Mysterious Zabbix Problems: How We Debug Them

This came as the first assignment for me, a new Zabbix employee – to fix a bug ZBX-3788 zabbix daemon processes hang on futex
Sometimes terminating a Zabbix agent with “killall -15 zabbix_agentd” resulted in one hanging process and other processes in the <defunct> state. strace utility showed the process was hanging on futex:

Process 10468 attached - interrupt to quit
futex(0xb783ca50, FUTEX_WAIT_PRIVATE, 2, NULL
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