Query related to usage of cpufreq_suspend() & cpufreq_resume

Query related to usage of cpufreq_suspend() & cpufreq_resume

[Prateek Sood]

Hi Viresh,

One scenario is there where a kernel panic is observed in
cpufreq during suspend/resume.

pm_suspend()
  suspend_devices_and_enter()
    dpm_suspend_start()
      dpm_prepare() 

Failure in dpm_prepare() happend with following dmesg:

[ 3746.316062] PM: Device xyz not prepared for power transition: code -16
[ 3746.316071] PM: Some devices failed to suspend, or early wake event detected


pm_suspend()
  suspend_devices_and_enter()
    dpm_suspend_start()
      dpm_prepare() //failed
    dpm_resume_end()
      dpm_resume()
        cpufreq_resume()
          cpufreq_start_governor()
            sugov_start()
              cpufreq_add_update_util_hook()

After failure in dpm_prepare(), dpm_resume() called
cpufreq_resume(). Corresponding cpufreq_suspend() was not
called due to failure of dpm_prepare(). 

This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu))
in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func
being inconsistent state. It caused crash in scheduler.

Following are some of the ways to mitigate this issue. Could
you please provide feedback on below two approaches or suugest
a better way to fix this problem.

-----------------------8<------------------------------

Co-developed-by: Gaurav Kohli <gkohli@codeaurora.org>
Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org> 
Signed-off-by: Prateek Sood <prsood@codeaurora.org>

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 02a497e..732e5a2 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state)
 {
        struct device *dev;
        ktime_t starttime = ktime_get();
+       bool valid_resume = false;

        trace_suspend_resume(TPS("dpm_resume"), state.event, true);
        might_sleep();
@@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state)
        }

        while (!list_empty(&dpm_suspended_list)) {
+               valid_resume = true;
                dev = to_device(dpm_suspended_list.next);
                get_device(dev);
                if (!is_async(dev)) {
@@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state)
        async_synchronize_full();
        dpm_show_time(starttime, state, 0, NULL);

-       cpufreq_resume();
+       if (valid_resume)
+               cpufreq_resume();
        trace_suspend_resume(TPS("dpm_resume"), state.event, false);
 }

--------------------8<--------------------------------------

Signed-off-by: Prateek Sood <prsood@codeaurora.org>

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 421f318..439eab8 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1648,7 +1648,7 @@ void cpufreq_suspend(void)
 {
        struct cpufreq_policy *policy;

-       if (!cpufreq_driver)
+       if (!cpufreq_driver || cpufreq_suspended)
                return;

        if (!has_target() && !cpufreq_driver->suspend)
@@ -1683,7 +1683,7 @@ void cpufreq_resume(void)
        struct cpufreq_policy *policy;
        int ret;

-       if (!cpufreq_driver)
+       if (!cpufreq_driver || !cpufreq_suspended)
                return;

        cpufreq_suspended = false;




Thanks

-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
Collaborative Project

Re: Query related to usage of cpufreq_suspend() & cpufreq_resume

[Rafael J. Wysocki]

On Friday, February 2, 2018 12:41:58 PM CET Prateek Sood wrote:
> Hi Viresh,
> 
> One scenario is there where a kernel panic is observed in
> cpufreq during suspend/resume.
> 
> pm_suspend()
>   suspend_devices_and_enter()
>     dpm_suspend_start()
>       dpm_prepare() 
> 
> Failure in dpm_prepare() happend with following dmesg:
> 
> [ 3746.316062] PM: Device xyz not prepared for power transition: code -16
> [ 3746.316071] PM: Some devices failed to suspend, or early wake event detected
> 
> 
> pm_suspend()
>   suspend_devices_and_enter()
>     dpm_suspend_start()
>       dpm_prepare() //failed
>     dpm_resume_end()
>       dpm_resume()
>         cpufreq_resume()
>           cpufreq_start_governor()
>             sugov_start()
>               cpufreq_add_update_util_hook()
> 
> After failure in dpm_prepare(), dpm_resume() called
> cpufreq_resume(). Corresponding cpufreq_suspend() was not
> called due to failure of dpm_prepare(). 
> 
> This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu))
> in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func
> being inconsistent state. It caused crash in scheduler.
> 
> Following are some of the ways to mitigate this issue. Could
> you please provide feedback on below two approaches or suugest
> a better way to fix this problem.
> 
> -----------------------8<------------------------------
> 
> Co-developed-by: Gaurav Kohli <gkohli@codeaurora.org>
> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org> 
> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
> 
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index 02a497e..732e5a2 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state)
>  {
>         struct device *dev;
>         ktime_t starttime = ktime_get();
> +       bool valid_resume = false;
> 
>         trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>         might_sleep();
> @@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state)
>         }
> 
>         while (!list_empty(&dpm_suspended_list)) {
> +               valid_resume = true;
>                 dev = to_device(dpm_suspended_list.next);
>                 get_device(dev);
>                 if (!is_async(dev)) {
> @@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state)
>         async_synchronize_full();
>         dpm_show_time(starttime, state, 0, NULL);
> 
> -       cpufreq_resume();
> +       if (valid_resume)
> +               cpufreq_resume();
>         trace_suspend_resume(TPS("dpm_resume"), state.event, false);
>  }
> 
> --------------------8<--------------------------------------
> 
> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 421f318..439eab8 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1648,7 +1648,7 @@ void cpufreq_suspend(void)
>  {
>         struct cpufreq_policy *policy;
> 
> -       if (!cpufreq_driver)
> +       if (!cpufreq_driver || cpufreq_suspended)
>                 return;
> 
>         if (!has_target() && !cpufreq_driver->suspend)
> @@ -1683,7 +1683,7 @@ void cpufreq_resume(void)
>         struct cpufreq_policy *policy;
>         int ret;
> 
> -       if (!cpufreq_driver)
> +       if (!cpufreq_driver || !cpufreq_suspended)
>                 return;
> 
>         cpufreq_suspended = false;

