diff -rup mysql-5.1.55_base/storage/innodb_plugin/fil/fil0fil.c mysql-5.1.55_test/storage/innodb_plugin/fil/fil0fil.c
--- mysql-5.1.55_base/storage/innodb_plugin/fil/fil0fil.c	2011-01-26 00:04:36.000000000 +0900
+++ mysql-5.1.55_test/storage/innodb_plugin/fil/fil0fil.c	2011-02-22 10:44:43.842776868 +0900
@@ -235,6 +235,7 @@ the ib_logfiles form a 'space' and it is
 struct fil_system_struct {
 #ifndef UNIV_HOTBACKUP
 	mutex_t		mutex;		/*!< The mutex protecting the cache */
+	mutex_t		file_extend_mutex;
 #endif /* !UNIV_HOTBACKUP */
 	hash_table_t*	spaces;		/*!< The hash table of spaces in the
 					system; they are hashed on the space
@@ -1539,6 +1540,7 @@ fil_init(
 	fil_system = mem_zalloc(sizeof(fil_system_t));
 
 	mutex_create(&fil_system->mutex, SYNC_ANY_LATCH);
+	mutex_create(&fil_system->file_extend_mutex, SYNC_OUTER_ANY_LATCH);
 
 	fil_system->spaces = hash_create(hash_size);
 	fil_system->name_hash = hash_create(hash_size);
@@ -3855,6 +3857,10 @@ fil_extend_space_to_desired_size(
 	ulint		page_size;
 	ibool		success		= TRUE;
 
+	/* file_extend_mutex is for http://bugs.mysql.com/56433 */
+	/* to protect from the other fil_extend_space_to_desired_size() */
+	/* during temprary releasing &fil_system->mutex */
+	mutex_enter(&fil_system->file_extend_mutex);
 	fil_mutex_enter_and_prepare_for_io(space_id);
 
 	space = fil_space_get_by_id(space_id);
@@ -3866,6 +3872,7 @@ fil_extend_space_to_desired_size(
 		*actual_size = space->size;
 
 		mutex_exit(&fil_system->mutex);
+		mutex_exit(&fil_system->file_extend_mutex);
 
 		return(TRUE);
 	}
@@ -3898,6 +3905,8 @@ fil_extend_space_to_desired_size(
 		offset_low  = ((start_page_no - file_start_page_no)
 			       % (4096 * ((1024 * 1024) / page_size)))
 			* page_size;
+
+		mutex_exit(&fil_system->mutex);
 #ifdef UNIV_HOTBACKUP
 		success = os_file_write(node->name, node->handle, buf,
 					offset_low, offset_high,
@@ -3909,6 +3918,8 @@ fil_extend_space_to_desired_size(
 				 page_size * n_pages,
 				 NULL, NULL);
 #endif
+		mutex_enter(&fil_system->mutex);
+
 		if (success) {
 			node->size += n_pages;
 			space->size += n_pages;
@@ -3954,6 +3965,7 @@ fil_extend_space_to_desired_size(
 	printf("Extended %s to %lu, actual size %lu pages\n", space->name,
 	size_after_extend, *actual_size); */
 	mutex_exit(&fil_system->mutex);
+	mutex_exit(&fil_system->file_extend_mutex);
 
 	fil_flush(space_id);
 
diff -rup mysql-5.1.55_base/storage/innodb_plugin/include/sync0sync.h mysql-5.1.55_test/storage/innodb_plugin/include/sync0sync.h
--- mysql-5.1.55_base/storage/innodb_plugin/include/sync0sync.h	2011-01-26 00:04:39.000000000 +0900
+++ mysql-5.1.55_test/storage/innodb_plugin/include/sync0sync.h	2011-02-22 10:44:43.843775855 +0900
@@ -490,6 +490,7 @@ or row lock! */
 #define	SYNC_BUF_POOL		150
 #define	SYNC_BUF_BLOCK		149
 #define SYNC_DOUBLEWRITE	140
+#define	SYNC_OUTER_ANY_LATCH	136
 #define	SYNC_ANY_LATCH		135
 #define SYNC_THR_LOCAL		133
 #define	SYNC_MEM_HASH		131