This is to resolve a hang situation in 5.1 builtin raised by

bug #49251 (deadlock/crash with concurrent truncate table and index
statistics calculation) by backporting a solution from #54678 fixed
for 5.1 plugin and 5.5.

storage/innobase/include/dict0dict.h

@@ -588,6 +588,22 @@ dict_table_is_comp_noninline(
 					/* out: TRUE if table uses the
 					compact page format */
 	const dict_table_t*	table);	/* in: table */
+/*********************************************************************//**
+Obtain exclusive locks on all index trees of the table. This is to prevent
+accessing index trees while InnoDB is updating internal metadata for
+operations such as truncate tables. */
+UNIV_INLINE
+void
+dict_table_x_lock_indexes(
+/*======================*/
+	dict_table_t*	table);	/* in: table */
+/*********************************************************************//**
+Release the exclusive locks on all index tree. */
+UNIV_INLINE
+void
+dict_table_x_unlock_indexes(
+/*========================*/
+	dict_table_t*	table);	/* in: table */
 /************************************************************************
 Checks if a column is in the ordering columns of the clustered index of a
 table. Column prefixes are treated like whole columns. */

storage/innobase/include/dict0dict.ic

@@ -298,6 +298,48 @@ dict_table_is_comp(
 	return(UNIV_LIKELY(table->flags & DICT_TF_COMPACT));
 }
 
+/*********************************************************************//**
+Obtain exclusive locks on all index trees of the table. This is to prevent
+accessing index trees while InnoDB is updating internal metadata for
+operations such as truncate tables. */
+UNIV_INLINE
+void
+dict_table_x_lock_indexes(
+/*======================*/
+	dict_table_t*	table)	/* in: table */
+{
+	dict_index_t*   index;
+
+	ut_a(table);
+	ut_ad(mutex_own(&(dict_sys->mutex)));
+
+	/* Loop through each index of the table and lock them */
+	for (index = dict_table_get_first_index(table);
+	     index != NULL;
+	     index = dict_table_get_next_index(index)) {
+		rw_lock_x_lock(dict_index_get_lock(index));
+	}
+}
+
+/*********************************************************************//**
+Release the exclusive locks on all index tree. */
+UNIV_INLINE
+void
+dict_table_x_unlock_indexes(
+/*========================*/
+	dict_table_t*	table)	/* in: table */
+{
+	dict_index_t*   index;
+
+	ut_a(table);
+	ut_ad(mutex_own(&(dict_sys->mutex)));
+
+	for (index = dict_table_get_first_index(table);
+	     index != NULL;
+	     index = dict_table_get_next_index(index)) {
+		rw_lock_x_unlock(dict_index_get_lock(index));
+	}
+}
 /************************************************************************
 Gets the number of fields in the internal representation of an index,
 including fields added by the dictionary system. */

storage/innobase/row/row0mysql.c

@@ -2830,6 +2830,15 @@ row_truncate_table_for_mysql(
 
 	trx->table_id = table->id;
 
+	/* Lock all index trees for this table, as we will
+	truncate the table/index and possibly change their metadata.
+	All DML/DDL are blocked by table level lock, with
+	a few exceptions such as queries into information schema
+	about the table, MySQL could try to access index stats
+	for this kind of query, we need to use index locks to
+	sync up */
+	dict_table_x_lock_indexes(table);
+
 	/* scan SYS_INDEXES for all indexes of the table */
 	heap = mem_heap_create(800);
 
@@ -2902,6 +2911,10 @@ row_truncate_table_for_mysql(
 
 	mem_heap_free(heap);
 
+	/* Done with index truncation, release index tree locks,
+	subsequent work relates to table level metadata change */
+	dict_table_x_unlock_indexes(table);
+
 	new_id = dict_hdr_get_new_id(DICT_HDR_TABLE_ID);
 
 	info = pars_info_create();