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SubjectRe: [PATCH] PM / OPP: optimize dev_pm_opp_set_rate() a bit
Dear Viresh,

On Fri, 22 Jul 2016 09:21:51 -0700 Viresh Kumar wrote:

> On 22-07-16, 20:42, Jisheng Zhang wrote:
> > static int _set_opp_voltage(struct device *dev, struct regulator *reg,
> > unsigned long u_volt, unsigned long u_volt_min,
> > unsigned long u_volt_max)
> > @@ -586,9 +565,24 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
> > return -EINVAL;
> > }
> >
> > - clk = _get_opp_clk(dev);
> > - if (IS_ERR(clk))
> > + rcu_read_lock();
> > +
> > + opp_table = _find_opp_table(dev);
> > + if (IS_ERR(opp_table)) {
> > + dev_err(dev, "%s: device opp doesn't exist\n", __func__);
> > + rcu_read_unlock();
> > + return PTR_ERR(opp_table);
> > + }
> > +
> > + clk = opp_table->clk;
> > + if (IS_ERR(clk)) {
> > + dev_err(dev, "%s: No clock available for the device\n",
> > + __func__);
> > + rcu_read_unlock();
> > return PTR_ERR(clk);
> > + }
> > +
> > + rcu_read_unlock();
>
> It is not _safe_ to use opp_table pointer after the rcu_read_unlock()

Oops, indeed. Thanks very much for pointing it out! Will fix it in v2, so
it seems we can only reduce the call of _find_opp_table to twice.

Thanks,
Jisheng

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