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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0E3BC433EF for ; Fri, 4 Mar 2022 13:49:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235731AbiCDNug (ORCPT ); Fri, 4 Mar 2022 08:50:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbiCDNuf (ORCPT ); Fri, 4 Mar 2022 08:50:35 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A019151C4A for ; Fri, 4 Mar 2022 05:49:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=HNYcvu5d6yHupXGxSdG8Lr5gBTdXYlSzilra3zCEZPM=; b=cxoGm8nC+jabu8Ld10yyV0RWmH JCCFYkwBvfbWiJhoKBoIZZn03ZJNgNbVC+UlubluJ2gvG5+yWol8ZZ2Jy7yMNnYYiEYpqYmOUb+r+ OVvgkMiSCDOyuJQRloMv8ZCO8G9+CluXX6yNk/6C+ylMxyykLQ2q6fCfKUJj+fH6EJ21Od9yOLiZI PH3ng8dl5r1oAQ0d4YPQkHb4qymDQLc0BPR6ZlsRDUKwwSqnJ25CAoxCsBPu2QThbicbPDl9t4jeI ksY3q1oHkEt3H+A+01zl/fGl2RVsg+pB7VMKjaAVCKQpdZcddKzq7PiqwPywC3J++q58h28dUEty3 PJPYPNcA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nQ8JB-00FCiw-1T; Fri, 04 Mar 2022 13:49:25 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 029F8300242; Fri, 4 Mar 2022 14:49:24 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E002E2019A5EC; Fri, 4 Mar 2022 14:49:23 +0100 (CET) Date: Fri, 4 Mar 2022 14:49:23 +0100 From: Peter Zijlstra To: Valentin Schneider Cc: K Prateek Nayak , aubrey.li@linux.intel.com, efault@gmx.de, gautham.shenoy@amd.com, linux-kernel@vger.kernel.org, mgorman@techsingularity.net, mingo@kernel.org, song.bao.hua@hisilicon.com, srikar@linux.vnet.ibm.com, vincent.guittot@linaro.org Subject: Re: [PATCH] sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains Message-ID: References: <20220218162743.1134-1-kprateek.nayak@amd.com> <87k0d9510z.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k0d9510z.mognet@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 04, 2022 at 12:56:44PM +0000, Valentin Schneider wrote: > On 18/02/22 21:57, K Prateek Nayak wrote: > > While investigating the sparse warning reported by the LKP bot [1], > > observed that we have a redundant variable "top" in the function > > build_sched_domains that was introduced in the recent commit > > e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when > > SD_NUMA spans multiple LLCs") > > > > The existing variable "sd" suffices which allows us to remove the > > redundant variable "top" while annotating the other variable "top_p" > > with the "__rcu" annotation to silence the sparse warning. > > > > [1] https://lore.kernel.org/lkml/202202170853.9vofgC3O-lkp@intel.com/ > > > > Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs") > > Reported-by: kernel test robot > > Signed-off-by: K Prateek Nayak > > --- > > kernel/sched/topology.c | 8 +++----- > > 1 file changed, 3 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > > index e6cd55951304..4b757fb8f661 100644 > > --- a/kernel/sched/topology.c > > +++ b/kernel/sched/topology.c > > @@ -2255,7 +2255,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > > > > if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child && > > (child->flags & SD_SHARE_PKG_RESOURCES)) { > > - struct sched_domain *top, *top_p; > > + struct sched_domain __rcu *top_p; > > unsigned int nr_llcs; > > > > /* > > @@ -2280,11 +2280,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > > sd->imb_numa_nr = imb; > > > > /* Set span based on the first NUMA domain. */ > > - top = sd; > > - top_p = top->parent; > > + top_p = sd->parent; > > while (top_p && !(top_p->flags & SD_NUMA)) { > > - top = top->parent; > > - top_p = top->parent; > > + top_p = top_p->parent; > > } > > imb_span = top_p ? top_p->span_weight : sd->span_weight; > > > So sd starts as the first domain without SD_SHARE_PKG_RESOURCES (but its > direct child has it), and the loop searches upward for a NUMA domain. This > indeed shouldn't require two variables. > > I was going to say that while you're at it, you could init top_p to sd > rather than sd->parent in case someone runs a non-default > sched_domain_topology[], but NODE should have neither > SD_SHARE_PKG_RESOURCES nor SD_NUMA, so that doesn't seem required. > > Reviewed-by: Valentin Schneider Thanks!