Re: reboot after panic

On Tue, May 06, 2008 at 06:56:42AM -0700, Jeremy Chadwick wrote:
On Tue, May 06, 2008 at 09:47:59AM -0400, Stephen Clark wrote:
...
but there is never one. It is like it hangs trying to dump the memory image.

This mother board has both sata and pata controllers but I am using only pata
drives.

A kernel panic causes the kernel to dump all memory contents (from start
to end) to whatever swap device is available. It's written to the disk
in a fairly "raw" format, with some header data of some sort I think.
After it's done, the system should reboot.

My guess is that you either don't have any swap defined, swap is defined
incorrectly (disklabel -r output would be useful), or your swap space is
smaller than your total amount of memory. (Swap should usually be 2x
RAM).

dumpdir and dumpdev are used during the startup process, where
savecore(8) is called. The memory dump on the swap device is extracted
and stored in a file in $dumpdir, which you can examine later. Keep in
mind that savecore(8) will use /dev/dumpdev, which is a symlink to
whatever device your swap lives on -- and that's determined by reading
/etc/fstab.

Does this help? :-)

You might consider the possibility that he is correct in what he has
said, rather precisely, is going on. FreeBSD 6.2 (and apparently 6.1)
can indeed double-fault or hang during the panic dump in which case no
reboot occurs and there is nothing successfully dumped to analyze for
debugging, either. It is likely that it only occurs with certain
hardware conditions or configurations, which is why not everyone would
see it, but that's not the same thing as it being a hardware problem.

I've been seeing this on all of my SMP machines since October, and
have reported it onlist, and I've been successfully running FreeBSD for
nearly 10 years (starting with 3.3) and BSD/OS for years before that.
It ain't necessarily PEBKAC.

-- Clifton

--
Clifton Royston -- cliftonr@xxxxxxxxxxxxxxxxxx / cliftonr@xxxxxxxx
President - I and I Computing * http://www.iandicomputing.com/
Custom programming, network design, systems and network consulting services
_______________________________________________
freebsd-stable@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-stable
To unsubscribe, send any mail to "freebsd-stable-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: Swap space
    ... > twice the amount of RAM if you need to capture a dump for debugging. ... > If you won't ever be doing that, you may not need so much swap. ... least the size of physical memory. ...
    (freebsd-questions)
  • RE: Hangs during "dump" with 6.0 and current ports
    ... Due to lack of memory I had added an additional swap-file via mdconfig 3 ... filesystem with snapshots active and the swapfile is in the same filesystem ... Hangs during "dump" with 6.0 and current ports ... Maybe you need some more swap space? ...
    (freebsd-questions)
  • Re: Dying processes (inetd, cron, syslogd, sshd)
    ... to fit by limiting the amount of memory seen by the kernel. ... bit less than actual size of your dump area in place of "100m"). ... such a process usually writes a core dump. ... nearly as large as your combined RAM + swap. ...
    (comp.unix.sco.misc)
  • Re: my first Forth program
    ... I'll start with a memory dump and dissasmbler ... I'm not sure, if locals would be easier in the "dump" word, because for me ... it looks too complicated to "swap" the stack all the time. ... TH NIBBLE EMIT SPACE ...
    (comp.lang.forth)
  • Re: Heaps and Foreigners
    ... >> can ask for the memory and get a pointer to it. ... cause unfathomable deaths when swap space gets low or is exhausted. ... It's probably because there is some reserve memory to print out errors ... of RAM and disk space) and virtual swap (which is just a number managed ...
    (comp.lang.lisp)