[PATCH] cpufreq: unlock when failing cpufreq_update_policy()

[PATCH] cpufreq: unlock when failing cpufreq_update_policy()

[Aaron Plattner]

Commit bd0fa9bb455d introduced a failure path to cpufreq_update_policy() if
cpufreq_driver->get(cpu) returns NULL.  However, it jumps to the 'no_policy'
label, which exits without unlocking any of the locks the function acquired
earlier.  This causes later calls into cpufreq to hang.

Fix this by creating a new 'unlock' label and jumping to that instead.

Fixes: bd0fa9bb455d ("cpufreq: Return error if ->get() failed in cpufreq_update_policy()")
Link: https://devtalk.nvidia.com/default/topic/751903/kernel-3-15-and-nv-drivers-337-340-failed-to-initialize-the-nvidia-kernel-module-gtx-550-ti-/
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
---
I haven't reproduced this problem so I couldn't test it, but the bug and its
solution seem obvious enough.

 drivers/cpufreq/cpufreq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index aed2b0cb83dc..5b6d04f3b9ea 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2264,7 +2264,7 @@ int cpufreq_update_policy(unsigned int cpu)
 		new_policy.cur = cpufreq_driver->get(cpu);
 		if (WARN_ON(!new_policy.cur)) {
 			ret = -EIO;
-			goto no_policy;
+			goto unlock;
 		}
 
 		if (!policy->cur) {
@@ -2279,6 +2279,7 @@ int cpufreq_update_policy(unsigned int cpu)
 
 	ret = cpufreq_set_policy(policy, &new_policy);
 
+unlock:
 	up_write(&policy->rwsem);
 
 	cpufreq_cpu_put(policy);
-- 
2.0.0

Re: [PATCH] cpufreq: unlock when failing cpufreq_update_policy()

[Viresh Kumar]

On 18 June 2014 05:42, Aaron Plattner <aplattner@nvidia.com> wrote:
> Commit bd0fa9bb455d introduced a failure path to cpufreq_update_policy() if
> cpufreq_driver->get(cpu) returns NULL.  However, it jumps to the 'no_policy'
> label, which exits without unlocking any of the locks the function acquired
> earlier.  This causes later calls into cpufreq to hang.
>
> Fix this by creating a new 'unlock' label and jumping to that instead.
>
> Fixes: bd0fa9bb455d ("cpufreq: Return error if ->get() failed in cpufreq_update_policy()")
> Link: https://devtalk.nvidia.com/default/topic/751903/kernel-3-15-and-nv-drivers-337-340-failed-to-initialize-the-nvidia-kernel-module-gtx-550-ti-/
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
> ---
> I haven't reproduced this problem so I couldn't test it, but the bug and its
> solution seem obvious enough.
>
>  drivers/cpufreq/cpufreq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index aed2b0cb83dc..5b6d04f3b9ea 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2264,7 +2264,7 @@ int cpufreq_update_policy(unsigned int cpu)
>                 new_policy.cur = cpufreq_driver->get(cpu);
>                 if (WARN_ON(!new_policy.cur)) {
>                         ret = -EIO;
> -                       goto no_policy;
> +                       goto unlock;
>                 }
>
>                 if (!policy->cur) {
> @@ -2279,6 +2279,7 @@ int cpufreq_update_policy(unsigned int cpu)
>
>         ret = cpufreq_set_policy(policy, &new_policy);
>
> +unlock:
>         up_write(&policy->rwsem);
>
>         cpufreq_cpu_put(policy);

Hmm, yes we do have a problem here but the code became a bit ugly
now.. Can you please consider this diff instead?

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index aed2b0c..6caced5 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2242,10 +2242,8 @@ int cpufreq_update_policy(unsigned int cpu)
        struct cpufreq_policy new_policy;
        int ret;

-       if (!policy) {
-               ret = -ENODEV;
-               goto no_policy;
-       }
+       if (!policy)
+               return = -ENODEV;

        down_write(&policy->rwsem);

@@ -2279,10 +2277,10 @@ int cpufreq_update_policy(unsigned int cpu)

        ret = cpufreq_set_policy(policy, &new_policy);

+no_policy:
        up_write(&policy->rwsem);

        cpufreq_cpu_put(policy);
-no_policy:
        return ret;
 }
 EXPORT_SYMBOL(cpufreq_update_policy);

