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 <[email protected]> > Signed-off-by: Keerthy <[email protected]> > --- > > 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.
> +
> 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)
Let's avoid hidden unsigned round up issues here.
Despite the above, you can add my
Acked-by: Eduardo Valentin <[email protected]>
BR,
Eduardo Valentin
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