Server crashes in mi_extra / ha_partition::loop_extra_alter upon REORGANIZE

--source include/have_partition.inc

CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM PARTITION BY RANGE (a) SUBPARTITION BY HASH (a) SUBPARTITIONS 2 (PARTITION p1 VALUES LESS THAN (100), PARTITION p2 VALUES LESS THAN MAXVALUE);

INSERT INTO t1 VALUES (4,6),(0,9);

UPDATE t1 SET a = 7;

SET max_session_mem_used= @@max_session_mem_used + 1024;

ALTER TABLE t1 REORGANIZE PARTITION p1,p2 INTO (PARTITION p1 VALUES LESS THAN (5), PARTITION p2 VALUES LESS THAN MAXVALUE);

# Cleanup

DROP TABLE t1;

--source include/have_sequence.inc

--source include/have_partition.inc

CREATE TABLE t1 (a INT, b INT) ENGINE=MyISAM PARTITION BY RANGE (a) SUBPARTITION BY HASH (a) SUBPARTITIONS 70 (PARTITION p1 VALUES LESS THAN (100), PARTITION p2 VALUES LESS THAN MAXVALUE);

INSERT INTO t1 SELECT 4, 6 FROM seq_1_to_131072;

UPDATE t1 SET a = 7;

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

--let conid= `select connection_id()`

--send

  ALTER TABLE t1 REORGANIZE PARTITION p1,p2 INTO (PARTITION p1 VALUES LESS THAN (5), PARTITION p2 VALUES LESS THAN MAXVALUE);

--connection default

--sleep 0.1

--eval KILL QUERY $conid

# Cleanup

DROP TABLE t1;

#3  <signal handler called>

#4  0x000055997af07a87 in mi_extra (info=0x0, function=HA_EXTRA_FORCE_REOPEN, extra_arg=0x0) at /data/src/10.3/storage/myisam/mi_extra.c:42

#5  0x000055997aee5a95 in ha_myisam::extra (this=0x7f083c014a88, operation=HA_EXTRA_FORCE_REOPEN) at /data/src/10.3/storage/myisam/ha_myisam.cc:2058

#6  0x000055997afb85ec in ha_partition::loop_extra_alter (this=0x7f083c0975b8, operation=HA_EXTRA_FORCE_REOPEN) at /data/src/10.3/sql/ha_partition.cc:9154

#7  0x000055997afb7c4b in ha_partition::extra (this=0x7f083c0975b8, operation=HA_EXTRA_FORCE_REOPEN) at /data/src/10.3/sql/ha_partition.cc:8882

#8  0x000055997a3c43fe in wait_while_table_is_used (thd=0x7f083c000af0, table=0x7f083c096510, function=HA_EXTRA_FORCE_REOPEN) at /data/src/10.3/sql/sql_base.cc:1264

#9  0x000055997a947483 in handle_alter_part_error (lpt=0x7f084d184fc0, action_completed=false, drop_partition=false, frm_install=false, close_table=true) at /data/src/10.3/sql/sql_partition.cc:6979

#10 0x000055997a948c1d in fast_alter_partition_table (thd=0x7f083c000af0, table=0x7f083c096510, alter_info=0x7f084d186420, create_info=0x7f084d1864e0, table_list=0x7f083c0129c0, db=0x7f084d185900, table_name=0x7f084d185910) at /data/src/10.3/sql/sql_partition.cc:7530

#11 0x000055997a546194 in mysql_alter_table (thd=0x7f083c000af0, new_db=0x7f083c0051d8, new_name=0x7f083c0055a0, create_info=0x7f084d1864e0, table_list=0x7f083c0129c0, alter_info=0x7f084d186420, order_num=0, order=0x0, ignore=false) at /data/src/10.3/sql/sql_table.cc:9685

#12 0x000055997a5d5672 in Sql_cmd_alter_table::execute (this=0x7f083c013928, thd=0x7f083c000af0) at /data/src/10.3/sql/sql_alter.cc:512

#13 0x000055997a46578a in mysql_execute_command (thd=0x7f083c000af0) at /data/src/10.3/sql/sql_parse.cc:6022

#14 0x000055997a46af3f in mysql_parse (thd=0x7f083c000af0, rawbuf=0x7f083c012818 "ALTER TABLE t1 REORGANIZE PARTITION p1,p2 INTO (PARTITION p1 VALUES LESS THAN (5), PARTITION p2 VALUES LESS THAN MAXVALUE)", length=122, parser_state=0x7f084d1875e0, is_com_multi=false, is_next_command=false) at /data/src/10.3/sql/sql_parse.cc:7810

#15 0x000055997a457786 in dispatch_command (command=COM_QUERY, thd=0x7f083c000af0, packet=0x7f083c1234d1 "ALTER TABLE t1 REORGANIZE PARTITION p1,p2 INTO (PARTITION p1 VALUES LESS THAN (5), PARTITION p2 VALUES LESS THAN MAXVALUE)", packet_length=122, is_com_multi=false, is_next_command=false) at /data/src/10.3/sql/sql_parse.cc:1848

#16 0x000055997a45609e in do_command (thd=0x7f083c000af0) at /data/src/10.3/sql/sql_parse.cc:1393

#17 0x000055997a5cf671 in do_handle_one_connection (connect=0x55997ddcd540) at /data/src/10.3/sql/sql_connect.cc:1403

#18 0x000055997a5cf3d3 in handle_one_connection (arg=0x55997ddcd540) at /data/src/10.3/sql/sql_connect.cc:1308

#19 0x000055997af870b8 in pfs_spawn_thread (arg=0x55997dde85f0) at /data/src/10.3/storage/perfschema/pfs.cc:1869

#20 0x00007f0854f114a4 in start_thread (arg=0x7f084d188700) at pthread_create.c:456

#21 0x00007f0853045d0f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97