Since we have cpufreq_suspended already, the second one is better.

Thanks,
Rafael

Re: Query related to usage of cpufreq_suspend() & cpufreq_resume

[Prateek Sood]

On 02/02/2018 05:18 PM, Rafael J. Wysocki wrote:
> On Friday, February 2, 2018 12:41:58 PM CET Prateek Sood wrote:
>> Hi Viresh,
>>
>> One scenario is there where a kernel panic is observed in
>> cpufreq during suspend/resume.
>>
>> pm_suspend()
>>   suspend_devices_and_enter()
>>     dpm_suspend_start()
>>       dpm_prepare() 
>>
>> Failure in dpm_prepare() happend with following dmesg:
>>
>> [ 3746.316062] PM: Device xyz not prepared for power transition: code -16
>> [ 3746.316071] PM: Some devices failed to suspend, or early wake event detected
>>
>>
>> pm_suspend()
>>   suspend_devices_and_enter()
>>     dpm_suspend_start()
>>       dpm_prepare() //failed
>>     dpm_resume_end()
>>       dpm_resume()
>>         cpufreq_resume()
>>           cpufreq_start_governor()
>>             sugov_start()
>>               cpufreq_add_update_util_hook()
>>
>> After failure in dpm_prepare(), dpm_resume() called
>> cpufreq_resume(). Corresponding cpufreq_suspend() was not
>> called due to failure of dpm_prepare(). 
>>
>> This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu))
>> in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func
>> being inconsistent state. It caused crash in scheduler.
>>
>> Following are some of the ways to mitigate this issue. Could
>> you please provide feedback on below two approaches or suugest
>> a better way to fix this problem.
>>
>> -----------------------8<------------------------------
>>
>> Co-developed-by: Gaurav Kohli <gkohli@codeaurora.org>
>> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org> 
>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>>
>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>> index 02a497e..732e5a2 100644
>> --- a/drivers/base/power/main.c
>> +++ b/drivers/base/power/main.c
>> @@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state)
>>  {
>>         struct device *dev;
>>         ktime_t starttime = ktime_get();
>> +       bool valid_resume = false;
>>
>>         trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>>         might_sleep();
>> @@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state)
>>         }
>>
>>         while (!list_empty(&dpm_suspended_list)) {
>> +               valid_resume = true;
>>                 dev = to_device(dpm_suspended_list.next);
>>                 get_device(dev);
>>                 if (!is_async(dev)) {
>> @@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state)
>>         async_synchronize_full();
>>         dpm_show_time(starttime, state, 0, NULL);
>>
>> -       cpufreq_resume();
>> +       if (valid_resume)
>> +               cpufreq_resume();
>>         trace_suspend_resume(TPS("dpm_resume"), state.event, false);
>>  }
>>
>> --------------------8<--------------------------------------
>>
>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 421f318..439eab8 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -1648,7 +1648,7 @@ void cpufreq_suspend(void)
>>  {
>>         struct cpufreq_policy *policy;
>>
>> -       if (!cpufreq_driver)
>> +       if (!cpufreq_driver || cpufreq_suspended)
>>                 return;
>>
>>         if (!has_target() && !cpufreq_driver->suspend)
>> @@ -1683,7 +1683,7 @@ void cpufreq_resume(void)
>>         struct cpufreq_policy *policy;
>>         int ret;
>>
>> -       if (!cpufreq_driver)
>> +       if (!cpufreq_driver || !cpufreq_suspended)
>>                 return;
>>
>>         cpufreq_suspended = false;
> 
> Since we have cpufreq_suspended already, the second one is better.
> 
> Thanks,
> Rafael
> 

Thanks Rafael for the inputs, I will send a formal patch.


