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Commit 3d8e3ad8 authored by Frans Pop's avatar Frans Pop Committed by Len Brown
Browse files

thermal: add sanity check for the passive attribute 



Values below 1000 milli-celsius don't make sense and can cause the
system to go into a thermal heart attack: the actual temperature
will always be lower and thus the system will be throttled down to
its lowest setting.

An additional problem is that values below 1000 will show as 0 in
/proc/acpi/thermal/TZx/trip_points:passive.

cat passive
0
echo -n 90 >passive
bash: echo: write error: Invalid argument
echo -n 90000 >passive
cat passive
90000

Signed-off-by: default avatarFrans Pop <elendil@planet.nl>
Acked-by: default avatarZhang Rui <rui.zhang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 7fb2616e

Documentation/thermal/sysfs-api.txt

+1 −0
Original line number Diff line number Diff line
@@ -206,6 +206,7 @@ passive 
	passive trip point for the zone. Activation is done by polling with

	an interval of 1 second.

	Unit: millidegrees Celsius

	Valid values: 0 (disabled) or greater than 1000

	RW, Optional



*****************************

drivers/thermal/thermal_sys.c

+6 −0
Original line number Diff line number Diff line
@@ -225,6 +225,12 @@ passive_store(struct device *dev, struct device_attribute *attr, 
	if (!sscanf(buf, "%d\n", &state))

		return -EINVAL;



	/* sanity check: values below 1000 millicelcius don't make sense

	 * and can cause the system to go into a thermal heart attack

	 */

	if (state && state < 1000)

		return -EINVAL;



	if (state && !tz->forced_passive) {

		mutex_lock(&thermal_list_lock);

		list_for_each_entry(cdev, &thermal_cdev_list, node) {