linux-kernel - Re: [PATCH v2 1/2] thermal: core: Allow orderly

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Message-ID: <20170413151558.GA8412@localhost.localdomain>
Date:   Thu, 13 Apr 2017 08:16:01 -0700
From:   Eduardo Valentin <edubezval@...il.com>
To:     Keerthy <j-keerthy@...com>
Cc:     rui.zhang@...el.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        nm@...com, t-kristo@...com
Subject: Re: [PATCH v2 1/2] thermal: core: Allow orderly_poweroff to be
 called only once

Hey,

On Thu, Apr 13, 2017 at 01:32:35PM +0530, Keerthy wrote:
> thermal_zone_device_check --> thermal_zone_device_update -->
> handle_thermal_trip --> handle_critical_trips --> orderly_poweroff
> 
> The above sequence happens every 250/500 mS based on the configuration.
> The orderly_poweroff function is getting called every 250/500 mS.
> With a full fledged file system it takes at least 5-10 Seconds to
> power off gracefully.
> 
> In that period due to the thermal_zone_device_check triggering
> periodically the thermal work queues bombard with
> orderly_poweroff calls multiple times eventually leading to
> failures in gracefully powering off the system.
> 
> Make sure that orderly_poweroff is called only once.
> 
> Reported-by: Nishanth Menon <nm@...com>

Was this reported by nm or found by you?

> Signed-off-by: Keerthy <j-keerthy@...com>
> ---
> 
> Changes in v2:
> 
>   * Added a global mutex to serialize poweroff code sequence.
> 
>  drivers/thermal/thermal_core.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 11f0675..7462ae5 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -45,6 +45,7 @@
>  
>  static DEFINE_MUTEX(thermal_list_lock);
>  static DEFINE_MUTEX(thermal_governor_lock);
> +static DEFINE_MUTEX(poweroff_lock);
>  
>  static atomic_t in_suspend;
>  
> @@ -326,6 +327,7 @@ static void handle_critical_trips(struct thermal_zone_device *tz,
>  				  int trip, enum thermal_trip_type trip_type)
>  {
>  	int trip_temp;
> +	static bool power_off_triggered;
>  
>  	tz->ops->get_trip_temp(tz, trip, &trip_temp);
>  
> @@ -338,11 +340,14 @@ static void handle_critical_trips(struct thermal_zone_device *tz,
>  	if (tz->ops->notify)
>  		tz->ops->notify(tz, trip, trip_type);
>  
> -	if (trip_type == THERMAL_TRIP_CRITICAL) {
> +	if (trip_type == THERMAL_TRIP_CRITICAL && !power_off_triggered) {
>  		dev_emerg(&tz->device,
>  			  "critical temperature reached(%d C),shutting down\n",
>  			  tz->temperature / 1000);
> +		mutex_lock(&poweroff_lock);
>  		orderly_poweroff(true);
> +		power_off_triggered = true;
> +		mutex_unlock(&poweroff_lock);

The above code does not fully prevent orderly_poweroff() to be called
only once, does it?

- thermal zone 0 goes all the way in the critical path, but gets
  preempted between orderly_poweroff(true)l and power_off_triggered =
  true;, i.e., preempted right before setting to true, therefore,
  power_off_triggered still 0.
- thermal zone 1 also enters critical path, but will sleep at the
  power_off_lock, right?
- then thermal zone 0 gets the CPU again, finishes the critical path,
  unlocks poweroff_lock.
- thermal zone 1 is unblocked, and call again orderly_poweroff(true);



BR,
>  	}
>  }
>  
> @@ -1463,6 +1468,7 @@ static int __init thermal_init(void)
>  {
>  	int result;
>  
> +	mutex_init(&poweroff_lock);
>  	result = thermal_register_governors();
>  	if (result)
>  		goto error;
> @@ -1497,6 +1503,7 @@ static int __init thermal_init(void)
>  	ida_destroy(&thermal_cdev_ida);
>  	mutex_destroy(&thermal_list_lock);
>  	mutex_destroy(&thermal_governor_lock);
> +	mutex_destroy(&poweroff_lock);
>  	return result;
>  }
>  
> -- 
> 1.9.1
> 

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