BBB freebsd-current backtrace. why?

[Jason Birch]

On Wed, Mar 11, 2015 at 11:35 AM, jungle Boogie <jungleboogie0 at gmail.com>
wrote:

> Hello All,
>
> Brand new download and install of -current on my beagle bone black and
> getting below backtrace, but the portsnap extract is continuing. If
> this is how it was on last weeks image, the backtrace will randomly
> print something similar to what's below even when the BBB is inactive.
>
> Downloaded from:
> ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/arm/armv6/ISO-IMAGES/11.0/
>
> Is this expected?
>
> root at beaglebone:~ # portsnap fetch extract update
> Looking up portsnap.FreeBSD.org mirrors... 7 mirrors found.
> Fetching public key from isc.portsnap.freebsd.org... done.
> Fetching snapshot tag from isc.portsnap.freebsd.org... done.
> Fetching snapshot metadata... done.
> Fetching snapshot generated at Tue Mar 10 00:05:13 UTC 2015:
> 248798a3bfb5e11c4a642a6254d9ec1573982894936270100% of   71 MB 2297 kBps
> 00m32s
> Extracting snapshot... lock order reversal:
>  1st 0xcd228ba0 bufwait (bufwait) @ /usr/src/sys/kern/vfs_bio.c:3097
>  2nd 0xc2fa0e00 dirhash (dirhash) @ /usr/src/sys/ufs/ufs/ufs_dirhash.c:285
> KDB: stack backtrace:
>

They're lock order reversals, as enabled by the WITNESS kernel option. You
probably don't need to worry, but it's helpful to check if they've been
reported and, if not, report them.

You might be running into this one:
http://sources.zabbadoz.net/freebsd/lor/261.html

Quick Googling turns up these resources:

lock order reversals - what do they mean?:
https://lists.freebsd.org/pipermail/freebsd-current/2003-December/016617.html
Glossary of Kernel Options for Debugging:
https://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-options.html
FreeBSD LOR(lock order reversal)s seen and comments:
http://sources.zabbadoz.net/freebsd/lor.html