em stability issues + panic

Well, I will admit I have a bit older if_em.c, v1.147, but I haven't
been doing much w/ my em, probably not even passing close to 100mbit
of traffic (in gige mode)...  I recently obtained a crash dump from
em_txeof where the tx_buffer is NULL at line 2958:
2958                    if (tx_buffer->m_head) {

If any one want some additional data, I can provide info from the
crash dump...   Just as a bit of trivia, I did load a few kld's..
bktr.ko, bktrau.ko and iic.ko (plus respective other kld's that got
auto loaded)...   It also seems that interactiveness is more likely
to hang em than other traffic...  I've been running the box as a nfs
server for a while w/o issues, but I log in and run ffmpeg, and it
almost immediately hangs requiring an down/up to bring back the
interface...

The panic was when I was bringing the interface back up... Though when
I it paniced, I had down/up'd the interface a few times w/o success in
bringing it back...

Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0x0
fault code              = supervisor read, page not present
instruction pointer     = 0x20:0xc047155e
stack pointer           = 0x28:0xe1d1cc50
frame pointer           = 0x28:0xe1d1cc64
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 12 (swi4: clock sio)
Physical memory: 999 MB
Dumping 225 MB: 210 194 178 162 146 130 114 98 82 66 50 34 18 2

#9  0xc066f56a in calltrap () at ../../../i386/i386/exception.s:138
#10 0xc047155e in em_txeof (adapter=0xc34df800) at ../../../dev/em/if_em.c:2956
#11 0xc046e502 in em_watchdog (ifp=0xc3502400) at ../../../dev/em/if_em.c:963
#12 0xc0585b22 in if_slowtimo (arg=0x0) at ../../../net/if.c:1415
#13 0xc0529fa9 in softclock (dummy=0x0) at ../../../kern/kern_timeout.c:271
#14 0xc050a57a in ithread_execute_handlers (p=0xc33c38d0, ie=0xc341c580)
    at ../../../kern/kern_intr.c:662
#15 0xc050a673 in ithread_loop (arg=0xc33a2940)
    at ../../../kern/kern_intr.c:745
#16 0xc050981b in fork_exit (callout=0xc050a624 <ithread_loop>, 
    arg=0xc33a2940, frame=0xe1d1cd38) at ../../../kern/kern_fork.c:818
#17 0xc066f5cc in fork_trampoline () at ../../../i386/i386/exception.s:199

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."