The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2c1b5a84669d2477d8fffe9136e86a2cff591729 Mon Sep 17 00:00:00 2001

From: Xiongfeng Wang wangxiongfeng2@huawei.com Date: Mon, 29 Nov 2021 16:02:48 +0800 Subject: [PATCH] cpufreq: Fix get_cpu_device() failure in add_cpu_dev_symlink()

When I hot added a CPU, I found 'cpufreq' directory was 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 call chain 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().

Fixes: 2f0ba790df51 ("cpufreq: Fix creation of symbolic links to policy directories") Signed-off-by: Xiongfeng Wang wangxiongfeng2@huawei.com Acked-by: Viresh Kumar viresh.kumar@linaro.org Cc: All applicable stable@vger.kernel.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com

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; }