sys/netinet/ip_input.c:1396: ipq already locked

[eric%tinker.cirr.com@localhost (Eric Schnoebelen)]

Argh!

For the last day, while running both a 4.99.73, and a 5.99.3
kernel, I've been receiving the following panic.  

  /home/builds/ab/HEAD/src/sys/netinet/ip_input.c:1396: ipq already locked
  panic: ipq_lock
  fatal breakpoint trap in supervisor mode
  trap type 1 code 0 rip ffffffff801f2f7d cs e030 rflags 246 cr2 7f7ffdfdc000 
cpl 0 rsp ffffa00047a53a90
  Stopped in pid 0.5 (system) at  netbsd:breakpoint+0x5:  leave
  breakpoint() at netbsd:breakpoint+0x5
  panic() at netbsd:panic+0x255
  ip_slowtimo() at netbsd:ip_slowtimo+0x172
  pfslowtimo() at netbsd:pfslowtimo+0x3b
  callout_softclock() at netbsd:callout_softclock+0x1ef
  softint_thread() at netbsd:softint_thread+0x88
  ds          0x3aa0
  es          0xa4fc
  fs          0x3aa0
  gs          0xa5d7
  rdi         0
  rsi         0x1
  rbp         0xffffa00047a53a90
  rbx         0xffffa00047a53aa0
  rdx         0
  rcx         0
  rax         0x1
  r8          0xffffffff80b0cc80  cpu_info_primary
  r9          0x1
  r10         0xffffa00047a539b0
  r11         0xffffffff8069eba0  xenconscn_putc
  r12         0x100
  r13         0xffffffff808d530b  copyright+0x17a2b
  r14         0xffffffff8060e0d0  pfslowtimo
  r15         0
  rip         0xffffffff801f2f7d  breakpoint+0x5
  cs          0xe030
  rflags      0x246
  rsp         0xffffa00047a53a90
  ss          0xe02b
  netbsd:breakpoint+0x5:  leave
  db>

The build is:

  NetBSD 5.99.3 (XEN3_DOM0) #0: Sat Nov 22 05:19:34 PST 2008
          
builds@wb28:/home/builds/ab/HEAD/amd64/200811220002Z-obj/home/builds/ab/HEAD/src/sys/arch/amd64/compile/XEN3_DOM0
  total memory = 2048 MB
  avail memory = 1965 MB

The system has been averaging an uptime (after full boot) of
about 10 minutes.

I was seeing similar panics about a month ago (with a 4.99.72/3
kenel), but uptime between panics was much longer. (on the order of days.)

What do I need to feed to ddb to get more information?

Thanks in advance,
        Eric