We have previously seen the server_audit plugin cause threads to hang in various states due to the problems described by
MDEV-18661 / MDEV-19291. These threads could hang in many different states, such as "System lock", "init", and "freeing items." This made the root cause of the issue quite difficult to diagnose on production systems.
In case a similar issue happens again, it might make sense to add a new "Auditing" thread state. This new thread state could be used anytime a thread calls a function in the audit plugin API.