freeze and crashes

Alexander Sack pisymbol at
Fri Apr 25 15:12:01 UTC 2008

Hi Alain:

Without more details its hard to understand where your hang or freeze
is coming from.  What I DO suggest is that you build a debug kernel
and/or minimally enable the kernel debugger (DDB).  Then when the box
is frozen you can get into the debugger (CTRL-ALT-ESC), type "bt", and
post it on the list to give everybody a chance to understand what is
hanging ("show msgbuf" as well actually).

Here is some good documentation on how to build kernels (and debug
ones) if you don't already know:

Generally speaking I would enable in my KERNCONF file (GENERIC, etc.
under src/sys/<arch>/conf/)

# Turn off debugging symbols
makeoptions	DEBUG=-g

# Debugger support
options		KDB
options		DDB
options		KDB_TRACE

If you want to go further, for example you believe this is a locking
issue then you can go whole hog and do:

# Heavy duty debugger options
options	WITNESS

Be warned that the kernel.debug KO (kernel object) will run a lot
slower than a stock non-debug kernel (the extra metadata the kernel is
keeping track off etc.) so there are instances where running a debug
kernels could make a timing bug disappear or appear more/less
frequently.  In any event, if the problem is easily reproducible, I
whole-heartily recommend you minimally enable KDB/DDB support so you
can dump things on the appropriate list AS WELL AS build a complete
debug kernel that may catch the issue (you will see console messages
including lock order reversals and other nastiness).

Here is some good documentation about kernel debugging:

Let us know how things go,


PS Make sure that new disk is good!
On Fri, Apr 25, 2008 at 9:01 AM, Alain G. Fabry <alainfabry at> wrote:
> Have a issue here. I've been running FreeBSD 6.3 release for about 6 months now without problem. Then last week I purchase another external HD and installed release 7.0.
>  Everything went great for about 3 weeks. Then suddenly my 7.0 started to crash (kde freezing, sudden reboots, etc). The first time happened when I was performing a portsnap on a FreeBSD Qemu session. It came up to the point where this 7.0 installation wasn't workable anymore.
>  Since I need to work to earn money as the rest of us, I fell back to my 6.3 release external HD -> copied over my data files and now I'm starting to get the same symthoms.
>  Input/output errors, reboot when performing a simple 'man something'. -> could this be a virus or something?
>  I'm not sure how or what I can do to find out what could be the cause of this problem?
>  Is there anywhere I can find out more about debugging such strange behavior. (everything works fine and then suddenly it freezes permanently or just reboots on its own)
>  Thanks,
>  PS: I'm about to reinstall the 7.0 release and hope that that will work normal again.
>  Alain
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