About configuring a kernel, and CONFIG_PREEMPT

[stan]

On Wed, 26 Aug 2009 08:23:26 -0700
Jonathan Ryshpan <jonrysh at pacbell.net> wrote:

> I need to rebuild the Fedora Kernel, something I haven't done for
> many years, to (hopefully) reduce the large number of xruns that I'm
> getting using jackd.  The plan is to build a preemtable kernel. 

Another alternative is to use a prebuilt kernel from planetccrma
repositories.  They apply Ingo Molnar's real time patch.
Because they run on Fedora, this is very convenient.  If you search on
linux, ingo molnar and realtime patch you will find descriptions of
this patch and you can probably apply it to a vanilla kernel yourself
also. When I look at the patches already in the Fedora kernels, it
seems to me that they have implemented some of this already.  When I
tried to apply it to the Fedora kernel, there were namespace
collisions, which implies the same.

> 
>      1. It look like the file .config in the kernel-devel RPM contains
>         the configuration parameters for the kernel that goes with
> that version of kernel-devel.  For example, right now, I'm running
>         kernel version 2.6.29.6-217.2.8.fc11.x86_64, so this would
> mean that /usr/src/kernels/2.6.29.6-217.2.3.fc11.x86_64/.config
>         contains the configuration parameters for that kernel. 

This is true, but it is also in the src.rpm from Fedora.

> 
>      2. This .config file generates a kernel with voluntary
> preemption. Is this to avoid a bug or suchlike, or just to generate a
> kernel that's best for general use?

I think it is to be best for general use, but I don't *know*.

> 
>      3. The natural way to build the new kernel would seem to be to
> unpack the kernel source, using 
> 		$ rpm --install kernel-2.6.29.6-217.2.8.fc11.src.rpm 
> 	copy in the .config file from the kernel-devel package, and
> then run 
> 		rpmbuild -bb --short-circuit 
> 	to generate the new kernel RPMs.
> 
> 	Unfortunately the --short-circuit argument cannot be combined
> with the -bb argument.  What's the best thing to do here?

Go the the link
http://fedoraproject.org/wiki/Building_a_custom_kernel
and use the instructions there.