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From: "Marven Lee" <mehs60@dsl.pipex.com>
Newsgroups: comp.lang.ada
Subject: Re: For the AdaOS folks
Date: Mon, 3 Jan 2005 10:30:47 -0000
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Date: 2005-01-03T10:30:47+00:00
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Luke A. Guest wrote...
> Yeah but, what you were saying was that you wanted OSes to use
> protection domains for libraries *as well*, this is the wrong way to
> go. The libraries are (and should be) mapped into an applications
> address space, libraries *should never* have their own address
> spaces. It is that idea which is wrong and would be slow, not the
> *proper* way to do it.

I'm not on about "normal" libraries becoming "protected shared
libraries".

"Protected shared libraries" are the same as servers in other microkernel
systems.  I could have called them servers, however the term
"protected shared libraries" seems to emphasise a passive object model
where a thread makes a cross-domain call into a server as opposed
to having a seperate thread in the client and a seperate pool of threads
in the server which would be an active object model.

You get to keep your normal libraries.

Just like a server, protected shared libraries keep data shared between
multiple processes private and you'd use them wherever you use servers.

Migrating threads / cross-domain calls / LRPC / thread tunnelling whatever
you want to call it allows for a more streamlined IPC between processes.
There is no need for a rendezvous between threads, there is no need to
block threads and the kernel path becomes simpler.