Bug#25856 (HANDLER table OPEN in one connection lock DROP TABLE in another one)

mysql_ha_open calls mysql_ha_close on the error path (unsupported) to close the (opened) table before inserting it into the tables hash list handler_tables_hash) but mysql_ha_close only closes tables which are on the hash list, causing the table to be left open and locked.

This change moves the table close logic into a separate function that is always called on the error path of mysql_ha_open or on a normal handler close (mysql_ha_close).

mysql-test/r/handler.result

@@ -482,3 +482,10 @@ ERROR 42S02: Table 'test.t1' doesn't exist
 drop table if exists t1;
 Warnings:
 Note	1051	Unknown table 't1'
+drop table if exists t1;
+create table t1 (a int) ENGINE=MEMORY;
+--> client 2
+handler t1 open;
+ERROR HY000: Table storage engine for 't1' doesn't have this option
+--> client 1
+drop table t1;

mysql-test/t/handler.test

@@ -427,3 +427,17 @@ select * from t1;
 # Just to be sure and not confuse the next test case writer.
 drop table if exists t1;
 
+#
+# Bug#25856 - HANDLER table OPEN in one connection lock DROP TABLE in another one
+#
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+create table t1 (a int) ENGINE=MEMORY;
+--echo --> client 2
+connection con2;
+--error 1031
+handler t1 open;
+--echo --> client 1
+connection default;
+drop table t1;

sql/sql_handler.cc

@@ -119,6 +119,44 @@ static void mysql_ha_hash_free(TABLE_LIST *tables)
   my_free((char*) tables, MYF(0));
 }
 
+/**
+ * Close a HANDLER table.
+ *
+ * @param thd Thread identifier.
+ * @param A list of tables with the first entry to close.
+ *
+ * @note Though this function takes a list of tables, only the first list entry
+ * will be closed.
+ * @note Broadcasts refresh if it closed the table.
+ */
+
+static void mysql_ha_close_table(THD *thd, TABLE_LIST *tables)
+{
+  TABLE **table_ptr;
+
+  /*
+    Though we could take the table pointer from hash_tables->table,
+    we must follow the thd->handler_tables chain anyway, as we need the
+    address of the 'next' pointer referencing this table
+    for close_thread_table().
+  */
+  for (table_ptr= &(thd->handler_tables);
+       *table_ptr && (*table_ptr != tables->table);
+         table_ptr= &(*table_ptr)->next)
+    ;
+
+  if (*table_ptr)
+  {
+    (*table_ptr)->file->ha_index_or_rnd_end();
+    VOID(pthread_mutex_lock(&LOCK_open));
+    if (close_thread_table(thd, table_ptr))
+    {
+      /* Tell threads waiting for refresh that something has happened */
+      broadcast_refresh();
+    }
+    VOID(pthread_mutex_unlock(&LOCK_open));
+  }
+}
 
 /*
   Open a HANDLER table.
@@ -145,7 +183,7 @@ static void mysql_ha_hash_free(TABLE_LIST *tables)
 
 bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
 {
-  TABLE_LIST    *hash_tables;
+  TABLE_LIST    *hash_tables = NULL;
   char          *db, *name, *alias;
   uint          dblen, namelen, aliaslen, counter;
   int           error;
@@ -197,7 +235,6 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
   {
     if (! reopen)
       my_error(ER_ILLEGAL_HA, MYF(0), tables->alias);
-    mysql_ha_close(thd, tables);
     goto err;
   }
 
@@ -225,11 +262,7 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
 
     /* add to hash */
     if (my_hash_insert(&thd->handler_tables_hash, (byte*) hash_tables))
-    {
-      my_free((char*) hash_tables, MYF(0));
-      mysql_ha_close(thd, tables);
       goto err;
-    }
   }
 
   if (! reopen)
@@ -238,13 +271,17 @@ bool mysql_ha_open(THD *thd, TABLE_LIST *tables, bool reopen)
   DBUG_RETURN(FALSE);
 
 err:
+  if (hash_tables)
+    my_free((char*) hash_tables, MYF(0));
+  if (tables->table)
+    mysql_ha_close_table(thd, tables);
   DBUG_PRINT("exit",("ERROR"));
   DBUG_RETURN(TRUE);
 }
 
 
 /*
-  Close a HANDLER table.
+  Close a HANDLER table by alias or table name
 
   SYNOPSIS
     mysql_ha_close()
@@ -252,9 +289,8 @@ err:
     tables                      A list of tables with the first entry to close.
 
   DESCRIPTION
-    Though this function takes a list of tables, only the first list entry
-    will be closed.
-    Broadcasts refresh if it closed the table.
+    Closes the table that is associated (on the handler tables hash) with the
+    name (table->alias) of the specified table.
 
   RETURN
     FALSE ok
@@ -264,7 +300,6 @@ err:
 bool mysql_ha_close(THD *thd, TABLE_LIST *tables)
 {
   TABLE_LIST    *hash_tables;
-  TABLE         **table_ptr;
   DBUG_ENTER("mysql_ha_close");
   DBUG_PRINT("enter",("'%s'.'%s' as '%s'",
                       tables->db, tables->table_name, tables->alias));
@@ -273,28 +308,7 @@ bool mysql_ha_close(THD *thd, TABLE_LIST *tables)
                                               (byte*) tables->alias,
                                               strlen(tables->alias) + 1)))
   {
-    /*
-      Though we could take the table pointer from hash_tables->table,
-      we must follow the thd->handler_tables chain anyway, as we need the
-      address of the 'next' pointer referencing this table
-      for close_thread_table().
-    */
-    for (table_ptr= &(thd->handler_tables);
-         *table_ptr && (*table_ptr != hash_tables->table);
-           table_ptr= &(*table_ptr)->next)
-      ;
-
-    if (*table_ptr)
-    {
-      (*table_ptr)->file->ha_index_or_rnd_end();
-      VOID(pthread_mutex_lock(&LOCK_open));
-      if (close_thread_table(thd, table_ptr))
-      {
-        /* Tell threads waiting for refresh that something has happened */
-        broadcast_refresh();
-      }
-      VOID(pthread_mutex_unlock(&LOCK_open));
-    }
+    mysql_ha_close_table(thd, hash_tables);
     hash_delete(&thd->handler_tables_hash, (byte*) hash_tables);
   }
   else