Re: [PATCH] platform/x86/intel-uncore-freq: fix inconsistent state on init failure

Ilpo Järvinen
2025-04-14T10:41:36Z

On Mon, 14 Apr 2025, shouyeliu wrote:

> When uncore_event_cpu_online() fails to initialize a control CPU (e.g.,
> due to memory allocation failure or uncore_freq_add_entry() errors),
> the code leaves stale entries in uncore_cpu_mask after that online CPU
> will not try to call uncore_freq_add_entry, resulting in no sys interface.

Please add () after any name that refers to a C function (you're not even
being consistent here as you had it in some cases but not here).

Please try to split the very long sentence a bit and make it more obvious
what causes what as the current wording is a bit vague, did you mean:
uncore_event_cpu_online() will not call uncore_freq_add_entry() for
another CPU that is being onlined or something along those lines?

Will this change work/matter? Documentation/core-api/cpu_hotplug.rst says
about cpuhp_setup_state():

"If a callback fails for CPU N then the teardown callback for CPU
0 .. N-1 is invoked to rollback the operation. The state setup fails,
the callbacks for the state are not installed and in case of dynamic
allocation the allocated state is freed."

>

Fixes tag?

> Signed-off-by: shouyeliu <shouyeliu@gmail.com>

The correct format for tags is documented in
Documentation/process/5.Posting.rst:

tag: Full Name <email address>

> ---
> .../x86/intel/uncore-frequency/uncore-frequency.c | 12 ++++++++----
> 1 file changed, 8 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..1de0a4a9d6cd 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 +161,13 @@ 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) {
> + /* Use this CPU on this die as a control CPU */
> + cpumask_set_cpu(cpu, &uncore_cpu_mask);
> + }
> +
> + return ret;

Please reverse to logic such that you return early on error, which is the
usual error handling pattern.

> }
>
> static int uncore_event_cpu_offline(unsigned int cpu)
>

--
i.