cvs commit: src/sys/sys bio.h

[Jeff Roberson]

On Sun, 12 Jun 2005, Marcel Moolenaar wrote:

>
> On Jun 12, 2005, at 3:33 PM, Jeff Roberson wrote:
>
> > jeff        2005-06-12 22:33:06 UTC
> >
> >   FreeBSD src repository
> >
> >   Modified files:
> >     sys/sys              bio.h
> >   Log:
> >    - switch_point is now unused.  This doesn't break module binary
> > compatability
> >      since the structure is shrinking, not growing.
>
> Not true. An array of bio_queue_head will be broken by this change.
> Other breakages may be caused by having the field remain uninitialized
> or clobbered from the perspective of a module. Passing by value is
> also broken.

Good point, although I don't think anyone makes arrays of bioq heads or
passes by value.  Nor did anyone access switch_point directly.  So I guess
modules in tree should be ok, but other modules may be broken.  It is
-CURRENT though.  I think breaking ABIs is a matter of course.

>
> If ABI breakage is a concern, this change better be reverted.
>
> --
>   Marcel Moolenaar         USPA: A-39004          marcel at xcllnt.net
>