Re: Status of revivesa

["Valeriy E. Ushakov" <uwe%stderr.spb.ru@localhost>]

On Mon, Sep 29, 2008 at 15:34:57 +0200, Alan Barrett wrote:

> On Mon, 29 Sep 2008, Andrew Doran wrote:
> > The "compatibility problem" is a myth.
> 
> You have a workaround, in which a special libpthread hides the
> incompatibility that remains present at the syscall level.  This
> workaround may be good enough for many purposes, but it's still not
> fair to call the compatibility problem a "myth".

That can we start by defining exactly what are the relevant scenarios?

If NetBSD 3.x or 4.x userland can work on NetBSD 5.0 kernel provided
that compatibility libpthread is present (that does not conflict with
3.x/4.x libpthread) - does that addresses typical upgrade scenarios
that people mentioned?  

Do I get it right that instead of just dropping in a 5.0 kernel, they
will have to also add a compat library and a line to ld.so.conf, after
which the old userland (with new compat libpthread thrown in) can run
either on the old kernel (using old libpthread) or on the new kernel
(using new compat libpthread)?

While system-call level compatibility would be nice in theory, if we
compare costs and benefits, I'd say that drop-in, non-conflicting
compat libpthread looks like a way more desirable solution.  It
unblocks 5.0 release *now*, it doesn't require changes to the kernel,
it doesn't require those (non-introduced) changes to support SA
syscalls to be maintained and then phased out, etc...

SY, Uwe
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