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 682D1CDB47E for ; Fri, 20 Oct 2023 11:53:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377258AbjJTLxm (ORCPT ); Fri, 20 Oct 2023 07:53:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1377257AbjJTLxl (ORCPT ); Fri, 20 Oct 2023 07:53:41 -0400 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:32c8:5054:ff:fe00:142]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D9AA0D41; Fri, 20 Oct 2023 04:53:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZnH9rsDzGO6weBMybmlTOxejgjbXoW+kfLP/Bw4OXUE=; b=PHFGq+CDzvcu05j4/9OwcnhS+3 dniZKELXdzZ7oE3K2oURHH1f7vOrijKdYXMxblKLxLQmksJTA+Mt1qwTWLN0NwzyHRluOQ8lEZtAu HO4GZ8rV19IGOzem3PNfDR9XeB4gH23tXyd21o7vRK9lx96fXGBSWBAanRKe1HlchPKpVvCy6pKZf ca456Hj718geltF8hQwoAYhOiW6BppDwcbxBVUtresfOLi2DSCWYrWw4884RjpK6mccRd8M3wL1IT VVeCBJYEoy1nrzTjZPmVe77zFRN6Luib8s+HX9uw2MImjvcrudZ2J7RK6bffVuxYVtslyuJqU7Adp XMNN3wlA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:48178) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1qto4K-0000LD-0H; Fri, 20 Oct 2023 12:53:32 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.94.2) (envelope-from ) id 1qto4H-0001Vh-On; Fri, 20 Oct 2023 12:53:29 +0100 Date: Fri, 20 Oct 2023 12:53:29 +0100 From: "Russell King (Oracle)" To: Jonathan Cameron , gregkh@linuxfoundation.org Cc: James Morse , linux-pm@vger.kernel.org, loongarch@lists.linux.dev, linux-acpi@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, kvmarm@lists.linux.dev, x86@kernel.org, Salil Mehta , Jean-Philippe Brucker , jianyong.wu@arm.com, justin.he@arm.com Subject: Re: [RFC PATCH v2 11/35] arch_topology: Make register_cpu_capacity_sysctl() tolerant to late CPUs Message-ID: References: <20230913163823.7880-1-james.morse@arm.com> <20230913163823.7880-12-james.morse@arm.com> <20230914130126.000069db@Huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230914130126.000069db@Huawei.com> Sender: Russell King (Oracle) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, Sep 14, 2023 at 01:01:26PM +0100, Jonathan Cameron wrote: > On Wed, 13 Sep 2023 16:37:59 +0000 > James Morse wrote: > > > 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 > > --- > > 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. > > I think we should do that anyway and then use an is_visible() if we want to > change whether it is visible in offline cpus. > > Dynamic sysfs file creation is horrible - particularly when done > from an totally different file from where the rest of the attributes > are registered. I'm curious what the history behind that is. > > Whilst here, why is there a common_cpu_attr_groups which is > identical to the hotpluggable_cpu_attr_groups in base/cpu.c? > > > +CC GregKH > Given changes in drivers/base/ It would be good to have a comment on this from Greg before I post an updated series of James' patches with most of the comments addressed, possibly later today. Thanks. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!