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 77722C4332F for ; Wed, 1 Dec 2021 01:29:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236614AbhLABdC (ORCPT ); Tue, 30 Nov 2021 20:33:02 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:14999 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230044AbhLABdA (ORCPT ); Tue, 30 Nov 2021 20:33:00 -0500 Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4J3hJd2CkKzZdHM; Wed, 1 Dec 2021 09:26:57 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Wed, 1 Dec 2021 09:29:38 +0800 Received: from [10.174.179.5] (10.174.179.5) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Wed, 1 Dec 2021 09:29:37 +0800 Subject: Re: [PATCH] cpufreq: Fix get_cpu_device() failed in add_cpu_dev_symlink() To: "Rafael J. Wysocki" , Viresh Kumar CC: Linux PM , Linux Kernel Mailing List , Hanjun Guo References: <20211129080248.46240-1-wangxiongfeng2@huawei.com> <20211129091039.s7bqq43o4ktuub6t@vireshk-i7> From: Xiongfeng Wang Message-ID: <558439df-9f0e-9c2a-6332-64e3e2a5c823@huawei.com> Date: Wed, 1 Dec 2021 09:29:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.5] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 2021/11/30 19:42, Rafael J. Wysocki wrote: > On Mon, Nov 29, 2021 at 10:10 AM Viresh Kumar wrote: >> >> On 29-11-21, 16:02, Xiongfeng Wang wrote: >>> When I hot added a CPU, I found 'cpufreq' directory is not created below >>> /sys/devices/system/cpu/cpuX/. It is because get_cpu_device() failed in >>> add_cpu_dev_symlink(). >>> >>> cpufreq_add_dev() is the .add_dev callback of a CPU subsys interface. It >>> will be called when the CPU device registered into the system. The stack >>> is as follows. >>> register_cpu() >>> ->device_register() >>> ->device_add() >>> ->bus_probe_device() >>> ->cpufreq_add_dev() >>> >>> But only after the CPU device has been registered, we can get the CPU >>> device by get_cpu_device(), otherwise it will return NULL. Since we >>> already have the CPU device in cpufreq_add_dev(), pass it to >>> add_cpu_dev_symlink(). I noticed that the 'kobj' of the cpu device has >>> been added into the system before cpufreq_add_dev(). >>> >>> Signed-off-by: Xiongfeng Wang >>> --- >>> drivers/cpufreq/cpufreq.c | 9 ++++----- >>> 1 file changed, 4 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c >>> index e338d2f010fe..22aa2793e4d2 100644 >>> --- a/drivers/cpufreq/cpufreq.c >>> +++ b/drivers/cpufreq/cpufreq.c >>> @@ -1004,10 +1004,9 @@ static struct kobj_type ktype_cpufreq = { >>> .release = cpufreq_sysfs_release, >>> }; >>> >>> -static void add_cpu_dev_symlink(struct cpufreq_policy *policy, unsigned int cpu) >>> +static void add_cpu_dev_symlink(struct cpufreq_policy *policy, unsigned int cpu, >>> + struct device *dev) >>> { >>> - struct device *dev = get_cpu_device(cpu); >>> - >>> if (unlikely(!dev)) >>> return; >>> >>> @@ -1391,7 +1390,7 @@ static int cpufreq_online(unsigned int cpu) >>> if (new_policy) { >>> for_each_cpu(j, policy->related_cpus) { >>> per_cpu(cpufreq_cpu_data, j) = policy; >>> - add_cpu_dev_symlink(policy, j); >>> + add_cpu_dev_symlink(policy, j, get_cpu_device(j)); >>> } >>> >>> policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req), >>> @@ -1565,7 +1564,7 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif) >>> /* Create sysfs link on CPU registration */ >>> policy = per_cpu(cpufreq_cpu_data, cpu); >>> if (policy) >>> - add_cpu_dev_symlink(policy, cpu); >>> + add_cpu_dev_symlink(policy, cpu, dev); >>> >>> return 0; >>> } >> >> Interesting that I never hit it earlier despite doing rigorous testing of >> hotplug stuff :( > > This is the real hot-add path which isn't tested on a regular basis. > >> Anyway the patch is okay, > > It would be good to add a Fixes: tag to it, though. Any idea about > the commit this should point to? When I look up the commit history, I found this one. 2f0ba790df51 ("cpufreq: Fix creation of symbolic links to policy directories") Before this commit, the 'dev' is passed to add_cpu_dev_symlink() in cpufreq_add_dev(). Maybe we can point to this one. > >> Acked-by: Viresh Kumar > . >