Server crashes in Locked_tables_list::mark_table_for_reopen upon ALTER TABLE

--source include/have_innodb.inc

CREATE TABLE t1 (pk INT, f TEXT NOT NULL) ENGINE=InnoDB;

ALTER TABLE t1 ALTER f SET DEFAULT NULL;

CREATE TABLE t2 (a INT) ENGINE=InnoDB;

CREATE TABLE t3 (b INT) ENGINE=InnoDB;

--error ER_BAD_FIELD_ERROR

ALTER TABLE t2 ORDER BY x;

LOCK TABLE t1 WRITE, t3 WRITE;

--error ER_BAD_NULL_ERROR

ALTER TABLE t1 ADD PRIMARY KEY(pk);

ALTER TABLE t3 CHANGE IF EXISTS b c INT;

# Cleanup

UNLOCK TABLES;

DROP TABLE t1, t2, t3;

#3  <signal handler called>

#4  Locked_tables_list::mark_table_for_reopen (this=0x7f3f800047f8, thd=0x7f3f80000d90, table=0x7f3f8009ac60) at /data/src/10.2/sql/sql_base.cc:2420

#5  0x000055c1e4ef8ff8 in TABLE::mark_table_for_reopen (this=0x7f3f8009ac60) at /data/src/10.2/sql/table.cc:8675

#6  0x000055c1e4eb5ad9 in mysql_prepare_alter_table (thd=0x7f3f80000d90, table=0x7f3f8009ac60, create_info=0x7f3fcb00b2f0, alter_info=0x7f3fcb00b240, alter_ctx=0x7f3fcb00a6d0) at /data/src/10.2/sql/sql_table.cc:7811

#7  0x000055c1e4eb9d76 in mysql_alter_table (thd=0x7f3f80000d90, new_db=0x7f3f80012e00 "test", new_name=0x0, create_info=0x7f3fcb00b2f0, table_list=0x7f3f800127e8, alter_info=0x7f3fcb00b240, order_num=0, order=0x0, ignore=false) at /data/src/10.2/sql/sql_table.cc:9291

#8  0x000055c1e4f39048 in Sql_cmd_alter_table::execute (this=0x7f3f80012ef8, thd=0x7f3f80000d90) at /data/src/10.2/sql/sql_alter.cc:333

#9  0x000055c1e4de743b in mysql_execute_command (thd=0x7f3f80000d90) at /data/src/10.2/sql/sql_parse.cc:6021

#10 0x000055c1e4dec28d in mysql_parse (thd=0x7f3f80000d90, rawbuf=0x7f3f800126f8 "ALTER TABLE t3 CHANGE IF EXISTS b c INT", length=39, parser_state=0x7f3fcb00c5f0, is_com_multi=false, is_next_command=false) at /data/src/10.2/sql/sql_parse.cc:7790

#11 0x000055c1e4dda4ca in dispatch_command (command=COM_QUERY, thd=0x7f3f80000d90, packet=0x7f3f80008b51 "ALTER TABLE t3 CHANGE IF EXISTS b c INT", packet_length=39, is_com_multi=false, is_next_command=false) at /data/src/10.2/sql/sql_parse.cc:1827

#12 0x000055c1e4dd8fc5 in do_command (thd=0x7f3f80000d90) at /data/src/10.2/sql/sql_parse.cc:1381

#13 0x000055c1e4f33a3e in do_handle_one_connection (connect=0x55c1e7495560) at /data/src/10.2/sql/sql_connect.cc:1336

#14 0x000055c1e4f337a3 in handle_one_connection (arg=0x55c1e7495560) at /data/src/10.2/sql/sql_connect.cc:1241

#15 0x000055c1e575c894 in pfs_spawn_thread (arg=0x55c1e7478950) at /data/src/10.2/storage/perfschema/pfs.cc:1869

#16 0x00007f3fd50b6609 in start_thread (arg=<optimized out>) at pthread_create.c:477

#17 0x00007f3fd4c90293 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

commit be647ff14d6196af825f05020acee8f18af4773d

Author: Monty

Date:   Fri May 22 18:02:24 2020 +0300

    Fixed deadlock with LOCK TABLES and ALTER TABLE

    MDEV-21398 Deadlock (server hang) or assertion failure in