how bind supports multi-processors?

[Florian Weimer]

* Ralf Peng:

> Is threads stable enough in product use of Bind?

It's stable on mainstream architectures.  GNU/Linux on i386 and amd64
is fine in general.  GNU/Linux on hppa, mips(el), ia64, and others is
problematic.  The hppa instability could be due to the lack of a
stable SMP kernel.  The ia64 issues seem to be a genuine BIND 9 issue.

Part of the problem is that BIND contains its own set of wrappers for
atomic CPU operations, instead of using GCC's intrinsics or
libatomicops.  Last time I tried to look at this, I couldn't find a
clear description of the flavor of atomic instructions required by
BIND (which barriers are implied etc.), so it's very difficult to make
the change.  I can't test on ia64 and sparc, either.  The x86-derived
architectures are just too forgiving about errors in this area to be
useful test cases.