r324421 amd64 kernel panics when entering multiuser mode

panic: freeing invalid range
cpuid = 0
time = 1507550062
Uptime: 2s
.........
#0  doadump (textdump=<value optimized out>) at pcpu.h:232
232     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) #0  doadump (textdump=<value optimized out>) at 
pcpu.h:232
#1  0xffffffff804d68b6 in kern_reboot (howto=260)
    at /usr/src/sys/kern/kern_shutdown.c:386
#2  0xffffffff804d6cdc in vpanic (fmt=<value optimized out>, 
    ap=<value optimized out>) at 
/usr/src/sys/kern/kern_shutdown.c:779
#3  0xffffffff804d6b33 in panic (fmt=<value optimized out>)
    at /usr/src/sys/kern/kern_shutdown.c:710
#4  0xffffffff80504013 in blst_meta_free 
(scan=0xfffffe00016e3048, 
    freeBlk=<value optimized out>, count=0, radix=<value 
optimized out>)
    at /usr/src/sys/kern/subr_blist.c:869
#5  0xffffffff80503fbf in blst_meta_free 
(scan=0xfffffe00016e3038, 
    freeBlk=<value optimized out>, count=<value optimized out>, 
    radix=<value optimized out>) at 
/usr/src/sys/kern/subr_blist.c:926
#6  0xffffffff80503fbf in blst_meta_free 
(scan=0xfffffe00016e3028, 
    freeBlk=<value optimized out>, count=<value optimized out>, 
    radix=<value optimized out>) at 
/usr/src/sys/kern/subr_blist.c:926
#7  0xffffffff80503fbf in blst_meta_free 
(scan=0xfffffe00016e3018, 
    freeBlk=<value optimized out>, count=<value optimized out>, 
    radix=<value optimized out>) at 
/usr/src/sys/kern/subr_blist.c:926
#8  0xffffffff8067568f in swaponsomething (vp=<value optimized 
out>, 
    id=0xfffff800052ad000, nblks=986109, 
    strategy=0xffffffff80675900 <swapgeom_strategy>, 
    close=0xffffffff80675b30 <swapgeom_close>, dev=87, flags=1)
    at /usr/src/sys/vm/swap_pager.c:2199
#9  0xffffffff80673aac in sys_swapon (td=<value optimized out>, 
    uap=<value optimized out>) at 
/usr/src/sys/vm/swap_pager.c:2728
#10 0xffffffff806bc512 in amd64_syscall (td=0xfffff80005387560, 
traced=0)
    at subr_syscall.c:132
#11 0xffffffff806a170b in Xfast_syscall ()
    at /usr/src/sys/amd64/amd64/exception.S:419
#12 0x0000000800a888ba in ?? ()
Previous frame inner to this frame (corrupt stack?)
Current language:  auto; currently minimal