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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 B8FB7C4361B for ; Mon, 7 Dec 2020 18:29:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7663923888 for ; Mon, 7 Dec 2020 18:29:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726396AbgLGS36 (ORCPT ); Mon, 7 Dec 2020 13:29:58 -0500 Received: from mail.skyhub.de ([5.9.137.197]:43648 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725823AbgLGS35 (ORCPT ); Mon, 7 Dec 2020 13:29:57 -0500 Received: from zn.tnic (p200300ec2f0a380064629ff712875f88.dip0.t-ipconnect.de [IPv6:2003:ec:2f0a:3800:6462:9ff7:1287:5f88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 37ACB1EC0266; Mon, 7 Dec 2020 19:29:16 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1607365756; 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: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=UcgJt3nxSKpwchL/iP2ux1Mxz2gg4VyE+PHYmJH7Ers=; b=TINAG4raZW9HXC9+zvnMHq3Hd/A/VIdV6GeOubaoSo9HZGEjZT4pf1/XZlQ5kEWK8sGRp1 W69ROu759QdWgoz3ZQDlVyYh/YF2ePApgEt9vm5MZbMIzXFFWkcDLVlDWDWgLlEAupu2kj oyMgjaAzIj8YfJkU9ubfRco9h4ieyXs= Date: Mon, 7 Dec 2020 19:29:12 +0100 From: Borislav Petkov To: Reinette Chatre Cc: tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com, kuo-lang.tseng@intel.com, shakeelb@google.com, valentin.schneider@arm.com, mingo@redhat.com, babu.moger@amd.com, james.morse@arm.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/3] x86/resctrl: Move setting task's active CPU in a mask into helpers Message-ID: <20201207182912.GF20489@zn.tnic> References: <77973e75a10bf7ef9b33c664544667deee9e1a8e.1607036601.git.reinette.chatre@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <77973e75a10bf7ef9b33c664544667deee9e1a8e.1607036601.git.reinette.chatre@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 03, 2020 at 03:25:48PM -0800, Reinette Chatre wrote: > From: Fenghua Yu > > The code of setting the CPU on which a task is running in a CPU mask is > moved into a couple of helpers. Pls read section "2) Describe your changes" in Documentation/process/submitting-patches.rst for more details. More specifically: "Describe your changes in imperative mood, e.g. "make xyzzy do frotz" instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy to do frotz", as if you are giving orders to the codebase to change its behaviour." > The new helper task_on_cpu() will be reused shortly. "reused shortly"? I don't think so. > > Signed-off-by: Fenghua Yu > Signed-off-by: Reinette Chatre > Reviewed-by: Tony Luck > Cc: stable@vger.kernel.org Fixes? I guess the same commit from the other two: Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files") ? > --- > arch/x86/kernel/cpu/resctrl/rdtgroup.c | 47 +++++++++++++++++++------- > 1 file changed, 34 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > index 6f4ca4bea625..68db7d2dec8f 100644 > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c > @@ -525,6 +525,38 @@ static void rdtgroup_remove(struct rdtgroup *rdtgrp) > kfree(rdtgrp); > } > > +#ifdef CONFIG_SMP > +/* Get the CPU if the task is on it. */ > +static bool task_on_cpu(struct task_struct *t, int *cpu) > +{ > + /* > + * This is safe on x86 w/o barriers as the ordering of writing to > + * task_cpu() and t->on_cpu is reverse to the reading here. The > + * detection is inaccurate as tasks might move or schedule before > + * the smp function call takes place. In such a case the function > + * call is pointless, but there is no other side effect. > + */ > + if (t->on_cpu) { > + *cpu = task_cpu(t); Why have an I/O parameter when you can make it simply: static int task_on_cpu(struct task_struct *t) { if (t->on_cpu) return task_cpu(t); return -1; } > + > + return true; > + } > + > + return false; > +} > + > +static void set_task_cpumask(struct task_struct *t, struct cpumask *mask) > +{ > + int cpu; > + > + if (mask && task_on_cpu(t, &cpu)) > + cpumask_set_cpu(cpu, mask); And that you can turn into: if (!mask) return; cpu = task_on_cpu(t); if (cpu < 0) return; cpumask_set_cpu(cpu, mask); Readable and simple. Hmm? -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette