dmlEQJ3xKL n+cZMARkSwBGJoRObsJ9ESE7MRrsHcPPlidimdgZ5XEYhj6BqCxi4T1Y9iIdDyEh3m SFlj7PyanqUS7NWMBYjNVZWfI/TDzQ2Bk7+DeYc5nrbllGAMJRP+t0cAv+iBhKlAiJ SYJHW/xpglJC8TDdNr+nP276JTUGiMIBg8xHcPRJzm62j9wr73Odm7V3qHkQohXM+G MgTvKez7Cx0OQ== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id B71AB352268C; Tue, 26 Jan 2021 14:17:55 -0800 (PST) Date: Tue, 26 Jan 2021 14:17:55 -0800 From: "Paul E. McKenney" To: Yury Norov Cc: Paul Gortmaker , Linux Kernel Mailing List , lizefan@huawei.com, Ingo Molnar , Thomas Gleixner , josh@joshtriplett.org, Peter Zijlstra , fweisbec@gmail.com, Rasmus Villemoes , Andy Shevchenko Subject: Re: [PATCH 8/8] rcu: deprecate "all" option to rcu_nocbs= Message-ID: <20210126221755.GH2743@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20210126171141.122639-1-paul.gortmaker@windriver.com> <20210126171141.122639-9-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 26, 2021 at 01:36:23PM -0800, Yury Norov wrote: > On Tue, Jan 26, 2021 at 9:12 AM Paul Gortmaker > wrote: > > > > With the core bitmap support now accepting "N" as a placeholder for > > the end of the bitmap, "all" can be represented as "0-N" and has the > > advantage of not being specific to RCU (or any other subsystem). > > > > So deprecate the use of "all" by removing documentation references > > to it. The support itself needs to remain for now, since we don't > > know how many people out there are using it currently, but since it > > is in an __init area anyway, it isn't worth losing sleep over. > > > > Cc: Yury Norov > > Cc: Peter Zijlstra > > Cc: "Paul E. McKenney" > > Cc: Josh Triplett > > Signed-off-by: Paul Gortmaker > > --- > > Documentation/admin-guide/kernel-parameters.txt | 4 +--- > > kernel/rcu/tree_plugin.h | 6 ++---- > > 2 files changed, 3 insertions(+), 7 deletions(-) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index a10b545c2070..a116c0ff0a91 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -4037,9 +4037,7 @@ > > see CONFIG_RAS_CEC help text. > > > > rcu_nocbs= [KNL] > > - The argument is a cpu list, as described above, > > - except that the string "all" can be used to > > - specify every CPU on the system. > > + The argument is a cpu list, as described above. > > > > In kernels built with CONFIG_RCU_NOCB_CPU=y, set > > the specified list of CPUs to be no-callback CPUs. > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > index 7e291ce0a1d6..56788dfde922 100644 > > --- a/kernel/rcu/tree_plugin.h > > +++ b/kernel/rcu/tree_plugin.h > > @@ -1463,14 +1463,12 @@ static void rcu_cleanup_after_idle(void) > > > > /* > > * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. > > - * The string after the "rcu_nocbs=" is either "all" for all CPUs, or a > > - * comma-separated list of CPUs and/or CPU ranges. If an invalid list is > > - * given, a warning is emitted and all CPUs are offloaded. > > + * If the list is invalid, a warning is emitted and all CPUs are offloaded. > > */ > > static int __init rcu_nocb_setup(char *str) > > { > > alloc_bootmem_cpumask_var(&rcu_nocb_mask); > > - if (!strcasecmp(str, "all")) > > + if (!strcasecmp(str, "all")) /* legacy: use "0-N" instead */ > > I think 'all' and 'none' is a good idea. It's simple and convenient. > But if you don't > like it, can you please at least put this comment in system log using > WARN_ON_ONCE(). It's quite possible that Linux users don't read source code > comments. Please leave it silent. This has been available to RCU users for quite some time, so suddenly spewing warnings at all of them is a bit unfriendly. The extra code is negligible, and the documentation will guide people more gently in the right direction. Plus I am the one who would end up receiving complaints about the warnings, and I have much better things to do with my time. Thanx, Paul > > cpumask_setall(rcu_nocb_mask); > > else > > if (cpulist_parse(str, rcu_nocb_mask)) { > > -- > > 2.17.1 > >