On Monday 17 April 2017 10:46 PM, Eduardo Valentin wrote:
> On Sat, Apr 15, 2017 at 08:38:29AM +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.
>>
>> Reported-by: Nishanth Menon <nm@xxxxxx>
>> Signed-off-by: Keerthy <j-keerthy@xxxxxx>
>> ---
>>
>> Changes in v5:
>>
>> * Mandated delay for thermal emergency poweroff to be a non-zero value.
>>
>> Changes in v4:
>>
>> * Updated documentation
>> * changed emergency_poweroff_func to thermal_emergency_poweroff_func
>>
>> Changes in v3:
>>
>> * Removed unnecessary mutex init.
>> * Added WARN messages instead of a simple warning message.
>> * Added Documentation.
>>
>> Documentation/thermal/sysfs-api.txt | 21 +++++++++++++++
>> drivers/thermal/Kconfig | 15 +++++++++++
>> drivers/thermal/thermal_core.c | 53 +++++++++++++++++++++++++++++++++++++
>> 3 files changed, 89 insertions(+)
>>
>> diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
>> index ef473dc..98dc04f 100644
>> --- a/Documentation/thermal/sysfs-api.txt
>> +++ b/Documentation/thermal/sysfs-api.txt
>> @@ -582,3 +582,24 @@ platform data is provided, this uses the step_wise throttling policy.
>> This function serves as an arbitrator to set the state of a cooling
>> device. It sets the cooling device to the deepest cooling state if
>> possible.
>> +
>> +6. thermal_emergency_poweroff:
>> +
>> +On an event of critical trip temperature crossing. Thermal framework
>> +allows the system to shutdown gracefully by calling orderly_poweroff().
>> +In the event of a failure of orderly_poweroff() to shut down the system
>> +we are in danger of keeping the system alive at undesirably high
>> +temperatures. To mitigate this high risk scenario we program a work
>> +queue to fire after a pre-determined number of seconds to start
>> +an emergency shutdown of the device using the kernel_power_off()
>> +function. In case kernel_power_off() fails then finally
>> +emergency_restart() is called in the worst case.
>> +
>> +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 emergency poweroff will not be supported. So a carefully
>> +profiled non-zero positive value is a must for emergerncy poweroff to be
>> +triggered.
>> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
>> index 9347401..2a748a6 100644
>> --- a/drivers/thermal/Kconfig
>> +++ b/drivers/thermal/Kconfig
>> @@ -15,6 +15,21 @@ 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 emergency poweroff will not be supported. So a carefully
>> + profiled non-zero positive value is a must for emergerncy poweroff to be
>> + triggered.
>
> Here is a suggestion for rephrase the above:
>
> + help
> + Thermal subsystem will issue a graceful shutdown when
> + critical temperatures are reached using orderly_poweroff(). In
> + case of failure of an orderly_poweroff(), the thermal emergency poweroff
> + kicks in after a delay has elapsed and shuts down the system.
> + This config is number of milliseconds to delay before emergency
> + poweroff kicks in. Similarly to the critical trip point,
> + the delay should be carefully profiled so as to give adequate
> + time for orderly_poweroff() to finish on regular execution.
> + If set to 0 emergency poweroff will not be supported.
> +
> + In doubt, leave as 0.
>
Okay.
>> +
>> 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 8337c27..de1f7be 100644
>> --- a/drivers/thermal/thermal_core.c
>> +++ b/drivers/thermal/thermal_core.c
>> @@ -324,6 +324,54 @@ static void handle_non_critical_trips(struct thermal_zone_device *tz,
>> def_governor->throttle(tz, trip);
>> }
>>
>> +/**
>> + * thermal_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 thermal_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
>> + */
>> + WARN(1, "Attempting kernel_power_off: Temperature too high\n");
>> + kernel_power_off();
>> +
>> + /*
>> + * Worst of the worst case trigger emergency restart
>> + */
>> + WARN(1, "Attempting emergency_restart: Temperature too high\n");
>> + emergency_restart();
>> +}
>> +
>> +static DECLARE_DELAYED_WORK(thermal_emergency_poweroff_work,
>> + thermal_emergency_poweroff_func);
>> +
>> +/**
>> + * thermal_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)
>> +{
>> + int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
>> + /*
>> + * poweroff_delay_ms must be a carefully profiled non-zero value.
>> + * Its a must for thermal_emergency_poweroff_work to be scheduled
>> + */
>> + if (!poweroff_delay_ms)
>
> This cannot be negative. I think it better suits here:
> + if (poweroff_delay_ms <= 0)
Sure. I will fix this.
>
> Let's avoid hidden unsigned round up issues here.
>
> Despite the above, you can add my
> Acked-by: Eduardo Valentin <edubezval@xxxxxxxxx>
Thanks. I will change this and post it in the v6.
>
> BR,
>
> Eduardo Valentin
>
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