main.shutdown failed in buildbot

main.shutdown                            w1 [ fail ]  Found warnings/errors in server log file!

        Test ended at 2016-08-16 16:45:38

line

160816 16:45:37 [ERROR] mysqld got signal 11 ;

Attempting backtrace. You can use the following information to find out

160816 16:45:38 [ERROR] mysqld: Table './mysql/servers' is marked as crashed and should be repaired

160816 16:45:38 [Warning] Checking table:   './mysql/servers'

160816 16:45:38 [ERROR] mysql.servers: 1 client is using or hasn't closed the table properly

160816 16:45:38 [ERROR] mysqld: Table './mysql/user' is marked as crashed and should be repaired

160816 16:45:38 [Warning] Checking table:   './mysql/user'

160816 16:45:38 [ERROR] mysql.user: 1 client is using or hasn't closed the table properly

160816 16:45:38 [ERROR] mysqld: Table './mysql/db' is marked as crashed and should be repaired

160816 16:45:38 [Warning] Checking table:   './mysql/db'

160816 16:45:38 [ERROR] mysql.db: 1 client is using or hasn't closed the table properly

^ Found warnings in /dev/shm/var/1/log/mysqld.1.err

ok

 - saving '/dev/shm/var/1/log/main.shutdown/' to '/dev/shm/var/log/main.shutdown/'

Retrying test main.shutdown, attempt(2/3)...