-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
Collaborative Project

Re: Query related to usage of cpufreq_suspend() & cpufreq_resume

[Rafael J. Wysocki]

On Fri, Feb 2, 2018 at 1:53 PM, Prateek Sood <prsood@codeaurora.org> wrote:
> On 02/02/2018 05:18 PM, Rafael J. Wysocki wrote:
>> On Friday, February 2, 2018 12:41:58 PM CET Prateek Sood wrote:
>>> Hi Viresh,
>>>
>>> One scenario is there where a kernel panic is observed in
>>> cpufreq during suspend/resume.
>>>
>>> pm_suspend()
>>>   suspend_devices_and_enter()
>>>     dpm_suspend_start()
>>>       dpm_prepare()
>>>
>>> Failure in dpm_prepare() happend with following dmesg:
>>>
>>> [ 3746.316062] PM: Device xyz not prepared for power transition: code -16
>>> [ 3746.316071] PM: Some devices failed to suspend, or early wake event detected
>>>
>>>
>>> pm_suspend()
>>>   suspend_devices_and_enter()
>>>     dpm_suspend_start()
>>>       dpm_prepare() //failed
>>>     dpm_resume_end()
>>>       dpm_resume()
>>>         cpufreq_resume()
>>>           cpufreq_start_governor()
>>>             sugov_start()
>>>               cpufreq_add_update_util_hook()
>>>
>>> After failure in dpm_prepare(), dpm_resume() called
>>> cpufreq_resume(). Corresponding cpufreq_suspend() was not
>>> called due to failure of dpm_prepare().
>>>
>>> This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu))
>>> in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func
>>> being inconsistent state. It caused crash in scheduler.
>>>
>>> Following are some of the ways to mitigate this issue. Could
>>> you please provide feedback on below two approaches or suugest
>>> a better way to fix this problem.
>>>
>>> -----------------------8<------------------------------
>>>
>>> Co-developed-by: Gaurav Kohli <gkohli@codeaurora.org>
>>> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
>>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>>>
>>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>>> index 02a497e..732e5a2 100644
>>> --- a/drivers/base/power/main.c
>>> +++ b/drivers/base/power/main.c
>>> @@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state)
>>>  {
>>>         struct device *dev;
>>>         ktime_t starttime = ktime_get();
>>> +       bool valid_resume = false;
>>>
>>>         trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>>>         might_sleep();
>>> @@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state)
>>>         }
>>>
>>>         while (!list_empty(&dpm_suspended_list)) {
>>> +               valid_resume = true;
>>>                 dev = to_device(dpm_suspended_list.next);
>>>                 get_device(dev);
>>>                 if (!is_async(dev)) {
>>> @@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state)
>>>         async_synchronize_full();
>>>         dpm_show_time(starttime, state, 0, NULL);
>>>
>>> -       cpufreq_resume();
>>> +       if (valid_resume)
>>> +               cpufreq_resume();
>>>         trace_suspend_resume(TPS("dpm_resume"), state.event, false);
>>>  }
>>>
>>> --------------------8<--------------------------------------
>>>
>>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>>>
>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>> index 421f318..439eab8 100644
>>> --- a/drivers/cpufreq/cpufreq.c
>>> +++ b/drivers/cpufreq/cpufreq.c
>>> @@ -1648,7 +1648,7 @@ void cpufreq_suspend(void)
>>>  {
>>>         struct cpufreq_policy *policy;
>>>
>>> -       if (!cpufreq_driver)
>>> +       if (!cpufreq_driver || cpufreq_suspended)
>>>                 return;
>>>
>>>         if (!has_target() && !cpufreq_driver->suspend)
>>> @@ -1683,7 +1683,7 @@ void cpufreq_resume(void)
>>>         struct cpufreq_policy *policy;
>>>         int ret;
>>>
>>> -       if (!cpufreq_driver)
>>> +       if (!cpufreq_driver || !cpufreq_suspended)
>>>                 return;
>>>
>>>         cpufreq_suspended = false;
>>
>> Since we have cpufreq_suspended already, the second one is better.
>>
>
> Thanks Rafael for the inputs, I will send a formal patch.

Bo Yan has posted something really similar already, however:

https://patchwork.kernel.org/patch/10181101/

so I would prefer to apply a new version of that one with the latest
comment taken into account:

https://patchwork.kernel.org/patch/10183075/

for the credit to go to the first submitter.

