mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-24 17:59:32 +00:00
![Michele Di Giorgio](/assets/img/avatar_default.png)
When multiple thermal zones are bound to the same cooling device, multiple kernel threads may want to update the cooling device state by calling thermal_cdev_update(). Having cdev not protected by a mutex can lead to a race condition. Consider the following situation with two kernel threads k1 and k2: Thread k1 Thread k2 || || call thermal_cdev_update() || ... || set_cur_state(cdev, target); call power_actor_set_power() || ... || instance->target = state; || cdev->updated = false; || || cdev->updated = true; || // completes execution call thermal_cdev_update() || // cdev->updated == true || return; || \/ time k2 has already looped through the thermal instances looking for the deepest cooling device state and is preempted right before setting cdev->updated to true. Now, k1 runs, modifies the thermal instance state and sets cdev->updated to false. Then, k1 is preempted and k2 continues the execution by setting cdev->updated to true, therefore preventing k1 from performing the update. Notice that this is not an issue if k2 looks at the instance->target modified by k1 "after" it is assigned by k1. In fact, in this case the update will happen anyway and k1 can safely return immediately from thermal_cdev_update(). This may lead to a situation where a thermal governor never updates the cooling device. For example, this is the case for the step_wise governor: when calling the function thermal_zone_trip_update(), the governor may always get a new state equal to the old one (which, however, wasn't notified to the cooling device) and will therefore skip the update. CC: Zhang Rui <rui.zhang@intel.com> CC: Eduardo Valentin <edubezval@gmail.com> CC: Peter Feuerer <peter@piie.net> Reported-by: Toby Huang <toby.huang@arm.com> Signed-off-by: Michele Di Giorgio <michele.digiorgio@arm.com> Reviewed-by: Javi Merino <javi.merino@arm.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
230 lines
6.7 KiB
C
230 lines
6.7 KiB
C
/*
|
|
* step_wise.c - A step-by-step Thermal throttling governor
|
|
*
|
|
* Copyright (C) 2012 Intel Corp
|
|
* Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
|
|
*
|
|
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; version 2 of the License.
|
|
*
|
|
* This program is distributed in the hope that it will be useful, but
|
|
* WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License along
|
|
* with this program; if not, write to the Free Software Foundation, Inc.,
|
|
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
|
|
*
|
|
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
*/
|
|
|
|
#include <linux/thermal.h>
|
|
#include <trace/events/thermal.h>
|
|
|
|
#include "thermal_core.h"
|
|
|
|
/*
|
|
* If the temperature is higher than a trip point,
|
|
* a. if the trend is THERMAL_TREND_RAISING, use higher cooling
|
|
* state for this trip point
|
|
* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
|
|
* state for this trip point
|
|
* c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
|
|
* for this trip point
|
|
* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
|
|
* for this trip point
|
|
* If the temperature is lower than a trip point,
|
|
* a. if the trend is THERMAL_TREND_RAISING, do nothing
|
|
* b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
|
|
* state for this trip point, if the cooling state already
|
|
* equals lower limit, deactivate the thermal instance
|
|
* c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
|
|
* d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
|
|
* if the cooling state already equals lower limit,
|
|
* deactivate the thermal instance
|
|
*/
|
|
static unsigned long get_target_state(struct thermal_instance *instance,
|
|
enum thermal_trend trend, bool throttle)
|
|
{
|
|
struct thermal_cooling_device *cdev = instance->cdev;
|
|
unsigned long cur_state;
|
|
unsigned long next_target;
|
|
|
|
/*
|
|
* We keep this instance the way it is by default.
|
|
* Otherwise, we use the current state of the
|
|
* cdev in use to determine the next_target.
|
|
*/
|
|
cdev->ops->get_cur_state(cdev, &cur_state);
|
|
next_target = instance->target;
|
|
dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
|
|
|
|
if (!instance->initialized) {
|
|
if (throttle) {
|
|
next_target = (cur_state + 1) >= instance->upper ?
|
|
instance->upper :
|
|
((cur_state + 1) < instance->lower ?
|
|
instance->lower : (cur_state + 1));
|
|
} else {
|
|
next_target = THERMAL_NO_TARGET;
|
|
}
|
|
|
|
return next_target;
|
|
}
|
|
|
|
switch (trend) {
|
|
case THERMAL_TREND_RAISING:
|
|
if (throttle) {
|
|
next_target = cur_state < instance->upper ?
