[META] Draft: Kernel mailing list use policy

Frohwalt Egerer (froh@twins.iconsult.com)
3 Apr 1997 20:01:33 +0200

This is a draft for a use policy and FAQ for the kernel mailing
list. If it is accepted by the list I'd volunteer to send it to the
list monthly. The contents of this draft are taken from the linux
kernel mailing list.

Please comment on it, only your input will make this draft reflect the
wishes of the list members exactly.

When you find spelling errors or bad grammar mail corrections to
froh@iconsult.com, they will be included in the next version of the
draft. English is not my native language, so expect a lot of these.




0. Policy / FAQ
1. Topic
2. Etiquette
3. Online resources
4. How to get started on kernel development
A. Appendix

0. Policy / FAQ

This is the Linux kernel mailing list use policy and FAQ. It is
mailed to the list on the first of every month.

1. Topic

This list discusses Linux kernel development. It shall have intellegent
debate on Linux kernel features past, present and future as well as
"here's a patch" and "oh dear, mine doesn't work" postings.

2. Etiquette

Before you post a question to this list think twice if it really is
kernel related. Maybe another newsgroup or mailing list may be
better suited for the question, see below for a list of online

When off topic mails ("I can't build the kernel", "how to convert
ASCII to EBDIC" or "Make money fast") mails arrive answer them directly
(ie off this list) politely and helpfully. These questions will always
be asked on this list, there is no easy way to avoid that without
moving away from creative anarchy. Dumb questions are a positive sign
of usage and growth. SPAMs can't be stopped by everyone on the list
following up with a flame mail.

3. Online resources

<I need to do some research here. This paragraph will list the linux
mailing lists, news groups and web sites and their purpose. Inform
me personally if you think something shall be listed here.>

4. How to get started on kernel development

Cameron MacKinnon (mailto:mackin@interlog.com) wrote a wonderful article
on that topic:

"...I'm not a pro, but I generally know what's going on for
least part of the time. Here's what I did:

I bought books. Here's reviews: LINUX Kernel Internals, Beck et
al, Addison Wesley, 0-201-87741-4. I read about a third of
it. It's dated (1.2 kernels) and doesn't have anything about
SCSI in it, but it's the only Linux kernel book out
there. There's a new version out for 2.0 kernels, but only in
the original German. "The Design and Implementation
of the 4.4 BSD Operating System", McKusick et al, Addison Wesley,
0-201-54979-4. A much more readable book, IMHO. It talks about the BSD
design in general, why things changed over time, why and how specific
performance tradeoffs were made, etcetera. Also, "The Magic Garden
Explained" or something like that, borrowed, pub. and ISBN unknown. This
book is a very thorough coverage of the design of System 5 Release 4
(SVR4), but not as easy to read as the BSD book. Bottom line: Beg,
borrow, check out or steal one book, any book, on the design of the UNIX
operating system. Sit in a library or a bookstore reading it, if you
haven't got the money. You need to understand how schedulers, pagers,
swappers, top and bottom halves, wait queues, inodes, ttys, the boot
process, init and some other stuff work. Most of this stuff will be
applicable to Linux at the concept level, regardless of the book (ignore
anything on SysV STREAMS). Unless you're extremely gifted, the concepts
won't reveal themselves to you from kernel source code. LEARN THE
CONCEPTS. The Linux community is not a good place to do this - this list
assumes that if you're here, you already know them. If you're one of
those truly unlucky people with no access to such a book, try to find
this info on the net. I've never really looked. If all else fails,
proceed to step two:

I read Michael Johnson's Kernel Hackers' Guide. It wasn't perfect when I
read it, but that was a while ago. 1) It's probably perfect by now. 2)
It's free. You can get it anywhere, including here:
It does a good job of mapping the concepts you just learned to actual
kernel function calls and processes in Linux. Also, many kernel
functions have man pages, though they're horribly out of date.

