Hey, On Fri, Apr 14, 2017 at 08:42:20AM -0700, Eduardo Valentin wrote: > Hello again, > > On Fri, Apr 14, 2017 at 08:38:40AM -0700, Eduardo Valentin wrote: > > Hey, > > > > On Fri, Apr 14, 2017 at 02:22:13PM +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 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 | 19 +++++++++++++++ > > > drivers/thermal/Kconfig | 13 +++++++++++ > > > drivers/thermal/thermal_core.c | 46 > > > +++++++++++++++++++++++++++++++++++++ > > > 3 files changed, 78 insertions(+) > > > > > > diff --git a/Documentation/thermal/sysfs-api.txt > > > b/Documentation/thermal/sysfs-api.txt > > > index ef473dc..e73cc12 100644 > > > --- a/Documentation/thermal/sysfs-api.txt > > > +++ b/Documentation/thermal/sysfs-api.txt > > > @@ -582,3 +582,22 @@ 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 happen immediately. > > > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig > > > index 9347401..0dd5b85 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 > > > > Only now I realized that merging this may break the working > > orderly_poweroff() out there, because you are defaulting this to 0, no > > delay, therefore giving no time for orderly_poweroff() to finish. This > > is not good. > > > > I think using 0 delay as immediate power off is not good as we give no > > time for graceful shutdown, and by default. My suggestion here > > is to use 0 delay as no forced shutdown. Meaning, by default, this > > feature is disabled, and all other systems out there, despite DRA7 with > > arago over NFS, work as before.
A better solution could be to have bool Kconfig, say
THERMAL_EMERGENCY_POWEROFF, which would default to false. If one selects
that option, you get the DELAY_MS configurable, and then you could get
the 0 ms still as a valid entry, with the same semantics of immediate
power off, no orderly_poweroff.
I just want to avoid breaking everybody (or changing userland
expectation) in honor of this change.
> >
> > > + 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 8337c27..aed614d 100644
> > > --- a/drivers/thermal/thermal_core.c
> > > +++ b/drivers/thermal/thermal_core.c
> > > @@ -324,6 +324,47 @@ 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)
> > > +{
> > > + schedule_delayed_work(&thermal_emergency_poweroff_work,
> > > +
> > > msecs_to_jiffies(CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS));
> >
> > So, please, only schedule if delay is greater than 0.
>
> Please update documentation accordingly..
>
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