bk commit into 5.1 tree (dlenev:1.2408)

[dlenev]

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5.1 repository of dlenev. When dlenev does a push these changes will
be propagated to the main repository and, within 24 hours after the
push, to the public repository.
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ChangeSet@stripped, 2007-01-19 23:23:45+03:00, dlenev@stripped +1 -0
  Merge mockturtle.local:/home/dlenev/src/mysql-5.0-bg25044
  into  mockturtle.local:/home/dlenev/src/mysql-5.1-bg25044
  MERGE: 1.1810.2443.1

  sql/sql_table.cc@stripped, 2007-01-19 23:23:41+03:00, dlenev@stripped +0 -0
    Auto merged
    MERGE: 1.239.42.1

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	dlenev
# Host:	mockturtle.local
# Root:	/home/dlenev/src/mysql-5.1-bg25044/RESYNC

--- 1.382/sql/sql_table.cc	2007-01-19 23:23:51 +03:00
+++ 1.383/sql/sql_table.cc	2007-01-19 23:23:51 +03:00
@@ -5542,19 +5542,30 @@ view_err:
   if (!(alter_info->flags & ~(ALTER_RENAME | ALTER_KEYS_ONOFF)) &&
       !table->s->tmp_table) // no need to touch frm
   {
-    VOID(pthread_mutex_lock(&LOCK_open));
-
     switch (alter_info->keys_onoff) {
     case LEAVE_AS_IS:
       error= 0;
       break;
     case ENABLE:
+      /*
+        wait_while_table_is_used() ensures that table being altered is
+        opened only by this thread and that TABLE::TABLE_SHARE::version
+        of TABLE object corresponding to this table is 0.
+        The latter guarantees that no DML statement will open this table
+        until ALTER TABLE finishes (i.e. until close_thread_tables())
+        while the fact that the table is still open gives us protection
+        from concurrent DDL statements.
+      */
+      VOID(pthread_mutex_lock(&LOCK_open));
       wait_while_table_is_used(thd, table, HA_EXTRA_FORCE_REOPEN);
+      VOID(pthread_mutex_unlock(&LOCK_open));
       error= table->file->enable_indexes(HA_KEY_SWITCH_NONUNIQ_SAVE);
       /* COND_refresh will be signaled in close_thread_tables() */
       break;
     case DISABLE:
+      VOID(pthread_mutex_lock(&LOCK_open));
       wait_while_table_is_used(thd, table, HA_EXTRA_FORCE_REOPEN);
+      VOID(pthread_mutex_unlock(&LOCK_open));
       error=table->file->disable_indexes(HA_KEY_SWITCH_NONUNIQ_SAVE);
       /* COND_refresh will be signaled in close_thread_tables() */
       break;
@@ -5570,6 +5581,16 @@ view_err:
 			  table->alias);
       error= 0;
     }
+
+    VOID(pthread_mutex_lock(&LOCK_open));
+    /*
+      Unlike to the above case close_cached_table() below will remove ALL
+      instances of TABLE from table cache (it will also remove table lock
+      held by this thread). So to make actual table renaming and writing
+      to binlog atomic we have to put them into the same critical section
+      protected by LOCK_open mutex. This also removes gap for races between
+      access() and mysql_rename_table() calls.
+    */
 
     if (!error && (new_name != table_name || new_db != db))
     {