lenovo t500 kernel hangs with flashing caps lock LED after installing intel-microcode

[Rob van der Linde]

Had a working system, just upgraded it to Kubuntu 16.04, everything great after the upgrade.

The driver tool then "recommended" me to install this CPU microcode package, after that the laptop failed to boot the kernel and the caps lock is flashing.

Laptop is a lenovo t500 core 2 duo with 8gb RAM, I just can't seem to boot the laptop at all anymore since installing this CPU microcode package.

My question is, is it really such a good idea to "recommend" this package under drivers if it can kill your system like this?

[Rob van der Linde (robvdl)]

It appears to be a kernel issue as the system now boots when booting the previous 14.04 kernel from before the upgrade, but hangs when booting the 16.04 kernel with flashing capslock LED again, kind of like described here:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/303276

The strange thing is that the 16.04 kernel only started playing up when the intel microcode package was installed, so I am going to try to uninstall it, boot the 16.04 kernel and see what that does.

[Rob van der Linde (robvdl)]

Kernel from 16.04 is now booting again after using old kernel to remove the intel-microcode package then booting into the new kernel again.

[Henrique de Moraes Holschuh (hmh)]

The flashing capslock LED is a kernel-has-crashed (aka "OOPS") indicator. It certainly looks like a bug in the microcode loader.

For the record: It is possible to bypass the microcode loader. That would allow you to test that it is indeed the microcode loader, or to fix the system if you did not have a backup kernel/initramfs.

To bypass the microcode loader, inside the boot loader (grub), instead of lauching the boot, you ask it to edit the boot config, scroll down to the "kernel command line" (starts with "linux"), and add "dis_ucode_ldr" (without the quotes). Then you tell grub to proceed booting.

More details:
https://help.ubuntu.com/community/Grub2/Troubleshooting#Editing_the_GRUB_2_Menu_During_Boot

Anyway, it looks like this bug should be reassigned to the kernel. You will have to provide a lot more information for anyone to be able to help you, though.

Relevant information: contents of /proc/cpuinfo, exactly what kernel is crashing (32 bit? 64 bit? package version?), and if at all possible, kernel logs when it crashes (boot in verbose mode to see).

Also could be of help if you want to provide more data (without which this bug cannot be solved):
https://wiki.ubuntu.com/DebuggingKernelBoot

[Henrique de Moraes Holschuh (hmh)]

Rob, are things working for you now? Can we close this bug report?

[Rob van der Linde (robvdl)]

Yeah I suppose. I don't use this laptop anymore because I got a better one, but I recall having to remove the intel-microcode package to get my laptop booting again at the time. It's an older laptop though, I am quite happy to close this issue.

[Henrique de Moraes Holschuh (hmh)]

Ok, I "closed" it by tagging it "invalid", since we don't know what really happened to that kernel (so "fixed" wouldn't really be correct).

Thanks.