Bug #11764779 (former 57649)

FLUSH TABLES under FLUSH TABLES <list> WITH READ LOCK leads 
to assert failure.

This assert was triggered if a statement tried up upgrade a metadata
lock with an active FLUSH TABLE <list> WITH READ LOCK. The assert 
checks that the connection already holds a global intention exclusive
metadata lock. However, FLUSH TABLE <list> WITH READ LOCK does not
acquire this lock in order to be compatible with FLUSH TABLES WITH
READ LOCK. Therefore any metadata lock upgrade caused the assert to
be triggered.

This patch fixes the problem by preventing metadata lock upgrade
if the connection has an active FLUSH TABLE <list> WITH READ LOCK.
ER_TABLE_NOT_LOCKED_FOR_WRITE will instead be reported to the client.

Test case added to flush.test.

1 files changed, 17 insertions, 3 deletions

diff --git a/sql/sql_reload.cc b/sql/sql_reload.cc
index 0810459cb49..a09aa5511bd 100644
--- a/sql/sql_reload.cc
+++ b/sql/sql_reload.cc
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -220,12 +220,26 @@ bool reload_acl_and_cache(THD *thd, unsigned long options,
         if (tables)
         {
           for (TABLE_LIST *t= tables; t; t= t->next_local)
-            if (!find_table_for_mdl_upgrade(thd->open_tables, t->db,
-                                            t->table_name, FALSE))
+            if (!find_table_for_mdl_upgrade(thd, t->db, t->table_name, false))
               return 1;
         }
         else
         {
+          /*
+            It is not safe to upgrade the metadata lock without GLOBAL IX lock.
+            This can happen with FLUSH TABLES <list> WITH READ LOCK as we in these
+            cases don't take a GLOBAL IX lock in order to be compatible with
+            global read lock.
+          */
+          if (thd->open_tables &&
+              !thd->mdl_context.is_lock_owner(MDL_key::GLOBAL, "", "",
+                                              MDL_INTENTION_EXCLUSIVE))
+          {
+            my_error(ER_TABLE_NOT_LOCKED_FOR_WRITE, MYF(0),
+                     thd->open_tables->s->table_name.str);
+            return true;
+          }
+
           for (TABLE *tab= thd->open_tables; tab; tab= tab->next)
           {
             if (! tab->mdl_ticket->is_upgradable_or_exclusive())