[Techtalk] Theory vs. practice

Val Henson val at nmt.edu
Wed Jan 16 16:00:01 EST 2002

On Wed, Jan 16, 2002 at 12:44:38AM -0600, Julie wrote:
> Val Henson wrote:
> > 
> > :) I'm sorry - I realize that many of the best kernel developers don't
> > even post on l-k.  When you see people who are pushing for (and have
> > written the patches for) a preemptive Linux kernel, and these selfsame
> > people don't understand priority inversion or think it is a
> > problem... That's when I *fear* for the future of Linux.
> So ... do these people even understand serialization?  Because
> life inside a pre-emptible kernel gets really =weird=.

See, that's the scary part.  If the preemptive kernel implementers
said, "I understand this problem, and here's why it doesn't apply to
us," I wouldn't be so concerned.  Instead, they're saying "That
problem doesn't apply to us," without explanation.  So I'm forced to
conclude that they don't understand what really happens in a
preemptive kernel.

To my great relief, Alan Cox and Arjan van de Ven and some other folks
are demonstrating that they understand the problem. :)

> I did a one-hour brown bag at work on kernel programming.  I
> described the AIX kernel as "not just multi-threaded, but
> =insanely= multi-threaded".

And that's the other annoying thing about some (not all) Linux
developers.  "Just because <some OS> did it wrong doesn't mean Linux
can't do it right."  I agree with that, but I also think you need to
have a good argument for *why* and *how* Linux is going to do things
right.  For example, a preemptive kernel: Solaris and IRIX implemented
it and paid a huge price in code complexity.  Please, do tell how
Linux is going to implement it differently?

Of course, you're welcome to do whatever you want with Linux if you're
not pushing to get it into the main tree.  Once you are asking
hundreds of other people to work with and maintain your code, you need
to have convincing arguments for why your changes are a Good Thing.


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