Bug #30193: crash during drop table and kill

When DROP TABLE detects that it has been killed
by another thread it must unlock the table names
it locked.

Fixed by backporting the 5.1 error handling code.

sql/sql_table.cc

@@ -256,8 +256,8 @@ int mysql_rm_table_part2(THD *thd, TABLE_LIST *tables, bool if_exists,
       drop_locked_tables(thd, db, table->table_name);
       if (thd->killed)
       {
-        thd->no_warnings_for_error= 0;
-	DBUG_RETURN(-1);
+        error=-1;
+        goto err_with_placeholders;
       }
       alias= (lower_case_table_names == 2) ? table->alias : table->table_name;
       /* remove form file and isam files */
@@ -338,6 +338,7 @@ int mysql_rm_table_part2(THD *thd, TABLE_LIST *tables, bool if_exists,
     }
   }
 
+err_with_placeholders:
   if (!drop_temporary)
     unlock_table_names(thd, tables, (TABLE_LIST*) 0);
   thd->no_warnings_for_error= 0;