执行smart_monkey指令报错，请帮忙分析下原因，多谢！

[xiayuzhu]

INSTRUMENTS_TRACE_PATH : /Users/ebao/CrashMonkey4IOS/custom_cfg/*.trace
RESULT_BASE_PATH : /Users/ebao/CrashMonkey4IOS/custom_cfg/smart_monkey_result
{:app_path=>"ebao.BlockTest", :device=>"55a4464ef4ee3f7563a36cb06761bcd99757f7d3", :run_count=>100, :time_limit_sec=>nil, :detail_event_count=>50}
2016-12-21 16:57:52.035 instruments[1065:18794] WebKit Threading Violation - initial use of WebKit from a secondary thread.
=================================== Start Test (1/100) =======================================
2016-12-21 16:57:53.338 instruments[1077:18829] WebKit Threading Violation - initial use of WebKit from a secondary thread.
2016-12-21 16:57:54.529 instruments[1083:18867] WebKit Threading Violation - initial use of WebKit from a secondary thread.
2016-12-21 16:57:55.762 instruments[1089:18939] WebKit Threading Violation - initial use of WebKit from a secondary thread.
ERROR: Could not connect to lockdownd, error code -21

[Graice]

sudo chmod -R 777 /var/db/lockdown/