Hot temperatures after recent kernel updates

Ask Fedora
1

I suspect this is related to the latest kernel updates. After applying last night’s updates, the system began overheating to the point of crashing. Since then, on every boot, the temperature spikes abnormally high almost immediately.

Out of curiosity, I consulted an AI assistant that is usually reliable for troubleshooting. However, in this case, it misdiagnosed the issue entirely and suggested a hardware-level fix (fan replacement), which is clearly irrelevant.

I have Ubuntu installed on a separate partition (accessible via GRUB), and booting into it confirmed that the issue is not hardware-related.

2

Hardware specs / make + model?

Some packages for helping track down cooling and/or power management issues:

  • lm_sensors
  • nvtop
  • powertop
3

Please share enough details so that people have a chance to help you.
For example what fedora kernel has the problem and which old fedora kernel does not?
Also post the output of inxi -Fzxx so we know your software and hardware details.
Post output as preformatted text, using the </> button.

4

To provide more details as requested: I am running Fedora 42 (Kernel 6.18.16). My hardware is an Acer Aspire with a Sandy Bridge i5 and NVIDIA GT 540M.

With the help of Google’s AI, I performed several deep-dive tests:

  1. GPU Isolation: I completely blacklisted nouveau and even ‘removed’ the NVIDIA card from the PCI bus via udev rules to ensure it wasn’t the heat source.

  2. ACPI Forced Fixes: I tried booting with acpi_osi=, acpi_enforce_resources=lax, and blacklisting acer_wmi to bypass kernel interference with the fan controller.

  3. The Proof: Despite the CPU being idle, Fedora 42 keeps the system at 70-75°C with the fan effectively ‘frozen’ or mismanaged by the kernel. The fan only spins up properly during reboot/POST, proving the hardware is fine.

The definitive proof is that on the same exact machine, Lubuntu (Kernel 6.8) manages the thermals perfectly, keeping the idle temp at 41°C.

It’s clear that recent F42 kernel updates have introduced a major regression in ACPI/Fan management for legacy hardware. If the OS can’t handle basic thermal safety that a 15-year-old BIOS manages easily, there’s a serious issue with current Fedora development.

I’m heading back to Lubuntu until Fedora stops acting as a space heater.

5

What does btop/htop/top/insert tool of choice say is burning cpu cycles?

6

htop says it is idle

7

witch DE you using?

8

no one, multi user target …. just a server

9

Bizarre. Running hot at basically zero load…

inxi output might throw up some clues, or at least give us something to search on, as I’m not seeing any other reports about 80c CPU’s doing nowt.

powertop offer any insight?

rolling back to an earlier kernel makes no difference?

10

run watch -n 1 sensors to see in real time temp if you install lm_sensors

11

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image1197×590 24.6 KB

I have a job sending sensors temp to uptime kuma but in short the temperature keeps going up till I have to power off

tried starting xfce and installing powertop


PowerTOP 2.15     Overview   Idle stats   Frequency stats   Device stats   Tunables   WakeUp

Summary: 341.7 wakeups/second,  0.0 GPU ops/seconds, 0.0 VFS ops/sec and 3.2% CPU use
12

Do update of kernel there is already 6.19.7 in repos and 6.19.8

13

Are all cores running at this 75c temperature or only one/some - something like btop or htop will show you per-core temps and per-core load.

14

upgrading and showing cores temp

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after the upgrade

Welcome to fish, the friendly interactive shell
Type help for instructions on how to use fish
giulio@myfedora ~> inxi
CPU: dual core Intel Core i5-2430M (-MT MCP-) speed/min/max: 798/800/3000 MHz
Kernel: 6.18.16-100.fc42.x86_64 x86_64 Up: 2m Mem: 663.2 MiB/7.6 GiB (8.5%)
Storage: 931.51 GiB (26.4% used) Procs: 187 Shell: fish inxi: 3.3.40
giulio@myfedora ~> sensors
coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +81.0°C  (high = +86.0°C, crit = +100.0°C)
Core 0:        +79.0°C  (high = +86.0°C, crit = +100.0°C)
Core 1:        +81.0°C  (high = +86.0°C, crit = +100.0°C)

BAT0-acpi-0
Adapter: ACPI interface
in0:         784.00 mV
curr1:         0.00 A

giulio@myfedora ~>

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image863×230 5.93 KB

15

Why you using same kernel?

16

ops it must be the mbr sector not updated, maybe I have to grub install it from fedora, thank you!

P.S. or just update-grub from lubuntu should do the same since it is the same exact machine…

Yep

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image3285×981 358 KB

17

To recap: Fedora’s latest kernel runs at around 70°C on this machine, compared to about 43°C with Lubuntu.

giulio@mylubuntu:~$ inxi
CPU: dual core Intel Core i5-2430M (-MT MCP-) speed/min/max: 1006/800/3000 MHz
Kernel: 6.8.0-106-generic x86_64 Up: 43m Mem: 869.9/7794.6 MiB (11.2%)
Storage: 931.51 GiB (2.7% used) Procs: 166 Shell: Bash inxi: 3.3.13
giulio@mylubuntu:~$

image
image2936×653 73.9 KB

18

Is that correct? looks like a very old kernel. I presume this is what Lubuntu currently has as the latest?

19

Correct, that is the 6.8.0-106 kernel from Lubuntu. I’m using it to demonstrate that the hardware is capable of idling at 43°C, whereas the recent Fedora updates have pushed it to 70°C (and also +90°C on load).

20

The only thing I can see is that the “speed” in the modern kernels seems to be pinned at 3 Ghz… or 2977 Mhz in the screenshot provided.

If that is the case, then that’s probably the root cause of the “temp is constantly high” issue - they are never allowed to ramp down to slower clock speeds.

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