Re: [PATCH] thermal: core: Add a back up thermal shutdown mechanism

[Keerthy <j-keerthy@ti.com>]

On Wednesday 12 April 2017 10:24 PM, Eduardo Valentin wrote:
> Keerthy,
> 
> On Wed, Apr 12, 2017 at 10:14:36PM +0530, Keerthy wrote:
>>
>>
>> On Wednesday 12 April 2017 10:01 PM, Grygorii Strashko wrote:
>>>
>>>
>>> On 04/12/2017 10:44 AM, Eduardo Valentin wrote:
>>>> Hello,
>>>>
>>> ...
>>>
>>>>
>>>> I agree. But there it nothing that says it is not reenterable. If you
>>>> saw something in this line, can you please share?
>>>>
>>>>>>> will you generate a patch to do this?
>>>>>> Sure. I will generate a patch to take care of 1) To make sure that
>>>>>> orderly_poweroff is called only once right away. I have already
>>>>>> tested.
>>>>>>
>>>>>> for 2) Cancel all the scheduled work queues to monitor the
>>>>>> temperature.
>>>>>> I will take some more time to make it and test.
>>>>>>
>>>>>> Is that okay? Or you want me to send both together?
>>>>>>
>>>>> I think you can send patch for step 1 first.
>>>>
>>>> I am happy to see that Keerthy found the problem with his setup and a
>>>> possible solution. But I have a few concerns here.
>>>>
>>>> 1. If regular shutdown process takes 10seconds, that is a ballpark that
>>>> thermal should never wait. orderly_poweroff() calls run_cmd() with wait
>>>> flag set. That means, if regular userland shutdown takes 10s, we are
>>>> waiting for it. Obviously this not acceptable. Specially if you setup
>>>> critical trip to be 125C. Now, if you properly size the critical trip to
>>>> fire before hotspot really reach 125C, for 10s (or the time it takes to
>>>> shutdown), then fine. But based on what was described in this thread,
>>>> his system is waiting 10s on regular shutdown, and his silicon is on
>>>> out-of-spec temperature for 10s, which is wrong.
>>>>
>>>> 2. The above scenario is not acceptable in a long run, specially from a
>>>> reliability perspective. If orderly_poweroff() has a possibility to
>>>> simply never return (or take too long), I would say the thermal
>>>> subsystem is using the wrong API.
>>>>
>>>
>>>
>>> Hh, I do not see that orderly_poweroff() will wait for anything now:
>>> void orderly_poweroff(bool force)
>>> {
>>> 	if (force) /* do not override the pending "true" */
>>> 		poweroff_force = true;
>>> 	schedule_work(&poweroff_work); 
>>> ^^^^^^^ async call. even here can be pretty big delay if system is under pressure
>>> }
>>>
>>>
>>> static int __orderly_poweroff(bool force)
>>> {
>>> 	int ret;
>>>
>>> 	ret = run_cmd(poweroff_cmd);
>>
>> When i tried with multiple orderly_poweroff calls ret was always 0.
>> So every 250mS i see this ret = 0.
>>
>>> ^^^^ no wait for the process - only for exec. flags == UMH_WAIT_EXEC
>>>
>>> 	if (ret && force) {
>>
>> So it never entered this path. ret = 0 so if is not executed.
> 
> I think your setup has two major problems then:
> 1. when kernel runs userspace power off, it execs properly, in fact, it
> is not triggered.

It does work neatly when orderly_poweroff is called once. It gracefully
shuts down the system. I see problem is when we call run_cmd every 250mS
multiple times.

> 2. when you finally exec it, it takes 5s to finish.

I will share the logs.

> 
> If this is correct, I think my suggestions on the other email
> still holds.
> 
> BR,
>