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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 44D5BC3A5A7 for ; Wed, 4 Sep 2019 10:16:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24D712339D for ; Wed, 4 Sep 2019 10:16:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728951AbfIDKQZ (ORCPT ); Wed, 4 Sep 2019 06:16:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:42742 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725840AbfIDKQY (ORCPT ); Wed, 4 Sep 2019 06:16:24 -0400 Received: from oasis.local.home (bl11-233-114.dsl.telepac.pt [85.244.233.114]) (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 CF72E21881; Wed, 4 Sep 2019 10:16:20 +0000 (UTC) Date: Wed, 4 Sep 2019 06:16:16 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Alessio Balsini , mingo@kernel.org, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, luca.abeni@santannapisa.it, bristot@redhat.com, dvyukov@google.com, tglx@linutronix.de, vpillai@digitalocean.com, kernel-team@android.com Subject: Re: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Message-ID: <20190904061616.25ce79e1@oasis.local.home> In-Reply-To: <20190902091623.GQ2349@hirez.programming.kicks-ass.net> References: <20190726145409.947503076@infradead.org> <20190726161357.397880775@infradead.org> <20190802172104.GA134279@google.com> <20190805115309.GJ2349@hirez.programming.kicks-ass.net> <20190822122949.GA245353@google.com> <20190822165125.GW2369@hirez.programming.kicks-ass.net> <20190831144117.GA133727@google.com> <20190902091623.GQ2349@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2 Sep 2019 11:16:23 +0200 Peter Zijlstra wrote: > in sched_dl_period_handler(). And do: > > + preempt_disable(); > max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC; > min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC; > + preempt_enable(); Hmm, I'm curious. Doesn't the preempt_disable/enable() also add compiler barriers which would remove the need for the READ_ONCE()s here? -- Steve