Re: [PATCH] platform/x86/intel-uncore-freq: Fix current_freq_khz after CPU hotplug

[srinivas pandruvada <srinivas.pandruvada@linux.intel.com>]

On Tue, 2026-06-02 at 10:07 +0800, Guixiong Wei wrote:
> When the last CPU of a legacy uncore die goes offline,
> uncore_freq_remove_die_entry() clears control_cpu. During CPU hotplug
> re-add, uncore_freq_add_entry() still populates sysfs attributes
> before
> assigning the new control CPU. As a result, the current frequency
> read
> returns -ENXIO and current_freq_khz is omitted from the recreated
> sysfs
> group.
> 
> Assign control_cpu before the initial read paths and before
> create_attr_group() so sysfs recreation uses the new online CPU. If
> sysfs creation fails, restore control_cpu to -1 to keep the error
> path
> state consistent.
> 
> Fixes: 4d73c6772ab7 ("platform/x86: intel-uncore-freq: Conditionally
> create attribute for read frequency")
> Cc: stable@vger.kernel.org
> Signed-off-by: Guixiong Wei <weiguixiong@bytedance.com>

Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>


> ---
>  .../x86/intel/uncore-frequency/uncore-frequency-common.c   | 7
> ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/intel/uncore-frequency/uncore-
> frequency-common.c b/drivers/platform/x86/intel/uncore-
> frequency/uncore-frequency-common.c
> index 7070c94324e0..f8137ee92e47 100644
> --- a/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-
> common.c
> +++ b/drivers/platform/x86/intel/uncore-frequency/uncore-frequency-
> common.c
> @@ -275,15 +275,20 @@ int uncore_freq_add_entry(struct uncore_data
> *data, int cpu)
>  			  data->package_id, data->die_id);
>  	}
>  
> +	/*
> +	 * Set the control CPU before any read path so entry
> recreation after CPU
> +	 * hotplug can populate read-only attributes from the new
> online CPU.
> +	 */
> +	data->control_cpu = cpu;
>  	uncore_read(data, &data->initial_min_freq_khz,
> UNCORE_INDEX_MIN_FREQ);
>  	uncore_read(data, &data->initial_max_freq_khz,
> UNCORE_INDEX_MAX_FREQ);
>  
>  	ret = create_attr_group(data, data->name);
>  	if (ret) {
> +		data->control_cpu = -1;
>  		if (data->domain_id != UNCORE_DOMAIN_ID_INVALID)
>  			ida_free(&intel_uncore_ida, data-
> >instance_id);
>  	} else {
> -		data->control_cpu = cpu;
>  		data->valid = true;
>  	}
>