Kernel Index page from LWN.net

As I was looking for some supplementary information on the kernel, I found this page which returns a categorized list of entries of articles in the LWN page.

Linux Config Archive

I found an interesting site which is an archive for configuration files from the linux kernel. Unfortunately, it did not work when I tried it. But at least the idea is quite good. I am sure I will try this from time to time.

Maintainers File in Kernel and SCM tools for the kernel

I have just had a look at the maintener file in the linux kernel Tree.

I have noticed that there are a number of orphaned project. The question is whether any of these orphaned project really needs to be taken care of.

Another interesting thing was to learn about the different scm and patching tools used in kernel development: git, quilt and hg.

Here is an interesting overview of the reason for the development of git and quilt.

I really start to like the patch approach, and the article linked above gives a good idea of the reasons to use this approach. I should try to summarise in a future post the advantages and disadvantages of the different source code management approaches.

Kernel Stuff

I did some little things with kernel programming (or more compiling) these days.

Part of the things I did were compiling kernel because I wanted to try UML (user mode linux).

So that's what I did:

• Download the kernel configs from: http://uml.nagafix.co.uk/kernels/.
• Download kernels from kernel.org.
• untar the kernels to some directory
• cd into the main directory of the kernel
• copy the config of the kernels into main directory as .config file
• $ make ARCH=um oldconfig
• answered the necessary questions as good as I could
• $ make ARCH=um

  At that point some errors appeared, so I tried to correct them.

• to help me in the debugging process I used $ make V=1 ARCH=um
• when I had some things that did not work well I used the gcc output to call it right away. For example, sometimes the architecture files would not be found right so I used -Iinclude sometimes a precompiler marks was not set correctly so I used -D__someprecompilermarks__. At some point I removed some problematic definition by using this together with a #ifndef in the header file. $ gcc ..... -Iinclude -D__someprecompilermarks__ ...
• then I also downloaded a few kernel repositories using git, though I still need to perfect this.
• I read (or skipped/read) quite a few Documentation files from the kernel or from the internet.
• I familiarised myself with the git web interface, this together with having a kernel RSS feed in my thunderbird.

And all this in one day and half together with other things.

Kernel Programming - WORKQUEUE Problems

I decided to look at the API for schedulling in the kernel modules. This turned out to be more time consuming than what I thought. The problem is that the tutorial I have been using is not up-to-date with the current version of the linux kernel. There used to be only one structure to represent some task to perform. But after a change in the kernel workqueue API, there are now to structures: struct work_struct and struct delayed_work. This was the reason why the kernel did not compile in a nice way. I will post here the rest of the small example module for documentation purposes.