8.0RC2 amd64 - kernel panic running make buildworld

[Alexandre "Sunny" Kovalenko]

On Sat, 2009-11-07 at 11:52 +0100, Gary Jennejohn wrote:
> On Sat, 07 Nov 2009 12:20:51 +0300
> S.N.Grigoriev <serguey-grigoriev at yandex.ru> wrote:
> 
> > I've recompiled the kernel with 'options DDB' (using 7-stable).
> > The sysctl variable 'debug.debugger_on_panic' is now set to '1'.
> > But I still have silent reboots every time I try to build world/kernel.
> > 'savecore -v' reports: 'no dumps found'. What did I do incorrectly?
> > 
> 
> It could be that you also need "options KDB" for the kernel to enter
> ddb on panic, but I'm not 100% sure about that.
> 
> Can't hurt to try it.
> 
> Do you also have dumpdev defined in /etc/rc.conf?  It's set to AUTO
> by default, <snip>
Apparently not on 8.0RC...

RabbitsDen# grep dumpdev defaults/rc.conf
dumpdev="NO"		# Device to crashdump to (device name, AUTO, or NO).
savecore_flags=""	# Used if dumpdev is enabled above, and present.
RabbitsDen# uname -a
FreeBSD RabbitsDen.RabbitsLawn.verizon.net 8.0-RC2 FreeBSD 8.0-RC2 #0
r198931: Sat Nov  7 12:07:32 EST 2009
root at RabbitsDen.RabbitsLawn.verizon.net:/usr/obj/usr/src/sys/TPX60  i386

while on 7.2

twinhead# grep dumpdev defaults/rc.conf
dumpdev="AUTO"		# Device to crashdump to (device name, AUTO, or NO).
savecore_flags=""	# Used if dumpdev is enabled above, and present.
twinhead# uname -a
FreeBSD twinhead.rabbitslawn.verizon.net 7.2-RELEASE-p3 FreeBSD
7.2-RELEASE-p3 #0: Sat Aug 22 12:43:26 EDT 2009
root at twinhead.rabbitslawn.verizon.net:/usr/obj/usr/src/sys/TWINHEAD
amd64

So one needs explicit dumpdev="AUTO" in the /etc/rc.conf. That caught me
by surprise too...

Sergey, I think it would be best if you follow 

http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html#KERNELDEBUG-OBTAIN

and the do an ultimate test:

  * quiesce your system
  * switch to the console
  * sync (few times, if you are really old school ;)
  * sysctl debug.kdb.panic=1 (this would *panic* the system and, given
everything is set-up properly, produce the crash dump)
  
if you do not have debug.kdb.panic sysctl, please, add option KDB to
your kernel configuration.

If you get crash dump from the kernel-induced panic and your system
keeps rebooting without a trace, I would suspect some hardware testing
might be in order.

-- 
Alexandre Kovalenko (Олександр Коваленко)