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thermal: core: Add a back up thermal shutdown mechanism

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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@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
This commit is contained in:
Keerthy 2017-04-18 09:59:59 +05:30 committed by Zhang Rui
parent e441fd6866
commit ef1d87e06a
3 changed files with 91 additions and 0 deletions
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21
Documentation/thermal/sysfs-api.txt
View File

@ -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.

17
drivers/thermal/Kconfig
View File

@ -15,6 +15,23 @@ menuconfig THERMAL
if THERMAL
config THERMAL_EMERGENCY_POWEROFF_DELAY_MS
int "Emergency poweroff delay in milli-seconds"
depends on THERMAL
default 0
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.
config THERMAL_HWMON
bool
prompt "Expose thermal sensors as hwmon device"

53
drivers/thermal/thermal_core.c
View File

@ -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 this is not scheduled.
*/
void thermal_emergency_poweroff(void)
{
int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
/*
* poweroff_delay_ms must be a carefully profiled positive value.
* Its a must for thermal_emergency_poweroff_work to be scheduled
*/
if (poweroff_delay_ms <= 0)
return;
schedule_delayed_work(&thermal_emergency_poweroff_work,
msecs_to_jiffies(poweroff_delay_ms));
}
static void handle_critical_trips(struct thermal_zone_device *tz,
int trip, enum thermal_trip_type trip_type)
{
@ -346,6 +394,11 @@ static void handle_critical_trips(struct thermal_zone_device *tz,
tz->temperature / 1000);
mutex_lock(&poweroff_lock);
if (!power_off_triggered) {
/*
* Queue a backup emergency shutdown in the event of
* orderly_poweroff failure
*/
thermal_emergency_poweroff();
orderly_poweroff(true);
power_off_triggered = true;
}