Page fault in thr_exit()

This came from running stress2 with libthr:

Fatal trap 12: page fault while in kernel mode
cpuid = 2; apic id = 02
fault virtual address   = 0xc96ca608
fault code    = supervisor read, page not present
instruction pointer     = 0x20:0xc0525803
stack pointer         = 0x28:0xee9feb38
frame pointer         = 0x28:0xee9feb54
code segment  = base 0x0, limit 0xfffff, type 0x1b
              = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 9192 (thr1)
[thread pid 9192 tid 103345 ]
Stopped at      _mtx_lock_sleep+0x121:  cmpl    $0x4,0x128(%ebx)
db> wh
Tracing pid 9192 tid 103345 td 0xc94fd9c0
_mtx_lock_sleep(c0786720,c94fd9c0,0,c0720007,9d) at _mtx_lock_sleep+0x121
_mtx_lock_flags(c0786720,0,c0720007,9d,156) at _mtx_lock_flags+0xcb
_sx_xlock(ca0f5b9c,c0737259,bb1,c8d034e0,ee9febe0) at _sx_xlock+0x32
_vm_map_lock_read(ca0f5b58,c0737259,bb1,200028d,ee9fec44) at _vm_map_lock_read+0x48
vm_map_lookup(ee9fec08,805b20c,2,ee9fec0c,ee9fec48) at vm_map_lookup+0x2e
umtx_key_get(c94fd9c0,805b20c,ee9fec44,1,c071e9d5) at umtx_key_get+0x57
kern_umtx_wake(c94fd9c0,805b20c,7fffffff,5e,1) at kern_umtx_wake+0x20
thr_exit(c94fd9c0,ee9fed04,4,445,ee9feca4) at thr_exit+0x45
syscall(3b,2807003b,bfbf003b,1,805b200) at syscall+0x2e7
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (431, FreeBSD ELF32, thr_exit), eip = 0x280d4e4f, esp = 0xb393eee0, ebp = 0xb393ef9c ---

Core available.

Kris