Re: kqueuex() system call was MFC'ed to releng/13 and releng/13.3?

On Thu, Mar 7, 2024, 8:30 AM Patrick M. Hausen <hausen@punkt.de> wrote:

> Hi!
>
> > Am 07.03.2024 um 16:44 schrieb Alan Somers <asomers@freebsd.org>:
> >> Isn't -stable implying there won't be incompatible ABI changes?
> >
> > Yes, there won't be any _incompatible_ ABI changes.  But the addition
> > of a new syscall is a _compatible_ change.  Similar changes have
> > happened before.
> >
> >>
> >> This creates a huge problem for everyone running jails on TrueNAS CORE
> when the packages for releng/13
> >> will switch from 13.2 to 13.3 ...
> >>
> >> Of course this is not the FreeBSD projects fault but that did come as
> an unpleasant surprise, nonetheless.
> >>
> >
> > Running jails that are newer than the host has never been supported.
> > It was just luck that your 13.2 jail worked on a 13.1 host.  The host
> > must always run a kernel at least as new as what the jail was built
> > for.
>
> Thanks for the explanation.
>

Yea. It's hard to know the future so old kernels can't know about new
system calls. Our support for forwards compatibility has typically been
confined to short periods in current when the issue affected bootstrapping.
New features in the kernel are often impossible to emulate on older kernels
which is why we generally don't support new binaries with old kernels.

Warner

>
> Kind regards,
> Patrick
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