I subscribed to mailing lists. Initially I was all over: gcc, kernel, a
few scsi lists, security... Now I've got it down to a core of kernel,
two SCSI driver lists, DIALD, security and SMP. Don't be afraid to
subscribe to a lot of lists (read-only!) for a few weeks to see what
interests you. You can always unsubscribe later. Some people prefer
reading the lists via news, but I'd recommend mail: You SAVE the mail on
your hard disk. It becomes your personal reference library (N.B. UNIX
has some really great text search and processing tools). You read all
the mail. This gives you a feel for what's being worked on and what's
not, who knows what they're talking about and who doesn't, and what
snags are troubling other users. This is important so you can ask senior
developers PRIVATELY when you have questions relating to The Code -
unless you genuinely believe that a lot of list subscribers also want
the answer. Also, some of the news gateways appear to be brutally
broken, randomly mixing messages from different linux lists like a
cypherpunk remailer gone mad. I recommend going straight to the source:
send "help" to mailto:majordomo@vger.rutgers.edu

I quickly got over the idea that I could learn everything about the
kernel. Last time I looked, it was over 600,000 lines of source. I can
muck around with SCSI and network device drivers, I understand the mid
level SCSI code, and I've got a reasonably good handle on the scheduler.
That leaves high level networking, filesystems, the buffer cache and
memory management, to name a few, ABOUT WHICH I HAVEN'T A CLUE. Pick an
area you want to diddle with, and concentrate on that. If you don't
believe me, grab a dictionary and look up "hubris".

I read most (some?) of the important stuff in Documentation/ (you should
read it all) and then: I dove into the code, wholeheartedly, for nights
(days?) at a time. Pick drivers. Concentrate on the simple ones - you
want concepts, not nasty workarounds for buggy hardware. Try 'wc
*.c|sort' in your favourite directory. Pick ones that look well
formatted and well commented, and see how they're written and how they
interact with the higher level stuff. Go into each subdirectory in the
whole linux/ tree, and learn what lives there. You should be able to
identify what's what from the stuff you read in those books. Note
especially mm/ and kernel/, along with their counterparts under arch/.
Here lie most of the important functions for juggling memory,
interrupts, processes etcetera. Learn to use grep, find and xargs
effectively. If you have a strong constitution, look in the scripts/
directory and the Makefiles everywhere to see how the kernel actually
gets built. If you're a bit twiddler at heart, look at the low level
stuff for your favourite architecture under arch/.

If you've still got the lust for knowledge at this point, you will
probably have found "that special something" that interests you in the
kernel. You will know generally how things work from the source, and you
will know the right people to ask from the source and the mailing lists.
If you have a question, go ahead and ask it. I've found developers to be
very helpful when asked questions by someone who's obviously studied the
sources. Play around. Recompile. Benchmark. Test.

One thing that's probably overlooked by a lot of Linux people: BSD, "the
other free UNIX". I can't even tell you the difference between FreeBSD
and NetBSD, but for my purposes, I don't care. They're available free on
the net or a CD, just like Linux (http://ftp.freebsd.org and
http://www.freebsd.org). If you're stumped by something in Linux, seeing
how BSD does it is often helpful, especially for device drivers. Also
(ahem) BSD code sometimes seems to be commented and formatted somewhat
better. I don't run it, I just look at the source.

At this stage your hats will no longer fit, and your dog will have run
off with your girlfriend. No matter, because you'll be able to ask, and
sometimes answer, intelligent questions about kernel design, in your
particular specialty areas. You'll be fixing insidious bugs, improving
performance, and posting things like "this patch is from memory and
untested, but it will solve your problem on 2.1.87: [proper patch

I'm not at this stage yet, and I've been working at it for a while.
That's why I usually post answers to questions like "where do I begin"
rather than "why did it hang". The above is working for me, it might
work for you. May the Source be With You, Always.

A. Appendix

This Policy is maintained by Frohwalt Egerer
(mailto:froh@iconsult.com). It is created from input on the linux
kernel mailing list. If desired by the members of the list a voting
will be performed to ratify it.

Paragraphs one and two are edited from David A Rusling's
(mailto:rusling@linux.reo.dec.com) mail on the list. I changed it a
little bit and added all those typing errors. Thank him, flame me.

Paragraph four was a mail by Cameron MacKinnon <mackin@interlog.com>


Frohwalt Egerer