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

[Dirk Brandewie]

On 04/15/2013 10:51 AM, Sedat Dilek wrote:
> On Mon, Apr 15, 2013 at 7:22 PM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> > On 15 April 2013 21:37, Dirk Brandewie <dirk.brandewie@xxxxxxxxx> 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 :)
>
> Hehe.
> Me myself and I was today chez-mon-docteur... Let's see the results on Thursday.
> Again, get well soon.
>
> Tested against...
>
>   "BROKEN" Linux-Next (next-20130411) with attached patchset (incl.
> your cpufreq-next-fixes).
>
> Test-Case...
>
> CONFIG_X86_INTEL_PSTATE=y
>
> root# echo 0 > /sys/devices/system/cpu/cpu3/online
>
> Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
>
> ...did not test on-reboot-case.
>
> ( Dirk promised to test as well... )

Tested with:
 while true
 do
 echo 0 > online
 echo 1 > online
 done
For several minutes and rebooting several times seems to have fixed the
issue.

Nathan, Sorry for calling out your patch erroneously I should have paid closer
attention.

Viresh you can add my Tested-by:

Thanks
--Dirk
> - Sedat -
>
> > @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.
> >
> > ------------x----------------------x------------------
> >
> > From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> > 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 <viresh.kumar@xxxxxxxxxx>
> > ---
> >   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;

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