From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D96810D0; Thu, 30 Nov 2023 08:46:49 -0800 (PST) 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) Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: lhrpeml100005.china.huawei.com (7.191.160.25) To lhrpeml500005.china.huawei.com (7.191.163.240) 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; > }