Message-ID: <492e72af-ff33-d193-071e-5bc00df9a8b0@ti.com>
Date:   Wed, 12 Apr 2017 09:09:36 +0530
From:   Keerthy <j-keerthy@...com>
To:     Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>
CC:     <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>, <nm@...com>, <t-kristo@...com>
Subject: Re: [PATCH] thermal: core: Add a back up thermal shutdown mechanism



On Wednesday 12 April 2017 08:50 AM, Zhang Rui wrote:
> On Wed, 2017-04-12 at 08:19 +0530, Keerthy wrote:
>>
>> On Tuesday 11 April 2017 10:59 PM, Eduardo Valentin wrote:
>>>
>>> Hey,
>>>
>>> On Fri, Mar 31, 2017 at 12:00:20PM +0530, Keerthy wrote:
>>>>
>>>> orderly_poweroff is triggered when a graceful shutdown
>>>> of system is desired. This may be used in many critical states of
>>>> the
>>>> kernel such as when subsystems detects conditions such as
>>>> critical
>>>> temperature conditions. However, in certain conditions in system
>>>> boot up sequences like those in the middle of driver probes being
>>>> initiated, userspace will be unable to power off the system in a
>>>> clean
>>>> manner and leaves the system in a critical state. In cases like
>>>> these,
>>>> the /sbin/poweroff will return success (having forked off to
>>>> attempt
>>>> powering off the system. However, the system overall will fail to
>>>> completely poweroff (since other modules will be probed) and the
>>>> system
>>>> is still functional with no userspace (since that would have shut
>>>> itself
>>>> off).
>>> OK... This seams to me, still a corner case supposed to be fixed at
>>> orderly_power_off, not at thermal. But..
>>>
>>>>
>>>>
>>>> However, there is no clean way of detecting such failure of
>>>> userspace
>>>> powering off the system. In such scenarios, it is necessary for a
>>>> backup
>>>> workqueue to be able to force a shutdown of the system when
>>>> orderly
>>>> shutdown is not successful after a configurable time period.
>>>>
>>> Given that system running hot is a thermal issue, I guess we care
>>> more
>>> on this matter then..
>> Yes!
>>
> I just read this thread again https://patchwork.kernel.org/patch/802458
> 1/ to recall the previous discussion.
> 
> https://patchwork.kernel.org/patch/8149891/
> https://patchwork.kernel.org/patch/8149861/
> should be the solution made based on Ingo' suggestion, right?
> 
> And to me, this sounds like the right direction to go, thermal does not
> need a back up shutdown solution, it just needs a kernel function call
> which guarantees the system can be shutdown/reboot immediately.
> 
> is there any reason that patch 1/2 is not accepted?

Zhang,

http://www.serverphorums.com/read.php?12,1400964

I got a NAK from Alan and was given this direction on a thermal_poweroff
which is more or less what is done in this patch.

