Re: [PATCH v2] platform/x86/intel-uncore-freq: Fix missing uncore sysfs during CPU hotplug

[srinivas pandruvada]

On Wed, 2025-04-16 at 11:38 +0800, shouyeliu wrote:
> From: Shouye Liu <shouyeliu@xxxxxxxxxxx>
> 
> In certain situations, the sysfs for uncore may not be present when
> all
> CPUs in a package are offlined and then brought back online after
> boot.
> 
> This issue can occur if there is an error in adding the sysfs entry
> due
> to a memory allocation failure. Retrying to bring the CPUs online
> will
> not resolve the issue, as the uncore_cpu_mask is already set for the
> package before the failure condition occurs.
> 
> This issue does not occur if the failure happens during module
> initialization, as the module will fail to load in the event of any
> error.
> 
> To address this, ensure that the uncore_cpu_mask is not set until the
> successful return of uncore_freq_add_entry().
> 
Fixes: dbce412a7733 ("platform/x86/intel-uncore-freq: Split common and
enumeration part")

> Signed-off-by: Shouye Liu <shouyeliu@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx

Thanks,
Srinivas

> ---
>  .../x86/intel/uncore-frequency/uncore-frequency.c   | 13 +++++++++--
> --
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/uncore-frequency/uncore-
> frequency.c b/drivers/platform/x86/intel/uncore-frequency/uncore-
> frequency.c
> index 40bbf8e45fa4..bdee5d00f30b 100644
> --- a/drivers/platform/x86/intel/uncore-frequency/uncore-frequency.c
> +++ b/drivers/platform/x86/intel/uncore-frequency/uncore-frequency.c
> @@ -146,15 +146,13 @@ static int uncore_event_cpu_online(unsigned int
> cpu)
>  {
>  	struct uncore_data *data;
>  	int target;
> +	int ret;
>  
>  	/* Check if there is an online cpu in the package for uncore
> MSR */
>  	target = cpumask_any_and(&uncore_cpu_mask,
> topology_die_cpumask(cpu));
>  	if (target < nr_cpu_ids)
>  		return 0;
>  
> -	/* Use this CPU on this die as a control CPU */
> -	cpumask_set_cpu(cpu, &uncore_cpu_mask);
> -
>  	data = uncore_get_instance(cpu);
>  	if (!data)
>  		return 0;
> @@ -163,7 +161,14 @@ static int uncore_event_cpu_online(unsigned int
> cpu)
>  	data->die_id = topology_die_id(cpu);
>  	data->domain_id = UNCORE_DOMAIN_ID_INVALID;
>  
> -	return uncore_freq_add_entry(data, cpu);
> +	ret = uncore_freq_add_entry(data, cpu);
> +	if (ret)
> +		return ret;
> +
> +	/* Use this CPU on this die as a control CPU */
> +	cpumask_set_cpu(cpu, &uncore_cpu_mask);
> +
> +	return 0;
>  }
>  
>  static int uncore_event_cpu_offline(unsigned int cpu)