Re: He's right. Again.
"You must have a short memory. What generally happened was that the unstable branch got dragged out too long and distros/maintainers would then try to backport required changes to the stable kernel resulting in TWO unstable branches. "
It may be short, perhaps people just tend to remember bad experiences more than good ones. I have fond memories of the 2.2.x kernel, for some reason 2.2.19 sticks out as a kernel I ran for a looooong time, and 2.0.36 as well. I remember some special security patch I would apply to my kernels back then as well(forgot the name of it).
But what sticks out more is the memories from about a decade ago(or more) of having to hack together kickstart disks with newer hardware (that CAME WITH DRIVER DISKS FOR REDHAT), but those drivers were not compatible with whatever kernel breed was in the kickstart kernel (the kernels were almost identical, not talking 2.2 to 2.4). Spend so many hours doing that, especially for Intel (or was it Broadcom, or both? I do specifically recall e1000e driver as problematic at the time) network cards (these were HP DL3x0 G3, G4, G5 and G6 servers). Also for one or more SATA controllers. So, it sort of came down to extracting the kickstart disks to find what kernel they are using, find the source for it, and the configuration. Build the kernel so I know it builds, and then compile the drivers against that kernel, re-insert the drivers back into the kickstart data files and try to boot the box(we booted over PXE at the time), and hope it works. I think it was the only time in my life I had to work with CPIO was with those driver modules/disks/files.
That stuck out so much that two years ago when I deployed the first bare metal servers in my data center in 6 years I really feared facing that situation again. Almost all my physical servers run Vmware and the drivers there have been solid as a rock for me at least for the past decade.
I much prefer back ported stuff myself. Most recently on my brand new laptop (Lenovo P50) I installed Linux Mint 17, ran for about a month or so and it was working great. Then I went to travel and that was the first time I tried to use wifi. The kernel with mint originally is 3.13 (or at least that is what my other Laptop with mint has on it right now, in any case a 3.x kernel).
It did not support the intel wifi chip in my laptop. OK so I go around hunting for a driver, totally ready and willing to compile the driver for my kernel. I come across Intel's open source website with their drivers that specifically says something like kernel 4.2 required. WTF ?
ok so I go hunting for a 4.2 kernel, and find that FORTUNATELY at this point the Mint people have included "unofficial" 4.2 kernel as an optional package in their repos (yay). So I install that and wireless starts working (along with the SD card slot which didn't work before). After about a day or so the system freezes and perhaps the caps lock light is flashing (kernel panic). I reboot, and it freezes again maybe a week or so later (not happy that I am on a 3 month trip and this starts happening).
Fortunately even more again Mint folks have a 4.4 kernel in their package repos as well and that resolved the issue, whatever it was that was causing the panics or lockups with 4.2.
Though now (I think even with 4.2) I ran into a problem where the system would just go nuts, so I put in a cron that runs every minute that runs
echo 0 > /sys/kernel/mm/transparent_hugepage/khugepaged/defrag
echo never > /sys/kernel/mm/transparent_hugepage/defrag
echo never > /sys/kernel/mm/transparent_hugepage/enabled
I forgot the background on the issue but that has since resolved it. Just running it once after bootup did not seem to be enough.
I have run across driver issues in linux for a long time of course, but this was my first experience where the driver wouldn't actually work (or so was advertised) unless you were on (what I would consider) a very bleeding edge kernel. This coming from Intel which is a really big company. I would not entirely expect a driver developed on 4.x to work on say 2.6 (though it would be nice), it should of worked on 3.x at the very least if compiled from source.
Now that things seem to be working again hopefully i don't have to touch the kernel for another 3-5 years.