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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 01896C10DC2 for ; Thu, 30 Nov 2023 16:47:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:CC:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yeG8JVVyA++B/zgbSPyDc5W7cPQ3PR0864B2rd0tdqU=; b=zfsVYtj7NZe4O2 f8OFfMyRycLnB9GVSAco0vadgMyKsu2zbDZq0tGTmzUj7Gfj0gVX09o00ktMiBEijctJj7L+yGNhf zsXrLPRqYqKhkgQ3k0wXnLa/jGAeTmEBSfnZAKl84tTq4Xa2oWP//zFHSNWfRseYvxiBfGeiQpG9h sEiA6xnmUmf+i9yOGOGn9dq4peUplqGi8YmnTHatTsOJq7BvnN2x4u61cKTD0/VGG5419M6tw5qkw +0f8VokP1fPKA0id9KEWdwWJ8jhlJfeoSzww9OaFd0oJbSR/2DJ/HRV/rumGKmvglYLlPcQA9UwrB NiusM+QfDNl2pQbSwCLg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r8kBi-00BNv8-0R; Thu, 30 Nov 2023 16:46:54 +0000 Received: from frasgout.his.huawei.com ([185.176.79.56]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1r8kBd-00BNth-18; Thu, 30 Nov 2023 16:46:50 +0000 Received: from mail.maildlp.com (unknown [172.18.186.231]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Sh2685pFkz6K5lJ; Fri, 1 Dec 2023 00:42:08 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (unknown [7.191.163.240]) by mail.maildlp.com (Postfix) with ESMTPS id 96EBF14058E; Fri, 1 Dec 2023 00:46:47 +0800 (CST) Received: from localhost (10.202.227.76) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Thu, 30 Nov 2023 16:46:46 +0000 Date: Thu, 30 Nov 2023 16:46:46 +0000 From: Jonathan Cameron To: Russell King CC: , , , , , , , , , , , , , Salil Mehta , Jean-Philippe Brucker , , , James Morse , Sudeep Holla , Greg Kroah-Hartman , "Rafael J. Wysocki" Subject: Re: [PATCH 01/21] arch_topology: Make register_cpu_capacity_sysctl() tolerant to late CPUs Message-ID: <20231130164646.00006770@Huawei.com> In-Reply-To: References: Organization: Huawei Technologies Research and Development (UK) Ltd. X-Mailer: Claws Mail 4.1.0 (GTK 3.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 X-Originating-IP: [10.202.227.76] X-ClientProxiedBy: lhrpeml100005.china.huawei.com (7.191.160.25) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231130_084649_671761_44C39E60 X-CRM114-Status: GOOD ( 25.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 21 Nov 2023 13:43:54 +0000 Russell King wrote: > From: James Morse > > register_cpu_capacity_sysctl() adds a property to sysfs that describes > the CPUs capacity. This is done from a subsys_initcall() that assumes > all possible CPUs are registered. > > With CPU hotplug, possible CPUs aren't registered until they become > present, (or for arm64 enabled). This leads to messages during boot: > | register_cpu_capacity_sysctl: too early to get CPU1 device! > and once these CPUs are added to the system, the file is missing. > > Move this to a cpuhp callback, so that the file is created once > CPUs are brought online. This covers CPUs that are added late by > mechanisms like hotplug. > One observable difference is the file is now missing for offline CPUs. > > Signed-off-by: James Morse > Reviewed-by: Gavin Shan > Signed-off-by: Russell King (Oracle) Reviewed-by: Jonathan Cameron > --- > If the offline CPUs thing is a problem for the tools that consume > this value, we'd need to move cpu_capacity to be part of cpu.c's > common_cpu_attr_groups. However, attempts to discuss this just end > up in a black hole, so this is a non-starter. Thus, if this needs > to be done, it can be done as a separate patch. > --- > drivers/base/arch_topology.c | 38 ++++++++++++++++++++++++------------ > 1 file changed, 26 insertions(+), 12 deletions(-) > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index b741b5ba82bd..9ccb7daee78e 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -220,20 +220,34 @@ static DECLARE_WORK(update_topology_flags_work, update_topology_flags_workfn); > > static DEVICE_ATTR_RO(cpu_capacity); > > -static int register_cpu_capacity_sysctl(void) > +static int cpu_capacity_sysctl_add(unsigned int cpu) > { > - int i; > - struct device *cpu; > + struct device *cpu_dev = get_cpu_device(cpu); > > - for_each_possible_cpu(i) { > - cpu = get_cpu_device(i); > - if (!cpu) { > - pr_err("%s: too early to get CPU%d device!\n", > - __func__, i); > - continue; > - } > - device_create_file(cpu, &dev_attr_cpu_capacity); > - } > + if (!cpu_dev) > + return -ENOENT; > + > + device_create_file(cpu_dev, &dev_attr_cpu_capacity); > + > + return 0; > +} > + > +static int cpu_capacity_sysctl_remove(unsigned int cpu) > +{ > + struct device *cpu_dev = get_cpu_device(cpu); > + > + if (!cpu_dev) > + return -ENOENT; > + > + device_remove_file(cpu_dev, &dev_attr_cpu_capacity); > + > + return 0; > +} > + > +static int register_cpu_capacity_sysctl(void) > +{ > + cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "topology/cpu-capacity", > + cpu_capacity_sysctl_add, cpu_capacity_sysctl_remove); > > return 0; > } _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel