Re: [PATCH V2 2/8] PM / OPP: Don't use OPP structure outside of rcu protected section

Viresh Kumar
2016-10-25T03:37:42Z

On 24-10-16, 15:52, Stephen Boyd wrote:
> On 10/20, Viresh Kumar wrote:
> > The OPP structure must not be used out of the rcu protected section.
> > Cache the values to be used in separate variables instead.
> >
> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
>
> Was this found by visual inspection or through some static
> checker? Just curious.

Visual inspection :)

> > @@ -633,6 +634,14 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
> > return ret;
> > }
> >
> > + if (IS_ERR(old_opp)) {
> > + old_u_volt = 0;
> > + } else {
> > + old_u_volt = old_opp->u_volt;
> > + old_u_volt_min = old_opp->u_volt_min;
> > + old_u_volt_max = old_opp->u_volt_max;
> > + }
> > +
> > u_volt = opp->u_volt;
> > u_volt_min = opp->u_volt_min;
> > u_volt_max = opp->u_volt_max;
> > @@ -677,9 +686,10 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
> > __func__, old_freq);
> > restore_voltage:
> > /* This shouldn't harm even if the voltages weren't updated earlier */
> > - if (!IS_ERR(old_opp))
> > - _set_opp_voltage(dev, reg, old_opp->u_volt,
> > - old_opp->u_volt_min, old_opp->u_volt_max);
> > + if (old_u_volt) {
>
> What if old_u_volt == 0 is valid?

How can that be valid ?

> We could have another variable
> like 'valid' or something that we use to figure out if we should
> set values instead. Then this isn't a potential pitfall.

I can do that but just wanted to know if we need that or not.

--
viresh