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Re: Mach on L4

From: Jan Atle Ramsli
Subject: Re: Mach on L4
Date: Mon, 23 Jul 2001 14:29:21 +0200

Hello, Farid!

You don't know me, but I know you - the dangers of the information age :-)
ENTWARNUNG: Well, I follow help-hurd, that's all ... 

> > Just a thought: How about introducing a kernel-abstraction layer to
> > the Hurd first?  As a tactical goal, port the Hurd to Unix as its
> > underlying ``microkernel'' while keeping it working on Mach.  This
> > refactoring should yield a Hurd that can easily be ported to other
> > kernels such as L4, and you don't need people acquainted with both
> > Mach and L4.
> I suggested exactly this approach in point 1. of:
>   http://mail.gnu.org/pipermail/bug-hurd/2000-October/003602.html
> The Hurd/Unix approach would be the libvk-{guest-os} variant. The
> more I think about it, the more sense it makes. You're the first
> one to suggest exactly this approach independently. That's quite
> an incentive to have a second try at it.

This made me happy.
I can only say I know one system like the 'inside of my pocket' - that system 
disappeared and was pushed out by ... MSDOS.

It had 5 functions for IPC, based on the idea of a synchronized FIFO (OK, so 
I'm lying, but it _feels_ like 5 functions).

QUEUE q = q_open(char *qname, int quesize)
q_read(QUEUE q, char* buffer) - q_cread(QUEUE q, char* buffer, BOOLEAN wait)
// the c is for 'conditional'
q_write(QUEUE q, char* buffer) - q_cwrite(QUEUE q, char* buffer, BOOLEAN wait)
q_close(QUEUE q)

It took me one week including testing to port a client server app from CDOS 
to NetBIOS, this was in 1989.

It is a shame when good things go to waste, so I thought you might want to 
know this.
A semaphore is easily constructed from this interface, and under CDOS, these 
functions were implemented in tight assembly, so they were lightning fast.

I never seize to admire the simplicity and familiarity of this interface, you 
have 5 functions to implement, even if you implement them using hex-codes, it 
will not be a big task.

That was all I had to say ...


Jan Atle Ramsli
Concurrent-DOS guru :-)
OK, so I know TRS-DOS, SinTran and maybe one or two other OS's that you have 
never heard of as well ...

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