Re: [PATCH 4/4] PM / devfreq: Handle monitor start/stop in the devfreq core

[Lukasz Luba <l.luba@partner.samsung.com>]

Hi Matthias,

On 2/14/19 8:07 PM, Matthias Kaehlcke wrote:
> Hi Lukasz,
> 
> On Thu, Feb 14, 2019 at 07:01:36PM +0100, Lukasz Luba wrote:
>> Hi Matthias,
>>
>> I have compiled and run your changes on Odroid xu3 and v5.0-rc6.
>> There are kernel warnings because of mutex not held in function
>> devfreq_monitor_[start|stop]() in use cases:
>>    1) a few times during registration of new devices devfreq_add_device()
>>    2) poking the device from sysfs
> 
> Thanks testing!
> 
> I messed up carrying over changes from my v4.19 device kernel
> to the tree used for upstreaming :(
> 
> Do you still see warnings with the below patch?
No, the warnings are no longer present in the log. The patch solves it.

Regards,
Lukasz
> 
> Thanks
> 
> Matthias
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index a42c37543c190..866fe711b43ca 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -440,7 +440,6 @@ static void devfreq_monitor_stop(struct devfreq *devfreq)
> 
>          mutex_lock(&devfreq->lock);
>          devfreq->monitor_state = DEVFREQ_MONITOR_STOPPED;
> -       mutex_unlock(&devfreq->lock);
>   }
> 
>   /**
> @@ -596,7 +595,9 @@ static int governor_start(struct devfreq *devfreq)
>                  return err;
>          }
> 
> +       mutex_lock(&devfreq->lock);
>          devfreq_monitor_start(devfreq);
> +       mutex_unlock(&devfreq->lock);
> 
>          return 0;
>   }
> @@ -614,7 +615,9 @@ static int governor_stop(struct devfreq *devfreq)
>                   "mutex must *not* be held by the caller\n"))
>                  return -EINVAL;
> 
> +       mutex_lock(&devfreq->lock);
>          devfreq_monitor_stop(devfreq);
> +       mutex_unlock(&devfreq->lock);
> 
>          err = devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_STOP, NULL);
>          if (err) {
> 
>