Re: Query related to usage of cpufreq_suspend() & cpufreq_resume

[Prateek Sood]

On 02/02/2018 06:49 PM, Rafael J. Wysocki wrote:
> On Fri, Feb 2, 2018 at 1:53 PM, Prateek Sood <prsood@codeaurora.org> wrote:
>> On 02/02/2018 05:18 PM, Rafael J. Wysocki wrote:
>>> On Friday, February 2, 2018 12:41:58 PM CET Prateek Sood wrote:
>>>> Hi Viresh,
>>>>
>>>> One scenario is there where a kernel panic is observed in
>>>> cpufreq during suspend/resume.
>>>>
>>>> pm_suspend()
>>>>   suspend_devices_and_enter()
>>>>     dpm_suspend_start()
>>>>       dpm_prepare()
>>>>
>>>> Failure in dpm_prepare() happend with following dmesg:
>>>>
>>>> [ 3746.316062] PM: Device xyz not prepared for power transition: code -16
>>>> [ 3746.316071] PM: Some devices failed to suspend, or early wake event detected
>>>>
>>>>
>>>> pm_suspend()
>>>>   suspend_devices_and_enter()
>>>>     dpm_suspend_start()
>>>>       dpm_prepare() //failed
>>>>     dpm_resume_end()
>>>>       dpm_resume()
>>>>         cpufreq_resume()
>>>>           cpufreq_start_governor()
>>>>             sugov_start()
>>>>               cpufreq_add_update_util_hook()
>>>>
>>>> After failure in dpm_prepare(), dpm_resume() called
>>>> cpufreq_resume(). Corresponding cpufreq_suspend() was not
>>>> called due to failure of dpm_prepare().
>>>>
>>>> This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu))
>>>> in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func
>>>> being inconsistent state. It caused crash in scheduler.
>>>>
>>>> Following are some of the ways to mitigate this issue. Could
>>>> you please provide feedback on below two approaches or suugest
>>>> a better way to fix this problem.
>>>>
>>>> -----------------------8<------------------------------
>>>>
>>>> Co-developed-by: Gaurav Kohli <gkohli@codeaurora.org>
>>>> Signed-off-by: Gaurav Kohli <gkohli@codeaurora.org>
>>>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>>>>
>>>> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
>>>> index 02a497e..732e5a2 100644
>>>> --- a/drivers/base/power/main.c
>>>> +++ b/drivers/base/power/main.c
>>>> @@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state)
>>>>  {
>>>>         struct device *dev;
>>>>         ktime_t starttime = ktime_get();
>>>> +       bool valid_resume = false;
>>>>
>>>>         trace_suspend_resume(TPS("dpm_resume"), state.event, true);
>>>>         might_sleep();
>>>> @@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state)
>>>>         }
>>>>
>>>>         while (!list_empty(&dpm_suspended_list)) {
>>>> +               valid_resume = true;
>>>>                 dev = to_device(dpm_suspended_list.next);
>>>>                 get_device(dev);
>>>>                 if (!is_async(dev)) {
>>>> @@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state)
>>>>         async_synchronize_full();
>>>>         dpm_show_time(starttime, state, 0, NULL);
>>>>
>>>> -       cpufreq_resume();
>>>> +       if (valid_resume)
>>>> +               cpufreq_resume();
>>>>         trace_suspend_resume(TPS("dpm_resume"), state.event, false);
>>>>  }
>>>>
>>>> --------------------8<--------------------------------------
>>>>
>>>> Signed-off-by: Prateek Sood <prsood@codeaurora.org>
>>>>
>>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>>> index 421f318..439eab8 100644
>>>> --- a/drivers/cpufreq/cpufreq.c
>>>> +++ b/drivers/cpufreq/cpufreq.c
>>>> @@ -1648,7 +1648,7 @@ void cpufreq_suspend(void)
>>>>  {
>>>>         struct cpufreq_policy *policy;
>>>>
>>>> -       if (!cpufreq_driver)
>>>> +       if (!cpufreq_driver || cpufreq_suspended)
>>>>                 return;
>>>>
>>>>         if (!has_target() && !cpufreq_driver->suspend)
>>>> @@ -1683,7 +1683,7 @@ void cpufreq_resume(void)
>>>>         struct cpufreq_policy *policy;
>>>>         int ret;
>>>>
>>>> -       if (!cpufreq_driver)
>>>> +       if (!cpufreq_driver || !cpufreq_suspended)
>>>>                 return;
>>>>
>>>>         cpufreq_suspended = false;
>>>
>>> Since we have cpufreq_suspended already, the second one is better.
>>>
>>
>> Thanks Rafael for the inputs, I will send a formal patch.
> 
> Bo Yan has posted something really similar already, however:
> 
> https://patchwork.kernel.org/patch/10181101/
> 
> so I would prefer to apply a new version of that one with the latest
> comment taken into account:
> 
> https://patchwork.kernel.org/patch/10183075/
> 
> for the credit to go to the first submitter.
> 

Thanks for the information Rafael. 

I believe safety check in both cpufreq_suspend() and
cpufreq_resume() would be a good thing to have. 


-- 
Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc., is a member of Code Aurora Forum, a Linux Foundation
Collaborative Project