See sub-issue (133) of ZBXNEXT-1263, ZBX-10034.

Description

Agents will not start In case of ...

• ... multiple agents running on the same Windows host...
• ... in the same session (e.g. the same user or as a service) ...
• ... if one of them fails or is closed while it has acquired some lock (for example logging lock).

Workarounds

• full system reboot;
• closing all Zabbix agents running in the affected session, waiting for Windows to remove the unused lock, then starting agents again.

Analysis

__zbx_mutex_lock() doesn't handle explicitly the WAIT_ABANDONED result from WaitForSingleObject() but instead exits.

More info on mutexes in Windows.

Important:

• lock namespaces are per-session (session 0 for services, other sessions - for users);
• contrary to SysV locks - Windows keeps track of users and removes the lock if it's unreferenced by any thread in the session.