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Date: Thu, 13 Apr 2017 23:02:43 +0530
From: Keerthy <j-keerthy@...com>
To: Eduardo Valentin <edubezval@...il.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 2/2] thermal: core: Add a back up thermal shutdown
mechanism
On Thursday 13 April 2017 08:55 PM, Eduardo Valentin wrote:
>
> Hey,
>
> On Thu, Apr 13, 2017 at 01:32:36PM +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).
>>
>> 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.
>
> Thanks for keeping this thread up and fixing it. Some requests to this
> patch too as follows.
>
>>
>> Reported-by: Nishanth Menon <nm@...com>
>> Signed-off-by: Keerthy <j-keerthy@...com>
>> ---
>>
>> * Changed the comment style
>> * Added backup shutdown call before orderly_poweroff
>>
>> drivers/thermal/Kconfig | 13 ++++++++++++
>> drivers/thermal/thermal_core.c | 47 ++++++++++++++++++++++++++++++++++++++++++
>
> I think this change in expectation should probably be documented under
> Documentation/ directory. Can you please patch thermal documentation
> too?
Okay.
>
>> 2 files changed, 60 insertions(+)
>>
>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>> index 9347401..971fd54 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 7462ae5..d60fa9e 100644
>> --- a/drivers/thermal/thermal_core.c
>> +++ b/drivers/thermal/thermal_core.c
>> @@ -323,12 +323,54 @@ 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 kernel_power_off
>> + * if populated
>> + */
>> + pr_warn("Attempting kernel_power_off\n");
>
> This message needs to be specific to thermal (forced) shutdown.
Sure.
>
>> + kernel_power_off();
>> +
>> + /*
>> + * Worst of the worst case trigger emergency restart
>> + */
>> + pr_warn("kernel_power_off has failed! Attempting emergency_restart\n");
>
> Same here..
okay.
>
> also, I think if your system reached this point, we should probably be more
> dramatic at the kernel log a scream louder, I would say a big farty WARN
> to say the least. Or a crash.
warning should do.
>
>> + 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_EMERGENCY_POWEROFF_DELAY_MS));
>> +}
>> +
>> 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;
>> + static struct mutex poweroff_lock;
>>
>> + mutex_init(&poweroff_lock);
>> tz->ops->get_trip_temp(tz, trip, &trip_temp);
>>
>
> the above is probably a quirk?
Ya unnecessary. Thanks for catching this.
>
>> /* If we have not crossed the trip_temp, we do not care. */
>> @@ -345,6 +387,11 @@ static void handle_critical_trips(struct thermal_zone_device *tz,
>> "critical temperature reached(%d C),shutting down\n",
>> tz->temperature / 1000);
>> mutex_lock(&poweroff_lock);
>> + /*
>> + * Queue a backup emergency shutdown in the event of
>> + * orderly_poweroff failure.
>> + */
>> + thermal_emergency_poweroff();
>> orderly_poweroff(true);
>> power_off_triggered = true;
>> mutex_unlock(&poweroff_lock);
>> --
>> 1.9.1
>>
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