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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 3465FC43382 for ; Tue, 25 Sep 2018 13:08:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E01782086B for ; Tue, 25 Sep 2018 13:07:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E01782086B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729126AbeIYTP0 (ORCPT ); Tue, 25 Sep 2018 15:15:26 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:40784 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727341AbeIYTP0 (ORCPT ); Tue, 25 Sep 2018 15:15:26 -0400 Received: by mail-wm1-f67.google.com with SMTP id o2-v6so6982174wmh.5 for ; Tue, 25 Sep 2018 06:07:56 -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:user-agent; bh=GF+XEB65jKqEgZdH3Agl+Fnid9wAvbq7dE4B3GIiOU0=; b=mmSS2koYadRq09q9C+A7PZPHmdODXiXHlMmnoZeh5SNvfhI8XLTHXK5sFexWicDH38 3DyxwlbYgj2qWrclBAuBoOjcsOaVXoV7S8jq2TogYisCGJbXICIz2o/nwnACh59hpMeV Vsn7iOsfhIT/hsIbVF6nfEe2sRfBPCQIFAbIcKilvnnu2uUugmOnAd2NIpDODpGd3U+Y yn6hzL5LyaDhgF2r4kxmR+EzRNmuVrWQvIT3eGWuEaJzfDIBmEfmRUOCojb1CyqMecJK wbfbu7fglXr3Z6K6K5bfixCyer/0sSGE1GkemRmogsjMqgJYAnJOwKjFT8ZY96KlHcX1 dLlA== X-Gm-Message-State: ABuFfohjLWQGVJt6ML3uzNPxGC77l9CY8vYWcR/VgtoAQSBuT8pvAgia OSde2Iy/6OFipzne+gH6/ls2sQ== X-Google-Smtp-Source: ACcGV61RUzMGFNN5qNIftzwT4m8J4JUw6+UbhacprAeNxeli8M9HhmwAPta/cy/ThXY0H12+CmUb5Q== X-Received: by 2002:a1c:de05:: with SMTP id v5-v6mr609583wmg.127.1537880876099; Tue, 25 Sep 2018 06:07:56 -0700 (PDT) Received: from localhost.localdomain ([151.82.116.90]) by smtp.gmail.com with ESMTPSA id h17-v6sm2649026wrq.73.2018.09.25.06.07.53 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 25 Sep 2018 06:07:55 -0700 (PDT) Date: Tue, 25 Sep 2018 15:07:50 +0200 From: Juri Lelli To: Peter Zijlstra Cc: mingo@redhat.com, rostedt@goodmis.org, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it, bristot@redhat.com, mathieu.poirier@linaro.org, lizefan@huawei.com, cgroups@vger.kernel.org Subject: Re: [PATCH v5 5/5] cpuset: Rebuild root domain deadline accounting information Message-ID: <20180925130750.GA25664@localhost.localdomain> References: <20180903142801.20046-1-juri.lelli@redhat.com> <20180903142801.20046-6-juri.lelli@redhat.com> <20180925123222.GA29985@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180925123222.GA29985@hirez.programming.kicks-ass.net> 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 25/09/18 14:32, Peter Zijlstra wrote: > On Mon, Sep 03, 2018 at 04:28:01PM +0200, Juri Lelli wrote: > > +/* > > + * Called with cpuset_mutex held (rebuild_sched_domains()) > > + * Called with hotplug lock held (rebuild_sched_domains_locked()) > > + * Called with sched_domains_mutex held (partition_and_rebuild_domains()) > > Isn't that what we have lockdep_assert_held() for? Indeed. I can put three of them inside the function, even though we have a single path to here atm. Guess makes sense to protect any future change. > > + */ > > +static void rebuild_root_domains(void) > > +{ > > + struct cpuset *cs = NULL; > > + struct cgroup_subsys_state *pos_css; > > + > > + rcu_read_lock(); > > + > > + /* > > + * Clear default root domain DL accounting, it will be computed again > > + * if a task belongs to it. > > + */ > > + dl_clear_root_domain(&def_root_domain); > > + > > + cpuset_for_each_descendant_pre(cs, pos_css, &top_cpuset) { > > + > > + if (cpumask_empty(cs->effective_cpus)) { > > + pos_css = css_rightmost_descendant(pos_css); > > + continue; > > + } > > + > > + css_get(&cs->css); > > + > > + rcu_read_unlock(); > > That looks really dodgy, but I suppose the comment near > css_next_descendant_pre() spells out that this is in fact OK. Plus update_cpumasks_hier() seems to do something similar. Maybe I should switch to use css_tryget_online() as well? Thanks, - Juri