To ascertain what your MySQL server is doing, it can be helpful to examine the process list, which indicates the operations currently being performed by the set of threads executing within the server. For example:

mysql> SHOW PROCESSLIST\G
*************************** 1. row ***************************
     Id: 5
   User: event_scheduler
   Host: localhost
     db: NULL
Command: Daemon
   Time: 2756681
  State: Waiting on empty queue
   Info: NULL
*************************** 2. row ***************************
     Id: 20
   User: me
   Host: localhost:52943
     db: test
Command: Query
   Time: 0
  State: starting
   Info: SHOW PROCESSLIST

Threads can be killed with the KILL statement. See Section 15.7.8.4, “KILL Statement”.