Re: [PATCH] cpufreq: unlock when failing cpufreq_update_policy()

[Aaron Plattner]

On 06/18/2014 12:40 AM, Viresh Kumar wrote:
> On 18 June 2014 05:42, Aaron Plattner <aplattner@nvidia.com> wrote:
>> Commit bd0fa9bb455d introduced a failure path to cpufreq_update_policy() if
>> cpufreq_driver->get(cpu) returns NULL.  However, it jumps to the 'no_policy'
>> label, which exits without unlocking any of the locks the function acquired
>> earlier.  This causes later calls into cpufreq to hang.
>>
>> Fix this by creating a new 'unlock' label and jumping to that instead.
>>
>> Fixes: bd0fa9bb455d ("cpufreq: Return error if ->get() failed in cpufreq_update_policy()")
>> Link: https://devtalk.nvidia.com/default/topic/751903/kernel-3-15-and-nv-drivers-337-340-failed-to-initialize-the-nvidia-kernel-module-gtx-550-ti-/
>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
>> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
>> ---
>> I haven't reproduced this problem so I couldn't test it, but the bug and its
>> solution seem obvious enough.
>>
>>   drivers/cpufreq/cpufreq.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index aed2b0cb83dc..5b6d04f3b9ea 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -2264,7 +2264,7 @@ int cpufreq_update_policy(unsigned int cpu)
>>                  new_policy.cur = cpufreq_driver->get(cpu);
>>                  if (WARN_ON(!new_policy.cur)) {
>>                          ret = -EIO;
>> -                       goto no_policy;
>> +                       goto unlock;
>>                  }
>>
>>                  if (!policy->cur) {
>> @@ -2279,6 +2279,7 @@ int cpufreq_update_policy(unsigned int cpu)
>>
>>          ret = cpufreq_set_policy(policy, &new_policy);
>>
>> +unlock:
>>          up_write(&policy->rwsem);
>>
>>          cpufreq_cpu_put(policy);
>
> Hmm, yes we do have a problem here but the code became a bit ugly
> now.. Can you please consider this diff instead?
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index aed2b0c..6caced5 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2242,10 +2242,8 @@ int cpufreq_update_policy(unsigned int cpu)
>          struct cpufreq_policy new_policy;
>          int ret;
>
> -       if (!policy) {
> -               ret = -ENODEV;
> -               goto no_policy;
> -       }
> +       if (!policy)
> +               return = -ENODEV;

I assume you meant "return -ENODEV"?

>          down_write(&policy->rwsem);
>
> @@ -2279,10 +2277,10 @@ int cpufreq_update_policy(unsigned int cpu)
>
>          ret = cpufreq_set_policy(policy, &new_policy);
>
> +no_policy:

'no_policy' implied to me that policy was NULL, so this label should 
still be renamed to 'unlock'.  I'll send out a v2 that does this.

>          up_write(&policy->rwsem);
>
>          cpufreq_cpu_put(policy);
> -no_policy:
>          return ret;
>   }
>   EXPORT_SYMBOL(cpufreq_update_policy);
>

-- 
Aaron

Re: [PATCH] cpufreq: unlock when failing cpufreq_update_policy()

[Viresh Kumar]

On 18 June 2014 20:09, Aaron Plattner <aplattner@nvidia.com> wrote:
> I assume you meant "return -ENODEV"?

Yeah, sorry :)

>>          down_write(&policy->rwsem);
>>
>> @@ -2279,10 +2277,10 @@ int cpufreq_update_policy(unsigned int cpu)
>>
>>          ret = cpufreq_set_policy(policy, &new_policy);
>>
>> +no_policy:
>
>
> 'no_policy' implied to me that policy was NULL, so this label should still
> be renamed to 'unlock'.  I'll send out a v2 that does this.

Yeah.

[PATCH v2] cpufreq: unlock when failing cpufreq_update_policy()

[Aaron Plattner]

Commit bd0fa9bb455d introduced a failure path to cpufreq_update_policy() if
cpufreq_driver->get(cpu) returns NULL.  However, it jumps to the 'no_policy'
label, which exits without unlocking any of the locks the function acquired
earlier.  This causes later calls into cpufreq to hang.

