main.events_restart failed in buildbot (Assertion `share == 0' failed in TDC_element::assert_clean_share)

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

        Test ended at 2016-10-31 13:03:47

line

safe_mutex: Trying to lock unitialized mutex at /home/buildbot/buildbot/build/mariadb-10.1.19/sql/tztime.cc, line 2308

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

2016-10-31 13:03:44 2973454144 [ERROR] Plugin 'MyISAM' has ref_count=2 after shutdown.

mysqld: /home/buildbot/buildbot/build/mariadb-10.1.19/sql/table_cache.h:65: void TDC_element::assert_clean_share(): Assertion `share == 0' failed.

^ Found warnings in /mnt/buildbot/build/mariadb-10.1.19/mysql-test/var/1/log/mysqld.1.err

ok

 - saving '/mnt/buildbot/build/mariadb-10.1.19/mysql-test/var/1/log/main.events_restart/' to '/mnt/buildbot/build/mariadb-10.1.19/mysql-test/var/log/main.events_restart/'