I'm seeing spontaneous reboots on an amd64 laptop with iwn
card. I haven't enabled a dump partition yet (will try to do),
so all I get is:

Fatal trap 3: breakpoint instruction fault while in kernel mode
cpuid = 0; apic id = 00
instruction pointer     = 0x20:0xffffffff805b173e
stack pointer           = 0x28:0xffffffff81018590
frame pointer           = 0x28:0xffffffff810185b0
code segment            = base rx0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = IOPL = 0
current process         = 12 (irq259: iwn0)
trap number             = 3
panic: breakpoint instruction fault
cpuid = 0
KDB: enter: panic

iwn behaves really badly, and disconnects every few minutes
with:

wlan0: Ethernet address: 00:21:5c:50:68:c3
wlan0: link state changed to UP
iwn0: iwn_intr: fatal firmware error
firmware error log:
  error type      = "FH_ERROR" (0x0000000C)
  program counter = 0x0000046C
  source line     = 0x000000D0
  error data      = 0x0000000802730000
  branch link     = 0x0000A332000004C2
  interrupt link  = 0x000006DE0000A37E
  time            = 2607530651
driver status:
  tx ring  0: qid=0  cur=22  queued=12
  tx ring  1: qid=1  cur=0   queued=0
  tx ring  2: qid=2  cur=0   queued=0
  tx ring  3: qid=3  cur=16  queued=0
  tx ring  4: qid=4  cur=81  queued=0
  tx ring  5: qid=5  cur=0   queued=0
  tx ring  6: qid=6  cur=0   queued=0
  tx ring  7: qid=7  cur=0   queued=0
  tx ring  8: qid=8  cur=0   queued=0
  tx ring  9: qid=9  cur=0   queued=0
  tx ring 10: qid=10 cur=0   queued=0
  tx ring 11: qid=11 cur=0   queued=0
  tx ring 12: qid=12 cur=0   queued=0
  tx ring 13: qid=13 cur=0   queued=0
  tx ring 14: qid=14 cur=0   queued=0
  tx ring 15: qid=15 cur=0   queued=0
  rx ring: cur=39
ifa_del_loopback_route: deletion failed: 3
wlan0: link state changed to DOWN
wlan0: Ethernet address: 00:21:5c:50:68:c3
wlan0: link state changed to UP

This is a known problem:
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/176104

It is interesting to note that iwn
disconnects a lot at work, and very rarely
at home. I suspect that it is too sensitive
to interference, or something like this.

Anyway, I'll try to provide textdump
if I set it up.