panic in nfsd in freebsd7-release and -stable

[Andrew Edwards]

I have a system that was running some version of redhat (I don't
remember now) and I upgraded it to freebsd7 and I would get an immediate
panic when nfsd is started.  I then updated to 7-stable (on May 24th)
and built a new kerenl and userland and the panic continued. 

This was happening 100% of the time whenever nfsd is started but what  I
later discovered was that because I had used the same IP's as the linux
host there were some systems that still had a filesystem mounted from
before the conversion.  I put in an ipfw rule to block those hosts and
then I was able to start nfsd without crashing and then create new
mounts.  I have been able to work-around the issue by forcing all of the
servers that were mounting from the linux os to remount, I am only
including this information just in case someone else runs into a similar
problem.

Thanks,
Andrew

Here's the backtrace

Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 06
fault virtual address   = 0x18
fault code              = supervisor read, page not present
instruction pointer     = 0x20:0xc06ce915
stack pointer           = 0x28:0xe8f32a48
frame pointer           = 0x28:0xe8f32a64
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = resume, IOPL = 0
current process         = 755 (nfsd)
trap number             = 12
panic: page fault
cpuid = 1
Uptime: 40m22s
Physical memory: 3318 MB
Dumping 93 MB: 78 62 46 30 14

#0  doadump () at pcpu.h:195
195     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) bt
#0  doadump () at pcpu.h:195
#1  0xc069a917 in boot (howto=260) at
/usr/src/sys/kern/kern_shutdown.c:418
#2  0xc069ac13 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:572
#3  0xc0926763 in trap_fatal (frame=0xe8f32a08, eva=24)
    at /usr/src/sys/i386/i386/trap.c:899
#4  0xc09270ff in trap (frame=0xe8f32a08) at
/usr/src/sys/i386/i386/trap.c:280
#5  0xc090c84b in calltrap () at /usr/src/sys/i386/i386/exception.s:139
#6  0xc06ce915 in turnstile_broadcast (ts=0x0, queue=0)
    at /usr/src/sys/kern/subr_turnstile.c:835
#7  0xc068d292 in _mtx_unlock_sleep (m=0xc0a47e10, opts=0, file=0x0,
line=0)
    at /usr/src/sys/kern/kern_mutex.c:611
#8  0xc0849b79 in nfsrv3_access (nfsd=0xc6ba5d00, slp=0xc6b7f700,
    td=0xc6856c60, mrq=0xe8f32c58) at
/usr/src/sys/nfsserver/nfs_serv.c:253
#9  0xc085bc71 in nfssvc (td=0xc6856c60, uap=0xe8f32cfc)
    at /usr/src/sys/nfsserver/nfs_syscalls.c:461
#10 0xc0926d35 in syscall (frame=0xe8f32d38)
    at /usr/src/sys/i386/i386/trap.c:1035
#11 0xc090c8b0 in Xint0x80_syscall ()
    at /usr/src/sys/i386/i386/exception.s:196
#12 0x00000033 in ?? ()