Muli Ben-Yehuda's journal

February 23, 2004

Filed under: Uncategorized — Muli Ben-Yehuda @ 11:29 AM

Creative Thinking – A Tale of Seven Hats

Yesterday at work we had a “creative thinking” workshop. It wasn’t
nearly as bad enough as I expected it to be, and I actually
enjoyed bits and parts of it. We learned techniques for
facilitating constructive discussion, how to do proper
brainstorming, how to come up with creative solutions to
problems and how to distill problems into their essence. I
particularly enjoyed the ‘provocation’ method. For example, when
discussing extreme
programming
, we took the sentence “in XP you write the
tests first”, and ended up with the provocative statement “never
write tests”. That led me to contemplate systems that are never
tested, and thus are expected to fail quite often, and thus must
learn to cope with their failures gracefully, which leads to
completely different ways of thinking about designing software
systems. Fun stuff.

syscalltrack – another bug that wasn’t squashed[0]

We support two methods of communication with the kernel in
syscalltrack. The first and oldest is via sysctl, and is fairly
ugly. The second is via a device file. While I was testing the
previously mentioned build fix to get it to build with Linux
2.4, I noticed that loading and unloading rules via the device
file was failing with -EBADF, while sysctl was
working. Yesterday I checked and figured out what was
happening (quoted here because it doesn’t show up in the
archives yet).

 
On Sat, Feb 21, 2004 at 11:57:18PM +0200, Muli Ben-Yehuda wrote:
> tea:/hydra/home/muli/src/syscalltrack-head# tests/stress/tester -d 
-t simple_syscall_usage
> starting test 'simple_syscall_usage' (subsystem module(1)) []
> 'dev_file_do_request': failed to send the request, with error 'Bad
> file descriptor'

-EBADF is returned in only one place, when someone tries to write to
the log device. Why would we be trying to write to the log device,
when we're actually trying to write to the control device?

Answer: because the major numbers on the device files /dev/sct_ctrl0
and /dev/sct_log0 are messed up?

Indeed, because I loaded the modules manually rather than via
sct_load, the device files had the wrong major numbers, and
/dev/sct_ctrl0 actually had the major number of the log
device. Oops. Fixing the device numbers for the /dev/sct_* files based
on the output from /proc/devices solved the problem.

On a side note, I think we should move to netlink for
communicating with the kernel, as that seems to be the standard
way to do it.
relayfs
could also be interesting, if and when it ever makes
it into the vanilla kernel.

[0] This title reminds me of the closing slide in the Creative
Thinking workshop. The slide said “opportunityisnowhere”, and
you could parse it either as “opportunity is no where” or
“opportunity is now here”, depending on your general outlook on
life. FWIW, It’s the bug that wasn’t, not the bug that wasn’t
squashed.

Advertisements

10 Comments »

  1. Bad use of the PRE tag ๐Ÿ˜ฆ

    Comment by compwiz — February 23, 2004 @ 6:51 AM | Reply

    • elaborate, please? works for me (TM)

      Comment by mulix — February 23, 2004 @ 6:53 AM | Reply

      • Scrolls too far to the right on friends pages.

        Comment by compwiz — February 23, 2004 @ 6:54 AM

      • displays fine in mozilla 1.4.1, konq 3.1.4-6 and even IE something. I’ll trim the long line, maybe that will help? the rest is not more than 80 chars per line.

        Comment by mulix — February 23, 2004 @ 6:59 AM

      • that should help.

        Comment by compwiz — February 23, 2004 @ 7:00 AM

      • suggestions on how to do it otherwise with HTML will be happily entertained.

        Comment by mulix — February 23, 2004 @ 7:02 AM

      • <tt> seems to do the trick most of the time for me. <pre> IMHO is way overused. People use it to put things in a typewriter font when it’s really designed for when the formatting of text absolutely matters, like for, say, ASCII art. It prevents normal wrapping of lines which should normally be left up to the browser.

        Comment by compwiz — February 23, 2004 @ 7:05 AM

      • I guess I’m old skool, since I think that the formatting of email absolutely matters ๐Ÿ˜‰ I’ll try to be more careful with ‘pre’ in the future, though. Thanks for bringing it to my attention!

        Comment by mulix — February 24, 2004 @ 1:48 AM

  2. If I were in a creative thinking class, I’d probably make the provocative statement “creative thinking classes are useless”, and see what comes out of it. I remember someone who attended a class on how to inculcate motivation in other people, and he decided to be the subject of inculcation. :-B And reportedly, the instructor didn’t know what to do!
    I think the claim that a person’s parse of “opportunityisnowhere” depends on his outlook of life is bull. Many factors can influence the parse, such as whether one’s more familiar with CV (consonant + vowel) or VC or CVC constructions, whether he’s more inclined to see large words or to see smaller words, etc.

    Comment by bicoherent — February 23, 2004 @ 8:13 AM | Reply

    • > I think the claim that a person’s parse of “opportunityisnowhere” depends
      > on his outlook of life is bull. Many factors can influence the parse,
      > such as whether one’s more familiar with CV (consonant + vowel) or VC or
      > CVC constructions, whether he’s more inclined to see large words or to
      > see smaller words, etc.
      In all fairness, the instructor didn’t make that claim, I did in the post. I agree I was guilty of gross over-simplification in order to get the basic point accross.

      Comment by mulix — February 24, 2004 @ 1:46 AM | Reply


RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Blog at WordPress.com.

%d bloggers like this: