main.partition_debug_sync failed in buildbot with deadlock

main.partition_debug_sync 'xtradb'       w4 [ fail ]

        Test ended at 2018-03-21 10:49:19

CURRENT_TEST: main.partition_debug_sync

mysqltest: At line 45: query 'DROP TABLE IF EXISTS t1' failed: 1213: Deadlock found when trying to get lock; try restarting transaction

The result from queries just before the failure was:

< snip >

# Con 1

SET DEBUG_SYNC= 'RESET';

CREATE TABLE t1

(a INTEGER,

b INTEGER NOT NULL,

KEY (b))

ENGINE = MYISAM

/*!50100  PARTITION BY RANGE (a)

(PARTITION p0 VALUES LESS THAN (2),

PARTITION p1 VALUES LESS THAN (20),

PARTITION p2 VALUES LESS THAN (100),

PARTITION p3 VALUES LESS THAN MAXVALUE ) */;

SET DEBUG_SYNC= 'alter_table_before_create_table_no_lock SIGNAL removing_partitioning WAIT_FOR waiting_for_alter';

SET DEBUG_SYNC= 'mdl_acquire_lock_wait SIGNAL waiting_for_upgrade';

ALTER TABLE t1 REMOVE PARTITIONING;

# Con default

SET DEBUG_SYNC= 'now WAIT_FOR removing_partitioning';

SET DEBUG_SYNC= 'mdl_acquire_lock_wait SIGNAL waiting_for_alter';

SET DEBUG_SYNC= 'rm_table_no_locks_before_delete_table WAIT_FOR waiting_for_upgrade';

DROP TABLE IF EXISTS t1;

More results from queries before failure can be found in D:\winx64-debug\build\mysql-test\var\4\log\partition_debug_sync.log