MDEV-7299 Assertion `m_status == DA_ERROR || m_status == DA_OK' fails on concurrent execution of DDL, queries from I_S, and KILL QUERY

Fix MDL to report an error when a wait was killed, but preserve
the old documented behavior of GET_LOCK() where killing it is not an error.

Also remove race conditions in main.create_or_replace test

mysql-test/r/create_or_replace.result

@@ -436,7 +436,9 @@ CREATE OR REPLACE TEMPORARY TABLE tmp LIKE t1;
 LOCK TABLE t1 WRITE;
 CREATE OR REPLACE TABLE t1 LIKE tmp;
 KILL QUERY con_id;
+ERROR 70100: Query execution was interrupted
 CREATE OR REPLACE TABLE t1 (a int);
 KILL QUERY con_id;
+ERROR 70100: Query execution was interrupted
 drop table t1;
 DROP TABLE t2;

mysql-test/t/create_or_replace.test

@@ -346,20 +346,26 @@ LOCK TABLE t1 WRITE;
 --let $con_id = `SELECT CONNECTION_ID()`
 --send CREATE OR REPLACE TABLE t1 LIKE tmp
 --connection default
+let $wait_condition= SELECT COUNT(*)=1 FROM information_schema.processlist
+  WHERE state= 'Waiting for table metadata lock';
+--source include/wait_condition.inc
 --replace_result $con_id con_id
 --eval KILL QUERY $con_id
 
 --connection con1
---error 0,ER_QUERY_INTERRUPTED
+--error ER_QUERY_INTERRUPTED
 --reap
 --send CREATE OR REPLACE TABLE t1 (a int)
 
 --connection default
+let $wait_condition= SELECT COUNT(*)=1 FROM information_schema.processlist
+  WHERE state= 'Waiting for table metadata lock';
+--source include/wait_condition.inc
 --replace_result $con_id con_id
 --eval KILL QUERY $con_id
 
 --connection con1
---error 0,ER_QUERY_INTERRUPTED
+--error ER_QUERY_INTERRUPTED
 --reap
 --disconnect con1
 --connection default

sql/item_func.cc

@@ -4179,9 +4179,10 @@ void mysql_ull_set_explicit_lock_duration(THD *thd)
   When MDL detects a lock wait timeout, it pushes
   an error into the statement diagnostics area.
   For GET_LOCK(), lock wait timeout is not an error,
-  but a special return value (0). NULL is returned in
-  case of error.
-  Capture and suppress lock wait timeout.
+  but a special return value (0).
+  Similarly, killing get_lock wait is not an error either,
+  but a return value NULL.
+  Capture and suppress lock wait timeouts and kills.
 */
 
 class Lock_wait_timeout_handler: public Internal_error_handler
@@ -4200,7 +4201,7 @@ public:
 
 bool
 Lock_wait_timeout_handler::
-handle_condition(THD * /* thd */, uint sql_errno,
+handle_condition(THD *thd, uint sql_errno,
                  const char * /* sqlstate */,
                  Sql_condition::enum_warning_level /* level */,
                  const char *message,
@@ -4211,6 +4212,9 @@ handle_condition(THD * /* thd */, uint sql_errno,
     m_lock_wait_timeout= true;
     return true;                                /* condition handled */
   }
+  if (thd->is_killed())
+    return true;
+
   return false;
 }
 

sql/mdl.cc

@@ -2413,6 +2413,7 @@ MDL_context::acquire_lock(MDL_request *mdl_request, ulong lock_wait_timeout)
       my_error(ER_LOCK_WAIT_TIMEOUT, MYF(0));
       break;
     case MDL_wait::KILLED:
+      get_thd()->send_kill_message();
       break;
     default:
       DBUG_ASSERT(0);