Yet another crash in FreeBSD 5.1

[Evan Dower]

I fear we may have gotten a bit off-topic.
E


>From: Greg 'groggy' Lehey <grog at FreeBSD.org>
>To: Terry Lambert <tlambert2 at mindspring.com>
>CC: ticso at cicely.de, current at freebsd.org
>Subject: Re: Yet another crash in FreeBSD 5.1
>Date: Sun, 3 Aug 2003 11:21:41 +0930
>
>On Saturday,  2 August 2003 at 18:36:24 -0700, Terry Lambert wrote:
> > Greg 'groggy' Lehey wrote:
> >>> The information I gave him gets him to lines of source code, instead
> >>> of just function names with strange hexadecimal numbers that resolve
> >>> to instruction offsets that may be specific to his compile flags,
> >>> date of checkout of the sources from CVS, etc..
> >>
> >> The first step of the link above does the same thing.  But it's only
> >> the first step.
> >>> by eyeballing the lines of source code in question and understanding
> >>> the code around it well enough that you can tell *how* a pointer
> >>> there could be NULL.  My instructions *get* him those lines of
> >>> source.
> >>
> >> You obviously still haven't read the reference.  Do that first, and
> >> come back when you have either understood things or are having
> >> difficulty understanding.  But don't shoot off your mouth without
> >> knowing what's going on.
> >
> > I read the reference.
> >
> > How does it apply in cases like this one, where you don't have a
> > vmcore file?
>
>You don't seem to have read the reference very well.  It also asks for
>other supporting information.  That's the most important thing at the
>moment.  I know that because I've been there before, and I've looked
>at a number of these dumps: it's almost certainly related to something
>he's doing which is not normal.  You don't know that, and that's
>excusable, but it's not excusable that after four or five requests,
>you still haven't RTFM'd.
>
> > The way I would approach finding this, with only:
> >
> > 1)	The line of code where the failure occurred
> > 2)	The stack traceback, with no arguments
> > 3)	The sources for the code in the stack traceback
> >
> > would be to eyeball the code in #1, and try to figure out how
> > I gould get to that point with that pointer having a NULL value,
> > given my apriori knowledge of the forward call graph.
>
>You have that?
>
> > I would examine every intermediate conditional and function call
> > that could effect the value of the pointer and cause it to be NULL
> > at the point in question.
>
>Go for it.  Once I get the log files, I'll start there.
>
> > One of the details I wish you would check is whether or not he has a
> > vmcore file, or the ability to get one...
>
>We'll address that issue when it becomes necessary.
>
>Greg
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