I'll use whatever works best for the problem. I normally start by trying to step through in a debugger, but often that is too slow so I'll introduce some extra

I'll use whatever works best for the problem. I normally start by trying to step through in a debugger, but often that is too slow so I'll introduce some extra prints and/or tracing - and try again. Conditional breakpoints might work for some folks but when doing kernel level development I've always found them too slow to really be useful. The biggest issue I have with prints is that I need to recompile, deploy my change and reboot - probably getting towards 10 minutes, whilst with a debugger I can inspect additional state without any work, and some times even do some limited patching to fixup variables or replace something with a NOP.