[SOLVED] 1 core stuck at 100%, igpu+nvidia

[anichang]

Hello,

I'm having a weird issue on gentoo-sources 6.1.41 @ intel Core-i5 12400 & z790 when some displays are attached at the integrated gpu connectors at boot: one random core goes 100% (95-99% wait) and stays there, no matter what, until halt. But no process is using that core. The only way to avoid this is to disconnect the display cables before turning on the computer. If I connect all the three displays at the nvidia card at boot, and then switch the cables after kde is loaded no core gets crunched.
I tried to rebuild the kernel multiple times playing with different options (and rebuild the nvidia driver and initramfs each time), play with uefi options, disable plasma compositor, switch to i3 WM, different cables combos, disable plymouth: as long as one display is connected to the intel UHD 730 integrated gpu, one core goes 100% until the computer is turned off.
Sysrescue kernel (mounting the same root fs as gentoo-sources kernel) doesn't show the same behaviour; but something else bad is going on under the hood on that kernel as I have stuttering if booted on that kernel.

It must be some kernel process, initramfs, sddm, or alike; but couldn't figure out using htop to show kernel processes. And I have no idea how to profile the kernel.

Any help out there?

Appreciated.

A

[wjb]

Two of my PCs (nvidia gpu) were doing that last month on gentoo-sources-6.1.41, but it was only showing in KSysGuard - not top or htop. I think I checked that the onboard GPU was still off in bios (it was). It has stopped happening since gentoo-sources updated to 6.1.46 last week. Or it could have been libksysguard-5.27.7-r1 which arrived the same time as the kernel update.

[anichang]

Yep, upgraded to gentoo-sources:6.1.46 and the problem disappeared. libksysguard-5.27.7-r1 was already at last stable. I suppose we'll never know what was going on...

Thanks @wjb for the tip.

A