I do not know where to put the printks off the top of my head as I am not a kernel developer. I provide similar debugging services for GDB where I know the codebase thoroughly. I could read+learn the kernel sources to find out where to put the printks but that does not scale, life is too short to know very every line of system sources, that is what developers specialization is there for.
The problem happens due to my scripts running nightly regression testing of various toolchain components in various (chrooted) operating system variants/versions. Currently I "do not do that" as you suggest because of that bug. Therefore users hit+bugreport those regressions. Formerly I was fixing the regressions before any user could hit them, that was a so-called proactive solution. Yes, I could code the scripts some other way (such as using KVM instead of chroot) but that would be a workaround, the scripts are not buggy, the kernel is. I can provide the scripts but there are many of them and setting up the whole system for them is not easy, it was done ad hoc: 1 2 3 4
The one day you'd sell your soul for something, souls are a glut.