Panic during shutdown

I'm running -CURRENT on an Acer One netbook.  Every kernel I've built 
since last Sunday panics on shutdown (see below).  The panic occurs 
whenever shutdown(8) is executed, even if only to drop to single-user. 
halt(8) does not trigger the panic.

I have a core dump and kernel with debugging symbols available if needed.

-- 
Greg Rivers


blue.tharned.org dumped core - see /var/crash/vmcore.0

Wed Jul  1 09:28:41 CDT 2009

FreeBSD blue.tharned.org 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Wed Jul  1 00:53:42 CDT 2009     root_at_blue.tharned.org:/usr/obj/usr/src/sys/SMALL-SMP  i386

panic: swap_reserved < decr

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Unread portion of the kernel message buffer:
<118>.
<118>.
<118>Jul  1 09:25:35 blue syslogd: exiting on signal 15
panic: swap_reserved < decr
cpuid = 0
KDB: stack backtrace:
db_trace_self_wrapper(c06bef5d,e649db30,c04fe90f,c06d6322,0,...) at db_trace_self_wrapper+0x26
kdb_backtrace(c06d6322,0,c06cdb69,e649db3c,0,...) at kdb_backtrace+0x29
panic(c06cdb69,c065575e,c11ac1b8,e649db6c,c064e52e,...) at panic+0x114
swap_release_by_uid(f5000,0,c3d10340,e649db78,c0652b30,...) at swap_release_by_uid+0x94
vm_object_destroy(c4300000,c06cf12d,c06442e5,c3d2f280,bfbe0000,bfc00000) at vm_object_destroy+0xd0
vm_object_terminate(c4300000,c4176708,c3d2f1d0,e649dbc8,c064314a,...) at vm_object_terminate+0x225
vm_object_deallocate(c4300000,0,0,c3d2f1d0,0,...) at vm_object_deallocate+0x6cf
_vm_map_unlock(c3d2f1d0,0,0,1,c3d2f1d0,...) at _vm_map_unlock+0x74
vm_map_remove(c3d2f1d0,0,bfc00000,c3effc40,0,...) at vm_map_remove+0x69
vmspace_exit(c417bd80,c41792a8,c41792a8,0,e649dc80,...) at vmspace_exit+0xbc
exit1(c417bd80,0,e649dd2c,c068d2ee,c417bd80,...) at exit1+0x61a
clear_entries(c417bd80,e649dcf8,4,c,e649dd2c,...) at clear_entries
syscall(e649dd38) at syscall+0x2ff
Xint0x80_syscall() at Xint0x80_syscall+0x20
--- syscall (1, FreeBSD ELF32, sys_exit), eip = 0x8832b27f, esp = 0xbfbfedac, ebp = 0xbfbfedb8 ---
Uptime: 1m4s
Physical memory: 1003 MB
Dumping 58 MB: 43 27 11

[snip]

#0  doadump () at pcpu.h:246
246	pcpu.h: No such file or directory.
 	in pcpu.h
(kgdb) #0  doadump () at pcpu.h:246
#1  0xc04fe634 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:419
#2  0xc04fe94b in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:575
#3  0xc063262d in swap_release_by_uid (decr=Unhandled dwarf expression opcode 0x93
)
     at /usr/src/sys/vm/swap_pager.c:267
#4  0xc064a60b in vm_object_destroy (object=0xc4300000)
     at /usr/src/sys/vm/vm_object.c:622
#5  0xc064cb76 in vm_object_terminate (object=0xc4300000)
     at /usr/src/sys/vm/vm_object.c:715
#6  0xc064d24c in vm_object_deallocate (object=0xc4300000)
     at /usr/src/sys/vm/vm_object.c:592
#7  0xc0644059 in _vm_map_unlock (map=0xc3d2f1d0, file=0x0, line=0)
     at /usr/src/sys/vm/vm_map.c:480
#8  0xc0644586 in vm_map_remove (map=0xc3d2f1d0, start=0, end=Variable "end" is not available.
)
     at /usr/src/sys/vm/vm_map.c:2765
#9  0xc0647548 in vmspace_exit (td=0xc417bd80) at /usr/src/sys/vm/vm_map.c:329
#10 0xc04d3c1c in exit1 (td=0xc417bd80, rv=0)
     at /usr/src/sys/kern/kern_exit.c:299
#11 0xc04d4c10 in sys_exit (td=Could not find the frame base for "sys_exit".
) at /usr/src/sys/kern/kern_exit.c:110
#12 0xc068d2ee in syscall (frame=0xe649dd38)
     at /usr/src/sys/i386/i386/trap.c:1073
#13 0xc0672790 in Xint0x80_syscall ()
     at /usr/src/sys/i386/i386/exception.s:261
#14 0x00000033 in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb)

[snip]