On Monday 01 of October 2012 15:42:39 Vincent Guittot wrote:
> Hi Rafael,
>
> Ping.
I'm considering this for v3.8, but I'd like Paul (CCed) to tell me what he
thinks about it.
Thanks,
Rafael
> On 25 September 2012 15:42, Vincent Guittot <vincent.guit...@linaro.org>
> wrote:
> > synchronize_rcu blocks the caller of opp_enable/disbale
> > for a complete grace period. This blocking duration prevents
> > any intensive use of the functions. Replace synchronize_rcu
> > by call_rcu which will call our function for freeing the old
> > opp element.
> >
> > The duration of opp_enable and opp_disable will be no more
> > dependant of the grace period.
> >
> > Signed-off-by: Vincent Guittot <vincent.guit...@linaro.org>
> > ---
> > drivers/base/power/opp.c | 19 ++++++++++++++-----
> > 1 file changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> > index ac993ea..49e4626 100644
> > --- a/drivers/base/power/opp.c
> > +++ b/drivers/base/power/opp.c
> > @@ -64,6 +64,7 @@ struct opp {
> > unsigned long u_volt;
> >
> > struct device_opp *dev_opp;
> > + struct rcu_head head;
> > };
> >
> > /**
> > @@ -441,6 +442,17 @@ int opp_add(struct device *dev, unsigned long freq,
> > unsigned long u_volt)
> > }
> >
> > /**
> > + * opp_free_rcu() - helper to clear the struct opp when grace period has
> > + * elapsed without blocking the the caller of opp_set_availability
> > + */
> > +static void opp_free_rcu(struct rcu_head *head)
> > +{
> > + struct opp *opp = container_of(head, struct opp, head);
> > +
> > + kfree(opp);
> > +}
> > +
> > +/**
> > * opp_set_availability() - helper to set the availability of an opp
> > * @dev: device for which we do this operation
> > * @freq: OPP frequency to modify availability
> > @@ -511,7 +523,7 @@ static int opp_set_availability(struct device *dev,
> > unsigned long freq,
> >
> > list_replace_rcu(&opp->node, &new_opp->node);
> > mutex_unlock(&dev_opp_list_lock);
> > - synchronize_rcu();
> > + call_rcu(&opp->head, opp_free_rcu);
> >
> > /* Notify the change of the OPP availability */
> > if (availability_req)
> > @@ -521,13 +533,10 @@ static int opp_set_availability(struct device *dev,
> > unsigned long freq,
> > srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE,
> > new_opp);
> >
> > - /* clean up old opp */
> > - new_opp = opp;
> > - goto out;
> > + return 0;
> >
> > unlock:
> > mutex_unlock(&dev_opp_list_lock);
> > -out:
> > kfree(new_opp);
> > return r;
> > }
> > --
> > 1.7.9.5
> >
> --
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