Panic from an hour ago's kernel (supped Tue Jul 13 13:47:15 1999 BST)
ie., after pmap commit was backed out and with a uvm change

db> t               
Debugger(0,f80017b8,0,f802cea0,f01d8434) at Debugger+0x4       
panic(f0249808,f80017b8,f8037930,f802ceb8,f01d7dba) at panic+0x55 
amap_wipeout(f80017b8,f8037930,f8037930,0,f802ced4) at amap_wipeout+0x30
amap_unref(f8037930,0) at amap_unref+0x1a 
uvm_unmap_detach(f80377c8,0,f801b7c4,f8026150,f80377c8) at uvm_unmap_detach+0x31
uvm_unmap(f801b7c4,0,efbfe000,f801b7c4,f802cf34) at uvm_unmap+0xaf
uvm_deallocate(f801b7c4,0,efbfe000) at uvm_deallocate+0x38
exit1(f8026150,0,f802cfa8,f01f0301,f8026150) at exit1+0x13e
sys_exit(f8026150,f802cf88,f802cf80,0,ffffffff) at sys_exit+0x14
syscall() at syscall+0x149
--- syscall (number 1) ---
0x480ce977:
db> ps
 PID             PPID       PGRP        UID S   FLAGS          COMMAND    WAIT
>6667            2533       6667       2171 2  0x6006             grep 

or, in a different form:

#3  0xf015a11d in panic () at ../../../../kern/subr_prf.c:164
#4  0xf01d8434 in amap_wipeout (amap=0xf80017b8)
    at ../../../../uvm/uvm_amap.c:1071
#5  0xf01d7dba in amap_unref (entry=0xf8037930, all=0)
    at ../../../../uvm/uvm_amap.c:1071
#6  0xf01dda15 in uvm_unmap_detach (first_entry=0xf80377c8, amap_unref_flags=0)
    at ../../../../uvm/uvm_map.c:3324
#7  0xf01dcdff in uvm_unmap (map=0xf801b7c4, start=0, end=4022329344)
    at ../../../../uvm/uvm_map.c:3324
#8  0xf01e59bc in uvm_deallocate (map=0xf801b7c4, start=0, size=4022329344)
    at ../../../../uvm/uvm_user.c:68
#9  0xf014d1fe in exit1 (p=0xf8026150, rv=0)
    at ../../../../kern/kern_exit.c:141
#10 0xf014d0bc in sys_exit (p=0xf8026150, v=0xf802cf88, retval=0xf802cf80)
    at ../../../../kern/kern_exit.c:141
#11 0xf01f0301 in syscall (frame={tf_es = -272695265, tf_ds = 31, tf_edi = 0, 
      tf_esi = -1, tf_ebp = -272641144, tf_ebx = 1208850768, tf_edx = 0, 
      tf_ecx = 134828032, tf_eax = 1, tf_trapno = 3, tf_err = 2, 
      tf_eip = 1208805751, tf_cs = 23, tf_eflags = 582, tf_esp = -272641168, 
      tf_ss = 31, tf_vm86_es = 0, tf_vm86_ds = 0, tf_vm86_fs = 0, 
      tf_vm86_gs = 0}) at ../../../../arch/i386/i386/trap.c:813
#12 0xf0100cc5 in syscall1 ()

Let me know if you want more information!

Cheers,

Patrick