An Ubuntu kernel bug causes container crashes

Posted Jul 9, 2022 19:32 UTC (Sat) by jafd (subscriber, #129642)
In reply to: An Ubuntu kernel bug causes container crashes by wtarreau
Parent article: An Ubuntu kernel bug causes container crashes

Look at this from another side.

> a non-LTS EOL kernel probably misses 2000 fixes, for as many bugs that are fixed in all maintained versions around it, but not that one.

What if on the systems running that kernel, none of the fixes touched modules actually used in them?

> Some will corrupt data, cause random hangs

Not experienced once for a year, let's say

> disconnect your WiFi during an audio conf, make your screen disappear after resume, leave fantom USB devices after some errors

Not happened once in the drivers actually used and on that specific hardware.

But what's more likely to happen is that a newer version, while bringing a minor fix to a module or a subsystem you need, will also bring a mighty regression in a driver or a subsystem your workflow absolutely depends upon. A couple articles ago someone commented about precisely this situation here on LWN [0].

That's why there exist users (think companies) which find a kernel that doesn't crap on their hardware 99.999% of the time, and pin it, and swear to never upgrade it ever. Have you thought they may have had enough of the Russian roulette?

Jumping from LTS to LTS can also be akin to jumping centuries in a time travel vehicle. So many changes, so many surprises, so much work to ensure it won't crap on something we absolutely need to work...

[0] https://lwn.net/Articles/889787/, you were in that thread too.

An Ubuntu kernel bug causes container crashes

Posted Jul 10, 2022 9:55 UTC (Sun) by smurf (subscriber, #17840) [Link] (1 responses)

> so much work to ensure it won't crap on something we absolutely need to work...

So up a reasonable CI system. Surprise: you probably need that anyway.

Yes, that's somewhat more effort … but you only need to spend it once, not with every release.

An Ubuntu kernel bug causes container crashes

Posted Jul 28, 2022 7:45 UTC (Thu) by daenzer (subscriber, #7050) [Link]

Any non-trivial CI requires constant development & maintenance effort. I'd argue it's effort well spent though.

An Ubuntu kernel bug causes container crashes

Posted Jul 11, 2022 16:47 UTC (Mon) by wtarreau (subscriber, #51152) [Link]

Oh I've known such people and even had to combat them because they were refusing to apply the mandatory fixes for a bug that was causing their firewall to leak memory like crazy and crash every two weeks or so. Instead they wanted to profit from a downtime caused by the crash to install more RAM and postpone the next crash! When insisting for applying fixes, to the question "but if it bugs?" I had to respond "in the worst case it will continue not to work".

But what you seem to be ignoring here is that the older the kernel, the harder it is to backport fixes, and the most likely they are to be wrong, particularly when taken out of the context of all other fixes that were surrounding the original patch. When I was a stable maintainer, I used to receive many messages like "do not take this patch without this one" or "I'll provide you a different one for this version as it's not sufficient" etc. The risk of getting a fix wrong when applying it yourself to a tree without the author's approval is quite high. Thus in addition to missing tons of fixes, the few you get (the so called "security fixes" that make vendors sell) are often bogus and are the ones that will take your system down.

Really, do not use EOL kernels.