Raspberry pi 11 Current panic

[Ian Lepore]

On Tue, 2014-03-25 at 16:32 -0700, jungleboogie0 wrote:
> And now to the group:
> 
> 
> U-Boot 2013.01-rc1-svn18531 (Mar 24 2014 - 09:11:00)
[...]
> > >
> > > I grabbed 11-CURRENT for raspberry pi here:
> > > ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/arm/armv6/ISO-IMAGES/11.0
> > >
> > > Booted up my pi and I'm trying to run vnstat but this occurs:
> > >
> > > root at raspberry-pi:~ # vmstat
> > >  procs      memory      page                    disks     faults
> > cpu
> > >  r b w     avm    fpanic: mutex process lock not owned at
> > > /usr/src/sys/kern/kern_sig.c:2874
> > > KDB: enter: panic
> > > [ thread pid 747 tid 100063 ]
> > > Stopped at      $d:     ldrb    r15, [r15, r15, ror r15]!
> > >
> > > So far I've been able to do this 3 times in a row by simply logging in
> > and
> > > typing vmstat.
> > >
> > > Is this expected behavior?
> > >

It took me a while to get around to this, but I can confirm that if you
download the r263665 rpi image it behaves exactly as shown.  On the
other hand, if I build r263665 locally and boot from it I have no
problems, but that's with an NFS root filesystem so it's not quite an
identical test.

The actual problem that causes the panic appears to be secondary fallout
from an attempt to kill the process because of a floating point
exception in supervisor mode.  I think we have another mail thread about
a similar problem.  The kernel isn't supposed to be using floating point
hardware, so I'll look into that.  I have a vague suspicion we may be
accidentally using an instruction not supported by the vfp version in
the rpi while saving/restoring the state or something like that.

-- Ian