Thanks,
Keerthy

> 
> thanks,
> rui
>>>
>>>
>>>>
>>>> Reported-by: Nishanth Menon <nm@...com>
>>>> Signed-off-by: Keerthy <j-keerthy@...com>
>>>> ---
>>>>  drivers/thermal/Kconfig        | 13 +++++++++++++
>>>>  drivers/thermal/thermal_core.c | 42
>>>> ++++++++++++++++++++++++++++++++++++++++++
>>>>  2 files changed, 55 insertions(+)
>>>>
>>>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>>>> index 0a16cf4..4cc55f9 100644
>>>> --- a/drivers/thermal/Kconfig
>>>> +++ b/drivers/thermal/Kconfig
>>>> @@ -15,6 +15,19 @@ menuconfig THERMAL
>>>>  
>>>>  if THERMAL
>>>>  
>>>> +config THERMAL_EMERGENCY_POWEROFF_DELAY_MS
>>>> +	int "Emergency poweroff delay in milli-seconds"
>>>> +	depends on THERMAL
>>>> +	default 0
>>>> +	help
>>>> +	  The number of milliseconds to delay before emergency
>>>> +	  poweroff kicks in. The delay should be carefully
>>>> profiled
>>>> +	  so as to give adequate time for orderly_poweroff. In
>>>> case
>>>> +	  of failure of an orderly_poweroff the emergency
>>>> poweroff
>>>> +	  kicks in after the delay has elapsed and shuts down
>>>> the system.
>>>> +
>>>> +	  If set to 0 poweroff will happen immediately.
>>>> +
>>>>  config THERMAL_HWMON
>>>>  	bool
>>>>  	prompt "Expose thermal sensors as hwmon device"
>>>> diff --git a/drivers/thermal/thermal_core.c
>>>> b/drivers/thermal/thermal_core.c
>>>> index 11f0675..dc7fdd4 100644
>>>> --- a/drivers/thermal/thermal_core.c
>>>> +++ b/drivers/thermal/thermal_core.c
>>>> @@ -322,6 +322,47 @@ static void handle_non_critical_trips(struct
>>>> thermal_zone_device *tz,
>>>>  		       def_governor->throttle(tz, trip);
>>>>  }
>>>>  
>>>> +/**
>>>> + * emergency_poweroff_func - emergency poweroff work after a
>>>> known delay
>>>> + * @work: work_struct associated with the emergency poweroff
>>>> function
>>>> + *
>>>> + * This function is called in very critical situations to force
>>>> + * a kernel poweroff after a configurable timeout value.
>>>> + */
>>>> +static void emergency_poweroff_func(struct work_struct *work)
>>>> +{
>>>> +	/**
>>>> +	 * We have reached here after the emergency thermal
>>>> shutdown
>>>> +	 * Waiting period has expired. This means
>>>> orderly_poweroff has
>>>> +	 * not been able to shut off the system for some reason.
>>>> +	 * Try to shut down the system immediately using
>>>> pm_power_off
>>>> +	 * if populated
>>>> +	 */
>>> The above is not a kernel doc entry...
>> I will fix that.
>>
>>>
>>>
>>>>
>>>> +	pr_warn("Attempting kernel_power_off\n");
>>>> +	if (pm_power_off)
>>>> +		pm_power_off();
>>> Why not calling kernel_power_off() directly instead? That is what
>>> is called by orderly
>>> power off in case it fails, which seams to be  the missing part
>>> when
>>> user land returns success, and therefore we don't call
>>> kernel_power_off(). That path goes through the machine_power_off(),
>>> which seams to be the default for pm_power_off() anyway.
>>>
>>> kernel_power_off() handles the power off system call too.
>> Yes. This is after orderly_poweroff fails so i felt why go through
>> kernel_power_off and directly call pm_power_off which directly pulls
>> out
>> the power plug. This is in dire straits situation. Hence preferred to
>> call the last piece directly.
>>
>>>
>>>
>>>>
>>>> +
>>>> +	/**
>>> not a kernel doc entry...
>> Okay.
>>
>>>
>>>
>>>>
>>>> +	 * Worst of the worst case trigger emergency restart
>>>> +	 */
>>>> +	pr_warn("kernel_power_off has failed! Attempting
>>>> emergency_restart\n");
>>>> +	emergency_restart();
>>>> +}
>>>> +
>>>> +static DECLARE_DELAYED_WORK(emergency_poweroff_work,
>>>> emergency_poweroff_func);
>>>> +
>>>> +/**
>>>> + * emergency_poweroff - Trigger an emergency system poweroff
>>>> + *
>>>> + * This may be called from any critical situation to trigger a
>>>> system shutdown
>>>> + * after a known period of time. By default the delay is 0
>>>> millisecond
>>>> + */
>>>> +void thermal_emergency_poweroff(void)
>>>> +{
>>>> +	schedule_delayed_work(&emergency_poweroff_work,
>>>> +			      msecs_to_jiffies(CONFIG_THERMAL_EM
>>>> ERGENCY_POWEROFF_DELAY_MS));
>>>> +}
>>>> +
>>>>  static void handle_critical_trips(struct thermal_zone_device
>>>> *tz,
>>>>  				  int trip, enum
>>>> thermal_trip_type trip_type)
>>>>  {
>>>> @@ -343,6 +384,7 @@ static void handle_critical_trips(struct
>>>> thermal_zone_device *tz,
>>>>  			  "critical temperature reached(%d
>>>> C),shutting down\n",
>>>>  			  tz->temperature / 1000);
>>>>  		orderly_poweroff(true);
>>>> +		thermal_emergency_poweroff();
>>> Shouldn't we start count the timeout before calling
>>> orderly_poweroff?
>> Okay yes. That makes more sense. Queue the emergency function, start
>> the
>> countdown and immediately call the orderly_poweroff. I will fix the
>> above comments and send a v2. I still want to go with pm_power_off
>> over
>> kernel_poweroff as we have already elapsed the time out and the first
>> thing we want is to shut off the SoC! Let me know.
>>
>>
>>>
>>>
>>>>
>>>>  	}
>>>>  }
>>>>  

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