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

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Message-ID: <CA+icZUVk1_Dw5Kb8uWwk7xjrgx6jPOfP8BZdFXQ9bqgmdckHuQ@mail.gmail.com>
Date:	Mon, 15 Apr 2013 19:51:48 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Dirk Brandewie <dirk.brandewie@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Dirk Brandewie <dirk.j.brandewie@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org, Linux PM list <linux-pm@...r.kernel.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Nathan Zimmer <nzimmer@....com>
Subject: Re: linux-next: Tree for Apr 9 [cpufreq: NULL pointer deref]

On Mon, Apr 15, 2013 at 7:22 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 15 April 2013 21:37, Dirk Brandewie <dirk.brandewie@...il.com> 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@...il.com>

...did not test on-reboot-case.

( Dirk promised to test as well... )

- 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@...aro.org>
> 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@...aro.org>
> ---
>  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;

View attachment "dmesg_3.9.0-rc6-next20130411-4-iniza-small_after-cpu3-offline.txt" of type "text/plain" (54353 bytes)

Download attachment "config-3.9.0-rc6-next20130411-4-iniza-small" of type "application/octet-stream" (112259 bytes)

Download attachment "3.9.0-rc6-next20130411-4-iniza-small.patch" of type "application/octet-stream" (4367 bytes)