Avoiding "WARNING: system temperature too high, shutting down soon!"

Platform

Problem

My FreeBSD machine shutted down with the following logs;

WARNING: system temperature too high, shutting down soon!
acpi_tz0: WARNING - current temperature (84.0C) exceeds safe limits

"sysctl hw.acpi.thermal.tz0.passive_cooling" showed zero.

Solution

The next configuration in /etc/sysctl.conf can stop this problem.

hw.acpi.thermal.user_override=1
hw.acpi.thermal.tz0._PSV=75C
hw.acpi.thermal.tz0.passive_cooling=1

I found that dev.cpu.0.freq decreased in high load.

$ sysctl dev.cpu.0.freq hw.acpi.thermal.tz0.temperature
dev.cpu.0.freq: 1000
hw.acpi.thermal.tz0.temperature: 75.0C

dev.cpu.0.freq had been always 1400 without the above configuration.