From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 7CC627D913 for ; Tue, 16 Jul 2019 22:02:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387781AbfGPWCJ (ORCPT ); Tue, 16 Jul 2019 18:02:09 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:42068 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728235AbfGPWCI (ORCPT ); Tue, 16 Jul 2019 18:02:08 -0400 Received: by mail-pf1-f194.google.com with SMTP id q10so9752906pff.9 for ; Tue, 16 Jul 2019 15:02:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=2z9KNQXlh1uTspFy4ArQuvTJcR1Rzwr1DildJveu51k=; b=Nj4Apsx7+yF16h8Bgn0/aVZptTaAfrLBte4ocvydTpKDQLn5zJH9m64VOqx0AGgMOA 9HALNTV6H66Ed1+hvZ8A79pTZKqASniWSBiSgJO+3qYxy/a0f7aH4C2yghsLt+aKszer Ko+jVULH3Uc8rJuQR+id5tzBt3QHpebPG2tfQ= 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:user-agent; bh=2z9KNQXlh1uTspFy4ArQuvTJcR1Rzwr1DildJveu51k=; b=XpKgRpv/qzgTfLZxn+p/Txxxv0SdH8DfHxbZHwimCKSG42fLRu10XzYHJolRsg2VU0 fTJKtLnESFTs3e6FS1YikXbGipiN7FO3MKh3vVZGdonV/0bJHXneRCigL9VxxiwfwUNn 81RmB2awHCxwbrxIuwGQuG88ZkLqEPbYpL8SFj5Bg3JL19WrmIKKhqvtnk9YoKEhWJzL A1C3G0n//nrZpZwk240Fc8v8rMX3SHMMlo1hOef+RUBFXmGTB50iN8kg3l65yI5DjLK3 ehSoAIX8ldllzJ0rKK+CmTwmvsADsoG+PJcEgfoLy0wgt4Cz02O4ZUwam3XckAF7n94G SpJw== X-Gm-Message-State: APjAAAVIu+LEclVdnq6IbwHzTCXD90/eI8k6LsonemscVps9MBzYE2LH w3XFcfNad5CqenbiU4h161I= X-Google-Smtp-Source: APXvYqxaEDRbasy8NySgdX0n0Gtordok4+zLKu64dtBW+xFIbgsDp3e73uVzAdPXDqTAj25BPb/h3Q== X-Received: by 2002:a65:500a:: with SMTP id f10mr5773696pgo.105.1563314527534; Tue, 16 Jul 2019 15:02:07 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id z4sm36091350pfg.166.2019.07.16.15.02.06 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 16 Jul 2019 15:02:06 -0700 (PDT) Date: Tue, 16 Jul 2019 18:02:05 -0400 From: Joel Fernandes To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, Alexey Kuznetsov , Bjorn Helgaas , Borislav Petkov , c0d1n61at3@gmail.com, "David S. Miller" , edumazet@google.com, Greg Kroah-Hartman , Hideaki YOSHIFUJI , "H. Peter Anvin" , Ingo Molnar , Jonathan Corbet , Josh Triplett , keescook@chromium.org, kernel-hardening@lists.openwall.com, kernel-team@android.com, Lai Jiangshan , Len Brown , linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, Mathieu Desnoyers , neilb@suse.com, netdev@vger.kernel.org, Oleg Nesterov , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3) Message-ID: <20190716220205.GB172157@google.com> References: <20190715143705.117908-1-joel@joelfernandes.org> <20190715143705.117908-3-joel@joelfernandes.org> <20190716183833.GD14271@linux.ibm.com> <20190716184649.GA130463@google.com> <20190716185303.GM14271@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190716185303.GM14271@linux.ibm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, Jul 16, 2019 at 11:53:03AM -0700, Paul E. McKenney wrote: [snip] > > > A few more things below. > > > > --- > > > > include/linux/rculist.h | 28 ++++++++++++++++++++----- > > > > include/linux/rcupdate.h | 7 +++++++ > > > > kernel/rcu/Kconfig.debug | 11 ++++++++++ > > > > kernel/rcu/update.c | 44 ++++++++++++++++++++++++---------------- > > > > 4 files changed, 67 insertions(+), 23 deletions(-) > > > > > > > > diff --git a/include/linux/rculist.h b/include/linux/rculist.h > > > > index e91ec9ddcd30..1048160625bb 100644 > > > > --- a/include/linux/rculist.h > > > > +++ b/include/linux/rculist.h > > > > @@ -40,6 +40,20 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list) > > > > */ > > > > #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) > > > > > > > > +/* > > > > + * Check during list traversal that we are within an RCU reader > > > > + */ > > > > + > > > > +#ifdef CONFIG_PROVE_RCU_LIST > > > > > > This new Kconfig option is OK temporarily, but unless there is reason to > > > fear malfunction that a few weeks of rcutorture, 0day, and -next won't > > > find, it would be better to just use CONFIG_PROVE_RCU. The overall goal > > > is to reduce the number of RCU knobs rather than grow them, must though > > > history might lead one to believe otherwise. :-/ > > > > If you want, we can try to drop this option and just use PROVE_RCU however I > > must say there may be several warnings that need to be fixed in a short > > period of time (even a few weeks may be too short) considering the 1000+ > > uses of RCU lists. > Do many people other than me build with CONFIG_PROVE_RCU? If so, then > that would be a good reason for a temporary CONFIG_PROVE_RCU_LIST, > as in going away in a release or two once the warnings get fixed. PROVE_RCU is enabled by default with PROVE_LOCKING, so it is used quite heavilty. > > But I don't mind dropping it and it may just accelerate the fixing up of all > > callers. > > I will let you decide based on the above question. But if you have > CONFIG_PROVE_RCU_LIST, as noted below, it needs to depend on RCU_EXPERT. Ok, will make it depend. But yes for temporary purpose, I will leave it as a config and remove it later. thanks, - Joel