Re: Linus replies. Re: Computer: Can We Make Operating Systems Reliable and Secure?

[Thomas Bushnell BSG]

Donnie Jones <address@hidden> quotes Linus Torvalds thus:

> The fundamental result of access space separation is that
> you can't share data structures. That means that you can't
> share locking, it means that you must copy any shared data,
> and that in turn means that you have a much harder time
> handling coherency. All your algorithms basically end up
> being distributed algorithms.
>
> And anybody who tells you that distributed algorithms
> are "simpler" is just so full of sh*t that it's not even
> funny.
>
> Microkernels are much harder to write and maintain
> exactly because of this issue. You can do simple
> things easily - and in particular, you can do things where
> the information only passes in one direction quite easily,
> but anythign else is much much harder, because there is
> no "shared state" (by design). And in the absense of shared
> state, you have a hell of a lot of problems trying to make
> any decision that spans more than one entity in the
> system.

Dare I say it.

Linus is right.  Of course, saying that something is harder doesn't
mean that it's a bad idea; it's harder to run a fair court system than
a kangaroo court, but that doesn't mean we should abandon efforts
toward the former.

Still, he is essentially right.  The conclusion is--dare I say
it--right as well.  The best computer systems *are* single address
space systems.  Of this, I have absolutely no doubt.

Linux, I hasten to add, as any *ix, is emphatically not a single
address space system.

Thomas