Re: oops pauser.

[Dave Jones <davej@redhat.com>]

On Thu, Jan 05, 2006 at 09:15:02AM +0100, Jan Engelhardt wrote:

 > Here's something interesting too:
 > Sometimes, an oops is even longer than 25 rows, and the usual user
 > does not have
 >  - VGA mode with a lot of lines (because it's hard to read)
 >  - FB mode with a lot of lines (slow, and it's also hard to read)

See the other patch I sent which halves the amount of lines needed
for a backtrace on i386 (like x86-64 uses). This helps too.

 > Is it be possible to change the VGA mode to 80x43/80x50/80x60
 > during protected mode?

After an oops, we can't really rely on anything. What if the
oops came from the console layer, or a framebuffer driver?

 > >With this patch, if we oops, there's a pause for a two minutes..
 > >which hopefully gives people enough time to grab a digital camera
 > >to take a screenshot of the oops.
 > >
 > It would be ideal to have something like BSD's "dump to predefined 
 > block device on oops", so extraction of oops logs requires neither 
 > pen-and-paper nor a digital camera. Requires another partition that
 > can be used for it, though.

I dislike most of the disk dump patches that I've seen out there
because most of them rely on the system being in a decent enough
state to be able to write out blocks of data.

If I had any faith in the sturdyness of the floppy driver, I'd
recommend someone looked into a 'dump oops to floppy' patch, but
it too relies on a large part of the system being in a sane
enough state to write blocks out to disk.

 > (*) If the oops is longer than 25 lines, ... you can't even use scrollback 
 > because scrollback is cleared when you change consoles. X runs by default 
 > on tty7, and the kernel dumps it somewhere else. (And even if it dumped to 
 > tty7 directly, you would not see it.)

What to do about oopses whilst in X has been the subject of much
head-scratching for years now.  It's come up at least at the
last two kernel summits, and I'll hazard a guess it'll come up
again this year.  The amount of work necessary to make it all
work on both kernel side and X side isn't unsubstantial however,
so I wouldn't count on it working too soon.

Hmm, SuSE/Novell folks, doesn't NKLD take over an X display?
ISTR during a demo at last years OLS the presenter was flipping
in/out of the debugger between slides. Is there anything
useful there ?

		Dave