watchdog timeout panic on shutdown

[Sean McNeil]

I get this panic about 80% of the time, but very rarely does it core
dump.  Even more rare is that I shutown for some reason other than a
kernel update.  Here is what the traceback of the dump shows me:

#0  doadump () at pcpu.h:172
172     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) bt
#0  doadump () at pcpu.h:172
#1  0xffffff0000c93610 in ?? ()
#2  0xffffffff802607f7 in boot (howto=260)
    at /usr/src/sys/kern/kern_shutdown.c:399
#3  0xffffffff80260e91 in panic (fmt=0xffffff007b96abe0 "@\223\226{")
    at /usr/src/sys/kern/kern_shutdown.c:555
#4  0xffffffff8022d44e in hardclock (frame=0xffffffff)
    at /usr/src/sys/kern/kern_clock.c:583
#5  0xffffffff803f848a in lapic_handle_timer (frame=
      {cf_rdi = 1000000, cf_rsi = -1097438155808, cf_rdx = 0, cf_rcx =
1000, cf_r8 = -1310696176, cf_r9 = -1098038762392, cf_rax = 1000, cf_rbx
= 0, cf_rbp = -1099499782104, cf_r10 = 0, cf_r11 = -2145842048, cf_r12 =
-1099499782144, cf_r13 = 4294967294, cf_r14 = 0, cf_r15 = 0, cf_rip =
-2143364478, cf_cs = 8, cf_rflags = 530, cf_rsp = -1310696520, cf_ss =
16})
    at /usr/src/sys/amd64/amd64/local_apic.c:629
#6  0xffffffff803f3cd6 in Xtimerint () at apic_vector.S:153
#7  0xffffffff803eda82 in acpi_cpu_c1 ()
    at /usr/src/sys/amd64/acpica/acpi_machdep.c:68
#8  0xffffffff80190e00 in acpi_cpu_idle ()
    at /usr/src/sys/dev/acpica/acpi_cpu.c:817
#9  0xffffffff80245aae in idle_proc (dummy=0xf4240)
    at /usr/src/sys/kern/kern_idle.c:115
#10 0xffffffff80245607 in fork_exit (callout=0xffffffff80245960
<idle_proc>,
---Type <return> to continue, or q <return> to quit---
    arg=0x0, frame=0xffffffffb1e05c50)
at /usr/src/sys/kern/kern_fork.c:789
#11 0xffffffff803f37de in fork_trampoline ()
    at /usr/src/sys/amd64/amd64/exception.S:394
#12 0x0000000000000000 in ?? ()
Previous frame identical to this frame (corrupt stack?)
(kgdb)