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

[Sedat Dilek]

On Mon, Apr 15, 2013 at 7:57 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> On Mon, Apr 15, 2013 at 7:51 PM, Sedat Dilek <sedat.dilek@xxxxxxxxx> 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.
>>

Reboot is also fine here.

>> ( Dirk promised to test as well... )
>>

Dirk confirmed your patch works for him.
Good!

- Sedat -

>
> Might be interesting as an extra-confirmation:
>
> root# echo 1 > /sys/devices/system/cpu/cpu3/online
>
> [ dmesg ]
>
> [  556.101961] smpboot: Booting Node 0 Processor 3 APIC 0x3
> [  556.113158] Disabled fast string operations
> [  556.116621] Intel pstate controlling: cpu 3
>
> - Sedat -
>
>> - 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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