Re: Upcoming ABI Breakage in RELENG_7

On 7/30/08, David Southwell <david_at_vizion2000.net> wrote:
> On Tuesday 29 July 2008 08:45:45 Ken Smith wrote:
>  > Normally the FreeBSD Project tries very hard to avoid ABI breakage in
>  > "Stable Branches".  However occasionally the fix for a bug can not be
>  > implemented without ABI breakage, and it is decided that the fix
>  > warrants the impact of the ABI breakage.  We have one of those
>  > situations coming along for RELENG_7 (what will become FreeBSD 7.1).
>  > The ABI breakage should only impact kernel modules that are not part of
>  > the baseline system (those will be patched by the MFC) which deal with
>  > advisory locks.  As such the impact should not cause many people
>  > problems.
>  >
>  > The work that will be MFCed fixes issues with filesystem advisory locks,
>  > and moves the advisory locks list from filesystem-private data
>  > structures into the vnode structure.
>  >
>  > The MFC will be done by Kostantin Belousov some time this coming Friday
>  > (August 1st, 2008) if you have concerns and want to watch for it.
>  >
>  > Thanks.
>
> Sometimes information gets posted to this list on the assumption that everyone
>  understand what the writer means.
>
>  This is one of those occasions!!
>
>  For those of us who are not as well informed and experienced  as others could
>  someone please explain what is meant by an  ABI breakage, its implications
>  and how to deal with them.
>

   ABI breakage occurs when internal data structures change (for
instance, when members of the structure are removed or added). Kernel
modules which expect those structures to look in a certain way will
need to be recompiled. Also, depending on what data structures suffer
the changes, ioctl() operations may fail, requiring a rebuild of the
userland programs which issue the ioctl()s. And I'm sure that there
are many other examples that I can't think of right now :)




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