Assertion `this == ticket->get_ctx()' failed in MDL_context::release_lock upon BACKUP STAGE END

CREATE TABLE t1 (a INT);

BACKUP STAGE START;

FLUSH TABLE t1 FOR EXPORT;

UNLOCK TABLES;

--connect (con1,localhost,root,,test)

BACKUP STAGE START;

--connection default

BACKUP STAGE END;

# Cleanup

--connection con1

BACKUP STAGE END;

--disconnect con1

--connection default

DROP TABLE t1;

mysqld: /data/src/10.4/sql/mdl.cc:2831: void MDL_context::release_lock(enum_mdl_duration, MDL_ticket*): Assertion `this == ticket->get_ctx()' failed.

181224 17:51:49 [ERROR] mysqld got signal 6 ;

#7  0x00007f64df92bee2 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6

#8  0x000055b996bd8c74 in MDL_context::release_lock (this=0x7f64c8000c20, duration=MDL_EXPLICIT, ticket=0x7f64bc01ac90) at /data/src/10.4/sql/mdl.cc:2831

#9  0x000055b996bd8d63 in MDL_context::release_lock (this=0x7f64c8000c20, ticket=0x7f64bc01ac90) at /data/src/10.4/sql/mdl.cc:2853

#10 0x000055b996cadedb in backup_end (thd=0x7f64c8000b00) at /data/src/10.4/sql/backup.cc:308

#11 0x000055b996cad894 in run_backup_stage (thd=0x7f64c8000b00, stage=BACKUP_END) at /data/src/10.4/sql/backup.cc:119

#12 0x000055b996a6b94b in mysql_execute_command (thd=0x7f64c8000b00) at /data/src/10.4/sql/sql_parse.cc:5233

#13 0x000055b996a748e4 in mysql_parse (thd=0x7f64c8000b00, rawbuf=0x7f64c8014f98 "BACKUP STAGE END", length=16, parser_state=0x7f64d9abd600, is_com_multi=false, is_next_command=false) at /data/src/10.4/sql/sql_parse.cc:8104

#14 0x000055b996a61b0e in dispatch_command (command=COM_QUERY, thd=0x7f64c8000b00, packet=0x7f64c800b421 "BACKUP STAGE END", packet_length=16, is_com_multi=false, is_next_command=false) at /data/src/10.4/sql/sql_parse.cc:1851

#15 0x000055b996a60532 in do_command (thd=0x7f64c8000b00) at /data/src/10.4/sql/sql_parse.cc:1396

#16 0x000055b996bcc6de in do_handle_one_connection (connect=0x55b9993c06a0) at /data/src/10.4/sql/sql_connect.cc:1402

#17 0x000055b996bcc462 in handle_one_connection (arg=0x55b9993c06a0) at /data/src/10.4/sql/sql_connect.cc:1308

#18 0x000055b99708b338 in pfs_spawn_thread (arg=0x55b999304960) at /data/src/10.4/storage/perfschema/pfs.cc:1862

#19 0x00007f64e13e7494 in start_thread (arg=0x7f64d9abe700) at pthread_create.c:333

#20 0x00007f64df9e893f in clone () from /lib/x86_64-linux-gnu/libc.so.6

#5  <signal handler called>

#6  0x0000000000000055 in ?? ()

#7  0x0000558f1155a24f in backup_end (thd=0x7f9db00009a8) at /data/src/10.4/sql/backup.cc:308

#8  0x0000558f1155a2d8 in run_backup_stage (thd=0x7f9db00009a8, stage=BACKUP_END) at /data/src/10.4/sql/backup.cc:119

#9  0x0000558f113f4399 in mysql_execute_command (thd=0x7f9db00009a8) at /data/src/10.4/sql/sql_parse.cc:5233

#10 0x0000558f113fa9a1 in mysql_parse (thd=0x7f9db00009a8, rawbuf=<optimized out>, length=16, parser_state=0x7f9dccc9d640, is_com_multi=<optimized out>, is_next_command=<optimized out>) at /data/src/10.4/sql/sql_parse.cc:8104

#11 0x0000558f113fd315 in dispatch_command (command=command@entry=COM_QUERY, thd=thd@entry=0x7f9db00009a8, packet=packet@entry=0x7f9db0009559 "BACKUP STAGE END", packet_length=packet_length@entry=16, is_com_multi=is_com_multi@entry=false, is_next_command=is_next_command@entry=false) at /data/src/10.4/sql/sql_parse.cc:1851

#12 0x0000558f113fdca0 in do_command (thd=0x7f9db00009a8) at /data/src/10.4/sql/sql_parse.cc:1396

#13 0x0000558f114cfd54 in do_handle_one_connection (connect=connect@entry=0x558f149900c8) at /data/src/10.4/sql/sql_connect.cc:1402

#14 0x0000558f114cfef4 in handle_one_connection (arg=arg@entry=0x558f149900c8) at /data/src/10.4/sql/sql_connect.cc:1308

#15 0x0000558f117c65a4 in pfs_spawn_thread (arg=0x558f14990668) at /data/src/10.4/storage/perfschema/pfs.cc:1862

#16 0x00007f9dd4613494 in start_thread (arg=0x7f9dccc9e700) at pthread_create.c:333

#17 0x00007f9dd2c1493f in clone () from /lib/x86_64-linux-gnu/libc.so.6