Re: Yet another crash in FreeBSD 5.1

On Saturday,  2 August 2003 at 18:06:36 -0700, Terry Lambert wrote:
> Greg 'groggy' Lehey wrote:
>>> Please take a look at an older thread named (IIRC) vinum or geom bug?
>>> Greg asked for special debug output, but it never happened again for me.
>>> A real murphy bug - it happend on three machines once a day and after
>>> Gregs response nothing happened over weeks.
>>
>> This is the real issue.  Until you supply the information I ask for in
>> the man page or at http://www.vinumvm.org/vinum/how-to-debug.html,
>> only Terry can help you.
>
> This is BS, Greg.
>
> I deal with about a traceback every other day, and sometimes as
> high as 5 in a single day, if it's a busy day for it.

Stack traces are pretty common stuff.  Your point?

> 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.

> I don't know about you, but I can't easily write assembly
> instructions to tape, run them the tape through my teeth, and read
> the bits using my dental fillings.

Terry, why don't you come to my debug tutorial at the BSDCon next
month?  I'll show you how to do this properly.  I'm not asking for
people to interpret hex.  I'm asking for people, you included, to find
out what debugging help is available.

> If it's a NULL pointer dereference, the place to find it is by
> turning on what debugging there is, and, if that fails, which it
> probably will,

No, that will find the null pointer dereference pretty quickly.

> 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.

> If you'll notice from his followup posting of the source in
> question, Vinum is loaded as a module, and it's the FreeBSD code
> that Vinum calls, not Vinum, that's causing the crash.

The bug is almost certainly in Vinum.

> There's no reason to be paranoid about your baby with me; unlike
> some people, personally I like Vinum, so relax and realize that I'm
> not trying to blame your code by trying to help him squeeze more
> information out of the data he *is* able to gather.

This has nothing to do with being paranoid about babies.  This has to
do with people shooting off their mouths in a public forum without
bothering to check details first.

Greg
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