Assertion `thd->mdl_context.is_lock_owner(...)` failed in close_thread_table() on ALTER TABLE vs concurrent FLUSH TABLES with two sequence defaults

CREATE SEQUENCE s1;

CREATE SEQUENCE s2;

CREATE TABLE t1 (a INT DEFAULT NEXTVAL(s1), b INT DEFAULT NEXTVAL(s2));

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

--let $i= 5

while ($i)

{

  --connection con1

  --send ALTER TABLE t1 FORCE

  --connection default

  FLUSH TABLES t1, s1;

  --connection con1

  --reap

  --dec $i

}

--disconnect con1

DROP TABLE t1;

DROP SEQUENCE s1, s2;

10.11.20-MariaDB-asan-debug source revision: dad5e3c968cfd71048fff37da643bfe5733d58ff

mariadbd: /10.11/src/sql/sql_base.cc:1030: void close_thread_table(THD*, TABLE**): Assertion `thd->mdl_context.is_lock_owner(MDL_key::TABLE, table->s->db.str, table->s->table_name.str, MDL_SHARED) || thd->mdl_context.is_lock_warrantee(MDL_key::TABLE, table->s->db.str, table->s->table_name.str, MDL_SHARED)' failed.

#7  close_thread_table (thd=thd@entry=0x52b00016c218, table_ptr=table_ptr@entry=0x52b00016c310) at /10.11/src/sql/sql_base.cc:1030

#8  close_thread_tables (thd=thd@entry=0x52b00016c218) at /10.11/src/sql/sql_base.cc:1006

#9  close_thread_tables_for_query (thd=thd@entry=0x52b00016c218) at /10.11/src/sql/sql_base.cc:815

#10 mysql_execute_command (thd=thd@entry=0x52b00016c218, is_called_from_prepared_stmt=false) at /10.11/src/sql/sql_parse.cc:6263

#11 mysql_parse (thd=thd@entry=0x52b00016c218, rawbuf=<optimized out>, length=<optimized out>, parser_state=parser_state@entry=0x77ffd19bd150) at /10.11/src/sql/sql_parse.cc:8219

#12 dispatch_command (command=command@entry=COM_QUERY, thd=thd@entry=0x52b00016c218, packet=packet@entry=0x52900010e219 "ALTER TABLE t1 FORCE", packet_length=packet_length@entry=20, blocking=blocking@entry=true) at /10.11/src/sql/sql_parse.cc:1924

#13 do_command (thd=thd@entry=0x52b00016c218, blocking=blocking@entry=true) at /10.11/src/sql/sql_parse.cc:1434

#14 do_handle_one_connection (connect=<optimized out>, connect@entry=0x508000007838, put_in_cache=put_in_cache@entry=true) at /10.11/src/sql/sql_connect.cc:1501

#15 handle_one_connection (arg=arg@entry=0x508000007838) at /10.11/src/sql/sql_connect.cc:1413