Re: [PATCH 3/4] PM / Domains: Search for the CPU device outside the genpd lock

Ulf Hansson
2019-04-25T10:15:19Z

On Thu, 25 Apr 2019 at 11:45, Viresh Kumar <viresh.kumar@linaro.org> wrote:
>
> On 25-04-19, 11:04, Ulf Hansson wrote:
> > While attaching/detaching a device to a PM domain (genpd) that has the
> > GENPD_FLAG_CPU_DOMAIN set, genpd iterates the cpu_possible_mask to check
> > whether the device corresponds to a CPU. This iteration is done while
> > holding the genpd's lock, which is unnecessary. Let's avoid the locking,
> > by restructuring the corresponding code a bit.
> >
> > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> > ---
> > drivers/base/power/domain.c | 52 +++++++++++++++++++------------------
> > 1 file changed, 27 insertions(+), 25 deletions(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 93298b7db408..da1c99178943 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -1450,8 +1450,8 @@ static void genpd_free_dev_data(struct device *dev,
> > dev_pm_put_subsys_data(dev);
> > }
> >
> > -static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> > - int cpu, bool set, unsigned int depth)
> > +static void genpd_update_cpumask(struct generic_pm_domain *genpd,
> > + int cpu, bool set, unsigned int depth)
> > {
> > struct gpd_link *link;
> >
> > @@ -1462,7 +1462,7 @@ static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> > struct generic_pm_domain *master = link->master;
> >
> > genpd_lock_nested(master, depth + 1);
> > - __genpd_update_cpumask(master, cpu, set, depth + 1);
> > + genpd_update_cpumask(master, cpu, set, depth + 1);
> > genpd_unlock(master);
> > }
> >
> > @@ -1472,38 +1472,37 @@ static void __genpd_update_cpumask(struct generic_pm_domain *genpd,
> > cpumask_clear_cpu(cpu, genpd->cpus);
> > }
> >
> > -static void genpd_update_cpumask(struct generic_pm_domain *genpd,
> > - struct device *dev, bool set)
> > +static void genpd_set_cpumask(struct generic_pm_domain *genpd, int cpu)
> > +{
> > + if (cpu >= 0)
> > + genpd_update_cpumask(genpd, cpu, true, 0);
> > +}
> > +
> > +static void genpd_clear_cpumask(struct generic_pm_domain *genpd, int cpu)
> > +{
> > + if (cpu >= 0)
> > + genpd_update_cpumask(genpd, cpu, false, 0);
> > +}
> > +
> > +static int genpd_get_cpu(struct generic_pm_domain *genpd, struct device *dev)
> > {
> > int cpu;
> >
> > if (!genpd_is_cpu_domain(genpd))
> > - return;
> > + return -1;
> >
> > for_each_possible_cpu(cpu) {
> > - if (get_cpu_device(cpu) == dev) {
> > - __genpd_update_cpumask(genpd, cpu, set, 0);
> > - return;
> > - }
> > + if (get_cpu_device(cpu) == dev)
> > + return cpu;
> > }
> > -}
> >
> > -static void genpd_set_cpumask(struct generic_pm_domain *genpd,
> > - struct device *dev)
> > -{
> > - genpd_update_cpumask(genpd, dev, true);
> > -}
> > -
> > -static void genpd_clear_cpumask(struct generic_pm_domain *genpd,
> > - struct device *dev)
> > -{
> > - genpd_update_cpumask(genpd, dev, false);
> > + return -1;
> > }
> >
> > static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev)
> > {
> > struct generic_pm_domain_data *gpd_data;
> > - int ret;
> > + int ret, cpu;
> >
> > dev_dbg(dev, "%s()\n", __func__);
> >
> > @@ -1514,13 +1513,15 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev)
> > if (IS_ERR(gpd_data))
> > return PTR_ERR(gpd_data);
> >
> > + cpu = genpd_get_cpu(genpd, dev);
> > +
> > ret = genpd->attach_dev ? genpd->attach_dev(genpd, dev) : 0;
> > if (ret)
> > goto out;
> >
> > genpd_lock(genpd);
> >
> > - genpd_set_cpumask(genpd, dev);
> > + genpd_set_cpumask(genpd, cpu);
>
> Should we check if "cpu" is valid here ? As that was done earlier.

This is being done in the new version of genpd_set|clear_cpumask(). Like below.

"if (cpu >= 0)"...

>
> > dev_pm_domain_set(dev, &genpd->domain);
> >
> > genpd->device_count++;
> > @@ -1560,13 +1561,14 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
> > {
> > struct generic_pm_domain_data *gpd_data;
> > struct pm_domain_data *pdd;
> > - int ret = 0;
> > + int cpu, ret = 0;
> >
> > dev_dbg(dev, "%s()\n", __func__);
> >
> > pdd = dev->power.subsys_data->domain_data;
> > gpd_data = to_gpd_data(pdd);
> > dev_pm_qos_remove_notifier(dev, &gpd_data->nb);
> > + cpu = genpd_get_cpu(genpd, dev);
> >
> > genpd_lock(genpd);
> >
> > @@ -1578,7 +1580,7 @@ static int genpd_remove_device(struct generic_pm_domain *genpd,
> > genpd->device_count--;
> > genpd->max_off_time_changed = true;
> >
> > - genpd_clear_cpumask(genpd, dev);
> > + genpd_clear_cpumask(genpd, cpu);
>
> Same here.

See above.

>
> > dev_pm_domain_set(dev, NULL);
> >
> > list_del_init(&pdd->list_node);
> > --
> > 2.17.1
>
> --
> viresh

Thanks for reviewing!

Kind regards
Uffe