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Fwd: Preemption and SMP settings

---------- Forwarded message ----------
From: Sven Luther <sven@powerlinux.fr>
Date: Wed, Apr 30, 2008 at 5:17 PM
Subject: Re: Preemption and SMP settings
To: Greeze Brown <automatic.gun@gmail.com>
Cc: debian-powerpc@lists.debian.org, akoshal@ipolicynetworks.com, nchaudhury@ipolicynetworks.com, vnsharma@ipolicynetworks.com

On Wed, Apr 30, 2008 at 05:02:47PM +0530, Greeze Brown wrote:
> We are exploring PowerQUICCII Pro and PowerQUICC III as a platform for some

Nice, ...

> of our products. As part of research we found that premption is not enabled
> by default in the debian kernel (
> http://lists.debian.org/debian-powerpc/2007/04/msg00028.html). Also the
> kernel configuration system recommends that SMP support be left disabled as
> its not supported in hardware.

Indeed, what you would need is a self built kernel, with the options
enabled. Notice also that your eval board also need uboot, and that upto
not, the default debian kernel is not built to work with uboot, only
with chrp boxes, both from IBM and from apple. The Genesi hardware
(pegasos and efika) is also supported, but none of the miriad of u-boot
based boards out there.

Notice also that at least for the powerquicc II pro, the kernel is not
compatible with the debian supported flavours, and a new flavour need to
be created, i suppose this is the same for powerquicc III platforms.

Our company has working debian kernels on the 8349 based mitx board, and
are planning of doing some poerquicc II pro based development ourself,
and we are ready to do commercial debian and general linux support on
powerpc hardware if this is interesting to you.

We could for example provide you a repository of security-updated
kernels for your specific hardware or something like this.

We are also working on a debian-derivative especifically targetted to
embedded systems, mostly powerpc oriented, which we will use in our own

> I would like to know:
> What is the default setting of SMP and preemption in the latest debian
> kernel.

I think it should be ok right now, i have been using PREEMPT on a
powerquicc I based board for some time now :


SMP can be disabled, and indeed , debian has a SMP and non-SMP flavour
on 32bit powerpc, which is what you would use. But as said, the current
debian flavours don't support your hardware, and a custom build would be

> What can go wrong if you run a kernel with both enabled (not boot, be slow,
> crash randomly etc), in case anyone of you has experimented.

I think the risk would be of random crashes, or at least local problems
with some processes or drivers, if they are not PREEMPT friendly.

Please forward to the list, since i am being censored.


Sven Luther

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