Subject: Re: linux-next: Tree for Apr 9 [cpufreq: NULL pointer deref]

From: "Rafael J. Wysocki" <[email-masked]>
Date: Wed, 17 Apr 2013 18:14:55 +0200

On Wednesday, April 17, 2013 04:04:46 PM Sedat Dilek wrote:
> On Mon, Apr 15, 2013 at 7:22 PM, Viresh Kumar <[email-masked]> wrote:
> > On 15 April 2013 21:37, Dirk Brandewie <[email-masked]> wrote:
> >> If the intel_pstate driver is being used __cpufreq_governor() should NOT be
> >> called intel_pstate does not implement the target() callback.
> >>
> >> Nathan's commit 5800043b2 changed the fence around the call to
> >> __cpufreq_governor() in __cpufreq_remove_dev() here is the relevant hunk.
> >
> > No it isn't.
> >
> >> +       if (has_target)
> >>                 __cpufreq_governor(data, CPUFREQ_GOV_STOP);
> >
> > As it has taken care of this limitation.
> >
> > BUT some of my earlier patches haven't. :(
> > Here is the fix (Sedat please try this and give your tested-by, use the attached
> > patch as gmail might break what i am copying in mail)..
> >
> > Sorry for being late in fixing this issue, i am still down with Tonsil infection
> > and fever.. Today only i got some power to fix it after seeing Dirk's mail.
> >
> > Your tested-by may help me to recover quickly :)
> >
> > @Rafael: I will probably be down for one more week and so not doing any
> > reviews for now... I do check important mails sent directly to me though.
> >
> 
> Hi Viresh,
> 
> can you sent a separate patch on this (with Reported/Tested-by#s)?
> AFAICS this is not in pm.git#linux-next?

That's because I'm traveling and not pushing things to the tree.  I'll start
doing that again on Saturday.  Till then, please apply the Viresh's patch
on top of linux-next.

Thanks,
Rafael

> > ------------x----------------------x------------------
> >
> > From: Viresh Kumar <[email-masked]>
> > Date: Mon, 15 Apr 2013 22:43:57 +0530
> > Subject: [PATCH] cpufreq: Don't call __cpufreq_governor() for drivers without
> >  target()
> >
> > Some cpufreq drivers implement their own governor and so don't need us to call
> > generic governors interface via __cpufreq_governor(). Few recent commits haven't
> > obeyed this law well and we saw some regressions.
> >
> > This patch tries to fix this issue.
> >
> > Signed-off-by: Viresh Kumar <[email-masked]>
> > ---
> >  drivers/cpufreq/cpufreq.c | 18 +++++++++++++-----
> >  1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 3564947..a6f6595 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -858,13 +858,18 @@ static int cpufreq_add_policy_cpu(unsigned int
> > cpu, unsigned int sibling,
> >                                   struct device *dev)
> >  {
> >         struct cpufreq_policy *policy;
> > -       int ret = 0;
> > +       int ret = 0, has_target = 0;
> >         unsigned long flags;
> >
> >         policy = cpufreq_cpu_get(sibling);
> >         WARN_ON(!policy);
> >
> > -       __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
> > +       rcu_read_lock();
> > +       has_target = !!rcu_dereference(cpufreq_driver)->target;
> > +       rcu_read_unlock();
> > +
> > +       if (has_target)
> > +               __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
> >
> >         lock_policy_rwsem_write(sibling);
> >
> > @@ -877,8 +882,10 @@ static int cpufreq_add_policy_cpu(unsigned int
> > cpu, unsigned int sibling,
> >
> >         unlock_policy_rwsem_write(sibling);
> >
> > -       __cpufreq_governor(policy, CPUFREQ_GOV_START);
> > -       __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
> > +       if (has_target) {
> > +               __cpufreq_governor(policy, CPUFREQ_GOV_START);
> > +               __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
> > +       }
> >
> >         ret = sysfs_create_link(&dev->kobj, &policy->kobj, "cpufreq");
> >         if (ret) {
> > @@ -1146,7 +1153,8 @@ static int __cpufreq_remove_dev(struct device
> > *dev, struct subsys_interface *sif
> >
> >         /* If cpu is last user of policy, free policy */
> >         if (cpus == 1) {
> > -               __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);
> > +               if (has_target)
> > +                       __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);
> >
> >                 lock_policy_rwsem_read(cpu);
> >                 kobj = &data->kobj;
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.