Distributions still suffering from s390 ABI change problems.

[David Miller]

From: "Carlos O'Donell" <carlos@redhat.com>
Date: Mon, 14 Jul 2014 16:15:26 -0400

> I've never seen a clean way to do a structure size increase, so in practice
> that's always a SO version bump. I also don't know what kind of breakage
> you have in the entire tooling when you do that. I expect some.
 ...
> We've already had an entire release out with this change. There are binaries
> with libc.so.6 already in the wild with the new ABI. So it seems like a mess
> any way we swing it.

We've told users we will maintain strict compatability against a given
SO version of glibc.

Now, s390 users cannot give eachother binaries neither backwards nor
forwards because of this change.  It breaks in _both_ directions.

I have two theories as to why we didn't do any SO bumps in the past,
it's either 1) we found alternative ways to solve the problem (symbol
versioning, etc.) or 2) the maintainer in the past was strongly
against SO version bumps and nobody felt strong enough to fight him on
this point.