|
|
(cur_state + 1) : instance->upper;
|
|
if (next_target < instance->lower)
|
|
next_target = instance->lower;
|
|
}
|
|
break;
|
|
case THERMAL_TREND_RAISE_FULL:
|
|
if (throttle)
|
|
next_target = instance->upper;
|
|
break;
|
|
case THERMAL_TREND_DROPPING:
|
|
if (cur_state <= instance->lower) {
|
|
if (!throttle)
|
|
next_target = THERMAL_NO_TARGET;
|
|
} else {
|
|
next_target = cur_state - 1;
|
|
if (next_target > instance->upper)
|
|
next_target = instance->upper;
|
|
}
|
|
break;
|
|
case THERMAL_TREND_DROP_FULL:
|
|
if (cur_state == instance->lower) {
|
|
if (!throttle)
|
|
next_target = THERMAL_NO_TARGET;
|
|
} else
|
|
next_target = instance->lower;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
return next_target;
|
|
}
|
|
|
|
static void update_passive_instance(struct thermal_zone_device *tz,
|
|
enum thermal_trip_type type, int value)
|
|
{
|
|
/*
|
|
* If value is +1, activate a passive instance.
|
|
* If value is -1, deactivate a passive instance.
|
|
*/
|
|
if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
|
|
tz->passive += value;
|
|
}
|
|
|
|
static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
|
|
{
|
|
int trip_temp;
|
|
enum thermal_trip_type trip_type;
|
|
enum thermal_trend trend;
|
|
struct thermal_instance *instance;
|
|
bool throttle = false;
|
|
int old_target;
|
|
|
|
if (trip == THERMAL_TRIPS_NONE) {
|
|
trip_temp = tz->forced_passive;
|
|
trip_type = THERMAL_TRIPS_NONE;
|
|
} else {
|
|
tz->ops->get_trip_temp(tz, trip, &trip_temp);
|
|
tz->ops->get_trip_type(tz, trip, &trip_type);
|
|
}
|
|
|
|
trend = get_tz_trend(tz, trip);
|
|
|
|
if (tz->temperature >= trip_temp) {
|
|
throttle = true;
|
|
trace_thermal_zone_trip(tz, trip, trip_type);
|
|
}
|
|
|
|
dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
|
|
trip, trip_type, trip_temp, trend, throttle);
|
|
|
|
mutex_lock(&tz->lock);
|
|
|
|
list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
|
|
if (instance->trip != trip)
|
|
continue;
|
|
|
|
old_target = instance->target;
|
|
instance->target = get_target_state(instance, trend, throttle);
|
|
dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
|
|
old_target, (int)instance->target);
|
|
|
|
if (instance->initialized && old_target == instance->target)
|
|
continue;
|
|
|
|
/* Activate a passive thermal instance */
|
|
if (old_target == THERMAL_NO_TARGET &&
|
|
instance->target != THERMAL_NO_TARGET)
|
|
update_passive_instance(tz, trip_type, 1);
|
|
/* Deactivate a passive thermal instance */
|
|
else if (old_target != THERMAL_NO_TARGET &&
|
|
instance->target == THERMAL_NO_TARGET)
|
|
update_passive_instance(tz, trip_type, -1);
|
|
|
|
instance->initialized = true;
|
|
mutex_lock(&instance->cdev->lock);
|
|
instance->cdev->updated = false; /* cdev needs update */
|
|
mutex_unlock(&instance->cdev->lock);
|
|
}
|
|
|
|
mutex_unlock(&tz->lock);
|
|
}
|
|
|
|
/**
|
|
* step_wise_throttle - throttles devices associated with the given zone
|
|
* @tz - thermal_zone_device
|
|
* @trip - the trip point
|
|
* @trip_type - type of the trip point
|
|
*
|
|
* Throttling Logic: This uses the trend of the thermal zone to throttle.
|
|
* If the thermal zone is 'heating up' this throttles all the cooling
|
|
* devices associated with the zone and its particular trip point, by one
|
|
* step. If the zone is 'cooling down' it brings back the performance of
|
|
* the devices by one step.
|
|
*/
|
|
static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
|
|
{
|
|
struct thermal_instance *instance;
|
|
|
|
thermal_zone_trip_update(tz, trip);
|
|
|
|
if (tz->forced_passive)
|
|
thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
|
|
|
|
mutex_lock(&tz->lock);
|
|
|
|
list_for_each_entry(instance, &tz->thermal_instances, tz_node)
|
|
thermal_cdev_update(instance->cdev);
|
|
|
|
mutex_unlock(&tz->lock);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct thermal_governor thermal_gov_step_wise = {
|
|
.name = "step_wise",
|
|
.throttle = step_wise_throttle,
|
|
};
|
|
|
|
int thermal_gov_step_wise_register(void)
|
|
{
|
|
return thermal_register_governor(&thermal_gov_step_wise);
|
|
}
|
|
|
|
void thermal_gov_step_wise_unregister(void)
|
|
{
|
|
thermal_unregister_governor(&thermal_gov_step_wise);
|
|
}
|