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SubjectRe: [PATCH v2 09/17] PM: EM: Add RCU mechanism which safely cleans the old data
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On 5/30/23 11:02, Dietmar Eggemann wrote:
> On 12/05/2023 11:57, Lukasz Luba wrote:
>> The EM is going to support runtime modifications of the power data.
>> In order to achieve that prepare the internal mechanism. This patch
>> introduces RCU safe mechanism to clean up the old allocated EM data.
>
> s/In order to achieve that prepare the internal mechanism. This patch
> introduces/Introduce ... much shorter, same information.

OK

>
> [...]
>
>> +static void em_perf_runtime_table_set(struct device *dev,
>> + struct em_perf_table *runtime_table)
>> +{
>> + struct em_perf_domain *pd = dev->em_pd;
>> + struct em_perf_table *tmp;
>> +
>> + tmp = pd->runtime_table;
>> +
>> + rcu_assign_pointer(pd->runtime_table, runtime_table);
>> +
>> + em_cpufreq_update_efficiencies(dev, runtime_table->state);
>> +
>> + if (trace_em_perf_state_enabled()) {
>> + unsigned long freq, power, cost, flags;
>> + int i;
>> +
>> + for (i = 0; i < pd->nr_perf_states; i++) {
>> + freq = runtime_table->state[i].frequency;
>> + power = runtime_table->state[i].power;
>> + cost = runtime_table->state[i].cost;
>> + flags = runtime_table->state[i].flags;
>> +
>> + trace_em_perf_state(dev_name(dev), pd->nr_perf_states,
>> + i, freq, power, cost, flags);
>> + }
>> + }
>> +
>> + /*
>> + * Check if the 'state' array is not actually the one from setup.
>> + * If it is then don't free it.
>> + */
>> + if (tmp->state == pd->table)
>
> It's unfortunate that you have the refactoring in 13/17 which would lead to:
>
> if (pd->runtime_table>state == pd->default_table->state)
> ^^^^^^^^^^^^^ ^^^^^^^^^^^^^
>
> so people would immediately grasp one of the core concepts of the
> design: non-modifiable default_table and modifiable runtime_table.
>
> I still belief that it would be the better idea to do the refactoring first.
>
> [...]

That make sense. Let me try that approach as see how the patch set would
look like.

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