Re: [PATCH] opp: Prepare for ->set_opp() helper to work without regulators

Viresh Kumar
2021-01-20T07:40:26Z

On 19-01-21, 20:16, Dmitry Osipenko wrote:
> 19.01.2021 09:35, Viresh Kumar пишет:
> > + mutex_lock(&opp_table->lock);
> > + opp_table->set_opp_data = data;
> > + if (opp_table->sod_supplies) {
> > + data->old_opp.supplies = opp_table->sod_supplies;
> > + data->new_opp.supplies = opp_table->sod_supplies +
> > + opp_table->regulator_count;
> > + }
> > + mutex_unlock(&opp_table->lock);
>
> Why do we need all these locks in this patch?

In case dev_pm_opp_set_regulators() and
dev_pm_opp_register_set_opp_helper() get called at the same time.
Which can actually happen, though is a corner case.

> The OPP API isn't thread-safe, these locks won't make the API
> thread-safe.

I am not sure what you mean by that, can you please explain ?

> At least both sod_supplies and set_opp() pointers should be
> set and unset under the lock.

The ->set_opp pointer isn't getting used for a comparison and so
putting that inside a lock won't get us anything. We are only using
set_opp_data and sod_supplies for comparison at both the places and so
they need to be updated within the lock.

--
viresh