From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 967E618A; Sat, 21 Oct 2023 10:56:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="hTcaPIRt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85359C433C8; Sat, 21 Oct 2023 10:56:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1697885818; bh=lWjx0bstoWSn8O+1+vq3s6PJ4JDA6SyKY8ViX2L7YW0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hTcaPIRtnQmlyxhrbVQzTkIF6yu1dZwfQH0HKzzZf+IdjhhVDBzohjKljAvRxu6ZC +EK0hYdtjcSMWn6+4ncGofksLqwZ6P5+pfIq4uHxdEPiU2xTLxyhLfke0SYjlmgd4x HJxhZl7xo4cAk+d9+HLkSGCqfb+thCkty+PvIYNY= Date: Sat, 21 Oct 2023 12:56:55 +0200 From: Greg KH To: "Russell King (Oracle)" Cc: Jonathan Cameron , 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: <2023102128-banter-circular-85a2@gregkh> References: <20230913163823.7880-1-james.morse@arm.com> <20230913163823.7880-12-james.morse@arm.com> <20230914130126.000069db@Huawei.com> Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Oct 20, 2023 at 12:53:29PM +0100, Russell King (Oracle) wrote: > 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. Sorry, I don't see what I am supposed to comment on, so please just send a new series and I'll look at that. thanks, greg k-h