Backport of:

------------------------------------------------------------ 
revno: 2630.9.1 
committer: Dmitry Lenev <dlenev@mysql.com> 
branch nick: mysql-6.0-3726-w3 
timestamp: Sun 2008-06-08 22:13:58 +0400 
message: 
  WL#3726 "DDL locking for all metadata objects" 
   
  After review fixes in progress. 
   
  Some adjustments to the patch that removes thd->locked_tables

sql/sp_head.cc:
  Fix conditions which were wrongly translated by previous patch.
sql/sql_base.cc:
  close_thread_tables():
    Add comment clarifying control flow in case of LTM_LOCK_TABLES
    mode and statements requiring prelocking.
    Be consistent with other places where we clear
    OPTION_TABLE_LOCK flag.
  lock_tables():
    Always set THD::lock to 0 after freeing memory to which it
    points.

sql/sp_head.cc

@@ -1257,7 +1257,7 @@ sp_head::execute(THD *thd)
       Will write this SP statement into binlog separately 
       (TODO: consider changing the condition to "not inside event union")
     */
-    if (thd->locked_tables_mode == LTM_NONE)
+    if (thd->locked_tables_mode <= LTM_LOCK_TABLES)
       thd->user_var_events_alloc= thd->mem_root;
 
     err_status= i->execute(thd, &ip);
@@ -1269,7 +1269,7 @@ sp_head::execute(THD *thd)
       If we've set thd->user_var_events_alloc to mem_root of this SP
       statement, clean all the events allocated in it.
     */
-    if (thd->locked_tables_mode == LTM_NONE)
+    if (thd->locked_tables_mode <= LTM_LOCK_TABLES)
     {
       reset_dynamic(&thd->user_var_events);
       thd->user_var_events_alloc= NULL;//DEBUG
@@ -2740,7 +2740,7 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
   thd->query_id= next_query_id();
   pthread_mutex_unlock(&LOCK_thread_count);
 
-  if (thd->locked_tables_mode == LTM_NONE)
+  if (thd->locked_tables_mode <= LTM_LOCK_TABLES)
   {
     /*
       This statement will enter/leave prelocked mode on its own.

sql/sql_base.cc

@@ -1375,6 +1375,7 @@ void close_thread_tables(THD *thd,
                          bool skip_mdl)
 {
   TABLE *table;
+  bool clear_table_lock_option= FALSE;
   DBUG_ENTER("close_thread_tables");
 
 #ifdef EXTRA_DEBUG
@@ -1446,6 +1447,11 @@ void close_thread_tables(THD *thd,
     /*
       We are under simple LOCK TABLES or we're inside a sub-statement
       of a prelocked statement, so should not do anything else.
+
+      Note that even if we are in LTM_LOCK_TABLES mode and statement
+      requires prelocking (e.g. when we are closing tables after
+      failing ot "open" all tables required for statement execution)
+      we will exit this function a few lines below.
     */
     if (! thd->lex->requires_prelocking())
       DBUG_VOID_RETURN;
@@ -1462,7 +1468,7 @@ void close_thread_tables(THD *thd,
       DBUG_VOID_RETURN;
 
     thd->locked_tables_mode= LTM_NONE;
-    thd->options&= ~OPTION_TABLE_LOCK;
+    clear_table_lock_option= TRUE;
 
     /*
       Note that we are leaving prelocked mode so we don't need
@@ -1502,6 +1508,9 @@ void close_thread_tables(THD *thd,
     mdl_remove_all_locks(&thd->mdl_context);
   }
 
+  if (clear_table_lock_option)
+    thd->options&= ~OPTION_TABLE_LOCK;
+
   DBUG_VOID_RETURN;
 }
 
@@ -5452,6 +5461,7 @@ int lock_tables(THD *thd, TABLE_LIST *tables, uint count,
               need to care about THD::locked_tables_root here.
             */
             mysql_unlock_tables(thd, thd->lock);
+            thd->lock= 0;
             thd->options&= ~(OPTION_TABLE_LOCK);
             DBUG_RETURN(-1);
           }