Fix this by creating a new 'unlock' label and jumping to that instead.

v2: Delete the no_policy label and just return early if policy is NULL.

Fixes: bd0fa9bb455d ("cpufreq: Return error if ->get() failed in cpufreq_update_policy()")
Link: https://devtalk.nvidia.com/default/topic/751903/kernel-3-15-and-nv-drivers-337-340-failed-to-initialize-the-nvidia-kernel-module-gtx-550-ti-/
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
---
v1 of this was tested by the user affected by the problem, but I don't have his
email address so I can't add it as a Tested-by line.

 drivers/cpufreq/cpufreq.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index aed2b0cb83dc..62259d27f03e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2242,10 +2242,8 @@ int cpufreq_update_policy(unsigned int cpu)
 	struct cpufreq_policy new_policy;
 	int ret;
 
-	if (!policy) {
-		ret = -ENODEV;
-		goto no_policy;
-	}
+	if (!policy)
+		return -ENODEV;
 
 	down_write(&policy->rwsem);
 
@@ -2264,7 +2262,7 @@ int cpufreq_update_policy(unsigned int cpu)
 		new_policy.cur = cpufreq_driver->get(cpu);
 		if (WARN_ON(!new_policy.cur)) {
 			ret = -EIO;
-			goto no_policy;
+			goto unlock;
 		}
 
 		if (!policy->cur) {
@@ -2279,10 +2277,10 @@ int cpufreq_update_policy(unsigned int cpu)
 
 	ret = cpufreq_set_policy(policy, &new_policy);
 
+unlock:
 	up_write(&policy->rwsem);
 
 	cpufreq_cpu_put(policy);
-no_policy:
 	return ret;
 }
 EXPORT_SYMBOL(cpufreq_update_policy);
-- 
2.0.0

Re: [PATCH v2] cpufreq: unlock when failing cpufreq_update_policy()

[Rafael J. Wysocki]

On Wednesday, June 18, 2014 11:27:32 AM Aaron Plattner wrote:
> Commit bd0fa9bb455d introduced a failure path to cpufreq_update_policy() if
> cpufreq_driver->get(cpu) returns NULL.  However, it jumps to the 'no_policy'
> label, which exits without unlocking any of the locks the function acquired
> earlier.  This causes later calls into cpufreq to hang.
> 
> Fix this by creating a new 'unlock' label and jumping to that instead.
> 
> v2: Delete the no_policy label and just return early if policy is NULL.
> 
> Fixes: bd0fa9bb455d ("cpufreq: Return error if ->get() failed in cpufreq_update_policy()")
> Link: https://devtalk.nvidia.com/default/topic/751903/kernel-3-15-and-nv-drivers-337-340-failed-to-initialize-the-nvidia-kernel-module-gtx-550-ti-/
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Signed-off-by: Aaron Plattner <aplattner@nvidia.com>

Applied, thanks!

> ---
> v1 of this was tested by the user affected by the problem, but I don't have his
> email address so I can't add it as a Tested-by line.
> 
>  drivers/cpufreq/cpufreq.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index aed2b0cb83dc..62259d27f03e 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2242,10 +2242,8 @@ int cpufreq_update_policy(unsigned int cpu)
>  	struct cpufreq_policy new_policy;
>  	int ret;
>  
> -	if (!policy) {
> -		ret = -ENODEV;
> -		goto no_policy;
> -	}
> +	if (!policy)
> +		return -ENODEV;
>  
>  	down_write(&policy->rwsem);
>  
> @@ -2264,7 +2262,7 @@ int cpufreq_update_policy(unsigned int cpu)
>  		new_policy.cur = cpufreq_driver->get(cpu);
>  		if (WARN_ON(!new_policy.cur)) {
>  			ret = -EIO;
> -			goto no_policy;
> +			goto unlock;
>  		}
>  
>  		if (!policy->cur) {
> @@ -2279,10 +2277,10 @@ int cpufreq_update_policy(unsigned int cpu)
>  
>  	ret = cpufreq_set_policy(policy, &new_policy);
>  
> +unlock:
>  	up_write(&policy->rwsem);
>  
>  	cpufreq_cpu_put(policy);
> -no_policy:
>  	return ret;
>  }
>  EXPORT_SYMBOL(cpufreq_update_policy);
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.