panic: assertion "tracenode->kn_refs > 0" failed in ktrdestroy at /usr/src/sys/kern/kern_ktrace.c:481
Trace beginning at frame 0xfffff801181b7758
ktrdestroy() at ktrdestroy+0x89 0xffffffff80646249 
ktrdestroy() at ktrdestroy+0x89 0xffffffff80646249 
ktrops() at ktrops+0x65 0xffffffff80646c55 
sys_ktrace() at sys_ktrace+0xe0 0xffffffff80646f10 
Stopped at      Debugger+0x7c:  movb    $0,0xbdaf09(%rip)
db>