Comment 15 for bug 1973167

My "prime suspect" is this commit:
https://kernel.ubuntu.com/git/ubuntu/ubuntu-bionic.git/commit/kernel/module.c?h=Ubuntu-4.15.0-177.186&id=3879f4364139acb2bd3932e6a15994f109c49d6b

Also see Linus' comments when this patch was submitted to the mainline kernel:
https://www.spinics.net/lists/kernel/msg4223720.html

"that might be a big deal slowing things down at boot time.
[...]
Comments? Maybe this is a "just apply it, see if somebody screams" situation?"

From what I understand, other measures taken in the kernel and modules make this issue no longer occur, so my hypothesis is that this may not have caused issues in the current kernel. So the mistake was that Canonical backported this commit to a very old kernel version that kernel.org no longer maintains...