Re: [PATCH AUTOSEL 5.2 190/249] cpufreq: Avoid calling cpufreq_verify_current_freq() from handle_update()

[Sasha Levin]

On Tue, Jul 16, 2019 at 11:25:00AM +0200, Rafael J. Wysocki wrote:
> On 7/15/2019 3:45 PM, Sasha Levin wrote:
> > From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> >
> > [ Upstream commit 70a59fde6e69d1d8579f84bf4555bfffb3ce452d ]
> >
> > On some occasions cpufreq_verify_current_freq() schedules a work whose
> > callback is handle_update(), which further calls cpufreq_update_policy()
> > which may end up calling cpufreq_verify_current_freq() again.
> >
> > On the other hand, when cpufreq_update_policy() is called from
> > handle_update(), the pointer to the cpufreq policy is already
> > available, but cpufreq_cpu_acquire() is still called to get it in
> > cpufreq_update_policy(), which should be avoided as well.
> >
> > To fix these issues, create a new helper, refresh_frequency_limits(),
> > and make both handle_update() call it cpufreq_update_policy().
> >
> > Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> > [ rjw: Rename reeval_frequency_limits() as refresh_frequency_limits() ]
> > [ rjw: Changelog ]
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> > ---
> >  drivers/cpufreq/cpufreq.c | 26 ++++++++++++++++----------
> >  1 file changed, 16 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index e84bf0eb7239..876a4cb09de3 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -1114,13 +1114,25 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
> >  	return ret;
> >  }
> > +static void refresh_frequency_limits(struct cpufreq_policy *policy)
> > +{
> > +	struct cpufreq_policy new_policy = *policy;
> > +
> > +	pr_debug("updating policy for CPU %u\n", policy->cpu);
> > +
> > +	new_policy.min = policy->user_policy.min;
> > +	new_policy.max = policy->user_policy.max;
> > +
> > +	cpufreq_set_policy(policy, &new_policy);
> > +}
> > +
> >  static void handle_update(struct work_struct *work)
> >  {
> >  	struct cpufreq_policy *policy =
> >  		container_of(work, struct cpufreq_policy, update);
> > -	unsigned int cpu = policy->cpu;
> > -	pr_debug("handle_update for cpu %u called\n", cpu);
> > -	cpufreq_update_policy(cpu);
> > +
> > +	pr_debug("handle_update for cpu %u called\n", policy->cpu);
> > +	refresh_frequency_limits(policy);
> >  }
> >  static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
> > @@ -2392,7 +2404,6 @@ int cpufreq_set_policy(struct cpufreq_policy *policy,
> >  void cpufreq_update_policy(unsigned int cpu)
> >  {
> >  	struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
> > -	struct cpufreq_policy new_policy;
> >  	if (!policy)
> >  		return;
> > @@ -2405,12 +2416,7 @@ void cpufreq_update_policy(unsigned int cpu)
> >  	    (cpufreq_suspended || WARN_ON(!cpufreq_update_current_freq(policy))))
> >  		goto unlock;
> > -	pr_debug("updating policy for CPU %u\n", cpu);
> > -	memcpy(&new_policy, policy, sizeof(*policy));
> > -	new_policy.min = policy->user_policy.min;
> > -	new_policy.max = policy->user_policy.max;
> > -
> > -	cpufreq_set_policy(policy, &new_policy);
> > +	refresh_frequency_limits(policy);
> >  unlock:
> >  	cpufreq_cpu_release(policy);
>
> I don't think this is suitable for -stable.

I've dropped it, thanks!

--
Thanks,
Sasha