Comment 35 for bug 1891768

If we find a problem in Ubuntu that has not already been fixed in the latest upstream kernel then we'll try to fix it ourselves and send the patch upstream. But most of the time we backport already existing upstream fixes to affected Ubuntu kernels.

The process of finding the fix for a specific problem is:
1) Find the first kernel version that works (good kernel).
2) Look at the changes between the previous (bad) and the good kernel.
3) If nothing jumps out that might indicate which commit fixed the problem: git bisect to narrow it further down.

But typically, if a user reports that a specific problem has been fixed with a kernel update then that's good enough for us even without knowing exactly which specific commit fixed it. Sometimes there are a lot of upstream changes that we pull into an update.

It's the distros responsibilities to keep their kernels up-to-date and every distro does it differently. Ubuntu updates kernels every 3 weeks (roughly): https://wiki.ubuntu.com/StableReleaseUpdates