[auto-backtrace via crash dump, debug.debugger_on_panic=0, kernel #0, false variant]
login: cmd_set_usage_all(): failed to create iterator
Fatal user address access from kernel mode from typeconfuse at ffffffff809d780f

Fatal trap 12: page fault while in kernel mode
fault virtual address	= 0x40
instruction pointer	= 0x8:0xffffffff809d780f   (strncpy+0x1f: movzbl -0x1(%rsi),%r8d)
current process		= 931
trap number		= 12
panic with 1 spinlocks held        <- ac_spin held across the mutex sleep path
panic: page fault
cpuid = 1
Trace beginning at frame 0xfffff8011829d4f8
trap_fatal() at trap_fatal+0x301
trap_pfault() at trap_pfault+0x431
trap() at trap+0x17c
calltrap() at calltrap+0x9
--- trap 000000000000000c, rip = ffffffff809d780f ---
strncpy() at strncpy+0x1f
_mtx_lock_ex() at _mtx_lock_ex+0x130      <- return addr of `callq mtx_wait_link`
boot() called on cpu#1
Dumping 630 MB: ... Dump complete

[_mtx_lock_ex+0x130 is the instruction after `callq mtx_wait_link`
 (objdump): mtx_wait_link -> tsleep(ident, flags, mtx->mtx_ident, to) —
 the wchan-string copy dereferences the aliased mtx_ident (0x40).]
savecore: reboot after panic: page fault
(/var/crash/vmcore.0 + kern.0 captured; vmcore header: "minidump DFlyBSD/x86-64")