Comment 8 for bug 1847892

16.04.6 turned out to have 4.15.0-45, which is one of the known-broken releases. Unsurprisingly, it delivered the same poor results as 5.3.

I'm running low on sensible options here.

I no longer have the bootable 18.04 stick I used before, but I can create a new one easily enough (as long as I remember to use the .0 image and avoid the HWE stack). But it's not going to tell us anything we don't already know, and it's no use for either normal use or testing.

I could wipe the machine and install 18.04, which would cost me years of customisation and bugfixing. Since the bug is in the HWE kernels it would also be possible to test those separately, though it would need a lot of messing around each time.
This is sort-of tempting for other reasons anyway, but it'll take weeks of elapsed time to get everything repaired, which is time I won't be able to spend on this bug.

I can't really repartition it while doing that, unfortunately. It just has a very small SSD to boot off, and is heavily dependent on the LAN. I could probably JUST about carve out another very small partition to put 18.04 on, which would make the backwards-migration easier and leave me able to validate a fix for this at some point, but it's already seriously hurting for space at times.

I'll give it some thought. In the meantime, do you have a preference or any suggestions that might influence that decision?

Returning to your original bisection request: since Ubuntu generates its own kernels, if you can give me the mapping from the not-broken 4.15.0-55 to the equivalent starting point in Linus's tree, and likewise for the broken 5.0.0-29, I'll see about sacrificing a USB HDD to that machine for a while for it to build on. No promises, and it'll still take weeks to actually complete, but I'll do what I can.