If we use the machine with shutdown + cold start: no issues.
But, if we use the sleep function (closing the lid, sleep) and opening the lid later, it will (but randomly, ex.: 2 days later or in just a few hours, etc.) produce very high fan speeds.
Ubuntu 18.04.1 LTS, installed a few months ago, all packages up-to-date.
Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz
Lenovo T560, bought a few months ago.
cpufreq-info says governor is on 1.62-1.8 GHz, all cpus are in powersave mode.
top says there is NOTHING that needs high cpu, only ~5-10% max.
max temperature is: acpitz-virtual-0 temp1 is 48C according to "sensors".
The big question: how can I debug or solve this issue? Looks like there is a bug with Ubuntu 18.04 + Lenovo T560?
Is there a software, which defines, at which temperature the fan should start? Normally, when we cold boot the machine, the fan doesn't even turns on.
Or should I open a bugreport?
Sometimes we can fix the high fan running with a lid close/open, but usually only a poweroff/cold start fixes it.
